可变长度进气歧管的失效分析

Failure Analysis of Variable Intake Manifold

在某款发动机台架耐久试验中,可变进气歧管的VGIS卡死无法动作,导致发动机扭矩突然下降。通过拆解分析、振动测试、振动试验故障重现等方法分析VGIS卡死原因。结果表明:在发动机振动作用下,VGIS执行机构驱动柄与限位块相对运动摩擦过大,满足摩擦焊接的机制造成粘连,导致VGIS卡死。分析优化方案,优选成本低、周期短的改进方案——将接触面改为塑料与金属接触,避免塑料粘连。改进后的可变进气歧管通过发动机台架耐久试验和整车耐久试验验证,VGIS卡死问题圆满解决,并为其他可变进气歧管的设计提供借鉴。

Intake manifold VGIS is locked in engine endurance test, leading to engine torque drop unexpectedly. The failure cause of VGIS was analyzed by teardown analysis, engine vibration measurement and vibration test fault recurrence. The result shows that the friction between VGIS driver dog and its stop block is large, and meets fiction welding conditions, driver dog sticks on stop block, and leads to VGIS lock. Several optimization schemes were analyzed, the low cost and simplest scheme was selected in which a steel slice was inserted on the contact surface, making driver dog contact with steel avoid plastic sticking. The optimized variable intake manifold has passed the engine rig test and vehicle endurance test. VGIS failure problem is solved successfully and it provides a reference for other variable intake manifold design.