JP2009009022A - Developing device, image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device for stably supplying developer to a latent image carrier, and an image forming apparatus equipped with the developer device, and a process cartridge. <P>SOLUTION: The developing device 4 has a supply conveyance path 9 and a stirring conveyance path 10 being a circulating conveyance path, is equipped with an excess aperture part 92 that is a circulating aperture part through which developer is delivered to the stirring conveyance path 10 in the vicinity of the downstream end of the supply conveyance path 9 in a conveying direction, and is equipped with a developer discharge port 94 that is a discharge aperture part through which the developer is discharged to the outside of the developing device 4 in the supply conveyance path 9. The developing device 4 is equipped with a developer accumulation means 80 accumulating the developer which reaches the vicinity of the downstream end of the supply conveyance path 9 in the conveying direction and does not enter the excess aperture part 92 in the vicinity of the excess aperture part 92. The developer discharge port 94 is arranged above the excess aperture part 92 so that the developer which reaches the position of the developer discharge port 94 out of the accumulated developer accumulated by the developer accumulation means 80 may pass therethrough. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device used for a copying machine, a facsimile, a printer, and the like, and an image forming apparatus and a process cartridge using the developing device.

  Conventionally, an image forming apparatus including a developing device using a two-component developer including toner and a magnetic carrier has been widely used. As an image forming apparatus of this type, the toner density of the developer is kept within a predetermined range by supplying toner from the toner container as necessary to the developer in the developing apparatus that consumes toner with development. There is something to keep in. In such a configuration, the carrier in the developer is hardly consumed and used repeatedly, and therefore the carrier deteriorates as the image is output. Specifically, the coating film on the carrier surface is scraped by mechanical stress or the toner component is spent on the carrier surface. When the carrier is deteriorated, the ability to charge the toner of the carrier is gradually reduced, causing problems such as background contamination, image density reduction, abnormal image density unevenness and toner scattering. For this reason, in this type of image forming apparatus, a service person regularly visits the user to exchange carriers. For this reason, maintenance costs are incurred, and the unit price for image formation is high.

  In Patent Document 1 and Patent Document 2, a premix developer in which a carrier and toner are mixed is supplied to the developer in the developing device to restore the toner density, and an increased amount of developer is removed from the developing device. A developing device to be discharged is described. In such a configuration, a new carrier in the premix developer is replenished to the developer in the developing device while the carrier that has become old due to the discharge of the developer is gradually discharged from the developing device. Then, the carrier replacement work can be omitted by replacing the carrier in the developer gradually with a new one by such discharge and replenishment.

In the developing device of Patent Document 1, a sensor that detects the amount of developer in the developing device and a shutter mechanism that opens and closes a developer discharge portion are provided. In normal operation, the shutter is closed so that the developer is not discharged, and when the sensor detects that the volume of the developer exceeds a certain level, the shutter opens and the developer is discharged. ing. However, in this method, the configuration becomes complicated and the cost increases.
In the developing device of Patent Document 2, the developer is provided on the side wall on the downstream side of the position where the developer is supplied to the developing roller of the supply conveyance path that conveys the developer in the axial direction of the developing roller while supplying the developer to the developing roller. The developer is discharged from the developing opening to the outside of the developing device. Further, on the downstream side of the position where the discharge opening is provided, a circulation opening that communicates with the circulation conveyance path that transfers the developer to the upstream end of the supply conveyance path is provided. In this developing device, when the premix developer is supplied and the amount of developer in the developing device increases, the bulk of the developer in the supply conveyance path increases. At this time, the developer that reaches the height of the discharge opening at the position where the discharge opening is provided is discharged from the discharge opening to the outside of the developing device, and the developer that is not discharged at the position where the discharge opening is provided is It is sent to the circulation conveyance path through the circulation opening. Further, in the state where the volume of the developer in the supply conveyance path does not change, the developer does not reach the height of the discharge opening at the position of the discharge opening, so the developer is not discharged, and the downstream of the supply conveyance path. The developer having reached the side is sent to the circulation conveyance path.
In such a developing apparatus, the developer in the developer in the apparatus is gradually replaced with a new one by discharging the increased amount of developer supplied from the premix developer through the discharge opening. I can go. Further, since the developer is not discharged in a state where the volume of the developer in the supply conveyance path does not change, it is possible to prevent the developer amount in the developing device from decreasing. Further, when the bulk of the developer reaches the height of the discharge opening at the position of the discharge opening, the developer that has reached the height of the discharge opening is naturally discharged from the discharge opening to the outside of the apparatus. For this reason, a complicated developer discharging mechanism including a sensor and a shutter as in the developing device described in Patent Document 1 is not required, and it is possible to prevent the configuration from becoming complicated and costly.

Japanese Patent No. 2891845 JP 2000-112238 A

However, even if the amount of developer in the developing device does not change, the volume of the developer in the supply conveyance path may change temporarily. For example, when the developing device is stopped for a while, the developer in the developing device is tightened, and when the developer is driven with the developer tightened, the developer conveyed in the supply conveyance path May cause a phenomenon in which the bulk of the developer partially increases. That is, the developer in the supply conveyance path has a part with a high bulk and a part with a low bulk in the conveyance direction.
In the developing device of Patent Document 2, when a bulky portion passes through the portion where the discharge opening is provided, the developer that has reached the height of the discharge opening is discharged, and a predetermined bulk having passed through this portion is discharged. Only the developer having the height reaches the circulation opening. On the other hand, when a portion having a low volume passes through the location where the discharge opening is provided, the developer is lower in volume than the discharge opening, so that the developer is not discharged and the above-mentioned predetermined bulk height is exceeded. Lower developer reaches the circulation opening.
In this developing device, if the volume of the developer partially fluctuates, even if the amount of developer in the apparatus does not increase, all the developer corresponding to the increased volume is discharged. For this reason, at the timing when the bulky developer reaches the circulation opening, an appropriate amount of the developer goes to the circulation conveyance path, and when the bulkiness of the developer reaches the circulation opening. In such a case, the amount of developer toward the circulation conveyance path is insufficient. As a whole, the amount of developer toward the circulation conveyance path becomes insufficient, and the amount of developer in the developing device decreases.
In such a developing device, even when the developer in the developing device is in an appropriate amount or less than the appropriate amount, the bulk of the developer at the position where the discharge opening is provided can When the height reached is reached, the developer is discharged. If the developer continues to be discharged from the developer discharge port even though the developer is in an appropriate amount or less, the amount of developer in the developing device falls below the required amount, and development to the latent image carrier is performed. The supply of the agent may become unstable. If the developer supply to the latent image carrier becomes unstable, an abnormal image such as missing image may occur.
Such a problem is not limited to the developing device using the two-component developer, but the developer is replenished by the developer replenishing means, and the amount of the developer in the developing device is increased by the developer discharging means. This is a problem that may occur even in a developing device using a one-component developer as long as it is a developing device having a configuration for discharging.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device capable of stably supplying a developer to a latent image carrier, and image formation provided with the developing device. An apparatus and a process cartridge are provided.

In order to achieve the above object, the invention according to claim 1 is characterized in that the developer is carried on the surface and rotated, and the toner is supplied to the latent image on the surface of the latent image carrier at a position facing the latent image carrier. A developer carrying body to be developed, a supply carrying path for carrying the developer along the axial direction of the developer carrying body while supplying the developer to the developer carrying body, and development in the supply carrying path A supply conveyance member that applies conveyance force to the agent, a circulation conveyance path that conveys the developer that has reached the downstream end in the conveyance direction of the supply conveyance path, to the upstream end in the conveyance direction of the supply conveyance path, and the circulation conveyance path A circulating and conveying member that imparts a conveying force to the developer inside, and a circulating opening through which the passed developer is transferred to the circulating and conveying path is provided near the downstream end in the conveying direction of the supply and conveying path, A developing device provided with a discharge opening through which the developer that has passed is discharged to the outside of the developing device. A developer retaining means for retaining the developer that has reached the vicinity of the downstream end in the transport direction of the supply transport path and has not entered the circulation opening in the vicinity of the circulation opening, and the discharge opening includes the discharge opening, It is characterized in that it is arranged to pass the developer that has reached the position of the discharge opening, among the staying developer retained by the developer retaining means, above the circulation opening. is there.
According to a second aspect of the present invention, in the developing device of the first aspect, the developer retention means is a wall surface at the downstream end in the transport direction of the supply transport path.
According to a third aspect of the present invention, in the developing device of the first aspect, the developer retention means generates a transport force in a direction opposite to the supply transport member at the most downstream end in the developer transport direction of the supply transport path. It is a reverse conveyance member to be made.
According to a fourth aspect of the present invention, in the developing device of the first, second, or third aspect, the discharge opening and the circulation opening overlap at least a part of the position of the supply conveyance path in the developer conveyance direction. It is characterized by doing.
According to a fifth aspect of the present invention, in the developing device according to the first, second, third, or fourth aspect of the present invention, the developing device of the first, second, third, or fourth is disposed adjacent to the supply conveyance path with a partition wall sandwiched downstream in the conveyance direction of the supply conveyance path A discharge conveyance path for conveying the developer that has passed through the discharge opening from the supply conveyance path to the outside of the developing device is provided, and the discharge opening is provided in the partition wall so as to communicate the supply conveyance path and the discharge conveyance path It is characterized by being.
According to a sixth aspect of the present invention, in the developing device according to the first, second, third, fourth, or fifth aspect, the circulation conveyance path is disposed adjacent to the supply conveyance path under the supply circulation partition wall. The circulation opening is provided in the supply circulation partition wall so as to communicate the supply conveyance path with the circulation conveyance path.
According to a seventh aspect of the present invention, in the developing device of the first, second, third, fourth, fifth or sixth aspect, the supply / conveying member includes a rotation shaft and a spiral wing, and rotates about the rotation shaft. Thus, the supply screw imparts a conveying force to the developer, and the discharge opening has a lowermost portion that is higher than an uppermost portion of the wing portion of the supply screw.
According to an eighth aspect of the present invention, there is provided the developing device according to the first, second, third, fourth, fifth, sixth or seventh aspect, on the surface of the developer bearing member after passing through a portion facing the latent image bearing member. A recovery conveyance path having a recovery conveyance member that collects the developer separated from the developer and conveys the developer along the axial direction of the developer carrier and in the same direction as the supply conveyance member, and the circulation conveyance path Is supplied with the developer transported to the most downstream side in the transport direction of the supply transport path and the developer transported to the most downstream side in the transport direction of the recovery transport path, The developer is transported along the axial direction and in the direction opposite to the supply transport member and is supplied to the upstream end in the transport direction of the supply transport path.
According to a ninth aspect of the present invention, at least a latent image carrier, a charging means for charging the surface of the latent image carrier, and formation of a latent image for forming an electrostatic latent image on the latent image carrier. In the image forming apparatus having a developing means for developing the electrostatic latent image into a toner image, the developing means is defined as claim 1, 2, 3, 4, 5, 6, 7 or 8. The developing device described in 1) is used.
According to a tenth aspect of the present invention, at least the latent image carrier and the development in an image forming apparatus comprising a latent image carrier that carries a latent image and a developing unit that develops the latent image on the latent image carrier. In the process cartridge in which the unit is held by a common holder as a unit and is detachable from the main body of the image forming apparatus, the developing unit is defined as claim 1, 2, 3, 4, 5, 6, 7 Alternatively, the developing device described in any one of 8 is used.

According to the first to tenth aspects of the present invention, it is possible to prevent the amount of developer in the developing device from falling below the required amount. This is due to the following reason.
The amount of staying developer increases or decreases depending on the balance between the amount of developer that reaches the vicinity of the downstream end in the transport direction of the supply transport path and the amount of developer that passes through the circulation opening. In a state where the developing device is driven, an amount of developer required for circulation is always transferred from the supply conveyance path to the circulation conveyance path via the circulation opening. In the state where the amount of developer reaching the downstream end in the conveyance direction of the supply conveyance path is larger than the amount of developer delivered from the supply conveyance path to the circulation conveyance path via the circulation opening, the amount of staying developer Increases, and in the opposite state, the amount of staying developer decreases. In addition, when the staying developer is present, the required amount of developer required for circulation is always transferred to the circulation conveyance path through the circulation opening, so that the amount of developer toward the circulation conveyance path is insufficient. Never do. That is, in the state where the staying developer exists, the necessary amount of developer is supplied from the circulation conveyance path to the supply conveyance path as the developer flows toward the circulation conveyance path. This is a state in which the developer amount maintains the necessary amount.
Further, since the developer discharged out of the developing device is the developer that has reached the position of the discharge opening of the staying developer, when the amount of the stay developer does not reach the position of the discharge opening, The developer is not discharged out of the developing device. At this time, since the staying developer exists in a state where the developer is not discharged out of the developing device, the amount of the developer in the developing device is maintained at a necessary amount.
With this developing device, there is a phenomenon in which the developer conveyed in the supply conveyance path undulates and the bulk of the developer partially increases while the amount of developer in the developing device has not increased. However, it is possible to prevent the developer from being continuously discharged. Specifically, when the amount of staying developer increases even in a small amount, it reaches the position of the discharge opening, and when the part where the bulk of the developer reaches the vicinity of the downstream end in the conveyance direction of the supply conveyance path, it passes through the circulation opening. The developer in excess of the developer amount is discharged from the discharge opening. However, the amount of staying developer decreases when the part where the bulk of the developer is low reaches the vicinity of the downstream end in the transport direction of the supply transport path, so that the staying developer does not reach the position of the discharge opening. Become. Thereafter, even if the part where the bulk of the developer has increased or decreased reaches the vicinity of the downstream end in the transport direction of the supply transport path, the developer is not discharged only by increasing or decreasing the amount of the staying developer. Further, if the amount of staying developer increases even if the amount is small, unless the developer reaches the position of the discharge opening, the part where the developer has increased or decreased reaches the vicinity of the downstream end in the transport direction of the supply transport path. However, the amount of staying developer only increases or decreases, and the developer is not discharged. In this way, it is possible to prevent the developer from being continuously discharged, so that the developer transported in the supply transport path undulates partially while the amount of developer in the developing device has not increased. Even if the phenomenon that the bulk of the developer increases occurs, the required amount of developer in the developing device can be maintained.

  According to the first to tenth aspects of the present invention, the developer amount in the developing device can be maintained at a necessary amount, so that the developer can be stably supplied from the developer carrier to the latent image carrier. There is an excellent effect.

Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of a tandem type color laser copier (hereinafter simply referred to as “copier 500”) in which a plurality of photoconductors are arranged in parallel will be described.
FIG. 1 is a schematic configuration diagram of a copying machine 500 according to the present embodiment. The copier 500 includes a printer unit 100, a paper feeding device 200 on which the printer unit 100 is placed, a scanner 300 fixed on the printer unit 100, and the like. An automatic document feeder 400 fixed on the scanner 300 is also provided.

  The printer unit 100 includes an image forming unit including four sets of process cartridges 18Y, 18M, 18C, and 18K for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K). 20 is provided. Y, M, C, and K attached to the numbers of the respective symbols indicate members for yellow, cyan, magenta, and black (the same applies hereinafter). In addition to the process cartridges 18Y, 18M, 18C, and 18K, an optical writing unit 21, an intermediate transfer unit 17, a secondary transfer device 22, a resist roller pair 49, a belt fixing type fixing device 25, and the like are disposed. .

The optical writing unit 21 includes a light source (not shown), a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates laser light onto a surface of a photoconductor described later based on image data.
The process cartridges 18Y, 18M, 18C, and 18K include a drum-shaped photoreceptor 1, a charger, a developing device 4, a drum cleaning device, a static eliminator, and the like.

Hereinafter, the yellow process cartridge 18 will be described.
The surface of the photoreceptor 1Y is uniformly charged by a charger as charging means. The surface of the photoreceptor 1 </ b> Y that has been subjected to charging processing is irradiated with laser light that has been modulated and deflected by the optical writing unit 21. Then, the potential of the irradiation part (exposure part) is attenuated. By this attenuation, an electrostatic latent image for Y is formed on the surface of the photoreceptor 1Y. The formed electrostatic latent image for Y is developed by the developing device 4Y as developing means to become a Y toner image.
The Y toner image formed on the Y photoconductor 1Y is primarily transferred to an intermediate transfer belt 110 described later. The surface of the photoreceptor 1Y after the primary transfer is cleaned of the transfer residual toner by a drum cleaning device.
In the Y process cartridge 18Y, the photoconductor 1Y cleaned by the drum cleaning device is discharged by the charge eliminator. Then, it is uniformly charged by the charger and returns to the initial state. The series of processes as described above is the same for the other process cartridges 18M, 18C, and 18K.

Next, the intermediate transfer unit will be described.
The intermediate transfer unit 17 includes an intermediate transfer belt 110, a belt cleaning device 90, and the like. Further, it also includes a tension roller 14, a driving roller 15, a secondary transfer backup roller 16, four primary transfer bias rollers 62Y, M, C, and K.
The intermediate transfer belt 110 is tensioned by a plurality of rollers including the tension roller 14. Then, it is endlessly moved clockwise in the drawing by the rotation of the driving roller 15 driven by a belt driving motor (not shown).
The four primary transfer bias rollers 62Y, 62M, 62C, and 62K are disposed so as to be in contact with the inner peripheral surface side of the intermediate transfer belt 110, respectively, and receive primary transfer bias from a power source (not shown). Further, the intermediate transfer belt 110 is pressed toward the photoreceptors 1Y, 1M, 1C, and 1K from the inner peripheral surface side to form primary transfer nips. In each primary transfer nip, a primary transfer electric field is formed between the photoreceptor 1 and the primary transfer bias roller 62 due to the influence of the primary transfer bias.
The above-described Y toner image formed on the Y photoconductor 1Y is primarily transferred onto the intermediate transfer belt 110 due to the influence of the primary transfer electric field and nip pressure. On the Y toner image, the M, C, K toner images formed on the M, C, K photoconductors 1M, C, K are sequentially superposed and primarily transferred. By this primary transfer of superposition, a four-color superposed toner image (hereinafter referred to as a four-color toner image) that is a multiple toner image is formed on the intermediate transfer belt 110.
The four-color toner image superimposed and transferred onto the intermediate transfer belt 110 is secondarily transferred onto a transfer sheet (not shown) as a recording medium at a secondary transfer nip described later. Transfer residual toner remaining on the surface of the intermediate transfer belt 110 after passing through the secondary transfer nip is cleaned by a belt cleaning device 90 that sandwiches the belt with the driving roller 15 on the left side in the drawing.

Next, the secondary transfer device 22 will be described.
Below the intermediate transfer unit 17 in the figure, a secondary transfer device 22 is disposed in which a paper conveying belt 24 is stretched by two stretching rollers 23. The paper transport belt 24 is moved endlessly in the counterclockwise direction in the drawing in accordance with the rotational drive of at least one of the stretching rollers 23. One of the two stretching rollers 23 arranged on the right side in the drawing sandwiches the intermediate transfer belt 110 and the paper transport belt 24 between the secondary transfer backup roller 16 of the intermediate transfer unit 17. It is out. By this sandwiching, a secondary transfer nip is formed in which the intermediate transfer belt 110 of the intermediate transfer unit 17 and the paper transport belt 24 of the secondary transfer device 22 are in contact with each other. A secondary transfer bias having a polarity opposite to that of the toner is applied to the one stretching roller 23 by a power source (not shown). By applying this secondary transfer bias, the four-color toner image on the intermediate transfer belt 110 of the intermediate transfer unit 17 is electrostatically moved from the belt side toward the one stretching roller 23 side in the secondary transfer nip. A next transfer electric field is formed. The transfer paper fed into the secondary transfer nip so as to synchronize with the four-color toner image on the intermediate transfer belt 110 by a registration roller pair 49 to be described later has four colors affected by the secondary transfer electric field and nip pressure. The toner image is secondarily transferred. Instead of the secondary transfer method in which the secondary transfer bias is applied to one of the stretching rollers 23 as described above, a charger for charging the transfer paper in a non-contact manner may be provided.

  In the paper feeding device 200 provided at the lower part of the copying machine 500 main body, a plurality of paper feeding cassettes 44 in which a plurality of transfer sheets can be stacked and stored in a bundle of sheets are arranged so as to overlap each other in the vertical direction. It is installed. Each paper feed cassette 44 presses the paper feed roller 42 against the uppermost transfer paper in the paper bundle. Then, by rotating the paper feed roller 42, the uppermost transfer paper is sent out toward the paper feed path 46.

  The paper feed path 46 that receives the transfer paper delivered from the paper feed cassette 44 includes a plurality of transport roller pairs 47 and a registration roller pair 49 provided near the end in the paper feed path 46. Then, the transfer paper is conveyed toward the registration roller pair 49. The transfer sheet conveyed toward the registration roller pair 49 is sandwiched between the rollers of the registration roller pair 49. On the other hand, in the intermediate transfer unit 17, the four-color toner image formed on the intermediate transfer belt 110 enters the secondary transfer nip as the belt moves endlessly. The registration roller pair 49 sends out the transfer paper sandwiched between the rollers at a timing at which the transfer paper can be brought into close contact with the four-color toner image at the secondary transfer nip. Thereby, in the secondary transfer nip, the four-color toner image on the intermediate transfer belt 110 is in close contact with the transfer paper. Then, it is secondarily transferred onto the transfer paper and becomes a full color image on the white transfer paper. The transfer paper on which the full-color image is formed in this manner exits the secondary transfer nip as the paper transport belt 24 moves endlessly, and then is sent from the paper transport belt 24 to the fixing device 25.

  The fixing device 25 includes a belt unit that moves the fixing belt 26 endlessly while being stretched by two rollers, and a pressure roller 27 that is pressed toward one roller of the belt unit. The fixing belt 26 and the pressure roller 27 are in contact with each other to form a fixing nip, and the transfer paper received from the paper transport belt 24 is sandwiched therebetween. Of the two rollers in the belt unit, the roller pressed from the pressure roller 27 has a heat source (not shown) inside, and heats the fixing belt 26 by the heat generated by the heat source. The heated fixing belt 26 heats the transfer paper sandwiched in the fixing nip. The full color image is fixed on the transfer paper by the influence of the heating and the nip pressure.

  The transfer paper subjected to the fixing process in the fixing device 25 is stacked on the stack portion 57 provided outside the left side plate in the drawing of the printer housing, or forms a toner image on the other surface. To the secondary transfer nip described above.

  When a document (not shown) is copied, for example, a bundle of sheet documents is set on the document table 30 of the automatic document feeder 400. However, when the original is a single-sided original that is closed in a main form, it is set on the contact glass 32. Prior to this setting, the automatic document feeder 400 is opened with respect to the copying machine main body, and the contact glass 32 of the scanner 300 is exposed. Thereafter, the single-bound original is pressed by the closed automatic document feeder 400.

  When a copy start switch (not shown) is pressed after the document is set in this way, the document reading operation by the scanner 300 starts. However, when a sheet document is set on the automatic document feeder 400, the automatic document feeder 400 automatically moves the sheet document to the contact glass 32 prior to the document reading operation. In the document reading operation, first, the first traveling body 33 and the second traveling body 34 start traveling together, and light is emitted from a light source provided in the first traveling body 33. Then, the reflected light from the document surface is reflected by a mirror provided in the second traveling body 34, passes through the imaging lens 35, and then enters the reading sensor 36. The reading sensor 36 constructs image information based on the incident light.

  In parallel with such a document reading operation, each device in each of the process cartridges 18Y, 18M, 18C, 18K, the intermediate transfer unit 17, the secondary transfer device 22, and the fixing device 25 starts driving. Based on the image information constructed by the reading sensor 36, the optical writing unit 21 is driven and controlled, and Y, M, C, and K toner images are formed on the respective photoreceptors 1Y, 1M, 1C, and 1K. Is done. These toner images become four-color toner images superimposed and transferred on the intermediate transfer belt 110.

  Further, almost simultaneously with the start of the document reading operation, the paper feeding operation is started in the paper feeding device 200. In this paper feeding operation, one of the paper feeding rollers 42 is selectively rotated, and the transfer paper is sent out from one of the paper feeding cassettes 44 accommodated in the paper bank 43 in multiple stages. The fed transfer sheets are separated one by one by the separation roller 45 and enter the reverse feeding path 46, and then conveyed toward the secondary transfer nip by the conveyance roller pair 47. In some cases, paper feeding from the manual feed tray 51 is performed instead of such paper feeding from the paper feeding cassette 44. In this case, after the manual feed roller 50 is selectively rotated to feed the transfer paper on the manual feed tray 51, the separation roller 52 separates the transfer paper one by one and feeds it to the manual feed path 53 of the printer unit 100. Make paper.

  When the copier 500 forms an image of another color composed of toner of two or more colors, the intermediate transfer belt 110 is stretched so that the upper stretched surface thereof is substantially horizontal, and all the upper stretched surface is placed on the upper stretched surface. Photoconductors 1Y, 1M, 1C, and 1K are brought into contact with each other. On the other hand, when forming a monochrome image consisting of only K toner, the intermediate transfer belt 110 is tilted to the lower left in the drawing by a mechanism (not shown) and the upper stretched surface is set to Y, M, C. The photoconductors 1Y, 1M, and 1C are separated. Of the four photoconductors 1Y, 1M, 1C, and 1K, only the K photoconductor 1K is rotated counterclockwise in the drawing to form only the K toner image. At this time, for Y, M, and C, not only the photosensitive member 1 but also the developing device 4 is stopped, and each member of the photosensitive member 1 and the developing device 4 and the developer in the developing device 4 are unnecessarily consumed. To prevent.

  The copier 500 includes a control unit (not shown) composed of a CPU and the like that controls each device in the copier 500, and an operation display unit (not shown) composed of a liquid crystal display, various key buttons, and the like. . The operator sends a command to the control unit by a key input operation on the operation display unit, so that one of the three modes is selected from the three-sided print mode, which is a mode for forming an image only on one side of the transfer paper. You can choose one. The three single-sided printing modes include a direct discharge mode, a reverse discharge mode, and a reverse decal discharge mode.

FIG. 2 is an enlarged configuration diagram illustrating the developing device 4 and the photosensitive member 1 included in one of the four process cartridges 18Y, 18M, 18C, and 18K. Since the four process cartridges 18Y, 18M, 18C, and 18K have substantially the same configuration except that the colors of the toners to be handled are different, they are referred to as “Y”, “M”, “C”, and “K” in FIG. Subscripts are omitted.
As shown in FIG. 2, the surface of the photosensitive member 1 is charged by a charging device (not shown) while rotating in the direction of arrow G in the drawing. The charged surface of the photoreceptor 1 is supplied with toner from the developing device 4 to a latent image on which an electrostatic latent image is formed by laser light emitted from an exposure device (not shown), thereby forming a toner image.

The developing device 4 has a developing roller 5 as a developer carrying member for supplying toner to the latent image on the surface of the photoreceptor 1 while moving the surface in the direction of arrow I in the drawing. The developing roller 5 includes a rotatable developing sleeve, and a magnetic body (not shown) including a plurality of magnetic poles is disposed therein. The magnetic material is necessary for holding the developer on the surface of the developing roller 5.
Further, a supply screw 8 is provided as a supply conveyance member that conveys the developer in the depth direction of FIG. 2 along the axial direction of the development roller 5 while supplying the development roller 5 with the developer.
A doctor blade 12 as a developer regulating means for regulating the developer supplied to the developing roller 5 to a thickness suitable for development is provided on the downstream side in the surface movement direction from the portion facing the supply screw 8 of the developing roller 5. ing.
A collection conveyance path 7 that collects the developed developer that has passed through the development area and separated from the surface of the development roller 5 on the downstream side in the surface movement direction from the development area that is the portion of the development roller 5 facing the photoreceptor 1. Faces the developing roller 5. The collection conveyance path 7 is a collection conveyance member that conveys the collected developer collected in the same direction as the supply screw 8 along the axial direction of the developing roller 5, and a spiral collection screw 6 arranged in parallel to the axial direction. I have. A supply conveyance path 9 provided with a supply screw 8 is provided in the lateral direction of the developing roller 5, and a collection conveyance path 7 provided with a collection screw 6 is provided in parallel below the development roller 5.
The developer can be separated from the developing roller 5 by setting the magnetic body in the developing sleeve described above to a state where there is no magnetic pole only at a position where the developer is desired to be separated. Yes. Further, a magnetic body having a magnetic pole arrangement in which a repulsive magnetic field is formed at a location to be separated may be used.

  The developing device 4 is provided with a stirring conveyance path 10 in parallel with the collection conveyance path 7 below the supply conveyance path 9. The agitating / conveying path 10 is arranged in parallel to the axial direction as an agitating / conveying member that conveys the developer along the axial direction of the developing roller 5 to the front side in the drawing, which is opposite to the supply screw 8 while stirring the developer. A helical stirring screw 11 is provided.

The supply conveyance path 9 and the stirring conveyance path 10 are partitioned by a first partition wall 133 as a partition wall. In the first partition wall 133, the supply conveyance path 9 and the agitation conveyance path 10 are partitioned at both ends on the front side and the back side in the drawing, and the supply conveyance path 9 and the agitation conveyance path 10 communicate with each other. is doing.
The supply conveyance path 9 and the recovery conveyance path 7 are both partitioned by the first partition wall 133, but an opening is provided at a location where the supply conveyance path 9 and the recovery conveyance path 7 of the first partition wall 133 are partitioned. Absent.
Further, the two conveyance paths of the stirring conveyance path 10 and the collection conveyance path 7 are partitioned by a second partition wall 134 as a partition member. The second partition wall 134 has an opening on the front side in the figure, and the agitation transport path 10 and the collection transport path 7 communicate with each other.
The developer screw, supply screw 8, recovery screw 6 and stirring screw 11 are made of resin or metal screws, and each screw has a diameter of φ22 [mm] and a screw pitch of 50 [mm]. The winding, the recovery screw 6 and the stirring screw 11 are one winding of 25 [mm], and the number of rotations is all set to about 600 [rpm].

The developer thinned by the doctor blade 12 made of stainless steel on the developing roller 5 is transported to a developing area which is a portion facing the photosensitive member 1 for development. The surface of the developing roller 5 is V-grooved or sandblasted and is made of an Al or SUS element tube of φ25 [mm], and the gap between the doctor blade 12 and the photoreceptor 1 is about 0.3 [mm].
The developer after development is collected in the collection conveyance path 7, conveyed to the front side of the cross section in FIG. 2, and to the agitation conveyance path 10 through the opening of the first partition wall 133 provided in the non-image area portion. Developer is transferred. The toner is supplied to the stirring and conveying path 10 from a toner replenishing port 95 (described later) provided on the upper side of the stirring and conveying path 10 near the opening of the first partition wall 133 on the upstream side in the developer conveying direction in the stirring and conveying path 10. Supplied.

Next, the circulation of the developer in the three developer conveyance paths will be described.
FIG. 3 is a perspective sectional view of the developing device 4 for explaining the flow of the developer in the developer transport path. Each arrow in the figure indicates the moving direction of the developer.
4 is a schematic diagram of the flow of the developer in the developing device 4. Like FIG. 3, each arrow in the drawing indicates the moving direction of the developer.

In the supply conveyance path 9 that has been supplied with the developer from the agitation conveyance path 10, the developer is conveyed downstream in the conveyance direction of the supply screw 8 while supplying the developer to the developing roller 5. Then, the excess developer that is supplied to the developing roller 5 and is not used for development and is transported to the downstream end in the transport direction of the supply transport path 9 is supplied to the stirring transport path 10 from the surplus opening 92 of the first partition wall 133 ( Arrow E) in FIG.
On the other hand, the developer supplied to the developing roller 5 is used for development in the developing region, and then separated / separated from the developing roller 5 and delivered to the collection conveyance path 7. The collected developer that has been transferred from the developing roller 5 to the collection conveyance path 7 and conveyed to the downstream end in the conveyance direction of the collection conveyance path 7 by the collection screw 6 enters the stirring conveyance path 10 from the collection opening 93 of the second partition wall 134. Supplied (arrow F in FIG. 4).
The agitating and conveying path 10 agitates the supplied surplus developer and the recovered developer, conveys the agitating screw 11 to the downstream side in the conveying direction, and conveys it to the upstream side in the conveying direction of the supplying screw 8. It is supplied to the supply conveyance path 9 from the supply opening 91 of 133 (arrow D in FIG. 4).
In the agitating and conveying path 10, the agitating screw 11 agitates and conveys the collected developer, the surplus developer, and the toner replenished as necessary in the transfer unit in the direction opposite to the developer in the collecting and conveying path 7 and the supply conveying path 9. . Then, the agitated developer is transferred to the upstream side in the conveyance direction of the supply conveyance path 9 communicating with the downstream side in the conveyance direction. A toner concentration sensor (not shown) is provided below the agitation transport path 10, and a toner supply control device (not shown) is operated by the sensor output to supply toner from a toner storage portion (not shown).

  In the developing device 4 shown in FIG. 4, a supply conveyance path 9 and a collection conveyance path 7 are provided, and developer supply and collection are performed in different developer conveyance paths, so that the developed developer is supplied to the supply conveyance path 9. There is no contamination. Accordingly, it is possible to prevent the toner density of the developer supplied to the developing roller 5 from decreasing toward the downstream side of the supply conveyance path 9 in the conveyance direction. Further, since the recovery conveyance path 7 and the agitation conveyance path 10 are provided and the developer recovery and agitation are performed in different developer conveyance paths, the developed developer does not fall during the agitation. Therefore, since the sufficiently agitated developer is supplied to the supply conveyance path 9, it is possible to prevent the developer supplied to the supply conveyance path 9 from being insufficiently agitated. In this way, the toner density of the developer in the supply conveyance path 9 can be prevented from decreasing, and the developer in the supply conveyance path 9 can be prevented from being insufficiently stirred. Can be constant.

As shown in FIG. 4, the developer moves from the lower part to the upper part of the developing device 4 only by the arrow D. The movement of the developer indicated by an arrow D is to push the developer by rotating the stirring screw 11 so that the developer is raised and supplied to the supply conveyance path 9.
Such movement of the developer gives stress to the developer and contributes to a decrease in the life of the developer.
When the developer is lifted from the bottom to the top, stress is applied to the developer, and the carrier film in the developer is scraped off and the toner is spent on the spot. Accordingly, the stability of the image quality is maintained. It will disappear.
Therefore, the life of the developer can be extended by reducing the stress of the developer in the movement of the developer indicated by the arrow D. By prolonging the life of the developer, it is possible to provide a developing device that prevents deterioration of the developer and is always stable in image quality without image density unevenness.

In the developing device 4 of the present embodiment, as shown in FIG. 2, the supply conveyance path 9 is disposed obliquely above the stirring conveyance path 10. By disposing it obliquely above, it is possible to reduce the developer stress in the movement of the developer indicated by the arrow D, compared to the case where the supply conveyance path 9 is provided vertically above the stirring conveyance path 10 and the developer is lifted. .
Further, in the developing device 4, the supply conveyance path 9 and the agitation conveyance path 10 are arranged obliquely so that the upper wall surface of the agitation conveyance path 10 is higher than the lower wall surface of the supply conveyance path 9 as shown in FIG. 2. It arranges so that it may become a position.
Lifting the supply conveyance path 9 vertically upward with respect to the stirring conveyance path 10 causes the developer to be stressed because the developer is lifted by the pressure of the stirring screw 11 against gravity. On the other hand, the developer present at the highest point of the agitating and conveying path 10 is placed at the bottom of the supplying and conveying path 9 by arranging the upper wall surface of the agitating and conveying path 10 to be higher than the lower wall surface of the supplying and conveying path 9. Since the point can flow without being against gravity, the stress applied to the developer can be reduced.
Note that a fin member may be provided on the shaft of the stirring screw 11 in a portion where the stirring transport path 10 and the supply transport path 9 communicate with each other on the downstream side of the developer transport path of the stirring transport path 10. This fin member is a plate-like member composed of a side parallel to the axial direction of the stirring screw 11 and a side perpendicular to the axial direction of the stirring screw. By scooping up the developer with this fin member, it is possible to more efficiently deliver the developer from the stirring conveyance path 10 to the supply conveyance path 9.

Further, in the developing device 4, the distance between the center A between the developing roller 5 and the supply conveyance path 9 is shorter than the distance B between the center between the development roller 5 and the agitation conveyance path 10. A conveyance path 10 is arranged. As a result, the developer can be supplied without difficulty from the supply conveyance path 9 to the developing roller 5, and the apparatus can be downsized.
Further, the stirring screw 11 is rotated counterclockwise as viewed from the front side in FIG. 2 (the direction of arrow C in the figure), and the developer is supplied by lifting the developer along the shape of the stirring screw 11. It is transferred to the conveyance path 9. As a result, the developer can be lifted efficiently, and the stress on the developer can be further reduced.

FIG. 5 is a cross-sectional explanatory view of the cross section at the rotation center of the supply screw 8 of the developing device 4 as viewed from the direction of arrow J in FIG. In the figure, H denotes a developing region in which the developing roller 5 that is a developer carrying member supplies toner to the photosensitive member 1 that is a latent image carrying member. The width in the axial direction of the rotation axis of the developing roller 5 in the developing area H is the developing area width α.
As shown in FIG. 5, the developing device 4 includes a supply opening 91 that is a place where the developer is lifted from the agitation conveyance path 10 to the supply conveyance path 9, and surplus that drops the developer from the supply conveyance path 9 to the agitation conveyance path 10. Both of the openings 92 are provided within the development region width α.

FIG. 6 is a schematic diagram of the developer flow in the developing device 4 having a configuration different from that in FIG. 4.
The developing device 4 shown in FIG. 6 is provided with a supply opening 91 and a surplus opening 92 outside the developing region width α. Since the supply opening 91 is provided outside the developing region width α, the upstream side in the transport direction of the supply transport path 9 is longer than the developing roller 5 by the upstream region β of the supply transport path. Further, since the surplus opening 92 is provided outside the developing region width α, the downstream side in the transport direction of the supply transport path 9 is longer than the developing roller 5 by the region γ on the downstream side of the supply transport path.

On the other hand, in the developing device 4 having the configuration shown in FIG. 4, since the supply opening 91 is provided within the developing region width α, the upstream side in the transport direction of the supply transport path 9 is on the supply transport path than the developing device 4 in FIG. The flow side region β can be shortened. Further, since the surplus opening 92 is provided in the developing area width α, the downstream side in the transport direction of the supply transport path 9 can be made shorter by the area γ on the downstream side of the supply transport path than the developing device 4 in FIG.
4 is provided with the supply opening 91 and the surplus opening 92 within the developing region width α, the upper portion of the developing device 4 is higher than that of the developing device 4 shown in FIG. Space saving can be achieved.

Next, the position at which toner is supplied to the developer conveyance path including the supply conveyance path 9, the agitation conveyance path 10 and the collection conveyance path 7 of the developing device 4 will be described. FIG. 7 is an external perspective view of the developing device 4.
As shown in FIG. 7, a toner replenishing port 95 for replenishing toner is provided above the upstream end of the agitating and conveying path 10 including the agitating screw 11 in the conveying direction. Since the toner replenishing port 95 is provided outside the end portion in the width direction of the developing roller 5, it is outside the developing region width α.
The portion where the toner replenishing port 95 is provided is on an extension line in the conveyance direction of the supply conveyance path 9 and corresponds to a vacant space in the region γ on the downstream side of the supply conveyance path in FIG. Providing the toner replenishment port 95 in an empty space by providing the surplus opening 92 within the developing region width α makes it possible to reduce the size of the developing device 4.
Further, the toner replenishing port 95 is not limited to the position above the upstream end portion in the transport direction of the stirring transport path 10 and may be provided above the downstream end portion of the collection transport path 7.
Further, a toner replenishing port 95 may be provided directly above the collection opening 93 where the developer is transferred from the collection conveyance path 7 to the stirring conveyance path 10. Since the space directly above the collection opening 93 is also an empty space provided by providing the surplus opening 92 within the developing region width α, the toner replenishing port 95 is provided at this position to reduce the size of the developing device 4. Can be planned. Furthermore, since the developer is likely to be mixed in the collection opening 93 serving as a delivery unit, the developer can be more efficiently stirred by replenishing at this position.

As in the developing device 4 described with reference to FIG. 4, a supply opening 91 that transfers the developer from the downstream end in the transport direction of the stirring transport path 10 to the upstream end in the transport direction of the supply transport path 9, and the supply transport path 9 Since the surplus opening 92 for transferring the developer from the downstream end to the upstream end in the transport direction of the stirring transport path 10 is provided in the development region width α, the upper portion of the development device 4 is higher than the conventional development device 4. Space can be saved, and the space of the entire developing device 4 can be saved.
Also, by providing the toner replenishing port 95 in the empty space by providing the surplus opening 92 within the developing region width α, the developing device 4 can be reduced in size.
Further, the developer can be more efficiently stirred by replenishing the toner from above the recovery opening 93 which is a developer delivery section from the recovery transport path 7 to the stirring transport path 10.
Further, by providing the developing device 4 as the developing means of the printer unit 100 of the copying machine as the image forming apparatus, it is possible to save the space of the entire apparatus.

Next, the characteristic part of the developing device 4 of the present embodiment will be described.
A toner replenishment control device (not shown) that is a developer replenishing unit replenishes toner in a toner storage unit (not shown) to the developing device 4 from the toner replenishing port 95. In the developing device 4 of this embodiment, a developer including toner and a carrier is supplied from a toner supply port 95 of the developing device 4. Hereinafter, the developer in which the toner supplied to the developing device 4 and the carrier are mixed is referred to as premix toner.
In the developing device 4 of the present embodiment, the circulation conveyance path that conveys the excess developer that has reached the downstream end in the conveyance direction of the supply conveyance path 9 to the upstream end in the conveyance direction of the supply conveyance path 9 is the agitation conveyance path 10. In addition, the circulating and conveying member that applies a conveying force to the developer in the agitating and conveying path 10 that is a circulating and conveying path is the agitating screw 11. Further, the circulation opening provided near the downstream end in the conveyance direction of the supply conveyance path 9 and through which the passed developer is transferred to the agitation conveyance path 10 which is a circulation conveyance path is a surplus opening 92. Further, the developing device 4 includes a developer discharge port 94 as a discharge opening through which the developer that has passed is discharged to the outside of the developing device 4. The developer that has passed through the developer discharge port 94 is transferred to the discharge conveyance path 2, and is conveyed to the outside of the developing device 4 by rotating the discharge screw 2 a that is a discharge conveyance member, and is discharged from the developing device 4. Made. The discharge conveyance path 2 is disposed on the downstream side in the conveyance direction of the supply conveyance path 9 so as to be adjacent to the supply conveyance path 9 with the discharge partition wall 135 interposed therebetween, and the developer discharge port 94 is connected to the supply conveyance path 9 and the discharge conveyance path 2. Are openings provided in the discharge partition wall 135 so as to communicate with each other.

  Further, the developing device 4 reaches the vicinity of the downstream end in the transport direction of the supply transport path 9, and retains the developer that has not entered the surplus opening 92 that is the circulation opening near the surplus opening 92. 80. Further, the developer discharge port 94 which is a discharge opening is located above the surplus opening 92 and the development that has reached the position of the developer discharge port 94 among the stayed developer retained by the developer retaining means 80. It arrange | positions so that an agent may pass. In other words, the developer that has reached the vicinity of the downstream end in the transport direction of the supply transport path 9 cannot enter the surplus opening 92, and the surplus developer overflowing from the surplus opening 92 is blocked by the developer retaining means 80. Stopped and becomes a stagnant developer. Then, when the bulk of the staying developer increases, the developer that has reached the developer discharge port 94 provided above the surplus opening 92 passes through the developer discharge port 94 to the outside of the developing device 4. To be discharged.

  The amount of staying developer includes the amount of developer that reaches the vicinity of the downstream end in the conveyance direction of the supply conveyance path 9 (arrow L in FIG. 4) and the amount of developer that passes through the excess opening 92 (arrow E in FIG. 4). Increase or decrease depending on the balance. In a state where the developing device 4 is driven, an amount of developer required for circulation is always transferred from the supply conveyance path 9 to the agitation conveyance path 10 through the surplus opening 92. Then, the amount of developer reaching the vicinity of the downstream end in the conveyance direction of the supply conveyance path from the amount of developer (arrow E in FIG. 4) delivered from the supply conveyance path 9 to the stirring conveyance path 10 through the excess opening 92. In the state where there is more (arrow L in FIG. 4), the amount of staying developer increases, and in the opposite state, the amount of staying developer decreases. Further, in the state where the staying developer is present, the necessary amount of developer required for circulation is always transferred to the agitation transport path 10 through the surplus opening 92, and therefore the developer toward the agitation transport path 10 There is no shortage of quantity. That is, in the state where the staying developer exists, a necessary amount of developer is supplied from the agitating / conveying path 10 to the supply / conveying path 9 when the necessary amount of developer is directed to the agitating / conveying path 10. This is a state where the developer amount in the apparatus 4 maintains the necessary amount.

Further, since the developer discharged out of the developing device 4 is the developer that has reached the position of the developer discharge port 94 in the staying developer, the staying developer does not reach the position of the developer discharge port 94. When the amount is less than the amount, the developer is not discharged out of the developing device 4. At this time, since the staying developer exists in a state where the developer is not discharged out of the developing device 4, the amount of developer in the developing device 4 is maintained at a necessary amount.
In the developing device 4, the developer conveyed in the supply conveyance path 9 undulates in a state where the amount of developer in the developing device 4 is not increased, and the bulk of the developer partially increases. Even if the phenomenon occurs, it is possible to prevent the developer from being continuously discharged. Specifically, when the amount of the staying developer increases even if the amount is small, when the portion where the volume of the developer reaches a position near the downstream end in the transport direction of the supply transport path 9 in the state where the developer reaches the position of the developer discharge port 94, the surplus opening portion The developer exceeding the amount of developer passing through 92 is discharged from the developer discharge port 94. However, the amount of staying developer decreases when the portion where the developer volume is low reaches the vicinity of the downstream end in the transport direction of the supply transport path 9, and the staying developer does not reach the position of the developer discharge port 94. The amount will be about. Thereafter, even if the part where the bulk of the developer becomes high or the part where the volume becomes low reaches the vicinity of the downstream end in the transport direction of the supply transport path 9, the developer is not discharged only by increasing or decreasing the amount of the staying developer. . In addition, if the amount of staying developer increases even if the amount is small, unless the state reaches the position of the discharge opening, the part where the developer volume is increased or decreased reaches the vicinity of the downstream end in the conveyance direction of the supply conveyance path 9. However, the amount of staying developer only increases or decreases, and the developer is not discharged. In this way, it is possible to prevent the developer from being continuously discharged, so that the developer transported in the supply transport path 9 undulates in a state where the amount of developer in the developing device 4 has not increased. Even if the phenomenon that the bulk of the developer becomes high occurs, the amount of developer in the developing device 4 can maintain the required amount. As described above, since the necessary amount of developer in the developing device 4 can be ensured, the developer can be stably supplied to the photoreceptor 1. As a result, the electrostatic latent image on the photoreceptor 1 can be favorably converted into a toner image, an abnormal image such as image omission can be prevented, and good image formation can be performed.

  The vicinity of the downstream end of the supply conveyance path 9 in the conveyance direction is, for example, the same position in the conveyance direction of the developer conveyance section 9 and the supply conveyance path 9 where the developer is transferred from the supply conveyance path 9 to the stirring conveyance path 10. It is a place. In other words, it is where the conveying force by the supply screw 8 ends, and is a portion where the developer is blocked by the developer retention means 80. By providing the developer discharge port 94 here, after being transported by the supply screw 8, it is received by the developer retention means 80 and finally reaches the height of the developer discharge port 94 among the retained developer. Can be discharged.

  FIG. 8 is a perspective explanatory view of the vicinity of the front end portion in a state where the stirring screw 11, the recovery screw 6, and the doctor blade 12 are removed from the developing device 4. FIG. 9 is an explanatory perspective view of the developing device 4 in the vicinity of the near side in a state where the supply screw 8 is further removed from the state of FIG. Further, FIG. 10 is a perspective explanatory view of the developing device 4 with the developing roller 5 further removed from the state of FIG. FIG. 11 is a perspective explanatory view of the developing device 4 when the developing device 4 in the same state as FIG. 10 is viewed from substantially the same direction as FIG.

The rotation direction of the supply screw 8 is clockwise (in the direction of the arrow M) as shown in FIG. 2, and rotates in a direction in which the developer is lifted and supplied to the developing roller 5 from below. Here, when the developer is supplied to the developing roller 5 so that the rotation direction of the supply screw 8 is counterclockwise and the developer is sprinkled from above, the developer is supplied to the developing roller 5 while being scattered. On the other hand, when the rotation direction of the supply screw 8 is clockwise as shown in FIG. 2, the developer is supplied to the developing roller 5 so as to lift the developer from below the supply conveyance path 9 where the developer is accumulated. It becomes like this. Since the developer supply performance is more stable when the developer is supplied from the lower side than when the developer is supplied while being scattered, the rotation direction of the supply screw 8 is set clockwise in FIG. is doing.
In particular, in the case where the developer supplied to the developing roller 5 is not returned to the supply conveyance path 9 but is collected to the collection conveyance path 7 as in the developing device 4 of this embodiment, the amount of developer goes downstream of the supply conveyance path 9. It decreases according to. For this reason, it is more excellent in terms of developer supply that the developer is drawn up from below and supplied to the developing roller 5.

  Here, in the supply conveyance path 9, the developer in the supply conveyance path 9 jumps by the momentum of movement in the supply conveyance path 9 by being conveyed and the rotating force of the supply screw 8 that is a developer conveyance screw. . When the developer discharge port 94 is simply provided at a predetermined height of the supply conveyance path 9 that is the developer conveyance path, the jumped developer flies and passes through the developer discharge port 94. May be discharged. When the developer jumps and is discharged, even if the developer transported through the position where the developer discharge port 94 in the supply transport path 9 is provided is in an appropriate amount or less than the appropriate amount, The jumped developer may be discharged. In such a state where the developer jumped off is discharged, the developer may be discharged from the developer discharge port even though the amount of the developer in the developing device 4 is not more than an appropriate amount. The amount of developer in the developing device 4 is less than the required amount, and the supply of developer to the photoreceptor 1 may become unstable. When the developer supply to the photosensitive member 1 becomes unstable, an abnormal image such as image omission occurs.

  In order to prevent such a problem, the developing device 4 has a path along which the developer flying as the supply screw 8 that is a developer conveying member rotates to convey the developer is directed toward the developer discharge port 94. A block member 3 is provided as a flying developer discharge preventing member for closing. The developer in the developing device 4 is provided with the block member 3, and the developer that flies by the conveying operation of the supply screw 8 blocks the path toward the developer discharge port 94, thereby preventing the jumped developer from being discharged. It is possible to prevent the developer from being discharged even though the amount is not increased. Therefore, the necessary amount of developer in the developing device 4 can be secured, and the developer can be stably supplied to the photoreceptor 1. As a result, the electrostatic latent image on the photoreceptor 1 can be favorably converted into a toner image, an abnormal image such as image omission can be prevented, and good image formation can be performed.

  The block member 3 is an R-shaped resin member whose bottom surface follows the shape of the supply screw 8 above the supply conveyance path 9. Due to the R shape along the shape of the supply screw 8, the bottom surface of the block member 3 can be brought close to the supply screw 8 as a whole so as to cover the entire supply screw 8. For this reason, it is possible to cover the upper part of the supply screw 8 that causes the developer to jump up, and to prevent the developer jumped up by the supply screw 8 from flying and reaching the developer discharge port 94.

Further, as shown in FIG. 11, since the block member 3 protrudes around the developer discharge port 94 of the supply conveyance path 9, the supply screw 8 on the upstream side in the conveyance direction of the supply screw 8 with respect to the block member 3. The supply conveyance path where the block member 3 is provided is narrower than the conveyance path 9. Therefore, the developer amount with respect to the capacity of the supply conveyance path 9 is larger at the position where the block member 3 is provided than at the upstream side in the conveyance direction with respect to the position where the block member 3 is provided. For this reason, the developer rises between the side wall of the block member 3 and the discharge partition wall 135 in the vicinity of the downstream end of the supply conveyance path 9 in the conveyance direction where no conveyance force is applied to the developer. As a result, the supply screw 8 is buried in the developer, and the splashing of the developer due to the rotation of the supply screw 8 is suppressed, and the upper part of the wing portion of the supply screw 8 protrudes from the developer surface. The change in the surface level due to the splashing of the supply screw 8 that occurs sometimes is mitigated in the vicinity of the developer discharge port 94. For this reason, it is possible to discharge with high sensitivity to the increase or decrease of the developer in the developing device 4.
By providing such a block member 3, when the developer amount in the developing device 4 increases due to the supply of the developer and the bulk of the developer in the supply conveyance path 9 increases, the development corresponding to the increased amount is achieved. The developer overflows from the developer discharge port 94.

12 and 13 show the flow of developer in the developing device 4 in a state where the amount of developer in the developing device 4 is small, that is, in a state where the staying developer does not reach the position of the developer discharge port 94. It is explanatory drawing shown. 12 is a cross-sectional explanatory view of the developing device 4 in the vicinity of the downstream end in the transport direction of the supply transport path 9 as viewed from the same direction as FIG. 2, and FIG. 13 is a side cross-sectional explanatory view as viewed from the same direction as FIG. It is. In the figure, P indicates a developer.
As shown in FIGS. 12 and 13, when the amount of developer in the developing device 4 is small, the developer is smoothly supplied from the supply conveyance path 9 to the stirring conveyance path 10 that is a circulation conveyance path. As a result, the developer P overflows in the surplus opening 92 that is an opening provided in the first partition wall 133 that is a supply circulation partition wall that is a boundary between the supply transport path 9 and the stirring transport path 10. The bulk of the material does not increase. For this reason, the developer is hardly led to the developer discharge port 94 for discharging the developer P to the outside of the developing device 4, and it is possible to prevent the developer from being discharged in a state where the amount of the developer is small.

14 and 15 show development in a state where the amount of developer in the developing device 4 is large, that is, in a state where the bulk of the staying developer near the downstream end in the transport direction of the supply transport path 9 has reached the position of the developer discharge port 94. 5 is an explanatory diagram showing a flow of developer P in the apparatus 4. FIG. 14 is a cross-sectional explanatory view of the developing device 4 in the vicinity of the downstream end in the transport direction of the supply transport path 9 as viewed from the same direction as FIG. 2, and FIG. 15 is a side cross-sectional explanatory view as viewed from the same direction as FIG. It is.
As shown in FIGS. 14 and 15, when the amount of developer in the developing device 4 is large, the developer P is in the vicinity of the surplus opening 92 where the developer P moves from the supply conveyance path 9 to the stirring conveyance path 10. Stay. As a result, the developer P at the most downstream portion in the conveyance direction of the supply conveyance path 9 has no place to go, and the staying developer increases in volume upward. When the bulk increases to the height of the developer discharge port 94, the developer P passes through the developer discharge port 94 and is discharged to the discharge conveyance path 2, and the discharge screw 2 a in the discharge conveyance path 2 causes the developing device 4. It will be discharged to the outside.

  The developing device 4 discharges the developer that has reached the height of the developer discharge port 94 when the volume of the staying developer near the downstream end in the transport direction of the supply transport path 9 exceeds the height of the developer discharge port 94. Therefore, it is possible to prevent the developer transporting the supply transport path 9 from being insufficient due to the discharge of the developer from the developer discharge port 94. Accordingly, a necessary amount of developer can be supplied from the supply conveyance path 9 to the developing roller 5, and the developer can be stably supplied from the developing roller 5 to the photosensitive member 1. For this reason, the electrostatic latent image on the photosensitive member 1 can be favorably converted into a toner image, an abnormal image such as image omission can be prevented, and good image formation can be performed.

In FIG. 13, the state in which the developer in the developing device 4 is small has been described. However, when the developer in the developing device 4 is not discharged and the developer amount is stable, the vicinity of the downstream end in the transport direction of the supply transport path 9 In this state, the developer is retained. Details of this state will be described below.
The developing device 4 is configured to discharge a part of the staying developer staying in the vicinity of the downstream end in the transport direction of the supply transport path 9 when the bulk exceeds a predetermined height (the height of the developer discharge port 94). It is. That is, the developer discharge port 94 and the discharge conveyance path 2 discharge the developer in which the bulk of the staying developer near the downstream end in the conveyance direction of the supply conveyance path 9 reaches the height of the developer discharge port 94. . Therefore, the developing amount in the developing device 4 becomes stable in a state where the staying developer exists in a volume that does not reach the height of the developer discharge port 94 near the downstream end in the transport direction of the supply transport path 9. . This is due to the balance between the amount of developer transported through the supply transport path 9 and reaching the downstream end in the transport direction, and the amount of developer delivered to the stirring transport path 10 through the supply transport path 9 surplus opening 92. In this state, the developer stays in a volume that does not reach the height of the developer discharge port 94 in the vicinity of the downstream end of the supply conveyance path 9 in the conveyance direction.

From this state, when the premix toner is supplied by the toner replenishment control device and the amount of developer in the developing device 4 increases, the amount of developer delivered from the supply conveyance path 9 to the agitation conveyance path 10 (arrow E in FIG. 4). ), The amount of developer (arrow L in FIG. 4) that is transported through the supply transport path 9 and reaches the downstream end in the transport direction is greater. At this time, the amount of the developer staying in the vicinity of the downstream end in the transport direction of the supply transport path 9 increases, and the bulk thereof increases. As a result, when the volume of the staying developer reaches the developer discharge port 94, the developer discharge port is used as a part of the developer that stays so that the bulk becomes lower than the position of the developer discharge port 94. The developer reaching 94 is discharged.
Note that the staying developer is difficult to jump, and the volume of the developer changes in accordance with the increase or decrease in the amount of developer in the developing device 4. Then, by discharging the developer when the volume of the staying developer exceeds a predetermined height (developer discharge port 94), development corresponding to the increased amount when the amount of developer in the developing device 4 increases. Since the developer is discharged, the amount of developer in the developing device 4 can be accurately maintained within a certain range.
As a result, the amount of developer transported along the supply transport path 9 is stabilized, so that a shortage of developer transporting along the supply transport path can be prevented, and a necessary amount from the supply transport path 9 to the developing roller 5 can be prevented. Developer can be supplied. For this reason, a stable developer can be supplied from the developing roller 5 to the photosensitive member 1, and the electrostatic latent image on the photosensitive member 1 can be favorably formed into a toner image. Can be prevented and good image formation can be performed.

In the developing device 4, the developer developer by the change in the developer transport amount by the stirring screw 11 when the premix toner is replenished or the change in the developer delivery amount from the stirring transport path 10 to the supply transport path 9. Trends are different.
For example, when the amount of developer transported by the stirring screw 11 does not change much even when the premix toner is supplied, the amount of developer supplied upstream in the transport direction of the supply transport path 9 does not change much. Further, even when the configuration in which the developer is transferred from the stirring conveyance path 10 to the supply conveyance path 9 is close to the upper limit of the amount that can be delivered per time in the state shown in FIGS. The amount of developer supplied upstream in the direction does not change much. In these configurations, the amount of developer in the agitating / conveying path 10 increases as the amount of developer in the developing device 4 increases, and the amount of developer supplied per hour in the agitating / conveying path 10 increases. Compared to the above, the amount of the developer that moves from the stirring conveyance path to the supply conveyance path 9 per unit time increases is reduced.

In the developing device 4 having such a configuration, even when the premix toner is replenished, the amount of developer conveyed through the supply conveyance path 9 does not change, and the amount of developer supplied from the supply conveyance path 9 to the developing roller 5 is changed. Therefore, the amount of the developer reaching the vicinity of the downstream end in the transport direction of the supply transport path 9 per time by the supply screw 8 hardly changes.
On the other hand, when the conveyance amount of the agitation conveyance path 10 does not change much, when the premix toner is replenished from the toner replenishing port 95, the increased developer stays in the vicinity of the upstream end of the agitation conveyance path 10 in the conveyance direction. Further, when the delivery amount from the agitation conveyance path 10 to the supply conveyance path 9 does not change, the increased amount of developer stays in the agitation conveyance path 10 and also stays in the vicinity of the upstream end in the conveyance direction.
When the developer stays in the vicinity of the upstream end in the transport direction, the surplus opening 92 that delivers the developer from the supply transport path 9 to the stirring transport path 10 is closed by the developer on the stirring transport path 10 side. When the excess opening 92 is blocked by the developer, the developer cannot be moved from the supply conveyance path 9 to the stirring conveyance path 10, but the developer is continuously conveyed by the supply screw 8, so that the conveyance of the supply conveyance path 9 is performed. The developer stays in the vicinity of the downstream end in the direction, and its bulk increases. When the volume of the developer near the downstream end in the conveyance direction of the supply conveyance path 9 rises to the height of the developer discharge port 94, the developer P is discharged to the discharge conveyance path 2 and developed through the discharge conveyance path 2. It is discharged outside the device 4.
In this configuration, when the developer in the agitation transport path 10 is full, the excess developer that has been transported to the most downstream side in the transport direction of the supply transport path 9 without being used for development is supplied and transported to the agitation transport path 10. By setting the surplus opening 92 to overflow with the developer, the movement of the developer from the supply conveyance path 9 to the agitation conveyance path 10 can be restricted, and as a result, the developer that has lost its destination is discharged from the developer. Guided to the outlet 94, the developer can be discharged.
As described above, even if the developer amount in the developing device 4 increases, even if the developer amount supplied per hour from the agitation transport path 10 to the supply transport path 9 does not change much, the supply transport path 9 By disposing the developer discharge port 94 at the downstream end in the transport direction, the developer in the developing device 4 can be replaced.

In addition, when the premix toner is replenished, the amount of the developer supplied to the upstream side of the supply conveyance path 9 in the conveyance direction increases, but the amount of developer from the supply conveyance path 9 to the stirring conveyance path 10 increases. Some configurations have an upper limit on the delivery amount. In this configuration, as the amount of developer in the developing device 4 increases, the amount of developer in the supply conveyance path 9 increases, and the conveyance of the supply screw 8 near the downstream end in the conveyance direction of the supply conveyance path 9 per time. Compared with the amount by which the amount of developer conveyed increases, the amount of developer that moves per hour from the downstream end in the conveyance direction of the supply conveyance path 9 to the agitation conveyance path 10 is reduced. Yes.
In the developing device 4 having such a configuration, when the premix toner is replenished, the conveyance amount of the agitation conveyance path 10 increases as the developer increases, and the developer from the agitation conveyance path 10 to the supply conveyance path 9 is increased. The amount of delivery will also increase. As a result, the amount of developer supplied to the upstream end of the supply conveyance path 9 in the conveyance direction increases, and the amount of developer conveyed in the supply conveyance path 9 also increases. However, since the amount of developer supplied from the supply conveyance path 9 to the developing roller 5 does not change, the amount of developer that reaches the vicinity of the downstream end in the conveyance direction of the supply conveyance path 9 increases per time. When the amount of developer that reaches the vicinity of the downstream end in the conveyance direction of the supply conveyance path 9 per time exceeds the upper limit of the delivery amount of developer from the supply conveyance path 9 to the stirring conveyance path 10 per hour, the supply conveyance The developer stays in the vicinity of the downstream end of the path 9 in the transport direction, and its bulk increases. Then, when the bulk of the staying developer near the downstream end in the conveyance direction of the supply conveyance path 9 rises to the height of the developer discharge port 94, the developer P is discharged to the discharge conveyance path 2 and passes through the discharge conveyance path 2. It is discharged to the outside of the developing device 4.
As described above, even when the developer amount in the developing device 4 increases, the amount of developer supplied from the agitation transport path 10 to the supply transport path 9 per unit time increases, even in the transport direction of the supply transport path 9. By disposing the developer discharge port 94 at the downstream end, the developer in the developing device 4 can be replaced.

In addition, the developer overflowed in the vicinity of the downstream end in the transport direction of the supply transport path 9, where the volume of the developer changes due to the change in the developer amount in the developing device 4, is discharged from the developer provided on the discharge partition wall 135. Since the developer is discharged through the outlet 94, the developer in the developing device 4 can be replaced with high accuracy with a simple structure.
Further, the supply conveyance path 9 and the agitation conveyance path 10 are arranged so as to be adjacent to each other with the first partition wall 133 serving as the supply circulation partition wall interposed therebetween, and the development that has reached the downstream end in the conveyance direction of the supply conveyance path 9 The agent is configured to move to the stirring and conveying path 10 through an excess opening 92 that is an opening provided so as to communicate the supply conveying path 9 and the stirring and conveying path 10. The bulk of the staying developer near the downstream end in the transport direction of the supply transport path 9 is determined by the amount of developer transported to the downstream end by the supply screw 8 per hour and the development passing through the excess opening 92 per time. It varies depending on the difference from the dosage. The amount of developer conveyed by the supply screw 8 or the amount of developer passing through the excess opening 92 per hour varies depending on the change in the amount of developer in the developing device 4, and the amount of developer in the developing device 4 increases. Since the bulk of the developer near the downstream end in the transport direction of the supply transport path 9 increases, the developer in the developing device 4 can be replaced with high accuracy with a simple configuration.

At least a part of the position of the supply transport path 9 in the developer transport direction overlaps with the developer discharge port 94 that is the discharge port opening of the developing device 4 and the surplus opening 92 that is the circulation opening. In the developing device 4 of this embodiment, as shown in FIGS. 4, 13, and 15, the developer discharge port 94 and the excess opening 92 are at the same position in the developer transport direction of the supply transport path 9. With such a configuration, the amount of developer delivered from the supply conveyance path 9 to the agitation conveyance path 10 and the amount of developer discharged out of the developing device 4 by retaining the developer in the vicinity of the surplus opening 92 are set. It becomes easy to balance.
Further, since the developer discharge port 94 is disposed above the surplus opening 92, the developer discharge port 94 reaches the downstream end in the transport direction of the supply transport path 9 when the amount of developer in the developing device 4 is an appropriate amount. The developer passes only through the excess opening 92 located below, moves to the agitation transport path 10 and circulates in the developing device 4. When the amount of the developer in the developing device 4 increases and the volume of the staying developer at the downstream end in the transport direction reaches the height of the developer discharge port 94 above, the developer exceeding the height is discharged. It passes through the outlet 94 and is discharged to the outside of the developing device 4. In this configuration, the developer discharge port 94 is arranged above the surplus opening 92, and the developer is supplied in a state where the amount of developer to be supplied to the stirring and conveying path 10 is not supplied to the stirring and conveying path 10. When the amount of developer in the developing device 4 exceeds a predetermined amount while preventing the developer from being discharged out of the developing device 4, the developer can be discharged out of the device. Accordingly, it is possible to realize a configuration in which the developer is circulated through the surplus opening 92 and the developer increased by the developer discharge port 94 is accurately discharged and the developer is replaced.

Further, in the one-way circulation developing device 4 including the supply conveyance path 9, the agitation conveyance path 10, and the collection conveyance path 7, the developer that reaches the downstream end in the conveyance direction of the supply conveyance path 9 does not contribute to development. It is an agent. In the one-way circulation developing device 4, it is suitable to discharge the developer increased by the replenishment of the premix toner at the position where the excess developer stays. This is due to the following reason.
Since the collection conveyance path 7 conveys the developer carried on the developing roller 5 and passed through the development region, even if the amount of the developer in the developing device 4 changes, almost no developer is conveyed in the collection conveyance path 7. There is no change, and the developer cannot be discharged due to an increase in the volume of the developer.
As the amount of developer in the developing device 4 increases, the amount of developer to be transported increases and the bulk of the agitation transport path 10 also increases. However, due to the jumping of the developer to be transported or unevenness in the transport amount, the developer is discharged even if the developer amount does not increase, and the required amount of developer cannot be delivered to the supply transport path 9. is there. For this reason, it is not appropriate to discharge the developer due to the increase in the volume of the developer in the stirring conveyance path 10. Further, the configuration of discharging in the middle of the supply conveyance path 9 may increase the volume of the developer even if the amount of the developer in the developing device 4 is not increased, and the downstream side in the conveyance direction from the discharged position. Is not suitable because the developer may be insufficient.
For this reason, the one-way circulating developing device 4 discharges the developer increased by replenishing the premix toner at the position where the developer that reaches the downstream end in the transport direction of the supply transport path 9 stays. Is suitable.

In the developing device 4 of the embodiment, the excessive opening 92 is larger than the developer discharge port 94, but the developer discharge port 94 may be larger than the excessive opening 92.
Further, in the above-described embodiment, FIG. 4 shows a configuration in which the developer discharging means discharges a part of the developer when the volume of the developer near the downstream end in the transport direction of the supply transport path 9 exceeds a predetermined height. The configuration applied to the developing device 4 having the configuration shown has been described. The configuration to which the characterizing portion of the present invention can be applied is not limited to that shown in FIG. 4, but can be similarly applied to the developing device 4 having the configuration shown in FIG.
In the above-described embodiment, the developing device using the two-component developer composed of the carrier and the toner as the developer has been described. The developing device to which the feature of the present invention is applied is not limited to a developing device using a two-component developer. A developing device using a one-component developer can be used as long as the developer is replenished by the developer replenishing unit and the developer discharging unit discharges the increased amount of developer in the developing device. Is applicable.

[Example 1]
Next, a first example (hereinafter referred to as Example 1) of the developer retention unit 80 will be described.
FIG. 16 is an enlarged schematic view of the vicinity of the downstream end in the transport direction of the supply transport path 9 of the developing device 4 according to the first embodiment. As shown in FIG. 16, the developing device 4 according to the first embodiment is a reverse conveying member that generates a conveying force in the direction opposite to the supply screw 8 at the most downstream end in the conveying direction of the supply conveying path 9 as the developer retention unit 80. The reverse screw 81 is provided. The reverse screw 81 is obtained by attaching a wing portion, which is reversely wound to the wing portion of the supply screw 8, to the end portion of the rotation shaft of the supply screw 8.
As the supply screw 8 rotates, the reverse screw 81 generates a conveyance force in the direction of arrow N in FIG. 16 as a conveyance force in the direction opposite to that of the supply screw 8. As a result, the developer P that has passed the position where the developer discharge port 94 and the excess opening 92 are disposed by the conveyance of the supply screw 8 is directed to the position of the developer discharge port 94 and the excess opening 92 by the reverse screw 81. be able to. Therefore, the developer P can be retained at the positions of the developer discharge port 94 and the excess opening 92 in the developer transport direction in the supply transport path 9.

By causing the developer P to stay at the position of the excess opening 92, in the state where the staying developer is present, the required amount of developer required for circulation is shown in the downward direction of the developer P indicated by arrow E in FIG. Can be passed to the agitation transport path 10 as Further, by retaining the developer P at the position of the developer discharge port 94, the bulk of the retained developer increases, and when the developer discharge port 94 is reached, the lowest point of the developer discharge port 94 is reached. The developer P at a higher position can be reliably delivered to the discharge conveyance path 2 as an upward flow of the developer P indicated by an arrow K in FIG.
In addition, the surplus opening 92 that is a circulation opening through which the developer P that has passed is transferred to the stirring and conveying path 10 that is a circulating and conveying path is connected to the stirring and conveying path 10 and the supply and conveying path 9 like the developing device 4. It is preferably a communication port provided in the first partition wall 133 for partitioning and communicating the agitation transport path 10 and the supply transport path 9. By using the communication port, the developer P can be transferred from the supply conveyance path 9 to the stirring conveyance path 10 with a simple configuration. Further, since the supply conveyance path 9 is arranged above the agitation conveyance path 10, by setting the opening to be communicated, excess developer is dropped downward like a pit and the excess developer is efficiently removed by the agitation conveyance path. 10 can be handed over.
Further, when the developer P that has passed the position where the developer discharge port 94 and the surplus opening 92 are disposed is further conveyed in the conveyance direction of the supply screw 8, the developer P enters the bearing of the rotating shaft of the supply screw 8. There is a risk of damaging the bearing. For such a problem, the reverse screw 81 is disposed, and the developer P that has passed the position where the developer discharge port 94 and the surplus opening 92 are disposed is pushed back to prevent the developer P from entering the bearing. Thus, damage to the bearing can be prevented.

[Example 2]
Next, a second embodiment (hereinafter referred to as a second embodiment) of the developer retention means 80 will be described.
FIG. 17 is an enlarged schematic view of the vicinity of the downstream end in the transport direction of the supply transport path 9 of the developing device 4 according to the second embodiment. As illustrated in FIG. 17, the developing device 4 according to the second exemplary embodiment has, as the developer retention unit 80, the downstream side in the transport direction of the supply transport path 9 at the downstream end in the transport direction of the supply transport path 9. A downstream end wall surface 82 that prevents the developer P from moving to the side is provided. By providing such a downstream end wall surface 82, the developer P can be retained at the positions of the developer discharge port 94 and the excess opening 92 in the developer transport direction in the supply transport path 9.
By retaining the developer P at the position of the excess opening 92, in the state where the retained developer exists, the required amount of the developer P required for circulation is below the developer P indicated by the arrow E in FIG. It can be passed to the stirring and conveying path 10 as a directional flow. Further, by retaining the developer P at the position of the developer discharge port 94, the bulk of the retained developer increases, and when the developer discharge port 94 is reached, the lowest point of the developer discharge port 94 is reached. The developer P at a higher position can be reliably transferred to the discharge conveyance path 2 as an upward flow of the developer P indicated by an arrow K in FIG.

Example 3
Next, a third embodiment (hereinafter referred to as embodiment 3) of the developer retaining means 80 will be described.
FIG. 18 is an enlarged schematic view of the vicinity of the downstream end in the transport direction of the supply transport path 9 of the developing device 4 of the third embodiment. As shown in FIG. 18, the developing device 4 of the third embodiment serves as the developer retention unit 80 at the most downstream end in the conveyance direction of the supply conveyance path 9 in the direction opposite to the conveyance direction of the supply screw 8 (arrow in FIG. 18). A plate 83 with a spring is provided as a pressing member for pressing the developer P in the N direction. Providing such a spring-equipped plate 83 makes it possible to retain the developer P at the position of the developer discharge port 94 and the excess opening 92 in the developer transport direction in the supply transport path 9.
By retaining the developer P at the position of the excess opening 92, in the state where the retained developer exists, the required amount of developer P required for circulation is below the developer P indicated by arrow E in FIG. It can be passed to the stirring and conveying path 10 as a directional flow. Further, by retaining the developer P at the position of the developer discharge port 94, the bulk of the retained developer increases, and when the developer discharge port 94 is reached, the lowest point of the developer discharge port 94 is reached. The developer P at a higher position can be reliably delivered to the discharge conveyance path 2 as an upward flow of the developer P indicated by an arrow K in FIG.

Example 4
Next, a fourth embodiment (hereinafter referred to as a fourth embodiment) of the developer retention means 80 will be described.
FIG. 19 is an enlarged schematic view of the vicinity of the downstream end in the transport direction of the supply transport path 9 of the developing device 4 of the third embodiment. As shown in FIG. 19, the developing device 4 according to the fourth embodiment has, as the developer retention unit 80, a wind toward the upstream side in the transport direction of the supply screw 8 at the downstream end in the transport direction of the supply transport path 9 ( 19 is provided with a blower 84 that is a blower for generating an arrow W). By providing such a blower 84, the developer P that has reached the most downstream end in the transport direction of the supply transport path 9 is pressed in a direction opposite to the transport direction of the supply screw 8. As a result, as shown in FIG. 19, the developer P can be retained at the positions of the developer discharge port 94 and the surplus opening 92 in the developer transport direction in the supply transport path 9.
By causing the developer to stay at the position of the excess opening 92, in the state where the staying developer is present, the required amount of developer required for circulation is the downward flow of the developer indicated by arrow E in FIG. Can be passed to the agitation transport path 10. Further, by retaining the developer at the position of the developer discharge port 94, the volume of the retained developer increases, and when the developer reaches the height of the developer discharge port 94, the lowest point of the developer discharge port 94 is reached. The developer at a higher position can be reliably delivered to the discharge conveyance path 2 as an upward flow of the developer indicated by an arrow K in FIG.

Example 5
Next, a fifth embodiment (hereinafter referred to as embodiment 5) of the developer retention means 80 will be described.
FIG. 20 is an enlarged schematic view of the vicinity of the downstream end in the transport direction of the supply transport path 9 of the developing device 4 according to the second embodiment. As illustrated in FIG. 20, the developing device 4 according to the fifth embodiment has, as the developer retention unit 80, the downstream side in the transport direction of the supply transport path 9 at the downstream end in the transport direction of the supply transport path 9. It is provided with a dog-shaped wall surface 85 that prevents the developer P from moving to the side. By providing such a dogleg-shaped wall surface 85, the developer discharge port 94 and the surplus opening 92 in the developer transport direction in the supply transport path 9 are the same as in the second embodiment including the downstream end wall surface 82. The developer P can be retained at the position.
By retaining the developer P at the position of the surplus opening 92, in the state where the retained developer exists, the required amount of developer P required for circulation is below the developer P indicated by arrow E in FIG. It can be passed to the stirring and conveying path 10 as a directional flow. Further, by retaining the developer P at the position of the developer discharge port 94, the bulk of the retained developer increases, and when the developer reaches the height of the developer discharge port 94, the lowest point of the developer discharge port 94 is reached. The developer P at a higher position can be reliably delivered to the discharge conveyance path 2 as an upward flow of the developer P indicated by an arrow K in FIG.
Further, as shown in FIG. 20, the U-shaped wall surface 85 has a shape in which the central portion in the vertical direction protrudes to the upstream side in the conveyance direction of the supply conveyance path 9. Can be increased. For this reason, it is possible to discharge the developer from the developer discharge port 94 in a state where the amount of the staying developer is smaller than that in the second embodiment.
Further, when the developer conveyed in the conveyance direction of the supply conveyance path 9 (in the direction of arrow L in FIG. 20) collides with the plane below the square-shaped wall surface 85, it bounces downward, and the excess opening 92 It is a plane that goes in the direction. For this reason, in a state where the amount of developer reaching the downstream end in the transport direction of the supply transport path 9 is reduced and the staying developer is decreased, the developer transported by the supply screw 8 is more reliably transferred to the surplus opening 92. Can be directed in the direction. As a result, the required amount of developer required for circulation can be more reliably delivered to the stirring and conveying path 10 even when the staying developer is reduced.

Example 6
Next, a sixth embodiment (hereinafter referred to as embodiment 6) of the developer retaining means 80 will be described.
FIG. 21 is an enlarged schematic view of the vicinity of the downstream end in the transport direction of the supply transport path 9 of the developing device 4 according to the second embodiment. As shown in FIG. 21, the developing device 4 according to the second embodiment has, as the developer retention unit 80, the downstream side in the transport direction of the supply transport path 9 at the most downstream end in the transport direction of the supply transport path 9. A downstream end wall surface 82 that prevents the developer P from moving to the side, and a magnetic plate 86 below the developer discharge port 94 are provided. By providing the downstream end wall surface 82, the developer P can be retained at the positions of the developer discharge port 94 and the excess opening 92 in the developer transport direction in the supply transport path 9.
By retaining the developer P at the position of the excess opening 92, in the state where the retained developer exists, the required amount of developer P required for circulation is below the developer P indicated by arrow E in FIG. It can be passed to the stirring and conveying path 10 as a directional flow. Further, by retaining the developer P at the position of the developer discharge port 94, the bulk of the retained developer increases, and when the developer discharge port 94 is reached, the lowest point of the developer discharge port 94 is reached. The developer P at a higher position can be reliably delivered to the discharge conveyance path 2 as an upward flow of the developer P indicated by an arrow K in FIG.

Further, since the developer P includes a magnetic carrier by providing the magnetic plate 86, the developer P that is spun up by the momentum being conveyed or the centrifugal force of the supply screw 8 toward the developer discharge port 94 is the magnetic plate. It is attracted to 86 and discharge is prevented. Further, in a state where the developer P is attached to the magnetic plate 86, the developer P that has been bounced up toward the developer discharge port 94 passes through the developer discharge port 94 by the developer P that adheres to the magnetic plate 86. To be prevented. In this way, the magnetic plate 86 can prevent the developer from splashing up and being discharged from the developer discharge port 94, so that the developer that has not entered the excess opening 92 is more reliably retained. be able to.
On the other hand, when the bulk of the staying developer increases and the volume of the developer reaches the height of the developer discharge port 94, the developer P adhering to the magnetic plate 86 is also pushed up. The developer can be discharged.

In the above-described embodiment, the developing device including the three developer transport paths of the supply transport path 9, the recovery transport path 7, and the stirring transport path 10 as the developer transport path in which the developer is transported in the developing device 4. 4 was explained.
A developer retaining means for retaining the developer that has not entered the circulation opening in the vicinity of the downstream end in the transport direction of the supply transport path, which is a feature of the present invention, and the discharge opening is disposed at a position where the retained developer passes. The developing device to which the configuration to be applied can be applied is not limited to a developing device having three developer conveyance paths.
Hereinafter, as a modified example, a developing device in which the characteristic portion of the present invention is applied to a configuration different from that of a developing device including three developer conveyance paths will be described. As an image forming apparatus using the developing device 4 according to the modification, the same image forming apparatus as that of the copying machine 500 according to the above-described embodiment can be used. Therefore, the description of the entire image forming apparatus is omitted in the modification.

[Modification 1]
22 and 23 are explanatory diagrams of the developing device 4 according to the first modification. FIG. 22 is a schematic configuration diagram illustrating the developing device 4 and the photosensitive member 1 according to the first modification. FIG. 23 is a schematic diagram illustrating the flow of the developer in the developing device 4 according to the first modification. Each arrow indicates the moving direction of the developer.
In the developing device 4, a supply / recovery conveyance path 402 that is a supply / conveyance path provided with a supply / recovery screw 401 that is a supply / conveyance member and a stirring / conveyance path 10 that is a circulation / conveyance path provided with a stirring screw 11 that is a circulation / conveyance member. Two developer conveyance paths are provided. The supply / recovery conveyance path 402 and the agitation conveyance path 10 are partitioned by a partition wall 403, and a circulation opening 96 and a supply opening 91 are provided at both ends of the partition wall 403 in the axial direction of the developing roller 5. Yes. The developer is transported in the opposite directions in the two developer transport paths, and the developer that has reached the downstream end in the transport direction of the supply and recovery transport path 402 passes through the circulation opening 96 to the upstream end in the transport direction of the stirring transport path 10. The developer that has been delivered and has reached the downstream end in the transport direction of the agitation transport path 10 is transferred to the upstream end in the transport direction of the supply and recovery transport path 402 via the supply opening 91, thereby allowing the developer in the developing device 4 to pass through. Circulates. In the developing device 4, the developer in the supply / recovery conveyance path 402 is supplied to the surface of the developing roller 5, and is used for development in a developing region that is a portion where the developing roller 5 and the photosensitive member 1 are opposed to each other. Then, the developer on the developing roller 5 that has passed through the developing region is collected in the supply / collection conveyance path 402. A toner replenishing port 95 is provided in the vicinity of the circulation opening 96 at the upstream end of the agitating / conveying path 10 in the conveying direction, and a premix toner including a carrier according to the sensor output of a toner density sensor (not shown). Is supplied from the toner supply port 95.

As shown in FIG. 23, the developing device 4 according to the modified example 1 allows the developer that has not entered the circulation opening 96 at the downstream end in the conveyance direction of the supply / recovery conveyance path 402, which is a supply conveyance path, in the vicinity of the circulation opening 96. A developer retaining means 80 for retaining is provided. Further, the developer discharge port 94 that is a discharge opening is located above the circulation opening 96 and the development that has reached the position of the developer discharge port 94 among the retained developer retained by the developer retention means 80. It arrange | positions so that an agent may be allowed to pass. As a specific example of the developer retention means 80, the same structure as that described in the first to sixth embodiments can be used.
The developing device 4 of Modification 1 also includes the circulation opening 96, the developer retaining means 80, and the developer discharge port 94 as described above, so that the development in the developing device 4 is performed as in the above-described embodiment. Since the required amount of the developer can be ensured, the developer can be stably supplied to the photoreceptor 1. As a result, the electrostatic latent image on the photoreceptor 1 can be favorably converted into a toner image, an abnormal image such as image omission can be prevented, and good image formation can be performed.

[Modification 2]
24 and 25 are explanatory diagrams of the developing device 4 according to the second modification. FIG. 24 is a schematic configuration diagram illustrating the developing device 4 and the photoreceptor 1 according to the second modification. FIG. 25 is a schematic diagram illustrating the flow of the developer in the developing device 4 according to the second modification. Each arrow indicates the moving direction of the developer.
In this developing device 4, two developer transport paths are provided: a supply transport path 9 including a supply screw 8 serving as a supply transport member, and a recovery transport path 7 serving as a circulation transport path including a recovery screw 6 serving as a circulation transport member. Prepare. The supply conveyance path 9 and the collection conveyance path 7 are partitioned by a partition wall 403, and the supply conveyance path 9 is positioned above the collection conveyance path 7 across the partition wall 403. In addition, a surplus opening 92 serving as a circulation opening and a supply opening 91 are provided at both ends of the partition wall 403 in the axial direction of the developing roller 5. The developer is transported in the opposite directions in the two developer transport paths, and the developer that has reached the downstream end in the transport direction of the supply transport path 9 is received by the upstream end in the transport direction of the recovery transport path 7 via the surplus opening 92. The developer that has passed and reaches the downstream end in the transport direction of the collection transport path 7 is transferred to the upstream end in the transport direction of the supply transport path 9 via the supply opening 91, whereby the developer circulates in the developing device 4. To do. In the developing device 4, the developer in the supply / conveyance path 9 is supplied to the surface of the developing roller 5, and is used for development in a developing region which is a facing portion between the developing roller 5 and the photoreceptor 1. Then, the developer on the developing roller 5 that has passed through the developing area is collected in the collecting conveyance path 7. A toner replenishing port 95 is provided in the vicinity of the surplus opening 92 at the upstream end of the collection transport path 7 in the transport direction, and a premix toner including a carrier is provided according to the sensor output of a toner density sensor (not shown). Is supplied from the toner supply port 95.

As shown in FIG. 25, the developing device 4 of Modification 2 retains the developer that has not entered the surplus opening 92 at the downstream end in the transport direction of the supply transport path 9 that is the supply transport path in the vicinity of the surplus opening 92. Developer retaining means 80 is provided. Further, the developer discharge port 94 that is a discharge opening is located above the surplus opening 92 and the developer that has reached the position of the developer discharge port 94 among the retained developer retained by the developer retention means 80. It arrange | positions so that an agent may be allowed to pass. As a specific example of the developer retention means 80, the same structure as that described in the first to sixth embodiments can be used.
Further, the developing device 4 of Modification 2 also includes the above-described excessive opening 92, the developer retaining means 80, and the developer discharge port 94, so that the development in the developing device 4 is performed as in the above-described embodiment. Since the required amount of the developer can be ensured, the developer can be stably supplied to the photoreceptor 1. As a result, the electrostatic latent image on the photoreceptor 1 can be favorably converted into a toner image, an abnormal image such as image omission can be prevented, and good image formation can be performed.

Further, in the developing device 4 of Modification 1, the conveyance path for supplying the developer to the developing roller 5 and the conveyance path for collecting the developer supplied to the developing roller 5 and having passed through the development area are common. Therefore, there is a problem that the toner concentration of the developer supplied to the developing roller decreases toward the downstream side in the conveying direction of the conveying path supplied to the developing roller. When the toner density supplied to the developing roller decreases, the image density during development also decreases.
Such a problem is that the developer conveying path for supplying the developer to the developing roller 5 as in the developing device 4 described in Modification 2 and the developer on the developing roller 5 that has passed through the developing region are collected. This can be solved by providing the developer transport path in a different developer transport path.
In the developing device 4 of Modification 2, the developer that has passed through the developing region is sent to the recovery conveyance path 7 and therefore does not enter the supply conveyance path 9. Thus, the toner concentration of the developer supplied to the developing roller 5 is constant without changing the toner concentration of the developer in the supply conveyance path 9.

Note that in the developing device 4 of the second modification, collection and agitation are performed in the collection conveyance path 7, and the collected developer that has passed through the development portion also falls in the middle of the agitation, so development in a state where the agitation is not sufficiently performed. There is a possibility that the agent goes to the supply conveyance path 9. When the developer with insufficient stirring is supplied to the supply conveyance path 9, there arises a problem that the toner concentration of the entire developer in the supply conveyance path 9 is lowered. Such a problem becomes more conspicuous as an image having a high printing rate in which the toner concentration of the collected developer is lowered.
Such a problem can be solved by the developing device 4 including the three developer transport paths of the supply transport path 9, the recovery transport path 7, and the agitation transport path 10 described in the above embodiment. In the developing device 4 of the embodiment, since the agitating and conveying path 10 is provided separately from the collecting and conveying path 7, the collected developer that has passed through the developing region does not fall during the agitation and the development is sufficiently agitated. The agent can be transferred to the supply conveyance path 9. Thereby, the toner density of the developer in the supply conveyance path 9 can be stabilized.

As described above, according to the present embodiment, the developing roller 5 that is a developer carrying member, the supply conveyance path 9 that conveys the developer along the axial direction of the developing roller 5 while supplying the developer to the developing roller 5, A supply screw 8 that is a supply conveyance member that applies a conveyance force to the developer in the supply conveyance path 9, and a developer that has reached the downstream end in the conveyance direction of the supply conveyance path 9 is the upstream end in the conveyance direction of the supply conveyance path 9. The agitating and conveying path 10 that is a circulating conveying path that conveys the toner and the agitating screw 11 that is a circulating and conveying member that imparts a conveying force to the developer in the agitating and conveying path 10, and the developer that has passed through the agitating and conveying path A developer that is a discharge opening that is provided with a surplus opening 92 that is a circulation opening that is transferred to the path 10 in the vicinity of the downstream end in the transport direction of the supply transport path 9 and that passes the developer out of the developing device 4. A developing device having a discharge port 94 in the supply conveyance path 9 4, a developer staying means 80 is provided to make the developer that has reached the vicinity of the downstream end in the transport direction of the supply transport path 9 and did not enter the surplus opening 92 stay in the vicinity of the surplus opening 92. Is disposed so as to allow the developer that has reached the position of the developer discharge port 94 out of the retained developer retained by the developer retaining means 80 to pass above the surplus opening 92. In the case of the apparatus 4, the developer is not discharged from the developer discharge port 94 unless the remaining developer reaches the position of the developer discharge port 94. The required amount of developer is supplied from the agitating and conveying path 10 to the supply and conveying path 9 when the required amount of developer is directed to the path 10, so that the amount of developer in the developing device 4 is maintained at the required amount. It becomes a state. That is, if the amount of developer in the developing device 4 does not exceed the required amount, the developer is not discharged from the developer discharge port 94, so that the amount of developer in the developing device 4 can maintain the required amount. it can. Therefore, a stable developer can be supplied from the developing roller 5 as the developer carrying member to the photosensitive member 1 as the latent image carrying member.
Further, as in the second embodiment, the developer retaining means 80 is the downstream end wall surface 82 which is the wall surface at the downstream end in the conveyance direction of the supply conveyance path 9, so that development is performed in the vicinity of the surplus opening 92 with a simple configuration. The agent can be retained.
Further, as in the first embodiment, the developer retaining means 80 is a reverse screw 81 as a reverse conveyance member that generates a conveyance force in the direction opposite to that of the supply screw 8 at the most downstream end of the supply conveyance path 9 in the developer conveyance direction. Even so, the developer can be retained in the vicinity of the surplus opening 92. Furthermore, by pushing back the developer P that has passed the position where the developer discharge port 94 and the surplus opening 92 are disposed with the reverse screw 81, the developer P is prevented from entering the bearing and the bearing is prevented from being damaged. Can do.
Further, the developer discharge port 94 and the surplus opening 92 are supplied by the developer discharge port 94 and the surplus opening 92 so that at least a part of the position of the supply transport path 9 in the developer transport direction overlaps. It is at the same position in the developer conveyance direction of the conveyance path 9. With such a configuration, the amount of developer delivered from the supply conveyance path 9 to the agitation conveyance path 10 and the amount of developer discharged out of the developing device 4 by retaining the developer in the vicinity of the surplus opening 92 are set. It becomes easy to balance.
Further, the developer that is disposed adjacent to the supply conveyance path 9 with the discharge partition wall 135 sandwiched downstream in the conveyance direction of the supply conveyance path 9 and that has passed through the developer discharge port 94 from the supply conveyance path 9 is removed from the developing device 4. And the developer discharge port 94 is provided in the discharge partition wall 135 so as to communicate the supply transport path 9 and the discharge transport path 2, thereby providing an opening in the partition wall. A configuration in which the developer is discharged from the supply conveyance path 9 can be realized with a simple configuration.
In addition, the agitation transport path 10 is disposed adjacent to the lower side of the supply transport path 9 with the first partition wall 133 that is a supply circulation partition wall interposed therebetween, and the surplus opening 92 is provided between the supply transport path 9 and the agitation transport path 10. By providing the first partition wall 133 so as to communicate with each other, excess developer can be dropped downward like a pit, and the excess developer can be efficiently transferred to the agitation transport path 10.
Further, the supply conveyance member is composed of a rotation shaft and a spiral wing portion, and is a supply screw 8 that imparts a conveyance force to the developer by rotating around the rotation shaft, thereby developing in the supply conveyance path 9. The developer discharging port 94 has a lowermost portion that is higher than the uppermost portion of the wing portion of the supply screw 8, so that the volume of the staying developer is increased. In the state reaching 94, the entire supply screw 8 is buried in the staying developer at the position where the developer stays. When the supply screw 8 is buried in the staying developer, the developer can be prevented from jumping due to the rotation of the supply screw 8, and the developer in the state where the amount of the developer in the developing device 4 is not increased. Can be more reliably prevented from jumping out of the developing device 4 by jumping off.
Further, the developer separated from the surface of the developing roller 5 after passing through the developing region facing the photoreceptor 1 is collected and conveyed along the axial direction of the developing roller 5 and in the same direction as the supply screw 8. The agitating and conveying path 10 having a collecting and conveying path 7 having a collecting screw 6 that is a collecting and conveying member and a circulating and conveying path includes a developer conveyed to the most downstream side in the conveying direction of the supply conveying path 9, and a collection Supplyed with the developer transported to the most downstream side in the transport direction of the transport path 7, transports the developer along the axial direction of the developing roller 5, and in the direction opposite to the supply screw 8. By supplying the upstream end of the path 9 in the transport direction, the developer on the developing roller 5 that has passed through the developing region is not mixed into the supply transport path 9, so the toner density of the developer in the supply transport path 9 Can be prevented from decreasing. Furthermore, since the developer on the developing roller 5 that has passed through the developer region is not mixed in the middle of the stirring and conveying path 10, the sufficiently stirred developer can be transferred to the supply and conveying path 9, The toner density of the developer in the supply conveyance path 9 can be stabilized.
Further, at least a photosensitive member 1 as a latent image carrier, a charger as a charging unit for charging the surface of the photosensitive member 1, and a latent image forming unit for forming an electrostatic latent image on the photosensitive member 1. A copying machine 500, which is an image forming apparatus having a certain optical writing unit 21 and a developing unit for developing an electrostatic latent image into a toner image, uses the developing device 4 as a developing unit to develop the image. By providing the device 4, it is possible to prevent the occurrence of abnormal images such as image omission and improve image formation while extending the life of the developing device 4 by replacing the developer.
In addition, at least the photosensitive member 1 and the developing unit in the copying machine 500 that is an image forming apparatus including the photosensitive member 1 that is a latent image carrier that carries a latent image and a developing unit that develops the latent image on the photosensitive member 1. The process cartridge 18 that is held on a common holding body as a unit and is detachable from the main body of the copying machine 500 includes the developing device 4 as the developing means, so that the life of the developing device 4 can be changed by replacing the developer. It is possible to prevent the occurrence of abnormal images such as missing images and to easily attach and detach the developing device 4 capable of forming a good image with respect to the copying machine 500.

1 is a schematic configuration diagram of a copier according to an embodiment. FIG. 2 is a schematic configuration diagram of a developing device and a photoreceptor. FIG. 3 is a perspective cross-sectional view of the developing device for explaining the flow of the developer. FIG. 3 is a schematic diagram of a developer flow in a developing device. Cross-sectional explanatory drawing of a developing device. FIG. 5 is a schematic diagram of a developer flow in a developing device having a shape different from that in FIG. 4. FIG. FIG. 6 is a perspective explanatory view of the vicinity of the front end in a state where the stirring screw, the recovery screw, and the developing doctor are removed from the developing device. FIG. 9 is an explanatory perspective view of the vicinity of the near side in a state where a supply screw is removed from the developing device shown in FIG. 8. FIG. 10 is a perspective explanatory view of the vicinity of the near side in a state where the developing roller is removed from the developing device shown in FIG. 9. FIG. 11 is an explanatory perspective view when the developing device shown in FIG. 10 is viewed from a direction different from FIG. 10. Cross-sectional explanatory drawing of the developing device in a state where the developer amount is small. Side surface explanatory drawing of the image development apparatus of a state with little developer amount. Cross-sectional explanatory drawing of the developing device in a state where the amount of developer is large. Side surface explanatory drawing of the image development apparatus of a state with much developer amount. FIG. 2 is an enlarged schematic view of the vicinity of a downstream end in a conveyance direction of a supply conveyance path of the developing device according to the first exemplary embodiment. FIG. 9 is an enlarged schematic view of the vicinity of a downstream end in a transport direction of a supply transport path of a developing device according to a second embodiment. FIG. 10 is an enlarged schematic view of the vicinity of a downstream end in a conveyance direction of a supply conveyance path of a developing device according to Embodiment 3. FIG. 10 is an enlarged schematic view of the vicinity of a downstream end in a transport direction of a supply transport path of a developing device according to a fourth embodiment. FIG. 10 is an enlarged schematic view of the vicinity of a downstream end in a transport direction of a supply transport path of a developing device according to a fifth embodiment. FIG. 10 is an enlarged schematic view of the vicinity of a downstream end in a transport direction of a supply transport path of a developing device according to Embodiment 6. FIG. 10 is a schematic configuration diagram illustrating a developing device and a photoconductor according to a first modification. FIG. 9 is a schematic diagram illustrating a flow of a developer in a developing device according to a first modification. FIG. 10 is a schematic configuration diagram illustrating a developing device and a photoconductor according to a second modification. FIG. 9 is a schematic diagram illustrating a flow of a developer in a developing device according to a second modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Discharge conveyance path 2a Discharge screw 4 Developing apparatus 5 Developing roller 6 Collecting screw 7 Collection conveyance path 8 Supply screw 9 Supply conveyance path 10 Stirring conveyance path 11 Stirring screw 12 Doctor blade 14 Stretching roller 15 Drive roller 16 Secondary Transfer backup roller 17 Intermediate transfer unit 18 Process cartridge 20 Image forming unit 21 Optical writing unit 22 Secondary transfer device 23 Stretching roller 24 Paper transport belt 25 Fixing device 26 Fixing belt 27 Pressure roller 80 Developer retaining means 81 Reverse screw 82 downstream end wall 83 spring plate 84 air blower 85 U-shaped wall 86 magnetic plate 90 belt cleaning device 91 supply opening 92 surplus opening 93 recovery opening 94 developer discharge port 95 toner supply port 96 circulation opening 100 Printer section 10 the intermediate transfer belt 133 first partition wall 134 a second partition wall 135 discharge partition wall 401 supplies the recovery screw 402 supply collection conveyance path 403 partition wall 500 copier

Claims (10)

A developer carrying member that rotates by carrying a developer on the surface, and supplies toner to the latent image on the surface of the latent image carrying member at a position facing the latent image carrying member;
A supply conveyance path for conveying the developer along the axial direction of the developer carrier while supplying the developer to the developer carrier;
A supply conveyance member that applies conveyance force to the developer in the supply conveyance path;
A circulation conveyance path for conveying the developer that has reached the downstream end in the conveyance direction of the supply conveyance path to the upstream end in the conveyance direction of the supply conveyance path;
A circulation conveyance member that applies a conveyance force to the developer in the circulation conveyance path;
A circulation opening through which the developer that has passed is transferred to the circulation conveyance path is provided near the downstream end in the conveyance direction of the supply conveyance path,
In the developing device provided in the supply conveyance path with a discharge opening through which the developer that has passed is discharged out of the developing device,
A developer retaining means for retaining the developer that has reached the vicinity of the downstream end in the transport direction of the supply transport path and has not entered the circulation opening, in the vicinity of the circulation opening;
The discharge opening is arranged above the circulation opening and to pass the developer that has reached the position of the discharge opening among the retained developer retained by the developer retention means. A developing device. The developing device according to claim 1.
The developing device, wherein the developer retaining means is a wall surface at a downstream end of the supply transport path in the transport direction. The developing device according to claim 1.
The developing device, wherein the developer retention means is a reverse conveyance member that generates a conveyance force in a direction opposite to the supply conveyance member at the most downstream end in the developer conveyance direction of the supply conveyance path. The developing device according to claim 1, 2 or 3,
The developing device according to claim 1, wherein the discharge opening and the circulation opening overlap at least a part of a position in the developer transport direction of the supply transport path. The developing device according to claim 1, 2, 3 or 4,
A discharge conveyance path that is arranged adjacent to the supply conveyance path with a partition wall sandwiched downstream in the conveyance direction of the supply conveyance path, and conveys the developer that has passed through the discharge opening from the supply conveyance path to the outside of the developing device. And the discharge opening is provided in the partition wall so as to communicate the supply conveyance path and the discharge conveyance path. The developing device according to claim 1, 2, 3, 4 or 5.
The circulation conveyance path is disposed adjacent to the supply conveyance path below the supply circulation partition wall, and the circulation opening is connected to the supply circulation partition so as to communicate the supply conveyance path and the circulation conveyance path. A developing device provided on a wall. The developing device according to claim 1, 2, 3, 4, 5 or 6.
The supply conveyance member is a supply screw that includes a rotation shaft and a spiral blade, and applies a conveyance force to the developer by rotating around the rotation shaft.
2. A developing device according to claim 1, wherein the discharge opening has a lowermost portion at a position higher than an uppermost portion of the wing portion of the supply screw. The developing device according to claim 1, 2, 3, 4, 5, 6 or 7.
The developer separated from the surface of the developer carrier after passing through the portion facing the latent image carrier is collected, and along the axial direction of the developer carrier, the same as the supply conveyance member. It has a collection conveyance path with a collection conveyance member that conveys in the direction,
The circulation conveyance path receives supply of the developer conveyed to the most downstream side in the conveyance direction of the supply conveyance path and the developer conveyed to the most downstream side in the conveyance direction of the recovery conveyance path, and the development A developing device characterized in that the developer is transported along the axial direction of the agent carrier and in the direction opposite to the supply transport member and is supplied to the upstream end in the transport direction of the supply transport path. At least a latent image carrier;
Charging means for charging the surface of the latent image carrier;
Latent image forming means for forming an electrostatic latent image on the latent image carrier;
In an image forming apparatus having developing means for developing the electrostatic latent image into a toner image,
An image forming apparatus using the developing device according to claim 1, 2, 3, 4, 5, 6, 7, or 8 as the developing means. In an image forming apparatus comprising a latent image carrier that carries a latent image and a developing unit that develops the latent image on the latent image carrier, at least the latent image carrier and the developing unit are shared as one unit. In a process cartridge that is held by a holding body and is detachable from the image forming apparatus main body,
9. A process cartridge comprising the developing device according to claim 1, wherein the developing device is any one of claims 1, 2, 3, 4, 5, 6, 7, and 8.

Images