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Oxygen Sensor The Advantages Of Easy Measurement And Accurate Use

Oxygen sensor is the standard configuration of the car, using the Nernst principle. It is the use of ceramic sensors to measure the oxygen potential in automotive exhaust pipe, the chemical equilibrium principle to calculate the corresponding oxygen concentration, to monitor and control the combustion air-fuel ratio, to ensure product quality and exhaust emission standards of the measurement elements. It has the advantages of simple structure, quick response, easy maintenance, convenient use and accurate measurement.

Oxygen sensors are essential components in an engine that uses a ternary catalytic converter to reduce exhaust pollution. As the air-fuel ratio of mixed gas deviates from the theoretical air-fuel ratio, the purification capability of the ternary catalysts to CO, HC and NOx will be reduced drastically, so the oxygen sensor is installed in the exhaust pipe to detect the concentration of oxygen in the exhaust gas, and to send the feedback signal to the ECU, and then the ECU controls the increase or decrease of fuel injection quantity, The air-fuel ratio of the mixed gas is controlled near the theoretical value.

1. function

In order to obtain high exhaust gas purification rate and reduce the carbon monoxide, (HC) hydrocarbons and NOx compounds in exhaust gas, the ternary catalyst must be used. However, in order to effectively use the ternary catalytic converter, the air-fuel ratio must be controlled precisely so that it is always close to the theoretical air-fuel ratio. The catalyst is usually installed between the exhaust manifold and the muffler. An oxygen sensor has a property that has a mutation in the voltage output near the theoretical air-fuel ratio (14.7:1). This feature is used to detect the concentration of oxygen in the exhaust and feed back to the computer to control the air-fuel ratio. When the actual Air-fuel ratio is higher, the oxygen concentration increases in the exhaust gas and the oxygen sensor informs the ECU of the state of the mixture (small electromotive force: o Volt). When the air-fuel ratio theory is low, the concentration of oxygen in the exhaust gas decreases while the state of the oxygen sensor (Big electromotive force: 1 volts) Notices (ECU) computer.

The ECU judges the low or high air-fuel ratio according to the electromotive force difference from the oxygen sensor, and controls the fuel injection duration accordingly. However, such as the oxygen transmitter failure to make the output electromotive force is not normal, (ECU) computer can not accurately control the air-fuel ratio. So the oxygen sensor can also make up for the error caused by the abrasion of other parts of mechanical and EFI system. It can be said that the only "smart" sensor in the EFI system.

The role of the sensor is to determine the excess of oxygen in the exhaust of the engine after combustion, namely oxygen content, and converts the oxygen content to the voltage signal to the engine computer, enables the engine to realize the closed-loop control with the excessive air factor as the target; to ensure the hydrocarbon (HC) in the exhaust of the ternary catalytic converter, Carbon monoxide (CO) and nitrogen oxides (NOx) three kinds of pollutants have the greatest conversion efficiency, the largest degree of emission of pollutants conversion and purification.

2. Principle

Oxygen sensor is the standard configuration of the automobile, it is the use of ceramic sensors to measure the oxygen potential in automobile exhaust pipe, the chemical equilibrium principle to calculate the corresponding oxygen concentration, to monitor and control the combustion air-fuel ratio, to ensure product quality and exhaust emission standards of the measurement elements. Oxygen sensor is widely used in various types of coal combustion, oil combustion, gas combustion and other furnace atmosphere control, it is the best measurement of combustion atmosphere at present, with simple structure, rapid response, easy maintenance, easy to use, accurate measurement and other advantages. Using the sensor to measure and control the combustion atmosphere can not only stabilize and improve the product quality, but also shorten the production cycle and save energy.

The oxygen sensor working on the car is similar to a dry cell, and the zirconia element in the sensor acts as an electrolyte. Its basic working principle is: Under certain conditions, the use of zirconia both inside and outside the oxygen concentration difference, the potential difference, and the greater the concentration difference, the greater the potential. The oxygen content in the atmosphere is 21%, and the exhaust gas after combustion of the concentrated mixture does not actually contain oxygen, and the waste gas produced after the combustion of the dilute mixture or the exhaust gas from the lack of fire contains more oxygen, but it is still much less than the oxygen in the atmosphere. Under the catalysis of high temperature and platinum, the negatively charged oxygen ions are adsorbed on the inner and outer surfaces of the zirconia casing. Because the oxygen in the atmosphere is much more than the oxygen in the exhaust gas, the casing and the atmosphere on one side of the gas adsorption than the other side of the negative ions, the concentration difference between the two ions produce electromotive force.

When the oxygen concentration of the exhaust side of the automobile casing is low, a high voltage (0.6~1v) is produced between the oxygen sensor electrodes, the voltage signal is sent to the automobile ECU to enlarge the processing, the ECU regards the high voltage signal as the concentrated mixture, and the low voltage signal as the dilute mixture. According to the voltage signal of the oxygen sensor, the computer is diluted or enriched by the best air-fuel ratio as close to 14.7:1 as possible. Therefore, oxygen sensor is the key sensor for electronic control of fuel metering. Oxygen sensor only at high temperature (at the end of the 300°c above) its characteristics can be fully reflected in order to output voltage. When it is about 800°c, it reacts the most quickly to the changes in the mixture, and it changes significantly at low temperatures.