| 摘要 |
PURPOSE:To enhance the water cooling effect of a closed back type cylinder block made of a light alloy, by forming water jackets substantially along the entire length of cylinder bores, and making the thickness of bottom walls of the water jackets substantially equal to that of inner walls of the water jackets. CONSTITUTION:In a cylinder portion 1 constituting the upper half of a cylinder block B, water jackets 6 are formed in the manner of surrounding cylinder bores 3, excluding the wall portions located between adjacent cylinder bores 3. The water jackets 6 are formed long to cover substantially the entire length of the cylinder bores 3, and the sectional area A1 of the upper half 6u of the water jackets 6 is made smaller than the sectional area A2 of the lower half 6d of the water jackets 6. Further, the thickness (d) of bottom walls 10 of the water jackets 6 is reduced and made equal to the thickness (di) of inner walls 11 and that (do) of outer walls 12 of the water jackets 6. By employing such an arrangement, it is enabled to make the temperature distribution of the cylin der portion 1 uniform and to cool the portion 1 uniformly by water. At the same time, failure of casting can be prevented. |
