Provning av parallellkopplade hydraulpumpar i hjullastare
Volvo Construction Equipment is a world leading company in construction machinery. Tomaintain the best products, development is prioritized. The master thesis regards sound reductionof the hydraulic system on a wheel loader. The background to the master thesis is asimulation made on the hydraulic system, performed autumn 2005. The result of the simulationshows that the energy of the pressure ripple is reduced when the paralleled hydraulicpumps are phase shifted and reduces each others pump pulsations. The aim of the masterthesis is to investigate if the reduction in pulsations also reduces the hydraulic sound.The test has been made on a wheel loader, model L180F, by measuring the pressure pulsationsin the hydraulic system and sound in the drivers cabin. The machine is equipped withtwo nine pistons hydraulic pumps in parallel to the main hydraulic actuators. The measurementshas been made when the sound is highest from the hydraulic system, which is whenthe lifting cylinders has maximum speed. The measurements has been made for differentangels in a range from 0 to 16 degrees phase shift.The result of the master thesis shows that the pulsations in the hydraulic system is reducedbut the sound does not improve with reduced pulsations. The cause to the resultshould be that the pulsations can not be reduced in the entire hydraulic system. The partof the hydraulic system that can not be affected is close to the drivers cabin floor and hastherefor a big contribution to the sound level in the cabin.Volvo is not recommended to introduce the concept because the lack of result in the soundreduction. The result are very dependent of the engine speed, the temperature and the systempressure which make the concept inappropriate for sound and pressure reduction in a wheelloader application. A recommendation is to investigate the possibility of a pulsation attenuatorafter each of the paralleled hydraulic pumps to reduce the pressure ripple in the wholehydraulic system and the hydraulic sound. Another suggestion for investigation is the possibilityto introduce damped attachment points for the hydraulic components to minimizetransmission of vibration to the main structure.