变速箱同步器失效过程与失效机理分析

Analysis on Failure Process and Failure Mechanism of Transmission Synchronizer

为分析变速箱同步器的失效过程和失效机理,在自行研制的试验台上对变速箱同步器进行试验。试验过程中,获得每一次换挡时锥体的转速、结合套的位移和摩擦力矩与换挡时间的关系曲线,以及摩擦因数与换挡次数的关系曲线。试验完成后,对摩擦副表面利用扫描电子显微镜和白光干涉形貌仪进行观察,对润滑油内的铁含量利用原子发射光谱仪进行测量。结果表明,随着换挡次数的增加,摩擦因数在不断降低,使得同步器锥体获得的加速度不断减少而在同步阶段所经历的时间不断延长,并最终导致同步器失效。在换挡过程中摩擦副表面的微凸体被磨损以致油膜难以破裂,使得固体摩擦因数所占比例不断降低而油膜摩擦因数逐渐占主导优势,是引起摩擦因数不断降低的主要原因。

Based on a custom-built experimental apparatus, the transmission synchronizer experiment is performed to analyze the failure process and failure mechanism of transmission synchronizer. During the experiment, the rotate speed of cone, the shift of sleeve, the moment of friction with shift time, and the friction coefficient as a function of shift number are obtained. After experiment, the surfaces of friction material are analyzed by scanning electronic microscope （SEM） and the non-contact surface profiler MicroXAMTM respectively, and the Fe content contained in lubricating oil is measured by atomic emission spectrometry. The results indicated that the friction coefficient goes down with the number of shifts, which led to the reduction of the acceleration and the increment of the synchronization time. The synchronizer becomes invalid because of low friction coefficient. During the shift process, the asperities of surface are worn, which makes the oil film rupture difficultly. The proportion of solid friction coefficient continues to reduce and the oil film friction coefficient occupies the dominance gradually, which is the main cause to induce the reduction of friction coefficient.