JP2006051849A - Bearing device for wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing device for wheel of which the reliability is increased by maintaining a strength of a wheel attaching flange while attaining the miniaturization/weight-reduction of the device, and at the same time, and by increasing and stabilizing the slip torque of a hub bolt. <P>SOLUTION: A bolt insertion hole 6a is drilled in the wheel attaching flange 6, and the hub bolt 7 on which a serration 7a is formed is press-fitted in the bolt insertion hole 6a in this bearing device for wheel. A tempering process is applied after a hub ring 4 is forged, and at the same time, a specified hardened layer 7b is formed by a high-frequency induction hardening on the surface of the serration 7a of the hub bolt 7. Therefore, the strength of the wheel attaching flange 6 is increased, and at the same time, a sufficient difference in harness between the hub bolt 7 and the bolt insertion hole 6a can be ensured. The inner peripheral surface of the bolt insertion hole 6a is plastically deformed, and the serration 7a sufficiently bites into the bolt insertion hole 6a. Thus, the fixing force of the hub bolt 7 can be increased and stabilized without impeding the assembly workability. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wheel bearing device that rotatably supports a wheel of an automobile or the like with respect to a suspension device, and more particularly to a wheel bearing device in which the slip torque of a hub bolt press-fitted into a wheel mounting flange is increased.

  In recent years, demands for improving fuel efficiency have been severe from the viewpoint of resource saving or pollution. The weight reduction of automobile parts, especially wheel bearing devices, has attracted attention as a factor to meet such demands and has been strongly desired for a long time. In particular, among vehicles such as automobiles, light vehicles such as light four-wheel vehicles or small cars are increasingly demanded for light weight as well as cost reduction. Under such circumstances, there have been various proposals related to wheel bearing devices that have been reduced in weight. However, in a wheel bearing device that supports a wheel rotatably together with weight reduction, it is also an important factor to suppress NVH (noise vibration harshness), which is contrary to this weight reduction.

  Among these NVHs, in particular, regarding the low frequency unpleasant noise generated when the brake is operated when the vehicle is running at low speed, the so-called brake judder, the clear cause has not been investigated yet. It has been pointed out that the hub and brake rotor are insufficiently fixed. These wheel hubs and brake rotors are fastened by hub bolts that are press-fitted into the wheel mounting flanges of the hub wheels. It is considered that vibration is generated and brake judder is generated by the vibration.

  In order to fix the hub bolt to the wheel mounting flange, a serration is usually formed on the neck of the hub bolt, and the outer diameter of this serration is formed larger than the inner diameter of the bolt insertion hole, and press-fitted so that the serration bites into the bolt insertion hole. Has been. In order to increase the slip torque of the hub bolt, the press-fitting allowance is set large. However, as the press-fitting allowance increases, there is a risk that the distortion of the wheel mounting flange increases and the surface runout deteriorates, and this surface runout is not preferable because it causes the brake judder.

  In view of this, there has been known one that increases the slip torque of the hub bolt and reduces the distortion of the flange due to the press-fitting of the hub bolt. As shown in FIG. 5, this wheel bearing device has an outer body 51b, 51a, 51a, which is integrally formed with a vehicle body mounting flange 51b attached to the suspension device 50 on the outer periphery, and is formed with double row outer rolling surfaces 51a, 51a on the inner periphery. One inner rolling surface that integrally has a side member 51 and a wheel mounting flange 52 for mounting a wheel (not shown) at one end and faces the double-row outer rolling surfaces 51a, 51a on the outer periphery. 53a, a hub wheel 53 formed with a cylindrical small-diameter step portion 53b extending in the axial direction from the inner raceway surface 53a, and a small-diameter step portion 53b of the hub wheel 53, and are inserted into the outer periphery of the double row. An inner member 55 comprising an inner ring 54 formed with the other inner rolling surface 54a opposite to the rolling surfaces 51a, 51a, and the inner member 55 and the outer member 51 are accommodated so as to be rollable. Double row rolling elements (balls) 56, 56 It is equipped with a.

  A bolt insertion hole 58 into which the hub bolt 57 is press-fitted is formed in the circumference of the wheel mounting flange 52, but the hub bolt 57 is formed in the axial direction of the neck as shown in FIG. Two serrations 59 and 60 are formed in which the tooth surfaces have a spire-shaped cross section. Here, the front side serration 59 has an outer diameter that is press-fitted into the bolt insertion hole 58 at a predetermined press-fitting allowance with respect to the press-fitting direction, and the rear-side serration 60 is smaller than the press-fitting allowance with respect to the press-fitting direction. It is assumed that the outer diameter is press-fitted in the bill. Then, the front side serration 59 is passed through the bolt insertion hole 58 while being press-fitted, and then the rear side serration 60 is press-fitted into the inner surface of the bolt insertion hole 58 whose diameter is reduced by the spring back phenomenon of the bolt insertion hole 58.

  That is, when the hub bolt 57 having the two-stage serrations 59 and 60 is press-fitted into the bolt insertion hole 58, the front serration 59 of the hub bolt 57 temporarily enlarges the hole diameter of the bolt insertion hole 58 and the bolt insertion hole 58 The front serration 59 is transferred and formed on the inner surface, but when the front serration 59 passes, the hole diameter is immediately reduced due to the springback phenomenon. Thereafter, when the rear side serration 60 of the hub bolt 57 enters the bolt insertion hole 58, the rear side serration 60 is inserted into the serration inside the bolt insertion hole 58 with a required press-fitting allowance. Become.

As described above, in the process of press-fitting the hub bolt 57 into the bolt insertion hole 58, the wheel mounting flange 52 is temporarily distorted when passing through the front side serration 59, but after the front side serration 59 passes, By returning to the original state due to the back phenomenon, the deformation of the wheel mounting flange 52 can be suppressed to a small level with less distortion. Then, since the rear side serration 60 stops in the bolt insertion hole 58, the hub bolt 57 is prevented from rotating by the biting action of the rear side serration 60 with respect to the bolt insertion hole 58.
JP 2001-253205 A

  However, in such a conventional wheel bearing device, when the front side serration 59 passes through the bolt insertion hole 58, it returns to its original state due to its springback phenomenon, and is in a state of less distortion and the wheel mounting flange 52. Since the rear side serration 60 stops in the bolt insertion hole 58, the hub bolt 57 is supposed to be prevented from rotating by the biting action of the rear side serration 60 with respect to the bolt insertion hole 58. In addition, the front side serration 59 of the hub bolt 57 itself is partly scraped off during the press-fitting process, and the slip torque of the hub bolt 57 is substantially equal to the press-fitting allowance of the front serration 59 having the larger press-fitting allowance. Will be determined by. Therefore, even if the deformation of the wheel mounting flange 52 is suppressed, an increase in slip torque cannot be expected so much. More recently, with the aim of reducing the weight, the wheel mounting flange 52 has been made slim, and the wheel back flange around the bolt insertion hole 58 has a reduced thickness. There was a risk that the slip torque of the hub bolt 57 could be reduced due to dimensional variation or the like.

  Furthermore, the inventors are studying to improve the modified hardness by subjecting the hub wheel 53 to a tempering treatment in order to compensate for the lack of strength as the wheel mounting flange 52 is slimmed. In the hub wheel that has been hardened by tempering treatment, if the surface hardness of the bolt insertion hole in the wheel mounting flange becomes high and the hardness difference from the hub bolt becomes small, the amount of biting of the serration when press-fitted decreases. The hub bolt slip torque may be reduced.

  The present invention has been made in view of such a conventional problem, and maintains the strength of the wheel mounting flange while reducing the size and weight of the apparatus, and increases and stabilizes the slip torque of the hub bolt to improve reliability. An object of the present invention is to provide a wheel bearing device having an improved height.

  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 formed on the inner periphery, and an outer rolling surface of the double row on the outer periphery. An inner member formed with opposing double-row inner rolling surfaces, and a double-row rolling element housed between the inner member and the outer member so as to roll freely. A wheel mounting flange is integrally provided on either the inner member or the outer member, and a bolt insertion hole is formed in the wheel mounting flange, and a serration is formed at the neck of the bolt insertion hole. In the wheel bearing device in which the hub bolt is press-fitted, the inner member or the outer member provided with the wheel mounting flange is subjected to a tempering treatment after forging, and a predetermined surface is provided on the surface of the serration of the hub bolt. Hardened layer is formed It was adopted formed.

  As described above, in the wheel bearing device in which the bolt mounting hole is formed in the wheel mounting flange, and the hub bolt in which serration is formed in the neck portion is press-fitted into the bolt mounting hole, the inner side in which the wheel mounting flange is provided. Since the member or outer member is tempered after forging and a predetermined hardened layer is formed on the surface of the serration of the hub bolt, the strength of the wheel mounting flange is increased, and the hub bolt and bolt insertion hole A sufficient hardness difference can be ensured during this period, the inner peripheral surface of the bolt insertion hole is plastically deformed, and the serration of the hub bolt sufficiently bites into the bolt insertion hole, so that the fixing force of the hub bolt can be obtained without hindering assembly workability. Can be increased and stabilized. Therefore, it is possible to provide a wheel bearing device with improved reliability and reduced NVH.

  Preferably, as in the invention described in claim 2, since the hardened layer is formed on the surface of the serration in a range of 35 to 50 HRC by induction hardening, the desired hardened layer is relatively easily formed. Can be formed, and the hardness difference from the bolt insertion hole is 10 HRC or more, so that the fixing force of the hub bolt can be increased and stabilized.

  Further, the invention according to claim 3 is formed by dividing the wheel mounting flange into a plurality of partial flanges separated in the circumferential direction by cutting out a portion excluding the vicinity of the bolt insertion hole. A reduction in size and weight can be achieved without impairing the strength and durability of the hub wheel.

  Preferably, as in the invention described in claim 4, the wheel mounting flange divided into the plurality of partial flanges is formed so as to protrude radially from the annular base portion with substantially the same width as the formation portion of the bolt insertion hole. In addition, if the rib is formed so that the side surface on the inboard side of the wheel mounting flange gradually becomes thicker toward the base portion, it is possible to further remove the thickness while ensuring the strength and durability of the hub wheel. As a result, it is possible to reduce the size and weight as much as possible.

  According to a fifth aspect of the present invention, the outer member integrally has a vehicle body mounting flange attached to a knuckle constituting a suspension device on the outer periphery, and a bolt insertion hole is formed in the outer peripheral portion. The vehicle body mounting flange has an R-shaped notch deeply formed between the bolt insertion holes, avoiding the periphery of the bolt insertion holes, from the pitch circle diameter of the bolt insertion holes to the inner diameter side. The weight can be reduced without impairing the rigidity of the device, and the device can be significantly reduced in size and weight in combination with the weight reduction of the hub wheel.

  The wheel bearing device according to the present invention includes an outer member having a double row outer raceway formed on the inner periphery, and a double row inner raceway facing the outer row raceway on the outer periphery. An inner member formed, and a double row rolling element that is rotatably accommodated between the rolling surfaces of the inner member and the outer member, the inner member or the outer member A wheel bearing device in which a wheel mounting flange is integrally provided on either side, a bolt insertion hole is formed in the wheel mounting flange, and a hub bolt with serrations formed in the neck portion is press-fitted into the bolt insertion hole. The inner member or the outer member provided with the wheel mounting flange is subjected to a tempering treatment after forging, and a predetermined hardened layer is formed on the surface of the serrations of the hub bolt. Mounting flange strength In addition, it is possible to secure a sufficient hardness difference between the hub bolt and the bolt insertion hole, the inner peripheral surface of the bolt insertion hole is plastically deformed, and the serration of the hub bolt sufficiently bites into the bolt insertion hole. The fixing force of the hub bolt can be increased and stabilized without hindering. Therefore, it is possible to provide a wheel bearing device with improved reliability and reduced NVH.

  An outer member having a double row outer raceway formed on the inner circumference, and a wheel mounting flange at one end, and one inner raceway facing the double row outer raceway on the outer circumference. And a hub wheel formed with a small-diameter step portion extending in the axial direction from the inner rolling surface, and the other inner side which is press-fitted into the small-diameter step portion of the hub wheel and faces the outer rolling surface of the double row on the outer periphery. An inner member composed of an inner ring formed with a rolling surface, and a double row rolling element that is slidably accommodated between the both rolling surfaces, and the end of the small-diameter step is radially outward. The inner ring is fixed in the axial direction with respect to the hub ring by a caulking portion formed by plastic deformation in the direction, and a bolt insertion hole is formed in the wheel mounting flange. In a wheel bearing device in which a hub bolt with a serration formed at the neck is press-fitted, the hub wheel With the refining after forging is subjected predetermined hardened layer is formed by high frequency induction quenching on the surface of the serration of the hub bolts

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a first embodiment of a wheel bearing device according to the present invention, FIG. 2 (a) is an enlarged view of a main part of FIG. 1, and (b) is a view of a hub bolt in FIG. It is a cross-sectional view along the II-II line. In the following description, the side closer to the outer side of the vehicle when assembled to the vehicle is referred to as the outboard side (left side in the drawing), and the side closer to the center is referred to as the inboard side (right side in the drawing).

This wheel bearing device is on the drive wheel side, and includes an inner member 1 and an outer member 2, double row rolling elements (balls) 3 accommodated between the inner member 1 and the outer member 2, 3 is provided. The inner member 1 includes a hub ring 4 and a separate inner ring 5 that is press-fitted into the hub ring 4.
The hub wheel 4 integrally has a wheel mounting flange 6 for mounting a wheel (not shown) at an end portion on the outboard side, and the wheel is fastened at a circumferentially equidistant position of the wheel mounting flange 6. The hub bolt 7 is press-fitted. Further, on the outer periphery of the hub wheel 4, an inner rolling surface 4a and a cylindrical small diameter step portion 4b extending in the axial direction from the inner rolling surface 4a are formed. The inner ring 5 having the inner raceway surface 5a formed on the outer periphery is press-fitted into the small-diameter step portion 4b, and the end portion of the small-diameter step portion 4b is plastically deformed outward in the radial direction. This prevents the inner ring 5 from coming off in the axial direction with respect to the hub ring 4. In this embodiment, by adopting such a self-retain structure, it is not necessary to manage the preload by tightening firmly with a nut or the like as in the prior art, so that the ease of incorporation into the vehicle is simplified. In addition, the preload amount can be maintained for a long time.

  The outer member 2 integrally has a vehicle body mounting flange 2b for mounting to the vehicle body (not shown) on the outer periphery, and faces the double row inner rolling surfaces 4a and 5a of the inner member 1 on the inner periphery. Double row outer rolling surfaces 2a, 2a are formed. And the double row rolling elements 3, 3 are accommodated between the respective rolling surfaces 4a, 2a and 5a, 2a, and the double row rolling elements 3, 3 are held by the cages 8, 8 so as to roll freely. ing. Further, seals 9 and 9 are attached to both ends of the outer member 2 to prevent leakage of the lubricating grease sealed inside the bearing and intrusion of rainwater and dust from the outside into the bearing.

  Here, the wheel bearing device referred to as the third generation in which the inner raceway surface 4a is formed directly on the outer periphery of the hub wheel 4 is illustrated, but the wheel bearing device according to the present invention is not limited to such a structure. For example, although not shown, a first generation or second generation structure in which a pair of inner rings are press-fitted into a small diameter step portion of the hub ring may be used. The outer member 2 may be an outer ring rotating type in which a wheel mounting flange 6 is provided, and may be either a driven wheel or a driving wheel. Furthermore, although the double row angular contact ball bearing which used the rolling elements 3 and 3 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.

  The hub wheel 4 is formed of medium carbon steel containing 0.40 to 0.80% by weight of carbon such as S53C, and is subjected to a tempering treatment after forging. The tempering treatment makes the structure fine and uniform, and a desired surface hardness is stably obtained, and the mechanical strength of the hub wheel 4 is increased. After cutting each part of the hub wheel 4, the surface hardness is increased by induction hardening over the inner rolling surface 4a on the outboard side, the seal land portion where the seal 9 on the outboard side is in sliding contact, and the small diameter step portion 4b. Curing treatment is performed in the range of 58 to 64 HRC. The caulking portion 4c has a surface hardness of 25 HRC or less after forging and tempering. As a result, the strength of the hub wheel 4 is improved, and the fretting wear of the fitting surface with the inner ring 5 is prevented to improve the durability of the hub wheel 4. In addition, the workability when plastically deforming the caulking portion 4c is improved, and the occurrence of cracks and the like during the processing is prevented, and the reliability of the quality is improved. The inner ring 5 is made of a high carbon chrome bearing steel such as SUJ2, and is hardened in the range of 58 to 64 HRC up to the core part by quenching.

  On the other hand, the outer member 2 is formed of medium carbon steel containing 0.40 to 0.80% by weight of carbon, such as S53C, like the hub wheel 4 described above, and the double row outer rolling surfaces 2a and 2a have high frequency. The surface hardness is hardened by quenching to a range of 58 to 64 HRC.

  The wheel mounting flange 6 of the hub wheel 4 is provided with a plurality of bolt insertion holes 6a into which hub bolts 7 are press-fitted at the circumferentially equidistant positions after forging and tempering, and the hub bolts 7 are press-fitted into the bolt insertion holes 6a. The The hub bolt 7 is made of chromium molybdenum steel (JIS standard SCM435 series or the like), and as shown in FIG. 2, a serration 7a is formed at the neck. The serration 7a is formed with a hardened layer 7b having a surface hardness of 35 to 50 HRC by induction hardening.

  As a result, a very fine martensite layer peculiar to induction hardening is formed on the surface layer, the amount of martensite decreases as the inner layer progresses, and the toughness of the hub bolt 7 can be maintained as the center portion becomes a structure before quenching. In addition, a desired surface hardness can be obtained. That is, the strength of the wheel mounting flange 6 is increased, the hardness difference between the hub bolt 7 and the bolt insertion hole 6a is 10 HRC or more, the inner peripheral surface of the bolt insertion hole 6a is plastically deformed, and the serration 7a of the hub bolt 7 is inserted into the bolt. The slip torque of the hub bolt 7 can be increased and stabilized without sufficiently getting into the hole 6a and hindering assembly workability. Therefore, it is possible to provide a wheel bearing device with improved reliability and reduced NVH. Here, if the hardness is increased beyond 50 HRC, the heat treatment deformation becomes large, which is not preferable. On the other hand, if it is less than 35 HRC, the hardness difference from the bolt insertion hole 6a becomes small, the amount of plastic deformation of the inner peripheral surface of the bolt insertion hole 6a decreases, and an increase in slip torque cannot be expected.

  In the present embodiment, the serrations 7a of the hub bolt 7 are exemplified by those whose surfaces are hardened by induction hardening that can relatively easily set the hardened layer depth, surface hardness, or quenching pattern, but the present invention is not limited thereto. It is sufficient that a desired hardness difference is obtained with respect to the bolt insertion hole 6a. For example, a hardened layer is formed on the surface of the serration 7a by carburizing, quenching or nitriding in a state where the screw portion of the hub bolt 7 is masked. You may do it.

  FIG. 3 is a longitudinal sectional view showing a second embodiment of the wheel bearing device according to the present invention, and FIG. 4 is a side view of FIG. In this embodiment, the hub wheel and the outer member are thinned to reduce the weight, and the same parts and portions having the same functions as those in the above-described embodiment are denoted by the same reference numerals and the details are given. The detailed explanation is omitted.

  The wheel bearing device is a wheel bearing device that rotatably supports a driven wheel, and includes an inner member 10 and an outer member 11, and a double row accommodated between the inner member 10 and the outer member 11. Rolling elements 3 and 3. Here, the inner member 10 refers to the hub ring 12 and the inner ring 5 press-fitted into the hub ring 12.

  The hub wheel 12 is made of medium carbon steel containing 0.40 to 0.80% by weight of carbon such as S53C, and is subjected to a tempering treatment after forging, as in the above-described embodiment. And it has integrally the wheel mounting flange 13 divided | segmented into the circumferential direction several (four) at the edge part of the outer peripheral outboard side, and the hub bolt 7 for fastening a wheel is press-fitted in the outer peripheral part. . The wheel mounting flange 13 is formed so as to protrude radially from the annular base portion with a width substantially the same as the formation portion of each bolt insertion hole 6a by cutting out a portion excluding the vicinity of the hub bolt insertion hole 6a. That is, the wheel mounting flange 13 is divided into a plurality of partial flanges 13a separated in the circumferential direction (see FIG. 4). Further, ribs 13b are formed on the side surface of the wheel mounting flange 13 on the inboard side so as to gradually increase in thickness toward the base. Thereby, weight reduction can be achieved without impairing the rigidity of the hub wheel 12.

  A cylindrical brake pilot portion 16 extending toward the outboard side is formed at the base portion of the wheel mounting flange 13 of the hub wheel 12 to guide the inner diameter surface of the brake rotor 17. Further, a wheel pilot portion 18 extending from the brake pilot portion 16 to the outboard side is formed. The wheel pilot portion 18 guides an inner diameter surface of a wheel hub 19 mounted on the brake rotor 17 so as to be slightly smaller in diameter than the brake pilot portion 16. And the notch is provided in the several places of the circumferential direction, and it is intermittently formed in the shape of a protrusion. Here, the intermittent wheel pilot portion 18 is formed between a plurality of partial flanges 13a (see FIG. 4). Thereby, further weight reduction can be achieved without reducing the rigidity of the hub wheel 12.

  In the present embodiment, as shown in FIG. 4, the wheel mounting flange 13 is cut out at a portion other than the vicinity of the bolt insertion hole 6 a and has an annular shape with substantially the same width as the formation portion of each bolt insertion hole 6 a. Although the example formed so as to protrude radially from the base is not limited to this, although not shown in the drawing, the pitch circle diameter of the bolt insertion hole is determined between the bolt insertion holes by avoiding the periphery of the bolt insertion hole. It may be a wheel mounting flange having a flower shape in which an R-shaped notch is deeply formed to the inner diameter side.

  The outer member 11 integrally has a vehicle body mounting flange 14 attached to a knuckle (not shown) constituting a suspension device on the outer periphery, and a bolt insertion hole 15 is formed in the outer periphery. The vehicle body mounting flange 14 is formed with an R-shaped notch 14b between the bolt insertion holes 15 so as to avoid the periphery of the bolt insertion holes 15 and deeper from the pitch circle diameter of the bolt insertion holes 15 to the inner diameter side. That is, the vehicle body mounting flange 14 is formed by being divided into a plurality of partial flanges 14a separated in the circumferential direction (see FIG. 4). Further, a cylindrical knuckle pilot portion 14c extending in the axial direction from the vehicle body mounting flange 14 is formed at an end portion on the inboard side of the outer member 11, and the knuckle is fitted to the outer diameter surface of the knuckle pilot portion 14c. Is done.

  A cup-shaped seal cap (not shown) is attached to the end of the outer member 11 on the inboard side, and closes the opening of the outer member 11. The seal cap and the seal 9 on the outboard side prevent the lubricating grease sealed inside the bearing from leaking to the outside and preventing rainwater, dust, etc. from entering the bearing from the outside.

  In the present embodiment, the wheel mounting flange 13 of the hub wheel 12 is cut out at a portion other than the vicinity of the bolt insertion hole 6a, and only the portion where each bolt insertion hole 6a is formed has substantially the same width from the annular base to the outer diameter side. Since it is formed so as to protrude, the knuckle bolt can be easily fastened with a tool without being obstructed by the wheel mounting flange 13 when the outer member 11 is fastened to the knuckle. Work can be simplified.

  Further, the hub wheel 12 and the outer member 11 are significantly thinned, and the wheel mounting flange 13 and the vehicle body mounting flange 14 are formed by being divided into four partial flanges 13a and 14a, unlike the conventional disk-shaped flange. Therefore, while ensuring strength and durability, it is possible to reduce the weight and size of the apparatus, and to effectively increase and stabilize the slip torque of the hub bolt 7 even in the slimmed partial flange 13a. It is possible to provide a wheel bearing device that is improved in reliability.

  Here, the thinner the thinned and thinned hub wheel 12, the faster the cooling rate after forging, and as a result, the surface hardness increases. Since the tempering treatment is performed after forging in order to suppress the increase in surface hardness and the variation in hardness, the strength of the wheel mounting flange 6 can be increased, and the hub bolt 7 can be increased as in the above-described embodiment. Since the hardened layer 7b is formed on the serration 7a by induction hardening so that the surface hardness is in the range of 35 to 50 HRC, the hardness difference between the hub bolt 7 and the bolt insertion hole 6a can be sufficiently secured, and the assembly workability is hindered. Therefore, the slip torque of the hub bolt 7 can be increased and stabilized.

  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 is applied to any wheel bearing device of a drive wheel, a driven wheel, or an inner ring rotating type or an outer ring rotating type having a wheel mounting flange into which a hub bolt for mounting a wheel is press-fitted. Can do.

It is a longitudinal section showing a 1st embodiment of a bearing device for wheels concerning the present invention. (A) is the principal part enlarged view same as the above. (B) is a cross-sectional view along the II-II line of the hub bolt in (a). It is a longitudinal cross-sectional view which shows 2nd Embodiment of the wheel bearing apparatus which concerns on this invention. It is a side view same as the above. It is a longitudinal cross-sectional view which shows the conventional wheel bearing apparatus. It is a principal part enlarged view same as the above.

Explanation of symbols

1, 10 ... inner member 2,11 ... outer member 2a ...・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Rolling surface 3 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Rolling elements 4, 12 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Hub wheel 4a, 5a ············ Inner rolling surface 4b ·············· Small diameter step 4c ······· ··································· 5 , 15 ... Bolt insertion hole 6b ... Chamfer 6c on the outboard side ...・ ・ ・ ・ ・ ・ ・ ・ Chamfered part 6d on the inboard side ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Counterbore 7 ・ ・ ・ ・ ・ ・ ・ ・Hub bolt 7a ... Serration 7b ... Hardened layer 7a1・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Front side serration 7a2 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Rear side serration 8 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ ・ Retainer 9 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Seal 13a, 14a ・ ・ ・ ・ ・ ・ Partial flange 13b ・ ・ ・ ・ ・ ・···················································· Body mounting flange 14b ..... Knuckle pilot part 16 ... Brake pilot part 17 ... .... Brake rotor 18・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Wheel pilot part 19 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Wheel hub 50 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・... Suspension device 51 ··············· Outside member 51a Car body mounting flange 52 ... Wheel mounting flange 53 ...・ Hub wheels 53a, 54a ... Inner rolling surface 53b ... Small diameter step 54 ... .... Inner ring 55 ... Inner member 56 ... Rolling element 57 ... ..... Hub bolt 58 ... .... Bolt insertion hole 59 ..... Front side serration 60 ..... Rear side serration

Claims (5)

An outer member having a double row outer raceway formed on the inner periphery;
An inner member in which a double row inner rolling surface facing the outer row rolling surface of the double row is formed on the outer periphery;
A double-row rolling element housed movably between the rolling surfaces of the inner member and the outer member;
A wheel mounting flange is integrally provided on either the inner member or the outer member, and a bolt insertion hole is formed in the wheel mounting flange, and a serration is formed at the neck of the bolt insertion hole. In the wheel bearing device in which the hub bolt is press-fitted,
The inner member or the outer member provided with the wheel mounting flange is tempered after forging, and a predetermined hardened layer is formed on the surface of the serrations of the hub bolt. Wheel bearing device.   2. The wheel bearing device according to claim 1, wherein a hardened layer is formed on the surface of the serration with a surface hardness of 35 to 50 HRC by induction hardening. 3.   3. The wheel bearing device according to claim 1, wherein the wheel mounting flange is divided into a plurality of partial flanges separated in a circumferential direction by cutting out a portion excluding the vicinity of the bolt insertion hole.   The wheel mounting flange divided into the plurality of partial flanges has a width substantially the same as that of the bolt insertion hole and protrudes radially from the annular base portion. The wheel bearing device according to claim 3, wherein the rib is formed so that the side surface gradually becomes thicker toward the base portion.   The outer member integrally has a vehicle body mounting flange attached to a knuckle constituting a suspension device on the outer periphery, and a bolt insertion hole is formed in the outer peripheral portion, and the vehicle body mounting flange is connected to the bolt insertion hole. 5. The wheel bearing device according to claim 1, wherein an R-shaped notch is formed between the bolt insertion holes so as to avoid the periphery of the bolt and deeper from the pitch circle diameter of the bolt insertion holes to the inner diameter side.

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