Air intake control system

An air intake control system comprising:

• an intake passage for supplying intake air to an internal combustion engine;
• a valve element disposed in the intake passage for varying the cross-sectional area of the intake passage by pivoting between fully opened and completely closed positions;
• a valve shaft for transmitting a driving force for pivoting the valve element to the valve element;
• an actuator including:
• a prime mover for supplying said driving force for pivoting the valve element;
• a driving force transmission gear which is fitted to the prime mover and rotated thereby;
• and
• a housing accommodating the prime mover and the driving force transmission gear;
• and
• a driving gear which is mounted on the valve shaft and meshes with the driving force transmission gear to transmit said driving force supplied from the actuator to the valve shaft, the driving gear including:
• a boss portion;
• a tooth portion which meshes with the driving force transmission gear to receive said driving force supplied from the actuator;
• and
• an elastic member which is sandwiched between and bonded to the boss portion and the tooth portion and elastically deforms when twisted;
• wherein the boss portion has a hole into which the valve shaft is inserted in such a manner that the boss portion rotates together with the valve shaft, the tooth portion and the elastic member have holes into which the valve shaft is inserted in such a manner that the tooth portion and the elastic member can rotate relative to the valve shaft, and wherein an impact load caused by opening and closing motion of the valve element is alleviated by torsional deformation of the elastic member in a turning direction of the valve shaft.