Effects of the dimensional and geometrical errors on the cylinder block tilt of a high-speed EHA pump

Abstract

The speed of Electro-Hydrostatic Actuator pump can recently reach 20,000 rpm and the cylinder block within such high-speed pump is more likely to tilt away from the valve plate, which results in wedge-shape oil film between cylinder block and valve plate and thus increase in leakage flow. In order to realize the cylinder block balance at high speed, more attentions should be given to the dimensional and geometrical errors of cylinder block since unreasonable dimensional and geometrical errors may significantly contribute to cylinder block tilt through inertial forces of piston-slipper assemblies, especially in high speed condition. This paper analyzes the influence of dimensional and geometrical errors on the cylinder block tilt. A detailed set of relevant equations is developed, which takes into account three typical types of dimensional and geometrical errors of the cylinder block. The maximum and minimum of the extra cylinder block tilting moments produced by these dimensional and geometrical errors are examined and compared with each other using rotating vector method. According to the analytical results, some valuable suggestion is given to decrease the extra cylinder block tilting moments and inhibit the tilting effect.