| 摘要 |
PROBLEM TO BE SOLVED: To provide a piston pump capable of preventing generation of negative pressure around a slide surface of a valve plate in inflow of high pressure working fluid from a discharge port of the valve plate to a cylinder port of a cylinder block. SOLUTION: In a piston pump provided with a piston 8 to suck and discharge working fluid and a valve plate 5 having a suction port and a discharge port contained in each cylinder 7 of a cylinder block 6, and comprising a notch extended from an end part of the discharge port toward the suction port in a slide surface 5D of the valve plate 5 around a lower dead center of the piston 8, a cylinder port 7A in an end surface 6A of the cylinder block 6, and a groove part in a tip part of a cylinder port 7A, the groove part is formed in a semi-arc form, each of end parts forming the semi-arc form is connected to an inner wall of the cylinder port 7A, and a bottom part of the groove part is formed to be roughly parallel to the slide surface 5D of the valve plate 5.
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