Abstract
This paper deals with simulation technologies for noise and vibration of
automobile engines. Prediction of engine vibration in the running condition is a challenging
subject because it is highly non-linear; the number of degrees of freedom is very large; the
target frequency range stretches from 10 Hz to several kHz. For predicting engine vibration in
such wide frequency range it is very important to consider coupling between kinematic
motions and structural vibrations. Therefore, we have been developing our in-house program
called EVAS: Engine Vibration Analysis System. EVAS is a flexible multibody dynamics
solver that can comprehensively analyze the coupled phenomena by using body elements
(finite element models) and several types of force elements (non-linear functions).
One possible difficulty of this setting is that the number of degrees of freedom may become
extremely large due to the detailed modelling of target systems. In the real engineering
context it is very important to carefully choose the decisive factors of target problems and
obtain meaningful solutions within a reasonable calculation time.
In this paper, we have reformulated the piston-conrod sub-systems based on multibody
dynamics theory. The proposed method can calculate the crank-pin transmitting forces
considering the vibrations of kinematic motions of piston-conrod induced by the elastic
torsional vibrations of crankshaft. The effectiveness of the proposed method is discussed by
comparing the calculation results to the experimental results.
Keywords - automobile engine, noise and vibration, flexible multibody dynamics,
kinematical and structural coupling, rotating speed sweep analysis