Method for manufacturing hub unit bearing

Abstract

To provide a method for manufacturing a hub unit bearing capable of reducing the number of manufacturing processes and reducing a manufacturing cost.SOLUTION: A method for manufacturing a hub unit bearing comprises: performing a finishing process by grinding using a grinding wheel in a range of a surface of a hub 3, including an axially outer inner ring raceway 8a and a flat part 11; and after the finishing process, performing a re-machining process on a range including the axially outer inner ring raceway 8a and the flat part 11 using an elastic grinding wheel 30, where an angle φ between a central axis O30 of the elastic grinding wheel 30 and the flat part 11 is greater than an angle θ between the central axis O30 of the elastic grinding wheel 30 and a central axis OH of the hub 3.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a hub unit bearing. [Background technology]

[0002] FIG. 5 shows a hub unit bearing 100, which is an example of a conventional structure.

[0003] With regard to the hub unit bearing 100, the axially outer side is the left side in Figure 5, which is the outer side in the width direction of the vehicle when assembled to the vehicle, and the axially inner side is the right side in Figure 5, which is the center side in the width direction of the vehicle when assembled to the vehicle.

[0004] The hub unit bearing 100 is used to rotatably support an automobile wheel relative to a suspension system, and includes an outer ring 101, a hub 102, a plurality of rolling elements 103a, 103b, and an outer seal ring 104.

[0005] The outer ring 101 has double-row outer ring raceways 105a and 105b on its inner circumferential surface. The outer ring 101 is fixedly coupled to the suspension device in use and does not rotate.

[0006] The hub 102 has double-row inner ring raceways 106a, 106b on its outer circumferential surface, and a rotating flange 107 that protrudes radially outward from a portion of the hub 102 located axially outward of the outer ring 101. In use, the hub 102 rotates integrally with the wheel and braking rotating member that are coupled and fixed to the rotating flange 107.

[0007] The hub 102 has a flat portion 108 provided on the axially inner surface of the radially inner end of the rotation flange 107. The flat portion 108 is used as a seal sliding surface.

[0008] The illustrated hub unit bearing 100 is for a drive wheel, and therefore the hub 102 has a spline hole 109 in the radial center for spline engagement with the drive shaft.

[0009] The hub 102 is formed by combining a hub ring 110 and an inner ring 111. The hub ring 110 has a rotation flange 107 on its axially outer side, an axially outer inner ring raceway 106a on its axially middle part of its outer peripheral surface, and a spline hole 109 in its radially central part. The hub ring 110 is provided with a flat part 108. The inner ring 111 has an axially inner inner ring raceway 106b on its outer peripheral surface, and is fitted and fixed to the inside of the hub ring 110 in its axial direction.

[0010] The rolling elements 103a, 103b are arranged between double-row outer ring raceways 105a, 105b and double-row inner ring raceways 106a, 106b, with a plurality of rolling elements arranged in each row.

[0011] The outer seal ring 104 closes the opening on the axial outside of the rolling element installation space that exists between the inner peripheral surface of the outer ring 101 and the outer peripheral surface of the hub 102. This prevents foreign matter such as muddy water from entering the rolling element installation space from the outside through the opening, and prevents lubricating grease from leaking from the rolling element installation space to the outside.

[0012] The outer seal ring 104 is supported and fixed to the axially outer end of the outer ring 101, and has a sliding lip 112 whose tip is in sliding contact with the flat surface portion .

[0013] In the hub unit bearing 100, the surface of the hub ring 110, from the outer peripheral surface of the axially inner portion where the inner ring 111 is fitted to the flat portion 108, is subjected to a finishing process that is conventionally known and is described in, for example, JP 2017-180599 A.

[0014] That is, as shown in FIGS. 6 and 7, the central axis O of the hub wheel 110 is located on the outer peripheral surface of the axially intermediate portion of the hub wheel 110. H The hub wheel 110 is radially positioned by being rotatably supported at two circumferential points located below the hub wheel 110 (in the illustrated example, at approximately 5 o'clock and approximately 9 o'clock on the clock face) by the tip of the shoe 113.

[0015] The hub wheel 110 is rotated by rotating the magnetic chuck 114 that is magnetically coupled to the axially outer surface of the rotating flange 107. M The central axis of the hub wheel 110 is O H The magnetic chuck 114 is offset by approximately 0.1 to 0.2 mm in the direction connecting the tips of the two shoes 113, and a pressing force F is applied from the magnetic chuck 114 to the hub wheel 110 in the direction toward the gap between the two shoes 113, i.e., a pressing force F against the two shoes 113.

[0016] In this state, the grinding wheel (rotary grinding wheel) 115 of the complete form, which is arranged so as to have the same center height as the hub wheel 110, is rotated along its own central axis O T While rotating the hub ring 110 in the opposite direction to the hub ring 110 around the center O, the outer peripheral surface of the grinding wheel 115 is pressed against the above-mentioned range of the surface of the hub ring 110, which is the surface to be processed, and the surface to be processed is subjected to finishing by grinding. The generatrix shape of the outer peripheral surface of the grinding wheel 115 is appropriately shaped by the diamond wheel 116 into a shape that matches the generatrix shape of the finished surface to be processed. Note that the center height of the hub ring 110 and the grinding wheel 115 is the distance from the center axis O of their rotation in FIG. 7. H , O T is the vertical position of the

[0017] When performing the above-mentioned finishing process, although the shoe 113 is made of cemented carbide to make it less susceptible to wear, wear of the shoe 113 is unavoidable during mass production of the hub ring 110, and so the center height of the hub ring 110 and the center height of the grinding wheel 115 tend to mismatch. As a result, the position of the grinding surface of the grinding wheel 115 relative to the axial inner surface of the rotating flange 107 changes in the radial direction of the hub ring 110, and logarithmic spiral grinding streaks may be formed on the flat portion 108, which is the location that forms an angle with the central axis of the hub ring 110.

[0018] When logarithmic spiral grinding marks are formed on the flat surface portion 108, the tip of the sliding lip 112 penetrates deep into the recess that forms the grinding marks, and when the hub ring 110 rotates, it is forced to move back and forth in the radial direction, causing vibration and potentially generating an abnormal noise known as seal squeal. Additionally, the sliding lip 112 may stick to the flat surface portion 108, increasing torque. Furthermore, the torque value may change depending on the direction of rotation of the hub 102.

[0019] Therefore, International Publication No. 2020 / 158161 describes a technique in which, after the above-mentioned finishing process, an elastic grinding wheel is used to re-process the flat surface and remove grinding streaks.

[0020] Elastic grinding wheels are grinding wheels in which abrasive grains are elastically supported by a porous resin-based binder, and can finish the grinding surface to a smooth surface without streaks, i.e., a surface close to a mirror finish. [Prior art documents] [Patent documents]

[0021] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-180599 [Patent Document 2] International Publication No. 2020 / 158161 Brochure Summary of the Invention [Problem to be solved by the invention]

[0022] In the prior art described in WO 2020 / 158161, after finishing by grinding with a full-form grinding wheel, two separate processes are performed: re-machining the flat surface with an elastic grinding wheel to remove grinding streaks, and super-finishing the inner ring raceway on the axially outer side. This increases the number of manufacturing processes for hub unit bearings, causing manufacturing costs to rise.

[0023] An object of the present disclosure is to provide a method for manufacturing a hub unit bearing that can reduce the number of manufacturing steps and reduce manufacturing costs. [Means for solving the problem]

[0024] The inventors of the present disclosure have conducted extensive research into the finish of the ground surface when grinding is performed using a form grinding wheel, and as a result have found that the surface roughness of a surface that forms a small angle with the central axis of the grinding wheel is greater than the surface roughness of a surface that forms a large angle with the central axis of the grinding wheel. The present disclosure has been completed based on this finding.

[0025] In a method for manufacturing a hub unit bearing according to one aspect of the present disclosure, the hub unit bearing to be manufactured includes an outer ring, a hub, a plurality of rolling elements, and an outer seal ring.

[0026] The outer ring has a double-row outer ring raceway on its inner circumferential surface.

[0027] The hub has a double row inner ring raceway on its outer circumferential surface, and a rotary flange that protrudes radially outward at a portion located axially outward of the outer ring.

[0028] The plurality of rolling elements are disposed so as to roll freely between the double row outer ring raceways and the double row inner ring raceways.

[0029] The outer seal ring closes an axially outer opening of a rolling element installation space that exists between the inner peripheral surface of the outer ring and the outer peripheral surface of the hub.

[0030] The hub has a flat portion provided on the axially inner surface of the radially inner end of the rotating flange.

[0031] The outer seal ring has a sliding lip whose tip is in sliding contact with the flat surface.

[0032] A method of manufacturing a hub unit bearing according to one embodiment of the present disclosure includes a step of performing finishing processing by grinding using a formed grinding wheel on an area including the axially outer inner ring raceway of the double-row inner ring raceway and the flat portion, and a step of re-processing the area including the axially outer inner ring raceway and the flat portion using an elastic grinding wheel after performing the finishing processing. That is, the manufacturing method of a hub unit bearing according to one aspect of the present disclosure includes a step of simultaneously re-machining the axially outer inner ring raceway and the flat surface portion using the elastic grindstone.

[0033] In the method for manufacturing a hub unit bearing according to one aspect of the present disclosure, the angle formed between the central axis of the elastic grindstone and the flat portion is larger than the angle formed between the central axis of the elastic grindstone and the central axis of the hub.

[0034] In one embodiment of the method for manufacturing a hub unit bearing of the present disclosure, in the step of performing the finishing process, the generatrix shape of the outer peripheral surface of the grinding wheel is shaped by a diamond wheel, and in the step of performing the reprocessing, the generatrix shape of the outer peripheral surface of the elastic grinding wheel can be shaped by a diamond wheel.

[0035] In the method for manufacturing a hub unit bearing according to one aspect of the present disclosure, the area on the surface of the hub where the finishing process is performed and the area on the surface of the hub where the re-processing is performed can be the same.

[0036] In one embodiment of the method for manufacturing a hub unit bearing of the present disclosure, the angle between the central axis of the elastic grinding wheel and the flat surface can be greater than 45° and less than 90°, preferably greater than 45° and less than 70°, and more preferably greater than 50° and less than 65°. [Effects of the Invention]

[0037] According to the manufacturing method of the hub unit bearing of one aspect of the present disclosure, the number of manufacturing steps can be reduced, thereby reducing manufacturing costs. [Brief explanation of the drawings]

[0038] [Figure 1] FIG. 1 is a cross-sectional view of a hub unit bearing manufactured by a method for manufacturing a hub unit bearing according to a first example of an embodiment of the present disclosure. [Figure 2] FIG. 2 is an enlarged view of part A in FIG. [Figure 3] FIG. 3 is a cross-sectional view showing a state in which re-processing is being performed after finish processing in the first example. [Figure 4] FIG. 4 is a schematic diagram showing the reworking process shown in FIG. 3 as viewed from the inside in the axial direction of the hub. [Figure 5] FIG. 5 is a cross-sectional view showing an example of a conventional structure of a hub unit bearing. [Figure 6] FIG. 6 is a cross-sectional view showing a state in which the hub of the hub unit bearing of FIG. 5 is being finished. [Figure 7] FIG. 7 is a schematic diagram showing the finish processing of FIG. 6 as viewed from the inside in the axial direction of the hub. DETAILED DESCRIPTION OF THE INVENTION

[0039] [Example 1] A method for manufacturing a hub unit bearing according to a first example of an embodiment of the present disclosure will be described with reference to FIGS.

[0040] FIG. 1 shows a hub unit bearing 1 that is the manufacturing object of this example, and FIG. 2 shows an enlarged view of part A in FIG.

[0041] The hub unit bearing 1 to be manufactured in this example comprises an outer ring 2, a hub 3, a plurality of rolling elements 4a, 4b, and an outer seal ring 5.

[0042] In the following description of the hub unit bearing 1, the axially outer side is the left side of FIG. 1, which is the outer side in the width direction of the vehicle when assembled to the vehicle, and the axially inner side is the right side of FIG. 1, which is the center side in the width direction of the vehicle when assembled to the vehicle.

[0043] The outer ring 2 is made of a hard metal such as medium carbon steel, and has double-row outer ring raceways 6a and 6b on its inner peripheral surface.

[0044] The outer ring 2 has a stationary flange 7 that protrudes radially outward from an axially intermediate portion. The stationary flange 7 is a portion used to connect and fix the outer ring 2 to a knuckle of a suspension system. In use, the outer ring 2 is connected and fixed to the knuckle of the suspension system and does not rotate.

[0045] The hub 3 is made of a hard metal such as medium carbon steel or bearing steel, and has double-row inner ring raceways 8a, 8b on its outer peripheral surface, and a rotating flange 9 that protrudes radially outward at a portion axially outer than the outer ring 2, and is disposed radially inside and coaxial with the outer ring 2. The rotating flange 9 is a part used to connect and fix a wheel and a rotating braking member to the hub 3.

[0046] The hub 3 has a cylindrical pilot portion 10 at its axially outer end. The pilot portion 10 is a portion onto which a wheel and a rotating braking member that are coupled and fixed to the rotating flange 9 are fitted. When in use, the hub 3 rotates integrally with the wheel and the rotating braking member that are coupled and fixed to the rotating flange 9.

[0047] The hub 3 has a flat portion 11 that is used as a seal sliding surface.

[0048] In this example, the hub 3 further has a cylindrical surface portion 12 and a curved surface portion 13, each of which is used as a seal sliding surface.

[0049] The flat surface portion 11 is provided on the axially inner surface of the radially inner end portion of the rotating flange 9 , and is configured as a circular flat surface that is perpendicular to the central axis of the hub 3 .

[0050] The cylindrical surface portion 12 is provided on the outer peripheral surface of the hub 3 at a portion adjacent to the axially outer side of the axially outer inner ring raceway 8a, and is configured by a cylindrical surface whose outer diameter does not change in the axial direction.

[0051] The curved surface portion 13 is configured by a curved surface having an arc-shaped cross section that connects the radially inner end of the flat surface portion 11 and the axially outer end of the cylindrical surface portion 12 in the hub 3. In other words, the curved surface portion 13 is curved and inclined radially outward as it extends axially outward.

[0052] In this example, the hub 3 is configured by combining a hub ring 14 and an inner ring 15. However, when implementing the manufacturing method of the present disclosure, the hub that constitutes the hub unit bearing to be manufactured may be configured by a combination of parts different from those in this example.

[0053] The hub ring 14 includes an inner ring raceway 8 a on the axially outer side, a rotation flange 9 , a pilot portion 10 , a flat portion 11 , a cylindrical surface portion 12 , and a curved surface portion 13 that constitute the hub 3 .

[0054] The hub ring 14 has a small diameter step 16 at a portion axially more inward than the axially outer inner ring raceway 8a, which has an outer diameter smaller than that of the portion adjacent to it on the axially outer side, and onto which the inner ring 15 is fitted. Furthermore, the hub ring 14 has a step surface 17 facing axially inward at the axially outer end of the small diameter step 16, and a crimped portion 18 bent radially outward from the axially inner end of the small diameter step 16.

[0055] The inner ring 15 has an inner ring raceway 8b on the axially inner side, which constitutes the hub 3, on its outer peripheral surface.

[0056] In this example, the hub 3 is constructed by fitting an inner ring 15 onto the axially inner portion of the hub wheel 14. More specifically, in this example, the hub 3 is constructed by fitting the inner ring 15 onto the small diameter step 16 of the hub wheel 14, and then clamping the inner ring 15 from both axial sides between the step surface 17 of the hub wheel 14 and the crimped portion 18, thereby joining and fixing the hub wheel 14 and the inner ring 15 together. Note that the crimped portion 18 is formed by plastically deforming a cylindrical portion provided at the axially inner end of the hub wheel 14 radially outward after the inner ring 15 has been fitted onto the small diameter step 16.

[0057] Alternatively, the hub wheel and the inner ring can be joined by threading a nut onto the axially inner end of the hub wheel that protrudes from the axially inner end of the inner ring.

[0058] Since the hub unit bearing 1 of this example is a hub unit bearing for a driven wheel, the hub 3 is constructed to be solid.

[0059] However, the manufacturing method of the hub unit bearing of the present disclosure can also be applied to a hub unit bearing for a drive wheel. In this case, the hub has a spline hole penetrating in the axial direction at the center. The tip of a drive shaft that is driven to rotate by an engine or electric motor as a drive source is spline-engaged with the spline hole. When the vehicle is running, the hub is driven to rotate by the drive shaft, which in turn drives to rotate the wheel and braking rotating member that are coupled and fixed to the rotating flange of the hub.

[0060] The rolling elements 4a, 4b are made of an iron alloy such as bearing steel or ceramics, and are arranged between the double-row outer ring raceways 6a, 6b and the double-row inner ring raceways 8a, 8b, with a plurality of rolling elements on each side held by cages 19a, 19b, so that the hub 3 is rotatably supported radially inside the outer ring 2.

[0061] The hub unit bearing 1 of this example has a so-called equal diameter PCD type structure, in which the pitch diameter of the rolling elements 4a in the axially outer row is the same as the pitch diameter of the rolling elements 4b in the axially inner row. However, the manufacturing method of a hub unit bearing of the present disclosure can also be applied to so-called different diameter PCD type hub unit bearings, in which the pitch diameter of the rolling elements in the axially outer row is different from the pitch diameter of the rolling elements 4b in the axially inner row. Also, while the hub unit bearing 1 of this example uses balls as the rolling elements 4a, 4b, tapered rollers can also be used instead of balls.

[0062] The outer seal ring 5 closes the opening on the axial outside of the rolling element installation space 20 that exists between the inner peripheral surface of the outer ring 2 and the outer peripheral surface of the hub 3. This prevents foreign matter from the external space from entering the rolling element installation space 20 through the opening, and prevents lubricants such as grease sealed in the rolling element installation space 20 from leaking into the external space.

[0063] The outer seal ring 5 has an outer lip 21, which is a sliding lip that is fixed to the axially outer end of the outer ring 2 and whose tip is in sliding contact with the flat surface portion 11. In this example, the outer lip 21 corresponds to the sliding lip described in the claims.

[0064] In this example, the outer seal ring 5 further has an inner lip 22 whose tip portion is in sliding contact with the cylindrical surface portion 12 , and an intermediate lip 23 whose tip portion is in sliding contact with the curved surface portion 13 .

[0065] In this example, the outer seal ring 5 includes a core metal 24 and a seal material 25 .

[0066] The core metal 24 is formed into an annular shape by bending a metal plate such as a mild steel plate. The core metal 24 includes a seal fitting cylindrical portion 26 that is tightly fitted into the axially outer end portion of the outer ring 2, and a support plate portion 27 that is bent radially inward from the axially outer end portion of the seal fitting cylindrical portion 26 and extends radially inward.

[0067] The seal member 25 is made of an elastic material containing an elastomer such as rubber, and is bonded and fixed to the surface of the core bar 24 by vulcanization adhesion. The seal member 25 is provided with an outer lip 21, an inner lip 22, and an intermediate lip 23. In addition to the outer lip 21, the inner lip 22, and the intermediate lip 23, the seal member 25 also has a base 28. Note that in FIG. 2, the outer lip 21, the inner lip 22, and the intermediate lip 23 are shown in a free state.

[0068] The base portion 28 covers the axially outer surface, the inner peripheral surface, and the radially inner portion of the axially inner surface of the support plate portion 27 among the surfaces of the core metal 24 .

[0069] The outer lip 21 extends axially and radially outward from the portion of the base 28 that covers the radially middle portion of the axially outer surface of the support plate portion 27, and its tip portion is in sliding contact with the flat portion 11.

[0070] The inner lip 22 extends in an axially and radially inward direction from the portion of the base 28 that covers the radially inner end of the support plate portion 27, and its tip portion is in sliding contact with the cylindrical surface portion 12.

[0071] The intermediate lip 23 extends from the portion of the base 28 that covers the radially inner end of the support plate portion 27 in the axially outward and radially outward direction, and its tip portion is in sliding contact with the curved portion 13.

[0072] The hub unit bearing 1 of this example further includes a cylindrical bearing cap 29 (see FIG. 1) with a bottom that closes the axially inner opening of the outer ring 2. This prevents foreign matter from the external space from entering the rolling element installation space 20 through the opening, and prevents the lubricant sealed in the rolling element installation space 20 from leaking into the external space. Note that instead of the bearing cap 29, the axially inner opening of the rolling element installation space 20 can also be closed with a combined seal ring.

[0073] The manufacturing method of the hub unit bearing of the present disclosure is characterized by the finishing of the area of ​​the surface of the hub 3 that includes the inner ring raceway 8a on the axially outer side and the flat portion 11, and the re-processing after that finishing, and in this example, this finishing and re-processing is performed on the hub ring 14 before the inner ring 15 of the hub 3 is assembled. For this reason, the following explanation of this finishing and re-processing will be based on the assumption that it is applied to the hub ring 14.

[0074] In the manufacturing method of the hub unit bearing 1 of this example, when manufacturing the hub ring 14, first, a metal material is subjected to forging, cutting, etc. to form the outer shape of the hub ring 14 before forming the crimped portion 18.

[0075] Next, the surface of the hub ring 14 is heat-treated from the small diameter step 16, where the inner ring 15 fits, to the flat surface 11. Then, the surface of the hub ring 14, including the axially outer inner ring raceway 8a and the flat surface 11, is subjected to a finishing process (centerless grinding) using a full-form grinding wheel (rotary grinding wheel) in the same manner as the conventional method shown in Figures 6 and 7. This improves the surface roughness of this area. In this example, the surface of the hub ring 14 is finished by grinding from the small diameter step 16 to the flat surface 11.

[0076] When carrying out the manufacturing method of this example, a grinding wheel for finishing can be used that is made of alumina (Al2O3)-based abrasive grains called A-type abrasive grains bonded with a glass-based binder, with a grain size of #100 to #150, a bonding strength of K to N, a concentration of 7 to 9, and a pore volume ratio of 20% to 40%.

[0077] Center axis of the grinding wheel O T (See Figure 6) and the central axis O of hub 3 H The angle formed by the angle θ and the angle θ is not limited to this, but can be 0° or more and 45° or less, preferably 20° or more and 45° or less, and more preferably 25° or more and 40° or less.

[0078] In this example, as in the conventional method, there is a possibility that logarithmic spiral grinding marks will be formed by the finishing process on the flat surface portion 11 and the curved surface portion 13 of the surface of the hub ring 14, which are surfaces that form an angle of intersection with the central axis of the hub ring 14. Furthermore, such logarithmic spiral grinding marks are more likely to be formed on the flat surface portion 11, which forms a larger angle of intersection with the central axis of the hub ring 14 than on the curved surface portion 13. Furthermore, on the surface of the hub ring 14, the inner ring raceway 8a on the axially outer side has a plurality of fine grooves, each of which is annular groove.

[0079] Therefore, in this example, after the finishing process is performed, the surface of the hub ring 14 is provided with a surface that includes the inner ring raceway 8a and the flat surface portion 11 on the axially outer side, and is provided with a surface that is parallel to the center axis O of the hub ring 14. 30In this example, the re-machining is performed using the elastic grindstone 30 which rotates around the center of the elastic grindstone 30. In this example, the re-machining is performed using the elastic grindstone 30 on the continuous range from the small diameter step portion 16 to the flat portion 11 on the surface of the hub wheel 14, which is the range that has been subjected to finish grinding using a full-form grinding wheel.

[0080] Center axis O of elastic grinding wheel 30 30 and the central axis of hub 3 H The angle θ between the center axis O of the elastic grindstone 30 and the center axis O of the elastic grindstone 30 can be set to 0° or more and 45° or less, preferably 20° or more and 45° or less, and more preferably 25° or more and 40° or less. 30 The angle φ between the center axis O of the elastic grindstone 30 and the flat surface 11 is greater than 45° and less than or equal to 90°, preferably greater than or equal to 45° and less than or equal to 70°, and more preferably greater than or equal to 50° and less than or equal to 65°. 30 The angle φ between the center axis O of the elastic grinding wheel 30 and the flat surface 11 is 30 and the central axis of hub 3 H In this example, the angle θ between the center axis O of the elastic grindstone 30 and the center axis O of the elastic grindstone 30 is larger than the angle θ between the center axis O of the elastic grindstone 30 and the center axis O of the elastic grindstone 30 (φ>θ). 30 and the central axis of hub 3 H The angle θ between the center axis O of the elastic grinding wheel 30 and the center axis O of the elastic grinding wheel 30 is set to about 30°. 30 The angle φ between the center axis O of the elastic grindstone 30 and the flat surface 11 is set to about 60°. 30 and the central axis of hub 3 H The angle θ is the center axis O of the grinding wheel in the finishing process. T and the central axis of hub 3 H The angle can be the same as or different from the angle formed by the arrows.

[0081] In this example, the area where the surface of the hub ring 14 is finish-machined and the area where the surface of the hub ring 14 is re-machined are the same. However, when carrying out a manufacturing method for a hub unit bearing according to one aspect of the present disclosure, the area where the finish-machining is performed and the area where the re-machining is performed may be different, as long as the inner ring raceway and flat portion on the axially outer side are included in the area where the finish-machining and the area where the re-machining is performed, respectively.

[0082] When reworking, as shown in FIGS. 3 and 4, the center axis O of the hub wheel 14 is located on the outer peripheral surface of the axially intermediate portion of the hub wheel 14. H The hub wheel 14 is radially positioned by being rotatably supported by the tip of the shoe 31 at two circumferential points located below the hub wheel 14 (in the illustrated example, at approximately 5 o'clock and approximately 9 o'clock on the clock face).

[0083] The hub wheel 14 is rotated by rotating the magnetic chuck 32 magnetically coupled to the axially outer surface of the rotating flange 9. At this time, the central axis O of the magnetic chuck 32 M The central axis of the hub wheel 14 is O H The shoes 31 are offset by approximately 0.1 to 0.2 mm in the direction connecting the tips of the two shoes 31, and a pressing force F is applied from the magnetic chuck 32 to the hub wheel 14 in the direction toward the gap between the two shoes 31, i.e., a pressing force F against the two shoes 31.

[0084] In this state, the elastic grinding wheel 30 of the full-form, which is arranged so as to have the same center height as the hub wheel 14, is moved along its own central axis O 30 While rotating the elastic grindstone 30 around the center, the outer peripheral surface of the elastic grindstone 30 is pressed against the above-mentioned range of the surface of the hub wheel 14, which is the surface to be processed, and the surface to be processed is re-processed by grinding. The rotation direction of the elastic grindstone 30 may be opposite to the rotation direction of the hub wheel 14, or may be the same as the rotation direction of the hub wheel 14.

[0085] When reprocessing, the insertion position of the elastic grindstone 30 may be moved 20 μm to 50 μm toward the rotary flange 9 so that the outer circumferential surface of the elastic grindstone 30 makes strong contact with the flat portion 11. The grinding allowance on the surface of the hub ring 14 is, for example, approximately 5 μm to 50 μm. When reprocessing, the generatrix shape of the outer circumferential surface of the elastic grindstone 30 can be appropriately shaped using a diamond wheel 33 to match the generatrix shape of the finished processed surface. Alternatively, after reprocessing is performed on one or more hub rings 14, the generatrix shape of the outer circumferential surface of the elastic grindstone 30 can be shaped using a diamond wheel 33.

[0086] The center height of the hub ring 14 and the elastic grindstone 30 is the distance from the center axis O of each of the hub ring 14 and the elastic grindstone 30 in FIG. H , O 30 is the vertical position of the

[0087] In this example, the reprocessing using the elastic grinding wheel 30 is performed using the same grinding machine as the finish processing using the grinding wheel for the form. In other words, after the finish processing is performed, only the grinding wheel on the same grinding machine is replaced from the grinding wheel for the form to the elastic grinding wheel 30, and reprocessing is performed.

[0088] In this example, because finishing with a form grinding wheel and re-processing with an elastic grinding wheel 30 are performed consecutively, a diamond wheel for shaping the grinding wheel used in finishing and a diamond wheel 33 for shaping the elastic grinding wheel used in re-processing are prepared separately. However, when additional processing (re-processing) is performed collectively on multiple hub wheels that have been subjected to finishing, the diamond wheel for shaping the grinding wheel and the diamond wheel 33 for shaping the elastic grinding wheel can be the same.

[0089] The elastic grinding wheel 30 may be, for example, a soft one having silicon carbide or alumina abrasive grains bonded with a binder made of a soft resin such as PVA (polyvinyl alcohol), with a grain size of about #800 to #1200 (preferably #1000) and a pore volume ratio of 50% to 60%.

[0090] As in this example, when the surface of the hub ring 14 is ground integrally using the elastic grindstone 30 of the full-form, the center axis O of the outer circumferential surface of the elastic grindstone 30 is 30 The surface roughness of the ground surface in the area where the angle of intersection of the generatrix with the central axis O is small (high degree of parallelism) 30 The surface roughness of the ground surface tends to be larger in the area where the angle of intersection of the generatrix with respect to the center axis O is large (the degree of parallelism is low). 30Since the grinding is performed at a portion where the angle of intersection of the generatrix with respect to the flat surface is small, the surface roughness of the inner ring raceway 8a on the axially outer side is greater than the surface roughness of the flat surface portion 11.

[0091] Although it varies depending on the type of abrasive grains constituting the elastic grinding wheel 30 and the direction of rotation of the elastic grinding wheel 30, the arithmetic mean roughness Ra of the inner ring raceway 8a on the outer axial side is approximately 0.1 μm to 0.2 μm, and the arithmetic mean roughness Ra of the flat portion 11 is approximately 0.05 μm to 0.1 μm.

[0092] Therefore, in this example, by re-machining the surface of the hub ring 14, including the axially outer inner ring raceway 8a and the flat surface 11, using a full-form elastic grindstone 30, grinding marks on the flat surface 11 are removed, and the flat surface 11 can be finished to a surface without logarithmic spiral grinding marks and with smooth peaks of roughness, i.e., a surface close to a mirror finish. Furthermore, the axially outer inner ring raceway 8a can be finished to a surface with smooth peaks of roughness and with fine grooves (valleys of the roughness curve after finishing) remaining on the surface to retain lubricant. Furthermore, by removing grinding marks from the flat surface 11, the generation of abnormal noise known as seal squeal can be suppressed, an increase in torque caused by the outer lip 21 sticking to the flat surface 11 can be suppressed, and torque differences depending on the direction of rotation of the hub 3 can be mitigated. Furthermore, the inner ring raceway 8a on the axially outer side is finished to have a smooth surface at the top of the roughness and to have fine grooves remaining on the surface to retain lubricant, thereby improving the lubricity of the rolling contact area between the inner ring raceway 8a and the rolling elements 4a and extending the bearing life.

[0093] In this example, the cylindrical surface portion 12 and the curved surface portion 13 are also re-machined using a formed elastic grindstone 30, and the peaks of the roughness are finished into smooth surfaces. Therefore, grinding streaks formed on the curved surface portion 13 during the finishing process are also removed by the re-machining.

[0094] In the present example described above, the axially outer inner ring raceway 8a and the flat surface 11 can be simultaneously re-machined to achieve the required surface properties. Therefore, compared to the conventional method described in WO 2020 / 158161, the number of manufacturing steps for the hub unit bearing 1 can be reduced, thereby reducing manufacturing costs. [Explanation of symbols]

[0095] 1 Hub unit bearing 2 outer ring 3. Hub 4a, 4b rolling elements 5 Outer seal ring 6a, 6b Outer ring raceway 7 Stationary Flange 8a, 8b Inner raceway 9 Rotating flange 10 Pilot Division 11 Plane part 12 Cylindrical surface part 13 Curved part 14 Hub wheel 15 Inner Circle 16 Small diameter stepped section 17 Step surface 18 Crimping part 19a, 19b retainer 20 Rolling element installation space 21 outer lip 22 Inner lip 23 Middle lip 24 Core 25 Sealing material 26 Seal fitting cylinder 27 Support plate part 28 Base 29 Bearing cap 30 Elastic grinding stone 31 Shoe 32 Magnetic chuck 33 Diamond Wheel 100 Hub unit bearing 101 outer ring 102 Hub 103a, 103b rolling elements 104 Outer seal ring 105a, 105b outer raceway 106a, 106b inner raceway 107 Rotating flange 108 Plane section 109 Spline hole 110 Hub Wheel 111 Inner circle 112 Sliding lip 113 Shoe 114 Magnetic chuck 115 Grinding Wheel 116 Diamond Wheel

Claims

1. an outer ring having a double-row outer ring raceway on its inner circumferential surface; a hub having a double row inner ring raceway on its outer peripheral surface and a rotary flange protruding radially outward at a portion located axially outward of the outer ring; a plurality of rolling elements arranged to roll freely between the double row outer ring raceways and the double row inner ring raceways; an outer seal ring that closes an axially outer opening of a rolling element installation space that exists between the inner peripheral surface of the outer ring and the outer peripheral surface of the hub; Equipped with The hub has a flat portion provided on an axially inner surface of a radially inner end portion of the rotating flange, The outer seal ring has a sliding lip that makes sliding contact with the flat surface at its tip end. A method for manufacturing a hub unit bearing, a step of performing a finishing process by grinding an area including an axially outer inner ring raceway of the double row inner ring raceway and the flat portion using a grinding wheel of a full-form; a step of re-machining an area including the axially outer inner ring raceway and the flat portion using an elastic grindstone after the finishing process; Equipped with an angle formed between the central axis of the elastic grindstone and the flat surface portion is larger than an angle formed between the central axis of the elastic grindstone and the central axis of the hub; A manufacturing method for a hub unit bearing.

2. 2. The method for manufacturing a hub unit bearing according to claim 1, wherein in the finishing process, the generatrix shape of the outer peripheral surface of the grinding wheel is shaped by a diamond wheel, and in the re-processing process, the generatrix shape of the outer peripheral surface of the elastic grinding wheel is shaped by a diamond wheel.

3. 2. The method for manufacturing a hub unit bearing according to claim 1, wherein the area of ​​the hub surface that is subjected to the finish processing and the area of ​​the hub surface that is subjected to the re-processing are the same.

Images