JP2014112135A - Image forming unit and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of print defects.SOLUTION: An image forming unit includes a first roller, a second roller that is in contact with the first roller, and a hollow gear that drives the second roller; and the second roller includes a shaft part to which the hollow gear is attached, and a tapered part that is an inclined surface formed on the shaft part to be in contact with an inner peripheral surface of the hollow gear.

Description

  The present invention relates to an image forming unit having a roller and an image forming apparatus.

  Conventional image forming units employ a method in which a charging roller is brought into contact with the image carrier, and once foreign matter, dust, toner or the like adheres to the surface of the charging roller, uneven charging occurs on the image carrier, and charging is performed. There is a possibility that printing defects such as vertical bands and stripes may occur in the portion where the unevenness occurs. Therefore, in order to clean the surface so that foreign matter, toner, etc. do not accumulate on the charging roller, the surface of the charging roller is brought into contact with the cleaning member to clean the surface of the charging roller. A cleaning roller using a foam material with a single bubble and low air permeability is used, and both ends of the cleaning roller are urged by a biasing member such as a coil spring, and the cleaning roller is moved in the same direction as the rotation of the charging roller, such as a gear. Some drive members are rotated while maintaining a constant peripheral speed difference (see, for example, Patent Document 1).

JP 2010-054795 A

  However, in the prior art, the first roller and the second roller are urged at both ends so as to contact each other, and are arranged at one end of the first roller and the second roller. Since the drive is transmitted by the drive gear to rotate the first roller and the second roller, the engagement of the drive gear is caused by the variation in the distance between the axes of the first roller and the second roller. The contact between the first roller and the second roller can be ensured due to the influence of the tooth skipping of the engagement of the drive gear, the jitter that is the drive feed unevenness, or the interference of the drive gear tooth bottom. There is a problem that printing failure occurs.

  For example, the pressing force of the urging member, the thickness of the cleaning roller, and the hardness of the cleaning roller should be good so that the cleaning roller can be urged to both ends of the roller and the cleaning roller can be stably cleaned by the cleaning roller. When the conditions are set, variations in the distance between the shafts in the contact between the charging roller and the cleaning roller may occur due to variations in the pressing force, the outer diameter of the cleaning roller, the hardness of the material, and the like.

The variation in the inter-shaft distance that occurs in this way affects the meshing of the drive gear, and the cleaning is caused by the tooth jump of the meshing of the drive gear, the jitter that is the drive feed unevenness, or the interference of the bottom of the drive gear. The contact of the roller with the charging roller cannot be ensured, and the cleaning performance is deteriorated. As a result, foreign matter, toner, and the like adhere to and accumulate on the charging roller, causing uneven charging of the image carrier. There is a problem that printing defects such as bands and stripes occur.
An object of the present invention is to solve such problems, and to suppress the occurrence of printing defects.

  Therefore, the present invention provides a first roller, a second roller in contact with the first roller, a hollow gear that drives the second roller, and the second roller on which the hollow gear is mounted. The shaft portion has a taper portion formed with an inclined surface that comes into contact with the inner peripheral surface of the hollow gear.

  The present invention thus configured has the effect of suppressing the occurrence of printing defects.

Explanatory drawing of the contact part of the charging roller and the cleaning roller in the first embodiment 1 is a schematic cross-sectional view showing the configuration of a color image recording apparatus according to a first embodiment. 1 is a perspective view of an image forming unit according to a first embodiment. The perspective view of the charging roller and the cleaning roller in the first embodiment The perspective view of the charging roller and the cleaning roller in the first embodiment Sectional drawing of the drum unit in 1st Example Sectional drawing of the charging roller and the cleaning roller in the first embodiment Sectional drawing of the contact part of the charging roller and cleaning roller in 1st Example Explanatory drawing of the drive gear in 1st Example The perspective view of the charging roller and the cleaning roller in the second embodiment Exploded perspective view of a charging roller and a cleaning roller in the second embodiment

  Embodiments of an image forming unit and an image forming apparatus according to the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic cross-sectional view showing the configuration of the image forming apparatus in the first embodiment.
In FIG. 2, a color image recording apparatus (printer) 55 as an image forming apparatus has an upper cover 33 that is openable and closable with respect to a lower cover 31 about a support shaft 32 from a dividing plane ZZ. 33 is provided with a stacker 34 on which printed recording sheets are discharged and stacked.
The lower cover 31 is provided with a paper transport path 39 having paper feed rollers 35, 36, 37 and 38, and a paper feed cassette 40 for storing recording paper is provided at the end of the paper transport path 39. Yes.

In the sheet conveyance path 39, a sheet feeding unit 41 that feeds the recording sheet from the sheet feeding cassette 40, a conveyance belt unit 43 that conveys the fed recording sheet to the conveyance belt 42 by an electrostatic effect, and an image toner A fixing unit 44 for fixing the recording paper is provided.
Further, a black image forming unit 45, a yellow image forming unit 46, a magenta image forming unit 47 from the upstream side in the recording sheet conveying direction across the sheet conveying path 39 with the conveying belt unit 43, A cyan image forming section 48 is arranged. The configuration of the image forming apparatuses 45 to 48 is the same, and the toner color as the developer stored therein is different.

Each of the image forming units 45 to 48 includes an image forming unit to be described later. The charging roller 5, a recording head 51 such as an LED (Light Emitting Diode) head, a developing roller 8, and a transfer roller are provided around the photosensitive drum 3. 54, and an electrostatic latent image is formed on the surface of the photosensitive drum 3 by the recording head 51, and a charged toner conveyed by the developing roller 8 is attached to the electrostatic latent image by an electrostatic effect, thereby forming a toner image. Form.
The transfer roller 54 transfers the toner image on the photosensitive drum 3 onto a recording sheet conveyed by the conveyance belt 42 by being charged with a polarity opposite to that of the charged toner.

  3 is a perspective view of the image forming unit in the first embodiment, FIGS. 4 and 5 are perspective views of the charging roller and the cleaning roller in the first embodiment, and FIG. 6 is a cross-sectional view of the drum unit in the first embodiment. FIG. 7 is a sectional view of the charging roller and the cleaning roller in the first embodiment.

  3 to 7, the image forming unit 1 includes a photosensitive drum 3 as an image carrier on which an electrostatic latent image is formed, and a first roller (charging member) that uniformly charges the surface of the photosensitive drum 3. As a charging roller 5, a cleaning roller 2 as a second roller (cleaning member) for cleaning the surface of the charging roller 5 in contact with the surface of the charging roller 5, and a cleaning blade for scraping off residual toner on the photosensitive drum 3. 9, a conveying spiral 20 that conveys the waste toner scraped off by the cleaning blade 9, a developing roller 8 that develops the electrostatic latent image formed on the photosensitive drum 3 with toner, and a removable toner cartridge. A supply roller 13 that supplies toner 19 to the developing roller 8, a developing blade 6 that regulates the toner layer on the developing roller 8, and a side plate that supports these members. Over preparative 7a, it is constituted by 7b, constituting a part of the image forming portions 45 to 48 shown in FIG.

A cleaning roller 2 that cleans foreign matter, dust, toner, and the like attached to the outer peripheral surface of the charging roller 5 is rotatably disposed on the outer peripheral surface of the charging roller 5.
The cleaning roller 2 is disposed so as to uniformly contact the charging roller 5 while holding a predetermined pressing force by the biasing springs 11a and 11b via the bearings 10a and 10b.
3 to 5, the photosensitive drum 3 is rotatably held by the side plates 7 a and 7 b, and the drum gear 4 is at one end in the rotation axis direction of the photosensitive drum 3 (the direction in which the rotation axis extends, the same applies hereinafter). It is fixed to.

The developing roller 8 is rotatably held by the side plates 7a and 7b, and the developing gear 8a is fixed to one end in the rotation axis direction. The drum gear 4 and the developing gear 8a are engaged with each other.
On the other hand, the charging roller 5 is rotatably held by the side plates 7a and 7b, and the charging roller gear 21 is fixed to one end portion in the rotation axis direction.
The cleaning roller 2 is rotatably held by the side plates 7a and 7b, and the cleaning roller gear 22 is supported at one end in the rotation axis direction.

FIG. 1 is an explanatory diagram of a contact portion between a charging roller and a cleaning roller in the first embodiment.
In FIG. 1, the cleaning roller 2 and the charging roller 5 are disposed so that the outer peripheral surfaces thereof are in contact with each other so that the pressing amount of the cleaning roller 2 into the charging roller 5 is m. Further, a cleaning roller gear 22 as a hollow gear that rotates and drives the cleaning roller 2 is disposed at the end of the shaft portion 2 b of the cleaning roller 2, and the charging roller 5 has a charging roller on the shaft portion 5 b. A charging roller gear 21 is attached as a fixed gear for rotationally driving 5.

An end portion in the longitudinal direction of the shaft portion 2b of the cleaning roller 2 on which the cleaning roller gear 22 is mounted has a tapered portion 2c that contacts the inner peripheral surface 22a of the cleaning roller gear 22, and the tapered portion 2c is a shaft portion. An inclined surface α whose outer diameter gradually decreases from the central portion side to the end portion side of 2b is formed, and a planar D-cut portion 2d is formed.
The cleaning roller gear 22 is formed so that its inner diameter is larger than the minimum diameter 2f of the tapered portion 2c and smaller than the maximum diameter 2e, and the inner peripheral surface 22a is rotatably provided in contact with the inclined surface α of the tapered portion 2c. And is provided so as to be movable in the axial direction of the shaft portion 2b indicated by an arrow A in the drawing.

In addition, a planar engaging portion that engages with the D-cut portion 2d formed in the tapered portion 2c is formed inside the cleaning roller gear 22, and the rotational drive of the cleaning roller gear 22 is transmitted to the shaft portion 2b. Be able to. The D-cut portion 2d is formed on a part of the taper portion 2c so as to extend in the axial direction of the shaft portion 2b, and engages with the engaging portion of the cleaning roller gear 22 that moves in the axial direction of the shaft portion 2b. It is possible.
The cleaning roller gear 22 and the charging roller gear 21 are meshed with each other while maintaining a gap amount r, and the rotation driving of the charging roller 5 is transmitted through the charging roller gear 21 and the cleaning roller gear 22 so that the cleaning roller 2 rotates. That is, the cleaning roller gear 22 moves in the longitudinal direction of the shaft portion 2 b of the cleaning roller 2 in accordance with the gap amount r in the meshing between the cleaning roller gear 22 and the charging roller gear 21.

Here, as shown in FIG. 9, the gap amount r is a value p which is half the pitch circle diameter of the cleaning roller gear 22 from the center distance L between the center 22a of the cleaning roller gear 22 and the center 21a of the charging roller gear 21. And a value obtained by subtracting a value q which is half the pitch circle diameter of the charging roller gear 21.
In this embodiment, the pitch circle diameter means the pitch circle diameters of the design of the cleaning roller gear 22 and the charging roller gear 21.

The operation of the above configuration will be described.
First, the operation of the image forming unit will be described with reference to FIG.
3, the photosensitive drum 3 rotatably held by the side plates 7a and 7b of the image forming unit 1 has the drum gear 4 fixed to one end in the rotation axis direction, and the color image recording device 55 shown in FIG. Drive is transmitted to the drum gear 4 by a gear train composed of a motor gear and a reduction gear, and rotates.
Since the developing gear 8a fixed to one end in the rotation axis direction of the developing roller 8 meshes with the drum gear 4, the developing roller 8 maintains a constant speed difference with respect to the rotational speed of the photosensitive drum 3. Rotate.

On the other hand, the charging roller 5 is rotatably held by the side plates 7a and 7b, and both end portions in the rotation axis direction are uniformly urged to the photosensitive drum 3 by a urging spring with a predetermined pressing force.
The charging roller 5 rotates in the accompanying direction by a biasing force according to the rotation of the photosensitive drum 3 at a peripheral speed substantially the same as that of the photosensitive drum 3. As shown in FIG. 4, the charging roller 5 is provided with bearings 10a and 10b at both ends in the rotation axis direction, and the cleaning roller 2 is rotatably held by the bearings 10a and 10b.
Both ends of the cleaning roller 2 in the rotation axis direction are uniformly urged to the charging roller 5 with a predetermined pressing force by urging springs 11a and 11b.

A charging roller gear 21 and a cleaning roller gear 22 shown in FIG. 4 are fixed and meshed with one end of each of the charging roller 5 and the cleaning roller 2 in the rotation axis direction, and the cleaning roller 2 is rotated by the rotation of the charging roller 5. Rotates with a constant speed difference from the rotation speed of the charging roller 5.
The cleaning roller 2 is made of a single foam sponge made of urethane or the like, and each single foam sponge is independent. The thickness of the sponge portion 2a and the diameter of the shaft portion 2b shown in FIGS. 5 and 8 are formed so that the thickness of the sponge portion 2a is 1 to 2 mm and the diameter of the shaft portion 2b is φ4 to 6 mm depending on processing and cleaning performance. The pushing amount m to the charging roller 5 is set to be within a range of 0.3 to 0.7 mm.

Here, the operation of the charging roller gear 21 of the charging roller 5 and the cleaning roller gear 22 of the cleaning roller 2 shown in FIG. 4 will be described with reference to FIG.
In FIG. 9, in order to maintain good engagement with the cleaning roller gear 22 and the charging roller gear 21, it is desirable that the gap amount r due to the gear engagement is 0 to 0.35 mm.
When the gap amount r is smaller than 0, the jitter (transverse stripe pattern of gear 1 tooth pitch), which is a gear feed unevenness, or the pushing amount of the cleaning roller 2 to the charging roller 5 near the side where the gear is mounted is 0.3 mm. As a result, the cleaning performance cannot be sufficiently exhibited, and charging unevenness occurs due to the accumulation of foreign matter, toner, and the like on the charging roller, and printing defects such as vertical bands and stripes occur.

On the other hand, when the gap amount r is larger than 0.35 mm, defects such as jitter and tooth skipping, which are gear feed unevenness, occur, and printing defects occur.
In this embodiment, as shown in FIG. 1, a tapered portion 2c is formed in the vicinity of the end portion of the shaft portion 2b of the cleaning roller 2 where the cleaning roller gear 22 is mounted. The tapered portion 2c is formed such that the outer diameter gradually decreases toward the end of the shaft portion 2b. In this embodiment, the difference between the maximum diameter 2e and the minimum diameter 2f is 0.4 mm (with a radius of 0.2 mm). 2 mm).

As shown in FIG. 4, the cleaning roller 2 is uniformly urged to the charging roller 5 by the urging springs 11 a and 11 b at a predetermined pressing force at both ends in the rotation axis direction. It is set to be within a range of 0.3 to 0.7 mm.
At this time, when the gap amount r is less than 0 due to the engagement of the cleaning roller gear 22 with the charging roller gear 21, the pressure caused by the interference between the bottom of the cleaning roller gear 22 and the charging roller gear 21 is applied to the cleaning roller gear 22 and the tapered portion 2c. Accordingly, the cleaning roller gear 22 moves to the small diameter side at the tapered portion 2c.

When the gap amount r is equal to or greater than 0, there is no interference between the bottom of the cleaning roller gear 22 and the charging roller gear 21, so that no pressure acts on the cleaning roller gear 22 and the taper portion 2c, and the taper portion 2c of the cleaning roller gear 22 Movement to the small diameter side stops.
Accordingly, the gap amount r can be maintained at 0 or more by the engagement of the cleaning roller gear 22 with the charging roller gear 21.
Even when the cleaning roller gear 22 is moved to the minimum diameter portion of the tapered portion 2c, the minimum diameter of the tapered portion 2c is set so that the gap amount r is 0.35 mm or less, which is good.

In the present embodiment, the charging roller gear 21 and the cleaning roller gear 22 employ a helical gear so that the gear meshing can be transmitted more stably. In driving the helical gear, since a thrust force is generated in the axial direction of the roller, the direction in which the thrust force is generated can be set by the rotation direction of the roller and the twisting direction of the gear. In the present embodiment, the direction in which the thrust force of the cleaning roller gear 22 is generated is set to be the same as the moving direction of the cleaning roller gear 22 in the tapered portion 2c.
This thrust force is much smaller than the force that the gear moves due to the inclination of the taper portion 2c, but there is a possibility that the force that the gear moves due to the inclination of the taper portion 2c may be affected depending on the way of inclination, so the good depending on the amount of inclination. A life test of the image forming unit was conducted in order to confirm a proper range.

  The content of the life test is that the taper amount [mm], which is the difference between the maximum radius and the minimum radius of the taper portion 2c, is “0”, “0.05”, “0.1”, “0.15”, “0”. .2 "and" 0.25 ", A3 size printing paper, which is the largest paper that can be printed with this experimental machine, is used, and the printed image is printed with foreign matter and toner accumulation on the charging roller 5. The higher the duty (print density) tends to be accumulated, the more frequently the general user uses the print duty. A printed image was obtained. In addition, the number of prints that reached the end of the life of the image forming unit was printed, and the presence or absence of foreign matter on the charging roller, streaks due to toner accumulation, banding, jitter, and tooth skipping was confirmed.

  After printing a specified number of sheets, if there are no streaks, bands, or jitter in the printed image, it will be marked as “O”, and if it has occurred, it will be marked as “X”. Table 1 shows the result of the experiment.

As shown in Table 1, when the difference between the maximum radius and the minimum radius of the tapered portion 2c is in the range of 0.1 to 0.2, streaks and bands are generated due to the accumulation of foreign matter and toner on the charging roller 5. In addition, there was no occurrence of jitter and tooth skipping in the meshing of the cleaning roller gear 22, and good results were obtained.
Further, during the lifetime of the image forming unit, the outer diameter of the cleaning roller 2 decreases by about 0.1 to 0.2 mm due to rotational friction caused by contact with the charging roller 5. When the outer diameter of the cleaning roller 2 decreases, the center distance L between the charging roller 5 and the cleaning roller 2 shown in FIG. 8 decreases, and the gear engagement gap amount r shown in FIG. 1 also decreases. However, since the cleaning roller gear 22 moves to the small diameter side of the taper portion 2c by the taper portion 2c, a good gap amount r is maintained.

As described above, when the gear is engaged to transmit the drive from the charging roller gear 21 of the charging roller 5 to the cleaning roller gear 22 of the cleaning roller 2 in the contact and driving of the charging roller 5 and the cleaning roller 2, the cleaning roller 2 By providing the taper portion 2c on the shaft portion 2b on which the cleaning roller gear 22 is provided, the pushing amount of the cleaning roller 2 into the charging roller 5 is appropriately secured, and the gap between the charging roller gear 21 and the cleaning roller gear 22 is secured. The amount r can be secured properly,
Occurrence of printing defects such as vertical bands and stripes can be suppressed.

Further, since the taper amount of the taper portion 2c is set to 0.1 to 0.2 mm, the gap amount r is set as the meshing of the gear that can secure a stable contact amount by the contact of the cleaning roller 2 with the charging roller 5. The value can be set to an appropriate range of 0 to 0.35 mm, and the amount of contact with which the cleaning roller 2 can stably clean the charging roller 5 is secured, and the cleaning roller gear 22 by the charging roller gear 21 is secured. Thus, it is possible to secure a gap amount that can stably drive the image, and it is possible to reliably suppress the occurrence of printing defects.
Further, it is possible to absorb a change in the gap amount due to wear of the cleaning roller 2, which is a change with time due to the operation of the image forming unit 1, and to extend the life of the image forming unit 1.

  In this embodiment, the charging roller 5 and the cleaning roller 2 are in contact with each other, and the inclined surface that is in contact with the inner peripheral surface 22a of the cleaning roller gear 22 is connected to the shaft portion 2b of the cleaning roller 2 on which the cleaning roller gear 22 is mounted. Although the taper portion 2c formed with α is described as being formed, the present invention is not limited to this, and the developing roller 8 (first roller) and the supply roller 13 (second roller) shown in FIG. By forming a tapered portion in contact with the inner peripheral surface of the drive gear on the shaft portion of the supply roller 13 (second roller) on which the drive gear is mounted, the developing roller 8 ( The first gear) and the supply roller 13 (second roller) have a gap between the shafts, and the driving gear meshes, the jitter that is the driving unevenness, or the driving gear. The contact between the developing roller 8 (first roller) and the supply roller 13 (second roller) cannot be ensured due to the interference of the tooth bottom, and the supply roller 13 to the developing roller 8 is prevented. It is possible to stabilize the toner supply and prevent the occurrence of printing defects by preventing the decrease in toner density and the occurrence of uneven toner density.

As described above, in the first embodiment, by providing the tapered portion on the shaft portion where the cleaning roller gear of the cleaning roller is provided, it is possible to appropriately ensure the pushing amount of the cleaning roller to the charging roller. In addition, the gap amount between the charging roller gear and the cleaning roller gear can be appropriately secured, and the effect of suppressing the occurrence of printing defects such as vertical bands and stripes can be obtained.
Further, the effect that the life of the image forming unit can be extended is obtained.

In the configuration of the second embodiment, a cushion material is provided between the bearing for holding the cleaning roller and the cleaning roller gear in the configuration of the first embodiment.
FIG. 10 is a perspective view of the charging roller and the cleaning roller in the second embodiment, and FIG. 11 is an exploded perspective view of the charging roller and the cleaning roller in the second embodiment. Note that parts similar to those of the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

  10 and 11, the cushion member 30 is provided between the bearing 10 a that holds the cleaning roller 2 and the cleaning roller gear 22. The cushion material 30 is an elastic member made of, for example, urethane sponge or felt, and is interposed between the bearing 10 a and the cleaning roller gear 22 so as to be pressed into contact with the side surface of the cleaning roller gear 22. . The cushion material 30 may be a leaf spring such as a wave washer.

The operation of the above configuration will be described.
The configurations and operations of the photosensitive drum, charging roller, and cleaning roller of the image forming unit are the same as those in the first embodiment shown in FIG.
As shown in FIGS. 10 and 11, the cushion member 30 is held in a compressed state by being sandwiched between the bearing 10 a and the cleaning roller gear 22 while being penetrated by the shaft portion 2 b of the cleaning roller 2.
As shown in FIG. 1, the cleaning roller gear 22 moves to the smaller diameter side of the taper portion 2c so that the gap amount r becomes 0 or more by the engagement of the charging roller gear 21 and the cleaning roller gear 22 by the taper portion 2c. It moves to the cushion material 30 side shown in FIG.

Thus, when the cleaning roller gear 22 moves until the gap amount r becomes 0, a gap is formed between the cleaning roller gear 22 and the bearing 10a, but the cleaning roller gear 22 does not move due to an external force. In addition, the cushion material 30 can stably suppress it.
The force with which the cushion material 30 restrains the cleaning roller gear 22 is set to be much smaller than the force with which the cleaning roller gear 22 moves so that the gap amount r is 0 or more.

  As described above, the cushion member 30 is provided between the bearing 10a and the cleaning roller gear 22, and the cushion member 30 suppresses the side surface of the cleaning roller gear 22, so that the clearance between the cleaning roller gear 22 and the bearing 10a is reduced. Since the backlash can be absorbed and a stable state can be maintained, the range of the gap amount in which jitter and tooth jump do not occur can be widened.

As described above, in the second embodiment, in addition to the effects of the first embodiment, a charging roller is provided between the side surface of the cleaning roller gear of the cleaning roller and the bearing of the cleaning roller. With a good contact amount between the cleaning roller and the cleaning roller gear, the charging roller gear and the cleaning roller gear can be meshed with each other so that a good gap amount can be secured, and the taper portion provided on the shaft portion of the cleaning roller. It is possible to maintain a stable contact state with the cleaning roller gear that has moved, and to maintain a stable state by absorbing the backlash between the cleaning roller gear and the bearing. The effect that the range of the gap amount that does not occur can be widened is obtained.
In the first and second embodiments, the image forming apparatus provided with the image forming unit has been described as a color image recording apparatus (printer). However, the present invention is not limited to this. An apparatus, a multifunction peripheral (MFP), or the like may be used.

DESCRIPTION OF SYMBOLS 1 Image forming unit 2 Cleaning roller 2a Sponge part 2b Shaft part 2c Taper part 2d D cut part 3 Photosensitive drum 4 Drum gear 5 Charging roller 5b Shaft part 6 Developing blade 7a, 7b Side plate 8 Developing roller 9 Cleaning blade 10a, 10b Bearing 11a 11b Energizing spring 21 Charging roller gear 22 Cleaning roller gear 22a Inner peripheral surface α Inclined surface 42 Conveying belts 45, 46, 47, 48 Image forming unit 51 Recording head 54 Transfer roller 55 Color image recording apparatus (printer)

Claims (10)

A first roller;
A second roller in contact with the first roller;
A hollow gear for driving the second roller;
An image forming unit, comprising: a tapered portion formed with an inclined surface in contact with an inner peripheral surface of the hollow gear on a shaft portion of the second roller on which the hollow gear is mounted. The image forming unit according to claim 1,
The taper portion is formed at an end portion in the longitudinal direction of the shaft portion of the second roller, and is formed so that an outer diameter decreases from a center portion side to an end portion side of the shaft portion of the second roller. An image forming unit. The image forming unit according to claim 1 or 2,
The first roller has a fixed gear that meshes with the hollow gear and drives the first roller;
The image forming unit, wherein the hollow gear moves in a longitudinal direction of a shaft portion of the second roller in accordance with a gap amount in meshing with the fixed gear. The image forming unit according to claim 3.
When the gap amount is represented by a value obtained by subtracting the pitch circle diameter of the fixed gear and the pitch circle diameter of the hollow gear from the distance between the rotation center of the fixed gear and the rotation center of the hollow gear,
The image forming unit, wherein the hollow gear moves to a small diameter side of the tapered portion so that the gap amount becomes 0 or more. The image forming unit according to any one of claims 1 to 4, wherein:
An image forming unit, wherein a difference between a maximum radius and a minimum radius of the tapered portion is 0.1 mm or more and 0.2 mm or less. The image forming unit according to any one of claims 1 to 5,
The tapered portion has a D-cut portion,
An image forming unit, wherein an engagement portion that engages with the D-cut portion is formed on an inner peripheral surface of the hollow gear. The image forming unit according to any one of claims 1 to 6,
An image forming unit, wherein an elastic member is disposed between the hollow gear and a side frame that supports a shaft portion of the second roller. The image forming unit according to claim 7.
The image forming unit, wherein the elastic member is a leaf spring. The image forming unit according to any one of claims 1 to 8,
The first roller is a charging member that charges the surface of the image carrier on which an electrostatic latent image is formed,
The image forming unit, wherein the second roller is a cleaning member that cleans the surface of the charging member. A first roller;
A second roller in contact with the first roller;
A hollow gear for driving the second roller;
An image forming unit comprising: a shaft portion of the second roller on which the hollow gear is mounted, and a tapered portion formed with an inclined surface in contact with the inner peripheral surface of the hollow gear. Forming equipment.

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