Rocker arm and method of manufacturing the rocker arm

A method of manufacturing a rocker arm comprising:

• stamping a flat plate material to form an arm body in a developed shape, the arm body in the developed shape extending from one of two ends thereof to the other in a longitudinal direction, the arm body in the developed shape having a longitudinal middle part formed with a housing space that is configured to house a roller positioned for contact with the cam, the arm body in the developed shape having two end corners at the one longitudinal end;
• pressing the end corners of the arm body in the developed shape by a press to form thinner portions;
• bending the arm body in the developed shape downward along a pair of imaginary broken lines parallel to the longitudinal direction of the arm body in the developed shape, thereby forming a pair of sidewalls and a receiving wall at the one longitudinal end, the pair of sidewalls respectively having the thinner portions in lower ends thereof, the receiving wall having an interior edge extending along a width direction so as to define one end of the housing space, the receiving wall having widthwise opposing side edges each extending in the longitudinal direction to respectively intersect ends of the interior edge;
• and
• pressing an upper side of the receiving wall by a press while the interior edge of the receiving wall is restricted at the housing space side, thereby forming a curved concave portion on an upper surface of the receiving wall, with the curved concave portion being recessed with respect to both the interior edge and the side edges.