车用氧传感器失效案例分析及微裂纹检测方法研究

Analysis of Failure Cases of Vehicle Oxygen Sensors&Study of Microcrack Detection Methods

为解决陶瓷片芯内部产生微裂纹而导致传感器总成失效的问题,研究分析了一种简单且无损检测陶瓷片芯微裂纹的方法,该方法利用酒精对陶瓷良好的浸润性,可填充到裂纹中间,利用酒精与空气电导率的差异,通过检测陶瓷片芯电流的变化快速判断片芯内部是否出现微裂纹;将该方法应用于某车型前氧传感器失效案例分析,采用光学显微镜和高精度CT进一步证明了微裂纹的产生及原因;结果表明,酒精检测法可准确判断陶瓷片芯内部产生微裂纹,裂纹产生的原因是加热器电压过高,内部热应力不均匀导致加热器电极与片芯主体脱离,进而导致片芯内部产生微裂纹。

In order to solve the problem of microcracks in the ceramic chips causing failure of the sensor assembly,this article studied and analyzed a simple and non-destructive method for detecting the microcracks in the ceramic chips,which can be filled in the middle of the crack by using the good wettability of alcohol to the ceramic,and the difference between the conductivity of alcohol and air was used to quickly determine whether there were microcracks in the chips by detecting the change of the current of the ceramic chips.This method was applied to the case study of the failure of the front oxygen sensor of a vehicle model.The cause of microcracks was further proved by optical microscopy and high-precision CT.The results show that the alcohol detection method could accurately determine the occurrence of microcracks inside ceramic chips,and the cause of cracks is excessively high heater voltage,and the uneven internal thermal stress,which cause the heater electrode to detach from the chips’body,which in turn leads to microcracks inside the chips.