Abstract
As a result of a shortage of energy resources such as oil and the need to protect the earth’s environment, energy saving efforts have been made in a number of fields. In the case of hydraulic equipment, energy saving in pump units is key because this unit is the major consumer of energy.
Up to the present, variable-displacement hydraulic pump units (VD pump units) and inverter-control hydraulic pump units (INV pump units) have been widely employed. Here the authors propose the use of an intermittently operated hydraulic pump unit coupled with an accumulator (ACC pump unit) . In a previous report, the superiority of the ACC pump unit was demonstrated through an experiment using a modeled machine tool and a simplified load model. In this report, we compare electric power consumption, pump output pressure, rotation speed and efficiency of the VD pump unit, INV pump unit and ACC pump unit when hydraulic fluid is supplied to the load at a fixed flow rate. In addition, the effects of the accumulator volume and the pressure ratio between the upper and lower limits on efficiency and the ON-OFF switching period of the ACC pump unit are determined.
