An Electromagnetically Actuated High Frequency Oscillation Pump

Electro-Hydraulic Power Units integrate an electric motor and a hydraulic pump in a single machine. The common solution, consisting of a conventional rotary motor coupled to a rotary pump, is for the fractional kilowatt range neither efficient nor compact. The alternative studied in this work is a High Frequency Oscillation Pump (HFOP): a pump with a single alternating piston that oscillates at high frequency, up to 300 Hz. In this concept, the piston is moved by a biased reluctance actuator. The limited number of moving parts of this design leads to a reduction of the friction and to an increase of the efficiency. The high frequency approach is a step towards superior power density. Typical applications are compact hand held devices, like spreaders and cutters for rescuing in car accidents, and complex machines, that require distributed compact high force actuators. This paper draws the focus to the main issues concerning the HFOP, starting from theoretical investigation over design to the experimental testing. Particular attention is given to the design optimization of a fast plate type check valve. Experimental tests with the constructed prototype confirm the benefits of the optimized design in terms of volumetric efficiency and reduction of cavitation.