In view of the fact that the connecting rod bearing wear of the diesel engine has exceeded the limit severely, in order to avoid the rigid impact of the piston-connecting rod mechanism on the crankshaft and to ensure the normal operation of various parts, we immediately replaced the connecting rod bearing. It was unexpectedly easy to install the diesel engine. Started. Although the problem is solved, why does the excessive wear of the connecting rod bush cause difficulty in starting the diesel engine? Find out the cause of the failure through careful analysis. It turns out that when the connecting rod bearing is severely worn, the fit clearance between the crankshaft connecting rod journal and the connecting rod bearing has far exceeded the wear limit, causing the piston to be at the farthest position from the crankshaft centerline, which cannot reach the design. The required top dead center position, and when the piston is at a position close to the crankshaft centerline position *, it cannot reach the bottom dead center position at design time. This affects the ratio of the total cylinder volume to the combustion chamber volume, reduces the compression ratio, and causes The diesel engine is difficult to start.
The repairman disassembled the gearbox and did not find the fault, but it still could not work normally after reinstalling it. I had to ask a repairman to replace the gears, forks, fork shafts, fork springs, steel balls, etc., but the failure was still unable to be eliminated. The operator went to the agricultural machinery station for help. I checked: 1. The position of the gear plate and the main gear lever is correct; 2. The gearbox cover is removed, and the installation of the fork’s engagement position meets the requirements; 3. Each The gears, shafts, bearings and other parts are all intact. When the gearbox of the rotary tiller was inspected in depth, it was found that the gears were worn and the teeth were not straight and inclined and slipped. Therefore, when the second and third gears are used, the inclination force of the rotary tiller gear is greater than the positioning force of the fork ball spring. Cause the reverse gear to slip to the reverse position and cause chaos. The first gear is normally used because a reverse gear is always meshed with the gearbox gear of the rotary tiller, and the first gear is meshed with the main shaft teeth. Therefore, after replacing the gear of the rotary tiller gear box, the fault will be eliminated.
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Link to this article：Research and Analysis on Wear of Connecting Rod Bush of Diesel Engine
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