Paper feed roll

Abstract

To provide a paper feed roll capable of ensuring durability by suppressing abrasion of a roll surface and suppressing paper jamming by removing paper dust stuck to the roll surface.SOLUTION: A paper feed roll 12 comprises: a shaft body 12a; and an elastic layer 12b formed on the outer peripheral surface of the shaft body 12a. A projected part 13 having a normal slope 13a larger in inclination in a paper passing direction is formed on the outer peripheral surface of the elastic body layer 12b. The angle θ1 of the normal slope 13a is 25°-55°. In a load 500 g, the radio of a nip area to the product of a nip width and a roll surface length is 0.2-0.6.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a paper feed roll that is suitably used in electrophotographic devices such as copying machines, printers, and facsimiles that employ an electrophotographic system. [Background technology]

[0002] Electrophotographic devices that use electrophotography, such as copiers, printers, and facsimiles, are equipped with a paper feeder. The paper feeder includes a pickup roll that feeds paper from a paper feed cassette, a feed roll that transports the paper that has been fed, and a separation roll (retard roll). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2000-281223 [Patent Document 2] Japanese Patent Application Publication No. 2022-164161 Summary of the Invention [Problem to be solved by the invention]

[0004] These paper feed rolls maintain friction with the paper due to the tackiness derived from the rubber, and transport the paper. The paper feed rolls must continue to maintain their paper transport function throughout their required service life. However, paper dust, such as calcium carbonate, falls off from the paper being transported and adheres to the roll surface. The paper dust adhering to the roll surface inhibits contact between the rubber and the paper, reducing the transport function. This causes paper jams.

[0005] In Patent Document 1, a protrusion is provided on the outer circumferential surface of a cylindrical rotating body in a direction parallel to the rotation axis, and the shape of the peak of the protrusion is made more acute than before, which improves the bite into the paper and ensures stable paper feeding. Also, in Patent Document 2, the protrusion of the feed roller extends in the axial direction and the protrusion of the retard roller extends in the circumferential direction, which allows fine powder such as paper dust to escape into the grooves between the protrusions of the feed roller and the grooves between the protrusions of the retard roller, thereby preventing paper dust from accumulating in the nip between the protrusions of the feed roller and the protrusions of the retard roller.

[0006] However, until now, little attention has been paid to how smoothly the paper dust adhering to the roll surface can be removed, and there has been room for improvement in preventing paper jams caused by paper dust.

[0007] The problem that the present invention aims to solve is to provide a paper feed roll that can reduce wear on the roll surface to ensure durability, and also remove paper dust adhering to the roll surface to reduce paper jams. [Means for solving the problem]

[0008] The paper feed roll of the present invention comprises a shaft body and an elastic layer formed on the outer peripheral surface of the shaft body, and a convex portion on the outer peripheral surface of the elastic layer having a slope with a gradient that increases in the paper feed direction, the angle of the slope with a gradient of 25° or more and 55° or less, and the ratio of the nip area to the product of the nip width and the roll face length at a load of 500 g is 0.2 or more and 0.6 or less.

[0009] The top of the convex portion may have a top surface with an angle smaller than that of the convex portion's forward-grain slope. In this case, the ratio of the circumferential length of the top surface to the circumferential length of the convex portion's base may be 0.05 or more and 0.3 or less. The convex portion may have a reverse-grain slope that increases in slope along the opposite direction to the paper feed direction. In this case, the angle of the reverse-grain slope may be greater than that of the forward-grain slope. The angle of the reverse-grain slope may be 60° or more and 90° or less. The height of the convex portion may be 40 μm or more and 200 μm or less. The JIS-A hardness of the surface of the elastic layer may be 35° or more and 75° or less.

[0010] (1) The paper feed roll of the present invention comprises a shaft body and an elastic layer formed on the outer peripheral surface of the shaft body, and the outer peripheral surface of the elastic layer is provided with a convex portion having a slope with a gradient that increases in the paper feed direction, the slope of the gradient being 25° or more and 55° or less, and the ratio of the nip area to the product of the nip width and the roll face length at a load of 500 g is 0.2 or more and 0.6 or less.

[0011] (2) In the above item (1), the apex of the protrusion may have a top surface with an angle smaller than that of a slope of the inclined grain of the protrusion.

[0012] (3) In the above item (2), it is preferable that a ratio of a circumferential length of the top surface to a circumferential length of the bottom surface of each of the projections is 0.05 or more and 0.3 or less.

[0013] (4) In any one of (1) to (3) above, the convex portion may have a reverse-grain slope that increases in slope in the opposite direction to the paper feed direction, and the angle of the reverse-grain slope may be greater than the angle of the forward-grain slope.

[0014] (5) In the above (4), the angle of the inclined surface of the reverse grain is preferably 60° or more and 90° or less.

[0015] (6) In any one of the above (1) to (5), the height of the protrusions may be 40 μm or more and 200 μm or less.

[0016] (7) In any one of the above (1) to (6), the JIS-A hardness of the surface of the elastic layer may be 35° or more and 75° or less. Effect of the Invention

[0017] According to the paper feed roll of the present invention, a spot for releasing paper dust can be formed by providing a convex portion having a slope of the normal grain that increases in slope along the paper feed direction on the surface of the elastic layer. By setting the angle of the slope of the normal grain to 25° or more, a strong shear force is applied to the convex portion and the paper dust, and the paper dust can be discharged to the spot. By setting the ratio of the nip area to the product of the nip width and the roll surface length at a load of 500 g to 0.6 or less, a strong shear force is applied to the convex portion and the paper dust can be discharged to the spot. This makes it possible to remove the paper dust adhering to the roll surface and prevent paper jams due to a decrease in friction force. By setting the angle of the slope of the normal grain to 55° or less, excessive shear force is not applied to the convex portion, and a decrease in the friction coefficient due to wear is suppressed. By setting the ratio of the nip area to 0.2 or more, excessive shear force is not applied to the convex portion, and a decrease in the friction coefficient due to wear is suppressed. This makes it possible to prevent paper jams.

[0018] By providing the top of the convex with a top surface with an angle smaller than the inclined surface of the convex, wear of the top of the convex is suppressed and deterioration of durability is suppressed. In this case, when the ratio of the circumferential length of the top surface to the circumferential length of the base surface of the convex is 0.05 or more, wear of the top of the convex is easily suppressed. When the ratio is 0.3 or less, paper dust is unlikely to accumulate on the top of the convex, and paper dust is easily discharged to the spot.

[0019] The convex portion preferably has a slope with a reverse grain that increases in slope in the opposite direction to the paper feed direction. In this case, if the angle of the slope with the reverse grain is larger than the angle of the slope with the forward grain, paper dust is less likely to accumulate on the top of the convex portion, and the paper dust is easily discharged to the spot. If the angle of the slope with the reverse grain is 60° or more, the angle of the slope with the reverse grain is not too gentle, and the paper dust is easily discharged to the spot. If the angle of the slope with the reverse grain is 90° or less, the strength of the convex portion is ensured, and shear force is easily applied to the convex portion, and shear force is easily applied to the paper dust, and the paper dust is easily discharged to the spot.

[0020] When the height of the protrusions is 40 μm or more, deterioration of durability due to wear can be easily suppressed. Also, shear force is easily applied to the paper powder, making it easy to discharge the paper powder to the spot. When the height of the protrusions is 200 μm or less, the strength of the protrusions is ensured, so shear force is easily applied to the protrusions, making it easy to apply shear force to the paper powder, making it easy to discharge the paper powder to the spot. Also, excessive shear force is not applied to the protrusions, making it easy to suppress deterioration of durability due to wear.

[0021] When the JIS-A hardness of the surface of the elastic layer is 35° or more, deterioration in durability due to wear is easily suppressed.When the JIS-A hardness of the surface of the elastic layer is 75° or less, excessive shear force is not applied to the protrusions, and deterioration in durability due to wear is suppressed. [Brief description of the drawings]

[0022] [Figure 1] FIG. [Diagram 2] This is a diagram of the paper feed operation of the paper feeder shown in Fig. 1. Fig. 2(a) shows the state before a sheet of paper arrives between the rolls, and Fig. 2(b) shows the operation when a sheet of paper arrives between the rolls. [Diagram 3] 3A and 3B are diagrams showing the paper feed operation of the paper feeder shown in Fig. 1. Fig. 3A shows the state before two sheets of paper arrive between the rolls, and Fig. 3B shows the operation when two sheets of paper arrive between the rolls. [Figure 4] FIG. 2 is a schematic diagram showing the appearance of a paper feed roll according to an embodiment of the present invention. [Diagram 5] FIG. 4 is a schematic diagram illustrating the shape of a protrusion. [Figure 6] 11A and 11B are schematic diagrams showing other embodiments of the protrusions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The paper feed roll according to the present invention will be described in detail. Fig. 1 is a schematic diagram of a paper feed device. Figs. 2 and 3 are diagrams showing the paper feeding operation of the paper feed device shown in Fig. 1. Fig. 4 is a schematic diagram of the appearance of a paper feed roll according to one embodiment of the present invention. Fig. 5 is a schematic diagram explaining the shape of the convex portion.

[0024] As shown in FIG. 1, the paper feeder 10 includes a paper feed roll 12 (feed roll) and a separation roll 14 (retard roll). The paper feed roll 12 includes a shaft body 12a and an elastic layer 12b formed on the outer periphery of the shaft body 12a. The separation roll 14 includes a shaft body 14a and an elastic layer 12bb formed on the outer periphery of the shaft body 14a. The paper feed roll 12 is driven to rotate by power from a driving source (motor) (not shown) and has a function of transporting paper P. The separation roll 14 is pressed against the paper feed roll 12 with a predetermined pressure by a biasing member (such as a spring) (not shown). The separation roll 14 also includes a built-in torque limiter (not shown) and is configured to apply a brake torque in the direction opposite to the rotation direction (direction of the arrow) in which the paper P is transported.

[0025] The paper sheets P to be transported are stacked in a paper feed cassette 16. The surface of a pull-in roll 18 (pickup roll) is in frictional contact with the upper surface of the stacked paper sheets P, and the pull-in roll 18 is configured to sequentially pay out the paper sheets P from the paper feed cassette 16 toward the paper feed roll 12. The pull-in roll 18 has a shaft body 18a and an elastic layer 18b formed on the outer periphery of the shaft body 18a. The pull-in roll 18 is configured to rotate in conjunction with the drive of the paper feed roll 12 by a connecting member (such as a gear or a timing belt) not shown.

[0026] As the paper feed roll 12 rotates, the retract roll 18 rotates, and paper P is fed one sheet at a time from the paper feed cassette 16 toward the paper feed roll 12. As shown in FIG. 2(a), the paper feed roll 12 starts rotating before the paper P arrives. As the paper feed roll 12 rotates, the separation roll 14, which is pressed against the paper feed roll 12, rotates against the brake torque due to the frictional force between the paper feed roll 12 and the separation roll 14 (between the rolls). When a sheet of paper P that has been fed out arrives between the rolls, the paper P passes between the rolls and is conveyed in the paper feed direction Y, as shown in FIG. 2(b).

[0027] When two sheets of paper P are fed from the paper feed cassette 16 toward the paper feed roll 12, as shown in FIG. 3(a), before the sheets P1 and P2 arrive, the paper feed roll 12 rotates and the separation roll 14 rotates against the brake torque as the paper feed roll 12 rotates. When the two sheets of paper P1 and P2 arrive between the rolls, as shown in FIG. 3(b), the separation roll 14 comes into contact with the paper feed roll 12 via the two sheets of paper P1 and P2. Because the frictional force acting between the two sheets of paper P1 and P2 is small, the separation roll 14 does not follow the rotation of the paper feed roll 12 and stops due to the brake torque. As a result, the paper P1 in contact with the paper feed roll 12 passes between the rolls as the paper feed roll 12 rotates and is conveyed in the paper passage direction Y, while the paper P2 in contact with the separation roll 14 is not conveyed. This prevents the paper P from being conveyed multiple times.

[0028] The paper feed roll according to the present invention can be suitably used as the paper feed roll 12 (feed roll), the separation roll 14 (retard roll), the pull-in roll 18 (pickup roll), and the like in the paper feed device 10.

[0029] Hereinafter, the configuration of the paper feed roll according to the present invention will be described using the paper feed roll 12 as an example. Other paper feed rolls (separation rolls, pull-in rolls) have the same configuration. In the paper feed rolls in Figures 4 and 5, the X direction is the axial direction, and the Y direction is the paper feed direction.

[0030] The paper feed roll 12 according to one embodiment of the present invention includes a shaft body 12a and an elastic layer 12b formed on the outer peripheral surface of the shaft body 12a. The elastic layer 12b is a layer (base layer) that becomes the base of the paper feed roll 10. The elastic layer 12b is a layer that appears on the surface of the paper feed roll 12.

[0031] The shaft body 12a may be a solid body or a hollow body (cylinder) made of metal or resin. Metal materials include iron, stainless steel, and aluminum. The elastic layer 12b may be bonded to the shaft body 12a via an adhesive layer (primer layer). The adhesive, primer, and the like may be made conductive as necessary.

[0032] The elastic layer 12b is formed in a roll shape on the outer peripheral surface of the shaft body 12a using an elastic material. The elastic layer 12b has a plurality of protrusions 13 on the outer peripheral surface. The protrusions 13 have a forward slope 13a that increases in slope along the paper feed direction Y. The protrusions 13 also have a reverse slope 13b that increases in slope along the opposite direction to the paper feed direction Y. Furthermore, the top of the protrusions 13 has a top surface 13c that is parallel to the bottom surface 13d of the protrusions 13. The top surface 13c is a surface with a smaller angle than the forward slope 13a of the protrusions 13. The protrusions 13 are trapezoidal in cross section in the circumferential direction.

[0033] The plurality of protrusions 13 are formed in the shape of independent islands in both the circumferential direction and the axial direction X of the elastic layer 12b. The plurality of protrusions 13 are regularly arranged in a staggered pattern on the outer peripheral surface of the elastic layer 12b. The first row of protrusions 13 are aligned along the axial direction X of the elastic layer 12b. Similarly, the second row of protrusions 13 and the third row of protrusions 13 are aligned along the axial direction X of the elastic layer 12b. When viewed in the circumferential direction of the elastic layer 12b, the second row of protrusions 13 are arranged at a position shifted in the axial direction from the first row of protrusions 13 and the third row of protrusions 13. The first row of protrusions 13 and the third row of protrusions 13 are arranged at the same position in the axial direction. Therefore, for example, a spot S is formed between the first row of protrusions 13 and the third row of protrusions 13 in the circumferential direction, and the spot S becomes a portion for collecting the paper powder discharged from the protrusions 13.

[0034] Here, the angle θ1 of the inclined surface 13a of the normal grain is set to 25° or more and 55° or less. If the angle θ1 of the inclined surface 13a of the normal grain is less than 25°, the shear force is not easily applied to the protrusions 13 and the paper powder, the discharge of the paper powder to the spot S is poor, the friction coefficient of the roll surface after durability is reduced, and paper jams are likely to occur. On the other hand, if the angle θ1 of the inclined surface 13a of the normal grain is more than 55°, the shear force is applied too much to the protrusions 13, the amount of wear of the protrusions 13 is increased, and the friction coefficient of the roll surface after durability is reduced due to the disappearance of the slope, and paper jams are likely to occur. In addition, since the inclined surface 13a of the normal grain of the protrusions 13 is too steep, it is difficult to discharge the paper powder to the spot S even if a shear force is applied to the protrusions 13 and the paper powder. The angle θ1 of the inclined surface 13a of the normal grain is preferably 30° or more, more preferably 35° or more, from the viewpoint of easy discharge of the paper powder to the spot S. On the other hand, the angle θ1 of the inclined surface 13a of the normal grain is preferably 50° or less, and more preferably 45° or less, from the viewpoint that the amount of wear of the protrusion 13 can be easily suppressed.

[0035] The angle θ2 of the reverse-grained slope 13b is not particularly limited, but is preferably larger than the angle θ1 of the normal-grained slope 13a. This makes it difficult for paper powder to accumulate on the top surface 13c of the convex portion 13, and makes it easy to discharge the paper powder to the spot S. The angle θ2 of the reverse-grained slope 13b is preferably 60° or more and 90° or less. When the angle θ2 of the reverse-grained slope 13b is 60° or more, the angle θ2 of the reverse-grained slope 13b is not too gentle, making it easy to discharge the paper powder to the spot S. When the angle θ2 of the reverse-grained slope 13b is 90° or less, the strength of the convex portion 13 is ensured, making it easy for shear force to be applied to the convex portion 13 and the paper powder, making it easy to discharge the paper powder to the spot S. From the above viewpoint, the angle θ2 of the reverse-grained slope 13b is more preferably 65° or more and 90° or less, and even more preferably 70° or more and 90° or less.

[0036] The angle of the top surface 13c is preferably 0° or more and 20° or less with respect to a plane parallel to the bottom surface 13d of the convex portion 13. More preferably, it is 0° or more and 15° or less, and even more preferably, it is 0° or more and 10° or less. Since the angle of the top surface 13c is smaller than the inclined surface 13a of the convex portion 13, wear of the top of the convex portion 13 is suppressed, and a decrease in durability is suppressed. Furthermore, since the angle of the top surface 13c is smaller, it is easy to increase the nip area. And, since the angle of the top surface 13c is larger, a shear force is easily applied to the paper powder, the paper powder is less likely to accumulate on the top surface 13c, and the paper powder is easily discharged to the spot S.

[0037] The ratio (A / B) of the circumferential length A of the top surface 13c to the circumferential length B of the bottom surface 13d of the convex portion 13 is preferably 0.05 or more and 0.3 or less. When the ratio is 0.05 or more, wear at the top of the convex portion 13 is easily suppressed. Furthermore, when the ratio is 0.3 or less, paper dust is less likely to accumulate at the top of the convex portion 13, and the paper dust is easily discharged to the spot S. The ratio is more preferably 0.10 or more and 0.3 or less, and even more preferably 0.10 or more and 0.25 or less.

[0038] The height C of the protrusions 13 is preferably 40 μm or more and 200 μm or less. When the height C of the protrusions 13 is 40 μm or more, the deterioration of durability due to wear is easily suppressed. In addition, shear force is easily applied to the paper powder, and the paper powder is easily discharged to the spot S. When the height C of the protrusions 13 is 200 μm or less, the strength of the protrusions 13 is ensured, so that shear force is easily applied to the protrusions 13, and the paper powder is easily discharged to the spot S. In addition, the shear force is not too strong on the protrusions 13, and the deterioration of durability due to wear is suppressed. The height C of the protrusions 13 is more preferably 50 μm or more and 150 μm or less, and even more preferably 60 μm or more and 100 μm or less.

[0039] The JIS-A hardness of the surface of the elastic layer 12b is preferably 35° or more and 75° or less. When the hardness is 35° or more, deterioration of durability due to wear is easily suppressed. Furthermore, when the hardness is 75° or less, excessive shear force is not applied to the protrusions 13, and deterioration of durability due to wear is suppressed. The hardness is more preferably 35° or more and 70° or less, and further preferably 40° or more and 65° or less.

[0040] In the paper feed roll according to the present invention, the nip area is important. The ratio of the nip area to the product of the nip width and the roll surface length at a load of 500 g is set to 0.2 or more and 0.6 or less. The nip width is the length of the nip in the circumferential direction, and the roll surface length is the roll length in the roll axial direction (the length of the elastic layer 12b). By setting the ratio of the nip area to 0.2 or more, excessive shear force is not applied to the protrusions 13, and a decrease in the friction coefficient due to wear is suppressed. This makes it possible to suppress paper jams. Furthermore, by setting the ratio of the nip area to 0.6 or less, a strong shear force is applied to the paper powder, and the paper powder can be discharged to the spot S. This makes it possible to remove the paper powder adhering to the roll surface and suppress paper jams due to a decrease in friction force. The ratio of the nip area is preferably 0.25 or more and 0.55 or less, more preferably 0.3 or more and 0.5 or less. The nip area can be determined from the contact area when a glass plate is pressed against the outer circumferential surface of the elastic layer 12a of the paper feed roll 10 with a load of 500 gf.

[0041] The elastic layer 12b is made of an elastic material such as rubber, elastomer, resin, etc. The material is not particularly limited as long as it is a rubber-like elastic material. For example, known materials such as urethane rubber, hydrin rubber, silicone rubber, and EPDM can be used.

[0042] Various additives may be added to the elastic layer 12b as necessary, such as a lubricant, a vulcanization accelerator, an antioxidant, a light stabilizer, a viscosity modifier, a processing aid, a flame retardant, a plasticizer, a filler, a dispersant, an antifoaming agent, a pigment, and a mold release agent.

[0043] The thickness of the elastic layer 12b is not particularly limited and may be set appropriately within the range of 2 to 25 mm.

[0044] The elastic layer 12b can be formed by molding using a mold. For example, a core material is coaxially placed in the hollow part of a roll mold, an uncrosslinked rubber composition is injected, and the core material is heated and cured (crosslinked), and then the core material is demolded to form a tube-shaped elastic layer 12b. The molding mold may have a recess formed on its inner circumferential surface in a shape corresponding to the protrusion 13. The paper feed roll 10 can be formed by inserting the shaft 12a into the elastic layer 12b formed in a cylindrical shape. The method of imparting a shape to the outer circumferential surface of the elastic layer 12b is not limited to transfer using a mold, and may be a method of imparting a shape by grinding or the like.

[0045] According to the paper feed roll 10 having the above configuration, the surface of the elastic layer 12b is provided with the convex portion 13 having the forward-grained slope 13a whose slope increases along the paper feed direction Y, so that the spot S for releasing the paper dust can be formed. Then, by setting the angle θ1 of the forward-grained slope 13a to 25° or more, a strong shear force is applied to the convex portion 13 and the paper dust, and the paper dust can be discharged to the spot S. Also, by setting the ratio of the nip area to the product of the nip width and the roll surface length at a load of 500 g to 0.6 or less, a strong shear force is applied to the convex portion 13 and the paper dust, and the paper dust can be discharged to the spot S. This makes it possible to remove the paper dust adhering to the roll surface and prevent paper jams due to a decrease in frictional force. Then, by setting the angle θ1 of the forward-grained slope 13a to 55° or less, the convex portion 13 is not subjected to too much shear force, and the decrease in the friction coefficient due to wear is suppressed. By setting the ratio of the nip area to 0.2 or more, excessive shear force is not applied to the protrusions 13, and a decrease in the coefficient of friction due to wear is suppressed, thereby making it possible to prevent paper jams.

[0046] Furthermore, by providing the top surface 13c at the top of the protrusion 13 with an angle smaller than that of the inclined surface 13a of the convex portion 13, wear at the top of the protrusion 13 is suppressed, and deterioration in durability is suppressed. In this case, if the ratio (A / B) of the circumferential length A of the top surface 13c to the circumferential length B of the bottom surface 13d of the protrusion 13 is 0.05 or more, wear at the top of the protrusion 13 is likely to be suppressed. If the ratio is 0.3 or less, paper dust is unlikely to accumulate at the top of the protrusion 13, and the paper dust is easily discharged into the spot S.

[0047] The convex portion 13 has a reverse-grained slope 13b that increases in slope in the opposite direction to the paper feed direction Y. In this case, the angle θ2 of the reverse-grained slope 13b is configured to be larger than the angle θ1 of the normal-grained slope 13a, so that paper dust is less likely to accumulate on the top of the convex portion 13 and the paper dust is easily discharged to the spot S. If the angle θ2 of the reverse-grained slope 13b is 60° or more, the angle θ2 of the reverse-grained slope 13b is not too gentle, so that the paper dust is easily discharged to the spot S. If the angle θ2 of the reverse-grained slope 13b is 90° or less, the strength of the convex portion 13 is ensured, so that shear force is easily applied to the convex portion 13, and shear force is easily applied to the paper dust, so that the paper dust is easily discharged to the spot S.

[0048] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0049] For example, the convex portion 13 in Fig. 5 has a top surface 13c at the top of the convex portion 13 that is smaller in angle than the inclined surface 13a of the convex portion 13, but in the paper feed roll of the present invention, the top of the convex portion does not have to have a top surface as shown in Fig. 5. Also, the top surface 13c of the convex portion 13 in Fig. 5 is a surface parallel to the bottom surface 13d of the convex portion 13, but the top surface 13c of the convex portion 13 does not have to be a surface parallel to the bottom surface 13d of the convex portion 13.

[0050] FIG. 6 shows another embodiment of the protrusion.

[0051] As shown in Fig. 6(a), the convex portion 131 has a forward slope 131a whose slope increases along the paper feed direction Y, and a reverse slope 131b whose slope increases along the opposite direction to the paper feed direction Y. The convex portion 131 does not have a top surface as shown in Fig. 5 at the top of the convex portion 131. When viewed in a circumferential cross section, the convex portion 131 has a triangular shape.

[0052] 6(b), the convex portion 132 has a forward slope 132a whose slope increases along the paper feed direction Y, and a reverse slope 132b whose slope increases along the opposite direction to the paper feed direction Y. The top of the convex portion 132 has a top surface 132c whose angle (θ32) is smaller than the angle θ12 of the forward slope 132a of the convex portion 132. The top surface 132c of the convex portion 132 is not parallel to the bottom surface of the convex portion 132.

[0053] 5 is a flat surface, it may be a curved surface. Also, the shape of the protrusion is not limited to the shape shown in FIG.

[0054] The multiple protrusions may be uniformly distributed or randomly arranged on the peripheral surface of the elastic layer 12b, or may be arranged in an array. EXAMPLES

[0055] The present invention will be described in detail below using examples and comparative examples.

[0056] Using a cylindrical molding die having multiple recesses on the inner peripheral surface, an elastic layer of a urethane rubber composition was formed on the outer peripheral surface of a core material (φ6, made of SUS304). As a result, a paper feed roll having multiple protrusions on the outer peripheral surface of the elastic layer, as shown in Figures 4 and 5, was obtained. By observing the radial cross section of the elastic layer of the prepared paper feed roll, the slope angle θ1 of the grain, the slope angle θ2 of the grain, the circumferential length A of the top surface, the circumferential length B of the bottom surface, and the height C of the protrusions were measured. In addition, the JIS-A hardness of the outer peripheral surface of the elastic layer of the prepared paper feed roll was measured.

[0057] (Nip area ratio) The nip area was determined from the contact area when a glass plate was pressed against the outer circumferential surface of the elastic layer of the paper feed roll with a load of 500 gf. A Keyence laser microscope was used for the measurement. The ratio of the nip area to the product of the nip width and the roll surface length was calculated.

[0058] (friction measurement) The feed roll was set in the friction coefficient measuring device with the rotation direction aligned, and the load was set to 2.94 N (300 gf) (W1) and the tensile speed to 180 mm / s. Next, paper (Ricoh 6200 A4) was set between the feed roll and the push-up plate, and the edge of the paper was connected to the load measuring device (load cell). Next, the feed roll was rotated for 10 seconds or more, and the tensile force (W2) at that time was measured. The tensile force was the average value of the stable region of the measurement chart. The friction coefficient was calculated from the value of W2 / W1. The friction coefficient was measured at the initial stage before the test and at the endurance stage after 20,000 sheets were passed through.

[0059] (Durability test) Using the prepared paper feed roll, printing was repeated until a paper jam occurred, and the number of sheets passed before the paper jam occurred was measured. In addition, after 20,000 sheets were passed, the friction coefficient of the outer surface of the elastic layer and the wear amount of the convex part (calculated from the difference in the height of the convex part before and after durability) were also measured. The evaluation machine was Ricoh's "MP C2503", and the evaluation was performed using Ricoh My Paper A4 in an environment of 10°C x 10% RH. If the number of sheets passed before the paper jam occurred was 100,000 or more, it was marked as "◎", if it was 50,000 or more but less than 100,000, it was marked as "○", and if it was less than 50,000, it was marked as "X".

[0060] [Table 1]

[0061] In Comparative Example 1, the slope angle θ1 of the convex part's forward grain is too small. In Comparative Example 1, shear force is not easily applied to the convex part and the paper powder, the paper powder is not easily discharged to the spot, the friction coefficient of the roll surface after durability testing is reduced, and paper jams are likely to occur. In Comparative Example 2, the slope angle θ1 of the convex part's forward grain is too large. In Comparative Example 2, too much shear force is applied to the convex part, causing the convex part to wear more, and the disappearance of the slope reduces the friction coefficient of the roll surface after durability testing, making paper jams more likely to occur.

[0062] In Comparative Example 3, the nip area ratio is too large. In Comparative Example 3, shear force is not easily applied to the protrusions and paper dust, the paper dust is not easily discharged to the spot, the friction coefficient of the roll surface after durability testing is reduced, and paper jams are likely to occur. In Comparative Example 4, the nip area ratio is too small. In Comparative Example 4, too much shear force is applied to the protrusions, causing the protrusions to wear more, and the slope disappears, causing the friction coefficient of the roll surface after durability testing to be reduced, and paper jams are likely to occur.

[0063] On the other hand, in the working example, the inclination angle θ1 of the convex portion is 25° or more and 55° or less. Also, the nip area ratio is 0.2 or more and 0.6 or less. And, in the working example, an appropriate shear force is applied to the convex portion and the paper powder, which improves the discharge of the paper powder to the spot, and reduces the reduction in frictional force and paper jams. Also, because too much shear force is not applied to the convex portion, the amount of wear on the convex portion is reduced, which reduces the occurrence of paper jams.

[0064] From the above, it can be seen that according to the examples and comparative examples, by providing a convex portion on the outer peripheral surface of the elastic layer with a slope of the grain that increases inclination along the paper feed direction, the angle of the slope of the grain being 25° or more and 55° or less, and the ratio of the nip area to the product of the nip width and the roll face length at a load of 500 g being 0.2 or more and 0.6 or less, wear on the roll surface is reduced to ensure durability, and paper dust adhering to the roll surface is removed to reduce paper jams.

[0065] Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments and examples, and various modifications are possible without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0066] 10 Paper feeder 12 Paper feed roll (paper feed roll) 12a Shaft body 12b Elastic layer 14 Separation roll 14a Shaft body 14b Elastic layer 16 Paper feed cassette 18 Pull-in roll 18a Shaft body 18b Elastic layer P,P1,P2 paper X Axial direction (of the feed roll) Y Paper feeding direction 13 Convex 13a (Convex) Slope 13b (Convex) Reverse Grain Slope 13c (top surface of convex part) 13d (Convex) Bottom Surface θ1 (Convex) Angle of the slope of the grain θ2 (Convex) Reverse Grain Slope Angle A (Convex part) Circumferential length of the top surface B Circumferential length of the base (of the convex part) C Height of the protrusion S Spot

Claims

1. A shaft body and an elastic layer formed on an outer circumferential surface of the shaft body, a protrusion having a slope that increases in slope along the paper feed direction on an outer peripheral surface of the elastic layer; The angle of the inclined surface of the said grain is 25° or more and 55° or less, A paper feed roll, in which the ratio of the nip area to the product of the nip width and the roll face length under a load of 500 g is 0.2 or more and 0.6 or less.

2. The paper feed roll according to claim 1 , wherein the top of the protrusion has a top surface with an angle smaller than a slope of the inclined grain of the protrusion.

3. The paper feed roll according to claim 2 , wherein a ratio of a circumferential length of the top surface of each of the protrusions to a circumferential length of the bottom surface of each of the protrusions is 0.05 or more and 0.3 or less.

4. A paper feed roll as described in any one of claims 1 to 3, wherein the convex portion has a reverse-grain slope that increases in slope in the opposite direction to the paper feed direction, and the angle of the reverse-grain slope is larger than the angle of the normal-grain slope.

5. The paper feed roll according to claim 4 , wherein an angle of the inclined surface of the reverse grain is equal to or greater than 60° and equal to or less than 90°.

6. The paper feed roll according to claim 1 , wherein the height of the protrusions is 40 μm or more and 200 μm or less.

7. 4. The paper feed roll according to claim 1, wherein the elastic layer has a surface having a JIS-A hardness of 35° or more and 75° or less.

8. The top of the protrusion has a top surface having an angle smaller than that of a slope of the grain of the protrusion, a ratio of a circumferential length of the top surface to a circumferential length of the bottom surface of the protrusion is 0.05 or more and 0.3 or less; The convex portion has a slope of the reverse grain that increases in slope in a direction opposite to the paper feed direction, and the angle of the slope of the reverse grain is configured to be larger than the angle of the slope of the normal grain, The angle of the inclined surface of the reverse grain is 60° or more and 90° or less, The height of the convex portion is 40 μm or more and 200 μm or less, 2. The paper feed roll according to claim 1, wherein the elastic layer has a surface having a JIS-A hardness of 35° or more and 75° or less.

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