The need for the variable displacement engine which can greatly improve fuel economy has become strong all over the world in recent years, and some of them have aleady reached production. Reducing the number of operating cylinders brings about significant inherent engine vibration. Because of this defect, it is necessary to redesign and refine the engine's mounting system to isolate vibrations effectively. In the present study, the three degrees-of-freedom dynamic model of an inline four-cylinder engine which has a three point mounting system is developed, and its excitation forces are analyzed at normal and misfiring conditions. Mount locations, inclined angles, and isolator shapes are selected as the design variable to minimize the vibration of the variable displacement engine. This optimization problem is solved by the gradient projection method. Simulation studies using the developed program show that by adjusting the engine's mounting system, the vibration level is reduced significantly, and thus, at the idling speed, the rms displacement of the engine under the misfiring condition is reduced by about thirty percent.
최근 활발한 연구와 생산에 놓여있는 가변기통 엔진은 연료비를 비약적으로 절감할 수 있는 반면, 일부 기통을 불점화시킴으로써 심한 진동이 초래된다. 가변기통 엔진의 진동을 감소시키기 위해 엔진마운트의 최적설계 문제가 고려되었다. 세 곳으로 지지되는 4기통 직렬 엔진에 대하여 3자유도의 동역학적 모델을 설정하였고 동작기통수에 따른 가진력을 해석하였다. 마운트의 위치와 경사각, 방진고무의 형상을 설계변수로 하는 최적 설계문제를 미분벡터 투영법을 이용하여 해결하였고, 시뮬레이션 결과로부터 가변기통 엔진의 진동은 공회전시에 특히 감소됨을 알 수 있었다.
