JP2007091078A - Bearing device for wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing device for a wheel which is light and made compact without lowering strength and rigidity of an outside member. <P>SOLUTION: A peripheral surface 16 slightly inclined by holding a car body mounting flange 5b and a cylindrical fitting surface 17 to be fitted on a knuckle are formed on the bearing device for the wheel constituted of second and fourth generation structures, a circular arc corner part 18 is formed on an intersection part of the car body mounting flange 5b and the peripheral surface 16, and a recessed part 20 extending in the axial direction is partially formed at a position corresponding to a screw hole 19 of this corner part 18. Consequently, no trouble is caused to working of a lower hole and the screw hole 19 even when the screw hole 19 is formed on the recessed part 20 by setting PCD of the screw hole 19 in a small diameter so that its part opens. Accordingly, it is possible to provide the bearing device for the wheel capable of endlessly making the PCD of the screw hole 19 small in diameter, light and attempted to compact without lowering strength and rigidity of the outside member 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wheel bearing device for rotatably supporting a wheel of an automobile or the like, and more particularly to a wheel bearing device in which an outer member is reduced in weight and size.

  2. Description of the Related Art Conventionally, a wheel bearing device for supporting a wheel of an automobile or the like is such that a hub wheel for mounting a wheel is rotatably supported via a rolling bearing, and there are a drive wheel and a driven wheel. For structural reasons, an inner ring rotation method is generally used for driving wheels, and an inner ring rotation method and an outer ring rotation method are generally used for driven wheels. As the wheel bearing device, a double-row angular ball bearing having a desired bearing rigidity, exhibiting durability against misalignment, and having a small rotational torque from the viewpoint of improving fuel efficiency is often used.

  Further, the wheel bearing device has a structure called a first generation in which a wheel bearing composed of a double row angular ball bearing or the like is fitted between a knuckle and a hub wheel constituting a suspension device. Second generation structure in which body mounting flange or wheel mounting flange is formed directly on the outer periphery of the member, third generation structure in which one inner rolling surface is directly formed on the outer periphery of the hub wheel, or hub wheel, etc. It is roughly classified into a fourth generation structure in which the inner rolling surface is directly formed on the outer periphery of the outer joint member of the speed universal joint.

  As an example of such a wheel bearing device, a structure as shown in FIG. 4 is known. This wheel bearing device is referred to as the third generation on the drive wheel side, an outer member 51 serving as a fixing member, and an inner member inserted into the outer member 51 via double rows of balls 52, 52. 53. The outer member 51 integrally has a vehicle body mounting flange 51b on the outer periphery, and double row outer rolling surfaces 51a and 51a are formed on the inner periphery. On the other hand, the inner member 53 is formed with double-row inner rolling surfaces 54a and 55a facing the outer rolling surfaces 51a and 51a of the outer member 51 described above. Of these double-row inner rolling surfaces 54a and 55a, one inner rolling surface 54a is integrally formed on the outer periphery of the hub wheel 54, and the other inner rolling surface 55a is formed on the outer periphery of the inner ring 55, respectively. The inner ring 55 is press-fitted into a cylindrical small-diameter step portion 54b extending in the axial direction from the inner rolling surface 54a of the hub ring 54. The double-row balls 52 and 52 are respectively accommodated between these rolling surfaces and held by the cages 56 and 56 so as to be freely rollable.

  The hub wheel 54 integrally has a wheel mounting flange 57 for mounting a wheel (not shown) on the outer periphery, and a hub bolt 58 for fixing the wheel is planted at a circumferentially equidistant position of the wheel mounting flange 57. It is installed. A serration 54c is formed on the inner periphery of the hub wheel 54, and a stem portion 63 of an outer joint member 61 constituting a constant velocity universal joint is fitted therein. The inner member 53 refers to the hub ring 54 and the inner ring 55. Seals 59 and 60 are attached to the end portion of the outer member 51 to prevent leakage of lubricating grease sealed inside the bearing and intrusion of rainwater, dust and the like into the bearing from the outside.

  The outer joint member 61 integrally has a stem portion 63 that extends in the axial direction from the shoulder portion 62. The stem portion 63 is spline-fitted to the inner periphery of the hub wheel 54 with the shoulder 62 abutting against the end surface of the inner ring 55, and the hub wheel 54 and the outer joint member 61 can be separated by the fixing nut 64. Are combined.

  Such a wheel bearing device is attached to the knuckle 66 together with the brake caliper 65. The knuckle 66 is provided with a center hole 66a into which the outer member 51 is fitted in a central portion, and a plurality of bolt insertion holes 67 are formed around the center hole 66a. The bolt insertion hole 67 corresponds to a screw hole 68 formed in the vehicle body mounting flange 51 b of the outer member 51.

  The brake caliper 65 brakes the rotation of the brake disc 69 by sandwiching the brake disc 69. As shown in FIG. 5, the brake caliper 65 has a fan-shaped outer shape as viewed from the side, and has a small diameter. Two attachment pieces 65a and 65a are provided on the side portion. Bolt insertion holes 70 and 70 penetrating in the thickness direction are formed in the attachment pieces 65a and 65a, respectively.

Here, the mounting pieces 65a, 65a of the brake caliper 65 are sandwiched between the vehicle body mounting flange 51b of the outer member 51 and the knuckle 66, and the bolt insertion hole 70 of the brake caliper 65 and the bolt insertion hole of the knuckle 66 67 and the screw hole 68 of the vehicle body mounting flange 51b are arranged coaxially. In this state, the bolt 71 is inserted from the bolt insertion hole 67 side of the knuckle 66 and screwed into the screw hole 68 of the vehicle body mounting flange 51 b of the outer member 51. Then, the three members of the vehicle body mounting flange 51b of the outer member 51, the knuckle 66, and the mounting piece 65a of the brake caliper 65 are fastened together with a bolt 71 as a common fastening member (see FIG. 4). As a result, the mounting pieces 65a, 65a of the brake caliper 65 are supported by both the vehicle body mounting flange 51b and the knuckle 66 of the outer member 51, so that the support rigidity of the brake caliper 65 is improved and the brake caliper 65 and the brake disc are The relative positional accuracy with respect to 69 is improved, and judder generation during braking can be suppressed.
JP 2005-48817 A

  In recent years, demands for improving fuel efficiency have been severe from the viewpoint of resource saving or pollution, and in this type of wheel bearing device, there is a demand for light weight and compactness as a factor to meet fuel efficiency improvement. In the bearing device, the screw hole 68 provided in the vehicle body mounting flange 51b of the outer member 51 is first penetrated through the vehicle body mounting flange 51b by a drill 72 to form a lower hole 68a as shown in FIG. Next, the screw hole 68 is formed by the tap 73, and the PCD (pitch circle diameter) of the screw hole 68 is preferably set small. This is because if the PCD of the screw hole 68 can be reduced, the height of the vehicle body mounting flange 51b itself can be suppressed, and the brake caliper 65 and the knuckle 66 attached to the vehicle body mounting flange 51b can be miniaturized, thereby reducing weight and size. Advances. However, when the PCD of the screw hole 68 is reduced, the drill 72 is pushed up in contact with the outer diameter of the outer member 51 as shown in FIG. The positional accuracy cannot be secured, and the desired prepared hole 68a cannot be formed. As described above, since the PCD of the screw hole 68 is restricted by the outer diameter of the outer member 51, it has been an obstacle to reducing the weight and size of the outer member 51.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a wheel bearing device that is lightweight and compact without reducing the strength and rigidity of the outer member.

  In order to achieve such an object, the invention according to claim 1 of the present invention has a vehicle body mounting flange integrally attached to the knuckle constituting the suspension device on the outer periphery, and a double row outer rolling surface on the inner periphery. A hub wheel having an outer member formed integrally with a wheel mounting flange for mounting a wheel at one end and a small-diameter step portion extending in the axial direction on the outer periphery, and a small-diameter step portion of the hub ring An inner ring or an outer joint member of a constant velocity universal joint, and an inner member formed with a double row inner rolling surface facing the double row outer rolling surface on the outer periphery, and the inner member And a plurality of rolling elements that are rotatably accommodated between the rolling surfaces of the member and the outer member, and a wheel having a plurality of screw holes into which fastening bolts are screwed to the vehicle body mounting flange. In the bearing device for a vehicle, the outer peripheral surface of the outer member and the vehicle body The intersection of the flange, the recess extending in the axial direction engaged with the screw hole is formed.

  Thus, in the wheel bearing device having the second to fourth generation structures, a recess extending in the axial direction by engaging with the screw hole is formed at the intersection of the outer peripheral surface of the outer member and the vehicle body mounting flange. Therefore, even if the screw hole is formed by setting the PCD of the screw hole to a small diameter so that a part of the hole opens in this recess, it does not interfere with the screw hole processing including the preparation of the lower hole. Absent. Therefore, it is possible to provide a wheel bearing device that can reduce the PCD of the screw hole as much as possible and reduce the weight and size of the outer member without reducing the strength and rigidity of the outer member.

  Further, as in the invention according to claim 2, an outer peripheral surface slightly inclined to the outer side with the vehicle body mounting flange interposed therebetween, and a cylindrical fitting surface fitted into the knuckle are formed, If the arcuate corner is formed by forging at the intersection of the vehicle body mounting flange and the outer peripheral surface, and the recess is formed in this corner, the strength of the vehicle body mounting flange is secured and the outer side It is possible to reduce the weight and size of the member.

  Further, as in the invention described in claim 3, the recess may be partially formed so as to cut out a part of the root portion, or as in the invention described in claim 4. The recess may be formed of a belt-like groove having a predetermined width formed over the entire circumference of the root portion.

  Further, as in the invention according to claim 5, if the fitting surface is set to have a smaller diameter than the outer peripheral surface, and the fastening bolt is inserted from the fitting surface side, the wheel mounting of the hub wheel is performed. Fastening bolts can be screwed together without interfering with the flange, improving assembly / disassembly workability.

  The wheel bearing device according to the present invention integrally has a vehicle body mounting flange for mounting on a knuckle that constitutes a suspension device on the outer periphery, and an outer member having a double row outer rolling surface formed on the inner periphery; A hub wheel integrally having a wheel mounting flange for mounting a wheel at one end and having a small-diameter step portion extending in the axial direction on the outer periphery, and an inner ring or a constant speed fitted in the small-diameter step portion of the hub ring An inner member comprising an outer joint member of a universal joint, and an inner member having a double row inner rolling surface facing the double row outer rolling surface on the outer periphery, and each of the inner member and the outer member A wheel bearing device including a plurality of rolling elements that are rotatably accommodated between rolling surfaces, and wherein a plurality of screw holes into which fastening bolts are screwed are formed in the vehicle body mounting flange. At the intersection of the outer peripheral surface of the Since a recess extending in the axial direction by engaging with the screw hole is formed, even if the screw hole is formed by setting the PCD of the screw hole to a small diameter so that a part of the recess opens, There is no hindrance to the drilling of the screw holes including the drilling of the pilot holes. Therefore, it is possible to provide a wheel bearing device that can reduce the PCD of the screw hole as much as possible and reduce the weight and size of the outer member without reducing the strength and rigidity of the outer member.

  An outer member having a body mounting flange integrally attached to the knuckle constituting the suspension device on the outer periphery, a double row outer rolling surface formed on the inner periphery, and a wheel attachment for attaching the wheel to one end A hub wheel having a flange integrally therewith formed on the outer periphery thereof one inner rolling surface facing the outer rolling surface of the double row, and a small-diameter step portion extending in the axial direction from the inner rolling surface, and An inner member comprising an inner ring press-fitted into a small-diameter step portion of the hub wheel and having an inner ring surface on the outer circumference facing the double-row outer rolling surface, and the inner member and the outer member A plurality of rolling elements that are rotatably accommodated between the respective rolling surfaces, and a plurality of screw holes into which fastening bolts are screwed onto the vehicle body mounting flange. Slightly inclined to the outer side with the body mounting flange A cylindrical fitting surface that is fitted in the knuckle is formed on the peripheral surface, and an arc corner is formed by forging at the intersection of the vehicle body mounting flange and the outer peripheral surface. A recess extending in the axial direction is partially formed at a position corresponding to the screw hole.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 is a longitudinal sectional view showing an embodiment of a wheel bearing device according to the present invention, FIG. 2 is a partially sectional perspective view showing an outer member of FIG. 1, and FIG. 3 (a) is an outer member. The partial cross section perspective view which shows other embodiment, (b) is a partial cross section perspective view which shows the modification of the outward member of FIG. 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 called the third generation for driving wheels, and an inner member 3 composed of a hub wheel 1 and an inner ring 2, and double row rolling elements (balls) 4, 4 are attached to the inner member 3. And an outer member 5 inserted through the outer periphery.

  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, and hub bolts 6 a are implanted at circumferentially equidistant positions of the wheel mounting flange 6. Yes. In addition, one (outer side) inner rolling surface 1a and a cylindrical small-diameter step portion 1b extending in the axial direction from the inner rolling surface 1a are formed on the outer periphery. An inner ring 2 in which the other (inner side) inner raceway surface 2a is formed on the outer periphery is press-fitted into the small-diameter stepped portion 1b via a predetermined shimiro.

  The outer member 5 is made of medium carbon steel containing 0.40 to 0.80 wt% of carbon such as S53C, and a vehicle body mounting flange 5b for mounting on a knuckle (not shown) constituting a suspension device is integrally formed on the outer periphery. And double row outer raceway surfaces 5a and 5a that are opposed to the inner raceway surfaces 1a and 2a. These outer rolling surfaces 5a and 5a are subjected to a hardening process in a range of 58 to 64 HRC by induction hardening. And the double-row rolling elements 4, 4 are accommodated between the outer rolling surfaces 5a, 5a of the outer member 5 and the double-row inner rolling surfaces 1a, 2a facing these, respectively, and the cage 7, 7 is held so as to roll freely. Further, seals 8 and 9 are attached to both ends of the outer member 5 to prevent leakage of lubricating grease sealed inside the bearing and intrusion of rainwater, dust, and the like from the outside into the bearing. The vehicle body mounting flange 5b is formed discontinuously in the circumferential direction, and screw holes 19 (to be described later) to be fastened to the knuckle are formed in the projecting three to four portions.

  The hub wheel 1 is made of medium carbon steel containing 0.40 to 0.80 wt% of carbon such as S53C, and extends from the seal land portion where the outer seal 8 is in sliding contact to the inner rolling surface 1a and the small diameter step portion 1b. Thus, the surface hardness is set to a range of 58 to 64 HRC by induction hardening. On the other hand, the inner ring 2 is made of high carbon chrome bearing steel such as SUJ2, and is hardened in the range of 58 to 64 HRC up to the core portion by quenching.

  A serration (or spline) 1c is formed on the inner periphery of the hub wheel 1, and an outer joint member 11 constituting the constant velocity universal joint 10 is fitted therein. The outer joint member 11 is integrally provided with a cup-shaped mouth portion 12, a shoulder portion 13 that forms the bottom portion of the mouth portion 12, and a stem portion 14 that extends from the shoulder portion 13 in the axial direction. A serration (or spline) 14 a is formed on the outer periphery of the stem portion 14 and is engaged with the serration 1 c of the hub wheel 1. The outer joint member 11 has a shoulder 13 abutted against the inner ring 2, and the hub wheel 1 and the outer joint member 11 are integrally coupled to each other in the axial direction by a fixing nut 15 so as to be separable. In addition, although the double row angular contact ball bearing which used the rolling elements 4 and 4 as a ball | bowl was illustrated here, it is not restricted to this, The double row tapered roller bearing which uses a tapered roller for a rolling element may be sufficient. Further, in the present embodiment, the structure called the third generation is exemplified, but the present invention is not limited to this, and may be, for example, a second generation or a fourth generation structure.

  Here, as shown in FIG. 2, the outer member 5 has a slightly inclined outer peripheral surface 16 formed on the outer side with the vehicle body mounting flange 5b interposed therebetween, and a cylinder fitted inside the knuckle on the inner side. A shaped fitting surface 17 is formed. Further, a large arcuate corner 18 is formed at the intersection of the vehicle body mounting flange 5b and the outer peripheral surface 16 by forging, and the inner fitting surface 17 has a smaller diameter than the outer peripheral surface 16 on the outer side. A fastening bolt (not shown) formed and fastened to the knuckle is inserted from the fitting surface 17 side. And the spot facing process is given in the position corresponding to the screw hole 19 of the base part of the vehicle body attachment flange 5b, and the recessed part 20 extended in an axial direction is partially formed in the corner part 18. As shown in FIG. The recess 20 is formed by cutting with a milling machine, and then a pilot hole is formed by drilling, and a screw hole 19 is formed in the pilot hole by tapping. Here, although the recess 20 is formed by cutting, it is not limited thereto, and may be formed by forging.

  Thus, in this embodiment, since the arcuate corner 18 is formed at the intersection of the vehicle body mounting flange 5b and the outer peripheral surface 16 of the outer member 5 in the outer member 5, the strength of the vehicle body mounting flange 5b. Since the recess 20 extending in the axial direction is formed at a position corresponding to the screw hole 19 in the corner portion 18, the screw hole so that a part of the recess 20 is engaged with the recess 20. Even if the PCD of 19 is set to a small diameter and the screw hole 19 is formed, it does not hinder the processing of the screw hole 19 including the preparation of the lower hole. Therefore, it is possible to provide a wheel bearing device that can reduce the PCD of the screw hole 19 as much as possible and reduce the weight and size of the outer member 5 without reducing the strength and rigidity of the outer member 5. Furthermore, since the fitting surface 17 is set to have a smaller diameter than the outer peripheral surface 16 and the fastening bolt is inserted from the fitting surface 17 side, the fastening bolt can be inserted without interfering with the wheel mounting flange 6 of the hub wheel 1. Since it can be screwed together, assembly / disassembly workability is improved.

  In addition, although what formed the partial recess 20 in the corner part 18 of the vehicle body attachment flange 5b was illustrated, it is not restricted to this, For example, as a means which can make PCD of the screw hole 19 small, the structure shown in FIG. It can be illustrated. In addition, the same code | symbol is attached | subjected to the site | part which has the same site | part or the same function as embodiment mentioned above, and the detailed description is abbreviate | omitted.

  In the outer member 21 shown in FIG. 3A, a belt-like groove 22 is formed over the entire circumference at the root of the vehicle body mounting flange 5 b that intersects the outer peripheral surface 16. The groove 22 is formed to a predetermined depth by turning, and then a pilot hole is formed by drilling, and a screw hole 19 is formed in the pilot hole by tapping. In the present embodiment, the PCD of the screw hole 19 can be reduced in diameter corresponding to the depth of the belt-like groove 22, and, as in the above-described embodiment, the outer member 21 is reduced in weight and size without reducing the strength and rigidity. Can be achieved.

  On the other hand, the outer member 5 ′ shown in FIG. 3B is a modification of the above-described embodiment (FIG. 2), and a large arcuate corner 18 is forged at the intersection of the vehicle body mounting flange 5b and the outer peripheral surface 16. In addition to being formed by processing, a recess 20 ′ is formed at a position corresponding to the screw hole 19, and a part of the outer periphery of the corner 18 is notched. The recess 20 'is formed by turning, and then a pilot hole is formed by drilling, and a screw hole 19 is formed in the pilot hole by tapping. Also in the present embodiment, the PCD of the screw hole 19 can be reduced in diameter corresponding to the step of the recess 20 ′, and as in the above-described embodiment, the outer member 5 ′ can be reduced in weight without reducing the strength and rigidity. Compactness can be achieved.

  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.

  The wheel bearing device according to the present invention can be applied to a wheel bearing device having a second to fourth generation structure in which a vehicle body mounting flange for mounting to a knuckle is integrally provided on the outer periphery of an outer member constituting the bearing portion.

It is a longitudinal section showing one embodiment of a wheel bearing device concerning the present invention. It is a partial cross section perspective view which shows the outward member of FIG. (A) is a partial cross-sectional perspective view which shows other embodiment of the outward member which concerns on this invention. (B) is a partial cross-sectional perspective view showing a modification of the outer member in FIG. 2. It is a longitudinal cross-sectional view which shows the conventional wheel bearing apparatus. FIG. 5 is an exploded perspective view of FIG. 4. (A) is explanatory drawing which shows the process process of the conventional outer member. (B) is explanatory drawing which shows the manufacturing process of an outward member same as the above.

Explanation of symbols

1 .... hub wheel 1a, 2a ... inner raceway surface 1b ... small diameter step 1c, 14a ... ...... Serration 2 ... Inner ring 3 ... Inner member 4 ... Roll Moving body 5, 5 ', 21 ... Outer member 5a ... Outer rolling surface 5b ... Car body mounting flange 6 ...・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Wheel mounting flange 6a ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Hub bolt 7 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Retainer 8 ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ Outer side seal 9 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Inner side seal 10 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Constant velocity universal joint 11 ・ ・ ・ ・ ・ ・ ・ ・... Outer joint member 12 ... Mouse part 13 ...・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Shoulder 14 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Stem 15 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Fixing nut 16 ・ ・ ・ ・ ・ ・ ・ ・ Outer circumference Surface 17 ... Fitting surface 18 ... Corner 19 ... Screw holes 20, 20 '... ...... Recess 22 ... Strip-like groove 51 ... Outer member 51a ... Outward roll Running surface 51b ... Body mounting flange 52 ... Ball 53 ... Inner member 54 ... ························ Hub Rings 54a, 55a ···· Inner Rolling Surface 54b ······ Small Diameter Step 54c .... Inner ring 56 ..... Retainer 57 ...・ ・ ・ ・ ・ ・ ・ ・ Wheel mounting flange 58 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Hub bolts 59, 60 ・ ・ ・ ・ ・ ・ ・ ・ Seal 61 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Outer joint Member 62 ... shoulder 63 ... stem 64 ... fixing nut 65 ... Brake caliper 65a ... Mounting piece 66 ... Knuckle 66a ... Center holes 67, 70 ... ············· Bolt insertion hole 68 ············ Screw hole 68a ····································· Disk 71 ... Bolt 72 ... Drill 73 ... Tap

Claims (5)

An outer member integrally having a vehicle body mounting flange for mounting on a knuckle that constitutes a suspension device on the outer periphery, and a double row outer rolling surface formed on the inner periphery;
A hub wheel integrally having a wheel mounting flange for mounting a wheel at one end thereof and having a small-diameter step portion extending in the axial direction on the outer periphery, and an inner ring or a constant speed fitted in the small-diameter step portion of the hub wheel An inner member formed of an outer joint member of a universal joint, and formed with a double row inner rolling surface facing the double row outer rolling surface on the outer periphery;
A double-row rolling element housed movably between the rolling surfaces of the inner member and the outer member;
In the wheel bearing device in which a plurality of screw holes into which fastening bolts are screwed onto the vehicle body mounting flange are formed,
A wheel bearing device, wherein a recess extending in the axial direction by engaging with the screw hole is formed at an intersection between the outer peripheral surface of the outer member and the vehicle body mounting flange.   An outer peripheral surface that is slightly inclined to the outer side across the vehicle body mounting flange and a cylindrical fitting surface that is fitted into the knuckle are formed, and a circle is formed at the intersection of the vehicle body mounting flange and the outer peripheral surface. The wheel bearing device according to claim 1, wherein an arc-shaped corner is formed by forging, and the recess is formed in the corner.   The wheel bearing device according to claim 1 or 2, wherein the recess is partially formed so as to cut out a part of the root portion.   The wheel bearing device according to claim 1 or 2, wherein the recess is configured by a belt-like groove having a predetermined width formed over the entire circumference of the root portion.   The wheel bearing device according to any one of claims 2 to 4, wherein the fitting surface is set to have a smaller diameter than the outer peripheral surface, and the fastening bolt is inserted from the fitting surface side.

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