Establishment of steering circuits and evaluation of oil temperature
Examensarbete för masterexamen
The master thesis has been performed for Volvo 3P on the site of Lyon in France, and in the premises of the design office front and rear axle installation of the product development department. This unit is in charge of the conception, the design and the production of the chassis and of the power steering system of all the trucks of the Volvo AB group. The sizing of the circuits is currently grounded on the experience of the member of the design office. Each new steering circuit has to follow a serial of test in different condition of utilization in order to be validated by Volvo and its suppliers. To secure the design process, the introduction of a simulation method in the design process of steering circuits has been wished. The simulation tool is intended to need input data simple enough so that it can be used in the early development stage of a design process. It has been decided to simulate static tests, when the engine runs at constant speed without air circulation. The tool has to be able to predict the oil temperature with an error of 10%. To validate the tool, the results need to be correlated on different circuit architectures. Finally the tool needs to be confronted to reality by comparing the prediction with measurement lead on a prototype vehicle. The software Amesim has been chosen to develop the simulation tool. In fact a pre study of the problem has shown that different scientific domains have to be taken in account to model the steering oil temperature evolution. In particular the heat transfers and the fluid mechanic have to be considered. Based on the bond graph theory, Amesim is a convenient software to model complex physical phenomena. To model correctly a steering circuit, the key components have to be identified and characterized in static functioning. The pump, the oil tank, the pipes and the steering gear are the principle components of interest. Their pressure losses and heat transfers have been thoroughly defined in static condition so as to obtain pertinent results. The Simulations have been realized on two completely different steering circuits, and the results obtain are encouraging. Four test cases have been studied on a Premium Lancer LC 8x4 MD 11 with results differences inferior to 5% with tests. Two test cases have also been studied on a Premium 4x2 MD11 and have given results with errors inferior to 7% compared to reality. Nevertheless it has been impossible to confront the models with the reality due to delaying of testing because of the international financial crisis. Then the steering gear hydraulic path has been identified as an influencing parameter on the oil temperature and has been approximated. A close work with the suppliers must lead in the future to a better knowledge of that component. Finally the influence of the surrounding temperature has also been highlighted. The next step is to consider the fan strategy in the modelling of steering circuit so as to enhance the accuracy of the model. Finally it is necessary to confront the simulation to the reality in order to validate the modelling method.
Transport , Teknisk mekanik , Farkostteknik , Transport , Applied Mechanics , Vehicle Engineering