The Synthesis And Analysis Of Planetary Gear Transmission Mechanisms Of Eight-speed Automatic Transmission

With the widespread application of the automatic transmission in the car area, the development of the automatic transmission has entered the stage of 8 speed ratios. Planetary gear transmission mechanisms have transformed from composed of three planet gear set to four planet gear sets. The automatic transmission of our country starts late and the base is weak, a mount of automatic transmissions are depended on importation. And also the configurations are relatively simple due to the monopoly of the foreign intellectual property. Based on this, the article puts forward a new method of synthesis of planetary gear transmission mechanism of 8-speed transmission based on topological graph atlas which has one multiple-joint from the perspective of mechanism innovation. The kinematics and the dynamics of comprehensive results are analyzed afterwards, and then compared with the classical mechanisms.This article follows the studying procedure of mechanisms synthesis, the verification of plane graph, the analysis of kinematics and the three-dimensional modeling and the motion simulation, the analysis of dynamics. The planetary gear transmission mechanisms are synthesized based on the atlas database of planar 12-link 3-Do F topological graphs which has one multiple-joint. Then several topological selection principles are built up according to the structure and the volume of the automatic transmission. The selected topological graphs are transformed into functional schematics by the way of Buchsbaum-Freudenstein method. Then the functional schematics are transformed into the equivalent levers and the levers formed by four planetary gear rows are analyzed based on the lever analogy. The lever which can realize 8 speed ratios can be gained. Last, the equivalent levers are selected which are in accordance with the lever which can realize 8 speed ratios. Then, the verification of plane graph is ensured for the synthesized level models according to graph theory. And the speed ratios are confirmed according to the lever analogy and MATLAB. Finally, suitable mechanisms are selected.Also the analysis of the kinematics and the dynamics based on the level analogy are introduced. Afterwards, the three-dimensional modeling and the motion simulation are done to prove the accuracy of the speed ratio which was given during the process of the analysis of kinematics. Finally, transmission ratio, step ratio, and the efficiency of the existing classical ZF and Lexus transmission mechanisms are made comparison with the new mechanisms.