Paper feeding device and image forming apparatus equipped therewith

Abstract

The present invention provides a paper feeding device and an image forming apparatus equipped therewith that can reduce sheet feeding failures while suppressing maintenance costs. [Solution] The paper feeding device comprises a feed roller and a retard roller. The retard roller has a roller body, a shaft, a torque limiter, a holding member, and a regulating member. The roller body rotates around a rotation axis. The shaft is attached to the roller body and extends along the rotation axis. The torque limiter switches the rotation and stopping of the roller body. The holding member is positioned on one axial side of the roller body and supports the shaft. The regulating member is positioned on the other axial side of the roller body and has a locking portion that engages with the shaft to restrict the axial movement of the roller body. The roller body is pivotably supported via a first support portion provided on the holding member and a second support member provided on the regulating member, and is pressed against the feed roller.

Description

Technical Field

[0001] The present invention relates to a paper feeding device and an image forming apparatus including the same.

Background Art

[0002] A conventional paper feeding device includes a feed roller and a retard roller. The feed roller rotates by transmitting a driving force to convey a sheet. The retard roller is pressed against the feed roller to form a nip portion and conveys the sheet while handling it. The retard roller has a roller body, a shaft, a torque limiter, a holding member, and a regulating member. The roller body rotates around a rotation axis. The shaft is attached to the roller body and extends along the rotation axis. The torque limiter switches between rotation and stop of the roller body. The holding member is disposed on one axial direction of the roller body and supports the shaft. The roller body is swingably supported via a support portion provided on the holding member and is pressed against the feed roller (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the conventional paper feeding device, the pressing force of the roller body against the feed roller may be biased in the axial direction. As a result, with continuous use, the roller body may be biased in one axial direction and wear, which may cause poor sheet feeding. In addition, the life of the roller body may be shortened, and the maintenance cost may increase.

[0005] The present invention aims to provide a paper feeding device and an image forming apparatus equipped therewith that can reduce sheet feeding failures while suppressing maintenance costs. [Means for solving the problem]

[0006] To achieve the above objective, a paper feeding device according to the first aspect of the present invention comprises a feed roller and a retard roller. The feed roller conveys the sheet by rotating when a driving force is transmitted to it. The retard roller is pressed against the feed roller to form a nip portion and conveys the sheet while separating it. The retard roller has a roller body, a shaft, a torque limiter, a holding member, and a regulating member. The roller body rotates around a rotation axis. The shaft is attached to the roller body and extends along the rotation axis. The torque limiter switches the rotation and stopping of the roller body. The holding member is positioned on one axial side of the roller body and supports the shaft. The regulating member is positioned on the other axial side of the roller body and has a locking portion that locks onto the shaft to restrict the axial movement of the roller body. The roller body is pivotably supported via a first support portion provided on the holding member and a second support member provided on the regulating member, and is pressed against the feed roller.

[0007] An image forming apparatus according to the second aspect of the present invention comprises the above-mentioned paper feeding device and prints an image on a sheet fed from the above-mentioned paper feeding device. [Effects of the Invention]

[0008] According to an exemplary version of the present invention, it is possible to provide a paper feeding device and an image forming apparatus equipped therewith that can reduce sheet feeding failures while suppressing maintenance costs. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic cross-sectional view showing the overall configuration of an image forming apparatus 100 according to one embodiment of the present invention. [Figure 2] Perspective view of a paper feed device 60 according to one embodiment of the present invention [Figure 3] A perspective view showing an enlarged portion of the paper feed device 60 according to one embodiment of the present invention. [Figure 4] Perspective view of the retard roller 64 of the paper feed device 60 according to one embodiment of the present invention. [Figure 5] Cross-sectional view of the torque limiter 644 of the retard roller 64 of the image forming apparatus 100 according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a cross-sectional view showing the internal structure of an image forming apparatus 100 according to the first embodiment of the present invention. For convenience of explanation, the vertical direction is defined as the up-down direction (Z1-Z2) when the image forming apparatus 100 is in a usable installation state (as shown in Figure 1). The front-to-back direction (Y1-Y2) is defined with the front side of the image forming apparatus 100 shown in Figure 1 as the front. The left-to-right direction (X1-X2) is defined with reference to the front of the image forming apparatus 100 in its installed state. In this embodiment, the left-to-right direction (X1-X2) is orthogonal to the up-to-down direction (Z1-Z2) and the front-to-back direction (Y1-Y2). The left-to-right direction (X1-X2) is the paper transport direction of the retard roller 64, and the front-to-back direction (Y1-Y2) is the axial direction of the retard roller 64. Note that this definition of the up-to-down direction does not limit the orientation and positional relationship of the image forming apparatus 100 when it is in use.

[0011] <Configuration of an image forming apparatus> The image forming apparatus 100 comprises an image forming section Pa to Pd, a paper feeder 60, a transfer section 50, a fixing section 14, an ejection section 17, a transport roller pair 40, a paper transport path 19, and a branch transport path 20. The image forming apparatus 100 prints an image on a sheet P fed from the paper feeder 60.

[0012] Specifically, the main body of the image forming apparatus 100 (in this case, a color printer) has four image forming units Pa, Pb, Pc, and Pd arranged in order from the upstream side in the transport direction (left side in Figure 1).

[0013] More specifically, the image forming sections Pa to Pd are provided to correspond to images of four different colors (yellow, cyan, magenta, and black). The image forming sections Pa to Pd sequentially form images of yellow, cyan, magenta, and black through the processes of charging, exposure, development, and transfer, respectively.

[0014] The image forming sections Pa to Pd form visible images (toner images) of each color on the photoreceptor drums (image carriers) 1a to 1d. In addition, an intermediate transfer belt (intermediate transfer body) 8, which rotates counterclockwise in Figure 1, is provided adjacent to each image forming section Pa to Pd. The toner images formed on the photoreceptor drums 1a to 1d are sequentially transferred and superimposed onto the intermediate transfer belt 8, which moves while in contact with each photoreceptor drum 1a to 1d.

[0015] The transfer unit 50 transfers the toner image formed in the image forming units Pa to Pd onto a sheet P (recording medium). The transfer unit 50 includes a drive roller 11 and a secondary transfer roller 9. Specifically, the toner image that has been primary transferred onto the intermediate transfer belt 8 is secondary transferred onto a sheet P, which is an example of a recording medium, by the secondary transfer roller 9. Furthermore, the sheet P on which the toner image has been secondary transferred is discharged from the main body of the image forming apparatus 100 after the toner image has been fixed in the fixing unit 14.

[0016] The paper feeder 60 supplies sheets P to the image forming units Pa~Pd. The paper feeder 60 includes a paper cassette 61, a pickup roller 62, a feed roller 63, and a retard roller 64. It is positioned above the paper cassette 61 at Z1. The paper cassette 61 is located at the bottom of the main body of the image forming apparatus 100 and contains the sheets P on which the toner image is secondarily transferred.

[0017] The pickup roller 62 presses against the upper surface of the sheet P with a predetermined pressure. The feeding of the sheet P is started by rotating the pickup roller 62. That is, the pickup roller 62 contacts the sheet P stored in the paper cassette 61 and feeds the sheet P into the paper transport path 19.

[0018] The feed roller 63 is rotated by the transmission of driving force, and conveys the sheet P sent out by the pickup roller 62. Specifically, a driving force transmission gear (not shown) for transmitting the rotation of the feed roller 63 to the pickup roller 62 is disposed between the feed roller 63 and the pickup roller 62.

[0019] The retard roller 所0 is pressed against the feed roller 63 to form a nip portion, and conveys the sheet P while controlling it. Specifically, the retard roller 64 incorporates a torque limiter 644 described later, and is pressed against the feed roller 63 and rotates in a driven manner.

[0020] Thereby, when a plurality of sheets P are simultaneously fed by the pickup roller 62, the sheets P are controlled by the feed roller 63 and the retard roller 64, and only the uppermost sheet is separated and sent out toward the paper conveyance path 所9. The sheet P that has passed through the paper conveyance path 所9 reaches the registration roller pair 所3, and is conveyed to the nip portion between the secondary transfer roller 9 and the drive roller 所所 of the intermediate transfer belt 8 in accordance with the image formation timing. Note that the retard roller 64 will be described in detail later.

[0021] A sheet made of a dielectric resin is used for the intermediate transfer belt 8, and a seamless belt having no seams is mainly used. Further, on the downstream side of the secondary transfer roller 9, a blade-shaped belt cleaner 25 for removing toner and the like remaining on the surface of the intermediate transfer belt 8 is disposed.

[0022] Around and below the rotatably mounted photoreceptor drums 1a to 1d are charging devices 2a, 2b, 2c, and 2d, an exposure device 5, developing devices 3a, 3b, 3c, and 3d, and cleaning devices 7a, 7b, 7c, and 7d. The charging devices 2a, 2b, 2c, and 2d charge the photoreceptor drums 1a to 1d. The exposure device 5 exposes each photoreceptor drum 1a to 1d with image information. The developing devices 3a, 3b, 3c, and 3d form toner images on the photoreceptor drums 1a to 1d. The cleaning devices 7a, 7b, 7c, and 7d remove any remaining developer (toner) from the photoreceptor drums 1a to 1d.

[0023] When image data is input from a higher-level device such as a personal computer, the charging devices 2a to 2d first uniformly charge the surfaces of the photoreceptor drums 1a to 1d. Next, the exposure device 5 irradiates the drums with light according to the image data, forming an electrostatic latent image on each photoreceptor drum 1a to 1d corresponding to the image data. The developing devices 3a to 3d are each filled with a predetermined amount of two-component developer containing yellow, cyan, magenta, and black toners. If the proportion of toner in the two-component developer filled in each developing device 3a to 3d falls below a specified value due to the formation of a toner image, toner is replenished from toner containers 4a to 4d to each developing device 3a to 3d.

[0024] The toner in the developer is supplied onto the photoreceptor drums 1a to 1d by the developing devices 3a to 3d and adheres electrostatically. This forms a toner image corresponding to the electrostatic latent image formed by exposure from the exposure device 5.

[0025] Then, the primary transfer rollers 6a to 6d apply an electric field at a predetermined transfer voltage between the primary transfer rollers 6a to 6d and the photoreceptor drums 1a to 1d, and the yellow, cyan, magenta, and black toner images on the photoreceptor drums 1a to 1d are primary transferred onto the intermediate transfer belt 8. These images are formed in predetermined positional relationships. Subsequently, in preparation for the formation of a new electrostatic latent image, any toner remaining on the surface of the photoreceptor drums 1a to 1d after the primary transfer is removed by the cleaning devices 7a to 7d.

[0026] The intermediate transfer belt 8 is stretched between the upstream driven roller 10 and the downstream drive roller 11. As the drive roller 11 rotates due to a belt drive motor (not shown), the intermediate transfer belt 8 begins to rotate counterclockwise, and the sheet P is transported from the resist roller pair 13 to the secondary transfer nip section N between the drive roller 11 and the adjacent secondary transfer roller 9 at a predetermined timing. The toner image on the intermediate transfer belt 8 is then secondary transferred onto the sheet P as it passes through the secondary transfer nip section N.

[0027] The sheet P on which the toner image has been secondarily transferred is transported to the fuser unit 14. The fuser unit 14 has a fuser belt 14a and a pressure roller 14b. The fuser belt 14a is heated by a heating device (not shown), such as a heater or an induction heating unit. The pressure roller 14b is pressed against the fuser belt 14a to form a fuser nip, and imparts rotational driving force to the fuser belt 14a.

[0028] The sheet P, transported to the fixing unit 14, is heated and pressurized by the fixing belt 14a and pressure roller 14b, fixing the toner image to the surface of the sheet P and forming a predetermined full-color image.

[0029] The sheet P on which the full-color image has been formed is directed in a different direction by a transport guide member 15 located at the branching point of the paper transport path 19, after passing through a transport roller pair 40, and is then discharged into the discharge tray 18 by a discharge roller pair (discharge section) 17 (or after being sent to the branching transport path 20 where images have been formed on both sides).

[0030] The transport roller pair 40 feeds the sheet P from the fixing unit 14 to the discharge roller pair (discharge unit) 17.

[0031] The paper transport path 19 connects the paper feed device 60, the transfer unit 50, the fixing unit 14, and the discharge unit 17. The branch transport path 20 branches off from the paper transport path 19 downstream of the transport roller pair 40 and communicates with the paper transport path 19 upstream of the registration roller pair 13. The branch transport path 20 extends vertically (Z1-Z2) along the side surface 102 of the image forming apparatus 100 and is curved in a roughly C-shape.

[0032] <Configuration of a retard roller> Figure 2 is a perspective view showing part of the paper feed device 60, and Figure 3 is a partial cross-sectional view showing an enlarged portion of the paper feed device 60. Figure 4 is a perspective view of the retard roller 64, and Figure 5 is a cross-sectional view of the torque limiter 644. The paper feed device 60 further comprises a feed roller 63 and a housing 69 that holds the retard roller 64.

[0033] The retard roller 64 comprises a roller body 641, a shaft 642, a holding member 643, and a torque limiter 644.

[0034] The roller body 641 rotates around the rotation axis J2. At least the circumferential surface of the roller body 641 is made of a material with a high coefficient of friction, such as silicone rubber, urethane rubber, or EPDM. The circumferential surface of the roller body 641 wears down with continued use. This makes it difficult for it to follow the feed roller 63 smoothly. For this reason, the roller body 641 with reduced performance needs to be replaced.

[0035] The shaft 642 is attached to the roller body 641 and extends along the rotation axis J2. The shaft 642 is, for example, a cylindrical metal body. At the other end of the shaft 642 in the axial direction Y2, a groove 642a is formed on the outer surface, which is recessed and extends in the circumferential direction.

[0036] The retaining member 643 is positioned on one axial side Y1 of the roller body 641 and supports the shaft 642. Specifically, the retaining member 43 is a resin molded product and has a retaining body portion 6431 extending in the axial direction (Y1-Y2) and a pair of side wall portions 6432. The side wall portions 6432 are positioned at both ends of the retaining body portion 6431 in the axial direction (Y1-Y2). The side wall portions 6432 have through holes 6432a that penetrate in the axial direction (Y1-Y2), and the shaft 642 is inserted through the through holes 6432a. The shaft 642 is fixed to the pair of side wall portions 6432 and is immovable (does not rotate around the rotation axis J2).

[0037] Furthermore, the retaining member 643 is provided with a pair of first support portions 6433. The first support portions 6433 each protrude axially (Y1-Y2) from the outer surface of the side wall portion 6432. The retaining member 643 is inserted into a support hole (not shown) formed in the housing 69. As a result, the retaining member 643 is supported in the housing 69 via the first support portions 6433 so as to be able to swing around the pivot axis J1.

[0038] Furthermore, the holding member 643 is provided with press-to-press pieces 6434 and 6435. The press-to-press pieces 6434 and 6435 protrude radially from the holding body 6431. The press-to-press piece 6434 is biased toward the feed roller 63 by a pressing mechanism (not shown). The press-to-press piece 6435 is biased toward the feed roller 31 by a separation mechanism (not shown).

[0039] The torque limiter 644 switches the rotation and stopping of the roller body 641. The torque limiter 644 has an inner cylinder portion 644a, an outer cylinder portion 644b, and a spring (elastic member) 644c (see Figure 5). The inner cylinder portion 644a and the outer cylinder portion 644b are arranged coaxially. The outer cylinder portion 644b is positioned on one axial side Y1 of the roller body 641 and is fixed to the shaft 642 and immovable (does not rotate around the rotation axis J2).

[0040] The inner cylinder portion 644a is a cylindrical body that is rotatably inserted onto the shaft 642. The other axial end Y2 of the inner cylinder portion 644a is fitted into the outer cylinder portion 644b via a spring 644c. On the other hand, the roller body 641 is fitted onto the other axial end Y1 of the inner cylinder portion 644a. The inner cylinder portion 644a and the roller body 641 are fixed together.

[0041] The spring 644c is a coil spring that transmits and releases torque between the inner cylinder portion 644a and the outer cylinder portion 644b.

[0042] When a sheet P enters the nip between the feed roller 63 and the retard roller 64, a corresponding torque is applied to the roller body 641 due to friction with the sheet P. At this time, the spring 644c loosens, and the inner cylinder 644a and the roller body 641 rotate around the rotation axis J2. As a result, the roller body 641 rotates in accordance with the feed roller 63, allowing the sheet P that has entered the paper feed nip to be sent downstream X1 in the conveying direction.

[0043] On the other hand, when multiple sheets P enter the nip section, no torque is applied to the retard roller 64. In this case, the spring 644c does not loosen, and the inner cylinder 644a and the roller body 641 do not rotate around the rotation axis J2. Therefore, only one sheet P in contact with the feed roller 63 can be sent downstream X1 in the conveying direction.

[0044] Furthermore, in this embodiment, the outer cylinder portion 644b also functions as a restricting member that restricts the axial movement Y2 of the roller body 641. The outer cylinder portion 644b is provided with a locking portion 6442 and a second support portion 6441.

[0045] The locking portion 6442 has a snap-fit ​​structure and is composed of a base portion 6442a and a claw portion 6442b. The base portion 6442a protrudes axially Y2 from the tip of the other axial direction Y2 of the outer cylinder portion 644b. The claw portion 6442b protrudes radially inward from the base portion 6442a and engages with the groove portion 642a of the shaft 642. This stably fixes the outer cylinder portion 644b to the shaft 642. Therefore, it is possible to prevent the roller body 641 and the inner cylinder portion 644a from shifting axially Y2. In other words, the outer cylinder portion (regulating member) 644b is positioned axially Y2 of the roller body 641 and restricts the movement of the roller body 641 axially Y2.

[0046] Furthermore, the locking portion 6442 can release the engagement between the claw portion 6442b and the groove portion 642a. This releases the locking and allows the outer cylinder portion 644b to be easily removed from the shaft 642. By removing the outer cylinder portion 644b from the shaft 642, the roller body 641 and the inner cylinder portion 644a can also be easily removed from the shaft 642. Therefore, the ease of replacing the roller body 641 can be improved.

[0047] The second support portion 6441 extends radially outward from the outer cylinder portion 644b and has a support projection 6441a at its tip. The support projection 6441a is arranged coaxially with the pivot axis J1 and protrudes in the axial direction of the pivot axis J1. The support projection 6441a is inserted into a support hole (not shown) formed in the housing 69. As a result, the roller body 641 is supported so as to be able to pivot around the pivot axis J1 via the first support portion 6433 and the second support portion 6441, which are arranged on both sides in the axial direction. The roller body 641 is also pressed against the feed roller 63 by the holding member 643 being pressed against it.

[0048] By supporting the roller body 641 from both sides in the axial direction, the pressing force of the roller body 641 against the feed roller 63 can be made uniform over the axial direction (Y1-Y2). This prevents uneven wear of the roller body 641 on one side in the axial direction (Y1-Y2) due to continued use. Consequently, sheet feeding failures can be reduced. In addition, the maintenance-free period of the roller body 641 is extended, and maintenance costs can be reduced.

[0049] Furthermore, the first support portion 6433 is positioned in two places on the holding member 643, which stabilizes the oscillation of the roller body 641 when the holding member 643 is pressed.

[0050] Furthermore, the regulating member is composed of a part of the torque limiter 644 (outer cylinder portion 644b), which helps to suppress an increase in the number of parts of the retard roller 64.

[0051] Furthermore, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the invention. For example, in this embodiment, the restricting member is composed of the outer cylinder portion 644b of the torque limiter 644, but the restricting member may be a separate member from the members constituting the torque limiter 644 (outer cylinder portion 644b). In this case, the outer cylinder portion 644b, which serves as the restricting member, is arranged independently of the spring 644c and the inner cylinder portion 644a, on the other axial direction Y2 of the roller body 641. Alternatively, the members constituting the torque limiter (inner cylinder portion 644a, outer cylinder portion, and spring (elastic member) 644c) are arranged inside the roller body 641. This allows the retard roller 64 to be miniaturized in the axial direction (Y1-Y2), and the same effects as described above can be obtained. [Explanation of Symbols]

[0052] 1a~1d Photoconductor drum 2a~2d Charging device 3a~3d developing device 4a~4d Toner container 5. Exposure apparatus 6a~6d Primary transfer roller 7a~7d Cleaning equipment 8. Intermediate transfer belt 9. Secondary transfer roller 10 Driven rollers 11 Drive rollers 13 Resist Roller vs 14 Fixing section 14a Fixing belt 14b Pressure Roller 15 Conveyor guide member 17 Discharge section 18 Output tray 19. Paper transport path 20 Branching transport routes 25 Belt Cleaner 31 Feed Roller 40 Conveyor Rollers 43 Retaining member 50 Transfer section 60 Paper feeder 61 Paper Cassette 62 Pickup Roller 63 Feed Roller 64 Retard Rollers 69 Housing 100 Image forming apparatus 641 Roller body 642 shaft 642a Groove 643 Retaining member 644 Torque Limiter 644a Inner cylinder 644b Outer cylinder 644c spring 6431 Holding body part 6432 Side wall section 6432a Through hole 6433 1st support part 6434, 6435 Pressed piece 6441 Second support part 6441a Support protrusion 6442 Locking part 6442a Base part 6442b Claw part J1 Oscillating axis J2 Rotation axis N Secondary transfer nip section P Sheet Pa~Pd Image Forming Unit X1 Downstream side in the transport direction Y1 Axial direction one side Y2 Axial other side Z1 upper

Claims

1. A feed roller that conveys a sheet by rotating when power is transmitted to it, The system comprises a retard roller that is pressed against the feed roller to form a nip portion and conveys the sheet while separating it, The retard roller is, A roller body that rotates around the axis of rotation, A shaft attached to the roller body and extending along the rotation axis, A torque limiter that switches the rotation and stopping of the roller body, A holding member is positioned on one axial side of the roller body and supports the shaft, The roller body has a restricting member positioned on the other side of its axial direction and having a locking portion that engages with the shaft, thereby restricting the axial movement of the roller body. A paper feeding device in which the roller body is pivotably supported via a first support portion provided on the holding member and a second support member provided on the regulating member, and is pressed against the feed roller.

2. The paper feeding device according to claim 1, wherein the first support portion is arranged in two places on the holding member.

3. The paper feeding device according to claim 1 or claim 2, wherein the regulating member is composed of a part of the torque limiter.

4. The regulating member is a separate component from the component that constitutes the torque limiter. The paper feeding device according to claim 1 or claim 2, wherein the member constituting the torque limiter is arranged inside the roller body.

5. A paper feeder according to claim 1 or claim 2, An image forming apparatus that prints an image on the sheet fed from the aforementioned paper feeding device.

Images