Spline design for the cylinder block within a high-speed electro-hydrostatic actuator pump of aircraft

The electro-hydrostatic actuator (EHA) pump of aircraft is usually characterized as high speed for improved power density. High-speed condition leads to a considerable tilting inertia moment acting on the cylinder block, which has a significant effect on the cylinder block balance. Therefore, the cylinder block spline is required to be designed properly to achieve the cylinder block balance at high speed. In this research, the spline design for the cylinder block within a high-speed EHA pump of aircraft will be investigated from the perspective of cylinder block balance. The design criterion for the cylinder block spline is derived based upon the analysis of the cylinder block balance, from which distances of both spline ends from the cylinder block bottom face can be obtained. These two main distances are computed for a series of typical pump designs and then compared with the geometries of actual splines. It is shown that the proposed design criterion for the cylinder block spline corresponds well with the existing data coming from actual products. Finally, a case study on the calculation of the cylinder block spline within a high-speed EHA pump is given, and experiments will be carried out on an EHA pump prototype at speeds of up to about 10,000 rpm.