*3.1. Typical Failure Type*

According to the operation record of the HMCVT test platform, the fault of the shift hydraulic system of the HMCVT can be defined as five types of modes to be identified, namely:


(5) Leakage of the branch of the oil pipeline (Fault Type 5): the fault generally occurs at the place of the pipe joint of the branch oil pipeline, and a partial external leakage occurs in the oil pipeline.

The oil pressure may be established normally, but the steady-state pressure of the clutch branch oil circuit is reduced, and it will cause air to mix in, causing cavitation and vibration of the hydraulic oil during the circulation process. This situation also reduces the shift section quality of the transmission.

Changes in the parameters of the hydraulic system can have a greater impact on the quality of the change section. Therefore, if the fault is not diagnosed in time, when this change reaches a certain level, it will inevitably have a significant impact on the shift section quality, thereby affecting driving comfort and threatening driving safety.
