JP2010256744A - Drum unit, and image forming apparatus mounted with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drum unit which prevents an increase in hardness of a cleaning roller with lapse of time, and to provide an image forming apparatus mounted with the same. <P>SOLUTION: The drum unit (17) includes rotating members (18 and 21) used to form a toner image, and cleaning rollers (54 and 22) grinding and rubbing surfaces (70) of the rotating members. The cleaning roller includes a shaft (56) rotatably supported in the unit, and a plurality of fiber-like brush pieces (58) erected on a peripheral wall (57) of the shaft in such a manner that respective base portions (60) dispersedly fill up the peripheral wall. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a drum unit that outputs a toner image to a medium and an image forming apparatus equipped with the drum unit.

  In this type of image forming apparatus, an electrophotographic system is used. When the charger precharges the photosensitive drum and the exposure device irradiates the image forming surface of the drum with light, an electrostatic latent image is formed on the image forming surface. An image is formed. Further, the developing device carries toner, and when a developing bias voltage is applied, the toner is excited and adheres to the electrostatic latent image to form a toner image. The toner image is transferred and fixed on the paper.

Here, in order to transfer the next toner image to the sheet by the image forming apparatus, it is necessary to clean the image forming surface after the previous transfer and to remove the remaining toner from the image forming surface.
Specifically, a cleaning roller or the like is provided on the downstream side of the transfer position with respect to the medium as viewed in the rotation direction of the photosensitive drum, and when the roller grinds and rubs the image forming surface, residual toner is removed. It can be removed from the image forming surface (see, for example, Patent Document 1).

JP 2004-139044 A

However, the above-described conventional technique has a problem that the frictional polishing force of the cleaning roller is gradually increased and the life of the photosensitive drum is shortened.
This is because the roller of the related art is composed of fibrous brush pieces, and a plurality of aggregates in which the root portions of the respective brush pieces are bundled are planted on an elongated base cloth, and the base cloth is spirally wound around the shaft. ing. This is because unevenness of rubbing polishing occurs at the boundary between adjacent base fabrics by winding, and a large gap is formed at each root portion of the aggregate.

  More specifically, large residual toner scraped from the image forming surface or paper dust of the paper is likely to enter the large gap formed between the root portions. Even if a fibrous brush piece is used for the cleaning roller, the hardness of the roller is high to a hardness substantially equal to the rubbing polishing force of, for example, a urethane rubber cleaning roller that does not have this brush piece. This is because wear of the image forming surface is promoted.

As described above, in the conventional technique, no special consideration is given to the point that the rubbing polishing force of the cleaning roller is not changed.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a drum unit that eliminates the above-described problems and does not increase the hardness of a cleaning roller over time, and an image forming apparatus equipped with the drum unit.

  A first invention for achieving the above object is a drum unit comprising a rotating member used for forming a toner image and a cleaning roller for polishing and rubbing the surface of the rotating member. A plurality of shafts that are rotatably supported, and a plurality of brush pieces that are provided on the peripheral wall of the shaft and that have respective root portions dispersed to fill the peripheral wall.

According to the first aspect, the drum unit includes the rotating member and the cleaning roller. The rotating member is used to form a toner image, while the cleaning roller polishes and rubs the surface of the rotating member.
Here, the cleaning roller is composed of a shaft rotatably supported by the drum unit and a fibrous brush piece, and a plurality of brush pieces are erected on the peripheral wall of the shaft, and each root portion of the cleaning roller is relative to the peripheral wall. Instead of being bundled, they are scattered at regular intervals so as not to allow the lump of residual toner to enter and fill the peripheral wall.

Therefore, since the lump residual toner is not deposited on the base part of the brush piece, the hardness of the cleaning roller can be maintained substantially equal to that when the cleaning roller is not used. As a result, the rubbing and polishing force of the cleaning roller does not change as compared with the conventional case, which contributes to a longer life of the cleaning roller.
In addition, since a spirally wound base fabric is not used, it is possible to prevent unevenness in rubbing and polishing as compared with the conventional case.

According to a second aspect of the invention, in the configuration of the first aspect of the invention, the rotating member is a photosensitive drum that forms a toner image on its surface when driven, and the cleaning roller polishes and rubs the surface having residual toner. It is characterized by.
According to the second invention, in addition to the action of the first invention, the surface of the photosensitive drum is liable to deteriorate when, for example, a paper containing a lot of paper dust or a paper containing a lot of talc or calcium bicarbonate is used. . However, since the cleaning roller that does not change the rubbing and polishing force is used, it is possible to remove the paper dust and the like to prevent the surface of the photosensitive drum from being deteriorated and to prevent the surface from being damaged. Therefore, it contributes to the long life of the photosensitive drum.

According to a third invention, in the configuration of the second invention, the distance between the root portions of the brush pieces is 0.3 mm or less.
According to the third invention, in addition to the action of the second invention, if the distance between the root portions of the brush pieces is 0.3 mm or less, the lump-like residual toner does not enter the root portion of the brush pieces at all. Further, the hardness of the cleaning roller can be more reliably maintained with a hardness substantially equal to that when the cleaning roller is not used.

According to a fourth invention, in the configuration of the third invention, the distance between the tip portions of the brush pieces for polishing and rubbing the surface of the photosensitive drum is the same as the distance between the root portions.
According to the fourth aspect of the invention, in addition to the action of the third aspect of the invention, the distance between the brush pieces is uniform from the root part to the tip part, and these brush pieces stand upright with respect to the shaft. Thus, the surface of the photosensitive drum can be uniformly ground and rubbed.

According to a fifth invention, in the configurations of the second to fourth inventions, the photosensitive drum is a photosensitive drum having an organic layer on the surface thereof.
According to the fifth invention, in addition to the effects of the second to fourth inventions, the surface of the photosensitive drum having an organic layer is particularly easily scraped, and the increase in the hardness of the cleaning roller over time is Although there is a concern that the drum may be greatly affected, according to the cleaning roller having the above-described configuration, the characteristics of the photosensitive drum can be maintained over a long period of time, and a particularly remarkable effect is achieved.

A sixth invention is characterized in that, in the configurations of the first to fifth inventions, the rotation ratio between the rotating member and the cleaning roller is in a non-integer multiple relationship.
According to the sixth invention, in addition to the effects of the first to fifth inventions, if the rotation ratio between the rotating member and the cleaning roller is a non-integer multiple relationship, the contact position of the cleaning roller with respect to the rotating member is Since it always changes, it is possible to more reliably eliminate unevenness of polishing and rubbing against the surface of the rotating member.

A seventh aspect of the invention is an image forming apparatus equipped with the drum unit of the first to sixth aspects of the invention.
According to the seventh aspect, in addition to the effects of the first to sixth aspects, if the above-described drum unit is mounted, good image formation can be performed over a long period of time. Contributes to improvement.

  According to the present invention, it is possible to provide a drum unit capable of maintaining the hardness of the cleaning roller at substantially the same hardness as that when the toner is not used, and an image forming apparatus equipped with the drum unit, since toner is not deposited on the root portion of the brush piece. .

1 is a schematic configuration diagram of an image forming apparatus in the present embodiment. FIG. 2 is an enlarged view around a drum unit in FIG. 1. FIG. 3 is a perspective view of the cleaning roller of FIG. 2. It is arrow sectional drawing seen from the IV-IV line of FIG. It is a figure which shows the use condition of the cleaning roller of FIG. It is an enlarged view of the drum unit periphery in another Example.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.
FIG. 1 schematically shows the structure of a printer 1 that performs monochrome printing, which is an example of an image forming apparatus. The cross section shown in the figure is seen from the left side of the printer 1. For this reason, the front surface of the printer 1 is positioned on the right side and the rear surface of the printer 1 is positioned on the left side.

  As shown in the figure, a paper feed cassette 4 is disposed below the inside of the apparatus main body 2 of the printer 1. Inside the cassette 4, sheets of paper P are stored in a stacked state. Then, the paper P is sent toward the upper right of the cassette 4 in the figure, and the sent paper P is reversed toward the back side inside the apparatus main body 2 and conveyed toward the back side as it is. The

In addition, the cassette 4 is configured to be drawn rightward in the drawing, and in this pulled-out state, a new sheet P is replenished in the cassette 4 or the sheet P is loaded with another type. It can be replaced with paper.
Inside the apparatus main body 2, a feed roller 10, a paper feeding path 12, a registration roller 14, and an image forming unit 16 are sequentially arranged on the downstream side in the paper conveying direction from the cassette 4.

The image forming unit 16 includes a drum unit 17 having a photosensitive drum (rotating member) 18. The drum 18 is rotatably installed and is driven clockwise by a driving motor (not shown). The drum 18 of the present embodiment is an OPC drum having an organic layer on the surface thereof.
At appropriate positions around the drum 18, a charger 20, an exposure unit 15, a developing unit 24, a transfer unit 30 and a cleaning unit 50 are provided.

  The charger 20 is located above the drum unit 17 and uniformly charges the image forming surface (surface) 70 of the drum 18 (FIG. 2). The exposure device 15 is disposed above the unit 17 and irradiates the laser beam L toward the drum 18 (FIG. 1). The developing device 24 is arranged on the right side of the unit 17 and has a developing roller 25 as shown in FIG. The developing roller 25 is driven counterclockwise in the figure by a driving motor (not shown).

Further, the transfer unit 30 is disposed below the unit 17 and includes a transfer roller 31. The roller 31 is configured to be able to press against the drum 18 from below.
The drum 18 and the transfer roller 31 use the toner supplied from the toner container 23 and the developing device 24 to form a transfer nip portion for transferring the toner image onto the paper P.

Returning again to FIG. 1, a fixing unit 32, a paper transport path 34 on the paper discharge side, and a paper discharge tray 36 are sequentially arranged on the downstream side of the transfer unit 30 in the paper transport direction.
The sheet conveyance path 34 extends upward from the downstream of the fixing unit 32 along the back surface of the apparatus main body 2, and further bends to the front side at the upper position of the apparatus main body 2. When printing on only one side of the paper P, the paper P that has passed through the fixing unit 32 is discharged to the tray 36 via the discharge roller 35 and stacked in the height direction. The printed paper P stacked on the tray 36 can be easily taken out from the outside.

  On the other hand, in this embodiment, a paper conveyance path 38 for double-sided printing is formed between the cassette 4 and the transfer unit 30 or the fixing unit 32. The sheet conveyance path 38 branches from the middle of the sheet conveyance path 34 at a position along the back surface of the apparatus main body 2, and then downwards. Then, the sheet conveyance path 38 is bent toward the front surface of the printer 1 and extends in the horizontal direction. It is connected to the upstream side of the roller 14, for example, between the rollers 8 and 10, and merges with the paper transport path 12. The paper P in the paper transport path 38 is transported toward the paper transport path 12 by the transport roller 40.

Here, the drum unit 17 of this embodiment includes a cleaning unit 50.
Specifically, as shown in FIG. 2, the cleaning unit 50 is provided on the downstream side of the transfer unit 30 as viewed in the rotational direction of the photosensitive drum 18, and includes a cleaning blade 52, a cleaning roller 54, a flicker 62, and a feed roller. 64.
The cleaning roller 54 is driven clockwise by a drive motor (not shown) to rub the image forming surface 70 after the toner image is transferred in the counter direction.

As a result, the cleaning roller 54 removes residual toner adhering to the organic layer on the image forming surface 70, paper dust from the paper P, talc and calcium bicarbonate contained in the paper P, and the like. The rotation ratio between the drum 18 and the roller 54 is set to a non-integer multiple such as 0.9 times or 1.1 times.
The flicker 62 is in contact with the surface of the roller 54 from above the roller 54, and scrapes off residual toner and the like that has moved from the drum 18 to the roller 54.

The cleaning blade 52 is provided on the downstream side of the roller 54 as viewed in the rotation direction of the drum 18, and scrapes off a small amount of residual toner attached to the image forming surface 70.
The toner scraped off from the image forming surface 70 and the surface of the cleaning roller 54 is collected in a collection container (not shown) via a feed roller 64 that is driven clockwise in FIG.

By the way, the cleaning roller 54 of the present embodiment is constituted by a fibrous brush piece instead of a urethane rubber layer having a predetermined thickness, and has been devised so as not to change the abrasive rubbing force.
Specifically, as shown in FIGS. 3 and 4, the cleaning roller 54 of this embodiment has a metal shaft 56 that is rotatably supported by the housing of the unit 17, and the brush piece 58 is a shaft 56. It is erected directly on the peripheral wall 57 having a larger diameter.

More specifically, each brush piece 58 is made of, for example, nylon resin having a length of 3 mm and a diameter of 30 to 50 μm (1 μm = 1 × 10 ⁻⁶ m), and about 70,000 to 10 for one shaft 56. About 10,000 brush pieces 58 are bonded to the peripheral wall 57.
The distance between the root portions 60 of these adjacent brush pieces 58 is as uniform and narrow as possible, for example, in the range of about 0.2 mm to 0.3 mm. Further, the interval between the tip portions 59 of the adjacent brush pieces 58 is also the same as the interval between the root portions 60, and each brush piece 58 extends in a direction substantially perpendicular to the rotation axis of the shaft 56.

  The cleaning roller 54 configured as described above is provided with a shaft 56 coated with an adhesive on the peripheral wall 57, and is disposed in an electric field with the shaft 56 grounded. This electric field is generated in the direction in which the root portion 60 of the brush piece 58 is directed toward the peripheral wall 57, and each of the root portions 60 of the brush piece 58 is dispersed (spread) at the above-described interval to fill the peripheral wall 57.

As a result, a single residual toner of about 8 μm (1 μm = 1 × 10 ⁻⁶ m) indicated by a black dot in FIG. 5 can adhere to the tip portion 59 of the brush piece 58. The lump has no room for entry into the root portion 60. Then, after the lump-like residual toner adheres to the tip portion 59, it is removed by the flicker 62 and travels to the collection container via the feed roller 64.

  When the printer 1 equipped with the drum unit 17 performs printing, the paper P is separated from the cassette 4 by the rollers 8 and sent out one by one. The sent paper P passes through the paper transport path 12 and reaches the registration roller 14. The roller 14 feeds the paper P to the transfer unit 30 at a predetermined paper feed timing while correcting the oblique feeding of the paper P and measuring the image transfer timing with the toner image formed by the image forming unit 16. To do.

On the other hand, for the photosensitive drum 18, first, the eraser lamp 19 is turned on (FIG. 2), and the charger 20 charges the image forming surface 70 of the drum 18. Next, when the exposure device 15 irradiates the image forming surface 70 with the laser light L, an electrostatic latent image is formed on the image forming surface 70.
When a developing bias voltage is applied to the surface of the developing roller 25, the toner from the container 23 adheres to the image forming surface 70 due to a potential difference from the charging voltage applied to the drum 18. As a result, a toner image corresponding to the electrostatic latent image is formed on the image forming surface 70.

When the paper P passes between the drum 18 and the transfer roller 31, the toner image formed on the image forming surface 70 is transferred to the paper P at the nip portion. Thereafter, the toner remaining on the image forming surface 70 is removed by the cleaning unit 50.
The sheet P is fed toward the fixing unit 32 with an unfixed toner image carried thereon, and is heated and pressed by a heat roller that has reached a predetermined temperature in the fixing unit 32 to fix the toner image. Next, the paper P sent out from the fixing unit 32 is discharged to the paper discharge tray 36.

  When performing double-sided printing on this single-sided printing, the transport direction of the paper P discharged from the fixing unit 32 is switched immediately before being discharged onto the tray 36. That is, the paper P printed on one side is pulled back into the apparatus main body 2 and is sent again toward the transfer unit 30 via the paper conveyance path 38 and the registration roller 14. As a result, the toner image is transferred to the surface of the paper P that has not been printed.

By the way, the cleaning roller having the fibrous brush piece described above can also be applied to the charger 20.
Specifically, a charger 20, a developing roller 25, a transfer roller 31, and a cleaning roller 54 are provided around the photosensitive drum 18 shown in FIG. The example charger 20 includes a charging roller (rotating member) 21 in contact with the drum 18 and a cleaning roller 22.

The cleaning roller 22 is a fibrous brush piece whose tip portion is capable of polishing and rubbing the surface of the charging roller 21, and the root portion of each of the cleaning roller 22 stands directly on the peripheral wall of the shaft, as in the above embodiment. Is filling this wall.
As described above, according to the present exemplary embodiment, the drum unit 17 corresponds to the cleaning roller 54 for polishing and rubbing the photosensitive drum 18 used for forming the toner image (the cleaning roller 22 for rubbing and rubbing the charging roller 21). The same shall apply hereinafter.

  Here, the cleaning roller 54 (22) includes a shaft 56 that is rotatably supported by the drum unit 17 and a fibrous brush piece 58. The brush piece 58 is provided on the peripheral wall 57 of the shaft 56 with an adhesive layer interposed therebetween. A plurality of base portions 60 are not directly bundled with the peripheral wall 57 but scattered at regular intervals so as not to allow the lump-like residual toner to enter, and fill the peripheral wall 57.

  Therefore, since the lump-like residual toner is not deposited on the root portion 60 of the brush piece 58, the hardness of the cleaning roller 54 (22) does not increase with time, and can be maintained at substantially the same hardness as when not used. As a result, the frictional polishing force of the cleaning roller 54 (22) is not gradually increased as compared with the conventional case where the root portion of the brush piece is bundled and planted on the base cloth, and the roller 54 (22 with constant performance). ) Can be used over a long period of time, which contributes to extending the life of the roller 54 (22). Furthermore, since the above-described spirally wound base fabric is not used, it is possible to prevent unevenness of the rubbing polishing.

  For example, if paper with a lot of paper dust or paper containing a large amount of talc or calcium bicarbonate is used, the image forming surface 70 of the photosensitive drum 18 is likely to deteriorate due to adhesion of these. However, since the cleaning roller 54 that does not increase the rubbing and polishing force is used, the paper dust and the like are removed to prevent the image forming surface 70 from being deteriorated, and damage to the image forming surface 70 can be avoided. Therefore, this contributes to a longer life of the photosensitive drum 18.

Further, if the distance between the root portions 60 of the brush pieces 58 is set to 0.3 mm or less, the lump-like residual toner hardly enters the root portion 60, so that the hardness of the cleaning roller 54 (22) is substantially equal to that when not used. The hardness can be maintained more reliably.
Furthermore, the intervals between the brush pieces 58 are uniform from the root portion 60 to the tip end portion 59, and these brush pieces 58 are erected straight with respect to the axis of the shaft 56. 70 and the surface of the charging roller 21 can be uniformly polished and rubbed.

  Further, the surface of the OPC drum is particularly easily scraped, and there is a concern that the increase in the hardness of the cleaning roller over time has a great influence on the drum. However, according to the cleaning roller 54 configured as described above, The film becomes difficult to be shaved. As a result, the drum characteristics can be maintained over a long period of time, and a particularly remarkable effect is obtained.

  Further, if the rotation ratio between the photosensitive drum 18 and the cleaning roller 54 and the rotation ratio between the charging roller 21 and the cleaning roller 22 are in a non-integer multiple relationship, the cleaning rollers 54 and 54 with respect to the photosensitive drum 18 and the charging roller 21. Since the contact position of 22 always changes, it is possible to more reliably eliminate unevenness of polishing and rubbing against the image forming surface 70 and the surface of the roller 21.

Furthermore, if the above-described drum unit 17 is installed, good image formation is performed over a long period of time, which contributes to improving the reliability of the printer 1.
The present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the claims.
For example, in the above embodiment, the peripheral wall 57 is configured with a larger diameter than the shaft 56, but may be configured with substantially the same diameter or the like as long as the above-described fibrous brush pieces can be erected in a desired number. .

In this embodiment, an example in which the image forming apparatus is embodied in a printer is shown. However, the image forming apparatus of the present invention can naturally be applied to a multifunction machine, a copier, a facsimile machine, and the like.
In any of these cases, as described above, there is an effect that the hardness of the cleaning roller is not increased with time.

1 Printer (image forming device)
17 Drum unit 18 Photosensitive drum (rotating member)
20 Charger 21 Charging roller (rotating member)
DESCRIPTION OF SYMBOLS 22 Cleaning roller 50 Cleaning part 54 Cleaning roller 56 Shaft 57 Perimeter wall 58 Brush piece 59 Tip part 60 Root part 70 Image formation surface (surface)

Claims (7)

A drum unit comprising: a rotating member used for forming a toner image; and a cleaning roller for polishing and rubbing the surface of the rotating member,
The cleaning roller
A shaft rotatably supported by the unit;
A drum unit comprising: a plurality of brush portions that are provided in a plurality on the peripheral wall of the shaft, and each of which has a base portion dispersed therein to fill the peripheral wall. The drum unit according to claim 1,
The rotating member is a photosensitive drum that forms the toner image on the surface by being driven;
The drum unit, wherein the cleaning roller grinds and rubs the surface having residual toner. The drum unit according to claim 2, wherein
The drum unit is characterized in that a distance between the base portions of the brush pieces is 0.3 mm or less. The drum unit according to claim 3, wherein
The drum unit, wherein a distance between the tip portions of the brush pieces for polishing and rubbing the surface of the photosensitive drum is the same as a distance between the root portions. The drum unit according to any one of claims 2 to 4,
The drum unit, wherein the photosensitive drum is a photosensitive drum having an organic layer on a surface thereof. The drum unit according to any one of claims 1 to 5,
A drum unit, wherein a rotation ratio between the rotating member and the cleaning roller is in a non-integer multiple relationship.   An image forming apparatus comprising the drum unit according to claim 1.

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