SLIDING-TYPE CONSTANT VELOCITY UNIVERSAL JOINT FOR REAR-WHEEL DRIVE SHAFT
FIG5A is a longitudinal sectional view (sectional view taken along the line Y-Y of FIG5B) for illustrating a fixed type constant velocity universal joint incorporated into the above-mentioned rear-wheel drive shaft
The outer joint member 31 integrally comprises a mouth section 31a and a stem section 31b. The mouth section 31a has a cup shape that is open toward one side in an axial direction of the joint (inboard side or right side in FIG5A). The stem section 31b extends from a bottom portion of the mouth section 31a to another side in the axial direction (outboard side or left side in FIG5A). Eight arc-shaped track grooves 31d extending in the axial direction are formed in a spherical inner peripheral surface 31c of the mouth section 31a. A spline 31e to be inserted into a spline hole on the wheel W side is formed in an outer peripheral surface of the stem section 31b. The mouth section 31a and the stem section 31b may be integrally made of the same material, or may be joined to each other by, for example, welding after the mouth section 31a and the stem section 31b are formed into separate sections . Further, a through hole extending in the axial direction may be formed along the axial centers of the mouth section 31a and the stem section 31b.
longitudinal sectional view
3
34
cage
33
balls
31
outer joint member
32
['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.']