JP2001080309A - Bearing unit for driving wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase durability by increasing the rigidity of a bearing unit for a driving wheel. SOLUTION: A hub wheel 11, an outer joint member 13 of a constant velocity universal joint 12, and an axle bearing 14 are unitized. In plural rows of inner races 17a, 17b of the axle bearing 14, the inner race 17b is formed on the outer joint member 13. The outer joint member 13 has a mouth portion 26 and an axle portion 27. An end face on an axle portion side of the mouth portion 26 is made to be an abutting surface 38 against the hub wheel 11, the axle portion 27 and the hub wheel 11 is joined by fitting portions 36b, 37b and serration portions 36a, 37a and a fixing nut 39, and the outer joint member 13 is formed of carburized hardened steel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive wheel bearing unit, and more particularly, to a drive unit used for a drive wheel of an automobile, in which a hub wheel, an outer joint member of a constant velocity universal joint, and an axle bearing are unitized. The present invention relates to a wheel bearing unit.

[0002]

2. Description of the Related Art A power transmission system for transmitting power from an engine of an automobile to driving wheels needs to cope with an angular displacement and an axial displacement due to a change in a relative positional relationship between the engine and the wheels. as shown in 4 and the engine-side interposed the drive shaft 1 between the drive wheel side, is connected to one end of the drive shaft 1 to a differential via a sliding type constant velocity joint J _1, secure the other end It is connected to the driving wheels 2 via a type constant velocity universal joint J _2. Axial displacement is absorbed by a so-called plunging the slide type constant velocity joint J _1. On the other hand, fixed type constant velocity universal joint J
₂ is only capable of angular displacement.

The fixed type constant velocity universal joint J ₂ includes an inner joint member 4 attached to the other end of the drive shaft 1,
The outer joint member 3 connected to the hub wheel 7, a plurality of torque transmitting balls 5 incorporated between the track grooves of the inner joint member 4 and the outer joint member 3, and the outer spherical surface of the inner joint member 4. A retainer 6 that is interposed between the outer joint member 3 and the inner spherical surface and retains the torque transmission ball 5 is a main component. The hub wheel 7 is rotatably supported by an axle bearing 8, and the wheel of the drive wheel 2 is fixed to the hub wheel 7.

[0004] outer joint member 3 and the axle bearing 8 of the hub 7 and the constant velocity universal joint J ₂ constitute a unitized with the bearing unit H for driving wheels.

[0005]

By the way, in the conventional drive wheel bearing unit H described above, the axle bearing 8
Is a double-row rolling bearing, which is supported by a suspension system of the vehicle body via a knuckle 9 and has double-row balls 8a, 8b.
Of these, one ball 8a is located on the outboard side of the vehicle, and the other ball 8b is located on the inboard side of the vehicle. Ball train the inboard side, on severe load compared to the ball row on the outboard side, is affected by the heat from the outer joint member 3 of the constant velocity universal joint J ₂ receives torque from the drive shaft 1, moreover Since it is difficult to obtain a good heat radiation state due to the inboard side, very strict conditions are required.

In particular, in a bearing unit called a fourth generation having a structure in which the raceway surface (inner race) on the inboard side of the axle bearing is formed on the outer diameter surface of the outer joint member, the inner race on the inboard side is not provided. In addition, the temperature rises remarkably due to being closer to the heat generating portion (track groove of the outer joint member) of the outer joint member, and the life is shorter than that of the inner race on the outboard side.

Accordingly, the present invention has been proposed in view of the above problems, and an object of the present invention is to increase the rigidity of a drive wheel bearing unit to improve durability.

[0008]

SUMMARY OF THE INVENTION As a technical means for achieving the above object, the present invention provides a unitized hub wheel, an outer joint member of a constant velocity universal joint and an axle bearing, and a double row of axle bearings. Wherein at least one of the inner races is formed on the outer joint member, wherein the outer joint member has a mouth portion and a shaft portion, and a shaft portion side end face of the mouth portion is abutting surface with a hub wheel. The shaft portion and the hub wheel are connected by a fitting portion, a torque transmitting portion, and a fixing portion, and the outer joint member is formed of carburized and quenched steel. The carburized and hardened steel forming this outer joint member is
For example, it can be realized by carburizing or carbonitriding case hardening steel such as SCr420. By this carburizing treatment or carbonitriding treatment, a hardened layer can be formed at the inner race portion formed on the outer joint member.

In the drive wheel bearing unit of the present invention, the hardened layer formed on the outer joint member has a retained austenite amount of 20 to 35% and a surface hardness of HR.
C58 to 63 is desirable. If the amount of retained austenite in the hardened layer is less than 20% (corresponding to surface hardness HRC63), the notch sensitivity is deteriorated and the life is shortened, and conversely, the amount of retained austenite is reduced to 35% (surface hardness HRC5).
8), the hardness is reduced and the life is shortened.

In the drive wheel bearing unit of the present invention, when forming the carburized and quenched steel of the outer joint member, the carburized and tempered temperature is desirably set to 180 ° C. or higher. By setting the tempering temperature higher than the normal tempering temperature (about 160 to 180 ° C.), the stability of the material under high-temperature use conditions is increased, and the heat resistance can be further improved.

The torque transmitting portion between the shaft portion of the outer joint member and the hub wheel may have a concave and convex meshing structure formed on the outer peripheral surface of the shaft portion and the inner peripheral surface of the hub wheel, for example, a spline or serration. It is. Further, the fixed portion between the shaft portion and the hub wheel can be realized by caulking by plastic deformation of the end portion of the shaft portion and a fixing nut screwed to the tip of the shaft portion. Further, the torque transmitting portion and the fixed portion between the shaft portion and the hub wheel can be realized by plastic coupling by increasing the outer diameter of the shaft portion or reducing the inner diameter of the hub wheel.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a drive wheel bearing unit according to the present invention will be described in detail below.

A bearing unit according to a first embodiment shown in FIG. 1 includes a hub wheel 11 and an outer joint member 1 of a constant velocity universal joint 12.
3 and an axle bearing 14 as a unit, and is referred to as a fourth generation of a structure in which the inboard side inner race of the axle bearing 14 is formed on the outer diameter surface of the outer joint member 13.

The axle bearing 14 has a double row outer race 15.
a, an outer race 16 provided with a and 15b, double-row inner races 17a and 17b, and double-row rolling elements 18a and 18b;
Cage 12 supporting rolling elements 18a, 18b for each row
a and 12b. Double Row Inner Race 17
a and 17b, one inner race 17a is formed integrally with the outer peripheral surface of the hub wheel 11 and the other inner race 1
7b is formed integrally with the outer peripheral surface of the outer joint member 13. The bearing outer ring 16 is fixed to a knuckle by a flange 19. Seals 20 are attached to the openings at both ends of the axle bearing 14 in order to prevent intrusion of foreign matter from outside and leakage of grease filled therein.

In the illustrated embodiment, the axle bearing 14 has a double-row angular contact ball bearing structure, but has a large bearing load capacity. As another axle bearing, it is also possible to adopt a double-row tapered roller bearing structure using tapered rollers for the rolling elements (having a large bearing load capacity).

The hub wheel 11 has a flange 21, and hub bolts 22 for fixing the wheel are attached to the flange 21 at circumferentially equal positions. As described above, the inner race 17 of the double row is
One inner race 17a is formed among a and 17b. A hardened layer is formed on the inner race portion by induction hardening or the like. An annular protruding edge 23 is formed on an outer peripheral portion of an end of the hub wheel 11 on the outer joint member side. Further, the hub wheel 11 has a hollow portion 24 opened on the end face on the side opposite to the outer joint member, and a through hole 25 is formed in the center portion of the hub wheel 11 in the axial direction.

The outer joint member 13 includes a substantially bowl-shaped mouth portion 26 and a shaft portion 2 formed integrally with the mouth portion 26.
And 7. The mouth portion 26 has a torque transmitting ball 2
The track grooves 29 on which the rollers 8 roll are formed so as to extend in the axial direction at circumferentially equal positions on the inner spherical surface 30. On the outer peripheral surface of the outer joint member 13, one of the inner races 1a of the double row inner races 17a and 17b of the axle bearing 14 is provided.
7b is formed.

Inside the mouth part 26, an inner joint member 31,
The torque transmission ball 28 and the retainer 32 are incorporated. The inner joint member 31 is coupled to a drive shaft (not shown) for transmitting power from the engine by serrations (or splines), and is provided at a position equally spaced in the circumferential direction of the outer spherical surface 33 in the outer joint member 13. And a corresponding track groove 34. A torque transmission ball 28 is interposed between the track groove 29 of the outer joint member 13 and the track groove 34 of the inner joint member 31, and transmits torque between the two. Each torque transmitting ball 28 is incorporated in a pocket 35 of a retainer 32, and the retainer 32 is
Between the inner spherical surface 30 and the outer spherical surface 33 of the inner joint member 31.

The shaft portion 27 of the outer joint member 13 has a distal end portion on which a male screw is formed, and further includes a serration portion 36a serving as a torque transmitting portion and a fitting portion 36b. The shaft-side end surface of the mouth portion 26, in other words, a portion that rises in the radial direction from the mouth-side end portion of the fitting portion 36 b is a butt surface 38 against the annular convex edge 23 of the hub wheel 11. Annular convex edge 23 and butting surface 3
8 determines the distance between the inner races 17a and 17b in the double row, and includes the annular convex edge 23 and the butting surface 38.
The bearing clearance (or preload) can be adjusted by increasing or decreasing either or both of the machining amounts.

In a bearing unit called a fourth generation having a structure in which the inner race 17b on the inboard side of the axle bearing 14 is formed on the outer diameter surface of the outer joint member 13, the inner race 17b on the inboard side has The temperature rise is remarkable because it is close to the heat generating portion of the outer joint member 13 (track groove of the outer joint member).

Therefore, in the present invention, the outer joint member 13 is formed of carburized and hardened steel. The case hardened steel forming the outer joint member 13 can be realized by carburizing or carbonitriding case hardening steel such as SCr420. By this carburizing treatment or carbonitriding treatment, a hardened layer can be formed at the inner race 17b formed on the outer joint member 13. The hardened layer is partially or entirely formed on the outer joint member 13 so as to include at least the inner race 17b.

The amount of retained austenite in the hardened layer formed on the outer joint member 13 by carburizing or carbonitriding is set to 20 to 35%, and the surface hardness is HRC58.
It is desirable to set it to 63. If the amount of retained austenite in the hardened layer is less than 20% (corresponding to surface hardness HRC63), the notch sensitivity is deteriorated and the life is shortened. As the hardness increases, the hardness decreases and the life is shortened. When carburizing or carbonitriding the outer joint member 13, the carburizing and tempering temperature is desirably set to 180 ° C. or higher. By setting the tempering temperature higher than the normal tempering temperature (about 160 to 180 ° C.), the stability of the material under high-temperature use conditions is increased, and the heat resistance can be further improved.

In the through hole 25 of the hub wheel 11, a serration portion 37a is provided at an axial position corresponding to the serration portion 36a and the fitting portion 36b of the outer joint member 13.
And a fitting portion 37b. A fixing portion is formed by tightening a fixing nut 39 to a male screw of the shaft portion 27 protruding from the through hole 25 of the hub wheel 11. Thus, the hub wheel 11 and the outer joint member 13
Are separable and serrations 36a, 37a
Thus, torque is transmitted.

In the first embodiment shown in FIG. 1, the shaft 27 of the outer joint member 13 is inserted into the through hole 25 of the hub wheel 11, and the shaft 27 protrudes from the through hole 25 of the hub wheel 11.
Although the fixing portion was formed by tightening the fixing nut 39 to the male screw of the present invention, the present invention is not limited thereto.
The present invention is also applicable to those having a fixing portion having another structure. 2 shows a second embodiment of the present invention, FIG. 3 shows a third embodiment, and the same parts as those in the first embodiment of FIG. The description is omitted here.

The second embodiment shown in FIG. 2 has a structure in which the shaft portion 27 of the outer joint member 13 is formed into a hollow cylindrical shape, and the outer joint member 13 is connected to the hub wheel 11 by caulking its end portion 40. An annular step is formed on the periphery of the opening of the through hole 25 of the hub wheel 11 to accommodate the spacer ring 41, and the spacer ring 41 is crimped so as to be sandwiched therebetween. Note that the spacer ring 41 may be omitted, and the end portion 40 of the shaft portion 27 may be directly crimped to the periphery of the opening of the through hole 25 of the hub wheel 11. By making the shaft portion 27 hollow, advantages such as weight reduction and improvement of heat radiation conditions can be obtained.

In the third embodiment shown in FIG. 3, the shaft portion 27 of the outer joint member 13 has a hollow cylindrical shape,
7 has a structure in which an uneven portion 42 is formed on the outer peripheral surface of the end portion, and the shaft portion 27 is fitted into the through hole 25 of the hub wheel 11. By expanding and caulking the portion of the shaft portion 27 where the uneven portion 42 is formed from the inner diameter side to the outer diameter side, the uneven portion 42 bites into the inner peripheral surface of the through hole 25 of the hub wheel 11, and the hub wheel 11 And the outer joint member 13 are plastically connected. The hub wheel 11 may be caulked by reducing its diameter from the outer diameter side. In this way, a torque transmitting portion and a fixed portion between the shaft portion 27 of the outer joint member 13 and the hub wheel 11 are formed. As the uneven portion 42, for example, screw, serration, knurling, or the like is preferable. Also in this structure, as in the above-described embodiment, since the shaft portion 27 is hollow, there is an advantage that the weight of the unit is reduced and heat radiation conditions are improved.

[0027]

According to the present invention, the hub wheel, the outer joint member of the constant velocity universal joint, and the axle bearing are unitized, and at least one of the double rows of inner races of the axle bearing is connected to the outer joint member. Wherein the outer joint member has a mouth portion and a shaft portion, the shaft portion side end surface of the mouth portion is a butt surface with a hub wheel, and the shaft portion and the hub wheel are fitted to each other with a torque and a torque. The outer joint member is formed of carburized and quenched steel while being connected by the transmission portion and the fixed portion, so that the life of the outer joint member can be prolonged, and the rigidity of the entire bearing unit is increased to increase durability. Performance can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of a drive wheel bearing unit according to the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing a third embodiment of the present invention.

FIG. 4 is a sectional view showing a conventional drive wheel bearing unit used in a power transmission system from an automobile engine to drive wheels.

[Explanation of symbols]

 Reference Signs List 11 hub wheel 12 constant velocity universal joint 13 outer joint member 14 axle bearing 17a, 17b inner race 26 mouth part 27 shaft part 36a, 37a torque transmitting part 36b, 37b fitting part 38 butting surface 39 fixing part (fixing nut)

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Keisuke Sone 1578 Higashikaizuka, Iwata City, Shizuoka Prefecture Inside (72) Inventor Yoshihiro Ozawa 1578 Higashikaizuka, Iwata City, Shizuoka Prefecture F Term (in reference) 3J101 AA02 AA16 AA25 AA32 AA43 AA54 AA62 AA72 BA53 BA70 BA77 EA02 FA15 FA31 GA03

Claims (8)

[Claims] 1. An outer joint member comprising a hub wheel, an outer joint member of a constant velocity universal joint, and an axle bearing, wherein at least one of double-row inner races of the axle bearing is formed on the outer joint member. The outer joint member has a mouth portion and a shaft portion, and a shaft portion side end surface of the mouth portion is a butt surface with a hub wheel, and the shaft portion and the hub wheel are fitted together, a torque transmitting portion, a fixing portion, And the outer joint member is formed of carburized and quenched steel. 2. The drive wheel according to claim 1, wherein the hardened layer formed on the outer joint member has a retained austenite amount of 20 to 35% and a surface hardness of 58 to 63 HRC. Bearing unit. 3. The carburizing and tempering temperature of the outer joint member is set to 1
3. The bearing unit for a drive wheel according to claim 1, wherein the temperature is 80 [deg.] C. or higher. 4. A torque transmitting portion between a shaft portion of the outer joint member and a hub wheel has an uneven engagement structure formed on an outer peripheral surface of the shaft portion and an inner peripheral surface of the hub wheel. Item 4. The drive wheel bearing unit according to any one of Items 1 to 3. 5. The bearing unit for a drive wheel according to claim 4, wherein the concave-convex engagement structure is a spline or a serration. 6. The driving wheel according to claim 4, wherein the fixed portion between the shaft portion of the outer joint member and the hub wheel is formed by caulking by plastic deformation of an end portion of the shaft portion. Bearing unit. 7. The drive wheel bearing unit according to claim 4, wherein the fixed portion between the shaft portion of the outer joint member and the hub wheel is a fixed nut screwed to a tip of the shaft portion. . 8. A torque transmission portion and a fixing portion between the shaft portion and the hub wheel of the outer joint member are formed by plastic coupling by expanding the outer diameter of the shaft portion or reducing the inner diameter of the hub wheel. The drive wheel bearing unit according to claim 1.