JP2008076753A - Transfer device, image forming apparatus and filming removing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of a filming phenomenon with simple constitution regardless of the abutting force of a cleaning blade. <P>SOLUTION: The image forming apparatus 100 is equipped with a transfer device 21 and a control part 70 or the like. The transfer device 21 is equipped with an endless intermediate transfer belt 211 tensioned and laid along a path in a loop state including abutting positions where its outer circumferential surface partially abuts on the parts of the surfaces of photoreceptor drums 221A to 221D driven to be rotated at prescribed linear velocity while carrying a toner image on their surfaces, and supported to freely rotate, and a drive motor 214A rotating the intermediate transfer belt 211. The control part 70 controls the operation of the drive motor 214A so as to perform filming removing operation that the linear velocity of the intermediate transfer belt 211 at a primary transfer position is made higher than that of the photoreceptor during post-rotation processing that is a prescribed period except a transfer operation period in which the toner image is transferred to paper. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transfer device for transferring a developer image carried on the surface of a photoconductor to an outer peripheral surface of a sheet or a transfer belt, an image forming apparatus having the transfer device, and a method for removing filming on the surface of the photoconductor About.

  In recent years, color image forming apparatuses adopting an intermediate transfer method have been developed along with the speeding up of image formation. An intermediate transfer type color image forming apparatus forms a developer image (hereinafter referred to as a toner image) corresponding to image information that has been color-separated into each hue on the surface of a photoreceptor corresponding to each hue. The toner image is once laminated on the outer peripheral surface of an intermediate transfer belt that bridges between the photoconductors, and then transferred onto a sheet at a time. The toner image is transferred onto the intermediate transfer belt by applying a primary transfer bias to the intermediate transfer belt and electrostatically adsorbing the toner image.

  In the above-described image forming apparatus, residual toner remaining on the surface of the photoconductor after the toner image is transferred to the intermediate transfer belt is removed using a cleaning blade or the like that contacts a part of the surface of the photoconductor. However, in recent years, as the toner particle size has been reduced, it has become difficult to completely remove residual toner with a cleaning blade, and a filming phenomenon has occurred in which residual toner that cannot be removed is fused to the surface of the photoreceptor. It was.

  The fusion of the residual toner occurs when the residual toner in the soft state is pressed against the surface of the photoconductor by the cleaning blade when passing between the contact portions of the cleaning blade and the photoconductor without being removed. . The residual toner is softened due to the heat of the intermediate transfer belt generated by the primary transfer bias.

  Residual toner mainly includes toner that is not transferred from the surface of the photoreceptor to the intermediate transfer belt, and toner that has been transferred to the intermediate transfer belt but not transferred to the sheet. There is toner that adheres to the photosensitive member again at the primary transfer position where the part comes into contact. The toner that remains on the surface of the photoreceptor is softened by the heat of the intermediate transfer belt when passing through the primary transfer position. Further, the toner once transferred to the intermediate transfer belt adheres to the photosensitive member again in a state of being softened by the heat of the intermediate transfer belt.

  When a filming phenomenon occurs on the surface of the photoconductor, the charged potential on the surface of the photoconductor becomes unstable, leading to a decrease in print quality. Therefore, the conventional image forming apparatus has a configuration in which the contact force of the cleaning blade to the surface of the photosensitive member is adjusted with high accuracy, and the photosensitive layer constituting the surface of the photosensitive member is scraped off by the cleaning blade and the fused toner is scraped off. There was a thing. In this image forming apparatus, the shaving thickness of the photosensitive layer that can be shaved is 10 μm, and the cleaning blade is arranged with a contact force equal to the shaving of the photosensitive layer 10 μm when the number of printed sheets is about 100,000.

  The setting of the contact force of the cleaning blade requires adjustment with high accuracy. However, since the contact force changes depending on the dimensional tolerance of the member forming the cleaning blade, the cleaning blade is accurately set for all the image forming apparatuses to be manufactured. It is difficult to set the contact force.

Further, some recent image forming apparatuses have a configuration in which a lubricant is applied to the surface of a photoreceptor using a lubricant application brush (see, for example, Patent Document 1). The lubricant lowers the coefficient of friction on the surface of the photoconductor and prevents it from fusing even when the cleaning blade comes into strong contact with the residual toner passing therethrough.
JP 2002-174990 A

  However, in the configuration of Patent Document 1 described above, it is not necessary to adjust the contact force of the cleaning blade with high accuracy, but the occurrence of the filming phenomenon cannot be completely prevented. On the other hand, if the lubricant is applied too much, the residual toner becomes difficult to remove by the cleaning blade, and the charging characteristics of the photoreceptor surface are adversely affected.

  An object of the present invention is to provide a transfer device capable of preventing the occurrence of a filming phenomenon with a simple configuration regardless of the contact force of a cleaning blade, an image forming apparatus having the transfer device, and a filming removal method. It is in.

  The present invention is configured as follows to solve the above-described problems.

  (1) The transfer device of the present invention includes a transfer belt, a drive device, and a control device. The transfer belt is stretched along a loop-shaped path including a contact position where a part of the outer peripheral surface comes into contact with a part of the surface of the photosensitive member that carries a toner image on the surface and is driven to rotate at a predetermined linear velocity. It has an endless shape that is mounted and supported rotatably. The driving device rotates the transfer belt. The control device is a driving device for performing a filming removal operation for making the linear velocity of the transfer belt at the contact position faster than the linear velocity of the photosensitive member in a predetermined period excluding the transfer operation period for transferring the toner image to the sheet. To control the operation.

  In this configuration, the filming removal operation is performed in a predetermined period except during the transfer operation, and the linear velocity of the transfer belt becomes faster than the linear velocity of the photosensitive member. That is, the linear velocity of the transfer belt is higher than that during the transfer operation. Therefore, the surface of the photoconductor is rubbed by the outer peripheral surface of the transfer belt, and the surface of the photoconductor is shaved. The transfer belt is in contact only to transfer the toner image to the paper or the outer peripheral surface, and the contact force is lower than that of a cleaning member such as a cleaning blade that contacts the surface of the photoreceptor.

  Further, the amount of scraping of the surface of the photoconductor is adjusted by the linear velocity. Therefore, by setting the linear velocity in advance, the linear velocity is always maintained constant by the control device, and the amount of scraping is also constant. Therefore, it is not necessary to adjust the contact force of the cleaning member that contacts the surface of the photosensitive member with high accuracy.

  (2) The transfer device of the present invention includes a transfer belt, a drive device, a separation / contact mechanism, and a control device. The transfer belt is stretched in a loop and is rotatably supported. The driving device rotates the transfer belt. The separation / contact mechanism is designed to form a color image on a sheet of paper. When a color image is formed, a part of the outer peripheral surface of the transfer belt carries color toners of different hues on the respective surfaces and rotates at the same predetermined linear velocity. Each contact position that contacts a part of the surface of a plurality of driven color image photoreceptors and a surface of a monochrome image photoreceptor that carries a black toner image on the surface and is driven to rotate at a predetermined linear velocity. A position where the outer peripheral surface of the transfer belt comes into contact with a part of the surface of the photosensitive member for monochrome images when a monochrome image is formed by stretching the transfer belt along the path including The transfer belt is stretched along a path including only The control device controls the operation of the driving device. The control device also includes a first transfer operation period in which the color toner and black toner at the time of color image formation are transferred to the paper, and a second transfer operation period in which only the black toner at the time of monochrome image formation is transferred to the paper. Except for a predetermined period, the linear velocity of the transfer belt at the contact position in a state where the transfer belt is in contact with the plurality of color image photosensitive members and the monochrome image photosensitive member. And a filming removal operation for a color image that is faster than the linear velocity of the photosensitive member for monochrome images, and a line of the transfer belt at the contact position with the transfer belt contacting only the photosensitive member for monochrome images. The operation of the driving device and the contact / separation mechanism is controlled so as to perform at least one of the filming removal operation for monochrome images in which the speed is higher than the linear velocity of the photoreceptor for monochrome images.

  In this configuration, at least one of a color image filming removal operation and a monochrome image filming removal operation is performed in a predetermined period excluding the first transfer operation and the second transfer operation, and the transfer belt The linear velocity becomes faster than the linear velocity of the photoreceptor. That is, the linear velocity of the transfer belt is higher than that during the transfer operation.

  Therefore, the surface of the photoconductor is rubbed by the outer peripheral surface of the transfer belt, and the surface of the photoconductor is shaved. The transfer belt is in contact only to transfer the toner image to the paper or the outer peripheral surface, and the contact force is lower than that of a cleaning member such as a cleaning blade that contacts the surface of the photoreceptor.

  Further, the amount of scraping of the surface of the photoconductor is adjusted by the linear velocity. Therefore, by setting the linear velocity in advance, the linear velocity is always maintained constant by the control device, and the amount of scraping is also constant. Therefore, it is not necessary to adjust the contact force of the cleaning member that contacts the surface of the photosensitive member with high accuracy.

  In addition, since the filming operation for color images and the filming operation for monochrome images are performed separately, the photoconductor is not scraped more than necessary.

  (3) In the configuration of the above (2), the filming operation for color images is performed while the transfer belt is moved until a time obtained by multiplying the rotation time for rotating a plurality of color image photoconductors by an integral number elapses. The linear velocity of the transfer belt at the contact position in contact with the plurality of color image photosensitive members and the monochrome image photosensitive member is set to the line of the plurality of color image photosensitive members and the monochrome image photosensitive member. In a state in which the transfer belt is in contact with only the monochrome image photosensitive member until a time obtained by multiplying the rotation time for one rotation of the monochrome image photosensitive member by an integer is passed after the speed is made higher than the speed. The linear velocity of the transfer belt is made higher than the linear velocity of the photosensitive member for monochrome images, and the filming operation for monochrome images is performed until a time obtained by multiplying the rotation time for rotating the photosensitive member for monochrome images by an integral number has elapsed. During Faster than the linear speed of the transfer belt at the contact position of the belt being in contact only with the photoreceptor for a monochrome image a linear velocity for the monochrome image.

  In this configuration, during the color image filming operation, the transfer belt is used for a plurality of color images until a time obtained by multiplying the rotation time for rotating a plurality of color image photosensitive members by an integer has elapsed. The linear velocity of the transfer belt is higher than the linear velocity of the plurality of photosensitive members for color images and the photosensitive member for monochrome images in a state where the photosensitive member and the photosensitive member for monochrome images are in contact with each other. Thereafter, the linear velocity of the transfer belt is changed to a monochrome image while the transfer belt is in contact with only the monochrome image photosensitive member until a time obtained by multiplying the rotation time of one rotation of the monochrome image photosensitive member by an integer. It will be faster than the line speed. That is, first, the surface of a plurality of color image photoreceptors and the surface of a monochrome image photoreceptor are shaved, and then only the surface of the monochrome image photoreceptor is shaved.

  The reason why the rotation time for which the plurality of color image photoreceptors rotate once is an integral multiple of the rotation time is to evenly scrape the entire surface of the plurality of color image photoreceptors. The reason why the monochrome image photosensitive member is rotated by an integral multiple of the rotation time for one rotation after the monochrome image formation is more frequent than the color image formation. This is because the diameter of the photosensitive member for monochrome images may be larger (different). In this case, the monochrome image photosensitive member is different in diameter from the color image photosensitive member only by a time obtained by multiplying the rotation time of the rotation of the plurality of color image photosensitive members by one integer, so that the monochrome image photosensitive member is different. There is a possibility that the entire surface of the body may not be evenly shaved, causing unevenness in the toner image.

  On the other hand, even at a predetermined timing resulting from the monochrome transfer operation, for the same reason as described above, the transfer belt is exposed to the monochrome image until the rotation time for which the monochrome image photosensitive member makes one rotation is multiplied by an integer. The linear velocity of the transfer belt in the state of being in contact with only the body is higher than the linear velocity for monochrome images.

  (4) In the configuration of (2) above, the filming removal operation for the color image is started at a first predetermined timing resulting from the first transfer operation. Also, the filming removal operation for monochrome images is started at a second predetermined timing resulting from the second transfer operation.

  In this configuration, the surfaces of all the photoconductors are shaved at the first predetermined timing resulting from the first transfer operation, and the surfaces of only the photoconductors for monochrome images at the second predetermined timing resulting from the second transfer operation. Is cut. Since the filming phenomenon often occurs by repeating the transfer operation, it is not necessary to execute it every time a transfer operation is performed. Accordingly, since the surface of each photoconductor is scraped according to the usage amount of each photoconductor, it is not shaved more than necessary.

  (5) In the configuration of (4), the first predetermined timing is when the number of sheets on which color images are formed reaches a predetermined number, and the second predetermined timing is when the number of sheets on which monochrome images are formed reaches a predetermined number. Is set when.

  In this configuration, when the number of sheets onto which the toner image has been transferred reaches a predetermined number, the linear velocity of the transfer belt becomes faster than the linear velocity of the photoconductor. Since the filming phenomenon often occurs by repeating the transfer operation, it is not necessary to execute it every time a transfer operation is performed. Therefore, since the process is performed every time the number of sheets reaches a predetermined number, the surface of the photoconductor is not wasted.

  Further, a filming removal operation for a color image and a filming removal operation for a monochrome image are performed according to the number of sheets on which a color image is formed and the number of sheets on which a monochrome image is formed. Accordingly, since the surface of each photoconductor is scraped according to the usage amount of each photoconductor, it is not shaved more than necessary.

  (6) In the configuration of (1), the filming removal operation is started at a predetermined timing resulting from the transfer operation.

  In this configuration, the surface of only the photoconductor is scraped at a predetermined timing resulting from the transfer operation. Since the filming phenomenon often occurs by repeating the transfer operation, it is not necessary to execute it every time a transfer operation is performed. Therefore, the surface of each photoconductor is scraped according to the usage amount of the photoconductor and the like, so that it is not shaved more than necessary.

  (7) In the configuration of (6) above, the predetermined timing is set when the number of sheets on which the toner images are transferred reaches a predetermined number.

  In this configuration, when the number of sheets onto which the toner image has been transferred reaches a predetermined number, the linear velocity of the transfer belt becomes faster than the linear velocity of the photoconductor. Since the filming phenomenon often occurs by repeating the transfer operation, it is not necessary to execute it every time a transfer operation is performed. Therefore, since the process is performed every time the number of sheets reaches a predetermined number, the surface of the photoconductor is not wasted.

  (8) In the configuration of (1), the filming removal operation is executed only until a time obtained by multiplying the rotation time for one rotation of the photosensitive member by an integer has elapsed.

  In this configuration, the linear velocity of the transfer belt is higher than the linear velocity of the photosensitive member until a time obtained by multiplying the rotation time of one rotation of the photosensitive member during the filming operation by an integer. The reason why the rotation time for one rotation of the photoconductor is an integral multiple is to scrape the entire surface of the photoconductor evenly. If it is not performed for an integral multiple of the time, the surface of the photoreceptor is scraped unevenly, resulting in unevenness in the formed toner image.

  (9) In the above configurations (1) to (8), the outer peripheral surface of the transfer belt can be made rougher than the surface of the photoreceptor.

  In this configuration, the surface of the transfer belt is formed to be rougher than the surface of the photoreceptor. For this reason, when the linear velocity of the transfer belt becomes higher than the linear velocity of the photoconductor, the surface of the photoconductor is easily scraped off by the transfer belt.

  (10) In the above configurations (1) to (9), the linear velocity of the transfer belt at the contact position during the filming removal operation is set to 1.05 to 1.07 times the linear velocity of the photosensitive member. Has been.

  In this configuration, the linear velocity of the transfer belt is 1.05 to 1.07 times the linear velocity of the photoconductor from a predetermined timing. For this reason, the amount of the surface of the photoconductor is not too much and not too small. If the linear velocity of the transfer belt is too higher than the linear velocity of the photoconductor, the surface of the photoconductor will be scraped too much. On the other hand, if the linear velocity of the transfer belt is high enough to be higher than the linear velocity of the photoconductor, the amount of the surface of the photoconductor is shaved too little.

  (11) In the above configurations (1) to (10), the filming removal operation is executed after the transfer operation is completed and until the rotation of the transfer belt is stopped.

  In this configuration, the filming operation is performed with the linear velocity of the transfer belt higher than the linear velocity of the photosensitive member either after the transfer operation is completed or until the rotation of the transfer belt is stopped. After the transfer operation is completed, post-rotation processing such as cleaning of the photoreceptor and transfer belt is usually performed. In the meantime, since the photosensitive member and the transfer belt continue to rotate, the filming phenomenon is prevented by using the post-rotation process.

  (12) An image forming apparatus according to the present invention includes a photoconductor and a transfer device, and forms an image on a sheet. The photoconductor is rotatably formed to carry a toner image corresponding to image information on the surface. The transfer device is the transfer device according to any one of (1) to (11).

  In this configuration, the filming removal operation is performed in a predetermined period except during the transfer operation, and the linear velocity of the transfer belt becomes faster than the linear velocity of the photosensitive member. That is, the linear velocity of the transfer belt is higher than that during the transfer operation. Therefore, the surface of the photoconductor is rubbed by the outer peripheral surface of the transfer belt, and the surface of the photoconductor is shaved. The transfer belt is in contact only to transfer the toner image to the paper or the outer peripheral surface, and the contact force is lower than that of a cleaning member such as a cleaning blade that contacts the surface of the photoreceptor.

  Further, the amount of scraping of the surface of the photoconductor is adjusted by the linear velocity. Therefore, by setting the linear velocity in advance, the linear velocity is always maintained constant by the control device, and the amount of scraping is also constant. Therefore, it is not necessary to adjust the contact force of the cleaning member that contacts the surface of the photosensitive member with high accuracy.

  (13) The filming removal method of the present invention includes a contact position where a part of the outer peripheral surface contacts a part of the surface of the photosensitive member that carries a toner image on the surface and is driven to rotate at a predetermined linear velocity. A rotatable endless transfer belt stretched along a loop path is applied within a predetermined period excluding a transfer operation period for transferring a toner image onto a sheet and at a predetermined timing resulting from the transfer operation. The transfer belt is rotated so that the linear velocity of the transfer belt at the contact position is higher than the linear velocity of the photosensitive member.

  In this configuration, the filming removal operation is performed in a predetermined period except during the transfer operation, and the linear velocity of the transfer belt becomes faster than the linear velocity of the photosensitive member. That is, the linear velocity of the transfer belt is higher than that during the transfer operation. Therefore, the surface of the photoconductor is rubbed by the outer peripheral surface of the transfer belt, and the surface of the photoconductor is shaved. The transfer belt is in contact only to transfer the toner image to the paper or the outer peripheral surface, and the contact force is lower than that of a cleaning member such as a cleaning blade that contacts the surface of the photoreceptor.

  Further, the amount of scraping of the surface of the photoconductor is adjusted by the linear velocity. Therefore, by setting the linear velocity in advance, the linear velocity is always maintained constant by the control device, and the amount of scraping is also constant. Therefore, it is not necessary to adjust the contact force of the cleaning member that contacts the surface of the photosensitive member with high accuracy.

  (14) According to the filming removal method of the present invention, when forming a color image on a sheet, a part of the outer peripheral surface carries color toners of different hues on the respective surfaces, and each has the same predetermined A plurality of color image photosensitive members that are rotationally driven at a linear velocity, and a part of the surface of a monochrome image photosensitive member that carries a black toner image on the surface and is rotationally driven at a predetermined linear velocity. A transfer belt in which a transfer belt is stretched in a loop shape along a path including each contact position, and when forming a monochrome image on a sheet, a part of the outer peripheral surface is a photoreceptor for monochrome image First transfer operation for transferring color toner and black toner onto a sheet on a rotatable endless transfer belt stretched in a loop along a path including only a contact position that contacts only a part of the surface of the sheet The transfer belt is used for a plurality of color images within a predetermined period excluding the interval and the second transfer operation period in which only the black toner is transferred to the paper, and at a first predetermined timing resulting from the first transfer operation. The linear velocity of the transfer belt at the contact position is higher than the linear velocity of the photosensitive members for a plurality of color images and the photosensitive member for monochrome images while being in contact with the photosensitive member for monochrome image and the photosensitive member for monochrome image. At the second predetermined timing resulting from the second transfer operation, the linear velocity of the transfer belt at the contact position is set for the monochrome image while the transfer belt is in contact with only the monochrome image photosensitive member. The photosensitive member is rotated so as to be faster than the linear velocity of the photosensitive member.

  In this configuration, the transfer belt is attached to a plurality of colors within a predetermined period excluding the first transfer operation period and the second transfer operation period and at a first predetermined timing resulting from the first transfer operation. The linear velocity of the transfer belt at the contact position in contact with the photosensitive member for image and the photosensitive member for monochrome image is higher than the linear velocity of the photosensitive member for color image and photosensitive member for monochrome image. Get faster. In addition, the transfer belt is used as a monochrome image photosensitive member within a predetermined period excluding the first transfer operation period and the second transfer operation period, and at a second predetermined timing resulting from the second transfer operation. The linear velocity of the transfer belt at the contact position becomes higher than the linear velocity of the photosensitive member for monochrome images in a state where only the contact is made.

  Accordingly, since the surface of each photoconductor is scraped according to the usage amount of each photoconductor, it is not shaved more than necessary.

  According to the present invention, the following effects can be obtained.

  (1) By making the linear velocity of the transfer belt faster than the linear velocity of the photosensitive member at a predetermined timing except during the transfer operation, the photosensitive member can be configured with a simple configuration regardless of the contact force of the cleaning member to the photosensitive member. It is possible to prevent the occurrence of filming phenomenon by always keeping the amount of surface cutting constant.

  (2) The photosensitive member of the cleaning member is sensitized by making the linear velocity of the transfer belt faster than the linear velocity of the photosensitive member at each of a predetermined timing caused by the first transfer operation and a predetermined timing caused by the second transfer operation. Regardless of the contact force on the body, the amount of scraping of the surface of the photosensitive member can be always kept constant with a simple structure, and the occurrence of filming phenomenon can be prevented. Further, since the filming removal operation for color image and monochrome image is performed separately, it is possible to prevent the life of the photoreceptor from being reduced.

  (3) The surface of the plurality of color image photoreceptors from a predetermined timing resulting from the first transfer operation until a time obtained by multiplying the rotation time of one rotation of the plurality of color image photoreceptors by an integral number has elapsed. Then, the surface of the photoconductor for monochrome image is shaved, and after that, only the surface of the photoconductor for monochrome image is scraped until a time obtained by multiplying the rotation time of one rotation of the photoconductor for monochrome image by an integral number has elapsed. Even if the diameters of a plurality of color image photoreceptors and monochrome image photoreceptors are different, the surface of the plurality of color image photoreceptors and the entire surface of the monochrome image photoreceptor The toner image can be evenly cut, and the occurrence of unevenness in the toner image formed on the surface can be prevented.

  (4) The surfaces of all the photoconductors are scraped at the first predetermined timing resulting from the first transfer operation, and the surfaces of only the photoconductors for monochrome images are shaved at the second predetermined timing resulting from the second transfer operation. Accordingly, it is possible to prevent the life of the photoreceptor from being reduced.

  (5) By performing the filming removal operation for color images and the filming removal operation for monochrome images according to the number of sheets on which color images are formed and the number of sheets on which monochrome images are formed, exposure is performed at an appropriate frequency. The surface of the body can be shaved and the life of the photoreceptor can be prevented from being reduced.

  (6) By reducing the surface of the photoconductor only at a predetermined timing due to the transfer operation, it is possible to prevent the life of the photoconductor from being reduced.

  (7) When the number of sheets on which the toner image has been transferred reaches a predetermined number, the surface of the photoconductor can be scraped at an appropriate frequency by making the linear velocity of the transfer belt faster than the linear velocity of the photoconductor. And reduction of the life of the photoreceptor can be prevented.

  (8) The entire surface of the photoconductor is evenly distributed by setting the linear velocity of the transfer belt to be higher than the linear velocity of the photoconductor until a time obtained by multiplying the rotation time for one rotation of the photoconductor by an integer has elapsed. The toner image formed on the surface can be prevented and unevenness can be prevented from occurring.

  (9) Since the surface of the transfer belt is formed to be rougher than the surface of the photoconductor, the surface of the photoconductor can be easily scraped off using the transfer belt.

  (10) The surface of the photoconductor is scraped with an appropriate amount by using the transfer belt by increasing the linear velocity of the transfer belt at 1.05 to 1.07 times the linear velocity of the photoconductor during the filming operation. Can do.

  (11) By performing the filming operation anywhere after the transfer operation is completed until the rotation of the transfer belt is stopped, the filming phenomenon can be prevented from occurring by using the post-rotation process. It is not necessary to separately provide a process for preventing the filming phenomenon from occurring by making the linear velocity of the transfer belt higher than the linear velocity of the photosensitive member. Thereby, increase of a process process can be suppressed.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram showing a schematic configuration of an image forming apparatus 100 according to an embodiment of the present invention. The image forming apparatus 1 forms electrophotographic multicolor (color) and single color (monochrome) images on paper based on image information read by the scanner unit 1 and image information input via a network or the like. Selectively. The image forming apparatus 100 includes a scanner unit 1, an image forming unit 2, a paper storage unit 3, a paper conveyance unit 4, and the like.

  The scanner unit 1 includes a platen glass 11, a light source 12, reflection mirrors 13 to 15, an optical lens 16, and a CCD (Charge Coupled Device) 17. The light source 12 irradiates light on a document placed on the upper surface of the platen glass 11. The reflection mirrors 13 to 15 guide the reflected light from the document to the optical lens 16. The optical lens 16 focuses the reflected light on the CCD 17. The CCD 17 outputs an electrical signal corresponding to the reflected light.

  The image forming unit 2 includes an exposure unit 20 and a transfer device 21, and includes image forming stations 22 </ b> A to 22 </ b> D arranged in a line between the transfer device 21 and the exposure unit 20. The exposure unit 20 includes a light source such as a semiconductor laser, a polygon mirror, a reflection mirror, and the like, and irradiates image light based on image information of each hue corresponding to the photosensitive drums 221A to 221D. The transfer device 21 includes an intermediate transfer belt 211, primary transfer rollers 212A to 212D, a secondary transfer roller 213, and the like. A toner image carried on the surface of the photosensitive drums 221A to 221D passes through the intermediate transfer belt 211. To transfer to paper. Details will be described later.

Each of the image forming stations 22 </ b> A to 22 </ b> D forms an image based on image information of each hue of a total of four colors including cyan, magenta, and yellow, which are three subtractive primary colors obtained by color separation of a color image. I do. The black image forming station 22A includes a photosensitive drum 221A, a charging charger 222A, a developing unit 223A, a cleaning unit 224A, and the like.

  The photosensitive drum 221 </ b> A is irradiated with image light based on black image information from the exposure unit 20 on the surface to form an electrostatic latent image. The charging charger 222A is a non-contact type charger that uniformly charges the entire surface of the photosensitive drum 221A to a predetermined potential. Instead of the charging charger 222A, a contact-type charger using a charging brush or a charging roller may be used.

  The developing unit 223A supplies black toner to the surface of the photosensitive drum 221A, and develops the electrostatic latent image into a toner image. The developing unit 223A includes two toner boxes 225A and 225A. The toner box 225A accommodates black unused toner. The stored toner is supplied to the developing unit 223A via a supply path (not shown). The cleaning unit 224A has a cleaning blade that contacts the surface of the photosensitive drum 221A, and removes and collects residual toner.

  The image forming stations 22B to 22D are configured similarly to the image forming station 22A. However, each of the image forming stations 22B, 22C, and 22D is irradiated from the exposure unit 20 with image light modulated by image information of each hue of cyan, magenta, and yellow. The developing units 223B, 223C, and 223D supply toners of cyan, magenta, and yellow hues to the photosensitive drums 221B, 221C, and 221D, respectively. To the developing units 223B, 223C, and 223D, toner boxes 225B, 225C, and 225D that store toner of each hue are connected one by one.

  As a result, toner images of hues of cyan, magenta, and yellow are formed on the photosensitive drums 221B, 221C, and 221D, respectively.

  The reason why the two toner boxes 225A and 225A are arranged like the developing unit 223A is that the amount of black toner used is larger than the toner of other hues, and therefore the amount of storage is increased. .

  Further, the black photosensitive drum 221A has a larger diameter than the photosensitive drums 221B to 221D of other hues. This is because the monochrome photosensitive drum 221A is used more frequently than the photosensitive drums 221B to 221D because the monochrome image forming is executed more frequently than the color image forming. Increasing the diameter increases the surface area of the photosensitive drum 221A and increases the area on which the toner image can be formed. Thereby, the lifetime of the photosensitive layer forming the surface of the photosensitive drum 221A is extended.

  The image forming apparatus 100 according to the present embodiment can execute a color image forming mode in which an image is formed with four colors and a monochrome image forming mode in which an image is formed with a single black color. When an image is formed in the color image forming mode, an electrostatic latent image and a toner image are formed in all four image forming stations 22A to 22D. Yellow, magenta, cyan, and black toner images are sequentially superimposed and transferred in this order on the outer peripheral surface of the intermediate transfer belt 211.

  When an image is formed in the monochrome image forming mode, the electrostatic latent image and the toner image are formed only in the black image forming station 22A, and the black toner is formed on the outer peripheral surface of the intermediate transfer belt 11. Only the image is transferred.

  The paper storage unit 3 includes paper feed cassettes 31, 32, 33, 34 and the like that each store a plurality of sheets of a single type.

  The paper transport unit 4 includes a first paper transport path 41 from the paper feed cassettes 31 to 34 via the secondary transfer position Q to the paper discharge tray 5 positioned between the scanner unit 1 and the image forming unit 2. ing. Pickup rollers 42A, 42B, 42C, and 42D, paper feed rollers 43A, 43B, 43C, and 43D, a registration roller 44, a fixing unit 45, a paper discharge roller 46, and the like are disposed on the first paper transport path 41. Yes.

  Further, the sheet conveying section 4 is connected to the upstream side of the registration roller 44 in the sheet conveying direction of the first sheet conveying path 41 between the fixing unit 45 and the paper discharge roller 46 in the first sheet conveying path 41. A two-sheet conveyance path 47 is provided. The second paper transport path 47 transports a single-sided image-formed paper that is switchback-conveyed by reversal of the paper discharge roller 46 when a double-sided image is formed on both sides of the paper.

  When the paper transported from the paper storage unit 3 on the first paper transport path 41 passes through the secondary transfer position Q, the transfer of the toner image from the intermediate transfer belt 211 is transferred. The registration roller 44 temporarily holds the leading edge of the sheet that has been conveyed in a state where the rotation is stopped. When the leading edge of the sheet that has passed through the registration roller 44 reaches the secondary transfer position Q, the registration roller 44 moves to the intermediate transfer belt 211. The rotation starts at the timing when the tip of the toner image adhering reaches the secondary transfer position Q.

The registration roller 44 also has a function of correcting the oblique feeding of the paper by the front end of the paper coming into contact while the rotation is stopped.

  The fixing device 45 includes a heating roller 451, a pressure roller 452, and the like, and fixes the toner image transferred to the sheet at the secondary transfer position Q. The heating roller 451 is heated to a toner melting temperature by a heater included in the peripheral surface, and melts the toner on the paper. The pressure roller 452 contacts a part of the peripheral surface of the heating roller 451 and presses the sheet passing between the heating roller 451 and the pressure roller 452. The sheet is heated and pressed when passing through the nip portion between the heating roller 451 and the pressure roller 452, and the toner image is firmly fixed on the surface. Thereafter, the paper is discharged to the paper discharge tray 5. Thus, the paper image forming process is completed.

  The image forming apparatus 100 includes a control unit 70. A control unit 70 corresponding to the control device of the present invention controls the overall operation of the image forming apparatus 100.

  FIG. 2 is an explanatory view showing the operation of the transfer device 21 according to the embodiment of the present invention. The transfer device 21 includes an intermediate transfer belt 211, primary transfer rollers 212A to 212D, a secondary transfer roller 213, a separation / contact mechanism 60, a driving roller 214, a driven roller 215, a tension roller 216, and the like.

  The driving roller 214 rotates the intermediate transfer belt 211 in the arrow direction. The drive roller 214 is rotationally driven by a drive motor 214A. The drive of the drive motor 214A is controlled by the control unit 70 via the driver 214B. The driven roller 215 rotates according to the rotation of the intermediate transfer belt 211. The driving roller 214 and the driven roller 215 stretch the intermediate transfer belt 211.

  The tension roller 216 is biased vertically upward by a tension mechanism (not shown) and is movable in the vertical direction. The tension roller 216 contacts the intermediate transfer roller 211 upward from the inner peripheral surface. As a result, the intermediate transfer belt 211 is stretched to prevent the occurrence of bending.

  The intermediate transfer belt 211 is formed endlessly using a film having a thickness of about 100 μm to 150 μm. The intermediate transfer belt 211 rotates in the direction of the arrow, and conveys the toner image transferred to the outer peripheral surface at the primary transfer positions PA to PD to the secondary transfer position Q. The primary transfer positions PA to PD correspond to the contact positions of the present invention.

  The primary transfer rollers 212 </ b> A to 212 </ b> D are applied with a high voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) for transferring the toner image to the intermediate transfer belt 211. The primary transfer rollers 212 </ b> A to 212 </ b> D are in contact with the inner peripheral surface of the intermediate transfer belt 211 on the upstream side immediately before the primary transfer positions PA to PD in the rotation direction of the intermediate transfer belt 211, and apply a high voltage to the intermediate transfer belt 211. To do.

  As a result, the toner image is transferred to the intermediate transfer belt 211 at the primary transfer positions PA to PD. The primary transfer rollers 212A to 212D are based on a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm, and the surface is covered with a conductive elastic agent (for example, EPDM or urethane foam).

  The primary transfer rollers 212 </ b> B to 212 </ b> D are supported by the separation / contact mechanism 60 so as to be movable in the vertical direction, and change the loop-shaped movement path of the intermediate transfer belt 211. The separation / contact mechanism 60 includes a cam 61, a slide member 62, and the like. The circumferential surface of the cam 61 abuts against the slide member 62, and is rotated by driving of a drive motor (not shown) to move the slide member 62 in the horizontal direction.

  The slide member 62 is supported so as to be movable in the horizontal direction, and includes contact portions 621B to 621D. The abutting portions 621B to 621D are projecting members that project vertically downward, and have a tip portion formed in a horizontal shape and a side surface formed in a curved shape. The front end portion and the side surface abut on the primary transfer rollers 212B to 212D, thereby moving the primary transfer rollers 212B to 212D in the vertical direction.

  In the color image forming mode, as shown in FIG. 2A, the slide member 62 moves to the left end side in the figure, and the tip portions of the contact portions 621B to 621D come into contact with the primary transfer rollers 212B to 212D. Therefore, the primary transfer rollers 212 </ b> B to 212 </ b> D are pressed down to come into contact with and stretch over the inner peripheral surface of the intermediate transfer belt 211. As a result, the outer peripheral surface of the intermediate transfer belt 211 comes into contact with the surfaces of the photoconductors 211B to 211D to form nip portions that become the primary transfer positions PB to PD. The state shown in FIG. 2A is a looped (moving) path of the intermediate transfer belt 211 in the color image forming mode.

  The black primary transfer roller 211A is fixed in movement and is always in contact with the inner peripheral surface of the intermediate transfer belt 211.

  On the other hand, in the monochrome image forming mode, as shown in FIG. 2B, the slide member 62 moves to the right end side in the figure. Since the primary transfer rollers 212B to 212D are urged vertically upward by a spring (not shown) and supported so as to be movable in the vertical direction, the primary transfer rollers 212B to 212D rise along the side surfaces of the contact portions 621B to 621D.

  As a result, the tension roller 216 moves, the intermediate transfer belt 211 is stretched without being bent, and is separated from the photosensitive drums 221B to 221D. For this reason, only the black photosensitive drum 221A comes into contact. The state shown in FIG. 2B is a looped (moving) path of the intermediate transfer belt 211 in the monochrome image forming mode.

  In this embodiment, the black primary transfer roller 212A is fixedly arranged. However, a similar contact / separation mechanism is newly provided separately from the contact / separation mechanism 60, and the primary transfer roller 212A is movable in the vertical direction. It is good. Accordingly, the photosensitive drums 221A to 221D can be separated from the intermediate transfer belt 211 during a standby time when image formation is not performed.

  The secondary transfer roller 213 is in contact with the driving roller 214 at the secondary transfer position Q with the intermediate transfer belt 211 interposed therebetween. The secondary transfer roller 213 applies a primary transfer bias to the sheet passing through the secondary transfer position Q, and transfers the toner image conveyed on the outer peripheral surface of the intermediate transfer belt 211 to the sheet.

  Further, the transfer device 21 includes a cleaning unit 217 as shown in FIG. The cleaning unit 217 includes a cleaning brush 217 </ b> A that contacts the outer peripheral surface of the intermediate transfer belt 211, and removes residual toner attached on the outer peripheral surface of the intermediate transfer belt 211.

  3 and 4 are flowcharts showing the procedure for forming an image. When an image formation request is received from an operation unit or the like (not shown) from the user, the control unit 70 determines whether or not color image formation is performed based on the received image formation request information (S1). When it is determined that the color image formation is performed, the control unit 70 performs a pre-rotation process (S2). The pre-rotation process prepares for image formation such as starting rotation of the photosensitive drums 221A to 221D and the intermediate transfer belt 211. In the pre-rotation process, the moving path of the intermediate transfer belt 211 is changed to the color image forming mode shown in FIG.

  Next, the control unit 70 reads out the color image formation total number value and the color filming start number value from a storage unit (not shown) (S3), and adds the requested color image formation number to the color image formation total number value. Then, it is stored again in the storage unit (S4). The total number of color image formations is the total number of color images formed on paper after filming removal described later is performed.

  Thereafter, an image forming process is performed (S5). Thereby, a color image is formed on one sheet. The image forming process is a process for forming an image on a sheet, and is a process from the start of sheet feeding until the sheet is discharged to the discharge tray 5. Thereafter, the control unit 70 determines whether or not to newly form an image (S6), and repeats the process of S5 until all requested image formations are completed. On the other hand, when it is determined that the image formation for all the sheets has been completed in the process of S6, the control unit 70 determines whether or not the total number of color image formation sheets is equal to or greater than the color filming start sheet value (S7). ), If it is determined that the value is less than the color filming start number, post-rotation processing (S8) is performed. Thereafter, the process ends. The post-rotation process is a process in which the intermediate transfer belt 211, the photosensitive drums 221A to 221D, and the like are continuously rotated and cleaned after the image forming process is completed.

  Here, in the image forming process and the post-rotation process, as shown in FIG. 5A, the linear velocity of the intermediate transfer belt 211 at the primary transfer positions PA to PD is the linear velocity of the photosensitive drums 221A to 221D. .03 times). This is because the toner images formed on the surfaces of the photosensitive drums 221A to 221D are transferred onto the intermediate transfer belt 211 without changing the shape. The post-rotation process is executed at a linear velocity equal to that of the image forming process since the photoconductive drums 221A to 221D are continuously rotated immediately after the end of the image forming process.

  The control unit 70 stops the drive motor 214A that rotates the drive motor 214 and the drive motor that rotates the drive drums 221A to 221D when the post-rotation process is finished.

  On the other hand, when it is determined in S7 that the total number of color image formation sheets is equal to or greater than the color filming start sheet value, the control unit 70 performs post-rotation processing including filming removal operation for color images (S9). ). In the post-rotation process including the filming removal operation, unlike the post-rotation process shown in FIG. 5 (A), the intermediate transfer belt 211 at the primary transfer positions PA to PD from the middle of the process as shown in FIG. 5 (B). Is made higher than the linear velocity of the photosensitive drums 221A to 221D. That is, it is faster than the linear velocity of the intermediate transfer belt 211 in the image forming process. In the present embodiment, the linear velocity of the photosensitive drums 221A to 221D is 1.05 times.

  Accordingly, the surfaces of the photosensitive drums 221A to 221D can be rubbed using the outer peripheral surface of the intermediate transfer belt 211, so that the surfaces of the photosensitive drums 221A to 221D can be shaved. Further, the intermediate transfer belt 211 is only in contact with the toner image to be transferred to the outer peripheral surface, and the contact force is lower than that of the cleaning blade 224A in contact with the surface of the photosensitive drums 221A to 221D.

  In addition, since the amount of the surface of the photoconductive drums 221A to 221D can be adjusted by the linear velocity, the linear velocity can always be kept constant by setting the linear velocity of the intermediate transfer speed 211 in advance, and the photosensitive drums 221A to 221A can be kept constant. The amount of cutting 221D can be made constant. Therefore, it is not necessary to adjust the contact force of the cleaning blade 224A that contacts the surfaces of the photosensitive drums 221A to 221D with high accuracy, and the amount of scraping the surface of the photosensitive drums 221A to 221D is always kept constant with a simple configuration. Thus, the occurrence of the filming phenomenon can be prevented.

  Further, since the outer peripheral surface of the intermediate transfer belt 211 is rougher than the surface of the photoconductor drums 221A to 221D, the surface of the photoconductor drums 221A to 221D can be surely scraped by rubbing.

  Further, the filming removal operation time T in which the linear velocity of the intermediate transfer belt 211 is 1.05 times that of the photosensitive drums 221A to 221D is an integral multiple of the rotation time per rotation of the photosensitive drums 221B to 221D. It is good. This is because the surfaces of the photosensitive drums 221B to 221D are evenly shaved. If it is not an integral multiple, the surfaces of the photoconductive drums 221B to 221D are shaved unevenly, and unevenness or the like occurs in the formed toner image.

  Next, the control unit 70 stops the rotation of the photosensitive drums 221B to 221D in the monochrome mode state shown in FIG. 2B, and separates the intermediate transfer belt 211 from the photosensitive drums 221B to 221D (S10). Thereafter, post-rotation processing including filming removal operation is performed (S11), the total number of color image formation sheets is returned to zero (initial value) (S12), and the processing is terminated. The post-rotation process in the process of S11 is the same as the process of S8, but only the black photosensitive drum 221A and the intermediate transfer belt 211 continue to rotate, and the intermediate transfer at the primary transfer position PA from the middle. The linear velocity of the belt 211 is set to 1.05 times that of the photosensitive drum 221A.

  Further, the filming removal process time T in which the linear velocity of the intermediate transfer belt 211 is 1.05 times that of the photosensitive drums 221A to 221D is the rotation time per rotation of the photosensitive drum 221A as in the process of S8. It should be an integer multiple of.

  Here, after the post-rotation process of S9, the post-rotation process of S11 is further performed because the photosensitive drum 221A for monochrome images is different in diameter from the photosensitive drums 221B to 221D for color images. This is because the surface of the photosensitive drum 221A is shaved unevenly.

  Even if the diameters of the photosensitive drums 221A to 221D for color images and the photosensitive drums for monochrome images are different from each other by the processes of S10 and S11, the entire surface of each of the photosensitive drums 221A to 221D is evenly distributed. It is possible to remove the unevenness and the like from the toner image formed on the surface. The shavings on the surfaces of the photosensitive drums 221 </ b> A to 221 </ b> D are conveyed by being electrostatically attracted to the outer peripheral surface of the intermediate transfer belt 211, and removed and collected by the cleaning unit 217.

  If all the photosensitive drums have the same diameter, or a configuration in which an integral multiple of the rotation time per rotation of the color image photosensitive member and the monochrome image photosensitive member is equal, or the like, S9. Only post-rotation processing may be used.

  In this embodiment, during the image forming process, the linear velocity of the intermediate transfer belt 211 at the primary transfer positions PA to PD is 1.03 times the linear velocity of the photosensitive drums 211A to 211D. It is desirable to be 1.04 times. In the filming removal process, the linear velocity of the intermediate transfer belt 211 at the primary transfer positions PA to PD is 1.05 times the linear velocity of the photosensitive drums 211A to 211D, but is 1.05 to 1.07 times. It is desirable that

  If the linear velocity of the intermediate transfer belt 211 is too higher than the linear velocity of the photosensitive drums 221A to 221D, the surfaces of the photosensitive drums 221A to 221D are excessively shaved. On the other hand, if the linear transfer belt 211 has a linear velocity that is almost the same as that of the photosensitive drums 221A to 221D, the amount of the surface of the photosensitive drums 221A to 221D is reduced too much. It is.

  Furthermore, in this embodiment, the intermediate transfer belt 211 is made faster than the linear velocity of the photosensitive drums 221A to 221D in order to rub the photosensitive drums 221A to 221D using the intermediate transfer belt 211. If only this is required, the linear velocity of the intermediate transfer belt 211 and the photosensitive drums 221A to 221D may be made different. Therefore, the intermediate transfer belt 211 can be rubbed even if it is slower than the linear velocity of the photosensitive drums 221A to 221D. The reason why the intermediate transfer belt 211 is made faster than the linear velocity of the photosensitive drums 221 </ b> A to 221 </ b> D as in this embodiment is that the scraps on the surface of the photosensitive drums 221 </ b> A to 221 </ b> D are in the rotational direction of the intermediate transfer belt 211. This is to prevent staying in the upstream immediately before the primary transfer positions PA to PD.

  Next, when it is determined in the process of S1 that monochrome image formation is performed, the control unit 70 performs a pre-rotation process (S13). The pre-rotation process at the time of monochrome image formation is performed before image formation such as the rotation of the photosensitive drum 221A or the intermediate transfer belt 211 is started. In the pre-rotation process, the movement path of the intermediate transfer belt 211 is changed to the monochrome image forming mode shown in FIG.

  Next, the control unit 70 reads out the monochrome image formation total number value and the monochrome filming start sheet number value from a storage unit (not shown) (S14), adds up the requested monochrome image formation number, and stores it again in the storage unit. (S15). The total number of monochrome images formed is the total number of monochrome images formed on the paper after the filming removal process.

  Thereafter, an image forming process is performed (S16). Thereby, a monochrome image is formed on one sheet. Thereafter, the control unit 70 determines whether or not a new image is to be formed (S17), and repeats the process of S16 until all requested image formation is completed. On the other hand, when it is determined that the image formation for all the sheets has been completed in the process of S17, the control unit 70 determines whether or not the total number of monochrome image formation sheets is equal to or greater than the monochrome filming start sheet value (S18). ), When it is determined that the value is less than the monochrome filming start sheet value, the post-rotation process (S19) shown in FIG. 5A is performed. Thereafter, the process ends.

  The post-rotation process of S19 has the same configuration as that of S8, but only the photosensitive drum 221A is in contact with the outer peripheral surface of the intermediate transfer belt 211 and is rotating as shown in FIG. Done.

  On the other hand, if it is determined in S18 that the total monochrome image formation sheet number value is equal to or greater than the monochrome filming start sheet value, the control unit 70 performs the post-rotation process including the monochrome image filming removal operation similar to S11. (S20). Thereafter, the total number of color image formation values is returned to zero (initial value) (S21), and the process is terminated. As a result, the same effects as described above can be obtained.

  The color filming start sheet number value and the monochrome filming start sheet number value may be arbitrary values, but it is preferable to set a sheet number value at which filming will occur. In this embodiment, the filming removal operation for color images and monochrome images is performed at the first and second predetermined timings when the total number of color and monochrome image formations reaches the number of color and monochrome filming starts. However, the present invention is not limited to this. For example, it may be performed at a first predetermined timing due to color image formation such as the density of an image to be formed and the number of rotations of the photosensitive drums 221A to 221D, and at a second predetermined timing due to monochrome image formation.

  Further, in this embodiment, since the filming removal process is performed during the post-rotation process shown in FIG. 5B, the rotation of the photosensitive drums 221A to 221D and the intermediate transfer belt 211 in the post-rotation process is used. Thus, the filming phenomenon can be prevented from occurring. Note that the filming removal process does not have to be performed during the post-rotation process, and the color transfer operation until the toner images formed on the surfaces of the photosensitive drums 221A to 221D are transferred onto the paper as in the pre-rotation process. Within a predetermined period except during the (first transfer operation) and during the monochrome transfer operation (second transfer operation) until the toner image formed only on the surface of the photosensitive drum 221A is transferred to the sheet. I just need it.

  As shown in FIG. 6, when stopping the drive motors of the photosensitive drums 221 </ b> A to 221 </ b> D and the intermediate transfer belt 211 when the post-rotation process is finished, the stop timing of the drive motor of the intermediate transfer belt 211 is shifted. Thus, the configuration may be such that the linear velocity of the intermediate transfer belt 211 is made higher than the linear velocity of the photosensitive drums 221A to 221D after the post-processing rotation is completed.

  In this embodiment, the linear velocity of the intermediate transfer belt 211 is controlled using the control unit 70 provided in the image forming apparatus 100. However, a control unit that controls the operation of the transfer device 21 is provided, and this control is performed. May be used to control the linear velocity of the intermediate transfer belt 211.

  In this embodiment, the toner images carried on the surfaces of the photosensitive drums 221 to 221D are not directly transferred to the paper, but transferred to the intermediate transfer belt 211 and then transferred to the paper. It may be. For example, the transfer device has a transfer belt that is a rotatable transfer belt in which a part of the outer peripheral surface is in contact with a part of the surface of the photosensitive drum, and that conveys the paper by adsorbing the sheet onto the outer peripheral surface. Also good.

  Furthermore, in the present embodiment, the transfer device provided in the image forming apparatus capable of forming a color image has been described. However, the transfer device provided in the image forming apparatus capable of only monochrome image formation is also applicable.

1 is an explanatory diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is explanatory drawing which shows operation | movement of the transfer apparatus which concerns on embodiment of this invention. 6 is a flowchart illustrating a procedure for performing image formation processing and post-rotation processing from the start of image formation. It is a flowchart which shows the procedure which performs image formation. FIG. 6 is an explanatory diagram showing a relationship between linear velocities of an intermediate transfer belt and a photosensitive drum in image forming processing and post-rotation processing. FIG. 6 is an explanatory diagram showing a relationship between linear velocities of an intermediate transfer belt and a photosensitive drum in image forming processing and post-rotation processing.

Explanation of symbols

21-transfer device 211-intermediate transfer belt 221A to 221D-photosensitive drum 60-separating mechanism 61-cam 62-sliding member 100-image forming apparatus PA-PD-primary transfer position

Claims (14)

A developer image is carried on the surface, and is stretched along a loop-shaped path including a contact position where a part of the outer peripheral surface comes into contact with a part of the surface of the photosensitive member that is rotationally driven at a predetermined linear velocity. And an endless transfer belt supported rotatably,
A driving device for rotating the transfer belt;
In order to perform a filming removal operation for making the linear velocity of the transfer belt at the contact position higher than the linear velocity of the photosensitive member during a predetermined period excluding a transfer operation period in which the developer image is transferred to a sheet. And a control device for controlling the operation of the driving device. An endless transfer belt stretched in a loop and supported rotatably;
A driving device for rotating the transfer belt;
When forming a color image on a sheet, a part of the outer peripheral surface of the transfer belt carries a color developer of a different hue on each surface and is rotated at the same predetermined linear velocity. A plurality of color image photoreceptors and respective contact positions that contact a part of the surface of the monochrome image photoreceptor that carries a black developer image on the surface and is driven to rotate at the predetermined linear velocity. The transfer belt is stretched along a path including the above, and when forming a monochrome image on a sheet, a part of the outer peripheral surface of the transfer belt is in contact with a part of the surface of the photosensitive member for the monochrome image. A separation / contact mechanism that stretches the transfer belt along a path including only the contact position;
A control device for controlling the operation of the drive device,
The controller is
A first transfer operation period in which the color developer and the black developer at the time of forming the color image are transferred to a sheet, and a second transfer operation period in which only the black developer is transferred to the sheet at the time of forming the monochrome image. In a predetermined period excluding
With the transfer belt in contact with the plurality of color image photoreceptors and the monochrome image photoreceptor, the linear velocity of the transfer belt at the contact position is determined as the plurality of color image photoreceptors. And a filming removal operation for a color image that is faster than the linear velocity of the photosensitive member for the monochrome image,
For a monochrome image, the linear velocity of the transfer belt at the contact position is higher than the linear velocity of the photosensitive member for monochrome image in a state where the transfer belt is in contact with only the photosensitive member for monochrome image. A transfer apparatus that controls operations of the driving device and the separation / contact mechanism to perform at least one of a filming removal operation. In the color image filming operation, the transfer belt is moved to the plurality of color image photosensitive members until a time obtained by multiplying the rotation time of the rotation of the plurality of color image photosensitive members by an integral number elapses. And the linear velocity of the transfer belt at the contact position in contact with the monochrome image photoreceptor is higher than the linear velocity of the plurality of color image photoreceptors and the monochrome image photoreceptor. After the speed is increased, the transfer belt is in contact with only the monochrome image photosensitive member until a time obtained by multiplying the rotation time for one rotation of the monochrome image photosensitive member by an integral number has elapsed. Making the linear velocity of the transfer belt faster than the linear velocity of the photoreceptor for the monochrome image,
In the monochrome image filming operation, the transfer belt is brought into contact with only the monochrome image photosensitive member until a time obtained by multiplying the rotation time of the single rotation of the monochrome image photosensitive member by an integer is elapsed. The transfer apparatus according to claim 2, wherein a linear velocity of the transfer belt at the contact position in the contacted state is made higher than a linear velocity for the monochrome image. The filming removal operation for the color image is started at a first predetermined timing resulting from the first transfer operation,
4. The transfer device according to claim 2, wherein the filming removal operation for monochrome images is started at a second predetermined timing resulting from the second transfer operation. 5. The first predetermined timing is when the number of sheets on which the color image is formed reaches a predetermined number,
5. The transfer device according to claim 4, wherein the second predetermined timing is when the number of sheets on which the monochrome image is formed reaches a predetermined number.   The transfer apparatus according to claim 1, wherein the filming removal operation is started at a predetermined timing resulting from the transfer operation.   The transfer device according to claim 6, wherein the predetermined timing is when the number of sheets on which the developer image has been transferred reaches a predetermined number.   The transfer apparatus according to claim 1, wherein the filming removing operation is executed only until a time obtained by multiplying a rotation time of one rotation of the photoconductor by an integer has elapsed.   The transfer device according to claim 1, wherein an outer peripheral surface of the transfer belt is rougher than a surface of the photoconductor.   10. The transfer belt according to claim 1, wherein a linear velocity at the abutting position during the filming removing operation is 1.05 to 1.07 times a linear velocity of the photosensitive member. A transfer apparatus according to claim 1.   The transfer device according to claim 1, wherein the filming removing operation is executed after the transfer operation is completed and before the rotation of the transfer belt is stopped. In an image forming apparatus that has a rotatable photosensitive member that carries a developer image corresponding to image information on the surface and performs image formation on paper,
An image forming apparatus comprising the transfer device according to claim 1.   A part of the outer peripheral surface is stretched along a loop-shaped path including a contact position where the developer image is carried on the surface and is contacted with a part of the surface of the photosensitive member that is rotationally driven at a predetermined linear velocity. The endless transfer belt that is rotatable is transferred to the transfer belt at the contact position within a predetermined period excluding a transfer operation period for transferring the developer image onto a sheet and at a predetermined timing resulting from the transfer operation. The filming removing method is characterized in that the film is rotated so that its linear velocity is higher than that of the photosensitive member. When forming a color image on a sheet, a plurality of color images in which part of the outer peripheral surface carries color developers of different hues on the respective surfaces and each is rotated at the same predetermined linear velocity And a path including a contact position for contacting a part of the surface of the photosensitive member for a monochrome image that carries a black developer image on the surface and is driven to rotate at the predetermined linear velocity. A transfer belt in which the transfer belt is stretched in a loop shape, and when forming a monochrome image on a sheet, a part of the outer peripheral surface is a part of the surface of the photoreceptor for the monochrome image. A rotatable endless transfer belt stretched in a loop along a path including only the abutting position to abut,
Within a predetermined period excluding a first transfer operation period for transferring the color developer and the black developer to a sheet and a second transfer operation period for transferring only the black developer to the sheet,
At the first predetermined timing resulting from the first transfer operation, the transfer belt is in contact with the plurality of color image photosensitive members and the monochrome image photosensitive member in the contact position. The linear velocity of the transfer belt is rotated so as to be faster than the linear velocity of the plurality of color image photoreceptors and the monochrome image photoreceptor,
At the second predetermined timing resulting from the second transfer operation, the linear velocity of the transfer belt at the contact position is the monochrome image in a state where the transfer belt is in contact with only the monochrome image photoreceptor. A filming removing method, wherein the film is rotated so as to be faster than a linear velocity of a photosensitive member for use.

Images