| 摘要 |
PURPOSE:To prevent the increase of an abnormal pressure at the time of a low temperature by a method wherein two relief valves having different set pressures from each other are provided, and at the time of a low temperature at which viscosity of oil is high, a pressure is escaped by means of a relief valve actuated in response to an increase in a pressure in the front of a throttle passage. CONSTITUTION:When a pressure at the rear of a throttle passage 25 is increased along with operation of a power steering device, the pressure is exerted on a first relief valve 41 through a damping orifice 27, a communicating hole 28, a second valve chamber 19, and a first introduction hole 33 and therefore, the pressure of the first relief valve 41 is held at a value lower than a set value. In this case, when viscosity of oil is high at the time of a low temperature, a pressure flows in delay to the first relief valve 41, and thereby a load pressure is immediately introduced to a second introduction hole 34. In which case, the pressure of a first valve chamber 18 is increased and a second relief valve 42 is actuated against the force of a spring 39. As a result, the pressure of the first valve chamber 18 is escaped to a bypass passage 15 through the second introduction hole 34, a valve hole 30, and a radial hole 40. |
