JP5765933B2 - Sheet reversing and conveying device - Google Patents

Description

  The present invention relates to a sheet reversing and conveying apparatus for reversing and conveying a sheet.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines, facsimile machines, and printers are provided with a sheet reversing and conveying apparatus that conveys a sheet on which images are formed on both sides.

  In the sheet reversing and conveying apparatus, the sheet is conveyed by a reversing roller capable of forward and reverse rotation. The sheet conveyed by the reverse roller is guided by the swing guide. The swing guide swings between a first position for guiding the sheet to the reversing roller rotating in the forward direction and a second position for guiding the sheet conveyed by the reversing roller rotating in the reverse direction. Then, after the swing guide is switched from the first position to the second position for guiding the sheet that is reversely conveyed by the reverse rotation of the reverse roller, the reverse roller is reversely conveyed to convey the sheet.

  In a sheet reversing and conveying apparatus, a motor is generally used to rotate a reversing roller, and a solenoid is generally used to move a swing guide. However, since the motor and solenoid, which are expensive electronic components, are used, the cost of the apparatus has been increased. Therefore, a configuration is known in which, without using a solenoid, the reverse roller is forward / reversely switched by forward / reverse switching of the motor, and the driving force of the motor is transmitted to the swing guide via a friction clutch to switch the position of the swing guide. (See Patent Document 1).

JP 2007-145476 A

  In the above configuration in which the driving force of the motor that rotates the reversing roller is transmitted to the swing guide to move the swing guide, the driving force is transmitted to the swing guide using a friction clutch that depends on the friction force between the members. Thus, the swing guide is swung. Therefore, due to the influence of the usage environment and the durability of the friction clutch, the time required to complete the switching of the swing guide position varies, and the sheet is rotated by the reversing roller that reverses before the swing guide position switching is completed. However, there is a problem that the sheet is transported backwards, resulting in sheet conveyance failure.

  The present invention has been made in view of the above problems, and an object thereof is to provide a sheet reversing and conveying apparatus that prevents a sheet conveyance failure when a sheet is reversely fed.

The present invention guides to the roller a first transport path for introducing a sheet to the forward rotating roller, a second transport path for receiving a sheet from the reverse rotating roller, and a sheet transported through the first transport path. A swing guide that is swingable between a first position that rotates and a second position that guides the sheet from the roller that rotates in the reverse direction to the second transport path, and is provided in the swing guide and is rotatable . A swing gear, a motor for generating a drive force for rotating the swing gear and a drive force for swinging the swing guide, and the swing gear when the swing guide is located at the first position; A first drive transmission portion that includes a meshing first input gear and that transmits the driving force transmitted from the motor to the swing gear so that the roller rotates in the forward direction, and the swing guide is positioned at the second position. When the rocking gear Meshing with the second input gear, a sheet reverse conveying apparatus characterized by having a second power transmitter which transmits to the roller driving force transmitted to the swing gear from the motor is reversed.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the sheet inversion conveyance apparatus which prevents the conveyance defect at the time of sheet | seat reverse feeding more reliably.

FIG. 3 is an explanatory diagram of an image forming apparatus including a sheet reversing and conveying apparatus according to the present invention. FIG. 6 is a schematic cross-sectional view for explaining the operation of the sheet reversing and conveying apparatus. FIG. 3 is a schematic perspective view of a sheet reversing conveyance device. Explanatory drawing for demonstrating the structure of the rocking | fluctuation guide of a sheet inversion conveyance apparatus. FIG. 4 is an explanatory diagram for explaining drive transmission in a sheet reversing and conveying apparatus.

  With reference to FIG. 1, an overall configuration of a color image forming apparatus (hereinafter referred to as an image forming apparatus) 100 provided with a sheet reversing and conveying apparatus according to the present invention will be described.

  FIG. 1A is an external perspective view of an image forming apparatus including a sheet reversing and conveying apparatus according to the present invention. FIG. 1B is a schematic cross-sectional view of the image forming apparatus.

  The image forming apparatus 100 is a four-color full-color laser printer using an electrophotographic process. That is, an image is formed on the sheet S based on an image signal input from an external host device such as a personal computer, an image reader, or a counterpart facsimile machine to the controller unit (control unit).

  The operation for forming a full-color image is as follows. The drums 1 of the first to fourth cartridges PY, PM, PC, and PK are rotationally driven in a counterclockwise direction indicated by arrows at a predetermined control speed. The intermediate transfer belt 13 is also rotationally driven at a speed corresponding to the speed of the drum 1 in the clockwise direction of the arrow (forward direction with respect to the drum rotation). The scanner unit 11 is also driven. In synchronization with this drive, the charging roller 2 uniformly charges the surface of the drum 1 to a predetermined polarity and potential at a predetermined control timing in each cartridge.

  The scanner unit 11 scans and exposes the surface of each drum 1 with a laser beam modulated in accordance with an image signal of each color. Thereby, on the surface of each drum 1, an area scanned and exposed by the laser beam becomes an electrostatic latent image corresponding to the image signal. The electrostatic latent image formed on the surface of each drum 1 is developed as a toner image by the developing device 3. Through the electrophotographic image forming process operation as described above, a toner image is formed on the drum 1 and the toner image is primarily transferred onto the belt 13.

  On the other hand, the paper feed roller 20 is driven at a predetermined control timing. As a result, the sheet P stacked on the sheet feeding tray 19 is separated and fed by the cooperation of the sheet feeding roller 20 and the separation pad 21, and the secondary transfer roller 22 and the intermediate transfer belt 13 It is introduced into the nip portion (secondary transfer nip portion). As a result, the four-color superimposed toner images on the intermediate transfer belt 13 are sequentially transferred onto the surface of the sheet P in sequence while the sheet P is nipped and conveyed through the nip portion. The sheet P is separated from the surface of the intermediate transfer belt 13 and introduced into the fixing device 23. In the fixing device 23, the sheet is heated and pressurized at the fixing nip portion of the pair of fixing rotators 23a and 23b. Thereby, the color toner images are mixed and fixed to the sheet.

(Outline of sheet transport operation after fixing)
The conveyance operation of the sheet P after passing through the fixing nip portion will be described. On the downstream side of the fixing nip portion in the sheet conveyance direction, a sheet reversal conveyance device whose schematic cross section is shown in FIG. 2 is provided. The sheet reversing and conveying device is a sheet that is fed back from the fixing nip portion to the discharge path (first conveying path) 201 for introducing the sheet to the discharge roller 24a as a roller that can be rotated in the forward and reverse directions. And a double-sided path (second transport path) 202 for receiving. A swing guide 30 is swingably provided between the discharge path 201 and the duplex path 202.

  FIG. 2A is a cross-sectional view showing a state when the paper discharge roller 24a is rotating forward. FIG. 2B is a view when the paper discharge roller 24a is reversely transporting a sheet. It is sectional drawing which shows this state. In the following description, the forward rotation direction of the discharge roller 24a is a rotation direction in which the sheet P is discharged to the discharge tray 25, and the reverse rotation direction is a rotation in the opposite direction.

  The swing guide 30 disposed on the downstream side in the sheet conveying direction of the fixing device 23 includes an open position (see FIG. 2A) where the discharge path 201 between the fixing nip and the discharge roller pair 24 is opened, and a discharge path. It moves between a closed position (see FIG. 2B) where 201 is closed. The position of the swing guide 30 is switched in conjunction with the rotation direction of the paper discharge roller 24a, and the open position is taken when the paper discharge roller 24a is rotating forward, and the closed position is taken when the paper discharge roller 24a is reverse. Has been. A configuration for driving transmission related to forward / reverse rotation of the paper discharge roller 24a and position switching of the swing guide 30 interlocked therewith will be described in detail later.

  When single-sided printing is performed on the sheet P, the paper discharge roller 24a is rotated forward, and the swing guide 30 is located at the open position shown in FIG. The sheet P heated and pressed at the fixing nip portion is discharged onto the discharge tray 25 by the discharge roller pair 24 as a full-color single-sided image formed product through the fixing device 23.

  On the other hand, when performing double-sided printing on the sheet P, the sheet P is discharged at the timing when the rear end of the sheet P on which image formation has been performed on one side through the above-described process reaches the vicinity of the pair of discharge rollers 24 The rotation direction of the roller pair 24 is switched to the reverse direction. The forward / reverse switching timing is performed according to the detection timing of the sheet detection sensor disposed downstream of the fixing nip. Here, the position of the swing guide 30 is configured to be changed in conjunction with switching of the rotation direction of the paper discharge roller 24a. That is, when the sheet starts to be reversed and conveyed by the reverse rotation of the paper discharge roller 24a, the swing guide 30 is positioned at the closed position shown in FIG. Guided to 202. The sheet guided to the duplex path 202 is guided to the duplex conveyance roller pair 26a. The sheet P is conveyed from the duplex conveying roller pair 26a to the registration roller pair 7 through the duplex conveying roller pair 26b and the duplex conveying roller pair 26c (see FIG. 1).

  In this way, by conveying the sheet P with its rear end reversed, the front and back of the sheet P with respect to the intermediate transfer belt 13 are interchanged. Then, through a process similar to that for single-sided printing, a full-color double-sided image formed product is discharged onto the discharge tray 25 by the discharge roller pair 24.

(About the drive transmission configuration in the sheet reversing and conveying apparatus)
A drive transmission configuration of the sheet reversing and conveying apparatus according to the present invention will be described in detail with reference to FIGS. 3, 4 and 5. FIG.

  FIG. 3 is a perspective view showing a main part of the sheet reversing and conveying apparatus. FIG. 4A is a schematic diagram for explaining the configuration of the swing guide 30, and FIG. 4B is an enlarged cross-sectional view of the region S in FIG. FIG. 5 is an explanatory diagram for explaining drive transmission in the sheet reversing and conveying apparatus.

  3 and 4, the swing guide 30 is rotatably supported by the apparatus main body by holding swing guide shafts 39a and 39b provided at both ends by swing guide bearings 35a and 35b. . A swing guide gear 29 and a clutch gear 32 are disposed at the end of the swing guide 30. The rotation center of the swing guide gear 29 coincides with the rotation center of the swing guide shafts 39a and 39b. The swing guide gear 29 meshes with a pinion gear 28 to which driving is transmitted from a motor M capable of forward and reverse rotation. The swing guide gear 29 and the clutch gear 32 are engaged with each other.

  As shown in FIG. 4, the clutch gear 32 is rotatably held by the swing guide 30 while receiving the pressing force of the sliding plate 37 pressed toward the clutch gear 32 by the compression spring 36. The force to stop the rotation of the clutch gear 32 generated between the sliding plate 37 pressed by the compression spring 36 and the clutch gear 32 is between the swing guide shafts 39a and 39b and the swing guide bearings 35a and 35b. Is sufficiently larger than the sliding resistance generated. Therefore, when the rotational driving force from the pinion gear 28 is transmitted to the swing guide gear 29, the swing guide 30 can be rotated about the swing guide shafts 39a and 39b. That is, the sliding plate 37 and the compression spring 36 constitute a torque limit mechanism. Even if a torque less than the set torque value acts between the clutch gear 32 and the swing guide 30, the clutch gear 32 and the swing guide 30 do not rotate relative to each other due to the frictional force between the sliding plate 37 and the clutch gear 32. When a force exceeding a set torque value is applied between the clutch gear 32 and the swing guide 30, the clutch gear 32 and the swing guide 30 rotate relative to each other when the sliding plate 37 and the clutch gear 32 slip.

  Further, the turning direction of the swing guide 30 is switched by switching the rotation direction of the pinion gear 28 that inputs a driving force to the swing guide gear 29. The driving force is directly transmitted from the motor M to the pinion gear 28. The rotation direction of the pinion gear 28 is changed as the rotation direction of the motor M is changed.

  A paper discharge roller gear 27 is provided at the end of the paper discharge roller 24a. A driving force is transmitted to the paper discharge roller gear 27 via one of a first drive transmission unit configured by the paper output idler gears 33a and 33b and a second drive transmission unit configured by the reverse idler gears 34a and 34b. The The paper discharge idler gear 33 a is a first input gear in the first drive transmission unit that can mesh with the clutch gear 32. The reverse idler gear 34 a is a second input gear in the second drive transmission unit that can mesh with the clutch gear 32.

  Next, transmission of driving from the motor M as a driving source to the paper discharge roller 24a will be described with reference to FIG. FIG. 5A is a schematic diagram for explaining a state when the paper discharge roller 24a is rotating forward. FIG. 5B is a schematic diagram showing a state during the position switching operation of the swing guide. FIG. 5C is a schematic diagram for explaining a state when the paper discharge roller 24a is reversely rotated.

  When the discharge roller 24a is rotated in the forward rotation direction (the rotation direction in which the sheet P is discharged to the discharge tray 25), the pinion gear 28 is driven to rotate clockwise as shown in FIG. .

  When the pinion gear 28 rotates clockwise, the swing guide 30 rotates counterclockwise around the swing guide shafts 39a and 39b with the above-described configuration. As the swing guide 30 rotates, a clutch gear 32 as a swing gear provided on the swing guide 30 meshes with the paper discharge idler gear 33a. The paper discharge idler gear 33a is connected to the paper discharge idler gear 33b, and transmits driving to the paper discharge roller gear 27 disposed at the end of the paper discharge roller 24a. In this way, as shown in FIG. 5A, the clutch gear 32 meshes with the paper discharge idler gear 33a, so that drive transmission from the motor M to the paper discharge roller 24a is performed, and the paper discharge roller 24a rotates forward. In the state shown in FIG. 5A, the swing guide 30 tries to swing counterclockwise, but its swing is restricted by the paper discharge idler gear 33a. The position of the swing guide 30 shown in FIG. 5A is an open position (FIG. 2A) as the first position of the present invention for guiding the sheet conveyed through the discharge path 201 to the discharge roller 24a. Reference). In the state of FIG. 5A, the clutch gear 32 and the sliding plate 37 (see FIG. 4B) slip and the clutch gear 32 rotates relative to the swing guide 30.

  After the trailing edge of the conveyed sheet has passed the leading edge of the swing guide 30, the rotation of the motor M is switched in the opposite direction. Then, the pinion gear 28 is driven to rotate counterclockwise as shown in FIG. When the pinion 28 rotates counterclockwise, the swing guide 30 rotates clockwise about the swing guide shafts 39a and 39b with the above-described configuration.

  As the swing guide 30 rotates, the clutch gear 32 provided on the swing guide 30 meshes with the reverse idler gear 34a (see FIG. 5C). The reverse idler gear 34a is connected to the reverse idler gear 34b and transmits a driving force to the paper discharge roller gear 27 disposed at the end of the paper discharge roller 24a. Thus, when the clutch gear 32 is engaged with the reverse idler gear 34a, drive transmission from the motor M to the paper discharge roller 24a is performed, and the paper discharge roller 24a rotates in the reverse direction. In the state shown in FIG. 5C, the swing guide 30 tries to swing clockwise, but its swing is restricted by the reverse idler gear 34a. The position of the swing guide 30 shown in FIG. 5C is a closed position (FIG. 2B) as the second position of the present invention for guiding the sheet reversely fed by the paper discharge roller 24a to the double-sided path 202. ))). In the state of FIG. 5C, the clutch gear 32 and the sliding plate 37 (see FIG. 4B) slip and the clutch gear 32 rotates relative to the swing guide 30.

  As described above, in the present embodiment, the discharge idler gear 33 a and the reverse idler gear 34 a are arranged so as not to mesh with the clutch gear 32 at the same time. During the switching operation of the swing guide 30 shown in FIG. 5B, drive transmission from the motor M to the paper discharge roller 24a is not performed, and the rotation of the paper discharge roller 24a stops.

  In the present embodiment, the swing guide 30 is provided with a swing guide 29 and a clutch gear 32 which are part of a drive transmission path from the motor M as a drive source to the paper discharge roller 24 a. Accordingly, the rotation of the paper discharge roller 24a is stopped while the swing guide 30 is being swung to switch the position of the swing guide 30. Only when the position switching of the swing guide 30 is completed, the drive transmission from the motor M to the paper discharge roller 24a is performed and the sheet is conveyed in the reverse direction. With such a configuration, the sheet reversing / conveying device in which the switching operation of the swing guide 30 is reliably completed when the sheet is transported in the reverse direction while the number of solenoids for switching the swing guide 30 is reduced. Can be provided.

24 discharge roller pair 24a discharge roller 24b discharge roller 27 discharge roller gear 28 pinion gear 29 swing guide gear 30 swing guide 32 clutch gear 33a discharge idler gear 33b discharge idler gear 34a reverse idler gear 34b reverse idler gear 36 compression spring 37 Sliding plate 39a, b Swing guide shaft

Claims (3)

A roller capable of forward and reverse rotation,
A first conveyance path for introducing a sheet to the positively rotating roller;
A second conveyance path for receiving a sheet from the reversely rotating roller;
A rockable swing between a first position for guiding the sheet conveyed in the first conveying path to the roller and a second position for guiding a sheet from the reversely rotating roller to the second conveying path. Motion guide,
A swing gear provided on the swing guide and rotatable;
A motor for generating a driving force for rotating the swing gear and a driving force for swinging the swing guide;
A first input gear that meshes with the rocking gear when the rocking guide is positioned at the first position, and transmits the driving force transmitted from the motor to the rocking gear so that the roller rotates forward. A first drive transmission unit,
A second input gear that meshes with the rocking gear when the rocking guide is located at the second position, and transmits the driving force transmitted from the motor to the rocking gear so that the roller reversely rotates. And a second drive transmission unit. When the swing guide is located at the first position, the swing gear that rotates forward by the driving force from the motor acts to rotate relative to the swing guide, and the swing guide Having a torque limit mechanism that acts so that the rocking gear that rotates reversely by the driving force from the motor rotates relative to the rocking guide when the moving guide is located at the second position; The sheet reversing and conveying apparatus according to claim 1, wherein   An image forming apparatus comprising: the sheet reversing and conveying apparatus according to claim 1; and an image forming unit that forms an image on a sheet conveyed by the sheet reversing apparatus.

Images