Method for machining raceway surface of rolling bearing, and methods for repairing and producing bearing ring of rolling bearing

Abstract

The present invention implements a method with which it is possible to prevent generation of an internal defect in a build-up layer having a raceway surface on a surface. The method comprises a build-up step of radiating a laser 10 emitted from a laser light source to a raceway surface 4a (or a portion where a raceway surface of a base material is formed) provided on an inner circumferential surface or an outer circumferential surface of a bearing ring 3a, and relatively rotating the laser light source with respect to the raceway ring 3a and relatively displacing the laser light source in a width direction of the raceway surface 4a (or a portion where the raceway surface is formed) while supplying welding material 11 to a portion of the raceway surface 4a irradiated with the laser 10, thereby forming a build-up portion 15 composed of a plurality of annular beads or beads wound without a gap on the raceway surface 4a. In the build-up step, the radiation direction of the laser 10 with respect to the raceway surface 4a is a direction inclined, with respect to a normal direction of the raceway surface 4, forward in relation to a relative displacement direction in an axial direction of the laser light source with respect to the raceway ring 3a.

Description

Method for processing the raceway surface of a rolling bearing, and method for repairing and manufacturing the raceway ring of a rolling bearing

[0001] The present disclosure relates to a method for processing the raceway surfaces of rolling bearings, and more particularly to a method for repairing and manufacturing races of radial rolling bearings or thrust bearings.

[0002] The rotating shafts of rotating machines such as machine tools and industrial machinery are supported by rolling bearings against parts that do not rotate during use, such as housings. A rolling bearing comprises a pair of bearing rings that have raceway surfaces on opposing surfaces around the entire circumference and are arranged coaxially with each other, and a plurality of rolling elements that are freely rollable between the raceway surfaces of the pair of bearing rings. Specific examples of such rolling bearings include radial rolling bearings that mainly support radial loads and thrust rolling bearings that mainly support axial loads.

[0003] A radial rolling bearing comprises an inner ring having an inner ring raceway on its outer peripheral surface, an outer ring having an outer ring raceway on its inner peripheral surface and arranged coaxially with the inner ring radially inside the inner ring, and a plurality of rolling elements arranged freely to roll between the inner ring raceway and the outer ring raceway.

[0004] A thrust rolling bearing comprises a pair of raceways arranged coaxially with each other, each having raceway surfaces on axially opposing sides thereof, and a plurality of rolling elements arranged to roll freely between the raceway surfaces of the pair of raceways.

[0005] Whether a rolling bearing is a radial rolling bearing or a thrust rolling bearing, when it is used for a long period of time under a load, the raceway surface may wear or may become fatigued, causing the raceway surface to flake off. When damage such as wear or flakes occurs on the raceway surface, it may be necessary to replace the raceway ring or the entire rolling bearing including the raceway ring.

[0006] However, from the perspective of reducing the operating costs of rotating machinery, it is desirable to repair raceway surfaces that have suffered wear, spalling, or other damage, and then continue using the races, rather than replacing the races or rolling bearings. This is particularly true for large bearings such as roll neck bearings in steel rolling mills. Large tapered roller bearings and cylindrical roller bearings, for example, are used as roll neck bearings.

[0007] Japanese Patent Application Laid-Open No. 2021-025598 describes a method for repairing a raceway, in which a cladding is formed on the inner raceway around the entire circumference by laser cladding, and the surface of the cladding is polished to form a new inner raceway. The method described in Japanese Patent Application Laid-Open No. 2021-25598 makes it possible to repair a raceway surface that has suffered damage such as wear or peeling, without providing a machining allowance in advance on the surface layer of the inner raceway.

[0008] Japanese Patent Application Laid-Open No. 2021-025598

[0009] When repairing a wide axial range using the conventional method described in JP 2021-025598 A, it is possible to form a cladding portion by arranging multiple annular beads closely spaced in the axial direction on the inner ring raceway using laser cladding, in which a laser light source is rotated relative to the inner ring and displaced axially relative to the inner ring while supplying a welding material, or by forming a cladding portion composed of beads wound spirally without gaps. However, when such a cladding portion is formed using the conventional method described in JP 2021-025598 A, there is a risk of internal defects occurring.

[0010] Internal defects occur when bubbles are generated in the molten metal material (molten pool) during laser cladding due to gases present in the molten material or gases mixed in from the outside, and the metal material solidifies before the bubbles are expelled to the outside.

[0011] Consider the case of forming an overlay portion on an inner ring raceway by arranging multiple annular beads axially without gaps, using the conventional method described in JP 2021-025598 A. For example, first, a laser is irradiated onto the inner ring raceway, and the inner ring is rotated once while supplying a welding material to the laser-irradiated portion to form an annular bead. Next, the inner ring is displaced axially relative to the laser light source. At this time, the amount of axial displacement of the inner ring relative to the laser light source is adjusted so that no gaps exist between two axially adjacent beads. Then, a laser is again irradiated onto the inner ring raceway, and the inner ring is rotated once while supplying a welding material to the laser-irradiated portion to form an annular bead. As described above, the overlay portion is formed by repeating the process of forming an annular bead and the process of displacing the inner ring axially relative to the laser light source.

[0012] As shown in Figure 8, when forming a buildup portion 103 on the inner ring raceway 101 of the inner ring 100 by arranging multiple annular beads 102 side by side with no gaps in the axial direction, of two axially adjacent beads 102, the axial side portion of the bead 102 on the other axial side (right side in Figure 8) of the bead 102 on one axial side (left side in Figure 8) is radially overlapped with the axial side portion of the bead 102 on the other axial side.

[0013] In reality, the bead 102 has a cross-sectional shape that is approximately a partial ellipse, as shown in an exaggerated manner in Fig. 9. In the conventional method described in JP 2021-025598 A, the laser 104 is irradiated radially onto the inner ring raceway 101. For this reason, when the laser 104 is irradiated radially onto a portion adjacent to the other axial side of the bead 102 on one axial side (the portion marked with diagonal grid in Fig. 9) in order to form the bead 102 on the other axial side, there is a possibility that the portion of the inner ring raceway 101 that is located radially inside the end portion on the other axial side of the bead 102 on one axial side cannot be sufficiently heated.

[0014] Even when the buildup portion is formed by a bead wound spirally without any gaps, when a laser is irradiated radially to form a bead on a portion of the bead that is axially adjacent to a previously formed portion, it may not be possible to sufficiently heat the portion located radially inside the axial end of the previously formed portion.

[0015] In any case, if there are areas where the laser cannot sufficiently heat the molten metal material in those areas, the molten metal material is likely to solidify early before the bubbles are expelled, making it more likely that internal defects caused by the bubbles will occur inside the buildup portion.

[0016] The above problems occur not only when a build-up portion is formed by laser cladding to repair a raceway surface, but also when a build-up portion is formed by laser cladding in the area where the raceway surface is to be formed when manufacturing a raceway ring from scratch.

[0017] An object of the present disclosure is to provide a method for repairing and manufacturing a bearing ring that can prevent internal defects from occurring in an overlay layer having a raceway surface on its surface.

[0018] A method for processing a raceway surface of a rolling bearing according to one aspect of the present disclosure includes a build-up step of irradiating a laser beam emitted from a laser light source onto the raceway surface of a raceway ring or a portion of a base material where the raceway surface is to be formed, and supplying a welding material to the portion irradiated with the laser while rotating the laser light source relative to the raceway ring or the base material and displacing the laser light source relative to the raceway ring or the base material in the width direction of the raceway surface or the portion where the raceway surface is to be formed, thereby forming an overlay portion on the raceway surface or the portion where the raceway surface is to be formed, the overlay portion being (1) constituted by arranging a plurality of annular beads side by side with no gaps in the width direction, or (2) constituted by beads wound around with no gaps in the width direction.

[0019] In particular, in one embodiment of the method for processing the raceway surface of a rolling bearing according to the present disclosure, in the build-up process, the direction of irradiation of the laser with respect to the raceway surface or the portion where the raceway surface is to be formed is inclined forward with respect to the normal direction of the portion irradiated with the laser and with respect to the relative displacement direction of the laser light source with respect to the raceway ring or the base material.

[0020] When the method for processing the raceway surface of a rolling bearing is applied to a method for repairing a raceway ring of a rolling bearing, the object of processing is the raceway surface of the raceway ring, and when applied to a method for manufacturing a raceway ring of a rolling bearing, the object of processing is the portion of the base material where the raceway surface is formed.

[0021] In one embodiment of the method for processing the raceway surface of a rolling bearing according to the present disclosure, the inclination angle relative to the normal direction can be set to 5 degrees or more and less than 90 degrees, preferably 10 degrees or more and 20 degrees or less, and more preferably 15 degrees or more and 20 degrees or less.

[0022] When the method for processing the raceway surface of a rolling bearing is applied to a method for repairing or manufacturing the raceway ring of a radial rolling bearing, the width direction, i.e., the direction of relative displacement of the laser light source with respect to the raceway ring or the base material, is the axial direction. On the other hand, when the method for processing the raceway surface of a rolling bearing is applied to a method for repairing or manufacturing the raceway ring of a thrust rolling bearing, the width direction, i.e., the direction of relative displacement of the laser light source with respect to the raceway ring or the base material, is the radial direction.

[0023] A method for repairing a raceway ring of a radial rolling bearing according to one aspect of the present disclosure includes a build-up process in which a laser emitted from a laser light source is irradiated onto a raceway surface provided on the inner or outer peripheral surface of the raceway ring, and while supplying welding material to the portion of the raceway surface irradiated by the laser, the laser light source is rotated relative to the raceway ring and displaced relative to the raceway ring in the axial direction, thereby arranging a plurality of annular beads side by side on the raceway surface with no gaps in the axial direction, or forming a build-up portion composed of beads wound spirally with no gaps.

[0024] In particular, in one embodiment of the method for repairing a raceway of a radial rolling bearing according to the present disclosure, in the build-up process, the direction of irradiation of the laser onto the raceway surface is tilted forward with respect to the axial relative displacement direction of the laser light source relative to the raceway surface with respect to the normal direction of the raceway surface (the normal direction of the portion of the raceway surface onto which the laser is irradiated).

[0025] In one embodiment of the method for repairing a raceway of a radial rolling bearing according to the present disclosure, the inclination angle of the laser irradiation direction relative to the normal to the raceway surface can be set to 5 degrees or more and less than 90 degrees, preferably 10 degrees or more and 20 degrees or less, and more preferably 15 degrees or more and 20 degrees or less.

[0026] A method for manufacturing a raceway of a radial rolling bearing according to one aspect of the present disclosure is a method for manufacturing a raceway of a radial rolling bearing comprising a cylindrical substrate, an overlay covering the entire inner or outer peripheral surface of the substrate, and a raceway provided on the surface of the overlay over the entire circumference, the method comprising: a buildup step of irradiating the inner or outer peripheral surface of the substrate with a laser emitted from a laser light source, and supplying a welding material to the portion of the inner or outer peripheral surface of the substrate that has been irradiated with the laser, while rotating the laser light source relative to the substrate and displacing it in the axial direction, thereby forming an overlay portion on the inner or outer peripheral surface of the substrate, the overlay portion being composed of a plurality of annular beads arranged side by side with no gaps in the axial direction, or composed of beads wound spirally with no gaps; and a machining step of machining the surface of the overlay portion to form the overlay having the raceway surface on its surface.

[0027] In particular, in one embodiment of the method for manufacturing a raceway of a radial rolling bearing according to the present disclosure, in the build-up process, the direction of irradiation of the laser onto the inner or outer surface of the substrate is set to a direction that is inclined forward with respect to the axial relative displacement direction of the laser light source relative to the substrate, with respect to the normal direction of the inner or outer surface of the substrate (the normal direction of the portion of the inner or outer surface of the substrate that is irradiated with the laser).

[0028] In one embodiment of the method for manufacturing a raceway of a radial rolling bearing according to the present disclosure, the inclination angle of the laser irradiation direction relative to the normal direction of the inner or outer peripheral surface of the substrate can be set to 5 degrees or more and less than 90 degrees, preferably 10 degrees or more and 20 degrees or less, and more preferably 15 degrees or more and 20 degrees or less.

[0029] The method for repairing a raceway ring of a thrust rolling bearing disclosed herein includes a build-up process in which a laser emitted from a laser light source is irradiated onto a raceway surface provided on the axial side of the raceway ring, and while supplying welding material to the portion of the raceway surface irradiated by the laser, the laser light source is rotated relative to the raceway ring and displaced radially relative to the raceway ring, thereby arranging a plurality of annular beads radially side by side on the raceway surface, or forming a build-up portion composed of beads wound spirally without gaps.

[0030] In particular, in one aspect of the method for repairing a raceway of a thrust rolling bearing disclosed herein, in the build-up process, the direction of irradiation of the laser onto the raceway surface is tilted forward with respect to the normal direction of the raceway surface and the radial relative displacement direction of the laser light source with respect to the raceway surface.

[0031] In one embodiment of the method for repairing a raceway of a thrust rolling bearing according to the present disclosure, the inclination angle of the laser irradiation direction relative to the normal direction of the raceway surface can be set to 5 degrees or more and less than 90 degrees, preferably 10 degrees or more and 20 degrees or less, and more preferably 15 degrees or more and 20 degrees or less.

[0032] A method for manufacturing a raceway of a thrust rolling bearing according to one aspect of the present disclosure is a method for manufacturing a raceway of a thrust rolling bearing comprising a hollow circular plate-shaped substrate, an overlay layer covering the entire axial side surface of the substrate, and a raceway surface provided on the surface of the overlay layer over the entire circumference, the method comprising: a buildup step of irradiating the axial side surface of the substrate with a laser emitted from a laser light source, and supplying a welding material to the portion of the axial side surface of the substrate that has been irradiated with the laser, while rotating and radially displacing the laser light source relative to the axial side surface of the substrate, thereby forming an overlay portion on the axial side surface of the substrate that is configured by arranging a plurality of annular beads side by side with no gaps in the radial direction, or configured by beads wound spirally with no gaps in between; and a machining step of machining the surface of the overlay portion to form the overlay layer having the raceway surface on its surface.

[0033] In particular, in one embodiment of the method for manufacturing a raceway of a thrust rolling bearing according to the present disclosure, in the build-up process, the direction of irradiation of the laser onto the axial side surface of the substrate is inclined forward with respect to the radial relative displacement direction of the laser light source relative to the raceway, relative to the normal direction of the axial side surface of the substrate.

[0034] In one embodiment of the method for manufacturing a raceway of a thrust rolling bearing according to the present disclosure, the inclination angle of the laser irradiation direction relative to the normal direction of the axial side surface of the substrate can be set to 5 degrees or more and less than 90 degrees, preferably 10 degrees or more and 20 degrees or less, and more preferably 15 degrees or more and 20 degrees or less.

[0035] According to the above-described method for processing the raceway surface of a rolling bearing, the method for repairing and manufacturing the raceway ring of a radial rolling bearing, and the method for repairing and manufacturing the raceway ring of a thrust rolling bearing of the present disclosure, it is possible to prevent the occurrence of internal defects in the buildup layer having a raceway surface on its surface.

[0036] Fig. 1 is a partially cutaway perspective view showing a radial cylindrical roller bearing including a raceway to which a method for repairing a raceway of a radial rolling bearing according to a first embodiment of the present disclosure can be applied. Fig. 2 is an enlarged schematic view of a portion corresponding to portion X in Fig. 1. Fig. 3(A) is a partially enlarged cross-sectional view showing the original inner raceway before repair, Fig. 3(B) is a partially enlarged cross-sectional view showing a state in which a buildup portion has been formed on the original inner raceway, and Fig. 3(C) is a partially enlarged cross-sectional view showing a state in which a new inner raceway has been formed by machining the buildup portion. Fig. 4(A) is a partially enlarged cross-sectional view showing the formation of a bead on the inner raceway, taken along a virtual plane perpendicular to the central axis of the inner ring, and Fig. 4(B) is a partially enlarged cross-sectional view showing the formation of a bead on the inner raceway, taken along a virtual plane including the central axis of the inner ring. Fig. 5 is a cross-sectional view schematically showing the inner peripheral surface of the inner ring being restrained by a deformation prevention jig when laser cladding is performed. Fig. 6 is a cross-sectional view showing a thrust cylindrical roller bearing including a raceway to which a method for repairing a raceway of a thrust rolling bearing according to a second embodiment of the present disclosure can be applied. Fig. 7 is a partially enlarged schematic view showing the formation of a bead on the raceway surface in a cross section taken along an imaginary plane including the central axis of the thrust raceway. Fig. 8 is a cross-sectional view showing an example of a buildup portion formed by arranging a plurality of annular beads in an axially spaced relationship. Fig. 9 is an enlarged cross-sectional view showing an annular bead.

[0037] The method for machining a raceway surface of a rolling bearing according to one aspect of the present disclosure can be applied to either a method for repairing a raceway ring of a rolling bearing or a method for manufacturing a raceway ring of a rolling bearing. When the method for machining a raceway surface of a rolling bearing is applied to a method for repairing a rolling bearing, the object to be machined is the raceway surface of the raceway ring, and when applied to a method for manufacturing a raceway ring of a rolling bearing, the object to be machined is the portion of the base material on which the raceway surface is formed.

[0038] The method for processing a raceway surface of a rolling bearing according to one aspect of the present disclosure can be applied to a method for repairing or manufacturing a raceway ring of a radial rolling bearing. The raceway ring of a radial rolling bearing, i.e., the outer ring or the inner ring, or the base material thereof, is cylindrical as a whole. The raceway surface or the portion on which the raceway surface is formed has a shape corresponding to the shape of the rolling element.

[0039] The method for processing the raceway surface of a rolling bearing according to one aspect of the present disclosure can be applied to a method for repairing or manufacturing a raceway ring of a thrust rolling bearing. The raceway ring of a thrust rolling bearing, or its substrate, is hollow and circular, at least in the portion that includes the raceway surface or in the portion where the raceway surface is formed. The raceway surface or the portion where the raceway surface is formed has a shape corresponding to the shape of the rolling element.

[0040] A method for processing a raceway surface of a rolling bearing according to one aspect of the present disclosure also includes a build-up step of irradiating the raceway surface of the bearing ring or a portion of the base material where the raceway surface is to be formed with a laser emitted from a laser light source, and supplying a welding material to the portion irradiated with the laser while rotating the laser light source relative to the bearing ring or the base material and displacing the laser light source relative to the raceway surface or the portion where the raceway surface is to be formed in the width direction of the raceway surface or the portion where the raceway surface is to be formed. Note that, although a powder welding material is usually used as the welding material, other forms of welding material such as a wire welding material can also be used.

[0041] When the rolling bearing is a radial rolling bearing, the width direction, i.e., the direction of relative displacement of the laser light source with respect to the raceway or the substrate, is the axial direction, whereas when the rolling bearing is a thrust rolling bearing, the width direction, i.e., the direction of relative displacement of the laser light source with respect to the raceway or the substrate, is the radial direction.

[0042] In a method for processing a raceway surface of a rolling bearing according to one aspect of the present disclosure, in the buildup step, (1) a buildup portion is formed on the raceway surface or the portion where the raceway surface is to be formed, by arranging a plurality of annular beads side by side with no gaps in the width direction. In this case, first, the laser light source is rotated relative to the raceway ring or the base material to form an annular bead at one width direction end of the raceway surface or the portion where the raceway surface is to be formed, then the laser light source is displaced in the width direction relative to the raceway ring or the base material and then rotated relative to the base material to form a next bead in a portion adjacent to the previous bead on the other width direction side, and further, in the same manner, next beads are formed in a portion adjacent to the previously formed bead on the other width direction side, thereby forming the buildup portion from one width direction end to the other width direction end of the raceway surface or the portion where the raceway surface is to be formed.

[0043] In a method for processing a raceway surface of a rolling bearing according to one aspect of the present disclosure, in the buildup step, (2) a buildup portion consisting of a single bead wound tightly around the raceway surface or the portion where the raceway surface is to be formed is formed on the raceway surface or the portion where the raceway surface is to be formed. In this case, the laser light source is rotated and displaced relative to the raceway ring or the base material so that, with each relative rotation of the laser light source, the laser light source reaches a portion adjacent to the other widthwise side of the bead already formed, thereby extending the single bead from one widthwise end to the other widthwise end of the raceway surface or the portion where the raceway surface is to be formed, thereby forming the buildup portion. If the rolling bearing is a radial rolling bearing, the single bead is wound spirally. On the other hand, if the rolling bearing is a thrust rolling bearing, the single bead is wound spirally.

[0044] In particular, in one embodiment of the method for processing the raceway surface of a rolling bearing according to the present disclosure, in the build-up process, the direction of irradiation of the laser with respect to the raceway surface or the portion where the raceway surface is to be formed is inclined forward with respect to the normal direction of the portion irradiated with the laser and with respect to the relative displacement direction of the laser light source with respect to the raceway ring or the base material.

[0045] In one embodiment of the method for processing the raceway surface of a rolling bearing according to the present disclosure, the inclination angle relative to the normal direction can be set to 5 degrees or more and less than 90 degrees, preferably 10 degrees or more and 20 degrees or less, and more preferably 15 degrees or more and 20 degrees or less.

[0046] The method for processing a raceway surface of a rolling bearing according to one aspect of the present disclosure can be applied to a method for repairing or manufacturing a raceway ring of a radial rolling bearing. In this case, the raceway surface is provided on the inner or outer peripheral surface of the raceway ring. Alternatively, the portion on which the raceway surface is formed is at least a portion of the axial direction of the inner or outer peripheral surface of a cylindrical substrate. The relative displacement direction of the laser light source is the axial direction. The raceway surface is provided over the entire circumference of the buildup layer by machining the surface of the buildup layer.

[0047] The method for processing a raceway surface of a rolling bearing according to one aspect of the present disclosure can be applied to a method for repairing or manufacturing a raceway ring of a thrust rolling bearing. In this case, the raceway surface is provided on the axial side surface of the raceway ring. Alternatively, the portion on which the raceway surface is formed is at least a portion of the radial direction of the axial side surface of a hollow circular plate-shaped substrate. The relative displacement direction of the laser light source is the radial direction. The raceway surface is provided around the entire circumference of the buildup layer by machining the surface of the buildup layer.

[0048] Below, a method for processing the raceway surface of a rolling bearing according to one embodiment of the present disclosure will be described in detail using a first example in which the processing method is applied to a method for repairing or manufacturing a raceway ring of a radial rolling bearing, and a second example in which the processing method is applied to a method for repairing or manufacturing a raceway ring of a thrust bearing.

[0049] [First Example] A first example of an embodiment of the present disclosure will be described with reference to Figures 1 to 5. In this example, a case will be described in which a method for repairing a raceway ring of a radial rolling bearing according to one aspect of the present disclosure is applied to an inner ring 3 of a radial cylindrical roller bearing 2 that uses cylindrical rollers (including needles) as rolling elements 1, as shown in Figure 1.

[0050] However, the method for repairing the raceway ring of a radial rolling bearing according to one embodiment of the present disclosure can also be applied to the outer ring of a radial cylindrical roller bearing, the inner ring and / or outer ring of a radial tapered roller bearing that uses tapered rollers as rolling elements, the inner ring and / or outer ring of a radial ball bearing that uses balls, or the inner ring and / or outer ring of a radial self-aligning roller bearing that uses spherical rollers.

[0051] Furthermore, the method for manufacturing a raceway ring of a radial rolling bearing according to one embodiment of the present disclosure can be applied to the inner ring and / or outer ring of a radial cylindrical roller bearing, the inner ring and / or outer ring of a radial tapered roller bearing that uses tapered rollers as rolling elements, the inner ring and / or outer ring of a radial ball bearing that uses balls, or the inner ring and / or outer ring of a radial self-aligning roller bearing that uses spherical rollers.

[0052] Furthermore, the method for repairing and manufacturing the raceway of a thrust rolling bearing according to one embodiment of the present disclosure can be applied to the raceway of a thrust cylindrical roller bearing that uses cylindrical rollers (including needles) as rolling elements as shown in the second example, the raceway of a thrust tapered roller bearing that uses tapered rollers, the raceway of a thrust ball bearing that uses balls, or the raceway of a thrust self-aligning roller bearing that uses spherical rollers.

[0053] The method for repairing a raceway of a radial rolling bearing according to an embodiment of the present disclosure and the method for repairing a raceway of a thrust rolling bearing according to an embodiment of the present disclosure can be preferably applied to large rolling bearings that support heavy loads, such as rolling bearings that support the roll necks of steel rolling mills. In other words, the method for repairing a raceway of a radial rolling bearing according to an embodiment of the present disclosure and the method for repairing a raceway of a thrust rolling bearing according to an embodiment of the present disclosure can achieve particularly significant effects in reducing costs and carbon dioxide emissions when applied to the raceway of a large rolling bearing.

[0054] Furthermore, according to the method for manufacturing a raceway for a radial rolling bearing and the method for manufacturing a raceway for a thrust rolling bearing of one aspect of the present disclosure, the buildup layer provided with the raceway surface can be made of a metal material different from the metal material constituting the base material, making it easy to adjust the raceway surface to the desired properties.

[0055] <Structure of radial cylindrical roller bearing> A radial cylindrical roller bearing 2 comprises an inner ring 3 having an inner ring raceway 4 on its outer peripheral surface around the entire circumference, an outer ring 6 having an outer ring raceway 5 on its inner peripheral surface around the entire circumference and arranged coaxially with the inner ring 3 on the radial outside of the inner ring 3, and a plurality of rolling elements 1 each of which is cylindrical and arranged to roll freely between the inner ring raceway 4 and the outer ring raceway 5.

[0056] In the description of this example, the axial direction, radial direction, and circumferential direction refer to the axial direction, radial direction, and circumferential direction of the inner ring 3, unless otherwise specified. The axial direction, radial direction, and circumferential direction of the inner ring 3 coincide with the axial direction, radial direction, and circumferential direction of the outer ring 6. In this example, the axial direction corresponds to the width direction of the raceway surface or the portion where the raceway surface is formed. Furthermore, one side in the axial direction (width direction) refers to the left side in Figures 1 to 3(C) and 4(B), and the other side in the axial direction (width direction) refers to the right side in Figures 1 to 3(C) and 4(B).

[0057] In this example, the inner ring 3 is repaired by the method for repairing raceways of a radial rolling bearing according to the present disclosure. The inner ring 3 is basically constructed using the original (used) inner ring 3a (see FIG. 3(A)) before repair as the substrate 7.

[0058] It should be noted that when a raceway ring is manufactured using the method for manufacturing a raceway ring for a radial rolling bearing according to one embodiment of the present disclosure or the method for manufacturing a raceway ring for a thrust rolling bearing according to one embodiment of the present disclosure, i.e., when an unused raceway ring is manufactured from scratch, the raceway ring is constructed using a cylindrical or hollow circular plate-shaped metal member as a base material with no raceway surface on its surface.

[0059] As shown in FIG. 2 , the inner ring 3 of this example is provided, from the surface side, with a buildup layer 8 made of a metal material different from that of the base material 7 on the surface portion including at least the inner ring raceway 4, and a mixed layer 9 of the metal material constituting the base material 7 and the metal material constituting the buildup layer 8 present in a portion located directly below the buildup layer 8.

[0060] The substrate 7 has a cylindrical shape and is made of a metallic material made of hard metal such as high-carbon chromium steel such as SUJ2-4, high-carbon chromium steel that has been carburized or carbonitrided, carbon steel such as S53C, or carburized steel such as SCr420 or SCM420. Before being repaired, the substrate 7 alone constitutes the inner ring 3a, and the original inner ring 3a has the original inner ring raceway 4a on its outer circumferential surface.

[0061] The buildup layer 8 covers the entire outer peripheral surface of the base material 7, including the original inner ring raceway 4a. The repaired inner ring raceway 4 is formed on the outer peripheral surface of the buildup layer 8. The buildup layer 8 is made of a metal material that can ensure sufficient bonding strength with the base material 7 and can also ensure sufficient performance of the inner ring raceway 4, such as an Fe-based alloy, a Cu-based alloy, a Ni-based alloy, a Co-based alloy, or a carbon alloy.

[0062] The mixed layer 9 is a layer in which the metal material constituting the base material 7 and the metal material constituting the buildup layer 8 are mixed. More specifically, the mixed layer 9 is formed during repair by melting, mixing, and solidifying the metal material constituting the original inner ring 3a (base material 7) and powdered welding material 11, which is the metal material (welding material) constituting the buildup portion 15. That is, as shown in Figures 4(A) and 4(B) , when forming each bead 16 constituting the buildup portion 15 by laser cladding, a laser 10 emitted from a laser light source is irradiated onto the original inner ring raceway 4a, and powdered welding material 11 is supplied to the portion of the original inner ring raceway 4a irradiated with the laser 10. As a result, the powdered welding material 11 is heated, melted, and solidified to form the bead 16.

[0063] At this time, the laser 10 irradiates the metal material present in the surface layer portion of the inner ring raceway 4a that was originally irradiated with the laser 10, and the metal material is heated to or above its melting point, melting and mixing with the molten powder welding material 11. Therefore, a mixed layer 9 is formed at the boundary between the substrate 7 and the buildup portion 15 as the metal material constituting the substrate 7 and the metal material constituting the buildup portion 15 solidify in a melted and mixed state. The mixed layer 9 remains in the portion directly below the buildup layer 8 even after the buildup portion 15 is subjected to appropriate machining such as cutting, grinding, and polishing to form the buildup layer 8 having the inner ring raceway 4 on its surface.

[0064] Inner ring 3 has a rehardened layer 12 in a portion located directly below mixed layer 9, and a retempered layer 13 in a portion located directly below rehardened layer 12. That is, inner ring 3 is provided with, in order from the outside in the radial direction, buildup layer 8, mixed layer 9, rehardened layer 12, and retempered layer 13 in the portion where inner ring raceway 4 is formed.

[0065] The re-hardened layer 12 is a portion of the base material 7 that has been re-hardened by being heated to a temperature above the hardening temperature but below the melting point when the original inner ring raceway 4a is irradiated with a laser 10 during the formation of the build-up layer 8 by laser cladding.

[0066] The re-tempered layer 13 is a portion of the base material 7 that has been tempered by being heated to a temperature above the tempering temperature but below the hardening temperature when the original inner ring raceway 4a is irradiated with a laser 10 to form the buildup layer 8 by laser cladding.

[0067] <Method of Repairing Inner Ring> First, as shown in Figure 3(A), a radial cylindrical roller bearing 2 in which damage such as wear or flaking has occurred in the original inner ring raceway 4a due to long-term use is removed from its installation location and disassembled, and the original inner ring 3a is taken out. If necessary, first, the surface of the original inner ring raceway 4a provided on the outer peripheral surface of the original inner ring 3a is degreased and cleaned. This removes oil present on the surface layer of the original inner ring raceway 4a, and also removes foreign matter such as wear powder and flaking debris adhering to the surface of the original inner ring raceway 4a, as well as moisture.

[0068] There are no particular limitations on the method for degreasing and cleaning the surface of the original inner ring raceway 4a. For example, solvent degreasing, alkaline degreasing in which the material is immersed in an alkaline solution, or electrolytic degreasing in which an electric current is passed between an electrode and a material immersed in an alkaline solution can be used. Additionally or alternatively, laser cleaning can be performed, or the material can be cleaned with an organic solvent and then dried by hot air drying or heat drying. If necessary, the surface of the original inner ring raceway 4a can be smoothed by appropriate machining such as cutting, grinding, or polishing before being degreased and cleaned.

[0069] Next, as shown in FIG. 3(B), a cladding process is performed in which a cladding portion 15 is formed by laser cladding so as to cover the entire outer peripheral surface of the portion of the original inner ring 3a (base material 7) where the original inner ring raceway 4a was formed.

[0070] In the build-up process, the original inner ring raceway 4a is irradiated with a laser 10 emitted from a laser light source (not shown), and a powder welding material 11 is supplied to the portion of the original inner ring raceway 4a irradiated with the laser 10 by spraying it together with shielding gas from a nozzle 14, while the laser light source and the original inner ring 3a are rotated relative to each other and displaced relative to each other in the axial direction. As a result, a build-up portion 15 is formed on the outer peripheral surface of the portion of the original inner ring 3a (base material 7) that includes the original inner ring raceway 4a, either by arranging a plurality of annular beads 16 side by side with no gaps in the axial direction, or by beads wound spirally with no gaps.

[0071] In the build-up process, the direction of irradiation of the laser 10 onto the original inner ring raceway 4a is tilted forward with respect to the normal direction of the repaired inner ring raceway 4 (the normal direction at the part irradiated by the laser 10) and the relative axial displacement direction of the laser light source with respect to the original inner ring 3a.

[0072] Specifically, in this example, the laser light source is displaced relative to the original inner ring 3a toward the other axial direction. The repaired inner ring raceway 4 is configured with a cylindrical surface whose outer diameter does not change in the axial direction. Therefore, the original inner ring raceway 4a is irradiated with a laser beam 10 emitted from the laser light source in a direction inclined toward the other axial direction (rightward in FIG. 4B ) with respect to the radial direction of the original inner ring 3a (up and down direction in FIG. 4B ), i.e., along a virtual straight line α that extends radially outward toward the other axial direction. Then, a powder welding material 11 is supplied from a nozzle 14 by spraying it with a shielding gas onto the portion irradiated with the laser beam 10, while the original inner ring 3a is rotated once relative to the laser light source to form a single annular bead 16. The bead 16 has a cross-sectional shape that is approximately partially elliptical or approximately rectangular.

[0073] The inclination angle θ of the irradiation direction of the laser 10 with respect to the normal direction of the inner ring raceway 4 (irradiation angle of the laser 10) is not limited to, but can be 5 degrees or more and less than 90 degrees, preferably 10 degrees or more and 20 degrees or less, and more preferably 15 degrees or more and 20 degrees or less. If the irradiation angle θ of the laser 10 is less than 5 degrees, when the laser 10 is irradiated to a portion adjacent to the other axial side of the previously formed bead 16 to form the next bead 16, it may not be possible to sufficiently heat the portion located radially inward of the end portion on the other axial side of the previously formed bead 16, and it may not be possible to sufficiently prevent the occurrence of internal defects.

[0074] In this example, a processing device is used in which a nozzle 14 that sprays the powder welding material 11 and the shielding gas is supported and fixed around a laser light source that emits the laser 10. Therefore, when the irradiation angle θ of the laser 10 is changed, the spray angle of the powder welding material 11 and the shielding gas from the nozzle 14 also changes. However, when implementing the present disclosure, a processing device having a structure that allows the spray angle of the powder welding material 11 and the shielding gas from the nozzle 14 to be adjusted independently of the irradiation angle of the laser 10 can also be used. In any case, when performing laser cladding, the powder welding material 11 and the shielding gas are sprayed onto the portion of the original inner ring raceway 4a that was irradiated with the laser 10.

[0075] The output of laser 10 is set appropriately according to the radial height H of bead 16 (the radial height of the portion of bead 16 that has the greatest radial height), the axial width W (the axial width of the portion of bead 16 that has the greatest axial width), and other factors. For example, in the case of the inner ring 3a of a single-row cylindrical roller bearing having a bearing number NUP206, if the radial height H of bead 16 is approximately 1.0 mm or more and 1.5 mm or less and the axial width W is approximately 4.0 mm or more and 6.0 mm or less, the output of laser 10 can be, but is not limited to, approximately 2.5 kW or more and 3.5 kW or less.

[0076] The powder welding material 11 is composed of a metal powder such as an Fe-based alloy, a Cu-based alloy, a Ni-based alloy, a Co-based alloy, or a carbon alloy. An appropriate amount of the powder welding material 11 is supplied depending on the outer diameter of the original inner ring 3a, the radial height H and the axial width W of the bead 16, etc. When implementing the present disclosure, a wire welding material can also be used instead of the powder welding material 11.

[0077] Next, the laser light source is displaced relative to the original inner ring 3a in the other axial direction. Specifically, the laser light source is displaced in the other axial direction, or the original inner ring 3a is displaced in the one axial direction. At this time, the amount of axial displacement of the original inner ring 3a relative to the laser light source is adjusted so that no gap exists between two axially adjacent beads 16, i.e., between the bead 16 previously formed on one axial side and the bead 16 to be formed next on the other axial side.

[0078] Specifically, of two axially adjacent beads 16, the first axial side portion of the bead 16 on the other axial side is arranged to overlap in the radial direction with the second axial side portion of the bead 16 on the first axial side that was formed earlier. In other words, the bead 16 on the other axial side is formed so that its first axial side portion covers the second axial side portion of the bead 16 on the first axial side.

[0079] The axial dimension L of the radially overlapping portion of two axially adjacent beads 16 is determined appropriately depending on the axial width W, radial height H, etc. of the beads 16. For example, in the case of an inner ring 3a of a single-row cylindrical roller bearing with a bearing number NUP206, where the axial width W of the beads 16 is approximately 4.0 mm to 6.0 mm and the radial height H is approximately 1.0 mm to 1.5 mm, the axial dimension L of the radially overlapping portion of two axially adjacent beads 16 is, but is not limited to, 1.0 mm to 3.5 mm, preferably 2.0 mm to 3.0 mm. If the axial dimension L is less than 1.0 mm, a gap may be formed between the beads 16, potentially exposing the original inner ring raceway 4a. If the axial dimension L is greater than 3.5 mm, material costs and processing time may increase.

[0080] After the laser light source is displaced relative to the original inner ring 3a toward the other axial side, the laser 10 is again irradiated onto the original inner ring raceway 4a from a direction inclined with respect to the normal direction of the inner ring raceway 4 (in this example, the radial direction of the original inner ring 3a), and while supplying powder welding material 11 from a nozzle 14 by spraying it together with shielding gas onto the part irradiated with the laser 10, the original inner ring 3a is rotated once relative to the laser light source, thereby forming a single annular bead 16.

[0081] As described above, in the buildup process of this example, the work of forming one annular bead 16 and the work of relatively displacing the laser light source and the original inner ring 3a in the axial direction are repeated to form a buildup portion 15 consisting of multiple annular beads 16 arranged side by side with no gaps in the axial direction.

[0082] When carrying out the method for repairing a raceway of a radial rolling bearing according to one aspect of the present disclosure, it is also possible to form a buildup portion consisting of a bead wound spirally without gaps on the outer peripheral surface of the original inner ring by rotating the original inner ring relative to the laser light source while displacing it in the axial direction. In this case, the amount of axial displacement per rotation of the original inner ring relative to the laser light source is adjusted so that no gaps exist between axially adjacent portions of the bead.

[0083] When the original inner ring raceway 4a is irradiated with a laser 10 to perform laser cladding, the metallic material present in the surface layer of the original inner ring raceway 4a irradiated with the laser 10 of the original inner ring 3a (base material 7) is melted together with the powder welding material 11, which is the metallic material constituting the weld bead 8b, to form a mixed molten pool 17. Then, as the laser light source and the original inner ring 3a rotate relative to each other, the irradiation position of the laser 10 shifts from the molten pool 17, and the metallic material constituting the molten pool 17 cools and solidifies. As a result, a cladding portion 15 (bead 16) is formed on the original inner ring raceway 4a, and at the same time, a mixed layer 9 of the metallic material constituting the base material 7 and the metallic material constituting the cladding portion 15 (bead 16) is formed at the boundary between the base material 7 and the bead 16.

[0084] Furthermore, when the original inner ring raceway 4a is irradiated with laser 10 to perform laser cladding, the metal material of the original inner ring 3a (substrate 7) in a portion that is below the surface layer portion of the original inner ring raceway 4a is also heated. The portion located directly below the mixed layer 9 is re-quenched by being heated to a temperature equal to or higher than the quenching temperature but lower than the melting point. As a result, a re-quenched layer 12 is formed in the portion located directly below the mixed layer 9.

[0085] Furthermore, the portion located directly below the re-hardened layer 12 is tempered by being heated to a temperature equal to or higher than the tempering temperature but lower than the quenching temperature. As a result, a re-tempered layer 13 is formed in the portion located directly below the re-hardened layer 12. Note that even if the portion located below the re-tempered layer 13 is heated, the temperature is lower than the tempering temperature, so almost no structural change occurs. Note that the re-hardened layer 12 and the re-tempered layer 13 are not shown in Figures 3(A) to 3(C) and 4.

[0086] When forming the cladding portion 15 on the original inner ring raceway 4a by laser cladding, it is possible to constrain at least a portion of the surface of the original inner ring 3a (substrate 7) excluding the portion where the original inner ring raceway 4a is present. This makes it possible to prevent the substrate 7 from being deformed by the effects of heat generated by the irradiation of the laser 10. For example, as shown in Fig. 5, a cylindrical deformation prevention jig 18 can be fitted inside the original inner ring 3a (substrate 7) to constrain the inner peripheral surface of the original inner ring 3a.

[0087] In addition to or instead of the inner peripheral surface of the original inner ring 3 a (substrate 7), the axial side surfaces of the original inner ring 3 a (side surfaces on one axial side and / or the other axial side) can also be restrained. Furthermore, if the heat generated by irradiation with the laser 10 does not deform the original inner ring 3 a or the deformation is to an inconsequential degree, then the attachment of the deformation prevention jig 18 can be omitted.

[0088] Furthermore, the original inner ring 3a (substrate 7) can be preheated before laser cladding. Preheating the original inner ring 3a prevents the temperature of the portion of the original inner ring 3a irradiated with the laser 10 from changing rapidly when the laser 10 is irradiated onto the original inner ring raceway 4a, causing damage such as cracks in that portion. However, the preheating temperature is preferably equal to or lower than the tempering temperature, specifically, 200°C or lower. In other words, if the preheating temperature exceeds the tempering temperature, the surface of the original inner ring 3a (substrate 7) will be tempered, which may reduce the surface hardness of the original inner ring 3a.

[0089] A machining process is performed in which a buildup portion 15 is formed by laser cladding on the outer peripheral surface of the portion of the original inner ring 3a (base material 7) that includes the original inner ring raceway 4a, and then a new inner ring raceway 4 is formed by applying appropriate machining such as cutting, grinding, or polishing to the buildup portion 15 (see FIG. 3(C)). This results in a new (repaired) inner ring 3. The processing for forming the new inner ring raceway 4 is basically the same as the processing for forming the original inner ring raceway 4a on the outer peripheral surface of the original inner ring 3a.

[0090] In this example, a grinding wheel is pressed against the outer peripheral surface of the buildup portion 15, and the original inner ring 3a equipped with the buildup portion 15 is rotated about its central axis while the grinding wheel is oscillated around the center of curvature of the generatrix shape (cross-sectional shape) of the new inner ring raceway 4. In this way, the outer peripheral surface of the buildup portion 15 is polished to form a new inner ring raceway 4, and a cleaning process is then performed as necessary to obtain a new inner ring 3. The outer peripheral surface of the part of the new inner ring 3 that includes the inner ring raceway 4a is made up of the buildup layer 8 formed after polishing.

[0091] The repaired inner ring 3 obtained as described above is combined with the outer ring 6 and the rolling elements 1 to assemble the repaired radial cylindrical roller bearing 2, which is then reassembled in its installation location.

[0092] When carrying out the method for manufacturing a raceway ring of a radial rolling bearing according to one embodiment of the present disclosure, the method can be carried out basically in the same manner as the repair method of this example, except that a cylindrical substrate without a raceway surface on its surface is used.

[0093] According to this example, the radial cylindrical roller bearing 2 can be repaired and reused, which reduces costs and carbon dioxide emissions compared to manufacturing a new radial cylindrical roller bearing 2 and replacing it.

[0094] Furthermore, in this example, the direction of irradiation of the laser 10 onto the original inner ring raceway 4a is inclined forward with respect to the normal direction of the inner ring raceway 4 (the radial direction of the original inner ring 3a in this example) with respect to the relative displacement direction in the axial direction of the laser light source with respect to the original inner ring 3a. Therefore, when the bead 16 on the other axial side is formed in a portion adjacent to the other axial side of the bead 16 on one axial side that was previously formed, it is possible to sufficiently heat the portion of the original inner ring raceway 4a that is located radially inward of the end portion on the other axial side of the bead 16 on one axial side.

[0095] Therefore, in the original inner ring raceway 4a, in the portion located radially inward of the end portion on the other axial side of the bead 16 formed earlier on one axial side, the molten metal material can be prevented from solidifying prematurely before the bubbles generated inside are expelled, thereby preventing the occurrence of internal defects due to bubbles inside the buildup portion 15 formed by the multiple annular beads 16.

[0096] Second Example A second example of the embodiment of the present disclosure will be described with reference to Figures 6 and 7. This example is an example in which one race 21 of a pair of races (thrust races) 21, 22 constituting a thrust cylindrical roller bearing 20 that uses cylindrical rollers (including needles) as rolling elements 19 is repaired by a method for repairing races of a thrust rolling bearing according to one aspect of the present disclosure.

[0097] <Structure of Thrust Cylindrical Roller Bearing> The thrust cylindrical roller bearing 20 comprises a pair of races 21 and 22 , a plurality of rolling elements 19 , and a cage 23 .

[0098] In the description of this example, the axial, radial, and circumferential directions refer to the axial, radial, and circumferential directions of one of the raceways 21, unless otherwise specified. The axial, radial, and circumferential directions of one of the raceways 21 coincide with the axial, radial, and circumferential directions of the other of the raceways 22. In this example, the radial direction corresponds to the width direction of the raceway surface or the portion where the raceway surface is formed. One width side corresponds to either the radially inner side or the radially outer side, and the other width side corresponds to the other of the radially inner side or the radially outer side. Furthermore, one axial side refers to the lower side in FIGS. 6 and 7, and the other axial side refers to the upper side in FIGS. 6 and 7.

[0099] Each of the pair of bearing rings 21, 22 is configured in the shape of a hollow circular plate, and has raceway surfaces 24, 25 on opposing axial side surfaces. That is, of the pair of bearing rings 21, 22, one bearing ring 21 arranged on one axial side has raceway surface 24 on its side surface on the other axial side, and the other bearing ring 22 arranged on the other axial side has raceway surface 25 on its side surface on the one axial side. Raceway surfaces 24, 25 are configured by flat surfaces that are perpendicular to the central axis O of thrust cylindrical roller bearing 20.

[0100] The rolling elements 19 are cylindrical in shape. Each rolling element 19 has its central axis facing in a radial direction and is held by a cage 23, and is disposed between the raceway surfaces 24, 25 of the pair of raceways 21, 22 so as to be able to roll freely.

[0101] In this example, one of the bearing rings 21 has been repaired by the method for repairing bearing rings of a thrust rolling bearing of the present disclosure. The bearing ring 21 is basically configured using the original bearing ring 21a before repair as the base material 7a.

[0102] The bearing ring 21 has basically the same layer structure as the inner ring 3 of the first example. That is, the bearing ring 21 has, on the surface portion including at least the raceway surface 24, a buildup layer made of a metal material different from the base material 7a, and a mixed layer of the metal material constituting the base material 7a and the metal material constituting the buildup layer, which is present in a portion located directly below the buildup layer.

[0103] The base material 7a is made of hard metal and has a hollow circular plate shape. Before being repaired, the base material 7a alone constitutes the bearing ring 21a, and the original bearing ring 21a has the original raceway surface 24a on the other axial side.

[0104] The buildup layer is made of a metal material that can ensure sufficient bonding strength with the base material 7a and sufficient performance of the raceway surface 24, and covers the entire periphery of the other axial side surface of the base material 7a, including the original raceway surface 24a. The new raceway surface 24 is provided on the other axial side surface of the buildup layer.

[0105] The mixed layer is formed during repair by melting, mixing, and solidifying the metal material constituting the original raceway 21a (base material 7a) and the powder welding material 11a, which is the metal material constituting the buildup portion 15a.

[0106] Furthermore, the bearing ring 21 has a re-hardened layer in the portion located directly below the mixed layer, which has been re-hardened by being heated to a temperature equal to or higher than the hardening temperature but lower than the melting point during repair, and also has a re-tempered layer in the portion located directly below the re-hardened layer, which has been tempered by being heated to a temperature equal to or higher than the tempering temperature but lower than the hardening temperature during repair.

[0107] <Method of Repairing Bearing Ring> First, the original bearing ring 21a to be repaired is taken out by disassembling the thrust cylindrical roller bearing 20. Furthermore, if necessary, the original raceway surface 24a is degreased and cleaned to remove oil and / or foreign matter.

[0108] Next, a cladding process is performed in which a cladding portion 15a is formed by laser cladding so as to cover the entire circumference of the side surface on the other axial side of the portion of the original raceway surface 24a (base material 7a) where the original raceway surface 24a was formed.

[0109] In the build-up process, the original raceway surface 24a is irradiated with a laser 10a emitted from a laser light source (not shown), and a powder welding material 11a is supplied to the portion of the original raceway surface 24a irradiated with the laser 10a by spraying it together with a shielding gas from a nozzle 14, while the laser light source and the original raceway surface 24a are rotated relative to each other and displaced relative to each other in the radial direction. As a result, a build-up portion 15 is formed on the other axial side of the portion of the original raceway ring 21 (base material 7a) that includes the original raceway surface 24a, by arranging a plurality of annular beads 16a side by side with no gaps in the radial direction, or by beads wound spirally with no gaps.

[0110] In the build-up process, the direction of irradiation of the laser 10a onto the original raceway surface 24a is tilted forward with respect to the normal direction of the repaired raceway surface 24 (the normal direction at the part irradiated by the laser 10a) and the radial relative displacement direction of the laser light source relative to the original raceway ring 21a.

[0111] In this example, the laser light source is displaced radially outward relative to original bearing ring 21a. Furthermore, raceway surface 24 after repair is formed by a flat surface perpendicular to central axis O of thrust cylindrical roller bearing 20. For this reason, laser 10a emitted from the laser light source is irradiated onto original raceway surface 24a radially outward with respect to the axial direction of original bearing ring 21a, that is, from the direction of imaginary straight line β that moves more radially outward as it moves toward the other axial side, and while powder welding material 11a is supplied from nozzle 14a by being sprayed together with shielding gas onto the portion irradiated with laser 10a, original bearing ring 21a is rotated once relative to the laser light source, thereby forming a single annular bead 16a.

[0112] The inclination angle θ of the irradiation direction of the laser 10 relative to the normal direction of the orbital plane 24 (irradiation angle of the laser 10) is not limited to this, but can be 5 degrees or more and less than 90 degrees, preferably 10 degrees or more and 20 degrees or less, and more preferably 15 degrees or more and 20 degrees or less.

[0113] Next, the laser light source is displaced radially outward relative to the original bearing ring 21a. Specifically, the laser light source is displaced radially outward, or the original bearing ring 21a is displaced radially inward. At this time, the amount of radial displacement of the original bearing ring 21a relative to the laser light source is adjusted so that no gap exists between two radially adjacent beads 16, i.e., between the radially inner bead 16 formed previously and the radially outer bead 16 to be formed next.

[0114] Specifically, of two radially adjacent beads 16, the radially inner portion of the radially outer bead 16 formed earlier is arranged to overlap in the axial direction with the radially outer portion of the radially inner bead 16. In other words, the radially outer bead 16 is formed so that its radially inner portion covers the radially outer portion of the radially inner bead 16.

[0115] After the laser light source is displaced radially outward relative to the original raceway ring 21a, the laser 10 is again irradiated onto the original raceway surface 24a from a direction inclined with respect to the axial direction of the original raceway ring 21a, and the powder welding material 11 is supplied to the part irradiated with the laser 10 by spraying it from the nozzle 14 together with shielding gas, while the original raceway ring 21a is rotated once relative to the laser light source, thereby forming a single annular bead 16a.

[0116] As described above, in this example, by repeating the steps of forming one annular bead 16a and displacing the laser light source and the original raceway 21a relative to each other in the radial direction, a buildup portion 15a is formed, which is composed of multiple annular beads 16a arranged side by side with no gaps in the axial direction.

[0117] In this example, the laser light source is displaced radially outward relative to the original raceway ring 21a, but when carrying out the method for repairing a raceway ring of a thrust rolling bearing according to one aspect of the present disclosure, the laser light source can also be displaced radially inward relative to the original raceway ring. In this case, the laser emitted from the laser light source is irradiated onto the original raceway surface from the radially outward direction in the axial direction of the original raceway ring.

[0118] Furthermore, when carrying out the method for repairing a raceway of a thrust rolling bearing according to one aspect of the present disclosure, it is also possible to form a buildup portion consisting of a tightly spirally wound bead on the outer circumferential surface of the original raceway by rotating the original raceway relative to the laser light source while displacing it radially relative to the laser light source. In this case, the amount of radial displacement of the original raceway relative to the laser light source per rotation is adjusted so that no gaps exist between radially adjacent portions of the bead.

[0119] When carrying out the method for manufacturing a raceway of a thrust rolling bearing according to one embodiment of the present disclosure, the method can be carried out basically in the same manner as the repair method of this example, except that a hollow circular substrate without a raceway surface on its surface is used.

[0120] According to this example, when the radially outer bead 16a is formed adjacent to the radially outer side of the previously formed radially inner bead 16a, the portion of the original raceway surface 24a located on one axial side of the radially outer end of the radially inner bead 16a can be sufficiently heated. This prevents the molten metal material from prematurely solidifying in the portion of the original raceway surface 24a located on one axial side of the radially outer end of the previously formed radially inner bead 16a before gas bubbles generated inside are expelled. This prevents internal defects caused by gas bubbles from occurring inside the buildup portion 15a formed by the multiple annular beads 16a.

[0121] The other configurations and effects of the second example are the same as those of the first example.

[0122] An experiment conducted to confirm the effects of the present disclosure will be described.

[0123] This experiment was carried out using a radial cylindrical roller bearing 2 as a specimen, as shown in Figure 1. Two types of specimens were prepared: one repaired by the method for repairing raceways of a radial rolling bearing according to one embodiment of the present disclosure (exemplary specimen), and one repaired by a conventional method (comparison specimen).

[0124] In the example, when forming the cladding portion 15 on the original inner ring raceway 4a by laser cladding, the inclination angle θ of the irradiation direction of the laser 10 relative to the radial direction of the original inner ring 3a was set to 15 degrees, and the cladding portion 15 was formed by arranging multiple annular beads 16 closely together on the original inner ring raceway 4a. The cladding portion 15 was then polished to form a new inner ring raceway 4.

[0125] On the other hand, in the comparative example, when forming the build-up portion, the laser was irradiated from the radial direction of the inner ring.

[0126] The conditions other than the laser irradiation direction during laser cladding were the same for the example product and the comparative product.

[0127] The specifications of the cylindrical roller bearing used as the test piece and the laser cladding conditions are as follows:

[0128] <Specifications of radial cylindrical roller bearing> Bearing number: NUP206 Inner diameter: 30 (mm) Outer diameter: 62 (mm) Width: 16 (mm) Material of inner ring 3 and outer ring 6: SUJ2 Material of rolling element 1: SUJ2 Number of rolling elements 1: 13 Diameter of rolling element 1: 9 (mm)

[0129] <Laser cladding conditions for the implemented product> Laser output: 3.0 (kW) Powder welding material: powder high-speed steel Powder welding material supply rate: 30 (g / min) Scanning speed (relative rotation speed of the laser light source to the inner ring): 900 (mm / min) Number of beads constituting the cladding portion: 3

[0130] <Laser cladding conditions for the comparative product> Laser output: 3.0 (kW) Powder welding material: powder high-speed steel Powder welding material supply rate: 30 (g / min) Scanning speed: 1000 (mm / min) Number of beads constituting the cladding portion: 2

[0131] The rolling fatigue life of the above-mentioned test specimens and comparative specimens was measured. Specifically, the test specimens and comparative specimens were operated under the conditions shown below, and the test was stopped when the vibration of the radial cylindrical roller bearing began to increase. The rolling fatigue life was determined to be the time when flaking was visible on the inner ring raceway.

[0132] <Operating conditions and life test conditions for radial cylindrical roller bearings> Lubrication conditions: ISO-VG68 equivalent mineral oil (oil bath method) Test load: 5 (kN) Dynamic equivalent load / basic dynamic load rating (P / C) = 0.13 Rotation speed: 500 (min －１ )

[0133] The radial cylindrical roller bearing incorporating the comparison product experienced large vibrations (vibration acceleration of 4.5 mm / s) immediately after the start of the test. ２ The above vibrations were observed. The reason for this is thought to be that in the comparative product, internal defects that existed inside the buildup portion were exposed on the surface of the inner ring raceway by grinding the buildup portion. After operating a radial cylindrical roller bearing incorporating the comparative product for 100 hours, the radial cylindrical roller bearing was disassembled and the inner ring raceway of the comparative product was visually inspected, and it was confirmed that peeling had occurred in multiple locations on the inner ring raceway. The comparative product was then cut and the cross section was examined.

[0134] In contrast, the radial rolling bearing incorporating the product did not generate any significant vibrations even after 300 hours of operation (vibration acceleration was 2.5 mm / s ２ (The damage was less than 300 hours.) After 300 hours had passed, the radial cylindrical roller bearing incorporating the test sample was disassembled and the inner ring raceway of the test sample was inspected, but no peeling was found. The test sample was then cut and the cross section was inspected, but no noticeable damage was found.

[0135] REFERENCE SIGNS LIST 1 Rolling element 2 Radial cylindrical roller bearing 3, 3a Inner ring 4, 4a Inner ring raceway 5 Outer ring raceway 6 Outer ring 7 Base material 8 Overlay layer 9 Mixed layer 10 Laser 11 Powder welding material 12 Requenched layer 13 Retempered layer 14 Nozzle 15 Overlay portion 16 Bead 17 Weld pool 18 Deformation prevention jig 19 Rolling element 20 Thrust cylindrical roller bearing 21 Raceway ring 22 Raceway ring 23 Cage 24 Raceway surface 25 Raceway surface 100 Inner ring 101 Inner ring raceway 102 Bead 103 Overlay portion 104 Laser

Claims

1. A build-up process for forming a build-up portion, which is configured by arranging a plurality of annular beads without gaps in the width direction or by beads wound in a spiral shape without gaps on the raceway surface or the portion where the raceway surface of the base material is formed, includes irradiating the raceway surface of the raceway ring or the portion where the raceway surface of the base material is formed with laser emitted from a laser light source, and while supplying a melting material to the irradiated portion of the laser, relatively rotating the laser light source with respect to the raceway ring or the base material and relatively displacing it in the width direction of the raceway surface or the portion where the raceway surface is formed. In the build-up process, the irradiation direction of the laser with respect to the raceway surface or the portion where the raceway surface is formed is set to be inclined forward with respect to the normal direction at the irradiated portion of the laser with respect to the relative displacement direction of the laser light source with respect to the raceway ring or the base material. A method for machining the raceway surface of a rolling bearing.

2. The method for machining the raceway surface of a rolling bearing according to claim 1, wherein the inclination angle of the irradiation direction of the laser with respect to the normal direction is 5 degrees or more and less than 90 degrees.

3. A repair method for a raceway ring of a radial rolling bearing, which includes a build-up process for forming a build-up portion, which is configured by arranging a plurality of annular beads without gaps in the axial direction or by beads wound in a spiral shape without gaps on the raceway surface provided on the inner circumferential surface or the outer circumferential surface of the raceway ring. In the build-up process, while irradiating the raceway surface provided on the inner circumferential surface or the outer circumferential surface of the raceway ring with laser emitted from a laser light source and supplying a melting material to the irradiated portion of the raceway surface, relatively rotating the laser light source with respect to the raceway ring and relatively displacing it in the axial direction. In the build-up process, the irradiation direction of the laser with respect to the raceway surface is set to be inclined forward with respect to the normal direction of the raceway surface with respect to the axial relative displacement direction of the laser light source with respect to the raceway ring.

4. The repair method for a raceway ring of a radial rolling bearing according to claim 3, wherein the inclination angle of the irradiation direction of the laser with respect to the normal direction of the raceway surface is 5 degrees or more and less than 90 degrees.

5. A method for manufacturing a raceway ring of a radial rolling bearing, comprising: a cylindrical base material; a build-up layer covering the entire inner peripheral surface or outer peripheral surface of the base material over the entire circumference; and a raceway surface provided over the entire circumference on the surface of the build-up layer, wherein a laser emitted from a laser light source is irradiated onto the inner peripheral surface or outer peripheral surface of the base material, and while supplying a melting material to a portion of the inner peripheral surface or outer peripheral surface of the base material irradiated with the laser, the laser light source is relatively rotated and relatively displaced in the axial direction with respect to the base material, so as to form a build-up portion constituted by arranging a plurality of annular beads axially without gaps on the inner peripheral surface or outer peripheral surface of the base material, or a build-up portion constituted by beads wound in a non-gapped spiral shape; and a machining step of forming the build-up layer having the raceway surface on the surface by machining the surface of the build-up portion, wherein in the build-up step, the irradiation direction of the laser with respect to the inner peripheral surface or outer peripheral surface of the base material is set to a direction inclined forward with respect to the normal direction of the inner peripheral surface or outer peripheral surface of the base material with respect to the axial relative displacement direction of the laser light source with respect to the base material. A method for manufacturing a raceway ring of a radial rolling bearing.

6. The method for manufacturing a raceway ring of a radial rolling bearing according to claim 5, wherein an inclination angle of the irradiation direction of the laser with respect to the normal direction of the inner peripheral surface or outer peripheral surface of the base material is 5 degrees or more and less than 90 degrees.

7. A method for repairing a raceway ring of a thrust rolling bearing, comprising a build-up step of irradiating a laser emitted from a laser light source onto a raceway surface provided on an axial side surface of the raceway ring, and while supplying a melting material to a portion of the raceway surface irradiated with the laser, relatively rotating and relatively displacing the laser light source in the radial direction with respect to the raceway ring, so as to form a build-up portion constituted by arranging a plurality of annular beads radially without gaps on the raceway surface, or a build-up portion constituted by beads wound in a non-gapped spiral shape, wherein in the build-up step, the irradiation direction of the laser with respect to the raceway surface is set to a direction inclined forward with respect to the normal direction of the raceway surface with respect to the radial relative displacement direction of the laser light source with respect to the raceway ring.

8. The method for repairing a raceway ring of a thrust rolling bearing according to claim 7, wherein an inclination angle of the irradiation direction of the laser with respect to the normal direction of the raceway surface is 5 degrees or more and less than 90 degrees.

9. A method for manufacturing a raceway ring of a thrust rolling bearing, comprising a hollow circular plate-like base material, a build-up layer covering the entire axial side surface of the base material over the entire circumference, and a raceway surface provided over the entire circumference on the surface of the build-up layer, the method comprising: irradiating the axial side surface of the base material with a laser emitted from a laser light source, and while supplying a melting material to a portion of the axial side surface of the base material irradiated with the laser, relatively rotating the laser light source with respect to the axial side surface of the base material and relatively displacing it in the radial direction, thereby arranging a plurality of annular beads side by side without gaps in the radial direction on the axial side surface of the base material, or forming a build-up portion composed of beads wound in a spiral shape without gaps, the method comprising a build-up step; a machining step of forming the build-up layer having the raceway surface on the surface by performing machining on the surface of the build-up portion; and in the build-up step, setting the irradiation direction of the laser with respect to the axial side surface of the base material to a direction inclined forward with respect to the normal direction of the axial side surface of the base material with respect to the radial relative displacement direction of the laser light source with respect to the base material. A method for manufacturing a raceway ring of a thrust rolling bearing.

10. The method for manufacturing a raceway ring of a thrust rolling bearing according to claim 9, wherein the inclination angle of the irradiation direction of the laser with respect to the normal direction of the axial side surface of the base material is 5 degrees or more and less than 90 degrees.

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