Abstract
AC induction motors have been widely used as prime movers in power sources for hydraulic servo systems. The authors have proposed and developed a new-type energy-saving power source for an electro-hydraulic servo system. In this power source, the rotational speed of AC induction motor driving a fixed displacement pump is controlled so as to fulfill the delivery requirements demanded by the system, and the transient shortage of the pump delivery flow rate is supplemented by an accumulator to supply the needed oil to the servo system.
In this paper at first, the design procedure of the hudraulic power source is investigated with an inverter-motor drive according to some duty cycle of the servo system. The pump and accumulator capacity selections are discussed and the optimal volume of accumulators is clarified. Moreover, from the viewpoint of energy savings, a two pressure control system based on the power source with an inverter-motor drive is proposed for a general work cycle of varying loads corresponding to a high flow rate and a low pressure conditions such as during rapid traverse or a high pressure and a low flow rate conditions such as during heavy cutting in the feeding of machine tools. In the two pressure control system, a dual accumulator system is adopted and the action of the accumulator is controlled by a solenoid-operated ON/OFF valve at the supply port. The results are experimentally verified
