关键词: 自动变速器；牙嵌离合器；长短齿；进挡概率；最优速差

Abstract: In this paper, a dog clutch of a nine-speed automatic transmission is used as the research object, and the dynamics model of each stage of clutch engagement is established. According to the design characteristics of long and short teeth, the probability of gear engagement under different initial speed difference conditions is calculated for four scenarios: without any tooth contact, long tooth contacting long tooth, long tooth contacting short tooth, long tooth contacting long tooth and long tooth contacting short tooth simultaneously. Considering final speed difference for random tooth contact position, the optimal initial speed difference of the dog clutch is calculated, which can be used for the formulation of the optimal shift strategy for coasting downshifts to improve the shift quality. The results are consistent with the theoretically calculated probabilities for coasting downshifts from fifth gear to fourth gear in real vehicle conditions.

Key words: Automatic transmission; Dog clutch; Long-short teeth; Engagement probability; Optimal speed difference