Study On Optimization Of The Balance Mechanism For An In-line Four-cylinder Diesel Engine Based On The Reliability Constraints

The in-line four-cylinder diesel engine was more and more widely used and had obvious matching advantage because of high power, small boundary dimension, better fuel economy.However, due to its specially characteristics of machinery, the second order reciprocating inertial force and inertial overturn moment of this kind of diesel engine could not be balanced and induced low frequency vibration.The vibration and noise would affect high-end application of the in-line four-cylinder diesel engine. It was the active vibration reduction key technology that an in-line four-cylinder diesel engine was installed the double shafts balance mechanism.The characteristic of the force induced vibration in in-line four-cylinder diesel engine was analyzed; the design principle for the double shafts balance mechanism was illuminated. When a nonfull-length A class balance mechanism for certain in-line four cylinder diesel engine was fixed, secondary reciprocating inertial force was only balanced. For partially balancing the inertial overturn moment and reducing change to the balance mechanism, a concept "thick-thin double shafts" was applied, it was optimum designed to installtion position of the balanc mechanism and structural parameter of the thick-thin shafts by Matlab optimization toolbox. When the balance mechanism was optimized, the overturn torque was attenuated 29.02%, the running noise reduced 5.0dB (A).Lubrication property of sliding bearing considering misalignment caused by shaft deformation under centrifugal inertial load was changed in balance mechanism. So sliding bearing operating in high-speed, its failure modes appeared in our eye was sliding bearings burnt or ceased. Hyperboloidal sliding bearing that has correct centering and better lubrication property was reliably optimum designed adopting the algorithm to integrate single objective based on grid method. When the sliding bearing is optimized, friction power wastage was reduced 23.1% and the lubricant temperature rise was fall to 54.0%. The hydrodynamic lubrication mathematical model for hyperboloidal or cylindrical sliding bearing was inferred, this model was solved by using the numerical method with Matlab optimization toolbox. Compare and contrast cylindrical sliding bearing with hyperboloidal sliding bearing in gradient of shaft, eccentricity ratio, film pressure distribution, maximum film pressure film thickness distribution, minimum film thickness, misalignment moment and static characteristic in varying rotate speed. The results show that the hyperboloidal sliding bearing had a stronger adaptability to misaligned sliding bearing caused by shaft deformation.Simplified FEM model of the bearing-balance rotor was established and modality analyzed by AN SYS software. The results show that first critical speed of the balance shaft was greater than 5000r/min maximum speed of the balance mechanism, namely it would avoid resonance vibration in speed range of the balance mechanism, sliding bearing parameter met design requirement. In order to verify the impact of operational reliability of the sliding bearing and machining errors to lubrication property of the balance mechanism, the measure experimentation for the lubricating film locus of the sliding bearing for the double shafts balance mechanism in different condition and orthogonal test of different machining accuracy for the double shafts balance mechanism in the same condition were designed, it was estimated operational of the sliding bearing in different condition and the foremost impact of machining errors to lubrication property of the balance mechanism by the experimentation.