Valve mechanism for internal combustion engine

A valve mechanism for an internal combustion engine comprising:

• a support shaft;
• a main arm that is swingably supported by the support shaft;
• two sub-arms arranged at both sides of the main arm in an axial direction of the support shaft;
• a coupling support portion that couples the two sub-arms to the main arm, and swingably supports the two sub-arms;
• a cam including a base circular portion;
• and
• a roller rotatably mounted to the main arm through the coupling support portion,
• wherein each of the two sub-arms includes:
• a drive unit at a first end thereof, the drive unit pressing and driving a valve;
• and
• a contact portion at a second end thereof, the contact portion
• contacting a plunger of a lash adjuster,
• the support shaft is immovably fixed to a main body of the internal combustion engine,
• the contact portion has a curved surface that slidably contacts a flat surface formed in a tip portion of the plunger,
• the curved surface has an arc-like curved surface shape, and
• a central axis line of the arc-like curved surface shape is configured to correspond to a central swing axis line of the main arm in a state where the cam abuts on the roller in the base circular portion.