Ngk Spark Plug Company, Limited

Hirohito Ito

Makoto Sugimoto

Takahiro Matsuura

Wataru Matsutani

Kuniharu Tanaka

Masaya Ito

Hiroaki Nasu

Yoshihiro Yamamoto

Kenji Nunome

Hiroyuki Tanabe

Katsura Matsubara

Yoshito Uemura

A spark plug having a protrusion amount t of not smaller than 0.3 mm and satisfying a relation93&#xb0; in which &#x3b8;is an included angle between virtual lines sand s, and &#x3b8;is an included angle between virtual lines sand swhen the virtual line sis taken as a line parallel to a direction of an axis and including the other end side edge on a leading end surface of a first precious metal tip, the virtual line sis taken as a line connecting the other end side edge and a point of intersection between an inner circumferential surface of a ground electrode body and the other end surface of the ground electrode body, the virtual line sis taken as a line parallel to the direction of the axis and including the other end side edge on a leading end surface of a center electrode, and the virtual line sis taken as a line including the other end side edge and tangent to an insulator.

Spark plug

A spark plug having a protrusion amount t of not smaller than 0.3 mm and satisfying a relation &#x3b8;&#x2266;93&#xb0; in which &#x3b8;is an included angle between virtual lines sand s, and &#x3b8;is an included angle between virtual lines sand swhen the virtual line sis taken as a line parallel to a direction of an axis and including the other end side edge on a leading end surface of a first precious metal tip, the virtual line sis taken as a line connecting the other end side edge and a point of intersection between an inner circumferential surface of a ground electrode body and the other end surface of the ground electrode body, the virtual line sis taken as a line parallel to the direction of the axis and including the other end side edge on a leading end surface of a center electrode, and the virtual line sis taken as a line including the other end side edge and tangent to an insulator.

A method for manufacturing a spark plug, the spark plug includes: a cylindrical metal shell having a portion to be caulked and a tool-engaging portion that is to be attached on an engine; an insulator that is inserted into the metal shell and extends axially; and a caulking metallic mold, the method including caulking the portion to be caulked to be fixed to an outer circumferential face of the insulator with the caulking metallic mold, where in the caulking metallic mold includes a face, the face including a hard carbon film that includes an amorphous carbon phase, and the face is contact with or sliding to the portion to be caulked.

Method for manufacturing spark plug and caulking metallic mold

An insulator for spark plug comprises an alumina-based sintered body comprising: Al O as a main component; and at least one component (hereinafter referred to as &ldquo;&bgr; component&rdquo;) selected from the group consisting of Ca component, Sr component and Ba component, wherein the alumina-based sintered body comprises particles comprising a compound comprising the &bgr; component and Al component, the compound having a molar ratio of the Al component to the &bgr; component of 4.5 to 6.7 as calculated in terms of oxides thereof, and has a relative density of 90% or more.

Alumina-based sintered body insulator for spark plugs

The invention provides a spark plug having an insulator which is composed mainly of alumina, and which is more superior in voltage endurance characteristics at high temperatures as compared with the prior-art materials. An insulator,of a spark plug,is made of an insulating material which is composed mainly of alumina, and which contains Al component within a range of 95 to 99.7 wt % in weight converted to Al,O,, and in which an area ratio occupied by alumina base principal-phase particles with particle size not less than 20 &mgr;m is not less than 50% as a cross-sectional structure of the insulator is observed. By making the alumina base principal-phase particles appropriately coarse like this, the voltage endurance characteristics of the insulator can be remarkably improved.

Spark plug, insulator for spark plug and process for fabricating the insulator

In a transfer sheet and a method of transferring a figuration to a ceramic product, an ink is provided by mixing a chromophoric pigment for expressing a desired coloration, a vitreous powder and thermoplastic resin. A sheet of paper or plastic film is prepared on which an appropriate figuration is screen printed with the use of the ink to transfer it to an outer surface of a ceramic product. A thermoplastic separable layer is provided between the mount sheet and a pigment layer. The pigment layer is coated with an adhesive layer.

Method of transfer printing a ceramic spark plug insulator

In a transfer sheet and a method of transferring a figuration to a ceramic product, an ink is provided by mixing a chromophoric pigment for expressing a desired coloration, a vitreous powder and thermoplastic resin. A sheet of paper or plastic film is perpared on which an appropriate figuration is screen printed with the use of the ink to transfer it to an outer surface of a ceramic product. A thermoplastic separable layer is provided between the mount sheet and a pigment layer. The pigment layer is coated with an adhesive layer.

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Kounan, Japan

Hirohito Ito