Oxygen sensor.

(1) the zirconia oxygen sensor

Zirconia oxygen sensor is the basic element of zirconia ceramic tube (solid electrolyte), also known as the zirconium tube. Zirconium tube fixed in with the installation of a fixed set of thread, both inside and outside surface is covered with a layer of porous membrane, lead them on the surface of contact with the atmosphere, outer surface in contact with the waste gas. Terminal of oxygen sensor with a metal sheath, it has one for zirconium tube cavity and atmospheric interlinked hole; Platinum wire will zirconium tube surface extremely the bushing terminal lead from now on.

Zirconium oxide after the temperature over 300 ℃, can work normally. Early use of oxygen sensor * exhaust heat, the sensors must be in the engine start running for several minutes before they can begin to work, it is only a wiring connected to the ECU. Now, most of the cars using oxygen sensor with heater, this kind of sensor with an electric heating element, can be 20-30 seconds after the engine start rapidly oxygen sensor is heated to working temperature. It has three wiring, smokes ECU, the other two grounding and power supply respectively. Zirconium tube of the ceramic body is porous, the infiltration of oxygen, there was an ionization at higher temperature. Because the zirconium tube, the outer oxygen content, concentration, and oxygen ions from one side of lateral exhaust air diffusion, so that the zirconium tube into a small battery, in two platinum electrode voltage is produced.

When the actual air/fuel ratio less than theory air-fuel ratio, namely the engine at a relatively strong mixture operation, less oxygen content in exhaust, but more CO, HC, H2, etc. These gases under the effect of lead zirconium tube outer surface catalytic react with oxygen, will run out of the exhaust of residual oxygen, make the zirconium tube outer surface oxygen concentration goes to zero, this makes the zirconium tube, the outer oxygen concentration increased, the two lead electrode voltage surge. Therefore, the zirconium tube oxygen sensor voltage mutation occurs when will in theory air-fuel ratio: lean mixture, the output voltage is almost zero; The rich mixture, the output voltage is close to 1 v.

To accurately keep the concentration for the theory of air/fuel ratio is not possible. Actually feedback control can only be made in the theory of air/fuel ratio near a narrow range of fluctuation, so the oxygen sensor output voltage between 0.1 0.8 V changing changes (usually every 10 seconds more than 8 times). If oxygen sensor output voltage change too slow (less than eight times per 1 OS) or voltage remains the same (either stay in the high voltage or low potential), suggests that oxygen sensor fault, need to repair.

(2) titanium oxide type oxygen sensor

Titanium oxide type oxygen sensor is the use of titanium dioxide material's resistance changes over the oxygen content in exhaust features, so it is also called resistance type oxygen sensor. Titanium dioxide type oxygen sensor are of a similar appearance and zirconia oxygen sensor in the sensor in the front shield is a titanium dioxide thick membrane element. Pure titanium dioxide is a kind of high resistance at room temperature of semiconductor, but once the surface oxygen, whose character defect, less resistance. Due to the resistance of the titanium dioxide also varies with temperature, therefore, in the titanium dioxide type oxygen sensor inside there is also an electric heater, to keep the titanium oxide type oxygen sensor in the engine working process temperature constant.

ECU terminal 2 # 1 v will be a constant voltage on one end of the titanium oxide type oxygen sensor, the sensor with ECU4 # on the other side of the terminal. When the concentration of oxygen in the exhaust fumes changes over the engine mixture concentration, the resistance of the oxygen sensor to change the ECU4 # also along with the change of the voltage drop on the terminal. When 4 # on the terminal voltage is higher than the reference voltage, the ECU for determining mixture too thick; When 4 # on the terminal voltage is lower than the reference voltage, ECU mixture too lean. Through feedback control ECU, can keep the mixture concentration near the theory air-fuel ratio. In the process of the actual feedback control, titanium dioxide oxygen sensor is connected to the ECU of 4 # terminals

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