seat 59 engaged with the input shaft 2 a stopper plate 60 is engaged with that portion of the input shaft 2 which is projected from the left end surface of the pump cylinder 4 the stopper plate 60 being opposed to the inner end surface of the motor cylinder 8 needle thrust bearings 61 are provided between the opposed surfaces of the stopper plate 60 and motor cylinder 8 thus the resilient force of the spring 57 serves to urge the pump cylinder 4 against the distribution plate d via the seat 58 so that the opposed surfaces of the pump cylinder 4 seat 58 and distribution plate d can be brought into close contact with one another the reaction force of the resilient force of the spring 57 is transmitted to and supported by the motor cylinder 8 via the seat 59 input shaft 2 stopper plate 60 and needle thrust bearings 61 the pump cylinder 4 is supported at the outer circumferential surface thereof on the inner circumferential surface of the annular portion i e the second section 8b of the motor cylinder 8 via a needle bearing 77 to allow the pump cylinder 4 to be held concentric with the motor cylinder 8 it is effective to provide a suitable clearance in the spline connected portion 3 of the input shaft 2 and pump cylinder 4 for the purpose.