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

摘要： 文章以某 9 挡自动变速器的牙嵌式离合器为研究对象，建立了离合器结合各阶段的动 力学模型。根据长短齿设计特征，分别计算无任何齿形接触、长齿接触长齿、长齿接触短齿、 长齿接触长齿和长齿接触短齿同时发生四种场景在不同初始速差条件下的进挡概率。考虑随 机齿形接触位置的终止速差，计算得到牙嵌式离合器进挡的最优速差，可用于滑行降挡最优 进挡策略的制定，提升换挡质量。选取实车滑行五挡降四挡工况，进行进挡概率校验，结果 和理论计算概率相符合。

关键词: 自动变速器；牙嵌离合器；长短齿；进挡概率；最优速差