As the whole world has been getting more concerned about the environmental protection, the emission regulations are getting stricter.
The requirement to diesel engine is to develop the high-level engine management system to reduce both PM(Particulate Matter)and NOx. For PM reduction, post-treatment technology using a pressure sensor and a diesel particulate filter (hereinafter referred to as DPF) is necessary. This system burns out the clogged PM at the filter that the pressure sensor detects. The pressure sensor used in the DPF system has to be at an affordable price and to be reliable against corrosion, freezing, moisture and clogged soot in the harsh environment of exhaust gas with high humidity where highly-acid condensation water and the produced soot can intrude.
This paper describes our newly developed pressure sensor that is suitable for the DPF system.
The main features are as follows:
a. Semiconductor type sensor with a simple structure and being less costly.
b. Employing back surface sensing method and gel protection structure to achieve high reliability against corrosion, freezing and clogging by keeping the surface of the sensor chip circuit away from the exhaust gas. The protection gel is highly acid-resistant to stand in such a tough condition, which was newly developed.