JP2019147674A - Image formation apparatus - Google Patents

Abstract

To provide an image formation apparatus capable of reducing the number of drive mechanisms for releasing nips of a pair of conveyance rollers individually arranged in a plurality of conveyance paths as compared with a conventional one.SOLUTION: An image formation apparatus 1 includes: a main conveyance path 50A, an intermediate roller pair 81, a double-sided conveyance path 50B, a third double-sided roller pair 84, and a drive mechanism 9. The intermediate roller pair 81 includes an intermediate drive roller 81A and an intermediate driven roller 81B, and the third double-sided roller pair 84 includes a third double-sided driving roller 84A and a third double-sided driven roller 84B. The drive mechanism 9 selectively executes a first separation/contact operation for separating the intermediate driving roller 81A from the intermediate driven roller 81B for predetermined time, and a second separation/contact operation for separating the third double-sided drive roller 84A from the third double-sided driven roller 84B for the predetermined time.SELECTED DRAWING: Figure 6

Description

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

  Conventionally, in an image forming apparatus that forms an image on a sheet, a toner image is formed on the photosensitive drum, and the toner image is transferred to the sheet at a transfer nip portion formed between the photosensitive drum and the transfer roller. The The image forming apparatus further includes a fixing unit, and the sheet on which the toner image is transferred is subjected to a fixing process in the fixing unit and then discharged.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses an image forming apparatus including a sheet feeding unit that accommodates a sheet bundle composed of a plurality of sheets and a manual sheet feeding tray. A plurality of pairs of conveyance rollers are respectively disposed on the conveyance path between the paper feeding unit and the transfer nip part and on the conveyance path between the paper feed tray and the transfer nip part. The conveying roller pair includes a driving roller and a driven roller.

Japanese Patent Laying-Open No. 2006-166065

  In the technique described in Patent Document 1, the rotation driving force of a predetermined driving mechanism (motor) is transmitted to the driving roller, whereby the conveying roller pair is rotated and the sheet is conveyed. In each conveyance path, the nip of the conveyance roller pair may be released as necessary. As an example, when the skew of the sheet is corrected in the registration roller pair, the nip of the conveying roller pair on the upstream side of the registration roller pair is temporarily released, thereby increasing the degree of freedom in movement of the sheet, and The skew is corrected. Thus, in order to cancel the nip of the conveyance roller pair in each conveyance path, it is necessary to provide a dedicated drive mechanism. As a result, there is a problem that the image forming apparatus is increased in size and cost.

  The present invention has been made to solve the above-described problems, and it is possible to reduce the number of drive mechanisms for releasing the nips of a pair of conveyance rollers respectively arranged in a plurality of conveyance paths. An object of the present invention is to provide a simple image forming apparatus.

  An image forming apparatus according to an aspect of the present invention includes a first conveyance path that guides a sheet along a predetermined conveyance direction, and a first conveyance roller pair that is disposed in the first conveyance path and conveys the sheet. A first conveying roller pair including a first roller and a second roller forming a first nip portion where the sheet is conveyed between the first roller, and the conveying direction with respect to the first conveying roller pair. A second conveyance path that is arranged so as to merge with the first conveyance path on the downstream side of the sheet and that guides the sheet, and a second conveyance roller pair that is arranged in the second conveyance path and conveys the sheet, A second conveying roller pair including a roller and a fourth roller forming a second nip portion where the sheet is conveyed between the third roller and the third roller abutting against the fourth roller In a state where the first roller is kept in the second roller for a predetermined time A first separating / contacting operation for contacting the second roller after the separation, and separating the third roller from the fourth roller for a predetermined time in a state where the first roller is in contact with the second roller. And a driving mechanism capable of selectively executing a second separating / contacting operation for contacting the fourth roller.

  According to this configuration, the two pairs of conveyance rollers disposed on the two conveyance paths of the first conveyance path and the second conveyance path can be selectively separated from each other by the common drive mechanism. As a result, there is no need to dispose a contact mechanism for each of the first transport roller pair and the second transport roller pair, and the drive mechanism for releasing the nips of the transport roller pairs respectively disposed in the plurality of transport paths. The number can be reduced as compared with the conventional case.

  In the above configuration, the drive mechanism includes a motor that can rotate in a first rotation direction and a second rotation direction opposite to the first rotation direction, and a rotational driving force of the motor in the first rotation direction. A first drive transmission mechanism for separating one roller from the second roller; and a second drive transmission mechanism for separating the third roller from the fourth roller by a rotational driving force of the motor in the second rotational direction. It is desirable.

  According to this configuration, the nips of a plurality of conveying roller pairs can be selectively released according to the rotation direction of a single motor.

  In the above configuration, the drive mechanism further includes a cam connected to the motor and rotatable in the first rotation direction and the second rotation direction, and the first drive transmission mechanism is opposed to the cam. A first pressed portion disposed; a first shaft portion connected to the first pressed portion; a first holder fixed to the first shaft portion and rotatably supporting the first roller; And the second drive transmission mechanism is connected to the second pressed portion and a second pressed portion disposed opposite to the first pressed portion and facing the cam. A second shaft portion extending in parallel with the two shaft portions, and a second holder fixed to the second shaft portion and rotatably supporting the third roller, wherein the motor is in the first rotation direction. When rotated, the cam presses the first pressed portion, so that the first holder becomes the first shaft portion. And when the first roller is separated from the second roller and the motor is rotated in the second rotation direction, the cam presses the second pressed portion, whereby the second It is desirable that the holder rotates around the second shaft portion and the third roller is separated from the fourth roller.

  According to this configuration, the first holder and the second holder rotate in different directions according to the rotation direction of the cam, so that one of the first roller and the third roller is stably separated. Realized.

  In the above configuration, a sheet storage unit that stores a plurality of sheets and communicates with an entrance of the first transport path, and is opposed to the first transport path on the downstream side in the transport direction with respect to the first transport roller pair. An image forming unit that is disposed and forms an image on a sheet conveyed through the first conveyance path, and a sheet discharge unit that communicates with an outlet of the first conveyance path and receives a sheet on which an image is formed in the image formation unit A pair of registration rollers disposed between the first conveyance roller pair and the image forming unit in the first conveyance path to correct the skew of the sheet and convey the sheet; and the drive mechanism. A drive control unit that controls the second conveyance path, the second conveyance path branches from the downstream side in the conveyance direction with respect to the image forming unit in the first conveyance path, and the second conveyance path in the first conveyance path. 1 transport b A double-sided conveyance path that joins a portion between a pair of rollers and the registration roller pair, wherein the drive control unit has a leading end portion of a sheet that is conveyed along the first conveyance path by the first conveyance roller pair. The first separation / contact operation is executed after reaching the registration roller pair, and the second separation operation is performed after the leading edge of the sheet conveyed on the second conveyance path by the second conveyance roller pair reaches the registration roller pair. It is desirable to perform the contact operation.

  According to this configuration, the skew feeding of the sheet conveyed on the first conveyance path or the second conveyance path is stably corrected at the registration roller pair.

  In the above configuration, the drive control unit may be configured such that, after the first roller is separated from the second roller in the first separation / contact operation, the rear end portion of the sheet passes through the first conveying roller pair. Before the first roller is brought into contact with the second roller, and after the third roller is separated from the fourth roller in the second separating operation, the trailing edge of the sheet is It is desirable that the third roller is brought into contact with the fourth roller before passing through the second conveying roller pair.

  According to this configuration, it is possible to suppress an unnecessary increase between the sheets as compared with the case where the contact operation is performed after the trailing edge of the sheet passes through the first conveyance roller pair or the second conveyance roller pair. it can.

  According to the present invention, there is provided an image forming apparatus capable of reducing the number of driving mechanisms for releasing the nips of a pair of conveyance rollers respectively arranged in a plurality of conveyance paths as compared with the conventional one.

1 is a cross-sectional view showing an internal structure of an image forming apparatus according to an embodiment of the present invention. 2 is a side view of a double-sided conveyance unit of the image forming apparatus according to the embodiment of the present disclosure. FIG. FIG. 2 is a plan view of a double-sided conveyance unit of the image forming apparatus according to an embodiment of the present invention. 2 is a front view of a double-sided conveyance unit of the image forming apparatus according to the embodiment of the present disclosure. FIG. FIG. 3 is a cross-sectional view of a double-sided conveyance unit of the image forming apparatus according to an embodiment of the present invention. It is a perspective view of the drive mechanism concerning one embodiment of the present invention. In one Embodiment of this invention, it is a flowchart in the case of single-sided continuous printing being performed. 6 is a flowchart when double-sided continuous printing is executed in an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing an internal structure of an image forming apparatus 1 according to an embodiment of the present invention. Here, as the image forming apparatus 1, a multi-function machine having a printer function and a copying function is illustrated, but the image forming apparatus may be a printer, a copier, or a facsimile machine.

<Description of Image Forming Apparatus>
The image forming apparatus 1 includes an apparatus main body 10 having a substantially rectangular parallelepiped housing structure, and an automatic document feeder 20 disposed on the apparatus main body 10. In the apparatus main body 10, a reading unit 25 that optically reads a document image to be copied, an image forming unit 30 that forms a toner image on the sheet S, a fixing unit 60 that fixes the toner image on the sheet, and an image A sheet feeding unit 40 that accommodates a plurality of sheets S conveyed to the forming unit 30, and the sheet S is conveyed from the sheet feeding unit 40 or the sheet feeding tray 46 to the discharge space 10 </ b> S via the image forming unit 30 and the fixing unit 60. And a conveyance path 50 to be accommodated. The discharge space 10 </ b> S (sheet discharge unit) receives the sheet S on which an image is formed in the image forming unit 30. The sheet S discharged to the discharge space 10S is stacked on the paper discharge unit 101.

  An automatic document feeder (ADF) 20 automatically feeds a document sheet to be copied toward a predetermined document reading position in the apparatus body 10. On the other hand, when the user manually places the document sheet on a predetermined document reading position, the ADF 20 is opened upward. The reading unit 25 optically reads an image of a document sheet automatically fed from the ADF 20 on the upper surface of the apparatus main body 10 or a manually placed document sheet.

  The image forming unit 30 generates a full-color toner image and transfers the toner image onto the sheet S conveyed through the main conveyance path 50A, thereby forming an image on the sheet S. Yellow (in tandem) ( Y), magenta (M), cyan (C), and black (Bk) image forming units 32 including four units 32Y, 32M, 32C, and 32Bk that form toner images; The image forming apparatus includes an intermediate transfer unit 33 disposed adjacent to the toner transfer unit 34 and a toner supply unit 34 disposed on the intermediate transfer unit 33.

  Each of the image forming units 32Y, 32M, 32C, and 32Bk includes a photosensitive drum 321 and a charger 322, an exposure device 323, a developing device 324, a primary transfer roller 325, and a cleaning device disposed around the photosensitive drum 321. 326.

  The photosensitive drum 321 rotates about its axis, and an electrostatic latent image and a toner image are formed on its peripheral surface. The charger 322 uniformly charges the surface of the photosensitive drum 321. The exposure device 323 includes a laser light source and optical system devices such as a mirror and a lens, and forms an electrostatic latent image by irradiating the peripheral surface of the photosensitive drum 321 with light based on image data of a document image. .

  The developing device 324 supplies toner to the peripheral surface of the photosensitive drum 321 in order to develop the electrostatic latent image formed on the photosensitive drum 321. The primary transfer roller 325 primarily transfers the toner image on the photosensitive drum 321 onto the intermediate transfer belt 331. The cleaning device 326 cleans the peripheral surface of the photosensitive drum 321 after the toner image is transferred.

  The intermediate transfer unit 33 includes an intermediate transfer belt 331, a belt driving roller 332, and a driven roller 333. On the outer peripheral surface of the intermediate transfer belt 331, toner images are transferred from a plurality of photosensitive drums 321 to be overlapped at the same location. The intermediate transfer belt 331 is rotated counterclockwise in FIG.

  A secondary transfer roller 35 is disposed to face the peripheral surface of the belt driving roller 332. A nip portion between the belt driving roller 332 and the secondary transfer roller 35 serves as a secondary transfer portion that transfers a full-color toner image overcoated on the intermediate transfer belt 331 onto a sheet.

  The toner replenishing section 34 includes a yellow toner container 34Y, a magenta toner container 34M, a cyan toner container 34C, and a black toner container 34Bk. The developing devices of the image forming units 32Y, 32M, 32C, and 32Bk corresponding to the respective colors. To 324, the toner of each color is supplied from the discharge screw 341 through a supply path (not shown).

  The paper feed unit 40 includes two-stage paper feed cassettes 40A and 40B that accommodate sheets S subjected to image forming processing. These paper feed cassettes 40A and 40B can be pulled out from the front of the apparatus body 10 toward the front.

  The sheet feeding cassette 40A (40B) includes a sheet storage portion 41 that stores a sheet bundle formed by stacking sheets S, and a lift plate 42 that lifts the sheet bundle for feeding. A pickup roller 43 and a roller pair of a paper feed roller 44 and a retard roller 45 are arranged on the upper right side of the paper feed cassette 40A (40B). By driving the pickup roller 43 and the paper feed roller 44, the uppermost sheet S of the sheet bundle in the paper feed cassette 40A is fed out one by one and carried into the upstream end of the transport path 50.

  The conveyance path 50 performs a double-sided printing on the main conveyance path 50 </ b> A (first conveyance path) that conveys the sheet S from the paper feeding unit 40 to the exit of the fixing unit 60 via the image forming unit 30. In this case, a double-sided conveyance path 50B (second conveyance path) for returning a sheet printed on one side to the image forming unit 30, and an upper discharge path for directing the sheet S from the downstream end of the main conveyance path 50A to the discharge space 10S. 50C and the lower discharge path 50D. The paper feed unit 40 communicates with the entrance of the main transport path 50A, and the image forming unit 30 is disposed opposite the main transport path 50A on the downstream side in the transport direction with respect to the intermediate roller pair 81 described later. Yes. Further, the discharge space 10S communicates with the outlet of the main conveyance path 50A.

  A registration roller pair 51 is disposed on the upstream side of the main transfer path 50A from the secondary transfer section 35A (between the intermediate roller pair 81 and the image forming section). The registration roller pair 51 corrects the skew (skew) of the sheet S and conveys the sheet S toward the secondary transfer unit 35A.

  The fixing unit 60 is an induction heating type fixing device that performs a fixing process for fixing the toner image on the sheet S, and has a fixing nip portion formed therein. As the sheet S passes through the fixing nip portion, the toner image transferred to the sheet S is fixed to the sheet.

  A switching guide (not shown) is swingably provided in the main conveyance path 50A above the fixing unit 60. When the switching guide is swung in one posture, the sheet S is carried into the lower discharge path 50D from the main conveyance path 50A. Then, the sheet S is discharged to the paper discharge unit 101 by the first discharge roller pair 7 </ b> A including the first discharge roller 71 and the first driven roller 72.

  On the other hand, when the switching guide is swung to another posture, the sheet S is carried into the upper discharge path 50C from the main conveyance path 50A. Then, the sheet S is discharged to the paper discharge unit 101 by the second discharge roller pair 7 </ b> B including the second discharge roller 73 and the second driven roller 74. When a paper discharge tray (not shown) is mounted above the discharge unit 101, the sheet S is discharged to the paper discharge tray by the second discharge roller pair 7B.

  Further, the image forming apparatus 1 includes a duplex conveying unit 8. As shown in FIG. 1, the double-sided conveyance unit 8 is provided at the right end of the apparatus body 10 and includes the above-described double-sided conveyance path 50 </ b> B inside. The duplex conveying unit 8 defines a part of the right wall 10R of the apparatus main body 10. When double-sided printing is performed on the sheet S, the second discharge roller pair 7B of the second discharge roller pair 7B is exposed with the leading end of the sheet S having an image formed on one surface exposed from the upper discharge path 50C to the discharge space 10S. The rotation direction is reversed and the sheet S is switched back. Then, the trailing edge of the sheet S that has stopped near the boundary between the upper discharge path 50C and the double-sided conveyance path 50B is carried into the double-sided conveyance path 50B as a new leading edge.

  2 to 5 are a side view, a plan view, a front view, and a cross-sectional view of the double-sided conveyance unit 8 according to this embodiment, respectively. The duplex conveyance unit 8 includes a unit main body 80, a conveyance unit 85, an intermediate roller pair 81, a first duplex roller pair 82, a second duplex roller pair 83, and a third duplex roller pair 84.

  The unit main body 80 is a main body portion of the duplex conveying unit 8. The transport unit 85 is disposed on the left side of the unit main body 80. The unit main body 80 includes a unit gripping portion 80S, a unit side rail 80R (FIG. 4), and a unit upper guide 80G. Further, as shown in FIG. 5, a part of the main transport path 50 </ b> A and a double-sided transport path 50 </ b> B are disposed in the unit main body 80 and the transport unit 85. As shown in FIG. 5, the secondary transfer roller 35 described above is rotatably supported by the transport unit 85, and the registration driven roller 51 </ b> B of the registration roller pair 51 is also supported. A fixing unit space 60 </ b> H in which the fixing unit 60 is disposed is formed above the secondary transfer roller 35.

  The unit gripping portion 80S is a gripping portion disposed on the right side surface of the unit main body 80. The unit-side rail 80R is a rail portion that is disposed at the lower end portion of the unit body 80 so as to extend along the horizontal direction. The unit side rail 80R slides along the left-right direction with respect to the apparatus main body side rail 10T provided in the apparatus main body 10. In addition to the front side portion of the unit main body 80 as shown in FIG. 4, a unit side rail 80R (device main body side rail 10T) is also provided on the rear side portion of the unit main body 80. When the unit main body 80 is pulled out to the right while the unit gripping portion 80S is gripped by a user or a maintenance worker (arrow DS in FIG. 4), the unit main body 80 and the transport unit 85 are slid integrally and moved to the main transport. A part of the path 50 </ b> A is exposed to the outside of the apparatus main body 10. As a result, the sheet S jammed in the main transport path 50A can be removed. At this time, as shown in FIG. 5, the secondary transfer roller 35 and the registration roller pair 51 also move to the right together with the unit body 80. In the double-sided conveyance unit 8 of FIG. 5, the right side part from the double-sided conveyance path 50B is separable from the left side part (conveyance unit 85) from the double-sided conveyance path 50B. As a result, the sheet S jammed in the duplex conveyance path 50B can also be removed.

  The unit upper guide 80G is disposed on the upper end side of the unit main body 80, and guides the sheet S switched back by the second discharge roller pair 7B to the duplex conveying path 50B.

  The intermediate roller pair 81 (first transport roller pair) is disposed on the upstream side of the registration roller pair 51 in the main transport path 50A and transports the sheet S upward. The sheet S fed from the sheet feeding unit 40 is conveyed to the registration roller pair 51 by the intermediate roller pair 81. The intermediate roller pair 81 includes an intermediate drive roller 81A (first roller) and an intermediate driven roller 81B (second roller). The intermediate driven roller 81B forms a nip portion (first nip portion) where the sheet S is conveyed with the intermediate drive roller 81A.

  The first double-sided roller pair 82 is disposed near the entrance of the double-sided conveyance path 50B (upper end portion of the double-sided conveyance path 50B) and conveys the sheet S downward. The first duplex roller pair 82 carries the sheet S guided by the unit upper guide 80G into the duplex conveyance path 50B. The first double-sided roller pair 82 includes a first double-sided driving roller 82A and a first double-sided driven roller 82B. The first double-sided roller pair 82 is supported by the unit main body 80.

  The second double-sided roller pair 83 is disposed at a substantially central portion in the vertical direction of the double-sided conveyance path 50B and conveys the sheet S. The second duplex roller pair 83 conveys the sheet S conveyed by the first duplex roller pair 82 further downward. The second double-sided roller pair 83 includes a second double-sided driving roller 83A and a second double-sided driven roller 83B. The second double-sided drive roller 83A is supported by the transport unit 85, and the second double-side driven roller 83B is supported by the unit body 80.

  The third double-sided roller pair 84 is disposed near the lower end portion of the double-sided conveyance path 50B and conveys the sheet S. As shown in FIG. 5, the lower end portion (downstream side) of the double-sided conveyance path 50 </ b> B is curved in an arc shape, upstream of the registration roller pair 51 and downstream of the intermediate roller pair 81. It communicates with the main conveyance path 50A. The third double-sided roller pair 84 includes a third double-sided drive roller 84A (third roller) and a third double-side driven roller 84B (fourth roller). The third double-side driven roller 84B forms a nip portion (second nip portion) through which the sheet S is conveyed with the third double-side drive roller 84A. The third double-side drive roller 84A is supported by the unit body 80, and the third double-side driven roller 84B is supported by the transport unit 85.

  In the periphery of the duplex conveying unit 8, the main conveying path 50A guides the sheet S along the conveying direction from the lower side to the upper side. On the other hand, the double-sided conveyance path 50B is branched from the downstream side in the conveyance direction with respect to the image forming unit 30 in the main conveyance path 50A, and is downstream of the intermediate roller pair 81 in the conveyance direction of the sheet S in the main conveyance path 50A ( Between the intermediate roller pair 81 and the registration roller pair 51), the sheet S is disposed so as to merge with the main conveyance path 50A.

  In the present embodiment, a motor (not shown) is connected to each of the registration roller 51A, the intermediate drive roller 81A, the first double-side drive roller 82A, the second double-side drive roller 83A, and the third double-side drive roller 84A. These motors are respectively driven to rotate. On the other hand, the registration driven roller 51B, the intermediate driven roller 81B, the first double-side driven roller 82B, the second double-side driven roller 83B, and the third double-side driven roller 84B rotate by being driven by opposing driving rollers.

  With reference to FIG. 5, in the present embodiment, as described above, the skew (skew) of the sheet S is corrected at the nip portion between the registration roller 51A and the registration driven roller 51B. When the leading edge of the sheet S fed from the sheet feeding section 40 enters the nip portion of the registration roller pair 51, if the sheet S is sandwiched between the nip portions of the intermediate roller pair 81, the registration roller pair 51 The skew correction function is difficult to work. Similarly, when the leading edge of the sheet S conveyed through the duplex conveying path 50B enters the nip portion of the registration roller pair 51, the sheet S is sandwiched between the nip portions of the third duplex roller pair 84. The skew correction function in the registration roller pair 51 is difficult to work. Therefore, in this embodiment, the nip portions of the intermediate roller pair 81 and the third double-sided roller pair 84 are temporarily released at a predetermined timing (separating operation).

  The duplex transport unit 8 further includes a drive mechanism 9 and a control unit 500 (drive control unit) that controls the drive mechanism 9. FIG. 6 is a perspective view of the drive mechanism 9 according to the present embodiment. In FIG. 6, the intermediate roller pair 81 and the third double-sided roller pair 84 are drawn one by one, but actually, the four intermediate roller pairs 81 and the four third double-sided roller pairs along the axial direction. 84 are spaced apart on the first transmission shaft 96 and the second transmission shaft 97, respectively. The drive mechanism 9 selectively selects the nip portion (first nip portion) of the intermediate roller pair 81 and the nip portion (second nip portion) of the third double-sided roller pair 84 based on the driving force of a single motor. release. In other words, the drive mechanism 9 moves the intermediate drive roller 81A away from the intermediate driven roller 81B for a predetermined time, and then brings the third double-side drive roller 84A into contact with the intermediate driven roller 81B again. After being separated from the third double-side driven roller 84B for a predetermined time, it is possible to selectively execute the second separation / contact operation in which the second double-side driven roller 84B comes into contact again. Note that the third double-sided drive roller 84A is in contact with the third double-sided driven roller 84B during the first separation / contact operation, and the intermediate drive roller 81A is in contact with the intermediate driven roller 81B during the second separation / contact operation. In each separating operation, the four intermediate roller pairs 81 and the four third double-sided roller pairs 84 are collectively driven. The drive mechanism 9 is disposed in the unit main body 80, respectively, and includes a motor 90, a drive gear 91, a drive shaft 92, an input cam 93 (cam), a first drive transmission mechanism 9A, and a second drive transmission mechanism. 9B.

  The motor 90 is rotatable in a first rotation direction and a second rotation direction opposite to the first rotation direction. On / off of rotation of the motor 90 and the rotation direction are controlled by the control unit 500. The drive gear 91 is a gear connected to an output shaft (not shown) of the motor 90. The drive shaft 92 corresponds to the rotation axis of the drive gear 91. 6, the arrow D1 direction corresponds to the first rotation direction of the motor 90, and the arrow D2 direction corresponds to the second rotation direction of the motor 90.

  The first drive transmission mechanism 9 </ b> A performs the first separation / connection operation by the rotational driving force of the motor 90 in the first rotational direction. The first drive transmission mechanism 9A includes a first transmission cam 94 (first pressed portion), a first transmission shaft 96 (first shaft portion), a first holder 98, and a first spring 98S.

  The first transmission cam 94 is disposed on the left side of the input cam 93 so as to face the input cam 93. The first transmission shaft 96 extends in the front-rear direction, and the front end portion of the first transmission shaft 96 is connected to the first transmission cam 94. As a result, the first transmission shaft 96 forms a fulcrum (first fulcrum 94S) for the rotation (swing) of the first transmission cam 94. The first holder 98 is fixed to the first transmission shaft 96 behind the first transmission cam 94. The first holder 98 rotatably supports the intermediate drive roller 81A. The first spring 98S biases the first holder 98 along the direction in which the intermediate driving roller 81A abuts on the intermediate driven roller 81B. Therefore, one end of the first spring 98S is fixed to the first holder 98, and the other end of the first spring 98S is fixed to a part of the unit main body 80.

  The second drive transmission mechanism 9 </ b> B executes the second separation / contact operation by the rotational driving force of the motor 90 in the second rotational direction. The second drive transmission mechanism 9B includes a second transmission cam 95 (second pressed portion), a second transmission shaft 97 (second shaft portion), a second holder 99, and a second spring 99S.

  The second transmission cam 95 is disposed on the right side of the input cam 93 (on the side opposite to the first transmission cam 94) to face the input cam 93. The second transmission shaft 97 extends in parallel with the first transmission shaft 96, and the front end portion of the second transmission shaft 97 is connected to the second transmission cam 95. As a result, the second transmission shaft 97 forms a fulcrum (second fulcrum 95S) in the rotation (swing) of the second transmission cam 95. The second holder 99 is fixed to the second transmission shaft 97 behind the second transmission cam 95. The second holder 99 rotatably supports the third double-sided drive roller 84A. The second spring 99S biases the second holder 99 along the direction in which the third double-sided roller pair 84A contacts the third double-side driven roller 84B. Therefore, one end of the second spring 99S is fixed to the second holder 99, and the other end of the second spring 99S is fixed to a part of the unit main body 80.

  Referring to FIG. 6, in the first separation / connection operation, when motor 90 is rotated in the first rotation direction by control unit 500, input cam 93 presses first transmission cam 94 while rotating in the direction of arrow D <b> 1. (Arrow D61). As a result, the first holder 98 rotates together with the first transmission cam 94 and the first transmission shaft 96 around the axis of the first transmission shaft 96, and the intermediate drive roller 81A is separated from the intermediate driven roller 81B (arrow D62). The controller 500 rotates the motor 90 in the second rotation direction after a predetermined time has elapsed as described later, and returns the input cam 93 to the standby position shown in FIG. As a result, the first holder 98 returns to the position shown in FIG. 6 by the urging force of the first spring 98S, and the intermediate drive roller 81A comes into contact with the intermediate driven roller 81B again.

  Similarly, in the second separation / connection operation, when the motor 90 is rotated in the second rotation direction by the controller 500, the input cam 93 presses the second transmission cam 95 while rotating in the arrow D2 direction (arrow D63). . As a result, the second holder 99 rotates together with the second transmission cam 95 and the second transmission shaft 97 around the axis of the second transmission shaft 97, and the third double-sided drive roller 84A is separated from the third double-side driven roller 84B ( Arrow D64). The controller 500 rotates the motor 90 in the first rotation direction after a predetermined time has passed as described later, and returns the input cam 93 to the standby position shown in FIG. As a result, the second holder 99 returns to the position shown in FIG. 6 by the urging force of the second spring 99S, and the third double-sided drive roller 84A comes into contact with the third double-side driven roller 84B again.

  Next, how the sheet S is conveyed in the image forming apparatus 1 will be described together with the operation of the drive mechanism 9. FIG. 7 is a flowchart when single-sided continuous printing is executed in the present embodiment. In single-sided continuous printing, after images are formed on one side of a plurality of sheets S, each sheet S is discharged into the discharge space 10S. FIG. 8 is a flowchart when double-sided continuous printing is executed in the present embodiment. In double-sided continuous printing, after images are formed on both sides of a plurality of sheets S, each sheet S is discharged into the discharge space 10S. Hereinafter, as an example, the sheet S is an A4 landscape sheet.

  In FIG. 7, steps S11 to S17 indicate operations for the first sheet S (sheet S1), steps S21 to S27 indicate operations for the second sheet S (sheet S2), and steps S31 to S34 indicate 3 operations. The operation for the first sheet S (sheet S3) is shown.

  When single-sided continuous printing is performed, each pair of transport rollers is rotated at any time, and the first sheet S1 is fed from the sheet feeding unit 40 (step S11). Eventually, the leading edge of the sheet S1 reaches the intermediate roller pair 81 (step S12), and further, the leading edge of the sheet S1 reaches the registration roller pair 51 that has been previously stopped in rotation (step S13). Here, the controller 500 rotates the motor 90 of the drive mechanism 9 in the first rotation direction to separate the intermediate drive roller 81A of the intermediate roller pair 81 from the intermediate driven roller 81B (step S14). As a result, the rear end side of the sheet S1 is restrained by the intermediate roller pair 81, and the skew of the sheet S1 is stably corrected by the registration roller pair 51. Thereafter, the controller 500 rotates the motor 90 in the second rotation direction, and causes the intermediate drive roller 81A to contact the intermediate driven roller 81B again (step S15). At this time, since the rear end portion of the sheet S1 has not yet passed through the intermediate roller pair 81, the sheet S1 is sandwiched by the intermediate roller pair 81. Thereafter, the trailing end of the sheet S1 passes through the intermediate roller pair 81 (step S16), and after the image is formed on the sheet S1, the sheet S1 is discharged (step S17). In FIG. 7, a series of operations in steps S12 to S15 is defined as a single-sided flow F1.

  In parallel with the conveyance of the sheet S1, the second sheet S2 is fed (step S21). In the present embodiment, step S21 is executed at a timing after step S15 and before step S16. As a result, a predetermined sheet interval (sheet interval) is formed between the preceding sheet S1 and the succeeding sheet S2. Soon, the leading edge of the sheet S2 reaches the intermediate roller pair 81 (step S22), and the leading edge of the sheet S2 reaches the registration roller pair 51 (step S23). Step S22 is executed after step S16, more specifically, after the trailing edge of the sheet has passed the registration roller pair 51 and before step S17. Step S23 is executed at a timing later than step S17. In step 23, when the leading edge of the sheet S2 reaches the registration roller pair 51, the control unit 500 rotates the motor 90 of the drive mechanism 9 in the first rotation direction, and causes the intermediate drive roller 81A of the intermediate roller pair 81 to move to the intermediate driven roller 81B. (Step S24). As a result, the rear end side of the sheet S2 is restrained by the intermediate roller pair 81, and the skew of the sheet S2 is stably corrected by the registration roller pair 51. Thereafter, the controller 500 rotates the motor 90 in the second rotation direction, and causes the intermediate drive roller 81A to contact the intermediate driven roller 81B again (step S25). Also at this time, since the rear end portion of the sheet S2 has not yet passed through the intermediate roller pair 81, the sheet S2 is sandwiched by the intermediate roller pair 81. Thereafter, the trailing end of the sheet S2 passes through the intermediate roller pair 81 (step S26), and after the image is formed on the sheet S2, the sheet S2 is discharged (step S27).

  Similarly, the third sheet S3 is fed in parallel with the conveyance of the sheet S2 (step S31). Step S31 is executed at a timing after step S25 and before step S26. As a result, a predetermined sheet interval (sheet interval) is also formed between the preceding sheet S2 and the succeeding sheet S3. Thereafter, the aforementioned single-sided flow F1 is executed on the sheet S3 (step S32). Then, the trailing edge of the sheet S3 passes through the registration roller pair 51 (step S33), an image is formed on the sheet S3, and after passing through the secondary transfer roller 35, the sheet S3 is discharged (step S33). .

  As described above, when single-sided printing is continuously performed on the sheet S, the control unit 500 controls the drive mechanism 9 so that the intermediate drive roller 81A of the intermediate roller pair 81 is intermediate driven roller at a predetermined timing. Separated from 81B.

  On the other hand, FIG. 8 shows a flow during double-sided continuous printing. Steps S41 to S52 show the operation for the first sheet S (sheet S1), and steps S61 to S67 show the second sheet S ( The operation on the sheet S2) is shown, and steps S71 to S75 show the operation on the third sheet S (sheet S3).

  When double-sided continuous printing is executed, each pair of transport rollers is rotated at any time, and the first sheet S1 is fed from the sheet feeding unit 40 (step S41). Then, in order to form an image on the surface of the sheet S1, the above-described single-sided flow F1 is performed on the sheet S1 (step S42). Then, the trailing edge of the sheet S1 sequentially passes through the intermediate roller pair 81 and the registration roller pair 51 (steps S43 and S44), and after the image is formed on the surface of the sheet S1 and fixed by the fixing unit 60, the sheet S1 is The upper discharge path 50C is switched back by the second discharge roller pair 7B and is carried into the duplex conveyance path 50B. While the sheet S1 is being conveyed by the first duplex roller pair 82 and the second duplex roller pair 83 arranged in the duplex conveyance path 50B, the leading edge of the sheet S1 eventually reaches the third duplex roller pair 84 (step S45). Then, when the leading edge of the sheet S1 reaches the merging portion GP of the duplex conveying path 50B, the rotation of the third duplex roller pair 84 (second duplex roller pair 83) is stopped by the control unit 500, and the sheet S1 is merged. It waits with the effort of GP (step S46). This operation is because the sheet S2 described later passes through the intermediate roller pair 81 and the registration roller pair 51. As shown in FIG. 8, a series of operations in step S45 and step S46 is defined as a double-sided flow F2.

  Thereafter, when the trailing edge of the sheet S2 passes the registration roller pair 51 (see step S64), the rotation of the third double-sided roller pair 84 (second double-sided roller pair 83) is resumed, and the waiting sheet S1 is main conveyed. It is carried into the path 50A. When the leading edge of the sheet S1 reaches the registration roller pair 51 with the trailing edge of the sheet S1 passing through the second double-sided roller pair 83 (step S47), the control unit 500 rotates the motor 90 of the driving mechanism 9 in the second rotation. The third double-sided driving roller 84A of the third double-sided roller pair 84 is separated from the third double-side driven roller 84B (step S48). As a result, the rear end side of the sheet S1 is restrained by the third double-sided roller pair 84, and the skew of the sheet S1 is stably corrected by the registration roller pair 51. Thereafter, the controller 500 rotates the motor 90 in the first rotation direction, and brings the third double-sided drive roller 84A into contact with the third double-side driven roller 84B again (step S49). Also at this time, since the rear end portion of the sheet S1 has not yet passed through the third double-sided roller pair 84, the sheet S1 is sandwiched by the third double-sided roller pair 84. Thereafter, the trailing edge of the sheet S1 passes through the third double-sided roller pair 84 and the registration roller pair 51 in order (steps S50 and S51). After an image is formed on the back surface of the sheet S1, the sheet S1 is discharged ( Step S52). As shown in FIG. 8, a series of operations from step S47 to step S51 is defined as a double-sided flow F3.

  Also in this operation, the second sheet S2 is fed in parallel with the conveyance of the sheet S1 (step S61). Step S61 is executed at a timing after step S42 and before step S43. As a result, a predetermined sheet interval (sheet interval) is also formed between the preceding sheet S1 and the succeeding sheet S2. Thereafter, the above-described single-sided flow F1 is executed on the sheet S2 (step S62). Then, after the trailing edge of the sheet S2 passes through the intermediate roller pair 81 and the registration roller pair 51 in order (steps S63 and S64) and an image is formed on the surface of the sheet S2, the sheet S2 is switched in the upper discharge path 50C. Backed and carried into the duplex conveying path 50B. While the sheet S2 is being conveyed by the first double-sided roller pair 82 and the second double-sided roller pair 83 arranged in the double-sided conveyance path 50B, the leading edge of the sheet S2 eventually reaches the third double-sided roller pair 84, and the double-sided flow F2 described above. (Standby operation) is executed (step S65). This operation is because the sheet S3 described later passes through the intermediate roller pair 81 and the registration roller pair 51. Thereafter, when the trailing edge of the sheet S3 passes the registration roller pair 51 (see step S74), the rotation of the third double-sided roller pair 84 (second double-sided roller pair 83) is restarted, and the waiting sheet S2 is main conveyed. It is carried into the path 50A. Thereafter, the above-described double-sided flow F3 is executed on the sheet S2 (step S66). Then, after an image is formed on the back surface of the sheet S2, the sheet S2 is discharged (step S67).

  Further, in parallel with the conveyance of the sheet S2, the third sheet S3 is fed (step S71). Step S71 is executed at a timing after step S62 and before step S63. As a result, a predetermined sheet interval (sheet interval) is also formed between the preceding sheet S2 and the succeeding sheet S3. Thereafter, the above-described single-sided flow F1 is executed on the sheet S3 (step S72). Then, after the trailing edge of the sheet S3 passes through the intermediate roller pair 81 and the registration roller pair 51 in order (steps S73 and S74) and an image is formed on the surface of the sheet S3, the sheet S3 is switched in the upper discharge path 50C. Backed and carried into the duplex conveying path 50B. While the sheet S3 is being conveyed by the first double-sided roller pair 82 and the second double-sided roller pair 83 disposed in the double-sided conveyance path 50B, the leading edge of the sheet S3 eventually reaches the third double-sided roller pair 84, and the double-sided flow F2 described above. (Standby operation) is executed (step S75). This operation is because the fourth sheet S passes through the intermediate roller pair 81 and the registration roller pair 51. Thereafter, processing similar to that for the sheets S1 and S2 is performed on the sheet S3.

  Note that the conveyance of the sheet S in the above-described double-sided continuous printing is shown in the order of passing through the image forming unit 30 (secondary transfer nip portion), the surface of the sheet S1, the surface of the sheet S2, the back surface of the sheet S1, and the sheet S3. It is conveyed in the order of the front surface and the back surface of the sheet S2.

  As described above, according to the present embodiment, when double-sided printing is continuously performed on the sheet S, the control unit 500 controls the drive mechanism 9 so that the intermediate roller pair 81 is controlled at a predetermined timing. While the intermediate driving roller 81A is separated from the intermediate driven roller 81B, the third double-sided driving roller 84A of the third double-sided roller pair 84 is separated from the third double-side driven roller 84B at a timing different from that of the intermediate roller pair 81. Therefore, the drive mechanism 9 can selectively separate the two transport roller pairs (the intermediate roller pair 81 and the third double-sided roller pair 84) arranged on the two transport paths of the main transport path 50A and the double-side transport path 50B. it can. As a result, it is not necessary to dispose a drive mechanism for separation in each of the intermediate roller pair 81 and the third double-sided roller pair 84, and the number of drive mechanisms for releasing the nips of the transport roller pairs respectively disposed in the plurality of transport paths. Can be reduced as compared with the prior art.

  In the present embodiment, the drive mechanism 9 includes a motor 90, a first drive transmission mechanism 9A, and a second drive transmission mechanism 9B. Therefore, the nips of a plurality of conveying roller pairs can be selectively released according to the rotation direction of the single motor 90. Further, the first holder 98 and the second holder 99 are rotated in different directions according to the rotation direction of the input cam 93, whereby one of the intermediate drive roller 81A and the third double-side drive roller 84A is separated. Is realized stably.

  In the present embodiment, the control unit 500 executes the first separation / contact operation after the leading end of the sheet S conveyed on the main conveyance path 50A by the intermediate roller pair 81 reaches the registration roller pair 51, After the leading edge of the sheet S conveyed on the duplex conveyance path 50B by the three duplex roller pair 84 reaches the registration roller pair 51, the second separation / contact operation is executed. As a result, the skew of the sheet conveyed through the main conveyance path 50A or the double-sided conveyance path 50B is corrected stably.

  Further, in the present embodiment, the control unit 500 moves the intermediate driving roller 81A to the intermediate driven roller 81B after the first separation / contact operation is performed and before the trailing end of the sheet S passes the intermediate roller pair 81. The third double-sided driving roller 84A is moved to the third double-sided driven roller 84B after the second separation / contact operation is performed and before the trailing edge of the sheet S passes through the third double-sided roller pair 84. Abut. Therefore, compared with the case where the contact operation is performed after the trailing edge of the sheet S passes the intermediate roller pair 81 or the third double-sided roller pair 84, an unnecessary increase between the sheets can be suppressed.

  The image forming apparatus 1 according to the embodiment of the present invention has been described above. However, the present invention is not limited to this, and for example, the following modified embodiment can be adopted.

  (1) In the above embodiment, the main conveyance path 50A and the double-side conveyance path 50B are described as the first conveyance path and the second conveyance path of the present invention, but the present invention is not limited to this. A mode in which the driving mechanism 9 performs nip release (separation / separation operation) of the other conveyance roller pairs respectively disposed in the plurality of conveyance paths in the image forming apparatus 1 may be employed.

  (2) In the above-described embodiment, the intermediate drive roller 81A and the third double-sided drive roller 84A are described as being separated from each other. However, the intermediate driven roller 81B and the third double-sided driven roller 84B may be separated from each other. .

  (3) In the above embodiment, the transport mode of the sheet S in single-sided continuous printing and double-sided continuous printing has been described in the flow shown in FIGS. 7 and 8, but the present invention is not limited to this. A mode in which a plurality of sheets S are conveyed based on other orders different from those in FIGS.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Apparatus main body 10S Discharge space (sheet | seat discharge part)
30 Image forming section 35 Secondary transfer roller 40 Paper feed section (sheet storage section)
46 Paper Tray 500 Control Unit (Drive Control Unit)
50A main transport path (first transport path)
50B Double-sided conveyance path (second conveyance path)
51 Registration roller pair 51A Registration roller 51B Registration driven roller 8 Double-sided conveyance unit 80 Unit body 81 Intermediate roller pair (first conveyance roller pair)
81A Intermediate drive roller (first roller)
81B Intermediate driven roller (second roller)
82 First duplex roller pair 83 Second duplex roller pair 84 Third duplex roller pair (second transport roller pair)
84A Third double-sided drive roller (third roller)
84B Third double-side driven roller (fourth roller)
9 drive mechanism 9A first drive transmission mechanism 9B second drive transmission mechanism 90 motor 91 drive gear 92 drive shaft 93 input cam (cam)
94 1st transmission cam (1st to-be-pressed part)
95 Second transmission cam (second pressed portion)
96 1st transmission shaft (1st axial part)
97 Second transmission shaft (second shaft)
98 1st holder 98S 1st spring 99 2nd holder 99S 2nd spring GP Merge part

Claims (5)

A first conveyance path for guiding the sheet along a predetermined conveyance direction;
A first conveying roller pair disposed in the first conveying path for conveying a sheet, the first roller and a second roller forming a first nip portion between which the sheet is conveyed; A first conveying roller pair including:
A second conveyance path arranged to join the first conveyance path downstream of the first conveyance roller pair in the conveyance direction and guiding the sheet;
A second conveying roller pair disposed in the second conveying path for conveying a sheet, wherein a third roller and a fourth roller forming a second nip portion for conveying the sheet between the third roller; A second conveying roller pair including
A first separation / contact operation in which the first roller is separated from the second roller for a predetermined time in a state where the third roller is in contact with the fourth roller; A second separation / contact operation in which the third roller is separated from the fourth roller for a predetermined time in a state where one roller is in contact with the second roller, and then is brought into contact with the fourth roller. A drive mechanism that can be implemented;
An image forming apparatus. The drive mechanism is
A motor rotatable in a first rotation direction and a second rotation direction opposite to the first rotation direction;
A first drive transmission mechanism for separating the first roller from the second roller by a rotational driving force of the motor in the first rotational direction;
A second drive transmission mechanism for separating the third roller from the fourth roller by a rotational driving force of the motor in the second rotational direction;
The image forming apparatus according to claim 1, comprising: The drive mechanism further includes a cam connected to the motor and rotatable in the first rotation direction and the second rotation direction,
The first drive transmission mechanism includes:
A first pressed portion disposed to face the cam;
A first shaft connected to the first pressed portion;
A first holder fixed to the first shaft portion and rotatably supporting the first roller;
Have
The second drive transmission mechanism is
A second pressed portion disposed on the side opposite to the first pressed portion and facing the cam;
A second shaft portion connected to the second pressed portion and extending in parallel with the second shaft portion;
A second holder fixed to the second shaft portion and rotatably supporting the third roller;
Have
When the motor is rotated in the first rotation direction, the cam presses the first pressed portion, so that the first holder rotates around the first shaft portion and the first roller When the motor is separated from the second roller and the motor is rotated in the second rotational direction, the second holder is rotated around the second shaft portion by the cam pressing the second pressed portion. The image forming apparatus according to claim 2, wherein the third roller is separated from the fourth roller. A sheet storage unit that stores a plurality of sheets and communicates with an inlet of the first conveyance path;
An image forming unit that is disposed opposite to the first conveyance path on the downstream side in the conveyance direction with respect to the first conveyance roller pair, and forms an image on a sheet conveyed through the first conveyance path;
A sheet discharge portion that communicates with an outlet of the first conveyance path and receives a sheet on which an image is formed in the image forming portion;
A registration roller pair that is disposed between the first conveyance roller pair and the image forming unit in the first conveyance path, corrects skew of the sheet, and conveys the sheet;
A drive control unit for controlling the drive mechanism;
Further comprising
The second transport path branches from the first transport path from the downstream side in the transport direction with respect to the image forming unit, and the first transport roller pair and the registration roller pair in the first transport path. It is a double-sided conveyance path that joins the part between,
The drive control unit performs the first separation / contact operation after a leading end of a sheet conveyed on the first conveyance path by the first conveyance roller pair reaches the registration roller pair, and the second conveyance roller 4. The image forming apparatus according to claim 1, wherein the second separation / contact operation is performed after a leading end of a sheet conveyed along the second conveyance path by the pair reaches the registration roller pair. 5. . The drive controller is configured to move the first roller after the first roller is separated from the second roller in the first separating operation and before the trailing edge of the sheet passes the first conveying roller pair. One roller is brought into contact with the second roller, and after the third roller is separated from the fourth roller in the second separation / contact operation, the trailing edge of the sheet is the second conveying roller pair. The image forming apparatus according to claim 4, wherein the third roller is brought into contact with the fourth roller before passing through.

Images