The fault diagnosis of diesel engine includes two aspects, that is to use a simple method to quickly reduce the fault range, and then to determine whether the states of each part in the fault section are good or bad. The differences between the two are different and interconnected.
1 septum Division
Partial separation or partition of a system or part of the work, by observing the changes in the signs to determine the range of the fault range, called "division division" generally separated or separated from a certain part, if the fault signs are immediately eliminated, that is, the fault occurs at the place; if the fault signs still exist, the fault is found to be in other places. Diagnosis diesel engine black If a cigarette is cut off, if a cylinder is cut off, the black smoke will be removed immediately, indicating that the fault occurred in the cylinder, and then the cylinder should be further inspected.
2- test method
In some parts of the fault range, it is called "exploratory method" to judge whether or not it is constant by exploratory removal or adjustment measures. This method is based on a thorough analysis, and should be reduced as far as possible, and the possibility of decomposing components into Part C for exploratory adjustment must be avoided, and the possibility of restoring the original sample must be taken into account. Sex, and it is confirmed that it will not cause adverse consequences, and should avoid several exploratory adjustments at the same time in several parts or in the same part, in order to prevent confusion and illusion.
3 comparison method
Replace the problem with the same parts of the normal work, and judge whether there is a fault according to the change of the sign. It is called a "comparison method". For example, when the injector of a certain cylinder is suspected to have abnormal work, the injector of this cylinder can be replaced by the other cylinder injector that works normally. If the fault signs are not changed, if the fault signs are not changed, the fault location is in other places. If the oil temperature is too high, if the radiator efficiency is too high, the normal radiator can be replaced by the replacement. If the engine oil temperature is restored to normal, that is to say the original radiator has problems. The measures taken to determine the technical state of each department should be determined. Therefore, the blind disassembly and replacement should be reduced as far as possible. In fact, a certain comparative component is included in various diagnostic methods, not only the comparison of parts.
4 experience method
Depending on the senses of the ear, eye, nose and body of the operator, the method of determining the technical state of each part is called "experience method".
(1) auscultation: according to the periodic abnormal characteristics of the tone, volume and sound of the diesel engine, the fault is judged by the contact with the ear or the metal bar. According to the sound characteristics of the locomotive (such as the tone, the periodicity of the volume change, etc.), it is called "auscultation", called "auscultation". When the machine is working normally, the sound is normal and can be made from the parts of the work. It can be roughly distinguished from the normal work. When you hear the abnormal sound, there will be an abnormal feeling. The obvious sounds can be clearly identified by the ear; the mixed and difficult different sounds can be heard by the stethoscope. Therefore, the auscultation can be heard. Therefore, by auscultation. Means can detect faults early and eliminate them in time.
Because of the size, shape and material of the parts, the noise varies, and it varies with the temperature of the diesel engine, the speed of the speed, the size of the load and the lubrication condition. Some are crisp, sharp, short, some sound is low and blunt, some sound is rough, some are slight, some are rhythmic and some are continuous knocking; Some are serious at high speed, some are prominent at idle speed; some are clear at the moment of speed change, some are obvious when the speed is stable; some appear when the cold car has just started, some are aggravated with the increase of temperature; some are aggravated in the empty car, some are heavy when the load is heavy; and some noise appears with the fever phenomenon. No matter what the noise is, it is very loud when it is poorly lubricated.
At the time of auscultation, in the cold car, at idle, middle speed, sudden increase in speed, or in the different conditions such as empty, load and other conditions, carefully distinguish the sound, sometimes close to the ringing part, sometimes need to be far away from the sound of the sound of auscultation.
(2) observation: through the observation of the eye, grasp the signs of failure. For example, observe the obvious defects and damage characteristics of the diesel engine's outer parts and assembly; observe the leakage of water, oil leakage and air leakage; observe the air leakage of the air Blowholes in the crankcase; observe the changes in the instrument readings and oil indicators; observe the oil color, The viscosity and the amount of metal debris; observe the exhaust smoke; observe whether the rotational speed is uniform and stable; observe the damage degree and deformation of the parts; observe the atomization quality of the injector and so on. The fault can be analyzed according to the observed abnormal signs.
(3) sniffing: that is to detect and distinguish faults in some parts in time by sniffing out the smell of exhaust smoke or burning the smell of raw diesel.
(4) touch: to touch or pull the machine parts by hand, to judge whether the working temperature or clearance is normal by the feeling of hand. After the load working end time, touch the temperature of the corresponding parts of each bearing, it can be found to be overheated. Generally, when the hand feels the heating of the machine, the temperature is about 40 degrees centigrade; feel hot but still touch for a few minutes, then 50~60 The temperature of the machine parts has reached over 50~90 degrees if the first touch is unbearable. The hand wicker can feel the compression of the cylinder is good, it can feel the loosening of the fastener with the hand touch and the motion parts are stuck and rubbed. The diesel engine can touch the exhaust pipe of each cylinder and compare the temperature difference between each cylinder soon. When the finger touches the high pressure oil pipe, the vibration is solid and powerful, which indicates that the piston pair and the oil outlet valve are in good technical condition; if the feeling is empty and weak, the piston pair and the oil outlet valve are worn and worn; high The pressure oil pipe has large vibration resistance and backflushing vibration, which indicates that the injector needle valve bite dead, non fuel injection or less fuel injection. The hand touch high pressure oil pipe feels empty and weak, the resistance is big and the impact feeling is strong. It shows that the needle valve and the needle valve seat are closed. In the case of no measure, the experienced person can roughly judge the gap and bearing clearance of the valve by the feeling of hand. Is it appropriate?
The experience method has some practical value. However, it is necessary to experience, find out and sum up in the long-term practice by judging the state of the technology by the sensory organs, so as to enrich the experience gradually.
5 instrument method
Using portable instruments and instruments, in the case of no disassembly or less disassembly, a more accurate understanding of the internal state of a diesel engine is known as the "instrument method". Using instruments to check the technical state of each part, the qualitative and quantitative analysis of the technical states of each part of the diesel engine must be taken to prevent and find faults in time. The technical state of the unified system has a good number of minds, that is, not only to make clear the technical state of each system is good or bad, but also to make clear the concrete degree achieved by the good and bad. In this way, the purely empirical examination is often not enough, and the use of instrument inspection can be more accurately qualitative and quantitative analysis. For example, the pressure of a well tightness of the plunger supply pressure Up to 50 MPa, when the plunger oil supply pressure drops to 15~18 MPa, it will cause the trouble of starting difficulty and power shortage. At this time, if the injector with normal fuel injection pressure is placed outside the cylinder, the tightness of the plunger is checked, and the nozzle is still able to be used because the outside cylinder is different from that in the cylinder (mainly the pressure is different). Normal injection, so people often do not suspect that the plunger has a problem and dismantling other parts blindly. When using a 60 MPa pressure three valve to check the tightness of the plunger, it is easy to find the problem by observing the reading of the needle. In addition, the cylinder pressure and the passing resistance of the oil filter can be determined regularly. When the cylinder pressure drops faster or the filter passes through a very small resistance, it can detect faults in time and exclude them at the initial stage.
