突跳式温控器的失效分析

Failure analysis of the snap-action thermostats

突跳式温控器失效会导致电茶壶、电饭煲等家电产品控温和过热保护功能失效.采用FMECA分析方法,确定导致突跳式温控器失效的关键元件,通过关键元件失效分析,得到突跳式温控器的失效机理,提出提高突跳式温控器工作可靠性的技术措施.FMECA分析表明,突跳式温控器的主要失效模式为触头粘结、簧片断裂和温度漂移,引起突跳式温控器失效的关键元件为触头、簧片、热双金属片.关键元件失效分析表明,触头粘结现象是由于触头燃弧引起的,簧片断裂现象是由于簧片受到的疲劳应力超过疲劳强度引起的,温度漂移现象是由于热双金属片尺寸参数改变或热双金属片层间分离引起的.

The failure of snap-action thermostats could result in failures of temperature control and overheating protection function for the electrical kettle, electrical cooker and other household electrical appliances. By applying FMECA analysis （failure mode effects and criticality analysis）, the key components resulting snap-action thermostats failure were determined. Then through key components failure analysis, failure mechanism of the snap-action thermostats were identified, and some measures were provided to improve the products＇ working reliability. FMECA analysis results indicate that the main failure modes of the snap-action thermostats are contact bonding, leaf-spring fracture and temperature drift failure, and key components resulting in failure of the snap-action thermostat are electrical contact, leaf-spring and thermostatic bimetal-strip. The re- sults of the key components failure analysis show that contact bonding phenomenon is caused by arc. The reason of leaf-spring fracture phenomenon is that fatigue stress exceeds fatigue intensity of leaf-spring. Temperature drift phenomenon of the snap-action thermostats is caused by size change or layers separation of the thermostatic bimetal-strip.