Patent ID: 6186748
Filing Date: 2001-02-13
Classification: F04B

Abstract:
An axial piston pump comprising a plurality of pistons, a cylinder block provided with a plurality of piston chambers in which the pistons slide, a valving element having a suction port and a discharge port formed therein, and a casing accommodating the cylinder block,the axial piston pump causing the pistons to reciprocate while relatively rotating the cylinder block with respect to the valving element, thereby receiving a fluid from the suction port into the piston chamber and discharging the fluid to the discharge port, the axial piston pump comprising:a first opening portion formed in the valving element connected to the discharge port configured for making a pressure fluctuation curve of each of the piston chambers smooth in an early stage of a pressure rise process, a second opening portion formed in the valving element to be connected to at least one of the suction port and an inside of the casing, for making the pressure fluctuation curve of the piston chamber smooth in an early stage of a pressure drop process, a first bypass port formed in the valving element communicating with at least one of the suction port and the inside of the casing, and a second bypass port formed in the valving element communicating with the discharge port, whereinan opening of the first bypass port is positioned so as to start overlapping with an opening of the piston chamber before a pressure of the piston chamber reaches that of the discharge port after the opening of the piston chamber starts to overlap with the first opening portion,an opening of the second bypass port is positioned at such a place as to start overlapping with an opening of the piston chamber before a pressure of the piston chamber reaches that of the suction port after the opening of the piston chamber starts to overlap with the second opening portion,an opening of one of the piston chambers starts overlapping with the second opening portion when a pressure of another piston chamber substantially reaches that of the discharge port, andan opening of one of the piston chambers starts overlapping with the first opening portion when a pressure of another piston chamber substantially reaches that of the suction port.