This paper describes an exhaust system using a new air-fuel ratio (hereinafter, A/F) sensor that contributes to low emissions and low fuel consumption of gasoline engines.
As the first technical feature, the water splash resistance of the A/F sensor has been substantially improved which allows A/F control to be enabled without delay during engine cold start. To realize this capability, it is important that the sensor characteristics are not affected by the condensed water generated in the exhaust pipe. Therefore, a technique that has the effectiveness of a water splash resistance layer with water repellent function is demonstrated.
As the second technical feature, the power consumption of the sensor has been substantially reduced. This is achieved by improving thermal efficiency of the sensor that the element can be activated at a low temperature. In addition, for vehicles with intermittent engine stops, a control system is developed to reduce the power consumption by lowering the sensor temperature while the engine stops. Moreover, by ensuring sensor output stability and reliability during ON-OFF cycles, the reduction of power consumption has been realized without any control error. This technology will be more beneficial for the vehicles with longer engine stop period such as hybrid electric vehicles (hereinafter, HEVs) and plug-in hybrid electric vehicles (hereinafter, PHEVs).
As a result, we reduced the emissions during engine cold start by 20% and sensor power consumption by 45%. In addition, we reduced HC by 50% at low temperature to address the expected tightening of cold environment emission regulations.