Influence Analysis of Machining Taper on Force of Piston

The piston-cylinder pair is one of the three key tribological interfaces in an axial piston pump. Machining taper and operational tilt jointly modify the oil-film thickness and, therefore, the pressure distribution, resultant hydraulic force, centre of pressure and viscous friction acting on the piston. In this study, an analytical model is established for the annular clearance while accounting for both piston tilt and machining taper. The effect of taper direction is then discussed through a case study of a CCY14-1B pump. The results show that taper direction has only a limited influence on the resultant hydraulic force, but it has a pronounced influence on viscous friction in both the suction and discharge zones. For the present case, the centre of pressure in the discharge zone is located close to the lower one-third of the sealing length measured from the piston bottom. The results should be interpreted as case-specific analytical/numerical predictions for the selected geometry and operating condition.