OPERATING DEVICE AND METHOD FOR HYDRAULIC PUMPS IN HYDRAULIC SYSTEMS

摘要

The rotational frequency of a variable speed motor is set to a normal rotational frequency setting value (N1). A pressure variation range (”P) is detected based on a pressure detection value P, of a variable displacement pump, detected by a pressure detector. It is determined whether a determination that the detected pressure variation range (”P) is less than or equal to a pressure maintained state detection level (L1) has been continuously given for a period indicated by a timer setting value (T1). If the determination that the detected pressure variation range (”P) is less than or equal to the pressure maintained state detection level (L1) has been continuously given for the predetermined period, then it is detected that the current state is a pressure maintained state, and the rotational frequency of the variable speed motor is switched from the normal rotational frequency setting value N1 to a pressure maintaining rotational frequency setting value (N2(