Hub unit bearing and manufacturing method therefor

Abstract

To provide a low-cost hub unit bearing capable of reducing a residual circumferential tensile stress itself in an inner ring to prevent cracking of the inner ring, and a manufacturing method therefor.SOLUTION: A manufacturing method for a hub unit bearing comprises: a fitting process of fitting an inner ring 40 into a small diameter step part 34; a diameter enlarging process of enlarging the diameters of the small diameter step part 34 and inner ring 40 when the inner ring 40 is fitted into the small diameter step part 34 in the fitting process; a crimping process of deforming an inboard side end part of the small diameter step part 34 radially outward to crimp and fix the inner ring 40 to a hub shaft 31 with the diameters of the small diameter step part 34 and inner ring 40 enlarged by the diameter enlarging process; and a process of reducing the diameters of the small diameter step part 34 and inner ring 40 after the crimping process.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hub unit bearing and a manufacturing method thereof, and more particularly to a crimped hub unit bearing and a manufacturing method thereof. [Background technology]

[0002] The inner ring made of bearing steel of a crimped hub unit bearing has residual tensile circumferential stress resulting from the crimping process on the shaft end of the hub axle, and if there is a dent or other defect in the chamfered portion at the inner end of the inner ring shoulder, there is a risk that a crack will spread from the defect and cause a break (delayed fracture).Patent Document 1 discloses a wheel bearing device that specifies the shape of the chamfer formed on the inner diameter end on the large end face side of the inner ring to prevent cracks resulting from the crimping process, thereby preventing the occurrence of dents or other defects even when the inner rings collide with each other or with an external obstacle.

[0003] Furthermore, Patent Document 2 describes a method for manufacturing an inner ring for a hub unit bearing in which a thick-walled portion that is thicker than other portions is provided in a portion that includes a raceway side chamfer, and dents are removed by subsequent turning to reduce the residual circumferential tensile stress itself.

[0004] Furthermore, Patent Document 3 discloses a technology in which residual compressive stress is imparted to the corners of the inner circumference of the inner ring or the corners of the outer circumference of the inner ring by laser peening, thereby reducing (or eliminating) the residual circumferential tensile stress after fitting with the hub axle or crimping, thereby preventing the occurrence of cracks or breakage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6661308 [Patent Document 2] Patent No. 7367379 [Patent Document 3] Patent No. 7021844 Summary of the Invention [Problem to be solved by the invention]

[0006] However, Patent Documents 1 and 2 require complex shaping of the chamfered portion and post-turning to remove dents. Furthermore, the laser peening process of Patent Document 3 can impart higher surface residual compressive stress than shot peening, but requires generating plasma on the material surface using high-density energy, which requires focusing the laser beam through a lens for scanning. This takes time and increases costs when treating a large area. Furthermore, because the process is performed underwater, post-treatments such as moisture removal and rust prevention are required when treating materials that rust easily, such as bearing steel, which also increase costs.

[0007] The present invention has been made in view of the above-mentioned problems, and its object is to provide a low-cost hub unit bearing and a manufacturing method thereof that can reduce the residual circumferential tensile stress itself in the inner ring and prevent cracking of the inner ring. [Means for solving the problem]

[0008] Therefore, the above object of the present invention is achieved by the following configuration [1] relating to a manufacturing method of a hub unit bearing. [1] An outer ring having a double-row outer ring raceway formed on its inner circumferential surface; a hub axle having a wheel mounting flange on the outboard side and a small diameter stepped portion formed on the inboard side, and at least one inner ring fitted onto the small diameter stepped portion of the hub axle and secured by caulking, the hub having double row inner ring raceways formed on its outer peripheral surface opposite the double row outer ring raceways; a plurality of rolling elements arranged to roll freely between the double row inner ring raceways and the double row outer ring raceways; A manufacturing method of a hub unit bearing comprising: a fitting step of fitting the inner ring to the small diameter step portion; a diameter expanding step of expanding diameters of the small diameter step portion and the inner ring in a state in which the inner ring is fitted into the small diameter step portion in the fitting step; a crimping step in which, with the diameters of the small diameter step and the inner ring expanded by the diameter expanding step, an inboard end of the small diameter step is deformed radially outward to crimp and fix the inner ring to the hub axle; a step of reducing diameters of the small diameter step portion and the inner ring after the crimping step; A method for manufacturing a hub unit bearing comprising: [2] An outer ring having a double-row outer ring raceway formed on its inner circumferential surface; a hub axle having a wheel mounting flange on the outboard side and a small diameter stepped portion formed on the inboard side, and at least one inner ring fitted onto the small diameter stepped portion of the hub axle and secured by caulking, the hub having double row inner ring raceways formed on its outer peripheral surface opposite the double row outer ring raceways; a plurality of rolling elements arranged to roll freely between the double row inner ring raceways and the double row outer ring raceways; A hub unit bearing comprising: The small diameter step portion has an inner diameter portion that overlaps the inner ring in the radial direction and has a tapered portion formed thereon. A hub unit bearing characterized by: [Effects of the Invention]

[0009] According to the hub unit bearing and manufacturing method thereof of the present invention, it is possible to reduce the residual circumferential tensile stress itself and prevent cracking of the inner ring using an inexpensive method. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a hub unit bearing according to a first embodiment of the present invention. [Figure 2] FIG. 6 is a cross-sectional view of a hub unit bearing according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] (First embodiment) A caulked hub unit bearing for a driven wheel according to a first embodiment of the present invention will be described in detail with reference to FIG. With regard to the hub unit bearing, throughout this specification and the claims, the "inboard side" refers to the side of the vehicle body of the hub unit bearing when attached to the vehicle body, the right side in Fig. 1, and is also referred to as the inside. The "outboard side" refers to the side of the wheel of the hub unit bearing when attached to the vehicle body, the left side in Fig. 1, and is also referred to as the outside.

[0012] As shown in FIG. 1, a crimped hub unit bearing 10 of this embodiment (hereinafter also simply referred to as a hub unit bearing) is a hub unit bearing for a driven wheel, and mainly comprises an outer ring 20, a hub 30, and a plurality of rolling elements 11, 11.

[0013] The outer ring 20 has a stationary flange 21 on its outer peripheral surface and double-row (two-row) outer ring raceways 20a, 20b on its inner peripheral surface. When in use, the stationary flange 21 is connected and fixed to a knuckle of a suspension device, so that the outer ring 20 does not rotate while supported by the suspension device.

[0014] The hub 30 is made up of a hub axle 31 and an inner ring 40 that is fitted onto the hub axle 31 and fixed by crimping, and is disposed coaxially (concentrically) with the outer ring 20 on the radially inner side of the outer ring 20.

[0015] The hub axle 31 is provided with a circular wheel mounting flange 32 that extends radially outward from a portion that protrudes axially outward from the axially outer (outboard side) opening of the outer ring 20 and is used to support and fix a wheel (driven wheel) and a braking rotating member such as a disc rotor. Specifically, the wheel mounting flange 32 is provided with a plurality of insertion holes 32a, and a hub bolt 12 is serrated and fitted into each insertion hole 32a. Note that the plurality of insertion holes 32a in the wheel mounting flange 32 can also be made into female threaded holes, and by threading a hub bolt into them, a wheel and a braking rotating member such as a disc rotor can be supported and fixed.

[0016] An outboard-side row (one row) inner ring raceway 33a is provided on a portion of the outer peripheral surface of the hub axle 31 that faces the outer ring raceway 20a of the axially outer (outboard side) row of the outer ring 20. A small diameter step 34 is provided on the axially inner end of the outer peripheral surface of the hub axle 31 that faces the outer ring raceway 20b of the axially inner (inboard side) row of the outer ring 20. The hub axle 31 also has a crimping portion 35 that partially constitutes the outer peripheral surface of the small diameter step 34 and whose inboard end deforms radially outward to crimp and fix the inner ring 40.

[0017] The small diameter step 34 has a tapered female thread 36 (tapered portion) formed in the inner diameter portion that radially overlaps the inner ring 40. A plug 45, which has a tapered male thread 45a formed on its outer circumferential surface, is threadedly engaged with the tapered female thread 36.

[0018] An inner ring raceway 33b of the inboard row (the other row) is provided on the outer peripheral surface of the inner ring 40. The inner ring 40 is fitted onto the small diameter step 34 of the hub axle 31 with its outboard end face 40a abutting against the step surface 34a of the small diameter step 34, and the inboard end is crimped and fixed to the hub axle 31 by a crimp portion 35 that is deformed radially outward.

[0019] The rolling elements 11, 11 are held by a pair of retainers 16, 16 and are freely rollable between the outer ring raceway 20a and the inner ring raceway 33a of the outboard row, and between the outer ring raceway 20b and the inner ring raceway 33b of the inboard row.

[0020] A seal ring 15 is fixedly supported on the outboard end of the inner peripheral surface of the outer ring 20. The seal ring 15 closes the axially outer end opening of an internal space 17, which is provided with multiple rolling elements 11, 11 and exists between the inner peripheral surface of the outer ring 20 and the outer peripheral surface of the hub axle 31. The seal ring 15 comes into sliding contact with a large diameter step 31a on the outer peripheral surface of the hub axle 31 that is on the outboard side of the inner ring raceway 33a.

[0021] Next, a method for caulking and fixing the inner ring 40 to the small diameter step portion 34 will be described. First, the inner ring 40 is fitted onto the small diameter step 34 and inserted until the outboard end face 40a of the inner ring 40 abuts against the step surface 34a of the small diameter step 34. Then, the tapered male thread portion 45a of the plug 45 is threaded into the tapered female thread portion 36 of the hub axle 31, and the plug 45 is screwed into the tapered female thread portion 36. This causes the small diameter step 34 and the inner ring 40 to expand in diameter, applying tensile circumferential stress to the inner ring 40.

[0022] Next, with the tensile circumferential stress applied to the inner ring 40 as described above, in other words, with the inner ring 40 expanded in diameter, a crimping device (not shown) is used to deform the inboard end of the small diameter step 34 radially outward, and the inner ring 40 is crimped and fixed to the hub axle 31 by the crimp portion 35. As a result, further tensile circumferential stress is applied to the small diameter step 34 and the inner ring 40 by crimping.

[0023] Next, the plug 45 is rotated in the opposite direction to the previous rotation, and the plug 45 is removed from the tapered female thread portion 36 of the hub axle 31. This reduces the diameter of the small diameter step portion 34 and the inner ring 40, and the tensile circumferential stress that had been applied to the small diameter step portion 34 and the inner ring 40 due to the crimping is removed.

[0024] When the inner ring 40 is crimped, the tensile circumferential stress generated in the inner ring 40 occurs because the inner ring 40 prevents the small diameter step 34 of the hub axle 31 from becoming thicker due to the crimping process. Therefore, regardless of whether the diameter of the assembly of the small diameter step 34 and the inner ring 40 is expanded or not, the increase in tensile circumferential stress of the inner ring 40 due to crimping is approximately the same.

[0025] As described above, in this embodiment, the small diameter step portion 34 and the inner ring 40 are crimped while they are in an expanded state, and then the small diameter step portion 34 and the inner ring 40 are reduced in diameter. This reduces the residual circumferential tensile stress by the amount of the reduced diameter, making it possible to suppress the occurrence of cracks in the inner ring.

[0026] (Second embodiment) A caulked hub unit bearing according to a second embodiment of the present invention will be described in detail with reference to FIG.

[0027] Hub unit bearing 10 of this embodiment differs from hub unit bearing 10 of the first embodiment in the method of expanding the diameter of small diameter step portion 34 and inner ring 40 and the method of crimping, but the other configurations and effects are similar, so only the method of expanding the diameter of small diameter step portion 34 and inner ring 40 and the method of crimping will be described and a detailed description will be omitted. Note that the method of expanding the diameter and crimping of this embodiment is an example of a method of implementing the method described in the first embodiment on a mass-production basis.

[0028] The hub axle 31 of this embodiment has an inner diameter portion that radially overlaps the inner ring 40, and is provided with a tapered hole 37 that expands in diameter toward the inboard side, and a through hole 38 that passes through the center of the hub axle 31 and connects the tapered hole 37 to the outboard side.

[0029] The crimping device 50 also includes a tapered jig 51 and a crimping mechanism 55. The tapered jig 51 has a tapered base 52 that is inserted into the tapered hole 37 at approximately the same inclination angle as the inclination angle of the tapered hole 37, and a connecting rod 53 that is inserted into the through hole 38 and has one end (the upper end in the figure) connected to the tapered base 52.

[0030] The other end of the connecting rod 53 is provided with a drive mechanism (not shown) that drives the connecting rod 53, i.e., the tapered base 52, in the axial direction (up and down direction in FIG. 2). The tapered base 52 and the connecting rod 53 are joined, for example, by threading a male thread 53a formed on one end of the connecting rod 53 into a female thread 52a formed on the tapered base 52.

[0031] The crimping mechanism 55 includes a punch 56 and a restraining member 57. The punch 56 is driven by an electric motor (not shown) and rotates about a rotation axis C2 that performs a precession motion while tilting at a predetermined angle relative to the central axis C1 of the hub axle 31. The restraining member 57 fits onto the inner ring 40 and receives the radial force generated by crimping the hub axle 31 (crimped portion 35).

[0032] Next, the crimping method will be explained. First, the hub axle 31 is fixed vertically on the mounting base 58. Then, the connecting rod 53 is moved axially downward by a drive mechanism (not shown), and the tapered base 52 is tightly fitted into the tapered hole 37 of the hub axle 31. This causes the small diameter step 34 and the inner ring 40 to expand in diameter, applying tensile circumferential stress to the inner ring 40.

[0033] Next, with tensile circumferential stress applied to the inner ring 40, in other words, with the inner ring 40 expanded in diameter, the punch 56 is driven by an electric motor (not shown) to rotate around the rotation axis C2 and lower it, pressing it against the inboard end of the small diameter step portion 34 of the hub axle 31 and deforming it radially outward, and the inner ring 40 is crimped and fixed to the hub axle 31 at the crimp portion 35.

[0034] After the above-described crimping, the connecting rod 53 is moved axially upward by a drive mechanism (not shown), and the tapered base 52 is removed from the tapered hole 37 of the hub axle 31. This reduces the diameter of the small diameter step portion 34 and the inner ring 40, and the tensile circumferential stress applied to the inner ring 40 is removed.

[0035] As explained above, after the crimping process is performed with the small diameter step portion 34 and the inner ring 40 in an expanded state, the small diameter step portion 34 and the inner ring 40 are reduced in diameter, so that the residual tensile circumferential stress of the inner ring 40 is reduced by the amount of the reduced diameter, and the occurrence of inner ring cracking can be suppressed.

[0036] The above method can be made suitable for continuous production by adding a mechanism that automatically screws the male thread 53a of the connecting rod 53 into the female thread 52a of the tapered base 52. Also, in a hub unit bearing for a driven wheel in which the end of the hub axle 31 is sealed with an end cap, water can be prevented from seeping into the hub unit bearing 10 by plugging the through hole 38 of the hub axle 31 with a plug or the like after the crimping process. Also, in a hub unit bearing 10 for a driving wheel, the connecting rod 53 can be positioned using the spline hole that is originally located in the center of the hub axle 31, making this method suitable for implementation.

[0037] The present invention is not limited to the above-described embodiments, and modifications and improvements are possible as appropriate.

[0038] As described above, the present specification discloses the following: (1) an outer ring having a double-row outer ring raceway formed on its inner peripheral surface; a hub axle having a wheel mounting flange on the outboard side and a small diameter stepped portion formed on the inboard side, and at least one inner ring fitted onto the small diameter stepped portion of the hub axle and secured by caulking, the hub having double row inner ring raceways formed on its outer peripheral surface opposite the double row outer ring raceways; a plurality of rolling elements arranged to roll freely between the double row inner ring raceways and the double row outer ring raceways; A manufacturing method of a hub unit bearing comprising: a fitting step of fitting the inner ring to the small diameter step portion; a diameter expanding step of expanding diameters of the small diameter step portion and the inner ring in a state in which the inner ring is fitted into the small diameter step portion in the fitting step; a crimping step in which, with the diameters of the small diameter step and the inner ring expanded by the diameter expanding step, an inboard end of the small diameter step is deformed radially outward to crimp and fix the inner ring to the hub axle; a step of reducing diameters of the small diameter step portion and the inner ring after the crimping step; A method for manufacturing a hub unit bearing comprising: According to this configuration, the residual circumferential tensile stress itself can be reduced by an inexpensive method, thereby preventing cracks in the inner ring.

[0039] (2) The diameter expanding step is a step of screwing a plug having a tapered male thread portion formed on an outer peripheral surface into a tapered female thread portion formed on an inner diameter portion of the small diameter step portion radially overlapping the inner ring. A method for manufacturing the hub unit bearing described in (1). According to this configuration, a residual circumferential tensile stress can be applied to the inner ring by a simple and inexpensive method before the inner ring is fixed to the hub axle by crimping.

[0040] (3) The diameter-expanding step is a step of press-fitting a tapered jig, the outer circumferential surface of which is tapered and which is movable in the axial direction of the hub spindle, into a tapered hole formed in an inner diameter portion of the small diameter step portion which radially overlaps the inner ring. A method for manufacturing the hub unit bearing described in (1). According to this configuration, residual circumferential tensile stress can be continuously applied to the inner ring in the manufacturing process of the hub unit bearing, facilitating mass production of hub unit bearings.

[0041] (4) an outer ring having a double-row outer ring raceway formed on its inner peripheral surface; a hub axle having a wheel mounting flange on the outboard side and a small diameter stepped portion formed on the inboard side, and at least one inner ring fitted onto the small diameter stepped portion of the hub axle and secured by caulking, the hub having double row inner ring raceways formed on its outer peripheral surface opposite the double row outer ring raceways; a plurality of rolling elements arranged to roll freely between the double row inner ring raceways and the double row outer ring raceways; A hub unit bearing comprising: The small diameter step portion has an inner diameter portion that overlaps the inner ring in the radial direction and has a tapered portion formed thereon. A hub unit bearing characterized by: According to this configuration, the diameters of the small diameter step and the inner ring can be expanded by pressing the tapered portion of a plug or the like against the tapered portion formed on the inner diameter portion of the small diameter step, and then the diameters of the small diameter step and the inner ring can be easily reduced by removing the plug or the like. This reduces the residual tensile circumferential stress by the amount of the diameter reduction, making it possible to suppress the occurrence of cracks in the inner ring. [Explanation of symbols]

[0042] 10 Hub unit bearing 11 Rolling elements 20 outer ring 20a, 20b Outer ring raceway 30 Hub 31 Hub axle 32 Wheel mounting flange 33a, 33b inner raceway 34 Small diameter stepped section 36 Tapered female thread (tapered part) 37 Tapered hole 40 Inner Circle 45 plug 45a tapered male thread 51 Tapered jig

Claims

1. an outer ring having a double-row outer ring raceway formed on its inner circumferential surface; a hub axle having a wheel mounting flange on the outboard side and a small diameter stepped portion formed on the inboard side, and at least one inner ring fitted onto the small diameter stepped portion of the hub axle and secured by caulking, the hub having double row inner ring raceways formed on its outer peripheral surface opposite the double row outer ring raceways; a plurality of rolling elements arranged to roll freely between the double row inner ring raceways and the double row outer ring raceways; A manufacturing method of a hub unit bearing comprising: a fitting step of fitting the inner ring to the small diameter step portion; a diameter expanding step of expanding diameters of the small diameter step portion and the inner ring in a state in which the inner ring is fitted into the small diameter step portion in the fitting step; a crimping step in which, with the diameters of the small diameter step and the inner ring expanded by the diameter expanding step, an inboard end of the small diameter step is deformed radially outward to crimp and fix the inner ring to the hub axle; a step of reducing diameters of the small diameter step portion and the inner ring after the crimping step; A method for manufacturing a hub unit bearing comprising:

2. the diameter expanding step is a step of threading a plug, the plug having a tapered male thread portion formed on its outer peripheral surface, into a tapered female thread portion formed on an inner diameter portion of the small diameter step portion that radially overlaps the inner ring, The method for manufacturing the hub unit bearing according to claim 1.

3. the diameter-expanding step is a step of press-fitting a tapered jig, the outer circumferential surface of which is tapered and which is movable in the axial direction of the hub spindle, into a tapered hole formed in an inner diameter portion of the small diameter step portion that radially overlaps the inner ring, The method for manufacturing the hub unit bearing according to claim 1.

4. an outer ring having a double-row outer ring raceway formed on its inner circumferential surface; a hub axle having a wheel mounting flange on the outboard side and a small diameter stepped portion formed on the inboard side, and at least one inner ring fitted onto the small diameter stepped portion of the hub axle and secured by caulking, the hub having double row inner ring raceways formed on its outer peripheral surface opposite the double row outer ring raceways; a plurality of rolling elements arranged to roll freely between the double row inner ring raceways and the double row outer ring raceways; A hub unit bearing comprising: The small diameter step portion has an inner diameter portion that overlaps the inner ring in the radial direction and has a tapered portion formed thereon. A hub unit bearing characterized by:

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