JP2001158206A - Bearing unit for driving wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To downsize a bearing unit for driving a wheel while suppressing the increase of a manufacturing cost. SOLUTION: Diameter of a tip circle of a female spine 21 on the outer diameter side is larger than a minimum inner diameter of the inner surface of a part of a housing 19b away from the female saline 21. An inner end of a hub 5b is projected from the inner end surface of an auxiliary ring 31, and a caulk part 16 is formed at a position facing to the inner end surface of the auxiliary ring 31. Because a caulk jig does not interfere with the auxiliary ring 31 in forming the caulk part 16, oscillating caulk can be employed to solve the problem discussed above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheel drive bearing unit in which a constant velocity joint and a hub unit are integrated, and a drive wheel #FF vehicle (front engine front wheel) supported by an independent suspension type suspension. Driving car) front wheel, F
The rear wheels of the R vehicle (front-engine rear-wheel drive vehicle) and the RR vehicle (rear-engine rear-wheel drive vehicle) and all the wheels の of the 4WD vehicle (four-wheel drive vehicle) are rotatably supported by the suspension system. In addition, 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 bearing units are used in which an outer ring and an inner ring are rotatably combined via rolling elements. or,
In addition to supporting the drive wheels on an independent suspension,
The wheel drive bearing 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 wheel drive bearing unit that can be configured to be relatively small and lightweight in combination with such a constant velocity joint, a unit described in European Patent Publication No. EP 0849097 A2 has been conventionally known.

FIG. 4 shows a conventional structure described in this publication. First, the structure of the wheel drive bearing unit 1 shown in the upper half of FIG. 4 will be described. Outer ring 2 that does not rotate while being mounted on a vehicle and supported by a suspension device
Has a first mounting flange 3 on the outer peripheral surface for supporting the suspension device, and a double-row outer raceway 4 for forming a double-row angular bearing on the inner peripheral surface. A hollow hub 5 is supported inside the outer ring 2 concentrically with the outer ring 2.

[0004] The hub 5 has a second mounting flange 6 for supporting the wheel at a portion closer to the outer end of the outer peripheral surface (the end which is outward in the width direction when assembled to an automobile, the left end in Figs. 1 to 4). A first inner raceway 8 is also formed directly at the center or via a separate inner race 7. Also, a small-diameter stepped portion 9 is provided near the inner end of the outer peripheral surface of the hub 5 (the end which is the center in the width direction when assembled to an automobile, and the right end in FIGS. 1 to 4). Male spline section 10
Each is formed. An inner ring 11 is externally fixed to the outer peripheral surfaces of the small-diameter step portion 9 and the inner-diameter-side male spline portion 10.

The inner race 11 has a second inner raceway 12 at the outer end of the outer peripheral surface, and an outer diameter side male spline portion 14 for assembling a constant velocity joint 13 to be described later at the inner end.
Each is formed. Further, on the inner peripheral surface of the inner ring 11, an inner diameter side female spline portion 15 which is spline-engaged with the inner diameter side male spline portion 10 is formed. And
The inner ring 11 is externally fitted to the inner end of the hub 5 and
The inner diameter side male spline section 10 and the inner diameter side female spline section 15 are spline-engaged. Further, the inner end surface of the inner ring 11 is suppressed by a caulking portion 16 formed at a portion protruding from the inner end surface of the inner ring 11 at the inner end portion of the hub 5, and the inner ring 11 is attached to the inner end portion of the hub 5. , Fixed without rattling.

[0006] A plurality of rolling elements 17, 17 are provided between the outer raceways 4, 4 and the first and second inner raceways 8, 12, respectively, so as to be freely rollable. The hub 5 is rotatably supported inside the housing. Seal rings 18 are provided between the inner peripheral surfaces of both ends of the outer race 2 and the intermediate outer peripheral surface of the hub 5 and the intermediate peripheral outer surface of the inner race 11, respectively. The openings at both ends of the space where the is installed are closed.

Further, the hub 5 is provided with a housing 19 serving as an outer ring of the constant velocity joint 13 and the inner ring 11.
And the hub 5 is rotatably driven. On the inner peripheral surface of the inner half portion of the housing portion 19, an engagement groove 27 is formed which is a trajectory of the ball 20 which constitutes the Zeppa type constant velocity joint 13. On the other hand, an outer diameter side female spline portion 21 is formed on the inner peripheral surface of the outer end portion. The outer-diameter female spline portion 21 and the outer-diameter male spline portion 14 formed on the outer peripheral surface of the inner end of the inner ring 11 are spline-engaged.

A retaining ring 22 is provided between the outer diameter side female spline portion 21 and the outer diameter side male spline portion 14 so that the housing portion 19 and the inner ring 11 are not separated. ing. That is, the ring-shaped retaining ring 2
The inner locking groove 23 is formed on the outer peripheral surface of the inner end of the inner ring 11 over the entire circumference, and the outer locking groove 23 is formed on the inner peripheral surface of the outer end of the housing portion 19 over the entire circumference. The housing portion 19 and the inner race 11 are prevented from moving in the axial direction by being bridged between the grooves 24.

When assembling the wheel drive bearing unit 1 configured as described above to an automobile, the outer ring 2 is supported on a suspension (knuckle) 38 by the first mounting flange 3,
The front wheel 25, which is also a driving wheel, for example, is fixed to the hub 5 by the second mounting flange 6. Further, the tip of a drive shaft (not shown), which is rotationally driven by the engine via a transmission, is connected to the inner race 26 constituting the constant velocity joint 13.
And spline engagement inside. When driving a car,
The rotation of the inner wheel 26 is transmitted to the hub 5 via a plurality of balls 20, and the front wheel 25 is rotationally driven.

Next, regarding the structure of the wheel drive bearing unit 1a shown in the lower half of FIG. 4, parts different from the structure of the wheel drive bearing unit 1 shown in the upper half of FIG. I will explain mainly. The inner ring 11a constituting the wheel drive bearing unit 1a has a large-diameter cylindrical portion 29 having an inner diameter larger than the inner diameter of the main body portion 28 of the inner ring 11a at an inner end thereof. An outer diameter side female spline portion 21a is formed on the inner peripheral surface. Then, the constant velocity joint 13 is attached to the outer diameter side female spline portion 21a.
The outer diameter side male spline portion 14a formed on the outer peripheral surface of the outer end portion of the housing portion 19a serving as the outer ring is spline-engaged. Further, a retaining ring 22 is stretched between the outer diameter side female spline portion 21a and the outer diameter side male spline portion 14a so that the housing portion 19a and the inner ring 11a do not shift in the axial direction. .

The main body portion 28 of the inner race 11a (portion deviating from the large-diameter cylindrical portion 29) is provided with an internal female spline portion 15a on one end inner peripheral surface and a diametrical direction on the entire inner peripheral surface of the intermediate portion. Inwardly protruding protrusions 30 are formed. The main body portion 28 of the inner race 11a is externally fitted to the inner end of the hub 5a, and the inner diameter side male spline portion 10a and the inner diameter side female spline portion 15a formed in the small diameter step 9 of the hub 5a are splined. Is engaged. Further, a caulking portion 1 formed at the inner end of the hub 5a
The inner ring 11a is fixed to the inner end of the hub 5a without rattling by holding down the inner end surface of the convex portion 30 by 6.

[0012]

In the conventional structure shown in FIG. 4, the work for forming the caulked portion 16 is performed when the diameter of the constant velocity joint 13 is small, regardless of whether the diameter of the constant velocity joint 13 is large. Becomes difficult. For example, the diameter of the circumscribed circle of each ball 20 constituting the constant velocity joint 13 is larger than or approximately equal to the diameter of the circumscribed circle of each rolling element 17, 17 constituting the bearing. In the case of the speed joint 13, as shown in the upper half of FIG. 4, the inner peripheral surface of the outer end of the housing portion 19 of the constant velocity joint 13 can be fitted to the outer peripheral surface of the other end of the inner race 11.
For this reason, the inner end of the hub 5 can be made to protrude from the inner end surface of the inner ring 11, and the caulked portion 16 can be formed at a position facing the inner end surface of the inner ring 11. On the other hand, as shown in the lower half of FIG. 4, the diameter of the minimum circumscribed circle of each ball 20 constituting the constant velocity joint 13 is equal to the diameter of the circumscribed circle of each rolling element 17 constituting the bearing. In the case of a relatively small diameter constant velocity joint 13 having a diameter smaller than or almost equal to the diameter, the constant velocity joint 1 is attached to the inner peripheral surface of the other end of the inner ring 11a.
3, the outer peripheral surface of the outer end of the housing portion 19a must be fitted inside. For this reason, since it is necessary to prevent interference between the caulking portion 16 and the housing portion 19a, the caulking portion 16 cannot be formed at a position facing the inner end surface of the inner ring 11a. Therefore, according to the housing portion 19a having the conventional shape,
As shown in the lower half of FIG. 4, a protrusion 30 must be formed on the inner peripheral surface of the intermediate portion of the inner ring 11a, and a caulked portion 16 must be formed at a position facing the inner end surface of the protrusion 30.
However, it is difficult to form the caulked portion 16 at a position on the inner diameter side of the inner ring 11a, which further enters the outer side in the axial direction (left side in FIG. 4) from the inner end face of the inner ring 11a.

That is, in order to caulk the inner ends of the hubs 5 and 5a to form the caulked portion 16, it is necessary to press the inner ends of the hubs 5 and 5a against a caulking jig with a larger load. For this reason, it is usually caulked with the smallest load possible,
In addition, in order to prevent a problem such as a crack from occurring in the caulked portion 16 after the formation, the caulking jig is connected to the hubs 5 and 5.
a, and swing in the circumferential direction along the inner edge of
While the inner end of 5a is partially plastically deformed diametrically outward, the entire circumference is gradually caulked, so-called rocking. However, when the caulking portion 16 is formed at a position further axially outward from the inner end face on the inner diameter side of the inner ring 11a as described above by this rocking, the caulking jig is moved to the inner periphery of the inner ring 11a. Will interfere with the surface. Also, if a method of caulking the entire circumference of the inner end portion of the hub 5a only by the axial load is adopted so that the caulking jig does not interfere with the inner peripheral surface of the inner ring 11a, the caulking portion 16 is formed. Not only does the press for forming the device become large, but also the crimping portion 16 after forming is liable to cause defects such as cracks, and the yield is reduced. As a result, the cost of the wheel drive hub unit increases. The wheel drive bearing unit of the present invention has been invented in view of such circumstances.

[0014]

The wheel drive bearing unit according to the present invention comprises an outer ring, a hub, a connecting member, and the like, similarly to the above-described conventionally known wheel drive bearing unit.
A rolling element and a housing part are provided. The outer ring has a first mounting flange on the outer peripheral surface for mounting to the suspension device, and a double-row outer ring raceway on the inner peripheral surface.
The hub is provided with a second mounting flange for supporting the wheel at a portion near the outer end of the outer peripheral surface, and a first inner raceway at the central portion. An inner race having a second inner raceway formed on its surface is externally fitted and fixed. Further, the coupling member is spline-engaged with the outer peripheral surface of the inner end of the hub, and the inner end surface of the hub is suppressed by a caulking portion formed by plastically deforming the inner end of the hub radially outward. , And is fixed to the hub. A plurality of rolling elements are provided between each of the outer raceways and the first and second inner raceways so as to freely roll. Further, the housing portion forms a track of a constant velocity joint on an inner peripheral surface thereof, and serves as an outer ring of the constant velocity joint. The female spline portion formed on the inner peripheral surface of the outer end portion of the housing portion and the male spline portion formed on the outer peripheral surface of the coupling member are spline-engaged, and the axial direction of the coupling member and the housing portion is adjusted. Is regulated so that torque can be freely transmitted from the housing portion to the hub.

In particular, in the wheel drive bearing unit according to the present invention, the diameter of the tooth tip of the female spline portion formed on the inner peripheral surface of the outer end portion of the housing portion (the diameter of the largest inscribed circle of the female spline portion). Is larger than the minimum inner diameter of a portion of the intermediate portion of the housing portion that deviates from the female spline portion.

[0016]

As described above, in the case of the wheel drive bearing unit of the present invention, the diameter of the addendum circle of the female spline portion is the minimum inner diameter of the inner peripheral surface other than the female spline portion on the inner peripheral surface of the housing portion. Greater than. For this reason, for example, use a small-diameter constant velocity joint in which the diameter of the minimum circumscribed circle of each ball constituting the constant velocity joint is smaller than or substantially equal to the diameter of the minimum circumscribed circle of each rolling element constituting the bearing. Even in this case, the female spline portion can be externally fitted to the connecting member. Therefore, unlike the conventional structure shown in the lower half of FIG. 4 described above, the inner end surface of this coupling member (in the case of the lower half of FIG. 4, the inner race 11 a) and the outer end surface of the housing are not in contact with each other. There is no close opposition. In other words, the inner end surface of the coupling member is exposed inward without being covered by the housing portion. As a result, the inner end portion of the hub is projected from the inner end surface of the coupling member, and the caulked portion can be formed at a position facing the inner end surface of the coupling member. Therefore, since the caulking portion can be formed by the above-described rocking, the caulking portion can be formed with good yield without introducing a large-sized press machine and the like, and a wheel drive bearing unit can be provided at low cost. .

[0017]

FIG. 1 shows a first embodiment of the present invention. The feature of the present invention lies in that the structure of the housing portion 19b to be assembled to the inner end portion of the hub 5b and serving as the outer ring of the constant velocity joint 13 of the Zeppler type is devised. Since the structure and operation of the other parts are the same as those of the conventional structure shown in the upper half of FIG. 4 described above, the same parts are denoted by the same reference numerals, and duplicated description is omitted or simplified. The following description focuses on features of the present invention and portions different from the conventional structure.

The wheel drive bearing unit of the present embodiment is provided with the housing portion 19 at the inner end of the hub 5b which is a solid body.
b are connected via an auxiliary ring 31. Of the inner and outer peripheral surfaces of this auxiliary ring 31 formed in a short cylindrical shape,
An inner diameter female spline portion 15 is formed on the inner peripheral surface, and an outer diameter male spline portion 14 is formed on the outer peripheral surface. Such an auxiliary ring 31 is provided on the inner end of the hub 5b, on the outer peripheral surface of the inner end.
And the inner diameter side female spline portion 15 are spline-engaged without play, and thus assembled. Then, in this state, the inner end surface of the auxiliary ring 31 is pressed down by the caulking portion 16 formed by plastically deforming the inner end portion of the hub 5b outward in the diametrical direction. It is fixed to the inner end without rattling. In this manner, in a state in which the inner end surface of the auxiliary ring 31 is suppressed by the caulking portion 16 and the inner end surface of the inner ring 11b externally fitted to the small-diameter step portion 9 is suppressed by the auxiliary ring 31,
The dimensions of each part are regulated so that an appropriate preload is applied to each of the rolling elements 17 constituting the bearing unit.
Note that the inner diameter side male spline section 10 and the inner diameter side female spline section 15 that constitute the inner diameter side spline section are
Fine pitches (serrations) formed by knurling or the like can also be used.

On the other hand, an outer female spline portion 21 formed on the inner peripheral surface of the outer end of the housing portion 19b is spline-engaged with the outer male spline portion 14 formed on the outer peripheral surface of the auxiliary ring 31. Let me. An engagement groove 27 is formed on the inner peripheral surface of the inner half portion of the housing portion 19b so as to orbit the ball 20 (see FIG. 4) constituting the constant velocity joint 13. On the other hand, a cylindrical surface portion 32 is formed on the inner peripheral surface of the outer end portion, and the outer diameter side female spline portion 21 is formed on the inner peripheral surface of the outer half portion (left half portion in FIG. 1) of the cylindrical surface portion 32. ing. It should be noted that an escape groove 33 is provided at an intermediate portion of the cylindrical surface portion 32.
Are formed to facilitate the operation of forming the spline grooves of the female spline portion 21 on the outer diameter side. Further, the diameter D ₂₁ of the smallest inscribed circle of the outer diameter side female spline portion 21 (the addendum circle of the female spline), the outer diameter side female spline portion 21 and the engagement with the intermediate inner peripheral surface of the housing portion 19b Mating groove 27
Is larger (D _21> D _min) than present, narrowest diameter of the inner peripheral surface of the constricted portion 39 D _min between. Also, the housing portion 19b is attached to the auxiliary ring 31.
In this state, the axial length L32 of the cylindrical surface portion ₃₂ is regulated so that the caulked portion 16 formed on the inner end surface of the hub 5b does not interfere with the outer end surface of the constricted portion 39.

[0020] In the case of the wheel drive bearing unit of the present invention as described above, the addendum circle of diameter D ₂₁ of the outer diameter side female spline portion 21 is constricted portion provided in the intermediate inner peripheral surface of the housing portion 19b 39 is larger than the diameter _Dmin of the inner peripheral surface. Therefore, the constant velocity joint 13 having a relatively small diameter such that the diameter of the circumcircle of each ball 20 constituting the constant velocity joint 13 is smaller than the diameter of the circumcircle of each of the rolling elements 17, 17 constituting the bearing. Even when used, the outer diameter side female spline portion 21 can be externally fitted to the auxiliary ring 31 which is a connecting member.
As a result, the inner end portion of the hub 5b is projected from the inner end surface of the auxiliary ring 31, and the caulked portion 16 can be formed at a position facing the inner end surface of the auxiliary ring 31. Accordingly, the caulking jig is swung in the circumferential direction along the inner edge of the hub 5b to gradually plastically deform the inner end of the hub 5b outward in the diametrical direction to gradually increase the entire circumference. The caulked portion 16 can be formed by caulking or rocking. Because of this,
Since the yield can be improved without introducing a large-sized press machine and at the same time, it is possible to suppress the occurrence of a defect in the caulking portion 16, a bearing unit for driving a wheel can be provided at low cost.

FIG. 2 shows a second embodiment of the present invention.
An example is shown. The inner ring 11c that constitutes the wheel drive bearing unit of the present example has a cylindrical portion 34 that projects axially inward from the inner end surface of the inner ring 11c toward the inner diameter side of the housing portion 19c that is the outer ring of the constant velocity joint 13. Are formed integrally with the inner ring 11c. In the case of this example, the cylindrical portion 34 functions as a connecting member described in the claims.
For this purpose, the inner diameter of the cylindrical portion 34 is made smaller than the inner diameter of the main body portion 35 (portion deviating from the cylindrical portion 34) of the inner ring 11c, and the inner diameter side female spline portion 15 is formed in the main body portion 35. ing. The inner peripheral surface of the main body 35 of the inner race 11c is a simple cylindrical surface.

The inner ring 11c integrally provided with the cylindrical portion 34 has the main body portion 35 fitted to the small-diameter step portion 9 formed near the inner end of the hub 5b by tight fitting, and the inner ring 11c has a cylindrical shape. The inner female spline portion 15 formed on the inner peripheral surface of the portion 34 and the inner male spline portion 10 formed on the outer peripheral surface of the inner end of the hub 5b are spline-engaged. Then, the inner end surface of the cylindrical portion 34 is suppressed by the caulking portion 16 formed by plastically deforming the inner end portion of the hub 5b outward in the diameter direction, and the cylindrical portion 34 and the cylindrical portion 34 are integrally formed. The provided inner ring 11c is fixed to the hub 5b.

The housing portion 19c has an inner end of a cylindrical surface portion 32 formed at an intermediate portion in the axial direction and an engagement groove 27 which is a track of the ball 20 (see FIG. 4) constituting the constant velocity joint 13. The outer end is directly continuous (without intervening another cylindrical surface portion or the like) by a step portion 40 existing in a direction perpendicular to the central axis of the housing portion 19. Therefore, the axial dimension of the housing portion 19c can be reduced. Other configurations and operations are the same as in the case of the above-described first example.

FIG. 3 shows a third embodiment of the present invention.
An example is shown. In the case of this example, an intermediate material having a basic shape is obtained by pressing a pipe-shaped material in order to form a housing portion 19d which is an outer ring of the constant velocity joint 13. That is, the above-mentioned steel pipe material is subjected to press working to produce the above-mentioned intermediate material having a diametrically inwardly protruding flange portion 36 on the inner peripheral surface of the intermediate portion. Further, the intermediate material is appropriately cut and ground. The housing portion 19d is made by processing. Therefore, the manufacturing cost of the housing 19d can be reduced.

Further, the auxiliary ring 31a, which is externally fitted to the inner end of the hub 5b, is axially inwardly attached to the outer peripheral edge of the inner end surface (FIG. 3).
(A right side of the figure) is formed.
A spline groove of the outer diameter side male spline portion 14 formed on the outer peripheral surface of the auxiliary ring 31a is formed up to the outer peripheral surface of the convex portion. For this reason, without increasing the axial length of the entire wheel drive bearing unit, the outer diameter side male spline portion 14 and the outer diameter side female spline portion 21 formed on the inner peripheral surface of the outer end portion of the housing portion 19d are formed. The axial length of the spline engagement portion can be increased. Therefore, the supporting rigidity of the spline engaging portion with respect to the bending moment and the magnitude (torque capacity) of the torque that can be transmitted at the spline engaging portion can be increased. Note that (horizontal direction in FIG. 3) the length L ₃₇ axial direction of the convex portion 37 is set to about several mm, sufficiently than the axial length L ₁₆ of the caulking portion 16 formed on the inner end of the hub 5b It is small (L ₃₇ ≪L ₁₆ ). The reason is, the axial length L ₃₇ of the convex portion 37 as approximately several mm, if sufficiently smaller than the axial length L ₁₆ of the crimped portion 16, the hub 5 on the inner end surface of the auxiliary ring 31a
When forming the caulked portion 16 by caulking the inner end of the b, even if the caulking jig is swung in the circumferential direction,
This is because the caulking jig does not interfere with the convex portion 37. Other configurations and operations are the same as in the case of the above-described first example.

[0026]

Since the present invention is constructed and operates as described above, it is possible to reduce the size of the wheel drive bearing unit while suppressing an increase in manufacturing costs.

[Brief description of the drawings]

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

FIG. 2 is a partial sectional view showing the second example.

FIG. 3 is a partial sectional view showing the third example.

FIG. 4 is a partially cut-away side view showing two examples of a conventional structure, showing different structures in an upper half and a lower half.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1a Wheel drive bearing unit 2 Outer ring 3 First mounting flange 4 Outer ring track 5, 5a, 5b Hub 6 Second mounting flange 7 Inner ring 8 First inner ring track 9 Small diameter step portion 10, 10a Inner diameter male spline Part 11, 11a, 11b, 11c Inner ring 12 Second inner ring raceway 13 Constant velocity joint 14, 14a Outer diameter side male spline part 15, 15a Inner diameter side female spline part 16 Caulking part 17 Rolling element 18 Seal ring 19, 19a, 19b , 19c, 19d Housing part 20 Ball 21, 21a Outer diameter side female spline part 22 Retaining ring 23 Inner locking groove 24 Outer locking groove 25 Front wheel 26 Inner ring 27 Engagement groove 28 Body part 29 Large diameter cylindrical part 30 Convex part 31 , 31a auxiliary ring 32 cylindrical surface part 33 relief groove 34 cylindrical part 35 main body part 36 flange part 37 convex part 3 Suspension system 39 constricted portion 40 step portion

Claims (3)

[Claims] 1. An outer ring having a first mounting flange for mounting to a suspension device on an outer peripheral surface, a double row of outer ring raceways on an inner peripheral surface, and a wheel supported on a portion of the outer peripheral surface near an outer end. A second mounting flange, also provided with a first inner raceway in the center portion, respectively, and a hub in which an inner race having a second inner raceway formed on the outer peripheral surface thereof is similarly fixed to a portion near the inner end, and a hub, The inner end of the hub is spline-engaged with the outer peripheral surface thereof, and the inner end of the hub is plastically deformed diametrically outward. A member, a plurality of rolling elements provided so as to be able to freely roll between each of the outer raceways and the first and second inner raceways, and a raceway of a constant velocity joint formed on an inner peripheral surface thereof. And the housing part that becomes the outer ring of the constant velocity joint A female spline portion formed on an inner peripheral surface of an outer end portion of the housing portion and a male spline portion formed on an outer peripheral surface of the coupling member are spline-engaged, and an axial direction of the coupling member and the housing portion is formed. In the wheel drive bearing unit which regulates the relative displacement of the female spline and transmits the torque from the housing to the hub, the tip of the female spline portion formed on the inner peripheral surface of the outer end portion of the housing portion. A wheel drive bearing unit characterized in that the diameter of the circle is larger than the minimum inner diameter of a portion deviating from the female spline portion on the inner peripheral surface of the intermediate portion of the housing portion. 2. The wheel drive bearing unit according to claim 1, wherein the coupling member is formed integrally with the inner race, and is a cylindrical portion protruding from an inner end surface of the inner race toward the inner diameter side of the housing. 3. The wheel driving device according to claim 1, wherein the coupling member is an auxiliary ring formed separately from the inner ring, and an outer end surface of the auxiliary ring and an inner end surface of the inner ring abut against each other. Bearing unit.