Bearing

Abstract

To provide a bearing capable of reducing slide resistance by reducing a contact area of slide faces.SOLUTION: A relationship between a radius of curvature of a concave surface on an outer peripheral surface of a slide member 12 and a radius of curvature of a convex surface on an inner peripheral surface of an outer ring 11 satisfies: radius of curvature of concave surface>radius of curvature of convex surface, and the difference between the radius of curvature of the concave surface on the outer peripheral surface of the slide member 12 and the radius of curvature of the convex surface on the inner peripheral surface of the outer ring 11 is minimum at an axial central portion, and increased toward axial both end portions from the axial central portion, thus the slide faces are only partially kept into contact with each other, a contact area of the slide faces is reduced, and slide resistance can be reduced. Further as a gap between the concave surface on the outer peripheral surface of the slide member 12 and the convex surface on the inner peripheral surface of the outer ring 11 is increased from the axial central portion toward the axial both end portions, discharging of abrasion powder generating in sliding is enhanced, and foreign matters entering the slide faces can be easily discharged.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a bearing composed of a metal inner ring and outer ring and a resin sliding member, wherein the inner ring, outer ring, and sliding member are each formed in a cylindrical shape.

Background Art

[0002] Conventionally, slide doors applied to vehicles typified by automobiles sometimes apply electric slide doors mainly in consideration of convenience during boarding and alighting. The door opening / closing mechanism of this electric slide door has a structure in which a wire cable opens and closes via a pulley mechanism. The pulley is mainly made of resin, and a rolling bearing is applied for driving the pulley (Patent Document 1).

[0003] Generally, a rolling bearing reduces friction by the rolling contact of rolling elements interposed between opposing raceway rings, and has become widely popular as a bearing for general machinery due to its excellent low torque property. However, since a rolling bearing consists of a large number of parts such as an inner ring, outer ring, rolling elements, and a cage, the assembly and manufacturing costs tend to increase. Also, since it requires a storage space for the rolling elements, there is a certain limit to the miniaturization of the bearing. Furthermore, for low noise, high-precision machining is required, resulting in a significant increase in manufacturing costs. Therefore, a sliding bearing is often used as an alternative.

[0004] The above-described sliding bearing is configured by providing a bearing hole in an outer peripheral member made of sintered oil-impregnated metal, resin, or the like, and inserting an inner peripheral member such as a shaft through a minute bearing clearance in the bearing hole. In such a sliding bearing, the bearing life, torque, contact accuracy, etc. are greatly affected by the size of the bearing clearance, so it is necessary to strictly manage the bearing clearance. Also, for a sliding bearing, since the mating member often has another function such as a support shaft, it is usually necessary to separately manufacture the inner peripheral member and the outer peripheral member. However, since both members must be precisely machined, it is laborious, and it is difficult to manage the dimensions and shape of the bearing clearance, easily leading to a decrease in functionality due to defects in the bearing clearance.

[0005] As means for solving these problems, there is known a sliding bearing composed of an outer ring and an inner ring, in which an annular projection or an annular groove formed on the inner peripheral portion of the outer ring engages with an annular groove or an annular projection formed on the outer peripheral portion of the inner ring (Patent Document 2). Further, there is known a sliding bearing composed of an outer ring and an inner ring, wherein the inner ring is made of a resin composition that has been melt-cured, and the bearing clearance between the inner ring and the outer ring is formed by the shrinkage of the resin during the curing of the inner ring (Patent Document 3). Further, there is known a sliding bearing composed of an outer ring and an inner ring, which, in a cross-sectional view in the axial direction, consists of an inner ring having a convex curved outer peripheral surface and an outer ring having an inner peripheral surface that is a concave curved surface corresponding to the convex curved surface of the outer peripheral surface of the inner ring (Patent Document 4).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in Patent Document 2, although it has a structure in which the inner ring and the outer ring respectively have an annular groove and an annular projection, the portion excluding the annular projection portion and the annular groove portion has a flat portion. As the sliding area increases, the sliding resistance relatively increases. Further, when the annular groove and the annular projection are worn, it is difficult for the wear powder to be discharged outside the bearing, and there is a concern that it will accumulate in the annular groove portion and deteriorate the bearing slidability.

[0008] In Patent Document 3, a sliding bearing is provided which is formed of an inner ring made of a molten resin and an outer ring made of a member such as ceramic or a member that is not affected by the temperature during injection molding of the inner ring in addition to metal. However, when assembling the bearing and the shaft, a clearance is provided to prevent the shaft from coming off or rotating. When the inner ring is made of resin, due to the difference in physical properties between the resin and the metal shaft, the inner ring expands during the assembly of the bearing, and sufficient clearance cannot be ensured between the shaft and the inner ring, resulting in a decrease in the bearing function due to the shaft coming off or rotating during the assembly operation. In addition, there is a concern that the sliding performance of the bearing deteriorates due to the expansion of the inner ring during assembly with the shaft and the narrowing of the gap with the outer ring.

[0009] In Patent Document 4, a concave curved surface on the inner peripheral surface of the outer ring and a convex curved surface on the outer peripheral surface of the inner ring cause an inclination in the axial direction and a relative displacement of the inner and outer rings in the axial direction along each other's surfaces, resulting in the generation of an uneven load on the bearing sliding portion and uneven wear due to this, which may lead to a decrease in the bearing function.

[0010] The present invention has been made in view of the above circumstances, and the object thereof is to (1) prevent the shaft from coming off or rotating during the assembly operation by ensuring a clearance with the shaft, (2) reduce the sliding resistance by reducing the contact area of the sliding surface, and (3) provide a bearing capable of promoting the discharge of wear powder generated during sliding.

Means for Solving the Problems

[0011] In order to achieve the above object, in the invention according to claim 1, A bearing comprising a metal inner ring and outer ring and a resin sliding member, wherein the inner ring, the outer ring, and the sliding member are each formed in a cylindrical shape, The sliding member is formed on the outer peripheral surface of the inner ring, The outer peripheral surface of the sliding member has a concave curved surface in the cross section in the axial direction over the entire circumferential length, The radius of curvature of the concave curved surface on the outer peripheral surface of the sliding member is minimum at the central portion in the axial direction and increases toward both ends in the axial direction, The inner peripheral surface of the outer ring has a convex curved surface in the axial cross-section over the entire circumferential length. The radius of curvature of the convex curved surface on the inner peripheral surface of the outer ring is constant in the axial direction. The relationship between the radius of curvature of the concave curved surface on the outer peripheral surface of the sliding member and the radius of curvature of the convex curved surface on the inner peripheral surface of the outer ring is that the radius of curvature of the concave curved surface > the radius of curvature of the convex curved surface. The difference between the radius of curvature of the concave curved surface on the outer peripheral surface of the sliding member and the radius of curvature of the convex curved surface on the inner peripheral surface of the outer ring is minimum at the central portion in the axial direction and increases towards both axial ends. The concave curved surface on the outer peripheral surface of the sliding member and the convex curved surface on the inner peripheral surface of the outer ring are in opposed contact and slide against each other.

[0012] In the invention according to claim 2, in the bearing according to claim 1, the sliding member is mainly composed of one or more synthetic resins selected from nylon, polyacetal, polyphenylene sulfide, polyetherimide, and polyethylene, and contains 1 to 15% by volume of one or more fibrous particles selected from glass fiber particles, ceramic fiber particles, carbon fiber particles, aramid fiber particles, acrylic fiber particles, and polyvinyl alcohol fiber particles. ru ko It is characterized by the above.

[0013] In the invention according to claim 3, in the bearing according to claim 2, the sliding member further contains 1 to 20% by volume of one or more solid lubricants selected from graphite, molybdenum disulfide, tungsten disulfide, boron nitride, and polytetrafluoroethylene. ru ko It is characterized by the above.

[0014] In the invention according to claim 4, in the bearing according to claim 2 or claim 3, the sliding member further contains 1 to 10% by volume of one or more fillers selected from CaF2, CaCo3, talc, mica, mullite, iron oxide, calcium phosphate, potassium titanate, and Mo2C. ru ko It is characterized by the above.

[0015] In the invention according to claim 5, in the bearing according to any one of claims 1 to 4, the inner ring and the outer ring are made of an iron alloy.

Advantages of the Invention

[0016] In the present invention, in a bearing composed of a metal inner ring and outer ring and a resin sliding member, the sliding member is formed on the outer peripheral surface of the inner ring, and the concave curved surface on the outer peripheral surface of the sliding member and the convex curved surface on the inner peripheral surface of the outer ring are in opposed contact and slide. In such a configuration, by making the inner ring made of metal, the expansion of the inner ring during the assembly of the bearing due to the difference in physical properties from the mating metal shaft is prevented, sufficient tightening allowance is ensured between the shaft and the inner ring, and a decrease in the bearing function due to the occurrence of disengagement or rotation during the assembly operation, and a deterioration in slidability due to the narrowing of the gap between the sliding surfaces of the inner ring and the sliding member can be prevented.

[0017] Further, the relationship between the radius of curvature of the concave curved surface on the outer peripheral surface of the sliding member and the radius of curvature of the convex curved surface on the inner peripheral surface of the outer ring is such that the radius of curvature of the concave curved surface > the radius of curvature of the convex curved surface, and the difference between the radius of curvature of the concave curved surface on the outer peripheral surface of the sliding member and the radius of curvature of the convex curved surface on the inner peripheral surface of the outer ring is minimized at the central portion in the axial direction and increases from the central portion in the axial direction toward both axial ends. Thus, the sliding surfaces only partially contact each other, the contact area of the sliding surfaces becomes small, and the sliding resistance can be reduced. Also, the gap between the concave curved surface on the outer peripheral surface of the sliding member and the convex curved surface on the inner peripheral surface of the outer ring increases from the central portion in the axial direction toward both axial ends. Therefore, the discharge of wear powder generated during sliding can be promoted, and foreign matter that has entered the sliding surface can be easily discharged.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

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Figure 15

Modes for Carrying Out the Invention

[0019] (Configuration of the bearing) Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings used in this description are schematic views of the bearing 1 according to the embodiment, and each part is drawn with exaggeration or omission in order to facilitate understanding of the configuration, structure, etc.

[0020] FIG. 1 is a perspective view of the bearing 1, and FIG. 2 is a cross-sectional perspective view of the bearing 1 divided into two halves. As shown in FIGS. 1 and 2, the bearing 1 is composed of an outer ring 11, a sliding member 12, and an inner ring 13. The sliding member 12 is formed on the outer peripheral surface 13a of the inner ring 13, and the concave curved surface 12a on the outer peripheral surface of the sliding member 12 and the convex curved surface 11c on the inner peripheral surface of the outer ring 11 are in opposed contact and slide. Further, the outer ring 11 and the inner ring 13 are made of metal, and the sliding member 12 is made of synthetic resin.

[0021] FIG. 3 is a perspective view of the outer ring 11 constituting the bearing 1, and FIG. 4 is a cross-sectional perspective view of the outer ring 11 divided into halves. As shown in FIGS. 3 and 4, the outer ring 11 has an outer peripheral surface 11a formed parallel to the axial direction on the outer periphery, and has a cylindrical shape with a convex surface 11c as an inner peripheral surface on the inner periphery. Further, chamfers 11d are provided at both axial ends of the outer peripheral surface of the outer ring 11 for the purpose of facilitating press-fitting and for alleviating the occurrence of damage such as catching during press-fitting.

[0022] More specifically, the inner peripheral surface of the outer ring 11 has a convex surface 11c that is convex toward the inner side (center side) in the radial direction of the bearing 1 over the entire circumferential length in the cross-section in the axial direction of the bearing 1. Also, the outer peripheral surface 11a of the outer ring 11 is circular when viewed from the axial direction of the bearing 1, and is parallel to the axial direction of the bearing 1 over the entire circumferential length in the cross-section in the axial direction of the bearing 1, but is not limited thereto. The outer peripheral surface 11a of the outer ring 11 may have irregularities in cross-section in order to enhance the joining with a pulley member (not shown) formed on the outer peripheral surface 11a.

[0023] FIG. 5 is a perspective view of the sliding member 12 constituting the bearing 1, and FIG. 6 is a cross-sectional perspective view of the sliding member 12 divided into halves. As shown in FIGS. 5 and 6, the sliding member 12 has an inner peripheral surface 12c formed parallel to the axial direction on the inner periphery, and has a cylindrical shape with a concave surface 12a as an outer peripheral surface on the outer periphery.

[0024] More specifically, the outer peripheral surface of the sliding member 12 has a concave surface 12a that is concave toward the inner side (center side) in the radial direction of the bearing 1 over the entire circumferential length in the cross-section in the axial direction of the bearing 1. Also, the inner peripheral surface 12c of the sliding member 12 is circular when viewed from the axial direction of the bearing 1, and is parallel to the axial direction of the bearing 1 over the entire circumferential length in the cross-section in the axial direction of the bearing 1.

[0025] FIG. 7 is a perspective view of the inner ring 13 constituting the bearing 1, and FIG. 8 is a cross-sectional perspective view of the inner ring 13 divided in half. As shown in FIGS. 7 and 8, the inner ring 13 has a cylindrical shape having an outer peripheral surface 13a and an inner peripheral surface 13c that are both parallel to the axial direction on the outer periphery and the inner periphery.

[0026] More specifically, the inner peripheral surface 13c of the inner ring 13 has a circular shape when viewed from the axial direction of the bearing 1, and is parallel to the axial direction of the bearing 1 over the entire circumferential length in the cross-section in the axial direction of the bearing 1. Further, the outer peripheral surface 13a of the inner ring 13 covered with the sliding member 12 has a circular shape when viewed from the axial direction of the bearing 1, and is parallel to the axial direction of the bearing 1 over the entire circumferential length in the cross-section in the axial direction of the bearing 1, but is not limited thereto. The outer peripheral surface 13a of the inner ring 13 may have irregularities in a cross-sectional view in order to enhance the joining with the sliding member 12.

[0027] Next, the relationship between the concave curved surface 12a on the outer peripheral surface of the sliding member 12 and the convex curved surface 11c on the inner peripheral surface of the outer ring 11 will be described with reference to FIGS. 9 to 11. FIG. 9 is a cross-sectional view of the inner ring 13, FIG. 10 is a cross-sectional view of the sliding member 12, and FIG. 11 is a cross-sectional view showing the bearing sliding portion of the bearing 1 composed of the outer ring 11, the sliding member 12, and the inner ring 13. FIGS. 9 to 11 are all views in the cross-section in the axial direction of the bearing 1.

[0028] As shown in FIG. 9, the convex curved surface 11c on the inner peripheral surface of the outer ring 11 has a maximum distance 11x from the outer peripheral surface 11a at the axial center portion CL11 and a minimum distance 11y from the outer peripheral surface 11a at both axial ends. Further, the convex curved surface 11c on the inner peripheral surface of the outer ring 11 has a constant radius of curvature R11 in the axial direction.

[0029] Further, the convex curved surface 11c on the inner peripheral surface of the outer ring 11 has the maximum distance 11x from the outer peripheral surface 11a at the central portion CL11 in the axial direction. However, in order to suppress a decrease in the bearing function and maintain the strength, the distance 11x is desirably 1.5 mm or more. Also, the convex curved surface 11c on the inner peripheral surface of the outer ring 11 has the minimum distance 11y from the outer peripheral surface 11a at both axial ends. However, the distance 11y is desirably 1.2 mm or more at both axial ends.

[0030] As shown in FIG. 10, the concave curved surface 12a on the outer peripheral surface of the sliding member 12 has the minimum distance 12x from the inner peripheral surface 12c at the central portion CL12 in the axial direction, and the maximum distance 12y from the inner peripheral surface 12c at both axial ends. Also, the concave curved surface 12a on the outer peripheral surface of the sliding member 12 has the minimum radius of curvature R121 at the central portion CL12 in the axial direction, and the maximum radius of curvature R122 at both axial ends in the axial direction. The radii of curvature R121 and R122 gradually increase from the central portion CL12 in the axial direction toward both axial ends. That is, in the concave curved surface 12a on the outer peripheral surface of the sliding member 12, the relationship between the radius of curvature R121 at the central portion CL12 in the axial direction and the radius of curvature R122 at both axial ends in the axial direction is R121 < R122 as follows.

[0031] Further, the concave curved surface 12a on the outer peripheral surface of the sliding member 12 has the minimum distance 12x from the inner peripheral surface 12c at the central portion CL12 in the axial direction. However, in order to suppress a decrease in the bearing function and maintain the strength, the distance 12x is desirably 1.2 mm or more. Also, the concave curved surface 12a on the outer peripheral surface of the sliding member 12 has the maximum distance 12y from the inner peripheral surface 12c at both axial ends. However, the distance 12y is desirably 1.5 mm or more at both axial ends.

[0032] As shown in FIG. 11, the radii of curvature R121 and R122 of the concave curved surface 12a on the outer peripheral surface of the sliding member 12 are bigThat is, the relationship between the radii of curvature R121 and R122 of the concave curved surface 12a on the outer peripheral surface of the sliding member 12 and the radius of curvature R11 of the convex curved surface 11c on the inner peripheral surface of the outer ring 11 is R121, R122 > R11 such that. Thus, with respect to the radii of curvature R121 and R122 of the concave curved surface 12a on the outer peripheral surface of the sliding member 12, by big making them smaller than the radius of curvature R11 of the convex curved surface 11c on the inner peripheral surface of the outer ring 11, only a part of the concave curved surface 12a on the outer peripheral surface of the sliding member 12 and the convex curved surface 11c on the inner peripheral surface of the outer ring 11 come into contact, the contact area of the sliding surface becomes small, and the sliding resistance can be reduced. Note that the relationship between the radii of curvature R121 and R122 of the concave curved surface 12a on the outer peripheral surface of the sliding member 12 and the radius of curvature R11 of the convex curved surface 11c on the inner peripheral surface of the outer ring 11 is R11 = R121, R122 × (80 - 95%) which is preferably the case.

[0033] Also, the difference between the radii of curvature R121 and R122 of the concave curved surface 12a on the outer peripheral surface of the sliding member 12 and the radius of curvature R11 of the convex curved surface 11c on the inner peripheral surface of the outer ring 11 is minimum at the central portion in the axial direction and maximum at both end portions in the axial direction, and the difference gradually increases from the central portion in the axial direction toward both end portions in the axial direction. That is, the gap between the concave curved surface 12a on the outer peripheral surface of the sliding member 12 and the convex curved surface 11c on the inner peripheral surface of the outer ring 11 is minimum at the central portion in the axial direction and maximum at both end portions in the axial direction, and the gap gradually increases from the central portion in the axial direction toward both end portions in the axial direction. Thus, with respect to the gap between the concave curved surface 12a on the outer peripheral surface of the sliding member 12 and the convex curved surface 11c on the inner peripheral surface of the outer ring 11, by making it larger from the central portion in the axial direction toward both end portions in the axial direction, it is possible to promote the discharge of wear powder generated during sliding and facilitate the discharge of foreign matter that has entered the sliding surface.

[0034] In the bearing 1 of the present invention, the outer ring 11 and the inner ring 13 are made of a metal material, and the sliding member 12 is made of a resin composition mainly composed of a synthetic resin and containing a filler such as a solid lubricant. As a specific example of the sliding member 12, one or more synthetic resins selected from nylon, polyacetal, polyphenylene sulfide, polyether imide, and polyethylene are used as the main component, and one or more fibrous particles selected from glass fiber particles, ceramic fiber particles, carbon fiber particles, aramid fiber particles, acrylic fiber particles, and polyvinyl alcohol fiber particles are contained in an amount of 1 to 15% by volume. Thereby, suitable sliding characteristics can be obtained.

[0035] Also, as the solid lubricant, it is desirable to contain 1 to 20% by volume of one or more selected from graphite, molybdenum disulfide, tungsten disulfide, boron nitride, and polytetrafluoroethylene. ru ko In addition, as a filler other than the solid lubricant, it is desirable to contain 1 to 10% by volume of one or more selected from CaF2, CaCo3, talc, mica, mullite, iron oxide, calcium phosphate, potassium titanate, and Mo2C. Further, the outer ring 11 and the inner ring 13 are preferably made of an iron alloy. By these, improvement of sliding characteristics can be achieved.

[0036] As described above, the bearing 1 of the present invention is a radial sliding bearing including an outer ring 11, a sliding member 12, and an inner ring 13. The outer ring 11 and the inner ring 13 are made of metal, the sliding member 12 is formed of a molded resin composition, the sliding member 12 is formed on the outer peripheral surface of the inner ring 13, and the concave curved surface 12a on the outer peripheral surface of the sliding member 12 and the convex curved surface 11c on the inner peripheral surface of the outer ring 11 slide while being in opposed contact with each other. The bearing 1 having such a configuration is composed of three parts: the outer ring 11, the sliding member 12, and the inner ring 13, and has fewer parts and a simpler structure compared to a ball bearing (rolling ball bearing). Further, by making the inner ring 13 made of metal, the bearing 1 prevents the inner ring 13 from expanding during assembly due to the difference in physical properties from the mating shaft made of metal, ensures sufficient tightening allowance between the mating shaft (not shown) and the inner ring 13, and prevents a decrease in the bearing function due to slipping or rotation during the assembly operation, and a deterioration in slidability due to a narrowing of the sliding surface gap between the inner ring 13 and the sliding member 12.

[0037] Further, in the bearing 1 of the present invention, since the concave curved surface 12a on the outer peripheral surface of the sliding member 12 and the convex curved surface 11c on the inner peripheral surface of the outer ring 11 slide while being in opposed contact with each other, unlike a resin sliding bearing that slides directly with the mating shaft, it is less affected by the material and surface roughness of the mating shaft with respect to the frictional torque and the amount of wear. Further, since the sliding contact surfaces of the inner ring 13 and the sliding member 12 are complementary concave and convex curved surfaces, it is possible to prevent misalignment in the axial direction of each other and suppress inclination in the axial direction.

[0038] Further, in the bearing 1 of the present invention, the outer ring 11 and the sliding member 12 are in a state where the concave and convex curved surfaces are in contact with each other. The radii of curvature R121 and R122 of the concave curved surface 12a on the outer peripheral surface of the sliding member 12 and the radius of curvature R11 of the convex curved surface 11c on the inner peripheral surface of the outer ring 11 are not the same. However, the radii of curvature R121 and R122 of the concave curved surface 12a are greater than the radius of curvature R11 of the convex curved surface 11c. The difference between the radii of curvature R121 and R122 of the concave curved surface 12a on the outer peripheral surface of the sliding member 12 and the radius of curvature R11 of the convex curved surface 11c on the inner peripheral surface of the outer ring 11 is minimized at the central portion in the axial direction and increases from the central portion in the axial direction toward both ends in the axial direction. As a result, the sliding surfaces only partially contact each other, the contact area of the sliding surfaces becomes small, and the sliding resistance can be reduced compared to conventional resin sliding bearings. Further, the gap between the concave curved surface 12a on the outer peripheral surface of the sliding member 12 and the convex curved surface 11c on the inner peripheral surface of the outer ring 11 increases from the central portion in the axial direction toward both ends in the axial direction. Therefore, it is possible to promote the discharge of wear powder generated during sliding and easily discharge foreign matter that has entered the sliding surface.

[0039] (Configuration of the bearing of Comparative Example 1) Next, the configuration of the bearing 111 of Comparative Example 1 will be described with reference to FIGS. 12 and 13. FIG. 12 is a cross-sectional view of the bearing 111 of Comparative Example 1 when not sliding, and FIG. 13 is a cross-sectional view of the bearing 111 of Comparative Example 1 when sliding.

[0040] As shown in FIG. 12, the bearing 111 of Comparative Example 1 is composed of an outer ring 111a, a sliding member 111b, and an inner ring 111c. Similar to the bearing 1 of the present invention, the sliding member 111b is formed on the outer peripheral surface of the inner ring 111c. Further, the sliding member 111b has a convex curved surface on the outer peripheral surface. The convex curved surface has the largest radius of curvature at the central portion in the axial direction and the smallest radius of curvature at both ends in the axial direction, which is different from the configuration of the bearing 1 of the present invention. On the other hand, the outer ring 111a has a concave curved surface on the inner peripheral surface. The concave curved surface has a constant radius of curvature in the axial direction, which is different from the configuration of the bearing 1 of the present invention. However, the gap between the convex curved surface on the outer peripheral surface of the sliding member 111b and the concave curved surface on the inner peripheral surface of the outer ring 111a increases from the central portion in the axial direction toward both ends in the axial direction, which is the same as the configuration of the bearing 1 of the present invention.

[0041] As shown in FIG. 13, the bearing 111 of Comparative Example 1 during sliding has a convex curved surface on the outer peripheral surface of the sliding member 111b and a convex curved surface on the inner peripheral surface of the outer ring 111a. Therefore, there is a concern that the sliding member 111b and the outer ring 111a may cause an inclination in the axial direction along their sliding surfaces, and this inclination may cause uneven load on the bearing sliding part and uneven wear, leading to a possible reduction in the bearing function.

[0042] (Configuration of the bearing of Comparative Example 2) Next, the configuration of the bearing 112 of Comparative Example 2 will be described with reference to FIG. 14. FIG. 14 is a cross-sectional view of the bearing 112 of Comparative Example 2.

[0043] As shown in FIG. 14, the bearing 112 of Comparative Example 2 is composed of an outer ring 112a, a sliding member 112b, and an inner ring 112c. Similar to the bearing 1 of the present invention, the sliding member 112b is formed on the outer peripheral surface of the inner ring 112c. Further, the sliding member 112b has a partially convex curved surface near the central portion in the axial direction and flat surfaces near both axial ends on the outer peripheral surface. The convex curved surface is different from the configuration of the bearing 1 of the present invention in that the distance from the inner peripheral surface is maximum at the central portion in the axial direction. On the other hand, the outer ring 112a has a partially concave curved surface near the central portion in the axial direction and flat surfaces near both axial ends on the inner peripheral surface. The concave curved surface is different from the configuration of the bearing 1 of the present invention in that the distance from the outer peripheral surface is minimum at the central portion in the axial direction.

[0044] In the bearing 112 of Comparative Example 2 described above, since the flat portions near both axial ends are in contact with each other over substantially the entire surface, the effect of reducing the sliding resistance cannot be obtained. Further, in the bearing 112 of Comparative Example 2, the end portion of the concave curved surface on the inner peripheral surface of the outer ring 113a may damage the sliding member 113b or cause local wear, and wear powder, foreign matter entering, etc. are likely to accumulate on the concave curved surface portion on the inner peripheral surface of the outer ring 113a. Since the gap between the sliding surfaces at the flat portions is constant, there is a concern that the wear powder and foreign matter entering are difficult to be discharged.

[0045] (Configuration of the sliding bearing of Comparative Example 3) Next, the configuration of the bearing 113 of Comparative Example 3 will be described with reference to FIG. 15. FIG. 15 is a cross-sectional view of the bearing 113 of Comparative Example 3.

[0046] As shown in FIG. 15, the bearing 113 of Comparative Example 3 is composed of an outer ring 113a, a sliding member 113b, and an inner ring 113c. Similar to the bearing 1 of the present invention, the sliding member 113b is formed on the outer peripheral surface of the inner ring 113c. Further, the sliding member 113b has a partially concave curved surface near the central portion in the axial direction and flat surfaces near both axial ends on the outer peripheral surface. The concave curved surface is different from the configuration of the bearing 1 of the present invention in that the distance from the outer peripheral surface is minimized at the central portion in the axial direction. On the other hand, the outer ring 113a has a partially convex curved surface near the central portion in the axial direction and flat surfaces near both axial ends on the inner peripheral surface. The convex curved surface is different from the configuration of the bearing 1 of the present invention in that the distance from the outer peripheral surface is maximized at the central portion in the axial direction.

[0047] In the bearing 113 of Comparative Example 3 described above, since the flat portions near both axial ends are in contact with each other over substantially the entire surface, the effect of reducing the sliding resistance cannot be obtained. Further, in the bearing 113 of Comparative Example 3, wear powder, foreign matter intrusion, etc. are likely to accumulate on the concave curved surface portion of the outer peripheral surface of the sliding member 112b, and since the gap between the sliding surfaces on the flat portion is constant, there is a concern that wear powder and foreign matter intrusion are difficult to be discharged.

Explanation of Reference Numerals

[0048] 1 Bearing 11 Outer ring 11a Outer peripheral surface 11c Convex curved surface (inner peripheral surface) 11d Chamfer 12 Sliding member 12a Concave curved surface (outer peripheral surface) 12c Inner peripheral surface 13 Inner ring 13a Outer peripheral surface 13c Inner peripheral surface

Claims

1. A bearing comprising a metal inner ring and outer ring, and a resin sliding member, wherein the inner ring, the outer ring, and the sliding member are each formed in a cylindrical shape, the sliding member is formed on the outer peripheral surface of the inner ring, the outer peripheral surface of the sliding member has a concave curved surface in a cross-section in the axial direction over the entire circumferential length, the radius of curvature of the concave curved surface on the outer peripheral surface of the sliding member is minimum at the central portion in the axial direction and increases toward both axial ends, the inner peripheral surface of the outer ring has a convex curved surface in a cross-section in the axial direction over the entire circumferential length, the radius of curvature of the convex curved surface on the inner peripheral surface of the outer ring is constant in the axial direction, the relationship between the radius of curvature of the concave curved surface on the outer peripheral surface of the sliding member and the radius of curvature of the convex curved surface on the inner peripheral surface of the outer ring is that the radius of curvature of the concave curved surface > the radius of curvature of the convex curved surface, the difference between the radius of curvature of the concave curved surface on the outer peripheral surface of the sliding member and the radius of curvature of the convex curved surface on the inner peripheral surface of the outer ring is minimum at the central portion in the axial direction and increases toward both axial ends, and the concave curved surface on the outer peripheral surface of the sliding member and the convex curved surface on the inner peripheral surface of the outer ring are in opposed contact and slide against each other.

2. The bearing according to claim 1, wherein the sliding member is mainly composed of one or more synthetic resins selected from nylon, polyacetal, polyphenylene sulfide, polyetherimide, and polyethylene, and contains 1 to 15% by volume of one or more fibrous particles selected from glass fiber particles, ceramic fiber particles, carbon fiber particles, aramid fiber particles, acrylic fiber particles, and polyvinyl alcohol fiber particles.

3. The bearing according to claim 2, wherein the sliding member further contains 1 to 20% by volume of one or more solid lubricants selected from graphite, molybdenum disulfide, tungsten disulfide, boron nitride, and polytetrafluoroethylene.

4. The sliding member further contains CaF ２ , CaCo ３ , talc, mica, mullite, iron oxide, calcium phosphate, potassium titanate, Mo ２ C, and contains 1 to 10% by volume of one or more fillers selected therefrom. The bearing according to claim 2 or claim 3, characterized in that.

5. The bearing according to any one of claims 1 to 4, wherein the inner ring and the outer ring are made of an iron alloy.

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