On October 26, 2006, entrusted by Jinan sales service station of Shaanxi fast Gear Co., Ltd., Japan company analyzed the accident of falling off of engine crankshaft thrust plate and damage of gearbox shaft cover of Rizhao Lanshan Auman customer of Steyr typical:
1. The mounting end faces of the crankshaft thrust plates of the upper and lower cylinder blocks (towards the flywheel) are worn by the crankshaft; a pair of crankshaft thrust plates fall into the oil pan of Steyr typical.
2. The working surface of the flywheel and the end face of the hub of the clutch plate have serious friction and form a bright friction belt, and the end face of the spline sleeve in the hub is seriously worn of Steyr typical.
3. Slip marks have appeared on the clutch plate, and the trace area is distributed on the outside of the clutch plate!
4. The guide end of the first shaft of the transmission has been seriously worn, and the inner ring of the flywheel guide bearing 6305-2rs1 (radial ball bearing) is damaged, resulting in the bearing falling apart.
5. The release bearing seat of 11203 is broken from the working end face of the release bearing; The worn residual part of f91409 first shaft cover can be seen inside.
6. One shaft cover is broken from the contact surface with 11203 release bearing seat, and its fracture surface is characterized by: one part is concave to the inside (there is a bright belt caused by impact); one part is extended to the outside (the broken stubble is inclined stubble).
Under the working condition of the engine, the probability of the crankshaft moving towards the front end is generally higher. Under the uphill working condition, the crankshaft moves towards the rear end by gravity, but if the vehicle often drives on the slope; In particular, forced downshifting during downhill driving or jerking up the clutch when starting due to heavy load can easily lead to excessive impact load and serious wear of the rear plate of the crankshaft thrust plate. In this accident, the guide bearing of the flywheel was damaged because the vehicle continued to drive when the crankshaft thrust plate fell off, and the radial runout and axial movement of one shaft were caused after the guide bearing was damaged, resulting in the fracture of one shaft cover and release bearing seat.
This accident is an independent but interrelated failure of three assemblies.
With regard to the situation reflected by the service station handling the accident, we raise the following questions:
1. The whole vehicle has been running for more than 10000 kilometers after leaving the factory. Whether the routine inspection of connecting rod bush and crankshaft thrust plate is carried out during the post maintenance and secondary maintenance.
2. The service station reported that the above faults occurred during routine maintenance. When the vehicle was not disassembled for inspection, there were no accident signs and abnormal noises. However, when the flywheel and clutch driven plate have been seriously worn and the crankshaft moves forward and backward too much, the engine cannot have abnormal noise!!
3. After the guide bearing is damaged, the first shaft cover and release bearing are damaged successively; The clutch plate cannot be separated normally, so it is impossible to shift smoothly. How can this car operate normally?
To sum up, the falling off of the crankshaft thrust plate of this engine is not directly related to the gearbox!
Sunday, 18 November 2007, Our company was invited to accept a customer in Jinan selling Binzhou Bohai piston (model: wd615e2-4a) in Wuhan, Hubei Province, the engine ran for one month after replacing the four supporting parts. According to the actual damage and photos fed back by the customer, and combined with the damaged cylinder block, piston, cylinder head and cylinder liner, we organized relevant technicians to analyze the cause of the accident:
Because the engine cylinder block was not on site, according to the above accident phenomena, the engine cylinder block was not completely smashed, because the driver stopped in time when the engine was abnormal or the engine was running at low speed; The cylinder block may be damaged locally.
The engine is a combined assembly. In the process of overhaul or assembly, if you do not pay attention to the matching tolerance and cleaning of various parts, early damage will occur in the later operation of WD615 Series engine, and these damage phenomena are most directly reflected in the piston, cylinder liner, valve and bearing bush.
When the engine is working, the valve distribution mechanism is driven by the camshaft, and the valve is in the process of normal vertical movement; Because of the torsional torque of the valve spring itself, the valve moves up and down and rotates. During this period, if the fit clearance between the valve and the valve guide is out of tolerance, the elasticity of the valve spring decreases, and the valve seat ring is seriously worn, the valve will work abnormally, such as ellipse, inclination, non rotation, etc. in the valve guide. This will increase the probability of valve ablation, jamming, block falling and valve fracture of the engine! Once it happens, the piston assembly of the engine may be broken, and serious tamping will occur.
The broken valve of this engine is an imported German TRW valve. According to the valve stem mark, this valve has been used for a long time. According to the actual measurement of wear, the fit clearance between valve and valve guide has already exceeded the maximum wear limit of normal installation of valve guide (normal values: inlet valve 0.05mm-0.086mm, exhaust valve 0.03-0.066mm, maximum wear limit 0.12mm).
The free length of the external valve spring of this engine has been less than the specified 64.5mm, and the difference exceeds the maximum limit of 1.5mm. The wear of the lock clip groove of the valve is large, the wear of the valve lock clip and the wear of the upper and lower seats of the valve spring are serious; The valve seat ring is seriously worn. The above factors are the direct factors that directly lead to the cylinder tamping of this engine.
Therefore, when maintaining the engine with a relatively long service life, the maintenance personnel should make a comprehensive inspection as far as possible and avoid blind repair!
After asking the owner, he learned that the engine had just been overhauled for 4 days due to the bearing of the engine, and a cylinder tamping accident occurred during the running in period. The broken connecting rod is the connecting rod replaced in this engine maintenance.
It can be seen from the figure that there are a large number of pores in the blank of the connecting rod, and these pores are where the alternating stress is most concentrated during the up and down movement of the connecting rod.
After eliminating the factors of engine cylinder tamping caused by engine crankshaft bearing and piston cylinder pulling; After discussion and analysis, our company has found that the connecting rod that does not meet the technical requirements of WD615 Series engine is used by the user, resulting in engine cylinder tamping.
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