JP2004315851A

JP2004315851A - Method and apparatus for induction hardening of rack bar

Info

Publication number: JP2004315851A
Application number: JP2003107856A
Authority: JP
Inventors: Seiichi Sawatsubashi; 精一沢津橋; Hideaki Katanuma; 秀明片沼; Takayuki Onozawa; 隆幸小野澤
Original assignee: Denki Kogyo Co Ltd
Current assignee: DKK Co Ltd
Priority date: 2003-04-11
Filing date: 2003-04-11
Publication date: 2004-11-11

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for induction hardening of a rack bar with which a hardened layer sufficiently securing the hardness in a desirable depth can be formed on the whole peripheral surfaces including a tooth surface and a back surface of the rack bar even in the case that the tooth quadrature module of the rack bar is e.g. ≥2. <P>SOLUTION: In the method for induction hardening in which the whole peripheral surfaces including the tooth surface 3 and the back surface 4 of the rack bar 1 is heated with a high frequency induction heating coil 22 and cooled, the high frequency currents having two or more frequencies, are simultaneously supplied into one set of the high frequency induction heating coil 22 and the whole peripheral surfaces including the tooth surface 3 and the back surface 4, are heated with the high frequency induction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、ラックバーの歯面及び背面を含めた全周面と、前記歯面及び背面を含めた全周面より連続する断面形状が円形の軸部の外周面とを移動焼入法により連続して高周波焼入するラックバーの高周波焼入方法及び装置に関するものである。
【０００２】
【従来の技術】
図６は、一般的に用いられているステアリング用ラックバー１（以下、単にラックバー１と記載する）を示すものである。このラックバー１は、片側面に軸線Ｐ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。また、ラックバー１は、図６に示すように、歯面３及び背面４を含む全周面より連続して延びる断面円形の軸部５を有している。従来、このようなラックバー１を焼入処理するに際しては、図７に示すような高周波焼入装置７を使用してラックバー１の歯面３及び背面４を含む全周面（ラック部の外周面）と、断面円形の軸部５の外周面とを移動焼入法により高周波焼入を連続的に行うようにしている（例えば、特許文献１参照）。
【０００３】
なお、高周波焼入装置７は、ラックバー１の外周面を囲む１巻き或いは多巻きの円形の高周波誘導加熱コイル１３と、この高周波誘導加熱コイル１３の下方に配置され、かつ、前記ラックバー１の歯面３及び背面４を含む全周面と軸部５の外周面を高周波誘導加熱コイル１３によって順次に焼入温度まで加熱した後に引き続き冷却するために設けられた冷却手段（多数の噴射孔１４ａを有する冷却液噴射環１４）と、ラックバー１を挟持状態で保持する保持治具１５，１６と、これらの保持治具１５，１６にて保持されたラックバー１を回転駆動する回転駆動機構（図示せず）と、高周波誘導加熱コイル１３とラックバー１とをラックバー１の軸線Ｐに沿って相対的に移動させる移動手段（図示せず）とをそれぞれ具備している。
【０００４】
従来、上述の高周波焼入装置７を用いてラックバー１を焼入処理する際には、次のような２つの焼入工程（Ｉ），（ＩＩ）を施行するようにしている。
（Ｉ）ラックバー１の軸部５の外周面を焼入処理する際には、ラックバー１をその軸線Ｐを中心に図７において矢印Ｒで示す方向に回転駆動することにより高周波誘導加熱コイル１３に対して相対的に回転させると共に、ラックバー１の軸線Ｐを高周波誘導加熱コイル１３の軸線に一致させた状態の下でラックバー１をその軸線方向に沿って図７において矢印Ｋで示す方向に下降させることにより高周波誘導加熱コイル１３に対して相対的に移動させながら、ラックバー１の軸部５の外周面を所要の焼入温度に高周波誘導加熱し、しかる後に冷却液噴射環１４から冷却液を噴射して軸部５の外周面を冷却する焼入工程を施行する。
（ＩＩ）ラックバー１の歯面３及び背面４を含めた全周面を焼入処理する際には、ラックバー１をその軸線Ｐを中心に回転させずに、ラックバー１の軸線Ｐに沿って平行に配置される高周波誘導加熱コイルの特定の加熱導体部がラックバー１の歯面３及び背面４にそれぞれ対向配置されるようにラックバー１を保持した状態の下で、ラックバー１をラックバー１の軸線Ｐ方向（図７における矢印Ｋ方向）に沿って高周波誘導コイルに対して相対的に移動させながら、ラックバー１の歯面３及び背面４を含めた全周面を高周波誘導加熱し、しかる後に冷却液噴射環１４から冷却液を噴射して軸部５の外周面を焼入冷却する焼入工程を施行する。
【０００５】
かくして、上記（Ｉ），（ＩＩ）にそれぞれ記載の２つの焼入工程を、ラックバー１の軸線Ｐ方向（矢印Ｋ方向）に沿う相対移動，高周波誘導加熱，及び焼入冷却を停止することなく連続して行うことによりラックバー１の焼入処理を施行するようにしている。
【０００６】
【特許文献１】
特開昭５４−１０７８１２号
【０００７】
【発明が解決しようとする課題】
ラックバー１の高周波焼入において、歯直角モジュールが約１．６を有するラック１を焼入対象としてラックバー１の歯底Ｎ（図８（Ａ）及び（Ｂ）参照）からの硬化層深さを１．０ｍｍにする場合には、３０ｋＨｚの発振周波数（高周波発振周波数）の高周波電源を用いて移動焼入を行っている。しかし、ラックバー１の歯直角モジュールが例えば２以上であるような場合には、高周波電源の発振周波数（電源周波数）を３０ｋＨｚにすると、ラックバー１の軸部５の外周面には図８（ｃ）に示すように均一な深さの焼入硬化層Ｓを形成することができるが、ラックバー１の歯底Ｎの部分には図８（Ａ）に示す如く焼入硬化層Ｓを形成し難いという問題点がある。
【０００８】
一方、電源周波数（高周波発振周波数）を１０ｋＨｚ以下にすることにより、ラックバー１の歯底Ｎの部分に焼入硬化層Ｓを形成することができるようになるが、その場合には、ラックバー１の歯山部Ｍの加熱温度が低くなり、従って所定の焼入硬さを満足できないという問題を生じる。更に、電源周波数が１０ｋＨｚ以下でラックバー１の軸部５の外表面を高周波誘導加熱して冷却することにより前記外表面に焼入硬化層深さが約１．５ｍｍ以上の焼入硬化層Ｓを形成しようとする場合には、所定の焼入硬さを満足できないという問題を生じる。
【０００９】
本発明は、以上のこのような実状に鑑みてなされたものであって、その目的は、ラックバーの歯直角モジュールが例えば２以上のものであっても、ラックバーの歯面及び背面を含めた全周面に、所望の深さでかつ硬さが充分に確保された焼入硬化層を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装置を提供することにある。
【００１０】
【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、ラックバーの歯面及び背面を含めた全周面を高周波誘導加熱コイルにて高周波誘導加熱して冷却することにより高周波焼入する方法において、２つ以上の周波数の高周波電流を前記高周波誘導加熱コイルに同時に供給して前記歯面及び背面を含めた全周面を高周波誘導加熱する工程を含むようにしている。
また、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と、前記歯面及び背面を含めた全周面より連続して延びる断面円形の軸部の外周面とを連続して高周波誘導加熱コイルにて高周波誘導加熱した後に冷却して高周波焼入を施行するようにしたラックバーの高周波焼入方法において、
（ａ）２つ以上の周波数の高周波電流を前記高周波誘導加熱コイルに同時に供給して前記歯面及び背面を含めた全周面を高周波誘導加熱する工程と、
（ｂ）１つの周波数の高周波電流を前記高周波誘導加熱コイルに供給して前記軸部の外周面を高周波誘導加熱する工程と、
を含むようにしている。
また、本発明では、前記（ａ）に記載の工程及び前記（ｂ）に記載の工程を、前記ラックバーを前記高周波誘導加熱コイルに対して相対的に移動させた状態の下で連続的に施行するようにしている。
また、本発明では、前記２つ以上の周波数が、それぞれ、１〜４００ｋＨｚであるようにしている。
また、本発明では、前記２つ以上の周波数の高周波電流をそれぞれ供給する高周波電源から出力される出力の割合を調整するようにしている。
また、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焼入するためのラックバーの高周波焼入装置において、
（ａ）電源周波数の異なる複数台の高周波電源と、
（ｂ）被焼入体であるラックバーを高周波誘導加熱するための高周波誘導加熱コイルと、
（ｃ）前記複数台の高周波電源からの出力のうちの２つ以上の出力を前記高周波誘導加熱コイルに供給する制御装置と、
を有する高周波誘導加熱装置を具備し、
前記制御装置により２つ以上の周波数の高周波電流を前記１台の高周波誘導加熱コイルに同時に供給することによって、ラックバーの歯面及び背面を含めた全周面を焼入処理するために高周波誘導加熱するようにしている。
また、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と、前記歯面及び背面を含めた全周面より連続して延びる断面円形の軸部の外周面とを連続して高周波誘導加熱コイルにて高周波誘導加熱した後に冷却して高周波焼入を施行するようにしたラックバーの高周波焼入装置において、
（ａ）電源周波数の異なる複数台の高周波電源と、
（ｂ）被焼入体であるラックバーを高周波誘導加熱するための高周波誘導加熱コイルと、
（ｃ）前記複数台の高周波電源からの出力のうちの１つ以上の出力を前記高周波誘導加熱コイルに供給する制御装置と、
を有する高周波誘導加熱装置を具備し、
前記制御装置により１つ以上の周波数の高周波電流を前記１台の高周波誘導加熱コイルに供給すると共に、前記複数台の高周波電源から前記高周波誘導加熱コイルへの出力の割合を調整することによって、前記歯面及び背面を含めた全周面並びに前記軸部の外周面に焼入硬化層を連続して形成するようにしている。
また、本発明では、前記高周波誘導加熱コイルは、被焼入体であるラックバーの軸線方向に沿って対向配置される一対の主加熱導体部、及び、これら一対の主加熱導体部の両端にそれぞれ接続されて互いに平行に配置される一対の環状副加熱導体部を有する１台の高周波誘導加熱コイルを有するようにしている。
また、本発明では、前記歯面及び背面を含めた全周面を高周波誘導加熱する際には、前記複数台の高周波電源から２つ以上の周波数の高周波電流を前記１台の高周波誘導加熱コイルに同時に供給し、前記軸部の外周面を高周波誘導加熱する際には、前記複数台の高周波電源のうちの１つから１つの周波数の高周波電流を前記１台の高周波誘導加熱コイルに供給するようにしている。
また、本発明では、前記歯面及び背面を含めた全周面並びに前記軸部の外周面を前記高周波誘導加熱コイルに対して移動させて高周波誘導加熱及びその後の冷却を連続して移動焼入するようにしている。
また、本発明では、前記複数台の高周波電源の電源周波数が、それぞれ、１〜４００ｋＨｚであるようにしている。
【００１１】
【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５を参照して説明する。なお、図１〜図５において、図６〜図８と同様の部分には同一の符号を付して重複する説明を省略する。
【００１２】
図１は、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に用いられる高周波焼入装置２０を示すものである。この高周波焼入装置２０は、図１に示すように、電源周波数（高周波発振周波数）の異なる２台の第１及び第２の高周波電源（高周波発振器）２１ａ，２１ｂと、被焼入体であるラックバー１を高周波誘導加熱するための１台の高周波誘導加熱コイル２２と、上述の第１及び第２の高周波電源（高周波発振器）２１ａ，２１ｂからの出力のうちの１つ又は２つの出力を交互に又は同時に高周波誘導加熱コイル２２に供給するように作動する制御装置２３とをそれぞれ備えている。また、第１及び第２の高周波電源２１ａ，２１ｂには第１及び第２の変成器２４ａ，２４ｂがそれぞれ接続されており、制御装置２３による制御により交互或いは同時に発振される第１及び第２の高周波発振器２１ａ，２１ｂから単一の周波数の高周波電流或いは２つの異なる周波数の高周波電流が変成器２４ａ，２４ｂを介して高周波誘導加熱コイル２２に供給されるように構成されている。なお、上述の第１及び第２の高周波電源２１ａ、２１ｂの電源周波数（発振周波数）ｆ_１，ｆ_２は、１〜４００ｋＨｚの範囲であるように設定されると共に、第１の高周波電源２１ａの電源周波数ｆ_１が相対的に高い周波数に設定され、第２の高周波電源２１ｂの電源周波数ｆ_２が相対的に低い周波数に設定されている（ｆ_１＞ｆ_２）。
【００１３】
本実施形態の高周波焼入装置２０に用いられる高周波誘導加熱コイル２２は、図１及び図２に示すように、被焼入体であるラックバー１の軸線Ｐ方向に沿って対向配置される一対の主加熱導体部２６ａ，２６ｂ（被焼入体であるラックバー１の歯面３及び背面４に対向するように互いに平行に配置されて上下方向にそれぞれ延びる左右一対の主加熱導体部２６ａ，２６ｂ）と、これら一対の主加熱導体部２６ａ，２６ｂの上下両端に接続されて互いに平行に配置される上下一対の環状副加熱導体部２７ａ，２７ｂと、一方の主加熱導体部２６ｂの中間の切断部の上下両端にそれぞれ接続された一対の電流供給導体部２８ａ，２８ｂとから構成されている。なお、後述の歯面及び背面を含む全周面焼入工程においてラックバー１の歯面３に対向配置される主加熱導体部２６ａの内側壁部は平坦面αとなっており、一方、ラックバー１の背面４に対向される主加熱導体部２６ｂの内側壁部は前記背面４の曲率に対応する形状の湾曲面（半円形面）βとなっている。
【００１４】
さらに、本実施形態の高周波焼入装置２０は、一対の環状副加熱導体部２７ａ，２７ｂにより囲まれた内側空間部２９ａ，２９ｂを通過し得る位置にラックバー１を静止状態で保持（挟持）するワーク保持治具３０，３１（図１参照）と、これらの保持治具３０，３１にて保持されたラックバー１をその軸線Ｐを中心に回転駆動する回転駆動機構（図示せず）と、この回転駆動機構によるラックバー１の回転を停止する際に、ラックバー１の歯面３及び背面４を上述の一対の主加熱導体部２６ａ，２６ｂに対向するように位置決めして停止させる位相決め機構（図示せず）と、高周波誘導加熱コイル２２とラックバー１とをラックバー１の軸線Ｐに沿って相対的に移動させる移動機構（図示せず）と、高周波誘導加熱コイル２２の下方に配置されてラックバー１に向けて冷却液を噴射する冷却液噴射機構（多数の噴射孔１４ａを有する冷却液噴射環１４）とを具備している。なお、ワーク保持治具３０，３１及び上述の各機構は、前記制御装置２３により適宜に作動制御されるように構成されており、冷却液噴射環１４には冷却液供給装置３２から冷却液が供給され、冷却液噴射環１４の多数の噴射孔１４ａから均一に噴射されるように構成されている。
【００１５】
次に、こ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の歯面３及び背面４を含む全周面及び軸部５の外周面を連続して焼入（移動焼入）する際の操作手順の一例について図２〜図５を参照して述べると、以下の通りである。
【００１６】
（１）まず、高周波焼入装置２０の下方に配置されているワーク保持治具３０にラックバー１の下端部（軸部５の側）を載置し、ラックバー１の上端部（歯面３を含む側）をワーク保持治具３１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。そして、高周波焼入装置２０内の所定の加熱位置、すなわち、ラックバー１を高周波誘導加熱コイル２２の一対の環状副加熱導体部２７ａ，２７ｂによりそれぞれ囲まれた内側空間部２９ａ，２９ｂを通過し得る位置に配置する。
（２）次に、ラックバー１を図外の昇降機構により下降させて、下側に向けられたラックバー１の軸部５を一対の環状副加熱導体部２７ａ，２７ｂの内側空間部２９ａ，２９ｂのほぼ中央を貫通する位置で停止させる。
（３）次いで、図外の回転駆動機構によりラックバー１にその軸線Ｐを中心とする回転を与える。
（４）しかる後に、制御装置２３により第１の高周波電源２１ａからの出力（発振周波数ｆ_１）を選択し、選択された所要周波数・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２２に所要時間にわたり供給して高周波誘導加熱コイル２２に所要周波数ｆ_１の高周波電流を流し、ラックバー１を軸線Ｐ方向に移動させずに、停止加熱を行う。
（５）所要時間にわたって停止加熱を行った後に、高周波誘導加熱コイル２２への高周波電力の供給を止めることなく、ラックバー１を図外の移動機構により所要速度で軸線Ｐ方向に沿って下降移動させて軸部５の外周面を連続的に所要の焼入温度まで移動加熱し、これに引き続いて制御装置２３による冷却液供給装置３２の制御によって冷却液噴射環１４の噴射孔１４ａから所要圧力・所要流量の冷却液をラックバー１の軸部５の外周面に噴射し、このラックバー１の軸部５の外周面を室温まで冷却して軸部５の焼入を完了する。
（６）ラックバー１の軸部５の外周面の焼入が完了した後にこれに引き続いて歯面３及び背面４を含む全周面の焼入工程に移行するに際して、ラックバー１の矢印Ｒ方向の回転を停止し、歯面３及び背面４をそれぞれ高周波誘導加熱コイル２２の主加熱導体部２６ａ及び主加熱導体部２６ｂにそれぞれ対向配置させた状態に図外の位置決め機構にて位置決めして固定保持する。一方、図外の昇降機構による移動及び高周波誘導加熱コイル２２への高周波電力の供給、並びに、冷却液の噴射は維続して行う。この時、歯面３及び背面４の焼入仕様に応じて高周波電力・移動速度を適宜に調整してよい。
（７）次いで、２台の第１及び第２の高周波電源２１ａ，２１ｂを同時発振させてこれらの高周波電源２１ａ，２１ｂからの出力（電力）を高周波誘導加熱コイル２２に同時に供給して、互いに異なる２つの高い周波数ｆ_１及び低い周波数ｆ_２の高周波電流を高周波誘導加熱コイル２２に流すことにより、ラックバー１を軸線Ｐ方向に沿って下降移動させながら歯面３及び背面４を含む全周面の必要範囲を移動加熱して冷却し、加熱完了位置までラックバー１が達した時点で、ラックバー１を移動させたままの状態の下で高周波誘導加熱コイル２２への高周波電流の供給を遮断する。
（８）ラックバー１を移動させた状態のままでの冷却液噴射環１４の噴射孔１４ａからの冷却液の噴射は引き続き行い、ラックバー１の加熱完了箇所を冷却する位置でラックバー１の移動を止め、所要時間にわたり停止冷却を行う。
（９）そして、ラックバー１の加熱完了箇所が室温まで急冷された時点で、冷却液の噴射を停止し、一連の焼入処理を終了する。
（１０）その後、ラックバー１を所定の位置まで上昇させ、ワーク保持治具３０，３１からラックバー１を取り外し、次工程に移送する。
【００１７】
なお、上述の操作手順においては、ラックバー１の軸部５を焼入した後にラックバー１の歯面３及び背面４を焼入するようにしているが、これとは逆に、ラックバー１の歯面３及び背面４を有するラック部を焼入した後にラックバー１の軸部５を焼入するようにしてもよい。
【００１８】
本実施形態に係るラックバーの高周波焼入方法及び装置にあっては、図３に示すように、ラックバー１の軸部５の外周面を焼入する場合と、ラックバー１の歯面３及び背面４を含む全周面を焼入する場合とでは、高周波誘導加熱時の周波数並びに出力（すなわち、電力）を変化させる（切り換える）ようにしている。
【００１９】
具体的には、ラックバー１の軸部５の外周面を焼入する際には、制御装置２３の機能により、第１及び第２の高周波電源２１ａ，２１ｂのうちの一方、例えば、電源周波数（発振周波数）が相対的に高い方の第１の高周波電源２１ａから出力される電力だけを変成器２４ａを介して高周波誘導加熱コイル２２に供給するようにしている。これにより、高い周波数かつ高い電力とすることによって、軸部５の外周面における焼入硬化層の深さが相対的に浅く設定されると共に、焼入硬化層の硬さが充分に確保されることとなる。
【００２０】
また、ラックバー１の歯面３及び背面４を含む全周面を焼入する際には、制御装置２３の機能により、第１及び第２の高周波電源２１ａ，２１ｂを作動させて高い周波数ｆ_１の高周波電流及び低い周波数ｆ_２の高周波電流を同時に高周波誘導加熱コイル２２に供給し、低い電源周波数である第２の高周波電源２１ｂの出力（電力）を高い電源周波数である第２の高周波電源２１ｂのよりも相対的に大きく設定する。これにより、ラックバー１の歯部３の歯底Ｎの周辺部分は、低い周波数の高周波電流により歯底Ｎの焼入硬化層深さが充分に確保され、ラックバー１の歯山部Ｍの周辺部分は、高い周波数の高周波電流により歯山部Ｍにおける焼入硬化層の硬さが充分に確保されることとなる。この場合、高い周波数の高周波電流を供給する第１の高周波電源２１ａから出力される電力を少なくすることにより、歯面３及び背面４を含めた全周面における表面部分の過熱を防止することができると共に、その全周面における焼入硬化層の深さ並びに表面硬さを良好に確保することができる。
【００２１】
本発明により、図４に示すように、軸部５の外周面から歯面３及び背面４にまで連続した焼入硬化層Ｓを形成した。被焼入体としてのラックバー１の歯直角ピッチが異なる場合であっても、高周波及び低周波の高周波電源２１ａ，２１ｂからの出力（電力）の割合を適宜に調整（配分）することにより、歯底Ｎの近傍箇所を目標の焼入硬化層深さにすることが可能である。本実施形態の方式により、軸部５の外周面から歯面３及び背面４に連続した焼入硬化層パターン（図４参照）を形成することができ、歯面３の底部Ｎに所望の焼入硬化層深さを確保し、かつ、所定の表面硬さとすることが可能である。
【００２２】
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例を示す。
【００２３】
第１実施例
（１）ワーク：ラックバー
（ａ）材質：Ｓ４５Ｃ
（ｂ）寸法
▲１▼ 軸径：直径２５．５ｍｍ
外形：直径２７．５ｍｍ
全長：６４２ｍｍ
▲２▼ 歯緒元
歯直角モジュール：１．６
歯高：３．２ｍｍ
歯幅：２４．０ｍｍ
歯直角ピッチ：５．０
（２）高周波誘導加熱条件
（Ａ）軸部
（ａ）周波数：２００ｋＨｚ
出力：１１５ｋＷ
移動速度：１９ｍｍ／ｓｅｃ
（Ｂ）歯面及び背面
（ａ）周波数：２００ｋＨｚ
出力：４０ｋＷ
移動速度：１２．５ｍｍ／ｓｅｃ
（ｂ）周波数：７．６ｋＨｚ
出力：６０ｋＷ
移動速度：１２．５ｍｍ／ｓｅｃ
【００２４】
上記加工条件によりラックバー１に焼入を施したところ、図４（ａ），（ｂ），（ｃ）に示すように軸部５の外周面から歯面３及び背面４にまで連続した硬化層パターンが形成された。この場合、軸部５の表面硬さは、Ｈｖ７００〜７２０であり、焼入硬化層深さは、１．５〜１．７ｍｍであった。背面４の表面硬さは、Ｈｖ６８０〜７００であり、硬化層深さは、２．４〜２．６ｍｍであった。歯底部Ｎの表面硬さは、Ｈｖ６８０〜７００であり、硬化層深さは、０．９〜１．１ｍｍであった。
【００２５】
第２実施例
（１）ワーク：ラックバー
（ａ）材質：Ｓ４５Ｃ
（ｂ）寸法
▲１▼ 軸径：直径２５．５ｍｍ
外形：直径２７．５ｍｍ
全長：６４２ｍｍ
▲２▼ 歯緒元
歯直角モジュール：２．４
歯高：４．７ｍｍ
歯幅：２４．５ｍｍ
歯直角ピッチ：７．６
（２）高周波誘導加熱条件
（Ａ）軸部
（ａ）周波数：２００ｋＨｚ
出力：１１５ｋＷ
移動速度：１９ｍｍ／ｓｅｃ
（Ｂ）歯面及び背面
（ａ）周波数：２００ｋＨｚ
出力：３０ｋＷ
移動速度：１２．５ｍｍ／ｓｅｃ
（ｂ）周波数：７．６ｋＨｚ
出力：７０ｋＷ
移動速度：１２．５ｍｍ／ｓｅｃ
【００２６】
上記加工条件によりラックバー１に焼入を施したところ、図４（ａ），（ｂ），（ｃ）に示すように軸部５の外周面から歯面３及び背面４にまで連続した焼入硬化層パターンが形成された。この場合、軸部５の表面硬さは、Ｈｖ７００〜７２０であり、硬化層深さは１．５〜１．７ｍｍであった。背面４の表面硬さは、Ｈｖ６８０〜７００であり、硬化層深さは、２．５〜２．７ｍｍである。歯底部Ｎの表面硬さは、Ｈｖ６８０〜７００であり、硬化層深さは、０．７〜０．８ｍｍであった。本方式により、歯直角モジュールが異なるラックにおいてもラックバー１の歯底部Ｎに良好な深さの硬化層パターンを確保し、その表面硬さを規定値の範囲内とすることができた。
【００２７】
以上、本発明の一実施形態について述べたが、本発明は、既述の実施形態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高周波電源（高周波発振器）の台数を２台としたが、２台に限定されるものでなく、必要に応じて３台以上に増やし、ラックバー１の歯部３及び歯面４を含めた全周面の焼入に際して３以上の周波数（それぞれ異なる周波数）の高周波電流を高周波誘導加熱コイル２２に同時に供給するようにしても良い。また、ラックバー１の歯面３及び背面４の高周波誘導加熱において、高周波と低周波の同時発振としたが、ラックバー１の歯直角モジュール及びねじれ角に応じて、高い周波数の高周波電流のみの供給（高周波のみの発振）や、低い周波数の高周波電流のみの供給（低周波のみの発振）でも可能である。また、ラックバー１の軸部５の高周波誘導加熱において、高周波のみの発振としたが、高周波と低周波の同時発振でも可能である。低周波と高周波の電力をそれぞれ一定の値としても良く、焼入硬化層の深さに応じて電力値を無段階に変化させても良い。
【００２８】
ラックバーには、例えば、図５に示す電動式ラックバー（パワーステアリング部品）４０のように軸部５と歯面３との間にボールネジ部４１を有する形状もある。このような電動式ラックバー４０についても本発明の高周波焼入方法及び高周波誘導加熱装置を使用して、例えば、ボールネジ部４１のボール径によりボールネジ部４１を、高い周波数及び低い周波数の高周波電流の同時供給、高い周波数の高周波電流のみの供給、及び低い周波数の高周波電流のみの供給という３つの加熱条件から１つの最適条件を選定することにより、軸部５からボールネジ部４１、歯面３及び背面４に連続した硬化層パターンを電動式ラックバー４０に形成することが可能である。さらに、軸部５，ボールネジ部４１，歯面３及び背面４を連続焼入するようにしたが、必要部位だけを部分的に加熱して部分焼入を行う場合でも本発明を適用可能である。
【００２９】
【発明の効果】
本発明に係るラックバーの高周波焼入方法及び装置は、２つ以上の周波数（電源周波数）の高周波電流を前記高周波誘導加熱コイルに供給してラックバーの歯面及び背面を含めた全周面を高周波誘導加熱するようにしたものであるから、ラックバーの歯直角モジュールが例えば２以上のものであっても、ラックバーの歯面及び背面を含めた全周面に、所要の深さでかつ硬さが充分に確保された焼入硬化層を形成することができる。また、ラックバーの歯面及び背面を含めた全周面と、前記歯面及び背面を含めた全周面より連続して延びる断面円形の軸部の外周面とに、連続しかつ良好な焼入硬化層を形成することも可能である。さらに、歯直角ピッチの異なるラックバーの高周波移動焼入において、複数台の高周波電源から２つ以上の周波数の高周波電流を同時に１台の高周波誘導加熱コイルに供給する際に加熱出力の割合（高周波誘導加熱コイルへ供給する電力の配分）を変化させることにより、ラックバーの軸部から歯面及び背面にまでの全領域に亘って連続した焼入硬化層パターンを形成することができ、ラックバーの歯底近傍における焼入硬化層の深さを確保し、焼入部全域にわたり所定の表面硬さとすることが可能である。
【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に用いられる高周波焼入装置の構成図である。
【図２】図１の高周波焼入装置に使用される高周波誘導加熱コイルの斜視図である。
【図３】ラックバーの軸部と、歯面及び背面を含めた全周面とを順次に高周波誘導加熱する際に高周波誘導加熱コイルに供給される高周波電流及び電力（高周波電源からの出力）を示す図である。
【図４】本発明に係る高周波焼入方法及び装置を用いてラックバーを焼入した場合にラックバーの外表面に得られる焼入硬化層パターンを示す断面図であって、図４（Ａ）はラックバーの軸線を含む平面における断面図、図４（Ｂ）は図４（Ａ）におけるＸ−Ｘ線拡大断面図、図４（Ｃ）は図４（Ａ）におけるＹ−Ｙ線拡大断面図である。
【図５】図５（Ａ）は電動式ラックバー（パワーステアリング部品）の側面図、図５（Ｂ）は電動式ラックバーの外表面に形成される焼入硬化層パターンを示す断面図である。
【図６】被焼入体であるステアリング用ラックバーの平面形状及び側面形状を示す図である。
【図７】従来の高周波焼入装置にて上述のラックバーを移動焼入している状態を示す断面図である。
【図８】図７の高周波焼入装置によって軸部の外周面並びに歯面及び背面を含めた全周面を１工程にて焼入処理した場合に得られるラックバーの焼入硬化層パターンを示す断面図であって、図８（Ａ）はラックバーの軸線を含む平面における断面図、図８（Ｂ）は図８（Ａ）におけるＸ−Ｘ線拡大断面図、図８（Ｃ）は図８（Ａ）におけるＹ−Ｙ線拡大断面図である。
【符号の説明】
１ラックバー
３歯面
４背面
５軸部
１４冷却液噴射環
２１ａ第１の高周波電源
２１ｂ第２の高周波電源
２２高周波誘導加熱コイル
２３制御装置
２４ａ第１の変成器
２４ｂ第２の変成器
４０電動式ラックバー
ｆ_１，ｆ_２電源周波数（発振周波数）[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, the entire peripheral surface including the tooth surface and the rear surface of the rack bar, and the outer peripheral surface of the shaft portion having a circular cross-sectional shape that is continuous from the entire peripheral surface including the tooth surface and the rear surface are formed by the moving quenching method. The present invention relates to a method and an apparatus for induction hardening of a rack bar which is continuously induction hardened.
[0002]
[Prior art]
FIG. 6 shows a generally used steering rack bar 1 (hereinafter simply referred to as rack bar 1). The rack bar 1 has, on one side surface, a bevel 2 at an angle θ with respect to the axis P, and a surface (semi-cylindrical surface) 4 of the bevel 2 opposite to the tooth surface 3 is formed. I have. Further, as shown in FIG. 6, the rack bar 1 has a shaft portion 5 having a circular cross section extending continuously from the entire peripheral surface including the tooth surface 3 and the back surface 4. Conventionally, when such a rack bar 1 is quenched, an induction hardening device 7 as shown in FIG. 7 is used to cover the entire peripheral surface including the tooth surface 3 and the back surface 4 (of the rack portion). The induction quenching is continuously performed on the outer peripheral surface) and the outer peripheral surface of the shaft portion 5 having a circular cross section by the moving quenching method (for example, see Patent Document 1).
[0003]
The induction hardening device 7 includes a single-turn or multiple-turn circular high-frequency induction heating coil 13 surrounding the outer peripheral surface of the rack bar 1, and is disposed below the high-frequency induction heating coil 13. Cooling means (a large number of injection holes) provided for sequentially cooling the entire peripheral surface including the tooth surface 3 and the rear surface 4 and the outer peripheral surface of the shaft portion 5 to the quenching temperature by the high-frequency induction heating coil 13 and subsequently cooling the same. A cooling liquid injection ring 14a having a holding member 14a, holding jigs 15 and 16 for holding the rack bar 1 in a sandwiched state, and a rotary drive for rotating the rack bar 1 held by the holding jigs 15 and 16 A mechanism (not shown) and a moving means (not shown) for relatively moving the high-frequency induction heating coil 13 and the rack bar 1 along the axis P of the rack bar 1 are provided.
[0004]
Conventionally, the following two quenching steps (I) and (II) are performed when quenching the rack bar 1 using the induction hardening apparatus 7 described above.
(I) When quenching the outer peripheral surface of the shaft portion 5 of the rack bar 1, the high frequency induction heating coil is driven by rotating the rack bar 1 around its axis P in the direction indicated by the arrow R in FIG. 7, the rack bar 1 is rotated along its axis along the axis of the rack bar 1 under the condition that the axis P of the rack bar 1 coincides with the axis of the high-frequency induction heating coil 13. In this way, the outer peripheral surface of the shaft portion 5 of the rack bar 1 is high-frequency induction-heated to a required quenching temperature while being relatively moved with respect to the high-frequency induction heating coil 13, and then the coolant injection ring 14 is cooled. A quenching step of injecting a cooling liquid from above to cool the outer peripheral surface of the shaft 5 is performed.
(II) When quenching the entire peripheral surface including the tooth surface 3 and the rear surface 4 of the rack bar 1, the rack bar 1 is not rotated around the axis P thereof, but is rotated along the axis P of the rack bar 1. The rack bar 1 is held under a state where the rack bar 1 is held such that specific heating conductor portions of the high-frequency induction heating coil arranged in parallel along the rack bar 1 face the tooth surface 3 and the back surface 4 of the rack bar 1, respectively. Is moved relative to the high-frequency induction coil along the direction of the axis P of the rack bar 1 (the direction of arrow K in FIG. 7), and the entire peripheral surface including the tooth surface 3 and the back surface 4 of the rack bar 1 is A quenching step is performed in which induction heating is performed, and then the cooling liquid is injected from the cooling liquid injection ring 14 to quench and cool the outer peripheral surface of the shaft portion 5.
[0005]
Thus, the two quenching steps described in (I) and (II) above are performed by stopping the relative movement of the rack bar 1 along the direction of the axis P (the direction of the arrow K), high-frequency induction heating, and quenching and cooling. The quenching process of the rack bar 1 is performed by continuously performing the quenching process.
[0006]
[Patent Document 1]
JP-A-54-107812
[0007]
[Problems to be solved by the invention]
In the induction quenching of the rack bar 1, the depth of the hardened layer from the root N of the rack bar 1 (see FIGS. 8A and 8B) is targeted for quenching the rack 1 having a right angle module of about 1.6. When the height is set to 1.0 mm, moving quenching is performed using a high-frequency power supply having an oscillation frequency (high-frequency oscillation frequency) of 30 kHz. However, in the case where the tooth perpendicularity module of the rack bar 1 is, for example, two or more, if the oscillation frequency (power supply frequency) of the high-frequency power supply is set to 30 kHz, the outer peripheral surface of the shaft portion 5 of the rack bar 1 becomes as shown in FIG. As shown in FIG. 8C, a hardened hardened layer S having a uniform depth can be formed, but the hardened hardened layer S is formed at the root N of the rack bar 1 as shown in FIG. There is a problem that it is difficult to do.
[0008]
On the other hand, by setting the power supply frequency (high-frequency oscillation frequency) to 10 kHz or less, the quenched and hardened layer S can be formed at the root N of the rack bar 1. This results in a problem that the heating temperature of the tooth ridge M becomes low, so that the predetermined quench hardness cannot be satisfied. Further, the outer surface of the shaft portion 5 of the rack bar 1 is cooled by high-frequency induction heating at a power supply frequency of 10 kHz or less so that the quenched hardened layer S having a depth of about 1.5 mm or more is formed on the outer surface. When it is intended to form a steel sheet, there arises a problem that a predetermined quench hardness cannot be satisfied.
[0009]
The present invention has been made in view of the above situation, and its purpose is to include the tooth surface and the back surface of the rack bar even if the rack right angle module is, for example, two or more. Another object of the present invention is to provide a method and an apparatus for induction hardening of a rack bar capable of forming a quenched hardened layer having a desired depth and sufficient hardness on the entire peripheral surface.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a method of induction hardening by cooling the entire circumference including a tooth surface and a back surface of a rack bar by high frequency induction heating with a high frequency induction heating coil. A step of simultaneously supplying high frequency currents of two or more frequencies to the high frequency induction heating coil to perform high frequency induction heating on the entire peripheral surface including the tooth surface and the back surface is included.
Further, in the present invention, the outer periphery of the shaft portion having a circular cross section extending continuously from the entire peripheral surface including the tooth surface and the rear surface of the rack bar, which is the quenched body, including the tooth surface and the rear surface. In the induction hardening method of the rack bar, the surface was continuously cooled by high-frequency induction heating with a high-frequency induction heating coil and then subjected to induction hardening.
(A) simultaneously supplying high-frequency currents of two or more frequencies to the high-frequency induction heating coil to perform high-frequency induction heating on the entire peripheral surface including the tooth surface and the back surface;
(B) supplying a high-frequency current of one frequency to the high-frequency induction heating coil to perform high-frequency induction heating on the outer peripheral surface of the shaft portion;
Is included.
Further, in the present invention, the step (a) and the step (b) are continuously performed under a state where the rack bar is relatively moved with respect to the high-frequency induction heating coil. I am trying to enforce it.
In the present invention, the two or more frequencies are each 1 to 400 kHz.
In the present invention, the ratio of the output from the high-frequency power supply that supplies the high-frequency currents of the two or more frequencies is adjusted.
Further, in the present invention, in the induction hardening device of the rack bar for quenching the entire peripheral surface including the tooth surface and the back surface of the rack bar that is the object to be quenched,
(A) a plurality of high-frequency power supplies having different power supply frequencies;
(B) a high-frequency induction heating coil for high-frequency induction heating of a rack bar to be quenched;
(C) a controller that supplies two or more outputs of the outputs from the plurality of high-frequency power supplies to the high-frequency induction heating coil;
Comprising a high-frequency induction heating device having
The control device simultaneously supplies high-frequency currents of two or more frequencies to the one high-frequency induction heating coil, thereby quenching the entire peripheral surface including the tooth surface and the back surface of the rack bar. I try to heat it.
Further, in the present invention, the outer periphery of the shaft portion having a circular cross section extending continuously from the entire peripheral surface including the tooth surface and the rear surface of the rack bar, which is the quenched body, including the tooth surface and the rear surface. In the induction hardening device of the rack bar, the surface was continuously cooled by high-frequency induction heating with a high-frequency induction heating coil and then subjected to induction hardening.
(A) a plurality of high-frequency power supplies having different power supply frequencies;
(B) a high-frequency induction heating coil for high-frequency induction heating of a rack bar to be quenched;
(C) a controller that supplies one or more outputs of the plurality of high-frequency power supplies to the high-frequency induction heating coil;
Comprising a high-frequency induction heating device having
By supplying high-frequency current of one or more frequencies to the one high-frequency induction heating coil by the control device, and by adjusting the ratio of output from the plurality of high-frequency power supplies to the high-frequency induction heating coil, A quench hardened layer is continuously formed on the entire peripheral surface including the tooth surface and the back surface and on the outer peripheral surface of the shaft portion.
Further, in the present invention, the high-frequency induction heating coil includes a pair of main heating conductors disposed to face each other along an axial direction of a rack bar that is a quenched object, and two ends of the pair of main heating conductors. One high-frequency induction heating coil having a pair of annular sub-heating conductor portions connected to each other and arranged in parallel with each other is provided.
Further, in the present invention, when high-frequency induction heating is performed on the entire peripheral surface including the tooth surface and the back surface, high-frequency currents of two or more frequencies are supplied from the plurality of high-frequency power sources to the one high-frequency induction heating coil. And simultaneously supplying high-frequency current of one frequency from one of the plurality of high-frequency power supplies to the one high-frequency induction heating coil when the outer peripheral surface of the shaft portion is subjected to high-frequency induction heating. Like that.
Further, in the present invention, the entire circumferential surface including the tooth surface and the back surface and the outer circumferential surface of the shaft portion are moved with respect to the high-frequency induction heating coil, so that high-frequency induction heating and subsequent cooling are continuously moved and quenched. I am trying to do it.
In the present invention, the power supply frequencies of the plurality of high-frequency power supplies are each 1 to 400 kHz.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In FIGS. 1 to 5, the same parts as those in FIGS. 6 to 8 are denoted by the same reference numerals, and redundant description will be omitted.
[0012]
FIG. 1 shows an induction hardening device 20 used for carrying out the rack bar induction hardening method according to the present invention. As shown in FIG. 1, this induction hardening device 20 is a first and second high-frequency power sources (high-frequency oscillators) 21a and 21b having different power supply frequencies (high-frequency oscillation frequencies), and an object to be hardened. One high-frequency induction heating coil 22 for high-frequency induction heating of the rack bar 1 and one or two of the outputs from the first and second high-frequency power sources (high-frequency oscillators) 21a and 21b described above. And a control device 23 that operates to supply the high frequency induction heating coil 22 alternately or simultaneously. Further, first and second transformers 24a and 24b are connected to the first and second high-frequency power supplies 21a and 21b, respectively, and the first and second transformers are oscillated alternately or simultaneously under the control of the control device 23. Are supplied to the high-frequency induction heating coil 22 from the high-frequency oscillators 21a and 21b through the transformers 24a and 24b. The power supply frequency (oscillation frequency) f of the first and second high-frequency power supplies 21a and 21b described above.₁, F₂Is set to be in the range of 1 to 400 kHz, and the power frequency f₁Is set to a relatively high frequency, and the power supply frequency f of the second high-frequency power supply 21b is₂Is set to a relatively low frequency (f₁> F₂).
[0013]
As shown in FIGS. 1 and 2, a high-frequency induction heating coil 22 used in the induction hardening device 20 of the present embodiment includes a pair of opposingly arranged along the axis P direction of the rack bar 1 that is the object to be hardened. Main heating conductors 26a, 26b (a pair of left and right main heating conductors 26a, 26b, which 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, which is the quenched object, and extend in the vertical direction, respectively). 26b), a pair of upper and lower annular sub-heating conductors 27a, 27b connected to upper and lower ends of the pair of main heating conductors 26a, 26b and arranged in parallel with each other, and an intermediate portion between the one main heating conductor 26b. It is composed of a pair of current supply conductors 28a and 28b connected to the upper and lower ends of the cut portion, respectively. The inner wall portion of the main heating conductor 26a opposed to the tooth surface 3 of the rack bar 1 in the entire peripheral surface quenching process including the tooth surface and the rear surface described later has a flat surface α. The inner wall portion of the main heating conductor portion 26b facing the back surface 4 of the bar 1 has a curved surface (semicircular surface) β having a shape corresponding to the curvature of the back surface 4.
[0014]
Further, the induction hardening apparatus 20 of the present embodiment holds (pinches) the rack bar 1 at a position where the rack bar 1 can pass through the inner spaces 29a and 29b surrounded by the pair of annular sub-heating conductors 27a and 27b. Work holding jigs 30 and 31 (see FIG. 1), and a rotation drive mechanism (not shown) for driving the rack bar 1 held by these holding jigs 30 and 31 to rotate about their axis P. When the rotation of the rack bar 1 by the rotation drive mechanism is stopped, the tooth surface 3 and the back surface 4 of the rack bar 1 are positioned so as to face the pair of main heating conductors 26a and 26b and stopped. A determining mechanism (not shown); a moving mechanism (not shown) for relatively moving the high frequency induction heating coil 22 and the rack bar 1 along the axis P of the rack bar 1; set on It is to have and a coolant injection system for injecting a cooling liquid toward the rack bar 1 (coolant injection ring 14 having a plurality of injection holes 14a). The work holding jigs 30 and 31 and each of the above-described mechanisms are configured to be appropriately operated and controlled by the control device 23. The coolant injection ring 14 receives coolant from a coolant supply device 32. It is configured to be supplied and uniformly jetted from a number of jet holes 14a of the coolant jet ring 14.
[0015]
Next, the entire peripheral surface including the tooth surface 3 and the rear surface 4 of the rack bar 1 and the outer peripheral surface of the shaft portion 5 are continuously quenched (moving quenching) by using the induction hardening device 20 having such a configuration. An example of the operation procedure at that time will be described below with reference to FIGS.
[0016]
(1) First, the lower end portion (the side of the shaft portion 5) of the rack bar 1 is placed on the work holding jig 30 arranged below the induction hardening device 20, and the upper end portion (tooth surface) of the rack bar 1 is set. 3) is held by the work holding jig 31 so that the rack bar 1 is held upright. Then, a predetermined heating position in the induction hardening device 20, that is, the rack bar 1 passes through inner space portions 29a and 29b surrounded by a pair of annular sub-heating conductor portions 27a and 27b of the high-frequency induction heating coil 22, respectively. Place where you want.
(2) Next, the rack bar 1 is lowered by an elevating mechanism (not shown), and the shaft portion 5 of the rack bar 1 directed downward is moved to the inner space portions 29a, 29a of the pair of annular sub-heating conductor portions 27a, 27b. Stop at a position penetrating substantially the center of 29b.
(3) Next, the rack bar 1 is rotated about its axis P by a rotation drive mechanism (not shown).
(4) After that, the controller 23 outputs the output from the first high-frequency power supply 21a (the oscillation frequency f₁) Is supplied to the high-frequency induction heating coil 22 of the quenching device 20 for a required time by supplying the high-frequency power of the selected required frequency and required output to the high-frequency induction heating coil 22 for the required frequency f.₁, And stop heating is performed without moving the rack bar 1 in the direction of the axis P.
(5) After performing the stop heating for the required time, the rack bar 1 is moved down along the axis P at a required speed by a moving mechanism (not shown) without stopping the supply of the high-frequency power to the high-frequency induction heating coil 22 after stopping the heating. Then, the outer peripheral surface of the shaft portion 5 is continuously moved and heated to a required quenching temperature, and subsequently the required pressure is applied from the injection hole 14a of the cooling liquid injection ring 14 by the control of the cooling liquid supply device 32 by the control device 23. A required amount of coolant is sprayed onto the outer peripheral surface of the shaft 5 of the rack bar 1, and the outer peripheral surface of the shaft 5 of the rack bar 1 is cooled to room temperature to complete the quenching of the shaft 5.
(6) After the quenching of the outer peripheral surface of the shaft portion 5 of the rack bar 1 is completed, when the process proceeds to the quenching process of the entire peripheral surface including the tooth surface 3 and the rear surface 4, the arrow R of the rack bar 1 is used. The rotation in the direction is stopped, and the tooth surface 3 and the back surface 4 are positioned by a positioning mechanism (not shown) in a state where the tooth surfaces 3 and the back surface 4 are respectively disposed to face the main heating conductor portions 26a and 26b of the high-frequency induction heating coil 22, respectively. Hold fixed. On the other hand, movement by an elevating mechanism (not shown), supply of high-frequency power to the high-frequency induction heating coil 22, and injection of coolant are continuously performed. At this time, the high-frequency power and the moving speed may be appropriately adjusted according to the hardening specifications of the tooth surface 3 and the back surface 4.
(7) Next, the two first and second high-frequency power supplies 21a and 21b are simultaneously oscillated, and the outputs (power) from these high-frequency power supplies 21a and 21b are simultaneously supplied to the high-frequency induction heating coil 22 so that Two different high frequencies f₁And low frequency f₂By flowing the high-frequency current through the high-frequency induction heating coil 22, the rack bar 1 is moved down along the direction of the axis P while moving and cooling the required range of the entire peripheral surface including the tooth surface 3 and the back surface 4, and cooled. When the rack bar 1 reaches the heating completion position, the supply of the high-frequency current to the high-frequency induction heating coil 22 is interrupted while the rack bar 1 is kept moving.
(8) The cooling liquid is continuously injected from the injection hole 14a of the cooling liquid injection ring 14 while the rack bar 1 is moved, and the rack bar 1 is cooled at the position where the heating of the rack bar 1 is completed. Stop the movement and perform stop cooling for the required time.
(9) Then, when the heating completion portion of the rack bar 1 is rapidly cooled to room temperature, the injection of the cooling liquid is stopped, and a series of quenching processes is ended.
(10) Thereafter, the rack bar 1 is raised to a predetermined position, the rack bar 1 is removed from the work holding jigs 30 and 31, and the rack bar 1 is transferred to the next step.
[0017]
In the above-described operation procedure, the tooth surface 3 and the back surface 4 of the rack bar 1 are quenched after the shaft portion 5 of the rack bar 1 is quenched. After the quenching of the rack having the tooth surface 3 and the back surface 4, the shaft 5 of the rack bar 1 may be quenched.
[0018]
In the method and apparatus for induction hardening of the rack bar according to the present embodiment, as shown in FIG. 3, the case where the outer peripheral surface of the shaft portion 5 of the rack bar 1 is hardened and the case where the tooth surface 3 In the case where the entire peripheral surface including the rear surface 4 is hardened, the frequency and output (that is, electric power) at the time of high-frequency induction heating are changed (switched).
[0019]
Specifically, when the outer peripheral surface of the shaft portion 5 of the rack bar 1 is quenched, one of the first and second high-frequency power sources 21a and 21b, for example, the power frequency Only the power output from the first high frequency power supply 21a having a relatively higher (oscillation frequency) is supplied to the high frequency induction heating coil 22 via the transformer 24a. Thus, by setting the frequency and power to be high, the depth of the quenched hardened layer on the outer peripheral surface of the shaft portion 5 is set to be relatively shallow, and the hardness of the quenched hardened layer is sufficiently ensured. It will be.
[0020]
Further, when the entire peripheral surface including the tooth surface 3 and the rear surface 4 of the rack bar 1 is hardened, the first and second high-frequency power sources 21a and 21b are operated by the function of the control device 23 to increase the high frequency f.₁High frequency current and low frequency f₂Are supplied to the high-frequency induction heating coil 22 at the same time, and the output (power) of the second high-frequency power supply 21b having a low power supply frequency is set to be relatively larger than that of the second high-frequency power supply 21b having a high power supply frequency. I do. As a result, in the peripheral portion of the tooth bottom 3 of the tooth portion 3 of the rack bar 1, the quenched and hardened layer depth of the tooth bottom N is sufficiently secured by the high frequency current of low frequency, and the tooth ridge M of the rack bar 1 is formed. In the peripheral portion, the hardness of the quench hardened layer in the tooth ridge portion M is sufficiently ensured by the high frequency high frequency current. In this case, by reducing the power output from the first high-frequency power supply 21a that supplies a high-frequency high-frequency current, it is possible to prevent overheating of the surface portion on the entire peripheral surface including the tooth surface 3 and the back surface 4. In addition to this, the depth and surface hardness of the quench hardened layer on the entire peripheral surface can be ensured well.
[0021]
According to the present invention, as shown in FIG. 4, a quench-hardened layer S continuous from the outer peripheral surface of the shaft portion 5 to the tooth surface 3 and the back surface 4 was formed. Even if the rack bar 1 as the quenched body has a different tooth perpendicular pitch, by appropriately adjusting (distributing) the ratio of the output (power) from the high-frequency and low-frequency high-frequency power supplies 21a and 21b, It is possible to set the location near the root N to the target quench hardened layer depth. According to the method of the present embodiment, a quench-hardened layer pattern (see FIG. 4) that is continuous from the outer peripheral surface of the shaft portion 5 to the tooth surface 3 and the back surface 4 can be formed. It is possible to secure the depth of the hardened layer and achieve a predetermined surface hardness.
[0022]
Below, the example of the concrete enforcement condition of the induction hardening method of the rack bar which concerns on this invention is shown.
[0023]
First embodiment
(1) Work: Rack bar
(A) Material: S45C
(B) Dimension
(1) Shaft diameter: 25.5 mm diameter
Outline: 27.5mm in diameter
Overall length: 642mm
▲ 2 ▼ Tooth
Tooth right angle module: 1.6
Tooth height: 3.2mm
Tooth width: 24.0mm
Tooth perpendicular pitch: 5.0
(2) High frequency induction heating conditions
(A) Shaft
(A) Frequency: 200 kHz
Output: 115kW
Moving speed: 19mm / sec
(B) Tooth surface and back surface
(A) Frequency: 200 kHz
Output: 40kW
Moving speed: 12.5mm / sec
(B) Frequency: 7.6 kHz
Output: 60kW
Moving speed: 12.5mm / sec
[0024]
When the rack bar 1 was hardened under the above processing conditions, as shown in FIGS. 4 (a), 4 (b) and 4 (c), continuous hardening from the outer peripheral surface of the shaft portion 5 to the tooth surface 3 and the back surface 4 was performed. A layer pattern was formed. In this case, the surface hardness of the shaft portion 5 was Hv700 to 720, and the quenched hardened layer depth was 1.5 to 1.7 mm. The surface hardness of the back surface 4 was Hv 680 to 700, and the depth of the hardened layer was 2.4 to 2.6 mm. The surface hardness of the tooth bottom N was Hv 680 to 700, and the depth of the hardened layer was 0.9 to 1.1 mm.
[0025]
Second embodiment
(1) Work: Rack bar
(A) Material: S45C
(B) Dimension
(1) Shaft diameter: 25.5 mm diameter
Outline: 27.5mm in diameter
Overall length: 642mm
▲ 2 ▼ Tooth
Tooth right angle module: 2.4
Tooth height: 4.7mm
Tooth width: 24.5mm
Tooth perpendicular pitch: 7.6
(2) High frequency induction heating conditions
(A) Shaft
(A) Frequency: 200 kHz
Output: 115kW
Moving speed: 19mm / sec
(B) Tooth surface and back surface
(A) Frequency: 200 kHz
Output: 30kW
Moving speed: 12.5mm / sec
(B) Frequency: 7.6 kHz
Output: 70kW
Moving speed: 12.5mm / sec
[0026]
When the rack bar 1 was hardened under the above processing conditions, as shown in FIGS. 4 (a), 4 (b) and 4 (c), continuous hardening from the outer peripheral surface of the shaft portion 5 to the tooth surface 3 and the back surface 4 was performed. A hardened layer pattern was formed. In this case, the surface hardness of the shaft 5 was Hv700 to 720, and the depth of the hardened layer was 1.5 to 1.7 mm. The surface hardness of the back surface 4 is Hv 680 to 700, and the depth of the hardened layer is 2.5 to 2.7 mm. The surface hardness of the tooth bottom N was Hv 680 to 700, and the depth of the hardened layer was 0.7 to 0.8 mm. According to this method, even in racks having different tooth right angle modules, a hardened layer pattern having a good depth was secured at the root N of the rack bar 1, and the surface hardness could be kept within a specified value range.
[0027]
As described above, one embodiment of the present invention has been described, but the present invention is not limited to the above-described 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 number of high-frequency power supplies (high-frequency oscillators) is two. However, the number is not limited to two. In addition, high-frequency currents of three or more frequencies (different frequencies) may be simultaneously supplied to the high-frequency induction heating coil 22 at the time of quenching the entire peripheral surface including the tooth surface 4. In the high-frequency induction heating of the tooth surface 3 and the back surface 4 of the rack bar 1, high-frequency and low-frequency simultaneous oscillations are performed. However, only the high-frequency high-frequency current of the high frequency Supply (oscillation of only high frequency) or supply of only high frequency current of low frequency (oscillation of only low frequency) is also possible. In the high-frequency induction heating of the shaft portion 5 of the rack bar 1, only high-frequency oscillation is performed. However, simultaneous high-frequency and low-frequency oscillation can be used. The low-frequency power and the high-frequency power may each be a constant value, and the power value may be changed steplessly according to the depth of the quench-hardened layer.
[0028]
The rack bar has a shape having a ball screw portion 41 between the shaft portion 5 and the tooth surface 3 like an electric rack bar (power steering component) 40 shown in FIG. 5, for example. For such an electric rack bar 40 as well, by using the induction hardening method and the induction heating device of the present invention, for example, the ball screw portion 41 is driven by the ball diameter of the ball screw portion 41 so that high-frequency and low-frequency high-frequency current By selecting one optimum condition from the three heating conditions of simultaneous supply, supply of only high-frequency high-frequency current, and supply of only low-frequency high-frequency current, the ball screw portion 41, the tooth surface 3, and the back surface are selected from the shaft portion 5. It is possible to form an electric rack bar 40 with a cured layer pattern that is continuous with the fourth. Furthermore, although the shaft portion 5, the ball screw portion 41, the tooth surface 3 and the back surface 4 are continuously quenched, the present invention can be applied to a case where only necessary portions are partially heated to perform partial quenching. .
[0029]
【The invention's effect】
The method and apparatus for induction hardening of a rack bar according to the present invention supplies a high frequency current of two or more frequencies (power supply frequency) to the high frequency induction heating coil to cover the entire peripheral surface including the tooth surface and the back surface of the rack bar. Is high-frequency induction heated, so that even if the rack right angle module is, for example, two or more, the rack bar has a required depth on the entire peripheral surface including the tooth surface and the back surface. In addition, it is possible to form a quenched and hardened layer having sufficient hardness. Further, the continuous and good burning is performed on the entire peripheral surface including the tooth surface and the rear surface of the rack bar and the external peripheral surface of the shaft portion having a circular cross section extending continuously from the entire peripheral surface including the tooth surface and the rear surface. It is also possible to form a hardened layer. Furthermore, in high-frequency moving quenching of rack bars having different tooth perpendicular pitches, when high-frequency currents of two or more frequencies are simultaneously supplied to one high-frequency induction heating coil from a plurality of high-frequency power sources, the ratio of heating output (high-frequency By changing the distribution of the power supplied to the induction heating coil, a continuous hardened layer pattern can be formed over the entire region from the shaft portion of the rack bar to the tooth surface and the back surface. It is possible to secure the depth of the quenched hardened layer in the vicinity of the tooth bottom and to obtain a predetermined surface hardness over the entire quenched portion.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an induction hardening apparatus used for performing an induction hardening method of a rack bar according to the present invention.
FIG. 2 is a perspective view of a high-frequency induction heating coil used in the high-frequency hardening apparatus of FIG.
FIG. 3 shows high-frequency current and power (output from a high-frequency power supply) supplied to a high-frequency induction heating coil when a shaft portion of a rack bar and a whole peripheral surface including a tooth surface and a back surface are sequentially subjected to high-frequency induction heating. FIG.
FIG. 4 is a cross-sectional view showing a quench-hardened layer pattern obtained on the outer surface of the rack bar when the rack bar is quenched using the induction hardening method and apparatus according to the present invention. ) Is a sectional view in a plane including the axis of the rack bar, FIG. 4B is an enlarged sectional view taken along line XX in FIG. 4A, and FIG. 4C is an enlarged sectional view taken along line YY in FIG. It is sectional drawing.
5 (A) is a side view of an electric rack bar (power steering component), and FIG. 5 (B) is a cross-sectional view showing a quench hardened layer pattern formed on the outer surface of the electric rack bar. is there.
FIG. 6 is a diagram showing a plan shape and a side surface shape of a steering rack bar which is a quenched object.
FIG. 7 is a cross-sectional view showing a state in which the above-described rack bar is movingly hardened by a conventional induction hardening apparatus.
8 is a diagram showing a quenched hardened layer pattern of a rack bar obtained when the outer peripheral surface of the shaft portion and the entire peripheral surface including the tooth surface and the back surface are quenched in one step by the induction hardening device of FIG. 7; 8A is a cross-sectional view in a plane including the axis of a rack bar, FIG. 8B is an enlarged cross-sectional view taken along line XX in FIG. 8A, and FIG. FIG. 9 is an enlarged cross-sectional view taken along line YY in FIG.
[Explanation of symbols]
1 rack bar
3 Tooth surface
4 back
5 Shaft
14 Coolant injection ring
21a First high frequency power supply
21b Second high frequency power supply
22 High frequency induction heating coil
23 Control device
24a first transformer
24b second transformer
40 Electric rack bar
f₁, F₂ Power frequency (oscillation frequency)

Claims

ラックバーの歯面及び背面を含めた全周面を高周波誘導加熱コイルにて高周波誘導加熱して冷却することにより高周波焼入する方法において、２つ以上の周波数の高周波電流を前記高周波誘導加熱コイルに同時に供給して前記歯面及び背面を含めた全周面を高周波誘導加熱する工程を含むことを特徴とするラックバーの高周波焼入方法。In a method for induction hardening by high-frequency induction heating and cooling of the entire peripheral surface including the tooth surface and the back surface of the rack bar by a high-frequency induction heating coil, the high-frequency induction heating coil A high-frequency induction hardening method for a rack bar, the method comprising: simultaneously supplying the steel sheet with the steel sheet and heating the entire peripheral surface including the tooth surface and the back surface by high-frequency induction heating.

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と、前記歯面及び背面を含めた全周面より連続して延びる断面円形の軸部の外周面とを連続して高周波誘導加熱コイルにて高周波誘導加熱した後に冷却して高周波焼入を施行するようにしたラックバーの高周波焼入方法において、
（ａ）２つ以上の周波数の高周波電流を前記高周波誘導加熱コイルに同時に供給して前記歯面及び背面を含めた全周面を高周波誘導加熱する工程と、
（ｂ）１つの周波数の高周波電流を前記高周波誘導加熱コイルに供給して前記軸部の外周面を高周波誘導加熱する工程と、
を含むことを特徴とするラックバーの高周波焼入方法。The entire peripheral surface including the tooth surface and the rear surface of the rack bar to be quenched, and the external peripheral surface of the shaft portion having a circular cross section extending continuously from the entire peripheral surface including the tooth surface and the rear surface are continuously formed. In a high-frequency induction hardening method of a rack bar, which is cooled by high-frequency induction heating with a high-frequency induction heating coil and then subjected to induction hardening,
(A) simultaneously supplying high-frequency currents of two or more frequencies to the high-frequency induction heating coil to perform high-frequency induction heating on the entire peripheral surface including the tooth surface and the back surface;
(B) supplying a high-frequency current of one frequency to the high-frequency induction heating coil to perform high-frequency induction heating on the outer peripheral surface of the shaft portion;
A method for induction hardening a rack bar, comprising:

前記（ａ）に記載の工程及び前記（ｂ）に記載の工程を、前記ラックバーを前記高周波誘導加熱コイルに対して相対的に移動させた状態の下で連続的に施行することを特徴とする請求項２に記載のラックバーの高周波焼入方法。The step of (a) and the step of (b) are continuously performed under a state in which the rack bar is relatively moved with respect to the high-frequency induction heating coil. The method of induction hardening a rack bar according to claim 2.

前記２つ以上の周波数が、それぞれ、１〜４００ｋＨｚであることを特徴とする請求項１乃至３の何れか１項に記載のラックバーの高周波焼入方法。The method according to any one of claims 1 to 3, wherein the two or more frequencies are 1 to 400 kHz, respectively.

前記２つ以上の周波数の高周波電流をそれぞれ供給する高周波電源から出力される出力の割合を調整するようにしたことを特徴とする請求項１乃至４の何れか１項に記載のラックバーの高周波焼入方法。The high frequency of the rack bar according to any one of claims 1 to 4, wherein a ratio of an output output from a high frequency power supply that supplies each of the high frequency currents of the two or more frequencies is adjusted. Quenching method.

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焼入するためのラックバーの高周波焼入装置において、
（ａ）電源周波数の異なる複数台の高周波電源と、
（ｂ）被焼入体であるラックバーを高周波誘導加熱するための高周波誘導加熱コイルと、
（ｃ）前記複数台の高周波電源からの出力のうちの２つ以上の出力を前記高周波誘導加熱コイルに供給する制御装置と、
を有する高周波誘導加熱装置を具備し、
前記制御装置により２つ以上の周波数の高周波電流を前記１台の高周波誘導加熱コイルに同時に供給することによって、ラックバーの歯面及び背面を含めた全周面を焼入処理するために高周波誘導加熱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。In the induction hardening device of the rack bar for quenching the entire peripheral surface including the tooth surface and the back surface of the rack bar to be quenched,
(A) a plurality of high-frequency power supplies having different power supply frequencies;
(B) a high-frequency induction heating coil for high-frequency induction heating of a rack bar to be quenched;
(C) a controller that supplies two or more outputs of the outputs from the plurality of high-frequency power supplies to the high-frequency induction heating coil;
Comprising a high-frequency induction heating device having
The control device simultaneously supplies high-frequency currents of two or more frequencies to the one high-frequency induction heating coil, thereby quenching the entire peripheral surface including the tooth surface and the back surface of the rack bar. An induction hardening device for a rack bar, wherein the device is heated.

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と、前記歯面及び背面を含めた全周面より連続して延びる断面円形の軸部の外周面とを連続して高周波誘導加熱コイルにて高周波誘導加熱した後に冷却して高周波焼入を施行するようにしたラックバーの高周波焼入装置において、
（ａ）電源周波数の異なる複数台の高周波電源と、
（ｂ）被焼入体であるラックバーを高周波誘導加熱するための高周波誘導加熱コイルと、
（ｃ）前記複数台の高周波電源からの出力のうちの１つ以上の出力を前記高周波誘導加熱コイルに供給する制御装置と、
を有する高周波誘導加熱装置を具備し、
前記制御装置により１つ以上の周波数の高周波電流を前記１台の高周波誘導加熱コイルに供給すると共に、前記複数台の高周波電源から前記高周波誘導加熱コイルへ出力される電力の割合を調整することによって、前記歯面及び背面を含めた全周面並びに前記軸部の外周面に焼入硬化層を連続して形成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。The entire peripheral surface including the tooth surface and the rear surface of the rack bar to be quenched, and the external peripheral surface of the shaft portion having a circular cross section extending continuously from the entire peripheral surface including the tooth surface and the rear surface are continuously formed. In a high-frequency induction hardening device of a rack bar, which was cooled after high-frequency induction heating with a high-frequency induction heating coil to perform induction hardening,
(A) a plurality of high-frequency power supplies having different power supply frequencies;
(B) a high-frequency induction heating coil for high-frequency induction heating of a rack bar to be quenched;
(C) a controller that supplies one or more outputs of the plurality of high-frequency power supplies to the high-frequency induction heating coil;
Comprising a high-frequency induction heating device having
By supplying a high-frequency current of one or more frequencies to the one high-frequency induction heating coil by the control device and adjusting a ratio of power output from the plurality of high-frequency power supplies to the high-frequency induction heating coil An induction hardening device for a rack bar, wherein a quench hardened layer is continuously formed on the entire peripheral surface including the tooth surface and the back surface and the outer peripheral surface of the shaft portion.

前記高周波誘導加熱コイルは、被焼入体であるラックバーの軸線方向に沿って対向配置される一対の主加熱導体部、及び、これら一対の主加熱導体部の両端にそれぞれ接続されて互いに平行に配置される一対の環状副加熱導体部を有することを特徴とする請求項６又は７に記載のラックバーの高周波焼入装置。The high-frequency induction heating coil has a pair of main heating conductors disposed to face each other along the axial direction of a rack bar that is a quenched object, and is connected to both ends of the pair of main heating conductors and is parallel to each other. 8. The induction hardening device for a rack bar according to claim 6, further comprising a pair of annular sub-heating conductors arranged in the rack bar. 9.

前記歯面及び背面を含めた全周面を高周波誘導加熱する際には、前記複数台の高周波電源から２つ以上の周波数の高周波電流を前記１台の高周波誘導加熱コイルに同時に供給し、前記軸部の外周面を高周波誘導加熱する際には、前記複数台の高周波電源のうちの１つから１つの周波数の高周波電流を前記１台の高周波誘導加熱コイルに供給するようにしたことを特徴とする請求項７又は８に記載のラックバーの高周波焼入装置。When high-frequency induction heating is performed on the entire peripheral surface including the tooth surface and the back surface, high-frequency currents of two or more frequencies are simultaneously supplied to the one high-frequency induction heating coil from the plurality of high-frequency power sources, When the outer peripheral surface of the shaft portion is subjected to high-frequency induction heating, a high-frequency current of one frequency is supplied from one of the plurality of high-frequency power supplies to the one high-frequency induction heating coil. The induction hardening device for a rack bar according to claim 7 or 8.

前記歯面及び背面を含めた全周面並びに前記軸部の外周面を前記高周波誘導加熱コイルに対して移動させて高周波誘導加熱及びその後の冷却を連続して移動焼入するようにしたことを特徴とする請求項６乃至９に何れか１項に記載のラックバーの高周波焼入装置。The entire peripheral surface including the tooth surface and the back surface and the outer peripheral surface of the shaft portion are moved with respect to the high-frequency induction heating coil so that high-frequency induction heating and subsequent cooling are continuously moved and quenched. The rack bar induction hardening apparatus according to any one of claims 6 to 9, wherein:

前記複数台の高周波電源の電源周波数が、それぞれ、１〜４００ｋＨｚであることを特徴とする請求項６乃至１０の何れか１項に記載のラックバーの高周波焼入装置。11. The high frequency hardening device for rack bars according to claim 6, wherein power supply frequencies of the plurality of high frequency power sources are each 1 to 400 kHz. 12.