Automobile oxygen sensor is an important part of the automotive electronic control system, it can effectively improve the engine performance and the economy of the vehicle. Understanding the working principle of automobile oxygen sensors and the reasons for the failure of automobile oxygen sensors are of great help to the overall control of automobile control systems. This article introduces the working principle of automobile oxygen sensor and its failure reasons.
1. Working principle of automobile oxygen sensor
Zirconia (ZrO2) is a kind of solid electrolyte. It has a characteristic that oxygen ions are easy to move at high temperature. This type of oxygen sensor sinters zirconia into a tube, and coats the inner and outer layers with platinum (Pt). This is the role of the oxidation catalyst. When the oxygen ions move, an electromotive force is generated, and the size of the electromotive force depends on the zirconia. The platinum on both sides is exposed to oxygen, and the outermost layer is covered with a protective shell.
The inner platinum surface is in contact with the atmosphere, so the oxygen concentration is high, and the outer platinum is in contact with the exhaust gas, and the oxygen concentration is low. When the mixing is relatively high, the oxygen contained in the exhaust gas is relatively reduced, so the platinum contacted by the platinum on both sides of the zirconia has a high and low drop, and the generated electromotive force is relatively high (nearly 1V); when the mixing is lean After burning, there is more excess oxygen, and the oxygen drop on the platinum layer on both sides of the zirconia is small, so the generated electromotive force is low (nearly 0V).
From this voltage signal, the engine control computer can detect the condition of the mixing ratio at that time. However, the oxygen sensor must be used normally at high temperature (400 ℃ ~ 900 ℃). Therefore, when the engine starts to start, the oxygen sensor has not yet started to function. It must wait until it reaches its working temperature before it begins to generate electromotive force, so the subsequent The oxygen sensors are all modified into heating type, as shown in the figure, that is, the ceramic heater is used to quickly reach the normal working state, so the current model can almost 30 seconds after the engine is started, the car oxygen sensor is It can provide the correct signal for the computer, and some models can even reach a lower time.
2. Reasons for the failure of automotive oxygen sensors
The main reason for the failure of automotive oxygen sensors is the aging and poisoning of sensing elements. The main reason for the aging of the oxygen sensor is that the local surface temperature of the sensing element is too high. The phenomenon that the sensing element of the oxygen sensor is contaminated and fails is called poisoning. Oxygen sensor poisoning mainly refers to lead poisoning, silicon poisoning, and phosphorus poisoning.
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