Sliding constant velocity universal joint

Abstract

To provide a DOJ-type slide-type constant velocity universal joint which is improved in workability, and also improved in low heat generation and durability.SOLUTION: In a slide-type constant velocity universal joint 1 in which a curvature center O2 of a spherical external peripheral face 11 of a cage 5 and a curvature center O1 of a spherical internal peripheral face 12 are offset to an opposite side in an axial direction with respect to a joint center O, a curvature center O1 of a spherical internal peripheral face 12 of the cage 5 and a curvature center O1 of a spherical external peripheral face 8 of an inside joint member 3 are made to coincide with each other, also, a curvature radius RCI of the spherical internal peripheral face 12 of the cage 5 and a curvature radius RI of the spherical external peripheral face 8 of the inside joint member 3 are made to substantially coincide with each other, and a spherical clearance δ which allows a contact guide is formed between the spherical internal peripheral face 12 of the cage 5 and the spherical external peripheral face 8 of the inside joint member 3. When the slide-type constant velocity universal joint takes an operation angle θ, the spherical internal peripheral face 12 of the cage 5 and the spherical external peripheral face 8 of the inside joint member 3 surface-contact with each other at an end part side of the spherical internal peripheral face 12 of the cage 5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a sliding constant velocity universal joint used in power transmission systems for automobiles and various industrial machines, such as the drive shafts and propeller shafts of automobiles. [Background technology]

[0002] Constant velocity universal joints applied to drive shafts can be broadly classified into fixed universal joints that allow only angular displacement between the two shafts, and sliding universal joints that allow both angular and axial displacement. Various types are selected depending on the operating conditions and applications. In automobile drive shafts, a fixed universal joint is usually used on the drive wheel side (also called the outboard side), and a sliding universal joint is used on the differential side (also called the inboard side), with these two universal joints connected by an intermediate shaft.

[0003] Typical sliding constant velocity universal joints include double offset universal joints (DOJ) and tripod universal joints (TJ). DOJ-type sliding constant velocity universal joints are widely used due to their low manufacturing cost and minimal rotational play within the joint. DOJ-type sliding constant velocity universal joints are known to have six or eight balls. Patent document 1 describes a compact DOJ with eight balls, while patent document 2 describes a DOJ with a higher operating angle, greater lightness, and a more compact design, capable of achieving a maximum operating angle of 30° or more. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-73129 [Patent Document 2] Japanese Patent Publication No. 2007-85488 [Overview of the project] [Problems that the invention aims to solve]

[0005] Incidentally, DOJ-type sliding constant velocity universal joints have a weakness in that they are slightly less durable than TJ-type sliding constant velocity universal joints. This is because, while TJ-type sliding constant velocity universal joints primarily rely on rolling contact for their components, DOJ-type sliding constant velocity universal joints primarily rely on sliding contact for their components, resulting in reduced durability due to heat generation.

[0006] In view of the above problems, the present invention aims to provide a DOJ-type sliding constant velocity universal joint that improves operability, reduces heat generation, and enhances durability.

[0007] Here, the findings of the development process leading to the present invention will be explained based on Figures 9 to 12. Figure 9 is a longitudinal cross-sectional view showing a conventional DOJ type sliding constant velocity universal joint that was the focus of the development process. This sliding constant velocity universal joint 101 mainly consists of an outer joint member 102, an inner joint member 103, a torque transmission ball 104, and a cage 105. Six track grooves 107 are formed on the cylindrical inner circumferential surface 106 of the outer joint member 102 at equal intervals in the circumferential direction and linearly along the axial direction, and track grooves 109 are formed on the spherical outer circumferential surface 108 of the inner joint member 103 at equal intervals in the circumferential direction and linearly along the axial direction, facing the track grooves 107 of the outer joint member 102. Multiple torque transmission balls (hereinafter also simply referred to as balls) 104 are incorporated between the track groove 107 of the outer joint member 102 and the track groove 109 of the inner joint member 103, and the balls 104 are housed in the pockets 105a of the cage 105.

[0008] The cage 105 has a spherical outer surface 111 and a spherical inner surface 112. The spherical outer surface 111 fits into contact with and is guided by the cylindrical inner surface 106 of the outer joint member 102, and the spherical inner surface 112 fits into contact with and is guided by the spherical outer surface 108 of the inner joint member 103. The spherical outer surface 108 of the inner joint member 103 and the spherical inner surface 112 of the cage 105 have their centers of curvature at O1, which is offset by F in the axial direction from the joint center O. The radius of curvature RCI of the spherical inner surface 112 and the radius of curvature RI of the spherical outer surface 108 are set to be approximately the same, and the spherical gap between the spherical inner surface 112 and the spherical outer surface 108 is set to approximately 0.010 to 0.200 mm. The inner diameter dimension DCI of the spherical inner surface 112 is twice the radius of curvature RCI, and the outer diameter dimension DI of the spherical outer surface 108 is curved It is twice the radius ratio RI. The spherical gap δ between the spherical inner surface 112 and the spherical outer surface 108 is δ = DCI - DI. The spherical outer surface 111 of the cage 105 is formed with a radius of curvature RCO, with its center of curvature at O2, which is offset by F from O1 in the axial direction relative to the joint center O. The pocket 105a of the ball 104 and cage 105 is set by clearance or overlap depending on the vehicle characteristics. In the case of clearance setting, the pocket width Lw shown in Figure 9 is equal to the ball diameter D BALL Formed to be slightly larger (Lw>D BALL ), when setting the closing allowance, the pocket width Lw is equal to the ball diameter D BALL It is formed to be slightly smaller (Lw≦D BALL ).

[0009] Figure 10 shows a longitudinal cross-section of the internal state of a DOJ type sliding constant velocity joint 101 when it takes a normal angle (θ = 5°) with respect to the axis No of the outer joint member 102 (which is also the joint axis N when the operating angle is 0°). The normal angle of the joint refers to the operating angle that occurs in the front drive shaft when the steering is in a straight-ahead position in an automobile with one passenger on a horizontal and flat road surface. The normal angle is usually selected and determined according to the design conditions for each vehicle type within the range of 2° to 15°. As shown in Figure 10, when the DOJ takes an operating angle, the ball 104 receives a force in the direction of the arrow due to the wedge angle formed by the track groove 107 of the outer joint member 102 and the track groove 109 of the inner joint member 103. Therefore, the inner joint member 103 and the cage 105 will come into contact at parts C and D shown in Figure 10.

[0010] As shown in Figure 11, which is an enlarged view of part C, the axial relative distance due to the spherical clearance between the inner joint member 103 and the cage 105 is smaller at the end position than at the center position of the spherical inner peripheral surface 112 of the cage 105 (L1 < L2). Since the axial clearance due to the spherical clearance between the inner joint member 103 and the cage 105 is in the relationship of L1 < L2, as shown in Figure 12, a line contact L state occurs at the end of the spherical inner peripheral surface 112 of the cage 105, and the contact at the end becomes stronger. As a result, it has been found that wear and heat generation increase, affecting durability.

[0011] Based on the findings in the above development process, the present invention was conceived by making the spherical inner peripheral surface of the cage and the spherical outer peripheral surface of the inner joint member come into surface contact on the end side of the spherical inner peripheral surface of the cage.

Means for Solving the Problem

[0012] As a technical means to achieve the aforementioned objective, the present invention provides: 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 opposite to the plurality of linear track grooves of the outer joint member; 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 mechanism for housing the torque transmission balls in a pocket, and the cylindrical inner circumferential surface of the outer joint member and the spherical outer circumferential surface of the inner joint member In a sliding constant velocity universal joint comprising a cage having a spherical outer surface and a spherical inner surface that are guided in contact with the joint, the center of curvature of the spherical outer surface of the cage and the center of curvature of the spherical inner surface of the cage are offset on opposite sides in the axial direction with respect to the joint center, wherein the center of curvature of the spherical inner surface of the cage and the center of curvature of the spherical outer surface of the inner joint member are the same, and the radius of curvature of the spherical inner surface of the cage and the radius of curvature of the spherical outer surface of the inner joint member are substantially the same, thereby forming a spherical gap that enables contact guidance between the spherical inner surface of the cage and the spherical outer surface of the inner joint member. The spherical outer surface of the inner joint member is given a small difference between the outer diameter dimension (DI) at the axial center and the diagonal outer diameter dimensions (DI') at both axial ends, such that DI > DI', and the spherical inner surface of the cage is given a small difference between the inner diameter dimension (DCI) at the axial center and the diagonal inner diameter dimensions (DCI') at both axial ends, such that DCI <DCI’とし、 When the sliding constant velocity universal joint takes an operating angle, the spherical inner surface of the cage and the spherical outer surface of the inner joint member are aligned at the end side of the spherical inner surface of the cage. The contact width was set to reduce the contact pressure. This configuration makes it possible to realize a DOJ-type sliding constant velocity universal joint that offers improved operability, reduced heat generation, and enhanced durability.

[0013] Specifically, the spherical outer surface of the inner joint member described above is made to have a small difference between the outer diameter dimension DI at the axial center and the diagonal outer diameter dimensions DI' at both axial ends, so that DI > DI', and the spherical inner surface of the cage described above is made to have a small difference between the inner diameter dimension DCI at the axial center and the diagonal inner diameter dimensions DCI' at both axial ends, so that DCI <DCI’と did. Since the above-mentioned minute difference between the outer diameter dimension of the spherical outer surface of the inner joint member and the inner diameter dimension of the cage can be suppressed, processing is easy, and the spherical inner surface of the cage and the spherical outer surface of the inner joint member make surface contact at the end side of the spherical inner surface of the cage.

[0014] Here, the outer diameter dimension DI at the axial center of the spherical outer surface of the inner joint member refers to the outer diameter dimension DI in the direction passing through the axial center of the inner joint member and perpendicular to the axis of the inner joint member. Furthermore, the diagonal outer diameter dimension DI' at both axial ends on the spherical outer surface of the inner joint member refers to the outer diameter dimension DI' that diagonally crosses both axial ends on the spherical outer surface of the inner joint member. In addition, the inner diameter dimension DCI at the axial center on the spherical inner surface of the cage refers to the inner diameter dimension DCI in a direction passing through the axial center of the spherical inner surface of the cage and perpendicular to the axis of the cage. Furthermore, the diagonal inner diameter dimension DCI' at both axial ends of the cage refers to the inner diameter dimension DCI' that diagonally crosses both axial ends on the spherical inner surface of the cage. The position where the diagonal crossing of both axial ends on the spherical inner surface of the cage is within a margin (for example, about 1-2 mm) from the chamfer at the end. The position where the diagonal crossing of both axial ends on the spherical outer surface of the inner joint member is axially equivalent to the position where the diagonal crossing of both axial ends on the spherical inner surface of the cage is axially equivalent to the position described above. In this specification and the claims, the spherical outer surface of the inner joint member is referred to as the outer diameter dimension (DI) at the axial center and the diagonal outer diameter dimensions DI' at both axial ends, and the spherical inner surface of the cage is referred to as the inner diameter dimension DCI at the axial center and the diagonal inner diameter dimensions DCI' at both axial ends, respectively, as defined above.

[0015] By setting the difference between DI and DI' to 0 < (DI - DI') ≤ 0.020 mm, and the difference between DCI and DCI' to 0 < (DCI' - DCI) ≤ 0.020 mm, the minute differences in the outer diameter of the spherical outer surface of the inner joint member and the inner diameter of the cage can be kept within the above dimensional ranges, thus facilitating processing.

[0016] The second invention comprises an outer joint member having a plurality of linear track grooves formed along the axial direction on its cylindrical inner surface, an inner joint member having a plurality of linear track grooves formed along the axial direction on its spherical outer surface opposite to the plurality of linear track grooves of the outer joint member, 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 having a spherical outer surface and a spherical inner surface that house the torque transmission balls in pockets and are guided in contact with the cylindrical inner surface of the outer joint member and the spherical outer surface of the inner joint member, wherein the center of curvature of the spherical outer surface and the center of curvature of the spherical inner surface of the cage are offset on opposite sides in the axial direction with respect to the joint center, forming a sliding constant velocity universal joint. The DOJ type sliding constant velocity universal joint is characterized in that the center of curvature of the spherical inner surface of the cage and the center of curvature of the spherical outer surface of the inner joint member are the same, and the radius of curvature of the spherical inner surface of the cage and the radius of curvature of the spherical outer surface of the inner joint member are made approximately the same, thereby forming a spherical gap that enables contact guidance between the spherical inner surface of the cage and the spherical outer surface of the inner joint member. The spherical outer surface of the inner joint member is characterized in that a small difference is made between the outer diameter dimension (DI) at the axial center and the diagonal outer diameter dimensions (DI') at both ends in the axial direction, so that DI > DI', and when the sliding constant velocity universal joint takes an operating angle, the spherical inner surface of the cage and the spherical outer surface of the inner joint member make surface contact with a contact width that reduces the contact pressure at the end side of the spherical inner surface of the cage. With the above configuration, a DOJ type sliding constant velocity universal joint can be realized that improves operability, reduces heat generation, and improves durability.

[0017] By setting the difference between DI and DI' to 0 < (DI - DI') ≤ 0.040 mm, a minute difference within the above dimensional range is provided only on the spherical outer surface of the inner joint member and the spherical inner surface of the cage, making processing easier and simpler.

[0018] The third invention is a sliding constant velocity joint comprising an outer joint member having a plurality of linear track grooves formed along the axial direction on a cylindrical inner peripheral surface, an inner joint member having a plurality of linear track grooves formed along the axial direction on a spherical outer peripheral surface and opposing the plurality of linear track grooves of the outer joint member, 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 peripheral surface and a spherical inner peripheral surface that are in contact and guided on the cylindrical inner peripheral surface of the outer joint member and the spherical outer peripheral surface of the inner joint member. In the sliding constant velocity joint in which 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 to the opposite side in the axial direction with respect to the joint center, the center of curvature of the spherical inner peripheral surface of the cage is made the same as the center of curvature of the spherical outer peripheral surface of the inner joint member, and the radius of curvature of the spherical inner peripheral surface of the cage and the radius of curvature of the spherical outer peripheral surface of the inner joint member are made substantially the same to form a spherical clearance that enables contact and guidance between the spherical inner peripheral surface of the cage and the spherical outer peripheral surface of the inner joint member. A slight difference is provided between the inner diameter dimension (DCI) at the axial center portion and the diagonal inner diameter dimension (DCI') at both axial ends of the spherical inner peripheral surface of the cage, such that DCI < DCI'. When the sliding constant velocity joint takes an operating angle, the spherical inner peripheral surface of the cage and the spherical outer peripheral surface of the inner joint member are in surface contact with a contact width in which the contact surface pressure is reduced on the end side of the spherical inner peripheral surface of the cage. With the above configuration, it is possible to realize a DOJ type sliding constant velocity joint with improved operability, low heat generation, and improved durability.

[0019] By setting the difference between the above DCI and DCI' to 0 < (DCI' - DCI) ≤ 0.040 mm, a minute difference within the above dimensional range is provided only on the spherical inner peripheral surface of the cage among the spherical outer peripheral surface of the inner joint member and the spherical inner peripheral surface of the cage, so that processing is easy and can be simplified.

[0020] By setting the number of the above plurality of torque transmission balls to 5 to 8, a sliding constant velocity universal joint suitable for a power transmission system such as an automobile or various industrial machines can be configured.

Effect of the Invention

[0021] According to the present invention, it is possible to realize a DOJ type sliding constant velocity universal joint with improved operability, low heat generation, and improved durability.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

[0023] A sliding constant velocity universal joint according to the first embodiment of the present invention will be described with reference to Figures 1 to 6. Figure 1 is a longitudinal cross-sectional view of a sliding constant velocity universal joint according to the first embodiment of the present invention, and is a longitudinal cross-sectional view along the line BNB in ​​Figure 2. Figure 2 is a transverse cross-sectional view of a sliding constant velocity universal joint according to the first embodiment of the present invention, and is a transverse cross-sectional view along the line AA in Figure 1. Figure 3 is a longitudinal cross-sectional view showing the internal state of the joint when the sliding constant velocity universal joint of this embodiment is set to its normal operating angle. Figure 4 is a longitudinal cross-sectional view showing details of the inner joint member and cage of the sliding constant velocity universal joint of this embodiment. Figure 5 is a partial longitudinal cross-sectional view showing an enlarged view of the gap between the spherical inner surface of the cage and the spherical outer surface of the inner joint member at the end side of the spherical inner surface of the cage in Figure 3. Figure 6 is a partial longitudinal cross-sectional view showing the state in which the spherical outer surface of the inner joint member is in surface contact with the end side of the spherical inner surface of the cage in Figure 5. Figures 1, 3 to 6 exaggerate the gap between the spherical inner surface of the cage and the spherical outer surface of the inner joint member for easier understanding.

[0024] As shown in Figures 1 and 2, the sliding constant velocity universal joint 1 is a so-called double offset sliding constant velocity universal joint (sometimes abbreviated as DOJ), and its main components are an outer joint member 2, an inner joint member 3, torque transmission balls 4, and a cage 5. Six track grooves 7 are formed on the cylindrical inner circumferential surface 6 of the outer joint member 2 at equal intervals in the circumferential direction and linearly along the axial direction. Track grooves 9 are formed on the spherical outer circumferential surface 8 of the inner joint member 3 at equal intervals in the circumferential direction and linearly along the axial direction, facing the track grooves 7 of the outer joint member 2. Six torque transmission balls (hereinafter simply referred to as balls) 4 are incorporated one by one between the track grooves 7 of the outer joint member 2 and the track grooves 9 of the inner joint member 3. The balls 4 are housed in pockets 5a of the cage 5.

[0025] The cage 5 has a spherical outer surface 11 and a spherical inner surface 12. The spherical outer surface 11 fits into contact with and guides the cylindrical inner surface 6 of the outer joint member 2, and the spherical inner surface 12 fits into contact with and guides the spherical outer surface 8 of the inner joint member 3. The spherical outer surface 11 of the cage 5 is formed with a radius of curvature RCO with a center of curvature O2. The center of curvature of the spherical inner surface 12 of the cage 5 and the center of curvature of the spherical outer surface 8 of the inner joint member 3 are both the same, O1. Details of the radius of curvature will be described later. The centers of curvature O1 and O2 are located on the axis N and are offset by an equidistant distance F in the axial direction with respect to the joint center O. As a result, when the joint takes an operating angle, the ball 4 is always guided on a plane that bisects the angle between the axes of the outer joint member 2 and the inner joint member 3, and rotation is transmitted between the two axes at a constant speed.

[0026] Although not shown in the diagram, a retaining ring groove is provided at the open end of the outer joint member 2, and a retaining ring is fitted into this groove to prevent the assembly of the inner joint member 3, ball 4, and cage 5 shown in Figure 1 from coming out of the open end of the outer joint member 2. A boot mounting groove is provided on the outer circumference of the open end of the outer joint member 2. A stem portion (shaft portion) is integrally formed on the side of the outer joint member 2 opposite the opening and is connected differentially. A spline (including serrations, the same applies hereinafter) 14 is formed in the connecting hole 13 of the inner joint member 3, and the shaft end of the intermediate shaft is spline-fitted and fixed axially to the inner joint member 3 by the shoulder portion of the intermediate shaft and the retaining ring.

[0027] Six pockets 5a are provided at equal intervals in the circumferential direction at the axial center of the cage 5, indicated by line AA in Figure 1, with column sections 5b (see Figure 2) between adjacent pockets 5a. A notch 5c for incorporating the inner joint member 3 is provided on the inner circumference of the large-diameter end of the cage 5. The gap between the ball 4 and the pockets 5a of the cage 5 is set according to the vehicle characteristics, either by clearance or overlap. In the case of clearance setting, the pocket width Lw shown in Figure 1 is equal to the ball diameter D BALL Formed to be slightly larger (Lw>D BALL ), when setting the closing allowance, the pocket width Lw is equal to the ball diameter D BALL It is formed to be slightly smaller (Lw≦D BALL ).

[0028] The overall configuration of the sliding constant velocity universal joint 1 of this embodiment is as described above. Next, the characteristic configuration will be explained based on Figures 3 to 6. As shown in Figure 4, a detailed longitudinal cross-sectional view of the inner joint member 3 and cage 5 of the sliding constant velocity universal joint 1 of this embodiment, the spherical inner circumferential surface 12 of the cage 5 is formed with an inner diameter dimension DCI at its axial center and with diagonal inner diameter dimensions DCI' at both axial ends. The inner diameter dimension DCI at the axial center is the inner diameter dimension in the direction perpendicular to the axis of the cage 5, passing through the curvature center O1 of the spherical inner circumferential surface 12, that is, the axial center of the spherical inner circumferential surface 12. Therefore, the inner diameter dimension DCI is twice the radius of curvature RCI of the spherical inner circumferential surface 12 with curvature center O1 (DCI = 2 × RCI). The diagonal inner diameter dimension DCI' at both ends in the axial direction is twice the radius of curvature RCI' of the spherical inner surface 12 with center of curvature O1, because the diagonal passes through the center of curvature O1 of the spherical inner surface 12 (DCI' = 2 × RCI').

[0029] The spherical outer surface 8 of the inner joint member 3 is formed with an outer diameter dimension DI at its axial center and with diagonal outer diameter dimensions DI' at both axial ends. The outer diameter dimension DI at the axial center is the outer diameter dimension in the direction perpendicular to the axis of the inner joint member 3, passing through the curvature center O1 of the spherical outer surface 8, i.e., the axial center of the spherical outer surface 8. Therefore, the outer diameter dimension DI is twice the radius of curvature RI of the spherical outer surface 8 with curvature center O1 (DI = 2 × RI). The diagonal outer diameter dimensions DI' at both axial ends are twice the radius of curvature RI' of the spherical outer surface 8 with curvature center O1, since the diagonal passes through the curvature center O1 of the spherical inner surface 12 (DI' = 2 × RI'). In this embodiment, the sliding constant velocity universal joint 1 has a small dimensional difference in both the outer diameter of the spherical outer surface 8 of the inner joint member 3 and the inner diameter of the spherical inner surface 12 of the cage 5.

[0030] The spherical gap δ between the spherical inner surface 12 of the cage 5 and the spherical outer surface 8 of the inner joint member 3 is δ = DCI - DI and is set to approximately 0.010 to 0.200 mm. The radius of curvature RCI at the axial center of the spherical inner surface 12 of the cage 5 gradually increases toward both axial ends of the spherical inner surface 12 and smoothly connects to the radius of curvature RCI' at both axial ends. The radius of curvature RI at the axial center of the spherical outer surface 8 of the inner joint member 3 gradually decreases toward both axial ends of the spherical outer surface 8 and smoothly connects to the radius of curvature RI' at both axial ends. In this embodiment, the sliding constant velocity universal joint 1 has the same center of curvature O1 of the spherical inner circumferential surface 12 of the cage 5 and the same center of curvature O1 of the spherical outer circumferential surface 8 of the inner joint member 3, and the radius of curvature RCI, RCI' of the spherical inner circumferential surface 12 of the cage 5 and the radius of curvature RI, RI' of the spherical outer circumferential surface 8 of the inner joint member 3 are substantially the same.

[0031] Specifically, the difference between the outer diameter dimension DI at the axial center of the spherical outer surface 8 of the inner joint member 3 and the diagonal outer diameter dimensions DI' at both axial ends is set to 0 < (DI - DI') ≤ 0.020 mm, and the difference between the inner diameter dimension DCI at the axial center of the spherical inner surface 12 of the cage 5 and the diagonal outer diameter dimensions DCI' at both axial ends is set to 0 < (DCI' - DCI) ≤ 0.020 mm. Since the minute differences between the outer diameter dimensions D1 and DI' of the spherical outer surface 8 of the inner joint member 3 and the inner diameter dimensions DCI and DCI' of the cage 5 can be suppressed to the above dimensional ranges, machining becomes easier.

[0032] The internal state of the sliding constant velocity universal joint 1 of this embodiment when the operating angle (θ=5°) is taken with respect to the axis No. of the outer joint member 102 (which is also the joint axis N when the operating angle is 0°) will be explained with reference to Figure 3. Similar to the conventional DOJ type sliding constant velocity universal joint described in Figure 10, as shown in Figure 3, the ball 4 receives a force in the direction of the arrow due to the wedge angle formed by the track groove 7 of the outer joint member 2 and the track groove 9 of the inner joint member 3. Therefore, the inner joint member 3 and the cage 5 come into contact at sections C and D shown in Figure 3.

[0033] In this embodiment, the sliding constant velocity universal joint 1 has a small difference between the outer diameter dimension DI at the axial center of the spherical outer surface 8 of the inner joint member 3 and the diagonal outer diameter dimensions DI' at both axial ends, and also a small difference between the inner diameter dimension DCI at the axial center of the spherical inner surface 12 of the cage 5 and the diagonal inner diameter dimensions DCI' at both axial ends. Therefore, as shown in Figure 5, which is an enlargement of section C in Figure 3, the relative axial distance between the spherical outer surface 8 of the inner joint member 3 and the spherical inner surface 12 of the cage 5 is equivalent at the end side of the spherical inner surface 12 of the cage 5 (L1 ≈ L2). With respect to the center of the spherical inner surface 12, the position of L1 is at approximately 25°, and the position of L2 is at approximately 20°. The positions of L1 and L2 correspond to positions that diagonally cross both axial ends on the spherical inner surface 12 of the cage 5, and are within a range that provides a margin (for example, about 1 to 2 mm) from the chamfer 12a of the end. In addition, the positions of L1 and L2 also correspond to positions that diagonally cross both axial ends on the spherical outer surface 8 of the inner joint member 3, and are in the same axial position as the positions that diagonally cross both axial ends on the spherical inner surface 12 of the cage 5 described above.

[0034] Therefore, as shown in Figure 6, the spherical inner surface 12 of the cage 5 and the spherical outer surface 8 of the inner joint member 3 make surface contact with a contact width W at the end side of the spherical inner surface 12 of the cage 5, thereby reducing the contact pressure. In addition, on the axial center side, the lubricating grease held in the spherical gap δ between the spherical inner surface 12 and the spherical outer surface 8 ensures good oil film formation at the surface contact area. As a result, wear and heat generation are suppressed, and durability is improved. In Figures 5 and 6, part D in Figure 3 is omitted from the illustration, but it is the same as part C.

[0035] A sliding constant velocity universal joint according to a second embodiment of the present invention will be described with reference to Figure 7. Figure 7 is a longitudinal cross-sectional view showing the cage 5 and the inner joint member 3 in the sliding constant velocity universal joint of this embodiment. In this embodiment, the difference from the sliding constant velocity universal joint of the first embodiment is that, among the spherical outer surface 8 of the inner joint member 3 and the spherical inner surface 12 of the cage 5, only the spherical outer surface 8 of the inner joint member 3 has a small difference in outer diameter dimension. The other configurations are the same as in the first embodiment, so the same reference numerals are used for parts having the same function, and only the essential points will be described.

[0036] As shown in Figure 7, the spherical inner surface 12 of the cage 5 is formed with a constant radius of curvature RCI with the center of curvature O1 over its entire axial region, and its inner diameter is also constant at DCI. On the other hand, the spherical outer surface 8 of the inner joint member 3 is formed with an outer diameter DI at its axial center, and with diagonal outer diameters DI' at both axial ends. The outer diameter DI at the axial center is twice the radius of curvature RI of the spherical outer surface 8 with the center of curvature O1 (DI = 2 × RI). The diagonal outer diameters DI' at both axial ends are twice the radius of curvature RI' with the center of curvature O1 (DI' = 2 × RI').

[0037] In this embodiment as well, the spherical gap δ (=DCI-DI) between the spherical inner surface 12 of the cage 5 and the spherical outer surface 8 of the inner joint member 3 is set to approximately 0.010 to 0.200 mm. The radius of curvature RI at the axial center of the spherical outer surface 8 of the inner joint member 3 gradually decreases toward both axial ends of the spherical outer surface 8, smoothly connecting to the radius of curvature RI' at both axial ends.

[0038] In this embodiment, of the spherical outer surface 8 of the inner joint member 3 and the spherical inner surface 12 of the cage 5, only the spherical outer surface 8 of the inner joint member 3 has a small difference in outer diameter dimension. Therefore, the difference between the outer diameter dimension DI at the axial center of the spherical outer surface 8 of the inner joint member 3 and the diagonal outer diameter dimensions DI' at both axial ends is set to 0 < (DI - DI') ≤ 0.040 mm. Since only the spherical outer surface 8 of the inner joint member 3 has a small difference in outer diameter dimension within the above dimension range, processing can be made easy and simple. In this embodiment as well, the center of curvature O1 of the spherical inner surface 12 of the cage 5 and the center of curvature O1 of the spherical outer surface 8 of the inner joint member 3 are the same, and the radius of curvature RCI of the spherical inner surface 12 of the cage 5 and the radii of curvature RI and RI' of the spherical outer surface 8 of the inner joint member 3 are approximately the same. Other configurations, effects, etc., which have not been explained, are the same as in the first embodiment, so the contents described in the first embodiment shall apply mutatis mutandis to this embodiment.

[0039] A sliding constant velocity universal joint according to a third embodiment of the present invention will be described with reference to Figure 8. Figure 8 is a longitudinal cross-sectional view showing the cage 5 and the inner joint member 3 in the sliding constant velocity universal joint of this embodiment. In this embodiment, a small difference in the inner diameter dimension is provided only on the spherical inner circumferential surface 12 of the cage 5, compared to the spherical outer circumferential surface 8 of the inner joint member 3 and the spherical inner circumferential surface 12 of the cage 5. This is the difference from the sliding constant velocity universal joint of the first embodiment. The other components are the same as in the first embodiment, so the same reference numerals are used for parts with similar functions, and only the essential points will be described.

[0040] As shown in Figure 8, the spherical outer surface 8 of the inner joint member 3 is formed with a constant radius of curvature RI with the center of curvature O1 over its entire axial area, and its outer diameter is also constant at DI. On the other hand, the spherical inner surface 12 of the cage 5 is formed with an inner diameter DCI at its axial center, and with diagonal inner diameters DCI' at both axial ends. The inner diameter DCI at the axial center is twice the radius of curvature RCI of the spherical inner surface 12 with the center of curvature O1 (DCI = 2 × RCI). The diagonal inner diameters DCI' at both axial ends are twice the radius of curvature RCI' with the center of curvature O1 (DCI' = 2 × RCI').

[0041] In this embodiment as well, the spherical gap δ (=DCI-DI) between the spherical inner surface 12 of the cage 5 and the spherical outer surface 8 of the inner joint member 3 is set to approximately 0.010 to 0.200 mm. The radius of curvature RCI at the axial center of the spherical inner surface 12 of the cage 5 gradually increases toward both axial ends of the spherical inner surface 12, smoothly connecting to the radius of curvature RCI' at both axial ends.

[0042] In this embodiment, a small difference in inner diameter dimension is provided only on the spherical inner surface 12 of the cage 5, compared to the spherical outer surface 8 of the inner joint member 3. Therefore, the difference between the inner diameter dimension DCI at the axial center of the spherical inner surface 12 of the cage 5 and the diagonal inner diameter dimensions DCI' at both axial ends is set to 0 < (DCI' - DCI) ≤ 0.040 mm. Because a small difference in inner diameter dimension within the above dimensional range is provided only on the spherical outer surface 12 of the cage 5, compared to the spherical outer surface 8 of the inner joint member 3, processing can be easily and simply performed. In this embodiment as well, the curvature center O1 of the spherical inner surface 12 of the cage 5 and the curvature center O1 of the spherical outer surface 8 of the inner joint member 3 are the same, and the curvature radii RCI and RCI' of the spherical inner surface 12 of the cage 5 and the curvature radius RI of the spherical outer surface 8 of the inner joint member 3 are substantially the same. Other configurations, effects, etc., which have not been described, are the same as in the first embodiment, so the contents described in the first embodiment are applied mutatis mutandis to this embodiment.

[0043] In the embodiment described above, a DOJ-type sliding constant velocity universal joint 1 using six torque transmission balls 4 was exemplified, but it is not limited to this, and the number of torque transmission balls 4 can be appropriately set in the range of 5 to 10. A sliding constant velocity universal joint suitable for power transmission systems in automobiles and various industrial machines can be constructed.

[0044] The present invention is not limited in any way to the embodiments described above, and can be implemented in various other forms without departing from the spirit of the invention. The scope of the present invention is indicated by the claims, and includes all modifications within the meaning and scope of equivalents set forth in the claims. [Explanation of symbols]

[0045] 1 Sliding Constant Velocity Joint 2 Outer Joint Member 3 Inner Joint Member 4 Torque Transmission Ball 5 Cage 5a Pocket 6 Cylindrical Inner Peripheral Surface 7 Track Groove 8 Spherical Outer Peripheral Surface 9 Track Groove 11 Spherical Outer Peripheral Surface 12 Spherical Inner Peripheral Surface D BALL Ball Diameter DCI Inner Diameter Dimension DCI’ Inner Diameter Dimension DI Outer Diameter Dimension DI’ Outer Diameter Dimension F Offset Amount Lw Width between Wall Surfaces O Joint Center O1 Center of Curvature O2 Center of Curvature RCI Radius of Curvature RCI’ Radius of Curvature RCO Radius of Curvature RI Radius of Curvature RI’ Radius of Curvature δ Spherical Clearance

Claims

1. A sliding constant velocity universal joint comprising: an outer joint member having a plurality of linear track grooves formed axially along its cylindrical inner surface; an inner joint member having a plurality of linear track grooves formed axially along its spherical outer surface opposite to the plurality of linear track grooves of the outer joint member; 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 having a spherical outer surface and a spherical inner surface that house the torque transmission balls in pockets and are guided in contact with the cylindrical inner surface of the outer joint member and the spherical outer surface of the inner joint member, wherein the center of curvature of the spherical outer surface and the center of curvature of the spherical inner surface of the cage are offset axially on opposite sides with respect to the joint center, The center of curvature of the spherical inner surface of the cage and the center of curvature of the spherical outer surface of the inner joint member are the same, and the radius of curvature of the spherical inner surface of the cage and the radius of curvature of the spherical outer surface of the inner joint member are substantially the same, thereby forming a spherical gap that allows contact guidance between the spherical inner surface of the cage and the spherical outer surface of the inner joint member. The spherical outer surface of the inner joint member is configured such that DI > DI', with a small difference between the outer diameter dimension (DI) at the axial center and the diagonal outer diameter dimensions (DI') at both axial ends. The spherical inner surface of the cage is configured such that DCI < DCI', with a small difference between the inner diameter dimension (DCI) at the axial center and the diagonal inner diameter dimensions (DCI') at both axial ends. A sliding constant velocity universal joint characterized in that, when the sliding constant velocity universal joint takes an operating angle, the spherical inner surface of the cage and the spherical outer surface of the inner joint member make surface contact with a contact width such that the contact pressure is reduced at the end side of the spherical inner surface of the cage.

2. The sliding constant velocity universal joint according to claim 1, characterized in that the difference between DI and DI' is 0 < (DI - DI') ≤ 0.020 mm, and the difference between DCI and DCI' is 0 < (DCI' - DCI) ≤ 0.020 mm.

3. A sliding constant velocity universal joint comprising: an outer joint member having a plurality of linear track grooves formed axially along its cylindrical inner surface; an inner joint member having a plurality of linear track grooves formed axially along its spherical outer surface opposite to the plurality of linear track grooves of the outer joint member; 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 having a spherical outer surface and a spherical inner surface that house the torque transmission balls in pockets and are guided in contact with the cylindrical inner surface of the outer joint member and the spherical outer surface of the inner joint member, wherein the center of curvature of the spherical outer surface and the center of curvature of the spherical inner surface of the cage are offset axially on opposite sides with respect to the joint center, The center of curvature of the spherical inner surface of the cage and the center of curvature of the spherical outer surface of the inner joint member are the same, and the radius of curvature of the spherical inner surface of the cage and the radius of curvature of the spherical outer surface of the inner joint member are substantially the same, thereby forming a spherical gap that allows contact guidance between the spherical inner surface of the cage and the spherical outer surface of the inner joint member. The spherical outer surface of the inner joint member is given a small difference between the outer diameter dimension (DI) at the axial center and the diagonal outer diameter dimensions (DI') at both axial ends, such that DI > DI'. A sliding constant velocity universal joint characterized in that, when the sliding constant velocity universal joint takes an operating angle, the spherical inner surface of the cage and the spherical outer surface of the inner joint member make surface contact with a contact width such that the contact pressure is reduced at the end side of the spherical inner surface of the cage.

4. The sliding constant velocity universal joint according to claim 3, characterized in that the difference between DI and DI' is 0 < (DI - DI') ≤ 0.040 mm.

5. A sliding constant velocity universal joint comprising: an outer joint member having a plurality of linear track grooves formed axially along its cylindrical inner surface; an inner joint member having a plurality of linear track grooves formed axially along its spherical outer surface opposite to the plurality of linear track grooves of the outer joint member; 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 having a spherical outer surface and a spherical inner surface that house the torque transmission balls in pockets and are guided in contact with the cylindrical inner surface of the outer joint member and the spherical outer surface of the inner joint member, wherein the center of curvature of the spherical outer surface and the center of curvature of the spherical inner surface of the cage are offset axially on opposite sides with respect to the joint center, The center of curvature of the spherical inner surface of the cage and the center of curvature of the spherical outer surface of the inner joint member are the same, and the radius of curvature of the spherical inner surface of the cage and the radius of curvature of the spherical outer surface of the inner joint member are substantially the same, thereby forming a spherical gap that allows contact guidance between the spherical inner surface of the cage and the spherical outer surface of the inner joint member. The spherical inner surface of the cage is given a small difference between the inner diameter dimension at the axial center (DCI) and the diagonal inner diameter dimensions at both axial ends (DCI'), such that DCI < DCI'. A sliding constant velocity universal joint characterized in that, when the sliding constant velocity universal joint takes an operating angle, the spherical inner surface of the cage and the spherical outer surface of the inner joint member make surface contact with a contact width such that the contact pressure is reduced at the end side of the spherical inner surface of the cage.

6. A sliding constant velocity universal joint according to claim 5, wherein the difference between DCI and DCI' is 0 < (DCI' - DCI) ≤ 0.040 mm.

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