Power transmission shaft

A power transmission shaft interposed between a first shaft section and a second shaft section, the first shaft section and the second shaft section being a pair of vehicle side rotational shaft sections, the first shaft section being disposed on a driving source side of the vehicle and the second shaft section being disposed on a driving wheel side, the power transmission shaft transmitting a rotation of the driving source to the driving wheel and comprising:

• a shaft section disposed between the first shaft section and the second shaft section;
• a cylindrical section rotated integrally with the shaft section and formed cylindrically, each of the pair of vehicle side rotational shaft sections being inserted into an inside of the cylindrical section and into an inner peripheral side of which a male spline section disposed on an outer peripheral side of a tip section of the vehicle side rotational shaft is inserted;
• a through hole penetrated through part of the cylindrical section in a peripheral directional range, the through hole placed at a location of the vehicle side rotational shaft that is closer to a withdrawal side of the vehicle side rotational shaft than the male spline section in a state in which the male spline section is inserted into the inner peripheral side of the cylindrical section, and the through hole aligned with an engagement stop groove disposed in a radial direction, the engagement stop groove being disposed in the outer peripheral side of the vehicle side rotational shaft at a location at which the male spline section is not disposed;
• and
• a circlip disposed to be engaged on at least a portion of the outer peripheral side of the cylindrical section and to enclose at least a portion of the outer peripheral side of the cylindrical section including the engaged portion, a portion of the circlip being inserted into the through hole from the outer peripheral side of the cylindrical section and being engaged on the engagement stop groove, the engagement stop groove including:
• a bottom surface;
• and a pair of rising surfaces disposed on both sides of the bottom surface in the direction of the rotational center axial line, one of the pair of rising surfaces in a direction opposite to the withdrawal direction of the vehicle side rotational shaft having an angle at the engagement stop groove side from among angles formed by the rising surface and the rotational shaft axial center axial line being larger than 90° but smaller than 180° and the whole of the engagement stop groove from the bottom surface of the engagement stop groove to an opening edge of the engagement stop groove being formed in a gradient shape.