Abstract: An ignition plug includes: an insulator provided with a shaft hole formed therein; a metal fitting caulked to support the insulator from an outer periphery side thereof; and a talc material filled in an annular space provided between an outer peripheral surface of the insulator and an inner peripheral surface of the metal fitting. A first annular member and a second annular member are provided at an end portion of the annular space, the end portion being positioned in a center electrode side along the center axis in the annular space, the second annular member is in contact with the first annular member from an opposite side of the center electrode.

Abstract: There is provided a spark plug for an internal combustion engine, including: a center electrode extending in the direction of an axis of the spark plug and having a core of higher thermal expansion coefficient than that of a front end thereof, the center electrode including a flanged portion radially outwardly protruding on a rear side thereof and a cylindrical portion located closer to a front end of the spark plug than the flanged portion and being smaller in diameter than the flanged portion; an insulator having an axial hole in the direction of the axis to retain the flanged portion in the axial hole with the cylindrical portion held in a loose-fit state in the axial hole; and a metal shell accommodating the insulator, wherein the spark plug satisfies the following condition: Cb<Cf where Cb is a difference between an inner diameter of the axial hole and an outer diameter of the cylindrical portion at an arbitrary axial position B in the direction of the axis; and Cf is a difference between the inner di

Abstract: A plasma jet ignition plug exhibiting high plasma generation efficiency while restraining occurrence of preignition. P1 represents the position of a rear end of a region of a metallic shell ledge, the region being in contact with an insulator. P2 represents the position of a rear end of a region of the insulator ledge, the region being in contact with the center electrode. Front end surfaces of the metallic shell, the insulator, and center electrode, an imaginary plane S1 which is perpendicular to the axis and contains position P1, and an imaginary plane perpendicular to the axis and contains position P2 are disposed in this order from front side to rear side along the axis. The axial distance A from the front end surface of the insulator to imaginary plane S1 and axial distance B from the imaginary plane S1 to imaginary plane S2 satisfy 0.5×A?B.

Abstract: A plasma jet spark plug capable of preventing a channeling progress and having excellent heat conduction. The plasma jet spark plug comprised of: a ceramic insulator having a small diameter portion which assumes a linear shape in an axial direction, and a center electrode has an outer diameter increasing in the order of a frontmost portion, a step portion, a front end portion and a body portion.

Abstract: A device for inspecting a spark plug insulator for bending, the spark plug insulator including a cylindrical body having a radially enlarged flange at an axially intermediate portion thereof, and a through hole formed in the body along an axial direction of the body. The inspection device includes an insulator supporting means for supporting the spark plug insulator so as to be slidable in an axial direction of the spark plug insulator, a linear inspection pin that is to be inserted into the through hole of the spark plug insulator supported by the insulator supporting means, and a detecting means for detecting a sliding movement of the spark plug insulator when the spark plug insulator is caused to slide in the axial direction thereof by the inspection pin by the inspection pin prevented from completely penetrating the through hole of the spark plug insulator owing to bending of the spark plug insulator which exceeds a predetermined tolerance.

Abstract: In a spark plug for an internal combustion engine, an insulator is vided at its inside with a center electrode. A tubular housing is disposed to surround an outer periphery of the insulator. An annular space portion is provided between the housing and the outer periphery of the insulator. A powder filling is filled in the annular space portion so as to be formed as a filled portion therein. The powder filling is composed of a plurality of filling grains. 80 weight percent and over of the filling grains, before the powder filling is filled in the annular space, have a range from 100 to 1000 ?m in grain diameter, respectively.

Abstract: In a spark plug for an internal combustion engine, an insulator is vided at its inside with a center electrode. A tubular housing is disposed to surround an outer periphery of the insulator. An annular space portion is provided between the housing and the outer periphery of the insulator. A powder filling is filled in the annular space portion so as to be formed as a filled portion therein. The powder filling is composed of a plurality of filling grains. 80 weight percent and over of the filling grains, before the powder filling is filled in the annular space, have a range from 100 to 1000 &mgr;m in grain diameter, respectively.

Abstract: An ignition plug for internal combustion engines in which a spark gap is established between a central electrode and a ground electrode opposed thereto and a spark discharge is generated in the spark gap so as to ignite a mixture, wherein the ground electrode takes a unique form such that it is provided with a kerf, groove, depression, projection or the like at its spark discharge area confronting the central electrode whereby the ignition ability is improved with the result that a lean mixture is useful to reduce the quantity of harmful components in the exhaust gas.