| 摘要 |
PROBLEM TO BE SOLVED: To prevent the generation of negative pressure in the vicinity of the sliding surface of a valve plate when hydraulic oil flows from the discharge port of the valve plate into a cylinder port. SOLUTION: A piston pump is provided with a piston 8 housed in the cylinder 7 of a cylinder block 6 for sucking and discharging hydraulic oil, and a valve plate 5 having suction and discharge ports. In the sliding surface 5D of the valve plate 5 in the vicinity of the lower dead point of the piston 8, a notch is provided to extend from the end part of the discharge port to the suction port, a cylinder port 7A is provided in the end surface 6A of the cylinder block 6 so as to be selectively communicated with any of the suction and discharge ports of the valve plate 5, the valve plate 5 is provided to penetrate between the end part of the suction port thereof in the vicinity of the lower dead point of the piston 8 and the notch, and an oil guiding hole is provided to guide a part of oil flowing out of the notch. Further, in a rear casing 3, a groove part 3A is provided to guide the oil guided by the oil guiding hole into a low pressure casing main body 2.
|
