What is a connecting rod bearing? What are the characteristics of engine connecting rod bearing noise?
The connecting rod bearing is a part that connects the crank pin, and its main function is to reduce the wear of the crank pin.
The big end bearing of the crosshead connecting rod is usually manufactured separately, and then connected to the shaft by connecting rod bolts, and its inner surface is often cast antifriction alloy.
For large end bearings without cross-head connecting rod, the upper half is usually integrated with the shaft, while the lower half bearing cover is manufactured separately, and then connected with the upper half by connecting rod bolts, and the inner surface of the upper and lower halves of the bearing are equipped with bearing bushing.
On the bearing structure, the inner surface of the shaft sleeve is drilled with oil holes, and some oil grooves are designed to facilitate the lubrication of lubricating oil. In addition, self-adjusting or platform rod small-head bearings are often used in the structure of connecting rod bearings.
The function of the connecting rod bearing is to reduce the wear of the crank pin, and the friction between the crank pin and the shaft can be effectively reduced by connecting the crank pin and the shaft, thus extending the service life of the crank pin.
At the same time, the connecting rod bearing can also improve the performance and efficiency of the engine, and reduce the noise and vibration of the engine. This is because connecting rod bearings can reduce friction and wear inside the engine, thereby improving the efficiency and stability of the engine.
The structure of connecting rod bearings usually includes crosshead connecting rod big end bearings and connecting rod bolts, of which the crosshead connecting rod big end bearings are usually manufactured separately, and the big end bearings without crosshead connecting rod are designed in one piece.
In addition, self-adjusting or platform connecting rod small-head bearings are often used in the structure of connecting rod bearings to ensure the normal operation and stability of the engine.
In short, connecting rod bearing is a very important part of the automobile engine, which can effectively reduce the wear of the crank pin, improve the performance and efficiency of the engine, and reduce the noise and vibration of the engine.
Therefore, the design and manufacture of connecting rod bearings need to be very strict to ensure their quality and performance. In the automotive manufacturing process, high-quality materials and manufacturing processes need to be selected to ensure the service life and performance of connecting rod bearings. At the same time, regular inspection and replacement of connecting rod bearings is also one of the important measures to ensure the normal operation of the engine.
The abnormal sound of connecting rod bearing is manifested as a continuous clank sound when the engine accelerates from idle speed, and the higher the speed, the greater the sound, which has nothing to do with the engine temperature change. When the bearing is seriously loose, there will be obvious noise at idle speed, the noise will be intensified when the load is increased, and the sound will be significantly weakened or disappeared when the fire occurs.
Ways to deal with the abnormal sound of connecting rods include:
1. Carry out variable speed test and cylinder misfire test, combined with auscultation repeatedly, if the noise increases with the increase of engine speed, jitter throttle instant abnormal noise is prominent, it is connecting rod bearing abnormal noise.
2. At idle speed, medium speed and high speed, cylinder by cylinder fire test, if the sound of the cylinder is significantly weakened or disappeared after extinguishing, and appears immediately at the moment of reignition, it can be determined that the connecting rod bearing of the cylinder is abnormal.
3. Use a stethoscope or long handle screwdriver for auscultation, if the sound is not obvious, but the abnormal sound under the engine is obvious, it is the abnormal sound of the connecting rod bearing.
4. Check the oil pressure. If the abnormal noise is serious and accompanied by low oil pressure, it means that the clearance between the bearing and the journal is too large.
The reason for the abnormal noise of connecting rod bearing may be due to the excessive clearance between the connecting rod bearing bush and the connecting rod journal, which leads to the reduction of oil film stiffness, the decrease of bearing capacity, the deterioration of lubrication condition, and the abnormal noise caused by boundary friction or dry friction. It may also be that the crankshaft main oil passage is blocked, the filter screen is dirty, the bypass valve is faulty, the oil pump is faulty, and other reasons lead to low oil pressure and poor lubrication of the bearing bush.
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