CN110431324B

CN110431324B - Sliding type constant velocity universal joint for rear wheel drive shaft

Info

Publication number: CN110431324B
Application number: CN201880018890.5A
Authority: CN
Inventors: 小林正纯; 小林智茂
Original assignee: NTN Corp
Current assignee: NTN Corp
Priority date: 2017-03-17
Filing date: 2018-03-08
Publication date: 2022-03-18
Anticipated expiration: 2038-03-08
Also published as: CN110431324A; WO2018168631A1; WO2018168631A8

Abstract

A plunging type constant velocity universal joint (2) is provided with an outer joint member (21), an inner joint member (22), 8 balls (23), and a retainer (24). A curvature center (O) of a spherical portion (24b) provided on the outer peripheral surface of the retainer (24)_24b) And a center of curvature (O) of a spherical portion (24d) provided on the inner peripheral surface of the retainer (24)_24d) Are offset by equal distances on axially opposite sides with respect to the coupling center (O (s)). The Pitch Circle Diameter (PCD) of the ball (23)_BALL) With the diameter (D) of the balls (23)_BALL) Ratio of (PCD)_BALL/D_BALL) 3.3 to 3.6. The wall thickness (T) of the inner joint member (22) in the radial direction_I) Diameter of ball (D)_BALL) Ratio of (T)_I/D_BALL) Set to 0.30-0.45.

Description

Sliding type constant velocity universal joint for rear wheel drive shaft

Technical Field

The present invention relates to a plunging constant velocity universal joint, and more particularly to a plunging constant velocity universal joint used for a rear wheel drive shaft of an automobile.

Background

In general, a drive shaft of an automobile is composed of a constant velocity universal joint attached to an outer disk side of a wheel, a constant velocity universal joint attached to an inner disk side of a differential gear, and an intermediate shaft connecting the two constant velocity universal joints. Generally, as the constant velocity universal joint on the outer disc side, a fixed type constant velocity universal joint which takes a large operating angle but is not displaced in the axial direction is used. On the other hand, as the inner-disc-side constant velocity universal joint, a plunging type constant velocity universal joint is used which has a small maximum operating angle but can be displaced in the axial direction while taking the operating angle.

There is still a high demand for weight reduction of motor vehicles, and further weight reduction and compactness are required for power transmission mechanisms including drive shafts. Therefore, the plunging type constant velocity universal joint to be incorporated into the inner disc side end portion of the drive shaft is also required to be further reduced in weight and size.

As a representative plunging type constant velocity universal joint, there is a double-race type constant velocity universal joint. In the double-race type constant velocity universal joint, the center of curvature of the spherical portion provided on the outer peripheral surface of the retainer and the center of curvature of the spherical portion provided on the inner peripheral surface of the retainer are offset by equal distances from the joint center toward the axially opposite side. Thus, the balls are always held in the bisector of the operating angle, and the constant velocity between the outer joint member and the inner joint member is ensured. The double-race type constant velocity universal joint generally has 6 torque transmission balls, but patent document 1 below discloses a double-race type constant velocity universal joint in which the number of torque transmission balls is 8. By setting the number of the balls to 8 in this way, it is possible to reduce the weight and the size while ensuring the strength, the load capacity, and the aging resistance equal to or higher than those of a double-race type constant velocity universal joint including 6 balls.

Prior art documents

Patent document

Patent document 1: japanese laid-open patent publication No. 10-73129

Patent document 2: japanese laid-open patent publication No. 2012-97797

Disclosure of Invention

Problems to be solved by the invention

The double-race type constant velocity universal joint having 8 balls as shown in patent document 1 has been put to practical use as a mass-produced product. The present invention has been made in view of further reduction in weight and size of the plunging type constant velocity universal joint.

For example, patent document 2 discloses a rear wheel drive shaft. In this rear wheel drive shaft, the hollow shaft is made thin and therefore the hollow shaft can be made light by increasing the diameter of the splines provided at both ends of the intermediate shaft (hollow shaft) to provide a margin in strength of the hollow shaft. However, the invention proposed in this document aims to reduce the weight and increase the strength of the hollow shaft used for the rear wheel drive shaft, and does not address the problem of reducing the weight and making the sliding type constant velocity universal joint compact.

Therefore, an object to be solved by the present invention is to provide a sliding type constant velocity universal joint used for a rear wheel drive shaft, particularly a double-race type constant velocity universal joint having 8 balls, which is further reduced in weight and size by studying the internal specifications.

Means for solving the problems

Since the fixed type constant velocity universal joint provided on the outer disk side of the drive shaft is directly attached to the wheel, the maximum operating angle is greatly different between the case of being attached to the front wheel as the steered wheel and the case of being attached to the rear wheel which is not steered. On the other hand, the plunging constant velocity universal joint provided on the inner disc side of the drive shaft is not directly attached to the wheel, and is therefore hardly affected by the steering angle of the wheel. Therefore, conventionally, from the viewpoint of mass production cost and the like, the plunging type constant velocity universal joint of the same specification is used for the front wheel drive shaft and the rear wheel drive shaft.

However, the present inventors have focused on the following points: in the plunging type constant velocity universal joint, the maximum operating angle can be reduced by exclusively using the rear wheel drive shaft. That is, since many components are arranged near the front wheels of the vehicle and the space is limited, for example, as shown in fig. 9A, the axial center of the front wheels FW and the axial center of the differential gear G may have to be arranged offset in the vehicle front-rear direction. In this case, a normal angle α in the vehicle front-rear direction (an operating angle when the vehicle travels straight at a constant speed) of the constant velocity universal joints J11 and J12 provided in the front wheel drive shaft DS1 is not 0 °, and the constant velocity universal joints are always rotated in a state of taking the operating angle in the vehicle front-rear direction. Therefore, in the plunging type constant velocity universal joint J12, the normal angle α in the vehicle front-rear direction described above and the vertical operating angle caused by vertical movement of the wheels relative to the vehicle body act in a combined manner, and therefore a large operating angle is required.

In contrast, in the vicinity of the rear wheels of the vehicle, the space for disposing the components is relatively large, and normally, as shown in fig. 9B, the axial center of the rear wheel RW and the axial center of the differential gear G are disposed in a state where there is almost no offset in the vehicle body front-rear direction. In this case, since the constant velocity universal joint J21, J22 of the rear wheel drive shaft DS2 has a normal angle in the vehicle front-rear direction of almost 0 °, it is sufficient that the plunging constant velocity universal joint J22 for the rear wheel drive shaft DS2 operates at a smaller operating angle than the plunging constant velocity universal joint J21 for the front wheel drive shaft DS 1. Therefore, the maximum operating angle can be reduced by exclusively using the plunging type constant velocity universal joint for the rear wheel drive shaft.

In view of the above-described findings, the present invention is a plunging type constant velocity universal joint used for a rear wheel drive shaft, the plunging type constant velocity universal joint including: an outer joint member having 8 track grooves formed in a cylindrical inner circumferential surface thereof and extending in an axial direction; an inner joint member having 8 track grooves formed on a spherical outer circumferential surface and extending in an axial direction, and having a spline hole formed in an axial center; 8 balls arranged on ball grooves formed by the track grooves of the outer joint member and the track grooves of the inner joint member; and a cage having 8 pockets for receiving the balls and being in sliding contact with the inner circumferential surface of the outer joint member and the outer circumferential surface of the inner joint member, wherein the center of curvature of a spherical portion provided on the outer circumferential surface of the cage and the center of curvature of a spherical portion provided on the inner circumferential surface of the cage are offset by equal distances from the joint center toward the opposite axial sides, respectively, and the ball has a pitch circle diameter PCD_BALLDiameter D of the ball_BALLRatio PCD_BALL/D_BALL3.3 to 3.6, the wall thickness T of the inner side coupling component in the radial direction_IDiameter D of the ball_BALLRatio of (A to (B))_I/D_BALL0.30 to 0.45.

In the plunging type constant velocity universal joint, the load is applied to the balls in a balanced manner in a state where the operating angle is 0 °, but if the operating angle is present, the load is applied to the balls unevenly, and the difference between the loads applied to the balls increases as the operating angle increases. Therefore, in the case of a high operating angle, the maximum load applied to each ball becomes large, and therefore, the members (the outer joint member, the inner joint member, and the cage) in contact with the balls are required to have a thick wall thickness capable of withstanding the maximum load received from the balls. Therefore, by reducing the maximum operating angle exclusively for the rear wheel drive shaft as described above, the maximum load applied to the balls is reduced, and the strength of each member in contact with the balls is made to be sufficient, so that the wall thickness of each member, for example, the wall thickness of the inner joint member in the radial direction (specifically, the radial distance between the groove bottom of the track groove of the inner joint member and the pitch circle of the spline hole) can be reduced without causing a reduction in load capacity and aging resistance. Accordingly, the track groove formed in the outer peripheral surface of the inner joint member can be positioned closer to the inner diameter side, and therefore the pitch circle diameter of the track groove, that is, the pitch circle diameter of the balls disposed in the track groove can be made smaller than that of a conventional product (a double-race type constant velocity universal joint having 8 balls with a high operating angle that can be applied to either one of the front wheel drive shaft and the rear wheel drive shaft). Thereby, the sliding type constant velocity universal joint can be made compact in the radial direction and light in weight.

When the plunging constant velocity universal joint rotates in a state in which the running angle is assumed, the balls rotate in the circumferential direction with respect to the cage. Therefore, the pockets of the cage are formed into a long and narrow shape that is long in the circumferential direction in order to allow the circumferential movement of the balls, and the circumferential dimension thereof is determined by the maximum operating angle of the constant velocity universal joint. In the conventional product, the maximum working angle is large, and therefore, the circumferential length of the pocket becomes large, and in order to secure the circumferential length of the pocket, the diameter of the retainer needs to be increased. Therefore, the outer peripheral surface of the inner joint member in sliding contact with the inner peripheral surface of the retainer has a large diameter, and as a result, has an excessively large thickness equal to or greater than a thickness necessary for strength.

In contrast, as described above, the sliding type constant velocity universal joint is used exclusively for the rear wheel drive shaft, and the maximum operating angle is reduced, whereby the circumferential dimension of each pocket of the retainer can be reduced, and therefore the diameter of the retainer can be reduced, and the diameter of the outer peripheral surface of the inner joint member that is in sliding contact with the inner peripheral surface of the retainer can be reduced. Accordingly, the wall thickness of the inner joint member in the radial direction can be made thinner than conventional products, and the wall thickness in the radial direction can be set to an appropriate value (minimum value required for strength), so that the plunging type constant velocity universal joint can be made compact in the radial direction by reducing the pitch circle diameter of the balls as described above.

However, since the constant velocity universal joint is a product that is mass-produced, it is common to set the dimensions in stages according to the torque load capacity and to set the internal specifications (the dimensions, the shapes, and the like of the respective members) for each dimension (serialization). When the diameter of the balls is reduced in order to reduce the weight and the size of the constant velocity universal joint having various dimensions, the surface pressure at the contact portion between the balls and the track grooves increases, which directly leads to a reduction in torque load capacity. Therefore, when a design change of the constant velocity universal joint is studied, the ball diameter is not changed in order to maintain the torque load capacity unless the number of balls is increased. Therefore, by expressing the dimensions of each member in a ratio to the diameter of the balls, it is possible to express the internal specifications of the constant velocity universal joint corresponding to the torque load capacity (i.e., the dimensions of the constant velocity universal joint). As described above, the maximum operating angle is reduced by exclusively using the plunging constant velocity universal joint for the rear wheel drive shaft, and the size of each member with respect to the ball diameter (specifically, the reference diameter of the ball is larger than the ball diameter PCD) is set to be smaller_BALL/D_BALLAnd the wall thickness of the inner coupling member in the radial direction is larger than the ball diameter T_I/D_BALL) A new lightweight and compact series of sliding constant velocity universal joints can be constructed by making the joint smaller than conventional ones.

In addition, by making the wall thickness of the inner joint member in the radial direction thinner as described above, the diameter of the spline hole provided in the axial center of the inner joint member can be increased. Thereby, by making the shaft inserted into the spline hole largeThe diameter of the steel plate is reduced, and the torsional strength can be improved. Specifically, the pitch circle diameter PCD of the spline bore of the inner coupling member can be adjusted_SPLDiameter D of ball_BALLRatio PCD_SPL/D_BALLIs set to 1.70 to 1.85 (preferably 1.75 to 1.85).

By reducing the maximum operating angle of the plunging constant velocity universal joint, the pitch circle diameter of the balls can be reduced as described above, and therefore the outer joint member can be reduced in diameter. Further, by reducing the maximum operating angle of the plunging constant velocity universal joint, the inner joint member can be made thin as described above, and therefore the spline hole of the inner joint member can be made larger in diameter. According to the above, the outer diameter D of the outer joint member can be reduced_OReference circle diameter PCD of spline hole of inner coupling member_SPLRatio of D_O/PCD_SPLSpecifically, D can be_O/PCD_SPLSet to 2.7 to 3.0. This makes it possible to achieve both weight reduction and compactness of the plunging constant velocity universal joint and strength improvement of the intermediate shaft.

In the plunging type constant velocity universal joint described above, the maximum operating angle can be set to 20 ° or less.

Effects of the invention

As described above, in the plunging type constant velocity universal joint used for the rear wheel drive shaft according to the present invention, the internal specifications (the pitch circle diameter of the balls based on the ball diameter and the radial thickness of the inner joint member) are designed based on a design concept different from that of the conventional art, so that the weight reduction and the size reduction can be further achieved while maintaining the torque load capacity.

Drawings

Fig. 1 is a plan view schematically showing a power transmission mechanism of a rear wheel drive vehicle.

Fig. 2 is a sectional view of the rear wheel drive shaft.

Fig. 3A is a longitudinal sectional view of the plunging constant velocity universal joint incorporating the rear wheel drive shaft (a sectional view taken along line X-X in fig. 3B).

Fig. 3B is a cross-sectional view of the plunging constant velocity universal joint (a cross-sectional view on the joint center plane of fig. 3A).

Fig. 4 is a longitudinal cross-sectional view showing a state where the plunging constant velocity universal joint of fig. 3A has assumed the maximum working angle.

Fig. 5A is a longitudinal sectional view of the fixed type constant velocity universal joint incorporating the rear wheel drive shaft (a sectional view taken along line Y-Y in fig. 5B).

Fig. 5B is a cross-sectional view of the fixed type constant velocity universal joint (a cross-sectional view on the joint center plane of fig. 5A).

Fig. 6 is a longitudinal sectional view of the plunging constant velocity universal joint, showing the product of the present invention in the upper half and the comparative product in the lower half.

Fig. 7 is a cross-sectional view on a joint center plane of the plunging constant velocity universal joint, with an upper half showing a product of the present invention and a lower half showing a comparative product.

Fig. 8 is a longitudinal sectional view of an inner joint member of the plunging constant velocity universal joint, with the upper half showing a product of the present invention and the lower half showing a comparative product.

Fig. 9A is a plan view showing a state in which the front wheel drive shaft is attached so as to be inclined with respect to the vehicle width direction.

Fig. 9B is a plan view showing a state where the rear wheel drive shaft is attached in parallel to the vehicle width direction.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Fig. 1 shows a power transmission mechanism of an independent suspension type rear wheel drive vehicle (e.g., FR vehicle). In this power transmission mechanism, a rotational driving force output from the engine E is transmitted to the differential gear G via the transmission M and the propeller shaft PS, and is transmitted from the differential gear G to the left and right rear wheels (wheels W) via the left and right rear wheel drive shafts 1.

As shown in fig. 2, the rear wheel drive shaft 1 has the following structure: a plunging constant velocity universal joint 2 that allows both axial displacement and angular displacement is provided on the inner disk side (right side in the figure), a fixed constant velocity universal joint 3 that allows only angular displacement is provided on the outer disk side (left side in the figure), and both constant velocity

universal joints

2, 3 are connected by an intermediate shaft 4. The inner-disc-side plunging constant velocity universal joint 2 is connected to a differential gear G, and the outer-disc-side fixed constant velocity universal joint 3 is connected to a wheel W (see fig. 1).

As shown in fig. 3B, the plunging type constant velocity universal joint 2 includes: an outer joint member 21 attached to the differential gear G (see fig. 1); an inner joint member 22 attached to an inner disc side end portion of the intermediate shaft 4 (see fig. 2); 8 balls 23 that transmit torque between the outer joint member 21 and the inner joint member 22; and a retainer 24 that retains the 8 balls 23.

The outer joint member 21 integrally has a cup-shaped mouth portion 21a that opens on one axial side (outer disc side, left side in fig. 3A), and a rod portion 21b that extends from the bottom of the mouth portion 21a to the other axial side (inner disc side, right side in fig. 3A). The cylindrical inner peripheral surface 21c of the mouth portion 21a is provided with 8 linear track grooves 21d extending in the axial direction. A spline 21e into which a spline hole of the differential gear G (see fig. 1) is inserted is provided on the outer peripheral surface of the inner disk side end of the rod portion 21 b. The mouth portion 21a and the stem portion 21b may be integrally formed of the same material, or they may be formed separately and then joined by welding or the like.

A spline hole 22c into which the intermediate shaft 4 is inserted is provided in the axial center of the inner joint member 22. The spherical outer circumferential surface 22d of the inner joint member 22 is provided with 8 linear track grooves 22e extending in the axial direction. That is, the inner joint member 22 integrally includes a cylindrical portion 22a having a spline hole 22c and a plurality of projecting portions 22b projecting from the cylindrical portion 22a in an outer diameter direction, and a track groove 22e is provided between the plurality of projecting portions 22b in a circumferential direction. The outer diameter surfaces of the plurality of protrusions 22b form a spherical outer peripheral surface 22d of the inner joint member 22.

The track grooves 21d of the outer joint member 21 and the track grooves 22e of the inner joint member 22 are opposed to each other in the radial direction to form 8 ball tracks, and one ball 23 is disposed on each ball track. The cross-sectional shapes of the

track grooves

21d, 22e are elliptical and pointed arch shapes, and thus the

track grooves

21d, 22e and the balls 23 form so-called angular contact with a contact angle of about 30 to 45 °. The cross-sectional shapes of the

track grooves

21d, 22e may be circular arc shapes, and the

track grooves

21d, 22e and the balls 23 may be in so-called circular contact.

The retainer 24 has 8 pockets 24a that hold the balls 23. The 8 pockets 24a are all of the same shape and are arranged at equal intervals in the circumferential direction. The outer peripheral surface of the retainer 24 is provided with a spherical portion 24b that is in sliding contact with the cylindrical inner peripheral surface 21c of the outer joint member 21, and a conical portion 24c that extends in the tangential direction from both axial end portions of the spherical portion 24 b. When the plunging type constant velocity universal joint 2 adopts the maximum operating angle θ as shown in fig. 4, the conical portion 24c comes into line contact with the inner peripheral surface 21c of the outer joint member 21, and functions as a stopper that restricts the operating angle from increasing further. The inclination angle of the conical portion 24c with respect to the axial center of the retainer 24 is set to a value of 1/2 which is the maximum operating angle θ of the plunging constant velocity universal joint 2. A spherical surface portion 24d that is in sliding contact with the spherical outer peripheral surface 22d of the inner joint member 22 is provided on the inner peripheral surface of the retainer 24. The spherical portion 24b of the outer peripheral surface of the retainer 24 and the cylindrical inner peripheral surface 21c of the outer joint member 21 slide in the axial direction, thereby allowing axial displacement between the outer joint member 21 and the inner joint member 22.

As shown in fig. 3A, the center of curvature O of the spherical portion 24b of the outer peripheral surface of the retainer 24_24bA center of curvature O of a spherical portion 24d with the inner peripheral surface of the holder 24_24d(i.e., the center of curvature of the spherical outer peripheral surface 22d of the inner joint member 22) is offset by an equal distance from the joint center o(s) toward the axially opposite side. In the illustrated example, the center of curvature O of the spherical portion 24b of the outer peripheral surface of the retainer 24_24bThe center of curvature O of the spherical portion 24d of the inner peripheral surface of the retainer 24 is offset toward the inner disk side (coupling back side) with respect to the coupling center O(s)_24dIs offset to the outer disc side (coupling opening side) with respect to the coupling center o(s). Thus, the balls 23 held by the cage 24 are always arranged in operation at an arbitrary operating angleThe bisected plane of the angle ensures constant velocity between the outer joint member 21 and the inner joint member 22.

As shown in fig. 5B, the fixed type constant velocity universal joint 3 includes: an outer joint member 31 attached to a wheel W (see fig. 1); an inner joint member 32 attached to an outer disc side end of the intermediate shaft 4 (see fig. 2); 8 balls 33 for transmitting torque between the outer joint member 31 and the inner joint member 32; and a retainer 34 that retains the 8 balls 33.

The outer joint member 31 integrally has a cup-shaped mouth portion 31a that opens on one axial side (inner disc side, right side in fig. 5A), and a rod portion 31b that extends from the bottom of the mouth portion 31a to the other axial side (outer disc side, left side in fig. 5A). The spherical inner peripheral surface 31c of the mouth portion 31a is formed with 8 circular arc-shaped track grooves 31d extending in the axial direction. A spline 31e inserted into a spline hole on the wheel W side is formed on the outer peripheral surface of the rod portion 31 b. The mouth portion 31a and the rod portion 31b may be integrally formed of the same material, or they may be formed separately and then joined by welding or the like. Further, an axial through hole may be formed in the axial center of the mouth portion 31a and the rod portion 31 b.

The axial center of the inner joint member 32 is provided with a spline hole 32c into which the intermediate shaft 4 (see fig. 2) is inserted. The spherical outer circumferential surface 32d of the inner joint member 32 is provided with 8 circular arc-shaped track grooves 32e extending in the axial direction. That is, the inner joint member 32 integrally includes a cylindrical portion 32a having a spline hole 32c and a plurality of projecting portions 32b projecting from the cylindrical portion 32a in an outer diameter direction, and a track groove 32e is provided between the plurality of projecting portions 32b in a circumferential direction. The outer diameter surfaces of the plurality of projections 32b form a spherical outer peripheral surface 32d of the inner joint member 32.

The track grooves 31d of the outer joint member 31 and the track grooves 32e of the inner joint member 32 are radially opposed to each other to form 8 ball tracks, and one ball 33 is disposed on each ball track. The cross-sectional shapes of the

track grooves

31d, 32e are elliptical shapes and pointed arch shapes, and thus the

track grooves

31d, 32e and the balls 33 form so-called angular contact with a contact angle of about 30 to 45 °. The cross-sectional shape of the

track grooves

31d and 32e may be an arc shape, and the

track grooves

31d and 32e and the balls 33 may be in so-called circular contact.

Center of curvature O of track groove 31d of outer joint member 31_31dWith the center of curvature O of the track groove 32e of the inner joint member 32_32eAre offset axially opposite sides by equal distances relative to the coupling center o (f). In the illustrated example, the center of curvature O of the track groove 31d of the outer joint member 31_31dA center of curvature O of the track groove 32e of the inner joint member 32 is offset toward the inner disc side (joint opening side) with respect to the joint center O (f)_32eIs offset to the outer disk side (coupling inner side) with respect to the coupling center o (f). Thus, at an arbitrary operating angle, the balls 33 held by the cage 34 are always arranged in the plane bisecting the operating angle, and the constant velocity between the outer joint member 31 and the inner joint member 32 is ensured.

The retainer 34 has 8 pockets 34a that hold the balls 33. The 8 pockets 34a are all of the same shape and are arranged at equal intervals in the circumferential direction. The spherical outer peripheral surface 34b of the cage 34 is in sliding contact with the spherical inner peripheral surface 31c of the outer joint member 31. The spherical inner peripheral surface 34c of the cage 34 is in sliding contact with the spherical outer peripheral surface 32d of the inner joint member 32. The center of curvature of the outer peripheral surface 34b of the cage 34 (i.e., the center of curvature of the spherical inner peripheral surface 31c of the outer joint member 31) and the center of curvature of the inner peripheral surface 34c (i.e., the center of curvature of the spherical outer peripheral surface 32d of the inner joint member 32) coincide with the joint center o (f), respectively.

As shown in fig. 2, a hollow shaft having an axial through hole 41 can be used for the intermediate shaft 4. The intermediate shaft 4 includes a large diameter portion 42 provided at the center in the axial direction, small diameter portions 43 provided at both ends in the axial direction, and a tapered portion 4 that continues the large diameter portion 42 and the small diameter portions 43. An annular groove 45 for attaching a shroud and a spline 46 are provided in the small diameter portion 43 of the intermediate shaft 4. The outer diameter of the small diameter portion 43 is constant at portions other than the annular groove 45 and the spline 46. The intermediate shaft 4 is not limited to a hollow shaft, and a solid shaft may be used.

The spline 46 at the inner disc side end of the intermediate shaft 4 is press-fitted into the spline hole 22c of the inner joint member 22 of the plunging constant velocity universal joint 2. Thereby, the intermediate shaft 4 and the inner joint member 22 are spline-fitted to each other to be connected to each other so as to be able to transmit torque. An annular groove is formed in the inner disk side end of the intermediate shaft 4, and a retaining ring 47 is fitted in the groove. The retainer ring 47 is engaged from the inner disc side (shaft end side) of the inner joint member 22, whereby the intermediate shaft 4 and the inner joint member 22 are prevented from coming off.

The spline 46 at the outer disc side end of the intermediate shaft 4 is press-fitted into the spline hole 32c of the inner joint member 32 of the fixed type constant velocity universal joint 3. Thus, the intermediate shaft 4 and the inner joint member 32 are spline-fitted to each other to be connected to each other so as to be able to transmit torque. An annular groove is formed in the outer disk side end of the intermediate shaft 4, and a retaining ring 47 is fitted in the groove. The retainer ring 47 is engaged from the outer disc side (shaft end side) of the inner joint member 32, whereby the intermediate shaft 4 and the inner joint member 32 are prevented from coming off.

Since the sliding type constant velocity universal joint 2 and the fixed type constant velocity universal joint 3 are dedicated to the rear wheel drive shaft, the maximum operating angle can be set smaller than that of a conventional product that can also be used for the front wheel drive shaft. In the present embodiment, the maximum operating angles of the plunging type constant velocity universal joint 2 and the fixed type constant velocity universal joint 3 are both set to 20 ° or less. This makes it possible to reduce the weight and the size of the plunging type constant velocity universal joint 2 and the fixed type constant velocity universal joint 3 while maintaining the load capacity. The internal specifications of the plunging type constant velocity universal joint 2 will be described in detail below.

In table 1 and fig. 6 to 8 below, the internal specifications of the plunging type constant velocity universal joint 2 of the present invention product are shown in comparison with a comparative product (a double-race type constant velocity universal joint with 8 balls at a maximum operating angle of 25 °) having the same ball diameter. In fig. 6 to 8, the upper half is a sectional view of the plunging constant velocity universal joint 2 of the present invention, and the lower half is a sectional view of the plunging constant velocity universal joint 2' of the comparative product. Each part of the comparative product is denoted by a reference numeral in which a prime is added to the reference numeral of each part of the product of the present invention.

[ Table 1]

	Products of the invention	Comparison product
			(1) Ball PCD (PCD)_BALL) Ball diameter	3.3～3.6	3.9～3.9
(2) Inner circle width (W)_I) Ball diameter	1.2～1.55	1.6～1.8
			(3) Inner ring wall thickness (T)_I) Ball diameter	0.30～0.45	0.45～0.60
(4) Splined PCD (PCD)_SPL) Ball diameter	1.70～1.85	1.65～1.75
			(5) Outer ring outer diameter (D)_O) Splined PCD (PCD)_SPL)	2.7～3.0	3.0～3.3
(6) Width of retainer (W)_C) Ball diameter	1.8～2.0	2.0～2.2

The above parameters are defined as follows.

(1) Ball PCD (reference circle diameter of ball) PCD_BALL: the axial center of the outer joint member 21 or the axial center of the inner joint member 22 is 2 times the distance from the center of the balls 23. I.e. the diameter of a circle passing through the centers of all the balls 23 in the state of the working angle of 0 deg..

(2) Inner ring width (axial width of inner coupling member) W_I: the maximum axial dimension of the inner joint member 22 is, in the illustrated example, the axial distance between both end surfaces of the inner joint member 22.

(3) Inner ring wall thickness (radial wall thickness of inner joint member) T_I: the groove bottom of the track groove 22e on the joint center plane P (a plane passing through the joint center o(s) and orthogonal to the axis) is spaced from the radial distance of the pitch circle of the spline hole 22 c. In the illustrated example, the wall thickness of the inner joint member in the radial direction is constant in the axial direction.

(4) Splined PCD (reference circle diameter of splined bore of inner coupling member) PCD_SPL: the diameter of the spline hole 22c of the inner joint member 22 and the diameter of the pitch circle of the spline 46 (see fig. 2) of the intermediate shaft 4.

(5) Outer diameter D of outer wheel_O: the maximum outer diameter of the outer coupling member 21.

(6) Width W of retainer_C: the maximum axial dimension of the retainer 24 is, in the illustrated example, the axial distance between the two end faces of the retainer 24.

The design concept for obtaining the above-described internal specification will be described in detail below.

Constant velocity universal joint of sliding typeIn the shaft device 2, since the maximum load applied to each ball 23 increases as the operating angle increases, the maximum load applied to each ball 23 decreases by decreasing the maximum operating angle as described above. As a result, a margin is generated in the strength of the inner joint member 22 in contact with the balls 23, the wall thickness of the inner joint member 22 in the radial direction can be made thin, and the pitch circle diameter of the track grooves 22e of the inner joint member 22, that is, the pitch circle diameter of the balls 23 fitted in the track grooves 22e can be made smaller than that of a comparative Product (PCD) without causing a reduction in load capacity and aging resistance (PCD)_BALL＜PCD_BALL', refer to (1) of table 1 above). This makes it possible to reduce the sliding type constant velocity universal joint 2 in the radial direction, and to reduce the weight.

Since the maximum working angle of the comparative product is large, the circumferential length of the pocket 24a 'of the retainer 24' is large, and the diameter of the retainer 24 'needs to be increased to ensure the circumferential length of the pocket 24 a'. Therefore, the outer peripheral surface of the inner joint member 22 ' which is in sliding contact with the inner peripheral surface of the retainer 24 ' has a large diameter, and as a result, the inner joint member 22 ' has an excessively large thickness equal to or greater than a thickness necessary for strength. In contrast, in the product of the present invention, the maximum operating angle is reduced as described above, so that the amount of circumferential movement of the balls 23 with respect to the cage 24 is reduced, and therefore the circumferential dimension of each pocket 24a of the cage 24 can be reduced (Lp < Lp'). Thus, the diameter of the retainer 24 can be reduced while maintaining the circumferential dimension of the pillar portion 24e between the pockets 24a (Lc ≈ Lc'), and the outer peripheral surface 22d of the inner joint member 22 that is in sliding contact with the spherical portion 24d of the inner peripheral surface of the retainer 24 can be reduced in diameter. As a result, the inner joint member 22 can be thinned to have a minimum wall thickness (T) required for strength_I＜T_I' referring to (3) of table 1), the plunging type constant velocity universal joint 2 can be made compact in the radial direction by reducing the pitch circle diameter of the balls 23 as described above.

By reducing the maximum operating angle of the plunging constant velocity universal joint 2, the maximum load applied to the balls 23 is reduced as described above, and therefore the maximum load is reducedThe strength of the retainer 24 with which the balls 23 contact creates a margin. Accordingly, the axial wall thickness of the annular portions provided at both axial ends of the retainer 24 can be reduced while maintaining the aging resistance equivalent to that of the comparative product, and therefore the axial width of the entire retainer 24 can be reduced to reduce the weight (W)_C＜W_C', refer to (6) of table 1 above).

By reducing the maximum operating angle of the plunging constant velocity universal joint 2, the angle of the conical portion 24c of the outer peripheral surface of the retainer 24 with respect to the axial center can be reduced, and in the present embodiment, the angle can be set to 10 ° or less. Thereby, the thickness of the thin portion of the retainer 24 (for example, the thickness T at the coupler opening side end portion) can be increased_C) Therefore, the strength of the retainer 24 can be improved.

By reducing the maximum operating angle of the plunging constant velocity universal joint 2, the wall thickness T in the radial direction of the inner joint member 22 can be reduced as described above_ITherefore, the diameter of the spline hole 22c of the inner joint member 22 can be increased (PCD)_SPL＞PCD_SPL', refer to (4) of table 1 above). This makes it possible to increase the diameter of the intermediate shaft 4 inserted into the spline hole 22c, thereby improving the torsional strength. Further, by reducing the maximum operating angle of the plunging constant velocity universal joint 2, the pitch circle diameter of the balls 23 can be reduced as described above, and therefore the outer joint member 21 can be reduced in diameter. As described above, in the product of the present invention, the outer diameter D of the outer joint member 21 can be set_OReference circle diameter PCD of spline hole of inner coupling member_SPLRatio of D_O/PCD_SPLIs smaller than the comparative product (D)_O/PCD_SPL＜D_O’/PCD_SPL', refer to (5) of table 1 above). This makes it possible to achieve both weight reduction and compactness of the plunging constant velocity universal joint 2 and strength improvement of the intermediate shaft 4.

When the maximum operating angle of the plunging constant velocity universal joint 2 is made small, the amount of axial movement of the balls 23 relative to the inner joint member 22 becomes small. Specifically, as shown in FIG. 8, the product of the present invention having a smaller maximum working angle is compared with the comparative product having a larger maximum working angleThe axial length (effective raceway length) of the contact point locus between the raceway groove 22e of the inner joint member 22 and the balls 23 is shorter (Z) than the axial length (effective raceway length)_I＜Z_I'). Thus, in the present invention product, the axial length of the track grooves 22e of the inner joint member 22, and hence the axial width of the entire inner joint member 22, can be made shorter than in a comparative product (W)_I＜W_I', refer to (2) of table 1 above).

However, if the axial width of the inner joint member 22 is too small, the axial length of the spline hole 22c provided in the axial center of the inner joint member 22 may be insufficient, and the strength of the spline fitting portion between the inner joint member 22 and the intermediate shaft 4 (see fig. 2) may be insufficient. In the plunging type constant velocity universal joint 2 according to the present invention, the wall thickness of the inner joint member 22 in the radial direction can be made thin as described above by reducing the maximum operating angle, and therefore the diameter of the spline hole 22 of the inner joint member 22 can be increased. Thereby, the axial length of the spline hole 22c of the inner joint member 22 can be shortened while maintaining the surface pressure of each spline tooth (i.e., while maintaining the strength of the spline fitting portion). As described above, by shortening the axial lengths of the track grooves 22e and the spline holes 22c of the inner joint member 22, the axial width of the entire inner joint member 22 can be reduced as described above, and weight can be reduced.

As described above, the present invention has been made in consideration of various conditions obtained by reducing the maximum operating angle of the plunging constant velocity universal joint, and has been made to consider the internal specifications of the plunging constant velocity universal joint, thereby achieving a weight reduction and a size reduction of the plunging constant velocity universal joint while maintaining a torque load capacity equivalent to that of a comparative product. Thus, a new lightweight and compact sliding type constant velocity universal joint series can be constructed which can be used exclusively for a rear wheel drive shaft.

However, if the plunging type constant velocity universal joint rotates in a state in which the operating angle is high, abnormal noise may occur. In order to suppress the occurrence of abnormal noise at a high operating angle as described above, in the conventional plunging type constant velocity universal joint, it is necessary to set the track PCD clearance (the difference between the pitch circle diameter of the track groove of the outer joint member and the pitch circle diameter of the track groove of the inner joint member), the clearance between the outer joint member and the cage (the difference between the diameter of the cylindrical inner peripheral surface of the outer joint member and the diameter of the spherical surface portion of the outer peripheral surface of the cage), and the spherical clearance between the cage and the inner joint member (the difference between the diameter of the spherical surface portion of the inner peripheral surface of the cage and the diameter of the spherical outer peripheral surface of the inner joint member) to very small values. In contrast, in the plunging type constant velocity universal joint 2 described above, the maximum operating angle is small and the possibility of abnormal noise can be reduced, so the clearances described above can be set to values larger than those of conventional products, which is advantageous in terms of manufacturing.

Further, since the conventional plunging type constant velocity universal joint is also used for a front wheel drive shaft, as a countermeasure against idle vibration, the inner peripheral surface of the retainer is processed into a special shape so that a large axial gap is provided between the inner peripheral surface of the retainer and the outer peripheral surface of the inner joint member (see, for example, fig. 3 and 4 of patent document 1). On the other hand, since the plunging type constant velocity universal joint 2 described above is dedicated to the rear wheel drive shaft, it is possible to form the inner peripheral surface of the cage (the sliding contact portion with the inner joint member) into a simple spherical shape without requiring measures against idling vibration, which is advantageous in terms of manufacturing compared to conventional products.

Preferable ranges (unit: mm) of the clearances of the respective portions set in consideration of the above are shown in the following table 2. The axial clearance between the pocket surface of the cage and the balls is equal to that of the conventional product. By providing a slight axial gap between the pocket surface of the retainer and the balls, the rolling performance of the balls is improved, and the torque transmission efficiency is improved.

[ Table 2]

Roller path PCD roomGap	0.005～0.200
		Clearance between outer ring and retainer	0.005～0.300
Clearance between retainer and inner ring	0.005～0.100
		Axial gap between cage and inner ring	0.005～0.300
Clearance between retainer pockets and balls	0.005～0.050

The present invention is not limited to the above-described embodiments. For example, the plunging type constant velocity universal joint described above is not limited to a rear wheel drive shaft of a rear wheel drive vehicle (for example, an FR vehicle) that is driven only by rear wheels, and can be used as a rear wheel drive shaft of a four-wheel drive vehicle (in particular, a four-wheel drive vehicle in which the rear wheels are main drive wheels). In the SUV vehicle, since the vertical movement of the wheels is large and the angular displacement of the drive shaft is also large, the low operating angle plunging type constant velocity universal joint as described above may not be applied. Therefore, the plunging type constant velocity universal joint is preferably applied to a rear wheel drive shaft of a passenger vehicle that is driven by rear wheels or four wheels.

Description of reference numerals:

1 drive shaft for rear wheel

2 sliding type constant velocity universal joint

21 outer coupling member

22 inner coupling component

23 ball bearing

24 holder

3 fixed type constant velocity universal joint

31 outer joint component

32 inner side coupling component

33 ball

34 holder

4 middle shaft

E engine

G differential gear

M speed changer

PS drive shaft

W wheels.

Claims

1. A plunging constant velocity universal joint which is a plunging constant velocity universal joint dedicated to a drive shaft for a rear wheel,

the sliding type constant velocity universal joint includes:

an outer joint member having 8 track grooves formed in a cylindrical inner circumferential surface thereof and extending in an axial direction;

an inner joint member having 8 track grooves formed on a spherical outer circumferential surface and extending in an axial direction, and having a spline hole formed in an axial center;

8 balls arranged on ball grooves formed by the track grooves of the outer joint member and the track grooves of the inner joint member; and

a cage having 8 pockets for receiving the balls and being in sliding contact with an inner peripheral surface of the outer joint member and an outer peripheral surface of the inner joint member,

the center of curvature of the spherical portion provided on the outer peripheral surface of the cage and the center of curvature of the spherical portion provided on the inner peripheral surface of the cage are offset by equal distances from the coupling center toward the opposite sides in the axial direction,

reference circle diameter (PCD) of the ball_BALL) And diameter (D) of said ball_BALL) Ratio of (PCD)_BALL/D_BALL) Is in the range of 3.3 to 3.6,

a radial wall thickness (T) of the inner coupling member_I) And diameter (D) of said ball_BALL) Ratio of (T)_I/D_BALL) Is in the range of 0.30 to 0.45,

the maximum working angle is 20 degrees or less.

2. The plunging constant velocity universal joint according to claim 1,

reference circle diameter (PCD) of splined bore of the inner coupling member_SPL) And diameter (D) of said ball_BALL) Ratio of (PCD)_SPL/D_BALL) 1.70 to 1.85.

3. The plunging constant velocity universal joint according to claim 1 or 2,

outer diameter (D) of the outer coupling member_O) Reference circle diameter (PCD) of splined bore of the inner coupling member_SPL) Ratio of (D)_O/PCD_SPL) 2.7 to 3.0.

4. The plunging constant velocity universal joint according to claim 1 or 2,

axial width (W) of the inner coupling member_I) And diameter (D) of said ball_BALL) Ratio of (W)_I/D_BALL) Is 1.2 to 1.55.

5. The plunging constant velocity universal joint according to claim 1 or 2,

axial width (W) of the retainer_C) And diameter (D) of said ball_BALL) Ratio of (W)_C/D_BALL) Is 1.8 to 2.0.