As for the diagnostic method, I will not repeat it here. I believe we are already familiar with it. When the engine idles and the temperature is normal, if the air-fuel ratio deviates slightly from the stoichiometric air-fuel ratio, then the oxygen sensor output voltage will change from low-pressure to high-pressure cycles. The typical oxygen sensor output voltage changes from a period of 0.3V to 0.8V.
2. Some advices when measuring.
A- The oxygen sensor must be tested with a digital voltmeter. Many data have shown that using other types of low-impedance multimeters will damage the oxygen sensor. However, in actual work, I mentioned that the use of digital meters is not based on information. But for practical work needs.
As we all know, the precise indication range of the analog multimeter is in the middle of its dial, but the voltage signal range of the oxygen sensor that we tested is exactly the opposite of the precision indication range of the analog multimeter. Its maximum value and minimum value are in the multimeter. The two ends, so that if you use an analog multimeter to test the voltage signal of the oxygen sensor is simply not accurate, this is why I use the number is a multimeter.
B-If the oxygen sensor in the exhaust pipe is contaminated and cannot come into contact with oxygen, it may give a continuous high voltage signal C - Sealant should be used as little as possible when replacing the oxygen sensor, for the reason that if an excessive seal is applied The sealant will burn due to high temperatures while the engine is working. The burning waste of the sealant will cause your newly replaced oxygen sensor to quickly age and fail in a relatively short period of time, but you can't find out where the problem is.
3. During measurement, A- If the voltmeter continues to read high voltage, it indicates that the air-fuel ratio may be too rich, or the sensor is contaminated. The B-voltmeter reading continues to low voltage, indicating that the air-fuel ratio may be too high or sensor failure. C- If the oxygen sensor voltage signal remains at an intermediate value, the computer circuit may be broken or the sensor may be damaged.
4. Some notes on the oxygen sensor voltage signal:
In most cases, when we conduct oxygen sensor testing, our maintenance personnel will let the engine work in advance for a few minutes to ten minutes, let the engine enter the closed-loop working state, measure whether the voltage signal output by the oxygen sensor changes between high and low, There is nothing wrong with this, but can you say why you would like to do this? I have met many repair engineers in their understanding that the oxygen sensor will generate a changing voltage signal as the operating temperature of the engine increases. If the output voltage signal remains basically constant, it is a basically stable constant value. The oxygen sensor is damaged. In fact, this is a mistaken understanding of oxygen sensors. In fact, the change in the voltage signal of the oxygen sensor is determined by the change in the oxygen content in the exhaust gas emitted by the engine. The size of the engine load and the different operating conditions directly lead to different oxygen levels in the exhaust gas of the engine. With the change of the oxygen content, the voltage signal of the oxygen sensor naturally changes. Therefore, the change of the oxygen sensor voltage signal is affected by the operating conditions of the engine. Try to think about what happens to the oxygen sensor if the engine is always in a rich state for some reason, or if the mixture is too busy. There are two answers - (1) Always output a high voltage signal, (2) Always output a low voltage signal, but this does not indicate that the oxygen sensor is damaged.
5. Errors in Diagnostic Ideas In the actual maintenance work, the engine is in poor working condition. For example, if the engine is in unstable condition, such as idle speed instability, idle engine black smoke, and insufficient power, etc., during the inspection process, we will read. The fault code of the engine control computer sometimes has information that the oxygen sensor has been damaged. We have performed clear code, randomly read the current fault code after a period of road tests, and find that other fault codes do not appear but the oxygen sensor The damaged fault message still exists, and then the performance of the oxygen sensor is tested, confirming that it is really damaged and will be replaced without hesitation.
A4 Paper Machine
This is A4 Paper Making Machine,writing and printing paper making machine.
According to the different paper grade and working speed, this kind of paper machine is needed to select the way of papermaking, dewatering structure of press section, dryer cylinder bank, sizing and finishing equipments.
Sheet forming can use the open-type headbox, air-cushion headbox, and hydraulic headbox, gap former and inclined wire former. According to the paper uniformity requirement, it can use distributor roll or finishing surface roll.
Press dewatering type is multi-roll and multi-press nip press rather than large-diameter press. As the low basis weight and wet strength of this kind of paper, it usually makes the low strength wet sheet attached to the felt or guide rolls during each section mutual transferring and full web leading as much as possible.
Dryer section: dryer cylinder group. Paper leading: active or passive paper rope system. Finishing equipment: To choose according to the paper grade requirement.
Now we introduce the technical proposal and structural drawing of Fourdrinier advanced printing paper machine, which we made for Taiqian Minrui Huatong Paper Company in Henan province, China. The advanced printing paper of this company is the famous brand in China.
Trimmed width: 2640mm
Working speed: 400m/min
Basis weight: 50-100g/sq.m.
Headbox: Air-cushion headbox
Forming table length: 15m
Suction flat box with all stainless steel micro-crystal cover.
Press section: four rolls two press nips
The wet sheet is stripped by pick-up suction unit.
The second under press nip rubber blind bottom roll diameter is Φ800mm, with drive unit;
The suction top roll diameter is Φ800mm, with drive unit.
The top press nip is made by a stone roll and a rubber roll. The rubber roll diameter isΦ800mm, with drive unit;
The stone roll diameter is Φ850mm, with cut squirt.
This structure ensures the low strength wet sheet can press smoothly and paper breaks can be reduced.
The smooth press rubber bottom roll diameter is Φ800mm; the top stone roll diameter isΦ850mm. The paper leading roll has the drive unit.
The dryer section has 32 dryer cylinders with the diameter of Φ1800mm, which is divided into five groups: three groups for before-sizing, two groups for after-sizing. The top and bottom felt of first group and the group at the back of sizing machine is equipped with six felt drying cylinder with the diameter of Φ1250mm, which can dry the moisture well and improve the drying efficiency.
The paper leading roll has the drive unit. The paper leading type is three-stage passive paper rope system.
Sizing machine: inclined type surface-sizing machine.
Calender: four roll three press nips; the number is decided by the demands.
Reeler: horizontal pneumatic reeling machine.
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