| 摘要 |
PROBLEM TO BE SOLVED: To improve the rigidity of a rocker arm while avoiding the enlargement in size by protrusively providing, on a rocking support part, a lower connecting wall for mutually connecting the base end lower parts of a pair of support wall parts opposed with a space, to which the base end of the rocker arm is integrally molded, so as to be opposite to the lower outer circumferential surface of a roller. SOLUTION: A drive rocker arm 19 in an intake-side valve system 17I comprises a support part 19a rockably supported by a rocker shaft 22, a pair of support wall parts 311 having base ends continuously provided on the part 19a, and a tip connection part 19b for mutually connecting the tips of the support wall parts 311, which are integrally molded. A lower connecting wall 85 for mutually connecting base end lower parts of the support wall parts 311 is protrusively provided on the rocking support part 19a of the drive rocker arm 19 so as to be adjacent and opposite to the lower outer circumference of a roller 28 cooperating with a valve system cam 25 on a camshaft 18. The space between the lower connecting wall 85 and the roller 28 is set smaller than the space between an upper connecting wall 86 and the roller 28 so as to improve the rigidity.
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