Noun explanation: 1. The main bearing hole alignment Diesel engine cylinder block is in use process, both the longitudinal deformation, and lateral deformation, deformation degree, the greater the seat hole alignment error.Alignment error is too big, not only increase the bearing, axis neck, wear a hole, and reduce the service life of diesel engine.In front of the main bearing assembly, therefore, we will strictly check hole alignment, to different degree of alignment error, should be taken

1. The main bearing hole alignment Diesel engine cylinder block is in use process, both the longitudinal deformation, and lateral deformation, deformation degree, the greater the seat hole alignment error.Alignment error is too big, not only increase the bearing, axis neck, wear a hole, and reduce the service life of diesel engine.In front of the main bearing assembly, therefore, we will strictly check hole alignment, to different degree of alignment error, should take corresponding measures to make its control within the scope of the repair technology standards.

Error in line with the original factory rules or is less than 0.04 mm, in accordance with the grinding shaft neck and choose the same size bearings directly with repair.At this time should be confirmed with clearance within the rules.Maximum error is close to standard (full length is not greater than 0.15 mm, two adjacent hole is not greater than 0.10 mm), can choose antifriction alloy bearing, also is choose a bit sticky, embedded Tibetan resistance, compliance, and corrosion resistance of the bearing, such as plastic aluminum alloy bearings, etc.If significantly more than standard, but on a hole boring (had better use processing of high precision bearing boring machine), and then selecting the steel back of thickening bearings.To reduce the influence of assembling deviation and position deviation, the boring or cut bearing must be corrected before horizontal line, is the side of the bearing on the inversion of cylinder block housings, then lift the crankshaft, in not to rotate the crankshaft several bearing cover of the case, then lift the crankshaft to check the contact pattern, and repair or adjustable bearing shell, made in equal contact pattern, to ensure the bearing on the contact surfaces in the same horizontal line.

2. The connecting rod bearing hole Before matching connecting rod bearing, should strictly control the seat hole roundness in repair technology standard range.After scraping the bearing, if the contact pattern has reached the requirements, but if remove its clearance is still greater than other places, the adjusting shim for looseness is consistent, if the use of the bearing cover and mounted on bearings together in its grinding emery cloth, can lead to bearing surface height is low.Direction of the connecting rod shaft seat hole diameter less than the diameter of perpendicular to the direction of the shaft, resulting in bearing installed after the loose, light person make the bearings on the back of the hair bright, followed by "roll", "holding shaft" and other accidents.When using the new bearing again, and can make the lap on the high side, after compaction cover extra material is pressed into convex shoulder, will eventually lead to fall off.So before matching bearing, deal with hole roundness inspection, control the roundness error.Wipe a hole, and bearing cover, tighten nut torque by the regulation, and then measuring roundness of holes.If roundness error is less than 0.03 mm, can no longer add gasket;If in 0.03?Within the scope of 0.07 mm, can add 0.05 mm thick, respectively, in each end bearing pad "no pressure";When more than 0.07 mm, should be on both ends of bearing cover welding or make face thickening by brush plating technology.

3. The free play of bearings For the bearing is easy to assemble and make it fit closely with the seat holes, to prevent the bearing cover after tightening under the action of pressure bearing cover work surface shrinkage, shall ensure that the bearing of the repair after loaded with free play potential requirements.General thin wall bearing free play potential minimum value is 0.25?0.50 mm, the maximum of 1.20?1.50 mm.When any potential is too small, can make into a hole on the back of the bearings after stick force reduction is small, easy to cause mild steel bearing back when fastening bearing cover metal materials in the pressure drop, and shrivel to antifriction alloy side convex, cause bearing the actual assembly interference quantity decrease and even disappear, lead to bearing under working state and back seat hole surface relative displacement.At the same time, the shrinkage in bearing the bulge in the work, friction and heat generation come into direct contact with the journal, but in the bearing shrinking bulge with a hole between the surface of the air gap will seriously resistance Hinder bearing to a hole heat transfer, lead to a sharp rise in the temperature contact point, melt metal layer, even cause a "pull" accidents.In case of a comprehensive "pull", when the diesel engine starting again, can make have clung on journal bearing with mandatory crankshaft (at this point positioning lip has stop the slippage between the bearing and a hole surface movement).Too much freedom, of course, play the potential of an adverse effect on reliability and life of bearing, the reason is that the antifriction alloy layer and back axle bearing joint shear stress increases, easy to make the alloy in joint spalling.

4. The joint imprint on the reverse of the bearing The mark can identify a hole of the cylindricity error, the lap of the bearing and substitute highly with camber, etc.When inspection, but this hole surface with a thin layer of red lead oil, mount bearing and the bearing cover, rules for torque tighten nut, and then remove the bearing the joint imprint on the reverse of the view its, normal joint area should be above 85%.Like two pieces of bearing end mark shallow, middle without stain, and ends when the nut without torque without clearance, bearing lap height is too low;Like two pieces of bearing end mark, the other end without stain, instructions Hole cylindricity error;Central such as deep imprint on both ends, no mark or mark shallow, then bent through small, if with a hammer hammer bearing back, or change big radian bearing to small radian bearing, also can appear this kind of situation.

5. Bearing replacement It is forbidden to selective scraping bearing working face.This form "star gathering" working face, in fact, have the effect that is less than good cooperation with the journal.Because its face is not normal, due to the change of the bulge oil film clearance, makes the oil film pressure and temperature in a dramatic increase in bulge, forming additional high temperature and high pressure.When the local high temperature and oil film on at the same time, the direction of the peak pressure of the oil wedge pressure, axial displacement is extrusion and bulge squeeze pressure superposition phenomenon, so the bulge forming a bigger than smooth surface oil film pulse load area.In addition, it also can produce stress concentration due to surface uneven, bearing alloy is fatigue rupture or take off a piece of important reasons.At the same time, as a result of the axial displacement, could happen in the bulge instantaneous metal contact, make local burning-out bearing alloy.At this time, although the bite resistance of alloy from "axis" and "burn", but life is greatly reduced, especially the third alloy layer on the surface of the bearing was scraped off when scraping, make its wear.Additional, still exist the discerning scraping bearing and the journal clearance is too large or too small.The current high-speed diesel engine bearing pressure than an average of more than 50 mpa, and the peak value of the oil film pressure can reach 12 times the average pressure of the left and right sides, bearing to bear such a high load, and to work for a long time, to ensure that the provisions of clearance is very important.The bearing of diesel engine working face, therefore, should be replaced by boring skiving process.

To meet the requirements of modern diesel engine Gao Jianghua degree, in addition to using sliding bearing working surface is the shape of a cylinder, and the following shape: rotary hyperboloid, namely on both sides in the middle of the shaft up for thick thin;Elliptical cylinder, the boundary between the two pieces of bearing thin and middle thick;Junk slot surface, near the boundary between the two pieces of bearing surface local cutting, cutting depth is apart from the working surface is about 0.02?0.07 mm, commonly known as junk slot sliding bearing of the new type of bearing.These bearings are composed of three layers of metal, the outer steel back, usually made from low carbon steel, thickness of about 2?5 mm;The middle layer is antifriction alloy layer, made from aluminum alloy or lead alloy, thickness of about 0.2?0.8 mm: the third layer alloy generally consists of metals such as lead, tin, thickness of about 0.02?0.04 mm, with excellent antifriction sex.In order to prevent the spread of metal, between the third alloy layer and antifriction Still have a layer of nickel plating, its thickness is about 0.001 mm.Such bearing on the sensitivity of the fault is very poor, so when the bearing was damaged when the normal working conditions, generally difficult to detect.In the event of "burning", "" holding shaft accident, its temperature is as high as 800?900 ℃.Under the high temperature, the crankshaft will local color annealing, even produce microcrack, generally can't continue to use.Due to the high temperature will cause the bearing seat becomes angry, and even the distortion, fix up to is also very difficult, therefore, in addition to the priority using copper lead bearing, when replacement should pay attention to the following questions: first, journal of wear of grinding, and then match the size of the corresponding bearing, must not scraping or boring bearing to match has worn shaft neck.Without crankshaft grinding machine and the crankshaft journal wear normal circumstances, the transition can be used for skiving method and replacement bearing, namely choose than journal increase the level of bearing, if the clearance is too small, you can use "pressure", and then depending on the situation near the boundary between two slices of bearing surface of the surface of the work appropriate to fix, but scraping amount shall not exceed half the thickness of the tile mat "pressure".Taking scraping should point 2?Three times to complete, until clearance within the rules.

6. Bearing cover retaining bolt tightening torque In the assembly, must tighten to specified torque bearing cover retaining bolt.Each cylinder of the main bearing cover tight sequence generally ends after the first intermediate.Tighten the order of 6 in-line diesel engine 4-3-5-2-6-1-7.Without scale wrench, just by feeling tight, this will affect the bearing clearance in different degrees.