The Research Of Vehicle Emission Properties Optimization Based On Oxygen Sensor

With the rapid development of automobile industry,the environmental pollution problem is increasingly serious,prompting car is becoming more and more strict emission regulations,for each big auto companies,how to reduce the discharge of pollutants is a leading technology research direction.Therefore,the related parts research and development is extremely necessary.The study found that gasoline engine cold start phase of THC and CO emissions accounted for about 50% of the vehicle testing process emissions to 80%,therefore,cold start of combustion optimization and emission control is one of the key technology of automotive engine emissions control.In order to improve the conversion efficiency of three yuan catalysts to fully purify exhaust to meet increasingly stringent emission regulations,the current widely used strategy is air-fuel ratio by oxygen sensor output signal,back to the ECU,so as to realize the closed loop correction of the injection pulse width,the actual air-fuel ratio close to the theory of air-fuel ratio,namely the air-fuel ratio closed-loop control.And in the process of cold start,due to guarantee the reliability of the starting,the control system by adjusting the injection pulse width makes partial rich mixture,and this will lead to the beginning of the cold start THC emissions grew rapidly,and because of the dew point is not the working temperature of oxygen sensor cannot reach effective output air-fuel ratio feedback signal,to realize the air-fuel ratio closed-loop control,the control system can only according to the theoretical calculation of adjusting the injection pulse width,the control of the air-fuel ratio is not accurate,resulting in a large number of emissions of pollutants.Oxygen sensor as an important parts in the engine emission control,the air-fuel ratio closed-loop control and optimize the emission performance is critical.Traditional two point oxygen sensor due to its output signal will appear near the theory air-fuel ratio jump features,can't accurately feedback air-fuel ratio can only distinguish partial rich mixture or slants thin,so even in closed loop,the control system can't accurate surface-to-air fuel ratio to control the correction,there is a deviation.And wide domain type oxygen sensor can be in a wide range of air-fuel ratio continuously output signal,can accurate surface-to-air fuel ratio control system to control the correction,in the case of the increasingly stringent emissions regulations,the use of wide domain type oxygen sensor is becoming more and more widely.At the same time,in order to reduce the emission of cold start phase now has a new no oxygen sensor,dew point during the cold start phase without dew point,can be directly to high-power heating of oxygen sensor,as soon as possible to the working temperature effectively,so as early as possible into the air-fuel ratio closed-loop control.Through the experiment,through the accurate control of air-fuel ratio,keep air-fuel ratio near the theory air-fuel ratio,can effectively reduce the HC emissions cold start phase,thus reducing the emission test phase of the discharge of pollutants,to meet the higher emissions regulations.