| 摘要 |
PURPOSE:To prevent flow from return in pressure operation of a power steering apparatus by closing controllably one of two throttle paths arranged in parallel according to the rise of rotational frequency of a pump irrespective of displacement of a spool valve for adjusting flow. CONSTITUTION:When a pump rotor is rotated by an engine, pressurized oil is supplied from a pressure chamber 16 to a power steering apparatus 24 through a supply path 14, first and second throttle paths 26, 29 and an exhaust port 23. When the rotational speed of the pump is low, a spool valve 17 closes a bypass path 15 with low discharge amount to send total amount of pressurized oil to the apparatus 24. Next, when the discharge flow increases as the rotational frequency of the pump rises, the spool valve 17 slides to maintain differential pressure before and after the throttle paths 26, 29 at a constant value and thereby open the bypass path 15. Further increase of the discharge flow of the pump displaces a control spool 35 according to the differential pressure between the chambers 16, 18 to close the throttle path 29. |
