| 摘要 |
PROBLEM TO BE SOLVED: To provide a cylinder block having improved bending and torsional rigidity and allowing vibration and noises to be abated by dispersing force resulting from combustion gas pressure in the cylinder block. SOLUTION: A first rib 21 and a second rib 22 crossing each other at an angle to the axial direction of a crank shaft are provided on a side wall 10 of the cylinder block 1. The first rib 21 ranges from a position 24 approximately corresponding to a cylinder partition wall 6 at the upper part of the side wall 10 of the cylinder block 1 to a position 25 approximately corresponding to a cylinder center C of a lower deck portion 4 and the second rib 22 ranges from a position 26 approximately corresponding to the cylinder center C at the upper part of the side wall 10 of the cylinder block 1 to a position 27 approximately corresponding to the cylinder partition wall 6 of the lower deck portion 4.
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