Image forming device

Abstract

To provide an image forming device with which it is possible to more reliably remove a residual waste toner and suppress the malfunctioning of a developing device.SOLUTION: An image forming device 100 comprises: a photoreceptor drum 3; an intermediate transfer belt 71; an intermediate transfer drive roller 72 for driving the intermediate transfer belt 71; a cleaning blade 91 located so as to contact the intermediate transfer belt 71; a developing roller 21 for supplying a toner to the photoreceptor drum 3; a doctor blade 22 for restricting a toner amount and located adjacent to the developing roller 21; and a common rotation drive device for simultaneously driving the photoreceptor drum 3, the intermediate transfer drive roller 72 and the developing roller 21. The photoreceptor drum 3 rotates in the forward direction in image forming operation, and in a maintenance operation which is carried out after the image forming operation terminates, the photoreceptor drum 3 rotates in the reverse direction under a different rotation condition from that during the image forming operation and thereafter rotates in the forward direction. Then the photoreceptor drum 3 stops after the maintenance operation terminates.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus that forms an image by transferring toner onto a recording medium. [Background technology]

[0002] Conventionally, in image forming devices such as copiers, facsimile machines, printers, and multifunction machines, a toner image is formed on a photosensitive drum, and the toner image is transferred to paper and fixed to form an image on the paper. Image forming devices that form color images on paper generally include photosensitive drums for each of a plurality of colors. Toner images of different colors are formed on each of these photosensitive drums, and the toner images of different colors are transferred from the plurality of photosensitive drums to an intermediate transfer belt to form color toner images on the intermediate transfer belt, and the toner images are transferred to paper and fixed to form a color image on the paper.

[0003] Here, when an image is formed on paper, some toner may remain on the photosensitive drum or intermediate transfer belt that transferred the toner image onto the paper. If such remaining toner (waste toner) is not removed, defects may occur in the subsequent image formation. Therefore, conventional image forming devices are provided with a cleaning blade arranged to contact the photosensitive drum or intermediate transfer belt. When the photosensitive drum or intermediate transfer belt is driven, the contacted cleaning blade scrapes off the waste toner remaining on the photosensitive drum or intermediate transfer belt, and the waste toner is removed.

[0004] However, repeated image formation causes foreign matter such as paper powder to accumulate at the contact point between the photosensitive drum or intermediate transfer belt and the cleaning blade, resulting in insufficient removal of waste toner.

[0005] To solve such problems, for example, there is a measure to mirror-finish the surface of the photosensitive drum or intermediate transfer belt to reduce the unevenness of the surface and make it difficult for foreign matter such as paper powder to accumulate, but this increases the cost of mirror-finishing.In addition, mirror-finishing the surface of the photosensitive drum or intermediate transfer belt increases the contact area with the cleaning blade, which increases the load on the cleaning blade.

[0006] In order to solve the above problem without mirror-finishing the surface of the photosensitive drum or intermediate transfer belt, for example, Patent Document 1 discloses an image forming device in which, after the photosensitive drum finishes rotating, the photosensitive drum is rotated in the reverse direction at least twice before stopping and entering a standby state. According to this image forming device, even if toner lumps or paper dust accumulate at the contact point between the photosensitive drum and the cleaning blade, the photosensitive drum is rotated in the reverse direction at least twice after the photosensitive drum finishes rotating, so that the accumulated paper dust and other foreign matter are removed. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2004-264553 A Summary of the Invention [Problem to be solved by the invention]

[0008] In some image forming apparatuses, the rollers of the developing device that supplies toner to the photosensitive drum, the photosensitive drum, and the transfer drive roller that drives the intermediate transfer belt are driven by the same drive device. In this type of image forming apparatus, the number of drive devices can be reduced compared to a configuration in which each roller of the developing device, the photosensitive drum, and the transfer drive roller each have a drive device, so that it is possible to reduce the size and cost. In addition, in the image forming operation, it is not necessary for the rollers of the developing device, the photosensitive drum, and the transfer drive roller to be driven in different modes, as long as they are driven in the same mode. Therefore, images can be formed without any problems using the same drive device.

[0009] However, the image forming apparatus disclosed in Patent Document 1 does not disclose a configuration in which the photosensitive drum and each roller of the developing device are driven by the same driving device. In other words, there is no description of a configuration in which each roller of the developing device rotates in the opposite direction when the photosensitive drum rotates in the opposite direction. In particular, when the developing roller that supplies toner to the photosensitive drum in the developing device rotates in the opposite direction, the magnetic tooth formed on the surface of the developing roller may interfere with the doctor blade that regulates the magnetic tooth, which may cause a malfunction of the developing device.

[0010] The present invention has been made in consideration of the above-mentioned circumstances, and its object is to provide an image forming apparatus that can more reliably remove remaining waste toner and suppress malfunctions of the developing device. [Means for solving the problem]

[0011] An image forming apparatus according to one aspect of the present invention includes an image carrier having a surface on which a toner image is formed, an endless intermediate transfer belt onto which the toner image is transferred from the image carrier and which forms a toner image on a recording medium, a transfer drive rotor around which the intermediate transfer belt is stretched and which drives the intermediate transfer belt, a removal unit arranged to contact the intermediate transfer belt and which removes waste toner remaining on the intermediate transfer belt after a toner image is formed on the recording medium, a development rotor arranged to face the image carrier and which supplies toner to the image carrier, and a regulation unit arranged adjacent to the development rotor and which regulates an amount of toner held on a surface of the development rotor in order to supply toner to the image carrier, the image carrier, and the transfer drive rotor. and a common rotation drive device which drives and rotates the developing rotor and the image carrier, and the developing rotor simultaneously, wherein during an image forming operation in which a toner image is formed on the recording medium, the common rotation drive device operates so that the image carrier, the transfer drive rotor, and the developing rotor rotate in a forward rotation direction, and during a maintenance operation performed after the image forming operation is completed, the common rotation drive device operates so that the image carrier, the transfer drive rotor, and the developing rotor rotate in a reverse direction which is the opposite direction to the forward rotation direction under rotation conditions which are different from those during the image forming operation, and then rotate in the forward rotation direction, and after the maintenance operation is completed, the common rotation drive device operates so that the image carrier, the transfer drive rotor, and the developing rotor stop.

[0012] As a result, the image carrier, the transfer drive rotor, and the developing rotor are all driven to rotate by a common rotary drive device, and after the image forming operation, the image carrier, the transfer drive rotor, and the developing rotor are driven to rotate in the reverse direction, which is the opposite direction to that during the image forming operation, and the rotation conditions are different from those during the image forming operation, so that foreign matter such as paper dust and residual waste toner remaining in the removing section can be removed, and even if a defect such as bending occurs in the removing section, it can be returned to a normal state, and cleaning characteristics can be improved. Furthermore, when the transfer drive rotor rotates in the reverse direction, the developing rotor also rotates in the reverse direction, but at this time, the magnetic chain formed on the developing rotor is unlikely to interfere with the regulating section. Therefore, it is possible to prevent defects from occurring in the developing device equipped with the developing rotor.

[0013] In addition, in the above-mentioned image forming apparatus, the rotational speed of the image carrier, the transfer drive rotor, and the developing rotor in the reverse direction during the maintenance operation may be slower than the rotational speed of the image carrier, the transfer drive rotor, and the developing rotor in the forward direction during the image forming operation.

[0014] In this way, the rotation speed of the developing rotor in the reverse direction during maintenance is slower than the rotation speed in the forward direction during image formation, so the inertial force acting on the magnetic brush formed on the developing rotor can be reduced. In other words, the magnetic brush can be prevented from rotating vigorously in the reverse direction, so that the magnetic brush can be prevented from interfering with the regulating portion, and the developing device equipped with the developing rotor can be prevented from malfunctioning.

[0015] In the above-described image forming apparatus, the rotational operation of the image carrier, the transfer driving rotor, and the developing rotor in the reverse direction during the maintenance operation may be performed intermittently a plurality of times.

[0016] In this way, because the rotation of the developing rotor in the reverse direction during maintenance is performed intermittently, the inertial force acting on the magnetic brush formed on the developing rotor can be reduced when the developing rotor rotates in the reverse direction. In other words, the magnetic brush can be prevented from rotating vigorously in the reverse direction, so that the magnetic brush can be prevented from interfering with the regulating portion, and the development device equipped with the developing rotor can be prevented from malfunctioning.

[0017] In addition, in the above-mentioned image forming apparatus, during the maintenance operation, a first distance traveled by the intermediate transfer belt when the image carrier, the transfer drive rotor, and the developing rotor rotate in a reverse direction may be less than or equal to a second distance traveled by the intermediate transfer belt when the intermediate transfer belt rotates in a forward direction after rotating in the reverse direction.

[0018] As a result, the amount of rotation in the reverse direction of the developing rotor during maintenance is equal to or less than the amount of rotation in the forward direction, which makes it possible to suppress interference of the magnetic brush with the regulating portion and to prevent malfunctions in the developing device having the developing rotor.

[0019] In addition, in the above-mentioned image forming apparatus, during the maintenance operation, the common rotation drive device may be operated so that the image carrier, the transfer drive rotor and the developing rotor alternately rotate in a reverse direction, which is opposite to the forward rotation direction, under rotation conditions different from those during the image forming operation, and rotate in the forward rotation direction multiple times.

[0020] In this way, during maintenance operations, the transfer drive rotor and the developing rotor alternate between rotating in the reverse direction and the forward direction multiple times, which more reliably improves the cleaning characteristics in the removal section and more reliably prevents the magnetic brush formed on the developing rotor from interfering with the regulating section, thereby more reliably preventing malfunctions in the developing device equipped with the developing rotor. Effect of the Invention

[0023] According to the present invention, it is possible to provide an image forming apparatus capable of more reliably removing residual waste toner and suppressing malfunctions of a developing device. [Brief description of the drawings]

[0024] [Figure 1] 1 is a perspective front view showing a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. [Diagram 2] 1 is a schematic diagram illustrating a configuration of a developing device in an image forming apparatus according to a first embodiment of the present invention. [Diagram 3] 1 is an enlarged schematic view of the periphery of a developing roller in an image forming apparatus according to a first embodiment of the present invention. [Figure 4] 2 is an enlarged schematic view of the periphery of a cleaning blade in the image forming apparatus according to the first embodiment of the present invention. FIG. [Diagram 5] FIG. 2 is an enlarged schematic view of the periphery of a cleaning blade in the image forming apparatus according to the first embodiment of the present invention, illustrating a state during an image forming operation. [Figure 6] FIG. 2 is an enlarged schematic view of the periphery of the developing roller in the image forming apparatus according to the first embodiment of the present invention, illustrating a state during maintenance operation. [Figure 7] 5 is a graph showing the operational states of the photosensitive drum during an image forming operation and during a maintenance operation in the image forming apparatus according to the first embodiment of the present invention. [Figure 8] FIG. 13 is an enlarged schematic view of the developing roller and its periphery according to Comparative Example 1, showing a state during maintenance operation. [Figure 9] 10 is a graph showing the operational states of the photosensitive drum during an image forming operation and during a maintenance operation in an image forming apparatus according to a second embodiment of the present invention. [Figure 10] 13 is a graph showing the operational states of the photosensitive drum during an image forming operation and during a maintenance operation in an image forming apparatus according to a third embodiment of the present invention. [Figure 11] 13 is an enlarged schematic view of the periphery of a photoconductor drum in an image forming apparatus according to a fourth embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. The names and functions of the components are also the same. Therefore, detailed description thereof will not be repeated.

[0026] (First embodiment) Hereinafter, an image forming apparatus 100 according to a first embodiment of the present invention will be described with reference to the drawings.

[0027] Fig. 1 is a perspective front view showing a schematic configuration of an image forming apparatus 100 according to a first embodiment of the present invention. In Fig. 1 and Figs. 2, 4, and 5 described below, the symbol X indicates the left-right direction, the symbol Y indicates the front-rear direction, and the symbol Z indicates the up-down direction.

[0028] The image forming apparatus 100 is a multifunction machine having a copy function, a scanner function, a facsimile function, and a printer function, and transmits to the outside an image of an original G read by an image reading device 102. The image forming apparatus 100 also forms an image of the original G read by the image reading device 102 or an image received from the outside on a sheet P such as paper in color or monochrome.

[0029] An original feeder 160 (automatic document feeder (ADF)) is provided above the image reading unit 130 and is supported so as to be freely opened and closed relative to the image reading unit 130. The image reading device 102 includes the original feeder 160. The original feeder 160 sequentially transports one or more originals G one by one. The image reading device 102 reads the originals G transported one by one of the one or more originals G by the original feeder 160. The image reading device 102 includes an original placement table 130a on which the originals G are placed, and a placed original reading function that reads the original placed on the original placement table 130a. When the original feeder 160 is opened, the image forming device 100 opens the original placement table 130a above the image reading unit 130, allowing the originals G to be placed manually. Further, the document feeder 160 includes a document placement tray 161 on which the document G is placed, and a document discharge tray 162 on which the document G discharged to the outside is stacked. The image reading device 102 includes a transported document reading function for reading the document G transported by the document feeder 160. The document feeder 160 transports the document G placed on the document placement tray 161 onto the document reading section 130b in the image reading section 130. The image reading section 130 scans the scanning optical system 130c to read the document placed on the document placement table 130a or reads the document G transported by the document feeder 160 to generate image data.

[0030] The image forming apparatus main body 101 includes an optical scanning device 1, a developing device 2, a photosensitive drum 3, a drum cleaning device 4, a charger 5, an intermediate transfer belt device 70, a secondary transfer device 11, a fixing device 12, a sheet transport path S, a paper feed cassette 18, and a sheet discharge tray 141.

[0031] The image forming apparatus 100 handles image data corresponding to color images using the colors black (K), cyan (C), magenta (M), and yellow (Y), or monochrome images using a single color (e.g., black). The image transfer section 50 of the image forming apparatus 100 is provided with four developing devices 2, four photoconductor drums 3, four drum cleaning devices 4, and four chargers 5 for forming four types of toner images, which correspond to black, cyan, magenta, and yellow, respectively, to form four image stations Pa, Pb, Pc, and Pd.

[0032] The optical scanning device 1 exposes the surface of the photoreceptor drum 3 to light to form an electrostatic latent image. The developing device 2 develops the electrostatic latent image on the surface of the photoreceptor drum 3 to form a toner image on the surface of the photoreceptor drum 3. The drum cleaning device 4 removes and collects residual toner on the surface of the photoreceptor drum 3. The charger 5 uniformly charges the surface of the photoreceptor drum 3 to a predetermined potential. Through the series of operations described above, a toner image of each color is formed on the surface of each photoreceptor drum 3.

[0033] Here, the configuration of the developing device 2 will be described with reference to the drawings. Fig. 2 is a schematic diagram showing the configuration of the developing device 2 in the image forming apparatus 100 according to the first embodiment of the present invention. Fig. 3 is an enlarged schematic diagram of the periphery of the developing roller 21 in the image forming apparatus 100 according to the first embodiment of the present invention.

[0034] The developing device 2 includes a developing roller 21, a doctor blade 22, a sealing mylar 23, transport members 24 and 25, and a developing tank 26. The developing roller 21 is disposed opposite the photosensitive drum 3, and is driven to rotate by a common rotary drive device, which is a motor, as a drive source. The transport members 24 and 25 are also driven to rotate.

[0035] Developing tank 26 contains a two-component developer (hereinafter referred to as developer) containing toner and magnetic carrier. Transporting members 24 and 25 are located in developing tank 26, and are both spaced apart from the inner wall surface of developing tank 26. Transporting members 24 and 25 are both screw augers equipped with helical transport blades, and rotate in opposite directions. The developer in developing tank 26 is circulated and transported while being stirred by the rotation of transporting members 24 and 25. Developer 27 (see FIG. 3) is transported in developing tank 26 by transporting members 24 and 25, and is pumped up and supported on the outer circumferential surface of developing roller 21 that is rotating.

[0036] During an image forming operation, as shown in FIG. 3, the toner in the developer 27 carried on the developing roller 21 moves to the photosensitive drum 3. Specifically, in a nip portion N where the developing roller 21 and the photosensitive drum 3 are close to each other, the developer 27 carried on the outer peripheral surface of the developing roller 21 comes into contact with the photosensitive drum 3. In this nip portion N, a developing bias voltage is applied to the developing roller 21, and toner is supplied from the developer 27 on the outer peripheral surface of the developing roller 21 to the electrostatic latent image on the outer peripheral surface of the photosensitive drum 3. The photosensitive drum 3 is also driven to rotate, and its drive source is the same as the drive source of the developing roller 21. In other words, both the photosensitive drum 3 and the developing roller 21 are driven to rotate by a common rotary drive device. Specifically, a drive force is transmitted from the common rotary drive device to each of the photosensitive drum 3 and the developing roller 21 via a gear (not shown), and they are driven simultaneously. During an image forming operation, the photosensitive drum 3 rotates in a forward rotation direction F3, and the developing roller 21 rotates in a forward rotation direction F4.

[0037] The thickness of the layer of developer 27 that is pumped up and carried on the outer peripheral surface of developing roller 21 is regulated by doctor blade 22 as developing roller 21 rotates in forward direction F4. Sealing mylar 23 is flexible and made of resin or the like. By providing sealing mylar 23, it is possible to prevent developer from scattering outside developing device 2.

[0038] The intermediate transfer belt device 70 includes an intermediate transfer roller 6, an endless intermediate transfer belt 71, an intermediate transfer driving roller 72, an intermediate transfer driven roller 73, and a cleaning device 9. Four intermediate transfer rollers 6 are provided inside the intermediate transfer belt 71 so as to form four types of toner images corresponding to the respective colors. The intermediate transfer rollers 6 transfer the toner images of the respective colors formed on the surfaces of the photosensitive drums 3 onto the intermediate transfer belt 71 which moves in a circumferential direction C.

[0039] The intermediate transfer belt 71 is stretched around an intermediate transfer drive roller 72 and an intermediate transfer driven roller 73. In the image forming apparatus 100, the toner images of each color formed on the surface of each photoconductor drum 3 are sequentially transferred and superimposed to form a color toner image on the surface of the intermediate transfer belt 71. The cleaning device 9 removes and collects waste toner remaining on the surface of the intermediate transfer belt 71 without being transferred to the sheet P.

[0040] The secondary transfer device 11 forms a transfer nip area TN between the secondary transfer roller 11a and the intermediate transfer belt 71, and conveys a sheet P conveyed through a sheet conveying path S by pinching it in the transfer nip area TN. When the sheet P passes through the transfer nip area TN, the toner image on the surface of the intermediate transfer belt 71 is transferred to the sheet P, and the sheet P is conveyed to the fixing device 12.

[0041] The fixing device 12 includes a fixing roller 31 and a pressure roller 32 that rotate while sandwiching the sheet P. The fixing device 12 sandwiches the sheet P, on which the toner image has been transferred, between the fixing roller 31 and the pressure roller 32, and applies heat and pressure to fix the toner image to the sheet P.

[0042] The paper feed cassette 18 is a cassette for storing sheets P used for image formation, and is provided below the optical scanning device 1. The sheet P is pulled out from the paper feed cassette 18 by a pickup roller 16 and conveyed to a sheet conveying path S. The sheet P conveyed to the sheet conveying path S is conveyed to a discharge roller 17 via a secondary transfer device 11 and a fixing device 12, and is discharged to a sheet discharge tray 141 in a discharge section 140. A conveying roller 13, a registration roller 14, and a discharge roller 17 are arranged on the sheet conveying path S. The conveying roller 13 promotes the conveyance of the sheet P. The registration roller 14 temporarily stops the sheet P and aligns the leading edge of the sheet P. The registration roller 14 conveys the stopped sheet P in accordance with the timing of the color toner image on the intermediate transfer belt 71. The color toner image on the intermediate transfer belt 71 is transferred to the sheet P in a transfer nip area TN between the intermediate transfer belt 71 and the secondary transfer roller 11a.

[0043] In FIG. 1, the number of sheet feed cassettes 18 is one, but the present invention is not limited to this. A configuration may be provided in which a plurality of sheet feed cassettes 18 are provided to stack different types of sheets P, respectively.

[0044] Furthermore, when forming an image on the back side of the sheet P in addition to the front side, the image forming apparatus 100 conveys the sheet P in the reverse direction from the discharge rollers 17 to a sheet inversion path Sr. The image forming apparatus 100 inverts the sheet P conveyed in the reverse direction and guides it again to the registration rollers 14. The image forming apparatus 100 also forms an image on the back side of the sheet P guided to the registration rollers 14 in the same manner as on the front side, and conveys the sheet P to the sheet discharge tray 141.

[0045] The intermediate transfer belt device 70 includes an intermediate transfer belt 71, an intermediate transfer driving roller 72, and an intermediate transfer driven roller 73. The intermediate transfer belt 71 is an endless belt that can rotate. The intermediate transfer belt 71 is wound around the intermediate transfer driving roller 72 and the intermediate transfer driven roller 73. That is, the intermediate transfer driving roller 72 and the intermediate transfer driven roller 73 stretch the intermediate transfer belt 71. The driving source for the rotational drive of the intermediate transfer driving roller 72 is common to the driving sources of the photosensitive drum 3 and the developing roller 21. That is, the intermediate transfer driving roller 72 is driven to rotate by a common rotational drive device, which is a motor, and specifically, a driving force is transmitted from the common rotational drive device via a gear (not shown). Therefore, the intermediate transfer driving roller 72, the photosensitive drum 3, and the developing roller 21 are all driven to rotate by the common rotational drive device, and are driven simultaneously.

[0046] Here, the relationship between the intermediate transfer belt 71 and the cleaning device 9 will be described with reference to the drawings. Fig. 4 is an enlarged schematic view of the periphery of the cleaning blade 91 in the image forming apparatus 100 according to the first embodiment of the present invention. Note that Fig. 4 also illustrates the intermediate transfer drive roller 72, which is disposed at a position separated from the cleaning blade 91.

[0047] The cleaning device 9 includes a collection casing 93, a support plate 92 installed in the collection casing 93, and a cleaning blade 91 fixed to the support plate 92. The cleaning blade 91 is disposed so as to come into contact with the intermediate transfer belt 71. Also, a tension spring 74 is provided, and the tension spring 74 applies a biasing force to the intermediate transfer driven roller 73 toward the cleaning device 9.

[0048] During image forming operation, when the intermediate transfer driving roller 72 is driven to rotate in the forward direction F1, the intermediate transfer belt 71 is driven in the circumferential direction C, and the intermediate transfer driven roller 73 is also driven to rotate in the forward direction F2. As a result, waste toner remaining on the intermediate transfer belt 71 is scraped off by the cleaning blade 91 installed in contact with the intermediate transfer belt 71. The waste toner scraped off by the cleaning blade 91 is collected in a collection casing 93. Note that, as will be described in detail later, during maintenance operation after the image forming operation, the intermediate transfer driving roller 72 may also be driven to rotate in the reverse direction R1. In this case, the intermediate transfer belt 71 moves around in the circumferential direction I, and the intermediate transfer driven roller 73 is driven to rotate in the reverse direction R2.

[0049] Next, the maintenance operation performed after the image forming operation in the image forming apparatus 100 will be described with reference to the drawings. Fig. 5 is an enlarged schematic diagram of the cleaning blade 91 and its periphery in the image forming apparatus 100 according to the first embodiment of the present invention, showing the state during the image forming operation. That is, it shows the state in which the intermediate transfer drive roller 72 and the intermediate transfer driven roller 73 rotate in the forward rotation directions F1 and F2, and the intermediate transfer belt 71 moves around in the circumferential direction C. Fig. 6 is an enlarged schematic diagram of the developing roller 21 and its periphery in the image forming apparatus 100 according to the first embodiment of the present invention, showing the state during the maintenance operation.

[0050] As described above, the image forming apparatus 100 forms an image on the sheet P using toner. In the image forming apparatus 100, the operation of forming an image on the sheet P in this manner is called an image forming operation. As described above, the waste toner remaining on the intermediate transfer belt 71 during this image forming operation is scraped off by the cleaning blade 91 and collected in the collection casing 93, and at this time, foreign matter such as paper powder and waste toner accumulates between the cleaning blade 91 and the intermediate transfer belt 71. Therefore, as the operating time of the image forming operation in the image forming apparatus 100 increases, the amount of foreign matter such as paper powder and waste toner that accumulates between the cleaning blade 91 and the intermediate transfer belt 71 increases. If the amount of the accumulated foreign matter such as paper powder and waste toner increases, the area of ​​direct contact between the cleaning blade 91 and the intermediate transfer belt 71 decreases, and the performance (cleaning characteristics) of the cleaning blade 91 to remove the waste toner decreases.

[0051] Furthermore, when the frictional force between the intermediate transfer belt 71 and the cleaning blade 91 increases, the cleaning blade 91 will bend as shown in Fig. 5. When the cleaning blade 91 is bent, the contact state with the intermediate transfer belt 71 changes, and the performance of the cleaning blade 91 in removing waste toner decreases. Furthermore, when the frictional force between the intermediate transfer driven roller 73 and the cleaning blade 91 increases too much, problems such as the cleaning blade 91 being damaged or the intermediate transfer belt 71 being unable to move may occur.

[0052] Therefore, in the image forming apparatus 100, a maintenance operation is performed after the image forming operation. This maintenance operation removes foreign matter such as paper powder and waste toner remaining between the cleaning blade 91 and the intermediate transfer belt 71, and prevents a decrease in the waste toner removal performance. In addition, it is possible to prevent problems such as damage to the cleaning blade 91 and a state in which the intermediate transfer belt 71 cannot move.

[0053] Here, as described above, during the image forming operation, the intermediate transfer driving roller 72 rotates in the forward direction F1 due to the driving force from the common rotary drive device. As a result, the intermediate transfer belt 71 moves in the circumferential direction C, and the intermediate transfer driven roller 73 rotates in the forward direction F2. In contrast, during the maintenance operation, the intermediate transfer driving roller 72 may rotate in the reverse direction R1. That is, the rotation of the common rotary drive device may be reversed. As a result, the intermediate transfer belt 71 moves in the circumferential direction I, and the intermediate transfer driven roller 73 rotates in the reverse direction R2. Note that the rotation speed of the intermediate transfer driving roller 72 in the reverse direction R1 during the maintenance operation is slower than the rotation speed of the intermediate transfer driving roller 72 in the forward direction F1 during the image forming operation. Specifically, during the maintenance operation, the common rotary drive device rotates in the opposite direction to that during the image forming operation, and the rotation speed is slower than that during the image forming operation. In particular, it is preferable that the rotation speed is 1 / 2 or less of the rotation speed during the image forming operation. As a result, even if the photosensitive drum 3 and the developing roller 21 rotate in the reverse directions R3 and R4 (see FIG. 6) in conjunction with the rotation of the intermediate transfer driving roller 72 in the reverse direction R1, the occurrence of malfunctions in the developing device 2 is suppressed. Details regarding the suppression of malfunctions in the developing device 2 will be described later.

[0054] As a result, during maintenance operations, the intermediate transfer belt 71 moves in a circumferential direction I relative to the cleaning blade 91, which is the opposite direction to that during image formation operations. Therefore, foreign matter such as paper powder and waste toner that has accumulated between the cleaning blade 91 and the intermediate transfer belt 71 during image formation operations is removed. Even if the cleaning blade 91 is bent, it returns to its original shape. This eliminates the deterioration of the performance of the cleaning blade 91 in removing waste toner, and more reliably removes waste toner from the intermediate transfer belt 71, making it possible to suppress problems in image formation.

[0055] As described above, the drive source of the photosensitive drum 3 and the developing roller 21 is the same as the drive source of the intermediate transfer driving roller 72, and is a common rotation drive device. Therefore, when the intermediate transfer driving roller 72 rotates in the reverse direction R1, the photosensitive drum 3 and the developing roller 21 also rotate in the opposite direction to the forward rotation directions F3 and F4, respectively. Specifically, when the intermediate transfer driving roller 72 rotates in the reverse direction R1 during maintenance operation, as shown in FIG. 6, the photosensitive drum 3 rotates in the reverse direction R3, and the developing roller 21 rotates in the reverse direction R4.

[0056] Here, the state of the rotation operation of the photosensitive drum 3 during the image forming operation and the maintenance operation is shown in a graph. FIG. 7 is a graph showing the operation state of the photosensitive drum 3 during the image forming operation and the maintenance operation in the image forming apparatus 100 according to the first embodiment of the present invention. In FIG. 7, the vertical axis is the rotation speed of the photosensitive drum 3, the positive side of the vertical axis indicates that the photosensitive drum 3 is rotating in the forward rotation direction F3, and the negative side of the vertical axis indicates that the photosensitive drum 3 is rotating in the reverse direction R3. The horizontal axis is time. Although the state of the rotation operation of the intermediate transfer driving roller 72 (intermediate transfer driven roller 73) and the developing roller 21 is not shown in the graph, these are also driven by a common rotation driving device and therefore rotate in the same manner as the photosensitive drum 3. In other words, when the rotational speed of the photosensitive drum 3 is on the positive side, the rotational speeds of the intermediate transfer drive roller 72 (intermediate transfer driven roller 73) and the developing roller 21 are also on the positive side, and when the rotational speed of the photosensitive drum 3 is on the negative side, the rotational speeds of the intermediate transfer drive roller 72 (intermediate transfer driven roller 73) and the developing roller 21 are also on the negative side.

[0057] As shown in FIG. 7, during image forming operation, the photoconductor drum 3 rotates in the forward direction F3 at a rotation speed A. Then, when the image forming operation is completed, the maintenance operation is started. During the maintenance operation, the photoconductor drum 3 stops rotating and then rotates in the reverse direction R3 at a rotation speed A / 2. In this way, the rotation speed during the maintenance operation is slower than the rotation speed during the image forming operation. Then, after rotating in the reverse direction R3 for a predetermined time, the photoconductor drum 3 stops rotating and then rotates again in the forward direction F at the rotation speed A. Then, when the maintenance operation is completed, the photoconductor drum 3 stops rotating.

[0058] Here, during the maintenance operation, the photosensitive drum 3 and the developing roller 21 rotate in the reverse directions R3 and R4, respectively, but the rotation speed is slower than the rotation in the forward directions F3 and F4 of the image forming operation. Here, the developer 27 supported by the developing roller 21 and forming a magnetic chain moves from the nip N to the doctor blade 22 and the sealing mylar 23 side because the developing roller 21 rotates in the reverse direction R4, but the inertial force acting on the magnetic chain is relatively small because the rotation speed is slow. Therefore, the developer 27 passes near the doctor blade 22 and the sealing mylar 23 with the layer thickness suppressed, and the developer 27 does not interfere with the doctor blade 22 and the sealing mylar 23. In particular, it is possible to prevent the sealing function from being deteriorated due to the deformation of the sealing mylar 23 due to the interference with the developer 27. Therefore, the occurrence of problems in the developing device 2 during the maintenance operation is suppressed. In addition, the amount by which the photosensitive drum 3 and the developing roller 21 rotate in the reverse direction R3 and R4 during the maintenance operation is preferably equal to or less than the amount by which the photosensitive drum 3 and the developing roller 21 rotate in the forward direction F3 and F4 during the maintenance operation. Therefore, the amount by which the intermediate transfer driving roller 72 (intermediate transfer driven roller 73) rotates in the reverse direction R1 (R2) during the maintenance operation is preferably equal to or less than the amount by which the intermediate transfer driving roller 72 (intermediate transfer driven roller 73) rotates in the forward direction F1 (F2) during the maintenance operation. In addition, the distance by which the intermediate transfer belt 71 moves in the circumferential direction I during the maintenance operation is preferably equal to or less than the distance by which the intermediate transfer belt 71 moves in the circumferential direction C during the maintenance operation. This makes it possible to suppress malfunctions in the developing device 2.

[0059] Comparative Example 1 Here, as a comparative example, a state in which the rotation speeds of the intermediate transfer driving roller 72, the intermediate transfer driven roller 73, the photosensitive drum 3, and the developing roller 21 in the reverse directions R1, R2, R3, and R4 during the maintenance operation are equal to the rotation speeds in the forward directions F1, F2, F3, and F4 during the image forming operation will be described with reference to the drawings. Fig. 8 is an enlarged schematic diagram of the developing roller periphery according to Comparative Example 1, showing the state during the maintenance operation.

[0060] During maintenance operations, when the photoconductor drum 3 rotates in the reverse direction R3 at the same rotation speed A as during image formation operations, the rotation has momentum, so that the developer 27 carried by the developing roller 21 and forming magnetic chains approaches the doctor blade 22 and the sealed mylar 23 from the nip portion N while retaining a high layer thickness, and rides up onto the doctor blade 22. As a result, the developer 27 becomes interposed between the doctor blade 22 and the sealed mylar 23, and the developer 27 causes the sealed mylar 23 to bend outward, causing the sealed mylar 23 to fail to function.

[0061] As described above, in the image forming apparatus 100 of this embodiment 1, the intermediate transfer drive roller 72, the photosensitive drum 3 and the developing roller 21 share a common drive source (common rotation drive device), which are driven simultaneously. In the maintenance operation performed after the image forming operation, these rotate in the reverse directions R1, R2 and R3 at a slower rotation speed than the rotation in the forward directions F1, F2 and F3 during the image forming operation. This allows the number of drive sources to be reduced, leading to cost reduction and miniaturization, and furthermore, removal of waste toner is more reliable and malfunctions in the developing device 2 can be prevented.

[0062] Second embodiment The image forming apparatus according to the second embodiment of the present invention has the same configuration as the image forming apparatus 100 according to the first embodiment, but the rotational modes of the intermediate transfer driving roller 72, the photosensitive drum 3, and the developing roller 21 in the reverse directions R1, R2, and R3 during maintenance operation are different. Therefore, these differences will be described with reference to the drawings, and descriptions of the rest will be omitted.

[0063] FIG. 9 is a graph showing the operation state of the photosensitive drum 3 during an image forming operation and a maintenance operation in the image forming apparatus 100 according to the second embodiment of the present invention. In FIG. 9, the vertical axis is the rotation speed of the photosensitive drum 3, the positive side of the vertical axis indicates that the photosensitive drum 3 rotates in the forward rotation direction F3, and the negative side of the vertical axis indicates that the photosensitive drum 3 rotates in the reverse direction R3. The horizontal axis is time. Although the rotation operation states of the intermediate transfer driving roller 72 (intermediate transfer driven roller 73) and the developing roller 21 are not shown in the graph, they are also driven by a common rotation drive device, so that they are in the same rotation state as the photosensitive drum 3. In other words, when the rotation speed of the photosensitive drum 3 is on the positive side, the rotation speeds of the intermediate transfer driving roller 72 (intermediate transfer driven roller 73) and the developing roller 21 are also on the positive side, and when the rotation speed of the photosensitive drum 3 is on the negative side, the rotation speeds of the intermediate transfer driving roller 72 (intermediate transfer driven roller 73) and the developing roller 21 are also on the negative side.

[0064] As shown in Fig. 9, during image forming operation, the photoconductor drum 3 rotates in the forward direction F3 at a rotation speed A. Then, when the image forming operation is completed, the operation proceeds to maintenance operation. During maintenance operation, the photoconductor drum 3 stops rotating and then intermittently rotates in the reverse direction R3 at the rotation speed A. More specifically, the photoconductor drum 3 repeats rotating in the reverse direction R3 at the rotation speed A and stopping. Then, after rotating and stopping three times, it again rotates in the forward direction F at the rotation speed A. Then, when the maintenance operation is completed, the photoconductor drum 3 stops rotating.

[0065] Here, during the maintenance operation, the intermediate transfer drive roller 72 and the developing roller 21 rotate intermittently in the reverse directions R1 and R4 together with the photosensitive drum 3. The rotation speeds are the same as the forward directions F1 and F4 of the image forming operation. During such maintenance operation, the developer 27 carried by the developing roller 21 and forming a magnetic chain rotates in the reverse direction R4 of the developing roller 21, but the momentum of the rotation is suppressed because the developing roller 21 rotates intermittently, and the inertial force acting on the magnetic chain is relatively small. Therefore, the layer thickness of the developer 27 carried by the developing roller 21 is suppressed when the developer 27 passes near the doctor blade 22 and the sealed mylar 23, and the developer 27 does not interfere with the doctor blade 22 and the sealed mylar 23. Therefore, the occurrence of problems in the developing device 2 during the maintenance operation is suppressed.

[0066] Furthermore, during the maintenance operation, the intermediate transfer drive roller 72 also rotates in the same manner as the photosensitive drum 3. This removes foreign matter such as paper powder and waste toner that has accumulated between the cleaning blade 91 and the intermediate transfer belt 71 during the image forming operation. Even if the cleaning blade 91 is bent, it returns to its original shape. This eliminates the deterioration of the performance of the cleaning blade 91 in removing waste toner, and more reliably removes waste toner from the intermediate transfer belt 71, thereby preventing problems from occurring in image formation.

[0067] In the above explanation, the rotational speed of the photosensitive drum 3 in the reverse direction R3 during maintenance operation is the same as the rotational speed A in the forward direction F3 during image formation operation, but it may also be configured to rotate in the reverse direction R3 at a speed slower than the rotational speed A.

[0068] Furthermore, during the maintenance operation, the photosensitive drum 3 is rotated in the reverse direction R3 at the rotation speed A and then stopped three times, but this number of times is not limited to three.

[0069] Third embodiment The image forming apparatus according to the third embodiment of the present invention has the same configuration as the image forming apparatus 100 according to the first embodiment, but the rotational modes of the intermediate transfer driving roller 72, the photosensitive drum 3, and the developing roller 21 in the reverse directions R1, R2, and R3 during maintenance operation are different. Therefore, these differences will be described with reference to the drawings, and descriptions of the rest will be omitted.

[0070] FIG. 10 is a graph showing the operation state of the photosensitive drum 3 during an image forming operation and a maintenance operation in the image forming apparatus 100 according to the third embodiment of the present invention. In FIG. 10, the vertical axis is the rotation speed of the photosensitive drum 3, the positive side of the vertical axis indicates that the photosensitive drum 3 rotates in the forward rotation direction F3, and the negative side of the vertical axis indicates that the photosensitive drum 3 rotates in the reverse direction R3. The horizontal axis is time. Although the rotation operation states of the intermediate transfer driving roller 72 (intermediate transfer driven roller 73) and the developing roller 21 are not shown in the graph, they are also driven by a common rotation drive device, so that they are in the same rotation state as the photosensitive drum 3. In other words, when the rotation speed of the photosensitive drum 3 is on the positive side, the rotation speeds of the intermediate transfer driving roller 72 (intermediate transfer driven roller 73) and the developing roller 21 are also on the positive side, and when the rotation speed of the photosensitive drum 3 is on the negative side, the rotation speeds of the intermediate transfer driving roller 72 (intermediate transfer driven roller 73) and the developing roller 21 are also on the negative side.

[0071] As shown in FIG. 10, during the image forming operation, the photosensitive drum 3 rotates in the forward direction F3 at a rotation speed A. Then, when the image forming operation is completed, the operation proceeds to a maintenance operation. During the maintenance operation, the photosensitive drum 3 stops rotating, then rotates in the reverse direction R3 at a rotation speed A / 2 for a predetermined time, then the photosensitive drum 3 stops rotating, and rotates again in the forward direction F at the rotation speed A. Furthermore, after the photosensitive drum 3 rotates in the forward direction F3 at the rotation speed A for a predetermined time, the photosensitive drum 3 stops rotating, then rotates again in the reverse direction R3 at the rotation speed A / 2 for a predetermined time, then the photosensitive drum 3 stops rotating, and rotates again in the forward direction F at the rotation speed A. Then, when the maintenance operation is completed, the photosensitive drum 3 stops rotating.

[0072] In this way, during the maintenance operation, the photosensitive drum 3 rotates alternately in the reverse direction R3 and the forward direction F3 multiple times. That is, the maintenance operation in the first embodiment is performed multiple times in succession. In the third embodiment, two sets of rotations in the reverse direction R3 and the forward direction F3 are performed, but the number of sets may be other than two. This more reliably eliminates the deterioration of the performance of the cleaning blade 91 in removing waste toner, and prevents problems from occurring in image formation. Also, problems with the developing device 2 are prevented.

[0073] (Fourth embodiment) The above first to third embodiments relate to the image forming apparatus 100 capable of forming a color image on the sheet P, but the present invention is also applicable to a monochrome image forming apparatus that uses only black ink. The image forming apparatus according to the present fourth embodiment is a monochrome one.

[0074] Fig. 11 is an enlarged schematic diagram of the periphery of the photoconductor drum 3a in an image forming apparatus according to a fourth embodiment of the present invention. A monochrome image forming apparatus does not require an intermediate transfer belt 71, and as shown in Fig. 11, the toner is transferred directly from the photoconductor drum 3a to a sheet P. A detailed description of the entire monochrome image forming apparatus will be omitted, but the developing device 2a, cleaning device 9a, photoconductor drum 3a, and transfer roller 11b related to the present invention will be described with reference to Fig. 11.

[0075] The photosensitive drum 3a is an image carrier on whose surface a toner image is formed, and is disposed opposite the transfer roller 11b. A transfer nip area Na is formed between the transfer roller 11b and the photosensitive drum 3a. The transfer roller 11b conveys the conveyed sheet P by pinching it in the transfer nip area Na. When the sheet P passes through the transfer nip area Na, the toner image on the surface of the photosensitive drum 3a is transferred to the sheet P. The sheet P to which the toner image has been transferred is conveyed to a fixing unit (not shown) where the toner image is fixed and an image is formed. The photosensitive drum 3a is driven to rotate by a common rotation drive device, which is a motor, as a drive source.

[0076] The developing device 2a develops the electrostatic latent image to form a toner image on the surface of the photosensitive drum 3a. The developing device 2a includes a developing roller 21a, a doctor blade 22a, conveying members 24a and 25a, and a developing tank 26a. The developing roller 21a is disposed opposite the photosensitive drum 3a, and is driven to rotate by a common rotary drive device, which is the drive source of the photosensitive drum 3a. Therefore, the photosensitive drum 3a and the developing device 2a are driven simultaneously and rotate in the same manner.

[0077] Developing tank 26a contains a developer containing toner and magnetic carrier. Transporting members 24a and 25a are located inside developing tank 26a, and are both spaced apart from the inner wall surface of developing tank 26a. The developer in developing tank 26a is circulated and transported while being stirred by the rotation of transporting members 24a and 25a, and is pumped up and supported on the outer circumferential surface of rotating developing roller 21a.

[0078] During the image forming operation, the toner in the developer carried by the developing roller 21a moves to the photosensitive drum 3a. As described above, the photosensitive drum 3a is also rotated and driven by the same driving source as the developing roller 21a. Specifically, a driving force is transmitted from a common rotation drive device to each of the photosensitive drum 3a and the developing roller 21a via gears (not shown). During the image forming operation, the photosensitive drum 3a rotates in a forward rotation direction F5, and the developing roller 21a rotates in a forward rotation direction F6. The layer thickness of the developer pumped up and carried in a layer on the outer peripheral surface of the developing roller 21a is regulated by the doctor blade 22a as the developing roller 21a rotates in the forward rotation direction F6.

[0079] The cleaning device 9a removes and collects waste toner remaining on the surface of the photosensitive drum 3a without being transferred to the sheet P. The cleaning device 9a includes a collection casing 93a, a support plate 92a installed in the collection casing 93a, and a cleaning blade 91a fixed to the support plate 92a. The cleaning blade 91a is disposed so as to come into contact with the photosensitive drum 3a.

[0080] During image forming operation, when the photosensitive drum 3a is driven to rotate in the forward direction F5, the waste toner remaining on the photosensitive drum 3a is scraped off by the cleaning blade 91a. The waste toner scraped off by the cleaning blade 91a is collected in the collection casing 93a. During maintenance operation after the image forming operation, the photosensitive drum 3a may be driven to rotate in the reverse direction R5. In this case, the developing roller 21a is also driven to rotate in the reverse direction R6.

[0081] In the monochrome image forming apparatus according to the fourth embodiment having such a configuration, image forming operations and maintenance operations are performed in the same manner as those described in the first to third embodiments. That is, during the image forming operation, the photosensitive drum 3a and the developing roller 21a rotate in the forward directions F5 and F6, and during the maintenance operation after the image forming operation, the photosensitive drum 3a and the developing roller 21a also rotate in the reverse directions R5 and R6.

[0082] In a maintenance operation performed after an image forming operation, the photosensitive drum 3a and the developing roller 21a rotate in the reverse directions R5 and R6, so that waste toner remaining on the photosensitive drum 3a can be more reliably removed, and problems caused by the developer in the developing device 2a can be prevented. In addition, because the driving source for the photosensitive drum 3a and the developing roller 21a is a common rotation driving device, the number of driving sources can be reduced, leading to cost reduction and size reduction.

[0083] Although the image forming apparatus according to the first to fourth embodiments of the present invention has been described above, the present invention is not limited to the above-mentioned embodiments. For example, in the first to fourth embodiments, the maintenance operation is performed after the image forming operation, but the maintenance operation does not have to be performed every time the image forming operation is performed. For example, the maintenance operation may be performed after the image forming operation is performed a predetermined number of times, or the time of the image forming operation may be accumulated and the maintenance operation may be performed when the accumulated time of the image forming operation reaches a predetermined time. In addition, the maintenance operation may be performed when it is determined that the maintenance operation is necessary by detecting the state of the waste toner remaining on the intermediate transfer belt 71 or the photosensitive drum 3a or the state of the cleaning blade 91 or 91a.

[0084] The present invention is not limited to the above-described embodiment, but can be embodied in various other forms. Therefore, the embodiment is merely illustrative in all respects and should not be interpreted as being limited. The scope of the present invention is indicated by the claims, and is not restricted in any way by the text of the specification. Furthermore, all modifications and changes within the equivalent scope of the claims are within the scope of the present invention. [Explanation of symbols]

[0085] 1 Optical scanning device 2, 2a Developing device 3, 3a Photoconductor drum (image carrier) 4 Drum cleaning device 5. Charger 6 Intermediate transfer roller 9, 9a Cleaning device 11 Secondary transfer device 11a Secondary transfer roller 11b Transfer roller 12 Fixing device 13 Conveyor roller 14 Registration roller 16 Pickup roller 17 Discharge roller 18 Paper feed cassette 21, 21a Developing roller (developing rotating body) 22, 22a Doctor blade (regulating part) 23 Sealing Mylar 24, 25, 24a, 25a Conveying member 26, 26a Developer tank 27 Developer 31 Fuser roller 32 Pressure roller 50 Image transfer section 70 Intermediate transfer belt device 71 Intermediate transfer belt 72 Intermediate transfer drive roller (transfer drive rotating body) 73 Intermediate transfer driven roller 74 Tension Spring 91, 91a cleaning blade (removal part) 92, 92a Support plate 93, 93a Recovery casing 100 Image forming device 101 Image forming apparatus main body 102 Image reading device 130 Image reading unit 130a Document stand 130b Document reading section 130c Scanning optics 141 Sheet output tray 160 Document feeder 161 Document tray 162 Document output tray C Circumferential direction (forward rotation) I Circumferential direction (reverse) F1~F4 Forward rotation direction R1~R4 Reverse direction Pa, Pb, Pc, Pd Imaging Station S Sheet transport path Sr sheet inversion pathway G Manuscript P sheet (recording medium) N Nip TN, Na transfer nip area

Claims

1. an image carrier on whose surface a toner image is formed; an endless intermediate transfer belt onto which a toner image is transferred from the image carrier and which forms a toner image on a recording medium; a transfer driving rotor around which the intermediate transfer belt is stretched and which drives the intermediate transfer belt; a removing unit disposed in contact with the intermediate transfer belt, for removing waste toner remaining on the intermediate transfer belt after a toner image is formed on the recording medium; a developing rotor disposed opposite the image carrier and supplying toner to the image carrier; a regulating portion disposed adjacent to the developing rotary body and regulating an amount of toner held on a surface of the developing rotary body in order to supply toner to the image carrier; a common rotation drive device that simultaneously drives and rotates the image carrier, the transfer drive rotor, and the developing rotor; the common rotation drive device operates so that the image carrier, the transfer drive rotor, and the developing rotor rotate in a forward direction during an image forming operation for forming a toner image on the recording medium; in a maintenance operation performed after the end of the image forming operation, the common rotation drive device is operated so that the image carrier, the transfer driving rotor, and the developing rotor rotate in a reverse direction that is the opposite direction to the forward rotation direction under rotation conditions different from those during the image forming operation, and then rotate in the forward rotation direction; 2. An image forming apparatus comprising: a transfer drive rotating body and a developing rotating body, the transfer drive rotating body being rotated by the transfer drive rotating body and the developing rotating body being rotated by the transfer drive rotating body;

2. 2. The image forming apparatus according to claim 1, an image forming apparatus characterized in that the rotational speed of the image carrier, the transfer drive rotor, and the developing rotor in the reverse direction during the maintenance operation is slower than the rotational speed of the image carrier, the transfer drive rotor, and the developing rotor in the forward direction during the image forming operation.

3. 3. The image forming apparatus according to claim 1, The image forming apparatus according to claim 1, wherein the rotational operations of the image carrier, the transfer driving rotor, and the developing rotor in the reverse direction in the maintenance operation are performed intermittently a plurality of times.

4. 4. The image forming apparatus according to claim 1, an image forming apparatus characterized in that, during the maintenance operation, a first distance traveled by the intermediate transfer belt when the image carrier, the transfer drive rotating body, and the developing rotating body rotate in a reverse direction is equal to or less than a second distance traveled by the intermediate transfer belt when the intermediate transfer belt rotates in a forward direction after rotating in the reverse direction.

5. 2. The image forming apparatus according to claim 1, an image forming apparatus characterized in that, during the maintenance operation, the common rotation drive device operates so that the image carrier, the transfer drive rotor, and the development rotor alternately rotate in a reverse direction, which is opposite to the forward rotation direction, under rotation conditions different from those during the image forming operation, and in the forward rotation direction multiple times.

Images