JP2016071021A - Paddle member and image forming unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the life of a photoreceptor drum.SOLUTION: A paddle member 50 is applied to an image forming unit comprising a photoreceptor drum 11, a development roller 14, a transfer roller 15, a cleaning blade 40 that scrapes toner from the peripheral surface of the photoreceptor drum 11, the paddle member 50 that conveys the scraped toner, and a conveyance screw 60 that collects the toner. The paddle member 50 is configured to have a low toner conveyance ability in specific areas A1 and A2 containing, in an axial direction X of the photoreceptor drum 11, at least an area from an inside of a paper passing area of a maximum paper size that can be passed to an outside of an area where the transfer roller 15 contacts with the photoreceptor drum 11, than a normal area B1 excluding the specific areas in the paper passing area.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a paddle member that transports toner scraped from the peripheral surface of a photosensitive drum, and an image forming unit including the paddle member.

  In the electrophotographic image forming apparatus, the toner remaining on the peripheral surface of the photosensitive drum after the transfer process is scraped off by a cleaning blade (see, for example, Patent Document 1). The toner scraped off by the cleaning blade is conveyed by the paddle member in a direction perpendicular to the axial direction of the photosensitive drum, and then collected by the collecting device.

  Among such image forming apparatuses, there is an image forming apparatus in which the peripheral surface of the transfer roller is in contact with the peripheral surface of the photosensitive drum. By passing the sheet between the photosensitive drum and the transfer roller, the toner image carried on the peripheral surface of the photosensitive drum is transferred to the sheet.

Japanese Patent Laid-Open No. 11-194692

  However, in the area outside the sheet passing area among the areas where the transfer roller contacts the photosensitive drum, the photosensitive drum and the transfer roller directly contact even during the sheet passing. Further, since the area outside the paper passing area is a non-image area, there is no lubricating effect due to residual toner in this area. For this reason, in the area where the transfer roller is in contact with the photosensitive drum, the frictional force between the photosensitive drum and the transfer roller is large in the area outside the paper passing area. The wear amount of the charge carrier moving layer on the peripheral surface of the body drum increases. When the charge carrier moving layer on the peripheral surface of the photosensitive drum is worn, there is a possibility that a toner fogging failure due to insufficient charging occurs and an end portion in the width direction of the sheet is stained. As described above, in the region where the transfer roller is in contact with the photosensitive drum, the region outside the sheet passing region has a large amount of wear on the peripheral surface of the photosensitive drum, and the amount of wear in this region is large. This is a major contributor to shortening the service life.

  An object of the present invention is to provide a paddle member capable of extending the life of a photosensitive drum and an image forming unit including the same.

  The paddle member according to the present invention has a photosensitive drum that carries an electrostatic latent image on its peripheral surface while rotating in one direction, and supplies the toner to the peripheral surface facing the peripheral surface, thereby converting the electrostatic latent image into toner. A developing roller that visualizes an image, a transfer roller that contacts the peripheral surface and transfers a toner image from the peripheral surface to a sheet, and a cleaning blade that scrapes off toner remaining on the peripheral surface from the peripheral surface after transfer. The image forming unit includes a paddle member that transports toner scraped off by the cleaning blade in a direction orthogonal to the axial direction of the photosensitive drum, and a recovery device that recovers the toner transported by the paddle member. . The paddle member is disposed so as to be close to the circumferential surface along the axial direction of the photosensitive drum. In the axial direction, the transfer roller is applied to the photosensitive drum from the inside of the maximum sheet passing area in which the sheet can pass. In the specific area including at least the area up to the outside of the contact area, the toner conveyance capability is configured to be lower than the normal area excluding the specific area in the sheet passing area.

  In this configuration, a part of the toner scraped off from the peripheral surface of the photosensitive drum by the cleaning blade accumulates in a specific area of the paddle member. For this reason, in the specific region in the axial direction on the peripheral surface of the photosensitive drum, a small amount of toner remains even after scraping by the cleaning blade. In a specific area, the residual toner provides a lubricating effect. For this reason, in the specific region, the frictional force between the photosensitive drum and the transfer roller is reduced, and the wear on the peripheral surface of the photosensitive drum is suppressed.

  In the above-described configuration, it is configured to rotate around a paddle shaft parallel to the axial direction, and a blade member for conveying toner is provided in a normal region of the paddle shaft, and a blade member is not provided in a specific region. It can be constituted as follows.

  In this configuration, since the blade member is not provided in the specific area, the toner is not conveyed and accumulates in the specific area. Thus, the frictional force between the photosensitive drum and the transfer roller can be reduced with a simple structure.

  The paddle shaft is configured to rotate around a paddle shaft parallel to the axial direction, and the paddle shaft is provided with a brush member composed of a plurality of linear members that convey toner. The specific region can be configured to be lower than the region.

  In this configuration, in the specific area, the density of the linear members of the brush member is low, and the toner transport capability is low, so that toner accumulates in the specific area. Thus, the frictional force between the photosensitive drum and the transfer roller can be reduced with a simple structure.

  Furthermore, the specific area is preferably an area from the inside of the paper passing area of the specific paper size that is used most frequently to the outside of the area where the transfer roller contacts the photosensitive drum.

  In this configuration, among the areas where the transfer roller is in contact with the photosensitive drum, in the area outside the sheet passing area of the specific paper size with the highest use frequency, the chance of friction between the photosensitive drum and the transfer roller is the most, It is possible to reduce the frictional force between the photosensitive drum and the transfer roller in the region having the greatest friction opportunity.

  The image forming unit of the present invention includes a photosensitive drum, a developing roller, a transfer roller, a cleaning blade, a paddle member, and a collecting device. The photosensitive drum carries an electrostatic latent image on its peripheral surface while rotating in one direction. The developing roller faces the circumferential surface and supplies toner to the circumferential surface to visualize the electrostatic latent image into a toner image. The transfer roller contacts the peripheral surface and transfers a toner image from the peripheral surface to the sheet. The cleaning blade scrapes off toner remaining on the peripheral surface after transfer from the peripheral surface. The paddle member conveys the toner scraped off by the cleaning blade in a direction orthogonal to the axial direction of the photosensitive drum. The collection device collects the toner conveyed by the paddle member. The paddle member is disposed so as to be close to the circumferential surface along the axial direction of the photosensitive drum. In the axial direction, the transfer roller is applied to the photosensitive drum from the inside of the maximum sheet passing area in which the sheet can pass. In the specific area including at least the area up to the outside of the contact area, the toner conveyance capability is configured to be lower than the normal area excluding the specific area in the sheet passing area.

  In this configuration, a part of the toner scraped off from the peripheral surface of the photosensitive drum by the cleaning blade accumulates in a specific area of the paddle member. For this reason, in the specific region in the axial direction on the peripheral surface of the photosensitive drum, a small amount of toner remains even after scraping by the cleaning blade. In a specific area, the residual toner provides a lubricating effect. For this reason, in the specific region, the frictional force between the photosensitive drum and the transfer roller is reduced, and the wear on the peripheral surface of the photosensitive drum is suppressed. As a result, toner fogging failure due to insufficient charging is suppressed, and smearing at the end in the width direction of the paper is suppressed.

  In the above-described configuration, it is preferable that the collecting device is configured to collect other toner while leaving a part of the toner accumulated in the specific area.

  In this configuration, when the amount of toner accumulated in the specific area of the paddle member exceeds a predetermined amount, the toner accumulated in the specific area of the paddle member is collected by the collecting device. For this reason, toner leakage due to excessive accumulation of toner to be discarded is prevented.

  According to this invention, the life of the photosensitive drum can be extended.

1 is a diagram illustrating a schematic configuration of an image forming apparatus including an image forming unit to which a paddle member according to a first embodiment of the present invention is applied. It is front sectional drawing of an image forming unit. It is a schematic diagram which shows the shape of a paddle member, and the arrangement | positioning relationship of each member. (A) is a cross-sectional view in the normal region of the paddle member, (B) is a cross-sectional view in the normal region of the paddle member that is conveying waste toner, and (C) is a cross-sectional view in the specific region of the paddle member. . (A) is a cross-sectional view in the normal region of the paddle member according to the second embodiment, and (B) is a cross-sectional view in the normal region of the paddle member according to the second embodiment while conveying waste toner. It is a figure which shows an experimental result. It is a side view of the paddle member concerning a 3rd embodiment.

  As shown in FIG. 1, the image forming apparatus 1 including the image forming unit 10 to which the paddle member 50 according to the first embodiment of the present invention is applied includes a paper feed tray 20 and a fixing unit in addition to the image forming unit 10. A device 30 is provided.

  The paper feed tray 20 supplies paper to the image forming unit 10.

  The image forming unit 10 includes a photosensitive drum 11, a charger 12, an exposure device 13, a developing roller 14, a transfer roller 15, and a cleaning device 16. The photosensitive drum 11 rotates in one direction. The charger 12, the exposure device 13, the developing roller 14, the transfer roller 15, and the cleaning device 16 are arranged around the photosensitive drum 11 in this order from the upstream side in the rotation direction of the photosensitive drum 11. As an example, the linear velocity of the photosensitive drum 11 is 255 mm / s.

  The photosensitive drum 11 includes a conductive base made of metal or resin, an undercoat layer formed on the surface of the conductive base, and a photosensitive layer formed on the undercoat layer. The photosensitive layer is composed of a relatively thin carrier generating layer formed on the undercoat layer and a carrier moving layer formed on the outermost layer. The carrier moving layer is mainly composed of polycarbonate or the like.

  The charger 12 charges the peripheral surface of the photosensitive drum 11 to a predetermined charge. For example, a scorotron charger using a corona charger is used as the charger 12. As an example, the charging potential is −650V.

  The exposure device 13 forms an electrostatic latent image on the peripheral surface of the photosensitive drum 11 by scanning the peripheral surface of the photosensitive drum 11 with a laser beam.

  In the carrier generation layer of the photosensitive drum 11, charge carriers are generated by irradiation with laser light. The charge carriers generated in the carrier generation layer move in the carrier moving layer, and the charges charged on the peripheral surface of the photosensitive drum 11 are offset by the charge carriers moved in the carrier moving layer. As an example, the potential of the portion irradiated with the laser light is attenuated to −130V. An electrostatic latent image is formed by a portion where the potential is attenuated by irradiation with the laser beam.

  The developing roller 14 is disposed so as to face and be close to the peripheral surface of the photosensitive drum 11. The developing roller 14 carries a developer containing negatively charged toner on its peripheral surface. A developing bias voltage is applied to the developing roller 14. As an example, the developing bias voltage is −475V. Due to the developing bias voltage, the toner in the developer carried on the developing roller 14 flies and adheres to the potential decay portion of the peripheral surface of the photosensitive drum 11. In this way, the electrostatic latent image is visualized and a toner image is formed.

  The transfer roller 15 is in contact with the peripheral surface of the photosensitive drum 11. As an example, the transfer roller 15 is brought into pressure contact with the circumferential surface of the photosensitive drum 11 with a predetermined pressure, and rotates in accordance with the rotation of the photosensitive drum.

  The paper P is supplied from the paper feed tray 20 to the transfer area where the photosensitive drum 11 and the transfer roller 15 are in contact with each other.

  A voltage having a polarity opposite to the polarity of the toner is applied to the transfer roller 15. The toner image carried on the peripheral surface of the photosensitive drum 11 is transferred to the sheet by the transfer bias voltage. As an example, the transfer current is 25 μA.

  The sheet having the toner image transferred between the photosensitive drum 11 and the transfer roller 15 is sent to the fixing device 30. The fixing device 30 heats and pressurizes the sheet to fix the toner image to the sheet. The sheet to which the toner image is fixed is discharged to a discharge tray (not shown).

  The toner remaining on the circumferential surface of the photosensitive drum 11 after the toner image is transferred to the paper is removed from the circumferential surface of the photosensitive drum 11 by the cleaning device 16 and collected.

  As shown in FIG. 2, the cleaning device 16 includes a cleaning blade 40, a paddle member 50, and a transport screw 60. The cleaning device 16 is disposed on the upper side of the photosensitive drum 11.

  The cleaning blade 40 is in pressure contact with the peripheral surface of the photosensitive drum 11 from above, and scrapes off toner remaining after transfer from the peripheral surface of the photosensitive drum 11.

As an example, Young's modulus of the cleaning blade 40 = 888 gf / mm ² , free length = 9.5 mm, blade linear pressure = 33.44 gf / cm, cleaning angle = 6 degrees, the cleaning blade 40 with respect to the circumferential surface of the photosensitive drum 11 The amount of bite = 1.6 mm.

  The paddle member 50 is disposed along the axial direction of the photosensitive drum 11 so as to be close to the peripheral surface of the photosensitive drum 11 in the vicinity of the press contact portion of the cleaning blade 40 to the peripheral surface of the photosensitive drum 11. Yes.

  The paddle member 50 conveys the toner scraped off by the cleaning blade 40 in a direction orthogonal to the axial direction of the photosensitive drum 11 by rotating clockwise in FIG. Specifically, the paddle member 50 lifts the toner scraped off by the cleaning blade 40 toward the transport screw 60. However, the toner conveying ability by the paddle member 50 is not the same in each part of the photosensitive drum 11 in the axial direction. Details will be described later.

  The conveying screw 60 has a spiral shape and is arranged in parallel to the axial direction of the paddle member 50 so as to face the paddle member 50 with a predetermined interval. The transport screw 60 is disposed obliquely above the paddle member 50. The conveyance screw 60 conveys the toner conveyed by the paddle member 50 toward a collection container (not shown) in parallel with the axial direction of the photosensitive drum 11 by rotating. As a result, the waste toner is collected in the collection container. The conveying screw 60 is included in a collecting device that collects the toner that is scraped off from the peripheral surface of the photosensitive drum 11 by the cleaning blade 40 and conveyed by the paddle member 50.

  Next, the shape of the paddle member 50 and the arrangement relationship of each member will be described.

  As shown in FIG. 3, in the axial direction X of the photosensitive drum 11, the photosensitive drum 11, the cleaning blade 40, the paddle member 50, the conveying screw 60, the exposure region 13 </ b> A by the exposure device 13, the developing roller 14, and the transfer roller 15. The respective center positions of these coincide with each other. Further, in the axial direction X, the center position of the conveyed paper also coincides with the center position of the photosensitive drum 11 and the like.

  In the image forming apparatus 1, image forming processing is performed on various sizes of paper such as letter-size paper P1, A4-size paper P2, and A3-size paper P3. As an example, it is assumed that the maximum sheet size on which image forming processing is performed in the image forming apparatus 1 is A3 size. The most frequently used paper size is roughly determined by the country or region to which the image forming apparatus 1 is shipped. In this embodiment, it is assumed that the size is a letter size.

  In the axial direction X, the transport screw 60 is longer than the photosensitive drum 11 and transports toner from the back side to the front side of the image forming apparatus 1.

  The magnetized portion 141 of the developing roller 14 is longer than the A3 size paper P3 which is the maximum size. The transfer roller 15 is longer than the magnetized portion 141 of the developing roller 14 and the exposure area 13A. The cleaning blade 40 is longer than the transfer roller 15. The photosensitive drum 11 is longer than the cleaning blade 40.

  The paddle member 50 includes a paddle shaft 51 and a blade member 52 and is configured to rotate around the paddle shaft 51. The paddle shaft 51 is parallel to the axial direction X.

  The paddle member 50 includes, in the axial direction X, a specific area A1 including at least an area from the inside of the paper passing area of the paper P3 having the maximum paper size that can pass through to the outside of the area where the transfer roller 15 contacts the photosensitive drum 11. , A2 is configured such that the toner carrying capability is lower than the normal area B1 excluding the specific areas A1 and A2 in the paper passing area of the paper P3 of the maximum paper size that can be passed.

  As an example, the specific areas A1 and A2 are areas in the axial direction X from the inside of the paper passing area of the letter-size paper P1 that is most frequently used to the outside of the area where the transfer roller 15 contacts the photosensitive drum 11. is there.

  In the first embodiment, in the paddle shaft 51, the normal region B1 and the end regions C1 and C2 on the end side of the paddle shaft 51 in the axial direction X with respect to the specific regions A1 and A2 are respectively shown in FIG. A blade member 52 for conveying toner is provided as shown in FIG. 4A, and the blade member 52 is not provided in the specific areas A1 and A2 as shown in FIG.

  As shown in FIG. 4C, in the region where the blade member 52 is provided, the paddle member 50 rotates about the paddle shaft 51, so that the toner scraped off by the cleaning blade is lifted by the blade member 52. , And conveyed in a direction orthogonal to the axial direction X.

  The blade member 52 is provided in at least one place in the circumferential direction of the paddle shaft 51.

  Since the specific areas A1 and A2 have lower toner transport capability than the normal area B1 and the end areas C1 and C2, a part of the toner scraped off from the peripheral surface of the photosensitive drum 11 by the cleaning blade 40 is a paddle member. It accumulates in 50 specific areas A1, A2. For this reason, in the specific areas A1 and A2 in the axial direction X on the peripheral surface of the photosensitive drum 11, a small amount of toner remains even after scraping by the cleaning blade 40. In the specific areas A1 and A2, a lubricating effect is exhibited by the remaining toner. For this reason, in the specific areas A1 and A2, the frictional force between the photosensitive drum 11 and the transfer roller 15 is reduced, and wear of the peripheral surface of the photosensitive drum 11 is suppressed. Therefore, the life of the photosensitive drum 11 can be extended.

  Further, the blade member 52 is provided in the normal region B1 and the end regions C1 and C2, and the blade member 52 is not provided in the specific regions A1 and A2. The frictional force can be reduced.

  Further, in the region where the transfer roller 15 is in contact with the photosensitive drum 11, there is an opportunity for friction between the photosensitive drum 11 and the transfer roller 15 in the region outside the sheet passing region of the letter-size paper P 1 that is used most frequently. It is possible to reduce the frictional force between the photosensitive drum 11 and the transfer roller 15 in the region where the number of friction opportunities is greatest.

  The transport screw 60 collects other toner while leaving a part of the toner accumulated in the specific areas A1 and A2. That is, when the amount of toner accumulated in the specific areas A1 and A2 of the paddle member 50 exceeds a predetermined amount, the toner accumulated in the specific areas A1 and A2 of the paddle member 50 is collected by the transport screw 60. For this reason, toner leakage due to excessive accumulation of toner in the specific areas A1 and A2 is prevented.

  The paddle member 50 preferably further includes a rib 55. The rib 55 is provided on the paddle shaft 51 along the axial direction X. By providing the rib 55 on the paddle shaft 51, the bending strength in the axial direction X of the paddle shaft is improved.

  In the image forming apparatus 1, it is preferable to use a toner that does not contain a silica having a large particle diameter of 100 nm or more as an external additive. This is because the lubricating effect of the toner is enhanced.

  As shown in FIGS. 5 (A) and 5 (B), as the paddle member 50A according to the second embodiment, blade members 521 and 522 may be provided at two locations in the circumferential direction of the paddle shaft 51. It is done. For example, the two blade members 521 and 522 are provided point-symmetrically about the paddle shaft 51. For convenience of explanation, the same reference numerals are used for the same configuration as the paddle member 50.

  According to the paddle member 50A according to the second embodiment, the toner scraped off by the cleaning blade 40 can be efficiently conveyed and collected in the normal region B1 and the end regions C1 and C2.

  FIG. 6 shows the experimental results. In this experiment, black toner that does not contain a large particle size silica of 100 nm or more as an external additive to styrene-acrylic resin, and uses a black copying machine SHARP MX-M503, a black belt chart with a printing rate of 6%. An original image formation process was performed. The image forming apparatus to which the paddle member 50A according to the embodiment having the two blade members 521 and 522 is applied, and the paddle according to the comparative example in which the specific areas A1 and A2 also have a transport capability equivalent to the normal area B1. With respect to the image forming apparatus to which the member is applied, the amount of wear in the normal region B1 and the amount of wear in the specific regions A1 and A2 of the peripheral surface of the photosensitive drum 11 when the image forming process is performed 100,000 times each. Each was measured several times and the average value was obtained. FIG. 6 shows the ratio of the wear amount in the specific regions A1 and A2 to the wear amount in the normal region B1.

  From this experimental result, it is understood that the image forming apparatus to which the paddle member 50A according to the example is applied has a 10% reduction in wear amount than the image forming apparatus to which the paddle member according to the comparative example is applied. It was.

  FIG. 7 shows a paddle member 50B according to the third embodiment. For convenience of explanation, the same reference numerals are used for the same configuration as the paddle member 50.

  In the paddle member 50B, the paddle shaft 51 is provided with brush members 53 and 54 composed of a plurality of linear members that convey toner. The density of the linear members of the brush members 53 provided in the specific regions A1 and A2 is lower than the density of the linear members of the brush members 54 provided in the normal region B1 and the end regions C1 and C2.

  In the specific areas A1 and A2, since the density of the linear members of the brush member 53 is low and the toner transport capability is low, toner accumulates in the specific areas A1 and A2. With such a simple structure, the frictional force between the photosensitive drum 11 and the transfer roller 15 can be reduced.

  The cleaning device 16 is not limited to be disposed on the upper side of the photosensitive drum 11, and may be any position where the toner collected by the cleaning blade 40 from the peripheral surface of the photosensitive drum 11 can be conveyed by the paddle member 50. For example, it is also possible to dispose it obliquely above or to the side of the photosensitive drum 11.

  Further, when the most frequently used paper size is a size other than the letter size, for example, A4 size, the specific areas A1 and A2 are arranged in the axial direction X from the inside of the sheet passing area of the A4 size paper. The area extending to the outside of the area where the transfer roller 15 abuts, and the toner conveyance capability of the paddle members 50, 50A, 50B in this specific area is lower than the normal area B1, thereby extending the life of the photosensitive drum 11. The effect that it is possible can be obtained.

  It is conceivable to construct a new embodiment by combining the technical features of the above-described embodiments.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 10 ... Image forming unit 11 ... Photosensitive drum 14 ... Developing roller 15 ... Transfer roller 40 ... Cleaning blade 50, 50A, 50B ... Paddle member 51 ... Paddle shaft 52, 521, 522 ... Blade member 53, 54 ... Brush member 60 ... Conveying screw (collection device)
A1, A2 ... specific area B1 ... normal area

Claims (6)

A photosensitive drum that carries an electrostatic latent image on its peripheral surface while rotating in one direction, and development that visualizes the electrostatic latent image into a toner image by supplying toner to the peripheral surface facing the peripheral surface A roller, a transfer roller that contacts the peripheral surface and transfers a toner image from the peripheral surface to a sheet, a cleaning blade that scrapes off toner remaining on the peripheral surface from the peripheral surface after transfer, and a cleaning blade that scrapes off the toner. A paddle member applied to an image forming unit comprising: a paddle member that conveys the toner that has been conveyed in a direction perpendicular to the axial direction of the photosensitive drum; and a collection device that collects the toner conveyed by the paddle member. There,
Arranged so as to be close to the peripheral surface along the axial direction, and outside the area where the transfer roller abuts the photosensitive drum from the inside of the maximum sheet size in the axial direction. A paddle member configured such that in a specific region including at least the region up to, a toner conveyance capability is lower than a normal region excluding the specific region in the sheet passing region. Configured to rotate about a paddle axis parallel to the axial direction;
2. The paddle member according to claim 1, wherein a blade member that conveys toner is provided in the normal region of the paddle shaft, and the blade member is not provided in the specific region. The paddle shaft is configured to rotate around a paddle shaft parallel to the axial direction, and the paddle shaft is provided with a brush member composed of a plurality of linear members that convey toner,
The paddle member according to claim 1, wherein the density of the linear member is lower in the specific region than in the normal region.   The specific area is an area from the inside of a paper passing area of a specific paper size having the highest use frequency to the outside of an area where the transfer roller is in contact with the photosensitive drum. The paddle member described. A photosensitive drum carrying an electrostatic latent image on its peripheral surface while rotating in one direction;
A developing roller that visualizes an electrostatic latent image into a toner image by supplying toner to the peripheral surface facing the peripheral surface;
A transfer roller that contacts the peripheral surface and transfers a toner image from the peripheral surface to a sheet;
A cleaning blade that scrapes off toner remaining on the peripheral surface from the peripheral surface after transfer;
A paddle member for conveying the toner scraped off by the cleaning blade in a direction perpendicular to the axial direction of the photosensitive drum;
A recovery device for recovering the toner conveyed by the paddle member;
The paddle member is disposed so as to be close to the peripheral surface along the axial direction, and the transfer roller is placed on the photosensitive drum from the inside of the maximum sheet size in the axial direction. An image forming unit configured to have a toner conveyance capability lower in a specific area including at least an area extending outside an abutting area than in a normal area excluding the specific area in the sheet passing area.   The image forming unit according to claim 5, wherein the collecting device collects another toner while leaving a part of the toner accumulated in the specific area.

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