JP5415999B2 - Wheel bearing device - Google Patents

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 that increases the fatigue strength of a hub wheel and improves strength and durability while reducing weight and size. It relates to the device.

  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. In this double row angular contact ball bearing, a plurality of balls are interposed between a fixed ring and a rotating ring, and a predetermined contact angle is given to the balls so as to contact the fixed ring and the rotating ring.

  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.

  In these wheel bearing devices, in recent years, there are severe demands for improving fuel efficiency in terms of resource saving or pollution. In automobile parts, in particular, weight reduction of a wheel bearing device has been attracting attention and strongly desired as a factor to meet such demands. On the other hand, it is conceivable to make the hub wheel have a hollow structure in order to reduce the weight, but the rigidity is reduced as the weight is reduced. That is, when a large load is applied, the hub wheel may be deformed, and abnormal vibration, early separation of the inner raceway surface, or so-called creep may occur in which the inner ring press-fitted into the hub wheel rotates relative to each other.

  As a solution to these problems, a wheel bearing device as shown in FIG. 8 is known. This wheel bearing device includes an inner member 51, an outer member 52, and double-row balls 53, 53 accommodated between the members 51, 52 so as to roll freely. The inner member 51 includes a hub ring 54 and an inner ring 55 that is press-fitted into the hub ring 54 through a predetermined shimiro.

  The hub wheel 54 integrally has a wheel mounting flange 56 for mounting a wheel (not shown) at one end, and has an inner rolling surface 54a on the outer periphery and an axial direction extending from the inner rolling surface 54a. A small diameter step portion 54 b is formed through the shaft-like portion 57. On the other hand, the inner ring 55 is formed by forming the other inner rolling surface 55a on the outer periphery, press-fitted into the small-diameter step portion 54b of the hub wheel 54, and forming the end portion of the small-diameter step portion 54b by plastic deformation. The portion 58 is fixed in the axial direction.

  The outer member 52 integrally has a vehicle body mounting flange 52b to be attached to a knuckle (not shown) on the outer periphery, and one outer rolling surface facing the inner rolling surface 54a of the hub wheel 54 on the inner periphery. 52a and the other outer rolling surface 52a facing the inner rolling surface 55a of the inner ring 55 are integrally formed. Double-row balls 53 and 53 are accommodated between these rolling surfaces, and are held by the cages 59 and 59 so as to be freely rollable. A seal 60 is attached to seal the annular space between the outer member 52 and the hub wheel 54, and the inner peripheral surface of the end portion of the outer member 52 is formed by pressing from a steel plate. A bottomed short cylindrical cover 61 is attached.

  Here, in the hub wheel 54, a solid structure portion 62 is formed in a portion corresponding only to the fitting surface A of the inner ring 55 of the small diameter step portion 54b, and the other portion is a hollow structure portion 63. That is, both end surfaces 62a and 62b of the solid structure portion 62 are provided on a plane orthogonal to the axial direction passing through the boundary between the chamfered portion 55b and the fitting surface A, and the inner end side of the solid structure portion 62 is newly provided. The hollow structure part 63 is provided in this. And the said hollow structure part 63 has the maximum volume in the range which can ensure the rigidity of the hub ring 54, and can achieve weight reduction, ensuring the intensity | strength and rigidity of the hub ring 54 ( For example, see Patent Document 1.)

JP 2007-269066 A

  In such a conventional wheel bearing device, the weight can be reduced as the volume of the hollow structure portion 63 of the hub wheel 54 increases. However, the heat treatment distortion generated when the contour of the hub wheel 54 is induction-hardened is reduced. Since it acts as a tensile residual stress on 63, there is a possibility that cracks may occur in the hollow structure portion 63 of the hub wheel when the stress amplitude due to the rotational bending load acts on this hollow structure portion 63. In addition, the flow of raw material due to the forging process deteriorates and the forgeability deteriorates, and there is a possibility that forging damage may occur during the forging process and the forging die life.

  The present invention has been made in view of such circumstances, and provides a wheel bearing device that increases the fatigue strength of the hub wheel and improves the strength and durability while reducing the weight and size. It is an object.

  In order to achieve such an object, the invention described in claim 1 of the present invention has a vehicle body mounting flange integrally attached to the knuckle on the outer periphery, and a double row outer rolling surface is integrally formed on the inner periphery. The outer member, and a wheel mounting flange for mounting the wheel at one end of the outer member, and one inner rolling surface facing the outer rolling surface of the double row on the outer periphery, and the inner rolling surface A hub wheel formed with a small-diameter step portion extending in the axial direction from the shaft to the shaft portion, and the other inwardly rolling member that is press-fitted into the small-diameter step portion of the hub wheel and that faces the outer rolling surface of the double row on the outer periphery. An inner member formed of an inner ring formed with a running surface, a double row rolling element accommodated between the rolling surfaces of the inner member and the outer member via a retainer, and A seal mounted at both ends of the annular space formed between the outer member and the inner member. In the wheel bearing device, an inner base portion of the wheel mounting flange that is a sliding contact surface of the outer seal of the seals is formed as an arc surface having a predetermined radius of curvature, and the inner rolling surface of the hub wheel. In addition, a predetermined hardened layer is formed in the range of 58 to 64 HRC by induction hardening from the base portion to the small-diameter step portion, and a mortar-like concave portion is formed on the outer side end portion of the hub wheel. The recess is formed by forging, and the depth of the recess is from the end surface on the outer side of the hub wheel to the vicinity corresponding to the position of the base, and after induction hardening of the hub wheel, further from the recess A stress relaxation hole is formed on the inner side by cutting.

  In this manner, in the third-generation wheel bearing device in which the inner rolling surface is directly formed on the outer periphery of the hub wheel, the base portion on the inner side of the wheel mounting flange that becomes the sliding contact surface of the seal on the outer side of the seal Is formed in a circular arc surface having a predetermined radius of curvature, and a predetermined hardened layer is formed within a range of 58 to 64 HRC by induction hardening from the inner rolling surface of the hub wheel to the small diameter step portion from the base portion. A mortar-shaped recess is formed in the outer end of the hub wheel by forging, and the depth of this recess extends from the end surface on the outer side of the hub wheel to the vicinity corresponding to the position of the base. After induction hardening of the hub wheel, stress relief holes are formed by cutting from the recess to the inner side, so that heat treatment distortion of the inner surface of the hub ring that is hollow while reducing weight and size By Residual tensile stress can be released, and the wheel bearing is designed to increase the fatigue strength of the hub wheel and improve its strength and durability even when a rotating bending moment is applied when the vehicle turns and a repeated stress is applied. An apparatus can be provided. Further, it is possible to improve the forging die life without impairing the forgeability and to prevent the forging damage from occurring during the forging process.

  Preferably, as in the invention described in claim 2, if the tip of the stress relaxation hole is stopped in the vicinity corresponding to the position of the shoulder where the small end surface of the inner ring contacts, Thus, the strength and durability of the hub wheel can be improved without causing stress concentration.

  According to a third aspect of the present invention, the stress is applied so that at least the minimum thickness of the base portion and the minimum thickness of the shaft-shaped portion of the outer end portion of the hub wheel are substantially equal. If the relaxation hole is set to a desired inner diameter, the fatigue strength of the hub wheel can be increased and the strength and durability can be improved while reducing the weight and size.

  Further, as in the invention described in claim 4, the stress relaxation hole may be formed in a tapered shape that gradually decreases in diameter toward the inner side.

  According to a fifth aspect of the present invention, the stress relaxation hole is formed in a tapered shape that gradually decreases in diameter toward the inner side, and a depth thereof is set between the two rows of rolling element rows. One stress relaxation hole and a second stress relaxation hole having a smaller diameter than the first stress relaxation hole may be used.

  According to a sixth aspect of the present invention, the stress relaxation hole is cylindrical and has a first stress relaxation hole whose depth is set between the two rows of rolling element rows. The second stress relaxation hole may have a smaller diameter than the stress relaxation hole.

  Further, as in the invention described in claim 7, the tip portion of the stress relaxation hole may be formed in an arc shape.

  Further, as in the invention described in claim 8, the tip portion of the stress relaxation hole may be formed in a conical hole serving as a center hole at the time of cutting.

  Further, as in the invention according to claim 9, the hub wheel is made of medium and high carbon steel containing C0.40 to 0.80wt%, and is subjected to a tempering treatment in advance, and its surface hardness is 35HRC. If set to the following, the structure is granulated, mechanical properties such as tension, bending, impact value are increased, ductility and toughness are increased, heat treatment deformation can be suppressed, and workability such as cutting is improved. Can be improved.

  Further, as in the invention according to claim 10, if compressive residual stress is applied to at least the inner diameter surface of the hub wheel by surface modification by shot peening, the fatigue strength is further increased while maintaining a desired shape and size. Can be increased.

  Further, as in the invention described in claim 11, if the inner diameter portion of the hub wheel is filled with foamed resin, rainwater, dust or the like enters the hollow portion without hindering the weight reduction or stress relaxation effect. And it can prevent reliably that it accumulates on the internal diameter part of a hub ring and rusts.

  The wheel bearing device according to the present invention has an outer member integrally formed with a vehicle body mounting flange to be attached to a knuckle on the outer periphery, and an outer member in which a double row outer rolling surface is integrally formed on the inner periphery, and one end portion A wheel mounting flange for mounting the wheel on the outer surface, and one inner rolling surface facing the outer rolling surface of the double row on the outer periphery, and the axial direction from the inner rolling surface via the shaft portion A hub ring formed with a small-diameter step portion extending to the inner ring, and an inner ring press-fitted into the small-diameter step portion of the hub ring and having the other inner rolling surface facing the outer rolling surface of the double row on the outer periphery. An inner member, a double row rolling element housed between the rolling surfaces of the inner member and the outer member via a cage, and the outer member and the inner member. In a wheel bearing device provided with seals attached to both end openings of an annular space formed between, The base part on the inner side of the wheel mounting flange that becomes the sliding contact surface of the seal on the outer side is formed in an arc surface having a predetermined radius of curvature, including the inner rolling surface of the hub wheel, and the base part. A predetermined hardened layer is formed in the range of 58 to 64 HRC by induction hardening over the small diameter step, and a mortar-shaped recess is formed by forging at the outer end of the hub wheel. The depth of the recess is from the end surface on the outer side of the hub wheel to the vicinity corresponding to the position of the base, and after induction hardening of the hub wheel, a stress relaxation hole is further formed on the inner side from the recess. Since it is formed by cutting, it is possible to release residual tensile stress due to heat treatment distortion of the inner surface of the hollow hub wheel while reducing the weight and size, and to rotate when the vehicle turns Also act repeatedly stresses are lower moment load, increases the fatigue strength of the wheel hub, it is possible to provide a wheel bearing apparatus with improved strength and durability. Further, it is possible to improve the forging die life without impairing the forgeability and to prevent the forging damage from occurring during the forging process.

It is a longitudinal section showing a 1st embodiment of a bearing device for wheels concerning the present invention. It is a Goodman diagram which shows the stress relaxation effect of the hub ring concerning this invention. It is a longitudinal cross-sectional view which shows 2nd Embodiment of the wheel bearing apparatus which concerns on this invention. It is a longitudinal cross-sectional view which shows 3rd Embodiment of the wheel bearing apparatus which concerns on this invention. It is a longitudinal cross-sectional view which shows 4th Embodiment of the wheel bearing apparatus which concerns on this invention. It is a longitudinal cross-sectional view which shows 5th Embodiment of the wheel bearing apparatus which concerns on this invention. It is a longitudinal cross-sectional view which shows 6th Embodiment of the wheel bearing apparatus which concerns on this invention. It is a longitudinal cross-sectional view which shows the conventional wheel bearing apparatus.

  A vehicle body mounting flange to be attached to the knuckle on the outer periphery, an outer member in which a double row outer rolling surface is integrally formed on the inner periphery, and a wheel mounting flange to mount a wheel on one end A hub that is integrally formed with one inner rolling surface facing the outer rolling surface of the double row on the outer periphery, and a small-diameter step portion extending in the axial direction from the inner rolling surface via the shaft-shaped portion. An inner member formed of an inner ring formed by press-fitting into a small-diameter step portion of the wheel and the hub wheel and having the other inner rolling surface facing the outer rolling surface of the double row on the outer periphery; and the inner member Both ends of an annular space formed between the outer row member and the inner member, and a double row rolling element accommodated between the rolling surfaces of the outer member via a cage. A bearing device for a wheel provided with a seal attached to a portion of the seal. The base portion on the inner side of the wheel mounting flange that becomes the sliding contact surface of the wheel is formed in an arc surface having a predetermined radius of curvature, and extends from the base portion to the small diameter step portion including the inner rolling surface of the hub wheel. A predetermined hardened layer is formed in the range of 58 to 64 HRC by induction hardening, and a mortar-shaped recess is formed by forging at the outer end of the hub wheel. From the outer end surface of the hub wheel to the vicinity corresponding to the position of the base, after induction hardening of the hub wheel, a stress relaxation hole is further formed from the recess to the inner side by cutting, The stress relaxation hole is formed in a tapered shape that gradually decreases in diameter toward the inner side, and the depth is set between the double row rolling element rows, and the first stress relaxation hole. Second response smaller in diameter than the hole Is composed of a relaxation hole, the tip portion of the second stress relieving holes, small end face of the inner ring is fastened in the vicinity corresponding to the position of the shoulder portion abuts.

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, and FIG. 2 is a Goodman diagram showing the stress relaxation effect of the hub wheel according to the present invention. In the following description, the side closer to the outer side of the vehicle when assembled to the vehicle is referred to as the outer side (left side in FIG. 1), and the side closer to the center is referred to as the inner side (right side in FIG. 1).

  This wheel bearing device is for a driven wheel referred to as a third generation, and is a double row rolling element housed in a freely rollable manner between the inner member 1 and the outer member 2, and both members 1 and 2. (Balls) 3 and 3. The inner member 1 includes a hub ring 4 and an inner ring 5 press-fitted into the hub ring 4.

  The hub wheel 4 integrally has a petal-like wheel mounting flange 6 for mounting a wheel (not shown) at one end, and is formed on an inner surface of the wheel mounting flange 6 formed on an arc surface having a predetermined radius of curvature. A small-diameter stepped portion 4b is formed on the outer periphery of the inner rolling surface 4a on one side (outer side) and a shaft-like portion 7 extending in the axial direction from the inner rolling surface 4a. Hub bolts (not shown) are implanted in the wheel mounting flange 6 at equal intervals in the circumferential direction.

  The inner ring 5 is formed with the other (inner side) inner raceway surface 5a on the outer periphery, and is press-fitted into the small-diameter step portion 4b of the hub wheel 4 via a predetermined shimiro, and the end portion of the small-diameter step portion 4b is It is fixed in the axial direction by a caulking portion 8 formed by plastic deformation.

  The hub wheel 4 is formed of medium and high carbon steel containing C0.40 to 0.80 wt% such as S53C, and extends from the inner raceway surface 4a to the small diameter step portion 4b from the base portion 6a on the inner side of the wheel mounting flange 6. Thus, a predetermined hardened layer 10 (indicated by cross-hatching in the figure) is formed in a surface hardness of 58 to 64 HRC by induction hardening. The caulking portion 8 is kept in the surface hardness after forging. This has sufficient mechanical strength against the rotational bending load applied to the wheel mounting flange 6, improves the fretting resistance of the small-diameter stepped portion 4b serving as the fitting portion of the inner ring 5, and performs caulking. There is no occurrence of minute cracks or the like during processing, and the plastic processing of the crimped portion 8 can be performed smoothly. The inner ring 5 and the rolling element 3 are made of high carbon chrome steel such as SUJ2, and are hardened in the range of 58 to 64 HRC to the core part by quenching.

  The outer member 2 integrally has a vehicle body mounting flange 2b to be attached to a knuckle (not shown) on the outer periphery, and a double row of inner rows facing the inner rolling surfaces 4a and 5a of the inner member 1 on the inner periphery. The outer rolling surfaces 2a and 2a are integrally formed. Double-row rolling elements 3 and 3 are accommodated between these rolling surfaces and are held by the cages 9 and 9 so as to roll freely.

  This outer member 2 is formed of medium and high carbon steel containing C0.40 to 0.80 wt% such as S53C, and at least double row outer raceway surfaces 2a and 2a have a surface hardness of 58 to 64HRC by induction hardening. Has been cured. A seal 11 is attached to the outer opening of the annular space formed between the outer member 2 and the inner member 1, and the rotational speed of the wheel is detected at the inner end (inner ring 5). A magnetic encoder 12 is fixed, and a cap (not shown) that covers the open end of the outer member 2 is attached. The seal 11 and the cap prevent leakage of grease sealed inside the bearing and intrusion of rainwater, dust, and the like from the outside into the bearing.

  In the present embodiment, a wheel bearing device configured by a double row angular contact ball bearing using a ball as the rolling element 3 has been exemplified. However, the present invention is not limited to this. For example, a double bearing using a tapered roller for the rolling element 3 is exemplified. You may comprise the row tapered roller bearing. Moreover, although the wheel attachment flange 6 illustrated the thing of a petal shape, an outer diameter shape is not restricted to this, A general circular shape may be sufficient.

  Here, a mortar-shaped recess 13 is formed at the outer end of the hub wheel 4 by forging. The depth of the recess 13 is from the end face on the outer side of the hub wheel 4 to the vicinity corresponding to the position of the base 6a on the inner side of the wheel mounting flange 6. Then, after induction hardening of the outer peripheral surface of the hub wheel 4 described above, the first stress relaxation hole 14 and the first stress relaxation hole are further formed on the inner side from the recess 13 by cutting using a lathe or a drill. A second stress relaxation hole 15 having a diameter smaller than 14 is formed. The first stress relaxation hole 14 is formed in a tapered shape that gradually decreases in diameter toward the inner side, the depth is set between the double row rolling elements 3 and 3 rows, and the second stress relaxation hole 15. The depth (tip portion) is stopped in the vicinity of the position corresponding to the position of the shoulder portion 4c with which the small end surface of the inner ring 5 comes into contact so that stress concentration does not occur due to the sudden deformation of the cross section.

  Further, the outer end of the hub wheel 4, that is, the minimum thickness L0 of the base 6a portion, the minimum thickness L1 of the inner rolling surface 4a portion, and the minimum thickness L2 of the shaft-like portion 7 are substantially equal. Further, the first stress relaxation hole 14 and the second stress relaxation hole 15 are set to have desired inner diameters. This makes it possible to release the residual tensile stress due to heat treatment distortion of the inner surface of the hollow hub wheel 4 while reducing the weight and size, and when the vehicle turns, a rotating bending moment is applied and repeated stress acts. Even so, it is possible to provide a wheel bearing device in which the fatigue strength of the hub wheel 4 is increased and the strength and durability are improved. Further, it is possible to improve the forging die life without impairing the forgeability and to prevent the forging damage from occurring during the forging process.

  In the present embodiment, the hub wheel 4 is subjected to a so-called tempering treatment in which high-temperature tempering at 400 ° C. or higher with a high frequency is performed in advance to obtain a troostite or sorbite structure. By this tempering treatment, the structure is granulated, and mechanical properties such as tension, bending, and impact value are increased, and ductility and toughness are increased. Here, the surface hardness of the hub wheel 4 after the tempering process is set to 35 HRC or less. Thereby, heat treatment deformation can be suppressed, workability such as cutting can be improved, and strength and fatigue strength can be further increased.

  Note that compressive residual stress may be applied to at least the inner diameter surface of the hub wheel 4 by surface modification by shot peening, or a tempering treatment and shot peening may be combined. As a result, the fatigue strength can be further increased while maintaining the desired shape and dimensions.

  As shown in FIG. 2, the stress relaxation hole 14 described above is apparent from the modified Goodman diagram represented by the stress amplitude and the average stress with the fatigue limit of the hub wheel 4, that is, the breaking stress as the intersection of the horizontal axes. , 15 can be used to reduce the repeated stress as compared with those having no stress relaxation holes of this type.

  FIG. 3 is a longitudinal sectional view showing a second embodiment of the wheel bearing device according to the present invention. This embodiment is basically different from the above-described embodiment (FIG. 1) only in the configuration of the stress relief holes of the hub wheel, and other parts having the same parts, the same parts, or the same functions. Parts are denoted by the same reference numerals and detailed description thereof is omitted.

  This wheel bearing device is for a driven wheel called a third generation, and is an inner member 16 and an outer member 2, and a double row rolling element housed between the members 16 and 2 so as to be freely rollable. 3 and 3. The inner member 16 includes a hub ring 17 and an inner ring 5 press-fitted into the hub ring 17 via a predetermined shimiro.

  The hub wheel 17 is made of medium-high carbon steel containing C0.40 to 0.80 wt% such as S53C, and a mortar-shaped recess 13 is formed on the outer end by forging. After induction hardening of the outer peripheral surface of the hub wheel 17, a stress relaxation hole 18 is formed further on the inner side from the recess 13 by cutting using a lathe or a drill. The stress relaxation hole 18 is formed in a tapered shape that gradually decreases in diameter toward the inner side, and its depth is stopped in the vicinity corresponding to the position of the shoulder 4c. Then, the stress relaxation hole 18 is set to a desired inner diameter so that the outer side end of the hub wheel 17, that is, the minimum thickness L 0 of the base portion 6 a and the minimum thickness L 2 of the shaft-like portion 7 are substantially equal. ing. This makes it possible to release the residual tensile stress due to heat treatment distortion of the inner diameter surface of the hub wheel 17 while achieving light weight and compactness. The fatigue strength of the hub wheel 17 can be increased, and the strength and durability can be improved.

  In the present embodiment, the foamed resin 19 is filled in the inner diameter portion of the hollow hub wheel 17. Accordingly, it is possible to reliably prevent rainwater, dust, and the like from entering the hollow portion and accumulating on the inner diameter portion of the hub wheel 17 and rusting without hindering weight reduction and stress relaxation effect. Here, examples of the foamed resin 19 include urethane resins such as PP (polypropylene) resin, hard urethane, and foamed urethane made of foamed urethane, foamed polyethylene, polyamide resin, and the like.

  FIG. 4 is a longitudinal sectional view showing a third embodiment of the wheel bearing device according to the present invention. This embodiment is basically different from the first embodiment (FIG. 1) described above except that the shape of the stress relief hole of the hub wheel is partially different, and the same parts, the same parts, or the same parts. Parts and parts having functions are denoted by the same reference numerals, and detailed description thereof is omitted.

  This wheel bearing device is for a driven wheel called a third generation, and is an inner member 20, an outer member 2, and a double row rolling element accommodated between the members 20 and 2 so as to roll freely. 3 and 3. The inner member 20 includes a hub ring 21 and an inner ring 5 that is press-fitted into the hub ring 21 through a predetermined shimiro.

  The hub wheel 21 is formed of medium-high carbon steel containing C0.40 to 0.80 wt% such as S53C, and a mortar-shaped recess 13 is formed at the outer end by forging. After induction hardening of the outer peripheral surface of the hub wheel 21, a cylindrical first stress relaxation hole 22 and a second stress relaxation hole 15 are formed further on the inner side from the recess 13 by cutting such as a lathe or a drill. Has been. The depth of the first stress relaxation hole 22 is set between the double-row rolling elements 3 and 3 and the tip of the second stress relaxation hole 15 is in the vicinity corresponding to the position of the shoulder 4c. Stopped. The outer end of the hub wheel 21, that is, the minimum thickness L0 of the base portion 6a, the minimum thickness L1 of the inner rolling surface 4a portion, and the minimum thickness L2 of the shaft-like portion 7 are substantially equal. In addition, the first stress relaxation hole 22 and the second stress relaxation hole 15 are set to a desired inner diameter. As in the above-described embodiment, this makes it possible to release residual tensile stress due to heat treatment distortion of the inner diameter surface of the hub wheel 21 while reducing the weight and size, and repeatedly applying a rotating bending moment when the vehicle turns. Even if stress acts, the fatigue strength of the hub wheel 21 can be increased, and the strength and durability can be improved.

  FIG. 5 is a longitudinal sectional view showing a fourth embodiment of the wheel bearing device according to the present invention. Note that this embodiment is basically different from the second embodiment (FIG. 3) described above except that the shape of the stress relief hole of the hub wheel is partially different, and the other parts are the same, the same parts, or the same. Parts and parts having functions are denoted by the same reference numerals, and detailed description thereof is omitted.

  This wheel bearing device is for a driven wheel called the third generation, and is an inner member 23, an outer member 2, and a double row rolling element accommodated between the two members 23, 2 so as to roll freely. 3 and 3. The inward member 23 includes a hub ring 24 and an inner ring 5 press-fitted into the hub ring 24 through a predetermined shimiro.

  The hub wheel 24 is made of medium and high carbon steel containing C0.40 to 0.80 wt% such as S53C, and a mortar-shaped recess 13 is formed on the outer end by forging. After induction hardening of the outer peripheral surface of the hub wheel 23, a stress relaxation hole 25 is further formed on the inner side from the recess 13 by cutting using a lathe or a drill. The stress relaxation hole 25 has a tapered shape gradually reducing in diameter toward the inner side, and its tip is formed in an arc shape, and is stopped in the vicinity corresponding to the position of the shoulder 4c. The stress relaxation hole 25 is set to have a desired inner diameter so that the outer end of the hub wheel 24, that is, the thickness L0 of the base portion 6a and the thickness L2 of the shaft-like portion 7 are substantially equal. . The residual tensile stress due to heat treatment distortion of the inner diameter surface of the hub wheel 24 can be released, and the shoulder 4c is deformed suddenly in cross section to prevent stress concentration. Even if stress is applied repeatedly and stress is applied, the fatigue strength of the hub wheel 24 can be increased, and the strength and durability can be improved.

  FIG. 6 is a longitudinal sectional view showing a fifth embodiment of the wheel bearing device according to the present invention. This embodiment basically differs from the second embodiment described above (FIG. 3) only in the shape of the stress relief hole of the hub wheel, and has the same parts, the same parts, or the same functions. The parts and parts that have the same reference numerals are assigned with the same reference numerals, and detailed description thereof is omitted.

  This wheel bearing device is for a driven wheel called the third generation, and is an inner member 26, an outer member 2, and a double row rolling element accommodated between the members 26, 2 so as to be freely rollable. 3 and 3. The inner member 26 includes a hub ring 27 and an inner ring 5 that is press-fitted into the hub ring 27 via a predetermined scissors.

  The hub wheel 27 is made of medium and high carbon steel containing C0.40 to 0.80 wt% such as S53C, and a mortar-shaped recess 13 is formed at the end on the outer side by forging. After induction hardening of the outer peripheral surface of the hub wheel 26, a cylindrical stress relaxation hole 28 is formed further on the inner side from the recess 13 by cutting such as a lathe or a drill, and the depth thereof is at the position of the shoulder 4c. It is stopped near the corresponding area. The outer end of the hub wheel 27, that is, the minimum thickness L0 of the base 6a portion, the minimum thickness L1 of the inner rolling surface 4a portion, and the minimum thickness L2 of the shaft-like portion 7 are substantially equal. Further, the stress relaxation hole 28 is set to a desired inner diameter. Thereby, the residual tensile stress due to the heat treatment distortion of the inner diameter surface of the hub wheel 27 can be effectively released while increasing the processing efficiency with a simple shape and reducing the cost.

  FIG. 7 is a longitudinal sectional view showing a sixth embodiment of the wheel bearing device according to the present invention. This embodiment basically differs from the above-described fifth embodiment (FIG. 6) only in part of the shape of the stress relief hole of the hub wheel, but the other parts, the same parts, or the same Parts and parts having functions are denoted by the same reference numerals, and detailed description thereof is omitted.

  This wheel bearing device is for a driven wheel referred to as a third generation, and is a double row rolling element which is accommodated so as to be freely rollable between the inner member 29 and the outer member 2, and both members 29 and 2. 3 and 3. The inner member 29 includes a hub ring 30 and an inner ring 5 press-fitted into the hub ring 30 through a predetermined shimiro.

  The hub wheel 30 is made of medium-high carbon steel containing C0.40 to 0.80 wt% such as S53C, and a mortar-shaped recess 13 is formed by forging at the outer end. After induction hardening of the outer peripheral surface of the hub wheel 30, a cylindrical stress relaxation hole 31 is formed further on the inner side from the recess 13 by cutting using a lathe or a drill. The stress relaxation hole 31 is stopped in the vicinity of the depth corresponding to the position of the shoulder portion 4c, and the outer end of the hub wheel 30, that is, the minimum thickness L0 of the base portion 6a and the inner rolling surface 4a. The stress relaxation hole 31 is set to a desired inner diameter so that the minimum thickness L1 of the portion and the thickness L2 of the shaft-like portion 7 portion are substantially equal. Further, a conical hole 31a is formed at the tip portion as a center hole at the time of cutting. Thereby, the residual tensile stress due to the heat treatment distortion of the inner diameter surface of the hub wheel 30 can be effectively released while further reducing the cost by increasing the processing efficiency.

  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 third-generation wheel bearing device on the driven wheel side in which one inner rolling surface is directly formed on the outer periphery.

1, 16, 20, 23, 26, 29 Inner member 2 Outer member 2a Outer rolling surface 2b Car body mounting flange 3 Rolling elements 4, 17, 21, 24, 27 Hub wheel 4a, 5a Inner rolling surface 4b Small diameter Stepped portion 4c Shoulder portion 5 Inner ring 6 Wheel mounting flange 6a Base portion 7 on the inner side of the wheel mounting flange 7 Shaft-shaped portion 8 Clamping portion 9 Cage 10 Hardened layer 11 Seal 12 Magnetic encoder 13 Recesses 14, 22 First stress relaxation Hole 15 Second stress relief hole 18, 25, 28, 31 Stress relief hole 19 Foamed resin 31a Conical hole 51 Inner member 52 Outer member 52a Outer rolling surface 52b Car body mounting flange 53 Ball 54 Hub wheels 54a, 55a Inside Rolling surface 54b Small diameter step portion 55 Inner ring 55b Chamfering portion 56 Wheel mounting flange 57 Shaft portion 58 Clamping portion 59 Cage 60 Seal 61 Cover 62 Solid structure portions 62a and 62b The minimum thickness of the minimum thickness L2 shaft-like portion of the minimum thickness L1 inner raceway surface portion of the end face 63 hollow part A mating surface L0 base portion of the solid structure portion

Claims (11)

An outer member integrally having a vehicle body mounting flange for being attached to the knuckle on the outer periphery, and an outer rolling surface of a double row integrally formed on the inner periphery;
It has a wheel mounting flange for mounting a wheel at one end, and has one inner rolling surface facing the outer rolling surface of the double row on the outer periphery, and a shaft-shaped portion from the inner rolling surface via the shaft-shaped portion. A hub ring having a small-diameter step portion extending in the axial direction, and an inner ring press-fitted into the small-diameter step portion of the hub ring and having the other inner rolling surface facing the outer rolling surface of the double row on the outer periphery An inner member comprising:
A double row rolling element housed between the rolling surfaces of the inner member and the outer member so as to be freely rollable via a cage;
In a wheel bearing device comprising a seal mounted at both ends of an annular space formed between the outer member and the inner member,
The base portion on the inner side of the wheel mounting flange that becomes the sliding surface of the seal on the outer side of the seal is formed in an arc surface having a predetermined radius of curvature, including the inner rolling surface of the hub wheel, and the base portion. A predetermined hardened layer is formed in the range of 58 to 64 HRC by induction hardening over the small diameter step, and a mortar-shaped recess is formed by forging at the outer end of the hub wheel. The depth of the recess is from the end surface on the outer side of the hub wheel to the vicinity corresponding to the position of the base, and after induction hardening of the hub wheel, a stress relaxation hole is further formed on the inner side from the recess. Is formed by cutting, a wheel bearing device.   The wheel bearing device according to claim 1, wherein a tip end portion of the stress relaxation hole is stopped in a vicinity corresponding to a position of a shoulder portion with which a small end surface of the inner ring abuts.   The stress relaxation hole is set to have a desired inner diameter so that at least the minimum thickness of the base portion and the minimum thickness of the shaft portion of the outer end portion of the hub wheel are substantially equal. The wheel bearing device according to 1 or 2.   The wheel bearing device according to claim 1, wherein the stress relaxation hole is formed in a tapered shape that gradually decreases in diameter toward the inner side.   The stress relaxation hole is formed in a tapered shape that gradually decreases in diameter toward the inner side, and the first stress relaxation hole whose depth is set between the two rows of rolling element rows, and the first stress relaxation hole The wheel bearing device according to any one of claims 1 to 3, comprising a second stress relaxation hole having a smaller diameter than the hole.   The stress relaxation hole is cylindrical and has a first stress relaxation hole whose depth is set between the two rows of rolling element rows, and a second stress relaxation having a smaller diameter than the first stress relaxation hole. The wheel bearing device according to any one of claims 1 to 3, comprising a hole.   The wheel bearing device according to any one of claims 1 to 6, wherein a tip portion of the stress relaxation hole is formed in an arc shape.   The wheel bearing device according to any one of claims 1 to 6, wherein a tip portion of the stress relaxation hole is formed in a conical hole serving as a center hole at the time of cutting.   The hub ring is made of medium-high carbon steel containing C0.40 to 0.80 wt%, and is subjected to a tempering treatment in advance, and its surface hardness is set to 35 HRC or less. The wheel bearing apparatus described in 1.   The wheel bearing device according to any one of claims 1 to 9, wherein a compressive residual stress is applied to at least an inner diameter surface of the hub wheel by surface modification by shot peening.   The wheel bearing device according to any one of claims 1 to 10, wherein a foamed resin is filled in an inner diameter portion of the hub wheel.

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