Optimization Design Research On Valve Train Of Internal-Combustion Engine

The valve train is one of the most important mechanisms in a internal combustion engine, whether the performances are good or bad, that affecting the power performance, economic performance, emissions performance of the engine, as well as affecting the reliability and wear performances of the whole engine. Along with the requests of the engine's high power, super-speed, people demand a higher index. That is, when the engine runs under a high speed, it can still work steadily and dependably, which demand that the valve train system should have a high performance. Cam profile is the hard core of the valve train, which design is one of the important ways to carry out valve train optimal design. Simulation calculation and experimentation research are two important ways to carry out research and development on valve train of internal-combustion engine.In this paper, the kinematics and dynamics model on valve train of the engine are built up with AVL TYCON, the performances on the valve train are calculated, some problems on the valve train are made certain, in order to solve the problems, the cam profiles are designed, some factors of cam profile designing are analyzed. Then forces testing on the mechanisms of the valve train are carried out on the engine experiment bench, to validate the validity of simulation calculation and the feasibility of the designing. The main research work include:(1) The kinematics and dynamics model on valve train of the engine are built up with TYCON. The performances calculation of the valve train indicate that the fullness ratios of intake valve curve is on the low side, and the maximum contact stress between intake cam and tappet is higher, the same problem exists in the exhaust part, and the lubrication function between exhaust cam and tappet is bad, to the problems existed in the valve train, some measures and approaches of cam design are put forward.(2) By carrying out cam profiles design and some mostly impacting factors are discussed, then some optimal design schemes are put forward.(3) In the light of the original cam profile schemes and the improved camprofiles schemes, a new camshaft is made, the corresponding cam profiles of the cylinder No.l, 3, 5 applying original cam profile schemes, the cylinder No.2,4,6 applying the new schemes. The new camshaft is installed into the engine to carry out the forces testing of the pushrod and rocker arm of the valve train, the results between simulation calculations and experiment testing are contrasted, the valve train correlative mechanisms forces variations on account of the cam profiles improved are also analyzed. The validity of the simulation calculations results on the valve train is validated by the forces testing.