PURPOSE: To prevent the repeated action of a load upon a drive shaft and a pump vane side bearing by providing a telescopic elastic material in a gap between the pump vane side bearing and a bearing case.

CONSTITUTION: At a given time when a prime mover 2 causes the rotation of a drive shaft about an x-axis, this drive shaft 3 rotates abut a y-axis and a z-axis by a fine angle θ with the center point A of a self-aligning bearing 7 as the center of rotation, due to a force (f) from a pump vane 4. In this case, an elastic material 12 positioned between pump vane side bearing 8 and a bearing case 10 expands and contracts. The center point B of the bearing 8, therefore, rotates by the fine angle θ with the center point A of the self-aligning bearing 7 as the center of rotation. Consequently, the center of the pump vane side bearing 8 comes to the aforesaid center point C. Namely, the pump vane side bearing 8 follows the rotary motion of the drive axis 3 about the y-axis and z-axis with the center point A of the self-aligning bearing 7 as the center of rotation. As a result, a pump bearing 3 is no bent even when exposed to the force (f) and a good rotational condition can be obtained.