Ngk Spark Plug Company, Limited

Ngk Spark Plug., Ltd.

Kenichi Nishikawa

Makoto Sugimoto

Yutaka Tanaka

Yoshihide Kouge

Toshitaka Honda

Masahiro Konishi

Hiroyuki Tanabe

A method for producing a spark plug, the spark plug comprising a center electrode, a metal shell and an alumina ceramic insulator disposed between the center electrode and the metal shell, wherein at least part of the surface of the insulator is covered with a glaze layer, the method comprising the steps of: preparing a plurality of kinds of element glaze powders wherein each kind of the element glaze powders has a different dilatometric softening point and a different linear expansion coefficient compared to other kinds of element glaze powders; coating a surface of the insulator with the plurality of kinds of element glaze powders so as to form a glaze powder layer; and baking the glaze powder layer to the surface of the insulator so as to form the glaze layer by heating the glaze powder layer.

Method for producing spark plug

A spark plug 100 has a glaze layer formed on a surface of an alumina based insulator contains 1 mol % or less of a Pb component in terms of PbO. The glaze layer comprises 35 to 55 mol % of a Si component in terms of SiO ; 15 to 35 mol % of a B component in terms of B O ; 5 to 20 mol % of a Zn component in terms of ZnO; 0.5 to 20 mol % of a Ba component in terms of BaO; and 10 to 15 mol % in total of at least one alkaline metal component of Na, K and Li, in terms of Na O, K O and Li O, respectively.

Spark plug

The present application is to provide a spark plug where a marking layer under a glaze layer can form a color stably, even if the Pb amount is decreased in the glaze layer. The glaze layer is formed on an insulator of the spark plug, and the marking layer is formed under the glaze layer . The glaze layer contains, e.g., 1 to 25 mol % of a Zn component in terms of Zno and 5 mol % or lower, e.g., 1 mol % or lower of a Pb component in terms of PbO. On the other hand, the marking layer is adjusted in kinds and amounts of metallic element components in such manners that a tint seen through the glaze layer is 3 or lower in brightness specified by JIS:Z8721 as well as 3 or lower in chroma specified by JIS:Z8721, or 4 or lower in the brightness specified by JIS:Z8721 as well as 2 or lower in the chroma specified by JIS:Z8721.

Spark plug with glaze and marking

A spark plug comprising: a center electrode; a metal shell; and an alumina ceramic insulator disposed between the center electrode and the metal shell, wherein at least part of the surface of the insulator is covered with a glaze layer comprising oxides, wherein the glaze layer comprises: 1 mol % or less of a Pb component in terms of PbO; 30 to 60 mol % of a Si component in terms of SiO ; 20 to 50 mol % of a B component in terms of B O ; 0.5 to 25 mol % of a Zn component in terms of ZnO; 0.5 to 15 mol % in total of at least one of Ba and Sr components in terms of BaO and SrO, respectively; 2 to 12 mol % in total of at least two alkaline metal components of Na, K and Li, in terms of Na O, K O, and Li O, respectively, wherein K and Li is essential; and 0.1 to 10 mol % of a F component in terms of F .

Glaze layer for a spark plug

A resistor-containing spark plug has an alumina insulator coated with a glaze layer the glaze layer has a lead component content of 1 mol % or lower in terms of PbO and containing a silicon component, a boron component, a zinc and/or alkaline earth metal component, and an alkali metal component. The insulator has, in an axially central position thereof, a projection part protruding from the outer circumferential surface thereof and extending in a circumferential direction. That main body of the insulator which is located adjacent to the projection part on the rear side thereof, which is the side opposite to the front side facing the center electrode in the axial direction, has a base portion having a cylindrical outer circumference. The outer circumference of the base portion is covered with the glaze layer which, when examined by the method as provided for in JIS B 0601, gives a surface roughness curve having a maximum height Ry of 10 &mgr;m or smaller.

A method for producing a spark plug, the spark plug comprising a center electrode, a metal shell and an alumina ceramic insulator disposed between the center electrode and the metal shell, wherein at least part of the surface of the insulator is covered with a glaze layer comprising oxides, the method comprising the steps of: preparing a coated glaze powder so that a surface of each particle of a glaze powder is covered by an elution-suppressing coating layer, the elution-suppressing coating layer suppressing an elution of water soluble component that is contained in each particle of the glaze powder; preparing a glaze slurry by suspending the glaze powder in a water solvent; applying the glaze slurry to a surface of the insulator so as to form a glaze powder-deposited layer; and baking the glaze powder-deposited layer to the surface of the insulator to form the glaze layer by heating the glaze powder-deposited layer.

A spark plug retains a resistor and has formed on alumina-based insulator a glaze layer, in which the glaze layer contains Pb component in a content of 1 mol % or less in terms of PbO, contains Si component, B component, Zn component, Al component, Ba component and/or Sr component, and contains F component in a content of 1 mol % or less. In addition, the glaze layer contains one kind or more of alkaline metal components, with Li component being necessary, and further contains one kind or more of phosphate ion, sulfate ion, fluoride ion and chloride ion in a content of 0.5 to 10 mol %. The glaze layer has a Vickers hardness Hv of 100 or more, shows excellent strength, especially impact resistance in spite of a reduced content of Pb component.

A glaze layer of the spark plug has the composition comprising 1 mol % or less of a Pb component in terms of PbO; 25 to 45 mol % of a Si component in terms of SiO ; 20 to 40 mol % of a B component in terms of B O ; 5 to 25 mol % of a Zn component in terms of ZnO; 0.5 to 15 mol % of Ba and/or Sr components in terms of BaO or SrO; 5 to 10 mol % in total of at least one alkaline metal component of of Na, K and Li in terms of Na O, K O, and Li , respectively, where K is essential; and further, 0.5 to 5 mol % in total of one or two kinds or more of Mo, W, Ni, Co, Fe and Mn in terms of MoO , WO , Ni O , Co O , Fe O , and MnO , respectively.

A spark plug having a glaze layer on the insulator thereof, wherein the glaze layer has a reduced Pb content, is capable of being fired at a relatively low temperature, exhibits excellent insulation properties, and can have a smooth surface.

Spark plug having a reduced lead glaze layer on the insulator thereof

The glaze layer of the spark plug includes oxides of: 15 to 60 mol % of a Si component in terms of SiO ; 22 to 50 mol % of a B component in terms of B O ; 10 to 30 mol % of a Zn component in terms of ZnO; 0.5 to 35 mol % of Ba and/or Sr components in terms of BaO or SrO; 1 mol % or less of an F component; 0.1 to 5 mol % of an Al component in terms of Al O ; and 5 to 10 mol % in total of at least one of alkaline metal components of Na, K and Li, in terms of Na O, K O, and Li , respectively, wherein Li is essential, and the amount of the Li component is 1.1 to 6 mol % in terms of Li O.

In a spark plug ( ), the resistor composition constituting a resistor ( ) contains semiconductive ceramic particles, offering a superior load life characteristic. Also, the value of (&agr; )/&agr; >&equals;&minus;0.30, where a value of electric resistance between a terminal ( ) and a center electrode ( ) is &agr; at 20&deg; C. and &agr; at 150&deg; C., so that deterioration of the radio frequency noise prevention performance at high temperatures can be effectively suppressed. The resistor composition contains semiconductive ceramic particles whose temperature coefficient of electric resistance shows a positive value, or a negative value of relatively small absolute value, (e.g., TiO particles having a rutile type crystalline structure, titanate or zirconate of alkali earth metal elements, titanium suboxide, etc.), or titanium metal. Thus, the invention provides a resistor-incorporated spark plug which is enabled to offer a stable load life characteristic even when a high load acts thereon, and which is unlikely to deteriorate in the radio frequency noise prevention performance even under high temperatures.

Manufacturing method of resistor-incorporated spark plug

A resistor spark plug includes an insulator having an axially extending through-hole. A center electrode is disposed within the through-hole of the insulator such that the center electrode projects from a tip end of the insulator. A terminal metal piece is disposed within the through-hole of the insulator such that the terminal metal piece projects from a tail end of the insulator. A conductive coupling layer is disposed within the through-hole and located between the center electrode and the terminal metal piece. The conductive coupling layer comprises a conductive glass seal layer formed on at least an end facing the terminal metal piece. A surface layer region of the terminal metal piece that comes into contact with the conductive glass seal layer is formed mainly of one or more metals selected from the group consisting of Zn, Sn, Pb, Rh, Pd, Pt, Cu, Au, Sb, and Ag.

Spark plug having a metal layer in a terminal metal piece

In a spark plug (100), the resistor composition constituting a resistor (15) contains semiconductive ceramic particles, offering a superior load life characteristic. Also, the value of (.alpha.2-.alpha.1)/.alpha.1 &gt;=-0.30, where a value of electric resistance between a terminal (13) and a center electrode (3) is .alpha.1 at 20.degree. C. and .alpha.2 at 150.degree. C., so that deterioration of the radio frequency noise prevention performance at high temperatures can be effectively suppressed. The resistor composition contains semiconductive ceramic particles whose temperature coefficient of electric resistance shows a positive value, or a negative value of relatively small absolute value, (e.g., TiO.sub.2 particles having a rutile type crystalline structure, titanate or zirconate of alkali earth metal elements, titanium suboxide, etc.), or titanium metal. Thus, the invention provides a resistor-incorporated spark plug which is enabled to offer a stable load life characteristic even when a high load acts thereon, and which is unlikely to deteriorate in the radio frequency noise prevention performance even under high temperatures.

Resistor-incorporated spark plug and manufacturing method of

A spark plug for an internal combustion engine. The spark plug includes an insulator coated with glaze in an area extending from a head portion to a trunk portion of the insulator. Preferably, the glaze is prepared from B.sub.2 O.sub.3 --SiO.sub.2 glass containing two or more oxides selected from the group consisting of Al.sub.2 O.sub.3, Na.sub.2 O, CaO, ZnO, BaO, Li.sub.2 O and Bi.sub.2 O.sub.3. The glaze is prepared by dry-mixing a plurality of powder materials, melting the resultant mixture in water for vitrification, wet-powdering the resultant vitrification, and adding an organic binder to the resultant powder. The glaze is applied to the insulater and fired at a glost temperature of not more than 1150.degree. C. The Pb content of the glaze is not more than 10 wt. % in terms of PbO. Accordingly, even when a strong electric field is induced at the trunk portion of the insulator, the conversion of Pb to conductive substances is very little or zero. As a result, the flashover voltage between the terminal electrode and the metallic shell of the spark plug is less likely to decrease, thus preventing a spark failure of the spark plug.

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Bisai, Japan

Kenichi Nishikawa