JP2005000951A

JP2005000951A - Hydraulic bulging method and device, and bulge article

Info

Publication number: JP2005000951A
Application number: JP2003167026A
Authority: JP
Inventors: Atsushi Tomizawa; 淳富澤
Original assignee: Sumitomo Metal Industries Ltd
Current assignee: Nippon Steel Corp
Priority date: 2003-06-11
Filing date: 2003-06-11
Publication date: 2005-01-06

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic bulging method and device that can suppress danger of crack of a base stock and that can greatly improve a forming limit of bulging by increasing metal flow to a cavity by axis extrusion, and also to provide a bulge article. <P>SOLUTION: This is a hydraulic bulging method in which a tube stock S1 is set in a pair of dies 11, 12, in which a high pressure liquid is supplied into the tube stock S1 while axis extrusion is imparted to the end face of the tube stock S1 with axis extruding tools 4, 5, and in which the tube stock S1 is bulged out into the cavity 7 of the dies 11, 12. In addition to the high pressure liquid to be supplied into the tube stock S1, a high pressure liquid is also supplied to the outer circumference of the entire tube stock including the ends and to the air gap including the cavity 7 of the dies 11, 12. Then, the machining is performed by controlling at least either the internal pressure or the external pressure working on the tube stock S1 from the inside and the outside thereof. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、液圧バルジ加工方法、及び、この方法を実施する液圧バルジ加工装置、並びに、液圧バルジ加工を施されたバルジ加工品に関するものである。
【０００２】
【従来の技術】
液圧バルジ加工には、通常の成形法に比べて以下の特長がある。
▲１▼ 長手方向に断面形状の異なるやや複雑な形状を得ることができるため、従来は溶接で組み付けられていた部品の一体成形が可能になる。
【０００３】
▲２▼ 製品の全体に亘って加工硬化が得やすいため、軟質な素管を用いても高強度な製品を得ることができる。
▲３▼ スプリングバックが少なく、製品の寸法精度が良好である（形状凍結性が良好である）ため、手直しの工程が省略できる。
【０００４】
以上のような優れた特長が評価され、近年、液圧バルジ加工は、特に自動車部品の製造工程に採用されるようになってきた。
一般的な管の液圧バルジ加工工程を次に説明する。
素材となる長手方向に均一な円断面を有するストレートな管（以下、「素管」と呼ぶ。）に対し、（１）曲げ加工、（２）押し潰し加工（以下、「プリフォーム加工」と呼ぶ。）、（３）液圧バルジ加工、の一連の加工を行うことによって製品を製造するものである。
【０００５】
図１３に示す最終工程である液圧バルジ加工では、上金型１，下金型２内にセットされた素管Ｓ１の中に注入孔３を通じて加工液を注入し、加工液の圧力（以下、「内圧」と呼ぶ）を高めることに加えて、シール工具を兼ねた軸押し工具４，５によって両管端から軸方向に素管Ｓ１を押し込む（以下、「軸押し」と呼ぶ。）ことで、種々の断面形状を有する製品Ｓ２を製造する。なお、シール工具を兼ねた軸押し工具４，５は図示しない油圧シリンダに接続されており、バルジ加工中に軸方向位置或いは軸押し力が制御されている。
【０００６】
ここで、液圧バルジ加工における、管端からの軸方向への軸押しは、膨出時のメタルフローを助長せしめて拡管限界を向上させる効果があり、極めて重要な役割を果している。
【０００７】
ところで、バルジ加工の素材となる素管の内周面側の空間には加工液が注入されるが、軸押し工具と素管の間には後述するシールが施されているため、加工液は外部へは流出することがなく、高圧を保持することが出来る。従って、加工液から受ける内圧によって素管は膨出し、金型に接触後、キャビティの形状に沿って押し付けられて、バルジ成形が完了する。
【０００８】
軸押し工具と素管の間のシール方法には、種々の方式があるが、軸押し工具４，５に形成したシール方法の代表的な例を図１４に示す。図１４（ａ）は素管の端面と接する端面４ａ，５ａでシールする場合の例、（ｂ）は同じく端面４ａ，５ａに突起４ｂ，５ｂを付与した例、（ｃ）は平行部４ｃ，５ｃの端面４ａ，５ａとの境界部に段差４ｄ，５ｄを付与した例、（ｄ）は平行部４ｃ，５ｃにＯリング６を設けた例である。
【０００９】
すなわち、このようなシールにより、軸押し工具４，５の少なくともどちらか一方に設けられた加工液の注入孔３を介して供給される高圧の加工液を、素管Ｓ１の内部に封じ込めることが可能となっている。
【００１０】
さて、近年、自動車部品には燃費や衝突安全性能の向上という観点から、さらなる部品の強度向上や薄肉化が求められている。
すなわち、従来以上に引張り強さ（Ｔ．Ｓ．）の高い硬質材（以下、「ハイテン材」と呼ぶ。）を素材とした溶接管や変形抵抗の高いシームレス鋼管を用いることによって、部品強度を高め、衝突安全性能の向上や、製品の薄肉化による軽量化の要求が高まっている。しかしながら、一般に、強度の高いハイテン材は伸びが小さく、同様のバルジ加工を行っても割れが発生する確率が高くなるという問題点がある。
【００１１】
また、衝突安全性能を向上するために、部品強度の向上や、部品強度を保持しつつ素材を薄肉化する別の方法として、バルジ加工での加工度を高めるという方法もある。すなわち、同一の材料を使用したとしても、バルジ加工での加工歪量を大きく（換言すればバルジ加工での拡管率を大きく）出来れば、材料の加工硬化により強度は向上するため、製品の板厚の減少も可能となる。そのためにも、バルジ加工の成形限界を飛躍的に向上させる技術が望まれていた。
【００１２】
以上、自動車部品について説明したが、これらの要求は自動車部品に限定されるものではなく、バルジ加工の成形限界が向上すれば、現在より幅広い用途への適用拡大が可能となることはいうまでもない。また、現状の加工割れを抑制可能な新たなバルジ加工方法が開発されれば、バルジ加工への適用が難しかった難加工材料の適用が可能となり、大幅に部品性能の向上がなされると期待されている。
【００１３】
これらの問題に対して、素管軸方向に圧縮力を付与しながら、素管の内周部に高圧加工液を供給すると共に、金型のキャビティと、このキャビティ内における素管の外周との間に高圧加工液を供給し、内圧と外圧の差を制御するバルジ加工装置が開示されている（例えば特許文献１参照。）。また、このバルジ加工装置を用いたバルジ加工において、加工がある程度進んだ状態で外圧を周期的に変動させる方法も開示されている（例えば特許文献２参照。）。
【００１４】
【特許文献１】
特許第３０２２５０６号公報（第１頁、図１）
【特許文献２】
特許第２９９９７５７号公報（第１頁、図１〜２）
【００１５】
一般に、大きな引張りの周方向応力は素材の割れを引き起こす危険性が高いが、前記特許文献１や特許文献２では、図１５に示したように、素管Ｓ１に内圧ｐｉと外圧ｐｏを作用させることによって、素管Ｓ１の円周方向に働く引張り力（周方向応力）σθを減少させ、バルジ加工時の割れを抑制しようとしているのである。
【００１６】
【発明が解決しようとする課題】
ところで、近年、さらに成形可能範囲を拡大したいという要求があるが、成形可能範囲の更なる拡大を図るためには、バルジ加工に際し、キャビティ７（図１３（ａ）参照）内における素管Ｓ１の膨出時、円周方向に働く引張り力σθの減少を図ることはもとより、前記膨出に合わせて素管Ｓ１の両端部分の軸押しをより円滑に行う必要がある。
【００１７】
しかしながら、前述の特許文献１や特許文献２に記載の装置や方法では、前述のように、キャビティ７内における素管Ｓ１の円周方向に働く引張り力σθを減少することのみに考慮が払われ、素管Ｓ１の両端部分は全く考慮されずに従来のバルジ加工となんら変わるところがなかったので、成形可能範囲の更なる拡大を図ることはできなかった。
【００１８】
また、前述の特許文献１や特許文献２に記載の装置や方法では、内圧に加えてキャビティとキャビティ内の素管の間に外圧も作用させるため、キャビティの外周部にこの外圧のシールを施す必要があるが、実際は、素管に外圧を付与するためのシール構造が難しいことから、特許文献１や特許文献２には、この外圧のシール構造について開示も示唆されていない。
【００１９】
すなわち、一般に、液圧バルジ加工装置においては、内圧による材料膨出によって上下金型が浮き上がるのを防止するために、通常、上下金型には油圧や機械的な力（以下「型締め力」と呼ぶ）を付与しているが、素管の外周部に高圧の外圧を作用させるので、前記型締め力だけでは、シールすることができない。加えて、上下金型と軸押し工具の間に隙間があるため、軸押し工具挿入部分からの漏れが発生してしまう。従って、如何に当業者であってもこの特許文献１や特許文献２に記載の内容のみに基づいて実用化することは不可能である。
【００２０】
本発明は、上記した従来の問題点に鑑みてなされたものであり、現状の液圧バルジ成形では、割れなどの不良が発生しやすい材質や寸法であっても、素材の割れの危険性を抑制できると共に、軸押し加工によるキャビティ部へのメタルフローを増大させることにより、バルジ加工の成形限界を飛躍的に向上させることができる液圧バルジ加工方法、加工装置、並びにその方法によって生産されるバルジ加工品を提供することを目的としている。
【００２１】
【課題を解決するための手段】
上記した目的を達成するために、本発明に係る液圧バルジ加工方法は、一対の金型内に素管をセットされた素管内部に供給する高圧液体に加えて、端部を含む素管全長の外周部と金型のキャビティを含む空隙内にも高圧液体を供給し、前記素管の内部及び外部から素管に作用させる内圧と外圧の少なくとも何れか一方を制御しつつ加工することとしている。
【００２２】
そして、一対の金型と、これら両金型の少なくとも何れか一方に夫々先端部を挿入されて素管の両端を挟持するシール工具を兼ねた軸押し工具とを備え、前記両軸押し工具の少なくとも何れか一方には素管の内部に加工液を注入する注入孔が、また、両金型の少なくとも何れか一方には素管の端部を含む全長の外周部と金型間に加工液を注入する注入孔が夫々設けられ、かつ、両金型の少なくとも何れか一方に、前記素管の端部を含む全長の外周部と金型間に注入された加工液の外部への流出を防ぐシール機構を設けた本発明に係る液圧バルジ加工装置に、素管をセットした後、軸押し加工を行いつつ素管の内外両面に高圧液を供給し、素管に作用させる内圧と外圧の少なくとも何れか一方を制御しつつ液圧バルジ加工を施した本発明に係るバルジ加工品では、現状の液圧バルジ成形では、割れなどの不良が発生しやすい材質や寸法であっても、素材の割れの危険性を抑制できると共に、軸押し加工によるキャビティ部へのメタルフローを増大させることにより、バルジ加工の成形限界を飛躍的に向上させることができる。
【００２３】
【発明の実施の形態】
本発明について、図１６を用いて説明する。図１６は、通常のバルジ成形である図１３における成形途中の一過程を示したものである。素管Ｓ１は、内圧ｐｉを受けており、さらに、管端部は図示しない軸押し工具によって、軸押し加工を受けつつ成形が進行している。
【００２４】
ここで、冒頭でも述べたように、軸押し加工は、素管Ｓ１の成形にとって極めて重要な加工である。すなわち、軸押しを行わないバルジ加工において、内圧ｐｉのみ作用させた場合には、軸方向の材料（素管Ｓ１）のメタルフローが少ないので、キャビティ７部での素管Ｓ１の膨出に伴って板厚が減少してしまうことになるため、割れが発生しやすくなるのである。
【００２５】
これに対して、軸押し加工を加えた場合は、素管Ｓ１が大きく膨出するキャビティ７部に軸端部から材料（素管Ｓ１）が供給されるため、前述の板厚減少が抑制され、成形可能範囲が拡大されることになる。
【００２６】
また、図１６には、成形中の素管Ｓ１に作用する力を示している。素管Ｓ１は全長に亘って受ける内圧ｐｉのほかに、キャビティ７以外の部分においては、上下の金型１，２からの面圧（垂直応力）ｐｋと、軸押し方向とは反対方向に摩擦応力ｐｍ（＝μｐｋ）を受ける。ここで、μは金型１，２と素管Ｓ１の摩擦係数である。
【００２７】
従って、この摩擦応力ｐｍが大きいほど、軸押し加工によるキャビティ７部への材料（素管Ｓ１）の供給は阻害されることになるが、従来方法において、軸押し加工によるキャビティ７部への材料（素管Ｓ１）の供給を増加させ、割れを抑制しようとする場合には、金型１，２と素管Ｓ１の摩擦係数μを減少させるために、素管Ｓ１に潤滑剤を塗布したり、金型１，２に特殊なコーティング処理を行うといった煩雑な対策をとらざるを得なかった。
【００２８】
しかしながら、キャビティ７以外の部分、すなわち素管Ｓ１の両端部にも外圧ｐｏを作用させることが出来れば、金型１，２からの面圧（垂直応力）ｐｋを小さくすることが出来、結果として軸押し方向とは反対方向の摩擦応力ｐｍを減少させることが出来る。従って、潤滑剤の塗布や剥離、さらには金型１，２に特殊なコーティング処理を施すような煩雑な方法をとらなくとも、軸押し加工によるキャビティ７部への材料（素管Ｓ１）の供給を増加させ、割れの抑制が可能になる。
【００２９】
本発明者は、上記知見を基に、さらに実験を積み重ねることで、素管の内外面に圧力を作用させることによるキャビティ部への別の効果も見出した。すなわち、図１７に示したような、従来の液圧バルジ加工装置を使用した、内圧のみで素管を膨出させるバルジ加工では、内圧がある程度高くなって素管の一部が上下金型１，２のキャビティ７内面と接触すると、接触した素管は上下金型１，２との摩擦によって自由な変形が妨げられてしまう。つまり、金型に接触した部分は変形を抑制される傾向にあることから、キャビティ７内における素管の伸びは上下金型１，２に接触していない別の部分に集中し、歪み分布が不均一になる。
【００３０】
これに対して、端部を含む素管全長の内外面に圧力をかけて膨出させていく方法では、端部を含む素管全長と金型内面の間に介在させる加工液に比較的高い外圧を作用させておけば、素管全長に亘って摩擦係数を低く保つことが出来る結果、加工歪みは均一化し、板厚が均一な製品を得ることが出来る。
【００３１】
ところで、端部を含む素管全長の内外面に圧力をかけて膨出させていく方法にあっては、キャビティ内のみならずキャビティ以外の部分でも変形が進むことになるが、素管に作用する面圧が増大して素管と金型間の摩擦応力が増加してしまった場合でも、少なくとも１回以上、
▲１▼ 外圧をそのままに保ち、内圧を減少させる、
▲２▼ 内圧をそのままに保ち、外圧を増大させる、
▲３▼ 内圧を減少させると共に外圧を増大させる、
▲４▼ 内圧を増加させるが、それ以上に外圧を増大させる、
の何れかを実施することで、金型と素管の摩擦応力ｐｍの高い部分が緩和され、続くバルジ加工時に、摩擦応力ｐｍが低下することが認められた。特に、変形の途中工程のサンプルを観察すると、素管が金型から離れ、後続するバルジ加工変形が均一化し、局部的な歪みの集中を防ぐことが出来る場合があった。
【００３２】
本発明は、上記の知見及びこの知見に基づく実験の積み重ねに基づいてなされたものである。
すなわち、本発明に係る液圧バルジ加工方法は、一対の金型内に素管をセットし、素管の端面より軸押し加工を付与しつつ、素管の内部に高圧液体を供給して、前記両金型のキャビティ内に素管を膨出する液圧バルジ加工方法において、
前記素管内部に供給する高圧液体に加えて、端部を含む素管全長の外周部と金型のキャビティを含む空隙内にも高圧液体を供給し、前記素管の内部及び外部から素管に作用させる内圧と外圧の少なくとも何れか一方を制御しつつ加工することを要旨とし、
必要に応じて、成形中、前記素管の内部及び外部から素管に作用させる内圧と外圧の何れか一方又は両方を、少なくとも１回以上変動させるものである。
【００３３】
また、本発明に係る液圧バルジ加工装置は、一対の金型と、これら両金型の少なくとも何れか一方に夫々先端部を挿入され、前記一対の金型にセッティングされた素管の両端を挟持するシール工具を兼ねた軸押し工具とを備え、
前記両軸押し工具の少なくとも何れか一方には前記素管の内部に加工液を注入する注入孔が、また、両金型の少なくとも何れか一方には前記素管の端部を含む全長の外周部と金型間に加工液を注入する注入孔が夫々設けられ、
かつ、両金型の少なくとも何れか一方に、前記素管の端部を含む全長の外周部と金型間に注入された加工液の外部への流出を防ぐシール機構を設けたことを要旨とするものである。
【００３４】
上記の本発明に係る液圧バルジ加工装置を使用すれば、素管内部に供給する高圧液体に加えて、端部を含む素管全長の外周部と金型のキャビティを含む空隙内にも高圧液体を供給でき、内外両面から素管全長に内圧と外圧を作用させることができるようになる。この本発明に係る液圧バルジ加工装置において、シール機構を、両金型の少なくとも何れか一方に設けるのに代えて、軸押し工具の外周面に設けた場合や、両金型を固定する金型ホルダーに設ける場合も同様の作用を奏するものであることは言うまでもない。
【００３５】
そして、その際、前記シール機構を装着する金型や金型ホルダーの面をほぼ平面とした場合には、シールの信頼性の向上を図ることができるようになる。
また、両金型の少なくとも何れか一方に加えて、前記軸押し工具の外周面にもシール機構を設けた場合には、軸押し工具の移動中にも、軸押し工具の外周面と金型の間からの液体漏れを防止することができる。
【００３６】
また、前記両金型の少なくとも何れか一方に、軸押し工具のガイド孔を設けた場合、当該部分には、両金型を重ね合わせたつなぎ目（いわゆる、「パーティングライン」）がなく、金型の段差や不連続部分がないので、シール機構の寿命延長が図れる。その際、前記軸押し工具の外周面に設けるシール機構に代えて、軸押し工具の前記ガイド孔にシール機構を設けた場合も、軸押し工具の移動中、軸押し工具の外周面と金型の間からの液体漏れを防止できる。
【００３７】
また、前記一対の金型の一方の金型を他方の金型にはめ込む構造とした場合には、更なるシールの信頼性の向上が図れる。
【００３８】
上記の本発明に係る液圧バルジ加工装置の一対の金型内に素管をセットした後、軸押し加工を行いつつ素管の内面と外面に高圧液を供給し、素管の内部及び外部から素管に作用させる内圧と外圧の少なくとも何れか一方を制御しつつ液圧バルジ加工を施した本発明に係る液圧バルジ加工品では、現状の液圧バルジ成形では、割れなどの不良が発生しやすい材質や寸法であっても、素材の割れの危険性を抑制でき、軸押し加工によるキャビティ部へのメタルフローの増大により、バルジ加工の成形限界が飛躍的に向上する。
【００３９】
また、上記の本発明に係る液圧バルジ加工品において、成形中、前記素管の内部及び外部から素管に作用させる内圧と外圧の何れか一方又は両方を、少なくとも１回以上変動させた場合には、素材割れの危険性の更なる抑制と、バルジ加工の成形限界の更なる向上が図れる。
【００４０】
【実施例】
以下、本発明を図１〜図１２に示す実施例に基づいて、詳細に説明する。
図１、図２は本発明の第１実施例を示した説明図であり、図１は金型と軸押し工具の見取り図、図２は金型の正面、平面、側面を表した図である。
【００４１】
図１及び図２において、１１，１２は本発明の液圧バルジ加工装置を構成する例えば上金型と下金型であり、上金型１１を下金型１２にはめ込む構造となっている。そして、このうちの例えば下金型１２に加工液を注入する注入孔１２ａを設けており、図示しない増圧機よりこの注入孔１２ａを通じて、図３に示すように、端部を含む素管全長の外周部とキャビティ７を含む空隙内に比較的高圧の加工液が注入され、素管Ｓ１の外表面全域に圧力が付加されるようになっている。
【００４２】
本発明の液圧バルジ加工装置では、素管Ｓ１の内面ｐｉのみならず、端部を含む全長の外表面にも外圧ｐｏを付加することから、上金型１１と下金型１２の間の側面部分と、上下金型１１，１２と軸押し工具４，５の隙間からの水漏れを防止するために、例えば平面となした下金型１２の上面１２ｃにシール１３を取り付けるのに加えて、例えば下金型１２に軸押し工具４，５のガイド孔１２ｂを設けることによって、軸押し工具４，５の挿入部分における段差や不連続部分をなくし、軸押し工具４，５の外周面にシール１４を取り付けている。
【００４３】
このように、上記構成の上下金型１１，１２と軸押し工具４，５を備えた本発明の液圧バルジ加工装置においては、バルジ加工中、素管Ｓ１の軸押し加工を行うために軸押し工具４，５が移動するが、軸押し工具４，５に取り付けられたシール１４は、下金型１２の端部のガイド孔１２ｂの内面に接して高圧を保持する。なお、シール１４は図４（ａ）に示したように、先端のシール工具４ｅ，５ｅに取り付けても良いし、図１や図４（ｂ）に示したように、先端のシール工具４ｅ，５ｅに連結されたロッド４ｆ，５ｆに取り付けても良い。
【００４４】
また、軸押し工具４，５の外周面にシール１４を取り付ける代わりに、図５に示す第２実施例のように、ガイド孔１２ｂの内周面にシール１５を取り付けても良く、この場合も上金型１１と下金型１２の間の側面部分からの水漏れと、上下金型１１，１２と軸押し工具４，５の隙間からの水漏れを防止することができる。この図５に示した場合には、軸押し工具４，５にはシール１４を取り付ける必要がないことは言うまでもない。
【００４５】
これら下金型１２に軸押し工具４，５のガイド孔１２ｂを設けた例では、外圧を保持するためのシール構造や金型構造も極めて簡単であり、加工液を内外圧共に高圧に保持することが出来、かつシール寿命も長い。また、素管Ｓ１の取り出し、挿入も従来の金型と同様に行うことが出来る。図１，２及び図５に示した例では、軸押し工具４，５のガイド孔１２ｂの長さは比較的長く表現されているが、少なくともバルジ加工中の軸押し量以上、望ましくは素管Ｓ１の挿入・取り出し時の軸押し工具４，５の可動長さとバルジ加工中の軸押し量を加えた長さを有すればよいため、このガイド孔１２ｂを設けても、金型のサイズはそれほど大型化するわけではない。
【００４６】
図６は本発明の第３実施例を示した説明図であり、図１とほぼ類似の構成となっている。但し、シール１３を取り付ける下金型１２の上面１２ｃが、中央部分で凹んだ形状とされ、この凹んだ中央水平面部１２ｃａと、この中央水平面部１２ｃａと両側の水平面部１２ｃｂを繋ぐ傾斜面部１２ｃｃにシール１３を取り付けている。この図６に示した第３実施例は、図１に示した上金型１１を下金型１２にはめ込む構造の第１実施例に比べて、金型構成がやや簡単になる。
【００４７】
図７は本発明の第４実施例を示した説明図であり、軸押し工具４，５に取り付けられたシール１４が接する軸押し工具のガイド孔１１ａ，１２ｂが、上金型１１と下金型１２にそれぞれ１個ずつ設けられている点を除いて、図６とほぼ類似の構成となっている。
【００４８】
この図７に示す第４実施例は、図１に示す第１実施例や図５に示す第２実施例に比べて、スペース的な余裕があるため素管Ｓ１の挿入・取り出しがし易いという長所がある。さらに、上下金型１１，１２は図示しない上下ベッドに取り付けられ、油圧あるいは機械的に上下の昇降を行うようになっているが、この図７に示す第４実施例において、軸押し工具４に接続する油圧シリンダを上金型１１と同じベッドに取り付けた場合には、軸押し工具４の移動距離が短くなると共に、素管Ｓ１の挿入・取り出しも容易であるため、大幅に作業性が向上する。
【００４９】
以上の第１〜第４実施例は、製品形状が略ストレートな場合についての実施例を示したが、本発明は通常の自動車部品に代表される３次元の複雑な形状の部品についても適用可能であることは言うまでもない。例えば、図８、図９は、それぞれ製品が、Ｃ型形状（直角曲げ形状）、Ｕ型形状（１８０°曲げ形状）の場合の図１に示した本発明の第１実施例に対応する第５、第６実施例を示したものである。
【００５０】
また、図１０は本発明の第７実施例を示した説明図である。この第７実施例は、図１に示した第１実施例のように、上下の金型１１，１２に軸押し工具のガイド孔を設けない点と、上金型１１を下金型１２にはめ込む構造とせずに、ただ単に上金型１１を下金型１２に載置する点を除いて、第１実施例と同じ構造である。
【００５１】
この第７実施例では、軸押し工具４，５の外周に取り付けられたシール１４と下金型１２に取り付けられたシール１３が軸方向の同一ライン上の位置にある場合には、図示しない素管の外表面に付加される圧力、すなわち、図示しない増圧機より注入孔１２ａを通じて注入される加工液の圧力を、第１実施例のように金型に軸押し工具４，５のガイド孔を設けた場合と同程度に、高圧に保持することが出来る。但し、シール構造はやや複雑になる。
【００５２】
しかしながら、軸押し工具４，５の外周に取り付けられたシール１４と下金型１２に取り付けられたシール１３の軸方向位置が一致しない場合には、圧力の保持のレベルは低下する。従って、この第７実施例では、例えば最初の段階では素管の外表面に作用する圧力を比較的低圧に設定し、軸押し工具４，５を移動させつつ成形を行い、シール１４と下金型１２に取り付けられたシール１３が軸方向の同一ライン上の位置まで到達した時点で、素管の外表面に高圧力を付加する等の制御を行えば良い。
【００５３】
また、この第７実施例では、上下金型１１，１２と軸押し工具４，５の隙間からの液漏れや、液圧バルジ加工中の軸押し工具４，５の移動時の液漏れは、軸押し工具４，５の外周に取り付けられているシール１４によって防止することができるが、上下金型１１，１２のパーティングラインにわずかな段差や不連続部分が存在するため、シールの寿命という観点からは、上述の第１〜第６実施例よりも若干劣ることになる。
【００５４】
図１１は本発明の第８実施例を示した説明図である。この第８実施例は、図１０に示した第７実施例の軸押し工具４，５の外周に取り付けたシール１４に代えて、下金型１２の軸押し工具４，５挿入部分にもシール１６を設け、このシール１６の位置に対応する上金型１１の部位にシール１７を取り付けたものである。
【００５５】
これらシール１６と１７の軸方向位置は、基本的には制約はないが、挿入するバルジ加工される素管の両端部より外側に配置することが望ましい。なぜなら、シール１６と１７の軸方向位置が素管の両端部より内側に位置する場合には、シール１６と１７が直接素管と接することになり、シールの寿命が短くなるからである。
【００５６】
この第８実施例の装置を用いれば、図示しない油圧シリンダに連結された軸押し工具４，５が液圧バルジ加工中に移動しても液漏れを防ぐことが出来、かつ、上下金型１１，１２内に注入された加工液を外へ漏らすことなく、高い圧力を保持することが可能である。但し、シール構造はやや複雑になる。
【００５７】
上記第１〜第８実施例は、下金型１２にシール１３を設けて上下金型１１，１２のパーティングラインからの液漏れを防止しようとするものであるが、下金型１２に設けたシール１３に代えて、図１２に示すように、上下金型ホルダー１８，１９の何れか一方にシール２０を設けることで、上下金型１１，１２のパーティングラインからの液漏れを防止しても良い。
【００５８】
例えば、図１２に示す第９実施例では、上記シール２０に加えて、下金型ホルダー１９に注入孔１９ａを設け、かつ、下金型ホルダー１９の両端部に軸押し工具４，５のガイド孔１９ｂを形成している。なお、図１２に示した第９実施例では、図示省略したが、軸押し工具４，５の外周にシール１４を取り付けることが望ましい。
【００５９】
この第９実施例を採用する場合は、従来の金型に、外圧を付与するための内部キャビティ内への加工液注入孔の位置を、下金型ホルダー１９の注入孔１９ａの位置に合わせる様に追加加工すれば、従来の金型を金型ホルダー１８，１９に挿入・固定することにより、内外圧を付与する本発明の液圧バルジ加工が可能となる。すなわち、現在の金型に最小の投資をするだけで良く、極めてコスト的に有効な方法である。
【００６０】
上記の本発明に係る液圧バルジ加工装置を用いてバルジ加工品を成形する場合には、素管Ｓ１を本発明に係る液圧バルジ加工装置の一対の金型１１，１２内にセットした後、注入孔３，１２ａを通じて、素管Ｓ１の内側のみならず外側全周に亘って加工液を注入する。
【００６１】
そして、上記の加工液の注入を、例えば加工液の内外両圧力を適正に制御しつつ高めるように行うことに加えて、軸押し工具４，５によって管端から軸押しする本発明の液圧バルジ加工方法により本発明の液圧バルジ加工品を製造する。
【００６２】
このような本発明によれば、キャビティ７のみならず、素管Ｓ１の両端部にも外圧ｐｏを作用させるので、上下金型１１，１２からの面圧ｐｋを小さくすることができ、その結果、軸押し方向と反対方向の摩擦応力ｐｍが減少し、軸押し加工でのキャビティ７への素管Ｓ１の供給が増加して加工歪みが均一化し、板厚の均一な、われのない製品を製造できるようになる。
【００６３】
そして、上記の本発明方法による液圧バルジ加工において、仮に素管Ｓ１に作用する面圧が増大して、素管Ｓ１と上下金型１１，１２間の摩擦応力ｐｍが増加した場合には、素管Ｓ１に作用させる内外圧の何れか一方又は両方を、少なくとも１回以上変動させれば、上記摩擦応力ｐｍが低下し、局部的な歪みの集中を防止することができる。
【００６４】
上記の実施例では、下金型１２に素管Ｓ１の外周面に作用させる加工液の注入孔１２ａを設けたものを示したが、この注入孔は上金型１１に設けても良い等、今回示した例は、あくまでも本発明の１つの具体例を示すものであり、本発明の技術的範囲内であれば、各種の設計変更は任意である。
【００６５】
【発明の効果】
以上説明したように、本発明によれば、バルジ加工の成形限界を飛躍的に向上させることが可能になり、現状の液圧バルジ成形では、割れなどの不良が発生しやすい材質や寸法であっても、液圧バルジ加工が可能になり、部品の軽量化や強度向上がなされた製品を得ることが出来るようになる。
【図面の簡単な説明】
【図１】本発明に係る液圧バルジ加工装置の第１実施例を示す斜視図である。
【図２】（ａ）は図１における金型の正面図、（ｂ）は同じく平面図、（ｃ）は同じく側面図である。
【図３】本発明のバルジ成形途中の一過程における素管に作用する力を説明する図である。
【図４】軸押し工具の外周面に設けるシールの取り付け位置の説明図で、（ａ）は先端のシール工具に取り付けた例、（ｂ）は先端のシールに連結されたロッドに取り付けた例を示す図である。
【図５】本発明に係る液圧バルジ加工装置の第２実施例を示す金型の図で、（ａ）は正面図、（ｂ）は平面図、（ｃ）は側面図である。
【図６】本発明に係る液圧バルジ加工装置の第３実施例を示す斜視図である。
【図７】本発明に係る液圧バルジ加工装置の第４実施例を示す斜視図である。
【図８】製品がＣ型形状（直角曲げ形状）の場合の図１に対応する第５実施例を示した斜視図である。
【図９】製品がＵ型形状（１８０°曲げ形状）の場合の図１に対応する第６実施例を示した斜視図である。
【図１０】本発明に係る液圧バルジ加工装置の第７実施例を示す斜視図である。
【図１１】本発明に係る液圧バルジ加工装置の第８実施例を示す斜視図である。
【図１２】本発明に係る液圧バルジ加工装置の第９実施例を示す斜視図である。
【図１３】従来の液圧バルジ加工の説明図で、（ａ）は加工前、（ｂ）加工終了時を示す縦断面図である。
【図１４】（ａ）〜（ｄ）は従来のシール工具を兼ねた軸押し工具のシール構成を夫々説明する図である。
【図１５】従来のキャビティ内のみに内外厚を作用させて液圧バルジ加工を行う従来技術の作用を説明する図で、（ａ）はキャビティ内の素管を側面から見た図、（ｂ）はキャビティ内の素管に作用する応力を説明する図である。
【図１６】通常のバルジ成形途中の一過程における素管に作用する力を説明する図である。
【図１７】従来の液圧バルジ加工装置の例を示す斜視図である。
【符号の説明】
３注入孔
４軸押し工具
５軸押し工具
７キャビティ
１１上金型
１１ａガイド孔
１２下金型
１２ａ注入孔
１２ｂガイド孔
１３〜１７シール
１８上金型ホルダー
１９下金型ホルダー
１９ａ注入孔
１９ｂガイド孔
２０シール[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic bulge processing method, a hydraulic bulge processing apparatus for performing the method, and a bulge processed product subjected to the hydraulic bulge processing.
[0002]
[Prior art]
The hydraulic bulge processing has the following features compared to normal molding methods.
{Circle around (1)} Since a slightly complicated shape having a different cross-sectional shape in the longitudinal direction can be obtained, it is possible to integrally form components that have been assembled by welding in the past.
[0003]
(2) Since work hardening is easily obtained over the entire product, a high-strength product can be obtained even if a soft blank tube is used.
(3) Since the spring back is small and the dimensional accuracy of the product is good (the shape freezing property is good), the rework process can be omitted.
[0004]
The excellent features as described above have been evaluated, and in recent years, hydraulic bulge processing has been adopted particularly in the manufacturing process of automobile parts.
A general pipe hydraulic bulging process will now be described.
For straight pipes (hereinafter referred to as “elementary pipes”) having a uniform circular cross section in the longitudinal direction as a raw material, (1) bending processing, (2) crushing processing (hereinafter referred to as “preform processing”) The product is manufactured by performing a series of processes such as (3) hydraulic bulge processing.
[0005]
In the hydraulic bulge processing, which is the final process shown in FIG. 13, the processing liquid is injected through the injection hole 3 into the raw pipe S1 set in the upper mold 1 and the lower mold 2, and the pressure of the processing liquid (hereinafter referred to as the processing liquid pressure). The inner pipe S1 is pushed in the axial direction from both pipe ends by the axial pushing tools 4 and 5 which also serve as a sealing tool (hereinafter referred to as "axial pushing"). Thus, products S2 having various cross-sectional shapes are manufactured. The shaft pushing tools 4 and 5 that also serve as a sealing tool are connected to a hydraulic cylinder (not shown), and the axial position or the shaft pushing force is controlled during bulging.
[0006]
Here, in the hydraulic bulge processing, the axial push from the pipe end in the axial direction has an effect of promoting the metal flow at the time of swelling and improving the pipe expansion limit, and plays an extremely important role.
[0007]
By the way, the machining fluid is injected into the space on the inner peripheral surface side of the blank tube that is the material for the bulge processing, but since the seal described later is applied between the axial push tool and the blank tube, the machining fluid is High pressure can be maintained without flowing out. Accordingly, the raw tube expands due to the internal pressure received from the machining fluid, and after pressing the mold, it is pressed along the shape of the cavity to complete the bulge forming.
[0008]
Although there are various methods for sealing between the shaft pushing tool and the raw tube, a typical example of the sealing method formed on the shaft pushing tools 4 and 5 is shown in FIG. FIG. 14A shows an example of sealing with end faces 4a and 5a in contact with the end face of the raw tube, FIG. 14B shows an example in which protrusions 4b and 5b are provided on the end faces 4a and 5a, and FIG. An example in which steps 4d and 5d are provided at the boundary between the end faces 4a and 5a of 5c, and (d) is an example in which an O-ring 6 is provided in the parallel parts 4c and 5c.
[0009]
That is, by such a seal, the high-pressure machining fluid supplied through the machining fluid injection hole 3 provided in at least one of the shaft pushing tools 4 and 5 can be contained in the raw tube S1. It is possible.
[0010]
In recent years, automobile parts are required to further improve the strength and thickness of the parts from the viewpoint of improving fuel consumption and collision safety performance.
That is, by using a welded pipe made of a hard material (hereinafter referred to as “high-tensile material”) having a higher tensile strength (T.S.) than that of the conventional material and a seamless steel pipe having a high deformation resistance, the strength of the parts can be reduced. There is a growing demand for weight reduction by improving collision safety performance and making products thinner. However, in general, a high-strength high-tensile material has a small elongation, and there is a problem that the probability of occurrence of a crack increases even if the same bulge processing is performed.
[0011]
In addition, in order to improve the collision safety performance, there is a method of increasing the degree of processing in the bulge processing as another method for improving the strength of the component or reducing the thickness of the material while maintaining the component strength. In other words, even if the same material is used, if the amount of strain in bulge processing can be increased (in other words, the tube expansion rate in bulge processing can be increased), the strength is improved by work hardening of the material. The thickness can also be reduced. For this purpose, there has been a demand for a technology that dramatically improves the forming limit of bulge processing.
[0012]
As described above, although automotive parts have been described, these requirements are not limited to automotive parts. Needless to say, if the bulge forming limit is improved, the application can be expanded to a wider range of applications. Absent. In addition, if a new bulge processing method that can suppress the current processing cracking is developed, it will be possible to apply difficult-to-process materials that were difficult to apply to bulge processing, and it is expected that the performance of parts will be greatly improved. ing.
[0013]
In response to these problems, while applying a compressive force in the axial direction of the pipe, a high-pressure working fluid is supplied to the inner periphery of the pipe, and the cavity of the mold and the outer circumference of the pipe in the cavity There has been disclosed a bulge processing apparatus that supplies a high-pressure machining fluid between them to control the difference between the internal pressure and the external pressure (see, for example, Patent Document 1). Also, a method of periodically changing the external pressure in a state where the processing has progressed to some extent in the bulge processing using this bulge processing apparatus is disclosed (for example, see Patent Document 2).
[0014]
[Patent Document 1]
Japanese Patent No. 3022506 (first page, FIG. 1)
[Patent Document 2]
Japanese Patent No. 2999757 (first page, FIGS. 1-2)
[0015]
Generally, a large tensile circumferential stress has a high risk of causing cracking of the material. However, in Patent Document 1 and Patent Document 2, as shown in FIG. 15, an internal pressure pi and an external pressure po are applied to the element tube S1. Thus, the tensile force (circumferential stress) σθ acting in the circumferential direction of the raw pipe S1 is reduced, and cracks during bulging are to be suppressed.
[0016]
[Problems to be solved by the invention]
By the way, in recent years, there is a demand for further expansion of the moldable range, but in order to further expand the moldable range, the bulge processing is performed in order to further expand the blank tube S1 in the cavity 7 (see FIG. 13A). At the time of bulging, it is necessary not only to reduce the tensile force σθ acting in the circumferential direction, but also to smoothly push the axial ends of both ends of the raw pipe S1 in accordance with the bulging.
[0017]
However, in the devices and methods described in Patent Document 1 and Patent Document 2 described above, as described above, only consideration is given to reducing the tensile force σθ acting in the circumferential direction of the raw tube S1 in the cavity 7. The both end portions of the raw tube S1 were not considered at all, and there was no difference from the conventional bulge processing, so that it was not possible to further expand the moldable range.
[0018]
In addition, in the devices and methods described in Patent Document 1 and Patent Document 2 described above, in addition to the internal pressure, an external pressure is also applied between the cavity and the raw pipe in the cavity. Although it is necessary, since a seal structure for applying an external pressure to the raw tube is difficult in practice, Patent Document 1 and Patent Document 2 do not disclose the seal structure of this external pressure.
[0019]
That is, in general, in a hydraulic bulge processing apparatus, in order to prevent the upper and lower molds from being lifted due to material bulging due to internal pressure, the upper and lower molds are usually hydraulic or mechanical force (hereinafter referred to as “clamping force”). However, since a high external pressure is applied to the outer peripheral portion of the raw tube, sealing cannot be performed only with the clamping force. In addition, since there is a gap between the upper and lower molds and the shaft pushing tool, leakage from the shaft pushing tool insertion portion occurs. Therefore, it is impossible for any person skilled in the art to put it to practical use based only on the contents described in Patent Document 1 and Patent Document 2.
[0020]
The present invention has been made in view of the above-mentioned conventional problems, and in the current hydraulic bulge molding, there is a risk of cracking of the material even if the material and size are likely to cause defects such as cracking. Produced by a hydraulic bulge processing method, processing apparatus, and method that can significantly reduce the forming limit of bulge processing by increasing the metal flow to the cavity by axial pressing. It aims to provide bulge processed products.
[0021]
[Means for Solving the Problems]
In order to achieve the above-described object, a hydraulic bulge processing method according to the present invention includes an element tube including an end portion in addition to a high-pressure liquid supplied to the inside of the element tube in which the element tube is set in a pair of molds. The high pressure liquid is also supplied into the gap including the outer peripheral part of the full length and the cavity of the mold, and the processing is performed while controlling at least one of the internal pressure and the external pressure applied to the raw pipe from the inside and the outside of the raw pipe. Yes.
[0022]
And a pair of molds, and a shaft pressing tool that also serves as a sealing tool that sandwiches both ends of the raw tube by inserting a tip portion into at least one of the two molds. At least one of the injection holes for injecting the processing liquid into the inside of the element pipe, and at least one of the two molds, the processing liquid is provided between the outer peripheral portion of the entire length including the end of the element pipe and the mold. And at least one of the two molds, the outer peripheral part of the entire length including the end of the raw pipe and the working fluid injected between the molds are discharged to the outside. After setting the raw pipe to the hydraulic bulge processing device according to the present invention provided with a sealing mechanism to prevent, internal pressure and external pressure are applied to the raw pipe by supplying high-pressure liquid to both the inner and outer surfaces while performing axial pressing. According to the present invention, a hydraulic bulge is applied while controlling at least one of For rugged processed products, the current hydraulic bulge molding can suppress the risk of material cracking, even with materials and dimensions that are prone to cracks and other defects, and the metal flow to the cavity by axial pressing. By increasing this, the forming limit of bulge processing can be dramatically improved.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described with reference to FIG. FIG. 16 shows one process in the middle of molding in FIG. 13 which is normal bulge molding. The raw tube S1 receives an internal pressure pi, and the tube end is being molded while being subjected to a shaft pressing process by a shaft pressing tool (not shown).
[0024]
Here, as described at the beginning, the axial pressing is extremely important for forming the raw tube S1. That is, when only the internal pressure pi is applied in the bulge processing in which the shaft is not pushed, the metal flow of the material in the axial direction (element tube S1) is small, so that the element tube S1 swells in the cavity 7 part. As a result, the plate thickness is reduced, so that cracking is likely to occur.
[0025]
On the other hand, when a shaft pressing process is applied, the material (element tube S1) is supplied from the end of the shaft to the cavity 7 where the element tube S1 bulges greatly, so that the reduction in the plate thickness is suppressed. As a result, the moldable range is expanded.
[0026]
FIG. 16 shows the force acting on the raw tube S1 during molding. In addition to the internal pressure pi that is received over the entire length of the pipe S1, the surface pressure (vertical stress) pk from the upper and lower molds 1 and 2 and friction in the direction opposite to the axial direction are applied to the portions other than the cavity 7. Stress pm (= μpk) is applied. Here, μ is a coefficient of friction between the molds 1 and 2 and the raw pipe S1.
[0027]
Therefore, as the friction stress pm increases, the supply of the material (element tube S1) to the cavity 7 part by the axial pressing process is inhibited. However, in the conventional method, the material to the cavity 7 part by the axial pressing process is inhibited. When the supply of (element tube S1) is increased to suppress cracking, a lubricant is applied to element tube S1 in order to reduce the friction coefficient μ between molds 1, 2 and element tube S1. Therefore, complicated measures such as performing a special coating process on the molds 1 and 2 have to be taken.
[0028]
However, if the external pressure po can be applied to portions other than the cavity 7, that is, both ends of the raw tube S1, the surface pressure (vertical stress) pk from the molds 1 and 2 can be reduced. The frictional stress pm in the direction opposite to the axial direction can be reduced. Accordingly, the material (element tube S1) is supplied to the cavity 7 by axial pressing without applying a complicated method such as applying or peeling the lubricant, or applying a special coating process to the molds 1 and 2. The cracks can be suppressed.
[0029]
Based on the above knowledge, the present inventor has found another effect on the cavity portion by applying pressure to the inner and outer surfaces of the raw tube by further experimenting. That is, in the bulge processing using the conventional hydraulic bulge processing apparatus as shown in FIG. 17 to bulge the raw tube only with the internal pressure, the internal pressure is increased to some extent, and the upper and lower molds 1 are part of the raw tube. , 2 is in contact with the inner surface of the cavity 7, the free deformation is prevented by the friction between the upper and lower molds 1, 2. That is, since the portion in contact with the mold tends to be restrained from being deformed, the elongation of the raw tube in the cavity 7 is concentrated in another portion not in contact with the upper and lower molds 1 and 2, and the strain distribution is It becomes uneven.
[0030]
On the other hand, in the method in which the inner and outer surfaces of the entire length of the pipe including the end are swelled by applying pressure, the working fluid interposed between the entire length of the pipe including the end and the inner surface of the mold is relatively high. If the external pressure is applied, the friction coefficient can be kept low over the entire length of the raw tube, and as a result, the processing strain becomes uniform and a product with a uniform plate thickness can be obtained.
[0031]
By the way, in the method in which the inner and outer surfaces of the entire length of the pipe including the end are bulged by applying pressure, the deformation progresses not only in the cavity but also in parts other than the cavity. Even if the surface pressure to increase and the friction stress between the blank tube and the mold increases, at least once,
(1) Keep the external pressure as it is and decrease the internal pressure.
(2) Keep the internal pressure as it is and increase the external pressure.
(3) Decrease the internal pressure and increase the external pressure,
(4) Increase internal pressure, but increase external pressure more than that,
By implementing any of the above, it was confirmed that the portion where the frictional stress pm between the mold and the raw pipe was high was relaxed, and the frictional stress pm was reduced during the subsequent bulge processing. In particular, when a sample in the middle of the deformation is observed, the raw tube is separated from the mold, and the subsequent bulging deformation is made uniform, and local strain concentration can be prevented in some cases.
[0032]
The present invention has been made on the basis of the above knowledge and the accumulation of experiments based on this knowledge.
That is, in the hydraulic bulge processing method according to the present invention, a raw pipe is set in a pair of molds, and a high-pressure liquid is supplied to the inside of the raw pipe while giving axial pressing from the end face of the raw pipe, In the hydraulic bulge processing method for expanding the raw pipe into the cavities of both molds,
In addition to the high-pressure liquid supplied to the inside of the element tube, the high-pressure liquid is also supplied to the outer periphery of the entire length of the element tube including the end and the gap including the cavity of the mold, and the element tube is supplied from inside and outside the element tube. The gist is to process while controlling at least one of the internal pressure and the external pressure to act on,
If necessary, during molding, one or both of the internal pressure and the external pressure applied to the raw pipe from the inside and the outside of the raw pipe are changed at least once.
[0033]
Further, the hydraulic bulge processing apparatus according to the present invention includes a pair of molds and at least one of these molds, each having a distal end inserted therein, and having both ends of the raw tube set in the pair of molds. It has a shaft pushing tool that also serves as a sealing tool for clamping,
An injection hole for injecting a working fluid into the element pipe is provided in at least one of the both-axis pressing tools, and an outer circumference of the entire length including the end of the element pipe in at least one of both molds. Injecting holes for injecting the machining fluid between the part and the mold are provided respectively.
In addition, at least one of both molds is provided with a seal mechanism that prevents the outer periphery of the entire length including the end of the raw tube and the working fluid injected between the molds from flowing out to the outside. To do.
[0034]
If the hydraulic bulge processing apparatus according to the present invention is used, in addition to the high-pressure liquid supplied to the inside of the pipe, the high-pressure liquid is also fed into the outer circumference of the whole pipe including the end and the gap including the mold cavity. A liquid can be supplied, and an internal pressure and an external pressure can be applied to the entire length of the raw tube from both the inner and outer surfaces. In this hydraulic bulge processing apparatus according to the present invention, when the seal mechanism is provided on the outer peripheral surface of the axial pushing tool instead of being provided on at least one of the two dies, or the mold for fixing both dies. Needless to say, the same effect can be obtained when the mold holder is provided.
[0035]
At this time, if the surface of the mold or mold holder on which the seal mechanism is mounted is substantially flat, the reliability of the seal can be improved.
Further, in the case where a seal mechanism is provided on the outer peripheral surface of the shaft pushing tool in addition to at least one of both molds, the outer peripheral surface of the shaft pushing tool and the mold are also moved during the movement of the shaft pushing tool. It is possible to prevent liquid leakage from between.
[0036]
Further, when a guide hole for a shaft pushing tool is provided in at least one of the two molds, there is no joint (so-called “parting line”) in which the two molds are overlapped in the part, and the mold Since there are no steps or discontinuities in the mold, the life of the sealing mechanism can be extended. At that time, in place of the seal mechanism provided on the outer peripheral surface of the shaft pushing tool, a seal mechanism is provided in the guide hole of the shaft pushing tool. It is possible to prevent liquid leakage from between.
[0037]
Further, when one of the pair of molds is configured to be fitted into the other mold, the reliability of the seal can be further improved.
[0038]
After setting the raw tube in the pair of molds of the hydraulic bulge processing apparatus according to the present invention described above, high pressure liquid is supplied to the inner surface and the outer surface of the raw tube while performing axial pressing, and the inner and outer surfaces of the raw tube In the hydraulic bulge processing product according to the present invention in which hydraulic bulge processing is performed while controlling at least one of the internal pressure and the external pressure applied to the raw pipe from the current hydraulic bulge molding, defects such as cracking occur. Even with materials and dimensions that are easy to handle, the risk of cracking of the material can be suppressed, and the molding flow limit for bulging is dramatically improved by increasing the metal flow to the cavity by axial pressing.
[0039]
Moreover, in the hydraulic bulge processed product according to the present invention, when molding, either or both of the internal pressure and the external pressure applied to the raw pipe from the inside and the outside of the raw pipe are changed at least once. Therefore, it is possible to further suppress the risk of material cracking and further improve the forming limit of bulge processing.
[0040]
【Example】
Hereinafter, the present invention will be described in detail based on the embodiments shown in FIGS.
FIG. 1 and FIG. 2 are explanatory views showing a first embodiment of the present invention, FIG. 1 is a sketch of a mold and a shaft pushing tool, and FIG. 2 is a view showing the front, plane, and side of the mold. .
[0041]
In FIGS. 1 and 2, reference numerals 11 and 12 denote, for example, an upper mold and a lower mold constituting the hydraulic bulge processing apparatus of the present invention, and the upper mold 11 is fitted into the lower mold 12. Of these, for example, the lower mold 12 is provided with an injection hole 12a for injecting a working fluid. Through the injection hole 12a from a pressure intensifier (not shown), as shown in FIG. A relatively high-pressure machining fluid is injected into the gap including the outer peripheral portion and the cavity 7 so that pressure is applied to the entire outer surface of the raw tube S1.
[0042]
In the hydraulic bulge processing apparatus according to the present invention, the external pressure po is applied not only to the inner surface pi of the raw pipe S1 but also to the outer surface of the entire length including the end portion. In addition to attaching the seal 13 to the upper surface 12c of the lower mold 12 which is flat, for example, in order to prevent water leakage from the side surface and the gap between the upper and lower molds 11 and 12 and the shaft pushing tools 4 and 5, For example, by providing the lower mold 12 with the guide holes 12b of the shaft pressing tools 4 and 5, the steps and discontinuous portions in the insertion portions of the shaft pressing tools 4 and 5 are eliminated, and the shaft pressing tools 4 and 5 are formed on the outer peripheral surface. A seal 14 is attached.
[0043]
As described above, in the hydraulic bulge processing apparatus of the present invention having the upper and lower molds 11 and 12 and the shaft pressing tools 4 and 5 having the above-described configuration, the shaft is pressed to perform the shaft pressing of the raw tube S1 during the bulging. The push tools 4 and 5 move, but the seal 14 attached to the shaft push tools 4 and 5 is in contact with the inner surface of the guide hole 12b at the end of the lower mold 12 and maintains a high pressure. The seal 14 may be attached to the tip sealing tool 4e, 5e as shown in FIG. 4 (a), or the tip sealing tool 4e, 5e, as shown in FIG. 1 or FIG. 4 (b). You may attach to the rods 4f and 5f connected with 5e.
[0044]
Further, instead of attaching the seal 14 to the outer peripheral surface of the shaft pushing tools 4, 5, a seal 15 may be attached to the inner peripheral surface of the guide hole 12b as in the second embodiment shown in FIG. Water leakage from the side surface portion between the upper mold 11 and the lower mold 12 and water leakage from the gap between the upper and lower molds 11 and 12 and the shaft pressing tools 4 and 5 can be prevented. In the case shown in FIG. 5, it goes without saying that the seal 14 need not be attached to the shaft pushing tools 4 and 5.
[0045]
In the example in which the guide holes 12b of the shaft pressing tools 4 and 5 are provided in the lower mold 12, the seal structure and the mold structure for holding the external pressure are very simple, and the working fluid is held at a high pressure both in the internal and external pressures. Can be used and the seal life is long. Further, the raw tube S1 can be taken out and inserted in the same manner as a conventional mold. In the example shown in FIGS. 1, 2 and 5, the length of the guide hole 12b of the shaft pushing tools 4 and 5 is expressed to be relatively long. Since it is only necessary to have a length obtained by adding the movable length of the shaft pushing tools 4 and 5 at the time of insertion and removal of S1 and the amount of shaft pushing during bulging, the size of the mold is not limited even if this guide hole 12b is provided. It is not so large.
[0046]
FIG. 6 is an explanatory view showing a third embodiment of the present invention, which has a configuration substantially similar to that of FIG. However, the upper surface 12c of the lower mold 12 to which the seal 13 is attached has a concave shape at the central portion, and the concave central horizontal surface portion 12ca and the inclined surface portion 12cc that connects the central horizontal surface portion 12ca and the horizontal surface portions 12cb on both sides. A seal 13 is attached. The third embodiment shown in FIG. 6 has a slightly simpler mold configuration than the first embodiment in which the upper mold 11 shown in FIG.
[0047]
FIG. 7 is an explanatory view showing a fourth embodiment of the present invention, in which the guide holes 11a and 12b of the shaft pushing tool with which the seals 14 attached to the shaft pushing tools 4 and 5 are in contact with the upper die 11 and the lower die. Except for the fact that one mold 12 is provided, the configuration is almost similar to that shown in FIG.
[0048]
The fourth embodiment shown in FIG. 7 is easier to insert and take out the element tube S1 because there is a space margin than the first embodiment shown in FIG. 1 and the second embodiment shown in FIG. There are advantages. Further, the upper and lower molds 11 and 12 are attached to an upper and lower bed (not shown) and are moved up and down hydraulically or mechanically. In the fourth embodiment shown in FIG. When the connecting hydraulic cylinder is mounted on the same bed as the upper mold 11, the moving distance of the shaft pushing tool 4 is shortened and the insertion and removal of the raw tube S1 are easy, so the workability is greatly improved. To do.
[0049]
The first to fourth embodiments described above show the embodiment in which the product shape is substantially straight. However, the present invention can also be applied to a three-dimensional complicated shape component represented by a normal automobile component. Needless to say. For example, FIGS. 8 and 9 show a first embodiment corresponding to the first embodiment of the present invention shown in FIG. 1 in the case where the product has a C-shape (right-angle bend shape) and a U-shape (180 ° bend shape), respectively. 5 and 6 show the sixth embodiment.
[0050]
FIG. 10 is an explanatory view showing a seventh embodiment of the present invention. The seventh embodiment is different from the first embodiment shown in FIG. 1 in that the upper and lower molds 11 and 12 are not provided with guide holes for the axial pushing tool, and the upper mold 11 is replaced by the lower mold 12. The structure is the same as that of the first embodiment except that the upper mold 11 is simply placed on the lower mold 12 without using the fitting structure.
[0051]
In the seventh embodiment, when the seal 14 attached to the outer periphery of the shaft pushing tools 4 and 5 and the seal 13 attached to the lower mold 12 are located on the same line in the axial direction, an unillustrated element is shown. The pressure applied to the outer surface of the pipe, that is, the pressure of the machining liquid injected through the injection hole 12a from a pressure intensifier (not shown), and the guide holes of the axial pressing tools 4 and 5 are provided in the mold as in the first embodiment. It can be maintained at a high pressure as much as when it is provided. However, the seal structure is somewhat complicated.
[0052]
However, when the axial positions of the seal 14 attached to the outer periphery of the shaft pushing tools 4 and 5 and the seal 13 attached to the lower mold 12 do not coincide with each other, the pressure holding level decreases. Accordingly, in the seventh embodiment, for example, in the first stage, the pressure acting on the outer surface of the raw pipe is set to a relatively low pressure, and the molding is performed while the shaft pushing tools 4 and 5 are moved, and the seal 14 and the lower metal When the seal 13 attached to the mold 12 reaches a position on the same line in the axial direction, control such as applying a high pressure to the outer surface of the raw tube may be performed.
[0053]
Further, in the seventh embodiment, liquid leakage from the gap between the upper and lower molds 11 and 12 and the axial pressing tools 4 and 5 and leakage during movement of the axial pressing tools 4 and 5 during hydraulic bulging are as follows. This can be prevented by the seal 14 attached to the outer periphery of the shaft pushing tools 4 and 5, but since there are slight steps and discontinuous portions in the parting lines of the upper and lower molds 11 and 12, the life of the seal is called From the viewpoint, it is slightly inferior to the first to sixth embodiments described above.
[0054]
FIG. 11 is an explanatory view showing an eighth embodiment of the present invention. In the eighth embodiment, instead of the seal 14 attached to the outer periphery of the shaft pressing tools 4 and 5 of the seventh embodiment shown in FIG. 16 is provided, and a seal 17 is attached to a portion of the upper mold 11 corresponding to the position of the seal 16.
[0055]
The axial positions of the seals 16 and 17 are basically not limited, but it is desirable to dispose them outside the both ends of the blank tube to be inserted. This is because when the axial positions of the seals 16 and 17 are located on the inner side of the both ends of the raw tube, the seals 16 and 17 are in direct contact with the raw tube and the life of the seal is shortened.
[0056]
If the apparatus of the eighth embodiment is used, liquid leakage can be prevented even if the axial push tools 4 and 5 connected to a hydraulic cylinder (not shown) move during the hydraulic bulging, and the upper and lower molds 11 can be prevented. , 12 can be maintained at a high pressure without leaking the machining fluid injected into the outside. However, the seal structure is somewhat complicated.
[0057]
In the first to eighth embodiments, the lower mold 12 is provided with the seal 13 to prevent liquid leakage from the parting lines of the upper and lower molds 11, 12. As shown in FIG. 12, instead of the seal 13, the seal 20 is provided in either one of the upper and lower mold holders 18 and 19, thereby preventing liquid leakage from the parting line of the upper and lower molds 11 and 12. May be.
[0058]
For example, in the ninth embodiment shown in FIG. 12, in addition to the seal 20, an injection hole 19a is provided in the lower mold holder 19, and guides for the axial pressing tools 4, 5 are provided at both ends of the lower mold holder 19. A hole 19b is formed. Although not shown in the ninth embodiment shown in FIG. 12, it is desirable to attach the seal 14 to the outer periphery of the shaft pushing tools 4 and 5.
[0059]
When this ninth embodiment is adopted, the position of the machining fluid injection hole into the internal cavity for applying external pressure to the conventional mold is matched with the position of the injection hole 19a of the lower mold holder 19. If additional processing is performed, the hydraulic bulge processing of the present invention for applying the internal / external pressure can be performed by inserting and fixing the conventional mold to the mold holders 18 and 19. That is, it is an extremely cost effective method that requires only minimal investment in the current mold.
[0060]
In the case of forming a bulged product using the above-described hydraulic bulge processing apparatus according to the present invention, after the base tube S1 is set in the pair of molds 11 and 12 of the hydraulic bulge processing apparatus according to the present invention. Through the injection holes 3 and 12a, the processing liquid is injected not only inside the raw tube S1 but also around the entire outer periphery.
[0061]
Then, in addition to performing the above-mentioned injection of the machining fluid so as to increase the pressure while appropriately controlling the inner and outer pressures of the machining fluid, for example, the hydraulic pressure of the present invention is axially pushed from the pipe end by the axial pushing tools 4 and 5. The hydraulic bulge processed product of the present invention is manufactured by the bulge processing method.
[0062]
According to the present invention as described above, the external pressure po is applied not only to the cavity 7 but also to both ends of the raw pipe S1, so that the surface pressure pk from the upper and lower molds 11 and 12 can be reduced, and as a result. The friction stress pm in the direction opposite to the axial direction decreases, the supply of the raw tube S1 to the cavity 7 in the axial pressing process increases, the processing strain becomes uniform, and the product with uniform thickness is obtained. Can be manufactured.
[0063]
In the hydraulic bulge processing according to the above-described method of the present invention, if the surface pressure acting on the raw pipe S1 increases and the friction stress pm between the raw pipe S1 and the upper and lower molds 11 and 12 increases, If either or both of the internal and external pressures acting on the element tube S1 are varied at least once or more, the frictional stress pm is reduced, and local strain concentration can be prevented.
[0064]
In the above-described embodiment, the lower mold 12 is provided with the machining liquid injection hole 12a that acts on the outer peripheral surface of the raw pipe S1, but this injection hole may be provided in the upper mold 11, etc. The example shown this time shows only one specific example of the present invention, and various design changes are arbitrary within the technical scope of the present invention.
[0065]
【The invention's effect】
As described above, according to the present invention, it becomes possible to dramatically improve the forming limit of bulge processing, and in the current hydraulic bulge forming, it is a material and size that are liable to cause defects such as cracks. However, hydraulic bulge processing becomes possible, and it becomes possible to obtain a product with reduced weight and improved strength.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a first embodiment of a hydraulic bulge processing apparatus according to the present invention.
2A is a front view of the mold in FIG. 1, FIG. 2B is a plan view, and FIG. 2C is a side view.
FIG. 3 is a diagram for explaining a force acting on a raw tube in a process during bulge forming according to the present invention.
FIGS. 4A and 4B are explanatory views of a position where a seal provided on an outer peripheral surface of a shaft pushing tool is attached, in which FIG. 4A is an example where the seal is attached to a tip seal tool, and FIG. FIG.
5A and 5B are diagrams of a mold showing a second embodiment of the hydraulic bulge processing apparatus according to the present invention, where FIG. 5A is a front view, FIG. 5B is a plan view, and FIG. 5C is a side view.
FIG. 6 is a perspective view showing a third embodiment of the hydraulic bulge processing apparatus according to the present invention.
FIG. 7 is a perspective view showing a fourth embodiment of the hydraulic bulge processing apparatus according to the present invention.
FIG. 8 is a perspective view showing a fifth embodiment corresponding to FIG. 1 in a case where the product has a C-shape (right-angled bending shape).
FIG. 9 is a perspective view showing a sixth embodiment corresponding to FIG. 1 when the product has a U shape (180 ° bent shape).
FIG. 10 is a perspective view showing a seventh embodiment of the hydraulic bulge processing apparatus according to the present invention.
FIG. 11 is a perspective view showing an eighth embodiment of the hydraulic bulge processing apparatus according to the present invention.
FIG. 12 is a perspective view showing a ninth embodiment of the hydraulic bulge processing apparatus according to the present invention.
FIGS. 13A and 13B are explanatory diagrams of conventional hydraulic bulge processing, where FIG. 13A is a longitudinal sectional view showing a state before processing and FIG. 13B at the end of processing;
FIGS. 14A to 14D are views for explaining a seal configuration of a shaft pushing tool that also serves as a conventional sealing tool. FIG.
15A and 15B are views for explaining the action of a conventional technique in which the inner and outer thicknesses are applied only to the inside of the cavity to perform the hydraulic bulge processing, and FIG. () Is a figure explaining the stress which acts on the raw pipe | tube in a cavity.
FIG. 16 is a diagram for explaining a force acting on a raw tube in a process during normal bulge forming.
FIG. 17 is a perspective view showing an example of a conventional hydraulic bulge processing apparatus.
[Explanation of symbols]
3 Injection hole
4-axis push tool
5 axis push tool
7 cavity
11 Upper mold
11a Guide hole
12 Lower mold
12a injection hole
12b Guide hole
13-17 Seal
18 Upper mold holder
19 Lower mold holder
19a injection hole
19b Guide hole
20 seals

Claims

一対の金型内に素管をセットし、素管の端面より軸押し加工を付与しつつ、素管の内部に高圧液体を供給して、前記両金型のキャビティ内に素管を膨出する液圧バルジ加工方法において、
前記素管内部に供給する高圧液体に加えて、端部を含む素管全長の外周部と金型のキャビティを含む空隙内にも高圧液体を供給し、前記素管の内部及び外部から素管に作用させる内圧と外圧の少なくとも何れか一方を制御しつつ加工することを特徴とする液圧バルジ加工方法。A raw tube is set in a pair of molds, and a high-pressure liquid is supplied to the inside of the raw tubes while applying axial pressing from the end faces of the raw tubes, and the raw tubes are expanded into the cavities of both molds. In the hydraulic bulge processing method to
In addition to the high-pressure liquid supplied to the inside of the element tube, the high-pressure liquid is also supplied to the outer periphery of the entire length of the element tube including the end and the gap including the cavity of the mold, and the element tube is supplied from inside and outside the element tube. A hydraulic bulge processing method, wherein the processing is performed while controlling at least one of an internal pressure and an external pressure applied to the bulge.

請求項１記載の液圧バルジ加工方法において、
成形中、前記素管の内部及び外部から素管に作用させる内圧と外圧の何れか一方又は両方を、少なくとも１回以上変動させることを特徴とする液圧バルジ加工方法。The hydraulic bulge processing method according to claim 1,
A hydraulic bulging method characterized in that, during molding, either or both of an internal pressure and an external pressure applied to the raw pipe from inside and outside the raw pipe are changed at least once.

一対の金型と、
これら両金型の少なくとも何れか一方に夫々先端部を挿入され、前記一対の金型にセッティングされた素管の両端を挟持するシール工具を兼ねた軸押し工具とを備え、
前記両軸押し工具の少なくとも何れか一方には前記素管の内部に加工液を注入する注入孔が、また、両金型の少なくとも何れか一方には前記素管の端部を含む全長の外周部と金型間に加工液を注入する注入孔が夫々設けられ、
かつ、両金型の少なくとも何れか一方に、前記素管の端部を含む全長の外周部と金型間に注入された加工液の外部への流出を防ぐシール機構を設けたことを特徴とする液圧バルジ加工装置。A pair of molds;
A shaft pushing tool that also serves as a sealing tool that sandwiches both ends of the raw tube set in the pair of molds, each having a tip inserted into at least one of these molds,
An injection hole for injecting a working fluid into the element pipe is provided in at least one of the both-axis pressing tools, and an outer circumference of the entire length including the end of the element pipe in at least one of both molds. Injecting holes for injecting the machining fluid between the part and the mold are provided respectively.
In addition, at least one of both molds is provided with a seal mechanism that prevents the outer periphery of the entire length including the end of the raw tube from flowing out of the machining liquid injected between the molds. Hydraulic bulge processing equipment.

請求項３記載の液圧バルジ加工装置において、
前記シール機構を、両金型の少なくとも何れか一方に設けるのに代えて、前記両金型を夫々固定する両金型ホルダーの少なくとも何れか一方に設けたことを特徴とする液圧バルジ加工装置。In the hydraulic bulge processing apparatus according to claim 3,
A hydraulic bulging apparatus characterized in that, instead of providing the sealing mechanism on at least one of both molds, the sealing mechanism is provided on at least one of both mold holders for respectively fixing the both molds. .

請求項３又は４記載の液圧バルジ加工装置において、
前記シール機構を装着する金型又は金型ホルダーの面がほぼ平面であることを特徴とする液圧バルジ加工装置。In the hydraulic bulge processing apparatus according to claim 3 or 4,
A hydraulic bulging apparatus characterized in that a surface of a mold or a mold holder on which the seal mechanism is mounted is substantially flat.

請求項３〜５の何れか記載の液圧バルジ加工装置において、
前記シール機構を、両金型又は金型ホルダーの少なくとも何れか一方に設けるのに代えて、前記軸押し工具の外周面に設けたことを特徴とする液圧バルジ加工装置。In the hydraulic bulge processing device according to any one of claims 3 to 5,
A hydraulic bulge processing apparatus, wherein the sealing mechanism is provided on an outer peripheral surface of the shaft pushing tool instead of being provided on at least one of both molds or a mold holder.

前記軸押し工具の外周面にもシール機構を設けたことを特徴とする請求項３〜５の何れか記載の液圧バルジ加工装置。The hydraulic bulge processing apparatus according to any one of claims 3 to 5, wherein a sealing mechanism is also provided on an outer peripheral surface of the shaft pushing tool.

前記両金型の少なくとも何れか一方に、軸押し工具のガイド孔を設けたことを特徴とする請求項３〜７の何れか記載の液圧バルジ加工装置。The hydraulic bulge processing apparatus according to any one of claims 3 to 7, wherein a guide hole for a shaft pressing tool is provided in at least one of the two molds.

請求項６又は７を引用する請求項８記載の液圧バルジ加工装置において、軸押し工具の外周面に設けるシール機構に代えて、軸押し工具の前記ガイド孔にシール機構を設けたことを特徴とする液圧バルジ加工装置。9. The hydraulic bulge processing apparatus according to claim 8, wherein a sealing mechanism is provided in the guide hole of the axial pushing tool instead of the sealing mechanism provided on the outer peripheral surface of the axial pushing tool. Hydraulic bulge processing equipment.

前記一対の金型の一方の金型を他方の金型にはめ込む構造としたことを特徴とする請求項３〜９の何れか記載の液圧バルジ加工装置。The hydraulic bulge processing apparatus according to claim 3, wherein one of the pair of molds is fitted into the other mold.

請求項３〜１０の何れか記載の液圧バルジ加工装置の一対の金型内に素管をセットした後、軸押し加工を行いつつ素管の内面と外面に高圧液を供給し、素管の内部及び外部から素管に作用させる内圧と外圧の少なくとも何れか一方を制御しつつ液圧バルジ加工を施したことを特徴とする液圧バルジ加工品。A high pressure liquid is supplied to the inner surface and the outer surface of the raw tube while performing a shaft pushing process after the raw tube is set in the pair of molds of the hydraulic bulge processing device according to any one of claims 3 to 10, A hydraulic bulge processed product, wherein hydraulic bulge processing is performed while controlling at least one of an internal pressure and an external pressure applied to the raw pipe from inside and outside.

請求項１１記載の液圧バルジ加工品において、
成形中、前記素管の内部及び外部から素管に作用させる内圧と外圧の何れか一方又は両方を、少なくとも１回以上変動させたことを特徴とする液圧バルジ加工品。In the hydraulic bulge processing product according to claim 11,
A hydraulic bulge processed product characterized in that, during molding, either or both of an internal pressure and an external pressure applied to the raw pipe from inside and outside the raw pipe are changed at least once.