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 power 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 between high- and low-pressure ports of the motor such that, during normal operation, 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 check valve from the second port to the first port is enabled. When the pilot control is activated, passage of fluid in the opposite direction is also enabled.