JP2011053604A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which suppresses the detection error of a toner concentration detection means due to toner characteristic fluctuations accompanying the lot change of replenished toner. <P>SOLUTION: The image forming apparatus includes: a developing means which includes the toner concentration detection means detecting the toner concentration of a two-component developer; a toner replenishing means which includes a toner container storage body storing a toner container and replenishes toner to the developing means; a storage means which is provided in the toner container and stores the toner characteristic information of the toner included in the toner container; a data processing means which allows the storage means to store data; a control means which changes the sensitivity of the toner concentration detection means; a passed sheet number obtaining means which obtains the number of passed sheets of the developing means; and an image area ratio obtaining means which obtains input image area ratio data. When the data possessed by the toner container are updated, the control means changes the sensitivity of the toner concentration detection means, based on the toner characteristic information, passed sheet number information and the information of an image area ratio. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer that develops using a two-component developer containing toner and a magnetic carrier.

  Currently, an image forming apparatus including a developing device using a two-component developer containing toner and a magnetic carrier is widely used. As the image forming apparatus as described above, the toner concentration of the developer is set within a predetermined range by supplying toner from the toner container as necessary to the developer in the developing apparatus that consumes the toner accompanying development. There is something to keep inside.

  For example, if the toner concentration indicating the ratio of the toner to the magnetic carrier in the developer, such as the weight ratio, is too high, background stains may occur in the formed image or the detail resolution may be reduced. On the other hand, when the toner density is lowered, the density of the solid image portion is lowered or carrier adhesion to the latent image carrier is generated. Therefore, it is important to control the toner replenishment operation by detecting the toner concentration in the developer in the developing device, and to control the toner concentration so that the toner concentration in the developer is always within the appropriate range.

  As a method for detecting the toner concentration, generally, a method for detecting the amount of toner or the amount of magnetic carrier in the two-component developer present in a predetermined detection area in the developing device is used. A typical example of the above method is a method using a magnetic permeability sensor as a detection means. The magnetic permeability sensor outputs the magnetic characteristics of the magnetic carrier in the developer existing in the detection region as an electrical signal such as frequency and voltage.

  The output value of the magnetic permeability sensor monotonously decreases as the amount of magnetic carrier present in the detection area is within the practical toner concentration range, so the toner concentration in the developer is detected based on this output value. can do. However, it is known that the magnetic permeability of the developer changes depending on factors other than the toner concentration.

  For example, if the charge amount of the developer changes, the electrostatic repulsion force between carriers in the developer changes even if the toner concentration is the same, so the bulk density of the developer changes. If the charge amount is increased, the repulsive force between carriers having the same polarity is increased, so that the bulk density of the developer is decreased. When the bulk density is lowered, the magnetic permeability of the developer is lowered, and the output value of the toner concentration detection sensor based on the magnetic permeability detection method is lowered. That is, when the bulk density decreases, an output value indicating that the toner density is high in the magnetic permeability detection method is obtained.

  In general, the bulk density of the developer changes with a certain tendency depending on the durability of the developer, the use environment, the stirring stop time, and the like. Therefore, there is a problem that the output value of the toner density detection sensor changes depending on the developer durability, usage environment, stirring stop time, and the like.

  In order to solve the above problems, techniques for improving and stabilizing toner density detection accuracy of a toner density detection sensor using a magnetic permeability detection method have been proposed (for example, Patent Documents 1 to 4).

  For example, Patent Document 1 discloses a technique including a drive time acquisition unit that acquires an accumulated drive time from the start of use of a developing device, an absolute humidity acquisition unit that acquires absolute humidity, and a storage unit. The storage unit of the image forming apparatus described in Patent Document 1 stores the relationship between the cumulative drive time and the input control voltage applied to the sensor for a plurality of absolute humidity, and the sensor actually sets a predetermined voltage in the initial setting. The correction amount ΔV is obtained from the difference value between the initial input control voltage shown and the input control voltage at the absolute humidity at the initial setting in the relationship of the storage unit. At the time of image formation, the correction amount ΔV is applied to the relationship stored in the storage unit, and an input control voltage obtained from the cumulative drive time and absolute humidity at that time is applied to the toner density sensor.

Further, Patent Document 2 discloses a toner density sensor using a magnetic permeability detection method, a control unit capable of changing an input control voltage applied to the toner density sensor, and a drive time for acquiring a cumulative drive time from the start of use of the developing device. A technique including an acquisition unit, an absolute humidity acquisition unit that acquires absolute humidity, and a storage unit is disclosed. The storage unit of the image forming apparatus described in Japanese Patent Application Laid-Open No. 2004-228561 has a cumulative drive time and an input control voltage applied to the toner density sensor for a plurality of absolute humidity (2.0, 6.0, 16.0 g / m ³ ). The relationship of each is memorize | stored. And if the absolute humidity obtained by the temperature sensor and the humidity sensor was ^{5.0g / m 3, 2.0g / m} 3, obtaining an input control voltage for the accumulated drive time at 6.0 g / m ³ of each relationship A voltage (linear interpolation) that internally divides between the two input control voltages by the ratio of the absolute humidity difference is defined as the input control voltage.

  Patent Document 3 controls an input control voltage applied to a magnetic density detection type toner density sensor, compares the output voltage of the sensor with a predetermined reference voltage Vstd, and supplies toner based on the comparison result. A control unit for controlling the supply screw for the toner is disclosed, and this control unit discloses a technique for changing the input control voltage when the target density of the developer toner is changed to a predetermined amount or more. On the other hand, when the change amount of the target density falls below a predetermined amount, an attempt is made to reduce the toner density detection error by a control method in which the reference voltage Vstd is changed without changing the input control voltage.

  Furthermore, in Patent Document 4, the external input voltage of the toner density sensor is changed under the condition that the toner density is constant with an unused two-component developer, and the toner density of the two-component developer is detected by the toner density sensor. A mode in which the external input voltage is adjusted so that an appropriate toner density detection signal can be obtained from the toner density sensor, and the two-component developer is used by utilizing the output change amount of the toner density sensor with respect to the change amount of the external input voltage. A technique is disclosed that includes toner density sensor output correction means for changing the external input voltage and correcting the output of the toner density sensor when the toner density greatly changes from the unused developer.

  However, Patent Documents 1 to 4 do not consider changes in toner characteristic values due to variations in toner production lots that occur when toners are replaced, and the effects on the toner density detection sensor associated therewith. Further, Patent Documents 1 to 4 do not propose correcting the sensor sensitivity in order to suppress the detection error of the toner density detection sensor. In other words, in the techniques described in Patent Documents 1 to 4, the detection error of the toner density detection sensor due to the change in the toner characteristic value due to the toner production lot variation caused when the toner is replaced and the influence on the toner density detection sensor accompanying the change. There was a problem that it could not be sufficiently suppressed.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that suppresses a detection error of a toner density detecting unit due to a change in toner characteristics accompanying a change in a lot of replenished toner.

  An image forming apparatus according to the present invention includes a developing unit including a toner concentration detecting unit that detects a toner concentration of a two-component developer, and a toner container container that stores a toner container, and a toner supplying unit that supplies toner to the developing unit. A storage means for storing toner characteristic information of the toner contained in the toner container, a data processing means for storing data in the storage means, and a control for changing the sensitivity of the toner density detection means And an image area ratio acquisition means for acquiring the input image area ratio data, and the control means updates the data held in the toner container. In this case, the sensitivity of the toner density detecting means is changed based on the toner characteristic information, the number of sheets to be passed, and the image area ratio information.

  According to the present invention, it is possible to prevent a toner density detection error due to a change in toner characteristics at the time of toner replacement, and to realize highly accurate toner density control. Furthermore, it is possible to stably obtain an appropriate image density.

1 is a schematic diagram illustrating an overall schematic configuration example of an image forming apparatus according to an exemplary embodiment. FIG. 2 is a schematic diagram illustrating a schematic configuration example of a process cartridge of the image forming apparatus according to the embodiment. FIG. 4 is a diagram for explaining a developer flow in a developer conveyance path in the image forming apparatus according to the embodiment. FIG. 4 is a schematic diagram for explaining a flow of a developer in a developing device provided in the image forming apparatus according to the embodiment. FIG. 4 is a diagram illustrating a cross-sectional example at the rotation center of a supply screw of a developing device provided in the image forming apparatus according to the present embodiment. FIG. 4 is a schematic diagram for explaining a flow of a developer in a developing device provided in the image forming apparatus according to the embodiment. 1 is an external perspective view illustrating an example of a developing device of an image forming apparatus according to an exemplary embodiment. FIG. 5 is an enlarged schematic diagram illustrating an example of a vicinity of a downstream end in a conveyance direction of a supply conveyance path of a developing device provided in the image forming apparatus according to the present exemplary embodiment. FIG. 5 is a perspective view showing an example of the vicinity of a front end portion in a state where a stirring screw, a collection screw, and a doctor blade are removed from a developing device provided in the image forming apparatus according to the present embodiment. FIG. 4 is a perspective view showing an example of the vicinity of the near side in a state where a stirring screw, a recovery screw, a doctor blade, and a supply screw are removed from the developing device of the image forming apparatus according to the present embodiment. FIG. 3 is a perspective view illustrating a state example in which a stirring screw, a collection screw, a doctor blade, a supply screw, and a developing roller are removed from the developing device of the image forming apparatus according to the present exemplary embodiment. FIG. 3 is a perspective view illustrating a state example in which a stirring screw, a collection screw, a doctor blade, a supply screw, and a developing roller are removed from the developing device of the image forming apparatus according to the present exemplary embodiment. FIG. 4 is a cross-sectional view illustrating an example of a developing device in the vicinity of a downstream end in a conveyance direction of a supply conveyance path in the image forming apparatus according to the exemplary embodiment. FIG. 4 is a side cross-sectional view illustrating an example of a developing device in the vicinity of a downstream end in a conveyance direction of a supply conveyance path in an image forming apparatus according to an exemplary embodiment. FIG. 4 is a cross-sectional view illustrating an example of a developing device in the vicinity of a downstream end in a conveyance direction of a supply conveyance path in the image forming apparatus according to the exemplary embodiment. FIG. 4 is a side cross-sectional view illustrating an example of a developing device in the vicinity of a downstream end in a conveyance direction of a supply conveyance path in an image forming apparatus according to an exemplary embodiment. FIG. 4 is a cross-sectional view illustrating an example of a developing device in the vicinity of a downstream end in a conveyance direction of a supply conveyance path in the image forming apparatus according to the exemplary embodiment. 3 is a perspective view illustrating an example of a toner supply mechanism that supplies toner to a developing device of the image forming apparatus according to the exemplary embodiment. FIG. 3 is a perspective view illustrating an example of a toner container of a toner supply mechanism that supplies toner to a developing device of the image forming apparatus according to the exemplary embodiment; FIG. FIG. 2 is a block diagram illustrating a schematic configuration example of a control system of the image forming apparatus according to the present embodiment. FIG. 3 is a diagram schematically illustrating the shape of a toner for explaining a shape factor. It is a graph which shows the relationship between a developer state and sensor sensitivity. 6 is a graph showing a transition between the number of sheets to be passed and a toner density detection error. 6 is a graph showing a transition of a toner density detection error.

  Hereinafter, examples of embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, a tandem color image forming apparatus will be described as an example of the image forming apparatus, but the present invention is not limited to this. In the following, as an example of a tandem type color image forming apparatus, a case where the present invention is applied to a tandem type color laser copier (hereinafter simply referred to as “copier CM”) in which a plurality of photoconductors are arranged in parallel will be described as an example. Will be described.

  FIG. 1 shows an overall schematic configuration example of a copying machine CM according to this embodiment. The copier CM according to the present embodiment 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, an automatic document feeder 400 fixed on the scanner 300, and the like. It has.

<Image formation processing>
The printer unit 100 includes an image forming unit having 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 added after the numbers of the respective symbols indicate members for yellow, magenta, cyan, and black (the same applies hereinafter). In addition to the process cartridges 18Y, 18M, 18C, and 18K, the image forming unit 20 includes 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. Have.

  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 the surface of a photoconductor to be described later with laser light based on image data. The process cartridges 18Y, 18M, 18C, and 18K include a drum-shaped photosensitive member 1, a charger, a developing device 4, a drum cleaning device, a static eliminator, and the like.

  Hereinafter, the yellow process cartridge 18Y provided in the copying machine CM according to the present embodiment will be described.

  The surface of the photoreceptor 1Y is uniformly charged by a charger that is a charging unit. The surface of the photoreceptor 1 </ b> Y that has been subjected to the charging process is irradiated with laser light modulated and deflected by the optical writing unit 21. Thereby, the electric potential of the surface of the irradiation part (exposure part) irradiated to the laser light among the surface of the photoreceptor 1Y attenuates. By this attenuation of the surface potential, an electrostatic latent image for yellow is formed on the surface of the photoreceptor 1Y. The formed electrostatic latent image for Y is developed into a toner image by the developing device 4Y as developing means. The Y toner image formed on the yellow photoreceptor 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 yellow process cartridge 18Y, the photoreceptor 1Y cleaned by the drum cleaning device is neutralized by the neutralizer. 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. The detailed configuration of the process cartridge will be described later.

  Next, the intermediate transfer unit 17 provided in the copying machine CM according to the present embodiment will be described. The intermediate transfer unit 17 includes an intermediate transfer belt 110, a belt cleaning device 90, and the like. Further, the tension roller 14, the driving roller 15, the secondary transfer backup roller 16, the four primary transfer bias rollers 62 </ b> Y, 62 </ b> M, 62 </ b> C, and 62 </ b> K are also provided.

  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 a 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, respectively. A primary transfer electric field is formed in each primary transfer nip due to the influence of the primary transfer bias. For example, a primary transfer electric field is formed between the photoreceptor 1Y and the primary transfer bias roller 62Y facing the photoreceptor 1Y.

  As described above, the toner image formed on the photoreceptor 1Y is primarily transferred onto the intermediate transfer belt 110 due to the influence of the primary transfer electric field and nip pressure. On this Y toner image, the M, C, K toner images formed on the photoreceptors 1M, 1C, 1K are sequentially superimposed 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 transferred on the intermediate transfer belt 110 in a superimposed manner is secondarily transferred onto a transfer sheet or the like which is a recording medium (not shown) 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 provided in the copying machine CM according to the present embodiment 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.

  Of the two stretching rollers 23, the first stretching roller 23 disposed on the right side of FIG. 1 is between the intermediate transfer belt 110 and the paper between the secondary transfer backup roller 16 of the intermediate transfer unit 17. The conveyor belt 24 is sandwiched. 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 first stretching roller 23 by a power source (not shown). Due to the secondary transfer bias, the four color toner images on the intermediate transfer belt 110 of the intermediate transfer unit 17 are electrostatically moved from the belt side toward the first stretching roller 23 side in the secondary transfer nip. A secondary transfer electric field is formed.

  The transfer paper fed into the secondary transfer nip so as to synchronize with the four-color toner images on the intermediate transfer belt 110 by a later-described registration roller pair 49 is affected by the secondary transfer electric field and nip pressure. A color toner image is secondarily transferred. Instead of the secondary transfer method in which the secondary transfer bias is applied to the first stretching roller 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 in the lower part of the main body of the copying machine CM according to the present embodiment, a paper feeding cassette 44 that can accommodate therein a plurality of transfer papers as recording media stacked in a bundle of sheets. Are arranged so as to overlap in the vertical direction. 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 paper 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 feeds 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. As a result, at the secondary transfer nip, the four-color toner image on the intermediate transfer belt 110 is in close contact with the transfer paper. That is, the four-color toner image is secondarily transferred onto the transfer paper, and becomes a full-color image on, for example, a white transfer paper. The transfer paper on which a full-color image is formed in this way exits the secondary transfer nip as the paper transport belt 24 moves endlessly, and is then sent from the paper transport belt 24 to the fixing device 25.

  The fixing device 25 provided in the copying machine CM according to this embodiment includes a belt unit that moves the fixing belt 26 endlessly while being stretched by two rollers, and a pressure that is pressed toward one roller of the belt unit. And a roller 27. 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. Here, of the two rollers that stretch the fixing belt 26, the roller that is pressed from the pressure roller 27 is a first roller.

  Of the two rollers in the belt unit, the first 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 fixed in the fixing device 25 is stacked on the stack portion 57 provided outside the left side plate in the drawing of the copying machine CM main body, or in order to form a toner image on the other surface. It returns to the above-mentioned secondary transfer nip.

  When the copying machine CM forms a multi-color image composed of two or more colors of toner as described above, the intermediate transfer belt 110 is stretched with the upper stretched surface substantially horizontal so that the upper All the photoreceptors 1Y, 1M, 1C, and 1K are brought into contact with the mount surface. On the other hand, when forming a monochrome image consisting only of 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 placed on the photoreceptor 1Y. 1M and 1C. Of the four photoconductors 1Y, 1M, 1C, and 1K, only the 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, so that each member of the photosensitive member 1 and the developing device 4 and the developer in the developing device 4 are unnecessary. Consumption can be prevented.

<Image reading process>
When copying a document (not shown), 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 one-sided original that is bound in a main form, the original 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. After the document is set on the contact glass 32, the one-bound document is pressed by the closed automatic document feeder 400.

  When a copy start switch or the like (not shown) is pressed after the document is set in this manner, 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 the original reading operation, each device in each of the process cartridges 18Y, 18M, 18C, and 18K, the intermediate transfer unit 17, the secondary transfer device 22, and the fixing device 25 start 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 photosensitive members 1Y, 1M, 1C, and 1K. . These toner images are four-color toner images that are superimposed and transferred onto the intermediate transfer belt 110.

  When the document reading operation is started, 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 multiple stages in the paper bank 43. The fed transfer paper is separated one by one by the separation roller 45 and enters the reverse feeding path 46, and is then transported toward the secondary transfer nip by the transport roller pair 47. Instead of such paper feeding from the paper feeding cassette 44, paper feeding from the manual feed tray 51 may be performed.

  Although not shown, the copier CM according to the present embodiment includes a control unit including a CPU that controls each device in the copier CM, an operation display unit including a liquid crystal display, various key buttons, and the like. It is equipped with. The operator sends a command to the control unit by a key input operation or the like on the operation display unit, so that the single-sided print mode, which is a mode for forming an image only on one side of the transfer paper, has, for example, three modes. You can select one of them. Examples of the three single-sided print modes include a direct discharge mode, a reverse discharge mode, and a curl discharge mode with reverse.

<Process cartridge>
FIG. 2 is an enlarged configuration diagram showing a developing device and a photoreceptor provided in one process cartridge among the four process cartridges provided in the copying machine according to the present embodiment. The four process cartridges 18Y, 18M, 18C, and 18K have substantially the same configuration except that the colors of toner to be handled are different. Therefore, in FIG. 2, the suffixes Y, M, C, and K attached to the developing device 4 and the photoreceptor 1 are omitted.

  As shown in FIG. 2, the surface of the photosensitive member 1 is charged by charging means (not shown) while rotating in the direction of arrow G in the drawing. The charged surface of the photosensitive member 1 is supplied with toner from the developing device 4 to an electrostatic latent image formed by laser light emitted from an exposure device (not shown) to form a toner image.

  The developing device 4 has a developing roller 5 that is a developer carrying member that supplies the toner to the electrostatic latent image on the surface of the photoreceptor 1 while moving in the direction of arrow I in the drawing. The developing roller 5 includes a rotatable developing sleeve, and a magnetic material (not shown) made up of a plurality of magnetic poles is disposed therein. With this magnetic body, the developer can be held on the surface of the developing roller 5.

  Further, the developing device 4 includes a supply screw 8 that is a supply conveying member that conveys the developer in the inner direction of FIG. 2 along the axial direction of the developing roller 5 while supplying the developer to the developing roller 5. Yes. A doctor blade 12 that is 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 developing area and separated from the surface of the developing roller 5 on the downstream side in the surface movement direction from the developing area that is the portion of the developing roller 5 facing the photoreceptor 1. Is provided opposite to the developing roller 5. The collection conveyance path 7 includes a spiral collection screw 6 that 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. The collection screw 6 is arranged in parallel to the axial direction. A supply / conveyance path 9 including the supply screw 8 is provided in the lateral direction of the developing roller 5, and a recovery / conveyance path 7 including the recovery screw 6 is provided below the developing roller 5.

  Note that the developer is 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. Further, a magnetic body having a magnetic pole arrangement in which a repulsive magnetic field is formed at a position 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 includes a spiral agitating screw 11 that is an agitating / conveying member that conveys the developer in the direction opposite to the supply screw 8 while stirring the developer along the axial direction of the developing roller 5. ing. The stirring screw 11 is disposed in parallel to the axial direction.

  The supply conveyance path 9 and the stirring conveyance path 10 are partitioned by a first partition wall 133 that is a partition member. 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 figure, and the supply conveyance path 9 and the agitation conveyance path 10 are separated from each other. Communicate. The supply conveyance path 9 and the recovery conveyance path 7 are also 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.

  In addition, the two developer conveyance paths of the agitation conveyance path 10 and the recovery 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.

  Here, as the supply screw 8, the recovery screw 6, and the stirring screw 11 that are developer conveying members, a resin or metal screw can be applied. In addition, for example, the diameter of each screw is set to φ22 mm, the screw pitch is set to 2 mm with the supply screw 8 being 50 mm, the collecting screw 6 and the stirring screw 11 are set to 1 mm with 25 mm, and the rotation speed is set to about 600 rpm. be able to.

  On the developing roller 5, for example, the developer thinned by a doctor blade 12 made of stainless steel, for example, is transported to a developing area that is a portion facing the photoreceptor 1 for development. The surface of the developing roller 5 may be subjected to, for example, a V groove or a sand blast process. Further, as the developing roller 5, an Al (aluminum) or SUS (stainless steel) element tube having a diameter of 25 mm can be applied, and the gap between the doctor blade 12 and the photoreceptor 1 is preferably about 0.3 mm. . In the above description, the developing device 4 has been described with specific numerical examples, but the present invention is not limited to this.

  The developed developer is recovered by the recovery transport path 7, transported to the front side of the cross section in FIG. 2, and transferred to the stirring transport path 10 through the opening of the first partition wall 133 provided in the non-image area. The The toner is conveyed to the agitating and conveying path 10 from a toner replenishment port 95 (described later) provided on the upper side of the agitating and conveying path 10 near the opening of the first partition wall 133 on the upstream side in the developer conveying direction in the agitating and conveying path 10. Is done.

  FIG. 3 is a perspective view of the developing device for explaining the flow of the developer in the developer transport path in the image forming apparatus according to the present embodiment. FIG. 4 is a schematic diagram illustrating the flow of the developer in the developing device provided in the image forming apparatus according to the present embodiment. Next, the circulation of the developer in the three developer conveyance paths will be described. 3 and 4, each arrow 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 conveyed to the downstream end in the conveyance direction of the supply conveyance path 9 is, as indicated by an arrow E in FIG. 4, an excessive opening portion of the first partition wall 133. 92 is supplied to the stirring and conveying path 10.

  On the other hand, the developer supplied to the developing roller 5 is used for development in the developing region, and then separated and 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, as indicated by an arrow F in FIG. It is supplied from the collection opening 93 to the stirring and conveying path 10.

  The agitating and conveying path 10 agitates the supplied excess developer and the collected developer, and conveys them to the downstream side of the agitating screw 11 in the conveying direction and to the upstream side of the supplying screw 8 in the conveying direction. Excess developer and recovered developer conveyed upstream in the conveyance direction of the supply screw 8 are supplied to the supply conveyance path 9 from the supply opening 91 of the first partition wall 133 as indicated by an arrow D in FIG. .

  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. To do. Then, the agitated developer is transported to the upstream side in the transport direction of the supply transport path 9 communicating with the supply opening 91 on the downstream side in the transport direction.

  A toner concentration detection sensor including a magnetic permeability sensor, which will be described later, is provided below the agitation conveyance path 10, and the toner concentration detection sensor has characteristics based on the magnetic permeability of the developer to be detected, that is, the carrier. The toner concentration in the developer is measured by detecting the density. A toner replenishment control device, which will be described later, is operated based on the sensor output, and toner is replenished from a toner storage portion, which will be described later.

  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. For this reason, it is possible to prevent the toner concentration 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.

  Thereby, since the sufficiently stirred 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 stirred. As described above, 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 made 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 the arrow D is to push the developer to the downstream side of the agitation transport path 10 by the rotation of the agitation screw 11 so that the developer is raised and transported to the supply transport 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, causing the carrier film in the developer to be scraped or the toner to become spent, and the stability of the image quality cannot be maintained accordingly. . That is, 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.

  Therefore, in the developing device 4 included in the image forming apparatus according to the present embodiment, the supply conveyance path 9 is disposed obliquely above the stirring conveyance path 10 as shown in FIG. By disposing it obliquely above, it is possible to reduce the stress of the developer in the movement of the developer indicated by the arrow D, as compared with the case where the supply conveyance path 9 is provided vertically above the stirring conveyance path 10 to lift the developer. it can. Further, in the developing device 4 of the image forming apparatus according to the present embodiment, the supply transport path 9 and the stirring transport path 10 are arranged obliquely so that the upper wall surface of the stirring transport path 10 is supplied as shown in FIG. It arrange | positions so that it may become a position higher than the lower wall surface of the conveyance path 9. FIG.

  Lifting the supply conveyance path 9 vertically upward with respect to the agitation conveyance path 10 raises the developer by the pressure of the agitation screw 11 against gravity, so that the developer is stressed. On the other hand, in this embodiment, since the upper wall surface of the agitation transport path 10 is arranged to be higher than the lower wall surface of the supply transport path 9, the developer present at the highest point of the agitation transport path 10 is supplied. It is possible to flow into the lowest point of the conveyance path 9 against the gravity and to reduce the stress applied to the developer.

  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. As this fin member, a plate-like member composed of a side parallel to the axial direction of the stirring screw 11 and a side orthogonal to the axial direction of the stirring screw 11 can be applied. By scooping up the developer with this fin member, the developer can be more efficiently delivered from the stirring conveyance path 10 to the supply conveyance path 9.

  In the developing device 4 of the image forming apparatus according to the present embodiment, as shown in FIG. 2, the center distance A between the developing roller 5 and the supply screw 8 is the center distance between the developing roller 5 and the stirring screw 11. The supply screw 8 and the stirring screw 11 are arranged so as to be shorter than B. Thereby, 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 rotates in the direction of arrow C in the drawing, which is a counterclockwise direction when viewed from the front side in FIG. 2, and the developer is lifted and supplied along the shape of the stirring screw 11. It is transferred to the conveyance path 9. Thereby, the developer can be lifted efficiently, and the stress applied to the developer can be further reduced.

  FIG. 5 is a view of a cross-sectional example at the rotation center of the supply screw of the developing device provided in the image forming apparatus according to the present embodiment as seen from the direction of arrow J in FIG. A development area H indicates a development area in which the developing roller 5 that is a developer carrying member supplies toner to the photoreceptor 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.

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

  On the other hand, in the developing device 4 configured as shown in FIG. 6, the supply opening 91 is provided within the developing region width α. That is, as illustrated in FIG. 5, the developing device 4 illustrated in FIG. 6 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 the agitation conveyance path 10 from the supply conveyance path 9. In addition, an excess opening 92 for dropping the developer is provided in the development region width α. Thus, since the supply opening 91 is provided in the developing region width α, the upstream side in the transport direction of the supply transport path 9 is upstream in the transport direction upstream region β of the supply transport path 9 relative to the developing device 4 in FIG. Can be shortened. Further, since the surplus opening 92 is provided in the developing region width α, the downstream side in the transport direction of the supply transport path 9 may be shorter than the developing device 4 in FIG. 4 by the downstream region γ of the supply transport path 9. it can. Therefore, since the developing device 4 shown in FIG. 6 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 saved as compared with the developing device 4 shown in FIG. Space can be further increased.

  FIG. 7 is an external perspective view showing an example of the developing device of the image forming apparatus according to the present embodiment. Next, a description will be given of a position where toner is supplied to the developer conveyance path including the supply conveyance path 9, the agitation conveyance path 10, and the recovery conveyance path 7 of the developing device 4 described above. In the image forming apparatus according to the present embodiment, as shown in FIG. 7, a toner replenishing port 95 for replenishing toner can be 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 the extended line in the conveyance direction of the supply conveyance path 9 and corresponds to a vacant space in the downstream region γ of the supply conveyance path 9 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. The toner replenishing port 95 is not limited to the upper part of the agitating / conveying path 10 in the conveying direction, but may be provided above the downstream end of the collecting / conveying path 7.

  Further, a toner replenishing port 95 may be provided just above the collection opening 93 which is a place 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. Further, since the developer is likely to be mixed in the collection opening 93 which is a delivery portion, the developer can be more efficiently stirred by replenishing at this position.

  As in the developing device 4 described with reference to FIG. 6, 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 delivering 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, further space saving of the upper portion of the developing device 4 can be achieved. Thus, the space of the entire developing device 4 can be saved.

  In addition, by providing the toner replenishing port 95 in an empty space by providing the surplus opening 92 within the developing region width α, the developing device 4 can be reduced in size. Furthermore, the developer can be efficiently stirred by replenishing the toner from above the collection opening 93 that is a developer delivery section from the collection conveyance path 7 to the stirring conveyance path 10. Further, by providing the developing device 4 as the developing means of the printer unit 100 provided in the copying machine CM as the image forming apparatus, it is possible to save the space of the entire apparatus.

  Toner replenishing port 95 is replenished with toner in the toner container by a toner replenishment control device as toner replenishing means. It is to be noted that a developer containing a mixture of toner and carrier is accommodated in the toner container, and also serves as a developer container for storing a replenishment developer for replenishing the carrier according to the toner replenishment amount. You can also.

  The carrier in the developer container is preferably the same as the carrier used for the developer in the developing device. As a result, even when the replenishment developer is supplied, the developer in the developing device can easily maintain the characteristics of the initial agent, and the change in image quality can be suppressed.

  The carrier concentration in the replenishment developer is preferably 1% by mass to 30% by mass, and particularly preferably 5% by mass to 20% by mass. When the amount is less than 1% by mass, the effect of suppressing the deterioration of the developer is hardly exhibited, and when it exceeds 30% by mass, the amount of developer discharged is too large, leading to an increase in cost.

  When the toner container does not serve as the developer container, a carrier supply control device (not shown) can supply the carrier in the carrier container (not shown) to the developing device from the toner supply port. .

  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 downstream end in the conveyance direction of the supply conveyance path 9 is the agitation conveyance path 10. The circulating conveyance member that applies a conveyance force to the developer in the agitation conveyance path 10 that is a circulation conveyance path is the agitation screw 11. Furthermore, 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 in the supply conveyance path 9 for discharging the passed developer 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 conveyed to the outside of the developing device 4 by rotating a discharge screw 2a that is a discharge conveyance member as shown in FIG. Ejection from the developing device 4 is performed. The discharge conveyance path 2 is provided on the downstream side of the supply conveyance path 9 in the conveyance direction so as to be adjacent to the supply conveyance path 9 with the discharge partition wall 135 interposed therebetween. The developer discharge port 94 is an opening provided in the discharge partition wall 135 so as to communicate the supply conveyance path 9 and the discharge conveyance path 2.

  FIG. 8 is an enlarged schematic view showing an example of the vicinity of the downstream end in the transport direction of the supply transport path of the developing device provided in the image forming apparatus according to the present embodiment. As shown in FIG. 8, the developing device 4 of the image forming apparatus according to the present embodiment reaches the vicinity of the downstream end in the transport direction of the supply transport path 9 and does not enter the surplus opening 92 that is the circulation opening. May be provided with a supply downstream end wall surface 80 as a developer retaining means for retaining in the vicinity of the surplus opening 92 near the developer discharge port 94. Further, the developer that has reached the position of the developer discharge port 94 is allowed to pass through the developer discharge port 94 out of the retained developer that has been retained by the supply downstream end wall surface 80 above the surplus opening 92. You may make it provide in.

  Of the developer P that reaches the vicinity of the downstream end in the transport direction of the supply transport path 9, the surplus developer that cannot enter the surplus opening 92 and overflows from the surplus opening 92 is blocked by the supply downstream end wall surface 80. The retained developer T is stopped. In this embodiment, by applying the above configuration, when the bulk of the staying developer T increases, the developer that reaches the developer discharge port 94 provided above the surplus opening 92 is indicated by an arrow K. As shown in FIG. 8, the developer is discharged out of the developing device 4 through the developer discharge port 94.

  The amount of the staying developer T is determined by the amount of developer that reaches the vicinity of the downstream end in the transport direction of the supply transport path 9 indicated by the arrow L in FIG. 8 and the development that passes through the excess opening 92 indicated by the arrow E in FIG. Increase / decrease depending on the balance with the dose. In a state where the developing device 4 is driven, an amount of developer P 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 conveyance of the supply conveyance path 9 indicated by the arrow L in FIG. 8 is larger than the amount of developer delivered from the supply conveyance path 9 to the stirring conveyance path 10 through the excessive opening 92 indicated by the arrow E in FIG. In the state where the amount of developer reaching the vicinity of the downstream end in the direction is larger, the amount of staying developer T increases, and in the opposite state, the amount of staying developer T decreases.

  Further, in the state where the staying developer T is present, the necessary amount of developer required for circulation is always transferred to the stirring and conveying path 10 through the surplus opening 92, and therefore, the direction toward the stirring and conveying path 10. There is no shortage of developer amount. That is, in the state where the staying developer T is present, the necessary amount of developer is supplied from the agitating and conveying path 10 to the agitating and conveying path 9 as the necessary amount of developer is directed to the agitating and conveying path 10. This is a state in which the developer amount in the developing device 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 T, the staying developer T is at the position of the developer discharge port 94. When the amount does not reach, the developer is not discharged out of the developing device 4. At this time, since the staying developer T 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 case of the developing device 4 as described above, the developer P transported in the supply transport path 9 undulates in a state where the amount of developer in the developing device 4 is not increased, and the developer is partially Even if the phenomenon of increasing the bulk occurs, it is possible to prevent the developer from being continuously discharged. That is, when the amount of the staying developer T increases even if the amount is small, the portion where the bulk of the developer reaches the position of the developer discharge port 94 and reaches the vicinity of the downstream end in the transport direction of the supply transport path 9. The developer exceeding the amount of developer passing through 92 is discharged from the developer discharge port 94.

  However, when the portion where the volume of the developer is low reaches the vicinity of the downstream end in the transport direction of the supply transport path 9, the amount of the staying developer T decreases, and the staying developer T reaches the position of the developer discharge port 94. It becomes the extent of not doing. 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 (volume) only increases or decreases. Will not be discharged.

  Further, if the amount of staying developer T increases even if the amount is small, unless the developer reaches the position of the developer discharge port 94, the portion where the bulk of the developer is increased or decreased is the downstream end in the conveyance direction of the supply conveyance path 9. Even if it reaches the vicinity, the amount (bulk) of the staying developer T only increases or decreases, and the developer is not discharged.

  According to the present embodiment, it is possible to prevent the developer from being continuously discharged, so that the developer P transported in the supply transport path 9 undulates while the amount of developer in the developing device 4 is not increasing. Even if the phenomenon that the bulk of the developer partially increases occurs, the required amount of the developer P in the developing device 4 can be maintained. Further, since the necessary amount of the developer P 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 in the transport direction of the supply transport path 9 is, for example, the same position in the transport direction of the developer transport section 9 and the developer transport section where the developer is transferred from the supply transport path 9 to the stirring transport path 10. It is a place to become. In other words, this is where the conveying force by the supply screw 8 ends, and where the developer is blocked by the supply downstream end wall surface 80. By providing the developer discharge port 94 here, after the developer is transported by the supply screw 8, it is received by the supply downstream end wall surface 80, and finally reaches the height of the developer discharge port 94 among the staying developer. It becomes possible to discharge only.

  FIG. 9 is a perspective view illustrating an example of the vicinity of the front end portion in a state where the stirring screw, the collection screw, and the doctor blade are removed from the developing device of the image forming apparatus according to the present embodiment. FIG. 10 is a perspective view of the developing device of the image forming apparatus according to the present embodiment, as seen from a different direction from FIG. 9, in the vicinity of the near side in a state where the supply screw is further removed from the state shown in FIG. 9. FIG. 11 is a perspective view showing an example of the developing device of the image forming apparatus according to the present embodiment, in which the developing roller is further removed from the state shown in FIG. FIG. 12 is a perspective view showing an example of the developing device of the image forming apparatus according to the present embodiment when the developing device in the same state as FIG. 11 is viewed from substantially the same direction as FIG.

  Referring to FIGS. 9 to 12, the rotation direction of the supply screw 8 is clockwise, that is, in the direction of the arrow M as shown in FIG. 2, and the developer is lifted from below with respect to the developing roller 5. It is rotating in the feeding direction. 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. In this embodiment, the rotation direction of the supply screw 8 of the developing device 4 is shown in FIG. 2 because the developer supply performance is more stable when the developer is supplied while being lifted from below than when the developer is supplied while being scattered. However, it is set clockwise.

  In particular, as in the developing device 4 of the present embodiment, when 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, the developer amount is downstream of the supply conveyance path 9. Decreases as you go. For this reason, it is better in terms of developer supply that the developer is pumped 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. . If the developer discharge port 94 is simply provided at a predetermined height of the supply transport path 9 in the developer transport path, the jumped developer flies and passes through the developer discharge port 94. May be discharged.

  As described above, when the developer jumps and is discharged, 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 state or less than the appropriate amount. Even so, the jumped developer may be discharged. When the developer that has jumped off is discharged, the developer may be discharged from the developer discharge port 94 even though the developer in the developing device 4 is in an appropriate amount or less. In addition, the amount of developer in the developing device 4 may be less than the required amount, and the supply of the 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.

  On the other hand, by making the developer stay in the vicinity of the developer discharge port 94 as in this embodiment, the developer can be prevented from jumping in the vicinity of the developer discharge port 94. However, even if the developer in the vicinity of the developer discharge port 94 is prevented from jumping, the developer at a location away from the developer discharge port 94 may jump and be discharged from the developer discharge port 94.

  In order to prevent such inconvenience, in the developing device 4 of the present embodiment, the developer ejected by the supply screw 8, which is a developer transporting screw, rotates to transport the developer. A block member 3 is provided as a small developer discharge preventing member that closes the path toward the bottom. The block member 3 is provided, and the developer that flies due to the conveying operation of the supply screw 8 is blocked so that the jumped developer is prevented from being discharged, and the development in the developing device 4 is prevented. It is possible to prevent the developer from being discharged despite the increase in the amount of the agent.

  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.

  As the block member 3, an R-shaped resin member whose bottom surface follows the shape of the supply screw 8 can be applied to the upper portion of the supply conveyance path 9. The R shape along the shape of the supply screw 8 enables the bottom surface of the block member 3 to be entirely close to the supply screw 8 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. 12, in this embodiment, the block member 3 protrudes around the developer discharge port 94 of the supply conveyance path 9, so that the supply screw 8 is conveyed with respect to the block member 3. The supply conveyance path 9 where the block member 3 is provided is narrower than the supply conveyance path 9 on the upstream side in the direction. For this reason, 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. 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 developer is prevented from jumping up due to the rotation of the supply screw 8, and the upper part of the wing portion of the supply screw 8 protrudes from the developer surface. The change in the developer surface due to the generated splash of the supply screw 8 is alleviated in the vicinity of the developer discharge port 94. That is, it is possible to discharge with high sensitivity to the increase or decrease of the developer in the developing device 4.

  By providing the block member 3 as described above, when the developer amount in the developing device 4 is increased by supplying the developer and the bulk of the developer in the supply conveyance path 9 is increased, this corresponds to the increased amount. The developer overflows from the developer discharge port 94.

  FIG. 13 is a cross-sectional view showing an example of the developing device near the downstream end in the transport direction of the supply transport path as viewed from the same direction as in FIG. FIG. 14 is a side cross-sectional view showing an example of the developing device near the downstream end in the transport direction of the supply transport path as seen from the same direction as FIG. 13 and 14 show the state of the developer P in the developing device 4 in a state where the amount of the 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. The flow is shown.

  As shown in FIGS. 13 and 14, 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 the circulation conveyance path. As a result, the developer P does not overflow at the surplus opening 92 provided in the first partition wall 133 that is the boundary between the supply conveyance path 9 and the agitation conveyance path 10, and the bulk of the staying developer does not increase. For this reason, the developer is hardly guided 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.

  FIG. 15 is a cross-sectional view showing an example of the developing device near the downstream end in the transport direction of the supply transport path as viewed from the same direction as FIG. FIG. 16 is a side sectional view showing an example of the developing device in the vicinity of the downstream end in the transport direction of the supply transport path as seen from the same direction as FIG. 15 and 16 show a state in which 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. The flow of the developer P of the developing device 4 is shown.

  As shown in FIGS. 15 and 16, 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 transport direction of the supply transport path 9 has no place to go, and the bulk of the staying developer increases in the upward direction. 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 developing device 4 is discharged by the discharge screw 2 a in the discharge conveyance path 2. It will be discharged to the outside.

  The developing device 4 in the present embodiment reaches the height of the developer discharge port 94 when the bulk of the staying developer at the most downstream portion in the conveyance direction of the supply conveyance path 9 exceeds the height of the developer discharge port 94. Since the developer is discharged, it is possible to prevent a shortage of the developer that transports the supply transport path 9 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 photoreceptor 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. 14, 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 supply transport path 9 in the transport direction most downstream end. The developer stays in the vicinity. Details of this state will be described below.

  In this embodiment, when the bulk of the staying developer staying in the vicinity of the most downstream end in the transport direction of the supply transport path 9 exceeds a predetermined height, for example, the height of the developer discharge port 94, the developing device 4 It is the structure which discharges a part. In other words, the developer discharge port 94 and the discharge conveyance path 2 discharge the developer whose bulk of the staying developer near the downstream end in the conveyance direction of the supply conveyance path 9 has reached the height of the developer discharge port 94. is there.

  Therefore, the developer amount in the developing device 4 is stable in a state where the stagnant developer is present in a volume that does not reach the height of the developer discharge port 94 near the most downstream end in the conveyance direction of the supply conveyance path 9. It becomes. This is because the amount of the developer that reaches the most downstream end in the conveyance direction conveyed through the supply conveyance path 9 and the amount of the developer that is delivered to the stirring conveyance path 10 through the supply conveyance path 9 and the surplus opening 62. Due to the equilibrium, the developer stays in a volume that does not reach the height discharged from the developer discharge port 94 in the vicinity of the downstream end in the conveyance direction of the supply conveyance path 9.

  In 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 developer delivered from the supply conveyance path 9 indicated by the arrow E in FIG. 6 to the stirring conveyance path 10. The amount of the developer that is transported through the supply transport path 9 indicated by the arrow L in FIG. 4 and reaches the most downstream end in the transport direction is larger than the amount. At this time, the amount of the developer staying in the vicinity of the most 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 (for example, the developer discharge port 94), the development for the increased amount when the amount of the developer in the developing device 4 is increased. Since the developer is discharged, the amount of developer in the developing device 4 can be maintained in a certain range with good accuracy.

  As a result, the amount of developer transported through the supply transport path 9 is stabilized, so that the shortage of developer transporting through the supply transport path 9 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.

  Further, 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 to the developer provided on the discharge partition wall 135. Since the developer is discharged from the outlet 94, the developer in the developing device 4 can be replaced with high accuracy with a simple structure.

  Furthermore, the supply conveyance path 9 and the agitation conveyance path 10 are provided so as to be adjacent in the vertical direction across the first partition wall 133 that is a supply circulation partition wall, 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 per hour by the supply screw 8 to the downstream end and the developer passing through the excess opening 92 per time. It changes depending on the difference from the amount. 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 in the vicinity of 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 the developer discharge port 94 that is the discharge opening of the developing device 4 and the surplus opening 92 that is the circulation opening. In the developing device 4 of the present embodiment, as shown in FIGS. 6, 14, and 16, the developer discharge port 94 and the surplus 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 provided 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 developer amount in the developing device 4 is an appropriate amount. The developer passes only through the excess opening 92 located below, moves to the stirring conveyance path 10 and circulates in the developing device 4. When the amount of the developer in the developing device 4 increases and the bulk 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 the above 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 corresponding to the amount increased at the developer discharge port 94 is accurately discharged to replace the developer.

  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 that has passed through the development region carried by the developing roller 5, the developer conveyed into the collection conveyance path 7 even if the amount of developer in the developing device 4 changes. Almost no change occurs, 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. 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. Inadequate because there is a risk of lack of developer.

  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.

  FIG. 17 is a cross-sectional view showing an example of the developing device in the vicinity of the downstream end in the transport direction of the supply transport path as seen from the same direction as in FIG. Referring to FIGS. 2 and 17, 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. The flow of the developer P is shown.

  As shown in FIGS. 2 and 17, 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 agitation conveyance path 10 that is a circulation conveyance path. As a result, the developer P does not overflow at the surplus opening 92 provided in the first partition wall 133 that is the boundary between the supply conveyance path 9 and the agitation conveyance path 10, and the bulk of the staying developer 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. Since other configurations have been described in detail with reference to FIGS. 2 and 13, the same portions are denoted by the same reference numerals and redundant description is omitted.

  FIG. 17 is a cross-sectional view showing an example of a developing device equipped with a toner concentration detection sensor in the image forming apparatus according to the exemplary embodiment. Here, the toner concentration detection sensor 140 based on the magnetic permeability detection method is applied, but the present invention is not limited to this. The toner density sensor 140 of the magnetic permeability detection method measures the toner density in the developer by detecting the characteristic based on the magnetic permeability of the developer to be detected, that is, the density of the carrier. For example, when the toner concentration is low, the density of the carrier, which is a magnetic material, is relatively high, so that the magnetic permeability is high and the output of the toner concentration sensor 140 is high. On the other hand, when the toner concentration is high, the density of the carrier, which is a magnetic material, is relatively low, so that the magnetic permeability is low and the output of the toner concentration sensor 140 is low.

  Although FIG. 17 shows an example in which the developer is attached to the lower part of the developer conveyance path for supplying the developer to the developing roller 5, the attachment position of the toner density sensor 140 is not limited to this. Generally, the residual developer once developed by the developing roller 5 is often collected because the toner component is reduced. Therefore, it is preferable to install the developer so that the toner concentration of the developer existing in the developer conveyance path before the development, which supplies the developer to the developing roller 5 in general, can be measured. Based on the detection result of the toner concentration detection sensor 140, separately stored toner can be supplied to the developing device 4 so that the toner concentration of the developer P can be managed within an appropriate range.

  FIG. 18 is a perspective view illustrating an example of a toner replenishing mechanism that replenishes toner to the developing device of the image forming apparatus according to the exemplary embodiment. FIG. 19 is a perspective view showing an example of a toner container of the toner supply mechanism shown in FIG. In the toner replenishing mechanism 150 shown in FIG. 18, toner serving as toner storage means that stores toner to be supplied to each developing device 4 provided for each process cartridge 18 that is an image forming unit of each color as shown in FIG. 1. In the present embodiment, four containers of black, magenta, cyan, and yellow are set and arranged in a set unit (not shown) provided in the main body of the copier CM from the lower left to the upper right in FIG. ing.

  Since the mechanism for supplying toner from each color toner container 141 to each developing device 4 is the same, the black toner container located at the forefront in FIG.

  In the set portion for setting the toner container 141, a nozzle 90 inserted into the container 141 is provided in a machine frame (not shown), and the nozzle 142 and the powder pump 70 are connected by a toner supply tube 143. Yes. By setting the toner container 141 in the setting portion, the tip of the nozzle is inserted into the valve chamber of the mounting member 101 attached to the lower part of the toner container 141, and the powder container 70 communicates with the toner container 141.

  The powder pump 70 is driven via a connection gear 74 from a drive shaft gear 73 mounted on a drive shaft 72 that is rotationally driven by a drive motor 71. As the powder pump 70, a well-structured MONO pump can be employed. The toner transferred by the powder pump 70 is once stored in the sub hopper 75, and is supplied to the developing device 4 from the toner replenishing port 76 below the sub hopper 75.

  A toner container 141 shown in a perspective view in FIG. 19 includes a bag-like toner container 144 and an attachment member 101 (discharge member). The toner container 144 can be formed of, for example, a bag-shaped resin formed by welding a film-like resin having a thickness of about 50 to 300 μm called a soft packaging material, or a molded resin, but is not limited thereto. It is not a thing.

  The storage unit 145 stores ID information unique to the toner container. As the unique information, for example, information unique to the toner contained in the toner container, such as the production date of the toner and the production lot, is recorded. The storage means 145 is preferably an ID chip, a barcode, or the like that can be automatically read in cooperation with the reading device on the main body side. When the toner is replaced, the storage unit 145 for acquiring the characteristic value information of the set toner is used as an ID chip, so that the image forming apparatus main body side can read the information without contact, and the manual input and the input error Can be prevented.

<Control>
FIG. 20 is a block diagram illustrating a schematic configuration example of a control system of the image forming apparatus according to the present embodiment. As shown in FIG. 20, the image forming apparatus according to this embodiment includes a two-component developing type developing device 4 and a toner replenishing mechanism 150 that replenishes the developing device 4 with toner, and the developing device 4 detects magnetic permeability. It has a toner concentration detection sensor 140 that detects the toner concentration of the two-component developer according to the method.

  The toner replenishing mechanism 150 includes a toner container housing 144 that houses the toner container 141. The image forming apparatus acquires sensor control means 151 that can change the sensor sensitivity given to the toner density detection sensor 140, sheet passing number acquisition means 152 that acquires the sheet passing number of the developing device 4, and input image area ratio data. Image area ratio acquisition means 153. In this embodiment, the sensor sensitivity is assumed to be a sensor output voltage change amount per 1% toner concentration.

  The toner container 141 includes the above-described storage unit 145 that can write and read toner characteristic information contained in the toner container 141. In the present exemplary embodiment, the image forming apparatus main body includes a data processing device (main body control device) 154 that writes data to and reads data from the storage unit 145 (hereinafter simply referred to as storage). When the data held in the toner container 141 is updated, the toner characteristic information from the storage unit 145, the sheet passing number information from the sheet passing number acquiring unit 152, and the image area from the image area rate acquiring unit 153 are updated. The sensor control unit 151 is configured to change the sensor sensitivity of the toner density detection sensor 140 based on the rate information.

<Toner characteristics information>
Hereinafter, various toner characteristic information will be described. Hereinafter, the toner characteristic information will be described with specific numerical examples, but the present invention is not limited to this.

(Shape factor)
FIG. 21 is a diagram schematically showing the shape of the toner in order to explain the shape factor SF-1. The shape factor SF-1 is preferably in the range of 100 to 180. The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is represented by the following formula (1). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.

  SF-1 = {(MXLNG) 2 / AREA} × (100π / 4) Expression (1)

  When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases. Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), introducing it into an image analyzer (LUSEX 3: manufactured by Nireco), and 100 particles can be analyzed and calculated.

  To provide an image forming apparatus capable of preventing toner density detection error by controlling the sensor sensitivity of the toner density detection sensor 140 based on the toner shape factor information at the time of toner replacement, and capable of highly accurate toner density control. it can.

  When the shape of the toner is close to a sphere, the contact state between the toner and the toner or the toner and the photoconductor becomes a point contact, so that the adsorbing force between the toners becomes weak and the fluidity becomes high. Further, the attracting force between the toner and the photoreceptor is weakened, and the transfer rate is increased. If either of the shape factors SF-1 and SF-2 exceeds 180, the transfer rate is lowered, which is not preferable.

(Roundness)
Next, the toner circularity preferably used in this embodiment will be described. The toner used in the exemplary embodiment preferably has an average circularity of 0.93 to 1.00. In this embodiment, the value obtained from the following formula (2) is defined as the circularity. The circularity is an index of the degree of unevenness of the toner particles, and indicates 1.00 when the toner is a perfect sphere, and the circularity becomes smaller as the surface shape becomes more complicated. In the following formula (2), L0 represents the circumference of a circle having the same projected area as the particle image, and L represents the circumference of the projected image of the particle.

  Circularity A = L0 / L (2)

  When the average circularity is in the range of 0.93 to 1.00, the surface of the toner particles is smooth, and the contact area between the toner particles and between the toner particles and the photosensitive member is small, so that the transferability is excellent. Since the toner particles have no corners, the developer agitation torque in the developing device is small, and the agitation drive is stabilized, so that no abnormal image is generated. If there is no angular toner particles in the toner that forms dots, the pressure is uniformly applied to the entire toner that forms dots when the pressure is brought into contact with the transfer medium during transfer, and transfer loss is unlikely to occur. Since the toner particles are not angular, the abrasive power of the toner particles themselves is small, and the surfaces of the photoreceptor, the charging member and the like are not damaged or worn.

  To provide an image forming apparatus capable of preventing toner density detection error by controlling the sensor sensitivity of the toner density detection sensor 140 based on the toner circularity information at the time of toner replacement, and capable of highly accurate toner density control. it can.

  Next, a method for measuring the circularity will be described. In addition, the measuring method of the following circularity is an example, and is not limited to this.

  The circularity can be measured using, for example, a flow type particle image analyzer FPIA-1000 manufactured by Toa Medical Electronics. As a specific measurement method, for example, 0.1 to 0.5 ml of a surfactant, preferably an alkylbenzene sulfonate is added as a dispersant in 100 to 150 ml of water from which impure solids have been removed in advance. Further, about 0.1 to 0.5 g of a measurement sample is added. The suspension in which the sample is dispersed is subjected to dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the shape and particle size of the toner are measured by the above apparatus with the dispersion concentration being 3000 to 10000 / μl.

(Degree of aggregation)
The method for measuring the degree of aggregation can be performed as follows. For example, a powder tester manufactured by Hosokawa Micron Corporation (manufactured by Hosokawa Micron Co., Ltd.) is used as the measuring device, and attached parts are set on the vibration table in the following procedure.

(B) Vibro chute (b) Packing (c) Space ring (d) Flui (3 types) Top>Medium> Bottom (e) Osaba

  Next, it fixes with a knob nut and operates a vibration stand. The measurement conditions are as follows.

Flute opening (top) 75μm
Flute opening (medium) 45μm
Flute opening (bottom) 22μm
Amplitude scale 1mm
Sampling amount 2g
Vibration time 15 seconds

  After the measurement, the degree of aggregation is obtained from the calculation shown below.

Weight% of powder remaining on upper stage sieve x 1 ... (a)
Weight% of powder remaining on the middle stage sieve x 0.6 (b)
Weight% of powder remaining on lower sieve x 0.2 (c)
The sum of the above three calculated values is defined as the degree of aggregation after deterioration (%).
That is, the aggregation value (%) = (a) + (b) + (c)

  By controlling the sensor sensitivity of the toner concentration detection sensor 140 based on the toner aggregation information at the time of toner replacement measured by the method as described above, a toner concentration detection error can be prevented and high-precision toner concentration control is possible. An image forming apparatus can be provided.

  FIG. 22 is a graph showing the relationship between the developer state and sensor sensitivity. Here, the sensor sensitivity with the initial agent and the sensor sensitivity with the deterioration agent after each of the image area ratios of 5%, 20%, 40%, and 70% and 5000 sheets passed are measured. It is showing.

  It can be seen from FIG. 22 that the sensor sensitivity differs between the initial agent and the deteriorated agent after passing the paper. For example, the deterioration agent after passing 5000 sheets at an image area ratio of 5% is 0.6, which is actually 0.25 higher than the initial sensor sensitivity of 0.35. It can be seen that the toner density cannot be detected accurately as it is. From this, it can be recognized that the sensor sensitivity of the toner concentration detection sensor 140 must be adjusted under a predetermined sheet passing condition.

  Next, using the image forming apparatus CM shown in FIG. 1 and the developing device 4 shown in FIG. 17, 10,000 sheets of solid images having an image area ratio of 5%, 20%, 50%, and 70% are passed through a predetermined number of sheets. The toner density detection error was measured at the sheet passing interval, and the detection error transition at the time of sheet passing was evaluated. Here, the toner density detection error is a value obtained by subtracting the converted toner density converted from the sensor output detection result from the actually measured toner density.

  FIG. 23 is a graph showing the transition of the number of sheets passed and the toner density detection error. FIG. 23 shows that the transition of the toner density detection error varies depending on the image area ratio. For example, when paper is passed with a low image area with an image area ratio of 5%, the detection error is greatly enlarged in the initial stage of paper passing, and when about 5000 sheets are passed, the error expansion stops and changes to a substantially constant value. I understand that On the other hand, in the case of passing the paper at an image area ratio of 40%, it can be seen that the detection error does not increase rapidly as compared with the case of 5%, and increases gradually with respect to the number of passed sheets. It can also be seen that when the image area ratio is 70%, as in the case of the image area ratio of 5%, the detection error greatly expands at the beginning of paper passing, and then changes at a constant value.

  Here, the sign of the detection error is different between the image area ratio 5% and 70%. This is because when the image area ratio is 5%, the amount of toner input is small, so that the toner and the carrier are deteriorated by passing the paper, and the density density of the developer is low because the bulk density of the developer is reduced. This is because the state is erroneously detected and detected to be higher than the actual toner density. On the other hand, when the image area ratio is 70%, the bulk density increases because the amount of toner input is large, which causes the density detection sensor to falsely detect that the carrier density is high, and to detect the density lower than the actual toner density. Yes. From this result, since the bulk density of the developer varies depending on the image area ratio, it is necessary to correct the sensor sensitivity in consideration of the image area ratio when the paper is passed.

  In addition, it can be seen that the number of sheets through which detection errors converge differs for each image area ratio. Accordingly, it is necessary to correct the sensor sensitivity at the optimum timing in consideration of the number of sheets to be passed and the image area ratio. Further, since the contribution of the bulk density of the developer can be considered as a cause of the detection error, attention should be paid to the toner characteristic value that contributes to the fluctuation of the bulk density.

  Here, similarly to the above evaluation, 5000 sheets were evaluated using the image forming apparatus CM shown in FIG. 1 and the developing device 4 shown in FIG. The image area ratio when passing paper was 40%. Here, attention is paid to the volume average particle diameter of the toner as a toner characteristic value that contributes to the change in the bulk density of the developer, and paper passing evaluation is performed using three toners having a volume average particle diameter of 4 μm, 5 μm, and 6 μm, respectively. It was. The results of this paper passing evaluation are shown in Table 1 below.

  In Table 1 above, the evaluation item evaluated the transition of the toner density detection error. From Table 1, it can be seen that the detection error increases as the volume average particle diameter of the toner decreases. This is presumably because the smaller the toner particle size, the larger the bulk density variation from the initial agent. That is, the smaller the toner, the larger the contact surface area in a unit volume, and the non-electrostatic adhesion between toners or carriers is likely to increase.

  That is, an image forming apparatus capable of preventing toner density detection error and controlling toner density with high accuracy by controlling the sensor sensitivity of the toner density detection sensor 140 based on the toner volume average particle diameter information at the time of toner replacement. be able to. From this, it can be seen that the smaller the volume average particle diameter of the toner, the higher the sensor sensitivity of the toner concentration detection sensor 140 needs to be corrected.

  Further, similarly to the above evaluation, 5000 sheets were evaluated using the image forming apparatus CM shown in FIG. 1 and the developing device 4 shown in FIG. The image area ratio when passing paper was 40%. The evaluation results are shown in Table 2 below. Focusing on the toner shape factor SF-1 as a toner characteristic value that contributes to the change in the bulk density of the developer, the toner shape factor SF-1 is evaluated using three toners 110, 130, and 150, respectively. went.

  Table 2 shows the evaluation result of the transition of the toner density detection error. As an evaluation item, the transition of the toner density detection error was similarly evaluated. From Table 2, it can be seen that the detection error is smaller as the shape factor SF-1 is larger, that is, the shape is indefinite, and the detection error is larger as the toner is closer to a true sphere. This is because the true spherical toner has a larger contact surface area with the carrier and toner existing around it, and the bulk density is likely to change due to an increase in non-electrostatic adhesion. From these results, it can be seen that the smaller the toner shape factor SF-1, the higher the sensor sensitivity of the toner density detection sensor needs to be corrected.

  Further, similarly to the above-described experiment, 5000 sheets were evaluated using the image forming apparatus CM shown in FIG. 1 and the developing device 4 shown in FIG. The image area ratio when passing paper was 40%. Here, attention is paid to the circularity of the toner as a toner characteristic value that contributes to fluctuations in the bulk density of the developer, and paper passing evaluation is performed using three toners having a circularity of 0.93, 0.95, and 0.97, respectively. Went. The evaluation results are shown in Table 3 below.

  Table 3 shows the evaluation result of the transition of the toner density detection error. As an evaluation item, the transition of the toner density detection error was similarly evaluated. From Table 3, it can be seen that the higher the circularity, the greater the detection error. This is because, as in the case of the shape factor SF-1, the closer to a true sphere, the more the initial bulk density fluctuation is associated with the increase in non-electrostatic adhesion force. Further, it is considered that the toner having a higher degree of circularity is more likely to cause the toner additive, particularly the external additive to be detached and peeled off, and the bulk density greatly varies in the initial stage of paper passing.

  Further, similarly to the above-described experiment, 5000 sheets were evaluated using the image forming apparatus CM shown in FIG. 1 and the developing device 4 shown in FIG. The image area ratio when passing paper was 40%. Here, attention is paid to the degree of aggregation of the toner as a toner characteristic value that contributes to fluctuations in the bulk density of the developer, and paper passing evaluation was performed using three toners having a degree of aggregation of the toner of 20%, 40%, and 60%, respectively. . The evaluation results are shown in Table 4 below.

  Table 4 shows the evaluation result of the transition of the toner density detection error. As an evaluation item, the transition of the toner density detection error was similarly evaluated. As can be seen from Table 4, with toner having a cohesion degree of 20%, the detection error increased to about 3% after the initial 1000 sheets passed, and thereafter remained at the same level. Thereby, it is considered that the detection error is likely to be increased as the degree of aggregation is lower. This is considered to be caused by the change in the fluidity of the developer, and the lower the degree of aggregation, the more severe the initial change in fluidity.

  Based on the results as described above, the sheet passing evaluation was performed using the image forming apparatus CM shown in FIG. 1 and the developing device 4 shown in FIG.

Example 1
In this embodiment, using the image forming apparatus CM shown in FIG. 1 and the developing device 4 shown in FIG. 17, a total of 20,000 solid images with an image area ratio of 5%, 20%, 50%, and 70% are 20,000 each. Was evaluated. In other words, the first 5000 sheets are passed at an image area ratio of 5%, and then the image area ratio is set to 20%, and 5000 sheets are passed. went. The sheet passing result is shown in (a) of Table 5 below. Table 5 is a control table corresponding to the toner having a toner volume average particle diameter of 5 μm. FIG. 24 is a graph showing the evaluation result of the transition of the toner density detection error. In FIG. 24, results of examples and comparative examples described later are also displayed in an overlapping manner.

  In this example, toner having a volume average particle diameter of 5 μm was used, and the sheet density was changed with the sensor sensitivity of the toner density detection sensor 140 being variable according to the relationship between the number of sheets and the image area ratio information shown in Table 5.

  Here, the control method shown in Table 5 will be specifically described. As shown in Table 5, the change value of the sensor sensitivity of the toner density detection sensor 140 is designated based on the image area ratio cumulative average information acquired from the image forming apparatus CM and the information on the cumulative number of sheets passed. For example, in the first line of (a) of Table 5, it is detected that the image area ratio of the input image data is 0% or more and less than 10% and the cumulative number of sheets to be passed is 2000 or more continuously. In this case, the sensor sensitivity of the toner density detection sensor 140 is changed to 0.54. In the fifth line of Table 5 (a), when it is detected that the image area ratio of the input image data is 70% or more and the cumulative number of sheets to be passed is 2000 or more, the toner is used. In this control method, the sensor sensitivity of the density detection sensor 140 is changed to 0.16. FIG. 24 shows the transition of the toner density detection error as Example 1. From FIG. 24, it can be seen that the toner density can be accurately detected regardless of the sheet passing condition without causing a large toner density detection error.

(Comparative Example 1)
In Comparative Example 1, paper passing evaluation was performed under the same toner, machine, and developer conditions as in Example 1 above. However, the sensor sensitivity of the toner density detection sensor 140 was not variable, and the paper passing evaluation was performed with the initial setting. The transition of the toner density detection error is shown as Comparative Example 1 in FIG. It can be seen from FIG. 24 that the toner density detection error varies greatly depending on the paper passing mode.

(Example 2)
In the second embodiment, as in the first embodiment, a solid image with an image area ratio of 5%, 20%, 50%, and 70% is obtained using the image forming apparatus CM shown in FIG. 1 and the developing device 4 shown in FIG. A total of 20,000 sheets were evaluated for 5,000 sheets. Here, a toner having a toner shape factor SF-1 of 130 is used, and the sensitivity of the toner density detection sensor 140 is made variable according to the relationship between the number of sheets to be passed and the image area ratio information shown in Table 5 (b). went. The transition of the toner density detection error is shown as Example 2 in FIG. It can be seen from FIG. 24 that the toner density can be accurately detected regardless of the sheet passing condition without causing a large toner density detection error.

(Example 3)
In the third embodiment, as in the first embodiment, a solid image with an image area ratio of 5%, 20%, 50%, and 70% is obtained using the image forming apparatus CM shown in FIG. 1 and the developing device 4 shown in FIG. A total of 20,000 sheets were evaluated for 5,000 sheets. In this case, toner having a circularity of 0.95 is used, and the sensor sensitivity of the toner density detection sensor 140 is variable according to the relationship between the number of sheets to be passed and the image area ratio information shown in (c) of Table 5 above. It was. The transition of the toner density detection error is shown as Example 3 in FIG. It can be seen from FIG. 24 that the toner density can be accurately detected regardless of the sheet passing condition without causing a large toner density detection error.

Example 4
In the fourth embodiment, as in the first embodiment, a solid image with an image area ratio of 5%, 20%, 50%, and 70% is obtained using the image forming apparatus CM shown in FIG. 1 and the developing device 4 shown in FIG. A total of 20,000 sheets were evaluated for 5,000 sheets. In this case, toner having a toner aggregation degree of 40% was used, and the sheet density was changed with the sensor sensitivity of the toner density detection sensor 140 varied according to the relationship between the number of sheets to be passed and the image area ratio information shown in (d) of Table 5 above. The transition of the toner density detection error is shown as Example 4 in FIG. It can be seen from FIG. 24 that the toner density can be accurately detected regardless of the sheet passing condition without causing a large toner density detection error.

(Comparative Example 2)
In Comparative Example 2, paper passing evaluation was performed under the same toner, machine, and developer conditions as in Example 4 above. However, the sensor sensitivity of the toner density detection sensor 140 was not variable, and the paper passing evaluation was performed with the initial setting. The transition of the toner density detection error is shown as Comparative Example 2 in FIG. From FIG. 24, it can be seen that the toner density detection error varies greatly depending on the paper passing mode.

  From the above results, when the toner is replaced, the toner density detection sensor 140 is referred to by referring to the toner characteristic value, the image area ratio corresponding to the characteristic value, and the sensor sensitivity correction table for each number of sheets to be passed. It is possible to reduce erroneous detection, and it is possible to stably control the toner density regardless of the sheet passing condition.

  According to the present embodiment, when the toner is replaced with the developing unit provided with the toner density detecting unit, the sensor sensitivity of the toner density detecting unit is made variable based on the characteristic value data of the set toner to obtain a sensor sensitivity suitable for each toner. As a result, it is possible to suppress the detection error of the toner density detecting means due to the toner characteristic fluctuation accompanying the lot change of the replenished toner.

  Although the present invention has been specifically described above based on the preferred embodiment, it is needless to say that the present invention is not limited to the above-described image forming apparatus and can be variously modified without departing from the gist thereof.

  The present invention can be applied not only to an image forming apparatus using toner but also to an image forming apparatus in which a supply such as an ink cartridge is replaced.

DESCRIPTION OF SYMBOLS 4 Developing apparatus 140 Toner density detection sensor 141 Toner container 144 Toner container container 145 Storage means 150 Toner replenishment mechanism 151 Sensor control means 152 Paper passing number acquisition means 153 Image area ratio acquisition means 154 Data processing apparatus CM Image forming apparatus

JP 2008-122471 A JP 2008-122466 A JP 2008-122539 A JP 2007-256469 A

Claims (7)

Developing means comprising toner concentration detecting means for detecting the toner concentration of the two-component developer;
A toner replenishing means for replenishing toner to the developing means, comprising a toner container housing for housing a toner container;
Storage means provided in the toner container for storing toner characteristic information of the toner contained in the toner container;
Data processing means for storing data in the storage means;
Control means for changing the sensitivity of the toner density detection means;
A sheet passing number acquiring unit for acquiring a sheet passing number of the developing unit;
Image area ratio acquisition means for acquiring input image area ratio data,
When the data stored in the toner container is updated, the control unit is configured to detect the sensitivity of the toner density detection unit based on the toner characteristic information, the sheet passing number information, and the image area ratio information. An image forming apparatus characterized by changing the above.   The image forming apparatus according to claim 1, wherein the toner concentration detection unit detects the toner concentration of the two-component developer by a magnetic permeability detection method.   The image forming apparatus according to claim 1, wherein the toner characteristic information is volume average particle diameter information of toner.   The image forming apparatus according to claim 1, wherein the toner characteristic information is toner shape factor information.   The image forming apparatus according to claim 1, wherein the toner characteristic information is toner circularity information.   The image forming apparatus according to claim 1, wherein the toner characteristic information is toner aggregation degree information.   The image forming apparatus according to claim 1, wherein the storage unit is an ID chip.

Images