Sliding constant velocity joint

Abstract

To provide a double-offset, sliding-type constant velocity universal joint which, on the basis of a practical accuracy level of hammering and heat treatment, enables a practical selection of an inner joint member combined in accordance with PCD dimensions of a track groove in an outer joint member, and can ensure durability, strength, and NVH characteristics.SOLUTION: In a sliding-type constant velocity universal joint 1, a center of curvature of a spherical outer peripheral surface and a center of curvature of a spherical inner peripheral surface in a cage 5 are offset to an opposite side in an axial direction with respect to a joint center. A range from 10 mm on a depth side to 10 mm on an opening side with respect to a slide range center C in a joint axis direction of a track groove 7 in an outer joint member 2 is defined as a central range W, and a portion 7a where a pitch circle diameter (PCD) of the track groove 7 of the outer joint member 2 is smallest is formed in the central range W. A minimum value of a PCD clearance Δ of the track grooves 7, 9 in the central range W is set to from 0.010 mm to 0.100 mm, and a mutual PCD error in the track groove 7 of the outer joint member 2 in the central range W is 0.150 mm or less.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a sliding type constant velocity universal joint used in power transmission systems of automobiles and various industrial machines, for example, in drive shafts and propeller shafts of automobiles. [Background technology]

[0002] Constant velocity universal joints applied to automobile drive shafts can be broadly divided into fixed type constant velocity universal joints, which only allow angular displacement between two shafts, and sliding type constant velocity universal joints, which allow angular and axial displacement. Automobile drive shafts usually use a fixed type constant velocity universal joint on the driving wheel side (also called the outboard side) and a sliding type constant velocity universal joint on the differential side (also called the inboard side), with these two constant velocity universal joints connected by an intermediate shaft. Various constant velocity universal joints are selected depending on the operating conditions and application.

[0003] Typical sliding type constant velocity universal joints are double offset type constant velocity universal joints (DOJ) and tripod type constant velocity universal joints (TJ). DOJ type sliding type constant velocity universal joints are widely used due to their low manufacturing cost and small rotational backlash inside the joint. DOJ type sliding type constant velocity universal joints with six or eight balls are known, and Patent Document 1 describes a DOJ with a compact design that has eight balls, and Patent Document 2 describes a DOJ with a maximum operating angle of 30° or more that has a higher operating angle and is lighter and more compact.

[0004] A DOJ type sliding type constant velocity universal joint comprises an outer joint member having a plurality of linear track grooves formed along the axial direction on its cylindrical inner circumferential surface; an inner joint member having a plurality of linear track grooves formed along the axial direction on its spherical outer circumferential surface opposing the plurality of linear track grooves of the outer joint member; a plurality of torque transmission balls assembled between the plurality of linear track grooves of the outer joint member and the plurality of linear track grooves of the inner joint member; and a cage which houses the torque transmission balls in pockets and has a spherical outer circumferential surface and a spherical inner circumferential surface which are guided in contact with the cylindrical inner circumferential surface of the outer joint member and the spherical outer circumferential surface of the inner joint member, and the center of curvature of the spherical outer circumferential surface of the cage and the center of curvature of the spherical inner circumferential surface are offset to the opposite side in the axial direction with respect to the joint center. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-73129 [Patent Document 2] JP 2007-85488 A Summary of the Invention [Problem to be solved by the invention]

[0006] In order to reduce manufacturing costs, DOJ type sliding constant velocity universal joints generally finish the track grooves of the cup portion of the outer joint member and the inner joint member by cold forging, and do not perform finishing such as grinding on the track grooves of the cup portion and the inner joint member after heat treatment. Therefore, in addition to the influence of the accuracy of cold forging, the pitch circle diameters PCD of the track grooves of the outer joint member and the inner joint member vary between track grooves due to the deformation caused by heat treatment of the track grooves. The pitch circle diameter PCD of the track groove (hereinafter simply referred to as PCD) is the center-to-center distance of balls on the joint diameter when torque transmission balls are pressed against the track grooves. A difference occurs between the maximum and minimum values ​​of PCD between track grooves. This difference between the maximum and minimum values ​​of PCD between track grooves is called the PCD difference.

[0007] The PCD difference affects the variation in the PCD gap, which is the track gap between the track groove and the ball. In other words, it affects the difference between the maximum and minimum PCD gap between the track grooves. The difference between the maximum and minimum PCD gap between the track grooves is also called the PCD gap difference.

[0008] If the difference in PCD clearance becomes too large, the load may not be distributed evenly between the track grooves when torque is applied, resulting in concentrated load on certain track grooves, which may result in deterioration of durability, strength, and NVH characteristics.

[0009] In addition, in order to ensure the appropriate PCD clearance, it is common to select and combine inner joint members according to the PCD dimensions of the track grooves of the outer joint member. It is important in terms of productivity and manufacturing costs to make this selection and combination possible efficiently.

[0010] In view of the above problems, an object of the present invention is to provide a double offset sliding type constant velocity universal joint which enables practical selection and combination of an inner joint member with respect to a PCD dimension of a track groove of an outer joint member based on a practical precision level of forging and heat treatment, and which can ensure durability, strength, and NVH characteristics. [Means for solving the problem]

[0011] In order to achieve the above object, the inventors have studied various aspects from various angles, such as (a) the precision at the limit of forging and heat treatment, (b) the possibility of efficient practical application of the selection and combination of inner joint members relative to the PCD dimensions of the track groove, and (c) ensuring durability, strength, and NVH characteristics (vibration characteristics). As a result, they have reached the conclusion that the key to the solution is to focus on the circumferential backlash in the central range in the joint axial direction of the track groove, which is the sliding range most frequently used in actual vehicles equipped with double offset type sliding type constant velocity joints, and have arrived at the present invention through the new idea of ​​setting the minimum value of the PCD clearance and the mutual PCD difference in the central range.

[0012] As technical means for achieving the above-mentioned object, the present invention provides an outer joint member having a cylindrical inner circumferential surface on which a plurality of linear track grooves are formed along an axial direction, an inner joint member having a spherical outer circumferential surface on which a plurality of linear track grooves facing the plurality of linear track grooves of the outer joint member are formed along an axial direction, a plurality of torque transmission balls incorporated between the plurality of linear track grooves of the outer joint member and the plurality of linear track grooves of the inner joint member, and a cage that houses the torque transmission balls in pockets and has a spherical outer circumferential surface and a spherical inner circumferential surface that are brought into contact with and guided by the cylindrical inner circumferential surface of the outer joint member and the spherical outer circumferential surface of the inner joint member. In the sliding type constant velocity universal joint, the center of curvature of the spherical outer peripheral surface of the cage and the center of curvature of the spherical inner peripheral surface are offset in the axial opposite direction from the joint center, the central range is from 10 mm on the rear side to 10 mm on the opening side with respect to the center of the sliding range in the joint axial direction of the track groove of the outer joint member, a portion where the PCD of the track groove of the outer joint member is minimum is formed in the central range, the minimum value of the PCD gap of the track groove in the central range is 0.010 mm to 0.100 mm, and the mutual PCD difference of the track groove of the outer joint member in the central range is 0.150 mm or less. With the above configuration, it is possible to realize a double offset sliding type constant velocity universal joint that enables practical use of a selective combination of the inner joint member with respect to the PCD dimension of the track groove of the outer joint member based on the practical accuracy level of forging and heat treatment, and that can ensure durability, strength, and NVH characteristics.

[0013] Specifically, by setting the mutual PCD difference of the track grooves of the outer joint member in the region excluding the central range to 0.170 mm or less, the balls can slide smoothly in the track grooves without unnecessary interference when, for example, the joint is assembled to a vehicle or the vehicle is pushed up due to road surface conditions while traveling.

[0014] Since the track grooves have a surface formed by plastic working, the manufacturing cost can be reduced.

[0015] By making the contact between the torque transmission balls and the track grooves of the outer joint member and the track grooves of the inner joint member be angular contact, it is possible to reliably suppress backlash in the circumferential direction.

[0016] By setting the number of the torque transmission balls to 6 to 8, it is possible to configure a double offset sliding type constant velocity universal joint that is suitable for power transmission systems of automobiles, various industrial machines, and the like. Effect of the Invention

[0017] According to the present invention, it is possible to realize a double offset sliding type constant velocity universal joint which enables practical selection and combination of an inner joint member with respect to a PCD dimension of a track groove of an outer joint member based on a practical precision level of forging and heat treatment, and which can ensure durability, strength, and NVH characteristics.

[0018] According to the present invention, since circumferential backlash can be suppressed and NVH characteristics can be ensured, it is possible to realize a double offset sliding type constant velocity universal joint that is particularly suitable for motor-driven electric vehicles, which require improved rotational torque transmission responsiveness and quietness. [Brief description of the drawings]

[0019] [Figure 1] 3 is a longitudinal sectional view of the slide type constant velocity universal joint according to the first embodiment of the present invention, taken along line BNB in ​​FIG. 2. [Diagram 2] 2 is a cross-sectional view of the slide type constant velocity universal joint according to the first embodiment of the present invention, taken along line AA in FIG. 1. [Diagram 3] 3 is an enlarged cross-sectional view of one track groove, a torque transmitting ball, and a cage taken along line BN in FIG. 2. [Figure 4] 2 is a vertical cross-sectional view showing the center of the sliding range of FIG. 1. [Diagram 5] FIG. 5 is a schematic diagram illustrating the center of the sliding range in FIG. 4. [Figure 6]4 is a cross-sectional view illustrating the variation in PCD between track grooves of the sliding type constant velocity universal joint of the present embodiment. FIG. [Figure 7] FIG. 4 is a schematic diagram of a measuring device for measuring a PCD difference between track grooves of an outer joint member. [Figure 8] FIG. 4 is a schematic diagram of a measuring machine for measuring a PCD difference between track grooves of an inner joint member. [Figure 9] FIG. 1(a) is a schematic diagram of a measuring device for measuring the minimum value of the PCD of the track groove of an outer joint member, and FIG. 1(b) is a diagram illustrating the principle of measuring the minimum value of the PCD of the track groove of an outer joint member. [Figure 10] 1A and 1B are schematic diagrams of a measuring device for measuring the maximum value of PCD of a track groove of an inner joint member, in which FIG. 1A is a plan view and FIG. 1B is a front view with a partial vertical cross section. [Figure 11] FIG. 4 is a diagram illustrating the principle of measuring the maximum value of PCD of a track groove of an inner joint member. [Figure 12] 14 is a longitudinal sectional view of a slide type constant velocity universal joint according to a second embodiment of the present invention, taken along line BN-B' in FIG. 13. FIG. [Figure 13] 13 is a cross-sectional view of a slide type constant velocity universal joint according to a second embodiment of the present invention, taken along line AA in FIG. 12. FIG. [Figure 14] FIG. 11 is a vertical sectional view of a first modified example of an inner assembly of a slide type constant velocity universal joint according to a second embodiment of the present invention. [Figure 15] FIG. 11 is a vertical sectional view of a second modified example of the inner assembly of the slide type constant velocity universal joint according to the second embodiment of the present invention. [Figure 16] FIG. 16 is an enlarged view of part E in FIG. [Figure 17] FIG. 11 is a vertical sectional view of a third modified example of the inner assembly of the slide type constant velocity universal joint according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] A double offset type sliding type constant velocity universal joint according to a first embodiment of the present invention will be described with reference to Figs. 1 to 11. Fig. 1 is a longitudinal sectional view of the sliding type constant velocity universal joint of this embodiment, taken along line BNB in ​​Fig. 2. Fig. 2 is a transverse sectional view of the sliding type constant velocity universal joint of this embodiment, taken along line AA in Fig. 1. Fig. 3 is an enlarged transverse sectional view of one track groove, torque transmission ball, and cage taken along line BN in Fig. 2.

[0021] As shown in Figs. 1 and 2, the sliding type constant velocity universal joint 1 is a so-called double offset type sliding type constant velocity universal joint (sometimes abbreviated as DOJ), and mainly comprises an outer joint member 2, an inner joint member 3, torque transmission balls 4, and a cage 5. Eight track grooves 7 are formed on a cylindrical inner peripheral surface 6 of the outer joint member 2 at equal intervals in the circumferential direction and linearly along the axial direction. Track grooves 9 facing the track grooves 7 of the outer joint member 2 are formed on a spherical outer peripheral surface 8 of the inner joint member 3 at equal intervals in the circumferential direction and linearly along the axial direction. Eight torque transmission balls (hereinafter also simply referred to as balls) 4 are incorporated between the track grooves 7 of the outer joint member 2 and the track grooves 9 of the inner joint member 3, one each. The balls 4 are accommodated in pockets 5a of the cage 5.

[0022] The cage 5 has a spherical outer peripheral surface 11 and a spherical inner peripheral surface 12. The spherical outer peripheral surface 11 is fitted and guided in contact with the cylindrical inner peripheral surface 6 of the outer joint member 2, and the spherical inner peripheral surface 12 is fitted and guided in contact with the spherical outer peripheral surface 8 of the inner joint member 3. The spherical outer peripheral surface 11 of the cage 5 is formed with a radius of curvature Rc1 with a center of curvature O1, and the spherical inner peripheral surface 12 is formed with a radius of curvature Rc2 with a center of curvature O2. The spherical outer peripheral surface 8 of the inner joint member 3 is formed with a radius of curvature Ri with a center of curvature O2. The centers of curvature O1 and O2 are located on the axis N and are offset by an equal distance F on the opposite side of the axial direction from the joint center O. As a result, when the joint has an operating angle, the balls 4 are always guided on a plane that bisects the angle formed by the axes of the outer joint member 2 and the inner joint member 3, and the rotation between the two shafts is transmitted at a constant speed.

[0023] A retaining ring groove 15 is provided at the open end of the outer joint member 2, and a retaining ring 17 is fitted in this retaining ring groove 15 to prevent an inner assembly I consisting of the inner joint member 3, ball 4, and cage 5 shown in Fig. 1 from slipping out from the open end of the outer joint member 2. A boot mounting groove 16 is provided on the outer periphery of the open end of the outer joint member 2. A stem portion (shaft portion) 2b is formed integrally with the outer joint member 2 on the side opposite the open end, and is connected to a differential (not shown).

[0024] Since linear track grooves 9 are formed on the spherical outer peripheral surface 8 of the inner joint member 3, the groove depth of the track grooves 9 becomes shallower from the axial center to both ends of the inner joint member 3. A spline (including serrations, the same applies below) 14 is formed in a connecting hole 13 of the inner joint member 3, and an axial end of an intermediate shaft (not shown) is spline-fitted thereinto, and the intermediate shaft is fixed in the axial direction to the inner joint member 3 by a shoulder portion of the intermediate shaft and a retaining ring (not shown).

[0025] Eight pockets 5a are provided at equal intervals in the circumferential direction at the axial center of the cage 5 shown by line AA in FIG. 1, and a column portion 5b (see FIG. 2) is provided between adjacent pockets 5a. A notch 5c is provided on the inner circumference of the large diameter end of the cage 5 for incorporating the inner joint member 3. The stopper surface 5d of the cage 5 is formed in a cone shape that is connected to the spherical outer peripheral surface 11 as a tangent. In the sliding type constant velocity universal joint 1 of this embodiment, the maximum operating angle is set to, for example, 25°. When the joint takes an operating angle, the cage 5 is inclined by half the angle formed by both the axes of the outer joint member 2 and the inner joint member 3, so the inclination angle S of the stopper surface 5d is set to 12.5°. This makes it possible to regulate the maximum allowable angle of the sliding type constant velocity universal joint 1.

[0026] 3, the angular contact between the track groove 7 of the outer joint member 2, the track groove 9 of the inner joint member 3 and the torque transmitting ball 4, and the PCD and PCD clearance of the track grooves 7, 9 will be described. FIG. 3 shows one track groove 7, 9, the torque transmitting ball 4 and the cage 5 on the line BN in FIG. 2. The cross sections of the track groove 7 of the outer joint member 2 and the track groove 9 of the inner joint member 3 are formed in a Gothic arch shape combining two circular arcs. Therefore, the ball 4 comes into angular contact with the track grooves 7, 9 at two points C1, C2, C3, and C4 respectively. The cross sectional shape of the track grooves 7, 9 is not limited to the Gothic arch shape described above, and may be an elliptical shape.

[0027] As shown in FIG. 3, when the pitch circle diameter of the track groove 7 of the outer joint member 2 and the pitch circle diameter of the track groove 9 of the inner joint member 3 are to be expressed separately, the pitch circle diameter of the track groove 7 of the outer joint member 2 is expressed as ToPCD, and the pitch circle diameter of the track groove 9 of the inner joint member 3 is expressed as TiPCD. ToPCD is set to be larger than TiPCD by, for example, about 0.050 mm as a median value. As a result, the center Ob of the torque transmission ball 4 is located in the radial middle between ToPCD and TiPCD, and in the no-load state, a track clearance is formed between the ball 4 and the track groove 7 of the outer joint member 2 and the track groove 9 of the inner joint member 3 in the direction of the track contact angle α. The radial clearance component based on the track clearance in the direction of the track contact angle α is the PCD clearance. Δ In other words, PCD clearance Δ is expressed by the following equation. PCD clearance Δ =ToPCD-TiPCD In this specification and claims, PCD clearance has the above meaning.

[0028] Diameter D of ball 4 BALL (See Fig. 2) is a reference diameter (constant dimension). Therefore, if the pitch circle diameter ToPCD of the track groove 7 of the outer joint member 2 and the pitch circle diameter TiPCD of the track groove 9 of the inner joint member 3 vary due to forging accuracy and heat treatment deformation, the PCD clearance ΔSpecifically, when the pitch circle diameter ToPCD of the track groove 7 of the outer joint member 2 becomes large and the pitch circle diameter TiPCD of the track groove 9 of the inner joint member 3 becomes small, the PCD clearance Δ Conversely, when ToPCD becomes smaller and TiPCD becomes larger, the PCD clearance Δ becomes smaller.

[0029] PCD clearance Δ In the sliding type constant velocity universal joint 1 of this embodiment, the cross-sectional shape of the track grooves 7, 9 is formed in a Gothic arch shape, so that the amount of rotational play inside the joint can be reliably suppressed, and the torque load response in the EV is also good. Δ is shown in an exaggerated manner.

[0030] The track contact angle α is the angle α between the lines La and Lb in Fig. 3. The line La is the center line of the cross section of the track grooves 7 and 9, and corresponds to the line BN in Fig. 2. The line Lb is a line connecting the contact points C1, C2, C3, and C4 of the ball 4 on the side surfaces of the track grooves 7 and 9 to the center Ob of the ball 4.

[0031] In the sliding-type constant velocity universal joint 1 of the present embodiment, the balls 4 and the track grooves 7, 9 are in angular contact with each other, but this is not limited to angular contact. The cross-sectional shapes of the track grooves 7, 9 of the outer joint member 2 and the inner joint member 3 may be arc-shaped, and the balls 4 and the track grooves 7, 9 may be in circular contact with each other at one point.

[0032] The overall configuration of the double offset type sliding type constant velocity universal joint 1 of this embodiment is as described above. Next, the characteristic configurations will be described. The characteristic configurations are as follows (1) to (3). (1) The central range is set to a range from 10 mm toward the rear side to 10 mm toward the opening side with respect to the center of the sliding range in the axial direction of the track groove of the outer joint member, and a portion where the PCD of the track groove of the outer joint member is smallest is formed in this central range. (2) PCD clearance of track grooves in the central area Δ The minimum value is set at 0.010mm to 0.100mm. (3) The PCD difference of the track grooves of the outer joint members in the central region is 0.150 mm or less.

[0033] The above characteristic configurations (1) to (3) were arrived at through the following process of investigation. That is, the inventors of the present invention have investigated various aspects including (a) the precision level at the limit of forging and heat treatment, (b) the possibility of efficient practical application of the selection and combination of the inner joint member with respect to the PCD dimension of the track groove, and (c) ensuring durability, strength, and NVH characteristics (low vibration characteristics), and have come to the conclusion that the key to solving the problem lies in focusing on the circumferential backlash in the central range in the joint axial direction of the track groove of the outer joint member, which is the sliding range most frequently used in an actual vehicle equipped with a double offset type sliding type constant velocity universal joint, and have determined that the PCD clearance in the central range is the key to solving the problem. Δ The above characteristic configurations (1) to (3) were arrived at by a new idea of ​​setting the minimum value of PCD and the mutual difference of PCD of the track grooves of the outer joint member.

[0034] The characteristic features will be described in order with reference to the drawings. The characteristic feature (1) is that the PCD clearance is provided in the central range in the axial direction of the track groove of the outer joint member, which is the sliding range most frequently used in an actual vehicle equipped with a double offset type sliding constant velocity universal joint. Δ In order to form the outer joint member with high precision, a portion where the PCD of the track groove of the outer joint member is smallest is formed in the central region. The characteristic configuration (1) will be specifically described with reference to Figs. 4 and 5. Fig. 4 is a vertical sectional view showing the central portion of the sliding range, showing details of the track groove of the outer joint member in Fig. 1 in the axial direction of the joint. Fig. 5 is a schematic view explaining the central portion of the sliding range in Fig. 4.

[0035] The outer joint member 2 of the double offset type sliding type constant velocity universal joint 1 is generally manufactured by a forging process, a cutting process, a quenching process, and a grinding process, and the inside of the cup portion is finished by cold forging (finishing processing such as grinding after the quenching process is not performed). The inner joint member 3 is generally manufactured by a forging process, a cutting process, a heat treatment process, and a grinding process, and the track grooves 9 are finished by cold forging (finishing processing such as grinding after the quenching process is not performed). As shown in FIG. 4, the central area W is defined as a range from w (=10 mm) on the inner side to w (=10 mm) on the opening side of the central area C of the sliding range of the track grooves 7 of the outer joint member 2 based on a central area C (which is also a set position) in the joint axial direction. Then, a portion 7a where the PCD of each of all the track grooves 7 of the outer joint member 2 is minimum is formed in the central area W as shown in the figure by the forging process and the heat treatment process. Here, in this specification and claims, "forming a portion in the central range W where the PCD of the track groove of the outer joint member is minimum" means forming a portion where the PCD is minimum for each of all the track grooves of the outer joint member. The portion 7a where the PCD (ToPCD, see FIG. 3) of the track groove 7 formed in the central range W is minimum becomes a reference for setting the PCD gap Δ between the track grooves 7, 9 and the PCD of the track groove 7 of the outer joint member 2, which will be described later.

[0036] 4, in order to easily understand the portion 7a where the PCD (ToPCD) of the track groove 7 formed in the central range W is minimum, a state in which the ball 4 is pressed against the track groove 9 of the inner joint member 3 (the groove bottom gap of the track groove 9 is omitted) and a PCD clearance Δ is shown between the groove bottom of the track groove 7 of the outer joint member 2 and the ball 4. The PCD clearance Δ shown between the groove bottom of the track groove 7 and the ball 4 is formed in the direction of the contact angle α as shown in FIG. 3, but the illustration has been partially modified for convenience.

[0037] The PCD (ToPCD) of the track groove 7 of the outer joint member 2 is gradually smaller from the opening side of the cup portion 2a toward the center C (central range W) of the sliding range, and gradually larger from the center C (central range W) of the sliding range toward the back side. The fluctuation dimension of the PCD that gradually fluctuates in the axial direction is about 0.100 mm to 0.300 mm.

[0038] The sliding range center C will be described. The sliding range center C is the axial position of the joint center O of the sliding type constant velocity universal joint 1 after the assembly of the sliding type constant velocity universal joint 1 is mounted on the vehicle, and is also the set position. As shown in FIG. 4, in the double offset type sliding type constant velocity universal joint 1, a retaining ring 17 is often attached to the opening side end of the outer joint member 2 to prevent the inner assembly I consisting of the inner joint member 3, the ball 4, and the cage 5 from falling off, and the sliding type constant velocity universal joint 1 is used in the area of ​​the sliding range shown in FIG. 5, centered on the sliding range center C (set position). Specifically, as shown in FIG. 5, the opening side of the cup portion 2a is restricted from sliding in the axial direction on the opening side by the ball 4 and the retaining ring 17 (see FIG. 4) interfering with each other at the position of the line X1. On the other hand, the axial sliding of the rear side of the cup portion 2a is restricted by interference between the cage 5 and the bottom of the cup portion 2a at the position of line X2, or between the shaft (not shown) and the opening 2c of the cup portion 2a (see FIG. 4) at the position of line X3. As shown in the figure, the amount of axial sliding enclosed by lines X1 to X3 decreases as the operating angle increases.

[0039] Here, the sliding range center C is defined. The sliding range center C is arbitrarily set according to the conditions of use of the vehicle. In other words, the sliding range center C may deviate from the central position in the axial direction surrounded by the lines X1-X3 from the opening of the cup portion 2a to the bottom of the cup portion 2a. Therefore, the center of the axial displacement of the joint center O of the sliding type constant velocity universal joint 1 during normal vehicle running is defined as the sliding range center C. Based on the sliding range center C, the area that is always used during normal vehicle running is included in the "sliding range center C±10 mm", and in this area, the PCD clearance Δ of the track grooves 7 and 9 and the PCD (ToPCD) of the track groove 7 are specified. In this specification and claims, the sliding range center in the joint axial direction of the track groove of the outer joint member has the above meaning.

[0040] The state of the PCD of the track grooves 7, 9 in the central range W of Fig. 4 and the method of measuring the PCD difference will be specifically described with reference to Fig. 6 to Fig. 8. Fig. 6 is a cross-sectional view illustrating the variation in PCD of the track grooves of the sliding type constant velocity universal joint of this embodiment, Fig. 7 is a schematic diagram of a measuring machine that measures the PCD difference of the track grooves of the outer joint member, and Fig. 8 is a schematic diagram of a measuring machine that measures the PCD difference of the track grooves of the inner joint member.

[0041] A method for measuring the PCD difference of the track grooves 7 of the outer joint member 2 in the central range W will be described with reference to Fig. 7. As shown in Fig. 7, a measuring machine 20 mainly comprises measuring balls 21 and a micrometer 23 provided on a pair of arms 22. The two measuring balls 21 are brought into contact with the track grooves 7 of the outer joint member 2 to measure the PCD. All of ToPCD(1) to ToPCD(4) in Fig. 6 are measured, and the PCD difference (ToPCD difference) is measured from the difference between the maximum and minimum values ​​of the micrometer 23.

[0042] A method for measuring the PCD difference of the track grooves 9 of the inner joint member 3 will be described with reference to Fig. 8. As shown in Fig. 8, a measuring machine 25 mainly comprises measuring balls 26 and a micrometer 28 provided on a pair of arms 27. The two measuring balls 26 are brought into contact with the track grooves 9 of the inner joint member 3 to measure the PCD. All of TiPCD(1) to TiPCD(4) in Fig. 6 are measured, and the PCD difference (TiPCD difference) is measured from the difference between the maximum and minimum values ​​of the micrometer 28.

[0043] As shown in Fig. 6, in the sliding type constant velocity universal joint 1 of this embodiment incorporating eight torque transmission balls 4, four PCDs are formed for each of the track grooves 7, 9 on the joint diameter. For the track grooves 7 of the outer joint member 2, the PCD at the phase angle ψ = 0° is ToPCD(1), the PCD at the phase angle ψ = 45° is ToPCD(2), the PCD at the phase angle ψ = 90° is ToPCD(3), and the PCD at the phase angle ψ = 135° is ToPCD(4). For the track grooves 9 of the inner joint member 2, the PCD at the phase angle ψ = 0° is TiPCD(1), the PCD at the phase angle ψ = 45° is TiPCD(2), the PCD at the phase angle ψ = 90° is TiPCD(3), and the PCD at the phase angle ψ = 135° is TiPCD(4).

[0044] As described above, the ToPCD(1) to ToPCD(4) of the track grooves 7 of the outer joint member 2 and the TiPCD(1) to TiPCD(4) of the track grooves 9 of the inner joint member 3 vary due to forging accuracy and deformation during heat treatment. However, in FIG. 6, the variations of ToPCD(1) to ToPCD(4) and TiPCD(1) to TiPCD(4) are not shown. Here, the difference between the maximum and minimum values ​​of the PCDs (ToPCD) of all the track grooves 7 of ToPCD(1) to ToPCD(4) is defined as the PCD difference between the track grooves 7 of the outer joint member 2. In this specification and claims, the PCD difference between the track grooves of the outer joint member has the above meaning. In addition, the difference between the maximum and minimum values ​​of TiPCD(1) to TiPCD(4) is defined as the PCD difference between the track grooves 9 of the inner joint member 3. As a result, the diameter D of the ball 4 BALLSince is a reference diameter (constant dimension), there is variation in the PCD clearance Δ. This embodiment was arrived at by focusing on such technical problems.

[0045] The cup portion 2a of the outer joint member 2 that houses the inner assembly I is cylindrical and has a relatively large diameter, so the PCD difference of the track grooves 7 formed on the inner surface of the cup portion 2a tends to be severe. However, due to recent developments in production technology, the PCD difference of the track grooves 7 of the outer joint member 2 has reached an upper limit of 0.150 mm. In contrast, the inner joint member 3 has a relatively small diameter, so the PCD difference of the track grooves 9 formed on its outer surface is suppressed to about 0.020 to 0.030 mm, and it was found that the PCD rank tolerance width of the inner joint member 3 in which the balls 4 are incorporated in the track grooves 9 can be suppressed to about 0.020 mm. As a result, it was found that the PCD rank tolerance width of the inner joint member 3 is extremely small compared to the value of the PCD difference of the track grooves 7 of the outer joint member 2, and is therefore suitable for handling selected combinations. These findings provided a clue to the solution.

[0046] The characteristic configuration (2) is that the minimum value of the PCD gap Δ of the track grooves in the central region is set to 0.010 mm to 0.100 mm.

[0047] By setting the lower limit of the minimum value of the PCD clearance Δ of the track groove to 0.010 mm or more, the ball 4 can slide smoothly in the track groove 7 without unnecessary interference, and the handling due to the sliding resistance when mounted on the vehicle is good. In addition, in the central range W of the sliding range that is most frequently used in the actual vehicle, PCD Since the clearance Δ is minimized, circumferential backlash can be suppressed, ensuring durability, strength, and NVH characteristics (low vibration characteristics).

[0048] In addition, by setting the upper limit of the minimum value of the PCD gap Δ to 0.100 mm or less, it is possible to bear the load in a balanced manner between the track grooves 7, 9 and the balls 4, thereby ensuring durability, strength, and NVH characteristics (low vibration characteristics).

[0049] Furthermore, by setting the minimum value of the PCD clearance Δ to 0.010 mm or more and 0.100 mm or less, a selective combination of inner joint members for the PCD of the track grooves of the outer joint member becomes practical. That is, a width of 0.090 mm is provided between the lower limit value 0.010 mm and the upper limit value 0.100 mm of the minimum value of the PCD clearance Δ, so that a selective combination of inner joint members 3 of an appropriate number of ranks having a PCD rank tolerance width of about 0.020 mm with balls 4 incorporated in the track grooves 9 becomes practical.

[0050] Specifically, a method for selecting and combining inner joint members 3 having balls 4 incorporated in track grooves 9 with respect to the PCD of the track grooves 7 of the outer joint member 2 will be described. Prior to the selecting and combining operation, the minimum value of PCD in the central range W of the track grooves 7 of the outer joint member 2 and the maximum value of PCD of the track grooves 9 of the inner joint member 3 are measured. As an example of the flow of the selecting and combining operation, a plurality of measured inner joint members 3 are stored, and the minimum value of PCD in the central range W of the track grooves 7 is collated with the measured data of the outer joint member 2, to select and combine inner joint members 3 that satisfy the range of the minimum value of the PCD clearance Δ of the track grooves in the central range (0.010 mm to 0.100 mm).

[0051] A method for measuring the minimum value of PCD of the track grooves will be described with reference to Figs. 9 to 11. Fig. 9(a) is a schematic diagram of a measuring machine for measuring the minimum value of PCD in a central region W of the track grooves of an outer joint member, and Fig. 9(b) is a principle diagram for measuring the minimum value of PCD of the track grooves of an outer joint member. Fig. 10(a) is a plan view of a measuring machine for measuring the maximum value of PCD of the track grooves of an inner joint member, and Fig. 10(b) is a front view with a partial vertical section of the measuring machine for measuring the maximum value of PCD of the track grooves of an inner joint member. Fig. 11 is a principle diagram for measuring the maximum value of PCD of the track grooves of an inner joint member.

[0052] As shown in FIG. 9(a), a measuring device 30 for measuring the minimum value of the PCD of the track groove 7 of the outer joint member 2 mainly comprises a base 31, a table 32, a measuring ball 33, a ball holding portion 34, a tapered shaft member 35, an operating lever 36, and a micrometer 37. The ball holding portion 34 is fixed on the table 32, and holds the measuring ball 33 in a pocket 34a so that the measuring ball 33 can be moved in the radial and circumferential directions. The tapered shaft member 35 has a conical outer circumferential surface 35a, and is disposed radially inside the inscribed circle of the measuring ball 33 held in the ball holding portion 34. The tapered shaft member 35 is configured to be movable in the vertical direction (axial direction of the outer joint member 2) by the operating lever 36, and the circumscribed circle of the measuring ball 33 expands and contracts in the radial direction due to the vertical movement of the tapered shaft member 35. The vertical movement of the tapered shaft member 35 is configured to be linked to the micrometer 37.

[0053] A method for measuring the minimum value of the PCD in the central range W of the track groove 7 of the outer joint member 2 will be described. With the circumscribing circle of the measuring balls 33 of the measuring device 30 contracting in the radial direction, the track grooves 7 of the outer joint member 2 are covered with the measuring balls 33 in phase with each other, and the outer joint member 2 is placed on the table 32. As shown in FIG. 9(a), the tapered shaft member 35 is moved downward to bring the conical outer circumferential surface 35a into contact with the measuring ball 33, and the measuring ball 33 is pressed against the track groove 7. Since the PCD of the track groove 7 varies, as shown in FIG. 9(b) showing the measurement principle, the minimum value (ToPCDmin) of the PCD (ToPCD) of the track groove 7 of the outer joint member 2 is measured by bringing three balls 33, which are shown as scattered dots, out of the eight measuring balls 33 into contact with the conical outer circumferential surface 35a of the tapered shaft member 35.

[0054] As shown in FIG. 10(a) and FIG. 10(b), a measuring device 40 for measuring the maximum value of the PCD of the track groove 9 of the inner joint member 3 mainly comprises a base 41, a table 42, a measuring ball 43, a ball holding part 44, a tapered hole member 45, an operating lever 46, and a micrometer 47. The ball holding part 44 is fixed on the base 41, and holds the measuring ball 43 in a pocket 44a so that the measuring ball 43 can be moved in the radial and circumferential directions. The tapered hole member 45 has a conical inner peripheral surface 45a, and is disposed radially outward of the circumscribing circle of the measuring ball 43 held in the ball holding part 44. The tapered hole member 45 is configured to be movable in the vertical direction (axial direction of the inner joint member 3) by the operating lever 46, and the inscribing circle of the measuring ball 43 expands and contracts in the radial direction due to the vertical movement of the tapered hole member 45. The vertical movement of the tapered hole member 45 is configured to be linked to the micrometer 47.

[0055] A method for measuring the maximum value of the PCD of the track groove 9 of the inner joint member 2 will be described. With the inscribed circle of the measuring ball 43 of the measuring device 40 expanded in the radial direction, the track groove 9 of the inner joint member 3 is covered with the measuring ball 43 in phase with each other, and the inner joint member 3 is placed on the table 42. As shown in FIG. 10(a), the tapered hole member 45 is moved downward to bring the conical inner peripheral surface 45a into contact with the measuring ball 43, and the measuring ball 43 is pressed against the track groove 9. Since the PCD of the track groove 9 varies, as shown in FIG. 11, the measurement principle is shown, and the maximum value (TiPCDmax) of the PCD (TiPCD) of the track groove 9 of the inner joint member 3 is measured by bringing three of the eight measuring balls 43 into contact with the conical inner peripheral surface 45a of the tapered hole member 45.

[0056] The difference between the minimum value of the PCD of the track groove 7 of the outer joint member 2 (ToPCDmin) and the maximum value of the PCD of the track groove 9 of the inner joint member 3 (TiPCDmax) and their mutual difference (TiPCD mutual difference) is the PCD clearance. ΔThat is, without considering the phase alignment of the PCD minimum phase of the track groove 7 of the outer joint member 2 and the PCD maximum phase of the track groove 9 of the inner joint member 3, the minimum value Δmin of the PCD gap Δ in the central range W of the track groove 7 of the outer joint member 2 is expressed by the following equation. Δmin=ToPCDmin-TiPCDmax-TiPCD mutual difference The minimum value of the PCD clearance Δ in the central region W of the track groove of the outer joint member in this specification and claims has the above meaning.

[0057] The outer joint member 2 and the inner joint member 3 are selected and combined such that the minimum value Δmin of the PCD clearance Δ measured by the above method satisfies the minimum value of the PCD clearance Δ in the central range W, that is, 0.010 mm to 0.100 mm.

[0058] On the other hand, as a result of various studies and verifications on the maximum value of the PCD clearance Δ in the central range W of the track groove of the outer joint member, it was found that the upper limit of the above-mentioned maximum value of the PCD clearance Δ is 0.250 mm. It was found that if the maximum value of the PCD clearance Δ exceeds 0.250 mm, rattling noise occurs under torque load, and NVH characteristics (vibration characteristics) cannot be ensured. Thus, the range of 0.010 mm to 0.100 mm, which is the minimum value of the PCD clearance Δ in the central range W, was led to a means of ensuring that the maximum value of the PCD clearance Δ is within the upper limit of 0.250 mm, in addition to the practical conditions of the selected combination described above.

[0059] Specifically, the PCD clearance in the central range W Δ The range of 0.010 mm to 0.100 mm, which is the minimum value of Δmax, is in a relationship that substantially changes the upper limit value 0.250 mm of the maximum value Δmax of the PCD clearance Δ in the central range W. ΔThe upper limit value of the PCD difference between the track grooves 7 of the outer joint member 2 in the central range W must be 0.150 mm, which is obtained by subtracting the upper limit value 0.100 mm of 0.010 mm to 0.100 mm, which is the minimum value Δmin of Δ, from the upper limit value 0.250 mm of the maximum value Δmax of the PCD clearance Δ, and this leads to the following characteristic configuration (3).

[0060] The characteristic configuration (3) is that the PCD difference between the track grooves of the outer joint member in the central region is set to 0.150 mm or less.

[0061] In addition to the measurement work of measuring the minimum value of PCD in the central range W of the track groove 7 of the outer joint member 2 described above, all of ToPCD(1) to ToPCD(4) in Fig. 6 are measured by a measuring machine 20 shown in Fig. 7. From the difference between the maximum and minimum values ​​among ToPCD(1) to ToPCD(4), it is confirmed that the mutual PCD difference of the track groove 7 of the outer joint member 2 in the central range W is 0.150 mm or less, and this outer joint member 2 is sent to the selection and assembly process.

[0062] As described above, the PCD difference between the track grooves of the outer joint member in the central region W is set to 0.150 mm or less. PCD Under the condition that the minimum value of the gap Δ is Δmin, 0.010mm to 0.100mm, PCD The upper limit of the maximum value of the gap Δmax can be secured at 0.250 mm. PCD The upper limit of the maximum value Δmax of the gap Δ is set to 0.250 mm, which makes it possible to suppress the occurrence of rattling noises under torque load.

[0063] In summary, the above-mentioned characteristic configurations (1) to (3) work together to enable practical selection and combination of the inner joint member with respect to the PCD dimension of the track groove of the outer joint member based on the practical precision level of forging and heat treatment, and also provide good handleability due to sliding resistance when mounted on a vehicle. In addition, it is possible to suppress circumferential backlash in the central range W of the slide range which is most frequently used in an actual vehicle, and therefore it is possible to ensure durability, strength, and NVH characteristics (low vibration characteristics).

[0064] A sliding type constant velocity universal joint according to a second embodiment of the present invention will be described with reference to Figs. 12 and 13. The double offset type sliding type constant velocity universal joint of this embodiment has six torque transmission balls, which is different from the number of torque transmission balls in the sliding type constant velocity universal joint of the first embodiment. Since the other configurations are the same as those of the first embodiment, the same reference numerals are used for parts having similar functions, and only the main points will be described. Fig. 12 is a vertical cross-sectional view of the sliding type constant velocity universal joint according to this embodiment, taken along line BN-B' in Fig. 13. Fig. 13 is a horizontal cross-sectional view of the sliding type constant velocity universal joint according to this embodiment, taken along line AA in Fig. 12.

[0065] 12 and 13, in a double offset sliding type constant velocity universal joint 1 according to this embodiment, six track grooves 7 are formed on a cylindrical inner peripheral surface 6 of an outer joint member 2 at equal intervals in the circumferential direction and linearly along the axial direction. Track grooves 9 opposing the track grooves 7 of the outer joint member 2 are formed on a spherical outer peripheral surface 8 of the inner joint member 3 at equal intervals in the circumferential direction and linearly along the axial direction. Six torque transmission balls (hereinafter also simply referred to as balls) 4 are incorporated between each of the track grooves 7 of the outer joint member 2 and the track grooves 9 of the inner joint member 3.

[0066] The cage 5 has a spherical outer peripheral surface 11 and a spherical inner peripheral surface 12. The spherical outer peripheral surface 11 is fitted and guided in contact with the cylindrical inner peripheral surface 6 of the outer joint member 2, and the spherical inner peripheral surface 12 is fitted and guided in contact with the spherical outer peripheral surface 8 of the inner joint member 3. The spherical outer peripheral surface 11 of the cage 5 is formed with a radius of curvature Rc1 with a center of curvature Oc1, and the spherical inner peripheral surface 12 is formed with a radius of curvature Rc2 with a center of curvature Oc2. The spherical outer peripheral surface 8 of the inner joint member 3 is formed with a radius of curvature Ri with a center of curvature Oi2, and the center of curvature Oi2 coincides with the center of curvature Oc2. The centers of curvature Oc1 and Oc2 are located on the axis N and are offset equidistantly in the axial opposite direction from the joint center O. As a result, when the joint has an operating angle, the ball 4 is always guided on a plane that bisects the angle formed by the axes of the outer joint part 2 and the inner joint part 3, and rotation is transmitted between the two shafts at a constant speed.

[0067] The double offset type sliding type constant velocity universal joint 1 of this embodiment also has the following characteristic configurations (1) to (3), similar to the double offset type sliding type constant velocity universal joint 1 of the first embodiment described above. (1) The central range is set to a range from 10 mm toward the rear side to 10 mm toward the opening side with respect to the center of the sliding range in the axial direction of the track groove of the outer joint member, and a portion where the PCD of the track groove of the outer joint member is smallest is formed in this central range. (2) PCD clearance of track grooves in the central area Δ The minimum value is set at 0.010mm to 0.100mm. (3) The PCD difference of the track grooves of the outer joint members in the central region is 0.150 mm or less.

[0068] The combination of the above characteristic configurations (1) to (3) enables practical selection and combination of the inner joint member with respect to the PCD dimension of the track groove of the outer joint member based on the practical precision level of forging and heat treatment, provides good handleability due to sliding resistance when mounted on a vehicle, and can suppress circumferential rattle in the central range W of the slide range which is most frequently used in an actual vehicle, thereby ensuring durability, strength, and NVH characteristics (low vibration characteristics). The contents of the above characteristic configurations (1) to (3) described for the double offset type sliding type constant velocity universal joint 1 of the first embodiment are also applicable to the double offset type sliding type constant velocity universal joint 1 of this embodiment, and therefore apply mutatis mutandis.

[0069] A first modified example of the inner assembly of the sliding type constant velocity universal joint according to the second embodiment of the present invention will be described with reference to Fig. 14. The inner assembly of this modified example differs from the second embodiment in that a positive axial clearance is provided between the cage pocket and the ball. The other configurations are the same as those of the second embodiment, so parts having similar functions are given the same reference numerals and only the main points will be described.

[0070] 14 is a vertical sectional view of a first modified example of the inner assembly of the sliding type constant velocity universal joint according to the second embodiment. As shown in FIG. 14, the inner assembly I includes an inner joint member 3, a cage 5, a ball A positive axial clearance δ2 is formed between the wall surface 5c of the pocket 5a of the cage 5, which faces the torque transmission ball 4 in the joint axial direction, and the torque transmission ball 4. The diameter of the ball 4 is D BALL If the width between the wall surfaces 5c of the pocket 5a of the cage 5 facing each other in the joint axial direction is Lw, the axial clearance δ2 is δ2=Lw-D BALL This is about +0.001 mm to +0.050 mm. This allows the balls 4 to roll smoothly within the pockets 5a, and reduces the sliding resistance.

[0071] A second modified example of the inner assembly of the sliding type constant velocity universal joint according to the second embodiment of the present invention will be described with reference to Figures 15 and 16. The inner assembly of this modified example differs from the second embodiment in that a positive axial clearance is provided between the cage pocket and the ball, and that an axial clearance is provided that allows relative axial movement between the inner joint member and the cage. The other configurations are the same as those of the second embodiment, so the same reference numerals are used for parts having similar functions, and only the main points will be described.

[0072] Fig. 15 is a vertical cross-sectional view of a second modified example of the inner assembly of the sliding type constant velocity universal joint according to the second embodiment, and Fig. 16 is an enlarged view of part E in Fig. 15. As shown in Fig. 15, the inner assembly I is composed of an inner joint member 3, a cage 5, and balls 4, and the joint of the pocket 5a of the cage 5 is A positive axial clearance δ2 is formed between the wall surface 5c and the torque transmission ball 4, which face each other in the axial direction. The spherical outer peripheral surface 11 of the cage 5 is formed with a radius of curvature Rc1 with a center of curvature Oc1, and the spherical inner peripheral surface 12 is formed with a radius of curvature Rc2 with a center of curvature Oc2. The spherical outer peripheral surface 8 of the inner joint member 3 is formed with a radius of curvature Ri with a center of curvature Oi2. The centers of curvature Oc1 and Oi2 are located on the axis N and are offset from the joint center O by an equal distance F in the axial direction. The center of curvature Oc2 of the spherical inner peripheral surface 12 of the cage 5 is offset from the axis N in the radial direction with respect to the center of curvature Oi2 so that Rc2>Ri, and is offset from the joint center O by a distance F in the axial direction.

[0073] As shown in FIG. 16, a spherical clearance δ3 is formed at the axial center of the spherical outer peripheral surface 8 of the inner joint member 3, which allows contact guiding with the spherical inner peripheral surface 12 of the cage 5, and an axial clearance δ4 is formed on both sides of the center, which allows relative axial movement between the inner joint member 3 and the cage 5. The spherical clearance δ3 is about 0.050 mm at the median. The axial clearance δ4 is about 1 mm. The axial movement of the inner joint member 3 relative to the outer joint member 2 is about 2 mm, which is twice the axial clearance δ4 of about 1 mm, and vibration is absorbed by this range of axial movement. In other words, the sliding resistance can be reduced under commonly used vibration conditions. The spherical clearance δ3 and the axial clearance δ4 are each exaggerated in the illustration.

[0074] The axial clearance δ4 between the cage 5 and the inner joint member 3 and the positive axial clearance δ2 between the ball 4 and the wall surface 5c facing the joint axial direction of the pocket 5a of the cage 5 combine to reduce the sliding resistance.

[0075] A third modified example of the inner assembly of the sliding type constant velocity universal joint according to the second embodiment of the present invention will be described with reference to Fig. 17. The inner assembly of this modified example differs from the second modified example in the shape of the spherical inner peripheral surface of the cage. The other configurations are the same as those of the second embodiment and the second modified example, so parts having similar functions are given the same reference numerals and only the main points will be described.

[0076] Fig. 17 is a longitudinal sectional view of a third modified example of the inner assembly of the sliding type constant velocity universal joint according to the second embodiment. As shown in Fig. 17, the spherical inner peripheral surface 12 of the cage 5 is composed of a spherical portion 12a having a radius of curvature Rc2 with a center of curvature Oc2, a spherical portion 12b having a radius of curvature Rc2 with a center of curvature Oc3, and a cylindrical portion 12c connecting the spherical portion 12a and the spherical portion 12b with a tangent line. The centers of curvature Oc2 and Oc3 are located on the axis N, and the axial center points of the centers of curvature Oc2 and Oc3 are offset by F with respect to the joint center O. The spherical outer peripheral surface 8 of the inner joint member 3 is formed with a radius of curvature Ri with a center of curvature Oi2. In the arrangement state of FIG. 17, the midpoint in the axial direction between the centers of curvature Oc2 and Oc3 of the spherical inner circumferential surface 12 of the cage 5 coincides with the center of curvature Oi2 of the spherical outer circumferential surface 8 of the inner joint member 3.

[0077] A spherical clearance δ3 is formed at the axial center of the spherical outer peripheral surface 8 of the inner joint member 3, which allows contact guiding with the cylindrical portion 12c of the cage 5, and an axial clearance δ4 is formed on both sides of the center, which allows relative axial movement between the inner joint member 3 and the cage 5. The length of the cylindrical portion 12c is about 1 mm, and the axial clearance δ4 corresponds to the length of the cylindrical portion 12c. The amount of axial movement of the inner joint member 3 relative to the outer joint member 2 is about 2 mm, which is twice the length of the cylindrical portion 12c (about 1 mm), and vibration is absorbed within this range of axial movement. In other words, the sliding resistance can be reduced under commonly used vibration conditions.

[0078] In this modification, the spherical inner peripheral surface 12 of the cage 5 is composed of a spherical portion 12a having a radius of curvature Rc2 with a center of curvature Oc2, a spherical portion 12b having a radius of curvature Rc2 with a center of curvature Oc3, and a cylindrical portion 12c connecting the spherical portion 12a and the spherical portion 12b with a tangent line. Since the radius of curvature Rc2 and the radius of curvature Ri are substantially the same, the contact guide between the spherical inner peripheral surface 12 of the cage 5 and the spherical outer peripheral surface 8 of the inner joint member 3 is smooth and stable. As in the first and second modifications, a positive axial clearance δ2 is formed between the wall surface 5c of the pocket 5a of the cage 5 facing the joint axial direction and the torque transmission balls 4.

[0079] The double offset type sliding type constant velocity universal joint 1 consisting of the inner assemblies of the first to third modified examples also has the following characteristic configurations (1) to (3) as with the double offset type sliding type constant velocity universal joint 1 according to the first embodiment described above. (1) The central range is set to a range from 10 mm toward the rear side to 10 mm toward the opening side with respect to the center of the sliding range in the axial direction of the track groove of the outer joint member, and a portion where the PCD of the track groove of the outer joint member is smallest is formed in this central range. (2) PCD clearance of track grooves in the central area Δ The minimum value is set at 0.010mm to 0.100mm. (3) The PCD difference of the track grooves of the outer joint members in the central region is 0.150 mm or less.

[0080] The combination of the above characteristic configurations (1) to (3) enables practical selection and combination of the inner joint member with respect to the PCD dimension of the track groove of the outer joint member based on the practical precision level of forging and heat treatment, provides good handleability due to sliding resistance when mounted on a vehicle, and can suppress circumferential rattle in the central range W of the slide range which is most frequently used in an actual vehicle, thereby ensuring durability, strength, and NVH characteristics (low vibration characteristics). The contents of the above characteristic configurations (1) to (3) described for the double offset type sliding type constant velocity universal joint 1 of the first embodiment are also applicable to the double offset type sliding type constant velocity universal joint 1 of this embodiment, and therefore apply mutatis mutandis.

[0081] The first to third modified examples of the inner assembly I of the sliding type constant velocity universal joint according to the second embodiment can be applied to the double offset type sliding type constant velocity universal joint 1 of the first embodiment by changing the number of torque transmission balls 4 from six to eight.

[0082] The present invention is not limited to the above-described embodiments and modified examples, and can of course be embodied in various other forms without departing from the spirit of the present invention. The scope of the present invention is indicated by the claims, and further includes the equivalent meanings set forth in the claims, and all modifications within the scope of the claims. [Explanation of symbols]

[0083] 1. Sliding constant velocity universal joint 2 Outer joint member 3 Inner joint member 4 Torque transmission ball 5 Cage 5a Pocket 6 Cylindrical inner surface 7 Track groove 7a The part where the PCD of the track groove is the smallest 8 Spherical outer surface 9 Track groove 11 Spherical outer surface 12 Spherical inner surface C Center of slide range D BALL Ball Diameter F Offset amount O Joint center O1 center of curvature O2 center of curvature PCD Pitch Circle Diameter W Mid Range Δ PCD clearance δ2 Positive axial clearance between ball and pocket δ3 Spherical gap δ4 Axial clearance between cage and inner joint member

Claims

1. A sliding type constant velocity universal joint comprising: an outer joint member having a cylindrical inner circumferential surface on which a plurality of linear track grooves are formed along the axial direction; an inner joint member having a spherical outer circumferential surface on which a plurality of linear track grooves facing the plurality of linear track grooves of the outer joint member are formed along the axial direction; a plurality of torque transmission balls assembled between the plurality of linear track grooves of the outer joint member and the plurality of linear track grooves of the inner joint member; and a cage which houses the torque transmission balls in pockets and has a spherical outer circumferential surface and a spherical inner circumferential surface which are contact-guided by the cylindrical inner circumferential surface of the outer joint member and the spherical outer circumferential surface of the inner joint member, wherein the center of curvature of the spherical outer circumferential surface and the center of curvature of the spherical inner circumferential surface of the cage are offset to opposite sides in the axial direction with respect to a joint center, a central range is defined as a range from 10 mm on the back side to 10 mm on the opening side with respect to a central portion of a sliding range in a joint axial direction of the track groove of the outer joint member, and a portion where a PCD of the track groove of the outer joint member is minimum is formed in the central range, The minimum value of the PCD gap of the track groove in the central region is 0.010 mm to 0.100 mm, A sliding type constant velocity universal joint, characterized in that a PCD difference between the track grooves of said outer joint member in said central region is 0.150 mm or less.

2. 2. The sliding type constant velocity universal joint according to claim 1, wherein a difference in PCD between the track grooves in the region excluding the central region is set to 0.170 mm or less.

3. 3. A sliding type constant velocity universal joint according to claim 1, wherein the track grooves have a surface formed by plastic working.

4. 3. The sliding type constant velocity universal joint according to claim 1, wherein the torque transmission balls are in angular contact with the track grooves of the outer joint member and the track grooves of the inner joint member, respectively.

5. 3. The sliding type constant velocity universal joint according to claim 1, wherein the number of the torque transmission balls is six to eight.

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