Theoretical and Experimental Investigation on Power Loss of Vehicle Transmission Synchronizers with Spray Lubrication 2019-01-0028
Besides optimal engine systems, high-efficiency vehicle transmissions are generally also required to improve fuel economy in automotive applications. For the energy loss analysis in transmissions, most researches focused on the major mechanical components, such as gears, bearings and seals, while the other mechanical losses, like synchronizer losses, were usually not considered. With increasing number of synchronizers in modern transmissions, a recent study of transmission power losses indicates that the power loss analysis of synchronizers should also be developed and appended for a more accurate investigation on overall power losses in transmissions. The synchronizer is an essential component of vehicle transmissions for equalizing the different rotational speeds of shafts and gear wheels by frictional torques, for which the synchronizers must be cooled and lubricated in order to enhance their service life. With the supplement of lubricants between synchronizer friction surfaces, fluid friction is generated due to the differential speed, when the synchronizers are in neutral position. This fluid friction can be principally regarded as load-independent synchronizer power losses. This paper will take the following approaches: theoretical and experimental investigations of synchronizer power losses with spray lubrication. Fluid states and fluid dynamics in synchronizers are analyzed analogously to multiple-plate clutches. Based on that, synchronizer power losses are modelled physically. With the physical model, possible influential factors on synchronizer power losses are determined. Together with consideration of the current test bench, experimental design is developed regarding individual power loss testing on the system test bench. Through investigating the test results, the synchronizer power loss behavior is comprehensively analyzed and the physical model is optimized by means of parameter sensitivity analysis and optimization methods. The model is then validated by the experimental data from literature. In the future, the synchronizer power loss model will be further developed based on more influential factor investigations and then be implemented into an overall transmission power loss model.
Zhihong Liu, Ye Shen, Stephan Rinderknecht
International Powertrains, Fuels & Lubricants Meeting