How to install the split sliding bearing and how to scrape the bearing bush.
1. How to install the split sliding bearing
Split sliding bearing, also known as bearing bush, is composed of upper and lower bearing shells. If the diameter of the bearing bush is too large, the bearing bush will be deformed after being installed in the bearing seat. If the diameter of the bearing bush is too small, the bearing bush will vibrate in the bearing seat after being installed in the bearing seat, which will shorten its service life. Under normal circumstances, when the bearing bush is in the free-state, the two end faces should be higher than the bearing seat. When the bearing bush is pressed to the center of the bearing seat, the end face should be one higher than the bearing seat. After assembly, the bearing bush should fit closely on the bearing seat. The bearing bush can be installed with a wooden hammer or a wooden pad, and the two ends can be hit with a hand hammer to press people. It is not allowed to directly hit the middle of the bearing bush with a hand hammer.
2. Installation precautions
1. The split sliding bearing shall be placed correctly when pressing people, and the force shall be uniform to prevent bias.
2. The oil groove and oil hole on the bearing bush shall be aligned with the oil hole on the connecting rod.
3. Between the outer surface of the bearing bush and the bearing, it is not allowed to pad paper or copper to change the matching condition and adjust the bearing clearance. Because adding pads cannot accurately ensure the clearance between the shaft and the bearing, especially the pad paper, will damage the heat transfer of the bearing bush and shorten the service life.
3. How to scrape the bearing bush
If the bearing bush is seriously worn or damaged, or the crankshaft is repaired, it is necessary to replace it with a new bearing bush of corresponding size. In order to ensure proper fit clearance between bearing bush and journal, the bearing bush must be scraped and matched.
Place the crankshaft vertically on the flywheel, install the connecting rod and bearing bush on the crankshaft according to the correct position and direction, screw the connecting rod bolt according to the standard torque, then pull the connecting rod to rotate around the crankshaft for several turns, and then loosen the connecting rod bolt. Remove the bearing bush, check the wear marks on the surface of the bearing bush, and scrape the marks on the surface of the bearing bush with a triangular scraper or an old piston ring. After repeated several times, the contact area between the bearing bush and the crankshaft will reach more than. The contact traces are evenly distributed on the surface of the bearing bush in a network.
4. Fit clearance between bearing bush and journal
After the bearing bush and journal are cleaned, apply a little oil, install the connecting rod and bearing bush on the crankshaft according to the correct position and direction, install the connecting rod bolts according to the regulations, and it is appropriate to rotate freely on the crankshaft after pushing the connecting rod.
5. Manifestations, causes and prevention of tile burning
Bush burning is caused by melting and falling off of the tile alloy of the engine crankshaft bearing and connecting rod bearing.
Performance: the engine was unable to work, emitting black smoke and "missing legs", resulting in sudden flameout. Test run after stopping for a while. The crankshaft cannot rotate or can still rotate, but there is abnormal noise when the engine is on fire.
The main reason is that the supply of lubricating oil is insufficient and the lubricating oil film is not easy to form, resulting in poor lubrication or dry friction of the shaft, rapid increase of temperature and mutual bite of bearing shells. The causes of poor lubrication are:
1. Insufficient lubricating oil. Due to the sudden leakage of engine lubricating oil, it is not added in time, resulting in the lack of oil in the lubricating system.
2. The quality and brand of engine oil do not meet the requirements. Improper storage of engine oil and water ingress cause the oil emulsion to deteriorate into earthy yellow and lose its lubricating performance.
3. The lubricating oil circuit is blocked. In particular, the oil path leading to the bearing bush is blocked by sundries and oil sludge, the oil path is blocked, the lubrication is lost, and the Bush is burned.
4. Bearing bush clearance is too small or too large. The clearance is too small, the lubricating oil is not easy to enter the bearing bush, the lubricating oil film cannot be formed, the bearing bush is in a semi dry friction state, the friction overheats and melts the alloy, and the Bush burning clearance is too large. The oil entering the bearing bush will be lost quickly, the oil film is difficult to maintain, and the bearing bush will lose good lubrication performance, resulting in Bush burning.
5. The oil pump does not supply oil. The oil pump is seriously worn and the transmission mechanism of the oil pump fails, so that the oil pump cannot supply oil to the lubricating oil circuit and burns the tile.
6. The oil pressure is too low and the oil required for the surface of all lubricating parts is insufficient, which is easy to cause Bush burning in the long run.
7. The oil viscosity is high or the oil is diluted. In cold seasons, the temperature is low and the oil viscosity is high. When the engine is not preheated well and forced to start, it is very easy to burn the tiles, so the walking tractor burns the tiles more. When part of the diesel oil flows into the oil pan and the engine oil is diluted, the lubricating performance is reduced, and the lubricating oil film between bearing shells is difficult to maintain, which may also cause Bush burning.
Prevention:
1. Select the lubricating oil that meets the specifications. The oil pan shall always maintain sufficient oil, and the oil passage shall be cleaned regularly, the dirty oil shall be replaced, and the normal oil pressure and oil temperature shall be maintained.
2. Before installing the bearing bush, carefully check the clearance of the bearing bush to keep its normal fit.
3. During maintenance and repair, pay attention to check the technical status of oil pump and transmission mechanism parts, which requires flexible and reliable rotation, standard oil pump efficiency and appropriate adjustment.
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