Research On Exhaust Temperature Sensor

Negative Temperature Coefficient (NTC) Thermistor's merit is more sensitive, stable, low cost and small volume. NTC is popular used for measuring the temperature sensitivity cell in testing and monitoring system, especially necessarily used in vehicle controlling system. The temperature sensor with thermistor as core cell is necessarily used in the vehicle controlling system. The most vehicles are used 3 to 5 temperature sensors, and the measuring scope is from below zero 30 centigrade to 150 centigrade. In order to protect environment, reduce the vehicle exhausting pollution, so that it causes continuous improvement of vehicle exhaust regulation. Owing to limit the diesel engine NOx exhaust volume, it isn't qualified the related regulation by the engine individually. Therefore, the selective catalytic reduction technology is occurred regard to the diesel engine NOx exhaust. SCR technology is after treatment for reducing NOx exhaust outside engine, which is inject 32.5% Urea solution in exhaust pipe before catalyst, in order to reacting NOx with Urea solution, and reduce the NOx exhaust. It is very important for controlling temperature in SCR system. It is necessary to include NH3 with suitable temperature in SCR deoxidizing reaction process. When the temperature is too high, and then the NH3 will fire by them, and no reaction; if the temperature is too low, and then the reaction speed is slowly, and it will destroy the catalysis.Therefore, we need monitor the exhaust temperature normally, and according to the temperature change to deal with the system parameter. The temperature sensor measuring scope is from below zero 30 centigrade to 220 centigrade in the system. Moreover, the reaction requirement is less than 4 seconds, and need bear strictly chemical resistance and mechanical shocking. The normal temperature sensor can't satisfy and reach the above requirements.With the development demand of exhaust controlling system, our company tries to design a new exhaust temperature sensor. This product is applied to whole plastic outer shell, and micro thermistor with glass shell. The whole outer shell reduces the product weight and producing process, in order to reduce the product cost. It is creative applied un-normal material LCP resin. When LCP resin change small and with mechanical strengthen after injected, and can satisfy the requirement of plastic fixing standard. Other merit is more heat-resistant, and it can work from 200 centigrade to 300 centigrade for a long time.The temperature sensor's core part thermistor is applied to EPCOS companies' G540 product. This product is minor and reacts quickly, which is used super higher anti-chemical resistance. This temperature sensor is used with standard design concept. Changing thermistor and LCP resin is too easy, so it produced with the same outer, but different function temperature sensor to fit different environment.My thesis is mainly talk about new exhaust temperature sensor design concept, production techniques design and laboratory research and analysis.With many researchers and suppliers active support, we try to produce small serial production. According to GM, VW and other OEM company automotive parts testing standard to verify and the result is arrived basic requirement. However, the module laboratory environment is different with reality, so the testing result won't be verify the product is reliable, and qualified with real requirement. In addition, at present it is lack of result of road test on vehicle, so it is necessary to work on continuous project and work.According to present China market, SCR system is still during try-out stage, and it is still need a long way to develop and research. The researchers need discover the sensor developing tendency and market requirement. In addition, small structure and low cost is the privilege of exhaust temperature sensor. We are believed that the exhaust temperature will be popular in the future market.