Sheet Feeding Device and Image Forming Apparatus

Abstract

To prevent a sheet from being conveyed toward a separation nip before a separation member produces a desired separation function.SOLUTION: A sheet feeder has: a feed member constituted so as to feed a sheet loaded on a tray; a conveyance member constituted so as to convey the sheet fed by the feeding member; a separation member constituted so as to separate one sheet from a plurality of sheets; and a transmission unit for transmitting driving force to the conveyance member and the feed member. The transmission unit includes a first part, and a second part constituted so as to drive the feed member, that is driven by the first part. The first part comprises a first transmission face. The second part comprises a second transmission face. The sheet feeder has an energization member for energizing any of the first part and the second part in such a manner that the first transmission face and the second transmission face separate from each other.SELECTED DRAWING: Figure 10

Description

Technical Field

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

Background Art

[0002] In a sheet feeding device that feeds sheets, in order to prevent a plurality of sheets from being fed, a configuration is adopted in which a single sheet is separated from a plurality of sheets. Patent Document 1 describes a sheet feeding device including a transport member that transports a sheet and a separation member that abuts against the transport member, and in which a single sheet is separated from a plurality of sheets by the separation member.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a sheet feeding device having a transport member that transports a sheet and a separation member that abuts against the transport member, it may take time from the start of driving of the transport member until the separation member exhibits a desired separation function (a function of separating a single sheet from a plurality of sheets).

[0005] An object of the present invention is to suppress the conveyance of a sheet toward a nip portion formed by the separation member and the transport member before the separation member exhibits a desired function.

Means for Solving the Problems

[0006] The configuration according to the present invention is as follows.

[0007] A tray configured to stack sheets, A feeding member configured to feed the sheet loaded on the tray; A conveying member configured to convey the sheet fed by the feeding member; A separating member capable of contacting the conveying member, It is movable between a contact position in contact with the conveying member and a retracted position retracted from the contact position. The separating member is configured to separate one sheet from a plurality of sheets fed by the feeding member; A separation moving unit configured to move the separation member between the contact position and the retracted position; A transmission unit that transmits driving force to the conveying member and the feeding member, including a first part and a second part driven by the first part and configured to drive the feeding member. The first part has a first transmission surface, the second part has a second transmission surface, and when the first transmission surface and the second transmission surface contact each other, the first part drives the second part; A biasing member that biases either the first part or the second part so that the first transmission surface and the second transmission surface are separated from each other; It has; The separating member contacts the conveying member, and in a state where the feeding member contacts the sheet loaded on the tray and stops, the conveying member is driven. After the conveying member is driven, the first transmission surface and the second transmission surface contact each other, and the feeding member is driven. 、 After the separation member comes into contact with the conveying member, the first transmission surface and the second transmission surface come into contact, and the feeding member is driven. A sheet feeding device characterized by the above.

Advantages of the Invention

[0008] According to the present invention, before the separating member exhibits a desired separating function, it is possible to suppress the sheet from being conveyed toward the nip portion formed by the separating member and the conveying member.

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

Figure 11

Figure 12

Best Mode for Carrying Out the Invention

[0010] Hereinafter, with reference to the drawings, the best mode for carrying out this invention will be exemplified and described in detail. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment are to be appropriately changed according to the configuration of the device to which the invention is applied and various conditions, and are not intended to limit the scope of this invention to the following embodiments.

Examples

[0011] <Image forming apparatus> With reference to FIG. 1, the image forming apparatus 1 according to the present embodiment will be described. FIG. 1 is a cross-sectional view showing the structure of the image forming apparatus 1 according to the present embodiment. FIG. 1 shows a laser beam printer that forms a color image on a sheet S as a recording material as an example of the image forming apparatus 1 according to the present embodiment.

[0012] The image forming apparatus 1 has an apparatus main body 1A as a housing. Inside the apparatus main body 1A, as an image forming unit, the first to fourth process cartridges PY, PM, PC, and PK are arranged side by side in a substantially horizontal direction.

[0013] Each of the first to fourth process cartridges PY, PM, PC, and PK includes a photosensitive drum as an image carrier that carries an electrostatic latent image, and a developing roller as a developing member that develops the electrostatic latent image formed on the photosensitive drum. The developing roller has a function as a developer carrier that carries toner as a developer.

[0014] The first process cartridge PY has a photosensitive drum 11a and a developing roller 12a, and is configured to form a yellow image. The second process cartridge PM has a photosensitive drum 11b and a developing roller 12b, and is configured to form a magenta image. The third process cartridge PC has a photosensitive drum 11c and a developing roller 12c, and is configured to form a cyan image. The fourth process cartridge PK has a photosensitive drum 11d and a developing roller 12d, and is configured to form a black image. Each of the first to fourth process cartridges PY, PM, PC, and PK includes a charging member (not shown) that charges each of the photosensitive drums 11a, 11b, 11c, and 11d.

[0015] In the present embodiment, each of the first to fourth process cartridges PY, PM, PC, and PK has the same configuration as each other except for the color of the toner to be accommodated.

[0016] Above the first to fourth process cartridges PY, PM, PC, and PK, a scanner unit 2 is arranged as an exposure device. The scanner unit 2 irradiates laser light toward each of the charged photosensitive drums 11a to 11d based on image information. As a result, an electrostatic latent image is formed on each of the photosensitive drums 11a to 11d. These electrostatic latent images are developed by the developing rollers 12a to 12d. Note that, as the exposure device, for example, an exposure device using light-emitting diodes can be used.

[0017] The image forming apparatus 1 has an intermediate transfer unit 20 arranged below the first to fourth process cartridges PY, PM, PC, and PK. The intermediate transfer belt unit 20 has an intermediate transfer belt 21, a driving roller 22, a driven roller 23, and a tension roller 24. The intermediate transfer belt 21 is stretched by the driving roller 22, the driven roller 23, and the tension roller 24, and is rotated in the direction of the arrow in the figure by the driving roller 22.

[0018] The lower surfaces of the photosensitive drums 11a to 11d are in contact with the upper surface of the intermediate transfer belt 21. Inside the intermediate transfer belt 21, primary transfer rollers (25a, 25b, 25c, 25d) as primary transfer members are arranged. A primary transfer portion is formed between each of the photosensitive drums 11a to 11d and each of the primary transfer rollers 25a to 25d. Each of the photosensitive drums 11a to 11d and each of the primary transfer rollers 25a to 25d are adjacent to each other with the intermediate transfer belt 21 interposed therebetween. In other words, each of the photosensitive drums 11a to 11d and each of the primary transfer rollers 25a to 25d face each other via the intermediate transfer belt 21. When a predetermined voltage is applied to the primary transfer rollers 25a to 25d, the toner image is transferred from the photosensitive drums 11a to 11d to the intermediate transfer belt 21.

[0019] The image forming apparatus 1 has a secondary transfer roller 26 that contacts an intermediate transfer belt 21. A secondary transfer portion is formed between the secondary transfer roller 26 and a driving roller 22. The secondary transfer roller 26 and the driving roller 22 are adjacent to each other with the intermediate transfer belt 21 interposed therebetween. In other words, the secondary transfer roller 26 and the driving roller 22 face each other via the intermediate transfer belt 21. When a predetermined voltage is applied to the secondary transfer roller 26, a toner image is transferred from the intermediate transfer belt 21 to a sheet S in the secondary transfer portion.

[0020] That is, the process cartridges PY, PM, PC, PK and the intermediate transfer unit 20 have a function as an image forming portion for forming an image on the sheet S.

[0021] The image forming apparatus 1 has a fixing device 30 and a pair of discharge rollers 40 as a discharge device. The fixing device 30 and the pair of discharge rollers 40 are disposed above the secondary transfer portion. Further, a discharge tray 43 is provided on the upper portion of the apparatus main body 1A. The fixing device 30 has a fixing film 31 and a pressure roller 32. The sheet S is heated and pressed by the fixing film 31 and the pressure roller 32, so that the toner image is fixed on the sheet S. The pair of discharge rollers 40 has a discharge roller 41 and a driven member 42. The sheet S on which the toner image is fixed is discharged to the discharge tray 43 by the pair of discharge rollers 40.

[0022] The image forming apparatus 1 according to the present embodiment has a feeding device 50 and a feeding device 70 as feeding devices for feeding the sheet S. The feeding device 50 is a tray type (cassette type) feeding device housed in the apparatus main body 1A. The feeding device 70 is a manual feed tray type feeding device.

[0023] First, a configuration in which the sheet S is fed from the feeding device 50 will be described. The feeding device 50 has a storage tray 51, a pick-up roller 52, a feed roller 53, and a separation roller 54 that contacts the feed roller 53.

[0024] The sheet S loaded on the storage tray 51 is fed by the pick roller 52. When a plurality of sheets S are fed, one sheet S is separated from the plurality of sheets S and conveyed at the separation nip formed between the feed roller 53 and the separation roller 54.

[0025] The image forming apparatus 1 has a pair of conveying rollers 60 including a conveying roller 61d and a driven roller 62d. At the nip portion formed by the conveying roller 61d and the conveying driven roller 62d, the skew of the sheet S is corrected, and the sheet S is conveyed toward the secondary transfer portion by the conveying roller 61d. The sheet S passes through the secondary transfer portion and the fixing device 30, and is discharged to the discharge tray 43 by the pair of discharge rollers 40.

[0026] Next, the case where the sheet S is fed from the feeding device 70 will be described. The image forming apparatus 1 has a door unit 80 configured to be openable and closable with respect to the apparatus main body 1A. The door unit has a door 82 and a loading tray 81 on which the sheet S is loaded.

[0027] The feeding device 70 includes a loading tray 81, a pick roller (pickup roller, feeding member, feeding roller) 71, a feed roller (conveying member, conveying roller) 72, and a separation roller 73. The image forming apparatus 1 includes a cover 83 that covers the pick roller 71.

[0028] The pick roller 71 is configured to feed the sheet S loaded on the loading tray 81. The pick roller 71 is configured to convey the sheet S loaded on the loading tray 81 toward the feed roller 72.

[0029] The feed roller 72 is configured to convey the sheet S fed by the pick roller 71 to the conveyance path of the apparatus main body 1A. The separation roller 73 is capable of abutting against the feed roller 72 and is configured to separate one sheet S from the plurality of sheets S fed by the pick roller 71. In the present embodiment, the separation roller 73 is used as the separation member, but a separation pad can also be used as the separation member.

[0030] The sheet S loaded on the loading tray 81 is fed by the pick roller 71. When a plurality of sheets S are fed, one sheet S is separated from the plurality of sheets S and conveyed at the separation nip formed between the feed roller 72 and the separation roller 73.

[0031] On the other hand, the image forming apparatus 1 includes conveyance rollers 61a, 61b, 61c and driven rollers 62a, 62b, 62c. The sheet S is conveyed toward the conveyance roller pair 60 by the conveyance rollers 61a, 61b, 61c. At the nip portion formed by the conveyance roller 61d and the driven roller 62d, the skew of the sheet S is corrected, and the sheet S is conveyed toward the secondary transfer portion by the conveyance roller 61d. The sheet S passes through the secondary transfer portion and the fixing device 30 and is discharged to the discharge tray 43 by the discharge roller pair 40.

[0032] <Configuration of the feeding device> The configuration and feeding operation of the feeding device 70 in the present embodiment will be described with reference to FIG. 2. FIG. 2 is a perspective view of the feeding device 70 according to the present embodiment. FIG. 2 is drawn with the loading tray 81 omitted.

[0033] As shown in FIG. 2, the feeding device 70 has a pick roller 71 for feeding the sheet S. Further, the feeding device 70 has a feed roller 72 for conveying the fed sheet S to the conveyance path, and a separation roller 73 facing the feed roller 72 for preventing a plurality of sheets S from being conveyed to the conveyance path. The separation roller 73 is configured to be rotatable and includes a torque limiter (not shown) inside. The torque limiter inside the separation roller 73 functions as a brake for increasing the rotational load of the separation roller 73.

[0034] In this embodiment, the separation roller 73 is configured to be movable between a contact position where it contacts the feed roller 72 and a retracted position where it retracts from the contact position. When the separation roller 73 is in the retracted position, a gap larger than the thickness of the sheet S is formed between the separation roller 73 and the feed roller 72. The retracted position can also be referred to as a separated position where the separation roller 73 is separated from the feed roller 72. When the separation roller 73 moves to the retracted position while the sheet S is being conveyed by the conveying roller 61a, the tension acting on the sheet S is suppressed, and the deterioration of the separation roller 73 is suppressed. When the feed roller 72 rotates with the separation roller 73 in the contact position, the separation function is exerted.

[0035] The feeding device 70 has a returning member 91 that returns the sheet S from the portion between the separation roller 73 and the feed roller 72 toward the stacking tray 81 when the separation roller 73 is in the retracted position. In this embodiment, a plurality of returning members 91 are arranged. Specifically, the returning members 91 are arranged on both sides of the separation roller 73.

[0036] The returning member 91 retracts from the conveyance path in conjunction with the operation of the separation roller 73 coming into contact with the feed roller 72 (the operation of moving from the retracted position to the contact position). Further, the returning member 91 protrudes into the conveyance path in conjunction with the operation of the separation roller 73 retracting from the feed roller 72 (the operation of moving from the contact position to the retracted position). The returning member 91 is configured to contact the leading end of the sheet S and control the leading end position of the sheet S.

[0037] The interval between the two returning members 91 is set to be able to contact the sheet S having the smallest size among the sizes that the feeding device 70 can feed. The mechanism that interlocks the separation roller 73 and the returning member 91 and the conveyance guide 99 that forms the conveyance path are fixed to the apparatus main body 1A via the conveyance guide frame 98.

[0038] <Configuration of the Returning Member and the Separation Roller> The configuration of the returning member 91 and the separation roller 73 will be described with reference to FIGS. 3 and 4.

[0039] FIG. 3 is a diagram showing the structure of a moving device 200 that moves the separation roller 73 and the return member 91. FIG. 3(a) is a perspective view showing the structure of the moving device 200 that moves the separation roller 73 and the return member 91. FIG. 3(b) is a top view showing the structure of the moving device 200 that moves the separation roller 73 and the return member 91. FIG. 4 is a diagram for explaining the movement of the separation roller 73 and the return member 91. FIG. 4(a) is a diagram showing a state where the separation roller 73 is separated from the feed roller 72 and the return member 91 protrudes. FIG. 4(b) is a diagram showing a state where the separation roller 73 abuts on the feed roller 72 and the return member 91 retracts.

[0040] The apparatus main body 1A of the image forming apparatus 1 has a moving device 200 that moves the separation roller 73 and the return member 91. The moving device 200 can be said to be a part of the feeding device 70. The moving device 200 includes a solenoid 79, a missing tooth gear 78, a control cam 84, a reciprocating gear 77, an idler gear 85, a first moving member 75a, a holder support member 86, a second moving member 75b, a connecting member 76, and a roller holder 87. The first moving member 75a and the second moving member 75b are connected by a connecting portion 76 and are configured to move integrally. Further, a holder support member 86 is connected to the first moving member 75a. The first moving member 75a and the holder support member 86 are configured to move integrally.

[0041] The missing tooth gear 78 receives a driving force from a motor M (see FIG. 12) as a driving source provided in the apparatus main body 1A. More specifically, the missing tooth gear 78 meshes with a driving gear (not shown) driven by the motor M, and is configured such that the driving force is transmitted from the driving gear.

[0042] The solenoid 79 has a regulating portion that regulates the missing-tooth gear 78. The regulating portion of the solenoid 79 regulates the missing-tooth gear 78 such that the missing-tooth portion of the missing-tooth gear 78 faces the driving gear. When the solenoid 79 operates and the regulation by the regulating portion is released, the missing-tooth gear 78 meshes with the driving gear and is configured to receive a driving force from the driving gear. Each time the solenoid 79 operates once, the missing-tooth gear 78 rotates once and a single sheet S is conveyed. After the missing-tooth gear 78 rotates once, the missing-tooth gear 78 is regulated by the regulating portion of the solenoid 79.

[0043] In the image forming apparatus 1 according to the present embodiment, the sheet feeding device 50 and the sheet feeding device 70 are driven by a common motor M. Therefore, the solenoid 79 operates only when the sheet S is conveyed from the sheet feeding device 70, and the sheet S is conveyed from the sheet feeding device 70.

[0044] Next, a configuration for interlocking the separation roller 73 and the return member 91 will be described.

[0045] The moving device 200 has an engaging portion 91a that engages with the return member 91. Each of the first moving member 75a and the second moving member 75b supports the engaging portion 91a such that the return member 91 protrudes toward the conveyance path.

[0046] As shown in FIG. 4(a), the roller holder 87 that holds the separation roller 73 is configured to be rotatable around a swing axis 87a. The roller holder 87 receives a force FP from a biasing member (not shown) that acts in a direction in which the separation roller 73 approaches the feed roller 73. The holder support member 86 has a support portion 86a. In the state shown in FIG. 4(a), since the roller holder 87 is supported by the support portion 86a, the separation roller 73 is positioned at a retracted position against the force FP.

[0047] The first moving member 75a is receiving a force FS by a biasing member 75c attached to the first moving member 75a. On the other hand, a control cam 84 is attached to the toothless gear 78. In the states shown in FIGS. 3(a), 3(b), and 4(a), the reciprocating gear 77 is regulated by the control cam 84. When the reciprocating gear 77 is pressed by the control cam 84, the reciprocating gear 77 swings around the swing axis 77a. The movement of the reciprocating gear 77 is transmitted to the first moving member 75a via the reciprocating idler gear 85. As a result, as shown in FIGS. 3(a), 3(b), and 4(a), against the force FS, the first moving member 75a and the second moving member 75b are held in a state of moving in the opposite direction of the force FS.

[0048] When the solenoid 79 operates, as the toothless gear 78 rotates, the control cam 84 rotates and the control cam 74 moves away from the reciprocating gear 77. As a result, as shown in FIG. 4(b), by the biasing member 75c, the first moving member 75a, the second moving member 75b, and the holder support member 86 move in the direction of the force FS. In this state, the roller holder 87 moves away from the support portion 86a and swings around the swing axis 87a. Then, the separating roller 73 is positioned at the contact position by the force FP. Also, the support portion of the first moving member 75a that supports the engaging portion 91a in the state shown in FIG. 4(a) moves away from the engaging portion 91a. As a result, the return member 91 retracts.

[0049] With the configuration described above, the start of the operation that interlocks the separating roller 73 and the return member 91 is controlled by the solenoid (switching device) 79.

[0050] As described above, the moving device 200 has a function as a separating moving portion configured to move the separating roller 73 between the contact position and the retracted position. Further, the moving device 200 has a function as a return member moving portion configured to move the return member 91 between a protruding position protruding into the conveyance path and a standby position retracted from the conveyance path.

[0051] Note that since the relationship among the second moving member 75b, the engaging portion 91a, and the returning member 91 is the same as the relationship among the first moving member 75a, the engaging portion 91a, and the returning member 91, the description of the movement of the returning member 91 by the second moving member 75b is omitted.

[0052] <Configuration of the Pick Roller Lifting Mechanism> Next, with reference to FIGS. 5, 6, 7, and 8, the configuration for lifting and lowering the pick roller 71 will be described. The pick roller 71 is configured to be movable between a first position where it can contact the sheet S loaded on the loading tray 81 and a second position where it is retracted from the first position.

[0053] FIG. 5 is a perspective view of the pick feed unit 100. FIG. 6 is a diagram for explaining the configuration for transmitting the driving force to the pick roller 71 and the feed roller 72. FIG. 7 is a perspective view showing the relationship between the pick feed unit 100 and the missing tooth gear 78. FIG. 8 is a diagram for explaining the lifting and lowering of the pick roller 71. FIG. 8(a) is a diagram showing the state where the pick roller 71 has risen. FIG. 8(b) is a diagram showing the state where the pick roller 71 has descended.

[0054] The feeding device 70 includes a pick feed unit 100. The pick feed unit 100 is configured to be removable from the apparatus main body 1A. The pick feed unit 100 is swingably supported via a bearing 104 on a conveyance guide frame 98 fixed to the apparatus main body 1A.

[0055] The feeding device 70 has a transmission unit 100A configured to transmit the driving force to the feed roller 72 and the pick roller 71. It can be said that the transmission unit 100A is a part of the pick feed unit 100. When the driving force is transmitted from the transmission unit 100A, the feed roller 72 and the pick roller 71 rotate, and the sheet S is conveyed from the loading tray 81.

[0056] As shown in FIG. 6, the transfer unit 100A has a feed shaft connecting portion 95 that receives a driving force from the missing-tooth gear 78 via a gear that meshes with the missing-tooth gear 78, and a roller drive shaft 90 that is connected to the feed shaft connecting portion 95. The transfer unit 100A has a feed gear 92 that drives the feed roller 72, and idler gears 93a, 93b, and 93c. The feed gear 92 is rotated by the roller shaft 90. Further, the transfer unit 100A has a pick gear (first part, force-applying part) 101 that receives drive from the feed gear 92 via the idler gears 93a to 93c and drives the pick roller 71, and a receiving part (pick roller latch, force-receiving part, second part) 102.

[0057] As shown in FIG. 5, the pick roller 71, the feed roller 72, the feed gear 92, the idler gears 93a to 93c, the pick gear 101, and the receiving part 102 are held by a lifting arm (arm) 74 and a roller cover 105. The arm 74 is connected to a cylindrical lifting arm shaft (arm shaft) 97. An arm connecting portion 96 is attached to an end of the arm shaft 97, and a roller shaft 90 is disposed inside the arm shaft 97.

[0058] As shown in FIG. 7, the pick-feed unit 100 has a pressed portion 111 and a pressing portion 110. The arm connecting portion 96 is connected to the pressed portion 111. The pressed portion 111 engages with the pressing portion 110. The missing-tooth gear 78 is provided with a regulating cam 78a that regulates the pressing portion 110.

[0059] As described above, the pick roller 71 is configured to be movable between a first position where it can contact the sheet S loaded on the loading tray 81 and a second position where it has retracted from the first position. More specifically, the pick roller 71 is configured to be swingable around the feed roller 72 between a feeding position (first position) where it contacts the sheet S loaded on the loading tray 81 and a separation position (second position) where it is separated from the sheet S.

[0060] As shown in FIGS. 8(a) and 8(b), the pressing portion 110 is biased clockwise in the figure by a biasing member (not shown). When the sheet S is not conveyed from the feeding device 70, as shown in FIG. 8(a), the pick roller 71 is positioned at a second position (standby position, separated position) away from the sheet S stacked on the stacking tray 81. In this state, the position of the pressing member 110 is regulated by the regulating cam 78a.

[0061] On the other hand, when the sheet S is conveyed from the feeding device 70, as shown in FIG. 8(b), the pick roller 71 is positioned at a first position (feeding position, contacting position) where it contacts the sheet S stacked on the stacking tray 81. As shown in FIG. 8(b), when the regulating cam 78a moves away from the pressing portion 110, the pressing portion 110 swings clockwise in the figure and presses the pressed portion 111. Then, the pick roller 71 swings counterclockwise in the figure around the feed roller 72. In this state, the pick roller 71 contacts the sheet S stacked on the stacking tray 81. When there is no sheet S stacked on the stacking tray 81, the pick roller 71 contacts the stacking tray 81.

[0062] As described above, each time the solenoid 79 operates, the toothless gear 78 rotates and one sheet S is fed. In conjunction with the rotation of the toothless gear 78, the rotations of the pick roller 71 and the feed roller 72, the movement of the pick roller 71 between the first position and the second position, the movement of the separation roller 73 between the contacting position and the retracted position, and the movement of the return member between the protruding position and the standby position are executed. That is, the rotations of the pick roller 71 and the feed roller 72, the movement of the pick roller 71 between the first position and the second position, the movement of the separation roller 73 between the contacting position and the retracted position, and the movement of the return member 91 between the protruding position and the standby position are executed by a common motor M via the toothless gear 78.

[0063] <Drive Transmission to Feed Roller and Pick Roller> With reference to FIG. 6, the drive transmission to the feed roller 72 and the pick roller 71 will be described in more detail.

[0064] When the feed roller 72 and the pick roller 71 are driven, the feed shaft connecting portion 95 is driven by a driven gear driven by the missing tooth gear 78. In other words, the feed shaft connecting portion 95 receives a driving force from the missing tooth gear 78. The driving force transmitted to the feed shaft connecting portion 95 is transmitted to the feed roller shaft 90 and then to the feed gear 92 connected to the feed roller shaft 90. The driving force transmitted to the feed gear 92 is transmitted to the pick gear 101 via the idler gears 93a to 93c.

[0065] Here, the feed roller 72 has a rubber holding portion 72a that holds a rubber portion. Also, the pick roller 71 has a rubber holding portion 71a that holds a rubber portion. In the present embodiment, the feed roller 72 and the pick roller 71 have the same shape. Therefore, one type of part can be used as both the feed roller 72 and the pick roller 71, and the cost of the feeding device 70 can be reduced.

[0066] Since the rubber holding portion 72a and the feed gear 92 are separate parts, and the rubber holding portion 71a and the receiving portion 102 are separate parts, one type of part can be used as both the feed roller 72 and the pick roller 71.

[0067] <Configuration of the Pick Roller Delay Mechanism> The transmission unit 100A according to the present embodiment has a drive transmission mechanism (hereinafter, delay mechanism) 106. The delay mechanism 106 is configured such that after a driving force is transmitted to the pick gear 101, the driving force is transmitted to the pick roller 71 after a predetermined time has elapsed.

[0068] Hereinafter, the delay mechanism 106 according to the present embodiment will be described with reference to FIGS. 9 and 10.

[0069] FIG. 9 is a diagram for explaining the delay mechanism 106. FIG. 9(a) is a perspective view of the delay mechanism 106 seen from one side. FIG. 9(b) is a perspective view of the delay mechanism 106 seen from the other side. FIG. 10 is a diagram for explaining the operation of the delay mechanism 106.

[0070] In the present embodiment, the delay mechanism 106 includes a pick gear (first part, force applying part) 101, a receiving part (second part, force receiving part) 102 that is driven by the pick gear 101 and configured to drive the pick roller 71, and a spring 103 as a biasing member.

[0071] In the present embodiment, the receiving part 102 is connected to the end of the pick roller 71. Specifically, the receiving part 102 is connected to the rubber holding part 71a of the pick roller 71. The pick gear 101 and the receiving part 102 are coaxially held by the arm 74. That is, the rotation axis of the pick gear 101 and the rotation axis of the receiving part 102 coincide. Also, the rotation axis of the pick gear 101, the rotation axis of the receiving part 102, and the rotation axis of the pick roller 71 coincide. In other words, the pick gear 101, the receiving part 102, and the pick roller 71 are configured to rotate around a common rotation axis.

[0072] The pick roller 71 abuts against the roller cover 105, and the end of the spring 103 abuts against the arm 74. Therefore, as shown in FIG. 10, in the rotation axis direction of the pick gear 101, the length L between the end of the pick roller 71 and the end of the spring 103 is constant.

[0073] As shown in FIGS. 9(a) and 9(b), the pick gear 101 has a drive transmission surface (first transmission surface, drive surface) 101a and a cam surface (first contact surface, first inclined surface) 101b. In the present embodiment, a plurality of drive transmission surfaces 101a and a plurality of cam surfaces 101b are provided. The cam surface 101b is inclined with respect to the rotation axis direction of the pick gear 101. In the present embodiment, the plurality of drive transmission surfaces 101a and the plurality of cam surfaces 101b are arranged concentrically around the rotation center of the pick gear 101.

[0074] In the present embodiment, the drive transmission surface 101a is located at a position farther from the rotation center of the pick gear 101 than the cam surface 101b. However, the cam surface 101b may be located at a position farther from the rotation center of the pick gear 101 than the drive transmission surface 101a.

[0075] As shown in FIGS. 9(a) and 9(b), the receiving portion 102 has a driving transmission surface (second transmission surface, driven surface) 102a and a cam surface (second contact surface, second inclined surface) 102b. In the present embodiment, a plurality of driving transmission surfaces 102a and cam surfaces 102b are provided. The cam surface 102b is inclined with respect to the rotation axis direction of the receiving portion 102. In the present embodiment, the plurality of driving transmission surfaces 102a and the plurality of cam surfaces 102b are arranged concentrically around the rotation center of the receiving portion 102.

[0076] In the present embodiment, the driving transmission surface 102a is located at a position farther from the rotation center of the pick gear 102 than the cam surface 102b. However, the cam surface 102b may be located at a position farther from the rotation center of the pick gear 102 than the driving transmission surface 102a.

[0077] Two driving transmission surfaces 101a and 102a, and two cam surfaces 101b and 102b are provided respectively. However, the number of each part may be one, or may be more than two.

[0078] When the driving transmission surface 101a abuts on the driving transmission surface 102a, the driving force is transmitted from the driving transmission surface 101a to the driving transmission surface 102a, and the pick gear 101 drives the receiving portion 102. As a result, when the pick gear 101 rotates, the receiving portion 102 and the pick roller 71 rotate.

[0079] When the driving transmission surface 101a and the driving transmission surface 102a are separated, the driving force is not transmitted from the driving transmission surface 101a to the driving transmission surface 102a. As a result, even if the pick gear 101 rotates, the receiving portion 102 and the pick roller 71 do not rotate.

[0080] <Operation of the Pick Roller Delay Mechanism> The operation of the delay mechanism 106 will be described with reference to FIGS. 9 and 10.

[0081] The spring 103 biases the pick gear 101 so that the drive transmission surfaces 101a and 102a move apart. The pick gear 101 is configured to be movable in the direction of the rotation axis of the pick gear 101 in a direction away from the receiving portion 102. In the present embodiment, in the direction of the rotation axis (thrust direction) of the pick gear 101, the pick gear 101 is always biased by the spring 103 in a direction approaching the receiving portion 102.

[0082] Due to the biasing force of the spring 103, the cam surface 101b of the pick gear 101 and the cam surface 102b of the receiving portion 102 are in contact. When the cam surface 101b and the cam surface 102b are in contact due to the biasing force of the spring 103, the drive transmission surfaces 101a and 102a are separated. Specifically, the cam surface 101b and the cam surface 102b are inclined so that the drive transmission surfaces 101a and 102a are separated when receiving the biasing force of the spring 103 in a state of being in contact with each other. As a result, as shown in the upper diagram of FIG. 10, a predetermined interval is maintained between the drive transmission surfaces 101a and 102a. That is, the spring 103 biases the pick gear 101 so that the drive transmission surfaces 101a and 102a move apart.

[0083] The biasing force of the spring 103 is set to a force that can maintain the interval between the drive transmission surfaces 101a and 102a as long as the pick roller 71 does not contact the sheet S.

[0084] When the pick roller 71 contacts the loading tray 81 or the sheet S loaded on the loading tray 81, the rotation of the pick roller 71 is restricted by the frictional force received from the sheet S or the loading tray 81. At the same time, the rotation of the receiving portion 102 connected to the pick roller 71 is also restricted.

[0085] When the pick gear 101 is driven in this state, against the biasing force of the spring 103, in the direction of the rotation axis of the pick gear 101, it moves in the direction away from the receiving portion 102 (the left side in FIG. 10). Specifically, the cam surface 101b slides along the cam surface 102b, and the pick gear 101 moves. And regarding the rotation direction of the pick gear 101, the drive transmission surface 101a and the drive transmission surface 102a approach each other, and as shown in the lower figure of FIG. 10, the drive transmission surface 101a and the drive transmission surface 102a come into contact. As a result, the pick roller 71 in contact with the sheet S rotates, and the sheet S is conveyed. That is, the sheet S loaded on the loading tray 81 is conveyed by the pick roller 71.

[0086] When the pick roller 71 separates from the loading tray 81 or the sheet S loaded on the loading tray 81, the rotation of the pick roller 71 is no longer restricted. On the other hand, in the state where the drive transmission surface 101a and the drive transmission surface 102a are in contact, the cam surface 101b is in contact with the cam surface 102b. Therefore, when the rotation of the pick roller 71 is no longer restricted, the cam surface 101b presses the cam surface 102b by the biasing force of the spring 103, and the drive transmission surface 101a and the drive transmission surface 102a are in a separated state. By repeating the above operations every time one sheet S is conveyed, the sheet S on the loading tray 81 is conveyed.

[0087] By the delay mechanism 106, the transmission unit 100A can take a first drive state in which the feed roller 72 is driven (rotates) and the pick roller 71 stops, and a second drive state in which the feed roller 72 is driven (rotates) and the pick roller 71 is driven (rotates).

[0088] 〈Conveying operation of sheet S〉 Using FIGS. 11 and 12, the conveying operation in which the sheet S is conveyed from the loading tray 81 will be described.

[0089] FIG. 11 is a diagram for explaining the conveying operation in which the sheet S is conveyed from the loading tray 81. FIG. 11(a) is a diagram showing a state where the pick roller 71 is separated from the sheet S loaded on the loading tray 81. FIG. 11(b) is a diagram showing a state where the pick roller 71 is in contact with the sheet S loaded on the loading tray 81. FIG. 11(c) is a diagram showing a state where the separation roller 73 is in contact with the feed roller 72. FIG. 12 is a diagram for explaining the control unit that controls the pick feed unit 100 and the moving device 200.

[0090] Before the sheet S is conveyed from the loading tray 81, as shown in FIG. 11(a), the pick roller 71 is raised and is in a second position separated from the loading tray 81 and the sheet S. By separating the pick roller 71 from the loading tray 81 and the sheet S, the user can easily install the sheet S on the loading tray 81. Also, the separation roller 73 is in a retracted position separated from the feed roller 72. Further, the return member 91 protrudes into the conveyance path (the path through which the sheet S passes).

[0091] In the present embodiment, the loading tray 81 is inclined so that the sheet S moves downstream in the conveyance direction DS due to the weight of the sheet S. In other words, the loading tray 81 is inclined such that the downstream end in the conveyance direction DS is lower than the upstream end in the conveyance direction DS. That is, the downstream end of the loading tray 81 is positioned below the upstream end of the loading tray 81 in the vertical direction. As a result, when the user installs the sheet S on the loading tray 81, the leading end of the sheet S waits near the return member 91. In the present embodiment, the sheet S waits in a state of being in contact with the return member 91.

[0092] As shown in FIG. 12, the apparatus main body 1A has a control unit CT. The control unit CT controls the operations of the motor M and the solenoid 79. In other words, the control unit CT controls the pick feed unit 100 and the moving device 200 via the motor M and the solenoid 79. Also, the motor M drives the pick feed unit 100 and the moving device 200.

[0093] When an instruction to form an image on the sheet S is sent to the apparatus main body 1A using the feeding device 70, the control unit CT determines whether or not there is a sheet S on the loading tray 81. This determination is made using a paper presence / absence flag protruding from the loading tray 81 and a photo interrupter (not shown).

[0094] When it is determined that there is a sheet S on the loading tray 81, the solenoid 79 is activated, the toothless gear 78 starts to rotate, and a driving force is transmitted from the motor M to the feeding device 70.

[0095] When the toothless gear 78 rotates, the arm 74 swings and the pick-up roller 71 descends. When the pick-up roller 71 moves to the paper feeding position (first position), it comes into contact with the sheet S loaded on the loading tray 81 (see Fig. 11(b)).

[0096] On the other hand, in conjunction with the rotation of the toothless gear 78, the control cam 84 rotates. When the control cam 84 rotates, the moving device 200 operates, and as described above, the first moving member 75a, the second moving member 75b, and the holder support member 86 move. As a result, the separating roller 73 moves toward the contact position where it contacts the feed roller 72, and the return member 91 retracts from the conveyance path of the sheet S (see Fig. 11(c)). In this state, the movement of the sheet S is restricted by the stopped pick-up roller 71.

[0097] In the present embodiment, the return member 91 may retract by its own weight or may retract in contact with the sheet S. In the present embodiment, since the movement of the return member 91 in the retracting direction is not restricted, even when it retracts in contact with the sheet S, the return member 91 can retract from the conveyance path without damaging the sheet S.

[0098] Subsequently, the transmission of the driving force to the feed roller 72 and the pick-up roller 71 is started. The driving force from the motor M is transmitted to the feed gear 92 through the toothless gear 78, the feed shaft connecting portion 95, and the roller shaft 90. The driving force transmitted to the feed gear 92 is transmitted to the pick gear 101 via the idler gears 93a to 93c.

[0099] At this time, while the feed roller 72 is rotated by the feed gear 92, the rotation of the pick roller 71 is restricted by the frictional force received from the sheet S, and the drive transmission surfaces 101a and 102a are separated.

[0100] When the pick gear 101 rotates with the pick roller 71 stopped, the drive transmission surfaces 101a and 102a gradually approach against the force that separates them by the spring 103, the cam surface 101b, and the cam surface 102b. At this time, the separation roller 73 is already in contact with the feed roller 72, and a separation nip (NS in FIG. 11(c)) is formed. That is, after the separation roller 73 comes into contact with the feed roller 72, the drive transmission surfaces 101a and 102a come into contact, and the pick roller 71 is driven. Further, since the feed roller 72 is already driven, before the drive transmission surfaces 101a and 102a come into contact, the separation roller 73 that has come into contact with the feed roller 72 is driven. That is, after the separation roller 73 is driven, the drive transmission surfaces 101a and 102a come into contact, and the pick roller 71 is driven.

[0101] In this way, with the separation roller 73 in contact with the feed roller 72 and the pick roller 71 in contact with and stopped on the sheet S loaded on the loading tray 81, the feed roller 72 is driven. Then, after the feed roller 72 is driven, the drive transmission surfaces 101a and 102a come into contact, and the pick roller 71 is driven. Note that the pick roller 71 remains stopped during a predetermined time period from when the feed roller 72 is driven until the drive transmission surfaces 101a and 102a come into contact and the pick roller 71 is driven.

[0102] Immediately after the rotation of the feed roller 72 is started, the separation function of the feed roller 73 (the function of separating a single sheet from a plurality of sheets) may not be fully exerted. For example, this may be caused by play in the member that holds the separation roller 73 or a delay in the response of the torque limiter built into the separation roller 73.

[0103] In this embodiment, after the rotation of the feed roller 72 is started, the pick roller 71 rotates after a predetermined time. Thereby, it is possible to prevent the sheet S from being conveyed to the separation nip in a state where the separation function of the separation roller 73 is not sufficiently exerted. For example, before the leading end of the sheet S reaches the separation nip, it is possible to eliminate the play in the holding portion of the separation roller 73 and the delay in the response of the torque limiter. Then, after the separation function is exerted, when the drive transmission surface 101a and the drive transmission surface 102a come into contact, the pick roller 71 is driven and the feeding of the sheet S is started. As a result, the sheet S is conveyed toward the separation nip in a state where the desired separation function is exerted.

[0104] The pick roller 71 is configured to be separated from the sheet S when the arm 74 rises after conveying the sheet S by a predetermined amount so that the leading end of the sheet S reaches the separation nip between the feed roller 72 and the separation roller 73. When the pick roller 71 is separated from the sheet S, the rotation of the pick roller 71 and the connected receiving portion 102 is no longer restricted. Therefore, the delay mechanism 106 returns to a state where the drive transmission surface 101a and the drive transmission surface 102a are separated by the biasing force of the spring 103.

[0105] Also, as described above, after the sheet S is conveyed to the downstream conveying roller by the feed roller 72 and the separation roller 73, the separation roller 73 separates from the feed roller 72. Further, in conjunction with the separation operation of the separation roller 73, the return member 91 rotates and pushes back the sheet S (subsequent sheet) remaining near the separation nip toward the stacking tray 81. Through the above operations, the feeding device 70 returns to the state shown in Fig. 11(a).

[0106] Each time the feeding device 70 conveys one sheet S, it performs the above-described operations. By repeating this, the feeding device 70 conveys the sheet S stacked on the stacking tray 81.

[0107] When the sheet S is conveyed to the separation nip formed between the separation roller 73 and the feed roller 72 in a state where the separation function is not sufficiently exerted, the sheet S stopped by the separation roller 73 may be conveyed downstream in the conveyance direction beyond a predetermined stop position.

[0108] When returning the sheet S to the stacking tray 81 with the return member 91, the sheet S needs to stay at a predetermined stop position so that the return member 91 can touch the leading end of the sheet S. In the present embodiment, with the separation roller 73 in contact with the feed roller 72, after the feed roller 72 rotates, the pick roller 71 rotates after a predetermined time. As a result, it is possible to suppress the sheet S from moving downstream in the conveyance direction beyond the position where the return member 91 can contact the leading end of the sheet S.

[0109] Also, in the configuration where the stacking tray 81 is inclined downward as in the present embodiment, the sheet S waits at a position close to the feed roller 72 and the separation roller 73. Therefore, when the pick roller 71 rotates, the sheet S reaches the position of the separation nip between the feed roller 72 and the separation roller 73 in a short time. Even with such a configuration, by delaying the start of rotation of the pick roller 71, the sheet S can be conveyed toward the separation nip at an appropriate timing.

[0110] In the feeding device 70 of the present embodiment, the stacking tray 81 is configured to be movable between a closed position and an open position with respect to the device main body 1A. Specifically, as shown in FIG. 1, the stacking tray 81 is provided in the vicinity of an openable and closable door 82. When not in use, the stacking tray 81 is housed inside the device main body 1A by closing the door 82. The pick - feed unit 100 is also configured to be movable in conjunction with the opening and closing of the door 82, with the feed roller 72 as the rotation center, from the position during use to the position housed inside the device main body 1A.

[0111] The sheet feeding device 70 of this embodiment can start transporting the sheet S after the separation roller 73 is driven, with the pick roller 71 moving up and down relative to the fixed loading tray 81 without moving the loading tray 81 up and down relative to the feed roller 72. Therefore, the noise when the transportation of the sheet S starts can be reduced.

[0112] In addition, the sheet feeding device 70 can adopt a small-diameter pick roller 71 that protrudes outside the apparatus main body 1A together with the loading tray 81 only during use, instead of a large-diameter sheet feeding roller fixed to the apparatus main body 1A, so that the image forming apparatus 1 can be miniaturized.

[0113] The operation of the return member 91 interlocked with the contact and separation of the separation roller 73, the contact and separation of the pick roller 71, and the start of driving of the pick roller 71 and the feed roller 72 are controlled by a single solenoid 79 provided in the apparatus main body 1A. For this reason, the cost of the sheet feeding device 70 can be reduced. In this embodiment, the solenoid 79 is used as the configuration of the switching device that selectively operates the sheet feeding device 70. However, as long as driving can be selectively transmitted, a configuration other than a solenoid (for example, an electromagnetic clutch, etc.) may be adopted.

[0114] As the means for urging the drive transmission surface 101a and the drive transmission surface 102a in the separating direction, a compression spring 103 is used, but as long as it is a biasing member having elasticity, a configuration other than the compression spring may be adopted.

[0115] The delay mechanism 106 may be arranged anywhere as long as it is between the feed roller 72 and the pick roller 71. For example, a mechanism corresponding to the delay mechanism 106 may be arranged at any part of the idler gears 93a to 93c.

[0116] Also, in this embodiment, the spring 103 is configured to bias the pick gear 101, but the present invention is not limited to this. The receiving portion 102 may be configured to be movable, and the spring 103 may be configured to bias the receiving portion 102 so that the drive transmission surface 101a and the drive transmission surface 102a are separated. That is, the spring 103 may bias either the first portion or the second portion. In this case, the receiving portion 102 is configured to be movable in the direction away from the pick gear 101 in the rotational axis direction of the pick gear 101.

[0117] Further, the feeding device 50 in the apparatus main body 1A may include a delay mechanism 106. Further, even if the separation roller 73 is not configured to be movable to the retracted position, the delay mechanism 106 can be employed.

[0118] The configuration of the image forming apparatus to which the sheet feeding device according to the present invention is applied is not limited to the above configuration. For example, the present invention can be applied to an image forming apparatus in which an image is directly formed on the sheet S from the photosensitive drum. Further, the present invention can be applied to an image forming apparatus that forms a monochromatic image on the sheet S. Furthermore, the present invention can be applied to an image forming apparatus other than a laser beam printer, such as an inkjet printer.

Explanation of Reference Numerals

[0119] 70 Feeding device 71 Pick roller 72 Feed roller 73 Separation roller 81 Loading tray 91 Return member 92 Feed gear 100 Pick feed unit 100A Transmission unit 101 Pick gear 102 Receiving portion 103 Biasing member

Claims

1. A tray configured to load sheets, A feeding member configured to feed the sheets loaded on the tray, A conveying member configured to convey the sheets fed by the feeding member, A separating member capable of contacting the conveying member, movable between a contact position where it contacts the conveying member and a retracted position where it is retracted from the contact position, and configured to separate a single sheet from a plurality of sheets fed by the feeding member, A separating movement unit configured to move the separating member between the contact position and the retracted position, A transmission unit that transmits driving force to the conveying member and the feeding member, including a first part, A second part driven by the first part and configured to drive the feeding member. The first part has a first transmission surface, the second part has a second transmission surface, and the first transmission surface and the second transmission surface contact each other, so that the first part drives the second part. The transmission unit, A biasing member that biases either the first part or the second part so that the first transmission surface and the second transmission surface separate from each other, having, The separating member contacts the conveying member, and the feeding member contacts the sheet loaded on the tray and stops. In this state, the conveying member is driven. After the conveying member is driven, the first transmission surface and the second transmission surface contact each other, and the feeding member is driven. A sheet feeding device, characterized in that after the separating member contacts the conveying member, the first transmission surface and the second transmission surface contact each other, and the feeding member is driven.

2. The feeding member is configured to be movable between a first position where it can contact the sheet loaded on the tray and a second position where it is retracted from the first position. The sheet feeding device according to claim 1.

3. The feeding member is configured to be swingable around the conveying member so as to move between the first position and the second position. The sheet feeding device according to claim 2.

4. In the axial direction of the rotation axis of the first part, one of the first part and the second part is configured to be movable in a direction away from the other of the first part and the second part. The sheet feeding device according to any one of claims 1 to 3.

5. The sheet feeding device according to any one of claims 1 to 4, characterized in that when the separation member is located at the retracted position, it includes a return member for returning the sheet from the portion between the conveying member and the separation member toward the tray.

6. The sheet feeding device according to claim 1 or 5, characterized in that before the sheet is conveyed from the tray, the separation member is in the retracted position.

7. The sheet feeding device according to any one of claims 1 to 6, characterized in that the second part is connected to an end of the feeding member.

8. The first part includes a first contact surface, The second part includes a second contact surface, The sheet feeding device according to any one of claims 1 to 7, characterized in that the first contact surface and the second contact surface are in contact by the force of the biasing member, so that the first transmission surface and the second transmission surface are separated from each other.

9. The sheet feeding device according to claim 8, characterized in that the first contact surface is inclined with respect to the rotation axis direction of the first part, and the second contact surface is inclined with respect to the rotation axis direction of the second part.

10. The sheet feeding device according to any one of claims 1 to 9, characterized in that the separation member is configured to be rotatable.

11. The sheet feeding device according to any one of claims 1 to 10, characterized in that the tray is inclined such that the downstream end in the sheet conveying direction is lower than the upstream end in the conveying direction.

12. The sheet feeding device according to any one of claims 1 to 11, characterized in that the tray is configured to be movable between a closed position and an open position with respect to the device main body.

13. A sheet feeding device according to any one of claims 1 to 12, An image forming unit configured to form an image on a sheet, An image forming apparatus characterized by comprising the above.

Images