Shaft-and-yoke coupling structure and vehicle steering system

摘要

Provided is a shaft-and-yoke coupling structure (P) for coupling a steering transmission shaft (5) and a yoke (41) of a universal joint (4). An end portion (5a) of the steering transmission shaft (5) joined to the yoke (41) has a stepped portion (51) and an insertion convex portion (52) protruding from the stepped portion (51) in the axial direction (X1) of the steering transmission shaft (5). The yoke (41) has an annular receiving portion (53) facing and fixed to the stepped portion (51) via a welded portion (55) and an insertion recess portion (54) surrounded by the receiving portion (53) in which the insertion convex portion (52) is inserted. The insertion convex portion (52) and the insertion recess portion (54) are arranged to be engaged with each other with a predetermined amount of play (Q1) in the direction of rotation when the welded portion (55) is broken.