<p class="MsoNormal" style="text-align: justify">There is a current trend towards the electrification of high force/torque density machines that have traditionally been dominated by hydraulics. Power dense electrical machine tends to favor high operating speed whereas a hydraulic pump is more efficient in low speed and high torque conditions. In an effort to increase power density, there is a trend toward decreasing the pump displacement and increasing the operating speed to provide the flow demand. This miniaturization of the pump allows it to be directly integrated into the electrical rotor of an electric motor inside a single casing. This integrated pump-motor is free of shaft seals and eliminates a set of bearings otherwise required when coupling an electric motor and pump with a shaft. Additionally, the leakage from the hydraulic pump can be directly used as a coolant for the electrical machine, thereby supporting higher current densities. Such an integrated machine is a perfect fit for bucking and boosting pressure in the Hybrid Hydraulic Electric Architecture (HHEA) power train proposed by Li. Et al. In the HHEA architecture, this integrated machine is used to implement the Hydraulic Electric Control Module (HECM). Previously, a candidate HECM design with a radial ball piston pump integrated with an axial flux PM electric machine was proposed, and both were optimized separately. In this work, a hydrostatic radial piston pump has been evaluated for integration with an identical axial flux PM machine. The proposed hydrostatic piston pump consists of a spherical head piston that can tilt while reciprocating inside the cylinder. The slipper is connected to the piston by a threaded joint instead of a ball and socket joint that reduces the additional frictional loss. To reduce the frictional loss between the slipper pad and the cam at operating speeds over 10,000 RPM, the cam is allowed to freely rotate. A detailed model of the hydrostatic piston slipper has been developed and a grid search approach has been utilized to select the critical parameters of the pump. Finally, an efficiency map has been presented for this pump at different operating conditions.</p>

Dynamic Modeling and Design of a Radial Hydrostatic Piston Pump for Integrated Pump-Motor

Paper Proceedings: https://asmedigitalcollection.asme.org/FPST/FPMC2021/volume/85239

2021 ASME/BATH Symposium on Fluid Power and Motion Control (FPMC2021)

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