Hydraulic system for vehicle - has engine driven main pump and vehicle motion or motor driven auxiliary pump feeding into common line with three-way control valve

摘要

The hydraulic pressure system is provided with two pumps one pump being driven by the engine and the second by vehicle movement or by an electric motor. The pumps feed a common pressure pipe leading to a three way valve. One outlet from the three way valve is the service pressure pipe. The second outlet is taken from behind a restrictor and leads to the auxiliary pump scavenging and lubrication chamber. A branch pipe leads to a regulator valve (48) with three switch positions. The main pump has a similar regulator valve. A pressure difference at the restrictor causes the auxiliary pump to give a nil delivery while ever the main ump can maintain its rated output. A lowering pressure difference causes the auxiliary pump to make up the original pressure difference.