Sliding type constant-velocity universal joint

Abstract

To realize a sliding type constant-velocity universal joint which is excellent in durability and has a long life, at low cost.SOLUTION: A double offset type constant-velocity universal joint 1 comprises an outside joint member 11, an inside joint member 2, a plurality of balls 16, and a retainer 5. A convex, spherical outside guide surface 6 that contacts and guides a cylindrical inner diameter surface of the outside joint member 11 is provided at an outer diameter surface of the retainer 5, and an inside guide surface 7 that contacts and guides a convex, spherical outer diameter surface 3 of the inside joint member 2 and an inside cylindrical surface 8 that the inside joint member 2 passes during installation of the inside joint member 2 are provided at an interval in an axial direction at an inner diameter surface of the retainer 5. At the convex, spherical outer diameter surface 3, the inside joint member 2 has a clearance surface S at which a radial-direction separation distance from the inside guide surface 7 as opposite in a state in which an operation angle is 0° is greater than a radial-direction separation distance from the inside cylindrical surface 8 as passed during installation at the inside guide surface 7 of the retainer 5.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a sliding type constant velocity universal joint. [Background technology]

[0002] As is well known, automobiles equipped with a drive source such as an engine or electric motor on their chassis are equipped with a power transmission device such as a drive shaft or propeller shaft to transmit the output (torque) of the drive source to the wheels. This power transmission device connects two shafts, a drive shaft and a driven shaft, and is equipped with a constant velocity universal joint that can transmit torque at a constant velocity regardless of the operating angle of the two connected shafts (regardless of relative angular displacement). Constant velocity universal joints are broadly divided into fixed-type constant velocity universal joints that allow only angular displacement of the two connected shafts, and sliding-type constant velocity universal joints that allow angular and axial displacement of the two connected shafts.

[0003] One type of sliding type constant velocity universal joint is a double offset type as described in Japanese Patent Laid-Open No. 10-73129 (Patent Document 1) and Japanese Patent Laid-Open No. 2007-85488 (Patent Document 2). Fig. 3 shows a schematic longitudinal sectional view of a known double offset type constant velocity universal joint 10 in a state where the operating angle is 0°, and Fig. 4 shows a partial enlarged view of Fig. 3. This constant velocity universal joint 10 includes an outer joint member 11 having a cylindrical cup portion 12 with a bottom and a plurality of linear outer track grooves 13 formed on the cylindrical inner diameter surface of the cup portion 12, an inner joint member 14 having a convex spherical outer diameter surface and a plurality of linear inner track grooves 15 formed on the convex spherical outer diameter surface, a plurality of balls 16 interposed between the paired track grooves 13, 15 to transmit torque between the two joint members 11, 14, and a cage 17 that holds the balls 16 at intervals in the circumferential direction.

[0004] 5(a) and 5(b) are a schematic perspective view and a longitudinal sectional view, respectively, of the cage 17. The cage 17 integrally includes a pair of annular portions 17a, 17b spaced apart in the axial direction and a plurality of column portions 17c spaced apart in the circumferential direction so as to connect the annular portions 17a, 17b. Pockets 17d for individually holding the balls 16 are formed between the pair of annular portions 17a, 17b and two adjacent column portions 17c. The outer and inner diameter surfaces of the cage 17 are provided with outer guide surfaces 17e that can contact and guide the cylindrical inner diameter surface of the outer joint member 11 and inner guide surfaces 17f that can contact and guide the convex spherical outer diameter surface of the inner joint member 14 during relative angular displacement of the two joint members 11, 14. The outer guide surface 17e is formed as a convex spherical surface with a spherical center Oq offset by a dimension La on one axial side from the pocket center Op (the intersection of an axially orthogonal plane passing through the axial center of the pocket 17d and the central axis of the joint), and the inner guide surface 17f is formed as a concave spherical surface with a spherical center Or offset by the same dimension La on the other axial side from the pocket center Op.

[0005] The inner diameter surface of the cage 17 is provided with a cylindrical surface (inner cylindrical surface) 17g of a constant diameter, spaced apart in the axial direction from the concave spherical inner guide surface 17f, and the inner joint member 14 is fitted to the inner circumference of the inner cylindrical surface 17g so as to pass through the inner cylindrical surface 17g. Therefore, as shown in Fig. 4, the diameter (circumscribed circle diameter) Dn of the outer diameter surface of the inner joint member 14 is set to be smaller than the diameter (maximum diameter) Dc of the inner guide surface 17f of the cage 17 and the diameter Dk of the inner cylindrical surface 17g. The diameter Dc of the inner guide surface 17f is set to be equal to or smaller than the diameter Dk of the inner cylindrical surface 17g. Therefore, the magnitude relationship between the above Dn, Dc and Dk is expressed as follows: Dn <Dc≦Dkである。 [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-73129 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-85488 Summary of the Invention [Problem to be solved by the invention]

[0007] When the constant velocity universal joint 10 described above is subjected to a high load while rotating at a large operating angle θ as shown in FIG. 6, the portion of the cage 17 indicated by arrow A in FIGS. 5(a) and 5(b) (the connection between the column portion 17c and the annular portion 17b) becomes a stress concentration area, and the cage 17 may be damaged starting from this stress concentration area A. Therefore, some damage prevention measures must be taken for the cage 17. One possible damage prevention measure is to provide an R portion with a large radius of curvature at the stress concentration area A to relieve the stress acting on the stress concentration area A. However, adopting such a measure may make it difficult for the cage 17 of the constant velocity universal joint 10 to properly perform its required functions, such as "guiding the inner joint member" and "retaining the balls." The reason for this is explained below.

[0008] [Guidance function for inner joint members] As described above, the inner diameter surface of the cage 17 is provided with the concave spherical inner guide surface 17f that contacts and guides the outer diameter surface of the inner joint member 14. It is preferable that the axial length X of this inner guide surface 17f be as long as possible to enable smooth angular displacement of the inner joint member 14 and to ensure the holding force of the cage 17 on the inner joint member 14 (to prevent the inner joint member 14 from jumping outward in the axial direction of the cage 17). However, if the stress relaxation measures described above are taken, the enlarged R portion and the like will erode part of the inner guide surface 17f, shortening the axial length X of the inner guide surface 17f, which may result in a deterioration in the guiding function and the like.

[0009] [Ball retention function] To ensure smooth assembly of the inner joint member 14, the inlet diameter (diameter Dk of the inner cylindrical surface 17g) of the annular portion 17b of the cage 17 must be set larger than the diameter Dn of the outer diameter surface of the inner joint member 14, as described above. However, if an R-shaped portion with a large radius of curvature is provided near the stress concentration portion A, the wall thickness t of the annular portion 17b decreases, reducing the strength of the cage 17. In this case, there is a concern that problems such as the balls 16 retained in the pockets 17d becoming more likely to fall out of the pockets 17d may occur. In particular, as shown in Figure 6, when the constant velocity universal joint 10 rotates at a large operating angle θ, the balls 16 repeatedly move up and down (radially) within the pockets 17d, which releases the constraint of the pockets 17d and causes the balls 16 to fall out of the pockets 17d. In this case, defects such as chips or scratches may occur in the edges of the pockets 17d or on the balls 16, significantly reducing the operability of the constant velocity universal joint 10 or potentially rendering the constant velocity universal joint 10 unusable.

[0010] In view of the above circumstances, an object of the present invention is to improve the strength of the cage without increasing costs, thereby realizing a double offset constant velocity universal joint that is highly durable and has a long life. [Means for solving the problem]

[0011] The sliding type constant velocity universal joint according to the present invention, which has been devised to achieve the above object, comprises: an outer joint member having a cylindrical cup portion with a bottom, the cylindrical cup portion having a plurality of linear outer track grooves formed on a cylindrical inner diameter surface thereof; an inner joint member having a plurality of linear inner track grooves formed on a convex spherical outer diameter surface thereof; and a cage for holding a plurality of balls arranged between pairs of outer track grooves and inner track grooves; The cage has a pair of annular portions and a plurality of pillar portions arranged at intervals in the circumferential direction so as to connect the pair of annular portions, and a plurality of pockets that individually hold balls are formed at intervals in the circumferential direction by the pair of annular portions and the plurality of pillar portions, an outer guide surface having a convex spherical shape is provided on an outer diameter surface of the cage, the outer guide surface contacting and guiding the cylindrical inner diameter surface of the outer joint member when both joint members are angularly displaced relative to each other; a concave spherical inner guide surface that contacts and guides the convex spherical outer diameter surface of the inner joint member when both joint members are angularly displaced relative to one another, and an inner cylindrical surface through which the inner joint member passes when the inner joint member is assembled onto the inner guide surface, the inner guide surface being spaced apart in the axial direction, The spherical center of the outer guide surface and the spherical center of the inner guide surface are offset by an equal distance on opposite sides in the axial direction from the pocket center, The inner joint member is characterized in that it has, on its convex spherical outer diameter surface, a relief surface that makes the radial distance from the opposing inner guide surface in a state where the operating angle is 0° larger than the radial distance from the inner cylindrical surface through which the inner joint member passes when assembled into the inner guide surface of the cage.

[0012] By providing the above-described flank on the convex spherical outer diameter surface of the inner joint member, the thickness of the portion of the cage where stress concentration occurs during heavy load input can be increased compared to the conventional cage shown in Figure 5(b). This increases the strength of the cage, which is subjected to heavy loads during operation of the sliding type constant velocity universal joint (double offset constant velocity universal joint). Note that the increase in the thickness (volume) of the cage described above can be compensated for by the reduction in volume of the inner joint member due to the provision of the flank on the inner joint member, thereby suppressing increases in cost and weight. Therefore, according to the present invention, a sliding type constant velocity universal joint with excellent durability and long life can be realized at low cost.

[0013] In the above-described configuration, the flank surface can be formed by a straight surface parallel to the central axis of the inner joint member, thereby making it possible to easily provide the flank surface to be provided on the inner joint member.

[0014] When the axial length of the flank surface formed by the straight surface is L1 and the axial offset amount of the inner guide surface from the pocket center is L2, it is preferable to satisfy the relational expression L1<2L2. This makes it possible to ensure a sufficient groove depth of the inner track grooves provided in the inner joint member (the engagement allowance of the balls with the inner track grooves).

[0015] The present invention can be suitably applied to a sliding type constant velocity universal joint having five, six, seven or eight balls. [Effects of the Invention]

[0016] As described above, according to the present invention, a sliding type constant velocity universal joint having excellent durability and a long life can be realized at low cost. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a partial vertical cross-sectional view of a sliding type constant velocity universal joint according to an embodiment of the present invention in a state where the operating angle is 0°. [Figure 2] FIG. 2 is a partially enlarged view of FIG. [Figure 3] FIG. 1 is a partial vertical cross-sectional view of a conventional sliding type constant velocity universal joint in a state where the operating angle is 0°. [Figure 4] FIG. 4 is a partially enlarged view of FIG. [Figure 5] 4(a) is a schematic perspective view of the cage shown in FIG. 3, and FIG. 4(b) is a vertical cross-sectional view of the cage. [Figure 6] 4 is a diagram showing a state in which the sliding type constant velocity universal joint shown in FIG. 3 has an operating angle θ. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0019] FIG. 1 shows a partial longitudinal cross-sectional view of a sliding-type constant velocity universal joint 1 according to one embodiment of the present invention in a state where the operating angle is 0° (a state where the central axis of the outer joint member and the central axis of the inner joint member are aligned), and FIG. 2 shows a partial enlarged view of FIG. 1. This sliding-type constant velocity universal joint 1 is used as a component of a drive shaft that transmits the output (torque) of a drive source such as an engine or electric motor mounted on the chassis of an automobile to the drive wheels of the automobile, and is disposed on the drive source side and connected to a differential (not shown). The drive shaft connects the sliding-type constant velocity universal joint 1 and a fixed constant velocity universal joint (not shown) that are spaced apart in the width direction of the automobile via a shaft member (not shown) also called an intermediate shaft (not shown) so as to be able to transmit torque. Note that hereinafter, the sliding-type constant velocity universal joint 1 will also be simply referred to as the "constant velocity universal joint 1."

[0020] The constant velocity universal joint 1 of the present embodiment shown in Fig. 1 is a double offset type in which, among the components of the conventional double offset type constant velocity universal joint 10 described above with reference to Figs. 3 to 6, an inner joint member 2 and a cage 5, which will be described below, are adopted instead of the inner joint member 14 and the cage 17. That is, the constant velocity universal joint 1 includes an outer joint member 11 and an inner joint member 2, a plurality of balls 16 (eight in this example) that transmit torque between the joint members 11 and 2, and a cage 5 that holds the balls 16, and the outer joint member 11 and the balls 16 have substantially the same structures as those shown in Fig. 3 etc. Therefore, detailed description of the outer joint member 11 and the balls 16 will be omitted.

[0021] The inner joint member 2 is formed in an annular shape and is disposed on the inner periphery of the cup portion 12 of the outer joint member 11. The outer diameter surface 3 of the inner joint member 2 is formed in a convex spherical shape bulging outward in the radial direction, and a plurality of inner track grooves 4 each having a linear shape (extending along the central axis of the inner joint member 11) are formed at equal intervals in the circumferential direction on this convex spherical outer diameter surface 3. One end of the shaft member is spline-fitted to the inner wall surface of the shaft hole of the inner joint member 2, and the inner joint member of a fixed type constant velocity universal joint is spline-fitted to the other end of the shaft member. In this way, (the inner joint member 2 of) the sliding type constant velocity universal joint 1 and (the inner joint member of) the fixed type constant velocity universal joint are connected via the shaft member so as to be able to transmit torque.

[0022] The cage 5 is disposed between the cylindrical inner diameter surface of the cup portion 12 of the outer joint member 11 and the convex spherical outer diameter surface 3 of the inner joint member 2, and holds a plurality of balls 16 arranged between a pair of outer track grooves 13 and inner track grooves 4 at intervals in the circumferential direction. That is, the cage 5 is provided with a plurality of pockets 5d at intervals in the circumferential direction for individually holding the plurality of balls 16. Similar to the cage 17 shown in Figures 5(a) and (b), this cage 5 integrally includes a pair of annular portions 5a, 5b spaced apart in the axial direction and a plurality of pillar portions 5c spaced apart in the circumferential direction so as to connect the two annular portions 5a, 5b, and pockets 5d are formed between the two annular portions 5a, 5b and two pillar portions 5c adjacent to each other in the circumferential direction.

[0023] An outer diameter surface of the cage 5 is provided with an outer guide surface 6 which contacts and guides the inner diameter surface of the outer joint part 11 during relative angular displacement between the outer joint part 11 and the inner joint part 2 (when the joint has an operating angle), and an inner diameter surface of the cage 5 is provided with an inner guide surface 7 which contacts and guides the convex spherical outer diameter surface 3 of the inner joint part 2 during relative angular displacement between both joint parts 11, 2. The outer guide surface 6 is formed in a convex spherical shape with a spherical center OQ at a position offset by a dimension L2 from the pocket center OP toward the bottom side of the cup part 12, and the inner guide surface 7 is formed in a concave spherical shape with a spherical center OR at a position offset by the same dimension L2 from the pocket center OP toward the opening side of the cup part 12.

[0024] When the constant velocity universal joint 1 having the above configuration rotates while forming an operating angle (transmitting torque), the cage 5 rotates together with the balls 16 that move on the linear track grooves 13, 4 according to the inclination of the inner joint member 2, and holds the balls 16 on the plane bisecting the operating angle. This maintains the constant velocity of the joint.

[0025] When the joint assumes an operating angle, as described above, the cylindrical inner diameter surface of the outer joint part 11 is contact-guided by the convex spherical outer guide surface 6 provided on the outer diameter surface of the cage 5, and the outer diameter surface 3 of the inner joint part 2 is contact-guided by the concave spherical inner guide surface 7 provided on the inner diameter surface of the cage 5. This allows smooth relative angular displacement between the two joint parts 11, 2. Furthermore, when the two joint parts 11, 2 are displaced axially relative to each other, sliding occurs between the outer guide surface 6 of the cage 5 and the inner diameter surface of the outer joint part 11. This allows smooth relative axial displacement between the two joint parts 11, 2.

[0026] The cage 5 has an inner diameter surface provided with a cylindrical surface (inner cylindrical surface) 8 of a constant diameter that is axially spaced apart from the concave spherical inner guide surface 7. This inner cylindrical surface 8 is formed by the inner diameter surface of the annular portion 5b, of the pair of annular portions 5a, 5b that make up the cage 5, that is located relatively closer to the bottom of the cup portion 12.

[0027] Although not shown in the drawings, the inner joint member 2 is disposed coaxially with the cage 5 outside the annular portion 5b of the cage 5 in the axial direction, and then moved relatively toward the cage 5 while maintaining the coaxial state with the cage 5, thereby being assembled to the inner periphery of the cage 5 (inside the inner guide surface 7). Therefore, the inner joint member 2 is configured to be able to pass through the inner cylindrical surface 8 of the cage 5 while being disposed coaxially with the cage 5. Note that, when assembling the inner joint member 2 to the inner periphery of the cage 5, the circumferential centers of the inner track grooves 4 are shifted circumferentially by a predetermined amount (45° in this embodiment in which a total of eight pockets 5d are provided) with respect to the circumferential centers of the pockets 5d. This makes it possible to prevent the inner joint member 2 from interfering with the post portions 5c of the cage 5 (the protrusions toward the inner diameter side provided on the post portions 5c).

[0028] On the outer diameter surface 3 of the inner joint member 2 of the present embodiment, a clearance surface S is provided such that the radial separation distance from the inner cylindrical surface 8 of the cage 5 through which the inner joint member 2 passes when being incorporated into the inner guide surface 7 of the cage 5 is smaller than the radial separation distance from the inner guide surface 7 facing in the state of the operating angle of 0° after being incorporated into the cage 5. That is, when the diameter of the inner cylindrical surface 8 of the cage 5 is DK, the maximum diameter of the inner guide surface 7 of the cage 5 is DC, and the diameter of the outer diameter surface 3 of the inner joint member 2 (the circumscribed circle diameter of the clearance surface S) is DN, the clearance surface S is provided on the outer diameter surface 3 of the inner joint member 2 so that the relational expression of DN < DK < DC holds.

[0029] On the other hand, in the conventional double offset constant velocity universal joint 10 described with reference to FIGS. 3 to 6, the magnitude relationship of the diameter dimensions Dk, Dc, and Dn corresponding to the above DK, DC, and DN respectively is, as described above, Dn < Dc ≤ Dk. In short, in the constant velocity universal joint 1 of the present embodiment, the magnitude relationship of Dc ≤ Dk in the conventional constant velocity universal joint 10 is replaced with the magnitude relationship of DK < DC, and such a magnitude relationship is realized by positioning the inner cylindrical surface 8 of the cage 5 radially inward compared to the conventional (inner cylindrical surface 17g of the cage 17), and further, by thickening the annular portion 5b in the radial direction. That is, when comparing the wall thickness t [see FIG. 5(b)] of the annular portion 17b of the conventional cage 17 with the wall thickness T of the annular portion 5b of the cage 5 of the present embodiment, the relational expression of t < T holds.

[0030] As described above, in the constant velocity universal joint 1 of the present embodiment, the wall thickness of the portion of the cage 5 that becomes the stress concentration portion when a large load is input to the operating constant velocity universal joint is increased compared to the conventional product. Thereby, the high strength of the cage 5 can be realized. In addition, the increased amount of the wall thickness (volume) of the cage 5 can be compensated by the decreased amount of the volume of the inner joint member 2 by providing the clearance surface S on the inner joint member 2, so that an increase in cost and weight can be suppressed. Therefore, according to the present invention, a long-life sliding constant velocity universal joint excellent in durability can be realized at low cost.

[0031] The relief surface S of the present embodiment is a surface formed by removing a part including the outermost diameter portion (axial center portion) of the outer diameter surface 3 of the inner joint member 2 having a convex spherical shape, and is a straight surface that extends parallel to the central axis of the inner joint member 2 and has its axial center portion coinciding with the axial center portion of the outer diameter surface 3. Thereby, the inner joint member 2 having the relief surface S can be easily obtained.

[0032] The axial length L1 of the relief surface S composed of the above straight surface is set to be not more than twice the axial offset amount L2 of the spherical center OQ (OR) of the guide surface 6 (7) of the cage 5 with respect to the pocket center OP. In terms of a relational expression, L1 ≦ 2L2. By adopting such a configuration, in the state of the operating angle of 0°, the engagement margin (groove depth of the inner track groove 4) WA of the ball 16 with respect to the inner track groove 4 of the inner ring 2 is made the same size as the engagement margin (groove depth of the inner track groove 13) Wa of the ball 16 with respect to the inner track groove 13 when the relief surface S is not provided (see Fig. 5(b)) (WA = Wa), and the convex spherical outer diameter surface 3 of the inner ring 2 and the concave spherical inner guide surface 7 of the cage 5 can be opposed (spherical fitting) on both axial sides of the relief surface S. Therefore, it is possible to prevent a decrease in operability and durability due to providing the relief surface S on the outer diameter surface 3 of the inner joint member 2.

[0033] As described above, the sliding constant velocity universal joint 1 according to the embodiment of the present invention has been described, but the embodiment of the present invention is not limited thereto. For example, the relief surface S provided on the inner joint member 2 only needs to satisfy the relational expression of DN < DK < DC described above, and it is also possible to configure it with a surface other than the straight surface parallel to the central axis of the inner joint member 2. Further, the present invention can be applied not only to the double offset type sliding constant velocity universal joint 1 having 8 balls but also to the double offset type sliding constant velocity universal joint 1 having 5, 6, or 7 balls.

[0034] The present invention is not limited to the embodiments described above at all, and can be further implemented in various forms without departing from the gist of the present invention.

Explanation of reference numerals

[0035] 1. Sliding constant velocity universal joint 2 Inner joint member 3 Outer diameter surface 4 Inner track groove 5 Cage 5d pocket 6 Outer guideway 7 Inner guide surface 8 Inner cylindrical surface 11 Outer joint member 16 balls OP pocket center S flank

Claims

1. an outer joint member having a cylindrical cup portion with a bottom, and a plurality of linear outer track grooves formed on a cylindrical inner diameter surface of the cup portion; an inner joint member having a plurality of linear inner track grooves formed on a convex spherical outer diameter surface; and a cage that holds a plurality of balls arranged between a pair of the outer track groove and the inner track groove, wherein the cage has a pair of annular portions and a plurality of pillar portions that are arranged at intervals in the circumferential direction so as to connect the pair of annular portions, and a plurality of pockets that are circumferentially spaced by the pair of annular portions and the plurality of pillar portions and that individually hold the balls, an outer guide surface having a convex spherical shape that contacts and guides the cylindrical inner diameter surface of the outer joint member when both joint members are angularly displaced relative to each other; a concave spherical inner guide surface that contacts and guides the convex spherical outer diameter surface of the inner joint member when both joint members are angularly displaced relative to one another, and an inner cylindrical surface through which the inner joint member passes when the inner joint member is assembled into the inner guide surface are provided on an inner diameter surface of the cage, the inner guide surface being spaced apart in the axial direction; In a sliding type constant velocity universal joint, the spherical center of the outer guide surface and the spherical center of the inner guide surface are offset by an equal distance on opposite sides in the axial direction with respect to the pocket center, the inner joint member has, on its convex spherical outer diameter surface, a relief surface that makes the radial distance from the opposing inner guide surface in a state of an operating angle of 0° larger than the radial distance from the inner cylindrical surface through which the inner joint member passes when assembled into the inner guide surface of the cage.

2. 2. The sliding type constant velocity universal joint according to claim 1, wherein the flank surface is formed as a straight surface parallel to the central axis of the inner joint member.

3. The axial length of the flank surface formed by the straight surface is L １ The axial offset amount of the inner guide surface with respect to the pocket center is L ２ When this is done, L １ <2L ２ 3. The sliding type constant velocity universal joint according to claim 2, which satisfies the following relational expression:

4. 4. A sliding type constant velocity universal joint according to claim 1, wherein the number of the balls is 5, 6, 7 or 8.

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