ELECTRO-HYDRAULIC CONTROL DESIGN FOR PUMP DISCHARGE PRESSURE CONTROL

摘要

An electro-hydraulic control system (22) manages speed of a hydraulic fan (17) by using a solenoid (25) to bias a three position pool (24) of a control valve (23) coupled to a hydraulic pump (30) driving the fan (17). In a first position, the spool (24) releases pressure on a de-stroke actuator (34) of the pump (30) and allows an on-stroke actuator (32) to increase output pressure corresponding to a speed of an engine (11) driving the pump (30). In a second position, the spool (24) isolates the de-stroke actuator (34) and fixes the pressure output of the pump (30). In a third position, the spool (24) couples the de-stroke actuator (34) to the pump output and causes a reduction in the pressure output of the pump (30). The solenoid (25) coupled to the spool (24) sets the output pressure at which the spool (24) is in the second position.