Minimum-pressure servo pump e.g. for vehicle diesel engine

摘要

The low pressure system provides low pressure for servos, e.g. vacuum brake servo, and has a pump (2) driven by the engine (1). A simple clutch (7) disengages the pump when a sensing circuit (9) recognises a programmed low pressure level in the servo circuit, monitored by a sensor (8). This reduces torque drag from the pump. An alternate solution is for a venting system for the low- pressure line which leaves the pump torque dependent on the friction drag only. A non-return valve (5) between the pump and the servo reservoir (4) isolates the reservoir and prevents loss of low pressure.