Low-Emission and Fuel-Efficient Exhaust System with new Air-fuel Ratio Sensor 2020-01-0655
This paper reviews an exhaust emission control system using a new Air-fuel ratio (hereafter, A/F) sensor that contributes to low emissions and low fuel consumption of gasoline engines.
The first technical highlight is that the newly designed A/F sensor enables feedback control immediately after the engine starts at any temperature. In order to achieve the delay-less feedback control, it was important not only that the sensor was not broken, but also that the sensor characteristics are not affected by the condensed water in the exhaust pipe. Specifically, the developed protective layer technology with water repellent function in the sensor element was effective in achieving both reliability and characteristics.
The second highlight is the reduction of sensor power consumption. Since the A/F sensor is usually kept at 700-800 ° C, it is one of the most power consuming parts of the engine. The new A/F sensor has the highest thermal efficiency by low-temperature activation. In addition, for vehicles such as hybrid electric vehicles (HEVs) that the engine stops intermittently, the sensor control method was built to reduce sensor power while the engine was stopped. The new control can reduce the power without any control error despite repeated sensor’s power ON/OFF by ensuring sensor output stability and reliability.
As a result, emissions during start-up were reduced by 20%, and power consumption of sensors was reduced by 50% in Federal esrt Procedure (FTP).
Furthermore, this technology has the potential to reduce 50% HC in the tightening of regulations on low-temperature emissions such as at -7 °C.
Go Hayashita, Kazuki Takahashi, Keiichiro Aoki, Makoto Ito
Toyota Motor Corporation, DENSO CORPORATION