The excavator engine oxygen sensor is divided into zirconium dioxide oxygen sensor, heating type zirconium dioxide oxygen sensor, titanium dichloride oxygen sensor, excavator broadband oxygen sensor and so on.
1. Excavator zirconium dioxide oxygen sensor
The zirconium dioxide oxygen sensor is composed of a zirconium tube, a platinum electrode and a protective cover. The zirconium tube is a solid electrolyte element made of chromium dioxide. A layer of porous platinum film is coated on the inner and outer sides of the zirconium tube as electrodes. The inside of the zirconium tube is open to the atmosphere, and the outside is in contact with the exhaust.
The oxygen sensor is installed in the exhaust pipe. During operation, oxygen is ionized under the high temperature of the exhaust gas. The concentration of oxygen ions on the inside of the zirconium tube is high, and the concentration of oxygen ions on the outside is low. The exhaust side diffuses, thereby forming an electromotive force between the two electrodes.
(1) When the mixed gas is lean, the oxygen content in the exhaust gas is high, the concentration difference between the inside and outside of the zirconium tube is small, and the generated electromotive force is small, about 100mV.
(2) When the mixed gas is rich, the oxygen content in the exhaust gas is low, the concentration difference is large, and the generated electromotive force is large, about 900mV. The size of the electromotive force changes suddenly with the theoretical air-fuel ratio as the boundary. No. Wisdom makes sense.
(3) The output characteristic of the oxygen sensor is related to the exhaust temperature. When the exhaust temperature is lower than a certain value (about 300 ° C), the output characteristic of the oxygen sensor is unstable, so the oxygen sensor is generally installed at a location where the exhaust temperature is high. Some models are also equipped with an exhaust temperature sensor. After the signal of the exhaust temperature sensor reaches a certain value, the electronic control unit begins to perform air-fuel ratio feedback correction based on the signal of the oxygen sensor, that is, to start the engine closed-loop operation.
2. Excavator heating type zirconium dioxide oxygen sensor
The heated zirconium dioxide oxygen sensor places a ceramic heater inside the zirconium tube. When the engine is working, the heater is controlled by the electronic control unit. When the engine load is small and the exhaust temperature is low, the heater is energized to ensure that the operating temperature of the oxygen sensor is normal.
The heating type zirconium dioxide oxygen sensor can be installed on the exhaust pipe far away from the engine, and can withstand long-term full-load operation without damage.
3. Titanium dichloride sensor for excavator
The titanium dioxide oxygen sensor is made of high-purity semiconductor titanium dioxide. Under normal conditions, this sensor has a high resistance value. Once the surrounding oxygen is insufficient, the crystal lattice causes defects and the resistance value decreases.
Titanium dioxide oxygen sensor When the oxygen content in the exhaust gas is high and the oxygen concentration is high, the titanium dioxide is in a high resistance state. When the oxygen concentration in the exhaust gas is low, the resistance value of thorium dioxide is greatly reduced, and its resistance value changes suddenly around the theoretical air-fuel ratio.
Compared with the osmium dioxide sensor, the titanium dioxide oxygen sensor has the advantages of simple structure, small size and low cost. However, because the resistance of titanium dioxide is greatly affected by temperature, it is necessary to add a temperature correction circuit or a built-in heater to make the characteristics Stable so that it can be tested even at high temperatures.
4. Broadband oxygen sensor for excavator
The characteristic of the broadband oxygen sensor is that it can receive oxygen signals in the entire engine speed range. The oxygen sensor can adjust the exhaust gas recirculation flow and correct the smoke emission.
Broadband oxygen sensor When the mixture is too rich, the sensor voltage exceeds 450mV, the unit pump works at the original working current, and the oxygen content of the test chamber is low. At this time, the electronic control unit increases the working current of the unit pump, which increases the rotation speed of the unit pump. , Increase the pump oxygen speed. The amount of oxygen pumped by the unit pump into the test chamber increases, and the sensor voltage is restored to 450mV.
When the mixed gas is too lean, the pump will pump more oxygen at the original speed. The oxygen content in the test chamber is more and the sensor voltage drops. At this time, the amount of fuel injection is increased, and the working current of the unit pump is reduced to make the pump The amount of oxygen in the human test room is reduced. The working current of the unit pump is transferred to the electronic control unit, which converts it into a voltage signal.
