Valve operating system in internal combustion engine

摘要

In a valve operating system in an internal combustion engine, one of adjacent rocker arms is provided with first and second support walls with the second support wall disposed on the side of the other rocker arm, and a roller is disposed between the first and second support walls to come into rolling contact with cams. A cylindrical roller shaft, on which the roller is rotatably supported, is provided between the first and second support walls, so that a switchover pin of an associative-operation switchover means can be slidably fitted into the roller shaft in response to the movement thereof to an associatively operating position. The roller shaft is press-fitted into at least second one of the first and second support walls, and a press-fit margin for the roller shaft press-fitted into the second support wall on the side of the other rocker arm is set smaller than a press-fit margin for the roller shaft press-fitted into the second support wall on the side of the roller. Thus, the roller shaft supporting the roller and guiding the switchover pin can be fixed easily to the rocker arm, while avoiding an increase in number of parts and an increase in number of processing steps. Moreover, during movement of the switchover pins to the associatively operating position, the deformation of an end of the roller shaft receiving the switchover pin due to the press-fitting is suppressed to a small level, thereby smoothening the press-fitting of the switchover pin into the roller shaft to smoothen the associative operation of the adjacent rocker arms and the releasing of the associative operation by the switchover pin.