Intake air control apparatus for an engine

An intake air control apparatus for an engine comprising:

• a shaft;
• a throttle valve fixedly secured to said shaft for adjusting the degree of opening in an intake passage through a rotational angle thereof;
• a first permanent magnet provided on an outer periphery of one end of said shaft with its N pole and S pole being positioned along an axis of said shaft;
• a second permanent magnet provided on the outer periphery of the one end of said shaft in opposition to said first permanent magnet with its N pole and S pole being positioned along the axis of said shaft;
• a rotational angle detection sensor having a magnetoresistive element disposed in a magnetic path formed by said first permanent magnet and said second permanent magnet in a spaced relation with respect to said shaft for detecting a change in the azimuth of magnetic flux of said permanent magnet thereby to sense a rotational angle of said throttle valve.