Optimization of a low noise piston pump

Manuel Rigosi



The use of compact axial piston pumps of the swashplate type as input power source for modern hydraulic circuitry is common, nowadays, on both fixed and mobile applications. Besides the constant focus on pump efficiency and performance improvements, within the last few years significant attention has grown on the pump noise reduction, especially for electrically powered systems as for example injection molding machines.
Machine noise mainly comes from pressure fluctuations in the hydraulic fluid (fluid-borne noise) and large alternating forces inside the pump, both of which leading to the structure vibration (structure-borne noise) and the sound propagation on surroundings (air-borne noise).
On axial piston pumps of the swashplate type one solution that can virtually break down flow ripple in the hydraulic circuit is the pre-compression volume: it consists of an additional oil chamber able to pre-compress the oil inside each piston before it is delivered to the pressure line. A key design feature for an effective result is a proper delivery timing, which is defined by the geometry of the pump portplate, further complicated by the presence of the pre-compression volume.
After an investigation phase on this device functioning through 1D circuital simulation, a modeFrontier workflow was implemented in order to find an optimal layout and the geometric parameters corresponding to an optimal delivery timing: the workflow included more than 20 input and output variables, a central core based on AMESim circuital simulations and a postprocessing calculation performed by an Octave node. modeFrontier allowed to merge a large number of information, coming from the simulation model, into a single environment: the first goal was to find the maximum potential of each different layout, then the final optimization, managed by MOGA II algorithm, was run and the best design was prototyped.
Experimental results confirmed expected improvements and a noise reduction was reached: a new product series is going to be launched on the market.