SAFE OVER-CENTER PUMP/MOTOR

摘要

A fail-safe system for a hybrid vehicle employing an over-center variable -displacement hydraulic motor includes an actuator configured to stroke the motor to a zero angle if each of two control ports is supplied with fluid at an equal pressure. A control valve is configured, in the event of loss of p ower to the valve, to default to a position in which high-pressure fluid is supplied to both control ports. A pilot-controlled check valve is coupled be tween high- and low-pressure ports of the motor such that, during normal ope ration, passage of fluid through the check valve from the high-pressure port to the low-pressure port is checked, while passage of fluid through the che ck valve from the second port to the first port is enabled. When the pilot c ontrol is activated, passage of fluid in the opposite direction is also enab led.