During engine combustion, piston engines produce unnecessary twisting vibrations of the crankshaft that interfere with the operation of the entire powertrain. This is especially true for vehicles equipped with a diesel engine.
This “harmful vibration” can even be expressed quantitatively. The amplitude of the crankshaft torsional vibration is approximately 30%. Torsional vibrations in the crankshaft will continually accelerate or decelerate the belt drive and the operation of connected auxiliary devices. This will cause auxiliary devices driven with relatively slow torque, such as generators, to place a huge maximum load on the auxiliary drive. This results in stronger and more wear-prone belt vibrations along the entire length.
Preventing this twisting vibration is almost impossible. And this vibration will inevitably be transferredreed to the V-belt that drives the engine's auxiliary devices (such as generators). As a result, the service life of the drive belt is reduced, in the most extreme cases, by almost 30,000 kilometers.
1
Fit clearance is too large
Fit clearance is an important indicator of assembly quality automotive in terms of lubrication, temperature and load. , and speed are combined. Over time, abnormal noise will become more evident as the adjustment clearance increases. Some moving engine parts will increase clearance beyond the range due to natural wear, resulting in abnormal noise, such as engine knocking noise. the piston and cylinder wall, connecting rod bearing and shaft The sound of hitting the neck, etc.
2
Poor lubrication
Lubrication is an important condition for normal engine operation. Llubrication, cooling, cleaning, sealing and rust prevention can be achieved. through the lubrication system. When the clearance is suitable, when the temperature, load and speed are constant, the thickness of the lubricating oil film is affected by the pressure of the lubrication system and the quality of good quality lubricating oil. and appropriate pressure can produce better lubricating oil film. The thicker the lubricating oil film, the lower the mechanical impact, less prone to abnormal noise. If the lubricating oil film is too thin, resulting in increased wear, abnormal noise will occur, which will be obvious and clear.
3
Loose fasteners
Vibrations are generated during engine operation, causing some parts to become loose and causing impact noises. If the flywheel mounting bolts are loose, the connecting rod bolts willloose fittings, etc., causing abnormal noise.
4
Individual parts are deformed and damaged
Abnormal noise is caused by deformation or damage of a certain part. For example, the bending of the connecting rod causes the cylinder to knock, and the abnormal noise caused by the valve spring breaking and the crankshaft breaking.
5
Abnormal combustion
The ignition time of the gasoline engine is too early or too hot, resulting in deflagration, and the injection time of the diesel engine is too early, resulting in premature roughness and metal damage. The sound of blows on the cylinder.
6
Incorrect adjustment or repair of the assembly
Incorrect adjustment or repair of the assembly results in misalignment of the mounting clearance of the machine parts. Abnormal noise may occur if the piston pin is too tight or the valve clearance is incorrectly adjusted.
7
Speed
Generally, the higher the speed, the louder the abnormal mechanical sound. However, at high speeds, various sounds are mixed. , and some abnormal sounds are mixed instead. It is difficult to distinguish, so the diagnosis of rotation speed depends on the abnormal sound situation. For example, when auscultating the sound of the valve and the sound of the piston knocking on the cylinder, the abnormal noise is very obvious at idle or low speed. When the main bearing makes noise, the connecting rod bearing noise and piston pin noise are more serious. It can also be heard at idle and low revs. In short, the diagnosis of abnormal noise must be carried out. the rotation speed with the most obvious noise, and should be carried out at low speed as much as possible to reduce noise and unnecessary losses.
8
Temperature
Some abnormal noises are related to temperatureof the engine, while some abnormal noises have little or nothing to do with engine temperature. diagnosis of abnormal mechanical noise For fittings with a high coefficient of thermal expansion, special attention should be paid to the operating conditions of the engine when hot, such as knocking of the piston on the cylinder. When the engine starts cold, the abnormal noise. is very obvious. Once the temperature increases, the sound will weaken or disappear, so diagnose cold cylinder knock. The response is carried out at low engine temperatures and has little effect on abnormal noise produced between mating pairs with low thermal expansion coefficients. Noises such as crankshaft main bearing noise, connecting rod bearing noise and valve noise have no special requirements for temperature diagnosis. One of the main causes of combustion noiseOne abnormality is that gasoline engines often produce ignition knocking noises. they overheat.