Paper feeder, paper feed roll and separation roll

Abstract

To provide a paper feeder which is excellent in paper transportability and prevents paper jams even after long-term use, a paper feed roll and a separation roll.SOLUTION: A paper feeder comprises a paper feed roll 12 which is rotationally driven and feeds a sheet, and a separation roll 14 which is pressure-welded to the paper feed roll 12, has a torque limiter built therein, and suppresses double feeding of sheet. The paper feed roll 12 and the separation roll 14 have a shaft body, and an elastic body layer formed on an outer peripheral surface of the shaft body. The elastic body layer of the paper feed roll 12 contains, as main components, a first phase containing ethylene-propylene-diene rubber (EPDM) and a second phase containing any one of isoprene rubber (IR) and natural rubber (NR), and JIS-A hardness of a surface of the paper feed roll 12 is 25 to 50°. The elastic body layer of the separation roll 14 contains polyurethane as a main component, a surface of the elastic body layer of the separation roll 14 has a protrusion with a height of 20 to 300 μm, and JIS-A hardness of the surface of the elastic body layer 14b of the separation roll 14 is 45 to 80°.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a paper feeder, a paper feed roll, and a separation roll that are suitable for use in electrophotographic devices such as copying machines, printers, and facsimiles that employ an electrophotographic system. [Background technology]

[0002] In electrophotographic devices such as copiers, printers, and facsimiles that use electrophotography, paper feed rolls are cylindrically formed from elastic materials such as crosslinked rubber, and their circumferential surfaces are the contact surfaces with the paper. Paper dust generated by the paper can adhere to the circumferential surface of the paper feed roll. Repeated contact with the paper can cause paper dust to accumulate on the circumferential surface of the paper feed roll. The accumulation of paper dust reduces the contact area of ​​the circumferential surface with the paper, lowering the coefficient of friction of the contact surface with the paper. Furthermore, if the paper feed roll and the separation roll are made of different materials or have different hardnesses, one roll (e.g., the separation roll) can wear down the surface of the elastic layer of the other roll (e.g., the paper feed roll). As a result, the coefficient of friction of the surface of the elastic layer decreases, which can lead to poor paper transport after long-term use.

[0003] It is known to form irregularities on the peripheral surface of a paper feed roll to prevent paper feed failure (Patent Document 1). For example, Patent Document 1 describes a paper feed roll having multiple ridges and grooves formed parallel to the axial direction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-065907 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-151371 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 addresses the coefficient of friction between the paper feed roll and the paper itself. Meanwhile, Patent Document 2 proposes a sheet feeder equipped with a feed roll and a separation roll. The feed roll is driven to rotate in the sheet transport direction, while the separation roll rotates in the same direction as the feed roll and uses a built-in torque limiter to prevent double-feeding of sheets. Patent Document 2 proposes a method for making the feed roll less hard than the separation roll, thereby creating a slight slippage between the separation roll and the feed roll at their contact points. This allows the feed roll to clean paper dust adhering to the surface of the elastic layer of the separation roll, thereby preventing a decrease in the coefficient of friction of the separation roll due to paper dust. However, the configuration of Patent Document 2 alone is insufficient to prevent double-feeding of sheets after extended use, resulting in a problem in that it cannot resolve paper transport problems (paper jams) after extended use.

[0006] The problem that the present invention aims to solve is to provide a paper feed device, paper feed roll, and separation roll that prevents a decrease in the coefficient of friction of the contact surface with the paper even if paper powder adheres to and accumulates on the surface of the elastic layer of the paper feed roll and the separation roll, and that prevents wear on the surface of the elastic layer of the paper feed roll even after long-term use, thereby providing excellent paper transportability and avoiding paper jams, even after long-term use, by having the separation roll suppress wear on the surface of the elastic layer of the paper feed roll even if there are differences in material type or hardness between the paper feed roll and the separation roll. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the paper feeding device of the present invention comprises a paper feed roll that is driven to rotate and transports paper, and a separation roll that is pressed against the paper feed roll and has a built-in torque limiter to prevent double paper feeding, wherein the paper feed roll and the separation roll each have a shaft and an elastic layer formed on the outer peripheral surface of the shaft, and the elastic layer of the paper feed roll contains a first phase containing ethylene propylene diene rubber (EPDM) and a second phase containing at least one of isoprene rubber (IR) and natural rubber (NR), the JIS-A hardness of the surface of the elastic layer of the paper feed roll is 25 to 50°, the elastic layer of the separation roll contains polyurethane, the surface of the elastic layer of the separation roll has convex portions with a height of 20 to 300 μm, and the JIS-A hardness of the surface of the elastic layer of the separation roll is 45 to 80°.

[0008] In any 2.5 μm×2.5 μm square area of ​​the elastic layer, the area ratio of the second phase is preferably in the range of 30 to 70%. The surface of the elastic layer of the separation roll preferably has convex portions with a height of 60 to 100 μm.

[0009] The paper feed roll according to the present invention is a paper feed roll used in the paper feed device.The separation roll according to the present invention is a separation roll used in the paper feed device. [Effects of the Invention]

[0010] According to the paper feeder of the present invention, the paper feed roll contains a first phase containing ethylene propylene diene rubber (EPDM) and a second phase containing at least one of isoprene rubber (IR) and natural rubber (NR) as its primary components. The JIS-A hardness of the surface of the elastic layer of the paper feed roll is 25 to 50°. The elastic body of the separation roll contains polyurethane as its primary component. The surface of the elastic body of the separation roll has convex portions with a height of 20 to 300 μm. The JIS-A hardness of the surface of the elastic layer of the separation roll is 45 to 80°. Therefore, even if paper powder adheres to and accumulates on the surfaces of the paper feed roll and the elastic layer of the separation roll, the coefficient of friction between the contact surface and the paper is prevented from decreasing, and the separation roll can suppress wear of the surface of the elastic layer of the paper feed roll. As a result, excellent paper transport performance is achieved even after long-term use, and paper jams can be avoided. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of a paper feeder according to an embodiment of the present invention; [Figure 2] This is a diagram of the paper feeding operation of the paper feeder shown in Figure 1. Figure 2(a) shows the state before a sheet of paper arrives between the rolls, and Figure 2(b) shows the operation when a sheet of paper arrives between the rolls. [Figure 3] This is a diagram of the paper feeding operation of the paper feeder shown in Figure 1. Figure 3(a) shows the state before two sheets of paper arrive between the rolls, and Figure 3(b) shows the operation when two sheets of paper arrive between the rolls. [Figure 4] Fig. 4(a) is a schematic view of the appearance of the paper feed roll according to one embodiment, and Fig. 4(b) is a schematic view of the appearance of the separation roll according to one embodiment. [Figure 5] FIG. 5 is a schematic diagram showing a method for measuring the area ratio of the first phase containing ethylene propylene diene rubber (EPDM) constituting the elastic layer of the paper feed roll, and the second phase containing at least one of isoprene rubber (IR) and natural rubber (NR). DETAILED DESCRIPTION OF THE INVENTION

[0012] The paper feeder according to the present invention will now be described in detail.

[0013] As shown in FIG. 1, a paper feeder 10 according to one embodiment of the present invention includes a paper feed roll 12 (feed roll) and a separation roll 14 (retard roll). The paper feed roll 12 includes a shaft 12a and an elastic layer 12b formed on the outer periphery of the shaft 12a. The separation roll 14 includes a shaft 14a and an elastic layer 14b formed on the outer periphery of the shaft 14a. The paper feed roll 12 is driven to rotate by power from a drive source (motor) (not shown) and functions to transport 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) that applies a brake torque in the direction opposite to the transport direction (direction of the arrow) of the paper P.

[0014] The paper sheets to be transported are stacked in a paper feed cassette 16. The surface of an elastic layer 18b 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 18a and an elastic layer 18b formed on the outer periphery of the shaft 18a. The pull-in roll 18 is configured to rotate in conjunction with the drive of the paper feed roll 12 via a connecting member (such as a gear or timing belt) not shown. The above configuration is an example and is not limited to the above configuration.

[0015] 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 has been rotating since before the paper P arrived. 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 the fed sheet of paper P arrives between the rolls, the paper P is conveyed out through the gap between the rolls, as shown in FIG. 2(b).

[0016] 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 is driven to rotate, and the separation roll 14 is driven to rotate against the brake torque as the paper feed roll 12 rotates. When the two fed sheets 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 P1 and P2. Because the frictional force acting between the two sheets P1 and P2 is small, the separation roll 14 stops due to the brake torque and does not follow the rotation of the paper feed roll 12. As a result, the paper P1 in contact with the paper feed roll 12 is conveyed through the rolls as the paper feed roll 12 rotates, while the paper P2 in contact with the separation roll 14 is not conveyed. This prevents multiple sheets of paper P from being fed.

[0017] The elastic layer 12b of the paper feed roll 12 has a first phase containing ethylene propylene diene rubber (EPDM) and a second phase containing at least one of isoprene rubber (IR) and natural rubber (NR). The surface of the elastic layer 12b of the paper feed roll 12 has a JIS-A hardness of 25 to 50°. The surface may be configured with any irregularities, which may be formed by a plurality of convex portions, a plurality of concave portions, or a plurality of convex portions and a plurality of concave portions, such as a grained shape.

[0018] Similarly, the elastic layer 14b of the separation roll 14 contains polyurethane. The elastic layer 14b of the separation roll 14 has convex portions with a height of 20 to 300 μm on its outer peripheral surface. The surface irregularities may be formed by a plurality of convex portions, a plurality of concave portions, or a plurality of convex portions and a plurality of concave portions such as a grained shape. The JIS-A hardness of the surface of the elastic layer 14b of the separation roll 14 is 45 to 80°.

[0019] FIG. 4(a) shows a schematic view of the appearance of the paper feed roll 12 according to one embodiment.

[0020] The elastic layer 12b of the paper feed roll 12 has a first phase containing ethylene propylene diene rubber (EPDM) and a second phase containing at least one of isoprene rubber (IR) and natural rubber (NR). The second phase is preferably isoprene rubber (IR). When the second phase is at least one of isoprene rubber (IR) and natural rubber (NR), the isoprene rubber (IR) or natural rubber (NR) of the second phase is a material with better abrasion resistance than the polyurethane contained in the elastic layer of the paper feed roll, thereby suppressing abrasion of the surface of the elastic layer 12b of the paper feed roll 12 caused by the separation roll 14. As a result, paper transport is excellent even after long-term use, and paper jams can be avoided.

[0021] The elastic layer 12b of the paper feed roll 12, which is composed of two phases of ethylene propylene diene rubber (EPDM) and one or more of isoprene rubber (IR) or natural rubber (NR), preferably has an area ratio of one or more of isoprene rubber (IR) or natural rubber (NR) in an arbitrary 2.5 μm × 2.5 μm square range of 30 to 70%. More preferably, the area ratio is in the range of 40 to 60%, and even more preferably, the area ratio is in the range of 45 to 55%. The area ratios of the first and second phases can be measured by surface analysis using a scanning probe microscope (SPM).

[0022] "Arbitrary" means "at any location." The area ratio of the ethylene propylene diene rubber (EPDM) phase and one or more of the isoprene rubber (IR) or natural rubber (NR) phases is within any 2.5 μm × 2.5 μm square area. Specifically, as shown in Figure 5, an arbitrary cross section of the elastic layer 12b of the paper feed roll 12 is observed, and an arbitrary 20 × 20 μm area in the cross section is divided into 64 sections. 16 diagonally arranged squares indicated by diagonal lines are selected, and the area ratios of the first and second phases within each 2.5 × 2.5 μm square are measured. The values ​​are those that apply to 14 or more of the 16 selected squares (85% or more). Images taken with a scanning probe microscope (SPM) are taken at four locations around the circumferential direction (12 locations in total) at the left end, center, and right end of the elastic layer in the axial direction.

[0023] When the elastic layer 12b of the paper feed roll 12 is uniformly dispersed (finely dispersed) at the paper dust level so that both the ethylene propylene diene rubber (EPDM) phase and one or more phases of either isoprene rubber (IR) or natural rubber (NR) are present in a predetermined ratio within any 2.5 μm x 2.5 μm square area, frictional force control at the paper dust size level and uneven wear on certain parts of the surface of the elastic layer 12b of the paper feed roll 12 by the separation roll 14 can be suppressed, resulting in excellent paper transport properties even after long-term use and avoiding paper jams.

[0024] In this way, in order to uniformly disperse (finely disperse) both the ethylene propylene diene rubber (EPDM) phase and one or more phases of either isoprene rubber (IR) or natural rubber (NR), methods such as using a dispersant that improves the dispersibility of both the ethylene propylene diene rubber (EPDM) phase and one or more phases of either isoprene rubber (IR) or natural rubber (NR) and thoroughly kneading the phases to the desired degree of dispersion can be considered.

[0025] The paper feed roll 12 is configured so that the JIS-A hardness of the surface of the elastic layer 12b is within the range of 25 to 50 degrees, preferably within the range of 30 to 40 degrees. The surface of the elastic layer 12b of the paper feed roll 12 refers to the outer peripheral surface of the elastic layer 12b. The surface hardness of the elastic layer 12b of the paper feed roll 12 can be adjusted by the material composition of the elastic layer 12b, etc. If the JIS-A hardness of the surface of the elastic layer 12b of the paper feed roll 12 is 25 degrees or more, wear of the surface of the elastic layer 12b of the paper feed roll 12 caused by the separation roll 14 can be suppressed. If the JIS-A hardness of the surface of the elastic layer 12b of the paper feed roll 12 is 50 degrees or less, wear of the surface of the elastic layer 14b of the separation roll 14 caused by the paper feed roll 12 can be suppressed. As a result, excellent paper transport properties are achieved even after long-term use, and paper jams can be avoided.

[0026] The elastic layer 12b of the paper feed roll 12 contains, as its main components, a first phase containing ethylene propylene diene rubber (EPDM) and a second phase containing at least one of isoprene rubber (IR) and natural rubber (NR), and may further contain other rubber components such as polypolyurethane rubber, EPDM, chlorinated polyethylene rubber, silicone rubber, and fluororubber. Here, the term "main component" means that the weight ratio of the component in the elastic layer is 60% by weight or more.

[0027] The diene monomer (third component) contained in the EPDM is preferably a diene monomer having 5 to 20 carbon atoms, and specific examples include 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 2,5-dimethyl-1,5-hexadiene, 1,4-octadiene, 1,4-cyclohexadiene, cyclooctadiene, dicyclopentadiene (DCP), 5-ethylidene-2-norbornene (ENB), 5-butylidene-2-norbornene, 2-methallyl-5-norbornene, 2-isopropenyl-5-norbornene, etc. Among these diene monomers (third components), dicyclopentadiene (DCP) and 5-ethylidene-2-norbornene (ENB) are preferred.

[0028] From the viewpoint of wear resistance, the EPDM preferably has a small content of diene monomer (third component), and the content of the third component is preferably in the range of 1 to 7, particularly preferably 10 to 50, in terms of iodine value.

[0029] The amount of diene in the EPDM is preferably 1.5 to 5% by weight, particularly preferably 2 to 4% by weight, from the viewpoint of wear resistance.

[0030] The at least one of isoprene rubber (IR) and natural rubber (NR) may be both isoprene rubber (IR) and natural rubber (NR), or may be either one of them. From the viewpoint of excellent wear resistance, isoprene rubber (IR) is preferred.

[0031] Examples of the dispersant include a polymer having a block made of an ethylene propylene diene rubber (EPDM) component and a block made of at least one of isoprene rubber (IR) and natural rubber (NR), modified natural rubber, and modified isoprene rubber.

[0032] Examples of modified natural rubbers include epoxidized natural rubber, chlorinated natural rubber, and nitrified natural rubber (acrylonitrile natural rubber). Examples of modified isoprene rubbers include epoxidized isoprene rubber, chlorinated isoprene rubber, nitrified isoprene rubber (acrylonitrile isoprene rubber), maleic acid-modified isoprene rubber, and (meth)acrylic acid-modified isoprene rubber. These may be used alone as dispersants, or two or more may be used in combination. Of these, epoxidized natural rubber and epoxidized isoprene rubber are particularly preferred from the viewpoint of particularly excellent dispersing effect.

[0033] Various additives may be added as needed to the elastic layer 12b of the paper feed roll 12. Examples of the additives include lubricants, vulcanization accelerators, antioxidants, light stabilizers, viscosity modifiers, processing aids, flame retardants, plasticizers, fillers, dispersants, antifoaming agents, pigments, and mold release agents.

[0034] Examples of materials for the shaft 12a of the paper feed roll 12 include synthetic resins such as polyacetal (POM), acrylonitrile butadiene styrene copolymer (ABS), polycarbonate, and nylon, and metal materials such as iron, stainless steel, and aluminum. The shaft 12a may be hollow or solid.

[0035] The elastic layer 12b of the paper feed roll 12 is formed by placing the shaft 12a coaxially in the center of a roll molding die, injecting an EPDM composition, heating and curing (crosslinking), and then removing the die from the die to form the elastic layer 12b on the outer periphery of the shaft 12a.

[0036] Fig. 4(b) shows a schematic view of the appearance of one embodiment of the separation roll 14. As shown in Fig. 4(b), the separation roll 14 has a plurality of protrusions 14c on the outer peripheral surface of the elastic layer 14c. The outer peripheral surface of the separation roll 14 is provided with surface irregularities by the plurality of protrusions 14c.

[0037] In Fig. 4(b), the plurality of protrusions 14c are composed of hemispherical protrusions. Also, in Fig. 4(b), the plurality of protrusions 14c are regularly arranged in a staggered pattern on the outer peripheral surface of the elastic layer 14b. Specifically, the second row of protrusions 14c aligned in the axial direction X of the separation roll 14 is arranged between the first row of protrusions 14c aligned in the axial direction X of the separation roll 14, the third row of protrusions 14c aligned in the axial direction X of the separation roll 14 is arranged between the second row of protrusions 14c aligned in the axial direction X of the separation roll 14, and the fourth row of protrusions 14c aligned in the axial direction X of the separation roll 14 is arranged between the third row of protrusions 14c aligned in the axial direction X of the separation roll 14. The multiple protrusions 14c are arranged on the peripheral surface of the elastic layer 14b in the axial direction X of the separation roll 14, but are also arranged in a direction at an angle of 45° with respect to the axial direction X of the separation roll 14. Note that the multiple protrusions 14c are not limited to hemispherical protrusions. Furthermore, the multiple protrusions 14c do not have to be arranged regularly or be arranged in an array.

[0038] The surface of the elastic layer 14b of the separation roll 14 has protrusions 14c with a height of 20 to 300 μm. By setting the height of the protrusions 14c to 20 μm or more, even if paper dust adheres to and accumulates on the surface of the elastic layer 14b of the separation roll 14, a decrease in the coefficient of friction of the contact surface with the paper can be prevented. As a result, paper transport performance is excellent even after long-term use, and paper jams can be avoided. The height of the protrusions 14c is more preferably 30 μm or more, and even more preferably 50 μm or more. On the other hand, the height of the protrusions 14c is 300 μm or less from the viewpoint of suppressing wear on the surface of the elastic layer 12b of the paper feed roll 12 by the separation roll 14. It is preferably 200 μm or less, and more preferably 150 μm or less.

[0039] The separation roll 14 is configured so that the JIS-A hardness of the surface of the elastic layer 14b is within the range of 45 to 80 degrees. The surface of the separation roll 14 refers to the outer peripheral surface of the elastic layer 14b. The surface hardness of the separation roll 14 can be adjusted by the material composition of the elastic layer 14b, etc. If the JIS-A hardness of the surface of the elastic layer 14b of the separation roll 14 is 40 degrees or more, the paper conveying force can be maintained. If the JIS-A hardness of the surface of the elastic layer 14 of the separation roll 14 is 80 degrees or less, the separation roll 14 suppresses abrasion of the surface of the elastic layer 12b of the paper feed roll 12. As a result, excellent paper conveyance properties are achieved even after long-term use, and paper jams can be avoided. The hardness is preferably within the range of 50 to 70 degrees, and more preferably within the range of 55 to 65 degrees.

[0040] The elastic layer 14b of the separation roll 14 is preferably made of a material containing polyurethane as a main component, meaning that the weight ratio of polyurethane in the elastic layer 14b of the separation roll 14 is 60% by weight or more.

[0041] Here, the polyurethane is a polymer having polyurethane bonds formed by the reaction of a polyol component and an isocyanate component. A catalyst or a reaction accelerator may be used to accelerate the addition reaction, and other additives may be used as needed.

[0042] Various additives may be added as needed to the elastic layer 14b and the surface layer 14c of the separation roll 14. Examples of the additives include lubricants, vulcanization accelerators, antioxidants, light stabilizers, viscosity modifiers, processing aids, flame retardants, plasticizers, fillers, dispersants, antifoaming agents, pigments, and mold release agents.

[0043] Examples of materials for the shaft 14a of the separation roll 14 include synthetic resins such as polyacetal (POM), acrylonitrile butadiene styrene copolymer (ABS), polycarbonate, and nylon, and metal materials such as iron, stainless steel, and aluminum. The shaft 14a may be hollow or solid.

[0044] The elastic layer 14b of the separation roll 14 is formed by placing the shaft 14a coaxially in the center of a roll molding die, injecting an unreacted polyurethane composition, heating and curing (crosslinking), and then demolding to form the elastic layer 14b on the outer periphery of the shaft 14a. The molding die may have recesses formed on its inner circumferential surface in shapes corresponding to the protrusions 14c. The protrusions 14c of the elastic layer 14b can be formed, for example, by mold transfer using the molding die.

[0045] In the paper feeder 10 described above, the elastic layer 12b of the paper feed roll 12 includes a first phase containing ethylene propylene diene rubber (EPDM) and a second phase containing at least one of isoprene rubber (IR) and natural rubber (NR), and the surface of the elastic layer 12b of the paper feed roll 12 has a JIS-A hardness of 25 to 50°. The elastic layer 14b of the separation roll 14 includes polyurethane as a main component, and the surface of the elastic layer 14b of the separation roll 14 has convex portions with a height of 20 to 300 μm. The surface of the elastic layer 14b of the separation roll 14 has a JIS-A hardness of 45 to 80°. This prevents wear on the surface of the elastic layer 12b of the paper feed roll due to the elastic layer 14b of the separation roll 14. As a result, paper transport performance is excellent even after long-term use, and paper jams are reduced.

[0046] Furthermore, in the paper feeder 10, the area ratio of the phase containing at least one of isoprene rubber (IR) and natural rubber (NR) is within the range of 30 to 70% within a 2.5 μm × 2.5 μm square area at any location on the elastic layer 12b of the paper feed roll 12, which further prevents uneven wear on the surface of the elastic layer 12b of the paper feed roll 12 due to the elastic layer 14b of the separation roll 14. As a result, paper transportability is excellent even after long-term use, and paper jams are reduced.

[0047] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention.

[0048] Although the paper feed roll 12 in FIG. 4(a) does not show any surface irregularities, it can be configured with any irregularities. The surface irregularities may be formed by a plurality of convex portions, a plurality of concave portions, or a plurality of convex portions and a plurality of concave portions, such as a grained shape. The grained shape refers to a wrinkled pattern. The grained shape can be formed using a molding die whose inner surface is processed by electrical discharge machining or the like. Examples of grained shapes include leather (scale), matte finish, wood grain, rock grain, sand grain, cloth grain, silk grain, streaks (hairline), and geometric patterns.

[0049] 4(b), the outer peripheral surface of the elastic layer 14b is provided with a plurality of convex portions 14c to form a surface irregularity, but the surface irregularity can be formed with any irregularity. The surface irregularity may be formed by a plurality of convex portions, a plurality of concave portions, or a plurality of convex portions and a plurality of concave portions, such as a grained shape.

[0050] Furthermore, in the above embodiment, the plurality of protrusions 14c of the separation roll 14 are hemispherical, but the shape of the plurality of protrusions 14c is not limited to hemispherical protrusions and may be various shapes. Note that the term "spherical" refers to a shape that is approximately spherical and close to a sphere with a curved surface. The term "spherical" includes a true sphere and an oval sphere. The term "semispherical" also includes a shape that is half a sphere cut along a plane passing through the center of a sphere, a shape that is larger than half a sphere cut along a plane not passing through the center of a sphere, or a shape that is smaller than half a sphere. When the protrusions 14c are hemispherical, the contact surface with the paper P is curved, which relatively reduces the generation of paper dust and also provides excellent paper feeding performance.

[0051] Examples of the shape of the protrusion 14c include an amorphous shape, a cylinder, a cone, a spherical truncation, and a wedge shape. Examples of the cylinder include a circular cylinder, an elliptical cylinder, a rectangular cylinder (such as a square cylinder or a pentagonal cylinder), a sector cylinder, a D-shaped cylinder, and a gear-shaped cylinder. The cone may also be a truncated cylinder (such as a truncated circular cylinder or a truncated rectangular cylinder) whose top is cut into a sloped or curved shape. Examples of the cone include a circular cone, an elliptical cone, and a pyramid (such as a square pyramid or a pentagonal pyramid). The cone may also be a truncated pyramid (such as a truncated cone or a truncated rectangular pyramid) whose top is cut into a flat shape (frustum), a sloped or curved shape. A spherical truncation is a solid shape like a sphere cut by two parallel planes. When a sphere intersects with two parallel planes, the portion of the sphere between these two planes is the spherical zone, and the solid body enclosed by the spherical zone and these two planes is the spherical truncation. One of the two planes of the spherical truncation may be a plane that passes through the center of the sphere, or neither of the two planes of the spherical truncation may be a plane that does not pass through the center of the sphere. The two planes of the spherical truncation may be surfaces that are close to flat, and may be curved surfaces with a larger radius of curvature than the spherical zone, for example. In addition, the upper base (upper flat surface) of each of the cylinders, elliptical cylinders, rectangular cylinders, sector-shaped cylinders, D-shaped cylinders, gear-shaped cylinders, truncated cones, and spherical truncations may be polished surfaces. The polished surface can be formed by polishing each upper base.

[0052] In the above embodiment, the multiple protrusions 14c of the separation roll 14 are arranged in a staggered pattern on the circumferential surface of the elastic layer 14b. However, the multiple protrusions 14c may be uniformly distributed or randomly arranged on the circumferential surface of the elastic layer 14b. They may also be arranged in an array. When the protrusions 14c are arranged along the circumferential surface of the elastic layer 14b, grooves are formed between the rows, providing escape routes for generated paper dust, making it easier to discharge the paper dust. The protrusions 14c may be arranged in the circumferential direction along the circumferential surface of the elastic layer 14b, or in a direction different from the circumferential direction. A direction different from the circumferential direction refers to an arrangement along the circumferential surface of the elastic layers 12b and 14b at a predetermined angle relative to the circumferential direction. The protrusions 14c may also be arranged in a spiral pattern along the circumferential surface of the elastic layer 14b. [Example]

[0053] The present invention will be described in detail below using examples and comparative examples.

[0054] (Elastic layer material) <Material 1> This was obtained by mixing 100 parts by mass of a trifunctional polyol (Asahi Glass's "Exenol 5030") with 6.7 parts by mass of a bifunctional polyol (Asahi Glass's "Exenol 2020"), 0.1 parts by mass of a catalyst (Tosoh's "TEDA-L33"), and 8.8 parts by mass of an isocyanate (Tosoh's "Millionate MT"). <Material 2> The material was prepared in the same manner as Material 1, except that the amount of isocyanate (Tosoh's "Millionate MT") was changed to 12.6 parts by mass. <Material 3> The material was prepared in the same manner as Material 1, except that the amount of isocyanate (Tosoh's "Millionate MT") was changed to 6.3 parts by mass. <Material 4> The material was prepared in the same manner as Material 1, except that the amount of isocyanate (Tosoh's "Millionate MT") was changed to 13.5 parts by mass. <Material 5> The material was prepared in the same manner as Material 1, except that the amount of isocyanate (Tosoh's "Millionate MT") was changed to 5.1 parts by mass. <Material 6> The composite was obtained by kneading 50 parts by mass of non-oil-extended EPDM (Sumitomo Chemical's "Esprene 512F") with 30 parts by mass of naphthenic oil (Idemitsu Kosan's "Diana Process NS-100"), 50 parts by mass of IR (Zeon Corporation's "IR2200"), 5 parts by mass of zinc oxide (Sakai Chemical Industry's "Zinc Oxide Type 2"), 0.25 parts by mass of carbon black (CABOT's "Show Black MAF-G"), silica (Tosoh Silica's "Nipseal VN3"), and 3 parts by mass of a peroxide crosslinking agent (NOF's "Perkmill D") using a 6-inch roll. <Material 7> The materials were the same except for the change to 25 parts by mass of naphthenic oil (Idemitsu Kosan's "Diana Process NS-100") 6 was adjusted in the same way. <Material 8> The materials were the same except for the change to 35 parts by mass of naphthenic oil (Idemitsu Kosan's "Diana Process NS-100"). 6 was adjusted in the same way. <Material 9> The materials were the same as above, except for adding 3 parts by mass of dispersant (Kuraray "LIR-290") 6 was adjusted in the same way. <Material 10> The materials are the same as those used in the previous example, except that 100 parts by mass of non-oil-extended EPDM (Sumitomo Chemical's "ESPLENE 512F") is used and IR (ZEON Corporation's "IR2200") is not used. 6 was adjusted in the same way as 。

[0055] (Adjustment of forming die for separation roll) A cylindrical molding die for the elastic layer with an inner diameter of 20 mm was prepared. The inner peripheral surface of the prepared molding die for the elastic layer was subjected to electrical discharge machining using an electrical discharge machine ("DIAX VX10" manufactured by Mitsubishi Electric Corporation). The electrical discharge machining was performed to impart a convex shape of any height to the surface of the elastic layer to be molded. The height of the elastic layer was adjusted according to the electrical discharge machining conditions.

[0056] (Production of paper feed roll) In Examples 1 to 11 and Comparative Examples 1 to 8, a shaft having a diameter of 6 mm was attached to a cylindrical inner layer molding die having an inner diameter of 12 mm. Elastic layer compositions (Materials 4 to 8) were injected into this die under pressure. The die was then heated to 150°C to crosslink the elastic layer composition, thereby forming the elastic layer of the paper feed roll. After heating, the molded body was removed from the die, and the paper feed rolls of Examples 1 to 11 and Comparative Examples 1 to 8 were produced.

[0057] (Preparation of separation roll) In Examples 1 to 11 and Comparative Examples 1 to 8, a 6 mm diameter shaft was attached to a cylindrical inner layer molding die with an inner diameter of 12 mm. The liquid polyurethane rubber compositions (Materials 1 to 3) prepared above were poured into this die. The die was then heated to 120°C to harden the polyurethane rubber composition and form an elastic layer made of polyurethane rubber. After heating, the cylindrical molded body with the elastic layer formed on the outer periphery of the shaft was removed from the die to produce the separation rolls of Examples 1 to 11 and Comparative Examples 1 to 8.

[0058] For the separation rolls of Examples 1 to 11 and Comparative Examples 1 to 8, the conditions for the electrical discharge machining of the molding die were adjusted so that the height of the convex portions on the surface of the formed elastic layer was 80 μm (Example 1), 20 μm (Example 2), 300 μm (Example 3), 80 μm (Examples 4 to 9, Comparative Examples 1 to 6), 60 μm (Example 10), 100 μm (Example 11), 350 μm (Comparative Example 7), and 10 μm (Comparative Example 8), respectively.

[0059] (surface hardness measurement) The surface hardness of the paper feed roll was measured as the JIS-A hardness of the surface of the elastic layer of the paper feed roll.Similarly, the surface hardness of the separation roll was measured as the JIS-A hardness of the surface of the elastic layer of the separation roll.

[0060] (surface height measurement) The surface height of the elastic layer of the paper feed roll is the distance from the elastic layer to the point where the convexity is at its highest, and was determined by analyzing a cross-sectional photograph.

[0061] (Durability evaluation) The paper feed roll and separation roll were installed in a commercially available copier with an FRR paper feed system, and paper feeding performance was evaluated. Commercially available PPC paper was used, and 300,000 sheets were fed through, and the number of paper jams was measured. Those with one or fewer paper jams were rated "A," those with two to four paper jams were rated "B," those with five to six paper jams were rated "C," those with seven to ten paper jams were rated "D," and those with 11 or more paper jams were rated "E."

[0062] (area ratio) Measurements were made using a scanning probe microscope (Shimadzu Corporation, "SPM-9700"), as shown in Figure 5. An arbitrary surface of the elastic layer was observed, and an arbitrary 20 × 20 μm area on that surface was divided into 64 sections, and 16 squares arranged diagonally with diagonal lines were selected. The area proportions of the first and second phases in each 2.5 μm × 2.5 μm square were measured, and the values ​​were determined to be those that applied to 14 or more of the 16 squares (8.5% or more). Measurement locations: 4 locations around the left, center, and right ends of the elastic layer (12 locations in total) Cantilever: SI-DF40 Scanning range: 5.0000μm Scanning speed: 1.00Hz

[0063] [Table 1]

[0064] [Table 2]

[0065] In Comparative Example 1, the material of the elastic layer of the paper feed roll did not contain at least one of isoprene rubber (IR) and natural rubber (NR), resulting in frequent paper jams in a durability test of 300,000 sheets. In Comparative Example 2, the material of the elastic layer of the separation roll was not polyurethane, resulting in frequent paper jams in a durability test of 300,000 sheets. In Comparative Example 3, the hardness of the elastic layer of the paper feed roll was greater than 50°, resulting in frequent paper jams in a durability test of 300,000 sheets. In Comparative Example 4, the hardness of the elastic layer of the paper feed roll was less than 25°, resulting in frequent paper jams in a durability test of 300,000 sheets. In Comparative Example 5, the hardness of the elastic layer of the separation roll was greater than 80°, resulting in frequent paper jams in a durability test of 300,000 sheets. In Comparative Example 6, the hardness of the elastic layer of the separation roll was less than 45°, resulting in frequent paper jams in a durability test of 300,000 sheets. In Comparative Example 7, the surface convex height of the elastic layer of the separation roll was more than 300 μm, so there were many paper jams in the durability test of passing 300,000 sheets.In Comparative Example 8, the surface convex height of the elastic layer of the separation roll was less than 20 μm, so there were many paper jams in the durability test of passing 300,000 sheets.

[0066] According to the examples and comparative examples, the paper feed roll has a first phase containing ethylene propylene diene rubber (EPDM) and a second phase containing at least one of isoprene rubber (IR) and natural rubber (NR). The JIS-A hardness of the surface of the elastic layer of the paper feed roll is 25 to 50°. The elastic body of the separation roll contains polyurethane. The surface of the separation roll elastic body has convex portions with a height of 20 to 300 μm. The JIS-A hardness of the surface of the elastic layer of the separation roll 14 is 45 to 80°. Therefore, even if paper powder adheres to and accumulates on the surfaces of the paper feed roll and the elastic layer of the separation roll, the coefficient of friction between the contact surface and the paper is prevented from decreasing, and wear of the surface of the elastic layer of the paper feed roll by the separation roll is suppressed. As a result, it can be seen that excellent paper transport performance is achieved even after long-term use, and paper jams can be avoided.

[0067] Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above embodiments and examples, and various modifications are possible within the scope of the invention. [Explanation of symbols]

[0068] 10 Paper feeder 12 Paper feed roll 12a Shaft body 12b Elastic layer 14 Separation Roll 14a Shaft body 14b Elastic layer 14c Convex part 16 Paper cassette 18 Pull-in roll 18a Shaft body 18b Elastic layer P paper

Claims

1. a paper feed roll that is driven to rotate and transports paper; a separation roll that is pressed against the paper feed roll and has a built-in torque limiter to prevent double paper feeding; The paper feed roll and the separation roll each have a shaft body and an elastic layer formed on an outer circumferential surface of the shaft body, the elastic layer of the paper feed roll has a first phase containing ethylene propylene diene rubber (EPDM) and a second phase containing at least one of isoprene rubber (IR) and natural rubber (NR); the JIS-A hardness of the surface of the elastic layer of the paper feed roll is 25 to 50°; the elastic layer of the separation roll contains polyurethane, the surface of the elastic layer of the separation roll has convex portions with a height of 20 to 300 μm; the JIS-A hardness of the surface of the elastic layer of the separation roll is 45 to 80°; A paper feeder characterized in that the area ratio of the second phase is in the range of 20 to 80% within a 2.5 μm×2.5 μm square area at any location on the elastic layer of the paper feed roll.

2. 2. The paper feed device according to claim 1, wherein the area ratio of the second phase is in the range of 30 to 70% within a 2.5 μm x 2.5 μm square area at any location on the elastic layer of the paper feed roll.

3. 3. The paper feeder according to claim 1, wherein the surface of the elastic layer of the separation roll has convex portions with a height of 60 to 100 μm.

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