HYDRAULIC SYSTEM HAVING LOW SPEED OPERATION

摘要

A hydraulic fan circuit (200) is provided. The hydraulic fan circuit (200) includes a tank (208), a motor (206) having a fluid inlet (214) and a fluid outlet (218) and a pump (202) to draw fluid at a low pressure from the tank (208) and discharge the fluid at elevated pressures to the motor (206) via the fluid inlet (214). The hydraulic fan circuit (200) further includes a directional control valve (245) disposed between the fluid outlet (218) of the motor (206) and the tank (208). The directional control valve (245) is operable to move between a flow blocking position (248) and a flow passing position (250). Further, the directional control valve (245) is configured to reduce a positive speed of the motor (206) below a lowest positive speed attainable through control of pump (202) output. Furthermore, the hydraulic fan circuit (200) includes a pressure control circuit (226) configured to provide a pilot fluid flow at varying pressure to move the directional control valve (245).