To provide a variable displacement rotary pump which prevents the occurrence of oil impulse when being switched from high capacity operation to low capacity operation.
A spool valve 55 of a solenoid pilot valve moves forward through energization to communicate an annular groove 56 to a through-hole 61. An inner space 50 of a bypass valve element 44 is brought into a low pressure state by forcing oil to flow out of a suction pressure communication passage 58 to a bypass passage 32. The bypass valve element 44 is moved backward by oil in a discharge passage 28 to open the bypass passage 32 and force oil to start flowing. At the same time, a valve element 35 of a check valve 33 moves in a direction of closing the discharge passage 28. Oil flowing through the bypass passage 32 is limited to a flow rate set by a throttle passage 49 to suppress rapid increase in the flow rate so that backflow of oil discharged from a main pump is controlled. The flow of oil in the bypass passage 32 is controlled until the check valve 33 closes the discharge passage 28 by the throttle passage 49, thereby preventing the occurrence of oil impulse.
SUZUKI SHIGERU
YAMASHITA KATSUMI
FUJII TOSHIRO
| JPS63105288A | 1988-05-10 |