On Running-In of A Swashplate-Type Axial Piston Pump

The effects of running-in on the performance of a small hydraulic pump were experimentally studied. A swashplate-type axial piston pump with a theoretical displacement of 10 mL/rev., a maximum discharge pressure of 21 MPa, and a maximum rotational speed of 30 s－1 (1800 rpm) was prepared. The test bench consisted of the test pump, driving devices (an electric motor and an inverter), valves, hydraulic auxiliaries (filters, an oil cooler, and a reservoir), and measuring instruments (a torque sensor, a flow meter, pressure sensors, thermistors, and a logger). A hydraulic oil with ISO VG32 was used. The pump was operated under the conditions of discharge pressure of 20 MPa and rotational speed of 25 s－1 (1500 rpm). The accumulated operation time was 100 h, while the continuous operating period was 5 or 10 h. The inlet oil temperature was maintained up to 30 ℃. The continuous operation was interrupted every 10 or 20 h since the pump performance curve was obtained. The discharge flow rate and input torque were measured under the conditions of the discharge pressure up to 20 MPa with the interval of 1 MPa and the rotational speed of 25 s－1 (1500 rpm). The mechanical and overall efficiencies increased approximately until 40 h and then became almost constant, whereas the changes in the volumetric efficiency were much smaller than these efficiencies.