JP2014133640A - Sheet transport device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet transport device capable of dealing with a wide range of sheets from thin sheets to thick sheets and performing skew correction.SOLUTION: A sheet transport device including: first transport drive means for transport-driving a sheet so as to transport the sheet along a transport path; shutter member that is provided on the transport path downstream of the first transport drive means in a sheet transport direction, and that can fluctuate between a first attitude at which the shutter member can abut on a tip end of the sheet transported and driven by the first transport drive means and can stop the sheet and a second attitude at which the shutter member can pass through the sheet; and a lock mechanism locking the shutter member so that the shutter member is kept at the first attitude, and unlocking the shutter member so that the shutter member can take the second attitude by allowing the tip end of the sheet to abut on and press a part of the lock mechanism.

Description

  The present invention relates to a sheet conveying apparatus equipped with a sheet skew correcting device and an image forming apparatus equipped with the sheet conveying apparatus.

  A conventional sheet skew correction apparatus will be described with reference to FIGS.

  First, the sheet skew correction device of Patent Document 1 will be described with reference to FIG.

  A shutter member 15 is rotatably provided on a rotation shaft 18 of a conveyance roller constituting the conveyance roller pair 13 and 14. The leading edge of the sheet S conveyed by the conveying roller pair is brought into contact with and abuts against the abutting surface 20a of the shutter member 15, and the sheet S forms a predetermined loop. When the force with which the sheet S pushes the surface 20 a exceeds a predetermined force, the shutter member 15 is rotated and retracted, and the sheet S passes through the shutter member 15.

  Accordingly, since the sheet S enters the conveying roller pair 13 and 14 in a state where the sheet S is aligned with the abutting surface 20a of the shutter member 15, the skew of the sheet S can be corrected.

  Next, the sheet skew correction device of Patent Document 2 will be described with reference to FIG.

  A registration roller 116 including a pair of sheet conveying rotators, and a first posture abutting on the leading edge of the sheet and passing the sheet upstream of and near the nip portion of the pair of sheet conveying rotators. The shutter member 30 is swingable in a second posture to be obtained.

  A spring 64 is provided to bias the shutter member 30 so as to maintain the first posture. In addition, a motor for driving the registration roller is provided, and control means for controlling the rotation direction of the motor is provided according to the type of sheet to be used.

  And it has the 1st drive train which carries out drive connection of the motor and the registration roller, and the 2nd drive train from which the reduction ratio differs from the 1st drive train, and the driving force of the motor according to the rotation direction of the motor Is switched to the first drive train or the second drive train for transmission.

  Furthermore, means for switching the urging force of the spring 64 against the shutter member according to the rotation direction of the motor is provided. The sheet is locked to the contact surfaces 32 a to 32 f of the shutter member 30 to correct the skew of the sheet.

  Therefore, by changing the rotation direction of the motor in accordance with the type of sheet, two types of optimum spring pressure can be set by rotating the motor forward and backward on the shutter member, and a corresponding sheet capable of correcting skew feeding can be obtained. It became possible to increase.

JP 09-183539 A Japanese Patent Application No. 2010-56945

  However, in response to the recent thin paper, in the sheet skew correction device described in Patent Document 1, it is necessary to set the opening force of the shutter weak so that the shutter can be opened even on thin paper with low rigidity. In such a case, when passing the thick paper, the shutter opens before the loop is formed, so that the thick paper enters the roller without sufficiently removing the skew, and a sufficient skew correction ability cannot be obtained.

  In addition, in the sheet skew correction device described in Patent Document 2, the user needs to set the switching of the opening force of the shutter, and the user does not always set the optimal spring pressure. The line correction ability may be reduced. Furthermore, since the opening force can be adjusted only in two stages of forward and reverse rotation of the motor, only limited paper types can be handled.

  The present invention has been made in view of such circumstances, and an object of the present invention is to make it possible to perform skew correction regardless of the basis weight without requiring user settings.

  In order to achieve this object, a sheet conveying apparatus of the present invention includes a first conveying driving unit that conveys and drives the sheet so as to convey the sheet along a conveying path, and a sheet of the first conveying driving unit. A first posture that is provided in the conveyance path on the downstream side in the conveyance direction and can be brought into contact with and locked to the leading edge of the sheet that is conveyed and driven by the first conveyance driving unit, and a second position that allows the sheet to pass therethrough. A shutter member that can swing between the first and second postures, and a lock mechanism that locks the shutter member so as to maintain the first posture, wherein a leading end of the sheet abuts against a part of the lock mechanism. And a lock mechanism that releases the lock so that the shutter member can take the second posture by pressing the shutter member.

  In the present invention, the shutter member swings between a first posture in which the shutter member can be brought into contact with the leading edge of the sheet that is driven and transported by the first transport driving means and a second posture in which the sheet can be passed. It is possible to move. The lock mechanism locks the shutter member to hold the first posture, and the shutter member takes the second posture by the front end of the sheet coming into contact with and pressing against a part of the lock mechanism. Unlock to get.

  Therefore, it is possible to correct the skew of the sheet widely from thin paper to thick paper regardless of the basis weight of the sheet.

It is sectional drawing which shows typically the whole structure of the laser beam printer of 1st Embodiment of this invention. 1 is a perspective view of a registration roller unit according to a first embodiment of the present invention. It is sectional drawing of the lock part which concerns on 1st Embodiment of this invention. 3A is a view showing a standby position of the lock member, FIG. 3B is a view showing a release position of the lock member, and FIG. 3C is a view showing a state where the sheet passes through the shutter. It is. In the first embodiment of the present invention, it is a diagram showing a registration roller unit having two locking mechanisms. FIG. 4A is a perspective view of a registration roller unit having two lock mechanisms. FIG. 4B is a top view of a registration roller unit having a locking mechanism in one place. FIG. 4C is a top view of a registration roller unit having two locking mechanisms. It is a figure which shows the structure of the registration roller unit which concerns on 2nd Embodiment of this invention. FIG. 5A is a perspective view of the registration roller unit, FIG. 5B is an enlarged perspective view of the lock portion, and FIG. 5C is a side view of the rotation lock member. It is a figure which shows sectional drawing of the locking mechanism which concerns on 2nd Embodiment of this invention. 6A is a view showing a standby position of the lock member, FIG. 6B is a view showing a release position of the lock member, and FIG. 6C is a view showing the way the sheet passes through the rotary shutter. FIG. 6D is a diagram illustrating a state where the sheet has passed through the rotary shutter. It is a figure which shows the structure of the registration roller unit which concerns on 3rd Embodiment of this invention. FIG. 7A is a perspective view of the registration roller unit, and FIG. 7B is an enlarged perspective view of the lock mechanism. It is sectional drawing of the crank shutter part which concerns on 3rd Embodiment of this invention. 8A is a diagram showing the standby position of the crank shutter, FIG. 8B is a diagram showing the release position of the crank lock portion, and FIG. 8C is a state in the middle of the sheet passing through the shutter. FIG. 8D is a diagram showing a state where the sheet has passed through the shutter. It is sectional drawing of the crank lock part which concerns on 3rd Embodiment of this invention. 9A is a diagram showing the standby position of the crank lock portion, FIG. 9B is a diagram showing the release position of the crank lock portion, and FIG. 9C is a state in the middle of the sheet passing through the shutter. FIG. 9D is a diagram illustrating a state in which the sheet has passed through the shutter. It is a perspective view which shows the structure of the conventional registration roller unit. It is a perspective view which shows the structure of the conventional registration roller unit.

  Hereinafter, a sheet skew correction device according to an embodiment of the present invention will be described with reference to the drawings.

  As an image forming apparatus to which the sheet skew correction device according to the embodiment of the present invention can be applied, the present invention is applied to a copier, a printer, a facsimile, and a composite device including the sheet skew correction device. In the following embodiments, a laser beam printer will be described as an example.

[First Embodiment]
(Overall configuration of image forming apparatus)
First, the overall configuration of the laser beam printer will be described. FIG. 1 is a cross-sectional view schematically showing the overall configuration of the laser beam printer.

  As shown in the figure, the laser beam printer 100 includes a feeding cassette 101 that stores sheets S. Further, the laser beam printer 100 includes, as mechanisms for forming and fixing an image on the sheet S, a conveyance path for conveying the sheet, an image forming unit P for forming an image, and a fixing unit Q for fixing the image. Yes.

  The separation roller pair 102 separates the sheets S stored in the feeding cassette 101 one by one. The sheet S is transported and driven by a pair of feed rollers 103 (first transport driving unit), and the skew of the sheet S is corrected by the registration roller unit 104 (sheet skew correcting device) to form an image. Part P is fed.

  The image forming unit P includes an exposure device 105, a process cartridge 106, and a transfer roller 107. The process cartridge 106 has a photosensitive drum 108. The exposure device 105 irradiates the photosensitive drum 108 with a laser beam L indicated by a broken line in FIG. 1 based on the image information to form an electrostatic latent image. Then, toner is attached to the electrostatic latent image to be visualized as a toner image. Thereafter, the toner image on the photosensitive drum 108 is transferred to the sheet S by the transfer roller 107. At this time, if the skew of the sheet S is not sufficiently corrected by the registration roller unit 104, the toner is not transferred to the correct location of the sheet S, and the print image is transferred obliquely on the sheet. An image defect will occur.

  The fixing unit Q includes a pressure roller 109 and a fixing roller 110 with a built-in heater, and fixes the transferred toner image on the sheet S by applying heat and pressure to the passing sheet S.

  Thereafter, the sheet S is sent to the discharge roller pair 112 by the conveyance roller pair 111 and discharged onto the discharge tray 113.

(Registration roller unit)
Next, the configuration of the registration roller unit 104 will be described with reference to FIG.

  FIG. 2 is a perspective view of the registration roller unit 104 according to the first embodiment.

  The registration roller unit 104 has a shutter 201 (shutter member). The shutter 201 is provided with sheet abutting surfaces 201a, 201b, 201c, and 201d (sheet abutting portions) on which the conveyed sheet S abuts.

  Furthermore, the shutter 201 is provided with a lock member 202 that locks at the sheet abutting position at a substantially central portion in the sheet S width direction (a chain line in FIG. 2). The roller shaft 203 is pressed by the left and right registration roller springs 208, and the rollers 204 and the registration rollers 206 form a nip portion for conveying the sheet S. The roller 204 and the registration roller 206 constitute a second transport driving unit. The roller 204 is supported so as to be rotatable with respect to the roller shaft 203. Further, the shutter 201 is supported so as to be rotatable with respect to the roller shaft 203.

  Further, the registration roller 206 is rotatably supported by the main body sheet metal 205 and is configured to convey the sheet S by rotating the drive gear 207 by a drive system (not shown).

  Next, the skew feeding correction operation of the registration roller unit 104 will be described.

  Sheet S in FIG. 2 shows a skew state. When the sheet S is conveyed toward the registration roller unit 104, the leading edge of the sheet S first hits the abutting surface 201a. At this time, since the shutter 201 is not rotated by the lock mechanism, the sheet S is pressed against the abutting surface 201a, and the sheet S forms a loop. Thereby, the skew of the sheet S is corrected.

  When the sheet S is further conveyed and the sheet S pushes the sheet abutting surface 202a of the lock member 202, the lock is released, the shutter 201 can be rotated, the shutter 201 is opened, and the sheet S passes. When the sheet S unlocks the lock member 202, the skew of the sheet S is corrected. As described above, since the shutter 201 cannot be operated unless the lock of the lock member 202 is released, it is possible to correct a wide skew of sheets regardless of the sheet basis weight.

(Lock mechanism)
Next, the operation of the lock mechanism of the registration roller unit 104 will be described with reference to FIG. FIG. 3A is a diagram showing the standby position of the lock unit, FIG. 3B is a diagram showing the release position of the lock unit, and FIG. 3C is a diagram showing the sheet S passing through the shutter.

  Before the sheet S reaches the registration roller unit 104, the lock member 202 stands by at the position shown in FIG.

  Since the rib 202b (convex portion) of the lock member 202 is fitted into the roller shaft groove 203a (concave portion), the shutter 201 cannot rotate. In this way, the posture of the lock member in a state where the shutter 201 is locked is defined as the first posture. That is, the shutter 201 is held in the first posture by the rib 202b engaging with the groove 203a.

  As described above, when the sheet S forms a loop and the skew is corrected, the sheet S presses the sheet abutting surface 202a of the lock member 202 while abutting the sheet abutting surface 201a. . When the sheet S pushes up the lock member 202 as shown in FIG. 3B and the sheet abutting surface 202a of the lock member 202 moves to the same position as the sheet-attached contact surface 201a in the conveying direction, the rib 202b of the lock member is moved. The roller shaft is disengaged from the groove 203a. As a result, the shutter 201 can rotate. As described above, the posture in which the shutter 201 is rotatable is set as the second posture.

  Then, as shown in FIG. 3C, the sheet S whose skew has been corrected enters the registration roller nip portion.

  Next, after passing through the sheet S, since the position of the center of gravity of the lock member 202 is at the position G in FIG. 3C, the lock member 202 moves by its own weight to the lock standby position in FIG.

  In this embodiment, the lock member 202 returns to the lock position by its own weight, but may be configured to apply a force by a spring to return to the standby position.

  In order to increase the skew correction capability, the sheet abutting surfaces 201a, 201b, 201c, and 201d need to be unlocked at the same position in the sheet conveying direction, and the accuracy is required. By providing a plurality of lock mechanisms, the correction capability can be increased. Next, a configuration in which a plurality of lock mechanisms are provided will be described with reference to FIG.

  As shown in FIG. 4A, a plurality of lock mechanisms 400 and 401 are provided in the sheet width direction so that the shutter 201 does not rotate unless all the locks are released.

  FIG. 4B is a top view showing a case where there is one lock member. It can be seen that the greater the positional variation δ of the sheet abutting surface 202a of the locking member with respect to the sheet abutting surface 201a, the greater the inclination θ1 of the sheet S and the lower the correction capability. FIG. 4C is a top view of the two locking members in FIG. The sheet width direction distance A2 between the abutting surface 201a and the sheet abutting surface 401a of the lock member is increased. For this reason, even if the conveyance direction position variation δ of the sheet abutting surface 401a is the same as that in FIG. 4B with respect to the sheet abutting surface 201a, the inclination θ2 of the sheet S is smaller than θ1, and the component variation It can be seen that the impact can be reduced.

  That is, by providing a plurality of locking mechanisms, the sheet width direction distance A2 between the sheet abutting surface 201a and the sheet abutting surface 401a is increased, thereby reducing the influence of component variations in the sheet conveying direction and increasing the correction capability. Things will be possible.

[Second Embodiment]
A laser beam printer according to another embodiment of the present invention will be described. This embodiment is different from the first embodiment only in the configuration of the registration roller unit. Parts that are the same as or similar to those in the first embodiment are given the same reference numerals, and redundant descriptions are omitted. In this embodiment, a rotating shutter is provided with a lock function.

  FIG. 5A is a perspective view of a registration roller unit according to the present embodiment, and FIG. 5B is an enlarged perspective view of a lock mechanism portion of the registration roller unit.

  As shown in the figure, four rotary shutters 501 for correcting the skew of the sheet S are fixed to a registration roller shaft 500 (axis). The rotary shutter 501 is provided with four shutter-attached contact surfaces 501a every 90 degrees in the rotation direction. The skew of the sheet is corrected by the front end of the sheet S coming into contact with the shutter abutting surface 501a.

  A roller 510 is rotatably attached to the registration roller shaft 500. A lock claw 509 is fixed to the registration roller shaft 500. Further, a lock member 505 is rotatably attached to the registration roller shaft 500 by a slight angle.

  FIG. 5C is a side view showing the configuration of the lock member 505.

  As shown in the figure, the lock member 505 is provided with a groove 505c, and a parallel pin 500a fixed to the registration roller shaft 500 is fitted in the groove. Since there are gaps in the parallel pins 500a and the grooves 505c, the registration roller shaft and the lock member can be attached so as to be rotatable within a predetermined angle range. For this reason, the lock member 505 can swing a predetermined angle with respect to the registration roller shaft 500, but rotates integrally with the registration roller shaft 500 beyond the swing region.

  A rotational force is transmitted from the registration gear 504 to the registration roller shaft 500. Further, the registration gear 504 and the registration roller shaft 500 are connected via a torque limiter. As a result, in a state where a certain load or more is applied to the registration roller shaft 500, even if the driving force is transmitted to the registration gear 504, the registration gear 504 only rotates and the registration roller shaft 500 does not rotate. That is, the rotational force is transmitted to the registration roller shaft 500 via the torque limiter that transmits the rotational force only when a certain force or less is applied. Further, the registration gear 504 meshes with the gear 503 to transmit the driving force.

  The lock member 505 is positioned at the standby position by the biasing force of the coil spring 506. The urging force of the coil spring 506 is set to a magnitude that can be swung from the standby position when the lock member 505 is pushed by the seat.

  Around the lock member 505, four cam portions 505b and four sheet abutting surfaces 505a are provided every 90 degrees in the rotation direction. On the other hand, the lock claw 509 is provided with four claw portions 509a every 90 degrees in the rotation direction.

  Further, a lever 507 is attached to the main body of the laser beam printer so as to be swingable about the shaft 520. The lever 507 is biased to the lock position by a lever spring 508.

  Next, the skew correction operation of the registration roller unit will be described.

  When the skewed sheet S is conveyed, it first hits the shutter-equipped contact surface 501a. Then, the rotary shutter 501 is locked by a lock mechanism, and the sheet S that abuts forms a loop. Accordingly, the skew of the sheet S is corrected, and when the sheet is pushed to the same position in the conveyance direction of the abutting surface 501a of the rotary shutter 501, the lock mechanism is unlocked and the rotary shutter is released. 501 rotates. When the sheet S releases the lock member 505 in this way, the skew of the sheet S is corrected.

  Next, the operation of the locking mechanism will be described with reference to FIG.

  FIG. 6A is a cross-sectional view of the standby position of the lock portion, and shows a view showing the standby position of the lock member 505. The lever 507 includes a first arm 507c and a second arm 507d. The first arm 507c is provided with a protrusion 507a (first protrusion), and the second arm is provided with a protrusion. 507b (second protrusion) is provided.

  When the protrusion 507b of the lever 507 hits the cam 505b of the lock member 505, the lever 507 rotates about the shaft 520 in the clockwise direction in the drawing. Then, the protrusion 507a of the lever 507 is engaged with the claw 509a of the lock claw 509 and the rotation is restricted, and the registration roller shaft 500 does not rotate. At this time, the rotational force is transmitted to the registration gear 504, but the rotation is not transmitted to the registration roller shaft 500 by the torque limiter. Similarly, the rotary shutter 501 attached to the registration roller shaft 500 cannot rotate as well. At this time, the sheet abutting surface 505a of the lock member 505 is disposed on the upstream side in the transport direction of the sheet S with respect to the shutter-equipped abutting surface 501a due to the ineffective force of the coil spring 506.

  Next, the unlocking operation will be described. FIG. 6B is a diagram illustrating a release position of the lock mechanism.

  When the sheet S forms a loop and the skew is corrected, the leading edge of the sheet S hits the shutter abutting surface 501a and pushes the sheet abutting surface 505a of the lock member to release the lock. That is, when the leading edge of the sheet S pushes the sheet abutting surface 505a of the lock member 505, the lock member 505 swings, the lever 507 rotates counterclockwise, and the protrusion 507b becomes the cam portion 505b of the lock member 505. Get over. As a result, the protrusion 507 a is detached from the claw 509 a of the lock claw 509 by the action of the lever spring 508. Therefore, the registration roller shaft 500 can be rotated, and the rotary shutter 501 can also be rotated in the same manner.

  Next, the operation after the lock is released will be described. FIG. 6C is a diagram showing the lock mechanism in a state after the lock is released.

  When the lock mechanism is unlocked, the registration roller shaft 500 to which the rotational force is transmitted via the torque limiter can be rotated. Then, the lock claw 509, the lock member 505, and the rotary shutter 501 rotate integrally with the registration roller shaft 500, so that the sheet S whose skew has been corrected can pass through the registration nip portion. When the sheet S passes through the registration nip portion, the lock claw 509, the lock member 505, and a part of the rotary shutter 501 are in contact with the upper surface of the sheet S, and further rotation is restricted by the torque limiter. Is done.

  Next, the operation of the lock mechanism after the lock is released and the sheet S passes will be described.

  When the trailing edge of the sheet S passes the registration nip portion, the lock claw 509 and the lock member 505 rotate again counterclockwise, and the cam portion 505b of the lock member 505 pushes the projection portion 507b of the lever 507. For this reason, the lever 507 rotates clockwise, and the projection 507a is engaged with the claw 509a of the lock claw 509, and is locked again to the state shown in FIG. 6A, and the rotary shutter 501 is moved to the next sheet S2. Be prepared for the rush.

[Third Embodiment]
A laser beam printer according to another embodiment of the present invention will be described. This embodiment is different from the first embodiment only in the configuration of the registration roller unit. Parts that are the same as or similar to those in the first embodiment are given the same reference numerals, and redundant descriptions are omitted. In this embodiment, a crank mechanism is used for the rotary shutter.

  FIG. 7A is a perspective view of the registration roller unit according to this embodiment. For ease of explanation, the conveyance frame 700 is partially cut.

  First, the configuration will be described first. In the present embodiment, four crank shutters 701 that correct the skew of the sheet S and are pivotally supported by the conveyance frame 700 are provided. The crank shutter 701 is provided with a sheet abutting surface 701a that is a surface for correcting the skew of the sheet S. Then, a driving force from a driving source (not shown) is transmitted to the registration roller unit by the registration roller gear 702. The crankshaft 703 is provided to rotate the crank shutter 701. Further, the crankshaft gear 704 is provided with a torque limiter that applies a constant rotational driving force to the crankshaft 703 and prevents transmission of the driving force when the load is above a certain level.

  FIG. 7B is an enlarged view of the lock mechanism of the registration roller unit shown in FIG.

  A crank lock member 705 (lock member) attached to the crank shaft 703 so as to be rotatable by a certain amount is provided. The coil spring 709 biases the crank lock member 705 to the standby position. The lever 706 is swung by a crank lock member 705 and is rotatably attached to the laser beam printer main body about the shaft 710. The lever 706 includes a first arm 706c and a second arm 706d. The first arm 706c is provided with a protrusion 706a (first protrusion), and the second arm is provided with a protrusion. 706b (second protrusion) is provided.

  The lever 706 is biased to the locked position by the lever spring 707. Further, a lock claw 708 is fixed to the crankshaft 703.

  Next, the skew correction operation of the sheet S by the registration roller unit will be described.

  When the skewed sheet S is conveyed, the leading end of the sheet S first hits the sheet contact surface 701a. Since the crank shutter 701 is locked by the lock mechanism, the sheet S forms a loop. Further, the sheet S is conveyed to correct the skew of the sheet S, and the lock is released by pushing the sheet abutting surface 705a of the crank lock member 705 to the same position in the conveying direction of the abutting surface 701a of the crank shutter 701. 701 rotates. That is, when the sheet S pushes the crank lock member 705, the skew of the sheet S is corrected.

  Next, the configuration of the crank shutter 701 will be described with reference to FIG.

  A crank 800 is fixed to the crankshaft 703, and the crank 800 can rotate integrally with the shaft 703 around the crankshaft 703. Further, the crank 800 is provided with a shaft 810 at a position eccentric from the rotation center of the crankshaft 703. The crank shutter 701 is pivotally attached to the shaft 810 so as to be rotatable. The crank shutter 701 is provided with a slit 720, and a fixed shaft 900 fixed to the transport frame 700 is movably inserted into the slit 720. Therefore, the crank shutter 701 swings up and down according to the rotation of the crank 800.

  FIG. 8A is a diagram illustrating a standby position of the crank shutter 701.

  Before the sheet S reaches the sheet abutting surface 701a of the crank shutter 701, the sheet S is prepared for sheet entry at the position shown in FIG. At this time, the registration roller unit is in a locked state, and when the leading edge of the sheet S reaches the sheet abutting surface 701a, the sheet S forms a loop.

  FIG. 8B is a diagram illustrating a lock release position of the lock mechanism.

  As shown in the figure, after the sheet S reaches the sheet abutting surface 701a and a loop is formed, the sheet abutting surface 705a of the crank lock member 705 is pushed. Although details will be described later, the lock mechanism is unlocked by this. Note that the crank shutter 701 is locked until the sheet S pushes the sheet abutting surface 705a of the crank lock member 705. For this reason, the sheet S creates a loop, and the lock is released at a position where the sheet S is aligned with the sheet abutting surface 701a and the sheet abutting surface 705a of the crank lock member 705. For this reason, the skew of the sheet S is corrected.

  FIG. 8C is a diagram illustrating a state in which the crank shutter 701 is opened and the sheet S passes through the registration nip portion.

  When the lock is released, the torque is transmitted to the crankshaft 703 by the torque limiter of the crankshaft gear 704, the crank 800 rotates, and the crank shutter 701 swings. As a result, the sheet abutting surface 701a of the crank shutter 701 moves backward in the conveyance direction, and the sheet S can pass through the registration nip portion.

  FIG. 8D is a diagram illustrating a state in which the sheet S is passing through the crank shutter 701.

  The crank shutter 701 rotates once by the crank 800 and comes into contact with the seat S. However, the crank 800 is idled by the action of a torque limiter provided in the crankshaft gear 704, and the crank shutter 701 remains at the position shown in the figure. Then, after the sheet S passes through the crank shutter 701, the sheet S returns to the standby position in FIG. 8A to prepare for the next sheet S2.

  Next, the operation of the lock mechanism of the registration roller unit will be described with reference to FIG. The operation of the lock mechanism of this embodiment is the same as that of the lock mechanism shown in the second embodiment, but the shapes of the crank lock member 705 and the lock pawl 708 are different.

  FIG. 9A is a diagram illustrating a case where the crank lock member 705 is in the first posture in the standby position.

  Before the sheet S reaches the crank shutter 701, the sheet S is prepared for the entry of the sheet at the position shown in FIG. The protrusion 706a of the lever 706 is locked by the lock claw 708, and the crankshaft 703 does not rotate, and the crank shutter 701 positioned on the crankshaft 703 does not rotate as well.

  FIG. 9B is a diagram illustrating a case where the crank lock member 705 is in the unlocked position.

  When the sheet S pushes the seat abutting surface 705a of the crank lock member 705, the crank lock member 705 rotates counterclockwise to take the second posture, and the protrusion 706b of the lever 706 is the cam portion 705b of the crank lock member. Get over. As a result, the protrusion 706 a is released from the lock claw 708 by the biasing force of the lever spring 707. As a result, the crankshaft 703 can rotate, and the crank shutter 701 can also rotate in the same manner.

  FIG. 9C is a diagram illustrating a state in which the leading edge of the sheet S is in the middle of passing through the crank shutter 701.

  When the lock mechanism is unlocked, the crank lock member 705 is rotated by the torque of the torque limiter provided in the crankshaft gear 704, and the cam portion 705b of the crank lock member 705 contacts the protrusion 706b of the lever.

  FIG. 9D is a diagram illustrating a state in which the rear end of the sheet S is about to pass through the registration nip portion.

  As shown in the figure, the cam portion 705 b of the crank lock member 705 pushes the projection 706 b of the lever 706, whereby the lever 706 rotates counterclockwise, and the projection 706 a of the lever 706 contacts the position of the lock claw 708. Move to lock. As a result, the crank shutter 701 is locked to prepare for the skew correction operation of the next sheet S2.

<Other configurations>
As described above, by providing the lock mechanism on the shutter, skew can be corrected regardless of the basis weight of the sheet. There is no need for user settings as in the prior art.

  The shutter configurations shown in the first embodiment, the second embodiment, and the third embodiment described above are one example, and other shutter configurations that perform skew correction by abutting a sheet against the shutter. Even so, the present invention is widely applicable.

DESCRIPTION OF SYMBOLS 103 ... Feed roller pair 104 ... Registration roller unit 201 ... Shutter 201a, 201b, 201c, 201d ... Sheet abutting surface 202 ... Locking member 202a ... Sheet abutting surface 203 ... Roller shaft 204 ... Roller 206 ... Registration roller 400, 401 ... Locking member 500 ... Registration roller shaft 501 ... Rotating shutter 501a, 501b, 501c, 501d ... Shuttering contact surface 502 ... Registration roller 505 ... Rotation locking member 505a ... Sheet abutting surface 505b ... Cam portion 507 ... Lever 509 ... Lock claw 700 ... Conveying frame 701 ... Crank shutter 701a, 701b, 701c, 701d ... Abutting surface 705 ... Crank lock member 705a ... Sheet abutting surface 705b ... Cam portion 706 ... Lever 707 ... Lever spring 708 ... Lock claw

Claims (11)

First transport driving means for transporting the sheet so as to transport the sheet along the transport path;
A first posture which is provided in the conveyance path on the downstream side in the sheet conveyance direction of the first conveyance driving unit and can be brought into contact with and locked to the leading end of the sheet which is driven and conveyed by the first conveyance driving unit. And a shutter member that can swing between a second posture that allows the sheet to pass therethrough,
A locking mechanism that locks the shutter member so as to hold the first posture, wherein the shutter member is moved to the second posture when a front end of the sheet contacts and presses a part of the locking mechanism; And a lock mechanism for releasing the lock so that the sheet can be taken.   The sheet conveying apparatus according to claim 1, wherein a plurality of the shutter members are provided in a width direction of the sheet.   The sheet conveying apparatus according to claim 1, wherein the lock mechanism is provided at a substantially central portion in the width direction of the sheet.   The lock mechanism is provided in a plurality in the width direction of the sheet, and the lock of the shutter member is released when all the locks of the plurality of lock mechanisms are released. The sheet conveying apparatus according to claim 2.   The position in the sheet conveying direction where the shutter member contacts the leading edge of the sheet and the position in the sheet conveying direction where the part of the locking mechanism contacts the leading edge of the sheet and the lock is released are the same position. The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is a sheet conveying apparatus.   6. The lock mechanism according to claim 1, wherein after the lock is released, the lock member locks the shutter member again before the leading edge of the next sheet reaches the shutter member. 6. The sheet conveying apparatus according to 1.   2. The apparatus according to claim 1, further comprising a second conveyance driving unit that conveys and drives the sheet that has passed through the shutter member, and the second conveyance driving unit includes a registration roller and a registration roller. Item 7. The sheet conveying device according to any one of Items 6 above. The shutter member is supported rotatably about the axis of the registration roller, and is configured to be able to take the first posture and the second posture,
The lock mechanism is rotatably supported by the shutter member and has a lock member having a convex portion,
The shaft of the registration roller has a recess for locking the projection.
The convex portion of the lock member and the concave portion of the shaft of the registration roller are locked to be locked, and the tip of the sheet comes into contact with and presses a part of the lock member from the concave portion. The sheet conveying apparatus according to claim 7, wherein the convex portion is released and the lock is released. The locking mechanism is
A lever provided with a first arm provided with a first protrusion and a second arm provided with a second protrusion and provided swingably;
A locking claw that is fixed to the shaft of the registration roller and that controls the rotation of the registration roller by engaging with the first protrusion;
The shaft of the registration roller is supported so as to be rotatable within a certain angular range, and is in contact with a sheet abutting portion for abutting the front end of the sheet around and the second projecting portion. A locking member having a cam portion for swinging the lever,
The rotational force is transmitted through a torque limiter that transmits the rotational force only when a certain force or less is applied to the shaft of the registration roller.
When the sheet abuts against the sheet abutting portion, the lock member rotates about the axis of the registration roller, so that the cam portion swings the lever, and the first protrusion portion The sheet conveying apparatus according to claim 7, wherein the sheet conveying device is released from the lock claw and unlocked. A crank that is rotatably supported integrally with the shaft about the axis of the registration roller;
2. The shutter member according to claim 1, wherein the shutter member is pivotally attached to the crank at a position eccentric from a rotation center of the crank, and is swingable between the first posture and the second posture by the rotation of the crank. The sheet conveying apparatus according to any one of claims 7 to 9. A sheet conveying device according to any one of claims 1 to 10,
An image forming apparatus comprising: an image forming unit that forms an image on a sheet conveyed by the sheet conveying apparatus.

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