JP2008155692A - Bearing device for wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing device for a wheel that makes small a friction coefficient of an abutting surface between an inside member and a shoulder part of an outside joint member and that prevents the generation of stick-slip noise. <P>SOLUTION: In the bearing device for a wheel in which a hub ring 2 and the outside joint member 14 are coupled in such a way as to be capable of transmitting torque via a serration and as to be separable in the axial direction, a large end surface 3b of an inner ring 3 has a low-friction membrane. This low-friction membrane is formed by the molybdenum shot in which a surface layer portion is melted by heat and a lubricant power made from molybdenum disulfide is taken into a prescribed depth from the surface layer and then re-crystallized, diffused, and permeated. Thus, the surface hardness of the abutting surface is increased so that abrasion can be suppressed. Further, the molybdenum disulfide layer is not abraded owing to an engraving phenomenon even if the surface is abraded, so that the low-friction membrane can be secured for a long period of time and thereby the generation of the stick-slip noise caused by a sudden slip on the abutting surface can be prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wheel bearing device for supporting a wheel of a vehicle such as an automobile, and more specifically, a drive wheel (a front wheel of an FF vehicle, FR) provided with a wheel bearing and a constant velocity universal joint and mounted on an independent suspension type suspension. The present invention relates to a wheel bearing device that rotatably supports a rear wheel of a car or an RR car and all wheels of a 4WD car) with respect to 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. 6 are known. The wheel bearing device 50 is connected to a hub wheel 51 for mounting a wheel (not shown) at one end, a double row rolling bearing 52 for rotatably supporting 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 a wheel at one end, an inner rolling surface 51a on the outer periphery, and a cylindrical small-diameter step portion 51b extending in the axial direction from the inner rolling surface 51a. Is formed. The double-row rolling bearing 52 has a vehicle body mounting flange 55b integrally fixed to a suspension device (not shown) on the outer periphery, and an outer side in which double-row outer rolling surfaces 55a and 55a are formed on the inner periphery. It comprises a member 55 and an inner member 57 inserted into the outer member 55 via double rows of balls 56.

  The inner member 57 includes a hub wheel 51 and a separate inner ring 58 that is press-fitted into the small-diameter step portion 51b of the hub wheel 51 and has an inner rolling surface 58a formed on the outer periphery. The inner ring 58 is fixed to the hub wheel 51 in the axial direction by a caulking portion 51 c formed by plastically deforming the end portion of the small-diameter stepped portion 51 b of the hub wheel 51 radially outward.

  The constant velocity universal joint 53 includes an outer joint member 62 integrally including a cup-shaped mouth portion 59, a shoulder portion 60 that forms the bottom of the mouth portion 59, and a shaft portion 61 that extends from the shoulder portion 60 in the axial direction. I have. The outer joint member 62 is fitted into the hub wheel 51 so that torque can be transmitted. That is, the female serration 63 is formed on the inner periphery of the hub wheel 51, and the male serration 64 is formed on the outer periphery of the shaft portion 61 of the outer joint member 62, and both the serrations 63 and 64 are engaged with each other. The shaft portion 61 of the outer joint member 62 is fitted into the hub wheel 51 until the shoulder portion 60 is abutted against the caulking portion 51 c of the hub wheel 51, and the male screw 65 formed at the end of the shaft portion 61. The fixing nut 66 is fastened with a predetermined tightening torque, and the hub wheel 51 and the outer joint member 62 are coupled so as to be separable in the axial direction.

  It is known that a large torque is applied to the wheels of the 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 is twisted. It has been. As a result, the inner member 57 of the double row rolling bearing 52 that supports the drive shaft is also twisted. When a large twist occurs in the drive shaft in this way, if there is a circumferential clearance between the female serration 63 of the hub wheel 51 and the male serration 64 of the shaft portion 61 fitted in the hub wheel 51, the outer side A stick-slip sound due to a sudden slip is generated on the contact surface between the joint member 62 and the inner member 57.

As a countermeasure, in the conventional wheel bearing device 50, a portion that contacts the shoulder portion 60 of the outer joint member 62, that is, a caulking portion 51c of the hub wheel 51 is formed on a flat surface, as shown in FIG. As described above, the concave groove 67 is formed in the central portion in the radial direction of the flat surface of the caulking portion 51c. Then, grease is filled in the concave groove 67. As a result, the surface pressure applied to the caulking portion 51c based on the tightening force of the fixing nut 66 can be reduced, and the plastic deformation of the caulking portion 51c and the loosening of the fixing nut 66 can be prevented, and contact with the grease can be achieved. Since the friction coefficient of the surface can be lowered, it is possible to reduce the friction energy of the contact surface and prevent the stick slip noise due to a sudden slip from occurring on the contact surface between the shoulder portion 60 and the caulking portion 51c. it can.
JP 2003-136908 A

  However, in this conventional wheel bearing device, processing for forming the concave groove 67 on the flat surface of the caulking portion 51c is necessary, which not only increases the cost but also reduces the strength of the caulking portion 51c. There is a fear. Further, the grease filled in the concave groove 67 of the caulking portion 51c leaks during operation, and it becomes difficult to prevent the occurrence of stick-slip noise over a long period of time.

  The present invention has been made in view of such circumstances, and a wheel bearing device in which the friction coefficient of the contact surface between the inner member and the shoulder of the outer joint member is reduced to prevent the occurrence of stick-slip noise. The purpose is to provide.

  In order to achieve such an object, the invention according to claim 1 of the present invention includes an outer member having a double row outer raceway formed on the inner periphery, and a wheel mounting flange for mounting a wheel at one end. And a hub ring formed with 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 inner rolling surface facing the running surface is formed, and a double-row rolling element accommodated so as to roll between the inner member and the outer member. A constant velocity universal joint connected to the inner member, and an outer joint member of the constant velocity universal joint includes a cup-shaped mouth portion, a shoulder portion that forms the bottom portion of the mouth portion, and the shoulder portion. A stem portion extending in the axial direction and fitted into the inner member so as to transmit torque via serrations. In a wheel bearing device, wherein the inner member and the outer joint member are fastened so as to be separable in the axial direction with the shoulder portion being in contact with the inner member, the inner member and the outer joint member A low friction film is formed by shot peening on at least one of the contact surfaces with the shoulder.

  As described above, in the wheel bearing device in which the inner member and the outer joint member constituting the wheel bearing are fastened so as to be able to transmit torque via serration and separable in the axial direction, the inner member and the outer joint member Since a low-friction film is formed by shot peening on at least one of the contact surfaces with the shoulder portion, the surface hardness of the contact surface is increased and wear can be suppressed. It is possible to prevent the occurrence of stick-slip sound due to a sudden slip on the contact surface.

  Preferably, as in the invention described in claim 2, the low-friction film melts the surface layer portion of the contact surface with heat and takes in the lubricant powder made of molybdenum disulfide from the surface layer to a predetermined depth. If it is formed of molybdenum shot that has been crystallized and diffused and penetrated, the molybdenum disulfide layer will not disappear due to the engraving phenomenon even if the surface is worn, and a low friction film can be secured over a long period of time.

  Further, as in the invention according to claim 3, the inner ring is fixed in the axial direction by a crimping portion formed by plastically deforming an end portion of the small-diameter step portion of the hub wheel radially outward, If the caulking portion is formed on a flat surface and the low friction film is formed on the surface of the caulking portion, the surface hardness of the caulking portion can be increased and wear can be suppressed. It is possible to prevent the occurrence of a stick-slip sound due to a sudden slip on the contact surface with the part.

  Preferably, if the low friction film is formed on the chamfered portion on the large end surface and the outer diameter side of the inner ring as in the invention described in claim 4, the residual compressive stress of the inner ring is increased, and the caulking process is performed. Accordingly, sufficient strength can be secured against hoop stress generated in the inner ring, and durability can be improved.

  Further, as in the invention according to claim 5, if the outer side inner rolling surface of the double row inner rolling surfaces is formed directly on the hub wheel, the rigidity of the hub wheel is increased, Lightweight and compact.

  The wheel bearing device according to the present invention integrally includes an outer member having a double row outer raceway formed on the inner periphery, and a wheel mounting flange for mounting the wheel on one end, and an axial direction on the outer periphery. A hub ring formed with a cylindrical small-diameter step portion extending to the inner ring, and at least one inner ring press-fitted into the small-diameter step portion of the hub ring. An inner member on which a running surface is formed, a double-row rolling element housed between the rolling surfaces of the inner member and the outer member, and connected to the inner member, etc. A constant velocity universal joint, and an outer joint member of the constant velocity universal joint includes a cup-shaped mouth portion, a shoulder portion that forms the bottom portion of the mouth portion, an axial direction extending from the shoulder portion, and the inner member. A stem portion that is internally fitted so that torque can be transmitted through the serration, and the shoulder portion is the inner portion. In the wheel bearing device in which the inner member and the outer joint member are fastened so as to be separable in the axial direction in a state of abutting with the member, at least one of contact surfaces of the inner member and the shoulder portion of the outer joint member A low-friction film is formed on the contact surface by shot peening treatment, so that the surface hardness of the contact surface is increased and wear can be suppressed, and stick-slip noise due to sudden slip on the contact surface Can be prevented.

  A vehicle body mounting flange is integrally formed on the outer periphery, an outer member having a double row outer rolling surface formed on the inner periphery, a wheel mounting flange is integrally formed on one end, and the double row outer rolling is formed on the outer periphery. A hub ring formed with an inner rolling surface facing one of the running surfaces, a cylindrical small-diameter stepped portion extending in the axial direction from the inner rolling surface, and a small-diameter stepped portion of the hub wheel are press-fitted to the outer periphery. An inner member formed of an inner ring formed with an inner rolling surface facing the other of the double row outer rolling surfaces, and accommodated in a freely rollable manner between both rolling surfaces of the inner member and the outer member. And a constant velocity universal joint connected to the hub wheel. An outer joint member of the constant velocity universal joint includes a cup-shaped mouth portion and a shoulder forming the bottom portion of the mouth portion. And a stem that extends in an axial direction from the shoulder and is fitted in the hub wheel so as to transmit torque via serrations. In the wheel bearing device in which the hub wheel and the outer joint member are fastened to be separable in the axial direction in a state where the shoulder portion is in contact with the large end surface of the inner ring, and the large end surface of the inner ring This low-friction film is made of molybdenum shot that is melted and diffused by melting the surface layer part with heat, taking in the lubricant powder composed of molybdenum disulfide from the surface layer to a predetermined depth, and recrystallizing it. Is formed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 is a longitudinal sectional view showing a first embodiment of a wheel bearing device according to the present invention, FIG. 2 is an enlarged view of a main part of FIG. 1, and FIG. 3 is a main part showing an outer joint member of FIG. It is an enlarged view. In the following description, the side closer to the outer side of the vehicle in a state assembled to the vehicle is referred to as the outer side (left side in the drawing), and the side closer to the center is referred to as the inner side (right side in the drawing).

  This wheel bearing device is referred to as a third generation for driving wheels, and is a double row rolling element (ball) accommodated in a freely rollable manner between the inner member 1, the outer member 10, and both members 1, 10. 8 and 8. The inner member 1 includes a hub ring 2 and an inner ring 3 press-fitted into the hub ring 2.

  The hub wheel 2 integrally has a wheel mounting flange 4 for attaching a wheel (not shown) to an end portion on the outer side, one (outer side) inner rolling surface 2a on the outer periphery, and this inner rolling. A cylindrical small diameter step 2b extending in the axial direction from the surface 2a is formed, and a serration (or spline) 5 for torque transmission is formed on the inner periphery. Hub bolts 6 for attaching the wheels are implanted at equal circumferential positions of the wheel attachment flanges 4.

  The hub wheel 2 is made of medium and high carbon steel containing 0.40 to 0.80% by weight of carbon, such as S53C, and a base portion serving as a seal land portion in which an inner rolling surface 2a and an outer side seal 11 described later come into sliding contact. 7 to a small diameter step portion 2b, and the surface hardness is set to a range of 58 to 64HRC by induction hardening. And the inner ring | wheel 3 is press-fitted and fixed to the small diameter step part 2b of the hub ring | wheel 2 via the predetermined | prescribed shimiro. On the other hand, the inner ring 3 is made of high carbon chrome steel such as SUJ2, the other (inner side) inner rolling surface 3a is formed on the outer periphery, and the core is hardened in the range of 58 to 64 HRC by quenching. .

  The outer member 10 integrally has a vehicle body mounting flange 10b for mounting to the vehicle body (not shown) on the outer periphery, and has a double row facing the inner rolling surfaces 2a and 3a of the inner member 1 on the inner periphery. Outer rolling surfaces 10a and 10a are integrally formed. The outer member 10 is made of medium and high carbon steel containing 0.40 to 0.80% by weight of carbon such as S53C, and the double row outer rolling surface 10a10a is hardened to a surface hardness of 58 to 64 HRC by induction hardening. Processing has been applied. And the double-row rolling elements 8 and 8 are accommodated so that rolling is possible via the holder | retainers 9 and 9 between each rolling surface 10a, 2a and 10a, 3a. Seals 11 and 12 are attached to the opening of the annular space formed between the outer member 10 and the inner member 1 to prevent leakage of the lubricating grease sealed inside the bearing and from the outside. It prevents rainwater and dust from entering the bearing.

  In the present embodiment, a double row angular contact ball bearing using a ball as the rolling element 8 is exemplified. However, the present invention is not limited to this. For example, a double row tapered roller bearing using a tapered roller as the rolling element 8 is provided. Also good. In addition, here, a so-called third generation structure in which one inner rolling surface 2a is directly formed on the outer periphery of the hub wheel 2 is illustrated, but although not illustrated, a pair of inner rings are provided on the small-diameter step portion of the hub wheel. It may be a so-called first or second generation structure that is press-fitted.

  The constant velocity universal joint 13 includes an outer joint member 14, a joint inner ring, a cage and a torque transmission ball (not shown). The outer joint member 14 is made of medium and high carbon steel containing 0.40 to 0.80% by weight of carbon such as S53C, and has a cup-shaped mouth portion (not shown) and a shoulder portion 15 that forms the bottom of the mouth portion. The stem portion 16 extending in the axial direction from the shoulder portion 15 is integrally provided.

  The stem portion 16 has a serration (or spline) 16a that engages with the serration 5 of the hub wheel 2 on the outer periphery, and a male screw 16b formed at the end of the serration 16a. The stem 16 is inserted into the inner member 1 until the shoulder 15 abuts against the large end surface 3b of the inner ring 3, and the large end surface 3b and the shoulder 15 are in contact with each other and fixed to the male screw 16b. The nut 17 is screwed, and the inner member 1 and the outer joint member 14 are fastened with a predetermined tightening torque so as to be separable in the axial direction.

  Here, in this embodiment, as shown in FIG. 2, a low friction film is formed by shot peening treatment on the large end surface 3b of the inner ring 3 that contacts the shoulder 15 of the outer joint member 14 (the film formation range is (Indicated by broken lines in the figure). This low friction coating may be formed by so-called molybdenum coating, in which a lubricant powder made of molybdenum disulfide is shot peened through a binder, but here the base material surface layer is melted with heat, A so-called molybdenum shot is used in which a lubricant powder made of molybdenum disulfide is taken up from the surface layer to about several μm, recrystallized and diffused. As a result, the surface hardness of the large end surface 3b is increased and wear can be suppressed, and even if the surface is worn, the molybdenum disulfide layer is not lost due to the engraving phenomenon, and the low-friction film is formed over a long period of time. Can be secured. Therefore, it is possible to prevent the occurrence of stick-slip noise due to a sudden slip on the contact surface between the shoulder portion 15 and the inner ring 3.

  On the other hand, as shown in FIG. 3, the low friction film may be formed by molybdenum shot on the surface of the shoulder portion 15 of the outer joint member 14 that contacts the large end surface 3 b of the inner ring 3 ( The film formation range is indicated by a broken line in the figure), and may be formed on both the large end surface 3b of the inner ring 3 and the contact surface of the shoulder 15 of the outer joint member 14. Thereby, while improving durability, generation | occurrence | production of the stick slip sound in a contact surface can be prevented further.

  FIG. 4 is a longitudinal sectional view showing a second embodiment of the wheel bearing device according to the present invention, and FIG. 5 is an enlarged view of a main part of FIG. This embodiment basically differs from the above-described embodiment only in the configuration of the inner member, and other parts having the same parts or the same functions are denoted by the same reference numerals and detailed description thereof is omitted. To do.

  This wheel bearing device is referred to as the third generation for driving wheels, and is a double row rolling element (ball) accommodated in a freely rolling manner between the inner member 18 and the outer member 10, and both members 1 and 18. 8 and 8. The inner member 18 includes a hub ring 19 and the inner ring 3 press-fitted into the hub ring 19.

  The hub wheel 19 integrally has a wheel mounting flange 4 at an end portion on the outer side, and has one (outer side) inner rolling surface 2a on the outer periphery and a cylindrical shape extending in the axial direction from the inner rolling surface 2a. A small diameter step 2b is formed, and a serration (or spline) 5 for torque transmission is formed on the inner periphery. The inner ring 3 is press-fitted into the small-diameter step portion 2b of the hub wheel 19 through a predetermined shimiro, and is further axially formed by a caulking portion 20 formed by plastically deforming an end portion of the small-diameter step portion 2b radially outward. It is fixed to. The caulking portion 20 is formed on a flat surface so as to make surface contact with the shoulder portion 15 of the outer joint member 14.

  The hub wheel 19 is made of medium and high carbon steel containing 0.40 to 0.80% by weight of carbon such as S53C, and has a surface hardness of 58 to 58 by induction hardening from the base 7 to the inner rolling surface 2a and the small diameter step 2b. The hardening process is performed in the range of 64 HRC. In addition, the crimping part 20 is made into the surface hardness after a forge process.

  Here, in the present embodiment, as shown in FIG. 5, a low friction coating is formed by molybdenum shot on the large end surface 3b, the outer diameter chamfered portion 3c, and the caulking portion 20 of the inner ring 3 that contacts the shoulder 15 of the outer joint member 14. (The film formation range is indicated by a broken line in the figure). As a result, the surface hardness of the crimped portion 20 can be increased and wear can be suppressed, and a low friction coating can be secured over a long period of time. Further, since the low friction film is formed on the surfaces of the large end surface 3b and the outer diameter chamfered portion 3c of the inner ring 3, the residual compressive stress of the inner ring 3 is increased, and the hoop stress generated in the inner ring 3 due to the caulking process is increased. Also, sufficient strength can be secured. Therefore, it is possible to prevent the occurrence of a stick-slip sound due to a sudden slip on the contact surface between the shoulder portion 15 and the inner ring 3 and improve the durability.

  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 an inner member composed of a hub wheel and an inner ring, and a constant velocity universal joint, and the inner member and the outer joint member of the constant velocity universal joint are detachably fastened in a butted state. Further, the present invention can be applied to wheel bearing devices having first to third generation structures.

It is a longitudinal section showing a 1st embodiment of a bearing device for wheels concerning the present invention. It is a principal part enlarged view of FIG. It is a principal part enlarged view which shows the outer joint member of FIG. It is a longitudinal cross-sectional view which shows 2nd Embodiment of the wheel bearing apparatus which concerns on this invention. It is a principal part enlarged view of FIG. It is a longitudinal cross-sectional view which shows the conventional wheel bearing apparatus. FIG. 7 is an arrow view taken along line VII-VII in FIG.

Explanation of symbols

1, 18 ... inner member 2, 19 ... hub wheel 2a, 3a ... inner rolling surface 2b ... ········ Small diameter step 3 ······························································· Large end surface 3c ··· Chamfered part 4 ············ Wheel mounting flange 5, 16a ··········································································· Rolling element 9 10. Outer member 10a ... Outer rolling surface 10b ... Car body mounting flange 11, 12・ ・ ・ ・ ・ ・ ・ ・ ・ Seal 13 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Constant velocity universal joint 14 ・Outer joint member 15 ... Shoulder 16 ... Stem 16b ...・ ・ ・ ・ ・ Male screw 17 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Fixing nut 20 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Clamping section 50 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・Wheel bearing device 51... Hub wheel 51a, 58a... ············································································· Double row rolling bearing 53・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Wheel mounting flange 55 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Outer member 55a ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Outer rolling surface 55b ・ ・ ・.... Body mounting flange 56 ... 57 ... Inward member 58 ... Inner ring 59 ... Mouse part 60 ...・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Shoulder 60a ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Contact surface 61 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Shaft 62 ・ ・ ・ ・ ・ ・Outer joint member 63 ... Female serration 64 ... Male serration 65 ...・ Male thread 66 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Fixing nut 67 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Dove groove

Claims (5)

An outer member having a double row outer raceway 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;
A constant velocity universal joint connected to the inner member;
The outer joint member of this constant velocity universal joint has a cup-shaped mouth part, a shoulder part that forms the bottom part of the mouth part, and extends axially from the shoulder part, and can transmit torque to the inner member via serrations. A wheel bearing device in which the inner member and the outer joint member are fastened so as to be separable in the axial direction, with the shoulder portion being in contact with the inner member. ,
A wheel bearing device, wherein a low friction film is formed by shot peening on at least one of the contact surfaces of the inner member and the shoulder of the outer joint member.   The low-friction film is formed of a molybdenum shot in which the surface layer portion of the contact surface is melted by heat, the lubricant powder made of molybdenum disulfide is taken from the surface layer to a predetermined depth, recrystallized, and diffused and penetrated. The wheel bearing device according to claim 1.   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 of the hub wheel radially outward, and the caulking portion is formed on a flat surface. The wheel bearing device according to claim 1, wherein the low friction film is formed on a surface of the tightening portion.   The wheel bearing device according to claim 3, wherein the low friction film is formed on a chamfered portion on a large end surface and an outer diameter side of the inner ring.   The wheel bearing device according to any one of claims 1 to 4, wherein an outer-side inner rolling surface of the double-row inner rolling surfaces is directly formed on the hub wheel.

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