Sheet feeding device and image forming device

Abstract

To easily replace a separation roller.SOLUTION: A sheet storage device includes: a feeding roller; a separation roller for nipping a sheet between itself and the feeding roller; a roller support mechanism; and a control part. The roller support mechanism includes: a support member rotatable around a rotation shaft extending in the width direction orthogonal to the sheet feeding direction; and a driving source for rotating the support member. The support member supports the plurality of separation rollers in a rotatable manner. The plurality of separation rollers are arranged having an interval with each other in the circumferential direction around the rotation shaft. By performing roller switching processing for controlling the driving source and rotating the support member, the control part allows the separation roller different from the separation roller pressure-contacted with the feeding roller before roller switching processing to be pressure-contacted with the feeding roller.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a sheet feeding device and an image forming apparatus.

Background Art

[0002] A conventional sheet feeding device includes a feed roller (conveying roller) and a separation roller (retard roller). The feed roller and the separation roller are in pressure contact with each other. The feed roller rotates when the driving force of a motor is transmitted thereto. The separation roller rotates in accordance with the rotation of the feed roller. The feed roller and the separation roller nip a sheet therebetween and rotate. Thereby, the sheet is fed. Such a sheet feeding device is disclosed in, 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] When the separation roller deteriorates, the separation roller slips with respect to the sheet. As a result, poor feeding of the sheet is likely to occur between the feed roller and the separation roller. When poor feeding of the sheet is likely to occur due to deterioration of the separation roller, by replacing the separation roller, it is possible to suppress the occurrence of poor feeding of the sheet.

[0005] However, for a user (including a maintenance worker), the work of replacing the separation roller is troublesome. Also, during the work of replacing the separation roller, the sheet feeding device (the image forming apparatus including the same) cannot be used. If the work of replacing the separation roller takes time, measures such as using another image forming apparatus must be taken, and the convenience of the user is reduced.

[0006] The present invention has been made to solve the above problems, and an object thereof is to provide a sheet feeding device and an image forming apparatus capable of easily replacing a separation roller.

Means for Solving the Problems

[0007] To achieve the above object, a sheet feeding device according to a first aspect of the present invention includes a feeding roller that is rotatably supported, contacts a sheet at a feeding position, and rotates by transmitting a driving force to feed the sheet; a separation roller that is rotatably supported, presses against the feeding roller at the feeding position, and nips the sheet between the separation roller and the feeding roller; a roller support mechanism that supports the separation roller; and a control unit. The roller support mechanism has a support member that is rotatable about a rotation axis extending in a width direction orthogonal to the sheet feeding direction, and a drive source that rotates the support member. The support member rotatably supports a plurality of separation rollers. The plurality of separation rollers are arranged at intervals in a circumferential direction about the rotation axis. The control unit performs a roller switching process of controlling the drive source to rotate the support member, thereby causing a separation roller different from the separation roller that was pressing against the feeding roller before the roller switching process to press against the feeding roller.

[0008] An image forming apparatus according to a second aspect of the present invention includes the above sheet feeding device, and prints an image on a sheet fed from the sheet feeding device.

Effects of the Invention

[0009] In the present invention, the separation roller can be easily replaced.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0011] Hereinafter, an embodiment of the present invention will be described by taking a tandem type color laser printer as an example. Note that the present invention is not limited to printers and is also applicable to multi-function devices having a copy function and the like. Further, the present invention is not limited to color devices and is also applicable to monochrome devices.

[0012] <Configuration of Image Forming Apparatus> The configuration of the image forming apparatus 1000 of the present embodiment is shown in FIG. 1. The image forming apparatus 1000 is installed on a flat floor surface FL. The vertical direction of the image forming apparatus 1000 is a direction perpendicular to the floor surface FL.

[0013] The image forming apparatus 1000 includes a main conveyance path MP (indicated by a thick dashed arrow). The main conveyance path MP extends from a feeding position P0, passes through a transfer position P1 and a fixing position P2, and reaches a discharge tray ET.

[0014] In a printing job, a sheet S is fed into the main conveyance path MP and conveyed along the main conveyance path MP. Also, an image using toner is formed. Then, the image is printed on the sheet S being conveyed. In other words, the transfer process of the image onto the sheet S being conveyed is performed at the transfer position P1. At the fixing position P2, the fixing process of the image on the sheet S is performed.

[0015] The image forming apparatus 1000 includes a pair of conveyance rollers. The pair of conveyance rollers has a pair of rollers that are in pressure contact with each other. The pair of conveyance rollers has a conveyance nip between the rollers. By rotating, the pair of conveyance rollers conveys the sheet S that has reached the conveyance nip. In other words, the pair of conveyance rollers nips the sheet S between the rollers and conveys the sheet S by rotating in that state.

[0016] The number of installed pairs of conveyance rollers is plural. The pairs of conveyance rollers are arranged on the main conveyance path MP. Also, the pairs of conveyance rollers are arranged on the duplex printing conveyance path DP (indicated by the thin dashed arrow) described later. In FIG. 1, among the plurality of pairs of conveyance rollers, the pair of conveyance rollers that conveys the sheet S at the position closest to the feeding position P0 is denoted by the reference numeral CR, and the reference numerals for the other pairs of conveyance rollers are omitted.

[0017] The image forming apparatus 1000 includes a sheet feeding device 100. The sheet feeding device 100 feeds the sheet S to the main conveyance path MP. The configuration of the sheet feeding device 100 will be described in detail later.

[0018] The image forming apparatus 1000 includes four image forming units 110. The four image forming units 110 respectively correspond to the colors cyan, magenta, yellow, and black. The four image forming units 110 form images using toner of the corresponding colors. Hereinafter, the configuration of one of the image forming units 110 will be described, but the configurations of the four image forming units 110 are the same as each other. Therefore, the description of the configurations of the other image forming units 110 will be omitted by referring to the following description.

[0019] The details of the image forming unit 110 are shown in FIG. 2. The image forming unit 110 includes a photosensitive drum 111. The photosensitive drum 111 is rotatably supported. The image forming unit 110 causes an image formed using toner to be carried on the outer peripheral surface of the photosensitive drum 111. The photosensitive drum 111 rotates while carrying a toner image on its outer peripheral surface.

[0020] The image forming unit 110 includes a charging device 112, an exposure device 113, a developing device 114, and a cleaning device 115. When the image forming unit 110 forms an image, the photosensitive drum 111 rotates. The charging device 112 charges the outer peripheral surface of the photosensitive drum 111. The exposure device 113 exposes the outer peripheral surface of the photosensitive drum 111 to form an electrostatic latent image on the outer peripheral surface of the photosensitive drum 111. The developing device 114 supplies toner to the outer peripheral surface of the photosensitive drum 111 and develops the electrostatic latent image into a toner image. Note that the toner image on the outer peripheral surface of the photosensitive drum 111 is primarily transferred to the intermediate transfer belt 120 described later. The cleaning device 115 removes the toner remaining on the outer peripheral surface of the photosensitive drum 111 without being transferred to the intermediate transfer belt 120.

[0021] Also, as shown in FIG. 1, the image forming apparatus 1000 includes an intermediate transfer belt 120. The intermediate transfer belt 120 is an endless belt. The intermediate transfer belt 120 is rotatably supported. The intermediate transfer belt 120 is stretched by a plurality of stretching rollers.

[0022] One of the plurality of stretching rollers is connected to a belt motor (not shown). In the following description, the stretching roller connected to the belt motor is referred to as a driving roller. In FIG. 1, among the plurality of stretching rollers, the driving roller is denoted by reference numeral 121, and the reference numerals of the other stretching rollers are omitted. The intermediate transfer belt 120 rotates driven by the rotation of the driving roller 121. The other stretching rollers rotate driven by the intermediate transfer belt 120.

[0023] The image forming apparatus 1000 includes four primary transfer rollers 130. The four primary transfer rollers 130 are respectively assigned to the colors cyan, magenta, yellow, and black. Each primary transfer roller 130 is disposed on the inner circumferential side of the intermediate transfer belt 120. Each primary transfer roller 130 faces the photosensitive drum 111 carrying the image of the corresponding color via the intermediate transfer belt 120. Each primary transfer roller 130 is pressed against the photosensitive drum 111 carrying the image of the corresponding color via the intermediate transfer belt 120.

[0024] The image forming apparatus 1000 includes a secondary transfer roller 140. The secondary transfer roller 140 is pressed against the outer peripheral surface of the intermediate transfer belt 120 at the transfer position P1. The secondary transfer roller 140 sandwiches the intermediate transfer belt 120 between itself and the drive roller 121, forming a transfer nip between itself and the outer peripheral surface of the intermediate transfer belt 120. Thereby, a transfer nip is formed at the transfer position P1. The main conveyance path MP passes through the transfer nip.

[0025] In a printing job, the sheet S is conveyed toward the transfer position P1 (i.e., the transfer nip). The sheet S being conveyed passes through the transfer nip.

[0026] Each image forming unit 110 forms an image using toner of the corresponding color. Each primary transfer roller 130 performs primary transfer of the image onto the outer peripheral surface of the intermediate transfer belt 120.

[0027] The intermediate transfer belt 120 rotates while carrying the image primarily transferred from each photosensitive drum 111 on its outer peripheral surface. While the sheet S passes through the transfer nip, the sheet S contacts the outer peripheral surface of the intermediate transfer belt 120. The secondary transfer roller 140 performs secondary transfer of the image onto the sheet S passing through the transfer nip.

[0028] The image forming apparatus 1000 includes a fixing unit 150. The fixing unit 150 includes a heating roller and a pressure roller. The fixing unit 150 is disposed at a fixing position P2. The heating roller incorporates a heater. The pressure roller is in pressure contact with the heating roller. The heating roller and the pressure roller are in pressure contact with each other to form a fixing nip at the fixing position P2.

[0029] In a printing job, the sheet S passes through the fixing position P2. That is, the sheet S is sandwiched between the fixing nips. The fixing unit 150 heats the sheet S passing through the fixing position P2. At the fixing position P2, pressure is applied to the sheet S. The fixing unit 150 heats and applies pressure to the sheet S to fix the toner image on the sheet S. The sheet S after the fixing process is discharged to a discharge tray ET.

[0030] In addition to a single-sided printing job in which an image is printed only on one side of the sheet S, the image forming apparatus 1000 can execute a double-sided printing job in which an image is printed on both sides of the sheet S. To execute the double-sided printing job, the image forming apparatus 1000 includes a double-sided printing conveyance path DP.

[0031] The double-sided printing conveyance path DP branches from the main conveyance path MP at a branch position P3 on the downstream side in the sheet conveyance direction from the fixing position P2 in the main conveyance path MP. Then, the double-sided printing conveyance path DP merges into the main conveyance path MP at a merging position P4 on the upstream side in the sheet conveyance direction from the transfer position P1 in the main conveyance path MP.

[0032] When the execution job is a single-sided printing job, the sheet S passes through the transfer nip only once, and the transfer process is performed once on the sheet S passing through the transfer nip. Then, after the first transfer process, the sheet S is directly discharged to the discharge tray ET.

[0033] When the execution job is a duplex printing job, since the transfer process is performed once on each of the front and back surfaces of the sheet S, the sheet S passes through the transfer nip twice. Specifically, when the sheet S passes through the transfer nip for the first time, the transfer process is performed on one surface of the sheet S. After the first transfer process, the sheet S is switched back after the rear end of the sheet S passes through the branch position P3 and before the sheet S is completely discharged to the discharge tray ET. As a result, the sheet S is drawn into the duplex printing conveyance path DP from its rear end.

[0034] Thereafter, the sheet S is conveyed along the duplex printing conveyance path DP. Then, the sheet S on the duplex printing conveyance path DP is returned to the main conveyance path MP from the merging position P4. The sheet S returned to the main conveyance path MP is conveyed along the main conveyance path MP and passes through the transfer nip again. At this time, the orientation of the front and back surfaces of the sheet S is reversed to the opposite direction compared to when it passed through the transfer nip last time. As a result, when the sheet S passes through the transfer nip for the second time, the transfer process is performed on the other surface opposite to one surface of the sheet S.

[0035] Also, as shown in FIG. 3, the image forming apparatus 1000 includes a control unit 10. The control unit 10 includes processing circuits such as a CPU and an ASIC. The control unit 10 also includes storage devices such as a ROM and a RAM. The control unit 10 controls the printing jobs executed in the image forming apparatus 1000.

[0036] The control unit 10 controls the feeding of the sheet S by the sheet feeding device 100. For this reason, it can be said that the control unit 10 is a component of the sheet feeding device 100. That is, the sheet feeding device 100 includes the control unit 10. Note that a feeding control unit for controlling the feeding of the sheet S may be installed in the sheet feeding device 100.

[0037] The image forming apparatus 1000 includes a communication unit 101. The communication unit 101 includes a communication circuit, a communication memory, a communication connector, and the like. The communication unit 101 is communicably connected to an external device via a network such as a LAN. A user terminal is an example of the external device. A personal computer (PC), a smartphone, a tablet computer, and the like can be the user terminal.

[0038] The communication unit 101 is connected to a control unit 10. The control unit 10 communicates with the external device using the communication unit 101. For example, print data of a print job is transmitted from the external device to the image forming apparatus 1000. The print data includes image data to be printed in the print job. The control unit 10 controls the print job based on the print data.

[0039] The image forming apparatus 1000 includes an operation unit 102. The operation unit 102 is an operation panel having a touch screen. The operation unit 102 receives settings and instructions from the user. The operation unit 102 displays various information.

[0040] The operation unit 102 is connected to the control unit 10. The control unit 10 detects settings and instructions received by the operation unit 102 from the user. The control unit 10 controls the display by the operation unit 102.

[0041] The image forming apparatus 1000 includes a storage unit 103. Various storage devices such as a flash memory, an HDD, and an SSD can be used as the storage unit 103. The storage unit 103 is connected to the control unit 10. The control unit 10 writes data to the storage unit 103 and reads data from the storage unit 103.

[0042] <Configuration of the Sheet Feeding Device> As shown in FIG. 1, the sheet feeding device 100 is disposed in the lower part of the main body of the image forming apparatus 1000 (hereinafter simply referred to as the apparatus main body). The sheet feeding device 100 includes a sheet cassette CA. The sheet cassette CA is attached to the apparatus main body. The sheet cassette CA is detachable from the apparatus main body.

[0043] The sheet cassette CA houses the sheet S. The sheet feeding device 100 feeds the sheet S housed in the sheet cassette CA to the main conveyance path MP. That is, in a printing job, the sheet S in the sheet cassette CA is used. When the printing job is executed, the sheet S in the sheet cassette CA is consumed and decreases. When the sheet S runs out from the sheet cassette CA due to the execution of the printing job, the sheet cassette CA is pulled out from the apparatus main body, and after the sheet S is housed in the sheet cassette CA, the sheet cassette CA is returned to the apparatus main body.

[0044] The number of attachable sheet cassettes CA is not particularly limited. A plurality of sheet cassettes CA may be attachable to the apparatus main body, or there may be one sheet cassette CA attachable to the apparatus main body. FIG. 1 illustrates, as an example, an image forming apparatus 1000 having one attachable sheet cassette CA.

[0045] In the following description, the feeding direction of the sheet S by the sheet feeding device 100 is simply referred to as the feeding direction. Also, the vertical direction and the direction orthogonal to the feeding direction (i.e., one horizontal direction) are referred to as the width direction. The front-rear direction of the image forming apparatus 1000 (in other words, the front-rear direction of the sheet feeding device 100) corresponds to the width direction. The sheet cassette CA is detachable from the apparatus main body in the width direction.

[0046] As shown in FIG. 4, the sheet feeding device 100 includes a lift plate 1. The lift plate 1 is disposed in the sheet cassette CA. By housing the sheet S in the sheet cassette CA, the sheet S is set on the lift plate 1. When there are a plurality of sheets S in the sheet cassette CA, a plurality of sheets S are stacked on the lift plate 1.

[0047] The lift plate 1 is displaceable such that the end on the upstream side in the feeding direction serves as a fulcrum and the end on the downstream side in the feeding direction swings vertically. In other words, the lift plate 1 is supported so as to be movable up and down. In the following description, the upward movement of the lift plate 1 means that the end on the downstream side in the feeding direction of the lift plate 1 is displaced upward, and the downward movement of the lift plate 1 means that the end on the downstream side in the feeding direction of the lift plate 1 is displaced downward.

[0048] The lift plate 1 is lifted by the lifting member 11 and moves upward. That is, the sheet feeding device 100 includes the lifting member 11. The lifting member 11 is disposed in the sheet cassette CA. Specifically, the lifting member 11 is disposed below the lift plate 1. The lifting member 11 has a rotating shaft 11A extending in the width direction at the end on the upstream side in the feeding direction. A lift motor (not shown) is connected to the rotating shaft 11A. When the lift motor is driven, the rotating shaft 11A rotates.

[0049] When the lift motor is driven, the lifting member 11 is displaced such that the end on the upstream side in the feeding direction (i.e., the rotating shaft 11A) serves as a fulcrum and the end on the downstream side in the feeding direction swings vertically. The lifting member 11 lifts the lift plate 1 by displacing the end on the downstream side in the feeding direction upward.

[0050] The sheet feeding device 100 includes a pickup roller 2. The pickup roller 2 is rotatably supported about an axis extending in the width direction. The pickup roller 2 is disposed at a position facing the lift plate 1 in the vertical direction. When the sheet S is set on the lift plate 1, the sheet S on the lift plate 1 and the pickup roller 2 face each other in the vertical direction.

[0051] The pickup roller 2 contacts the uppermost layer sheet S on the lift plate 1 from above. In order to bring the pickup roller 2 into contact with the sheet S, the lift plate 1 moves upward. The pickup roller 2 contacts and rotates the uppermost layer sheet S on the lift plate 1 from above, thereby pulling out the sheet S from the lift plate 1 and feeding the sheet S toward the feeding position P0.

[0052] The sheet feeding device 100 includes a feeding roller 3. The feeding roller 3 is rotatably supported about an axis extending in the width direction. A feeding motor FM is connected to the rotating shaft of the feeding roller 3. When the feeding motor FM is driven, a driving force is transmitted from the feeding motor FM to the feeding roller 3, causing it to rotate. The feeding motor FM is connected to the control unit 10. The control unit 10 controls the feeding motor FM.

[0053] For example, the rotating shafts of the pickup roller 2 and the feeding roller 3 are connected to each other via a coupling mechanism (not shown) including gears or the like. That is, when one rotating shaft rotates, the other rotating shaft rotates due to the function of the coupling mechanism. Thereby, the pickup roller 2 rotates by the driving force transmitted from the feeding motor FM.

[0054] The feeding roller 3 is disposed at the feeding position P0. The feeding roller 3 contacts the sheet S at the feeding position P0 and rotates in that state. Thereby, the feeding roller 3 feeds the sheet S pulled out from the lift plate 1 to the main conveyance path MP.

[0055] Note that the feeding roller 3 contacts one surface of the sheet S at the feeding position P0. One surface of the sheet S is the surface facing upward on the lift plate 1 and is the surface that the pickup roller 2 contacts. That is, the other surface opposite to one surface of the sheet S is the surface facing downward on the lift plate 1 and is the surface that contacts one surface of the sheet S one below on the lift plate 1.

[0056] The sheet feeding device 100 includes a separating roller 4. The separating roller 4 is rotatably supported about an axis extending in the width direction. The separating roller 4 is pressed against the feeding roller 3 at the feeding position P0. The separating roller 4 nips the sheet S between itself and the feeding roller 3.

[0057] The separation roller 4 eliminates the double feeding of the sheet S that occurs when the topmost sheet S on the lift plate 1 and the sheet S one below it are overlapped and pulled out. In other words, due to the function of the separation roller 4, at the feeding position P0, the sheets S are separated one by one.

[0058] To eliminate the double feeding of the sheet S, the separation roller 4 has a torque limiter 41 that applies a rotational load to the separation roller 4. The torque limiter 41 corresponds to the "load mechanism". The torque limiter 41 is connected to the separation roller 4.

[0059] When the rotational driving force transmitted from the feeding roller 3 to the separation roller 4 is equal to or less than the threshold value, the torque limiter 41 makes the separation roller 4 non-rotatable. Specifically, when the topmost sheet S (herein referred to as the first sheet S) on the lift plate 1 and the sheet S one below it (herein referred to as the second sheet S) overlap and enter the feeding position P0, the feeding roller 3 contacts the first sheet S and advances the first sheet S in the feeding direction, while the separation roller 4 does not contact the first sheet S but contacts the second sheet S. For this reason, it is difficult for the rotational driving force to be transmitted from the feeding roller 3 to the separation roller 4. As a result, the rotational driving force transmitted from the feeding roller 3 to the separation roller 4 becomes equal to or less than the threshold value, and the separation roller 4 stops rotating.

[0060] While the feeding roller 3 rotates, the non-rotation of the separation roller 4 suppresses the advancement of the second sheet S that contacts the separation roller 4 but not the feeding roller 3 in the feeding direction. Thereby, the first sheet S and the second sheet S can be separated. That is, the double feeding in which the first sheet S and the second sheet S are overlapped and fed can be eliminated.

[0061] <Configuration of the roller support mechanism> The sheet feeding device 100 includes a roller support mechanism 5 as shown in FIG. 5. The roller support mechanism 5 rotatably supports the separation roller 4. In other words, the roller support mechanism 5 rotatably supports the rotation shaft 40 (corresponding to the "roller shaft") of the separation roller 4.

[0062] The roller support mechanism 5 includes a support member 51. The support member 51 has a pair of support portions 511 facing each other in the width direction. The pair of support portions 511 are connected by a base portion 500 located between the pair of support portions 511 in the width direction.

[0063] Each of the pair of support portions 511 has a support hole 510 for supporting the rotary shaft 40. In other words, the support member 51 has a pair of support holes 510. One end in the width direction of the rotary shaft 40 is inserted into one support hole 510, and the other end in the width direction of the rotary shaft 40 is inserted into the other support hole 510. Thereby, the separation roller 4 is rotatably supported by the support member 51.

[0064] Each of the pair of support holes 510 is a long hole. Thereby, the rotary shaft 40 can swing in the longitudinal direction of the support hole 510. That is, the separation roller 4 can swing in the longitudinal direction of the support hole 510.

[0065] The roller support mechanism 5 includes a biasing member 52. The biasing member 52 is, for example, a compression coil spring. The biasing member 52 is disposed on one end side and the other end side in the width direction of the rotary shaft 40, respectively. Only one biasing member 52 on one side is shown in FIG. 5. One end of the biasing member 52 is attached to the base portion 500. The other end of the biasing member 52 is attached to the rotary shaft 40 via an attachment (not shown).

[0066] The biasing member 52 biases the rotary shaft 40 in the longitudinal direction of the support hole 510 (long hole). The biasing direction of the biasing member 52 is the direction in which the separation roller 4 faces the feed roller 3. Thereby, the separation roller 4 can be pressed against the feed roller 3.

[0067] The roller support mechanism 5 includes a rotating shaft 50. The rotating shaft 50 extends in the width direction. The rotating shaft 50 penetrates the support member 51 in the width direction. Specifically, the rotating shaft 50 penetrates one support portion 511, the base portion 500, and the other support portion 511. The support member 51 is fixed to the rotating shaft 50. Thus, the support member 51 rotates together with the rotating shaft 50 when the rotating shaft 50 rotates. That is, the support member 51 is rotatable about the rotating shaft 50.

[0068] In the following description, for convenience, the rotating shaft 40 of the separation roller 4 is referred to as the roller rotating shaft 40, and the rotating shaft 50 of the support member 51 is referred to as the support rotating shaft 50. Also, when viewed from the width direction, the radial direction of the circle centered on the support rotating shaft 50 is simply referred to as the radial direction.

[0069] The support member 51 is in a sector shape with a central angle of about 90° when viewed from the width direction. That is, the pair of support portions 511 are in a sector shape with a central angle of about 90° when viewed from the width direction. The support rotating shaft 50 is disposed at a portion corresponding to the arc of the sector of the support member 51 when viewed from the width direction. Thus, the support member 51 is rotatable about a portion corresponding to the arc of the sector when viewed from the width direction.

[0070] The roller rotating shaft 40 is disposed at the radially outer edge portion of the support member 51 when viewed from the width direction. In other words, the support hole 510 is disposed at the radially outer edge portion of the support member 51 when viewed from the width direction. Further in other words, the separation roller 4 is disposed at the radially outer edge portion of the support member 51 when viewed from the width direction. Therefore, when the support member 51 rotates about the support rotating shaft 50, the separation roller 4 moves in the circumferential direction centered on the support rotating shaft 50.

[0071] The support member 51 rotatably supports a plurality of separation rollers 4 singly. For this reason, the support member 51 has a plurality of sets of a pair of support holes 510. For example, there are two separation rollers 4. In this case, the support member 51 has two sets of a pair of support holes 510. That is, the support member 51 has a pair of support holes 510 for each separation roller 4.

[0072] The plurality (two) of separation rollers 4 are arranged at intervals from each other in the circumferential direction centered on the support rotation shaft 50 when viewed from the width direction. One separation roller 4 is arranged at one end in the circumferential direction centered on the support rotation shaft 50 of the support member 51 when viewed from the width direction. The other separation roller 4 is arranged at the other end in the circumferential direction centered on the support rotation shaft 50 of the support member 51 when viewed from the width direction. Thereby, the arrangement positions of the two separation rollers 4 are shifted from each other by approximately 90° in the circumferential direction centered on the support rotation shaft 50 when viewed from the width direction.

[0073] The roller support mechanism 5 includes a switching motor 53. The switching motor 53 corresponds to the "driving source". The switching motor 53 is connected to the joint 501 of the support rotation shaft 50. The switching motor 53 rotates the support rotation shaft 50 by driving. That is, the switching motor 53 rotates the support member 51 by driving. When the support member 51 rotates, the plurality of separation rollers 4 move in the circumferential direction centered on the support rotation shaft 50.

[0074] The switching motor 53 is connected to the control unit 10. The control unit 10 controls the switching motor 53. In other words, the control unit 10 controls the rotation angle of the support member 51. When the support member 51 rotates, the separation roller 4 that presses against the feed roller 3 is switched.

[0075] Here, since the support hole 510 is a long hole, the separation roller 4 can swing in the longitudinal direction of the support hole 510, but the long hole as the support hole 510 has the radial direction as the longitudinal direction (see FIG. 6). And the biasing member 52 biases the roller rotation shaft 40 radially outward. Thereby, even if the support member 51 rotates and the separation roller 4 is switched, the separation roller 4 can be pressed against the feed roller 3.

[0076] The roller support mechanism 5 includes an actuator 54. The actuator 54 is fixed to the support rotation shaft 50. The actuator 54 rotates together with the support rotation shaft 50.

[0077] The actuator 54 has a plurality of detection pieces 540. The number of the detection pieces 540 is the same as the number of the separation rollers 4. When there are two separation rollers 4, there are two detection pieces 540. The plurality of detection pieces 540 are respectively assigned to different separation rollers 4.

[0078] For example, when viewed from the width direction, the actuator 54 has a plurality (two) of portions that extend in different directions toward the radially outer side. The radially outer tip portions of the plurality of portions respectively become the detection pieces 540. Thereby, the plurality of detection pieces 540 are arranged at intervals in the circumferential direction centered on the support rotation shaft 50. Further, when the support rotation shaft 50 rotates, the plurality of detection pieces 540 move in the circumferential direction centered on the support rotation shaft 50.

[0079] The roller support mechanism 5 includes a roller sensor 55 (see FIG. 8). The roller sensor 55 is, for example, a transmissive optical sensor having a light emitting portion and a light receiving portion. The light emitting portion and the light receiving portion of the roller sensor 55 are arranged to face each other with the movement paths of the plurality of detection pieces 540 interposed therebetween. In other words, the roller sensor 55 has a predetermined position on the movement path of the plurality of detection pieces 540 as a detection position. When the detection piece 540 is at the predetermined position, the optical path (the region between the light emitting portion and the light receiving portion) of the roller sensor 55 is blocked. When the detection piece 540 is not at the predetermined position, the optical path of the roller sensor 55 is not blocked. Thereby, the roller sensor 55 changes the output when the detection piece 540 is at the predetermined position and when it is not.

[0080] When any one of the detection pieces 540 is at the predetermined position, the separation roller 4 corresponding to the detection piece 540 at the predetermined position is in pressure contact with the feed roller 3. That is, when one separation roller 4 is in pressure contact with the feed roller 3, the detection piece 540 corresponding to the one separation roller 4 blocks the optical path of the roller sensor 55. When the other separation roller 4 is in pressure contact with the feed roller 3, the detection piece 540 corresponding to the other separation roller 4 blocks the optical path of the roller sensor 55.

[0081] The roller sensor 55 is connected to the control unit 10. The control unit 10 monitors the output of the roller sensor 55. Thereby, in a configuration where the separation roller 4 is movable in the circumferential direction, it is possible to easily determine whether or not the separation roller 4 is in pressure contact with the feed roller 3. In other words, it can easily be brought into a state where the separation roller 4 is in pressure contact with the feed roller 3.

[0082] <Judgment of feeding failure> The separation roller 4 deteriorates over time. When the separation roller 4 deteriorates, the separation roller 4 slips with respect to the sheet S. When the deterioration of the separation roller 4 becomes large, a feeding failure of the sheet S occurs at the feeding position P0, and the arrival of the sheet S at a position downstream of the feeding position P0 in the feeding direction is delayed. As a result, for example, it is determined that a jam has occurred and the printing job is stopped.

[0083] In order to suppress this inconvenience, when the old separation roller 4 in use deteriorates, it is preferable to replace it with a new separation roller 4. Therefore, the control unit 10 determines whether or not a feeding failure of the sheet S has occurred at the feeding position P0 (in other words, performs a feeding failure determination).

[0084] Here, a plurality of sheet sensors including a sheet sensor 56 (see FIG. 7) are connected to the control unit 10. The control unit 10 controls the feeding of the sheet S by the sheet feeding device 100 based on the outputs of the plurality of sheet sensors. In this configuration, the plurality of sheet sensors including the sheet sensor 56 can be said to be a component of the sheet feeding device 100. That is, the sheet feeding device 100 includes a plurality of sheet sensors including the sheet sensor 56. For convenience, only the sheet sensor 56 is illustrated in FIG. 7, and the illustration of other sheet sensors is omitted. The detection position of the sheet sensor 56 is denoted by a reference sign DP.

[0085] A plurality of sheet sensors detect the presence or absence of the sheet S at different positions downstream of the feeding position P0 in the feeding direction. Hereinafter, each detection position of the plurality of sheet sensors is referred to as a sheet detection position. The plurality of sheet sensors change their outputs according to the presence or absence of the sheet S at the corresponding sheet detection positions. The control unit 10 detects the arrival timing of the sheet S at each sheet detection position of the plurality of sheet sensors based on each output of the plurality of sheet sensors.

[0086] In the determination of feeding failure for the feeding position P0, the sheet sensor 56 is used. The control unit 10 determines whether a feeding failure of the sheet S has occurred at the feeding position P0 based on the output of the sheet sensor 56. Here, the sheet detection position DP of the sheet sensor 56 is the closest to the feeding position P0. That is, the control unit 10 determines whether a feeding failure of the sheet S has occurred at the feeding position P0 based on the arrival timing of the sheet S at the sheet detection position DP closest to the feeding position P0. Thereby, when a feeding failure occurs at the feeding position P0, it can be surely determined that a feeding failure has occurred at the feeding position P0.

[0087] For example, the control unit 10 measures the required arrival time from the start of feeding of the sheet S by the pickup roller 2 until the same sheet S reaches the sheet detection position DP closest to the feeding position P0. The greater the degree of feeding failure at the feeding position P0 (that is, the more the separation roller 4 is deteriorated), the longer the required arrival time. Therefore, when the required arrival time is longer than a predetermined threshold time, the control unit 10 determines that a feeding failure has occurred at the feeding position P0. Thereby, it can be easily determined whether a feeding failure has occurred at the feeding position P0.

[0088] <Separation Roller Switching Process> The control unit 10 controls the switching motor 53 to perform a roller switching process. The control unit 10 performs, as the roller switching process, a process of rotating the support member 51 around the support rotation shaft 50.

[0089] In the roller switching process, since the support member 51 rotates around the support rotation shaft 50, the plurality of separation rollers 4 move in the circumferential direction around the support rotation shaft 50. The separation roller 4 that was in pressure contact with the feed roller 3 separates from the feed roller 3, and another separation roller 4 approaches the feed roller 3.

[0090] Hereinafter, with reference to FIGS. 8 and 9, it will be specifically described. Note that the rotation direction of the support member 51 is indicated by a white arrow in FIG. 8.

[0091] In the following description, the separation roller 4 that was in pressure contact with the feed roller 3 before the roller switching process is denoted by reference numeral 4A, and the separation roller 4 that newly comes into pressure contact with the feed roller 3 by the roller switching process is denoted by reference numeral 4B. Further, the detection piece 540 assigned to the separation roller 4A is denoted by reference numeral 540A, and the detection piece 540 assigned to the separation roller 4B is denoted by reference numeral 540B.

[0092] Also, in the following description, when the detection piece 540 is present at the detection position of the roller sensor 55 (that is, when the optical path of the roller sensor 55 is blocked), a signal of the first level is output from the roller sensor 55, and when the detection piece 540 is not present at the detection position of the roller sensor 55 (that is, when the optical path of the roller sensor 55 is not blocked), a signal of the second level is output from the roller sensor 55.

[0093] The state before the roller switching process is shown in FIG. 8. At the time before the roller switching process, since the separation roller 4A is in pressure contact with the feed roller 3, the detection piece 540A is present at the detection position of the roller sensor 55. Therefore, the signal level output from the roller sensor 55 is the first level.

[0094] Then, as shown in FIG. 9, when switching from the separation roller 4A to the separation roller 4B, the control unit 10 rotates the support member 51. The control unit 10 starts driving the switching motor 53 in order to rotate the support member 51. As a result, the support member 51 starts to rotate. In FIG. 9, the rotation direction of the support member 51 is the clockwise direction.

[0095] First, when the support member 51 starts to rotate, as shown in the left diagram of FIG. 9, the separation roller 4A moves in the circumferential direction, and the separation roller 4A moves away from the feed roller 3. At this time, as the detection piece 540A moves in the circumferential direction together with the support member 51 (support rotation shaft 50), the detection piece 540A moves out of the detection position of the roller sensor 55. As a result, the signal level output from the roller sensor 55 changes from the first level to the second level.

[0096] Since the support member 51 is rotating, the separation roller 4B also moves in the circumferential direction. Also, the detection piece 540B moves in the circumferential direction. The separation roller 4B moves toward a position where it can contact the feed roller 3. The detection piece 540B moves toward the detection position of the roller sensor 55.

[0097] Thereafter, the separation roller 4B approaches the feed roller 3. Then, as shown in the central diagram of FIG. 9, the separation roller 4B contacts the feed roller 3, and in this state, the rotation of the support member 51 continues. At this time, the separation roller 4B is displaced radially inward against the biasing force of the biasing member 52. In other words, since the separation roller 4B (roller rotation shaft 40) is biased radially outward by the biasing member 52, the separation roller 4B is pressed against the feed roller 3.

[0098] After that, the rotation of the support member 51 continues further. As a result, as shown in the right diagram of FIG. 9, the detection piece 540B reaches the detection position of the roller sensor 55. That is, the optical path of the roller sensor 55 is blocked by the detection piece 540B. As a result, the signal level output from the roller sensor 55 changes from the second level to the first level. At this time, the pressing contact of the separation roller 4B against the feed roller 3 is maintained.

[0099] After starting the drive of the switching motor 53 (i.e., rotation of the support member 51), when the signal level output from the roller sensor 55 changes from the second level to the first level, the control unit 10 stops the drive of the switching motor 53. That is, when the separation roller 4B is in pressure contact with the feed roller 3, the control unit 10 stops the rotation of the support member 51.

[0100] When the roller switching process is performed, the state shown in FIG. 8 transitions to the state shown in the right diagram of FIG. 9. Specifically, it transitions from a state where the separation roller 4A is in pressure contact with the feed roller 3 to a state where the separation roller 4B is in pressure contact with the feed roller 3. That is, the switching of the separation roller 4 used for feeding the sheet S is performed.

[0101] In the present embodiment, as described above, the control unit 10 performs the roller switching process to newly bring a separation roller 4 different from the separation roller 4 that was in pressure contact with the feed roller 3 before the roller switching process into pressure contact with the feed roller 3. In the examples shown in FIGS. 8 and 9, the separation roller 4A is the separation roller 4 that was in pressure contact with the feed roller 3 before the roller switching process, and the separation roller 4B is the separation roller 4 that is newly brought into pressure contact with the feed roller 3 by the roller switching process.

[0102] Thereby, in the present embodiment, the separation roller 4 can be automatically replaced, so the replacement of the separation roller 4 becomes easy. In this configuration, the convenience for the user (including maintenance workers) is improved in the replacement of the separation roller 4.

[0103] For example, in a configuration where the roller switching process is not performed (i.e., a configuration where the separation roller 4 cannot be automatically replaced), when it is necessary to replace the old separation roller 4 in use due to deterioration with another new separation roller 4, the user has to perform the operation of removing the old separation roller 4 and attaching the new separation roller 4. Such replacement work takes time, and during that time, the sheet feeding device 100 (i.e., the image forming apparatus 1000) cannot be used, so the convenience is poor.

[0104] On the other hand, in this embodiment, the replacement of the separation roller 4 is completed promptly. Furthermore, the maintenance-free period of the separation roller 4 is extended, and the maintenance cost can be suppressed.

[0105] <Timing of Executing Roller Switching Process> Based on the result of the paper feed failure determination, the control unit 10 determines whether to execute the roller switching process. When it is determined that a paper feed failure has occurred at the paper feed position P0 as a result of the paper feed failure determination, the control unit 10 performs the roller switching process.

[0106] In this embodiment, as described above, the roller switching process is performed when a paper feed failure occurs at the paper feed position P0. Here, one of the causes of the paper feed failure at the paper feed position P0 is the deterioration of the separation roller 4. In other words, when the separation roller 4 is deteriorated, a paper feed failure occurs at the paper feed position P0. Therefore, it is preferable to perform the roller switching process when a paper feed failure occurs at the paper feed position P0.

[0107] Thereby, in this embodiment, the separation roller 4 can be replaced at an appropriate timing. In other words, it is possible to suppress the unnecessary replacement of the separation roller 4. Further, even if one of the plurality of separation rollers 4 is deteriorated and is in a state where a paper feed failure is likely to occur, the occurrence of the paper feed failure is suppressed by replacing it with another separation roller 4, so that the long life of the sheet feeding device 100 can be achieved.

[0108] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the description of the above embodiments but by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

Explanation of Reference Numerals

[0109] 3 Feed roller 4 Separation roller 5 Roller Support Mechanism 10 Control Unit 40 Rotating Shaft (Roller Shaft) 41 Torque Limiter (Load Mechanism) 50 Rotating Shaft 51 Support Member 52 Biasing Member 53 Switching Motor (Drive Source) 55 Roller Sensor 56 Sheet Sensor 100 Sheet Feeding Device 510 Support Hole (Slot) 540 Detection Piece 1000 Image Forming Apparatus DP Sheet Detection Position (Detection Position) P0 Feeding Position S Sheet

Claims

1. A feed roller that is rotatably supported, contacts the sheet at the feed position, and rotates by transmitting a driving force to feed the sheet; A separation roller that is rotatably supported, presses against the feed roller at the feed position, and nips the sheet between the separation roller and the feed roller; A roller support mechanism that supports the separation roller; A control unit, and is provided with, The roller support mechanism is, A support member that is rotatable about a rotation axis extending in the width direction orthogonal to the feed direction of the sheet; A drive source for rotating the support member, and has, The support member rotatably supports a plurality of the separation rollers; The plurality of separation rollers are arranged at intervals from each other in the circumferential direction centered on the rotation axis; The control unit performs a roller switching process of controlling the drive source to rotate the support member, so that a separation roller different from the separation roller that was pressing against the feed roller before the roller switching process is pressed against the feed roller. A sheet feeding device.

2. The control unit determines whether or not a sheet feeding failure has occurred at the feed position based on the arrival timing of the sheet at a position downstream of the feed position in the feed direction, When it is determined that the feeding failure has occurred, the control unit performs the roller switching process. The sheet feeding device according to claim 1.

3. Comprising a plurality of sheet sensors for detecting the presence or absence of the sheet at different positions downstream of the feed position in the feed direction, The control unit detects the arrival timing of the sheet at each detection position of the plurality of sheet sensors based on the output of each of the plurality of sheet sensors, The control unit determines whether or not a feeding failure has occurred at the feed position based on the arrival timing of the sheet at the detection position closest to the feed position. The sheet feeding device according to claim 2.

4. The control unit measures the required arrival time from the start of feeding of the sheet upstream of the feed position in the feed direction until the same sheet reaches the detection position closest to the feed position, When the required arrival time is longer than a predetermined threshold time, the control unit determines that a feeding failure has occurred at the feed position. The sheet feeding device according to claim 3.

5. The roller support mechanism is, A plurality of detection pieces that are arranged at intervals in the circumferential direction and move in the circumferential direction when the rotating shaft rotates; A roller sensor that changes an output according to the presence or absence of the detection piece at a predetermined position on the movement path of the detection piece; and The plurality of detection pieces are each assigned to different separation rollers; When any one of the detection pieces is at the predetermined position, the separation roller corresponding to the detection piece at the predetermined position is in pressure contact with the feed roller; The control unit determines, based on the output of the roller sensor, whether a separation roller different from the separation roller that was in pressure contact with the feed roller before the roller switching process is in pressure contact with the feed roller. The sheet feeding device according to claim 1.

6. The roller support mechanism has a biasing member that generates a biasing force outward in the radial direction of a circle centered on the rotating shaft for each separation roller; The support member has a long hole having the radial direction as a longitudinal direction for each separation roller; The roller shafts of the plurality of separation rollers are respectively arranged in the corresponding long holes and biased by the corresponding biasing members. The sheet feeding device according to claim 1.

7. The separation roller has a load mechanism that applies a rotational load to the separation roller; The separation roller rotates in a driven manner following the rotation of the feed roller; When the rotational driving force transmitted from the feed roller to the separation roller is equal to or less than a predetermined threshold value, the load mechanism restricts the rotation of the separation roller. The sheet feeding device according to claim 1.

8. An image forming apparatus including the sheet feeding device according to any one of claims 1 to 7, and printing an image on the sheet fed from the sheet feeding device.

Images