Fluid control valve

1. A fluid control valve comprising:

a pressure chamber including an output port;

an air supply nozzle and an air exhaust nozzle which are communicatively connected to said pressure chamber and positioned on a common straight line;

a flapper assembly which is movable between said air supply nozzle and said air exhaust nozzle and includes a pair of opening/closing control surfaces that face an opening end of said air supply nozzle and an opening end of said air exhaust nozzle, respectively; and

an electromagnetic drive mechanism which moves said flapper assembly so that a distance between said opening end of said air supply nozzle and one of said pair of opening/closing control surfaces increases while a distance between said opening end of said air exhaust nozzle and the other of said pair of opening/closing control surfaces decreases,

wherein said electromagnetic drive mechanism comprises:

a permanent magnet fixed to said flapper assembly, said permanent magnet being formed in a cylindrical columnar shape; and

a fixed coil portion which produces an electromagnetic effect between said fixed coil-yoke portion and said permanent magnet to move said flapper assembly,

wherein said flapper assembly comprises a pair of flappers including said pair of opening/closing control surfaces, respectively,

wherein central portions of said pair of flappers are connected to each other via a connecting member which includes two magnet yokes positioned at opposite ends of said permanent magnet,

wherein said fixed coil portion includes a pair of fixed coils which are positioned around said permanent magnet and said two magnet yokes to be symmetrical with respect to a central position of said flapper assembly; a pair of coil yokes positioned on opposite sides of said pair of fixed coils, respectively; and a pair of coil yokes positioned around said pair of fixed coils, respectively,

wherein opposite end surfaces of said pair of coil yokes on said pair of flappers sides are positioned outside of outward end surfaces of said two magnet yokes, respectively, and

wherein said fluid control valve is controlled so that directions of flow of currents passing through said pair of fixed coils become opposite to each other.

2. The fluid control valve according to claim 1 , further comprising a spring device which biases said flapper assembly to move said flapper assembly in a direction to make said one of said pair of opening/closing control surfaces come into intimate contact with said air supply nozzle to close said air supply nozzle.

3. The fluid control valve according to claim 1 , further comprising a tapered surface which is formed at said opening end of said air supply nozzle on said flapper assembly side so that a diameter of said tapered surface gradually increases,

wherein said one of said pair of opening/closing control surfaces, which is adjacent to said air supply nozzle, comprises a conical-shaped opening/closing control surface shaped to correspond to a shape of said tapered surface.

4. The fluid control valve according to claim 1 , wherein a diameter of said air exhaust nozzle is constant, and

wherein said other of said pair of opening/closing control surfaces, which is adjacent to said air exhaust nozzle, comprises a needle-like opening/closing control surface which is tapered in a direction away from said flapper assembly.

5. The fluid control valve according to claim 1 , wherein said flapper assembly comprises a pair of flappers outer edges of which are fixed, said pair of opening/closing control surfaces being formed integral with central portions of said pair of flappers, respectively.

6. The fluid control valve according to claim 5 , wherein said pair of flappers are provided at opposite ends of said flapper assembly, respectively, and

wherein said pair of opening/closing control surfaces are formed integral with said pair of flappers to face said opening end of said air supply nozzle and said opening end of said air exhaust nozzle, respectively.

7. The fluid control valve according to claim 1 , wherein said flapper assembly moves linearly in a direction orthogonal to both a plane in which said opening end of said air supply nozzle lies and a plane in which said opening end of said air exhaust nozzle lies.