To make the interior space of a housing side mounting member large to widen thus the degree of freedom of layout when providing a damper mechanism and the other members in the inside of the housing side mounting member.

Rotation energizing means 20 rotationally energizing first and second links 3, 4 is constituted of a compression coil spring 21, a receiving shaft 22 holding one end of the compression coil spring 21, and a spring receiver 23 holding the other end of the compression coil spring 21. The receiving shaft 22 is fitted into a bearing hole 3a of the first link 3 so as to be rotatable and not to be movable in its radial direction. The spring receiver 23 is inseparably engaged with a recess 24 of the second link 4 by an energizing force of the compression coil spring 21. The receiving shaft 22 and the spring receiver 23 are engaged with the first and second links, respectively, thereby holding the rotation energizing means 20 only by the first and second links 3, 4.