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This paper describes a new method for engine design using dynamic optimization and substructure synthesis method. A very important theme in engine design is how to shift the peak of the natural frequency of the vibration mode that causes some noise and vibration problems. This must be resolved by effective modification of structural design. In order to carry out effectively vibration analysis of a large scaled structure like engine assembly and conduct dynamic optimization with many iterative calculations, we have used substructure synthesis method that devides a whole structure into a number of substructures and solves each substructure. Vibration analysis of engine assembly (cylinder block, crank shaft, bearing caps and flywheel systems) was carried out by using this substructure synthesis method.

A finite element model for an entire frame-structured sports utility vehicle was made to evaluate the characteristics of the idling vibrations for the vehicle. The engine exciting forces were determined by Souma's method to simulate the idling vibrations. The modeling of the power plant and the entire vehicle was verified by the reasonable agreement of the experiment and calculation results. Attention was focused on the frequency of the first-order vertical bending mode for the frame. It has become clear that the idling vibration level of the vehicle is lowered by decreasing the frequency of the first-order frame bending mode.

A new method is introduced here to identify modal parameters by fitting curves with multiple degrees of freedom to experimental data in frequency domain. Unknown parameters in our method are natural frequencies and modal damping ratios, and, from these parameters natural modes and residual terms are determined. In comparing our method with the conventional Van Loon's method, fewer unknown parameters are dealt with, and thus computing time is shorter with better convergence of solution. Simulation results obtained show that our method is useful especially in refering to many data simultaneously.

In this study, the air suspension is newly applied to the engine mounting layout for getting the significant vibration isolation effect. In this case, the genetic algorithm so called GA is also applied for the optimization of many parameters, calculations of stiffness matrix and inverse stiffness matrix to prevent the coupled vibration of lateral and rolling modes and to obtain the displacement of each mounting point. As a result, inexperienced engineers can easily obtain the optimum engine mounting layout in a minute. By the confirmation test of FEM, the engine lateral vibration level at 25Hz dropped below 1/10 and its effect was significant.

There are two analytical methods for optimizing automotive structural dynamic characteristics to improve vehicle ride quality and minimize structural mass for improved fuel economy. The first method, the traditional approach, is to move the undesired structural resonant frequencies out of the range of the forcing functions by modifying the mass and stiffness parameters appropriately. However, in some cases the resonant frequencies are insensitive to parameters; these cases normally are difficult to improve. Fortunately, there is a second method, based on the natural phenomena that an anti-resonance exists for each resonant frequency. Furthermore, the sensitivity of these anti-resonance nodes to the structural parameters of mass, stiffness and damping are uniquely different. It is this difference in sensitivity that permits cases to be solved, which resist solution by the traditional first method.

In this study, the genetic algorithm so called GA is newly applied for the optimization of many engine mounting parameters, calculations of stiffness matrix and inverse matrix to obtain 6 degrees of freedoms displacements at mounting points and a center of gravity. As a result, the optimized result could be shortly obtained in a minute, and an inexperienced engineer could easily make the optimum engine mounting layout, which can satisfy the vibration isolation and the non-interference in an engine compartment.

This paper describes a method for effectively reducing a level of idling vibration in heavy-duty trucks, which has been the point at issue lately. In this method, the vibration level is significantly reduced by using a full vehicle model, which is made by finite elements, and varying parameters to study effects. In order to achieve high accuracy, engine excitation forces calculated from the measured fluctuation in the flywheel angular velocity are input to the model. An effective use of this method in an early development stage has enabled us to reduce development cost and the lead-time.

This paper reports on the analysis of mechanisms concerning the engine exciting force and the rotational couple of forces. Because the new V10 engine has the biggest power and displacement which is 441kw and 30 litters respectively, its exciting force of 2.5th and 5th orders are very large. On the other hand, as the V-bank angular is 80 degrees, the additional 1st order yawing vibration is also occurred by the generation of the rotational couple of forces. So, the optimum design is needed to reduce these vibrations by the frequency response analysis when these forces are added to the engine crank shaft. Finally, the vibration level could be reduced much lower than the lower-powered engine by the optimum design of engine mounting by using the FEM and the adoption of the new mechanism for the cancellation of a rotational couple of force.