JP2016170289A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device that allows a simple configuration to keep a pressure of a transfer nip and an interval between a pair of guide plates constant.SOLUTION: An image formation device 1 comprises a transfer conveyance unit 4 that is rotatably supported by a device main body 2, and forms a conveyance route 28 of a sheet between the device main body 2 and the transfer conveyance unit. In the device main body 2, provided are: an image carrier 13; and a stationary guide plate 44 forming one surface of the conveyance route 28. In the transfer conveyance unit 4, a transfer roller 34 is supported that forms a transfer nip 33 between the image carrier 13 and the transfer roller, and a movable guide plate 45 is supported in an oscillatable manner and is rotated in one direction, and thereby the conveyance route 28 is opened. In the transfer conveyance unit 4, provided is a pressurizing member 49 that presses the transfer roller 34 against the image carrier 13 in conjunction with rotation in another direction to form the transfer nip 33, and causes the movable guide plate 45 to oscillate, and positions the transfer roller via a prescribed gap between the stationary guide plate 44 and the movable guide plate 45.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus that forms an image by transferring a toner image from an image carrier to a sheet.

  An image forming apparatus such as a color printer is provided with a transfer roller that forms a transfer nip opposite to an intermediate transfer belt on which a toner image is formed. By applying a voltage to the transfer roller at the transfer nip, an intermediate is provided. The toner image is transferred from the transfer belt to the sheet. The sheet is conveyed to the transfer nip along a conveyance path formed between the pair of guide plates.

  In Patent Document 1, a transfer conveyance unit provided with a transfer roller and one guide plate of a pair of guide plates is rotatably supported, and the conveyance path can be opened by rotating the transfer conveyance unit. An image forming apparatus configured as described above is disclosed. In Patent Document 2, the transfer roller is swingably supported so as to advance and retreat in the direction of the intermediate transfer belt, and one guide plate is supported swingably by a spring member so as to face the other guide plate. An image forming apparatus is disclosed.

JP 2010-32693 A JP 2005-331606 A

  When the transfer conveyance unit is rotatably supported as described in Patent Document 1, the pressure between the transfer roller and the intermediate transfer belt and the distance between the pair of guide plates vary when the transfer conveyance unit is opened and closed. It is easy to cause a sheet conveyance failure or a transfer toner image shift. Further, as described in Patent Document 2, when the distance between the transfer roller and the intermediate transfer belt and the distance between the pair of guide plates are regulated by different mechanisms, the number of parts increases. There is a problem that the cost increases or the structure becomes complicated and it takes time and labor for assembly and maintenance.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an image forming apparatus capable of maintaining a pressure between a transfer roller and an intermediate transfer belt and a distance between a pair of guide plates constant by a simple mechanism. And

  In order to achieve the above object, an image forming apparatus of the present invention includes a transfer conveyance unit that is rotatably supported by an apparatus body and forms a sheet conveyance path between the apparatus body and the apparatus body. The image bearing member that carries the toner image is rotatably supported, and a fixed guide plate that forms one surface of the conveying path upstream of the image bearing member in the sheet conveying direction is provided. A transfer roller that forms a transfer nip with the image carrier is supported by the transport unit so as to be rotatable about a support shaft, and the other surface of the transport path is opposed to the fixed guide plate. An image forming apparatus, wherein a movable guide plate to be formed is swingably supported, and is configured to open the transport path by rotating the transfer transport unit in one direction, wherein the transfer transport unit In conjunction with rotation in the other direction, the transfer roller is pressed against the image carrier to form the transfer nip, and the movable guide plate is oscillated between the fixed guide plate and A pressurizing member for positioning through a predetermined gap is provided.

  By adopting such a configuration, the transfer nip and the transport path can be formed with a single component, so the number of components is reduced, the cost of the transfer transport unit can be reduced, and the configuration is simplified. This improves the assembly and maintenance of the transfer / conveyance unit.

  In the image forming apparatus according to the aspect of the invention, the pressure member may be a regulated portion that comes into contact with a regulating portion provided in the apparatus main body by rotation in the other direction of the transfer conveyance unit, and the sheet of the transfer conveyance unit. A shaft support portion rotatably supported on both sides in the width direction, a contact portion that contacts the support shaft of the transfer roller, and an elastic arm piece having elasticity in a direction along the swinging direction of the movable guide plate And a hook portion that is provided at a tip of the elastic arm piece and that is engaged with the movable guide plate and protrudes from the movable side guide plate to the fixed guide plate side, and the contact portion is the transfer portion The urging member is urged so as to rotate in the direction of pressing the support shaft of the roller. When the transfer conveyance unit is rotated in the other direction, the regulated portion is controlled by the regulated portion. Abut Thus, the transfer roller is pressed against the image carrier against the urging force of the urging member to form the transfer nip, and the hook portion comes into contact with the fixed guide plate so that the elastic arm piece is elastic. By deforming, the movable guide plate may be positioned with respect to the fixed guide plate via the gap to form the transport path.

  By adopting such a configuration, the transfer conveyance unit is rotated in the direction of forming the conveyance path, thereby forming the transfer nip between the transfer roller and the image carrier and the conveyance path between the fixed guide plate and the movable guide plate. As a result, the assembly is improved. Further, since the pressure between the transfer roller and the image carrier and the gap between the fixed guide plate and the movable guide plate are unlikely to change due to the rotation of the transfer conveyance unit, it is possible to suppress paper feed failure and image formation failure.

  In the image forming apparatus of the present invention, the elastic arm piece may be formed to extend in a substantially U shape on the movable guide plate side.

  By adopting such a configuration, the elastic arm piece is easily elastically deformed following the swing of one guide plate, and it is difficult to apply a load in a direction other than the swing direction to the one guide plate. It is easy to reproduce the distance between the guide plates.

  In the image forming apparatus of the present invention, the movable guide plate is formed with engaging portions on both sides in the sheet width direction, and the hook portion of the pressure member is engaged with the engaging portion, The movable guide plate may swing integrally with the pressure member by rotating the transfer / conveying unit in the other direction.

  By having such a configuration, the movable guide plate can be easily engaged with the hook portion of the pressurizing member, so that the mounting operation of the pressurizing member is facilitated.

  According to the present invention, the pressure between the transfer roller and the intermediate transfer belt and the distance between the pair of guide plates can be kept constant using a single pressure member.

1 is a cross-sectional view schematically showing an internal structure of a color printer according to an embodiment of the present invention. FIG. 3 is a perspective view of a transfer conveyance unit of a color printer according to an embodiment of the present invention. It is a front view of a transfer conveyance unit of a color printer according to an embodiment of the present invention. FIG. 5 is a front view showing the periphery of a movable guide plate of a transfer conveyance unit in a color printer according to an embodiment of the present invention. FIG. 5 is a perspective view illustrating a pressure member of a transfer conveyance unit in a color printer according to an embodiment of the present invention. In the color printer according to an embodiment of the present invention, it is a front view showing a change in the posture of the pressure member accompanying the rotation of the transfer conveyance unit.

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

  First, the overall configuration of the color printer 1 (image forming apparatus) will be described with reference to FIG. FIG. 1 is a cross-sectional view schematically showing the internal structure of the color printer 1 according to this embodiment. In the following description, the front side in FIG. 1 is the front side (front side) of the color printer, and the left and right direction is based on the direction of the color printer viewed from the front side.

  The color printer 1 includes a box-shaped printer body 2. A conveyance cover unit 3 is supported on the left side surface of the printer body 2 so as to be rotatable about the lower end portion. Inside the conveyance cover unit 3, the transfer conveyance unit 4 is rotatable about the lower end portion. It is supported by. A paper discharge tray 5 is formed on the upper surface of the printer body 2.

  Inside the printer main body 2, a paper feed cassette 7 containing sheets at the bottom is detachably mounted. A paper feeding device 8 that feeds sheets from the paper feeding cassette 7 is provided on the upper left side of the paper feeding cassette 7. Above the sheet feeding cassette 7, an exposure unit 9 configured by a laser scanning unit (LSU) is provided. Above the exposure unit 9, a tension roller is provided between the driving roller 10 and the driven roller 11. An intermediate transfer belt 13 (image carrier) is installed via 12. In addition, above the driving roller 10, front and rear side plates of the printer body 2 are provided with bosses 14 (regulating portions) extending in the front-rear direction.

  Below the intermediate transfer belt 13, four image forming units 15 are arranged for each toner color (Y, M, C, K). Each image forming unit 15 is rotatably provided with a photosensitive drum 16, and around the photosensitive drum 16, a charger 17, a developing device 18, a cleaning device 19, and a static eliminator 20 are provided. The photosensitive drum 16 is disposed along the rotation direction. A primary transfer roller 21 is disposed between the developing device 18 and the cleaning device 19 so as to face the photoconductive drum 16 with the intermediate transfer belt 13 interposed therebetween, and between the intermediate transfer belt 13 and the primary transfer roller 21. The primary transfer portion 22 is formed on the surface. Above each developing device 18, four toner containers 23 corresponding to each image forming unit 15 are provided for each toner color.

  Further, inside the printer main body 2, a fixing device 25 is provided at the upper left, and a paper discharge unit 26 is provided at the upper left of the fixing device 25 so as to face the paper discharge tray 5.

  In addition, a part of the main conveyance path 28 of the sheet from the sheet feeding device 8 to the sheet discharge unit 26 through the fixing device 25 is formed between the printer main body 2 and the transfer conveyance unit 4. In the main conveyance path 28, in order from the downstream side, a pair of registration rollers 31, a pre-transfer guide 32 (a pair of guide plates), and the intermediate transfer belt 13 are opposed to the driving roller 10 and the secondary transfer unit 33 ( A secondary transfer roller 34 (transfer roller) that forms a transfer nip is disposed.

  Further, the transfer conveyance unit 4 and the conveyance cover unit 3 branch from the main conveyance path 28 between the fixing device 25 and the paper discharge unit 26, and enter the main conveyance path 28 on the downstream side of the sheet feeding device 8. A double-sided printing path 36 that merges is formed. Conveying roller pairs 37 are arranged at predetermined intervals along the double-sided printing path 36.

  Next, an image forming operation of the color printer 1 having such a configuration will be described. After the surface of the photosensitive drum 16 is charged by the charger 17, exposure corresponding to the image data is performed on the photosensitive drum 16 by laser light (see arrow) from the exposure device 9, and the photosensitive drum 16 is exposed. An electrostatic latent image is formed on the surface. The electrostatic latent image is developed into a toner image of a corresponding color by the developing device 18, and the toner image is primarily transferred to the surface of the intermediate transfer belt 13 in the primary transfer unit 22. Each image forming unit 15 sequentially repeats the above operation, whereby a full-color toner image is formed on the intermediate transfer belt 13. The toner and charge remaining on the photosensitive drum 16 are removed by the cleaning device 19 and the static eliminator 20.

  On the other hand, the sheet fed from the sheet feeding cassette 7 to the main conveyance path 28 by the sheet feeding device 8 is timed with the above-described image forming operation by the registration roller pair 31, and the secondary transfer section along the pre-transfer guide 32. It is conveyed to 33. In the secondary transfer unit 33, the full-color toner image on the intermediate transfer belt 13 is secondarily transferred to the sheet, and the sheet on which the toner image is secondarily transferred is conveyed to the downstream side through the main conveyance path 28 to be a fixing device. The fixing device 25 fixes the toner image on the sheet. The sheet on which the toner image is fixed is discharged from the paper discharge unit 26 to the paper discharge tray 5. When double-sided printing is performed, the sheet that has passed through the fixing device 25 is switched back by the paper discharge unit 26 and enters the double-sided printing path 36. The sheet with the front and back reversed in this manner is conveyed along the main conveyance path 28, and after the toner image for the back surface is transferred by the secondary transfer unit 33 and fixed by the fixing device 25, the sheet is discharged from the discharge unit 26 to the discharge tray. 5 is discharged.

  Next, the transfer conveyance unit 4 will be described with reference to FIGS. 2 is a perspective view of the transfer conveyance unit, FIG. 3 is a side view of the transfer conveyance unit, and FIG. 4 is a side view of the movable guide plate.

  First, the main conveyance path 28 formed between the printer main body 2 and the transfer conveyance unit 4 will be described with reference to FIG. As described above, the registration roller pair 31, the pre-transfer guide 32, and the secondary transfer roller 34 are arranged in this order from the downstream side in the main conveyance path 28. The registration roller pair 31 includes a registration roller 41 that is rotatably supported on the left side surface of the printer main body 2, and a pressure roller 42 that is rotatably supported by the transfer conveyance unit 4. The pre-transfer guide 32 is fixed to the left side surface of the printer main body 2, and the movable guide plate 45 is disposed to face the fixed guide plate 44 and is supported by the transfer conveyance unit 4 so as to be swingable. And. As described above, the secondary transfer roller 34 is opposed to the driving roller 10 with the intermediate transfer belt 13 interposed therebetween, and forms a secondary transfer portion 33.

  The transfer conveyance unit 4 includes a housing 47 that supports the secondary transfer roller 34, the movable guide plate 45, and the pressure roller 42. The housing 47 is further provided with a pressure member 49 that supports the secondary transfer roller 34 and the movable guide plate 45 so as to press the intermediate transfer belt 13 and the fixed guide plate 44 respectively.

  The housing 47 has a substantially rectangular shape that is vertically long when viewed from the front, has a rectangular parallelepiped shape that is long in the width direction (front-rear direction) of the seat, a substantially vertical left side surface 47a, and a right side surface 47b that is gently curved to the right. And front and rear side surfaces 47c, a substantially flat upper surface 47d, and a lower surface 47e curved downwardly. The housing 47 is rotatably supported on the left side surface of the printer main body 2 around a support shaft (not shown) provided in the lower portion, and is interposed between the right side surface 47 b of the housing 47 and the left side surface of the printer main body 2. It rotates between a path forming position (see FIGS. 2 and 3) that forms the main transport path 28 and an open position that is spaced apart from the left side surface of the printer body 2 and opens the main transport path 28.

  A plurality of ribs 51 extending in the vertical direction are formed on the left side surface 47 a of the housing 47. Moreover, one conveyance roller 37a of the conveyance roller pair 37 is rotatably supported by the upper part of the left side surface 47a.

  On the right side surface 47b of the housing 47, a plurality of ribs 53 extending in the vertical direction are formed at the top. Below the rib 53, when the housing 47 is rotated to the path forming position, the secondary transfer roller housing portion facing the drive roller 10 of the intermediate transfer belt 13 obliquely from the lower left and the fixed guide plate 44 are opposed. A movable guide plate housing portion and a pressure roller housing portion (both not shown) that face the registration roller 41 obliquely from the upper left are formed.

  The secondary transfer roller 34 supports the front and rear side surfaces 47c of the housing 47 so as to correspond to the secondary transfer roller housing portion, the movable guide plate housing portion, and the pressure roller housing portion, respectively, along the right edge. A shaft hole 55, a shaft portion 56 that supports the movable guide plate 45, and a shaft hole 57 that supports the pressure roller 42 are formed. The shaft hole 55 for supporting the secondary transfer roller is formed in a long hole shape extending obliquely in the upper right direction. The roller support shaft hole 57 is a long hole extending obliquely from the upper right, and a guide rib 58 is formed along the periphery. A shaft portion 59 for supporting the pressure member is provided between the shaft hole 55 for supporting the secondary transfer roller and the shaft portion 56 for supporting the movable guide plate.

  Further, hooks 61 that engage with the printer main body 2 when the housing 47 is rotated to the path forming position are provided on the upper portions of the front and rear side surfaces 47c. Further, ribs 62 extending in the up-down direction, the left-right direction, and the oblique direction are formed on the front and rear side surfaces 47c.

  The lower surface 47e of the housing 47 is formed so as to be smoothly curved downward and convex between the lower end of the left side surface 47a and the lower end of the right side surface 47b, so that one of the transport rollers 37a of the transport roller pair 37 can rotate. It is supported.

  The secondary transfer roller 34 has a cylindrical roller body 34 a extending in the sheet width direction and a support shaft 34 b provided at the axis of the roller body 34 a, and is formed on the right side surface 47 b of the housing 47. The both ends of the support shaft 34b are supported by the secondary transfer roller support shaft hole 55 so as to be rotatable in the secondary transfer roller support shaft hole 55 and to be able to advance and retreat on the main transport path 28 side.

  As shown in FIG. 4, the movable guide plate 45 includes a plate-like guide portion 65 that is long in the sheet width direction, a support portion 66 that is bent leftward from the lower ends of both ends of the guide portion 65 in the sheet width direction, Have The guide portion 65 is bent at an obtuse angle so as to protrude rightward in the vicinity of the center in the sheet conveying direction. A folded portion 67 folded in the left direction is formed at the upper end. Further, notches 68 are formed on both side edges of the guide portion 65 in the sheet width direction on the upstream side of the folding portion 67 in the sheet conveying direction. The movable guide plate 45 is accommodated in a movable guide plate accommodating portion formed on the right side surface 47 b of the housing 47, and both support portions 66 are movable guide plate support provided on both side surfaces 47 c of the housing 47 in the sheet width direction. The shaft portion 56 is rotatably supported. As a result, the movable guide plate 45 swings with respect to the fixed guide plate 44 around the movable guide plate support shaft portion 56.

  The pressure roller 42 has a cylindrical roller body extending in the width direction of the sheet, and a support shaft provided at the axis of the roller body, and both ends of the support shaft are for supporting the pressure roller. Supported by the shaft hole 57 and urged toward the main transport path 28 along the guide rib 58 by the spring member 71.

  Next, the pressure member 49 will be described with reference to FIG. FIG. 5 is a perspective view of the pressure member. The pressing member 49 has a flat plate-like main body 75, and ribs 75 a are provided along the periphery of the main body 75. A shaft hole 76 (axial support portion) extending in the sheet width direction is formed in the main body portion 75 at an upstream corner in the sheet conveyance direction. Further, a rectangular parallelepiped pressure member 77 is formed on the outer surface of the rib 75a extending from the downstream side edge of the shaft hole 76 in the sheet conveying direction to the downstream side in the sheet conveying direction and in the direction opposite to the main conveying path 28. Is formed. Further, a semicircular arc-shaped recess 78 (a regulated portion) faces the main conveyance path 28 on the outer surface of the rib 75a on the downstream side of the pressure unit 77 in the sheet conveyance direction. Is formed. Further, a boss 79 for receiving a spring is provided upright on the outer surface of the rib 75 a on the side opposite to the concave portion 78. Further, an elastic arm piece 80 that is curved in a U shape in the direction of the main conveyance path 28 extends from the rib 75a on the upstream side of the shaft hole 76 in the sheet conveyance direction. At the tip of the elastic arm piece 80, a hook portion 81 is formed that protrudes in the direction of the main transport path 28. The hook portion 81 includes a base portion 81a having a narrow width when viewed from the sheet width direction, and a semicircular gap forming portion 81b having a width wider than that of the base portion 81a.

  As shown in FIG. 3, the pressing member 49 is inserted into the shaft hole 76 by a pressing member supporting shaft portion 59 erected on the front and rear side surfaces 47 c of the housing 47, so that the pressing member supporting shaft portion is inserted. The pressure portion 77 is supported by both ends of the support shaft of the secondary transfer roller 34, and the hook portion 81 is engaged with the notch 68 of the movable guide plate 45. . Specifically, as shown in FIG. 4, the flat surface 80 a formed at the tip of the elastic arm piece 80 abuts on the left surface of the movable guide plate 45, and the hook portion 81 has a base portion 81 a that is a movable guide. The gap 45 enters the notch 68 of the plate 45, and the gap forming portion 81 b protrudes from the right surface of the guide portion 65. Further, the pressing member 49 is urged clockwise in FIG. 3 by a spring member 83 interposed between the rib 62 and the boss 79 formed on the front and rear side surfaces 47 c of the housing 47.

  The opening / closing operation of the transfer / conveying unit 4 having the above configuration will be described with reference to FIG. FIG. 6 is a front view for explaining a change in the posture of the pressure member accompanying the opening / closing operation of the transfer / conveyance unit, and a two-dot chain line indicates the posture of the pressing member in a state where the transfer / conveyance unit is opened. In a state in which the transfer conveyance unit 4 is rotated to the path forming position indicated by the solid line in FIG. 6, the concave portion 78 of the pressure member 49 abuts on the boss 14 provided in the printer main body 2 and the spring member 83 is compressed. doing. Due to the compressive force of the spring member 83, the support shaft 34b of the secondary transfer roller 34 is pressed by the pressurizing portion 77 of the pressurizing member 49, and the roller main body 34a is pressed against the intermediate transfer belt 13, and the secondary transfer roller. A secondary transfer portion 33 is formed between the intermediate transfer belt 13 and the intermediate transfer belt 13. Further, a main conveyance path 28 having a height of the gap forming portion 81b is formed between the movable guide plate 45 and the fixed guide plate 44.

  When a paper jam occurs in the main transport path 28, the transport cover unit 3 shown in FIG. 1 is rotated counterclockwise, and then the transfer transport unit 4 is moved in one direction (counterclockwise in FIG. 6). The main transport path 28 is opened. Then, the concave portion 78 of the pressing member 49 is separated from the boss 14, and the pressing member 49 is illustrated by the spring member 83 around the pressing member supporting shaft 59 as shown by a two-dot chain line in FIG. 6. 6 is biased clockwise. As a result, the pressure unit 77 presses the support shaft 34b of the secondary transfer roller 34, the secondary transfer roller 34 advances most to the main conveyance path 28 side, and the concave portion 78 also advances most to the main conveyance path 28 side. The elastic arm piece 80 protrudes toward the main transport path 28 in a free posture, and swings the movable guide plate 45 about the movable guide plate support shaft portion 56 in the clockwise direction in FIG.

  When the transfer conveyance unit 4 is rotated in the other direction (clockwise direction in FIG. 6) after the paper jam processing of the main conveyance path 28 is completed, the recess 78 of the pressure member 49 eventually becomes the boss 14 of the printer main body 2. The pressure member 49 starts to rotate counterclockwise in FIG. 6 against the urging force of the spring member 83. Further, as the transfer conveyance unit 4 rotates, the roller main body 34 a of the secondary transfer roller 34 also comes into contact with the intermediate transfer belt 13 and moves away from the main conveyance path 28 in the shaft hole 55 for supporting the secondary transfer roller. Since it moves backward, the pressure member 49 is rotated counterclockwise in FIG. 6 against the urging force of the spring member 83. Due to the compressive force of the spring member 83, the pressurizing portion 77 of the pressurizing member 49 presses the support shaft 34 b of the secondary transfer roller 34, and the roller main body 34 a is pressed against the intermediate transfer belt 13, so that the secondary transfer roller 34 is pressed. A secondary transfer portion 33 is formed between the transfer roller 34 and the intermediate transfer belt 13.

  When the transfer conveyance unit 4 is rotated in the clockwise direction in FIG. 6, the gap forming portion 81b of the hook portion 81 protruding from the movable guide plate 45 contacts the fixed guide plate 44, and the elastic arm piece 80 is bent. It is elastically deformed. Due to the elastic force of the elastic arm piece 80, the movable guide plate 45 is urged in the direction of the fixed guide plate 44 and positioned relative to the fixed guide plate 44. As a result, the main transport path 28 having the width of the gap forming portion 81 b is formed between the fixed guide plate 44 and the movable guide plate 45.

  As shown in FIG. 3, the pressure roller 42 is pressed against the registration roller 41 by the spring member 71. When the transfer conveyance unit 4 is rotated to the path forming position, the transfer conveyance unit 4 is locked to the printer main body 2 by the hook 61.

  As described above, in the transfer conveyance unit 4 of the present invention, the secondary transfer roller 34 is pressed against the intermediate transfer belt 13 by the single pressure member 49 to form the secondary transfer portion 33, and the transfer is performed. A constant gap can always be formed between the fixed guide plate 44 and the movable guide plate 45 in the front guide 32. Further, by rotating the transfer conveyance unit 4 to the path forming position, the secondary transfer roller 34 can be automatically brought into pressure contact with the intermediate transfer belt 13 and the interval between the pre-transfer guides 32 can be ensured to be constant. Further, if the pressure member 49 is attached to the front and rear side surfaces 47c of the housing 47 from the outside, the pressure member supporting shaft portion 59 can be easily inserted into the shaft hole 76, and the notch 68 of the movable guide plate 45 can be inserted. The movable guide plate 45 can be prevented from coming off by simply engaging the hook portion 81.

  Accordingly, the cost of the transfer / conveyance unit 4 can be reduced, and the assemblability and maintenance can be improved. Further, the secondary transfer roller 34 and the movable guide plate 45 are respectively positioned on the intermediate transfer belt 13 and the fixed guide plate 44 via the pressure member 49 by rotating the transfer conveyance unit 4 to the path forming position. Therefore, the pressure of the secondary transfer portion 33 and the interval between the pre-transfer guides 32 due to the rotation of the transfer conveyance unit 4 are not easily changed, and image defects such as toner image blurring and paper feed defects can be suppressed.

  Further, since the elastic arm piece 80 is formed in a U-shape, the swinging direction of the movable guide plate 45 and the elastic deformation direction of the elastic arm piece 80 are substantially the same, and the movable guide plate 45 is moved in a direction other than the swinging direction. Therefore, it is easy to reproduce the interval between the pre-transfer guides 32. However, the shape of the elastic arm piece 80 is not limited to the U shape.

  In this embodiment, the pressing member 49 is rotated against the urging force of the spring member 83 by bringing the concave portion 78 formed in the pressing member 49 into contact with the boss 14 formed in the printer main body 2. However, the pressure member 49 may be rotated against the urging force of the spring member 83 by bringing the transfer roller 34 into contact with the intermediate transfer belt 13.

  Note that the above description of the embodiment of the present invention describes a preferred embodiment of the image forming apparatus according to the present invention, and thus may have various technically preferable limitations. The technical scope of the present invention is not limited to this embodiment unless specifically described to limit the present invention. Furthermore, the constituent elements in the embodiments of the present invention described above can be appropriately replaced with existing constituent elements, and various variations including combinations with other existing constituent elements are possible. The description of the embodiment of the present invention is not intended to limit the content of the invention described in the claims.

1 Color printer (image forming device)
4 Transfer conveyance unit 13 Intermediate transfer belt (image carrier)
14 Boss (Regulation Department)
28 Main transport route (transport route)
33 Secondary transfer section (transfer nip)
34 Secondary transfer roller (transfer roller)
44 Movable guide plate 45 Fixed guide plate 49 Pressure member 76 Axial support portion 77 Pressurization portion 78 Recessed portion (regulated portion)
80 Elastic arm piece 81 Hook part 83 Spring member (biasing member)

Claims (4)

A transfer conveyance unit that is rotatably supported by the apparatus main body and forms a sheet conveyance path between the apparatus main body,
The apparatus main body is provided with a fixed guide plate that rotatably supports an image carrier that carries a toner image and that forms one surface of the conveyance path upstream of the image carrier in the sheet conveyance direction. And
A transfer roller that forms a transfer nip with the image carrier is rotatably supported by the transfer conveyance unit so as to be rotatable about a support shaft, and is opposed to the fixed guide plate. The movable guide plate forming the surface is supported so as to be swingable,
An image forming apparatus configured to open the transport path by rotating the transfer transport unit in one direction,
In conjunction with the rotation in the other direction, the transfer conveying unit presses the transfer roller against the image carrier to form the transfer nip and swings the movable guide plate to fix the fixed guide. An image forming apparatus, characterized in that a pressure member for positioning with a predetermined gap is provided between the plate and the plate. The pressure member is
A regulated portion that comes into contact with a regulating portion provided in the apparatus main body by rotation in the other direction of the transfer conveyance unit;
A shaft support part rotatably supported on both sides in the sheet width direction of the transfer conveyance unit;
A contact portion that contacts the support shaft of the transfer roller;
An elastic arm piece having elasticity in a direction along the swinging direction of the movable side guide plate;
A hook portion provided at a tip of the elastic arm piece, the movable guide plate being locked and protruding from the movable side guide plate to the fixed guide plate side;
The contact portion is biased by a biasing member so as to rotate in a direction of pressing the support shaft of the transfer roller;
When the transfer conveyance unit is rotated in the other direction,
The pressurizing member forms the transfer nip by pressing the transfer roller against the image carrier against the urging force of the urging member when the regulated portion is in contact with the regulating portion.
When the hook portion comes into contact with the fixed guide plate and the elastic arm piece is elastically deformed, the movable guide plate is positioned with respect to the fixed guide plate via the gap to form the conveyance path. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 2, wherein the elastic arm piece is formed to extend in a substantially U shape on the movable guide plate side.   Engaging portions are formed on both sides of the movable guide plate in the sheet width direction, and the hook portions of the pressure member are engaged with the engaging portions. 4. The image forming apparatus according to claim 2, wherein the movable guide plate swings integrally with the pressure member by rotation.

Images