JP5408503B2

JP5408503B2 - Spark plug electrode and spark plug manufacturing method

Info

Publication number: JP5408503B2
Application number: JP2010227711A
Authority: JP
Inventors: 悟落合
Original assignee: NGK Spark Plug Co Ltd
Current assignee: Niterra Co Ltd
Priority date: 2010-10-07
Filing date: 2010-10-07
Publication date: 2014-02-05
Anticipated expiration: 2030-10-07
Also published as: JP2012084272A

Description

本発明は、スパークプラグの中心電極や接地電極の製造方法、並びに前記のスパークプラグ用電極の製造方法を含めたスパークプラグの製造方法に関する。 The present invention relates to a method for manufacturing a center electrode and a ground electrode of a spark plug, and a method for manufacturing a spark plug including the method for manufacturing a spark plug electrode.

内燃機関には、点火のためのスパークプラグが用いられている。一般的なスパークプラグは、軸孔内の先端側に中心電極を保持し、後端側に接続端子を保持した絶縁碍子と、その絶縁碍子の胴部の周囲を取り囲んで保持する主体金具と、この主体金具の先端に一端が溶接され、他端が中心電極の先端に対向し火花放電ギャップを形成する接地電極とから構成されている。 A spark plug for ignition is used in the internal combustion engine. A general spark plug has an insulator that holds the center electrode on the front end side in the shaft hole and holds the connection terminal on the rear end side, and a metal shell that surrounds and holds the periphery of the trunk of the insulator, One end is welded to the tip of the metal shell, and the other end is composed of a ground electrode that faces the tip of the center electrode and forms a spark discharge gap.

このようなスパークプラグの中心電極を製造するには、従来では電極材料を切削加工していたが、本出願人は先に、電極材料からなる柱状のワークを金型に収容し、パンチで押し出して所定の電極形状に加工する方法を提案している（例えば、特許文献１参照）。 In order to manufacture the center electrode of such a spark plug, the electrode material has been conventionally cut, but the applicant first puts a columnar workpiece made of the electrode material in a mold and extrudes it with a punch. Have proposed a method of processing into a predetermined electrode shape (see, for example, Patent Document 1).

特開平８−２１３１５０号公報JP-A-8-213150

しかしながら、スパークプラグの中心電極は、先端に向かうほど縮径しており、ワークはその下方部分、即ち底面に近い部分ほど細く、また長くなるように押出成形される。そのため、ワークは、押し出し時の抵抗を小さくするために、その側面及び底面に金属のメッキ膜を施すことも行われているが、成形後の中心電極の側面、特に先端に近い側面に、軸線に沿った線状の傷（縦傷）が発生する場合がある。 However, the diameter of the center electrode of the spark plug is reduced toward the tip, and the work is extruded so that the lower part thereof, that is, the part closer to the bottom face is thinner and longer. Therefore, in order to reduce the resistance when extruding the workpiece, a metal plating film is applied to the side surface and the bottom surface, but the axis line is formed on the side surface of the center electrode after molding, particularly on the side surface close to the tip. In some cases, linear scratches (longitudinal scratches) may occur.

また、接地電極も電極材料からなるワークを押出成形して製造することがあり、同様の縦傷が発生することがある。 In addition, the ground electrode may be manufactured by extruding a workpiece made of an electrode material, and the same vertical flaw may occur.

そこで本発明は、スパークプラグの中心電極や接地電極を、電極材料からなるワークを押出成形して製造する際に、縦傷の発生を抑えることを目的とする。 Accordingly, an object of the present invention is to suppress the occurrence of vertical flaws when the center electrode and the ground electrode of a spark plug are manufactured by extruding a workpiece made of an electrode material.

上位目的を達成するために本発明は、下記のスパークプラグ用電極及びスパークプラグの製造方法を提供する。
（１）太径部とその一端面に縮径部とを有する柱状のワークを準備する準備工程と、
前記ワークにメッキ膜を形成するメッキ工程と、
前記メッキ膜が形成されたワークを押出成形する押出工程と、
を備えるスパークプラグ用電極の製造方法であって、
前記メッキ工程において、前記縮径部に形成されるメッキ膜は、前記太径部に形成されるメッキ膜よりも厚く形成されることを特徴とするスパークプラグ用電極の製造方法。
（２）前記縮径部に形成されるメッキ膜において、前記縮径部とその端面との境界部に形成されるメッキ膜が、最も厚く形成されることを特徴とする上記（１）記載のスパークプラグ用電極の製造方法。
（３）前記太径部に形成されるメッキ膜の厚さが１０μｍ以下であることを特徴とする上記（１）または（２）に記載のスパークプラグ用電極の製造方法。
（４）前記縮径部及び前記境界部に形成されるメッキ膜の厚さが、前記太径部に形成されるメッキ膜の厚さの１．５〜３倍であることを特徴とする上記（１）〜（３）の何れか１項に記載のスパークプラグ用電極の製造方法。
（５）前記ワークが、ニッケルを主成分とし、クロムを１０質量％以上含有する金属であることを特徴とする上記（１）〜（４）の何れか１項に記載のスパークプラグ用電極の製造方法。
（６）前記ワークが、ニッケルを主成分とし、クロムを２０質量％以上含有する金属であることを特徴とする上記（５）に記載のスパークプラグ用電極の製造方法。
（７）前記太径部に形成されるメッキ膜の厚さが５μｍ以下であることを特徴とする請求項６に記載のスパークプラグ用電極の製造方法。
（８）前記メッキ膜が、白金、金、銀、銅、錫または亜鉛のうち少なくとも一種を主成分とする金属であることを特徴とする上記（１）〜（７）の何れか１項に記載のスパークプラグ用電極の製造方法。
（９）前記太径部に形成されるメッキ膜の厚さが０．３μｍ以上であることを特徴とする上記（１）〜（８）の何れか１項に記載のスパークプラグ用電極の製造方法。
（１０^）軸線方向に延びる軸孔を有する絶縁体と、
前記軸孔に保持される中心電極と、
前記絶縁体の外周に設けられた主体金具と、
基端部が前記主体金具に接合され、その先端部と前記中心電極の先端部との間に間隙を形成する接地電極とを備えたスパークプラグの製造方法であって、
前記中心電極及び前記接地電極の少なくとも一つを、上記（１）〜（９）の何れか１項に記載の方法で製造する工程を有することを特徴とするスパークプラグの製造方法。 In order to achieve the overall object, the present invention provides the following spark plug electrode and spark plug manufacturing method.
(1) a preparation step of preparing a columnar workpiece having a large diameter portion and a reduced diameter portion at one end surface thereof;
A plating step of forming a plating film on the workpiece;
An extrusion process for extruding the workpiece on which the plating film is formed;
A method for producing an electrode for a spark plug comprising:
In the plating process, the plating film formed on the reduced diameter portion is formed thicker than the plating film formed on the large diameter portion.
(2) In the plating film formed on the reduced diameter portion, the plating film formed on the boundary portion between the reduced diameter portion and the end surface thereof is formed to be the thickest. Manufacturing method of electrode for spark plug.
(3) The method for producing an electrode for a spark plug as described in (1) or (2) above, wherein the thickness of the plating film formed on the large diameter portion is 10 μm or less.
(4) The thickness of the plating film formed on the reduced diameter portion and the boundary portion is 1.5 to 3 times the thickness of the plating film formed on the large diameter portion. (1) The manufacturing method of the electrode for spark plugs of any one of (3).
(5) The spark plug electrode according to any one of (1) to (4), wherein the workpiece is a metal containing nickel as a main component and chromium in an amount of 10% by mass or more. Production method.
(6) The method for producing an electrode for a spark plug as described in (5) above, wherein the workpiece is a metal containing nickel as a main component and 20% by mass or more of chromium.
(7) The method for manufacturing an electrode for a spark plug according to (6), wherein the thickness of the plating film formed on the large diameter portion is 5 μm or less.
(8) In any one of the above (1) to (7), the plating film is a metal mainly composed of at least one of platinum, gold, silver, copper, tin, and zinc. The manufacturing method of the electrode for spark plugs of description.
(9) The spark plug electrode according to any one of (1) to (8) above, wherein the thickness of the plating film formed on the large-diameter portion is 0.3 μm or more. Method.
(10 ⁾ an insulator having an axial hole extending in the axial direction;
A center electrode held in the shaft hole;
A metal shell provided on the outer periphery of the insulator;
A method for producing a spark plug comprising a base electrode joined to the metal shell, and a ground electrode that forms a gap between the tip and the tip of the center electrode,
A method for producing a spark plug, comprising the step of producing at least one of the center electrode and the ground electrode by the method according to any one of (1) to (9) above.

本発明によれば、押出成形によりワークから中心電極や接地電極を製造する際に、縦傷の発生を抑えることができる。 According to the present invention, when a center electrode and a ground electrode are manufactured from a workpiece by extrusion molding, occurrence of vertical flaws can be suppressed.

スパークプラグの一例を示す断面図である。It is sectional drawing which shows an example of a spark plug. 中心電極の製造工程を示す工程図である。It is process drawing which shows the manufacturing process of a center electrode. 第１製造工程を示す断面図である。It is sectional drawing which shows a 1st manufacturing process. 第２製造工程を示す断面図である。It is sectional drawing which shows a 2nd manufacturing process. 第３製造工程を示す断面図である。It is sectional drawing which shows a 3rd manufacturing process. 第５製造工程を示す断面図である。It is sectional drawing which shows a 5th manufacturing process. 第６製造工程を示す断面図である。It is sectional drawing which shows a 6th manufacturing process. 第８製造工程を示す断面図である。It is sectional drawing which shows an 8th manufacturing process. 第９製造工程を示す断面図である。It is sectional drawing which shows a 9th manufacturing process. 本発明で用いるワークの一例を示す側面図である。It is a side view which shows an example of the workpiece | work used by this invention.

以下、本発明に関して、中心電極の製造方法を例示して説明する。 Hereinafter, the manufacturing method of a center electrode is illustrated and demonstrated regarding this invention.

図１はスパークプラグの一例を示す断面図である。図示されるように、スパークプラグ１００は、筒状の主体金具１１１と、この主体金具１１１の軸方向に沿って貫通孔１１６が内部に形成され、且つ両端部１１２ａ，１１２ｂが主体金具１１１から露出されるようにこの主体金具１１１の内部に嵌め込まれて保持された絶縁体１１２と、先端部１１３ａが露出されるように貫通孔１１６の一端部（図中下方）１１６ａに挿入固定された中心電極１１３と、後端部１１７ａが露出されるように貫通孔１１６の他端部（図中上方）１１６ｂに挿入固定された端子金具１１７と、貫通孔１１６内において中心電極１１３と端子金具１１７との間に設けられ、且つ中心電極１１３及び端子金具１１７のそれぞれに対し軸方向で離間配置された抵抗体１１８と、貫通孔１１６内において抵抗体１１８と中心電極１１３との間に隙間なく設けられた第１の導電性ガラスシール層１１９と、貫通孔１１６内において抵抗体１１８と端子金具１１７との間に隙間なく設けられた第２の導電性ガラスシール層１２０と、主体金具１１１に一端部（基部）１１４ａが抵抗溶接等により結合され、且つ中間部１１４ｃが曲げられて他端部１１４ｂが中心電極１１３の先端部１１３ａに対向配置された略Ｌ字形の接地電極１１４と、を備えている。また、主体金具１１１の外周面には、エンジン等の内燃機関のシリンダヘッド（相手部材）に取り付けられるための取付け用の雄ねじ１１５が周方向にわたって形成されている。更に、中心電極１１３の先端には、貴金属チップ１２１がレーザ溶接等により固着されており、接地電極１１４にも貴金属チップ１２２が固着され、両基金毒チップの間には火花放電ギャップｇが形成される。 FIG. 1 is a cross-sectional view showing an example of a spark plug. As shown in the figure, the spark plug 100 has a cylindrical metallic shell 111 and a through hole 116 formed along the axial direction of the metallic shell 111, and both ends 112 a and 112 b are exposed from the metallic shell 111. The insulator 112 fitted and held in the metal shell 111 and the center electrode inserted and fixed to one end (downward in the figure) 116a of the through-hole 116 so that the tip 113a is exposed. 113, a terminal fitting 117 inserted and fixed to the other end portion (upper side in the figure) 116b of the through hole 116 so that the rear end portion 117a is exposed, and the center electrode 113 and the terminal fitting 117 in the through hole 116. A resistor 118 provided between the center electrode 113 and the terminal fitting 117 and spaced apart in the axial direction; and the resistor 118 in the through-hole 116. A first conductive glass seal layer 119 provided with no gap between the core electrode 113 and a second conductive glass provided with no gap between the resistor 118 and the terminal fitting 117 in the through hole 116. One end portion (base portion) 114a is joined to the seal layer 120 and the metal shell 111 by resistance welding or the like, and the intermediate portion 114c is bent, and the other end portion 114b is disposed to face the front end portion 113a of the center electrode 113. And a letter-shaped ground electrode 114. Further, on the outer peripheral surface of the metal shell 111, a male screw 115 for attachment to be attached to a cylinder head (a mating member) of an internal combustion engine such as an engine is formed in the circumferential direction. Further, a noble metal tip 121 is fixed to the tip of the center electrode 113 by laser welding or the like, a noble metal tip 122 is also fixed to the ground electrode 114, and a spark discharge gap g is formed between both base poison tips. The

上記の中心電極１１３を製造するには、図２に示す一例の工程に従うことができる。尚、図２に示す各工程について、図３〜図９を基にその詳細を説明する。 In order to manufacture the center electrode 113 described above, an example process shown in FIG. 2 can be followed. Details of each step shown in FIG. 2 will be described with reference to FIGS.

（第１製造工程）
初めに、耐熱性および耐食性に優れたニッケルまたはニッケル合金等の第１金属材製の線材から円柱状の素材を切断する。そして、図３に示すように、この素材を金型１の丸穴１ａ内に挿入してパンチ２で平行打ちすることによって、断面形状が円柱形状のビレット３を形成する。このとき、ビレット３の先端部の外周には円弧状のコーナー４が成形され、ビレット３の後端面には平坦面５が成形される。ここで、２ａは成形後のビレット３を金型１の丸穴１ａ内から突き出すためのキックアウトピンである。 (First manufacturing process)
First, a cylindrical material is cut from a wire made of a first metal material such as nickel or a nickel alloy having excellent heat resistance and corrosion resistance. Then, as shown in FIG. 3, this material is inserted into the round hole 1 a of the mold 1 and hit in parallel with the punch 2, thereby forming a billet 3 having a cylindrical cross section. At this time, an arcuate corner 4 is formed on the outer periphery of the tip of the billet 3, and a flat surface 5 is formed on the rear end surface of the billet 3. Here, 2a is a kick-out pin for projecting the billet 3 after molding from the round hole 1a of the mold 1.

（第２製造工程）
次に、図４に示すように、このビレット３を金型６の丸穴６ａ内に挿入してパンチ７で強く押して、断面形状が円柱形状のビレット８を形成する。このとき、ビレット８の後端面には略円形状の下孔９が成形される。ここで、７ａは成形後のビレット８を金型６の丸穴６ａ内から突き出すためのキックアウトピンである。 (Second manufacturing process)
Next, as shown in FIG. 4, the billet 3 is inserted into the round hole 6 a of the mold 6 and pressed strongly by the punch 7 to form a billet 8 having a cylindrical cross-sectional shape. At this time, a substantially circular prepared hole 9 is formed on the rear end face of the billet 8. Here, 7a is a kick-out pin for projecting the billet 8 after molding from the round hole 6a of the mold 6.

（第３製造工程）
次に、図５に示すように、このビレット８を金型１０の丸穴１０ａ内に挿入して下孔９をパンチ１１でさらに穿つことによって、図２（ｂ）に示すように、断面形状が円筒形状のカップ１２を形成する。このとき、カップ１２の内部には、先端が閉塞され、後端が開口した軸方向穴（凹部）１３が成形される。ここで、１１ａは成形後のカップ１２を金型１０の丸穴１０ａ内から突き出すためのキックアウトピンである。 (Third manufacturing process)
Next, as shown in FIG. 5, the billet 8 is inserted into the round hole 10 a of the mold 10, and the lower hole 9 is further punched with the punch 11. Forms a cylindrical cup 12. At this time, an axial hole (concave portion) 13 having a front end closed and a rear end opened is formed inside the cup 12. Here, 11a is a kick-out pin for protruding the molded cup 12 from the round hole 10a of the mold 10.

（第４製造工程）
一方、熱伝導性に優れた銅または銅合金等の第２金属材に塑性加工を施すことにより、図２（ａ）に示すように、断面形状が円柱形状の軸芯１４を形成する。この軸芯１４には、先端側にカップ１２の軸方向穴１３の深さよりやや長い軸方向寸法で、且つ軸方向穴１３の内径とほぼ同じ外径を持つ軸状の円柱部１５、および後端側に円柱部１５より外径が大きい円板部１５ａが成形される。 (4th manufacturing process)
On the other hand, by performing plastic working on the second metal material such as copper or copper alloy having excellent thermal conductivity, as shown in FIG. 2A, an axial core 14 having a cylindrical cross section is formed. The axial core 14 has an axial columnar portion 15 having an axial dimension slightly longer than the depth of the axial hole 13 of the cup 12 on the front end side and an outer diameter substantially the same as the inner diameter of the axial hole 13, and the rear A disc portion 15a having an outer diameter larger than that of the cylindrical portion 15 is formed on the end side.

（第５製造工程）
次に、図６に示したように、カップ１２の軸方向穴１３内に軸芯１４の円柱部１５を挿入してなる複合体を、金型１７の丸穴１７ａ内に挿入してパンチ１６で平行打ちすることによって、図２（ｃ）に示すように、ワーク１８を形成する。このとき、軸芯１４は、円板部１５ａが軸方向穴１３の後端面より突出した状態でカップ１２内に緊密的に保持される。ここで、１６ａは成形後の第１複合材１８を金型１７の丸穴１７ａ内から突き出すためのキックアウトピンである。 (Fifth manufacturing process)
Next, as shown in FIG. 6, a composite formed by inserting the cylindrical portion 15 of the shaft core 14 into the axial hole 13 of the cup 12 is inserted into the round hole 17 a of the mold 17, and the punch 16. 2 to form a workpiece 18 as shown in FIG. 2 (c). At this time, the shaft core 14 is tightly held in the cup 12 with the disk portion 15a protruding from the rear end face of the axial hole 13. Here, 16 a is a kick-out pin for projecting the first composite material 18 after molding from the round hole 17 a of the mold 17.

（第６製造工程）
次に、図７に示すように、ワーク１８を、その縮径部（図１０におけるテーパ面１２ｃ）の側から金型１９の丸穴１９ａ内に挿入してパンチ２０で押し込んで前方押出し成形することによって、ワーク１８の先端側を細径化して、図２（ｄ）に示すように、丸棒状の押出し成形体２１を形成する。この押出し成形体２１の先端側にはワーク１８より外径が小さい丸軸状の軸状部（φｄ１：例えばφ２．６）２２が成形され、後端側には前方押出し成形が施されない残部２３が成形される。 (Sixth manufacturing process)
Next, as shown in FIG. 7, the workpiece 18 is inserted into the round hole 19 a of the mold 19 from the reduced diameter portion (tapered surface 12 c in FIG. 10) and pushed by the punch 20 to be forward extruded. As a result, the tip end side of the work 18 is reduced in diameter to form a round bar-like extruded product 21 as shown in FIG. A round shaft-shaped shaft portion (φd1: for example, φ2.6) 22 having an outer diameter smaller than that of the workpiece 18 is formed on the front end side of the extrusion-molded body 21, and a remaining portion 23 not subjected to forward extrusion molding is formed on the rear end side. Is formed.

（第７製造工程）
次に、押出し成形体２１の後端側の残部２３を含む部分２４を切断することにより、図２（ｅ）に示すように、ワーク１８を細径化した第１の柱状部材２５を形成する。 (Seventh manufacturing process)
Next, by cutting the portion 24 including the remaining portion 23 on the rear end side of the extruded molded body 21, as shown in FIG. 2E, the first columnar member 25 in which the workpiece 18 is reduced in diameter is formed. .

（第８製造工程）
次に、図８に示すように、第１の柱状部材２５を金型２６の丸穴２６ａ内に挿入してパンチ２７で押し込んで前方押出し成形することによって、第１の柱状部材２５の先端側をさらに細径化して、図２（ｆ）に示すように、段付の第２の柱状部材２８を形成する。この第２の柱状部材２８の軸状部２２の先端側には、軸状部２２よりも外径が小さい丸軸状の径小部（φｄ３：例えばφ２．０）２９が成形される。 (Eighth manufacturing process)
Next, as shown in FIG. 8, the first columnar member 25 is inserted into the round hole 26 a of the mold 26, pushed in with the punch 27, and forward-extruded to form the front end side of the first columnar member 25. As shown in FIG. 2F, the stepped second columnar member 28 is formed. On the distal end side of the shaft-shaped portion 22 of the second columnar member 28, a round shaft-shaped small diameter portion (φd3: φ2.0) 29 having an outer diameter smaller than that of the shaft-shaped portion 22 is formed.

（第９製造工程）
次に、図９に示したように、第２の柱状部材２８を丸穴形状の金型３０の丸穴３０ａ内に挿入してパンチ３１で押し込んで押通し成形することによって、第２の柱状部材２８の軸状部２２の先端側をさらに細径化して、図２（ｇ）に示すように、２段付の第３の柱状部材３２を形成する。この第３の柱状部材３２の軸状部２２と径小部２９との間には、軸状部２２よりも外径が小さく、径小部２９よりも外径が大きい段部としての丸軸状の径中部（φｄ２：例えばφ２．５）３３が成形され、且つ第３の柱状部材３２の後端側には鍔部３４が成形される。第３の柱状部材３２は中心電極４１（図１参照）として使用される。ここで、３１ａは成形後の第４複合材３２を金型３０の待つ穴３０ａから突き出すためのキックアウトピンである。 (9th manufacturing process)
Next, as shown in FIG. 9, the second columnar member 28 is inserted into the round hole 30 a of the round hole-shaped mold 30, pushed in with the punch 31, and pressed to form the second columnar member. The tip end side of the shaft-like portion 22 of the member 28 is further reduced in diameter to form a second stepped third columnar member 32 as shown in FIG. A round shaft as a step portion between the shaft-like portion 22 and the small-diameter portion 29 of the third columnar member 32 having a smaller outer diameter than the shaft-like portion 22 and a larger outer diameter than the small-diameter portion 29. A diameter middle portion (φd2: φ2.5, for example) 33 is formed, and a collar portion 34 is formed on the rear end side of the third columnar member 32. The third columnar member 32 is used as the center electrode 41 (see FIG. 1). Here, 31a is a kickout pin for protruding the molded fourth composite material 32 from the hole 30a where the mold 30 waits.

本発明では、押し出し抵抗を下げるために、ワーク１８（図２（ｃ）参照）のカップ１２の太径部（以下「側面」）１２ａ、一方の端面（以下「底面」）１２ｂ、及び側面１２ａから底面１２ｂに向かって漸次縮径する縮径部（以下「テーパ面」）１２ｃにメッキ膜を形成するが、その際、テーパ面１２ｃ、並びにテーパ面１２ｃと底面１２ｂとの境界部Ａのメッキ膜を、側面１２ａのメッキ膜よりも厚く形成する。好ましくは、境界部Ａのメッキ膜を最も厚く形成する。 In the present invention, in order to lower the extrusion resistance, the large-diameter portion (hereinafter referred to as “side surface”) 12a of the cup 12 of the workpiece 18 (see FIG. 2C), one end surface (hereinafter referred to as “bottom surface”) 12b, and the side surface 12a. A plating film is formed on the reduced diameter portion (hereinafter referred to as “tapered surface”) 12c that gradually decreases in diameter from the bottom surface 12b to the bottom surface 12b. At this time, the tapered surface 12c and the plating on the boundary portion A between the tapered surface 12c and the bottom surface 12b are formed. The film is formed thicker than the plating film on the side surface 12a. Preferably, the plating film at the boundary portion A is formed to be the thickest.

上記した押出工程では、図７に示す第１段の押出成形によりワーク１８を押出して第１の柱状部材２５を成形した後、図８に示す第２段の押出成形により第１の柱状部材２５の軸状部２２を更に細径化して径小部２９を形成する。その際、第１段の押出成形において、ワーク１８の軸線方向の変形量は、側面１２ａよりもテーパ面１２ｃ及び境界部Ａの方が大きく、更に第２段の押出成形においてはテーパ面１２よりも境界部Ａの方が大きい。そこで、ワーク１８のテーパ面１２ｃ及び境界部Ａのメッキ膜を側面１２ａのメッキ膜よりも厚く、更には境界部Ａのメッキ膜を最も厚くすることにより、第１段及び第２段の押出工程において、ワーク１８の主たる変形部分にメッキ膜が残存した状態で押出しが行われるようになる。その結果、縦傷の発生も抑えられる。 In the above-described extrusion process, the first columnar member 25 is formed by extruding the workpiece 18 by forming the first columnar member 25 by the first-stage extrusion molding shown in FIG. 7, and then the first columnar member 25 by the second-stage extrusion molding shown in FIG. The shaft portion 22 is further reduced in diameter to form a small diameter portion 29. At that time, in the first-stage extrusion, the amount of deformation of the workpiece 18 in the axial direction is larger in the tapered surface 12c and the boundary portion A than in the side surface 12a, and in the second-stage extrusion, more than the tapered surface 12. Is larger at the boundary A. Therefore, the taper surface 12c of the workpiece 18 and the plating film on the boundary portion A are thicker than the plating film on the side surface 12a, and further, the plating film on the boundary portion A is made thickest, so that the first step and the second step extrusion process. Then, extrusion is performed with the plating film remaining in the main deformed portion of the workpiece 18. As a result, the occurrence of vertical scratches can be suppressed.

従来でもワーク１８のカップ１２の側面１２ａやテーパ面１２ｃ、底面１２ｂにメッキ膜を設けることが行われているが、メッキ膜の厚さは各部で一様であるため、多段の押出しを行うと、後段になるほどメッキ膜が無くなって縦傷が発生しやすくなる。しかし、本発明によれば、上記のようにメッキ膜が十分に残存するので縦傷を発生することなく押出しを行うことができる。 Conventionally, a plating film is provided on the side surface 12a, the tapered surface 12c, and the bottom surface 12b of the cup 12 of the work 18, but since the thickness of the plating film is uniform in each part, multi-stage extrusion is performed. In the later stage, the plating film disappears and vertical scratches are more likely to occur. However, according to the present invention, since the plating film remains sufficiently as described above, the extrusion can be performed without causing a vertical flaw.

成形時のメッキ膜の剥離を無くして縦傷を発生し難くする効果を確実にするためには、押し出しによる変形量に合わせて側面１２ａのメッキ膜と、テーパ面１２ｂｃ及び境界部１２ｂのメッキ膜との膜厚差を設定すればよいが、実用上は、テーパ面１２ｃ及び境界部Ａのメッキ膜の厚さを、側面１２ａのメッキ膜の厚さの１．５〜３倍にすることが好ましい。テーパ面１２ｃ及び境界部Ａのメッキ膜の厚さをこれより厚くしても更なる押し出し抵抗の低減は見込めず、むしろメッキ膜が剥離しやすくなる。また、この範囲において、境界部Ａのメッキ膜を最も厚くする。 In order to eliminate the peeling of the plating film at the time of molding and to ensure the effect of preventing the occurrence of vertical flaws, the plating film on the side surface 12a and the plating film on the tapered surface 12bc and the boundary portion 12b according to the amount of deformation due to extrusion. However, in practice, the thickness of the plating film on the taper surface 12c and the boundary portion A may be 1.5 to 3 times the thickness of the plating film on the side surface 12a. preferable. Even if the thickness of the plating film on the taper surface 12c and the boundary portion A is made thicker than this, further reduction of the extrusion resistance cannot be expected, but rather the plating film is easily peeled off. In this range, the plating film at the boundary A is made thickest.

また、側面１２ａのメッキ膜の厚さは１０μｍ以下にすることが好ましく、５μｍ以下にすることがより好ましい。尚、側面１２ａのメッキ膜の膜厚の下限は、押し出し抵抗を低減する効果を確実にし、更に成形時のメッキ膜の剥離を無くして縦傷を発生し難くするために、０．３μｍ以上とするのが好ましい。 Further, the thickness of the plating film on the side surface 12a is preferably 10 μm or less, and more preferably 5 μm or less. Note that the lower limit of the thickness of the plating film on the side surface 12a is 0.3 μm or more in order to ensure the effect of reducing the extrusion resistance and to prevent the occurrence of vertical scratches by eliminating the peeling of the plating film during molding. It is preferable to do this.

尚、本発明においてメッキ膜の厚さとは、側面１２ａやテーパ面１２ｃについては、メッキ後のワークの軸線を通る軸線方向の断面を、日本電子株式会社製のＳＥＭ（型式：ＪＳＭ−６４６０ＬＡ）を用いて倍率５０００倍で観察し、複数箇所（例えば１０点）でメッキ膜厚を測定し、平均した値である。境界部Ａについては、テーパ面１２ｃと側面１２ｂとの境界は円周であるため、円周上を同様にＳＥＭ観察して複数箇所でメッキ膜厚を測定し、平均した値である。 In the present invention, the thickness of the plating film refers to the cross section in the axial direction passing through the axis of the workpiece after plating with respect to the side surface 12a and the tapered surface 12c, and SEM (model: JSM-6460LA) manufactured by JEOL Ltd. It is observed at a magnification of 5000 times, and the plating film thickness is measured at a plurality of locations (for example, 10 points) and averaged. Regarding the boundary portion A, since the boundary between the tapered surface 12c and the side surface 12b is the circumference, the SEM observation is similarly performed on the circumference, and the plating film thickness is measured at a plurality of locations and averaged.

このように側面１２ａ、底面１２ｂ、テーパ面１２ｃ及び境界部Ａに膜厚を変えてメッキ膜を形成するには、例えば、マスキングしてメッキする方法がある。カップ１２の全面に一様にメッキ膜を形成した後、膜厚を増したい部分以外をマスキングし、再度メッキしてもよいし、膜厚を増したい部分以外をマスキングしてメッキした後、マスキングを剥がして全体を再度メッキしてもよい。具体的には、例えば、ワーク１８のカップ１２をメッキ液に浸漬して電解メッキして側面１２ａ、テーパ面１２ｃ及び底面１２ｂに同一の膜厚にてメッキ膜を形成した後、側面１２ａ及び底面１２ｂをマスキングして再度メッキ液に浸漬して電解メッキを行うことにより、テーパ面１２ｃ及び境界部Ａのメッキ膜を側面１２ａのメッキ膜よりも厚くすることができる。尚、メッキ膜の膜厚は、メッキ時間を調整することにより調整できる。 In order to form a plating film by changing the film thickness on the side surface 12a, the bottom surface 12b, the tapered surface 12c and the boundary portion A in this way, for example, there is a method of plating by masking. After the plating film is uniformly formed on the entire surface of the cup 12, masking may be performed on portions other than the portion where the film thickness is desired to be increased, and plating may be performed again. May be removed and the whole may be plated again. Specifically, for example, after the cup 12 of the work 18 is immersed in a plating solution and electrolytically plated to form a plating film with the same film thickness on the side surface 12a, the tapered surface 12c, and the bottom surface 12b, the side surface 12a and the bottom surface are formed. By masking 12b and immersing it again in a plating solution and performing electrolytic plating, the plating film on the taper surface 12c and the boundary portion A can be made thicker than the plating film on the side surface 12a. The film thickness of the plating film can be adjusted by adjusting the plating time.

メッキ膜の材質は潤滑性を有する限り制限はないが、白金、金、銀、銅、錫及び亜鉛のうち少なくとも一種を主成分とする金属であることが好ましい（なお、「主成分」とあるのは、材料中において、最も含有量が多いことを意味する）。特に金は展性に優れることから、押出しによる変形に良好に追随でき、薄いメッキ膜でも十分な効果が得られる。また、銅や錫、亜鉛は安価である。 The material of the plating film is not limited as long as it has lubricity, but is preferably a metal containing at least one of platinum, gold, silver, copper, tin and zinc as a main component (note that “main component” is included). Means the highest content in the material). In particular, since gold is excellent in malleability, it can follow the deformation due to extrusion well, and a sufficient effect can be obtained even with a thin plating film. Copper, tin, and zinc are inexpensive.

また、中心電極４１では近年、耐食性を向上させるために、クロム含有量を高めたニッケル合金が使用される傾向にある。クロム含有量が多いほど耐食性に優れ、クロム含有量が１０質量％以上のニッケル合金が使用されてきており、中にはクロム含有量が２０質量％以上のニッケル合金も使用されている。例えば、鉄を８重量％、クロムを１６重量％、銅を０．２重量％含有し、残部ニッケルとするインコネル６００（商標名）等が多用されている。しかし、クロム高含有ニッケル合金は変形し難く、このクロム高含有ニッケル合金製のカップ１２を用いたワーク１８を押出成形すると縦傷が発生しやすい。しかし、本発明によれば、テーパ面１２ｃ及び境界部Ａのメッキ膜を厚くすることにより縦傷の発生を抑えることができるため、ニッケルを主成分とし、クロムを１０質量％以上含有する合金製のカップ１２を用いたワーク１８を用いた場合に有用であり、クロムを２０％以上含有するニッケル合金製のカップ１２に用いた場合に特に有用である。 Further, in recent years, a nickel alloy having a high chromium content tends to be used for the center electrode 41 in order to improve the corrosion resistance. As the chromium content is higher, the corrosion resistance is more excellent, and nickel alloys having a chromium content of 10% by mass or more have been used. Among them, nickel alloys having a chromium content of 20% by mass or more are also used. For example, Inconel 600 (trade name) containing 8% by weight of iron, 16% by weight of chromium, 0.2% by weight of copper, and the balance being nickel is frequently used. However, the chromium-rich nickel alloy is not easily deformed, and if the workpiece 18 using the cup 12 made of the chromium-rich nickel alloy is extruded, vertical flaws are likely to occur. However, according to the present invention, since the occurrence of vertical scratches can be suppressed by increasing the thickness of the plating film on the tapered surface 12c and the boundary portion A, the alloy is made of nickel as a main component and containing 10 mass% or more of chromium. This is useful when the workpiece 18 using the cup 12 is used, and is particularly useful when used for the cup 12 made of nickel alloy containing 20% or more of chromium.

また、クロムを２０％以上含有するニッケル合金製のカップ１２に用いた場合は、側面１２ａのメッキ膜の膜厚を５μｍ以下にしても縦傷の発生を抑えることができる。 Further, when used in a nickel alloy cup 12 containing 20% or more of chromium, the occurrence of vertical scratches can be suppressed even if the thickness of the plating film on the side surface 12a is 5 μm or less.

クロム含有量が多くなると、メッキ膜が酸化して不動態が形成されやすくなり、メッキ膜の密着性が悪くなる。また、メッキ膜は、その膜厚が厚いほど剥離しやすいため、上記のようにクロム含有量が１０質量％以上に多くなると、膜厚を薄くする必要がある。そこで、側面１２ａのメッキ膜の膜厚を１０μｍ以下にしてメッキ膜の剥離を抑えるとともに、テーパ面１２ｃ及び境界部Ａのメッキ膜を厚くすることにより、ワーク変形時にメッキ膜が残存するようにする。 When the chromium content is increased, the plating film is oxidized and a passive state is easily formed, and the adhesion of the plating film is deteriorated. Moreover, since the plating film is more easily peeled off as the film thickness increases, it is necessary to reduce the film thickness when the chromium content increases to 10% by mass or more as described above. Therefore, the plating film on the side surface 12a is set to 10 μm or less to suppress the peeling of the plating film, and the plating film on the taper surface 12c and the boundary portion A is made thick so that the plating film remains when the workpiece is deformed. .

尚、テーパ面１２ｃ及び境界部Ａのメッキ膜の膜厚を、側面１２ａのメッキ膜の膜厚の１．５〜３倍にすることが好ましいとする規定によれば、側面１２ａのメッキ膜の膜厚を最大の１０μｍにした場合、テーパ面１２ｃ及び境界部Ａのメッキ膜の膜厚は最大で３０μｍとなる。しかし、テーパ面１２ｃ及び境界部Ａのメッキ膜の膜厚を最大で３０μｍにすることは、側面１２ａのメッキ膜の膜厚を１０μｍ以下にすることとは矛盾しない。 According to the regulation that the thickness of the plating film on the tapered surface 12c and the boundary portion A is preferably 1.5 to 3 times the thickness of the plating film on the side surface 12a, the plating film on the side surface 12a When the film thickness is 10 μm at the maximum, the film thickness of the plating film on the tapered surface 12 c and the boundary portion A is 30 μm at the maximum. However, the maximum thickness of the plating film on the tapered surface 12c and the boundary A is 30 μm, which is consistent with the thickness of the plating film on the side surface 12a being 10 μm or less.

以上、中心電極１１３の製造を例にした実施態様を説明したが、接地電極１１４についても押出成形により作製する場合は、電極材料からなるワークを、上記と同様にメッキ膜の厚さを調整することにより、縦傷を発生することなく、円滑に押し出すことができるようになる。接地電極１１４を押出成形する場合、ワークを押し出して縮径し、全体が同一太さの、あるいは先端に向かうほど細くなる柱状体とした後、先端側端部が中心電極の先端と対向するように湾曲するが、ワークを押し出す際に縦傷が発生することが多い。そこで、上記のようにメッキ膜を調整することにより、押し出し時の縦傷の発生を抑えることができるようになる。 In the above, the embodiment in which the production of the center electrode 113 is taken as an example has been described. However, when the ground electrode 114 is produced by extrusion molding, the thickness of the plating film is adjusted in the same manner as above for the workpiece made of the electrode material As a result, it can be pushed out smoothly without causing vertical flaws. When the ground electrode 114 is extruded, the workpiece is extruded and reduced in diameter so that the entire body has the same thickness or becomes a columnar body that becomes narrower toward the tip, and the tip side end faces the tip of the center electrode. In many cases, vertical scratches occur when the workpiece is pushed out. Therefore, by adjusting the plating film as described above, it is possible to suppress the occurrence of vertical scratches during extrusion.

また、上記ではワーク１８をカップ１２と軸芯１４との複合部材としたが、ニッケル合金の単一部材であってもよい。 Moreover, although the workpiece | work 18 was made into the composite member of the cup 12 and the axial core 14 in the above, the nickel alloy single member may be sufficient.

更に、本発明によれば、上記の如く押出成形により中心電極４１や接地電極４５を用い、例えば図１に示したようなスパークプラグ４２を組み立てることができる。中心電極４１や接地電極４５以外の部材は従来と同様にして作製することができ、それらの組み立ても従来と同様で構わない。 Furthermore, according to the present invention, the spark plug 42 as shown in FIG. 1 can be assembled using the center electrode 41 and the ground electrode 45 by extrusion as described above. Members other than the center electrode 41 and the ground electrode 45 can be produced in the same manner as in the past, and their assembly may be the same as in the past.

尚、上記では接地電極１１４が単極のスパークプラグを例示したが、接地電極１１４を複数設けた多極接地電極のスパークプラグであってもよい。 In the above description, the ground electrode 114 is a unipolar spark plug, but a multipolar ground electrode spark plug having a plurality of ground electrodes 114 may be used.

以下に試験例を挙げて本発明を更に説明するが、本発明はこれにより何ら制限されるものではない。 Hereinafter, the present invention will be further described with reference to test examples, but the present invention is not limited thereto.

（試験１：側面のメッキ厚の検証）
表１に示すように、クロム含有量の異なるニッケル合金でカップを作製し、銅合金からなる軸芯と複合化して図１０に示すようなテーパ面を有するワークを作製した。そして、ワークを銅メッキ液に浸漬し、側面のメッキ膜の厚さが表１に示す厚さになるように銅メッキ膜を形成した。尚、メッキ膜の膜厚は、ワークの側面を、日本電子株式会社製のＳＥＭ（型式：ＪＳＭ−６４６０ＬＡ）を用いて倍率５０００倍で観察し、任意の１０点でメッキ膜厚を測定し、平均した値である。 (Test 1: Verification of side plating thickness)
As shown in Table 1, cups were made of nickel alloys having different chromium contents, combined with an axial core made of a copper alloy, and a workpiece having a tapered surface as shown in FIG. 10 was produced. Then, the work was immersed in a copper plating solution, and a copper plating film was formed so that the thickness of the plating film on the side surface was as shown in Table 1. In addition, the film thickness of the plating film was observed at a magnification of 5000 using the SEM (model: JSM-6460LA) manufactured by JEOL Ltd., and the plating film thickness was measured at any 10 points. The average value.

そして、上記の如く銅メッキ膜が成膜されたワークを各１００個用意して押出成形を行い、銅メッキ膜が剥離したワークの個数を求めた。結果を表１に併記する。 Then, 100 workpieces each having the copper plating film formed as described above were prepared and extruded to obtain the number of workpieces from which the copper plating film was peeled off. The results are also shown in Table 1.

ワークのクロムの含有量が増すほど、メッキ剥離が多くなる傾向になることがわかる。また、銅メッキ膜の膜厚が０．３〜１０μｍの範囲で、メッキ剥離を抑える効果が発現することがわかる。更に、クロムを２０質量％含有するニッケル合金からなるワークでは、側面のメッキ膜の膜厚が５μｍ以下であれば、メッキ剥離を抑えることができる。 It can be seen that as the chromium content of the workpiece increases, the plating peeling tends to increase. Moreover, it turns out that the effect which suppresses plating peeling expresses in the range whose film thickness of a copper plating film is 0.3-10 micrometers. Furthermore, in a workpiece made of a nickel alloy containing 20% by mass of chromium, plating peeling can be suppressed if the thickness of the plating film on the side surface is 5 μm or less.

（試験２：側面と境界部とのメッキ厚差の検証）
クロム含有量が２０質量％のニッケル合金でカップを作製し、銅合金からなる軸芯と複合化して図１０に示すようなテーパ面を有するワークを作製した。そして、ワークの側面のメッキ膜（Ｘ）と境界部のメッキ膜（Ｙ）がそれぞれ表２に示す厚さになるように銅メッキ膜を形成した。このような膜厚差とするには、ワーク全体に均一に銅メッキ膜を形成した後、境界部を露出させて側面と底面とをマスキングし、再度電解メッキを行った。尚、メッキ膜の膜厚は、ワークの側面及び境界部を、日本電子株式会社製のＳＥＭ（型式：ＪＳＭ−６４６０ＬＡ）を用いて倍率５０００倍で観察し、任意の１０点でメッキ膜厚を測定し、平均した値である。 (Test 2: Verification of plating thickness difference between side and boundary)
A cup was made of a nickel alloy having a chromium content of 20% by mass and combined with an axial core made of a copper alloy to produce a workpiece having a tapered surface as shown in FIG. Then, a copper plating film was formed so that the plating film (X) on the side surface of the workpiece and the plating film (Y) at the boundary part had thicknesses shown in Table 2, respectively. In order to achieve such a film thickness difference, after a copper plating film was uniformly formed on the entire workpiece, the boundary portion was exposed to mask the side surface and the bottom surface, and electrolytic plating was performed again. In addition, the film thickness of the plating film was observed at a magnification of 5000 times using a SEM (model: JSM-6460LA) manufactured by JEOL Ltd., and the plating film thickness was measured at any 10 points. It is the value measured and averaged.

そして、上記の如く銅メッキ膜が成膜されたワークを各１００個用意して押出成形を行い、縦傷が発生したワークの個数を求めた。結果を表２に併記する。 Then, 100 workpieces each having a copper plating film formed as described above were prepared and extruded, and the number of workpieces with vertical flaws was determined. The results are also shown in Table 2.

側面のメッキ膜と境界部とのメッキ膜の膜厚差（Ｙ／Ｘ）が１．５倍未満になると、ワークの変形量が大きい境界部でメッキ量が不足して縦傷が発生しやすくなる。一方、膜厚差（Ｙ／Ｘ）が３倍超になると、メッキ膜の膜厚差が大きすぎてワークの変形にメッキ膜が追随しにくくなり、メッキ膜が剥離する箇所が生じて縦傷がより多く発生するようになる。これに対し、膜厚差（Ｙ／Ｘ）が１．５〜３倍の範囲では、ワークの伸張にメッキ膜が良好に追従してメッキ膜の剥離もなく、縦傷が発生しにくくなる。 If the film thickness difference (Y / X) between the plating film on the side surface and the boundary is less than 1.5 times, the amount of plating is insufficient at the boundary where the amount of deformation of the workpiece is large, and vertical scratches are likely to occur. Become. On the other hand, if the film thickness difference (Y / X) exceeds three times, the film thickness difference of the plating film is too large, making it difficult for the plating film to follow the deformation of the workpiece, resulting in a part where the plating film is peeled off and causing vertical scratches. Will occur more often. On the other hand, when the film thickness difference (Y / X) is in the range of 1.5 to 3 times, the plating film follows the work extension well, and there is no peeling of the plating film, and vertical scratches are less likely to occur.

１２カップ
１２ａ側面
１２ｂ底面
１２ｃテーパ面
１４軸芯
１８ワーク
２２軸状部
２５第１の柱状部材
２８第２の柱状部材
２９径小部
３２第３の柱状部材
３３径中部
３４鍔部
１００スパークプラグ
１１３中心電極
１１４接地電極
Ａ境界部 12 Cup 12a Side surface 12b Bottom surface 12c Tapered surface 14 Axle core 18 Work 22 Shaft-shaped portion 25 First columnar member 28 Second columnar member 29 Small diameter portion 32 Third columnar member 33 Diameter middle portion 34 Gutter portion 100 Spark plug 113 Center electrode 114 Ground electrode A Boundary part

Claims

A preparation step of preparing a columnar workpiece having a large diameter portion and a reduced diameter portion at one end surface thereof;
A plating step of forming a plating film on the workpiece;
An extrusion process for extruding the workpiece on which the plating film is formed;
A method for producing an electrode for a spark plug comprising:
In the plating process, the plating film formed on the reduced diameter portion is formed thicker than the plating film formed on the large diameter portion.

2. The spark plug electrode according to claim 1, wherein the plated film formed at a boundary portion between the reduced diameter portion and an end surface thereof is formed to be the thickest in the plated film formed at the reduced diameter portion. Manufacturing method.

The method for manufacturing an electrode for a spark plug according to claim 1 or 2, wherein a thickness of the plating film formed on the large-diameter portion is 10 µm or less.

The thickness of the plating film formed on the reduced diameter portion and the boundary portion is 1.5 to 3 times the thickness of the plating film formed on the large diameter portion. 4. The method for producing an electrode for a spark plug according to any one of 3 above.

The method for manufacturing an electrode for a spark plug according to any one of claims 1 to 4, wherein the workpiece is a metal containing nickel as a main component and containing 10 mass% or more of chromium.

6. The method for manufacturing an electrode for a spark plug according to claim 5, wherein the workpiece is a metal containing nickel as a main component and containing chromium by 20% by mass or more.

The method for manufacturing an electrode for a spark plug according to claim 6, wherein a thickness of the plating film formed on the large-diameter portion is 5 μm or less.

The electrode for a spark plug according to any one of claims 1 to 7, wherein the plating film is a metal mainly composed of at least one of platinum, gold, silver, copper, tin, and zinc. Manufacturing method.

The method for producing an electrode for a spark plug according to any one of claims 1 to 8, wherein a thickness of the plating film formed on the large diameter portion is 0.3 µm or more.

An insulator having an axial hole extending in the axial direction;
A center electrode held in the shaft hole;
A metal shell provided on the outer periphery of the insulator;
A method for producing a spark plug comprising a base electrode joined to the metal shell, and a ground electrode that forms a gap between the tip and the tip of the center electrode,
A method for manufacturing a spark plug, comprising a step of manufacturing at least one of the center electrode and the ground electrode by the method according to any one of claims 1 to 9.