Abstract: As a core component of the heavy-duty truck automated mechanical transmission (AMT) assembly, the shift actuator completes the shift commands issued by the transmission control unit (TCU) during the gear shifting process, while also withstanding various active and passive stresses in multiple directions. Addressing the issue of lower housing fracture during the front auxiliary section durability test, this paper proposes a new research approach. First, a strain test is conducted on the actuator fork to obtain the maximum force experienced by the fork. This maximum force is then used as an input for finite element analysis to calculate the maximum stress at the fracture location, enabling targeted improvement of the housing strength. After structural optimization, the stress at the housing fracture is reduced by 60%, and the housing ultimately passes 1.4 million shift durability cycles, validating the effectiveness of the proposed improvement solution.

Key words: heavy-duty truck AMT; lower housing fracture; shift fork

摘要： 换挡执行机构作为重卡电控机械式自动变速器（AMT）总成的核心零部件，在变速器 换挡过程中完成自动变速器控制单元（TCU）所发出的换挡指令，在此过程中也承受各向主 动和被动应力。针对前副箱耐久试验中下壳体断裂问题，文章提出了一个新的研究思路，首 先对执行机构的拨叉进行应变测试，将获得的拨叉所受的最大力作为输入，再通过有限元分 析，计算出断裂处的最大应力，针对性对壳体强度进行改进。经过结构优化，壳体断裂处应 力降低 60%，并最终通过了 140 万次换挡耐久试验，验证了改进方案的有效性。

关键词: 重卡 AMT；下壳体断裂；拨叉