밸런스샤프트 모듈을 갖는 직렬 3 기통 엔진의 동역학적 모델 기반 진동해석

The paper presents the dynamic model of a balance shaft module for an in-line three cylinders engine that has each cylinder’s phase interval of 120 deg. The balance shaft module (in addition to counter weights on crank arms) plays a key role to compensate for the engine vibrations caused by the pistons, crank arms and connecting rods which rotate or reciprocate in the engine. For three cylinders engines, the vibrations are attributed to pitching and yawing moments because all lateral forces (horizontal and vertical) cancel each other out. Therefore, the balance shaft is designed to compensate for those moments in three cylinders engines. First, the paper predicts the excitation forces from each cylinder and then assembles them to predict the total excitation forces and moments. Prediction shows that the resultant forces are null and the maximum amplitude of the pitching moment is 1225 N-m at 3000 rpm. Installation of the counter weights to the crank arms and the balance shaft (with out-of-phase unbalance) to the engine removes the major vibration component arising due to the primary pitching moment. Additional two balance shafts (with lightweight unbalance) to the engine are suggested to remove the minor vibration component arising due to the secondary pitching moment. The model predictions show that the no vibration occurs due to the engine pitching moment and the pitching moment reduction per added unbalance are very high, thus implying the effectiveness of the suggested balance shaft module.