Patent ID: 8006658

Claim:
A variable valve actuation apparatus of an internal combustion engine comprising: a drive shaft having a drive support shaft and a drive eccentric cam whose geometric center is displaced from a shaft axis of the drive support shaft, and adapted to rotate about the shaft axis of the drive support shaft in synchronism with rotation of an engine crankshaft; a control shaft having a control support shaft and a control eccentric cam whose geometric center is displaced from a shaft axis of the control support shaft, and adapted to rotate about the shaft axis of the control support shaft; a rockable cam pivotably supported by a pivot, and having a cam nose portion and a connecting portion such that the cam nose portion and the connecting portion are arranged on opposite sides of the pivot, and adapted to actuate an engine valve by a cam contour surface portion defined between the cam nose portion and the connecting portion; a rocker arm configured to pivot about the control eccentric cam as a fulcrum; a link arm linked at a first end to the drive eccentric cam in such a manner as to pivot about a first fulcrum X corresponding to the geometric center of the drive eccentric cam, and further linked at a second end to the rocker arm in such a manner as to pivot about a second fulcrum R provided on the rocker arm; and a link rod linked at a first end to the rocker arm in such a manner as to pivot about a third fulcrum S provided on the rocker arm at a position different from the second fulcrum R, and further linked at a second end to the connecting portion of the rockable cam in such a manner as to pivot about a fourth fulcrum T provided on the connecting portion of the rockable cam, wherein at least a working angle of the engine valve varies by rotating the control shaft; and wherein a position of rotation of the control shaft is set, so that, at a peak lift during a valve opening period of the engine valve, an angle γ 2 between an extension line of a line segment X-R between and including the first and second fulcrums X and R and a line segment R-S between and including the second and third fulcrums R and S midway between minimum and maximum working-angle control modes is less than both an angle γ 1 between the extension line of the line segment X-R and the line segment R-S at the minimum working-angle control mode and an angle γ 3 between the extension line of the line segment X-R and the line segment R-S at the maximum working-angle control mode.