Bearing Lubrication And Wear Performance Improvement Of Crank-connecting Rod Mechanism

At present, the study of bearing of crank-connecting rod mechanism of diesel engine both in China and in foreign countries focuses mainly on its steel back material, plating material performance of alloy layer, wall thickness of bearing, bearing clearance, oil film, anti-seizing property of bearing material, corrosion resistance, running-in property, so the bearing material designed has various disadvantages, such as low utilization ratio, expensive cost, vulnerable to scoring or seizure during running-in period, large bearing clearance, evident wear, low service life, high lube oil flow rate required in the whole oil system, alarm at low speed of diesel engine due to extremely low lube oil pressure, poor cooling property of piston, etc. With respect to these problems, this paper performs study against operation of crank-connecting rod mechanism of diesel engine, and lays emphasis on the impact of arrangement of oil holes and grooves of the bearing on lubrication and strain of the bearing, as well as on pressure and flow rate of oil system.Based on kinematics, this paper analyzes load distribution on journals and bearing of crankshaft of CW6250 diesel engine, and knows the heavy load areas which shall be avoided in design of arrangement of oil grooves and holes of crankshaft and bearing. Then it carries out rationality analysis on key points of bearing of CW6250 crank-connecting rod mechanism on the basis of special characteristics in operation of bearing, such as heavy load, high speed, high temperature, restricted structural space, etc, and makes out that design of the main bearing shells and the small-end bushing of connecting rod of CW6250 diesel engine is reasonable, while the design of arrangement of oil grooves and holes of big-end bearing shells of connecting rod is significantly irrational and should be improved. Next, the paper establishes oil supply model of bearing of crank-connecting rod mechanism on the basis of oil-hole arrangement of crankshaft and piston cooling method of CW6250 diesel engine, and analyzes load and oil supply of bearing shell at big end of connecting rod, piston cooling, lube oil pressure and flow rate consumption of whole engine before and after first improvement of the oil grooves and holes, and put forward new solution. Finally, Excite-Designer simulation software and bench test are used to simulate and verify the improved bearing.It is believed to achieve expected result by bearing shells of connecting rod with improved oil grooves and oil holes if judged from wear of bearings and journals, piston cooling, lube oil pressure and flow rate. So the improvement solves the disadvantages such as abnormal uneven wear, poor piston cooling, high flow rate of whole oil system and alarm at low lube oil pressure, increases reliability of the bearings and satisfies operating requirements of the diesel engine; meanwhile, the improvement also decreases flow rate of oil system and negative power consumption of the whole engine, thus to increase economy of the diesel engine.