HYDRAULIC FAN DRIVE SYSTEM HAVING A NON-DEDICATED FLOW SOURCE

摘要

A specific type of hydraulic fan drive system is provided for engine drive machines, such as on road and off road machines, such as buses, construction equipment, agricultural equipment, and so on. The hydraulic fan drive systems turn a cooling fan (39) which provides airflow to cool the engine on such machines. This system uses a proportional pressure reducing valve (34) (or combination of valves providing a pressure reducing function) between the pump (12) and the fan motor (38). This valve (34) or (combination of valves) controls the pressure drop across the fan motor (38) based on a control signal from an electronic controller (50). The valve allows as little or as much flow to pass as is required to maintain this pressure drop at the load (the fan motor (38)).