Plunging type constant velocity universal joint

A plunging type constant velocity universal joint, comprising:

• an outer joint member comprising a cylindrical inner peripheral surface having six linear track grooves extending along an axial direction;
• an inner joint member comprising a spherical outer peripheral surface having six linear track grooves being opposed to the linear track grooves of the outer joint member and extending along the axial direction, the inner joint member having a coupling hole at a center portion thereof for coupling a shaft;
• six torque transmission balls incorporated between the linear track grooves of the outer joint member and the linear track grooves of the inner joint member;
• and
• a cage, which is configured to retain the torque transmission balls, and comprises a spherical outer peripheral surface and a spherical inner peripheral surface, which are guided in contact with the cylindrical inner peripheral surface of the outer joint member and the spherical outer peripheral surface of the inner joint member, respectively,
• wherein a curvature center of the spherical outer peripheral surface and a curvature center of the spherical inner peripheral surface of the cage are offset toward opposite sides in the axial direction with respect to a joint center,
• wherein the plunging type constant velocity universal joint is used at a normal operating angle of from 8° to 12°,
• wherein a ratio DBALL/DSPCD of a diameter (DBALL) of the torque transmission ball to a spline pitch circle diameter (DSPCD) of the coupling hole of the inner joint member is set within a range of from 0.80 to 0.86,
• wherein a contact angle (α) of the torque transmission ball and the linear track groove is set within a range of from 32° to 35°,
• wherein a contact ratio (ψ) of the torque transmission ball and the linear track groove is set within a range of from 1.05 to 1.08, and
• wherein a ratio DTPCD/DSPCD of a pitch circle diameter (DTPCD) of the torque transmission balls to the spline pitch circle diameter (DSPCD) is set within a range of from 2.25 to 2.40.