Knock detecting apparatus for internal combustion engines

Claim 2

A knock detecting apparatus for internal combustion engines comprising: a housing having a substantially cylindrical side peripheral wall; a vibrating member disposed in said housing in the radial direction and having a ring-shaped support member and a reed segment extending from an inner peripheral edge of said support member toward the center, said reed segment being integral with said ring-shaped support member and the peripheral portion of said ring-shaped support member being secured to the inner peripheral surface of said housing, said vibrating member having a resonant characteristic set at a knocking frequency; a bar-shaped central magnetic path member having one end spaced from said vibrating member to form an air gap and extending in the axial direction substantially in the center within said housing; a radial magnetic path member extending from the other end of said central magnetic path member in the radial direction of said housing; an outer cylindrical magnetic path member extending between the outer peripheral side of said radial magnetic path member and said vibrating member; a magnetic circuit being formed by said bar-shaped central magnetic path member, air gap, vibrating member, outer cylindrical magnetic path member and radial magnetic path member; a permanent magnet member located and included in said magnetic circuit; and a magnetic flux detecting means placed in said housing and magnetically coupled with said bar-shaped central magnetic path members for detecting change of the magnetic reluctance of said magnetic circuit due to a change in the width of said air gap caused by vibrations of said vibrating member.

Claim 3

A knock detecting apparatus according to claim 1, wherein said vibrating member is made from a sheet of magnetic material.

Claim 4

A knock detecting apparatus according to claim 1, further comprising a ring-shaped spacer made of a nonmagnetic material and which is interposed between the support member of said vibrating member and said central magnetic path member so as to frictionally lock said central magnetic path member to said support member.

Claim 5

A knock detecting apparatus according to claim 3, wherein the integral coupling of the central magnetic path member and the support member of said vibrating member is achieved by forcibly inserting said central magnetic path member in said spacer to be fastened therein and fixedly driving a knock pin in said spacer and said support member of said vibrating member.

Claim 6

A knock detecting apparatus for internal combustion engines comprising: a housing having a substantially cylindrical side peripheral wall and being made of magnetic material; a vibrating member of magnetic material disposed in said housing in the radial direction and having its peripheral portion supported by said housing, said vibrating member having a resonant characteristic set at a knocking frequency; a bar-shaped central magnetic path member having one having one end spaced from said vibrating member to form an air gap and extending in the axial direction substantially in the center within said housing; a radial magnetic path member extending from the other end of said central magnetic path member in the radial direction of said housing; an outer cylindrical magnetic path member extending between the outer peripheral side of said radial magnetic path member and said vibrating member, said outer cylindrical magnetic path member being formed by a magnetic seal plate fixed to the opening end of said housing, whereby a magnetic gap is formed between said outer cylindrical magnetic path member and the side peripheral wall of said housing so as to provide a double magnetic structure; and a magnetic circuit being formed by said bar-shaped central magnetic path member, air gap, vibrating member, outer cylindrical magnetic path member and radial magnetic path member; a permanent magnet member located and included in said magnetic circuit; and a magnetic flux detecting means placed in said housing and magnetically coupled with said bar-shaped central magnetic path members for detecting change of the magnetic reluctance of said magnetic circuit due to a change in the width of said air gap caused by vibrations of said vibrating member.

Claim 7

A knock detecting apparatus for internal combustion engines comprising: a housing having a substantially cylindrical side peripheral wall and being made of magnetic material; a vibrating member of magnetic material disposed in said housing in the radial direction and having its peripheral portion supported by said housing, said vibrating member having a resonant characteristic set at a knocking frequency; a bar-shaped central magnetic path member having one having one end spaced from said vibrating member to form an air gap and extending in the axial direction substantially in the center within said housing; a radial magnetic path member extending from the other end of said central magnetic path member in the radial direction of said housing; an outer cylindrical magnetic path member extending between the outer peripheral side of said radial magnetic path member and said vibrating member, said outer cylindrical magnetic path member being formed by a magnetic seal plate fixed to the opening end of said housing, whereby a magnetic gap is formed between said outer cylindrical magnetic path member and the side peripheral wall of said housing so as to provide a double magnetic structure; and a magnetic circuit being formed by said bar-shaped central magnetic path member, air gap, vibrating member, outer cylindrical magnetic path member and radial magnetic path member; a permanent magnet member located and included in said magnetic circuit; and a magnetic flux detecting means placed in said housing and magnetically coupled with said bar-shaped central magnetic path members for detecting change of the magnetic reluctance of said magnetic circuit due to a change in the width of said air gap caused by vibrations of said vibrating member.