Inspection and repair of bearings

1) Inspection and correction of bearing seat holes: Damage to crankshaft bearings during use mainly includes wear, fatigue peeling, and burning. During engine overhaul, new bearings must be replaced. Before repairing bearings, it is necessary to first check whether the bearing seat hole meets the requirements, and the roundness and cylindricity errors of the bearing seat hole should not exceed 0.015mm. The method of inspection and correction is to clean the bearing seat, install the bearing cover, tighten the fixing bolts or nuts according to the specified torque, and use a cylinder gauge to check if the roundness and cylindricity of the seat hole exceed the specified value. When the roundness and cylindricity of the seat hole exceed the specified value, it can be welded or adjusted at both ends of the bearing cover, and it is not allowed to file the bearing cover.

The method for checking the wear of bearings is shown in Figure 2-16. Clean the journal and bearing oil, cut the plastic clearance gauge into a length equal to the width of the bearing, and then place it on the crank pin so that it is parallel to the centerline of the shaft. Carefully install the bearing cover, tighten the nut to the specified torque, and then carefully remove the bearing cover. Use the measuring tape printed on the plastic clearance gauge packaging bag to measure the width of the widest part of the flattened plastic line, Obtain the gap value. When the limit value is exceeded, a new bearing should be replaced.

2) Selection and matching of bearings At present, the common bearing alloys for crankshaft bearings of gasoline engines are babbitt alloy and high tin aluminum alloy. The thickness of the alloy layer is 0.30~0.35mm. In addition to the standard size, the bearing specification also has a repair size of 0.25 mm smaller than the inner diameter, which corresponds to the crankshaft journal, so that it can be selected for repair.