Driven bearing, driven bearing module, and method for manufacturing inner member of driven bearing

Abstract

The driven bearing includes an inner member including an inner wall surface defining a through-hole, an outer ring, and a plurality of rolling elements, a portion of the through-hole having a smallest diameter has a diameter of 40% or more of an outer diameter of a portion of the inner member having a smallest outer diameter, and the inner member is made of steel. The inner member comprises a steel containing 0.12 mass% to 0.39 mass% of carbon, 0.05 mass% to 0.40 mass% of silicon, 0.55 mass% to 0.95 mass% of manganese, and 0.60 mass% to 1.25 mass% of chromium, with the remainder being iron and unavoidable impurities, and the inner member comprises a carburized layer constituting at least a part of the surface thereof, in which the carburized layer has a thickness of 1-10 [mu] m and a thickness of 1-10 [mu] m. The grain size number of the prior austenite grains as specified in JIS G 0551 is 8.6 or more.

Description

Technical Field

[0001] The present disclosure relates to a driven bearing, a driven bearing module, and a method for manufacturing an inner member of a driven bearing. This application claims priority based on Japanese application No. 2022-097876 filed on June 17, 2022, and all the contents described in the above Japanese application are cited. Background Art

[0002] A driven bearing including a cylindrical stud and a driven bearing module for mounting such a driven bearing on a mounted member are known (for example, refer to Patent Documents 1 and 2).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 10-2400

[0006] Patent Document 2: Japanese Patent Application Publication No. 2000-346173 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] It is desired to facilitate mounting such that the driven bearing can be easily mounted on the mounted member. Also, it is desired to suppress a decrease in fatigue strength of the stud (inner member) of the driven bearing.

[0009] The present disclosure has been made in view of the above circumstances, and one of its objects is to provide a driven bearing, a driven bearing module, and a method for manufacturing an inner member of a driven bearing that suppresses a decrease in fatigue strength of an inner member and is excellent in ease of assembly.

[0010] Means used to solve problems

[0011] The first driven bearing according to the present disclosure has: an inner member including an outer peripheral surface and an inner wall surface, the outer peripheral surface including an annular first track surface having a central axis, the inner wall surface defining a through hole including the central axis; an outer ring including an annular second track surface opposite to the first track surface on the inner peripheral surface; and a plurality of rolling elements arranged on an annular track along the first track surface and the second track surface in a manner of contacting the first track surface and the second track surface. The portion with the smallest diameter in the through hole has a diameter of more than 40% of the outer diameter of the portion with the smallest outer diameter in the inner member. The inner member is made of steel containing carbon of more than 0.12 mass % and less than 0.39 mass %, silicon of more than 0.05 mass % and less than 0.40 mass %, manganese of more than 0.55 mass % and less than 0.95 mass %, and chromium of more than 0.60 mass % and less than 1.25 mass %, and the remainder is made of iron and unavoidable impurities. The inner member includes a carburized layer, which constitutes at least a portion of the surface of the inner member and contains 0.60 mass % or more and 1.20 mass % or less of carbon. In the carburized layer, the grain size number of prior austenite grains specified in JIS (Japanese Industrial Standards) G0551 is 8.6 or more.

[0012] Effects of the Invention

[0013] According to the driven bearing of the present disclosure, it is possible to easily mount the driven bearing to the mounted member while suppressing a decrease in fatigue strength of the inner member. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic perspective view of a driven bearing module in Embodiment 1 of the present disclosure.

[0015] Figure 2 is along Figure 1 Schematic diagram of the cross section along line II-II.

[0016] Figure 3 is along Figure 1 Schematic diagram of the cross section along line III-III in FIG.

[0017] Figure 4 It roughly indicates Figure 1 An exploded perspective view of the driven bearing module is shown.

[0018] Figure 5 This is a schematic perspective view of the mounting fixture in Embodiment 1 of the present disclosure as viewed from the first direction.

[0019] Figure 6 is viewed from a second direction opposite to the first direction Figure 5 A schematic three-dimensional diagram of the installation parts.

[0020] Figure 7 is viewed from the direction opposite to the tenth end face of the plate-like portion Figure 5 Schematic diagram of the installation parts.

[0021] Figure 8 Cut along a plane including the central axis of the cylindrical portion Figure 5 A schematic cross-sectional view of a mounting member.

[0022] Fig. 9 It is a flowchart showing each process of the manufacturing method of the shaft member.

[0023] Fig.10 This is a diagram showing an example of a part of the heating pattern in the manufacturing process of the shaft member.

[0024] Fig.11 It is a schematic perspective view of a driven bearing module in Embodiment 2 of the present disclosure.

[0025] Fig.12 is along Fig.11 Schematic diagram of the cross section taken along line IV-IV in FIG.

[0026] Fig.13 is along Fig.11 Schematic diagram of the cross section along line VV in FIG.

[0027] Fig.14 It roughly indicates Fig.11 An exploded perspective view of the driven bearing module is shown.

[0028] Fig.15 This is a schematic perspective view of the mounting fixture in Embodiment 2 of the present disclosure as viewed from the first direction.

[0029] Fig.16 is viewed from a second direction opposite to the first direction Fig.15 A schematic three-dimensional diagram of the installation parts.

[0030] Fig.17 is viewed from the direction opposite to the tenth end face of the plate-like portion Fig.15 Schematic diagram of the installation parts.

[0031] Fig.18 This is a diagram showing an example of prior austenite grains in a carburized layer of a shaft member manufactured by the method for manufacturing a shaft member disclosed in the present invention.

[0032] Fig.19 It is a diagram showing a comparative example of prior austenite grains in a carburized layer of a shaft member.

[0033] Fig. 20 This is a schematic diagram of a test piece used in the rotating bending fatigue test of Example 2.

[0034] Fig.21 yes Fig. 20 An enlarged view of the cut in the test piece.

[0035] Fig. 22 This is a diagram showing the SN curve in Example 2.

[0036] Fig.23 This is a diagram showing an example of prior austenite grains in a carburized layer of a test piece heated to a temperature of 860° C. in a carburizing gas atmosphere.

[0037] Fig.24 This is a diagram showing an example of prior austenite grains in a carburized layer of a test piece heated to a temperature of 900° C. in a carburizing gas atmosphere.

[0038] Fig.25 This is a diagram showing an example of prior austenite grains in a carburized layer of a test piece heated to a temperature of 930° C. in a carburizing gas atmosphere.

[0039] Fig.26 This is a graph showing the relationship between the fatigue limit and the grain size number of the prior austenite grains. DETAILED DESCRIPTION

[0040] [Overview of Embodiments]

[0041] First, the embodiments of the present disclosure are listed and described. The first driven bearing of the present disclosure has: an inner member, which includes an outer peripheral surface and an inner wall surface, the outer peripheral surface includes a first annular track surface having a central axis, and the inner wall surface is defined for a through hole including the central axis; an outer ring, which includes a second annular track surface opposite to the first track surface on the inner peripheral surface; and a plurality of rolling elements, which are arranged on the annular track along the first track surface and the second track surface in a manner of contacting the first track surface and the second track surface. The portion with the smallest diameter in the through hole has a diameter of more than 40% of the outer diameter of the portion with the smallest outer diameter in the inner member. The inner member is composed of steel, which contains carbon of 0.12 mass % or more and less than 0.39 mass %, silicon of 0.05 mass % or more and less than 0.40 mass %, manganese of 0.55 mass % or more and less than 0.95 mass %, and chromium of 0.60 mass % or more and less than 1.25 mass %, and the remainder is composed of iron and unavoidable impurities. The inner member includes a carburized layer which constitutes at least a portion of the surface of the inner member and contains 0.60 mass % or more and 1.20 mass % or less of carbon. In the carburized layer, the grain size number of prior austenite grains specified in JIS G 0551 is 8.6 or more.

[0042] By having the inner member include an inner wall surface that defines a through hole including the center axis, that is, by forming a through hole in the inner member, the driven bearing can be mounted on the mounted member using the through hole. As a result, the driven bearing can be easily mounted on the mounted member. Since the through hole is formed in the inner member, there is a concern that the fatigue strength of the inner member will be reduced, but by having the original austenite grains in the carburized layer have a grain size number of 8.6 or more and are fine, the reduction in the fatigue strength of the inner member can be suppressed. In this way, according to the first driven bearing disclosed in the present invention, the reduction in the fatigue strength of the inner member can be suppressed, and the driven bearing can be easily mounted on the mounted member.

[0043] In addition, the second driven bearing disclosed in the present invention comprises: an inner member including an outer peripheral surface and an inner wall surface, the outer peripheral surface including an annular first track surface having a central axis, the inner wall surface defining a through hole including the central axis; an outer ring including an annular second track surface opposite to the first track surface on the inner peripheral surface; and a plurality of rolling elements arranged on an annular track along the first track surface and the second track surface in a manner of contacting the first track surface and the second track surface. The smallest diameter portion in the through hole has a diameter of 40% or more of the outer diameter of the smallest outer diameter portion in the inner member. The inner member is made of steel containing 0.12% by mass or more and 0.39% by mass or less carbon, 0.05% by mass or more and 0.40% by mass or less silicon, 0.55% by mass or more and 0.95% by mass or less manganese, 0.60% by mass or more and 1.25% by mass or less chromium, and 0.15% by mass or more and 0.35% by mass or less molybdenum, and the remainder is made of iron and inevitable impurities. The inner member includes a carburized layer, which constitutes at least a portion of the surface of the inner member and contains 0.60% by mass or more and 1.20% by mass or less carbon. In the carburized layer, the grain size number of the original austenite grain specified in JIS G 0551 is 8.6 or more.

[0044] In the second driven bearing of the present disclosure, similarly to the first driven bearing of the present disclosure, the inner member includes an inner wall surface that defines a through hole including a center axis, that is, by forming a through hole in the inner member, the driven bearing can be mounted on the mounted member using the through hole. Thus, the driven bearing can be easily mounted on the mounted member. Since the through hole is formed in the inner member, there is a concern that the fatigue strength of the inner member will be reduced, but the reduction in the fatigue strength of the inner member can be suppressed by having the grain size of the original austenite grains in the carburized layer be numbered 8.6 or more and be fine. In this way, according to the second driven bearing of the present disclosure, the reduction in the fatigue strength of the inner member can be suppressed, and the driven bearing can be easily mounted on the mounted member.

[0045] The hardness of the surface of the inner member composed of the carburized layer can be 700 HV or more. This makes it easy to impart high fatigue strength to the inner member.

[0046] In the driven bearing, the inner member may include: a large diameter portion including a first raceway surface on an outer peripheral surface; and a small diameter portion, an end portion in a direction along the central axis, i.e., a first end portion, connected to the large diameter portion and having an outer diameter smaller than an outer diameter of the large diameter portion. The carburized layer may be configured to include an outer peripheral surface corresponding to the first end portion in the small diameter portion. Thus, it is possible to suppress a reduction in fatigue strength of a portion of the inner member where stress is likely to be concentrated.

[0047] The driven bearing module disclosed in the present invention has the above-mentioned driven bearing, a mounting member and a fastener. The mounting member includes: a cylindrical portion including a thread groove on the inner peripheral surface; and a plate-shaped portion, which is arranged at one axial end of the cylindrical portion and extends radially outward from the cylindrical portion. The fastener includes: a main body portion, which includes a thread tooth that can be combined with the thread groove of the cylindrical portion on the outer peripheral surface; and a head portion, which is connected to one end portion of the main body portion in the length direction and has a larger outer diameter than the main body portion. In a state where the plate-shaped portion of the mounting member is located on one side when viewed from the through hole in the direction along the center axis, and in a state where the head of the fastener is located on the other side when viewed from the through hole in the direction along the center axis, the thread groove of the cylindrical portion inserted into the through hole is combined with the thread tooth of the main body portion inserted into the through hole, thereby enabling the driven bearing to be fastened to the mounting member. As a result, the driven bearing can be more easily mounted on the mounted component using the through hole.

[0048] In the above-mentioned driven bearing module, the mounting piece may further include an arc-shaped portion connected to the cylindrical portion and the plate-shaped portion. The radius of curvature of the arc-shaped portion may be greater than 0.5 mm and less than 1.5 mm. By having a radius of curvature of the arc-shaped portion greater than 0.5 mm, stress concentration between the cylindrical portion and the plate-shaped portion can be suppressed. By having a radius of curvature of the arc-shaped portion less than 1.5 mm, interference between the inner member and the mounting piece when the cylindrical portion of the mounting piece is inserted into the through hole of the inner member of the driven bearing can be suppressed.

[0049] In the manufacturing method of the inner member of the driven bearing disclosed in the present invention, the inner member includes an outer peripheral surface and an inner wall surface, the outer peripheral surface includes a first annular track surface having a central axis, and the inner wall surface defines a through hole including the central axis. The smallest diameter portion of the through hole has a diameter of more than 40% of the outer diameter of the smallest outer diameter portion of the inner member. The manufacturing method of the inner member includes: a step of preparing a formed body having the shape of the inner member and composed of steel containing 0.12 mass % or more and 0.39 mass % or less of carbon, 0.05 mass % or more and 0.40 mass % or less of silicon, 0.55 mass % or more and 0.95 mass % or less of manganese and 0.60 mass % or more and 1.25 mass % or less of chromium, and the remainder is composed of iron and inevitable impurities; a step of forming a carburized layer constituting at least a part of the surface of the formed body by heating the formed body to a temperature of more than the A1 point of steel and less than 900° C. in a carburizing gas atmosphere; and a step of quenching and hardening the formed body by cooling the formed body with the carburized layer formed from a temperature range of more than the A1 point of steel to a temperature range of less than the MS point. Thus, the inner member including the carburized layer constituting at least a part of the surface of the inner member can be easily manufactured, and the grain size number of the prior austenite grains specified in JIS G0551 is 8.6 or more.

[0050] [Specific example of embodiment]

[0051] Next, an example of a specific embodiment of the driven bearing disclosed in the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and their description will not be repeated.

[0052] (Implementation Method 1)

[0053] 〔Driven bearing module〕

[0054] First, Embodiment 1 of the present disclosure will be described. Figure 1 It is a schematic perspective view of a driven bearing module A in Embodiment 1 of the present disclosure. Figure 2 is along Figure 1 Schematic diagram of the cross section along line II-II.

[0055] Figure 3 is along Figure 1 Schematic diagram of the cross section along line III-III in FIG. Figure 4 It roughly indicates Figure 1 An exploded perspective view of the driven bearing module A is shown.

[0056] exist Figure 1 In the following figures, the Y direction indicates a direction parallel to the rotation axis of the driven bearing B. The X direction and the Z direction are orthogonal to the Y direction. The X direction and the Z direction are orthogonal to each other. Figure 1 In FIG. 1 , the mounted component 9 is indicated by a single-dot chain line. Figure 2 and Figure 3 In the figure, the central axis δ is represented by a single-dot dash line. Figure 4 In the figure, the mounted member 9 is omitted.

[0057] Refer to Figure 1 , Figure 2 , Figure 3 and Figure 4 , the driven bearing module A in embodiment 1 includes a driven bearing B, a mounting member 6 and a bolt 7 as a fastener. The driven bearing module A is mounted on a mounted component 9 having a specified thickness. The mounted component 9 includes: a first surface 90; a second surface 91, which is arranged parallel to the first surface 90 and faces a direction opposite to the direction of the first surface 90; and an inner wall surface 93, which defines a mounting hole 92 that passes from the first surface 90 to the second surface 91. The driven bearing B is mounted on the mounted component 9 using the mounting hole 92. The mounting hole 92 is in the shape of a circular hole. The inner wall surface 93 has a cylindrical shape. Such a mounting hole 92 can be formed more easily than a mounting hole in which the inner wall surface 93 includes a step surface, for example.

[0058] <Driven bearing>

[0059] Refer to Figure 2 and Figure 3 , the driven bearing B has a shaft member 1 (inner member), an outer ring 2, a plurality of rollers 3 (rolling elements), a retainer 4 and a side plate 5. The shaft member 1 includes a large diameter portion 10 and a small diameter portion 11, the small diameter portion 11 is connected to the large diameter portion 10 and has an outer diameter smaller than the outer diameter of the large diameter portion 10. The outer diameter or diameter may be a diameter or an equivalent circle diameter (a diameter of a circle having an area corresponding to the structure of the object in a cross section when the shaft member 1 is cut by a plane perpendicular to the axial direction).

[0060] The large diameter portion 10 includes: a first outer peripheral surface 100; a second outer peripheral surface 101 having a smaller diameter than the first outer peripheral surface 100; a first step surface 102 connecting the first outer peripheral surface 100 and the second outer peripheral surface 101; a first end surface 103 connected to the end edge of the first outer peripheral surface 100; and a second end surface 104 connected to the end edge of the second outer peripheral surface 101. The first outer peripheral surface 100 and the second outer peripheral surface 101 have a cylindrical shape. The first outer peripheral surface 100 and the second outer peripheral surface 101 are arranged concentrically. The second outer peripheral surface 101 includes a first track surface P1 having a circular ring shape with a central axis δ. That is, the large diameter portion 10 includes the first track surface P1 on the outer peripheral surface. In addition, the first outer peripheral surface 100 may also have a polygonal or elliptical cylindrical shape. The first end surface 103 is parallel to the second end surface 104.

[0061] The end of the small diameter portion 11 in the direction along the central axis δ, i.e., the first end 11a, is connected to the second end face 104 of the large diameter portion 10. The small diameter portion 11 has an outer diameter D1 of a degree that can be fitted into the mounting hole 92 in the mounted component 9. The small diameter portion 11 is arranged concentrically with the large diameter portion 10. The small diameter portion 11 includes: an outer peripheral surface 110, one end edge of which is connected to the second end face 104 of the large diameter portion 10; and a third end face 111, which is connected to the end edge of the outer peripheral surface 110 opposite to the end edge connected to the second end face 104 of the large diameter portion 10. The outer peripheral surface 110 has a cylindrical shape. In addition, the outer peripheral surface 110 may also have a polygonal or elliptical cylindrical shape. The third end face 111 is parallel to the first end face 103. A portion 11b having an outer diameter larger than the area fitted into the mounting hole 92 is formed at the first end 11a.

[0062] The shaft member 1 includes an outer peripheral surface 12 including a first raceway surface P1 and an inner wall surface 13 defining a through hole TH including a central axis δ. The outer peripheral surface 12 includes a first outer peripheral surface 100 and a second outer peripheral surface 101 of the large diameter portion 10 and an outer peripheral surface 110 of the small diameter portion 11.

[0063] The through hole TH penetrates from the first end surface 103 of the large diameter portion 10 to the third end surface 111 of the small diameter portion 11. The inner wall surface 13 defining the through hole TH includes: a first inner wall surface 130 connected to the first end surface 103 of the large diameter portion 10; a second inner wall surface 131; a third inner wall surface 132 connected to the third end surface 111 of the small diameter portion 11; a second step surface 133 connecting the first inner wall surface 130 and the second inner wall surface 131; and a third step surface 134 connecting the second inner wall surface 131 and the third inner wall surface 132. The first inner wall surface 130, the second inner wall surface 131, and the third inner wall surface 132 have a cylindrical shape. The third inner wall surface 132 has a smaller diameter than the first inner wall surface 130. The second inner wall surface 131 has a smaller diameter than the third inner wall surface 132. The first inner wall surface 130, the second inner wall surface 131, and the third inner wall surface 132 have a cylindrical shape. Alternatively, the first inner wall surface 130, the second inner wall surface 131, and the third inner wall surface 132 may have a polygonal or elliptical cylindrical shape.

[0064] The portion with the smallest diameter in the through hole TH has a diameter of 40% or more of the outer diameter of the portion with the smallest outer diameter in the shaft member 1. The portion with the smallest diameter in the through hole TH may be the portion with the smallest nominal diameter in the through hole TH, or the portion with the smallest local diameter of the through hole TH, or the portion with the smallest moving average value of the diameter of the through hole TH when observing the displacement of the diameter of the through hole TH relative to the position along the direction of the central axis δ. The portion with the smallest outer diameter in the shaft member 1 may be the portion with the smallest nominal diameter in the shaft member 1, or the portion with the smallest local outer diameter of the shaft member 1, or the portion with the smallest moving average value of the outer diameter of the shaft member 1 when observing the displacement of the outer diameter of the shaft member 1 relative to the position along the direction of the central axis δ.

[0065] In the present embodiment, the portion with the smallest diameter (the portion with the smallest nominal diameter) in the through hole TH, i.e., the portion corresponding to the second inner wall surface 131, has a diameter D2 of 40% or more of the outer diameter D1 of the small diameter portion 11, i.e., the portion with the smallest outer diameter (the portion with the smallest nominal diameter) in the shaft member 1. For example, when the outer diameter D1 of the small diameter portion 11 is 8 mm, the diameter D2 of the portion with the smallest diameter in the through hole TH is 3.3 mm, when the outer diameter D1 of the small diameter portion 11 is 10 mm, the diameter D2 of the portion with the smallest diameter in the through hole TH is 4.4 mm, and when the outer diameter D1 of the small diameter portion 11 is 12 mm, the diameter D2 of the portion with the smallest diameter in the through hole TH is 5.4 mm. The diameter D2 is, for example, 40% or more and 65% or less of the outer diameter D1 of the small diameter portion 11.

[0066] The shaft member 1 is made of steel containing 0.12 mass % or more and 0.39 mass % or less of carbon, 0.05 mass % or more and 0.40 mass % or less of silicon, 0.55 mass % or more and 0.95 mass % or less of manganese, and 0.60 mass % or more and 1.25 mass % or less of chromium, and the remainder is made of iron and inevitable impurities. "Inevitable impurities" refer to substances that are present in raw materials or are inevitably mixed in the manufacturing process in metal products, which are originally unnecessary substances but are difficult to completely remove and are allowed as unavoidable substances.

[0067] The shaft member 1 may be made of steel having a composition containing 0.12 mass % to 0.39 mass % carbon, 0.05 mass % to 0.40 mass % silicon, 0.55 mass % to 0.95 mass % manganese, 0.60 mass % to 1.25 mass % chromium, and 0.15 mass % to 0.35 mass % molybdenum, with the remainder being iron and inevitable impurities. The shaft member 1 may be made of, for example, SCr415, SCr420, SCr430, SCr435, SCM415, SCM418, SCM420, SCM421, SCM425, SCM430, SCM432, or SCM435 specified in JIS G 4053.

[0068] The shaft component 1 includes a carburized layer, which constitutes at least a portion of the surface of the shaft component 1 and contains carbon of 0.60 mass % or more and 1.20 mass % or less. In the carburized layer, the grain size number of the original austenite grains specified in JIS G0551 (hereinafter referred to as "the grain size number of the original austenite grains") is 8.6 or more. The hardness of the surface of the shaft component 1 composed of the carburized layer is, for example, 700 HV or more. In the present embodiment, the carburized layer is configured to include an outer peripheral surface corresponding to the first end portion 11a in the small diameter portion 11. In addition, the shaft component 1 is not limited to the above, and may also have the same outer diameter.

[0069] Refer to Figure 1 , Figure 2 , Figure 3 and Figure 4 The outer ring 2 includes an outer circumferential surface 20, a fourth end surface 21 connected to one end edge of the outer circumferential surface 20, and a fifth end surface 22 connected to the other end edge of the outer circumferential surface 20. The fourth end surface 21 is parallel to the fifth end surface 22. The outer ring 2 includes a first inner circumferential surface 23 connected to the fourth end surface 21, a second inner circumferential surface 24 having a smaller diameter than the first inner circumferential surface 23, a third inner circumferential surface 25 connected to the fifth end surface 22 and having a larger diameter than the second inner circumferential surface 24, a fourth step surface 26 connecting the first inner circumferential surface 23 and the second inner circumferential surface 24, and a fifth step surface 27 connecting the second inner circumferential surface 24 and the third inner circumferential surface 25.

[0070] The diameter of the first inner circumferential surface 23 may be the same as the diameter of the third inner circumferential surface 25 (may also include an error within the usual dimensional tolerance range). The diameter of the first inner circumferential surface 23 may be different from the diameter of the third inner circumferential surface 25. The outer circumferential surface 20, the first inner circumferential surface 23, the second inner circumferential surface 24 and the third inner circumferential surface 25 are arranged concentrically. The first inner circumferential surface 23 is opposite to the first outer circumferential surface 100 of the large diameter portion 10 of the shaft member 1. The second inner circumferential surface 24 is opposite to the second outer circumferential surface 101 of the large diameter portion 10. The third inner circumferential surface 25 is opposite to the side plate 5. The second inner circumferential surface 24 includes an annular second track surface P2 opposite to the first track surface P1. That is, the outer ring 2 has a second track surface P2 on the second inner circumferential surface 24. The second track surface P2 has a central axis common to the central axis δ. That is, the central axis δ is the rotation axis of the driven bearing B. The outer ring 2 is made of steel. The area of ​​the outer ring 2 including the second track surface P2 is quench-hardened. The outer ring 2 may be quench-hardened by quenching only a portion including the second raceway surface P2 or may be quench-hardened entirely.

[0071] The roller 3 is arranged on an annular track along the first track surface P1 and the second track surface P2 in a manner of contacting the first track surface P1 and the second track surface P2. The roller 3 has a solid cylindrical shape. The roller 3 includes an outer peripheral surface 30 and a pair of end surfaces 31, 32 connected to the two end edges of the outer peripheral surface 30. The end surfaces 31, 32 of the roller 3 may also be spherical. The roller 3 is made of steel such as bearing steel. The roller 3 is quench-hardened. In addition, as a rolling element, a ball may be used instead of the roller 3.

[0072] The retainer 4 retains the roller 3 in such a manner that the roller 3 contacts the first track surface P1 and the second track surface P2 on the annular track along the first track surface P1 and the second track surface P2 and the adjacent rollers 3 do not contact each other. The retainer 4 has an annular shape. The retainer 4 is arranged concentrically with the shaft member 1 and the outer ring 2 in the space sandwiched by the shaft member 1 and the outer ring 2. The retainer 4 includes a plurality of pockets 40 arranged at equal intervals in the circumferential direction. A roller 3 is arranged in each of the plurality of pockets 40. The retainer 4 is made of steel, for example. The retainer 4 may also be made of resin.

[0073] The side plate 5 has a circular ring shape. The side plate 5 includes an outer peripheral surface 50, an inner peripheral surface 51, a sixth end surface 52 connected to one end edge of the outer peripheral surface 50 and the inner peripheral surface 51, and a seventh end surface 53 connected to the other end edge of the outer peripheral surface 50 and the inner peripheral surface 51. The outer peripheral surface 50 and the inner peripheral surface 51 are arranged concentrically. The sixth end surface 52 and the seventh end surface 53 are parallel. The side plate 5 is pressed into the small diameter portion 11 of the shaft member 1. Pressing means that the side plate 5 is fitted to the small diameter portion 11 of the shaft member 1 to a degree of being fixed. The inner peripheral surface 51 of the side plate 5 has a diameter slightly larger than the outer diameter D1 of the small diameter portion 11. The inner peripheral surface 51 of the side plate 5 has a diameter to a degree that can fit with the part 11b of the small diameter portion 11 with a larger outer diameter. The side plate 5 is pressed and fixed at the part 11b with a larger outer diameter. The side plate 5 is arranged to contact the second end surface 104 of the large diameter portion 10 at the sixth end surface 52. The side plates 5 are made of steel, for example. The side plates 5 may also be quench-hardened.

[0074] <Mounting parts>

[0075] Figure 5 This is a schematic perspective view of the mounting member 6 in Embodiment 1 of the present disclosure as viewed from the first direction. Figure 6 is viewed from a second direction opposite to the first direction Figure 5 A schematic three-dimensional diagram of the mounting member 6. Figure 7 The plate-shaped portion 61 is viewed from the direction opposite to the tenth end surface 613. Figure 5 A schematic diagram of the installation part 6. Figure 8 The cylindrical portion 60 is cut by a plane including the central axis δ1. Figure 5 A schematic cross-sectional view of the mounting member 6.

[0076] Refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 The mounting member 6 includes a cylindrical portion 60, a plate-shaped portion 61 disposed at one axial end of the cylindrical portion 60 and extending radially outward from the cylindrical portion 60, and an arc-shaped portion 62 connected to the cylindrical portion 60 and the plate-shaped portion 61. The curvature radius R1 of the arc-shaped portion 62 is greater than or equal to 0.5 mm and less than or equal to 1.5 mm. The mounting member 6 is formed, for example, by cold forging.

[0077] The cylindrical portion 60 is arranged in the through hole TH of the shaft member 1 when assembled in the driven bearing module A. The cylindrical portion 60 is arranged inside the portion of the through hole TH corresponding to the third inner wall surface 132. The cylindrical portion 60 has an outer peripheral surface 600, an eighth end surface 601 connected to the outer peripheral surface 600, and a fourth inner peripheral surface 602 connected to the eighth end surface 601. The outer peripheral surface 600 has a cylindrical shape. The diameter of the outer peripheral surface 600 is larger than the diameter of the second inner wall surface 131 of the inner wall surface 13. The diameter of the outer peripheral surface 600 is smaller than the diameter of the third inner wall surface 132 of the inner wall surface 13 of the shaft member 1. The eighth end surface 601 faces the same direction as the insertion direction when the cylindrical portion 60 is inserted into the through hole TH. A thread groove is formed on the fourth inner peripheral surface 602. That is, the cylindrical portion 60 includes a thread groove on the fourth inner peripheral surface 602.

[0078] The plate-like portion 61 is arranged to be orthogonal to the central axis δ1 of the cylindrical portion 60. The plate-like portion 61 includes an outer peripheral surface 610, an inner peripheral surface 611, a ninth end surface 612 connecting the outer peripheral surface 610 and the arc-shaped portion 62, and a tenth end surface 613 connecting the outer peripheral surface 610 and the inner peripheral surface 611. The outer peripheral surface 610 includes a pair of flat plane portions 614 and 615 arranged parallel to each other and a pair of arc-shaped arc surface portions 616 and 617 connecting the plane portion 614 and the plane portion 615. Figure 7 As shown, the planar portions 614 and 615 are respectively arranged at positions away from the central axis δ1 of the cylindrical portion 60 by a predetermined distance L1. The arc surface portions 616 and 617 have a predetermined radius L2 with the intersection of the central axis δ1 of the cylindrical portion 60 and the surface of the extended plate-like portion 61 as the center. The distance L1 is smaller than the radius L2. The arc surface portions 616 and 617 are arranged concentrically with the cylindrical portion 60. By using the planar portions 614 and 615, the mounting member 6 can be rotated with the central axis δ1 of the cylindrical portion 60 as the rotation axis using a tool such as a wrench. By clamping the outer peripheral surface 610 of the plate-like portion 61 with a pair of clamping members (not shown) in contact with the planar portions 614 and 615, the rotation of the mounting member 6 with the central axis δ1 of the cylindrical portion 60 as the rotation axis can be suppressed.

[0079] The inner peripheral surface 611 has a regular hexagonal cylindrical shape. By inserting a hexagonal wrench or the like into the inside of the cylindrical portion 60 so as to contact the inner peripheral surface 611, the rotation of the attachment 6 about the central axis δ1 of the cylindrical portion 60 can be suppressed.

[0080] Refer to Figure 2 and Figure 3, the thickness TK1 of the cylindrical portion 60 is different from the thickness TK2 of the plate-like portion 61. The different thickness means that the ratio of the thickness TK2 of the plate-like portion 61 to the thickness TK1 of the cylindrical portion 60 is less than 1.0 or exceeds 1.3. The thickness TK1 of the cylindrical portion 60 is equal to the interval between the outer peripheral surface 600 and the fourth inner peripheral surface 602. The thickness TK2 of the plate-like portion 61 is equal to the interval between the ninth end surface 612 and the tenth end surface 613. The thickness TK2 of the plate-like portion 61 is greater than 1 mm and less than 5 mm. Thus, the installation space of the mounting member 6 can be made compact while ensuring the minimum rigidity of the plate-like portion 61. The thickness TK2 of the plate-like portion 61 is preferably 2 mm.

[0081] <Bolt>

[0082] Refer to Figure 1 , Figure 2 , Figure 3 and Figure 4 The bolt 7 includes: a main body 70, which includes a thread tooth on the outer peripheral surface that can be combined with the thread groove of the cylindrical part 60; and a head 71, which is connected to one end of the main body 70 in the longitudinal direction and has an outer diameter larger than that of the main body 70. The outer diameter of the main body 70 is smaller than the diameter D2 of the smallest diameter portion in the through hole TH. The outer diameter of the head 71 is preferably larger than the diameter D2 of the smallest diameter portion in the through hole TH. The head 71 includes a recess 710 on the end face opposite to the end face connected to the main body 70. The recess 710 includes an inner wall surface 711 having a cylindrical shape of a regular hexagon. The bolt 7 can be tightened by inserting a hexagonal wrench or the like into the interior of the recess 710 in a manner that contacts the inner wall surface 711.

[0083] 〔Installation order of driven bearing〕

[0084] Next, an example of the installation sequence when the driven bearing B is installed on the mounted member 9 is briefly described. First, the small diameter portion 11 of the shaft member 1 of the assembled driven bearing B is inserted into the mounting hole 92 of the mounted member 9 in a direction opposite to the first surface 90 of the mounted member 9 (the direction indicated by the arrow Y in the figure). The outer peripheral surface 110 of the small diameter portion 11 is opposite to the inner wall surface 93 of the mounting hole 92. The seventh end surface 53 of the side plate 5 is in contact with the first surface 90 of the mounted member 9. At this time, the outer ring 2 is not in contact with the mounted member 9.

[0085] Next, the mounting member 6 is inserted into the mounting hole 92 of the mounted member 9 in a direction opposite to the second surface 91 of the mounted member 9 (the direction opposite to the direction indicated by the arrow Y in the figure). The outer peripheral surface 600 of the cylindrical portion 60 is opposite to the third inner wall surface 132 of the inner wall surface 13 of the shaft member 1. The bolt 7 is inserted into the through hole TH in a direction opposite to the first end surface 103 of the shaft member 1. By rotating the bolt 7, the thread teeth of the main body 70 are combined with the thread groove of the cylindrical portion 60. The head 71 contacts the second step surface 133 of the inner wall surface 13 of the shaft member 1.

[0086] In this way, when the plate-like portion 61 of the mounting member 6 is located on one side when viewed from the through hole TH in the direction along the center axis δ, and when the head 71 of the bolt 7 is located on the other side when viewed from the through hole TH in the direction along the center axis δ, the thread groove of the cylindrical portion 60 inserted into the through hole TH is combined with the thread teeth of the main body portion 70 inserted into the through hole TH, thereby enabling the driven bearing B and the mounting member 6 to be fastened.

[0087] [Manufacturing method of shaft member of driven bearing]

[0088] Fig. 9 It is a flowchart showing each process of the manufacturing method of the shaft member 1. Fig.10 FIG. 1 is a diagram showing an example of a portion of a heating pattern in the manufacturing process of the shaft member 1. Fig.10 In the figure, the vertical axis represents temperature. Fig.10 In the figure, the horizontal axis represents time. Fig. 9 and Fig.10 , a method for manufacturing the shaft member 1 (inner member) of the driven bearing B described above is described. The method for manufacturing the shaft member 1 includes: a step of preparing a formed body (step ST1); a step of forming a carburized layer (step ST2); and a step of quenching and hardening the formed body (step ST3). The method for manufacturing the shaft member 1 also includes: a step of tempering the formed product (step ST4); and a step of finishing the formed product by grinding or the like (step ST5).

[0089] In step ST1, a formed body is prepared, which has the shape of the shaft member 1 and is composed of steel (hereinafter referred to as "steel" in steps ST1 to ST5), the steel containing 0.12 mass% or more and 0.39 mass% or less carbon, 0.05 mass% or more and 0.40 mass% or less silicon, 0.55 mass% or more and 0.95 mass% or less manganese and 0.60 mass% or more and 1.25 mass% or less chromium, and the remainder is composed of iron and inevitable impurities. The shaft member 1 includes: an outer peripheral surface 12, which includes an annular first track surface P1 having a central axis δ; and an inner wall surface 13, which defines a through hole TH including the central axis δ. The through hole TH has a diameter of 40% or more of the outer diameter of the smallest outer diameter portion of the shaft member 1. For example, after forming by cold forging, the shape is adjusted by turning, thereby preparing the above-mentioned formed body. By forming the formed body by cold forging, the forging flow lines of the shaft member 1 become continuous, and thus the strength of the shaft member 1 can be ensured.

[0090] Next, in step ST2, a carburized layer is formed by heating the formed body prepared in step ST1 to a temperature not less than the A1 point of steel and not more than 900°C in a carburizing gas environment so as to form at least a portion of the surface of the formed body. In the present embodiment, the carburized layer is formed over the entire surface of the formed body. The carburizing gas environment is, for example, a gas environment in which a hydrocarbon gas such as propane, butane, acetylene, etc. is introduced as an enriched gas into an endothermic reforming gas mainly composed of carbon monoxide, hydrogen, and nitrogen. Fig.10 As shown, the process of forming the carburized layer includes, for example, a carburizing process and a subsequent quenching heating process.

[0091] In the carburizing process, the temperature is maintained at a temperature above the A1 point of the steel and below 900°C during the prescribed carburizing time Tc. The carburizing time Tc is, for example, 160 minutes. In the carburizing process, the carbon potential in the gas atmosphere is maintained at a prescribed value CP1 (for example, 1.1%) during the first time T1 (for example, 130 minutes) during the carburizing time Tc. Thereafter, the carbon potential in the gas atmosphere is maintained at a prescribed value CP2 (for example, 0.9%) lower than the value CP1 during the second time T2 (for example, 30 minutes) during the carburizing time Tc.

[0092] In the quenching heating step, the temperature is maintained at a predetermined temperature (e.g., 860° C.) during a predetermined quenching heating time Te. The quenching heating time Te is, for example, 30 minutes. During the quenching heating time, the carbon potential in the gas atmosphere is maintained at a value CP3 (e.g., 0.9%) equivalent to the value CP2.

[0093] In step ST3, the formed body with the carburized layer formed thereon is cooled from a temperature range above the A1 point of the steel to a temperature range below the MS point, thereby quenching and hardening the formed body. For example, the formed body is quenched and hardened by cooling it in oil to a predetermined temperature (for example, 60° C.).

[0094] In step ST4, the formed product hardened by quenching in step ST3 is tempered. For example, the tempering is performed by heating at a temperature of 175°C for 120 minutes.

[0095] In step ST5, the formed product tempered in step ST4 is finished by grinding or the like. For example, the carburized abnormal layer (grain boundary oxidation layer) generated by the carburizing treatment is removed by grinding the outer peripheral surface including the first raceway surface P1 in the large diameter portion 10 of the shaft member 1. At this time, the outer peripheral surface corresponding to the first end portion 11a in the small diameter portion 11 is not ground. That is, in the small diameter portion 11, there is a carburized abnormal layer in the area including the outer peripheral surface corresponding to the first end portion 11a. After such processes in steps ST1 to ST5, the shaft member 1 is manufactured.

[0096] In addition, in the above-mentioned step ST1, a formed body may be prepared, which has the shape of the shaft member 1 and is made of steel containing 0.12 mass % or more and 0.39 mass % or less of carbon, 0.05 mass % or more and 0.40 mass % or less of silicon, 0.55 mass % or more and 0.95 mass % or less of manganese, 0.60 mass % or more and 1.25 mass % or less of chromium, and 0.15 mass % or more and 0.35 mass % or less of molybdenum, and the remainder is made of iron and inevitable impurities. Even in such a case, the processes in steps ST2 to ST5 are the same as those described above.

[0097] (Implementation Method 2)

[0098] Next, Embodiment 2 of the present disclosure will be described. Fig.11 It is a schematic perspective view of a driven bearing module A in Embodiment 2 of the present disclosure. Fig.12 is along Fig.11 Schematic diagram of the cross section taken along line IV-IV in FIG. Fig.13 is along Fig.11 Schematic diagram of the cross section along line VV in FIG. Fig.14 It roughly indicates Fig.11 The exploded perspective view of the driven bearing module A is shown. Fig.11 In FIG. 1 , the mounted component 9 is indicated by a single-dot chain line. Fig.12 and Fig.13 In the figure, the central axis δ is represented by a single-dot dash line. Fig.14 In the figure, the mounted member 9 is omitted.

[0099] 〔Driven bearing module〕

[0100] Refer to Fig.11 , Fig.12 and Fig.14 The small diameter portion 11 of the shaft member 1 further includes cutouts 112 and 113 formed by cutting off a portion of a corner formed by the outer peripheral surface 110 and the third end surface 111. The cutouts 112 and 113 are arranged at intervals of 180 degrees from each other in the circumferential direction of the small diameter portion 11. The cutouts 112 and 113 have rectangular profiles when viewed from the axial direction and when viewed from the radial direction, respectively.

[0101] Fig.15 This is a schematic perspective view of the mounting fixture 6 in Embodiment 2 of the present disclosure as viewed from the first direction. Fig.16 is viewed from a second direction opposite to the first direction Fig.15 A schematic three-dimensional diagram of the mounting member 6. Fig.17 The plate-shaped portion 61 is viewed from the direction opposite to the tenth end surface 613. Fig.15 A schematic diagram of the installation part 6.

[0102] Refer to Fig.11 , Fig.12 , Fig.14 , Fig.15 , Fig.16 and Fig.17 The mounting member 6 further includes protrusions 63 and 64 protruding from the portion of the outer peripheral surface 600 of the cylindrical portion 60 close to the plate-shaped portion 61 toward the radially outer side of the cylindrical portion 60. The protrusion 63 is embedded in the inside of the cutout 112 of the small diameter portion 11 of the shaft member 1. The protrusion 64 interferes with the inner wall surface of the cutout 112, thereby suppressing the rotation of the shaft member 1 with the central axis δ or an axis parallel to the central axis δ as the rotation axis. The protrusion 64 is embedded in the inside of the cutout 113 of the small diameter portion 11. The protrusion 64 interferes with the inner wall surface of the cutout 113, thereby suppressing the rotation of the shaft member 1 with the central axis δ or an axis parallel to the central axis δ as the rotation axis. By such protrusions 63 and 64, the rotation of the shaft member 1 with the central axis δ or an axis parallel to the central axis δ as the rotation axis can be suppressed.

[0103] Refer to Fig.12 , Fig.13 , Fig.14 , Fig.15 , Fig.16 and Fig.17The cylindrical portion 60 further includes a fifth inner peripheral surface 603 connected to the fourth inner peripheral surface 602. The fifth inner peripheral surface 603 has a regular hexagonal cylindrical shape. By inserting a hexagonal wrench or the like into the inside of the cylindrical portion 60 in a manner in contact with the fifth inner peripheral surface 603, the rotation of the mounting member 6 with the central axis δ1 of the cylindrical portion 60 as the rotation axis can be suppressed. The inner peripheral surface 611 of the plate-shaped portion 61 has an arc shape connecting the tenth end surface 613 of the plate-shaped portion 61 and the fifth inner peripheral surface 603 of the cylindrical portion 60.

[0104] Two plate-like through holes 618 and 619 are formed in the plate-like portion 61. The plate-like through holes 618 and 619 are arranged at intervals of 180 degrees in the circumferential direction of the cylindrical portion 60. The plate-like through holes 618 and 619 are arranged at a position farther from the central axis δ1 of the cylindrical portion 60 than the protrusions 63 and 64. By forming such plate-like through holes 618 and 619 in the mounting member 6, for example, when the mounting member 6 is manufactured by stamping, a part of the plate-like portion 61 can be deformed by using the plate-like through holes 618 and 619, thereby easily forming the protrusions 63 and 64. In addition, as required, the cutout of the small-diameter portion 11 and the protrusion of the mounting member 6 can be one each, or three or more each. In addition, the number of cutouts in the small-diameter portion 11 can also be more than the number of protrusions of the mounting member 6.

[0105] 〔Installation order of driven bearing〕

[0106] The following is a supplement to the installation sequence of the driven bearing B in the above-mentioned embodiment 1 regarding the installation sequence of the driven bearing B in the second embodiment. The mounting member 6 is inserted into the mounting hole 92 of the mounted member 9 in such a manner that the bosses 63 and 64 of the mounting member 6 are fitted into the inside of the cutouts 112 and 113 of the small diameter portion 11 of the shaft member 1. When fastened by the bolt 7, the bosses 63 and 64 fitted into the cutouts 112 and 113 of the small diameter portion 11 are hooked, thereby suppressing the rotation of the mounting member 6. Thus, the so-called co-rotation of the bolt 7 and the mounting member 6 can be suppressed.

[0107] The method for manufacturing the shaft member 1 (inner member) of the driven bearing B in the second embodiment is the same as the method for manufacturing the shaft member 1 (inner member) in the first embodiment described above.

[0108] Example 1

[0109] According to the manufacturing method of the shaft member 1 (inner member) described above, the shaft member 1 is manufactured by SCM415 specified in JISG4053. The grain size number of the original austenite grains in the carburized layer of the manufactured shaft member 1 is measured based on JISG0551. First, the shaft member 1 is cut at a section intersecting the front of the shaft member 1. Then, for the section formed by cutting, after the original austenite grain boundary is revealed using a corrosive solution such as a saturated aqueous solution of picric acid, an optical microscope is used to observe the vicinity of the surface of the carburized layer, thereby measuring the grain size number of the original austenite grains.

[0110] Fig.18 This is a diagram showing an example of prior austenite grains in a carburized layer of the shaft member 1 manufactured by the method for manufacturing the shaft member 1 of the present disclosure. Fig.18 The example shown is an example of heating to a temperature of 860° C. in the carburizing step. Fig.19 The example shown is an example of heating to a temperature of 930°C in the carburizing process. Fig.18 In the example shown, the grain size number of the prior austenite grains is 9.5. Fig.19 It is a diagram showing a comparative example of prior austenite grains in the carburized layer of the shaft member 1 . Fig.19 The example shown is an example of heating to a temperature of 930°C in the carburizing process. Fig.19 In the example shown, the grain size number of the prior austenite grains is 7.8.

[0111] like Fig.18 As shown, by heating the formed body in a carburizing gas atmosphere to a temperature of not less than the A1 point of steel and not more than 900° C. in the carburizing step, a carburized layer having a grain size number of 8.6 or more of prior austenite grains is obtained.

[0112] (Example 2)

[0113] Fig. 20 This is a schematic diagram of a test piece used in the rotating bending fatigue test in Example 2. Fig.21 yes Fig. 20 This is an enlarged view of the cut N in the test piece. Fig. 20 and Fig.21 In the figure, the number indicates the size (in mm). Fig. 20 and Fig.21 middle, Indicates diameter. Fig. 20 and Fig.21 In the example, "R" indicates the radius. Fig. 20 The test piece shown was subjected to a rotating bending fatigue test in accordance with JIS Z 2274. The load frequency was set to 50 kHz. If the rotation speed of the test piece increased from the start of the test to 10 7 If the test piece does not break after the test, the test is terminated.

[0114] Reference Fig. 20 The test piece has the shape of the No. 1 (1-8) test piece specified in JIS Z 2274. A notch N is formed in the parallel portion L of the test piece. Fig.21 , the notch N has an opening of 1.44 mm in the length direction of the test piece and a depth of 0.75 mm in the radial direction of the test piece. The profile C of the notch N includes a pair of inclined surfaces S1 and S2 arranged at an angle of 60 degrees when observed from the radial direction of the test piece, and a curved surface SC connecting the inclined surface S1 and the inclined surface S2 and having a curvature radius of 0.5 mm. As a test piece, a test piece composed of SCM415 specified in JISG 4053 was prepared. As test pieces, three types of test pieces were prepared, namely, a test piece heated to a temperature of 860°C in a carburizing gas environment, a test piece heated to a temperature of 900°C in a carburizing gas environment, and a test piece heated to a temperature of 930°C in a carburizing gas environment. As in the manufacturing method of the shaft component 1 described above, after the carburized layer is formed, a quenching process and a tempering process are performed, thereby producing any test piece. The surface of the notch N becomes a state where no grinding process is performed (a state where a carburized abnormal layer exists). The results of the rotating bending fatigue test using these test pieces were applied to the regression model described in the Metal Material Fatigue Reliability Evaluation Standard (JSMS-SD-6-02) of the Japan Society for Materials Science and Technology to obtain the SN curve.

[0115] Fig. 22 SN curve obtained in the rotating bending fatigue test of Example 2. Fig. 22 In the figure, the vertical axis represents the stress amplitude on a normal scale. Fig. 22 In the example, the horizontal axis shows the number of repetitions in a logarithmic scale. Fig. 22 In the figure, the arrow indicates the termination of the experiment. Fig. 22 In the figure, circles represent data points of test pieces heated to 860°C in a carburizing gas environment, diamonds represent data points of test pieces heated to 900°C in a carburizing gas environment, and triangles represent data points of test pieces heated to 930°C in a carburizing gas environment. Fig. 22 In the figure, the bold line represents the SN curve of the test piece heated to 860°C in a carburizing gas environment, the dotted line represents the SN curve of the test piece heated to 900°C in a carburizing gas environment, and the dotted line represents the SN curve of the test piece heated to 930°C in a carburizing gas environment.

[0116] like Fig. 22As shown, the fatigue limit of the test piece heated to 860°C in a carburizing gas environment is about 547 MPa, the fatigue limit of the test piece heated to 900°C in a carburizing gas environment is about 529 MPa, and the fatigue limit of the test piece heated to 930°C in a carburizing gas environment is about 417 MPa.

[0117] Fig.23 This is a diagram showing an example of prior austenite grains in a carburized layer of a test piece heated to 860°C in a carburizing gas atmosphere. Fig.23 In the example shown, the grain size number of the prior austenite grains is 9.6. Fig.24 This is a diagram showing an example of prior austenite grains in a carburized layer of a test piece heated to 900°C in a carburizing gas atmosphere. Fig.24 In the example shown, the grain size number of the prior austenite grains is 8.6. Fig.25 This is a diagram showing an example of prior austenite grains in a carburized layer of a test piece heated to 930°C in a carburizing gas atmosphere. Fig.25 In the example shown, the grain size number of the prior austenite grains is 8.0.

[0118] Fig.26 It is a graph showing the relationship between fatigue limit and the grain size number of the prior austenite grain. Fig.26 In the figure, the vertical axis represents the fatigue limit. Fig.26 In the figure, the horizontal axis represents the grain size number of the original austenite grains. Fig.26 The dotted line in is an approximate curve showing the transition of fatigue limit relative to the grain size number of the original austenite grain. Fig. 22 After the relationship between the fatigue limit and the heating temperature of each test piece is obtained from each SN curve in the above, the heating temperature of each test piece is replaced by the grain size number of the original austenite grain in the carburized layer of each test piece, thereby obtaining the relationship between the fatigue limit and the grain size number of the original austenite grain. Fig.26 As shown, before the grain size of the original austenite grains in the carburized layer is numbered 8.6, the fatigue limit rises sharply as the grain size number rises. On the other hand, if it exceeds 8.6, the rise becomes slow and an excellent fatigue limit can be obtained. Therefore, it can be said that in order to obtain a good fatigue limit, it is effective to set the grain size of the original austenite grains to be above 8.6.

[0119] It should be understood that the embodiments disclosed this time are illustrative in all aspects and are not restrictive in any respect. The scope of the present invention is defined by the claims, and includes all modifications within the meaning and scope equivalent to the claims.

[0120] Description of reference numerals:

[0121] 1 shaft member (inner member), 2 outer ring, 3 roller (rolling element), 4 retainer, 5 side plate, 6 mounting member, 7 bolt, 9 mounted member, 10 large diameter portion, 11 small diameter portion, 11a first end portion, 11b portion, 12 outer peripheral surface, 13 inner wall surface, 20 outer peripheral surface, 21 fourth end surface, 22 fifth end surface, 23 first inner peripheral surface, 24 second inner peripheral surface, 25 third inner peripheral surface, 26 fourth step surface, 27 fifth step surface, 30 outer peripheral surface, 31 end surface, 32 end surface surface, 40 pocket hole, 50 outer peripheral surface, 51 inner peripheral surface, 52 sixth end surface, 53 seventh end surface, 60 cylindrical portion, 61 plate portion, 62 arc portion, 63 raised portion, 64 raised portion, 70 main body portion, 71 head portion, 90 first surface, 91 second surface, 92 mounting hole, 93 inner wall surface, 100 first outer peripheral surface, 101 second outer peripheral surface, 102 first step surface, 103 first end surface, 104 second end surface, 110 outer peripheral surface, 111 third end surface, 112 cut surface opening, 113 notch, 130 first inner wall surface, 131 second inner wall surface, 132 third inner wall surface, 133 second step surface, 134 third step surface, 600 outer circumference, 601 eighth end surface, 602 fourth inner circumference, 603 fifth inner circumference, 610 outer circumference, 611 inner circumference, 612 ninth end surface, 613 tenth end surface, 614 plane portion, 615 plane portion, 616 arc surface portion, 617 arc surface portion, 618 plate-shaped portion through hole, 619 plate-shaped portion Through hole, 710 recess, 711 inner wall surface, A driven bearing module, B driven bearing, C contour, D1 outer diameter, D2 diameter, L parallel portion, L1 distance, L2 radius, N cut, P1 first track surface, P2 second track surface, S1 inclined surface, S2 inclined surface, SC curved surface, T1 first time, T2 second time, TH through hole, TK1 thickness, TK2 thickness, Tc carburizing time, Te quenching heating time, Y arrow, δ center axis, δ1 center axis.

Claims

1. A driven bearing, wherein: have: An inner member including an outer peripheral surface and an inner wall surface, wherein the outer peripheral surface includes an annular first track surface having a central axis, and the inner wall surface defines a through hole including the central axis; an outer ring, comprising an annular second track surface on an inner circumference thereof and opposite to the first track surface; and A plurality of rolling elements are arranged on an annular track along the first track surface and the second track surface in a manner of contacting the first track surface and the second track surface, The smallest diameter portion of the through hole has a diameter that is 40% or more of the outer diameter of the smallest outer diameter portion of the inner member, The inner member is made of steel containing 0.12 mass % to 0.39 mass % carbon, 0.05 mass % to 0.40 mass % silicon, 0.55 mass % to 0.95 mass % manganese and 0.60 mass % to 1.25 mass % chromium, with the remainder being iron and inevitable impurities, The inner member includes a carburized layer, the carburized layer constituting at least a portion of a surface of the inner member and containing 0.60 mass % or more and 1.20 mass % or less of carbon, In the carburized layer, the grain size number of prior austenite grains specified in JIS G 0551 is 8.6 or more.

2. A driven bearing, wherein: have: An inner member including an outer peripheral surface and an inner wall surface, wherein the outer peripheral surface includes an annular first track surface having a central axis, and the inner wall surface defines a through hole including the central axis; an outer ring, comprising an annular second track surface on an inner circumference thereof and opposite to the first track surface; and A plurality of rolling elements are arranged on an annular track along the first track surface and the second track surface in a manner of contacting the first track surface and the second track surface, The smallest diameter portion of the through hole has a diameter that is 40% or more of the outer diameter of the smallest outer diameter portion of the inner member, The inner member is made of steel containing 0.12 mass % to 0.39 mass % carbon, 0.05 mass % to 0.40 mass % silicon, 0.55 mass % to 0.95 mass % manganese, 0.60 mass % to 1.25 mass % chromium, and 0.15 mass % to 0.35 mass % molybdenum, with the remainder being iron and inevitable impurities, The inner member includes a carburized layer, the carburized layer constituting at least a portion of a surface of the inner member and containing 0.60 mass % or more and 1.20 mass % or less of carbon, In the carburized layer, the grain size number of prior austenite grains specified in JIS G 0551 is 8.6 or more.

3. The driven bearing according to claim 1 or 2, wherein: The hardness of the surface of the inner member composed of the carburized layer is 700 HV or more.

4. The driven bearing according to claim 1 or 2, wherein: The inner member comprises: a large diameter portion including the first track surface on an outer peripheral surface; and The small diameter portion is connected to the large diameter portion at an end portion, i.e., a first end portion, in a direction along the central axis and has an outer diameter smaller than an outer diameter of the large diameter portion. The carburized layer is arranged to include an outer peripheral surface corresponding to the first end portion in the small diameter portion.

5. A driven bearing module, wherein: have: The driven bearing according to claim 1 or 2; Mounting parts; as well as fastener, The mounting member comprises: a cylindrical portion including a thread groove on an inner peripheral surface; and The plate-shaped portion is arranged at one axial end of the cylindrical portion and extends radially outward from the cylindrical portion. The fastener comprises: a main body portion including, on an outer peripheral surface, threads capable of engaging with the thread groove of the cylindrical portion; and A head portion connected to one end portion of the main body portion in the longitudinal direction and having an outer diameter larger than that of the main body portion, In a state where the plate-like portion of the mounting piece is located on one side when viewed from the through hole in the direction along the center axis, and where the head of the fastener is located on the other side when viewed from the through hole in the direction along the center axis, the thread groove of the cylindrical portion inserted into the through hole is combined with the thread teeth of the main body portion inserted into the through hole, thereby enabling the driven bearing to be fastened to the mounting piece.

6. The driven bearing module according to claim 5, wherein: The mounting member further includes an arc-shaped portion connected to the cylindrical portion and the plate-shaped portion. The radius of curvature of the arc-shaped portion is greater than or equal to 0.5 mm and less than or equal to 1.5 mm.

7. A method for manufacturing an inner member of a driven bearing, wherein: The inner member includes an outer peripheral surface and an inner wall surface, the outer peripheral surface includes an annular first track surface having a central axis, and the inner wall surface defines a through hole including the central axis. The smallest diameter portion of the through hole has a diameter that is 40% or more of the outer diameter of the smallest outer diameter portion of the inner member, The manufacturing method of the inner member comprises: a step of preparing a formed body having a shape of the inner member and composed of steel containing 0.12 mass % to 0.39 mass % carbon, 0.05 mass % to 0.40 mass % silicon, 0.55 mass % to 0.95 mass % manganese, and 0.60 mass % to 1.25 mass % chromium, with the remainder being iron and unavoidable impurities; A step of forming a carburized layer constituting at least a portion of a surface of the formed body by heating the formed body to a temperature of not less than the A1 point of the steel and not more than 900° C. in a carburizing gas atmosphere; and A step of quench-hardening the formed body by cooling the formed body having the carburized layer from a temperature range of the steel at or above the A1 point to a temperature range of or below the MS point.

Images