JP2016212386A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can determine the degree of smoothness of a surface of an image carrier without providing new detection means.SOLUTION: An image forming apparatus comprises: an image carrier; a driving device that drives to rotate the image carrier; a charging member that charges the image carrier; a cleaning member that is in contact with a surface of the image carrier; a voltage application device that applies a voltage to the charging member; a torque detection part that detects torque of the driving device when driving to rotate the image carrier; a storage part that stores a prescribed torque value Tc; and a control part. The control part acquires torque Ton when a voltage is applied to the charging member and torque Toff when a voltage is not applied to the charging member, and determines that the degree of smoothness of the surface of the image carrier is predetermined value or more when the relationships Toff(0)<Toff and Tc<Ton/Toff are satisfied, wherein Toff(0) is torque when a charging voltage is not applied at the start of use of the image carrier.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus that forms an image on recording paper, and more particularly to a method for determining the surface state of an image carrier on which a toner image is formed.

  In image forming apparatuses such as printers, copiers, facsimiles, or multifunction devices having these functions, a photosensitive drum as an example of an electrophotographic photosensitive member, and a charging member such as a charging roller that charges the surface of the photosensitive drum And a cleaning blade that is disposed in contact with the surface of the photosensitive drum and removes toner and external additives remaining on the surface of the photosensitive drum.

  Such a charging member is disposed in contact with or close to the image carrier, and a discharge product generated by discharge from the charging member adheres to the surface of the image carrier. As a result, the frictional resistance between the surface of the image carrier and the cleaning blade increases, chattering, chipping, and stick slip of the cleaning blade are likely to occur, and the cleaning ability of the cleaning blade decreases. As a result, the amount of toner and external additives slipping through increases, the charging member is contaminated, and the toner and external additives left uncleaned adhere to the surface of the image carrier, resulting in deterioration in image quality and poor image formation. May occur.

  In particular, when an image carrier having an amorphous silicon layer formed on the surface is used as the photosensitive layer, the contact area between the image carrier surface and the cleaning blade is initially reduced due to the unevenness of crystal grains generated when the amorphous silicon layer is formed. Although it is small, the frictional resistance is small, but the unevenness on the surface of the image carrier is worn and smoothed during use, and the frictional resistance between the surface of the image carrier and the cleaning blade increases, resulting in the above problems. It becomes easy.

  Therefore, in order to reduce the load on the cleaning blade, the generation of discharge products is suppressed by a method such as supplying toner as a lubricant as in Patent Document 1 or reducing the charging bias as in Patent Document 2. Such measures are taken.

JP 2007-25270 A JP 2007-108421 A

  However, the suppression of the increase in frictional resistance is greatly affected by the surface roughness of the image carrier, so it must be controlled accordingly, but it is predicted that there is no means to detect the surface roughness of the image carrier. Control must be done by Providing a new means for detecting the surface roughness of the image bearing member causes an increase in cost.

  In view of the above problems, an object of the present invention is to provide an image forming apparatus capable of determining the degree of smoothness of the surface of an image carrier without providing new detection means.

  In order to achieve the above object, the first configuration of the present invention includes an image carrier, a driving device, a charging member, a cleaning member, a voltage applying device, a torque detection unit, a storage unit, a control unit, And an image forming apparatus. A toner image is formed on the surface of the image carrier. The driving device rotationally drives the image carrier. The charging member charges the image carrier. The cleaning member is disposed so as to contact the surface of the image carrier, and cleans the surface of the image carrier. The voltage application device applies a charging voltage to the charging member. The torque detector detects the torque of the driving device when the image carrier is rotationally driven. The storage unit stores a torque regulation value Tc that is a constant larger than 1 related to the torque of the drive device. The controller determines the surface state of the image carrier based on the torque of the driving device detected by the torque detector. The control unit obtains the torque Ton when the charging voltage detected by the torque detection unit is applied and the torque Toff when the charging voltage is not applied, and the charging voltage at the start of use of the image carrier. When the torque when T is not applied is Toff (0), the smoothing degree of the surface of the image carrier is not less than a predetermined value when the relationship of Toff (0) <Toff and Tc <Ton / Toff is satisfied. judge.

  When the surface of the image carrier is worn and smoothed, the contact area between the image carrier and the cleaning member increases, so that the frictional resistance between the image carrier and the cleaning member increases, and the image carrier rotates. The torque of the driving device to drive increases. The torque Toff when no voltage is applied to the charging member and the torque Ton when a bias voltage is applied are substantially equal for a while from the start of use of the image carrier, but there are many cumulative image forming processes. Then, Ton becomes larger than Toff. According to the first configuration of the present invention, when Toff (0) <Toff and Tc <Ton / Toff, that is, when the width of deviation between Ton and Toff exceeds a predetermined size, It is determined that the degree of smoothing of the image carrier surface is greater than or equal to a predetermined level. Thereby, it is possible to easily and accurately determine whether or not the surface of the image carrier is smoothed without newly providing a sensor or the like for detecting the surface state of the image carrier.

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 formation processing unit 15 of an image forming apparatus 11 according to the present embodiment. A graph showing the relationship between the cumulative number of image forming processes, the torque of the drive motor 36, and the surface roughness of the photosensitive drum 20. The flowchart which shows the processing content of the image quality fall suppression control in the image forming apparatus 11 of this 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 image forming processing on recording paper supplied from a cassette 13 or a manual feed tray (not shown), and a recording paper transport path 16 that transports recording paper supplied from the paper feed cassette 13 or the manual feed tray. The secondary transfer unit 17 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 is recorded on the recording paper. And a fixing unit 18 for fixing to the head.

(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 serving as image carriers, a plurality of developing devices 21 for supplying toner to the respective photosensitive drums 20, and formed on the respective photosensitive drums 20. The endless intermediate transfer belt 22 to which the toner image thus transferred is primarily transferred and the upstream side of the photosensitive drum 20 on the most upstream side in the rotational movement direction of the intermediate transfer belt 22 are attached to the surface of the intermediate transfer belt 22. A belt cleaning device 24 that removes the residual toner and the like, and an exposure unit 25 that emits beam light to each photosensitive drum 20 are provided.

(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.

  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. Then, the image is transferred by the secondary transfer unit 17 to the recording paper conveyed.

(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 develops the electrostatic latent image formed on the surface of the photosensitive drum 20 into a toner image by attaching a toner containing a toner external additive (abrasive particles) made of metal particles such as titanium oxide. A conventionally known developing device 21 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 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. Note that the charging roller 26 may be disposed close to the photosensitive drum 20.

(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.

  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.

(Configuration of control circuit 30)
The control circuit 30 controls each photosensitive drum 20 based on various control programs related to the entire image forming process stored in the ROM 31, and supplies toner to each developing device 21, voltage applied to the developing device 21, and the like. Development conditions, exposure conditions such as the voltage applied to the bias circuit 34 that applies a superimposed voltage of a DC voltage and an AC voltage to the charging roller 26, the laser power of the laser beam P (see FIG. 1) emitted from the exposure unit 25, and static elimination Calibration of the erase light quantity of the device 29 is executed.

  Further, the control circuit 30 controls a drive motor (drive device) 36 that rotates the photosensitive drum 20 via a motor drive driver 35, and detects the detected value from the torque detection unit 37 that detects the torque of the drive motor 36. Based on this, image quality deterioration suppression control is performed. Further, the count value from the counter 39 that counts the cumulative number of image forming processes is input to the control circuit 30.

  In the present embodiment, the torque detector 37 detects the output current of the drive motor 36. That is, in this embodiment, the output current of the drive motor 36 is used as an index representing torque. Note that a means for detecting the torque of the drive motor 36 is usually provided in the image forming apparatus in order to prevent the drive motor 36 from being damaged due to an excessive load.

  The ROM 31 also stores a control program related to image formation processing correction according to the present invention, and a microcomputer is configured with the control circuit 30 that executes the image formation processing control program. Note that image data and the like when executing the image forming process are temporarily stored in the RAM 32 or the HDD 33.

2. 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 surface of the photosensitive drum 20 is first uniformly charged by the charging roller 26, and then the laser beam P is applied to the surface of the photosensitive drum 20 by the exposure unit 25. And an electrostatic latent image corresponding to the image data is formed on each 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. . The toner in the developer is supplied onto the photosensitive drum 20 by the developing device 21 and electrostatically adheres, whereby a toner image corresponding to the electrostatic latent image formed by exposure from the exposure unit 25 is formed. It is formed.

  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. .

  The primary transfer roller 27 applies an electric field between the primary transfer roller 27 and the photosensitive drum 20 at a predetermined transfer voltage, and yellow, magenta, cyan, and black toner images on the photosensitive drum 20 are transferred to the intermediate transfer belt. 22 is primarily transferred onto 22. These four color images are formed with a predetermined positional relationship predetermined for forming a predetermined full color image. 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 discharged onto a discharge tray 12a that also serves as the upper surface of the printer main body 12 by a discharge roller pair.

3. Determination of Surface State of Photosensitive Drum 20 Using Torque Variation Hereinafter, characteristic portions of the image forming apparatus 11 of the present invention will be described. In the above configuration, the control circuit 30 executes an image forming process (print job) based on various control programs related to the entire image forming process stored in the ROM 31, and applies the charging roller 26 during the image forming process. The voltage applied to the bias circuit 34 that applies a superimposed voltage of the DC voltage and the AC voltage is controlled. Note that the voltage of the DC component of the superimposed voltage is constant.

  FIG. 3 is a graph showing the relationship between the cumulative number of image forming processes from the start of use of the photosensitive drum 20 and the torque of the drive motor 36, and the relationship between the cumulative number of image forming processed sheets and the surface roughness Ra of the photosensitive drum 20. It is. Note that “Ra” refers to “arithmetic mean roughness” defined in 1994 edition of JISB0601.

  In FIG. 3, Toff is a torque when no voltage is applied to the charging roller 26, and Ton is a torque when a voltage is applied to the charging roller 26. Further, Toff (0) is a value of Toff in the initial use of the photosensitive drum 20 (the state at the start of use, in other words, the state after factory shipment).

  As shown in FIG. 3, both Toff and Ton increase as the number of accumulated image forming processes increases from the start of use of the photosensitive drum 20. Further, the surface roughness Ra decreases as the cumulative number of image forming processes increases. Since the rising speed of Ton is larger than the rising speed of Toff, the width of the difference between Ton and Toff increases as the number of accumulated image forming processes increases. In particular, in the cumulative image forming number of sheets 100K (sheets) to 300K (sheets), the rising speed of Ton is larger than the rising speed of Toff, and the width of the difference between Ton and Toff is large.

  In the present embodiment, the width of the difference between Ton and Toff is represented by the ratio of Ton to Toff (Ton / Toff), and the value of Ton / Toff when the surface of the photosensitive drum 20 is smoothed is a torque specified value. Let Tc. The specified torque value Tc is a constant larger than 1, and is previously determined in consideration of the material of the photosensitive drum 20, the surface roughness before shipment (before starting use), the material of the cleaning blade 42 and the rubbing roller 43, and the like. It is set and stored in the HDD (storage unit) 33.

4). Image Quality Reduction Suppression Control FIG. 4 is a flowchart showing the processing content of image quality reduction suppression control performed by the control circuit 30 in the image forming apparatus 11 according to 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. 4 is a subroutine of the main routine. The subroutine for image quality deterioration suppression control shown in FIG. 4 starts when the image forming apparatus 11 is turned on.

  First, the control circuit 30 monitors whether or not a print job has been accepted (step S1). 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 S1), the control circuit 30 continues monitoring.

  When a print job is received (Yes in step S1), Toff is detected by the torque detector 37 (step S2), and the control circuit 30 compares the detected Toff with Toff (0) to compare Toff ( It is determined whether or not 0) <Toff (step S3). Note that Toff (0) may be detected in advance and stored in the HDD 33 before the image forming apparatus 11 is shipped from the factory, or detected when the user first uses the image forming apparatus 11 and stored in the HDD 33. It may be memorized. Alternatively, Toff (0) may be detected and stored in the HDD 33 each time the photosensitive drum 20 is replaced.

  If Toff (0) <Toff is not satisfied (No in step S3), the process returns to step S1 to continue monitoring whether a print job has been accepted. When Toff (0) <Toff (Yes in Step S3), Ton is detected by the torque detector 37 (Step S4). Then, the control circuit 30 determines whether or not Tc <Ton / Toff (step S5). If Tc <Ton / Toff is not satisfied (No in step S5), the process returns to step S1 to continue monitoring whether a print job has been accepted.

  If Tc <Ton / Toff (Yes in step S5), the control circuit 30 determines that the surface of the photosensitive drum 20 has been smoothed (step S6), and performs a frictional resistance suppression process (step S7). As the frictional resistance suppressing process, when the cleaning device 28 cleans the surface of the photosensitive drum 20, a method of increasing the amount of toner and external additive supplied to the surface of the photosensitive drum 20 as a lubricant, charging from the bias circuit 34 is performed. There is a method for reducing the AC voltage applied to the roller 26.

  Thereafter, returning to step S1, the control circuit 30 monitors whether a print job has been accepted, and thereafter repeats the same procedure (steps S1 to S7). In the flow of FIG. 4, Steps S <b> 1 to S <b> 6 can be regarded as a photosensitive drum (image carrier) surface smoothing determination process.

  By increasing the supply amount of the toner and the external additive when the cleaning device 28 cleans the surface of the photosensitive drum 20, the frictional resistance between the cleaning blade 42 and the photosensitive drum 20 can be reduced. Further, by reducing the charging bias applied to the charging roller 26, the generation of discharge products and the adhesion of the generated discharge products to the photosensitive layer are suppressed, so that the friction between the cleaning blade 42 and the photosensitive drum 20 occurs. The increase in resistance is suppressed.

  As a result, chattering of the cleaning blade 42, chipping (wear) of the edge portion, and stick slip can be suppressed. Further, the toner and the external additive can be easily removed at the time of cleaning by the cleaning blade 42, and the effect that the amount of the external additive that slips between the surface of the photosensitive drum 20 and the cleaning blade 42 can be expected.

  Note that, as in this embodiment, not only whether Tc <Ton / Toff but also whether Toff (0) <Toff is determined, the surface of the photosensitive drum is still flattened. It is possible to prevent the surface of the photosensitive drum from being erroneously determined to be flattened when Tc <Ton / Toff is temporarily satisfied for some reason at the initial stage of use.

  As described above, according to the image forming apparatus 11 of the present embodiment, whether the surface (photosensitive layer surface) of the photosensitive drum (image carrier) 20 has been smoothed is determined by the drive motor that drives the photosensitive drum 20. The judgment is based on 36 torque. When the relationship of Toff (0) <Toff and Tc <Ton / Toff is satisfied, it is determined that the surface of the photosensitive drum 20 has been smoothed. Further, the image forming apparatus 11 detects the torque by using means for detecting the torque of the drive motor 36 provided to prevent the drive motor 36 from being damaged. Thereby, it can be determined whether the surface of the photosensitive drum 20 has been smoothed without providing a new device, which can contribute to cost reduction. If it is determined that the surface of the photosensitive drum 20 has been smoothed, a frictional resistance suppression process is performed to suppress the frictional resistance between the cleaning blade 42 and the surface of the photosensitive drum 20, Occurrence of defects and stick-slip can be suppressed. As a result, it is possible to suppress slipping of the external additive and suppress deterioration in image quality.

<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 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 specified torque value Tc is not limited to the configuration set in advance and stored in the HDD 33. For example, the value of Toff and Ton detected at the start of use, and other values on the surface of the photosensitive drum 20 are used. It may be calculated after the start of use from a factor value that affects the smoothness and stored in the HDD 33.
(Modification 3) The storage unit in which the specified torque value Tc is stored is not limited to the HDD 33. When the torque regulation value Tc is set in advance before shipment, it may be stored in the ROM 31. In this case, the ROM 31 serves as a storage unit.
(Modification 4) The frictional resistance suppressing process is not limited to the process of increasing the supply amount of the toner and the external additive and the process of decreasing the charging voltage. For example, the urging force with which the cleaning blade 42 is pressed against the surface of the photosensitive drum may be weakened, or a lubricant other than the toner and the external additive may be supplied. In the latter case, it is necessary to select a lubricant that does not negatively affect the image forming process.

  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 using the present invention, it is possible to provide an image forming apparatus capable of detecting the degree of smoothness of the surface of an image carrier without using a new detection means, using torque fluctuations of a driving device that drives the image carrier. it can.

11 Image forming apparatus 20 Photosensitive drum (image carrier)
21 Developing device 26 Charging roller (charging member)
30 Control circuit (control unit)
31 ROM (storage unit)
33 HDD (storage unit)
34 Bias circuit (voltage application device)
36 Drive motor (drive device)
37 Torque detector 42 Cleaning blade (cleaning member)
43 Rub roller (cleaning member)

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 charging member for charging the image carrier;
A cleaning member arranged to contact the surface of the image carrier and cleaning the surface of the image carrier;
A voltage applying device for applying a charging voltage to the charging member;
A torque detector for detecting torque of the driving device when the image carrier is rotationally driven;
A storage unit that stores a torque regulation value Tc that is a constant larger than 1 relating to the torque of the drive device;
A controller that determines the surface state of the image carrier based on the torque of the driving device detected by the torque detector;
An image forming apparatus having
The control unit acquires the torque Ton when the charging voltage detected by the torque detection unit is applied, and the torque Toff when the charging voltage is not applied, and acquires the image carrier. When the torque when the charging voltage is not applied at the start of use is Toff (0),
Toff (0) <Toff and Tc <Ton / Toff
When the above relationship is satisfied, it is determined that the degree of smoothing of the surface of the image carrier is not less than a predetermined level.   The controller performs a frictional resistance suppressing process for reducing a frictional resistance between the surface of the image carrier and the cleaning member when the degree of smoothing of the surface of the image carrier is determined to be a predetermined level or more. The image forming apparatus according to claim 1. 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;
The image forming apparatus according to claim 2, wherein the control unit performs the frictional resistance suppression process by supplying toner from the developing device to the image carrier during non-image formation.   The image forming apparatus according to claim 3, wherein the control unit increases the amount of toner supplied from the developing device to the image carrier as the degree of smoothing of the surface of the image carrier increases. The voltage application device applies the charging voltage obtained by superimposing a DC voltage and an AC voltage to the charging member,
The image forming apparatus according to claim 2, wherein the controller performs the frictional resistance suppression process by reducing the AC voltage applied to the charging member from the voltage application device during image formation.   The image forming apparatus according to claim 5, wherein the charging member is disposed in contact with or close to a surface of the image carrier.   The image forming apparatus according to claim 1, wherein the torque detection unit detects an output current value of the driving device required for rotationally driving the image carrier.   The image forming apparatus according to claim 1, wherein an amorphous silicon photosensitive layer is formed on a surface of the image carrier.

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