Long Term Stable NOx Sensor with Integrated In-Connector Control Electronics

This paper describes improvements achieved with regard to the long term stability and the system integrability of a previously described thick film NOx sensor for gasoline lean burn and diesel applications. ^{(1, 2, 3)}

Durability test up to 1000 hours consisting of a temperature cycle have been carried out by a stoichiometric operating gasoline engine test bench. The NOx sensor demonstrates the NOx output shift in terms of the NOx sensitivity less than 5 % on a model gas apparatus and ± 7 % measuring accuracy in practical operating condition on a diesel engine after 1000 hours that is equivalent to approximately 60K miles driving.

The integration of the control electronics for the sensor in its connector is achieved for the sensitive measuring current in the μA-range or less on vehicle applications. The developed electronics functions closed-loop controls for a tip temperature and oxygen pumps as well as a diagnosis of sensor malfunctions.

It also allows a bi-directional data transmission with the engine management system. The NOx sensor demonstrates a feasibility for a regeneration control and an OBD of a NOx storage catalyst system.