HYDRAULIC ROTATING MACHINE

摘要

PROBLEM TO BE SOLVED: To prevent noise of a detection signal of a line sensor so as to improve reliability by suitably setting dimensions of a recessed part to be detected provided in a cylinder block. SOLUTION: A plurality of recessed parts 15 to be detected are provided at spaces in the circumferential direction on the outer peripheral surface 6A of the cylinder block 6. When the cylinder block 6 is rotated, the recessed part 15 to be detected is detected by an electromagnetic pickup rotation sensor 14 to output a detection signal S, and the rotational frequency of the cylinder block 6 is measured. The circumferential dimensionθ1 of the recessed part 15 to be detected is made larger than the circumferential dimensionθ2 of a projecting part 16 positioned between the respective recessed parts 15 to be detected. Thus, the circumferential dimensionθ2 of the projecting part 16 liable to cause noise in a detection signals when it faces to the rotation sensor 14 can be made smaller so that the rotational frequency of the cylinder block 6 can be detected with high accuracy by simple structure.