JP6698454B2 - Ignition device - Google Patents

Ignition device Download PDF

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JP6698454B2
JP6698454B2 JP2016140635A JP2016140635A JP6698454B2 JP 6698454 B2 JP6698454 B2 JP 6698454B2 JP 2016140635 A JP2016140635 A JP 2016140635A JP 2016140635 A JP2016140635 A JP 2016140635A JP 6698454 B2 JP6698454 B2 JP 6698454B2
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insulator
base end
ignition device
end side
tip
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JP2018010841A (en
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翔太 木下
翔太 木下
健二 服部
健二 服部
文明 青木
文明 青木
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Denso Corp
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本発明は、点火プラグと電力ケーブルを備える点火装置に関する。   The present invention relates to an ignition device including a spark plug and a power cable.

特許文献１には、点火プラグの頭部に電力供給用の同軸ケーブルを取り付けたケーブル一体型プラグが開示されている。一般に、点火プラグは、筒状の金属製ハウジングの内側に、絶縁碍子を収容して中心電極を保持し、ハウジングに設けた接地電極との間に高電圧を印加して、放電を生起する。絶縁碍子は、ハウジングの段付内周面に当接支持されて、両端部がハウジングから突出位置し、同軸ケーブルが取り付けられるハウジングの基端開口縁は、絶縁碍子に対してカシメ固定されて、カシメ部を構成する。   Patent Document 1 discloses a cable-integrated plug in which a coaxial cable for power supply is attached to the head of an ignition plug. Generally, a spark plug accommodates an insulator inside a cylindrical metal housing to hold a center electrode and applies a high voltage to a ground electrode provided in the housing to generate a discharge. The insulator is abutted and supported on the stepped inner peripheral surface of the housing, both ends are positioned to project from the housing, and the base end opening edge of the housing to which the coaxial cable is attached is caulked and fixed to the insulator. Configure the caulking part.

特許文献１において、同軸ケーブルは、中心線に沿って設けられた内部導体と、同軸ケーブルの外表面となる外部導体と、両導体の間を絶縁する同軸ケーブル内絶縁体を備えている。同軸ケーブルの外部導体は、点火プラグのハウジングに固着される。外部導体は、例えば、先端部をテーパ状に縮径する形状として、ハウジングの外側面に当接させ、レーザ溶接等により固定される。   In Patent Document 1, the coaxial cable includes an inner conductor provided along the center line, an outer conductor that is an outer surface of the coaxial cable, and an inner conductor of the coaxial cable that insulates between the conductors. The outer conductor of the coaxial cable is fixed to the housing of the spark plug. The outer conductor has, for example, a shape in which the tip portion has a tapered diameter, is brought into contact with the outer surface of the housing, and is fixed by laser welding or the like.

特開２０１３−２３２３８３号公報JP, 2013-223383, A

しかしながら、特許文献１に記載される取付構造では、ハウジングの基端に設けられるカシメ部が、同軸ケーブルの外部導体より内側に位置する。そのため、カシメ部の先端に形成される鋭利な金属端に電界集中を起こし、この電界集中部を起点としてリーク放電が発生しやすくなる。リーク放電が発生すると、点火エネルギを十分に伝達できないおそれがあるばかりか、印加電圧の上昇に伴いカシメ部から、高電圧源が接続されるプラグ頭部側へと放電するフラッシオーバが発生しやすくなる。特に、高周波ではフラッシオーバ電圧が低下するため、主放電が起きなくなり点火プラグとしての機能が低下するおそれがある。   However, in the mounting structure described in Patent Document 1, the caulking portion provided at the base end of the housing is located inside the outer conductor of the coaxial cable. Therefore, electric field concentration occurs at a sharp metal end formed at the tip of the crimped portion, and leak discharge easily occurs starting from the electric field concentration portion. If a leak discharge occurs, not only may ignition energy not be sufficiently transmitted, but a flashover that easily discharges from the crimped portion to the plug head side to which the high voltage source is connected is likely to occur as the applied voltage rises. Become. In particular, at high frequencies, the flashover voltage decreases, so that main discharge may not occur and the function as an ignition plug may deteriorate.

本発明は、かかる背景に鑑みてなされたものであり、リーク放電やフラッシオーバの発生を防止して、点火プラグの機能低下を抑制し、点火のためのエネルギを確実に伝達することができる点火装置を提供しようとするものである。   The present invention has been made in view of the above background, and it is possible to prevent the occurrence of leak discharge and flashover, suppress the functional deterioration of the spark plug, and reliably transmit the energy for ignition. It is intended to provide a device.

本発明の一態様は、
点火プラグ（Ｐ）と、上記点火プラグへ電力を伝送する電力ケーブル（４）とを備える点火装置（１）であって、
上記点火プラグは、金属筒状のハウジング（Ｈ）と、上記ハウジングの内側に同軸的に保持され、軸方向（Ｘ）に貫通する軸孔（２１）を有する絶縁碍子（２）と、上記軸孔の先端側に収容される長軸状の中心電極（３１）と、上記ハウジングの先端側に設けられる接地電極（３２）とを有しており、
上記電力ケーブルは、上記中心電極と電気的に接続される中心導体（４１）と、上記中心導体の外側を取り囲み、上記ハウジングと電気的に接続される外側導体（４２）と、上記中心導体及び上記外側導体の間に介在する絶縁体（４３）と、を有しており、
上記外側導体は、上記ハウジングと接続される先端部（４２１）において、上記ハウジングの基端側開口部（Ｈ１）に隣接し、滑らかな曲面状の内表面（５１）を有する膨出部（５）を備え、かつ、上記膨出部が最小内径となる部位より内側に、上記基端側開口部が位置しない、点火装置にある。
なお、括弧内の符号は、参考のために付したものであり、本発明はこれら符号により限定されるものではない。 One aspect of the present invention is
An ignition device (1) comprising a spark plug (P) and a power cable (4) for transmitting power to the spark plug,
The spark plug includes a metal cylindrical housing (H), an insulator (2) coaxially held inside the housing and having a shaft hole (21) penetrating in the axial direction (X), and the shaft. It has a long-axis center electrode (31) housed on the tip side of the hole and a ground electrode (32) provided on the tip side of the housing.
The power cable includes a center conductor (41) electrically connected to the center electrode, an outer conductor (42) surrounding the outside of the center conductor and electrically connected to the housing, the center conductor, and An insulator (43) interposed between the outer conductors,
The outer conductor is adjacent to a base end side opening (H1) of the housing at a tip (421) connected to the housing, and has a bulged portion (5) having a smooth curved inner surface (51). ), and the base end side opening is not located inside the portion where the bulging portion has the minimum inner diameter.
The reference numerals in parentheses are provided for reference, and the present invention is not limited to these reference numerals.

上記点火装置によれば、点火プラグのハウジングに接続される電力ケーブルが、外側導体の先端部に膨出部を有し、その最小内径部より内側に、基端側開口部の端縁が突出することがない。そして、膨出部は、内表面が滑らかな曲面で構成されるので、基端側開口部に隣接して配置されて、周囲の電界強度を低下させる効果が得られる。
これにより、外側導体とハウジングとの接続部において、局部的な電界集中が生じて、リーク放電やフラッシオーバが発生することが抑制される。したがって、点火のためのエネルギを確実に伝達することができ、点火プラグの機能低下を抑制することができる。 According to the above-mentioned ignition device, the power cable connected to the housing of the spark plug has the bulging portion at the tip of the outer conductor, and the end edge of the base end side opening projects inside the minimum inner diameter portion. There is nothing to do. Further, since the bulging portion is formed of a curved surface having a smooth inner surface, it is arranged adjacent to the base end side opening portion, and an effect of lowering the surrounding electric field strength can be obtained.
As a result, local electric field concentration is suppressed at the connecting portion between the outer conductor and the housing, and leakage discharge or flashover is suppressed. Therefore, the energy for ignition can be reliably transmitted, and the functional deterioration of the spark plug can be suppressed.

実施形態１における、点火装置の主要部構造を示す概略断面図。1 is a schematic cross-sectional view showing the main part structure of an ignition device in Embodiment 1. FIG. 実施形態１における、点火装置を構成する点火プラグと電力ケーブルの接続構造を示す要部拡大断面図。FIG. 3 is an enlarged cross-sectional view of a main part showing a connection structure between an ignition plug and an electric power cable that form an ignition device according to the first embodiment. 実施形態１における、点火装置の全体構成を示す断面図。1 is a sectional view showing an overall configuration of an ignition device according to a first embodiment. 実施形態２における、点火プラグと電力ケーブルの接続構造を示す要部拡大断面図。FIG. 6 is an enlarged cross-sectional view of a main portion showing a connection structure between a spark plug and an electric power cable in the second embodiment. 実施形態３における、点火プラグと電力ケーブルの接続構造を示す要部拡大断面図。FIG. 6 is an enlarged cross-sectional view of a main part showing a connection structure between a spark plug and an electric power cable according to a third embodiment. 試験例１における、実施形態１の接続構造を有する点火装置の電界強度分布図。6 is a field intensity distribution diagram of the ignition device having the connection structure of Embodiment 1 in Test Example 1. FIG. 試験例１における、従来の接続構造を有する点火装置の電界強度分布図。The electric field strength distribution map of the ignition device which has the conventional connection structure in the test example 1. 従来の接続構造を有する点火装置における、フラッシオーバの発生の様子を模式的に示す要部拡大断面図。FIG. 9 is an enlarged cross-sectional view of a main part schematically showing how flashover occurs in an ignition device having a conventional connection structure. 試験例１における、実施形態１と従来の接続構造を有する点火装置の最大電界強度を比較して示す図。The figure which compares and shows the maximum electric field strength of the ignition device which has Embodiment 1 and the conventional connection structure in test example 1. 実施形態４における、点火プラグと電力ケーブルの接続構造を示す要部拡大断面図。FIG. 8 is an enlarged cross-sectional view of a main part showing a connection structure between a spark plug and an electric power cable according to a fourth embodiment. 実施形態５における、点火プラグと電力ケーブルの接続構造を示す要部拡大断面図。FIG. 9 is an enlarged cross-sectional view of a main part showing a connection structure between a spark plug and an electric power cable in the fifth embodiment. 試験例２における、先端部のＲ／ａが０．２〜３の範囲となる形状例を示す図The figure which shows the example of a shape which becomes R/a of the front-end|tip part in the range of 0.2-3 in the test example 2. 試験例２における、先端部のＲ／ａと最大電界強度の関係を示す図The figure which shows the relationship between R/a of a front-end|tip part and the maximum electric field strength in Test Example 2. 実施形態６における、点火プラグと電力ケーブルの接続構造を示す要部拡大断面図。FIG. 16 is an enlarged cross-sectional view of a main part showing a connection structure between a spark plug and an electric power cable in the sixth embodiment. 実施形態７における、点火プラグと電力ケーブルの接続構造を示す要部拡大断面図。FIG. 16 is an enlarged cross-sectional view of a main part showing a connection structure between a spark plug and an electric power cable according to a seventh embodiment. 実施形態８における、点火プラグと電力ケーブルの接続構造を示す要部拡大断面図。FIG. 16 is an enlarged cross-sectional view of a main part showing a connection structure between a spark plug and an electric power cable in the eighth embodiment. 実施形態９における、点火プラグと電力ケーブルの接続構造の変形例８を示す要部拡大断面図。The principal part expanded sectional view which shows the modification 8 of the connection structure of an ignition plug and an electric power cable in Embodiment 9. 実施形態１０における、点火装置の主要部構造を示す概略断面図。FIG. 13 is a schematic cross-sectional view showing the main part structure of the ignition device in the tenth embodiment. 実施形態１０における、点火装置を構成する点火プラグと電力ケーブルの接続構造を示す要部拡大断面図。FIG. 16 is an enlarged cross-sectional view of a main part showing a connection structure between an ignition plug and an electric power cable that form an ignition device according to a tenth embodiment. 試験例３における、実施形態１０の接続構造を有する点火装置の電界強度分布図。11 is a field intensity distribution diagram of the ignition device having the connection structure of Embodiment 10 in Test Example 3. FIG. 試験例３における、実施形態１０と従来の接続構造を有する点火装置の最大電界強度を比較して示す図。The figure which shows the maximum electric field strength of the ignition device which has Embodiment 10 and the conventional connection structure in test example 3 in comparison. 試験例３における、実施形態１、実施形態１０と従来の接続構造を有する点火装置の最大電界強度を比較して示す図。The figure which shows the maximum electric field strength of Embodiment 1 and Embodiment 10 and the ignition device which has the conventional connection structure in test example 3 in comparison. 実施形態１１における、点火装置の主要部構造を示す概略断面図。FIG. 13 is a schematic cross-sectional view showing the main part structure of the ignition device in the eleventh embodiment. 実施形態１１における、電力ケーブルの外側導体の接続構造を示す要部拡大断面図。FIG. 16 is an enlarged cross-sectional view of a main part showing the connection structure of the outer conductor of the power cable in the eleventh embodiment.

（実施形態１）
内燃機関に適用される点火装置１の実施形態１につき、図１〜図３を用いて説明する。図１に示されるように、点火装置１は、点火プラグＰと、この点火プラグＰに電力を伝送するための電力ケーブル４とを有している。点火プラグＰは、金属筒状のハウジングＨを有し、その内側に絶縁碍子２を同軸的に保持している。絶縁碍子２は、軸方向Ｘ（すなわち、図１の上下方向）に貫通する軸孔２１を有しており、軸孔２１の先端側（すなわち、図１の下側）には、長軸状の中心電極３１が収容されている。接地電位となるハウジングＨの先端面には、接地電極３２が設けられる。 (Embodiment 1)
A first embodiment of an ignition device 1 applied to an internal combustion engine will be described with reference to FIGS. 1 to 3. As shown in FIG. 1, the ignition device 1 has a spark plug P and a power cable 4 for transmitting electric power to the spark plug P. The spark plug P has a housing H in the shape of a metal cylinder, and holds the insulator 2 coaxially inside the housing H. The insulator 2 has a shaft hole 21 penetrating in the axial direction X (that is, the vertical direction in FIG. 1), and the distal end side of the shaft hole 21 (that is, the lower side in FIG. 1) has a long axis shape. The central electrode 31 of is accommodated. A ground electrode 32 is provided on the front end surface of the housing H that is at ground potential.

内燃機関は、例えば自動車用エンジンであり、点火プラグＰは、図示しないエンジン燃焼室内に供給される燃料への点火を行う。点火プラグＰは、ハウジングＨの中間部外周に設けた取付ネジ部Ｈ２によって、例えば、エンジン燃焼室に臨むシリンダヘッドの取付穴に、螺結される。このとき、点火プラグＰは、取付ネジ部Ｈ２より先端側に位置する中心電極３１及び接地電極３２が、エンジン燃焼室内に突出する。点火プラグＰの取付ネジ部Ｈ２より基端側（すなわち、図１の上側）は、シリンダヘッドの外部に位置し、電力ケーブル４は、ハウジングＨの基端側開口部Ｈ１を閉鎖するように、基端側開口部Ｈ１から突出する絶縁碍子２に外挿固定される。   The internal combustion engine is, for example, an automobile engine, and the spark plug P ignites fuel supplied to an engine combustion chamber (not shown). The spark plug P is screwed by, for example, a mounting screw portion H2 provided on the outer periphery of the middle portion of the housing H to a mounting hole of the cylinder head facing the engine combustion chamber. At this time, in the ignition plug P, the center electrode 31 and the ground electrode 32 located on the tip side of the mounting screw portion H2 protrude into the engine combustion chamber. The base end side (that is, the upper side in FIG. 1) of the mounting screw portion H2 of the spark plug P is located outside the cylinder head, and the power cable 4 closes the base end side opening H1 of the housing H. It is externally fixed to the insulator 2 protruding from the base end side opening H1.

電力ケーブル４は、中心導体４１と、この中心導体４１の外側を同軸的に取り囲む外側導体４２と、中心導体４１と外側導体４２の間に介在する絶縁体４３とを有している。電力ケーブル４は、先端側にプラグ接続部４０を有して、点火プラグＰの基端側に取り付けられる。プラグ接続部４０は、中心導体４１の先端部４１１と、外側導体４２の先端部４２１（以下、外導体先端部４２１と称する）と、絶縁体４３の先端部４３１とで形成される。中心導体４１の先端部４１１は、絶縁碍子２の軸孔２１内に挿通され、外導体先端部４２１は、ハウジングＨの基端側開口部Ｈ１に設けられる、開口端縁部としてのカシメ部Ｈ１１に当接する。   The power cable 4 includes a center conductor 41, an outer conductor 42 that coaxially surrounds the outside of the center conductor 41, and an insulator 43 that is interposed between the center conductor 41 and the outer conductor 42. The power cable 4 has a plug connecting portion 40 on the tip side and is attached to the base end side of the spark plug P. The plug connection portion 40 is formed of a tip portion 411 of the center conductor 41, a tip portion 421 of the outer conductor 42 (hereinafter, referred to as an outer conductor tip portion 421), and a tip portion 431 of the insulator 43. The tip portion 411 of the center conductor 41 is inserted into the shaft hole 21 of the insulator 2, and the outer conductor tip portion 421 is provided at the base end side opening portion H1 of the housing H, and is a caulking portion H11 as an opening end edge portion. Abut.

このとき、中心導体４１及び外側導体４２は、それぞれ中心電極３１及びハウジングＨと電気的に接続される。外導体先端部４２１には、ハウジングＨの基端側開口部Ｈ１に隣接して、膨出部５が設けられる。膨出部５は、滑らかな曲面状の内表面５１を有し、最小内径となる部位より内側に、基端側開口部Ｈ１が位置しないように配置される。これにより、外導体先端部４２１と基端側開口部Ｈ１との接続部に、電界緩和部６が形成される。プラグ接続部４０及び電界緩和部６の具体的構成については、後述する。
まず、点火装置１の各部構造について詳述する。 At this time, the center conductor 41 and the outer conductor 42 are electrically connected to the center electrode 31 and the housing H, respectively. The outer conductor tip portion 421 is provided with a bulging portion 5 adjacent to the base end side opening portion H1 of the housing H. The bulging portion 5 has an inner surface 51 having a smooth curved surface, and is arranged so that the base end side opening H1 is not located inside the portion having the smallest inner diameter. As a result, the electric field relaxing portion 6 is formed at the connecting portion between the outer conductor tip portion 421 and the base end side opening portion H1. Specific configurations of the plug connection portion 40 and the electric field relaxation portion 6 will be described later.
First, the structure of each part of the ignition device 1 will be described in detail.

点火プラグＰのハウジングＨは、例えば、ステンレス鋼等の鉄系合金材料からなる筒状体であり、ハウジングＨの筒穴Ｈ３は、絶縁碍子２の外形に沿う形状としてある。絶縁碍子２は、例えば、アルミナ等の絶縁材料からなる筒状体であり、その先端部及び基端部は、筒穴Ｈ３からそれぞれ軸方向Ｘに突出して位置する。筒穴Ｈ３は、取付ネジ部Ｈ２より基端側の内周面がテーパ段部Ｈ３１を有して拡径する一方、取付ネジ部Ｈ２より先端側の内周面が段付きに縮径している。このとき、筒穴Ｈ３の基端側のテーパ段部Ｈ３１上に、絶縁碍子２の中間部外周に設けた拡径部２２のテーパ面が当接支持され、先端側の段付部Ｈ３２上に、絶縁碍子２の先端側外周に設けた段部２３が当接支持される。また、筒穴Ｈ３の段付部Ｈ３２と絶縁碍子２の段部２３との間に、図示しないシールリング等を介在させて気密性を保持することができる。   The housing H of the spark plug P is, for example, a cylindrical body made of an iron-based alloy material such as stainless steel, and the cylindrical hole H3 of the housing H has a shape along the outer shape of the insulator 2. The insulator 2 is, for example, a tubular body made of an insulating material such as alumina, and the tip end portion and the base end portion thereof are located so as to project from the tubular hole H3 in the axial direction X, respectively. In the cylindrical hole H3, the inner peripheral surface on the proximal end side of the mounting screw portion H2 has a tapered step portion H31 and the diameter increases, while the inner peripheral surface on the distal end side of the mounting screw portion H2 has a stepped diameter. There is. At this time, the tapered surface of the enlarged diameter portion 22 provided on the outer periphery of the intermediate portion of the insulator 2 is abutted and supported on the tapered stepped portion H31 on the proximal end side of the cylindrical hole H3, and on the stepped portion H32 on the distal end side. The stepped portion 23 provided on the outer periphery of the insulator 2 on the tip side is abutted and supported. Further, an airtightness can be maintained by interposing a seal ring (not shown) between the stepped portion H32 of the cylindrical hole H3 and the stepped portion 23 of the insulator 2.

ハウジングＨは、基端側開口部Ｈ１にカシメ部Ｈ１１を設けて、絶縁碍子２の外周にカシメ固定される。カシメ部Ｈ１１は、基端側開口部Ｈ１の薄肉筒状の開口端縁部を、プレス機等を用いて、軸直方向Ｙ（すなわち、軸方向Ｘと直交する方向）内方へ屈曲変形させて形成される。このとき、基端側開口部Ｈ１と絶縁碍子２の間の空間部に、図示しないタルクやガスケット等を充填して圧縮する構成とすると、気密性が向上する。   The housing H is provided with a caulking portion H11 in the base end side opening H1 and is caulked and fixed to the outer periphery of the insulator 2. The caulking portion H11 bends and deforms the thin-walled tubular opening end edge portion of the base end side opening portion H1 inward in the axial direction Y (that is, in the direction orthogonal to the axial direction X) by using a press or the like. Formed. At this time, if the space between the base end side opening H1 and the insulator 2 is filled with a talc, a gasket or the like (not shown) and compressed, the airtightness is improved.

図２に示されるように、基端側開口部Ｈ１は、絶縁碍子２に近接するカシメ部Ｈ１１において、その基端側に位置する外側導体４２と密接する。ここでは、カシメ部Ｈ１１の基端側の端面Ｈ１２は、軸直方向Ｙと平行な環状面であり、プラグ接続部４０を構成する外導体先端部４２１は、軸直方向Ｙと平行な先端面４４を有して、互いに密着可能となっている。端面Ｈ１２に続く内表面Ｈ１３は、内径が一定の筒状面となっている。なお、カシメ部Ｈ１１の端面Ｈ１２と、外側導体４２の先端面４４は、電気的に接続可能に密接していればよく、必ずしも軸直方向Ｙと平行に形成されていなくてもよい。   As shown in FIG. 2, the base end side opening H1 is in close contact with the outer conductor 42 located on the base end side in the crimped portion H11 adjacent to the insulator 2. Here, the end surface H12 on the base end side of the crimped portion H11 is an annular surface parallel to the axis perpendicular direction Y, and the outer conductor tip portion 421 forming the plug connection portion 40 is a tip surface parallel to the axis perpendicular direction Y. 44, they can be in close contact with each other. The inner surface H13 following the end surface H12 is a cylindrical surface having a constant inner diameter. The end surface H12 of the crimped portion H11 and the end surface 44 of the outer conductor 42 need only be in close contact with each other so as to be electrically connectable, and do not necessarily have to be formed parallel to the perpendicular direction Y.

図１において、絶縁碍子２の軸孔２１は、先端側の半部がテーパ段部２４を有して縮径している。中心電極３１は、大径の基端部３１ａに設けたテーパ面が、軸孔２１のテーパ段部２４上に当接支持される。絶縁碍子２の先端部は、ハウジングＨの先端より先端側へ突出して、エンジン燃焼室に露出し、中心電極３１の先端部は、軸孔２１の先端開口より先端側へ突出している。ハウジングＨの円環状の先端面は、接地電極３２として機能し、電力ケーブル４から中心電極３１へ電力を供給すると、絶縁碍子２の露出表面を介して、中心電極３１と接地電極３２との間に沿面放電が生起する。   In FIG. 1, the shaft hole 21 of the insulator 2 has a tapered half portion on the front end side and has a reduced diameter. The tapered surface of the center electrode 31 provided on the large-diameter base end portion 31 a is abutted and supported on the tapered step portion 24 of the shaft hole 21. The tip portion of the insulator 2 projects from the tip of the housing H toward the tip side and is exposed to the engine combustion chamber, and the tip portion of the center electrode 31 projects from the tip opening of the shaft hole 21 toward the tip side. The annular end surface of the housing H functions as the ground electrode 32, and when power is supplied from the power cable 4 to the center electrode 31, the center electrode 31 and the ground electrode 32 are separated via the exposed surface of the insulator 2. A creeping discharge occurs.

軸孔２１の基端側半部内には、プラグ接続部４０となる中心導体４１の先端部４１１が挿通されて、中心電極３１の大径基端部３１ａに近接位置している。軸孔２１内において、中心導体４１の先端部４１１と大径基端部３１ａとの間には、導電シール部１１が介設される。導電シール部１１は、導電性ガラス等からなるガラスシール部１２、１３と、これらガラスシール部１２、１３間に配置される抵抗体１４にて構成される。抵抗体１４は、例えば、カーボン等の導電性材料とガラス材料と骨材とを含み、所望の抵抗値に調整されて、中心電極３１への伝送経路の一部を形成すると共に、電磁波ノイズを吸収する機能を有する。   The tip portion 411 of the central conductor 41, which serves as the plug connecting portion 40, is inserted into the proximal half portion of the shaft hole 21, and is located near the large-diameter proximal end portion 31 a of the central electrode 31. In the shaft hole 21, the conductive seal portion 11 is provided between the distal end portion 411 of the central conductor 41 and the large-diameter base end portion 31a. The conductive seal portion 11 is composed of glass seal portions 12 and 13 made of conductive glass and the like, and a resistor 14 arranged between the glass seal portions 12 and 13. The resistor 14 includes, for example, a conductive material such as carbon, a glass material, and an aggregate, and is adjusted to have a desired resistance value to form a part of a transmission path to the center electrode 31 and to prevent electromagnetic noise. Has the function of absorbing.

図３に示すように、電力ケーブル４の基端部は、昇圧トランス６と電気的に接続される。昇圧トランス６は、軟磁性材料からなるコア６１と、コア６１にギャップを形成するギャップ部材６２と、一次ボビン６３に巻回された一次巻線６４と、二次ボビン６５に巻回された二次巻線６６とを、トランスケース６７内に収容して構成される。トランスケース６７は、例えば、ステンレス鋼等の鉄系合金材料やアルミニウム合金材料、あるいは、導電性コーティングを施した合成樹脂材料にて構成される。   As shown in FIG. 3, the base end of the power cable 4 is electrically connected to the step-up transformer 6. The step-up transformer 6 includes a core 61 made of a soft magnetic material, a gap member 62 forming a gap in the core 61, a primary winding 64 wound around a primary bobbin 63, and a secondary winding 64 wound around a secondary bobbin 65. The secondary winding 66 is housed in the transformer case 67. The transformer case 67 is made of, for example, an iron-based alloy material such as stainless steel or an aluminum alloy material, or a synthetic resin material with a conductive coating.

コア６１は、２個のＥ型コア６１１を組み合わせて形成され、２個のＥ型コア６１１の間には、ギャップ部材６２が配置されている。ギャップ部材６２は、例えば、樹脂材料からなる。一次巻線６４と二次巻線６６は、コア６１内に形成される環状空間部に、同軸的に配置される。二次巻線６６は、一端が電力ケーブル４の中心導体４１に接続され、他端は、例えば、トランスケース６７を介して、電力ケーブル４の外側導体４２と電気的に接続されている。なお、二次巻線６６の他端を、トランスケース６７を介さずに取り出して、任意の位置に電気接続することも可能である。一次巻線６３の一端には、パルス発振部７が接続され、一次巻線６３の他端は、共通電位に接続される。   The core 61 is formed by combining two E-shaped cores 611, and a gap member 62 is arranged between the two E-shaped cores 611. The gap member 62 is made of, for example, a resin material. The primary winding 64 and the secondary winding 66 are coaxially arranged in an annular space formed in the core 61. One end of the secondary winding 66 is connected to the center conductor 41 of the power cable 4, and the other end is electrically connected to the outer conductor 42 of the power cable 4 via the transformer case 67, for example. It is also possible to take out the other end of the secondary winding 66 without passing through the transformer case 67 and electrically connect it to an arbitrary position. The pulse oscillator 7 is connected to one end of the primary winding 63, and the other end of the primary winding 63 is connected to a common potential.

パルス発信部７は、発振器７１と、ゲートドライバ７２と、ハーフブリッジ回路を形成する一対のスイッチング素子７３、７４と、分圧回路７５とからなる。スイッチング素子７３、７４は、電源７６に接続される高電位配線７６１と、接地された低電位配線７６２との間に配置され、スイッチング素子７３、７４の間には、一次巻線６４の一端が接続される。パルス発信部７は、スイッチング素子７３、７４を、交互にオンオフ動作させることにより、パルス状の出力電圧を発生し、一次巻線６４に印加する。スイッチング素子７３、７４は、例えばＭＯＳＦＥＴ（ＭＯＳ型電界効果トランジスタ）、ＩＧＢＴ（絶縁ゲートバイポーラトランジスタ）等の半導体素子からなる。   The pulse transmission unit 7 includes an oscillator 71, a gate driver 72, a pair of switching elements 73 and 74 forming a half bridge circuit, and a voltage dividing circuit 75. The switching elements 73 and 74 are arranged between a high potential wiring 761 connected to the power supply 76 and a grounded low potential wiring 762, and one end of the primary winding 64 is located between the switching elements 73 and 74. Connected. The pulse transmission unit 7 alternately turns on and off the switching elements 73 and 74 to generate a pulsed output voltage, which is applied to the primary winding 64. The switching elements 73 and 74 are semiconductor elements such as MOSFET (MOS type field effect transistor) and IGBT (insulated gate bipolar transistor).

分圧回路７５は、電源７６に接続される高電位配線７６１と、接地された低電位配線７６２との間に、互いに直列に接続された一対の抵抗７７ａ、７７ｂと、互いに直列に接続された一対のコンデンサ７８ａ、７８ｂとを有する。一対の抵抗７７ａ、７７ｂの中点と、一対のコンデンサ７８ａ、７８ｂの中点は、共通電位に接続される。   The voltage dividing circuit 75 is connected in series with a pair of resistors 77a and 77b connected in series with each other between a high potential wiring 761 connected to the power supply 76 and a grounded low potential wiring 762. It has a pair of capacitors 78a and 78b. The midpoint of the pair of resistors 77a and 77b and the midpoint of the pair of capacitors 78a and 78b are connected to a common potential.

パルス発信部７に、図示しない内燃機関のＥＣＵから点火信号が入力すると、発振器７１が生成する矩形波のパルス信号に基づいて、ゲートドライバ７２から駆動信号が出力される。この駆動信号により、スイッチング素子７３、７４のゲート電圧が制御され、スイッチング素子７３、７４がオンオフ駆動される。これに伴い、昇圧トランス６の一次巻線６４に、一定の周波数、一定のパルス幅のパルス正電圧及びパルス負電圧が送られる。二次巻線６６には、一次巻線６４と二次巻線６６の巻き数比と共振効率に応じて、一定の周波数の一次電圧より高い二次電圧が発生する。   When an ignition signal is input to the pulse transmission unit 7 from an ECU of an internal combustion engine (not shown), a drive signal is output from the gate driver 72 based on the rectangular pulse signal generated by the oscillator 71. The drive signal controls the gate voltages of the switching elements 73 and 74, and the switching elements 73 and 74 are driven on and off. Along with this, the positive voltage and the negative pulse voltage having a constant frequency and a constant pulse width are sent to the primary winding 64 of the step-up transformer 6. In the secondary winding 66, a secondary voltage higher than the primary voltage of a constant frequency is generated according to the winding ratio of the primary winding 64 and the secondary winding 66 and the resonance efficiency.

このようにして、沿面放電型プラグである点火プラグＰに、高周波を印加することにより、ストリーマ放電等を生起することができる。このとき、昇圧トランス６と点火プラグＰとを接続する電力ケーブル４は、中心導体４１と外側導体４２と絶縁体４３（すなわち、誘電体）とからなる同軸ケーブル構造を有して、高周波電力を伝送する。中心導体４１は、一定の外径を有する金属線であり、一定の外径を有する金属管状の外側導体４２の内側に同軸配置される。中心導体４１と外側導体４２の間には、所定厚さの筒状に形成された絶縁体４３が配置される。絶縁体４３の内周面及び外周面は、それぞれ中心導体４１の外周面及び外側導体４２の内周面に密接している。   In this way, streamer discharge or the like can be generated by applying a high frequency to the spark plug P which is a creeping discharge type plug. At this time, the power cable 4 that connects the step-up transformer 6 and the ignition plug P has a coaxial cable structure including a center conductor 41, an outer conductor 42, and an insulator 43 (that is, a dielectric), and outputs high-frequency power. To transmit. The center conductor 41 is a metal wire having a constant outer diameter, and is coaxially arranged inside the metal tubular outer conductor 42 having a constant outer diameter. Between the center conductor 41 and the outer conductor 42, a cylindrical insulator 43 having a predetermined thickness is arranged. The inner peripheral surface and the outer peripheral surface of the insulator 43 are in close contact with the outer peripheral surface of the central conductor 41 and the inner peripheral surface of the outer conductor 42, respectively.

中心導体４１又は外側導体４２を構成する金属材料は、特に制限されるものではなく、銅、アルミニウム、ニッケル、鉄等の金属又はそれらの合金等から適宜選択される。好適には、中心導体４１は、例えば、銅又は銅合金等の導電性の高い金属材料にて構成され、外側導体４２は、例えば、ステンレス鋼等の耐熱性の高い金属材料にて構成することができる。絶縁体４３は、例えば、ポリエチレン、架橋ポリエチレン、フッ素樹脂等の絶縁性樹脂材料にて構成することができる。絶縁体４３を、例えば、アルミナ等の絶縁性セラミックス材料にて構成することもできる。   The metal material forming the center conductor 41 or the outer conductor 42 is not particularly limited, and is appropriately selected from metals such as copper, aluminum, nickel and iron, or alloys thereof. Preferably, the center conductor 41 is made of a highly conductive metal material such as copper or copper alloy, and the outer conductor 42 is made of a highly heat resistant metal material such as stainless steel. You can The insulator 43 can be made of, for example, an insulating resin material such as polyethylene, cross-linked polyethylene, or fluororesin. The insulator 43 may be made of an insulating ceramic material such as alumina.

絶縁体４３は、予め筒状に成形した後に、中心導体４１と外側導体４２の間に充填されても、中心導体４１と外側導体４２の間に樹脂材料を注入後、硬化させて形成してもよい。注入硬化による場合には、樹脂材料として、シリコーン系樹脂の他、エポキシ系樹脂等の熱硬化性樹脂材料を用いることもできる。高周波電力を伝送するためには、誘電損が小さい樹脂材料が適しており、特に、フッ素系樹脂、シリコーン系樹脂が好適に使用される。   Even if the insulator 43 is preliminarily formed into a tubular shape and then filled between the center conductor 41 and the outer conductor 42, the insulator 43 is formed by injecting a resin material between the center conductor 41 and the outer conductor 42 and then curing the resin material. Good. In the case of injection curing, a thermosetting resin material such as an epoxy resin can be used as the resin material in addition to the silicone resin. A resin material having a small dielectric loss is suitable for transmitting high-frequency power, and a fluorine resin or a silicone resin is particularly preferably used.

電力ケーブル４は、中心導体４１の外径と外側導体４２の内径との比と、絶縁体４３（すなわち、誘電体）の比誘電率とによって決まる特性インピーダンスを有し、インピーダンス整合が図られる。電力ケーブル４は、特性インピーダンスを含む諸特性が、所望の値となるように、各部材の形状（例えば、内外径、厚さ等）や材料等が適宜選択される。   The power cable 4 has a characteristic impedance determined by the ratio of the outer diameter of the central conductor 41 to the inner diameter of the outer conductor 42 and the relative permittivity of the insulator 43 (that is, the dielectric), and impedance matching is achieved. In the power cable 4, the shape (for example, inner and outer diameters, thickness, etc.) of each member, the material, and the like are appropriately selected so that various characteristics including the characteristic impedance have desired values.

図１、図２に示されるように、電力ケーブル４は、先端側に設けたプラグ接続部４０によって、点火プラグＰの基端側から軸方向Ｘに装着され、電気的に接続される。すなわち、中心導体４１の先端部４１１が、軸孔２１内において、導電シール部１１を介して中心電極３１に接続されると共に、外導体先端部４２１が、絶縁碍子２の外側において、ハウジングＨの基端側開口部Ｈ１に接続される。絶縁碍子２の基端部に隣接する絶縁体４３の先端部４３１は、絶縁碍子２の基端部に覆着される凹部４３２を有し、膨出部５の内側に、膨出部５に沿う形状の先端薄肉部４３１ａが隣接位置する。すなわち、先端薄肉部４３１ａは、膨出部５に対応する滑らかな凹曲面状の外表面を有し、先端側ほど外径が膨出部５の内表面５１に密接する。   As shown in FIGS. 1 and 2, the power cable 4 is mounted in the axial direction X from the base end side of the ignition plug P and electrically connected by the plug connecting portion 40 provided on the front end side. That is, the tip portion 411 of the center conductor 41 is connected to the center electrode 31 in the shaft hole 21 via the conductive seal portion 11, and the outer conductor tip portion 421 is located outside the insulator 2 in the housing H. It is connected to the base end side opening H1. The tip end portion 431 of the insulator 43 adjacent to the base end portion of the insulator 2 has a recessed portion 432 that is covered by the base end portion of the insulator 2, and is provided inside the bulge portion 5 and on the bulge portion 5. The tip thin-walled portion 431a having a conformal shape is adjacently located. That is, the thin tip portion 431 a has a smooth concave curved outer surface corresponding to the bulging portion 5, and the outer diameter is closer to the inner surface 51 of the bulging portion 5 toward the tip side.

先端薄肉部４３１ａを含む筒状の先端部４３１は、所定厚さの絶縁体４３の筒状本体部と共に予め一体成形された絶縁体４３として構成することができる。あるいは、中心導体４１を装着後、外側導体４２の内側に樹脂材料を注入硬化することにより、絶縁碍子２と外側導体４２の間に樹脂材料を充填して、先端部４３１を形成し、膨出部５に密接する先端薄肉部４３１ａを形成することができる。電力ケーブル４を、昇圧トランス６と一体的に形成する場合には、トランスケース６７内に充填されるモールド樹脂材料を用いて、先端薄肉部４３１ａを含む絶縁体４３を、トランスケース６７内のモールド樹脂と一体成形してもよい。   The tubular tip portion 431 including the thin tip portion 431a can be configured as an insulator 43 integrally preliminarily formed with the tubular body portion of the insulator 43 having a predetermined thickness. Alternatively, after mounting the center conductor 41, a resin material is injected and cured inside the outer conductor 42 to fill the resin material between the insulator 2 and the outer conductor 42 to form the tip portion 431 and to bulge. It is possible to form the thin tip portion 431a that is in close contact with the portion 5. When the power cable 4 is formed integrally with the step-up transformer 6, a molding resin material filled in the transformer case 67 is used to mold the insulator 43 including the thin tip portion 431 a into the transformer case 67. It may be integrally molded with the resin.

ここで、電力ケーブル４の外表面を形成する外側導体４２は、継ぎ目のない金属管からなり、一定の外径を有する。外側導体４２は、一定外径の絶縁体４３に隣接する位置においては、一定の内径を有し、それより先端側においては、内周面の全面に厚肉筒状の膨出部５が形成されて、先端側ほど内径が小さくなる。具体的には、膨出部５は、外導体先端部４２１の内周面から軸直方向Ｙの内方へ、弧を描くように膨出している。膨出部５は、軸方向Ｘの断面形状が、例えば、１／４円断面形状で、軸方向Ｘにおける膨出部５の内径の縮小率は単調減少となり、先端側へ向けて内径が徐々に小さくなって、先端面４４において最小内径となる。膨出部５の内表面５１は、１／４円弧状の輪郭形状を有する滑らかな曲面となっており、基端側において、外導体先端部４２１の内表面４５に連続する。膨出部５は、先端面４４へ開口する内側端縁を除いて角部を有しない。   Here, the outer conductor 42 forming the outer surface of the power cable 4 is made of a seamless metal tube and has a constant outer diameter. The outer conductor 42 has a constant inner diameter at a position adjacent to the insulator 43 having a constant outer diameter, and a thick-walled cylindrical bulging portion 5 is formed on the entire inner peripheral surface on the tip side from the outer conductor 42. Thus, the inner diameter becomes smaller toward the tip side. Specifically, the bulging portion 5 bulges from the inner peripheral surface of the outer conductor tip portion 421 inward in the direction Y perpendicular to the axis so as to draw an arc. The bulging portion 5 has a cross-sectional shape in the axial direction X of, for example, a ¼ circular cross-sectional shape, and the reduction ratio of the inner diameter of the bulging portion 5 in the axial direction X monotonically decreases, and the inner diameter gradually increases toward the tip side. To the minimum inner diameter at the tip surface 44. The inner surface 51 of the bulging portion 5 is a smooth curved surface having a 1/4 arc-shaped contour shape, and is continuous with the inner surface 45 of the outer conductor tip portion 421 on the base end side. The bulging portion 5 does not have a corner portion except for the inner end edge that opens to the front end surface 44.

外側導体４２は、膨出部５がカシメ部Ｈ１１に押し当てられて一体となり、絶縁碍子２の外表面に僅かな間隙を有して近接する。具体的には、絶縁碍子２に近接する内周側において、先端面４４の一部がカシメ部Ｈ１１の端面Ｈ１２に密着し、最小内径となるカシメ部Ｈ１１の内周端縁は、膨出部５の内側端縁と重なる。すなわち、カシメ部Ｈ１１の内表面Ｈ１３は、膨出部５の内表面５１と滑らかに接続し、膨出部５の最小内径となる部位より内側に位置しない。膨出部５の内側の先端薄肉部４３１ａは、先端側へ向けて外径が徐々に小さくなる、円錐状の外形を有し、先端は、外側導体４２の先端面４４と一致する。   The bulging portion 5 of the outer conductor 42 is pressed against the caulking portion H11 to be integrated, and comes close to the outer surface of the insulator 2 with a slight gap. Specifically, on the inner peripheral side close to the insulator 2, a part of the front end surface 44 is in close contact with the end surface H12 of the crimped portion H11, and the inner peripheral end edge of the crimped portion H11 having the minimum inner diameter is the bulging portion. The inner edge of 5 overlaps. That is, the inner surface H13 of the crimped portion H11 is smoothly connected to the inner surface 51 of the bulging portion 5 and is not located inside the portion having the minimum inner diameter of the bulging portion 5. The tip thin-walled portion 431a inside the bulging portion 5 has a conical outer shape in which the outer diameter gradually decreases toward the tip side, and the tip thereof coincides with the tip surface 44 of the outer conductor 42.

このとき、膨出部５の内表面５１とカシメ部Ｈ１１の内表面Ｈ１３とが、連続する内表面となり、絶縁碍子２の近傍に、滑らかな金属表面からなる電界緩和部６が形成される。このように、金属管からなる外側導体４２によって、電界がシールディングされる構成において、さらに、絶縁碍子２の近傍に鋭利な金属端や凸部、鋭角の角部、段部等が露出しない構成とすることで、電界集中を抑制し、電界緩和部６として機能させることができる。これにより、プラグ接続部４０におけるリーク放電の発生を抑制し、電力ケーブル４から点火プラグＰへ、点火エネルギを効率よく伝達することができる。   At this time, the inner surface 51 of the bulging portion 5 and the inner surface H13 of the crimped portion H11 become a continuous inner surface, and the electric field relaxing portion 6 made of a smooth metal surface is formed in the vicinity of the insulator 2. As described above, in the configuration in which the electric field is shielded by the outer conductor 42 made of the metal tube, the sharp metal end, the convex portion, the acute corner portion, the step portion, etc. are not exposed in the vicinity of the insulator 2. Thus, the electric field concentration can be suppressed and the electric field alleviating section 6 can be made to function. As a result, the occurrence of leak discharge in the plug connection portion 40 can be suppressed, and the ignition energy can be efficiently transmitted from the power cable 4 to the spark plug P.

（実施形態２）
図４に、実施形態２として示すように、外側導体４２は、膨出部５がカシメ部Ｈ１１に押し当てられて一体となり、絶縁碍子２の外表面に当接する位置にあってもよい。この場合、電界緩和部６を形成する金属表面は、より滑らかな曲面状であることが望ましい。具体的には、カシメ部Ｈ１１の内表面Ｈ１３を、一定径の筒状面とする代わりに、基端側へ向けて内径が徐々に小さくなり、端面Ｈ１２において最小内径となる曲面状に形成するとよい。このとき、図示するように、内表面Ｈ１３が、膨出部５の内表面５１の延長上に位置して、連続する滑らかな曲面を形成する。 (Embodiment 2)
As shown as a second embodiment in FIG. 4, the outer conductor 42 may be located at a position where the bulging portion 5 is pressed against the crimp portion H11 to be integrated and abuts on the outer surface of the insulator 2. In this case, it is desirable that the metal surface forming the electric field relaxation portion 6 has a smoother curved surface. Specifically, when the inner surface H13 of the crimped portion H11 is formed as a curved surface having a minimum inner diameter at the end surface H12, the inner diameter gradually decreases toward the base end side, instead of a cylindrical surface having a constant diameter. Good. At this time, as shown in the figure, the inner surface H13 is located on the extension of the inner surface 51 of the bulging portion 5 and forms a continuous smooth curved surface.

このように、膨出部５とカシメ部Ｈ１１が、絶縁碍子２の外表面と接触する位置にあっても、カシメ部Ｈ１１の内表面Ｈ１３を曲面状とすることで、電界集中を緩和する効果が得られる。したがって、電界緩和部６による、電界強度の低減効果を高めて、リーク放電の発生を抑制することができる。   Thus, even if the bulging portion 5 and the crimped portion H11 are in contact with the outer surface of the insulator 2, the effect of alleviating the electric field concentration by making the inner surface H13 of the crimped portion H11 into a curved surface shape Is obtained. Therefore, the effect of reducing the electric field strength by the electric field relaxation portion 6 can be enhanced, and the occurrence of leak discharge can be suppressed.

なお、実施形態２以降において用いた符号のうち、既出の実施形態において用いた符号と同一のものは、特に示さない限り、既出の実施形態におけるものと同様の構成要素等を表す。図中の符号についても、同様である。   In addition, among the reference numerals used in the second and subsequent embodiments, the same reference numerals as those used in the already-described embodiments represent the same components and the like as those in the already-described embodiments, unless otherwise specified. The same applies to the reference numerals in the figure.

（実施形態３）
図５に、実施形態３として示すように、実施形態２の構成において、電界緩和部６を形成する膨出部５とカシメ部Ｈ１１が、絶縁碍子２の外表面から離れて配置されていても、もちろんよい。これにより、電界緩和部６と絶縁碍子２の外表面との間の電界強度がさらに低下し、リーク放電の発生を抑制する効果を高めることができる。 (Embodiment 3)
As shown in FIG. 5 as a third embodiment, in the configuration of the second embodiment, even if the bulging portion 5 and the crimped portion H11 forming the electric field relaxation portion 6 are arranged apart from the outer surface of the insulator 2. , Of course good. As a result, the electric field strength between the electric field relaxation portion 6 and the outer surface of the insulator 2 is further reduced, and the effect of suppressing the occurrence of leak discharge can be enhanced.

これら実施形態２、３の構成のように、絶縁碍子２の外表面に当接又は近接する金属表面が、連続する曲面状に形成されていると、電界強度を低下させる効果が大きくなる。カシメ部Ｈ１１の内表面Ｈ１３と、膨出部５の内表面１５の曲率半径Ｒは、必ずしも同じでなくてもよく、接続部において滑らかに連続する面を形成していることが望ましい。   When the metal surface that is in contact with or close to the outer surface of the insulator 2 is formed into a continuous curved surface as in the configurations of Embodiments 2 and 3, the effect of lowering the electric field strength is increased. The radii of curvature R of the inner surface H13 of the crimped portion H11 and the inner surface 15 of the bulging portion 5 do not necessarily have to be the same, and it is desirable that a smoothly continuous surface be formed at the connection portion.

また、上記実施形態では、先端薄肉部４３１ａを含む先端部４３１全体を、絶縁体４３の筒状本体部と一体に形成したが、絶縁体４３の一部、例えば、先端薄肉部４３１ａを別体に構成することもできる。ここでは、先端薄肉部４３１ａに相当する形状の絶縁部４３３を、膨出部５の内側に配置している。絶縁部４３３は、内径が絶縁碍子２の外径と一致し、外径が先端側ほど小さくなる円錐状の筒状体からなる。絶縁部４３３は、例えば、予め所定の形状に成形したものを、膨出部５の内側に密接するように配置し、その基端側に一定の外径を有する先端部４３１及び絶縁体４３の筒状本体部を密着配置させて、一体の絶縁体４３とすることができる。   Further, in the above-described embodiment, the entire tip portion 431 including the tip thin portion 431a is formed integrally with the tubular main body portion of the insulator 43, but a part of the insulator 43, for example, the tip thin portion 431a is formed separately. It can also be configured as. Here, the insulating portion 433 having a shape corresponding to the thin tip portion 431 a is arranged inside the bulging portion 5. The insulating portion 433 is made of a conical tubular body whose inner diameter matches the outer diameter of the insulator 2 and whose outer diameter becomes smaller toward the tip end side. The insulating portion 433 is formed, for example, in a predetermined shape in advance so as to be placed in close contact with the inside of the bulging portion 5 and has a fixed outer diameter on the proximal end side thereof. The tubular body portion can be closely arranged to form an integral insulator 43.

絶縁部４３３は、例えば、絶縁体４３と同様の絶縁性樹脂材料又は絶縁性セラミックス材料にて構成される。この場合、絶縁部４３３と絶縁体４３とは、同じ材質としても異なる材質としてもよい。あるいは、絶縁部４３３を、絶縁性の弾性材料にて構成することもできる。この場合は、弾性材料からなる絶縁部４３３と膨出部５との密着性が向上する。   The insulating portion 433 is made of, for example, the same insulating resin material or insulating ceramic material as the insulator 43. In this case, the insulating portion 433 and the insulating body 43 may be made of the same material or different materials. Alternatively, the insulating portion 433 may be made of an insulating elastic material. In this case, the adhesion between the insulating portion 433 made of an elastic material and the bulging portion 5 is improved.

上記実施形態２のように、膨出部５が絶縁碍子２の外表面に当接する位置にある場合には、絶縁部４３３を、所定形状の成形体とする代わりに、絶縁グリスにて構成することもできる。この場合は、予め膨出部５の内側の空間に、絶縁グリスを充填し、その基端側に、一定の外径を有する先端部４３１及び絶縁体４３の筒状本体部を配置して、一体の絶縁体４３とする。あるいは、膨出部５の内側の空間に、微量の絶縁性樹脂材料又は絶縁グリスを充填し、さらに、膨出部５に沿う形状の絶縁部４３３を配置することもできる。この場合は、部材間の密着性がさらに向上する。   When the bulging portion 5 is located at the position where it contacts the outer surface of the insulator 2 as in the second embodiment, the insulating portion 433 is made of insulating grease instead of being a molded body having a predetermined shape. You can also In this case, the space inside the bulging portion 5 is filled with insulating grease in advance, and the distal end portion 431 having a constant outer diameter and the tubular main body portion of the insulating body 43 are arranged on the base end side thereof, The insulator 43 is integrated. Alternatively, the space inside the bulging portion 5 may be filled with a small amount of an insulating resin material or insulating grease, and the insulating portion 433 having a shape along the bulging portion 5 may be arranged. In this case, the adhesion between the members is further improved.

（試験例１）
以下の条件で、有限要素法を用いた解析を行い、電界緩和部６の効果を調べた。ハウジングＨのカシメ部Ｈ１１に膨出部５が密接する実施形態１の構成と、膨出部５を有しない従来の構成のそれぞれについて、解析モデルを用意し、分割された要素毎に電界強度を計算して、電界強度分布を求めた。
[解析条件]
・中心導体４１：銅（外径φ３ｍｍ）
・絶縁碍子２：アルミナ（内径φ３ｍｍ、外径φ９ｍｍ）
・ハウジングＨ：ステンレス鋼（最小内径φ９ｍｍ）
・外側導体４２：ステンレス鋼（内径φ１８ｍｍ）
・印加電圧：２０ｋＶ
・比誘電率（アルミナ）：９
・要素サイズ：０．１ｍｍ (Test Example 1)
An analysis using the finite element method was performed under the following conditions to examine the effect of the electric field relaxation section 6. An analytical model is prepared for each of the configuration of the first embodiment in which the swollen portion 5 is in close contact with the crimped portion H11 of the housing H and the conventional configuration without the swollen portion 5, and the electric field strength is calculated for each divided element. The electric field strength distribution was calculated.
[Analysis conditions]
・Center conductor 41: copper (outer diameter φ3 mm)
・Insulator 2: Alumina (inner diameter 3 mm, outer diameter 9 mm)
・Housing H: Stainless steel (Minimum inner diameter 9 mm)
・Outer conductor 42: Stainless steel (inner diameter φ18 mm)
・Applied voltage: 20kV
・Relative permittivity (alumina): 9
・Element size: 0.1 mm

図６に示されるように、実施形態１の構成では、カシメ部Ｈ１の内表面Ｈ１３とこれに連なる膨出部５の内表面５１において、近接する絶縁碍子２の外表面との間の電界強度が高くなっている（最大電界強度：４５ｋＶ／ｍｍ）。膨出部５の内表面５１が、絶縁碍子２の外表面から離れるに従って、電界強度は徐々に低下し、ハウジングＨ又は外側導体４２の内表面４５と絶縁碍子２の外表面との間に形成される空間部で、電界強度は最小となる。   As shown in FIG. 6, in the configuration of the first embodiment, the electric field strength between the inner surface H13 of the caulked portion H1 and the outer surface of the insulator 2 that is adjacent to the inner surface 51 of the bulging portion 5 continuous with the inner surface H13. Is high (maximum electric field strength: 45 kV/mm). The electric field strength gradually decreases as the inner surface 51 of the bulging portion 5 moves away from the outer surface of the insulator 2, and is formed between the inner surface 45 of the housing H or the outer conductor 42 and the outer surface of the insulator 2. The electric field strength becomes the minimum in the defined space.

一方、図７に示されるように、従来の構成では、カシメ部Ｈ１の内表面Ｈ１３と、その内側の絶縁碍子２の外表面との間において、電界強度が局部的に高くなっている（最大電界強度：５２ｋＶ／ｍｍ）。カシメ部Ｈ１の基端側又は先端側では、電界強度は急減している。この場合、図８に示されるように、電界集中部となるカシメ部Ｈ１の端縁を起点として、絶縁碍子２の沿面を這うリーク放電Ｌが発生しやすくなる。   On the other hand, as shown in FIG. 7, in the conventional configuration, the electric field strength is locally high between the inner surface H13 of the caulked portion H1 and the outer surface of the insulator 2 inside thereof (maximum). Electric field strength: 52 kV/mm). The electric field strength sharply decreases on the base end side or the tip end side of the crimped portion H1. In this case, as shown in FIG. 8, a leak discharge L crawls along the creeping surface of the insulator 2 from the end edge of the crimped portion H1 serving as an electric field concentration portion is likely to occur.

これに対して、図９に示されるように、実施形態１の構成とすることで、最大電界強度は、従来の構成に対して、１４％低減する。すなわち、外導体先端部４２１に、カシメ部Ｈ１と一体に膨出部５を接続することにより、電界緩和部６として機能させることができ、電界集中を抑制する効果が得られることが確認された。   On the other hand, as shown in FIG. 9, the configuration of the first embodiment reduces the maximum electric field strength by 14% as compared with the conventional configuration. That is, it was confirmed that by connecting the bulging portion 5 integrally with the caulking portion H1 to the outer conductor tip portion 421, the outer conductor tip portion 421 can function as the electric field relaxation portion 6 and an effect of suppressing electric field concentration can be obtained. ..

（実施形態４）
図１０に、実施形態４として示すように、電界緩和部６を形成する膨出部５とカシメ部Ｈ１１は、軸直方向Ｙにおいて、膨出部５の最小内径となる部位よりも、カシメ部Ｈ１１が内側に位置しないように配置されていればよい。その場合には、膨出部５とカシメ部Ｈ１１は、接続部において連続する面を形成していなくてもよい。このとき、上記実施形態１のように、膨出部５を１／４円断面形状とし、最小内径となる先端面４４において、絶縁碍子２の外表面と当接させることもできるが、図示するように、内側端縁に、角を有しないＲ形状部５２を形成することもでき、より望ましい。 (Embodiment 4)
As shown in FIG. 10 as the fourth embodiment, the swollen portion 5 and the swaged portion H11 forming the electric field relaxation portion 6 are closer to each other than the portion having the minimum inner diameter of the swollen portion 5 in the direction Y perpendicular to the axis. It is sufficient that H11 is arranged so as not to be located inside. In that case, the bulging portion 5 and the crimped portion H11 do not have to form a continuous surface in the connecting portion. At this time, as in the first embodiment, the bulging portion 5 may have a quarter circular cross-sectional shape, and the tip surface 44 having the smallest inner diameter may be brought into contact with the outer surface of the insulator 2, but it is shown in the drawing. As described above, the R-shaped portion 52 having no corner can be formed on the inner edge, which is more preferable.

具体的には、膨出部５は、略１／４円断面形状であり、内側端縁の全周に設けたＲ形状部５２が、絶縁碍子２の外表面と当接又は近接する位置にある。カシメ部Ｈ１１の内表面Ｈ１３は、膨出部５が最小内径となる位置よりも外側において、例えば、Ｒ形状部５２と連続するように構成することができる。これにより、膨出部５とカシメ部Ｈ１１の接続部に角部が形成されず、角を有しないＲ形状部５２によって、滑らかに接続されるので、電界集中を抑制する効果が高まる。   Specifically, the bulging portion 5 has a substantially ¼ circular cross-sectional shape, and the R-shaped portion 52 provided on the entire circumference of the inner end edge is located at a position where the R-shaped portion 52 comes into contact with or approaches the outer surface of the insulator 2. is there. The inner surface H13 of the crimped portion H11 can be configured to be continuous with the R-shaped portion 52, for example, outside the position where the bulging portion 5 has the minimum inner diameter. As a result, no corner is formed at the connecting portion between the bulging portion 5 and the crimped portion H11, and the R-shaped portion 52 having no corner allows smooth connection, so that the effect of suppressing electric field concentration is enhanced.

したがって、カシメ部Ｈ１の内側の微小空間において、電界強度の緩和効果が高められ、リーク放電が生じるのを抑制できる。カシメ部Ｈ１１の内表面Ｈ１３は、図示するように、絶縁碍子２の外表面と平行な筒状面であっても、上記実施形態２、３と同様の曲面状であってもよい。   Therefore, in the minute space inside the crimped portion H1, the effect of relaxing the electric field strength is enhanced, and the occurrence of leak discharge can be suppressed. The inner surface H13 of the crimped portion H11 may be a cylindrical surface parallel to the outer surface of the insulator 2 as shown in the drawing, or may be a curved surface similar to those in the second and third embodiments.

（実施形態５）
図１１に、実施形態５として示すように、電界緩和部６を形成する膨出部５は、１／４円断面形状に限らず、内表面５１が、円弧状の輪郭形状を有する曲面にて構成されていればよい。具体的には、図示するように、上記実施形態２の膨出部５を基本形状として、その内表面５１の曲率半径Ｒを大きくし、より緩やかな曲面形状とすることで、電界緩和効果が大きくなる。カシメ部Ｈ１１の形状は、上記実施形態４と同様とすることができる。 (Embodiment 5)
As shown in FIG. 11 as a fifth embodiment, the bulging portion 5 forming the electric field relaxing portion 6 is not limited to the ¼ circular cross-sectional shape, and the inner surface 51 is a curved surface having an arc-shaped contour shape. It only has to be configured. Specifically, as shown in the figure, the bulging portion 5 of the second embodiment is used as a basic shape, the radius of curvature R of the inner surface 51 thereof is increased, and a more gentle curved surface shape is provided, whereby the electric field relaxation effect is obtained. growing. The shape of the crimped portion H11 can be the same as that of the fourth embodiment.

また、カシメ部Ｈ１１との接続部は、上記実施形態４と同様に、膨出部５の内側端縁に角を有しないＲ形状部５２が形成されていても、図示するように、膨出部５の内側端縁にＲ形状部５２を有しなくてもよい。その場合でも、内表面５１の曲率半径Ｒが大きくなることにより、電界集中が緩和され、最大電界強度が低下することによって、リーク放電を抑制する効果が得られる。   Further, as in the fourth embodiment, the connecting portion with the crimped portion H11 is swollen as shown, even if the R-shaped portion 52 having no corner is formed on the inner end edge of the swollen portion 5. The R-shaped portion 52 may not be provided on the inner edge of the portion 5. Even in this case, the radius of curvature R of the inner surface 51 is increased, the concentration of the electric field is relieved, and the maximum electric field strength is reduced, so that the effect of suppressing the leak discharge can be obtained.

具体的には、膨出部５の最小内径と最大内径との差である内径差ａと、内表面５１の曲率半径Ｒとが、下記式１で表される関係を満たすような形状であるとよい。
式１：Ｒ／ａ≧０．５
Ｒ／ａ＝０．５、すなわち、１／４円断面形状よりも、内径差ａに対する曲率半径Ｒが大きくなり、より緩やかな曲面状であるほど、電界強度の低減効果は大きくなる。好適には、Ｒ／ａ≧１となるように、設定されるとより好ましい。 Specifically, the inner diameter difference a, which is the difference between the minimum inner diameter and the maximum inner diameter of the bulging portion 5, and the radius of curvature R of the inner surface 51 satisfy the relationship represented by the following formula 1. Good.
Formula 1: R/a≧0.5
R/a=0.5, that is, the radius of curvature R with respect to the inner diameter difference a is larger than that of the 1/4 circular cross-sectional shape, and the more gently curved the shape, the greater the effect of reducing the electric field strength. It is more preferable to set so that R/a≧1.

（試験例２）
上記実施形態５の構成において、電界緩和部６となる膨出部５のＲ／ａを変更したときの、電界強度の低減効果を、以下のようにして調べた。図１２に示されるように、膨出部５の内径差ａを一定とし、曲率半径Ｒを変化させて、（ａ）Ｒ／ａ＝０．２、（ｂ）Ｒ／ａ＝０．５、（ｃ）Ｒ／ａ＝１、（ｄ）Ｒ／ａ＝３、となるように、膨出部５の形状を変化させた。これら（ａ）〜（ｄ）の構成について、上記試験例１においてカシメ部Ｈ１１を有しない構成として、それぞれ同様に電界強度分布を算出し、最大電界強度を比較した。 (Test Example 2)
In the configuration of Embodiment 5 described above, the effect of reducing the electric field strength when R/a of the bulging portion 5 serving as the electric field relaxing portion 6 was changed was examined as follows. As shown in FIG. 12, with the inner diameter difference a of the bulging portion 5 being constant and the radius of curvature R being varied, (a) R/a=0.2, (b) R/a=0.5, The shape of the bulging portion 5 was changed so that (c) R/a=1 and (d) R/a=3. Regarding these configurations (a) to (d), the field intensity distributions were calculated in the same manner as in the above Test Example 1 without the caulking portion H11, and the maximum field intensities were compared.

図１３に示されるように、Ｒ／ａが大きくなるに従い、最大電界強度が低下する。特に、（ａ）Ｒ／ａ＝０．２から、（ｂ）Ｒ／ａ＝０．５とすることで、４０ｋＶ／ｍｍを超えていた最大電界強度が４０ｋＶ／ｍｍ以下に急減し、（ｃ）Ｒ／ａ＝１とすることで、さらに最大電界強度が低下する。（ｄ）Ｒ／ａ＝３において、最大電界強度はより低減して３５ｋＶ／ｍｍ程度となるが、低減効果はやや小さくなる。また、平均電界強度が比較的高い領域が、絶縁碍子２の近傍に形成されることになるため、リーク放電が起こりやすくなるおそれがある。したがって、Ｒ／ａは、０．５以上、好適には、１〜３の範囲とするとよいことがわかる。   As shown in FIG. 13, the maximum electric field intensity decreases as R/a increases. In particular, by changing (a) R/a=0.2 to (b) R/a=0.5, the maximum electric field strength, which had exceeded 40 kV/mm, suddenly decreased to 40 kV/mm or less, and (c ) By setting R/a=1, the maximum electric field strength further decreases. (D) When R/a=3, the maximum electric field strength is further reduced to about 35 kV/mm, but the reduction effect is slightly reduced. Further, since a region having a relatively high average electric field strength is formed in the vicinity of the insulator 2, there is a possibility that leak discharge is likely to occur. Therefore, it is understood that R/a should be 0.5 or more, and preferably in the range of 1 to 3.

（実施形態６）
図１４に、実施形態６として示すように、上記実施形態４の構成において、膨出部５の内側端縁に、角を有しないＲ形状部５２を設ける代わりに、内側端縁２から、カシメ部Ｈ１１の内表面Ｈ１３を覆うように延出する延出部５３を設けてもよい。このとき、延出部５３は、膨出部５の内表面５１に連なる滑らかな曲面をなし、延出端は、カシメ部Ｈ１１の内表面Ｈ１３より基端側の微小空間に入り込んで位置する。電界緩和部６を形成する膨出部５は、先端面４４の内側の位置で最小内径となり、絶縁碍子２の外表面と当接又は近接位置する。 (Embodiment 6)
As shown in FIG. 14 as Embodiment 6, in the configuration of Embodiment 4 described above, instead of providing the R-shaped portion 52 having no corners on the inner edge of the bulging portion 5, the caulking is performed from the inner edge 2. You may provide the extension part 53 extended so that the inner surface H13 of the part H11 may be covered. At this time, the extending portion 53 forms a smooth curved surface continuous with the inner surface 51 of the bulging portion 5, and the extending end is positioned so as to enter the minute space on the base end side of the inner surface H13 of the caulking portion H11. The bulging portion 5 forming the electric field relaxation portion 6 has a minimum inner diameter at a position inside the tip end surface 44, and is in contact with or close to the outer surface of the insulator 2.

このように、延出部５３を設けることで、カシメ部Ｈ１１の内側に嵌合させ、接触面積を大きくすることができる。したがって、電力ケーブル４のプラグ接続部４０と点火プラグＰとの接続を良好に保持することができる。   In this way, by providing the extending portion 53, it is possible to fit the inside of the crimped portion H11 and increase the contact area. Therefore, the connection between the plug connecting portion 40 of the power cable 4 and the spark plug P can be maintained well.

（実施形態７）
図１５に、実施形態７として示すように、上記実施形態４の構成において、膨出部５の内側端縁にＲ形状部５２を設けず、先端面４４とカシメ部Ｈ１１の端面Ｈ１２との隙間を埋めるように、導電性の接合層５４を介設してもよい。このとき、接合層５４は、例えば、カシメ部Ｈ１１の基端側において、端面Ｈ１２とこれに続く外側表面と先端面４４との間を埋めると共に、カシメ部Ｈ１１の内側において、内表面Ｈ１３と先端面４４の段差部を埋めるように形成することができる。 (Embodiment 7)
As shown in FIG. 15 as Embodiment 7, in the configuration of Embodiment 4 described above, the R-shaped portion 52 is not provided on the inner end edge of the bulging portion 5, and the gap between the tip surface 44 and the end surface H12 of the crimped portion H11 is provided. A conductive bonding layer 54 may be provided so as to fill the gap. At this time, the bonding layer 54 fills the space between the end surface H12 and the outer surface and the front end surface 44 following the end surface H12 on the base end side of the caulking portion H11, and the inner surface H13 and the tip end on the inner side of the caulking portion H11. It can be formed so as to fill the stepped portion of the surface 44.

このように、導電性の接合層５４を設けることで、外側導体４２とカシメ部Ｈ１１との電気的な接続を確保しつつ、両者を確実に固定することができる。また、段差部を埋めて滑らかな曲面で接続することで、電界緩和部６の効果を高めることができる。
（実施形態８）
図１６に、実施形態８として示すように、上記実施形態７の構成において、導電性の接合層５４が、膨出部５の内表面５１に形成されていてもよい。このとき、膨出部５の内側端縁は、絶縁碍子２の外表面と間隙を有して位置し、軸方向Ｘにおいてカシメ部Ｈ１１の内表面Ｈ１３と重なるようになっている。接合層５４は、例えば、カシメ部Ｈ１１の外側表面と先端面４４との隙間を埋めるとともに、両者の接続部の内側を覆うように形成される。 As described above, by providing the conductive bonding layer 54, it is possible to securely fix the outer conductor 42 and the crimped portion H11 while ensuring electrical connection between them. Further, the effect of the electric field relaxation portion 6 can be enhanced by filling the stepped portion and connecting with a smooth curved surface.
(Embodiment 8)
As shown as an eighth embodiment in FIG. 16, in the configuration of the seventh embodiment, the conductive bonding layer 54 may be formed on the inner surface 51 of the bulging portion 5. At this time, the inner end edge of the bulging portion 5 is positioned with a gap from the outer surface of the insulator 2, and overlaps the inner surface H13 of the crimped portion H11 in the axial direction X. The bonding layer 54 is formed, for example, so as to fill the gap between the outer surface of the crimped portion H11 and the front end surface 44, and to cover the inside of the connection portion between the two.

このように、膨出部５とカシメ部Ｈ１１との接続部に段差部を有しない構成においても、導電性の接合層５４が、接続部の内側表面を覆って形成されることで、接合性をより高めることができる。   As described above, even in the configuration in which the connecting portion between the bulging portion 5 and the crimped portion H11 does not have the step portion, the conductive joining layer 54 is formed so as to cover the inner surface of the connecting portion, and thus the joining property is improved. Can be increased.

（実施形態９）
あるいは、図１７に、実施形態９として示すように、上記実施形態７の構成において、接合層５４を、カシメ部Ｈ１１の外側表面と先端面４４との間のみ形成され、カシメ部Ｈ１１の内側に形成されない構成とすることもができる。接合層５４の構成材料が、絶縁碍子２に対して濡れ性を有する場合には、絶縁碍子２との間に接合層５４が配置されると、絶縁碍子２に近接する表面に突状部が形成されることがあるが、本形態の構成では、カシメ部Ｈ１１の内側に接合部５４が形成されないので、突状部の形成による不具合が生じることもない。 (Embodiment 9)
Alternatively, as shown as a ninth embodiment in FIG. 17, in the configuration of the seventh embodiment, the bonding layer 54 is formed only between the outer surface of the caulking portion H11 and the tip end surface 44, and is provided inside the caulking portion H11. It is also possible to adopt a configuration in which it is not formed. When the constituent material of the bonding layer 54 has wettability with respect to the insulator 2, when the bonding layer 54 is arranged between the constituent material of the bonding layer 54 and the insulator 2, a protrusion is formed on the surface adjacent to the insulator 2. Although it may be formed, in the configuration of the present embodiment, since the joint portion 54 is not formed inside the crimped portion H11, the problem due to the formation of the protrusion does not occur.

接合層５４は、金属材料との濡れ性が良好な導電性材料からなる。好適には、外側導体４２及びカシメ部Ｈ１１を構成する金属材料との濡れ性が良好で、絶縁碍子２を構成するセラミックス材料との濡れ性が低い導電性材料を用いるのがよい。これにより、接合層５４が、絶縁碍子２に当接可能に位置する場合において、外側導体４２とカシメ部Ｈ１１とが良好に接合され、絶縁碍子２と内表面Ｈ１３又は先端面２４３とは接合されないようにして、使用環境において絶縁碍子２に熱膨張係数差による損傷等が生じるのを防止できる。このような導電性接合材料としては、例えば、半田、銀ロウ等が挙げられ、外側導体４２及びカシメ部Ｈ１１の材質に応じて選択される。例えば、ステンレス鋼からなる外側導体４２及びカシメ部Ｈ１１に対しては、ステンレス鋼用の半田（例えば、錫６０％）等を用いることが望ましい。   The bonding layer 54 is made of a conductive material having good wettability with a metal material. It is preferable to use a conductive material that has good wettability with the metal material forming the outer conductor 42 and the caulked portion H11 and has low wettability with the ceramic material forming the insulator 2. As a result, when the bonding layer 54 is positioned so as to be able to contact the insulator 2, the outer conductor 42 and the crimped portion H11 are well bonded, and the insulator 2 is not bonded to the inner surface H13 or the front end surface 243. In this way, it is possible to prevent the insulator 2 from being damaged due to the difference in thermal expansion coefficient in the use environment. Examples of such a conductive bonding material include solder and silver solder, which are selected according to the materials of the outer conductor 42 and the crimped portion H11. For example, it is desirable to use stainless steel solder (for example, 60% tin) for the outer conductor 42 and the crimped portion H11 made of stainless steel.

（実施形態１０）
図１８、図１９に、実施形態１０として示すように、ハウジングＨの基端側開口部Ｈ１に、カシメ部Ｈ１１を有しない構成とすることもできる。電力ケーブル４のプラグ接続部４０は、外導体先端部４２１に、膨出部５を備える厚肉筒部５５が設けられて、基端側開口部Ｈ１の内側に密接配置される。これにより、基端側開口部Ｈ１の内側に、電界緩和部６が形成される。点火プラグＰ及び電力ケーブル４の基本構成は、上記実施形態１と同様であり、以下、両者の相違点である、プラグ接続部４０の接続構造について説明する。 (Embodiment 10)
As shown in FIG. 18 and FIG. 19 as a tenth embodiment, the proximal end side opening H1 of the housing H may not have the crimped portion H11. The plug connecting portion 40 of the power cable 4 is provided with a thick-walled cylinder portion 55 having the bulging portion 5 at the outer conductor tip portion 421, and is closely arranged inside the base end side opening portion H1. As a result, the electric field relaxing portion 6 is formed inside the base end side opening H1. The basic configuration of the spark plug P and the power cable 4 is the same as that of the first embodiment, and the difference between the two will be described below.

ハウジングＨは、基端側開口部Ｈ１を一定の外径を有する薄肉筒状体として構成される。基端側開口部Ｈ１の外径は、これに連なる基端部Ｈ１４の外径と同等であり、基端側開口部Ｈ１の内周面と絶縁碍子２の外表面との間に、厚肉筒部５５が挿入される筒状の空間部Ｈ１５を有している。空間部Ｈ１５の内径は、薄肉の基端側開口部Ｈ１と厚肉の基端部Ｈ１４との接続部において、段付きに縮径している。   The housing H has a proximal end opening H1 configured as a thin-walled tubular body having a constant outer diameter. The outer diameter of the base end side opening H1 is equal to the outer diameter of the base end part H14 connected to the base end side opening H1, and a thick wall is formed between the inner peripheral surface of the base end side opening H1 and the outer surface of the insulator 2. It has a tubular space portion H15 into which the tubular portion 55 is inserted. The inner diameter of the space H15 is stepwise reduced at the connecting portion between the thin base end side opening H1 and the thick base end H14.

外側導体４２は、継ぎ目のない金属管からなり、プラグ接続部４０を形成する外導体先端部４２１は、基端側開口部Ｈ１内に配置される厚肉筒部５５と、厚肉筒部５５の先端側に設けられる膨出部５と、基端側開口部Ｈ１の外方に露出するくびれ部５６を有する。厚肉筒部５５は、基端側の外径が、基端側開口部Ｈ１の内径と同等であり、先端側の外径は、空間部Ｈ１５の内周形状に沿って、段付きに縮径している。この段付きの縮径部の内側に、滑らかな曲面状の内表面５１を有する膨出部５が設けられる。   The outer conductor 42 is made of a seamless metal tube, and the outer conductor tip portion 421 forming the plug connection portion 40 has a thick-walled tubular portion 55 and a thick-walled tubular portion 55 arranged in the proximal end opening H1. Has a bulging portion 5 provided on the distal end side and a constricted portion 56 exposed to the outside of the base end side opening H1. The thick-walled cylinder portion 55 has an outer diameter on the base end side equal to the inner diameter of the base end side opening H1, and the outer diameter on the tip end side is stepwise reduced along the inner peripheral shape of the space H15. It has a diameter. Inside the stepped reduced diameter portion, a bulging portion 5 having a smooth curved inner surface 51 is provided.

膨出部５は、円弧状の輪郭形状を有して膨出し、絶縁碍子２の外表面に対向する。最小内径となる部位の内径は、絶縁碍子２の外表面と同等であり、僅かな間隙を有して近接又は当接する。膨出部５の内表面５１は、例えば、Ｒ／ａが０．５より大きく、比較的緩やかな曲面形状を有することで、電界強度を低減する効果が得られる。膨出部５より基端側において、厚肉筒部５５の厚さは、概略一定であり、空間部Ｈ１５の内外径差よりも小さい。これにより、厚肉筒部５５と絶縁碍子２の外表面の間には、隙間が形成される。   The bulging portion 5 has a circular arc-shaped contour and bulges to face the outer surface of the insulator 2. The inner diameter of the portion having the smallest inner diameter is the same as the outer surface of the insulator 2, and is close to or abuts with a slight gap. The inner surface 51 of the bulging portion 5 has, for example, R/a of more than 0.5 and a relatively gentle curved surface shape, so that the effect of reducing the electric field strength can be obtained. On the base end side of the bulging portion 5, the thickness of the thick-walled tubular portion 55 is substantially constant and smaller than the difference between the inner and outer diameters of the space portion H15. As a result, a gap is formed between the thick-walled cylinder portion 55 and the outer surface of the insulator 2.

外側導体４２は、一定径の金属管の先端側が、径方向内方へテーパ状に屈曲して縮径し、厚肉筒部５５との接続部に、薄肉のくびれ部５６を形成する。薄肉のくびれ部５６の内径は、厚肉筒部５５の内径と同等となっている。厚肉筒部５５は、一定径の基端側外周に、ネジ部５５１を有し、基端側開口部Ｈ１の内周に形成されるネジ溝にネジ固定されるようになっている。   The outer conductor 42 has a tip end side of a metal tube having a constant diameter bent inward in the radial direction to be reduced in diameter, and a thin constricted portion 56 is formed at a connection portion with the thick-walled tubular portion 55. The inner diameter of the thin constricted portion 56 is the same as the inner diameter of the thick tubular portion 55. The thick-walled cylinder portion 55 has a threaded portion 551 on the outer circumference of the base end side having a constant diameter, and is screwed into a thread groove formed on the inner circumference of the base end side opening H1.

プラグ接続部４０は、外導体先端部４２１の厚肉筒部５５を、ハウジングＨの基端側開口部Ｈ１内に螺挿し、内側導体４１の先端部４１１を絶縁碍子２の軸孔２１に挿通することにより、点火プラグＰに取り付けられる。このとき、厚肉筒部５５は、ネジ部５５１を介して基端側開口部Ｈ１の内側に一体的に固定される。膨出部５は、厚肉筒部５５より内側に位置して、絶縁碍子２の外表面に隣接する膨出部５の内表面５１が、電界緩和部６を構成する。膨出部５の内側端縁は、角を有しないＲ形状部５２となっており、対向する絶縁碍子２のテーパ面に沿って配置される。   In the plug connection portion 40, the thick-walled cylinder portion 55 of the outer conductor tip portion 421 is screwed into the proximal end side opening portion H1 of the housing H, and the tip portion 411 of the inner conductor 41 is inserted into the shaft hole 21 of the insulator 2. By doing so, it is attached to the spark plug P. At this time, the thick-walled cylinder portion 55 is integrally fixed to the inside of the base end side opening H1 via the screw portion 551. The bulging portion 5 is located inside the thick-walled tubular portion 55, and the inner surface 51 of the bulging portion 5 adjacent to the outer surface of the insulator 2 constitutes the electric field relaxing portion 6. The inner edge of the bulging portion 5 is an R-shaped portion 52 having no corners, and is arranged along the tapered surface of the opposing insulator 2.

外導体先端部４２１は、基端側開口部Ｈ１の内側を覆うように、厚肉筒部５５及び膨出部５が配置され、くびれ部５６は、厚肉筒部５５の基端から外側へ、基端側開口部Ｈ１の開口縁部を覆うように、テーパ状に屈曲する。好ましくは、くびれ部５６の内表面を曲面状とし、屈曲角度が９０度より大きい鈍角となるように形成して、絶縁碍子２の外表面との対向面に鋭角の角部が形成されないようにするとよい。   The outer conductor tip portion 421 has the thick-walled tubular portion 55 and the bulging portion 5 arranged so as to cover the inside of the proximal-end side opening portion H1, and the constricted portion 56 extends outward from the proximal end of the thick-walled tubular portion 55. , Is bent in a taper shape so as to cover the opening edge portion of the base end side opening portion H1. Preferably, the inner surface of the constricted portion 56 is formed into a curved surface so that the bending angle is an obtuse angle larger than 90 degrees so that an acute-angled corner portion is not formed on the surface facing the outer surface of the insulator 2. Good to do.

このように、基端側開口部Ｈ１の内側に、膨出部５を備える厚肉筒部５５を配置することで、電界緩和部６として機能させることができる。この構成では、薄肉の基端開口部Ｈ１が、絶縁碍子２の外表面と対向しないので、局部的な電界集中を抑制する効果が高く、形状の自由度も大きい。また、厚肉筒部５５のネジ部５５１により、基端開口部Ｈ１にネジ固定されるので、接合層５４を設けたり、固定用部材を別途用意したりする必要がない。したがって、電界集中によるリーク放電の発生を抑制し、電力ケーブル４から点火プラグＰへ、効率よく点火エネルギを伝達することができる。   In this way, by arranging the thick-walled tubular portion 55 including the bulging portion 5 inside the base end side opening portion H1, it is possible to function as the electric field relaxation portion 6. In this configuration, since the thin base end opening H1 does not face the outer surface of the insulator 2, the effect of suppressing local electric field concentration is high and the degree of freedom of shape is large. Further, since the screw portion 551 of the thick-walled cylinder portion 55 is screwed and fixed to the base end opening H1, it is not necessary to provide the bonding layer 54 or separately prepare a fixing member. Therefore, it is possible to suppress the occurrence of leak discharge due to the electric field concentration and to efficiently transmit the ignition energy from the power cable 4 to the spark plug P.

（試験例３）
実施形態１０の構成について、試験例１と同様の条件で、有限要素法を用いた解析を行って、電界強度分布を得た。図２０に示されるように、絶縁碍子２の外表面に近接する膨出部５の内表面５１周辺において、電界強度が比較的高い領域が見られるものの、最大電界強度は、上記実施形態１と比べて、さらに低くなっている（最大電界強度：３５ｋＶ／ｍｍ）。これにより、図２１に示されるように、従来の構成と比較して、３３％の低減効果が得られ、電界集中を抑制する効果がより大きくなることが確認された。 (Test Example 3)
An electric field strength distribution was obtained by performing an analysis using the finite element method on the configuration of the tenth embodiment under the same conditions as in Test Example 1. As shown in FIG. 20, a region having a relatively high electric field strength is seen around the inner surface 51 of the bulging portion 5 close to the outer surface of the insulator 2, but the maximum electric field strength is the same as that of the first embodiment. Compared with this, it is even lower (maximum electric field strength: 35 kV/mm). As a result, as shown in FIG. 21, it was confirmed that a reduction effect of 33% was obtained and the effect of suppressing electric field concentration was greater than that of the conventional configuration.

また、実施形態１、実施形態１０の構成について、点火プラグＰへの印加電圧を上昇させてフラッシオーバが生じる電圧（すなわち、フラッシオーバ電圧）を測定し、従来の構成と比較した。図２２に示されるように、従来の構成では、フラッシオーバ電圧が３０ｋＶであったのに対し、実施形態１では３４ｋＶ、実施形態１０では４０ｋＶとより高くなっている。近年、点火プラグＰの放電部における要求電圧が高くなる傾向にあり、例えば、従来の２０ｋＶ程度から、３０ｋＶを超える場合にもフラッシオーバを抑制することが望ましい。この場合でも、実施形態１、実施形態１０の構成とすることで、フラッシオーバの発生を十分抑制できることがわかる。   Further, regarding the configurations of the first and tenth embodiments, the voltage applied to the spark plug P is increased to measure the voltage at which flashover occurs (that is, the flashover voltage), and the result is compared with the conventional configuration. As shown in FIG. 22, in the conventional configuration, the flashover voltage was 30 kV, whereas in the first embodiment, it was 34 kV, and in the tenth embodiment, it was higher than 40 kV. In recent years, the required voltage in the discharge part of the spark plug P tends to be high, and it is desirable to suppress the flashover even when it exceeds 30 kV from the conventional 20 kV, for example. Even in this case, it is understood that the configurations of the first and tenth embodiments can sufficiently suppress the occurrence of flashover.

（実施形態１１）
図２３、図２４に、実施形態１１として示すように、点火プラグＰを、上記実施形態のような沿面放電型プラグに代えて、火花放電型プラグとして構成することもできる。電力ケーブル４のプラグ接続部４０は、中心導体４１を絶縁碍子２の軸孔２１内に挿通する構成とする代わりに、軸孔２１の外部で点火プラグＰと接続されている。また、上記実施形態のように、プラグ接続部４０に膨出部５を形成する構成に加えて、外側導体４２の他の部位に、電界緩和部６を形成してもよい。 (Embodiment 11)
As shown as an eleventh embodiment in FIGS. 23 and 24, the spark plug P can be configured as a spark discharge type plug instead of the creeping discharge type plug as in the above embodiment. The plug connection portion 40 of the power cable 4 is connected to the ignition plug P outside the shaft hole 21 instead of having the structure in which the center conductor 41 is inserted into the shaft hole 21 of the insulator 2. In addition to the configuration in which the bulging portion 5 is formed in the plug connecting portion 40 as in the above embodiment, the electric field relaxing portion 6 may be formed in another portion of the outer conductor 42.

具体的には、点火プラグＰには、軸孔２１内に挿通され、軸孔２１の基端側に突出する端部を有する電極端子３３が設けられる。電力ケーブル４は、中心導体４１の先端部４１１が電極端子３３の突出端部に接続され、外導体先端部４２１は、例えば、上記実施形態１と同様の構成を有して、ハウジングＨのカシメ部Ｈ１１に接続される。中心導体４１は、電極端子３３及び導電シール部１１を介して、中心電極３１に接続する。中心電極３１の先端側には、ハウジングＨの先端面からＬ字状に延びる接地電極３２が軸方向に対向位置している。   Specifically, the spark plug P is provided with an electrode terminal 33 which is inserted into the shaft hole 21 and has an end portion protruding toward the base end side of the shaft hole 21. In the power cable 4, the tip portion 411 of the center conductor 41 is connected to the projecting end portion of the electrode terminal 33, and the outer conductor tip portion 421 has, for example, the same configuration as that of the first embodiment, and the caulking of the housing H is performed. It is connected to the section H11. The center conductor 41 is connected to the center electrode 31 via the electrode terminal 33 and the conductive seal portion 11. On the tip side of the center electrode 31, a ground electrode 32 extending in an L shape from the tip surface of the housing H is axially opposed.

また、図示されるように、外側導体４２は、例えば、複数の同径の導体管４６を継ぎ合わせた構造とすることができる。複数の導体管４６は、例えば、ステンレス鋼等の鉄系合金材料からなる金属管であり、通常、軸方向Ｘに対向する端面を一致させて溶接等により接合される。その場合、接合部の内側に溶接材料が凝固した凸部や段部が形成されると、電界集中が生じ易くなる。   Further, as shown in the drawing, the outer conductor 42 may have a structure in which a plurality of conductor tubes 46 having the same diameter are joined together. The plurality of conductor tubes 46 are, for example, metal tubes made of an iron-based alloy material such as stainless steel, and are normally joined by welding or the like with their end faces facing each other in the axial direction X aligned. In that case, if a convex portion or a step portion in which the welding material is solidified is formed inside the joint portion, electric field concentration is likely to occur.

そこで、２つの導体管４６ａ、４６ｂの継ぎ合わせ部４６１において、一方の導体管４６ａに、その内端縁から軸方向に延出し、継ぎ合わせ部４６１を覆う、Ｒ形状部としての延出部４７を設ける。ここでは、一方の導体管４６ａは、他方の導体管４６ｂと外径が同一で、より厚肉に形成されており、延出部４７の内表面４７ａは、Ｒ形状の滑らかな曲面を有して、他方の導体管４６ｂの内表面に接続される。このとき、延出部４７の内表面４７ａは、一方の導体管４６ａの内表面よりも内側に位置していない。   Therefore, in the joint portion 461 of the two conductor pipes 46a and 46b, an extension portion 47 as an R-shaped portion that extends in the axial direction from the inner end edge of one conductor pipe 46a and covers the joint portion 461. To provide. Here, one conductor tube 46a has the same outer diameter as the other conductor tube 46b and is formed to be thicker, and the inner surface 47a of the extending portion 47 has an R-shaped smooth curved surface. And is connected to the inner surface of the other conductor tube 46b. At this time, the inner surface 47a of the extending portion 47 is not located inside the inner surface of the one conductor pipe 46a.

この場合も、上記式１に示した関係を満たすように、２つの導体管４６ａ、４６ｂの内径差ａと、延出部４７の内表面４７ａの曲率半径Ｒが設定されることがのぞましい。すなわち、Ｒ／ａ≧０．５、好ましくは、Ｒ／ａ≧１、となるように、延出部６１が形成されるとよい。   Also in this case, it is desirable that the inner diameter difference a between the two conductor tubes 46a and 46b and the radius of curvature R of the inner surface 47a of the extending portion 47 be set so as to satisfy the relationship shown in the above-mentioned formula 1. That is, the extension 61 may be formed so that R/a≧0.5, and preferably R/a≧1.

これにより、２つの導体管４６ａ、４６ｂの継ぎ合わせ部４６１において、外表面に溶接部４８が形成される場合でも、その内側において、継ぎ合わせ部４６１を覆って延出部４７が配置されるので、溶接部４８がはみ出して凸部等が形成されることはない。また、延出部４７の内表面４７ａは、滑らかな曲面状であり、導体管４６ａ、４６ｂの内表面よりも内側に位置しないので、継ぎ合わせ部４６１の周辺における電界強度を低減することができる。   As a result, even when the welded portion 48 is formed on the outer surface of the spliced portion 461 of the two conductor tubes 46a and 46b, the extending portion 47 is arranged inside the spliced portion 461 so as to cover the spliced portion 461. The welded portion 48 does not protrude and a convex portion or the like is not formed. Further, the inner surface 47a of the extending portion 47 has a smooth curved surface shape and is not located inside the inner surfaces of the conductor tubes 46a and 46b, so that the electric field strength around the joint portion 461 can be reduced. .

したがって、電力ケーブル４と点火プラグＰとの接続部、さらには、電力ケーブル４の全長に亘って、局部的な電界集中によるリーク放電の発生を抑制し、電力ケーブル４から点火プラグＰへ、効率よく点火エネルギを伝達することができる。   Therefore, the generation of leak discharge due to local electric field concentration is suppressed over the connection portion between the power cable 4 and the spark plug P, and further over the entire length of the power cable 4, and the efficiency is improved from the power cable 4 to the spark plug P. Ignition energy can be transmitted well.

好適には、電力ケーブル４の基端側に配置される昇圧トランス６との接続部においても、外側導体４２とトランスケース６７とが一体的に構成され、接続部の内表面に電界集中が生じる金属端や鋭角の角部、段部等を有しない形状とすることが望ましい。具体的には、それら金属端や角部、段部等に隣接して、滑らかな曲面状の内表面を有する膨出部を配置し、又は延出部で覆って、電界緩和部６を形成することで、伝送効率をさらに向上させることができる。   Preferably, the outer conductor 42 and the transformer case 67 are also integrally formed in the connection portion with the step-up transformer 6 arranged on the proximal end side of the power cable 4, and electric field concentration occurs on the inner surface of the connection portion. It is desirable to have a shape that does not have metal edges, sharp corners, steps, or the like. Specifically, the electric field relaxation portion 6 is formed by arranging a bulging portion having a smooth curved inner surface adjacent to the metal end, corner portion, step portion, or the like, or by covering the bulging portion with an extending portion. By doing so, the transmission efficiency can be further improved.

上記実施形態１１の電力ケーブル４の構成は、上記実施形態１〜１０のいずれに適用してもよい。また、上記実施形態１１の点火プラグＰを、沿面放電型プラグとして、上記実施形態１〜１０の点火プラグＰを、火花放電型プラグとすることもできる。さらに、沿面放電型プラグ、火花放電型プラグの他、プラズマ放電型プラグ等に適用することもできる。   The configuration of the power cable 4 of the eleventh embodiment may be applied to any of the first to tenth embodiments. The spark plug P of the eleventh embodiment may be a creeping discharge type plug, and the spark plugs P of the first to tenth embodiments may be a spark discharge type plug. Further, it can be applied to a plasma discharge type plug and the like in addition to a creeping discharge type plug and a spark discharge type plug.

点火装置を構成する点火プラグＰや電力ケーブル４の構造、各部材形状や材料等は、上記実施形態に示したものに限らず、適宜変更することができる。また、点火装置は、自動車エンジン等の各種内燃機関の他、任意の用途に用いることができる。   The structures of the ignition plug P and the electric power cable 4 constituting the ignition device, the shape and material of each member, and the like are not limited to those shown in the above-described embodiment, but can be changed as appropriate. Further, the ignition device can be used for various purposes other than various internal combustion engines such as automobile engines.

１ 点火装置
２ 絶縁碍子
３１ 中心電極
４ 電力ケーブル
４１ 中心導体
４１１ 先端部
４２ 外側導体
５ 膨出部
Ｈ ハウジング
Ｈ１ 基端開口部 1 Ignition device 2 Insulator 31 Center electrode 4 Power cable 41 Center conductor 411 Tip part 42 Outer conductor 5 Bulging part H Housing H1 Base end opening

Claims (10)

点火プラグ（Ｐ）と、上記点火プラグへ電力を伝送する電力ケーブル（４）とを備える点火装置（１）であって、
上記点火プラグは、金属筒状のハウジング（Ｈ）と、上記ハウジングの内側に同軸的に保持され、軸方向（Ｘ）に貫通する軸孔（２１）を有する絶縁碍子（２）と、上記軸孔の先端側に収容される長軸状の中心電極（３１）と、上記ハウジングの先端側に設けられる接地電極（３２）とを有しており、
上記電力ケーブルは、上記中心電極と電気的に接続される中心導体（４１）と、上記中心導体の外側を取り囲み、上記ハウジングと電気的に接続される外側導体（４２）と、上記中心導体及び上記外側導体の間に介在する絶縁体（４３）と、を有しており、
上記外側導体は、上記ハウジングと接続される先端部（４２１）において、上記ハウジングの基端側開口部（Ｈ１）に隣接し、滑らかな曲面状の内表面（５１）を有する膨出部（５）を備え、かつ、上記膨出部が最小内径となる部位より内側に、上記基端側開口部が位置しない、点火装置。 An ignition device (1) comprising a spark plug (P) and a power cable (4) for transmitting power to the spark plug,
The spark plug includes a metal cylindrical housing (H), an insulator (2) coaxially held inside the housing and having a shaft hole (21) penetrating in the axial direction (X), and the shaft. It has a long-axis center electrode (31) housed on the tip side of the hole and a ground electrode (32) provided on the tip side of the housing.
The power cable includes a center conductor (41) electrically connected to the center electrode, an outer conductor (42) surrounding the outside of the center conductor and electrically connected to the housing, the center conductor, and An insulator (43) interposed between the outer conductors,
The outer conductor is adjacent to the base end side opening (H1) of the housing and has a bulged portion (5) having a smooth curved inner surface (51) at a tip portion (421) connected to the housing. ), and the base end side opening is not located inside the portion where the bulging portion has the minimum inner diameter. 上記膨出部は、上記先端部の内側に、円弧状の輪郭形状を有して膨出する、請求項１に記載の点火装置。   The ignition device according to claim 1, wherein the bulging portion bulges inside the tip portion so as to have an arcuate contour shape. 上記膨出部は、最小内径と最大内径との差である内径差ａと、上記内表面の曲率半径Ｒとが、Ｒ≧ａ／２の関係にある、請求項２に記載の点火装置。   The ignition device according to claim 2, wherein an inner diameter difference a, which is a difference between a minimum inner diameter and a maximum inner diameter, and a radius of curvature R of the inner surface of the bulging portion have a relationship of R≧a/2. 上記膨出部は、内側端縁にＲ形状部（５２）を有する、請求項２又は３に記載の点火装置。   The ignition device according to claim 2 or 3, wherein the bulging portion has an R-shaped portion (52) at an inner edge thereof. 上記膨出部は、内側端縁から上記基端開口部の内側に延出する延出部（５３）を有する、請求項４に記載の点火装置。   The ignition device according to claim 4, wherein the bulging portion has an extending portion (53) extending from an inner edge to an inner side of the base end opening. 上記基端側開口部は、内方に屈曲する開口端縁部（Ｈ１１）を有し、上記開口端縁部の基端側の端面（Ｈ１２）が上記膨出部に接続される、請求項２〜５のいずれか１項に記載の点火装置。   The said base end side opening part has an opening end edge part (H11) bent inward, and the end surface (H12) on the base end side of the said opening end edge part is connected to the said bulging part. The ignition device according to any one of 2 to 5. 上記開口端縁部の上記軸方向の端面（Ｈ１２）と、上記膨出部との間に、導電性の接合層（５４）が介設される、請求項６に記載の点火装置。   The ignition device according to claim 6, wherein a conductive bonding layer (54) is provided between the axial end surface (H12) of the opening edge portion and the bulging portion. 上記基端側開口部は、上記軸方向に延びる筒状体であり、その内側に、上記膨出部を備える厚肉筒部（５５）が密接配置される、請求項２〜５のいずれか１項に記載の点火装置。   The said base end side opening part is a cylindrical body extended in the said axial direction, and the thick-walled cylinder part (55) provided with the said bulging part is closely arrange|positioned inside that. The ignition device according to item 1. 上記厚肉筒部は、外周面にネジ部（５５１）を有して、上記基端側開口部の内周面にネジ固定される、請求項８に記載の点火装置。   The ignition device according to claim 8, wherein the thick-walled cylinder portion has a threaded portion (551) on an outer peripheral surface and is screwed to an inner peripheral surface of the base end side opening portion. 上記外側導体は、複数の導体管（４６）を継ぎ合わせて構成され、継ぎ合わせ部（４６１）を内側から覆い、滑らかな曲面状の内表面（４７ａ）を有するＲ形状部（４７）を備える、請求項１〜９のいずれか１項に記載の点火装置。   The outer conductor is configured by joining a plurality of conductor tubes (46), covers the joining portion (461) from the inside, and includes an R-shaped portion (47) having a smooth curved inner surface (47a). The ignition device according to any one of claims 1 to 9.
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