JP2017090569A - Image forming device, control method of image forming device, and control program of image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device, a control method of the image forming device, and a control program of the image forming device which can efficiently improve a life of a photoreceptor.SOLUTION: An image forming device includes; a photoreceptor 104 formed with a visible image; and a primary transfer roller 108 for transferring the visible image formed on the photoreceptor 104 to a recording medium. The image forming device presses the primary transfer roller 108 to the photoreceptor 104 by a first pressure when a position of the photoreceptor 104 pressed by the primary transfer roller 108 during image formation is a non-visible image formation area which is not formed with the visible image on the photoreceptor 104. The image forming device presses the primary transfer roller 108 to the photoreceptor 104 by the second pressure larger than the first pressure when the position of the photoreceptor 104 pressed by the primary transfer roller 108 during image formation of the image forming device is a visible image formation area formed with the visible image on the photoreceptor 104.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus, an image forming apparatus control method, and an image forming apparatus control program. More specifically, the present invention relates to an image forming apparatus including a photoconductor on which a visible image is formed, a method for controlling the image forming apparatus, and a control program for the image forming apparatus.

  The electrophotographic image forming apparatus includes a scanner function, a facsimile function, a copying function, a function as a printer, a data communication function, and a server function, an MFP (Multi Function Peripheral), a facsimile apparatus, a copying machine, a printer, and the like. is there.

  Recent electrophotographic image forming apparatuses in the office area are required to have higher image quality, higher speed, and longer life. Of these, it is particularly important to achieve both high image quality and long life. However, there are many trade-offs between high image quality and long life. That is, when the image quality is improved, the lifetime is shortened, and when the lifetime is increased, the image quality is often lowered.

  In general, an image forming apparatus develops an electrostatic latent image formed on an image carrier to form a toner image, transfers the toner image onto a sheet using a transfer roller as a transfer member, and then fixes the toner by a fixing device. An image is formed on a sheet by fixing the image on the sheet. Further, in the image forming apparatus, the electrostatic latent image on the photosensitive member is developed using a developing device to form a toner image, and the toner image is transferred to a transfer belt using a primary transfer roller. There is also a secondary transfer roller that secondarily transfers a toner image on a transfer belt onto a sheet. In this case, the transfer belt becomes a transfer member.

  With respect to the photoconductor as a member constituting the image forming apparatus, discharge products adhere to the photoconductor due to ozone exposure by the charging device. If the discharge product is left for a long period of time, the photosensitive member cannot be properly maintained at the exposure potential due to moisture absorption of the discharge product, and image noise is generated. Therefore, in order to remove discharge products from the photoconductor, the photoconductor is often scraped with an increase in the number of printed sheets of the image forming apparatus.

  The amount of abrasion of the photosensitive member needs to be set in an appropriate range in order to prevent a decrease in the life of the photosensitive member. That is, when the amount of abrasion of the photoconductor is large, the electronic conductive layer becomes thin, and the ability of the photoconductor to maintain a charged potential is lowered. On the other hand, if the amount of shaving of the photoconductor is small, the deposits of the discharge product are not sufficiently removed, and image noise occurs. In either case, it becomes a factor that reduces the life of the photoreceptor.

  When the photoconductor is scraped, an external additive contained in the toner supplied from the developing device and a cleaning blade for removing residual toner on the photoconductor are used. The amount of toner supplied from the developing device to the photoconductor affects the amount of wear of the photoconductor. This is because the amount of the external additive supplied to the photoreceptor varies depending on the amount of toner supplied. Further, the contact force of the cleaning blade to the photoconductor also affects the amount of abrasion of the photoconductor. If the contact force is too strong, the photosensitive member is easily scraped, and if the contact force is weak, the photosensitive member is difficult to scrape. Therefore, in order to make the photoconductor scraping amount appropriate, the driving conditions of the developing device and the cleaning device are set to be severe. In this way, the life of the photoreceptor is greatly influenced by external factors.

  With respect to a transfer device which is another member constituting the image forming apparatus, recently, there is a tendency that the transfer member is hardened for the purpose of extending the life. For example, in the case of a belt transfer system in which the transfer member is a transfer belt (endless belt), the hardness of the transfer belt does not greatly affect the electrophotographic process. This is because when the toner image is moved from the photosensitive member to the transfer belt, the electric force is dominant, and the residual toner on the transfer belt is also collected by the electric force with a fur brush or the like. is there.

  Note that conventional control methods of a transfer device in an image forming apparatus are disclosed in Patent Documents 1 and 2 below. In Patent Document 1 below, as a background amount detection mode for detecting the degree of background contamination on a photoconductor, a blank image formed on the surface of the photoconductor is transferred to an intermediate transfer belt, and toner is attached by a reflection type photosensor. A printer that performs control to detect the amount is disclosed. In the background amount detection mode, this printer sets transfer conditions from the photosensitive member to the intermediate transfer belt so that the transfer rate is higher than that during normal image formation.

  In Patent Document 2 below, when an image is formed on the first surface and the second surface of a transfer material, a contact pressure larger than usual is applied by a transfer blade during non-image formation such as when the photosensitive drum is rotated backward. Discloses a technique for bringing a transfer belt into contact with a photosensitive drum.

JP 2014-224968 A Japanese Patent Application Laid-Open No. 10-11608

  However, when the transfer belt becomes hard, the followability of the photoreceptor to the unevenness becomes lower than that of a conventional belt material, so that the transfer belt is pressed against the photoreceptor with a large pressure in order to maintain transferability. For this reason, there has been a problem that the amount of abrasion of the photosensitive member increases unnecessarily.

  Also, in the case of the direct transfer method in which the transfer member is a transfer roller, if the transfer roller becomes hard, the outer diameter of the transfer member is less likely to change, while the transfer roller is in contact with the photoreceptor in order to maintain transferability. And pressed with great pressure. For this reason, there is a problem that the amount of abrasion (depletion) of the photosensitive member increases unnecessarily.

  In recent years, from the viewpoint of environmental protection, an increasing number of image forming apparatuses employ a charging roller system that hardly generates ozone as a charging system using a charging device. The problem of unnecessarily increasing the amount of photoconductor scraping was particularly noticeable when the charging roller method was employed. In the charging roller method, for the purpose of uniformly charging the photosensitive member, the photosensitive member is brought into contact with the photosensitive member with a pressure larger than that of the conventional discharging charging method, or an AC (alternating current) charging method is adopted. There are many cases. For this reason, the abrasion amount of the photosensitive member has increased.

  Incidentally, in general, in an image forming apparatus, the state of the transfer device can be switched between a state in which the transfer device is in contact with the photoconductor and a state in which the transfer device is separated from the photoconductor. When the transfer device is in contact with the photoconductor for a long time, chemicals such as additives exude from the photoconductor or the transfer device on the contact surface between the photoconductor and the transfer device, and adhere to the photoconductor or the transfer device. There is. As a result, a so-called bleed in which the image is white or black may occur. In order to suppress the occurrence of bleeding, in many image forming apparatuses, when the photosensitive member and the transfer device are not driven, the transfer device is separated from the photosensitive member.

  Therefore, as a method of suppressing an unnecessary increase in the amount of abrasion of the photosensitive member, during printing, while the image forming region on the transfer member passes the transfer position, the transfer device is brought into contact with the photosensitive member, and the image on the transfer member is A method of separating the transfer device from the photosensitive member while the region not to be formed passes the transfer position is conceivable.

  However, with this method, there is a problem in that when switching between a state in which the transfer device is in contact with the photoconductor and a state in which the transfer device is separated from the photoconductor, a time loss occurs and productivity decreases. there were. In addition, when the transfer device is brought into contact with the photoconductor, a speed difference may occur for a moment between the photoconductor and the transfer device, causing the transfer device to slip. The slip may damage the photoconductor and the transfer device, and the photoconductor may be worn out. Further, in the case of the belt transfer method, image distortion is caused by a shock (vibration) applied to the transfer belt when switching between a state in which the transfer belt is in contact with the photoconductor and a state in which the transfer vest is separated from the photoconductor. Could occur.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus, an image forming apparatus control method, and an image forming apparatus control program capable of effectively improving the life of a photoconductor. Is to provide.

  An image forming apparatus according to one aspect of the present invention includes a photoreceptor on which a visible image is formed, a transfer device that transfers the visible image formed on the photoreceptor to a recording medium, and during image formation of the image forming apparatus. When the position of the photosensitive member pressed by the transfer device is a non-visible image forming region that is a region where a visible image is not formed on the photosensitive member, the first pressure pressing the transfer device against the photosensitive member with the first pressure The first pressure is applied when the position of the pressing unit and the photosensitive member pressed by the transfer device during image formation of the image forming apparatus is a visible image forming region that is a region where a visible image is formed on the photosensitive member. And a second pressing unit that presses the transfer device against the photosensitive member with a second pressure greater than that.

  Preferably, in the image forming apparatus, the transfer device includes a transfer belt that contacts the photoconductor, a primary transfer device that transfers a visible image formed on the photoconductor to the transfer belt, and a visible image transferred to the transfer belt. A secondary transfer device that transfers an image to a recording medium, and the first pressing means has a non-visible image forming region where the position of the photosensitive member pressed by the primary transfer device during image formation of the image forming device is In this case, the primary transfer device is pressed against the photosensitive member with a first pressure via the transfer belt, and the second pressing unit is a position of the photosensitive member that is pressed by the primary transfer device during image formation of the image forming device. Is the visible image forming region, the primary transfer device is pressed against the photoconductor with the second pressure through the transfer belt.

  Preferably, in the image forming apparatus, the first pressing unit includes the transfer device, the photosensitive member, and the photosensitive member when the position of the photosensitive member pressed by the transfer device during image formation of the image forming device is a non-visible image forming region. The transfer device is pressed against the photosensitive member with a first pressure in a state in which the image forming device is in contact, and the second pressing means is configured so that the position of the photosensitive member pressed by the transfer device during image formation of the image forming device is the visible image forming region. In this case, the transfer device is pressed against the photosensitive member with the second pressure through the recording medium.

  In the image forming apparatus, preferably, the first pressure is not less than 30% and not more than 70% of the second pressure.

  In the image forming apparatus, preferably, the position of the transfer device when pressed by the first pressing means is the same as the position of the transfer device when pressed by the second pressing means.

  Preferably, in the image forming apparatus, the position where the photosensitive member is pressed when pressed by the first pressing unit is transferred more than the position where the photosensitive member is pressed when pressed by the second pressing unit. It is a position existing on the upstream side or the downstream side along the rotation direction of the belt or the conveyance direction of the recording medium.

  Preferably, in the image forming apparatus, a distance between a position where the photoconductor is pressed when pressed by the first pressing unit and a position where the photoconductor is pressed when pressed by the second pressing unit. The distance along the rotation direction of the transfer belt or the conveyance direction of the recording medium is 0.5 mm or more and 5 mm or less.

  Preferably, in the image forming apparatus, the first pressing unit moves the transfer device.

  Preferably, in the image forming apparatus, the photoreceptor does not include an overcoat layer on the outermost surface.

  In the image forming apparatus, preferably, a charging device that charges the photosensitive member, an exposure device that forms an electrostatic latent image on the photosensitive member, a developing device that forms a visible image by developing the electrostatic latent image, and And a cleaning device for removing toner remaining on the photoconductor after the transfer.

  An image forming apparatus control method according to another aspect of the present invention includes a photoconductor on which a visible image is formed, and a transfer device that transfers the visible image formed on the photoconductor to a recording medium. And when the position of the photosensitive member pressed by the transfer device during image formation of the image forming apparatus is a non-visible image forming region where a visible image is not formed on the photosensitive member. A first pressing step for pressing the transfer device against the photosensitive member with a pressure of 1, and a position of the photosensitive member pressed by the transfer device during image formation of the image forming device is an area where a visible image is formed on the photosensitive member. A second pressing step of pressing the transfer device against the photosensitive member with a second pressure larger than the first pressure when the visible image forming region is present.

  An image forming apparatus control program according to still another aspect of the present invention includes: a photosensitive member on which a visible image is formed; and a transfer device that transfers the visible image formed on the photosensitive member to a recording medium. When the position of the photosensitive member pressed by the transfer device during image formation of the image forming apparatus is a non-visible image forming region that is a region where a visible image is not formed on the photosensitive member. The first pressing step of pressing the transfer device against the photosensitive member with the first pressure, and the position of the photosensitive member pressed by the transfer device during image formation of the image forming device are areas where a visible image is formed on the photosensitive member. In the case of the visible image forming area, the computer is caused to execute a second pressing step of pressing the transfer device against the photosensitive member with a second pressure larger than the first pressure.

  It is possible to provide an image forming apparatus, an image forming apparatus control method, and an image forming apparatus control program capable of effectively improving the life of the photoreceptor.

1 is a cross-sectional view illustrating a configuration of a main part of an image forming apparatus 100 according to a first embodiment of the present invention. FIG. 2 is a block diagram illustrating a control configuration of the image forming apparatus 100 according to the first embodiment of the present invention. It is a figure which shows the relationship between the image formation area IR and the non-image formation area NR when the annular surface 104e of the photoconductor 104 is developed linearly. 2 is a cross-sectional view showing a configuration in the vicinity of the image forming unit 21 of the image forming apparatus 100 according to the first embodiment of the present invention. FIG. FIG. 6 is a sequence diagram showing an operation of the transfer device 112 in the first embodiment of the present invention. FIG. 6 is a cross-sectional view showing a configuration near an image forming unit 21 of an image forming apparatus 100 according to a second embodiment of the present invention. FIG. 10 is a sequence diagram illustrating an operation of a transfer device 112 according to a second embodiment of the present invention. FIG. 6 is a cross-sectional view illustrating a configuration of a main part of an image forming apparatus 100 according to a third embodiment of the present invention. It is a sequence diagram which shows operation | movement of the transfer apparatus 112 in the 3rd Embodiment of this invention. 4 is a table showing image forming conditions and evaluation results of Invention Example A, Invention Example B, Comparison Example C, and Comparison Example D in an example of the present invention. 4 is a graph showing the relationship between the number of printed sheets and the amount of photoconductor scraping in one embodiment of the present invention. 6 is a graph showing the relationship between the number of printed sheets and the amount of scraping of the intermediate transfer belt in one embodiment of the present invention. 6 is a graph showing the relationship between the ratio P1 / P2 and the amount of abrasion of the photoreceptor in one embodiment of the present invention. 6 is a graph showing the relationship between the distance (S1-S2) and the amount of photoconductor abrasion in an example of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In the following embodiment, a case where the image forming apparatus is an MFP will be described. The image forming apparatus may be a facsimile machine, a copier, or a printer in addition to the MFP.

  [First Embodiment]

  First, the configuration of the image forming apparatus in the present embodiment will be described.

  FIG. 1 is a cross-sectional view showing a configuration of main parts of an image forming apparatus 100 according to the first embodiment of the present invention.

  Referring to FIG. 1, image forming apparatus 100 according to the present embodiment is a tandem MFP in which image forming units 21Y, 21M, 21C, and 21K are arranged in the horizontal direction. And a fixing device 30. The toner image forming unit 20 synthesizes four color images of Y (yellow), M (magenta), C (cyan), and K (black) by a so-called tandem method, and transfers the toner image onto a sheet. The toner image forming unit 20 includes four sets of image forming units (process units) 21Y, 21M, 21C, and 21K, an exposure device 106, an intermediate transfer belt 109 (an example of a transfer belt), a primary transfer roller 108a, 108b, 108c, and 108d, a secondary transfer roller 111 (an example of a secondary transfer device), a cleaning device 113, and the like.

  Each of the image forming units 21 </ b> Y, 21 </ b> M, 21 </ b> C, and 21 </ b> K faces the intermediate transfer belt 109 and is juxtaposed directly below the intermediate transfer belt 109. The image forming unit 21Y includes a photoreceptor 104a, a charging roller 105a, a developing device 107a, a cleaning device 110a, and the like. The photoconductor 104a has a cylindrical shape and holds an electrostatic latent image on the surface thereof. The photoconductor 104a is rotationally driven in a direction indicated by an arrow AR1 in FIG. Around the photoconductor 104a, a charging roller 105a, a developing device 107a, and a cleaning device 110a are arranged.

  The image forming unit 21M includes a photoreceptor 104b, a charging roller 105b, a developing device 107b, a cleaning device 110b, and the like. The image forming unit 21C includes a photoreceptor 104c, a charging roller 105c, a developing device 107c, a cleaning device 110c, and the like. The image forming unit 21K includes a photoreceptor 104d, a charging roller 105d, a developing device 107d, a cleaning device 110d, and the like. Each of the image forming units 21M, 21C, and 21K has the same configuration as the image forming unit 21Y.

  The exposure device 106 is provided below the image forming units 21Y, 21M, 21C, and 21K. The intermediate transfer belt 109 is provided above the image forming units 21Y, 21M, 21C, and 21K. The intermediate transfer belt 109 has an annular shape and is driven to rotate in a direction indicated by an arrow AR2 in FIG. 1 in conjunction with a conveyance unit (not shown) that conveys a recording medium. Each of the primary transfer rollers 108a, 108b, 108c, and 108d is opposed to each of the photoreceptors 104a, 104b, 104c, and 104d with the intermediate transfer belt 109 interposed therebetween. The secondary transfer roller 111 is in contact with the intermediate transfer belt 109 in the transport path TR.

  The fixing device 30 includes a heating roller 116 and a pressure roller 117. The fixing device 30 fixes the toner image on the sheet by conveying it along the conveyance path TR while gripping the sheet carrying the toner image by the nip portion between the heating roller 116 and the pressure roller 117.

  When the image forming apparatus 100 receives a print job execution instruction, recording media such as paper stored in a paper feed tray (not shown) are taken out one by one and transported along a transport path TR. In parallel with the conveyance of the recording medium, the surfaces of the photoreceptors 104a, 104b, 104c, and 104d for each color of YMCK are charged to a desired potential by the charging rollers 105a, 105b, 105c, and 105d for each color of YMCK. After that, exposure based on the image data is performed by a laser beam (arrow AR3 in FIG. 1) generated from the exposure apparatus 106. Thereby, an electrostatic latent image is formed on the surface of each of the photosensitive members 104a, 104b, 104c, and 104d. The photosensitive member 104 is preferably charged by an AC charging method in which an AC (alternating current) voltage is applied to the charging roller 105. The electrostatic latent image is developed with toner by the developing rollers 121 of the developing devices 107a, 107b, 107c, and 107d for each color of YMCK. Thereby, a toner image (an example of a visible image) is formed on the surface of each of the photoreceptors 104a, 104b, 104c, and 104d, and the electrostatic latent image is visualized. These toner images are transferred onto the intermediate transfer belt 109 by a transfer bias applied to each of the primary transfer rollers 108a, 108b, 108c, and 108d for each color of YMCK. As a result, toner images of each color of YMCL are formed on the intermediate transfer belt 109 in an overlapping manner.

  The toner image on the intermediate transfer belt 109 is collectively transferred onto a recording medium conveyed between the intermediate transfer belt 109 and the secondary transfer roller 111 by the secondary transfer roller 111. The toner remaining on the surface of each of the photoreceptors 104a, 104b, 104c, and 104d after the transfer is removed by each of the cleaning devices 110a, 110b, 110c, and 110d (an example of a cleaning device). The toner remaining on the intermediate transfer belt 109 after the transfer is removed by the cleaning device 113.

  The toner image formed on the recording medium is fixed to the recording medium by applying heat and pressure when the recording medium passes through the fixing device 30. The recording medium on which the toner image is fixed is discharged out of the image forming apparatus 100.

  The configuration and arrangement of each member in the image forming apparatus 100 described above is merely an example. The image forming apparatus may have other configurations and arrangements.

  Hereinafter, an arbitrary image forming unit among the image forming units 21Y, 21M, 21C, and 21K may be referred to as an image forming unit 21. Each of the photosensitive member, the charging roller, and the developing device in the image forming unit 21 may be referred to as a photosensitive member 104, a charging roller 105 (an example of a charging device), and a developing device 107, respectively. Further, the primary transfer roller corresponding to the image forming unit 21 may be referred to as a primary transfer roller 108 (an example of a primary transfer device).

  FIG. 2 is a block diagram showing a control configuration of the image forming apparatus 100 according to the first embodiment of the present invention.

  Referring to FIG. 2, the image forming apparatus 100 includes a control unit 200, a charge control unit 211, an exposure control unit 212, a development control unit 213, a transfer control unit 214, a fixing control unit 215, and image processing. Part 216.

  The control unit 200 includes a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, and a RAM (Random Access Memory) 203. The CPU 201, the ROM 202, the RAM 203, the charge control unit 211, the exposure control unit 212, the development control unit 213, the transfer control unit 214, the fixing control unit 215, and the image processing unit 216 are connected to each other.

  The CPU 201 controls the operation of the entire image forming apparatus 100. The CPU 201 performs processing based on the control program.

  The ROM 202 stores a control program executed by the CPU 201 and the like.

  A RAM 203 is a working memory for the CPU 201 and temporarily stores data regarding various jobs.

  The charging controller 211 controls the operation of the charging roller 105 such as the voltage applied to the charging roller 105 and the rotation speed of the charging roller 105.

  The exposure control unit 212 controls the operation of the exposure apparatus 106 such as the intensity of exposure light and the timing of irradiating each of the photoconductors 104 with exposure light.

  The development control unit 213 controls the operation of the development device 107 such as the development bias of the development device 107, the replenishment of toner to the development device 107, and the rotational speed of the motor that drives each member in the development device 107.

  In the present embodiment, the primary transfer roller 108, the intermediate transfer belt 109, and the secondary transfer roller 111 constitute a transfer device 112 (FIG. 2) that transfers a visible image formed on the photoreceptor 104 to a recording medium. To do. The transfer control unit 214 controls the operation of the transfer device 112. Specifically, the transfer control unit 214 performs primary transfer bias, primary transfer current, rotational speed of the primary transfer roller 108, pressure contact or separation between the primary transfer roller 108 and the photoreceptor 104, and the primary transfer roller 108. Controls the operation of the primary transfer roller 108 such as the force of pressing the photoreceptor 104 via the intermediate transfer belt 109. The transfer control unit 214 controls the operation of the intermediate transfer belt 109 such as the rotation speed of the intermediate transfer belt 109. Further, the transfer control unit 214 controls operations of the secondary transfer roller 111 such as a secondary transfer bias, a secondary transfer current, and a force by which the secondary transfer roller 111 presses the intermediate transfer belt 109.

  The fixing control unit 215 controls the operation of the fixing device 30 such as the temperature of the heating roller 116 and the rotation speed of the pressure roller 117.

  The image processing unit 216 creates an image pattern for image formation.

  FIG. 3 is a diagram showing the relationship between the image forming region IR and the non-image forming region NR when the annular surface 104e of the photoconductor 104 is linearly developed.

  Referring to FIG. 3, surface 104e of photoconductor 104 is formed of a photosensitive layer that holds an electrostatic latent image. The photoreceptor 104 preferably does not include an overcoat layer on the outermost surface. The surface 104e of the photoreceptor 104 is divided into an image forming region IR (an example of a visible image forming region) and a non-image forming region NR (an example of a non-visible image forming region). The image forming area IR is an area where a toner image is formed on the surface 104e of the photoreceptor 104. The non-image forming region NR is a region other than the image forming region IR on the surface 104e of the photoconductor 104, and is a region where a toner image is not formed on the surface 104e of the photoconductor 104. When an image related to a print job is composed of a plurality of pages, a plurality of image forming areas IR are arranged at equal intervals on the surface 104e of the photoreceptor 104 with the non-image forming area NR interposed therebetween. For example, when an image relating to a print job is composed of three pages, an image forming region IR1 in which a toner image of the first page image is formed on the surface 104e of the photoreceptor 104 and a toner of the second page image. The image forming region IR2 where the image is formed and the image forming region IR3 where the toner image of the third page image is formed are along the direction opposite to the rotation direction of the photoconductor 104 (the direction indicated by the arrow AR1). Provided. A non-image forming region NR is provided between each of the image forming regions IR1, IR2, and IR3.

  The image forming apparatus 100 forms an image of the region of the surface 104e of the photoconductor 104 based on the timing of starting the irradiation of the laser beam by the exposure device 106, the rotation speed of the photoconductor 104, and the rotation speed of the intermediate transfer belt 109. The area is divided into an area IR and a non-image forming area NR.

  FIG. 4 is a cross-sectional view showing a configuration in the vicinity of the image forming unit 21 of the image forming apparatus 100 according to the first embodiment of the present invention.

  Referring to FIG. 4, the primary transfer roller 108 is biased toward the photoconductor 104 by a spring 143, and presses the intermediate transfer belt 109 against the photoconductor 104. The intermediate transfer belt 109 comes into contact with the photoreceptor 104 by the pressing force from the primary transfer roller 108. The transfer control unit 214 controls the pressing force of the primary transfer roller 108 against the photosensitive member 104 by controlling the free length of the spring 143.

  The pressing force of the primary transfer roller 108 against the photosensitive member 104 may be controlled using the spring 143 as described above, or may be controlled using another member such as an eccentric cam, an actuator, or a gear. . The image forming apparatus 100 includes a cleaning roller 105e for removing dirt such as a toner external additive attached on the charging roller 105.

  FIG. 5 is a sequence diagram showing the operation of the transfer device 112 according to the first embodiment of the present invention. FIG. 5A shows the driving state of the photoconductor 104. FIG. 5B shows the pressing position on the photoconductor 104. ON indicates that the pressed position is the image forming area IR, and OFF indicates that the pressed position is the non-image forming area NR. FIG. 5C shows a pressing state of the primary transfer roller 108 against the photoconductor 104. FIG. 5D shows the driving state of the primary transfer roller 108.

  4 and 5, image forming apparatus 100 starts image formation upon accepting a print job. At time T1, the image forming apparatus 100 starts rotating the photosensitive member 104, and at the same time, rotates the primary transfer roller 108, the intermediate transfer belt 109, and the secondary transfer roller 111 that constitute the transfer device 112. Start driving. The image forming apparatus 100 separates the primary transfer roller 108 and the intermediate transfer belt 109 from the photoconductor 104 at the time T1 when the transfer device 112 starts to rotate.

  The image forming apparatus 100 applies the pressure P1 (an example of the first pressure) to the primary transfer roller 108 via the intermediate transfer belt 109 at time T2 after the photoreceptor 104 and the intermediate transfer belt 109 reach a predetermined rotation speed. ) To the photosensitive member 104. As a result, the intermediate transfer belt 109 contacts the photoconductor 104, and the photoconductor 104 and the intermediate transfer belt 109 rotate in synchronization.

  Hereinafter, the position of the photoconductor 104 pressed by the transfer device 112 (in this embodiment, the primary transfer roller 108) (in other words, the position of the photoconductor 104 in contact with the intermediate transfer belt 109) may be referred to as a press position. is there. At time T2, the pressed position is the non-image forming area NR1 that exists in the rotation direction of the photoconductor 104 (the direction indicated by the arrow AR1) relative to the image forming area IR1 of the first page.

  When the pressing position reaches the image forming region IR1 at time T3, the image forming apparatus 100 changes the pressing force of the transfer device 112 against the photosensitive member 104 from the pressure P1 to the pressure P2 (> P1). As a result, the intermediate transfer belt 109 is brought into strong contact with the photoconductor 104, and the toner image is transferred from the photoconductor 104 to the intermediate transfer belt 109.

  The image forming apparatus 100 changes the pressing force of the primary transfer roller 108 against the photoconductor 104 from the pressure P2 to the pressure P1 at each of times T4, T6, and T8 when the pressing position reaches the non-image forming area NR. The image forming apparatus 100 changes the pressing force of the primary transfer roller 108 against the photoconductor 104 from the pressure P1 to the pressure P2 at each of times T5 and T7 when the pressing position reaches the image forming region IR.

  The image forming apparatus 100 separates the primary transfer roller 108 and the intermediate transfer belt 109 from the photosensitive member 104 at time T9 when the formation of all copy images or print images related to the print job is completed. After performing a series of end sequences, the image forming apparatus 100 resets the potential of the photoconductor 104, and stops the photoconductor 104 at time T10. In the image forming apparatus 100, in order to remove the residual toner on the intermediate transfer belt 109, the intermediate transfer belt 109 rotates at least one turn, and the transfer device 112 is stopped at time T11.

  As described above, when the position of the photoconductor 104 pressed by the primary transfer roller 108 during image formation is in the non-image forming region NR, the image forming apparatus 100 performs the primary operation with the pressure P1 via the intermediate transfer belt 109. The transfer roller 108 is pressed against the photoconductor 104. The image forming apparatus 100 performs primary transfer with the pressure P2 (> P1) via the intermediate transfer belt 109 when the position of the photoconductor 104 pressed by the primary transfer roller 108 during image formation is in the image forming region IR. The roller 108 is pressed against the photoconductor 104. The position of the primary transfer roller 108 when pressing with the pressure P1 is the same as the position of the primary transfer roller 108 when pressing with the pressure P2.

  The pressure P1 is preferably 30% or more and 70% or less of the pressure P2. By setting the pressure P1 to be 30% or more of the pressure P2, it becomes easy to switch the pressure when the pressing position changes between the image forming region IR and the pressing position between the non-image forming region NR. By setting the pressure P1 to 70% or less of the pressure P2, the abrasion amount of the photoconductor 104 can be particularly effectively suppressed.

  Then, the effect of this Embodiment is demonstrated.

  If the pressing force of the primary transfer roller against the photoconductor during image formation is maintained constant (pressure P2), the print job such as a copy job or a print job is executed from the primary transfer roller and the intermediate transfer belt. Due to the pressing force received and the strong electric field applied from the primary transfer roller, microscopic destruction occurs in the surface layer of the photoreceptor. As a result, depletion of the photoconductor is promoted, and the potential holding power of the photoconductor itself is eventually reduced. As a result, fogging occurs in the image, and uneven wear such as white stripes and black stripes becomes noticeable.

  According to the present embodiment, the pressing force of the primary transfer roller 108 on the photosensitive member 104 in the non-image forming region NR is lower than the pressing force of the primary transfer roller 108 on the photosensitive member 104 in the image forming region IR. By doing so, the amount of wear (promotion of the amount of wear) of the photoconductor 104 can be suppressed, and the life of the photoconductor can be improved. Further, even if the pressing force applied to the photoconductor 104 in the non-image forming area NR is lowered, the image quality is not adversely affected. Further, since the integrated value of the pressing force of the primary transfer roller 108 with respect to the intermediate transfer belt 109 also decreases, it is possible to suppress wear and resistance fluctuation of the intermediate transfer belt 109 due to the pressing force. Further, since it is not necessary to switch between the state where the primary transfer roller 108 is pressed against the photoconductor 104 and the state where the primary transfer roller 108 is separated from the photoconductor 104 during image formation, the productivity of the image forming apparatus is increased. The life of the photoreceptor can be effectively improved while maintaining the above.

  [Second Embodiment]

  FIG. 6 is a cross-sectional view showing a configuration near the image forming unit 21 of the image forming apparatus 100 according to the second embodiment of the present invention.

  Referring to FIG. 6, transfer control unit 214 in the present embodiment moves primary transfer roller 108 along the direction of rotation of intermediate transfer belt 109 (the direction indicated by arrow AR2). The transfer control unit 214 controls the pressing force of the primary transfer roller 108 against the photoconductor 104 by controlling the position of the primary transfer roller 108.

  The primary transfer roller 108 is movable to each of the positions S1A and S2. The position S2 is, for example, a position facing the upper end portion of the photoconductor 104, and is a position where the distance from the photoconductor 104 is the smallest. When the primary transfer roller 108 exists at the position S2, the pressing force of the primary transfer roller 108 against the photoconductor 104 becomes the pressure P2.

  The position S1A exists on the upstream side in the rotation direction of the intermediate transfer belt 109 with respect to the position S2. The distance between the primary transfer roller 108 and the photoconductor 104 when the primary transfer roller 108 exists at the position S1A is the same as that between the primary transfer roller 108 and the photoconductor 104 when the primary transfer roller 108 exists at the position S2. Wider than the interval. Accordingly, when the primary transfer roller 108 exists at the position S1A, the pressing force of the primary transfer roller 108 against the photosensitive member 104 is the pressure P1 (<P2).

  The primary transfer roller 108 may be movable to each of the positions S1B and S2. The position S1B exists on the downstream side in the rotation direction of the intermediate transfer belt 109 with respect to the position S2. The distance between the primary transfer roller 108 and the photoconductor 104 when the primary transfer roller 108 exists at the position S1B is the same as that between the primary transfer roller 108 and the photoconductor 104 when the primary transfer roller 108 exists at the position S2. Wider than the interval. Accordingly, when the primary transfer roller 108 exists at the position S1B, the pressing force of the primary transfer roller 108 against the photosensitive member 104 is the pressure P1 (<P2).

  As the position S2, an optimal position for transferring the toner image from the photosensitive member 104 to the intermediate transfer belt 109 is selected. With the position S2 as a reference, the position S1A is further away from the photoconductor 104 at the upstream side in the rotation direction of the intermediate transfer belt 109 than the position S2. The position S1B is more distant from the photoreceptor 104 on the downstream side in the rotation direction of the intermediate transfer belt 109 than the position S2.

  The primary transfer roller 108 may be moved by fixing a rack-like member to the primary transfer roller 108 and rotating a pinion gear meshing with the member, or may be an eccentric cam, an actuator, or an air squeeze, etc. It may be moved using the member.

  Hereinafter, the positions S1A and S1B may be collectively referred to as a position S1.

  FIG. 7 is a sequence diagram showing the operation of the transfer device 112 according to the second embodiment of the present invention. FIG. 7A shows the driving state of the photoconductor 104. FIG. 7B shows the pressing position on the photoconductor 104. ON indicates that the pressed position is the image forming area IR, and OFF indicates that the pressed position is the non-image forming area NR. FIG. 7C shows the position of the primary transfer roller 108. FIG. 7D shows the driving state of the primary transfer roller 108.

  Referring to FIGS. 6 and 7, image forming apparatus 100 starts image formation upon accepting a print job. At time T21, the image forming apparatus 100 starts to rotate the photosensitive member 104, and at the same time, each of the primary transfer roller 108, the intermediate transfer belt 109, and the secondary transfer roller 111 constituting the transfer device 112 is rotated. Start driving. The image forming apparatus 100 separates the primary transfer roller 108 and the intermediate transfer belt 109 from the photosensitive member 104 at time T21 when the rotation driving of the transfer device 112 is started.

  The image forming apparatus 100 moves the primary transfer roller 108 to the position S1 at the time T22 when the pressing position becomes the non-image forming area NR1 after the photosensitive member 104 and the intermediate transfer belt 109 reach a predetermined rotational speed. Moving. As a result, the non-image forming area NR1 is pressed with the pressure P1.

  When the pressing position reaches the image forming area IR1 at time T23, the image forming apparatus 100 moves the primary transfer roller 108 from the position S1 to the position S2. As a result, the image forming area IR1 is pressed with the pressure P2.

  Thereafter, the image forming apparatus 100 moves the primary transfer roller 108 from the position S2 to the position S1 at each of times T24, T26, and T28 when the pressing position reaches the non-image forming area NR. The image forming apparatus 100 moves the primary transfer roller 108 from the position S1A or the position S1B to the position S2 at each of times T25 and T27 when the pressing position reaches the image forming area IR.

  The image forming apparatus 100 separates the primary transfer roller 108 and the intermediate transfer belt 109 from the photoconductor 104 at time T29 when the formation of all copy images or print images related to the print job is completed. After performing a series of end sequences, the image forming apparatus 100 resets the potential of the photoconductor 104 and stops the photoconductor 104. In the image forming apparatus 100, in order to remove the residual toner on the intermediate transfer belt 109, the intermediate transfer belt 109 rotates at least one turn, and the transfer device 112 is stopped at time T30.

  The distance along the rotation direction of the intermediate transfer belt 109 between the position S1 and the position S2 along the rotation direction of the intermediate transfer belt 109 is preferably 0.5 mm or more and 5 mm or less. When the distance between the position S1 and the position S2 is 5 mm or less, the primary transfer roller 108 can be easily moved. Further, the intermediate transfer belt 109 can easily come into contact with the photoconductor 104, and it is possible to avoid shock to the intermediate transfer belt 109 during the switching operation. By setting the distance between the position S1 and the position S2 to be 0.5 mm or more, the difference in pressing force is increased, and the amount of abrasion of the photoconductor 104 can be particularly effectively suppressed.

  Since the configuration and operation of the image forming apparatus 100 in the present embodiment other than those described above are the same as the configuration and operation of the image forming apparatus in the first embodiment, description thereof will not be repeated.

  According to the present embodiment, the same effect as in the first embodiment can be obtained. In addition, by changing the position of the primary transfer roller 108, the pressing force of the primary transfer roller 108 with respect to the photoconductor 104 is switched, so that the pressing force can be easily controlled.

  [Third Embodiment]

  FIG. 8 is a cross-sectional view showing the configuration of the main part of the image forming apparatus 100 according to the third embodiment of the present invention.

  Referring to FIG. 8, image forming apparatus 100 in the present embodiment is a monochrome MFP having only one-color image forming unit 21K. The toner image forming unit 20 includes an image forming unit 21K, an exposure device 106, a transfer device (transfer roller) 112, and the like. The transfer device 112 does not include a primary transfer roller or an intermediate transfer belt, and includes only a transfer roller. The toner image formed on the surface of the photosensitive member 104d (hereinafter sometimes referred to as the photosensitive member 104) of the image forming unit 21K is directly transferred to the recording medium by the transfer device 112 without passing through the intermediate transfer belt. .

  The transfer device 112 is biased toward the photoreceptor 104 by a spring 143. The transfer control unit 214 controls the pressing force of the transfer device 112 on the photosensitive member 104 by controlling the free length of the spring 143.

  FIG. 9 is a sequence diagram showing the operation of the transfer device 112 according to the third embodiment of the present invention. FIG. 9A shows the driving state of the photoconductor 104. FIG. 9B shows the pressing position on the photoconductor 104. ON indicates that the pressed position is the image forming area IR, and OFF indicates that the pressed position is the non-image forming area NR. FIG. 9C shows a pressing state of the transfer device 112 against the photosensitive member 104. FIG. 9D shows the driving state of the transfer device 112.

  Referring to FIGS. 8 and 9, image forming apparatus 100 starts image formation upon accepting a print job. At time T41, the image forming apparatus 100 starts to rotate the transfer device 112 at the same time as starting to rotate the photoreceptor 104. The image forming apparatus 100 separates the transfer device 112 from the photoconductor 104 at time T41 when the rotation drive of the transfer device 112 is started.

  In the image forming apparatus 100, after the photosensitive member 104 and the transfer device 112 reach a predetermined rotation speed, at time T42 when the pressing position becomes the non-image forming region NR1, the transfer device 112 is pressed with the pressure P1 to the photosensitive member 104. Press on. As a result, the transfer device 112 contacts the photoconductor 104, and the photoconductor 104 and the intermediate transfer belt 109 rotate in synchronization.

  When the pressed position reaches the image forming region IR1 at time T43 (in other words, when a recording medium is sandwiched between the photoconductor 104 and the transfer device 112), the image forming apparatus 100 transfers the transfer device 112 to the photoconductor 104. Is changed from the pressure P1 to the pressure P2 (> P1). As a result, the transfer device 112 is strongly pressed against the photoconductor 104 through the recording medium, and the toner image is transferred from the photoconductor 104 to the recording medium between time T43 and time T44.

  The image forming apparatus 100 changes the pressing force of the transfer device 112 against the photoconductor 104 from the pressure P2 to the pressure P1 at each of times T44, T46, and T48 when the pressing position reaches the non-image forming area NR. The image forming apparatus 100 changes the pressing force of the transfer device 112 against the photoconductor 104 from the pressure P1 to the pressure P2 at each of times T45 and T47 when the pressing position reaches the image forming region IR.

  The image forming apparatus 100 moves the transfer device 112 away from the photoconductor 104 at time T49 when the formation of all copy images or print images related to the print job is completed. After performing a series of end sequences, the image forming apparatus 100 resets the potential of the photoconductor 104 and stops the operations of the photoconductor 104 and the transfer device 112 at time T50.

  As described above, when the pressing position is the non-image forming region NR during image formation, the image forming apparatus 100 causes the transfer device 112 to be in contact with the photosensitive member 104 with the pressure P1 while the transfer device 112 and the photosensitive member 104 are in contact with each other. Press to 104. The image forming apparatus 100 presses the transfer device 112 against the photoreceptor 104 with the pressure P2 through the recording medium when the pressing position is the image forming region IR during image formation.

  Since the configuration and operation of the image forming apparatus 100 in the present embodiment other than those described above are the same as the configuration and operation of the image forming apparatus in the first embodiment, description thereof will not be repeated.

  According to the present embodiment, the same effect as in the first embodiment can be obtained. By combining the control method of the second embodiment and the configuration of the present embodiment, the transfer device 112 is moved along the recording medium transport direction TR, and the transfer device 112 is pressed against the photosensitive member 104. You may make it switch a position. In this case, the distance between the position S1 and the position S2 along the transport direction TR is preferably 0.5 mm or more and 5 mm or less.

  [Example]

  The inventor of the present application uses the image forming apparatus shown in FIG. 1 to perform printing on paper under each of the four image forming conditions of Invention Example A, Invention Example B, Comparative Example C, and Comparative Example D. The relationship between the number of printed sheets and the amount of abrasion of the photosensitive member under the above conditions and the relationship between the number of printed sheets and the amount of abrasion of the intermediate transfer belt were examined. Further, the inventor of the present application examined whether or not image noise was generated on the formed image after printing a predetermined number of sheets under each condition.

  FIG. 10 is a table showing image forming conditions and evaluation results for each of Invention Example A, Invention Example B, Comparative Example C, and Comparative Example D in one example of the present invention.

  Referring to FIG. 10, in Invention Example A, Invention Example B, and Comparative Example D, a hard intermediate transfer belt was used. In Comparative Example C, a soft intermediate transfer belt was used. In each of Invention Examples A and B, the pressing force was switched by the method described in the first and second embodiments, respectively, during image formation. In Comparative Examples C and D, the pressing force was not changed and the pressing force during image formation was constant.

  FIG. 11 is a graph showing the relationship between the number of printed sheets and the amount of photoconductor abrasion in one embodiment of the present invention.

  Referring to FIGS. 10 and 11, in the present invention example A, the present invention example B, and the comparative example C, the amount of abrasion of the photoreceptor is small, and the abrasion amount (photosensitiveness) of the abrasion limit even after printing on a predetermined number of sheets. The body did not exceed the limit amount of wear that could hold an electrostatic latent image. On the other hand, in Comparative Example D, the amount of abrasion of the photosensitive member was large, and the amount of abrasion exceeding the abrasion limit was exceeded before the number of printed sheets reached the predetermined number. As a result, in Comparative Example D, image noise due to density reduction occurred.

  FIG. 12 is a graph showing the relationship between the number of printed sheets and the scraping amount of the intermediate transfer belt in one embodiment of the present invention.

  Referring to FIG. 10 and FIG. 12, in the present invention example A, the present invention example B, and the comparative example D, the amount of abrasion of the intermediate transfer belt is small, and the amount of wear (the abrasion limit) even after printing on a predetermined number of sheets ( The limit amount of wear that the intermediate transfer belt can hold the toner image) was not exceeded. On the other hand, in Comparative Example C, the amount of abrasion of the intermediate transfer belt was small, and the wear amount at the abrasion limit was exceeded before the number of printed sheets reached the predetermined number. As a result, in Comparative Example C, image noise due to transfer failure occurred.

  From the above results, it was found that when a soft intermediate transfer belt is used, the amount of abrasion of the photosensitive member can be reduced, but the wear of the intermediate transfer belt is deteriorated. Further, when a hard intermediate transfer belt is used, the amount of abrasion of the photosensitive member can be reduced and the wear of the intermediate transfer belt can be suppressed by performing the control of the above-described embodiment. I understood. It has been found that when a hard intermediate transfer belt is used, the amount of abrasion of the photoreceptor increases unless the control of the above-described embodiment is performed.

  Subsequently, the inventor of the present application sets the ratio P1 / P2 between the pressure P1 and the pressure P2 in the control of the first embodiment to 0, 15%, 30%, 45%, 70%, 85%, and 100%, respectively. After printing a predetermined number of sheets, the amount of abrasion of the photoconductor was measured.

  FIG. 13 is a graph showing the relationship between the ratio P1 / P2 and the amount of photoconductor abrasion in one embodiment of the present invention.

  Referring to FIG. 13, when the ratio P1 / P2 is 70% or less, the amount of abrasion of the photoconductor is smaller than when the ratio P1 / P2 is greater than 70%. When the ratio P1 / P2 is 30% or more, switching between the pressure P1 and the pressure P1 is facilitated, and the productivity is improved.

  From the above results, it is understood that the pressure P1 is preferably 30% to 70% of the pressure P2.

  Further, the inventor of the present application sets the distance (S1-S2) between the position S1 and the position S2 along the rotation direction of the intermediate transfer belt in the control of the second embodiment to 0, ± 0.5 mm, ± 1 mm, After printing a predetermined number of prints set to ± 3 mm, ± 5 mm, ± 7 mm, and ± 10 mm, the amount of abrasion of the photoreceptor was measured.

  FIG. 14 is a graph showing the relationship between the distance (S1-S2) and the amount of photoconductor abrasion in one embodiment of the present invention. In FIG. 14, when the position S1 is located upstream of the position S2 in the rotation direction of the intermediate transfer belt, the distance (S1-S2) is shown as a negative value, and the position S1 is located at the intermediate transfer position than the position S2. When it is on the downstream side in the belt rotation direction, the distance (S1-S2) is shown as a negative value.

  Referring to FIG. 14, when distance (S1-S2) is not less than 0.5 mm and not more than 5 mm, compared to the case where distance (S1-S2) is not less than 0 and less than 0.5 mm and greater than 5 mm. The amount of shaving of the photoreceptor was small. Further, when the distance (S1-S2) is -5 mm or more and -0.5 mm or less, the distance (S1-S2) is greater than -0.5 mm and less than or equal to 0 and less than -5 mm. The amount of shaving of the photoreceptor was small.

  From the above results, it can be seen that the distance between the position S1 and the position S2 along the rotation direction of the intermediate transfer belt is preferably 0.5 mm or more and 5 mm or less.

  The above-described embodiments and examples are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

20 toner image forming unit 21, 21C, 21K, 21M, 21Y image forming unit 30 fixing device 100 image forming device 104 photoconductor 104, 104a, 104b, 104c, 104d photoconductor 104e surface of photoconductor 105, 105a, 105b, 105c , 105d Charging roller (an example of a charging device)
105e Cleaning roller 106 Exposure device 107, 107a, 107b, 107c, 107d Developing device 108, 108a, 108b, 108c, 108d Primary transfer roller (an example of a primary transfer device)
109 Intermediate transfer belt (an example of a transfer belt)
110a, 110b, 110c, 110d, 113 Cleaning device 111 Secondary transfer roller (an example of a secondary transfer device)
DESCRIPTION OF SYMBOLS 112 Transfer apparatus 116 Heating roller 117 Pressure roller 121 Developing roller 143 Spring 200 Control part 201 CPU (Central Processing Unit)
202 ROM (Read Only Memory)
203 RAM (Random Access Memory)
211 Charging control unit 212 Exposure control unit 213 Development control unit 214 Transfer control unit 215 Fixing control unit 216 Image processing unit IR, IR1, IR2, IR3 Image forming area NR, NR1 Non-image forming area TR Transport path

Claims (12)

A photoreceptor on which a visible image is formed;
A transfer device for transferring a visible image formed on the photoreceptor to a recording medium;
When the position of the photoreceptor pressed by the transfer device during image formation of the image forming apparatus is a non-visible image forming area that is an area where a visible image is not formed on the photoreceptor, the first pressure is used. First pressing means for pressing the transfer device against the photoreceptor;
When the position of the photoconductor pressed by the transfer device during image formation of the image forming apparatus is a visible image forming region that is a region where a visible image is formed on the photoconductor, An image forming apparatus comprising: a second pressing unit that presses the transfer device against the photoconductor with a second pressure larger than the pressure. The transfer device includes:
A transfer belt in contact with the photoreceptor;
A primary transfer device for transferring a visible image formed on the photosensitive member to the transfer belt;
A secondary transfer device that transfers the visible image transferred to the transfer belt to the recording medium,
When the position of the photoconductor that the primary transfer device presses during the image formation of the image forming apparatus is the invisible image forming area, the first pressing unit is configured to pass the transfer belt through the transfer belt. Pressing the primary transfer device against the photoreceptor with a first pressure;
When the position of the photoconductor that the primary transfer device presses during the image formation of the image forming apparatus is the visible image forming area, the second pressing unit is configured to perform the first pressing via the transfer belt. The image forming apparatus according to claim 1, wherein the primary transfer device is pressed against the photoconductor with a pressure of 2. The first pressing unit is configured such that when the position of the photoconductor pressed by the transfer device during image formation of the image forming device is the invisible image forming region, the transfer device and the photoconductor are In the contact state, the transfer device is pressed against the photoconductor with the first pressure,
When the position of the photosensitive member pressed by the transfer device during image formation of the image forming apparatus is the visible image forming area, the second pressing unit is configured to perform the second pressing unit via the recording medium. The image forming apparatus according to claim 2, wherein the transfer device is pressed against the photoconductor with pressure.   The image forming apparatus according to claim 1, wherein the first pressure is not less than 30% and not more than 70% of the second pressure.   The position of the transfer device when pressed by the first pressing means is the same as the position of the transfer device when pressed by the second pressing means. The image forming apparatus described in 1.   The position at which the photosensitive member is pressed when pressed by the first pressing unit is greater in the rotation direction of the transfer belt than the position at which the photosensitive member is pressed when pressed by the second pressing unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is located on an upstream side or a downstream side along a conveyance direction of the recording medium.   The distance between the position where the photoconductor is pressed when pressed by the first pressing means and the position where the photoconductor is pressed when pressed by the second pressing means, The image forming apparatus according to claim 6, wherein a distance along a rotation direction of the belt or a conveyance direction of the recording medium is 0.5 mm or more and 5 mm or less.   The image forming apparatus according to claim 6, wherein the first pressing unit moves the transfer device.   The image forming apparatus according to claim 1, wherein the photoconductor does not include an overcoat layer on an outermost surface. A charging device for charging the photoreceptor;
An exposure device that forms an electrostatic latent image on the photoreceptor;
A developing device that forms a visible image by developing the electrostatic latent image;
The image forming apparatus according to claim 1, further comprising a cleaning device that removes toner remaining on the photosensitive member after transfer. A method for controlling an image forming apparatus, comprising: a photoreceptor on which a visible image is formed; and a transfer device that transfers the visible image formed on the photoreceptor to a recording medium.
The first pressure is applied when the position of the photoreceptor pressed by the transfer device during image formation of the image forming apparatus is a non-visible image forming area in which a visible image is not formed on the photoreceptor. A first pressing step of pressing the transfer device against the photoconductor;
When the position of the photoconductor pressed by the transfer device during image formation of the image forming apparatus is a visible image forming region that is a region where a visible image is formed on the photoconductor, And a second pressing step of pressing the transfer device against the photoconductor with a second pressure larger than the pressure. A control program for an image forming apparatus, comprising: a photoreceptor on which a visible image is formed; and a transfer device that transfers the visible image formed on the photoreceptor to a recording medium,
The first pressure is applied when the position of the photoreceptor pressed by the transfer device during image formation of the image forming apparatus is a non-visible image forming area in which a visible image is not formed on the photoreceptor. A first pressing step of pressing the transfer device against the photoconductor;
When the position of the photoconductor pressed by the transfer device during image formation of the image forming apparatus is a visible image forming region that is a region where a visible image is formed on the photoconductor, A control program for an image forming apparatus for causing a computer to execute a second pressing step of pressing the transfer device against the photosensitive member with a second pressure larger than the pressure.

Images