Image formation device

Abstract

To provide an image formation device achieving both suppression of image defect and improvement in jam processing.SOLUTION: The image formation device comprises: a belt member; a second transfer roller forming a transfer nip via the belt member with a first transfer roller; a tension unit including a tension member stretching the belt member; a guide member forming a conveyance path on which a sheet passes, and movable between a guiding position for guiding the sheet toward the transfer nip and an open position for opening the conveyance path; an opening and closing member moving from the closed position to the open position when opening the conveyance path; and a support member linked with the opening and closing member and supporting the guide member. The support member engages with the tension unit and positions the guide member with respect to the tension member while locating the guide member on the guiding position when the opening and closing member is on the closed position, and positions the guide member on the open position when the opening and closing member is on the open position.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an image forming apparatus that forms an image on a sheet.

Background Art

[0002] Conventionally, an image forming apparatus has been proposed that includes an intermediate transfer belt wound by a driving roller, a secondary transfer opposing roller, and a driven roller, and a lower conveyance guide and an upper conveyance guide that guide a recording material toward the intermediate transfer belt (see Patent Document 1). The lower conveyance guide and the upper conveyance guide are positioned and fixed by a guide support member, and the guide support member is rotatably supported by the rotation axis of the driven roller. Therefore, the guide support member moves according to the position of the driven roller, and the lower conveyance guide and the upper conveyance guide fixed to the guide support member also move following the movement of the driven roller. Thereby, the positional relationship between the recording material entering the secondary transfer portion and the intermediate transfer belt is maintained, and image defects are suppressed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the lower conveyance guide and the upper conveyance guide described in Patent Document 1 are both fixed to the guide support member, and the conveyance path formed in the lower conveyance guide and the upper conveyance guide cannot be opened. For this reason, there has been a problem in jam processing performance.

[0005] An object of the present invention is to provide an image forming apparatus that achieves both suppression of image defects and improvement in jam processing performance.

Means for Solving the Problems

[0006] The present invention relates to an image forming apparatus, comprising an endless belt member that carries a toner image, a first transfer roller that abuts against the inner peripheral surface of the belt member, a second transfer roller that forms a transfer nip together with the first transfer roller via the belt member and transfers the toner image on the belt member to a sheet while conveying the sheet in the sheet conveyance direction at the transfer nip, a tension unit having a tension member that is disposed upstream of the transfer nip in the sheet conveyance direction and that stretches the belt member by pressing against the inner peripheral surface of the belt member, a guide member that forms a conveyance path through which the sheet passes and guides the sheet, the guide member being movable between a guide position for guiding the sheet toward the transfer nip and an open position for opening the conveyance path, an opening / closing member that is movable between a closed position and an open position and that can open the conveyance path when moved from the closed position to the open position, and a support member that is interlocked with the opening / closing member and supports the guide member. The support member engages with the tension unit when the opening / closing member is in the closed position, positions the guide member at the guide position and positions the guide member with respect to the tension member, and positions the guide member at the open position when the opening / closing member is in the open position.

Advantages of the Invention

[0007] According to the present invention, it is possible to achieve both suppression of image defects and improvement of jam processability.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0009] <First Embodiment> 〔Overall Configuration〕 First, the first embodiment of the present invention will be described. FIG. 1(a) is an overall schematic view showing the image forming apparatus 100 with the door unit 90 closed, and FIG. 1(b) is an overall schematic view showing the image forming apparatus 100 with the door unit 90 open.

[0010] As shown in FIGS. 1(a) and 1(b), the image forming apparatus 100 is a laser beam printer of the electrophotographic system. Note that the image forming apparatus includes a printer, a copier, a facsimile machine, and a multifunction machine, and refers to an apparatus that forms an image on a sheet used as a recording medium based on image information input from an external PC or image information read from a document. In addition, in addition to the main body having an image forming function, the image forming apparatus may be connected with accessory devices such as an optional feeder, an image reading device, and a sheet processing device. However, the entire system to which such accessory devices are connected is also a kind of image forming apparatus.

[0011] The image forming apparatus 100 includes an image forming unit 20 that forms an image on a sheet P, a sheet feeding device 40, a fixing device 80, and a discharge roller pair 85. The image forming unit 20 includes four process cartridges PY, PM, PC, and PK that form toner images of four colors, namely yellow (Y), magenta (M), cyan (C), and black (K), an exposure device 3, and an intermediate transfer device 10.

[0012] Note that the four process cartridges PY, PM, PC, and PK have the same configuration except that the colors of the images they form are different. Therefore, only the configuration and the image forming process of the process cartridge PY will be described, and the descriptions of the process cartridges PM, PC, and PK will be omitted.

[0013] The process cartridge PY includes a photosensitive drum 1, a charging roller 2, and a developing roller 4. The photosensitive drum 1 is configured by applying an organic photoconductive layer on the outer periphery of an aluminum cylinder and rotates by a drive motor (not shown).

[0014] The intermediate transfer device 10 disposed below the four process cartridges PY, PM, PC, and PK has an endless intermediate transfer belt 11. The intermediate transfer belt 11 as a belt member is stretched by a drive roller 13, a secondary transfer opposing roller 14, and a tension roller 15 and rotates by the drive roller 13. That is, the drive roller 13, the secondary transfer opposing roller 14, and the tension roller 15 are in contact with the inner peripheral surface 11b of the intermediate transfer belt 11. Further, primary transfer rollers 12Y, 12M, 12C, and 12K are provided inside the intermediate transfer belt 11. A secondary transfer roller 51 as a second transfer roller is disposed on the opposite side of the secondary transfer opposing roller 14 as a first transfer roller across the intermediate transfer belt 11. The secondary transfer roller 51 forms a transfer nip N with the secondary transfer opposing roller 14 via the intermediate transfer belt 11.

[0015] The fixing device 80 includes a fixing film 81 heated by a heater as a heating means, and a pressure roller 82 that presses against the fixing film 81. The sheet feeding device 40 is provided below the image forming apparatus 100 and includes a cassette 41 that houses the sheet P and a feeding roller 42.

[0016] The image forming apparatus 100 includes an apparatus main body 100A that houses the process cartridges PY, PM, PC, and PK, and a door unit 90 that is supported by the apparatus main body 100A so as to be openable and closable. The door unit 90 includes a door 92 that is rotatable about a rotation axis 91, and a secondary transfer device 50 that is instructed in a state where the door 92 as an opening / closing member has play. In other words, the door unit 90 and the door 92 are supported by the apparatus main body 100A so as to be openable and closable between a closed position and an open position, and are moved to the open position when opening a conveyance path CP described later.

[0017] The secondary transfer device 50 includes a secondary transfer roller 51, a biasing member 54 that biases the secondary transfer roller 51 toward the secondary transfer counter roller 14, and a conveyance guide 52. The biasing member 54 is constituted by a spring such as a compression spring, for example, but is not limited to a spring, and may be other elastic members such as rubber or sponge. The conveyance guide 52 is movable between a guide position (see FIG. 1(a)) that forms a conveyance path CP through which the sheet P passes together with the intermediate transfer belt 11 and guides the sheet P toward the transfer nip N, and an open position (see FIG. 1(b)) that opens the conveyance path CP. That is, the conveyance guide 52 as a guiding member is located at the guide position when the door 92 is located at the closed position, and is located at the open position when the door 92 is located at the open position. Further, when the door 92 is located at the closed position, the secondary transfer roller 51 is biased toward the secondary transfer counter roller 14 by the biasing member 54 and is positioned with respect to the secondary transfer counter roller 14.

[0018] Next, the image forming operation of the image forming apparatus 100 configured as described above will be described. When an image signal is input from a personal computer or the like (not shown) to the exposure device 3, laser light corresponding to the image signal is irradiated from the exposure device 3 onto the photosensitive drum 1 of the process cartridge PY.

[0019] At this time, the surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity and potential in advance by the charging roller 2, and an electrostatic latent image is formed on the surface by irradiating laser light from the exposure device 3. The electrostatic latent image formed on the photosensitive drum 1 is developed by the developing roller 4, and a yellow (Y) toner image is formed on the photosensitive drum 1.

[0020] Similarly, the photosensitive drums of the process cartridges PM, PC, and PK are also irradiated with laser light from the exposure device 3, and magenta (M), cyan (C), and black (K) toner images are formed on the respective photosensitive drums. The toner images of each color formed on each photosensitive drum are transferred to and carried on the intermediate transfer belt 11 by the primary transfer rollers 12Y, 12M, 12C, and 12K, and are conveyed to the transfer nip N by the intermediate transfer belt 11 rotated by the drive roller 13. Note that each color image forming process is performed at a timing to overlap with the upstream toner image primarily transferred onto the intermediate transfer belt 11.

[0021] In parallel with this image forming process, the sheet P housed in the sheet feeding device 40 is sent out by the feeding roller 42 as a feeding unit. Then, the sheet P fed by the feeding roller 42 and passing through the conveyance path CP is guided to the transfer nip N by the conveyance guide 52. The conveyance guide 52 can contact the second surface (non-printing surface) of the sheet P, which is opposite to the first surface (printing surface) onto which the toner image is transferred by the transfer nip N. On the sheet P, the full-color toner image on the intermediate transfer belt 11 is transferred at the transfer nip N by the secondary transfer bias applied to the secondary transfer roller 51. That is, at the transfer nip N, the sheet P is conveyed in the sheet conveyance direction D1 while the toner image on the intermediate transfer belt 11 is transferred.

[0022] The sheet P onto which the toner image has been transferred is given a predetermined heat and pressure by the fixing film 81 and the pressure roller 82 of the fixing device 80, and the toner is melted and fixed (fixed). The sheet P that has passed through the fixing device 80 is discharged to the discharge tray 86 by the discharge roller pair 85.

[0023] Note that the image forming apparatus 100 of the present embodiment is configured to be printable only on one side of the sheet P, but is not limited thereto. For example, the image forming apparatus 100 may have a duplex conveyance path that guides the sheet P to the transfer nip N again while inverting the sheet P after a toner image is formed on the first surface of the sheet P. In this way, the image forming apparatus 100 may be configured to be able to form toner images on both the first surface and the second surface of the sheet P.

[0024] [Engagement unit] Next, the engagement unit 70 will be described with reference to FIGS. 2 to 3(b). FIG. 2 is a perspective view showing the engagement unit 70 according to the first embodiment. FIG. 3(a) is a side view showing the engagement unit 70 when the door 92 is in the closed position, and FIG. 3(b) is a side view showing the engagement unit 70 when the door 92 is in the open position.

[0025] As shown in FIG. 2, the engagement unit 70 includes first support members 21L and 21R, biasing members 31L and 31R, second support members 61L and 61R, and biasing members 71L and 71R. A pair of these members are provided so as to be arranged in parallel in the width direction W orthogonal to the sheet conveyance direction D1, and the "L" and "R" attached as subscripts to the reference numerals indicate whether they are provided on one side or the other side of the width direction W. Further, these pair of members each have the same configuration, and only one of the pair may be described as appropriate and the description of the other may be omitted.

[0026] The first support members 21L and 21R are supported by a frame (not shown) of the intermediate transfer device 10 so as to be movable in the direction of arrow A, and rotatably support both ends of the tension roller 15. The tension roller 15 as a tension member is disposed upstream of the transfer nip N in the sheet conveyance direction D1. The biasing members 31L and 31R bias the first support members 21L and 21R respectively so that the tension roller 15 is biased toward the inner peripheral surface 11b of the intermediate transfer belt 11. These tension roller 15, first support members 21L and 21R, and biasing members 31L and 31R constitute a tension unit 30.

[0027] Thereby, the tension roller 15 applies a predetermined tension to the intermediate transfer belt 11, and the position of the tension roller 15 is determined by the balance between the biasing force of the biasing members 31L and 31R and the tension of the intermediate transfer belt 11. Further, when the position of the tension roller 15 is determined, the position of the surface 11a of the intermediate transfer belt 11 stretched between the secondary transfer counter roller 14 and the tension roller 15 is determined.

[0028] The second support members 61L and 61R are rotatably supported at both ends of the rotation shaft 51a of the secondary transfer roller 51, and are biased by the biasing members 71L and 71R toward the tension roller 15 and the first support members 21L and 21R. That is, the second support members 61L and 61R are interlocked with a door 92 that supports the secondary transfer device 50. In other words, the second support members 61L and 61R are rotatably supported by the door 92. Both ends in the width direction W of the conveyance guide 52 are supported by the second support members 61L and 61R. The biasing members 31L, 31R, 71L, and 71R are constituted by springs such as compression springs, for example, but are not limited to springs, and may be other elastic members such as rubber and sponge.

[0029] The first support members 21L and 21R have abutting surfaces 21La and 21Ra, and these abutting surfaces 21La and 21Ra extend in a direction intersecting the moving direction MD when the door 92 moves from the closed position to the open position. Further, the second support members 61L and 61R have bosses 61La and 61Ra that can abut against and separate from the abutting surfaces 21La and 21Ra. The bosses 61La and 61Ra extend in the width direction W.

[0030] Next, the operation of the engaging unit 70 will be described with reference to FIGS. 3(a) and 3(b). Only one side of the engaging unit 70 (the side with the subscript "L") in the width direction W will be described, and the description of the other side (the side with the subscript "R") will be omitted. As shown in FIG. 3(a), when the door 92 is in the closed position, the boss 61La abuts against the abutting surface 21La. At this time, the boss 61La is pressed against the abutting surface 21La because the second support member 61L is biased by the biasing member 71L as the first biasing member.

[0031] That is, the first support member 21L and the second support member 61L are engaged with each other at the boss 61La and the abutting surface 21La. Therefore, the conveyance guide 52 supported by the second support member 61L as a support member is positioned with respect to the tension roller 15 supported by the first support member 21L as an engaged member.

[0032] The position of the boss 61La follows the change in the position of the first support member 21L in the direction of arrow A that supports the tension roller 15. Therefore, even if the position of the tension roller 15 changes, the relative position of the conveyance guide 52 with respect to the tension roller 15 hardly changes. For this reason, the positional relationship between the surface 11a of the intermediate transfer belt 11 that moves following the tension roller 15 and the sheet P whose non-printing surface side is guided by the conveyance guide 52 is maintained.

[0033] As described above, when the door 92 is in the closed position as shown in Fig. 3(a), the first support member 21L and the second support member 61L engage with each other. As a result, the conveyance guide 52 is positioned with respect to the tension roller 15 so as to be in a guiding position that forms the conveyance path CP together with the surface 11a of the intermediate transfer belt 11. Therefore, it is possible to reduce the displacement of the contact position P1 where the sheet P guided by the conveyance guide 52 begins to contact the surface 11a of the intermediate transfer belt 11.

[0034] As a result, it is possible to suppress the occurrence of image defects at a position upstream of the transfer nip N in the sheet conveyance direction D1. For example, when the contact position P1 is too close to the transfer nip N and is located within a region where the electric field for secondary transfer is strong, the toner image held on the intermediate transfer belt 11 may be disturbed due to discharge occurring between the intermediate transfer belt 11 and the sheet P. Also, when the contact position P1 is too far from the transfer nip N and the distance at which the sheet P and the intermediate transfer belt 11 rub against each other becomes long, there is a risk of image defects occurring due to vibrations and friction generated by the rubbing of the sheet P and the intermediate transfer belt 11. In the present embodiment, since the conveyance guide 52 is positioned with respect to the tension roller 15, the contact position P1 can be stably maintained within a predetermined appropriate distance range from the transfer nip N, so that image defects as described above can be suppressed.

[0035] Also, the biasing member 31L and the biasing member 71L bias the first support member 21L and the second support member 61L in opposite directions to each other, but the biasing force of the biasing member 71L is set to be smaller than the biasing force of the biasing member 31L as the second biasing member. For this reason, the tension roller 15 can press the inner peripheral surface 11b of the intermediate transfer belt 11 without problems. Also, the biasing forces of the biasing members 31L and 71L are set so that even when a sheet P with a relatively large stiffness such as cardboard contacts the conveyance guide 52, the conveyance guide 52 does not move due to the reaction force from the sheet P.

[0036] Next, when the door 92 is in the open position as shown in FIG. 3(b), the boss 61La is separated from the abutting surface 21La. That is, the tension unit 30 including the first support member 21L and the second support member 61L are separated from each other, and the positioning of the conveyance guide 52 with respect to the tension roller 15 is released.

[0037] Then, the conveyance guide 52 moves together with the door 92 and the second support member 61L, and is positioned at the open position that opens the conveyance path CP. In other words, the conveyance guide 52 is movable between the guide position (the position in FIG. 3(a)) that forms the conveyance path CP and the open position (the position in FIG. 3(b)) that opens the conveyance path CP. When the door 92 moves from the closed position to the open position, the conveyance guide 52 moves from the guide position to the open position. Thereby, the sheet P jammed in the conveyance path CP can be easily processed, and the jam processability can be improved.

[0038] As described above, in the present embodiment, when the door 92 is in the closed position, the conveyance guide 52 can be positioned at the guide position with respect to the tension roller 15, and image defects can be suppressed. Further, when the door 92 is in the open position, the conveyance guide 52 moves together with the door 92 to open the conveyance path CP, and the jam processability can be improved. Further, since the abutting surface 21La of the first support member 21L extends in a direction substantially orthogonal to the direction of arrow A, the engagement relationship between the boss 61La that rotates about the rotation axis 51a and the abutting surface 21La that linearly moves in the direction of arrow A can be maintained with a simple configuration.

[0039] In addition, in the present embodiment, the abutting surface 21La as a surface is provided on the first support member 21L, and the boss 61La as the abutting portion is provided on the second support member 61L. However, the present invention is not limited to this. For example, the boss 61La may be provided on the first support member 21L, and the abutting surface 21La may be provided on the second support member 61L. Further, the abutting surface 21La may be provided on the rotation axis of the tension roller 15 or the like. That is, the abutting surface 21La may be provided on either the tension unit 30 or the second support member 61L, and the boss 61La may be provided on the other of the tension unit 30 and the second support member 61L.

[0040] <Second Embodiment> Next, a second embodiment of the present invention will be described. The second embodiment is obtained by changing the configuration of the engagement unit 70 of the first embodiment. For this reason, the same configurations as those in the first embodiment will be described with illustration omitted or the same reference numerals in the drawings. FIG. 4(a) is a side view showing the engagement unit 170 according to the second embodiment when the door 92 is in the closed position, and FIG. 4(b) is a side view showing the engagement unit 170 when the door 92 is in the open position.

[0041] As shown in FIG. 4(a), the engagement unit 170 according to the second embodiment includes a first support member 22L, a second support member 62L, and a biasing member 31L. Similar to the first embodiment, a pair of the first support member 22L, the second support member 62L, and the biasing member 31L are provided side by side in the width direction W. However, only one side in the width direction W will be described.

[0042] The first support member 22L as the engaged member is supported by a frame (not shown) of the intermediate transfer device 10 so as to be movable in the direction of arrow A, and rotatably supports the tension roller 15. The biasing member 31L biases the first support member 22L so that the tension roller 15 is biased toward the inner peripheral surface 11b of the intermediate transfer belt 11. Thereby, the tension roller 15 applies a predetermined tension to the intermediate transfer belt 11, and the position of the tension roller 15 is determined by the balance between the biasing force of the biasing member 31L and the tension of the intermediate transfer belt 11. These tension roller 15, first support member 22L, and biasing member 31L constitute a tension unit 230.

[0043] The second support member 62L as the support member is rotatably supported by the rotation shaft 51a of the secondary transfer roller 51, and is not biased by a biasing member as in the first embodiment. The conveyance guide 52 is supported by the second support member 62L.

[0044] The first support member 22L has a groove 22La formed so that one side is open. The groove 22La extends in a direction intersecting the moving direction MD when the door 92 moves from the closed position to the open position. The moving direction MD also intersects the direction of arrow A which is the moving direction of the first support member 22L. Further, the second support member 62L has a boss 62La that can be engaged with and separated from the groove 22La. The boss 62La extends in the width direction W.

[0045] Next, the operation of the engagement unit 170 will be described. As shown in FIG. 4(a), when the door 92 is in the closed position, the boss 62La is engaged with the groove 22La. At this time, since the groove 22La extends so as to intersect the direction of arrow A and the moving direction MD, the first support member 22L and the second support member 62L are in an interlocking relationship. That is, the first support member 22L and the second support member 62L are engaged with each other at the boss 62La and the groove 22La. Therefore, the conveyance guide 52 supported by the second support member 62L is positioned at the guiding position with respect to the tension roller 15 supported by the first support member 22L.

[0046] The position of the boss 62La follows the change in the position of the first support member 22L that supports the tension roller 15 in the direction of arrow A. Therefore, even if the position of the tension roller 15 changes, the relative position of the conveyance guide 52 with respect to the tension roller 15 hardly changes. For this reason, the positional relationship between the surface 11a of the intermediate transfer belt 11 that moves following the tension roller 15 and the sheet P whose non-printing surface side is guided by the conveyance guide 52 is maintained. For this reason, it is possible to reduce the displacement of the contact position P1 where the sheet P guided by the conveyance guide 52 starts to contact the surface 11a of the intermediate transfer belt 11.

[0047] Next, as shown in FIG. 4(b), when the door 92 is moved from the closed position to the open position, the second support member 62 rotates about the rotation shaft 51a, and the boss 62La comes out of the groove 22La. When the engagement between the boss 62La and the groove 22La is released, the second support member 62 is held in a posture such that the center of gravity G of the second support member 62 and the rotation shaft 51a are aligned in a straight line in the vertical direction. And when the door 92 is located at the open position, the boss 62La is separated from the groove 22La. That is, the tension unit 230 including the first support member 21L and the second support member 62L are separated from each other, and the positioning of the conveyance guide 52 with respect to the tension roller 15 is released.

[0048] Then, the conveyance guide 52 moves together with the door 92 and the second support member 62L and is located at an open position that opens the conveyance path CP. Thereby, the sheet P jammed in the conveyance path CP can be easily processed, and the jam processability can be improved.

[0049] Incidentally, when the door 92 is closed again from the open position to the closed position, the boss 62La of the second support member 62L is guided toward the groove 22La by the guide surface 22Lb of the first support member 22L. Then, the second support member 62L rotates about the rotation shaft 51a, and the boss 62La engages with the groove 22La.

[0050] As described above, also in the second embodiment, similar to the first embodiment, it is possible to achieve both suppression of image defects and improvement of jam disposability. Further, since the biasing member for biasing the second support member 62L can be omitted, cost reduction can be achieved.

[0051] In this embodiment, the groove 22La is provided in the first support member 22L and the boss 62La as the engaging portion is provided in the second support member 62L, but the present invention is not limited to this. For example, the boss 62La may be provided in the first support member 22L and the groove 22La may be provided in the second support member 62L. Further, the groove 22La may be provided in the rotation shaft of the tension roller 15 or the like. That is, the groove 22La may be provided in either the tension unit 230 or the second support member 62L, and the boss 62La may be provided in the other of the tension unit 230 and the second support member 62L.

[0052] <Third Embodiment> Next, a third embodiment of the present invention will be described. The third embodiment is a modification of the configuration of the engaging unit 70 of the first embodiment. For this reason, for the same configurations as those in the first embodiment, illustration is omitted or the same reference numerals are given in the drawings and description. FIG. 5(a) is a side view showing the engaging unit 270 according to the third embodiment when the door 92 is in the closed position, and FIG. 5(b) is a side view showing the engaging unit 270 when the door 92 is in the open position.

[0053] As shown in FIG. 5(a), the engaging unit 270 according to the third embodiment includes a first support member 21L, a second support member 63L, and biasing members 31L and 71L. Similar to the first embodiment, a pair of the first support member 21L, the second support member 63L, and the biasing members 31L and 71L are provided side by side in the width direction W. Only one side in the width direction W will be described. In this embodiment, the configuration and operation of the second support member 63L are particularly different from those in the first embodiment.

[0054] The second support member 63L as a support member is supported so as to be slidable in the direction of arrow B with respect to the frame 55 of the secondary transfer device 50, and is biased by the biasing member 71L toward the tension roller 15 and the first support member 21L. In other words, the second support member 63L is supported so as to be slidable on the door 92. The conveyance guide 52 is supported by the second support member 63L. The second support member 63L has a boss 63La that can contact and separate from the abutting surface 21La of the first support member 21L. The boss 63La extends in the width direction W. Note that the direction of arrow B is substantially the same as the direction of arrow A, which is the linear motion direction of the first support member 21L, when the door 92 is in the closed position.

[0055] Next, the operation of the engagement unit 270 will be described. As shown in FIG. 5(a), when the door 92 is in the closed position, the boss 63La is in contact with the abutting surface 21La. At this time, the boss 63La is pressed against the abutting surface 21La because the second support member 63L is biased by the biasing member 71L.

[0056] That is, the first support member 21L and the second support member 63L are engaged with each other at the boss 63La and the abutting surface 21La. Therefore, the conveyance guide 52 supported by the second support member 63L is positioned with respect to the tension roller 15 supported by the first support member 21L.

[0057] The position of the boss 63La follows the change in the position of the first support member 21L in the direction of arrow A that supports the tension roller 15. Therefore, even if the position of the tension roller 15 changes, the relative position of the conveyance guide 52 with respect to the tension roller 15 does not change. For this reason, the positional relationship between the surface 11a of the intermediate transfer belt 11 that moves following the tension roller 15 and the sheet P whose non-printing surface side is guided by the conveyance guide 52 is maintained. Therefore, it is possible to reduce the positional deviation of the contact position P1 where the sheet P guided by the conveyance guide 52 starts to contact the surface 11a of the intermediate transfer belt 11.

[0058] Next, as shown in FIG. 5(b), when the door 92 is moved from the closed position to the open position, after the biasing members 31L and 71L return to their natural states, the boss 63La separates from the abutting surface 21La. That is, the tension unit 30 including the first support member 21L and the second support member 63L move apart from each other, and the positioning of the conveyance guide 52 with respect to the tension roller 15 of the conveyance guide 52 is released.

[0059] Then, the conveyance guide 52 moves together with the door 92 and the second support member 63L and is positioned at an open position that opens the conveyance path CP. As a result, the sheet P jammed in the conveyance path CP can be easily processed, and the jam processability can be improved.

[0060] As described above, also in the third embodiment, similar to the first embodiment, it is possible to achieve both suppression of image defects and improvement of jam processability. Further, when the door 92 is in the closed position, since the direction of arrow B, which is the linear movement direction of the conveyance guide 52, is substantially the same as the direction of arrow A, which is the linear movement direction of the tension roller 15, the conveyance guide 52 can be accurately positioned with respect to the tension roller 15.

[0061] <Fourth Embodiment> Next, a fourth embodiment of the present invention will be described. The fourth embodiment is a modification of the configuration of the engagement unit 70 in the first embodiment. For this reason, for the same configurations as those in the first embodiment, illustration will be omitted or the same reference numerals will be used in the drawings for explanation. FIG. 6(a) is a side view showing the engagement unit 370 according to the fourth embodiment when the door 92 is in the closed position, and FIG. 6(b) is a side view showing the engagement unit 370 when the door 92 is in the open position.

[0062] As shown in Fig. 6(a), the engaging unit 370 according to the fourth embodiment has a first support member 24L, a second support member 64L, and biasing members 31L and 71L. Similar to the first embodiment, a pair of the first support member 24L, the second support member 64L, and the biasing members 31L and 71L are provided side by side in the width direction W. Only one side in the width direction W will be described herein.

[0063] The first support member 24L as the engaged member is supported by a frame (not shown) of the intermediate transfer device 10 so as to be movable in the direction of arrow A, and rotatably supports the tension roller 15. The biasing member 31L biases the first support member 24L so that the tension roller 15 is biased toward the inner peripheral surface 11b of the intermediate transfer belt 11. Thereby, the tension roller 15 applies a predetermined tension to the intermediate transfer belt 11, and the position of the tension roller 15 is determined by the balance between the biasing force of the biasing member 31L and the tension of the intermediate transfer belt 11. These tension roller 15, first support member 24L, and biasing member 31L constitute a tension unit 430.

[0064] The second support member 64L as the support member is rotatably supported by the rotation shaft 51a of the secondary transfer roller 51, and is biased by the biasing member 71L toward the tension roller 15 and the first support member 24L. Further, the second support member 64L has a long hole 64Lb extending in the direction of arrow C, and the rotation shaft 51a is inserted into the long hole 64Lb. That is, the second support member 64L is movable in the direction of arrow C within the range of the long hole 64Lb with respect to the rotation shaft 51a. The conveyance guide 52 is supported by the second support member 64L.

[0065] The first support member 24L has a first contact surface 24La extending in a first direction (a direction orthogonal to the arrow x direction) intersecting the moving direction MD of the second support member 64L when the door 92 moves from the closed position to the open position, and a second contact surface 24Lb. The second contact surface 24Lb extends in a second direction (a direction orthogonal to the arrow y direction) intersecting the moving direction MD and the first direction. Further, the second support member 64L has a boss 64La that can contact and separate from the first contact surface 24La and the second contact surface 24Lb. The boss 64La extends in the width direction W as the seat width direction, and the conveyance guide 52 is arranged so as to overlap the boss 64La when viewed in the width direction W.

[0066] Next, the operation of the engagement unit 370 will be described. As shown in FIG. 6(a), when the door 92 is in the closed position, the boss 64La is engaged with the first contact surface 24La and the second contact surface 24Lb of the first support member 24L. At this time, the boss 64La is pressed against the first contact surface 24La and the second contact surface 24Lb in the arrow x direction and the arrow y direction, respectively, due to the second support member 64L being biased by the biasing member 71L.

[0067] That is, the boss 64La of the first support member 24L is positioned with respect to the first contact surface 24La and the second contact surface 24Lb of the second support member 64L, and the conveyance guide 52 supported by the first support member 24L is positioned with respect to the tension roller 15. Since the position of the boss 64La follows the change in the position of the first support member 21L supporting the tension roller 15 in the arrow A direction, even if the position of the tension roller 15 changes, the relative position of the conveyance guide 52 with respect to the tension roller 15 does not change.

[0068] In particular, in the present embodiment, the second support member 64L is movable in the direction of arrow C, and the movement of the boss 64La in the direction of arrow C, which follows the first contact surface 24La and the second contact surface 24Lb, is absorbed by the long hole 64Lb. And since the conveyance guide 52 is arranged so as to overlap the boss 64La when viewed in the width direction W, the conveyance guide 52 can be accurately positioned with respect to the tension roller 15. For this reason, the positional relationship between the surface 11a of the intermediate transfer belt 11 that moves following the tension roller 15 and the sheet P whose non-printing surface side is guided by the conveyance guide 52 is maintained. Therefore, it is possible to reduce the displacement of the contact position P1 where the sheet P guided by the conveyance guide 52 starts to contact the surface 11a of the intermediate transfer belt 11.

[0069] Next, as shown in FIG. 6(b), when the door 92 is moved from the closed position to the open position, after the biasing members 31L and 71L return to the natural state, the boss 64La separates from the first contact surface 24La and the second contact surface 24Lb. That is, the tension unit 430 including the first support member 24L and the second support member 64L are separated from each other, and the positioning of the conveyance guide 52 with respect to the tension roller 15 is released.

[0070] Then, the conveyance guide 52 moves together with the door 92 and the second support member 64L, and is located at the open position where the conveyance path CP is opened. Thereby, the sheet P jammed in the conveyance path CP can be easily processed, and the jam processability can be improved.

[0071] As described above, also in the fourth embodiment, as in the first embodiment, it is possible to achieve both suppression of image defects and improvement of jam processability. Further, when the door 92 is located at the closed position, the boss 64La of the second support member 64L that supports the conveyance guide 52 is positioned in two directions intersecting each other by the first contact surface 24La and the second contact surface 24Lb. For this reason, the conveyance guide 52 can be accurately positioned with respect to the tension roller 15.

[0072] In addition, in the present embodiment, the first contact surface 24La and the second contact surface 24Lb are provided on the first support member 24L, and the boss 64La as the boss portion is provided on the second support member 64L. However, the present invention is not limited to this. For example, the boss 64La may be provided on the first support member 24L, and the first contact surface 24La and the second contact surface 24Lb may be provided on the second support member 64L. Further, the first contact surface 24La and the second contact surface 24Lb may be provided on the rotation axis of the tension roller 15 or the like. That is, the first contact surface 24La and the second contact surface 24Lb may be provided on either the tension unit 430 or the second support member 64L, and the boss 64La may be provided on the other of the tension unit 430 and the second support member 64L.

[0073] <Other Embodiments> In addition, in any of the above-described embodiments, the conveyance guide 52 is held by the secondary transfer device 50. However, the present invention is not limited to this. For example, the conveyance guide 52 may be held by a member other than the secondary transfer device 50 that moves integrally with the door unit 90, such as the door 92.

[0074] Further, the conveyance guide 52 may be held by the apparatus main body 100A instead of the door unit 90. In this case, the conveyance guide 52 is movably supported by a frame (not shown) or the like of the apparatus main body 100A and has a locking portion. When the door 92 moves from the open position to the closed position, the locking portion is locked to the tension roller 15. Therefore, the conveyance guide 52 is positioned with respect to the tension roller 15. On the other hand, when the door 92 moves from the closed position to the open position, the locking portion is separated from the tension roller 15, and the conveyance guide 52 may be configured to move to the open position.

[0075] In addition, in any of the above-described embodiments, the conveyance guide 52 moves between the guide position and the open position in conjunction with the opening and closing of the door 92 that forms a part of the exterior surface of the image forming apparatus 100. However, the present invention is not limited to this. For example, there may be another opening and closing member between the door 92 and the apparatus main body 100A, and the conveyance guide 52 may move between the guide position and the open position in conjunction with the opening and closing of the opening and closing member.

[0076] Also, in any of the above-described forms, the conveyance guide 52 forms the conveyance path CP together with the surface 11a of the intermediate transfer belt 11 at the guiding position, but is not limited thereto. For example, the conveyance guide 52 may form the conveyance path CP together with other guide members disposed between the conveyance guide 52 and the surface 11a of the intermediate transfer belt 11 at the guiding position. At this time, it is preferable that the other guide members are positioned with respect to the tension roller 15 when the door 92 is in the closed position together with the conveyance guide 52. Further, when the door 92 is in the open position, the other guide members may or may not be released from the positioning with respect to the tension roller 15, as long as the conveyance path CP is opened.

[0077] Also, in any of the above-described forms, the tension roller 15 is a roller that rotates in a driven manner with respect to the intermediate transfer belt 11, but is not limited thereto. For example, instead of the tension roller 15, a non-rotating member that presses the inner peripheral surface 11b of the intermediate transfer belt 11 may be used.

[0078] Also, in any of the above-described forms, the second support members (61L, 62L, 63L, 64L) are separated from the first support members (21L, 22L, 24L) when the door 92 is in the open position, but are not limited thereto. For example, the second support members may be engaged with the first support members when the door 92 is in the open position.

[0079] Also, in any of the above-described forms, the second support members (61L, 62L, 63L, 64L) are provided separately from the conveyance guide 52, but are not limited thereto. For example, the second support members and the conveyance guide 52 may be integrally formed.

[0080] Also, the above-described first to fourth embodiments may be arbitrarily combined. For example, in the second embodiment, a biasing member 71L that biases the second support member 62L toward the tension roller 15 may be provided.

[0081] Also, the disclosure of the present embodiment includes the following configuration examples and method examples. (Configuration 1) An endless belt member that carries a toner image, A first transfer roller that abuts on the inner peripheral surface of the belt member, A second transfer roller that forms a transfer nip together with the first transfer roller via the belt member, and transfers the toner image on the belt member to a sheet while conveying the sheet in the sheet conveyance direction at the transfer nip, A tension unit having a tension member that is disposed upstream of the transfer nip in the sheet conveyance direction and that stretches the belt member by pressing the inner peripheral surface of the belt member, A guide member that forms a conveyance path through which a sheet passes and guides the sheet, the guide member being movable between a guide position for guiding the sheet toward the transfer nip and an open position for opening the conveyance path, An opening / closing member that is movable between a closed position and an open position and that can open the conveyance path by being moved from the closed position to the open position, A support member that is interlocked with the opening / closing member and supports the guide member, When the opening / closing member is in the closed position, the support member engages with the tension unit to position the guide member at the guide position and position the tension member, and when the opening / closing member is in the open position, the support member positions the guide member at the open position. An image forming apparatus characterized by the above. (Configuration 2) The support member is separated from the tension unit when the opening / closing member is in the open position. The image forming apparatus according to Configuration 1, characterized by the above. (Configuration 3) The image forming apparatus according to Configuration 1 or 2, further comprising a first biasing member that biases the support member toward the tension unit. characterized by the above. (Configuration 4) The tension unit includes an engaged member that supports the tension member and can engage with the support member, and a second biasing member that biases the engaged member toward the support member so that the tension member presses the inner peripheral surface of the belt member. The image forming apparatus according to Configuration 3, characterized in that. (Configuration 5) The biasing force of the second biasing member is greater than the biasing force of the first biasing member. The image forming apparatus according to Configuration 4, characterized in that. (Configuration 6) Either one of the tension unit and the support member has a surface extending in a direction intersecting the moving direction of the support member when the opening / closing member moves from the closed position to the open position. The other of the tension unit and the support member has an abutting portion that abuts against the surface when the opening / closing member is in the closed position. The image forming apparatus according to any one of Configurations 1 to 5, characterized in that. (Configuration 7) Either one of the tension unit and the support member has a groove extending in a direction intersecting the moving direction of the support member when the opening / closing member moves from the closed position to the open position. The other of the tension unit and the support member has an engaging portion that engages with the groove when the opening / closing member is in the closed position. The image forming apparatus according to any one of Configurations 1 to 5, characterized in that. (Configuration 8) Either one of the tension unit and the support member has a guiding surface that guides the engaging portion toward the groove when the opening / closing member moves from the open position to the closed position. The image forming apparatus according to Configuration 7, characterized in that. (Configuration 9) Either one of the tension unit and the support member has a first contact surface extending in a first direction intersecting the moving direction of the support member when the opening / closing member moves from the closed position to the open position, and a second contact surface extending in a second direction intersecting the moving direction and the first direction. The other of the tension unit and the support member has a boss portion that contacts the first contact surface and the second contact surface when the opening / closing member is in the closed position. The image forming apparatus according to any one of Configurations 1 to 5, characterized in that. (Configuration 10) The guide member is arranged so as to overlap the boss portion when viewed in the sheet width direction orthogonal to the sheet conveyance direction when the opening / closing member is in the closed position. The image forming apparatus according to Configuration 9, characterized in that. (Configuration 11) The support member is rotatably supported by the opening / closing member. The image forming apparatus according to any one of Configurations 1 to 10, characterized in that. (Configuration 12) The support member is slidably supported by the opening / closing member. The image forming apparatus according to any one of Configurations 1 to 10, characterized in that. (Configuration 13) The opening / closing member rotatably supports the second transfer roller. The image forming apparatus according to any one of Configurations 1 to 12, characterized in that. (Configuration 14) The opening / closing member is a door that forms a part of the exterior surface of the image forming apparatus when in the closed position. The image forming apparatus according to any one of Configurations 1 to 13, characterized in that. (Configuration 15) The tension member is a roller rotatably supported by the tension unit. The image forming apparatus according to any one of Configurations 1 to 14, characterized in that. (Configuration 16) The guide member forms the conveyance path together with the belt member at the guide position. The image forming apparatus according to any one of Configurations 1 to 15, characterized in that... (Configuration 17) The guide member can contact the second surface of the sheet, which is opposite to the first surface on which the toner image is transferred by the transfer nip. The image forming apparatus according to any one of Configurations 1 to 16, characterized in that...

Explanation of Signs

[0082] 11: Belt member (intermediate transfer belt) / 11b: Inner peripheral surface / 14: First transfer roller (secondary transfer opposing roller) / 15: Tension member (tension roller) / 21L, 22L, 24L: Engaged member (first support member) / 21La: Surface (abutting surface) / 22La: Groove / 22Lb: Guide surface / 24La: First contact surface / 24Lb: Second contact surface / 30, 230, 430: Tension unit / 31L: Second biasing member (biasing member) / 51: Second transfer roller (secondary transfer roller) / 52: Guide member (conveyance guide) / 61L, 62L, 63L, 64L: Support member (second support member) / 61La: Abutting portion (boss) / 62La: Engaging portion (boss) / 64La: Boss portion (boss) / 71L: First biasing member (biasing member) / 92: Opening / closing member (door) / CP: Conveyance path / D1: Sheet conveyance direction / MD: Movement direction / P: Sheet / N: Transfer nip

Claims

1. An endless belt member that carries a toner image, A first transfer roller that abuts against the inner peripheral surface of the belt member, A second transfer roller that forms a transfer nip together with the first transfer roller via the belt member, and transfers the toner image on the belt member to a sheet while conveying the sheet in the sheet conveyance direction at the transfer nip, A tension unit having a tension member that is disposed upstream of the transfer nip in the sheet conveyance direction and that stretches the belt member by pressing against the inner peripheral surface of the belt member, A guide member that forms a conveyance path through which a sheet passes and guides the sheet, the guide member being movable between a guide position for guiding the sheet toward the transfer nip and an open position for opening the conveyance path, An opening / closing member that is movable between a closed position and an open position and that can open the conveyance path by being moved from the closed position to the open position, A support member that is interlocked with the opening / closing member and supports the guide member, When the opening / closing member is in the closed position, the support member engages with the tension unit to position the guide member at the guide position and position the tension member relative to the tension unit, and when the opening / closing member is in the open position, the support member positions the guide member at the open position, An image forming apparatus characterized by the above.

2. The support member is separated from the tension unit when the opening / closing member is in the open position, The image forming apparatus according to claim 1, characterized by the above.

3. The image forming apparatus according to claim 1, further comprising a first biasing member that biases the support member toward the tension unit. The image forming apparatus according to claim 1, characterized by the above.

4. The tension unit includes an engaged member that supports the tension member and can engage with the support member, and a second biasing member that biases the engaged member toward the support member so that the tension member presses against the inner peripheral surface of the belt member. The image forming apparatus according to claim 3, characterized by the above.

5. The biasing force of the second biasing member is greater than the biasing force of the first biasing member. The image forming apparatus according to claim 4, characterized by the above.

6. Either the tension unit or the support member has a surface that extends in a direction intersecting the moving direction of the support member when the opening / closing member moves from the closed position to the open position. Either the tension unit or the other of the support members has an abutting portion that abuts against the surface when the opening / closing member is in the closed position. The image forming apparatus according to claim 1, wherein the image forming apparatus is characterized in that.

7. Either the tension unit or one of the support members has a groove extending in a direction intersecting the moving direction of the support member when the opening / closing member moves from the closed position to the open position. Either the tension unit or the other of the support members has an engaging portion that engages with the groove when the opening / closing member is in the closed position. The image forming apparatus according to claim 1, wherein the image forming apparatus is characterized in that.

8. Either the tension unit or one of the support members has a guiding surface that guides the engaging portion toward the groove when the opening / closing member moves from the open position to the closed position. The image forming apparatus according to claim 7, wherein the image forming apparatus is characterized in that.

9. Either the tension unit or one of the support members has a first abutting surface extending in a first direction intersecting the moving direction of the support member when the opening / closing member moves from the closed position to the open position, and a second abutting surface extending in a second direction intersecting the moving direction and the first direction. Either the tension unit or the other of the support members has a boss portion that abuts against the first abutting surface and the second abutting surface when the opening / closing member is in the closed position. The image forming apparatus according to claim 1, wherein the image forming apparatus is characterized in that.

10. The guide member is arranged so as to overlap the boss portion when viewed in the sheet width direction orthogonal to the sheet conveyance direction when the opening / closing member is in the closed position. The image forming apparatus according to claim 9, wherein the image forming apparatus is characterized in that.

11. The support member is rotatably supported by the opening / closing member. The image forming apparatus according to any one of claims 1 to 10, wherein the image forming apparatus is characterized in that.

12. The support member is slidably supported by the opening / closing member. The image forming apparatus according to any one of claims 1 to 10, wherein the image forming apparatus is characterized in that.

13. The opening / closing member rotatably supports the second transfer roller. The image forming apparatus according to any one of claims 1 to 10, wherein the image forming apparatus is characterized in that.

14. The opening / closing member is a door that forms a part of the exterior surface of the image forming apparatus when in the closed position. The image forming apparatus according to any one of claims 1 to 10, wherein the image forming apparatus is characterized in that.

15. The tension member is a roller rotatably supported by the tension unit. The image forming apparatus according to any one of claims 1 to 10, characterized in that.

16. The guide member forms the conveyance path together with the belt member at the guide position. The image forming apparatus according to any one of claims 1 to 10, characterized in that.

17. The guide member can contact the second surface of the sheet on the side opposite to the first surface on which the toner image is transferred by the transfer nip. The image forming apparatus according to any one of claims 1 to 10, characterized in that.

Images