| 摘要 |
PROBLEM TO BE SOLVED: To ensure a sufficient assist force even when the load on a gear box side is reduced, in an orifice plate arranged in a pressure compensating oil passage, by setting the passage area of an operating oil carried from a spring chamber to the oil passage smaller than the passage area of the operating oil carried from the oil passage to the spring chamber. SOLUTION: When a wheel gets on a difference in level, and the load inputted to a gear box is instantaneously minimized thereby, the pressure within an oil passage 20 is reduced, and a pump pressure P1 is also reduced. Then, the valve member 12d of a flow control valve 12 is moved in the direction of extending the opening area of a circulating port 12e to discharge the operating oil within a spring chamber 12c on the oil passage 20 side through a control orifice 22. Since the passage of the operating oil Q3 becomes only the fixed hole 22e of a passage area variable member 22a, however, the operation responsiveness of the valve member 12d is suppressed. When the wheel is thereafter grounded to raise the pressure within the oil passage 20, the flow rate Q4 of the operating oil carried to a control valve 6 can be kept without reduction, and a sufficient assist force can be exhibited. |
