JP6195366B2 - Sheet feeding apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet feeding apparatus that separates and feeds sheets one by one and an image forming apparatus including the sheet feeding apparatus.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copiers, printers, facsimiles, and multifunction peripherals have a sheet feeding unit that feeds sheets to an image forming unit. The sheet feeding unit includes two or more pickup rollers. Separation means for separating the sheets one by one when the sheets are sent out is provided.

  As the separating means, there is known a retard roller system having a feed roller that rotates in the same direction in synchronism with the pickup roller and a retard roller that presses against the feed roller with a predetermined pressure contact force (hereinafter referred to as “retard pressure”). . In the retard roller method, a torque in the direction opposite to the direction in which the sheet is fed to the retard roller is applied via a torque limiter. When two or more sheets enter the nip portion between the feed roller and the retard roller, the retard roller is reversed. Rotates to prevent sheet double feed.

  Here, among the sheets to be used, there are a sheet having a lot of paper dust and the retard roller easily slipping, a sheet that is difficult to separate due to a cutting burr and a use environment, and the like. In this case, in the case of a sheet that easily slips, it is necessary to increase the retard pressure to improve the feeding performance. However, if the retard pressure is increased, the separation performance decreases when feeding a sheet that is difficult to separate. There is a fear.

  In response to this, a sheet feeding apparatus has been proposed in which the retard pressure can be adjusted by moving a drive gear for transmitting drive to the retard roller in the axial direction of the retard shaft (see Patent Document 1).

Japanese Patent Laid-Open No. 06-263280

  However, the sheet feeding apparatus described in Patent Document 1 requires an operation of adjusting the position of the adjustment gear with the adjustment lever after removing the feeding unit and reattaching the feeding unit after the adjustment. This is a very complicated operation for the operator, and a configuration capable of easily adjusting the retard pressure has been desired.

  SUMMARY An advantage of some aspects of the invention is that it provides a sheet feeding apparatus that can easily adjust the retard pressure with a simple and inexpensive configuration, and an image forming apparatus including the sheet feeding apparatus.

  The present invention relates to a sheet feeding device, a pickup roller that feeds a sheet, a feed roller that transports a sheet fed by the pickup roller, a retard roller that is in pressure contact with the feed roller and can rotate forward and backward. When one sheet enters the nip between the feed roller and the retard roller, the retard roller is driven by the feed roller, and when two or more sheets enter the nip, the retard roller is moved. A torque limiter for reverse rotation, a retard shaft attached to one end of the retard roller via the torque limiter, the other end swingably supported, a retard gear supported by the retard shaft, and a plurality of grooves A drive shaft disposed substantially parallel to the retard shaft and meshed with the retard gear A movable gear capable of moving the drive shaft in the state, the movable gear being engaged with the plurality of grooves and rotating integrally therewith, and for rotating integrally with the drive shaft. Second engagement means, and the movable gear is moved in the axial direction, and the first engagement means is engaged with any one of the plurality of grooves so that the meshing position with the retard gear is obtained. And changing the nip pressure of the retard roller with respect to the feed roller.

  According to the present invention, it is possible to provide a sheet feeding apparatus capable of easily adjusting the retard pressure with a simple and inexpensive configuration and an image forming apparatus including the sheet feeding apparatus.

1 is a cross-sectional view schematically showing a printer according to an embodiment of the present invention. It is a perspective view of the separation feeding part concerning this embodiment. It is a figure for demonstrating rotation of a feed roller and a retard roller. It is a figure for demonstrating the moment around the axis | shaft of a retard roller. It is a figure for demonstrating the moving method of the moving gear which concerns on 1st Embodiment. It is a figure for demonstrating the movement gear which concerns on 1st Embodiment. It is a figure which shows the state which moved the movement gear which concerns on 1st Embodiment. It is a figure for demonstrating the moving method of the moving gear which concerns on 2nd Embodiment. It is a figure for demonstrating the movement gear which concerns on 2nd Embodiment. It is a figure for demonstrating the movement gear which concerns on 3rd Embodiment.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. An image forming apparatus according to an embodiment of the present invention includes a separation feeding unit as a sheet feeding apparatus capable of separating and feeding sheets one by one, such as a copying machine, a printer, a facsimile machine, and a multifunction machine. It is. In the following embodiments, an intermediate transfer tandem type laser beam printer (hereinafter, referred to as a four-color toner cartridge) arranged side by side on an intermediate transfer belt from the advantage of excellent applicability to a wide variety of sheets and productivity. This will be described using “printer”).

<First Embodiment>
A printer 50 according to a first embodiment of the present invention will be described with reference to FIGS. First, a schematic configuration of the printer 50 will be described along the flow of the sheet P with reference to FIG. FIG. 1 is a cross-sectional view schematically showing a printer according to an embodiment of the present invention.

  As shown in FIG. 1, sheets P on which images are formed are stored in a stacking manner in storages 61 to 63, and image forming timings are separated by separation feeding units (sheet feeding devices) 61a to 63a. At the same time, the sheets are fed while being separated one by one. Note that the separation feeding units 61a to 63a will be described in detail later.

  The sheet P fed by the separation feeding sections 61a to 63a is conveyed to the registration roller pair 76 by the conveyance roller pairs 70 to 72, and the skew feeding is corrected by the registration roller pair 76, and at a predetermined timing. It is conveyed to the secondary transfer unit 41.

  The image forming process is executed in the image forming unit 10 at the same timing as the above sheet feeding process. Specifically, first, the exposure devices 13Y to 13K irradiate laser beams onto the surfaces of the photosensitive drums 11Y to 11K that are uniformly charged by the charging devices 12Y to 12K, and the electrostatic drums 11Y to 11K are electrostatically charged on the photosensitive drums 11Y to 11K. A latent image is formed. The electrostatic latent images formed on the photosensitive drums 11Y to 11K are developed by the developing devices 14Y to 14K, and are visualized as toner images.

  Thereafter, predetermined pressurizing force and electrostatic bias are applied by the primary transfer devices 35Y to 35K, and each color (yellow (Y), magenta (M), cyan (C) and black ( K)) toner image is superimposed and transferred onto the intermediate transfer belt 31. As a result, a full-color toner image is formed on the intermediate transfer belt 31. Note that the untransferred toner remaining on the photosensitive drums 11Y to 11K is collected by the photosensitive cleaners 15Y to 15K to prepare for the next image formation again. The intermediate transfer belt 31 is stretched around a driving roller 33, a tension roller 34 and a secondary transfer inner roller 32, and is conveyed and driven by the rotation of the driving roller 33.

  The full-color toner image formed on the intermediate transfer belt 31 is conveyed to the secondary transfer unit 41 and transferred to the sheet P conveyed at a synchronized timing by applying a predetermined pressure and electrostatic bias. The The sheet P on which the full-color toner image has been transferred is conveyed to the fixing device 5 by an adsorption conveyance means 42 that adsorbs and conveys air by a fan or the like. The sheet P conveyed to the fixing device 5 is pressurized and heated by the fixing device 5 so that the toner image is melted and fixed (fixed). Thereafter, the sheet P on which the toner image is fixed is conveyed to the discharge unit 80. The sheet P conveyed to the discharge unit 80 is discharged to the outside by the discharge roller pair 77 and is stacked on the discharge tray 66.

  Here, when images are formed on both surfaces of the sheet P, the sheet P is guided to the reverse guiding path 83 by switching the switching member 81 that swings by the action of a solenoid (not shown) to the upper side. Then, after being pulled into the switchback path 84, it is transported to the double-sided transport path 85 with the front and rear ends switched by switching back with the reverse B roller pair 79.

  The sheet P conveyed to the duplex conveyance path 85 is re-conveyed to the registration roller pair 76 in synchronization with the sheet P of the subsequent job, and is conveyed to the secondary transfer unit 41 by the registration roller pair 76. The image forming process on the back surface (second surface) is the same as that on the front surface (first surface), and the description thereof is omitted. When the double-sided image sheet P is reversed and discharged, the switching member 81 is switched to the upper side to re-guide to the reverse guiding path 83. Then, after being pulled into the switchback path 84, the reverse B roller pair 79 and the reverse A roller pair 78 are used to switch back, so that the rear end when fed in is at the top and in the opposite direction to the fed direction. It is withdrawn and loaded on the discharge tray 66.

  Next, the separation feeding units 61a to 63a described above will be specifically described with reference to FIGS. Since the separation feeding units 61a to 63a have the same configuration, the separation feeding unit 61a will be described here. First, a schematic configuration of the separation feeding unit 61a will be described with reference to FIGS. FIG. 2 is a perspective view of the separation feeding unit 61a according to the present embodiment. FIG. 3 is a view for explaining the rotation of the feed roller 2 and the retard roller 3. FIG. 4 is a view for explaining the moment around the axis of the retard roller 3.

  As shown in FIG. 2, the separation feeding unit 61 a includes a pickup roller 1 disposed above the storage 61, a feed roller 2 disposed downstream of the pickup roller 1 in the feeding direction, and a feed roller 2. And a retard roller 3 that can be rotated in forward and reverse directions.

  The pickup roller 1 sends out the sheet P stored in the storage 61, and the feed roller 2 conveys the sheet P sent out by the pickup roller 1. The retard roller 3 prevents double feeding of the sheet P conveyed by the feed roller 2. Specifically, the retard roller 3 is attached so as to rotate via a torque limiter 4 provided on the retard shaft 107, and the retard shaft 107 has a direction opposite to the rotation direction for conveying the sheet. Rotation is given. Therefore, when the sheet P is double-fed (conveyed two or more sheets), the friction force between the sheets is small, so the retard roller 3 rotates in the direction opposite to the rotation direction for conveying the sheet, and the second and subsequent sheets The sheet P is pulled back. As a result, only the uppermost sheet P is conveyed by the feed roller 2. On the other hand, when one sheet P enters the nip with the feed roller 2, the load received from the sheet P increases, so that the drive transmission of the torque limiter 4 is cut off, and the retard roller 3 passes through the sheet P. The sheet is rotated in the direction of conveying the sheet following the feed roller 2. That is, the sheet P is conveyed together with the feed roller 2.

  Further, the separation feeding unit 61 a is configured to be driven by a feeding motor 122 controlled by a signal from the control unit 200. Specifically, the driving of the feeding motor 122 is transmitted to the pulley stage gear 125 via the driving belt 124, and the first driving gear 123 that meshes with the gear portion of the pulley stage gear 125 is rotated. The first drive gear 123 is fixed to one end of the feed roller drive shaft 108, and the feed roller 2 fixed to the other end of the feed roller drive shaft 108 is rotated by the rotation of the first drive gear 123. Then, the pickup roller 1 is rotated by the rotation drive being transmitted from the pickup input gear 132 attached to the other end of the feed roller drive shaft 108 to the pickup gear 131 via the idler gear 133.

  Further, the driving of the feeding motor 122 is input to the nip pressure adjusting unit 100 via the first driving gear 123. Specifically, the drive of the feed motor 122 is transmitted to the second drive gear 126 that meshes with the first drive gear 123 to rotate the second drive gear 126. The second drive gear 126 is fixed to one end of the drive shaft 106, and the rotation of the second drive gear 126 rotates the moving gear 102 supported so as to be movable in the axial direction of the drive shaft 106. The drive shaft 106 is rotatable on a support plate 112 and a support plate 111 fixed to a body frame (not shown) by a bearing 135 (see FIG. 4) and a one-way bearing 134 so as to be substantially parallel to the retard shaft 107. It is supported. The drive shaft 106 is formed with a plurality of grooves 106a to 106d (four in the present embodiment) at predetermined intervals in the axial direction.

  The moving gear 102 meshes with the retard gear 103, and the retard gear 103 rotates the retard shaft 107 in a direction opposite to the rotation in the direction in which the retard roller 3 conveys the sheet. The retard gear 103 is formed such that the axial length is longer than the axial length of the moving gear 102, and is configured to be able to change the axial engagement position with the moving gear 102. . The retard roller 3 is attached to one end of the retard shaft 107 via the torque limiter 4, and the other end is supported by a bearing 117 of the support plate 111 so as to be swingable. In the vicinity of the torque limiter 4 of the retard shaft 107, a retard roller pressure arm 101 that can be rotated about the drive shaft 106 as a rotation fulcrum is disposed. The retard roller pressure arm 101 rotatably supports the retard shaft 107 so that the distance between the retard shaft 107 and the drive shaft 106 is restricted and the force of the pressure spring 150 is applied to the retard shaft 107. .

  Here, as shown in FIG. 3A, the retard roller pressure arm 101 is always urged in the direction of arrow A (feed roller direction) by a pressure spring 150 as urging means. That is, the retard roller 3 is urged in the direction of arrow A by the pressure spring 150 via the retard roller pressure arm 101. Note that the urging force (pressing force) by the pressure spring 150 is a nip pressure (hereinafter referred to as “retard”) required to reliably separate and feed sheets that have entered the nip between the feed roller 2 and the retard roller 3 one by one. Pressure)).

  Further, as shown in FIG. 3B, when the drive shaft 106 and the moving gear 102 are rotated by the rotation of the feeding motor 122 in the separation feeding unit 61a configured as described above, the retarded gear 103 that meshes with each other. Rotate in the direction of arrow E. When the retard gear 103 rotates, the retard shaft 107 rotates in the direction of arrow E integrally with the retard gear 103. At this time, pressure is applied to the teeth of the retard gear 103 by the teeth of the moving gear 102. The retard roller 3 is urged toward the feed roller 2 on the swingable retard shaft 107 by the pressure (hereinafter referred to as “tooth surface pressure”) applied by the teeth of the moving gear 102 to the teeth of the retard gear 103. A directional moment is generated.

  As in the conventional example, the moment relationship around the retard roller 3 is as shown in FIG. The retard roller 3 on the retard shaft 107 can swing about a bearing 117 indicated by an arrow S as a swing fulcrum.

For example, when the retard shaft 107 rotates in the direction of arrow E in FIG. 3B (the direction in which the sheet is fed back), the retard shaft 107 swings the bearing 117 due to the moment due to the tooth surface pressure in the direction of arrow B of the moving gear 102. It swings as a moving fulcrum. When the retard shaft 107 swings, the retard roller 3 is pressurized in the direction of arrow A, and a pressure F ₁ shown in FIG. 4 is generated. As a result, the retard pressure F _R of the feed roller 2 and the retard roller 3, a plus pressure F ₁ the biasing force F ₂ due to the pressing spring 150.

The moment balance relational expression around the fulcrum S at this time is as follows.
L ₁ · F ₁ + L ₂ · F ₂ = L ₃ · F ₃ + L _R · F _R (1)

Here, F ₃ indicates a force considering the weight on the retard shaft. _{L 1, L 2, L 3} , L R indicates the distance to the respective forces from the fulcrum.
Accordingly, the retard pressure _{F R} is
F _R = (L ₁ · F ₁ + L ₂ · F ₂ −L ₃ · F ₃ ) / L _R (2)

From equation (2), the retard pressure _{F R} is the distance from the fulcrum to the force _{(L 1, L 2, L} 3, L R) by it can be seen that a numerical value to be changed. That is, the engagement position of the movable gear 102 and Ritadogia 103 is moved in the axial direction, it is possible to adjust the retard pressure F _R by a distance L ₁ of the fulcrum S and pressure F ₁ to the variable.

Next, the configuration for adjusting the retard pressure F _R described above, i.e., the method of moving the movable gear 102 will be described with reference to FIGS. 5-7. FIG. 5 is a diagram for explaining a moving method of the moving gear 102 according to the first embodiment. FIG. 6 is a diagram for explaining the moving gear 102 according to the first embodiment. FIG. 7A is a diagram in which the moving gear 102 is moved in the axial direction of the arrow G, and the snap fit claw 102 b is inserted into the groove portion 106 a of the drive shaft 106. 7B and 7C are diagrams in which the moving gear 102 is moved in the axial direction of the arrow H, and the snap fit claws 102b are inserted into the groove 106c and the groove 106d of the drive shaft 106. FIG.

  As shown in FIGS. 5 and 6, the moving gear 102 includes a snap fit claw (first engagement portion, claw portion) 102b, and a hook portion (first engagement portion) 102a for moving the snap fit claw 102b. , Are connected. Further, the drive shaft 106 is provided with a plurality of grooves 106a to 106d that can engage with the snap fit claws 102b in the axial direction. When moving the moving gear 102, by pulling the hook portion 102a in the direction of arrow D, the snap-fit claw 102b is detached from the groove portion 106b of the drive shaft 106, and can move in the axial direction.

  Further, the moving gear 102 is configured to rotate integrally with the drive shaft 106 by the second engaging means. In this embodiment, the drive shaft 106 has a D-cut portion 106e having a substantially D-shaped cross section on at least a part of the outer peripheral surface, and the inner peripheral surface 102c of the moving gear 102 is a D-cut having a substantially D-shaped cross section. By forming in a shape, the drive shaft 106 and the moving gear 102 can rotate together. By forming at least a part of the outer peripheral surface of the drive shaft 106 and the inner peripheral surface 102c of the moving gear 102 in a D-cut shape having a substantially D-shaped cross section, movement in the axial direction is also facilitated. Further, as shown in FIGS. 7A to 7C, even when the moving gear 102 moves to a different position in the axial direction, if it is located in the D-cut region, it is rotated integrally with the drive shaft 106. be able to.

  As described above, in the present embodiment, the moving gear 102 can be fixed at three positions in addition to the initial position (see FIG. 2). At that time, the moving gear 102 can be moved with one action by the snap-fit claws 102b. Therefore, the nip pressure (retard pressure) of the retard roller 3 with respect to the feed roller 2 can be easily changed. Accordingly, for example, even when a sheet that easily slips or a sheet that is difficult to separate is fed, it can be easily handled. As a result, workability can be improved.

  Further, since the user can change the retard pressure to be suitable for the state of the sheet (media), it is possible to reduce the feeding failure such as jam. Therefore, productivity can be improved.

  Further, since the snap fit claw 102b provided on the moving gear 102 is merely engaged with the grooves 106a to 106d provided on the drive shaft 106, the retard pressure can be adjusted with a simple and inexpensive configuration.

Second Embodiment
Next, a printer according to a second embodiment of the present invention will be described with reference to FIGS. The printer according to the second embodiment is different from the first embodiment in the configuration of the second engagement means. Therefore, in 2nd Embodiment, it demonstrates centering around a 2nd engagement means, and it abbreviate | omits description about another structure using the same code | symbol as 1st Embodiment. FIG. 8 is a diagram for explaining a moving method of the moving gear 202 according to the second embodiment. FIG. 9 is a diagram for explaining the moving gear 202 according to the second embodiment.

  As shown in FIGS. 8 and 9, pins (projections) 210a and 210b are press-fitted into the drive shaft 206 in place of the D-cut portion. The moving gear 202 does not interfere with the pins 210a and 210b when the pins 210a and 210b are moved in the axial direction, and engages with the pins 210a and 210b when rotating together with the drive shaft 206. A key groove 202c that can be rotationally driven is formed. Thereby, the moving gear 202 can rotate integrally with the drive shaft 206.

  Note that the hook portion 202a and snap fit claw 202b of the moving gear 202, the plurality of grooves 206a to 206d of the drive shaft 206, the retard shaft 207, and the retard gear 203 shown in FIG. 8 are the same as in the first embodiment. Description is omitted.

  As described above, since the printer according to the second embodiment requires less processing of the drive shaft than the first embodiment, manufacturing costs (processing costs) can be reduced.

<Third Embodiment>
Next, a printer according to a third embodiment of the invention will be described with reference to FIG. The printer according to the third embodiment is different from the first embodiment in the configuration of the groove portion of the drive shaft. Therefore, in 3rd Embodiment, it demonstrates centering around the groove part of a drive shaft, About the other structure, the same code | symbol as 1st Embodiment is attached | subjected and description is abbreviate | omitted. FIG. 10 is a diagram for explaining the moving gear 302 according to the third embodiment.

  As shown in FIG. 10, in the third embodiment, the drive shaft 306 is provided with a plurality of mountain-shaped engaged portions 306a. Further, the moving gear 302 is provided with a hook portion 302a and a snap fit claw 302b that can be engaged with the engaged portion 306a. Note that the retard shaft 307 and the retard gear 303 shown in FIG. 10 are the same as those in the first embodiment, and thus description thereof is omitted.

  As described above, the printer according to the third embodiment can adjust the retard pressure in more detail because the moving gear 302 can be fixed to more engagement positions than in the first embodiment.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above. In addition, the effects described in the embodiments of the present invention only list the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments of the present invention.

  For example, although the present embodiment has been described using the configuration in which the retard gear 103 is fixed to the retard shaft 107, the present invention is not limited to this. For example, when the retard gear 103 is configured so as to be rotatable integrally with the retard shaft 107, the configuration may be such that the mesh position with the moving gear 102 is changed by moving the retard gear 103 in the axial direction.

  In this embodiment, the electrophotographic printer has been described. However, the present invention is not limited to this. For example, the present invention can also be used for an ink jet printer (image forming apparatus) that forms an image on a sheet by ejecting ink liquid from a nozzle.

DESCRIPTION OF SYMBOLS 1 Pickup roller 2 Feed roller 3 Retard roller 4 Torque limiter 10 Image formation part 61a-63a Separation feeding part (sheet feeding apparatus)
102 moving gear 102a hook part (first engaging means)
102b Snap-fit claw (first engaging means)
102c Inner peripheral surface (second engaging means)
103 retard gear 106 drive shaft 106a to 106d groove portion 106e D cut portion 107 retard shaft 202 moving gear 202c key groove 206 drive shaft 210a, 210b pin (protrusion portion)
P sheet

Claims (6)

A pickup roller for feeding the sheet;
A feed roller for conveying a sheet fed by the pickup roller;
A retard roller that is in pressure contact with the feed roller and is capable of forward and reverse rotation;
When one sheet enters the nip of the feed roller and the retard roller, the retard roller is driven by the feed roller, and when two or more sheets enter the nip, the retard roller is reversed. A torque limiter to rotate,
A retard shaft having one end attached to the retard roller via the torque limiter and the other end supported to be swingable;
A retard gear supported by the retard shaft;
A drive shaft having a plurality of grooves and disposed substantially parallel to the retard shaft;
A movable gear capable of moving the drive shaft in mesh with the retard gear,
The moving gear includes first engaging means that can engage with the plurality of grooves and rotate integrally, and second engaging means for rotating integrally with the drive shaft,
By moving the moving gear in the axial direction and engaging the first engaging means with any of the plurality of grooves, the meshing position with the retard gear is changed, and the nip of the retard roller with respect to the feed roller is changed. Change the pressure,
A sheet feeding apparatus characterized by that. The first engagement means includes a hook portion that is rotatably coupled integrally with the moving gear, and a snap-fit claw provided on the hook portion.
The sheet feeding apparatus according to claim 1. The retard gear is fixed to the retard shaft, and the axial length of the retard gear is longer than the axial length of the moving gear;
The sheet feeding apparatus according to claim 1, wherein the sheet feeding apparatus is a sheet feeding apparatus. The drive shaft has a D-cut portion having a substantially D-shaped cross section on at least a part of the outer peripheral surface,
The second engagement means is formed by forming the inner peripheral surface of the moving gear into a D-cut shape having a substantially D-shaped cross section that can be engaged with the D-cut portion.
The sheet feeding device according to any one of claims 1 to 3, wherein the sheet feeding device is provided. The drive shaft has a plurality of protrusions on the outer peripheral surface,
The second engagement means is a keyway that can be engaged with the plurality of protrusions.
The sheet feeding device according to any one of claims 1 to 3, wherein the sheet feeding device is provided. A sheet feeding device according to any one of claims 1 to 5,
An image forming unit that forms an image on the sheet fed by the sheet feeding device,
An image forming apparatus.

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