New technology for the next generation axial piston pumps

Noise and vibration levels need to be reduced in all new development of hydraulic pumps and motors. This is obvious for Industrial and Mobile Hydraulics. Following on from previous company research carried out in collaboration with the University of Linkoping, we have now successfully developed a new pump for truck hydraulics, which gives excellent value levels on noise and vibration levels. The axial bearings will have a more uniform bearing load when an even number of pistons are used in the unit. This solution decreases both the structure-born noise and the air-born noise from the pump. It is shown that the dynamic forces from the cylinder pressure in the pump are the major cause of noise emission from the pump unit. Both axial force and corresponding moment are significant. The port plate geometry strongly affects the axial force and moment. This is because the pressurization and depressurization of the cylinders are affected in a special way. By making this design in an optimized way, it is possible to produce a unit with an even number of pistons with low flow pulsation and low structural vibrations. This paper will present our background research work and actions taken in a product development project. This project will be finalized by mid of 1999 and the product came into serial production from September 1998. This project is at the cutting edge of the hydraulic industry and is rightly seen as a "state of the art" development.