On December 28, 2011, Jimin industry and Trade Co., Ltd. accepted an accident that WP10 series electronic control engine ran for a short time after replacing four supporting parts in Shandong. According to the actual damage feedback from customers; Combined with the pictures of damaged piston rings, analyze some causes of the accident:
Because the damage of engine parts has different causes and manifestations, for the same damage, one or more causes may occur alone or at the same time. We must analyze the essential cause of the fault through the surface phenomenon of part damage. However, in many cases, the essential cause can not be accurately judged only from the surface damage trace of a certain part. It is also necessary to understand the working time, working conditions, service conditions, maintenance conditions, oil quality and damage of related parts of the faulty engine, and conduct comprehensive analysis to find out the real cause of the fault.
After maintenance, the vehicle in the accident suddenly rammed the cylinder when the empty vehicle was driving at a high speed on a flat road. After the accident, the vehicle was towed back to the maintenance enterprise by Trailer.
The engine piston shows scattered damage, and the piston pin shows no signs of high temperature caused by poor lubrication; The exhaust valve of the engine is broken, the oil head of the electronically controlled injector is covered by small fragments of the piston, and there is no serious impact damage on the working surface of the cylinder head; The big end of the connecting rod is not deformed, but the connecting rod body is bent; The piston pin circlip is intact.
Therefore, the detailed configuration of the vehicles equipped with the engine is unknown. The coal is pulled from the Shanxi of Chiping Road, Shandong Province. The one-way cargo type is in the state of empty running on the national highway. This type of abnormal cylinder tamping is rare.
For the current electronically controlled engine, the combustion control is basically completely controlled by computer, but if you want the engine to work normally, in fact, the position tolerance of the mechanical part is also very important; For example, the engine valve clearance, bearing bush clearance, and even the meshing clearance of gears in the oil supply timing system need to be strictly adjusted by the factory adjustment method. At the same time, because the explosion pressure is much higher than that of non electronic control engine, there are strict requirements for the strength and high reliability of assembly parts.
The piston is called the heart of the engine. It is one of the most important parts in the engine. Because the piston is constantly doing high-speed reciprocating motion under the action of high-temperature and high-pressure gas, it bears the thermal load and mechanical load of high-temperature and high-pressure, and its working conditions are very bad.
In most Steyr engines, the piston is the only aluminum part in the main moving parts of the engine. The failure of any relevant part in the engine or the working state of the engine is likely to cause the piston to be damaged or broken. Therefore, the engine failure is often exposed on the piston, but the part that really causes the engine failure is not necessarily the piston, Specific analysis needs to be carried out according to specific conditions. Many friends don’t know how to analyze a pile of damaged parts. In fact, they can see the essence through the phenomenon. After mastering enough basic knowledge, they can analyze some parts as long as they think carefully!
1. Although the valve of this engine is broken, there is no impact trace on the working plane of the cylinder head. From the trace of valve breaking, it can be basically recognized that it is caused by excessive lateral impact, but there is no collision trace in the broken area of the valve head and the edge of the working surface of the valve head. If according to the conventional analysis, the valve head is inserted into the piston combustion chamber after the valve cylinder is dropped, Because of the increase of the overall height, it is almost impossible for the engine with piston online speed of nearly 7 meters per second to run at medium and high speed without impact on the working surface of the cylinder head; Then there is only one case where a similar phenomenon may occur, and the piston suddenly breaks during operation.
2. For the damaged piston, in order to check whether the engine is damaged, for example, if the cylinder liner bearing hole of WD615 engine is deformed and enlarged, and the stop table of cylinder liner support shoulder is inclined, the piston is damaged due to the fracture of cylinder liner support shoulder, and if the piston is broken due to severe cylinder pulling of single cylinder of the engine, We specifically check from different locations:
There is no sign of cylinder pulling on the piston, and there is no coking in the internal cooling oil passage from the piston residue due to high temperature. From the current signs, there are no major mistakes in the maintenance process.
During the inspection of the wear of the piston pin seat hole, no impact trace and abnormal wear trace caused by the improper fit clearance between the seat hole and the piston pin were found. On the contrary, there were traces formed by lateral impact between the end face of the piston pin and the periphery of the pin seat hole in some residues.
On the contrary, the piston stubble in this accident is more interesting. Basically, most of them belong to the instantaneous tearing state, and the macro observation of the structural area level of the end face is relatively loose, which is very different from the stubble formed by the external force of the normal piston. The blank of the piston is marked as Jiangbin piston, but it is hard to say that it is a genuine part from the overall observation.
In this event, the parts failed. Because there is no data support from relevant electronic control, it can only be summarized in part:
It may be that the electronic control part and the engine timing part cause the rough operation of a single cylinder, which leads to the overall fracture of the piston when the explosion pressure exceeds the fatigue limit of the piston;
It is possible that the piston produced by a fake enterprise was used.
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