JP2012141521A - Cleaning device and image forming apparatus including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning device capable of feeding waste toner scraped off from an image carrier smoothly into a waste toner storage part and preventing uneven abrasion of a photosensitive layer on a surface of an image carrier and increase in pressure contact force of a toner shield seal, and to provide an image forming apparatus including the cleaning device.SOLUTION: A cleaning device 17 comprises: a sweep roller 37 for feeding waste toner scraped off by a cleaning blade 33 into a waste toner storage part 35; and a toner shield seal 41 in pressure-contact with a photoreceptor drum 14 at predetermined pressure. A base end of the toner shield seal 41 is fixed to a seal holding part 43 and a tip portion of the toner shield seal 41 is in pressure-contact with the photoreceptor drum 14. A tip portion 43a of the seal holding part 43 is formed so as to protrude above a straight line L connecting a rotation center 14a of the photoreceptor 14 to a rotation center 37a of a sweep roller 37.

Description

  The present invention relates to a cleaning device having a mechanism for removing residual toner on the surface of an image carrier using a cleaning blade, and more particularly, a cleaning device having a waste toner container for storing waste toner scraped off from the surface of an image carrier. It relates to the device.

  In an image forming apparatus using an electrophotographic system such as a copying machine, a printer, or a FAX, a powder developer is mainly used, and an electrostatic latent image formed on an image carrier such as a photosensitive drum using the developing apparatus. A general process is to make an image visible, transfer the visible image (toner image) onto a recording medium, and perform a fixing process. The toner remaining on the surface of the image carrier is removed by a cleaning device, and a new toner image is formed.

  As a method for storing waste toner removed from the surface of the image carrier by the cleaning device, a method for discharging the waste toner to the outside of the cleaning device using a toner discharge screw and storing it in a waste toner collecting container, There is known a system in which waste toner is stored in a waste toner container provided on the side opposite to the image carrier.

  In the method of storing waste toner in the waste toner container of the cleaning device, it is not necessary to provide a waste toner collection container or a waste toner collection path for connecting the waste toner collection container and the cleaning device, so that the image forming apparatus can save space. It becomes possible. In addition, by setting the capacity of the waste toner container in accordance with the service life of the drum unit including the cleaning device, it is possible to replace the waste toner container simultaneously with the replacement of the drum unit, thereby improving maintainability.

  However, in the configuration in which the waste toner container is provided in the cleaning device, the longer the service life of the drum unit including the cleaning device, the greater the number of printed sheets during the service life and the greater the amount of waste toner collected. Therefore, it is necessary to increase the capacity of the waste toner container. Therefore, in order to efficiently fill the waste toner container with the waste toner, a mechanism for positively feeding the waste toner from the image carrier side to the waste toner container is required.

  For example, Patent Document 1 discloses a cleaning provided with a rubbing member having an elliptical or rectangular cross section for sending waste toner scraped off from the surface of the photosensitive drum to a waste toner container and polishing and rubbing the surface of the photosensitive drum. An apparatus is disclosed.

JP 2006-10858 A

  In Patent Document 1, since an amorphous silicon photoconductor having a large surface hardness is used as an image carrier, there is no problem of abrasion of the photosensitive layer due to the rubbing member, but OPC using an organic photosensitive layer having a small surface hardness and easy to remove. In the case of a photoreceptor, a rubbing member cannot be used. Therefore, instead of the rubbing member, it is conceivable to provide a sweep roller that is disposed in the vicinity of the image carrier and has only a function of feeding the waste toner into the waste toner storage unit.

  However, even when a sweep roller that does not contact the image carrier is used, the pressing force generated through the waste toner by the rotation of the sweep roller acts on the surface of the image carrier. As a result, there is a difference in the amount of abrasion of the photosensitive layer between the place where the sweep roller is close and the place where the sweep roller is not close, which may cause image unevenness and image defects.

  The above-described unevenness of the scraping amount can be eliminated by arranging the sweep roller at a certain distance from the image carrier. However, for example, in a cleaning device that is disposed on the side of the image carrier and scrapes residual toner on the surface of the image carrier from above with a cleaning blade, the sweep roller is usually provided below the housing. When the sweep roller is disposed away from the image bearing member, a waste toner wall is formed between the toner shielding seal provided at the lower end of the opening of the housing and the sweep roller, and the waste toner wall passes through the waste toner wall. An excessive pressing force is applied to the toner shielding seal.

  If the toner shielding seal is too strongly pressed against the surface of the image carrier, foreign matter such as residual toner, paper powder, and toner additive aggregates on the surface of the image carrier cannot pass through the toner shielding seal, and the toner shielding seal It stays with the image carrier. As a result, the photosensitive layer in the portion where the foreign matter stays is scraped in a streak pattern in the circumferential direction of the drum, causing vertical streaks in the output image, or a gap is formed between the toner shielding seal and the image carrier, so that the inside of the cleaning device There is a problem that the waste toner leaks to the outside.

  In view of the above problems, the present invention can smoothly feed waste toner scraped off from the image carrier to the waste toner container, and can cause unevenness of the photosensitive layer on the surface of the image carrier and pressure contact of the toner shielding seal. It is an object of the present invention to provide a cleaning device capable of suppressing an increase in force and an image forming apparatus including the same.

  In order to achieve the above object, the present invention provides a housing in which an opening facing the side of an image carrier and a waste toner container for storing waste toner scraped from the surface of the image carrier are formed. A cleaning blade that is disposed in the vicinity of the opening of the housing and scrapes from the upper direction the residual toner on the surface of the image carrier that rotates so that the lower side of the opening is on the upstream side in the rotation direction, and the opening of the housing A toner shielding seal whose tip is pressed against the surface of the image carrier at a predetermined pressure, and a rotatable arrangement so as to face the image carrier across the toner shielding seal, A cleaning roller having a sweep roller for feeding the waste toner scraped off by the cleaning blade into the waste toner container, and a lower end edge of the opening of the housing Is provided with a seal holding portion for holding the base end portion of the toner shielding seal, and the tip of the seal holding portion is more than a straight line connecting the rotation center of the image carrier and the rotation center of the sweep roller. The cleaning device protrudes upward.

  According to the present invention, in the cleaning device configured as described above, the seal holding portion is formed as a separate member from the housing.

  According to the present invention, in the cleaning device configured as described above, the waste toner storage portion is partitioned by a partition wall disposed with a gap between the housing bottom surface, and a base end portion is fixed to the partition wall. In addition, a scraper is provided in which the vicinity of the front end portion sequentially comes into contact with the outer peripheral surface on the side of the waste toner storage portion downstream from the closest position to the image carrier with respect to the rotation direction of the sweep roller.

  According to the present invention, in the cleaning device configured as described above, a cross-sectional shape of the sweep roller is an ellipse.

  The present invention is also an image forming apparatus provided with the cleaning device having the above-described configuration.

  According to the first configuration of the present invention, since the pressing force generated by the rotation of the sweep roller is stopped by the seal holding portion, the pressure contact force of the toner shielding seal against the image carrier is properly maintained. Accordingly, the waste toner can be smoothly fed into the waste toner container by the rotation of the sweep roller, and untransferred toner, paper dust, and toner external additive aggregates can be transferred from the contact portion between the image carrier and the toner shielding seal to the housing. Since the toner is smoothly collected inside, the surface of the image carrier is scraped or damaged due to foreign matter caught between the image carrier and the toner shielding seal, or the waste toner is effectively prevented from leaking from the housing. Can do.

  According to the second configuration of the present invention, in the cleaning device of the first configuration, the seal holding portion is formed as a separate member from the housing, thereby simplifying the structure of the mold used when molding the housing. Thus, the workability at the time of molding is improved, and the manufacturing cost of the housing can be reduced.

  According to the third configuration of the present invention, in the cleaning device having the first or second configuration, the waste toner container is partitioned by the partition wall disposed with a gap between the bottom surface of the housing. A scraper is provided in which the base end is fixed to the partition wall, and the vicinity of the tip is sequentially brought into contact with the outer peripheral surface on the side of the waste toner storage unit downstream from the closest position to the image carrier with respect to the rotation direction of the sweep roller. As a result, the waste toner sent to the waste toner container by the sweep roller is prevented from flowing back to the photosensitive member side, and a decrease in the conveyance force of the sweep roller due to the adhesion of the waste toner to the outer peripheral surface of the sweep roller is suppressed. Can do.

  According to the fourth configuration of the present invention, in the cleaning device having any one of the first to third configurations, the sweep roller has an elliptical cross-sectional shape so that the waste toner is conveyed by the sweep roller. improves. In addition, when the scraper is brought into contact with the outer peripheral surface of the sweep roller, it becomes easy to scrape off the waste toner by the scraper.

  Further, according to the fifth configuration of the present invention, by mounting the cleaning device having any one of the first to fourth configurations, it is possible to remove vertical stripes due to shaving or scratching of the photosensitive layer on the surface of the image carrier. It is possible to effectively suppress the occurrence of image defects and the leakage of waste toner from the cleaning device, and the image forming apparatus is excellent in maintainability with easy replacement work of the waste toner container.

1 is a schematic cross-sectional view showing a configuration of an image forming apparatus equipped with a cleaning device of the present invention. Enlarged view around the drum unit in FIG. Partial enlarged view of the periphery of the sweep roller in the cleaning device of the present invention Partial enlarged view of the periphery of the sweep roller showing the configuration with the seal holder as a separate member

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the overall configuration of an image forming apparatus equipped with a cleaning device of the present invention. As shown in FIG. 1, an image forming apparatus (in this case, a monochrome printer) 100 includes a sheet feeding cassette 2 that accommodates stacked sheets at the bottom of the main body. Above this paper feed cassette 2 is formed a paper transport path 4 extending substantially horizontally from the front of the main body (right side in FIG. 1) to the rear of the main body and further upward to reach the paper discharge unit 3 formed on the upper surface of the main body. A pickup roller 5, a feed roller 6, an intermediate conveyance roller 7, a registration roller pair 8, an image forming unit 9, a fixing unit 10, and a discharge roller pair 11 are arranged in this order along the paper conveyance path 4 from the upstream side. Has been.

  The paper feed cassette 2 is provided with a paper stacking plate 12 that is rotatably supported with respect to the paper feed cassette 2 by a rotation fulcrum 12a provided at the rear end in the paper transport direction. The paper sheet thus pressed is pressed against the pickup roller 5. A retard roller 13 is disposed in front of the paper feed cassette 2 so as to be in pressure contact with the feed roller 6, and when a plurality of sheets are simultaneously fed by the pickup roller 5, the feed roller 6 and the retard roller 13 are used to roll the paper, and only the topmost sheet is conveyed.

  Then, the paper rolled by the feed roller 6 and the retard roller 13 is conveyed to the registration roller pair 8 by changing the conveyance direction to the rear of the apparatus by the intermediate conveyance roller 7, and the timing is adjusted by the registration roller pair 8. And conveyed to the image forming unit 9.

  The image forming unit 9 forms a predetermined toner image on a sheet by an electrophotographic process. The image forming unit 9 is a photosensitive drum 14 that is an image carrier rotatably supported in the clockwise direction in FIG. Above the charging drum 15, the developing device 16, the cleaning device 17, the transfer roller 18 disposed so as to face the photosensitive drum 14 across the sheet conveyance path 4, and the photosensitive drum 14. A toner container 20 for supplying toner to the developing device 16 as necessary is disposed above the developing device 16.

  For example, the photosensitive drum 14 is formed by laminating a photosensitive layer on an aluminum drum. Here, an OPC photoreceptor having an organic photosensitive layer (OPC) formed on the outer peripheral surface of an aluminum drum is used. As the charging device 15, a scorotron charging device using a corona discharge charger is used, and a metal shield case having a U-shaped cross section disposed so that the opening faces the photosensitive drum 14 is disposed inside. Corona wires and grids, which are discharge members made of tungsten, stainless steel, etc., are provided, and a predetermined charging bias is applied to the corona wires and grids to generate corona discharge and control the amount of charge. As a result, the surface of the photosensitive drum 14 is uniformly charged with a predetermined polarity and potential.

  Next, the photosensitive drum 14 is exposed by a laser beam from a laser scanning unit (LSU) 19 to attenuate charging, and an electrostatic latent image based on the image data input to the surface of the photosensitive drum 14 is formed. . Then, the developing device 16 attaches toner to the electrostatic latent image to form a toner image on the surface of the photosensitive drum 14. The toner image formed on the photoconductive drum 14 is transferred by the transfer roller 18 to a sheet supplied to the nip portion (transfer position) between the photoconductive drum 14 and the transfer roller 18.

  The sheet on which the toner image is transferred is separated from the photosensitive drum 14 and conveyed toward the fixing unit 10. The fixing unit 10 is disposed on the downstream side of the image forming unit 9 in the paper conveyance direction, and includes a heating roller 21 and a pressure roller 22 that is pressed against the heating roller 21. The sheet on which the toner image has been transferred in the image forming unit 9 is heated and pressed by passing through the nip portion between the heating roller 21 and the pressure roller 22, and the toner image transferred to the sheet is fixed.

  The paper that has passed through the fixing unit 10 is discharged to the paper discharge unit 3 by the discharge roller pair 11. On the other hand, the toner remaining on the surface of the photosensitive drum 14 is removed by the cleaning device 17. The photosensitive drum 14 is neutralized by a neutralizing device (not shown) and then charged again by the charging device 15, and image formation is performed in the same manner. The cleaning device 17 is integrally formed with the photosensitive drum 14 and the charging device 15 and constitutes a drum unit 30 (see FIG. 2). The detailed configuration and operation of the cleaning device 17 will be described later.

  FIG. 2 is an enlarged view of the drum unit 30 in FIG. Note that an arrow A in FIG. 2 indicates the sheet conveyance direction. The cleaning device 17 constituting the drum unit 30 together with the photosensitive drum 14 and the charging device 15 includes a housing 17 a having an opening on the side of the photosensitive drum 14. The interior of the housing 17a is divided into two by a partition wall 31, and a toner scraping portion 34 in which a cleaning blade 33 is disposed is provided on the photosensitive drum 14 side of the partition wall 31. In addition, a waste toner storage unit 35 that stores waste toner scraped from the photosensitive drum 14 by the cleaning blade 33 is provided on the opposite side of the partition wall 31 from the toner scraping unit 34.

  The toner scraping unit 34 and the waste toner storage unit 35 communicate with each other below the partition wall 31 and include a sweep roller 37 that feeds the waste toner of the toner scraping unit 34 to the communication unit. A scraper 40 that contacts the sweep roller 37 is attached to the partition wall 31.

  The cleaning blade 33 is used for scraping the residual toner adhering to the surface of the photosensitive drum 14 in sliding contact with the photosensitive drum 14. The cleaning blade 33 is provided on the downstream side in the rotation direction (clockwise direction) of the photosensitive drum 14 in the opening of the housing 17a. The proximal end portion of the cleaning blade 33 is attached to a stay 36 fixed to the opening of the housing 17a, and the distal end portion of the cleaning blade 33 is pressed against the surface of the photosensitive drum 14 with a predetermined pressure. As the material of the cleaning blade 33, for example, polyurethane rubber having a JIS hardness of 60 to 80 ° is used, and the material, hardness and dimensions of the cleaning blade 33, the amount of biting into the photosensitive drum 14 and the pressure contact force, etc. It is set as appropriate according to the 14 specifications.

  The sweep roller 37 is for sending the waste toner scraped off by the cleaning blade 33 from the toner scraping portion 34 to the waste toner storage portion 35, and is driven in the same direction (clockwise) as the photosensitive drum 14 by a driving device (not shown). Direction). That is, the sweep roller 37 is rotationally driven on the surface facing the photosensitive drum 14 such that the movement direction of the outer peripheral surface is opposite to the movement direction of the outer peripheral surface of the photosensitive drum 14 (counter direction).

  The cross-sectional shape of the sweep roller 37 is an ellipse, and when the end point of the major axis of the ellipse is directed to the photosensitive drum 14 (indicated by the solid line in the figure), the surface of the photosensitive drum 14 approaches and the major axis of the ellipse When the end point is separated from the photosensitive drum 14 (indicated by a dotted line in the figure), the sweep roller 37 is separated from the surface of the photosensitive drum 14. That is, the sweep roller 37 rotates while intermittently approaching or separating from the surface of the photosensitive drum 14, thereby generating a force for pressing waste toner around the sweep roller 37. The waste toner is fed into the storage unit 35.

  As the sweep roller 37, for example, a roller integrally molded with a resin such as polycarbonate is used. The rotational speed of the sweep roller 37 is controlled by a motor (not shown) attached to the shaft end of the sweep roller 37. The cross-sectional shape of the sweep roller 37 is not limited to an ellipse, but may be a rectangular shape, for example. However, when the cross-sectional shape is an ellipse, the waste toner conveyance force is improved and the scraper 40 scrapes off the waste toner. Becomes easy.

  The scraper 40 is composed of a flexible film member, and scrapes off the waste toner adhering to the outer peripheral surface of the sweep roller 37. The base end portion of the scraper 40 is attached to the partition wall 31, and the tip end portion of the scraper 40 is in contact with the outer peripheral surface on the opposite side of the sweep roller 37 when viewed from the photosensitive drum 14 side. Then, the rotation of the sweep roller 37 causes the vicinity of the tip of the scraper 40 to sequentially come into contact with the outer peripheral surface on the side of the waste toner container 35 downstream of the closest position with the photosensitive drum 14 in the rotation direction of the sweep roller 37. Is in pressure contact.

  Note that the major axis direction of the sweep roller 37 is the rotation center 14a of the photosensitive drum 14 with respect to the outer peripheral surface on the side of the waste toner container 35 downstream of the position closest to the photosensitive drum 14 with respect to the rotational direction of the sweep roller 37. And an outer peripheral surface located on the downstream side (below the straight line L) in the rotation direction of the photosensitive drum 14 when it is located at a position overlapping a straight line L (see FIG. 3) connecting the rotation center 37a of the sweep roller 37. . Further, since the base end portion of the scraper 40 is attached to the inner surface of the partition wall 31 on the side of the waste toner storage portion 35, the waste toner sent to the waste toner storage portion 35 by the sweep roller 37 is transferred to the toner scraping portion 34. It also works to prevent backflow.

  FIG. 3 is a partially enlarged view of the periphery of the sweep roller 37 of the cleaning device 17. As shown in FIG. 3, the toner shield is pressed against the photosensitive drum 14 at a predetermined pressure at the upstream end (the lower end side of the opening) of the opening of the housing 17 a with respect to the rotation direction of the photosensitive drum 14. A seal 41 is arranged. The toner shielding seal 41 is a flexible film member that extends in the longitudinal direction of the housing 17a (the front and back direction in FIG. 3). The toner transfer seal 41 is a non-transferred toner on the surface of the photosensitive drum 14, paper dust, and toner external additive aggregation. It has a function of blocking the waste toner in the housing 17a from leaking outside while allowing an object or the like to pass through the housing 17a. The toner shielding seal 41 has a base end portion fixed to a seal holding portion 43 formed integrally with the housing 17 a and a tip end portion pressed against the photosensitive drum 14.

  Here, the tip end portion 43a of the seal holding portion 43 protrudes above a straight line L (indicated by a one-dot chain line in FIG. 3) connecting the rotation center 14a of the photosensitive drum 14 and the rotation center 37a of the sweep roller 37. Is formed. With this configuration, since the pressing force generated by the rotation of the sweep roller 37 is stopped by the seal holding portion 43, the pressure contact force of the toner shielding seal 41 against the photosensitive drum 14 is properly maintained. Therefore, untransferred toner, paper dust, and toner external additive aggregates are smoothly collected in the housing 17a from the contact portion between the photosensitive drum 14 and the toner shielding seal 41. Therefore, the photosensitive drum 14 and the toner shielding seal 41 are recovered. It is possible to effectively prevent the surface of the photosensitive drum 14 from being scraped or scratched due to the foreign matter sandwiched between them or the leakage of the waste toner from the housing 17a.

  When the major axis of the ellipse of the sweep roller 37 is increased, the pressing force generated by the rotation of the sweep roller 37 also reaches the upper part of the opening of the housing 17a. However, as the major axis of the sweep roller 37 increases, the position of the rotation center 37a also moves upward, so the straight line L connecting the rotation center 14a of the photosensitive drum 14 and the rotation center 37a of the sweep roller 37 also moves upward. Therefore, as long as the tip 43a of the seal holding portion 43 and the straight line L satisfy the relationship shown in FIG. 3, the pressure contact force of the toner shielding seal 41 with respect to the photosensitive drum 14 can be properly maintained.

  FIG. 4 is an enlarged view showing another configuration example of the cleaning device 17 of the present invention. In FIG. 4, the seal holding portion 43 is configured as a separate member from the housing 17 a. The structure of other parts is the same as that shown in FIG.

  Since the seal holding portion 43 protrudes inward from the opening of the housing 17a, when the seal holding portion 43 is integrally formed with the housing 17a as shown in FIG. 3, a part of a mold used for molding the housing 17a is used. It is necessary to use a split mold, which complicates the mold structure and reduces the workability during molding. When the seal holding portion 43 is a separate member as shown in FIG. 4, the structure of the mold is simplified and the workability at the time of molding is improved, so that the manufacturing cost of the housing 17a can be reduced. For example, by using a sheet material having a larger elastic force than the toner shielding seal 41 as the seal holding portion 43, a compact configuration in which the arrangement space of the seal holding portion 43 is reduced is possible.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, the materials, shapes, relative arrangements, and the like of the component parts described in the above embodiments are not intended to limit the scope of the present invention, but merely illustrative examples, unless otherwise specified. . For example, the photosensitive drum 14 of the above embodiment has an organic photosensitive layer (OPC) made of an organic material, but is made of an a-Si based inorganic photosensitive layer or other inorganic material (for example, Se based inorganic material). Even in the configuration having the inorganic photosensitive layer, the effect of the present invention can be obtained.

  Further, the present invention is not limited to the monochrome laser printer shown in FIG. 1, but includes various types of digital multifunction peripherals, rotary or tandem color copying machines, color printers, copying machines such as analog monochrome copying machines, facsimiles, and the like. Needless to say, the present invention can be applied to other image forming apparatuses.

  INDUSTRIAL APPLICABILITY The present invention can be used in a cleaning device including a waste toner storage portion that stores waste toner scraped off from the surface of an image carrier by a cleaning blade, and a base end of a toner shielding seal is provided at the lower end edge of the opening of the housing. A seal holding portion is provided to hold the portion, and the tip of the seal holding portion protrudes above a straight line connecting the rotation center of the image carrier and the rotation center of the sweep roller.

  By utilizing the present invention, waste toner can be smoothly fed into the waste toner container, and untransferred toner and foreign matter are smoothly collected in the housing from the contact portion between the image carrier and the toner shielding seal. It is possible to provide a cleaning device capable of effectively suppressing the scraping or scratching of the surface of the image carrier or the leakage of waste toner from the housing.

14 Photosensitive drum (image carrier)
14a Rotation center (of photosensitive drum) 15 Charging device 16 Development device 17 Cleaning device 17a Housing 18 Transfer roller 30 Drum unit 31 Partition wall 33 Cleaning blade 35 Waste toner container 37 Sweep roller 37a (Rotation roller) Rotation center 40 Scraper 41 Toner shielding seal 43 Seal holding portion 43a Tip portion 100 Image forming apparatus

Claims (5)

A housing formed with an opening facing the side of the image carrier, and a waste toner container for storing waste toner scraped from the surface of the image carrier;
A cleaning blade that is disposed in the vicinity of the opening of the housing and scrapes the residual toner on the surface of the image carrier rotating from above so that the lower side of the opening is on the upstream side in the rotation direction;
A toner shielding seal disposed on the lower end side of the opening of the housing and having a tip portion pressed against the surface of the image carrier at a predetermined pressure;
A sweep roller that is rotatably arranged to face the image carrier with the toner shielding seal interposed therebetween, and that feeds the waste toner scraped off by the cleaning blade into the waste toner storage unit;
In a cleaning device having
A seal holding portion that holds a base end portion of the toner shielding seal is provided at a lower end edge of the opening of the housing, and a tip end of the seal holding portion includes a rotation center of the image carrier and the sweep roller. A cleaning device that protrudes above a straight line connecting the rotation center of the cleaning device.   The cleaning device according to claim 1, wherein the seal holding portion is formed as a member separate from the housing.   The waste toner container is partitioned by a partition wall disposed with a gap between the bottom surface of the housing, a base end portion is fixed to the partition wall, and a vicinity of the tip portion is a rotation direction of the sweep roller. 3. The cleaning device according to claim 1, further comprising a scraper that sequentially contacts an outer peripheral surface on the side of the waste toner storage portion downstream of a position closest to the image carrier.   The cleaning device according to claim 1, wherein a cross-sectional shape of the sweep roller is an ellipse.   An image forming apparatus comprising the cleaning device according to claim 1.