JP2006235347A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To hold a transfer unit at a state that it does not contact a photoreceptor drum at the time of attachment/detachment of the transfer unit which does not perform an image forming operation, etc. <P>SOLUTION: This image forming apparatus is constituted so that the transfer unit has an intermediate transfer belt on which toner images formed in a plurality of image carriers by every color component are sequentially transferred, a plurality of transfer rollers provided progressively or retractively between a pressure welded position for holding the intermediate transfer belt at a pressure welded state to the image carriers and a retracted position for releasing the pressure welded state, a transfer roller energization member for energizing the transfer rollers on the side of the pressure welded position and a belt elevation means capable of pressurizing the transfer roller on the side of the retracted position against energization force of the transfer roller energization member to elevate the intermediate transfer means and pressurization of the belt elevation means to the transfer roller is released by providing a pressurization releasing means on the side of the apparatus main frame and engaging the pressurization releasing member into the belt elevation means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus including a transfer unit having an intermediate transfer belt for transferring a toner image formed on an image carrier onto recording paper or the like.

  Conventionally, in an image forming apparatus such as a copying machine, a copying machine, a facsimile machine, and a multifunction machine having these functions, a toner image formed on a photosensitive drum is transferred to a recording paper or the like by a transfer device and then fixed. A method of fixing a toner image on recording paper or the like by an apparatus is widely used.

  In recent years, an image forming apparatus capable of forming a color image in addition to a monochrome image has become common. As this type of color image forming apparatus, a photosensitive drum corresponding to each color (for example, cyan, magenta, yellow, and black). A so-called tandem type is known in which a plurality of toners are arranged along the moving direction of the intermediate transfer belt. The tandem apparatus includes a transfer device having an intermediate transfer belt and a plurality of rollers that stretch the belt, and a transfer unit that forms a main part of the transfer device is detachable for maintenance and inspection of the device. Generally, it has a configuration. Also, during the image forming operation of the image forming apparatus, the toner image is transferred onto a recording paper or the like with the intermediate transfer belt pressed against the surface of the photosensitive drum by a roller. If the transfer unit is attached or detached in this state, the surface may be damaged due to rubbing between the intermediate transfer belt and the photosensitive drum, and various techniques for separating the transfer unit from the photosensitive drum are proposed. Has been.

As a conventional technique for separating such a transfer unit and the photosensitive drum, for example, a guide pin protruding from the transfer unit is guided by a guide rail provided in the apparatus main body, so that the transfer unit is moved to the apparatus main body. In a case where the image forming apparatus is configured such that a part of the guide rail extending substantially horizontally is bent downward toward the photosensitive drum, and the transfer unit is located at a position other than the regular mounting position. A technique is known in which the intermediate transfer belt is in contact with the surface of the photosensitive drum when the intermediate transfer belt is separated from the surface of the photosensitive drum and the transfer unit is in the regular mounting position (for example, Patent Document 1). reference).
JP 2000-275987 A (FIG. 4)

  However, in the technique disclosed in Patent Document 1, it is necessary to provide a guide pin on the transfer unit side and a guide rail having a complicated structure for guiding the guide pin on the apparatus main body side. In particular, the guide rail must be curved rather than straight, so that the guide rail is worn and deformed by repeatedly passing the guide pin through the curved portion, and the positioning accuracy of the transfer unit There are problems such as lowering of the image quality and the inability to smoothly attach and detach the transfer unit. Further, since the entire transfer unit moves in the apparatus so as to be close to or away from the photosensitive drum according to the guide rail, there is a problem that the space in the apparatus is wasted.

  The present invention has been made based on such knowledge. With a simple configuration, the transfer unit is brought into contact with the photosensitive drum during an image forming operation, while the transfer unit not performing the image forming operation is attached or detached. The main object of the present invention is to provide an image forming apparatus capable of holding the transfer unit in a state not in contact with the photosensitive drum.

  In order to solve the above problems, an image forming apparatus according to the present invention is an image forming apparatus including a transfer unit that can be attached to and detached from the apparatus main body. Between the intermediate transfer belt to which the toner images formed on the image carrier are sequentially transferred, a press-contact position for holding the intermediate transfer belt in a press-contact state with respect to the image support, and a retracted position for releasing the press-contact state. A plurality of transfer rollers provided so as to be able to advance and retreat, a transfer roller urging member that urges the transfer roller toward the pressure contact position, and an urging force of the transfer roller urging member to raise and lower the intermediate transfer belt A belt lifting means capable of pressing the transfer roller toward the retracted position, and a press release member for releasing the pressure of the belt lifting means against the transfer roller by engaging with the belt lifting means on the apparatus main body side. To.

  According to this, when performing image formation with a relatively simple structure, the belt elevating means is engaged with the pressure release member to hold the transfer unit in contact with the image carrier, while image formation is performed. When the transfer unit is not attached or detached, the transfer unit can be held in contact with the image carrier without engaging the belt lifting means with the pressing release member. Therefore, when image formation is not performed, it is possible to prevent the surface from being damaged due to friction between the intermediate transfer belt and the photosensitive drum when the transfer unit is attached or detached. The transfer unit has a very simple configuration. For example, the transfer unit does not need to include means for moving the intermediate transfer belt up and down by electric drive.

  In this case, by properly disposing the pressing release member, when the transfer unit is in a position other than the normal mounting position, the transfer unit is held in a state not in contact with the image carrier, while the transfer unit is in the normal mounting position. The transfer unit can be held in contact with the image carrier.

  According to a second aspect of the present invention, the image forming apparatus further includes a transfer roller driving mechanism on the apparatus main body side that causes the transfer roller to advance and retreat in a state where the pressing of the belt elevating unit to the transfer roller is released. can do.

  According to this, even after the transfer unit is mounted on the apparatus main body, the transfer roller is caused to advance and retreat according to the image forming operation of the image forming apparatus even if the pressing of the belt lifting means is released by the press releasing member. be able to. In this case, the transfer of the belt lifting / lowering means can be performed by engaging the transfer roller driving mechanism with the transfer roller at the same time or before the pressing of the belt lifting / lowering means to the transfer roller is released, thereby enabling the forward / backward movement. Even after the pressure on the roller is released (usually, after the transfer unit is set at the normal mounting position), the forward / backward movement of the transfer roller can be properly controlled.

  According to a third aspect of the present invention, the belt elevating means may be a link mechanism having an arm member that is movably supported so as to press the transfer roller. According to this, it becomes possible to press the transfer roller by the belt elevating means using a relatively simple mechanical structure.

  According to a fourth aspect of the present invention, the belt elevating means has an arm urging member that urges the arm member toward the pressing side of the transfer roller, and the arm urging member is engaged with the press releasing member. It can be set as the structure by which the urging | biasing with respect to the arm member of a member is cancelled | released. According to this, it becomes possible to press the transfer roller by the belt raising / lowering means using a relatively simple mechanical structure, and it is not necessary to provide an electric drive source in the transfer unit.

  In the image forming apparatus, the arm urging member urges a pressure releasing member that engages with the belt elevating means, and the transfer unit is a pressure releasing member for urging the arm urging member. It can be set as the structure pressed in the direction removed from an apparatus main body by reaction force of.

  According to this, when the operator removes the transfer unit from the apparatus main body, the transfer unit is pressed in the removal direction by the reaction force of the pressing release member, so that the transfer unit can be easily removed and the maintainability is improved. In particular, when a fixing tool (such as a latch) that fixes the transfer unit to the regular mounting position is released, the transfer unit is partially pushed out in the removal direction by the reaction force of the pressing release member, thereby removing the transfer unit. Becomes easier.

  In the image forming apparatus, the transfer roller driving mechanism may cause the arm member to move in a state where the urging force of the arm urging member to the arm member is released. According to this, with a relatively simple configuration, even after the transfer unit is mounted on the apparatus body and the pressing of the belt elevating means against the transfer roller is released, the transfer roller moves forward and backward according to the image forming operation of the image forming apparatus. Can be made.

  In the image forming apparatus, as described in claim 7, the belt elevating means moves the plurality of arm members that press the plurality of transfer rollers corresponding to the image carrier for each color component excluding black in conjunction with each other. It can be set as the structure further provided with the arm drive member to be made. According to this, a plurality of transfer rollers corresponding to the image carrier of each color component excluding black and a transfer roller corresponding to the black image carrier can be driven at different operation timings, thereby reducing the driving load. be able to.

  As described in claim 8, the image forming apparatus further includes a guide member that guides attachment / detachment of the transfer unit on the apparatus main body side, and the transfer unit moves itself linearly while contacting the guide member. It can be set as the structure further provided. According to this, the structure for attaching / detaching the transfer unit to / from the apparatus main body is simplified, and the transfer unit can be accurately positioned relative to the apparatus main body. Further, since it is not necessary to make the guide rail curved, it is difficult for the guide rail to be worn or deformed even if the guide pin is repeatedly passed.

  In the image forming apparatus, the transfer unit is disposed between the pair of support rollers around which the intermediate transfer belt is wound, and the support roller and the transfer roller, and is in a pressure contact position like the transfer roller. And a tension roller provided so as to be movable back and forth between the retracted position and a tension roller urging member for urging the tension roller toward the pressure contact position. The tension roller can be pressed toward the retracted position against the urging force, and the pressing release member can be configured to release the pressing of the belt lifting means against the tension roller by engaging with the belt lifting means. .

  According to this, when performing image formation with a relatively simple structure, the belt elevating means is engaged with the pressure release member to hold the transfer unit in contact with the image carrier, while image formation is performed. When the transfer unit is not attached or detached, the transfer unit can be held in contact with the image carrier without engaging the belt lifting means with the pressing release member.

  According to the present invention, in an image forming apparatus including a transfer unit that can be attached to and detached from the apparatus main body, a transfer unit that does not perform an image forming operation while bringing the transfer unit into contact with a photosensitive drum during an image forming operation with a simple configuration. The transfer unit can be kept out of contact with the photosensitive drum when attaching or detaching.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram showing a schematic structure of a copying machine according to the present invention. This multi-function machine (image forming apparatus) 1 is a photosensitive drum (image carrier) 3A-3D that forms toner images for each color component of cyan, magenta, yellow, and black in a housing 2 that defines the apparatus main body. And a transfer device 4 that superimposes toner images formed on the plurality of photosensitive drums 3A to 3D and combines them into a color image and transfers them to a recording sheet, and is set in a paper feed cassette 5 The recording paper is sent to the transfer device 4 along the conveyance path 6 and the toner image is transferred to the recording surface. Then, the recording paper is sent to the fixing device 7 and the toner image on the recording surface is heated and fixed. Discharged to the top.

  The transfer device 4 includes an intermediate transfer belt 11 to which toner images formed on a plurality of image carriers for each color component are sequentially transferred, a pair of support rollers 12A and 12B around which the intermediate transfer belt 15 is wound, and a photosensitive member. A plurality of transfer rollers 13A-13D provided so as to be able to advance and retreat between a press-contact position for holding the intermediate transfer belt 11 in a press-contact state with respect to the body drum 3A-3D and a retracted position for releasing the press-contact state, and transfer thereof Similar to the rollers 13A to 13D, a tension roller 14 provided so as to be able to advance and retreat between the pressure contact position and the retracted position, and a pressure roller 15 for secondary transfer of the toner image on the intermediate transfer belt 11 to the recording paper are provided. is doing. Here, the intermediate transfer belt 11, the support rollers 12 </ b> A and 12 </ b> B, the transfer rollers 13 </ b> A to 13 </ b> D, and the tension roller 14 constitute a transfer unit 16.

  Although a detailed description is omitted here, a document placing table, a document cover, an ADF, an optical image reading unit, and the like are provided on the upper portion of the multifunction device 1. Further, a laser unit for forming an electrostatic latent image on the photosensitive drums 3A to 3D by irradiating laser light on the periphery of the photosensitive drums 3A to 3D based on the image data, and the photosensitive drums 3A to 3D. A charging device for uniformly charging the image forming surface, a developing roller for developing toner by supplying toner to the photosensitive drums 3A to 3D, and the like, constitute an image forming unit. ing.

  FIG. 2 is a schematic diagram showing an outline of a transfer unit attaching / detaching method in the multifunction machine shown in FIG. In the multifunction machine 1, the transfer unit 16 can be attached to and detached from the apparatus main body during maintenance inspection of the transfer unit 16 and its peripheral devices. As shown in FIG. 2, when removing the transfer unit from the apparatus main body, the transfer unit 16 is exposed by tilting an opening / closing door 21 rotatably supported by a support shaft 20 of the apparatus main body, and then the transfer unit. 16 can be pulled out in the horizontal direction. On the other hand, when the transfer unit 16 is mounted on the apparatus main body, the transfer unit 16 can be set in the normal mounting position by pushing it in the horizontal direction.

  Here, as a preferred example, a configuration in which the attaching / detaching operation of the transfer unit 16 is achieved only by a linear movement in the horizontal direction is shown, but the present invention is not necessarily limited to such an attaching / detaching operation. In some cases, the moving direction of the transfer unit may be a direction inclined upward or downward, or a configuration in which the transfer unit is further moved in the vertical direction after being moved in the horizontal direction is also possible.

  3 is a perspective view showing a schematic configuration of a transfer unit in the image forming apparatus shown in FIG. The transfer unit 16 includes a pair of support rollers 12A and 12B around which the intermediate transfer belt 11 is wound, a pair of side plates 25 and 26 that hold transfer rollers and tension rollers (not shown), and an upper plate 27. have.

  Although details will be described later, the upper plate 27 is provided with rotating members 28-31 that are rotatably supported by the support shafts 28A-31A. A tension spring (arm urging member) 32-35 is connected to one end of these rotating members 28-31, and the other end of these tension springs 32-35 is fixed to the upper plate 27 to rotate. The members 28-31 can be urged to rotate in one direction. An opening 36-39 provided in the upper plate 27 has an arm drive rail for moving the arm members for transfer rollers 13A-13C corresponding to cyan, magenta, and yellow (not shown) in conjunction with each other. 42, and one end of the arm member 48 for the transfer roller 13D corresponding to black are inserted so as to protrude upward from the upper plate 27, and these protruding portions are the engaging portions of the rotating members 28-31, respectively. It is configured to engage with 28B-31B. Further, as will be described later with reference to FIGS. 6 to 8, the protruding portion of the arm member 48 corresponds to the engaging portions 28 </ b> B- 31 </ b> B of the rotating member 28-31 when the transfer unit 16 is attached to the apparatus main body. The engagement is released and the transfer roller driving mechanism is engaged.

  The rotating member 28-31 is provided with contact pieces 28C-31C so as to protrude upward from the side ends thereof, and these contact pieces 28C-31C attach the transfer unit 16 to the apparatus main body. At the time of the movement operation (in the direction of the arrow in the drawing), the leg release portions 51 and 52 provided on the apparatus main body side are configured to come into contact with the leg portions 51A, 51B, 52A and 52B, respectively.

  The side plate portion 25 is provided with a slide groove (slide member) 54 along the longitudinal direction thereof, and a guide rail (guide member) 55 provided in the apparatus main body is drawn into the slide groove 54, thereby transferring the slide. The unit 16 is allowed to slide in the horizontal direction and guides its movement. Similarly, a slide groove (not shown) is provided on the side plate portion 26 side, and the transfer unit 16 can be slid in the horizontal direction and guided by the guide rail 56 provided in the apparatus main body. Further, a positioning groove 57 is provided at the tip of the side plate portion 25 in the mounting direction, and a positioning member provided on the apparatus main body (not shown) is fitted into the positioning groove 57A, so that the transfer unit 16 is fitted. It is possible to attach to the regular attachment position. Similarly, a positioning groove (not shown) is also provided on the side plate portion 26 side, so that the transfer unit 16 can be mounted at the regular mounting position. Furthermore, latches 58 and 59 are provided at the rear ends in the mounting direction of the side plate portions 25 and 26, and these latches 58 and 59 are respectively engaged with fixing pins provided on the apparatus main body side (not shown). Thus, the transfer unit 16 mounted at the regular mounting position can be fixedly held. In this case, in order to securely fix and hold the transfer unit 16 at the regular mounting position, in addition to the fixing by the latches 58 and 59, the transfer unit 16 can be screwed to the apparatus main body.

  When the transfer unit 16 is attached to the apparatus main body, the tension springs 32-35 are in a state of urging the pressure release members 51 and 52 provided on the apparatus main body side via the rotating members 28-31, respectively. The transfer unit 16 is in a state of being pressed away from the apparatus main body by the reaction force of the pressing release members 51 and 52 against the biasing force of the tension springs 32-35. Therefore, when removing the transfer unit 16 from the apparatus main body, the latches 58 and 59 for fixing the transfer unit 16 are released, so that the transfer unit 16 is slid in the removal direction and partially pushed out. It is configured as follows.

  FIG. 4 is a perspective view showing a schematic configuration inside the transfer unit shown in FIG. The internal structure of the transfer unit shown in the drawing is a state as seen from below with some of the members constituting the upper plate 27, the intermediate transfer belt 11 and the side plate portions 25, 26 of the transfer unit 16 of FIG. In the frame of the transfer unit 16, four transfer rollers 13A-13D and tension rollers 14 corresponding to the photosensitive drums 3A-3D for forming toner images for the respective color components of cyan, magenta, yellow, and black are provided. ing.

  Although details will be described later, each of the transfer roller 13A-13D and the tension roller 14 is rotatably supported by bearing portions 61A-61D and 64 attached to the side plate portions 25 and 26, respectively. In 61A-61D and 64, the transfer roller 13A-13D and the tension roller 14 are in a direction close to the photosensitive drum 3A-3D (more specifically, the intermediate transfer belt 11 is pressed against the photosensitive drum 3A-3D. Compression springs 62A-62D, 63 that are urged in the direction of the pressure contact position held in).

  Further, near both ends of the support shafts of the transfer roller 13A-13D and the tension roller 14, the transfer roller 13A-13D and the tension roller 14 are separated from the photosensitive drum 3A-3D against the urging force of the compression springs 62A-62E. Arm members 45-49 that are movably supported so as to be respectively pressed in the direction in which the intermediate transfer belt 11 is pressed against the photosensitive drums 3A to 3D. ing. These arm members 45-49 are substantially L-shaped, and rotate with their engaging portions 45D-49D engaged with the support shafts of the transfer roller 13A-13D and the tension roller 14 from below. Thus, the transfer rollers 13A to 13D and the tension roller 14 can be moved up and down between the press contact position and the retracted position. These arm members 45-49 constitute a belt elevating mechanism (belt elevating means) together with the arm drive rail 42, the rotating members 28-31 and the tension springs 32-35.

  5 to 8 are schematic diagrams for explaining the lifting and lowering operation of the intermediate transfer belt of the transfer unit shown in FIGS. 3 and 4. Hereinafter, for convenience of explanation, only the configuration on one end side of each roller in the transfer unit is shown, but the configuration on the other end side is also the same.

  FIGS. 5A and 5B are a plan view and a side view, respectively, schematically showing the lifted state of the intermediate transfer belt of the transfer unit that is not attached to the apparatus main body. At this time, the intermediate transfer belt 11 is moved upward from a position (indicated by a broken line in the drawing) where the transfer unit 16 is in pressure contact with the photosensitive drums 3A to 3D when the transfer unit 16 is mounted at the normal mounting position of the apparatus main body. Is in a state. That is, all the transfer rollers 13A to 13D and the tension roller 14 are in the retracted positions where the pressure contact state of the intermediate transfer belt 11 with respect to the photosensitive drums 3A to 3D is released. The retracted state of the intermediate transfer belt 11 is achieved as a result of the operation of the belt lifting mechanism as follows.

  Regarding the cyan, magenta, and yellow photosensitive drums 3A to 3C, first, the tension spring 34 urges the rotating member 30 to rotate in the direction indicated by the arrow in the drawing, thereby rotating the rotating member 30. The engaging portion 30B presses the engaging portion 42A of the arm drive rail 42. As a result, the arm drive rail 42 moves in the direction indicated by the arrow in the drawing, and each of the transfer rollers 13A-13C and the tension roller 14 provided for the cyan, magenta, and yellow photoreceptor drums 3A-3C are provided. The arm members 45, 46, 47, 49 rotate around the support shafts 45A, 46A, 47A, 49A in the direction indicated by the arrows in the drawing. These support shafts 45A, 46A, 47A, 49A are provided substantially parallel to the central shafts 70A, 70B, 70C, 71 of the transfer rollers 13A-13C and the tension roller 14. Therefore, the center axes 70A, 70B, 70C of the transfer roller 13A-13C and the tension roller 14 that come into contact with the engaging portions 45D, 46D, 47D, 49D by the rotation of the arm members 45, 46, 47, 49, 71 is pressed upward against the urging force of the compression springs 62A, 62B, 62C, 63, and the transfer rollers 13A-13C and the tension roller 14 are held at the retracted positions.

  The upper end portions 45B, 46B, 47B, 49B of the arm members 45, 46, 47, 49 are inserted into the mounting holes 42B, 42C, 42D, 42E provided in the arm drive rail 42, and the arm drive rail 42 According to the movement, the movement operation can be performed in conjunction with each other. The arm drive rail 42 is supported on the frame by support pins 73 and 74 so as to be slidable substantially parallel to the attaching / detaching direction of the transfer unit 16.

  Similarly, with respect to the black photosensitive drum 3D, first, the tension spring 35 urges the rotating member 31 to rotate in the direction indicated by the arrow in the drawing, whereby the engaging portion of the rotating member 31 is engaged. 31D presses the engaging portion 48B of the arm member 48. As a result, the arm member 48 rotates around the support shaft 48A in the direction indicated by the arrow in the drawing. The support shaft 48A is provided substantially parallel to the central shaft 70D of the transfer roller 13D. Therefore, as the arm member 48 rotates, the central shaft 70D of the transfer roller 13D that contacts the engaging portion 48D is pressed upward against the urging force of the compression spring 62D, and the transfer roller 13D is held in the retracted position. Is done.

  FIGS. 6A and 6B are a plan view and a side view, respectively, schematically showing the lifted state of the intermediate transfer belt of the transfer unit immediately after being mounted on the apparatus main body. As in the case of FIG. 5, the intermediate transfer belt 11 starts from a position (indicated by a broken line in the figure) where the intermediate transfer belt 11 is in pressure contact with each of the photosensitive drums 3A-3D when the transfer unit 16 is mounted at the regular mounting position of the apparatus body. It is in the retracted state moved upward. That is, immediately after being mounted on the apparatus main body (that is, before the multifunction peripheral starts image forming operation), all the transfer rollers 13A to 13D and the tension roller 14 are exposed to the respective photosensitive elements of the intermediate transfer belt 11 as before the mounting. The retracted position is released from the pressure contact state with respect to the body drums 3A to 3D. The retracted state of the intermediate transfer belt 11 is achieved as a result of the following operation of the belt lifting mechanism and the operation of the transfer roller driving mechanism provided on the apparatus main body side.

  Here, the transfer roller driving mechanism 80 includes a first cam slider 81 that can engage with the engaging portion 42A of the arm driving rail 42, and a second cam slider 82 that can engage with the engaging portion 48B of the arm member 48. Are provided so as to be slidable in the direction indicated by the arrows in the figure. The first and second eccentric cams 83 and 84 disposed inside the transfer roller driving mechanism 80 are in contact with the outer peripheral surfaces of the engaging members 85 and 86 fixed to the cam sliders 81 and 82, respectively. By performing the rotation operation, the first and second cam sliders 81 and 82 can independently advance and retreat by the displacement of the contact surfaces of the eccentric cams 83 and 84, respectively. The moving directions of the first and second eccentric cams 83 and 84 are substantially parallel to the moving direction of the arm drive rail 42.

  Regarding the cyan, magenta, and yellow photosensitive drums 3A-3C, first, the transfer unit 16 is normally attached to the rotating member 30 that is biased by the tension spring 34 before the transfer unit 16 is attached to the apparatus main body. When mounted in the position, the contact piece 30C contacts the leg 51B of the press release member 51 provided on the apparatus main body side. Further, the leg 51B presses the contact piece 30C against the urging force of the tension spring 34, and as a result, the rotating member 30 has an arrow in the figure opposite to the direction in which the tension spring 34 is urged. It rotates in the direction indicated by. At this time, the pressure on the engaging portion 42A of the arm drive rail 42 by the engaging portion 30B of the rotating member 30 is released. Thus, in a state where the transfer unit 16 is mounted on the apparatus main body, the pressing of the arm driving rail 42 by the rotating member 30 remains released.

 At substantially the same time as the release of the pressing, the first cam slider 81 of the transfer roller drive mechanism 80 is engaged with the arm drive rail 42 by the side surface 81A, like the rotating member 30 before the transfer unit 16 is mounted on the apparatus main body. The joint portion 42A is pressed. The pressing against the engaging portion 42A by the first cam slider 81 is started at least before the pressing by the rotating member 30 is released, and the position of the arm drive rail 42 is the same as that before the transfer unit 16 is mounted on the apparatus main body. It does not change. Accordingly, the positions of the arm members 45, 46, 47, 49 provided for the transfer rollers 13A-13C and the tension roller 14 are not changed from those before the transfer unit 16 is mounted on the apparatus main body, and the engaging portions thereof. The central shafts 70A, 70B, 70C, 71 of the transfer rollers 13A-13C and the tension roller 14 contacting the 45D, 46D, 47D, 49D are pressed upward against the urging force of the compression springs 62A, 62B, 62C, 63. Thus, the transfer rollers 13A-13C and the tension roller 14 are held at the retracted position.

  Similarly, with respect to the black photosensitive drum 3D, first, the rotating unit 31 that has been urged by the tension spring 35 before the transfer unit 16 is mounted on the apparatus main body is mounted at the regular mounting position. In this case, the contact piece 31C comes into contact with the leg portion 52B of the press release member 52 provided on the apparatus main body side. Further, the leg 52B presses the contact piece 31C against the urging force of the tension spring 35, and the rotating member 31 is in the direction indicated by the arrow in the drawing opposite to the direction in which the tension spring 35 is urged. Rotate. At this time, the pressure on the engaging portion 48B of the arm member 48 by the engaging portion 31B of the rotating member 31 is released.

 At substantially the same time as the release of the pressing, the second cam slider 82 of the transfer roller drive mechanism 80 is armed by the projecting portion 82A below it, like the rotating member 31 before the transfer unit 16 is mounted on the apparatus main body. The engaging portion 48B is pressed. The pressing of the engaging portion 48B by the second cam slider 82 is started at least before the pressing by the rotating member 31 is released, and the rotating position of the arm member 48 is set before the transfer unit 16 is mounted on the apparatus main body. And does not change. Accordingly, the central shaft 70D of the transfer roller 13D that contacts the engaging portion 48D of the arm member 48 is pressed upward against the urging force of the compression spring 62D, and the transfer roller D is held in the retracted position. .

  FIGS. 7A and 7B are a plan view and a side view, respectively, schematically showing the lifted state of the intermediate transfer belt of the transfer unit during full color printing. At this time, the intermediate transfer belt 11 is in pressure contact with all the photosensitive drums 3A-3D. That is, all the transfer rollers 13A to 13D and the tension roller 14 are in a pressure contact position where the intermediate transfer belt 11 is in pressure contact with the photosensitive drums 3A to 3D. The pressure contact state of the intermediate transfer belt 11 is achieved as a result of the following operation of the transfer roller driving mechanism.

  Regarding the cyan, magenta, and yellow photosensitive drums 3A-3C, first, after the transfer unit 16 is mounted on the apparatus main body, the first transfer roller drive mechanism 80 that presses the engaging portion 42A of the arm drive rail 42 is used. As the first eccentric cam 83 rotates and changes its angular position, the cam slider 81 moves in the direction indicated by the arrow in the drawing to release the pressure on the engaging portion 42A. By releasing the pressure, the center axes 70A, 70B, 70C, 71 of the transfer roller 13A-13C and the tension roller 14 biased by the compression springs 62A, 62B, 62C, 63 are close to the photosensitive drum 3A-3C. The transfer rollers 13A-13C and the tension roller 14 reach the pressure contact position. At that time, the engaging portions 45D, 46D, 47D, and 49D of the arm members 45, 46, 47, and 49 are pressed and rotated in the directions indicated by the arrows in the drawing, and the transfer rollers 13A-13C and the tension roller The outer peripheral surface 14 presses the intermediate transfer belt 11 and is held in pressure contact with the photosensitive drums 3A-3C.

  Similarly, with respect to the black photosensitive drum 3D, first, the second cam slider 82 that presses the engaging portion 48B of the arm member 48 after the transfer unit 16 is mounted on the apparatus main body is the second eccentric cam 84. Rotates to change its angular position, thereby moving in the direction indicated by the arrow in the figure to release the pressure on the engaging portion 48B. By releasing the pressure, the central shaft 70D of the transfer roller 13D biased by the compression spring 62D moves in the direction approaching the photosensitive drum 3D, and the transfer roller 13D reaches the pressure contact position. At that time, the engaging portion 48D of the arm member 48 is pressed and rotated in the direction indicated by the arrow in the drawing, and the outer peripheral surface of the transfer roller 13D presses the intermediate transfer belt, and the photosensitive drum 3D is pressed against. Hold in pressure contact.

  FIGS. 8A and 8B are a plan view and a side view, respectively, schematically showing the lifted state of the intermediate transfer belt of the transfer unit during monochrome printing. At this time, the intermediate transfer belt 11 is in pressure contact with only each photosensitive drum 3D. That is, the transfer rollers 13A-13C and the tension roller 14 are in the retracted positions where the intermediate contact belt 11 is released from the pressure contact state with respect to the respective photosensitive drums 3A-3C, while the transfer roller 13D moves the intermediate transfer belt 11 to each photosensitive drum. It is in a pressure contact position where it is in pressure contact with the body drum 3D. This partial pressure contact state of the intermediate transfer belt 11 is achieved as a result of the following operation of the transfer roller driving mechanism.

  For the cyan, magenta, and yellow photosensitive drums 3A to 3C, the first cam slider 81 of the transfer roller driving mechanism 80 is engaged with the arm driving rail 42 in the same manner as immediately after the transfer unit 16 is mounted on the apparatus main body. The transfer roller 13A-13C and the tension roller 14 are pressed upward by the arm members 45, 46, 47, 49, and the transfer rollers 13A-13C and the tension roller 14 are pressed upward by the arm members 45, 46, 47, 49. 13A-13C and the tension roller 14 are held at the retracted position.

  On the other hand, with respect to the black photosensitive drum 3D, first, the second eccentric cam 84 of the second cam slider 82 that has pressed the engaging portion 48B of the arm member 48 after the transfer unit 16 is mounted on the apparatus main body. By rotating and changing its angular position, it moves in the direction indicated by the arrow in the figure to release the pressure on the engaging portion 48B. By releasing the pressure, the central shaft 70D of the transfer roller 13D biased by the compression spring 62D moves in the direction approaching the photosensitive drum 3D, and the transfer roller 13D reaches the pressure contact position. At that time, the engaging portion 48D of the arm member 48 is pressed and rotated in the direction indicated by the arrow in the drawing, and the outer peripheral surface of the transfer roller 13D presses the intermediate transfer belt, and the photosensitive drum 3D is pressed against. Hold in pressure contact.

  Although the present invention has been described in detail based on specific embodiments, these embodiments are merely examples, and the present invention is not limited to these embodiments. For example, in the above-described embodiment, an example of a multifunction peripheral is shown as the image forming apparatus of the present invention. However, the present invention can also be applied to a copying machine, a copying machine, and a facsimile machine capable of performing the same image forming operation. Further, the arrangement of the photosensitive drum and the intermediate transfer belt is not limited to the arrangement shown in the above embodiment, and various configurations are possible. Further, the arm urging member, the transfer roller urging member, and the tension roller urging member are not limited to the spring members shown in the above embodiments, and may be replaced with members having the same urging function (for example, elastic rubber). Is also possible.

  The image forming apparatus according to the present invention, with a simple configuration, brings the transfer unit into contact with the photosensitive drum during the image forming operation, while contacting the transfer unit with the photosensitive drum when the transfer unit not performing the image forming operation is attached or detached. It is useful as an image forming apparatus provided with a transfer unit having an intermediate transfer belt for transferring a toner image formed on an image carrier onto a recording paper or the like.

Schematic diagram showing a schematic structure of a copying machine according to the present invention. FIG. 2 is a schematic diagram showing an outline of a transfer unit attaching / detaching method in the multifunction machine of FIG. 1 is a perspective view showing a schematic configuration of a transfer unit in the copying machine of FIG. The perspective view which shows schematic structure inside the transfer unit of FIG. The figure which shows typically the raising / lowering state of the intermediate transfer belt of the transfer unit which is not mounted | worn with the apparatus main body The figure which shows typically the raising / lowering state of the intermediate transfer belt of the transfer unit immediately after mounting | wearing with an apparatus main body. The figure which shows typically the raising / lowering state of the intermediate transfer belt of the transfer unit at the time of full color printing The figure which shows typically the raising / lowering state of the intermediate transfer belt of the transfer unit at the time of monochrome printing

Explanation of symbols

1 MFP (image forming device)
3A-3D photosensitive drum (image carrier)
11 Intermediate transfer belt 13A-13D Transfer roller 14 Tension roller 16 Transfer unit 32-35 Tension spring (arm biasing member)
45-49 Arm members 51, 52 Press release member 54 Slide groove (slide member)
55 Guide rail (guide member)
62A-62D, 63 Compression spring (transfer roller / tension roller urging member)
80 Transfer roller drive mechanism

Claims (9)

An image forming apparatus including a transfer unit that can be attached to and detached from the apparatus body,
A transfer unit that sequentially transfers toner images formed on a plurality of image carriers for each color component; a pressure contact position that holds the intermediate transfer belt in pressure contact with the image carrier; and A plurality of transfer rollers provided so as to be capable of advancing and retreating with respect to a retracted position for releasing the pressure contact state; a transfer roller biasing member for biasing the transfer roller toward the pressure contact position; and for moving the intermediate transfer belt up and down Belt lifting means capable of pressing the transfer roller toward the retracted position against the biasing force of the transfer roller biasing member,
An image forming apparatus, comprising: a pressing release member that releases the pressing of the belt lifting unit against the transfer roller by engaging with the belt lifting unit on the apparatus main body side.   2. The transfer roller driving mechanism according to claim 1, further comprising a transfer roller driving mechanism that causes the transfer roller to advance and retreat in a state where the pressing of the belt elevating unit to the transfer roller is released on the apparatus main body side. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the belt elevating unit is a link mechanism having an arm member that is movably supported so as to press the transfer roller.   The belt elevating means has an arm urging member that urges the arm member toward the pressing side of the transfer roller, and the urging of the arm urging member with respect to the arm member is caused by the engagement with the press releasing member. The image forming apparatus according to claim 3, wherein the image forming apparatus is released.   The arm urging member urges the pressing release member that engages with the belt lifting means, and the transfer unit is moved from the apparatus main body by a reaction force of the pressing releasing member with respect to the urging force of the arm urging member. The image forming apparatus according to claim 4, wherein the image forming apparatus is pressed in a removing direction.   5. The image forming apparatus according to claim 4, wherein the transfer roller driving mechanism causes the arm member to move in a state where the urging of the arm urging member to the arm member is released.   The belt elevating means further includes an arm driving member that moves the plurality of arm members that press the plurality of transfer rollers corresponding to the image carrier for each color component other than black in conjunction with each other. The image forming apparatus according to claim 3. A guide member for guiding attachment / detachment of the transfer unit is further provided on the apparatus main body side,
The image forming apparatus according to claim 1, wherein the transfer unit further includes a slide member that linearly moves the transfer unit while making contact with the guide member. The transfer unit is disposed between a pair of support rollers around which the intermediate transfer belt is wound, and the support roller and the transfer roller, and can advance and retract between a pressure contact position and a retracted position like the transfer roller. And a tension roller urging member that urges the tension roller toward the pressure contact position side,
The belt elevating means is capable of pressing the tension roller toward the retracted position against the urging force of the tension roller urging member,
The image forming apparatus according to claim 1, wherein the pressing release member releases the pressing of the belt lifting / lowering unit against the tension roller by engaging with the belt lifting / lowering unit.

Images