JP7712779B2 - Bearings - Google Patents

Description

The present invention relates to a bearing consisting of an inner ring and an outer ring made of metal and a sliding member made of resin, where the inner ring, the outer ring and the sliding member are each formed into a cylindrical shape.

Conventionally, electric sliding doors have been used for vehicles such as automobiles, mainly for the convenience of getting in and out of the vehicle. The door opening and closing mechanism of such electric sliding doors is structured so that a wire cable opens and closes via a pulley mechanism. The pulley is mainly made of resin, and a rolling bearing is used to drive the pulley (Patent Document 1).

Generally, rolling bearings reduce friction through the rolling contact of rolling elements placed between paired raceways, and are widely used as bearings for general machinery due to their excellent low torque characteristics. However, rolling bearings are made up of many parts such as inner and outer rings, rolling elements, and cages, so assembly and manufacturing costs tend to rise, and there is also a certain limit to how small the bearings can be made because space is required to store the rolling elements. Furthermore, high-precision machining is required to reduce noise, which has the disadvantage of significantly increasing manufacturing costs, so sliding bearings are often used as an alternative.

The sliding bearings described above are constructed by providing a bearing hole in an outer peripheral member made of sintered oil-impregnated metal, resin, etc., and inserting an inner peripheral member such as a shaft into this bearing hole with a small bearing gap in between. However, with such sliding bearings, the bearing life, torque, contact accuracy, etc. are greatly affected by the size of the bearing gap, so the bearing gap must be strictly controlled. Furthermore, with sliding bearings, since the mating member often also has another function such as a support shaft, it is common for the inner peripheral member and the outer peripheral member to be manufactured separately, but both members must be precision machined, which is time-consuming, making it difficult to control the dimensions and shape of the bearing gap, and can easily lead to a decrease in functionality due to a defective bearing gap.

As a means of resolving these problems, a sliding bearing composed of an outer ring and an inner ring in which an annular protrusion or annular groove formed on the inner circumference of the outer ring engages with an annular groove or annular protrusion formed on the outer circumference of the inner ring is known (Patent Document 2). Another sliding bearing is known which is composed of an outer ring and an inner ring, in which the inner ring is made of a melt-curved resin composition and the bearing gap between the inner ring and the outer ring is formed by resin contraction as the inner ring hardens (Patent Document 3). Another sliding bearing is known which is composed of an outer ring and an inner ring, in which, when viewed in axial cross section, the inner ring has an outer peripheral surface that is a convexly curved surface and the outer ring has an inner peripheral surface that is a concavely curved surface that corresponds to the convex curved surface of the outer peripheral surface of the inner ring (Patent Document 4).

JP 2019-112025 A Japanese Utility Model Application Publication No. 59-39316 Japanese Patent Application Publication No. 9-32856 JP 2011-74975 A

However, in Patent Document 2, the inner ring and outer ring have an annular groove and annular protrusion, respectively, but the parts other than the annular protrusion and annular groove have flat parts, and the sliding resistance increases relatively due to the increased sliding area. Furthermore, when the annular groove and annular protrusion wear, the wear powder is difficult to discharge outside the bearing and accumulates in the annular groove, raising concerns about a deterioration in the sliding properties of the bearing.

Patent Document 3 also provides a sliding bearing formed of an inner ring made of molten resin and an outer ring made of metal, ceramic, or a material that is not affected by the temperature during injection molding of the inner ring. However, although the interference provided when assembling the bearing and shaft serves to prevent the shaft from slipping out or rotating, if the inner ring is made of resin, the inner ring expands when the bearing is assembled due to differences in physical properties with the metal shaft, and sufficient interference is not ensured between the shaft and the inner ring, raising concerns about reduced bearing function due to slipping out or rotating during assembly and operation. There is also concern that the inner ring expands when assembled to the shaft, narrowing the gap with the outer ring and deteriorating the bearing's sliding properties.

In addition, in Patent Document 4, the concave curved surface on the inner circumferential surface of the outer ring and the convex curved surface on the outer circumferential surface of the inner ring cause inclination in the axial direction along their respective surfaces and relative misalignment of the inner and outer rings in the axial direction, and this inclination or misalignment can cause uneven loads on the sliding parts of the bearing and result in uneven wear, which can lead to reduced bearing function.

The present invention was made in consideration of the above circumstances, and its objectives are to (1) provide a bearing that can prevent slipping out or rotation during assembly and operation by ensuring a tight fit with the shaft, (2) reduce the contact area of the sliding surfaces to reduce sliding resistance, and (3) facilitate the discharge of wear particles generated during sliding.

In order to achieve the above object, the present invention relates to a method for manufacturing a semiconductor device comprising the steps of:
A bearing comprising an inner ring and an outer ring made of metal, and a sliding member made of resin, the inner ring, the outer ring, and the sliding member each being formed into a cylindrical shape,
The sliding member is formed on an outer peripheral surface of the inner ring,
The outer peripheral surface of the sliding member has a concave curved surface in an axial cross section over the entire circumferential length,
the radius of curvature of the concave curved surface on the outer circumferential surface of the sliding member is smallest at the center 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 an axial cross section over the entire circumferential length,
a radius of curvature of the convexly curved surface on the inner peripheral surface of the outer ring is constant in the axial direction,
the radius of curvature of the concavely curved surface on the outer peripheral surface of the sliding member and the radius of curvature of the convexly curved surface on the inner peripheral surface of the outer ring satisfy the following relationship: the radius of curvature of the concavely curved surface > the radius of curvature of the convexly curved surface,
the difference between the radius of curvature of the concavely curved surface on the outer peripheral surface of the sliding member and the radius of curvature of the convexly curved surface on the inner peripheral surface of the outer ring is smallest at the axial central portion and increases toward both axial ends,
The concavely curved surface on the outer peripheral surface of the sliding member and the convexly curved surface on the inner peripheral surface of the outer ring slide in opposing contact.

The invention according to claim 2 is the bearing according to claim 1, characterized in that the sliding member is mainly made of one or more synthetic resins selected from nylon, polyacetal, polyphenylene sulfide, polyetherimide, and polyethylene, and contains 1 to 15 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.

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

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

The invention according to claim 5 is characterized in that 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.

In the present invention, in a bearing consisting 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 come into opposing contact and slide. In this configuration, by making the inner ring out of metal, expansion of the inner ring during assembly of the bearing due to differences in physical properties with the metal mating shaft is prevented, sufficient tightening is ensured between the shaft and the inner ring, and deterioration of bearing function due to slippage or rotation during assembly and operation, and deterioration of sliding properties due to narrowing of the gap between the sliding surfaces of the inner ring and the sliding member, can be prevented.

Furthermore, the relationship between the radius of curvature of the concavely curved surface on the outer peripheral surface of the sliding member and the radius of curvature of the convexly curved surface on the inner peripheral surface of the outer ring is such that the radius of curvature of the concavely curved surface is greater than the radius of curvature of the convexly curved surface, and the difference between the radius of curvature of the concavely curved surface on the outer peripheral surface of the sliding member and the radius of curvature of the convexly curved surface on the inner peripheral surface of the outer ring is smallest at the axial center and increases from the axial center toward both axial ends, so that the sliding surfaces only come into contact in parts, reducing the contact area of the sliding surfaces and reducing sliding resistance. Furthermore, the gap between the concavely curved surface on the outer peripheral surface of the sliding member and the convexly curved surface on the inner peripheral surface of the outer ring increases from the axial center toward both axial ends, promoting the discharge of wear powder generated during sliding and making it easier to expel foreign matter that has entered the sliding surfaces.

FIG. FIG. 2 is a cross-sectional perspective view of a bearing divided in half. FIG. 2 is a perspective view of an outer ring that constitutes a bearing. FIG. 2 is a cross-sectional perspective view of the outer ring divided in half. FIG. 2 is a perspective view of a sliding member that constitutes a bearing. FIG. 2 is a cross-sectional perspective view of a sliding member divided in half. FIG. 2 is a perspective view of an inner ring that constitutes a bearing. FIG. 2 is a cross-sectional perspective view of the inner ring divided in half. FIG. FIG. 2 is a cross-sectional view showing a bearing sliding portion of a bearing composed of an outer ring, a sliding member, and an inner ring. FIG. FIG. 4 is a cross-sectional view of the bearing of Comparative Example 1 when not sliding. FIG. 4 is a cross-sectional view of the bearing of Comparative Example 1 during sliding. FIG. 4 is a cross-sectional view of a bearing of Comparative Example 2. FIG. 11 is a cross-sectional view of a bearing of Comparative Example 3.

(Bearing configuration)
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the drawings used in this description are schematic diagrams of a bearing 1 according to an embodiment, and various parts are exaggerated or omitted in order to make the configuration, structure, etc. easier to understand.

Figure 1 is a perspective view of bearing 1, and Figure 2 is a cross-sectional perspective view of bearing 1 divided in half. As shown in Figures 1 and 2, bearing 1 is composed of outer ring 11, sliding member 12, and inner ring 13, with sliding member 12 formed on outer peripheral surface 13a of inner ring 13, and concave curved surface 12a on the outer peripheral surface of sliding member 12 and convex curved surface 11c on the inner peripheral surface of outer ring 11 contacting each other and sliding. In addition, outer ring 11 and inner ring 13 are made of metal, and sliding member 12 is made of synthetic resin.

Figure 3 is a perspective view of the outer ring 11 that constitutes the bearing 1, and Figure 4 is a cross-sectional perspective view of the outer ring 11 divided in half. As shown in Figures 3 and 4, the outer ring 11 has an outer peripheral surface 11a that is parallel to the axial direction on the outer periphery, and is cylindrical with a convex curved surface 11c as the inner peripheral surface on the inner periphery. In addition, chamfers 11d are provided on both axial ends of the outer peripheral surface of the outer ring 11 for the purpose of facilitating press-fitting and mitigating the occurrence of damage such as galling during press-fitting.

More specifically, the inner peripheral surface of the outer ring 11 has a convex curved surface 11c that is convex toward the radial inside (center) of the bearing 1 over the entire circumferential length in a cross section taken along the axial direction of the bearing 1. The outer peripheral surface 11a of the outer ring 11 has a circular shape when viewed along the axial direction of the bearing 1, and is parallel to the axial direction of the bearing 1 over the entire circumferential length in a cross section taken along the axial direction of the bearing 1, but is not limited to this. The outer peripheral surface 11a of the outer ring 11 may have irregularities in cross section in order to improve the connection with a pulley member (not shown) formed on the outer peripheral surface 11a.

Figure 5 is a perspective view of the sliding member 12 that constitutes the bearing 1, and Figure 6 is a cross-sectional perspective view of the sliding member 12 divided in half. As shown in Figures 5 and 6, the sliding member 12 has an inner peripheral surface 12c that is parallel to the axial direction on the inner circumference, and is cylindrical in shape with a concave curved surface 12a on the outer circumference.

More specifically, the outer peripheral surface of the sliding member 12 has a concave curved surface 12a that is concave toward the inside (center) in the radial direction of the bearing 1 over the entire circumferential length in a cross section taken along the axial direction of the bearing 1. The inner peripheral surface 12c of the sliding member 12 has a circular shape when viewed along the axial direction of the bearing 1, and is parallel to the axial direction of the bearing 1 over the entire circumferential length in a cross section taken along the axial direction of the bearing 1.

Figure 7 is a perspective view of the inner ring 13 that constitutes the bearing 1, and Figure 8 is a cross-sectional perspective view of the inner ring 13 divided in half. As shown in Figures 7 and 8, the inner ring 13 is cylindrical in shape, with an outer peripheral surface 13a and an inner peripheral surface 13c that are both parallel to the axial direction on the outer and inner peripheries.

More specifically, the inner peripheral surface 13c of the inner ring 13 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 a cross section taken along the axial direction of the bearing 1. The outer peripheral surface 13a of the inner ring 13, which covers 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 a cross section taken along the axial direction of the bearing 1, but is not limited to this. The outer peripheral surface 13a of the inner ring 13 may have irregularities in cross section to enhance bonding with the sliding member 12.

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, sliding member 12, and inner ring 13. Figs. 9 to 11 are all views of a cross section of the bearing 1 in the axial direction.

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 CL11, and a minimum distance 11y from the outer peripheral surface 11a at both axial ends. In addition, 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.

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 CL11, and it is desirable that the distance 11x be 1.5 mm or more in order to prevent deterioration of the bearing function and maintain strength. The convex curved surface 11c on the inner peripheral surface of the outer ring 11 has a minimum distance 11y from the outer peripheral surface 11a at both axial ends, and it is desirable that the distance 11y be 1.2 mm or more at both axial ends.

10, the concave curved surface 12a on the outer peripheral surface of the sliding member 12 has a minimum distance 12x from the inner peripheral surface 12c at the axial center CL12 and a maximum distance 12y from the inner peripheral surface 12c at both axial ends. The concave curved surface 12a on the outer peripheral surface of the sliding member 12 has a minimum radius of curvature R121 at the axial center CL12 and a maximum radius of curvature R122 at both axial ends, and the radii of curvature R121, R122 gradually increase from the axial center CL12 toward both axial ends. In other words, the relationship between the radius of curvature R121 at the axial center CL12 and the radius of curvature R122 at both axial ends of the concave curved surface 12a on the outer peripheral surface of the sliding member 12 is as follows:
R121 < R122
It is as follows.

The concave curved surface 12a on the outer peripheral surface of the sliding member 12 has a minimum distance 12x from the inner peripheral surface 12c at the axial center CL12, but it is desirable that the distance 12x be 1.2 mm or more in order to prevent deterioration of the bearing function and maintain strength. The concave curved surface 12a on the outer peripheral surface of the sliding member 12 has a maximum distance 12y from the inner peripheral surface 12c at both axial ends, but it is desirable that the distance 12y be 1.5 mm or more at both axial ends.

11 , the radii of curvature R121, R122 of the concavely curved surface 12a on the outer peripheral surface of the sliding member 12 are greater than the radius of curvature R11 of the convexly curved surface 11c on the inner peripheral surface of the outer ring 11. In other words, the relationship between the radii of curvature R121, R122 of the concavely curved surface 12a on the outer peripheral surface of the sliding member 12 and the radius of curvature R11 of the convexly curved surface 11c on the inner peripheral surface of the outer ring 11 is as follows:
R121, R122 > R11
By making the radii of curvature R121, R122 of the concavely curved surface 12a on the outer peripheral surface of the sliding member 12 greater than the radius of curvature R11 of the convexly curved surface 11c on the inner peripheral surface of the outer ring 11, the concavely curved surface 12a on the outer peripheral surface of the sliding member 12 and the convexly curved surface 11c on the inner peripheral surface of the outer ring 11 only partially come into contact, reducing the contact area of the sliding surfaces and reducing sliding resistance. The relationship between the radii of curvature R121, R122 of the concavely curved surface 12a on the outer peripheral surface of the sliding member 12 and the radius of curvature R11 of the convexly curved surface 11c on the inner peripheral surface of the outer ring 11 is as follows:
R11 = R121, R122 × (80-95%)
It is desirable that:

Furthermore, the difference between the radii of curvature R121, 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 smallest at the axial center and largest at both axial ends, with the difference gradually increasing from the axial center toward both axial ends. In other words, 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 smallest at the axial center and largest at both axial ends, with the gap gradually increasing from the axial center toward both axial ends. In this way, 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 made larger from the axial center toward both axial ends, which promotes the discharge of wear powder generated during sliding and makes it easier to discharge foreign matter that has entered the sliding surface.

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 made of synthetic resin and containing a filler such as a solid lubricant. Specific examples of the sliding member 12 include a material mainly made of one or more synthetic resins selected from nylon, polyacetal, polyphenylene sulfide, polyetherimide, and polyethylene, and containing 1 to 15 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. This allows for favorable sliding characteristics to be obtained.

The solid lubricant preferably contains 1 to 20 volume percent of one or more selected from graphite, molybdenum disulfide, tungsten disulfide, boron nitride, and polytetrafluoroethylene. The filler other than the solid lubricant preferably contains 1 to 10 volume percent of one or more selected from CaF ₂ , CaCo ₃ , talc, mica, mullite, iron oxide, calcium phosphate, potassium titanate, and Mo ₂ C. The outer ring 11 and the inner ring 13 are preferably made of an iron alloy. This can improve the sliding characteristics.

As described above, the bearing 1 of the present invention is a radial sliding bearing comprising an outer ring 11, a sliding member 12, and an inner ring 13, the outer ring 11 and the inner ring 13 being made of metal, the sliding member 12 being made of a molded body of a resin composition, and the sliding member 12 being formed on the outer peripheral surface of the inner ring 13, with 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 sliding in opposing contact with each other. The bearing 1 thus configured is made up of three parts, the outer ring 11, the sliding member 12, and the inner ring 13, and has fewer parts and a simpler structure than a ball bearing (rolling ball bearing). In addition, by making the inner ring 13 of the bearing 1 out of metal, the inner ring 13 is prevented from expanding during assembly due to differences in physical properties with the metallic mating shaft, and sufficient interference is ensured between the mating shaft (not shown) and the inner ring 13, preventing a decrease in bearing function due to slippage or rotation during assembly and operation, and a decrease in sliding performance due to narrowing of the sliding surface gap between the inner ring 13 and the sliding member 12.

In addition, in the bearing 1 of the present invention, 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 opposing contact and slide, so unlike a plastic sliding bearing that slides directly against the mating shaft, the friction torque and wear amount are less affected by the material and surface roughness of the mating shaft. In addition, because the sliding 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 and suppress tilt in the axial direction.

Furthermore, the outer ring 11 and sliding member 12 in the bearing 1 of the present invention are configured so that the concave and convex surfaces come into contact with each other, and the radii of curvature R121, R122 of the concave surface 12a on the outer peripheral surface of the sliding member 12 and the radius of curvature R11 of the convex surface 11c on the inner peripheral surface of the outer ring 11 are not identical; however, the radii of curvature R121, R122 of the concave surface 12a are greater than the radius of curvature R11 of the convex surface 11c, and the difference between the radii of curvature R121, R122 of the concave surface 12a on the outer peripheral surface of the sliding member 12 and the radius of curvature R11 of the convex surface 11c on the inner peripheral surface of the outer ring 11 is smallest at the axial center and increases from the axial center toward both ends in the axial direction, so that the sliding surfaces only come into contact partially and the contact area of the sliding surfaces is smaller, making it possible to reduce sliding resistance compared to conventional resin sliding bearings. In addition, 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 becomes larger from the axial center toward both axial ends, facilitating the discharge of wear particles generated during sliding and making it easier to discharge foreign matter that has entered the sliding surface.

(Configuration of Bearing of Comparative Example 1)
Next, the configuration of the bearing 111 of Comparative Example 1 will be described with reference to Fig. 12 and Fig. 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.

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, and the sliding member 111b is formed on the outer peripheral surface of the inner ring 111c, as in the bearing 1 of the present invention. The sliding member 111b has a convex curved surface on the outer peripheral surface, which has a maximum radius of curvature at the axial center and a minimum radius of curvature at both axial ends, 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, which 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 axial center toward both axial ends, which is the same as the configuration of the bearing 1 of the present invention.

As shown in FIG. 13, when the bearing 111 of Comparative Example 1 slides, the sliding member 111b has a convex curved surface on the outer peripheral surface, and the outer ring 111a has a convex curved surface on the inner peripheral surface. This raises the concern that the sliding member 111b and the outer ring 111a may tilt in the axial direction along their respective sliding surfaces. This tilt may cause an uneven load to be generated on the sliding portion of the bearing, resulting in uneven wear and possibly reducing the bearing function.

(Configuration of Bearing of Comparative Example 2)
Next, the configuration of the bearing 112 of the second comparative example will be described with reference to Fig. 14. Fig. 14 is a cross-sectional view of the bearing 112 of the second comparative example.

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, and the sliding member 112b is formed on the outer peripheral surface of the inner ring 112c, as in the bearing 1 of the present invention. The sliding member 112b has a partially convex curved surface near the axial center and flat surfaces near both ends in the axial direction on the outer peripheral surface, and the distance between the convex curved surface and the inner peripheral surface is maximum at the axial center, which is different from the configuration of the bearing 1 of the present invention. On the other hand, the outer ring 112a has a partially concave curved surface near the axial center and flat surfaces near both ends in the axial direction on the inner peripheral surface, and the distance between the concave curved surface and the outer peripheral surface is minimum at the axial center, which is different from the configuration of the bearing 1 of the present invention.

In the bearing 112 of Comparative Example 2 described above, the flat portions near both ends in the axial direction are in contact with each other over almost the entire surface, so the effect of reducing sliding resistance is not obtained. In addition, in the bearing 112 of Comparative Example 2, the end of the concave curved surface on the inner surface of the outer ring 113a may scratch the sliding member 113b or cause localized wear, and wear powder and intruding foreign matter may easily accumulate on the concave curved surface on the inner surface of the outer ring 113a, and since the gap between the sliding surfaces on the flat portions is constant, there is a concern that wear powder and intruding foreign matter may not be easily discharged.

(Configuration of sliding bearing of comparative example 3)
Next, the configuration of the bearing 113 of the comparative example 3 will be described with reference to Fig. 15. Fig. 15 is a cross-sectional view of the bearing 113 of the comparative example 3.

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, and the sliding member 113b is formed on the outer peripheral surface of the inner ring 113c, as in the bearing 1 of the present invention. The sliding member 113b has a partially concave surface near the axial center and flat surfaces near both ends in the axial direction on the outer peripheral surface, and the concave surface is different from the configuration of the bearing 1 of the present invention in that the distance between the outer peripheral surface and the outer peripheral surface is smallest at the axial center. On the other hand, the outer ring 113a has a partially convex surface near the axial center and flat surfaces near both ends in the axial direction on the inner peripheral surface, and the distance between the outer peripheral surface and the outer peripheral surface is largest at the axial center, which is different from the configuration of the bearing 1 of the present invention.

In the bearing 113 of Comparative Example 3 described above, the flat portions near both ends in the axial direction are in contact with each other over almost the entire surface, so the effect of reducing sliding resistance is not obtained. In addition, in the bearing 113 of Comparative Example 3, wear powder and intruding foreign matter are likely to accumulate on the concave curved surface portion on the outer circumferential surface of the sliding member 112b, and since the gap between the sliding surfaces at the flat portions is constant, there is a concern that wear powder and intruding foreign matter are difficult to remove.

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 (5)

A bearing comprising an inner ring and an outer ring made of metal, and a sliding member made of resin, the inner ring, the outer ring, and the sliding member each being formed into a cylindrical shape,
The sliding member is formed on an outer peripheral surface of the inner ring,
The outer peripheral surface of the sliding member has a concave curved surface in an axial cross section over the entire circumferential length,
the radius of curvature of the concave curved surface on the outer circumferential surface of the sliding member is smallest at the center 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 an axial cross section over the entire circumferential length,
a radius of curvature of the convexly curved surface on the inner peripheral surface of the outer ring is constant in the axial direction,
the radius of curvature of the concavely curved surface on the outer peripheral surface of the sliding member and the radius of curvature of the convexly curved surface on the inner peripheral surface of the outer ring satisfy the following relationship: the radius of curvature of the concavely curved surface > the radius of curvature of the convexly curved surface,
the difference between the radius of curvature of the concavely curved surface on the outer peripheral surface of the sliding member and the radius of curvature of the convexly curved surface on the inner peripheral surface of the outer ring is smallest at the axial central portion and increases toward both axial ends,
a concavely curved surface on the outer peripheral surface of the sliding member and a convexly curved surface on the inner peripheral surface of the outer ring, the concavely curved surface being in opposing contact and sliding relative to each other. The bearing according to claim 1, characterized in that the sliding member is mainly made of one or more synthetic resins selected from nylon, polyacetal, polyphenylene sulfide, polyetherimide, and polyethylene, and contains 1 to 15 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. The bearing according to claim 2, characterized in that the sliding member further contains 1 to 20 volume percent of one or more solid lubricants selected from graphite, molybdenum disulfide, tungsten disulfide, boron nitride, and polytetrafluoroethylene. The bearing according to claim ₂ or ₃ , characterized in that the sliding member further contains 1 to 10 volume % of one or more fillers selected from CaF2, CaCo3, talc, mica, mullite, iron oxide, calcium phosphate, potassium titanate, and _Mo2C . A bearing according to any one of claims 1 to 4, characterized in that the inner ring and the outer ring are made of an iron alloy.