JP2006118610A - Bearing device for wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing device for wheel capable of increasing the durability and reliability of an inner ring by preventing cracking from occurring in the inner ring due to hoop stress in a caulking step. <P>SOLUTION: In this bearing device for wheel of self-retaining structure, the inner ring 3 is press-fitted into the small diameter step part 2b of a hub wheel 2, and axially fixed to the hub wheel 2 by a caulked part 2c formed by elastically deforming the end part of the small diameter step part 2b in the radial outer direction. The inner ring 3 is formed of a pre-refined medium carbon steel containing 0.40 to 0.80 wt.% carbon, and a hard layer with a hardness of 58 to 64 HRC is formed on the surfaces of an inner rolling surface 3a and small end faces 3c by induction hardening. Also, a core part, an outer diameter surface 3b, large end faces, and an inner diameter surface 3e are formed in such a refined structure that is lower in hardness than the hard layer. <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 that improves durability of an inner ring that is crimped and fixed to a hub wheel. .

  There are two types of wheel bearing devices for vehicles such as automobiles, one for driving wheels and one for driven wheels, but it goes without saying that the cost has been reduced, and that the weight and size have been reduced for improving fuel efficiency. As a typical example of the conventional structure, a wheel bearing device for a driven wheel as shown in FIG. 4 is known.

  This wheel bearing device is referred to as a third generation, and includes a hub wheel 51, an inner ring 52, an outer ring 53, and double row rolling elements 54, 54. The hub wheel 51 integrally has a wheel mounting flange 55 for mounting a wheel (not shown) at one end thereof, an inner rolling surface 51a on the outer periphery, and a small diameter extending in the axial direction from the inner rolling surface 51a. A step portion 51b is formed. Further, hub bolts 56 for fixing the wheels are planted at the circumferentially equidistant positions of the wheel mounting flanges 55.

  An inner ring 52 having an inner rolling surface 52a formed on the outer periphery is press-fitted into the small diameter step portion 51b of the hub wheel 51. The inner ring 52 is prevented from coming off from the hub wheel 51 in the axial direction by a caulking portion 51c formed by plastically deforming the end portion of the small diameter step portion 51b of the hub wheel 51 radially outward. .

  The outer ring 53 integrally has a vehicle body mounting flange 53b for mounting to a suspension device (not shown), and double row outer rolling surfaces 53a and 53a are formed on the inner periphery. Between the inner rolling surfaces 51a and 52a facing the double-row outer rolling surfaces 53a and 53a, double-row rolling elements 54 and 54 are accommodated so as to roll freely.

  The hub wheel 51 is integrally formed by forging a carbon steel material having a carbon content of 0.40 to 0.80% by weight, and a portion indicated by cross hatching, that is, a wheel mounting flange 55. The surface is hardened by induction hardening or the like from the base portion to the inner rolling surface 51a and the small diameter step portion 51b. In addition, the caulking part 51c is left with the raw material surface hardness after forging. On the other hand, the inner ring 52 is made of high carbon steel such as high carbon chromium bearing steel such as SUJ2, and is hardened and hardened to the core.

As a result, a wheel bearing device having sufficient durability can be realized at low cost, and the caulking portion 51c is prevented from being damaged such as a crack, and is fixed to the hub wheel 51 by the caulking portion 51c. It is possible to prevent the diameter of the inner ring 52 from changing to an extent that causes a practical problem. And while reducing possibility that this inner ring | wheel 52 will be damaged with the fixing operation | work, a preload can be maintained to an appropriate value, and also cost reduction can be aimed at by reduction of a number of parts, parts processing, and an assembly man-hour.
JP-A-11-129703

  In such a conventional wheel bearing device, the force that greatly deforms the inner diameter of the inner ring 52 is prevented so as to affect the durability such as the preload and the rolling fatigue life accompanying the caulking work. be able to. However, when the end portion of the small diameter step portion 51b is plastically deformed radially outward to form the crimping portion 51c, the vicinity of the crimping portion 51c of the small diameter step portion 51c is also plastically deformed in the radial direction. With the plastic deformation, the inner diameter of the inner ring 52 is expanded, and it cannot be denied that a hoop stress is generated in the outer diameter 57 of the inner ring 52.

  As means for lowering the hoop stress, it has also been proposed to variously change the end shape of the small-diameter stepped portion 51b of the hub wheel 51 to suppress the amount of plastic deformation at the time of swing caulking. Even when a large moment load or the like is applied, the crimped portion 51c is required to have a strength sufficient to firmly fix the inner ring 52. Therefore, it is said that the amount of plastic deformation is suppressed and the strength of the crimped portion is secured. There are conflicting issues.

  Here, when a hoop stress is generated in the outer diameter surface 57 of the inner ring 52, when corrosion occurs in this portion, diffusible hydrogen existing in the environment enters the structure of the inner ring 52 and the metal grain boundary is destroyed. This is not preferable because so-called “delayed fracture” is likely to occur.

  The present invention has been made in view of such a conventional problem, and prevents a crack associated with the hoop stress generated in the inner ring in the caulking process, thereby improving the durability and reliability of the inner ring. The purpose is to provide.

  In order to achieve such an object, the invention according to claim 1 of the present invention integrally has an outer member having a double row outer rolling surface formed on the inner periphery and a wheel mounting flange at one end. A hub wheel formed with a small-diameter step portion extending in the axial direction from the wheel mounting flange, and an inner ring press-fitted into the small-diameter step portion of the hub wheel, and opposed to the outer surface of the double row on the outer periphery. An inner member in which a double row inner rolling surface is formed, and a double row rolling element accommodated between the inner member and the outer member via a cage between the rolling surfaces of the inner member and the outer member. A wheel bearing device in which the inner ring is fixed in the axial direction with respect to the hub wheel by a caulking portion formed by plastically deforming an end portion of the small-diameter stepped portion radially outward. It is made of pre-tempered alloy steel or non-tempered steel, and the inner rolling surface is induction hardened What is hardened layer formed in the range of 58~64HRC the surface, including the core, was adopted a structure that is at least the radially outer surface is left thermally refined structure of lower hardness than the cured layer.

  In this way, the inner ring is fixed to the hub ring in the axial direction by the caulking portion formed by press-fitting the inner ring into the small-diameter step portion of the hub wheel and plastically deforming the end of the small-diameter step portion radially outward. In the so-called self-retained wheel bearing device, the inner ring is made of a tempered alloy steel or non-tempered steel, and the inner rolling surface is in the range of 58 to 64 HRC by induction hardening. The hardened layer is formed and the tempered structure having a lower hardness than that of the hardened layer, including the core part, at least on the outer diameter surface is maintained, so that a desired rolling fatigue life can be obtained and the crystal grains are fine. Thus, mechanical strength and crack strength are improved, and durability can be maintained even when the inner diameter of the inner ring is expanded with plastic deformation and hoop stress is generated on the outer diameter surface.

  Preferably, as in the second aspect of the invention, if both end faces and the inner diameter face of the inner ring have a predetermined hardened layer formed on the surface by induction hardening, the fretting resistance is increased and the durability of the inner ring is increased. Will improve.

  Further, as in the invention described in claim 3, the inner ring may be made of medium carbon steel containing 0.40 to 0.80% by weight of carbon.

  According to a fourth aspect of the present invention, the hub wheel is made of medium carbon steel containing 0.40 to 0.80% by weight of carbon, and from the base of the wheel mounting flange to the small diameter step portion by induction hardening. The surface hardness is set in a range of 58 to 64 HRC, and the crimped portion is an unquenched portion having a surface hardness of 25 HRC or less after forging. Such an induction hardening pattern improves the strength of the hub wheel and suppresses fretting wear on the fitting surface of the inner ring, thereby improving durability. Moreover, the workability of the caulking portion can be improved, and the occurrence of cracks and the like due to plastic deformation can be prevented.

  The wheel bearing device according to the present invention integrally has an outer member having a double row outer raceway formed on the inner periphery and a wheel mounting flange at one end, and extends in an axial direction from the wheel mounting flange. A hub ring formed with a small-diameter step portion and an inner ring press-fitted into the small-diameter step portion of the hub ring, and a double-row inner rolling surface facing the double-row outer rolling surface is formed on the outer periphery. An inner member, and a double-row rolling element that is rotatably accommodated between the rolling surfaces of the inner member and the outer member via a cage, and an end portion of the small-diameter step portion. In the wheel bearing device in which the inner ring is fixed in the axial direction with respect to the hub ring by a caulking portion formed by plastically deforming the outer ring in a radially outward direction, the inner ring is pre-heated alloy steel or It is made of non-tempered steel and the inner rolling surface is 58-64 HRC on the surface by induction hardening. A hardened layer of a range is formed, and the tempered structure having at least the outer diameter surface including the core portion having a lower hardness than the hardened layer is maintained, so that a desired rolling fatigue life can be obtained and crystal grains However, the mechanical strength and the cracking strength are improved and the inner diameter of the inner ring is expanded with plastic deformation, so that durability can be maintained even if a hoop stress is generated on the outer diameter surface.

  A vehicle body mounting flange is integrally formed on the outer periphery, an outer member having a double row outer rolling surface formed on the inner periphery, a wheel mounting flange is integrally formed on one end, and the double row outer rolling is formed on the outer periphery. One inner rolling surface facing the running surface, a hub wheel formed with a small-diameter step portion extending in the axial direction from the inner rolling surface, and press-fitted into the small-diameter step portion of the hub wheel, and the double row on the outer periphery An inner member comprising an inner ring formed with the other inner rolling surface opposite to the outer rolling surface of the inner rolling surface, and rolling between the both rolling surfaces of the inner member and the outer member via a cage. A wheel bearing device including a double row rolling element accommodated freely, wherein the inner ring is fixed in an axial direction by a caulking portion formed by plastically deforming an end portion of the small diameter step portion radially outward. And the inner ring is formed of medium carbon steel containing 0.40 to 0.80% by weight of tempered carbon. The inner rolling surface and the small end surface are hardened in the range of 58 to 64 HRC on the surface by induction hardening, and the outer diameter surface, the large end surface and the inner diameter surface including the core portion are adjusted to have a lower hardness than the hardened layer. It is considered as a quality organization.

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 longitudinal sectional view of a single inner ring. 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 referred to as the third generation on the drive wheel side, and is a double row rolling element (ball) accommodated in a freely rollable manner between the inner member 1, the outer member 10, and both members 1, 10. 6 and 6. The inner member 1 includes a hub ring 2 and an inner ring 3 that is press-fitted into the hub ring 2 through a predetermined scissors.

  The hub wheel 2 integrally has a wheel mounting flange 4 for mounting a wheel (not shown) at an end portion on the outboard side, and is used for fixing the wheel at a circumferentially equidistant position of the wheel mounting flange 4. Hub bolts 5 are planted. Further, on the outer periphery of the hub wheel 2, an inner rolling surface 2a and a cylindrical small-diameter step portion 2b extending in the axial direction from the inner rolling surface 2a are formed. The inner ring 3 having the inner raceway surface 3a formed on the outer periphery is press-fitted into the small-diameter step portion 2b, and the end portion of the small-diameter step portion 2b is plastically deformed outward in the radial direction. Thus, the inner ring 3 is prevented from coming off in the axial direction with respect to the hub ring 2.

  The outer member 10 integrally has a vehicle body mounting flange 10b for mounting to a vehicle body (not shown) on the outer periphery, and double row outer rolling surfaces 10a, 10a are formed on the inner periphery. And the double row rolling elements 6 and 6 are accommodated between each rolling surface 10a, 2a and 10a, 3a, and these double row rolling elements 6 and 6 are rollably hold | maintained by the holder | retainers 7 and 7. ing. Further, seals 8 and 9 are attached to the end portion of the outer member 10 to prevent leakage of the lubricating grease sealed inside the bearing and intrusion of rainwater, dust and the like from the outside into the bearing.

  Here, the wheel bearing device referred to as the third generation in which the inner raceway surface 2a is directly formed on the outer periphery of the hub wheel 2 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. In addition, although the double row angular contact ball bearing which used the rolling elements 6 and 6 as the ball | bowl was illustrated, it is not restricted to this, The double row tapered roller bearing which uses a tapered roller for a rolling element may be sufficient.

  Outer member 10 is formed of medium carbon steel (carbon steel for SC system mechanical structure of JIS standard) containing carbon of 0.40 to 0.80% by weight such as S53C, and double row outer rolling surface 10a, 10a. Is hardened by induction hardening to a surface hardness of 58 to 64 HRC.

  On the other hand, the hub wheel 2 is also formed of medium carbon steel containing 0.40 to 0.80% by weight of carbon such as S53C, like the outer member 10, and includes the inner rolling surface 2a on the outboard side and the seal 8 A hardened layer 11 is formed in the range of 58 to 64 HRC by induction hardening over the seal land portion and the small-diameter step portion 2b in sliding contact with each other (indicated by cross hatching in the figure). The caulking portion 2c is an unquenched portion having a material surface hardness of 25 HRC or less after forging. Such an induction hardening pattern improves the strength of the hub wheel 2 and suppresses fretting wear on the fitting surface of the inner ring 3 to improve durability. Moreover, the workability of the caulking portion 2c can be improved, and the occurrence of cracks and the like due to plastic deformation can be prevented.

  Further, the inner ring 3 is made of alloy steel, unlike the conventional high carbon chrome steel made of SUJ2 or the like. Specifically, it is made of medium carbon steel (carbon steel for SC system mechanical structure of JIS standard) containing 0.40 to 0.80% by weight of carbon such as S53C. The material of the inner ring 3 is so-called tempered, after being heated to an austenite phase region around 850 ° C., quenched and quenched into a martensite phase, and then reheated to 550 to 650 ° C. Heat treatment is performed in advance. This tempering heat treatment refines the crystal grains to improve the mechanical strength and the cracking strength. As the plastic deformation occurs, the inner diameter of the inner ring 3 is expanded and a hoop stress is generated on the outer diameter surface 3b of the inner ring 3. Even so, durability can be maintained.

  Furthermore, in this embodiment, the material of the inner ring 3 is finished into a desired shape and size by cutting after cold forging, and as shown in an enlarged view in FIG. A hardened layer 12 (indicated by cross-hatching in the figure) is formed in the surface hardness of 58 to 64 HRC by induction hardening over the rolling surface 3a, and the largest hoop stress including the core is generated and cracked. The outer diameter surface 3b, the rear end large end surface 3d, and the inner diameter surface 3e, which are the starting points, are kept as a tempered structure having a hardness lower than that of the hardened layer 12. As a result, a desired rolling fatigue life can be obtained, and the delayed fracture resistance of the portion where the deformation occurs with the plastic deformation is improved.

  FIG. 2B is a modification of FIG. 2A, and extends from the inner rolling surface 13a of the inner ring 13 in which the material is tempered in advance to the small end surface 13c on the front side, the inner diameter surface 13e, and the large end surface 13d on the back side. A hardened layer 14 (indicated by cross-hatching in the figure) is formed with a surface hardness in the range of 58 to 64 HRC by induction hardening, and the outer diameter that causes the largest hoop stress, including the core, is the starting point of cracking. The surface 13b remains as a tempered thermal structure having a hardness lower than that of the hardened layer 14. As a result, a desired rolling fatigue life can be obtained, the delayed fracture resistance of the portion where the deformation is caused by the plastic deformation is improved, and the fretting resistance of the inner diameter surface 13e and the large end surface 13d is increased and the inner ring 13 is improved. Durability is improved.

  Also, as the material for the inner rings 3 and 13, Mn (manganese), Cr (chromium), V (vanadium), Ti (titanium), etc. are added to the alloy steel to reduce C (carbon), and quenching and tempering. Heat treatment in the hot forging process of the material is performed without performing temper heat treatment, and this is controlled and cooled to perform tempering, so-called hot tempered steel for hot forging, or alloy steel with C, Mn, Furthermore, non-tempered steel for so-called cold forging may be applied in which Si (silicon) or the like is reduced to ensure cold forgeability in the rolled state and tempering heat treatment can be omitted. Thereby, the number of times of handling of equipment, processes and materials can be reduced, and the cost can be reduced.

  FIG. 3 is a longitudinal sectional view showing a second embodiment of the wheel bearing device according to the present invention. In this embodiment, the wheel bearing device according to the present invention is applied to the driven wheel side. The same parts as those in the above-described embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  This wheel bearing device is referred to as the third generation on the driven wheel side, and is a double row rolling element 6, 6 accommodated between the inner member 15, outer member 10, and both members 15, 10 so as to roll freely. And. The inner member 15 includes a hub ring 16 and an inner ring 3 press-fitted into the hub ring 16 through a predetermined shimiro.

  The hub wheel 16 integrally has a wheel mounting flange 4 for mounting a wheel (not shown) at an end portion on the outboard side, an inner rolling surface 16a on the outer periphery, and an axial direction from the inner rolling surface 16a. A shaft-shaped small-diameter step portion 16b extending in the direction is formed. The inner ring 3 is axially inserted into the hub wheel 16 by the crimping portion 16c formed by press-fitting the inner ring 3 into the small-diameter step portion 16b and plastically deforming the end of the small-diameter step portion 16b radially outward. It prevents it from slipping out.

  The hub wheel 16 is formed of medium carbon steel containing carbon of 0.40 to 0.80% by weight such as S53C, and includes an inner rolling surface 16a on the outboard side, a seal land portion with which the seal 8 is in sliding contact, and a small diameter. The hardened layer 11 is formed in a range of 58 to 64 HRC by induction hardening on the stepped portion 16b (indicated by cross hatching in the figure). The caulking portion 16c is an unquenched portion having a surface hardness of 25HRC or less after forging.

  On the other hand, as described above, the inner ring 3 is formed of medium carbon steel that has been subjected to tempering heat treatment in advance, and a predetermined hardened layer 12 is formed by induction quenching from the small end surface 3c on the front side to the inner rolling surface 3a. In addition, the outermost surface 3b where the largest hoop stress is generated including the core portion, and the large end surface 3d and the inner surface 3e on the back side are tempered with lower hardness than the hardened layer 12. It is said to remain in the thermal structure. As a result, as with the wheel bearing device on the drive wheel side described above, the desired rolling fatigue life is obtained, and the delayed fracture resistance of the portion where deformation occurs due to plastic deformation is improved. Therefore, it is possible to provide a wheel bearing device on the side of the driving wheel that prevents the crack associated with the hoop stress generated in the wheel 3 and improves the durability and reliability of the inner ring 3.

  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.

  In the wheel bearing device according to the present invention, the inner ring is fixed by a caulking portion formed by press-fitting an inner ring into a small-diameter step portion of a hub wheel and plastically deforming an end portion of the small-diameter step portion. It can be applied to a self-retained wheel bearing device.

It is a longitudinal section showing a 1st embodiment of a bearing device for wheels concerning the present invention. (A) is the longitudinal cross-sectional view which expanded and showed the inner ring single-piece | unit of FIG. (B) is a longitudinal section showing a modification of (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 longitudinal cross-sectional view which shows the conventional wheel bearing apparatus.

Explanation of symbols

1, 15 ..... Inner member 2, 16 ..... Hub wheels 2a, 3a, 13a, 16a · Inner rolling surfaces 2b, 16b ··· ··· Small diameter step 2c, 16c ··· Clamping portions 3 and 13 · · · Inner rings 3b and 13b · · · Outer surface 3c , 13c ... Small end faces 3d, 13d ... Large end faces 3e, 13e ... Inner diameter face 4 ... ··· Wheel mounting flange 5 ············· Hub bolt 6 ··············· Cage 8, 9 ... Seal 10 ... Outer member 10a ... Outer rolling surface 10b・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Car body mounting flange 11, 12, 14 ・································································ Hub Ring 51a, 52a 51c ················································ 52 Outer rolling surface 53b ... Body mounting flange 54 ... Rolling body 55 ...・ ・ Wheel mounting flange 56 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Hub bolt 57 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Outer diameter surface

Claims (4)

An outer member having a double row outer raceway formed on the inner periphery;
It consists of a hub wheel that has a wheel mounting flange at one end and a small-diameter step portion extending in the axial direction from the wheel mounting flange, and an inner ring that is press-fitted into the small-diameter step portion of this hub wheel. An inner member in which a double row inner rolling surface facing the double row outer rolling surface is formed;
A double-row rolling element accommodated between the rolling surfaces of the inner member and the outer member via a cage so as to freely roll,
In the wheel bearing device in which the inner ring is fixed in the axial direction with respect to the hub wheel by a crimping portion formed by plastically deforming an end portion of the small diameter step portion radially outwardly,
The inner ring is formed of alloy steel or non-tempered steel that has been tempered in advance, and a hardened layer in the range of 58 to 64 HRC is formed on the surface by induction hardening on the inner rolling surface, including the core, A wheel bearing device, wherein at least the outer diameter surface remains a tempered structure having a lower hardness than the hardened layer.   2. The wheel bearing device according to claim 1, wherein a predetermined hardened layer is formed on a surface of both end faces and an inner diameter face of the inner ring by induction hardening.   The wheel bearing device according to claim 1 or 2, wherein the inner ring is made of medium carbon steel containing 0.40 to 0.80% by weight of carbon.   The hub wheel is made of medium carbon steel containing 0.40 to 0.80% by weight of carbon, and the surface hardness is hardened in the range of 58 to 64 HRC by induction hardening from the base of the wheel mounting flange to the small diameter step. The wheel bearing device according to any one of claims 1 to 3, wherein the wheel bearing device is processed and the caulking portion is an unquenched portion having a surface hardness of 25HRC or less after forging.

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