Valve driving apparatus for an internal combustion engine

Claim 1

A valve driving apparatus in an internal combustion engine having plural valve stems for each cylinder in a cylinder head on an upper portion of a main body of the engine which are aligned radially about the cylinder head with the intersection of their longitudinal axes substantially coinciding with a center of curvature of an upper wall surface of a combustion chamber, the cylinder head including a lower half portion having the valve stems therein and an upper half portion constituted by a detachable head cover; the valve driving apparatus including: at least one cam shaft rotatably clamped in between the lower half portion of the cylinder head and the head cover, a plurality of subsidiary rocker arms, each having one end in abutment with a head of one of the valve stems, subsidiary rocker arm shafts, each pivotally mounting one of the subsidiary rocker arms and being inserted in and supported by a bearing bore formed directly in one of the lower half portion and the upper half portion of the cylinder head, each shaft having a center axis positioned in a plane which crosses a longitudinal axis of the corresponding one of the valve stems at a right angle and which also is substantially located to include a mid-point of a range of up and down stroke of the head of the valve stem, a plurality of respective rocker arms driven by said at least one cam shaft and driving the subsidiary rocker arms, and respective rocker arm shafts pivotally mounting the respective rocker arms and each being inserted in and supported by at least one bearing bore formed directly in one of the lower half portion and the upper half portion of the cylinder head; at least one pair of the subsidiary rocker arms which are in abutment with a corresponding pair of valve stems being positioned between the corresponding pair of valve stems, the subsidiary rocker arm shafts mounting said at least one pair of subsidiary rocker arms being disposed in parallel with one another and in parallel with a plane at right angles with the corresponding respective rocker arm shaft.