JP2001150904A - Bearing unit for driving wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce assembling man-hours by reducing the number of parts, while preventing generation of displacement in the axial direction in a spline engaging part between a spline hole and a spline shaft. SOLUTION: Elastic force in the direction of reducing a dimension of a diameter is applied to a snap ring 17a straddled between a locking groove 15 and a step surface 16, and an outside surface of the snap ring 17a is formed with an inclined surface 29. An inner end surface of a hub 6a and an outer end surface of a housing 13 are abutted to each other via a seal member 26 while engaging the inclined surface 29 to an outer end periphery in an axial direction of the locking groove 15, thereby preventing the displacement in the axial direction from being generated in the spline engaging part. Accordingly, manhour can be reduced without separate provision of a member such as a spring for preventing the displacement in the axial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION A wheel drive axle unit according to the present invention is a so-called fourth-generation hub unit in which a constant velocity joint and a hub unit are disassembled and integrated, and is provided as an independent suspension type suspension. Supported drive wheels: Front wheels of front-wheel drive front-wheel drive vehicles (FR), FR
The rear wheels 4 of a vehicle (front-engine rear-wheel drive vehicle) and RR vehicle (rear-engine rear-wheel drive vehicle) and a 4WD vehicle (four-wheel drive vehicle) are rotatably supported with respect to the suspension device. Along with
It is used to rotationally drive the drive wheels.

[0002]

2. Description of the Related Art In order to rotatably support wheels with respect to a suspension device, various axle units in which an outer wheel and an inner wheel are rotatably combined via rolling elements have been used. or,
In addition to supporting the drive wheels on an independent suspension,
The wheel drive axle unit for rotating this drive wheel, in combination with a constant velocity joint, controls the rotation of the drive shaft regardless of the relative displacement between the differential gear and the drive wheel and the steering angle given to the wheel. It must be transmitted smoothly (with constant velocity) to the wheels. As a so-called fourth-generation hub unit, a wheel drive axle unit that can be configured to be relatively small and lightweight in combination with such a constant velocity joint, see, for example, Japanese Patent Application Laid-Open No. 7-3177.
No. 54 or U.S. Pat. No. 4,881,842 is known.

[0003] FIG.
42 shows an example of the conventional structure described in Japanese Patent No. 42. An outer ring 1 that is not rotated while being supported by a knuckle 4 constituting a suspension device when assembled to a vehicle has an outward flange-shaped mounting portion 2 for supporting the knuckle 4 on the outer peripheral surface, and a plurality of mounting portions 2 on the inner peripheral surface. It has a row of outer raceways 3,3, respectively. A hub 6 and an inner ring 5 are arranged concentrically with the outer ring 1 on the inner diameter side of the outer ring 1. Of these, the hub 6 is a mounting flange for supporting the wheel at a portion closer to the outer end of the outer peripheral surface (the end that is the outer side in the width direction of the vehicle when assembled to the vehicle, the left end in FIGS. 1, 3, and 5). 7, and an inner raceway 8a is also provided in the middle part.

The inner race 5 has an inner raceway 8b on its outer peripheral surface.
Is formed. Such an inner ring 5 is fitted to a portion closer to the inner end of the hub 6 (the end that is closer to the center in the width direction of the vehicle when assembled to the vehicle, and the right end in FIGS. 1, 3, and 5). The hub 6 is fixed to a portion near the inner end of the hub 6 by holding the end face by a holding ring 9 locked to a portion near the inner end of the outer peripheral surface of the hub 6. Then, each of the outer ring raceways 3,
By providing a plurality of rolling elements 10 between the inner ring track 8a and the inner ring tracks 8b, respectively, the outer ring 1
The hub 6 and the inner race 5 are rotatably supported on the inner diameter side of the hub. Sealing rings 20 and 2 are respectively provided at openings at both ends of a space in which the rolling elements 10 and 10 are located between the inner peripheral surface of the outer ring 1 and the outer peripheral surface of the hub 6.
0 is provided to block the space in which the rolling elements 10 and 10 are installed from the external space.

A spline shaft 12 which forms a drive shaft member 21 together with a housing portion 13 described below is spline-engaged with a spline hole 11 formed in the center of the hub 6. At the base end (the right end in FIG. 5) of the spline shaft 12, there is provided a housing portion 13 which forms an outer raceway 19 of a Zeppa type constant velocity joint on the inner peripheral surface thereof, and serves as an outer ring of the constant velocity joint. ing. On the other hand, a locking portion 14 for locking a tool for drawing the spline shaft 12 into the spline hole 11 is formed on the tip end surface (left end surface in FIG. 5) of the spline shaft 12. . Further, a locking groove 15 is formed over the entire circumference in a portion of the spline shaft 12 near the front end of the outer peripheral surface. On the other hand, a step surface 16 is formed on the inner peripheral surface of the hub 6 around the outer end edge of the spline hole 11 so as to be continuous from the outer end edge. The spline shaft 12 is moved from the spline hole 11 by locking a retaining ring 17 formed in a partially annular shape (C shape) with an elastic material between the locking groove 15 and the step surface 16. It prevents getting out.

In this state, an elastic ring 18 is provided between the inner end face of the hub 6 and the outer end face of the housing portion 13.
Are elastically held. The elastic ring 18 has a V-shaped cross section and is formed in an annular or partially annular shape by bending a metal plate such as a steel plate. The axial dimension of the elastic ring 18 in the free state is larger than the distance between the inner end face of the hub 6 and the outer end face of the housing portion 13. Therefore, as described above, the elastic ring 18
Is elastically held between the inner end face of the hub 6 and the outer end face of the housing portion 13.
8 presses these two end surfaces in a direction away from each other.

When the wheel drive axle unit configured as described above is assembled to a vehicle, the outer ring 1 is supported on the knuckle 4 by the mounting portion 2, and the driving wheel is fixed to the hub 6 by the mounting flange 7. Further, the outer end of a drive shaft (not shown), which is rotationally driven by the engine via a transmission, is spline-engaged with the inside of a constant velocity joint inner ring (not shown) provided inside the housing portion 13. When the car is running, the rotation of the inner ring for this constant velocity joint is
This is transmitted to the spline shaft 12 via a plurality of balls (not shown) and the housing portion 13, and the spline shaft 12
Thus, the drive wheels fixed to the hub 6 are driven to rotate.

[0008]

In the case of the conventional structure constructed as described above, the hub 6 and the spline shaft 12
In addition to providing a retaining ring 17 to prevent separation from the spline shaft, an elastic ring 18 is provided to prevent the spline engagement portion between the spline shaft 12 and the spline hole 11 from rattling. On the other hand, in order to reduce the cost of the wheel drive axle unit as described above, while reducing the number of parts,
It is desirable to reduce the number of assembly steps (reduce the assembly cost). In view of the above-described circumstances, the wheel drive axle unit of the present invention can prevent the spline engagement portion from rattling with the retaining ring 17 without providing a separate component such as the elastic ring 18. It was invented to realize the structure.

[0009]

The wheel drive axle unit according to the present invention has an outer raceway on its inner peripheral surface, similar to the conventional wheel drive axle unit shown in FIG. An outer ring that does not rotate, a mounting flange for supporting the wheel at the outer end portion of the outer peripheral surface, an inner ring raceway at the intermediate portion and the inner end portion directly or via the inner ring, and a spline hole at the center, respectively A hub provided, a spline shaft engaging with the spline hole is provided at an outer end, a drive shaft member having an inner end serving as a housing portion serving as an outer ring of a constant velocity joint, the outer raceway and the inner raceway, And a plurality of rolling elements provided so as to be freely rotatable between the outer peripheral edge of the spline hole on the inner peripheral surface of the hub and the entire periphery in a continuous state from the outer peripheral edge. The formed step surface and the tip of the spline shaft A locking groove formed over the entire outer peripheral surface of the recessed portion, and an annular member made of an elastic material, wherein the spline shaft is connected to the spline shaft in a state of being extended over the locking groove and the step surface. A retaining ring that prevents the hole from coming out of the hole. In particular, in the wheel drive axle unit of the present invention, the retaining ring has an elasticity in a direction of reducing a diameter dimension in a state of being bridged between the locking groove and the step surface, and has an axial direction. At least a portion of the outer side surface that comes into contact with the axially outer end edge of the locking groove is an inclined surface that is inclined inward in the axial direction as it goes inward in the diametrical direction. Then, the retaining ring is bridged between the locking groove and the stepped surface, so that the inclined surface is formed on the outer edge of the locking groove in the axial direction (outside the inner surface of the locking groove in the axially outward direction). The inner end face of the hub and the outer end face of the housing part are in contact with each other directly or via another member in a state of contact with the peripheral part).

[0010]

In the case of the wheel drive axle unit of the present invention configured as described above, the retaining ring bridged between the locking groove and the step surface has elasticity in the direction of decreasing the diameter dimension. Because of this,
Based on the elasticity of the retaining ring, a vertical force acts on the inclined surface formed on the outer surface of the retaining ring and the axially outer edge of the locking groove based on the elasticity of the retaining ring. . Since the inclined surface is inclined inward in the axial direction as it goes inward in the diameter direction of the retaining ring, the force acting on the inclined surface is a component (component force) directed inward in the axial direction. have. Therefore, a component force directed inward in the axial direction is applied to the hub. As a result, the inner end face of the hub is pressed against the outer end face of the housing part constituting the drive shaft member, and is provided at the center of the hub regardless of the thrust load repeatedly applied in different directions during operation of the vehicle. An axial displacement can be prevented from occurring in the spline engagement portion between the spline hole and the spline shaft constituting the drive shaft member, and the spline engagement portion can be prevented from being worn. In particular, in the case of the present invention, in order to prevent the spline engaging portion from being displaced in the axial direction as described above, a separate member (elastic ring) having the above-described conventional structure shown in FIG. It is not necessary to provide 18). For this reason, the number of assembling steps associated with the reduction in the number of parts can be reduced.

[0011]

1 and 2 show a first embodiment of the present invention. The feature of the present invention is that the retaining ring 1
The structure of the portion for preventing separation between the hub 6a and the drive shaft member 21a by 7a. Since the structure and operation of the other parts are almost the same as those of the conventional structure shown in FIG. 5 described above, the same parts are denoted by the same reference numerals, and redundant description is omitted or simplified. Will be described focusing on different parts and characteristic parts of the present invention.

In the case of the present embodiment, the inner race 5 having an inner raceway 8b formed in the axial direction on its outer peripheral surface fits externally on a step 22 formed on the outer peripheral surface of the inner end of the hub 6a.
The inner end of the inner ring 5 is fixed to the hub 6a by a caulking portion 23 formed by caulking and expanding a portion protruding from the inner end surface of the inner ring 5 outward in the diameter direction. Further, a seal member 26 composed of a metal core 24 and an elastic plate 25 is arranged between the outer end surface of the housing portion 13 constituting the drive shaft member 21a and the inner end surface of the hub 6a. This sealing member 2
The core metal 24 constituting the metal part 6 is formed by forming a metal plate such as a mild steel plate into an annular shape with an L-shaped cross section, and tightens a cylindrical part 27 formed on an outer peripheral edge to an outer end of the housing part 13. It is fixed to the outer end of the housing portion 13 by external fitting. The elastic plate 25 is formed by annularly forming an elastomer such as rubber, and is attached to the outer surface of the annular portion 28 constituting the cored bar 24 over the entire periphery by baking, bonding, or the like. I have.

The elastic plate 25 has an inner end surface of the hub 6a and an outer end surface of the housing portion 13 in a state where the retaining ring 17a is stretched over the locking groove 15 and the step surface 16 as described below. Between the inner end face of the hub 6a and the outer end face of the housing portion 13. And
Through this interval, foreign matters such as rainwater and dust are prevented from entering the spline engagement portion between the spline hole 11 provided in the center of the hub 6a and the spline shaft 12a constituting the drive shaft member 21a.

In the case of this embodiment, the spline shaft 12a
Locking groove 15 formed at the tip of the outer peripheral surface of the
2a and the stepped surface 16 formed near the tip of the inner peripheral surface of FIG.
-Shaped annular retaining ring 1 having a cross-sectional shape as shown in detail in FIG.
7a. This retaining ring 17a is made of spring steel,
By forming an elastic metal, such as stainless steel spring, into a substantially C-shaped broken ring, the diameter can be elastically expanded and contracted. In particular, in the case of the present example, in a state where the retaining ring 17a is stretched over the locking groove 15 and the step surface 16, the retaining ring 17a is provided with elasticity in a direction of reducing the diameter dimension. The diameter of the ring 17a in the free state is regulated. Also, the inner side of the retaining ring 17a (the surface that is axially outward in the assembled state and the left side in FIGS. 1 and 2) is closer to the inner side as the inner side is shifted toward the inner side. On the side that is inward in the direction, an inclined surface 29 that is inclined in the direction toward the right (the right side in FIGS. 1 and 2) is formed. On the contrary,
The other side surface of the retaining ring 17a is a simple flat surface over the entire surface.

The above-described retaining ring 17a elastically enlarges the diameter, passes through the outer peripheral surface of the distal end of the spline shaft 12a, and then elastically reduces (restores) the diameter. As a result, the locking groove 15 exposed from the outer edge of the spline hole 11 and the step surface 16 are bridged. When the retaining ring 17a is stretched in this manner, the inclined surface 29 is formed at the outer edge of the locking groove 15 in the axial direction (the outer peripheral edge of the inner surface of the locking groove 15 at the outer side in the axial direction). , And the outer diameter side portion of the other side surface of the retaining ring 17 a contacts the step surface 16. Also, in this state,
As described above, the elastic plate 25 forming the seal member 26
The inner end surface of the caulking portion 23 formed at the inner end portion of the hub 6 a and the outer end surface of the housing portion 13 are elastically sandwiched. Further, in this state, a gap is formed between the inner surface of the retaining ring 17a on the other side and the inner surface of the retaining groove 15 in the axial direction, so that these two surfaces do not contact each other.
The size of each part is regulated. Further, the cap 30 is fitted and fixed to the outer end opening of the hub 6a to close the outer end opening, and from the outer end opening to the spline engaging portion between the spline shaft 12a and the spline hole 11. Foreign matter such as rainwater and dust is prevented from entering.

In the case of this embodiment, the retaining ring 17a is provided as described above.
The inner end face of the hub 6a and the housing portion 1 are in a state where the inclined surface 29 of the hub abuts on the outer end in the axial direction of the locking groove 15.
The dimensional tolerance of each part is set so that the outer end surface of the third member 3 comes into contact with the outer end surface (via the seal member 26). However, when it is difficult to adopt such a method of setting the dimensional tolerance of each part due to processing accuracy, a plurality of types of retaining rings 17a having different axial thicknesses are prepared and the hub 6 is used.
It is also possible to employ a method of appropriately selecting and using these plural types of retaining rings 17a in accordance with the finished condition of the spline shaft 12a and the spline shaft 12a.

In the case of the wheel drive axle unit of the present embodiment configured as described above, the retaining ring 17a bridged between the locking groove 15 and the step surface 16 has elasticity in the direction of reducing the diameter. For this reason, the contact portion between the inclined surface 29 formed on the outer surface of the retaining ring 17a and the axial outer edge of the locking groove 15 is provided on the inclined surface 2 based on the elasticity of the retaining ring 17a.
A vertical force acts on 9. In the illustrated mounted state, the inclined surface 29 is inclined inward in the axial direction as it goes inward in the diametrical direction. Therefore, the force acting on the inclined surface 29 has a component (component force) directed inward in the axial direction.
Therefore, a component force directed inward in the axial direction is applied to the hub 6a. As a result, the inner end surface of the caulking portion 23 is pressed against the outer end surface of the housing portion 13 constituting the drive shaft member 21a. In other words, the retaining ring 17a
Due to its own elasticity, the diameter of the locking groove 15 is reduced while increasing the distance between the axially outer end edge of the locking groove 15 and the stepped surface 16.
3 is pressed against the outer end surface of the housing portion 13.

As a result, regardless of the thrust loads repeatedly applied in different directions during operation of the automobile, the spline hole 11 provided at the center of the hub 6a and the drive shaft member 21
This prevents axial displacement of the spline engagement portion with the spline shaft 12a that constitutes a, and prevents the spline engagement portion from being worn. In particular, in the case of the present invention, in order to prevent the spline engaging portion from being displaced in the axial direction as described above, a separate member (elastic ring) having the above-described conventional structure shown in FIG. It is not necessary to provide 18). For this reason, the number of assembly steps can be reduced due to the reduction in the number of parts. In the case of this example, the drive shaft member 21a is formed on the axial outer end edge of the locking groove 15 from the inclined surface 29 based on a vertical reaction acting on the elasticity of the retaining ring 17a.
, A state in which an axially outward force is constantly applied. For this reason, even if the elastic plate 25 is settled during operation and a slight permanent deformation occurs in the elastic plate 25, the contact state between the outer surface of the elastic plate 25 and the inner end surface of the hub 6a is maintained. And good sealing performance by the elastic plate 25 can be maintained.

When the wheel drive axle unit of the present invention having the above-described structure is used, when a force is applied in a direction in which the spline shaft 12a is pulled out from the hub 6a, the inclined surface 29 of the retaining ring 17a is A vertical force (a force in a direction opposite to the above-described vertical reaction) is applied from the axially outer end edge of the locking groove 15. As described above, in the assembled state shown in the drawing, the inclined surface 29 is inclined inward in the axial direction toward the inside in the diameter direction. Therefore, the vertical force acting on the inclined surface 29 from the axially outer end edge of the locking groove 15 has a component (component force) directed outward in the diameter direction. Therefore, a component force directed outward in the diameter direction acts on the retaining ring 17a via the inclined surface 29.

In this case, the retaining ring 17a falls out of the locking groove 15 diametrically outward on the basis of the above-described component force directed outward in the diametrical direction acting on the retaining ring 17a. In order to prevent this, the design is made such that the static friction force acting on the contact portion between the inner surface of the retaining ring 17a and the step surface 16 is larger than the component force directed outward in the diameter direction. There is a need. That is, the inclination angle of the inclined surface 29 with respect to an imaginary plane orthogonal to the central axis of the retaining ring 17a is α, and the coefficient of static friction at the contact portion between the inner surface of the retaining ring 17a and the stepped surface 16 is μ. Further, assuming that the radial elastic resistance of the retaining ring 17a is so small as to be negligible (for performing a design with a margin), the inner and outer side surfaces of the retaining ring 17a, the step surface 16 and the Locking groove 1
In order to make the static frictional force acting on the contact portion with the axially outer end edge 5 larger than the diametrically outward component force, α
It is necessary to satisfy the relationship of ≦ 2 · tan ⁻¹ μ. For example, when the static friction coefficient μ is 0.15, in order to prevent the retaining ring 17a from dropping from the locking groove 15,
The inclination angle α of the inclined surface 29 may be set to about 17 degrees or less. However, by increasing the spring constant of the retaining ring 17a,
The magnitude of the component force directed outward in the axial direction, which is included in the vertical force acting on the locking groove 15 from the inclined surface 29, is determined by the axis of a tripod joint used on the differential side (the center in the width direction of the vehicle). If the thrust load based on the sliding resistance in the direction is equal to or greater than the thrust load, the inclination angle α of the inclined surface 29 can be increased (for example, to about 30 degrees).

When the present invention is implemented, even if the retaining ring 17a is elastically reduced in diameter, the retaining ring 17
The inner diameter surface of a and the bottom surface of the locking groove 15 (the outer diameter surface of the cylindrical portion)
And do not touch. For this reason, the diameter of the bottom surface of the locking groove 15 is made sufficiently smaller than the inner diameter of the retaining ring 17a. Thus, an axial component force is generated based on the engagement between the inclined surface 29 and the axially outer edge of the locking groove 15.

Next, FIGS. 3 and 4 show a second example of the embodiment of the present invention. In the case of this example, inclined surfaces 29, 29 are respectively formed on the inner halves on both sides of the retaining ring 17b. Therefore, in the case of this example, one of the inclined surfaces 29 can be securely engaged with the axially outer edge of the locking groove 15 regardless of the mounting direction of the retaining ring 17b. For this reason, it is possible to prevent the inconvenience of moving the retaining ring in the wrong direction, and to improve the efficiency of the assembling work. In the case of this example, the outer peripheral surface of the distal end portion of the spline shaft 12b beyond the locking groove 15 is simply a cylindrical surface 35, and the outer diameter of the cylindrical surface 35 is determined by the spline shaft 1b.
The diameter of the male spline groove formed on the outer peripheral surface of 2b is smaller than the diameter of the groove bottom circle. Thus, the axial length of the male spline groove is reduced, and broaching for forming the male spline groove is facilitated.

In the case of the present embodiment, a seal ring 31 is provided between the inner end of the outer race 1 and the outer peripheral surface of the outer end of the housing portion 13a to provide a space in which a plurality of rolling elements 10, 10 are installed. And the inner end of the space communicating with the spline engagement portion between the spline shaft 12b and the spline hole 11 are sealed. The seal ring 31
A seal lip 33 made of an elastic material such as rubber or the like is adhered to the inner peripheral edge of a core metal 32 formed in an annular shape as a whole with a crank-shaped cross section. Such a seal ring 31 fixes the cored bar 32 to the inner end of the outer ring 1 by external fitting and tightly fits the sealing lip 3.
The inner peripheral edge of 3 is in sliding contact with the outer peripheral surface of the outer end of the housing portion 13a over the entire circumference. In the illustrated example, a part of the cored bar 32 is abutted against the inner end surface of the outer ring 1,
The positioning of the seal ring 31 in the axial direction is achieved. Further, a garter spring 34 is externally fitted on the outer peripheral surface of the seal lip 33, and the inner peripheral edge of the seal lip 33 and the outer peripheral surface of the outer end of the housing portion 13a are securely and properly applied over the entire circumference. Sliding contact is made by contact pressure so that good sealing performance can be obtained. The housing 13a
The outer peripheral surface of the outer end is made a smooth cylindrical surface by turning or the like to ensure the sealing performance.

In the case of the present embodiment, the seal member 26 is provided between the inner end face of the hub 6a and the outer end face of the housing portion 13a in accordance with the provision of the seal ring 31 as described above.
(See FIG. 1), the inner end surface of the hub 6a and the outer end surface of the housing portion 13a are directly in contact with each other. However, even when a relative displacement in the circumferential direction occurs at the contact portion between the inner end surface of the hub 6a and the outer end surface of the housing portion 13 due to the torque applied during operation, the contact portion is rubbed. In order to prevent generation of a loud noise based on the above, the contact load at the contact portion is set to a small value of about several hundred N. The contact load at the contact portion can be adjusted, for example, by selecting the spring constant of the retaining ring 17b. Other configurations and operations are the same as those of the above-described first example.

[0025]

Since the wheel drive axle unit of the present invention is constructed and operates as described above, it is possible to not only prevent wear of the spline engagement portion between the spline hole and the spline shaft, but also to make it easier than the conventional structure. As the number of parts can be reduced,
The number of assembly steps can be reduced. Therefore, the cost can be reduced while maintaining the durability of the product.

[Brief description of the drawings]

FIG. 1 is a half sectional view showing a first example of an embodiment of the present invention.

FIG. 2 is a partial sectional view of a retaining ring.

FIG. 3 is a half sectional view showing a second example of the embodiment of the present invention.

FIG. 4 is a partial sectional view of a retaining ring.

FIG. 5 is a partially cut-away side view showing one example of a conventional structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer ring 2 Mounting part 3 Outer ring track 4 Knuckle 5 Inner ring 6, 6a Hub 7 Mounting flange 8a, 8b Inner ring track 9 Retaining ring 10 Rolling element 11 Spline hole 12, 12a, 12b Spline shaft 13, 13a Housing part 14 Locking part 15 Lock groove 16 Step surface 17, 17a, 17b Retaining ring 18 Elastic ring 19 Outer ring raceway 20 Seal ring 21, 21a, 21b Drive shaft member 22 Step portion 23 Caulking portion 24 Core metal 25 Elastic plate 26 Seal member 27 Cylindrical portion 28 yen Ring part 29 Inclined surface 30 Cap 31 Seal ring 32 Core metal 33 Seal lip 34 Garter spring 35 Cylindrical surface

Claims (1)

[Claims] 1. An outer ring having an outer ring raceway on an inner peripheral surface and not rotating during use, and a mounting flange for supporting a wheel at a portion near the outer end of the outer peripheral surface. A hub provided with an inner raceway directly or through an inner race, a spline hole in the center, and a spline shaft engaged with the spline hole at an outer end, and an inner end formed with an outer race of a constant velocity joint. A drive shaft member serving as a housing part, a plurality of rolling elements rotatably provided between the outer raceway and the inner raceway, and an outer periphery of the spline hole on an inner peripheral surface of the hub. A step surface formed over the entire circumference in a continuous state from the outer edge, a locking groove formed over the entire circumference on the outer peripheral surface near the tip of the spline shaft, and an elastic material. It is formed in a ring shape, and it is hung on this locking groove and the step surface. In a wheel drive axle unit provided with a retaining ring for preventing the spline shaft from falling out of the spline hole in a handed state, the retaining ring is
A portion having a resilience in a direction to reduce a diameter dimension in a state of being bridged between the locking groove and the step surface, and a portion of the axial outer surface which abuts at least an axial outer edge of the locking groove; Is inclined in a direction inward in the axial direction as it goes inward in the diametrical direction, and the retaining ring is hooked on the locking groove and the stepped surface, thereby locking the inclined surface. An axle for driving a wheel, wherein the inner end surface of the hub and the outer end surface of the housing portion abut directly or via another member in a state where the abutment is in contact with an axial outer edge of the groove. unit.