| 摘要 |
PURPOSE:To further improve the steering stability with a positive reduction in the supply flow rate in a high vehicle speed range by arranging a variable orifice whose opening reduces as the gear position detected moves to a high speed side between a pump port and a supply port. CONSTITUTION:Now when a gear position detecting means 23 detects a low gear, a control circuit 24 fails to excite a solenoid 13 and a mobile sleeve 12 is limited on the left with a spring 15 with the min. diameter section of a measuring unit 17 positioned at an orifice port 20 in a control rod 8 so that the opening of a variable orifice 21 will be maximized to increase the flow rate to a supply port 3. On the other hand, at the top gear position, the excitation of the solenoid 13 reaches its maximum to minimize the opening of the variable orifice 21 while at the second and third speed position, it takes the intermediate opening whereby the supply flow rate is afforded as required from the low to high speed. As the pressure on the downstream of the variable orifice 21 rises with a load change on the side of a supply port 3, a spool 7 moves with a rise in pressure of a rear pressure chamber 9 to reduce the opening of a bypass port 4 thereby raising the pressure in a pump port 2. |
