JP2016015258A - Spark plug for internal combustion engine - Google Patents

Spark plug for internal combustion engine Download PDF

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JP2016015258A
JP2016015258A JP2014136947A JP2014136947A JP2016015258A JP 2016015258 A JP2016015258 A JP 2016015258A JP 2014136947 A JP2014136947 A JP 2014136947A JP 2014136947 A JP2014136947 A JP 2014136947A JP 2016015258 A JP2016015258 A JP 2016015258A
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insulator
end side
inner peripheral
peripheral surface
packing
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JP6414398B2 (en
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柴田　正道
Masamichi Shibata
正道 柴田
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Denso Corp
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Denso Corp
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Abstract

PROBLEM TO BE SOLVED: To provide a spark plug capable of effectively burning out carbon adhered onto an outer peripheral surface of an insulator by generating a leakage current between an inner peripheral surface of a packing and the outer peripheral surface of the insulator.SOLUTION: A spark plug 1 comprises: a cylindrical housing 2 provided with a ground electrode 21; a cylindrical insulator 3 inserted into an inner peripheral side of the housing 2; and a center electrode 4 inserted into an inner peripheral side of the insulator 3. The housing 2 has a shelf part 22 formed by diameter reduction of a part in a central axis line direction O, of its inner peripheral surface 201. The insulator 3 has a step surface 33 between a front end side insulator part 31 and a rear end side insulator part 32. An annular packing 5 is held between a rear end side end surface 221 of the shelf part 22 and the step surface 33. On an inner peripheral surface 501 of the packing 5, an unevenness 51 is repeatedly formed at a plurality of points in a circumferential direction C.

Description

本発明は、中心電極と接地電極との間に火花放電間隙が形成された、内燃機関用のスパークプラグに関する。   The present invention relates to a spark plug for an internal combustion engine in which a spark discharge gap is formed between a center electrode and a ground electrode.

エンジン等の内燃機関においては、点火コイルによって発生させたスパーク用電圧を放電して、混合気に着火するためのスパークプラグが多用されている。スパークプラグは、筒状のハウジングの内周側に筒状の絶縁碍子が挿通され、絶縁碍子の内周側に中心電極が挿通されて形成されている。スパークプラグは、ハウジングの先端部に設けられた接地電極と中心電極との間に形成された火花放電間隙に、放電による火花を発生させるよう構成されている。   In an internal combustion engine such as an engine, a spark plug for discharging a spark voltage generated by an ignition coil and igniting an air-fuel mixture is often used. The spark plug is formed by inserting a cylindrical insulator on the inner peripheral side of a cylindrical housing and inserting a center electrode on the inner peripheral side of the insulator. The spark plug is configured to generate a spark due to discharge in a spark discharge gap formed between a ground electrode and a center electrode provided at a front end portion of the housing.

例えば、特許文献１においては、中心電極、中心電極を保持する絶縁碍子、絶縁碍子を保持する主体金具、及び絶縁碍子と主体金具との間に介在する環状のパッキンを備えるスパークプラグについて開示されている。パッキンは、絶縁碍子の碍子先端向き面と、主体金具の金具後端向き面との間に配置されている。そして、主体金具の金具縮径部とパッキンとの位置関係を規定し、コロナ放電による清浄効果を利用して、スパークプラグの耐汚損性を向上させることが開示されている。   For example, Patent Document 1 discloses a spark plug including a center electrode, an insulator holding the center electrode, a metal shell holding the insulator, and an annular packing interposed between the insulator and the metal shell. Yes. The packing is disposed between the insulator leading end surface of the insulator and the metal rear end facing surface of the metal shell. Then, it is disclosed that the positional relationship between the reduced-diameter portion of the metal shell and the packing is defined and the antifouling property of the spark plug is improved by utilizing the cleaning effect by corona discharge.

特開２００９−１７６５２５号公報JP 2009-176525 A

近年、エンジンにおいては、低燃費化、高効率化等を目標としており、エンジン内の混合気が燃えにくい環境にあり、エンジン内の燃焼温度も低下している。燃焼温度が低下すると、特に低温始動時等の燃焼時にカーボンが発生しやすくなり、このカーボンが絶縁碍子に付着しやすくなる。特許文献１のスパークプラグにおいては、主体金具の金具縮径部とパッキンとの位置関係を規定しているのみであり、主体金具の構造に工夫をしていない。また、特許文献１においては、絶縁碍子がカーボンの付着によって汚損されたときの漏洩（リーク）電流の発生を抑え、コロナ放電を発生させることによって、カーボンの清浄効果を得ることを目的としている。
しかしながら、コロナ放電の際に流れるコロナ電流の大きさは、漏洩電流の大きさに比べて小さい。そのため、特許文献１のスパークプラグにおいては、絶縁碍子に付着したカーボンを焼失させる十分な効果を得ることができない。 In recent years, the engine has aimed to reduce fuel consumption and efficiency, and is in an environment where the air-fuel mixture in the engine is difficult to burn, and the combustion temperature in the engine is also decreasing. When the combustion temperature is lowered, carbon is likely to be generated particularly at the time of combustion such as at low temperature start, and this carbon is likely to adhere to the insulator. In the spark plug of Patent Document 1, only the positional relationship between the reduced diameter portion of the metal shell and the packing is defined, and the structure of the metal shell is not devised. Moreover, in patent document 1, it aims at obtaining the carbon cleaning effect by suppressing generation | occurrence | production of the leakage (leak) electric current when an insulator is soiled by adhesion of carbon, and generating corona discharge.
However, the magnitude of the corona current that flows during corona discharge is smaller than the magnitude of the leakage current. Therefore, in the spark plug of Patent Document 1, it is not possible to obtain a sufficient effect of burning off carbon adhering to the insulator.

本発明は、かかる背景に鑑みてなされたもので、パッキンの内周面と、絶縁碍子の外周面との間に漏洩電流を発生させて、絶縁碍子の外周面に付着したカーボンを効果的に焼失させることができるスパークプラグを提供しようとして得られたものである。   The present invention has been made in view of such a background, and generates a leakage current between the inner peripheral surface of the packing and the outer peripheral surface of the insulator, thereby effectively removing the carbon adhering to the outer peripheral surface of the insulator. It was obtained in an attempt to provide a spark plug that can be burned out.

本発明の一態様は、接地電極が設けられた筒状のハウジングと、該ハウジングの内周側に挿通された筒状の絶縁碍子と、該絶縁碍子の内周側に挿通された中心電極とを備え、該中心電極の先端と上記接地電極の先端とが対向する先端側位置において火花放電間隙が形成されたスパークプラグにおいて、
上記ハウジングは、その内周面における中心軸線方向の一部が縮径して形成された棚部を有しており、
上記絶縁碍子は、上記先端側位置に近い位置に形成された先端側碍子部と、該先端側碍子部の後端側に位置して、該先端側碍子部よりも拡径して形成された後端側碍子部と、該後端側碍子部と上記先端側碍子部との間に形成された段差面とを有しており、
上記棚部の後端側端面と上記段差面との間には、環状のパッキンが挟持されており、
該パッキンの内周面には、周方向の複数箇所において、凹凸が繰り返し形成されていることを特徴とする内燃機関用のスパークプラグにある。 One embodiment of the present invention includes a cylindrical housing provided with a ground electrode, a cylindrical insulator inserted into the inner peripheral side of the housing, and a center electrode inserted into the inner peripheral side of the insulator In a spark plug in which a spark discharge gap is formed at a tip side position where the tip of the center electrode and the tip of the ground electrode face each other,
The housing has a shelf formed by reducing the diameter of a part of the inner peripheral surface in the central axis direction,
The insulator is formed at a distal end side insulator portion formed at a position close to the distal end side position and at a rear end side of the distal end side insulator portion and having a diameter larger than that of the distal end side insulator portion. A rear end side insulator portion, and a step surface formed between the rear end side insulator portion and the front end side insulator portion,
An annular packing is sandwiched between the rear end side end surface of the shelf and the step surface,
The spark plug for an internal combustion engine is characterized in that irregularities are repeatedly formed at a plurality of locations in the circumferential direction on the inner peripheral surface of the packing.

上記スパークプラグにおいては、パッキンの内周面における周方向の複数箇所に、凹凸が繰り返し形成されている。そして、この凹凸の形成により、漏洩電流を意図的に発生させて、絶縁碍子に付着したカーボンを焼失させるようにしている。
パッキンの内周面に凹凸が形成されていることにより、パッキンの内周面と絶縁碍子の先端側碍子部の外周面との隙間、及びパッキンの内周面の中心軸線方向の位置の少なくとも一方は、周方向の複数箇所において繰り返し変化している。そして、内燃機関の燃焼が行われると、先端側碍子部の外周面にカーボンが付着していく。このとき、凹凸における凸部と先端側碍子部の外周面に付着したカーボンとの隙間が所定の隙間以下になると、凸部における電界集中により絶縁破壊が発生して、この隙間において漏洩電流が流れる。この漏洩電流は、コロナ電流に比べて、数十〜数百倍の大きさになる。 In the spark plug, irregularities are repeatedly formed at a plurality of locations in the circumferential direction on the inner peripheral surface of the packing. And by forming this unevenness, a leakage current is intentionally generated to burn out carbon adhering to the insulator.
By forming irregularities on the inner peripheral surface of the packing, at least one of the gap between the inner peripheral surface of the packing and the outer peripheral surface of the insulator side of the tip side of the packing and the position of the inner peripheral surface of the packing in the central axis direction Changes repeatedly at a plurality of locations in the circumferential direction. When combustion of the internal combustion engine is performed, carbon adheres to the outer peripheral surface of the tip side insulator portion. At this time, if the gap between the convex portion of the projections and depressions and the carbon adhering to the outer peripheral surface of the tip side insulator portion is equal to or less than the predetermined gap, dielectric breakdown occurs due to electric field concentration in the projections, and leakage current flows in this gap. . This leakage current is several tens to several hundreds times as large as the corona current.

これにより、凸部の先端が放電の起点となり、パッキンの周方向におけるいずれかの凸部において、選択的に漏洩電流が流れる。そして、凸部に対向する、絶縁碍子の外周面におけるカーボンを、漏洩電流によって効果的に焼失させることができる。
それ故、上記スパークプラグによれば、パッキンの内周面と、絶縁碍子の外周面との間に漏洩電流を発生させて、絶縁碍子の外周面に付着したカーボンを効果的に焼失させることができる。 Thereby, the tip of the convex portion becomes a starting point of discharge, and a leakage current selectively flows in any convex portion in the circumferential direction of the packing. And the carbon in the outer peripheral surface of an insulator facing a convex part can be effectively burned down by a leakage current.
Therefore, according to the spark plug, it is possible to generate a leakage current between the inner peripheral surface of the packing and the outer peripheral surface of the insulator, and to effectively burn off carbon adhering to the outer peripheral surface of the insulator. it can.

実施例にかかる、スパークプラグの先端側部分を示す断面図。Sectional drawing which shows the front end side part of the spark plug concerning an Example. 実施例にかかる、中心軸線方向から見た状態のスパークプラグを示す図で、図１のI−I線矢視断面図。It is a figure which shows the spark plug of the state concerning the Example seen from the center axis line direction, and is the II sectional view taken on the line of FIG. 実施例にかかる、パッキンの周辺を拡大して示す断面図。Sectional drawing which expands and shows the periphery of packing concerning an Example. 実施例にかかる、中心軸線方向から見た状態のパッキンの周辺を拡大して示す断面図。Sectional drawing which expands and shows the periphery of the packing of the state concerning the Example seen from the center axis direction. 実施例にかかる、他のパッキンの周辺を拡大して示す断面図。Sectional drawing which expands and shows the periphery of the other packing concerning an Example. 実施例にかかる、中心軸線方向から見た状態の他のパッキンの周辺を拡大して示す断面図。Sectional drawing which expands and shows the periphery of the other packing of the state concerning the Example seen from the center axis direction. 実施例にかかる、中心軸線方向から見た状態の他のパッキンの周辺を拡大して示す断面図。Sectional drawing which expands and shows the periphery of the other packing of the state concerning the Example seen from the center axis direction. 実施例にかかる、中心軸線方向から見た状態の他のパッキンの周辺を拡大して示す断面図。Sectional drawing which expands and shows the periphery of the other packing of the state concerning the Example seen from the center axis direction. 実施例にかかる、隣り合う凸部同士の間の周方向の角度間隔と、絶縁抵抗値が１０ＭΩ未満になるときのサイクル数との関係を示すグラフ。The graph which shows the relationship between the angular interval of the circumferential direction between adjacent convex parts concerning an Example, and the cycle number when an insulation resistance value becomes less than 10 Mohm. 実施例にかかる、隣り合う凸部同士の間の周方向の角度間隔と、電界強度との関係を示すグラフ。The graph which shows the relationship between the angular interval of the circumferential direction between adjacent convex parts concerning an Example, and electric field strength. 実施例にかかる、パッキンの内周面における凹凸の凸部の先端の中心軸線方向における突出量と、絶縁抵抗値が１０ＭΩ未満になるときのサイクル数との関係を示すグラフ。The graph which shows the relationship between the protrusion amount in the central-axis direction of the front-end | tip of the uneven | corrugated convex part in the internal peripheral surface of packing concerning an Example, and the cycle number when an insulation resistance value becomes less than 10 Mohm. 実施例にかかる、パッキンの凹凸における凸部の内周側先端の角部の曲率半径と、絶縁抵抗値が１０ＭΩ未満になるときのサイクル数との関係を示すグラフ。The graph which shows the relationship between the curvature radius of the corner | angular part of the inner peripheral side tip of the convex part in the unevenness | corrugation of packing, and the cycle number when an insulation resistance value becomes less than 10 Mohm concerning an Example.

以下に、内燃機関用のスパークプラグにかかる実施例について、図面を参照して説明する。
（実施例）
本例のスパークプラグ１は、図１、図２に示すように、接地電極２１が設けられた筒状のハウジング２と、ハウジング２の内周側に挿通された筒状の絶縁碍子３と、絶縁碍子３の内周側に挿通された中心電極４とを備えている。また、中心電極４の先端と接地電極２１の先端とが対向する先端側位置においては、火花放電間隙Ｓが形成されている。 Embodiments of a spark plug for an internal combustion engine will be described below with reference to the drawings.
(Example)
As shown in FIGS. 1 and 2, the spark plug 1 of this example includes a cylindrical housing 2 provided with a ground electrode 21, a cylindrical insulator 3 inserted on the inner peripheral side of the housing 2, and And a center electrode 4 inserted on the inner peripheral side of the insulator 3. Further, a spark discharge gap S is formed at the tip side position where the tip of the center electrode 4 and the tip of the ground electrode 21 face each other.

ハウジング２は、図３に示すように、その内周面２０１における中心軸線方向Ｏの一部が縮径して形成された棚部２２を有している。絶縁碍子３は、先端側位置に近い位置に形成された先端側碍子部３１と、先端側碍子部３１の後端側に隣接して、先端側碍子部３１よりも拡径して形成された後端側碍子部３２と、後端側碍子部３２と先端側碍子部３１との間に形成された段差面３３とを有している。棚部２２の後端側端面２２１と段差面３３との間には、環状のパッキン５が挟持されている。図４に示すように、パッキン５の内周面５０１には、周方向Ｃの複数箇所において、凹凸５１が繰り返し形成されている。
なお、図２、図４においては、パッキン５が中心軸線方向Ｏに変形していない状態を示して、図示を簡略化している。 As shown in FIG. 3, the housing 2 has a shelf portion 22 formed by reducing the diameter of a part of the inner peripheral surface 201 in the central axis direction O. The insulator 3 is formed adjacent to the front end side insulator part 31 formed at a position close to the front end side position and the rear end side of the front end side insulator part 31 and having a diameter larger than that of the front end side insulator part 31. It has a rear end side insulator portion 32 and a step surface 33 formed between the rear end side insulator portion 32 and the front end side insulator portion 31. An annular packing 5 is sandwiched between the rear end side end surface 221 of the shelf 22 and the step surface 33. As shown in FIG. 4, unevenness 51 is repeatedly formed on the inner peripheral surface 501 of the packing 5 at a plurality of locations in the circumferential direction C.
2 and 4, the packing 5 is not deformed in the central axis direction O, and the illustration is simplified.

以下に、本例のスパークプラグ１について、図１〜図１２を参照して詳説する。
スパークプラグ１は、内燃機関としてのエンジンにおいて、スパーク用の高電圧を発生させる点火コイルに接続して用いられる。スパークプラグ１の中心電極４の後端部は、点火コイルの高電圧ターミナルに接続され、スパークプラグ１のハウジング２は、エンジンのシリンダヘッドに接続される。
ハウジング２の先端側部分の外周には、シリンダヘッドのプラグホールの端部に設けられたねじ穴に螺合するおねじ部２４が形成されている。接地電極２１は、ハウジング２の先端部から突出して、中心電極４の先端に先端側から対向するよう屈曲して形成されている。 Below, the spark plug 1 of this example is explained in detail with reference to FIGS.
The spark plug 1 is used by being connected to an ignition coil that generates a high voltage for spark in an engine as an internal combustion engine. The rear end of the center electrode 4 of the spark plug 1 is connected to the high voltage terminal of the ignition coil, and the housing 2 of the spark plug 1 is connected to the cylinder head of the engine.
On the outer periphery of the front end side portion of the housing 2, a male screw portion 24 that is screwed into a screw hole provided at an end portion of the plug hole of the cylinder head is formed. The ground electrode 21 is formed so as to protrude from the front end portion of the housing 2 and bend so as to face the front end of the center electrode 4 from the front end side.

図１、図３に示すように、ハウジング２の棚部２２は、絶縁碍子３の段差面３３を下方から受けるよう、ハウジング２の内周面２０１から突出して形成されている。棚部２２は、ハウジング２の内周面２０１の全周に形成されており、段差面３３は、絶縁碍子３の外周面３０１の全周に形成されている。棚部２２の後端側端面２２１及び絶縁碍子３の段差面３３は、後端側に向かうほど拡径する傾斜面として形成されている。
絶縁碍子３の先端側碍子部３１の外周面３０１は、先端側に向かうに連れて縮径するテーパ状に形成されている。ハウジング２の先端側部分の内周面２０１は、中心軸線方向Ｏに平行に形成されている。ハウジング２の先端側部分の内周面２０１と、絶縁碍子３の先端側碍子部３１の外周面３０１との隙間は、後端側に向かうに連れて狭くなるよう変化している。中心電極４の先端部４１は、絶縁碍子３の先端側碍子部３１の先端から突出している。 As shown in FIGS. 1 and 3, the shelf 22 of the housing 2 is formed so as to protrude from the inner peripheral surface 201 of the housing 2 so as to receive the stepped surface 33 of the insulator 3 from below. The shelf 22 is formed on the entire circumference of the inner circumferential surface 201 of the housing 2, and the step surface 33 is formed on the entire circumference of the outer circumferential surface 301 of the insulator 3. The rear end side end surface 221 of the shelf 22 and the step surface 33 of the insulator 3 are formed as inclined surfaces that increase in diameter toward the rear end side.
The outer peripheral surface 301 of the front end side insulator portion 31 of the insulator 3 is formed in a tapered shape whose diameter decreases toward the front end side. The inner peripheral surface 201 of the front end side portion of the housing 2 is formed in parallel to the central axis direction O. The gap between the inner peripheral surface 201 of the front end side portion of the housing 2 and the outer peripheral surface 301 of the front end side insulator portion 31 of the insulator 3 changes so as to become narrower toward the rear end side. The tip portion 41 of the center electrode 4 protrudes from the tip of the tip side insulator portion 31 of the insulator 3.

環状のパッキン５は、導電性のある金属材料から構成されており、鋼板から打ち抜かれて形成されている。パッキン５は、ハウジング２との導電性が確保され、絶縁碍子３との緩衝部材となる種々の材料から構成することができる。
図３に示すように、パッキン５の内周面５０１における凹凸５１の凸部５１１の先端は、棚部２２の後端側端面２２１と段差面３３との間から先端側に突出している。棚部２２の後端側端面２２１と内周側面２２２との間の角位置２２３から、パッキン５の内周面５０１における凹凸５１の凸部５１１の先端までの中心軸線方向Ｏにおける突出量Ｌは、０〜１ｍｍの範囲内にある。なお、内周面５０１の突出量Ｌが０ｍｍの場合は、パッキン５の内周面５０１における凹凸５１の凸部５１１の先端と、棚部２２における角位置２２３とが合っている場合をいう。
また、図４に示すように、パッキン５の内周面５０１における凹凸５１の凸部５１１の内周側先端の角部５１３は、曲率半径Ｒが０．３ｍｍ以下の曲面形状に形成されている。なお、この角部５１３は、面取り幅が０．３ｍｍ以下の面取り形状に形成されていてもよい。 The annular packing 5 is made of a conductive metal material and is formed by punching from a steel plate. The packing 5 can be made of various materials that ensure conductivity with the housing 2 and serve as a buffer member with the insulator 3.
As shown in FIG. 3, the tip of the convex portion 511 of the unevenness 51 on the inner peripheral surface 501 of the packing 5 protrudes from the space between the rear end side end surface 221 and the step surface 33 of the shelf portion 22 to the front end side. The protrusion amount L in the central axial direction O from the angular position 223 between the rear end side end surface 221 of the shelf 22 and the inner peripheral side surface 222 to the tip of the convex portion 511 of the uneven portion 51 on the inner peripheral surface 501 of the packing 5 is In the range of 0 to 1 mm. In addition, when the protrusion amount L of the inner peripheral surface 501 is 0 mm, the tip of the convex part 511 of the unevenness | corrugation 51 in the inner peripheral surface 501 of the packing 5 and the corner | angular position 223 in the shelf part 22 are in agreement.
Moreover, as shown in FIG. 4, the corner | angular part 513 of the inner peripheral side tip of the convex part 511 of the unevenness | corrugation 51 in the inner peripheral surface 501 of the packing 5 is formed in the curved-surface shape whose curvature radius R is 0.3 mm or less. . In addition, this corner | angular part 513 may be formed in the chamfering shape whose chamfering width is 0.3 mm or less.

ハウジング２と絶縁碍子３との間に挟まれるパッキン５の内周側端部（凸部５１１）は、パッキン５の内周側端部が棚部２２の角位置２２３からはみ出す量、棚部２２の内周面２０１と先端側碍子部３１の外周面３０１との隙間の大きさ、この隙間とパッキン５の厚みとの関係等によって、中心軸線方向Ｏに折り曲げられる量（角度）が異なる。
図３に示すように、棚部２２の内周面２０１と先端側碍子部３１の外周面３０１との隙間が、パッキン５の厚みに比べて大幅に大きい場合には、パッキン５の内周側端部が中心軸線方向Ｏに折れ曲がる量が小さい。この場合には、パッキン５の内周面５０１における凹凸５１と、絶縁碍子３の外周面３０１との隙間が、周方向Ｃの複数箇所において繰り返し変化することになる。
一方、図５に示すように、棚部２２の内周面２０１と先端側碍子部３１の外周面３０１との隙間が、パッキン５の厚みに近い場合には、パッキン５の内周側端部が中心軸線方向Ｏに沿うように折れ曲がる。この場合には、パッキン５の内周面５０１における凹凸５１の中心軸線方向Ｏの位置が、周方向Ｃの複数箇所において繰り返し変化することになる。 The inner peripheral side end (convex portion 511) of the packing 5 sandwiched between the housing 2 and the insulator 3 is an amount by which the inner peripheral side end of the packing 5 protrudes from the angular position 223 of the shelf 22, the shelf 22 The amount (angle) of bending in the central axis direction O differs depending on the size of the gap between the inner circumferential surface 201 of the inner circumferential surface 201 and the outer circumferential surface 301 of the distal end side insulator portion 31, the relationship between the gap and the thickness of the packing 5, and the like.
As shown in FIG. 3, when the gap between the inner peripheral surface 201 of the shelf 22 and the outer peripheral surface 301 of the tip side insulator portion 31 is significantly larger than the thickness of the packing 5, the inner peripheral side of the packing 5 The amount of bending of the end portion in the central axis direction O is small. In this case, the gap between the unevenness 51 on the inner peripheral surface 501 of the packing 5 and the outer peripheral surface 301 of the insulator 3 changes repeatedly at a plurality of locations in the circumferential direction C.
On the other hand, as shown in FIG. 5, when the gap between the inner peripheral surface 201 of the shelf portion 22 and the outer peripheral surface 301 of the distal end side insulator portion 31 is close to the thickness of the packing 5, the inner peripheral side end portion of the packing 5. Is bent along the central axis direction O. In this case, the position of the unevenness 51 on the inner peripheral surface 501 of the packing 5 in the central axis direction O repeatedly changes at a plurality of locations in the circumferential direction C.

図４に示すように、パッキン５の内周面５０１における凹凸５１の凸部５１１は、中心軸線方向Ｏから見た形状が、三角形状を有している。そして、凸部５１１における、三角形状を形成する一対の側面５１４は、直線状に形成されている。また、図６に示すごとく、凸部５１１における一対の側面５１４は、曲線状に形成されていてもよい。これらの場合、内周面５０１の突出量Ｌは、三角形状の各凸部５１１の内周側頂点において最も大きくなる。また、凸部５１１と、絶縁碍子３の先端側碍子部３１の外周面３０１との間の隙間は、三角形状の凸部５１１の内周側頂点において最も小さくなる。   As shown in FIG. 4, the protrusion 511 of the unevenness 51 on the inner peripheral surface 501 of the packing 5 has a triangular shape as viewed from the central axis direction O. A pair of side surfaces 514 forming a triangular shape in the convex portion 511 are formed in a linear shape. Further, as shown in FIG. 6, the pair of side surfaces 514 of the convex portion 511 may be formed in a curved shape. In these cases, the protrusion amount L of the inner peripheral surface 501 is the largest at the inner peripheral apex of each triangular projection 511. Moreover, the clearance gap between the convex part 511 and the outer peripheral surface 301 of the front end side insulator part 31 of the insulator 3 becomes the smallest in the inner peripheral side vertex of the triangular-shaped convex part 511. FIG.

また、図７に示すように、パッキン５の内周面５０１における凹凸５１の凸部５１１は、中心軸線方向Ｏから見た形状が、四角形状を有していてもよい。この場合、凸部５１１における、四角形状を形成する一対の側面５１５は、直線状に形成されていてもよく、曲線状に形成されていてもよい。この場合、内周面５０１の突出量Ｌは、四角形状の凸部５１１の周方向Ｃの両側の角部５１３又は内周側側面５１６において最も大きくなる。また、凸部５１１と、絶縁碍子３の先端側碍子部３１の外周面３０１との間の隙間は、四角形状の凸部５１１の周方向Ｃの両側の角部５１３又は内周側側面５１６において最も小さくなる。   Moreover, as shown in FIG. 7, the convex part 511 of the unevenness | corrugation 51 in the internal peripheral surface 501 of the packing 5 may have a quadrilateral shape when seen from the central axis direction O. In this case, the pair of side surfaces 515 forming a quadrangular shape in the convex portion 511 may be formed in a straight line shape or a curved shape. In this case, the protrusion amount L of the inner peripheral surface 501 is largest at the corner portions 513 or the inner peripheral side surface 516 on both sides in the circumferential direction C of the quadrangular convex portion 511. In addition, a gap between the convex portion 511 and the outer peripheral surface 301 of the distal end side insulator portion 31 of the insulator 3 is a corner portion 513 or inner peripheral side surface 516 on both sides in the circumferential direction C of the quadrangular convex portion 511. The smallest.

図４に示すように、パッキン５の内周面５０１における凹凸５１の凸部５１１は、周方向Ｃに等間隔に、５〜３０°の角度間隔θで繰り返し形成されている。この角度間隔θは、パッキン５の内周面５０１の周方向Ｃにおける凸部５１１の形成数によって決定される。三角形状の凸部５１１は、凸部５１１の突出高さ（凹部５１２の深さ）及び凸部５１１の形成数に応じて、鈍角状又は鋭角状に形成することができる。
また、パッキン５の内周面５０１における凹凸５１は、図４に示すごとく、凸部５１１と凹部５１２とが周方向Ｃに連続して隣接する形状に形成することができ、図８に示すように、凸部５１１が円周形状の内周面５０１から部分的に突出する形状に形成することもできる。 As shown in FIG. 4, the convex portions 511 of the irregularities 51 on the inner peripheral surface 501 of the packing 5 are repeatedly formed at equal intervals in the circumferential direction C at an angular interval θ of 5 to 30 °. This angular interval θ is determined by the number of protrusions 511 formed in the circumferential direction C of the inner peripheral surface 501 of the packing 5. The triangular convex portion 511 can be formed in an obtuse or acute angle shape depending on the protruding height of the convex portion 511 (depth of the concave portion 512) and the number of convex portions 511 formed.
Moreover, the unevenness | corrugation 51 in the internal peripheral surface 501 of the packing 5 can be formed in the shape which the convex part 511 and the recessed part 512 adjoin continuously in the circumferential direction C, as shown in FIG. In addition, the convex portion 511 may be formed in a shape that partially protrudes from the circumferential inner peripheral surface 501.

本例においては、ＪＩＳＤ１６０６のくすぶり汚損試験において、試験条件に従う１サイクル終了ごとの、ハウジング２と絶縁碍子３との間の絶縁抵抗値を測定し、絶縁抵抗値が１０ＭΩ未満になるときのサイクル数Ｎを測定した。具体的には、４気筒、１．８Ｌのエンジンを用い、パッキン５の内周面５０１における凹凸５１が三角形状の凸部５１１によって形成されたハウジング２について測定を行った。また、パッキン５の内周面５０１における凹凸５１の凸部５１１の、角度間隔θ、突出量、曲率半径Ｒの各寸法を変化させて、サイクル数Ｎを測定した。図９〜図１２は、測定を行った結果を示す。   In this example, in the smoldering fouling test of JIS D1606, the insulation resistance value between the housing 2 and the insulator 3 is measured at the end of each cycle according to the test conditions, and the number of cycles when the insulation resistance value is less than 10 MΩ. N was measured. Specifically, the measurement was performed on the housing 2 in which the unevenness 51 on the inner peripheral surface 501 of the packing 5 was formed by the triangular protrusions 511 using a 4-cylinder, 1.8 L engine. Further, the number N of cycles was measured by changing the dimensions of the convex portion 511 of the unevenness 51 on the inner peripheral surface 501 of the packing 5 such as the angle interval θ, the protrusion amount, and the curvature radius R. 9 to 12 show the results of measurement.

図９は、横軸に、隣り合う凸部５１１同士の間の周方向Ｃの角度間隔θをとり、縦軸に、絶縁抵抗値が１０ＭΩ未満になるときのサイクル数Ｎをとって、両者の関係を示す。同図に示すように、角度間隔θが３０°を超えると、サイクル数Ｎは１０回にまで低下し、３０°以下においては、サイクル数Ｎが多いことが分かった。また、角度間隔θが２２．５°以下になると、サイクル数Ｎがより多くなることが分かった。また、角度間隔θが小さくなり過ぎると、図１０に示すように、隣り合う凸部５１１同士の間に電界干渉が発生し、電界強度が低下する。
以上の結果より、パッキン５の内周面５０１における凹凸５１の凸部５１１は、周方向Ｃに等間隔に、５〜３０°の角度間隔θで繰り返し形成することが好ましく、５〜２２．５°の角度間隔θで繰り返し形成することがさらに好ましいことが分かった。 In FIG. 9, the horizontal axis represents the angular interval θ in the circumferential direction C between adjacent convex portions 511, and the vertical axis represents the number of cycles N when the insulation resistance value is less than 10 MΩ, Show the relationship. As shown in the figure, it was found that when the angular interval θ exceeds 30 °, the cycle number N decreases to 10 times, and when it is 30 ° or less, the cycle number N is large. It was also found that the cycle number N was increased when the angular interval θ was 22.5 ° or less. If the angle interval θ is too small, as shown in FIG. 10, electric field interference occurs between adjacent convex portions 511 and the electric field strength decreases.
From the above results, it is preferable that the convex portions 511 of the irregularities 51 on the inner peripheral surface 501 of the packing 5 are repeatedly formed at equal intervals in the circumferential direction C at an angular interval θ of 5 to 30 °. It has been found that it is more preferable to repeatedly form at an angle interval θ of °.

図１１は、横軸に、パッキン５の内周面５０１における凹凸５１の凸部５１１の先端の、棚部２２の後端側端面２２１と内周側面２２２との間の角位置２２３から先端側への中心軸線方向Ｏにおける突出量Ｌをとり、縦軸に、絶縁抵抗値が１０ＭΩ未満になるときのサイクル数Ｎをとって、両者の関係を示す。同図に示すように、突出量が０ｍｍ未満になると（凸部５１１の先端が角位置２２３よりも後端側に引き込まれた状態にあると）、サイクル数Ｎは１０回にまで低下し、０ｍｍ以上においては、サイクル数Ｎが多いことが分かった。また、突出量が１ｍｍ超過になると、スパークプラグ１の組付時に、絶縁碍子３を圧迫し、絶縁碍子３の割れが発生するおそれがある。
以上の結果より、パッキン５の内周面５０１における凹凸５１の凸部５１１の先端の突出量Ｌは、０〜１ｍｍとすることが好ましいことが分かった。 In FIG. 11, the horizontal axis indicates the front end side from the angular position 223 between the rear end side end surface 221 of the shelf 22 and the inner peripheral side surface 222 at the front end of the convex portion 511 of the unevenness 51 on the inner peripheral surface 501 of the packing 5. The amount of protrusion L in the central axis direction O is taken, and the vertical axis represents the number N of cycles when the insulation resistance value is less than 10 MΩ, and the relationship between them is shown. As shown in the figure, when the protrusion amount is less than 0 mm (when the tip of the convex portion 511 is in a state of being pulled to the rear end side from the corner position 223), the cycle number N decreases to 10 times It was found that the number of cycles N was large at 0 mm or more. If the protruding amount exceeds 1 mm, the insulator 3 may be pressed when the spark plug 1 is assembled, and the insulator 3 may be cracked.
From the above results, it was found that the protrusion amount L of the tip of the convex portion 511 of the unevenness 51 on the inner peripheral surface 501 of the packing 5 is preferably 0 to 1 mm.

図１２は、横軸に、パッキン５の内周面５０１における凹凸５１の凸部５１１の内周側先端の角部５１３の曲率半径Ｒをとり、縦軸に、絶縁抵抗値が１０ＭΩ未満になるときのサイクル数Ｎをとって、両者の関係を示す。同図に示すように、曲率半径Ｒが０．３ｍｍを超えると、サイクル数Ｎは１０回にまで低下し、０．３ｍｍ以下においては、サイクル数Ｎが多いことが分かった。また、曲率半径Ｒが０．２ｍｍ以下になると、サイクル数Ｎがより多くなることが分かった。また、上記曲率半径Ｒは、小さいほど電界強度が大きくなって好ましいが、製造上の理由により、０．０５ｍｍ未満とすることは困難であると考えられる。
以上の結果より、凸部５１１の内周側先端の角部５１３の曲率半径Ｒは、０．０５〜０．３ｍｍとすることが好ましく、０．０５〜０．２ｍｍとすることがさらに好ましいことが分かった。 In FIG. 12, the horizontal axis represents the radius of curvature R of the corner 513 at the inner peripheral end of the convex portion 511 of the irregularities 51 on the inner peripheral surface 501 of the packing 5, and the vertical axis represents an insulation resistance value of less than 10 MΩ. The relationship between the two is shown by taking the number of cycles N. As shown in the figure, when the radius of curvature R exceeds 0.3 mm, the cycle number N decreases to 10 times, and when the radius of curvature is 0.3 mm or less, the cycle number N is large. Moreover, it turned out that the cycle number N increases when the curvature radius R becomes 0.2 mm or less. The smaller the radius of curvature R is, the smaller the electric field strength is. However, it is considered difficult to make it less than 0.05 mm for manufacturing reasons.
From the above results, the radius of curvature R of the corner 513 at the tip on the inner peripheral side of the convex portion 511 is preferably 0.05 to 0.3 mm, and more preferably 0.05 to 0.2 mm. I understood.

次に、本例のスパークプラグ１の作用効果について説明する。
本例のスパークプラグ１においては、パッキン５の内周面５０１における周方向Ｃの複数箇所に、凹凸５１が繰り返し形成されている。そして、この凹凸５１の形成により、漏洩電流を意図的に発生させて、絶縁碍子３に付着したカーボンＸを焼失させるようにしている。
図３に示したように、棚部２２の内周面２０１と先端側碍子部３１の外周面３０１との隙間が、パッキン５の厚みに比べて大幅に大きい場合には、パッキン５の内周面５０１における凹凸５１と絶縁碍子３の先端側碍子部３１の外周面３０１との隙間は、周方向Ｃの複数箇所において繰り返し変化している。そして、内燃機関の燃焼が行われると、先端側碍子部３１の外周面３０１にカーボンＸが付着していく（図２、図３参照）。このとき、凹凸５１における凸部５１１と先端側碍子部３１の外周面３０１に付着したカーボンＸとの間における径方向の隙間が所定の隙間以下になると、凸部５１１における電界集中により絶縁破壊が発生して、この隙間において漏洩電流が流れる。この漏洩電流は、コロナ電流に比べて、数十〜数百倍の大きさになる。 Next, the effect of the spark plug 1 of this example is demonstrated.
In the spark plug 1 of this example, irregularities 51 are repeatedly formed at a plurality of locations in the circumferential direction C on the inner peripheral surface 501 of the packing 5. And by forming this unevenness | corrugation 51, the leakage current is intentionally generated and the carbon X adhering to the insulator 3 is burned out.
As shown in FIG. 3, when the gap between the inner peripheral surface 201 of the shelf 22 and the outer peripheral surface 301 of the tip side insulator portion 31 is significantly larger than the thickness of the packing 5, the inner periphery of the packing 5 The gap between the unevenness 51 on the surface 501 and the outer peripheral surface 301 of the tip side insulator portion 31 of the insulator 3 is repeatedly changed at a plurality of locations in the circumferential direction C. When the internal combustion engine is combusted, the carbon X adheres to the outer peripheral surface 301 of the tip side insulator portion 31 (see FIGS. 2 and 3). At this time, if the radial gap between the convex portion 511 in the concave and convex portion 51 and the carbon X adhering to the outer peripheral surface 301 of the distal end side insulator portion 31 is equal to or smaller than a predetermined gap, dielectric breakdown is caused by electric field concentration in the convex portion 511. And leakage current flows in this gap. This leakage current is several tens to several hundreds times as large as the corona current.

一方、図５に示したように、棚部２２の内周面２０１と先端側碍子部３１の外周面３０１との隙間が、パッキン５の厚みに近い場合には、凹凸５１の中心軸線方向Ｏの位置が、周方向Ｃの複数箇所において繰り返し変化している。この場合、凹凸５１における凸部５１１と先端側碍子部３１の外周面３０１に付着したカーボンＸとの間における中心軸線方向Ｏの隙間が所定の隙間以下になると、凸部５１１における電界集中により、この隙間において漏洩電流が流れる。この漏洩電流は、コロナ電流に比べて、数十〜数百倍の大きさになる。   On the other hand, as shown in FIG. 5, when the gap between the inner peripheral surface 201 of the shelf portion 22 and the outer peripheral surface 301 of the distal end side insulator portion 31 is close to the thickness of the packing 5, Are repeatedly changed at a plurality of locations in the circumferential direction C. In this case, when the gap in the central axis direction O between the convex portion 511 in the concave and convex portion 51 and the carbon X attached to the outer peripheral surface 301 of the tip side insulator portion 31 is equal to or less than a predetermined gap, electric field concentration in the convex portion 511 causes Leakage current flows in this gap. This leakage current is several tens to several hundreds times as large as the corona current.

これにより、凸部５１１の角部５１３が放電の起点となり、パッキン５の周方向Ｃにおけるいずれかの凸部５１１において、選択的に漏洩電流が流れる。そして、凸部５１１に対向する、絶縁碍子３の外周面３０１におけるカーボンＸを、漏洩電流によって効果的に焼失させることができる。
パッキン５の内周面５０１における凹凸５１の凸部５１１が三角形状を有している場合には、凸部５１１の内周側頂点において漏洩電流が発生し、この凸部５１１の内周側頂点に対向する部分を起点として、カーボンＸを焼失させることができる。
また、パッキン５の内周面５０１における凹凸５１の凸部５１１が四角形状を有している場合には、凸部５１１の周方向Ｃの両側の角部５１３において漏洩電流が発生し、この凸部５１１の周方向Ｃの両側の角部５１３に対向する部分を起点として、カーボンＸを焼失させることができる。 Thereby, the corner | angular part 513 of the convex part 511 becomes a starting point of discharge, and the leakage current selectively flows in any convex part 511 in the circumferential direction C of the packing 5. And the carbon X in the outer peripheral surface 301 of the insulator 3 which opposes the convex part 511 can be burned off effectively by a leakage current.
When the convex part 511 of the unevenness 51 on the inner peripheral surface 501 of the packing 5 has a triangular shape, a leakage current is generated at the inner peripheral vertex of the convex part 511, and the inner peripheral apex of the convex part 511 The carbon X can be burned off starting from the portion facing the surface.
Further, when the convex portion 511 of the unevenness 51 on the inner peripheral surface 501 of the packing 5 has a quadrangular shape, a leakage current is generated at the corner portions 513 on both sides in the circumferential direction C of the convex portion 511. The carbon X can be burned out starting from the portions facing the corners 513 on both sides in the circumferential direction C of the part 511.

それ故、本例のスパークプラグ１によれば、パッキン５の内周面５０１と、絶縁碍子３の外周面３０１との間に漏洩電流を発生させて、絶縁碍子３の外周面３０１に付着したカーボンＸを効果的に焼失させることができる。   Therefore, according to the spark plug 1 of this example, a leakage current is generated between the inner peripheral surface 501 of the packing 5 and the outer peripheral surface 301 of the insulator 3 and is attached to the outer peripheral surface 301 of the insulator 3. Carbon X can be burned out effectively.

１ スパークプラグ
２ ハウジング
２０１ 内周面
２１ 接地電極
２２ 棚部
２２１ 後端側端面
３ 絶縁碍子
３０１ 外周面
３１ 先端側碍子部
３２ 後端側碍子部
３３ 段差面
４ 中心電極
５ パッキン
５１ 凹凸 DESCRIPTION OF SYMBOLS 1 Spark plug 2 Housing 201 Inner peripheral surface 21 Ground electrode 22 Shelf part 221 Rear end side end surface 3 Insulator 301 Outer peripheral surface 31 Front end side insulator part 32 Rear end side insulator part 33 Step surface 4 Center electrode 5 Packing 51 Unevenness

Claims (5)

接地電極（２１）が設けられた筒状のハウジング（２）と、該ハウジング（２）の内周側に挿通された筒状の絶縁碍子（３）と、該絶縁碍子（３）の内周側に挿通された中心電極（４）とを備え、該中心電極（４）の先端と上記接地電極（２１）の先端とが対向する先端側位置において火花放電間隙（Ｓ）が形成されたスパークプラグ（１）において、
上記ハウジング（２）は、その内周面（２０１）における中心軸線方向（Ｏ）の一部が縮径して形成された棚部（２２）を有しており、
上記絶縁碍子（３）は、上記先端側位置に近い位置に形成された先端側碍子部（３１）と、該先端側碍子部（３１）の後端側に位置して、該先端側碍子部（３１）よりも拡径して形成された後端側碍子部（３２）と、該後端側碍子部（３２）と上記先端側碍子部（３１）との間に形成された段差面（３３）とを有しており、
上記棚部（２２）の後端側端面（２２１）と上記段差面（３３）との間には、環状のパッキン（５）が挟持されており、
該パッキン（５）の内周面（５０１）には、周方向（Ｃ）の複数箇所において、凹凸（５１）が繰り返し形成されていることを特徴とする内燃機関用のスパークプラグ（１）。 A cylindrical housing (2) provided with a ground electrode (21), a cylindrical insulator (3) inserted through the inner periphery of the housing (2), and an inner periphery of the insulator (3) A spark having a spark discharge gap (S) formed at a tip side position where the tip of the center electrode (4) and the tip of the ground electrode (21) face each other. In plug (1)
The housing (2) has a shelf (22) formed by reducing the diameter of a portion of the inner peripheral surface (201) in the central axis direction (O).
The insulator (3) is positioned on the distal end side of the distal end side insulator portion (31) formed at a position close to the distal end side position, and on the rear end side of the distal end side insulator portion (31). (31) a rear end side insulator part (32) formed with a larger diameter, and a stepped surface formed between the rear end side insulator part (32) and the front end side insulator part (31) ( 33)
An annular packing (5) is sandwiched between the rear end side surface (221) of the shelf (22) and the step surface (33),
A spark plug (1) for an internal combustion engine, wherein irregularities (51) are repeatedly formed at a plurality of locations in the circumferential direction (C) on the inner peripheral surface (501) of the packing (5). 上記凹凸（５１）における凸部（５１１）は、上記中心軸線方向（Ｏ）から見た形状が、三角形状又は四角形状を有していることを特徴とする請求項１又は２に記載の内燃機関用のスパークプラグ（１）。   3. The internal combustion engine according to claim 1, wherein the convex portion (511) in the concave / convex portion (51) has a triangular shape or a quadrangular shape as viewed from the central axis direction (O). 4. Spark plug for engine (1). 上記凹凸（５１）における凸部（５１１）は、上記周方向（Ｃ）に等間隔に、５〜３０°の角度間隔（θ）で繰り返し形成されていることを特徴とする請求項１又は２に記載の内燃機関用のスパークプラグ（１）。   The convex portions (511) in the concave and convex portions (51) are repeatedly formed at equal intervals in the circumferential direction (C) at an angular interval (θ) of 5 to 30 °. A spark plug (1) for an internal combustion engine according to 1. 上記パッキン（５）の内周面（５０１）における上記凹凸（５１）の凸部（５１１）の先端は、上記棚部（２２）の後端側端面（２２１）と上記段差面（３３）との間から先端側に突出しており、
該凸部（５１１）の先端の上記中心軸線方向（Ｏ）における突出量（Ｌ）は、０〜１ｍｍの範囲内にあることを特徴とする請求項１〜３のいずれか一項に記載の内燃機関用のスパークプラグ（１）。 The tip of the projection (511) of the unevenness (51) on the inner peripheral surface (501) of the packing (5) is the rear end side end surface (221) of the shelf (22) and the step surface (33). Protruding to the tip side from between
The protrusion amount (L) in the central axis direction (O) at the tip of the convex portion (511) is in the range of 0 to 1 mm, according to any one of claims 1 to 3. A spark plug (1) for an internal combustion engine. 上記凹凸（５１）における凸部（５１１）の内周側先端に形成される角部（５１３）は、曲率半径（Ｒ）又は面取り幅が０．３ｍｍ以下であることを特徴とする請求項１〜４のいずれか一項に記載の内燃機関用のスパークプラグ（１）。   The corner portion (513) formed at the tip on the inner peripheral side of the convex portion (511) in the concave and convex portion (51) has a radius of curvature (R) or a chamfer width of 0.3 mm or less. The spark plug (1) for internal combustion engines as described in any one of -4.
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2016015259A (en) * 2014-07-02 2016-01-28 株式会社デンソー Spark plug for internal combustion engine

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS428006Y1 (en) * 1965-06-02 1967-04-24
JPS60160490U (en) * 1984-04-02 1985-10-25 日本特殊陶業株式会社 spark plug
JP2002260817A (en) * 2000-12-27 2002-09-13 Ngk Spark Plug Co Ltd Spark plug
WO2010035717A1 (en) * 2008-09-24 2010-04-01 日本特殊陶業株式会社 Spark plug

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS428006Y1 (en) * 1965-06-02 1967-04-24
JPS60160490U (en) * 1984-04-02 1985-10-25 日本特殊陶業株式会社 spark plug
JP2002260817A (en) * 2000-12-27 2002-09-13 Ngk Spark Plug Co Ltd Spark plug
WO2010035717A1 (en) * 2008-09-24 2010-04-01 日本特殊陶業株式会社 Spark plug

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2016015259A (en) * 2014-07-02 2016-01-28 株式会社デンソー Spark plug for internal combustion engine

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