3D orbit design for overcoming the dead-point problem in spherical pump based on virtual prototyping

Spherical pump is a new type of hydraulic pump. One of its drawbacks is the spatial dead-point problem, which may cause abnormal vibration, squeal and even obstruction. In this paper, we propose a 3D orbit to overcome the spatial dead-point. The orbit is machined on the internal surface of cylinder block by means of milling, while two guide balls are embedded on the rotary disc surface and move in the pre-set 3D trajectory. Dead-point mechanism is analyzed by investigating kinematic characteristics of piston, rotary disc and shaft. Then we establish the kinematic equations of guide balls through following the pump working mechanism, and 3D orbit trajectory can be shaped by analyzing the movement trail of guide balls. Finally the 3D orbit is modeled based on the trajectory analysis, and the multibody dynamic approach is utilized to simulate the operating condition. Results indicate our proposed theory is effective in overcoming the spatial dead-point issue of spherical pump.