JP6781141B2 - Spark plug - Google Patents

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JP6781141B2
JP6781141B2 JP2017235958A JP2017235958A JP6781141B2 JP 6781141 B2 JP6781141 B2 JP 6781141B2 JP 2017235958 A JP2017235958 A JP 2017235958A JP 2017235958 A JP2017235958 A JP 2017235958A JP 6781141 B2 JP6781141 B2 JP 6781141B2
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insulator
tip
peripheral surface
metal fitting
main metal
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JP2019102409A (en
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鳥居　計良
計良 鳥居
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NGK Spark Plug Co Ltd
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NGK Spark Plug Co Ltd
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Priority to JP2017235958A priority Critical patent/JP6781141B2/en
Priority to CN201811488055.6A priority patent/CN110011183B/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/02—Details
    • H01T13/06—Covers forming a part of the plug and protecting it against adverse environment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T13/00—Sparking plugs
    • H01T13/20—Sparking plugs characterised by features of the electrodes or insulation

Description

本発明はスパークプラグに関し、特に耐汚損性を向上できるスパークプラグに関するものである。 The present invention relates to a spark plug, and more particularly to a spark plug capable of improving stain resistance.

スパークプラグは、一般に、筒状の主体金具に接合された接地電極と、軸線方向へ延びる筒状の絶縁体によって主体金具と隔てられた中心電極と、の間に火花放電を生じさせて内燃機関の燃焼室内の混合気に点火する。しかし、混合気の不完全燃焼等によって生じたカーボンが燃焼ガスにのって主体金具と絶縁体との間の隙間に侵入し、絶縁体の表面にカーボンが堆積して電極間の絶縁抵抗が低下し、要求電圧（火花放電が生じる電圧）よりも低い電圧でリークが生じると、火花放電が生じなくなる。絶縁体の汚損によるリークの発生を防ぐため、特許文献１には、主体金具と絶縁体との間の径方向の隙間を、軸線方向の中央の部分で最も拡大する技術が開示されている。 A spark plug is generally an internal combustion engine that generates a spark discharge between a ground electrode joined to a tubular main metal fitting and a center electrode separated from the main metal fitting by a tubular insulator extending in the axial direction. Ignite the air-fuel mixture in the combustion chamber. However, the carbon generated by the incomplete combustion of the air-fuel mixture gets on the combustion gas and invades the gap between the main metal fitting and the insulator, and the carbon is deposited on the surface of the insulator to increase the insulation resistance between the electrodes. If the voltage drops and a leak occurs at a voltage lower than the required voltage (voltage at which spark discharge occurs), spark discharge will not occur. In order to prevent the occurrence of leakage due to contamination of the insulator, Patent Document 1 discloses a technique for expanding the radial gap between the main metal fitting and the insulator most in the central portion in the axial direction.

特開２０１６−１８４５７１号公報JP-A-2016-184571

しかしながら上記従来の技術では、隙間に侵入した燃焼ガスが、隙間が拡大された部分で滞留し易いため、燃焼ガスにのったカーボンが絶縁体の表面に堆積して汚損が生じることがある。 However, in the above-mentioned conventional technique, since the combustion gas that has entered the gap tends to stay in the portion where the gap is expanded, carbon on the combustion gas may be deposited on the surface of the insulator to cause contamination.

本発明は上述した問題点を解決するためになされたものであり、耐汚損性を向上できるスパークプラグを提供することを目的としている。 The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a spark plug capable of improving stain resistance.

この目的を達成するために本発明のスパークプラグは、軸線に沿って先端側から後端側へと延びる軸孔が形成される絶縁体と、絶縁体から自身の先端を突出させて軸孔に配置される中心電極と、絶縁体の先端が自身の先端から突出するように絶縁体を外周側から保持する円筒状の主体金具と、主体金具に接続され中心電極との間に火花ギャップを形成する接地電極と、を備えている。主体金具は、径方向の内側へ向かって凸状に張り出す棚部を備え、絶縁体は、棚部の後端面に係止される係止部を備え、主体金具の先端と絶縁体との間の径方向の隙間の大きさをＬ０とし、主体金具のうち棚部よりも先端側の部分と絶縁体との間の径方向の隙間のうち最も小さい部分の大きさをＬとすると、０．９Ｌ０≦Ｌ≦Ｌ０を満たす。 In order to achieve this object, the spark plug of the present invention has an insulator in which a shaft hole extending from the front end side to the rear end side along the axis is formed, and an insulator having its own tip protruding from the insulator to form a shaft hole. A spark gap is formed between the center electrode to be arranged, the cylindrical main metal fitting that holds the insulator from the outer peripheral side so that the tip of the insulator protrudes from its own tip, and the center electrode that is connected to the main metal fitting. It is equipped with a ground electrode. The main metal fitting has a shelf portion that projects inward in the radial direction in a convex shape, and the insulator has a locking portion that is locked to the rear end surface of the shelf portion, and the tip of the main metal fitting and the insulator Assuming that the size of the radial gap between the main metal fittings is L 0 and the size of the smallest radial gap between the tip side of the main metal fitting and the insulator is L. Satisfy 0.9L 0 ≤ L ≤ L 0 .

請求項１記載のスパークプラグによれば、主体金具のうち棚部よりも先端側の部分と絶縁体との間の径方向の隙間のうち最も小さい部分の大きさＬは、主体金具の先端と絶縁体との間の径方向の隙間の大きさをＬ０とすると、０．９Ｌ０≦Ｌ≦Ｌ０を満たす。これにより、主体金具と絶縁体との隙間に侵入した燃焼ガスの掃気性を高めることができる。その結果、燃焼ガスに運ばれたカーボンが絶縁体の表面に堆積し難くできるので、耐汚損性を向上できる。 According to the spark plug according to claim 1, the size L of the smallest part of the radial gap between the tip side of the main metal fitting and the insulator is the tip of the main metal fitting. Assuming that the size of the radial gap between the insulator and the insulator is L 0 , 0.9 L 0 ≤ L ≤ L 0 is satisfied. As a result, the scavenging property of the combustion gas that has entered the gap between the main metal fitting and the insulator can be improved. As a result, the carbon carried to the combustion gas can hardly be deposited on the surface of the insulator, so that the stain resistance can be improved.

請求項２記載のスパークプラグによれば、主体金具の外周面に形成されたおねじの呼び径は１２ｍｍ以下である。おねじの呼び径が小さくなると主体金具と絶縁体との隙間の大きさＬも小さくなり、カーボンが絶縁体の表面に堆積することによる影響が大きくなる。よって、本発明の適用が特に効果的である。 According to the spark plug according to claim 2, the nominal diameter of the male screw formed on the outer peripheral surface of the main metal fitting is 12 mm or less. As the nominal diameter of the male screw becomes smaller, the size L of the gap between the main metal fitting and the insulator also becomes smaller, and the influence of carbon depositing on the surface of the insulator becomes larger. Therefore, the application of the present invention is particularly effective.

本発明の一実施の形態におけるスパークプラグの片側断面図である。It is one side sectional view of the spark plug in one Embodiment of this invention. 図１の一部を拡大したスパークプラグの断面図である。It is sectional drawing of the spark plug which enlarged a part of FIG.

以下、本発明の好ましい実施形態について添付図面を参照して説明する。図１は本発明の第１実施の形態におけるスパークプラグ１０の軸線Ｏを境にした片側断面図であり、図２は図１の一部を拡大したスパークプラグ１０の断面図である。図２では、軸線Ｏを境にした片側の図示が省略されている。図１及び図２では、紙面下側をスパークプラグ１０の先端側、紙面上側をスパークプラグ１０の後端側という。図１に示すようにスパークプラグ１０は、絶縁体１１、中心電極３０、主体金具４０及び接地電極５４を備えている。 Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a one-sided cross-sectional view of the spark plug 10 in the first embodiment of the present invention with the axis O as a boundary, and FIG. 2 is a cross-sectional view of the spark plug 10 in which a part of FIG. 1 is enlarged. In FIG. 2, the illustration on one side with the axis O as a boundary is omitted. In FIGS. 1 and 2, the lower side of the paper surface is referred to as the front end side of the spark plug 10, and the upper side of the paper surface is referred to as the rear end side of the spark plug 10. As shown in FIG. 1, the spark plug 10 includes an insulator 11, a center electrode 30, a main metal fitting 40, and a ground electrode 54.

図１に示すように絶縁体１１は、高温下の絶縁性や機械的特性に優れるアルミナ等により形成された略円筒状の部材である。絶縁体１１は、軸線Ｏに沿って軸孔が貫通する。軸孔を形成する絶縁体１１の内周面１２の先端側には、先端側に向かって縮径する後端向き面１３が形成されている。 As shown in FIG. 1, the insulator 11 is a substantially cylindrical member made of alumina or the like, which is excellent in insulating properties and mechanical properties at high temperatures. A shaft hole penetrates the insulator 11 along the axis O. On the tip end side of the inner peripheral surface 12 of the insulator 11 forming the shaft hole, a rear end facing surface 13 whose diameter is reduced toward the tip end side is formed.

絶縁体１１は、後端側から先端側へ順に、後端部１４、大径部１５、小径部１６及び先端部１７が連接されている。大径部１５は、絶縁体１１のうち外径が最も大きい部位である。小径部１６は、大径部１５よりも外径の小さい部位であり、小径部１６の先端側に、係止部１８（図２参照）を介して、小径部１６よりも外径の小さい先端部１７が隣接している。係止部１８は、先端側へ向かうにつれて縮径する。 In the insulator 11, the rear end portion 14, the large diameter portion 15, the small diameter portion 16, and the tip portion 17 are connected in this order from the rear end side to the front end side. The large diameter portion 15 is a portion of the insulator 11 having the largest outer diameter. The small diameter portion 16 is a portion having a smaller outer diameter than the large diameter portion 15, and the tip having an outer diameter smaller than that of the small diameter portion 16 is placed on the tip side of the small diameter portion 16 via a locking portion 18 (see FIG. 2). The parts 17 are adjacent to each other. The diameter of the locking portion 18 is reduced toward the tip side.

絶縁体１１の先端部１７のうち、後端側の外周面１９は先端側に向かうにつれて縮径している。絶縁体１１の先端部１７のうち、外周面１９の先端側に隣接する外周面２０は、軸線Ｏ方向に亘って外径が一定である。 Of the tip portion 17 of the insulator 11, the outer peripheral surface 19 on the rear end side is reduced in diameter toward the tip side. Of the tip portion 17 of the insulator 11, the outer peripheral surface 20 adjacent to the tip side of the outer peripheral surface 19 has a constant outer diameter along the axis O direction.

中心電極３０は、軸孔の先端側に挿入され軸線Ｏに沿って絶縁体１１に保持される棒状の電極である。中心電極３０は、軸線Ｏ方向に延びる軸部３１と、軸部３１に対して軸直角方向へ張り出す頭部３２と、が連接されている。頭部３２は後端向き面１３に係止されている。中心電極３０は、熱伝導性に優れる芯材が電極母材に埋設されている。電極母材は、Ｎｉを主体とする合金またはＮｉからなる金属材料で形成されており、芯材は銅または銅を主成分とする合金で形成されている。 The center electrode 30 is a rod-shaped electrode that is inserted into the tip end side of the shaft hole and held by the insulator 11 along the axis O. The center electrode 30 is connected to a shaft portion 31 extending in the axis O direction and a head portion 32 projecting in a direction perpendicular to the shaft portion 31. The head 32 is locked to the rear end facing surface 13. In the center electrode 30, a core material having excellent thermal conductivity is embedded in the electrode base material. The electrode base material is formed of an alloy mainly composed of Ni or a metal material composed of Ni, and the core material is formed of copper or an alloy containing copper as a main component.

端子金具３４は、高圧ケーブル（図示せず）が接続される棒状の部材であり、導電性を有する金属材料（例えば低炭素鋼等）によって形成されている。端子金具３４は先端側が絶縁体１１の軸孔に挿入される。端子金具３４は、導電性を有するガラスからなる導電性シール等によって、中心電極３０の頭部３２と電気的に接続されている。 The terminal fitting 34 is a rod-shaped member to which a high-voltage cable (not shown) is connected, and is made of a conductive metal material (for example, low carbon steel). The tip side of the terminal fitting 34 is inserted into the shaft hole of the insulator 11. The terminal fitting 34 is electrically connected to the head portion 32 of the center electrode 30 by a conductive seal or the like made of conductive glass.

主体金具４０は、導電性を有する金属材料（例えば低炭素鋼等）によって形成された略円筒状の部材である。主体金具４０は、絶縁体１１の先端部１７から小径部１６までを取り囲む胴部４１と、胴部４１の後端側に連接される座部４３と、座部４３の後端側に連接される接続部４４と、接続部４４の後端側に連接される工具係合部４５と、工具係合部４５の後端側に連接される後端部４６と、を備えている。胴部４１は、内燃機関（図示せず）のねじ穴に螺合するおねじ４２が外周に形成されている。本実施の形態では、おねじ４２の呼び径は１２ｍｍ以下に設定される。 The main metal fitting 40 is a substantially cylindrical member formed of a conductive metal material (for example, low carbon steel or the like). The main metal fitting 40 is connected to the body portion 41 surrounding the insulator 11 from the tip portion 17 to the small diameter portion 16, the seat portion 43 connected to the rear end side of the body portion 41, and the rear end side of the seat portion 43. It is provided with a connecting portion 44, a tool engaging portion 45 connected to the rear end side of the connecting portion 44, and a rear end portion 46 connected to the rear end side of the tool engaging portion 45. The body 41 is formed with a male screw 42 screwed into a screw hole of an internal combustion engine (not shown) on the outer periphery thereof. In the present embodiment, the nominal diameter of the male screw 42 is set to 12 mm or less.

座部４３は、内燃機関（図示せず）のねじ穴とおねじ４２との隙間を塞ぐための部位であり、胴部４１の外径よりも外径が大きく形成されている。接続部４４は、主体金具４０を絶縁体１１に組み付けるときに湾曲状に塑性変形した部位である。工具係合部４５は、内燃機関のねじ穴におねじ４２を締め付けるときに、レンチ等の工具を係合させる部位である。後端部４６は径方向の内側へ向けて屈曲し、絶縁体１１の大径部１５よりも後端側に位置する。大径部１５と後端部４６との間に、タルク等の粉末を充填させたシール部５６が形成されている。 The seat portion 43 is a portion for closing the gap between the screw hole of the internal combustion engine (not shown) and the male screw 42, and is formed to have an outer diameter larger than the outer diameter of the body portion 41. The connecting portion 44 is a portion that is plastically deformed in a curved shape when the main metal fitting 40 is assembled to the insulator 11. The tool engaging portion 45 is a portion for engaging a tool such as a wrench when tightening the screw 42 into the screw hole of the internal combustion engine. The rear end portion 46 bends inward in the radial direction and is located on the rear end side of the large diameter portion 15 of the insulator 11. A seal portion 56 filled with powder such as talc is formed between the large diameter portion 15 and the rear end portion 46.

接地電極５４は、主体金具４０の胴部４１に接合された棒状の金属製（例えばニッケル基合金製）の部材である。本実施の形態では、接地電極５４は先端側が屈曲している。図２に示すように、接地電極５４は、中心電極３０の先端３３と火花ギャップ５５を介して対向する。中心電極３０の先端３３は、絶縁体１１の先端２１よりも先端側に位置する。 The ground electrode 54 is a rod-shaped metal (for example, nickel-based alloy) member joined to the body 41 of the main metal fitting 40. In the present embodiment, the tip side of the ground electrode 54 is bent. As shown in FIG. 2, the ground electrode 54 faces the tip 33 of the center electrode 30 via the spark gap 55. The tip 33 of the center electrode 30 is located closer to the tip than the tip 21 of the insulator 11.

図２に示すように主体金具４０は、径方向の内側へ向かって凸状に張り出す棚部４７が、胴部４１に形成されている。棚部４７は、胴部４１の全周に亘って環状に連続する。棚部４７の後端面４８は、先端側に向かうにつれて縮径している。本実施の形態では、棚部４７の先端面４９は錐状に形成されており、先端側に向かうにつれて拡径している。棚部４７の後端面４８と絶縁体１１の係止部１８との間にパッキン５３が介在する。パッキン５３は、主体金具４０を構成する金属材料よりも軟質の軟鋼板等の金属材料で形成される円環状の板材である。 As shown in FIG. 2, in the main metal fitting 40, a shelf portion 47 projecting inward in the radial direction is formed on the body portion 41. The shelf portion 47 is continuous in an annular shape over the entire circumference of the body portion 41. The rear end surface 48 of the shelf 47 is reduced in diameter toward the tip side. In the present embodiment, the tip surface 49 of the shelf 47 is formed in a conical shape, and the diameter increases toward the tip side. A packing 53 is interposed between the rear end surface 48 of the shelf portion 47 and the locking portion 18 of the insulator 11. The packing 53 is an annular plate material formed of a metal material such as a mild steel plate that is softer than the metal material constituting the main metal fitting 40.

主体金具４０の棚部４７から後端部４６（図１参照）までの部分は、パッキン５３やシール部５６を介して、絶縁体１１のうち小径部１６から大径部１５（図１参照）までの部分に、軸線Ｏ方向の圧縮荷重を加える。その結果、絶縁体１１の外周に主体金具４０が固定される。絶縁体１１の係止部１８は、全周に亘って、パッキン５３を介して棚部４７の後端面４８に係止される。棚部４７の後端面４８及び係止部１８にパッキン５３が密着して、パッキン５３が全周に亘って軸線Ｏ方向に圧縮される。これにより、棚部４７の後端面４８と係止部１８との間の気密を確保できる。 The portion of the main metal fitting 40 from the shelf portion 47 to the rear end portion 46 (see FIG. 1) is formed from the small diameter portion 16 to the large diameter portion 15 (see FIG. 1) of the insulator 11 via the packing 53 and the seal portion 56. A compressive load in the O-axis direction is applied to the parts up to. As a result, the main metal fitting 40 is fixed to the outer periphery of the insulator 11. The locking portion 18 of the insulator 11 is locked to the rear end surface 48 of the shelf portion 47 via the packing 53 over the entire circumference. The packing 53 is in close contact with the rear end surface 48 and the locking portion 18 of the shelf portion 47, and the packing 53 is compressed in the axis O direction over the entire circumference. As a result, airtightness can be ensured between the rear end surface 48 of the shelf portion 47 and the locking portion 18.

主体金具４０は、絶縁体１１の先端２１が、主体金具４０の先端５２から突出するように絶縁体１１を外周側から保持する。主体金具４０のうち棚部４７よりも先端側の部分は、自身の内径が、先端部１７の形状に応じて調整されている。具体的には、棚部４７よりも先端側の部分のうち、絶縁体１１の外周面１９と隙間２２を介して対向する内周面５０は、外周面１９の形状におおよそ沿うように、先端側に向かうにつれて縮径する。棚部４７よりも先端側の部分のうち、絶縁体１１の外周面２０と隙間２２を介して対向する内周面５１は、外周面２０の形状に沿って、軸線Ｏ方向に亘って内径が一定である。 The main metal fitting 40 holds the insulator 11 from the outer peripheral side so that the tip 21 of the insulator 11 protrudes from the tip 52 of the main metal fitting 40. The inner diameter of the main metal fitting 40 on the tip side of the shelf 47 is adjusted according to the shape of the tip 17. Specifically, of the portion on the tip side of the shelf portion 47, the inner peripheral surface 50 facing the outer peripheral surface 19 of the insulator 11 via the gap 22 has a tip so as to roughly follow the shape of the outer peripheral surface 19. The diameter shrinks toward the side. Of the portion on the tip side of the shelf portion 47, the inner peripheral surface 51 facing the outer peripheral surface 20 of the insulator 11 via the gap 22 has an inner diameter along the shape of the outer peripheral surface 20 along the axis O direction. It is constant.

スパークプラグ１０は、主体金具４０の先端５２と絶縁体１１との間の径方向の隙間２２の大きさ（軸線Ｏと垂直な方向の距離）をＬ０とし、主体金具４０のうち棚部４７よりも先端側の部分の内周面５０，５１と絶縁体１１との間の隙間２２の大きさ（軸線Ｏと垂直な方向の距離）をＬとすると、０．９Ｌ０≦Ｌ≦Ｌ０を満たす。本実施の形態では、主体金具４０の内周面５１と絶縁体１１の外周面２０とが対向する部分では、隙間２２の大きさＬは、軸線Ｏ方向に亘って一定である。主体金具４０の内周面５０と絶縁体１１の外周面１９とが対向する部分では、隙間２２の大きさＬは、０．９Ｌ０≦Ｌ≦Ｌ０の範囲内で、後端側へ向かうにつれて次第に小さくなる。 In the spark plug 10, the size of the radial gap 22 (distance in the direction perpendicular to the axis O) between the tip 52 of the main metal fitting 40 and the insulator 11 is set to L 0, and the shelf portion 47 of the main metal fitting 40 Assuming that the size of the gap 22 (distance in the direction perpendicular to the axis O) between the inner peripheral surfaces 50 and 51 of the tip side portion and the insulator 11 is L, 0.9L 0 ≤ L ≤ L 0 Meet. In the present embodiment, the size L of the gap 22 is constant over the axis O direction at the portion where the inner peripheral surface 51 of the main metal fitting 40 and the outer peripheral surface 20 of the insulator 11 face each other. In the portion where the inner peripheral surface 50 of the main metal fitting 40 and the outer peripheral surface 19 of the insulator 11 face each other, the size L of the gap 22 tends toward the rear end side within the range of 0.9L 0 ≤ L ≤ L 0. It gets smaller and smaller.

なお、棚部４７は内周面５０の後端側から径方向の内側へ向かって張り出しているので、棚部４７（先端面４９を含む）と絶縁体１１との間の隙間２２の大きさは、Ｌに比べて小さい。また、主体金具４０の先端５２と絶縁体１１との間のリークを防ぐため、Ｌ０は火花ギャップ５５の大きさＧに比べて大きい。 Since the shelf portion 47 projects inward in the radial direction from the rear end side of the inner peripheral surface 50, the size of the gap 22 between the shelf portion 47 (including the tip surface 49) and the insulator 11 is large. Is smaller than L. Further, in order to prevent leakage between the tip 52 of the main metal fitting 40 and the insulator 11, L 0 is larger than the size G of the spark gap 55.

スパークプラグ１０が、内燃機関（図示せず）のねじ穴に主体金具４０のおねじ４２を締結して内燃機関に取り付けられると、絶縁体１１のうち係止部１８よりも先端側の先端部１７の外周面１９，２０は、燃焼室内の燃焼ガスに曝される。混合気の不完全燃焼等によって生じたカーボンは、燃焼ガスの気流にのって隙間２２に侵入する。隙間２２は０．９Ｌ０≦Ｌ≦Ｌ０を満たす大きさなので、隙間２２に侵入した燃焼ガスの掃気性を高めることができる。よって、燃焼ガスにのったカーボンを絶縁体１１の先端部１７の外周面１９，２０に堆積させ難くできる。よって、耐汚損性を向上できる。 When the spark plug 10 is attached to the internal combustion engine by fastening the screw 42 of the main metal fitting 40 to the screw hole of the internal combustion engine (not shown), the tip of the insulator 11 on the tip side of the locking portion 18 The outer peripheral surfaces 19 and 20 of 17 are exposed to the combustion gas in the combustion chamber. The carbon generated by the incomplete combustion of the air-fuel mixture or the like enters the gap 22 along with the air flow of the combustion gas. Since the gap 22 has a size satisfying 0.9 L 0 ≤ L ≤ L 0 , the scavenging property of the combustion gas that has entered the gap 22 can be improved. Therefore, it is difficult to deposit carbon on the combustion gas on the outer peripheral surfaces 19 and 20 of the tip portion 17 of the insulator 11. Therefore, the stain resistance can be improved.

さらに、主体金具４０の内周面５０と絶縁体１１の外周面１９とが対向する部分では、隙間２２の大きさＬは、０．９Ｌ０≦Ｌ≦Ｌ０の範囲内で、後端側へ向かうにつれて次第に小さくなるので、隙間２２の後端側へ向かうにつれて、燃焼ガスの流速が速くなるようにできる。よって、絶縁体１１の係止部１８に近い部分に、燃焼ガスにのったカーボンを堆積させ難くできる。その結果、絶縁体１１の係止部１８に近い部分（先端５２側に比べて隙間２２の狭い部分）で生じるリークを抑制できる。 Further, in the portion where the inner peripheral surface 50 of the main metal fitting 40 and the outer peripheral surface 19 of the insulator 11 face each other, the size L of the gap 22 is within the range of 0.9L 0 ≤ L ≤ L 0 , and the rear end side. Since it gradually becomes smaller toward the rear end side of the gap 22, the flow velocity of the combustion gas can be increased toward the rear end side of the gap 22. Therefore, it is possible to make it difficult to deposit carbon on the combustion gas in the portion of the insulator 11 near the locking portion 18. As a result, it is possible to suppress a leak that occurs in a portion of the insulator 11 near the locking portion 18 (a portion having a narrow gap 22 as compared with the tip 52 side).

また、主体金具４０に形成されたおねじ４２の呼び径は１２ｍｍ以下なので、主体金具４０を小径化しつつ隙間２２の大きさＬを確保し、耐汚損性を向上できる。 Further, since the nominal diameter of the male screw 42 formed on the main metal fitting 40 is 12 mm or less, the size L of the gap 22 can be secured while reducing the diameter of the main metal fitting 40, and the stain resistance can be improved.

本発明を実施例によりさらに詳しく説明するが、本発明はこの実施例に限定されるものではない。 The present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

スパークプラグ１０の絶縁体１１の先端部１７の外周面１９，２０における外径、主体金具４０の内周面５０，５１における内径を調整して、主体金具４０の先端５２と絶縁体１１との間の径方向の隙間２２の大きさＬ０、主体金具４０のうち棚部４７よりも先端側の部分の内周面５０，５１と絶縁体１１との間の隙間２２のうち最も狭い部分の大きさＬｍｉｎ、及び、火花ギャップ５５の大きさＧが異なる種々のサンプル１〜１０を作成した。サンプル１〜１０のＬ０（単位：ｍｍ）、Ｌｍｉｎ（単位：ｍｍ）、Ｌｍｉｎ／Ｌ０、Ｇ（単位：ｍｍ）を表１に示した。 By adjusting the outer diameters of the outer peripheral surfaces 19 and 20 of the tip 17 of the insulator 11 of the spark plug 10 and the inner diameters of the inner peripheral surfaces 50 and 51 of the main metal fitting 40, the tip 52 of the main metal fitting 40 and the insulator 11 are brought together. The size of the radial gap 22 between them is L 0 , and the narrowest portion of the gap 22 between the inner peripheral surfaces 50 and 51 of the main metal fitting 40 on the tip side of the shelf 47 and the insulator 11 Various samples 1 to 10 having different sizes L min and size G of the spark gap 55 were prepared. Table 1 shows L 0 (unit: mm), L min (unit: mm), L min / L 0 , and G (unit: mm) of samples 1 to 10.

なお、サンプル１〜１０は主体金具４０のおねじ４２の呼び径を１２ｍｍとし、Ｇ／Ｌ０＝０．７０とした。また、サンプル１〜１０は、Ｌ０，Ｌｍｉｎ，Ｇ以外の要素（例えば各部材の材質や形状、寸法など）は一定にした。 In Samples 1 to 10, the nominal diameter of the screw 42 of the main metal fitting 40 was 12 mm, and G / L 0 = 0.70. In the samples 1 to 10, elements other than L 0 , L min , and G (for example, the material, shape, and dimensions of each member) were made constant.

Figure 0006781141
サンプル１〜３は、Ｌ０を１．３５ｍｍ、Ｇを０．９５ｍｍとし、Ｌｍｉｎを１．２０ｍｍ，１．２５ｍｍ，１．３０ｍｍのいずれかにした。これにより、サンプル１〜３は、Ｌｍｉｎ／Ｌ０を０．８９〜０．９６に設定した。
Figure 0006781141
 In Samples 1 to 3, L 0 was 1.35 mm, G was 0.95 mm, and L min was 1.20 mm, 1.25 mm, or 1.30 mm. As a result, samples 1 to 3 set L min / L 0 to 0.89 to 0.96.

サンプル４〜６は、Ｌ０を１．５７ｍｍ、Ｇを１．１０ｍｍとし、Ｌｍｉｎを１．４０ｍｍ，１．４５ｍｍ，１．５０ｍｍのいずれかにした。これにより、サンプル４〜６は、Ｌｍｉｎ／Ｌ０を０．８９〜０．９６に設定した。 In Samples 4 to 6, L 0 was 1.57 mm, G was 1.10 mm, and L min was 1.40 mm, 1.45 mm, or 1.50 mm. As a result, in the samples 4 to 6, L min / L 0 was set to 0.89 to 0.96.

サンプル７〜１０は、Ｌ０を１．６５ｍｍ、Ｇを１．１５ｍｍとし、Ｌｍｉｎを１．４５ｍｍ，１．５０ｍｍ，１．５５ｍｍ，１．６０ｍｍのいずれかにした。これにより、サンプル７〜１０は、Ｌｍｉｎ／Ｌ０を０．８８〜０．９７に設定した。 In the samples 7 to 10, L 0 was 1.65 mm, G was 1.15 mm, and L min was 1.45 mm, 1.50 mm, 1.55 mm, or 1.60 mm. As a result, in the samples 7 to 10, L min / L 0 was set to 0.88 to 0.97.

排気量１．５Ｌの４気筒エンジンをもつ試験用自動車（図示せず）の燃焼室に各サンプルの中心電極３０及び接地電極５４が突出するように、各サンプルをシリンダヘッドに取り付けた。エンジンコントロールユニット（図示せず）を用いて回路に点火指令信号を出力し、各サンプルの中心電極３０と接地電極５４との間に電圧を印加した。各サンプルに印加する電圧は一定にした。 Each sample was attached to the cylinder head so that the center electrode 30 and the ground electrode 54 of each sample protruded into the combustion chamber of a test vehicle (not shown) having a 4-cylinder engine with a displacement of 1.5 L. An ignition command signal was output to the circuit using an engine control unit (not shown), and a voltage was applied between the center electrode 30 and the ground electrode 54 of each sample. The voltage applied to each sample was constant.

これにより、中心電極３０と接地電極５４との間に火花放電を生じさせ、燃焼室内の混合気に着火した。正常な火花放電のときに回路に現れる正常な電流波形とは異なる異常な電流波形が検出されたときに、絶縁体１１の汚損によるリークが発生したと判断した。以下に示す試験運転の間、常に電流波形を測定した。 As a result, a spark discharge was generated between the center electrode 30 and the ground electrode 54, and the air-fuel mixture in the combustion chamber was ignited. When an abnormal current waveform different from the normal current waveform appearing in the circuit during normal spark discharge was detected, it was determined that a leak due to contamination of the insulator 11 had occurred. During the test run shown below, the current waveform was constantly measured.

試験運転は、１０℃の低温試験室内のシャシダイナモメータの上に置いた試験用自動車を用いて行った。試験運転は、第１運転とこれに続く第２運転とを１サイクルとし、これを１０サイクル繰り返すものであった。第１運転では、エンジン始動直後の３回の空吹かしの後、３速段で４０秒間の前進走行（３５ｋｍ／ｈ）を行い、９０秒間のアイドリングの後、再び３速段で４０秒間の前進走行（３５ｋｍ／ｈ）を行った後、エンジンを停止し、エンジンの冷却水の温度が１０℃になるまで放置した。 The test run was carried out using a test vehicle placed on a chassis dynamometer in a low temperature test room at 10 ° C. In the test run, the first run and the second run following the first run were set as one cycle, and this was repeated for 10 cycles. In the first operation, after three air blows immediately after the engine is started, the vehicle runs forward for 40 seconds (35 km / h) in the 3rd speed, and after idling for 90 seconds, moves forward again in the 3rd speed for 40 seconds. After running (35 km / h), the engine was stopped and left until the temperature of the cooling water of the engine reached 10 ° C.

第２運転では、エンジン始動直後の３回の空吹かしの後、１速段で１５秒間の前進走行（１５ｋｍ／ｈ）を行い、３０秒間エンジンを停止した後、再び１速段で１５秒間の前進走行（１５ｋｍ／ｈ）を行い、３０秒間エンジンを停止した後、みたび１速段で１５秒間の前進走行（１５ｋｍ／ｈ）を行った後、エンジンを停止し、エンジンの冷却水の温度が１０℃になるまで放置した。 In the second operation, after three times of air-blowing immediately after the engine is started, the vehicle runs forward for 15 seconds (15 km / h) in the 1st speed, stops the engine for 30 seconds, and then runs again in the 1st speed for 15 seconds. After running forward (15 km / h) and stopping the engine for 30 seconds, after running forward for 15 seconds (15 km / h) at the 1st speed stage, stop the engine and the temperature of the cooling water of the engine. Was left until the temperature reached 10 ° C.

この試験運転は、低速運転の時間が長く、さらに気温も低いので、絶縁体１１の先端部１７の表面にカーボンが付着し易い（くすぶり汚損が生じ易い）運転条件である。この試験運転の間、連続して測定された電流波形において、異常な電流波形が１０回以上検出されたサンプルは「耐汚損性が低い（×）」と評価し、異常な電流波形の検出が９回以下のサンプルは「耐汚損性が高い（〇）」と評価した。 In this test operation, since the low-speed operation time is long and the temperature is low, carbon easily adheres to the surface of the tip portion 17 of the insulator 11 (smoldering stains are likely to occur). In the current waveform measured continuously during this test operation, a sample in which an abnormal current waveform is detected 10 times or more is evaluated as "low stain resistance (x)", and an abnormal current waveform is detected. Samples 9 times or less were evaluated as "high stain resistance (〇)".

その結果、表１に示すようにサンプル１，２，４，５，７〜９は耐汚損性が高く、サンプル３，６，１０は耐汚損性が低いと評価された。耐汚損性が高いと評価されたサンプルはＬｍｉｎ／Ｌ０≧０．９を満たし、耐汚損性が低いと評価されたサンプルはＬｍｉｎ／Ｌ０の値が０．９未満であった。説明は省略したが、Ｇ／Ｌ０＝０．７０以外のサンプルにおいてもこの傾向はみられた。本実施例によれば、０．９Ｌ０≦Ｌ≦Ｌ０を満たすことより、耐汚損性を向上できることが明らかになった。 As a result, as shown in Table 1, Samples 1, 2, 4, 5, 7 to 9 were evaluated to have high stain resistance, and Samples 3, 6 and 10 were evaluated to have low stain resistance. The sample evaluated as having high stain resistance satisfied L min / L 0 ≥ 0.9, and the sample evaluated as having low stain resistance had a value of L min / L 0 less than 0.9. Although the explanation is omitted, this tendency was also observed in samples other than G / L 0 = 0.70. According to this example, it was clarified that the stain resistance can be improved by satisfying 0.9L 0 ≤ L ≤ L 0 .

以上、実施の形態に基づき本発明を説明したが、本発明は上記実施の形態に何ら限定されるものではなく、本発明の趣旨を逸脱しない範囲内で種々の改良変形が可能であることは容易に推察できるものである。 Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention. It can be easily inferred.

実施の形態では、棚部４７の先端面４９が錐状（円錐面）に形成される場合について説明したが、必ずしもこれに限られるものではない。例えば、先端面４９を、先端側へ向かうにつれて拡径する凹面状や凸面状（球帯状）にすることは当然可能である。また、先端面４９を、軸線Ｏと垂直な平面状にすることは当然可能である。 In the embodiment, the case where the tip surface 49 of the shelf portion 47 is formed in a conical shape (conical surface) has been described, but the present invention is not necessarily limited to this. For example, it is naturally possible to make the tip surface 49 into a concave surface shape or a convex surface shape (spherical band shape) whose diameter increases toward the tip side. Further, it is naturally possible to make the tip surface 49 a flat surface perpendicular to the axis O.

実施の形態では、絶縁体１１の先端部１７が、先端側へ向かうにつれて縮径する外周面１９と、外径が一定の外周面２０と、を備える場合について説明したが、必ずしもこれに限られるものではない。外周面２０を省略して、縮径する外周面１９を絶縁体１１の先端２１まで延長することは当然可能である。先端部１７の外周面１９を先端２１まで延長した場合には、０．９Ｌ０≦Ｌ≦Ｌ０を満たすように、主体金具４０の形状を整える。例えば、先端部１７の外周面２０に対向する主体金具４０の内周面５１を省略して、主体金具４０の内周面５０を主体金具４０の先端５２まで延長する。 In the embodiment, the case where the tip portion 17 of the insulator 11 includes an outer peripheral surface 19 whose diameter decreases toward the tip side and an outer peripheral surface 20 having a constant outer diameter has been described, but the present invention is not necessarily limited to this. It's not a thing. Of course, it is possible to omit the outer peripheral surface 20 and extend the outer peripheral surface 19 whose diameter is reduced to the tip 21 of the insulator 11. When the outer peripheral surface 19 of the tip portion 17 is extended to the tip 21, the shape of the main metal fitting 40 is adjusted so as to satisfy 0.9L 0 ≤ L ≤ L 0 . For example, the inner peripheral surface 51 of the main metal fitting 40 facing the outer peripheral surface 20 of the tip portion 17 is omitted, and the inner peripheral surface 50 of the main metal fitting 40 is extended to the tip 52 of the main metal fitting 40.

反対に、先端部１７の縮径した外周面１９を省略して、円筒状の外周面２０を後端側の係止部１８まで延長することは当然可能である。先端部１７の外周面２０を係止部１８まで延長した場合には、０．９Ｌ０≦Ｌ≦Ｌ０を満たすように、主体金具４０の形状を整える。例えば、先端部１７の外周面１９に対向する主体金具４０の内周面５０を省略して、主体金具４０の内周面５１を棚部４７まで延長する。 On the contrary, it is naturally possible to omit the reduced diameter outer peripheral surface 19 of the tip portion 17 and extend the cylindrical outer peripheral surface 20 to the locking portion 18 on the rear end side. When the outer peripheral surface 20 of the tip portion 17 is extended to the locking portion 18, the shape of the main metal fitting 40 is adjusted so as to satisfy 0.9L 0 ≤ L ≤ L 0 . For example, the inner peripheral surface 50 of the main metal fitting 40 facing the outer peripheral surface 19 of the tip portion 17 is omitted, and the inner peripheral surface 51 of the main metal fitting 40 is extended to the shelf portion 47.

実施の形態では、主体金具４０の内周面５０と絶縁体１１の外周面１９とが対向する部分では、隙間２２の大きさＬが、後端側へ向かうにつれて次第に小さくなる場合について説明した。しかし、必ずしもこれに限られるものではない。０．９Ｌ０≦Ｌ≦Ｌ０の範囲内であれば、隙間２２の大きさＬが、後端側へ向かうにつれて次第に大きくなるように、又は、後端側へ向かうにつれて大きくなる部分と小さくなる部分とが存在するように、主体金具４０及び絶縁体１１の形状を設定することは当然可能である。０．９Ｌ０≦Ｌ≦Ｌ０の範囲内であれば、隙間２２の大きさＬが、後端側へ向かうにつれて次第に大きくなるように、又は、後端側へ向かうにつれて大きくなる部分と小さくなる部分とが存在するようにしても、燃焼ガスの著しい滞留が生じないからである。 In the embodiment, the case where the size L of the gap 22 gradually decreases toward the rear end side in the portion where the inner peripheral surface 50 of the main metal fitting 40 and the outer peripheral surface 19 of the insulator 11 face each other has been described. However, it is not always limited to this. Within the range of 0.9L 0 ≤ L ≤ L 0 , the size L of the gap 22 gradually increases toward the rear end side, or becomes larger and smaller toward the rear end side. Of course, it is possible to set the shapes of the main metal fitting 40 and the insulator 11 so that the portions are present. Within the range of 0.9L 0 ≤ L ≤ L 0 , the size L of the gap 22 gradually increases toward the rear end side, or becomes larger and smaller toward the rear end side. This is because the combustion gas does not significantly stay even if the portion is present.

実施の形態では、パッキン５３を介して主体金具４０の棚部４７に絶縁体１１を係止する場合について説明したが、必ずしもこれに限られるものではない。パッキン５３を省略して、主体金具４０の棚部４７に絶縁体１１を係止することは当然可能である。 In the embodiment, the case where the insulator 11 is locked to the shelf portion 47 of the main metal fitting 40 via the packing 53 has been described, but the present invention is not necessarily limited to this. Of course, it is possible to omit the packing 53 and lock the insulator 11 to the shelf portion 47 of the main metal fitting 40.

実施の形態では説明を省略したが、耐火花消耗性を向上させるため、貴金属を含有するチップを中心電極３０や接地電極５４に設けることは当然可能である。 Although the description is omitted in the embodiment, it is naturally possible to provide a chip containing a noble metal on the center electrode 30 and the ground electrode 54 in order to improve the spark consumption resistance.

実施の形態では、主体金具４０に接合された接地電極５４を屈曲させ、接地電極５４と中心電極３０とが軸線Ｏ方向に対向する場合（火花ギャップ５５が軸線Ｏ方向に形成される場合）について説明した。しかし、必ずしもこれに限られるものではない。例えば、中心電極３０の側面と接地電極５４とを軸線Ｏと交差する方向に対向させること（軸線Ｏと垂直な方向に火花ギャップを形成すること）は当然可能である。また、屈曲した接地電極５４を用いる代わりに、直線状の接地電極５４を用いることは当然可能である。 In the embodiment, when the ground electrode 54 joined to the main metal fitting 40 is bent and the ground electrode 54 and the center electrode 30 face each other in the axis O direction (when the spark gap 55 is formed in the axis O direction). explained. However, it is not always limited to this. For example, it is naturally possible to make the side surface of the center electrode 30 and the ground electrode 54 face each other in the direction intersecting the axis O (forming a spark gap in the direction perpendicular to the axis O). Further, it is naturally possible to use a linear ground electrode 54 instead of using the bent ground electrode 54.

実施の形態では、主体金具４０に接地電極５４が１本接合される場合について説明したが、必ずしもこれに限られるものではない。接地電極を複数本、主体金具４０に接合することは当然可能である。 In the embodiment, the case where one ground electrode 54 is joined to the main metal fitting 40 has been described, but the present invention is not necessarily limited to this. Of course, it is possible to join a plurality of ground electrodes to the main metal fitting 40.

１０ スパークプラグ
１１ 絶縁体
１８ 係止部
２１ 絶縁体の先端
２２ 隙間
３０ 中心電極
３３ 中心電極の先端
４０ 主体金具
４２ おねじ
４７ 棚部
４８ 後端面
５２ 主体金具の先端
５４ 接地電極
５５ 火花ギャップ
Ｌ０，Ｌ 隙間の大きさ
Ｏ 軸線 10 Spark plug 11 Insulator 18 Locking part 21 Insulator tip 22 Gap 30 Center electrode 33 Center electrode tip 40 Main metal fitting 42 Male screw 47 Shelf part 48 Rear end surface 52 Main metal fitting tip 54 Ground electrode 55 Spark gap L 0 , L Gap size O Axis

Claims (2)

軸線に沿って先端側から後端側へと延びる軸孔が形成される絶縁体と、
前記絶縁体から自身の先端を突出させて前記軸孔に配置される中心電極と、
前記絶縁体の先端が自身の先端から突出するように前記絶縁体を外周側から保持する円筒状の主体金具と、
前記主体金具に接続され前記中心電極との間に火花ギャップを形成する接地電極と、を備えるスパークプラグであって、
前記主体金具は、径方向の内側へ向かって凸状に張り出す棚部と、
前記棚部よりも先端側の部分に、第１の内周面と、前記第１の内周面の先端側に隣接する第２の内周面と、を備え、
前記絶縁体は、前記棚部の後端面に係止される係止部と、
前記棚部よりも先端側の部分に、第１の外周面と、前記第１の外周面の先端側に隣接する第２の外周面と、を備え、
前記第１の外周面は先端側に向かうにつれて縮径し、前記第２の外周面は軸線方向に亘って外径が一定であり、
前記第１の内周面は、前記第１の外周面に沿うように先端側に向かうにつれて縮径し、前記第２の内周面は軸線方向に亘って内径が一定であり、
前記主体金具の前記先端と前記絶縁体との間の径方向の隙間の大きさをＬ０とし、前記主体金具のうち前記棚部よりも先端側の部分と前記絶縁体との間の径方向の隙間のうち最も小さい部分の大きさをＬとすると、０．９Ｌ０≦Ｌ≦Ｌ０を満たすスパークプラグ。 An insulator in which a shaft hole extending from the front end side to the rear end side along the axis is formed,
A center electrode having its tip protruding from the insulator and arranged in the shaft hole,
A cylindrical main metal fitting that holds the insulator from the outer peripheral side so that the tip of the insulator protrudes from its own tip.
A spark plug comprising a ground electrode connected to the main metal fitting and forming a spark gap with the center electrode.
The main metal fitting has a shelf portion that projects inward in the radial direction and a shelf portion .
A first inner peripheral surface and a second inner peripheral surface adjacent to the tip side of the first inner peripheral surface are provided on a portion on the tip side of the shelf portion .
The insulator has a locking portion that is locked to the rear end surface of the shelf portion and a locking portion .
A first outer peripheral surface and a second outer peripheral surface adjacent to the tip side of the first outer peripheral surface are provided on a portion on the tip end side of the shelf portion .
The diameter of the first outer peripheral surface is reduced toward the tip side, and the outer diameter of the second outer peripheral surface is constant in the axial direction.
The diameter of the first inner peripheral surface is reduced toward the tip side along the first outer peripheral surface, and the inner diameter of the second inner peripheral surface is constant along the axial direction.
The size of the radial gap between the tip of the main metal fitting and the insulator is set to L 0, and the radial direction between the main metal fitting on the tip side of the shelf and the insulator. A spark plug that satisfies 0.9L 0 ≤ L ≤ L 0 , where L is the size of the smallest part of the gap. 前記主体金具は自身の外周面におねじが形成され、
前記おねじの呼び径は１２ｍｍ以下である請求項１記載のスパークプラグ。 The main metal fitting has a screw formed on its outer peripheral surface.
The spark plug according to claim 1, wherein the male screw has a nominal diameter of 12 mm or less.
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