Image formation apparatus

Abstract

To provide an image formation apparatus that can feed paper with a simple constitution.SOLUTION: An image formation apparatus comprises a paper feeding cassette 21 and a paper feeding device 23. The paper feeding cassette 21 comprises a lifting plate 33 capable of rotating to lift paper. The paper feeding device 23 comprises: a pickup roller 51 which comes into contact with paper placed on the lifting plate 33 and rotates to deliver the paper; and a holder 55 which is rotatably supported so that the pickup roller 51 comes into contact with the uppermost paper. The image formation apparatus further comprises an interlock mechanism 70 in which the paper is lifted by rotating the lifting plate 33 until the pickup roller 51 reaches a prescribed paper feed height by the rotation of the holder 55 and the rotation of the holder 55 is interlocked with the rotation of the lifting plate 33 so that the rotation of the lifting plate 33 is stopped after the pickup roller 51 reaches the paper feed height.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus equipped with a paper feed cassette and a paper feed device. [Background technology]

[0002] The image forming apparatus includes a paper feed cassette that stores paper sheets and a paper feed device that feeds the stored paper sheets toward a transport path. As described in Patent Document 1, the paper sheets are placed on a lift plate provided in the paper feed cassette. The lift plate is rotatable so as to lift the leading edge of the paper sheets in the paper feed direction. The paper feed device includes a pickup roller that rotates to contact the topmost sheet of paper sheets placed on the lift plate at a predetermined paper feed height and feeds the paper sheets. The pickup roller is biased downward so as to contact the topmost sheet of paper.

[0003] The lift plate rotates until the pickup roller is lifted by the loaded paper and rises to the paper feed height, and then stops rotating. As the paper is transported and the number of sheets loaded on the lift plate decreases, the contact height between the pickup roller and the top sheet decreases, so the lift plate rotates again so that the pickup roller rises to the paper feed height. In this way, the lift plate repeatedly rotates and stops rotating as the paper is transported. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-37745 Summary of the Invention [Problem to be solved by the invention]

[0005] The configuration described in Patent Document 1 requires multiple sensors, such as a sensor that detects the rotation angle of the holder that holds the pickup roller and a sensor that detects the presence or absence of paper on the lift plate. Also, components such as a solenoid that transmits and blocks the rotational force from the motor to the lift plate may be used. The need for many electrical components increases costs and complicates the control of each electrical component.

[0006] SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide an image forming apparatus that can feed paper with a simple configuration. [Means for solving the problem]

[0007] The image forming apparatus of the present invention is an image forming apparatus comprising a paper feed cassette in which paper is stored, and a paper feed device that feeds the paper stored in the paper feed cassette, wherein the paper feed cassette has a lift plate on which paper is placed and which can rotate to lift the paper, and the paper feed device has a pickup roller that contacts the topmost sheet of paper placed on the lift plate and rotates to feed the paper, and a holder that houses the pickup roller and is rotatably supported so that the pickup roller contacts the topmost sheet of paper, and further comprises a linkage mechanism that links the rotation of the holder to the rotation of the lift plate, so that the holder rotates to rotate the lift plate to lift the paper until the pickup roller reaches a predetermined paper feed height, and stops the rotation of the lift plate after the pickup roller reaches the paper feed height.

[0008] In the present invention, the interlocking mechanism may be characterized by comprising: a cassette side gear assembly that is connected to the lift plate when the paper feed cassette is attached to the cassette attachment section and rotates the lift plate only in the direction of lifting the paper; a gear link that is rotatable between a transmission position in which a rotational force generated by a drive source is transmitted to the cassette side gear assembly to rotate the lift plate, and a separated position in which the rotational force is not transmitted to the cassette side gear assembly; and a holder side gear assembly that moves the gear link to the transmission position until the pickup roller reaches the paper feed height, and moves the gear link to the separated position after the paper feed height is reached.

[0009] In the present invention, the gear link includes a drive gear that is driven to rotate by the drive source, and the holder side gear assembly includes an external gear that rotates in mesh with the drive gear and whose rotation is restricted by the holder when the holder rotates until the pickup roller rises to the paper feed height, and a pin that can protrude into the rotation area of ​​the gear link from a position retracted from the rotation area of ​​the gear link due to the rotation of the external gear, and the pin protrudes as the external gear rotates until its rotation is restricted by the holder, and the protruding pin rotates the gear link from the transmission position to the separated position.

[0010] In the present invention, the external gear may have a tooth-missing portion, and when rotation is restricted by the holder, the tooth-missing portion may face the drive gear.

[0011] In the present invention, the paper feed cassette may further include a lifting plate disposed below the lift plate and rotating to lift and rotate the lift plate, and the cassette side gear assembly may be connected to the lift plate via the lifting plate. [Effects of the Invention]

[0012] According to the present invention, the lift plate can be automatically rotated in response to the rotation of the holder, so a sensor for detecting the angle of the holder is not required, and control of the paper feeding operation can be simplified. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a front view schematically illustrating an internal configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] 1 is a side view schematically illustrating a paper feed cassette and a paper feed device of an image forming apparatus according to an embodiment of the present invention. [Figure 3] 1 is a perspective view showing a paper feed cassette, a paper feed device, and an interlocking mechanism of an image forming apparatus according to an embodiment of the present invention; [Figure 4] 10 is a view of a cassette-side gear assembly of an interlocking mechanism as viewed from the right side in an image forming apparatus according to an embodiment of the present invention. FIG. [Figure 5] FIG. 2 is an exploded perspective view showing a gear link of an interlocking mechanism in the image forming apparatus according to one embodiment of the present invention. [Figure 6] FIG. 2 is a perspective view showing a holder-side gear assembly of an interlocking mechanism in an image forming apparatus according to an embodiment of the present invention. [Figure 7] FIG. 2 is an exploded perspective view showing a holder-side gear assembly of the interlocking mechanism in the image forming apparatus according to one embodiment of the present invention. [Figure 8] 1 is a perspective view showing a fixed plate and an inner disk of a holder-side gear assembly in an image forming apparatus according to an embodiment of the present invention; [Figure 9] 5 is a flowchart showing an example of a paper feeding operation in the image forming apparatus according to an embodiment of the present invention. [Figure 10] 1 is a side view of a holder and an interlocking mechanism in an image forming apparatus according to an embodiment of the present invention, viewed from the right side, in an S1 (initial state). [Figure 11] 1 is a side view of a holder and an interlocking mechanism in an image forming apparatus according to an embodiment of the present invention, viewed from the left side, in an S1 (initial state). [Figure 12]10 is a perspective view showing a pin of a holder-side gear assembly and a link bar of a gear link (in a state where the pin is retracted) in the image forming apparatus according to one embodiment of the present invention. FIG. [Figure 13] 10 is a cross-sectional view showing a pin of a holder-side gear assembly and a link bar of a gear link (in a state where the pin is retracted) in an image forming apparatus according to one embodiment of the present invention. FIG. [Figure 14] 10 is a view of the holder and the interlocking mechanism as viewed from the right side at S3 (lift plate rotation start) in the image forming apparatus according to one embodiment of the present invention. FIG. [Figure 15] 10 is a view of the holder and the interlocking mechanism as viewed from the left side at S3 (lift plate starts to rotate) in the image forming apparatus according to one embodiment of the present invention. FIG. [Figure 16] FIG. 10 is a view of the holder and interlocking mechanism as viewed from the left side in the image forming apparatus according to one embodiment of the present invention, at S5 (the pickup roller is raised to the paper feeding height). [Figure 17] FIG. 10 is a view of the holder and interlocking mechanism as viewed from the right side in the image forming apparatus according to one embodiment of the present invention, at S5 (the pickup roller is raised to the paper feeding height). [Figure 18] 10 is a perspective view showing a pin of a holder-side gear assembly and a link bar of a gear link (in a state where the pin protrudes) in the image forming apparatus according to one embodiment of the present invention. FIG. [Figure 19] FIG. 10 is a view of the holder and the interlocking mechanism as viewed from the left side in the image forming apparatus according to one embodiment of the present invention in S6 (lift plate rotation stopped). [Figure 20] FIG. 10 is a view of the holder and the interlocking mechanism as viewed from the right side in the image forming apparatus according to one embodiment of the present invention, in S6 (lift plate rotation stopped). [Figure 21] FIG. 10 is a view of the holder and the interlocking mechanism as viewed from the left side in the image forming apparatus according to one embodiment of the present invention, in S8 (the pickup roller is lowered to a predetermined height). [Figure 22] FIG. 10 is a view of the holder and the interlocking mechanism as viewed from the right side in the image forming apparatus according to one embodiment of the present invention, in S8 (the pickup roller is lowered to a predetermined height). DETAILED DESCRIPTION OF THE INVENTION

[0014] An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

[0015] First, the overall configuration of an image forming apparatus 1 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view that schematically shows the internal structure of the image forming apparatus 1. In each drawing, Fr, Rr, L, and R indicate the front, rear, left, and right sides of the image forming apparatus 1, respectively.

[0016] The device body 2 of the image forming device 1 is equipped with a paper feed unit 3, an electrophotographic image forming unit 5, a fixing device 7, and a discharge device 9. A discharge tray 11 is formed on the top surface of the device body 2. The device body 2 is formed with a paper transport path 13 that runs from the paper feed unit 3, through the image forming unit 5 and the fixing device 7, and toward the discharge device 9.

[0017] The paper feed section 3 includes a paper feed cassette 21 that stores paper sheets, and a paper feed device 23 that feeds paper sheets along a paper feed direction from the paper feed cassette 21 toward the transport path 13. The paper feed cassette 21 is attached to and detached from a cassette attachment section of the device body 2 along the front-rear direction through an opening (not shown) formed in the front of the device body 2. The paper feed section 3 will be described later.

[0018] The image forming unit 5 includes four process cartridges 25 corresponding to toner of four colors (yellow, magenta, cyan, and black), a circulating intermediate transfer belt 27, and a transfer roller 29. The four process cartridges 25 are arranged side by side along the running direction of the intermediate transfer belt 27, facing the lower track of the intermediate transfer belt 27. The four process cartridges 25 overlay toner images of each color on the running intermediate transfer belt 27 to form a full-color toner image. The formed toner image is transferred to paper transported along the transport path 13 at a transfer nip formed between the transfer roller 29 and the intermediate transfer belt 27.

[0019] The fixing device 7 fixes the toner image transferred onto the paper, and the discharge device 9 discharges the paper with the fixed toner image. The discharged paper is stacked on a discharge tray 11.

[0020] Next, the paper feed unit 3 will be further described with reference to Figures 2 and 3. Figure 2 is a side view showing the paper feed unit 3, and Figure 3 is a perspective view showing the paper feed unit 3. As described above, the paper feed unit 3 includes the paper feed cassette 21 that stores paper sheets, and the paper feed device 23 that feeds paper sheets from the paper feed cassette 21 in the paper feed direction.

[0021] First, the paper feed cassette 21 will be described. The paper feed cassette 21 includes a cassette body 31 that stores paper sheets, a lift plate 33 that is disposed on the bottom plate of the cassette body 31, and a lift plate 35 (see FIG. 2, not shown in FIG. 3) that is disposed below the lift plate 33.

[0022] First, the cassette body 31 will be described. The cassette body 31 has a shallow box shape with an open top, and is composed of a bottom plate, front and rear side plates that face each other in the front-rear direction, and left and right side plates that face each other in the left-right direction. The front side plate is provided with an outer cover 37 that closes the opening of the device body 2 when the paper feed cassette 21 is attached to the cassette attachment section.

[0023] Next, the lift plate 33 will be described with reference to FIG. 2. The lift plate 33 has a mounting portion 33a that is large enough to support the leading edge of a sheet of paper (approximately half of the leading edge in the paper feed direction), and left and right support portions 33b that are provided along the left and right side edges of the mounting portion 33a. The left and right support portions 33b are rotatably supported on the inner surfaces of the left and right side plates of the cassette body 31. This allows the lift plate 33 to rotate from a horizontal position (see solid lines in FIG. 2) in which the mounting portion 33a overlaps the bottom plate of the cassette body 31 and allows paper to be placed thereon, to an inclined position (see chain double-dashed lines in FIG. 2) in which the mounting portion 33a is inclined upward toward the paper feed direction. By tilting the lift plate 33 in this way, the leading edge of the paper placed on the mounting portion 33a is raised.

[0024] Next, the lifting plate 35 will be described. The lifting plate 35 is disposed between the bottom plate of the cassette body 31 and the lift plate 33. A shaft 39 is fixed to the front side edge of the lifting plate 35. Both ends of the shaft 39 are rotatably supported by the left and right side plates of the cassette body 31. When the lifting plate 35 rotates around the shaft 39 (see the two-dot chain line in FIG. 2), the lifting plate 33 is lifted and rotates from a horizontal position to an inclined position.

[0025] The right end of the shaft 39 protrudes through the right side plate of the cassette body 31. A sector gear 41 is fixed to the right end protruding from the right side plate.

[0026] Next, the paper feeder 23 will be described. The paper feeder 23 includes a pickup roller 51, a paper feed roller 53, and a holder 55 that holds both rollers 51 and 53. The pickup roller 51 and the paper feed roller 53 are arranged in order along the paper feed direction and are rotatably supported by the holder 55. The rotation shaft 53a of the paper feed roller 53 and the rotation shaft 51a of the pickup roller 51 are connected via an idle gear 57. The rotation shaft 53a of the paper feed roller 53 is driven and rotated by a motor (not shown), causing the paper feed roller 53 and the pickup roller 51 to rotate in the same direction.

[0027] The holder 55 is supported by the device body 2 so as to be rotatable in the vertical direction around the rotation axis 53a of the paper feed roller 53. The holder 55 is also biased by a coil spring 59 so that the pickup roller 51 descends. The holder 55 is supported by the coil spring at a predetermined initial tilt angle α. When the lift plate 33, on which the sheets are placed, rotates to an inclined position, the pickup roller 51 eventually contacts the topmost sheet. As the lift plate 33 further rotates, the pickup roller 51 is lifted by the sheets. The holder 55 then rotates around the rotation axis 53a of the paper feed roller 53 against the biasing force of the coil spring 59 until the pickup roller 51 rises to the predetermined paper feed height. In other words, the tilt angle β of the holder 55 when the pickup roller 51 rises to the paper feed height is smaller than the initial tilt angle α.

[0028] An extension piece 61 is formed on the holder 55, extending downstream in the paper feed direction relative to the rotation shaft 53a of the paper feed roller 53. A downward claw portion 63 (see FIG. 2) is formed at the tip of the extension piece 61.

[0029] 3, the paper feed unit 3 is provided with an interlocking mechanism 70 between the holder 55 of the paper feed device 23 and the fan-shaped gear 41 of the paper feed cassette 21, which rotates the fan-shaped gear 41 in response to the rotation of the holder 55. In other words, the interlocking mechanism 70 rotates the lifting plate 35 in response to the rotation of the holder 55, thereby tilting the lift plate 33.

[0030] Next, the interlocking mechanism 70 will be described with reference to Fig. 3. The interlocking mechanism 70 includes a cassette-side gear assembly 71 that rotates the sector gear 41 only in the direction that tilts the lift plate 33 (counterclockwise in Fig. 3), a gear link 73 that is rotatable between a transmission position in which the rotational force generated by the drive source is transmitted to the cassette-side gear assembly 71 and a separated position in which the rotational force is not transmitted, and a holder-side gear assembly 75 that rotates the gear link 73 between the transmission position and the separated position in response to rotation of the holder 55.

[0031] First, the cassette-side gear assembly 71 will be described with reference to FIG. 4. FIG. 4 is a view of the cassette-side gear assembly 71 as seen from the right side. The cassette-side gear assembly 71 is composed of a driven gear 81, a unidirectional gear 83 provided integrally with the driven gear 81, and a pawl 85 that can mesh with the unidirectional gear 83. In this example, the driven gear 81 rotates only in the clockwise direction (see arrow A1 in FIG. 4). Each tooth of the unidirectional gear 83 is inclined in the direction opposite to the rotational direction A1. The pawl 85 is biased by a spring 87 so as to abut against the tooth surface of the unidirectional gear 83 on the downstream side in the rotational direction A1.

[0032] With this configuration, when a rotational force in the rotational direction A1 is applied to the driven gear 81, the pawl 85 is pushed by the downstream tooth flank of the tooth of the unidirectional gear 83. Then, the pawl 85 is guided along the downstream tooth flank and moves away from the tooth of the unidirectional gear 83. This causes the driven gear 81 to rotate in the rotational direction A1. On the other hand, when a rotational force in the direction opposite to the rotational direction A1 is applied to the driven gear 81, the upstream tooth flank of the tooth of the unidirectional gear 83 is locked by the pawl 85, and the driven gear 81 does not rotate.

[0033] As shown in Fig. 3, the driven gear 81 is connected to the sector gear 41 via two idle gears 89. That is, when the driven gear 81 rotates in the rotation direction A1 (clockwise direction), the sector gear 41 rotates counterclockwise via the two idle gears 89. As a result, the shaft 39 (see Fig. 2) to which the sector gear 41 is fixed rotates counterclockwise, and the lifting plate 35 rotates upward. Then, the lift plate 33 is lifted by the lifting plate 35 and rotates to an inclined position.

[0034] Furthermore, when the rotation of the driven gear 81 stops, the lift plate 33 attempts to return to a horizontal position due to its own weight. That is, a clockwise force is applied to the shaft 39 via the lifting plate 35, causing the sector gear 41 to rotate clockwise. Then, a counterclockwise rotational force (opposite the rotational direction A1) is applied to the driven gear 81 via the two idle gears 89. As described above, when a rotational force in the direction opposite to the rotational direction A1 is applied to the driven gear 81, the upstream tooth surface of the unidirectional gear 83 is locked by the pawl 85, and the driven gear 81 does not rotate. As a result, the lift plate 33 is maintained in an inclined position.

[0035] Next, the gear link 73 will be described with reference to FIG. 5. FIG. 5 is an exploded perspective view showing the gear link 73. The gear link 73 is made up of a drive gear 91, a planetary gear 93 that meshes with the drive gear 91, and a link bar 95. A rotation shaft (not shown) of the drive gear 91 is rotatably supported by the device main body 2. The rotation shaft is connected to a drive source (not shown) such as a motor. When the rotation shaft is driven by the drive source, the drive gear 91 rotates in the clockwise direction in FIG. 5 (see arrow A2 in FIG. 5). In the following description, the rotation direction of the drive gear 91 refers to this rotation direction A2.

[0036] The link bar 95 is a long, plate-like member. A central boss 101 and an end boss 103 are erected on one surface of the link bar 95, approximately at the center in the longitudinal direction and at one end, respectively. The other end of the link bar 95 (hereinafter referred to as the free end 105) is formed so as to protrude slightly from the one surface. The height of the free end 105 is lower than the heights of both bosses 101 and 103, and the end face is formed flat.

[0037] The central boss 101 and the end bosses 103 of the link bar 95 are fitted into the shaft holes of the drive gear 91 and the planetary gears 93. This keeps the planetary gears 93 meshed with the drive gear 91. When the drive gear 91 rotates in the rotational direction A2, the planetary gears 93 move in the rotational direction A1 of the drive gear 91 (clockwise in FIG. 5) along the circumferential direction centered on the central boss 101 of the link bar 95 while rotating in the direction opposite to the rotational direction A2 of the drive gear 91 (counterclockwise in FIG. 5).

[0038] Furthermore, this movement of the planetary gear 93 causes the link bar 95 to rotate clockwise in FIG. 5 around the central boss 101.

[0039] 3, the drive gear 91 is positioned relative to the cassette-side gear assembly 71 so that the planetary gears 93 mesh with the driven gear 81 of the cassette-side gear assembly 71 when the link bar 95 rotates clockwise in FIG. 3. The planetary gears 93 mesh with the driven gear 81 of the cassette-side gear assembly 71, thereby transmitting the rotational force of the drive gear 91 to the driven gear 81 via the planetary gears 93. In this way, the link bar 95 rotates between a transmission position in which the planetary gears 93 mesh with the driven gear 81 of the cassette-side gear assembly 71, and a separation position in which the planetary gears 93 are separated from the driven gear 81.

[0040] Next, the holder side gear assembly 75 will be described with reference to Figures 6, 7, and 8. Figure 6 is a perspective view showing the holder side gear assembly 75, and Figure 7 is an exploded perspective view showing the holder side gear assembly 75. Figure 8 is a perspective view showing the inner disc 113 and the fixed plate 115. The holder side gear assembly 75 includes an outer gear 111, the inner disc 113, the fixed plate 115, and a push disc 117. The fixed plate is not shown in Figure 6.

[0041] First, the external gear 111 will be described. As shown in Fig. 7, the external gear 111 has a disk portion 121, a shaft cylinder portion 123 provided in the center of the disk portion 121, and a gear portion 125 provided coaxially with the shaft cylinder portion 123 along the periphery of the disk portion 121. Two arc-shaped elongated holes 127 are formed in the disk portion 121 along the circumferential direction centered on the shaft cylinder portion 123. A slit 129 is formed in the tip end of the shaft cylinder portion 123 along the diameter. In addition, a tooth-missing portion 131 without gear teeth is provided in a portion of the circumferential direction of the gear portion 125.

[0042] As will be described later, the external gear 111 rotates in a predetermined rotation direction A3 (clockwise in FIG. 6, counterclockwise in FIG. 7) by meshing with the drive gear 91 of the gear link 73. In the following description, the rotation direction of the external gear 111 refers to this rotation direction A3.

[0043] Next, the inner disk 113 will be described. As shown in FIG. 7, the inner disk 113 is a disk-shaped member with a shaft hole 141 bored in the center. A pin 143 extending in the axial direction of the shaft hole 141 is provided on one surface of the inner disk 113. As shown in FIG. 6, two inclined portions 145 are formed on the other surface of the inner disk 113 in point symmetry with respect to the shaft hole 141. Each inclined portion 145 is formed in a quarter-circumference portion centered on the shaft hole 141 so as to gradually decrease in height along the rotational direction A3 (clockwise direction in FIG. 6, counterclockwise direction in FIG. 7). In the circumferential direction, the pin 143 is arranged so as to overlap with the highest portion of one of the inclined portions 145.

[0044] Next, the fixed plate 115 will be described. The fixed plate 115 is fixed to the device body 2 and supports the external gear 111, the inner disk 113, and the push disk 117. As shown in FIG. 7, a circular opening 151 is formed in the fixed plate 115. Two inclined portions 153 are formed on one surface of the fixed plate 115, symmetrically with respect to the opening 151. Each inclined portion 153 is formed in a quarter-circle portion centered on the opening 151, so that its height gradually increases along the rotation direction A3 (counterclockwise direction in FIG. 7). In detail, the two inclined portions 153 are formed in the upper right and lower left quarter-circle portions centered on the opening 151.

[0045] Next, the push disk 117 will be described. As shown in FIG. 7, the push disk 117 is a disc-shaped member with an axial hole 161 drilled in the center. A rib 163 is formed along the diameter of the axial hole 161. On the outer peripheral surface of the push disk 117, a claw portion 165 is formed whose outer diameter gradually increases along the circumferential direction. In this example, the claw portion is formed so that its outer diameter gradually increases along the rotation direction A3 (clockwise direction in FIG. 6, counterclockwise direction in FIG. 7). A pin 167 is erected on one surface of the push disk 117.

[0046] The holder-side gear assembly 75 is constructed by supporting an external gear 111, an internal disk 113, and a push disk 117 on a fixed plate 115. As shown in FIG. 7, the external gear 111 and the internal disk 113 are arranged on one side of the fixed plate 115 (the side on which the inclined portions 153 are formed). The internal disk 113 is housed in a space surrounded by the circular plate portion 121 and the gear portion 125 of the external gear 111 with the two inclined portions 145 exposed. As a result, the side of the internal disk 113 on which the two inclined portions 145 are formed faces the side of the fixed plate 115 on which the two inclined portions 153 are formed. A compression coil spring 171 (see FIG. 7) is fitted onto the shaft tube portion 123 of the external gear 111. The compression coil spring 171 biases the internal disk 113 toward the fixed plate 115. As a result, the surface of the inner disk 113 on which the two inclined portions 145 are formed comes into contact with the surface of the fixed plate 115 on which the two inclined portions 153 are formed.

[0047] The pin 143 of the inner disc 113 is inserted into one of the elongated holes 127 of the disk portion 121 of the external gear 111. The shaft tube portion 123 of the external gear 111 is inserted into the shaft hole 141 of the inner disc 113 and protrudes from the shaft hole 141. The shaft tube portion 123 of the external gear 111 protruding from the shaft hole 141 of the inner disc 113 is inserted into an opening 151 of the fixed plate 115 and its tip protrudes from the opening 151. The external gear 111 and the inner disc 113 are rotatable together via a key and a key groove.

[0048] The push disk 117 is arranged on the other side of the fixed plate 115 (the side opposite to the side on which the inclined portion 153 is formed) in such a position that the pin 167 faces away from the fixed plate 115 and the end face of the claw portion 165 faces downstream in the rotation direction A3 (downstream in the clockwise direction in Figure 6, downstream in the counterclockwise direction in Figure 7).

[0049] As described above, the tip of the shaft tube portion 123 of the external gear 111 protrudes from the opening 151 of the fixed plate 115. As shown in Fig. 6, the tip of the shaft tube portion 123 is inserted into the shaft hole 161 of the push disk 117, and the rib 163 of the shaft hole 161 engages with the slit 129 of the shaft tube portion 123. This causes the external gear 111 and the push disk 117 to rotate integrally. In other words, when the external gear 111 rotates in the rotation direction A3, the inner disk 113 and the push disk 117 rotate integrally with the external gear 111 in the rotation direction A3.

[0050] 6, the push disk 117 is biased in the circumferential direction by a torsion coil spring 173. The coil portion of the torsion coil spring 173 is supported by a boss 155 provided on the fixed plate 115 below the push disk 117. One arm portion is supported by a locking piece 157 provided on the fixed plate 115, and the other arm portion abuts against a pin 167 of the push disk 117. The push disk 117 is biased in the circumferential direction by the torsion coil spring 173.

[0051] Furthermore, when the external gear 111, the internal disc 113, and the push disc 117 rotate relative to the fixed plate 115 in the rotation direction A3, the two inclined portions 145 of the internal disc 113 ride up onto the two inclined portions 153 of the fixed plate 115, as shown by the solid lines in FIG. 8 . Then, the internal disc 113 moves toward the external gear 111 along the axial direction of the shaft tube portion 123 against the biasing force of the compression coil spring 171. As a result, the pin 143 of the internal disc 113 gradually protrudes from the elongated hole 127 of the external gear 111.

[0052] 8, the inner disk 113 is biased toward the fixed plate 115 by the compression coil spring 171. As a result, the pin 167 of the inner disk 113 is retracted into the elongated hole 127 of the external gear 111.

[0053] As described above, the two inclined portions 153 of the fixed plate 115 are formed on the upper right and lower left quarter-circumference portions centered on the opening 151 (see FIG. 7). The pin 143 of the inner disk 113 is disposed so as to overlap the highest portion of one of the inclined portions 145 in the circumferential direction. Therefore, when the inner disk 113 rotates so that the pin 143 moves toward the highest and lowest positions of the rotational orbit, the pin 143 gradually protrudes. After that, when the pin 143 passes through the highest and lowest positions, the pin 143 retracts into the elongated hole 127 of the external gear 111. In this way, the pin 143 protrudes from the elongated hole 127 twice during one rotation of the inner disk 113.

[0054] Next, the arrangement of the holder-side gear assembly 75 will be described with reference to FIG. 3. The holder-side gear assembly 75 is disposed below the extension piece 61 of the holder 55 of the paper feeder 23, with the push disk 117 facing inward (left side) and the external gear 111 facing outward (right side). More specifically, the fixed plate 115 is positioned relative to the holder 55 so that, when the holder 55 rotates clockwise in FIG. 3, the claw portion 63 of the extension piece 61 of the holder 55 moves on the rotational path of the claw portion 165 of the push disk 117 of the holder-side gear assembly 75. Furthermore, as described above, the fixed plate 115 is positioned relative to the gear link 73 so that the external gear 111 meshes with the drive gear 91 of the gear link 73 and the free end portion 105 of the link bar 95 fits along the outer surface of the disc portion 121 of the external gear 111 with a small gap therebetween.

[0055] The operation of interlocking the rotation of the holder 55 with the rotation of the lift plate 33 by the interlocking mechanism 70 having the above configuration will be described below.

[0056] First, an example of the movement of the holder 55 and lift plate 33 during a paper feed operation will be described with reference to the flowchart in FIG. 9. In the following description, the rotation of the lift plate 33 refers to the lift plate 33 rotating to an inclined position. In S1 (initial state), the holder 55 is held in the initial position (inclination angle α), and the lift plate 33 is held in a horizontal position. Next, in S2, paper is placed on the lift plate 33, and the paper feed cassette 21 is attached to the cassette attachment portion. Then, in S3, the lift plate 33 begins to rotate to an inclined position. As the lift plate 33 rotates, the topmost paper eventually contacts the pickup roller 51. As the lift plate 33 further rotates, the paper pushes up the pickup roller 51, and in S4, the holder 55 begins to rotate in the direction in which the pickup roller 51 rises.

[0057] Then, in S5, after the pickup roller 51 has risen to the paper feeding height (tilt angle β (β<α)), in S6 the lift plate 33 stops rotating. Thereafter, in S7 the paper is transported. As the paper is transported and the number of sheets of paper placed on the lift plate 33 decreases, the holder 55 begins to rotate so that the pickup roller 51 descends. In S8, when the pickup roller 51 has rotated until it has descended to a predetermined height (β<tilt angle<α), the lift plate 33 begins to rotate in S9. That is, the pickup roller 51 is pushed up by the paper, and the holder 55 begins to rotate in the direction in which the pickup roller 51 ascends. Then, in S10, the holder 55 rotates until the pickup roller 51 has risen to the paper feeding height, and the lift plate 33 stops rotating in S11.

[0058] Thereafter, steps S7 to S11 are repeated until all the sheets have been conveyed.

[0059] Next, the operation of the interlocking mechanism 70 in the above S1 to S11 will be described. First, S1 (initial state) will be described with reference to Figs. 10, 11, 12, and 13. Fig. 10 is a view of the holder 55 and the interlocking mechanism 70 as seen from the right side, and Fig. 11 is a view of the holder 55 and the interlocking mechanism 70 as seen from the left side. Fig. 12 is a perspective view showing the gear link 73 and the holder-side gear assembly 75, and Fig. 13 is a cross-sectional view showing the gear link 73 and the holder-side gear assembly 75.

[0060] 10 and 11, the holder 55 is biased by the coil spring 59 and rotates at an inclination angle α so that the pickup roller 51 faces downward. Also, as shown in FIG. 11, the claw portion 63 of the holder 55 is spaced above the holder-side gear assembly 75.

[0061] 11, the pin 167 of the push disk 117 of the holder-side gear assembly 75 is biased by a torsion coil spring 173, and a force is applied to the external gear 111 to rotate in the circumferential direction (clockwise in FIG. 11). As shown in FIG. 10, the drive gear 91 faces the toothless portion 131 of the gear portion 125 of the external gear 111, and as the external gear 111 is biased in this manner, the gear portion 125 meshes with the drive gear 91. Also, the link bar 95 of the gear link 73 is rotated in a separated position. That is, the planetary gear 93 is separated from the driven gear 81 of the cassette-side gear assembly 71. The free end 105 of the link bar 95 is separated upstream in the clockwise direction from the pin 143 of the internal disk 113 when viewed from the right side (see FIG. 10).

[0062] In the holder-side gear assembly 75, the inclined portion 145 of the inner disk 113 is spaced circumferentially away from the inclined portion 153 of the fixed plate 115, and the inner disk 113 is biased toward the fixed plate 115 by the compression coil spring 171 (see the two-dot chain line in FIG. 8). As a result, as shown in FIGS. 12 and 13, the pin 143 of the inner disk 113 is retracted into the elongated hole 127 of the external gear 111. Thereafter, in S2, the sheet cassette 21 is mounted in the cassette mounting portion, whereby the sector gear 41 of the sheet cassette 21 meshes with the idle gear 89, as shown in FIG.

[0063] Next, S3 (start of lift plate rotation) will be described with reference to Figures 14 and 15. Figure 14 is a view of the holder 55 and the interlocking mechanism 70 seen from the right side, and Figure 15 is a view of the holder 55 and the interlocking mechanism 70 seen from the left side.

[0064] In S3, first, the drive gear 91 of the gear link 73 is driven by the motor to rotate in rotational direction A2 (clockwise in FIG. 14, counterclockwise in FIG. 15). Then, the planetary gear 93 moves in rotational direction A2 along the circumferential direction around the central boss 101 of the link bar 95 while rotating in the direction opposite to rotational direction A2 (counterclockwise in FIG. 14) (see hollow arrow B1 in FIGS. 14 and 15). The planetary gear 93 eventually meshes with the driven gear 81 of the cassette-side gear assembly 71. This causes the driven gear 81 to rotate in rotational direction A1 (clockwise in FIG. 14, counterclockwise in FIG. 15), and the sector gear 41 (see FIG. 2) to rotate counterclockwise via the two idle gears 89 (see FIG. 3). As a result, shaft 39 (see FIG. 2) rotates, lifting plate 35 rotates, lifting plate 33 rotates to an inclined position, and the leading edge of the paper placed on lifting plate 33 is lifted (see the two-dot chain line in FIG. 2).

[0065] 14, the rotation of the drive gear 91 also causes the outer gear 111, inner disk 113, and push disk 117 of the holder-side gear assembly 75 to rotate (see arrow A3), so that the pin 143 of the inner disk 113 does not overlap with the link bar 95 when viewed from the left-right direction. Therefore, the link bar 95 rotates without the free end 105 interfering with the pin 143.

[0066] Next, S4 (holder rotation starts) will be described. When the lift plate 33 rotates to the inclined position, the uppermost sheet of paper loaded on the lift plate 33 eventually comes into contact with the pickup roller 51, as shown by the two-dot chain lines in Figures 14 and 15. The lift plate 33 continues to rotate even after the paper comes into contact with the pickup roller 51. Then, the pickup roller 51 is lifted by the loaded paper, and the holder 55 begins to rotate around the rotation axis 53a of the paper feed roller 53 so that the pickup roller 51 rises. In other words, the holder 55 begins to rotate so that the claw portion 63 descends.

[0067] Next, S5 (the pickup roller rises to the paper feeding height) will be described with reference to Figures 16, 17, and 18. Figure 16 is a view of the holder 55 and interlocking mechanism 70 as seen from the left side, and Figure 17 is a view of the holder 55 and interlocking mechanism 70 as seen from the right side. Figure 18 is a perspective view showing the holder-side gear assembly 75 and gear link 73.

[0068] When the pickup roller 51 is lifted by the paper placed on the lift plate 33 and the holder 55 rotates until the pickup roller 51 rises to a predetermined paper feeding height, as shown in Figure 16, the claw portion 63 of the holder 55 descends forward in the rotation direction A3 (clockwise direction in Figure 16) further than the claw portion 165 of the push disk 117 of the holder side gear assembly 75.

[0069] 18, rotation of the inner disk 113 of the holder-side gear assembly 75 causes the pin 143 to protrude from the elongated hole 127 of the outer gear 111 into the rotation area of ​​the free end 105 of the link bar 95. The pin 143 protrudes upstream of the free end 105 in the rotation direction A3 of the inner disk 113 (counterclockwise in FIGS. 17 and 18).

[0070] Next, S6 (stopping the lift plate) will be described with reference to Figures 19 and 20. Figure 19 is a view of the holder 55 and the interlocking mechanism 70 as seen from the left side, and Figure 20 is a view of the holder 55 and the interlocking mechanism 70 as seen from the right side.

[0071] As the external gear 111, the internal disc 113, and the push disc 117 of the holder-side gear assembly 75 further rotate in the rotation direction A3, the claw portion 165 of the push disc 117 eventually comes into contact with the claw portion 63 of the holder 55, as shown in Figure 19. This causes the push disc 117, i.e., the external gear 111 and the internal disc 113, to stop rotating.

[0072] As described above, the pin 167 of the inner disc 113 protrudes from the outer gear 111 until the outer gear 111, the inner disc 113, and the push disc 117 stop rotating. As shown in Figure 20, when the inner disc 113 rotates in the rotation direction A3 (counterclockwise in Figure 20) in this state, the pin 167 pushes the free end 105 of the link bar 95 of the gear link in the rotation direction A3, and the link bar 95 rotates counterclockwise in Figure 20 around the central boss 101 (see the outline arrow B2 in Figure 20).

[0073] As a result, as shown in FIGS. 19 and 20, the planetary gear 93 moves away from the driven gear 81 of the cassette-side gear assembly 71. Then, the force that rotates the driven gear 81, i.e., the force that rotates the lift plate 33, disappears, and the lift plate 33 attempts to rotate downward due to its own weight. This force is transmitted from the lift plate 35 to the driven gear 81 via the shaft 39 (see FIG. 2), the sector gear 41, and the two idle gears 89 (see FIG. 3), and a force that rotates the driven gear 81 counterclockwise is applied. However, as described above, if a rotational force in the direction opposite to the rotational direction A1 is applied to the driven gear 81, the upstream tooth surface of the unidirectional gear 83 is locked by the pawl 85, and the driven gear 81 does not rotate. Therefore, the lift plate 33 stops rotating and is maintained in the predetermined inclined position.

[0074] 20, the drive gear 91 faces the tooth-missing portion 131 of the external gear 111 of the holder-side gear assembly 75, so the drive gear 91 continues to rotate without interfering with the external gear 111. Note that the pin 167 of the push disk 117 is biased in the circumferential direction (clockwise in FIG. 19) by the torsion coil spring 173, but the claw portion 165 of the push disk 117 abuts against the claw portion 63 of the holder 55, so the push disk 117 does not rotate, and the drive gear 91 remains facing the tooth-missing portion 131 of the external gear 111.

[0075] Next, S7 (paper transport) will be described. After the pickup roller 51 rises to the paper feed height, the pickup roller 51 rotates and sends out the paper sheets placed on the lift plate 33. The sent-out paper sheets are transported to the transport path 13 by the paper feed roller 53. As the paper sheets are transported in this manner, the number of sheets placed on the lift plate 33 decreases, and the height of the topmost sheet decreases. Accordingly, the holder 55 rotates so that the pickup roller 51 descends. In other words, the holder 55 rotates so that the claw portion 63 ascends.

[0076] Next, S8 (the pickup roller descends to a predetermined height) will be described with reference to Figures 21 and 22. Figure 21 is a view of holder 55 and interlocking mechanism 70 as seen from the left side, and Figure 22 is a view of holder 55 and interlocking mechanism 70 as seen from the right side.

[0077] When the holder 55 rotates so that the claws 63 rise, the claws 63 of the holder 55 eventually move upward away from the push disk 117 of the holder-side gear assembly 75, as shown in Fig. 21. Then, the push disk 117 is urged in the circumferential direction by the torsion coil spring 173, causing the external gear 111 to rotate together with the push disk 117, and as shown in Fig. 22, the external gear 111 meshes with the drive gear 91. Then, the external gear 111 rotates together with the inner disk 113 in the rotation direction A3 (counterclockwise in Fig. 22). As a result, the pin 143 of the inner disk 113 retracts into the elongated hole 127 of the external gear 111 (see Figs. 12 and 13).

[0078] Next, S8 (lift plate and holder start rotating) will be described. When the pin 143 of the inner disk 113 retracts, the pin 143 leaves the rotation area of ​​the link bar 95, allowing the link bar 95 to rotate freely. Then, the planetary gear 93 rotates in the direction opposite to the rotation direction A2 of the drive gear 91 (counterclockwise in FIG. 22), while moving clockwise in FIG. 22 around the central boss 101 of the link bar 95 (see the outline arrow B3 in FIG. 22). The planetary gear 93 eventually meshes with the driven gear 81 of the cassette-side gear assembly 71, causing the driven gear 81 to rotate in the rotation direction A1 (clockwise in FIG. 22). This rotates the sector gear 41 via the idle gear 69. Then, the shaft 39 rotates, causing the lift plate 35 to rotate, further tilting the lift plate 33. As a result, the sheets placed on the lift plate 33 rise.

[0079] Next, S10 (the pickup roller rotates to the paper feeding height) and S11 (the lift plate stops rotating) will be described. The operations of S10 and S11 are the same as the operations of S5 and S6 described with reference to FIGS.

[0080] When the paper placed on the lift plate 33 rises, the holder 55 rotates so that the pickup roller 51 rises to the paper feeding height and the claw portion 63 descends. As shown in Fig. 16, the claw portion 63 of the holder 55 descends forward of the claw portion 165 of the push disk 117 of the holder-side gear assembly 75 in the rotation direction A3 of the push disk 117. Also, as shown in Fig. 18, the external gear 111 is driven to rotate by the drive gear 91, causing the pin 143 of the internal disk 113 to protrude from the elongated hole 127 of the external gear 111.

[0081] As the push disc 117 further rotates in the rotation direction A3 together with the external gear 111, the claws 165 of the push disc 117 eventually come into contact with the claws 63 of the holder 55, as shown in Figure 19. This causes the push disc 117, i.e., the external gear 111 and the internal disc 113, to stop rotating.

[0082] Furthermore, as described above, until the external gear 111, the internal disk 113, and the push disk 117 stop rotating, the pin 143 of the internal disk 113 protrudes from the elongated hole 127 of the external gear 111. When the internal disk 113 rotates in this state, as shown in FIG. 20 , the pin 143 pushes the free end 105 of the link bar 95 of the gear link 73 in the rotational direction A3, and the link bar 95 rotates counterclockwise in FIG. 20 around the central boss 101 (see arrow B1). As a result, the planetary gear 93 moves away from the driven gear 81 of the cassette-side gear assembly 71. Then, as described above, the unidirectional gear 83 of the cassette-side gear assembly 71 is engaged with the pawl 85, and the rotation of the driven gear 81 stops. That is, the lift plate 33 stops rotating and is maintained in the predetermined inclined position.

[0083] As described above, the steps S7 to S11 are repeated until all the sheets have been conveyed.

[0084] The presence or absence of paper placed on the lift plate 33 is detected by a paper detection sensor (not shown). When all the paper has been transported and the paper detection sensor detects that there is no more paper placed on the lift plate 33, a message indicating that paper needs to be replenished is displayed on the display unit (not shown). After that, the paper feed cassette 21 is pulled out from the cassette mounting portion to replenish paper. Then, the fan-shaped gear 41 moves away from the interlocking mechanism 70 (idle gear 89), and the lift plate 33 returns to a horizontal position under its own weight.

[0085] As is clear from the above description, according to the present invention, the lift plate 33 can be automatically rotated in response to the rotation of the holder 55, eliminating the need for a sensor to detect the angle of the holder 55. Furthermore, the transmission and interruption of rotational force from the drive gear 91 of the gear link 73, which is the drive source of the lift plate 33, to the sector gear 41 can be achieved without using a solenoid. In this way, the number of electrical components, such as sensors and solenoids, required for executing the paper feed operation can be reduced. This reduces the cost of the image forming apparatus 1 and simplifies the control of the paper feed operation.

[0086] Specifically, by rotating or stopping the rotation of the external gear 111 in response to the rotation of the holder 55 as the amount of paper decreases, the gear link 73 can be rotated between the transmission position and the retracted position.

[0087] Furthermore, when the rotation of the lift plate 33 is stopped and the lift plate 33 is maintained in the inclined position, the drive gear 91 and the planetary gear 93 continue to rotate, and the planetary gear 93 moves away from the driven gear 81 of the cassette-side gear assembly 71, blocking the transmission of rotational force to the sector gear 41. Therefore, there is no need to use a solenoid to transmit and block the transmission of the rotational force of the drive gear 91 to the sector gear 41. Furthermore, although the drive gear 91 is always rotating, when the external gear 111 stops rotating, the drive gear 91 faces the missing tooth portion 131 of the external gear 111, so the rotation of the drive gear 91 is not interfered with by the external gear 111.

[0088] Furthermore, since the cassette-side gear assembly 71 rotates the lift plate 33 via the lift plate 35, the lift plate 33 can be rotated with a small force.

[0089] Although the present invention has been described with reference to specific embodiments, the present invention is not limited to the above embodiments, and those skilled in the art may modify the above embodiments without departing from the scope and spirit of the present invention. [Explanation of symbols]

[0090] 1. Image forming device 21 Paper cassette 23 Paper feeder 33 Lift board 35 Lifting board 51 Pickup roller, 55 Holder 70 Interlocking mechanism 71 Cassette side gear assembly 73 Gear Link 75 Holder side gear assembly 91 Drive gear 111 outer gear 131 Missing teeth 143 pins

Claims

1. An image forming apparatus including a paper feed cassette for storing paper sheets, and a paper feed device for feeding the paper sheets stored in the paper feed cassette, The paper feed cassette is a lift plate on which paper is placed and which is rotatable to lift the paper; The paper feeder is a pickup roller that rotates in contact with the topmost sheet of paper placed on the lift plate to feed the sheet; a holder that houses the pickup roller and is rotatably supported so that the pickup roller contacts the topmost sheet of paper; An image forming apparatus characterized in that it further comprises a linkage mechanism that links the rotation of the holder with the rotation of the lift plate, so that the holder rotates and the lift plate rotates to lift the paper until the pickup roller reaches a predetermined paper feed height, and then stops the rotation of the lift plate after the pickup roller reaches the paper feed height.

2. The interlocking mechanism includes: a cassette-side gear assembly that is connected to the lift plate when the paper feed cassette is attached to the cassette attachment portion and rotates the lift plate only in a direction that lifts the paper; a gear link that is rotatable between a transmission position in which a rotational force generated by a drive source is transmitted to the cassette side gear assembly to rotate the lift plate and a separated position in which the rotational force is not transmitted to the cassette side gear assembly; 2. The image forming apparatus according to claim 1, further comprising: a holder-side gear assembly that moves the gear link to the transmission position until the pickup roller reaches the paper feed height, and moves the gear link to the separated position after the pickup roller reaches the paper feed height.

3. The gear link is a drive gear that is driven to rotate by the drive source, The holder side gear assembly is an external gear that rotates while meshing with the drive gear, and whose rotation is restricted by the holder when the holder rotates until the pickup roller rises to the paper feeding height; a pin that can protrude into the rotation area of ​​the gear link from a position retracted from the rotation area of ​​the gear link by rotation of the external gear, 3. The image forming apparatus according to claim 2, wherein the pin protrudes when the external gear rotates until its rotation is restricted by the holder, and the protruding pin rotates the gear link from the transmission position to the separated position.

4. 3. The image forming apparatus according to claim 2, wherein the external gear has a tooth-missing portion, and when rotation is restricted by the holder, the tooth-missing portion faces the drive gear.

5. the paper feed cassette further includes a lift plate disposed below the lift plate and rotating to lift and rotate the lift plate; 2. The image forming apparatus according to claim 1, wherein the cassette side gear assembly is connected to the lift plate via the lift plate.

Images