| 摘要 |
PURPOSE:To economize the consumed energy by half reducing the discharge flow-rate characteristic of a vane pump by permitting the bypass of working fluid through a capacity selector valve without generating pressure loss when the pressure necessary for the hydraulic operating apparatus such as power steering apparatus is low. CONSTITUTION:When, in a power steering apparatus, a handle is not operated and the load pressure of a hydraulic operating apparatus 57 is lower than a prescribed pressure, also each pressure in the first discharge passage 50 and the first chamber 23 of a capacity switching valve 20 is below a prescribed pressure, and a spool 21 is advanced rightward by a spring 22, and the ports 27 and 28 are allowed to communicate through the second chamber 24. Therefore, the working fluid supplied from the discharge port OP2 of a vane pump 10 passes through the second discharge passage 51, port 27, second chamber 24, port 28, return passage 52, and a suction passage 53a, and is introduced into the suction ports IP1 and IP2 through bypass without generating pressure loss. Therefore, the discharge flow-rate characteristic of the vane pump 10 becomes half in comparison with the conventional, and the consumption energy can be reduced half. |
