| 摘要 |
A cylinder block structure with a small number of ribs is provided which can favorably prevent the deformation of a crankshaft bearing portion and the like. In a cylinder block 1 having bolt holes 3 formed on the upper surface for connecting a cylinder head with bolts, arc-shaped coupling surfaces 5 formed on the rear end surface for mounting a housing, such as a transmission housing, and a crankshaft bearing portion 6 formed in the central part between the lower ends of the coupling surfaces: the upper parts of the coupling surfaces 5 are joined into an arch-shape by an arch-shaped rib 7; the lower ends of right and left bosses 4 respectively having bolt hole 3 formed therein, are extended and connected to the lower parts of the arch-shaped rib 7; and right and left main radial ribs 10, respectively extend from the outside of the lower end of the bolt hole boss 4 to the center of the crankshaft bearing portion 6. <IMAGE> |
