JP2009149182A - Bearing device for wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing device for a wheel capable of preventing generation of stick slip noise by regulating the surface property of a calked part to realize smooth sliding on an abutting counter member. <P>SOLUTION: In the bearing device for the wheel, an outer joint member 14 integrally having a shaft part 13 internally fitted to a hub ring 1 via serrations 1c, 13a; an inner ring 2 is axially fixed by a calked part 7 formed by the oscillation calking; a fixing nut 15 is fastened to an end of the shaft part 13 while a shoulder part 12 of the outer joint member 14 is abutted on the calked part 7; and the hub ring 1 and a constant velocity universal joint 11 are coupled with each other in an axially separable manner. An end face 7a of the calked part 7 to be abutted on the shoulder part 12 of the outer joint member 14 is formed on a flat surface through the grinding work. The end face 7a is constituted of concentric turning pattern, the end face 7a is subjected to the shotblasting after the turning, and its surface roughness is set in Ra range of 1.5-4.5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wheel bearing device for supporting a drive wheel of a vehicle such as an automobile, and more particularly, to a drive wheel (an FF vehicle front wheel, an FR vehicle or an RR vehicle rear wheel, and a 4WD vehicle) mounted on an independent suspension. The present invention relates to a wheel bearing device that rotatably supports a suspension device.

  A power transmission device that transmits engine power of a vehicle such as an automobile to a wheel transmits power from the engine to the wheel, and also causes radial or axial displacement from the wheel that occurs when the vehicle bounces or turns when traveling on a rough road. For example, one end of the drive shaft interposed between the engine side and the drive wheel side is connected to the differential through a sliding type constant velocity universal joint, and the like. The end is connected to the drive wheel via a wheel bearing device including a fixed type constant velocity universal joint.

  Various types of wheel bearing devices have been proposed in the past, and for example, those shown in FIG. 4 are known. The wheel bearing device 50 is connected to a hub wheel 51 on which one end of the wheel W and the brake rotor B is mounted, a double-row rolling bearing 52 that rotatably supports the hub wheel 51, and the hub wheel 51. A fixed type constant velocity universal joint 53 that transmits power of a drive shaft (not shown) to the hub wheel 51 is provided.

  The hub wheel 51 integrally has a wheel mounting flange 54 for mounting the wheel W and the brake rotor B at one end portion, and a cylindrical small-diameter step portion 51 a extending in the axial direction from the wheel mounting flange 54 is formed. .

  The double-row rolling bearing 52 is mounted between the knuckle N constituting the suspension device and the small-diameter step portion 51a of the hub wheel 51, and an outer ring 55 in which double-row outer rolling surfaces 55a and 55a are formed on the inner periphery, A pair of inner rings 56, 56 each having an inner rolling surface 56 a opposite to the outer circumferential rolling surfaces 55 a, 55 a in a double row on the outer periphery, and a cage 57 between both rolling surfaces 55 a, 56 a are freely rollable. And a double-row angular ball bearing having double-row balls 58 and 58 accommodated in the ball.

  The constant velocity universal joint 53 is an outer joint member integrally having a cup-shaped mouth portion (not shown), a shoulder portion 59 that forms the bottom portion of the mouth portion, and a shaft portion 60 that extends in the axial direction from the shoulder portion 59. 61 is provided. The outer joint member 61 is fitted into the hub wheel 51 through serrations so as to transmit torque. Then, the shaft portion 60 is fitted into the hub wheel 51 until the shoulder portion 59 abuts against the inner ring 56 of the double row rolling bearing 52, and the fixing nut 63 is attached to the male screw 62 formed at the end of the shaft portion 60. Are fastened with a predetermined tightening torque, and the hub wheel 51 and the outer joint member 61 are coupled so as to be separable in the axial direction.

  A large torque is applied to the wheel W of such a vehicle from the engine via a sliding type constant velocity universal joint (not shown) when the engine rotates at a low speed, for example, when the vehicle starts, and the drive shaft may be twisted. Are known. As a result, the inner ring 56 of the double row rolling bearing 52 supporting the drive shaft is also twisted. Thus, when a large twist occurs in the drive shaft, a so-called stick-slip sound is generated due to a sudden slip at the contact surface between the shoulder 59 of the outer joint member 61 and the end face of the inner ring 56.

As a countermeasure against this, in the conventional wheel bearing device 50, a surface treatment for reducing the frictional resistance is applied to a portion of the outer joint member 61 that contacts the shoulder 59. Specifically, as shown in FIGS. 5A and 5B, grease grooves 64 are formed in the circumferential direction on the end faces 56 b and 56 c of the inner ring 56. With this surface treatment, the lubricating oil, such as grease, can easily enter between the abutting mating member, reducing the frictional resistance of the abutting surface, resulting in smooth slipping and suppressing stick-slip noise Can be demonstrated.
JP 2000-110840 A

  However, in such a conventional wheel bearing device, the end surfaces 56b and 56c of the inner ring 56 are subjected to surface treatment including the grease grooves 64, and the frictional resistance with the abutting member is reduced to suppress stick-slip noise. However, it is necessary to perform such surface treatment on a plurality of parts, which increases the number of processing steps and complicated the process management, which has been a factor in hindering cost reduction.

  Further, in the case where a so-called self-retain structure is employed in which the inner ring 56 is fixed by a caulking portion formed by plastically deforming the end surface of the hub wheel 51, it is difficult to form such a grease groove 64 in the caulking portion. In the self-retain structure, a wheel bearing device that can effectively prevent the occurrence of stick-slip noise has been desired.

  The present invention has been made in view of such circumstances, and for wheels that regulate the surface properties of the crimped portion and prevent the occurrence of stick-slip noise by realizing smooth sliding with the abutting counterpart member. It aims at providing a bearing device.

  In order to achieve such an object, the invention according to claim 1 of the present invention includes an outer member in which a double row outer rolling surface is integrally formed on the inner periphery, and a wheel for attaching a wheel to one end. The double row comprises a hub ring integrally having a mounting flange and having a cylindrical small-diameter step portion extending in the axial direction on the outer periphery, and at least one inner ring press-fitted into the small-diameter step portion of the hub ring. An inner member in which a double row of inner rolling surfaces facing the outer rolling surface of the inner member is formed, and a double row of the inner member and the outer member that are accommodated so as to roll freely between the rolling surfaces of the inner member and the outer member. A rolling element and an outer joint member of a constant velocity universal joint integrally having a shaft portion fitted into the hub wheel via serrations, and plastically deforming an end portion of the small diameter step portion radially outward. The inner ring is fixed in the axial direction by the caulking portion formed in this manner, and the shoulder portion of the outer joint member is For a wheel in which a fixing nut is fastened to a male screw formed at an end portion of the shaft portion in contact with the caulking portion, and the hub wheel and the constant velocity universal joint are detachably coupled in the axial direction. In the bearing device, an end surface of the crimping portion that comes into contact with a shoulder portion of the outer joint member is formed into a flat surface by turning, and the end surface is formed by concentric turning stitches.

  Thus, the inner ring is fixed in the axial direction by the crimping portion formed by plastically deforming the end portion of the small diameter step portion radially outward, and the shoulder portion of the outer joint member is brought into contact with the crimping portion. In the wheel bearing device in which the fixing nut is fastened to the male screw formed at the end of the shaft portion and the hub wheel and the constant velocity universal joint are detachably coupled in the axial direction, the shoulder portion of the outer joint member The end surface of the caulking portion that comes into contact with is formed into a flat surface by turning, and this end surface is composed of concentric turning stitches, so that the caulking portion of the hub wheel and the shoulder portion of the outer joint member are smooth. It is possible to provide a wheel bearing device capable of realizing slipping and preventing the occurrence of stick-slip noise over a long period of time.

  In addition, as in the invention described in claim 2, the end surface of the crimped portion may be set to a predetermined surface roughness by shot blasting after turning, or in claim 3. As in the invention, the end surface of the crimping portion may be set to a predetermined surface roughness by lapping after turning. Thereby, the burr | flash and the edge of a corner | angular part by turning are removed, a friction coefficient becomes small, a contact surface can be slid smoothly, and generation | occurrence | production of a stick-slip sound can be suppressed.

  If the surface roughness of the end face of the caulking portion is set in the range of Ra 1.5 to 4.5 as in the invention described in claim 4, the surface is prevented from being caught by unevenness, and the stick Generation of slip noise can be reliably prevented.

  Further, as in the invention described in claim 5, if the shoulder of the outer joint member has a surface roughness Ra of 1.5 or less by turning or grinding, a reference for internal processing of the outer joint member In addition to being able to form a surface, the coefficient of friction with the caulking portion in contact with the shoulder can be reduced, and the occurrence of stick-slip noise can be suppressed.

  Further, as in the invention described in claim 6, the serration of the hub wheel is formed parallel to the axis, and the serration of the shaft portion is provided with a twist angle inclined at a predetermined angle with respect to the axis. Therefore, even if a preload is applied to the serration fitting portion and a large twist occurs in the drive shaft, a sudden slip does not occur on the abutting surface between the caulking portion of the hub wheel and the outer joint member. Slip noise can be further prevented.

  The wheel bearing device according to the present invention integrally has an outer member integrally formed with a double row outer rolling surface on the inner periphery, and a wheel mounting flange for mounting the wheel on one end, and on the outer periphery. A double row comprising a hub wheel formed with a cylindrical small-diameter step portion extending in the axial direction and at least one inner ring press-fitted into the small-diameter step portion of the hub wheel, the double row facing the double row outer rolling surface An inner member formed with an inner rolling surface, a double row rolling element housed between the inner member and the outer member so as to roll freely, and serrations on the hub wheel. And an outer joint member of a constant velocity universal joint integrally having a shaft portion fitted therein, and the inner ring is formed by a caulking portion formed by plastically deforming an end portion of the small diameter step portion radially outward. While being fixed in the axial direction, the shoulder portion of the outer joint member is in contact with the caulking portion. In a wheel bearing device in which a fixing nut is fastened to a male screw formed at an end portion of the shaft portion, and the hub wheel and a constant velocity universal joint are detachably coupled in an axial direction, a shoulder portion of the outer joint member and The end surface of the crimping portion that comes into contact is formed into a flat surface by turning, and this end surface is formed by concentric turning stitches, so that the smoothing between the crimping portion of the hub wheel and the shoulder portion of the outer joint member is smooth. It is possible to provide a wheel bearing device capable of realizing slipping and preventing the occurrence of stick-slip noise over a long period of time.

  A vehicle body mounting flange to be attached to the knuckle on the outer periphery, an outer member in which a double row outer rolling surface is integrally formed on the inner periphery, and a wheel mounting flange to mount a wheel on one end The inner rolling surface is formed on the outer periphery and is opposed to one of the outer rolling surfaces of the double row, and a small-diameter step portion extending in the axial direction from the inner rolling surface is formed on the outer periphery. An inner member comprising a hub ring formed with serrations, and an inner ring press-fitted into a small-diameter step portion of the hub ring and having an inner rolling surface facing the other of the outer rolling surfaces of the double row on the outer periphery. A double row rolling element accommodated between the rolling surfaces of the inner member and the outer member via a cage, and a shaft portion fitted into the hub wheel via serrations. And an outer joint member of a constant velocity universal joint integrally having an end of the small diameter step portion The inner ring is fixed in the axial direction by a caulking portion formed by plastically deforming the outer side in the radial direction, and the shaft portion is in a state where the shoulder portion of the outer joint member is in contact with the caulking portion. In a wheel bearing device in which a fixing nut is fastened to a male screw formed at an end of the wheel and the hub wheel and the constant velocity universal joint are detachably coupled in the axial direction, the abutting against the shoulder of the outer joint member The end surface of the crimped portion is formed into a flat surface by turning, and the end surface is formed of concentric turning stitches, and the end surface is shot blasted after turning, and the surface roughness is Ra 1.5 to The range is set to 4.5.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing an embodiment of a wheel bearing device according to the present invention, FIG. 2 is a schematic view showing the surface properties of a caulking portion, and FIG. 3 shows the surface roughness of the end surface of the caulking portion. It is a graph which shows the relationship with a stick slip sound. In the following description, the side closer to the outer side of the vehicle when assembled to the vehicle is referred to as the outer side (left side in FIG. 1), and the side closer to the center is referred to as the inner side (right side in FIG. 1).

  This wheel bearing device is called the third generation for driving wheels, and includes an inner member 3 composed of a hub wheel 1 and an inner ring 2 press-fitted into the hub wheel 1, and a double row of inner members 3. And an outer member 5 inserted through rolling elements (balls) 4 and 4.

  The hub wheel 1 integrally has a wheel mounting flange 6 for attaching a wheel (not shown) to an end portion on the outer side, one (outer side) inner rolling surface 1a on the outer periphery, and this inner rolling. A cylindrical small-diameter step portion 1b extending in the axial direction from the surface 1a is formed, and a serration (or spline) 1c for torque transmission is formed on the inner periphery. Further, hub bolts 6a for fastening the wheels are planted on the wheel mounting flange 6 at equal intervals in the circumferential direction.

  The inner ring 2 is formed with the other (inner side) inner rolling surface 2a on the outer periphery, and is press-fitted into the small-diameter step portion 1b of the hub ring 1 via a predetermined squeeze. The end portion of the small-diameter stepped portion 1b is fixed in the axial direction to the hub wheel 1 in a state where a predetermined bearing preload is applied by a crimping portion 7 formed by plastic deformation, so-called swing caulking.

  The outer member 5 integrally has a vehicle body mounting flange 5b to be attached to a knuckle (not shown) on the outer periphery, and faces the double row inner rolling surfaces 1a, 2a of the inner member 3 on the inner periphery. Double row outer rolling surfaces 5a and 5a are integrally formed. And the double row rolling elements 4 and 4 are accommodated so that rolling is possible between the rolling surfaces of the outer member 5 and the inner member 3 via the holder | retainers 8 and 8. FIG. In addition, seals 9 and 10 are attached to the opening of the annular space formed between the outer member 5 and the inner member 3 to prevent leakage of lubricating grease sealed inside the bearing, rainwater from the outside, Dust and the like are prevented from entering the bearing.

  The constant velocity universal joint 11 includes an outer joint member 14 that integrally includes a shoulder portion 12 that forms the bottom of a cup-shaped mouth portion (not shown) and a shaft portion 13 that extends from the shoulder portion 12 in the axial direction. Yes. A serration (or spline) 13 a that is engaged with the serration 1 c of the hub wheel 1 is formed on the outer periphery of the shaft portion 13. The serration 1c of the hub wheel 1 is formed in parallel to the axis, while the serration 13a of the shaft portion 13 is provided with a twist angle inclined by a predetermined angle with respect to the axis. The shaft portion 13 is fitted into the hub wheel 1 until the shoulder portion 12 of the outer joint member 14 abuts against the caulking portion 7, and is press-fitted into the serration 1 c of the hub wheel 1. Further, the fixing nut 15 is fastened with a predetermined tightening torque to the male screw 13b formed at the end of the shaft portion 13, and the hub wheel 1 and the outer joint member 14 are coupled so as to be separable in the axial direction. As a result, a preload is applied to the fitting portions of the serrations 1c and 13a and the play in the circumferential direction is killed. Therefore, even if a large twist occurs in the drive shaft, the end surface 7a of the crimping portion 7 and the outer joint member 14 Abrupt slip is unlikely to occur on the contact surface with the shoulder 12.

  The hub wheel 1 is formed of medium and high carbon steel containing carbon of 0.40 to 0.80 wt% such as S53C, and includes an inner rolling surface 1a and an inner portion of a wheel mounting flange 6 that serves as a seal land portion of the seal 9 on the outer side. The surface hardness is hardened to a range of 58 to 64 HRC by induction hardening from the side base 6b to the small diameter step 1b. In addition, the crimping part 7 is made into the surface hardness after a forge process. Thereby, while having sufficient mechanical strength with respect to the rotational bending load applied to the wheel mounting flange 6, the fretting resistance of the small-diameter step portion 1b to which the inner ring 2 is fitted is improved, and the hub wheel 1 is improved. Durability is further improved.

  The outer member 5 is formed of medium and high carbon steel containing 0.40 to 0.80 wt% of carbon such as S53C, and at least the double row outer rolling surfaces 5a and 5a have a surface hardness in the range of 58 to 64HRC by induction hardening. Has been cured. On the other hand, the inner ring 2 and the rolling element 4 are made of high carbon chrome bearing steel such as SUJ2, and are hardened in the range of 58 to 64 HRC to the core part by quenching. Further, the outer joint member 14 is formed of medium and high carbon steel containing 0.40 to 0.80 wt% of carbon such as S53C, and has a surface hardness of 58 to 58 by induction quenching from the shoulder portion 12 to the base portion of the shaft portion 13. Hardened to a range of 64 HRC.

  Here, the wheel bearing device constituted by a double row angular contact ball bearing in which the rolling element 4 is a ball is illustrated, but the present invention is not limited to this, and a double row tapered roller bearing using a tapered roller for the rolling element 4 is used. May be. In addition, here, the third-generation wheel bearing device in which the inner rolling surface is directly formed on the outer periphery of the hub wheel is illustrated, but the present invention is not limited to this, and a pair of inner rings are press-fitted into the small-diameter step portion of the hub wheel. The first or second generation structure may be used.

  Here, since the stick-slip noise is considered to be generated due to discontinuous slip between the shoulder portion 12 of the outer joint member 14 and the end surface 7a of the caulking portion 7, these abutments Generation of stick-slip noise can be suppressed by smoothly sliding the surfaces. In order to smoothly slide the contact surface, the present applicant pays attention to the finished surface state of the end surface 7a of the crimped portion 7, and verifies the relationship between the surface roughness of the end surface 7a and the occurrence of stick-slip noise. did.

  There are generally two types of processing methods for the shoulder portion 12 of the outer joint member 14 that abuts the end surface 7a of the crimping portion 7: turning and grinding. Since the contact surface of the shoulder portion 12 is used as a reference surface for internal processing of the outer joint member 14, the surface roughness by finishing of the turning and grinding is set to Ra 1.5 or less. On the other hand, the end surface 7a of the caulking portion 7 that comes into contact with the shoulder portion 12 is formed by swinging caulking or turning after rocking caulking, and generally has a surface roughness of about Ra 4.5 to 6.5. It has been finished.

  In this embodiment, the end surface 7a of the caulking portion 7 is formed into a flat surface by turning after swing caulking. As schematically shown in FIG. 2, the end surface 7a is formed of concentric turning lines, and the end surface 7a is further set to a surface roughness Ra of 4.5 or less by shot blasting. . Thereby, the burr | flash and the edge of a corner | angular part by turning are removed, a friction coefficient becomes small, a contact surface can be slid smoothly, and generation | occurrence | production of a stick-slip sound can be suppressed.

  In the experiment conducted by the present applicant, the surface roughness of the shoulder 12 of the outer joint member 14 is Ra1.5, and the surface roughness of the end surface 7a of the crimped portion 7 is Ra1.5, 3.5, 4 .5, 5.1, and 6.1, as shown in FIG. 3, in Ra 5.1 and 6.1, a stick-slip sound was generated at a load torque of 350 N · m, whereas Ra 4.5 Below, the result that stick-slip noise does not occur was obtained. In addition, it is not preferable that the surface roughness of the end surface 7a of the caulking portion 7 is Ra 1.5 or less because the processing time increases and the shape of the end surface 7a is deformed to reduce the flatness. Further, when the surface roughness becomes worse than Ra4.5, it is considered that a stick-slip sound is generated due to catching by unevenness on the surface. Ra is one of the JIS roughness shape parameters (JIS B0601-1994), and means the arithmetic average roughness, that is, the average value of the absolute value deviation from the average line.

  Here, the end surface 7a of the caulking portion 7 is formed on a flat surface where concentric turning marks remain, and thereafter, the surface roughness is restricted to Ra 4.5 or less by shot blasting, but not limited thereto. Alternatively, lapping may be performed after turning, and the surface roughness may be set to Ra 4.5 or less.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and is merely an example, and various modifications can be made without departing from the scope of the present invention. Of course, the scope of the present invention is indicated by the description of the scope of claims, and further, the equivalent meanings described in the scope of claims and all modifications within the scope of the scope of the present invention are included. Including.

  A wheel bearing device according to the present invention includes a hub ring and an inner ring press-fitted into the hub ring, and in a self-retained structure in which the inner ring is fixed in the axial direction by the crimping portion, the butted state is in contact with the crimping portion. The outer joint member is fitted inside, a fixing nut is fastened to the outer joint member, and the present invention can be applied to a wheel bearing device in which the hub wheel and the outer joint member are detachably coupled in the axial direction.

It is a longitudinal section showing one embodiment of a wheel bearing device concerning the present invention. It is a schematic diagram which shows the surface property of a crimping part. It is a graph which shows the relationship between the surface roughness of the end surface of a crimping part, and a stick slip sound. It is a longitudinal cross-sectional view which shows the conventional wheel bearing apparatus. (A) is a fragmentary perspective view which shows the inner ring single-piece | unit of FIG. (B) is a partial perspective view showing a single inner ring as in the above.

Explanation of symbols

1. Hub wheel 1a, 2a ... Inner rolling surface 1b ... Small diameter step 1c, 13a ...・ Serration 2 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Inner ring 3 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Inner member 4 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Rolling element 5 ・ ・ ・· · · Outer member 5a · · · Outer rolling surface 5b · · · Body mounting flange 6 · · · Wheel mounting flange 6a ... hub bolt 6b ... base 7 ... caulking part 7a ... ... End face 8 ... Cage 9, 10 ... Seal 11 ... Constant velocity universal joint 12 ...・ ・ ・ ・ ・ ・ Shoulder 13 ・ ・ ・ ・ ・ ・ ・ ・ Shaft 13b ・ ・ ・ ・ ・ ・ ・ ・ ・ Male 14 ... Outer joint member 15 ... Fixing nut 50 ... Wheel bearing device 51 ... ··········· Hub wheel 51a ·········· Small diameter stepped portion 52 ·········· Double row rolling bearing 53 ······ Constant velocity universal joint 54 ... Wheel mounting flange 55 ... Outer ring 55a ... Outer rolling surface 56 ... · Inner ring 56a ·········· Inner rolling surfaces 56b, 56c ··· End surface 57 ····························· 59 ... shoulder 60 ... shaft 61 ... outer joint member 62 ...・ Male thread 63 ・ ・ ・ ・ ・ ・ ・ Fixing nut 64 ・ ・....... grease groove

Claims (6)

An outer member in which a double row outer rolling surface is integrally formed on the inner periphery;
A hub wheel integrally having a wheel mounting flange for mounting a wheel at one end and having a cylindrical small-diameter step portion extending in the axial direction on the outer periphery, and at least one press-fitted into the small-diameter step portion of the hub ring An inner member formed of two inner rings and formed with a double-row inner rolling surface facing the double-row outer rolling surface,
A double row rolling element housed so as to be freely rollable between both rolling surfaces of the inner member and the outer member;
An outer joint member of a constant velocity universal joint integrally having a shaft portion fitted into the hub wheel via a serration;
The inner ring is fixed in the axial direction by a caulking portion formed by plastically deforming an end portion of the small diameter step portion radially outward,
With the shoulder portion of the outer joint member in contact with the caulking portion, a fixing nut is fastened to the male screw formed at the end portion of the shaft portion, so that the hub wheel and the constant velocity universal joint are in the axial direction. In a wheel bearing device coupled in a separable manner,
The wheel bearing device according to claim 1, wherein an end face of the caulking portion that comes into contact with a shoulder portion of the outer joint member is formed into a flat surface by turning, and the end face is formed by concentric turning stitches.   2. The wheel bearing device according to claim 1, wherein an end surface of the caulking portion is set to a predetermined surface roughness by shot blasting after turning. 3.   2. The wheel bearing device according to claim 1, wherein an end surface of the caulking portion is set to a predetermined surface roughness by performing lapping after turning. 3.   The wheel bearing device according to any one of claims 1 to 3, wherein a surface roughness of an end face of the caulking portion is set in a range of Ra 1.5 to 4.5.   The wheel bearing device according to any one of claims 1 to 4, wherein the shoulder of the outer joint member has a surface roughness Ra of 1.5 or less by turning or grinding.   The wheel according to any one of claims 1 to 5, wherein serrations of the hub wheel are formed parallel to an axis, and a serration of the shaft portion is provided with a twist angle inclined by a predetermined angle with respect to the axis. Bearing device.

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