Axial piston pump

An axial piston pump comprising a swash plate, 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 according to an inclination of the swash plate while relatively rotating the cylinder block with respect to the valving element, thereby receiving a fluid from the suction port into the piston chambers 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 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 the suction port or the inside of the casing, and a second bypass port formed in the valving element communicating with the discharge port, wherein
• an 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 so 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, and
• an 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.

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 chambers 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 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 the suction port or the inside of the casing, and a second bypass port formed on the valving element communicating with the discharge port, wherein
• during rotation of the cylinder block an opening of each piston chamber overlaps with the first opening portion, an opening of the first bypass port, the second opening portion and an opening of the second bypass port in such a manner that pressure fluctuation curves in the pressure rise process and the pressure drop process of the piston chambers substantially follow a sine-wave curves in all the piston chambers.

An axial piston pump comprising a swash plate, 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 according to an inclination of the swash plate while relatively rotating the cylinder block with respect to the valving element, thereby receiving a fluid from the suction port into the piston chambers and discharging the fluid to the discharge port, the axial piston pump comprising:
• a first opening portion formed in the valving element to be connected to the discharge port 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, making the pressure fluctuation curve of the piston chamber smooth in an early stage of a pressure drop process, a first bypass port formed on the valving element communicating with at least one of the suction ports and the inside of the casing, and a second bypass port formed on the valving element communicating with the discharge port, wherein
• during rotation of the cylinder block an opening of the piston chamber overlaps with the first opening portion, an opening of the first bypass port, the second opening portion and an opening of the second bypass port in such a manner that the pressure fluctuation curves in the pressure rise process and the pressure drop process of the piston chambers substantially make a sine-wave curve in all the piston chambers.