JP4965843B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus incorporated in a copying machine, a printer, a facsimile, or the like.

  As an image forming apparatus in recent years, there is an image forming apparatus in which a layer of an amorphous silicon photoconductor is deposited on the surface of a photoconductor drum or belt as an image carrier in order to improve durability. This amorphous silicon photoconductor has a high hardness and a long life, but may have a problem in image flow.

In this image stream, when water-soluble ion products such as NO _X and SO _X generated by the discharge of the charger adhere to the surface of the photoconductor, moisture in the air is absorbed particularly in a high humidity environment, and the photoconductor The surface resistance decreases, and the electrostatic latent image formed on the photoconductor leaks in the surface direction when an image is formed.

In addition to NO _X and SO _X , the oxidative degradation of the surface of the photoreceptor gradually progresses due to the oxidizing action of ozone generated by the discharge, and when the deteriorated layer increases, not only in a high humidity environment but also in a normal humidity environment. Image flow phenomenon occurs.

  Therefore, in order to prevent the image flow phenomenon, the surface of the amorphous silicon photoconductor is polished with a rubbing roller in contact with the surface to remove the water-soluble ion product adhering layer and the oxidized deterioration layer on the photoconductor surface. An apparatus is disclosed (for example, refer to Patent Document 1).

  FIG. 11 is a side configuration diagram of the image forming apparatus disclosed in Patent Document 1. In FIG. As shown in FIG. 11, the image forming apparatus of Patent Document 1 includes a photosensitive drum 100, a charger 101 for charging the surface of the photosensitive drum 100, and a photosensitive drum 100 other than a portion where an image is formed. The exposure device 102 for removing the charged charges by applying light to the surface of the toner and forming an electrostatic latent image, and developing the visible image by attaching toner to the electrostatic latent image formed on the surface of the photosensitive drum 100 And a container 103. Further, a transfer bias having a polarity opposite to the charging potential of the toner is applied, and the conductive transfer roller 104 that uniformly presses the circumferential surface of the photosensitive drum 100 to transfer the toner to the paper, and the surface of the photosensitive drum 100 are connected. A rubbing roller 105 for polishing, a cleaning blade 106 for removing toner remaining on the photosensitive drum 100 without being transferred, and a static eliminator 107 for removing charge on the surface of the photosensitive drum 100 are provided.

  Note that the charger 101, the exposure device 102, the developing device 103, the transfer roller 104, the rubbing roller 105, the cleaning blade 106, and the static eliminator 107 are sequentially arranged with respect to the rotation direction of the photosensitive drum 100.

  In addition, an image forming apparatus is disclosed in which an elastic roller having magnetism is disposed in a cleaning unit, and the elastic roller is configured to contact and separate from the surface of the image carrier (see, for example, Patent Document 2). ).

Further, the position of the rubbing roller is set so that the rubbing roller is separated from the surface of the image carrier when image formation is being performed and the rubbing roller is in contact with the surface of the image carrier when image formation is not being performed. An image forming apparatus that performs a change is disclosed (for example, see Patent Document 3).
JP-A-9-292732 JP-A-7-28366 JP-A-2005-148609

  For example, since Patent Document 1 is intended to polish the surface of the photosensitive drum 100, the rubbing roller 105 is exposed to light so that toner containing abrasive is interposed in the nip portion L between the rubbing roller 105 and the photosensitive drum 100. The body drum 100 was in contact with the surface. Therefore, the residual toner is removed from the surface of the photosensitive drum 100 by the rubbing roller 105, and the amount of residual toner reaching the cleaning blade 106 arranged on the downstream side in the rotation direction is reduced.

  When the residual toner amount is reduced in this manner, the toner also has a role as a lubricant, so that the friction coefficient between the cleaning blade 106 and the photosensitive drum 100 increases, and the toner is fused to the surface of the photosensitive drum 100. In some cases, it was likely to occur. In addition, since the amount of toner is small, the ratio of impurities such as paper dust increases, so that cleaning failure may occur easily. That is, in order to scrape off the toner remaining on the photosensitive member by the cleaning blade, it is necessary that a certain amount or more of the toner reaches the cleaning blade. There was a problem of shortage.

  The present invention provides an image forming apparatus capable of satisfying both the polishing performance of the surface of the image carrier and the cleaning performance of the toner remaining on the surface of the image carrier in consideration of the problems of the conventional image forming apparatus. For the purpose.

To achieve the above objective,
The first aspect of the present invention is
An image carrier on which an electrostatic latent image is formed on the surface;
Developing means for forming a toner image containing an abrasive based on the electrostatic latent image;
Transfer means for transferring the toner image to a transfer material or an intermediate transfer member;
A rubbing roller arranged to be pressed against the surface of the image carrier for polishing the surface of the image carrier using the toner not transferred by the transfer means and remaining on the image carrier. When,
A cleaning blade disposed on the downstream side of the rubbing roller with respect to the rotation direction of the image carrier for removing the remaining toner from the surface of the image carrier;
An image forming apparatus comprising: a pressing force changing unit that periodically changes a pressing force of the rubbing roller against the image carrier while pressing the rubbing roller against the image carrier at least during image formation. It is.

The second aspect of the present invention is
In the image forming apparatus according to the first aspect of the present invention, the change in the pressing force includes a case where the pressing force is zero.

The third aspect of the present invention
The pressing force changing unit is the image forming apparatus according to the first aspect of the present invention, which changes the pressing force even during non-image formation.

The fourth aspect of the present invention is
The surface of the rubbing roller is formed of an elastic body,
The rubbing roller is the image forming apparatus according to the first aspect of the present invention, which is disposed so as to be pressed against the surface of the image carrier via the elastic body.

The fifth aspect of the present invention is
The pressing force changing means is a contact member that is fixed to both ends of the rubbing roller and contacts the surface of the image carrier,
The shape of the cross section of the contact member orthogonal to the rotation axis of the rubbing roller is different from the shape of the cross section of the rubbing roller orthogonal to the rotation axis,
A fourth book in which the distance between the rotation shaft of the contact member and the rotation shaft of the image carrier changes when the outer peripheral surface of the contact member rotates in contact with the surface of the image carrier. It is an image forming apparatus of the invention.

The sixth aspect of the present invention
The image forming apparatus according to the fifth aspect of the present invention further includes a spring-like member for pressing the rubbing roller against the surface of the image carrier.

The seventh aspect of the present invention
The cross-sectional shape of the rubbing roller perpendicular to the rotation axis is a circular shape,
The rotation of the abutting member so that the rubbing roller has an elastic force with respect to the image carrier even when the distance is shortest and longest while the distance changes. In the image forming apparatus according to the fifth aspect of the present invention, the length from the center of the shaft to the outer peripheral surface is determined.

  According to the present invention, it is possible to provide an image forming apparatus capable of achieving both the polishing performance of the surface of the image carrier and the cleaning performance of the toner remaining on the surface of the image carrier.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment)
In the present embodiment, a case where the image forming apparatus according to the present invention is applied to a copying machine will be described.

Figure 1 is a configuration view seen from the front the copier in the form status of the embodiment according to the present invention. As shown in FIG. 1, the copying machine in the form status of the present embodiment, the paper feed cassette 31 for supplying paper to the main body, a manual sheet feeding mechanism 32 for feeding the body with manual feed paper, exposure lamp, a lens, An exposure unit 30 that forms image light of a document by a mirror or the like, an image forming apparatus 33 that transfers a toner image to a supplied sheet based on the imaged image light, and a toner image that is transferred to the sheet And a fixing unit 34 that fixes the toner by heat.

  In addition, when performing duplex copying, a transport unit 35 that transports a sheet from the image forming apparatus 33 to the fixing unit 34, a discharge unit 37 that discharges the sheet that has been fixed by the fixing unit 34 to the outside of the main body, and a sheet. An inversion / branching unit 36 is provided to invert the. In addition, the dotted-line arrow shown in FIG. 1 indicates an optical path, and the solid-line arrow indicates a paper conveyance path.

  Next, the image forming apparatus in the present embodiment will be described.

  FIG. 2 is a front configuration diagram of the image forming apparatus 33 according to the embodiment of the present invention. As shown in FIG. 2, the surface of the photosensitive drum 1 other than the portion where the image is formed, and the charger 2 for charging the surface of the photosensitive drum 1 and the surface of the photosensitive drum 1 are formed. An exposure device 3 that forms an electrostatic latent image by removing light by applying light, and a developing device 4 that attaches toner to the electrostatic latent image formed on the surface of the photosensitive drum 1 to form a visible image; In addition, a transfer bias having a polarity opposite to the charging potential of the toner is applied, and a conductive transfer roller 5 that uniformly presses the peripheral surface of the photosensitive drum 1 and transfers the toner onto the sheet is provided.

  Furthermore, a sliding roller 6 for polishing the surface of the photosensitive drum 1 using toner that is not transferred onto the sheet by the transfer roller 5 but remains on the photosensitive drum 1, and a photosensitive drum without being transferred. A cleaning blade 7 that removes the toner remaining on the surface 1 and a static eliminator 8 that removes the charge on the surface of the photosensitive drum 1 are provided. The rubbing roller 6 and the cleaning blade 7 constitute a part of the cleaning unit 9.

  In the drawing, the photosensitive drum 1 rotates clockwise (in the direction of arrow a), and the charger 2, the exposure device 3, the developing device 4, the transfer roller 5, the rubbing roller 6, the cleaning blade 7, and the static eliminator 8 are The photosensitive drums 1 are arranged in order with respect to the rotation direction of the photosensitive drum 1.

  FIG. 2 shows a sheet 16 conveyed in the direction of the arrow d by the photosensitive drum 1 and the transfer roller 5, and on the upstream side of the transfer roller 5 with respect to the conveyance direction of the sheet 16. A paper detection sensor 17 is provided. Control means for determining whether or not an image is being formed by detection using the paper detection sensor 17 is provided (not shown). During image formation, since the paper 16 is continuously supplied, after the trailing edge of the previous paper 16 passes the position of the paper detection sensor 17, the leading edge of the next paper 16 is detected by the paper detection sensor 17 within a predetermined time. Therefore, the paper detection sensor 17 has a paper detection OFF time limited to a predetermined time or less. On the other hand, when the image formation is completed, since the next sheet 16 is not supplied after the trailing edge of the last sheet 16 passes the position of the sheet detection sensor 17, the sheet detection OFF time is equal to or longer than the predetermined time. .

  In other words, as an example of image formation according to the present invention, in the image forming apparatus according to the present embodiment, when the paper is detected by the paper detection sensor 17 by the control unit and when the paper detection OFF time is detected by the paper detection sensor 17 This corresponds to a case where it is shorter than time. When the paper detection OFF time of the paper detection sensor 17 is longer than the predetermined time, the control means determines that the standby state is set.

  In the toner used for the image formation, an abrasive is attached to the toner base particles. As the abrasive, various inorganic particles can be used, and alumina and titanium oxide can be particularly used as those having a high polishing effect.

  Further, as the rubbing roller 6, a rubber roller such as EPDM (ethylene-propylene-diene rubber) which is an example of the elastic member of the present invention can be used in order to secure a nip width with the photosensitive drum 1. . If the hardness of the rubbing roller 6 is too small, it is difficult to effectively polish the surface of the photosensitive drum 1, and if the hardness is too large, it is difficult to secure a sufficient nip width necessary for polishing. Therefore, the hardness is preferably 40 ° to 75 °, particularly 45 ° to 60 °. Furthermore, the rubber is preferably foamed rubber. This is because the use of the foam makes it possible to hold the toner used as an abrasive on the roller surface and perform uniform and stable polishing. The size of the foam cell of such foam rubber is preferably about 100 to 300 μm from the viewpoint of toner retention. In addition, when a magnetic toner is used as the toner, it is also effective from the viewpoint of toner retention to provide a magnet inside the rubbing roller 6. The entire rubbing roller 6 may not be made of rubber, and a rubber layer may be provided on the surface using a cylindrical member having rigidity at the center. Further, a driving means is connected to the rotary shaft 10 provided with the rubbing roller 6 and can be driven independently of the photosensitive drum 1.

  Further, as the cleaning blade 7, a rubber blade made of polyurethane or the like is used.

  Next, the configuration of the cleaning unit 9 will be described.

  FIG. 3 is a structural perspective view of the cleaning unit 9.

  As shown in FIGS. 2 and 3, the rubbing roller 6 has a circular cross section and is fixed to the rotating shaft 10. At both ends of the rotating shaft 10, L-shaped supports 11 having a pair of L-shapes are provided. The L-shaped support 11 holds the rotary shaft 10 in a rotatable manner. The L-shaped support 11 includes a first member 11b having a rectangular portion from the rotation shaft 10 to the bent portion 11a with the bent portion 11a as the center, and a second member having a long side portion extending upward with the bent portion 11a as the center. 11c. The tip of the second member 11c is 11d. One end of a spring member 12 is attached to the photosensitive drum 1 side of the leading end portion 11d, and the other end of the spring member 12 is attached to the side wall 9a of the cleaning unit 9 on the photosensitive drum 1 side. A fulcrum 13 is provided substantially at the center of the second member 11c.

  With the above configuration, a force is applied to the end portion 11d side of the L-shaped support 11 with respect to the fulcrum 13 in the opposite direction (arrow b direction) of the photosensitive drum 1 by the elastic force of the spring member 12. Thus, a force is applied in the direction of the photosensitive drum 1 (the direction of the arrow C) to the bent portion 11a side. Therefore, a force is applied to the rubbing roller 6 provided with the rotating shaft 10 on the bent portion 11a side in the direction in which the photosensitive drum 1 is pressed.

  In the cleaning unit 9, a recovery screw 14 for recovering residual toner is provided. Further, as shown in FIG. 3, a pair of rollers 15 is fixedly disposed on the rotation shaft 10 between the rubbing roller 6 and the pair of L-shaped supports 11.

  Next, the configuration of the roller 15 will be described.

  FIG. 4 is a side view of only the roller 15. The center of the rotating shaft 10 to which the roller 15 is fixed is 10a. As shown in FIG. 4, the roller 15 of the present embodiment is composed of a semicircular portion 15a (corresponding to the shaded portion) and a semi-elliptical portion 15b (corresponding to a portion other than the shaded portion). The radius of 15a is 15c, the short axis of the semi-elliptical part 15b is equal to the diameter of the semi-circular part 15a, and the half of the long axis is 15d. That is, the maximum length of the roller 15 from the center 10a to the outer peripheral surface is 15d, and the minimum length is 15c. Hereinafter, the distance from the center 10 a of the roller 15 to the outer peripheral surface is referred to as the diameter of the roller 15. The position of the outer peripheral surface of the roller 15 corresponding to the maximum diameter 15d is 15e, and the position of the outer peripheral surface facing the position 15e is 15f. In FIG. 4, the position of the uppermost outer peripheral surface is 15 g, and the position of the lowermost outer peripheral surface is 15 h. The diameter at the positions 15g and 15h is 15c. The roller 15 is formed of POM or a POM base resin.

  FIG. 5 is a side configuration diagram of the roller 15 and the rubbing roller 6 as viewed from the direction of the rotating shaft 10. As shown in FIG. 5, when the diameter from the center 10a when the rubbing roller 6 is not pressed against the photosensitive drum 1 is 6a, the maximum diameter 15d of the roller 15 is slightly smaller than the diameter 6a. Further, if there is no roller 15, the diameter from the center 10a at the time of maximum pressing of the rubbing roller 6 when the rubbing roller 6 is pressed against the photosensitive drum 1 by the force of the spring member 12 is 6b (in the drawing). 6b <15c. In FIG. 5, the shrinkage of the rubbing roller 6 when pressed against the photosensitive drum 1 is largely expressed for the sake of explanation.

  That is, when the rubbing roller 6 and the roller 15 are pressed against the photosensitive drum 1 by the spring member 12, the position between the positions 15f, 15g, and 15h corresponding to the minimum diameter 15c of the roller 15 when viewed from the direction of the rotating shaft 10 is obtained. Since the position of the outer peripheral surface is located between the diameter 6b when the rubbing roller 6 is maximum pressed and the diameter 6a at the normal time, the outer peripheral surface of the roller 15 is always in contact with the surface of the photosensitive drum 1. become. Further, since the maximum diameter 15 d of the roller 15 is slightly smaller than the diameter 6 a of the rubbing roller 6, the surface of the rubbing roller 6 is always pressed against the photosensitive drum 1.

  An example of the image carrier of the present invention corresponds to the photosensitive drum 1 of the present embodiment, and an example of the developing unit of the present invention corresponds to the developing device 4 of the present embodiment. An example of the transfer means of the present invention corresponds to the transfer roller 5 of the present embodiment.

  The operation of the copying machine of the present embodiment having the above configuration will be described, and an example of the operation of the image forming apparatus of the present invention will be described at the same time.

  The operation of the copying machine during image formation will be described below with reference to FIGS.

Part of the surface of the photosensitive drum 1 is uniformly charged by the charger 2, based on the data to be copied, it is exposed by the exposure device 3, the charge in the portion other than the image is removed and the electrostatic latent image formed Is done. Then, in the developing device 4, toner charged to a polarity opposite to that of the electrostatic latent image is attached to the electrostatic latent image to form a visible image. Along with this operation, the paper 16 fed from the paper feed cassette 31 or the manual paper feed mechanism 32 is conveyed between the photosensitive drum 1 and the transfer roller 5. Then, the toner attached to the surface of the photosensitive drum 1 is transferred onto the paper 16 by the transfer roller 5.

  The paper 16 to which the toner image has been transferred is conveyed to the fixing unit 34 by the conveyance unit 35. The toner image is fixed on the paper 16 by heat and pressure in the fixing unit 34. Here, when image formation is performed on both sides of the sheet 16, the sheet 16 is conveyed again to the image forming apparatus 33 by the reversing / branching unit 36. When image formation is not performed on both sides of the sheet 16, the sheet 16 is discharged out of the copying machine by the discharge unit 37.

  On the other hand, not all of the toner on the photosensitive drum 1 is transferred to the paper 16 by the transfer roller 5, and a part of the toner remains on the photosensitive drum 1. The surface of the photosensitive drum 1 is polished by the rubbing roller 6 using the abrasive adhered to the residual toner (details will be described later). Then, the residual toner on the photosensitive drum 1 is removed by the cleaning blade 7.

  Then, the charge on the surface of the photosensitive drum 1 transferred to the paper 16 is removed by the static eliminator 8. The portion from which the charge on the surface of the photosensitive drum 1 is removed is charged again by the charger 2, and the above-described image forming operation is repeated.

  Next, the operation of the rubbing roller 6 will be described in detail.

  6A to 6E are views for explaining a state in which the surface of the photosensitive drum 1 is polished by the rubbing roller 6.

  FIG. 6A is a diagram showing a state where the position 15 f on the outer peripheral surface of the roller 15 is in contact with the surface of the photosensitive drum 1. In this state, the surface of the rubbing roller 6 is pressed against the surface of the photosensitive drum 1, and a nip region 20 is formed. In FIG. 6, reference numeral 21 denotes toner.

  Next, when the photosensitive drum 1 rotates clockwise (arrow a direction) and the roller 15 rotates counterclockwise (arrow e direction), as shown in FIG. Comes into contact with the photosensitive drum 1. The rollers 15 and the rubbing roller 6 are controlled so as to be faster than the rotation speed of the photosensitive drum 1.

  Since the diameter of the roller 15 at the position 15h is 15c similarly to the diameter at the position 15f, the pressing force of the surface of the rubbing roller 6 against the photosensitive drum 1 does not change. Further, the width of the nip region 20 is the same as the state of FIG.

  When further rotated, the outer peripheral surface between the position 15h and the position 15e comes into contact with the surface of the photosensitive drum 1 as shown in FIG. As the roller 15 moves from the position 15h to the position 15e, the diameter of the roller 15 increases. Therefore, the amount of the surface of the rubbing roller 6 pressed against the photosensitive drum 1 is reduced. That is, the pressing force of the rubbing roller 6 against the photosensitive drum 1 becomes smaller in the state shown in FIG. 6C than in the state shown in FIGS. 6A and 6B. In addition, the width of the nip region 20 is also smaller than the state of FIGS. 6 (a) and 6 (b).

  When further rotated, as shown in FIG. 6D, the position 15e on the outer peripheral surface comes into contact with the surface of the photosensitive drum 1. Since the diameter 15d at the position 15e is the maximum diameter of the roller 15, the pressing force of the rubbing roller 6 against the photosensitive drum 1 is the smallest, and the width of the nip region 20 is also the smallest.

  When further rotated, as shown in FIG. 6 (e), the position 15 g on the outer peripheral surface comes into contact with the surface of the photosensitive drum 1. Since the diameter at the position 15g is 15c, the pressing force of the rubbing roller 6 against the photosensitive drum 1 is the same as in the states of FIGS. 6A and 6B, and the width of the nip region 20 is also the same. It becomes.

  By further rotating, the position of the roller 15 in contact with the photosensitive drum 1 returns to the state of FIG.

  As described above, the toner remaining on the surface of the photosensitive drum 1 is interposed in the nip region 20 formed when the rubbing roller 6 is pressed against the photosensitive drum 1, and acts as an abrasive. The surface of the photosensitive drum 1 is polished.

  Here, the pressing force of the rubbing roller 6 against the photosensitive drum 1 is the same between the positions 15g, 15f, and 15h, and the pressing force gradually decreases as it moves from the outer peripheral position 15h to the outer peripheral position 15e. The pressing force gradually increases as the position moves from the position 15e to the outer peripheral position 15g. As described above, the pressing force against the photosensitive drum 1 periodically changes with the rotation of the rubbing roller 6.

  Note that when the distance between the rotating shafts of the present invention is the shortest, for example, as shown in FIG. 6, in the present embodiment, the positions 15f, 15h, and 15g of the outer peripheral surface where the distance from the center 10a is the smallest. This corresponds to the contact with the surface of the photosensitive drum 1 and the distance between the rotating shafts of the present invention is the longest. For example, in the present embodiment, the distance from the center 10a is the maximum on the outer peripheral surface. The position 15e corresponds to contact with the surface of the photosensitive drum 1, and the distance between the rotating shaft 10a of the roller 15 and the rotating shaft of the photosensitive drum 1 changes periodically.

  Further, in the present invention, “the sliding roller has an elastic force with respect to the image carrier even when the distance is shortest and longest while the distance changes” In the present embodiment, the positions 15f, 15h, 15g and the position 15e correspond to being positioned between the diameter 6b when the sliding roller 6 is fully pressed and the diameter 6a at the normal time. That is, when the position of the outer peripheral surface whose distance from the center 10a of the roller 15 is shorter than 6b abuts against the photosensitive drum 1, the rubbing roller 6 is crushed to the maximum at that position, and beyond that, the crushed roller 6 is crushed. Therefore, it does not have elastic force. Further, when the position of the outer peripheral surface whose distance from the center 10a of the roller 15 is longer than 6a contacts the photosensitive drum 1, the rubbing roller 6 is not in contact with the photosensitive drum 1 at that position, so that the elastic force Will not have.

  As the pressing force changes as described above, the amount of residual toner 21 that passes through the nip region 20 and reaches the cleaning blade 7 changes. That is, when the pressing force of the rubbing roller 6 against the photosensitive drum 1 is small, the amount of residual toner 21 that passes through the nip region 20 and reaches the cleaning blade 7 increases, and as a result, the amount of toner reaching the cleaning blade 7 is constant. It becomes possible to keep more than the amount. Therefore, the coefficient of friction between the cleaning blade 7 and the photosensitive drum 1 does not increase, and it is possible to avoid poor cleaning due to toner fusion or the like, and the residual toner can be efficiently removed from the photosensitive drum 1. It becomes possible.

  Next, the operation of the image forming apparatus at the start-up after the power of the copying machine of the present embodiment is turned on and at the standby time will be described. The start-up time and standby time correspond to an example during non-image formation according to the present invention.

  During the start-up of the copying machine and the standby time, the following operations are performed a predetermined number of times or every predetermined time.

  The surface of the photosensitive drum 1 is uniformly charged by the charger 2, and the toner adheres without forming an electrostatic latent image. Then, the surface of the photosensitive drum 1 is polished by the rubbing roller 6 using this toner as an abrasive. The operations of the rubbing roller 6 and the roller 15 during the polishing are the same as those during the image formation. Subsequently, the toner on the photosensitive drum 1 is removed by the cleaning blade 7.

  That is, since the toner image is not transferred onto the paper during the start-up and standby time of the copying machine, the nip region 20 is compared with the case where the above-described transfer is performed (during image formation according to the present invention). The amount of toner intervening in the toner increases, and the polishing efficiency increases.

  In this way, by performing the polishing operation on the surface of the photosensitive drum 1 at the time of start-up and standby time, a good image free from image flow phenomenon can be formed from the start after the start-up and after the standby. It becomes possible.

  An example of the pressing force changing means of the present invention corresponds to the roller 15 of the present embodiment, but a solenoid may be used instead of the roller 15. In this case, a pressing force of the rubbing roller 6 against the photosensitive drum can be changed by installing a solenoid in the spring member 12 and periodically operating the solenoid. Further, a rigid cylindrical member may be used around the center of the rubbing roller 6 and an elastic member may be wound around the surface of the rubbing roller 6 to change the thickness of the elastic member. In short, the rubbing roller 6 against the photosensitive drum 1 may be used. It is only necessary to be able to change the pressing force.

  In this embodiment, the rotation speed of the roller 15 and the rubbing roller 6 is controlled to be higher than the rotation speed of the photosensitive drum 1, but may be controlled to be slower. .

  An example of the transfer material of the present invention corresponds to the paper 16 of the present embodiment, but may be, for example, an intermediate transfer member used for a one-drum system in a color copying machine.

  The image carrier of the present invention corresponds to the photosensitive drum 1 in the present embodiment, but an image bearing member having an amorphous silicon photosensitive layer deposited on the surface of a belt or the like may be used.

An example of the contact member of the present invention corresponds to the roller 15 of the present embodiment, but the roller 15 is not limited to the cross-sectional shape shown in FIG. Furthermore, as shown in FIG. 7, to the cross-sectional shape may be used a circular roller 24 and the rubbing roller 6 'of the elliptical shape, both but it may also have an elliptical shape. In short, the cross-sectional shape of the abutting member is different from the cross-sectional shape of the rubbing roller, and when the outer peripheral surface of the abutting member rotates in contact with the surface of the image carrier, the rotational axis of the abutting member and the image It is only necessary to change the distance between the rotation axes of the carriers.

  In the image forming apparatus of the present embodiment, the maximum diameter 15d of the roller 15 is slightly shorter than the radius 6a of the rubbing roller 6, but it may be the same length as shown in FIG. It may be longer than the radius 6a. The roller 22 shown in FIG. 8 has a maximum diameter 22 d larger than the normal diameter 6 a of the rubbing roller 6. That is, the rubbing roller 6 is pressed against the photosensitive drum 1 on the outer peripheral surface where the diameter of the roller 22 is shorter than the normal diameter 6 a of the rubbing roller 6, but corresponds to the maximum diameter 22 d of the roller 22. When the outer peripheral position 22 e that contacts the photosensitive drum 1, a gap is generated between the rubbing roller 6 and the photosensitive drum 1. The state where the gap is generated indicates a state where the pressing force of the rubbing roller 6 against the photosensitive drum 1 is zero. Even when the pressing force is changed by the solenoid, a gap may be provided between the photosensitive drum 1 and the rubbing roller 6.

  Further, as shown in FIG. 5, in this embodiment, the diameter of the roller 15 is longer than the diameter 6b at the time of maximum pressing of the rubbing roller 6 in all the outer peripheral positions. As shown, it may be longer only at some outer peripheral positions. The position of the outer peripheral surface of the roller 23 corresponding to the portion where the diameter of the roller 23 is longer than the diameter 6b at the time of maximum pressing of the rubbing roller 6 corresponds to a region 23a indicated by a thick line in FIG. . The outer peripheral surface of the roller 23 can abut on the photosensitive drum 1 in the region 23a, and the pressing force is smaller than in other portions.

  In this embodiment, the roller 15 is provided on the rotating shaft 10 of the rubbing roller 6. However, as shown in FIG. 10, rollers 25 may be fixedly provided on the rotating shafts at both ends of the photosensitive drum 1. . In this case, the maximum roller diameter 25 a needs to be larger than the diameter 1 a of the photosensitive drum 1 in order to cause a change in pressing force. Further, since it is necessary to polish the entire surface of the photosensitive drum 1, the difference between the maximum diameter 25 a of the roller and the radius 1 a of the photosensitive drum 1 is as follows so as not to generate a state where the pressing force is zero. The difference between the normal diameter 6a of the rubbing roller 6 and the diameter 6b at the time of maximum pressing needs to be smaller.

  However, if the roller is fixed on the photosensitive drum 1 side, the pressing force is reduced at the same place on the surface of the photosensitive drum 1 and the polishing force is weakened. Therefore, the roller is provided on the rubbing roller 6 side. Is more preferable.

  The image forming apparatus of the present invention can achieve both the polishing performance of the surface of the image carrier and the cleaning performance of the toner remaining on the surface of the image carrier, and is useful as a copying machine, a printer, a facsimile machine, and the like. .

1 is a configuration diagram viewed from the front of a copying machine according to an embodiment of the present invention. 1 is a front configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is an external perspective view of the cleaning unit according to the embodiment of the present invention. The side view of the roller in embodiment concerning this invention Side configuration diagram of rubbing roller and roller according to an embodiment of the present invention (A)-(e) The figure for demonstrating grinding | polishing operation | movement of the photosensitive drum in the image forming apparatus of embodiment concerning this invention. Side structure diagram of a modified example of a roller and a rubbing roller in an embodiment according to the present invention Side structure diagram of a modified example of the roller in the embodiment according to the present invention Side structure diagram of a modified example of a roller and a rubbing roller in an embodiment according to the present invention FIG. 6 is a side view of a modification of the image forming apparatus according to the embodiment of the present invention. Configuration of conventional image forming apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging device 3 Exposure device 4 Developing device 5 Transfer roller 6 Rub roller 7 Cleaning blade 8 Static eliminator 9 Cleaning unit 10 Rotating shaft 11 L-shaped member 12 Spring member 13 Support point 14 Recovery screw 15 Roller 16 Paper 17 Paper detection sensor

Claims (7)

An image carrier on which an electrostatic latent image is formed on the surface;
Developing means for forming a toner image containing an abrasive based on the electrostatic latent image;
Transfer means for transferring the toner image to a transfer material or an intermediate transfer member;
A rubbing roller arranged to be pressed against the surface of the image carrier for polishing the surface of the image carrier using the toner not transferred by the transfer means and remaining on the image carrier. When,
A cleaning blade disposed on the downstream side of the rubbing roller with respect to the rotation direction of the image carrier for removing the remaining toner from the surface of the image carrier;
An image forming apparatus comprising: a pressing force changing unit that periodically changes a pressing force of the rubbing roller against the image carrier while pressing the rubbing roller against the image carrier at least during image formation. .   The image forming apparatus according to claim 1, wherein the change in the pressing force includes a case where the pressing force is zero. −
The image forming apparatus according to claim 1, wherein the pressing force changing unit changes the pressing force even during non-image formation. The surface of the rubbing roller is formed of an elastic body,
The image forming apparatus according to claim 1, wherein the rubbing roller is disposed so as to be pressed against the surface of the image carrier via the elastic body. The pressing force changing means is a contact member that is fixed to both ends of the rubbing roller and contacts the surface of the image carrier,
The shape of the cross section of the contact member orthogonal to the rotation axis of the rubbing roller is different from the shape of the cross section of the rubbing roller orthogonal to the rotation axis,
The distance between the rotation shaft of the contact member and the rotation shaft of the image carrier changes when the outer peripheral surface of the contact member rotates in contact with the surface of the image carrier. Image forming apparatus.   6. The image forming apparatus according to claim 5, further comprising a spring-like member for pressing the rubbing roller against the surface of the image carrier. The cross-sectional shape of the rubbing roller perpendicular to the rotation axis is a circular shape,
The rotation of the abutting member so that the rubbing roller has an elastic force with respect to the image carrier even when the distance is shortest and longest while the distance changes. 6. The image forming apparatus according to claim 5, wherein a length from the center of the shaft to the outer peripheral surface is determined.

Images