Patent ID: 7695372

Claim:
A yoke for a universal joint, the yoke being formed by punching out sheet metal and press forming the sheet metal, comprising: a cylindrical base for fixing a shaft, an end of the cylindrical base being formed with a first relief portion including a concave curved surface; and a pair of arms extending from an end of the cylindrical base in parallel to a center axis of the cylindrical base and swingably connectable with a counterpart yoke via a cross shaft, each of the arms being formed with a support hole for supporting a corresponding trunnion of the cross shaft via a bearing, each of the support holes having a center axis extending in a direction orthogonal to the center axis of the cylindrical base, each of the pair of arms including an edge portion having an inverted-U shape and a pair of side edges extending in parallel to the center axis of the base, each of the side edges including a second relief portion, a width of the second relief portion progressively decreasing toward the center axis of the cylindrical base in a direction orthogonal to the center axis of the base and to the center axis of the support hole, and each of the second relief portions including a flat plane defining a parallelogram, the flat plane intersecting with the corresponding side edge of the corresponding arm on first and second intersections extending in parallel to the center axis of the base, the first intersection being relatively closer to the center axis of the base and the second intersection being relatively farther from the center axis of the base, and the first intersection being relatively farther from the center of the joint than the second intersection, with respect to a direction parallel to the center axis of the base, wherein the concave curved surface has a center of curvature offset from a center of the joint toward a distal end of the arms.