JP2003136908A - Bearing unit for driving wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent any abnormal noise at an abutting part of an inner end face of a caulking part 30 on an outer end face of an outer ring 14 for a constant velocity joint or any wear of the abutting part caused by the fluctuation of the torque transmitted between a drive shaft member 18 and a hub 4b. SOLUTION: A recessed groove 34 is formed in a center part in the radial direction of a flat surface 32 formed on the inner end face of the caulking part 30, and grease is filled in the recessed groove 34. Since the pressure can be applied to rolling elements 6 and 6 by the caulking part 30, the tightening force of a nut 24a is suppressed to reduce the bearing pressure of the abutting part. In addition, the coefficient of friction of the abutting part can be reduced by the grease, the friction energy of the abutting part is reduced to solve the above problems.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The wheel drive bearing unit according to the present invention has a constant velocity joint and a wheel support bearing unit integrated with each other, and has drive wheels supported by an independent suspension type suspension (FF vehicle (front Stationary engine front-wheel drive vehicle)
Front wheel, FR vehicle (front engine rear wheel drive vehicle) and RR vehicle (rear engine rear wheel drive vehicle) rear wheel, 4WD vehicle (four-wheel drive vehicle)} are freely rotatable with respect to the suspension system. It is used to rotate and drive the drive wheels.

[0002]

2. Description of the Related Art In order to rotatably support a wheel with respect to a suspension device, various wheel supporting bearing units in which an outer ring and an inner ring are rotatably combined via rolling elements are used. Further, a wheel drive bearing unit for supporting a drive wheel on an independent suspension type suspension and for rotationally driving the drive wheel is a combination of the wheel support bearing unit and a constant velocity joint, and a differential gear and a drive wheel. It is necessary to smoothly transmit the rotation of the drive shaft (while ensuring constant velocity) to the wheel regardless of the relative displacement between the wheel and the steering angle given to the wheel. FIG. 7 shows a general wheel driving bearing unit in which a wheel supporting bearing unit 1 and a constant velocity joint 2 are combined for such a purpose.

Of these, the wheel supporting bearing unit 1 is
A hub 4 and an inner ring 5 are rotatably supported on the inner diameter side of the outer ring 3 via a plurality of rolling elements 6, 6. Outer ring 3 among them does not rotate during use in a state where it is fixedly coupled to a knuckle (not shown) that constitutes a suspension device by a first flange 7 provided on the outer peripheral surface thereof. Further, a pair of outer ring raceways 8, 8 are provided on the inner peripheral surface of the outer ring 3, and the hub 4 and the inner ring 5 are rotatably supported on the inner diameter side of the outer ring 3 concentrically with the outer ring 3. ing.

Of these, the hub 4 is the outer end of the outer peripheral surface (the outer side in the axial direction means the side which is the outer side in the width direction of the vehicle when assembled in a vehicle, and is not shown in each drawing except FIGS. The left side of the figure is the same throughout this specification.) A second flange 9 for supporting the wheel is provided at the side portion. Further, a first inner ring raceway 10 is formed at an intermediate portion of the outer peripheral surface of the hub 4, and the inner end (inwardly in the axial direction) means a side which is the center side in the width direction of the vehicle when assembled to the vehicle. , Figures 2, 4,
Right side of each drawing except 5. Same throughout this specification. ) Part, the second inner ring raceway 1 is formed on the outer peripheral surface of the small-diameter step part 11.
The inner ring 5 having the shape 2 is externally fitted and fixed. A spline hole 13 is provided in the center of the hub 4.

On the other hand, the constant velocity joint 2 includes an outer ring 14 for constant velocity joint, an inner ring 15 for constant velocity joint, a plurality of balls 16, 16 and a spline shaft 17. The constant velocity joint outer ring 14 and the spline shaft 17 constitute a drive shaft member 18. That is, the spline shaft 17 is provided in the outer half portion of the drive shaft member 18 and can be engaged with the spline hole 13, and the outer ring 14 for constant velocity joint is provided in the inner half portion of the drive shaft member 18. It is provided. Outer engagement grooves 19, 19 are provided at a plurality of circumferential positions on the inner peripheral surface of the outer ring 14 for constant velocity joints.
Each is formed in a direction perpendicular to the circumferential direction.
The inner ring 15 for a constant velocity joint has a second spline hole 20 at the center thereof, and the outer engagement groove 1 is formed on the outer peripheral surface thereof.
Inner engaging grooves 21 and 21 are formed in the portions aligned with 9 and 19 in a direction perpendicular to the circumferential direction. The balls 16, 16 are held between the inner engagement grooves 21, 21 and the outer engagement grooves 19, 19 by the retainer 22, and the engagement grooves 21, 19 are held.
It is provided so that it can roll along. The shape of each component of the constant velocity joint 2 is the same as that of the well-known Rzeppa type or Barfield type constant velocity joint, and is not related to the gist of the present invention. Is omitted.

In the constant velocity joint 2 and the wheel supporting rolling bearing unit 1 as described above, the spline shaft 17 is inserted into the spline hole 13 of the hub 4 from the inside toward the outside. Then, a nut 24 is screwed into a male screw portion 23 provided on a portion of the spline shaft 17 protruding from the outer end surface of the hub 4, and is further tightened to be fixedly coupled to each other. In this state, the inner end surface of the inner ring 5 contacts the outer end surface of the outer ring 14 for constant velocity joint, so that the inner ring 5 is not displaced in the direction of coming out of the small-diameter step portion 11. At the same time, an appropriate preload is applied to each of the rolling elements 6, 6.

Further, when the vehicle is mounted on the suspension system of the vehicle, the male spline portion 26 provided at the outer end of the drive shaft 25 is inserted into the second spline hole 20 provided at the center of the inner ring 15 for constant velocity joint. Are spline engaged. Then, a retaining ring 28 engaged with a retaining groove 27 formed on the outer peripheral surface of the outer end portion of the male spline portion 26 is formed at the peripheral edge portion of the outer end opening of the second spline hole 20. The male spline portion 26 is prevented from coming out of the second spline hole 20 by engaging with the locking step portion 29.
The inner end of the drive shaft 25 is fixedly coupled to the center of the trunnion of a tripod type constant velocity joint (not shown) provided on the output shaft of a differential gear (not shown). Therefore, when the vehicle is running, the drive shaft 25 is
Rotate at a constant speed.

Further, in Japanese Unexamined Patent Publication No. 11-5404, as shown in FIG. 8, the inner end portion of the hub 4a is present at a portion protruding inward from the inner ring 5 fitted on the small-diameter step portion 11. A caulking portion 30 formed by caulking and expanding (plastically deforming) a cylindrical portion outwardly in the diametrical direction causes the inner ring 5 to move the inner ring 5 to the small diameter stepped portion 11.
A structure for holding down the step surface 31 is described.
In the case of the second example of the conventional structure, a preload is applied to the rolling elements 6 by the pressing force of the caulking portion 30. The wheel supporting bearing unit 1 and the constant velocity joint 2 are coupled to each other by screwing the male screw portion 23 provided on the outer end portion of the spline shaft 17 and the nut 24, as in the case of the first example of the conventional structure described above.・ It is done by tightening. This nut 2
In the state in which 4 is tightened, the flat surface 32 provided on the inner side surface of the caulking portion 30 and the outer end surface of the outer ring 14 for constant velocity joint contact.

[0009]

The above-described wheel drive bearing unit as shown in FIGS. 7 to 8 often produces an abnormal noise called a bucking noise during operation. The generation of such abnormal noise is based on the fluctuation of the torque transmitted between the constant velocity joint 2 and the wheel supporting bearing unit 1 and the inner end surface of the inner ring 5 or the caulking portion 30 and the outer side of the constant velocity joint outer ring 14. It is known that this is caused by the friction of the contact portion with the end face. That is, the torque changes frequently due to repeated acceleration and deceleration. Further, the spline shaft 17 provided on the constant velocity joint 2 side is elastically deformed in the torsional direction due to the torque transmission between the constant velocity joint 2 and the wheel supporting bearing unit 1, but the deformation amount is There is a tendency for the torque to change frequently as the torque changes.

When the force for deforming the spline shaft 17 in the torsional direction or the force for the torsionally deformed spline shaft 17 to return to the original state becomes larger than the frictional force acting on the contact portion. A slight slip occurs at this contact portion. In this case, if the frictional force acting on the abutting portion is large, the inner ring 5 or the caulking portion 30 is caused by the slip.
The energy that rubs the inner end surface of the outer peripheral surface of the outer ring 14 for constant velocity joints becomes large, and an unpleasant noise is generated.

In order to prevent the occurrence of such abnormal noise, the inner end surface of the inner ring 5 and the outer ring 14 for the constant velocity joint are conventionally arranged as described in, for example, Japanese Patent Laid-Open No. 2000-110840. It has been considered to form a film for reducing friction on the contact portion with the outer end surface by using grease or the like. If the abutting portion is made slippery, the energy for rubbing the inner end surface of the inner race 5 and the outer end surface of the outer race 14 for constant velocity joints can be suppressed to a small level even if the slight slip occurs, which is annoying. It is possible to prevent abnormal noise. It is known that such a method can obtain a certain effect. However, as shown in FIG. 7, in the case of the structure in which the preload is applied by tightening the nut 24, a sufficient noise reduction effect cannot always be obtained. The reason for this is that since the tightening force of the nut 24 is increased in order to apply a preload, the contact pressure between the inner end surface of the inner ring 5 and the outer end surface of the constant velocity joint outer ring 14 becomes high. This is because even if a friction reducing film is formed on the contact portion, the energy at which the both end surfaces forming the contact portion rub against each other cannot be sufficiently suppressed.

In order to reduce the friction, it is possible to weaken the tightening force of the nut 24 and lower the surface pressure between the inner end surface of the inner ring 5 and the outer end surface of the outer ring 14 for constant velocity joint. In the case of the first example of the conventional structure shown in FIG. 7, it is difficult to adopt it because the rolling elements 6, 6 are preloaded based on the tightening force of the nut 24. In the case of the second example shown in FIG. 8, the tightening force of the nut 24 can be suppressed to be small even when this preload is taken into consideration.
If the friction coefficient of the contact portion between the inner end surface of the caulking portion 30 and the outer end surface of the constant velocity joint outer ring 14 is left unchanged by simply suppressing the tightening force of No. 4 above, the above abnormal noise is sufficiently generated. I can't hold back. In view of such circumstances, the present invention has been devised to realize a wheel drive bearing unit having a structure capable of sufficiently obtaining the effect of preventing the generation of abnormal noise called bucking noise.

[0013]

A wheel drive bearing unit according to the present invention comprises a drive shaft member, a hub, a flange, a first inner ring raceway, a small diameter step portion, an inner ring, an outer ring, and a plurality of members. And a rolling element. Among these, the drive shaft member is provided with an outer ring for a constant velocity joint for forming a constant velocity joint in the inner half portion, and a spline shaft in the outer half portion.
Further, the hub is rotationally driven through the constant velocity joint at the time of use by engaging the spline shaft with a spline hole provided at the center. Further, the flange is provided on the outer peripheral surface of the outer end portion of the hub for supporting and fixing the wheel to the hub. The first inner ring raceway is provided on the outer peripheral surface of the intermediate portion of the hub directly or through an inner ring separate from the hub. The small-diameter step portion is formed on the inner end portion of the hub, and has an outer diameter smaller than that of the portion where the first inner ring raceway is provided. The inner ring has a second inner ring raceway on the outer peripheral surface,
It is fitted onto the small diameter step portion. Also, the outer ring has a pair of outer ring raceways facing the first inner ring raceway and the second inner ring raceway on the inner peripheral surface, and does not rotate during use. Further, a plurality of each rolling element is provided between each outer ring raceway and each of the first and second inner ring raceways.

In particular, in the wheel drive bearing unit of the present invention, the inner ring externally fitted to the small-diameter step portion is a cylinder present at the inner end portion of the hub projecting inward from the inner ring. The portion is pressed toward the stepped surface of the small diameter stepped portion by the crimped portion formed by crimping outwardly in the diametrical direction, and is fixedly connected to the hub in a state in which each rolling element is preloaded. In addition, the hub has an inner end surface of a retaining member such as a nut or a cotter whose outer end surface is engaged with the tip end portion of the drive shaft member by screwing or wedge engagement. The end faces are joined and fixed to the drive shaft member in a state where they are brought into contact with the outer end faces of the outer ring for a constant velocity joint, respectively. Further, a friction reducing structure for reducing frictional resistance with the outer end face in the circumferential direction is provided at a portion of the surface of the caulked portion that abuts the outer end face of the outer ring for a constant velocity joint.

[0015]

According to the wheel drive bearing unit of the present invention configured as described above, the surface pressure of the contact portion between the inner end surface of the caulked portion and the outer end surface of the outer ring for a constant velocity joint can be suppressed to be low. Since this structure is adopted and a friction reducing structure is provided at the contact portion, the energy for rubbing the inner end surface and the outer end surface can be suppressed to a low level, and an annoying noise can be prevented.

[0016]

1 and 2 show a first example of an embodiment of the present invention. The feature of the present invention is that the hub 4b is
The inner ring 5 fitted to the small-diameter step portion 11 provided at the inner end portion of the hub is fixed to the small-diameter step portion 11 by the caulking portion 30 formed at the inner end portion of the hub 4b, and is suitable for each rolling element 6, 6. This structure is designed to apply a large amount of preload, and is to prevent the generation of abnormal noise called bucking noise during operation. Regarding the structure of the fixed part of the inner ring 5, the second example of the conventional structure shown in FIG. 8 described above and the structure of the other parts are the same as the first example of the conventional structure shown in FIG. 7 described above. Therefore, the same parts are designated by the same reference numerals to omit or simplify the overlapping description, and hereinafter, the characteristic part of the present invention and the part different from the above-described conventional structure will be mainly described.

In the case of this example, a separate inner ring 5a having the first inner ring raceway 10 provided on the outer peripheral surface thereof is externally fitted and fixed to the intermediate portion of the hub 4b. The inner ring 5 is externally fitted to a portion of the inner end of the hub 4b that projects inward in the axial direction from the inner end surface of the separate inner ring 5a, that is, the small-diameter step portion 11. In the case of such an example, the inner end surface of the separate inner ring 5a corresponds to the step surface described in the claims. With the inner ring 5 fitted onto the small-diameter step portion 11 in this manner, the hub 4b is
The cylindrical portion formed on the inner end portion of the is plastically deformed outward in the radial direction to form the caulked portion 30 having the flat surface 32.
A concave groove 34 is formed over the entire circumference in a part of the inner end surface of the crimped portion 30 manufactured in this manner and in the radial intermediate portion of the flat surface 32. After forming the caulked portion 30, the recessed groove 34 is formed in the radial intermediate portion of the flat surface 32 by turning using a lathe or the like. Or
It can also be formed by subjecting this flat surface to plastic working such as coining. In any case, the flat surfaces 32 remain on the inner side and the outer side of the concave groove 34 in the radial direction, so that the contact area between the inner end surface of the caulked portion 30 and the outer end surface of the constant velocity joint outer race 14 is increased. Have secured. Therefore, when the nut 24a is tightened as described below, the flat surface 32
And the outer end surface of the outer ring 14 for constant velocity joints are brought into contact with each other over a sufficiently wide area to prevent the caulked portion 30 from being further plastically deformed (sag). Further, the groove 34 is filled with grease.

On the other hand, a cylindrical portion 33 is formed on the outer end surface of the nut 24a screwed into the male screw portion 23 formed on the outer end portion of the spline shaft 17 in the outer half portion of the drive shaft member 18, and the cylindrical portion 33 is formed. Notches 44, 44 are formed at even locations (six locations in the illustrated example) at equal intervals in the circumferential direction. On the other hand, at the outer end of the male screw portion 23,
A through hole (not shown) is formed in a portion that can be aligned with the notches 44, 44 while the nut 24a is screwed and tightened.
The male screw 23 is formed so as to penetrate in the diametrical direction. Then, a nut 24a is screwed into the male screw portion 23 and further tightened by a necessary amount, and in the state where the nut 24a is tightened by a necessary amount, the through hole and a pair of notches 44 present at positions aligned with both end openings of the through hole are not shown. Insert the pin through the nut 24
It is designed such that a remains in the position where the necessary amount is tightened.

Such a tightening force (tightening torque) of the nut 24a causes a relative displacement in the axial direction between the drive shaft member 18 and the hub 4b regardless of the thrust load applied to the drive shaft member 18 during operation. It is regulated from the viewpoint of preventing That is, during operation, the drive shaft member 18 and the hub 4b are relatively displaced in the axial direction by the axial force generated at the tripod type constant velocity joint portion provided on the differential gear side, and further by the centrifugal force generated at the time of turning. Axial force is applied. When the surface pressure of the contact portion between the flat surface 32 formed on the inner end surface of the caulking portion 30 and the outer end surface of the constant velocity joint outer ring 14 is small, the contact portion is elastically deformed by the axial force, and the drive is performed. The shaft member 18 and the hub 4b are relatively displaced in the axial direction. Such relative displacement is caused by the spline shaft 17 that constitutes the drive shaft member 18.
Not only does this cause wear of the spline engagement portion with the spline hole 13 provided at the center of the hub 4b, but also annoying noise is generated at the spline engagement portion. On the other hand, in the case of this example, since the tightening force of the nut 24a is secured to some extent, the spline engagement portion can be prevented from shifting regardless of the axial force applied during operation. For this purpose, the minimum value of the tightening force of the nut 24a is preferably about 3.5 KN in consideration of the safety factor in the case of a wheel drive bearing unit for a general passenger car. Also, this tightening force is this value (3.5K
N) and the outer ring 14 for constant velocity joint, which will be described later, should be as low as possible.
This is preferable from the viewpoint of preventing abnormal noise from being generated at the contact portion with the outer end surface of.

Further, in the case of this example, the outer peripheral surface of the outer ring 3a is simply a cylindrical surface, and the outer ring 3a is fitted and fixed in the support hole 36 formed in the knuckle 35 constituting the suspension device. An inward flange-shaped locking flange 37 is formed at the inner end opening of the support hole 36.
The inner end surface of the outer ring 3a is abutted against. In this state,
A retaining ring 38 engaged with a retaining groove formed on the inner peripheral surface of the outer end portion of the support hole 36 holds the outer end surface of the outer ring 3a so that the outer ring 3a does not come out of the support hole 36. . Further, seal rings 39a, 39b are provided between the inner peripheral surfaces of both ends of the outer ring 3a and the outer peripheral surface of the outer end of the separate inner ring 5a and the outer peripheral surface of the inner end of the inner ring 5, respectively. The openings at both ends of the space 40 in which the rolling elements 6, 6 are installed are closed.

According to the wheel drive bearing unit of the present embodiment constructed as described above, a difference is caused due to the contact portion between the inner end surface of the caulked portion 30 and the outer end surface of the constant velocity joint outer ring 14 rubbing against each other. The sound is low enough (almost inaudible)
Can be suppressed. The reason for this is that the surface pressure of the contact portion can be kept low, and the friction coefficient of the contact portion is further reduced. That is, in the case of the structure of this example, proper preload application to the rolling elements 6, 6 is performed by the caulking portion 3
This is completed by holding down both inner rings 5, 5a at 0. Therefore, the tightening force of the nut 24a only needs to have a value that can secure the coupling strength between the hub 4b and the drive shaft member 18, and as shown in FIG. It can be made lower than in the case of the structure. Then, since the tightening force of the nut 24a is suppressed to a low level, the surface pressure of the abutting part is suppressed to a low level, and the abutting part can be slippery.

Further, in the case of the present embodiment, the grease filled in the concave groove 34 oozes out to the abutting portion, lowers the friction coefficient of the abutting portion, and makes the abutting portion slippery. . In the case of the structure of the present example, these actions are combined to reduce the energy for rubbing the inner end surface of the caulked portion 30 and the outer end surface of the outer ring 14 for constant velocity joint to a small value. Then, by suppressing this energy to be small, it is possible to generate an abnormal noise that is offensive to the ear and prevent wear of the contact portion. Prevention of the generation of abnormal noise leads to prevention of discomfort to passengers and pedestrians. Further, the prevention of wear leads not only to the improvement of the durability of the wheel drive bearing unit but also to the improvement of the reliability of the rotation speed detecting device. That is, at the inner end of the hub 4b or the inner ring 5 that rotates with the wheel, an encoder made of a magnetic material or a permanent magnet, which constitutes a rotation speed detecting device, is incorporated in a part of the seal ring 39b, for example. Install by. If the magnetic wear powder generated at the contact portion adheres to the detected portion of the encoder, the reliability of the rotation speed detection device may be impaired. On the other hand, in the case of the wheel drive bearing unit of this example,
Since the generation of the magnetic abrasion powder can be suppressed, the reliability of the rotation speed detecting device can be ensured.

Next, FIGS. 3 to 4 show a second example of the embodiment of the present invention. In the case of this example, concentric circular lines 41, 41 (fine ridges) are formed in the circumferential direction on the flat surface 32 formed on the inner end surface of the caulking portion 30 at the inner end portion of the hub 4b. There is. Also in the case of this example, the flat surface 32
The contact portion with the outer end surface of the constant velocity joint outer ring 14 can be made slippery so that an abnormal noise is generated and wear of the contact portion is prevented. In addition, it is preferable that the lines 41 and 4 are
Grease is applied to one part for the purpose of reducing the coefficient of friction. Other configurations and operations are similar to those in the case of the first example described above, and therefore, the same reference numerals are given to the same parts,
A duplicate description will be omitted.

Next, FIG. 5 shows a third embodiment of the present invention.
An example is shown. In the case of this example, a coating layer 42 made of a low friction material is formed on the flat surface 32 formed on the inner end surface of the caulking portion 30 at the inner end portion of the hub 4b. As the low-friction material forming the coating layer 42, various low-friction materials such as molybdenum disulfide and polytetrafluoroethylene resin can be used in addition to the bonder and the grease. Also in the case of this example as described above, the flat surface 32 and the outer ring 1 for a constant velocity joint are
4 (see, for example, FIG. 1) makes the contact portion with the outer end surface slippery so that an abnormal noise is generated and the contact portion is prevented from wearing. Other configurations and operations are similar to those in the case of the first example described above, and therefore illustration and description of equivalent parts will be omitted.

Next, FIG. 6 shows a fourth embodiment of the present invention.
An example is shown. In the case of this example, similar to the case of the conventional structure shown in FIGS. 7 to 8 described above, the first flange 7 is formed on the outer peripheral surface of the outer ring 3, and the first flange 7 is attached to the knuckle 35. , Are fixed by a plurality of bolts 43. Further, the first inner ring raceway 10 is directly formed on the intermediate portion of the outer peripheral surface of the hub 4a. Also in the case of this example which is premised on such a structure, the caulking portion 3 formed on the inner end portion of the hub 4a is also used.
A friction reducing structure similar to that of any of the first to third examples described above is provided at the contact portion between the flat surface 32 of 0 and the outer end surface of the outer ring 14 for constant velocity joint.

[0026]

Since the present invention is constructed and operates as described above, the wheel drive bearing unit can surely apply the preload to the rolling elements and effectively suppress the annoying noise generated during the operation. Can be realized.

[Brief description of drawings]

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

FIG. 2 is an AA view of FIG. 1 with a part omitted.

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

FIG. 4 is a BB view of FIG. 3 with a part omitted.

FIG. 5 is a view similar to FIG. 4, showing a third example of the embodiment of the present invention.

FIG. 6 is a sectional view showing the fourth example.

FIG. 7 is a sectional view showing a first example of a conventional structure.

FIG. 8 is a half sectional view showing the second example.

[Explanation of symbols]

1 Wheel support bearing unit 2 constant velocity joint 3,3a outer ring 4, 4a, 4b hub 5, 5a inner ring 6 rolling elements 7 First flange 8 Outer ring track 9 Second flange 10 First inner ring raceway 11 Small diameter step 12 Second inner ring raceway 13 Spline hole 14 Outer ring for constant velocity joint 15 Inner ring for constant velocity joint 16 balls 17 Spline shaft 18 Drive shaft member 19 Outer engagement groove 20 Second spline hole 21 inner engagement groove 22 cage 23 Male thread 24, 24a nut 25 drive shaft 26 Male spline part 27 locking groove 28 retaining ring 29 Locking step 30 caulking section 31 step surface 32 flat surface 33 Cylindrical part 34 groove 35 knuckles 36 Support hole 37 Locking collar 38 retaining ring 39a, 39b Seal ring 40 space 41 streak 42 coating layer 43 volts 44 cutout

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F16D 3/20 F16D 1/06 Q

Claims (2)

[Claims] 1. An outer ring for a constant velocity joint for constituting a constant velocity joint in an inner half portion, a drive shaft member provided with a spline shaft in the outer half portion, and a spline hole provided in a central portion of the spline. By engaging the shaft, the hub is driven to rotate through the constant velocity joint during use, and a flange provided on the outer peripheral surface of the outer end of the hub for supporting and fixing the wheel to the hub, On the outer peripheral surface of the intermediate portion of the hub, a first inner ring raceway provided directly or via an inner ring separate from the hub, and formed on the inner end portion of the hub,
A small-diameter stepped portion having an outer diameter smaller than that of the portion provided with the first inner ring raceway, and a second inner ring raceway on the outer peripheral surface,
An inner ring externally fitted to the small-diameter step portion, an outer ring having a pair of outer ring raceways facing the first inner ring raceway and the second inner ring raceway on the inner peripheral surface, and not rotating even during use, and In a wheel drive bearing unit including a plurality of rolling elements provided between each outer ring raceway and the first and second inner ring raceways, the inner ring fitted onto the small diameter step portion is , The inner end portion of the hub is pressed toward the stepped surface of the small-diameter step portion by a caulking portion formed by caulking and expanding a cylindrical portion existing in a portion projecting inwardly from the inner ring, In addition, in a state where a preload is applied to each of the rolling elements, the hub is coupled and fixed to the hub, and the hub has the outer end surface engaged with the inner end surface of the restraining member which is engaged with the front end portion of the drive shaft member. Contact the inner end surface of the part with the outer end surface of the outer ring for constant velocity joint. In this state, it is fixedly connected to the drive shaft member, and the friction resistance between the caulking portion and the outer end surface of the outer ring for a constant velocity joint on the surface of the caulking portion is reduced in the circumferential direction. A bearing unit for driving a wheel, which is characterized by being provided with a friction reducing structure. 2. A friction-reducing structure is formed on the surface of the caulking portion in the circumferential direction and has grease stored therein, and concentric circular lines formed on the surface of the caulking portion in the circumferential direction.
The wheel drive bearing unit according to claim 1, which is one or more selected from a coating layer made of a low-friction material coated on the surface of the caulked portion.