JP2016164645A - Image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation apparatus capable of stably cleaning an image carrier over a long period by suppressing inversion, oscillation and wear of a cleaning member.SOLUTION: An image formation apparatus comprises: an image carrier in which a toner image is formed on the surface; a drive device which rotationally drives the image carrier; a development device; a cleaning member; and a control part. The development device develops an electrostatic latent image formed on the surface of the image carrier to a toner image with adhesion of toner including abrasive particles. The cleaning member is arranged so as to be in contact with the surface of the image carrier to clean the surface of the image carrier. The image formation apparatus can execute friction resistance suppression processing for suppressing the friction resistance between the cleaning member and the surface of the image carrier by discharging toner to the image carrier from the development device at the time of non-image formation. The control part adjusts the toner amount to be discharged from the development device to the image carrier at the time of execution of the friction resistance suppression processing in accordance with the estimation result of the surface condition of the image carrier.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus that forms an image on recording paper, and more particularly to an image forming apparatus that includes a cleaning member that contacts an image carrier on which a toner image is formed.

  In an image forming apparatus such as a printer, a copying machine, a facsimile, or a multifunction machine having these functions, a photosensitive drum as an example of an electrophotographic photosensitive member, a charging device that charges the surface of the photosensitive drum, and a photosensitive member A device is known that includes a cleaning device that is disposed in contact with the drum surface and removes toner and external additives remaining on the surface of the photosensitive drum.

  When performing image formation in the image forming apparatus as described above, for example, after charging the surface of the photosensitive drum with a charging device, exposure is performed by an exposure unit to form an electrostatic latent image on the surface of the photosensitive drum, Toner is supplied from the developing device to the electrostatic latent image to form a toner image on the surface of the photosensitive drum, and then the toner image is transferred from the photosensitive drum to the recording paper by the transfer / separation unit.

  Then, the recording paper onto which the toner image has been transferred is guided to a fixing unit, and the toner image is fixed on the recording paper by a fixing roller, while the toner remaining on the surface of the photosensitive drum after transfer is removed by a cleaning device, Thereafter, the potential remaining on the surface of the photosensitive drum is neutralized by a method such as irradiating the photosensitive member with light from a static eliminator.

  As a cleaning device, for example, a device that removes toner by pressing the end of a cleaning blade (cleaning member) formed in a plate shape with an elastic material such as urethane rubber against the surface of the photosensitive drum is widely used. Has been. On the other hand, as a photosensitive drum, a photosensitive layer is provided on the drum surface. As this photosensitive layer, an organic photosensitive layer made of an organic material and an inorganic photosensitive layer made of an inorganic material such as selenium or amorphous silicon are known. It has been.

  In the above image forming apparatus, when charging the surface of the photosensitive drum with a charging device or transferring / separating the toner image formed on the surface of the photosensitive drum with a transfer / separation unit, A discharge product with high hydrophilicity such as ozone or nitrogen oxide is generated with the discharge performed in the separation unit, and the generated discharge product adheres to the surface of the image carrier.

  Here, in the case where the photosensitive layer is an organic photosensitive layer made of an organic material, the photosensitive layer is relatively soft. Therefore, when the cleaning member is pressed against the surface of the photosensitive drum to remove the toner, the surface of the photosensitive drum is The discharge product adhered by being gradually scraped by the cleaning member is removed from the surface of the photosensitive drum.

  On the other hand, when the photosensitive layer is made of amorphous silicon, the surface hardness of the photosensitive layer is high and the amount of scraping of the surface of the photosensitive drum by the cleaning member is small, so that the discharge product is not removed by the cleaning member. Remains on the surface. In the portion where the discharge product remains, there is a problem that the electric resistance of the surface of the photosensitive drum is lowered, and electric charges flow when an electrostatic latent image is formed, causing an image flow in the formed image. is there.

  In order to solve the above problems, for example, Patent Document 1 proposes a technique for removing discharge products by polishing irregularities on the surface of a photoreceptor. Japanese Patent Application Laid-Open No. H10-228688 proposes a photoconductor having a surface roughness that is greater at the end in the width direction than at the center in the width direction. In the method of Patent Document 2, the cleaning capability is improved by reducing the surface roughness at the central portion in the width direction (axial direction) of the photosensitive member, and at the same time, the surface roughness is increased at both ends in the width direction to reduce the surface roughness. By reducing the frictional force, the cleaning member can be prevented from reversing or vibrating with the rotation of the photoconductor, and toner remaining on the surface of the photoconductor and electrostatic products adhering to the surface can be reduced. It is described that the cleaning member can be stably removed from the surface of the photoreceptor, and a good image can be obtained stably.

Japanese Patent Publication No.7-89231 Japanese Patent Laid-Open No. 11-2910

  However, in the method described in Patent Document 1, when the unevenness on the surface of the photoconductor is reduced, the contact area between the cleaning member and the photoconductor increases, and the frictional force between the photoconductor and the cleaning member increases. . As a result, the cleaning member is pulled (pulled in) with the rotation of the photosensitive member, the cleaning member is inverted or vibrated, the cleaning member is damaged, and the surface of the photosensitive member is sufficiently cleaned. There was a problem that could not be. Another problem is that the toner external additive slips through the gap between the photosensitive member and the cleaning member, and the charging device is contaminated.

  In the method described in Patent Document 2, the surface of the photosensitive layer is worn by long-term durable printing, although it is established in the initial use state of the photosensitive member. In particular, the surface roughness becomes small at the center in the width direction of the photoconductor, and the frictional force with the cleaning member increases. As a result, the central portion in the width direction of the cleaning member is pulled (pulled) to the photosensitive member side, and the same problem as in Patent Document 1 occurs.

  In view of the above problems, an object of the present invention is to provide an image forming apparatus that can suppress reversal, vibration, and wear of a cleaning member and can stably clean an image carrier over a long period of time.

  In order to achieve the above object, a first configuration of the present invention is an image forming apparatus including an image carrier, a driving device, a developing device, a cleaning member, and a control unit. A toner image is formed on the surface of the image carrier. The driving device rotationally drives the image carrier. The developing device develops the electrostatic latent image formed on the surface of the image carrier by attaching toner containing abrasive particles into a toner image. The cleaning member is disposed so as to contact the surface of the image carrier, and cleans the surface of the image carrier. The control unit can control the amount of toner discharged from the developing device to the image carrier. The image forming apparatus can execute a frictional resistance suppressing process for discharging the toner from the developing device to the image carrier during non-image formation and suppressing the frictional resistance between the cleaning member and the surface of the image carrier. The control unit adjusts the amount of toner discharged from the developing device to the image carrier side when executing the frictional resistance suppression process according to the estimation result of the surface state of the image carrier.

  According to the first configuration of the present invention, the amount of toner accumulated in the pressure contact portion between the cleaning member and the image carrier can be adjusted according to the estimation result of the surface state of the image carrier, so that the pressure contact between the cleaning member and the image carrier can be adjusted. It is possible to suppress slipping of the external additive from the portion, and to reduce the frictional force between the cleaning member and the image carrier. Thus, the image carrier can be stably cleaned over a long period of time.

1 is a schematic cross-sectional view showing a schematic configuration of a tandem color printer as an image forming apparatus 11 according to an embodiment of the present disclosure. 1 is a diagram illustrating a schematic configuration of a main part including an image forming processing unit 15 of the image forming apparatus 11. A block diagram illustrating a control path used in the image forming apparatus 11 The figure which shows the uneven | corrugated shape when skewness Rsk is larger than 0 The figure which shows the uneven | corrugated shape when skewness Rsk is smaller than 0 A flowchart showing processing contents of toner amount adjustment control in the image forming apparatus 11 of the first embodiment. 7 is a flowchart showing processing details of toner amount adjustment control in the image forming apparatus 11 according to the second embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus 11 according to an embodiment of the present invention. FIG. 2 is a diagram showing a schematic configuration of a main part including the image forming processing unit 15 of the image forming apparatus 11 shown in FIG.

1. Configuration of image forming apparatus 11 (overall configuration)
As shown in FIG. 1, the image forming apparatus 11 according to the present embodiment is a tandem color printer. The image forming apparatus 11 includes, inside a printer main body 12, a paper feed cassette 13 that stores recording paper (not shown), a paper feeding unit 14 that feeds recording paper one by one from the paper feeding cassette 13, and paper feeding An image forming processing unit 15 that performs an image forming process on the recording paper supplied from the cassette 13 or the manual feed tray (not shown), and a recording paper transport path for transporting the recording paper supplied from the paper feed cassette 13 or the manual feed tray 16, a secondary transfer unit 17 that transfers the toner image formed in the image forming processing unit 15 to the recording paper conveyed along the recording paper conveyance path 16, and the toner image transferred in the secondary transfer unit 17 And a fixing unit 18 that fixes the recording paper.

(Configuration of the image forming processing unit 15)
For example, the image forming processing unit 15 employs a tandem system that performs image forming processing using toner (developer) of four colors of yellow (Y), magenta (M), cyan (C), and black (K). ing. In the following explanation, only in the case of color designation, the symbol of each arithmetic numeral is attached with a color of (Y, M, C, K) in parentheses, and in the common case, only the arithmetic numeral is included. A description will be given with reference numerals.

  The image forming processing unit 15 corresponds to each color (Y, M, C, K) and print data (images) transmitted from a plurality of toner containers 19 containing replenishing toner and an externally connected device such as a personal computer. A plurality of photosensitive drums 20 for forming toner images of respective colors based on the data), a plurality of developing devices 21 for supplying toner to each of the photosensitive drums 20, and a toner image formed on each of the photosensitive drums 20. The endless intermediate transfer belt 22 to which the toner image is primarily transferred, the residual toner attached to the surface of the intermediate transfer belt 22 and disposed upstream of the photosensitive drum 20 on the most upstream side in the rotational movement direction of the intermediate transfer belt 22 A belt cleaning device 24 that removes the light, and an exposure unit 25 that emits beam light to each photosensitive drum 20.

(Configuration of Photosensitive Drum 20)
The photosensitive drum 20 is formed by forming a photosensitive layer on the surface of a support (base). Here, the photosensitive drum 20 includes a cylindrical cylindrical tube made of metal and a photosensitive layer formed on the surface of the tube. Examples of the metal forming the base tube include aluminum, iron, titanium, and magnesium. As the photosensitive layer, an organic photosensitive layer using an organic photoconductor or an inorganic photosensitive layer using an inorganic photoconductor can be used. However, because of its high durability, an amorphous silicon photosensitive film formed by vapor deposition of silane gas or the like is used. A layer is preferred. Each photosensitive drum 20 carries a toner image of each color on the surface thereof based on the beam light emitted from the exposure unit 25 and transfers the toner image to the intermediate transfer belt 22, as shown in FIG. As described above, the developing device 21 is disposed below the intermediate transfer belt 22. The surface state of the photosensitive drum 20 in the initial use will be described later.

  As shown in FIGS. 1 and 2, a charging roller (charging member) 26, an exposure unit 25, a developing device 21, a cleaning device 28, and a static eliminating device 29 are disposed around the photosensitive drum 20, A primary transfer roller 27 is disposed opposite to the photosensitive drum 20 with the transfer belt 22 interposed therebetween.

  The toner image transferred onto the intermediate transfer belt 22 at each primary transfer portion configured by the cooperation of the photosensitive drum 20 and the primary transfer roller 27 passes through the recording paper transport path 16 from the paper feed cassette 13 or the manual feed tray. The recording paper that has been conveyed through is transferred by the secondary transfer unit 17.

(Configuration of developing device 21)
Each developing device 21 basically has the same configuration and is arranged below the intermediate transfer belt 22 along the rotational movement direction. The developing device 21 includes a developing container 31 that stores a two-component developer (hereinafter, also simply referred to as a developer), two stirring screws 32 a and 32 b, a magnetic roller 34, and a developing roller 35. A developing type, a magnetic brush standing on the surface of the magnetic roller 34 is used to form a thin toner layer on the developing roller 35, and a developing bias having the same polarity (positive) as that of the toner is applied to the developing roller 35. The toner is allowed to fly on the surface of 20. As a result, the electrostatic latent image on the surface of the photosensitive drum 20 is developed into a toner image.

  The developing device 21 is configured to be able to supply (discharge) the toner on the developing roller 35 to the photosensitive drum 20 side during non-image formation. Thus, toner can be supplied to the periphery of the edge of the cleaning blade 42 for the purpose of reducing the frictional force between the photosensitive drum 20 and the cleaning blade 42 and preventing the external additive from slipping through. This toner supply is performed after printing a predetermined number of sheets (in this example, 100 sheets). The toner supplied to the photosensitive drum 20 side is removed by the cleaning blade 42 of the cleaning device 28. The toner contains a toner external additive (abrasive particles) made of metal particles such as titanium oxide.

  The developing container 31 is partitioned by a partition wall 31a, and first and second stirring screws 32a and 32b are provided in the first and second stirring chambers 31b and 31c. The first and second stirring screws 32a and 32b mix the toner (positively charged toner) supplied from the toner container 19 with the carrier, stir and charge the toner. The developer in the first and second stirring chambers 31b and 31c is conveyed in the axial direction while being stirred by the first stirring screw 32a and the second stirring screw 32b, and between the first and second stirring chambers 31b and 31c. Circulate.

  A magnetic roller 34 is disposed in the developing container 31 at a position facing the second stirring screw 32b, and a developing roller 35 is disposed on the opposite side of the magnetic roller 34 from the second stirring screw 32b. The developing roller 35 faces the photoconductive drum 20.

  The magnetic roller 34 includes a nonmagnetic rotating sleeve 36 and a fixed magnet body 37 having a plurality of magnetic poles arranged in the rotating sleeve 36. The magnetic pole of the fixed magnet body 37 has a five-pole configuration including a main pole 37a, a regulation pole 39, a transport pole 37c, a peeling pole 37d, and a pumping pole 37e.

  A regulating blade 38 is attached to the developing container 31 along the longitudinal direction of the magnetic roller 34 (the front and back direction in FIG. 2). The regulating blade 38 is provided on the upstream side of the opposing position (proximal position) between the developing roller 35 and the magnetic roller 34 in the rotation direction of the magnetic roller 34.

  The developing roller 35 includes a cylindrical developing sleeve 35a and a magnet member 35b fixed in the developing sleeve 35a. The magnet member 35 b has a different polarity from the opposing magnetic pole (main pole) 37 a of the fixed magnet body 37.

  The developer circulating in the developing container 31 is conveyed to the magnetic roller 34 by the second stirring screw 32b. By making the regulating blade 38 and the regulating pole 37b of the fixed magnet body 37 face each other and using a non-magnetic material or a magnetic material as the regulating blade 38, a magnetic field in a direction attracting the gap between the tip of the regulating blade 38 and the rotating sleeve 36 is generated. Occur. Due to this magnetic field, a magnetic brush is formed between the regulating blade 38 and the rotary sleeve 36.

  When the thickness of the magnetic brush on the magnetic roller 34 is regulated by the regulating blade 38 and then moves to a position facing the developing roller 35, the magnetic field attracted by the main pole 37 a of the fixed magnet body 37 and the magnet member 35 b on the developing roller 35 side. Therefore, the magnetic brush contacts the surface of the developing roller 35. Then, a toner thin layer is formed on the developing roller 35 by a potential difference ΔV between Vmag (DC) applied to the magnetic roller 34 and Vslv (DC) applied to the developing roller 35 and a magnetic field. The toner layer thickness on the developing roller 35 varies depending on the resistance of the developer, the rotational speed difference between the magnetic roller 34 and the developing roller 35, and the like, but can be controlled by ΔV. Specifically, when ΔV is increased, the toner layer on the developing roller 35 is thickened, and when ΔV is decreased, the toner layer is thinned. The developing device 21 is not limited to the above configuration, and a conventionally known device can be used.

(Configuration of the intermediate transfer belt 22)
The intermediate transfer belt 22 is an endless belt that is horizontally stretched between a driving roller and a driven roller in the printer main body 12, and accompanies an image forming operation as the driving roller is rotated by a belt driving motor (not shown). It is circulated and driven.

(Configuration of toner density detection sensor 23)
The toner density detection sensor 23 measures the reflection density of the toner image on the intermediate transfer belt 22 and outputs the detected value to the CPU 51 (see FIG. 3). The toner density detection sensors 23 can be provided at a plurality of locations along the rotational movement direction of the intermediate transfer belt 22 and the width direction orthogonal to the rotational movement direction. At this time, if the toner density detection sensor 23 detects the toner density only on one side in the width direction of the intermediate transfer belt 22, for example, a phenomenon in which a density difference occurs on both ends in the width direction of the intermediate transfer belt 22 (single burn phenomenon). It is preferable to dispose near the both ends in the width direction because it is not possible to cope with the occurrence of this.

(Configuration of charging roller 26)
The charging roller 26 is made of, for example, conductive rubber and is disposed so as to contact the photosensitive drum 20. As shown in FIG. 2, when the photosensitive drum 20 rotates in the clockwise direction, the charging roller 26 that contacts the surface of the photosensitive drum 20 is driven to rotate counterclockwise. At this time, the surface of the photosensitive drum 20 is uniformly charged by applying a predetermined voltage to the charging roller 26. Further, as the charging roller 26 rotates, a charging cleaning roller (not shown) that contacts the charging roller 26 is driven to rotate in the clockwise direction to remove foreign matters attached to the surface of the charging roller 26.

(Configuration of the cleaning device 28)
The cleaning device 28 has a cleaning housing 40 having a depth in the recording paper width direction (a direction orthogonal to the recording paper conveyance direction), and is disposed near the lower inside of the cleaning housing 40 and rotates clockwise in FIG. A collection spiral 41 that conveys the collected toner to one side in the paper width direction and sends it to a waste toner container (not shown), a cleaning blade 42 attached to the outside lower side of the cleaning housing 40, and an inside upper side of the cleaning housing 40 A rubbing roller (cleaning roller) 43 disposed in contact with the surface of the photosensitive drum 20, and a scraper 44 disposed above the rubbing roller 43 and in contact with the surface of the rubbing roller 43.

  The cleaning blade 42 is made of urethane rubber or the like. The cleaning blade 42 is disposed so that the tip abuts against the surface of the photosensitive drum 20 from below the rotational axis of the photosensitive drum 20. At this time, the tip of the cleaning blade 42 is in contact with the rotation direction of the photosensitive drum 20 (see the arrow in FIG. 2) in the counter direction. A contact portion between the end portion of the cleaning blade 42 and the surface of the photosensitive drum 20 is a “pressure contact portion”.

  The rubbing roller 43 collects waste toner from the surface of the photoconductive drum 20 and polishes the surface of the photoconductive drum 20 with the waste toner adhering to the surface of the rubbing roller 43. For this reason, the rubbing roller 43 is formed in a cylindrical shape that extends in the recording paper width direction using foamed rubber (for example, carbon-containing conductive foamed EPDM) in order to maintain high retention of waste toner. It is arranged upstream of the front end in the rotational direction of the photosensitive drum 20. Further, the rotation direction of the rubbing roller 43 is opposite to the rotation direction of the photosensitive drum 20. The scraper 44 is made of a thin sheet metal that ensures durability, and in order to make the amount of toner adhering to the surface of the rubbing roller 43 uniform, a counter direction is provided downstream of the rubbing roller 43 in the rotation direction. The tip is in contact.

(Configuration of static elimination device 29)
The static eliminator 29 is disposed on the downstream side of the cleaning device 28 along the rotation direction of the photosensitive drum 20. An LED (light emitting diode) is used for the static elimination device 29, and a reflector is provided as necessary. The static eliminator 29 irradiates the photosensitive drum 20 with static elimination light (erase light), thereby removing the charged charges on the surface thereof and preparing for the charging process in the next image forming operation.

2. Next, the control of the image forming apparatus 11 according to the present embodiment will be described. FIG. 3 is an explanatory diagram of the control unit 50 used in the image forming apparatus. Since the image forming apparatus 11 performs various controls of each apparatus, the control of the entire apparatus is complicated. Therefore, here, a portion of the control path that is necessary for the implementation of the present invention will be mainly described.

  The controller 50 mainly controls the rotational drive of each photosensitive drum 20, the developing bias applied to the developing device 21, the primary transfer bias applied to the primary transfer roller 27, and the charging bias applied to the charging roller 26. In addition to controlling the power of the laser beam P (see FIG. 1) emitted from the exposure unit 25, controlling the erase light quantity of the static eliminator 29, the pressure contact between the photosensitive drum 20 and the cleaning blade 42 Control of the amount of toner accumulated between the two parts. This toner amount adjustment control is hereinafter referred to as “toner amount adjustment control”.

  When the arithmetic average roughness Ra of the surface of the photosensitive drum 20 is 30 nm or more or 10 nm or less in the toner amount adjustment control, the control unit 50 is within a range in which the arithmetic average roughness Ra is larger than 10 nm and smaller than 30 nm. Control is performed so that the amount of toner supply increases compared to the case.

  When the arithmetic average roughness Ra is 30 nm or more, that is, when the unevenness of the surface is large, by supplying the toner in an increased amount, it acts between the external additive present on the photosensitive drum 20 and the supplied toner. The external additive is adsorbed to the toner by the force between particles (van der Waals force, linear electric force). As a result, the damming effect of the external additive at the press contact portion between the photosensitive drum 20 and the cleaning blade 42 is increased, and slipping of the external additive from the gap between the photosensitive drum 20 and the cleaning blade 42 can be prevented. . Therefore, contamination of the charging roller 26 is suppressed, and a good image without uneven charging can be obtained. The reason why the arithmetic average roughness Ra is 30 nm or more is that if it is less than 20 nm, the gap between the photosensitive drum 20 and the pressure contact portion of the cleaning blade 42 is small, and it is difficult for the external additive to slip through the pressure contact portion. .

  Further, when the arithmetic average roughness Ra is 10 nm or less, the toner amount is increased and supplied, whereby the supplied toner functions as a lubricant and the frictional force at the press contact portion can be reduced. Note that the arithmetic average roughness Ra is set to 10 nm or less because, if it is larger than 10 nm, the frictional force between the photosensitive drum 20 and the cleaning blade 42 is small, and the cleaning blade 42 is less likely to be inverted or vibrated. It is.

  The control unit 50 includes a CPU 51 serving as a central processing unit, a ROM 52 serving as a read-only storage unit, a RAM 53 serving as a readable / writable storage unit, an HDD 54 that temporarily stores image data and the like, a counter 55, the photosensitive drum 20, and the like. A motor driving driver 56 for driving and controlling the driving motor 48, a torque detecting unit 57 for detecting the torque of the driving motor 48, a developing bias circuit 58 for applying a developing bias to the developing device 21, and a charging roller 26 A charging bias circuit 59 for applying a charging bias, a transfer bias circuit 60 for applying a transfer bias to the primary transfer roller 27 and the secondary transfer unit 17, and the like.

  The ROM 52 stores a control program for the image forming apparatus 11, numerical values and data necessary for control, and the like. The RAM 53 stores necessary data generated during the control of the image forming apparatus 11, data temporarily necessary for controlling the image forming apparatus 11, and the like. The storage unit of the ROM 52, RAM 53, or HDD 54 stores a toner supply amount used for toner discharge amount adjustment control, which will be described later.

3. Image Forming Procedure Next, an image forming procedure of the image forming apparatus 11 will be described. When image data is input from an external connection device such as a personal computer, the CPU 51 first applies a charging bias to the charging roller 26 via the charging bias circuit 59, and the charging roller 26 controls the surface of the photosensitive drum 20. To charge. Next, the exposure unit 25 irradiates the surface of the photosensitive drum 20 with the laser beam P. As a result, an electrostatic latent image corresponding to the image data of the accepted job is formed on each photosensitive drum 20.

  The CPU 51 applies a bias voltage having a potential difference to the magnetic roller 34 and the developing roller 35 via the developing bias circuit 58. As a result, a thin toner layer is formed on the developing roller 35. Then, due to the potential difference between the developing roller 35 and the photosensitive drum 20, the toner on the developing roller 35 flies to the photosensitive drum 20 side, and a toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive drum 20. . The developing device 21 is filled with a predetermined amount of a two-component developer (hereinafter, also simply referred to as a developer) containing toner of each color of yellow, magenta, cyan, and black. In addition, when the ratio of the toner in the two-component developer filled in each developing device 21 is less than a predetermined value due to the formation of a toner image described later, the toner is supplied from the toner container 19 to each developing device 21. .

  On the other hand, the recording paper is fed from the paper feed cassette 13 (or the manual feed tray) in accordance with the toner image formation timing in the image forming processing unit 15, and conveyed to the registration roller pair 30 a through the recording paper conveyance path 16. .

  Then, the CPU 51 applies a transfer bias having a polarity opposite to that of the toner (negative polarity when using positively charged toner) to the primary transfer roller 27 via the transfer bias circuit 60. As a result, a predetermined electric field is applied between the primary transfer roller 27 and each photoconductor drum 20, and the yellow, magenta, cyan, and black toner images on each photoconductor drum 20 are primarily transferred onto the intermediate transfer belt 22. Is done. These four color images are formed with a predetermined positional relationship predetermined for forming a predetermined full color image. Next, the CPU 51 applies a negative transfer bias to the secondary transfer unit 17 via the transfer bias circuit 60. As a result, the toner image on the intermediate transfer belt 22 is transferred to the recording paper conveyed from the registration roller pair 30a. Thereafter, the toner remaining on the surface of the photosensitive drum 20 after the primary transfer is removed by the cleaning device 28 in preparation for the subsequent formation of a new electrostatic latent image. Further, the residual charge on the surface of the photosensitive drum 20 is removed by the static eliminator 29.

  When the intermediate transfer belt 22 starts to rotate counterclockwise in FIG. 1, the recording paper is conveyed from the registration roller pair 30a to the secondary transfer portion 17 provided adjacent to the intermediate transfer belt 22 at a predetermined timing. The full color image on the intermediate transfer belt 22 is secondarily transferred onto the recording paper. The recording paper on which the toner image is secondarily transferred is conveyed to the fixing unit 18. Residual toner or the like adhering to the surface of the intermediate transfer belt 22 is removed by the belt cleaning device 24.

  The recording paper conveyed to the fixing unit 18 is heated and pressurized to fix the toner image on the surface of the recording paper, thereby forming a predetermined full color image. The recording paper on which the full-color image is formed is guided to the end portion of the recording paper transport path 16 and is discharged onto the discharge tray 12a that also serves as the upper surface of the printer body 12 by the discharge roller pair 30b.

<First Embodiment>
The image forming apparatus 11 according to the present invention has the developing device 21 when the frictional resistance between the cleaning blade 42 and the surface of the photosensitive drum 20 increases, such as when a predetermined number of prints are continuously performed at a low printing rate. The toner on the developing roller 35 is forcibly ejected to the photosensitive drum 20 side and supplied to the cleaning blade 42 of the cleaning device 28, and the frictional resistance is suppressed to suppress the friction between the cleaning blade 42 and the surface of the photosensitive drum 20. The process is configured to be executable. Hereinafter, a frictional resistance suppressing process and related control of the image forming apparatus 11 according to the first embodiment of the present invention will be described.

(1) Drive Torque Detection of Photosensitive Drum 20 The CPU 51 controls a drive motor (drive device) 48 that rotates the photosensitive drum 20 via a motor drive driver 56 and detects torque of the drive motor 48. The detection value from the unit 57 is acquired. In the present embodiment, the torque detector 57 detects the output current value of the drive motor 48. That is, the output current value of the drive motor 48 is used as a torque index. Note that a means for detecting the torque of the drive motor 48 is usually provided in the image forming apparatus 11 in order to prevent the drive motor 48 from being damaged due to an excessive load.

(2) Surface State of Photosensitive Drum 20 in Initial Use The photosensitive drum 20 used in the image forming apparatus 11 of the present embodiment has an arithmetic average roughness Ra of the photosensitive layer surface in the initial use of 20 [nm] or more and 100 [ nm] or less, the ten-point average roughness Rz is in the range of 0.2 [μm] or more and 1.0 [μm] or less, and the average interval Sm between the irregularities is 20 [μm] or less, The surface roughness is such that the ratio (Ra [nm] / Sm [μm]) of the arithmetic average roughness Ra [nm] to the average interval Sm [μm] of the unevenness is 3 or more and the skewness Rsk is 0.3 or more. preferable. In this specification, the initial use of the photosensitive drum 20 refers to a new state before durable printing. Further, the surface state described above may be at least in the initial use of the photosensitive drum 20 (the state at the start of use, in other words, the state after factory shipment). The arithmetic average roughness Ra, the ten-point average roughness Rz, and the average interval Sm are measured by a surface roughness measuring method defined in 1994 edition of JIS B0601 using a stylus type two-dimensional roughness measuring instrument.

(2-1) Arithmetic average roughness Ra
When the arithmetic average roughness Ra is smaller than 20 [nm], the cleaning blade 42 is worn by long-term use, and the amount of slipping through of the external additive that leads to image defects increases. When the arithmetic average roughness Ra is larger than 100 [nm], the amount of slipping out of the external additive is large from the beginning, and the contamination of the charging roller 26 starts from a relatively early stage of durable printing, which makes it difficult to use for a long time. Become. Accordingly, the arithmetic average roughness Ra of the surface of the photosensitive layer in the initial use is preferably in the range of 20 [nm] to 100 [nm].

(2-2) Ten-point average roughness Rz
When the arithmetic average roughness Ra of the photosensitive layer surface in the initial use of the photosensitive drum 20 is in the range of 20 [nm] to 100 [nm], the ten-point average of the photosensitive layer surface in the initial use of the photosensitive drum 20 is used. The roughness Rz is preferably in the range of 0.2 [μm] to 1.0 [μm].

  Even if the arithmetic average roughness Ra is within the above range, if there are large irregularities, the cleaning blade 42 is not able to follow the surface of the photosensitive drum 20 although it deforms to some extent, and the photosensitive drum 20 and the cleaning blade 42 This is a rule for preventing the gap between the two. Note that when the interval between the photosensitive drum 20 and the cleaning blade 42 is increased, slipping of external additives or the like occurs.

  In other words, if a large convex portion exists on the surface of the photosensitive drum 20 and the tip of this convex portion comes into contact with the cleaning blade 42, the concave portion located between the large convex portions contacts the cleaning blade 42. This is because it does not make sense to define the magnitude of the arithmetic average roughness Ra. That is, it is preferable that the surface of the photoconductor drum 20 has no irregularities and has minute irregularities, and this condition is defined by the ten-point average roughness Rz and the arithmetic average roughness Ra. . Note that the ten-point average roughness Rz defines that there are no sudden irregularities.

(2-3) Average spacing Sm between the irregularities
Even if the arithmetic average roughness Ra and the ten-point average roughness Rz are within the above ranges, the cleaning blade 42 contacts (supports) the large convex portion when the large convex portion exists apart. . Here, the average interval Sm of the unevenness is used for determining whether or not the large convex portion is separated.

  The cleaning blade 42 is elastically deformable, and is deformed so as to come into contact with the photosensitive drum 20 between large protrusions (portions). In particular, when the interval between the convex portions is wide, the contact area between the cleaning blade 42 and the photosensitive drum 20 increases. When the contact area increases, the driving torque of the photosensitive drum 20 increases due to friction with the cleaning blade 42 and the wear of the cleaning blade 42 increases, eventually causing stick slip of the cleaning blade 42 and slipping of the external additive. Or the edge of the cleaning blade 42 is lost. Needless to say, if the edge of the cleaning blade 42 is lost, a good image cannot be obtained.

  Further, when the average interval Sm is increased, the convex portion (mountain) is increased (the crest of the peak is wide), and when the top portion of the convex portion is worn due to long-term use, a wide flat portion is formed at the top portion and contact with the cleaning blade 42 is achieved. The area increases. Accordingly, the arithmetic average roughness Ra of the surface of the photosensitive layer in the initial use of the photosensitive drum 20 is in the range of 20 [nm] to 100 [nm], and the ten-point average roughness Rz is 0.2 [μm] to 1 When it is in the range of 0.0 [μm] or less, the average interval Sm of the unevenness is preferably 20 [μm] or less.

  By forming irregularities on the surface of the photosensitive layer irregularly in the axial direction and the circumferential direction so that the surface roughness satisfies the above range, friction between the photosensitive drum 20 and the cleaning blade 42 is reduced. As a result, it is possible to reduce the driving torque of the photosensitive drum 20 and the wear of the edge of the cleaning blade 42. In particular, when Ra [nm] / Sm [μm] ≧ 3 is satisfied, the uneven shape having a height (depth) of three times or more with respect to the average interval Sm is obtained, so that the photosensitive drum 20 and the cleaning blade 42 are obtained. The contact area is reduced, and friction is effectively reduced. The unevenness of the surface of the photosensitive layer that satisfies the above range is obtained by, for example, subjecting the outer peripheral surface of a metal tube (aluminum base tube, etc.) such as aluminum as a support to a surface roughening treatment by blasting or the like. It can be adjusted by forming an amorphous silicon layer (photosensitive layer).

(2-4) Skewness Rsk
Further, by satisfying the skewness Rsk ≧ 0.3, the contact area between the photosensitive drum 20 and the cleaning blade 42 is reduced, and friction is effectively reduced. The surface roughness is such that the skewness Rsk is 0.3 or more. The arithmetic average roughness Ra, the ten-point average roughness Rz, and the average interval Sm are measured in the same manner as in the first and second embodiments.

Here, the skewness Rsk is one of the parameters representing the strength of the surface roughness, and represents the symmetry (degree of distortion of the irregularities) between the peak and valley when the average line is the center, and the following formula ( In the reference length made dimensionless by the cube of the root mean square height Rq as in 1), it is represented by the root mean square of Z (x).
... (1)

  When Rsk is larger than 0, the unevenness is in a shape biased downward with respect to the average line L as shown in FIG. On the other hand, when Rsk is smaller than 0, as shown in FIG. 5, the unevenness has a shape biased upward with respect to the average line. In other words, it is considered that when the skewness Rsk of the photosensitive layer is larger than 0, the contact area is reduced because the contact with the cleaning blade 42 is more pointed.

(2-5) DUH Hardness It is preferable that the DUH hardness of the photosensitive layer in the initial use of the photosensitive drum 20 is in the range of 500 [kgf / mm ² ] to 1200 [kgf / mm ² ]. This is because if the DUH hardness is smaller than 500 [kgf / mm ² ], the photosensitive layer of the photosensitive drum 20 is easily worn by contact with the cleaning blade 42 and the rubbing roller 43 and cannot be used for a long time. From this viewpoint, a higher DUH hardness is preferable. For this reason, the upper limit of the DUH hardness is defined by the hardness of the photosensitive layer having the highest hardness that can be used at present. The DUH hardness refers to an indentation hardness (Martens hardness) measured by a dynamic ultra-micro hardness meter (DUH series, manufactured by Shimadzu Corporation).

(2-6) Form of Unevenness It is preferable that unevenness on the drum surface is present irregularly in the axial direction and the circumferential direction of the photosensitive drum 20. Irregular means that the irregularity does not have a certain regularity when the irregularity is seen in any one direction within a certain plane.

(2-7) Area The arithmetic average roughness Ra, the ten-point average roughness Rz, and the average interval Sm are preferably in the above ranges over the entire image forming area on the surface of the photosensitive drum 20.

(2-8) External toner additive Toner is externally added with conductive abrasive fine particles such as titanium oxide and silica as an external additive. If the arithmetic average roughness Ra of the photosensitive layer surface is large, a cleaning blade is used. The external additive slips through the concavo-convex gap that 42 cannot follow. For this reason, it is preferable that the toner external additive used in the photosensitive drum 20 of the present embodiment has an average primary particle diameter of 10 nm or more.

(3) Toner discharge onto the surface of the photoconductor drum 20 When the toner is discharged from the developing device 21 to the photoconductor drum 20, the control unit 50 performs the same control as the image formation described above. The transfer bias circuit 60 is controlled so that the toner image is not transferred to the intermediate transfer belt 22. Specifically, the CPU 51 instructs the transfer bias circuit 60 to apply a transfer bias having the same polarity as the toner (here, positive polarity) to the primary transfer roller 27.

  The shape (toner discharge pattern) of the toner image discharged onto the photoconductive drum 20 is not particularly limited, but is supplied in a belt shape having a predetermined width in the circumferential direction of the photoconductive drum 20, for example. This toner discharge pattern can be implemented by making the shape of the electrostatic latent image formed on the photosensitive drum 20 into a strip shape.

(4) Toner discharge amount adjustment control In the present embodiment, the CPU 51 adjusts the amount of toner discharged to the photosensitive drum 20 during the execution of the frictional resistance suppression process according to the surface state of the photosensitive drum 20. The surface state of the photosensitive drum 20 is estimated based on the torque of the drive motor 48 detected by the torque detector 57. This is because the use of the photoconductor drum 20 causes the convex portions of the surface to be polished and smoothed, and the torque increases due to friction between the photoconductor drum 20 and the cleaning blade 42. The relationship between the surface state of the photosensitive drum 20 (arithmetic average roughness Ra of the surface) and the torque of the drive motor 48 can be grasped by conducting a test or the like in advance.

  Here, the relationship between the torque of the drive motor 48 detected by the torque detector 57 and the toner discharge amount is preset and stored in a storage unit such as the RAM 53 or the HDD 54. In this embodiment, the frictional resistance suppression process is executed every time the number of printed sheets reaches 100, and the toner discharge amount adjustment control is also executed every time the frictional resistance suppression process is executed.

  Table 1 shows an example of a correspondence relationship between the arithmetic average roughness Ra of the surface of the photosensitive drum 20, the torque of the drive motor 48, and the toner discharge amount. Table 1 is prepared based on the experimental results. Here, the length of the belt-like toner discharge pattern in the circumferential direction of the photosensitive drum 20 (toner discharge length B [mm]) is used as an index of the toner discharge amount.

  As shown in Table 1, when the torque T is less than 12 mNm (Ra is 30 nm or more), the toner discharge length B is 15 mm. ), The toner discharge length B is 5 mm and 10 mm, respectively, and when the torque is 30 mNm or more (Ra is less than 10 nm), the toner discharge length is 15 mm. The CPU 51 controls the developing device 21, the exposure unit 25, the charging roller 26, and the like so that the toner is discharged onto the photosensitive drum 20 with the toner discharge length B corresponding to the torque detected by the torque detector 57.

  FIG. 6 is a flowchart showing the processing content of the frictional resistance suppression processing in the image forming apparatus 11 of the present embodiment. Note that there is a main routine (not shown) for controlling the entire image forming apparatus 11, and the flow shown in FIG. 6 is a subroutine of the main routine. The subroutine of the frictional resistance suppressing process shown in FIG. 6 starts when the image forming apparatus 11 is turned on.

  First, the CPU 51 clears 0 of the variable “N” indicating the number of printed sheets (step S1), and monitors whether a print job has been accepted (step S2). A print job is received by an input from a user via the operation panel of the image forming apparatus 11 or an input from a PC connected via a communication line such as a LAN or the Internet. If a print job has not been received (No in step S2), monitoring is continued as it is.

  When the print job is received (Yes in step S2), the CPU 51 sets a value obtained by adding 1 to the variable N as a new “N” (step S3). Thereafter, it is determined whether or not the number of printed sheets has reached 100 or more (step S4). If the number of printed sheets is less than 100 (No in step S4), the process returns to step S2. On the other hand, when the number of printed sheets is 100 or more (Yes in step S4), the CPU 51 acquires the torque T of the drive motor 48 that drives the photosensitive drum 20 from the torque detector 57 (step S5).

  Next, the CPU 51 determines whether or not the acquired torque T is less than 12 mNm (step S6). When the torque T is less than 12 mNm (Yes in Step S6), the toner discharge length B that is an index of the toner supply amount is set to 15 mm (Step S7). If the torque T is not less than 12 mNm (No in step S6), it is determined whether the torque T is not less than 12 mNm and less than 20 mNm (step S8). When the torque T is 12 mNm or more and less than 20 mNm (Yes in Step S8), the toner discharge length B is set to 5 mm (Step S9).

  When the torque T is not 12 mNm or more and less than 20 mNm (No in step S8), it is determined whether or not the torque T is 20 mNm or more and less than 30 mNm (step S10). When the torque T is 20 mNm or more and less than 30 mNm (Yes in step S10), the toner discharge length B is set to 10 mm (step S11). If the torque T is not 20 mNm or more and less than 30 mNm, that is, if it is 30 mNm or more (No in step S10), the toner discharge length B is set to 15 mm (step S12).

  The CPU 51 determines whether or not the print job has ended (step S13). If the print job has ended (Yes in step S13), the toner ejection length B set in steps S7, S9, S11, and S12 is determined. Thus, toner is discharged onto the photosensitive drum 20 (step S14). The discharged toner is supplied to the cleaning blade 42 and the rubbing roller 43 by the rotation of the photosensitive drum 20.

  Thereafter, returning to step S1, the variable “N” indicating the number of prints is cleared to 0, and the same procedure is repeated thereafter (steps S1 to S13). In the flow of FIG. 6, Steps S5 to S12 can be regarded as toner discharge amount adjustment control.

  As described above, according to the image forming apparatus 11 of the present embodiment, the minimum toner necessary for polishing the surface of the photosensitive drum 20 according to the surface state of the photosensitive drum 20 is supplied to the cleaning blade 42 and the rubbing roller. Therefore, the surface of the photosensitive drum 20 can be polished without wasteful consumption of toner.

  In this embodiment, the surface state of the photosensitive drum 20 is estimated using the torque of the drive motor 48 that drives the photosensitive drum 20, and the toner discharge amount is determined based on the estimation result. Specifically, the toner discharge amount when the torque is less than a predetermined value T1 (T1 = 12 mNm in FIG. 6) and when the torque is equal to or greater than the predetermined value T2 (T2> T1, T2 = 30 mNm in FIG. 6) Is increased compared to the toner discharge amount in the case of T1 or more and less than T2.

  As a result, unevenness on the surface remains, and friction with the cleaning blade 42 is reduced (torque is reduced), so that the toner discharge amount is increased in the initial use of the photosensitive drum 20, so that the external addition The agent adheres to the toner supplied by van der Waals force or electrostatic force. As a result, it is possible to suppress slipping of the external additive from the gap between the surface of the photosensitive drum 20 and the cleaning blade 42, and it is possible to suppress deterioration in image quality due to adhesion of the external additive to the charging roller 26. Further, since the discharge product adheres to the surface of the photosensitive drum 20 and is roughened, and the friction with the cleaning blade 42 is small (torque is small), the toner discharge amount is increased. The image flow phenomenon due to the adhesion of the discharge product to the surface of the photosensitive drum 20 can be suppressed.

  On the other hand, when the unevenness of the surface of the photosensitive drum 20 is cut and smoothed, and the friction with the cleaning blade 42 increases (torque increases), the toner discharge amount is increased as the torque increases. The supplied toner functions as a lubricant and can effectively suppress chattering, chipping and stick-slip of the cleaning blade 42. Furthermore, the surface state of the photosensitive drum 20 can be determined without providing a new device, which can contribute to cost reduction.

Second Embodiment
A frictional resistance suppressing process and related control of the image forming apparatus 11 according to the second embodiment of the present invention will be described. The surface state of the photosensitive drum 20 in the initial use and the method of discharging the toner onto the surface of the photosensitive drum 20 are the same as in the first embodiment. In the second embodiment, the surface state of the photosensitive drum 20 is estimated from the cumulative number of printed sheets from the initial use of the photosensitive drum 20. This is because the use of the photosensitive drum 20 causes the convex portion on the surface to be polished and smoothed by recording paper or the like. The relationship between the surface state (arithmetic average roughness Ra of the surface) of the photosensitive drum 20 and the cumulative number of printed sheets can be grasped by performing a test or the like in advance.

  Specifically, the relationship between the cumulative number of prints counted by the counter 55 and the toner supply amount is preset and stored in a storage unit such as the RAM 53 or the HDD 54. In the second embodiment, as in the second embodiment, the toner amount adjustment control is performed every time the number of printed sheets reaches 100.

  Table 2 shows an example of a correspondence relationship between the arithmetic average roughness Ra of the surface of the photosensitive drum 20, the cumulative number of printed sheets, and the toner supply amount. Table 2 is created based on the experimental results. Similar to Table 1 of the first embodiment, the length of the belt-like toner discharge pattern in the circumferential direction of the photosensitive drum 20 (toner discharge length B [mm]). Is used as an index of the toner discharge amount.

  As shown in Table 2, when the cumulative number of printed sheets P is less than 10,000 (Ra is 30 nm or more), the toner ejection length B is 15 mm, and the cumulative number of printed sheets P is 10,000 or more and less than 50,000. And when the cumulative number of printed sheets P is 50,000 or more and less than 500,000 Nm (Ra is 10 nm or more and less than 30 nm), the toner discharge length B is 5 mm and 10 mm, respectively, and the cumulative number of printed sheets P is 500,000 sheets. In the above case (Ra is less than 10 nm), the toner discharge length is 15 mm. The CPU 51 controls the developing device 21, the exposure unit 25, the charging roller 26, and the like so that the toner is discharged onto the photosensitive drum 20 with the toner discharge length B corresponding to the cumulative number of prints counted by the counter 55.

  FIG. 7 is a flowchart showing the processing content of the frictional resistance suppression processing in the image forming apparatus 11 of the present embodiment. Note that there is a main routine (not shown) for controlling the entire image forming apparatus 11, and the flow shown in FIG. 7 is a subroutine of the main routine. The frictional resistance suppression subroutine shown in FIG. 7 starts when the image forming apparatus 11 is turned on.

  First, after clearing the variable “N” indicating the number of prints to 0, it is monitored whether or not a print job has been accepted. If a print job is accepted, a value obtained by adding 1 to the variable N and adding a new “N”. Steps (steps S1 to S4) until it is determined whether or not the number of printed sheets has reached 100 or more are the same as in FIG.

  If the number of printed sheets is less than 100 (No in step S4), the process returns to step S2. On the other hand, when the number of printed sheets reaches 100 or more (Yes in step S4), the CPU 51 acquires the accumulated number of printed sheets P from the counter 55 (step S105).

  Next, the CPU 51 determines whether or not the acquired cumulative number of printed sheets P is less than 10,000 (step S106). If the cumulative number of printed sheets P is less than 10,000 (Yes in step S106), the toner discharge length B, which is an index of the toner supply amount, is set to 15 mm (step S107). If the cumulative number of printed sheets P is not less than 10,000 (No in step S106), it is determined whether or not the cumulative number of printed sheets P is not less than 10,000 and less than 50,000 (step S108). When the cumulative number P of prints is 10,000 or more and less than 50,000 (YES in step S108), the toner discharge length B is set to 5 mm (step S109).

  If the cumulative number of printed sheets P is not 10,000 or more and less than 50,000 (No in Step S108), it is determined whether or not the cumulative number of printed sheets P is 50,000 or more and less than 500,000 (Step S108). S110). When the cumulative number P of prints is 50,000 or more and less than 500,000 (Yes in step S110), the toner discharge length B is set to 10 mm (step S111). If the cumulative number of printed sheets P is not 50,000 or more and less than 500,000, that is, 500 or more (No in step S110), the toner discharge length B is set to 15 mm (step S112).

  The CPU 51 determines whether or not the print job has ended (step S113). If the print job has ended (Yes in step S113), the toner ejection length B set in steps S107, S109, S111, and S112 is determined. Thus, toner is discharged onto the photosensitive drum 20 (step S114). The discharged toner is supplied to the cleaning blade 42 and the rubbing roller 43 by the rotation of the photosensitive drum 20.

  Thereafter, returning to step S1, the variable “N” indicating the number of printed sheets is cleared to 0, and the same procedure is repeated thereafter (steps S1 to S114). In the flow of FIG. 7, steps S105 to S112 can be regarded as toner discharge amount adjustment control.

  As described above, according to the image forming apparatus 11 of the present embodiment, the minimum amount of toner necessary for polishing the surface of the photoconductive drum 20 according to the surface state of the photoconductive drum 20 as in the first exemplary embodiment. Since the toner can be supplied to the cleaning blade 42 and the rubbing roller 43, the polishing performance of the surface of the photosensitive drum 20 can be improved without wastefully consuming toner.

  In the present embodiment, the surface state of the photosensitive drum 20 is estimated using the cumulative number of printed sheets from the initial use of the photosensitive drum 20, and the toner discharge amount is determined based on the estimation result. Specifically, when the cumulative number of printed sheets is less than a predetermined number P1 (P1 = 10,000 in FIG. 7), and the predetermined number P2 (P2> P1, P2 = 500,000 in FIG. 7) or more. In this case, the toner discharge amount is increased as compared with the toner discharge amount when the cumulative number of printed sheets is P1 or more and less than P2.

  As a result, when the cumulative number of printed sheets is small and the surface of the photosensitive drum 20 has unevenness, the toner discharge amount is increased so that the external additive adheres to the toner supplied by van der Waals force or electrostatic force. Can be made. As a result, it is possible to suppress slipping of the external additive from the gap between the unevenness of the surface of the photoconductor drum 20 and the cleaning blade 42, and to suppress deterioration in image quality due to adhesion of the external additive to the charging roller 26. it can.

  On the other hand, when the accumulated number of printed sheets is large, the unevenness on the surface of the photosensitive drum 20 is scraped and smoothed by the recording paper, and the friction with the cleaning blade 42 is increased, the toner discharge amount is increased, thereby increasing the photosensitive drum. The frictional force between the cleaning blade 20 and the cleaning blade 42 can be reduced. As a result, an image flow phenomenon due to adhesion of discharge products to the surface of the photosensitive drum 20, a decrease in transfer (primary transfer) efficiency to the intermediate transfer belt 22 due to an increase in surface frictional resistance, an image deterioration due to cleaning blade streaks, Generation of chattering, chipping and stick slip of the cleaning blade 42 is effectively suppressed. Furthermore, the surface state of the photosensitive drum 20 can be determined without providing a new device, which can contribute to cost reduction.

<Modification>
As described above, the embodiment of the image forming apparatus 11 of the present invention has been described as an example. However, the present invention is not limited to the above embodiment, and for example, the following modification may be used. Moreover, what combined embodiment, a modification, and modifications may be sufficient. In addition, examples that are not described in the embodiment and design changes that do not depart from the gist of the present invention are also included in the present invention.

(Modification 1) The method of detecting the torque of the drive motor 36 is not limited to the detection of the output current value of the drive motor 36, and the torque of the rotating shaft of the drive motor 36 may be directly detected by a torque sensor.
(Modification 2) The method of counting the cumulative number of printed sheets is not limited to the counting by the counter 55, and for example, the number of times may be stored in the RAM 53 or the like.
(Modification 3) The toner discharge pattern formed on the photosensitive drum 29 in the frictional resistance suppressing process is not limited to the belt-like shape extending in the axial direction of the photosensitive drum 20, but, for example, a zigzag belt-like shape or a plurality of rows It may be in the form of a staggered dot or a plurality of strips.
(Modification 4) The adjustment of the toner discharge amount in the toner discharge amount adjustment control is performed by the discharge length of the belt-like toner discharge pattern, but may be performed by adjusting the thickness of the toner image, for example. In this case, the adjustment can be performed by adjusting Vmag (DC) applied to the magnetic roller 34 and Vslv (DC) applied to the developing roller 35.
(Modification 5) The frictional resistance suppression process is performed for every 100 printed sheets. For example, after a predetermined drive time has elapsed or when the continuous printing operation has been completed, the image forming apparatus is set up, or in sleep mode (power saving). You may make it perform at the time of return from mode.
(Modification 6) The image carrier is not limited to the photosensitive drum 20 in which a photosensitive layer is formed on the surface of a cylindrical support. For example, a photosensitive layer is formed on the surface of a plate-like support. You can also use what has been done. Further, the cleaning member is not limited to the flat plate-shaped craning blade 42, and may be, for example, a columnar shape.

  The present invention is applicable to an image forming apparatus including an image carrier on which a toner image is formed on the surface. By utilizing the present invention, it is possible to provide an image forming apparatus capable of suppressing the reversal, vibration, and wear of the cleaning member and stably cleaning the image carrier over a long period of time.

11 Image forming apparatus 20 Photosensitive drum (image carrier)
21 Developing device 26 Charging roller (charging member)
28 Cleaning device 42 Cleaning blade (cleaning member)
43 Rub roller (cleaning member)
48 Drive motor (drive device)
50 Control unit 52 ROM
54 HDD
55 Counter (Number of printed pages)
57 Torque detector

Claims (8)

An image carrier on which a toner image is formed on the surface;
A driving device for rotationally driving the image carrier;
A developing device that develops an electrostatic latent image formed on the surface of the image carrier by attaching toner containing abrasive particles into a toner image;
A cleaning member arranged to contact the surface of the image carrier and cleaning the surface of the image carrier;
A control unit capable of controlling the amount of toner discharged from the developing device to the image carrier;
With
In the image forming apparatus capable of executing a frictional resistance suppressing process for discharging a toner from the developing device to the image carrier during non-image formation and suppressing a frictional resistance between the cleaning member and the surface of the image carrier.
The control unit adjusts an amount of toner discharged from the developing device to the image carrier side during execution of the frictional resistance suppression process according to an estimation result of a surface state of the image carrier. .   The control unit determines the toner discharge amount when the arithmetic average roughness Ra of the surface of the image carrier is in a range of 30 nm or more or less than 10 nm, and the arithmetic average roughness Ra is in a range of 10 nm or more and less than 30 nm. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus increases the toner discharge amount when it is estimated that the toner is discharged. A torque detector for detecting the torque of the driving device when the image carrier is rotationally driven;
The image forming apparatus according to claim 2, wherein the control unit estimates an arithmetic average roughness Ra of the surface of the image carrier based on the torque detected by the torque detection unit.   The control unit determines the toner discharge amount when the torque detected by the torque detection unit is less than a predetermined value T1 and when the torque is greater than or equal to a predetermined value T2 (T2> T1), and the torque is greater than or equal to T1 and less than T2. The image forming apparatus according to claim 3, wherein the image forming apparatus increases the toner discharge amount in the case. A print number counting unit for counting the number of accumulated prints from the initial use of the image carrier,
The image forming apparatus according to claim 2, wherein the control unit estimates an arithmetic average roughness Ra of the surface of the image carrier based on the cumulative number of printed sheets counted by the number of printed sheet counting unit.   The control unit determines the toner discharge amount when the cumulative number of printed sheets counted by the number of printed sheet counting unit is less than the predetermined number P1, and when the cumulative number of printed sheets is P1 (P2> P1) or more. The image forming apparatus according to claim 5, wherein the image forming apparatus increases the toner discharge amount in the case of less than P2 as described above.   The arithmetic average roughness Ra of the surface of the image carrier in the initial use of the image carrier is 20 nm or more, and the average interval Sm of the irregularities is 20 μm or less. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein an amorphous silicon photosensitive layer is formed on a surface of the image carrier.

Images