<p style="text-align: justify">Internal gear devices such as gerotor machines find their principal employment in several technological domains such as: automotive, robotic, mechatronic and aerospace applications. In the context of mechatronic actuators, gerotor units are often preferred over other technologies due to their high efficiency, low wear, low noise and compactness. The approach to design these hydraulic machines, either for motoring or pumping applications, involves the definition of many geometrical parameters such as eccentricity, gear diameters, gear clearances, axial thickness, volume aspect ratio and tooth aspect ratio, which affect the overall efficiency of the component. Among these, eccentricity represents the distance between gears rotating axes; it is directly proportional to the pump’s volumetric displacement. The selection of this parameter is of particular interest when producing compact mechatronic devices. On the other hand, the tooth aspect ratio is the driven gear cutting lobe radius over the driver gear tooth radius. It directly influences the gerotor hydraulic efficiency since it defines the sealing capability among high and low pressure chambers in the pump. These two parameters have a strong influence on the overall performance and efficiency of the device.</p><p style="text-align: justify">The state of the art has addressed the definition of important design features, such as geometric clearances and their influence over hydraulic leakages and mechanical losses. However, selecting a proper eccentricity and tooth aspect ratio is often left to the designer’s experience or defined through empirical formulations. In this perspective, the present research aims at providing a general design methodology for gerotor machines related to their integration into high-efficiency mechatronic devices.The study focuses on the analytical and numerical characterization of the optimal tooth aspect ratio and eccentricity between gears. Both parameters mainly depend on the number of gerotor chambers and the outer diameter of the gerotor machine. Thus, a parametric study of these two independent variables is developed and processed in order to (a) understand how they influence the parameters variation, (b) define the optimal pair of parameters that, for each combination, minimize the leakage flow rate and increase the volumetric displacement, and (c) develop a gerotor machine through the choice of the optimal parameters from the design methodology. Our analytical approach is validated by means of computational fluid dynamic models to assess the gerotor’s performance in terms of efficiency, hydraulic and mechanical losses. Moreover, experiments are carried out with a prototype designed according to the outlined approach. Finally, we give specific guidelines regarding the integration of the gerotor unit onto a mechatronic actuation system. In particular, the coupling and matching with the electric motor and actuator casing are dealt with.</p>

Design Methodology of Gerotor Hydraulic Machines for Mechatronic Applications

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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