Hall effect type sensing device and magnetic circuit device for a hall effect type sensor

Claim 1

A Hall effect type sensing device for an ignition distributor for detecting the crank angle to control ignition timing of an internal combustion engine, said distributor including a shaft which is rotated by the internal combustion engine and a magnetic flux shutter fixed to the shaft so as to rotate therewith, said device comprising: (a) a magnetic circuit including a magnet for producing a magnetic field, a first magnetic flux guide for supporting said magnet and a second magnetic flux guide; (b) a Hall IC disposed in said magnetic circuit; (c) a holder for supporting said Hall IC and said second magnetic flux guide; and (d) a frame having a first holding block for holding said first magnetic flux guide and a second holding block for holding said holder in which said Hall IC and said second magnetic flux guide are supported, said first and second holding blocks being formed integrally with said frame, said first magnetic flux guide and said second magnetic flux guide being supported on said frame in spaced apart relation with respect to one another such that an air gap is formed therebetween, the air gap adapted to allow message of the rotating magnetic flux shutter so as to change the magnetic flux, said Hall IC converting the change of magnetic flux into an electric signal corresponding to a revolution of the internal combustion engine; wherein said second holding block has a pair of vertically extending grooves and said holder has a corresponding pair of vertically extending projections for engagement with said grooves.