JP7742771B2 - Paper feeder, paper feed roll and separation roll - Google Patents

Description

The present invention relates to a paper feeder, paper feed roll, and separation roll that are suitable for use in electrophotographic devices such as copying machines, printers, and facsimiles that employ electrophotography.

In electrophotographic devices such as copiers, printers, and facsimiles that use electrophotography, paper feed rolls are cylindrically formed from elastic materials such as cross-linked rubber, and their circumferential surfaces are the contact surfaces with the paper. Paper dust generated from 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. As paper dust accumulates, the contact area of the circumferential surface with the paper decreases, lowering the coefficient of friction of the contact surface with the paper. Furthermore, if the paper feed roll and separation roll are made of different materials or have different hardness levels, 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 extended use.

It is known to form irregularities on the peripheral surface of a paper feed roll to prevent paper transport problems (Patent Document 1). For example, Patent Document 1 describes a paper feed roll with multiple raised ridges and recessed grooves formed parallel to the axial direction.

Japanese Patent Application Laid-Open No. 2017-065907 Japanese Patent Application Laid-Open No. 2001-151371

Patent Document 1 addresses the coefficient of friction between the paper feed roll and the paper itself. Meanwhile, Patent Document 2 proposes an invention for a sheet supplying device 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. In Patent Document 2, the hardness of the feed roll is lower than that of the separation roll, creating slight slippage between the separation roll and the feed roll at the pressure contact point between them. This allows the feed roll to clean paper dust adhering to the surface of the separation roll's elastic layer, preventing a decrease in the coefficient of friction of the separation roll due to paper dust. However, the configuration in Patent Document 2 alone is insufficient to prevent double-feeding of sheets after extended use, resulting in the problem of being unable to resolve paper transport problems (paper jams) after extended use.

The problem that this invention aims to solve is to provide a paper feeder, 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 dust adheres to and accumulates on the surface of the elastic layer of the paper feed roll and the separation roll, and that suppresses wear on the surface of the elastic layer of the paper feed roll even if the paper feed roll and the separation roll are made of different materials or have different hardnesses, thereby providing excellent paper transport performance and preventing paper jams even after long-term use.

To solve the above problem, the paper feed 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. The paper feed roll and separation roll each have a shaft and an elastic layer formed on the outer surface of the shaft. 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. The JIS-A hardness of the surface of the elastic layer of the separation roll is 45 to 80°.

It is preferable that the area ratio of the second phase is in the range of 30 to 70% within any 2.5 μm×2.5 μm square area of the elastic layer.
The surface of the elastic layer of the separation roll preferably has convex portions with a height of 60 to 100 μm.

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.

In the paper feed device according to the present invention, the paper feed roll contains, as its primary 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). 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, as its primary component, polyurethane. 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 dust adheres to and accumulates on the surfaces of the paper feed roll and the elastic layer of the separation roll, a decrease in the coefficient of friction of the contact surface with the paper is prevented, and wear of the surface of the elastic layer of the paper feed roll by the separation roll is suppressed. As a result, excellent paper transport performance is achieved even after long-term use, and paper jams can be avoided.

1 is a schematic diagram of a paper feeder according to an embodiment of the present invention; 2A and 2B are diagrams illustrating the paper feeding operation of the paper feeder shown in Fig. 1. Fig. 2A illustrates the state before a sheet of paper arrives between the rolls, and Fig. 2B illustrates the operation when a sheet of paper arrives between the rolls. 3A and 3B are diagrams illustrating the paper feeding operation of the paper feeder shown in Fig. 1. Fig. 3A illustrates the state before two sheets of paper arrive between the rolls, and Fig. 3B illustrates the operation when the two sheets of paper arrive between the rolls. 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. 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).

The paper feeder according to the present invention will be described in detail below.

As shown in FIG. 1, a paper feed device 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 has a shaft 12a and an elastic layer 12b formed on the outer periphery of the shaft 12a. The separation roll 14 has 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 has a built-in torque limiter (not shown) that is configured to apply a brake torque in the direction opposite to the transport direction of paper P (the direction of the arrow).

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.

As the paper feed roll 12 rotates, the retraction roll 18 rotates, and paper P is unwound one sheet at a time from the paper feed cassette 16 toward the paper feed roll 12. As shown in Figure 2(a), the paper feed roll 12 begins to rotate before the paper P arrives. The separation roll 14, which is pressed against the paper feed roll 12, rotates against the brake torque as the paper feed roll 12 rotates due to the frictional force between the paper feed roll 12 and the separation roll 14 (between the rolls). When a single unwound sheet of paper P arrives between the rolls, the paper P is conveyed out through the gap between the rolls, as shown in Figure 2(b).

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 arrival of the sheets P1 and P2, 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 sheet P1 in contact with the paper feed roll 12 is conveyed through the rolls as the paper feed roll 12 rotates, while the sheet P2 in contact with the separation roll 14 is not conveyed. This prevents multiple sheets of paper P from being fed.

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 JIS-A hardness of the surface of the elastic layer 12b of the paper feed roll 12 is 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.

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 multiple convex portions, multiple concave portions, or multiple convex portions and multiple concave portions, such as a grained pattern. The JIS-A hardness of the surface of the elastic layer 14b of the separation roll 14 is 45 to 80°.

Figure 4(a) shows a schematic diagram of the appearance of one embodiment of the paper feed roll 12.

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 one or more of isoprene rubber (IR) or natural rubber (NR). The second phase is preferably isoprene rubber (IR). When the second phase is one or more of isoprene rubber (IR) or 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.

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) phases in the range of 30 to 70% within any 2.5 μm x 2.5 μm square area. 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).

"Arbitrary" means anywhere. The area ratio of the ethylene propylene diene rubber (EPDM) phase and one or more phases of isoprene rubber (IR) or natural rubber (NR) is within any 2.5 μm x 2.5 μm square. Specifically, as shown in Figure 5, an arbitrary cross section of the elastic layer 12b of the paper feed roll 12 is observed, and any 20 x 20 μm area on that cross section is divided into 64 sections. 16 diagonally lined squares are selected, and the area ratios of the first and second phases within each 2.5 x 2.5 μm square are measured. At least 14 of the 16 selected squares (at least 8.5%) meet these values. Scanning probe microscope (SPM) imaging is performed at four circumferential locations (12 locations total) on the left, center, and right ends of the elastic layer in the axial direction.

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 performance and avoidance of paper jams even after long-term use.

In this way, to achieve uniform dispersion (fine dispersion) of 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), or thoroughly kneading the mixture to the desired degree of dispersion, can be considered.

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, it is 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 on 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 on 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, paper transport performance is excellent even after long-term use, and paper jams can be avoided.

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.

The diene monomer (third component) contained in the EPDM is preferably a diene monomer having 5 to 20 carbon atoms, specifically 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.

From the standpoint of abrasion resistance, the above-mentioned EPDM preferably has a low content of diene monomer (third component), and the content of the third component is preferably in the range of 1 to 7 in terms of iodine value, and particularly preferably in the range of 10 to 50.

In addition, from the standpoint of abrasion resistance, the diene content of the above EPDM is preferably 1.5 to 5% by weight, and particularly preferably 2 to 4% by weight.

The aforementioned at least one of isoprene rubber (IR) and natural rubber (NR) may be both isoprene rubber (IR) and natural rubber (NR), or just one of them. Isoprene rubber (IR) is preferred from the standpoint of excellent abrasion resistance, etc.

Examples of the dispersant include a polymer having a block of ethylene propylene diene rubber (EPDM) and a block of at least one of isoprene rubber (IR) and natural rubber (NR), as well as modified natural rubber and modified isoprene rubber.

Examples of modified natural rubber include epoxidized natural rubber, chlorinated natural rubber, and nitrified natural rubber (acrylonitrile natural rubber). Examples of modified isoprene rubber 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 because of their particularly excellent dispersing effect.

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

The shaft 12a of the paper feed roll 12 can be made of synthetic resins such as polyacetal (POM), acrylonitrile butadiene styrene copolymer (ABS), polycarbonate, and nylon, or metals such as iron, stainless steel, and aluminum. The shaft 12a can be hollow or solid.

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 the EPDM composition, heating and curing (crosslinking), and then removing it from the die to form the elastic layer 12b on the outer periphery of the shaft 12a.

Figure 4(b) shows a schematic view of the appearance of one embodiment of the separation roll 14. As shown in Figure 4(b), the separation roll 14 has multiple convex portions 14c on the outer peripheral surface of the elastic layer 14c. The multiple convex portions 14c provide surface irregularities on the outer peripheral surface of the separation roll 14.

In FIG. 4(b), the multiple protrusions 14c are composed of hemispherical protrusions. Also, in FIG. 4(b), the multiple 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° 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 arranged in an array.

The surface of the elastic layer 14b of the separation roll 14 has convex portions 14c with a height of 20 to 300 μm. By ensuring that the height of the convex portions 14c is 20 μm or more, it is possible to prevent a decrease in the coefficient of friction of the contact surface with the paper, even if paper dust adheres to and accumulates on the surface of the elastic layer 14b of the separation roll 14. As a result, paper transport is excellent even after long-term use, and paper jams can be avoided. The height of the convex portions 14c is more preferably 30 μm or more, and even more preferably 50 μm or more. On the other hand, the height of the convex portions 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.

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 higher, 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, wear on the surface of the elastic layer 12b of the paper feed roll 12 by the separation roll 14 is suppressed. As a result, excellent paper conveyance is 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.

The elastic layer 14b of the separation roll 14 is preferably made of a material containing polyurethane as its main component. "Main component" means that the weight percentage of polyurethane in the elastic layer 14b of the separation roll 14 is 60% or more.

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

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

The shaft 14a of the separation roll 14 can be made of synthetic resins such as polyacetal (POM), acrylonitrile butadiene styrene copolymer (ABS), polycarbonate, and nylon, or metals such as iron, stainless steel, and aluminum. The shaft 14a can be hollow or solid.

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 unreacted polyurethane composition, heating and curing (crosslinking), and then demolding to form the elastic layer 14b on the outer periphery of the shaft 14a. A molding die with recesses formed on its inner circumferential surface in a shape corresponding to the protrusions 14c can be used. The protrusions 14c of the elastic layer 14b can be formed, for example, by mold transfer using the molding die.

In the paper feed device 10 described above, the elastic layer 12b of the paper feed roll 12 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 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 contains polyurethane as a primary component. 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, excellent paper transport performance is achieved, even after long-term use, and paper jams are reduced.

In addition, in the paper feed device 10, the area ratio of phases 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 x 2.5 μm square area at any location on the elastic layer 12b of the paper feed roll 12, thereby further preventing 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 transport performance is excellent even after long-term use, and paper jams are reduced.

The above describes an embodiment of the present invention, but the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the spirit of the present invention.

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

The separation roll 14 in Figure 4(b) has multiple convex portions 14c that provide surface irregularities on the outer peripheral surface of the elastic layer 14b, but the surface irregularities can be configured with any type of irregularity. The surface irregularities may be formed by multiple convex portions, multiple concave portions, or multiple convex portions and multiple concave portions, such as a grained shape.

In the above embodiment, the multiple protrusions 14c of the separation roll 14 are hemispherical, but the shape of the multiple protrusions 14c is not limited to hemispherical protrusions and may be various shapes. Note that a "spherical" refers to a shape that is approximately spherical and close to a sphere with a curved surface. Spheres include true spheres and ellipsoidal shapes. Hemispherical shapes also include shapes that are half a sphere cut along a plane passing through the center of a sphere, shapes that are larger than half a sphere cut along a plane that does not pass through the center of a sphere, and shapes that are smaller than half a sphere. When the protrusions 14c are hemispherical, the surface that comes into contact with the paper P is curved, which relatively reduces the generation of paper dust and also provides excellent paper feeding performance.

Positions 14c may have an irregular shape, a cylinder, a cone, a spherical truncation, a wedge, or the like. Examples of cylinders include circular cylinders, elliptical cylinders, rectangular cylinders (e.g., square cylinders, pentagonal cylinders), fan-shaped cylinders, D-shaped cylinders, and gear-shaped cylinders. They may also be truncated cylinders (e.g., truncated circular cylinders and truncated rectangular cylinders) in which the head of a cylinder is cut into a sloped or curved shape. Examples of cones include circular cones, elliptical cones, and pyramids (e.g., square pyramids and pentagonal pyramids). They may also be truncated cones (e.g., truncated cones and truncated rectangular pyramids) in which the head of a cone is cut into a flat shape (frustum), a sloped or curved shape. A spherical truncation is a solid shape resembling 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 a spherical truncation. One of the two planes of the spherical truncation may pass through the center of the sphere, or neither of the two planes may pass through the center of the sphere. The two planes of the spherical truncation may be nearly flat, and may be curved surfaces with a larger radius of curvature than the spherical zone, for example. Furthermore, 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. A polished surface can be formed by polishing each upper base.

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 and arranged on the circumferential surface of the elastic layer 14b, or may be arranged randomly. 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 in a direction at a predetermined angle to the circumferential direction along the circumferential surfaces of the elastic layers 12b and 14b. The protrusions 14c may also be arranged in a spiral pattern along the circumferential surface of the elastic layer 14b.

The present invention will be explained in detail below using examples and comparative examples.

(Material of Elastic Layer)
<Material 1>
This was obtained by mixing 100 parts by mass of a trifunctional polyol ("EXCENOL 5030" manufactured by Asahi Glass Co., Ltd.), 6.7 parts by mass of a bifunctional polyol ("EXCENOL 2020" manufactured by Asahi Glass Co., Ltd.), 0.1 parts by mass of a catalyst ("TEDA-L33" manufactured by Tosoh Co., Ltd.), and 8.8 parts by mass of an isocyanate ("Millionate MT" manufactured by Tosoh Co., Ltd.).
<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>
Material 1 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>
Material 1 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 mixture was obtained by kneading 50 parts by mass of non-oil-extended EPDM (Esprene 512F manufactured by Sumitomo Chemical Co., Ltd.) with 30 parts by mass of naphthenic oil (Diana Process NS-100 manufactured by Idemitsu Kosan Co., Ltd.), 50 parts by mass of IR (IR2200 manufactured by Zeon Corporation), 5 parts by mass of zinc oxide (Zinc Oxide Type 2 manufactured by Sakai Chemical Industry Co., Ltd.), 0.25 parts by mass of carbon black (Showblack MAF-G manufactured by CABOT Corporation), silica (Nipseal VN3 manufactured by Tosoh Silica Co., Ltd.), and 3 parts by mass of a peroxide crosslinking agent (Perkmyl D manufactured by NOF Corporation) using a 6-inch roll.
<Material 7>
The same preparation as for Material 6 was carried out, except that naphthenic oil (Diana Process NS-100 manufactured by Idemitsu Kosan) was used in place of 25 parts by mass.
<Material 8>
The same preparation as for Material 6 was carried out, except that naphthenic oil (Diana Process NS-100 manufactured by Idemitsu Kosan) was used in place of 35 parts by mass.
<Material 9>
The same preparation as for Material 6 was carried out except that 3 parts by mass of a dispersant ("LIR-290" manufactured by Kuraray) was added.
<Material 10>
A mixture of 100 parts by mass of non-oil-extended EPDM (Esprene 512F manufactured by Sumitomo Chemical) was prepared in the same manner as in Material 6 , except that IR (IR2200 manufactured by Zeon Corporation) was not used .

(Adjustment of molding 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.

(Preparation of paper feed 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. 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 and form the elastic layer of the paper feed roll. After heating, the molded body was removed from the die to produce the paper feed rolls of Examples 1 to 11 and Comparative Examples 1 to 8.

(Preparation of Separation 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. 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 cure 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.

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 dies 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.

(Measurement of surface hardness)
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.

(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.

(Durability evaluation)
The paper feed roll and separation roll were installed in a commercially available copier with an FRR paper feed system, and paper feed performance was evaluated. Commercially available PPC paper was used, and 300,000 sheets were passed through, and the number of paper jams was measured. A rating of "A" was given for a paper jam that occurred once or less, a rating of "B" for a paper jam that occurred between two and four times, a rating of "C" for a paper jam that occurred between five and six times, a rating of "D" for a paper jam that occurred between seven and ten times, and a rating of "E" for a paper jam that occurred 11 or more times.

(area ratio)
Measurement was performed using a scanning probe microscope (Shimadzu Corporation, "SPM-9700"), as shown in Figure 5. Any surface of the elastic layer was observed, and any 20 x 20 µm area on the surface was divided into 64 sections, and 16 squares arranged diagonally with diagonal lines were selected. The area proportions of the first phase and the second phase within each 2.5 µm x 2.5 µm square were measured, and the values corresponding to 14 or more squares (8.5% or more) of the 16 squares were determined.
Measurement locations: 4 locations in the circumferential direction on the left end, center, and right end of the elastic layer (12 locations in total)
・Cantilever: SI-DF40
Scanning range: 5.0000 μm
Scanning speed: 1.00 Hz

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) or 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 lower 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 higher than 300 μm, resulting in frequent paper jams in a durability test of 300,000 sheets. In Comparative Example 8, the surface convex height of the elastic layer of the separation roll was lower than 20 μm, resulting in frequent paper jams in a durability test of 300,000 sheets.

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 dust adheres to and accumulates on the surfaces of the elastic layers of the paper feed roll and separation roll, the coefficient of friction of the contact surface with 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.

The above describes embodiments and examples of the present invention, but the present invention is not limited to these embodiments and examples, and various modifications are possible within the scope of the spirit of the present invention.

10 Paper feeding device 12 Paper feed roll 12a Shaft body 12b Elastic layer 14 Separation roll 14a Shaft body 14b Elastic layer 14c Convex portion 16 Paper feed cassette 18 Pull-in roll 18a Shaft body 18b Elastic layer P Paper

Claims (3)

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 . The paper feed device described in claim 1, characterized in that the area ratio of the second phase is within 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. The paper feeder described in claim 1 or 2, characterized in that the surface of the elastic layer of the separation roll has convex portions with a height of 60 to 100 μm.