Tripod type constant velocity universal joint

A tripod type constant velocity universal joint comprising:

• an outer joint member including track grooves, which extend in an axial direction, at three locations in a circumferential direction, each of the track grooves having a pair of roller guide surfaces arranged to face each other in the circumferential direction;
• a tripod member including a body portion having a central hole, three leg shafts protruding in a radial direction of the body portion, and an intermediate portion located between the body portion and the leg shafts and having a longitudinal cross section formed in an arc shape, the tripod member having a spline formed in the central hole of the body portion;
• a roller mounted on each of the leg shafts;
• and
• an inner ring that is externally fitted to each of the leg shafts and rotatably supports the roller,
• wherein a step is provided between the intermediate portion and each of the leg shafts, the step being reduced in diameter from the intermediate portion toward a radial direction of the leg shaft and connected to an outer peripheral surface of the leg shaft,
• wherein the roller is movable in the axial direction of the outer joint member along the roller guide surfaces,
• the roller and the inner ring form a roller unit, the roller unit being swingable with respect to each of the leg shafts,
• the tripod member has a carbon content of 0.23% to 0.44% at a core portion, and a hardened layer is provided on a surface of each of the leg shafts by carburizing, hardening, and tempering, and
• 0.0850≤R/PCD≤0.20 and t/PCD≥0.145, where PCD is a pitch circle diameter of the roller guide surfaces of the outer joint member, R is a radius of curvature at the intermediate portion of the tripod member, and t is a minimum distance from a large-diameter portion of the spline of the tripod member to the intermediate portion.