| 摘要 |
Provided is a power transmission shaft (12), including: a male spline (19) formed in an outer periphery thereof; and a diameter increasing portion (23) formed on a part of a tooth bottom (19b) of the male spline (19), which is located on an opposite side to an axial end of the power transmission shaft (12), by gradually increasing an outer diameter dimension of the tooth bottom (19b). The tooth bottom (19b) of the male spline (19) has a substantially constant circumferential width (c) extending up to an axial region of the diameter increasing portion (23). The diameter increasing portion (23) includes a chamfered portion (25) formed in the axial region of the diameter increasing portion (23), the chamfered portion (25) connecting the tooth bottom (19b) and a tooth flank (19a) of the male spline (19) to each other to reduce a tooth groove width (d). The tooth bottom (19b), the tooth flank (19a), and the chamfered portion (25) each have a press-formed surface. The power transmission shaft (12) satisfies a relationship of C>D, where C represents an axial dimension between a diameter increase start position (P1)and a tooth groove width reduction start position (P2) of the male spline (19), and D represents an axial dimension between the tooth groove width reduction start position (P2) and a diameter increase finish position (P3) of the male spline (19). |
