Modelling of Oil Heating of Disengaged Lubricated Clutches in Hybrid Vehicles

摘要

Due to increasing series development of hybrid vehicles many conventional components of the powertrain have to be replaced or changed. To avoid new technical failures, mostly well-known components are being used to create these new types of powertrains in series production. This chapter focuses on the drag torque of lubricated clutches which could be used in full parallel hybrids to disconnect the combustion engine from the powertrain instead of using a torque converter. There are some reasons to replace the torque converter with a clutch. Many cases and situations have to be calculated to forecast possible reduction of fuel consumption. Because of the complex interactions between NVH, comfort, wear and efficiency, there are a lot of boundary conditions to consider for these clutches. Therefore, special clutch types were developed for upper class cars with high torque engines. In aspects of high heat inputs there are newly developed designs of clutches. In the early state of product development the fuel consumption of different concepts is one important criterion for decision making. For a generic calculation of the drag torque, the heating of the oil in the clutch has to be paid attention to. The approach in this chapter is to firstly analyse the drag torque at a specific disengaged clutch. Therefore any other powertrain influences are cut off, by running tests on a test bench. Furthermore manoeuvres/test cases are defined in order to receive drag torques as objective as possible without temperature or bearing influences for example. By using analytical equations based on fluid dynamics, first hypotheses can be created. This chapter shows the previous works regarding the analytic modelling on lubricated clutches (e.g. Yuan et al. J Fluids Eng Bd. 129:333) and their correlation to the specific clutch and secondly the important extension of the present models regarding the heating of oil in the clutch. In addition, the model results are validated by test bench measurements and the relative error is shown. Moreover, the methods for analysing and modelling lubricated clutches are described in this chapter using the example of one lubricated clutch.