JP2018154209A - Bearing device for wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing device for a wheel, which prevents idling of a hub bolt, which can suppress deformation of a wheel attachment flange without one-sided distortion on the periphery of a bolt hole, and which can reduce run-out of the wheel attachment flange by extension.SOLUTION: In a bearing device 1 for a wheel, a wheel attachment flange 3h is formed for either an outer member 2 or an inner member 3, and a plurality of bolt holes 3i are provided on a concentric circle centering on a rotating shaft A of the wheel attachment flange 3h. A hub bolt 7 pressed into the bolt hole 3i is provided. The hub bolt 7 has a serration part 72 surface-hardening by shot-peening.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a wheel bearing device.

  2. Description of the Related Art Conventionally, a wheel bearing device that supports a wheel rotatably is known (see Patent Document 1). In the wheel bearing device, an outer member is fixed to a knuckle constituting the suspension device. Further, in the wheel bearing device, an inner member is disposed inside the outer member, and a plurality of rolling elements are interposed between the rolling surfaces of the outer member and the inner member. In this way, the wheel bearing device constitutes a rolling bearing structure, and the wheel attached to the inner member is rotatable.

  By the way, in such a wheel bearing device, a wheel mounting flange is formed at one end of the inner member. Further, there is a type in which an outer member is rotatable and a wheel mounting flange is formed on the outer member. The wheel mounting flange is provided with a plurality of bolt holes on a concentric circle with the rotation axis as the center. Hub bolts for fixing the wheels are press-fitted into these bolt holes. The hub bolt is provided with a so-called serration portion, and it is preferable that the projection of the serration portion is fixed in a state of being bitten into the inner peripheral surface of the bolt hole. Therefore, as in Patent Document 1, a method has been proposed in which the inner peripheral surface of the bolt hole is annealed to lower the surface hardness.

Japanese Patent No. 5509966

  When the nut is tightened, the hub bolt needs to be securely fixed together with the nut so as not to idle (indicating sliding). However, if the protrusion of the serration portion does not sufficiently penetrate into the inner peripheral surface of the bolt hole, it may rotate idle together with the nut (see arrow T in FIG. 8). Also, if the protrusions do not bite all around the inner peripheral surface of all the bolt holes, the distortion around the bolt holes will be biased and the deformation of the wheel mounting flange will increase, which in turn may increase the runout of the wheel mounting flange. (See arrow D in FIG. 8). Therefore, there has been a demand for a wheel bearing device that can prevent the hub bolt from spinning around, suppress deformation of the wheel mounting flange without causing distortion in the periphery of the bolt hole, and thus reduce rotational runout of the wheel mounting flange.

The first invention is
An outer member having an outer rolling surface formed on the inner periphery;
An inner member having an inner rolling surface formed on the outer periphery;
A plurality of rolling elements interposed between the rolling surfaces of the outer member and the inner member,
A wheel bearing device in which a wheel mounting flange is formed on one of the outer member and the inner member, and a plurality of bolt holes are provided on concentric circles centering on the rotation axis of the wheel mounting flange. In
Comprising a hub bolt press-fitted into the bolt hole;
The hub bolt is such that the serration portion is subjected to surface hardening treatment by shot peening.

2nd invention is the wheel bearing apparatus which concerns on 1st invention,
The wheel mounting flange is formed of carbon steel;
The hub bolt is formed of chromium steel or chromium-molybdenum steel;
The serration portion has a surface hardness of 1000 HV to 1100 HV.

A third invention is the wheel bearing device according to the first or second invention,
The serration portion has a sharp shape in which the cross section of each protrusion is pointed radially outward.

  As effects of the present invention, the following effects can be obtained.

  The wheel bearing device according to the first invention includes a hub bolt press-fitted into the bolt hole. The hub bolt is subjected to surface hardening treatment by shot peening on the serration portion. According to such a wheel bearing device, the protrusion of the serration portion bites into the inner peripheral surface of the bolt hole due to the difference in surface hardness, so that it is possible to prevent the hub bolt from spinning around. Further, since the protrusions bite in on the entire inner peripheral surface of all the bolt holes, the deformation of the wheel mounting flange can be suppressed without distortion in the vicinity of the bolt holes, and thus the rotational runout of the wheel mounting flange can be reduced.

  In the wheel bearing device according to the second invention, the wheel mounting flange is made of carbon steel, and the hub bolt is made of chromium steel or chromium-molybdenum steel. The serration portion has a surface hardness of 1000 HV to 1100 HV. According to such a wheel bearing device, since the protrusion of the serration portion bites into the inner peripheral surface of the bolt hole without being crushed due to a large difference in surface hardness, it is possible to reliably prevent the hub bolt from idling. In addition, since the protrusion does not collapse on the entire inner periphery of all the bolt holes and stably bites in, the deformation of the wheel mounting flange can be reliably suppressed without distortion in the periphery of the bolt hole, and thus the rotation of the wheel mounting flange. Shake can be reliably reduced.

  In the wheel bearing device according to the third aspect of the invention, the serration portion has a sharp shape in which the cross section of each projection is pointed radially outward. According to such a wheel bearing device, since the protrusion of the serration portion bites deeply into the inner peripheral surface of the bolt hole, it is possible to reliably prevent the hub bolt from idling. In addition, since the protrusion deeply and stably bites all around the inner peripheral surface of all bolt holes, the deformation of the wheel mounting flange can be reliably suppressed without distortion in the surroundings of the bolt hole, and thus the rotational vibration of the wheel mounting flange can be prevented. It can be reliably reduced.

The perspective view which shows the bearing apparatus for wheels. Sectional drawing which shows the structure of the bearing apparatus for wheels. Sectional drawing which shows the partial structure of the bearing apparatus for wheels. Sectional drawing which shows the partial structure of the bearing apparatus for wheels. The figure which shows the shape of a hub bolt. The figure which shows the manufacturing process of a hub bolt. The figure which shows the condition where the hub bolt is press-fitted in the bolt hole of the wheel mounting flange. Sectional drawing which shows the structure of the wheel bearing apparatus which is a conventional product.

  First, the wheel bearing device 1 according to the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is a perspective view showing a wheel bearing device 1. FIG. 2 is a sectional view showing the structure of the wheel bearing device 1. 3 and 4 are sectional views showing a partial structure of the wheel bearing device 1.

  The wheel bearing device 1 supports a wheel rotatably. The wheel bearing device 1 includes an outer member 2, an inner member 3, a rolling element 4, an inner side seal member 5, and an outer side seal member 6. In this specification, the “inner side” represents the vehicle body side of the wheel bearing device 1 when attached to the vehicle body, and the “outer side” represents the wheel bearing device 1 attached to the vehicle body. Represents the wheel side.

  The outer member 2 constitutes the outer ring portion of the rolling bearing structure. The outer member 2 is made of medium-high carbon steel such as S53C, for example. A sealing surface 2 a is formed at the inner side end of the outer member 2. Further, a sealing surface 2 b is formed at the outer side end of the outer member 2. Furthermore, two outer rolling surfaces 2c and 2d are formed on the inner periphery of the outer member 2. The outer rolling surface 2c faces an inner rolling surface 3c described later. The outer rolling surface 2d faces an inner rolling surface 3d described later. The outer rolling surfaces 2c and 2d are subjected to induction hardening, for example, and the surface hardness is in the range of 58 to 64 HRC. In addition, a knuckle mounting flange 2 e is integrally formed on the outer periphery of the outer member 2. The knuckle mounting flange 2e is provided with a plurality of bolt holes 2f.

  The inner member 3 constitutes an inner ring portion of the rolling bearing structure. The inner member 3 includes a hub ring 31 and an inner ring 32.

  The hub wheel 31 is made of medium-high carbon steel such as S53C, for example. The hub wheel 31 is formed with a small-diameter step portion 3a from the inner side end portion to the axial center portion. The small-diameter step portion 3a indicates a portion where the outer diameter of the hub wheel 31 is reduced, and the outer peripheral surface thereof has a cylindrical shape centered on the rotation axis A. The hub wheel 31 is formed with a universal joint mounting hole 3b penetrating from the inner side end to the outer side end. The universal joint mounting hole 3b refers to a through hole provided in the center of the hub wheel 31, and a part of the inner peripheral surface thereof has an uneven shape (spline hole) in which concave portions and convex portions are alternately arranged. Further, an inner rolling surface 3 c is formed on the outer periphery of the hub wheel 31. The inner rolling surface 3c faces the outer rolling surface 2c described above. For example, induction hardening is performed from the small-diameter step portion 3a through the inner rolling surface 3c to the seal land portion (configured by a shaft surface portion 3e, a curved surface portion 3f, and a side surface portion 3g, which will be described later), and the surface hardness is increased. Is in the range of 58-64 HRC. In addition, a wheel mounting flange 3 h is integrally formed on the outer periphery of the hub wheel 31. The wheel mounting flange 3h is provided with a plurality of bolt holes 3i, and hub bolts 7 are press-fitted into the respective bolt holes 3i. Details of the hub bolt 7 will be described later.

  The inner ring 32 is made of a high carbon chrome bearing steel such as SUJ2. A sealing surface 3 j is formed on the outer periphery of the inner ring 32. Further, an inner rolling surface 3d is formed on the outer periphery of the inner ring 32. The inner ring 32 is fitted (externally fitted) to the small-diameter step portion 3 a of the hub ring 31, thereby forming an inner rolling surface 3 d on the outer periphery of the hub ring 31. The inner rolling surface 3d faces the aforementioned inner rolling surface 2d. In addition, the inner ring 32 is subjected to, for example, so-called quenching quenching, and is in a range of 58 to 64 HRC to the core.

  The rolling element 4 constitutes a rolling part of the rolling bearing structure. The rolling element 4 is made of high carbon chrome bearing steel such as SUJ2. The rolling element row 4R on the inner side is formed by arranging a plurality of rolling elements 4 in a ring shape by a cage. Each rolling element 4 is interposed between the outer rolling surface 2d of the outer member 2 and the inner rolling surface 3d of the inner member 3 so as to be freely rollable. On the other hand, the rolling element row 4R on the outer side also has a plurality of rolling elements 4 arranged in a ring shape by a cage. Each rolling element 4 is interposed between the outer rolling surface 2 c of the outer member 2 and the inner rolling surface 3 c of the inner member 3 so as to be freely rollable. In addition, the rolling element 4 is subjected to, for example, so-called quenching quenching and is in a range of 62 to 67 HRC up to the core.

  The inner side seal member 5 seals the inner side end portion of the annular space S formed between the outer member 2 and the inner member 3. However, the inner side seal member 5 has various specifications and is not limited to the specification of the present application. There are also specifications in which a cap can be attached instead of the inner seal member 5 and specifications in which nothing can be attached.

  The inner side seal member 5 includes a slinger 51. The slinger 51 is fitted (externally fitted) to the sealing surface 3j of the inner ring 32. The slinger 51 is made of, for example, a stainless steel plate such as SUS430 or SUS304, or a cold rolled steel plate such as SPCC. The slinger 51 has a shape in which an annular steel plate is deformed by press working and an axial cross section is bent into an approximately L shape. Thereby, the slinger 51 is formed with a cylindrical fitting portion 51 a and a disk-like side plate portion 51 b extending from the end portion toward the outer ring 2.

  The inner side seal member 5 includes a seal ring 52. The seal ring 52 is fitted (internally fitted) into the fitting portion 2 a of the outer ring 2. The seal ring 52 includes a metal core 53 and an elastic member 54. The core metal 53 is made of, for example, a stainless steel plate such as SUS430 or SUS304, or a cold rolled steel plate such as SPCC. The core metal 53 has a shape in which an annular steel plate is deformed by press working and an axial cross section is bent into an approximately L shape. As a result, the cored bar 53 is formed with a cylindrical fitting part 53 a and a disk-shaped side plate part 53 b extending from the end part toward the inner ring 32. An elastic member 54 is integrally formed on the fitting portion 53a and the side plate portion 53b by, for example, vulcanization adhesion.

  The elastic member 54 is, for example, NBR (acrylonitrile-butadiene rubber), HNBR (hydrogenated acrylonitrile-butadiene rubber), EPDM (ethylene propylene rubber), ACM (polyacrylic rubber), FKM (fluororubber), or silicon rubber. Consists of synthetic rubber. The tip of the seal lip 54 a formed on the elastic member 54 is in contact with the fitting portion 51 a of the slinger 51. Further, the seal lips 54 b and 54 c are in contact with the side plate portion 51 b of the slinger 51 at the tip portion. In this way, the inner seal member 5 prevents foreign matters such as muddy water and dust from entering the annular space S and prevents grease from leaking out of the annular space S.

  The outer side seal member 6 seals the outer side end portion of the annular space S formed between the outer member 2 and the inner member 3. However, the outer side seal member 6 has various specifications and is not limited to the specifications of the present application.

  The outer side seal member 6 is fitted (internally fitted) into the fitting portion 2 b of the outer ring 2. The outer side seal member 6 includes a core metal 62 and an elastic member 63. The core metal 62 is made of, for example, a stainless steel plate such as SUS430 or SUS304, or a cold rolled steel plate such as SPCC. The cored bar 62 has a shape in which an annular steel plate is deformed by press working and the axial cross section is bent into an approximately L shape. As a result, the cored bar 62 is formed with a cylindrical fitting portion 62 a and a disc-shaped side plate portion 62 b extending from the end portion toward the hub wheel 31. Note that the elastic member 63 is integrally formed on the side plate portion 62b by, for example, vulcanization adhesion.

  The elastic member 63 is, for example, NBR (acrylonitrile-butadiene rubber), HNBR (hydrogenated acrylonitrile-butadiene rubber), EPDM (ethylene propylene rubber), ACM (polyacrylic rubber), FKM (fluororubber), or silicon rubber. Consists of synthetic rubber. The tip of the seal lip 63 a formed on the elastic member 63 is in contact with the shaft surface portion 3 e of the hub wheel 31. The tip of the seal lip 63 b is in contact with the curved surface portion 3 f of the hub wheel 31. Further, the seal lip 63 c is in contact with the side surface portion 3 g of the hub wheel 31 at the tip portion. In this way, the outer seal member 6 prevents foreign matters such as muddy water and dust from entering the annular space S and prevents grease from leaking out of the annular space S.

  Next, characteristic points of the hub bolt 7 will be described with reference to FIGS. 5 and 6. FIG. 5 is a view showing the shape of the hub bolt 7. 5A is a side view of the hub bolt 7, and FIG. 5B is a cross-sectional view corresponding to the XX portion in FIG. FIG. 6 is a diagram illustrating a manufacturing process of the hub bolt 7. 6A to 6E show a rough flow until the hub bolt 7 is completed. At the same time, the effect of the present invention will be described with reference to FIG. FIG. 7 is a view showing a state in which the hub bolt 7 is press-fitted into the bolt hole 3i of the wheel mounting flange 3h. FIG. 7A is a cross-sectional view showing a state in which the hub bolt 7 is press-fitted into the bolt hole 3i of the wheel mounting flange 3h, and FIG. 7B corresponds to the XX portion in FIG. FIG. In the present specification, “outside in the radial direction” represents a direction away from the central axis C of the hub bolt 7.

  As described above, the hub bolt 7 fixes the wheel to the wheel mounting flange 3h. The hub bolt 7 is made of chromium steel such as SCr430 or chromium-molybdenum steel such as SCM435. As for the hub bolt 7, the steel rod which is a raw material is pressed to an axial direction, and the head 71 is formed by this (refer (A) of FIG. 6). Then, a serration portion 72 is formed in the large-diameter portion of the shaft body by being press-fitted into the serration forming die Da (see FIG. 6B), and is further sandwiched between the screw forming die Db and rotated. As a result, a threaded portion 73 is formed in the small diameter portion of the shaft body (see FIG. 6C). Thereafter, the hub bolt 7 is put into the heating furnace Ho and carburized and quenched (see FIG. 6D). Thereby, the surface hardness of the hub bolt 7 becomes the range of 560-600HV. In addition, the hub bolt 7 is subjected to surface hardening treatment by shot peening only on the serration portion 72 (see the * mark portion in FIG. 6E). Thereby, the surface hardness of the serration part 72 becomes the range of 1000-1100HV from the surface to the depth of 20 micrometers-30 micrometers. By doing so, the hub bolt 7 having high fatigue strength and good stress corrosion cracking resistance is completed.

  Here, the surface hardening process by shot peening will be briefly described. Shot peening is a surface processing method that hardens the surface of a workpiece and maintains compressive residual stress. Specifically, by projecting a granular material called a projecting material, the surface of the serration portion 72 of the hub bolt 7 that is a workpiece is plastically deformed to form a hardened layer. At this time, since the surrounding portion restrains the elastic force that the deformed portion tries to return, the compressive residual stress is held on the surface of the serration portion 72. By carrying out such a surface processing method, the surface hardness of the serration portion 72 can be increased and the compressive residual stress can be maintained, and the fatigue strength and the stress corrosion cracking resistance are improved. In addition, although the magnitude | size of a projection material, a projection speed, etc. influence the characteristic acquired, these are not limited.

  In addition, the shape of the serration portion 72 will be briefly described. The serration portion 72 refers to a large-diameter portion that is press-fitted into the bolt hole 3i of the wheel mounting flange 3h, and is provided with a plurality of protrusions 72p along the central axis C, and the protrusions 72p adjacent to each other are equally spaced from one another ( Serration axis). In the hub bolt 7, the serration portion 72 has a sharp shape (wedge shape) in which the cross section of each protrusion 72p is pointed radially outward (see (C) in FIG. 5). Therefore, the protrusion 72p bites into the inner peripheral surface 3k of the bolt hole 3i when the hub bolt 7 is press-fitted (see FIGS. 7A and 7B). In the wheel bearing device 1, the wheel mounting flange 3 h is formed of carbon steel, whereas the hub bolt 7 is formed of chrome steel or chrome-molybdenum steel, and the serration portion 72 has a surface hardness of 1000 to 1000. Since it is 1100HV, the protrusion 72p bites into the entire inner peripheral surface 3k of the bolt hole 3i without being crushed. In addition, since the protrusion 72p of the serration portion 72 has a sharp shape, the protrusion 72p deeply and stably bites around the entire inner peripheral surface 3k of the bolt hole 3i.

  As described above, the wheel bearing device 1 according to the present invention includes the hub bolt 7 that is press-fitted into the bolt hole 3i. The hub bolt 7 is subjected to surface hardening treatment by shot peening on the serration portion 72. According to the wheel bearing device 1, the protrusion 72 p of the serration portion 72 bites into the inner peripheral surface 3 k of the bolt hole 3 i due to the difference in surface hardness, so that the hub bolt 7 can be prevented from spinning freely. Further, since the protrusion 72p bites in the entire inner peripheral surface 3k of all the bolt holes 3i, the deformation of the wheel mounting flange 3h can be suppressed without causing a distortion in the periphery of the bolt hole 3i, and thus the rotational deflection of the wheel mounting flange 3h can be suppressed. Can be reduced.

  In the wheel bearing device 1, the wheel mounting flange 3h is made of carbon steel, and the hub bolt 7 is made of chrome steel or chrome-molybdenum steel. The serration portion 72 has a surface hardness of 1000 HV to 1100 HV. According to such a wheel bearing device 1, the protrusion 72 p of the serration portion 72 bites into the inner peripheral surface 3 k of the bolt hole 3 i deeply without being crushed due to a large difference in surface hardness. it can. In addition, since the protrusion 72p bites stably without being crushed on the entire inner peripheral surface 3k of all the bolt holes 3i, the deformation of the wheel mounting flange 3h can be reliably suppressed without causing distortion in the periphery of the bolt holes 3i, and thus The rotational runout of the wheel mounting flange 3h can be reliably reduced.

  Further, in the wheel bearing device 1, the serration portion 72 has a sharp shape in which the cross section of each protrusion 72 p is pointed radially outward. According to such a wheel bearing device 1, since the protrusion 72 p of the serration portion 72 deeply bites into the inner peripheral surface 3 k of the bolt hole 3 i, the idle rotation of the hub bolt 7 can be reliably prevented. Further, since the protrusion 72p stably bites in the entire inner peripheral surface 3k of all the bolt holes 3i, the deformation of the wheel mounting flange 3h can be surely suppressed without distortion in the periphery of the bolt hole 3i, and consequently the wheel mounting flange. The rotational runout of 3h can be reliably reduced.

  The wheel bearing device 1 according to the present invention includes an outer member 2 and an inner member 3 each having a hub ring 31 fitted with one inner ring 32 as the inner member 3 and having a knuckle mounting flange. Although it is set as the 3rd generation structure of the inner ring | wheel rotation specification comprised by the fitting body of the inner ring | wheel 31 and the hub ring | wheel 32, it is not limited to this. For example, a support shaft in which one inner ring is fitted as an inner member is provided, and the outer member is formed as a hub ring. The hub ring that is the outer member, the inner ring that is the inner member, and the support shaft It may be a third generation structure of an outer ring rotation specification constituted by a fitting body. In addition, the outer ring has a knuckle mounting flange and a pair of inner rings which are inner members, and this pair of inner rings is a second generation structure of an inner ring rotation specification in which the outer rings are fitted to the outer periphery of the hub ring. May be. Further, the outer member may be formed as a hub ring, and a second generation structure of an outer ring rotation specification constituted by a hub ring as the outer member and a pair of inner rings as the inner members may be used. Further, it may be a first generation structure that includes an outer ring that is an outer member and a pair of inner rings that are inner members, and the outer ring is fitted to the inner periphery of the housing.

DESCRIPTION OF SYMBOLS 1 Wheel bearing apparatus 2 Outer member 2c Outer rolling surface 2d Outer rolling surface 3 Inner member 31 Hub wheel 32 Inner ring 3c Inner rolling surface 3d Inner rolling surface 3h Wheel mounting flange 3i Bolt hole 3k Inner peripheral surface 4 Rolling element 7 Hub bolt 71 Head 72 Serration part 72p Protrusion 73 Screw part A Rotation axis C Center axis

Claims (3)

An outer member having an outer rolling surface formed on the inner periphery;
An inner member having an inner rolling surface formed on the outer periphery;
A plurality of rolling elements interposed between the rolling surfaces of the outer member and the inner member,
A wheel bearing device in which a wheel mounting flange is formed on one of the outer member and the inner member, and a plurality of bolt holes are provided on concentric circles centering on the rotation axis of the wheel mounting flange. In
Comprising a hub bolt press-fitted into the bolt hole;
The hub bolt is a bearing device for wheels, wherein the serration portion is subjected to surface hardening treatment by shot peening. The wheel mounting flange is formed of carbon steel;
The hub bolt is formed of chromium steel or chromium-molybdenum steel;
2. The wheel bearing device according to claim 1, wherein the serration portion has a surface hardness of 1000 HV to 1100 HV.   The wheel bearing device according to claim 1, wherein the serration portion has a sharp shape in which a cross section of each protrusion is pointed radially outward.

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