| 摘要 |
PURPOSE:To reduce noise by supporting a crank shaft by a divided boss for bearing arranged in an united body on the lower surface of a cylinder block and a bearing frame which has divided boss for bearing. CONSTITUTION:On the lower surface of a cylinder block 2, a divided boss part 4 for bearing is installed in an united body, positioned between each cylinder, and an under frame 6 formed on the lower surface of a bearing frame 3 having a divided boss part 5 for bearing correspoinding to the divided boss part 4 is connected with each divided boss part 5. A crank shaft is retained by said upper and lower divided boss parts 4 and 5. Accordingly, the flexural rigidity in the axial direction of the crank shaft is improved remarkably, and even if the repulsive force of bending vibration acts on the crank shaft, the vibration of the engine body is reduced remarkably, and the noise due to the vibration in relaxively low frequency range can be reduced. |
