Variable valve apparatus of internal combustion engine

1. A variable valve apparatus of an internal combustion engine, the variable vale apparatus comprising:

a cam shaft rotatably provided to the internal combustion engine, a drive cam formed integrally with the cam shaft, and a rocker arm mechanism for transmitting an opening/closing operating force from an operating end portion thereof to an intake or an exhaust valve of the internal combustion engine by receiving the opening/closing operating force by a drive cam opposed roller brought into contact with the drive cam;

wherein for displacing a lift time period, in which the drive cam opposed roller receives the opening/closing operating force by the rocker arm mechanism, frontward/rearward in a direction of rotating the drive cam, an up section of a cam lift face of the drive cam is formed to be longer than a down section thereof such that a change region of a lift valve closing time point of the lift time period becomes larger than a change region of a lift valve opening time point thereof.

2. The variable valve apparatus of an interval combustion engine according to claim 1 , wherein a cam projected face curvature at a vicinity of a cam top of the drive cam is set to be smaller on a side of the down section than on a side of the up section.

3. The variable valve apparatus of an internal combustion engine according to claim 1 , wherein in the down section of the cam lift face of the drive cam, a post section of the down section is formed by a shape by which an amount of operating a member driven by the drive cam can maintain a positive acceleration having substantially a constant value.

4. The variable valve apparatus of an internal combustion engine according to claim 1 , wherein the rocker arm mechanism comprises:

a first arm pivoted around a fulcrum position by receiving a press force by an axially supported rocker arm roller for driving the intake or the exhaust valve brought into contact with the operating end portion;

a second arm having an axially supporting portion for axially supporting the drive cam opposed roller and a fulcrum end portion remote from the axially supporting portion by a predetermined amount for receiving a switch operating force for displacing a position of bringing the drive cam opposed roller and the drive cam into contact with each other frontward/rearward in the direction of rotating the drive cam;

a fulcrum moving mechanism having a fulcrum member engaged with the fulcrum end portion of the second arm for displacing the second arm by receiving the switch operating force from a drive source; and

a third arm axially supported by a supporting shaft arranged at a vicinity of the cam shaft at an axially supporting end portion and formed with a rocking cam face capable of exerting the opening/closing operating force of the rocker arm roller at a rocking end of a rocking extended portion extended from the axially supporting end portion.

5. The variable valve apparatus of an interval combustion engine according to claim 4 , wherein a cam projected face curvature at a vicinity of a cam top of the drive cam is set to be smaller on a side of the down section than on a side of the up section.

6. The variable valve apparatus of an internal combustion engine according to claim 4 , wherein in the down section of the cam lift face of the drive cam, a post section of the down section is formed by a shape by which an amount of operating a member driven by the drive cam can maintain a positive acceleration having substantially a constant value.