JP3587024B2

JP3587024B2 - Ignition coil for internal combustion engine

Info

Publication number: JP3587024B2
Application number: JP21494197A
Authority: JP
Inventors: 美孝佐藤; 明光杉浦; 雅彦青山; 川井　　一秀
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 1997-06-30
Filing date: 1997-08-08
Publication date: 2004-11-10
Anticipated expiration: 2017-08-08
Also published as: JPH1174139A

Description

【０００１】
【発明の属する技術分野】
本発明は、内燃機関用点火コイルに関し、特にプラグホールに直接搭載するスティック状の内燃機関用点火コイルに関する。
【０００２】
【従来の技術】
従来のスティック状の内燃機関用点火コイル（以下、「内燃機関用点火コイル」を点火コイルという）として、棒状のコア本体を有する中心コア部を軸中心に配設し、その外周に一次コイルおよび二次コイルを巻回した樹脂製のスプールを配設し、点火コイルのハウジング内に部材間の絶縁材として樹脂を充填するものが知られている。ハウジング内に充填する樹脂は絶縁材としてだけではなく、コイルの線材間に浸透しコイルの巻線崩れを防ぐ役割を果たしている。また、コア本体の軸方向両端の少なくともいずれか一方に永久磁石を配設して中心コア部を構成し、点火コイルで発生する電圧を高める構成の点火コイルも知られている。
【０００３】
【発明が解決しようとする課題】
しかしながら、樹脂絶縁材だけでなく、中心コア部の外周を取り囲むスプール等のケース部材が直接中心コア部と接した状態において、膨張率の異なる中心コア部と樹脂絶縁材やケース部材とが温度変化により膨張および収縮を繰り返すと、中心コア部と接している樹脂絶縁材やケース部材、特に中心コア部の軸方向の端部角部と接する樹脂絶縁材やケース部材に絶縁欠損部であるクラック(crack)が発生することがある。中心コア部周囲の樹脂絶縁材やケース部材にクラックが発生すると、高電圧部である二次コイルや高圧ターミナルと低電圧部である中心コア部との間でクラックを通って放電する恐れがある。高電圧部と中心コア部との間で放電が発生すると、高電圧部と中心コア部との間の絶縁が破壊されて二次コイルに発生する電圧が低下するので点火プラグに所望の高電圧を印加できなくなる。
【０００４】
また、中心コア部と樹脂絶縁材やケース部材とが温度変化により膨張および収縮を繰り返すと、膨張率の差により樹脂絶縁材やケース部材から径方向および軸方向に中心コア部が荷重を受ける。特に軸方向に中心コア部が荷重を受けると、コア本体の透磁率が低下する（以下、「中心コア部が荷重を受けて透磁率が低下すること」を磁歪という）ことがあり、点火コイルの発生電圧が低下するという問題がある。
【０００５】
本発明の目的は、中心コア部の軸方向の両端角部近傍にクラックが発生することを防止し、所望の高電圧を発生する点火コイルを提供することにある。
本発明の他の目的は、温度変化に伴い中心コア部に加わる荷重を低減し、所望の高電圧を発生する点火コイルを提供することにある。
【０００６】
【課題を解決するための手段】
本発明の請求項１及び２記載の点火コイルによると、棒状のコア本体あるいは、棒状のコア本体およびコア本体の軸方向両端の少なくともいずれか一方に配設された永久磁石からなる中心コア部の軸方向の両端角部を緩衝部材で覆っている。したがって、中心コア部の外周を取り囲むスプール等のケース部材や樹脂絶縁材が中心コア部の軸方向の両端角部と直接接することを防止するとともに、中心コア部と樹脂絶縁材やケース部材との膨張率の差を第１の緩衝部材が吸収するので、中心コア部とともに中心コア部と膨張率の異なる樹脂絶縁材やケース部材が温度変化に伴い膨張および収縮を繰り返しても、第１の緩衝部材で覆われた中心コア部の軸方向の両端角部付近の樹脂絶縁材およびケース部材に絶縁欠損部としてのクラックが発生することを防止できる。これにより、高電圧部としての二次コイルや高圧ターミナル等と低電圧部としての中心コア部との間で放電することを防止し、高電圧部と中心コア部との間の絶縁破壊を防止できるので、二次コイルに発生する電圧が低下することを防止し所望の高電圧を点火プラグに印加できる。
【０００８】
本発明の請求項４記載の点火コイルによると、緩衝部材を袋状に成形するので緩衝部材を一体成形できる。これにより部品点数が減少し、組付工数が低減する。さらに、中心コア部の径よりも小さい径を有する孔を緩衝部材の軸方向両端の少なくともいずれか一方に設けているので、一体成形した緩衝部材の孔からコア本体や永久磁石を緩衝部材内に挿入できる。
【０００９】
本発明の請求項５記載の点火コイルによると、緩衝部材を複数の部材から構成することにより、緩衝部材の製造が容易になる。
本発明の請求項６、７または８記載の点火コイルによると、中心コア部と緩衝部材とが一体成形されているので、組付時に緩衝部材が中心コア部から脱落せず、組付けが容易になる。ここで一体成形とは、中心コア部に形成した緩衝部材が脱着不能であり、中心コア部の外周に緩衝部材を形成した状態で全体として一部品を構成していることを意味する。
【００１０】
本発明の請求項９記載の点火コイルによると、緩衝部材が中心コア部の全表面を覆うことにより、中心コア部は樹脂絶縁材やケース部材と接することがない。したがって、中心コア部周囲の樹脂絶縁材やケース部材にクラックが発生することを防止できる。
本発明の請求項１０記載の点火コイルによると、中心コア部の端部角部が面取りされているので、中心コア部の端部角部と接する緩衝部材に亀裂が発生することを防止できる。
【００１４】
【発明の実施の形態】
以下、本発明の実施の形態を示す複数の実施例について図面に基づいて説明する。
（第１実施例）
本発明の第１実施例による点火コイルを図１〜図４に示す。
【００１５】
図１に示す点火コイル１０は、図示しないエンジンブロックの上部に気筒毎に形成されたプラグホール内に収容され、図示しない点火プラグと図１の下側で電気的に接続している。
点火コイル１０は樹脂材料からなる円筒状のハウジング１１を備えており、このハウジング１１内に形成された収容室１１ａに、中心コア部１２、二次スプール２０、二次コイル２１、一次スプール２３、一次コイル２４、外周コア２５等が収容されている。中心コア部１２は、コア本体１３と、コア本体１３の両端に配設された永久磁石１４、１５とからなる。収容室１１ａに充填されたエポキシ樹脂２６は点火コイル１０内の各部材間に浸透し、樹脂絶縁材として部材間の電気絶縁を確実なものとしている。
【００１６】
円柱棒状のコア本体１３は薄い珪素鋼板を横断面がほぼ円形となるように径方向に積層して組立てられている。永久磁石１４、１５は、コイルにより励磁されて発生する磁束の方向とは逆方向の極性を有している。また、コア本体１３の外周を緩衝部材としてのゴム製の筒部材１７が覆っている。さらに、筒部材１７で覆われた永久磁石１４に貫通孔を有するキャップ１９が嵌合している。キャップ１９および二次スプール２０は中心コア部１２の外周を取り囲むケース部材を構成している。
【００１７】
筒部材１７は図２に示すように円筒袋状に一体成形されている。筒部材１７は、円筒部１７ａと、円筒部１７ａの軸方向両端に設けられ中央に貫通孔１８を形成した環状部１７ｂ、１７ｃと、円筒部１７ａと環状部１７ｂ、１７ｃとの間にそれぞれ位置する角部１７ｄとからなる。図３および図４に示すように、円筒部１７ａは中心コア部１２の外周側面を覆い、環状部１７ｂ、１７ｃは中心コア部１２の軸方向両端面の一部を覆い、角部１７ｄは中心コア部１２の両端角部である永久磁石１４、１５の端部角部を覆っている。環状部１７ｂ、１７ｃは円筒部１７ａよりも厚くなるように成形されており、緩衝部材の一部を構成している。貫通孔１８の径は永久磁石１４、１５の径よりも小さいので、コア本体１３、永久磁石１４、１５は、貫通孔１８を広げながら筒部材１７内に挿入される。
【００１８】
図１に示すように、二次スプール２０は筒部材１７の外周に配設されており、永久磁石１５側が閉塞した有底筒状に樹脂材料で成形されている。二次コイル２１は二次スプール２０の外周に巻回されており、二次コイル２０の高電圧側にさらにダミーコイル２２が一重巻き程度に巻回されている。ダミーコイル２２は二次コイル２１とターミナルプレート４０とを電気的に接続している。単線ではなくダミーコイル２２で二次コイル２１とターミナルプレート４０とを電気的に接続することにより、二次コイル２１とターミナルプレート４０との電気的接続部の表面積を大きくし、電気的接続部への電界集中を避けている。
【００１９】
一次スプール２３は二次コイル２１の外周に配設されており、樹脂材料で成形されている。一次コイル２４は一次スプール２３の外周に巻回されている。一次コイル２４へ制御信号を供給するスイッチング回路は点火コイル１０の外部に設けられており、コネクタ３０にインサート成形されたターミナルを介して一次コイル２４と図示しないスイッチング回路とが電気的に接続されている。
【００２０】
外周コア２５は一次コイル２４のさらに外側に装着されている。外周コア２５は、薄い珪素鋼板を筒状に巻回し巻回開始端と巻回終了端とを接続していないので軸方向に隙間を形成している。外周コア２５は永久磁石１４の外周位置から石１５の外周位置にわたる軸方向長さを有する。
高圧ターミナル４１はハウジング１１の下方にインサート成形されている。ターミナルプレート４０の中央部は高圧ターミナル４１を挿入する方向に折り曲げられた爪部を構成している。この爪部に高圧ターミナル４１の先端が挿入することにより、高圧ターミナル４１はターミナルプレート４０と電気的に接続している。ダミーコイル２２の高電圧端の線材は、フュージングまたははんだ付け等でターミナルプレート４０に電気的に接続されている。スプリング４２は高圧ターミナル４１と電気的に接続するとともにプラグホールに点火コイル１０を挿入した際に点火プラグと電気的に接続する。ハウジング１１の高電圧側開口端にゴムからなるプラグキャップ４３が装着されており、このプラグキャップ４３に点火プラグを挿入する。スイッチング回路から一次コイル２４に制御信号を供給すると二次コイル２１に高電圧が発生し、この高電圧がダミーコイル２２、ターミナルプレート４０、高圧ターミナル４１、スプリング４２を介して点火プラグに印加される。
【００２１】
次に、温度変化に伴う点火コイル１０の作動について説明する。
中心コア部１２の外周を取り囲む二次スプール２０やエポキシ樹脂２６の膨張率は中心コア部１２を構成するコア本体１３、永久磁石１４、１５の膨張率と異なっている。通常二次スプール２０やエポキシ樹脂２６の膨張率の方が中心コア部１２の膨張率よりも大きい。したがって、中心コア部１２が筒部材１７で覆われておらず、二次スプール２０やエポキシ樹脂２６が中心コア部１２と直接接していると、温度変化により中心コア部１２と二次スプール２０やエポキシ樹脂２６とが膨張および収縮を繰り返すことにより中心コア部１２と接する二次スプール２０やエポキシ樹脂２６にクラックが発生することがある。特に永久磁石１４、１５の端部角部と接する二次スプール２０やエポキシ樹脂２６にクラックが発生し易い。永久磁石１４、１５の端部角部と接する二次スプール２０やエポキシ樹脂２６にクラックが発生すると、高電圧部である二次コイル２１の高電圧側、ダミーコイル２２、ターミナルプレート４０または高圧ターミナル４１と、低電圧部である中心コア部１２との間でクラックを通って放電することがある。高電圧部と中心コア部１２との間で放電すると、高電圧部と中心コア部１２との間の絶縁が破壊され二次コイルに発生する電圧が低下するので点火プラグに所望の高電圧を印加できなくなる。
【００２２】
しかしながら第１実施例では、中心コア部１２の外周側面、ならびに永久磁石１４、１５の端部角部を弾性材である筒部材１７が覆い、中心コア部１２の外周側面、ならびに永久磁石１４、１５の端部角部と二次スプール２０やエポキシ樹脂２６とが直接接することを防止している。さらに、温度変化に伴い膨張率の異なる中心コア部１２と二次スプール２０やエポキシ樹脂２６とが膨張および収縮を繰り返しても、筒部材１７が弾性変形することにより膨張率の差を吸収することができる。したがって、中心コア部１２の外周側面の周囲、ならびに特にクラックの発生し易い中心コア部１２の両端角部付近の二次スプール２０やエポキシ樹脂２６にクラックが発生することを防止するので、高電圧部と中心コア部１２との間で放電することを防止できる。これにより、点火プラグに所望の高電圧を印加することができる。
【００２３】
また、キャップ１９、二次スプール２０およびエポキシ樹脂２６の膨張率は、コア本体１３、永久磁石１４、１５からなる中心コア部１２の膨張率と異なり大きいので、温度が低下すると、キャップ１９、二次スプール２０およびエポキシ樹脂２６の収縮により中心コア部１２を径方向および軸方向に収縮させようとする力が働く。特に中心コア部１２の軸方向に力が加わると、コア本体１３の透磁率が低下する磁歪が発生し、二次コイル２１に発生する電圧が低下する恐れがある。しかしながら、中心コア部１２の外周側面を円筒部１７ａが覆い、軸方向両端の一部を円筒部１７よりも厚い環状部１７ｂ、１７ｃが覆っているので、筒部材１７が弾性変形することにより中心コア部１２が径方向および軸方向に受ける力は緩和され、コア本体１３に磁歪が発生しない。これにより、点火プラグに所望の高電圧を印加することができる。
【００２４】
第１実施例では、コア本体１３の両端に永久磁石１４、１５を配設したが、コア本体１３の一端にだけ永久磁石を配設してもよい。
（第２実施例）
本発明の第２実施例による点火コイルを図５に示す。第１実施例と実質的に同一構成部分には同一符号を付す。
【００２５】
第２実施例では、コア本体２７の両端に永久磁石を配設せず、コア本体２７単体で中心コア部を構成している。コア本体２７の外周側面、両端角部および両端面の一部を筒部材１７が覆っている。
したがって、第２実施例においても、コア本体２７の外周側面の周囲、ならびに特にクラックの発生し易いコア本体２７の両端角部付近の二次スプール２０やエポキシ樹脂２６にクラックが発生することを防止するので、高電圧部と中心コア部１２との間で放電することを防止できる。これにより、点火プラグに所望の高電圧を印加することができる。
【００２６】
さらに、筒部材１７が弾性変形することによりコア本体２７が径方向および軸方向に受ける力は緩和され、コア本体２７に磁歪が発生しない。これにより、点火プラグに所望の高電圧を印加することができる。
（第３実施例）
本発明の第３実施例による点火コイルを図６および図７に示す。第１実施例と実質的に同一構成部分には同一符号を付す。
【００２７】
ゴム製の筒部材５０は、円筒部５０ａ、角部５０ｂおよび円板部５０ｃからなり、永久磁石１５側が閉塞した有底の円筒袋状に成形されている。円筒部５０ａが中心コア部１２の外周側面を覆い、環状の角部５０ｂが永久磁石１５の端部角部を覆い、円板部５０ｃが永久磁石１５の端面を覆っている。筒部材５０は、永久磁石１４側に永久磁石１４の端面よりも延びて成形されている。ゴム製の板部材５１は筒部材５０と別体に円形状に成形されており、永久磁石１４よりも径が大きい。ゴム製の筒部材５０およびゴム製の板部材５１は緩衝部材を構成している。永久磁石１４の端部角部は筒部材５０および板部材５１に覆われており、永久磁石１４の端面は板部材５１により覆われている。さらに、板部材５１はケース部材としてのキャップ１９と永久磁石１４との間をシールしているので、中心コア部１２にエポキシ樹脂２６が進入してこない。
【００２８】
第３実施例においても、中心コア部１２の外周側面の周囲、ならびに特にクラックの発生し易い中心コア部１２の両端角部付近の二次スプール２０やエポキシ樹脂２６にクラックが発生することを防止するので、高電圧部と中心コア部１２との間で放電することを防止できる。これにより、点火プラグに所望の高電圧を印加することができる。
【００２９】
さらに、筒部材５０および板部材５１が弾性変形することにより中心コア部１２が径方向および軸方向に受ける力は緩和され、中心コア部１２に磁歪が発生しない。これにより、点火プラグに所望の高電圧を印加することができる。
緩衝部材は筒部材５０および板部材５１の二つの部材で構成され、筒部材５０は軸方向の一端に端面をもたない有底筒状に成形されているので、緩衝部材の製造が容易である。
【００３０】
（第４実施例）
本発明の第４実施例による点火コイルを図８および図９に示す。第３実施例と実質的に同一構成部分には同一符号を付す。
ゴム製の筒部材５２は、円筒部５２ａ、角部５２ｂおよび環状部５２ｃからなり、円筒袋状に成形されている。円筒部５２ａが中心コア部１２の外周側面を覆い、環状の角部５２ｂが永久磁石１５の端部角部を覆い、環状部５２ｃが永久磁石１５の端面の一部を覆っている。円筒部５２ａは永久磁石１４側に延びているが、その端部は永久磁石１４の端面に達していない。
【００３１】
ゴム製の板部材５３、５４は筒部材５２と別体に円形状に成形されている。ゴム製の筒部材５２およびゴム製の板部材５３、５４は緩衝部材を構成している。板部材５３、５４は永久磁石１４、１５よりも径が小さく、それぞれ永久磁石１４、１５の端面に当接している。
図８に示すように、永久磁石１４の端部角部は空間部１００に面し、どの部材とも非接触である。さらに、板部材５３はケース部材としてのキャップ１９と永久磁石１４との間をシールしているので、中心コア部１２にエポキシ樹脂２６が進入してこない。
【００３２】
第４実施例では、永久磁石１４の端部角部が空間部１００に面し、永久磁石１５の端部角部が筒部材５２で覆われているので、中心コア部１２の軸方向の両端角部が二次スプール２０やエポキシ樹脂２６と接していない。さらに、中心コア部１２の外周側面を円筒部５２ａが覆っているので、温度変化にともない中心コア部１２、二次スプール２０およびエポキシ樹脂２６が膨張および収縮を繰り返しても、中心コア部１２の外周側面の周囲、ならびに特にクラックの発生し易い中心コア部１２の両端角部付近の二次スプール２０やエポキシ樹脂２６にクラックが発生することを防止するので、高電圧部と中心コア部１２との間で放電することを防止できる。これにより、点火プラグに所望の高電圧を印加することができる。
【００３３】
さらに、板部材５３、５４が弾性変形することにより中心コア部１２が径方向および軸方向に受ける力は緩和され、中心コア部１２に磁歪が発生しない。これにより、点火プラグに所望の高電圧を印加することができる。また、緩衝部材である板部材５３は永久磁石１４の端面とキャップ１９との間のシール部材を兼ねているので、部品点数が減少し組付け工数が低減する。
【００３４】
第４実施例では、永久磁石１４側の端部角部が空間部１００に面し、他部材と非接触にしたが、永久磁石１５の端部角部が空間部に面するようにしてもよいし、永久磁石１４、１５の両方の端部角部が空間部に面するようにしてもよい。
以上説明した本発明の上記複数の実施例では、中心コア部の外周側面および軸方向の両端角部の少なくとも一方を緩衝部材である筒部材で覆い、他方を筒部材で覆うか、空間部に面するようにしている。したがって、中心コア部と膨張率の異なる二次スプール２０やエポキシ樹脂２６等が中心コア部の外周側面および両端角部と接触することを防止するとともに、緩衝部材が弾性変形することにより膨張率の差を吸収している。したがって、温度変化に伴い中心コア部、二次スプール２０やエポキシ樹脂２６が膨張および収縮を繰り返しても、中心コア部の外周側面の周囲、ならびに特にクラックの発生しやすい中心コア部の軸方向の両端角部付近において二次スプール２０やエポキシ樹脂２６にクラックが発生することを防止できる。これにより、点火コイル内の高電圧部と低電圧部である中心コア部との間でクラックに沿って放電が発生することを防止できるので、所望の高電圧を点火プラグに印加することができる。
【００３５】
さらに、中心コア部の外周側面を筒部材が覆い、中心コア部の軸方向両端面を筒部材または緩衝部材の一部としての板部材が覆っているので、温度変化にともない中心コア部とともに中心コア部と膨張率の異なる二次スプール２０やエポキシ樹脂２６が膨張および収縮しても、筒部材または板部材が弾性変形することにより、中心コア部が径方向および軸方向に受ける力が緩和される。したがって、中心コア部に磁歪が発生せず所望の高電圧を点火プラグに印加することができる。
【００３６】
上記複数の実施例では、緩衝部材を構成する筒部材は、中心コア部の軸方向に延び、中心コア部の少なくとも一方の端部角部、ならびに外周側面を覆うように成形されているが、緩衝部材を複数の部材で構成し、緩衝部材が中心コア部の端部角部だけを覆うようにしてもよい。
また本発明の上記複数の実施例では、筒部材および板部材をゴムで成形したが、筒部材および板部材をエラストマー樹脂で成形し、筒部材に中心コア部をインサート成形することもできる。また、エラストマー樹脂で成形した筒部材に中心コア部を挿入してもよい。
【００３７】
また、射出成形、焼き付けまたはディップ（dipping)による一体成形によりエラストマー樹脂やゴム等の弾性部材が中心コア部１２の表面を覆って緩衝部材を形成してもよい。この場合、緩衝部材は中心コア部１２の全表面を覆ってもよいし、中心コア部１２の端部を識別するために一方の端部に小さい貫通孔を設けてもよい。中心コア部１２と緩衝部材とを一体成形することにより組付け時に緩衝部材が中心コア部１２から脱落しないので、組付けが容易になる。
【００３８】
また、予めコア本体１３に永久磁石１４、１５を装着して中心コア部１２を構成し、中心コア部１２に熱収縮チューブを被せて熱収縮チューブを熱収縮させることにより緩衝部材を形成してもよい。
また、中心コア部１２の端部角部、つまり永久磁石１４、１５の端部角部に研磨またはボール通し等の処理を施して面取りすることにより、中心コア部１２の端部角部に接する緩衝部材が損傷することを防止してもよい。
【図面の簡単な説明】
【図１】本発明の第１実施例による点火コイルを示す断面図である。
【図２】第１実施例の筒部材を示す断面図である。
【図３】図１のIII 線部分の拡大図である。
【図４】図１のIV線部分の拡大図である。
【図５】本発明の第２実施例による点火コイルを示す断面図である。
【図６】本発明の第３実施例による点火コイルの一方の端部を示す断面図である。
【図７】第３実施例による点火コイルの他方の端部を示す断面図である。
【図８】本発明の第４実施例による点火コイルの一方の端部を示す断面図である。
【図９】第４実施例による点火コイルの他方の端部を示す断面図である。
【符号の説明】
１０点火コイル
１１ハウジング
１２中心コア部
１３コア本体（中心コア部）
１４、１５永久磁石（中心コア部）
１７筒部材（緩衝部材）
１７ｂ、１７ｃ環状部（緩衝部材）
１７ｄ角部（緩衝部材）
１８貫通孔
１９キャップ（ケース部材）
２０二次スプール（ケース部材）
２１二次コイル
２３一次スプール
２４一次コイル
２５外周コア
２６エポキシ樹脂（樹脂絶縁材）
２７コア本体（中心コア部）
５０筒部材（緩衝部材）
５０ｃ円板部（緩衝部材）
５１板部材（緩衝部材）
５２筒部材（緩衝部材）
５３、５４板部材（緩衝部材）
１００空間部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ignition coil for an internal combustion engine, and more particularly to a stick-shaped ignition coil for an internal combustion engine that is directly mounted on a plug hole.
[0002]
[Prior art]
As a conventional stick-shaped ignition coil for an internal combustion engine (hereinafter, an “ignition coil for an internal combustion engine” is referred to as an ignition coil), a central core portion having a rod-shaped core body is disposed around an axis, and a primary coil and 2. Description of the Related Art It is known that a resin spool around which a secondary coil is wound is provided, and a resin is filled in a housing of the ignition coil as an insulating material between members. The resin filling the housing not only serves as an insulating material but also permeates between the wire members of the coil and plays a role in preventing winding collapse of the coil. There is also known an ignition coil in which a permanent magnet is provided on at least one of both ends in the axial direction of a core body to form a central core portion and increase a voltage generated by the ignition coil.
[0003]
[Problems to be solved by the invention]
However, in a state where not only the resin insulating material but also a case member such as a spool surrounding the outer periphery of the central core portion is in direct contact with the central core portion, the temperature changes between the central core portion having a different expansion coefficient and the resin insulating material or the case member. When the expansion and contraction are repeated, the resin insulating material and the case member in contact with the central core portion, particularly the resin insulating material and the case member in contact with the axial end corners of the central core portion are cracks (insulation deficient portions). crack) may occur. If a crack occurs in the resin insulating material or the case member around the central core, there is a risk of discharging through the crack between the secondary coil or the high voltage terminal as the high voltage part and the central core as the low voltage part. . When a discharge occurs between the high-voltage part and the central core, the insulation between the high-voltage part and the central core is broken, and the voltage generated in the secondary coil decreases. Cannot be applied.
[0004]
Further, when the center core and the resin insulating material or the case member repeatedly expand and contract due to a temperature change, the center core portion receives a load in the radial direction and the axial direction from the resin insulating material and the case member due to a difference in expansion rate. In particular, when a load is applied to the central core portion in the axial direction, the magnetic permeability of the core body may decrease (hereinafter, “permeability decreases due to the load on the central core portion” is referred to as magnetostriction), and the ignition coil There is a problem that the generated voltage decreases.
[0005]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an ignition coil that prevents a crack from being generated in the vicinity of both end corners in the axial direction of a central core portion and generates a desired high voltage.
It is another object of the present invention to provide an ignition coil that reduces a load applied to a central core portion due to a temperature change and generates a desired high voltage.
[0006]
[Means for Solving the Problems]
According to the ignition coil according to the first and second aspects of the present invention, the central core portion composed of a rod-shaped core body or a permanent magnet disposed on at least one of both ends of the rod-shaped core body and the core body in the axial direction is provided. Both end corners in the axial direction are covered with cushioning members. Accordingly, it is possible to prevent a case member such as a spool surrounding the outer periphery of the central core portion or a resin insulating material from directly contacting both end corners in the axial direction of the central core portion, and to prevent a contact between the central core portion and the resin insulating material or the case member. Since the first cushioning member absorbs the difference in the expansion coefficient, the first cushioning member can be expanded even if the center core portion and the resin insulating material and the case member having different expansion ratios from the center core portion repeatedly expand and contract with the temperature change. It is possible to prevent the resin insulating material and the case member near the two corners in the axial direction of the central core portion covered with the member from being cracked as an insulating defect. This prevents discharge between the secondary coil or high-voltage terminal as the high-voltage part and the central core as the low-voltage part, and prevents dielectric breakdown between the high-voltage part and the central core. Therefore, it is possible to prevent the voltage generated in the secondary coil from lowering and apply a desired high voltage to the spark plug.
[0008]
According to the ignition coil according to claim 4 of the present invention, it can be integrally molded cushioning member so shaping the cushioning member into a bag shape. As a result, the number of parts is reduced and the number of assembling steps is reduced. Further, since the provided at least on one of both axial ends of the bore of the buffer member having a smaller diameter than the diameter of the central core portion, the core body and the permanent magnets in the buffer member from the pores of the integral molded cushioning member Can be inserted.
[0009]
According to the ignition coil according to the fifth aspect of the present invention, since the buffer member is composed of a plurality of members, the manufacture of the buffer member is facilitated.
According to the ignition coil according to the sixth, seventh or eighth aspect of the present invention, the central core portion and the cushioning member are integrally formed, so that the cushioning member does not fall off the central core portion at the time of assembling, and the assembling is easy. become. Here, the integral molding means that the cushioning member formed on the central core portion is not detachable and forms a part as a whole with the cushioning member formed on the outer periphery of the central core portion.
[0010]
According to the ignition coil according to the ninth aspect of the present invention, since the cushioning member covers the entire surface of the central core, the central core does not come into contact with the resin insulating material or the case member. Therefore, generation of cracks in the resin insulating material and the case member around the central core portion can be prevented.
According to the ignition coil according to the tenth aspect of the present invention, since the end corners of the center core are chamfered, it is possible to prevent cracks from being generated in the buffer member in contact with the end corners of the center core.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a plurality of examples showing embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
1 to 4 show an ignition coil according to a first embodiment of the present invention.
[0015]
The ignition coil 10 shown in FIG. 1 is housed in a plug hole formed for each cylinder above an engine block (not shown), and is electrically connected to an ignition plug (not shown) on the lower side of FIG.
The ignition coil 10 includes a cylindrical housing 11 made of a resin material. A housing 11a formed in the housing 11 has a central core 12, a secondary spool 20, a secondary coil 21, a primary spool 23, The primary coil 24, the outer core 25, and the like are housed. The central core portion 12 includes a core body 13 and permanent magnets 14 and 15 disposed at both ends of the core body 13. The epoxy resin 26 filled in the accommodating chamber 11a penetrates between the members in the ignition coil 10 to ensure electrical insulation between the members as a resin insulating material.
[0016]
The cylindrical rod-shaped core body 13 is assembled by laminating thin silicon steel plates in the radial direction so that the cross section is substantially circular. The permanent magnets 14 and 15 have polarities opposite to the direction of the magnetic flux generated when excited by the coil. Further, the outer periphery of the core body 13 is covered with a rubber cylindrical member 17 as a buffer member . Further, a cap 19 having a through hole is fitted to the permanent magnet 14 covered by the cylindrical member 17. The cap 19 and the secondary spool 20 constitute a case member surrounding the outer periphery of the central core portion 12.
[0017]
The cylindrical member 17 is integrally formed in a cylindrical bag shape as shown in FIG. The cylindrical member 17 is located between the cylindrical portion 17a, the annular portions 17b and 17c provided at both ends in the axial direction of the cylindrical portion 17a and having a through hole 18 at the center, and the cylindrical portion 17a and the annular portions 17b and 17c. Corner 17d. As shown in FIGS. 3 and 4, the cylindrical portion 17 a covers the outer peripheral side surface of the central core portion 12, the annular portions 17 b and 17 c cover a part of both axial end surfaces of the central core portion 12, and the corner portion 17 d is located at the center. The end corners of the permanent magnets 14 and 15 which are the end corners of the core 12 are covered. The annular portions 17b and 17c are formed so as to be thicker than the cylindrical portion 17a, and constitute a part of the cushioning member. Since the diameter of the through hole 18 is smaller than the diameter of the permanent magnets 14 and 15, the core body 13 and the permanent magnets 14 and 15 are inserted into the cylindrical member 17 while expanding the through hole 18.
[0018]
As shown in FIG. 1, the secondary spool 20 is provided on the outer periphery of the cylindrical member 17, and is formed of a resin material into a closed-end cylindrical shape with the permanent magnet 15 side closed. The secondary coil 21 is wound around the outer periphery of the secondary spool 20, and a dummy coil 22 is further wound around the high voltage side of the secondary coil 20 in a single winding. The dummy coil 22 electrically connects the secondary coil 21 and the terminal plate 40. By electrically connecting the secondary coil 21 and the terminal plate 40 with the dummy coil 22 instead of a single wire, the surface area of the electrical connection between the secondary coil 21 and the terminal plate 40 is increased, and the electrical connection is made. Avoid electric field concentration.
[0019]
The primary spool 23 is provided on the outer periphery of the secondary coil 21 and is formed of a resin material. The primary coil 24 is wound around the primary spool 23. A switching circuit for supplying a control signal to the primary coil 24 is provided outside the ignition coil 10, and the primary coil 24 and a switching circuit (not shown) are electrically connected to each other via a terminal formed by insert-molding the connector 30. I have.
[0020]
The outer core 25 is mounted further outside the primary coil 24. The outer peripheral core 25 is formed by winding a thin silicon steel sheet in a cylindrical shape and does not connect the winding start end and the winding end end, and thus forms a gap in the axial direction. The outer peripheral core 25 has an axial length extending from the outer peripheral position of the permanent magnet 14 to the outer peripheral position of the stone 15.
The high-voltage terminal 41 is insert-molded below the housing 11. The central portion of the terminal plate 40 forms a claw portion bent in the direction in which the high-voltage terminal 41 is inserted. The high-voltage terminal 41 is electrically connected to the terminal plate 40 by inserting the tip of the high-voltage terminal 41 into the claw portion. The wire at the high voltage end of the dummy coil 22 is electrically connected to the terminal plate 40 by fusing or soldering. The spring 42 is electrically connected to the high voltage terminal 41 and is electrically connected to the ignition plug when the ignition coil 10 is inserted into the plug hole. A plug cap 43 made of rubber is attached to the open end of the housing 11 on the high voltage side, and an ignition plug is inserted into the plug cap 43. When a control signal is supplied from the switching circuit to the primary coil 24, a high voltage is generated in the secondary coil 21, and this high voltage is applied to the ignition plug via the dummy coil 22, the terminal plate 40, the high voltage terminal 41, and the spring 42. .
[0021]
Next, the operation of the ignition coil 10 according to the temperature change will be described.
The expansion coefficients of the secondary spool 20 and the epoxy resin 26 surrounding the outer periphery of the central core section 12 are different from the expansion coefficients of the core body 13 and the permanent magnets 14 and 15 which constitute the central core section 12. Usually, the expansion coefficients of the secondary spool 20 and the epoxy resin 26 are larger than the expansion coefficient of the central core portion 12. Therefore, if the center core portion 12 is not covered with the cylindrical member 17 and the secondary spool 20 or the epoxy resin 26 is in direct contact with the center core portion 12, the temperature change causes the center core portion 12 and the secondary spool 20. When the epoxy resin 26 repeatedly expands and contracts, cracks may occur in the secondary spool 20 and the epoxy resin 26 that are in contact with the central core 12. In particular, cracks are likely to occur in the secondary spool 20 and the epoxy resin 26 that are in contact with the end corners of the permanent magnets 14 and 15. If a crack occurs in the secondary spool 20 or the epoxy resin 26 which is in contact with the corners of the end portions of the permanent magnets 14 and 15, the high voltage side of the secondary coil 21 which is a high voltage portion, the dummy coil 22, the terminal plate 40 or the high voltage terminal Discharge may occur through a crack between the central core portion 12 and the low voltage portion. When a discharge occurs between the high-voltage portion and the central core portion 12, the insulation between the high-voltage portion and the central core portion 12 is broken, and the voltage generated in the secondary coil decreases. It cannot be applied.
[0022]
However, in the first embodiment, the outer peripheral side surface of the central core portion 12 and the end corners of the permanent magnets 14 and 15 are covered with the cylindrical member 17 made of an elastic material. The end portion 15 is prevented from coming into direct contact with the secondary spool 20 or the epoxy resin 26. Furthermore, even if the center core portion 12 and the secondary spool 20 and the epoxy resin 26 which have different expansion rates due to the temperature change repeatedly expand and contract, the difference in the expansion rates is absorbed by the cylindrical member 17 being elastically deformed. Can be. Accordingly, it is possible to prevent the secondary spool 20 and the epoxy resin 26 from being cracked around the outer peripheral side surface of the central core portion 12 and especially near both corners of the central core portion 12 where cracks are easily generated. It is possible to prevent discharge from occurring between the portion and the central core portion 12. Thereby, a desired high voltage can be applied to the ignition plug.
[0023]
Also, since the expansion coefficient of the cap 19, the secondary spool 20, and the epoxy resin 26 is different from the expansion coefficient of the central core portion 12 composed of the core body 13 and the permanent magnets 14 and 15, it is large. Due to the contraction of the next spool 20 and the epoxy resin 26, a force acts to contract the central core portion 12 in the radial direction and the axial direction. In particular, when a force is applied in the axial direction of the central core portion 12, magnetostriction in which the magnetic permeability of the core body 13 is reduced occurs, and the voltage generated in the secondary coil 21 may be reduced. However, since the cylindrical portion 17a covers the outer peripheral side surface of the central core portion 12 and the annular portions 17b and 17c that are thicker than the cylindrical portion 17 cover a part of both ends in the axial direction, the cylindrical member 17 is elastically deformed so that The forces applied to the core portion 12 in the radial direction and the axial direction are reduced, and no magnetostriction occurs in the core body 13. Thereby, a desired high voltage can be applied to the ignition plug.
[0024]
In the first embodiment, the permanent magnets 14 and 15 are provided at both ends of the core body 13, but permanent magnets may be provided only at one end of the core body 13.
(Second embodiment)
FIG. 5 shows an ignition coil according to a second embodiment of the present invention. Components substantially the same as those in the first embodiment are denoted by the same reference numerals.
[0025]
In the second embodiment, a permanent core is not disposed at both ends of the core main body 27, and the core main body 27 alone forms a central core portion. The cylindrical member 17 covers the outer peripheral side surface, both end corners, and part of both end surfaces of the core main body 27.
Accordingly, also in the second embodiment, cracks are prevented from being generated around the outer peripheral side surface of the core main body 27, and especially near the corners at both ends of the core main body 27 where cracks are easily generated. Therefore, it is possible to prevent discharge between the high voltage portion and the central core portion 12. Thereby, a desired high voltage can be applied to the ignition plug.
[0026]
Further, since the cylindrical member 17 is elastically deformed, the force applied to the core main body 27 in the radial direction and the axial direction is reduced, and no magnetostriction occurs in the core main body 27. Thereby, a desired high voltage can be applied to the ignition plug.
(Third embodiment)
6 and 7 show an ignition coil according to a third embodiment of the present invention. Components substantially the same as those in the first embodiment are denoted by the same reference numerals.
[0027]
The rubber tubular member 50 includes a cylindrical portion 50a, a corner portion 50b, and a disk portion 50c, and is formed into a closed-end cylindrical bag with the permanent magnet 15 side closed. The cylindrical portion 50a covers the outer peripheral side surface of the central core portion 12, the annular corner portion 50b covers the end corner portion of the permanent magnet 15, and the disk portion 50c covers the end surface of the permanent magnet 15. The tubular member 50 is formed on the permanent magnet 14 side so as to extend beyond the end face of the permanent magnet 14. The rubber plate member 51 is formed in a circular shape separately from the cylindrical member 50, and has a larger diameter than the permanent magnet 14. The rubber tubular member 50 and the rubber plate member 51 constitute a buffer member. The end corners of the permanent magnet 14 are covered by the cylindrical member 50 and the plate member 51, and the end surface of the permanent magnet 14 is covered by the plate member 51. Further, since the plate member 51 seals the gap between the cap 19 as the case member and the permanent magnet 14, the epoxy resin 26 does not enter the central core portion 12.
[0028]
Also in the third embodiment, cracks are prevented from being generated around the outer peripheral side surface of the central core portion 12, and especially near the corners at both ends of the central core portion 12 where cracks are easily generated. Therefore, it is possible to prevent discharge between the high voltage portion and the central core portion 12. Thereby, a desired high voltage can be applied to the ignition plug.
[0029]
Furthermore, since the cylindrical member 50 and the plate member 51 are elastically deformed, the force applied to the central core portion 12 in the radial direction and the axial direction is reduced, and no magnetostriction occurs in the central core portion 12. Thereby, a desired high voltage can be applied to the ignition plug.
The cushioning member is composed of two members, a tubular member 50 and a plate member 51. Since the tubular member 50 is formed in a bottomed tubular shape having no end face at one end in the axial direction, it is easy to manufacture the cushioning member. is there.
[0030]
(Fourth embodiment)
FIGS. 8 and 9 show an ignition coil according to a fourth embodiment of the present invention. Components substantially the same as those of the third embodiment are denoted by the same reference numerals.
The rubber tubular member 52 includes a cylindrical portion 52a, a corner portion 52b, and an annular portion 52c, and is formed into a cylindrical bag shape. The cylindrical portion 52a covers the outer peripheral side surface of the central core portion 12, the annular corner portion 52b covers an end corner portion of the permanent magnet 15, and the annular portion 52c covers a part of the end surface of the permanent magnet 15. The cylindrical portion 52a extends toward the permanent magnet 14, but its end does not reach the end surface of the permanent magnet 14.
[0031]
The rubber plate members 53 and 54 are formed in a circular shape separately from the cylindrical member 52. The rubber tubular member 52 and the rubber plate members 53 and 54 constitute a buffer member. The plate members 53 and 54 are smaller in diameter than the permanent magnets 14 and 15, and are in contact with the end faces of the permanent magnets 14 and 15, respectively.
As shown in FIG. 8, the end corner of the permanent magnet 14 faces the space 100 and is not in contact with any member. Further, since the plate member 53 seals the gap between the cap 19 as the case member and the permanent magnet 14, the epoxy resin 26 does not enter the central core portion 12.
[0032]
In the fourth embodiment, since the end corners of the permanent magnet 14 face the space 100 and the end corners of the permanent magnet 15 are covered with the cylindrical member 52, both ends of the central core 12 in the axial direction are provided. The corner is not in contact with the secondary spool 20 or the epoxy resin 26. Further, since the cylindrical portion 52a covers the outer peripheral side surface of the center core portion 12, even if the center core portion 12, the secondary spool 20, and the epoxy resin 26 repeatedly expand and contract with a change in temperature, the center core portion 12 is not covered. Since the secondary spool 20 and the epoxy resin 26 are prevented from generating cracks around the outer peripheral side surface, and especially near both corners of the central core portion 12 where cracks are easily generated, the high voltage portion and the central core portion 12 are prevented from cracking. It is possible to prevent discharge between the two. Thereby, a desired high voltage can be applied to the ignition plug.
[0033]
Further, the elastic deformation of the plate members 53 and 54 reduces the force applied to the central core portion 12 in the radial and axial directions, so that magnetostriction does not occur in the central core portion 12. Thereby, a desired high voltage can be applied to the ignition plug. Further, since the plate member 53 serving as a buffer member also serves as a seal member between the end face of the permanent magnet 14 and the cap 19, the number of parts is reduced and the number of assembling steps is reduced.
[0034]
In the fourth embodiment, the end corner of the permanent magnet 14 faces the space 100 and is not in contact with other members. However, the end corner of the permanent magnet 15 may face the space. Alternatively, both end corners of the permanent magnets 14 and 15 may face the space.
In the above-described plurality of embodiments of the present invention, at least one of the outer peripheral side surface of the central core portion and the both end corners in the axial direction is covered with a cylindrical member which is a buffer member , and the other is covered with a cylindrical member or in a space portion. Face to face. Therefore, it is possible to prevent the secondary spool 20 and the epoxy resin 26 having different expansion rates from the center core part from coming into contact with the outer peripheral side face and the corners at both ends of the center core part, and to reduce the expansion rate by elastically deforming the cushioning member . Absorb the difference. Therefore, even if the center core portion, the secondary spool 20 and the epoxy resin 26 repeatedly expand and contract with the temperature change, the periphery of the outer peripheral side surface of the center core portion, and especially the axial direction of the center core portion where cracks are liable to occur. Cracks can be prevented from occurring in the secondary spool 20 and the epoxy resin 26 near the corners at both ends. This can prevent a discharge from occurring along a crack between the high-voltage portion and the central core portion, which is a low-voltage portion, in the ignition coil, so that a desired high voltage can be applied to the ignition plug. .
[0035]
Furthermore, the outer peripheral side surface of the central core portion is covered by the cylindrical member, and both end surfaces in the axial direction of the central core portion are covered by the plate member as a part of the cylindrical member or the cushioning member. Even if the secondary spool 20 and the epoxy resin 26 having different expansion rates from the core part expand and contract, the cylindrical member or the plate member is elastically deformed, so that the force applied to the central core part in the radial direction and the axial direction is reduced. You. Therefore, a desired high voltage can be applied to the ignition plug without generating magnetostriction in the central core portion.
[0036]
In the above plurality of embodiments, the cylindrical member constituting the cushioning member extends in the axial direction of the central core portion, and is formed so as to cover at least one end corner of the central core portion, as well as the outer peripheral side surface, The buffer member may be composed of a plurality of members, and the buffer member may cover only the end corners of the central core portion.
In the above embodiments of the present invention, the cylindrical member and the plate member are formed of rubber. However, the cylindrical member and the plate member may be formed of an elastomer resin, and the center core portion may be insert-molded in the cylindrical member. Further, the center core may be inserted into a cylindrical member formed of an elastomer resin.
[0037]
Further, an elastic member such as an elastomer resin or rubber may cover the surface of the central core portion 12 to form the cushioning member by integral molding by injection molding, baking, or dipping. In this case, the cushioning member may cover the entire surface of the central core 12, or a small through hole may be provided at one end to identify the end of the central core 12. By integrally molding the central core portion 12 and the cushioning member , the cushioning member does not drop off from the central core portion 12 at the time of assembling, so that the assembling becomes easier.
[0038]
Also, the permanent magnets 14 and 15 are mounted on the core body 13 in advance to form the central core portion 12, and the heat shrinkable tube is put on the central core portion 12 and the heat shrinkable tube is thermally shrunk to form a buffer member. Is also good.
In addition, the corners of the center core 12, that is, the corners of the permanent magnets 14 and 15 are chamfered by grinding or grinding them so that they come into contact with the corners of the center core 12. The damping member may be prevented from being damaged.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an ignition coil according to a first embodiment of the present invention.
FIG. 2 is a sectional view showing a cylindrical member of the first embodiment.
FIG. 3 is an enlarged view of a portion taken along line III of FIG. 1;
FIG. 4 is an enlarged view of a portion taken along a line IV in FIG. 1;
FIG. 5 is a sectional view showing an ignition coil according to a second embodiment of the present invention.
FIG. 6 is a sectional view showing one end of an ignition coil according to a third embodiment of the present invention.
FIG. 7 is a sectional view showing the other end of the ignition coil according to the third embodiment.
FIG. 8 is a sectional view showing one end of an ignition coil according to a fourth embodiment of the present invention.
FIG. 9 is a sectional view showing the other end of the ignition coil according to the fourth embodiment.
[Explanation of symbols]
Reference Signs List 10 ignition coil 11 housing 12 central core 13 core body (central core)
14, 15 permanent magnet (center core)
17 Tube member ( buffer member )
17b, 17c Annular part ( buffer )
17d corner ( buffer )
18 Through hole 19 Cap (case member)
20 Secondary spool (case member)
21 Secondary coil 23 Primary spool 24 Primary coil 25 Outer core 26 Epoxy resin (resin insulating material)
27 core body (center core)
50 Tube member ( buffer member )
50c disk ( buffer )
51 Board member ( buffer member )
52 Tube member ( buffer member )
53, 54 Plate member ( buffer member )
100 space

Claims

An internal combustion engine ignition coil that generates a high voltage applied to an internal combustion engine ignition device,
A central core portion composed of a rod-shaped core body,
A primary spool and a secondary spool disposed on the outer periphery of the center core,
A primary coil wound on the primary spool, and a secondary coil wound on the secondary spool,
An ignition comprising a housing forming a housing chamber for housing the center core portion, the primary spool, the secondary spool, the primary coil and the secondary coil, and a resin insulating material filled in the housing chamber of the housing. A coil,
A cushioning member that covers both end corners in the axial direction of the central core portion, and has a thickness at an axial end surface of the central core portion larger than a thickness at an outer peripheral side surface of the central core portion,
An ignition coil for an internal combustion engine, comprising:

The ignition coil for an internal combustion engine according to claim 1, wherein the center core portion further includes a permanent magnet disposed on at least one of both ends in the axial direction of the core body.

The cushioning member includes a cylindrical portion that covers an outer peripheral side surface of the central core portion, and an annular portion provided at an axial end of the cylindrical portion and having a through hole formed in the center, and the annular portion includes the cylindrical portion. The ignition coil for an internal combustion engine according to claim 1, wherein the ignition coil is formed so as to be thicker.

The said buffer member is shape | molded in bag shape, The hole which has a diameter smaller than the diameter of the said center core part is provided in at least any one of the axial direction both ends of the said center core part, The Claims 1 thru | or 1 characterized by the above-mentioned. 4. The ignition coil for an internal combustion engine according to claim 3.

The ignition coil according to any one of claims 1 to 4, wherein the buffer member includes a plurality of members.

The ignition coil for an internal combustion engine according to claim 1, wherein the center core portion and the cushioning member are integrally formed.

The ignition coil according to claim 6, wherein the buffer member is made of an elastomer resin.

7. The ignition coil for an internal combustion engine according to claim 6, wherein said buffer member comprises a heat-shrinkable tube.

9. The ignition coil for an internal combustion engine according to claim 1, wherein the cushioning member covers the entire surface of the central core portion.

The ignition coil for an internal combustion engine according to any one of claims 1 to 9, wherein an end corner of the center core portion is chamfered.