JP2010117449A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that removes foreign matter clogging the cleaning blade of a cleaning means and thereby obtains the same effect as the reverse rotation of a transfer belt, by rotating the cleaning means around a counter roller relative to a transfer belt to be cleaned. <P>SOLUTION: The image forming apparatus includes: the transfer belt disposed in contact with at least one image carrier in a nip part and extended by at least two support rollers; and the cleaning means for removing residual toner on the surface of the transfer belt. In the image forming apparatus, the cleaning means 8 is disposed opposite to one of the support rollers, and has a mechanism that rotates the cleaning means around the counter roller (10) during the stop of the rotation of the transfer belt (7). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, and a fax machine, and more specifically, an intermediate transfer belt that is disposed in contact with at least one image carrier at a nip portion and is stretched between at least two support rollers. The present invention relates to an image forming apparatus including a transfer belt and a cleaning unit that removes residual toner on the surface of the transfer belt.

  As a conventional intermediate transfer type image forming apparatus, for example, as disclosed in Patent Document 1 according to the proposal of the present applicant, a photosensitive as an image carrier on which a toner image corresponding to an electrostatic latent image is formed. An intermediate transfer belt on which a toner image on the photosensitive drum is transferred intermediately, a primary transfer device for transferring the toner image on the photosensitive drum to the intermediate transfer belt, and an intermediate transfer belt 2. Description of the Related Art There is known a device including a secondary transfer device that collectively transfers a toner image transferred above onto a recording medium.

  This intermediate transfer belt has a multilayer structure, and the base layer is made of, for example, a fluororesin, PVDF sheet, or polyimide resin with little elongation, and the surface is covered with a smooth coat layer such as a fluororesin. The toner image formed on the image carrier is primarily transferred to the intermediate transfer belt and then secondarily transferred onto the recording medium to form a color image. After the secondary transfer, the toner image remaining on the intermediate transfer belt is cleaned by a cleaning unit.

  As the cleaning means, a method of physically scraping off toner with a cleaning blade, a method of electrostatically removing residual toner using a brush roller, and the like are known. When a cleaning blade is used as the cleaning means, the cleaning blade is clogged with foreign matters such as paper dust, which deteriorates the cleaning performance, and also causes damage to the surface of the object to be cleaned.

  As a method of physically scraping off toner with a cleaning blade, many mechanisms for contacting and separating the cleaning blade have been proposed (Patent Documents 2 to 4). That is, in Patent Document 2, a mechanism that uses both the separation of the cleaning blade and the reverse rotation of the intermediate transfer belt when rotation of the intermediate transfer belt is stopped, in Patent Document 3, a mechanism that separates each cleaning means, and in Patent Document 4, the cleaning blade is connected. An anti-shock mechanism has been proposed. However, the mechanism for separating the cleaning means as described above has many problems such as not only the impact at the time of contact and separation, but also toner dropping and toner scattering, and blade traces at the time of separation forming a streak image. .

  Therefore, a method is often used in which the transfer belt, which is the object to be cleaned, is reversely rotated by a small amount after the cleaning blade is kept in contact to remove foreign matter caught between the cleaning blades. However, in the above method, since the reverse rotation time of the motor is managed by using a timer as the reverse rotation amount control, the reverse rotation amount varies due to the control timing variation and the transfer belt torque variation.

In addition, since the transfer belt is disposed in contact with at least one photosensitive drum, if the amount of reverse rotation and the reverse rotation time differ between the transfer belt and the photosensitive drum, the transfer belt and the photosensitive drum may be damaged due to the speed difference. Cause the occurrence. Further, when the driving source for the transfer belt and the photosensitive drum is different, it is difficult to completely match the reverse rotation amount and the reverse rotation time depending on the specifications of the driving source and the driving torque difference between the transfer belt and the photosensitive drum.
Japanese Patent Laid-Open No. 5-323704 JP-A-8-63071 Japanese Patent Laid-Open No. 11-295999 Japanese Patent Laid-Open No. 11-352791

  Accordingly, the present invention solves the conventional problems as described above, and rotates the cleaning means around the opposing roller with respect to the transfer belt that is the object to be cleaned, so that the foreign matter clogged in the cleaning blade of the cleaning means. An object of the present invention is to provide an image forming apparatus that can be removed and can obtain the same effect as reverse transfer belt reversal.

  In order to solve the above-mentioned problems, the invention described in claim 1 is characterized in that at least one image carrier and a transfer belt arranged in contact with each other at a nip portion and stretched between at least two support rollers, and the transfer belt. In the image forming apparatus including a cleaning unit that removes residual toner on the belt surface, the cleaning unit is disposed to face one of the support rollers, and the cleaning unit is opposed to the facing roller when rotation of the transfer belt is stopped. It has a mechanism that rotates around a roller.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the mechanism for rotating the cleaning unit is configured such that the cleaning unit pivotally supported by the rotation center of the opposing roller moves from the position at the time of image formation to the transfer belt. It has an operation member that rotates to a position at the time of stopping rotation, and a rotation amount regulating mechanism that makes the rotation amount of the cleaning means constant. According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the mechanism that rotates the cleaning unit further includes a biasing member that holds the cleaning unit at a position at the time of image formation. .

  According to a fourth aspect of the present invention, in the image forming apparatus according to the second or third aspect, the rotation amount restricting mechanism includes a guide groove formed on a side plate of the transfer belt unit to guide the rotation of the cleaning unit, and the cleaning device. A boss provided on the side wall of the casing of the means and movably engaged with the guide groove; a base end pivotally supported at the rotation center of the counter roller; and a tip facing the scale provided on the side plate of the transfer belt unit. And an adjustment arm that is positioned on the guide groove and adjusts the rotation amount of the cleaning means by regulating the amount of movement of the guide groove of the boss. According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the rotation direction of the cleaning unit is the same as the rotation direction of the opposing roller during image formation. To do.

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the cleaning unit has a mechanism that prevents the transfer belt from being displaced during rotation. According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the mechanism in which the transfer belt is not displaced includes a cam-like member pivotally supported at the rotation center of the opposing roller, a brake piece, and the brake piece. The brake piece urging member urges the brake piece so that the cam-like member contacts the cleaning means at the time of image formation, and rotates the brake piece when the transfer belt stops rotating. Thus, as the cam-like member rotates in the same direction, the transfer belt is pressed and urged so as to prevent the transfer belt from rotating.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the transfer belt is a direct transfer (paper transfer) belt. According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the transfer belt is an intermediate transfer belt.

  The present invention is as described above. According to the invention described in claim 1, the transfer is arranged in contact with at least one image carrier at the nip portion and is stretched between at least two supporting rollers. In the image forming apparatus including a belt and a cleaning unit that removes residual toner on the surface of the transfer belt, the cleaning unit is disposed to face one of the support rollers, and the cleaning belt is stopped when rotation of the transfer belt is stopped. Since the mechanism has a mechanism that rotates the counter roller around the counter roller, the cleaning unit rotates around the counter roller when the transfer belt stops rotating (non-image formation), and the cleaning blade of the cleaning unit is clogged. The foreign matter can be removed, and the same effect can be obtained as when the transfer belt is reversed. In addition, since it is not necessary to use a timer as in the prior art, there is no variation in the amount of reverse rotation due to variations in control timing and torque variations in the transfer belt. Further, since it is not necessary to make the rotation amount the same as that of, for example, a photosensitive drum that is an image carrier, an optimum rotation amount for the transfer belt can be independently determined, which is effective for removing foreign matters from the cleaning blade. And so on.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

<Configuration and operation of image forming apparatus>
FIG. 1 shows an embodiment and is a schematic diagram of an electrophotographic apparatus (image forming apparatus) of a tandem type intermediate (indirect) transfer system. In FIG. 1, reference numeral 1 denotes a main body of an image forming apparatus, and an intermediate transfer unit 2 as a transfer belt unit is provided in a horizontal direction in the center of the main body of the apparatus. A secondary transfer unit 3 serving as a door that can also be opened and closed is pivotally supported on one side of the apparatus main body 1 on the right side of the intermediate transfer unit 2 so that it can swing left and right around the lower pivot 4. Has been. Although not shown, when the secondary transfer unit 3 swings greatly to the right, an opening is formed in the apparatus main body 1, the intermediate transfer unit 2 can be detached from the opening, and the opening is formed. As a result, the conveyance path of the paper P, which is a recording medium in the apparatus main body 1, is greatly opened, and the jammed paper P can be easily processed. That is, the opening also serves as an opening for jamming the paper P.

  The intermediate transfer unit 2 includes an endless intermediate transfer belt 7 stretched around a plurality of support rollers as an intermediate transfer member, a cleaning unit 8 that removes residual toner on the surface of the intermediate transfer belt, the plurality of support rollers, And a unit main body (not shown) for supporting the cleaning means 8. The intermediate transfer belt 7 has a multilayer structure, and the base layer is made of, for example, a fluororesin, PVDF sheet, or polyimide resin with little elongation, and the surface is covered with a smooth coat layer such as a fluororesin. ing. The intermediate transfer belt 7 is not limited to a multilayer structure, and may be composed of a single layer polyimide resin. As shown in FIG. 1, the intermediate transfer belt 7 is wound around the support rollers 10, 11, 12, and 13 and can be rotated and conveyed counterclockwise as indicated by arrows in the drawing.

  In the illustrated example, among the support rollers, the support roller 13 is a drive roller for rotating the intermediate transfer belt 7. The support roller 10 is a driven roller provided at a position facing the cleaning means 8. The support rollers 11 and 12 are driven rollers and have a function of stabilizing the primary transfer nip. In the illustrated example, the support roller 10 at a position facing the cleaning unit 8 also serves as a tension roller, and functions to apply a constant tension to the intermediate transfer belt 7. Four primary transfer rollers 15 are provided corresponding to the image forming units Y, M, C, and K of yellow, magenta, cyan, and black.

  On the intermediate transfer belt 7 stretched between the support roller 11 and the support roller 12, four image forming units Y to K of yellow, magenta, cyan, and black are arranged side by side along the conveyance direction. A tandem image forming apparatus is configured. Each image forming unit includes a photosensitive drum 21 as an image carrier, a charging unit 23 for uniformly charging the surface of the photosensitive drum, an exposure device 24, and a latent image written by light from the exposure device. Are provided with a developing unit 25 for forming a toner image, a cleaning unit 22 for removing residual toner adhering to the photosensitive drum 21 after the primary transfer, and a static eliminating device L for eliminating the surface of the photosensitive drum. The photosensitive drum 21 is driven to rotate clockwise in the drawing. In the configuration described above, at least the photosensitive drum 21 and the developing unit 25 may be integrally configured to be a process cartridge that can be detached from the apparatus main body 1.

  In the illustrated example, the secondary transfer unit 3 is configured by an endless secondary transfer belt 33 being stretched between two rollers 31 and 32 and pressed against the support roller 12 via the intermediate transfer belt 7. The image on the intermediate transfer belt 7 is transferred to the paper P. A belt cleaning device 35 is disposed outside the secondary transfer belt loop, that is, on the opposite side of the intermediate transfer unit 2, to wipe off unnecessary toner remaining after the toner is transferred to the paper P. Further, the intermediate transfer belt 7 and the secondary transfer belt 33 come into contact with each other by the transfer unit 36, the roller 37, and the roller 12 that supports the belt to form a predetermined secondary transfer nip. The sheets P are stored in sheet feeding devices (sheet feeding cassettes) 40-1 and 40-2 in the lower part of the drawing, and the uppermost sheet is separated and fed one by one by the sheet feeding roller 41. It is conveyed to the registration roller pair 43 through the guide 42.

  On the secondary transfer unit 3, a fixing device 45 for fixing the transferred image transferred onto the paper P is provided. The fixing device 45 includes a fixing roller 46 and a pressure roller 47, and is configured by pressing both rollers. The secondary transfer unit 3 is also provided with a paper transport function for transporting the paper P after image transfer to the fixing device 45. Of course, a transfer roller or a non-contact charger may be disposed as the secondary transfer unit 3, and in such a case, it is difficult to provide this sheet conveying function together. 48 is a pair of paper discharge guides, 49 is a paper discharge roller, 50 is a paper discharge section, and a toner storage section TS capable of storing replenishment toner is provided below the paper discharge section 50. There are four colors of toner, yellow, magenta, cyan, and black. The toner is in the form of a cartridge TC and is appropriately supplied to the developing means 25 of the corresponding color by a powder pump or the like. Reference numeral 51 denotes a waste toner tank of the secondary transfer unit 3.

  The operation of the image forming apparatus will be described. When a start switch (not shown) is pressed, a support roller 13 that is one of support rollers is driven to rotate by a drive motor (not shown), while the other support rollers are driven to rotate and rotate and convey the intermediate transfer belt 7. . At the same time, the photosensitive drums 21 are rotated by the individual image forming units Y to K, and single-color images of yellow, magenta, cyan, and black are formed on the photosensitive drums 21, respectively. Then, as the intermediate transfer belt 7 is conveyed, the single color images are sequentially transferred to form a composite color image on the intermediate transfer belt 7.

  On the other hand, when the start switch is pressed, one of the paper feed rollers 41 of the paper feed cassettes 40-1 and 40-2 positioned below the image forming units Y to K is selectively rotated to prepare the paper bank in multiple stages. The paper P is fed out from one of the paper feed cassettes 40-1 and 40-2, separated one by one by the paper feed roller 41, guided by the guide 42, and put into the paper feed path. Then, it is further transported by the transport roller and abuts against the registration roller pair 43 and stops.

Then, the registration roller pair 43 rotates in synchronization with the composite color image on the intermediate transfer belt 7, and the sheet P is fed between the intermediate transfer belt 7 and the secondary transfer unit 3, and transferred by the secondary transfer unit 3. A color image is recorded on the paper P. The sheet P after the image transfer is conveyed by the secondary transfer unit 3 and sent to the fixing device 45, and heat and pressure are applied when passing between the fixing roller 46 and the pressure roller 47 of the fixing device 45. After the transferred image is fixed, the paper is discharged by a paper discharge roller 49 as indicated by an arrow A and stacked on the paper discharge unit 50.
On the other hand, the residual toner remaining on the intermediate transfer belt 7 after the image transfer is removed from the intermediate transfer belt 7 after the image transfer by the cleaning unit 8 to prepare for the image formation again by the tandem image forming apparatus.

<Configuration and operation of intermediate transfer unit>
In the image forming apparatus as described above, when the intermediate transfer unit 2 or the cleaning unit 8 reaches the end of its life, it is necessary to remove it from the apparatus body 1 and replace it. Therefore, the secondary transfer unit 3 pivotally supported on one side of the apparatus body 1 is swung to form an opening, and the intermediate transfer unit 2 is rotated from the opening to the horizontal position of the cleaning unit 8. The image forming means Y to K are pulled out without being buffered, but the configuration for detaching the unit and the like is not directly related to the present invention and will not be described. Hereinafter, the cleaning unit 8 attached to the intermediate transfer unit 2 will be mainly described.

  2 is an enlarged cross-sectional view of the cleaning unit 8, and FIGS. 3A and 3B are a rotation mechanism and a rotation amount of the cleaning unit 8 during image formation and when rotation is stopped (when rotation of the intermediate transfer belt 7 is stopped). 4A and 4B are schematic sectional views showing a displacement prevention mechanism for the intermediate transfer belt 7 of the cleaning unit 8 during image formation and rotation stop, respectively.

  As shown in detail in FIG. 2, the cleaning unit 8 has a width corresponding to the belt width of the intermediate transfer belt 7, and can rotate on both sides of the rotation shaft that is the rotation center of the support roller 10 of the intermediate transfer unit 2. And a casing 53 supported by the housing. The casing 53 has a hollow box-type structure in which a portion facing the intermediate transfer belt 7 wound around the support roller 10 is opened, and a cleaning blade 54 has a tip of the intermediate transfer belt 7 in the casing 53. It is arranged in the vertical direction in contact with the surface. A brush roller 55 for removing paper dust is provided on the upstream side of the cleaning blade 54 in the rotation direction of the support roller 10, and a brush roller 56 for applying lubricant is provided on the downstream side. 57 is a lubricant made of zinc stearate, 58 is flicker, 59 is a waste toner collecting coil, 60 is a belt winding start end, 61 is a belt winding end, and 62 is a blade contact position.

  As described above, the cleaning unit 8 is disposed so as to face the support roller 10 and rotates around the facing roller. The rotation direction of the cleaning unit 8 is the same as the rotation direction of the counter roller during image formation. The rotation timing is when the rotation of the intermediate transfer belt 7 is stopped. As shown in FIG. 3, the mechanism for rotating the cleaning means 8 places the casing 53 of the cleaning means 8 pivotally supported on a rotation shaft of a support roller 10 as a counter roller through a bearing (not shown) at a position during normal operation. A holding spring 63, a solenoid 65 with a spring 64 as an operating member that rotates the casing 53 against the urging force of the spring, and a rotation amount regulating mechanism 66 that regulates the rotation amount to be constant. ing.

That is, the casing 53 of the cleaning means 8 is balanced by the spring 63 and the other side by the solenoid 65 with the spring 64 at the time of image formation by the rotating mechanism (the spring 63 and the spring 64 are free length), respectively. Although the vertical orientation as shown in the figure is maintained and held at a predetermined position (A in the same figure), when the rotation of the intermediate transfer belt 7 is stopped, the solenoid 65 is activated to resist the bias of the spring 63 and the casing 53. By pulling, the casing 53 is brought into a tilted position by rotating counterclockwise around the opposing roller (FIG. 5B).
On / off of the solenoid 65 is controlled by a signal from a main body control unit (not shown). Since this on / off control must be interlocked with the operation of the intermediate transfer belt 7, it is preferably turned on / off by a signal from the same control unit (timer) that gives a signal to the drive motor of the intermediate transfer belt 7.

  By the rotation of the cleaning means 8 during this period, the contact pressure at the tip of the cleaning blade 54 that has contacted the surface of the intermediate transfer belt 7 is temporarily relaxed, and foreign matter sandwiched between the tip edges is removed (see the arrow in FIG. 4B). ). In this case, even when the rotation of the intermediate transfer belt 7 is not stopped, that is, even when the cleaning means 8 rotates while the intermediate transfer belt 7 is rotating, a certain effect can be expected, but the rotation of the intermediate transfer belt 7 is expected. When the cleaning means 8 rotates at times, the distance that the intermediate transfer belt 7 travels is long while the contact pressure is relaxed. Therefore, foreign matter and toner that have rubbed through the cleaning blade 54 due to the decrease in the contact pressure flow out downstream, resulting in image contamination. It may become obvious. Therefore, in this embodiment, the cleaning means 8 is rotated when the rotation of the intermediate transfer belt 7 is stopped.

  As shown in FIG. 3, the rotation amount regulating mechanism 66 is formed on guide grooves 67 formed on the front and rear side plates 71 of the intermediate transfer unit 2 to guide the rotation of the cleaning unit 8 and on the inner surfaces of both side walls of the casing 53 of the cleaning unit 8. A boss 68 that is movably engaged with the guide groove 67, and a base end is pivotally supported by a slide bearing 72 on a rotation shaft that is a rotation center of the opposing roller, and a distal end is positioned so as to straddle the guide groove 67. It has a scale 73 provided on the side plate 71 of the intermediate transfer belt unit 2, and an adjustment arm 69 that adjusts the amount of rotation of the cleaning means 8 by arbitrarily regulating the amount of movement of the guide groove 67 of the boss 68. The scale 73 displays the length from the lower end of the guide groove 67. By aligning the tip of the adjustment arm 69 with the scale 73, the movement amount of the boss 68 is regulated and the rotation amount of the cleaning means 8 is controlled. It can be adjusted.

  If the rotation amount of the cleaning means 8 is too large, a problem such as a problem of the inlet seal 78 occurs, so the rotation amount needs to be optimized. In the present embodiment, the boss 68 moves in the guide groove 67 that guides the rotation of the cleaning means 8 instead of controlling the rotation time of the intermediate transfer belt with a timer as used in the normal reverse rotation control as the rotation amount regulating mechanism 66. The rotation time is adjusted by regulating the amount of rotation. That is, the boss 68 provided on the cleaning unit 8 moves in the guide groove 67 provided on the front and rear side plates 71 of the intermediate transfer unit 2, thereby rotating the cleaning unit 8 by a certain amount. When it is desired to adjust the constant amount, that is, the value of the rotation amount, the adjustment arm 69 for regulating the rotation amount is manually rotated around the opposing roller and fixed to the scale 73. As a result, the size (length) of the guide groove 67 changes and the amount of rotation can be adjusted. In the present embodiment, since the timer is not used for adjusting the rotation amount, the rotation amount can be adjusted with a simple mechanism without causing a variation in the rotation amount due to variations in timing or inertia.

  As described above, the adjustment of the rotation amount of the cleaning means 8 is performed manually while aligning the tip of the adjustment arm 69 with the scale 73, but it is manually determined to be a constant value at the time of design and manufacturing, and may not be adjusted thereafter. Depending on the conditions used, the service person may adjust. For example, when paper with a lot of paper dust is used, or when it is often used for continuous paper feeding and there is little stopping action, it is possible to intentionally increase the amount of reverse rotation to increase the foreign matter removal effect. .

  The maximum amount is the distance from the leading edge of the cleaning blade 54 to the leading end of the inlet seal 78 (L in FIG. 4A). The reason is that dirt accumulated on the leading edge of the cleaning blade 54 flows out to the outside of the entrance seal 78, and the outside of the entrance seal 78 is contaminated by dirt that flows out when the belt rotates. This is because the user operability may deteriorate. The minimum value needs to be set so that the amount of rotation does not become zero at worst in consideration of component tolerance.

  Since the intermediate transfer belt 7 is also displaced at the same time by the pressing of the cleaning blade 54 during the rotation of the cleaning unit 8, it is considered that the effect of the rotation is reduced. It is necessary to physically press and hold the intermediate transfer belt 7 to prevent displacement of the intermediate transfer belt 7. In the present embodiment, the latter means for physically pressing and holding the intermediate transfer belt 7 is adopted. The displacement prevention mechanism 79 is shown in FIG.

  That is, the mechanism 79 for preventing the intermediate transfer belt 7 from being displaced during the rotation of the cleaning unit 8 is a cam-like member 75 that is pivotally supported by the slide bearing 74 on the rotation shaft that is the rotation center of the support roller 10 that is a counter roller. And a brake piece 76 and a brake piece spring 77. The brake piece spring 77 urges the brake piece 76 at the time of image formation so that the cam-like member 75 contacts the casing 53 of the cleaning means 8, and the brake piece 76 of the cleaning means 8 when the intermediate transfer belt 7 stops rotating. As the cam 53 is rotated in the same direction by the rotation of the casing 53, the intermediate transfer belt 7 is pressed and urged to prevent the rotation of the intermediate transfer belt 7. At this time, if the rotation direction of the casing 53 of the cleaning unit 8 is the same as the rotation direction of the opposing roller at the time of image formation, the cleaning blade 54 has the same effect as when the intermediate transfer belt 7 is operated in reverse after the image formation. Foreign matter such as paper dust sandwiched between the leading edges of the paper can be removed, and the removed paper dust is collected on the collecting coil 59 together with the waste toner. Reference numeral 80 denotes a round bar that abuts the cam-like member 75, and moves with a small force along the profile (mountain shape) of the cam-like member 75. It is not always necessary to use a round bar, and instead of the round bar, a rotatable roller may be used.

  The operation of the intermediate transfer unit will be described with reference to FIGS. During operation in which the image forming apparatus is performing image formation, that is, during image formation, the intermediate transfer belt 7 is rotated and conveyed in the direction indicated by the arrow as shown in FIG. At this time, the cleaning means 8 is held with the casing 53 in a vertical orientation. The boss 68 is also in a position engaged with the lower end of the guide groove 67. The cam-like member 75 receives the bias of the brake piece spring 77 through the round bar 80 of the brake piece 76 and abuts against the casing 53 of the cleaning means 8 at the left end. The paper dust remaining on the intermediate transfer belt 7 after the secondary transfer in such a state is scraped off by the brush roller 55 and the remaining foreign matters such as toner are removed by the leading edge of the cleaning blade 54. . When the cleaned intermediate transfer belt 7 passes through the image forming units Y to K again, the toner images on the respective photosensitive drums 21 are transferred from the primary transfer roller 15 and the photosensitive drums 21 to the belts. A rigid color image is formed on the surface.

  On the other hand, when the image forming operation by the image forming apparatus is completed, the rotation transfer of the intermediate transfer belt 7 is stopped by a signal from the main body control unit. At the same time, the solenoid 65 is also turned on to operate. As a result, as shown in FIG. 5B, the cleaning means 8 is pulled counterclockwise about the rotation axis of the opposing roller 10 by the casing 53 being pulled against the spring 63 by the solenoid 65. This rotation is until the boss 68 is engaged with the upper end of the guide groove 67. When the boss 68 is engaged with the upper end, the rotation is stopped. Due to the rotation of the casing 53 of the cleaning means 8, the leading edge of the cleaning blade 54 also moves while sliding on the surface of the intermediate transfer belt 7. During this movement, as shown by the arrow, the foreign matter accumulated at the leading edge is subject to the contact pressure of the edge. Removed by loosening. At the time of this removal, the intermediate transfer belt 7 moves from the crest side to the trough side of the profile with which the round bar 80 of the brake piece 76 abuts, so that the brake piece 76 presses the belt surface with a spring 77. As a result, the intermediate transfer belt 7 is maintained in a stopped state and prevented from being displaced. Accordingly, the displacement of the intermediate transfer belt 7 cannot be prevented and the rotation effect is not reduced.

  When the image forming apparatus is operated to perform image formation again, the solenoid 65 is turned off by the signal from the main body control unit and becomes inoperative, and the casing 53 is shown in FIG. Brought to the original position shown. At this time, the boss 68 moves from the upper end to the lower end of the guide groove 67 to be engaged, and the cam-like member 75 is pushed by the casing 53 and rotated in the clockwise direction so that the profile from the valley side to the peak side. Move and push the round bar 80 up. Thereby, the brake piece 76 is returned to the original position.

As described above, when the rotation of the intermediate transfer belt 7 is stopped, the cleaning means 8 is rotated in the same direction as the facing roller 10 to easily remove foreign substances clogged at the leading edge of the cleaning blade 54. That is, the casing 53 of the cleaning unit 8 rotates in the same direction as the rotation direction of the opposing roller at the time of image formation when the rotation of the intermediate transfer belt 7 is stopped, and the intermediate transfer belt 7 is reversely operated after image formation as in the prior art. Similar results can be obtained. In other words, the same effect can be obtained without the need to reverse the transfer belt as in the prior art.
In a normal image forming apparatus, since the intermediate transfer belt is disposed in contact with at least one photosensitive drum, the reverse rotation amount of the photosensitive drum and the intermediate transfer belt needs to be the same. In the configuration, the reverse rotation amount can be uniquely determined for the intermediate transfer belt.

  In the above-described embodiment, the intermediate transfer belt 7 is shown as the transfer belt. However, when such an intermediate transfer belt is used, foreign matter biting into the cleaning blade 54 becomes obvious as defective cleaning or transfer belt scratches. It is effective because it is easy. In addition, a direct (paper) transfer belt may be used as the transfer belt, and in this case, it is effective for the cleaning blade of the direct transfer belt in which a large amount of paper dust is input to the cleaning blade.

  FIG. 5 is a schematic configuration diagram showing another embodiment in which a secondary transfer roller 85 is used in place of the secondary transfer belt 33 as a secondary transfer unit. Again, the support roller 13 is a drive roller for rotating the intermediate transfer belt 7 and also serves as a counter roller for the secondary transfer roller 85. A spring 86 is provided for abutting and urging the secondary transfer roller 85 against the support roller 13 and is provided in the secondary transfer unit together with the roller. Other configurations of the intermediate transfer unit 2 are the same as those described above. Even in such a secondary transfer unit using the secondary transfer roller 85, it is possible to expect the same operation as in the above-described embodiment.

  As mentioned above, each said embodiment showed a preferable example, and is not limited to this embodiment. For example, the image forming apparatus of the tandem type intermediate (indirect) transfer method has been described, but the present invention is also applicable to an image forming apparatus that is not such a tandem type intermediate (indirect) transfer method. Further, although the spring 63, the solenoid 65 with the spring 64, and the rotation amount regulating mechanism 66 are shown as the mechanism for rotating the cleaning means 8, it is needless to say that other mechanisms may be used. Further, the rotation amount restricting mechanism 66 is also provided with guide grooves 67 formed in the front and rear side plates 71 of the intermediate transfer unit 2 and bosses 68 provided on the inner surfaces of both side walls of the casing 53 of the cleaning means 8 movably engaged with the guide grooves. However, a mechanism other than this may be used, and the formation location of the guide groove 67 and the boss 68 may be reversed. Further, the displacement prevention mechanism 79 is also composed of the cam-like member 75, the brake piece 76, and the brake piece spring 77. However, the present invention is not limited to this, and the cam-like member 75 is fixed to the casing 53 with a screw or the like. (It is possible because the center of rotation is the same).

Next, the specific effects of the invention described in claim 2 and the following claims will be described.
According to the second aspect of the present invention, the cleaning unit is accurately moved from the position at the time of image formation to the position at which the rotation of the transfer belt is stopped by the rotation of the cleaning unit by the operating member and the rotation amount regulation by the rotation amount regulation mechanism. A certain amount can be rotated. According to the third aspect of the present invention, it is possible to operate the position balanced with the operating member by the biasing member.

  According to the fourth aspect of the invention, since the rotation amount regulating mechanism includes the guide groove, the boss, and the adjustment arm, it is easy to regulate the rotation amount of the casing of the cleaning unit.

  According to the fifth aspect of the present invention, the same effect as when the transfer belt is reversed can be obtained by setting the rotation direction of the cleaning unit to the same direction as the rotation direction of the opposing roller at the time of image formation. it can. In other words, it is possible to remove foreign matters such as paper dust sandwiched between cleaning blades with the same effect as when the transfer belt is operated in reverse after image formation, and the removed paper dust can be collected together with the waste toner on the collecting coil. it can.

  According to the sixth and seventh aspects of the present invention, it is possible to prevent the transfer belt as a cleaning target from being displaced by the pressure of the blade or the like when the cleaning unit is rotated, and the effect of the cleaning rotation is reduced. Can be prevented.

  According to the invention described in claim 8, it is effective for the cleaning blade of the direct transfer belt in which a large amount of paper dust is input to the cleaning blade. According to the ninth aspect of the invention, when the transfer belt is an intermediate transfer belt, foreign matter biting into the cleaning blade tends to manifest itself as defective cleaning or transfer belt scratches, which is effective.

1 is a schematic view of an electrophotographic apparatus (image forming apparatus) of a tandem type intermediate (indirect) transfer system, showing an embodiment of the present invention. It is an expanded sectional view of a cleaning means same as the above. (A) and (B) are schematic diagrams respectively showing a rotation mechanism and a rotation amount regulating mechanism of the cleaning unit 8 at the time of image formation and stop (when the rotation of the intermediate transfer belt is stopped). (A) and (B) are schematic cross-sectional views respectively illustrating a transfer belt displacement prevention mechanism of the cleaning means 8 during image formation and when stopped. FIG. 6 is a schematic configuration diagram showing another embodiment using a secondary transfer roller as a secondary transfer unit in place of a secondary transfer belt.

Explanation of symbols

1 Image forming apparatus body 2 Intermediate transfer unit (transfer belt unit)
3 Secondary transfer unit 4 Lower pivot point 7 Intermediate transfer belt (intermediate transfer belt)
8 Cleaning means 10, 11, 12, 13 Support roller 15 Primary transfer roller 33 Secondary transfer belt 53 Casing 54 Cleaning blades 63, 64 Spring (biasing member)
65 Solenoid (actuating member)
66 Rotation amount restriction mechanism 67 Guide groove 68 Boss 69 Adjustment arm 71 Front and rear side plate 73 of intermediate transfer unit Scale 75 Cam-like member 76 Brake piece 77 Brake piece spring 78 Inlet seal 79 Displacement prevention mechanism

Claims (9)

An image forming apparatus comprising: a transfer belt disposed in contact with at least one image carrier at a nip portion, and stretched between at least two support rollers; and a cleaning unit that removes residual toner on the surface of the transfer belt. In
The cleaning means is disposed opposite one of the support rollers;
An image forming apparatus comprising: a mechanism for rotating the cleaning unit around the opposing roller when the transfer belt stops rotating.   2. The image forming apparatus according to claim 1, wherein the mechanism for rotating the cleaning unit rotates the cleaning unit pivotally supported by the rotation center of the opposing roller from a position at the time of image formation to a position at which the rotation of the transfer belt is stopped. An image forming apparatus comprising: a member; and a rotation amount regulating mechanism that makes a rotation amount of the cleaning unit constant.   3. The image forming apparatus according to claim 2, wherein the mechanism that rotates the cleaning unit further includes a biasing member that holds the cleaning unit at a position at the time of image formation.   4. The image forming apparatus according to claim 2, wherein the rotation amount regulating mechanism is provided on a guide groove formed on a side plate of the transfer belt unit to guide the rotation of the cleaning unit, and on a side wall of the casing of the cleaning unit. A boss movably engaged with the guide groove; a base end pivotally supported at the rotation center of the opposing roller; and a tip positioned on the guide groove facing a scale provided on a side plate of the transfer belt unit; And an adjusting arm that adjusts the amount of rotation of the cleaning means by restricting the amount of movement of the guide groove.   5. The image forming apparatus according to claim 1, wherein the rotation direction of the cleaning unit is the same as the rotation direction of the opposing roller during image formation.   6. The image forming apparatus according to claim 1, wherein the cleaning unit has a mechanism that does not displace the transfer belt during rotation.   7. The image forming apparatus according to claim 6, wherein the mechanism that does not displace the transfer belt includes a cam-like member pivotally supported at the rotation center of the opposing roller, a brake piece, and the brake piece biasing member, The brake piece urging member urges the brake piece so that the cam-like member contacts the cleaning means at the time of image formation, and the cam-like member rotates in the same direction by rotation of the cleaning means when the transfer belt stops rotating. An image forming apparatus characterized in that the image forming apparatus urges the transfer belt to be pressed to prevent rotation of the transfer belt.   8. The image forming apparatus according to claim 1, wherein the transfer belt is a direct transfer (paper transfer) belt.   8. The image forming apparatus according to claim 1, wherein the transfer belt is an intermediate transfer belt.

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