热膜式空气质量流量微型传感器的自诊断

以微硅片传感器件为对象,研究汽车进气的热膜式空气质量流量微型传感器的自诊断原理及其实现方法.该方法根据内燃机中的热量传递和空气质量流量测量的基本原理,设计了基于自诊断的热膜式空气质量流量微型传感器,该传感器由基于Heraeus微硅片的加热传感单元与温度传感单元、信号处理与转换器、加热器、加热控制器和微型计算机组成.针对该传感器结构和空气在传感器中的强制对流方式,从理论与仿真实验两方面.推导出在一定的发动机工况下,加热器的热流量与空气质量流量的关系,获取了加热器表面温度、加热器上流区域的温度和其下流区域的温度随发动机工况变化而改变的关系,并以此来对该微型传感器进行故障的自诊断,理论与仿真实验表明,该方法具有可行和实用的特点.

Self diagnosis for hot film mass airflow microsensor

The self-diagnosis method on hot film mass airflow microsensor has been developed for ve-hicle intake air in the paper. Based on the theory of heat transfer and mass airflow rate measurement for internal combustion engine, first, a hot film mass airflow microsensor on serf-diagnosis is designed. It is composed of heat sensing unit, temperature sensing unit with Heraeus silicon, signal processor and con-verters, heater, heating controller and computer. The temperature sensing unit is separated into heater upstream temperature sensor resistor and heater downstream temperature sensor resistor according to in-take air flow direction. Then, from both theory and experiments, the relation between the heat transfer rate of heater and the mass airflow rate on intake air are deduced in a certain engine working condition, and the temperature distributing rules in heater surface, heater upstream and heater downstream are ob-tained. These relations rules are regarded as the reference models of self-diagnosis in the microsensor. Fi-nally, the failure of microsensor can be detected to compare the real-time measurement model with the reference one. Thus, this method can not only measure mass airflow rate in real time, but also inspect di-agnosis fault by heat sensing unit and temperature sensing unit automatically.