OPERATION - Pressure Regulator Valve

The hydraulic control valve assembly consists of:

The pressure regulator valve ensures that optimum hydraulic pressure is maintained at the secondary (output) pulley and determines secondary pulley groove width according to primary pulley groove width. Pressure in circuits 1 and 2 is balanced by spring 1. Pressure is determined by speed ratio, engine rev/min and a torque signal from the ECU. The pulley ratio sensor detects the position of the primary pulley and alters the regulator valve spring length accordingly. The speed of the pulley is sensed and pitot pressure (proportional to primary pulley rev/min) acts upon circuit 7 opposite the spring. When primary pulley (engine) rev/min increases, pitot pressure also increases, and the pressure regulator valve moves to the right to prevent line pressure increasing (due to increased oil pump speed). When it becomes necessary to change from low to high pressure (or vice versa), line pressure is delivered to chamber 3 from the control solenoid valve 4 via circuit 5. Under partial load conditions, line pressure is controlled by the solenoid valve 4 (ON) and the difference in diameter of the spool valves D1 and D2. Diameter D2 is larger than D1, working area is increased, line pressure is reduced. Under heavy load conditions, the solenoid valve 4 (OFF) closes and shuts off the oil pressure chamber lines. Pressure from circuit 5 is drained via circuit 6. Line pressure increases.