| 摘要 |
PURPOSE:To control the tensile force of a power transmission belt with high accuracy by connecting one of a pair of hydraulic actuators to a second line oil passage by means of a bypass and approximating to a second line oil pressure when one of the actuators becomes a low pressure side. CONSTITUTION:When both first and second solenoid valves 272, 290 are turned on, oil pressure Pl1 in a high-pressure first line oil passage 80 is fed into a primary side hydraulic actuator 70 via a speed change directional selector valve 262 and a flow rate switchover valve 264, while oil pressure Pl2 in a low- pressure second line oil passage 82 is fed into a secondary side hydraulic actuator 72 via a check valve 308 and a bypass 309. On the other hand, when the first solenoid valve 272 is turned off, the first line oil pressure Pl1 is fed to the secondary side hydraulic actuator 72 side and flow-out from the bypass 309 into the second line oil passage 82 is prevented by the check valve 308. Also, the second line oil pressure Pl2 is fed into the primary side hydraulic actuator 70. Thereby, the oil pressure in the secondary side hydraulic actuator is securely approximated to the second line oil pressure, to ensure the tensile force of a belt.
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