Rolling bearing race and manufacturing method thereof

Abstract

[Problem] To provide a manufacturing method whereby it is possible to obtain, at a low cost, a raceway ring for a roller bearing that ensures hardness of not only a rolling element guide surface, but also the surface of a prescribed location offset from the rolling element guide surface. [Solution] This manufacturing method comprises: a step for obtaining a base material (12); a step for forming, by means of laser cladding on any one surface among an outer peripheral surface, inner peripheral surface, and side surfaces on both sides in the axial direction of the base material (12), build-up layers (13a), (13b) made of a metal material having a hardness which is greater than a section of the base material (12) offset from a cured layer (14); a step for forming surface layer portions of rolling element guide surfaces (8), (9) by performing finish processing on the surfaces of the build-up layers (13a), (13b); and a step for forming the cured layer (14) by means of laser quenching along the entire circumference on the surface layer portions including at least a part of the section of the surface of the base material (12) covered by the build-up layers (13a), (13b).

Description

[Technical field]

[0001] The present disclosure relates to a raceway that constitutes a rolling bearing and a method for manufacturing the same. [Background technology]

[0002] 2. Description of the Related Art Rolling bearings are used as rotation support devices incorporated in various mechanical devices.

[0003] Among rolling bearings, radial rolling bearings that mainly support radial loads include an outer ring, which is a raceway ring having a raceway surface on its inner circumferential surface, an inner ring, which is a raceway ring having a raceway surface on its outer circumferential surface, and a number of rolling elements arranged to roll between the raceway surfaces of the outer ring and the inner ring. Among rolling bearings, thrust rolling bearings that mainly support thrust loads include a pair of raceways having raceways on side surfaces opposing each other in the axial direction, and a number of rolling elements arranged to roll between the raceway surfaces of the pair of raceways. The raceway surfaces form rolling element guide surfaces that bring the rolling elements into rolling contact to guide them.

[0004] In radial rolling bearings, when rollers are used as the rolling elements, one of the raceways, the outer or inner, may have a rib portion at a location axially adjacent to the raceway surface, and the axial end face of the roller may be in sliding contact with the rib surface, which is the axial side surface of the rib portion. In thrust rolling bearings, one of the raceways, the pair of raceways, may have a rib portion at a location radially adjacent to the raceway surface, and the axial end face of the roller may be in sliding contact with the rib surface, which is the peripheral surface of the rib portion. The rib surface constitutes a rolling element guide surface that makes sliding contact with the rolling elements to guide them.

[0005] Among the surfaces of the raceway, the rolling element guideway formed by the raceway surface and the rib surface must have a long service life against spalling and wear. For this reason, the raceway has been made of bearing steel or subjected to heat treatment in a heat treatment furnace.

[0006] JP 2020-190274 A describes a manufacturing method for forming a raceway surface, which is a guideway for rolling elements, from a material containing a Ni-based alloy in order to improve the wear resistance of the raceway surface in a high-temperature environment. In this manufacturing method, a build-up layer made of a material containing a Ni-based alloy and having a harder property than the base material is formed on the peripheral surface of a base material constituting a raceway ring by laser cladding, and then the surface of the build-up layer is ground to form the raceway surface. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2020-190274 A Summary of the Invention [Problem to be solved by the invention]

[0008] In order to provide the rolling element guideway of the raceway with a long service life against spalling and wear resistance, the raceway is made of a hard metal such as a high-hardness chromium bearing steel that can be hardened by heat treatment, but this increases the material cost of the raceway. In addition, heat treatment is generally performed using a heat treatment furnace, which increases the cost of equipment and operation for the heat treatment. From the viewpoint of protecting the global environment, it is also necessary to reduce the environmental load caused by heat treatment.

[0009] According to the method for manufacturing the raceway ring described in JP 2020-190274 A, even if inexpensive high carbon steel or medium carbon steel is used as the metal material constituting the base material, the build-up layer formed by laser cladding can ensure a raceway surface with sufficient hardness. This reduces the manufacturing cost of the raceway ring and provides the raceway surface with excellent spalling life and wear resistance. However, there is a problem in that the hardness of the completed raceway ring is not sufficiently ensured in the parts other than the raceway surface.

[0010] That is, the peripheral surfaces of the raceway ring, such as the raceway surface and the flange surface, on which the rolling element guide surface is not formed, are used as fitting surfaces for mating peripheral surfaces, such as the inner peripheral surface of the housing and the outer peripheral surface of the rotating shaft. Also, the axial side surfaces on which the rolling element guide surface is not formed are used as axial positioning side surfaces that come into contact with mating side surfaces provided on the housing, the rotating shaft, etc. If sufficient hardness is not ensured for these fitting surfaces and positioning side surfaces, damage such as fretting wear and dents will easily occur, and it may become difficult to sufficiently ensure the rotation support performance of the rolling bearing.

[0011] If a base material having a raceway surface formed on the surface of a buildup layer is subjected to a heat treatment, sufficient hardness can be ensured for the fitting surface and the positioning side surface. However, not only does the cost of equipment and operation for the heat treatment increase, but the metal structure of the buildup layer may change due to the heat treatment, making it impossible to obtain the desired hardness for the raceway surface.

[0012] The present disclosure aims to provide a raceway for a rolling bearing at low cost that ensures sufficient surface hardness not only of the rolling element guide surface, but also of specified locations outside the rolling element guide surface, such as the mating surface and the positioning side surface. [Means for solving the problem]

[0013] A raceway for a rolling bearing to which one aspect of the present disclosure is applied is as follows: A substrate having an outer peripheral surface, an inner peripheral surface, and side surfaces on both axial sides; A build-up layer covering any one of the outer peripheral surface, the inner peripheral surface, and the side surfaces on both axial sides; A rolling element guide surface provided on the surface of the buildup layer over the entire periphery; A hardened layer formed on the entire periphery of a surface layer portion of the base material, including at least a part of a portion of the surface of the base material that is not covered by the buildup layer; Equipped with The hardened layer has a higher hardness than a portion of the substrate that is not covered by the hardened layer.

[0014] In one aspect of the present disclosure, a method for manufacturing a race for a rolling bearing includes the steps of: Obtaining the substrate; forming the build-up layer by laser cladding on any one of the outer peripheral surface, the inner peripheral surface, and the side surfaces on both axial sides of the base material, the build-up layer being made of a metal material having a higher hardness than a portion of the base material that is not covered by the hardened layer; forming the rolling element guide surface by performing a finishing process on a surface of the buildup layer; forming the hardened layer over the entire periphery of a surface layer portion of the base material, including at least a portion of a surface of the base material that is not covered by the buildup layer, by laser hardening; Equipped with.

[0015] In the race for a rolling bearing according to one aspect of the present disclosure, the hardness of the buildup layer is higher than the hardness of a portion of the base material that is not covered by the hardened layer.

[0016] The at least one portion corresponds to, for example, a portion of the base material that fits into an adjacent mating member when in use and / or a portion that abuts against an adjacent mating member when in use.

[0017] The substrate may be constructed from high carbon steel or medium carbon steel.

[0018] The buildup layer can be made of at least one selected from an Fe-based alloy, a Ni-based alloy, and a Co-based alloy. Effect of the Invention

[0019] According to one aspect of the rolling bearing race and its manufacturing method disclosed herein, a rolling bearing race that ensures sufficient surface hardness not only in the rolling element guideway but also in specified locations outside the rolling element guideway can be obtained at low cost. [Brief description of the drawings]

[0020] [Figure 1]FIG. 1 is a partial cross-sectional view of a rolling bearing including an outer ring which is a raceway ring according to a first embodiment of the present disclosure. [Diagram 2] 2A to 2C are partial cross-sectional views showing a method for manufacturing the outer ring shown in FIG. 1 in the order of steps. [Diagram 3] FIG. 3 is a partial cross-sectional view showing an inner ring which is a raceway ring according to a second example of an embodiment of the present disclosure. [Figure 4] FIG. 4 is a partial cross-sectional view of a rolling bearing including an outer ring which is a raceway ring according to a third embodiment of the present disclosure. [Diagram 5] FIG. 5 is a partial cross-sectional view of the outer ring shown in FIG. [Figure 6] FIG. 6 is a partial cross-sectional view of an inner ring which is a raceway ring according to a fourth example of an embodiment of the present disclosure. [Figure 7] FIG. 7 is a partial cross-sectional view of a rolling bearing including an outer ring which is a raceway ring according to a fifth embodiment of the present disclosure. [Figure 8] FIG. 8 is a partial cross-sectional view of the outer ring shown in FIG. [Figure 9] FIG. 9 is a partial cross-sectional view of an inner ring which is a raceway ring according to a sixth example of an embodiment of the present disclosure. [Figure 10] FIG. 10(a) is a cross-sectional view of a raceway ring that was used in a test to verify the effects of the present disclosure, and FIG. 10(b) is a view of the raceway ring as viewed from the right side of FIG. 10(a). [Figure 11] FIG. 11 is a diagram showing the results of evaluation of the appearance of sample A (Example) and sample B (Comparative Example). [Figure 12] FIG. 12 is a diagram showing the evaluation results of the degree of scratches on Sample A (Example) and Sample B (Comparative Example). [Figure 13] FIG. 13 is a diagram showing the evaluation results of shape collapse for sample A (Example) and sample B (Comparative Example). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] [Example 1] A first example of an embodiment of the present disclosure will be described with reference to FIGS. 1 and 2. FIG.

[0022] The rolling bearing 1 is a radial cylindrical roller bearing, and includes an outer ring 2, an inner ring 3, and a plurality of cylindrical rollers 4, which serve as rolling elements. However, the present disclosure is not limited to raceways constituting radial cylindrical roller bearings, and can also be applied to raceways constituting various radial rolling bearings and raceways constituting various thrust rolling bearings.

[0023] This example is applied to an outer ring 2 that constitutes a rolling bearing 1.

[0024] The outer ring 2 comprises a substrate 12 having an outer peripheral surface 5, an inner peripheral surface 6, and side surfaces 7 on both axial sides, buildup layers 13a, 13b covering one of the outer peripheral surface 5, the inner peripheral surface 6, and the side surfaces 7 on both axial sides, an outer ring raceway surface 8 and a pair of flange surfaces 9 serving as rolling element guide surfaces provided over the entire circumference on the surfaces of the buildup layers 13a, 13b, and a hardened layer 14 formed over the entire circumference on a surface layer portion including at least a portion of the surface of the substrate 12 outside the portions covered by the buildup layers 13a, 13b. Note that in Fig. 1, the reference numerals for the buildup layers 13a, 13b, and the hardened layer 14, as well as the boundaries between the substrate 12 and the buildup layers 13a, 13b, and the hardened layer 14 are omitted.

[0025] The substrate 12 is configured to be annular as a whole, more specifically, substantially cylindrical, and has a pair of inward flanges 10 that protrude radially inward at both axial ends. The inner peripheral surface 6 of the substrate 12 has a recess 24 that recesses radially outward in an axially intermediate portion located between the pair of inward flanges 10. A bottom surface 25 of the recess 24 is configured as a cylindrical surface. Side surfaces 26 on both axial sides of the recess 24, i.e., the opposing axial side surfaces of the pair of inward flanges 10, are configured as planes perpendicular to the axial direction.

[0026] The inner circumferential surface 11 of the pair of inward flanges 10 of the base material 12 is formed of a cylindrical surface. The outer circumferential surface 5 of the base material 12 is formed of a cylindrical surface. The side surfaces 7 on both axial sides of the base material 12 are formed of flat surfaces perpendicular to the axial direction.

[0027] In this example, the base material 12 can be made of a metal material such as high carbon steel (SK material) with a carbon content of 0.6% to 2.14%, or medium carbon steel (a part of SS material and SC material) with a carbon content of 0.25% to 0.6%.

[0028] The buildup layer 13a is formed over the entire periphery of the inner circumferential surface 6 of the base material 12 so as to cover the bottom surface 25 of the recess 24, and the outer ring raceway surface 8 is formed over the entire periphery on the surface of the buildup layer 13a, i.e., the inner circumferential surface. In other words, the buildup layer 13a constitutes a surface layer portion of the outer ring 2 including the outer ring raceway surface 8.

[0029] The buildup layer 13b is formed over the entire periphery of the inner circumferential surface 6 of the base material 12 so as to cover side surfaces 26 on both axial sides of the recess 24, and a flange surface 9 is formed over the entire periphery on the surface of each buildup layer 13b, i.e., on the axial side surfaces. In other words, each buildup layer 13b constitutes a surface layer portion of the outer ring 2 including the flange surface 9.

[0030] The thickness of the build-up layers 13a, 13b is not limited to this, but can be 1000 μm or less, and is preferably 200 μm or more and 500 μm or less.

[0031] The build-up layers 13a, 13b are made of a metal material, such as an Fe-based alloy, a Ni-based alloy, or a Co-based alloy, that is harder than the portion of the substrate 12 that is not covered by the hardened layer 14. In this embodiment, the build-up layers 13a, 13b preferably have a hardness of HRC58 or higher. The build-up layers 13a, 13b preferably have a hardness higher than that of the hardened layer 14. However, when implementing the present disclosure, the hardness of the build-up layers can be the same as that of the hardened layer, or can be lower than that of the hardened layer.

[0032] In this example, hardened layer 14 is formed over the entire periphery of the surface layer portion of substrate 12, including at least a portion of the surface of substrate 12 constituting outer ring 2 that is separate from the portions covered by buildup layers 13a, 13b (see FIG. 2(d)). Specifically, hardened layer 14 is formed over the entire periphery of the surface layer portion of substrate 12, including outer peripheral surface 5 and side surfaces 7 on both axial sides. Hardened layer 14 has a higher hardness than the portions of substrate 12 that are separate from hardened layer 14.

[0033] The thickness of the hardened layer 14 is not limited to this value, but may be 1000 μm or less, and is preferably 200 μm or more and 500 μm or less.

[0034] When carrying out the present disclosure, the hardened layer 14 can additionally be formed over the entire periphery on the surface layer portion of the base material 12 including the inner circumferential surfaces 11 of the pair of inward flanges 10. Alternatively, the hardened layer 14 can be formed over the entire periphery only on the surface layer portion of the base material 12 including the outer circumferential surface 5, the side surfaces 7 on both axial sides, and a part of the inner circumferential surfaces 11 of the pair of inward flanges 10.

[0035] In this embodiment, the surface hardness of the hardened layer 14 is preferably HRC58 or more.

[0036] The inner ring 3 constituting the rolling bearing 1 of this example is made of hard metal such as bearing steel and is generally annular. The inner ring 3 has an outer peripheral surface 15, an inner peripheral surface 16, and side surfaces 17 on both axial sides, and has an inner ring raceway surface 18 formed by a cylindrical surface at the axial middle portion of the outer peripheral surface 15.

[0037] The multiple cylindrical rollers 4 are made of a hard metal such as bearing steel or ceramics, and are arranged between the outer ring raceway surface 8 and the inner ring raceway surface 18 so that they can roll freely while being held by a cylindrical cage 19. During use, the axial position of the multiple cylindrical rollers 4 with respect to the inner ring 3 is regulated by having the end faces on both axial sides guided by a pair of rib surfaces 9, specifically by being brought into sliding contact with each other.

[0038] The cage 19 is made of metal or synthetic resin. The outer peripheral surfaces of both axial ends of the cage 19 are guided by, specifically, brought into sliding contact with, the inner peripheral surfaces 11 of the pair of inward flanges 10 of the outer ring 2, thereby regulating the radial position of the cage 19 relative to the outer ring 2. When the cage 19 is made of metal, it is preferable to provide a hardened layer 14 over the entire circumference also on the surface layer portion of the base material 12 including the inner peripheral surfaces 11 of the pair of inward flanges 10 in order to improve the wear resistance of the inner peripheral surfaces 11 of the pair of inward flanges 10 that serve as guide surfaces for the cage 19.

[0039] The rolling bearing 1 of this example is assembled between an outer member 27 and an inner member 28, thereby allowing relative rotation between the outer member 27 and the inner member 28 and supporting a radial load acting between the outer member 27 and the inner member 28. In this example, the outer peripheral surface 5 of the outer ring 2 can be used as a portion that fits with an inner peripheral surface 29 or the like of the outer member 27, which is the adjacent mating member, during use, more specifically as a fitting surface. At least one of the side surfaces 7 on both axial sides of the outer ring 2 can be used as a portion that abuts against a stepped surface 30 or the like provided on the outer member 27, more specifically as a side surface for positioning in the axial direction.

[0040] The inner peripheral surface 16 of the inner ring 3 can be used as a fitting surface that fits with, for example, the outer peripheral surface 31 of the inner member 28. At least one of the side surfaces 17 on both axial sides of the inner ring 3 can be used as an axial positioning side surface that abuts against, for example, a step surface 32 provided on the inner member 28.

[0041] The manufacturing method of the outer ring 2, which is the raceway ring of this example, to which this example is applied, includes first to fourth steps.

[0042] In the first step, an initial material (not shown) is subjected to appropriate processing such as forging and cutting to obtain a base material 12 (see FIG. 2(a)).

[0043] In the second step, build-up layers 13a, 13b are formed by laser cladding on the surface of the base material 12, on a bottom surface 25 of the recess 24 and on both axial side surfaces 26 of the recess 24 (see FIG. 2(b)).

[0044] Specifically, a laser is applied to the bottom surface 25 of the recess 24 and a circumferential portion of the side surfaces 26 on both axial sides by a laser device, and the base material 12 is rotated relative to the laser device while supplying powder of the metal material constituting the buildup layers 13a, 13b, i.e., Fe-based alloy, Ni-based alloy, Co-based alloy, etc., to the portion irradiated with the laser. As a result, the buildup layers 13a, 13b are formed so as to cover the bottom surface 25 of the recess 24 and the side surfaces 26 on both axial sides over the entire circumference.

[0045] The build-up layers 13a, 13b are formed on the bottom surface 25 and both axial side surfaces 26 of the recess 24 by melting the powdered metal material with a laser and then solidifying the molten metal material by cooling.

[0046] The operations of forming the three buildup layers 13a, 13b can be carried out one by one in sequence, or can be carried out simultaneously.

[0047] In the third step, the surfaces of the buildup layers 13a, 13b formed in the second step are subjected to finishing processes such as cutting, grinding, and polishing to form an outer ring raceway surface 8 and a pair of flange surfaces 9 (see Figure 2(c)).

[0048] In the fourth step, at least a portion of the surface of the substrate 12 outside the buildup layers 13a, 13b, specifically, in this example, the surface layer of the substrate 12 including the outer peripheral surface 5 and both axial side surfaces 7 is heated by irradiating with a laser, i.e., laser hardening is performed to form a hardened layer 14 having a harder layer than the metal material constituting the substrate 12 around the entire surface of the substrate 12 including the outer peripheral surface 5 and both axial side surfaces 7 (see Figure 2(d)), and finally the outer ring 2 is obtained.

[0049] 2(d), the hardened layer 14 is continuous between the portion including the outer peripheral surface 5 of the substrate 12 and the portion including the side surface 7. However, the hardened layer 14 including the outer peripheral surface 5 and the hardened layer 14 including the side surface 7 may be discontinuous.

[0050] When carrying out the present disclosure, the formation of the hardened layer 14 in the fourth step can also be carried out before the formation of the build-up layers 13a, 13b in the second step, or before the finish processing in the third step.

[0051] In this example, an outer ring 2 can be obtained at low cost in which sufficient surface hardness is ensured not only for the outer ring raceway surface 8 and a pair of rib surfaces 9, which are the rolling element guide surfaces, but also for the outer peripheral surface 5, which is the portion that fits into an adjacent mating member during use, and for the side surfaces 7 on both axial sides, which are the portions that abut against adjacent mating members during use.

[0052] That is, since high carbon steel or medium carbon steel, which is less expensive than bearing steel, can be used as the metal material constituting the base material 12, the outer ring 2 can be obtained at low cost.

[0053] In this example, build-up layers 13a, 13b are formed by laser cladding on the surface of the base material 12, on the bottom surface 25 of the recess 24 and on both axial side surfaces 26 of the recess 24, and an outer ring raceway surface 8 and a pair of flange surfaces 9 are formed on the surfaces of the build-up layers 13a, 13b. The build-up layers 13a, 13b are made of a metal material harder than the metal material constituting the base material 12. This ensures sufficient surface hardness of the outer ring raceway surface 8 and the pair of flange surfaces 9, and provides the outer ring raceway surface 8 and the pair of flange surfaces 9, which are the rolling element guide surfaces, with excellent spalling life and wear resistance.

[0054] In this example, a hardened layer 14 is formed over the entire surface of the base material 12, including the outer peripheral surface 5 and the side surfaces 7 on both axial sides, by laser hardening. This ensures sufficient surface hardness for the outer peripheral surface 5 and the side surfaces 7 on both axial sides, and provides excellent wear resistance and scratch resistance to the outer peripheral surface 5 and the side surfaces 7 on both axial sides, which are portions that fit into adjacent mating members during use and / or portions that come into contact with adjacent mating members during use.

[0055] When the hardened layer 14 is formed by laser hardening, only the portion where the hardened layer 14 is to be formed is strongly heated by laser irradiation, so that the thermal influence on the buildup layers 13a, 13b is suppressed. Therefore, the hardness of the outer ring raceway surface 8 and the pair of rib surfaces 9 can be maintained at the desired hardness while avoiding changes in the metal structure of the buildup layers 13a, 13b.

[0056] In this embodiment, the hardened layer 14 is formed by laser hardening. Therefore, firstly, a heat treatment furnace is not required, and the amount of environmentally hazardous substances such as CO2 emissions and hardening oil can be significantly reduced. Water washing after hardening, which is required when hardening oil is used, is also not required, and water resources can be conserved. In this way, this embodiment significantly reduces the environmental impact.

[0057] Secondly, laser hardening does not require a heat treatment furnace and its associated equipment, and furthermore, the amount of water and oil used in the heat treatment can be reduced or eliminated, which allows the equipment area to be reduced and facilitates the introduction of equipment for forming the hardened layer 14.

[0058] Thirdly, compared to a heat treatment furnace, the introduction cost, running cost, and maintenance cost of the equipment can be reduced, so that the hardened layer 14 can be formed at low cost.

[0059] If hardened layer 14 is formed by induction hardening, a heating coil according to the size of outer ring 2 is required, and the equipment costs for forming hardened layer 14 are high. In this example, a common laser device can be used regardless of the size of outer ring 2, so the equipment costs for forming hardened layer 14 can be reduced.

[0060] In this example, buildup layers 13a, 13b are formed on the surface of the outer ring 2, including the outer ring raceway surface 8 and a pair of rib surfaces 9, which are rolling element guide surfaces, and a hardened layer 14 is formed on the surface of the base material 12, including the outer peripheral surface 5 and side surfaces 7 on both axial sides, which constitute the surface of the base material 12 and which fit into an adjacent mating member during use and / or which abut against an adjacent mating member during use.

[0061] The outer ring raceway 8 and the pair of rib surfaces 9 are required to have an excellent spalling life (fatigue life). Spalling occurs starting from large inclusions, so it is necessary that the outer ring raceway 8 and the pair of rib surfaces 9 are free of large inclusions. Since the material used for laser cladding is a powder, there are no large inclusions that deviate from the particle size distribution, whereas there is a high possibility that large inclusions are present in the base material, which is a general steel type that does not control inclusions. For this reason, in this example, the cladding layers 13a and 13b are formed by laser cladding on the surface layer portion of the outer ring 2, including the outer ring raceway 8 and the pair of rib surfaces 9, from the viewpoint of spalling life. However, since the material of the cladding layers 13a and 13b is expensive compared to the base material, the hardened layer 14, which is advantageous in terms of cost, is formed on the surface layer portion of the outer ring 2, including the outer peripheral surface 5 and the side surfaces 7 on both axial sides, which do not require spalling life.

[0062] [Example 2] A second embodiment of the present disclosure will be described with reference to FIG.

[0063] This example is applied to an inner ring 3a that constitutes a radial cylindrical roller bearing.

[0064] The inner ring 3a has a base material 12a that is generally circular, more specifically, generally cylindrical. The base material 12a has four surfaces: an outer circumferential surface 15, an inner circumferential surface 16, and side surfaces 17 on both axial sides.

[0065] The inner ring 3a includes a buildup layer 13c that covers an outer peripheral surface 15 of the four surfaces of the base material 12a. An inner ring raceway surface 18, which is a rolling guideway surface, is formed on the surface of the buildup layer 13c.

[0066] In this example, the hardened layer 14 is formed over the entire circumference of the surface layer portion of the base material 12a, which constitutes the inner ring 3a, including at least a portion of the surface of the base material 12a that is not covered by the buildup layer 13c. Specifically, the hardened layer 14 is formed over the entire circumference of the surface layer portion of the base material 12a, including the inner circumferential surface 16 and the side surfaces 17 on both axial sides.

[0067] The manufacturing method of the inner ring 3a of this example, like the first example, includes the steps of obtaining a base material 12a, forming a buildup layer 13c by laser cladding on a portion covering the outer peripheral surface 15 of the base material 12a, forming an inner ring raceway surface 18 by finishing the surface of the buildup layer 13c, and forming a hardened layer 14 over the entire circumference by laser hardening on a surface layer portion of the base material 12a including the inner peripheral surface 16 and both axially opposite side surfaces 17. The other configurations and effects are the same as those of the first example.

[0068] [Example 3] A third embodiment of the present disclosure will be described with reference to FIGS.

[0069] The rolling bearing 1a is a radial tapered roller bearing, and includes an outer ring 2a, an inner ring 3b, and a plurality of tapered rollers 20 that serve as rolling elements.

[0070] This example is applied to an outer ring 2a that constitutes a rolling bearing 1a.

[0071] The outer ring 2a has a base material 12b that is entirely annular, more specifically, substantially cylindrical. The base material 12b has four surfaces, namely, an outer peripheral surface 5a, an inner peripheral surface 6a, and side surfaces 7a, 7b on both axial sides. The outer ring 2a has a buildup layer 13d that covers the inner peripheral surface 6a of the four surfaces of the base material 12b. An outer ring raceway surface 8a is provided over the entire circumference on the surface of the buildup layer 13d. In this example, the rolling element guideway of the outer ring 2a is constituted by the outer ring raceway surface 8a.

[0072] The outer ring raceway surface 8a is configured with a conical surface that is inclined in a direction in which the diameter becomes larger toward one axial side (the right side in Figs. 4 and 5).

[0073] The outer peripheral surface 5a of the base material 12b is formed of a cylindrical surface. Side surfaces 7a and 7b on both axial sides of the base material 12b are formed of flat surfaces perpendicular to the axial direction.

[0074] In this example, the hardened layer 14 is formed over the entire circumference of the surface layer portion of the base material 12b constituting the outer ring 2a, including at least a portion of the surface of the base material 12b that is not covered by the buildup layer 13d. Specifically, the hardened layer 14 is formed over the entire circumference of the surface layer portion of the base material 12b, including the outer peripheral surface 5a and the side surfaces 7a, 7b on both axial sides.

[0075] The inner ring 3b constituting the rolling bearing 1a of this example is made of hard metal such as bearing steel and is entirely annular. The inner ring 3b has an outer peripheral surface 15a, an inner peripheral surface 16a, and side surfaces 17a, 17b on both axial sides, and has an inner ring raceway surface 18a and a flange surface 9a at the axial middle portion of the outer peripheral surface 15. The inner ring raceway surface 18a is made of a conical surface that is inclined in a direction in which the diameter increases toward one axial side (the right side in Figs. 4 and 5).

[0076] The inner ring 3b has a large rib portion 21 that protrudes radially outward from an end portion on the large diameter side adjacent to the large diameter side of the inner ring raceway surface 18a, and a small rib portion 22 that protrudes radially outward from an end portion on the small diameter side adjacent to the small diameter side of the inner ring raceway surface 18a. The rib surface 9a is provided on a side surface of the large rib portion 21 that faces the inner ring raceway surface 18a in the axial direction. The rib surface 9a is formed of a conical surface that is inclined toward the other axial side (the left side in Figures 4 and 5) as it moves radially outward.

[0077] An inner peripheral surface 16a of the inner ring 3b is formed of a cylindrical surface. Side surfaces 17a, 17b on both axial sides of the inner ring 3b are formed of flat surfaces perpendicular to the axial direction.

[0078] The multiple tapered rollers 20 are made of hard metal such as bearing steel or ceramics, and are arranged between the outer ring raceway surface 8a and the inner ring raceway surface 18a so that they can roll freely while being held by a cage 19a. During use, the multiple tapered rollers 20 have their large-diameter end faces guided by the rib surface 9a, specifically, brought into sliding contact with each other, thereby regulating the axial position of the multiple tapered rollers 20 relative to the inner ring 3b.

[0079] The retainer 19a is made of metal or synthetic resin. The outer peripheral surface of the column portion of the retainer 19a is guided by the outer ring raceway surface 8a of the outer ring 2a, specifically, is brought into sliding contact with the outer peripheral surface of the retainer 19a, thereby restricting the radial position of the retainer 19a with respect to the outer ring 2a.

[0080] The manufacturing method of the outer ring 2a of this example includes the steps of obtaining a base material 12b, forming a buildup layer 13d by laser cladding on a portion covering the inner peripheral surface 6a of the base material 12b, forming an outer ring raceway surface 8a by finishing the surface of the buildup layer 13d, and forming a hardened layer 14 over the entire circumference by laser hardening on a surface layer portion of the base material 12b including the outer peripheral surface 5a and both axially opposite side surfaces 7a, 7b. The other configurations and effects are the same as those of the first example.

[0081] [Example 4] A fourth embodiment of the present disclosure will be described with reference to FIG.

[0082] This example is applied to an inner ring 3c that constitutes a radial tapered roller bearing.

[0083] The inner ring 3c has a base material 12c that is entirely formed in a circular ring shape and is made of a metal material such as high carbon steel or medium carbon steel.

[0084] The base material 12c has four surfaces, namely, an outer peripheral surface 15a, an inner peripheral surface 16a, and side surfaces 17a, 17b on both axial sides, and has an inclined peripheral surface 36 and an inclined side surface 37 in an axially intermediate portion of the outer peripheral surface 15a. The inclined peripheral surface 36 is formed of a conical surface that is inclined in a direction such that the diameter increases toward one axial side (the right side in FIG. 6).

[0085] The base material 12c has a large flange portion 21 that protrudes radially outward at a large diameter end portion adjacent to the large diameter side of the inclined circumferential surface 36, and a small flange portion 22 that is adjacent radially outward at a small diameter end portion adjacent to the small diameter side of the inclined circumferential surface 36. The inclined side surface 37 is provided on the side surface of the large flange portion 21 that is on the inclined circumferential surface 36 side in the axial direction. The inclined side surface 37 is composed of a conical surface that inclines in the direction toward the other axial side (the left side in FIG. 6) as it moves radially outward.

[0086] The inner ring 3c includes a buildup layer 13e covering the inclined peripheral surface 36 and a buildup layer 13f covering the inclined side surface 37. An inner ring raceway surface 18a is formed on the surface of the buildup layer 13e, and a flange surface 9a is formed on the surface of the buildup layer 13f.

[0087] In this example, the hardened layer 14 is formed over the entire circumference of the surface layer portion of the base material 12c, including at least a portion of the surface of the base material 12c constituting the inner ring 3c that is not covered by the buildup layers 13e and 13f. Specifically, the hardened layer 14 is formed over the entire circumference of the surface layer portion of the base material 12c, including the inner circumferential surface 16a and the side surfaces 17a and 17b on both axial sides.

[0088] The manufacturing method of the inner ring 3c of this example includes, as in the first example, the steps of obtaining a base material 12c, forming buildup layers 13e, 13f by laser cladding on the portions of the base material 12c covering the inclined peripheral surface 36 and inclined side surface 37, forming the inner ring raceway surface 18a and the flange surface 9a by applying a finishing process to the surfaces of the buildup layers 13e, 13f, and forming a hardened layer 14 over the entire circumference by laser hardening on the surface layer portion of the base material 12c, including the inner peripheral surface 16a and the side surfaces 17a, 17b on both axial sides. The other configurations and effects are the same as those of the first and third examples.

[0089] [Example 5] A fifth embodiment of the present disclosure will be described with reference to FIGS.

[0090] The rolling bearing 1b is a self-aligning roller bearing, and includes an outer ring 2b, an inner ring 3d, and a plurality of spherical rollers 23 which serve as rolling elements.

[0091] This example is applied to the outer ring 2b constituting the rolling bearing 1b.

[0092] The outer ring 2b has a base material 12d and a buildup layer 13g. The base material 12d is configured to be annular as a whole, more specifically, to be substantially cylindrical, and has four surfaces consisting of an outer peripheral surface 5b, an inner peripheral surface 6b, and side surfaces 7c on both axial sides. The buildup layer 13g is provided over the entire circumference so as to cover the inner peripheral surface 6b of the base material 12d. An outer ring raceway surface 8b is provided over the entire circumference on the surface of the buildup layer 13g. The outer ring raceway surface 8b is configured as a spherical concave surface having a single center. In this example, the rolling element guide surface of the outer ring 2b is configured by the outer ring raceway surface 8b.

[0093] The outer peripheral surface 5b of the base material 12d is formed of a cylindrical surface. Side surfaces 7c on both axial sides of the base material 12d are formed of flat surfaces perpendicular to the axial direction.

[0094] In this example, the hardened layer 14 is formed over the entire circumference of the surface layer portion of the base material 12d, including at least a portion of the surface of the base material 12d constituting the outer ring 2b that is not covered by the buildup layer 13g. Specifically, the hardened layer 14 is formed over the entire circumference of the surface layer portion of the base material 12d, including the outer peripheral surface 5b and the side surfaces 7c on both axial sides.

[0095] The inner ring 3d constituting the rolling bearing 1b of this example is made of hard metal such as bearing steel and is entirely annular. The inner ring 3d has an outer peripheral surface 15b, an inner peripheral surface 16b, and side surfaces 17c on both axial sides, and has double-row inner ring raceway surfaces 18b on the outer peripheral surface 15b. Each row of the double-row inner ring raceway surfaces 18b has an arc-shaped cross section.

[0096] An inner peripheral surface 16b of the inner ring 3d is formed of a cylindrical surface. Side surfaces 17c on both axial sides of the inner ring 3d are formed of flat surfaces perpendicular to the axial direction.

[0097] The spherical rollers 23 are made of a hard metal such as bearing steel or of ceramics, and are arranged between the outer ring raceway surface 8b and the double-row inner ring raceway surface 18b, with multiple spherical rollers per row, and are held by a retainer 19b made of metal or synthetic resin so as to be able to roll freely.

[0098] The manufacturing method of the outer ring 2b of this example includes, as in the first example, the steps of obtaining a base material 12d, forming a buildup layer 13g by laser cladding on a portion covering the inner peripheral surface 6b of the base material 12d, forming an outer ring raceway surface 8b by performing a finishing process on the surface of the buildup layer 13g, and forming a hardened layer 14 over the entire circumference by laser hardening on a surface layer portion of the base material 12d, including the outer peripheral surface 5b and the side surfaces 7c on both axial sides of the surface of the base material 12d. The other configurations and effects are the same as those of the first example.

[0099] [Example 6] A sixth embodiment of the present disclosure will be described with reference to FIG.

[0100] This example is applied to an inner ring 3e that constitutes a spherical roller bearing.

[0101] The inner ring 3e has a base material 12e and a buildup layer 13h. The base material 12e is made of a metal material such as high carbon steel or medium carbon steel and is generally annular, and has an outer peripheral surface 15c, an inner peripheral surface 16b, and side surfaces 17c on both axial sides. The outer peripheral surface 15c has a pair of concave curved surfaces 38 on both axial sides, each of which has a generatrix shape of an arc whose diameter decreases as it moves away from the other in the axial direction. The buildup layer 13h is provided over the entire circumference so as to cover the pair of concave curved surfaces 38. An inner ring raceway surface 18b is provided over the entire circumference on the surface of each buildup layer 13h. In this example, the rolling element guide surface of the inner ring 3e is formed by the double row inner ring raceway surface 18b.

[0102] In this example, the hardened layer 14 is formed over the entire circumference of the surface layer portion of the base material 12e, including at least a portion of the surface of the base material 12e constituting the inner ring 3e that is not covered by the buildup layer 13h. Specifically, the hardened layer 14 is formed over the entire circumference of the surface layer portion of the base material 12e, including the inner circumferential surface 16b and the side surfaces 17c on both axial sides.

[0103] The manufacturing method of the inner ring 3e of this example includes, as in the first example, the steps of obtaining a base material 12e, forming a build-up layer 13h by laser cladding on a portion covering the outer peripheral surface 15c of the base material 12e, forming double-row inner ring raceway surfaces 18b by performing a finishing process on the surface of the build-up layer 13h, and forming a hardened layer 14 over the entire circumference by laser hardening on a surface layer portion of the base material 12e, including the inner peripheral surface 16b and the side surfaces 17c on both axial sides of the surface of the base material 12e. The other configurations and effects are the same as those of the first and fifth examples.

[0104] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited thereto, and can be modified as appropriate without departing from the technical concept of the present disclosure.

[0105] The present disclosure is applicable to raceways that make up various radial and thrust rolling bearings, including deep groove ball bearings, angular contact ball bearings, cylindrical roller bearings, needle bearings, tapered roller bearings, and spherical roller bearings. EXAMPLES

[0106] The effects of the presently disclosed rolling bearing raceway and manufacturing method thereof were verified. Specifically, sample A (Example) was prepared, which was made up of a raceway on which a hardened layer was formed by laser hardening in a portion of the surface of the base material other than the portion covered by the build-up layer, and sample B (Comparative Example) was prepared, which was made up of a raceway on which a hardened layer was not formed by laser hardening in a portion of the surface of the base material other than the portion covered by the build-up layer, and the scratch resistance of the portions other than the portion covered by the build-up layer for each of samples A and B was confirmed.

[0107] (For samples A and B) As shown in Figures 10(a) and 10(b), both samples A (Example) and B (Comparative Example) have an overall shape simulating an inner ring constituting a radial cylindrical roller bearing, and are provided with an outward flange portion 33 at the end on one axial side (the left side of Figure 10(a)). Both samples A and B are provided with a substrate 12s made of SUJ2, and an overlay layer 13s that covers a portion of the outer circumferential surface of the substrate 12s that is axially offset from the outward flange portion 33. The overlay layer 13s is formed by laser cladding using an M2 material equivalent to high-speed steel.

[0108] Sample A has a hardened layer formed over the entire circumference by laser hardening on the inner peripheral surface 34 and both axial side surfaces 35a, 35b of the base material 12s. Sample B does not have such a hardened layer. In both samples A and B, the inner peripheral surface 34 and both axial side surfaces 35a, 35b of the base material 12s are polished to a predetermined dimension. However, since the purpose of this experiment is to confirm the scratch resistance of the part other than the part covered by the buildup layer 13s, the surface of the buildup layer 13s is not finished.

[0109] (Evaluation method) Samples A and B were fitted onto the outer circumferential surface of a cylindrical test shaft with a tightening margin, and then a test was conducted in which the test shaft was pulled out from inside of samples A and B. The scratch resistance was evaluated based on the presence or absence of scratches on the inner circumferential surface 34 of samples A and B and the extent of the scratches. In order to set strict test conditions, the outer circumferential surface of the test shaft was made to be a rough surface where fretting had occurred.

[0110] Specifically, the tests and evaluations were carried out in the order of (1) to (5) below.

[0111] (1) The sample is heated and thermally expanded to such an extent that a sufficient gap is formed between the inner peripheral surface 34 of the sample and the outer peripheral surface of the test shaft.

[0112] (2) The test shaft is inserted inside the heated sample.

[0113] (3) The sample and the test shaft are cooled to room temperature to cause thermal shrinkage, so that the sample is fitted onto the outer circumferential surface of the test shaft with a tightening margin.

[0114] (4) While supporting the entire side surface 35a of the sample on one axial direction side by a hollow disk-shaped spacer arranged adjacent to the sample on one axial direction side, the test shaft is pulled out from inside the sample and the spacer toward the one axial direction side.

[0115] (5) After the test shaft is pulled out, the inner peripheral surface 34 of the sample is checked to see whether or not any damage has occurred due to the pulling out, and the extent of the damage.

[0116] The diameter dimension (average value) of the inner surfaces 34 of samples A and B at room temperature was 29.996 mm, the diameter dimension (average value) of the outer surface of the test shaft at room temperature was 30.029 mm, and the tightening margin (calculated value) of the fitting portion between the inner surfaces 34 of samples A and B and the outer surface of the test shaft was 0.033 mm.

[0117] (Evaluation result 1: Appearance evaluation result) The condition of the inner peripheral surface 34 of each of the samples A and B before and after the test was observed using a microscope. The observation results are shown in FIG.

[0118] In sample B (Comparative Example), many streak-like scratches extending in the axial direction were visible on the inner circumferential surface 34. In contrast, in sample A (Example) having a hardened layer, almost no streak-like scratches extending in the axial direction were visible on the inner circumferential surface 34.

[0119] (Evaluation result 2: Evaluation result of the degree of damage) For samples A and B, the unevenness in the circumferential direction of the inner peripheral surface 34 was measured before and after the test using a roundness measuring device. The measurement results are shown in FIG.

[0120] As shown in the measurement results, in sample B (comparative example), circumferential irregularities were confirmed in a circumferential portion (portion surrounded by a dashed line) of the inner circumferential surface 34. In contrast, in sample A (example) having a hardened layer, substantially no circumferential irregularities were confirmed in the inner circumferential surface 34.

[0121] (Evaluation result 3: Evaluation result of shape collapse) For samples A and B, the linear shape (shape in the axial direction) of the inner peripheral surface 34 was measured using a linear shape measuring device before and after the test. The measurement results are shown in FIG.

[0122] As shown in the measurement results, in sample B (comparative example), inclined deformation in which the radial height changes with respect to the axial direction was confirmed in an axial portion (portion surrounded by a dashed line) of the inner circumferential surface 34. In contrast, in sample A (example) having a hardened layer, inclined deformation in which the radial height changes with respect to the axial direction was not substantially confirmed in the inner circumferential surface 34.

[0123] (Summary of evaluation results) As described above, it was confirmed that the scratch resistance of the portion of the base material surface other than the portion covered by the build-up layer differs depending on whether or not the hardened layer is formed in the portion, and that the portion is less likely to be scratched when the hardened layer is formed. It was also confirmed that the resistance is ensured not only against scratches but also against deformation of the linear shape of the peripheral surface that fits into the mating member. [Explanation of symbols]

[0124] 1, 1a, 1b Rolling bearings 2, 2a, 2b Outer ring 3, 3a, 3b, 3c, 3d, 3e inner ring 4 Cylindrical rollers 5, 5a, 5b outer surface 6, 6a, 6b Inner surface 7, 7a, 7b, 7c side 8, 8a, 8b Outer ring raceway surface 9, 9a Tsubamen 10 Inward flange 11 Inner surface 12, 12a, 12b, 12c, 12d, 12e, 12s substrate 13a, 13b, 13c, 13d, 13e, 13f, 13g, 13h, 13s Meat layer 14 Hardened layer 15, 15a, 15b Outer surface 16, 16a, 16b Inner circumference 17, 17a, 17b, 17c Side 18, 18a, 18b Inner wheel track surface 19, 19a, 19b Retainer 20 yen 21 Oebu 22 small crotch 23 spherical surface 24 recess 25 Bottom 26 Side 27 Outer member 28 Inner member 29 Inner Surface 30 segment difference 31 Outer Surface 32 segment difference surface 33 Outward facing flange 34 Inner Surface 35a, 35b Side 36 Inclined Surface 37 Slanted side 38 concave surface

Claims

1. A base material having an outer peripheral surface, an inner peripheral surface, and side surfaces on both axial sides, the base material being made of high carbon steel or medium carbon steel; A build-up layer covering any one of the outer peripheral surface, the inner peripheral surface, and the side surfaces on both axial sides; A rolling element guide surface provided on the surface of the buildup layer over the entire periphery; A hardened layer formed on the entire periphery of a surface layer portion of the base material, including at least a part of a portion of the surface of the base material that is not covered by the buildup layer; Equipped with The hardened layer has a hardness higher than a portion of the base material other than the hardened layer, Obtaining the substrate; forming the build-up layer by laser cladding on any one of the outer peripheral surface, the inner peripheral surface, and the side surfaces on both axial sides of the base material, the build-up layer being made of a metal material having a higher hardness than the portion of the base material that is not covered by the hardened layer; forming the rolling element guide surface by performing a finishing process on a surface of the buildup layer; forming the hardened layer over the entire periphery of a surface layer portion including at least a part of a portion of the surface of the base material that is not covered by the buildup layer, by laser hardening; A method for manufacturing a race for a rolling bearing comprising the steps of:

2. 2. The method for manufacturing a raceway for a rolling bearing according to claim 1, wherein the at least one portion is a portion of the base material that fits into an adjacent mating member in use and / or a portion that abuts against an adjacent mating member in use.

3. 2. The method for producing a race for a rolling bearing according to claim 1, wherein the buildup layer is made of at least one alloy selected from the group consisting of an Fe-based alloy, an Ni-based alloy, and a Co-based alloy.

4. A substrate having an outer peripheral surface, an inner peripheral surface, and side surfaces on both axial sides; A build-up layer covering any one of the outer peripheral surface, the inner peripheral surface, and the side surfaces on both axial sides; A rolling element guide surface provided on the surface of the buildup layer over the entire circumference; and A hardened layer formed on the entire periphery of a surface layer portion of the base material, including at least a part of a portion of the surface of the base material that is not covered by the buildup layer; Equipped with The substrate is made of high carbon steel or medium carbon steel, The hardened layer has a higher hardness than a portion of the base material other than the hardened layer, and the buildup layer has a higher hardness than a portion of the base material other than the hardened layer.

5. 5. The raceway for a rolling bearing according to claim 4, wherein the at least one portion is a portion of the base material that fits into an adjacent mating member in use and / or a portion that abuts against an adjacent mating member in use.

6. 5. The raceway for a rolling bearing according to claim 4, wherein the buildup layer is made of at least one material selected from the group consisting of an Fe-based alloy, an Ni-based alloy, and a Co-based alloy.

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