Hydraulic system for extreme climates

摘要

A method of operating a hydraulic system and hydraulic system for raising and lowering a boom in extreme climates. When the temperature is below a low temperature the system is operated open center while a variable displacement pump providing a constant flow of hydraulic fluid. When the temperature is between the low temperature and a moderate temperature the variable displacement pump provides at least a minimum flow of hydraulic fluid to the system, and the minimum flow decreases linearly with an increase of the temperature. When the temperature is above the moderate temperature, the system is operated closed center while maintaining at least a system pressure when in neutral and wherein the variable displacement pump provides hydraulic fluid to the actuator when a control valve is actuated.

主权项

1. A method of operating a hydraulic system and comprising a variable displacement pump, a hydraulic fluid having a temperature and at least one actuating assembly comprising an actuator operated by a control valve, the method comprising:
when the fluid temperature is below a low temperature, operating the control valve open center while the variable displacement pump provides a constant flow of hydraulic fluid to the control valve; when the fluid temperature is between said low temperature and a moderate temperature above said low temperature, operating the control valve open center while the variable displacement pump provides at least a minimum flow of hydraulic fluid to the control valve, wherein said minimum flow decreases with an increase of the fluid temperature; and when the fluid temperature is above said moderate temperature, operating the control valve closed center while maintaining at least a system pressure at the control valve when in neutral and wherein the variable displacement pump provides hydraulic fluid to the actuator when the control valve is actuated.