JP4235336B2 - Induction hardening method of rack bar and induction hardening apparatus thereof - Google Patents

Induction hardening method of rack bar and induction hardening apparatus thereof Download PDF

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JP4235336B2
JP4235336B2 JP2000048422A JP2000048422A JP4235336B2 JP 4235336 B2 JP4235336 B2 JP 4235336B2 JP 2000048422 A JP2000048422 A JP 2000048422A JP 2000048422 A JP2000048422 A JP 2000048422A JP 4235336 B2 JP4235336 B2 JP 4235336B2
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rack bar
frequency induction
induction heating
back surface
high frequency
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精一 沢津橋
啓一 久保
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Denki Kogyo Co Ltd
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Description

【０００１】
【発明の属する技術分野】
本発明は、ラックバーの歯面を含んだ全周面を一発焼入法により高周波焼入する方法及びその焼入装置に関するものである。
【０００２】
【従来の技術】
図８は、従来より一般的に用いられているステアリング用ラックバー１を示すものであって、このステアリング用ラックバー１は片側面に軸線Ｘに対して角度θをなす斜歯２を有し、この斜歯２の歯面３とは反対側の面が背面（半円筒面）４となされている。従来においては、この種のステアリング用ラックバー１の歯面３を焼入するために図９に示される高周波直接通電焼入装置５ａが用いられ、その背面４を焼入するために図１０に示される高周波直接通電焼入装置５ｂが用いられている。また、前記歯面３及び背面４を同時に焼入するために図１１に示される高周波直接通電装置６が用いられている。
【０００３】
これらの装置５ａ，５ｂ或いは６は、図９，図１０及び図１１に示すように、電気的絶縁材７，７’を介して第一導体８，８’と第二導体９，９’をそれぞれサンドイッチ状に組み合わせて成る部材であって、被焼入体であるステアリンググラックバー１の歯面３或いは背面４にそれぞれ対向して配設される単位導体１０，１０’と、これらの単位導体１０，１０’の第一導体８，８’に接続され、前記歯面３或いは背面４の長手方向の一端に当接配置される第一接触電極１１，１１’と、前記単位導体１０，１０’の第二導体９，９’に接続され、前記歯面３或いは背面４の長手方向の他端に当接配置される第二接触電極１２，１２’と、これらの第二接触電極１２，１２’の間の領域において前記歯面３或いは背面４に冷却液を噴出し得る冷却液噴射手段１３，１３’を備えた近接導体１４、１４’と、前記一対の第一導体８，８’と第二導体９，９’が接続される高周波電源１５、１５’とをそれぞれ備えている。さらに、ラックバー押圧用の一対の油圧シリンダー１６，１６’も備えられている。
【０００４】
【発明が解決しようとする課題】
上述の如き従来の高周波直接通電焼入装置５ａ，５ｂ或いは６を用いて、ラックバー１の歯面３及び背面４を焼入した場合、次の如き問題点が生ずる。すなわち、高周波直接通電焼入装置５ａ，５ｂを用いてラックバー１の歯面３及び背面４を二工程で高周波焼入した場合の焼入硬化層パターンは、図１２に示す如き焼入硬化層パターンＴとなる。この焼入硬化層パターンＴにおいて斜線部Ｗで示した硬化層部分は、焼入処理が重複した部分であり、始めの焼入処理により得られる硬化層部分とその後の焼入処理荷より得られる硬化層部分の境界部分Ｗが軟化し、その上、焼割れが発生しやすい。また、二工程で焼入するため焼入処理時間を長く要することとなり、作業性並びに生産性が著しく低くなるという不具合がある。さらに、二台の高周波直接通電焼入装置５ａ，５ｂを必要とするので、設備費が高くなるという問題点がある。
【０００５】
また、高周波直接通電焼入装置６を用いてラックバー１の歯面３及び背面４を一工程で同時に高周波焼入した場合の焼入硬化層パターンは、図１３に示す如き焼入硬化層パターンＴとなる。本装置６による焼入では、上述の境界部分Ｗ（図１２参照）に相当する部分Ｗ’の硬化層が浅くなる。また、設備上の問題点として、ワーク押圧機構、着脱機構等が非常に複雑となり、既述の二台の焼入装置５ａ，５ｂよりもさらに高価なものとなる。
【０００６】
本発明は、このような問題点を解消すべくなされたものであって、その目的は、直接通電法を用いずにラックバーの歯面及び背面を同時に効率良く焼入でき、しかも良好な焼入硬化層パターンをラックバーの全周面に形成することができるようなラックバーの高周波焼入方法及び高周波焼入装置を提供することにある。
【０００７】
【課題を解決するための手段】
上述の目的を達成するために、本発明では、被焼入体であるラックバーの歯面及び背面を含めた全周面を高周波焼入する方法において、
前記ラックバーの軸線方向に沿って配置され、かつ、前記ラックバーの歯面及び背面にそれぞれ対向する一対の主導体を有する高周波誘導加熱コイルを用い、（ａ） 前記ラックバーを前記高周波誘導加熱コイルに対して静止させた状態の下で高周波誘導加熱する工程と、
（ｂ） 次いで、前記ラックバーをその軸線を中心に回転させることにより、前記ラックバーを前記高周波誘導加熱コイルに対して回転させた状態下で高周波誘導加熱をさらに継続して行なう工程と、
（ｃ） しかる後に、前記ラックバーの全周面が所要の焼入温度に高周波誘導加熱された時点で、前記ラックバーの全周面を急速冷却する工程と、
をそれぞれ順次に施行するようにしている。
また、本発明では、前記ラックバーを静止状態で高周波誘導加熱する静止加熱、及び、前記ラックバーを回転状態で高周波誘導加熱する回転加熱を、同一の周波数電流、或いは、それぞれ異なる周波数電流を前記高周波誘導加熱コイルに流すことにより行うようにしている。
また、本発明では、前記静止加熱及び回転加熱を、同一電力、或いはそれぞれ異なる電力を前記高周波誘導加熱コイルに供給することにより行うようにしている。
また、本発明では、
（ａ） 被焼入体であるラックバーの軸線方向に沿って配置され、かつ、前記ラックバーの歯面及び背面にそれぞれ対向する一対の主導体を有する高周波誘導加熱コイルと、
（ｂ） 前記ラックバーの歯面及び背面を前記一対の主導体に対向した状態で前記ラックバーを静止状態で保持する保持機構と、
（ｃ） 前記保持機構にて保持された前記ラックバーを回転駆動する回転駆動機構と、
（ｄ） 前記ラックバーに向けて冷却液を噴射する冷却液噴射機構と、
をそれぞれ具備し、
前記ラックバーを前記保持機構にて静止状態に保持した状態の下で前記高周波誘導加熱コイルにて予備加熱した後に、前記ラックバーを前記回転駆動機構にてその軸線を中心に回転駆動させた状態の下で前記高周波誘導加熱コイルにて本加熱し、前記ラックバーの歯面及び背面を含む全周面が所要の焼入温度に達した直後に前記冷却液噴射機構から冷却液を噴射して前記ラックバーの全周面を焼入するようにしたことを特徴とするラックバーの高周波焼入装置。
また、本発明では、中空部を有するパイプ部材にて前記一対の主導体をそれぞれ構成すると共に、前記ラックバーの歯面及び背面に対向配置される前記一対の主導体の対向壁部に複数の冷却液噴射口をそれぞれ設け、前記複数の冷却液噴射口から冷却液を噴射するようにしている。
また、本発明では、前記ラックバーの歯面に対向する前記主導体の対向壁部を平坦状の壁部とし、前記ラックバーの背面に対向する前記主導体の対向壁部を断面半円形状の壁部としている。
【０００８】
【発明の実施の形態】
以下、本発明の一実施形態について図１〜図７を参照して説明する。
【０００９】
図１及び図２は、本発明に係る高周波焼入方法を施行するために用いられる高周波焼入装置２０を示すものである。本装置２０は、図１及び図２に示すように、ラックバー１の歯面３及び背面４に対向するように互いに平行状に配置されて上下方向に沿って延びる左右一対の主導体２１ａ，２１ｂと、これらの主導体２１ａ，２１ｂの上下両端部に接続されて互いに平行状に配置された上下一対の環状副導体２２ａ，２２ｂと、前記主導体２１ｂの中間箇所の切断部の上下両部にそれぞれ接続された一対の電流供給導体２３ａ，２３ｂとから成る高周波誘導加熱コイル１９を具備している。
【００１０】
図２及び図３に示す如く、上述の主導体２１ａ，２１ｂは冷却液流通用の中空部２４ａ，２４ｂを有する導電性のパイプ部材にて構成されており、環状副導体２２ａ，２２ｂは中空部を有しない導電性のリング部材にて構成されている。そして、前記主導体２１ａ，２１ｂの中空部２４ａ，２４ｂにそれぞれ連通する各一対の冷却液導入管２５ａ，２５ｂが主導体２１ａ，２１ｂの外側壁部２６ａ，２６ｂに接続されている。さらに、ラックバー１の歯面３及び背面４に対向する主導体２１ａ，２１ｂの内側壁部２７ａ，２７ｂには、所要の孔径を有し、かつ、所要のピッチ間隔を隔てて開口された複数の冷却液噴射孔２８ａ，２８ｂが設けられている。かくして、主導体２１ａ，２１ｂの中空部２４ａ，２４ｂ内にそれぞれ導入された冷却液（焼入液）がこれらの冷却液導入管２５ａ，２５ｂから噴射されるようになっている。
【００１１】
なお、後述の静止加熱時及び焼入冷却時にラックバー１の歯面３に対向配置される主導体２１ａの内側壁部２７ａは、平面となされる一方、焼入冷却時にラックバー１の背面４に対向される主導体２１ｂの内側壁部２７ｂは前記背面４の曲率の対応する形状の湾曲面（半円形面）となされている（図１，図２及び図３参照）。
【００１２】
ここで、高周波焼入装置２０の製作手順について述べると、次の通りである。
【００１３】
（ａ） まず、ラックバー１の歯面３に沿うように形成される一方の主導体２１ａの一端部（上端部）αを、一方の環状副導体２２ａの軸方向と直交する下面にろう付けにより接合すると共に、ラックバー１の背面４に沿うように形成される主導体２１ｂの一端部（上端部）βを、一方の環状副導体２２ｂの軸方向に直交する下面であってかつ前記主導体２１ａの一端部αが接合されている接合位置に対して１８０度離間した箇所にろう付けにより接合する（図１及び図２参照）。
【００１４】
（ｂ） 次いで、前記一方の主導体２１ａの他端部（下端部）γを、前記他方の環状副導体２２ｂの軸方向に直交する面にろう付けにより接合すると共に、前記他方の主導体２１ｂの他端部（下端部）δを前記一方の主導体２１ａの他端部γが接合されている接合位置に対して１８０゜離間した位置において、前記他方の環状副導体２２ｂの軸方向に直交する面にろう付けにより接合する。
【００１５】
（ｃ） そして、一方の主導体２１ａ若しくは他方の主導体２１ｂの所定の中間位置に電流供給導体２３ａ，２３ｂの一端部を上記と同様の方法で接合してコイル電路を形成し、このコイル電路に高周波電源２９から電流供給導体２３ａ，２３ｂを介して高周波誘導加熱コイル１９に高周波電力が供給されるように構成する。なお、電流供給導体２３ａ，２３ｂの間には、例えば４フッ化エチレン（商標名；テフロン）等の耐熱性絶縁材からなる板状絶縁部材３０を挿入配設することにより、これらの間の電気的絶縁を図るように構成する。
【００１６】
次に、上述のような構成の高周波焼入装置２０を用いてラックバー１の全周面（歯面３及び背面４を含む）を一発焼入する際の操作手順について述べると、以下の通りである。
【００１７】
（１） まず、高周波焼入装置２０の上方に配置されている図外のワーク固定治具にラックバー１の下端部を載置し、ラックバー１の上端部を図外のセンターにより押さえることにより、ラックバー１を垂直に立てた状態で保持する。
（２） 次に、ラックバー１を図外のワーク昇降機構により下降させ、焼入装置２０内の所定の加熱位置で停止させる。
（３） 次いで、ラックバー１の歯面３及び背面４をそれぞれ高周波誘導加熱コイル１９の主導体２１ａ及び主導体２１ｂにそれぞれ対向せしめた状態で、ラックバー１を固定配置する。
（４） この後に、高周波電源２９から所要周波数・所要出力の高周波電力を焼入装置２０の高周波誘導加熱コイル１９に供給してこのコイル１９に高周波電流を流すことにより、ラックバー１の歯面３及び背面４の静止加熱（ラックバー１を静止させた状態の下での高周波誘導加熱）を開始して所要時間にわたって高周波誘導加熱を行なう。
（５） 歯面３及び背面４が所要加熱温度及び所要加熱深さに到達した時点でラックバー１をその軸線Ｘ（図８参照）を中心に図外の回転機構により所要の回転数をもって回転させ、ラックバー１の全周面（ワーク全周面）の回転加熱（ラックバー１を回転させた状態の下での高周波誘導加熱）を行う。
（６） そして、この回転加熱によりラックバー１の全周面が所要の焼入温度に到達した時点で、高周波誘導加熱コイル１９への通電を遮断し加熱を停止する。
（７） 次いで、歯面３側の主導体２１ａ及び背面４側の主導体２２ｂの内側壁部（ワーク対向面）２７ａ，２７ｂに開孔された冷却液噴射冷孔２８ａ，２８ｂから所要圧力・所要流量の冷却液を回転状態のラックバー１の周面に向けて噴射し、このラックバー１の周面の表面温度が常温になるまで急冷する。
（８） そして、ラックバー１の周面の表面温度が常温にまで急冷された時点で、冷却液の噴射及びラックバー１の回転を共に停止し、一連の焼入処理を終了する。
（９） しかる後に、ワークを所定の位置まで上昇させ、ワーク固定治具３０及びセンター３１よりラックバーを取り外し、次工程に移送する。
【００１８】
上述の一連の焼入操作を要約して述べると、ラックバー１を高周波焼入装置２０内の所定の位置、すなわち、図２に示す如く主導体２１ａにラックバー１の歯面３が対向配置されかつ主導体２１ｂにラックバー１の背面４が対向配置されるような位置に配置して静止状態で固定し、この静止状態の下で高周波誘導加熱コイル１９に通電することにより前記歯面３及び背面４の静止加熱を行う。そして、所要時間にわたる静止加熱にて前記歯面３及び背面４が所要温度に到達すると同時に、図外のワーク保持治具を図外の回転駆動手段によりラックバー１の軸線Ｘを中心に所要の回転速度で回転させながら、所要時間にわたり回転加熱を行い（高周波誘導加熱コイル１９の通電状態は維持）、歯面３及び背面４を含むラックバー１の全周面が所要焼入温度に到達した時点で、高周波誘導加熱コイル１９への高周波電流の供給を遮断すると同時に、一対の主導体２１ａ，２１ｂに設けられた複数の冷却液噴射孔２８ａ，２８ｂから所要圧力・所要流量の冷却液を回転状態のラックバー１に向けて噴射し、このラックバー１の表面を所要時間にわたって急速冷却することにより焼入処理を行なう。
【００１９】
なお、図１に示されている矢印Ｒは瞬間における電流の流れ方向を示すものであるが、本実施形態で用いられている高周波誘導加熱コイル１９は既述の如く各一対の主導体２１ａ，２１ｂ及び環状副導体２２ａ，２２ｂから構成されたものであるため、高周波誘導加熱コイル１９の通電時には、環状副導体２２ａ，２２ｂに流れる電流の２倍の電流が主導体２１ａ，２１ｂに流れることとなる。すなわち、一対の環状副導体２２ａ，２２ｂのそれぞれは環状の導体を２つに分岐してこの２つの同形状の導体が一対の主導体２１ａ，２１ｂを介して互いに並列接続されたコイル電路を形成しているため、主導体２１ａ，２１ｂのそれぞれに流れる高周波電流を例えばＩアンペアとすると、それぞれの環状副導体２２ａ，２２ｂに流れる高周波電流は、Ｉ／２アンペアとなる。
【００２０】
上述の如き高周波焼入装置２０を使用した本発明の高周波焼入方法によりラックバー１の全周面を焼入した場合、図４に示すような焼入硬化層パターンが得られた。この場合、図４に示すように、歯面３の歯高よりも深く、かつ、歯高に対して直交する歯面３の長手方向（図４において左右方向）の中央部からその左右両側に向かうにつれて徐々に深くなるような硬化層パターンＴ1 が歯面３の側に形成されると共に、前記硬化層パターンＴ1 の両部にそれぞれ連なる均一な断面円弧状の硬化層パターンＴ2 が背面４の側に形成された。
【００２１】
このような本発明の高周波焼入方法により得られる焼入硬化層パターンＴと、本発明の高周波焼入方法を用いずにその他の方法で得られる焼入硬化層パターンとの相違を確認するために、次のような実験を行った。
【００２２】
まず、高周波誘導加熱の開始から終了までの全期間においてラックバー１に回転を与えることなく常に静止させた状態で高周波誘導加熱を行ない、その他の加熱条件は、図４に示したものと同一として、静止加熱のみによる高周波誘導加熱を行って急速冷却したところ、図５に示す如き焼入硬化層パターンが得られた。具体的には、図５に示すように、歯面３の歯高よりも深く、かつ、深さが均一な硬化層パターンＴ1 ’が歯面３の側に形成されると共に、この硬化層パターンＴ1 ’の左右両部からかなり遠くに離れた位置から均一に延びる断面円弧状の硬化層パターンＴ2 ’が背面４の側に形成された。すなわち、この場合には、歯面３の側の主導体２１ａと背面４の側の主導体２１ｂとによって歯面３と背面４とが別々に分離したかたちで加熱されることとなるため、歯面３及び背面４における硬化層パターンＴ1 ’，Ｔ2 ’が連続せずに、互いに分離したものとなった。
【００２３】
また、高周波誘導加熱の開始から終了までの全期間において静止加熱を全く行わず、その他の加熱条件は図４に示したものと同一として、回転加熱のみを行ったところ、図６に示す如き焼入硬化層パターンが得られた。具体的には、図６に示すように、背面４の側には均一な硬化層パターンＴ1 ''が得られるが、歯面３の側には左右方向の中央部が最も浅くかつその左右両部にいくにつれて徐々に深くなる硬化層パターンＴ2 ''となる。すなわち、この場合には、一対の主導体２１ａ，２１ｂによって、歯面３及び背面４の表面が連続したかたちで加熱されることとなるため、歯面３の表面に形成される硬化層パターンＴ1 ''と背面４の表面に形成される硬化層パターンＴ2 ''とは互いに分離せずに連続した硬化層パターンとなるが、歯面３の左右両部に近ずくにつれて硬化層は深くなるものの、歯面３の中央部では、歯底３ａの領域まで加熱されずに浅い硬化層となる。このような硬化層パターンＴ1 ''、Ｔ2 ''となるのは、歯面３側の負荷が軽いことと、回転加熱のみによって加熱されるため、歯底３ａの領域まで充分に深く加熱されなかったことに起因する。
【００２４】
また、図４のものと同様の条件で静止加熱を行った後に、回転加熱をすることなく直ちに急速冷却を行ったところ、図７に示す如き焼入硬化層パターンが得られた。この焼入硬化層パターンの形状は、図５に示す焼入硬化層パターンと類似した形状であり、因みに、これら両者の硬化層の深さを互いに比較した場合には、歯面３側の硬化層パターンＴ1 ''' については歯面３の中央部において前者が後者の約２／３であり、背面４側の硬化層パターンＴ2 ''' については前者が後者の約２／３である。
【００２５】
本発明に係る高周波焼入方法により得られる図４の硬化層パターンと、従来の高周波焼入方法により得られる図５，図６及び図７の硬化層パターンとを比較すれば明らかなように、図４の硬化層パターンは理想的なパターン、すなわち歯面３側の表面に形成される硬化層パターンＴ1 と背面４側の表面に形成される硬化層パターンＴ2 とが分離することなく互いに連続し、かつ、歯面３側の硬化層パターンＴ1 が歯面３の全域において歯底３ａよりも充分に深く形成されるようなパターン（図４参照）となっていることがわかる。このような理想的なパターンとなるのは、本発明に係る高周波焼入方法では、第１段階において静止加熱により歯面３及び背面４を所要深さに予備加熱し、しかる後の第２段階において回転加熱により歯面３及び背面４を含めたラックバー１の全周面を本加熱するようにしているため（すなわち、静止加熱と回転加熱を組み合わせて行うようにしているため）である。
【００２６】
以下に、本発明に係るラックバーの高周波焼入方法の具体的な施行条件の一例を述べる。
（１） ラックバーの寸法
寸法条件
（ア） 全長 ： ６２０ｍｍ
（イ） 焼入部： １７５ｍｍ
（ウ） 外径 ： ３２ｍｍ
（エ） 歯高 ： ５ｍｍ
（オ） 歯幅 ： １８ｍｍ

Figure 0004235336
【００２７】
以上、本発明の一実施形態につき述べたが、本発明はこの実施例に限定されるものではなく、本発明の技術的思想に基づいて各種の変形及び変更が可能である。例えば、既述の実施形態では、ラックバー１を縦置きにして静止加熱及び回転加熱を行なうようにしたが、ラックバー１を横置きにして静止加熱及び回転加熱を行なうようにしても良い。また、既述の実施形態では、一対の主導体２１ａ，２１ｂに冷却液噴射孔２８ａ，２８ｂを設けてこれら一対の主導体２１ａ，２１ｂを冷却液噴射機構として兼用するようにしたが、これとは別個独立の冷却液噴射環を冷却液噴射機構として設けてこの冷却液噴射環から冷却液をラックバー１に噴射し、或いはこの冷却液噴射環及び前記主導体２１ａ，２１の冷却液噴射孔２８ａ，２８ｂから同時に冷却液をラックバー１に噴射するようにしても良い。
【００２８】
【発明の効果】
請求項１に記載の本発明に係る高周波焼入方法は、ラックバーの歯面及び背面を含む全周面を高周波焼入する方法において、ラックバーの歯面及び背面にそれぞれ対向配置される一対の主導体を有する高周波誘導加熱コイルを用い、所要時間にわたり静止加熱（予備加熱）を行った後に、所要時間にわたり回転加熱（本加熱）を行い、所要焼入温度に加熱されたラックバーの全周面（表面）を急速冷却して焼入するようにしたものであるから、本発明によれば、ラックバーの歯面及び背面にそれぞれ形成される焼入硬化層が分離することなく互いに連続し、かつ、ラックバーの歯面部分においては歯底まで充分に深い焼入硬化層になると共にラックバーの背面部分においては比較的薄い均一な焼入硬化層になる良好な（理想的な）焼入硬化層パターンを得ることができる。
【００２９】
また、請求項２に記載の本発明に係る高周波焼入方法は、ラックバーを静止状態で高周波誘導加熱する静止加熱、及び、ラックバーを回転状態で高周波誘導加熱する回転加熱を、同一の周波数電流、或いはそれぞれ異なる周波数電流を高周波誘導加熱コイルに流すことにより行うようにしたものであるから、本発明によれば、被焼入体であるラックバーの形状、寸法、或いは焼入仕様に応じた焼入が可能となる。
【００３０】
また、請求項３に記載の本発明に係る高周波焼入方法は、静止加熱及び回転加熱を、同一電力、或いはそれぞれ異なる電力を高周波誘導加熱コイルに供給することにより行うようにしたものであるから、本発明によれば、上記と同様にラックバーの形状、寸法或いは焼入仕様に応じた焼入が可能となる。
【００３１】
また、請求項４に記載の本発明に係る高周波焼入装置は、被焼入体であるラックバーの軸線方向に沿って配置され、かつ、ラックバーの歯面及び背面にそれぞれ対向配置される一対の主導体を有する高周波誘導加熱コイルと、ラックバーの歯面及び背面を一対の主導体に対向した状態でラックバーを静止状態で保持する保持機構と、保持機構にて保持されたラックバーを回転駆動する回転駆動機構と、ラックバーに向けて冷却液を噴射する冷却液噴射機構とをそれぞれ具備し、ラックバーを保持機構にて静止状態に保持した状態の下で高周波誘導加熱コイルにて予備加熱した後に、ラックバーを回転駆動機構にてその軸線を中心に回転駆動させた状態の下で高周波誘導加熱コイルにて本加熱し、ラックバーの歯面及び背面を含む全周面が所要の焼入温度に達した直後に冷却液噴射機構から冷却液を噴射してラックバーの全周面を焼入するようにしたものであるから、本発明の高周波焼入方法を容易に実施することができ、安価で、実用的で利用価値が高く、産業上極めて有益なラックバーの高周波焼入装置を提供することができる。
【００３２】
また、請求項５に記載の本発明に係る高周波焼入装置は、中空部を有するパイプ部材にて一対の主導体をそれぞれ構成すると共に、ラックバーの歯面及び背面に対向配置される一対の主導体の対向壁部に複数の冷却液噴射口をそれぞれ設け、複数の冷却液噴射口から冷却液を噴射するようにしたものであるから、高周波誘導加熱コイルの主導体を冷却液噴射手段として兼用することができ、従って冷却液噴射環などの部材を別個に配設する必要がなく、構成がシンプルな装置にすることが可能となる。
【００３３】
また、請求項６に記載の本発明に係る高周波焼入装置は、ラックバーの歯面に対向する主導体の対向壁部を平坦状の壁部とし、ラックバーの背面に対向する主導体の対向壁部を断面半円形状の壁部としたものであるから、ラックバーの静止加熱の際にラックバーの背面と高周波誘導加熱コイルとの間の間隔を対向領域において均一にすることができ、ひいては前記背面に均一な焼入硬化層を形成することが可能となる。
【図面の簡単な説明】
【図１】本発明に係るラックバーの高周波焼入方法を実施するための高周波焼入装置を示す斜視図である。
【図２】図１におけるＡ−Ａ線断面図である。
【図３】図１におけるＢ−Ｂ線断面図である。
【図４】本発明に係る高周波焼入方法及び高周波焼入装置にて焼入されたラックバーの焼入硬化層パターンを示す断面図である。
【図５】回転加熱を加えず加熱開始から加熱終了までの全期間にわたり静止加熱のみで加熱して焼入処理した場合のラックバーの焼入硬化層パターンを示す断面図である．
【図６】静止加熱をせず加熱関始から加熱終了まで回転加熱のみで加熱して焼入処理した場合のラックバーの焼入硬化硬化層パターンを示す断面図である。
【図７】静止加熱後に回転加熱を行なうことなく焼入処理した場合のラックバーの焼入硬化層パターンを示すラックバーの断面図である。
【図８】被焼入体であるステアリング用ラックバーの側面図である。
【図９】従来の歯面焼入用の高周波直接通電焼入装置の側面図である。
【図１０】従来の背面焼入用の高周波直接通電焼入装置の側面図である。
【図１１】従来の歯面及び背面同時焼入用の高周波直接通電焼入装置の側面図である。
【図１２】図９及び図１０にそれぞれ示す従来の高周波直接通電焼入装置にて、歯面と背面とを二工程で焼入処理した場のラックバーの焼入硬化層パターンを示す断面図である。
【図１３】図１１に示す従来の高周波直接通電焼入装置にて、歯面及び背面を同時に一工程で焼入処理した場合のラックバーの焼入硬化層パターンを示す断面図である。
【符号の説明】
１ ステアリング用ラックバー
３ 歯面
４ 背面
１９ 高周波誘導加熱コイル
２０ 焼入装置
２１ａ，２１ｂ 主導体
２２ａ，２２ｂ 環状副導体
２３ａ，２３ｂ 電流供給導体
２４ａ，２４ｂ 中空部
２５ａ，２５ｂ 冷却液導入管
２６ａ，２６ｂ 外側壁部
２７ａ，２７ｂ 内側壁部（対向壁部）
２８ａ，２８ｂ 冷却液噴射孔
２９ 高周波電源
３０ 板状絶縁部材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of induction hardening the entire peripheral surface including the tooth surfaces of a rack bar by a single quenching method and a quenching apparatus thereof.
[0002]
[Prior art]
FIG. 8 shows a steering rack bar 1 generally used conventionally. The steering rack bar 1 has inclined teeth 2 having an angle θ with respect to the axis X on one side surface. The surface opposite to the tooth surface 3 of the inclined tooth 2 is a back surface (semi-cylindrical surface) 4. Conventionally, a high frequency direct current quenching apparatus 5a shown in FIG. 9 is used to quench the tooth surface 3 of this type of steering rack bar 1, and FIG. 10 illustrates that the back surface 4 is quenched. A high-frequency direct current quenching apparatus 5b shown is used. Moreover, in order to quench the tooth surface 3 and the back surface 4 at the same time, a high-frequency direct energization device 6 shown in FIG. 11 is used.
[0003]
As shown in FIGS. 9, 10 and 11, these devices 5a, 5b or 6 connect the first conductors 8, 8 ′ and the second conductors 9, 9 ′ via the electrical insulating materials 7, 7 ′. The unit conductors 10 and 10 ', which are members combined in a sandwich shape, respectively, are disposed so as to oppose the tooth surface 3 or the back surface 4 of the steering gruck bar 1 that is to be hardened, and these unit conductors. A first contact electrode 11, 11 ′ connected to the first conductors 8, 8 ′ of the 10, 10 ′ and abuttingly disposed at one end in the longitudinal direction of the tooth surface 3 or the back surface 4; A second contact electrode 12, 12 ′ connected to the second conductor 9, 9 ′ and abuttingly disposed at the other longitudinal end of the tooth surface 3 or the back surface 4, and the second contact electrode 12, A coolant sprayer capable of spraying coolant onto the tooth surface 3 or the back surface 4 in the region between 12 ' And 'proximal conductor 14, 14 provided with a' 13, the pair of first conductor 8, 8 'and the second conductor 9, 9' are provided with respective high-frequency power source 15, 15 'and the connected. Furthermore, a pair of hydraulic cylinders 16 and 16 'for pressing the rack bar are also provided.
[0004]
[Problems to be solved by the invention]
When the tooth surface 3 and the back surface 4 of the rack bar 1 are quenched using the conventional high-frequency direct current quenching apparatus 5a, 5b or 6 as described above, the following problems occur. That is, when the tooth surface 3 and the back surface 4 of the rack bar 1 are induction-hardened in two steps using the high-frequency direct current hardening apparatus 5a, 5b, the hardened hardened layer pattern is a hardened hardened layer as shown in FIG. Pattern T is obtained. The hardened layer portion indicated by the hatched portion W in this hardened and hardened layer pattern T is a portion where the hardening treatment is overlapped, and is obtained from the hardened layer portion obtained by the first hardening treatment and the subsequent hardening treatment load. The boundary portion W of the hardened layer portion is softened, and furthermore, cracking is likely to occur. In addition, since quenching is performed in two steps, a long quenching time is required, and workability and productivity are remarkably lowered. Furthermore, since two high frequency direct current quenching apparatuses 5a and 5b are required, there is a problem that the equipment cost becomes high.
[0005]
Further, when the tooth surface 3 and the back surface 4 of the rack bar 1 are simultaneously induction-hardened in one process using the high-frequency direct current quenching apparatus 6, the hardened hardened layer pattern as shown in FIG. T. In hardening by this apparatus 6, the hardened layer of the part W 'equivalent to the above-mentioned boundary part W (refer FIG. 12) becomes shallow. Further, as a problem on the equipment, the work pressing mechanism, the attaching / detaching mechanism and the like become very complicated, and more expensive than the two quenching apparatuses 5a and 5b described above.
[0006]
The present invention has been made to solve such problems. The object of the present invention is to efficiently quench the tooth surface and the back surface of the rack bar at the same time without using the direct energization method. An object of the present invention is to provide an induction hardening method and an induction hardening apparatus for a rack bar which can form a hardened layer pattern on the entire circumferential surface of the rack bar.
[0007]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, in the present invention, in the method of induction hardening the entire peripheral surface including the tooth surface and the back surface of the rack bar that is the object to be hardened,
A high-frequency induction heating coil having a pair of main conductors arranged along the axial direction of the rack bar and opposed to the tooth surface and the back surface of the rack bar is used. (A) The rack bar is subjected to the high-frequency induction heating. High-frequency induction heating under a stationary state with respect to the coil;
(B) Next, the step of rotating the rack bar about its axis to further continue high frequency induction heating in a state where the rack bar is rotated with respect to the high frequency induction heating coil;
(C) After that, when the entire circumferential surface of the rack bar is induction-heated to the required quenching temperature by high frequency induction, the step of rapidly cooling the entire circumferential surface of the rack bar;
Are enacted sequentially.
Further, in the present invention, static heating for high-frequency induction heating of the rack bar in a stationary state and rotational heating for high-frequency induction heating of the rack bar in a rotating state are performed using the same frequency current or different frequency currents. This is done by flowing it through a high frequency induction heating coil.
In the present invention, the static heating and the rotary heating are performed by supplying the same electric power or different electric powers to the high-frequency induction heating coil.
In the present invention,
(A) a high-frequency induction heating coil having a pair of main conductors arranged along the axial direction of the rack bar, which is a body to be hardened, and facing the tooth surface and the back surface of the rack bar;
(B) a holding mechanism that holds the rack bar in a stationary state with the tooth surfaces and the back surface of the rack bar facing the pair of main conductors;
(C) a rotation drive mechanism that rotationally drives the rack bar held by the holding mechanism;
(D) a coolant injection mechanism that injects coolant toward the rack bar;
Each with
The rack bar is preliminarily heated by the high-frequency induction heating coil in a state where the rack bar is held stationary by the holding mechanism, and then the rack bar is rotationally driven around its axis by the rotational drive mechanism. The main body is heated by the high-frequency induction heating coil, and the coolant is sprayed from the coolant spray mechanism immediately after the entire circumferential surface including the tooth surface and back surface of the rack bar reaches the required quenching temperature. An induction hardening apparatus for a rack bar, wherein the entire circumferential surface of the rack bar is hardened.
In the present invention, the pipe member having a hollow portion constitutes the pair of main conductors, and a plurality of opposing wall portions of the pair of main conductors disposed to face the tooth surfaces and the back surface of the rack bar. Coolant spray ports are provided, respectively, and coolant is sprayed from the plurality of coolant spray ports.
In the present invention, the opposing wall portion of the main conductor facing the tooth surface of the rack bar is a flat wall portion, and the opposing wall portion of the main conductor facing the back surface of the rack bar is semicircular in cross section. And the walls.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[0009]
FIG.1 and FIG.2 shows the induction hardening apparatus 20 used in order to enforce the induction hardening method which concerns on this invention. As shown in FIGS. 1 and 2, the device 20 includes a pair of left and right main conductors 21 a that are arranged in parallel with each other so as to face the tooth surface 3 and the back surface 4 of the rack bar 1 and extend in the vertical direction. 21b, a pair of upper and lower annular sub-conductors 22a and 22b connected to both upper and lower ends of these main conductors 21a and 21b and arranged in parallel with each other, and upper and lower portions of a cut portion at an intermediate position of the main conductor 21b Are provided with a high frequency induction heating coil 19 comprising a pair of current supply conductors 23a and 23b connected to each other.
[0010]
As shown in FIGS. 2 and 3, the main conductors 21a and 21b described above are formed of conductive pipe members having hollow portions 24a and 24b for circulating coolant, and the annular sub-conductors 22a and 22b are hollow portions. It is comprised with the electroconductive ring member which does not have. A pair of coolant introduction pipes 25a and 25b communicating with the hollow portions 24a and 24b of the main conductors 21a and 21b are connected to the outer wall portions 26a and 26b of the main conductors 21a and 21b, respectively. Furthermore, the inner wall portions 27a and 27b of the main conductors 21a and 21b facing the tooth surface 3 and the back surface 4 of the rack bar 1 have a plurality of holes having a predetermined hole diameter and spaced by a predetermined pitch interval. The coolant injection holes 28a and 28b are provided. Thus, the cooling liquid (quenched liquid) introduced into the hollow portions 24a and 24b of the main conductors 21a and 21b is jetted from these cooling liquid introduction pipes 25a and 25b.
[0011]
The inner wall portion 27a of the main conductor 21a disposed opposite to the tooth surface 3 of the rack bar 1 during static heating and quenching cooling, which will be described later, is flat, while the back surface 4 of the rack bar 1 is subjected to quench cooling. The inner wall portion 27b of the main conductor 21b opposed to each other is a curved surface (semicircular surface) having a shape corresponding to the curvature of the back surface 4 (see FIGS. 1, 2 and 3).
[0012]
Here, the production procedure of the induction hardening apparatus 20 will be described as follows.
[0013]
(A) First, one end (upper end) α of one main conductor 21a formed along the tooth surface 3 of the rack bar 1 is brazed to the lower surface orthogonal to the axial direction of one annular sub-conductor 22a. And one end (upper end) β of the main conductor 21b formed along the back surface 4 of the rack bar 1 is a lower surface orthogonal to the axial direction of one annular sub-conductor 22b and the main The body 21a is joined by brazing at a position 180 degrees away from the joining position where the one end α of the body 21a is joined (see FIGS. 1 and 2).
[0014]
(B) Next, the other end (lower end) γ of the one main conductor 21a is joined to a surface orthogonal to the axial direction of the other annular sub-conductor 22b by brazing, and the other main conductor 21b is joined. Is perpendicular to the axial direction of the other annular sub-conductor 22b at a position 180 ° away from the joining position where the other end γ of the one main conductor 21a is joined. Join to the surface to be brazed.
[0015]
(C) Then, one end portions of the current supply conductors 23a and 23b are joined to a predetermined intermediate position of the one main conductor 21a or the other main conductor 21b by the same method as described above to form a coil electric circuit. The high-frequency power is supplied from the high-frequency power source 29 to the high-frequency induction heating coil 19 through the current supply conductors 23a and 23b. A plate-like insulating member 30 made of a heat-resistant insulating material such as tetrafluoroethylene (trade name: Teflon) is inserted and disposed between the current supply conductors 23a and 23b. It is configured to achieve mechanical insulation.
[0016]
Next, an operation procedure when the entire circumferential surface (including the tooth surface 3 and the back surface 4) of the rack bar 1 is quenched by using the induction hardening apparatus 20 having the above-described configuration will be described. Street.
[0017]
(1) First, the lower end portion of the rack bar 1 is placed on a workpiece fixing jig (not shown) disposed above the induction hardening apparatus 20, and the upper end portion of the rack bar 1 is pressed by a center (not shown). Thus, the rack bar 1 is held vertically.
(2) Next, the rack bar 1 is lowered by a workpiece lifting mechanism (not shown) and stopped at a predetermined heating position in the quenching apparatus 20.
(3) Next, the rack bar 1 is fixedly disposed in a state where the tooth surface 3 and the back surface 4 of the rack bar 1 are opposed to the main conductor 21a and the main conductor 21b of the high-frequency induction heating coil 19, respectively.
(4) Thereafter, the high frequency power of the required frequency / required output from the high frequency power supply 29 is supplied to the high frequency induction heating coil 19 of the quenching apparatus 20 and a high frequency current is caused to flow through the coil 19, whereby the tooth surface of the rack bar 1. 3 and the back surface 4 are heated statically (high frequency induction heating with the rack bar 1 being stationary) and high frequency induction heating is performed over a required time.
(5) When the tooth surface 3 and the back surface 4 reach the required heating temperature and the required heating depth, the rack bar 1 is rotated around the axis X (see FIG. 8) at a required rotational speed by a rotation mechanism not shown. Then, rotational heating (high-frequency induction heating under a state in which the rack bar 1 is rotated) is performed on the entire circumferential surface (work circumferential surface) of the rack bar 1.
(6) Then, when the entire circumferential surface of the rack bar 1 reaches the required quenching temperature by this rotational heating, the energization to the high frequency induction heating coil 19 is cut off and the heating is stopped.
(7) Next, the required pressure from the coolant injection cold holes 28a, 28b opened in the inner wall portions (work-opposing surfaces) 27a, 27b of the main conductor 21a on the tooth surface 3 side and the main conductor 22b on the back surface 4 side. A coolant having a required flow rate is sprayed toward the peripheral surface of the rotating rack bar 1 and rapidly cooled until the surface temperature of the peripheral surface of the rack bar 1 reaches room temperature.
(8) Then, when the surface temperature of the peripheral surface of the rack bar 1 is rapidly cooled to room temperature, both the injection of the coolant and the rotation of the rack bar 1 are stopped, and the series of quenching processes is completed.
(9) After that, the work is raised to a predetermined position, the rack bar is removed from the work fixing jig 30 and the center 31, and transferred to the next process.
[0018]
To summarize the above-described series of quenching operations, the rack bar 1 is disposed at a predetermined position in the induction hardening apparatus 20, that is, the tooth surface 3 of the rack bar 1 faces the main conductor 21a as shown in FIG. In addition, the tooth surface 3 is fixed by placing it at a position where the back surface 4 of the rack bar 1 is opposed to the main conductor 21b and fixing it in a stationary state, and energizing the high frequency induction heating coil 19 in this stationary state. And static heating of the back surface 4 is performed. Then, the tooth surface 3 and the back surface 4 reach the required temperature by static heating over the required time, and at the same time, the workpiece holding jig (not shown) is driven around the axis X of the rack bar 1 by the rotation driving means (not shown). While rotating at the rotation speed, the heating was performed over the required time (the energized state of the high frequency induction heating coil 19 was maintained), and the entire circumferential surface of the rack bar 1 including the tooth surface 3 and the back surface 4 reached the required quenching temperature. At the time, the supply of the high-frequency current to the high-frequency induction heating coil 19 is interrupted, and at the same time, the coolant having the required pressure and the required flow rate is rotated from the plurality of coolant injection holes 28a and 28b provided in the pair of main conductors 21a and 21b. A quenching process is performed by spraying toward the rack bar 1 in a state and rapidly cooling the surface of the rack bar 1 over a required time.
[0019]
Note that the arrow R shown in FIG. 1 indicates the current flow direction at the moment, but the high-frequency induction heating coil 19 used in this embodiment has a pair of main conductors 21a, 21b and the annular subconductors 22a and 22b, when the high-frequency induction heating coil 19 is energized, a current twice as large as the current flowing through the annular subconductors 22a and 22b flows through the main conductors 21a and 21b. Become. That is, each of the pair of annular sub-conductors 22a and 22b divides the annular conductor into two and forms a coil electric circuit in which the two identical conductors are connected in parallel to each other via the pair of main conductors 21a and 21b. Therefore, if the high-frequency current flowing through each of the main conductors 21a and 21b is, for example, I amperes, the high-frequency current flowing through each of the annular sub-conductors 22a and 22b is I / 2 amperes.
[0020]
When the entire circumferential surface of the rack bar 1 was quenched by the induction hardening method of the present invention using the induction hardening apparatus 20 as described above, a quenched hardened layer pattern as shown in FIG. 4 was obtained. In this case, as shown in FIG. 4, it is deeper than the tooth height of the tooth surface 3 and from the central part in the longitudinal direction (left and right direction in FIG. 4) of the tooth surface 3 perpendicular to the tooth height to the left and right sides thereof. gradually with depth comprising such cured layer pattern T 1 is formed on the side of the tooth surfaces 3, the hardened layer pattern T hardened layer pattern T 2 of the uniform arcuate cross section contiguous respectively to both parts 1 back toward 4 side formed.
[0021]
In order to confirm the difference between the quench hardening layer pattern T obtained by the induction hardening method of the present invention and the quench hardening layer pattern obtained by other methods without using the induction hardening method of the present invention. In addition, the following experiment was conducted.
[0022]
First, during the entire period from the start to the end of the high frequency induction heating, the high frequency induction heating is performed in a state where the rack bar 1 is always kept stationary without giving rotation, and other heating conditions are the same as those shown in FIG. When rapidly cooled by high frequency induction heating only by static heating, a hardened and hardened layer pattern as shown in FIG. 5 was obtained. Specifically, as shown in FIG. 5, a hardened layer pattern T 1 ′ deeper than the tooth height of the tooth surface 3 and having a uniform depth is formed on the tooth surface 3 side. A hardened layer pattern T 2 ′ having an arc cross section extending uniformly from a position far away from both the left and right portions of the pattern T 1 ′ was formed on the back surface 4 side. That is, in this case, the tooth surface 3 and the back surface 4 are heated separately by the main conductor 21a on the tooth surface 3 side and the main conductor 21b on the back surface 4 side. The cured layer patterns T 1 ′ and T 2 ′ on the surface 3 and the back surface 4 were not continuous but separated from each other.
[0023]
In addition, static heating is not performed at all during the period from the start to the end of the high frequency induction heating, and the other heating conditions are the same as those shown in FIG. A cured layer pattern was obtained. Specifically, as shown in FIG. 6, a uniform hardened layer pattern T 1 ″ is obtained on the back surface 4 side, but the central portion in the left-right direction is the shallowest on the tooth surface 3 side and the left and right sides thereof. The cured layer pattern T 2 ″ is gradually deepened as it goes to both portions. That is, in this case, since the surfaces of the tooth surface 3 and the back surface 4 are heated in a continuous manner by the pair of main conductors 21a and 21b, the hardened layer pattern T formed on the surface of the tooth surface 3 is used. 1 ″ and the cured layer pattern T 2 ″ formed on the surface of the back surface 4 become a continuous cured layer pattern without being separated from each other, but the cured layer becomes deeper as it approaches the left and right parts of the tooth surface 3. However, in the central part of the tooth surface 3, it becomes a shallow hardened layer without being heated up to the region of the tooth bottom 3a. Such hardened layer patterns T 1 ″ and T 2 ″ are heated sufficiently deeply to the region of the tooth bottom 3a because the load on the tooth surface 3 side is light and only the rotary heating is used. Due to not being done.
[0024]
In addition, after static heating was performed under the same conditions as in FIG. 4, rapid cooling was performed immediately without rotating heating, and a quenched hardened layer pattern as shown in FIG. 7 was obtained. The shape of this hardened and hardened layer pattern is similar to that of the hardened and hardened layer pattern shown in FIG. 5. Incidentally, when the depths of both hardened layers are compared with each other, the hardened surface on the tooth surface 3 side is hardened. For the layer pattern T 1 ″ ″, the former is about 2/3 of the latter at the center of the tooth surface 3, and for the cured layer pattern T 2 ″ ″ on the back surface 4 side, the former is about 2/3 of the latter. is there.
[0025]
As can be seen by comparing the cured layer pattern of FIG. 4 obtained by the induction hardening method according to the present invention with the cured layer pattern of FIGS. 5, 6 and 7 obtained by the conventional induction hardening method, The cured layer pattern in FIG. 4 is an ideal pattern, that is, the cured layer pattern T 1 formed on the surface on the tooth surface 3 side and the cured layer pattern T 2 formed on the surface on the back surface 4 side are not separated from each other. It can be seen that the hardened layer pattern T 1 on the tooth surface 3 side is a pattern (see FIG. 4) that is continuous and sufficiently deeper than the tooth bottom 3a. In the induction hardening method according to the present invention, such an ideal pattern is obtained by preheating the tooth surface 3 and the back surface 4 to a required depth by static heating in the first step, and then the second step. This is because the entire peripheral surface of the rack bar 1 including the tooth surface 3 and the back surface 4 is heated by rotation heating (that is, static heating and rotation heating are performed in combination).
[0026]
Below, an example of the concrete enforcement conditions of the induction hardening method of the rack bar which concerns on this invention is described.
(1) Dimensions and dimensions of rack bar (A) Total length: 620mm
(I) Hardened part: 175mm
(C) Outer diameter: 32 mm
(D) Tooth height: 5mm
(E) Tooth width: 18mm
Figure 0004235336
[0027]
Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and various modifications and changes can be made based on the technical idea of the present invention. For example, in the above-described embodiment, the rack bar 1 is placed vertically to perform stationary heating and rotational heating. However, the rack bar 1 may be placed horizontally to perform stationary heating and rotational heating. In the above-described embodiment, the pair of main conductors 21a and 21b are provided with the coolant injection holes 28a and 28b, and the pair of main conductors 21a and 21b are also used as the coolant injection mechanism. Is provided with a separate and independent cooling liquid injection ring as a cooling liquid injection mechanism, and the cooling liquid is injected from the cooling liquid injection ring onto the rack bar 1, or the cooling liquid injection ring and the cooling liquid injection holes of the main conductors 21a and 21 are provided. You may make it spray a cooling liquid simultaneously to the rack bar 1 from 28a, 28b.
[0028]
【The invention's effect】
The induction hardening method according to the present invention as set forth in claim 1 is a method of induction hardening the entire circumferential surface including the tooth surface and back surface of the rack bar, and a pair of electrodes disposed facing the tooth surface and back surface of the rack bar. Using a high-frequency induction heating coil having a main conductor, static heating (preliminary heating) is performed for the required time, followed by rotational heating (main heating) for the required time, and the entire rack bar heated to the required quenching temperature. Since the peripheral surface (surface) is rapidly cooled and hardened, according to the present invention, the hardened and hardened layers respectively formed on the tooth surface and the back surface of the rack bar are continuous with each other without being separated. In addition, a hardened and hardened layer sufficiently deep to the bottom of the tooth surface of the rack bar and a relatively thin and hardened hardened layer on the back surface of the rack bar are good (ideal). Quenched hardened layer It is possible to obtain a turn.
[0029]
Further, the induction hardening method according to the second aspect of the present invention is the same frequency for the stationary heating for high-frequency induction heating in a stationary state and the rotational heating for high-frequency induction heating in a rotating state of the rack bar. According to the present invention, according to the shape, size, or quenching specification of the rack bar to be hardened, the current or different frequency currents are passed through the high frequency induction heating coil. Hardening is possible.
[0030]
Further, the induction hardening method according to the third aspect of the present invention is such that static heating and rotary heating are performed by supplying the same power or different power to the high frequency induction heating coil. According to the present invention, quenching according to the shape, size, or quenching specification of the rack bar is possible as described above.
[0031]
In addition, the induction hardening apparatus according to the fourth aspect of the present invention is disposed along the axial direction of the rack bar, which is the object to be hardened, and is disposed to face the tooth surface and the back surface of the rack bar. A high-frequency induction heating coil having a pair of main conductors, a holding mechanism for holding the rack bar in a stationary state with the tooth surfaces and back of the rack bar facing the pair of main conductors, and a rack bar held by the holding mechanism Respectively, and a high-frequency induction heating coil under a state where the rack bar is held stationary by the holding mechanism. After the preliminary heating, the rack bar is heated by a high frequency induction heating coil under a state in which the rack bar is rotated around its axis by the rotation drive mechanism, and the entire circumferential surface including the tooth surface and the back surface of the rack bar is obtained. Required Immediately after reaching the quenching temperature, the coolant is sprayed from the coolant spray mechanism to quench the entire circumferential surface of the rack bar, so that the induction hardening method of the present invention can be easily carried out. Thus, it is possible to provide an induction hardening apparatus for a rack bar that is inexpensive, practical, highly useful, and extremely useful in industry.
[0032]
In addition, the induction hardening apparatus according to the present invention described in claim 5 includes a pair of main conductors each formed by a pipe member having a hollow portion, and a pair of opposingly arranged on the tooth surface and the back surface of the rack bar. A plurality of coolant injection ports are provided on the opposing wall portion of the main conductor, and the coolant is injected from the plurality of coolant injection ports. Therefore, the main conductor of the high frequency induction heating coil is used as the coolant injection means. Therefore, it is not necessary to separately provide a member such as a cooling liquid injection ring, and it is possible to provide a device having a simple configuration.
[0033]
According to a sixth aspect of the present invention, the induction hardening apparatus according to the present invention is configured such that the opposing wall portion of the main conductor facing the tooth surface of the rack bar is a flat wall portion, and the main conductor opposing the back surface of the rack bar is used. Since the opposing wall portion has a semicircular cross section, the space between the back surface of the rack bar and the high-frequency induction heating coil can be made uniform in the opposing region during static heating of the rack bar. As a result, a uniform hardened and hardened layer can be formed on the back surface.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an induction hardening apparatus for carrying out an induction hardening method for a rack bar according to the present invention.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
FIG. 3 is a cross-sectional view taken along line BB in FIG.
FIG. 4 is a cross-sectional view showing a hardened hardened layer pattern of a rack bar quenched by an induction hardening method and an induction hardening apparatus according to the present invention.
FIG. 5 is a cross-sectional view showing a hardened hardened layer pattern of a rack bar when the heat treatment is performed only by static heating over the entire period from the start of heating to the end of heating without applying rotary heating.
FIG. 6 is a cross-sectional view showing a quench-hardened hardened layer pattern of a rack bar when subjected to a quenching process by heating only by rotary heating from the beginning of heating to the end of heating without static heating.
FIG. 7 is a cross-sectional view of a rack bar showing a hardened hardened layer pattern of the rack bar when subjected to a quenching process without performing a rotary heating after static heating.
FIG. 8 is a side view of a steering rack bar that is to be hardened.
FIG. 9 is a side view of a conventional high-frequency direct current quenching apparatus for tooth surface quenching.
FIG. 10 is a side view of a conventional high frequency direct current quenching apparatus for backside quenching.
FIG. 11 is a side view of a conventional high frequency direct current quenching apparatus for simultaneous quenching of tooth surfaces and back surfaces.
12 is a cross-sectional view showing a hardened hardened layer pattern of a rack bar in a case where a tooth surface and a back surface are hardened in two steps by the conventional high-frequency direct current hardening apparatus shown in FIGS. 9 and 10, respectively. It is.
13 is a cross-sectional view showing a hardened hardened layer pattern of a rack bar when the tooth surface and the back surface are simultaneously hardened in one step by the conventional high frequency direct current hardening apparatus shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steering rack bar 3 Tooth surface 4 Back surface 19 High frequency induction heating coil 20 Hardening device 21a, 21b Main conductor 22a, 22b Annular subconductor 23a, 23b Current supply conductor 24a, 24b Hollow part 25a, 25b Coolant introduction pipe 26a, 26b Outer wall part 27a, 27b Inner wall part (opposing wall part)
28a, 28b Coolant injection hole 29 High frequency power supply 30 Plate-like insulating member

Claims (6)

被焼入体であるラックバーの歯面及び背面を含めた全周面を高周波焼入する方法において、
前記ラックバーの軸線方向に沿って配置され、かつ、前記ラックバーの歯面及び背面にそれぞれ対向配置される一対の主導体を有する高周波誘導加熱コイルを用い、
（ａ） 前記ラックバーを前記高周波誘導加熱コイルに対して静止させた状態の下で高周波誘導加熱する工程と、
（ｂ） 次いで、前記ラックバーをその軸線を中心に回転させることにより、前記ラックバーを前記高周波誘導加熱コイルに対して回転させた状態下で高周波誘導加熱をさらに継続して行なう工程と、
（ｃ） しかる後に、前記ラックバーの全周面が所要の焼入温度に高周波誘導加熱された時点で、前記ラックバーの全周面を急速冷却する工程と、
をそれぞれ順次に施行することを特徴とするラックバーの高周波焼入方法。In the method of induction-quenching the entire circumferential surface including the tooth surface and back surface of the rack bar that is to be hardened,
Using a high frequency induction heating coil having a pair of main conductors arranged along the axial direction of the rack bar and opposed to the tooth surface and the back surface of the rack bar,
(A) high-frequency induction heating in a state where the rack bar is stationary with respect to the high-frequency induction heating coil;
(B) Next, the step of rotating the rack bar about its axis to further continue high frequency induction heating in a state where the rack bar is rotated with respect to the high frequency induction heating coil;
(C) After that, when the entire circumferential surface of the rack bar is induction-heated to the required quenching temperature by high frequency induction, the step of rapidly cooling the entire circumferential surface of the rack bar;
The induction hardening method of the rack bar, which is performed sequentially. 前記ラックバーを静止状態で高周波誘導加熱する静止加熱、及び、前記ラックバーを回転状態で高周波誘導加熱する回転加熱を、同一の周波数電流、或いはそれぞれ異なる周波数電流を前記高周波誘導加熱コイルに流すことにより行うことを特徴とする請求項１に記載のラックバーの高周波焼入方法。The same frequency current or different frequency currents are caused to flow through the high frequency induction heating coil for stationary heating for high frequency induction heating of the rack bar in a stationary state and for rotary heating for high frequency induction heating of the rack bar in a rotating state. The method of induction hardening of a rack bar according to claim 1, wherein: 前記静止加熱及び回転加熱を、同一電力、或いはそれぞれ異なる電力を前記高周波誘導加熱コイルに供給することにより行うことを特徴とする請求項１に記載のラックバーの高周波焼入方法。2. The induction hardening method for a rack bar according to claim 1, wherein the stationary heating and the rotary heating are performed by supplying the same electric power or different electric powers to the high frequency induction heating coil. （ａ） 被焼入体であるラックバーの軸線方向に沿って配置され、かつ、前記ラックバーの歯面及び背面にそれぞれ対向配置される一対の主導体を有する高周波誘導加熱コイルと、
（ｂ） 前記ラックバーの歯面及び背面を前記一対の主導体に対向した状態で前記ラックバーを静止状態で保持する保持機構と、
（ｃ） 前記保持機構にて保持された前記ラックバーを回転駆動する回転駆動機構と、
（ｄ） 前記ラックバーに向けて冷却液を噴射する冷却液噴射機構と、
をそれぞれ具備し、
前記ラックバーを前記保持機構にて静止状態に保持した状態の下で前記高周波誘導加熱コイルにて予備加熱した後に、前記ラックバーを前記回転駆動機構にてその軸線を中心に回転駆動させた状態の下で前記高周波誘導加熱コイルにて本加熱し、前記ラックバーの歯面及び背面を含む全周面が所要の焼入温度に達した直後に前記冷却液噴射機構から冷却液を噴射して前記ラックバーの全周面を焼入するようにしたことを特徴とするラックバーの高周波焼入装置。(A) a high-frequency induction heating coil having a pair of main conductors arranged along the axial direction of the rack bar, which is a to-be-hardened body, and opposed to the tooth surface and the back surface of the rack bar;
(B) a holding mechanism that holds the rack bar in a stationary state with the tooth surfaces and the back surface of the rack bar facing the pair of main conductors;
(C) a rotation drive mechanism that rotationally drives the rack bar held by the holding mechanism;
(D) a coolant injection mechanism that injects coolant toward the rack bar;
Each with
The rack bar is preliminarily heated by the high-frequency induction heating coil in a state where the rack bar is held stationary by the holding mechanism, and then the rack bar is rotationally driven around its axis by the rotational drive mechanism. The main body is heated by the high-frequency induction heating coil, and the coolant is sprayed from the coolant spray mechanism immediately after the entire circumferential surface including the tooth surface and back surface of the rack bar reaches the required quenching temperature. An induction hardening apparatus for a rack bar, wherein the entire circumferential surface of the rack bar is hardened. 中空部を有するパイプ部材にて前記一対の主導体をそれぞれ構成すると共に、前記ラックバーの歯面及び背面に対向配置される前記一対の主導体の対向壁部に複数の冷却液噴射口をそれぞれ設け、前記複数の冷却液噴射口から冷却液を噴射するようにしたことを特徴とする請求項４に記載のラックバーの高周波焼入装置。Each of the pair of main conductors is configured by a pipe member having a hollow portion, and a plurality of coolant injection ports are provided on opposing wall portions of the pair of main conductors arranged to face the tooth surface and the back surface of the rack bar. The induction hardening apparatus for a rack bar according to claim 4, wherein the cooling liquid is provided from the plurality of cooling liquid injection ports. 前記ラックバーの歯面に対向する前記主導体の対向壁部を平坦状の壁部とし、前記ラックバーの背面に対向する前記主導体の対向壁部を断面半円形状の壁部としたことを特徴とする請求項５に記載のラックバーの高周波焼入装置。The facing wall portion of the main conductor facing the tooth surface of the rack bar is a flat wall portion, and the facing wall portion of the main conductor facing the back surface of the rack bar is a semicircular wall portion. The induction hardening apparatus for a rack bar according to claim 5.
JP2000048422A 2000-02-25 2000-02-25 Induction hardening method of rack bar and induction hardening apparatus thereof Expired - Fee Related JP4235336B2 (en)

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JP4978767B2 (en) * 2005-09-16 2012-07-18 株式会社ジェイテクト Steering device
JP5072234B2 (en) * 2006-02-21 2012-11-14 株式会社ミヤデン Rack bar induction hardening equipment
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JP5331171B2 (en) * 2011-07-22 2013-10-30 電気興業株式会社 High frequency induction heating coil and high frequency induction heating method
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JP6628398B2 (en) * 2015-09-15 2020-01-08 株式会社ミヤデン Electric heating device for steering rack bar
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JP7101092B2 (en) * 2018-09-25 2022-07-14 高周波熱錬株式会社 Quenching equipment and quenching method for rack bars
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WO2023026903A1 (en) * 2021-08-23 2023-03-02 日本精工株式会社 Rack shaft, method for manufacturing same, and rack-and-pinion steering gear unit

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