| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce amplitude of resonance frequency by removing a frequency band amplitude of which vibration becomes large due to resonance at the time of driving an engine by increasing the intermediate cross-sectional area of an intermediate portion in the longitudinal direction of a hollow part formed inside of a stiffner larger than each side end cross-sectional area in the longitudinal direction. SOLUTION: A stiffner 36 has a hollow part 72 long in the longitudinal direction extending toward directions of a cylinder lock and an air intake manifold between an installing member 44 and a reinforcing member 46. An intermediate cross-sectional area S1 of an intermediate portion in the longitudinal direction is formed larger than each of side end cross-sectional areas of each of side ends in the longitudinal direction on the hollow part 72. A part of the intermediate scross-sectional area S1 to be the maximum area is provided biased to the side of an installing part 50 for a block from a center in the longitudinal direction on the hollow part 72. Relation of length L2 from a part of the intermediate cross-sectional area S1 of the maximum area to a part of the one side end cross-sectional area S2 in the longitudinal direction and length L3 to a part of the other side end cross-sectional area S3 of the other side end in the longitudinal direction is made L2<L3 against length L1 of the hollow part 72 on the stiffner 36.</p> |
