Thermal Modeling And Analysis On The Hydraulic Power Steering System Used In A Commercial Vehicle

Hydraulic power steering (HPS) system has the traits of accurately handling,direct sense of road, rich feedbacks; the hydraulic pump of HPS has abundant steeringpower driven by engine; mature technology, high reliability, low averagemanufacturing cost of it lead to widely used. However, due to power loss of HPS, theoil temperature becomes high, causing the poor power effect, shortening the servicelife of it and other series of issues.The content of this paper is derived from the research project about acommercial vehicle’s HPS in the cooperation with FAW R&D Center. The oil of thisvehicle’s HPS rises abnormally, which often leads to the pump burning out. Thisresearch paper focuses on ball-nut type HPS system on a commercial vehicle, thethermal properties are studied and analyzed. Firstly, by reading relevant papers andbooks，the contents of previous research and working on the thermal theories andthe pressure loss and thermal properties of the hydraulic system are summarized.Detailed observation on the structure of HPS, dismantling steering gear and so on aremade,the internal structure of the various components, working principle, heatproduction and dissipation mechanism of the HPS are grasped,and based on whichthe researching and working line of this paper is developed. Then the reasons ofpressure loss and heat dissipation of each component of HPS are analyzed. Eachcomponent’s thermal model of HPS is established by using AMESim software, whoseheat production and dissipation are analyzed. Each thermal model is connected to be asystem model, the pressure and temperature simulation curves are compared to HPSbench test pressure and temperature curves, which verifies the correctness of thesystem thermal model. The correct thermal model provides the basis for subsequentanalysis in depth. Finally, heat production proportion of each component in the wholesystem, the impact of rise in oil temperature on the HPS hand force and sealcharacteristics,and the effects of the main parameters and factors on the oil temperature are analyzed, and based on of which the matching and arrangementprinciples of each component are proposed.HPS system’s stability determines the vehicle’s steering and safety, oiltemperature is the main factor affecting the HPS stability. This paper studies the HPSoil temperature, gets the heat contribution of each component to the whole system, theimpact of rise in oil temperature on the HPS hand force and seal characteristics aswell as the effects of the main parameters and factors on the oil temperature, proposesthe matching and arrangement principles of each component. This paper’s researchhas some significance on the HPS system designing and assembly.