JP2018155319A - Fixed constant velocity universal joint used in drive shaft for rear wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further reduce a weight and a size by studying an internal specification, in a fixed constant velocity universal joint used in a drive shaft for a rear wheel.SOLUTION: A fixed constant velocity universal joint 3 includes an outer joint member 31, an inner joint member 32, eight balls 33 and a retainer 34. A center of curvature Oof a track groove 31d of the outer joint member 31 and a center of curvature Oof a track groove 32e of the inner joint member 32 are respectively offset to axial opposite sides to a joint center O(f) by an equal distance. A ratio of PCD/Dof a pitch circle diameter PCDof the ball 33 and a diameter Dof the ball 33 is 3.70-3.87. A ratio W/Dof an axial length Wof the track groove 32e of the inner joint member 32 and the diameter Dof the ball is 1.1-1.3.SELECTED DRAWING: Figure 5

Description

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

  In general, a drive shaft of an automobile is composed of an outboard constant velocity universal joint attached to a wheel, an inboard constant velocity universal joint attached to a differential gear, and an intermediate shaft connecting both constant velocity universal joints. Is done. Usually, a fixed type constant velocity universal joint that can take a large operating angle but is not displaced in the axial direction is used as the constant velocity universal joint on the outboard side. On the other hand, for the constant velocity universal joint on the inboard side, a slidable constant velocity universal joint that can be displaced in the axial direction while having a relatively small maximum operating angle is used.

  The drive shaft includes a front wheel drive shaft attached to the front wheel and a rear wheel drive shaft attached to the rear wheel. Since the fixed type constant velocity universal joint on the outboard side of the front wheel drive shaft is attached to the front wheel which is a steering wheel, one having a large maximum operating angle (for example, 45 ° or more) is used. On the other hand, the fixed constant velocity universal joint on the outboard side of the rear wheel drive shaft is attached to the rear wheel that is not steered, so that the maximum operating angle is smaller than the fixed constant velocity universal joint of the front wheel drive shaft. . However, at present, fixed constant velocity universal joints having the same specifications are used for the front wheel drive shaft and the rear wheel drive shaft from the viewpoint of mass production costs and the like. That is, a fixed constant velocity universal joint with a high operating angle used for the front wheel drive shaft is also used for the rear wheel drive shaft.

  On the other hand, the demand for weight reduction of automobiles is still high, and the power transmission mechanism including the drive shaft is also required to be lightweight and compact. For this reason, further light weight and compactness are also demanded for the fixed type constant velocity universal joint incorporated in the end portion on the outboard side of the drive shaft.

  As a typical fixed type constant velocity universal joint, there is a zeppa type constant velocity universal joint. In the Zepper type constant velocity universal joint, the center of curvature of the track groove of the outer joint member and the center of curvature of the track groove of the inner joint member are offset by an equal distance on the opposite side in the axial direction with respect to the joint center. As a result, the ball is always held within the bisector of the operating angle, and uniform velocity is ensured between the outer joint member and the inner joint member. A zeppa type constant velocity universal joint usually has six torque transmission balls. However, in Patent Document 1 below, the number of torque transmission balls of a zepper type constant velocity universal joint is eight. It is shown. By making the number of balls 8 in this way, lightness and compactness are achieved while ensuring strength, load capacity, and durability equal to or higher than those of a zeppa type constant velocity universal joint with six balls. be able to.

  Further, Patent Document 2 below shows a rear wheel drive shaft. In this rear wheel drive shaft, by increasing the spline diameter provided at both ends of the intermediate shaft (hollow shaft), the hollow shaft has a sufficient strength, so that it can be thinned. Weight reduction is achieved.

JP-A-10-103365 Japanese Patent Application Laid-Open No. 2012-97797

  A zeppa type constant velocity universal joint having eight balls as disclosed in Patent Document 1 has been put into practical use as a mass-produced product. The present invention examines further reduction in weight and size of this type of fixed constant velocity universal joint.

  The invention proposed in Patent Document 2 is intended to reduce the weight and increase the strength of a hollow shaft used for a drive shaft for a rear wheel. However, this document does not mention the problem of making the fixed type constant velocity universal joint lightweight and compact.

  Therefore, the problem to be solved by the present invention is that a fixed type constant velocity universal joint used for a drive shaft for a rear wheel, particularly an eight-ball zepper type constant velocity universal joint, can be further improved by examining internal specifications. The goal is to reduce weight and size.

In order to solve the above-mentioned problems, the present invention is a fixed type constant velocity universal joint used for a drive shaft for a rear wheel, wherein eight track grooves extending in the axial direction are formed on a spherical inner peripheral surface. An outer joint member, an inner joint member in which eight track grooves extending in the axial direction are formed on a spherical outer peripheral surface, and a spline hole is formed in the shaft center, and a track groove of the outer joint member and the inner joint member And eight pockets for accommodating the balls, and formed on the outer peripheral surface of the outer joint member and the outer peripheral surface of the inner joint member. A cage that is in sliding contact, and the center of curvature of the track groove of the outer joint member and the center of curvature of the track groove of the inner joint member are offset by an equal distance on the opposite side in the axial direction with respect to the joint center. of Pitch circle diameter _{PCD BALL} and the ratio _PCD BALL _{/ D BALL} of the diameter _{D BALL} of the ball is 3.70 to 3.87, wherein the axial length _{W I · TRUCK} track grooves of the inner joint member Provided is a fixed type constant velocity universal joint having a ratio WI _{· TRUCK} / D _BALL of 1.1 to 1.3 with respect to a ball diameter D _BALL .

  With fixed type constant velocity universal joints, even when the operating angle is 0 °, a load is evenly applied to each ball. However, when the operating angle is applied, an uneven load is applied to each ball. The difference in applied load increases. Therefore, in the case of a high operating angle, the maximum load applied to each ball becomes large, so members (outer joint member, inner joint member, and cage) that come into contact with the ball can only withstand the maximum load received from the ball. A thick wall thickness is required. Therefore, as described above, the fixed type constant velocity universal joint is dedicated to the rear wheel drive shaft and the maximum operating angle is reduced, so that the maximum load applied to the ball is reduced, and there is a margin in the strength of each member in contact with the ball. Therefore, the thickness of each member, such as the radial thickness of the inner joint member (specifically, the groove bottom of the track groove of the inner joint member and the pitch circle of the spline hole, without causing a decrease in load capacity or durability) ) In the radial direction). As a result, the track grooves formed on the outer peripheral surface of the inner joint member can be brought closer to the inner diameter side, so that the pitch circle diameter of the track grooves, that is, the pitch circle diameter of the balls arranged in the track grooves, It can be made smaller than the 8-ball zeppa type constant velocity universal joint having a high operating angle applicable to both the front wheel drive shaft and the rear wheel drive shaft. Thereby, the fixed type constant velocity universal joint can be made compact in the radial direction to reduce the weight.

  FIG. 7 shows a state in which the fixed type constant velocity universal joint 3 according to the present invention has a maximum operating angle (20 °), and FIG. 8 shows a state in which the fixed type constant velocity universal joint 3 ′ according to the conventional product has a maximum operation. The state where the angle (47 °) is taken is shown. As is apparent from these figures, the fixed type constant velocity universal joint is dedicated to the rear wheel drive shaft and the maximum operating angle is reduced, so that the amount of axial movement of the ball relative to the inner joint member is reduced, and the track groove and ball Therefore, the length of the track groove of the inner joint member in the axial direction can be shortened. Thereby, an inner joint member can be made compact in an axial direction, and weight reduction can be achieved.

By the way, since constant velocity universal joints are mass-produced products, sizes are usually set in stages according to torque load capacity, and internal specifications (dimensions and shapes of each member) are set for each size. (Serialized). In order to reduce the weight and size of the constant velocity universal joint of each size, if the ball diameter is reduced, the surface pressure at the contact portion between the ball and the track groove increases, which directly reduces torque load capacity. For this reason, when considering a design change of the constant velocity universal joint, it is general that the ball diameter is not changed unless the number of balls is increased in order to maintain the torque load capacity. Therefore, the internal specification of the constant velocity universal joint according to the torque load capacity (that is, the size of the constant velocity universal joint) can be represented by expressing the dimensions of the respective members as a ratio to the ball diameter. As described above, the fixed type constant velocity universal joint is exclusively used for the rear wheel drive shaft, the maximum operating angle is reduced, and the size of each member relative to the ball diameter {specifically, the pitch diameter of the ball relative to the ball diameter (PCD _BALL / D _BALL ) and the axial length of the track groove of the inner joint member (WI _{· TRUCK} / D _BALL )} are smaller than the conventional products, a new lightweight and compact series of fixed constant velocity universal joints Can be built.

By reducing the maximum operating angle of the fixed type constant velocity universal joint, the maximum load applied to the ball is reduced as described above. Therefore, the maximum load that the pocket surface of the cage (the inner surface of the pocket) receives from the ball is reduced. As a result, there is a margin in the strength of the cage, so that the axial width of the cage can be reduced while ensuring the durability equal to or higher than that of the conventional product. Specifically, the ratio W _C / D _BALL between the axial width W _C of the cage and the ball diameter D _BALL can be set to 1.63 to 1.80.

By reducing the maximum operating angle of the fixed type constant velocity universal joint, it is possible to reduce the thickness of the inner joint member in the radial direction as described above. Therefore, it is possible to increase the diameter of the spline hole of the inner joint member. it can. As a result, the axial length of the spline hole of the inner joint member can be shortened while maintaining the surface pressure per spline tooth. Thus, only the axial length of the track groove of the inner joint member can be reduced. Instead, by shortening the axial length of the spline hole, the entire inner joint member can be made compact in the axial direction. Specifically, the ratio W _I / D _BALL between the axial width W _I of the inner joint member and the ball diameter D _BALL can be set to 1.40 to 1.55.

  By the way, in the assembly of the conventional 8-ball Zepper type constant velocity universal joint, as shown in FIG. 12, the axis of the inner joint member 102 and the axis of the cage 104 are orthogonal to each other, and in this state, the inner joint member 102 Was slid in the axial direction of the cage 104 and inserted into the inlet 104a of the cage 104. At this time, in order to incorporate the inner joint member 102 into the inner periphery of the cage 104, it is necessary to make the inner diameter B of the inlet portion 104a of the cage 104 larger than the maximum width C of the outer diameter surface 102a of the inner joint member 102. Yes (B> C). For this reason, the radial thickness at the inlet 104a of the cage 104 is reduced, and the strength of this portion may be insufficient.

In the fixed type constant velocity universal joint of the present invention, the axial length of the track groove of the inner joint member can be shortened as described above by reducing the maximum operating angle. Specifically, the inner joint member the axial length W _{I · tRUCK} track grooves of can be less than the circumferential length L _P of the respective pockets of the cage (see Figure 10). As a result, with the inner joint member and the cage orthogonal to each other, the protrusions between the track grooves of the inner joint member are inserted into the cage pocket from the inner diameter side, while the inner circumference of the cage is An inner joint member can be incorporated (see FIG. 11). Thereby, since it is not necessary to form the thin part for incorporating an inner joint member in the inlet part of a cage, the thickness in the radial direction of the cage can be made substantially uniform in the circumferential direction to ensure the strength. .

  The fixed type constant velocity universal joint can have a maximum operating angle of 20 ° or less.

  As described above, according to the present invention, in the fixed type constant velocity universal joint used for the drive shaft for the rear wheel, the internal specifications (the ball pitch circle diameter and the inner side when the ball diameter is used as a reference) are different from the conventional design philosophy. By setting the axial length of the track groove of the joint member, it is possible to further reduce the weight and size while maintaining the torque load capacity.

It is a top view which shows roughly the power transmission mechanism of a rear-wheel drive vehicle. It is sectional drawing of the drive shaft for rear wheels. (A) is the longitudinal cross-sectional view {cross-sectional view in the XX line of (B) figure} of the sliding constant velocity universal joint integrated in the said rear-wheel drive shaft, (B) is the cross-sectional view same. It is a figure {cross-sectional view in the joint center plane of FIG. (A) is the longitudinal cross-sectional view {cross-sectional view in the YY line of (B) figure} of the fixed type constant velocity universal joint integrated in the said rear-wheel drive shaft, (B) is the cross-sectional view. {Cross sectional view in the joint center plane in FIG. (A) is a longitudinal cross-sectional view of a fixed type constant velocity universal joint, and an upper half shows this invention product and a lower half shows a conventional product. (B) is a cross-sectional view in the joint central plane of the fixed type constant velocity universal joint, with the upper half showing the product of the present invention and the lower half showing the conventional product. It is a longitudinal cross-sectional view of the inner joint member and cage of a fixed type constant velocity universal joint, and the upper half shows this invention product and the lower half shows a conventional product. It is sectional drawing which shows the state which the fixed type constant velocity universal joint which concerns on this invention product took the maximum operating angle (20 degrees). It is sectional drawing which shows the state which the fixed type constant velocity universal joint which concerns on the conventional product took the maximum operating angle (47 degrees). (A) is a locus of contact between the pocket surface of the cage of the present invention and the ball, and (B) is a locus of contact between the pocket surface of the conventional cage and the ball. It is the figure which piled up the cross-sectional view of the holder | retainer of this invention goods, and the side view (dashed line) of an inner side coupling member. It is sectional drawing which shows a mode that an inner joint member is integrated in the inner periphery of the holder | retainer of this invention product. It is sectional drawing which shows a mode that an inner side coupling member is integrated in the inner periphery of the conventional holder | retainer.

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

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

  As shown in FIG. 2, the rear wheel drive shaft 1 includes a sliding type constant velocity universal joint 2 that allows both axial displacement and angular displacement on the inboard side (right side in the drawing), and the outboard side (see FIG. A fixed type constant velocity universal joint 3 that allows only angular displacement is provided on the middle left side, and both the constant velocity universal joints 2 and 3 are connected by an intermediate shaft 4. The sliding constant velocity universal joint 2 on the inboard side is connected to the differential gear G, and the fixed constant velocity universal joint 3 on the outboard side is connected to the wheels W (see FIG. 1).

  As shown in FIG. 3, the sliding type constant velocity universal joint 2 is attached to the outer joint member 21 attached to the differential gear G (see FIG. 1) and the inboard side end of the intermediate shaft 4 (see FIG. 2). An inner joint member 22, eight balls 23 that transmit torque between the outer joint member 21 and the inner joint member 22, and a cage 24 that holds the eight balls 23.

  The outer joint member 21 includes a cup-shaped mouth portion 21a having an opening in the axial direction {outboard side, left side in FIG. 3A} and the other axial end {inboard side, FIG. In A), it integrally has a stem portion 21b extending to the right side}. Eight linear track grooves 21d extending in the axial direction are provided on the cylindrical inner peripheral surface 21c of the mouse portion 21a. A spline 21e to be inserted into the spline hole of the differential gear G is provided on the outer peripheral surface of the end portion on the inboard side of the stem portion 21b. In addition, the mouse | mouth part 21a and the stem part 21b may be joined by welding etc., after forming these separately in addition to integrally forming with the same material.

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

  Eight ball tracks are formed with the track grooves 21d of the outer joint member 21 and the track grooves 22e of the inner joint member 22 facing each other in the radial direction, and one ball 23 is arranged on each ball track. The cross-sectional shape of the track grooves 21d and 22e is an elliptical shape or a Gothic arch shape, whereby the track grooves 21d and 22e and the ball 23 are in contact with a so-called angular contact that has a contact angle of about 30 to 45 °. Is done. The cross-sectional shape of the track grooves 21d and 22e may be an arc shape, and the track grooves 21d and 22e and the ball 23 may be so-called circular contacts.

  The holder 24 has eight pockets 24 a for holding the balls 23. The eight pockets 24a all have the same shape and are arranged at equal intervals in the circumferential direction. The outer peripheral surface of the cage 24 is provided with a spherical portion 24b that is in sliding contact with the cylindrical inner peripheral surface 21c of the outer joint member 21, and a conical portion 24c that extends tangentially from both axial ends of the spherical portion 24b. The conical portion 24c is a stopper that restricts the contact angle of the sliding type constant velocity universal joint 2 with the inner peripheral surface 21c of the outer joint member 21 from being increased further when the sliding joint constant velocity universal joint 2 takes the maximum operating angle. Function as. The inclination angle of the conical portion 24 c with respect to the axial center of the cage 24 is set to a value that is ½ of the maximum operating angle of the sliding type constant velocity universal joint 2. On the inner peripheral surface of the cage 24, a spherical surface portion 24d that is in sliding contact with the spherical outer peripheral surface 22d of the inner joint member 22 is provided.

The center of curvature O _24b of the spherical surface portion 24b of the outer peripheral surface of the cage 24 and the center of curvature O _24d of the spherical surface portion 24d of the inner peripheral surface of the cage 24 (that is, the center of curvature of the spherical outer peripheral surface 22d of the inner joint member 22). Are offset by an equal distance on the opposite side in the axial direction with respect to the joint center O (s). In the illustrated example, the curvature center O _24b of the spherical surface portion 24b on the outer peripheral surface of the cage 24 is offset to the inboard side (joint back side) with respect to the joint center O (s), and the spherical surface on the inner peripheral surface of the cage 24 center of curvature _{O 24d} parts 24d is offset to the outboard side (joint opening side) with respect to the joint center O (s). As a result, the ball 23 held by the cage 24 is always disposed within the bisector of the operating angle at an arbitrary operating angle, and constant velocity between the outer joint member 21 and the inner joint member 22 is ensured. Secured.

  As shown in FIG. 4, the fixed type constant velocity universal joint 3 includes an outer joint member 31 attached to the wheel W (see FIG. 1) and an inner side attached to the outboard side end portion of the intermediate shaft 4 (see FIG. 2). A joint member 32, eight balls 33 that transmit torque between the outer joint member 31 and the inner joint member 22, and a cage 34 that holds the eight balls 33 are provided.

  The outer joint member 31 includes a cup-shaped mouth portion 31a having an opening in one axial direction {inboard side, right side in FIG. 4A} and the other axial end {outboard side, FIG. A) is integrally provided with a stem portion 31b extending to the left side}. On the spherical inner peripheral surface 31c of the mouse portion 31a, eight arc-shaped track grooves 31d extending in the axial direction are formed. Each track groove 31d extends to the opening side end face of the mouse portion 31a. That is, although a slight chamfered portion necessary for processing is provided between the track groove 31d of the outer joint member 31 and the opening side end surface of the mouth portion 31a, in order to incorporate the ball as in the conventional product. The necessary tapered surface K1 {see FIG. 5A} is not provided. Further, at the open end of the inner peripheral surface 31c of the outer joint member 31, a tapered surface K2 that abuts against the intermediate shaft and defines the maximum operating angle of the fixed type constant velocity universal joint {FIG. (A) Reference} is not provided. A spline 31e to be inserted into the spline hole on the wheel W side is provided on the outer peripheral surface of the stem portion 31b. In addition, the mouse | mouth part 31a and the stem part 31b may be joined by welding etc., after forming these separately in addition to integrally forming with the same material. Moreover, you may form the through-hole of an axial direction in the axial center of the mouse | mouth part 31a and the stem part 31b.

  A spline hole 32 c into which the intermediate shaft 4 is inserted is provided in the axial center of the inner joint member 32. On the spherical outer peripheral surface 32d of the inner joint member 32, eight arc-shaped track grooves 32e extending in the axial direction are provided. In other words, the inner joint member 32 integrally includes a cylindrical portion 32a having a spline hole 32c and a plurality of protruding portions 32b protruding from the cylindrical portion 32a to the outer diameter, and between the circumferential directions of the plurality of protruding portions 32b. A track groove 32e is provided. The outer diameter surfaces of the plurality of projecting portions 32 b become spherical outer peripheral surfaces 32 d of the inner joint member 32.

  Eight ball tracks are formed with the track grooves 31d of the outer joint member 31 and the track grooves 32e of the inner joint member 32 facing each other in the radial direction, and one ball 33 is disposed on each ball track. The cross-sectional shape of the track grooves 31d and 32e is an elliptical shape or a Gothic arch shape, whereby the track grooves 31d and 32e and the ball 33 are in contact with a so-called angular contact with a contact angle of about 30 to 45 °. Is done. The cross-sectional shape of the track grooves 31d and 32e may be an arc shape, and the track grooves 31d and 32e and the ball 33 may be so-called circular contacts.

And the curvature center _{O 31d} of the track grooves 31d of the outer joint member 31, the center of curvature _{O 32e} of the track grooves 32e of the inner joint member 32, and an equal distance in the axial direction opposite to the offset with respect to the joint center O (f) Yes. In the illustrated example, the center of curvature O _31d of the track groove 31d of the outer joint member 31 is offset to the inboard side (joint opening side) with respect to the joint center O (f), and the curvature of the track groove 32e of the inner joint member 32 is increased. The center O _32e is offset to the outboard side (the joint back side) with respect to the joint center O (f). As a result, the ball 33 held by the cage 34 is always arranged in the bisector of the operating angle at an arbitrary operating angle, and the constant velocity between the outer joint member 31 and the inner joint member 32 is ensured. Secured.

  The holder 34 has eight pockets 34 a for holding the balls 33. The eight pockets 34a all have the same shape and are arranged at equal intervals in the circumferential direction. The spherical outer peripheral surface 34 b of the cage 34 is in sliding contact with the spherical inner peripheral surface 31 c of the outer joint member 31. The spherical inner peripheral surface 34 c of the cage 34 is in sliding contact with the spherical outer peripheral surface 32 d of the inner joint member 32. Center of curvature of outer peripheral surface 34b of cage 34 (ie, center of curvature of spherical inner peripheral surface 31c of outer joint member 31) and center of curvature of inner peripheral surface 34c (ie, spherical outer peripheral surface of inner joint member 32) 32d curvature center) coincides with the joint center O (f).

  As the intermediate shaft 4, as shown in FIG. 2, a hollow shaft having an axial through hole 41 can be used. The intermediate shaft 4 includes a large diameter portion 42 provided at the center in the axial direction, a small diameter portion 43 provided at both ends in the axial direction, and a tapered portion 44 that continues the large diameter portion 42 and the small diameter portion 43. The small-diameter portion 43 of the intermediate shaft 4 is provided with an annular groove 45 and a spline 46 for boot mounting. The outer diameter of the small diameter portion 43 is constant except for the annular groove 45 and the spline 46. The intermediate shaft 4 is not limited to a hollow shaft, and a solid shaft can also be used.

  The spline 46 at the end on the inboard side of the intermediate shaft 4 is press-fitted into the spline hole 22 c of the inner joint member 22 of the sliding type constant velocity universal joint 2. Thereby, the intermediate shaft 4 and the inner joint member 22 are connected so as to be able to transmit torque by spline fitting. An annular groove is formed at the end of the intermediate shaft 4 on the inboard side, and a retaining ring 47 is attached to the groove. By engaging the retaining ring 47 from the inboard side (shaft end side) of the inner joint member 22, the intermediate shaft 4 and the inner joint member 22 are prevented from coming off.

  The spline 46 at the end on the outboard side of the intermediate shaft 4 is press-fitted into the spline hole 32 c of the inner joint member 32 of the fixed type constant velocity universal joint 3. Thereby, the intermediate shaft 4 and the inner joint member 32 are connected so as to be able to transmit torque by spline fitting. An annular groove is formed at the end of the intermediate shaft 4 on the outboard side, and a retaining ring 47 is attached to the groove. By engaging the retaining ring 47 from the outboard side (shaft end side) of the inner joint member 32, the intermediate shaft 4 and the inner joint member 32 are prevented from coming off.

  The above-mentioned sliding type constant velocity universal joint 2 and fixed type constant velocity universal joint 3 are exclusively used for the rear wheel drive shaft. Therefore, the maximum operating angle is smaller than that of the conventional product that can also be used for the front wheel drive shaft. Can be set. In this embodiment, the maximum operating angles of the sliding type constant velocity universal joint 2 and the fixed type constant velocity universal joint 3 are both set to 20 ° or less. Accordingly, it is possible to reduce the weight and size of the sliding type constant velocity universal joint 2 and the fixed type constant velocity universal joint 3 while maintaining the load capacity. Hereinafter, the internal specifications of the fixed type constant velocity universal joint 3 will be described in detail.

  The internal specifications of the fixed type constant velocity universal joint 3 according to the present invention are shown in the following Table 1, FIG. 5 and FIG. 6 as conventional products having the same ball diameter (eight ball zepper type constant velocity with a maximum operating angle of 47 °). It is shown in comparison with a universal joint. 5 and 6 are sectional views of the fixed type constant velocity universal joint 3 according to the present invention, and the lower half is a sectional view of the fixed type constant velocity universal joint 3 'according to the conventional product. is there. Each part of the conventional product is given a reference numeral with “′ (dash)” added to the part of the product of the present invention.

  The definition of each parameter is as follows.

(1) (pitch circle diameter of the _ball) ball PCD _{PCD BALL:} connecting the center of curvature center of the track groove 32e of the center of curvature of the track grooves 31d of the outer joint member 31 _{O 31d} or the inner joint member 32 _{O 32e} and the ball 33 The length of the line segment (the length of the line segment connecting the center of curvature O _31d of the track groove 31d of the outer joint member 31 and the center of the ball 33, and the center of curvature O _32e of the track groove 32e of the inner joint member 32 and the ball 33 It is equal to the length of the line segment connecting the center and this dimension is called PCR.) (PCD _BALL = 2 × PCR).
(2) Inner ring track length (axial length of track groove of inner joint member) W _{I · TRUCK} : Strictly speaking, it is an axial length of a contact locus between track groove 32e of inner joint member 32 and ball 33 However, in this specification, it refers to the axial length of the spherical outer peripheral surface 32d of the inner joint member 32, that is, the axial distance between the end surfaces extending from the both axial ends of the outer peripheral surface 32d to the inner diameter side.
(3) Inner ring width (axial width of the inner joint member) W _I : The maximum axial dimension of the inner joint member 32. In the illustrated example, the inner ring width is the axial distance between both end faces of the cylindrical portion 32a of the inner joint member 32. is there.
(4) Inner ring wall thickness (thickness in the radial direction of the inner joint member) T _I : groove bottom and spline hole of the track groove 32e in the joint center plane P {plane passing through the joint center O (f) and perpendicular to the axis} The radial distance from the pitch circle of 32c.
(5) Spline PCD (Pitch circle diameter of spline hole of inner joint member) PCD _SPL : The diameter of the meshing pitch circle between spline hole 32c of inner joint member 32 and spline 46 of intermediate shaft 4.
(6) Outer ring outer diameter D _O : The maximum outer diameter of the outer joint member 31.
(7) Joint center to outer ring opening end face length W1 _O : A distance in the axial direction between the joint center O (f) and the opening end face (end face on the inboard side) of the mouth portion 31a of the outer joint member 31.
(8) Cage thickness T _C : The radial thickness of the cage 34 on the joint center plane P.
(9) Cage width W _C : The maximum axial dimension of the cage 34, and in the illustrated example, the axial distance between both end faces of the cage 34.

  Hereinafter, the design philosophy that led to the above internal specifications will be described in detail.

In the fixed type constant velocity universal joint 3, the maximum load applied to each ball 33 increases as the operating angle increases. Therefore, the maximum load applied to each ball 33 decreases by reducing the maximum operating angle as described above. As a result, there is a margin in the strength of the inner joint member 32 in contact with the ball 33, so that the radial thickness of the inner joint member 32 can be reduced while maintaining the same durability as the conventional product {T _I <T _I ', see (4) in Table 1 above}. By reducing the thickness of the inner joint member 32 in this way, the pitch diameter of the track grooves 32e of the inner joint member 32, that is, the balls 33 arranged in the track grooves 32e, without reducing the load capacity and durability. The pitch circle diameter can be made smaller than before (PCD _BALL <PCD _BALL ', see (1) in Table 1 above). Thereby, the fixed type constant velocity universal joint 3 can be made compact in the radial direction, and light weight can be achieved.

By reducing the maximum operating angle of the fixed type constant velocity universal joint 3, the maximum load applied to each ball 33 is reduced, and there is a margin in the strength of the cage 34 in contact with the ball 33. while maintaining the gender, radius thickness direction can be reduced to the retainer _{34 {T C <T C '} , in table 1 (8) see}. Further, the locus C of the contact between the pocket surface S of the cage of the present invention product (maximum operating angle 20 °) shown in FIG. 9A and the ball and the conventional product shown in FIG. 9B (maximum operating angle 47). As is clear from the pocket surface S ′ of the cage and the locus C ′ of the contact point between the balls, the inside of the pocket 34a of the cage 34 can be reduced by reducing the maximum operating angle of the fixed type constant velocity universal joint 3. The movement amount of the ball 33 in the radial direction (vertical direction in FIG. 9) becomes small. Also from this viewpoint, the thickness of the cage 34 in the radial direction can be reduced. As described above, while the wall thickness _{T C} of the cage 34, by decreasing the pitch circle diameter _{PCD BALL} of the ball 33, the track grooves 31d, the depth of the 32e of the outer joint member 31 and the inner joint member 32 The fixed type constant velocity universal joint 3 can be reduced in weight and size while securing the ball 33 to prevent the ball 33 from climbing onto the track groove edge.

FIG. 7 shows a state in which the fixed type constant velocity universal joint 3 according to the present invention has a maximum operating angle (20 °), and FIG. 8 shows a state in which the fixed type constant velocity universal joint 3 ′ according to the conventional product has a maximum operation. The state where the angle (47 °) is taken is shown. As is apparent from these drawings, the length of the contact locus L1 between the track groove 32e of the inner joint member 32 and the ball 33 in the product of the present invention is the length of the track groove 32e 'and ball 33 of the inner joint member 32' in the conventional product. It is shorter than the length of the contact locus L1 with “. Thus, by reducing the maximum operating angle of the fixed type constant velocity universal joint 3, the amount of movement of the ball 33 in the axial direction is reduced, so that the axial length of the track groove 32 e of the inner joint member 32 is shortened. {W _{I · TRUCK} <W _{I · TRUCK} ', see (1) in Table 1 above}. Thereby, the inner joint member 32 can be made compact in the axial direction to reduce the weight.

Further, as shown in FIGS. 7 and 8, the length of the contact locus L2 between the track groove 31d of the outer joint member 31 and the ball 33 in the product of the present invention is the track groove 31d ′ of the outer joint member 31 ′ in the conventional product. And the length of the contact locus L2 ′ between the ball 33 ′ and the ball 33 ′. Thus, since the axial movement amount of the ball 33 with respect to the outer joint member 31 is shortened by reducing the maximum operating angle of the fixed type constant velocity universal joint 3, the axial length of the track groove 31d of the outer joint member 31 is shortened. In particular, the axial length of the opening side portion from the joint center O (f) of the track groove 31d, specifically, from the joint center O (f) to the opening side end surface of the mouth portion 31a of the outer joint member 31. Can be shortened {W1 _O <W1 _O ', see (7) in Table 1 above}. Thereby, the outer joint member 31 can be made compact in the axial direction to reduce the weight.

By reducing the maximum operating angle of the fixed type constant velocity universal joint 3, there is a margin in the strength of the cage 34 as described above, so that the axial direction of the cage 34 is maintained while maintaining the same durability as the conventional product. The width can be reduced {W _C <W _C ', see (9) above}. Thereby, it is possible to reduce the weight by reducing the size of the cage 34 in the axial direction.

By reducing the maximum operating angle of the fixed type constant velocity universal joint 3, it is possible to reduce the radial thickness T _I of the inner joint member 32 as described above, the spline hole 32c of the inner joint member 32 large The diameter can be increased {PCD _SPL > PCD _SPL ', see (5) in Table 1 above}. Thereby, the diameter of the intermediate shaft 4 (see FIG. 2) inserted into the spline hole 32c can be increased, and the torsional strength can be increased. Moreover, since the pitch circle diameter of the ball | bowl 33 can be reduced as mentioned above by making the maximum operating angle of the fixed type constant velocity universal joint 3 small, the diameter of the outer joint member 31 can be reduced. As described above, in the product of the present invention, the ratio D _O / PCD _SPL between the outer diameter D _O of the outer joint member 31 and the pitch circle diameter PCD _SPL of the spline hole 32c of the inner joint member 32 can be made smaller than that of the conventional product. Yes {D _O / PCD _SPL <D _O '/ PCD _SPL ', see (1) in Table 1 above}. Thereby, the lightweight and compact size of the fixed type constant velocity universal joint 3 and the strength improvement of the intermediate shaft 4 can be achieved simultaneously.

Further, by increasing the diameter of the spline hole 32c of the inner joint member 32 as described above, the pitch circle of the fitting portion between the spline hole 32c of the inner joint member 32 and the spline 46 (see FIG. 2) of the intermediate shaft 4 is increased. Since the diameter is increased, the surface pressure at the contact portion between the spline teeth is reduced. Thereby, since the axial direction length of the spline hole 32c of the inner joint member 32 can be shortened while maintaining the surface pressure per spline tooth, the axial width of the cylindrical portion 32a of the inner joint member 32 can be reduced. It can be shortened. Thus, not only to shorten the axial length of the track grooves 32e of the inner joint member 32, by shortening the axial length of the spline hole 32c, and the axial width W _I of the entire inner joint member 32 It can be shortened {W _I <W _I ', see (3) in Table 1 above}.

As described above, by reducing the maximum operating angle of the fixed type constant velocity universal joint 3, the axial length of the track groove 32 e of the inner joint member 32 can be shortened. In this embodiment, as shown in FIG. 10, the axial length W _{I · TRUCK} of the track groove 32 e (see FIG. 6) of the inner joint member 32 (that is, from both axial ends of the outer peripheral surface 32 d of the inner joint member 32). The axial distance between the end faces extending to the inner diameter side) is made shorter than the circumferential length L _P of the pocket 34a of the cage 34 (specifically, the distance between the wall surfaces facing the circumferential direction of the pocket 34a). (W _{I · TRUCK} <L _P ). As a result, when the inner joint member 32 is incorporated into the inner periphery of the cage 34, the inner joint member 32 is placed in a state where the axis of the cage 34 and the axis of the inner joint member 32 are orthogonal to each other as shown in FIG. 11. The protrusion 32b can be inserted into the pocket 34a of the cage 34 from the inner diameter side. In this case, the inner joint member 32 can be incorporated in the inner periphery of the retainer 34 while avoiding interference with the retainer 34 even when the radial thickness of the retainer 34 is substantially uniform throughout the entire axial direction. it can. Therefore, since it is not necessary to form a thin portion for incorporating the inner joint member 32 at the axial end of the cage 34, the strength of the cage 34 can be ensured.

In the present embodiment, as shown in FIG. 6, the axial length WI _{· TRUCK} of the track groove 32 e of the inner joint member 32 is equal to the axial width of the cylindrical portion 32 a of the inner joint member 32 (= inner joint member). Less than 32 axial widths W _I ). This enables the method of assembling the inner joint member 32 and the retainer 34 as shown in FIG. 11 while ensuring the thickness of the retainer 34, while reducing the axial length of the spline hole 32c formed in the cylindrical portion 32a. Can be secured.

  As described above, the present invention considers various conditions obtained by reducing the maximum operating angle of the constant velocity universal joint, and by examining the internal specifications of the constant velocity universal joint, it is equivalent to the conventional product. The constant velocity universal joint is lighter and more compact while maintaining torque load capacity. This makes it possible to build a new series of lightweight and compact fixed constant velocity universal joints that can be used exclusively for the rear wheel drive shaft.

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

DESCRIPTION OF SYMBOLS 1 Rear wheel drive shaft 2 Sliding type constant velocity universal joint 21 Outer joint member 22 Inner joint member 23 Ball 24 Cage 3 Fixed type constant velocity universal joint 31 Outer joint member 31d Track groove 32 Inner joint member 32c Spline hole 32e Track Groove 33 Ball 34 Cage 34a Pocket 4 Intermediate shaft E Engine M Transmission PS Propeller shaft G Differential gear W Wheel

Claims (5)

A fixed type constant velocity universal joint used for a drive shaft for a rear wheel,
An outer joint member in which eight track grooves extending in the axial direction are formed on the spherical inner peripheral surface, and eight track grooves extending in the axial direction are formed in the spherical outer peripheral surface, and a spline hole is formed in the shaft center. 8 balls disposed in a ball track formed by the formed inner joint member, the track groove of the outer joint member and the track groove of the inner joint member, and eight pockets for receiving the balls. A retainer that slidably contacts the inner peripheral surface of the outer joint member and the outer peripheral surface of the inner joint member;
The center of curvature of the track groove of the outer joint member and the center of curvature of the track groove of the inner joint member are offset by an equal distance on the opposite side in the axial direction with respect to the joint center, respectively.
A ratio PCD _BALL / D _BALL between the pitch circle diameter PCD _BALL of the ball and the diameter D _{BALL of the} ball is 3.70 to 3.87,
A fixed type constant velocity universal joint in which a ratio W _{I · TRUCK} / D _BALL of the axial length W _{I · TRUCK of the} inner joint member to the diameter D _{BALL of the} ball is 1.1 to 1.3. The fixed type constant velocity universal joint according to claim 1, wherein a ratio W _C / D _BALL between an axial width W _C of the cage and a diameter D _{BALL of the} ball is 1.63 to 1.80. The fixed constant velocity universal joint according to claim 1 or 2, wherein a ratio W _I / D _BALL between the axial width W _I of the inner joint member and the diameter D _{BALL of the} ball is 1.40 to 1.55. The axial length W _{I · TRUCK} track grooves of the inner joint member, fixed type according to any one of smaller claims 1-3 than the circumferential length L _P of the respective pockets of the cage Fast universal joint. The fixed type constant velocity universal joint according to any one of claims 1 to 4, wherein the maximum operating angle is 20 ° or less.

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