| 摘要 |
<p>A pre-tensioner unit provided to a retractor comprises: a pinion gear capable of rotating in association with the operation of a winding drum; a piston having a rack meshing with the pinion gear and rotating the winding drum through the pinion gear in the direction in which webbing is wound up; a tube-shaped cylinder for housing the piston and having a circular cross-section; a gas generation member for filling gas into an inner space formed by the piston and the inner wall of a pipe cylinder and driving the piston by the pressure of the gas; and a plate-shaped seal member (163) attached to the piston and sealing between the piston and the inner wall of the cylinder. The seal member (163) has a protrusion (631) engaged in an engagement groove formed in the piston. The cross-sectional shape of both the engagement groove and the protrusion (631), taken in the direction perpendicular to the direction of the engagement, is a polygon.</p> |
