JP6341179B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including an intermediate transfer unit that can be attached to and detached from an apparatus main body.

  Conventionally, as an image forming apparatus such as a printer or a copying machine employing an electrophotographic method, a photosensitive drum that carries an electrostatic latent image, and an intermediate transfer unit that transfers a toner image from the photosensitive drum to a sheet, What you have is known. In order to transfer an image composed of a plurality of colors typified by a full-color image onto a sheet, the intermediate transfer unit includes an intermediate transfer belt and a primary transfer roller. The intermediate transfer belt is circulated so as to face the plurality of photosensitive drums, and a toner image is transferred from each photosensitive drum onto the intermediate transfer belt by a primary transfer voltage applied to the primary transfer roller. Further, a technique is known in which a primary transfer roller is brought into contact with or separated from a photosensitive drum in accordance with an execution condition of an image forming operation.

  Patent Document 1 discloses a technique in which an intermediate transfer unit and a drum unit that supports a photosensitive drum can be attached to and detached from the main body of the image forming apparatus. Patent Document 1 discloses an interference preventing member that prevents interference between the intermediate transfer belt and the drum unit during attachment and detachment.

JP 2003-43764 A

  Conventionally, the detection unit for detecting the contact / separation state of the primary transfer roller with respect to the photosensitive drum has been arranged inside the circular orbit of the intermediate transfer belt in the intermediate transfer unit. For this reason, there is a problem that the toner scattered during the transfer enters the inner peripheral portion of the intermediate transfer belt and the detection portion becomes dirty, and the detection accuracy of the contact / separation operation of the primary transfer roller is lowered.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus in which contamination of a detection unit that detects a contact / separation state of a primary transfer roller with respect to a photosensitive drum is suppressed.

  An image forming apparatus according to an aspect of the present invention includes an apparatus main body and a second interval that is disposed within the apparatus main body and is rotated about an axis extending in the first direction and has a predetermined interval in the second direction intersecting the first direction. A plurality of photosensitive drums disposed adjacent to each other, and an intermediate transfer unit mounted on the apparatus main body along the second direction so as to be adjacent to the plurality of photosensitive drums. The transfer unit is driven around in the second direction and has an intermediate transfer belt that carries toner images transferred from the plurality of photosensitive drums on a surface thereof, and a photosensitive drum that sandwiches the intermediate transfer belt, respectively. A plurality of primary transfer rollers arranged opposite to each other; a contact / separation mechanism for contacting / separating the plurality of primary transfer rollers with respect to the photosensitive drum in the apparatus body; and the first side of the intermediate transfer unit. At least three at the lower ends of the pair of side walls, the intermediate transfer unit being arranged to extend in the second direction at both ends of the pair, and disposed at the lower ends of the pair of side walls. A plurality of legs that come into contact with a predetermined installation surface when detached from the apparatus main body, and in conjunction with the contact / separation operation of the primary transfer roller by the contact / separation mechanism, A moving unit that slides one of the legs, and a detection unit that is disposed outside a circular orbit of the intermediate transfer belt and detects the sliding movement of the one leg. To do.

  According to this configuration, it is possible to detect the contact / separation state of the intermediate transfer belt with respect to the photosensitive drum by the detection unit disposed outside the orbit of the intermediate transfer belt. For this reason, even when the toner on the intermediate transfer belt flows into the inside of the circular orbit of the intermediate transfer belt due to the air flow in the apparatus main body, the toner contamination of the detection unit can be suppressed. At this time, one leg portion can also function as a detection piece detected by the detection portion.

  In the above configuration, the one leg portion includes a fulcrum portion, is rotatable about the fulcrum portion, and supports the intermediate transfer unit detached from the apparatus main body by contacting the installation surface. It is desirable that the movable leg portion be capable of changing the posture between the first possible posture and the second posture rotated around the fulcrum portion from the first posture.

  According to this configuration, the intermediate transfer unit can be placed directly on the installation surface by the movable leg portion taking the first posture. Further, since the movable leg portion takes the second posture, the movable leg portion and other units are prevented from strongly colliding with each other inside the apparatus main body, and damage to these members is prevented.

  In the above configuration, the movable leg portion is rotated from the first posture to the second direction front end side or the second direction rear end side around the fulcrum portion, so that the second posture is reached. It is desirable to change posture.

  According to this configuration, it is possible to prevent the movable leg and the other unit from strongly colliding with each other inside the apparatus main body when the intermediate transfer unit is attached to the apparatus main body or pulled out from the apparatus main body. Is done.

  In the above configuration, the intermediate transfer unit supports the intermediate transfer belt on one end side in the second direction, drives the intermediate transfer belt to rotate, and the other end side in the second direction. It is preferable that a tension roller that supports the intermediate transfer belt and applies tension to the intermediate transfer belt is provided, and the movable leg portion is disposed around the tension roller.

  According to this configuration, the tension roller and the movable leg can be supported by the same unit.

  In the above configuration, the intermediate transfer unit rotatably supports the tension roller and is slidably movable with respect to the pair of side walls, and compressed between the pair of side walls and the movement unit. A biasing member that is deformed and biases the tension roller toward a side opposite to the driving roller, the movable leg is provided in the moving unit, and the contact / separation mechanism is the primary transfer roller. The moving unit slides in the direction away from the driving roller by the biasing force of the biasing member in accordance with the separation operation for separating the photosensitive drum from the photosensitive drum, so that the detection unit slides the movable leg. It is desirable to detect.

  According to this configuration, the movable leg can be slid using the operation in which the moving unit slides in accordance with the separation operation of the primary transfer roller.

  In the above configuration, the intermediate transfer unit further includes a tension roller that stretches the intermediate transfer belt between the tension roller and the primary transfer roller, and the contact / separation mechanism includes the tension roller as the tension roller. When the moving unit is moved away from the inner peripheral surface of the intermediate transfer belt, it is preferable that the moving unit slides in a direction away from the driving roller by the urging force of the urging member.

  According to this configuration, the moving unit can be slid using the lowering of the tension of the intermediate transfer belt and the urging force of the urging member when the stretching roller moves away from the intermediate transfer belt. it can.

  In the above configuration, it is desirable that the detection unit is provided in the apparatus main body.

  According to this configuration, toner contamination of the detection unit can be reduced as compared with the case where the detection unit is attached to the intermediate transfer unit.

  According to the present invention, there are provided an intermediate transfer unit that prevents interference with other units in the apparatus main body while preventing damage to the intermediate transfer belt when placed on the floor, and an image forming apparatus including the intermediate transfer unit. .

1 is a cross-sectional view illustrating an internal structure of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a perspective view of an intermediate transfer unit according to an embodiment of the present invention. FIG. 3 is a perspective view of an intermediate transfer unit according to an embodiment of the present invention. FIG. 2 is an enlarged perspective view of a part of an intermediate transfer unit according to an embodiment of the present invention. FIG. 3 is an enlarged perspective view of a leg portion of an intermediate transfer unit according to an embodiment of the present invention. FIG. 4 is an enlarged perspective view of the periphery of a movable leg portion of an intermediate transfer unit according to an embodiment of the present invention. FIG. 2 is a perspective view of a state where an intermediate transfer belt is removed from an intermediate transfer unit according to an embodiment of the present invention. FIG. 4 is a perspective view of an intermediate transfer unit contact / separation mechanism according to an embodiment of the present invention. FIG. 4 is a perspective view of the periphery of an urging spring of an intermediate transfer unit according to an embodiment of the present invention. FIG. 3 is a perspective view of an intermediate transfer unit according to an embodiment of the present invention. 1 is a cross-sectional perspective view of an intermediate transfer unit according to an embodiment of the present invention. FIG. 3 is a perspective view of an intermediate transfer unit and a detection unit according to an embodiment of the present invention. It is a perspective view of the movable leg part and detection part which concern on one Embodiment of this invention. It is a perspective view of the movable leg part and detection part which concern on one Embodiment of this invention.

  Hereinafter, an image forming apparatus 10 according to an embodiment of the present disclosure will be described in detail with reference to the drawings. In this embodiment, a tandem color printer is illustrated as an example of an image forming apparatus. The image forming apparatus may be, for example, a copying machine, a facsimile machine, and a complex machine of these.

  FIG. 1 is a cross-sectional view showing the internal structure of the image forming apparatus 10. The image forming apparatus 10 includes an apparatus main body 11 having a box-shaped housing structure. In the apparatus main body 11, a sheet feeding unit 12 that feeds the sheet P, an image forming unit 13 that forms a toner image to be transferred to the sheet P fed from the sheet feeding unit 12, and the toner image are primarily transferred. Intermediate transfer unit 14, secondary transfer roller 145, toner replenishing unit 15 for replenishing toner to the image forming unit 13, and fixing unit for performing a process of fixing an unfixed toner image formed on the sheet P to the sheet P 16 are decorated. Further, a discharge unit 17 that discharges the sheet P that has been subjected to the fixing process by the fixing unit 16 is provided on the upper portion of the apparatus main body 11.

  At an appropriate position on the upper surface of the apparatus main body 11, an unillustrated operation panel for inputting an output condition for the sheet P and the like is provided. This operation panel is provided with a power key, a touch panel for inputting output conditions, and various operation keys. In the apparatus main body 11, a sheet conveying path 111 extending in the vertical direction is further formed on the right side of the image forming unit 13. The sheet conveyance path 111 is provided with a conveyance roller pair 112 that conveys a sheet to an appropriate position. A registration roller pair 113 that corrects the skew of the sheet and feeds the sheet to a nip portion of secondary transfer described later at a predetermined timing is also provided on the upstream side of the nip portion in the sheet conveyance path 111. The sheet conveyance path 111 is a conveyance path that conveys the sheet P from the paper feeding unit 12 to the paper discharge unit 17 via the image forming unit 13 (secondary transfer nip unit) and the fixing unit 16.

  The paper feed unit 12 includes a paper feed tray 121, a pickup roller 122, and a paper feed roller pair 123. The sheet feeding tray 121 is detachably mounted at a lower position of the apparatus main body 11 and stores a sheet bundle P1 in which a plurality of sheets P are stacked. The pickup roller 122 feeds the uppermost sheet P of the sheet bundle P1 stored in the sheet feeding tray 121 one by one. The pair of paper feed rollers 123 sends out the sheet P fed out by the pickup roller 122 to the sheet conveyance path 111. The paper feeding unit 12 includes a manual paper feeding unit attached to the left side surface of the apparatus main body 11 shown in FIG. The manual paper feed unit includes a manual feed tray 124, a pickup roller 125, and a paper feed roller pair 126. The manual feed tray 124 is a tray on which the manually fed sheet P is placed, and is opened from the side surface of the apparatus main body 11 as shown in FIG. 1 when the sheet P is manually fed. The pickup roller 125 feeds out the sheet P placed on the manual feed tray 124. The pair of paper feed rollers 126 sends out the sheet P fed out by the pickup roller 125 to the sheet conveyance path 111.

  Further, the image forming apparatus 10 includes a right cover unit 10R (FIG. 1). The right cover unit 10 </ b> R defines a right side portion of the apparatus main body 11. The right cover unit 10R includes a cover fulcrum portion 10R1. The right cover unit 10R can be opened with respect to the apparatus main body 11 in the direction of the arrow DA around the cover fulcrum portion 10R1. On the right cover unit 10R, the secondary transfer roller 145, the right roller of the registration roller pair 113, and the like are rotatably supported. When the right cover unit 10R is opened, the sheet conveyance path 111 is exposed to the outside of the apparatus main body 11. In this state, the intermediate transfer unit 14 can be mounted inside the apparatus main body 11.

  The image forming unit 13 forms a toner image to be transferred to the sheet P, and includes a plurality of image forming units that form toner images of different colors. As this image forming unit, in the present embodiment, a developer of magenta (M) color sequentially disposed from the upstream side to the downstream side in the rotation direction of the intermediate transfer belt 141 (from the left side to the right side in FIG. 1). 13M for magenta, 13C for cyan using cyan (C) developer, 13Y for yellow using yellow (Y) developer, and black using black (Bk) developer A unit 13Bk is provided. Each of the units 13M, 13C, 13Y, and 13Bk includes a photosensitive drum 20 (image carrier), a charging device 21, a developing device 23, and a cleaning device 25 disposed around the photosensitive drum 20. An exposure device 22 common to the units 13M, 13C, 13Y, and 13Bk is disposed below the image forming unit.

  The photosensitive drum 20 is driven to rotate about its axis, and an electrostatic latent image and a toner image are formed on its peripheral surface. Note that the rotation axis of the photosensitive drum 20 extends in the front-rear direction (first direction, a direction perpendicular to the paper surface of FIG. 1). As this photosensitive drum 20, a photosensitive drum using an amorphous silicon (a-Si) material can be used. Further, as shown in FIG. 1, the plurality of photosensitive drums 20 corresponding to the respective colors are arranged at predetermined intervals in a second direction (left-right direction and horizontal direction) intersecting the first direction.

  The charging device 21 uniformly charges the surface of the photosensitive drum 20. As the charging device 21, a charging device using a contact charging method including a charging roller and a charging cleaning brush for removing toner attached to the charging roller can be used. The exposure device 22 has various optical system devices such as a light source, a polygon mirror, a reflection mirror, and a deflection mirror, and irradiates light that has been modulated based on image data onto the circumferential surface of the uniformly charged photoreceptor drum 20. Thus, an electrostatic latent image is formed. The cleaning device 25 cleans the peripheral surface of the photosensitive drum 20 after the toner image is transferred.

  The developing device 23 supplies toner to the peripheral surface of the photosensitive drum 20 in order to develop the electrostatic latent image formed on the photosensitive drum 20. The developing device 23 is for a two-component developer composed of toner and carrier. The toner of the developing device 23 is supplied to the peripheral surface of the photosensitive drum 20, and the electrostatic latent image is developed. In this embodiment, the toner has a characteristic of being charged to a positive polarity.

  The intermediate transfer unit 14 is disposed in a space provided between the image forming unit 13 and the toner supply unit 15. The intermediate transfer unit 14 includes an intermediate transfer belt 141, a driving roller 142, a tension roller 143, a plurality of primary transfer rollers 24, and a belt cleaning device 144. The intermediate transfer unit 14 is mounted on the apparatus main body 11 along the left direction (second direction, arrow DH direction in FIG. 1) so as to be adjacent to the plurality of photosensitive drums 20.

  The intermediate transfer belt 141 is an endless belt-like rotator, and is stretched around the drive roller 142 and the tension roller 143 so that the circumferential surface side thereof is in contact with the circumferential surface of each photosensitive drum 20. The intermediate transfer belt 141 is driven to rotate in the direction along the second direction, and carries the toner images transferred from the plurality of photosensitive drums 20 on the surface. The intermediate transfer belt 141 is a conductive soft belt having a laminated structure including a base layer, an elastic layer, and a coat layer.

  The drive roller 142 stretches the intermediate transfer belt 141 on the right end side of the intermediate transfer unit 14 and drives the intermediate transfer belt 141 to rotate. The driving roller 142 is a metal roller. The tension roller 143 stretches the intermediate transfer belt 141 on the left end side of the intermediate transfer unit 14. The tension roller 143 applies tension to the intermediate transfer belt 141. In the vicinity of the tension roller 143, a belt cleaning device 144 (FIG. 1) that removes toner remaining on the peripheral surface of the intermediate transfer belt 141 is disposed.

  The primary transfer roller 24 is disposed to face the photosensitive drum 20 with the intermediate transfer belt 141 interposed therebetween. As a result, the primary transfer roller 24 forms a primary transfer nip portion with the photosensitive drum 20, and primarily transfers the toner image on the photosensitive drum 20 onto the intermediate transfer belt 141. As shown in FIG. 1, a primary transfer roller 24 is disposed to face the photosensitive drum 20 of each color. The primary transfer roller 24 is a roller extending in the front-rear direction and is rotated together with the intermediate transfer belt 141. A primary transfer bias is applied to the primary transfer roller 24 from a bias application unit (not shown).

  The secondary transfer roller 145 is disposed to face the driving roller 142 with the intermediate transfer belt 141 interposed therebetween. The secondary transfer roller 145 is pressed against the peripheral surface of the intermediate transfer belt 141 to form a secondary transfer nip portion. The toner image primarily transferred onto the intermediate transfer belt 141 is secondarily transferred to the sheet P supplied from the paper feeding unit 12 at the secondary transfer nip portion. A secondary transfer bias is applied to the secondary transfer roller 145 from a bias application unit (not shown).

  The toner replenishing unit 15 stores toner used for image formation, and includes a magenta toner container 15M, a cyan toner container 15C, a yellow toner container 15Y, and a black toner container 15Bk in this embodiment. These toner containers 15M, 15C, 15Y, and 15Bk replenish toner from the toner discharge port 15H formed on the bottom surface of the container to the developing device 23 corresponding to each color of MCYBk.

  The fixing unit 16 includes a heating roller 161 having a heating source therein, a fixing roller 162 oriented with the heating roller 161, a fixing belt 163 stretched between the fixing roller 162 and the heating roller 161, and a fixing belt A pressure roller 164 which is disposed to face the fixing roller 162 via the H.163 and forms a fixing nip portion. The sheet P supplied to the fixing unit 16 is heated and pressurized by passing through the fixing nip portion. As a result, the toner image transferred to the sheet P at the secondary transfer nip is fixed to the sheet P.

  The paper discharge unit 17 is formed by recessing the top of the apparatus main body 11, and a paper discharge tray 171 for receiving the discharged sheet P is formed at the bottom of the concave portion. The sheet P on which the fixing process has been performed is discharged toward the discharge tray 151 via the sheet conveyance path 111 extending from the upper part of the fixing unit 16.

  Next, the intermediate transfer unit 14 according to this embodiment will be described in detail with reference to FIGS. 2A to 4 in addition to FIG. 2A and 2B are perspective views of the intermediate transfer unit 14 according to the present embodiment. 3A and 3B are enlarged perspective views of a part of the intermediate transfer unit 14 according to the present embodiment. Similarly, FIG. 4 is an enlarged perspective view of a part of the intermediate transfer unit 14 according to the present embodiment.

  The intermediate transfer unit 14 is a unit having a flat rectangular parallelepiped shape extending in the front-rear and left-right directions. As shown in FIG. 2A, the intermediate transfer unit 14 extends long in the left-right direction. The intermediate transfer unit 14 includes a unit front wall 51 (side wall) and a unit rear wall 52 (side wall). The unit front wall 51 and the unit rear wall 52 are a pair of side walls arranged so as to extend in the left-right direction at both ends in the front-rear direction. The unit front wall 51 and the unit rear wall 52 are frames made of a resin material. The unit front wall 51 and the unit rear wall 52 support the intermediate transfer belt 141 so as to be able to go around. Specifically, the drive roller 142 and the plurality of primary transfer rollers 24 described above are rotatably supported by the unit front wall 51 and the unit rear wall 52.

  Further, the intermediate transfer unit 14 includes a slide portion front wall 53 and a slide portion rear wall 54. The slide part front wall 53 and the slide part rear wall 54 are slidable in the left-right direction with respect to the unit front wall 51 and the unit rear wall 52, respectively. The slide part front wall 53 and the slide part rear wall 54 constitute a moving unit of the present invention. The slide portion front wall 53 and the slide portion rear wall 54 support the tension roller 143 in a rotatable manner. Further, the belt cleaning device 144 is supported by the slide portion front wall 53 and the slide portion rear wall 54 so as to connect the slide portion front wall 53 and the slide portion rear wall 54 in the front-rear direction.

  When the right cover unit 10R is opened from the apparatus main body 11, the intermediate transfer unit 14 is attached to the apparatus main body 11 along the direction of the arrow DH in FIGS. 1 and 2A. At this time, the intermediate transfer unit 14 is disposed above the plurality of photosensitive drums 20 so as to be adjacent to the photosensitive drums 20.

  The intermediate transfer unit 14 further includes a first fixed leg portion 51S (leg portion), a second fixed leg portion 52S (leg portion), and a movable leg portion 60 (leg portion). The first fixed leg portion 51 </ b> S and the second fixed leg portion 52 </ b> S are leg portions arranged at the lower ends of the unit front wall 51 and the unit rear wall 52. Further, the movable leg portion 60 is supported by the slide portion front wall 53. These legs have a function of supporting the intermediate transfer unit 14 by contacting a predetermined installation surface (floor surface) when the intermediate transfer unit 14 is detached from the apparatus main body 11.

  With reference to FIG. 2A and FIG. 3A, the first fixed leg portion 51 </ b> S protrudes downward from the lower portion on the right end side of the unit front wall 51. 2B and 3B, the second fixed leg portion 52S protrudes downward from the lower portion of the central portion of the unit rear wall 52 in the left-right direction.

  Referring to FIG. 4, the slide part front wall 53 includes a main body wall part 53 </ b> A and a cover sheet metal 53 </ b> B. The main body wall portion 53A is made of a plate-like resin member that faces in the front-rear direction and extends long in the left-right direction. The main body wall portion 53A has a substantially rectangular shape. The cover metal plate 53B is a metal plate fixed to the front side surface of the main body wall 53A with a plurality of screws.

  The main body wall portion 53 </ b> A includes a shaft portion 510. The shaft portion 510 is a columnar protrusion protruding forward from the main body wall portion 53A. As shown in FIG. 4, the cover sheet metal 53B is previously opened with a hole through which the shaft 510 is inserted. When the cover sheet metal 53B is fastened to the main body wall part 53A, the shaft part 510 is inserted into the hole of the cover sheet metal 53B.

  The movable leg portion 60 is composed of a plate-like member that intersects with the front-rear direction and is opposed to the main body wall portion 53A. The movable leg 60 is disposed around the tension roller 143. The movable leg portion 60 includes a fulcrum portion (circular hole portion) (not shown) inserted through the shaft portion 510. As a result, the movable leg portion 60 is rotatable around the shaft portion 510.

  When the intermediate transfer unit 14 is detached from the apparatus main body 11, the movable leg 60 has a first posture capable of supporting the intermediate transfer unit 14 by contacting the floor surface (installation surface), and a first posture. The posture can be changed between the second posture rotated around the shaft portion 510 from the posture. In the first posture, the lower end portion (outer peripheral portion) of the movable leg portion 60 having a fan shape has the same height as the lower end portions of the first fixed leg portion 51S and the second fixed leg portion 52S. On the other hand, in the second posture, the lower end portion of the movable leg portion 60 retracts above the lower end portions of the first fixed leg portion 51S and the second fixed leg portion 52S.

  Further, the intermediate transfer unit 14 includes a coil spring (not shown). The coil spring biases the movable leg 60 around the shaft 510 so that the movable leg 60 is in the first posture. The coil spring is disposed between the movable leg portion 60 and the main body wall portion 53 </ b> A and is externally fitted to the shaft portion 510.

  When the intermediate transfer unit 14 is detached from the apparatus main body 11, the intermediate transfer unit 14 can be placed directly on the floor surface (predetermined installation surface). As a result, the maintainability of the detached intermediate transfer unit 14 and the apparatus main body 11 having a hollow inside is improved. As described above, the intermediate transfer unit 14 includes at least three legs (first fixed leg 51S, second fixed leg 52S, and movable leg 60). For this reason, when placed directly, the intermediate transfer belt 141 does not contact the floor surface, and the intermediate transfer belt 141 is prevented from being damaged.

  As described above, the coil spring urges the movable leg 60 so that the movable leg 60 is in the first posture (FIGS. 2A and 4). For this reason, when the intermediate transfer unit 14 is detached from the apparatus main body 11, the movable leg 60 is quickly brought into the first posture. For this reason, direct placement of the intermediate transfer unit 14 is easily realized.

  Further, as described above, the intermediate transfer unit 14 is disposed adjacent to the plurality of photosensitive drums 20. Inside the apparatus main body 11, the intermediate transfer belt 141 of the intermediate transfer unit 14 needs to abut on the photosensitive drum 20. On the other hand, when the intermediate transfer unit 14 is detached from the apparatus main body 11, the movable leg 60 needs to protrude below the intermediate transfer belt 141 in order to protect the intermediate transfer belt 141. When the intermediate transfer unit 14 is attached to the apparatus main body 11 with the movable leg 60 continuously protruding below the intermediate transfer belt 141, the movable leg 60 interferes with the photosensitive drum 20 and other units. There is. In this case, the mounting of the intermediate transfer unit 14 may be hindered, or the units may be damaged.

  In this embodiment, when the detached intermediate transfer unit 14 is mounted in the apparatus main body 11 again, the movable leg 60 can be rotated around the shaft 510. For this reason, even when the intermediate transfer unit 14 is mounted in close proximity to the photosensitive drum 20 and other units, interference (strong contact) between the movable leg 60 and these units is prevented. In other words, when the movable leg portion 60 comes into contact with and is pressed with these units, the movable leg portion 60 quickly changes its posture to the second posture, thereby preventing mutual damage.

  In particular, the movable leg portion 60 is rotated from the first posture around the shaft portion 510 in the second direction front end side (arrow D2 direction in FIG. 4) or the second direction rear end side (arrow D1 direction in FIG. 4). Thus, the posture is changed to the second posture. That is, the movable leg portion 60 can rotate in any direction around the shaft portion 510. For this reason, when the intermediate transfer unit 14 is attached or detached, interference between the movable leg 60 and other units is prevented.

  When the intermediate transfer unit 14 is mounted on the apparatus main body 11, when the movable leg 60 comes into contact with a drum unit (not shown) that supports the photosensitive drum 20, the movable leg 60 rotates in the direction of the arrow D1. After that, when the intermediate transfer unit 14 is mounted inside the apparatus main body 11, the movable leg 60 is changed to the first posture again because the movable leg 60 can be disposed in a predetermined space. On the other hand, when the movable leg portion 60 comes into contact with a drum unit (not shown) that supports the photosensitive drum 20 when the intermediate transfer unit 14 is detached from the apparatus main body 11, the movable leg portion 60 rotates in the arrow D2 direction. To do. Thereafter, when the intermediate transfer unit 14 is detached from the apparatus main body 11, the movable leg 60 changes its posture again to the first posture. As a result, the intermediate transfer unit 14 can be placed on the floor.

  When the intermediate transfer unit 14 is placed on the floor, the outer peripheral portion 604 of the movable leg 60 has an arc shape. Therefore, even if the posture of the movable leg 60 changes, the intermediate transfer belt 141 and the floor surface The distance between and is maintained stably.

  Next, the contact / separation operation of the primary transfer roller 24 of the intermediate transfer unit 14 according to this embodiment with respect to the photosensitive drum 20 will be described with reference to FIGS. The intermediate transfer unit 14 includes a contact / separation mechanism 14M (FIG. 5). The contact / separation mechanism 14 </ b> M has a function of bringing a plurality of primary transfer rollers 24 into and away from the photosensitive drum 20 in the apparatus main body 11. FIG. 5 is a perspective view of the intermediate transfer unit 14 according to this embodiment with the intermediate transfer belt 141 removed. FIG. 6 is a perspective view of the drive unit 56 of the contact / separation mechanism 14M of the intermediate transfer unit 14 according to the present embodiment. FIG. 7 is a perspective view of the periphery of the urging spring 143S of the intermediate transfer unit 14. FIG. FIG. 8 is a perspective view of the intermediate transfer unit 14. FIG. 9 is a cross-sectional perspective view of the intermediate transfer unit 14.

  Referring to FIG. 5, when intermediate transfer belt 141 is removed from intermediate transfer unit 14, black roller 24BK, yellow roller 24Y, cyan roller 24C, and magenta roller 24M, which are primary transfer rollers 24 corresponding to the respective colors. Is exposed. The intermediate transfer unit 14 includes a support unit 55, a first stretching roller 240, a second stretching roller 241, and a third stretching roller 242 (stretching roller). The support unit 55 rotatably supports the four primary transfer rollers 24. The support unit 55 is a unit disposed between the unit front wall 51 and the unit rear wall 52. The support unit 55 is a unit having a flat rectangular parallelepiped shape. The support unit 55 can swing up and down around the right end side in the intermediate transfer unit 14. The primary transfer roller 24 of each color is brought into contact with and separated from the photosensitive drum 20 by the swing of the support unit 55.

  The first stretching roller 240 is a roller that supports the intermediate transfer belt 141 on the right end side of the intermediate transfer unit 14. The first stretching roller 240 is disposed between the black roller 24BK and the driving roller 142 (FIG. 9). The second stretching roller 241 is a roller that supports the intermediate transfer belt 141 on the left side of the black roller 24BK. The second stretching roller 241 is rotatably supported by the support unit 55. The third stretching roller 242 is a roller that supports (stretches) the intermediate transfer belt 141 between the magenta roller 24M and the tension roller 143. The third tension roller 242 is rotatably supported at the left end portion of the support unit 55. Further, the third stretching roller 242 can be moved up and down by a drive unit 56 described later.

  The contact / separation mechanism 14M includes a drive unit 56. As shown in FIGS. 5 and 6, the drive unit 56 is disposed on the support unit 55 of the intermediate transfer unit 14. The driving unit 56 includes a motor that generates a driving force for moving the third stretching roller 242 up and down. Further, the drive unit 56 includes a shaft 561 and a cam 562. The shaft 561 is rotated by the driving force generated by the driving unit 56. The cam 562 is a cam member fixed to the tip of the shaft 561, and is formed so that its outer diameter varies along the circumferential direction. The circumferential surface of the cam 562 is in contact with a shaft (not shown) of the third stretching roller 242. When the cam 562 is rotated by the driving force generated by the driving unit 56, the third stretching roller 242 is moved up and down in the intermediate transfer unit 14.

  Referring to FIG. 7, as described above, the slide portion front wall 53 is slidable in the left-right direction with respect to the unit front wall 51. Hereinafter, although the shape and structure of the unit front wall 51 and the slide part front wall 53 will be described in detail, the unit rear wall 52 and the slide part rear wall 54 on the rear side of the intermediate transfer unit 14 have the same shape and structure. . The unit front wall 51 includes a guide protrusion 51P. The guide protrusion 51P is a columnar protrusion protruding from the front side surface of the unit front wall 51. On the other hand, the slide part front wall 53 includes an opening 53P. The opening 53P is opened to the slide portion front wall 53 in a substantially rectangular shape. The aforementioned guide protrusion 51P is fitted in the opening 53P and moves in the left-right direction within the opening 53P.

  Further, the intermediate transfer unit 14 includes a biasing spring 143S (FIG. 7) (a biasing member). The urging spring 143S is compressed and deformed between the unit front wall 51 and the slide portion front wall 53, and urges the tension roller 143 toward the opposite side (left side) of the drive roller 142. Similarly, an urging spring 143 </ b> S is provided between the unit rear wall 52 and the slide portion rear wall 54. As shown in FIG. 7, the spring base end portion 143M of the urging spring 143S is in contact with the peripheral surface of the guide protrusion 51P. On the other hand, the tip end portion (left end portion) of the biasing spring 143S is in contact with a bearing (not shown) that supports the tension roller shaft portion 143A of the tension roller 143.

  The slide part front wall 53, the slide part rear wall 54, and the biasing spring 143S constitute the moving part 60S of the present embodiment. The moving unit 60S has a function of sliding the movable leg 60 in conjunction with the contact / separation operation of the primary transfer roller 24 by the contact / separation mechanism 14M. As described above, in this embodiment, the movable leg portion 60 is supported by the slide portion front wall 53. For this reason, when the slide part front wall 53 slides, the movable leg part 60 can also be slid to right and left.

  In the image forming apparatus 10, when a full-color image is printed, the third stretching roller 242 is arranged at the lowest first position by the drive unit 56 as shown in FIGS. 7 and 8. At this time, as shown in FIG. 8, the intermediate transfer belt 141 stretched by the third stretching roller 242 forms a bent portion 141A. Further, a folded portion 141B of the intermediate transfer belt 141 is formed by a tension roller 143 on the upper left side of the bent portion 141A. When the third tension roller 242 is disposed at the first position, the lower end surface of the intermediate transfer belt 141 is disposed so as to extend in a substantially horizontal direction. The support unit 55 that supports each primary transfer roller 24 is swung downward with the right end portion as a fulcrum. As a result, the primary transfer roller 24 of each color comes into contact with the photosensitive drum 20 with the intermediate transfer belt 141 interposed therebetween, and a primary transfer nip portion is formed. At this time, strong tension is applied to the intermediate transfer belt 141 by the third stretching roller 242 on the left end side of the intermediate transfer belt 141. Therefore, the intermediate transfer belt 141 is tension roller in a state where the urging spring 143S (FIG. 7) is compressed between the unit front wall 51 and the unit rear wall 52 and the slide portion front wall 53 and the slide portion rear wall 54. 143. Then, the toner image is stably transferred from the photosensitive drum 20 to the intermediate transfer belt 141 at the primary transfer nip portion of each color.

  On the other hand, in the image forming apparatus 10, when a black-and-white monochrome image is printed, the result is that the third tension roller 242 is moved upwardly away from the inner peripheral surface of the intermediate transfer belt 141 by the drive unit 56. The second position is higher than the first position. At this time, since the tension of the intermediate transfer belt 141 is weakened as the third tension roller 242 moves, the slide portion front wall 53 and the slide portion rear wall 54 are separated from the drive roller 142 by the biasing force of the biasing spring 143S. Slide in the direction to the left (to the left). As the third stretching roller 242 moves, the intermediate transfer belt 141 around the magenta roller 24M, the cyan roller 24C, and the yellow roller 24Y is pushed upward, so that the support unit 55 supports the right end. Is swung upward. As a result, at the lower end surface of the intermediate transfer belt 141, only the black roller 24BK contacts the photosensitive drum 20, and the other primary transfer rollers 24 are separated upward from the photosensitive drum 20. Note that the position of the second stretching roller 241 does not change in order to stably maintain the nip pressure of the black primary transfer nip. That is, the intermediate transfer belt 141 is maintained so as to extend in the horizontal direction in a small region from the second tension roller 241 to the black roller 24BK. Then, the toner image is stably transferred from the photosensitive drum 20 to the intermediate transfer belt 141 in the black primary transfer nip portion.

  Further, when the image forming apparatus 10 shifts to the sleep mode or when the intermediate transfer unit 14 is removed from the apparatus main body 11 for maintenance, the third tension roller 242 is moved from the second position by the drive unit 56 in advance. Is also arranged at the upper third position. At this time, since the tension of the intermediate transfer belt 141 is further weakened as the third stretching roller 242 moves, the slide part front wall 53 and the slide part rear wall 54 are urged to compensate for the tension of the intermediate transfer belt 141. By the urging force of the spring 143S, it further slides in the direction away from the drive roller 142 (left direction). As the third tension roller 242 moves, the intermediate transfer belt 141 from the magenta roller 24M to the periphery of the black roller 24BK is pushed upward, so that the support unit 55 further moves upward with the right end as a fulcrum. Is swung. As a result, all the primary transfer rollers 24 are separated upward from the photosensitive drum 20 on the lower end surface of the intermediate transfer belt 141. Thus, in this embodiment, the contacting / separating mechanism 14M moves the third tension roller 242 up and down. In other words, the contact / separation mechanism 14M moves the third stretching roller 242 so as to be separated from the inner peripheral surface of the intermediate transfer belt 141, or moves the third stretching roller 242 to the inner peripheral surface of the intermediate transfer belt 141. The primary transfer roller 24 of each color is brought into contact with and separated from the photosensitive drum 20 by being moved closer to. At this time, the urging spring 143 </ b> S slides the slide portion front wall 53 and the slide portion rear wall 54 relative to the unit front wall 51 and the unit rear wall 52 in order to compensate for the tension of the intermediate transfer belt 141.

  FIG. 10 is a perspective view of the intermediate transfer unit 14 and the unit detector 70 (detector) according to the present embodiment. 11A and 11B are perspective views of the movable leg 60 and the unit detector 70 according to the present embodiment. The image forming apparatus 10 includes a unit detection unit 70. The unit detection unit 70 is fixed to a frame (not shown) facing the intermediate transfer unit 14 inside the apparatus main body 11. In other words, the unit detection unit 70 is disposed outside the circulation path of the intermediate transfer belt 141 in the apparatus main body 11 and detects the sliding movement of the movable leg 60.

  The unit detection unit 70 is a PI (photo interrupter) sensor including a light emitting unit 701 and a light receiving unit 702. The light emitting unit 701 emits detection light (not shown) toward the light receiving unit 702. When the light receiving unit 702 receives the detection light, a light reception signal is output to a control unit (not shown) provided in the image forming apparatus 10. When the light receiving unit 702 receives detection light, the unit detection unit 70 outputs a HIGH signal (5 V). On the other hand, when the movable leg portion 60 enters between the light emitting portion 701 and the light receiving portion 702 and the detection light is blocked, the unit detecting portion 70 outputs a LOW signal (0 V). As a result, it is grasped whether or not the movable leg 60 is positioned between the light emitting unit 701 and the light receiving unit 702.

  As described above, in the present embodiment, when the contact / separation mechanism 14M brings the primary transfer roller 24 into contact with or separates from the photosensitive drum 20, the slide part front wall 53 and the slide part rear wall 54 slide by the moving part 60S. . In particular, when the primary transfer rollers 24 of all colors are in contact with the photosensitive drum 20, the movable leg 60 supported by the slide portion front wall 53 and the slide portion rear wall 54 is positioned at the rightmost predetermined position. (FIG. 11A). At this time, the movable leg 60 is not detected by the unit detector 70. On the other hand, when the black monochrome (single K) mode is selected in the image forming apparatus 10, the movable leg 60 slides to the left from the position shown in FIG. 11A. Further, when the image forming apparatus 10 is instructed to move the primary transfer rollers 24 of all colors apart, the movable leg 60 is further slid leftward by the biasing force of the biasing spring 143S, as shown in FIG. 11B. It is arranged at the position. As a result, the movable leg 60 is detected by the unit detector 70. In other words, the controller of the image forming apparatus 10 recognizes that the primary transfer rollers 24 of all colors are separated from the photosensitive drum 20.

  As described above, in this embodiment, it is possible to detect the contact / separation state of the intermediate transfer belt 141 with respect to the photosensitive drum 20 by the unit detection unit 70 disposed outside the circulation path of the intermediate transfer belt 141. For this reason, even when the toner on the intermediate transfer belt 141 flows into the inside of the circulation track of the intermediate transfer belt 141 due to the air flow in the apparatus main body 11, the toner contamination of the unit detection unit 70 can be suppressed. it can. At this time, the movable leg 60 which is one leg of the intermediate transfer unit 14 can also serve as a detection piece detected by the unit detection unit 70.

  Furthermore, since the movable leg 60 takes the first posture, the intermediate transfer unit 14 can be placed directly on the installation surface. Further, since the movable leg portion 60 takes the second posture, it is possible to prevent the movable leg portion 60 and other units from strongly colliding with each other within the apparatus main body 11 and to prevent damage to these members. In addition, when the intermediate transfer unit 14 is attached to the apparatus main body 11 or pulled out from the apparatus main body 11, the movable leg 60 and another unit may collide strongly inside the apparatus main body 11. Deterred.

  Furthermore, since the movable leg portion 60 is disposed around the tension roller 143, the tension roller 143 and the movable leg portion 60 can be supported by the same unit (the slide portion front wall 53 and the slide portion rear wall 54). Then, the movable leg portion 60 can be slid using the operation in which the slide portion front wall 53 and the slide portion rear wall 54 slide in accordance with the separation operation of the primary transfer roller 24. In particular, using the lower tension of the intermediate transfer belt 141 and the urging force of the urging spring 143S when the third tension roller 242 moves away from the intermediate transfer belt 141, the slide portion front wall 53 and The slide part rear wall 54 can be slid. In addition, since the unit detection unit 70 is disposed outside the circular orbit of the intermediate transfer belt 141 and on the apparatus main body 11 side, compared to the case where the unit detection unit 70 is attached to the intermediate transfer unit 14, Toner contamination of the unit detection unit 70 can be reduced.

  As described above, in the present embodiment, the black roller 24BK is less separated from the photosensitive drum 20 than the other primary transfer rollers 24. The support unit 55 that supports each primary transfer roller 24 swings up and down with the right end portion as a fulcrum. For this reason, in the third stretching roller 242 adjacent to the magenta roller 24M, a large vertical movement stroke can be set. Therefore, the movable leg portion 60 detected by the unit detection unit 70 is disposed around the tension roller 143 on the opposite side of the black roller 24BK, and the slide roller front wall 53 and the slide portion rear wall 54 together with the tension roller 143. By being supported, the vertical movement of the third tension roller 242 can be effectively converted into the sliding movement of the movable leg 60.

  The image forming apparatus 10 including the intermediate transfer unit 14 according to an embodiment of the present invention has been described in detail above, but the present invention is not limited to this. The present invention can take, for example, the following modified embodiments.

  (1) In the above-described embodiment, the leg portion of the intermediate transfer unit 14 has been described in the form of the first fixed leg portion 51S, the second fixed leg portion 52S, and the movable leg portion 60. Is not limited to this. The intermediate transfer unit 14 only needs to include at least three legs. In this case, it is only necessary that at least one leg is provided on the unit front wall 51 and the unit rear wall 52.

  (2) In the above-described embodiment, the mode has been described in which only the movable leg 60 among the three legs is rotatable, but the present invention is not limited to this. The first fixed leg portion 51 </ b> S and the second fixed leg portion 52 </ b> S may also be configured to be rotatable similarly to the movable leg portion 60.

  (3) In the above embodiment, the mode has been described in which the movable leg portion 60 moves in the horizontal direction in conjunction with the operation in which the primary transfer roller 24 moves away from the photosensitive drum 20. Is not limited to this. As another modified embodiment, when the movable leg 60 is provided at the left end portion of the support unit 55, the movable leg 60 is also separated upward at the same time as the third stretching roller 242 is separated upward. Therefore, the unit detecting unit 70 may detect such a movement of the movable leg 60 in the vertical direction, so that the contact / separation state of the primary transfer roller 24 with respect to the photosensitive drum 20 may be detected in the image forming apparatus 10. Further, the leg detected by the unit detector 70 is not limited to the movable leg 60. The unit detector 70 may detect the sliding movement of the first fixed leg 51S or the second fixed leg 52S. In this case, the first fixed leg portion 51S or the second fixed leg portion 52S may be arranged in a unit that can slide relative to the main body (unit front wall 51, unit rear wall 52) of the intermediate transfer unit 14.

  (4) Further, in the above embodiment, as shown in FIG. 11B, the movable leg 60 enters between the light emitting unit 701 and the light receiving unit 702. For this reason, a cleaning member such as a sponge material may be attached to the side surface of the movable leg 60 in advance. In this case, the sliding movement of the movable leg portion 60 can clean foreign matters attached to the light emitting surface of the light emitting portion 701 and the light receiving surface of the light receiving portion 702.

  (5) Further, in the above-described embodiment, the unit detection unit 70 has been described in the form of detecting the slide movement of the movable leg 60 in two stages, but the present invention is not limited to this. Even if the unit detector 70 includes two adjacent PI sensors, or the notch portion (not shown) is provided in the movable leg 60, the slide movement of the movable leg 60 is detected in three stages. Good. In this case, in the intermediate transfer unit 14, the primary transfer roller 24 of each color is in contact with the photosensitive drum 20, the state where only the black primary transfer roller 24 is in contact with the photosensitive drum 20, and all A state where 24 is separated from the photosensitive drum 20 is detected.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Apparatus main body 14 Intermediate transfer unit 141 Intermediate transfer belt 142 Drive roller 143 Tension roller 143S Energizing spring (urging member)
14M contact / separation mechanism 20 photosensitive drum 24 primary transfer roller 240 first tension roller 241 second tension roller 242 third tension roller (stretching roller)
24BK Black roller 24C Cyan roller 24M Magenta roller 24Y Yellow roller 51 Unit front wall (side wall)
51S First fixed leg (leg)
52 Unit rear wall (side wall)
52S Second fixed leg (leg)
53 Front slide wall (moving unit)
54 Slider rear wall (moving unit)
55 Support Unit 56 Drive Unit 60 Movable Leg (Leg)
60S moving part 70 unit detection part (detection part)
701 Light emitting unit 702 Light receiving unit

Claims (7)

The device body;
A plurality of photosensitive drums arranged within the apparatus main body, rotated around an axis extending in the first direction, and arranged adjacent to each other at a predetermined interval in a second direction intersecting the first direction;
An intermediate transfer unit mounted on the apparatus main body along the second direction so as to be adjacent to the plurality of photosensitive drums;
Have
The intermediate transfer unit is
An intermediate transfer belt which is driven to circulate along the second direction and carries toner images transferred from the plurality of photosensitive drums on the surface;
A plurality of primary transfer rollers disposed to face the photosensitive drums with the intermediate transfer belt interposed therebetween,
A contact / separation mechanism for contacting and separating the plurality of primary transfer rollers with respect to the photosensitive drum in the apparatus main body;
A pair of side walls arranged to extend in the second direction at both ends of the intermediate transfer unit in the first direction, and supporting the intermediate transfer belt so as to be able to go around;
A plurality of legs disposed at the lower ends of the pair of side walls, and when the intermediate transfer unit is detached from the apparatus main body, a plurality of legs that contact a predetermined installation surface;
With
In conjunction with the contact and separation operation of the primary transfer roller by the contact and separation mechanism, a moving unit that slides one of the plurality of legs, and
A detection unit that is disposed outside a circular orbit of the intermediate transfer belt and detects the sliding movement of the one leg;
And an image forming apparatus.   The one leg portion includes a fulcrum portion, is rotatable about the fulcrum portion, and can support the intermediate transfer unit detached from the apparatus main body by contacting the installation surface. The image forming apparatus according to claim 1, wherein the movable leg portion is capable of changing a posture between a posture and a second posture rotated around the fulcrum from the first posture. apparatus.   The movable leg portion changes its posture to the second posture by rotating from the first posture to the front end side in the second direction or the rear end side in the second direction around the fulcrum portion. The image forming apparatus according to claim 2. The intermediate transfer unit is
A driving roller that supports the intermediate transfer belt on one end side in the second direction and drives the intermediate transfer belt to rotate.
A tension roller that supports the intermediate transfer belt on the other end side in the second direction and applies tension to the intermediate transfer belt;
With
The image forming apparatus according to claim 2, wherein the movable leg portion is disposed around the tension roller. The intermediate transfer unit is
A movable unit that rotatably supports the tension roller and is slidable relative to the pair of side walls;
A biasing member that is compressed and deformed between the pair of side walls and the moving unit, and biases the tension roller toward a side opposite to the driving roller;
With
The movable leg is provided in the moving unit,
The moving unit slides in a direction away from the driving roller by the urging force of the urging member in accordance with a separating operation in which the contact / separation mechanism separates the primary transfer roller from the photosensitive drum, thereby detecting the detection. The image forming apparatus according to claim 4, wherein a part detects a sliding movement of the movable leg part. The intermediate transfer unit further includes a tension roller that stretches the intermediate transfer belt between the tension roller and the primary transfer roller,
When the contact / separation mechanism moves the stretching roller away from the inner peripheral surface of the intermediate transfer belt, the moving unit slides in a direction away from the driving roller by the urging force of the urging member. The image forming apparatus according to claim 5. The image forming apparatus according to claim 1, wherein the detection unit is provided in the apparatus main body.

Images