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Early damage and avoidance of the starter sliding bearing
Source: China Bearing Network Time: 2014-07-14
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1. The way of early damage is in the normal operation process; because it gradually wears until the final operation is lost, and the service life is completed; this natural damage is difficult to avoid. However, if the equipment is not properly adjusted due to the startup equipment, the quality of the lubricant Inadequate or poorly applied conditions cause the bearing to wear prematurely or present various damages; it is the early damage caused by man-made. Early damage not only greatly reduces the service life of the bearing; it also affects the normal operation of the initiator. According to the long-term experience of diesel engine repair, the common methods of early damage of sliding bearings are mechanical damage, bearing cavitation, fatigue pitting, corrosion and so on.
(1) Mechanical damage The mechanical damage of the sliding bearing means that the alloy surface of the bearing bush exhibits a different degree of groove marks; in severe cases, the metal peeling occurs on the touch surface and a large area of ​​messy scratches is present, usually; the touch surface is damaged and burned. The eclipse appears together. The primary cause of the mechanical damage of the bearing is that the bearing surface is difficult to form an oil film or the oil film is severely damaged.
(2), the bearing cavitation sliding bearing in the cylinder pressure impact load) of the repeated effect; the outer layer of plastic deformation and cold work hardening; some loss of deformation ability; gradually form the pattern and continue to expand; then followed by the falling of the grinding debris; In the outer surface of the loaded surface, the hole is formed. Usually, the hole is cavitation; the pit is firstly formed; then the pit is gradually enlarged and the interface of the alloy layer is cracked; the crack expands along the parallel direction of the interface; until the drop stops. The primary cause of the cavitation of the sliding bearing is that the cross-section of the layout elements such as the oil groove and the oil hole is suddenly changed, causing a fierce imbalance of the oil flow; the bubble is formed in the vacuum zone where the oil is lost; then the pressure rises; the bubble collapses Eclipse. Cavitation usually occurs in the high load zone of the bearing; such as the lower bearing of the main bearing of the crankshaft.
(3), fatigue pitting bearing fatigue pitting refers to; because the initiator overload operation; the bearing operation overheating and bearing clearance is too large; the formation of the middle of the bearing fatigue damage, fatigue pitting may be tired and fall. This damage is mostly Because of overload, the bearing clearance is too large; perhaps the lubricant is unsanitary, and the inside is mixed with foreign matter. Therefore, the application should focus on avoiding overloading of the bearing, do not operate at too low or too high speed, and adjust the initiator when idling To ensure stability, ensure normal bearing clearance; avoid excessive or low engine speed, check and adjust the operation of the cooling system; ensure that the operating temperature of the initiator is suitable.
(4), bearing alloy corrosion bearing alloy corrosion is usually the area is not pure oil; chemical impurities (acid oxides, etc.) in the lubricating oil to oxidize the bearing alloy to produce acidic substances; caused some bearing alloys to fall; Irregular small holes or small pits. The primary cause of corrosion of bearing alloys is improper selection of lubricating oil and poor corrosion resistance of bearing data. Perhaps the roughing of the machine is too high and the temperature is too high.
(5), there is a small convex metal surface between the bearing burning fuse journal and the bearing conflicting pair; the composition is somewhat high temperature; in the case of lack of lubrication, poor cooling; the bearing alloy is black or some is melted. This problem is often caused by the cooperation between the journal and the bearing. The lack of lubricating oil pressure also makes the bearing burned.
(6), bearing the outer circle bearing outer circle is the bearing has a relative transformation in the seat hole. After the bearing goes outside the circle; not only affects the heat dissipation of the bearing; simply makes the bearing inside and outside the bearing ablate; and also causes the bearing back surface damage; Burning bearings in severe conditions. The primary reason is that the bearings are too short, the crown is damaged, the processing may not meet the standards.
2. Avoiding methods Early damage of sliding bearings is much more common than bearing burning; therefore, it is important to avoid early damage of sliding bearings. Correct protection of sliding bearings is an effective way to reduce early damage of bearings; it is also a reliable guarantee for extending the life of bearings. In the normal protection and repair of the initiator; it is necessary to pay attention to the appearance of the bearing's alloy appearance, reverse surface, end and marginal edge; if there is an abnormal display of half-wearing signs; it is necessary to carefully identify the cause; and adopt the corresponding Ways; improve the working conditions of the bearing; pay attention to the early damage to the sliding bearing.
(1) Improve the depiction of the bearing and the process of drawing or selecting the bearing; consider the heat balance of the bearing to control the temperature rise. Because the bearing works in conflict situations; because of the internal conflict (viscosity) of the lubricating oil, it constitutes power consumption; After being converted into heat, the temperature rise of the bearing is caused; the viscosity of the lubricating oil is lowered, and the gap is changed; the Babbitt alloy of the bearing is softened; when it is severe, the "burning of the shaft" is caused. Therefore, in the layout drawing; the upper bearing of the bearing (non-load bearing area) open the oil hole at the top; make the lubricating oil from the non-load bearing area, open the oil groove in the longitudinal direction or the lateral direction with the oil inlet hole in the inner and outer parts of the bearing bush; help the lubricating oil to be evenly distributed on the journal to control the temperature rise .
According to the operation of the bearing; the bearing information needs to have the following functions: conflict coefficient. Bad both the blade and the smashing stool. The ridiculous 20. The mellow oyster mushroom Hanxia 芰 浚 浚 浚 愎 愎 慷 慷Applying benzyl. Therefore; the bearing material can be selected from babbitt. The babbitt alloy can work well under stable load; but it is easy to cavitation under unsteady load; so it is not suitable for high power initiator. Tin-lead-based alloys and low-tin-lead-based alloys have higher strength and hardness; they are more resistant to fatigue and cavitation; they are better used in high-powered initiators. In recent years, foreign countries have used physical vapor deposition. Sputtering method for plating copper alloy with 20% tin on copper-lead bearing outer nickel gate or plating pure tin; the effect is very good. In addition; the whole round oil groove bearing bush is changed to semi-circular oil groove or some oil groove bearing bush; this can not only be improved Initiator lubrication of the sliding bearing; and can also improve its bearing capacity.
(2), the repair of the improved bearing and the quality of the equipment improve the quality of the hinge of the bearing; ensure that the reverse lubrication of the bearing is not mottled; the positioning bump is intact, and the amount of the elastic opening is 0. 5-1. 5mm; The bearing shell is tightly attached to the bearing housing hole by its own elastic force. Each end of the upper and lower bearing bushes installed in the bearing housing should be 30-501 μm higher than the bearing seat plane; the high output can ensure the bearing cap bolts are tightened according to the regular torque. Close cooperation with the bearing seat; the conflict self-locking force of the attack; the bearing is not loose; the heat dissipation effect is good; the bearing ablation and wear are avoided; the working surface of the bearing cannot be measured by the scraping method to reach 75%-85% touch impression; The cooperation gap between the bearing and the journal should be brought to the demand without scraping.
In addition, the equipment should pay attention to the processing quality of the crankshaft journal and bearing; strictly implement the repairing process standard; avoid the equipment is not correct due to improper loading method and the torque of the bearing bolt is not uniform or does not conform to the rules; Stress gathering; incurring early damage to the bearing.
(3) Reasonable selection and filling of lubricating oil In the process of application, lubricating oil with small oil film surface tension should be selected; the impact of oil flow will be reduced when the bubble formed is reduced.çŸ—è ¡ ã–鹊 ã–鹊 ã–鹊 ã–鹊 æ«è±¢ åº é»¾ åº é»¾ åº é»¾ åº é»¾ åº é»¾ åº é»¾ ç° ç° ç° ç° . . . . . . . . . . . . . . . . . . . .啵 ä¹ ä¹ è°· é é é é é é é é é é 北 北 北 北 北 北 北 北 北 北 北 北 芊庑Ч 芊庑Ч 芊庑Ч 芊庑Ч æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡ æ³¨é‡. , not the same quality, different viscosity grades and different types of lubricants to prevent mixing; the deposition time before the lubricant is usually not less than 48h.
(4) When properly protecting and protecting the bearing of the protection equipment; the surface of the shaft and the bearing should be coated with the regular brand of sanitary oil. After the bearing is installed, the fuel switch should be closed before the initial start; The starter of the machine starts to idle several times; when the engine oil pressure gauge is displayed, it is turned on and turned on, and the fuel switch is turned on; and the throttle is set at a low speed; the starter is started to conduct the operation investigation. The idle operation time cannot exceed 5 minutes. After the new machine and the overhaul, the grinding machine cooperates in the grinding-in period; in the running-in period, the machine is operated at a high speed in the long run, and the machine is operated at a high speed. The machine is not fully stopped after a long time; it is necessary to let the machine start. After only 15 minutes of idling at low and medium speeds, it will stop after another operation; otherwise the internal heat will not be able to escape.
Strengthen the sanitation and protection of the oil filter and crankcase ventilation equipment; replace the filter element in time according to the requirements of the manual to ensure the normal operation of the engine cooling system; control the normal temperature of the initiator; avoid the "opening" of the radiator; prohibit the cooling Water will drive, correct fuel selection; precise adjustment of gas phase and incineration timing; avoid improper firing of the initiator, timely view and adjustment of crankshaft and bearing skills.
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