Swash plate oscillation in a variable displacement floating cup pump

The oscillation of a swash plate has been studied in a variable displacement floating cup pump. Servo valves have been designed and built into the pump. These so called s-valves define a certain operating angle, while leaving the swash plate free to oscillate, in the same way as during real pump operation. Measurements have been performed in a wide range of operating conditions. A simulation model has been built to get a better understanding of the dynamic behaviour. The study has proven the large impact of the swivel torque of the swash plate on the pump behaviour. The swash plate oscillation creates an additional displacement of the pump, especially during commutation, which is often larger than the original sinusoidal movement. The dynamic oscillation of the swash plate therefore dominates the commutation phenomena. It has also been proven that the overall efficiency is substantially reduced if the swash plate is free to oscillate, like in real pump operation. Although this study is performed on a floating cup pump, the authors of this paper believe that these effects also occur in conventional types of pumps and motors. It is recommended that a similar study should be performed on slipper type and bent axis pumps and motors.