Variable valve operating system for internal combustion engine

Abstract

A variable valve operating system includes a position changing mechanism, which is configured by a circular eccentric portion provided for a control shaft of a engine valve in a manner decentered from an axis of the control shaft, an external gear formed on a cam follower swingably supported on the eccentric shaft portion, and an internal gear formed on a rocking cam so as to be engaged with the external gear. The control shaft is rotated when opening/closing characteristics of the engine valve are changed, the external gear is revolved by the eccentric shaft portion around the axis of the control shaft, an engaged portion of the internal gear with the external gear is moved in a circumferential direction of the internal gear by the revolution of the external gear, and the position of the rocking cam with respect to the cam follower is changed by the movement of the engaged portion of the internal gear.

1 . A variable valve operating system for an internal combustion engine including an engine valve and a cam shaft operating the engine valve, the variable valve operating system comprising:
 a rocking cam, which lifts the engine valve, supported to a control shaft to be swingable;   a cam follower rocking the rocking cam; and   a position changing mechanism which couples the cam follower with the rocking cam, the position changing mechanism being configured to change a relative positional relationship of the rocking cam with respect to the cam follower to thereby change lift characteristics of the engine valve,   the position changing mechanism comprising: a circular eccentric portion which is formed to the control shaft in a manner decentered from an axis of the control shaft; an external gear formed on the cam follower swingably supported on the eccentric shaft portion with the eccentric shaft portion as the rotating shaft; and an internal gear formed on the rocking cam with the control shaft as the rotating shaft so as to be engaged with the external gear,   wherein the control shaft is rotated when opening/closing characteristics of the engine valve are changed, the external gear is revolved by the eccentric shaft portion around the axis of the control shaft, an engaged portion of the internal gear with the external gear is moved in a circumferential direction of the internal gear by the revolution of the external gear, and the position of the rocking cam with respect to the cam follower is changed by the movement of the engaged portion of the internal gear.   
     
     
         2 . The variable valve operating system for an internal combustion engine according to  claim 1 , wherein when the control shaft is rotated, the cam follower moves such that a contact point to the rotating cam moves along an outer circumference of the rotating cam and the movement of the rocking cam causes a lift amount of the engine valve to be changed, and when the control shaft is rotated in a direction to reduce the lift amount of the engine valve, the contact point between the cam follower and the rotating cam moves in a direction opposite to the rotating direction of the rotating cam. 
     
     
         3 . The variable valve operating system for an internal combustion engine according to  claim 1 , wherein the rocking cam includes a base circle portion which prevents the engine valve from being lifted and a cam portion which is projected radially from the base circle portion, a hollow portion is formed on an inner circumference of the base portion, the internal gear is formed on an inner circumference surface of the hollow portion, and the external gear and the eccentric shaft portion are arranged inside the hollow portion.