Valve operating system and engine intake control system

An engine intake control system in which an intake manifold is formed from a surge chamber communicating with an air inlet, a first intake passage that bypasses one side wall of the surge chamber and that has an upstream end portion and a downstream end portion opening in the surge chamber, and a second intake passage that has an upstream end portion opening in the surge chamber so as to oppose the downstream end portion of the first intake passage across a gap and a downstream end portion connected to an intake port of an engine, a sleeve-shaped valve body is slidably fitted around one of the opposing end portions, that is, the first intake passage end portion, of the first and second intake passages, the valve body moving between a first position in which the valve body is distanced from the other of the opposing end portions, that is, the second intake passage end portion, and a second position in which the valve body is in contact with the second intake passage end portion, and an actuator is connected to the valve body via a valve operating system,

• wherein the valve operating system comprises a drive shaft that is rotatably supported on the intake manifold and connected to the actuator, a drive lever that is fixedly provided on the drive shaft and can pivot in a direction of movement of the valve body, a follower arm that is fixedly provided on the valve body, a link, a first connecting shaft that pivotably connects one end of the link and the drive lever, and a second connecting shaft that pivotably connects the other end of the link and the follower arm;
• in response to a movement of the valve body from the first position to the second position by pivoting of the drive lever, a center of the first connecting shaft approaches from one side a straight line connecting two centers of the drive shaft and the second connecting shaft, and after the valve body reaches the second position, further pivoting of the drive lever is carried out through a predetermined angle so that the center of the first connecting shaft moves to the other side of a dead point on the straight line.