JP2004363112A5

JP2004363112A5 -

Info

Publication number: JP2004363112A5
Application number: JP2004210017A
Authority: JP
Filing date: 2004-07-16
Publication date: 2007-09-06
Anticipated expiration: 2020-07-31

Description

本発明に係るスパークプラグの構成は、中心電極と主体金具との間にアルミナ系セラミックからなる絶縁体を配したスパークプラグにおいて、その絶縁体の表面の少なくとも一部を覆う形態で酸化物主体の釉薬層が形成され、該釉薬層が、
Ｐｂ成分の含有量がＰｂＯ換算にて１ｍｏｌ％以下とされ、
Ｓｉ成分をＳｉＯ_２に酸化物換算した値にて２５〜６０ｍｏｌ％、Ｂ成分をＢ_２Ｏ_３に酸化物換算した値にて１０〜４０ｍｏｌ％、Ｚｎ成分をＺｎＯに酸化物換算した値にて０．５〜９．５ｍｏｌ％、Ｂａ成分をＢａＯに酸化物換算した値にて５〜２５ｍｏｌ％含有するとともに、それらＳｉ成分、Ｂ成分、Ｚｎ成分及びＢａ成分の酸化物換算含有量の合計が６０〜９８ｍｏｌ％であり、
Ｚｎ成分とＢａ成分との酸化物換算含有量における合計が９〜３０ｍｏｌ％であり、
また、アルカリ金属成分として、ＮａはＮａ_２Ｏ、ＫはＫ_２Ｏ、ＬｉはＬｉ_２Ｏに酸化物換算した値にて、それらの１種又は２種以上を合計で２〜１５ｍｏｌ％の範囲にて含有し、
前記釉薬層は、アルカリ土類金属成分Ｒ（ただし、ＲはＣａ、Ｓｒ、Ｂａから選ばれる１種又は２種以上）の組成式ＲОに酸化物換算した含有率をＮRO（ｍｏｌ％）として、ＮRO＞１０ｍｏｌ％を満足し、かつ、ＺｎＯ換算したＺｎ成分の含有量をＮZnO（ｍｏｌ％）として、
０．１≦ＮZnO／（ＮRO＋ＮZnO）≦０．４
を満足することを特徴とする。 The configuration of the spark plug according to the present invention is a spark plug in which an insulator made of alumina-based ceramic is arranged between a center electrode and a metal shell, in which at least a part of the surface of the insulator is covered mainly with an oxide. A glaze layer is formed, and the glaze layer is
The content of the Pb component is 1 mol% or less in terms of PbO,
25 to 60 mol% of the Si component converted to oxides of SiO ₂ , 10 to 40 mol% of the B component converted to oxides of B ₂ O ₃ , and the Zn component of the oxide converted to ZnO. 0.5 to 9.5 mol%, the Ba component is contained in an amount of 5 to 25 mol% in terms of oxide as BaO, and the total of the oxide equivalent contents of the Si component, the B component, the Zn component and the Ba component is 60-98 mol%,
The sum of the Zn component and the Ba component in terms of oxide content is 9 to 30 mol%,
In addition, as alkali metal components, Na is Na ₂ O, K is K ₂ O, and Li is a value converted to Li ₂ O as an oxide, and one or more of them are in a range of 2 to 15 mol% in total. Contained in
The glaze layer has a composition ratio of alkaline earth metal component R (where R is one or two or more selected from Ca, Sr, and Ba) converted into oxides as NRO (mol%). NRO> 10 mol% is satisfied, and the content of Zn component in terms of ZnO is defined as NZnO (mol%).
0.1 ≦ NZnO / (NRO + NZnO) ≦ 0.4
Is satisfied .

上記本発明は、前述の環境問題への適合性を図るため、使用する釉薬層が、Ｐｂ成分の含有量がＰｂＯ換算にて１．０ｍｏｌ％以下とすることを前提とする（以下、このレベルにＰｂ成分含有量が低減された釉薬層を無鉛釉薬層と称する）。また、釉薬層中にＰｂ成分が価数の低いイオン（例えばＰｂ^２＋）の形で含有されていると、コロナ放電等によりこれが価数の高いイオン（例えばＰｂ^３＋）に酸化され、釉薬層の絶縁性が低下して耐フラッシュオーバ性が損なわれる場合もあるので、Ｐｂ含有量を上記のように削減することはこの観点においても好都合である。なお、Ｐｂの含有量は望ましくは０．１ｍｏｌ％以下、より望ましくは実質的に含有しない（ただし、釉薬原料等から不可避的に混入するものを除く）のがよい。 The present invention is based on the premise that the glaze layer used has a Pb component content of 1.0 mol% or less in terms of PbO in order to achieve compatibility with the above-mentioned environmental problems (hereinafter, this level is referred to as this level). The glaze layer having a reduced Pb content is referred to as a lead-free glaze layer.) Further, when the Pb component is contained in the form of low-valent ions (for example, Pb ²⁺ ) in the glaze layer, it is oxidized to high-valent ions (for example, Pb ³⁺ ) by corona discharge or the like, and the glaze layer is formed. Since the insulation property may be reduced and the flashover resistance may be impaired, reducing the Pb content as described above is also advantageous from this viewpoint. The content of Pb is desirably 0.1 mol% or less, and more desirably, it is substantially not contained (however, excluding those that are inevitably mixed from glaze raw materials and the like).

そして、本発明では、Ｐｂ含有量を上記のように低減しつつ、絶縁性能確保、釉焼温度の最適化及び釉焼面の仕上がり状態を良好に確保するために、上記特有の組成が選択されている。従来の釉薬においては、Ｐｂ成分が釉薬の軟化点調整（具体的には釉薬の軟化点を適度に下げ、釉焼時の流動性を確保する）に関して重要な役割を果たしていたが、無鉛釉薬では、Ｂ成分（Ｂ_２Ｏ_３）やアルカリ金属成分が軟化点調整に深く関係する。本発明者らの検討によれば、Ｂ成分には、釉焼面の仕上がり改善を図る上で好都合な特有の含有量範囲が存在すること（具体的にはＢ_２Ｏ_３換算にて１０〜４０ｍｏｌ％）がわかった。特に、ガス炉など釉焼時の雰囲気に比較的多くの水蒸気が含有される場合においては、Ｂ成分の含有量を上記範囲に設定することが特に有効となる。 In the present invention, the above-mentioned specific composition is selected in order to secure the insulation performance, optimize the glaze baking temperature, and properly secure the finished state of the glaze baking surface while reducing the Pb content as described above. ing. In conventional glazes, the Pb component played an important role in adjusting the softening point of the glaze (specifically, lowering the softening point of the glaze moderately and securing the fluidity during baking the glaze). , B component (B ₂ O ₃ ) and alkali metal component are deeply related to the adjustment of the softening point. According to the study of the present inventors, the B component has a specific content range which is convenient for improving the finish of the glazed surface (specifically, 10 to 10 in terms of B ₂ O ₃₎ . 40 mol%). In particular, when the atmosphere at the time of baking the glaze contains a relatively large amount of water vapor, such as in a gas furnace, setting the content of the B component within the above range is particularly effective.

以下、本発明における釉薬層構成成分の各含有量範囲の臨界的意味について詳しく説明する。Ｓｉ成分含有量が２５ｍｏｌ％未満になると、釉薬層の熱膨張係数が大きくなりすぎて貫入（クレージング）等の欠陥が生じやすくなり、第一発明の課題である釉焼面の仕上がり確保が不十分となる。他方、該Ｓｉ成分含有量が６０ｍｏｌ％を超えると、釉薬の軟化点が上昇しすぎ、釉溶け不足等により外観不良を生ずる場合がある。なお、該Ｓｉ成分含有量は、望ましくは３５〜５５ｍｏｌ％の範囲で設定するのがよい。 Hereinafter, the critical meaning of each content range of the constituent components of the glaze layer in the present invention will be described in detail. When the content of the Si component is less than 25 mol%, the thermal expansion coefficient of the glaze layer becomes too large, and defects such as penetration (crazing) are likely to occur. It becomes. On the other hand, when the content of the Si component exceeds 60 mol%, the softening point of the glaze is too high, and poor appearance may occur due to insufficient melting of the glaze. The content of the Si component is desirably set in the range of 35 to 55 mol%.

上記本発明における釉薬層には、上記説明した成分以外にも、Ａｌ_２Ｏ_３に酸化物換算した値にて０．５〜１０ｍｏｌ％のＡｌ成分、ＣａОに酸化物換算した値にて０．５〜１０ｍｏｌ％のＣａ成分、及びＳｒＯに酸化物換算した値にて０．５〜３０ｍｏｌ％のＳｒ成分の１種又は２種以上を合計で０．５〜３０ｍｏｌ％含有させることができる。Ａｌ成分は釉薬層の失透を抑制する効果を有し、Ｃａ成分とＳｒ成分とは釉薬層の絶縁性向上に寄与する。添加量が上記の各下限値未満では効果に乏しく、また、個々の成分の上限値又は合計含有量の上限値を超えた場合には、釉薬軟化点の過度の上昇により釉焼が困難あるいは不能となる場合がある。 In the glaze layer according to the present invention , in addition to the components described above, an Al component of 0.5 to 10 mol% in terms of oxide as Al ₂ O ₃ , and a 0.1% in terms of oxide as CaО. One or more of 0.5 to 30 mol% of Sr component in terms of oxides to SrO can be contained in a total of 0.5 to 30 mol% in 5 to 10 mol% of Ca component and SrO. The Al component has an effect of suppressing devitrification of the glaze layer, and the Ca component and the Sr component contribute to improving the insulating properties of the glaze layer. If the added amount is less than the above lower limits, the effect is poor, and if it exceeds the upper limit of each component or the upper limit of the total content, it is difficult or impossible to bake the glaze due to excessive rise of the softening point of the glaze. It may be.

以下、本発明にさらに付加可能な要件について説明する。
まず、釉薬層には、Ｍｏ、Ｆｅ、Ｗ、Ｎｉ、Ｃｏ及びＭｎの１種又は２種以上の成分を、ＭｏはＭｏＯ_３、ＦｅはＦｅ_２Ｏ_３、ＷはＷＯ_３、ＮｉはＮｉ_３О_４、ＣｏはＣｏ_３О_４、ＭｎはＭｎО_２にそれぞれ酸化物換算した値にて合計で０．５〜５ｍｏｌ％の範囲にて含有させることができる。これにより、釉焼時の流動性が著しく高められ、ひいては比較的低温で釉焼可能であって絶縁性に優れ、かつ平滑な釉焼面を有する釉薬層を一層容易に得ることができる。 Hereinafter, requirements that can be further added to the present invention will be described.
First, the glaze layer contains one or more components of Mo, Fe, W, Ni, Co and Mn, Mo is MoO ₃ , Fe is Fe ₂ O ₃ , W is WO ₃ , and Ni is Ni ₃ _{４ 4} and Co can be contained in the range of 0.5 to 5 mol% in total as Co ₃ _{４ 4} and Mn as Mn 酸化物₂ in terms of oxide. Thereby, the fluidity at the time of baking the glaze is remarkably enhanced, and as a result, a glaze layer which can be baked at a relatively low temperature, has excellent insulation properties, and has a smooth baked glaze surface can be more easily obtained.

Claims

In a spark plug in which an insulator made of alumina-based ceramic is arranged between a center electrode and a metal shell, an oxide-based glaze layer is formed so as to cover at least a part of the surface of the insulator, and the glaze layer is formed. ,
The content of the Pb component is 1 mol% or less in terms of PbO,
25 to 60 mol% of the Si component converted to oxides of SiO ₂ , 10 to 40 mol% of the B component converted to oxides of B ₂ O ₃ , and the Zn component of the oxide converted to ZnO. 0.5 to 9.5 mol%, the Ba component is contained in an amount of 5 to 25 mol% in terms of oxide as BaO, and the total of the oxide equivalent contents of the Si component, the B component, the Zn component and the Ba component is 60-98 mol%,
The sum of the Zn component and the Ba component in terms of oxide content is 9 to 30 mol%,
In addition, as alkali metal components, Na is Na ₂ O, K is K ₂ O, and Li is a value converted to Li ₂ O as an oxide, and one or more of them are in a range of 2 to 15 mol% in total. Contained in
The glaze layer has a composition ratio of alkaline earth metal component R (where R is one or more selected from Ca, Sr, and Ba) converted into oxides as NRO (mol%). NRO> 10 mol% is satisfied, and the content of Zn component in terms of ZnO is NZnO (mol%),
0.1 ≦ NZnO / (NRO + NZnO) ≦ 0.4
Spark plug characterized by satisfying the following .

A circumferential projection is formed on the outer peripheral surface of the insulator at an intermediate position in the axial direction,
A base end outer peripheral surface of an insulator main body adjacent to a rear side with respect to the protruding portion is formed in a cylindrical shape, with a side facing the tip of the center electrode in the axial direction as a front side,
2. The spark plug according to claim 1, wherein the glaze layer is formed in a thickness of 7 to 50 [mu] m so as to cover the outer peripheral surface of the base end portion .

The glaze layer is oxidized to 0.5 to 10 mol% of an Al component in terms of oxide converted to Al ₂ O ₃ , 0.5 to 10 mol% of a Ca component in terms of oxide converted to CaО, and SrO. The spark plug according to claim 1, wherein the spark plug contains 0.5 to 30 mol% of one or more Sr components of 0.5 to 30 mol% in terms of a substance in total .

The glaze layer, Mo, Fe, W, Ni , one or more components of Co and Mn, Mo is _MoO 3, Fe is _Fe 2 _O 3, W is _WO 3, Ni is Ni ₃ o ₄ , Co is Co ₃ o _4, Mn spark plug according to any one of claims 1 to 3 containing at 0.5～5Mol% range in total at value converted respectively oxide MnО _2.

The glaze layer contains one or more components of Zr, Ti, Mg, Bi, Sn, Sb and P, Zr is ZrO ₂ , Ti is TiO ₂ , Mg is MgO, and Bi is Bi ₂ _{2. The} total content of O ₃ , Sn in SnO ₂ , Sb in Sb ₂ O ₅ , and P in P ₂ O ₅ in the range of 0.5 to ₅ mol% in terms of oxide. 5. The spark plug according to any one of claims 1 to 4 .

The spark plug, in the through hole of the insulator, integrally with the center electrode, or comprises a shaft-shaped terminal fitting portion provided separately from the center electrode with a conductive coupling layer interposed therebetween,
The insulation resistance measured by maintaining the entire spark plug at about 500 ° C. and conducting electricity between the terminal fitting and the metallic shell through the insulator is 200 MΩ or more. 5. The spark plug according to any one of 5 .

The insulator is constituted by alumina insulating material containing 85～98Mol% by weight was in terms of oxide of Al component to the _Al 2 _{O 3,}
The glaze layer according to any one of claims 1 to 6, wherein an average coefficient of thermal expansion of the glaze layer in a temperature range of 20 to 350 ° C is 50 × 10 ⁻⁷ / ° C to 85 × 10 ⁻⁷ / ° C. The described spark plug.

The spark plug according to any one of claims 1 to 7, wherein the glaze layer has a softening temperature of 600 to 700C .