Knock detecting apparatus for internal combustion engines

A knock detecting apparatus for internal combustion engines, comprising:

• vibrator means including at least one reed member and a ring-shaped support member, said reed member being projected from an inner wall of said ring-shaped support member toward the center thereof, both of said reed member and said support member being made as a unitary body of a magnetic material, said reed member having a resonance characteristic corresponding to a knocking frequency of an engine;
• a bar-shaped magnetic core having one end being located adjacent to but spaced from said reed member to form an air gap therebetween;
• a cup-shaped housing of a magnetic material for accommodating said vibrator means and said bar-shaped magnetic core so that said support member of said vibrator means is fixed to an inside surface of said cup-shaped housing;
• magnetic flux generating means for generating magnetic flux through a magnetic path formed by said bar-shaped magnetic core, said air gap, said reed member, said support member and a side wall of said cup-shaped housing, said magnetic flux generating means including an excitation coil for generating controllable magnetic flux;
• and
• magnetic flux sensing means disposed adjacent to and coupled with said magnetic path to sense changes in the magnetic reluctance of said magnetic path caused by changes in the width of said gap due to vibrations of said reed member.