Ngk Spark Plug Company, Limited

Sumitomo Electric Industries, Limited

Ngk Spark Pulg Co., Ltd.

Kenji Nunome

Osamu Yoshimoto

Tsutomu Shibata

Wataru Matsutani

Yoshihiro Matsubara

Yoshikuni Sato

Tomoo Tanaka

Takehito Kuno

Takaaki Kikai

Yoshihiro Nakai

Hiroyuki Kameda

Taichiro Nishikawa

Makoto Sugimoto

Kuniharu Tanaka

Masaya Ito

Yoshihiro Yamamoto

Kazumasa Yoshida

Hiroaki Kuki

Kazuo Yamazaki

Katsura Matsubara

Toru Tanji

Hirohito Ito

Shoichiro Nagatomo

Tomo-O Tanaka

Yohihiro Nakai

A spark plug including a center electrode and a ground electrode having a core portion and an outer layer covering the core portion, the core portion being formed from a material having a thermal conductivity higher than that of the outer layer. At least a portion in which thickness of the outer layer is 0.5 mm or less is present at a cross-section perpendicular to a direction in which the ground electrode is extended. Further, the composition of the electrode material forming the outer layer is as follows: Ni is 96 mass % or more, total of at least one kind selected from Y and rare earth elements is 0.05 mass % or more, Al is 0.5 mass % or less, and Si is 0.5 mass % or more and 1.5 mass % or less, where the total of Ni, Y, rare earth elements, Al, Si does not exceed 100 mass %.

Spark plug

A spark plug including a center electrode and a ground electrode having a gap between the center electrode and the ground electrode, the ground electrode has an outer layer which is formed from an Ni-based alloy and a core portion which is covered by the outer layer and formed from a material having a thermal conductivity higher than that of the outer layer. Further, the melting point of the Ni-based alloy forming the outer layer is 1150&#xb0; C. or more and 1350&#xb0; C. or less.

A spark plug includes a tubular metallic shell; a tubular insulator in the tubular metallic shell located at a front end of the metallic shell and having an axial hole extending in the axial direction; and a center electrode inserted into the axial hole. The center electrode has a space-forming portion which forms, in cooperation with a wall surface of the axial hole, an annular space open frontward in the axial direction, and a main body portion extending rearward from the rear end of the space-forming portion. The thickness of the insulator is 0.6 mm or less as measured on a cross section and contains the front end of the metallic shell. The axial distance between the boundary portion and the front end of the metallic shell is 0.4 mm or greater, where the boundary portion is formed between the space-forming portion and the main body portion.

Spark plug with a center electrode having a space-forming portion

A spark plug comprising a center electrode, a first noble metal tip joined to the center electrode, an insulator, a metallic shell, a ground electrode joined to the metallic shell and including an outer layer and an inner layer, and a second noble metal tip joined to the ground electrode by way of a melted portion, wherein in a cross section of the ground electrode, the protrusion height A of the second noble metal tip is 0.4mm or more, the ground electrode includes a substantially flat joining surface to which the second noble metal tip is joined and an outwardly curved surface, the inner layer has at the joining surface side a substantially flat surface or recessed surface, and the minimum distance F between the melted portion and the inner layer is 0.1mm or more.

The object of the invention is to provide a spark plug including a central electrode and/or a ground electrode with a gap, which can suppress generation of corrosion-like generated foreign substances while maintaining high thermal conductivity and high strength. The gap between the central electrode and the ground electrode with at least one of the central electrode and the ground electrode formed from an electrode material including 96% by mass or more of Ni, in which the electrode material includes a total content of from 0.05% by mass to 0.45% by mass of at least one selected from a group consisting of Y and rare earth elements, 0.05% by mass or more of Mn, and a total content of 0.01% by mass or more of at least one selected from a group consisting of Ti, V, and Nb, and the ratio (a/b) of the total content (a) of Ti, V, and Nb to the content (b) of Mn is from 0.02 to 0.40.

Spark plug containing specific ratio content

A spark plug has a center electrode, a ceramic insulator having an axial hole to support the center electrode therein, a metal shell holding the ceramic insulator, and a ground electrode, one end portion of which is fixedly connected with the metal shell, the other end portion of which is located apart from an outer circumferential surface of a top end portion of the center electrode for defining a spark discharge gap therebetween. The ceramic insulator is provided with recesses at an edge portion between a top end surface of the ceramic insulator and an inner circumferential surface of the axial hole. When defining first and second imaginary circles with the axis being their respective centers as circles passing through portions of the recesses whose radial distances from the axis are a maximum and a minimum respectively, a difference of diameters of the first and second imaginary circles is 0.08 mm or less.

A spark plug () includes: a center electrode (); and a ground electrode () which is to be exposed in a combustion chamber of an internal combustion engine and which forms a spark discharge gap with the center electrode (), wherein at least one of the center electrode () and the ground electrode () contains an electrode material whose principal component is Ni and in which an intermetallic compound is precipitated at least intergranularly and intragranularly.

A spark plug having a center electrode; an insulator having an axial hole extending in the direction of an axis; a metallic shell; a ground electrode extending from a front end portion of the metallic shell; a center-electrode-side noble metal chip joined to a distal end surface of the center electrode; and a ground-electrode-side noble metal chip joined to a distal end surface of the ground electrode, the ground-electrode-side noble metal chip having a distal end surface facing toward a side surface portion of the center-electrode-side noble metal chip, and the ground electrode being bent at an angle that falls within a range of 120&#xb0; to 140&#xb0; inclusive.

Spark plug for internal combustion engine

A spark plug () including a noble metal tip () disposed on a distal end portion () of a ground electrode (). The noble metal tip () is joined to the top surface of an intermediate member (), which is a member separate from the ground electrode (). The bottom surface of the intermediate member () is joined to the ground electrode (), whereby the noble metal tip () is fixed to the ground electrode (). The intermediate member () is formed such that its average hardness is higher than the average hardness of a portion of the ground electrode (), excluding an intermediate portion () to be bent.

A spark plug including a center electrode and a ground electrode. A center electrode noble metal tip is joined to a leading end portion of a center electrode, and a ground electrode noble metal tip is joined to a center-electrode-side side surface of the ground electrode. A distal end portion of the ground electrode noble metal tip protrudes from a distal-end surface of the ground electrode by 0.1 mm to 1.5 mm. A center-electrode-side side surface of the ground electrode noble metal tip projects from a center-electrode-side side surface by 0.15 mm to 0.6 mm. The ground electrode includes chamfered portions. Thickness lengths and widthwise lengths of the respective chamfered portions achieved within a cross section perpendicular to a center axis of the ground electrode are set to 0.2 mm or more.

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

A plurality of insulator samples of different dimensions are subjected to multiple regression analysis to thereby induce an expression for estimating the amount of unevenness in wall thickness of an insulator; specifically, 0.01 (17.527+0.141A&#x2212;0.285B&#x2212;6.124C&#x2212;0.14D+1.105E), where A is an overall length of the insulator, B is the outside diameter of a rear trunk portion of the insulator, C is the diameter of a large diameter portion of the axial bore of the insulator, D is the length of the large diameter portion of the bore, and E is the diameter of a small diameter portion of the axial bore. The insulator is designed such that the amount of unevenness in wall thickness thereof estimated through calculation by this expression is less than 0.07 mm.

An object of the invention is to provide a spark plug having a discharge portion made of a precious metal tip, in which peeling of the precious metal tip from a surface of the discharge portion can be suppressed while spark abrasion, oxidation abrasion and abnormal abrasion of the discharge portion can be suppressed.

Spark plug having a precious metal tip

An object of the invention is to provide a higher-durability spark plug provided with a center electrode and a side electrode. At least one of the center electrode and the side electrode includes a precious metal member facing a spark discharge gap between the electrodes. A sweating phenomenon of the precious metal member can be suppressed while spark abrasion, oxidation abrasion and abnormal abrasion of the precious metal member are suppressed. The precious metal member contains Ir as a main component, and smaller amounts of Rh, Ru, and Ni.

Spark plug with electrode including precious metal

A spark plug comprising an insulator, on at least a part of a surface of the insulator being formed a marking layer and a glaze layer, wherein the marking layer is exposed on the surface of the insulator and has a composition as described herein.

Spark plug with marking layer composition

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.

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Nagoya, Japan

Kenji Nunome