Abstract
Energy savings have been made in a number of fields due to a shortage of energy resources such as oil and the need to protect the earth’s environment. If an accumulator is coupled with a hydraulic pump unit, intermittent operation of the electric motor powering the pump drive, called “idling stop type operation,” can be attained by using a pressure-holding function. Consequently, a reduction in unneeded power consumption can be realized. In this research, an intermittently operated hydraulic pump unit coupled with an accumulator (ACC pump unit), an inverter control-type hydraulic pump unit (INV pump unit), and a variable displacement-type hydraulic pump unit (VD pump unit) are tested. The relation among electric power consumption, pump output pressure, rotation speed and efficiency for one cycle of an ACC pump unit, an INV pump unit, and a VD pump unit was clarified by experiments conducted using a modeled machine tool. Next, the relation among electricity consumption, efficiency, and duty ratio in the case of supplying working fluid to the load intermittently with a fixed cycle period was investigated, and the predominance of the ACC pump unit was made clear. The ACC pump unit was shown to clearly have the best energy-saving effect. In addition, the static characteristics of each hydraulic pump unit were measured.
