| 摘要 |
A valve operating system in an internal combustion engine includes a cam shaft provided with a plurality of valve operating cams, a plurality of rocker arms positioned adjacent one another, an associative operation switch capable of being switched between a state in which it permits the rocker arms adjacent each other to be operated associatively with each other, and a state in which it releases the associative operation. An urging means for urging the free rocker arm of the plurality of rocker arms toward the valve operating cam corresponding to the free rocker arm, which becomes free relative to an engine valve, when the associative operation switch is brought into the associative operation releasing state. The free rocker arm is provided with first and second support walls spaced apart and opposed to each other, and a roller is provided in rolling contact with a valve operating cam corresponding to the free rocker arm, and is rollably supported on a support shaft mounted to extend between the support walls through a bearing. In such valve operating system, one of the support walls included in the free rocker arm is integrally provided with a receiving portion which contacts with the urging means. Therefore, the structure of the free rocker arm can be simplified in such a manner that the receiving portion is positioned to the side of the roller. In addition, an increase in size of the free rocker arm can be avoided, and the inertial weight is reduced. Thus, it is possible to conveniently accommodate the high-speed rotation of the internal combustion engine.
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