JP2011086612A

JP2011086612A - Spark plug

Info

Publication number: JP2011086612A
Application number: JP2010193411A
Authority: JP
Inventors: Takuya Inoue; 拓也井上
Original assignee: NGK Spark Plug Co Ltd
Current assignee: Niterra Co Ltd
Priority date: 2009-09-17
Filing date: 2010-08-31
Publication date: 2011-04-28

Abstract

<P>PROBLEM TO BE SOLVED: To improve ignitability, productivity, and durability of a ground electrode. <P>SOLUTION: An ignition part 36 of a spark plug 100 is formed, on an opposing face 32 of the ground electrode 30, opposed to the tip of the center electrode 20, so as to protrude in numerous stages by press molding. Out of respective stages formed in numerous stages, from the root stage 36a closest to the root side, toward the tip stage 36b closest to the center electrode side, the ignition part 36 is formed so that the average cross-sectional area of a cross-section perpendicular to a protruding direction of the respective stages becomes smaller. The ignition part 36 is a columnar protrusion having a round cross-section. By press molding when forming the ignition part 36, a dent part 37 is formed to be in a recessed shape toward the inside of a ground electrode base material 35 from the rear face 33. By doing this, the ignitability, the productivity, and the durability of the spark plug 100 can be improved. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

本発明は、内燃機関において電気的に火花を発生させることによって燃料に着火させるスパークプラグ（点火プラグ）に関し、特に、スパークプラグの接地電極に関する。 The present invention relates to a spark plug (ignition plug) for igniting fuel by electrically generating a spark in an internal combustion engine, and more particularly to a ground electrode of the spark plug.

スパークプラグには、良好な着火性が望まれており、例えば、接地電極の中心電極に対向する部位に突き出し部分を備えることによって、火炎の広がりを良好にし、着火性を向上させる技術が提案されている。このようなスパークプラグでは、押圧治具を用いて、接地電極の、中心電極に対向する面において、中心電極側に向けて、接地電極の一部を押圧して突き出し部分を形成することにより、着火性を向上させる技術が開示されている。 Spark plugs are desired to have good ignitability. For example, a technique has been proposed that improves the spread of flame and improves the ignitability by providing a protruding portion at a portion of the ground electrode that faces the center electrode. ing. In such a spark plug, by using a pressing jig, on the surface of the ground electrode facing the center electrode, by pressing a part of the ground electrode toward the center electrode side, a protruding portion is formed, A technique for improving ignitability is disclosed.

特開２００９−５４５７９号公報JP 2009-54579 A

一般的に、突き出し部分の先端部分の径が大きい場合には着火性が低下するため、突き出し部分の先端部分の径を小さく形成することが望まれている。しかしながら、従来の技術では、突き出し部分の径が根元部分と先端部分とにおいて同一となるように、突き出し部分が形成されている。このため、チップの径を小さく形成すると、製造時に突き出し部分に歪みやひびわれが発生する虞がある。 Generally, since the ignitability decreases when the diameter of the tip portion of the protruding portion is large, it is desired to make the diameter of the tip portion of the protruding portion small. However, in the conventional technique, the protruding portion is formed so that the diameter of the protruding portion is the same in the root portion and the tip portion. For this reason, when the diameter of the chip is formed small, there is a risk that distortion or cracking may occur in the protruding portion during manufacturing.

本発明は上述の課題に鑑みてなされたものであり、接地電極の着火性、生産性の向上および耐久性の向上を目的とする。 The present invention has been made in view of the above problems, and aims to improve the ignitability, productivity, and durability of the ground electrode.

本発明は、上述の課題の少なくとも一部を解決するためになされたものであり、以下の形態又は適用例として実現することが可能である。 SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

［適用例１］
軸線方向に延びる中心電極と、前記中心電極の先端を露出させつつ前記中心電極の外周に形成された絶縁体と、前記絶縁体の外周に形成された主体金具と、前記主体金具に接合された基端部と、前記中心電極の端面と対向するように配置された先端部と、を有する接地電極と、を備えたスパークプラグであって、前記先端部は、前記中心電極側に多段状に突出するように形成された発火部を備え、前記発火部は、前記多段状に形成された各段のうち、最も根元側の段である根元段から、最も前記中心電極側の段である先端段に向けて、前記各段の前記突出方向に直交する断面の平均断面積が小さくなるように形成されている、スパークプラグ。 [Application Example 1]
A center electrode extending in the axial direction, an insulator formed on the outer periphery of the center electrode while exposing a tip of the center electrode, a metal shell formed on the outer periphery of the insulator, and the metal shell joined A spark plug having a base electrode and a ground electrode having a tip arranged to face the end face of the center electrode, wherein the tip is multi-staged on the center electrode side A firing portion formed so as to protrude, and the firing portion is a tip that is the step closest to the center electrode from a root step that is the step closest to the root among the steps formed in a multi-stage shape. A spark plug formed so that an average cross-sectional area of a cross section perpendicular to the protruding direction of each stage is reduced toward the stage.

適用例１のスパークプラグによれば、中心電極側に突出するように多段状に形成された発火部が、最も根元側の段である根元段から先端段に向けて、各段の突出方向に直交する断面の平均断面積が小さくなるように形成されている。従って、根元段の断面積を先端段の断面積に比して大きく形成できるので、製造時に、発火部にひずみやひび割れが発生することを抑制できる。よって、接地電極の生産性を向上できる。また、先端段の径を小さく形成できるので着火性を向上できる。 According to the spark plug of Application Example 1, the firing portion formed in a multi-stage shape so as to protrude toward the center electrode side is directed in the protruding direction of each stage from the root stage, which is the most proximal stage, toward the tip stage. It is formed so that the average cross-sectional area of the cross sections orthogonal to each other becomes small. Therefore, since the cross-sectional area of the root step can be formed larger than the cross-sectional area of the tip step, it is possible to suppress the occurrence of strain and cracks in the ignition portion during manufacturing. Therefore, the productivity of the ground electrode can be improved. Moreover, since the diameter of the tip step can be reduced, the ignitability can be improved.

なお、前記発火部は、たとえば、前記根元段の径をＡとし、前記先端段の径をＢとし、前記軸線方向と直交し、且つ前記接地電極の延長方向と直交する方向における前記接地電極の幅をＸとしたとき、０．３≦Ａ／Ｘ≦０．９、かつ、０．２≦Ｂ／Ａ≦０．９の関係が成立するように形成され、前記多段状に形成された各段のうち、最も根元側の段である根元段の突出量をＣ、最も前記中心電極側の段である先端段の突出量をＤとしたとき、０＜Ｃ≦１．０ｍｍ、かつ、０＜Ｄ≦１．０ｍｍの関係が成立するように形成されていても良い。この構成を備えるスパークプラグによれば、０．３≦Ａ／Ｘ≦０．９、かつ、０．２≦Ｂ／Ａ≦０．９の関係が成立するように形成することにより、着火性および生産性を向上できる。また、発火部を、０＜Ｃ≦１．０ｍｍ、かつ、０＜Ｄ≦１．０ｍｍとなるように形成することにより、製造時において、発火部にひび割れが発生することを抑制できる。従って、生産性の向上を図ることができる。 In addition, the ignition portion may be configured such that, for example, the diameter of the root step is A, the diameter of the tip step is B, the ground electrode in the direction perpendicular to the axial direction and perpendicular to the extension direction of the ground electrode. When the width is X, it is formed so that the relationship of 0.3 ≦ A / X ≦ 0.9 and 0.2 ≦ B / A ≦ 0.9 is established. Of the steps, when C is the protrusion amount of the root step that is the most proximal step, and D is the protrusion amount of the tip step that is the center electrode-side step, 0 <C ≦ 1.0 mm, and 0 <D ≦ 1.0 mm may be formed to satisfy the relationship. According to the spark plug having this configuration, by forming so that the relationship of 0.3 ≦ A / X ≦ 0.9 and 0.2 ≦ B / A ≦ 0.9 is established, Productivity can be improved. Further, by forming the ignition part so that 0 <C ≦ 1.0 mm and 0 <D ≦ 1.0 mm, it is possible to suppress the occurrence of cracks in the ignition part during manufacturing. Therefore, productivity can be improved.

［適用例２］
適用例１のスパークプラグであって、前記発火部は、前記根元段の径をＡとしたとき、Ａ≦２．０ｍｍである。適用例２のスパークプラグによれば、発火部を、Ａ≦２．０ｍｍとなるように形成することにより、着火性を向上できる。 [Application Example 2]
In the spark plug of Application Example 1, the ignition portion has A ≦ 2.0 mm, where A is the diameter of the root stage. According to the spark plug of Application Example 2, the ignitability can be improved by forming the ignition portion so that A ≦ 2.0 mm.

［適用例３］
適用例１または２のスパークプラグであって、前記発火部は、０．３ｍｍ≦Ｃ≦１．０ｍｍ、かつ、０．３ｍｍ≦Ｄ≦１．０ｍｍである。適用例３のスパークプラグによれば、発火部を、０．３ｍｍ≦Ｃ≦１．０ｍｍ、かつ、０．３ｍｍ≦Ｄ≦１．０ｍｍとなるように形成することにより、着火性を更に向上できる。 [Application Example 3]
In the spark plug according to application example 1 or 2, the ignition portion satisfies 0.3 mm ≦ C ≦ 1.0 mm and 0.3 mm ≦ D ≦ 1.0 mm. According to the spark plug of Application Example 3, the ignitability can be further improved by forming the ignition portion so that 0.3 mm ≦ C ≦ 1.0 mm and 0.3 mm ≦ D ≦ 1.0 mm. .

［適用例４］
適用例１ないし適用例３いずれかのスパークプラグであって、前記発火部は、前記多段状に形成された各段のうち、最も根元側の段である根元段の径が、１．４ｍｍ以上である。適用例４のスパークプラグによれば、発火部の最根元段の径が、１．４ｍｍ以上となるように形成することにより、耐久性を更に向上できる。 [Application Example 4]
The spark plug according to any one of Application Example 1 to Application Example 3, wherein the ignition portion has a diameter of a root step, which is the step on the most base side, of each of the steps formed in the multi-stage shape is 1.4 mm or more. It is. According to the spark plug of Application Example 4, durability can be further improved by forming the most base stage diameter of the ignition portion to be 1.4 mm or more.

［適用例５］
適用例１ないし適用例４いずれかのスパークプラグであって、前記接地電極は、ニッケルを主成分として形成されている。適用例５のスパークプラグによれば、安価なニッケルを主成分とする材料により接地電極を形成できる。従って、コストを削減できる。 [Application Example 5]
The spark plug according to any one of Application Examples 1 to 4, wherein the ground electrode is formed mainly of nickel. According to the spark plug of Application Example 5, the ground electrode can be formed from an inexpensive nickel-based material. Therefore, the cost can be reduced.

［適用例６］
軸線方向に延びる中心電極と、前記中心電極の先端を露出させつつ前記中心電極の外周に形成された絶縁体と、前記絶縁体の外周に形成された主体金具と、前記主体金具に接合された基端部と、前記中心電極の端面と対向するように配置された先端部と、を有する接地電極と、備えるスパークプラグの製造方法であって、プレス成形により、前記先端部に、前記中心電極側に多段状に突出するとともに、前記多段状に形成された各段のうち、最も根元側の段である根元段から、最も前記中心電極側の段である先端段に向けて、前記各段の前記突出方向に直交する断面の平均断面積が小さくなる発火部を形成する。適用例６のスパークプラグの製造方法によれば、プレス成形により、接地電極の先端部に、中心電極側に多段状に突出するとともに、前記多段状に形成された各段のうち、最も根元側の段である根元段から、最も前記中心電極側の段である先端段に向けて、前記各段の前記突出方向に直交する断面の平均断面積が小さくなる発火部が形成される。従って、根元段の断面積を先端段の断面積に比して大きく形成できるので、発火部にひずみやひび割れが発生することを抑制できる。よって、接地電極の耐久性を向上できる。また、先端段の径を小さく形成できるので着火性を向上できる。 [Application Example 6]
A center electrode extending in the axial direction, an insulator formed on the outer periphery of the center electrode while exposing a tip of the center electrode, a metal shell formed on the outer periphery of the insulator, and the metal shell joined A spark plug manufacturing method comprising: a ground electrode having a proximal end portion and a distal end portion disposed so as to face an end face of the center electrode, wherein the center electrode is formed on the distal end portion by press molding. Of each of the stages formed in a multi-stage shape, from the root stage that is the most proximal stage to the tip stage that is the most central-stage stage. An ignition portion is formed in which the average cross-sectional area of the cross section perpendicular to the projecting direction is small. According to the method for manufacturing a spark plug of Application Example 6 , by press molding, the tip of the ground electrode protrudes in a multi-stage shape toward the center electrode side, and among the stages formed in the multi-stage shape, the most base side From the base stage, which is the stage, to the tip stage, which is the stage closest to the center electrode, an ignition portion is formed in which the average cross-sectional area of the cross section perpendicular to the projecting direction of each stage is reduced. Therefore, since the cross-sectional area of the root step can be formed larger than the cross-sectional area of the tip step, it is possible to suppress the occurrence of strain and cracks in the ignition portion. Therefore, the durability of the ground electrode can be improved. Moreover, since the diameter of the tip step can be reduced, the ignitability can be improved.

本発明において、上述した種々の態様は、適宜、組み合わせたり、一部を省略したりして適用することができる。 In the present invention, the various aspects described above can be applied by appropriately combining or omitting some of them.

スパークプラグ１００の部分断面を主に示す説明図である。4 is an explanatory view mainly showing a partial cross section of a spark plug 100. FIG. 第１実施例における接地電極３０の詳細構造を主に示す説明図である。It is explanatory drawing which mainly shows the detailed structure of the ground electrode 30 in 1st Example. 第１実施例における発火部３６の形状について詳細に説明する平面図である。It is a top view explaining in detail the shape of the ignition part 36 in 1st Example. 第１実施例における接地電極３０の製造工程を示すフローチャートである。It is a flowchart which shows the manufacturing process of the ground electrode 30 in 1st Example. 固定治具を説明する斜視図である。It is a perspective view explaining a fixing jig. 発火部３６の成型について説明するための断面図である。FIG. 6 is a cross-sectional view for explaining molding of the ignition part 36. 変形例における発火部３６の形状について詳細に説明する平面図である。It is a top view explaining in detail about the shape of ignition part 36 in a modification.

Ａ．実施例：
Ａ１．スパークプラグの構成：
図１は、スパークプラグ１００の部分断面を主に示す説明図である。スパークプラグ１００は、絶縁碍子１０と、中心電極２０と、接地電極３０と、端子金具４０と、主体金具５０とを備える。絶縁碍子１０の一端から突出する棒状の中心電極２０は、絶縁碍子１０の内部を通じて、絶縁碍子１０の他端に設けられた端子金具４０に電気的に接続されている。中心電極２０の外周は、絶縁碍子１０によって絶縁され、絶縁碍子１０の外周は、端子金具４０から離れた位置で主体金具５０によって保持されている。主体金具５０に電気的に接続された接地電極３０は、火花を発生させる隙間である火花ギャップを中心電極２０の先端との間に形成する。スパークプラグ１００は、内燃機関（図示しない）のエンジンヘッド２００に設けられた取付ネジ孔２０１に主体金具５０を介して取り付けられ、２万〜３万ボルトの高電圧が端子金具４０に印加されると、中心電極２０と接地電極３０との間に形成された火花ギャップに火花が発生する。 A. Example:
A1. Spark plug configuration:
FIG. 1 is an explanatory view mainly showing a partial cross section of the spark plug 100. The spark plug 100 includes an insulator 10, a center electrode 20, a ground electrode 30, a terminal fitting 40, and a metal shell 50. The rod-shaped center electrode 20 protruding from one end of the insulator 10 is electrically connected to a terminal fitting 40 provided at the other end of the insulator 10 through the inside of the insulator 10. The outer circumference of the center electrode 20 is insulated by the insulator 10, and the outer circumference of the insulator 10 is held by the metal shell 50 at a position away from the terminal fitting 40. The ground electrode 30 electrically connected to the metal shell 50 forms a spark gap, which is a gap for generating a spark, between the tip of the center electrode 20. The spark plug 100 is attached to an attachment screw hole 201 provided in an engine head 200 of an internal combustion engine (not shown) via a metal shell 50, and a high voltage of 20,000 to 30,000 volts is applied to the terminal fitting 40. Then, a spark is generated in a spark gap formed between the center electrode 20 and the ground electrode 30.

スパークプラグ１００の絶縁碍子１０は、アルミナを始めとするセラミックス材料を焼成して形成された絶縁体である。絶縁碍子１０は、中心電極２０および端子金具４０を収容する軸孔１２が中心に形成された筒状体である。絶縁碍子１０の軸方向中央には外径を大きくした鍔部１９が形成されている。鍔部１９よりも端子金具４０側には、端子金具４０と主体金具５０との間を絶縁する後端側胴部１８が形成されている。鍔部１９よりも中心電極２０側には、後端側胴部１８よりも外径が小さい先端側胴部１７が形成され、先端側胴部１７の更に先には、先端側胴部１７よりも小さい外径であって中心電極２０側へ向かうほど外径が小さくなる脚長部１３が形成されている。 The insulator 10 of the spark plug 100 is an insulator formed by firing a ceramic material such as alumina. The insulator 10 is a cylindrical body in which the shaft hole 12 that accommodates the center electrode 20 and the terminal fitting 40 is formed at the center. At the center of the insulator 10 in the axial direction, a flange portion 19 having an increased outer diameter is formed. A rear end side body portion 18 that insulates between the terminal metal fitting 40 and the metal shell 50 is formed on the terminal metal fitting 40 side of the flange portion 19. A front end side body portion 17 having an outer diameter smaller than that of the rear end side body portion 18 is formed on the center electrode 20 side with respect to the flange portion 19, and the front end side body portion 17 is further forward than the front end side body portion 17. The leg length portion 13 is formed with a smaller outer diameter, and the outer diameter decreases toward the center electrode 20 side.

スパークプラグ１００の主体金具５０は、絶縁碍子１０の後端側胴部１８の一部から脚長部１３に亘る部位を包囲して保持する円筒状の金具であり、本実施例では、低炭素鋼から成る。主体金具５０は、工具係合部５１と、取付ネジ部５２と、シール部５４と、先端面５７とを備える。主体金具５０の工具係合部５１は、スパークプラグ１００をエンジンヘッド２００に取り付ける工具（図示しない）が嵌合する。主体金具５０の取付ネジ部５２は、エンジンヘッド２００の取付ネジ孔２０１に螺合するネジ山を有する。主体金具５０のシール部５４は、取付ネジ部５２の根元に鍔状に形成され、シール部５４とエンジンヘッド２００との間には、板体を折り曲げて形成した環状のガスケット５が嵌挿される。主体金具５０の先端面５７は、取付ネジ部５２の先端に形成された中空円状の面であり、先端面５７の中央には、脚長部１３に包まれた中心電極２０が突出する。 The metal shell 50 of the spark plug 100 is a cylindrical metal fitting that surrounds and holds a portion ranging from a part of the rear end side body portion 18 to the leg long portion 13 of the insulator 10. In this embodiment, the low-carbon steel is used. Consists of. The metal shell 50 includes a tool engaging portion 51, a mounting screw portion 52, a seal portion 54, and a tip surface 57. A tool (not shown) for attaching the spark plug 100 to the engine head 200 is fitted into the tool engaging portion 51 of the metal shell 50. The mounting screw portion 52 of the metal shell 50 has a thread that is screwed into the mounting screw hole 201 of the engine head 200. The seal portion 54 of the metal shell 50 is formed in a hook shape at the base of the mounting screw portion 52, and an annular gasket 5 formed by bending a plate is inserted between the seal portion 54 and the engine head 200. . The distal end surface 57 of the metal shell 50 is a hollow circular surface formed at the distal end of the mounting screw portion 52, and the center electrode 20 wrapped in the leg long portion 13 projects from the center of the distal end surface 57.

スパークプラグ１００の中心電極２０は、有底筒状に形成された中心電極母材２１の内部に、中心電極母材２１よりも熱伝導性に優れる芯材２５を埋設した棒状の電極である。本実施例では、中心電極母材２１は、インコネル（登録商標）を始めとするニッケルを主成分とするニッケル合金から成り、芯材２５は、銅または銅を主成分とする合金から成る。中心電極２０は、中心電極母材２１の先端が絶縁碍子１０の軸孔１２から突出した状態で絶縁碍子１０の軸孔１２に挿入され、セラミック抵抗３およびシール体４を介して端子金具４０に電気的に接続されている。 The center electrode 20 of the spark plug 100 is a rod-like electrode in which a core material 25 having better thermal conductivity than the center electrode base material 21 is embedded in a center electrode base material 21 formed in a bottomed cylindrical shape. In this embodiment, the center electrode base material 21 is made of a nickel alloy containing nickel as a main component such as Inconel (registered trademark), and the core member 25 is made of copper or an alloy containing copper as a main component. The center electrode 20 is inserted into the shaft hole 12 of the insulator 10 with the end of the center electrode base material 21 protruding from the shaft hole 12 of the insulator 10, and is connected to the terminal fitting 40 via the ceramic resistor 3 and the seal body 4. Electrically connected.

スパークプラグ１００の接地電極３０は、主体金具５０の先端面５７に接合され、中心電極２０の軸方向に交差する方向に屈曲して中心電極２０の先端に対向する電極である。本実施例では、接地電極３０は、インコネル（登録商標）を始めとするニッケルを主成分とするニッケル合金から成る。 The ground electrode 30 of the spark plug 100 is an electrode that is joined to the front end surface 57 of the metal shell 50, bent in a direction intersecting the axial direction of the center electrode 20, and opposed to the front end of the center electrode 20. In the present embodiment, the ground electrode 30 is made of a nickel alloy mainly composed of nickel such as Inconel (registered trademark).

図２は、第１実施例における接地電極３０の詳細構造を主に示す説明図である。接地電極３０は、接地電極母材３５と、発火部３６とから構成されており、接地電極母材３５の先端部３９を構成する先端面３１と、接地電極３０の表面のうち中心電極２０に対向する対向面３２と、対向面３２とは反対側の面であり接地電極３０に背を向ける背面３３とを備える。 FIG. 2 is an explanatory view mainly showing a detailed structure of the ground electrode 30 in the first embodiment. The ground electrode 30 is composed of a ground electrode base material 35 and an ignition portion 36, and a tip surface 31 constituting a tip portion 39 of the ground electrode base material 35 and the center electrode 20 among the surfaces of the ground electrode 30. An opposing facing surface 32 and a back surface 33 opposite to the facing surface 32 and facing away from the ground electrode 30 are provided.

発火部３６は、接地電極３０の対向面３２に、中心電極２０の先端に対向して、多段状に突出するようにプレス成形により形成されている。発火部３６は、多段状に形成された各段のうち、最も根元側の段である根元段３６ａから、最も中心電極側の段である先端段３６ｂに向けて、各段の突出方向に直交する断面の平均断面積が小さくなるように形成されている。本実施例では、発火部３６は、円形の断面を有する円柱状の突起である。窪み部３７は、発火部３６を形成する際のプレス成形により、背面３３から接地電極母材３５の内側に向けて凹状に形成される。 The ignition part 36 is formed on the facing surface 32 of the ground electrode 30 by press molding so as to protrude in a multi-stage shape, facing the tip of the center electrode 20. The firing part 36 is orthogonal to the protruding direction of each stage from the root stage 36a, which is the most proximal stage, to the tip stage 36b, which is the most central stage side, among the stages formed in a multi-stage shape. The average cross-sectional area of the cross section to be formed is reduced. In the present embodiment, the ignition part 36 is a cylindrical protrusion having a circular cross section. The hollow portion 37 is formed in a concave shape from the back surface 33 toward the inside of the ground electrode base material 35 by press molding when the ignition portion 36 is formed.

図２に示すように、発火部３６と中心電極２０との間には、火花ギャップと呼ばれる間隙が形成される。発火部３６の重心は、中心電極２０の中心軸（軸線）Ｏの延長線上に略沿って位置する。 As shown in FIG. 2, a gap called a spark gap is formed between the ignition part 36 and the center electrode 20. The center of gravity of the ignition part 36 is positioned substantially along an extension of the center axis (axis line) O of the center electrode 20.

図３は、第１実施例における発火部３６の形状について詳細に説明する平面図である。図３（ａ）は、接地電極３０の対向面３２を中心電極２０側から見た平面図である。図３（ｂ）は、接地電極３０を、先端面３１側から見た平面図である。発火部３６は、以下の式１〜式４を満たすように形成されている。ただし、図３（ａ）および図３（ｂ）において、根元段３６ａの最も中心電極２０側の部分の径をＡ、先端段３６ｂの最も中心電極２０側の部分の径をＢ、軸線方向と直交し、且つ接地電極３０の延長方向と直交する方向における接地電極３０の幅をＸ、根元段３６ａの突出量をＣ、先端段３６ｂの突出量をＤとする。なお、突出量とは、各段の軸線方向に沿った高さを表す。 FIG. 3 is a plan view for explaining in detail the shape of the ignition part 36 in the first embodiment. FIG. 3A is a plan view of the facing surface 32 of the ground electrode 30 as viewed from the center electrode 20 side. FIG. 3B is a plan view of the ground electrode 30 viewed from the front end face 31 side. The ignition part 36 is formed so as to satisfy the following expressions 1 to 4. However, in FIGS. 3A and 3B, the diameter of the portion of the root step 36a closest to the center electrode 20 is A, the diameter of the portion of the tip step 36b closest to the center electrode 20 is B, and the axial direction Let X be the width of the ground electrode 30 in the direction perpendicular to the extension direction of the ground electrode 30, C be the protrusion amount of the root step 36a, and D be the protrusion amount of the tip step 36b. In addition, protrusion amount represents the height along the axial direction of each step | level.

０．３≦Ａ／Ｘ≦０．９、かつ、０．２≦Ｂ／Ａ≦０．９ …（式１）
Ａ≦２．０ｍｍ …（式２）
０＜Ｃ≦１．０ｍｍ、かつ、０＜Ｄ≦１．０ｍｍ …（式３）
Ｂ≦１．４ｍｍ …（式４） 0.3 ≦ A / X ≦ 0.9 and 0.2 ≦ B / A ≦ 0.9 (Formula 1)
A ≦ 2.0 mm (Formula 2)
0 <C ≦ 1.0 mm and 0 <D ≦ 1.0 mm (Formula 3)
B ≦ 1.4mm (Formula 4)

Ａ２．製造工程：
図４は、第１実施例における接地電極３０の製造工程を示すフローチャートである。図５は、固定治具を説明する斜視図である。図６は、発火部３６の成型について説明するための断面図である。なお、図５、図６に示すように、一段目固定治具３００は、押さえ型３１０と受け型３２０と加工ピン３４０とから構成されており、二段目固定治具４００は、押さえ型４１０と受け型４２０と加工ピン４４０とから構成されている。押さえ型３１０、押さえ型４１０および受け型３２０、４２０は、押出しプレス成型に用いられる金型である。 A2. Manufacturing process:
FIG. 4 is a flowchart showing a manufacturing process of the ground electrode 30 in the first embodiment. FIG. 5 is a perspective view illustrating the fixing jig. FIG. 6 is a cross-sectional view for explaining molding of the ignition part 36. As shown in FIGS. 5 and 6, the first stage fixing jig 300 includes a pressing mold 310, a receiving mold 320, and a processing pin 340, and the second stage fixing jig 400 includes a pressing mold 410. And a receiving mold 420 and a processing pin 440. The pressing mold 310, the pressing mold 410, and the receiving molds 320 and 420 are molds used for extrusion press molding.

まず、ニッケルを主成分とする材料により、接地電極母材３５を作製する（ステップＳ１０）。本実施例では、電極部材３０１は、略長方形の断面を有する棒状のニッケル合金である。次に、一段目固定治具３００の押さえ型３１０と受け型３２０との間に接地電極母材３５を配置する（ステップＳ１２）。図５に示すように、受け型３２０には、接地電極母材３５と略同じ形状である成形溝部３５０が形成されており、接地電極母材３５は、受け型３２０の成形溝部３５０に収容される。受け型３２０に形成された成形溝部３５０の位置に合わせて、押さえ型３１０には、接地電極３０の発火部３６に対応する位置にピン孔部３１４が形成され、受け型３２０には、接地電極３０の発火部３６に対応する位置に段形成部３３０が形成されている。 First, the ground electrode base material 35 is made of a material containing nickel as a main component (step S10). In this embodiment, the electrode member 301 is a rod-shaped nickel alloy having a substantially rectangular cross section. Next, the ground electrode base material 35 is disposed between the pressing mold 310 and the receiving mold 320 of the first stage fixing jig 300 (step S12). As shown in FIG. 5, the receiving die 320 is formed with a forming groove 350 having substantially the same shape as the ground electrode base 35, and the ground electrode base 35 is accommodated in the forming groove 350 of the receiving die 320. The A pin hole 314 is formed in the holding die 310 at a position corresponding to the ignition portion 36 of the ground electrode 30 in accordance with the position of the forming groove 350 formed in the receiving die 320. A step forming portion 330 is formed at a position corresponding to thirty firing portions 36.

押さえ型３１０と受け型３２０との間に接地電極母材３５を配置した後（ステップＳ１２、図６（ａ））、押さえ型３１０のピン孔部３１４に加工ピン３４０をプレス挿入することによって、接地電極母材３５の一部が受け型３２０の段形成部３３０に押し込まれる。このように、接地電極母材３５に押出しプレス加工が施され、発火部３６の一段目（根元段）が成型される（ステップＳ１４、図６（ｂ））。受け型３２０の段形成部３３０は、径が、加工ピン３４０の径とほぼ同一もしくは若干小さくなるように形成されている。こうすることにより、段形成部３３０の形状に沿うように段が形成される。なお、発火部３６の突出量Ｃは、予め、段形成部３３０の形状により規定される。ピン孔部３１４に加工ピン３４０がプレス挿入されると、接地電極母材３５において押さえ型３１０のピン孔部３１４に隣接する部位は、加工ピン３４０に押されて窪むことによって一段目に対応する窪み部３７ａを形成し、接地電極母材３５において受け型３２０の段形成部３３０に隣接する部位は、加工ピン３４０によって段形成部３３０に押し出されて発火部３６の根元段３６ａを形成する。 After the ground electrode base material 35 is disposed between the holding die 310 and the receiving die 320 (step S12, FIG. 6A), the processing pin 340 is press-inserted into the pin hole portion 314 of the holding die 310, A part of the ground electrode base material 35 is pushed into the step forming portion 330 of the receiving mold 320. In this way, the ground electrode base material 35 is subjected to extrusion pressing, and the first stage (root stage) of the ignition part 36 is molded (step S14, FIG. 6B). The step forming portion 330 of the receiving mold 320 is formed so that the diameter is substantially the same as or slightly smaller than the diameter of the processing pin 340. By doing so, a step is formed along the shape of the step forming portion 330. Note that the protrusion amount C of the ignition part 36 is defined in advance by the shape of the step forming part 330. When the processing pin 340 is press-inserted into the pin hole portion 314, the portion adjacent to the pin hole portion 314 of the holding die 310 in the ground electrode base material 35 corresponds to the first stage by being depressed by the processing pin 340. The portion of the ground electrode base material 35 adjacent to the step forming portion 330 of the receiving mold 320 is pushed out to the step forming portion 330 by the processing pin 340 to form the root step 36a of the ignition portion 36. .

発火部３６の一段目（根元段３６ａ）を押出しプレスで成型した後（ステップＳ１４）、一段目固定治具３００から接地電極母材３５を取り出し、二段目固定治具４００の押さえ型４１０と受け型４２０との間に接地電極母材３５を配置する（ステップＳ１６、図６（ｃ））。二段目固定治具４００は、ピン孔部の径が小さく形成されている点、および、受け型４２０に、一段目（根元段）を収容する収容部４６０が形成されている点以外は、一段目固定治具３００と同様の構成を備える。接地電極母材３５を二段目固定治具４００に固定する際、一段目（根元段３６ａ）が収容部４６０に収容されるように配置する。 After the first stage (base stage 36a) of the ignition part 36 is formed by extrusion press (step S14), the ground electrode base material 35 is taken out from the first stage fixing jig 300, and the holding die 410 of the second stage fixing jig 400 The ground electrode base material 35 is disposed between the receiving mold 420 (step S16, FIG. 6C). The second stage fixing jig 400 has a point that the pin hole part is formed with a small diameter, and the receiving part 420 is formed with an accommodating part 460 that accommodates the first stage (base stage). A configuration similar to that of the first stage fixing jig 300 is provided. When the ground electrode base material 35 is fixed to the second stage fixing jig 400, the first stage (base stage 36 a) is disposed so as to be accommodated in the accommodating portion 460.

接地電極母材３５を二段目固定治具４００に固定した後（ステップＳ１６）、押さえ型４１０のピン孔部４１４に加工ピン４４０をプレス挿入することによって、押出しプレス加工を接地電極母材３５に施し、発火部３６の２段目（先端段３６ｂ）を成型する（ステップＳ１８、図６（ｄ））。この際、接地電極母材３５において押さえ型４１０のピン孔部４１４に隣接する部位は、加工ピン４４０に押されて窪むことによって二段目に対応する窪み部３７ｂが形成される。なお、第１実施例では、発火部３６の段数を２段としているため、押し出しプレス加工は２回行われるが、発火部３６の段数を３段以上とする場合、押し出しプレス加工を段数分行えばよい。この場合、根元側の段から先端側（中心電極側）の段に向けて径が小さくなるように形成することが好ましい。 After fixing the ground electrode base material 35 to the second-stage fixing jig 400 (step S16), the processing pin 440 is press-inserted into the pin hole portion 414 of the presser die 410, thereby performing the extrusion press processing to the ground electrode base material 35. Then, the second stage (tip stage 36b) of the ignition part 36 is molded (step S18, FIG. 6 (d)). At this time, a portion of the ground electrode base material 35 adjacent to the pin hole portion 414 of the pressing die 410 is depressed by being pressed by the processing pin 440, thereby forming a hollow portion 37 b corresponding to the second stage. In the first embodiment, since the number of stages of the ignition unit 36 is two, the extrusion press process is performed twice. However, when the number of stages of the ignition unit 36 is three or more, if the extrusion press process is performed for the number of stages, Good. In this case, it is preferable to form such that the diameter decreases from the step on the base side toward the step on the tip side (center electrode side).

発火部３６および窪み部３７が形成された接地電極母材３５を、二段目固定治具４００から取り出し（ステップＳ２０）、二段目固定治具４００から取り出された接地電極母材３５の先端を曲げ加工により折り曲げることによって（ステップＳ２２）、接地電極３０が完成する。以上説明した工程で接地電極３０が製造され、主体金具５０に組み付けられる。 The ground electrode base material 35 in which the ignition part 36 and the hollow part 37 are formed is taken out from the second stage fixing jig 400 (step S20), and the tip of the ground electrode base material 35 taken out from the second stage fixing jig 400 is taken. Is bent by bending (step S22), and the ground electrode 30 is completed. The ground electrode 30 is manufactured through the steps described above and assembled to the metal shell 50.

Ａ３．実験結果１：
上述のように製造された接地電極３０の着火性、生産性および耐久性を評価する評価試験を行った結果を表１および表２に示す。表１、２において、図３（ａ）および図３（ｂ）に示すように、根元段３６ａの径をＡ、先端段３６ｂの径をＢ、軸線方向と直交し、且つ接地電極３０の延長方向と直交する方向における接地電極３０の幅をＸ、根元段３６ａの突出量をＣ、先端段３６ｂの突出量をＤとする。 A3. Experimental result 1:
Tables 1 and 2 show the results of evaluation tests for evaluating the ignitability, productivity, and durability of the ground electrode 30 manufactured as described above. In Tables 1 and 2, as shown in FIGS. 3 (a) and 3 (b), the diameter of the root step 36a is A, the diameter of the tip step 36b is B, orthogonal to the axial direction, and the ground electrode 30 is extended. The width of the ground electrode 30 in the direction orthogonal to the direction is X, the protrusion amount of the root step 36a is C, and the protrusion amount of the tip step 36b is D.

第１実施例では、着火性の評価試験方法として、アイドル回転域における安定性試験を行った。この評価試験方法は、点火時期をパラメータとし、徐々に進角させ、平均有効圧の変動率をプロットしていき、変動率が２０％のときを閾値として、そのときの点火時期をそのスパークプラグの進角限界とする着火性評価法である。表１において、進角限界が５０ｄｅｇＢＴＤＣ以上のプラグをＯＫ（○、◎）とし、それ以外のプラグをＮＧ（Ｘ）とした。なお、ＯＫのうち、進角限界が５０ｄｅｇＢＴＤＣ以上のプラグを○、進角限界が５５ｄｅｇＢＴＤＣ以上のプラグを◎とした。 In the first example, a stability test in an idle rotation range was performed as an ignitability evaluation test method. In this evaluation test method, the ignition timing is used as a parameter, the angle is gradually advanced, and the variation rate of the average effective pressure is plotted. When the variation rate is 20%, the ignition timing at that time is the spark plug. It is an ignitability evaluation method with the advance angle limit of. In Table 1, plugs having an advance angle limit of 50 deg BTDC or more are OK (◯, ◎), and other plugs are NG (X). Of the OK, plugs with an advance angle limit of 50 deg BTDC or more were marked with ◯, and plugs with an advance angle limit of 55 deg BTDC or more were marked with ◎.

また、第１実施例では、生産性の評価試験方法として、表１に示す寸法で、接地電極３０を１０個生産し、プレス成形した突状の発火部３６を拡大鏡を用いて確認し、われ、ひびがあるか否かにより生産性を評価した。表１において、われ、ひびがあったプラグをＮＧ（Ｘ）とし、われ、ひびがなかったプラグをＯＫ（○）とした。 Further, in the first example, as a productivity evaluation test method, 10 ground electrodes 30 were produced with the dimensions shown in Table 1, and the press-formed projecting portion 36 was confirmed using a magnifying glass. The productivity was evaluated based on whether or not there were cracks. In Table 1, plugs with cracks and cracks were designated as NG (X), and plugs with cracks and cracks were designated as OK (◯).

また、第１実施例では、耐久性の評価試験方法として、５０００ｒｐｍ＊ＷＯＴの条件で２００時間の耐久試験を実施した。生産時点（新品時）での放電電圧と、耐久試験後の放電電圧を比較し、電圧上昇率が３０％を超えたプラグをＮＧ（Ｘ）とし、電圧上昇率が３０％以下のプラグをＯＫ（○）とした。なお、ＷＯＴとは、ＷｉｄｅＯｐｅｎＴｈｒｏｔｔｌｅを示す。 In the first example, a durability test for 200 hours was performed as a durability evaluation test method under the condition of 5000 rpm * WOT. Comparing the discharge voltage at the time of production (when new) and the discharge voltage after the endurance test, plugs with a voltage increase rate exceeding 30% are NG (X), and plugs with a voltage increase rate of 30% or less are OK (○). In addition, WOT shows Wide Open Throttle.

表１に示すように、式１および式３を満たすサンプル２〜４、７〜９、１２〜１４、１７〜１９は、着火性および生産性のいずれの評価においてもＯＫであることがわかった。一方、式１および式３の少なくとも一方を満たさないサンプル１、５、６、１０、１１、１５、１６および２０は、着火性もしくは生産性のいずれかにおいて、ＮＧであることがわかった。 As shown in Table 1, it was found that Samples 2 to 4, 7 to 9, 12 to 14, and 17 to 19 satisfying Equation 1 and Equation 3 were OK in any evaluation of ignitability and productivity. . On the other hand, Samples 1, 5, 6, 10, 11, 15, 16, and 20 that do not satisfy at least one of Formula 1 and Formula 3 were found to be NG in either ignitability or productivity.

また、表１において、サンプル１２とサンプル１３を比較した場合、および、サンプル１７とサンプル１８を比較した場合、Ａ／ＸおよびＢ／Ａの値が同一であっても、ＣもしくはＤの少なくとも一方が０．３ｍｍ未満である場合には、着火性が低いことがわかった。よって、発火部３６は、式３を満たすとともに、更に、以下の式５を満たすことにより、着火性を向上できる。 In Table 1, when sample 12 and sample 13 are compared, and when sample 17 and sample 18 are compared, even if the values of A / X and B / A are the same, at least one of C or D It was found that the ignitability is low when is less than 0.3 mm. Therefore, the ignition part 36 can improve the ignitability by satisfying Expression 3 and further satisfying Expression 5 below.

０．３ｍｍ≦Ｃ≦１．０ｍｍ、かつ、０．３ｍｍ≦Ｄ≦１．０ｍｍ …（式５） 0.3 mm ≦ C ≦ 1.0 mm and 0.3 mm ≦ D ≦ 1.0 mm (Formula 5)

また、表２に示すように、式２を満たすサンプル２１〜２３は、着火性が安定しており、式２を満たさないサンプル２４は、着火性が安定しないことがわかった。 In addition, as shown in Table 2, it was found that Samples 21 to 23 satisfying Equation 2 have stable ignitability, and Sample 24 that does not satisfy Equation 2 has unstable ignitability.

また、表２に示すように、式４を満たすサンプル２２〜２４は、耐久性が高いが、式４を満たさないサンプル２１は、耐久性が低いことがわかった。 Moreover, as shown in Table 2, it was found that samples 22 to 24 satisfying formula 4 have high durability, but sample 21 not satisfying formula 4 has low durability.

以上説明した第１実施例のスパークプラグ１００によれば、中心電極２０側に突出するように多段状に形成された発火部３６が、最も根元側の段である根元段３６ａから先端段３６ｂに向けて、各段の突出方向に直交する断面の平均断面積が小さくなるように形成されている。更に、第１実施例では、発火部３６が、式１〜式３および式５を満たすように形成されている。こうすることにより、根元段３６ａの断面積を先端段３６ｂの断面積に比して大きく形成できるので、製造時に、発火部３６にひずみやひび割れが発生することを抑制できる。よって、接地電極３０の生産性を向上できる。また、先端段３６ｂの径を小さく形成できるので着火性を向上できる。 According to the spark plug 100 of the first embodiment described above, the ignition part 36 formed in a multi-stage shape so as to protrude toward the center electrode 20 side is changed from the root stage 36a which is the most base stage to the tip stage 36b. The average cross-sectional area of the cross section orthogonal to the protruding direction of each step is reduced. Furthermore, in the first embodiment, the ignition part 36 is formed so as to satisfy Equations 1 to 3 and Equation 5. By doing so, the cross-sectional area of the root step 36a can be formed larger than the cross-sectional area of the tip end step 36b, so that it is possible to suppress the occurrence of strain and cracks in the ignition part 36 during manufacturing. Therefore, the productivity of the ground electrode 30 can be improved. Moreover, since the diameter of the front end step 36b can be reduced, the ignitability can be improved.

また、第１実施例のスパークプラグによれば、式４を満たすように形成されていることにより、耐久性を向上できる。 Moreover, according to the spark plug of 1st Example, durability can be improved by being formed so that Formula 4 may be satisfy | filled.

Ｂ．変形例
（１）上述の実施例では、発火部３６の段数を２段としているが、３段以上であってもよい。この場合、式１〜式５を満たすように形成することが好ましい。こうすれば、スパークプラグによればの着火性、耐久性、生産性を向上できる。 B. Modification (1) In the above-described embodiment, the number of stages of the ignition unit 36 is two, but it may be three or more. In this case, it is preferable to form so that Formula 1-Formula 5 may be satisfy | filled. In this way, the ignitability, durability, and productivity according to the spark plug can be improved.

（２）図７は変形例における発火部３６の形状について詳細に説明する平面図である。図７（ａ）は、接地電極３０の対向面３２を中心電極２０側から見た平面図である。図７（ｂ）は、接地電極３０を、先端面３１側から見た平面図である。図７（ａ）および（ｂ）に示すように、発火部３６の先端面には、貴金属チップ３８、たとえば、プラチナ（Ｐｔ）チップが備えられていても良い。貴金属チップ３８を供えることによって、発火部３６の耐久性を向上させることができる。 (2) FIG. 7 is a plan view for explaining in detail the shape of the ignition part 36 in the modification. FIG. 7A is a plan view of the facing surface 32 of the ground electrode 30 as viewed from the center electrode 20 side. FIG. 7B is a plan view of the ground electrode 30 viewed from the front end face 31 side. As shown in FIGS. 7A and 7B, a noble metal tip 38, for example, a platinum (Pt) tip may be provided on the tip surface of the ignition portion 36. By providing the noble metal tip 38, the durability of the ignition part 36 can be improved.

以上、本発明の種々の実施例について説明したが、本発明はこれらの実施例に限定されず、その趣旨を逸脱しない範囲で種々の構成をとることができる。 As mentioned above, although the various Example of this invention was described, this invention is not limited to these Examples, A various structure can be taken in the range which does not deviate from the meaning.

３…セラミック抵抗
４…シール体
５…ガスケット
１０…絶縁碍子
１２…軸孔
１３…脚長部
１７…先端側胴部
１８…後端側胴部
１９…鍔部
２０…中心電極
２１…中心電極母材
２５…芯材
３０…接地電極
３１…先端面
３２…対向面
３３…背面
３５…接地電極母材
３６…発火部
３６ａ…根元段
３６ｂ…先端段
３７…窪み部
３９…先端部
４０…端子金具
５０…主体金具
５１…工具係合部
５２…取付ネジ部
５４…シール部
５７…先端面
１００…スパークプラグ
２００…エンジンヘッド
２０１…取付ネジ孔
３００…一段目固定治具
３０１…電極部材
３１０…押さえ型
３１４…ピン孔部
３２０…受け型
３３０…段形成部
３４０…加工ピン
３５０…成形溝部
４００…二段目固定治具
４１０…押さえ型
４１４…ピン孔部
４２０…受け型
４４０…加工ピン
４６０…収容部 DESCRIPTION OF SYMBOLS 3 ... Ceramic resistance 4 ... Sealing body 5 ... Gasket 10 ... Insulator 12 ... Shaft hole 13 ... Leg long part 17 ... Front end side trunk | drum 18 ... Rear end side trunk | drum 19 ... Ridge part 20 ... Center electrode 21 ... Center electrode base material 25 ... Core material 30 ... Ground electrode 31 ... Tip surface 32 ... Opposite surface 33 ... Back surface 35 ... Ground electrode base material 36 ... Ignition part 36a ... Root stage 36b ... Tip stage 37 ... Depression part 39 ... Tip part 40 ... Terminal metal fitting 50 ... Metal fitting 51 ... Tool engaging part 52 ... Mounting screw part 54 ... Seal part 57 ... Tip surface 100 ... Spark plug 200 ... Engine head 201 ... Mounting screw hole 300 ... First stage fixing jig 301 ... Electrode member 310 ... Presser type 314: Pin hole 320 ... Receiving die 330 ... Step forming portion 340 ... Processing pin 350 ... Molding groove portion 400 ... Second stage fixing jig 410 ... Holding die 414 ... Pin hole portion 420 ... Receiving Type 440 ... working pin 460 ... housing part

Claims

A central electrode extending in the axial direction;
An insulator formed on an outer periphery of the center electrode while exposing a tip of the center electrode;
A metal shell formed on the outer periphery of the insulator;
A spark plug comprising a ground electrode having a base end joined to the metal shell and a tip arranged to face the end face of the center electrode,
The tip portion includes an ignition portion formed so as to protrude in a multi-stage shape on the center electrode side,
The ignition portion has a diameter of the root step as A, a diameter of the tip step as B, a width of the ground electrode in a direction perpendicular to the axial direction and a direction perpendicular to the extension direction of the ground electrode as X When formed, the relationship of 0.3 ≦ A / X ≦ 0.9 and 0.2 ≦ B / A ≦ 0.9 is established.
Of the stages formed in the multi-stage shape, the firing portion is defined as C, which is the protrusion amount of the root stage, which is the most proximal stage, and D, which is the protrusion quantity of the tip stage, which is the most central electrode side. Is formed so that the relationship of 0 <C ≦ 1.0 mm and 0 <D ≦ 1.0 mm is satisfied,
Spark plug.

The spark plug according to claim 1, wherein
The ignition part is A ≦ 2.0 mm, where A is the diameter of the root step.
Spark plug.

The spark plug according to claim 1 or 2,
The ignition part is 0.3 mm ≦ C ≦ 1.0 mm and 0.3 mm ≦ D ≦ 1.0 mm.
Spark plug.

The spark plug according to any one of claims 1 to 3,
The firing portion has a diameter of a tip step which is the step on the most tip side among the steps formed in the multi-stage shape is 1.4 mm or more.
Spark plug.

The spark plug according to any one of claims 1 to 4,
The ground electrode is formed mainly of nickel.
Spark plug.

A central electrode extending in the axial direction;
An insulator formed on an outer periphery of the center electrode while exposing a tip of the center electrode;
A metal shell formed on the outer periphery of the insulator;
A grounding electrode having a base end joined to the metal shell and a tip arranged to face the end face of the center electrode, and a spark plug manufacturing method comprising:
By press molding, the tip protrudes in a multi-stage shape toward the center electrode side, and among the stages formed in the multi-stage shape, from the root stage, which is the most root-side stage, to the center electrode side most To form a firing portion where the average cross-sectional area of the cross section perpendicular to the protruding direction of each stage is reduced toward the tip stage which is a stage,
Spark plug manufacturing method.