| A three-dimensional, pushrod-type valve train is found in some racing cars as well as certain passenger cars. Because a vertical pushrod can cause interference with the intake port, which reduces engine power, the pushrod is sometimes tilted to increase the cross-sectional area of the intake port. To analyze this mechanism, a three dimensional valve train model is developed. In addition to pushrod angles, the moving direction of the lifter can be in any dimension, and the initial position of the rocker arm is also considered. The pivot point of the rocker arm is not necessarily aligned with both contact points of the pushrod and the valve. The verification of this model is made by two laboratory experiments. Simulation and experiments show that the valve train performance is not affected by pushrod angles less than 20 degrees.;In addition to the three-dimensional model, the valve head and valve seat models are incorporated to improve the valve train simulation. Hydraulic lash adjusters affect the valve train dynamic behavior significantly, so they are investigated by both simulation and experiment. While the system of the differential equations is highly nonlinear in valve train models, a global optimizer, IFFCO, is employed to speed up the system parameter identification. Finally, the optimal design of the three-dimensional valve trains is performed by running the integrated valve train software package with the modified or previous optimization algorithm. |
