Sheet conveyance device

Abstract

To provide a sheet conveyance device that can effectively utilize a space around rollers.SOLUTION: A sheet conveyance device conveys a sheet using a first roller and a second roller. The first roller is urged by an urging member to come into pressure contact with the second roller. A first guide and a second guide movably support and guide a first guided object and a second guided object of a roller holder that holds the first roller. A first direction in which the first guide guides the first guided object is inclined with respect to a second direction in which the second guide guides the second guided object, and an angle that the first direction makes with a direction of a straight line passing through a rotation center of the first roller and a rotation center of the second roller when looking at the first roller from a direction of a rotation axis of the first roller, is smaller than an angle that the second direction makes with the direction of the straight line.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a sheet transport device, and more particularly to a sheet transport device that is provided in an image forming apparatus such as a printer, a facsimile, or a copier, and that transports sheets such as recording sheets and original documents. [Background technology]

[0002] In a sheet conveying device, one method of nipping a sheet with a pair of conveying rollers is to bias one roller against the other roller to make them contact each other. In such a configuration, a well-known example of a roller pair is one in which one roller is a drive roller that rotates by the driving force of a drive source, and the other roller is a driven roller that rotates following the drive roller. As a method of making the driven roller contact the drive roller, there is a method in which a driven roller holder that holds the driven roller so that it can slide and rotate is made rotatable or linearly movable, and a spring presses the driven roller holder to form a nip pressure between the pair of conveying rollers. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication 2019-137517 Summary of the Invention [Problem to be solved by the invention]

[0004] FIG. 17 shows an example of a pair of conveying rollers in an image forming apparatus, the conveying roller being rotated by receiving a driving force and the driven roller being rotated by the conveying roller.

[0005] 17(a) is a configuration in which driven roller 24' is held so as to be rotatable and a roller holder 31' rotatable around a rotation center 25c' is pressed toward conveying roller 23b' by a spring (not shown), forming a nip between conveying roller pair (23b', 24'). However, if the intersection angle λ between the conveying direction T of the conveying path that conveys the sheet to the nip between conveying roller pair (23b', 24') and the conveying direction N of the conveying roller pair is an obtuse angle, the position of the rotation center 25c' overlaps with the conveying path, and therefore it may not be possible to locate the rotation center 25c'.

[0006] 17(b) is a pair of conveying rollers (23b', 24') that discharges the sheet S to a discharge tray 60' that holds the sheet S. The driven roller 24' is rotatably held by a roller holder 31'.

[0007] Roller holder 31' is provided with two pairs of bosses (25a', 25b') in a direction perpendicular to the nip line, and while sliding along groove 30' that is part of frame 29', roller holder 31' is pressed by a spring (not shown) to move linearly in the direction of nip pressure F. Groove 30' is provided so that upstream boss 25a' and downstream boss 25b' of roller holder 31' are located on a line connecting the center of conveying roller 23b' and the center of driven roller 24'.

[0008] The conveying direction N of the conveying roller pair (23b', 24') is angled with respect to the horizontal direction H, and conveys the sheet S diagonally upward. However, in this configuration, in order to secure space for arranging the spring, roller holder 31', and frame 29', the distance HD from the outer diameter end of driven roller 24' to frame 29' that holds roller holder 31' in the horizontal direction H becomes large. If the distance HD is large, there is a high possibility that the rear end of the discharged sheet S will get caught on frame 29'.

[0009] 17(c) is a configuration in which the conveying direction of the conveying roller pair (23b', 24') is diagonally upward, and the driven roller holder 24' is moved linearly in the vertical direction. In this configuration in which the linear movement direction of the driven roller holder 24' and the nip pressure direction of the conveying roller pair (23b', 24') are different, when the conveying roller 23b' is deflected by the nip pressure and shifts from the solid line position to the dotted line position, the driven roller 24' moves from the solid line position to the dotted line position.

[0010] As a result, the driven roller 24' rotates counterclockwise relatively around the conveying roller 23b', so that the angle of the conveying direction changes by the angle θ formed by the line connecting the centers of the conveying roller pair (23b', 24') shown by the solid line and the line connecting the centers of the conveying roller pair (23b', 24') shown by the dotted line, and the conveying direction changes from N1 to N2. In particular, if the outer diameter of the conveying roller 23b' is small, the conveying direction changes significantly, and it is considered that the sheets will not be stacked normally on the sheet discharge tray.

[0011] The present invention has been developed in consideration of the above-mentioned circumstances, and aims to provide a sheet transporting device that can press the roller and transport the sheet by effectively utilizing the space around the roller without significantly changing the sheet transport direction. [Means for solving the problem]

[0012] In order to achieve the above object, the present invention provides A sheet conveying device, a first roller and a second roller for sandwiching and transporting a sheet; a biasing member for biasing the first roller toward the second roller; a roller holder including a guided portion having a first guided portion and a second guided portion located upstream of the first guided portion in a biasing direction of the biasing member, the roller holder holding the first roller and biased by the biasing member; a first guide that movably supports and guides the first guided member, and a second guide that movably supports and guides the second guided member, and a guide portion that movably guides the roller holder so that the first roller and the second roller sandwich and convey a sheet and the pressure contact state is released; having a first direction in which the first guide guides the first guided object is inclined with respect to a second direction in which the second guide guides the second guided object, When the first roller and the second roller are in pressure contact and viewed in the direction of the rotation axis of the first roller, the angle that the first direction makes with respect to the direction of a straight line passing through the center of rotation of the first roller and the center of rotation of the second roller is smaller than the angle that the second direction makes with the direction of the straight line. Effect of the Invention

[0013] According to the present invention, the arrangement of the rollers and the pressing force of the rollers are such that overlap with other components can be avoided, and space can be utilized efficiently. [Brief description of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view of an image forming apparatus according to the present invention; [Diagram 2] FIG. 3 is a cross-sectional view showing the periphery of a pair of discharge rollers 22 according to the first embodiment of the present invention. [Diagram 3] FIG. 2 is a cross-sectional view showing the periphery of a pair of discharge rollers 22 from an axial direction according to the first embodiment of the present invention. [Figure 4] FIG. 1 is a diagram showing the periphery of a paper discharge driven roller 24 according to a first embodiment of the present invention. [Diagram 5] FIG. 1 is a perspective view showing a roller holder 31 according to a first embodiment of the present invention; [Figure 6] FIG. 1 is a cross-sectional view showing the trajectory of a pair of discharge rollers 22 according to the first embodiment of the present invention. [Figure 7] FIG. 3 is a cross-sectional view showing the state in which the paper discharge driven roller 24 and the roller holder 31 according to the first embodiment of the present invention are tilted. [Figure 8]FIG. 3 is a cross-sectional view showing a paper discharge roller 23 and a paper discharge driven roller 24 according to the first embodiment of the present invention. [Figure 9] FIG. 1 is a cross-sectional view showing a paper ejection direction according to a first embodiment of the present invention. [Figure 10] FIG. 1 is a diagram showing a modified example different from the present invention according to the first embodiment of the present invention. [Figure 11] 1 is a cross-sectional view of a paper feed unit 5a and its periphery according to a second embodiment of the present invention; [Figure 12] FIG. 11 is a perspective view of a paper feed cassette 6a according to a second embodiment of the present invention; [Figure 13] FIG. 1 is a diagram showing a separation roller unit 100 according to a second embodiment of the present invention. [Figure 14] FIG. 11 is a perspective view showing a separation roller holder 104 according to a second embodiment of the present invention. [Figure 15] FIG. 13 is a diagram showing a separation guide 105 according to a second embodiment of the present invention. [Figure 16] FIG. 1 is a diagram showing the periphery of a separation roller unit 100 according to a second embodiment of the present invention. [Figure 17] Cross-sectional views showing a conventional configuration and an assumed configuration DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] [Example 1] As an example of the configuration of an image forming apparatus according to the present invention, an embodiment in which the image forming apparatus is applied to an electrophotographic laser printer will be specifically described. In the following, the overall configuration of the image forming apparatus according to the present invention will be described first, and then the configuration of a paper discharge unit of the image forming apparatus according to the present invention will be described.

[0016] 1 is a cross-sectional view showing the configuration of an example of an image forming apparatus when applied to an electrophotographic laser printer having a double-sided image forming function. However, unless otherwise specified, the dimensions, materials, shapes, and relative positions of the components described in this embodiment are not intended to limit the scope of the invention to those alone. Furthermore, the image forming apparatus according to the present invention is not limited to laser printers, and may be applied to other image forming apparatuses such as copiers and facsimiles.

[0017] The image forming apparatus 1 shown in FIG. 1 is roughly composed of a sheet feeding section, an image forming section (photosensitive drum 3, transfer roller 9) that forms an image on a sheet, a fixing section (fixing device 10), and a paper discharge section 20.

[0018] The image forming apparatus 1 is equipped with a process cartridge 2 that is detachable from the main body of the apparatus. The process cartridge 2 is composed of a photosensitive drum 3 and process means such as a developing unit and a charging roller (not shown). A scanner unit 4 is disposed vertically above the process cartridge 2, and exposes the photosensitive drum 3 to light based on an image signal.

[0019] After the photosensitive drum 3 is charged to a predetermined negative potential by a charging roller (not shown), an electrostatic latent image is formed on the photosensitive drum 3 by the scanner unit 4. This electrostatic latent image is reverse-developed into a toner image by a developing unit (not shown) in the process cartridge 2, in which negative toner is attached to the electrostatic latent image.

[0020] The sheet feeding section is composed of a paper feeding section 5a attached to the image forming apparatus 1, and a paper feeding cassette 6a that stores sheets S and is detachable from the image forming apparatus 1. The sheets S stored in the paper feeding cassette 6a are separated and fed one by one from the paper feeding cassette 6a by the paper feeding section 5a that is rotated by the power of a paper feeding drive unit (not shown). The fed sheet S is transported to a registration roller pair 8 by a transport roller pair 7a, where skew correction is performed, and the sheet S is transported to a transfer section.

[0021] The paper feed cassette 6b is also a paper feed cassette that stores sheets S, and can store sheets of a different size than those stored in the paper feed cassette 6a, or can store sheets of the same size.

[0022] In the transfer portion, a bias voltage of positive polarity is applied by a bias voltage applying means (not shown) to the transfer roller 9. As a result, the toner image is transferred as an unfixed image onto the sheet S conveyed to the transfer portion.

[0023] The sheet S onto which the toner image has been transferred is transported to a fixing device 10 provided downstream in the transport direction of the transfer section. The fixing device 10 fixes the toner image transferred onto the sheet S, and has a heating roller 11, which is a fixing member heated by a heater, which is a heating means (not shown), and a pressure roller 12, which is a pressure member that rotates while being in pressure contact with the heating roller 11. The sheet S is transported while being sandwiched in a fixing nip formed by the heating roller 11 and the pressure roller 12, and the toner image is fixed onto the surface of the sheet S by applying heat and pressure.

[0024] Thereafter, the sheet S on which the toner image has been fixed is discharged from the fixing device 10 onto a discharge tray 60 on which the sheets S discharged by a pair of discharge rollers 22 shown in FIG. 3, which will be described later, are stacked.

[0025] Next, the paper discharge section 20, which is a feature of this embodiment, will be described with reference to Figs. 2 to 10. Fig. 2 is a diagram showing the periphery of the paper discharge roller pair 22 as viewed from the direction of the arrow H' in Fig. 1. Fig. 3(a) is a partial cross-sectional view taken at the position AA in Fig. 2, and Fig. 3(b) is a partial cross-sectional view taken at the position BB in Fig. 2.

[0026] The pair of discharge rollers 22 has a discharge roller 23 as a second roller that is rotated by a driving source (not shown). The pair of discharge rollers 22 further has a discharge driven roller 24 as a first roller that is pressed by a pressure spring 26 to come into contact with the discharge roller 23 to sandwich and transport the sheet S, forming a nip, and is driven to rotate in accordance with the rotation of the discharge roller 23. The discharge driven roller 24 is located vertically below the discharge roller 23.

[0027] The discharge roller 23 has a discharge roller shaft 23a and two rubber rollers 23b provided in the direction of the discharge roller shaft 23a, and a discharge driven roller 24 is abutted against each rubber roller 23b. The discharge driven roller 24 is rotatably held by a roller holder 31. The roller holder 31 has a protrusion for engaging with a groove 30 described later to restrict the movement, and is detachable from the device body together with the first roller. The roller holder 31 has, as the protrusion 25 (guided portion), a first protrusion 25b (first guided portion) and a second protrusion 25a (second guided portion) located upstream of the first protrusion 25b in the biasing direction of a biasing member described later.

[0028] The paper discharge frame 29 (guide portion) is a part of the frame of the device body of the image forming device 1, and has a groove 30 as an opening for accommodating the protrusion 25. The groove 30 has a first groove 30b (first guide) that movably supports and guides the first protrusion 25b, and a second groove 30a (second guide) that movably supports and guides the second protrusion 25a. In other words, the first protrusion 25b and the second protrusion 25a are accommodated in the groove 30, and the first protrusion 25b and the second protrusion 25a are movably guided by the parts (surfaces) that form the first groove 30b and the second groove 30a. As a result, the paper discharge frame 29 allows the roller holder 31 to move between a state in which the paper discharge roller 23 and the paper discharge driven roller 24 are in pressure contact and a state in which the pressure contact state is released.

[0029] In this embodiment, when the discharge roller 23 and the discharge driven roller 24 are in pressure contact with each other, the sheet S can be conveyed, and when the pressure contact state is released, the discharge roller 23 and the discharge driven roller 24 can be separated. Also, in this embodiment, a configuration has been shown in which both rollers can be separated when the pressure contact state of the rollers is released, but this is not limiting, and the pressure contact force between the rollers may be reduced to an extent that the rollers are in light contact with each other, so that a jam of the sheet S can be cleared.

[0030] Further, the groove 30 has an intermediate groove 30c that connects the first groove 30b and the second groove 30a. The intermediate groove 30c is a groove through which the second protrusion 25a passes when the roller holder 31 is attached to the paper discharge frame 29. In other words, the first groove 30b and the second groove 30a are provided in a portion that forms an opening. In this embodiment, a groove is provided as an opening in the paper discharge frame 29, but any shape is acceptable as long as it is an opening that can guide the protrusion, and it may be a shape such as an elongated hole.

[0031] Here, the first groove 30b is inclined with respect to the second groove 30a. Specifically, the direction in which the first groove 30b guides the first protrusion 25b (first direction), i.e., the direction in which the first protrusion 25b moves within the first groove 30b, is inclined with respect to the direction in which the second groove 30a guides the second protrusion 25a (second direction), i.e., the direction in which the second protrusion 25a moves within the second groove 30a.

[0032] In a relationship in which the first groove 30b is inclined with respect to the second groove 30a, when the paper discharge driven roller 24 and the paper discharge roller 23 are in pressure contact and viewed in the direction of the rotation axis of the paper discharge driven roller 24, the angle that the first direction makes with respect to the direction of a straight line passing through the center of rotation of the paper discharge driven roller 24 and the center of rotation of the paper discharge roller 23 is smaller than the angle that the second direction makes with the direction of the straight line.

[0033] Since the first groove 30b and the second groove 30a are not parallel in this way, the roller holder 31 and the paper discharge driven roller 24 move while rotating relative to the device body along the groove 30. Due to this operation, the path of movement of the paper discharge driven roller 24 differs from the biasing direction and the directions of the first groove 30b and the second groove 30a. In this embodiment, the first groove 30b and the second groove 30a are formed so that the paper discharge driven roller 24 moves toward the paper discharge roller shaft 23a.

[0034] More specifically, if a line along the first direction is called line A1, a line along the second direction is called line A2, and a straight line passing through the center of rotation of paper discharge driven roller 24 and the center of rotation of paper discharge roller 23 is called line A3, then line A2 is at an angle between the acute angles formed by line A1 and line A3. In other words, line A2 is a line at an angle closer to the vertical direction than line A3. When the roller holder 31 and paper discharge driven roller 24 move while rotating relative to the device main body due to the relationship between line A1, line A2, and line A3, paper discharge driven roller 24 moves toward paper discharge roller shaft 23a.

[0035] The structure of A1, A2, and A3 will be described in more detail. In this embodiment, the line A2 is a vertical line. That is, the second groove 30a extends in the vertical direction. In FIG. 3(b), the line A1 is a line obtained by rotating the line A2 counterclockwise by 10°. That is, the angle x=10°.

[0036] 3(b), line A3 is a line obtained by rotating line A1 counterclockwise by 10°. In other words, line A3 is a line obtained by rotating line A2 counterclockwise by 20°, and the angle y is 10°. The linear distance between first protrusion 25b and second protrusion 25a is 8 mm, and the linear distance between first protrusion 25b and the rotation center of paper discharge driven roller 24 is 9 mm.

[0037] The configuration of these angles and the like may be changed as appropriate depending on the direction in which the discharge driven roller 24 is to be biased. <x<90°であり、0°<=y<90°である。

[0038] One end of the pressure spring 26, which is a compression spring and serves as a biasing member, is held by the paper discharge frame 29 and the other end is held by the roller holder 31, thereby pressing the paper discharge driven roller 24 toward the paper discharge roller 23 and bringing the paper discharge driven roller 24 and the paper discharge roller 23 into pressure contact. The biasing direction of the pressure spring 26 is vertically upward, and the angle with the extension direction of the second groove 30a is smaller than the angle with the extension direction of the first groove 30b. Although a compression spring is used as the biasing member in this embodiment, any spring capable of pressing the roller holder 31 can be used as appropriate.

[0039] The discharged paper full-load detection flag 27 is provided so as to be rotatable around a rotation center 27c as shown by an arrow α. The sheet being transported by the discharge roller pair 22 pushes up the discharged paper full-load detection flag 27 and is transported to the discharge tray 60.

[0040] Fig. 4(a) is a cross-sectional view of the image forming apparatus 1 as seen in the direction of the arrow H' in Fig. 1. Only the paper discharge frame 29, the rubber roller 23b which is a part of the paper discharge roller 23, the paper discharge driven roller 24, and the roller holder 31 are shown. Fig. 4(b) is a cross-sectional view at the position CC in Fig. 4(a). Fig. 5 is a perspective view showing the roller holder 31.

[0041] 4(b), the position of the discharge driven roller 24 is closer to the image forming unit than the discharge roller 23 in a direction perpendicular to the axial direction of the discharge roller 23 and the discharge driven roller 24 and perpendicular to the vertical direction (the direction in which the discharge tray 60 extends when viewed from the vertical direction). In other words, the discharge driven roller 24 is located closer to the front of the image forming apparatus 1 than the discharge roller 23. With this configuration, the direction in which the pair of discharge rollers 22 transports the sheet S is an angle β upward (arrow N) from the horizontal direction H. Therefore, the discharged sheet is less likely to disturb the alignment of the sheets on the discharge tray 60.

[0042] 5, in this embodiment, the roller holder 31 supports one paper discharge driven roller 24. Two roller holders 31 are provided in the rotation axis direction of the paper discharge driven roller 24, and form two nip portions.

[0043] 6 is a diagram showing the trajectories of the paper discharge driven roller 24 and the roller holder 31 when the position of the paper discharge roller 23 is fixed. Starting from the position where the paper discharge roller 23 and the paper discharge driven roller 24 are in contact, the upstream boss 25a is moved a distance of L downward and L upward, totaling four positions of 2L.

[0044] The above-mentioned configuration makes it possible to make the movement direction K of the discharge driven roller 24 and the nip pressure direction F substantially parallel to each other. As a result, even if the discharge roller shaft 23a is bent by the nip pressure, the angle of the conveying direction N of the sheet S does not change, so stable conveyance is possible. Therefore, it becomes possible to use a molding material with low rigidity for the discharge roller shaft 23a instead of a metal with high rigidity, thereby reducing costs.

[0045] Next, the inclination of the nip will be more simply explained with reference to Figures 7 and 8. Figure 7 is a diagram showing how the paper discharge driven roller 24 and roller holder 31 are inclined when the protrusion 25 moves while being guided by the groove 30. Figure 7(a) is a simplified diagram showing the driven roller 24 and the driven roller holder 31, and Figures 7(b) and 7(c) are diagrams showing the state in which the protrusion 25 is guided by the groove 30.

[0046] Fig. 8 is a diagram showing the discharge roller 23 and the discharge driven roller 24. Fig. 8(a) is a diagram showing a state in which a thin sheet S1 is sandwiched between the discharge roller 23 and the discharge driven roller 24. Fig. 8(b) shows a state in which the discharge roller 23 and the discharge driven roller 24 sandwich a thick sheet S2 when the discharge driven roller 24 moves in the vertical direction as shown in Fig. 17(c). Fig. 8(c) shows a state in which the discharge roller 23 and the discharge driven roller 24 in this embodiment sandwich a thick sheet S2.

[0047] When the discharge driven roller 24 is in contact with the discharge roller 23 as shown in Fig. 7(b), a thick sheet S2 passes through the nip formed by the discharge roller 23 and the discharge driven roller 24, and the discharge driven roller 24 retreats, so that the discharge driven roller 24 moves to the position shown in Fig. 7(c). At this time, the angle of the line Z1 passing through the first protrusion 25b and the second protrusion 25a in Fig. 7(b) is different from the angle of the line Z2 passing through the first protrusion 25b and the second protrusion 25a in Fig. 7(c). In this way, the discharge driven roller 24 and the roller holder 31 move relative to the device body while rotating.

[0048] In Fig. 8, Fig. 8(b) showing a state in which the paper discharge driven roller 24 has moved vertically downward is compared with Fig. 8(c) showing a state in which the paper discharge driven roller 24 has moved to the lower right in the figure, with Fig. 8(a) being used as a reference. The point of contact between the paper discharge roller 23 and the paper discharge driven roller 24 in the state of Fig. 8(a) is designated as P1. The point of contact between the sheet S2 and the paper discharge driven roller 24 in Fig. 8(b) is designated as P2, and the point of contact between the sheet S2 and the paper discharge driven roller 24 in Fig. 8(c) is designated as P3.

[0049] 8(b), a line passing through the respective rotation centers of the discharge roller 23 and the discharge driven roller 24 is designated as line A4. A line passing through the respective rotation centers of the discharge roller 23 and the discharge driven roller 24 is designated as line A5.

[0050] In Fig. 8(b), the thick sheet S2 causes the discharge driven roller 24 to move vertically downward. This causes the line A4 to tilt with respect to the line A3. Here, the distance between P1 and P2 in the conveying direction of the sheet S is L1. In Fig. 8(c), the line A5 tilts with respect to the line A3, but since the moving direction of the discharge driven roller 24 is the lower right in the figure, the tilt is smaller than the tilt between A4 and A3. Furthermore, the distance between P1 and P3 in the conveying direction of the sheet S is L2.

[0051] Since the moving directions of the discharge driven rollers 24 are different, when L1 and L2 are compared, L1>L2. In the configuration of this embodiment shown in Fig. 8(c), the conveying direction of the sheet S is less likely to change due to the difference in L1>L2 than in the configuration shown in Fig. 8(b), and the discharge performance is superior.

[0052] In the above description, a thick sheet S2 is used for explanation. When the sheet S is thick, the effect of this embodiment is more pronounced, but even when a thin sheet S is used, the effect of making it difficult for the conveying direction of the sheet S to change can be obtained.

[0053] 9, the groove 30 is disposed upstream of the line of the arrow F (a straight line passing through the rotation centers of the discharge roller 23 and the discharge driven roller 24) in the conveying direction of the sheet S, so that it is possible to reduce the protrusion amount of the roller holder 31 and the discharge frame 29. This makes it possible to reduce the possibility that the trailing edge of the discharged sheet S will get caught on the discharge frame 29.

[0054] Fig. 10 shows a comparative example of this embodiment. Fig. 10(a) shows a comparative example which is a modification of this embodiment, and Fig. 10(b) shows the configuration of this embodiment. This embodiment has a configuration in which the sliding resistance when the roller holder 31 moves is smaller than that of the comparative example, and the mechanism behind this will be explained.

[0055] 10(a) shows a configuration in which the movement direction U' of the first protrusion 25b and the movement direction D' of the second protrusion 25a are parallel to the nip pressure direction F in order to move the roller holder 31 linearly in the nip pressure direction F. Furthermore, in order to reduce the movement area of ​​the roller holder 31 downstream in the horizontal direction H, the positions of the first protrusion 25b and the second protrusion 25a are arranged on the upstream side of the conveying direction (arrow N') of the dotted line of the nip pressure direction F.

[0056] The roller holder 31 is pressed upward in the figure by the force of the pressure spring 26, and the first protrusion 25b abuts against the groove 30' at point 25b'. If the distance between point 25b' and the dotted line in the nip pressure direction F is L', the roller holder 31 receives a reaction force of the nip pressure in the F' direction, and a moment M'=F'×L' is generated around point 25b'. As a result, the second protrusion 25a abuts against the groove 30' at point 25a' and receives the moment M'.

[0057] Because the direction Z1 of the force due to the moment M' at point 25a' and the direction Z2 perpendicular to the surface receiving the force at point 25a' form an angle ε1, the upstream boss 25a generates a force that bites into the groove 30'. Therefore, when the roller holder 31 tries to move downward, the sliding friction at point 25a' becomes large, making it difficult for it to move downward.

[0058] On the other hand, in a configuration in which arrow D shown in Figure 10(b) is inclined with respect to arrow U, if the angle between Z1 and direction Z3 perpendicular to the surface receiving the force at point 25a' is ε2, then angle ε2 is smaller than angle ε1, and therefore the sliding friction at point 25a' becomes relatively smaller, and roller holder 31 becomes more likely to move downward.

[0059] [Example 2] This embodiment is an example in which the configuration characteristic of the present invention is applied to the paper feed unit 5a. This embodiment will be described with reference to Figs. 11 to 16. Fig. 11 is a cross-sectional view of the periphery of the paper feed unit 5a. The pick roller 103 comes into contact with the uppermost sheet S and rotates to feed the sheet S to a nip portion formed by a feed roller 101 and a separation roller 102. A torque limiter (not shown) is built into the separation roller 102, and the sheets S are separated and fed one by one by the feed roller 101 and the separation roller 102.

[0060] On the right side of the paper feed section 5a in the figure, a transport path 120 for the sheet S fed from the paper feed section 6b shown in Fig. 1 is provided. Fig. 12 is a perspective view of the paper feed cassette 6a. Fig. 13 shows the separation roller unit 100, with Fig. 13(a) being a front view, Fig. 13(b) being a right side view, Fig. 13(c) being a rear view, and Fig. 13(d) being a cross-sectional view taken along the line EE in Fig. 13(c).

[0061] The separation roller unit 100 is composed of a separation roller 102, a separation roller holder 104, a separation guide 105, and a pressure spring 107. The separation roller 102 is held by the separation roller holder 104, and the separation roller holder 104 is held by the separation guide 105. The separation roller holder 104 is pressed towards the feed roller 101 by the pressure spring 107, thereby applying nip pressure between the feed roller 101 and the separation roller 102.

[0062] Fig. 14 is a perspective view of the separation roller holder 104 that holds the separation roller 102, and Fig. 15 is a perspective view and a side view of the separation guide 105. The separation roller holder 104 is provided with two pairs of bosses in the sheet width direction, a pair of upstream bosses 104a and a pair of downstream bosses 104b. In addition, long holes 106 including an upstream long hole 106a and a downstream long hole 106b are provided on both side surfaces of the separation guide 105 in the sheet width direction, and the separation roller holder 104 is held by the separation guide 105 by fitting the upstream boss 104a into the upstream long hole 106a and the downstream boss 104b into the downstream long hole 106b.

[0063] Figure 16 shows the separation roller unit 100, and Figure 16(a) is a view of the separation roller unit 100 seen in the same direction as Figure 13(c). Figure 16(b) is a cross-sectional view taken along line GG in Figure 16(a), showing the position where the separation roller 102 and separation roller holder 104 are in contact with the feed roller 101, and the position where the separation roller 102 is separated from the feed roller 101.

[0064] The direction of movement of downstream boss 104b towards feed roller 101 is indicated by arrow D, and the direction of movement of upstream boss 104a towards feed roller 101 is indicated by arrow U. In this embodiment, in order to ensure stable feeding as in the first embodiment, arrow D is inclined at an angle γ upstream of arrow U in the conveying direction N, so that the movement direction K of separation roller 102 and nip pressure direction F become closer to each other.

[0065] Furthermore, as in Example 1, the angle that arrow D makes with respect to the direction of a straight line passing through the center of rotation of separation roller 102 and the center of rotation of feed roller 101 when viewed in the direction of the rotation axis of separation roller 102 is smaller than the angle that arrow U makes with respect to the direction of said straight line.

[0066] Further, the guide path formed by the groove 106, the downstream boss 104b, and the upstream boss 104a is disposed upstream of the line of the arrow F in the sheet conveying direction. By adopting this configuration, it is possible to reduce the downstream side of the separation roller 102 and the separation roller holder 104 in the horizontal direction H, so that it is possible to provide a conveying path 120 as shown in FIG. [Explanation of symbols]

[0067] 23 Paper discharge roller (second roller) 24 Paper discharge driven roller (first roller) 25 Protrusion (guided part) 26 Spring (biasing member) 29 Paper ejection frame (guide section) 30 grooves 31 Roller holder 60 Output Tray

Claims

1. A sheet conveying device, comprising: A pair of rollers for conveying a sheet, the pair of rollers including a first roller and a second roller; A biasing member; A roller holder that holds the first roller and is biased by the biasing member so that the first roller is biased toward the second roller, the roller holder including a guided portion, the guided portion having a first guide and a second guide located upstream of the first guide with respect to the biasing direction of the biasing member; A first guide that movably supports and guides the first guide, and a second guide that movably supports and guides the second guide, and a guide portion that movably guides the roller holder so that the first roller and the second roller take a first state in which the first roller contacts the second roller with a predetermined force and a second state in which the force is reduced; And having A first direction in which the first guide guides the first guide is inclined with respect to a second direction in which the second guide guides the second guide; When the first roller and the second roller are in the first state, an angle formed between a straight line passing through the rotation center of the first roller and the rotation center of the second roller and the first direction as viewed in the direction of the rotation axis of the first roller is smaller than an angle formed between the straight line and the second direction. A sheet conveying device characterized by this.

2. The first guide and the second guide are each a protrusion, and the first guide and the second guide accommodate the first guide and the second guide. The sheet conveying device according to claim 1, characterized by this.

3. The first guide and the second guide are each a groove, and the first guide and the second guide are connected. The sheet conveying device according to claim 2, characterized by this.

4. The second roller is a driving roller that receives driving. The sheet conveying device according to claim 1, characterized by this.

5. The first roller rotates idly by contacting the second roller. The sheet conveying device according to claim 4, characterized by this.

6. The first roller is located below the second roller with respect to the vertical direction. The sheet conveying device according to claim 1, characterized by this.

7. The pair of rollers is configured to discharge a sheet on which an image is formed. The sheet conveying device according to claim 1, characterized by this. The sheet conveying device according to claim 7, further comprising a discharge tray for stacking the sheet discharged by the first roller and the second roller.

9. The sheet conveying device according to claim 1, wherein the first roller and the roller holder are removable.

10. The sheet conveying device according to claim 1, wherein the biasing member biases the roller holder upward in the vertical direction.

11. The sheet conveying device according to claim 1, wherein the first roller and the second roller are separated in the second state.

12. The sheet conveying device according to claim 1, wherein the rotation centers of the first roller and the second roller in the vertical direction do not overlap.

13. The sheet conveying device according to claim 12, wherein the sheet is conveyed obliquely upward by the first roller and the second roller.

14. The image forming apparatus according to claim 1, wherein the first roller, the second roller, and the roller holder are provided at a plurality of positions in the direction of the rotation axis of the first roller.

15. The sheet conveying device according to claim 1, wherein, when viewed in the direction of the rotation axis of the first roller, the first guide and the second guide are located on the upstream side of the straight line with respect to the conveying direction of the sheet.

16. An image forming apparatus comprising the sheet conveying device according to claim 1 and an image forming unit that forms an image on a sheet.

17. A sheet conveying device, A pair of rollers for conveying a sheet, the pair of rollers including a first roller and a second roller, A biasing member, A roller holder that holds the first roller and is biased by the biasing member so that the first roller is biased toward the second roller, the roller holder including a guided portion, the guided portion having a first guide and a second guide located upstream of the first guide in the biasing direction of the biasing member, A first guide that movably supports and guides the first guide, and a second guide that movably supports and guides the second guide, and a guide portion that movably guides the roller holder so that the first roller and the second roller take a first state in which the first roller contacts the second roller with a predetermined force and a second state in which the force is reduced, having The first direction in which the first guide guides the first guided member is inclined with respect to the second direction in which the second guide guides the second guided member. As viewed in the direction of the rotation axis of the first roller, with respect to the sheet conveyance direction, the first guide and the second guide are positioned on the upstream side of a straight line passing through the rotation center of the first roller and the rotation center of the second roller. A sheet conveyance device characterized by this.

18. The sheet conveyance device according to claim 17, wherein the sheet is conveyed obliquely upward by the first roller and the second roller.

Images