Sheet feed device and image formation device

Abstract

To suppress noise generation caused by a return member.SOLUTION: A sheet storage device comprises: a pickup roller which comes into contact with one surface of a sheet on the top layer to draw sheets out of a storage part; a feed part which separates the sheets drawn out of the storage part one by one and feeds them; and a return member which performs a return operation to move from the downstream side to the upstream side in a feeding direction of the sheet after entering a position on the feed path of the sheet and in contact with the other surface from a retraction position out of contact with the sheet, wherein the return member performs the return operation to return a sheet separated from the other surface of an object sheet which is a sheet that the feed part should feed to the storage part, and after the return operation, the return member retracts to the retraction position before a rear end of the object sheet passes through the return member.SELECTED DRAWING: Figure 10

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 pulls out a sheet stored in a storage section from the storage section and separates and feeds the sheets one by one. For example, a sheet feeding device is provided with a returning member. The returning member returns a double-fed sheet that has been pulled out from the storage section following the target sheet to be fed to the storage section. An example of the returning member is disclosed in Patent Document 1.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, in a configuration where the tip portion of the returning member protrudes onto the sheet feeding path and the tip portion is brought into contact with the double-fed sheet to return the double-fed sheet to the storage section, there is a problem that when the rear end of the target sheet passes the tip portion of the returning member, the rear end of the target sheet bounces and an abnormal noise is generated.

[0005] 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 suppressing the generation of abnormal noise caused by the returning member.

Means for Solving the Problems

[0006] In order to achieve the above object, a sheet feeding device according to a first aspect of the present invention includes a pickup roller that contacts one surface of the uppermost sheet among a plurality of sheets stacked and stored in a storage unit and pulls out the sheet from the storage unit, a feeding unit that separates and feeds the sheets pulled out from the storage unit one by one, and a return member that enters a position on the sheet feeding path from a retracted position where it does not contact the sheet and can contact the other surface opposite to the one surface of the sheet, and then performs a return operation of moving from the downstream side to the upstream side in the sheet feeding direction. The return member returns the sheet separated from the other surface of the target sheet, which is the sheet to be fed by the feeding unit, to the storage unit by performing the return operation. After the completion of the return operation, the return member retracts to the retracted position before the rear end of the target sheet passes through the return member.

[0007] An image forming apparatus according to a second aspect of the present invention includes the above sheet feeding device, and prints an image on the sheet fed from the sheet feeding device.

Advantages of the Invention

[0008] In the present invention, the generation of abnormal noise caused by the return member can be suppressed.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0010] 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 multifunction devices having a copying function and the like. Further, the present invention is not limited to color devices and is also applicable to monochrome devices.

[0011] <Configuration of the Image Forming Apparatus> The configuration of the image forming apparatus 1000 according to 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.

[0012] The image forming apparatus 1000 includes a sheet cassette CA. The sheet cassette CA corresponds to the "accommodation part". A plurality of sheets S are stacked and accommodated in the sheet cassette CA. In a printing job, the sheet S in the sheet cassette CA is used. The sheet cassette CA is detachable from the main body of the image forming apparatus 1000.

[0013] The image forming apparatus 1000 includes a main conveyance path MP. The main conveyance path MP extends from the supply position P0, passes through the transfer position P1 and the fixing position P2, and reaches the discharge tray ET.

[0014] In a printing job, the sheet S in the sheet cassette CA is fed from the supply position P0 to the main conveyance path MP. The sheet S is 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 sheet feeding device 100. The sheet feeding device 100 feeds the sheet S from the sheet cassette CA to the main conveyance path MP. The configuration of the sheet feeding device 100 will be described in detail later.

[0016] 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 rotates in that state to convey the sheet S.

[0017] 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 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 supply position P0 is labeled 10, and the symbols for the other pairs of conveyance rollers are omitted.

[0018] The image forming apparatus 1000 includes four image forming units 110. The four image forming units 110 respectively correspond to the four colors of cyan, magenta, yellow, and black. The four image forming units 110 each form an image using the toner of the corresponding color. 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 carries an image formed using toner 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 forming an image by the image forming unit 110, 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 for the other stretching rollers are omitted. The intermediate transfer belt 120 rotates passively when the driving roller 121 rotates. The other stretching rollers rotate passively following 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 each of 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 driving roller 121 to form 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 conveyed sheet S 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 on its outer peripheral surface the image primarily transferred from each photosensitive drum 111. 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 fixes the toner image on the sheet S by heating and applying pressure to 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 images are 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 double-sided printing job, since the transfer process is performed once on each of the front and back sides 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 side of the sheet S. After the first transfer process, the sheet S is switched back after the trailing edge of the sheet S has passed through the branch position P3 and before the sheet S is completely discharged onto the discharge tray ET. As a result, the sheet S is drawn into the double-sided printing conveyance path DP from its trailing edge.

[0034] Thereafter, the sheet S is conveyed along the double-sided printing conveyance path DP. Then, the sheet S on the double-sided printing conveyance path DP is returned to the main conveyance path MP from the confluence 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 with respect 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 side opposite to one side of the sheet S.

[0035] <Configuration of the Sheet Feeding Device> The sheet feeding device 100 feeds the sheet S from the sheet cassette CA to the main conveyance path MP. 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. The direction orthogonal to the vertical direction and the feeding direction is referred to as the width direction. The direction in which the rotation axis of the conveyance roller pair 10 extends is the width direction.

[0036] Details of the sheet feeding device 100 are shown in FIGS. 3 to 7. The sheet feeding device 100 includes a pickup roller 1, a feeding unit 2, and a returning member 3. The pickup roller 1, the feeding unit 2, and the returning member 3 are arranged in the same housing and unitized. The conveyance roller pair 10 may be arranged in the housing. That is, the conveyance roller pair 10 may be a component of the sheet feeding device 100.

[0037] Note that FIG. 3 is a perspective view of the sheet feeding device 100 as viewed from below on the upstream side in the feeding direction. FIGS. 4 and 6 correspond to cross-sections obtained by cutting the pickup roller 1 (including the feeding roller 21 and the separating roller 22) so as to pass through a plane orthogonal to the width direction. FIGS. 5 and 7 correspond to cross-sections obtained by cutting the contact portion 30 (described later) of the return member 3 so as to pass through a plane orthogonal to the width direction. In FIGS. 4 to 7, the feeding direction is indicated by a broken-line arrow. The sheet feeding device 100 feeds the sheet S along the broken-line arrow. That is, the broken-line arrow corresponds to the feeding path of the sheet S.

[0038] The pickup roller 1 is rotatably supported about an axis extending in the width direction. The pickup roller 1 is swingable (rotatable) about an axis 210 extending in the width direction as a fulcrum. The pickup roller 1 swings in the vertical direction about the axis 210. As a result, the lower end of the pickup roller 1 is displaced in the vertical direction.

[0039] The pickup roller 1 is disposed at a position facing the sheet S accommodated in the sheet cassette CA in the vertical direction in a state where the sheet cassette CA is mounted on the main body of the image forming apparatus 1000. In a state where the sheet cassette CA is mounted on the main body of the image forming apparatus 1000, the front end portion of the sheet S accommodated in the sheet cassette CA faces the pickup roller 1 in the vertical direction. The pickup roller 1 is disposed above the sheet S accommodated in the sheet cassette CA. Note that, of the sheet S, the end on the downstream side in the feeding direction is the front end, and the end on the upstream side in the feeding direction is the rear end.

[0040] By being displaced downward, the pickup roller 1 contacts one surface of the sheet S accommodated in the sheet cassette CA (see FIG. 6). Of the two surfaces of the sheet S, the surface facing upward in a state where the sheet S is accommodated in the sheet cassette CA is one surface of the sheet S. That is, the other surface opposite to one surface of the sheet S is the surface facing downward in a state where the sheet S is accommodated in the sheet cassette CA.

[0041] When a plurality of sheets S are stacked and stored in the sheet cassette CA, the uppermost sheet S among the plurality of sheets S stored in the sheet cassette CA becomes the object of feeding by the sheet feeding device 100. In other words, the uppermost sheet S among the plurality of sheets S stored in the sheet cassette CA is the sheet S to be fed. In the following description, the sheet S to be fed is referred to as the target sheet S.

[0042] Note that the sheet feeding device 100 feeds the plurality of sheets S stored in the sheet cassette CA in order from the uppermost sheet S. When the uppermost sheet S is fed, the sheet S one below that sheet S appears at the uppermost layer and becomes the new target sheet S.

[0043] When the sheet S is fed by the sheet feeding device 100, the pickup roller 1 is displaced downward and contacts one surface of the target sheet S from above (see Fig. 6). The pickup roller 1 rotates while contacting one surface of the target sheet S. Thereby, the pickup roller 1 pulls out the target sheet S from the sheet cassette CA. The target sheet S advances in the feeding direction from the sheet cassette CA.

[0044] The feeding unit 2 feeds the target sheet S pulled out from the sheet cassette CA by the pickup roller 1 to the main conveyance path MP. The target sheet S advances toward the conveyance roller pair 10 by the feeding by the feeding unit 2 and enters the conveyance nip of the conveyance roller pair 10. At this time, the conveyance roller pair 10 is rotating. Thereby, the target sheet S is conveyed along the main conveyance path MP.

[0045] The feeding unit 2 has a feeding roller 21. The feeding roller 21 is rotatably supported around the shaft 210. The feeding roller 21 is arranged on the downstream side in the feeding direction of the pickup roller 1. The shaft 210 is connected to a feeding motor (not shown), and the driving force of the feeding motor is transmitted and rotates. The feeding roller 21 rotates together with the shaft 210.

[0046] Note that the driving source of the pickup roller 1 is the same as that of the feeding roller 21. Specifically, a transmission mechanism 20 (see FIG. 3) including a cam and gears is connected to the feeding motor. Only a part of the transmission mechanism 20 is shown in FIG. 3. The pickup roller 1 is connected to the feeding motor via the transmission mechanism 20. When the driving force of the feeding motor is transmitted to the pickup roller 1, the pickup roller 1 rotates about an axis extending in the width direction and pivots about the shaft 210.

[0047] For example, double feeding may occur when feeding the sheet S. In other words, when the target sheet S is pulled out from the sheet cassette CA by the pickup roller 1, the sheet S one below the target sheet S (that is, the sheet S in a lower layer than the uppermost layer) may also be pulled out along with the target sheet S. In the following description, the sheet S pulled out along with the target sheet S is referred to as the double-fed sheet S. For example, the double-fed sheet S is in close contact with the other surface of the target sheet S and is pulled out from the sheet cassette CA together with the target sheet S. Note that the double-fed sheet S is the sheet S to be fed next to the target sheet S.

[0048] In order to eliminate the double feeding of the sheet S, the feeding unit 2 separates and feeds the sheets S pulled out from the sheet cassette CA by the pickup roller 1 one by one. That is, the feeding unit 2 separates the target sheet S and the double-fed sheet S.

[0049] Specifically, the feeding unit 2 has a separating roller 22. The separating roller 22 is rotatably supported about an axis extending in the width direction. The separating roller 22 is pressed against the feeding roller 21 with the feeding path of the sheet S interposed therebetween (see FIG. 6). Thereby, the separating roller 22 forms a feeding nip with the feeding roller 21. The separating roller 22 rotates following the rotation of the feeding roller 21.

[0050] The separation roller 22 is capable of reciprocating between a position where it is in pressure contact with the feed roller 21 and a position where it is separated from the feed roller 21. For example, the separation roller 22 is biased toward the feed roller 21 by a biasing member (not shown) such as a coil spring. The separation roller 22 moves in a direction away from the feed roller 21 against the biasing force of the biasing member when the cam of the transmission mechanism 20 rotates. The separation roller 22 is biased by the biasing member and comes into pressure contact with the feed roller 21 when the engagement with the cam of the transmission mechanism 20 is released.

[0051] When feeding the sheet S, the feed roller 21 and the separation roller 22 are in pressure contact with each other, and a feed nip is formed between the feed roller 21 and the separation roller 22 (see FIG. 6). The target sheet S drawn out from the sheet cassette CA enters the feed nip. At this time, the feed roller 21 is rotating. Thereby, the target sheet S is fed by the feeding unit 2.

[0052] A torque limiter (not shown) is connected to the rotation shaft of the separation roller 22. The torque limiter restricts the rotation of the separation roller 22.

[0053] When the rotational driving force transmitted from the feed roller 21 to the separation roller 22 exceeds the threshold value, the torque limiter idles the rotation shaft of the separation roller 22. That is, the torque limiter rotates the separation roller 22. When only the target sheet S enters the conveyance nip between the feed roller 21 and the separation roller 22, the rotational driving force transmitted from the feed roller 21 to the separation roller 22 exceeds the threshold value.

[0054] On the one hand, when the rotational driving force transmitted from the feeding roller 21 to the separating roller 22 is equal to or less than the threshold value, the torque limiter renders the rotating shaft of the separating roller 22 non-rotatable. That is, the torque limiter does not rotate the separating roller 22. When the target sheet S and the double-fed sheet S enter overlapping the conveyance nip between the feeding roller 21 and the separating roller 22, the feeding roller 21 contacts the target sheet S and advances the target sheet S in the feeding direction, while the separating roller 22 does not contact the target sheet S but contacts the double-fed sheet S. For this reason, it is difficult for the rotational driving force to be transmitted from the feeding roller 21 to the separating roller 22. As a result, the rotational driving force transmitted from the feeding roller 21 to the separating roller 22 becomes equal to or less than the threshold value, and the separating roller 22 does not rotate.

[0055] While the feeding roller 21 rotates, the non-rotation of the separating roller 22 suppresses the advancement in the feeding direction of the double-fed sheet S that contacts the separating roller 22 without contacting the feeding roller 21. That is, double feeding of the sheet S is eliminated. Thereby, the target sheet S and the double-fed sheet S are separated.

[0056] The returning member 3 has contact portions 30. There are two contact portions 30. The two contact portions 30 face each other in the width direction with the arrangement position of the pickup roller 1 (including the feeding roller 21 and the separating roller 22) interposed therebetween when viewed from the feeding direction.

[0057] Further, the returning member 3 has a long hole 300 that opens in the width direction. A shaft 310 extending in the width direction is inserted into the long hole 300. The returning member 3 is swingable around the shaft 310 and is swingable in the longitudinal direction of the long hole 300.

[0058] <Returning operation> The returning member 3 performs a returning operation. Thereby, the returning member 3 returns the double-fed sheet S to the sheet cassette CA. This will be specifically described below.

[0059] When the feeding of the sheet S from the sheet cassette CA is started, the pickup roller 1 descends. As a result, the pickup roller 1 comes into contact with the target sheet S. Then, the pickup roller 1 rotates. The feeding roller 21 rotates. The separating roller 22 moves toward the feeding roller 21 and presses against the feeding roller 21. That is, the state changes from the state shown in FIG. 4 to the state shown in FIG. 6.

[0060] Also, when the feeding of the sheet S from the sheet cassette CA is started, the return member 3 retracts from the standby position to the retracted position. The position of the return member 3 shown in FIG. 5 is the standby position, and the position of the return member 3 shown in FIG. 7 is the retracted position. The retracted position (see FIG. 7) is a position where the return member 3 does not contact the sheet S. That is, the retracted position is a position outside the feeding path of the sheet S by the sheet feeding device 100. When the return member 3 is in the retracted position, the return member 3 does not contact the sheet S. Note that the standby position (see FIG. 5) is also the position at the end point of the return operation by the return member 3.

[0061] When the pickup roller 1 rotates while in contact with the target sheet S, the target sheet S is pulled out from the sheet cassette CA, and the target sheet S reaches the feeding unit 2. At this time, the target sheet S enters the feeding nip between the feeding roller 21 and the separating roller 22. That is, the feeding unit 2 nips the target sheet S.

[0062] The feeding unit 2 feeds the target sheet S that has entered the feeding nip to the main conveyance path MP. The feeding unit 2 feeds the sheet S that has entered the feeding nip toward the conveyance roller pair 10. As a result, the target sheet S reaches the conveyance roller pair 10. At this time, the target sheet S enters the conveyance nip of the conveyance roller pair 10. That is, the conveyance roller pair 10 nips the target sheet S. The conveyance roller pair 10 conveys the target sheet S that has entered the conveyance nip toward the transfer position P1.

[0063] After the target sheet S reaches the conveying roller pair 10, the pickup roller 1 rises. The feeding roller 21 continues to rotate. The separating roller 22 moves away from the feeding roller 21. When the separating roller 22 moves away from the feeding roller 21, the feeding of the target sheet S by the feeding unit 2 stops. However, since the conveying roller pair 10 is nipping the target sheet S, the conveyance of the target sheet S continues.

[0064] After the separating roller 22 starts to move away from the feeding roller 21, the return member 3 starts a return operation. The return operation of the return member 3 may start substantially simultaneously with the separating roller 22 starting to move away from the feeding roller 21.

[0065] Note that the return operation of the return member 3 is interlocked with the operations of the pickup roller 1 and the separating roller 22. To interlock the return operation of the return member 3 with the operations of the pickup roller 1 and the separating roller 22, the driving force of the feeding motor is transmitted to the return member 3 via the transmission mechanism 20. In conjunction with the rotation of the cam of the transmission mechanism 20, the return member 3 performs a return operation.

[0066] Before the start of the return operation, the return member 3 is held at a retracted position (see Fig. 7) where it does not contact the sheet S. When performing the return operation, the return member 3 enters the feeding path of the sheet S (i.e., the position where it contacts the sheet S) from the retracted position. In a state where the return member 3 has entered the feeding path of the sheet S, at least the contact portion 30 of the return member 3 protrudes onto the feeding path of the sheet S. That is, when performing the return operation, the return member 3 causes the contact portion 30 to enter the feeding path of the sheet S.

[0067] When performing the return operation, the position where the return member 3 enters is a position where the contact portion 30 can contact the other surface of the sheet S drawn out from the sheet cassette CA. That is, when the return member 3 enters the feeding path of the sheet S, the contact portion 30 contacts the other surface of the sheet S. When there is no double feeding of the sheet S, the return member 3 (contact portion 30) contacts the other surface of the target sheet S. When double feeding of the sheet S has occurred, the return member 3 (contact portion 30) contacts the other surface (or the leading edge of the double-fed sheet S) of the double-fed sheet S.

[0068] After entering a position on the conveyance path of the sheet S where it can contact the other surface of the sheet S, the return member 3 performs a return operation of moving from the downstream side to the upstream side in the feeding direction. At this time, on the feeding path of the sheet S, the contact portion 30 moves from the downstream side to the upstream side in the feeding direction.

[0069] As a result, when there is no double feeding of the sheet S, the contact portion 30 moves from the downstream side to the upstream side in the sheet feeding direction while in contact with the other surface of the target sheet S. At this time, the conveyance roller pair 10 nips the target sheet S. Therefore, even if the contact portion 30 contacts the other surface of the target sheet S, the conveyance of the target sheet S is not inhibited.

[0070] When double feeding of the sheet S has occurred, it becomes as shown in FIG. 8. In FIG. 8, the target sheet S is labeled with reference numeral S1, and the double-fed sheet S is labeled with reference numeral S2 for distinction. Also, the direction toward the downstream side in the feeding direction is indicated by arrow D1, and the direction toward the upstream side in the feeding direction is indicated by arrow D2.

[0071] When double feeding of the sheet S has occurred, due to the function of the separation roller 22, the double-fed sheet S stays without reaching the conveyance roller pair 10. Therefore, the contact portion 30 contacts the other surface (or the leading edge of the double-fed sheet S) of the double-fed sheet S from the downstream side in the feeding direction. In that state, the contact portion 30 moves upstream in the feeding direction. The contact portion 30 moves from the downstream side to the upstream side in the feeding direction so as to rub the double-fed sheet S. As a result, the double-fed sheet S is returned to the sheet cassette CA.

[0072] <Retracting operation> Hereinafter, with reference to FIGS. 9 and 10, the retracting operation of the return member 3 will be specifically described. FIG. 9 shows the state at the start point of the retracting operation (i.e., the end point of the returning operation). FIG. 10 shows the state from the start of the retracting operation to the completion of the retracting operation. The state shown in the upper diagram of FIG. 10 is the state during the retracting operation, and the state shown in the lower diagram of FIG. 10 is the state when the retracting operation is completed. Note that the sheet S indicated by the thick line in FIGS. 9 and 10 is the target sheet S. The double-fed sheet S is not shown in FIGS. 9 and 10.

[0073] After the completion of the returning operation, the return member 3 performs a retracting operation of retracting to the retracted position before the rear end E of the target sheet S passes through the contact portion 30. Note that the retracting operation of the return member 3 is interlocked with the operations of the pickup roller 1 and the separation roller 22. In order to interlock the retraction of the return member 3 with the operations of the pickup roller 1 and the separation roller 22, the driving force of the feed motor is transmitted to the return member 3 via the transmission mechanism 20. In conjunction with the rotation of the cam of the transmission mechanism 20, the return member 3 performs a retracting operation.

[0074] Here, after the completion of the returning operation, the positional relationship between the return member 3 and the target sheet S becomes as shown in FIG. 9. If the return member 3 does not perform the retracting operation as it is, the rear end E of the target sheet S passes through the contact portion 30. At this time, the rear end E of the sheet S behaves like it bounces and collides with the surrounding members. And in some cases, an abnormal noise (bouncing noise) is generated. Some users feel uncomfortable with this abnormal noise at this time. Or they may misunderstand that an abnormality (failure) has occurred.

[0075] Therefore, the return member 3 starts the retraction operation before the rear end E of the target sheet S passes through the contact portion 30. The return member 3 reaches the retracted position by moving from the upstream side to the downstream side in the feeding direction. That is, the contact portion 30 moves from the upstream side to the downstream side in the feeding direction. When the return member 3 performs the retraction operation, the state shown in the upper diagram of FIG. 10 shifts to the state shown in the lower diagram of FIG. 10. The contact portion 30 moves from the upstream side to the downstream side in the feeding direction while contacting the other surface of the target sheet S and reaches the retracted position. As a result, the rear end E of the target sheet S moves from the upstream side to the downstream side in the feeding direction, but since the contact portion 30 also moves from the upstream side to the downstream side in the feeding direction, the rear end E of the target sheet S does not pass through the contact portion 30.

[0076] In the present embodiment, as described above, after the return operation is completed, the return member 3 retracts to the retracted position before the rear end E of the target sheet S passes through the return member 3. Thereby, it is possible to suppress the behavior that the rear end E of the target sheet S bounces. As a result, it is possible to suppress the generation of abnormal noise.

[0077] Also, in the present embodiment, as described above, after the return operation is completed, the return member 3 reaches the retracted position by moving from the upstream side to the downstream side in the feeding direction. Thereby, it is possible to easily retract the return member 3 to the retracted position while suppressing the rear end E of the target sheet S from passing through the return member 3.

[0078] Note that, in the present embodiment, during the retraction operation of the return member 3, the rear end E of the target sheet S is supported by the return member 3. That is, the return member 3 moves to the retracted position while supporting the rear end E of the target sheet S. Thereby, it is possible to suppress the behavior that the rear end E of the target sheet S bounces during the retraction operation of the return member 3.

[0079] 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

[0080] 1 pickup roller 2 feeding section 3 return member 100 sheet feeding device 1000 image forming apparatus CA sheet cassette (accommodating section) E rear end S sheet

Claims

1. A pickup roller that contacts one surface of the uppermost sheet among a plurality of sheets stacked and stored in a storage section and pulls out the sheet from the storage section; A feeding section that separates and feeds the sheets pulled out from the storage section one by one; A return member that enters a position on the sheet feeding path that does not contact the sheet and can contact the other surface opposite to the one surface of the sheet, and then performs a return operation of moving from the downstream side to the upstream side in the sheet feeding direction; and By performing the return operation, the return member returns the sheet separated from the other surface of the target sheet, which is the sheet to be fed by the feeding section, to the storage section. A sheet feeding device, wherein after the completion of the return operation, the return member retracts to the retracted position before the rear end of the target sheet passes through the return member.

2. The sheet feeding device according to claim 1, wherein after the completion of the return operation, the return member reaches the retracted position by moving from the upstream side to the downstream side in the feeding direction.

3. The sheet feeding device according to claim 2, wherein the return member moves to the retracted position while supporting the rear end of the target sheet.

4. An image forming apparatus comprising the sheet feeding device according to any one of claims 1 to 3, and printing an image on the sheet fed from the sheet feeding device.

Images