JP2009151029A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized developing device capable of stably forming a developer layer as a thin layer by suppressing the deterioration of a two-component developer on a developer carrier, and obtaining a stable image of high image quality over a long period of time. <P>SOLUTION: The developing device includes a developing roller 41 including a plurality of magnetic poles which supports and carries a developer 43 composed of toner and a carrier to develop an electrostatic latent image formed on a photoreceptor 1; and a doctor 42 which regulates the layer thickness of the developer supported and carried by the developing roller 41. The developing device further comprises a recovery part 52 for recovering the developer after development from the developing roller and agitating the developer while replenishing the toner as needed; and a feed part 51 for feeding the developer agitated in the recovery part to the developing roller 41. Since the position of the supply part 51 is located above the developing roller, a means for adjusting the feed quantity of the developer from the feed part to the developing roller is provided, and the doctor is disposed closer to the photoreceptor from the apex of the developing roller, the quantity of developer supported by the developing roller can be appropriately controlled. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device for developing an electrostatic latent image carried on a latent image carrier with a two-component developer containing toner and a magnetic carrier, a process cartridge using the developing device, and the developing device. Alternatively, the present invention relates to an image forming apparatus such as a copying machine, a facsimile, a printer, or a complex machine including a process cartridge.

2. Description of the Related Art Conventionally, developing devices using a two-component developer made of a magnetic carrier and toner are known. In the developing device using the two-component developer, the developer is carried on a developer carrier as a so-called magnetic brush, and the developer is regulated to a predetermined thickness by the developer regulating member, and then conveyed to the development area. In general, an electrostatic latent image on a latent image carrier such as a photoconductor is developed.
As the developer carrying member, for example, a cylindrical developing sleeve that is rotatably arranged and carries and conveys a two-component developer, and a plurality of magnetic field generating means (for example, a plurality of surroundings) fixedly arranged in the developing sleeve. A developing roller provided with a magnet roll or a plurality of magnets).

  In order to faithfully develop the electrostatic latent image on the latent image carrier, it is necessary to reduce the distance between the latent image carrier and the developer carrier. As the distance between the latent image carrier and the developer carrier becomes smaller, it is necessary to form a thinner developer layer on the developer carrier. Conventionally, as a method of regulating the thickness of the developer layer on the developer carrying member, a developer regulating member (for example, a doctor) is opened with a certain gap (hereinafter referred to as a doctor gap) with respect to the developer carrying member. A method of arranging in contact is widely adopted. In this method, the amount of developer passing through the developer regulating member can be adjusted by controlling the doctor gap, but in order to form a thin layer, the doctor gap needs to be set very small.

  However, when the doctor gap is set to be small, the amount of developer passing through the doctor gap varies greatly as compared with the case where the doctor gap is set to be large, and the developer layer formed on the developer carrier becomes non-uniform. Further, when the developer passes through the doctor gap, a great stress is applied to the developer, and the life of the developer is shortened.

  In order to solve such a problem, for example, in the developing device described in Patent Document 1, magnetic poles of the same polarity are arranged adjacent to each other on the magnet roll of the developer carrying member, and the maximum magnetic force position of the magnetic poles on the upstream side in the developer transport direction A developer regulating member is provided between the minimum magnetic positions between these magnetic poles. Thereby, the packing density of the developer in the doctor gap is lowered, and the amount of developer passing through the doctor gap can be reduced. In addition, the developer passing through the doctor gap is hardly affected by the force to pass through the doctor gap other than the rotational force of the developing sleeve. Therefore, even if the doctor gap is set small, the variation in the amount of developer passing through the doctor gap is small, and a thin uniform layer can be formed on the developer carrying member.

JP-A-5-6103

  However, in the developing device described in Patent Document 1 described above, since the repulsive force between the magnetic poles of the same polarity is strong, the developer conveying force for passing through the doctor gap is too low. For this reason, if the characteristics of the developer fluctuate due to environmental fluctuations or the like, the developer conveyance amount is likely to fluctuate, and the developer layer formation may become unstable.

The present invention has been made in order to solve the above-described problems of the prior art, and an object of the present invention is to make it possible to adjust the amount of developer supplied to the developer carrier to an appropriate amount. An object of the present invention is to provide a developing device capable of suppressing deterioration of the above two-component developer, stably forming a developer layer into a thin layer, and obtaining a small and stable high-quality image over a long period of time.
More specifically, an appropriate amount of developer is supplied to the developer carrier to prevent excessive supply of the developer, and the developer regulating member prevents the developer from being overpacked, and the developer is carried. An object of the present invention is to provide a developing device capable of suppressing deterioration of a two-component developer on a body and forming a developer layer stably in a thin layer. Further, it is possible to eliminate the stagnation of the developer in the developer recovery unit and the supply unit, and to provide a small-sized developing device. Further, the developer immediately after the replenishment of toner and the developer that has been sufficiently stirred Is intended to prevent mixing on the developer carrier.
An object of the present invention is to provide a process cartridge and an image forming apparatus that use a developing device that can achieve the above object and that can obtain a small and stable high-quality image over a long period of time.

In the present invention, in order to achieve the above object, the following means are adopted.
The first means of the present invention has a plurality of magnetic field generating means inside, carries and conveys a two-component developer comprising toner and a magnetic carrier as a magnetic brush, and forms an electrostatic image formed on the latent image carrier. A developer carrying member that develops the latent image with the developer toner into a visible image, and a developer regulating member that regulates a layer thickness of the developer carried and carried by the developer carrying member. In the developing device, the developer after the development is recovered from the developer carrying member, and if necessary, a recovery unit for replenishing the toner and stirring the developer, and the developer stirred in the recovery unit as the developer A supply unit that supplies the carrier, the position of the supply unit being above the developer carrier, and means for adjusting the amount of developer supplied from the supply unit to the developer carrier. In addition, the developer regulating member is more likely to bear the latent image than the top of the developer carrier. Characterized in that arranged on side.

According to a second means of the present invention, in the developing device of the first means, a magnetic field located at a position opposite to the developer regulating member on the upstream side of the developer carrying member in the developer conveying direction with respect to the developer regulating member. The magnetic flux density in the normal direction of the generating means is 30 mT or less.
According to a third means of the present invention, in the developing device of the second means, the magnetic field generating means at the site facing the developer regulating member is the developer supplied from the supply section to the developer carrier. It is a magnetic field generating means for carrying

According to a fourth means of the present invention, in the developing device of any one of the first to third means, the recovery unit and the supply unit are screw-like developer agitating and conveying for conveying the developer in the axial direction. And a developer carrying member having a diameter smaller than a screw diameter of a developer agitating / conveying member of the recovery unit and the supply unit.
According to a fifth means of the present invention, in the developing device of any one of the first to fourth means, the normal magnetic flux density formed by the magnetic field generating means at the agent separation position of the developer carrier is substantially 0. Is formed on the downstream side with respect to the rotation direction of the developer carrier relative to the line connecting the center of the developer carrier and the center of the developer agitating / conveying member of the supply unit. It is characterized by.

  The sixth means of the present invention includes a latent image carrier, charging means for uniformly charging the latent image carrier, means for forming an electrostatic latent image on the charged latent image carrier, and the latent image carrier. An image forming apparatus including an image forming unit having a developing unit that develops an electrostatic latent image on an image carrier and a cleaning unit that cleans transfer residual toner remaining on the latent image carrier; In a process cartridge in which at least one of the latent image carrier, the charging unit, the cleaning unit, and the developing unit constituting the image unit is integrated with the image forming apparatus main body so as to be removable. The developing means includes a developing device of any one of first to fifth means.

The seventh means of the present invention includes a latent image carrier, charging means for uniformly charging the latent image carrier, means for forming an electrostatic latent image on the charged latent image carrier, and the latent image carrier. In an image forming apparatus having an image forming unit having a developing unit that develops an electrostatic latent image on an image carrier and a cleaning unit that cleans transfer residual toner remaining on the latent image carrier, the developing unit includes: The developing device of any one of the first to fifth means is provided.
According to an eighth means of the present invention, in the image forming apparatus of the seventh means, a plurality of the image forming sections are provided to form a single color, a multicolor or a full color image.
Further, the ninth means of the present invention is characterized in that, in the image forming apparatus of the seventh or eighth means, a process cartridge of the sixth means is provided in the image forming section.

In the developing device of the present invention, the developer after development is collected from the developer carrying member, and if necessary, a collecting unit that replenishes toner and agitates, and the developer that is stirred in the collecting unit carries the developer. A supply unit for supplying to the body, the position of the supply unit is above the developer carrier, and there is means for adjusting the amount of developer supplied from the supply unit to the developer carrier, and development. Since the agent regulating member is arranged on the latent image carrier side with respect to the vertex of the developer carrier, the magnetic force is not used when supplying the developer from the supply unit to the developer carrier. Supply by gravity can be performed, and the magnetic binding force can be lowered. In addition, since it has means for adjusting the supply amount of the developer, the supply amount of the developer to the developer carrying member is set to an appropriate amount, and the developer reservoir due to the excessive developer is placed in front of the developer regulating member (doctor). Can be eliminated.
Further, by disposing the developer regulating member (doctor) on the latent image carrier side with respect to the vertex of the developer carrier, the developer in front of the doctor portion is not made to move by using gravity. Can be. For this reason, since it is not exposed to a pressure for a long time, it becomes possible to suppress generation | occurrence | production of the deteriorated developer.
Therefore, according to the present invention, the deterioration of the two-component developer on the developer carrying member can be suppressed, the developer layer can be stably formed into a thin layer, and a small and stable high-quality image can be obtained over a long period of time. It is possible to realize a developing device capable of performing the above.
Further, according to the present invention, by using the developing device having the above-described effects, it is possible to realize a process cartridge and an image forming apparatus that can obtain a small and stable high-quality image over a long period of time.

First, configuration examples of an image forming apparatus, a developing device, and a process cartridge according to the present invention will be described.
FIG. 1 is a schematic configuration diagram of an image forming apparatus having a developing device to which the present invention is applied. The image forming apparatus 100 according to the embodiment illustrated in FIG. 1 is a tandem printer that forms a color image, but may be a device that forms a single-color image. If a document image reading device (scanner) is installed on the upper part of the housing of the image forming apparatus (printer) 100 shown in FIG. 1, a configuration of a copying machine, a facsimile, or a complex machine of these is obtained.

The image forming apparatus 100 shown in FIG. 1 is a plain paper such as plain paper that is generally used for copying, 90K paper such as an OHP sheet, card, postcard, thick paper equivalent to a grammage of about 100 g / m ² or more, and envelope. Any so-called special sheet having a larger heat capacity can be used as a sheet-like recording medium. These are hereinafter referred to as recording media.

  The image forming apparatus 100 forms an image for each color in the housing in accordance with image information of a document image read by a reading device (scanner) (not shown) (or image information input from an external personal computer or the like). The image forming devices 7C, 7Y, 7M, and 7K, the transfer device 8 disposed to face the image forming devices 7C, 7Y, 7M, and 7K, the image forming devices 7C, 7Y, 7M, and 7K, and the transfer device 8 Feed cassettes 11, 12, 13 serving as recording medium supply means for supplying various recording media P to the transfer areas facing each other, and the recording medium P conveyed from the paper feed cassettes 11, 12, 13 as an image forming device 7C. , 7Y, 7M, and 7K, and registration rollers 18 that are supplied in accordance with the timing of image formation.

  The image forming apparatus 100 includes photosensitive drums 1C, 1Y, 1M, and 1K, which will be described later, provided in the image forming apparatuses 7C, 7Y, 7M, and 7K, and transfer rollers 5C, 5Y, 5M, and the like of the transfer apparatus 8, respectively. A fixing device 19 for fixing the recording medium P after the toner image has been transferred in at least one of the transfer regions opposite to 5K; and a fixing device disposed on the top of the housing. And a paper discharge tray 22 for stacking the recording medium P on which the toner image is fixed after passing through 19.

  The image forming apparatus 100 also includes pickup rollers 14, 15, and 16 that feed the recording medium P from the paper feed cassettes 11, 12, and 13, and the recording medium P that is conveyed from the paper feed cassettes 11, 12, and 13. A roller structure 17 that conveys toward the registration roller 18, a discharge roller 21 that conveys the recording medium P toward the paper discharge tray 22 and discharges it to the outside of the housing 100, and discharges the recording medium P fixed by the fixing device 19. It has a roller structure 20 that conveys toward the roller 21.

  The transfer device 8 is composed of a transfer belt stretched around a plurality of rollers 9, 10, and is disposed in an oblique direction so that the housing 100 of the image forming apparatus is small in the left-right direction in the drawing, and is indicated by an arrow B. The sheet-like medium conveyance direction is an oblique direction. Thus, in the image forming apparatus, the width of the casing 100 in the left-right direction in the figure is slightly longer than the length in the longitudinal direction of the A3 size sheet-like medium. That is, the image forming apparatus 100 is greatly reduced in size by being the minimum size required to accommodate the sheet-like medium therein.

  Each of the image forming devices 7C, 7Y, 7M, and 7K forms an image of each color of cyan (C), yellow (Y), magenta (M), and black (K), and the color of the toner used in the developing device. However, since the configuration is almost the same, the configuration of the black imaging device 7K will be described as a representative of the imaging devices 7C, 7Y, 7M, and 7K. The image forming device 7K includes a photosensitive drum 1K as a latent image carrier, a charging device 2K arranged in order in the rotation direction A of the photosensitive drum 1K, an exposure device (optical writing device) 3K, a developing device 4K, a cleaning device. It has a well-known configuration that includes an apparatus 6K and the like and receives exposure light L from an exposure apparatus (optical writing apparatus) 3K between the charging apparatus 2K and the developing apparatus 4K. The latent image carrier may be a belt-like photosensitive member instead of a drum.

  In the image forming device 7K configured as described above, the photosensitive drum 1K is charged by the charging device 2K, and the photosensitive drum 1K is irradiated with the exposure light L from the exposure device (optical writing device) 3K, thereby electrostatic latent. An image is formed, and the electrostatic latent image is developed with toner of the developing device 4K to form a visible image. Then, the toner image on the photosensitive drum 1K is transferred to the recording medium P conveyed by the transfer device 8. Similarly, the image forming apparatuses 7C, 7Y, and 7M for other colors are similarly charged, exposed, and developed, and the toner images of the respective colors are transferred to the recording medium P conveyed by the transfer apparatus 8. Depending on how many of the image forming devices 7C, 7Y, 7M, and 7K are used, a single color image, a multicolor image, or a full color image is formed on the recording medium P, and is fixed by the fixing device 19. The paper is discharged to the paper discharge tray 22.

Next, a configuration example of the developing device 4 used in each of the image forming units (image forming devices) 7C, 7Y, 7M, and 7K of the image forming apparatus illustrated in FIG. 1 will be described.
FIG. 2 shows a configuration example of a general developing device using a two-component developer. A developing device 4-1 shown in FIG. 2 has a plurality of magnetic field generating means (for example, a plurality of magnetic poles P1 to P5) fixedly disposed therein, and a developer (two-component developer) 43 including toner and a magnetic carrier. And a developer carrier (hereinafter referred to as a developer) that rotates the carrier and supplies toner to the electrostatic latent image formed on the photosensitive drum 1 as a latent image carrier to visualize the electrostatic latent image. 41) and a rotation axis about a center line parallel to the axis of the developing roller 41, and the developer 43 is conveyed while stirring in the axial direction of the rotation axis. A first developer stirring and conveying member 44 having a function of collecting the developer 43 from the roller 41 and a function of supplying the developer to the developing roller 41; and a direction in which the first developer stirring and conveying member 44 conveys the developer 43 Second developer agitating and conveying unit for agitating and conveying developer 43 in the opposite direction to And a 45. That is, in the developing device 4-1 shown in FIG. 2, the first developer agitating / conveying member 44 that is disposed in parallel with the center line of the axis of the developing roller 41 and conveys the developer 43 in one direction of the axis, for example, the front side of the sheet. And a second developer agitating / conveying member 45 that is arranged in parallel with the first developer agitating / conveying member 44 and conveys the developer in the other direction of the shaft, that is, on the back side of the sheet. The conveying member 44 and the second developer agitating / conveying member 45 are arranged in a substantially horizontal direction. Further, in the rotation direction of the developing roller 41 that rotates counterclockwise in FIG. 2, the developer 43 pumped up by the developing roller 41 on the downstream side of the facing region between the developing roller 41 and the first developer stirring and conveying member 44. A developer regulating member (for example, a doctor) 42 is provided above the developing roller 41 to regulate the layer thickness. A partition plate 46 is provided between the first developer agitating / conveying member 44 and the second developer agitating / conveying member 45, and openings are provided at both ends of the partition plate 46. The developer is transferred at both ends of the first developer agitating / conveying member 44 and the second developer agitating / conveying member 45, and the developer is transferred between the first developer agitating / conveying member 44 and the second developer agitating / conveying member 45. It is designed to circulate while being stirred and conveyed. Although not shown, a toner replenishing portion is provided on the upstream side of the second developer agitating and conveying member 45 in the carrying direction so that the toner contained in the toner containing portion not shown is replenished. .

  The developing roller 41, which is a developer carrying member, has a magnet roller (or a plurality of magnets) (not shown) in which a plurality of magnetic poles are arranged in the circumferential direction as magnetic field generating means, and has a cylindrical shape (not shown) around it. The developing sleeve rotates. The developing sleeve is made of a nonmagnetic metal such as aluminum. The magnet roller is fixed so that each magnetic pole faces a predetermined direction, and the developing sleeve rotates around the magnetic roller to carry and transport the developer attracted by the magnetic pole.

More specifically, the magnetic roller of the developing roller 41 is provided with a main magnetic pole P1, a conveying magnetic pole P2, an agent separating magnetic pole P3, an agent pumping magnetic pole P4, and a conveying magnetic pole P5. After the developer 43 stirred and conveyed by the first developer agitating / conveying member 44 is pumped up on the developing sleeve by the magnetic force of the agent pumping magnetic pole P4, the developer on the developing sleeve is used with magnetic poles whose polarity is changed alternately. Thus, a developer chain-like magnetic brush is formed. When the developing sleeve is rotated, the magnetic brush is transported to the developing unit while being rolled over.
That is, the magnetic field generated by the magnetic pole P4 for pumping up the agent of the magnet roller of the developing roller 44 flows into the adjacent transporting magnetic pole P5 of opposite polarity, and when a carrier composed of magnetic particles passes through such a magnetic field, Magnetization of the carriers occurs along the magnetic flux density, and a magnetic brush is formed along the magnetic vector. At this time. When the developing sleeve is rotated, the developer is conveyed on the developing sleeve while changing its shape along the magnetic vector generated by the magnetic field. Then, the developer conveyed to the developing unit rises with the magnetic force of the main magnetic pole P1 to form a magnetic brush, and the electrostatic latent image on the photoreceptor is developed with the toner in the developer. The developed developer is conveyed into the developing device by the rotation of the developing sleeve, passes through the agent separating magnetic pole P3, and is collected by the first developer agitating / conveying member 44.

  By the way, in the developing device 4-1 of the type in which the two developer agitating / conveying members 44 and 45 as shown in FIG. The first developer agitating / conveying member 44 supplies and recovers the developer to the developing roller 41, and the second developer agitating / conveying member 45 performs toner replenishment, mixing, and agitation. However, if the developer conveyed by the first developer agitating / conveying member 44 and the collected developer are not sufficiently mixed and agitated, toner density unevenness will be generated in the developer 43 supplied to the developing roller 41. In addition, abnormal images such as defective charging and uneven image density are formed. In particular, when the developer after development is not sufficiently separated from the developing roller 41 and the developer after development reaches the supply side with the developing roller 41 as it is, the developer with insufficient toner concentration reaches the developing portion. As a result, the developed image has uneven density and insufficient density. Further, if the position of the agent pumping magnetic pole P4 of the developing roller 41 is not appropriate, the developer separated from the agent may be pumped up to the developing roller 41 before being stirred and conveyed by the first developer stirring and conveying member 44. Similarly, uneven density or insufficient density of the developed image occurs.

  Next, FIG. 3 shows another configuration example of a developing device using a two-component developer. A developing device 4-2 shown in FIG. 3 has a plurality of magnetic field generating means fixedly disposed therein, and carries and rotates a developer (two-component developer) 43 containing toner and a magnetic carrier, thereby rotating a latent image. A developer carrier (hereinafter referred to as a developing roller) 41 for supplying toner to the electrostatic latent image formed on the photosensitive drum 1 as a carrier to visualize the electrostatic latent image, and a developing roller Rotate on a rotation axis centering on a center line parallel to the center line of the shaft 41, feed the developer 43 to the developing roller 41 by transporting the developer 43 while stirring the developer 43 in the axial direction of the rotation shaft. The developer 43 is recovered from the one developer agitating / conveying member 47 and the developing roller 41, and the first developer agitating / conveying member 47 conveys the developer in a direction opposite to the direction in which the developer is conveyed, thereby first developing the developer. A second developer agitating and conveying member 48 that delivers the developer to the agent agitating and conveying member 47 There.

  That is, the developing device 4-2 shown in FIG. 3 has the same configuration as the developing roller 41 in FIG. 2, but separates the functions of supplying and collecting the developer by the developer stirring and conveying members 47 and 48. A developer supplying section provided with a first developer stirring and conveying member 47 for stirring and conveying the developer 43 composed of toner and carrier and supplying the developer 43 to the developing roller 41; and a developer 43 after development from the developing roller 41 And a developer collecting section in which a second developer agitating / conveying member 48 for mixing and conveying the collected developer and the toner replenished from a toner replenishing port (not shown) is disposed, and above the collecting section. In this configuration, the supply unit is arranged on the wall and partitioned by the wall portion 49, and the supply unit and the recovery unit are connected in the vertical direction. Thus, by adopting a configuration in which the supply unit and the collection unit are connected in the vertical direction adjacent to the developing roller 41, space is saved as compared with the developing device having the configuration of FIG.

In the developing device 4-2 shown in FIG. 3, the developer 43 separated from the developer passing through the agent separating magnetic pole P <b> 3 of the developing roller 41 is collected from the developing roller 41 by the second developer stirring and conveying member 48, and is not shown in the drawing. The toner supplied to the recovery unit through the toner supply port (not shown) from the storage unit and the recovered developer 43 are mixed and stirred. Then, the developer 43 conveyed to the end in the axial direction by the second developer agitating / conveying member 48 is supplied to the first developer agitating / conveying member 47 side through an opening provided in the axial end of the wall portion 49. Is done. Thereafter, the developer 43 is agitated and conveyed in the axial direction by the first developer agitating and conveying member 47, and in the conveying path, the developer 43 attracts the developer 43 to the developing roller 41 due to the magnetic force of the agent pumping magnetic pole P4 of the developing roller 41. Supplying. Then, after performing development in the same manner as in the developing device of FIG. 2, the developer after development is collected by the second developer agitating and conveying member 48 as described above.
As described above, in the developing device 4-2 shown in FIG. 3, the functions of supplying and collecting the developer are separated by the two developer agitating and conveying members 47 and 48, and the developer after the development is supplied for supply. By adopting a configuration in which the developer is not returned to the first developer agitating / conveying member 47 as it is, the second developer agitating / conveying member 48 is sufficiently mixed and agitated with the replenishing toner, and is delivered to the first developer agitating / conveying member 47. Since the developer 43 is supplied to the developing roller 41, an image having a stable image density can be obtained.

By the way, in the developing device 4-2 configured as shown in FIG. 3, the developer stirred and conveyed by the first developer agitating and conveying member 47 of the supply unit is pumped up by the magnetic force of the agent pumping magnetic pole P4 of the developing roller 41. However, since the developer is attracted by the magnetic force from the supply unit, all the developer that passes through the suction range is attracted to the developing roller 41, which may result in excessive supply of the developer. When an excessive developer is carried on the developing roller, the developer regulating member (doctor) 42 may be in an excessive developer packing state.
Therefore, in the present invention, the amount of developer supplied from the developer supply unit to the developing roller 41 can be lowered to an appropriate amount, so that an excessive amount of developer cannot be accumulated in front of the doctor 42. A specific embodiment will be described later.

  Next, FIG. 4 is a schematic configuration diagram showing a configuration example of the process cartridge according to the present invention. The process cartridge 7 is one in which the developing device 4, the photosensitive drum 1, the charging device 2, and the cleaning device 6 of each image forming section shown in FIG. It is removable.

  As described above, the process cartridge 7 shown in FIG. 4 has an integral structure in which the developing device 4, the photosensitive drum 1, the charging device 2, and the cleaning device 6 are integrally stored in the cartridge, and can be attached to and detached from the image forming apparatus main body. By configuring as a product, maintainability and exchangeability can be improved even during long-term use.

  The configuration examples of the image forming apparatus, the developing apparatus, and the process cartridge according to the present invention have been described above. However, in the present invention, the developer carrier (developing roller) is used in the developing apparatus used in the process cartridge and the image forming apparatus as described above. ) 41 to suppress excessive supply of the developer to 41 and excessive developer packing due to the developer regulating member (doctor) 42. The present invention also provides a small developing device that eliminates the stagnation of the developer in the lifting portion from the developer collecting portion to the supply portion. Furthermore, the developer immediately after the replenishment of toner and the developer whose stirring has been sufficiently completed are prevented from being mixed into the developer carrying member (developing roller) at the same time.

As described in the above solution, the developing device according to the present invention recovers the developer after development, replenishes the toner as necessary, and stirs the recovery unit (52). A supply unit (51) for supplying the developer (43) stirred in (52) to the developing roller (41), the position of the supplying unit (51) being above the developing roller (41); A means for adjusting the amount of developer supplied from the section (51) to the developing roller (41), and the developer regulating member (doctor) (42) is more sensitive than the top of the developing roller (41). 1) It is set as the structure arrange | positioned at the side (FIG. 5, FIG. 7, FIG. 8).
In other words, in the present invention, the supply amount of the developer to the developing roller (41) is lowered to an appropriate amount, so that an excessive developer pool is not generated before the developer regulating member (doctor) (42). The developer restricting position is arranged closer to the photoreceptor (1) than the apex of the developing roller (41).

Therefore, in the present invention, the supply portion (51) for supplying the developer can be provided further above the developing roller (41) than in the configuration of FIG. 3, and the developing portion (51) is developed from the supply portion (51). When supplying the agent, the agent can be supplied by gravity without using magnetic force. As a result, the magnetic restraining force can be reduced as compared with the conventional case, and the developer can be prevented from being excessively carried.
Furthermore, by providing the doctor part (42) closer to the photoreceptor (1) than the apex of the developing roller (41), gravity is used to supply the developer in front of the doctor part, and the developer does not move. Can not be. In addition, since it is not exposed to pressure for a long time, it is possible to suppress the generation of deteriorated developer.
As a means for controlling the supply amount of the developer, a wall portion (49) is simply provided in the supply portion (51), and a developer agitating / conveying member (screw) (47) is disposed inside (49) ( For example, the supply amount can be easily controlled by changing the rotation speed thereof.
Further, by providing the doctor part (42) closer to the photoreceptor (1) than the apex of the developing roller (41), it is possible to suppress the generation of the developer flowing directly to the collecting part without passing through the doctor. Therefore, it is advantageous in stabilizing the concentration.
As another means for controlling the supply amount of the developer, simply, the wall portion (49) is provided in the supply portion (51), and the height of the supply side to the developing roller is set to the developer in the supply portion. It can be changed according to the height. For example, in the configuration of FIG. 3, the developer is supplied to the sleeve as it goes downstream, so the height of the developer becomes lower. Therefore, it is possible to adjust by increasing the height of the upstream wall portion (49) and decreasing the height of the wall portion (49) as it becomes downstream.

  In the developing device of the present invention, in addition to the above configuration, the magnetic restraint force generated in the doctor section (42) is further reduced, and the developing roller (41) is developed more than the doctor (42). The magnetic flux density in the normal direction of the magnetic field generating means at the site facing the doctor (42) on the upstream side in the agent transport direction is set to 30 mT or less. The magnetic field generating means at the opposite part of the doctor is a magnetic pole for carrying the developer (43) supplied from the supply unit (51) to the developing roller (41), and is a conventional pumping pole or agent regulating pole. Equal to

Here, in the conventional pumping electrode and the agent regulating electrode (for example, P4 and P5 in FIG. 3), a magnetic flux density of about 45 to 60 mT is usually formed. This is because, in order to supply the developer stably, the excess agent is retained and the regulation is performed with a strong force.
For this reason, when the magnetic flux density is lowered to 30 mT, for example, the amount of developer pumped up varies depending on the position of the agitating / conveying member (screw). For this reason, the amount of developer passing through the developer regulating portion becomes uneven. An abnormal image such as an image density variation occurs.

However, in the developing device of the present invention, the supply unit (51) is provided on the upper part of the developing roller (41), and the developer is supplied using gravity. Supply can be made.
When the magnetic flux density is lowered, there is a problem in the circulation of the developer. The first is to pass the developer stably through the developer restricting portion (doctor portion) (42). The second is that the developer before developer regulation flows to the developer collection side without passing through the developer regulation part (doctor part). For this reason, the amount of developer before the doctor fluctuates, and the amount of developer passing through the developer restricting portion (doctor portion) becomes non-uniform.

  However, according to the present invention, with respect to the first problem, there is an effect that even the developer accumulated in front of the doctor can easily pass through the developer regulating portion using gravity. Also, with respect to the second problem, by disposing the doctor (42) on the side of the photosensitive member (1) with respect to the apex of the developing roller (41), first, the developer accumulates in the doctor part, so that the collecting unit The developer does not flow to the (52) side. Moreover, even when it flows, the volume can be secured.

By the above-described method, the amount of developer passing through the developer regulating unit (42) can be kept constant according to the developer supply amount controlled by the developer supply unit (51).
In addition, since the magnetic attractive force is proportional to the square of the magnitude of the magnetic flux or more, if the magnetic flux density is halved, the deterioration state is also improved more than twice.
Since the stress of the developer is proportional to the weight of the developer deposited before the doctor, the stress can be reduced by reducing the deposition amount.

Furthermore, in the developing device of the present invention, in addition to the above-described configuration, the collection unit (52) and the supply unit (51) include a screw-like developer stirring and conveying member that conveys the developer in the axial direction. It is preferable that the diameter of the developing roller (41) is smaller than the screw diameter of the developer stirring and conveying member of (52) and the supply section (51) (FIG. 8).
Here, when the collected developer is lifted up to the supply unit (51), there is a problem that the developer accumulates in the collection unit (52). However, if the distance between the centers of the collection unit and the supply unit is shortened, the collection unit and the supply unit Therefore, it is easy to lift the collected developer to the supply unit, and the problem that the developer accumulates in the collecting unit can be solved. Further, if the developing roller diameter is reduced, even if the distance is shortened, the angle is opened, so that a good circulation can be obtained.
When the diameter of the developing roller is reduced, the strength of the developing roller is weakened. For this reason, there is a problem that the roller is bent due to the load generated in the developer regulating portion. As a result, almost no excessive weight is generated in the doctor portion, so that the deflection of the developing roller is suppressed and a uniform image can be formed.

By the way, when the developing roller has a small diameter, the distance between the supply unit (51) and the recovery unit (52) becomes narrow, so that the insufficiently agitated developer passes over the developing roller and reaches the supplied developer. It becomes easy to mix.
In order to prevent this mixing problem, it is preferable to completely separate the recovery and the supply. However, when the member to be separated comes into contact with the developing roller, the developing roller is scraped. As a result, the transportability decreases with the passage of time, and the developer does not pass through the doctor.
Therefore, in the present invention, by not forming a magnetic restraining force, the rotation is prevented, and the developer with insufficient stirring is prevented from being mixed with the developer with sufficient stirring.

More specifically, the point that the normal magnetic flux density formed by the magnetic field generating means (for example, corresponding to the agent separating magnetic pole P3 shown in FIG. 3) at the agent separating position of the developing roller (41) is substantially zero is developed. It is formed downstream of the line connecting the center of the roller (41) and the center of the developer stirring / conveying member (screw) 47 of the supply unit (51) with respect to the rotation direction of the developing roller (41). It is a thing.
That is, the configuration of the present invention has a normal magnetic flux density formed by the agent separating magnetic poles upstream of the straight line connecting the center of the screw having the function of collecting the developer on the developing roller and the center of the developing roller. After forming a point that becomes substantially zero, and without pumping up the developer, the developer with insufficient stirring reaches the supply side through the developing roller so as not to have a magnetic binding force. This prevents the developer from being supplied from the supply unit.

Next, more specific examples of the present invention will be described.
[Example 1]
FIG. 5 is a schematic block diagram of the developing device showing the first embodiment of the present invention. In this developing device, a developer supply unit (developer supply mechanism) 51 is provided above the developing roller 41.
A developer recovery unit (collection mechanism) 52 that collects and agitates the developer is provided below the developing roller 41, and the developer is lifted to transport the developer 43 from the developer recovery mechanism 52 to the supply mechanism 51. A mechanism 53 is provided. Further, the supply of the developer 43 to the developing roller 41 is adjusted by optimizing the size of the supply port 51 a of the developer supply unit 51.

The developer lifting mechanism 53 that lifts the developer from the collection unit 52 to the supply unit 51 can lift the developer using a powder pair pump or the like in addition to a mechanical conveying unit such as a screw or an auger. .
Further, the doctor 42 as a developer regulating member is provided on the photosensitive member 1 side with respect to the apex of the developing roller 41, and excess developer can be accumulated in front of the doctor.

  As a means for adjusting the amount of developer supplied from the supply port 51a of the developer supply unit 51, for example, as shown in FIG. 6, an electric shutter 56 for opening and closing the supply port 51a is provided and a developer regulating member is used. A pressure sensor is attached to a doctor 42. Then, when an excessive amount of developer is supplied, pressure is generated in the doctor 42. Therefore, the pressure generated in the doctor 42 is monitored by the pressure sensor 55, and the electric shutter 56 is driven. A mechanism such as “feeding back to the controller 54 to be controlled to adjust the size of the supply port 51 a” may be provided.

  In the case of the developing device of the configuration of the present embodiment, the developer regulating member does not need to store the developer in front of the doctor and regulate the passing amount as in the conventional case, and has a function of leveling the developer. Therefore, the developer layer can be stably formed into a thin layer even if a member having low rigidity is used.

[Example 2]
FIG. 7 is a schematic block diagram of a developing device showing a second embodiment of the present invention. The basic configuration of the developing device is substantially the same as the developing device having the configuration shown in FIG. 3 described above, but in this embodiment, a developer supply unit (supply mechanism) 51 is provided above the developing roller 41. Furthermore, a doctor 42 as a developer regulating member is provided on the photosensitive member 1 side with respect to the apex of the developing roller 41.
For this reason, the magnetic field generated by the magnetic field generating means of the developing roller 41 is provided in the vicinity of the doctor 42, and the direction of the normal of the magnetic pole at the site facing the doctor 42 is located upstream of the doctor 42 in the developer transport direction of the developing roller 41. Is set to 30 mT or less so that the supply mechanism is not affected by the magnetic field.

The supply amount of the developer 43 is limited by providing the supply port 51a, and the supply amount can be adjusted by adjusting the rotation speed of the developer stirring and conveying member (screw) 47.
Since the developer supplied from the screw 47 has a velocity component also in the axial direction, excess developer flows in the axial direction while accumulating in front of the doctor. Therefore, the developer packing state does not occur.

The developer 43 in the developer recovery unit 52 is lifted upward at the end of the screw 48 in the axial direction, and moved to the supply unit 51. Therefore, the end of the recovery unit is provided with a screw shape so that the developer can easily collect.
In the configuration shown in FIG. 7, since the diameter of the developing roller 41 is larger than the diameter of the screws 47 and 48 and the distance between the axes of the screws 47 and 48 is wide, the developer 43 is lifted from the collection unit 52 to the supply unit 51. For this, a method is required in which the rotational speed of the screw 48 of the collection unit 52 is made faster than the rotational speed of the screw 47 of the supply unit 51.

[Example 3]
FIG. 8 is a schematic block diagram of a developing device showing a third embodiment of the present invention. The basic configuration of this developing device is substantially the same as that of the configuration of the second embodiment shown in FIG. 7, but in this embodiment, the diameter of the developing roller 41 is set to a screw as compared with the configuration of the second embodiment. The diameter is smaller than 47 and 48.
Therefore, the distance between the axes of the screws 47 and 48 of the developer recovery unit 52 and the developer supply unit 51 can be set narrow, so that the conveyance direction end necessary for lifting the developer from the recovery unit 52 to the supply unit 51 Since the amount of developer accumulated in the section is small, the rotational speed of the screw 48 on the collection section side can be reduced.
Further, by making the diameter of the developing roller 41 small and setting the distance between the axes of the screws 47 and 48 narrow, the entire developing unit can be made small.
In this configuration, since an appropriate amount of developer is supplied onto the developing roller 41, since the developer is lightly overloaded, the occurrence of bending is suppressed even if the developing roller 41 has a small diameter. Problems such as development failure due to bending can also be avoided.

The embodiment of the developing device according to the present invention has been described above. However, in the image forming apparatus of the embodiment shown in FIG. 1, the developing device 4 having any one of the configurations of Embodiments 1 to 3 is used as the developing unit. By providing the image forming devices 7C, 7Y, 7M, and 7K for the respective colors, it is possible to reliably collect, stir and convey the developer, and to appropriately supply the two-component developer on the developing roller 41. Since stable development can be performed over a long period of time, an image forming apparatus capable of obtaining high-quality single-color, multicolor, and full-color images can be realized.
Further, in the image forming apparatus of the embodiment shown in FIG. 1, a process cartridge 7 as shown in FIG. 4 is provided as the image forming devices 7C, 7Y, 7M, and 7K for each color, thereby obtaining a stable high-quality image over a long period of time. Therefore, it is possible to realize an image forming apparatus that is excellent in operability and can easily replace the process cartridge 7.

1 is a schematic configuration diagram of an image forming apparatus showing an embodiment of the present invention. It is a schematic sectional drawing which shows the structural example of the general image development apparatus using a 2 component developing agent. It is a schematic sectional drawing which shows another structural example of the image development apparatus using a two-component developer. It is a schematic block diagram which shows the structural example of the process cartridge which concerns on this invention. 1 is a schematic configuration diagram of a developing device showing a first embodiment of the present invention. FIG. 6 is a diagram illustrating an example of a developer supply amount adjusting unit. It is a schematic sectional drawing of the image development apparatus which shows the 2nd Example of this invention. It is a schematic sectional drawing of the image development apparatus which shows the 3rd Example of this invention.

Explanation of symbols

1, 1C, 1Y, 1M, 1K: Photosensitive drum (latent image carrier)
2, 2C, 2Y, 2M, 2K: Charging device 3C, 3Y, 3M, 3K: Exposure device (optical writing device)
4 (4C, 4Y, 4M, 4K), 4-1, 4-2: Developing device 5C, 5Y, 5M, 5K: Transfer roller 6, 6C, 6Y, 6M, 6K: Cleaning device 7: Process cartridge (image forming) Part)
7C, 7Y, 7M, 7K: Image forming device 8: Transfer device 11, 12, 13: Paper feed cassette 14, 15, 16: Pickup roller 18: Registration roller 19: Fixing device 21: Paper discharge roller 22: Paper discharge tray 41: Developer carrier (developing roller)
42: Developer regulating member (doctor)
43: Developer 47: Developer stirring / conveying member (screw) in the supply section
48: Developer stirring / conveying member (screw) in the collecting section
49: Wall of supply unit P: Recording medium P1 to P5: Magnetic pole

Claims (9)

It has a plurality of magnetic field generating means inside, and carries and conveys a two-component developer comprising toner and magnetic carrier as a magnetic brush, and the electrostatic latent image formed on the latent image carrier is transferred with the developer toner. A developer carrier that develops to a visible image;
In a developing device comprising a developer regulating member that regulates the layer thickness of the developer carried and conveyed by the developer carrying member,
The developer after the development is recovered from the developer carrier, a recovery unit that replenishes toner as necessary and agitates, and the developer that is agitated in the recovery unit is supplied to the developer carrier. A supply unit,
The position of the supply unit is above the developer carrier, and there is means for adjusting the amount of developer supplied from the supply unit to the developer carrier, and the developer regulating member is the A developing device, wherein the developing device is disposed closer to the latent image carrier than the apex of the developer carrier. The developing device according to claim 1,
The magnetic flux density in the normal direction of the magnetic field generating means located at the upstream side of the developer carrying member in the developer conveying direction of the developer carrying member with respect to the developer regulating member is 30 mT or less. Developing device. The developing device according to claim 2, wherein
2. A developing apparatus according to claim 1, wherein the magnetic field generating means located at a portion facing the developer regulating member is a magnetic field generating means for carrying the developer supplied from the supply section to the developer carrying member. The developing device according to any one of claims 1 to 3,
The collection unit and the supply unit have a screw-like developer stirring and conveying member that conveys the developer in the axial direction, and the screw diameter of the developer stirring and conveying member of the collection unit and the supply unit is greater than the screw diameter. A developing device characterized in that the diameter of the developer carrying member is small. In the developing device according to any one of claims 1 to 4,
The point where the normal magnetic flux density formed by the magnetic field generating means at the agent separation position of the developer carrier becomes substantially zero connects the center of the developer carrier and the center of the developer stirring and conveying member of the supply unit. A developing device, wherein the developing device is formed on the downstream side with respect to the rotation direction of the developer carrying member with respect to the straight line. A latent image carrier, charging means for uniformly charging the latent image carrier, means for forming an electrostatic latent image on the charged latent image carrier, and an electrostatic latent image on the latent image carrier The latent image carrier that is included in an image forming apparatus that includes an image forming unit that includes a developing unit that develops the toner and a cleaning unit that cleans residual toner remaining on the latent image carrier, and constitutes the image forming unit. In a process cartridge in which at least one of a body, the charging unit, and the cleaning unit and the developing unit are integrated and detachable from the image forming apparatus main body,
A process cartridge comprising the developing device according to claim 1 as the developing unit. A latent image carrier, charging means for uniformly charging the latent image carrier, means for forming an electrostatic latent image on the charged latent image carrier, and an electrostatic latent image on the latent image carrier In an image forming apparatus including an image forming unit having a developing unit that develops the toner and a cleaning unit that cleans residual toner remaining on the latent image carrier,
An image forming apparatus comprising the developing device according to claim 1 as the developing unit. The image forming apparatus according to claim 7.
An image forming apparatus comprising a plurality of the image forming units and forming a single color, a multicolor or a full color image. The image forming apparatus according to claim 7 or 8,
An image forming apparatus comprising the process cartridge according to claim 6 in the image forming section.

Images