JPH11166524A - Rolling bearing unit for wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize and reduce weight while securing durability. SOLUTION: A housing part 11a for constituting a constant velocity joint 10a is provided at the end part of a hub 28 constituting an inner ring equivalent member 30 together with an inner ring 29. The number of outer engaging grooves 26a, 26a formed at the inner peripheral surface of the housing part 11a and that of inner engaging grooves 25a, 25a formed at the outer peripheral surface of an inner ring 22a provided in the housing part 11a are to be eight, and the number of balls 24, 24 are to be eight. The outer diameters of the balls 24, 24 can be made small by the increased portion of the number of the balls 24, 24 so as to miniaturize and reduce weight based on the decrease of pitch circle diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION A rolling bearing unit for a wheel according to the present invention is a so-called fourth-generation hub unit, and is provided with a drive wheel #FF vehicle (front engine front wheel drive vehicle) supported by an independent suspension type suspension. ) Front wheels, rear wheels of FR vehicles (front-engine rear-wheel drive vehicles) and RR vehicles (rear-engine rear-wheel drive vehicles), and all wheels of 4WD vehicles (four-wheel drive vehicles).
Is used to rotatably support the suspension device.

[0002]

2. Description of the Related Art In order to rotatably support a wheel with respect to a suspension device, various types of rolling bearing units for wheels are used in which an outer ring and an inner ring are rotatably combined via rolling elements. In addition, the rolling bearing unit for wheels for supporting the driving wheels on the independent suspension type suspension is combined with a constant velocity joint to drive the wheels regardless of the relative displacement between the differential gear and the driving wheels and the steering angle given to the wheels. It is necessary to transmit the rotation of the shaft to the wheels smoothly (with constant speed). A so-called fourth-generation hub rolling unit for a wheel, which can be constructed in combination with such a constant velocity joint and is relatively small and light, has been described in Japanese Patent Application Laid-Open No. 7-317754. It has been known.

FIG. 4 shows a conventional structure described in this publication. An outer ring 1 (an outer ring-equivalent member) that does not rotate in a state of being mounted on a vehicle and supported by a suspension device has a first mounting flange 2 on its outer peripheral surface for supporting the suspension device.
On the inner peripheral surface, respectively. Inside the outer ring 1, first and second inner ring members 4,
A hub 6 (member corresponding to an inner ring) formed by combining the five hubs 5 is disposed. The first inner race member 4 has a second mounting flange 7 for supporting the wheel at one end (leftward in FIG. 4) of the outer peripheral surface, and a second mounting flange 7 at the other end (rightward in FIG. 4). The first inner raceway 8 is formed in a cylindrical shape provided for each. On the other hand, the second inner race member 5 has one end (the left end in FIG. 4) as a cylindrical portion 9 for externally fitting and fixing the first inner race member 4, and the other end (FIG. 4). Right end)
Is a housing part 11 which becomes an outer ring of a zeppa type constant velocity joint 10, and a second inner ring raceway 12 is provided on the outer peripheral surface of the intermediate part.
Is provided. By providing a plurality of rolling elements 13, 13 between the outer raceways 3, 3 and the first and second inner raceways 8, 12, respectively, the hub 6 is provided inside the outer race 1. Is rotatably supported.

[0004] Locking grooves 14 and 15 are formed at positions where the inner peripheral surface of the first inner race member 4 and the outer peripheral surface of the second inner race member 5 are aligned with each other, and a retaining ring is provided. 16 are provided in such a manner as to extend over both of the locking grooves 14 and 15 so that the first inner ring member 4 is connected to the second inner ring member 5.
Prevents getting out of. Further, welding is performed between the outer peripheral edge of one end surface (the left end surface in FIG. 4) of the second inner race member 5 and the inner peripheral edge of the step 17 formed on the inner peripheral surface of the first inner race member 4. 18 to fix the first and second inner ring members 4 and 5 to each other.

Further, between the openings at both ends of the outer race 1 and the outer peripheral surface of the intermediate portion of the hub 6, a substantially cylindrical cover 19a, 19b made of a metal such as a stainless steel plate is provided. Annular seal ring 20a, 2
0b. The covers 19a and 19b and the seal rings 20a and 20b
The part where the parts 3 and 13 are installed is shielded from the outside, so that the grease existing in this part is prevented from leaking out, and foreign matters such as rainwater and dust are prevented from entering the part. Further, inside the middle portion of the second inner ring member 5, a partition plate portion 21 for closing the inside of the second inner ring member 5 is provided,
The rigidity of the second inner race member 5 is ensured, and foreign matter that has entered the inside of the second inner race member 5 from the opening (the left end in FIG. 4) of the second inner race member 5 is removed by the housing portion 11. To reach the portion of the constant velocity joint 10 provided inside the inside.

The constant velocity joint 10 includes the housing portion 11, an inner ring 22, a retainer 23, and a plurality of balls 24. The inner ring 22 is fixed to a distal end of a drive shaft (not shown) that is rotationally driven by the engine via a transmission. On the outer peripheral surface of the inner ring 22, six inner engaging grooves 25 having an arc-shaped cross section are formed at regular intervals in the circumferential direction and at right angles to the circumferential direction. Also, at the position on the inner peripheral surface of the housing portion 11 facing the inner engaging groove 25, six outer engaging grooves 26 also having an arc-shaped cross section are formed in a direction perpendicular to the circumferential direction. I have. The retainer 23 has an arcuate cross section and is formed in an annular shape as a whole, and is held between the outer peripheral surface of the inner ring 22 and the inner peripheral surface of the housing portion 11. At the six positions in the circumferential direction of the retainer 23, pockets 27 are formed at positions corresponding to the inner and outer engagement grooves 25 and 26, and one pocket 27 is formed inside each of the pockets 27. A total of six balls 24 are held. These balls 24 are rollable along the inner and outer engagement grooves 25 and 26 while being held in the respective pockets 27.

When assembling the rolling bearing unit for a wheel configured as described above to a vehicle, the first mounting flange 2
To support the outer ring 1 on the suspension device, and the second mounting flange 7 fixes the drive wheel to the first inner ring member 4. Further, the tip of a drive shaft (not shown), which is rotationally driven by the engine via a transmission, is spline-engaged with the inside of the inner ring 22 constituting the constant velocity joint. When the automobile is running, the rotation of the inner wheel 22 is transmitted to the hub 6 including the second inner wheel member 5 via the plurality of balls 24, and the driving wheels are rotated.

[0008]

In the case of the conventional rolling bearing unit for a wheel shown in FIG. 4, it is difficult to reduce the size and weight of the device. The reason is as follows. The inner and outer engagement grooves 25, 2 provided in the constant velocity joint 10 integrated with the above-described conventional rolling bearing unit for a wheel.
The number of balls 6 and balls 24 is usually six each. In the case of a conventional rolling bearing unit for a wheel in which such a constant velocity joint 10 is integrally incorporated, the two engagement grooves 25 and 26 and each ball 24 which constitute the constant velocity joint 10 are used.
The outer diameter of each ball 24 constituting the constant velocity joint 10 needs to be increased to a certain extent for the purpose of enabling transmission of the required torque while securing the rolling fatigue life with the rolling surface of the bearing. There is.

For this reason, in the case of the above-mentioned conventional rolling bearing unit for a wheel, the portion of the constant velocity joint 10 becomes large,
The weight of the entire apparatus increases accordingly. Since an increase in the weight of the wheel rolling bearing unit leads to an increase in unsprung load of the automobile, it is desired to reduce the size and weight of the wheel rolling bearing unit. The rolling bearing unit for a wheel according to the present invention has been invented in view of the above-described circumstances to reduce the size and weight of the rolling bearing unit for a wheel.

[0010]

According to the rolling bearing unit for a wheel of the present invention, a first mounting flange for supporting a suspension device on an outer peripheral surface is provided inside the rolling bearing unit, similarly to the above-described conventional rolling bearing unit for a wheel. An outer ring raceway on the peripheral surface, a member equivalent to the outer ring that does not rotate even during use, a second mounting flange for supporting the wheel on a portion near one end of the outer peripheral surface, an inner ring raceway in the middle part, respectively An inner ring-equivalent member which rotates at the time of use, and a plurality of rolling elements rotatably provided between the outer ring raceway and the inner ring raceway, wherein the other end portion is a housing portion serving as an outer ring of the constant velocity joint. And a plurality of outer engagement grooves formed in the inner peripheral surface of the housing portion in a direction perpendicular to the circumferential direction and having an arc-shaped cross section. In particular, in the rolling bearing unit for a wheel according to the present invention, the number of the outer engagement grooves is eight.

[0011]

In the case of the rolling bearing unit for a wheel according to the present invention configured as described above, since the number of outer engaging grooves constituting the constant velocity joint is eight, when the rolling bearing unit for a wheel is used, The magnitude of the load applied to each ball of the constant velocity joint including the outer engagement grooves can be made smaller than in the case of the conventional structure described above. Therefore, the outer diameter of each of the balls can be reduced by that much, and the diameter of the circumscribed circle of each of the balls and the diameter of the circumscribed circle of the plurality of outer engagement grooves can be reduced. In addition, the outer diameter of the wheel rolling bearing unit is reduced by an amount corresponding to the reduced diameter of the circumcircle of the outer engagement groove, thereby reducing the size and size of the entire device.
The weight can be reduced.

The reason why the number of the outer engagement grooves is eight is that the wheel bearing unit is reduced in size and weight while stably transmitting the rotational force by the constant velocity joint. In addition, this is for ensuring the durability of the constant velocity joint. That is, in order to stably transmit the rotational force by the Zeppa-type constant velocity joint including the outer engagement groove, the outer engagement groove, the inner engagement groove, and the ball must be In order to be located on the diametrically opposite side of the speed joint, the number of the outer engagement groove, the inner engagement groove, and the number of balls must be an even number. Therefore, in order to increase the number of the outer engagement groove, the inner engagement groove, and the balls, which is conventionally six (pieces), and to reduce the size and weight of the constant velocity joint, the number is increased to eight (pieces). Or it is necessary to make ten pieces. On the other hand, in order to reduce the size and weight, it is necessary to reduce the diameter of the ball as the number is increased. When the number is 10, the diameter becomes too small, and the load capacity of the ball is secured. Things get harder. Therefore, the number of the inner engagement groove and the number of balls are the same.
The number of the outer engagement grooves was eight.

More specifically, the load capacity of the constant velocity joint, which affects the separation life of the constant velocity joint, is 2/3 of the number of balls, assuming that the diameter of the balls is the same.
It is proportional to the power. When the number of balls is increased from six to eight in accordance with the number of the outer engagement grooves, the load capacity of the constant velocity joint becomes (8/6) ^2/3 ≒ 1.21 times. As described above, by increasing the number of balls, the load capacity of the constant velocity joint can be increased by about 21%. Therefore, when the load capacity is the same, the diameter of each ball can be reduced accordingly. Then, the cross-sectional area of the outer engagement groove formed on the inner peripheral surface of the housing portion and the cross-sectional area of the inner engagement groove formed on the outer peripheral surface of the inner ring can be reduced by the reduced diameter of the ball. With these arrangements, the diameter of the constant velocity joint can be reduced, so that the wheel rolling bearing unit, which is the fourth generation hub unit, can be reduced in size and weight.

[0014]

1 to 3 show an example of an embodiment of the present invention. The outer ring 1 (outer ring equivalent member) that does not rotate while being supported by the suspension device has a first mounting flange 2 for supporting the suspension device on the outer peripheral surface, and a double-row outer ring raceway 3a, 3b on the inner peripheral surface. , Respectively. Outer ring 1
An inner ring-equivalent member 30 including a hub 28 and an inner ring 29 is disposed concentrically with the outer ring 1 on the inner diameter side of the outer ring 1. A portion of the outer peripheral surface of the inner ring-equivalent member 30 facing each of the outer ring raceways 3a and 3b is provided with a first and a second inner raceway 8 respectively.
a and 12a are provided. These inner ring raceways 8a, 12
The first inner raceway 8a is formed directly on the outer peripheral surface of the intermediate portion of the hub 28. The inner ring 29 is externally fitted to an intermediate portion (closer to the right end in FIG. 1) of the intermediate portion of the hub 28 than the portion where the first inner raceway 8a is formed. The second inner raceway 12a is formed on the outer peripheral surface of the inner race 29. A plurality of rolling elements 13, 13 are provided between the outer raceways 3a, 3b and the first and second inner raceways 8a, 12a, respectively, so that the outer races 1a, 3b can rotate freely. The inner ring-equivalent member 30 is rotatably supported inside.

In the case of the illustrated example, as described above, the first inner raceway 8a is formed directly on the outer peripheral surface of the hub 28 so that the diameter of the first inner raceway 8a is reduced. The diameter is smaller than the diameter of the second inner raceway 12a formed on the outer peripheral surface of the outer ring 29. Also, as described above, the first inner raceway 8
1 is smaller than the diameter of the second inner raceway 12a, the outer side facing the first inner raceway 8a (the outer side in the width direction when assembled to an automobile, and refers to the side shown in FIG. 1). The diameter of the outer raceway 3a (on the left side) is smaller than the diameter of the outer raceway 3b on the inner side (the side that is the center in the width direction when assembled to an automobile and on the right side in FIG. 1). Further, the outer race 1 having the outer race 3a formed thereon is formed.
The outer diameter of the outer half is smaller than the outer diameter of the inner half of the outer race 1, which is the part where the inner outer raceway 3b is formed. In the illustrated example, the first inner raceway 8
a and the number of the rolling elements 13 provided between the first inner raceway 8a and the outer raceway 3a are reduced by reducing the diameters of the outer raceway 3a and the outer raceway 3a. And the number of the rolling elements 13 provided between the inner race 3b and the inner race 3b.

Further, on the outer peripheral surface of the outer end of the hub 28, a second mounting flange 7 for supporting and fixing wheels to the hub 28 is provided integrally with the hub 28. The base ends of a plurality of studs 31 for connecting the wheels are fixed to the mounting flange 7. In the case of the illustrated example, the pitch circle diameter of the plurality of studs 31 is equal to the outer diameter of the outer half of the outer ring 1 smaller than the outer diameter of the inner half of the outer ring 1 as described above. The head 32 of the outer ring 1 is so small that it does not interfere with the outer peripheral surface of the outer end of the outer ring 1. The diameter of a portion of the outer peripheral surface of the hub 28 which is located inward in the axial direction from the portion where the first inner raceway 8a is formed has a rolling element 13 corresponding to the first inner raceway 8a. , 13 are smaller than the diameter of the inscribed circle. The reason for this is that at the time of assembling the rolling bearing unit for a wheel, the plurality of rolling elements 13 are assembled on the inner diameter side of the outer raceway 3a formed on the inner peripheral surface of the outer end of the outer race 1,
This is because the hub 28 can be freely inserted into the inner diameter side of the outer ring 1 in a state where the seal ring 33 is internally fitted and fixed to the inner peripheral surface of the outer end of the outer ring 1. In addition, on the outer peripheral surface of the intermediate portion of the hub 28, between the first inner raceway 8a and the portion where the inner race 29 is externally fitted, a groove-like stealing portion 3 is formed over the entire circumference.
4 to reduce the weight of the hub 28.

Further, the inner race 29 externally fitted to the hub 28 is prevented from shifting toward the inner end side in the axial direction, so that each of the outer raceways 3
a, 3b and the first and second inner ring raceways 8a, 12a, each of which is provided so as to be able to roll freely by a plurality of pieces, in order to maintain the preload applied to each of the rolling elements 13, 13 at an appropriate value. A retaining ring 36 is locked in a locking groove 35 formed over the entire circumference near the inner end of the outer peripheral surface of the hub 28. The retaining ring 36 is composed of a pair of retaining ring elements each having a semicircular arc shape. Such a retaining ring 36 is used to apply an appropriate preload to the rolling elements 13, 13 so that the inner ring 2
The inner peripheral edge portion is engaged with the locking groove 35 while pressing the hub 9 axially outward with respect to the hub 28. The retaining ring 36 should have an appropriate thickness dimension so as to keep the rolling elements 13 and 13 properly applied with a preload even when the force pressing the inner ring 29 outward in the axial direction is released. Select what you have. That is, as the retaining ring 36,
A plurality of types having slightly different thickness dimensions are prepared, and a retaining ring 36 having an appropriate thickness dimension in relation to the dimensions of the components of the rolling bearing unit, such as the groove width of the locking groove 35, is provided.
Is selected, and is engaged with the locking groove 35. Therefore, if the retaining ring 36 is locked in the locking groove 35, even if the pressing force is released, the inner ring 29 is prevented from shifting toward the inner end in the axial direction. The rolling elements 13, 13 can be maintained while being given an appropriate preload.

Further, in order to prevent the pair of retaining ring elements constituting the retaining ring 36 from being displaced radially outward and to prevent the retaining ring 36 from accidentally falling out of the retaining groove 35,
A part of the spacer 50 is disposed around the retaining ring 36. The spacer 50 is a constant velocity joint 10 constituted by a housing portion 11a provided at an inner end portion of the hub 28.
This is for externally fitting and supporting an outer end portion of the boot 37 for preventing foreign matters such as rainwater and dust from entering into the area a.
The boot 37 is integrally formed of an elastic material such as rubber or synthetic resin, and has a bellows-shaped intermediate portion and a cylindrical end portion.
Each is formed. The outer end of the boot 37 is externally fitted to a metal spacer 50 externally fixed to the inner end of the hub 28 by interference fit, and is pressed against the outer peripheral surface of the spacer 50 by a restraining band 38. ing. The inner peripheral surface of the outer end of the boot 37 is engaged with the engaging groove 39 formed on the outer peripheral surface of the spacer 50 over the entire circumference.

At the outer edge of the spacer 50, the boot 37
A portion protruding outward in the axial direction is formed in a crank shape in cross section, and constitutes a holding portion 40 over the entire circumference. In order to constitute the holding portion 40, the spacer 50 is attached to the hub 28.
A small-diameter cylindrical portion 41 externally fitted and fixed to the inner end portion, a circular portion 42 bent radially outward from the outer end edge of the small-diameter cylindrical portion 41, and an axially outer portion from the outer peripheral edge of the circular portion 42. And a large-diameter cylindrical portion 43 bent toward the center. The outer surface of the circular ring portion 42 abuts or approaches the inner surface of the retaining ring 36, and the large-diameter cylindrical portion 43.
Of the retaining ring 36 is in contact with or close to the outer peripheral surface of the retaining ring 36. A seal ring 33 is provided between the inner peripheral surface of the outer end of the outer race 1 and the outer peripheral surface of the intermediate portion of the hub 28.
A combination seal ring 45 is provided between the inner peripheral surface of the inner end of the outer race 1 and the outer peripheral surface of the inner end of the inner race 29 to form a space 46 in which the plurality of rolling elements 13 and 13 are installed. Both ends are closed.

Further, a portion of the inner end of the hub 28 where the inner race 29 and the outer end of the boot 37 are fitted to each other is a housing portion 11a which becomes the outer race of the constant velocity joint 10a. Eight outer engagement grooves 26a each having an arc-shaped cross section are formed on the inner peripheral surface of the housing portion 11a.
26a are formed at right angles to the circumferential direction (the left-right direction in FIG. 1 and the front and back directions in FIG. 2). Also, the housing portion 11a is provided inside the housing portion 11a.
At the same time, an inner ring 22a for constituting the above-mentioned constant velocity joint 10a of the Zeppa type is arranged. Eight inner engagement grooves 25a, 25a are formed on the outer peripheral surface of the inner race 22a.
Each is formed in a direction perpendicular to the circumferential direction. And between each of these inner engagement grooves 25a, 25a and each of the outer engagement grooves 26a, 26a, these engagement grooves 25a,
A total of eight balls 24, 24, one for each 26 a, are provided rotatably while being held in the pocket 27 of the holder 23. Further, a spline hole 47 is formed in the center of the inner ring 22a in the axial direction. An end of a drive shaft (not shown) is spline-engaged with the spline hole 47 in a state where the hub 28 is mounted on the automobile, and the hub 28 is rotatably driven via the inner ring 22a and the eight balls 24, 24. I do.

The function of rotatably supporting the wheel with respect to the suspension device by the wheel rolling bearing unit of the present embodiment configured as described above is the same as that of the above-described conventional wheel rolling bearing unit. In particular, in the case of the wheel rolling bearing unit of the present invention, the number of the inner and outer engagement grooves 25a and 26a constituting the constant velocity joint 10a is eight, and the number of the balls 24 and 24 is eight. And the inner ring equivalent member 3 associated with the use of the rolling bearing unit for wheels.
At the time of torque transmission between 0 and the outer ring 1, the magnitude of the load applied to each of the balls 24 constituting the constant velocity joint 10a can be made smaller than in the case of the conventional structure described above. Therefore, the outer diameter of each of the balls 24, 24 is reduced by that much, the diameter of the circumscribed circle of each of the balls 24, 24 arranged in a ring, and the plurality of outer engagement grooves 26a, 26
The diameter of the circumcircle of a can be reduced. The outer diameter of the wheel rolling bearing unit is reduced by the reduced diameter of the circumcircle of the outer engagement grooves 26a, 26a, thus making it possible to reduce the size and weight of the entire apparatus. In particular, as shown in the illustrated example, if the outer halves of the outer engagement grooves 26a, 26a are arranged on the inner diameter side of the second inner raceway 12a, not only the outer diameter dimension of the wheel rolling bearing unit but also By reducing the axial dimension, the size and weight of the entire apparatus can be more effectively reduced. In such a structure of this example, the second inner raceway 12a constituting the rolling bearing unit main body is
The diameter must be larger than 6a and 26a. In such a structure of the present example, the outer diameter of the rolling bearing unit main body becomes large. In such a structure of this example, the ball 24,
Increase the number of 24 from 6 to 8
In particular, the effect of the present invention that the outer diameter of the rolling bearing unit 4 can be reduced and the outer diameter of the rolling bearing unit can be reduced.

Furthermore, in the case of the illustrated example, as described above, the pitch circle diameter of each of the rolling elements 13 constituting the outer row of rolling elements is reduced so that the outer half of the outer ring 1 can be formed. The diameter can be reduced. Then, the pitch diameter of the plurality of studs 31 fixed to the second mounting flange 7 provided on the outer peripheral surface of the hub 28 can be reduced by the reduced outer diameter of the outer half of the outer ring 1. Therefore, without increasing the axial dimension of the hub 28, the outer diameter of the second mounting flange 7 for supporting and fixing the stud 31 is reduced, thereby further reducing the size and weight of the wheel rolling bearing unit. Effectively.

As described above, the pitch circle diameter of each of the rolling elements 13 constituting the outer row of rolling elements should be smaller than the pitch circle diameter of each of the rolling elements 13 constituting the inner rolling element row. Accordingly, the basic dynamic load rating of the outer rolling element row portion becomes smaller than the basic dynamic load rating of the inner rolling element row portion. Therefore, if the load applied to both rows is the same, the life of the outer rolling element row is shorter than the life of the inner rolling element row. On the other hand, in a general automobile, the load applied to the outer rolling element row portion is smaller than the load applied to the inner rolling element row portion. For this reason, it is easy to design the two row portions to have almost the same life, and it is possible to design without waste. In the illustrated example, balls are used as the rolling elements 13 and 13. However, in the case of a heavy-duty rolling bearing unit for an automobile, tapered rollers may be used as the rolling elements. The present invention is, of course, also applicable to a rolling bearing unit using a tapered roller as a rolling element.

In practicing the present invention, both the inner and outer engagement grooves 25a, which constitute the constant velocity joint 10a,
The curvature radii R _25a and R 26a of the cross section of _26a and each ball 24,
The relationship between the outer diameter d ₂₄ of 24, when the same as the conventional structure, when it is not possible to secure these flaking life of the rolling surface of the balls 24, 24 are contemplated. In view of such circumstances, when implementing the present invention, the curvature radius R _25a of the cross section of both the inner and outer engagement grooves 25a, 26a in relation to the outer diameter d 24 of each ball 24, ₂₄ , It is preferable to make R _26a slightly larger than in the case of the conventional structure. For this reason, FIG.
3 will be described.

At the time of transmitting the rotational force between the inner ring 29 and the housing portion 11a constituting the constant velocity joint 10a, the inner and outer engagement grooves 25a and 26a and each ball 2
As shown exaggeratedly in FIG.
The rolling surfaces 4 and 24 are displaced in a direction in which the one side surface of each of the engagement grooves 25a and 26a abuts. With this displacement, these balls 24, 24 are connected to the inner and outer engagement grooves 25a,
It is displaced toward the opening 26a so as to ride up. At the same time, the rolling surfaces of the balls 24, 24 and the inner surfaces of the inner and outer engagement grooves 25a, 26a abut on each other at a contact elliptical portion whose major axis is in the circumferential direction of the constant velocity joint 10a. For example, the rolling surface of each ball 24, 24 and the inner surface of each outer engagement groove 26a are in contact ellipse 48 as shown in FIG.
Abut each other at the parts. On the other hand, the inner and outer engagement grooves 25a and 26a are provided with chamfers 49a and 49b, respectively.
The engaging grooves 25a and 26a are formed over the entire length. Based on the displacement, the contact ellipse 48 for each of the balls 24, 24 moves toward the openings of the two engagement grooves 25a, 26a, and the contact ellipse 48 becomes the chamfer 49a,
When reaching the portion 49b, these chamfers 49a, 49b
Edge loading occurs in the part. Such an edge load is not preferred because it reduces the peeling life of the rolling surfaces of the balls 24 and 24 and impairs the durability of the constant velocity joint 10a.

In order to prevent a decrease in durability due to the above-described causes, the contact ellipse 48 is formed by the chamfers 49a,
9b. On the other hand, in the case of the conventional constant velocity joint, the radius of curvature of the cross section of each engagement groove is set to 0.504 to 0.51 times the outer diameter of each ball (50.
4 to 51%), which is slightly larger than the radius of curvature of the rolling surface, so that the major axis of the contact ellipse becomes large, and the end of the contact ellipse becomes the chamfered portion 49a,
It was easy to reach 49b. Therefore, when practicing the present invention, preferably, the inner and outer engagement grooves 25a, 26a
The curvature radii R _25a and R _26a of the cross section of
From 0.51 to 0.52 times the 4 outer diameter d ₂₄ (51~52%)
The degree and the degree to be larger than the radius of curvature of the rolling surface are made slightly remarkable. Thus, the inner and outer engagement grooves 25
a, the radius of curvature R _25a in 26a of the cross-section, a R _26a, to be larger than the radius of curvature of the rolling surface of the balls 24, 24, the major axis of the contact ellipse 48 is decreased, the contact ellipse 48 Is difficult to reach the chamfers 49a and 49b. As a result, an edge load is less likely to be applied to the rolling surfaces of the balls 24, 24, the separation life of the rolling surfaces is increased, and the durability of the constant velocity joint 10a can be improved. In addition, if the required durability is the same as the durability can be improved, the size and weight of the wheel rolling bearing unit including the constant velocity joint 10a can be further reduced. In order to shorten the major axis of the contact ellipse 48, the radius of curvature of the section of the engagement groove 25a, 26a near the opening may be increased. The curvature of the cross section of the central portion of each of the engagement grooves 25a and 26a may be the same as the conventional one. For this purpose, the cross-sectional shape of the two engaging grooves 25a and 26a may be a semi-elliptical shape or a Gothic arch shape.

[0027]

Since the present invention is constructed and operates as described above, it is possible to reduce the size and weight of the wheel rolling bearing unit and to improve the performance of a vehicle incorporating the wheel rolling bearing unit.

[Brief description of the drawings]

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

FIG. 2 is a view corresponding to an AA cross section in FIG. 1, showing only a constant velocity joint part in a state in which a retainer is omitted.

FIG. 3 is a view taken in the direction of arrow B in FIG. 2, showing a contact ellipse between the rolling surface of the ball and the inner surface of the outer engagement groove.

FIG. 4 is a partial cross-sectional view showing one example of a conventional structure.

[Explanation of symbols]

 Reference Signs List 1 outer ring 2 first mounting flange 3, 3a, 3b outer ring track 4 first inner ring member 5 second inner ring member 6 hub 7 second mounting flange 8, 8a first inner ring track 9 cylindrical portion 10, 10a, etc. Speed joint 11, 11a housing part 12, 12a second inner raceway 13 rolling element 14 locking groove 15 locking groove 16 retaining ring 17 stepped portion 18 welding 19a, 19b cover 20a, 20b seal ring 21 partition plate 22, 22a Inner ring 23 Retainer 24 Ball 25, 25a Inner engaging groove 26, 26a Outer engaging groove 27 Pocket 28 Hub 29 Inner ring 30 Inner ring equivalent member 31 Stud 32 Head 33 Seal ring 34 Meat steal part 35 Locking groove 36 Stop ring 37 Boots 38 Suppression band 39 Engagement groove 40 Suppression part 41 Small diameter cylindrical part 42 Ring part 43 Large diameter cylindrical part 45 Combination The seal ring 46 space 47 spline 48 contact ellipse 49a, between 49b chamfer 50 seats

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] December 8, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

Claims (1)

[Claims] An outer peripheral surface has a first mounting flange for supporting the suspension device, and an inner peripheral surface has an outer raceway.
An outer ring-equivalent member that does not rotate during use, a second mounting flange for supporting the wheel at a portion near one end of the outer peripheral surface, an inner ring track is also provided at the intermediate portion, and the other end is an outer ring of a constant velocity joint An inner ring-equivalent member that rotates during use, a plurality of rolling elements rotatably provided between the outer raceway and the inner raceway, and an inner peripheral surface of the housing portion, In a rolling bearing unit for a wheel having a plurality of outer engaging grooves formed in a direction perpendicular to the circumferential direction and having an arc-shaped cross section, the number of the outer engaging grooves is eight. Rolling bearing unit for wheels.