SLIDING-TYPE CONSTANT VELOCITY UNIVERSAL JOINT FOR REAR-WHEEL DRIVE SHAFT
FIG3A is a longitudinal sectional view (sectional view taken along the line X-X of FIG3B) for illustrating a plunging type constant velocity universal joint incorporated into the above-mentioned rear-wheel drive shaft
The outer joint member 21 integrally comprises a mouth section 21a and a stem section 21b. The mouth section 21a has a cup shape that is open toward one side in an axial direction of the joint (outboard side or left side in FIG3A). The stem section 21b extends from a bottom portion of the mouth section 21a to another side in the axial direction (inboard side or right side in FIG3A). Eight linear track grooves 21d extending in the axial direction are formed in a cylindrical inner peripheral surface 21c of the mouth section 21a. A spline 21e to be inserted into a spline hole of the differential gear G is formed in an outer peripheral surface of an inboard-side end portion of the stem section 21b. The mouth section 21a and the stem section 21b may be integrally made of the same material, or may be joined to each other by, for example, welding after the mouth section 21a and the stem section 21b are formed into separate sections.
longitudinal sectional view
21
outer joint member
24
cage
23
balls ball
22
member
['1. A plunging type constant velocity universal joint for a rear-wheel drive shaft, comprising: an outer joint member having a cylindrical inner peripheral surface in which eight track grooves extending in an axial direction of the plunging type constant velocity universal joint are formed; an inner joint member having a spherical outer peripheral surface in which eight track grooves extending in the axial direction are formed, and having a spline hole formed along an axial center of the inner joint member; eight balls arranged in ball tracks formed by the track grooves of the outer joint member and the track grooves of the inner joint member; and a cage, which has eight pockets configured to receive the balls, and is held in slide contact with the inner peripheral surface of the outer joint member and the outer peripheral surface of the inner joint member, wherein a curvature center of a spherical portion formed on an outer peripheral surface of the cage and a curvature center of a spherical portion formed on an inner peripheral surface of the cage are offset to opposite sides in the axial direction with respect to a joint center by an equal distance, wherein a ratio PCD BALL /D BALL  of a pitch circle diameter PCD BALL  of the balls to a diameter D BALL  of each of the balls is set from 3.3 to 3.6, and wherein a ratio T I /D BALL  of a radial thickness T I  of the inner joint member to the diameter D BALL  of each of the balls is set from 0.30 to 0.']