| 摘要 |
PURPOSE:To reduce a load in the driving system of an oil pump, by changing relief pressure in accordance with a pressure drop in a throttle of a valve casing. CONSTITUTION:When an oil pump is rotated at a low speed, a small pressure drop in a throttle 26 of the pump causes a small difference between pressures in an upstream pressure chamber 31 and downstream pressure chamber 32, and relief pressure in such case is substantially determined by only the spring constant of a valve spring 18 pressing a relief valve 15 to a valve seat of a back pressure chamber side port 28. If a rotary speed of the oil pump is increased, an oil return control spool 12 is gradually slid against a valve spring 33 while a pressure drop in the throttle 26 is increased almost in proportion to the speed of the oil pump, and pressure in the chamber 31 is gradually increased larger than pressure in the chamber 32. |
