Superfinishing method, roller bearing manufacturing method, vehicle manufacturing method, machine manufacturing method, and superfinishing device

Abstract

A component (17) of a roller bearing includes: a central section (27) that has a peripheral surface having a linear profile extending at least in the axial direction; and end sections (25) that each have a peripheral surface having a crown profile. A superfinishing method involves: using first grinding wheels (31) to subject the end sections (25) to superfinishing while rotating the component (17); and using a second grinding wheel (33), which was prepared separately from the first grinding wheels (31), to subject the central section (27) to superfinishing while rotating the component (17).

Description

Superfinishing method, roller bearing manufacturing method, vehicle manufacturing method, machine manufacturing method, and superfinishing device

[0001] The present invention relates to a superfinishing method, a roller bearing manufacturing method, a vehicle manufacturing method, a machine manufacturing method, and a superfinishing apparatus. This application claims priority to Japanese Patent Application No. 2024-007501, filed January 22, 2024, the contents of which are incorporated herein by reference.

[0002] Generally, to superfinish rollers (rolling elements) of a roller bearing using the infeed method (stop grinding), the rollers are sandwiched between a pair of drive rollers, which are then rotated in the same direction to rotate the rollers. A superfinishing stone is then pressed against the rollers with a predetermined pressure while vibrating in the generatrix direction of the roller rolling surface, and the superfinishing stone traverses in the generatrix direction of the roller rolling surface. Furthermore, rollers of roller bearings may be provided with a crowning shape to prevent excessive contact pressure due to stress concentration at the contact ends between the rollers and the raceway surface of the bearing ring. Examples of crowning shapes include a compound crowning shape, in which the generatrix shape of the roller rolling surface is a small-radius arc near both ends of the rolling surface, and a logarithmic crowning shape, in which the generatrix shape of the roller rolling surface is a logarithmic shape.

[0003] When rollers having a compound crowning shape or a logarithmic crowning shape are superfinished by the above-mentioned method, wear of the grinding wheel becomes uneven, which significantly shortens the life of the grinding wheel, and also causes problems such as insufficient machining and uneven surface roughness. Therefore, various superfinishing methods have been proposed.

[0004] For example, Patent Document 1 discloses a superfinishing method for a roller rolling surface (transfer surface) having a compound crowning surface with a large-diameter arc in the axial center and a small-diameter arc at the axial end. In this processing method, the entire roller rolling surface is processed in the axial direction, and then only the large-diameter arc in the axial center of the rolling surface is processed separately. Patent Document 1 also describes that this processing method solves the above-mentioned problem by stopping the traverse motion for a predetermined period of time in the small-diameter arc at the axial end, and that a uniform finished surface roughness can be obtained in both the large-diameter arc and the small-diameter arc, even for compound crowning and logarithmic crowning shapes.

[0005] Patent No. 6517105

[0006] However, in superfinishing, the grinding wheel wears during the processing cycle so that it follows the shape of the workpiece surface. Therefore, when machining a large-diameter arc in the axial center of a roller with a crowned shape and a small-diameter arc at the axial end in the same cycle, the shape that the grinding wheel follows varies significantly depending on the processing position. Furthermore, in the case of the small-diameter arc at the axial end, where the generatrix shape is significantly curved, it takes time for the grinding wheel shape to follow the shape of the workpiece surface, which can result in insufficient processing and a failure to achieve the desired crowning shape. Furthermore, the above-mentioned problem is not limited to the rolling surfaces of rollers, but also occurs in the processing of the raceway surfaces of bearing rings.

[0007] An object of the present invention is to provide a superfinishing method, a roller bearing manufacturing method, a vehicle manufacturing method, a machine manufacturing method, and a superfinishing apparatus that can efficiently superfinish a machined surface to a good surface roughness in a short time while suppressing a decrease in the life of the grinding wheel due to uneven wear, even when the shape of the machined surface varies depending on the location. Another object of the present invention is to provide a technology that is advantageous for improving product quality and reducing costs.

[0008] One aspect of the present invention is a method for superfinishing a roller bearing component, the component having a central portion with a peripheral surface having a linear profile extending at least in the axial direction, and end portions with peripheral surfaces having crown profiles transitioning from the linear profile, the method comprising: superfinishing the end portions with a first grinding stone while rotating the component; and superfinishing the central portion with a second grinding stone, prepared separately from the first grinding stone, while rotating the component.

[0009] Another aspect of the present invention is a method for manufacturing a roller bearing, in which the roller bearing is manufactured using the above-described superfinishing method.

[0010] Another aspect of the present invention is a method for manufacturing a vehicle, comprising manufacturing a roller bearing using the manufacturing method described above, and assembling a vehicle using the roller bearing.

[0011] Another aspect of the present invention is a method for manufacturing a machine, comprising manufacturing a roller bearing using the manufacturing method described above, and assembling a machine using the roller bearing.

[0012] Another aspect of the present invention is an apparatus for superfinishing a roller bearing component, the component having a central portion with a peripheral surface having a linear profile extending at least in the axial direction, and an end portion with a peripheral surface having a crown profile transitioning from the linear profile. The apparatus includes a drive unit that rotates the component, a first grinding stone, a second grinding stone prepared separately from the first grinding stone, and a mechanism that presses the first grinding stone and the second grinding stone against the component. The mechanism has a first mode in which the end portion is superfinished with the first grinding stone, and a second mode in which the central portion is superfinished with the second grinding stone.

[0013] According to the present invention, even when the shape of the processed surface varies depending on the location, it is possible to efficiently superfinish the processed surface to a good surface roughness in a short time while suppressing a decrease in the life of the grinding wheel due to uneven wear. Furthermore, according to the present invention, it is advantageous for improving product quality and reducing costs.

[0014] FIG. 1 is a cross-sectional view of a main portion of a cylindrical roller bearing. FIG. 2 is a partial side view of a cylindrical roller. FIG. 3 is a process explanatory diagram schematically showing the procedure for superfinishing the crowning portion and central portion of the rolling surface of a cylindrical roller. FIG. 4 is a schematic configuration diagram schematically showing the main portion of a superfinishing device. FIG. 5 is a schematic configuration diagram schematically showing the configuration of a crowning finishing unit. FIG. 6 is a schematic configuration diagram schematically showing the configuration of a central portion finishing unit. FIG. 7 is a process explanatory diagram schematically showing how the crowning portion is superfinished (part 1). FIG. 8 is an explanatory diagram showing how the grinding wheel shape of the first grinding wheel imitates the crowning portion in the case of the superfinishing shown in FIG. 7. FIG. 9 is a process explanatory diagram schematically showing how the crowning portion is superfinished (part 2). FIG. 10 is a schematic configuration diagram of a grinding wheel holder equipped with a swing mechanism. FIG. 11 is a process explanatory diagram schematically showing how the central portion is superfinished (part 1). Fig. 12 is a process explanatory diagram that schematically shows how the central portion is superfinished (part 2). Fig. 13 is a schematic configuration diagram of a grinding wheel holder equipped with a swing mechanism. Fig. 14 is a process explanatory diagram that schematically shows how the inner ring or outer ring, which is the raceway ring of a cylindrical roller, is superfinished. Fig. 15 is a process explanatory diagram that schematically shows how the inner ring or outer ring, which is the raceway ring of a cylindrical roller, is superfinished. Fig. 16 is a process explanatory diagram that schematically shows how the inner ring raceway surface of the inner ring is superfinished. Fig. 17 is a schematic cross-sectional view of a motor.

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In one embodiment, the roller bearing is a cylindrical roller bearing having cylindrical rollers. The type of roller bearing is not limited to this. In other embodiments, the roller bearing may be of another type, such as a needle roller bearing, a tapered roller bearing, or a spherical roller bearing, and may be either a radial type or a thrust type.

[0016] <Roller bearing> Figure 1 is a cross-sectional view of a main portion of a cylindrical roller bearing 11. In one embodiment, the cylindrical roller bearing 11 comprises an inner ring 13 having an inner ring raceway surface 13a on its outer peripheral surface, an outer ring 15 having an outer ring raceway surface 15a on its inner peripheral surface, a plurality of cylindrical rollers (rolling elements) 17 arranged to roll freely between the inner ring raceway surface 13a and the outer ring raceway surface 15a, and a cage 19 that holds the plurality of cylindrical rollers 17 at approximately equal intervals in the circumferential direction. An inner ring rib 21 is provided at one end of the inner ring 13 in the axial direction. A pair of outer ring ribs 23a, 23b are provided at both ends of the outer ring 15 in the axial direction. A relief groove 13b is formed circumferentially between the inner ring raceway surface 13a and the inner ring rib 21. A relief groove 15b is formed in the circumferential direction between the outer ring raceway surface 15a and the outer ring flange portion 21a, and between the outer ring raceway surface 15a and the outer ring flange portion 21b.

[0017] 2 is a partial side view of the cylindrical roller 17. In one embodiment, the cylindrical roller 17 has a central portion 27 located near the center in the axial direction and end portions (crowning portions, partial crowning portions, crown portions) 25 located near the ends in the axial direction. The central portion 27 has a circumferential surface having a linear profile extending at least in the axial direction. The end portions 25 have circumferential surfaces having a crown profile (partial crown profile) that transitions from the linear profile of the central portion 27. The circumferential surface of the central portion 27 has a major linear profile extending at least in the axial direction, and the circumferential surfaces of the end portions 25 have inclined profiles that are inclined relative to the major linear profile. The inclined profile includes a curved profile and / or a linear profile. In the cylindrical roller 17, the circumferential surface 17a of the central portion 27 is formed along the axial center of the roller shaft, which is the rotation axis of the cylindrical roller 17. In one example, the peripheral surface of the end portion 25 includes a pair of first crowning surfaces (first crown surfaces, first partial crown surfaces) 17b and a pair of second crowning surfaces (second crown surfaces, second partial crown surfaces) 17c. The first crowning surfaces 17b are formed from the axially outer end of the peripheral surface 17a toward both axially outer sides. The second crowning surfaces 17c are formed from the axially outer ends of the first crowning surfaces 17b toward the roller axially outer sides, respectively. In this example, the cylindrical roller 17 has a compound crown profile (compound crowning shape) in which a plurality of crown profiles with different curvatures and / or profiles are arranged axially and / or combined. For example, the peripheral surface of the end portion 25 has a compound crowning shape in which crowning surfaces 17b, 17c with a plurality of radii of curvature are formed on both sides of the peripheral surface 17a of the central portion 27. If necessary, chamfered portions 17d may be formed on both axial edges of the cylindrical roller 17. The boundary portion (transition region) between the peripheral surface 17a of the cylindrical roller 17 and the first crowning surface 17b can be machined into a smooth, continuous curved surface (transition surface).

[0018] 2 is shown with an exaggerated curvature compared to the actual curvature, and in the drawings used in the following description, the shape of the crowning is also shown with an exaggerated curvature. In the following description, the axial direction of the roller (the direction along the central axis, the roller axial direction, the rotational axis direction) is also referred to as the "axial direction."

[0019] In one example, the crowning shape (crown profile) may have a logarithmic crowning shape (a shape in which the crown profile follows a logarithmic curvature or profile). For example, in the above-described compound crowning shape, the radius of curvature R1 of the first crowning surface 17b along the axial direction is set to be larger than the radius of curvature R2 of the second crowning surface 17c along the axial direction so as to approximate the logarithmic crowning shape. Furthermore, the center position P1 of the radius of curvature R1 of the first crowning surface 17b and the center position P2 of the radius of curvature R2 of the second crowning surface 17c may be set so that tangents along the axial direction at the boundary between the first crowning surface 17b and the second crowning surface 17c coincide with each other. For example, as shown in FIG. 2 , the center position P1 of the radius of curvature R1 of the first crowning surface 17b is located on an axially perpendicular line Lp passing through the center P0 in the axial and radial directions of the cylindrical roller 17. The center position P2 of the radius of curvature R2 of the second crowning surface 17c may be located on a line connecting the center position P1 of the radius of curvature R1 of the first crowning surface 17b and the boundary point (intersection point) P3 between the first crowning surface 17b and the second crowning surface 17c.

[0020] In one example, the cylindrical roller 17 has a peripheral surface 17a, a first crowning surface 17b, and a second crowning surface 17c, and the radii of curvature of these crowning surfaces change in two stages. In this case, the surface shape can be made closer to a logarithmic crowning shape. As a result, the rolling contact function (high load-bearing capacity) as a rolling element is improved. Note that while the above example shows a two-stage change, a configuration in which the radii change in three or more stages or a configuration in which the radii change continuously may also be used. Furthermore, the first crowning surface 17b and the second crowning surface 17c may have a logarithmic crowning shape in which the rolling surface of the axial cross-sectional shape of the cylindrical roller 17 is expressed by a continuous logarithmic function. Note that the logarithmic crowning shape and the compound crowning shape referred to here are not particularly limited. For example, the ratio D / L of the drop amount D at the roller effective length end of the cylindrical roller 17 to the axial length L of the crowning shaped portion (crowning portion) is classified as follows: if the drop amount D is relatively small, it is 0.001 or more and 0.002 or less; if the drop amount D is relatively large, it is 0.005 or more; and if the drop amount D is somewhere between the above, it is 0.002 or more and 0.005 or less. The above numerical values ​​are merely examples, and the invention is not limited to these.

[0021] In the cylindrical roller bearing 11, the inner ring raceway surface 13a and / or the outer ring raceway surface 15a may have a full crowning shape (full crown profile) or a partial crowning shape (partial crown profile). In one example, the full crowning shape has a shape in which the axial cross section has an overall gentle arc (crown profile), a cross-sectional shape having a shape in which a plurality of different arcs are combined, or a cross-sectional shape that does not substantially include a straight shape. In one example, the partial crowning shape has a shape in which a linear shape (linear profile) and a circular arc shape (crown profile) are combined. In the following description, the first crowning surface 17b and the second crowning surface 17c are collectively referred to as the crowning portion.

[0022] <Outline of Superfinishing Procedure> Next, we will explain the procedure for superfinishing the circumferential surfaces (rolling surfaces) of the rollers of cylindrical roller bearing 11, and the procedure for superfinishing the circumferential surfaces (raceway surfaces) of the raceways provided in cylindrical roller bearing 11. First, we will explain the procedure for superfinishing the rolling surfaces of cylindrical rollers 17.

[0023] FIG. 3 is a process explanatory diagram that schematically shows the procedure for superfinishing the rolling surface of the cylindrical roller 17. FIG. 3 shows the state after a crowning shape has been formed on the cylindrical roller 17. The cylindrical roller 17 has a central portion (flat portion) 27 located near the center in the axial direction, and end portions (crowning portions, partial crowning portions) 25 located near the ends in the axial direction. The central portion 27 has a peripheral surface that has a linear profile that extends at least in the axial direction. The end portions 25 have a peripheral surface that has a crown profile (partial crown profile) that transitions from the linear profile of the central portion 27. The end portions 25 are formed at both axial ends of the cylindrical roller 17 (rolling surface (outer peripheral surface)). The central portion 27 is located in the axial center of the rolling surface, and both ends are connected to the pair of end portions 25. A cross section of the central portion 27 along the axial direction has a linear profile that extends at least in the axial direction.

[0024] The end portion 25 and central portion 27 are superfinished using a first grinding stone 31 and a second grinding stone 33, which are prepared separately. The superfinishing process includes superfinishing the end portion 25 with the first grinding stone 31 while rotating the cylindrical roller 17, and superfinishing the central portion 27 with a second grinding stone 33 prepared separately from the first grinding stone 31 while rotating the cylindrical roller 17. In general, the end portion 25 is superfinished with the first grinding stone 31 while the cylindrical roller 17 is driven to rotate about the axis of the rolling surface, and then the central portion 27 is superfinished with the second grinding stone 33 which is different from the first grinding stone 31.

[0025] The first grinding stone 31 is pressed against the surfaces of both axial ends of the cylindrical roller 17. The superfinishing process includes pressing the first grinding stone 31 against the end (crowning portion) 25 in a direction (pressing direction) perpendicular to the axial direction of the cylindrical roller 17. The contact portion (contact surface) 31a of the first grinding stone 31 contacts the end 25 of the cylindrical roller 17. The contact portion 31a can have an inclined profile that is inclined with respect to the pressing direction. At least a portion of the inclined profile (concave profile) of the first grinding stone 31 can include one formed by wear. The first grinding stone 31 is arranged so that at least a portion of the contact portion (contact surface) 31a having the inclined profile intersects the axial direction. The inclined profile is a profile shown in a cross section taken along a plane including the axial direction and pressing direction of the cylindrical roller 17, and has an inclination with respect to the axial direction of the cylindrical roller 17. The inclined profile has an inclination that gradually extends forward in the pressing direction from the inner side to the outer side of the cylindrical roller 17 in the axial direction. In one example, the inclination profile of the contact portion 31 a has a concave profile. For example, the concave profile of the contact portion 31 a at least partially corresponds to the crown profile of the end portion 25. In one example, the end portion 25 of the cylindrical roller 17 includes one end portion (first end portion) 25 and the other end portion (second end portion) 25 that are spaced apart from each other. The superfinishing process includes machining the first end portion 25 and the second end portion 25 at different times. Alternatively, the superfinishing process includes machining the first end portion 25 and the second end portion 25 substantially simultaneously. For example, the first grinding stone 31 may include two grinding stones 31, 31 that are spaced apart from each other. The orientation of the inclination profile (concave profile) of the contact portion 31 a pressed against the first end portion 25 is different from the orientation of the inclination profile (concave profile) of the contact portion 31 a pressed against the second end portion 25. The two first grinding wheels 31, 31 can be arranged so that at least a portion of the contact portion 31 a (the inclined profile of the contact portion 31 a) faces each other. At least a portion of the contact portion (contact surface) 31 a is arranged so as to face axially inward of the cylindrical roller 17. In superfinishing of the end portion 25, a slight vibration in the axial direction (arrow S) is applied to the first grinding wheel 31.In one example, when the grinding wheel width W1 of the first grinding wheel 31 is shorter than the axial width Lc of the crowning portion 25, the entire width of the end portion 25 is machined by traversing the first grinding wheel 31 in the axial direction. When the first grinding wheel 31 has a shank width smaller than the shank width (axial length) of the end portion 25, the superfinishing process includes slightly oscillating the first grinding wheel 31 along the axial direction and traversing the first grinding wheel 31 along the axial direction. When the first grinding wheel 31 has a shank width larger than the shank width (axial length) of the end portion 25, the superfinishing process includes slightly oscillating the first grinding wheel 31 along the axial direction.

[0026] The second grinding wheel 33 is pressed against the surface of the axial center of the cylindrical roller 17, and micro-vibrations (arrow S) are applied in the axial direction to superfinish the central portion 27. The superfinishing process involves pressing the second grinding wheel 33 against the central portion 27 in a direction perpendicular to the axial direction of the cylindrical roller 17. In one example, when the grinding wheel width W2 of the second grinding wheel 33 is shorter than the axial width Lf of the central portion 27, the second grinding wheel 33 is made to traverse in the axial direction (arrow T) to process the entire width of the central portion 27. The grinding wheel widths W1 and W2 referred to here refer to the axial width of the workpiece, which is the cylindrical roller 17, that is ground by the first grinding wheel 31 and the second grinding wheel 33.

[0027] In the superfinishing method, the crowning portion 25 and the central portion 27 are superfinished using separate grinding wheels. This method requires time for the grinding wheel shape to conform to the shape of the crowning portion 25, particularly in the crowning portion 25. However, by superfinishing with a grinding wheel specifically designed for the crowning portion 25, the processing time can be significantly reduced. In other words, when the crowning portion 25 and the central portion 27 are superfinished using a common grinding wheel, the grinding wheel shape must be sequentially tailored to suit the crowning portion 25 and the central portion 27, respectively. However, the difference in shape between the two portions is large, and it takes a long time for the grinding wheel shape to conform to each. In this case, the grinding wheel wears unevenly, inevitably shortening the life of the grinding wheel. Furthermore, the longer processing time makes the grinding wheel more susceptible to clogging by shavings and the like.

[0028] On the other hand, by machining the crowning portion 25 and the central portion 27 separately, the first grinding wheel 31 that machines the crowning portion 25 can start machining the next workpiece (cylindrical roller) while maintaining the grinding wheel shape that follows the shape of the crowning portion 25 through superfinishing. In this case, the grinding wheel shape of the first grinding wheel 31 already matches the shape of the crowning portion 25, which is the target shape of the next workpiece. Therefore, machining of the next workpiece into the shape of the crowning portion 25 can be performed smoothly. In this case, uneven wear of the grinding wheel is suppressed. Furthermore, the time required for one grinding wheel to traverse between the crowning portion 25 and the central portion 27 can be reduced, thereby shortening the superfinishing time for the crowning portion 25.

[0029] <Superfinishing Apparatus> Next, an example of the configuration of a superfinishing apparatus that carries out the steps of the superfinishing method described above will be described. Various configurations can be adopted for the superfinishing apparatus depending on the shape, material, size, etc. of the workpiece. The apparatus configuration shown here is merely an example, and can be modified as appropriate depending on the workpiece and its processing conditions, etc.

[0030] 4 is a schematic diagram showing the main components of the superfinishing apparatus 100. The superfinishing apparatus 100 includes a rotation drive unit (drive unit) 37 having a pair of rollers 35, 35 that rotate a workpiece (cylindrical roller) W around the axis of the rolling surface, a pair of first grinding stones 31, 31, a second grinding stone 33 prepared separately from the first grinding stones 31, 31, and mechanisms 39, 41 that press the first grinding stone 31 and the second grinding stone 33 against the workpiece W. The mechanisms 39, 41 include a first mode in which the end portion of the workpiece W is superfinished by the first grinding stones 31, 31, and a second mode in which the center portion of the workpiece W is superfinished by the second grinding stone 33. The mechanisms 39, 41 include a first mechanism (crowning finishing unit) 39 and a second mechanism (center finishing unit) 41. The crowning finishing unit 39 uses a pair of first grinding wheels 31, 31 to superfinish the crowned portions at both axial ends of the workpiece W. The center finishing unit 41 uses a second grinding wheel 33 to superfinish the center of the workpiece W's rotation axis. The grain sizes of the first grinding wheels 31, 31 and the second grinding wheel 33 are set to a target roughness depending on various conditions, since a smaller roughness extends the bearing life, while a larger roughness increases productivity. The crowning finishing unit 39 and the center finishing unit 41 are movably supported, for example, along a rail 43 arranged parallel to the rollers 35, 35. This allows one of them to move to the position of the workpiece W and the other to move to a retracted position, allowing the crowning finishing unit 39 and the center finishing unit 41 to perform processing sequentially. Alternatively, the crowning finishing unit 39 and the center finishing unit 41 may be fixed, while the workpiece W is movable. In FIG. 4, the contact surfaces of the grinding wheels 31 and 33 have curved surfaces that conform to the circumferential surface of the workpiece W, but this is not necessarily limited to this.

[0031] 5 is a schematic diagram illustrating the configuration of the crowning finishing unit 39. The pair of first grinding wheels 31, 31 are fixed to a grinding wheel holder 45. The grinding wheel holder 45 is supported by a slide block 47 and is movable in a feed direction Df toward the workpiece W by a feed drive unit 49 fixed to the slide block 47. The slide block 47 is supported by a base 53 so as to be movable in the axial direction of the workpiece W. A vibration is applied to the slide block 47 in the axial direction by a vibration unit 51 fixed to the base 53, causing the pair of first grinding wheels 31, 31 to vibrate slightly in the axial direction (arrow S). The base 53 is capable of traversing (arrow T) along a rail 43 by a drive source (not shown).

[0032] In other words, the grinding wheel holder 45 and the feed drive unit 49 function as a first pressure mechanism that pressurizes the first grinding wheels 31, 31 toward the workpiece, and the slide block 47 and the vibration unit 51 function as a first grinding wheel micro-vibration mechanism that micro-vibrates the first grinding wheels 31, 31 in the axial direction.

[0033] 6 is a schematic diagram showing the configuration of the center finishing unit 41. Similar to the crowning finishing unit 39, the center finishing unit 41 includes a grinding wheel holder 55 for fixing the second grinding wheel 33, a slide block 57, a feed drive unit 59, a vibration unit 61, and a base 63. This configuration enables the second grinding wheel 33 to be fed in the feed direction Df, to vibrate slightly as indicated by the arrow S, and to perform a traverse motion as indicated by the arrow T.

[0034] Similarly, the grinding wheel holder 55 and the feed drive unit 59 function as a second pressure mechanism that pressurizes the second grinding wheel 33 toward the workpiece, and the slide block 57 and the vibration unit 61 function as a second grinding wheel micro-vibration mechanism that micro-vibrates the second grinding wheel 33 in the axial direction.

[0035] A mechanism for traversing the base 53 along the rails 43 by a drive source (not shown) functions as a first grindstone moving mechanism. A mechanism for traversing the base 63 along the rails 43 functions as a second grindstone moving mechanism. The crowning finishing unit 39 and the central finishing unit 41 are fixed. When the workpiece moves, the mechanism for moving the workpiece functions as the first grindstone moving mechanism and the second grindstone moving mechanism.

[0036] The drive mechanisms (drive sources) for the feed drive units 49, 59, the vibration units 51, 61, etc. can be well-known mechanisms such as ball screw mechanisms, electromagnetic or hydraulic actuators, air cylinders, etc., but the operating mechanisms (drive sources) for each unit are not particularly limited.

[0037] <Superfinishing of Crowning Portion> Figure 7 is a process explanatory diagram schematically illustrating the superfinishing of the crowning portion 25 (part 1). In the example shown in Figure 7, the first grinding stones 31, 31 each have a grinding stone width W1 that is equal to or greater than the axial width Lc of the crowning portion 25 (Lc≦W1). Due to the difference between the grinding stone width W1 and the axial width Lc of the crowning portion 25, the first grinding stones 31, 31 are positioned so that they extend to the inside toward the center portion 27 and the outside opposite the center portion 27. In this case, while the cylindrical roller 17 is rotated about its axis, the first grinding stones 31, 31 are pressed against the crowning portion 25 of the cylindrical roller 17 with a predetermined load P. At the same time, the position of the grinding stone holder 45 (crowning finishing portion 39) of the first grinding stones 31, 31 is stopped, and the first grinding stone micro-vibration mechanism micro-vibrates the first grinding stones 31 in the axial direction (arrow S).

[0038] 8 is an explanatory diagram showing how the grinding wheel shape of the first grinding wheel 31 follows the crowning portion 25 in the case of the superfinishing shown in FIG. 7. In this case, the grinding wheel width W1 of the first grinding wheel 31 is wider than the axial width Lc of the crowning portion 23, so the crowning portion 25 fits within the grinding wheel width W1, and axial traverse operation is unnecessary or can be reduced. In this way, the crowning portion 25 is superfinished by the rotation of the cylindrical rollers 17, the pressure from the first grinding wheel 31, and the slight vibration of the first grinding wheel 31.

[0039] In this superfinishing process, the grinding wheel holder 45 that holds the pair of first grinding wheels 31 and the vibration unit 51 are integrated, and the first grinding wheels 31 vibrate slightly without tilting in the axial direction. Therefore, the posture of the first grinding wheels 31 (grinding wheel posture) is maintained constant during processing, and uneven wear of the grinding wheels is suppressed.

[0040] 9 is a process explanatory diagram that schematically shows how the crowning portion 25 is superfinished (part 2). In the example shown in FIG. 9, the first grinding stones 31, 31 each have a grinding stone width W1 that is narrower than the axial width Lc of the crowning portion 25 (Lc>W1). In this case, while the cylindrical roller 17 is rotated about its axis, the first grinding stones 31, 31 are pressed against the crowning portion 25 of the cylindrical roller 17 with a predetermined load P. At the same time, the first grinding stones 31, 31 are traversed in the axial direction by the first grinding stone moving mechanism, and are slightly vibrated in the axial direction (arrow S) by the first grinding stone micro-vibration mechanism.

[0041] In this superfinishing process, the grinding wheel holder 45 holding the pair of first grinding wheels 31 is integrated with the vibration unit 51, and the first grinding wheels 31 vibrate slightly without tilting in the axial direction. Therefore, the attitude (grinding wheel attitude) of the first grinding wheels 31 is maintained constant during processing, suppressing excessive uneven wear of the grinding wheels. Furthermore, processing involving a traverse motion increases the area where the grinding wheels act on a single point on the surface of the crowning portion 25, changing axially rather than in a constant position, resulting in a smoother, more continuous machined surface. In this case, the grinding wheel surface wears in accordance with the surface shape of the crowning portion 25, resulting in the desired crowning shape.

[0042] 10 is a schematic diagram of a grindstone holder 45A equipped with a swing mechanism. The grindstone holder 45A is equipped with a swing mechanism that swings (arrow R) the direction in which the first grindstones 31, 31 pressurize the cylindrical rollers 17 along the axial direction of the cylindrical rollers 17. This swing mechanism changes the attitude of the first grindstones 31, 31 so that, in an axial cross section passing through the rotation axis of the cylindrical rollers 17, the roller outer peripheral surfaces are pressed from a direction inclined at a predetermined angle from the normal direction to the roller outer peripheral surfaces.

[0043] The swing mechanism can be configured to include, for example, a grinding wheel gripping portion 65 that grips the first grinding wheels 31, 31, a support portion 67, and a pair of compression springs 69, 69. The support portion 67 has a pivot Pt provided at the midpoint between the arrangement position of one first grinding wheel 31 and the arrangement position of the other first grinding wheel 31, and supports the grinding wheel gripping portion 65 around the pivot Pt. The pair of compression springs 69, 69 are provided between the grinding wheel gripping portion 65 and the support portion 67, and urge the grinding wheel gripping portion 65 to the neutral position of the swing stroke.

[0044] If the grinding wheel holder 45A equipped with the above-described swing mechanism is provided instead of the grinding wheel holder 45 shown in Figure 7, the grinding wheel holder 45 swings even if the machining position of the first grinding wheel 31 changes. The direction in which the grinding wheels 31 press against the roller outer peripheral surface approaches the normal direction of the roller outer peripheral surface, thereby minimizing the change in the shape required of the grinding wheel. As a result, when superfinishing the crowning portion 25, the occurrence of insufficient machining due to insufficient contact with the grinding wheel in localized areas is prevented. In other words, because the grinding wheel position can be freely changed depending on the machining situation, the grinding wheel can more reliably and evenly contact the entire crowning portion 25, resulting in a more continuous machined surface.

[0045] Furthermore, if a grindstone holder 45A equipped with the above-described swing mechanism is provided instead of the grindstone holder 45 shown in FIG. 9, the grindstone posture can be optimized as the first grindstones 31, 31 traverse.

[0046] <Superfinishing of Center Portion> Figure 11 is a process explanatory diagram schematically illustrating the superfinishing of the center portion 27 (part 1). In the example shown in Figure 11, the second grinding stone 33 has a grinding stone width W2 that is equal to or greater than the axial width Lf of the center portion 27 (Lf ≤ W2). The second grinding stone 33 is positioned so that it extends beyond the crowning portions 25 at both ends due to the difference between the grinding stone width W2 and the axial width Lf of the center portion 27. In this case, while the cylindrical roller 17 is rotated about its axis, the second grinding stone 33 is pressed against the center portion 27 of the cylindrical roller 17 with a predetermined load P. At the same time, the second grinding stone 33 is stopped at the position of the grinding stone holder 55 (center portion finishing portion 41), and is micro-vibrated in the axial direction (arrow S) by the second grinding stone micro-vibration mechanism.

[0047] In this case, the grinding wheel width W2 of the second grinding wheel 33 is wider than the axial width Lf of the central portion 27, so the central portion 27 fits within the grinding wheel width W2, making the axial traverse operation unnecessary or reducing it. In this way, the central portion 27 is superfinished by the rotation of the cylindrical rollers 17, the pressure from the second grinding wheel 33, and the slight vibration of the second grinding wheel 33.

[0048] In this superfinishing process, the grinding wheel holder 55 that holds the second grinding wheel 33 and the vibration unit 61 are integrated, and the second grinding wheel 33 vibrates slightly without tilting in the axial direction. Therefore, the posture of the second grinding wheel 33 (grinding wheel posture) is maintained constant during processing, and uneven wear of the grinding wheel is suppressed.

[0049] Figure 12 is a process explanatory diagram that schematically shows how the central portion 27 is superfinished (part 2). In the example shown in Figure 12, the second grinding stone 33 has a grinding stone width W2 that is narrower than the axial width Lf of the central portion 27 (Lf > W2). In this case, while the cylindrical roller 17 is rotated about its axis, the second grinding stone 33 is pressed against the central portion 27 of the cylindrical roller 17 with a predetermined load P. At the same time, the second grinding stone 33 is traversed in the axial direction by the second grinding stone moving mechanism described above, and is slightly vibrated in the axial direction (arrow S) by the second grinding stone micro-vibration mechanism.

[0050] In this superfinishing process, the grinding wheel holder 55 that holds the second grinding wheel 33 and the vibration unit 61 work together to vibrate the second grinding wheel 33 slightly without tilting it in the axial direction. This allows the attitude of the second grinding wheel 33 (grinding wheel attitude) to be maintained constant during processing, suppressing uneven wear of the grinding wheel. Furthermore, processing involving a traverse motion means that the location of the grinding wheel acting on a single point on the surface of the central portion 27 is not constant, but the area over which it changes in the axial direction increases, resulting in a smoother, more continuous machined surface.

[0051] 13 is a schematic diagram of a grindstone holder 55A equipped with a swing mechanism. The grindstone holder 55A is equipped with a swing mechanism that swings (arrow R) the direction in which the second grindstone 33 applies pressure to the cylindrical rollers 17 along the axial direction of the cylindrical rollers 17. This swing mechanism changes the attitude of the second grindstone 33 so that, in an axial cross section passing through the rotation axis of the cylindrical rollers 17, the second grindstone 33 applies pressure to the outer peripheral surface of the rollers from a direction inclined at a predetermined angle from the normal direction to the outer peripheral surface of the rollers.

[0052] The swing mechanism may have the same configuration as that of the swing mechanism shown in FIG. 10, except that a second grinding stone 33 is provided instead of the pair of first grinding stones 31, 31.

[0053] 12, if a grinding wheel holder 55A equipped with the above-described swing mechanism is provided, it is possible to reduce the change in the shape required of the grinding wheel even when the machining point of the second grinding wheel 33 changes. As a result, when superfinishing the central portion 27, the grinding wheel attitude can be freely changed depending on the machining conditions, so that the grinding wheel comes into contact with the entire central portion 27 more evenly, resulting in a more continuous machined surface.

[0054] Furthermore, if a grindstone holder 55A equipped with the above-described swing mechanism is provided instead of the grindstone holder 45 shown in FIG. 13, the grindstone posture can be optimized as the second grindstone 33 traverses.

[0055] <Superfinishing of raceway surfaces> The superfinishing described above is directed to the rolling surfaces of the cylindrical rollers 17, but superfinishing can also be performed on the inner ring raceway surface 13 a and the outer ring raceway surface 15 a of the cylindrical roller bearing 11 shown in FIG. 1 in the same way.

[0056] 14 and 15 are process diagrams schematically illustrating how the inner ring 13 or the outer ring 15, which is a raceway of a cylindrical roller, is superfinished. When superfinishing the raceway, the raceway is rotated via a cylindrical backing plate 71 connected to a rotational drive source such as a motor (not shown). That is, as shown in FIG. 14 , one end face of the raceway is abutted against the annular shaft end 71 a of the backing plate 71, and the raceway is pressed against the backing plate 71. This transmits the rotational drive force from the backing plate 71 to the raceway. The raceway may be pressed against the other end face of the raceway by pressing the circumferential surfaces of multiple pressure rolls 73 (two in FIG. 15 as an example) against the other end face of the raceway, for example, as shown in FIG. 15 . In this case, the pressure roll 73 is pressed against the other end face of the raceway by a biasing mechanism (not shown), and rotates in response to the rotation of the backing plate 71 and the raceway. In this way, the bearing ring is rotatable integrally with the backing plate 71 .

[0057] FIG. 16 is a process diagram illustrating the superfinishing of the inner ring raceway surface 13a of the inner ring 13. The first grinding stone 31 provided in the crowning finishing portion 39 is pressed against the outer peripheral surface of the inner ring 13, which is fixed to the backing plate 71, from the radially outer side toward the inner side with a predetermined load, while the inner ring 13 is rotated. As with the cylindrical rollers 17 described above, the first grinding stone 31 is slightly vibrated in the inner ring axial direction. Furthermore, the first grinding stone 31 is selectively traversed in the inner ring axial direction depending on the axial width of the crowning portion and the grinding stone width of the first grinding stone 31. This completes the superfinishing of the crowning portion. The superfinishing of the central portion is performed using the second grinding stone 33 from the radially outer side of the inner ring 13, as with the cylindrical rollers 17 described above.

[0058] Although not shown in the drawings, superfinishing of the outer ring raceway surface 15a of the outer ring 15 can be performed in the same manner as described above. For example, the first grinding stone 31 and the second grinding stone 33 are pressed against the inner peripheral surface of the inner ring 13 from the inside to the outside in the radial direction. In addition, while the outer ring 15 is rotationally driven, micro-vibration in the outer ring axial direction, or micro-vibration in the outer ring axial direction and traverse motion are performed.

[0059] In the superfinishing of the crowning portion 25 and the central portion 27 in each of the examples described above, it is preferable to overlap the respective processing ranges. In other words, the grinding wheel width or traverse range is set so that the respective processing ranges of the first grinding wheel 31 and the second grinding wheel 33 overlap. This prevents insufficient processing at the joints between the respective processing ranges, and obtains continuous surface roughness along the axial direction of the cylindrical roller and the width direction of the raceway.

[0060] Furthermore, the above-mentioned superfinishing processes are particularly suitable for machining surfaces whose generatrix shape is greatly curved, such as a compound crowning shape made up of arcs with a small radius of curvature, or a logarithmic crowning shape, on the end of the rolling surface of the cylindrical roller 17 and the raceway surfaces of the inner ring 13 and outer ring 15. Even when the machined surface shape as described above varies greatly from place to place, it is possible to efficiently machine the machined surface to a good, continuous surface roughness in a short time while suppressing a decrease in the life of the grinding wheel due to uneven wear of the grinding wheel.

[0061] Up until now, it has been common to perform processing by traversing one grinding wheel between the crowning portion 25 and the central portion 27, but the time required for this processing can be shortened or eliminated by using two grinding wheels. This shortens the processing cycle time and is expected to significantly improve productivity.

[0062] Furthermore, because the central portion 27 of the rolling surface of the cylindrical roller 17 comes into contact with the raceway surface of the inner ring 13 or the outer ring 15, it is expected that the bearing life will be extended by reducing the surface roughness of the central portion 27. Furthermore, in this superfinishing method, different grinding stones can be used to process the crowning portion 25 and the central portion 27, so that the type of grinding stone can be selected according to the target roughness for each portion, thereby making it possible to superfinish each portion under optimal conditions.

[0063] In one embodiment, the machine comprises the above-mentioned bearing, which is advantageous for reducing the cost of the bearing.

[0064] In one embodiment, a vehicle includes the above-described bearing, which is advantageous in reducing the cost of the bearing.

[0065] The bearing can be applied to, for example, bearings 900A and 900B that support a rotating shaft 963 of a motor 961 shown in FIG.

[0066] 17, motor 961 is a brushless motor that has a cylindrical center housing 965 and a substantially disk-shaped front housing 967 that closes one open end of the center housing 965. A rotatable rotating shaft 963 is supported inside the center housing 965 along its axis via bearings 900A, 900B that are located at the bottom of the front housing 967 and the center housing 965. A rotor 969 for driving the motor is provided around the rotating shaft 963, and a stator 971 is fixed to the inner circumferential surface of the center housing 965.

[0067] The motor 961 is generally mounted on a machine or vehicle, and rotates a rotary shaft 963 supported by bearings 900A and 900B.

[0068] The bearing can be applied to machines with rotating parts and various manufacturing equipment. The bearing can also be applied to machines equipped with bearings (including manually powered machines) or vehicles. Examples of machines include hydroelectric, thermal, nuclear, and wind power generation facilities (applicable to bearings supporting the main shaft or rotating shaft of generators), as well as bearings used in rotating parts of ball screw devices, screw devices, devices combining linear guide bearings with ball screws, actuators such as XY tables, various industrial machines such as machine tools, home appliances, and household appliances. Examples of vehicles include bearings used in rotating parts of automobiles, motorcycles, railway vehicles, and special vehicles. The bearing can also be applied to bearings used in rotating parts of steering devices such as steering columns, universal joints, intermediate gears, rack and pinions, electric power steering devices, worm reducers, and torque sensors, as well as vehicles equipped with such devices. The resulting machines, vehicles, and the like can be configured at lower cost and with higher quality than conventional models.

[0069] The above example is just one example, and as an application example of a bearing, the bearing of this configuration can be suitably applied to any location where there is relative rotation, which can lead to improved product quality and reduced costs.

[0070] The technical scope of the present invention is not limited to the scope of the embodiments. Various modifications or improvements can be made to the embodiments. Forms incorporating such modifications or improvements can also be included in the technical scope of the present invention. Furthermore, the present invention is not limited to the described embodiments, and any combination of these configurations may be used.

[0071] The present disclosure includes the following configurations and / or combinations.

[0072] (A1) A method for superfinishing a roller bearing component, the component having a central portion having a circumferential surface with a linear profile extending at least in the axial direction, and end portions having circumferential surfaces with crown profiles transitioning from the linear profile, the method comprising: superfinishing the end portions with a first grinding stone while rotating the component, and superfinishing the central portion with a second grinding stone prepared separately from the first grinding stone while rotating the component. (A2) The superfinishing method according to (A1), wherein the first grinding stone has an axial width larger than the axial width of the end portions, and the superfinishing comprises micro-vibrating the first grinding stone along the axial direction. (A3) The superfinishing method according to (A1), wherein the first grinding stone has an axial width smaller than the axial width of the end portion, and wherein the superfinishing includes micro-vibrating the first grinding stone along the axial direction and traversing the first grinding stone along the axial direction. (A4) The superfinishing method according to any one of (A1) to (A3), wherein the superfinishing includes pressing the first grinding stone against the end portion in a direction perpendicular to the axial direction of the part. (A5) The superfinishing method according to any one of (A1) to (A4), wherein the contact portion of the first grinding stone has a concave profile that is inclined with respect to the pressing direction in which the first grinding stone is pressed against the end portion. (A6) The superfinishing method according to (A5), wherein at least a portion of the concave profile of the first grinding stone is formed by wear. (A7) The superfinishing method according to any one of (A1) to (A6), wherein the end includes a first end and a second end that are spaced apart from each other, and the superfinishing includes processing the first end and the second end substantially simultaneously. (A8) A method for manufacturing a roller bearing, in which a roller bearing is manufactured using the superfinishing method according to any one of (A1) to (A7). (A9) A method for manufacturing a vehicle, comprising: manufacturing a roller bearing using the manufacturing method according to (A8), and assembling a vehicle using the roller bearing.(A10) A method for manufacturing a machine, comprising manufacturing a roller bearing using the manufacturing method described in (A8), and assembling a machine using the roller bearing. (A11) A superfinishing apparatus for superfinishing a roller bearing component, wherein the component has a central portion having a circumferential surface with a linear profile extending at least in the axial direction, and an end portion having a circumferential surface with a crown profile that transitions from the linear profile, the apparatus comprising: a drive unit that rotates the component, a first grinding stone, a second grinding stone prepared separately from the first grinding stone, and a mechanism that presses the first grinding stone and the second grinding stone against the component, the mechanism including a first mode in which the end portion is superfinished with the first grinding stone, and a second mode in which the central portion is superfinished with the second grinding stone.

[0073] (B1) A superfinishing method for superfinishing crowning portions formed at both ends of the rolling surfaces of rollers included in a roller bearing or raceway surfaces of raceways included in said roller bearing in the direction of the rotational axis, and a central portion connected to the crowning portions at the center of the surface in the direction of the rotational axis and having a linear cross section along the axial direction, while rotating the surface about the axis of the rolling surface or the raceway surface, superfinishing the crowning portions with a first grinding stone, and superfinishing the central portion with a second grinding stone prepared separately from the first grinding stone. (B2) The superfinishing method according to (B1), wherein the first grinding stone, having a grinding stone width equal to or greater than the axial width of the crowning portions formed on the surface, is brought into contact with the crowning portions that are rotated about the axis of rotation, and the first grinding stone is micro-vibrated in the axial direction to superfinish the crowning portions. (B3) The superfinishing method according to (B1), in which the first grinding stone, having a grinding stone width narrower than the axial width of the crowning portion formed on the surface, is brought into contact with both axial ends of the surface rotated about the rotation axis, and the first grinding stone is traversed and slightly vibrated in the axial direction, thereby wearing the grinding stone in accordance with the shape of the surface, thereby superfinishing the crowning portion. (B4) The superfinishing method according to (B1), in which the second grinding stone, having a grinding stone width equal to or greater than the axial width of the central portion formed on the surface, is brought into contact with the central portion rotated about the rotation axis, and the second grinding stone is slightly vibrated in the axial direction, thereby superfinishing the central portion. (B5) The superfinishing method according to (B1), in which the second grinding stone, having a grinding stone width narrower than the axial width of the central portion formed on the surface, is brought into contact with the central portion rotated about the rotation axis, and the second grinding stone is traversed and slightly vibrated in the axial direction, thereby superfinishing the central portion. (B6) The superfinishing method according to any one of (B1) to (B5), wherein superfinishing is performed so that a processing area by the first grindstone and a processing area by the second grindstone overlap. (B7) The superfinishing method according to any one of (B1) to (B6), wherein the crowning portion has a logarithmic crowning shape or a compound crowning shape.(B8) A superfinishing method according to any one of (B1) to (B7), wherein the roller bearing is a tapered roller bearing or a cylindrical roller bearing. (B9) A method for manufacturing a roller bearing using the superfinishing method according to any one of (B1) to (B8). (B10) A method for manufacturing a vehicle equipped with a roller bearing manufactured using the superfinishing method according to any one of (B1) to (B8). (B11) A method for manufacturing a machine equipped with a roller bearing manufactured using the superfinishing method according to any one of (B1) to (B8). (B12) A superfinishing device comprising: a first grinding stone for superfinishing the surface of either the rolling surfaces of rollers included in a roller bearing or the raceway surfaces of raceways included in the roller bearing; and a second grinding stone separate from the first grinding stone; a crowning finishing section that, while rotating the surface about the axis of the rolling surface or the raceway surface, superfinishes crowning portions formed on both ends of the surface in the direction of the rotation axis with the first grinding stone; and a central finishing section that, while rotating the surface about the axis of the rolling surface or the raceway surface, superfinishes a central portion that is formed in the center of the rotation axis of the surface and has a linear cross section along the axial direction that is connected to the crowning portions, with the second grinding stone. (B13) The superfinishing device according to (B12), wherein the first grinding stone has a grinding stone width equal to or greater than the axial width of the crowning portion formed on the surface, and the crowning finishing unit comprises: a rotation drive unit that rotates the surface about the axis of the roller if the surface is the rolling surface, or about the axis of the raceway ring if the surface is the raceway surface; a first pressure mechanism that pressurizes the first grinding stone at both axial ends of the surface; and a first grinding stone micro-vibration mechanism that micro-vibrates the first grinding stone in the axial direction.(B14) The superfinishing apparatus according to (B12), wherein the first grinding wheel has a grinding wheel width narrower than the axial width of the crowning portion formed on the surface, and the crowning finishing unit comprises: a rotation drive unit that rotates the surface about the axis of the roller if the surface is the rolling surface, or about the axis of the raceway ring if the surface is the raceway surface; a first pressure mechanism that applies pressure to both axial ends of the surface with the first grinding wheel; a first grinding wheel moving mechanism that traverses the first grinding wheel in the axial direction; and a first grinding wheel micro-vibration mechanism that micro-vibrates the first grinding wheel in the axial direction. (B15) The superfinishing apparatus according to (B12), wherein the second grinding stone has a grinding stone width equal to or greater than the axial width of the central portion formed on the surface, and the central portion finishing unit comprises: a rotation drive unit that rotates the surface around the axis of the roller if the surface is the rolling surface, or around the axis of the raceway ring if the surface is the raceway surface; a second pressure mechanism that presses the second grinding stone against the axial center of the surface; and a second grinding stone micro-vibration mechanism that micro-vibrates the second grinding stone in the axial direction. (B16) The superfinishing apparatus according to (B12), wherein the second grinding stone has a grinding stone width narrower than the axial width of the central portion formed on the surface, and the central portion finishing unit comprises: a rotation drive unit that rotates the surface about the axis of the roller if the surface is the rolling surface, or about the axis of the raceway ring if the surface is the raceway surface, a second pressure mechanism that presses the second grinding stone against the axial center of the surface, a second grinding stone moving mechanism that traverses the second grinding stone in the axial direction, and a second grinding stone micro-vibration mechanism that micro-vibrates the second grinding stone in the axial direction. (B17) The superfinishing apparatus according to (B13) or (B14), comprising an oscillation mechanism that oscillates the direction in which the first grinding stone applies pressure to the surface along the axial direction. (B18) The superfinishing apparatus according to (B15) or (B16), comprising an oscillation mechanism that oscillates the direction in which the second grinding stone applies pressure to the surface along the axial direction. (B19) The superfinishing device according to any one of (B12) to (B16), wherein the crowning portion has a logarithmic crowning shape or a compound crowning shape.

[0074] REFERENCE SIGNS LIST 11 Cylindrical roller bearing 13 Inner ring 13a Inner ring raceway surface 13b Relief groove 15 Outer ring 15a Outer ring raceway surface 15b Relief groove 17 Cylindrical roller (rolling element) 17a Circumferential surface 17b First crowning surface 17c Second crowning surface 17d Chamfered portion 19 Cage 21 Inner ring flange portion 23a, 23b Outer ring flange portion 25 End portion (crowning portion) 27 Central portion 31 First grinding stone 33 Second grinding stone 35 Roller 37 Rotation drive portion 39 Crowning finishing portion 41 Central finishing portion 43 Rail 45 Grinding stone holder 47 Slide block 49 Feed drive portion 51 Vibration portion 53 Base 55 Grinding stone holder 57 Slide block 59 Feed drive unit 61 Vibration unit 63 Base 65 Grinding wheel gripping unit 67 Support unit 69 Compression spring 71 Backing plate 100 Super-finishing device

Claims

1. A method for superfinishing a roller bearing component, wherein the component has a central portion having a peripheral surface with a linear profile extending at least in the axial direction, and end portions having peripheral surfaces with crown profiles that transition from the linear profile, the method comprising: superfinishing the end portions with a first grinding stone while rotating the component; and superfinishing the central portion with a second grinding stone that is prepared separately from the first grinding stone while rotating the component.

2. The superfinishing method according to claim 1, wherein the first grinding stone has a shaft width greater than the shaft width of the end portion, and the superfinishing process includes micro-vibrating the first grinding stone along the axial direction.

3. The superfinishing method according to claim 1, wherein the first grinding stone has an axial width smaller than that of the end portion, and the superfinishing process includes slightly vibrating the first grinding stone along the axial direction and traversing the first grinding stone along the axial direction.

4. A superfinishing method according to any one of claims 1 to 3, wherein the superfinishing includes pressing the first grinding stone against the end portion along a direction perpendicular to the axial direction of the part.

5. A superfinishing method according to any one of claims 1 to 4, wherein the contact portion of the first grinding stone has a concave profile that is inclined with respect to the pressing direction in which the first grinding stone is pressed against the end portion.

6. The superfinishing method according to claim 5, wherein at least a portion of the concave profile of the first grinding wheel is formed by wear.

7. A superfinishing method according to any one of claims 1 to 6, wherein the end portion includes a first end portion and a second end portion spaced apart from each other, and the superfinishing process includes machining the first end portion and the second end portion substantially simultaneously.

8. A method for manufacturing a roller bearing, comprising manufacturing a roller bearing using the superfinishing method according to any one of claims 1 to 7.

9. A method for manufacturing a vehicle, comprising: manufacturing a roller bearing using the manufacturing method according to claim 8; and assembling a vehicle using the roller bearing.

10. A method for manufacturing a machine, comprising: manufacturing a roller bearing using the manufacturing method according to claim 8; and assembling a machine using the roller bearing.

11. A superfinishing apparatus for superfinishing a roller bearing part, wherein the part has a central portion with a peripheral surface having a linear profile extending at least in the axial direction, and an end portion with a peripheral surface having a crown profile that transitions from the linear profile, the apparatus comprising: a drive unit that rotates the part; a first grinding stone; a second grinding stone that is prepared separately from the first grinding stone; and a mechanism that presses the first grinding stone and the second grinding stone against the part, the mechanism having a first mode in which the end portion is superfinished with the first grinding stone, and a second mode in which the central portion is superfinished with the second grinding stone.

Images