Experimental verification of oil whirl of piston in axial piston pump and motor

Piston motion which interacts with lubrication characteristics including friction force between the piston and cylinder has been measured bg means of eddy current displacement sensors in order to prove the oil whirl phenomena in axial piston pump and motor which had been found theoretically in the previous paper, and been compared with the calculated results. It has been verified that the piston has whirled in the cylinder under certain operating conditions and specifications, similar to the oil whirl phenomena in journal bearings as a self-excited vibration. The phenomena have not occurred for large clearance and narrow bearing width between the piston and the cylinder as the predicated results in the previous paper. The period of the piston whirl has coincided with that of friction force variation.