PUB - Design of a high speed internal gear pump for mobile applications
The electrification of mobile machinery becomes more and more important. Therefore, it is necessary to increase the power density of electro-hydraulic drives in order to meet the structural restrictions in mobile hydraulics.
Author: Pietrzyk, Tobias
The use of high speed components (n > 10000 rpm) contributes significantly to improving the power density, but fails due to the speed limit of current pumps. Within the scope of this thesis, the suitability for high speed operation is investigated using the example of a gap compensated internal gear pump was investigated for a drive speed up to 10000 rpm and a displacement of about 4 cm³. For this purpose the kinematical, mechanical and hydraulical processes within the pump are analyzed. The forces and torques acting in an internal gear pump are considered and the kinematical displacement process is discussed. Furthermore, the influence of the geometric dimensions of gears on the speed limit is considered with the help of numerical flow simulations. For the calculation of the radial gap compensation, the pressure build-up using different pressure compensation notches is examined and the radial compensation ratio at different speeds is calculated. For the design of the axial gap compensation a simulation model is built in MATLAB to solve the Reynolds equation in the lubrication gap. The calculations influence the design of a high speed internal gear pump. In the component testing, the suitability for high speed is experimentally proven and the partial and total efficiencies are discussed. One possible application for the high speed internal gear pump are decentralized electrohydraulic actuators (EHA), which replaces the stick cylinder of a compact excavator. For this purpose, a hydraulic system architecture with corresponding control and regulation concept in 4-quandrantum operation is presented. Subsequently, the constructive implementation of the EHA is explained and the results of the test series are shown.