PURPOSE: To increase the strength of a slider pin by increasing the diameter of a root part in comparison with that at the top edge part of the slider pin and rotatably supporting a slider by the small diameter part at the top edge and setting the large diameter part in eccentric form for the top edge part.

CONSTITUTION: A slider 10 is guided in slidable ways on the sliding surface 8b of a vane 8, and supported in rotatable ways by the small diameter part 11a at the top edge of a slider pin 11. The axis center of the small diameter part 11a at the top edge of the slider pin 11 is separated by a prescribed distance for the axis center of a rotor shaft 1, and the eccentricity part 11b of the large diameter part at the root part is set eccentric in the direction close to the rotor shaft 1 in comparison with the small diameter part 11a. Therefore, the max. stress generated by the bending moment can be reduced.