Study On Efficiency Of Planetary Gear Train Of Automatic Transmission

Automatic transmission is a very important Invention in the development of transmission technology for vehicle. It can give automobile smooth starting and gear shifting, convenient operation, and comfortable driving. Automatic transmission meanly use hydraulic torque converter and planetary gear-box, which is called hydraulic automatic transmission (AT). Planetary gear-box is widely used in AT for its many virtues. It can realize shifting, power transmission and larger torque converter area, which also has empty and reverse gear shift, small volume, comfortable operation and large shifting ratio. The fatal weakness of AT is the low efficiency which is obviously lower than manual transmission. It's the product of efficiency for hydraulic torque converter and planetary gear-box. According to improve efficiency of AT, new equations are derived for correctly calculating the efficiency for planetary gear train of different shifts in AT. This paper involves followed contents: (1) The structure and characteristic of different kinds of planetary gear train is briefly analyzed, based on this, JR405E produced of JATCO which is 4AT with 2 planetary gear train is selected as the research object. Power transmission routes of different shifts are analyzed, transmission ratios are also calculated respectively. (2) Refers to "approach contact ratio"and "recess contact ratio", involute gear train is divided to four cases which are internal or external mesh for speed increase and speed reduction. Accurate equations to calculate reference efficiencies of different cases are derived. Validation of planetary gear train in JR405E is done. (3) Equations for calculating efficiency between meshing teeth and efficiency at bearings, and also the whole efficiency of planetary gear train are derived. results after comparison show: efficiency for speed increase is higher than that for speed reduction. (4) Considering usage frequency of different shifts which is got according to the ECE+EUDC, an multi-target optimization to get the highest efficiency is done used generalized grads and matlab, with no change of the transmission ratios. Efficiency of AT is improved obviously.