Image forming apparatus, image forming method, and image forming program

Abstract

To improve the performance of cleaning performed by a cleaning blade.SOLUTION: An image forming apparatus comprises: an image carrier that carries a toner image formed of toner; a driving unit that rotates the image carrier; a toner removing unit that is in contact with the image carrier and removes the toner remaining on the image carrier while the image carrier is regularly rotated by the driving unit; a deterioration degree evaluation unit 230 that evaluates the degree of deterioration of the image carrier or the toner removing unit; an execution number-of-times determination unit 240 that, based on the degree of deterioration evaluated by the deterioration evaluation unit 230, determines the number of times of the execution of removing operations of reversely rotating the image carrier and subsequently regularly rotating the image carrier; and a removing operation execution unit 250 that controls the driving unit so that the removing operations are executed by the number of times of execution determined b the execution number-of-times determination unit 240.SELECTED DRAWING: Figure 14

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus, an image forming method, and an image forming program, and more particularly to an image forming apparatus having a cleaning blade arranged to contact an intermediate transfer belt, and an image forming method and an image forming program executed in the image forming apparatus. [Background technology]

[0002] In an intermediate transfer type image forming apparatus, a toner image is formed by developing a latent image on a photosensitive drum. The toner image formed on the photosensitive drum is transferred to an intermediate transfer belt. The toner image transferred to the intermediate transfer belt is further transferred to a recording medium such as paper, thereby forming an image on the recording medium. The toner image remaining on the intermediate transfer belt is removed by a cleaning blade provided so as to come into contact with the intermediate transfer belt. Here, poor cleaning may occur due to paper dust being caught between the intermediate transfer belt and the cleaning blade. The caught paper dust can be removed by rotating the intermediate transfer belt in the reverse direction. Furthermore, if the amount of reverse rotation is increased, a larger amount of paper dust is removed.

[0003] For example, Japanese Patent Application Laid-Open No. 2010-26380 describes an image forming apparatus including an image forming unit having at least a latent image carrier and a developing means for developing the latent image on the latent image carrier into a toner image and configured to be detachable from the device main body, an endless belt in contact with the image forming unit which transports a toner image or recording paper, a cleaning means for removing residual toner on the endless belt, and a driving means for driving the endless belt to rotate in both forward and reverse directions, the image forming apparatus being characterized in that it performs a first reversal in which the endless belt rotates in the reverse direction at regular intervals and a second reversal in which the endless belt rotates in the reverse direction after the life end of the image forming unit is detected, and the amount of reversal of the second reversal is greater than the amount of reversal of the first reversal.

[0004] According to the image forming apparatus described in JP 2010-26380 A, when the image forming unit is at the end of its life, the amount of reverse rotation of the endless belt is increased, so that foreign matter on the cleaning unit can be removed more effectively than before. However, before the image forming unit is at the end of its life, the cleaning performance of the cleaning unit is about the same as before. Therefore, it is desired to improve the cleaning performance of the cleaning unit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-26380 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve the above-mentioned problems, and one of the objects of the present invention is to provide an image forming apparatus capable of improving the cleaning performance of a cleaning blade.

[0007] Another object of the present invention is to provide an image forming method capable of improving the cleaning performance of a cleaning blade.

[0008] It is still another object of the present invention to provide an image forming program capable of improving the cleaning performance of a cleaning blade. [Means for solving the problem]

[0009] The present invention has been made to solve the above-mentioned problems, and according to one aspect of the present invention, an image forming apparatus includes an image carrier that carries a toner image composed of toner, a drive unit that rotates the image carrier, a toner removal unit that contacts the image carrier and removes toner remaining on the image carrier while the image carrier is rotated forward by the drive unit, a deterioration degree evaluation unit that evaluates a degree of deterioration of the image carrier or the toner removal unit, an execution count determination unit that determines the number of times to perform a removal operation in which the image carrier is rotated in reverse and then forward based on the degree of deterioration evaluated by the deterioration degree evaluation unit, and a removal operation execution unit that controls the drive unit so that the removal operation is performed the number of times determined by the execution count determination unit.

[0010] According to this aspect, the number of times the removal operation is performed is determined based on the degree of deterioration of the image carrier or the toner removal unit, so that even if the degree of deterioration of the image carrier or the toner removal unit is high, foreign matter caught between the image carrier and the toner removal unit can be efficiently removed. Also, when the degree of deterioration of the image carrier or the toner removal unit is low, the occurrence of turning over of the toner removal unit due to friction between the toner removal unit and the image carrier during the removal operation is suppressed. This improves the cleaning performance of the toner removal unit.

[0011] Preferably, the deterioration degree evaluation section evaluates the deterioration degree of the image carrier or the toner removal section based on the roughness of the surface of the image carrier, the wear degree of the toner removal section, or the distortion of the toner removal section.

[0012] According to this aspect, the degree of deterioration of the image carrier or the toner removal unit can be easily evaluated.

[0013] Preferably, the deterioration degree evaluation unit evaluates the deterioration degree of the image carrier or the toner removal unit based on a total rotation amount of the image carrier.

[0014] According to this aspect, the degree of deterioration of the image carrier or the toner removal unit can be easily evaluated.

[0015] Preferably, the image forming apparatus further includes a simultaneous drive member that rotates simultaneously with the image carrier by the rotational force of the drive unit, and the removal operation execution unit reverses the image carrier by a limited amount of rotation during the removal operation so that the simultaneous drive member does not rotate in reverse.

[0016] According to this aspect, the image carrier and the simultaneous driving member are driven by a common driving unit. Therefore, the image forming apparatus can be made smaller and the cost of the image forming apparatus can be reduced. In addition, since the simultaneous driving member is prevented from rotating in the reverse direction when the image carrier rotates in the reverse direction, problems caused by the simultaneous driving member rotating in the reverse direction can be prevented.

[0017] Preferably, in the removal operation, the removal operation execution portion drives the drive portion such that a rotation amount of the image carrier during forward rotation is greater than a rotation amount of the image carrier during reverse rotation.

[0018] According to this aspect, the foreign matter extracted from between the image carrier and the toner removing section by the reverse rotation of the image carrier can be reliably removed by the forward rotation of the image carrier.

[0019] Preferably, the image forming device further includes an image formation execution unit that causes an image carrier to carry a toner image corresponding to each page based on a job including an image of one or more pages, and the removal operation execution unit controls the drive unit so that a removal operation is executed after the toner image corresponding to the job is carried on the image carrier by the image formation execution unit.

[0020] According to this aspect, the foreign matter caught between the image carrier and the toner removal section is removed while the toner image corresponding to the job is being carried on the image carrier. This makes it possible to prevent a decrease in image quality in the next job. Also, image formation is not hindered by the removal operation. This makes it possible to prevent a decrease in productivity.

[0021] Preferably, when the image forming execution unit accepts the next job while the removal operation execution unit is controlling the drive unit to execute the removal operation, the removal operation execution unit omits execution of the forward rotation of the image carrier in the final removal operation.

[0022] According to this aspect, even if the forward rotation of the image carrier in the final removal operation is omitted, the foreign matter extracted from between the image carrier and the toner removal unit by the reverse rotation of the image carrier in the final removal operation is removed by the first forward rotation of the image carrier during image formation corresponding to the next job. This allows the time for the removal operation to be shortened while maintaining the cleaning performance of the toner removal unit, thereby enabling high-speed image formation corresponding to the next job.

[0023] Preferably, the execution count determination unit determines the execution count of the removing operation based on the type of recording medium onto which the toner image in response to the job is transferred.

[0024] According to this aspect, the number of times the removal operation is performed can be determined more appropriately.

[0025] Preferably, the execution count determination unit determines the execution count of the removing operation based on the number of recording media onto which a toner image has been transferred in response to the job.

[0026] According to this aspect, the number of times the removal operation is performed can be determined more appropriately.

[0027] Preferably, the image forming apparatus further includes a transport unit that transports the recording medium onto which the toner image is transferred, and the execution count determination unit determines the number of times to perform the removal operation based on the supply history of the transport unit transporting the recording medium.

[0028] According to this aspect, the number of times the removal operation is performed can be determined more appropriately.

[0029] Preferably, when a selection of the number of times to be performed of the removal operation is accepted, the execution count determination unit determines the number of times to be performed of the removal operation to be the selected number of times.

[0030] According to this aspect, the removal operation can be performed as many times as the user desires.

[0031] According to another aspect of the present invention, the image forming method includes an image carrying step of carrying a toner image composed of toner by an image carrier, a driving step of rotating the image carrier by a driving unit, a toner removal step of removing toner remaining on the image carrier by a toner removal unit in contact with the image carrier while the image carrier is rotated forward by the driving unit, a deterioration degree evaluation step of evaluating a deterioration degree of the image carrier or the toner removal unit, an execution count determination step of determining the number of times to perform a removal operation in which the image carrier is rotated in reverse and then forward based on the evaluated deterioration degree, and a removal operation execution step of performing the removal operation by the driving unit the number of executions determined by the execution count determination step.

[0032] According to this aspect, the cleaning performance of the toner removal section can be improved.

[0033] According to yet another aspect of the present invention, the image forming program is an image forming program executed by a computer that controls an image forming apparatus, and causes the computer to execute an image carrying step of carrying a toner image composed of toner by an image carrier, a driving step of rotating the image carrier by a driving unit, a toner removal step of removing toner remaining on the image carrier by a toner removal unit in contact with the image carrier while the image carrier is rotated forward by the driving unit, a deterioration degree evaluation step of evaluating the deterioration degree of the image carrier or the toner removal unit, an execution count determination step of determining the number of times to perform a removal operation in which the image carrier is rotated in reverse and then forward based on the evaluated deterioration degree, and a removal operation execution step of performing the removal operation by the driving unit the number of executions determined by the execution count determination step.

[0034] According to this aspect, the cleaning performance of the toner removal section can be improved. [Brief description of the drawings]

[0035] [Figure 1] 1 is a perspective view showing the appearance of an MFP according to the present embodiment. [Diagram 2] 2 is a block diagram showing an outline of the hardware configuration of the MFP. [Diagram 3] FIG. 2 is a schematic side view showing the internal configuration of an image forming unit and a part of a paper feeding unit. [Figure 4] 2 is a schematic diagram showing a part of a drive mechanism for an intermediate transfer belt and an image forming unit; [Diagram 5] FIG. 2 is a side cross-sectional view showing a cleaning blade. [Figure 6] FIG. 2 is a side cross-sectional view showing a cleaning blade. [Figure 7] FIG. 13 is a diagram for explaining a removal operation. [Figure 8] FIG. 13 is a diagram for explaining a removal operation. [Figure 9] 5 is a schematic diagram showing a part of a drive mechanism for the intermediate transfer belt and the image forming unit during reverse rotation. FIG. [Figure 10] 1 is a graph showing the relationship between the degree of deterioration of an intermediate transfer belt or a cleaning blade and the number of pieces of paper dust trapped therein. [Figure 11] 11 is a graph showing a change in the number of trapped paper particles when a removal operation is performed. [Figure 12] 10 is a graph showing the change in static friction coefficient between the intermediate transfer belt and the cleaning blade when the number of times the removing operation is performed is changed. [Figure 13] 10 is a graph showing a change in the number of trapped paper particles when the number of times the removal operation is performed is changed. [Figure 14] 2 is a diagram showing an example of functions of a CPU of the MFP according to the present embodiment. FIG. [Figure 15] 10 is a graph showing an example of a relationship between a deterioration degree of an intermediate transfer belt and the number of pieces of paper dust trapped therein. [Figure 16] 11 is a graph showing an example of the relationship between the number of printed sheets and the number of trapped paper particles. [Figure 17]13 is a graph showing another example of the relationship between the number of printed sheets and the number of trapped paper particles. [Figure 18] 10 is a flowchart showing an example of the flow of an image forming process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings. In the following description, the same components are given the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. In the following description, an MFP will be described as an example of an image forming apparatus. Furthermore, in the MFP (Multi Function Peripheral) described below, recording media on which an image is formed include paper such as plain paper, high-quality paper, recycled paper, or photo paper, and OHP (Over Head Projector) film.

[0037] Fig. 1 is a perspective view showing the appearance of an MFP in this embodiment. Fig. 2 is a block diagram showing an outline of the hardware configuration of the MFP. With reference to Figs. 1 and 2, MFP 100 is an example of an image forming device, and includes a main circuit 110, a document reading unit 130 for reading a document, an automatic document feeder 120 for conveying the document to document reading unit 130, an image forming unit 140 for forming an image on a recording medium based on image data, a paper feed unit 150 for supplying the recording medium to image forming unit 140, and an operation panel 160 as a user interface.

[0038] The automatic document feeder 120 automatically transports multiple documents set on the document tray 125 one by one to a document reading position of the document reading unit 130, and discharges the documents from which images formed on the documents have been read by the document reading unit 130 onto the document discharge tray 127. The automatic document feeder 120 is equipped with a document detection sensor that detects documents placed on the document tray 125.

[0039] The document reading unit 130 has a rectangular reading surface for reading a document. The reading surface is formed by, for example, a platen glass. The automatic document feeder 120 is connected to the main body of the MFP 100 so as to be rotatable about an axis parallel to one side of the reading surface, and can be opened and closed. The document reading unit 130 is disposed below the automatic document feeder 120, and when the automatic document feeder 120 is rotated and opened in an open state, the reading surface of the document reading unit 130 is exposed. Therefore, a user can place a document on the reading surface of the document reading unit 130. The automatic document feeder 120 can change its state between an open state in which the reading surface of the document reading unit 130 is exposed, and a closed state in which the reading surface is covered. The automatic document feeder 120 is provided with a state detection sensor that detects the open state of the automatic document feeder 120.

[0040] The document reading unit 130 includes a light source that irradiates light and a photoelectric conversion element that receives the light, and scans an image formed on a document placed on the reading surface. When a document is placed in the reading area, the light irradiated from the light source is reflected by the document, and the reflected light forms an image on the photoelectric conversion element. When the photoelectric conversion element receives the light reflected by the document, it generates image data by converting the received light into an electrical signal. The document reading unit 130 outputs the image data to a CPU (Central Processing Unit) 111 provided in the main circuit 110.

[0041] The paper feed unit 150 takes out a recording medium stored in one of a plurality of paper feed trays or in a manual feed tray, and conveys the recording medium to the image forming unit 140 .

[0042] Image forming unit 140 is controlled by CPU 111 and forms an image on a recording medium transported by paper feed unit 150 using a well-known electrophotographic method. In this embodiment, image forming unit 140 forms an image of image data input from CPU 111 on a recording medium transported by paper feed unit 150. The recording medium on which the image has been formed is discharged to paper discharge tray 159. The image data output by CPU 111 to image forming unit 140 includes image data input from document reading unit 130 as well as image data such as print data received from the outside.

[0043] The main circuit 110 includes a CPU 111 that controls the entire MFP 100, a communication interface (I / F) unit 112, a ROM (Read Only Memory) 113, a RAM (Random Access Memory) 114, a hard disk drive (HDD) 115 as a large-capacity storage device, a facsimile unit 116, and an external storage device 118. The CPU 111 is connected to an automatic document feeder 120, a document reading unit 130, an image forming unit 140, a paper feeding unit 150, and an operation panel 160, and controls the entire MFP 100.

[0044] The ROM 113 stores a program executed by the CPU 111 or data required to execute the program. The RAM 114 is used as a work area when the CPU 111 executes the program. The RAM 114 also temporarily stores image data continuously sent from the document reading unit 130.

[0045] Operation panel 160 is provided on the top of MFP 100. Operation panel 160 includes display unit 161 and operation unit 163. Display unit 161 is, for example, a liquid crystal display (LCD), and displays an instruction menu for the user, information related to acquired image data, and the like. Note that instead of an LCD, for example, an organic EL (electroluminescence) display can be used as long as it is a device that displays images.

[0046] The operation unit 163 includes a touch panel 165 and a hard key unit 167. The touch panel 165 is of a capacitance type. Note that the touch panel 165 is not limited to the capacitance type, and other types such as a resistive film type, a surface acoustic wave type, an infrared type, or an electromagnetic induction type can be used.

[0047] Touch panel 165 is provided with its detection surface superimposed on the upper or lower surface of display unit 161. Here, the size of the detection surface of touch panel 165 is the same as the size of the display surface of display unit 161. Therefore, the coordinate system of the display surface and the coordinate system of the detection surface are the same. Touch panel 165 detects, on the detection surface, a position indicated by the user on the display surface of display unit 161, and outputs the coordinates of the detected position to CPU 111. Since the coordinate system of the display surface and the coordinate system of the detection surface are the same, the coordinates output by touch panel 165 can be replaced with the coordinates of the display surface.

[0048] Hard key unit 167 includes a plurality of hard keys. The hard keys are, for example, contact switches. Touch panel 165 detects a position on the display surface of display unit 161 designated by the user. Since the user often operates MFP 100 in an upright position, the display surface of display unit 161, the operation surface of touch panel 165, and hard key unit 167 are arranged facing upward. This is so that the user can easily view the display surface of display unit 161 and can easily designate operation unit 163 with a finger.

[0049] The communication I / F unit 112 is an interface for connecting the MFP 100 to a network. The communication I / F unit 112 communicates with other computers connected to the network using a communication protocol such as TCP (Transmission Control Protocol) or UDP (User Datagram Protocol). The network to which the communication I / F unit 112 is connected is a local area network (LAN), and the connection form may be either wired or wireless. The network is not limited to a LAN, and may be a wide area network (WAN), a public switched telephone network (PSTN), the Internet, or the like.

[0050] Facsimile unit 116 is connected to a public switched telephone network (PSTN) and transmits facsimile data to the PSTN or receives facsimile data from the PSTN. Facsimile unit 116 stores the received facsimile data in HDD 115, converts the data into print data that can be printed by image forming unit 140, and outputs the data to image forming unit 140. As a result, image forming unit 140 forms an image of the facsimile data received by facsimile unit 116 on paper. Facsimile unit 116 also converts the data stored in HDD 115 into facsimile data and transmits the data to a facsimile device connected to the PSTN.

[0051] External storage device 118 is controlled by CPU 111, and is equipped with CD-ROM (Compact Disk Read Only Memory) 118A or a semiconductor memory. In this embodiment, an example in which CPU 111 executes a program stored in ROM 113 will be described, but CPU 111 may control external storage device 118 to read a program to be executed by CPU 111 from CD-ROM 118A, store the read program in RAM 114, and execute it.

[0052] The recording medium for storing the program executed by CPU 111 is not limited to CD-ROM 118A, but may be a flexible disk, a cassette tape, an optical disk (MO (Magnetic Optical Disc) / MD (Mini Disc) / DVD (Digital Versatile Disc)), an IC card, an optical card, a semiconductor memory such as a mask ROM or an EPROM (Erasable Programmable ROM), or the like. Furthermore, CPU 111 may download a program from a computer connected to the network and store it in HDD 115, or a computer connected to the network may write a program to HDD 115, and the program stored in HDD 115 may be loaded into RAM 114 and executed by CPU 111. The program here includes not only a program that can be directly executed by CPU 111, but also a source program, a compressed program, an encrypted program, and the like.

[0053] FIG. 3 is a schematic side view showing the internal configuration of a part of the image forming unit and the paper feeding unit. Referring to FIG. 3, inside MFP 100, main transport path 41 indicated by a thick dotted arrow is formed so as to basically extend in the vertical direction. Main transport path 41 is a path for guiding paper transported from paper feeding unit 150 to paper discharge tray 159 through image forming unit 140. In the main transport path 41 of this example, lower end 30 opposite to upper end 13 located above image forming unit 140 constitutes an entrance for receiving paper from paper feeding unit 150. In addition, upper end 13 of main transport path 41 constitutes an exit for discharging paper after image formation to paper discharge tray 159. Paper discharge roller 15 is provided at upper end 13 of main transport path 41.

[0054] The paper feed unit 150 includes three paper feed trays 151, 152, and 153 and a manual feed tray 154. The three paper feed trays 151, 152, and 153 are stacked and arranged in this order from top to bottom. The manual feed tray 154 is provided on a side wall of the MFP 100 and is located below the image forming unit 140. As indicated by thick dashed lines in FIG. 3, the paper feed trays 151, 152, and 153 and the manual feed tray 154 are connected to the lower end 30 of the main transport path 41 through sub-transport paths SP1, SP2, SP3, and SP4, respectively.

[0055] A pickup roller 151p and a paper feed roller 151r are provided corresponding to paper feed tray 151. Paper feed roller 151r is provided on sub-transport path SP1. A pickup roller 152p and a paper feed roller 152r are provided corresponding to paper feed tray 152. Paper feed roller 152r is provided on sub-transport path SP2. A pickup roller 153p and a paper feed roller 153r are provided corresponding to paper feed tray 153. Paper feed roller 153r is provided on sub-transport path SP3. A pickup roller 154p and a paper feed roller 154r are provided corresponding to manual feed tray 154. Paper feed roller 154r is provided on sub-transport path SP4. The operation of taking out and transporting a recording medium from each of paper feed trays 151, 152, 153 and manual feed tray 154 is the same, so here, paper feed tray 151 will be described as an example.

[0056] One or more recording media are stored in a stacked state in the paper feed tray 151. The paper feed tray 151 has a lift-up mechanism that pushes up the one or more recording media stored therein. The pickup roller 151p is biased by an elastic member such as a spring so as to abut from above against the uppermost recording medium of the one or more recording media stored in the paper feed tray 151. The pickup roller 151p presses the recording medium from above. As the pickup roller 151p rotates, the uppermost recording medium is sent to the sub-transport path SP1 due to friction between the pickup roller 151p and the recording medium. The recording medium sent to the sub-transport path SP1 is supplied to the main transport path 41 by the paper feed roller 151r.

[0057] In the MFP 100, during image formation, a tray that contains a recording medium on which an image is to be formed is selected as a target tray from among the three paper feed trays 151, 152, and 153 and the manual feed tray 154. A pickup roller and a paper feed roller corresponding to the tray selected as the target tray from among the three paper feed trays 151, 152, and 153 and the manual feed tray 154 are operated, and the recording medium is supplied from the tray selected as the target tray to the main transport path 41 through one of the sub-transport paths SP1, SP2, SP3, and SP4.

[0058] The image forming section 140 forms an image by an intermediate transfer method. The image forming section 140 includes image forming units 51Y, 51M, 51C, and 51K for yellow, magenta, cyan, and black, respectively. At least one of the image forming units 51Y, 51M, 51C, and 51K is driven to form an image on a recording medium. A full-color image is formed by driving all of the image forming units 51Y, 51M, 51C, and 51K. Print data for yellow, magenta, cyan, and black are input to the image forming units 51Y, 51M, 51C, and 51K, respectively. The image forming units 51Y, 51M, 51C, and 51K differ only in the color of the toner they handle, so here, the image forming unit 51Y for forming a yellow image will be described.

[0059] The image forming unit 51Y includes an exposure head 52Y to which yellow printing data is input, a photoconductor drum 53Y, a charging roller 54Y, a developing roller 55Y, and a primary transfer roller 56Y. The exposure head 52Y emits a laser beam in response to the received printing data (electrical signal). The emitted laser beam is one-dimensionally scanned by a polygon mirror included in the exposure head 52Y to expose the photoconductor drum 53Y. The direction in which the photoconductor drum 53Y is one-dimensionally scanned is the main scanning direction. The charging roller 54Y is an elastic body and is disposed so as to be in pressure contact with the photoconductor drum 53Y. After the photoconductor drum 53Y is charged by the charging roller 54Y, the laser beam emitted by the exposure head 52Y is irradiated onto the photoconductor drum 53Y. As a result, an electrostatic latent image is formed on the photoconductor drum 53Y. Subsequently, the developing roller 55Y places toner on the electrostatic latent image to form a toner image. The toner image formed on the photosensitive drum 53Y is transferred onto an intermediate transfer belt 57 (image carrier) by a primary transfer roller 56Y.

[0060] Similarly, image forming unit 51M includes exposure head 52M to which magenta print data is input, photoconductor drum 53M, charging roller 54M, developing roller 55M, and primary transfer roller 56M. Image forming unit 51C includes exposure head 52C to which cyan print data is input, photoconductor drum 53C, charging roller 54C, developing roller 55C, and primary transfer roller 56C. Image forming unit 51K includes exposure head 52K to which black print data is input, photoconductor drum 53K, charging roller 54K, developing roller 55K, and primary transfer roller 56K.

[0061] The intermediate transfer belt 57 is suspended by the drive roller 54 and the roller 54A so as not to slacken. When the drive roller 54 rotates counterclockwise in the figure, the intermediate transfer belt 57 rotates counterclockwise in the figure at a predetermined speed. In conjunction with the rotation of the intermediate transfer belt 57, the roller 54A rotates counterclockwise.

[0062] As a result, the image forming units 51Y, 51M, 51C, and 51K sequentially transfer the toner images onto the intermediate transfer belt 57. The timing at which each of the image forming units 51Y, 51M, 51C, and 51K transfers a toner image onto the intermediate transfer belt 57 is adjusted by detecting a reference mark provided on the intermediate transfer belt 57. As a result, the yellow, magenta, cyan, and black toner images are superimposed on the intermediate transfer belt 57.

[0063] In the above-mentioned main transport path 41, a timing roller 45, a secondary transfer roller 47, and a fixing roller 49 are arranged in this order at intervals from the lower end 30 to the upper end 13. The secondary transfer roller 47 is made of an elastic body such as foamed rubber, and is in pressure contact with roller 54A with intermediate transfer belt 57 sandwiched therebetween. The recording medium supplied from paper supply unit 150 to main transport path 41 is sent to timing roller 45.

[0064] The timing roller 45 adjusts the transport state of the recording medium in the main transport path 41 so that the recording medium reaches between the roller 54A and the secondary transfer roller 47 at the timing when the toner image formed on the intermediate transfer belt 57 reaches between the roller 54A and the secondary transfer roller 47. The recording medium transported by the timing roller 45 is pressed against the intermediate transfer belt 57 by the secondary transfer roller 47, and the yellow, magenta, cyan or black toner image formed on the intermediate transfer belt 57 in a superimposed manner is transferred to the recording medium by charging the secondary transfer roller 47. The voltage applied to the secondary transfer roller 47 is controlled by the CPU 111 so that the charge amount of the secondary transfer roller 47 is a value suitable for the basis weight of the recording medium.

[0065] The recording medium onto which the toner image has been transferred is transported to and heated by fixing rollers 49. This melts the toner and fixes it to the recording medium. Thereafter, the recording medium on which the image has been formed is discharged by discharge rollers 15 from the upper end 13 of the main transport path 41 onto a discharge tray 159. The temperature of the fixing rollers 49 is controlled by the CPU 111 so that it is a value suitable for the basis weight of the recording medium.

[0066] Fig. 4 is a schematic diagram showing a part of the drive mechanism of the intermediate transfer belt and the image forming unit. In Fig. 4, the drive mechanism for driving the photoconductor drum 53Y of the image forming unit 51Y is shown, and the drive mechanism for driving the developing roller 55Y is omitted. In addition, the drive mechanisms for driving the image forming units 51M, 51C, and 51K are omitted, but these drive mechanisms have the same configuration as the drive mechanism for driving the image forming unit 51Y. The same applies to Fig. 9 described later.

[0067] 4, the image forming section 140 includes a common motor 60 (drive section) for driving the intermediate transfer belt 57 and the image forming units 51Y, 51M, 51C, and 51K. A belt drive gear 61, a photoconductor drive gear 62, and a development drive gear (not shown) are attached to the rotation shaft of the motor 60. The belt drive gear 61 is shown by a dotted line. A belt driven gear 63 is attached to the rotation shaft of the drive roller 54 of the intermediate transfer belt 57. A photoconductor driven gear 65 is attached to the rotation shaft of the photoconductor drum 53Y. A relay gear 64 is disposed between the photoconductor drive gear 62 and the photoconductor driven gear 65. A development driven gear (not shown) is attached to the rotation shaft of the development roller 55Y.

[0068] The belt driving gear 61 engages with the belt driven gear 63. The photoconductor driving gear 62 engages with the photoconductor driven gear 65 via the relay gear 64. The development driving gear engages with the development driven gear. As described later, the backlash between the photoconductor driving gear 62 and the photoconductor driven gear 65 and the backlash between the development driving gear and the development driven gear are larger than the backlash between the belt driving gear 61 and the belt driven gear 63. When the motor 60 rotates in one direction, the intermediate transfer belt 57, the photoconductor drums 53Y, 53M, 53C, and 53K, and the development rollers 55Y, 55M, 55C, and 55K all rotate in a predetermined direction. On the other hand, when the motor 60 rotates in the reverse direction, the intermediate transfer belt 57, the photoconductor drums 53Y, 53M, 53C, and 53K, and the development rollers 55Y, 55M, 55C, and 55K all rotate in a direction opposite to the above-mentioned predetermined direction. Therefore, the photoconductor drums 53Y, 53M, 53C, and 53K and the developing rollers 55Y, 55M, 55C, and 55K are simultaneously driven members that rotate simultaneously with the intermediate transfer belt 57 by the torque of the motor 60.

[0069] In this example, the image forming section 140 does not have a clutch mechanism for disconnecting the motor 60 from the image forming units 51Y, 51M, 51C, and 51K. Therefore, the MFP 100 can be reduced in cost and size. In the following description, the rotation of the intermediate transfer belt 57, the photoconductor drums 53Y, 53M, 53C, and 53K, and the developing rollers 55Y, 55M, 55C, and 55K during toner image transfer is called forward rotation. The rotation of the intermediate transfer belt 57, the photoconductor drums 53Y, 53M, 53C, and 53K, and the developing rollers 55Y, 55M, 55C, and 55K in the direction opposite to the forward rotation is called reverse rotation. In FIG. 4, the rotation direction of each gear during forward rotation is indicated by an arrow.

[0070] Image forming section 140 further includes cleaning blade 58 (toner removal section). FIGS. 5 and 6 are side cross-sectional views showing the cleaning blade. Referring to FIG. 5, cleaning blade 58 is formed of, for example, a urethane rubber-based elastic body, and is disposed so as to be able to rub against intermediate transfer belt 57. After a toner image is transferred to a recording medium, cleaning blade 58 removes remaining toner image RT by scraping it off on intermediate transfer belt 57 as intermediate transfer belt 57 rotates forward. This cleans intermediate transfer belt 57.

[0071] When the recording medium passes between the drive roller 54 and the secondary transfer roller 47, paper dust PD such as fine fibers or fillers generated from the recording medium may adhere to the intermediate transfer belt 57. In this case, the paper dust PD is carried to the cleaning blade 58 by the intermediate transfer belt 57, and is removed from the intermediate transfer belt 57 together with the remaining toner image RT by the cleaning blade 58. However, referring to FIG. 6, the paper dust PD may not be removed by the cleaning blade 58 and may be caught between the cleaning blade 58 and the intermediate transfer belt 57. When the paper dust PD is caught between the cleaning blade 58 and the intermediate transfer belt 57, the contact between the cleaning blade 58 and the intermediate transfer belt 57 becomes uneven, causing a cleaning failure. In this case, the remaining toner image RT is not sufficiently removed, so that streaky noise adheres to the recording medium during the next image formation, degrading the image quality.

[0072] Therefore, a removal operation is performed to remove the paper dust PD caught between the cleaning blade 58 and the intermediate transfer belt 57. FIGS. 7 and 8 are diagrams for explaining the removal operation. Referring to FIG. 7, the intermediate transfer belt 57 is rotated in the reverse direction, so that the caught paper dust PD is pulled out from between the cleaning blade 58 and the intermediate transfer belt 57. Thereafter, referring to FIG. 8, the intermediate transfer belt 57 is rotated in the forward direction, so that the paper dust PD pulled out from between the cleaning blade 58 and the intermediate transfer belt 57 is scraped off by the cleaning blade 58. The removal operation, which is composed of the reverse rotation of the intermediate transfer belt 57 in FIG. 7 and the forward rotation of the intermediate transfer belt 57 in FIG. 8, is performed, so that the paper dust PD is removed from the intermediate transfer belt 57.

[0073] The removal operation is preferably performed, for example, at a timing when MFP 100 stops immediately after the image forming operation is completed. In this case, while a toner image corresponding to a print job is carried on intermediate transfer belt 57, foreign matter caught between intermediate transfer belt 57 and cleaning blade 58 is removed. Therefore, it is possible to prevent a decrease in image quality in the next print job. In addition, image formation is not hindered by the removal operation. This prevents a decrease in productivity. However, the execution timing of the removal operation is not limited to this example, and the removal operation may be performed at any timing.

[0074] In the removal operation, by increasing the amount of reverse rotation of the intermediate transfer belt 57, it is possible to remove a larger amount of paper powder PD caught between the cleaning blade 58 and the intermediate transfer belt 57. However, as described above, the intermediate transfer belt 57, the photoconductor drums 53Y, 53M, 53C, and 53K, and the developing rollers 55Y, 55M, 55C, and 55K are each driven by the common motor 60. In this case, when the amount of reverse rotation of the intermediate transfer belt 57 is increased, the amount of reverse rotation of the photoconductor drum 53Y also increases.

[0075] When the toner adhering to the photoconductor drum 53Y from the developing roller 55Y reaches the charging roller 54Y due to the reverse rotation of the photoconductor drum 53Y, the charging roller 54Y may be contaminated, causing a charging failure of the photoconductor drum 53Y. In addition, when the photoconductor drum 53Y rotates in the reverse direction, the amount of developer transported from the developing roller 55Y to the photoconductor drum 53Y is not adjusted. Therefore, a large amount of developer is transported to the photoconductor drum 53Y, which may cause clogging of the developer. In addition, when the developer is a two-component developer containing toner and carrier, the carrier may adhere to the photoconductor drum 53Y. These problems also occur in the photoconductor drums 53M, 53C, and 53K.

[0076] 9 is a schematic diagram showing a part of the drive mechanism of the intermediate transfer belt and the image forming unit during reverse rotation. In order to prevent the above-mentioned problem, referring to FIG. 9, even if the intermediate transfer belt 57 rotates in reverse, the amount of reverse rotation of the intermediate transfer belt 57 in the removal operation is limited so that the photoconductor drums 53Y, 53M, 53C, and 53K and the developing rollers 55Y, 55M, 55C, and 55K do not rotate in reverse.

[0077] Specifically, the backlash between the photoconductor driving gear 62 and the photoconductor driven gear 65 is larger than the backlash between the belt driving gear 61 and the belt driven gear 63. Also, the backlash between the development driving gear (not shown) and the development driven gear is larger than the backlash between the belt driving gear 61 and the belt driven gear 63. Therefore, the amount of reverse rotation of the intermediate transfer belt 57 in the removal operation is set to be less than the backlash between the photoconductor driving gear 62 and the photoconductor driven gear 65 and less than the backlash between the development driving gear and the development driven gear.

[0078] That is, the amount of rotation of the motor 60 during reverse rotation is equal to or greater than the backlash between the belt driving gear 61 and the belt driven gear 63, less than the backlash between the photoconductor driving gear 62 and the photoconductor driven gear 65, and less than the backlash between the development driving gear and the development driven gear. As a result, as shown by the arrows in Fig. 9, even if the belt driven gear 63 (intermediate transfer belt 57) rotates in reverse due to the motor 60 rotating in the reverse direction, the photoconductor driven gear 65 (photoconductor drum 53Y) is prevented from rotating in reverse. Similarly, the development roller 55Y is prevented from rotating in reverse.

[0079] In addition, by performing the removing operation multiple times, it is possible to increase the overall amount of reverse rotation of the intermediate transfer belt 57 while limiting the amount of reverse rotation of the intermediate transfer belt 57 per removing operation. In each removing operation, it is preferable that the amount of rotation of the intermediate transfer belt 57 during forward rotation is greater than the amount of rotation of the intermediate transfer belt 57 during reverse rotation. This allows the foreign matter removed from between the intermediate transfer belt 57 and the cleaning blade 58 by the reverse rotation of the intermediate transfer belt 57 to be reliably removed by the forward rotation of the intermediate transfer belt 57. In addition, even if the removing operation is repeated, it is possible to reliably prevent the photoconductor drums 53Y, 53M, 53C, and 53K and the developing rollers 55Y, 55M, 55C, and 55K from rotating in the reverse direction.

[0080] In this way, in this example, even when the intermediate transfer belt 57 rotates in the reverse direction, the operation of the motor 60 is controlled so that the photoconductor drums 53Y, 53M, 53C, and 53K and the developing rollers 55Y, 55M, 55C, and 55K do not rotate in the reverse direction, but the embodiment is not limited to this. When the reverse rotation amount of the photoconductor drums 53Y, 53M, 53C, and 53K and the developing rollers 55Y, 55M, 55C, and 55K is equal to or less than a certain amount, the above-mentioned problem does not occur. Therefore, when the intermediate transfer belt 57 rotates in the reverse direction, the operation of the motor 60 may be controlled so that the reverse rotation amount of the photoconductor drums 53Y, 53M, 53C, and 53K and the developing rollers 55Y, 55M, 55C, and 55K is equal to or less than a certain amount. Also, in each removal operation, the rotation amount of the intermediate transfer belt 57 during forward rotation may be equal to or slightly smaller than the rotation amount of the intermediate transfer belt 57 during reverse rotation.

[0081] The number of pieces of paper dust PD caught between the cleaning blade 58 and the intermediate transfer belt 57 (number of pieces of paper dust caught) varies depending on the degree of deterioration of the intermediate transfer belt 57 or the cleaning blade 58. FIG. 10 is a graph showing the relationship between the degree of deterioration of the intermediate transfer belt or the cleaning blade and the number of pieces of paper dust caught. Referring to FIG. 10, when the degree of deterioration of the intermediate transfer belt 57 or the cleaning blade 58 is small, the number of pieces of paper dust PD caught is small. On the other hand, due to deterioration over time, the surface of the intermediate transfer belt 57 becomes rough and the cleaning blade 58 becomes deformed or worn. In this way, when the degree of deterioration of the intermediate transfer belt 57 or the cleaning blade 58 increases, the number of pieces of paper dust PD caught increases.

[0082] Fig. 11 is a graph showing the change in the number of pieces of paper dust caught when a removal operation is performed. Fig. 12 is a graph showing the change in the static friction coefficient between the intermediate transfer belt and the cleaning blade when the number of times the removal operation is performed is changed. In Fig. 11, the removal operation is performed every time a certain number of print jobs are completed. Also, the change in the number of pieces of paper dust PD caught due to the intermediate transfer belt 57 rotating forward during the image forming operation is shown by a solid line, and the change in the number of pieces of paper dust PD caught due to the intermediate transfer belt 57 rotating backward during the removal operation is shown by a dotted line. The same is true in Fig. 13 described later.

[0083] 11, when the deterioration degree of the intermediate transfer belt 57 or the cleaning blade 58 is small, the number of pieces of paper dust PD caught is small, so that the caught paper dust PD can be sufficiently removed each time the removal operation is performed. On the other hand, when the removal operation is performed, the lubricant supplied to the tip of the cleaning blade 58 is removed by the cleaning blade 58 together with the remaining toner image RT and the paper dust PD. Therefore, referring to FIG. 12, when the deterioration degree of the intermediate transfer belt 57 or the cleaning blade 58 is small, if the number of times the removal operation is performed is increased, the lubricant is removed excessively, and the static friction coefficient between the intermediate transfer belt 57 and the cleaning blade 58 increases. When the static friction coefficient increases to a certain value or more, the cleaning blade 58 turns over.

[0084] When the intermediate transfer belt 57 or cleaning blade 58 is highly deteriorated, the number of pieces of paper dust PD trapped is large, and therefore the trapped paper dust PD cannot be sufficiently removed by performing the removal operation only once. Therefore, when the number of times the removal operation is performed is small, the number of pieces of paper dust PD trapped increases with an increase in the number of printed sheets. When the number of pieces of paper dust PD trapped increases to a certain value or more, a cleaning failure occurs. On the other hand, when the intermediate transfer belt 57 or cleaning blade 58 is deteriorated, the static friction coefficient between the intermediate transfer belt 57 and the cleaning blade 58 decreases, so that the cleaning blade 58 hardly turns over even if the lubricant supplied to the tip of the cleaning blade 58 runs out.

[0085] Therefore, the number of times the removal operation is performed is changed according to the degree of deterioration of the intermediate transfer belt 57 or the cleaning blade 58. FIG. 13 is a graph showing the change in the number of pieces of paper dust trapped when the number of times the removal operation is performed is changed. Referring to FIG. 13, when the degree of deterioration of the intermediate transfer belt 57 or the cleaning blade 58 is small, the number of times the removal operation is performed is determined to be one. In this case, as in the example of FIG. 11, the trapped paper dust PD can be sufficiently removed each time the removal operation is performed. On the other hand, when the degree of deterioration of the intermediate transfer belt 57 or the cleaning blade 58 is large, the number of times the removal operation is performed is determined to be two. According to this configuration, the number of pieces of paper dust PD trapped is reduced compared to the example of FIG. 11. This can delay the time until a cleaning failure occurs.

[0086] FIG. 14 is a diagram showing an example of functions of the CPU of the MFP in the present embodiment. The functions shown in FIG. 14 are realized by CPU 111 included in MFP 100 by executing a recording medium conveying program stored in ROM 113, HDD 115, or CD-ROM 118A. Referring to FIG. 14, CPU 111 includes image formation reception unit 210, image formation execution unit 220, deterioration degree evaluation unit 230, execution count determination unit 240, and removal operation execution unit 250. Image formation reception unit 210 receives an execution instruction for image formation from a user as a print job including an image of one or more pages. In response to image formation reception unit 210 receiving the print job, image formation execution unit 220 controls image formation unit 140 to cause intermediate transfer belt 57 to carry a toner image corresponding to each page, and controls paper feed unit 150 to convey the recording medium, thereby executing image formation on the recording medium.

[0087] The deterioration degree evaluation unit 230 evaluates the deterioration degree of the intermediate transfer belt 57 or the cleaning blade 58. In response to the image formation reception unit 210 receiving a print job, the deterioration degree of the intermediate transfer belt 57 or the cleaning blade 58 may be evaluated based on some or all of the roughness of the surface of the intermediate transfer belt 57, the wear degree of the cleaning blade 58, or the distortion of the cleaning blade 58.

[0088] In this example, deterioration degree evaluation unit 230 includes a print history acquisition unit 231 and a rotation history acquisition unit 232. Print history acquisition unit 231 acquires the total number of recording media on which images are formed (printed) by MFP 100 as the print history. Rotation history acquisition unit 232 acquires the total amount of rotation of intermediate transfer belt 57 as the rotation history. Deterioration degree evaluation unit 230 evaluates the deterioration degree of intermediate transfer belt 57 or cleaning blade 58 based on at least one of the print history acquired by print history acquisition unit 231 and the rotation history acquired by rotation history acquisition unit 232.

[0089] The execution count determination unit 240 determines the execution count of the removal operation according to the deterioration level of the intermediate transfer belt 57 or the cleaning blade 58 evaluated by the deterioration level evaluation unit 230. The relationship between the deterioration level of the intermediate transfer belt 57 or the cleaning blade 58 and the execution count of the removal operation is determined in advance. An example of the relationship between the deterioration level of the intermediate transfer belt 57 or the cleaning blade 58 and the execution count of the removal operation will be described later.

[0090] In this example, the execution count determination unit 240 includes a selection receiving unit 241, a medium type acquisition unit 242, a paper feed history acquisition unit 243, and a print count acquisition unit 244. The selection receiving unit 241 receives a selection of the number of times to perform the removal operation. The user can select the number of times to perform the removal operation by operating the operation unit 163 of the operation panel 160. When the selection of the number of times to perform the removal operation is received by the selection receiving unit 241, the execution count determination unit 240 determines the number of times to perform the removal operation selected by the user without determining the number of times to perform the removal operation according to the deterioration degree of the intermediate transfer belt 57 or the cleaning blade 58. Note that the execution count determination unit 240 may change the number of times to the number of times selected by the user after determining the number of times to perform the removal operation according to the deterioration degree of the intermediate transfer belt 57 or the cleaning blade 58.

[0091] The medium type acquisition unit 242 acquires the type of recording medium on which an image is formed. The types of recording medium include, for example, plain paper, fine paper, recycled paper, photo paper, and OHP film. The type of recording medium may be acquired based on a user's selection. Alternatively, if the paper feed unit 150 has a sensor for identifying the type of recording medium, the type of recording medium may be acquired based on the identification result of the sensor. When the type of recording medium is acquired by the medium type acquisition unit 242, the execution count determination unit 240 corrects the determined execution count of the removal operation based on the acquired type of recording medium. For example, the amount of paper dust PD caught between the cleaning blade 58 and the intermediate transfer belt 57 when the recording medium is recycled paper is greater than the amount of paper dust PD caught between the cleaning blade 58 and the intermediate transfer belt 57 when the recording medium is plain paper. Therefore, when the recording medium is recycled paper, the execution count of the removal operation is corrected to be greater than when the recording medium is plain paper.

[0092] The paper feed history acquisition unit 243 acquires the usage amount (for example, the total rotation amount) of the paper feed rollers 151r, 152r, 153r, and 154r as the paper feed history. When the paper feed history acquisition unit 243 acquires the paper feed history, the execution count determination unit 240 corrects the determined execution count of the removal operation based on the acquired paper feed history. The more the paper feed rollers 151r, 152r, 153r, and 154r are used, the more the amount of paper dust PD adhering to the paper feed rollers 151r, 152r, 153r, and 154r increases. Therefore, the more the paper feed rollers 151r, 152r, 153r, and 154r are used, the more the amount of paper dust PD transported together with the recording medium increases. For example, the amount of paper dust PD caught between the cleaning blade 58 and the intermediate transfer belt 57 when the paper feed history is long is greater than the amount of paper dust PD caught between the cleaning blade 58 and the intermediate transfer belt 57 when the paper feed history is short. Therefore, when the paper feed history is long, the removal operation is corrected to be performed more frequently than when the paper feed history is short.

[0093] The print number acquisition unit 244 acquires the number of copies of the recording medium on which image formation is performed in the print job as the print number. When the print number acquisition unit 244 acquires the print number, the execution count determination unit 240 corrects the determined execution count of the removal operation based on the acquired print number. An example of the relationship between the print number and the execution count of the removal operation will be described later.

[0094] When two or more pieces of information among the type of recording medium, the paper feed history, and the number of printed sheets are acquired, the number of times the removal operation is performed may be corrected as the sum of the number of times based on each of the acquired two or more pieces of information. On the other hand, depending on the combination of two or more pieces of information among the type of recording medium, the paper feed history, and the number of printed sheets, the appropriate number of times the removal operation is performed may differ from the sum of the number of times based on each of the acquired two or more pieces of information. Therefore, when two or more pieces of information among the type of recording medium, the paper feed history, and the number of printed sheets are acquired, the number of times the removal operation is performed may be corrected based on the combination of the acquired two or more pieces of information. The relationship between the combination of two or more pieces of information among the type of recording medium, the paper feed history, and the number of printed sheets and the appropriate number of times the removal operation is performed may be stored in advance as a table in the HDD 115 or the like.

[0095] The removal operation execution unit 250 drives the intermediate transfer belt 57 so that the removal operation is executed the number of times determined or corrected by the execution count determination unit 240. During reverse rotation in the removal operation, the rotation amount of the intermediate transfer belt 57 is limited to a predetermined constant rotation amount so that the photoconductor drums 53Y, 53M, 53C, and 53K and the developing rollers 55Y, 55M, 55C, and 55K do not rotate in reverse. Furthermore, during forward rotation in the removal operation, the absolute value of the rotation amount of the intermediate transfer belt 57 is made larger than the absolute value of the rotation amount of the intermediate transfer belt 57 during reverse rotation.

[0096] Furthermore, in this example, if there is a next print job, the execution of the forward rotation of the intermediate transfer belt 57 in the final removal operation is omitted. Even if the execution of the forward rotation of the intermediate transfer belt 57 in the final removal operation is omitted, the foreign matter removed from between the intermediate transfer belt 57 and the cleaning blade 58 by the reverse rotation of the intermediate transfer belt 57 in the final removal operation is removed by the first forward rotation of the intermediate transfer belt 57 at the time of image formation corresponding to the next job. Therefore, while maintaining the cleaning performance of the cleaning blade 58, the time of the removal operation is shortened, and the image formation corresponding to the next job can be performed at high speed. In other words, the image formation corresponding to the next print job can be started quickly. On the other hand, even if there is a next print job, the execution of the forward rotation of the intermediate transfer belt 57 in the final removal operation may be performed without being omitted.

[0097] 15 is a graph showing an example of the relationship between the deterioration degree of the intermediate transfer belt and the number of pieces of paper dust trapped. Referring to FIG. 15, when the deterioration degree of the intermediate transfer belt 57 is small, specifically, when the total rotation amount of the intermediate transfer belt 57 is 30 km, the number of pieces of paper dust PD trapped per 10 printed sheets of the recording medium is 1. On the other hand, when the deterioration degree of the intermediate transfer belt 57 is large, specifically, when the total rotation amount of the intermediate transfer belt 57 is 150 km, the number of pieces of paper dust PD trapped per 10 printed sheets of the recording medium is 5. Therefore, the number of pieces of paper dust PD trapped is proportional to the deterioration degree of the intermediate transfer belt 57.

[0098] 15, when the degree of deterioration of the intermediate transfer belt 57 is small and 50 recording media are continuously printed on, the number of trapped paper dust PD will be 5. When the degree of deterioration of the intermediate transfer belt 57 is large and 50 recording media are continuously printed on, the number of trapped paper dust PD will be 25. Here, when a removal operation is performed once, about 30% of the trapped paper dust PD is removed, and the remaining about 70% remains without being removed.

[0099] FIG. 16 is a graph showing an example of the relationship between the number of printed sheets and the number of paper dust particles trapped. Referring to FIG. 16, the removal operation is performed every time a print job of 50 printed sheets is completed. Here, when the deterioration level of the intermediate transfer belt 57 is low, the number of paper dust particles PD trapped can be sufficiently reduced each time the removal operation is performed once. However, when the deterioration level of the intermediate transfer belt 57 is high, the number of paper dust particles PD trapped cannot be sufficiently reduced by performing the removal operation only once. Therefore, a cleaning failure occurs when responding to five to six print jobs. On the other hand, when the deterioration level of the intermediate transfer belt 57 is high, the number of paper dust particles PD trapped can be sufficiently reduced by performing the removal operation twice. This prevents the occurrence of a cleaning failure.

[0100] FIG. 17 is a graph showing another example of the relationship between the number of printed sheets and the number of paper dust particles trapped. Referring to FIG. 17, the removal operation is performed every time a print job of 100 printed sheets is completed. In this case, similar to the example of FIG. 16, when the deterioration level of the intermediate transfer belt 57 is low, the number of paper dust particles PD trapped can be sufficiently reduced each time the removal operation is performed once. However, when the deterioration level of the intermediate transfer belt 57 is high, the number of paper dust particles PD trapped cannot be sufficiently reduced by performing the removal operation only once. Therefore, a cleaning failure occurs when responding to two to three print jobs. On the other hand, when the deterioration level of the intermediate transfer belt 57 is high, the number of paper dust particles PD trapped can be sufficiently reduced by performing the removal operation four times. This prevents the occurrence of a cleaning failure.

[0101] In this way, the number of times the removal operation is performed is determined in accordance with the degree of deterioration of intermediate transfer belt 57 or cleaning blade 58 so as to prevent cleaning failures, based on the relationship between the degree of deterioration of intermediate transfer belt 57 or cleaning blade 58 and the number of pieces of paper dust PD trapped, as shown in Fig. 15. Also, the number of times the removal operation is performed is corrected based on the number of printed sheets in a print job so as to prevent cleaning failures.

[0102] Fig. 18 is a flowchart showing an example of the flow of image formation processing. The image formation processing is executed by CPU 111 included in MFP 100 as CPU 111 executes an image formation program. With reference to Fig. 18, CPU 111 included in MFP 100 determines whether a print job has been accepted (step S01). The process waits until a print job is accepted (NO in step S01), and if a print job is accepted (YES in step S01), the process proceeds to step S02. In step S02, image formation (printing) is executed, and the process proceeds to step S03.

[0103] In step S03, it is determined whether or not the user has selected the number of times to perform the removal operation. If the user has selected the number of times to perform the removal operation, the process proceeds to step S04, but if not, the process proceeds to step S05. In step S04, the number of times to perform the removal operation is determined to be the number of times selected by the user, and the process proceeds to step S13.

[0104] In step S05, the print history is acquired, and the process proceeds to step S06. In step S06, the rotation history of the intermediate transfer belt 57 is acquired, and the process proceeds to step S07. Steps S05 and S06 may be performed first, or may be performed simultaneously. In step S07, the deterioration level of the intermediate transfer belt 57 or the cleaning blade 58 is evaluated based on at least one of the print history and the rotation history of the intermediate transfer belt 57, and the process proceeds to step S08. In step S08, the number of times the removal operation is to be performed is determined according to the evaluated deterioration level of the intermediate transfer belt 57 or the cleaning blade 58, and the process proceeds to step S09.

[0105] In step S09, the type of recording medium on which the image was formed in step S02 is obtained, and the process proceeds to step S10. In step S10, the paper feed history is obtained, and the process proceeds to step S11. In step S11, the number of printed sheets in the print job is obtained, and the process proceeds to step S12. Any of steps S09, S10, and S11 may be performed first, or they may be performed simultaneously. In step S12, the number of times the removal operation was performed, determined in step S08, is corrected based on the type of recording medium, the paper feed history, or the number of printed sheets obtained, and the process proceeds to step S13.

[0106] In step S13, the value of the variable i is set to 1, and the process proceeds to step S14. In step S14, the intermediate transfer belt 57 is rotated in the reverse direction, and the process proceeds to step S15. In step S15, it is determined whether the value of the variable i is n. Here, n is the number of times the removal operation has been performed, determined in step S04 or corrected in step S12. If the value of the variable i is n, the process proceeds to step S18, but if not, the process proceeds to step S16. In step S16, the intermediate transfer belt 57 is rotated forward, and the process proceeds to step S17. In step S17, the value of the variable i is updated to i+1, and the process proceeds to step S14. Steps S14 to S17 are repeated until the value of the variable i becomes n.

[0107] In step S18, it is determined whether or not there is a next print job. If there is a next print job, the image forming process ends without performing the forward rotation in the last (nth) removal operation. In this case, another image forming process corresponding to the next print job is started. If there is no next print job, the process proceeds to step S19. In step S19, the forward rotation in the last (nth) removal operation is performed, and the image forming process ends.

[0108] <Modification> The intermediate transfer belt 57, the photoconductor drums 53Y, 53M, 53C, 53K, and the developing rollers 55Y, 55M, 55C, 55K are driven by a common motor 60, but the embodiment is not limited thereto. The intermediate transfer belt 57 and the photoconductor drums 53Y, 53M, 53C, 53K may be driven by the same motor 60, and the developing rollers 55Y, 55M, 55C, 55K may be driven by another motor. Alternatively, the intermediate transfer belt 57 and the developing rollers 55Y, 55M, 55C, 55K may be driven by the same motor 60, and the photoconductor drums 53Y, 53M, 53C, 53K may be driven by another motor.

[0109] Furthermore, the number of times the removal operation is performed is determined according to the deterioration degree of the intermediate transfer belt 57 or the cleaning blade 58, and then corrected based on at least one of the type of recording medium, the paper feed history, and the number of printed sheets, but the embodiment is not limited to this. The number of times the removal operation is performed may be determined based on at least one of the type of recording medium, the paper feed history, and the number of printed sheets, in addition to the deterioration degree of the intermediate transfer belt 57 or the cleaning blade 58. Alternatively, the number of times the removal operation is performed may be determined according to the deterioration degree of the intermediate transfer belt 57 or the cleaning blade 58, and may not be corrected based on the type of recording medium, the paper feed history, and the number of printed sheets. In this case, steps S05 to S12 of the image forming process are omitted.

[0110] As described above, the MFP 100 in this embodiment functions as an image forming apparatus, the intermediate transfer belt 57 carries a toner image formed of toner, and the motor 60 rotates the intermediate transfer belt 57. The cleaning blade 58 contacts the intermediate transfer belt 57, and removes the toner remaining on the intermediate transfer belt 57 while the intermediate transfer belt 57 is rotated forward by the motor 60. In the MFP 100, the deterioration degree of the intermediate transfer belt 57 or the cleaning blade 58 is evaluated, and the number of times to perform the removal operation of rotating the intermediate transfer belt 57 in the reverse direction and then in the forward direction is determined based on the deterioration degree, and the motor 60 is controlled so that the removal operation is performed the determined number of times. Therefore, even if the deterioration degree of the intermediate transfer belt 57 or the cleaning blade 58 is large, foreign matter caught between the intermediate transfer belt 57 and the cleaning blade 58 can be efficiently removed. Also, when the deterioration degree of the intermediate transfer belt 57 or the cleaning blade 58 is small, the occurrence of the turning over of the cleaning blade 58 due to friction between the cleaning blade 58 and the intermediate transfer belt 57 during the removal operation is suppressed. This makes it possible to improve the cleaning performance of the cleaning blade 58.

[0111] Preferably, the degree of deterioration of the intermediate transfer belt 57 or the cleaning blade 58 is evaluated based on the surface roughness of the intermediate transfer belt 57, the degree of wear of the cleaning blade 58, or the distortion of the cleaning blade 58. Therefore, the degree of deterioration of the intermediate transfer belt 57 or the cleaning blade 58 can be easily evaluated.

[0112] Preferably, the degree of deterioration of the intermediate transfer belt 57 or the cleaning blade 58 is evaluated based on the total amount of rotation of the intermediate transfer belt 57. Therefore, the degree of deterioration of the intermediate transfer belt 57 or the cleaning blade 58 can be easily evaluated.

[0113] Preferably, the MFP 100 further includes photoconductor drums 53Y, 53M, 53C, and 53K or developing rollers 55Y, 55M, 55C, and 55K that rotate simultaneously with the intermediate transfer belt 57 by the rotational force of a motor 60. In the removal operation, the intermediate transfer belt 57 is rotated in reverse by a limited amount of rotation so that the photoconductor drums 53Y, 53M, 53C, and 53K or developing rollers 55Y, 55M, 55C, and 55K do not rotate in reverse. Therefore, the intermediate transfer belt 57 and the photoconductor drums 53Y, 53M, 53C, and 53K or developing rollers 55Y, 55M, 55C, and 55K are driven by a common motor 60, so that the MFP 100 can be made smaller and the cost of the MFP 100 can be reduced. In addition, since the photosensitive drums 53Y, 53M, 53C, and 53K or the developing rollers 55Y, 55M, 55C, and 55K are prevented from rotating in reverse when the intermediate transfer belt 57 rotates in reverse, malfunctions caused by the photosensitive drums 53Y, 53M, 53C, and 53K or the developing rollers 55Y, 55M, 55C, and 55K rotating in reverse can be prevented.

[0114] Preferably, in the removal operation, the motor 60 is driven so that the amount of rotation of the intermediate transfer belt 57 during forward rotation is greater than the amount of rotation of the intermediate transfer belt 57 during reverse rotation. Therefore, the foreign matter removed from between the intermediate transfer belt 57 and the cleaning blade 58 by the reverse rotation of the intermediate transfer belt 57 can be reliably removed by the forward rotation of the intermediate transfer belt 57.

[0115] Preferably, the motor 60 is controlled so that a toner image corresponding to each page is carried on the intermediate transfer belt 57 based on a job including an image of one or more pages, and the removal operation is performed after the toner image corresponding to the job is carried on the intermediate transfer belt 57. Therefore, foreign matter caught between the intermediate transfer belt 57 and the cleaning blade 58 while the toner image corresponding to the job is carried on the intermediate transfer belt 57 is removed. This makes it possible to prevent a decrease in image quality in the next job. Also, image formation is not hindered by the removal operation. This makes it possible to prevent a decrease in productivity.

[0116] Preferably, when the next job is accepted while the motor 60 is controlled to perform the removal operation, the forward rotation of the intermediate transfer belt 57 in the final removal operation is omitted. Even if the forward rotation of the intermediate transfer belt 57 in the final removal operation is omitted, the foreign matter removed from between the intermediate transfer belt 57 and the cleaning blade 58 by the reverse rotation of the intermediate transfer belt 57 in the final removal operation is removed by the first forward rotation of the intermediate transfer belt 57 during image formation corresponding to the next job. Therefore, the time for the removal operation is shortened while maintaining the cleaning performance of the cleaning blade 58, and the image formation corresponding to the next job can be performed at high speed.

[0117] Preferably, the number of times the removing operation is to be performed is determined based on the type of recording medium onto which the toner image in response to the job is transferred, so that the number of times the removing operation is to be performed can be determined more appropriately.

[0118] Preferably, the number of times the removing operation is to be performed is determined based on the number of recording media onto which a toner image has been transferred in response to the job, so that the number of times the removing operation is to be performed can be determined more appropriately.

[0119] Preferably, the number of times the removing operation is to be performed is determined based on a supply history of the recording medium conveyed by the conveying unit, so that the number of times the removing operation is to be performed can be determined more appropriately.

[0120] Preferably, when a selection of the number of times to perform the removal operation is accepted, the number of times to perform the removal operation is determined to be the selected number of times, so that the removal operation can be performed a number of times desired by the user.

[0121] <Additional Notes> Preferably, the image forming apparatus comprises: a first transmission member provided between the drive unit and the image carrier and configured to transmit a rotational force of the drive unit to the image carrier; A second transmission member is provided between the drive unit and the simultaneous drive member, and transmits a rotational force of the drive unit to the simultaneous drive member. The backlash of the first transmission member is smaller than the backlash of the second transmission member.

[0122] Preferably, the image forming apparatus comprises: a photoconductor on which an electrostatic latent image is formed by being exposed to light after being charged; a developing unit that develops the electrostatic latent image formed on the photoconductor with toner; a transfer unit that transfers a toner image formed on the photoconductor by the developing unit developing the electrostatic latent image with toner to the image carrier, The simultaneously driven member is at least one of the photoconductor and the developing unit.

[0123] Preferably, the removal operation executing unit controls the drive unit so that an amount of rotation of the drive unit during reverse rotation is equal to or greater than a backlash of the first transmission member and less than a backlash of the second transmission member. [Explanation of symbols]

[0124] 13 upper end, 15 paper discharge roller, 30 lower end, 41 main transport path, 45 timing roller, 47 secondary transfer roller, 49 fixing roller, 51C, 51K, 51M, 51Y image forming unit, 52C, 52K, 52M, 52Y exposure head, 53C, 53K, 53M, 53Y photoconductor drum, 54 drive roller, 54A roller, 54C, 54K, 54M, 54Y charging roller, 55C, 55K, 55M, 55Y developing roller, 56C, 56K, 56M, 56Y primary transfer roller, 57 intermediate transfer belt, 58 cleaning blade, 60 motor, 61 belt drive gear, 62 photoconductor drive gear, 63 belt driven gear, 64 relay gear, 65 photoconductor driven gear, 100 MFP, 110 Main circuit, 111 CPU, 112 I / F section, 113 ROM, 114 RAM, 115 HDD, 116 Facsimile section, 118 External storage device, 118A CD-ROM, 120 Automatic document feeder, 125 Document tray, 127 Document output tray, 130 Document reading section, 140 Image forming section, 150 Paper feed section, 151, 152, 153 Paper feed tray, 151p, 152p, 153p, 154p Pickup roller, 151r, 152r, 153r, 154r Paper feed roller, 154 Manual feed tray, 159 Output tray, 160 Operation panel, 161 Display section, 163 Operation section, 210 Image forming reception section, 220 Image forming execution section, 230 Deterioration evaluation section, 231 Print history acquisition unit, 232 rotation history acquisition unit, 240 execution count determination unit, 241 selection reception unit, 242 medium type acquisition unit, 243 paper feed history acquisition unit, 244 print count acquisition unit, 250 removal operation execution unit, RT remaining toner image, SP1, SP2, SP3, SP4 sub-transport path

Claims

1. an image carrier that carries a toner image formed of toner; A drive unit that rotates the image carrier; a toner removing unit that comes into contact with the image carrier and removes toner remaining on the image carrier while the image carrier is rotated forward by the driving unit; a deterioration degree evaluation unit for evaluating a deterioration degree of the image carrier or the toner removal unit; an execution count determination unit that determines the execution count of a removal operation in which the image carrier is rotated in a reverse direction and then in a forward direction based on the deterioration level evaluated by the deterioration level evaluation unit; a removal operation execution unit that controls the drive unit so that the removal operation is executed the number of times determined by the execution number determination unit; an image forming execution unit that causes the image carrier to carry a toner image corresponding to each page on the basis of a job including an image of one or more pages; The removal operation execution unit is controlling the driving unit so that the removing operation is performed after the toner image corresponding to the job is carried on the image carrier by the image forming execution unit; An image forming apparatus that omits the forward rotation of the image carrier in the final removal operation when the next job is accepted by the image forming execution unit while the drive unit is being controlled to perform the removal operation.

2. The image forming apparatus according to claim 1 , wherein the deterioration degree evaluation unit evaluates the deterioration degree of the image carrier or the toner removal unit based on a roughness of a surface of the image carrier, a wear degree of the toner removal unit, or a distortion of the toner removal unit.

3. 3. The image forming apparatus according to claim 1, wherein the deterioration degree evaluation unit evaluates the deterioration degree of the image carrier or the toner removal unit based on a total rotation amount of the image carrier.

4. a simultaneous driving member that is rotated simultaneously with the image carrier by a rotational force of the driving unit, 4. The image forming apparatus according to claim 1, wherein the removing operation executing section rotates the image carrier in the reverse direction by a limited amount of rotation so that the simultaneously driven member does not rotate in the reverse direction during the removing operation.

5. An image forming apparatus according to any one of claims 1 to 4, wherein the removal operation execution unit drives the drive unit so that, during the removal operation, the amount of rotation of the image carrier during forward rotation is greater than the amount of rotation of the image carrier during reverse rotation.

6. 6. The image forming apparatus according to claim 1, wherein the execution count determination unit determines the execution count of the removing operation based on a type of recording medium onto which a toner image corresponding to the job has been transferred.

7. 7. The image forming apparatus according to claim 1, wherein the execution count determination unit determines the execution count of the removing operation based on the number of recording media onto which a toner image has been transferred in response to the job.

8. A conveying unit that conveys a recording medium onto which the toner image is transferred, 8. The image forming apparatus according to claim 1, wherein the execution count determination unit determines the execution count of the removing operation based on a supply history of the recording medium conveyed by the conveyance unit.

9. 9. The image forming apparatus according to claim 1, wherein, when a selection of the number of times to be performed of the removal operation is accepted, the execution count determination unit determines the number of times to be performed of the removal operation to be the selected number of times.

10. an image carrying step of carrying a toner image formed of toner on an image carrier; a driving step of rotating the image carrier by a driving unit; a toner removing step of removing toner remaining on the image carrier by a toner removing unit that contacts the image carrier while the image carrier is rotated forward by the driving unit; a deterioration degree evaluation step of evaluating a deterioration degree of the image carrier or the toner removal unit; an execution count determination step of determining the number of execution counts of a removal operation in which the image carrier is rotated in a reverse direction and then in a forward direction based on the evaluated deterioration degree; a removal operation execution step of executing the removal operation by the driving unit a determined number of times; an image forming execution step of carrying, on the image carrier, a toner image corresponding to each page, based on a job including an image of one or more pages; The removal operation performing step includes: performing the removing operation after a toner image corresponding to the job is carried on the image carrier in the image forming execution step; omitting execution of forward rotation of the image carrier in the final removal operation when a next job is accepted in the image formation execution step while the removal operation is being performed.

11. An image forming program executed by a computer that controls an image forming apparatus, an image carrying step of carrying a toner image formed of toner on an image carrier; a driving step of rotating the image carrier by a driving unit; a toner removing step of removing toner remaining on the image carrier by a toner removing unit that contacts the image carrier while the image carrier is rotated forward by the driving unit; a deterioration degree evaluation step of evaluating a deterioration degree of the image carrier or the toner removal unit; an execution count determination step of determining the number of execution counts of a removal operation in which the image carrier is rotated in a reverse direction and then in a forward direction based on the evaluated deterioration degree; a removal operation execution step of executing the removal operation by the driving unit a determined number of times; an image forming execution step of carrying, on the image carrier, a toner image corresponding to each page, based on a job including an image of one or more pages, by the computer; The removal operation performing step includes: performing the removing operation after a toner image corresponding to the job is carried on the image carrier in the image forming execution step; omitting execution of forward rotation of the image carrier in the final removal operation when a next job is accepted in the image formation execution step while the removal operation is being performed.

Images