Ngk Spark Plug Company, Limited

Mai Nakamura

Akira Suzuki

Mamoru Musasa

Tomoaki Kato

Jiro Kyuno

The spark plug includes: an insulator having an axial hole formed along an axial line; and a metal terminal provided on a rear side of the axial hole of the insulator. The metal terminal has, at a rear end portion thereof, a bottom surface facing rearward and a projection projecting rearward from an outer edge of the bottom surface, and a mark is provided to at least a part of the bottom surface. The Vickers hardness of the projection is 100 HV or higher. A rear end surface of the projection is positioned on a rear side with respect to a rear end of the mark. An area of the rear end surface is 3 mmor greater.

Spark plug

A spark plug includes: a metal shell including a tool engagement portion and having a through hole; an insulator disposed in the through hole of the metal shell; and a metal terminal including: a trunk portion disposed in an axial hole of the insulator; a flange portion having a larger diameter than the trunk portion; and a head portion having a smaller diameter than the flange portion. A minimum thickness of an exposed portion of the insulator is equal to or less than 2.5 mm. A diameter difference between the maximum outer diameter of the head portion and the maximum outer diameter of the tool engagement portion is equal to or less than 9 mm, or a diameter difference between the maximum outer diameter of the exposed portion and the maximum outer diameter of the head portion is equal to or less than 2.3 mm.

An ignition plug having a ceramic insulator with an axial bore, a metallic shell provided around the ceramic insulator, and a terminal electrode having a leg portion inserted into a rear end portion of the axial bore and a head portion projecting from the rear end of the ceramic insulator, wherein the length L of a portion of the ceramic insulator projecting from the rear end of the metallic shell is not less than 28 mm but not greater than 34 mm. The thickness t of the thinnest portion of the ceramic insulator is 1.0 mm or greater within a region which extends 5.5 mm from the rear end of the ceramic insulator toward the forward end side with respect to the direction of the axis.

A spark plug includes a ceramic insulator having a tapered rear end stepped portion whose diameter decreases from front to rear and a metal shell having a crimp portion which crimps the rear end stepped portion from the rear end. An area defined by an outer edge of the rear end stepped portion and an inner edge of the crimp portion is 5-25 mmwhen the spark plug is projected on a plane perpendicular to an axial line. An angle formed by a tapered surface of the rear end stepped portion and a plane perpendicular to the axial line is 20-60 degrees. A distance along the axial line from a front end of a proximal portion of the crimp portion to a frontmost position of a contact portion between an inner surface of the crimp and the rear end stepped portion is 0.4-1.8 mm.

Spark plug having a crimp portion in the metal shell to firmly engage with the ceramic insulator

A spark plug comprised of an insulator having a stepped portion on an outer circumferential portion thereof, the stepped portion tapering frontward in the direction of the axis of the spark plug, an annular sheet packing and a metallic shell having a taper portion provided on an inner circumferential portion thereof and tapering frontward in the direction of the axis of the spark plug, the metallic shell holding the insulator through a rear end portion thereof being crimped, the stepped portion being seated on the taper portion via the sheet packing, and the taper portion having a groove therein.

Surface for supporting a sheet packing in a spark plug

A spark plug () includes an insulator () and a metal shell (), including a middle section () positioned between a collar section () and a tool engaging section (). The middle section () has a bulged section (), a first slender section () and a second slender section () that is the most slender at a portion positioned further to the leading end side than the bulged section (). In a cross-section including the axis CL, when the distance between both slender sections () and () along the axis CLis F (mm) and the bulged amount to the inside in diametrical direction of a most bulged section (M) with respect to an imaginary line that connects a portion that is positioned furthest to the inside in diametrical direction of both slender sectionsandis G (mm), the relationship 0.00&#x3c;G/F&#x2266;0.18 is satisfied.

Spark plug for internal combustion engine and method of manufacturing spark plug

A spark plug including a center electrode; an insulator; and a metal shell, the metal shell including: a tool engaging section; a body section; and a groove section formed between the tool engaging section and the body section, and having bulges which bulge in an outer peripheral direction and in an inner peripheral direction. When a portion of the groove section having a largest outer diameter is a first section, a thinnest portion from the first section to the body section is a second section, and a portion having a thickness that is the same as that of the first section is a third section, a relation between a thickness A of the second section and a radius of curvature R of an outer surface of the metal shell that continues from the second section to the third section satisfies R&#xd7;A&#x2267;0.20 mm.

Spark plug and manufacturing method thereof

A spark plug is provided which can ensure gastightness between a metal shell and an insulator while preventing the cracking of the insulator. There is provided a spark plug in which a ledge portionis formed on the metal shellwhose inside diameter is reduced gradually towards a front end portion, a step portionis formed on an insulatorwhose outside diameter is reduced gradually towards the front end portion and which confronts the ledge portion, and packingis disposed between the ledge portionand the step portion, characterized in that a distance between the ledge portionand the step portiongets narrower as the ledge portionand the step portionextend radially inwards, and in that an angle &#x3b8; formed by the ledge portionand the step portionis one degree or larger and 10 degrees or smaller.

Spark plug having specific configuration of packing area

A method for manufacturing a spark plug which includes: (a) preparing a metal shell; (b) preparing an insulator; (c) inserting the insulator in an insertion hole of the metal shell; (d) forming an intended crimping portion of the metal shell into a crimping portion; and (e) pressing a lower side portion of the metal shell closer to a position lower than the intended compressive deformation portion, and pressing the crimping portion of the metal shell in an axial direction to compressively deform the intended compressive deformation portion of the metal shell and thus seal a space between a stepped portion of the metal shell and a stepped portion of the insulator, wherein step (e) controls a pressing amount of a press in a constant value from the start of compressive deformation to the end thereof.

Method for manufacturing spark plug

A spark plug including an insulator and a metallic shell having an outer surface and an inner surface. The outer surface has a taper portion which comes into contact with a peripheral region around a mounting hole of an internal combustion engine, a tool engagement portion, and a trunk portion formed between the tool engagement portion and the taper portion. The inner surface has an annular step portion projecting toward the insulator and an internal trunk portion extending from the base of the step portion toward the rear end of the metallic shell. When the insulator and the metallic shell are fixed to each other by one of either cold and hot crimping, the projected area of the taper portion is at least two times or at least 1.5 times that of the step portion, respectively.

Growing community of inventors

Inazawa, Japan

Mai Nakamura