JP2007047554A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent a cleaning means from being curled without increasing running cost. <P>SOLUTION: An end patch image Idp1 is formed on both sides of an end area on the outer side than an area 71a (area between broken lines) in which a toner image is formed in normal image forming operation on the surface of an intermediate image forming operation on the surface of an intermediate transfer belt 71. The end patch image Idp1 is formed to a width Wdr to which toner can be supplied from a developing roller. The toner constituting an end patch image is scraped by a cleaner blade abutting on the intermediate transfer belt 71 and accumulated at the edge part thereof. The patch image is not formed in the image forming area 71a where the toner is supplied in the normal image forming operation, whereby unnecessary toner consumption is restrained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including an intermediate transfer member that temporarily carries a toner image and a cleaning unit that contacts the toner transfer member and removes the toner, and an image forming method using the image forming apparatus.

  Some electrophotographic image forming apparatuses are provided with a cleaning blade (hereinafter also simply referred to as “blade”) for cleaning and removing toner remaining on the image carrier. In this type of apparatus, wear of the image bearing member due to friction between the image bearing member and the cleaning blade, and blade curl / breakage may be problematic. In order to prevent this, toner is always deposited on the contact portion between the image carrier and the blade. For example, in the image forming apparatus described in Patent Document 1, an output patch is formed across the width of a cleaning blade that abuts a photoconductor that is an image carrier, and is scraped off by the cleaning blade. By doing so, the occurrence of wobbling from the blade end is prevented.

Japanese Patent No. 3026035

  In the above-described conventional technology, the output patch is formed to the full width of the cleaning blade including the inside of the image area. Therefore, a large amount of toner is consumed for forming the output patch, and there is a problem that the running cost of the apparatus increases. Further, since normal image formation cannot be performed while the output patch is formed, there remains a problem that throughput of image formation is reduced.

  The present invention has been made in view of the above problems. In an image forming apparatus including an intermediate transfer member and a cleaning unit that contacts the intermediate transfer member, and an image forming method using the apparatus, the cleaning unit does not cause an increase in running cost. It is a first object of the present invention to provide a technique that can surely prevent drooling. It is a second object of the present invention to provide a technique capable of reliably preventing the cleaning unit from curling without reducing the image forming throughput.

  In order to achieve the first object, an image forming apparatus according to the present invention develops a latent image carrier capable of carrying an electrostatic latent image and the electrostatic latent image carried on the latent image carrier by toner. A developing means for forming a toner image by forming an image; an intermediate transfer body for transferring the toner image from the latent image carrier and moving around, transferring the toner image to a predetermined transfer position and transferring it to a recording material; A cleaning unit that contacts the surface of the intermediate transfer member and removes toner adhering to the surface of the intermediate transfer member after transfer to the recording material; and a direction perpendicular to the moving direction of the intermediate transfer member as a width direction. When defined, a predetermined toner image is applied to an end patch on an outer end region in the width direction of the intermediate transfer member surface outside the image forming region where a toner image corresponding to the size of the recording material is formed. The end patch image is formed as an image. It is characterized in that a control means for executing a toner deposition process to remove the serial cleaning means.

  The image forming method according to the present invention also visualizes the electrostatic latent image carried on the latent image carrier with toner to form a toner image, and transfers the toner image to an intermediate transfer member for conveyance. An image forming method for transferring to a recording material, wherein, in order to achieve the first object, when a direction perpendicular to the moving direction of the intermediate transfer member is defined as a width direction, Forming a predetermined toner image as an end patch image in an end region outside the image forming region in which the toner image corresponding to the size of the recording material is formed in the width direction; and And a step of removing the toner by a cleaning means brought into contact with the intermediate transfer member.

  In these inventions, an end patch image is formed in the end area outside the image forming area and scraped off by the cleaning means. Since the toner image transfer efficiency from the intermediate transfer member to the recording material is less than 100%, when the image forming operation is performed, the toner that could not be transferred to the recording material inside the image forming region on the surface of the intermediate transfer member. Will remain. Such toner is removed by the cleaning unit, and a part of the toner is deposited on the contact portion between the intermediate transfer member and the cleaning unit. That is, it is not always necessary to supply toner for acting as a lubricant to the inside of the image forming area. Therefore, in the present invention, by supplying toner to the end region outside the image forming region, it is possible to reliably prevent the cleaning unit from curling in a wide region from the inside to the outside of the image forming region. . Further, since the toner consumption can be significantly reduced as compared with the prior art, an increase in the running cost of the apparatus can be suppressed.

  Here, for example, when the width of the cleaning unit is larger than the width of the maximum developing region where toner can be applied onto the intermediate transfer member from the developing unit via the latent image carrier, the end portion The outermost end portion in the width direction of the patch image may be formed so as to include the outermost end portion in the width direction of the maximum development region. In order to reliably prevent the cleaning unit from curling, it is preferable to feed the toner to the entire contact portion between the intermediate transfer member and the cleaning unit. Therefore, in order to feed the toner as far as possible in the width direction, it is desirable to form an end patch image up to the outermost end of the maximum development area. However, if the toner is fed beyond the width of the cleaning unit, it cannot be removed by the cleaning unit and the recording material may be soiled.

  In the case where the developing unit includes a plurality of developing units that store toner, it is preferable that each of the plurality of developing units is used to form the end patch image. Due to the dimensional variation of the developing units, backlash, and the like, there is a possibility that the maximum developing area described above is slightly shifted in the width direction for each developing unit. Therefore, if an end patch image is formed in each of the developing devices, the toner can be expanded to the maximum in the width direction, including the variation.

  Here, if the end patch image is formed only in the end region, that is, not including the inside of the image forming region, the toner consumption can be further suppressed. On the other hand, the end patch image may be formed so that a part thereof covers the inside of the image forming area. By doing so, there is no portion where toner is not sent near the boundary between the end region and the image forming region, and it is possible to reliably prevent the cleaning means from curling from that portion.

  The control means executes density control processing for optimizing the density control factor based on the density detection result of the toner image as the control patch image formed while changing and setting the density control factor that affects the image density. In this case, when the control patch image is formed, the end patch image may be formed together. In this way, by forming the end patch image when forming the control patch image, it is not necessary to interrupt the image forming operation to form the end patch image, and the image forming throughput is improved. Can be made. Thereby, the second object is achieved.

  This effect further includes density detecting means for detecting the image density of the control patch image downstream of the transfer position in the moving direction of the intermediate transfer body, and the control means detects the density by the density detecting means. This is particularly noticeable in an apparatus configured to execute the density control process based on the result. This is because, in the apparatus configured as described above, in order to detect the density of the control patch image, a measure for passing the transfer position without transferring the control patch image to the recording material or other members. This is because the measures for this purpose are also effective for passing the end patch image through the transfer position. In other words, the control patch image and the end patch image can be formed simultaneously or successively without changing the state of the apparatus, thereby further reducing the processing time.

  In particular, in the apparatus further comprising an exposure unit that forms an electrostatic latent image by irradiating a light beam onto the surface of the photoreceptor charged to a predetermined surface potential, the latent image carrier being a photoreceptor. After the development bias to be applied to the means is optimized as the density control factor, a process for optimizing the light beam intensity as the density control factor under the optimized development bias condition is executed as the density control process. It is desirable to form the end patch image under optimized development bias conditions.

  As described above, by forming the end patch image under the optimized developing bias, the amount of toner constituting the end patch image can be stabilized. Therefore, the end patch image need not be enlarged unnecessarily, and the control of the amount of toner sent to the contact portion between the intermediate transfer member and the cleaning means is simplified.

  Further, the cleaning means extends in the width direction and has a width larger than the width of the image forming area, and a blade-like scraping member that contacts the intermediate transfer member and scrapes toner, and the scraping member. And a toner storage member that is provided at both ends of the removing member in the width direction and stores toner scraped off from the intermediate transfer member in the vicinity of the front end of the cleaning unit. The patch image may be formed on the surface area of the intermediate transfer member corresponding to the position where the toner storage member is provided in the width direction.

  According to such a configuration, when the end patch image is scraped off by the scraping member, the scraped toner is stored by the toner storing member and is held near the tip of the cleaning unit. Therefore, the frequency of toner replenishment due to the toner accumulation process can be reduced. The toner storage member is preferably extended from both end portions of the scraping member in the width direction to at least a boundary portion between the end portion region and the image forming region. In this way, a constant amount of toner can be always deposited on the portion of the contact portion between the intermediate transfer member and the cleaning means outside the image forming region. In the image forming area, residual toner generated by the image forming operation can be scraped off and used as a lubricant. Thereby, it is possible to minimize the amount of toner fed by the toner accumulation process.

  FIG. 1 is a view showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus of FIG. This apparatus forms a full color image by superposing four color toners (developers) of yellow (Y), cyan (C), magenta (M), and black (K), or only black (K) toner. The image forming apparatus forms a monochrome image using In this image forming apparatus, when an image signal is given to the main controller 11 from an external device such as a host computer, the CPU 101 provided in the engine controller 10 controls each part of the engine unit EG in response to a command from the main controller 11. Then, a predetermined image forming operation is executed, and an image corresponding to the image signal is formed on the sheet S.

  In the engine unit EG, the photosensitive member 22 is provided to be rotatable in the arrow direction D1 in FIG. A charging unit 23, a rotary developing unit 4 and a cleaning unit 25 are arranged around the photosensitive member 22 along the rotation direction D1. The charging unit 23 is applied with a predetermined charging bias, and uniformly charges the outer peripheral surface of the photoconductor 22 to a predetermined surface potential. The cleaning unit 25 removes the toner remaining on the surface of the photosensitive member 22 after the primary transfer, and collects it in a waste toner tank provided inside. The photosensitive member 22, the charging unit 23, and the cleaning unit 25 integrally constitute the photosensitive member cartridge 2, and the photosensitive member cartridge 2 is detachably attached to the apparatus main body as a whole.

  Then, the light beam L is irradiated from the exposure unit 6 toward the outer peripheral surface of the photosensitive member 22 charged by the charging unit 23. The exposure unit 6 exposes the light beam L onto the photosensitive member 22 in accordance with an image signal given from an external device, and forms an electrostatic latent image corresponding to the image signal.

  The electrostatic latent image thus formed is developed with toner by the developing unit 4. That is, in this embodiment, the developing unit 4 is configured as a support frame 40 that is rotatably provided about a rotation axis center orthogonal to the paper surface of FIG. A yellow developing device 4Y, a cyan developing device 4C, a magenta developing device 4M, and a black developing device 4K are provided. The developing unit 4 is controlled by the engine controller 10. Based on the control command from the engine controller 10, the developing unit 4 is driven to rotate, and the developing units 4Y, 4C, 4M, and 4K are selectively brought into contact with the photoreceptor 22 or have a predetermined gap. When positioned at a predetermined position facing each other, a developing roller 44 that is provided in the developing unit and carries toner of a selected color is disposed to face the photosensitive member 22, and at the facing position, the developing roller 44 performs photosensitive. Toner is applied to the surface of the body 22. As a result, the electrostatic latent image on the photosensitive member 22 is visualized with the selected toner color.

  The toner image developed by the developing unit 4 as described above is primarily transferred onto the intermediate transfer belt 71 of the transfer unit 7 in the primary transfer region TR1. The transfer unit 7 includes an intermediate transfer belt 71 stretched between a plurality of rollers 72 to 75, and a drive unit (not shown) that rotates the intermediate transfer belt 71 in a predetermined rotation direction D2 by rotationally driving the roller 73. It has. When a color image is transferred to the sheet S, each color toner image formed on the photosensitive member 22 is superimposed on the intermediate transfer belt 71 to form a color image and taken out from the cassette 8 one by one. The color image is secondarily transferred onto the sheet S conveyed to the secondary transfer region TR2 along the conveyance path F. That is, the toner image carried on the intermediate transfer belt 71 and conveyed to the secondary transfer region TR2 is secondarily transferred to the sheet S passing through the nip portion between the intermediate transfer belt 71 and the secondary transfer roller 80. The secondary transfer roller 80 is configured so as to be able to be separated from and contacted with the surface of the intermediate transfer belt 71. When the secondary transfer roller 80 is separated from the intermediate transfer belt 71, the toner on the intermediate transfer belt 71. The image passes through the secondary transfer region TR2 as it is and is conveyed further downstream.

  In order to correctly transfer the image on the intermediate transfer belt 71 to a predetermined position on the sheet S, the timing of feeding the sheet S to the secondary transfer region TR2 is managed. Specifically, a gate roller 81 is provided on the transport path F on the front side of the secondary transfer region TR2, and the gate roller 81 rotates in accordance with the timing of the circumferential movement of the intermediate transfer belt 71. S is sent to the secondary transfer region TR2 at a predetermined timing.

  Further, the sheet S on which the color image is formed in this manner is fixed with the toner image by the fixing unit 9 and is conveyed to the discharge tray portion 89 provided on the upper surface portion of the apparatus main body via the pre-discharge roller 82 and the discharge roller 83. The Further, when images are formed on both sides of the sheet S, when the rear end portion of the sheet S on which the image is formed on one side as described above is conveyed to the reversal position PR behind the pre-discharge roller 82. The rotation direction of the discharge roller 83 is reversed, whereby the sheet S is conveyed in the direction of the arrow D3 along the reverse conveyance path FR. Then, the sheet is again placed on the transport path F before the gate roller 81. At this time, the surface of the sheet S to which the image is transferred by contacting the intermediate transfer belt 71 in the secondary transfer region TR2 is first transferred. It is the opposite surface. In this way, images can be formed on both sides of the sheet S.

  A cleaner 76 is disposed in the vicinity of the roller 75. The cleaner 76 can be moved toward and away from the roller 75 by an electromagnetic clutch (not shown). Then, the blade of the cleaner 76 abuts on the surface of the intermediate transfer belt 71 that is stretched over the roller 75 while moving to the roller 75 side, and the toner that remains on the outer peripheral surface of the intermediate transfer belt 71 after the secondary transfer. Remove.

  The cleaner 76 is controlled to be separated and abutted so as to remove toner remaining on the intermediate transfer belt 71 during the same rotation as the transfer of the image onto the sheet S in the secondary transfer region TR2. . Therefore, for example, when the apparatus continuously forms monochrome images, the image transferred to the intermediate transfer belt 71 in the primary transfer region TR1 is immediately transferred to the sheet S in the secondary transfer region TR2, so that the cleaner 76 is The contact state is maintained. On the other hand, when forming a color image, the cleaner 76 needs to be separated from the intermediate transfer belt 71 while the toner images of the respective colors are superimposed on each other. Then, the toner images of the respective colors are superimposed on each other to complete a full-color image, and the cleaner 76 is brought into contact with the intermediate transfer belt 71 in order to remove residual toner in the same round as the secondary transfer onto the sheet S. It will be. The configuration and operation of the cleaner 76 will be described in detail later.

  A density sensor 60 is disposed in the vicinity of the roller 75. The density sensor 60 is provided to face the surface of the intermediate transfer belt 71 and measures the image density of the toner image formed on the outer peripheral surface of the intermediate transfer belt 71 as necessary. Based on the measurement result, this apparatus adjusts the operating conditions of each part of the apparatus that affects the image quality, for example, the developing bias applied to each developing cartridge, the intensity of the light beam L, and the like. The density sensor 60 is configured to output a signal corresponding to the image density of a region of a predetermined area on the intermediate transfer belt 71 using, for example, a reflection type photosensor. The CPU 101 can detect the image density of each part of the toner image on the intermediate transfer belt 71 by periodically sampling the output signal from the density sensor 60 while rotating the intermediate transfer belt 71.

  Further, as shown in FIG. 2, each of the developing cartridges 4Y, 4C, 4M and 4K is provided with memories 91 to 94 for storing data relating to the manufacturing lot and usage history of the developing cartridge, the remaining amount of the built-in toner, and the like. ing. Further, the developing cartridges 4Y, 4C, 4M, and 4K are provided with wireless communication devices 49Y, 49C, 49M, and 49K, respectively. Then, if necessary, these selectively communicate with the wireless communication device 109 provided on the main body side in a non-contact manner, and data is transmitted between the CPU 101 and each of the memories 91 to 94 via the interface 105. Various information such as consumable management for the developing cartridge is managed by sending and receiving. In this embodiment, non-contact data transmission / reception is performed using electromagnetic means such as wireless communication. However, a connector is provided on the main body side and each developing cartridge side, and the connector is mechanically fitted. By doing so, you may make it mutually transmit / receive data.

  Further, as shown in FIG. 2, this apparatus includes a display unit 12 that is controlled by the CPU 111 of the main controller 11. The display unit 12 is constituted by, for example, a liquid crystal display, and in accordance with a control command from the CPU 111, the operation guidance to the user, the progress of the image forming operation, the occurrence of an abnormality in the apparatus, the replacement timing of any unit, etc. A predetermined message for notification is displayed.

  In FIG. 2, reference numeral 113 denotes an image memory provided in the main controller 11 for storing an image given from an external device such as a host computer via the interface 112. Reference numeral 106 is a ROM for storing a calculation program executed by the CPU 101, control data for controlling the engine unit EG, and the like. Reference numeral 107 is a RAM for temporarily storing calculation results in the CPU 101 and other data. is there.

  In addition, the image forming apparatus is used by being mounted with four developing units that store toners of different colors as described above, as well as one developing unit or a plurality of developing units that store toner of the same color. It is also used as an image forming apparatus dedicated to monochrome images in a state where the device is mounted. That is, this image forming apparatus operates as an apparatus for forming a monochrome image with the toner color in a state where only one developing device is attached. In addition, in a state where a plurality of developing devices that store toner of the same color are mounted, the apparatus operates as an apparatus that forms a monochrome image with the toner color while switching one of them or appropriately switching between them.

  FIG. 3 is a view showing the structure of the cleaner in this embodiment. As shown in FIG. 3A, the cleaner 76 is provided with a blade 763 that contacts the intermediate transfer belt 71 and scrapes off toner on an arm member 761 that is rotatable about a rotation shaft 762. The blade 763 is made of, for example, an elastic material such as urethane rubber, and is formed in a plate shape extending in the width direction orthogonal to the moving direction of the intermediate transfer belt 71 (direction orthogonal to the paper surface of FIG. 3A). A toner reservoir sheet 764 is provided on the end surface of the blade 763 opposite to the surface facing the roller 75. The toner reservoir sheet 764 is a resin sheet-like member provided so as to line the blade 763.

  The cleaner 76 configured in this manner is rotated about the rotation shaft 762 by a drive mechanism (not shown). As a result, the blade 763 is switched between a state where it is in contact with the intermediate transfer belt 71 (FIG. 3A) and a state where it is separated from the belt 71 (FIG. 3B). More specifically, when the rotation shaft 762 is driven clockwise when the cleaner 76 is in the standby position (FIG. 3B) where the blade 763 is separated from the intermediate transfer belt 71, the blade 763 moves from the left to the right in the drawing and contacts the intermediate transfer belt 71 (cleaning position, FIG. 3A). In this case, the blade tip portion moves in a substantially horizontal direction.

  The blade 763 scrapes off the toner adhering to the intermediate transfer belt 71 in contact with the intermediate transfer belt 71. As shown in FIG. 3A, the scraped toner T is disposed upstream of the contact portion between the intermediate transfer belt 71 and the blade 763 in the conveyance direction of the intermediate transfer belt 71, and the intermediate transfer belt 71 and the blade 763. The toner is accumulated in a space surrounded by the toner reservoir sheet 764. The accumulated toner T acts as a lubricant at the contact portion between the intermediate transfer belt 71 and the blade 763 to reduce frictional resistance therebetween, thereby preventing the intermediate transfer belt 71 from being worn and the blade 763 from curling. Demonstrate the effect.

  On the other hand, when the cleaner 76 moves to the standby position, the blade 763 is separated from the intermediate transfer belt 71. At this time, the toner T accumulated in the vicinity of the tip of the blade 763 falls from the blade 763 when the toner reservoir sheet is not provided. However, in this embodiment, since the toner reservoir sheet 764 is provided, the toner T Does not fall, and remains in the space (toner storage space) SP sandwiched between the blade 763 and the toner reservoir sheet 764 as shown in FIG.

  As described above, in this embodiment, even when the blade 763 is separated from the intermediate transfer belt 71, a certain amount of toner is accumulated near the tip of the blade 763. For this reason, when the blade 763 again moves toward the intermediate transfer belt 71 and hits the surface of the intermediate transfer belt 71 and stops moving, due to the reaction, the upstream side of the contact portion in the moving direction of the contact portion or the intermediate transfer belt 71 is caused. The toner T stored in the toner storage space SP is sent to the area. Due to the lubricating action of the toner, it is possible to significantly reduce the wear of the intermediate transfer belt 71 and the occurrence of wobbling of the blade 763.

FIG. 4 is a perspective view for explaining dimensions of the cleaner and the intermediate transfer belt. On the intermediate transfer belt 71, an image is not formed all the way in the width direction, but only in a predetermined image forming area (area between two broken lines in FIG. 4) 71a corresponding to the size of the sheet S. Is formed. The width of the blade 763 of the cleaner 76 is set to be larger than the width of the image forming area 71 a and smaller than the width of the intermediate transfer belt 71. That is, when the width of the intermediate transfer belt 71 is represented by the symbol Wtb, the width of the image forming area of the intermediate transfer belt 71 is represented by the symbol Wim, and the width of the blade 763 is represented by the symbol Wcl, the following relationship is established:
Wtb>Wcl> Wim
Is true.

  By making the width Wcl of the blade 763 larger than the width Wim of the image forming area 71a, it is possible to reliably remove the toner adhering to the inside of the image forming area and its peripheral portion, and to stain the image to be formed next. Is prevented. However, if the width of the blade 763 is made too large and, for example, widened to the same level as the width Wtb of the intermediate transfer belt 71, there may be a negative effect. That is, the blade 763 that contacts the intermediate transfer belt 71 serves as a load for a motor (not shown) that drives the belt 71 to rotate, and further contacts and separates from the belt 71, so that the rotation speed of the intermediate transfer belt 71 is changed. It will be a factor. In the image forming area 71a, residual toner that cannot be completely transferred to the sheet S is generated in the secondary transfer area TR2 during the image forming operation. Such toner is scraped off by the blade 763 and lubricated. Acts. On the other hand, since a small amount of such toner is present outside the image forming area 71a, the friction between the intermediate transfer belt 71 and the blade 763 increases outside the image forming area 71a. The transfer belt 71 and the blade 763 are likely to be worn or damaged. Therefore, the width Wcl of the blade 763 is desirably as small as possible, but needs to be larger than the width 71a of the image forming region.

  If the apparatus supports a plurality of types of sheets having different sizes, the width of the blade 763 may be larger than the width of the image forming area corresponding to the widest sheet. .

  Next, the width of the toner reservoir sheet will be considered. Problems, such as wear of the intermediate transfer belt 71 due to friction between the intermediate transfer belt 71 and the blade 763, and deflection of the blade 763, may occur in the entire region where both are in contact. Therefore, it is desirable that the toner reservoir sheet 764 for suppressing this also be provided all the way in the width direction of the blade 763. That is, the width of the toner reservoir sheet 764 is desirably equal to or greater than the width Wcl of the blade 763. The blade 763 may extend to the outside.

FIG. 5 is a diagram for explaining the relationship between the widths of the respective members. As shown in FIG. 5, the photosensitive member 22 has a width Wpc larger than the width Wtb of the intermediate transfer belt 71. The width Wdr of the developing roller 44 is naturally larger than the width Wim of the image forming area on the intermediate transfer belt 71 and slightly smaller than the width Wcl of the cleaner blade 763. In other words, the cleaner blade 763 is formed wider than the developing roller 44. This is because the cleaner blade 763 is made wider than the developing roller 44 so that the toner moved from the developing roller 44 to the intermediate transfer belt 71 through the photosensitive member 22 can be reliably cleaned. This is because it is possible to prevent the sheet S and the secondary transfer roller 80 from being soiled by the toner that cannot be removed. The developing roller width Wdr here is the width of the toner-carrying region on the surface of the developing roller 44. In this embodiment, since the toner is supported on the entire surface of the developing roller 44, the length of the developing roller is equal to the developing roller width Wdr, but the toner is not configured to be supported on the entire surface. In the developing roller, the actual length of the developing roller does not necessarily match the developing roller width Wdr. Summarizing these, the following relationships between each member:
Wpc>Wtb>Wcl>Wdr> Wim
Is established.

  As a result of such a dimensional relationship, the blade 763 of the cleaner 76 comes into contact with the surface of the intermediate transfer belt 71 even in an area outside the image forming area 71a. In the image forming area 71a, the toner that has not been transferred to the sheet S in the secondary transfer area TR2 is conveyed to a contact portion with the blade 763. That is, since the transfer efficiency of the toner image from the intermediate transfer belt 71 to the sheet S is less than 100%, a part of the toner constituting the toner image carried on the intermediate transfer belt 71 is on the intermediate transfer belt 71. Remains. Further, when a jam of the sheet S (clogging on the sheet conveyance path) occurs inside the apparatus, the toner image already carried on the intermediate transfer belt 71 at that time is not transferred to the sheet by the blade 763. It will be scraped off. Such toner acts to reduce friction by being interposed between the intermediate transfer belt 71 and the blade 763.

  However, such toner is hardly generated outside the image forming area 71a. In addition, since the cleaner 76 moves away from and contacts the intermediate transfer belt 71, the toner deposited on the blade tip is likely to be scattered and lost. For this reason, the friction with the intermediate transfer belt 71 tends to increase at this portion. Further, the end portion of the blade 763 originally tends to be bent or broken due to stress concentration.

  Therefore, in this embodiment, an end patch image described below is formed on the intermediate transfer belt 71 at a predetermined timing to be examined later, and is scraped off by the blade 763 so that the end portion of the blade 763 is scraped. The toner is always deposited.

  FIG. 6 is a diagram illustrating a first example of the end patch image. The end patch image Idp1 is an area outside the image forming area 71a (hereinafter, referred to as a width direction orthogonal to the moving direction D2 of the surface of the intermediate transfer belt 71, more specifically, both ends of the surface of the intermediate transfer belt 71. Each of the “end regions” is formed at one place. In the width direction, the inner edge of the end patch image Idp1 is provided at the boundary between the image forming area 71a and the end area (broken line in FIG. 6). Further, the outer end portion of the end patch image Idp1 is extended to the maximum area where the toner can be adhered by the developing roller 44 (maximum developing area: area having a width Wdr in FIG. 6).

  The image pattern of the end patch image Idp1 and its length Ldp1 are arbitrary. For example, the following is preferable. The image pattern of the end patch image Idp1 is preferably a solid image or a high-density image equivalent thereto. This is because a part of the scraped toner spreads outside the developing roller width Wdr along the ridgeline of the blade 763 by feeding as much toner as possible to the tip of the blade 763 at a stroke. This is because the toner is expected to reach the end in the width direction. In particular, a solid image is the simplest as such an image pattern, and image formation is easy. Further, regarding the length Ldp1 of the end patch image Idp1, an amount of toner necessary and sufficient as toner to be deposited on the blade 763 is sent to the contact portion between the intermediate transfer belt 71 and the blade 763 in consideration of the image pattern. Such a length may be used.

  FIG. 7 is a diagram illustrating a second example of the end patch image. The end patch image Idp2 of the second example is different from the first example described above in that a part of the end patch image Idp2 covers the image forming area 71a. Basically, an end patch image is unnecessary because the untransferred toner is sent in the image forming area. In particular, when a large amount of toner is fed as described above, a part of the toner spreads to the side along the ridge line of the blade 763. Therefore, the inner edge of the end patch image is the outer edge of the image forming area 71a (FIG. 6). May be provided somewhat outside the broken line. However, if the inner edge of the end patch image Idp2 is provided in the image forming area 71a as in this example, an area where no toner exists at the boundary between the image forming area and the end area is generated. It can be surely prevented.

  Note that in an apparatus configured to form an image on a plurality of types of sheets having different sizes, the width of the image forming area varies depending on the sheet size. In such an apparatus, for example, the following can be performed. First, an end patch image is formed in accordance with the image forming area corresponding to the smallest minimum size. In this way, it is possible to reliably prevent a region where no toner exists between the intermediate transfer belt 71 and the blade 763 regardless of the size of the actually formed image.

  Second, one of the most frequently used sheets of each size is set as a standard size, and an end patch image is formed in accordance with an image forming area corresponding to the standard size. In the image forming area corresponding to the standard size, toner remaining after transfer due to image formation is frequently generated. Therefore, if the end patch image is formed on the outer side, there is virtually no possibility that an area where no toner exists between the intermediate transfer belt 71 and the blade 763, and more than the first case described above. It is possible to reduce the amount of toner consumed by the end patch image formation.

  FIG. 8 is a view showing a modified example of the toner reservoir sheet. In the modification shown in FIG. 8, toner reservoir sheets 7641 are provided only at both ends of the blade 763. The toner reservoir sheet 7641 has an inner end 7641 a extending inward from an end (broken line) of the image forming area 71 a of the intermediate transfer belt 71. On the other hand, the outer end portion 7641 b of the toner reservoir sheet 7641 extends to the end portion of the blade 763. The reason for this is as follows.

  As described above, in the image forming area of the intermediate transfer belt 71, a certain amount of residual toner is always conveyed along with the image forming operation. For example, in an apparatus where the secondary transfer efficiency is not so high, image formation is performed. The toner reservoir sheet may be omitted from the contact portion between the region and the blade 763. On the other hand, it is not expected that residual toner will be sent outside the image forming area, and curling tends to occur at the end of the blade 763. Therefore, it is desirable to provide a toner reservoir sheet for preventing curling. It is. Therefore, it is desirable that the outer end portion 7641b of the toner reservoir sheet 7641 is extended to at least the end portion of the blade 763. Further, in order to replenish the stored toner, it is desirable that the inner end portion 7641a of the toner storage sheet 7641 extends to at least the end portion of the image forming region, more preferably to the inner side. In this way, a part of the residual toner scraped off in the image forming area goes around to the outside of the image forming area, so that such toner can be effectively used as a lubricant outside the image forming area.

  In the apparatus having such a configuration, an end patch image Idp3 having the same shape as the end patch image Idp1 shown in FIG. 6 is formed. The toner scraped off by the blade 763 is stored at the tip of the blade 763 by the action of the toner reservoir sheet 7641. Even when the cleaner 76 performs the separation and contact operation, the toner reservoir sheet 7641 prevents the toner from dropping. Therefore, toner always accumulates at the end portion of the blade 763, and the blade 763 is prevented from curling from this portion. Further, inside the image forming area 71a, the toner that has not been transferred to the sheet S is scraped off by the blade 763 and accumulates on the leading end portion of the blade, thereby preventing the blade from curling at this portion.

  FIG. 9 is a diagram illustrating a third example of the end patch image. The example of FIG. 9 is particularly effective in an apparatus having an intermediate transfer belt 71 having a seam oblique to the width direction. The intermediate transfer belt 71 is an endless belt, and as a manufacturing method thereof, there are a method of seamlessly forming from the beginning by extrusion molding or the like, and a method of joining both ends of a belt-shaped belt material. The latter method is widely used because a belt having a complicated structure in which materials having different functions are combined can be formed. As a belt having such a seam, there is one in which the seam is inclined with respect to the belt width direction as described in, for example, Japanese Patent Application Laid-Open No. 2004-163503.

  In the apparatus having the intermediate transfer belt having such a structure, as shown in FIG. 9, both end portions of the intermediate belt 71 are end portions whose positions are different from each other in the moving direction D2 in accordance with the inclination of the seam 711. Patch images Idp4a and Idp4b may be formed.

  Next, the execution timing of the toner accumulation process for forming the end patch image will be considered. As described above, in the image forming apparatus of this embodiment, the cleaner blade 763 that is in contact with the intermediate transfer belt 71 is provided with the toner reservoir sheet 764 or 7641 for depositing toner at the tip portion thereof. The toner is prevented from dropping from the part. Therefore, the frequency of the toner accumulation process for re-supplying the toner to the tip of the blade 763 can be kept low, and one or several sheets as in the apparatus described in Patent Document 1 described in the “Background Art” section. It is not necessary to form between the sheets for each image formation.

  Further, since the end patch image on the intermediate transfer belt 71 needs to pass through the secondary transfer position TR2 and be conveyed to the contact portion with the blade 763, the secondary patch image is formed at the time of forming the end patch image. It is necessary to prevent secondary transfer in the transfer region TR2. For example, such a state can be manifested by reversing the polarity of the secondary transfer bias or by separating the secondary transfer roller 80 from the intermediate transfer belt 71. In any case, since an operation different from the normal image forming operation is required, if the toner accumulation process is incorporated in the normal image forming operation, the image forming operation is temporarily interrupted, or the toner During the execution of the deposition process, the image forming operation cannot be performed, which causes a reduction in image forming throughput.

  Therefore, in this embodiment, the toner accumulation process is executed together with the density control operation executed at a predetermined timing such as immediately after the apparatus is turned on or at the time of returning from sleep. This density control operation forms a predetermined control patch image while changing and setting density control factors that affect the image density in multiple stages, and prints the image density as a target density based on the density detection result. This is a process for obtaining the optimum value of the concentration control factor. In this embodiment, the density control factor is the developing bias applied to the developing roller 44 and the intensity (exposure power) of the exposure beam L irradiated from the exposure unit 6 to the photosensitive member 22. Hereinafter, the density control operation in the present embodiment will be described.

  FIG. 10 is a flowchart showing the density control operation in this embodiment. First, the development bias is optimized. First, one of the developing devices attached to the developing unit 4 is moved to a developing position facing the photosensitive member 22 (step S101). Then, a predetermined control patch image (for example, a solid image) is formed with each bias value while changing and setting the developing bias applied to the developing device in multiple stages (step S102). The control patch image thus formed is conveyed to the position facing the density sensor 60 via the secondary transfer region TR2 by the movement of the intermediate transfer belt 71, and the density sensor 60 detects the density of each patch image (step S103). ). Based on the detected patch image density, an optimum value of the developing bias at which the image density becomes the target density is calculated (step S104). The processes in steps S101 to S104 are repeated using each developing device until all the colors are completed (step S105).

  Subsequently, the exposure power is optimized. One of the developing units is moved again to the developing position (step S106), and the developing bias is set to the optimum value obtained previously (step S107), while the exposure power is changed and set in multiple stages and predetermined at each exposure power. A control patch image (for example, a halftone image) is formed (step S108). Here, in order to prevent the influence of the history remaining on the photosensitive member, the exposure power is changed from a small value to a gradually large value. Then, an end patch image is formed under the same image forming conditions as the last control patch image, that is, under the optimum development bias and the maximum exposure power condition (step S109).

  Then, as in the case of optimizing the developing bias, the density of each control patch image is detected (step S110), and the optimum exposure power is calculated based on the density detection result (step S111). This series of processing (steps S106 to S111) is repeated until all colors are finished (step S112).

  FIG. 11 is a diagram showing a patch image formed on the intermediate transfer belt. More specifically, FIG. 11 is a diagram showing the surface of the intermediate transfer belt 71 at the time when the above-described density control operation is completed up to step S109. At this time, a plurality of control patch images Icp formed while gradually increasing the exposure power, and subsequently end patch images Idp5a and Idp5b formed on both ends are carried on the surface of the intermediate transfer belt 71.

  As described above, in this embodiment, when the patch image Icp formed in the density control operation is formed, the end patch images Idp5a and Idp5b are formed together therewith. By doing so, the following advantages can be obtained. First, in order to form a control patch image, the apparatus performs an image forming operation, but by performing a series of image forming operations up to an end patch image, an operation for forming an end patch image is separately performed. Since it is not necessary, control becomes easy and processing time can be shortened. Further, in order to detect the density of the control patch image Icp, it is necessary to pass through the secondary transfer region TR2 and further to the downstream side. It is set so that no transfer is performed. More specifically, the secondary transfer roller 80 is separated from the surface of the intermediate transfer belt 71. The edge patch image also needs to pass through the secondary transfer region TR2 in order to be conveyed to the contact portion with the blade 763. In other words, both the control patch image and the end patch image need to pass through the secondary transfer region TR2 in a state where the secondary transfer is not performed. There is no need to change.

  In this embodiment, the end patch image is formed under the optimized developing bias and under the maximum exposure power. The reason why the end patch image is formed under such conditions is as follows. The purpose of forming the end patch image is to deposit toner on the blade tip by sending a batch of toner to the end of the blade 763. From this point, the amount of toner constituting the end patch image needs to be appropriately controlled. Here, it is known that the influence of the developing bias is dominant on the density of the solid image, and the influence of the exposure power is small. Accordingly, as an image forming condition when forming a solid image or a high density image equivalent thereto as an end patch image, at least the developing bias needs to be set to an optimum value.

  On the other hand, the exposure power is not necessarily the optimum value, but if the exposure power is too small, the solid image density may be affected, so that it is desirable to use a relatively high exposure power. Therefore, in this embodiment, the end patch image is formed with the exposure power set to the maximum. Of course, the end patch image may be formed with the optimum exposure power.To do this, after the formation of each control patch image, the density is detected and the optimum exposure power is calculated. Since the procedure of forming the end patch image after resetting the exposure power to the optimum value is required, the processing time becomes long.

  In this embodiment, when an end patch image is formed, the image density is appropriately controlled by setting the developing bias to an optimum value. As described above, by controlling the density of the end patch image, the amount of toner sent to the blade 763 is stabilized, and the length of the end patch image along the moving direction D2 of the intermediate transfer belt 71 is minimized. Since it can be suppressed, unnecessary toner consumption can be suppressed. As for the exposure power, the end patch image is formed in the state set to the maximum value without waiting for the optimum value to be calculated, so that the end portion is formed following the formation of a series of control patch images Icp. A patch image can be formed. Therefore, no extra time is consumed for forming the end patch image, and the processing time can be shortened.

  Further, in this embodiment, the end patch image is formed by each of a plurality of developing devices. Even if the end patch image is formed with any toner color, the effect is not greatly different, and it is sufficient that the end patch image is formed with at least one toner color. In this embodiment, the end patch image is formed for each of all color toners. By forming, the following effects are obtained. First, by supplying the toner to be deposited on the blade 763 from each developing device, it is possible to avoid the reduction of only the toner of a specific developing device.

Further, it is desirable that the toner is deposited up to the outermost end portion of the blade 763. Also in this respect, it is effective to form an end patch image with a plurality of developing units as described above.
This is because the positional relationship between the photosensitive member 22 and the developing roller 44 at the development position varies from one developer to another due to dimensional variations in the apparatus, backlash, and the like. This is because the position of the end patch image is slightly different for each developing device, so that the toner can be fed into a wider range than when one developing device is used.

  As described above, in this embodiment, toner accumulation processing is performed in which an edge patch image for feeding toner to the edge in the width direction of the blade 763 is formed and scraped off by the blade 763, while in the image forming area 71 a. Residual toner generated during the image forming operation is scraped off by the blade 763. As a result, toner accumulates over the entire width of the ridgeline at the tip of the blade 763, and friction with the intermediate transfer belt 71 is reduced. For this reason, the blade 763 is reliably prevented from being twisted. Further, since the patch image is formed only near the end of the intermediate transfer belt, the toner consumption is small and the running cost of the apparatus can be kept low.

  Further, since the end patch image is formed together with the control patch image formed in the density control operation, it is not necessary to perform the image forming operation again for the end patch image formation, and the processing is performed. Can be shortened. In addition, while setting the development bias to the optimum value and setting the exposure power to the maximum value to form the edge patch image, the image density of the edge patch image is properly controlled, so the toner amount is stable Therefore, the size of the end patch image can be minimized. Further, since it is not necessary to wait for the optimum exposure power to be calculated, the processing time can be further shortened.

  Further, since both the control patch image and the end patch image are images that should pass through the secondary transfer region TR2, an operation for changing the state of the apparatus (specifically, forming them all together) Does not require the separation / contact operation of the secondary transfer roller 80).

  As described above, in this embodiment, the photosensitive member 22, the rotary developing unit 4, and the intermediate transfer belt 71 function as the “latent image carrier”, “developing unit”, and “intermediate transfer member” of the present invention, respectively. is doing. The cleaner 76 functions as the “cleaning means” of the present invention. The blade 763 provided on the cleaner 76 functions as a “scraping member” of the present invention, and the toner reservoir sheets 764 and 7641 function as “toner storage members” of the present invention. In this embodiment, the engine controller 10 functions as the “control unit” of the present invention. In this embodiment, the density sensor 60 and the exposure unit 6 function as “density detection means” and “exposure means” of the present invention, respectively.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, the end patch images in the above embodiment are all rectangular, but the shape of the end patch image is not limited to this, and may be arbitrary. Further, the patch images formed at both ends of the intermediate transfer belt 71 are not necessarily the same shape, and may be different from each other. Also, the image pattern is not limited to the solid image described above, and may be a halftone image or a line image, for example.

  In the example of FIG. 11, the end patch images Idp5a and Idp5b are formed so as to move back and forth along the moving direction D2 of the intermediate transfer belt 71. However, as shown in FIG. May be aligned.

  In the above embodiment, the toner accumulation process is executed together with the density control operation. However, the density control operation is not always necessary in the present invention, and the end patch image is also necessary. Alternatively, it may be formed at a timing different from the density control operation. In this case, in order to prevent a reduction in image formation throughput, it is preferable to perform the toner accumulation process at a timing different from that during execution of the image formation operation. For example, the toner accumulation process can be performed when the number of image formations exceeds a predetermined number and the job being executed is completed.

  Further, the present invention is not only an apparatus including a rotary developing unit as in the above-described embodiment, but also a so-called tandem image forming apparatus and an image forming apparatus that forms an image based on a principle other than an electrophotographic system, The present invention can be applied to all image forming apparatuses that include an intermediate transfer member and a cleaning unit that contacts the intermediate transfer member and removes toner.

1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus in FIG. 1. The figure which shows the structure of the cleaner of 1st Embodiment. The perspective view for demonstrating the dimension of a cleaner and an intermediate transfer belt. The figure explaining the magnitude relationship of the width of each member. The figure which shows the 1st example of an edge part patch image. The figure which shows the 2nd example of an edge part patch image. FIG. 9 is a diagram illustrating a modified example of a toner reservoir sheet. The figure which shows the 3rd example of an edge part patch image. The flowchart which shows the density | concentration control operation in this embodiment. FIG. 4 is a diagram showing a patch image formed on an intermediate transfer belt.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Photoconductor cartridge, 4 ... Developing unit (developing means), 4C, 4K, 4M, 4Y ... Developing device, 6 ... Exposure unit (exposure means), 10 ... Engine controller (control means), 22 ... Photoconductor (latent Image bearing member), 60 ... Density sensor (density detecting means), 71 ... Intermediate transfer belt (intermediate transfer member), 76 ... Cleaner (cleaning means), 763 ... Blade (scraping member), 764, 7641 ... Toner reservoir sheet (Toner storage member), Idp1 to Idp3 ... end patch image

Claims (10)

A latent image carrier capable of carrying an electrostatic latent image;
Developing means for visualizing the electrostatic latent image carried on the latent image carrier with toner to form a toner image;
An intermediate transfer member for transferring the toner image from the latent image carrier and moving around, transferring the toner image to a predetermined transfer position and transferring it to a recording material;
Cleaning means for removing toner adhering to the surface of the intermediate transfer body after transfer to the recording material, in contact with the surface of the intermediate transfer body;
When the direction perpendicular to the moving direction of the intermediate transfer member is the width direction,
A predetermined toner image is formed as an end patch image in an outer end region in the width direction of the intermediate transfer member surface in the width direction from an image forming region where a toner image corresponding to the size of the recording material is formed. An image forming apparatus comprising: a control unit that executes toner accumulation processing for removing the end patch image by the cleaning unit.   The width of the cleaning unit is larger than the width of the maximum developing region where toner can be applied to the intermediate transfer member from the developing unit via the latent image carrier, and the width of the end patch image in the width direction is larger. The image forming apparatus according to claim 1, wherein the outer end portion is formed to include an outermost end portion in the width direction of the maximum developing region. The developing means includes a plurality of developing devices for storing toner,
The image forming apparatus according to claim 2, wherein the control unit forms the end patch image with each of the plurality of developing devices.   The image forming apparatus according to claim 1, wherein the end patch image is formed only in the end region.   The image forming apparatus according to claim 1, wherein a part of the end patch image is formed in the image forming area.   The control means is configured to execute a density control process that optimizes a density control factor based on a density detection result of a toner image as a control patch image formed while changing and setting a density control factor that affects the image density. The image forming apparatus according to claim 1, wherein when the control patch image is formed, the end patch image is also formed. Further comprising density detecting means for detecting the image density of the control patch image on the downstream side of the transfer position in the moving direction of the intermediate transfer member;
The image forming apparatus according to claim 6, wherein the control unit executes the density control process based on a detection result by the density detection unit. The latent image carrier is a photoreceptor;
Exposure means for forming an electrostatic latent image by irradiating a light beam onto the surface of the photoreceptor charged to a predetermined surface potential;
The control means optimizes the developing bias applied to the developing means as the density control factor, and then optimizes the intensity of the light beam as the density control factor under the optimized developing bias condition. The image forming apparatus according to claim 6, wherein the end patch image is formed as a control process and is optimized under a development bias condition. The cleaning means extends in the width direction and has a width larger than the width of the image forming region, and a blade-shaped scraping member that contacts the intermediate transfer member and scrapes toner, and the scraping member And a toner storage member that stores toner scraped off from the intermediate transfer member in the vicinity of the front end of the cleaning means,
The image forming apparatus according to claim 1, wherein the end patch image is formed on a surface region of the intermediate transfer member corresponding to a position where the toner storage member is provided in the width direction. In an image forming method in which an electrostatic latent image carried on a latent image carrier is visualized with toner to form a toner image, and the toner image is transferred to an intermediate transfer member and conveyed to a recording material.
When the direction perpendicular to the moving direction of the intermediate transfer member is the width direction,
On the surface of the intermediate transfer member, a predetermined toner image is formed as an end patch image in an end region outside the image forming region in which the toner image corresponding to the size of the recording material is formed in the width direction. Process,
And a step of removing the edge patch image by a cleaning unit in contact with the intermediate transfer member.

Images