Zirconia oxygen probe (oxygen sensor)(ZRO2-II) working principle

The zirconia oxygen sensor works as follows: The ceramic body of the zirconium tube is porous, and oxygen can penetrate into the porous solid electrolyte. At higher temperatures, oxygen ionizes. As long as the oxygen content outside the zirconium tube (atmosphere) (exhaust gas) side is different and there is a difference in oxygen concentration, oxygen ions in the solid electrolyte are diffused from the atmosphere side to the exhaust side, so that the zirconium tube forms a microbattery and generates voltage between the platinum electrode of the zirconium tube. When the mixture is thin, the oxygen content in the exhaust is more, the oxygen concentration difference between the two sides is small, the voltage is small; When the mixture is concentrated, the oxygen content in the exhaust is less, and the content of CO, CH and NOx is more. Under the catalytic action of the platinum on the outer surface of the zirconium tube, these components react with oxygen, consume the residual oxygen in the waste gas, so that the oxygen concentration on the outer surface of the zirconium tube becomes zero, so that the oxygen concentration difference on both sides of the zirconium tube suddenly increases, and the voltage generated between the poles also increases.

Therefore, the voltage generated by oxygen sensor in excess air coefficient λ=1 up and down mutation, λ>1, oxygen sensor output voltage is almost zero, λ<1, oxygen sensor output voltage is close to 1V. In the closed-loop control process of the engine mixture, the oxygen sensor is equivalent to a concentration switch. According to the change of the air-fuel ratio of the mixture, the electrical pulse signal with the change of the width is input to the ECU. The ECU controls the amount of fuel injection according to the feedback signal of the oxygen sensor, so that the harmful gas composition in the exhaust is reduced to the minimum.