JP5455704B2 - Conveying device and image forming apparatus provided with the conveying device - Google Patents

Description

  The present invention relates to a conveying device that conveys a sheet such as paper while correcting skew feeding, and an image forming apparatus including the conveying device.

  In electrophotography, a toner image (developer image) is formed on a photoreceptor (image carrier) through various processes such as charging, exposure, and development, and the toner image (developer image) is transferred to a sheet such as paper and heated and pressed. Thus, an image is formed on the sheet. At this time, the sheet is conveyed while being nipped by a pair of rollers disposed on the conveyance path.

  The sheet is conveyed obliquely on the conveyance path because it is supplied obliquely when picked up from a paper feed cassette or the like, and the roller diameter of the upstream conveyance unit is formed uneven in the axial direction. May end up. Such a conveyance state is called skew. In order to correct the skew of the sheet, the rotation of a roller pair called a registration roller pair is temporarily stopped on the sheet conveyance path upstream from the transfer position of the toner image, and the leading edge of the sheet is placed at the roller nip of the registration roller pair. The sheet is distorted by a pair of conveying rollers (pre-registration roller pair) disposed on the upstream side of the conveying path from the abutting and registration roller pair, thereby forming a loop (registration loop). The skew is corrected by turning the sheet by the formed loop.

  By the way, in the case of a thick and strong sheet such as thick paper, when the sheet skews and hits the registration roller, the leading edge of the sheet may bite into the roller nip of the registration roller pair. Since it does not contact the roller nip, skew cannot be corrected sufficiently. Further, even in the case of a sheet having low rigidity such as thin paper, the sheet may bite into the roller nip due to the thinness of the sheet, and similarly skew cannot be corrected sufficiently.

  In order to solve this problem, there has been proposed a conveying apparatus having a function of reversing the registration roller pair to release the biting of the leading edge of the sheet by reversing the registration roller driving motor that drives the registration roller pair ( Patent Document 1).

Patent No. 4016621

  The sheet biting release mechanism by reversing the registration roller pair described above reverses the registration roller drive motor after the sheet abuts the roller nip, releases the bite at the leading edge of the sheet, and then forwards the sheet by forward rotation. To do. However, when the rotation of the registration roller drive motor is switched from reverse rotation to normal rotation, it is necessary to wait for the motor settling time as shown in FIG. By waiting for this settling time, the sheet interval is increased, and there is a possibility that productivity (the number of prints per unit time) is reduced.

  The present invention has been made in view of the above circumstances, and does not require the reverse rotation of the motor for the bite release operation of the sheet leading edge, that is, skew correction that does not require settling time as shown in FIG. 7B. It is an object of the present invention to provide a transport device to be performed and an image forming apparatus including the transport device.

  The above object is achieved by a transport device according to the present invention and an image forming apparatus including the transport device. In summary, the present invention includes a first roller and a second roller that forms a nip between the first roller and a pair of registration rollers disposed on a sheet conveyance path. A driving gear that is rotationally driven by a motor; and a driving force transmission gear mechanism that includes a driven gear that is coaxially fixed to the first roller and coaxial with the first roller. Via a driving force transmission gear mechanism for transmitting a driving force from the driving gear to the first roller via an upstream side of the sheet conveying path that is disposed upstream of the registration roller pair and conveys the sheet. A sheet conveying means, and with the drive gear stopped rotating, the leading edge of the sheet conveyed by the upstream conveying means is brought into contact with the nip to form a loop on the sheet, and then the driving Drive the gears forward In the conveyance device that conveys the sheet while being nipped by the nip by rotating the driven gear forward, it is a link member that rotatably supports the first roller and supports the driving force transmission gear mechanism. A link supported on the shaft coaxial with the drive gear so as to be swingable between the first position and the second position while the first roller is in contact with the second roller. The link member is moved to the second position when viewed from the first position in a state where the drive gear is stopped rotating and the leading end of the sheet is in contact with the nip. The first driving roller is reversely rotated through the gear mechanism by the drive gear that is rotated in the direction of rotation, and the drive is performed after the link member is swung toward the second position. Rotate the gear to drive the nip Initiating the conveying of the sheet by, providing a conveying apparatus according to claim.

  As described above, according to the present invention, it is possible to reverse the registration roller pair without using the reverse rotation control of the driving motor of the registration roller pair, and thereby, the registration roller is driven immediately after the loop is formed. Is possible.

1 is an overall view showing an example of an image forming apparatus provided with a conveying device according to the present invention. The structure schematic (perspective view) of the conveying apparatus according to this invention. 1 is a schematic configuration diagram (a perspective view and a synchronous configuration) of a transport device according to the present invention. FIG. 3 is a schematic configuration diagram of a roller reverse mechanism of the transport device shown in the first embodiment. The control block diagram of the conveying apparatus according to this invention. The flowchart which shows the operation | movement flow of the conveying apparatus according to this invention. The figure which shows the operation timing of a pre-registration roller pair and a registration roller pair. FIG. 6 is a schematic configuration diagram of a roller reverse mechanism of the transport device shown in the third embodiment. FIG. 9 is a schematic configuration diagram of a roller reverse mechanism of the transport device shown in the fourth embodiment. FIG. 9 is a schematic configuration diagram of a roller reverse mechanism of the transport device shown in the fifth embodiment. FIG. 6 is a schematic configuration diagram of a roller reverse mechanism of the transport device shown in the second embodiment. FIG. 10 is a schematic configuration diagram of a roller reversing mechanism of the transport device shown in the sixth embodiment.

[Example 1]
Embodiment 1 of the present invention will be described below. The image forming apparatus shown in FIG. 1 has a tandem-type image having each color image forming unit for forming toner images of cyan, magenta, yellow, and black toners along a transfer belt 6 that is an intermediate transfer member. Forming device. The charging devices 2a, 2b, 2c and 2d charge the surfaces of the photoreceptors (image carriers) 1a, 1b, 1c and 1d corresponding to the respective color image forming units, and the charged photoreceptors are exposed to the exposure devices 3a and 3b. By exposing 3c and 3d, an electrostatic latent image is formed on the surface of each photoreceptor. The formed electrostatic latent image is developed by the developing devices 4a, 4b, 4c, and 4d to form toner images of respective colors. The respective color toner images are sequentially superimposed and transferred from the photoreceptors 1a, 1b, 1c, and 1d to the transfer belt 6 by primary transfer rollers 5a, 5b, 5c, and 5d. On the other hand, a recording sheet (sheet) as a final transfer body is separated and fed one by one by a sheet feeding device 7 from a stacked sheet bundle before printing, and is conveyed by a conveyance roller disposed on a conveyance path. It is conveyed to the secondary transfer roller 10. In the secondary transfer roller 10, the toner images in which the respective color toner images are superimposed are transferred onto the sheet, and the toner is fixed by heat and pressure by the fixing device 11. The sheet with the image formed on the surface by heat fixing is discharged by the discharge unit 12.

  The plurality of conveyance roller pairs arranged on the sheet conveyance path nipping the sheet at the roller nip and rotating the roller pair conveys the sheet to the downstream of the conveyance path. The pre-registration roller pair 8 (upstream conveying means) and the registration roller pair 9 that are upstream of the conveyance path of the secondary transfer roller 10 among these conveyance roller pairs correct the skew of the sheet and perform the secondary transfer that is the transfer position of the sheet. Transport to roller 10.

  FIG. 2 shows a schematic diagram of the configuration of the transport device according to the present invention. The conveying device according to the present invention includes a pre-registration roller pair 8 that nipped and conveys the sheet 13 fed from the sheet feeding device 7 and a registration unit 900 that corrects skew by forming a registration loop by abutting the leading end of the sheet 13. And a registration loop space 91 formed between the two opposing sheet guide plates for forming the registration loop.

  The registration unit 900 sandwiches a sheet and conveys it to a secondary transfer roller 10 that is a transfer position downstream of the conveyance path, a registration motor gear 902 (drive gear), and a registration roller drive gear 903 (driven gear). A registration roller drive motor 904 (motor), a registration roller link 905 (link member), and an urging spring 906. Further, the registration unit 900 includes a pre-registration sensor 920 that detects the presence or absence of a sheet on a conveyance path between the pre-registration roller pair 8 and the registration roller pair 9. The registration roller pair 9 is pressed by a registration driving roller 9a (first roller) driven by a registration roller driving motor 904 and a spring (not shown) against the registration driving roller 9a, and the registration driving roller 9a surface or sheet It is comprised from the resist driven roller 9b (2nd roller) driven by the frictional force via.

  The registration motor gear 902 is driven by a registration roller driving motor 904, meshes with a registration roller driving gear 903 that is coaxial with the registration driving roller 9a and fixed to the registration driving roller 9a, and drives the registration driving roller 9a to rotate forward. . The registration roller links 905 are disposed at both ends of the registration driving roller 9a, rotatably support the registration driving roller 9a and the registration roller driving gear 903, and can swing on a swing shaft 921 coaxial with the registration motor gear 902. It is supported by. However, the position of the swing shaft 921 of the registration roller link 905 is such that the registration drive roller 9a rolls on the surface of the registration driven roller 9b when the registration drive roller 9a swings along with the swing of the registration roller link 905. It is prescribed. Therefore, the rocking shaft 921 of the registration roller link 905 is positioned coaxially or in the vicinity of the rotation shaft of the roller 9b.

  FIG. 4 shows a schematic configuration diagram of a roller reverse mechanism of the transport device described in this embodiment. The registration roller link 905 swings between a first position upstream in the sheet conveyance direction and a second position downstream in the sheet conveyance direction. In the first position, the registration roller link 905 abuts against the first stopper 911a provided on the conveyance apparatus main body side plate, so that the registration driving roller 9a cannot move upstream of the first stopper 911a in the sheet conveyance direction. So that it is regulated. The registration roller link 905 is connected to an urging spring 906 that is fixed to the apparatus main body side plate 910. The urging force of the urging spring 906 makes contact with the first stopper 911a when the sheet is not being conveyed. It is biased to position 908a. In the second position, similarly to the first position, a second stopper 911b is provided on the conveyance apparatus main body side plate, and the registration roller link 905 is located downstream of the second stopper 911b in the sheet conveyance direction. Are restricted from moving. Note that the registration roller link may be positioned at the first and second positions so that the rotation shaft of the registration driving roller 9a abuts against the first and second stoppers instead of the registration roller link 905.

  In the case of the apparatus of FIG. 2, when a situation occurs in which the phase of the swing of the registration roller link 905 is not synchronized at both ends of the registration drive roller 9a, the registration drive roller 9a and the registration driven roller 9b are moved when the registration roller link 905 swings. May be twisted. This problem is solved by a mechanism using a registration drive synchronization axis 901 as shown in FIG. A gear 901a and a gear 901b are fixed to both ends of the registration drive synchronization shaft 901, the gear 901a meshes with the registration motor gear 902, and the gear 901b meshes with the idler gear 902b. The idler gear 902b meshes with the registration roller synchronous drive gear 903b. The registration roller synchronous drive gear 903b is fixed to the registration drive roller 9a coaxially with the registration drive roller 9a. With this configuration, the oscillating phases of the registration roller links 905 on both sides of the registration driving roller 9a when the rotation of the registration roller driving motor 904 is stopped are synchronized. The synchronization means is not limited to this, and for example, the idler gear 902b may be driven by a motor instead of the registration drive synchronization shaft 901. When the motor rotates, the registration roller synchronous drive gear 903b of FIG. 3 rotates, and the registration drive roller 9a is driven to rotate at both ends. If the rotation of the idler gear 902b and the registration motor gear 902 by the motor and the registration roller driving motor 904 are synchronized and stopped, the phase of the oscillation of the registration roller link 905 is synchronized at both ends of the registration driving roller 9a.

  The registration roller pair 9 is driven forward by a registration roller driving motor 904 (the registration driving roller 9a is rotated counterclockwise and the registration driven roller 9b is rotated clockwise in FIGS. 2 and 3), and the sheet is conveyed to the secondary transfer roller 10. To do.

  In correcting the skew of the sheet, first, the rotation of the registration roller driving motor 904 is stopped, the rotation of the registration roller pair 9 is stopped, and the sheet is abutted against the nip of the registration roller pair 9. The registration roller pair 9 that is not rotationally driven in the normal rotation direction functions as an abutting member, and the sheet 13 that is in contact with the nip of the registration roller pair 9 is continuously conveyed by the pre-registration roller pair 8 and is curved in the registration loop space 91 to be registered loop. Form. The skew of the sheet 13 is corrected by turning the pushing force of the registration loop so that the leading edge of the sheet 13 is parallel to the registration roller pair 9. Thereafter, the registration roller pair 9 and the pre-registration roller pair 8 are simultaneously driven to rotate forward, and the sheet 13 is conveyed downstream in the sheet conveying direction.

  In the conventional skew correction of the registration roller pair, when the conveyed sheet comes into contact with the nip of the registration roller pair, the leading edge of the sheet bites into the nip. May be. In this embodiment, the registration driving roller 9a is rotated in the reverse direction (rotation in the direction opposite to the normal rotation direction) by the stiffness of the sheet 13 where the leading edge of the sheet 13 presses the registration driving roller 9a, which increases as the registration loop grows. Then, the biting of the leading end of the sheet 13 into the registration roller pair 9 is released.

  Details of the bite release operation of this embodiment will be described below. 4 is a side view seen from the direction of arrow F in the perspective view of FIG.

  In this embodiment, in the loop formation period of FIG. 7B, the leading end of the sheet 13 comes into contact with the nip of the registration roller pair 9 whose rotation has stopped, and a registration loop is formed. In the process of forming the registration loop, the force (abutting force) that pushes the nip at the leading end of the sheet 13 urges the registration roller link to the first position 908a by the urging force of the urging spring 906 or the weight of the registration driving roller 9a. When the force is exceeded, during the reverse rotation period of FIG. 7B, the registration roller link 905 starts to swing from the first position 908a in the direction of the arrow 907a around the swing shaft 921, as shown in FIG. To do. The registration roller link 905 swinging in the direction of the arrow 907a is stopped at the second position 908b by the second stopper 911b. The registration driving roller 9a supported by the registration roller link 905 is also in contact with the registration driven roller 9b about the swing shaft 921 as the registration roller link 905 swings, and the first position 908a of the registration roller link 905 is maintained. From the first position corresponding to the second position 908b of the registration roller link 905 to the second position corresponding to the second position 908b. The registration roller drive gear 903 fixed coaxially to the registration drive roller 9 a is also engaged with the registration motor gear 902 around the swing shaft 921 of the registration roller link 905, and the first of the registration roller link 905. Swings from a first position corresponding to the second position 908 a to a second position corresponding to the second position 908 b of the registration roller link 905. When the registration roller driving gear 903 swings, the registration motor gear 902 engaged with the registration roller driving gear 903 is stopped, so that the registration roller driving gear 903 itself swings while being reversed. That is, the resist driving roller 9a also reverses. When the registration driven roller 9b is a driven roller, the registration driven roller 9b is also rotated in the reverse direction following the registration driving roller 9a. Therefore, as shown in FIG. 4, the new nip of the registration roller pair 9 when the registration roller link 905 is at the second position 908b is downstream of the nip when the registration roller pair 905 is at the first position 908a. However, the leading edge of the sheet 13 that has been caught is discharged upstream of the position of the new nip due to the reverse rotation of the registration driving roller 9a. Then, the skew correction of the sheet 13 is appropriately performed due to the disappearance of the leading edge portion.

  In this way, the registration roller link 905 is swung using the stiffness of the sheet to perform the reverse operation of the registration drive roller 9a, thereby preventing or canceling the biting without reversing the registration roller drive motor 904, The skew can be corrected. In this embodiment, the registration motor gear 902 and the registration roller driving gear 903 have the same number of teeth. However, as long as the registration driven roller 9b is driven by the registration driving roller 9a, the registration roller gear 902 has more teeth than the registration motor gear 902. By designing the number of teeth of the drive gear 903 to be small, the amount of reverse rotation of the registration drive roller 9a can be increased.

  After the skew correction of the sheet 13, the registration roller drive motor 904 and a pre-registration drive motor 801 (not shown) are simultaneously driven to rotate forward. Since the maximum value T1 from the time t1 when the leading edge of the sheet 13 is detected by the pre-registration sensor 920 to the time when the registration driving roller 9a reaches the second position is known in advance, the timer T1 + α (α When a very short time) is counted, the registration roller pair 9 and the pre-registration roller pair 8 are started to rotate forward, and the sheet 13 is conveyed to the transfer position downstream in the conveyance direction. When the trailing edge of the sheet 13 passes through the pre-registration roller pair 8 and the registration loop of the sheet 13 disappears, the stiffness of the sheet 13 pressing the registration roller pair 9 is lost, but the registration roller link is caused by the rotational driving force applied to the registration roller driving gear 903. 905 and the resist drive roller 9a continue to hold the second positions against the pulling force of the biasing spring 906. In the sheet conveyance, a sufficient time T2 from the time t2 when the trailing edge of the sheet 13 is detected by the pre-registration sensor 920 until the trailing edge of the sheet 13 passes through the nip of the registration roller pair 9 is known in advance. When the time T2 is counted from the time point t2, the registration roller driving motor 904 is stopped, and the registration roller link 905 is rotated in the direction to be urged to the first position 908a by the urging spring 906, so that the next sheet Waits at the first position 908a until it is conveyed to the nip. That is, the resist driving roller 9a also stands by at the first position.

  A control block diagram of the present embodiment is shown in FIG. The control unit 999 includes a CPU, a ROM, and a RAM. A signal from the pre-registration sensor 920 is input to the control unit 999. The control unit 999 controls driving of a pre-registration drive motor 801 and a registration roller drive motor 904 (not shown) for driving the pre-registration roller pair 8. In this embodiment, stepping motors are used as the pre-registration drive motor 801 and the registration roller drive motor 904. The operation will be described with reference to the flowchart of FIG.

  The control unit 999 drives the pre-registration drive motor 801 to rotate the pre-registration roller pair 8 (S101a). At the stage of S101a, the registration roller pair 9 stops rotating, and the registration roller link 905 is positioned at the first position 908a by the biasing force of the biasing spring 906.

  It is determined whether or not the leading edge of the sheet conveyed using the pre-registration roller pair 8 is detected by the pre-registration sensor 920 (S102a). If the front edge of the sheet is detected by the pre-registration sensor 920, the pre-registration drive motor 801 is rotated by p1 steps so that a predetermined amount of registration loop is formed (S104a), and then the rotation of the pre-registration roller pair 8 is stopped (S107a). ). At the stage between S102a and S107a, the leading edge of the sheet 13 hits the registration roller pair 9 to form a registration loop, and the registration roller link 905 is swung to the second position 908b by the stiffness of the sheet. . As the registration roller link 905 swings, the registration driving roller 9a reverses, and the biting of the sheet leading edge into the nip is released. The skew correction of the sheet 13 is performed by the pushing force of the sheet 13 into the nip by the registration loop.

  Thereafter, the pre-registration drive motor 801 and the registration roller drive motor 904 are synchronously driven to rotate forward so that the registration roller pair 9 and the pre-registration roller pair 8 start to rotate simultaneously (S108a). The timing at which the registration roller pair 9 and the pre-registration roller pair 8 start to rotate is set to a timing at which the toner image on the transfer belt 6 is transferred to a predetermined position on the sheet 13.

  Thereafter, when it is detected that the trailing edge of the sheet 13 has passed the pre-registration sensor 920, the registration roller driving motor 904 is rotated by r1 steps so that the trailing edge of the sheet 13 passes the nip of the registration roller pair 9. (S109a). When the trailing edge of the sheet 13 passes through the nip of the registration roller pair 9, the driving of the registration roller drive motor 904 is stopped so as to stop the rotation of the registration roller pair 9 (S110a). The control unit 999 determines whether there is a next sheet (S113a). If there is no next sheet, the drive of the pre-registration drive motor 801 is stopped (S114a), and the process is terminated. If there is a next sheet, the process proceeds to S102a.

  In the above description of the present embodiment, the urging spring 906 is used to urge the registration roller link 905 to the first position. The biasing spring 906 is not always necessary if it can be biased to the first position.

[Example 2]
In the conveying apparatus shown in the first embodiment, the urging force of the urging spring 906 is constant regardless of the stiffness of the sheet. However, in an image forming apparatus having an input unit (not shown) that allows a user to input parameters (paper type information) for determining sheet stiffness such as sheet type and basis weight, the biasing spring 906 is attached depending on the stiffness of the sheet to be used. It is good also as a structure which can adjust power. In this embodiment, a configuration is shown in which the biasing force of the biasing spring 906 can be adjusted in accordance with the stiffness of the seat. As a specific method for adjusting the urging force, as shown in FIG. 11, one urging spring 906 is fixed to the urging force adjusting rack 914, and the position of the urging force adjusting rack 914 is urged by a motor (not shown). By moving with the adjustment pinion 915, the tension of the biasing spring 906 can be adjusted. The adjusting means is not limited to this method, and any means may be used.

  The adjustment operation of the urging force of the urging spring 906 by the rack and pinion is performed by means as shown in the control block diagram of FIG. The difference between FIG. 5A and FIG. 5B is that the ROM of the control unit 999 stores a data table in which the paper type information and the rack position of the biasing force adjustment rack 914 are associated with each other, and the control unit. 999 controls the driving of the urging force adjusting motor 916 and determines the rack position of the urging force adjusting rack.

  In the stage before S101a in FIG. 6A, the pulling force of the biasing spring 906 is adjusted according to the input paper type information. That is, when the rigidity of the sheet 13 is strong, the pulling force is increased, and when the rigidity of the sheet 13 is weak, the pulling force is decreased. After this adjustment is completed, the process proceeds to step S101a.

Example 3
In Examples 1 and 2, in the skew correction of the conveying device, the front end of the sheet is brought into contact with the nip, and the registration roller link 905 is swung to the second position 908b by the contact force due to the formation of the registration loop. However, in a sheet with weak stiffness such as thin paper, the contact force cannot always exceed the urging force due to the elasticity of the urging spring 906 and the self-weight of the registration driving roller 9a, and the registration roller link 905 cannot be swung. is there. The present embodiment is an example of a conveying device that can reliably rock the registration roller link 905 and perform the biting release operation even when the sheet is thin paper. Hereinafter, the sheet biting release operation, skew correction, and sheet conveyance will be described in detail. In addition, the thing of the structure similar to Example 1 is demonstrated with the same code | symbol as Example 1. FIG.

  In this embodiment, the urging spring 906 is connected to the urging force releasing solenoid 917 as shown in FIG. In addition, the first position 908a of the registration roller link 905 is positioned upstream of the second position 908b in the sheet conveyance direction, and the registration roller pair 9 is disposed at an angle with respect to the direction of gravity. That is, when the registration roller link 905 is at the first position 908a and the second position 908b, the line connecting the central axes of the registration driving roller 9a and the registration driven roller 9b is inclined with respect to the direction of gravity. The inclination angle is larger when the registration roller link 905 is at the first position 908a than when it is at the second position 908b. The energizing force of the energizing spring 906 is released by cutting off the energization of the solenoid 917 after the sheet 13 abuts the nip of the registration roller pair 9 or immediately before the sheet 13 abuts. The registration roller link 905 is swung from the first position 908a to the second position 908b. By the registration motor gear 902 that has stopped driving, the registration roller driving gear 903 and the registration driving roller 9a are reversed in accordance with the swinging of the registration roller link 905, and the bite of the sheet 13 is released to correct the skew. After the registration roller link 905 reaches the second position 908b, the registration roller drive motor 904 is operated, and the registration motor gear 902 is driven to rotate and the skew-corrected sheet 13 is nipped and conveyed at the nip. In sheet conveyance, when the trailing end of the sheet 13 passes through the nip of the registration roller pair 9, the registration roller drive motor 904 is stopped, the solenoid 917 is energized, and the registration roller link 905 is re-biased by the urging spring 906. As a result, the registration roller link 905 rotates in a direction biased to the first position 908a, and waits at the first position 908a until the next sheet is conveyed to the nip.

  FIG. 5C shows a block diagram of control in this embodiment, and the operation will be described with reference to the flowchart of FIG. 6B. The difference between FIG. 5C and FIG. 5A is that the control unit 999 of this embodiment controls energization of the solenoid 917.

  The control unit 999 drives the pre-registration drive motor 801 to rotate the pre-registration roller pair 8 and excites the solenoid 917 (S101b). The registration roller link 905 is positioned at the first position 908a by the biasing force of the biasing spring 906 by the excitation of the solenoid 917.

  The control unit 999 determines whether the leading edge of the sheet conveyed using the pre-registration roller pair 8 is detected by the pre-registration sensor 920 (S102b). The control unit 999 releases the excitation of the solenoid 917 T seconds after the leading edge of the sheet 13 is detected by the pre-registration sensor 920 (S103b, S104b). The time T seconds until the solenoid 917 is de-energized is the first time when the registration roller link 905 is first before the leading edge of the sheet 13 sent by the pre-registration roller pair 8 contacts the nip of the registration roller pair 9 or after de-energization. It is an appropriate time such that the conveyed sheet 13 comes into contact with the nip during the swing from the first position 908a to the second position 908b. Since the excitation release timing is set in this way, the registration driving roller 9a rotates in the reverse direction while the sheet 13 is in contact, and the sheet biting into the nip can be suppressed or released.

  Then, the pre-registration drive motor 801 rotates by p1 steps so that a predetermined amount of the registration loop is formed without the sheet 13 biting (S105b), and then the rotation of the pre-registration roller pair 8 is stopped (S106b). Thereafter, the control unit 999 drives the pre-registration drive motor 801 and the registration roller drive motor 904 so that the registration roller pair 9 and the pre-registration roller pair 8 start to rotate (S107b). Note that the excitation of the solenoid 917 may be canceled between S106b and S107b. Even if the bite of the sheet 13 is released in a state where the registration loop is completed in the step S106b, the skew can be corrected by the stiffness of the sheet. Further, the timing at which the registration roller pair 9 and the pre-registration roller pair 8 start to rotate is set to a timing at which the image on the transfer belt 6 is transferred to a predetermined position on the sheet 13.

  Thereafter, when it is detected that the trailing edge of the sheet 13 has passed the pre-registration sensor 920, the registration roller driving motor 904 is rotated by r1 steps so that the trailing edge of the sheet 13 passes the nip of the registration roller pair 9. (S108b). When the conveyance of the sheet 13 is completed, the control unit 999 stops driving the registration roller drive motor 904 so as to stop the rotation of the registration roller pair 9 (S109b), re-excites the solenoid 917 (S110b), and proceeds to the next step. Move.

  The control unit 999 determines whether there is a next sheet to be conveyed (S111b). If there is no next sheet, the control unit 999 stops driving the pre-registration drive motor 801 (S112b), and the process is ended. If there is a next sheet, the process proceeds to S102b.

Example 4
In the example of FIG. 8, the configuration in which the registration roller link 905 is swung by the self-weight of the registration driving roller 9 a has been described, but the registration roller link 905 is connected to the second roller as shown in FIG. 9 without depending on the weight of the registration roller. A biasing spring 918 that biases the position 908b may be disposed. The biasing spring 918 connects the apparatus main body side plate 919 and the registration roller link 905. When the registration roller link 905 is at the first position 908a with the solenoid 917 energized, the biasing force of the biasing spring 918 is applied so that the registration roller link 905 does not swing in the direction of the arrow 907a. The urging force is smaller than the urging force of the urging spring 906.

  Although FIG. 9 shows a configuration in which the registration roller link 905 is swung from the first position 908a to the second position 908b by releasing the excitation of the solenoid 917, the registration roller link is excited by exciting the solenoid 917. A configuration may be adopted in which 905 is swung from the first position 908a to the second position 908b. That is, the connection destination of the solenoid 917 in FIG. 9 is the urging spring 918 and the urging spring 906 is connected to the apparatus main body side plate 919. By configuring the biasing force of the biasing spring 918 to be greater than the biasing force of the biasing spring 906, the registration roller link 905 is biased to the first position 908a when the solenoid 917 is de-energized. When the solenoid 917 is excited, it is biased to the second position 908b.

Example 5
In the conveying apparatus described in the first to fourth embodiments, the registration motor gear 902 and the registration roller driving gear 903 are directly meshed with each other, and a driving force transmission gear mechanism (the transmission roller gear 903 is mounted on the registration roller link 905). However, as shown in FIG. 10, the effect of the present invention can be obtained even in a gear mechanism having idler gears 912a and 912b between the registration motor gear 902 and the registration roller driving gear 903, as shown in FIG. Each of the registration roller driving gear 903 and idler gears 912a and 912b constituting the gear mechanism of FIG. 10 is rotatably supported by a frame 913 fixed to the registration roller link 905, and each gear is a registration motor together with the frame 913. It swings around the rotation axis of the gear 902. The respective gears may be supported by the registration roller link 905 without using the frame 913. Further, a gear mechanism that reversely rotates the registration roller driving gear 903 when the registration roller link 905 swings in the direction from the first position 908a to the second position 908b while the driving of the registration motor gear 902 is stopped. In this configuration, the number of idler gears and the like may be determined as an even number. FIG. 10 shows such a gear mechanism applied to the first embodiment, but the gear mechanism may be applied to the second to fourth embodiments.

Example 6
In the first to fifth embodiments, when the registration roller link 905 is swung from the first position 908a on the upstream side in the sheet conveying direction to the second position 908b on the downstream side, the gear is arranged so that the registration driving roller 9a is reversed. The mechanism was configured. However, as shown in FIG. 12, the registration driving roller 9a is positioned downstream in the transport direction, and the registration motor gear 902 and the registration roller driving gear 903 are connected via one or an odd number of idler gears to form a gear mechanism. May be configured. In this example, the registration roller link 905 is inclined in the direction opposite to that in FIG. 8 with respect to the sheet conveyance direction, and the registration driving roller 9a is moved to the second position from the first position toward the upstream side in the sheet conveyance direction by its own weight. Reverses when rocking. In FIG. 12, the registration roller link 905 is swung from the first position 908a to the second position 908b by the self-weight of the registration driving roller 9a. However, as in the fourth and fifth embodiments, the second is applied by the urging force of the urging spring. It may be configured to swing to the position 908b.

9a Registration driving roller 9b Registration driven roller 902 Registration motor gear 903 Registration roller driving gear 904 Registration roller driving motor 905 Registration roller link 906 Biasing spring 911a First stopper 911b Second stopper 914 Biasing force adjustment rack 915 Biasing force adjustment pinion 917 Solenoid 918 Biasing spring 920 Sensor before registration 91 Registration loop space

Claims (6)

A pair of registration rollers disposed on the sheet conveyance path, and a drive gear that is rotationally driven by a motor, and includes a first roller and a second roller that forms a nip between the first roller and the first roller. And a driving force transmission gear mechanism comprising a driven gear that is coaxially fixed to the first roller and coaxial with the first roller, and is driven from the driving gear via the driven gear. A driving force transmission gear mechanism that transmits a force to the first roller; and an upstream conveying unit that is disposed upstream of the registration roller pair in the sheet conveyance path and conveys the sheet. After the rotation of the drive gear stops, the leading end of the sheet conveyed by the upstream conveying means is brought into contact with the nip to form a loop on the sheet, and then the drive gear is rotated to drive the cover. Drive the drive gear forward In conveying apparatus for conveying by nipping the sheet by the nip by,
A link member that rotatably supports the first roller and supports the driving force transmission gear mechanism, and is disposed between a first position and a second position on a shaft coaxial with the driving gear. A link member supported so as to be able to swing while keeping the first roller in contact with the second roller,
With the drive gear stopped and the leading edge of the sheet in contact with the nip, the link member is swung in the direction from the first position toward the second position. Then, after the rotation of the drive gear, the first roller is reversed via the drive force transmission gear mechanism, and the link member swings toward the second position, and then the drive gear is moved. A conveying apparatus characterized in that it is rotationally driven to start conveying a sheet by the nip.   The link member swings in the direction from the first position toward the second position by the force of the sheet pushing the nip, and the trailing end of the sheet passes through the nip and is driven. 2. The conveying device according to claim 1, wherein after the rotation of the gear stops, the conveying device swings from the second position to the first position. First biasing means for resiliently biasing the link member to the first position;
Second urging means for elastically urging the link member in the direction toward the second position by an urging force smaller than the urging force of the first urging means;
Biasing release means for releasing the biasing force of the first biasing means;
Have
When the urging force of the first urging means is released by the urging release means, the link member is urged by the second urging means, and the link member is viewed from the first position. When the operation of the bias release means is stopped, the biasing means is re-biased from the second position to the first position. The conveying device according to claim 1, wherein the conveying device swings. First biasing means for resiliently biasing the link member to the first position;
Second urging means for elastically urging the link member in the direction toward the second position by an urging force larger than the urging force of the first urging means;
Biasing release means for releasing the biasing force of the second biasing means;
Have
The link member is urged by the first urging means when the urging force of the second urging means is released by the urging releasing means, and the link member is viewed from the second position. When the operation of the bias release means is stopped, the bias release means is re-biased from the first position to the second position. The conveying device according to claim 1, wherein the conveying device swings. Biasing means for resiliently biasing the link member to the first position;
An urging release means for releasing the urging force of the urging means;
Have
When the urging force of the urging means is released by the urging release means, the link member swings in the direction from the first position to the second position by the weight of the first roller. Then, when the operation of the urging release means is stopped, the urging force is re-biased by the first urging means and swings from the second position to the first position. Item 2. The transfer device according to Item 1. A rotating image carrier;
Exposure means for exposing the surface of the image carrier to form an electrostatic latent image;
Developing means for developing the electrostatic latent image to form a developer image;
Transfer means for transferring the developer image to the sheet at a transfer position;
The conveyance device according to any one of claims 1 to 5, wherein the conveyance device is located upstream of the transfer position on the conveyance path and conveys the sheet to the transfer position.
An image forming apparatus comprising:

Images