Development Of Environmental Friendly Automatic Transmission Fluid For Natural Gas City Bus

The automatic transmission realizes the non-rigid transmission of torque between the engine and the transmission mechanism and automatic gear switching by the flow of the automatic transmission fluid in the torque converter,which greatly improves the driving load and ride stability for driver and passengers.The matching between automatic transmission and natural gas city bus not only provides power compensation for natural gas engine during vehicle start-up,but also greatly improves the braking performance of natural gas city bus.Since the selection of the transmission is affected by the fuel characteristics,engine performance and operating conditions of the natural gas city bus,more special and strict requirements are imposed on the automatic transmission fluid.In order to promote the development of green public transport system in China,the lubrication characteristics of the automatic transmission matched by natural gas city bus are studied in this paper.On this basis,a kind of environment-friendly automatic transmission fluid suitable for heavy duty automatic transmission in natural gas city bus is developed.Based on the medium and high load automatic transmission fluid standards proposed by mainstream OEMs at home and abroad,the main technical indexes for the developed oil are put forward after comprehensive selection.In term of the proposed indexes,pentaerythritol ester(PE305)and poly alpha olefin(PA06)were selected as the base oil of the developed oil at a volume ratio of 55:45.After analyzing the working condition of automatic transmission in city bus,the suitable components of the functional additive such as friction modifier,antioxidant and detergent were determined.Based on the determined components and compound test results,the optimal ratio and additive amount of each component were determined by stepwise linear regression analysis and linear programming analysis with MATLAB and PASW Statistics software.In the analysis of the competitiveness among rust inhibitor,friction modifier,extreme pressure anti-wear agent and by response surface methodology(RSM),it was found that there were some antagonistic effects among the three additives.After summarizing the test results,the Combined Weight-ELECTR-I method was used to optimize the formula of the developed oil,and the optimal formula of T5 was obtained.The formula uses PE305 and PA06 with a volume ratio of 55:45 as base oil,supplemented by appropriate functional additives.Through the overall test of physical and chemical property,developed oil is proved to have excellent comprehensive performance and meets the engineering requirements.