Mechanical efficiency of cartridge two-dimensional (2D) piston pump for electro-hydrostatic actuators

The cartridge two-dimensional (2D) piston pump studied is the core component of an aircraft electro-hydrostatic actuator (EHA). Its mechanical efficiency is a very important performance which is closely related to heat generation and energy saving. This paper first established the dynamic equations and solved the normal force on the tapered roller and the input torque on the fork shaft. The profile of the cam guide and the four spatial angles necessary to calculate the normal pressure and input torque were obtained using the envelope method. Afterwards, based on this mathematical model, the characteristics of positive pressure and input torque, and the proportion of friction loss are analyzed. Finally, in order to verify the correctness of the simulation model and determine the coefficient of rolling friction, a prototype was processed and a test rig was built. It can be observed from the test results that when the speed is 1000 r/min, as the load pressure increases from 1 to 28 MPa, the mechanical efficiency rises from 36.19 to about 88.46%, which is in good agreement with the simulation results. However, when the pump speed is 3000 r/min, the experimental results are slightly lower than simulation, adding the mechanical losses caused by shearing and churning oil in the mathematical model can reduce the deviation.