JP2007025244A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the wear of an intermediate transfer body, particularly, the wear of the surface layer thereof, in an image forming apparatus having a multilayer structure intermediate transfer body and the image forming method. <P>SOLUTION: The apparatus includes a cleaner which is made attachable/detachable to/from the intermediate transfer belt 71. A toner deposition patch image Idp1 whose width Wdp is larger than the width Wim of an image forming area 71a, but, smaller than the width of the cleaner is formed on the surface of the intermediate transfer belt 71, and then, scraping the toner patch image by a cleaner blade is carried out. The wear of the surface layer formed on the surface of the intermediate transfer belt 71 is prevented by the lubricating action of the deposited toner. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including an intermediate transfer member having a surface layer capable of carrying a toner image on the surface thereof, and a cleaning unit that contacts the intermediate transfer member and removes residual toner. The present invention relates to an image forming method.

  An image forming apparatus that forms an image using toner is configured to temporarily transfer a toner image formed by an image forming unit to an intermediate transfer member and then transfer the toner image onto a recording medium such as paper. There is something. As such an intermediate transfer member, there is one having a multi-layer structure in which different materials are laminated to each other in order to satisfy both required sufficient toughness and good transferability. For example, the image forming apparatus described in Patent Document 1 includes an intermediate transfer member having an insulating base material made of a synthetic resin, a conductive layer formed thereon, and a resistance layer formed thereon. Good transfer characteristics are obtained by applying a predetermined primary transfer voltage to the conductive layer.

Japanese Patent Laid-Open No. 11-282288 (paragraph 0035, FIG. 1)

  This type of image forming apparatus is often provided with a cleaning unit that contacts the intermediate transfer member and removes residual toner, but in this case, wear of the intermediate transfer member due to friction with the cleaning unit becomes a problem. This is a particularly serious problem when an intermediate transfer member having a multilayer structure is used as in the prior art described above. This is because the surface layer is thin, so that damage and performance changes are likely to occur due to wear, and if the conductive layer under the surface layer is exposed due to wear, a short circuit accident may occur.

  The present invention has been made in view of the above problems, and an object of the present invention is to suppress wear of an intermediate transfer member, particularly its surface layer, in an image forming apparatus having an intermediate transfer member having a multilayer structure and an image forming method thereof.

  In order to achieve the above object, an image forming apparatus according to the present invention forms an intermediate transfer body having a surface layer capable of carrying a toner image on the surface thereof, and forms a toner image to be carried on the intermediate transfer body. An image forming unit; a cleaning unit that contacts the surface of the intermediate transfer member to remove toner remaining on the surface of the intermediate transfer member; and a toner image for depositing a predetermined pattern on the intermediate transfer member by the image forming unit. And a control unit that performs a toner accumulation process for sending the toner image to a contact portion between the intermediate transfer member and the cleaning unit and depositing the toner on the contact portion. .

  The image forming method according to the present invention includes an intermediate transfer member having a surface layer capable of carrying a toner image formed on the surface thereof, and a toner that contacts the surface of the intermediate transfer member and remains on the surface of the intermediate transfer member. An image forming method using an image forming apparatus including a cleaning unit that removes the toner, and in order to achieve the above object, a toner depositing toner image having a predetermined pattern is formed on the intermediate transfer member, and the toner A toner accumulation process is performed, which includes a toner accumulation step of depositing toner on the contact portion by sending the image to a contact portion between the intermediate transfer member and the cleaning unit and removing the image by the cleaning unit. It is said.

  According to these inventions, the toner deposited on the contact portion where the cleaning unit and the intermediate transfer member are in contact is interposed between the cleaning unit and the intermediate transfer member and performs a lubricating action. Can be effectively suppressed. Further, since the toner is deposited on the contact portion by removing the toner image formed by the image forming unit with the cleaning unit, a special configuration for toner deposition processing is not required.

  Here, the intermediate transfer member includes, for example, a base material made of an insulating material, a conductive layer formed of a conductive material on the base material, and the conductive material on the conductive layer. And the surface layer formed of a resistive material having a high specific resistance. Thus, by combining different materials as appropriate, both necessary and sufficient mechanical strength and good transfer characteristics can be achieved. Further, in the apparatus having such a configuration, the transfer characteristics are greatly deteriorated due to the abrasion of the surface layer, so that the effect of applying the present invention is remarkable.

  Further, the present invention can be suitably applied to an apparatus in which the cleaning unit is configured to be able to come into contact with and separate from the intermediate transfer member. In the apparatus having such a configuration, since the cleaning means comes in contact with and comes into contact with each other, it is difficult to deposit a stable amount of toner, and as a result, the intermediate transfer member is easily worn.

  In addition, when the intermediate transfer member is new, the toner is not deposited, so that the intermediate transfer member is likely to be worn. In such a case, it is desirable to perform the toner deposition process promptly.

  When the control unit can further execute a condition control operation for controlling an image forming condition of the apparatus based on a density detection result of a toner image as a patch image formed by the image forming unit. The toner accumulation process is preferably executed when the condition control operation is executed. By doing so, it is possible to shorten the waiting time of the user and improve the throughput of image formation, compared with the case where the condition control operation and the toner accumulation process are performed individually.

  Further, for example, the toner accumulation processing may be executed when the number of images formed by the image forming unit reaches a predetermined value. As described above, by regularly performing the toner deposition process, it is possible to deposit a stable amount of toner, and it is possible to more reliably prevent the intermediate transfer member from being worn.

  Further, for example, a surface area on the intermediate transfer member to which toner can be adhered by the image forming means is a maximum developing area, and a toner image is formed in a normal image forming operation by the image forming means of the maximum developing area. When the area to be formed is an image forming area, at least a part of the toner image for toner accumulation is outside the image forming area and in the width direction orthogonal to the moving direction on the intermediate transfer member. You may make it form in the area | region inside a largest image development area | region. Since a certain amount of residual toner is generated in the course of a normal image forming operation inside the image forming region, a lubricating action can be expected by depositing this toner. However, in principle, such residual toner does not occur outside the image forming area. For this reason, it is particularly effective to form a toner image for toner accumulation in this region.

  The surface area on the intermediate transfer member where the toner is removed by the cleaning unit is a cleaning region, and the surface region on the intermediate transfer member is a toner image in a normal image forming operation by the image forming unit. When the formed region is an image forming region, the width of the cleaning region in the width direction perpendicular to the moving direction on the intermediate transfer member is larger than the width of the image forming region, and the toner image for toner deposition May be formed at least in a region outside the image forming region and inside the cleaning region in the width direction. As described above, there is no residual toner due to a normal image forming operation in an area outside the image forming area. Therefore, inside the cleaning region and outside the image forming region, the intermediate transfer member and the cleaning unit are rubbed with each other without depositing toner that performs a lubricating action. Therefore, it is particularly effective to form a toner image for toner accumulation in such a region.

  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.

  FIG. 3 shows the structure of the intermediate transfer belt. The intermediate transfer belt 71 includes a base material 710a made of an insulating synthetic resin, a conductive layer 710b made of a conductive material, and a resistive surface layer made of a resistive material having a higher specific resistance than the conductive layer. This is an endless belt in which 710c is laminated in this order. Here, as the base material 710a, a PET (polyethylene terephthalate) resin can be typically used, but other materials such as a polyester resin, an acrylic resin, a polycarbonate resin, and a polyimide can be used. It is. As the conductive layer 710b, for example, a conductive paint in which conductive particles such as metal or carbon particles are mixed in a resin material can be used in addition to a metal vapor deposition film such as tin or aluminum. Further, as the surface layer 710c, for example, a conductive material (tin oxide, indium oxide, zinc oxide, titanium oxide, carbon, etc.) for adjusting the specific resistance and urethane paint containing fluororesin fine particles are used. it can.

  In the intermediate transfer belt 71 configured as described above, necessary mechanical strength and flexibility are secured by the base material 710a. Further, the primary transfer characteristics of the toner image from the photosensitive member 22 in the primary transfer region TR2 are improved by applying a predetermined primary transfer bias to the conductive layer 710b from a bias applying unit (not shown). Further, by providing a resistive surface layer 710c on the surface, the transfer characteristics to the sheet S in the secondary transfer region TR2 described later are improved. The structure of the intermediate transfer belt 71 is not limited to the structure described above, and for example, the structure described in JP-A-2002-365930 can be suitably applied.

  Returning to FIG. 1, the description of the image forming operation will be continued. 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 is taken out from the cassette 8 and conveyed one by one. The color image is secondarily transferred onto the sheet S conveyed along the path F to the secondary transfer region TR2.

  At this time, 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.

  FIG. 4 is a view showing the structure of the cleaner of this embodiment. As shown in FIG. 4A, 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. 4A). 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. 4A) and a state where it is separated from the belt 71 (FIG. 4B). More specifically, when the rotation shaft 762 is driven clockwise when the cleaner 76 is in a standby position (FIG. 4B) 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. 4A).

  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. 4A, the toner T thus scraped off is 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. 4B.

  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. 5 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 in the entire width direction, but a predetermined image forming area corresponding to the size of the sheet S, that is, having a width obtained by subtracting a predetermined margin from the sheet width. An image is formed only in 71a (area between two broken lines in FIG. 5). 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.

  In addition, when the apparatus is configured to be able to execute a plurality of image forming operation modes for forming an image having a size corresponding to each of a plurality of types of sheets having different sizes, the widest sheet among them is selected. What is necessary is just to make it the width | variety of the braid | blade 763 larger than the width | variety of a corresponding image formation area.

  In consideration of the width of the toner reservoir sheet, problems such as wear of the intermediate transfer belt 71 due to friction between the intermediate transfer belt 71 and the blade 763 and wobbling 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. 6 is a view showing the surface of the intermediate transfer belt. Hereinafter, an area on the intermediate transfer belt 71 with which the blade 763 provided on the cleaner 76 is in contact at a certain time is referred to as a contact area CR. The contact region CR moves on the intermediate transfer belt 71 in the direction opposite to the belt moving direction D2 as the intermediate transfer belt 71 moves. Of the surface area of the intermediate transfer belt 71, the area that has passed through the contact portion with the cleaner 76 when the intermediate transfer belt 71 makes one turn while the cleaner 76 is in contact, that is, two two in FIG. A region sandwiched between the chain lines is a region where the residual toner can be removed by the cleaner 76, and this region corresponds to the “cleaning region” of the present invention. The width of the contact region CR and the cleaning region in the direction (width direction) orthogonal to the moving direction D2 of the intermediate transfer belt 71 is the same as the width Wcl of the cleaner blade 763. 7, the width Wim of the image forming area 71a sandwiched between two broken lines is larger.

  When a normal image forming operation is performed, residual toner that cannot be transferred onto the sheet S in the secondary transfer region TR2 is inevitably generated inside the image forming region 71a. This is because the secondary transfer efficiency is less than 100%. Such residual toner is scraped off by the cleaner 76, and a part of the toner is accumulated in the toner accumulation space SP at the tip of the blade 763, which contributes to reducing friction between the blade 763 and the intermediate transfer belt 71.

  On the other hand, in principle, such residual toner does not occur outside the image forming area 71a. This is greatly different from the phenomenon on the surface of the photosensitive member 22 and is a phenomenon specific to the intermediate transfer member such as the intermediate transfer belt 71. That is, the toner image is formed only on the inside of the image forming area by the normal image forming operation on the photosensitive member 22, but the reverse is generally referred to as “fogging toner” on the photosensitive member after development. The toner charged to the polarity is distributed over the whole, and such toner is not transferred to the intermediate transfer belt 71 by the action of the primary transfer bias but remains on the photosensitive member 22. Therefore, a small amount of toner adheres to the outer surface of the image forming area on the surface of the photoreceptor 22 that has passed the primary transfer area TR1.

  On the other hand, in the intermediate transfer belt 71 that has passed through the primary transfer region TR1 and the secondary transfer region TR2, the toner hardly adheres outside the image forming region 71a. Therefore, outside the image forming region, the blade 763 and the surface of the intermediate transfer belt 71 are rubbed with almost no toner performing the lubricating action being supplied. Therefore, the blade 763 is bent and the surface layer 710c of the intermediate transfer belt 71 is easily worn at this portion. When the surface layer 711c of the intermediate transfer belt 71 is worn, the transfer characteristics of the toner image fluctuate and affect the image quality. When the inner conductive layer 711b is exposed, a short circuit accident or discharge occurs between the photosensitive layer 22 and the inner layer. Risk of damage to equipment.

  Furthermore, since the cleaner 76 is in contact with and separate from the intermediate transfer belt 71, it is difficult to deposit a stable amount of toner on the tip of the blade 763. This is also a point that is not considered in the cleaning technique for the photosensitive member 22 that can always be kept in contact with the cleaner.

Therefore, in this embodiment, the toner accumulation process described below is executed as necessary.
The toner accumulation process is intended to always deposit a stable amount of toner on the contact portion between the blade 763 and the intermediate transfer belt 71 in order to prevent the intermediate transfer member 71 from being worn and the blade 763 from curling. Is. In this embodiment, (1) when the photosensitive unit 2 or the transfer unit 7 is new, (2) when the number of formed images reaches a predetermined number, and (3) an image forming operation for maintaining the image quality. The toner accumulation process is executed at three timings when a condition control operation (described later) for optimizing the operation conditions of the apparatus is performed. The mode of the process differs depending on the start condition of the process described above. It will be a thing.

(1) Toner Accumulation Processing When the Photosensitive Unit 2 or the Transfer Unit 7 is New When the transfer unit 7 is new, the toner is naturally not deposited on the tip of the blade 763. Further, when the photosensitive unit 2 is replaced, the tension applied to the intermediate transfer belt 71 is temporarily released, so that the toner at the blade tip may be scattered due to vibration or the like at that time. is there. Therefore, when these units are new, a first toner accumulation process described below is executed. Whether or not these units are new can be determined, for example, as follows.

  That is, a fuse is provided in the photoconductor unit 2 and the transfer unit 7, and immediately after the power of the apparatus is turned on, a voltage sufficient to flow a current sufficient to blow the fuse is applied to the fuse. Here, if the unit is new, a current flows until the fuse is blown. On the other hand, if the unit is not new, no current flows because the fuse has already blown. Therefore, immediately after the power of the apparatus is turned on, the CPU 101 provided in the engine controller 10 can detect whether a current is flowing through the fuse provided in each unit, thereby detecting the newness of each unit. . In addition to this, for example, a memory is provided in each unit, and unit-specific information stored in the memory, for example, information such as a serial number and operating time is read to determine whether the unit is new. You may do it.

  FIG. 7 is a flowchart showing the operation immediately after the power is turned on. After the apparatus is turned on, the CPU 101 detects new products of the photosensitive unit 2 and the transfer unit 7 (step S101). Here, when any unit is new, the toner accumulation process after step S103 is executed, but when none is new, the process is ended as it is (step S102). In step S103, the toner accumulation patch image shown in FIG. 8 is formed.

  FIG. 8 is a diagram showing a first toner accumulation patch image. The first toner accumulation patch image Idp1 is a belt-like image extending in the width direction perpendicular to the moving direction D2 of the intermediate transfer belt 71, as shown in FIG. Although the image pattern is arbitrary, it can be a uniform solid image or a halftone image, for example, for ease of creation. The length Ldp of the toner accumulation patch image Idp1 along the moving direction D2 of the intermediate transfer belt 71 is necessary for supplying a sufficient amount of toner to be accumulated in the toner storage space SP to the contact portion with the blade 763. Length.

  The width Wdp of the toner accumulation patch image Idp1 is as follows. From the standpoint of preventing the intermediate transfer belt 71 from being worn and the blade 763 from curling, it is necessary to deposit toner over the entire width of the blade 763. Accordingly, the width Wdp of the toner accumulation patch image Idp1 is larger than the width Wim of the image forming area 71a provided corresponding to the sheet size on the intermediate transfer belt 71, and preferably about the same as the blade width Wcl. Is desirable. However, since the toner adhered to the intermediate transfer belt 71 beyond the blade width cannot be removed by the cleaner 76, the width Wdp of the toner accumulation patch image Idp1 should not be larger than the blade width. It can also be expected that a part of the scraped toner spreads outside the width of the toner accumulation patch image in the toner storage space SP. Accordingly, the width Wdp of the toner accumulation patch image Idp1 is preferably larger than the width Wim of the image forming region and slightly smaller than the width Wcl of the blade.

  It should be noted that to what extent toner can be adhered in the width direction of the intermediate transfer belt 71, that is, the width of the “maximum development area” in the present invention depends on the dimensions of the photosensitive member 22 and the developing roller 44. When these widths are smaller than the blade width Wcl and the width of the maximum development region is restricted by the size, it is preferable to form the toner accumulation patch image Idp over the maximum development width.

  By forming such a toner accumulation patch image Idp1 and scraping it off by the blade 763 (step S104 in FIG. 7), the toner can be accumulated in the toner storage space SP at the tip of the blade 763. It acts to effectively prevent the transfer belt 71 from being worn and the blade 763 from being damaged. When the toner is thus accumulated, the blade 763 is separated from the intermediate transfer belt 71, and the apparatus shifts to a standby state (step S105).

(2) Toner accumulation processing when the number of image formation reaches a predetermined number The contents of the toner accumulation processing in this case are the same as the toner accumulation processing after detection of a new article (steps S103 to S105 in FIG. 7). However, the toner accumulation patch image to be formed is different from the first toner accumulation patch image.

  FIG. 9 is a diagram showing a second toner accumulation patch image. The second toner accumulation patch image Idp2 is formed only in the vicinity of the end of the intermediate transfer belt 71 in the width direction, as shown in FIG. The shape of the second toner accumulation patch image Idp2 corresponds to the shape of the first toner accumulation patch image Idp1 except for the portion included in the image forming area 71a. This is because it is expected that residual toner generated in the image forming region by performing a normal image forming operation is accumulated in a portion corresponding to the image forming region in the tip portion of the blade 763. It is. Thus, by forming the toner accumulation patch image Idp2 excluding the image forming area, the lubricating action by the toner is ensured over the entire cleaning area, while preventing the intermediate transfer belt 71 from wearing and the blade 763 from curling. , Unnecessary toner consumption can be suppressed.

  Note that the toner accumulation patch image Idp2 shown in FIG. 9 has its inner end slightly inside the outer edge (broken line) of the image forming area 71a and its outer end from the outer edge (two-dot chain line) of the cleaning area. It is a little inside. The inner edge of the toner depositing patch image Idp2 is located on the inner side of the outer edge of the image forming area 71a by overlapping a part of the toner depositing patch image with the image forming area. This is to ensure toner accumulation near the portion. However, the present invention is not limited to this, and the inner edge of the toner accumulation patch image Idp2 may be substantially coincident with the outer edge of the image forming region or may be positioned slightly outside. Further, the outer edge of the toner accumulation patch image Idp2 is located inside the outer edge of the cleaning area because the scraped toner overflows beyond the cleaning area and cannot be removed and remains on the belt. This is to prevent this from happening.

  Also, instead of simply counting the number of image formations, the number of color image formations and the number of monochrome image formations are counted separately, and when they are weighted appropriately and added to each other, a predetermined value is reached. The toner accumulation process may be performed. This is because even when the number of formed images is the same for color images and monochrome images, the number of separation and contact of the cleaner 76 between them differs, resulting in different amounts of toner deposited on the tip of the blade 763. It is because it is thought that it is. That is, when forming a monochrome image, it is sufficient to keep the cleaner 76 in contact with the intermediate transfer belt 71, whereas when forming a color image, each color toner on the intermediate transfer belt 71. It is necessary to repeat the operation in which the cleaner 76 is separated while the images are overlapped and the color image is secondarily transferred to the sheet S and then the cleaner is brought into contact.

(3) Toner Accumulation Processing Performed with Condition Control Operation In this apparatus, a condition control operation is performed in which a patch image is formed immediately after the apparatus is turned on, and the image forming operation condition of the apparatus is adjusted based on the density detection result. Execute. In parallel with this, toner accumulation processing is executed. It should be noted that there are many known techniques for the condition control operation, and these known techniques can be applied as appropriate in this embodiment, and therefore the explanation of the principle and details of the operation is omitted here.

  FIG. 10 is a flowchart showing the condition control operation. When the apparatus is turned on, the engine controller 10 performs an initialization operation for each part of the apparatus (step S201). The initialization operation here is an operation for moving the developing unit 4 to a predetermined home position, an operation for detecting the position of the intermediate transfer belt 71, and an operation for raising the temperature of the fixing unit 9 to a predetermined fixing temperature. Etc. At this time, the number of times of contact of the blade 763 with the intermediate transfer belt 71 from the previous toner accumulation process to the current time stored in the RAM 107 is read, and based on this value, the length of the toner accumulation patch image Idp3 to be formed later Ldp3 is determined (step S202). Details will be described later.

  Next, among the operation parameters of each part of the apparatus, one or more parameters that affect the image density are used as density control factors, and these values are changed and set in multiple stages to form a predetermined control patch image ( Step S203). Here, the developing bias applied to the developing roller 44 will be described as a density control factor.

  FIG. 11 shows a patch image in the condition control operation. The control patch image Icp shown in FIG. 11 is composed of four image pieces of the same pattern formed with respective setting values while changing and setting the developing bias in four stages. The image pieces are formed at different positions along the moving direction D2 of the intermediate transfer belt 71. These control patch images Icp are used later to detect the density by the density sensor 60 and calculate the optimum value of the developing bias.

  Further, following the control patch image Icp, a toner accumulation patch image Idp3 is formed near the end in the width direction of the intermediate transfer belt 71 (step S204). The arrangement and the width of the toner accumulation patch image Idp3 in the width direction of the intermediate transfer belt 71 may be the same as those in the second toner accumulation patch image (FIG. 9). However, the length Ldp3 of the toner accumulation patch image Idp3 is the length determined in the previous step S202.

  Specifically, the length Ldp3 of the toner accumulation patch image Idp3 is increased as the blade contact count from the previous toner accumulation process to the present is increased. By doing this, the more the number of contacts, the greater the amount of toner sent to the contact portion between the blade 763 and the intermediate transfer belt 71, and the amount of toner accumulated at the blade tip lost due to separation and contact is recovered. Can be made. As described above, in this embodiment, since the length Ldp3 of the toner accumulation patch image Idp3 is changed depending on the number of contact times, the toner accumulation amount at the blade tip is kept stable and the blade is bent. It is preventing.

  Next, the density of each image piece constituting the control patch image Icp is detected by sampling the output of the density sensor 60 at the timing when the control patch image Icp on the intermediate transfer belt 71 passes immediately below the density sensor 60. (Step S205). The control patch image Icp and the toner accumulation patch image Idp3 whose density has been detected are scraped off by the blade 763, and the toner constituting these images is deposited near the tip of the blade 763. Further, the toner accumulated in this way is held near the tip of the blade 763 without being dropped even when the cleaner is separated by providing the toner reservoir sheet 764.

  Subsequently, from the density detection result of the control patch image Icp, an optimum value of the developing bias at which the image density becomes a predetermined target density is calculated (step S206). The optimum development bias value for each toner color thus obtained is stored in the RAM 107, and the optimum development bias thus obtained is applied to the developing roller 44 when an image is formed with each toner color. Thereby, an image can be formed with the target density.

  If the image formation is to be continued, the image formation operation is performed under the optimum development bias thus obtained. If not, the apparatus is shifted to the standby state and waits for an image formation command to be given. (Step S207). At this time, the cleaner 76 is also moved to the standby position.

  As described above, in this embodiment, a toner accumulation process for forming a toner accumulation patch image and scraping the blade 763 is performed in parallel with the condition control operation for determining the operation condition of the apparatus. By doing so, the time required for operations other than the image forming operation can be shortened, and the waiting time of the user can be reduced. Further, the toner accumulation patch image Idp3 of this embodiment is such that toner is attached only to the vicinity of the end of the intermediate transfer belt 71. This is because the toner constituting the control patch image Icp can be expected to be scraped off and accumulated on the tip of the blade 763 at the center of the intermediate transfer belt 71, and it is not necessary to supply further toner by the toner accumulation image. It is. That is, in this embodiment, the control patch image Icp formed for controlling the operating conditions of the apparatus is used as a part of the toner accumulation patch image.

  On the other hand, outside the image forming area, it is not expected that the toner scraped off near the central portion will come around. In view of this, for such a portion, the toner is supplied by the toner accumulation image Idp3, so that the occurrence of the curl or the like can be effectively prevented over the entire area of the blade 763. In this way, in areas where toner is expected to be supplied due to other factors, unnecessary toner consumption can be suppressed by omitting toner supply using a toner accumulation patch image.

  As described above, in this embodiment, when the photosensitive unit 2 or the transfer unit 7 is new, when the number of formed images reaches a predetermined number, and the condition control operation for optimizing the operation conditions of the apparatus is executed. At this time, a toner accumulation process for depositing toner on the blade tip is performed by forming a toner image for toner accumulation and scraping it off with the blade 763. In particular, toner is deposited outside the image forming area. Therefore, the friction between the intermediate transfer belt 71 and the blade 763 can be reduced by the lubricating action of the toner. As a result, in this embodiment, wear of the intermediate transfer belt 71 and damage to the blade 763 can be suppressed. .

  Among these, in the toner accumulation process when the photoconductor unit or the transfer unit is new, the toner accumulation patch image Idp1 having the full width of the cleaning area is formed. Wear of the transfer belt 71 can be suppressed. Further, in the toner accumulation process performed when the number of formed images reaches the predetermined number, the toner accumulation patch image Idp2 is formed only near the end of the cleaning area, so that the intermediate transfer belt 71 is effectively worn away. While suppressing, unnecessary toner consumption can be suppressed. Further, by using the control patch image Icp formed in the condition control operation as a part of the toner accumulation patch image, it is possible to further suppress toner consumption.

  As described above, in this embodiment, the exposure unit 6, the photoreceptor unit 2, the developing unit 4 and the like function as an “image forming unit” of the invention. Further, the intermediate transfer belt 71 and the cleaner 76 function as the “intermediate transfer member” and “cleaning unit” of the present invention, respectively. The engine controller 10 functions as a “control unit” of the present invention. Further, the toner accumulation patch image Idp1 and the like correspond to the “toner accumulation toner image” of the present invention.

  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 toner accumulation patch image in the above-described embodiment is a belt-like image (FIG. 8) straddling the image forming area 71a on the intermediate transfer belt 71, or an image extending outward from the vicinity of both ends of the image forming area 71a (see FIG. As shown in FIG. 9, the shape of the toner accumulation patch image is not limited to this and is arbitrary. For example, an image having a shape in which toner is attached only to the outside of the image forming area on the intermediate transfer belt 71 may be used.

  Further, the cleaner 76 in the above embodiment is provided with a toner reservoir sheet 763 for holding a predetermined amount of toner even in the standby position, but the toner reservoir sheet is not an essential component in the present invention. The present invention can also be applied to an apparatus using a cleaner not provided with a toner reservoir sheet, and rather exhibits an excellent effect in an apparatus having such a configuration. This is because in a cleaner that does not have a toner reservoir sheet, the accumulated toner at the blade tip tends to be lost due to the separation and contact operation. This is because it can be suppressed.

  In addition, the cleaner in the above-described embodiment is configured to be separated from and contacted to the intermediate transfer belt by rotating about a predetermined rotation axis. However, the separation and contact mechanism is not limited to this. Instead, for example, the present invention can also be applied to an apparatus configured such that the cleaner is separated and brought into contact with the intermediate transfer member by a sliding operation.

  The apparatus of each of the above embodiments includes the intermediate transfer belt 71 that is an endless belt as the “intermediate transfer body” of the present invention. For example, the apparatus includes a drum-shaped intermediate transfer body. The present invention can be applied.

  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 including an intermediate transfer member that temporarily carries a toner image and a cleaning unit that comes into contact with and separates from the intermediate transfer member.

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 an intermediate transfer belt. The figure which shows the structure of the cleaner of this embodiment. The perspective view for demonstrating the dimension of a cleaner and an intermediate transfer belt. The figure which shows the surface of an intermediate transfer belt. The flowchart which shows the operation | movement immediately after power activation. The figure which shows the 1st patch image for toner accumulation. The figure which shows the 2nd patch image for toner accumulation. The flowchart which shows condition control operation | movement. The figure which shows the patch image in condition control operation | movement.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Photoconductor unit (image formation means), 4 ... Development unit (image formation means), 6 ... Exposure means (image formation means), 10 ... Engine controller (control means), 71 ... Intermediate transfer belt (intermediate transfer body) 76 ... Cleaner (cleaning means), 761 ... Arm member, 763 ... Blade, 764 ... Toner reservoir sheet, Idp1, Idp2, Idp3 ... Toner accumulation patch image (toner accumulation toner image)

Claims (9)

An intermediate transfer body on which a surface layer capable of carrying a toner image is formed;
Image forming means for forming a toner image and carrying the toner image on the intermediate transfer member;
A cleaning unit that contacts the surface of the intermediate transfer member and removes toner remaining on the surface of the intermediate transfer member;
A toner image for toner deposition having a predetermined pattern is formed on the intermediate transfer member by the image forming unit, and the toner image is sent to a contact portion between the intermediate transfer member and the cleaning unit, and the toner is applied to the corresponding contact portion. An image forming apparatus comprising: a control unit that executes a toner accumulation process for depositing toner.   The intermediate transfer member has a base material made of an insulating material, a conductive layer formed of the conductive material on the base material, and a specific resistance higher than that of the conductive material on the conductive layer. The image forming apparatus according to claim 1, further comprising the surface layer formed of a resistive material.   The image forming apparatus according to claim 1, wherein the cleaning unit is configured to be able to be separated from and contacted with the intermediate transfer member.   The image forming apparatus according to claim 1, wherein the control unit executes the toner accumulation process when it is detected that the intermediate transfer member is new.   The control means can further execute a condition control operation for controlling an image forming condition of the apparatus based on a density detection result of a toner image as a patch image formed by the image forming means, and the condition control operation 4. The image forming apparatus according to claim 1, wherein the toner accumulation process is performed when the operation is performed.   The image forming apparatus according to claim 1, wherein the control unit executes the toner accumulation process when the number of images formed by the image forming unit reaches a predetermined value. A surface area on the intermediate transfer member to which toner can be adhered by the image forming means is a maximum development area, and a toner image is formed in a normal image forming operation by the image forming means in the maximum development area. Is the image forming area,
The toner image for toner accumulation is at least partially formed in an area outside the image forming area and inside the maximum developing area in the width direction perpendicular to the moving direction on the intermediate transfer member. The image forming apparatus according to claim 1. Of the surface area on the intermediate transfer body, the area where the toner is removed by the cleaning means is the cleaning area, and among the surface area on the intermediate transfer body, the toner image is formed in the normal image forming operation by the image forming means. When the image forming area is an image forming area,
The width of the cleaning region in the width direction orthogonal to the moving direction on the intermediate transfer member is larger than the width of the image forming region;
7. The toner accumulation toner image according to claim 1, wherein at least a part of the toner accumulation toner image is formed in an area outside the image forming area and inside the cleaning area in the width direction. Image forming apparatus. An image forming apparatus comprising: an intermediate transfer member having a surface layer capable of carrying a toner image on the surface; and a cleaning unit that contacts the surface of the intermediate transfer member and removes toner remaining on the surface of the intermediate transfer member. In an image forming method using
Forming a toner image for toner deposition of a predetermined pattern on the intermediate transfer member;
Performing a toner accumulation process including a toner accumulation step of depositing toner on the contact portion by sending the toner image to a contact portion between the intermediate transfer member and the cleaning unit and removing the toner image by the cleaning unit. An image forming method.

Images