1. Inspection of crankshaft bearing housing bore and matching of bearings
1. Before the bearing is matched, first check whether the bearing housing hole meets the standard. Clean the housing and cover, crankshaft and crankcase. Check whether the end face of the bearing cap is flat, and the flatness and the maximum depth of the bore should conform to the specified data.
2. As needed, place a number of gaskets (copper or steel) on both ends of the bearing cap to make the bearing seat hole cushion to a perfect circle, install the bearing cap, tighten the bolt, and measure the inner diameter of the bearing housing bore with the inner diameter gauge. And its roundness and cylindricity error. If the roundness and cylindricity error exceeds 0.05mm, the boring should be repaired according to the specified size.
3. Select the bearing according to the repair size of the crankshaft journal. The bearing thickness and its uniformity are measured by a special centimeter card. The outer diameter of the bearing should be adapted to the size of the bearing housing hole, and the thickness deviation should not exceed 0.03 mm. Tap the bearing with a metal object, such as a crisp sound, indicating that the alloy is well bonded to the bottom plate.
4. Insert the appropriate bearing into the bearing seat and cover to check whether the bearing is in close contact with the bearing seat (the degree of fit between the back of the bearing and the seat hole is not less than 85% of the contact area), whether the notch and the bearing seat are The groove of the cover is fitted, and the oil hole on the bearing is in communication with the oil passage on the seat.
5. After the bearing is in close contact with the seat hole, the edge of the two ends must be higher than the plane of the bearing seat by 0.04 to 0.06 mm, so that the fitting can be better sealed. The test method is as follows: the bearing and the bearing cover are installed, and the bolt is properly tightened until the bearing is in close contact with the base. The thickness gauge is inserted into the plane of the bearing cover, and the gap between the bearing cover and the contact surface of the cylinder seat hole is measured to 0.10. The mm thick gauge insert feels fit, and a 0.15mm thick gauge cannot be inserted as appropriate. If the clearance is too large, both ends of the bearing should be trimmed; if it is too small, a separate bearing is required.
6, the bearing matching requirements can be summarized in four sentences, namely: according to the journal selection of bearings; bearing length standards; good smooth back convex; elastic suitable without dumb sound.
7. The back of the bearing is generally marked with a reduced size (indicated by the “—” sign). If there is no mark or the thickness does not match, the bearing level can be checked by measuring the bearing thickness.
Second, the crankshaft bearing matching method
This method is to repair the size of the light-grinding crankshaft according to the regulations, and then select the thin-walled bearing with the specified repair size. After the thickness gauge or soft wire is used, if the gap between the two is suitable, it is qualified.
The inspection method is to place a thick paper sheet having a width of 13 mm and a thickness corresponding to a predetermined gap on the lower bearing, and tighten the bearing cap bolt with a predetermined torque, and then rotate the crankshaft to be able to rotate and feel a certain resistance to pass. If it does not move, the gap is too small. If there is no resistance when turning, it means that the gap is too large.
If the copper thickness gauge is used, the edge should be polished with oil stone and coated with a little oil. Check the above method: When turning the crankshaft, do not turn the whole circle, only turn 80°～90°, so as to avoid damage to the bearing bush. And check the tightness according to the above method.
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