JP3850196B2

JP3850196B2 - Pipe body manufacturing method, manufacturing apparatus, pipe body manufactured by these, and image forming apparatus using this pipe body

Info

Publication number: JP3850196B2
Application number: JP2000027841A
Authority: JP
Inventors: 崇史近藤; 圭二石野
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 2000-02-04
Filing date: 2000-02-04
Publication date: 2006-11-29
Anticipated expiration: 2020-02-04
Also published as: JP2001212615A

Description

【０００１】
【発明の属する技術分野】
本発明は、金属プレートを曲げ加工することによって断面が多角形状のパイプ体を製造するパイプ体の製造方法、製造装置、製造されたパイプ体及びこのパイプ体を用いた画像形成装置に関する。
【０００２】
【従来の技術】
従来から、断面が多角形状のパイプ体を製造する技術として、特公平７−３４９３６号公報、特開平１１−２９０９４０号公報に記載のものが知られている。
【０００３】
その特公平７−３４９３６号公報においては、金属プレートをロール成形して角パイプ状とした後に、金属プレートの合わせ目（すなわち、金属プレートの幅方向両端縁をなす一対の辺同士）を溶接してパイプ体を製造している。
【０００４】
また、特開平１１−２９０９４０号公報においては、矩形状の金属プレートを素材として、プレス加工（曲げ加工）により断面が長方形状のパイプ体を製造している。この製造方法は、金属プレートの幅方向両端部（一対の辺部）を長さ方向に沿って折り曲げ略直角に起立させることにより一次成形品を成形する第１曲げ工程と（図４参照）、その一次成形品の未折曲げ部（図４における符号９）の中央部分を上方に凸となるように湾曲させ、かつ、この中央部分に対して両側部分を略直角に折り曲げ起立させることにより二次成形品を成形する第２曲げ工程と（図６参照）、その二次成形品の一対の側壁部（図６における符号３，４）を互いに内側に向けて押圧することにより、金属プレートの一対の辺同士（図６においては符号５ｃ，５ｄで表される端面同士）を突き合わせるリストライク工程とからなっている。
【０００５】
【発明が解決しようとする課題】
ところで、上記特公平７−３４９３６号公報に記載のパイプ体の製造方法では、ロール成形後に金属プレートの一対の辺同士を溶接する必要があるが、一般にロール成形及び溶接にはコストがかかるほか、溶接時に生じる金属の熱ひずみにより製品の精度が劣化するという問題がある。
【０００６】
一方、特開平１１−２９０９４０号公報に記載のパイプ体の製造方法では、溶接を伴わずプレス成形のみによってパイプ体を製造することができるが、このように製造されたパイプ体については金属プレートの一対の辺同士の接合部に隙間が目立つことが多く、その一対の辺同士が密着したパイプ体を量産時にばらつきなく安定して製造することは難しい。
【０００７】
本発明は、上記の事情に鑑みて為されたもので、金属プレートをプレス成形により加工して溶接することなくパイプ体を製造する場合であっても、量産時にばらつきなく安定して隙間の目立たないパイプ体を製造することのできるパイプ体の製造技術を提供することを課題としている。
【０００８】
【課題を解決するための手段】
上記課題を解決するため、請求項１の発明は、互いに平行な一対の辺を有する金属プレートを該一対の辺と平行な直線に沿って複数箇所で折り曲げるとともに該一対の辺同士を接合させることにより断面が四角形の一辺が形成されるパイプ体を製造するパイプ体の製造方法であって、
前記接合部が形成される辺と隣接する辺に対応する面に内側に向かって凸となるように凸部を設け、該凸部に生じるスプリングバック力によって前記一対の辺同士を密着させることを特徴とするパイプ体の製造方法。
請求項２の発明は、請求項１に記載のパイプ体の製造方法において、前記凸部を前記接合部が形成される辺と対向する辺に対応する面の近くに設けることを特徴とするパイプ体の製造方法。
請求項３の発明は、互いに平行な一対の辺を有する金属プレートを該一対の辺と平行な直線に沿って複数箇所で折り曲げるとともに該一対の辺同士を接合させることにより断面が四角形の一辺が形成されるパイプ体を製造するパイプ体の製造方法であって、前記接合部が形成される辺と対向する辺に対応する面に内側に向かって凸となるように凸部を設け、該凸部に生じるスプリングバック力によって前記一対の辺同士を密着させることを特徴とする。
請求項４の発明は、互いに平行な一対の辺を有する金属プレートを該一対の辺と平行な直線に沿って複数箇所で折り曲げるとともに該一対の辺同士を接合させることにより断面が三角、五角形、六角形、八角形のうちのいずれかの角形の一辺が形成されるパイプ体を製造するパイプ体の製造方法であって、
前記接合部が形成される辺以外のいずれかの辺に対応する面に内側に向かって凸となるように凸部を設け、該凸部に生じるスプリングバック力によって前記一対の辺同士を密着させることを特徴とする。
請求項５の発明は、請求項１乃至請求項４のいずれか１項に記載のパイプ体の製造方法において、前記金属プレートを前記直線に沿って前記多角形の各頂点の角度に合わせて折り曲げるとともに、前記接合部が形成される辺以外のいずれかの辺に対応する面を前記多角形の内側に向かって凸となるように湾曲させて中間成形品を成形し、
該中間成形品の湾曲した面以外の面であって前記接合部が形成される辺以外の辺に対応する面に外力を加えることにより、前記湾曲した面の湾曲を取り除きつつ前記一対の辺同士を接合させるとともに前記凸部を形成することを特徴とする。
請求項６の発明は、請求項５に記載のパイプ体の製造方法において、
前記金属プレートを前記多角形のいくつかの頂点の角度に合わせて折り曲げ断面凹状とし、前記金属プレートを加圧する内部加圧パンチ部材をその凹状の内部に進入させ、該内部加圧パンチ部材により前記湾曲した面を形成するとともに前記金属プレートを前記多角形の残余の頂点の角度に合わせて折り曲げ、前記一対の辺同士の間を通して前記内部加圧パンチ部材を引き抜くことにより前記中間成形品を成形することを特徴とする。
請求項７の発明は、互いに平行な一対の辺を有する金属プレートを該一対の辺と平行な直線に沿って複数箇所で折り曲げるとともに該一対の辺同士を接合させることにより、断面が四角形の一辺が形成されるパイプ体を製造するパイプ体の製造装置であって、
前記接合部が形成される辺と隣接する辺に対応する面に該多角形の内側に向かって凸となるように凸部を形成する凸部形成手段を備え、前記凸部に生じるスプリングバック力によって前記一対の辺同士を密着させることを特徴とする。
請求項８の発明は、請求項７に記載のパイプ体の製造装置において、前記凸部形成手段は前記凸部を前記接合部が形成される辺と対向する辺に対応する面の近くに形成することを特徴とする。
請求項９の発明は、互いに平行な一対の辺を有する金属プレートを該一対の辺と平行な直線に沿って複数箇所で折り曲げるとともに該一対の辺同士を接合させることにより、断面が四角形の一辺が形成されるパイプ体を製造するパイプ体の製造装置であって、
前記接合部が形成される辺と対向する辺に対応する面に該多角形の内側に向かって凸となるように凸部を形成する凸部形成手段を備え、前記凸部に生じるスプリングバック力によって前記一対の辺同士を密着させることを特徴とする。
請求項１０の発明は、互いに平行な一対の辺を有する金属プレートを該一対の辺と平行な直線に沿って複数箇所で折り曲げるとともに該一対の辺同士を接合させることにより断面が三角形、五角形、六角形、八角形のうちのいずれかの角形の一辺が形成されるパイプ体を製造するパイプ体の製造装置であって、
前記接合部が形成される辺以外のいずれかの辺に対応する面に内側に向かって凸となるように凸部を設ける凸部形成手段を備え、該凸部に生じるスプリングバック力によって前記一対の辺同士を密着させることを特徴とする。
請求項１１の発明は、請求項７乃至請求項１０のいずれか１項に記載のパイプ体の製造装置において、
前記金属プレートを前記直線に沿って前記多角形の各頂点の角度に合わせて折り曲げるとともに前記接合部が形成される辺以外のいずれかの辺に対応する面を前記多角形の内側に向かって凸となるように湾曲させてなる中間成形品がセットされる加工装置本体と、該加工装置本体にセットされた前記中間成形品の湾曲した面以外の面であって前記接合部が形成される辺以外の辺に対応する面に外力を加えるパンチ部材とを備え、前記凸部形成手段は前記パンチ部材に設けられ、該パンチ部材は前記湾曲した面の湾曲を取り除きつつ前記一対の辺同士を接合させるとともに、前記凸部形成手段により前記外力を加える面に前記凸部を形成することを特徴とする。
請求項１２の発明は、互いに平行な一対の辺を有する金属プレートを該一対の辺と平行な直線に沿って複数箇所で折り曲げるとともに、該一対の辺同士を接合させることにより製造された断面が四角形の一辺が形成されたパイプ体であって、
前記接合部が形成される辺と隣接する辺に対応する面に内側に向かって凸となるように凸部が設けられ、該凸部に生じるスプリングバック力によって前記一対の辺同士が密着していることを特徴とする。
請求項１３の発明は、請求項１２に記載のパイプ体であって、前記凸部が前記接合部が形成された辺と対向する辺に対応する面の近くに設けられていることを特徴とする。
請求項１４の発明は、互いに平行な一対の辺を有する金属プレートを該一対の辺と平行な直線に沿って複数箇所で折り曲げるとともに、該一対の辺同士を接合させることにより製造された断面が四角形の一辺が形成されたパイプ体であって、
前記接合部が形成される辺と対向する辺に対応する面に内側に向かって凸となるように凸部が設けられ、該凸部に生じるスプリングバック力によって前記一対の辺同士が密着していることを特徴とする。
請求項１５の発明は、互いに平行な一対の辺を有する金属プレートを該一対の辺と平行な直線に沿って複数箇所で折り曲げるとともに該一対の辺同士を接合させることにより断面が三角、五角形、六角形、八角形のうちのいずれかの角形の一辺が形成されたパイプ体であって、
前記接合部が形成される辺以外のいずれかの辺に対応する面に内側に向かって凸となるように凸部を設けられ、該凸部に生じるスプリングバック力によって前記一対の辺同士が密着していることを特徴とする。
請求項１６の発明は、請求項１２ないし請求項１５のいずれか１項に記載のパイプ体を有する画像形成装置である。
【００２９】
上記請求項１、請求項３、請求項４、請求項７、請求項９、請求項１０、請求項１２、請求項１４、請求項１５の発明によれば、凸部の変形が弾性的に回復する際に生じるスプリングバック力によって金属プレートの一対の辺同士を密着させることになるので、金属プレートをプレス成形により加工して溶接することなくパイプ体を製造する場合であっても、量産時にばらつきなく安定して隙間の目立たないパイプ体を製造することができる。
【００３０】
また、請求項１乃至請求項４、請求項７乃至請求項１０、請求項１２乃至請求項１５のいずれかの発明によれば、金属プレートの一対の辺の接合部が多角形の一辺上に形成される際に、この接合部が形成される辺と異なる辺に対応する面に凸部を設けることになるので、例えば凸部を多角形の外側から加圧して形成する場合に、その加圧力の影響により一対の辺同士がずれて接合に支障をきたす等の事態を防止することができる。とりわけ請求項２、請求項８又は請求項１３の発明によれば、断面が四角形のパイプ体について、接合部が形成される辺と隣接する辺に対応する面上であって、その接合部が形成される辺と対向する辺に対応する面の近くに凸部を設けることになるので、凸部に生じるスプリングバック力により金属プレートの一対の辺同士を効率的に密着させることができるという効果も得られる。
【００３１】
さらに、請求項５、請求項６又は請求項１１の発明によれば、多角形の内側に向かって凸となるように湾曲した面を有して一対の辺同士が離間した状態にある中間成形品を成形し、その湾曲した面の湾曲を取り除きつつ一対の辺同士を接合させるように外力を加えてパイプ体を製造することになるので、製造されたパイプ体の各面の平坦性を、事後的に大幅な修正加工を施すことなく容易に確保することができる。
【００３４】
【発明の実施の形態】
本発明の実施の形態を図面に基づいて説明する。
【００３５】
［断面が四角形状のパイプ体の製造］
図１は断面が長方形状のパイプ体の概略構成を示す斜視図であり、図２はそのパイプ体の断面形状を示す正面図である。このパイプ体１は、図２に示す長方形の各辺に対応する四つの面（構成壁部）として、底壁部２、底壁部２に隣接する一対の側壁部３，４、及び底壁部２に対向する上壁部５を有している。
【００３６】
側壁部３，４にはそれぞれパイプ体１の内側に向かって凸となるように凸部３ａ，４ａが複数形成されている。上壁部５は一対の合わせ目構成壁部５ａ，５ｂがそれぞれの端面５ｃ，５ｄで互いに密着してなり、上壁部５の中央には合わせ目（接合部）５ｅが形成されている。側壁部３，４に形成された凸部３ａ，４ａは、その合わせ目５ｅ及びパイプ体１の軸線を通る中心線Ｏ１に対して左右対称をなしている。
【００３７】
このパイプ体１は、図３に示す互いに平行な一対の辺６ｅ，６ｅを有する矩形状の金属プレート６を素材として、プレス加工により成形される。金属プレート６にはあらかじめネジ穴６ａ，６ａが適宜箇所に形成され、このネジ穴６ａ，６ａは、パイプ体１を後述のフレームとして用いる際に取付用の係合部（パイプ体１に他のパイプ体等を取り付ける場合に、又はパイプ体１を他の部材に取り付ける場合に用いられる係合部）として使用される。なお、このような係合部としてネジ穴６ａ，６ａの代わりに切欠き等が形成されていてもよい。
【００３８】
そのプレス加工においては、まず、第１加工ステップとして、一対の辺６ｅ，６ｅと同方向に延びる折曲げ線６ｃ，６ｃに沿って、金属プレート６の辺部６ｂ，６ｂを直角（９０°）に折り曲げ起立させる。これにより、その辺部６ｂ，６ｂが一対の合わせ目構成壁部５ａ，５ｂをなし、図４に示す断面凹状の一次中間成形品８が成形される。なお、図４において符号９は未折曲げ部、符号６ｄ，６ｄは後に未折曲げ部９を折り曲げる際の基準となる折曲げ線であり、金属プレート６の寸法、折曲げ線６ｃ及び折曲げ線６ｄの位置は、プレス加工による金属の伸び量を考慮して決定されている。
【００３９】
この一次中間成形品８のプレス加工には、例えば図５に示すプレス装置１０を使用する。プレス装置１０は第一固定プレート１１と第一加圧パンチ部材１２と可動プレート１２’とから概略構成され、第一固定プレート１１には一次中間成形品８の外形状（合わせ目構成壁部５ａ，５ｂの外形状）に対応する形状の周壁１１ａに囲まれてなる凹所１３が設けられている。また、第一加圧パンチ部材１２は一次中間成形品８の内形状に対応する形状を有し、凹所１３に対して図示を略す油圧シリンダ装置により上下動するようになっている。可動プレート１２’は第一加圧パンチ部材１２の上下動に伴い第一固定プレート１１の周壁１１ａに対して摺動するように、図示を略す他の油圧シリンダ装置に接続されている。
【００４０】
その第一加圧パンチ部材１２及び可動プレート１２’が上方に位置する状態で固定プレート１１よりもＨだけ高い位置にある可動プレート１２’上に金属プレート６を載置し（図５（ａ））、第一加圧パンチ部材１２を下降させてこれと可動プレート１２’とで金属プレート６を挟持し加圧することにより、一次中間成形品８が成形される（図５（ｂ））。
【００４１】
次いで、第２加工ステップとして、一対の辺６ｅ，６ｅと同方向に延びる折曲げ線６ｄ，６ｄに沿って一次中間成形品８の未折曲げ部９を直角に折り曲げるとともに、その折曲げ線６ｄ，６ｄに挟まれる部分を上方に向かって凸となるように湾曲させ、合わせ目構成壁部５ａ，５ｂ以外の残余の構成壁部である底壁部２と側壁部３，４とを形成する。これにより、図６、図７に示すように、中間成形品としての二次中間成形品１４が成形される。
【００４２】
この二次中間成形品１４のプレス加工には、例えば図８に示すプレス装置１７を使用する。プレス装置１７は、凹所１８を有する第二固定プレート１９と、内部加圧パンチ部材としての第二加圧パンチ部材２０と、可動プレート２０’とから概略構成されている。凹所１８は二次中間成形品１４の外形状（側壁部３，４の外形状）に対応する形状の周壁１９ａに囲まれてなる。第二加圧パンチ部材２０は凹所１８に対して図示を略す油圧シリンダ装置により上下動し、その下部には二次中間成形品１４の底壁部２の内形状と側壁部３，４の下部内形状とに対応する形状のパンチ部２０ａが設けられている。可動プレート２０’は第二加圧パンチ部材２０の上下動に伴い第二固定プレート１９に対して摺動するように、図示を略す他の油圧シリンダ装置に接続されている。この可動プレート２０’の上面２０ａ’は、二次中間成形品１４の底壁部２の外形状と対応する形状に仕上げられている。
【００４３】
その第二加圧パンチ部材２０及び可動プレート２０’が上方に位置する状態で固定プレート１９よりもＨ’だけ高い位置にある可動プレート２０’上に一次中間成形品８を載置し（図８（ａ））、第二加圧パンチ部材２０を下降させて一次中間成形品８の凹状内部に進入させ、第二加圧パンチ部材２０のパンチ部２０ａ及び可動プレート２０’の上面２０ａ’により未折曲げ部９を挟持し加圧することによって、二次中間成形品１４が成形される（図８（ｂ））。この二次中間成形品１４のプレス装置１７からの取外しは、第二加圧パンチ部材２０を上昇させて加圧状態を解除した後に、二次中間成形品１４を長手方向（図８における紙面垂直方向）に引き抜くことによって行う。但し、例えば図９に示すように底壁部２の湾曲を大きくした場合や、図１０に示すように底壁部２に対する側壁部３，４の長さの割合が大きい場合には、第二加圧パンチ部材２０を上昇させるだけでこれを一対の辺６ｅ，６ｅの間を通して引き抜くことができる。これにより、二次中間成形品１４を長手方向に引き抜くという作業工程を省くことができ、成形作業の効率化、作業スペースの狭小化を図ることができる。
【００４４】
なお、図１１に示すプレス装置を使用することによって、図１２に示す底壁部２が平坦な（湾曲していない）二次中間成形品を成形してもよいが、このとき底壁部２と側壁部３，４とのなす角度θ１は鈍角となり、これは後述の第三加圧パンチ部材により直角とする必要がある。また、パイプ体１が完成したときの底壁部２の平坦性を考慮すると、あるいは、二次中間成形品１４のプレス装置１７からの取外しが第二加圧パンチ部材２０を上昇させるだけで済むことを考慮すると、底壁部２は図６、図７に示すように湾曲していることが好ましい。但し、図６、図７では湾曲状態にある底壁部２は中央の平坦部２ｂとその両側の湾曲部２ｃ，２ｃと平坦部２ａ，２ａとからなっているが（図６（ｂ）参照）、湾曲の態様はこれに限られるものではない。
【００４５】
次に、その二次中間成形品１４を完成品としてのパイプ体１に成形するために、図１３に示すプレス成形装置（加工装置本体）２１を使用する。このプレス成形装置２１は下型（固定型）２２と上型（可動型）２３とから概略構成され、下型２２は第三固定プレート２４を有し、上型２３は図示を略すシリンダ装置により上下動する可動プレート２５を有している。
【００４６】
第三固定プレート２４には一対のストッパー部材２６，２６と、パンチ部材としての第三加圧パンチ部材２７，２７とが設けられている。この一対の第三加圧パンチ部材２７，２７は図１３中左右方向に延びる図示を略す摺動レール上にスライド可能に設けられ、図示を略すカム機構により互いに接近する方向又は離反する方向に連動して移動するようになっている。また、同図に示すように下型２２と上型２３とが分離している状態では、第三加圧パンチ部材２７，２７は図示を略すスプリング部材によって互いに離反する方向に付勢されている。
【００４７】
第三加圧パンチ部材２７，２７の互いに相対向する面には、二次中間成形品１４の側壁部３，４を加圧するパンチ面２７ｂ，２７ｂがそれぞれ形成されている。各パンチ面２７ｂには、凸部形成手段としての突起部２７ｃが長手方向（図１３における紙面垂直方向）に複数並んで設けられている。
【００４８】
可動プレート２５には、第三加圧パンチ部材２７，２７を駆動するための駆動部材２９，２９が設けられるとともに、一対の合わせ目構成壁部５ａ，５ｂを加圧するための第四加圧パンチ部材３０が設けられている。駆動部材２９，２９の下部内側にはテーパー部２９ａ，２９ａが形成され、第三加圧パンチ部材２７，２７の上部外側にはテーパー部２９ａ，２９ａと係合するテーパー部２７ａ，２７ａが形成されている。
【００４９】
二次中間成形品１４は、第３加工ステップとして、まず、底壁部２が下向きとなるように第三加圧パンチ部材２７，２７の対向空間２８にセットされる（図１３）。この状態から矢印Ａ１で示すように上型２３を下降させると、駆動部材２９，２９のテーパー部２９ａ，２９ａが第三加圧パンチ部材２７，２７のテーパー部２７ａ，２７ａに係合し、第三加圧パンチ部材２７，２７が上記スプリング部材の付勢力に抗して互いに接近する方向に駆動される（図１４）。これにより、第三加圧パンチ部材２７，２７のパンチ面２７ｂ，２７ｂが側壁部３，４と合わせ目構成壁部５ａ，５ｂとの境をなす屈曲部３１ａ，３１ｂに当接し、側壁部３，４がそのパンチ面２７ｂ，２７ｂにより加えられる外力によって互いに接近する方向に加圧される。
【００５０】
第三加圧パンチ部材２７，２７が互いに接近する方向にさらに駆動されると、底壁部２の湾曲が取り除かれつつ端面５ｃ，５ｄが接近して最終的には密着し、上壁部５が形成される（図１５）。また、このとき、突起部２７ｃにより側壁部３，４の底壁部２に近い場所（少なくとも、側壁部３，４の高さ方向中央よりも下側の箇所）には凸部３ａ，４ａが形成される。
【００５１】
続いて、第４加工ステップとして上型２３をさらに下降させると、第三加圧パンチ部材２７，２７のテーパー部２７ａ，２７ａと駆動部材２９，２９のテーパー部２９ａ，２９ａとの係合が解除され、第三加圧パンチ部材２７，２７がその位置に停止する。この状態で（すなわち、側壁部３，４に対する加圧力を維持した状態で）上型２３を下降させると、第四加圧パンチ部材３０が上壁部５に当接して上壁部５が加圧される（図１６）。この第四加圧パンチ部材３０の加圧によって、上壁部５及び底壁部２をより確実に平坦化することができるが、この第４加工ステップは必ずしも必須ではない。
【００５２】
そして、上型２３を上昇させて下型２２と分離させると、第三加圧パンチ部材２７，２７が再度互いに離反する方向に移動して、完成したパイプ体１を得る。
【００５３】
図１７はこのようにして製造されたパイプ体の説明図、図１８は比較のために示す凸部を有しないパイプ体の説明図である。この図１８に示すパイプ体１’は、第３加工ステップにおいて凸部を形成しなかった点以外は図１７に示すパイプ体１と同様に製造され、そのパイプ体１’のパイプ体１と対応する部分にはパイプ体１と同じ符号を付している。
【００５４】
一般に、プレス加工（曲げ加工）により工作物に変形を与えるとスプリングバック（その加工力を除去した後に工作物の有する弾性によって変形が多少元に戻る現象）が生じるため、パイプ体１及びパイプ体１’の各底壁部２はそのスプリングバックに伴い発生する応力（スプリングバック力）によって図１８に鎖線で示すように湾曲面に戻ろうとする傾向がある。すなわち、第三加圧パンチ部材２７，２７による外力が取り除かれた後、合わせ目構成壁部５ａ，５ｂの端面５ｃ，５ｄは互いに離れる傾向にあるため、同図に示すパイプ体１’において溶接等を行うことなくその端面５ｃ，５ｄ間の隙間を確実に防止することは困難である。
【００５５】
一方、本実施の形態に係る方法により製造された図１７に示すパイプ体１には凸部３ａ，４ａが形成され、この凸部３ａ，４ａの箇所には同図に示すようにスプリングバック力ｆ１が生じるため、このスプリングバック力ｆ１が底壁部２に生じるスプリングバック力を相殺し、あるいはそれ以上の大きさをもって合わせ目５ｅを閉じるように作用することにより、溶接等を行うことなく端面５ｃ，５ｄを密着させて隙間を防止することができる。具体的には、底壁部２に生じるスプリングバック力のみによって端面５ｃ，５ｄ間が開く量をδ１とし（図１９（ａ）参照）、スプリングバック力ｆ１のみによって端面５ｃ，５ｄ間が閉じる量をδ２とすると（但し、端面５ｃ，５ｄは互いに干渉せずに自由に移動し得るものとする。図１９（ｂ）参照）、δ１≦δ２となるときに端面５ｃ，５ｄは密着する。
【００５６】
また、その凸部３ａ，４ａを底壁部２の近く、つまり合わせ目５ｅから遠い側に設けているので、図２０に示すように合わせ目構成壁部５の近く、つまり合わせ目５ｅから近い側に設けるよりも効率的に端面５ｃ，５ｄ間が閉じる方向の力を作用させることができる。さらに、凸部３ａ，４ａは合わせ目５ｅに対して左右対称位置にあるので、その端面５ｃ，５ｄ間が閉じる方向の力をバランスよく作用させることができる。
【００５７】
この実施の形態に係るパイプ体の製造装置は、従来から使用されている汎用のプレス機に突出部２７ｃ，２７ｃを設けるだけで構成することができるので、既存の設備を有効に利用し設備投資を抑制しつつ製品の精度向上を図ることができる。なお、そのパイプ体の製造装置のプレス成形装置２１では、合わせ目構成壁部５ａ，５ｂからなる上壁部５とは異なる面（側壁部３，４）に凸部を形成するので、この凸部形成のための加圧力の影響により合わせ目構成壁部５ａ，５ｂがずれて上壁部５がうまく形成されない等の事態は防止される。
【００５８】
以上の例では、上壁部５の中央に合わせ目５ｅを形成することとしたが、図２１に示すように、断面の一頂点近傍である上壁部５と側壁部３との境界付近に合わせ目５ｅを形成してもよい。また、凸部を側壁部３，４に設けるのではなく、底壁部２に設けることとしてもよい。このような場合には、例えば図２２に示すように、第三加圧パンチ部材２７，２７ではなく固定プレート２２に突起部を設け（突起部２２ａ）、第四加圧パンチ部材３０で上方から加圧する際に底壁部２の中央に凸部２ａを形成すればよい。さらに、複数の凸部３ａ，４ａを図１に示すように点状に設けるのではなく、より少ない数（一つでもよい。）の線状の凸部をパイプ体１の長手方向に沿って設けてもかまわない。
【００５９】
［断面が他の多角形状のパイプ体の製造］
図２３は断面が三角形状のパイプ体の製造方法を、図２４は断面が五角形状のパイプ体の製造方法を、図２５は断面が六角形状のパイプ体の製造方法を、図２６は断面が八角形状のパイプ体の製造方法をそれぞれ示す。これら各図において、（ａ）は二次中間成形品をプレス成形装置にセットした状態を、（ｂ）は第三加圧パンチ部材により加圧して凸部を形成している状態を、（ｃ）は完成した多角形状のパイプ体を示し、図中の各符号は上記断面四角形（長方形）状のパイプ体の製造における各要素と対応している。すなわち、１はパイプ体、２は二次中間成形品１４の段階で湾曲している面、３，４は凸部３ａ，４ａが形成される面、５ａ，５ｂは合わせ目構成壁部、５ｃ，５ｄは端面、５は合わせ目５ｅを有する面、２４は第三固定プレート、２７は第三加圧パンチ部材、２７ｃは突起部をそれぞれ示し、また、５’はパイプ体の２，３，４，５で表される面以外の他の面を示している。各パイプ体１は凸部３ａ，４ａ、合わせ目５ｅを含めて左右対称であり、その凸部３ａ，４ａに生じるスプリングバック力によって端面５ｃ，５ｄが密着している。
【００６０】
［製造されたパイプ体の使用例］
上記のように製造されたパイプ体１は、例えば図２７（ａ）、（ｂ）に示すように、画像形成装置としてのファックス兼用複写機のフレーム（支持部材）に用いられる。すなわち、パイプ体１には載置フレーム３９が取り付けられてフレームとしての片持ち式フレーム体３８が構成され、その載置フレーム３９には図示を略すスキャナーユニット等が載置される。このように片持ち式フレーム体３８にパイプ体１を用いることにより、複写機のフレームを低コストかつ高品質、高精度に製造することができる。
【００６１】
【発明の効果】
以上説明したように、請求項１、請求項３、請求項４、請求項９、請求項１０、請求項１２、請求項１４、請求項１５の発明によれば、凸部の変形が弾性的に回復する際に生じるスプリングバック力によって金属プレートの一対の辺同士を密着させることになるので、金属プレートをプレス成形により加工して溶接することなくパイプ体を製造する場合であっても、量産時にばらつきなく安定して隙間の目立たないパイプ体を製造することができる。
【００６２】
また、請求項１乃至請求項４、請求項７乃至請求項１０、請求項１２乃至請求項１５のいずれかの発明によれば、金属プレートの一対の辺の接合部が多角形の一辺上に形成される際に、この接合部が形成される辺と異なる辺に対応する面に凸部を設けることになるので、例えば凸部を多角形の外側から加圧して形成する場合に、その加圧力の影響により一対の辺同士がずれて接合に支障をきたす等の事態を防止することができる。とりわけ請求項２、請求項８又は請求項１３の発明によれば、断面が四角形のパイプ体について、接合部が形成される辺と隣接する辺に対応する面上であって、その接合部が形成される辺と対向する辺に対応する面の近くに凸部を設けることになるので、凸部に生じるスプリングバック力により金属プレートの一対の辺同士を効率的に密着させることができるという効果も得られる。
【００６３】
さらに、請求項５、請求項６又は請求項１１の発明によれば、多角形の内側に向かって凸となるように湾曲した面を有して一対の辺同士が離間した状態にある中間成形品を成形し、その湾曲した面の湾曲を取り除きつつ一対の辺同士を接合させるように外力を加えてパイプ体を製造することになるので、製造されたパイプ体の各面の平坦性を、事後的に大幅な修正加工を施すことなく容易に確保することができる。
また、請求項１６に記載の発明によれば、低コストかつ高品質、高精度のフレームを有する画像形成装置を提供できる。
【図面の簡単な説明】
【図１】本発明に係るパイプ体を示す斜視図である。
【図２】図１のパイプ体を示す正面図である。
【図３】図１、図２のパイプ体の製造に用いる金属プレートを示す平面図である。
【図４】一次中間成形品を示す正面図である。
【図５】図４の一次中間成形品の成形に用いるプレス装置を示し、（ａ）は金属プレートを可動プレートに載置した状態の説明図、（ｂ）はその金属プレートを加圧した状態の説明図である。
【図６】二次中間成形品を示す正面図であり、（ａ）はその全体図、（ｂ）は部分拡大図である。
【図７】図６の二次中間成形品を示す斜視図である。
【図８】図６、図７の二次中間成形品の成形に用いるプレス装置を示し、（ａ）は一次中間成形品を可動プレートに載置した状態の説明図、（ｂ）はその一次中間成形品を加圧した状態の説明図である。
【図９】二次中間成形品及びその成形に用いるプレス装置の他の例を示す説明図である。
【図１０】本発明に係るパイプ体の他の例を示す正面図である。
【図１１】二次中間成形品の成形に用いるプレス装置のさらに他の例を示す説明図である。
【図１２】図１１のプレス装置により成形された二次中間成形品を示す正面図である。
【図１３】図６、図７の二次中間成形品をプレス成形装置にセットした状態を示す説明図である。
【図１４】プレス成形装置にセットした二次中間成形品の屈曲部に第三加圧パンチ部材が当接した状態を示す説明図である。
【図１５】プレス成形装置において第三加圧パンチ部材の駆動が完了した状態を示す説明図である。
【図１６】プレス成形装置において第四加圧パンチ部材が上壁部を加圧した状態を示す説明図である。
【図１７】図１、図２のパイプ体に生じるスプリングバックを説明するための模式図である。
【図１８】凸部を有しないパイプ体に生じるスプリングバックを説明するための模式図である。
【図１９】図１７のパイプ体についてスプリングバック力の影響を分離して、かつ、強調して示し、（ａ）は底壁部に生じるスプリングバック力の影響を示す模式図、（ｂ）は凸部に生じるスプリングバック力の影響を示す模式図である。
【図２０】上壁部の近くに凸部を有するパイプ体に生じるスプリングバックを説明するための模式図である。
【図２１】本発明に係るパイプ体のさらに他の例を示す正面図である。
【図２２】凸部を底壁部に形成する場合のパイプ体の製造例を示す説明図である。
【図２３】断面が三角形のパイプ体の製造方法を示し、（ａ）は二次中間成形品をプレス成形装置にセットした状態を、（ｂ）は第三加圧パンチ部材により加圧して凸部を形成している状態を、（ｃ）は完成したパイプ体を示す説明図である。
【図２４】断面が五角形のパイプ体の製造方法を示し、（ａ）は二次中間成形品をプレス成形装置にセットした状態を、（ｂ）は第三加圧パンチ部材により加圧して凸部を形成している状態を、（ｃ）は完成したパイプ体を示す説明図である。
【図２５】断面が六角形のパイプ体の製造方法を示し、（ａ）は二次中間成形品をプレス成形装置にセットした状態を、（ｂ）は第三加圧パンチ部材により加圧して凸部を形成している状態を、（ｃ）は完成したパイプ体を示す説明図である。
【図２６】断面が八角形のパイプ体の製造方法を示し、（ａ）は二次中間成形品をプレス成形装置にセットした状態を、（ｂ）は第三加圧パンチ部材により加圧して凸部を形成している状態を、（ｃ）は完成したパイプ体を示す説明図である。
【図２７】本発明に係る複写機のフレームを示し、（ａ）はその斜視図、（ｂ）は側面図である。
【符号の説明】
１パイプ体
２底壁部（接合部が形成される辺と対向する辺に対応する面）
３，４側壁部（接合部が形成される辺と隣接する辺に対応する面）
３ａ，４ａ凸部
５上壁部（接合部が形成される辺に対応する面）
５ｅ合わせ目（接合部）
６金属プレート
６ｃ，６ｄ折曲げ線（直線）
６ｅ，６ｅ一対の辺
８一次中間成形品
１４二次中間成形品（中間成形品）
２１プレス成形装置（加工装置本体）
２７第三加圧パンチ部材（パンチ部材）
２７ｃ突起部（凸部形成手段）
３０第四加圧パンチ部材（内部加圧パンチ部材）
３８片持ち式フレーム体（フレーム）
ｆ１スプリングバック力[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pipe body manufacturing method, a manufacturing apparatus, a manufactured pipe body, and an image forming apparatus using the pipe body, which manufacture a pipe body having a polygonal cross section by bending a metal plate.
[0002]
[Prior art]
Conventionally, as a technique for manufacturing a pipe body having a polygonal cross section, those described in Japanese Patent Publication No. 7-34936 and Japanese Patent Application Laid-Open No. 11-290940 are known.
[0003]
In Japanese Patent Publication No. 7-34936, a metal plate is roll-formed into a square pipe shape, and then the joint of the metal plate (that is, a pair of sides forming both edges in the width direction of the metal plate) is welded. The pipe body is manufactured.
[0004]
In Japanese Patent Application Laid-Open No. 11-290940, a rectangular metal plate is used as a raw material to manufacture a pipe body having a rectangular cross section by pressing (bending). This manufacturing method includes a first bending step of forming a primary molded product by bending both ends (a pair of sides) in the width direction of the metal plate along the length direction and standing up at a substantially right angle (see FIG. 4). The center part of the unfolded part (reference numeral 9 in FIG. 4) of the primary molded product is bent so as to be convex upward, and both side parts are bent upright at a substantially right angle with respect to the center part. The second bending step for molding the next molded product (see FIG. 6) and the pair of side wall portions (reference numerals 3 and 4 in FIG. 6) of the secondary molded product are pressed toward each other, thereby It comprises a re-striking process that abuts a pair of sides (end faces represented by reference numerals 5c and 5d in FIG. 6).
[0005]
[Problems to be solved by the invention]
By the way, in the method for manufacturing a pipe body described in the above Japanese Patent Publication No. 7-34936, it is necessary to weld a pair of sides of a metal plate after roll forming, but generally roll forming and welding are costly, There is a problem that the accuracy of the product deteriorates due to the thermal strain of the metal generated during welding.
[0006]
On the other hand, in the pipe body manufacturing method described in JP-A-11-290940, the pipe body can be manufactured only by press molding without welding. In many cases, a gap is conspicuous at the joint between a pair of sides, and it is difficult to stably manufacture a pipe body in which the pair of sides are in close contact with each other during mass production.
[0007]
The present invention has been made in view of the above circumstances, and even in the case of manufacturing a pipe body without processing and welding a metal plate by press molding, the gap is stably noticeable without variation during mass production. It is an object of the present invention to provide a manufacturing technique of a pipe body that can manufacture a pipe body that does not exist.
[0008]
[Means for Solving the Problems]
    In order to solve the above problems, the invention of claim 1 is to bend a metal plate having a pair of sides parallel to each other at a plurality of locations along a straight line parallel to the pair of sides and to join the pair of sides.Will form one side of the square cross sectionA pipe body manufacturing method for manufacturing a pipe body,
  On the surface corresponding to the side adjacent to the side where the joint is formedA manufacturing method of a pipe body, wherein a convex portion is provided so as to be convex toward the inside, and the pair of sides are brought into close contact with each other by a springback force generated in the convex portion.
  According to a second aspect of the present invention, in the pipe body manufacturing method according to the first aspect, the convex portion is provided in the vicinity of a surface corresponding to a side facing the side where the joint portion is formed. Body manufacturing method.
In the invention of claim 3, a metal plate having a pair of sides parallel to each other is bent at a plurality of locations along a straight line parallel to the pair of sides, and the pair of sides are joined to each other so that one side of the quadrilateral is square. A pipe body manufacturing method for manufacturing a pipe body to be formed, wherein a convex portion is provided so as to be convex inward on a surface corresponding to a side opposite to the side on which the joint portion is formed. The pair of sides are brought into close contact with each other by a springback force generated in the portion.
In the invention of claim 4, the metal plate having a pair of sides parallel to each other is bent at a plurality of locations along a straight line parallel to the pair of sides and the pair of sides is joined to form a triangle, a pentagon, A pipe body manufacturing method for manufacturing a pipe body in which one side of a hexagon or an octagon is formed,
A convex portion is provided on the surface corresponding to any side other than the side where the joint portion is formed so as to be convex toward the inside, and the pair of sides are brought into close contact with each other by a springback force generated in the convex portion. It is characterized by that.
According to a fifth aspect of the present invention, in the pipe body manufacturing method according to any one of the first to fourth aspects, the metal plate is bent along the straight line in accordance with an angle of each vertex of the polygon. And forming an intermediate molded product by curving the surface corresponding to any side other than the side where the joint is formed to be convex toward the inside of the polygon,
By applying an external force to a surface other than the curved surface of the intermediate molded product and corresponding to a side other than the side on which the joint is formed, the pair of sides is removed while removing the curvature of the curved surface. And the convex part is formed.
The invention of claim 6 is the method of manufacturing a pipe body according to claim 5,
The metal plate is bent in accordance with the angles of some vertices of the polygon to have a concave cross section, and an internal pressure punch member that pressurizes the metal plate enters the concave shape, and the internal pressure punch member The intermediate molded product is formed by forming a curved surface, bending the metal plate according to the angle of the remaining vertex of the polygon, and pulling out the internal pressure punch member through the pair of sides. It is characterized by that.
The invention according to claim 7 is a method in which a metal plate having a pair of sides parallel to each other is bent at a plurality of locations along a straight line parallel to the pair of sides and the pair of sides are joined to each other so that the cross section is one side of a quadrangle. A pipe body manufacturing apparatus for manufacturing a pipe body in which is formed,
A spring back force generated in the convex portion, comprising convex portion forming means for forming a convex portion on the surface corresponding to the side adjacent to the side on which the joint portion is formed to be convex toward the inside of the polygon. The pair of sides are brought into close contact with each other.
The invention of claim 8 is the pipe body manufacturing apparatus according to claim 7, wherein the convex portion forming means forms the convex portion in the vicinity of a surface corresponding to a side opposite to the side where the joint portion is formed. It is characterized by doing.
According to the ninth aspect of the present invention, a metal plate having a pair of sides parallel to each other is bent at a plurality of locations along a straight line parallel to the pair of sides, and the pair of sides are joined to each other so that the cross section has one side of a quadrangle. A pipe body manufacturing apparatus for manufacturing a pipe body in which is formed,
A spring back force generated in the convex portion, comprising convex portion forming means for forming a convex portion on the surface corresponding to the side opposite to the side where the joint portion is formed so as to be convex toward the inside of the polygon. The pair of sides are brought into close contact with each other.
In the invention of claim 10, the metal plate having a pair of sides parallel to each other is bent at a plurality of locations along a straight line parallel to the pair of sides and the pair of sides is joined to form a triangle, a pentagon, A pipe body manufacturing apparatus for manufacturing a pipe body in which one side of a hexagon or octagon is formed,
Protruding portion forming means for providing a protruding portion so as to protrude inward on a surface corresponding to any side other than the side where the joint portion is formed, and the pair of springs by the springback force generated in the protruding portion. The sides are closely attached to each other.
The invention of claim 11 is the pipe body manufacturing apparatus according to any one of claims 7 to 10,
The metal plate is bent along the straight line according to the angle of each vertex of the polygon, and a surface corresponding to any side other than the side where the joint is formed protrudes toward the inside of the polygon. A processing apparatus main body on which an intermediate molded product that is curved to be set is set, and a side other than the curved surface of the intermediate molded product set on the processing apparatus main body, on which the joint portion is formed A punch member that applies an external force to a surface corresponding to the other side, and the convex portion forming means is provided on the punch member, and the punch member joins the pair of sides while removing the curvature of the curved surface. The convex portion is formed on the surface to which the external force is applied by the convex portion forming means.
According to the invention of claim 12, a cross section manufactured by bending a metal plate having a pair of sides parallel to each other at a plurality of locations along a straight line parallel to the pair of sides and joining the pair of sides. It is a pipe body in which one side of a rectangle is formed,
A convex portion is provided so as to be convex inward on a surface corresponding to a side adjacent to the side where the joint portion is formed, and the pair of sides are brought into close contact with each other by a springback force generated in the convex portion. It is characterized by being.
A thirteenth aspect of the present invention is the pipe body according to the twelfth aspect, wherein the convex portion is provided in the vicinity of a surface corresponding to a side facing the side on which the joint portion is formed. To do.
According to the invention of claim 14, a cross section manufactured by bending a metal plate having a pair of sides parallel to each other at a plurality of locations along a straight line parallel to the pair of sides and joining the pair of sides. It is a pipe body in which one side of a rectangle is formed,
A convex portion is provided so as to be convex toward the inside on a surface corresponding to the side opposite to the side on which the joint portion is formed, and the pair of sides are brought into close contact with each other by a springback force generated in the convex portion. It is characterized by being.
In the invention of claim 15, the metal plate having a pair of sides parallel to each other is bent at a plurality of locations along a straight line parallel to the pair of sides, and the cross-section is triangular, pentagonal, by joining the pair of sides. A pipe body in which one side of a hexagon or an octagon is formed,
A convex portion is provided on the surface corresponding to any side other than the side where the joint portion is formed so as to be convex inward, and the pair of sides are brought into close contact with each other by a springback force generated in the convex portion. It is characterized by.
    The invention of claim 16An image forming apparatus having the pipe body according to any one of claims 12 to 15.
[0029]
  According to the first, third, fourth, seventh, ninth, tenth, tenth, twelfth, fourteenth, fifteenth, and fifteenth inventions, the deformation of the convex portionIn this case, a pair of sides of the metal plate is brought into close contact with each other by the springback force generated when the metal plate elastically recovers. However, it is possible to manufacture a pipe body that is stable and not conspicuous in gaps during mass production.
[0030]
  Also,According to any one of claims 1 to 4, claim 7 to claim 10, and claim 12 to claim 15,When the joint part of the pair of sides of the metal plate is formed on one side of the polygon, the convex part is provided on the surface corresponding to the side different from the side on which the joint part is formed. Can be formed by pressing from the outside of the polygon, such that the pair of sides are displaced due to the influence of the applied pressure, causing a problem in joining. Above allAccording to the invention of claim 2, claim 8 or claim 13,For a pipe body having a quadrangular cross section, a convex portion is provided on the surface corresponding to the side adjacent to the side where the joint is formed, and near the surface corresponding to the side opposite to the side where the joint is formed. Since it is provided, the effect that the pair of sides of the metal plate can be efficiently brought into close contact with each other by the springback force generated in the convex portion is also obtained.
[0031]
  further,According to the invention of claim 5, claim 6 or claim 11,Forming an intermediate molded product having a curved surface so as to be convex toward the inside of the polygon and having a pair of sides separated from each other, and removing the curved surface from the pair of sides Since the pipe body is manufactured by applying an external force so as to be joined, the flatness of each surface of the manufactured pipe body can be easily ensured without performing a significant correction process afterwards.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
[0035]
[Manufacture of a pipe body with a square cross section]
FIG. 1 is a perspective view showing a schematic configuration of a pipe body having a rectangular cross section, and FIG. 2 is a front view showing a cross sectional shape of the pipe body. The pipe body 1 includes a bottom wall portion 2, a pair of side wall portions 3 and 4 adjacent to the bottom wall portion 2, and a bottom wall as four surfaces (constituting wall portions) corresponding to the sides of the rectangle shown in FIG. An upper wall portion 5 facing the portion 2 is provided.
[0036]
A plurality of convex portions 3 a and 4 a are formed on the side wall portions 3 and 4 so as to be convex toward the inside of the pipe body 1. The upper wall portion 5 has a pair of seam-constituting wall portions 5a and 5b in close contact with each other at their end faces 5c and 5d, and a seam (joint portion) 5e is formed at the center of the upper wall portion 5. The convex portions 3a and 4a formed on the side wall portions 3 and 4 are symmetrical with respect to the center line O1 passing through the joint 5e and the axis of the pipe body 1.
[0037]
The pipe body 1 is formed by pressing using a rectangular metal plate 6 having a pair of parallel sides 6e and 6e shown in FIG. Screw holes 6a, 6a are formed in the metal plate 6 in advance at appropriate positions, and these screw holes 6a, 6a are used for engaging portions (others for the pipe body 1 when the pipe body 1 is used as a frame described later). It is used as an engaging portion used when attaching a pipe body or the like, or when attaching the pipe body 1 to another member. In addition, a notch etc. may be formed instead of the screw holes 6a and 6a as such an engaging part.
[0038]
In the press working, first, as the first working step, the side portions 6b and 6b of the metal plate 6 are perpendicular (90 °) along the folding lines 6c and 6c extending in the same direction as the pair of sides 6e and 6e. Bend to stand. Thereby, the side parts 6b and 6b form a pair of seam-constituting wall parts 5a and 5b, and the primary intermediate molded product 8 having a concave cross section shown in FIG. 4 is formed. In FIG. 4, reference numeral 9 denotes an unfolded portion, and reference numerals 6d and 6d denote fold lines that serve as a reference when the unfolded portion 9 is bent later. The dimensions of the metal plate 6, the fold line 6c, and the fold line The position of the line 6d is determined in consideration of the amount of metal elongation due to press working.
[0039]
For the press working of the primary intermediate molded product 8, for example, a press device 10 shown in FIG. 5 is used. The pressing device 10 is roughly constituted by a first fixed plate 11, a first pressure punch member 12, and a movable plate 12 ′, and the first fixed plate 11 has an outer shape (joint constituting wall portion 5a) of the primary intermediate molded product 8. , 5b outer shape) is provided with a recess 13 surrounded by a peripheral wall 11a having a shape corresponding to the outer shape. The first pressure punch member 12 has a shape corresponding to the inner shape of the primary intermediate molded product 8 and is moved up and down by a hydraulic cylinder device (not shown) with respect to the recess 13. The movable plate 12 'is connected to another hydraulic cylinder device (not shown) so as to slide relative to the peripheral wall 11a of the first fixed plate 11 as the first pressure punch member 12 moves up and down.
[0040]
The metal plate 6 is placed on the movable plate 12 ′ which is higher than the fixed plate 11 by H with the first pressure punch member 12 and the movable plate 12 ′ positioned upward (FIG. 5A). The first intermediate punch 8 is formed by lowering the first pressure punch member 12 and sandwiching and pressing the metal plate 6 with the movable plate 12 ′ (FIG. 5B).
[0041]
Next, as a second processing step, the unfolded portion 9 of the primary intermediate molded product 8 is bent at a right angle along the fold lines 6d and 6d extending in the same direction as the pair of sides 6e and 6e, and the fold line 6d. , 6d are curved so as to be convex upward to form the bottom wall portion 2 and the side wall portions 3 and 4, which are the remaining constituent wall portions other than the seam constituting wall portions 5a and 5b. . Thereby, as shown in FIG. 6, FIG. 7, the secondary intermediate molded product 14 as an intermediate molded product is molded.
[0042]
For example, a press device 17 shown in FIG. 8 is used to press the secondary intermediate molded product 14. The press device 17 is schematically configured by a second fixed plate 19 having a recess 18, a second pressure punch member 20 as an internal pressure punch member, and a movable plate 20 '. The recess 18 is surrounded by a peripheral wall 19a having a shape corresponding to the outer shape of the secondary intermediate molded product 14 (the outer shape of the side wall portions 3 and 4). The second pressurizing punch member 20 is moved up and down by a hydraulic cylinder device (not shown) with respect to the recess 18. A punch portion 20a having a shape corresponding to the lower inner shape is provided. The movable plate 20 ′ is connected to another hydraulic cylinder device (not shown) so as to slide relative to the second fixed plate 19 as the second pressure punch member 20 moves up and down. The upper surface 20 a ′ of the movable plate 20 ′ is finished in a shape corresponding to the outer shape of the bottom wall portion 2 of the secondary intermediate molded product 14.
[0043]
The primary intermediate molded product 8 is placed on the movable plate 20 ′ that is higher than the fixed plate 19 by H ′ in a state where the second pressure punch member 20 and the movable plate 20 ′ are positioned upward (FIG. 8). (A)) The second pressure punch member 20 is moved down to enter the concave shape of the primary intermediate molded product 8 and is not moved by the punch portion 20a of the second pressure punch member 20 and the upper surface 20a ′ of the movable plate 20 ′. By sandwiching and pressing the bent portion 9, the secondary intermediate molded product 14 is formed (FIG. 8B). The removal of the secondary intermediate molded product 14 from the press device 17 is performed by raising the second pressure punch member 20 to release the pressurized state, and then moving the secondary intermediate molded product 14 in the longitudinal direction (perpendicular to the paper surface in FIG. 8). Direction). However, for example, when the curvature of the bottom wall portion 2 is increased as shown in FIG. 9 or when the ratio of the length of the side wall portions 3 and 4 to the bottom wall portion 2 is large as shown in FIG. By simply raising the pressure punch member 20, it can be pulled out through a pair of sides 6e, 6e. Thereby, the work process of pulling out the secondary intermediate molded product 14 in the longitudinal direction can be omitted, and the efficiency of the molding work and the reduction of the work space can be achieved.
[0044]
In addition, by using the press apparatus shown in FIG. 11, the bottom wall 2 shown in FIG. 12 may be formed into a flat (not curved) secondary intermediate molded product. And the side walls 3 and 4 form an obtuse angle, which needs to be a right angle by a third pressure punch member described later. Further, considering the flatness of the bottom wall portion 2 when the pipe body 1 is completed, the removal of the secondary intermediate molded product 14 from the press device 17 only needs to raise the second pressure punch member 20. Considering this, the bottom wall portion 2 is preferably curved as shown in FIGS. However, in FIGS. 6 and 7, the bottom wall portion 2 in a curved state is composed of a central flat portion 2b, curved portions 2c and 2c on both sides thereof, and flat portions 2a and 2a (see FIG. 6B). ), The bending mode is not limited to this.
[0045]
Next, in order to form the secondary intermediate molded product 14 into the pipe body 1 as a finished product, a press molding apparatus (processing apparatus main body) 21 shown in FIG. 13 is used. The press molding apparatus 21 is generally composed of a lower mold (fixed mold) 22 and an upper mold (movable mold) 23. The lower mold 22 has a third fixed plate 24, and the upper mold 23 is formed by a cylinder device (not shown). It has a movable plate 25 that moves up and down.
[0046]
The third fixed plate 24 is provided with a pair of stopper members 26 and 26 and third pressure punch members 27 and 27 as punch members. The pair of third pressure punch members 27, 27 are slidably provided on a slide rail (not shown) extending in the left-right direction in FIG. 13, and interlocked in a direction toward or away from each other by a cam mechanism (not shown). To move. In the state where the lower die 22 and the upper die 23 are separated as shown in the figure, the third pressure punch members 27 and 27 are urged away from each other by a spring member (not shown). .
[0047]
Punch surfaces 27b and 27b for pressing the side wall portions 3 and 4 of the secondary intermediate molded product 14 are formed on the surfaces of the third pressure punch members 27 and 27 that face each other. Each punch surface 27b is provided with a plurality of protrusions 27c as convex portion forming means arranged in the longitudinal direction (perpendicular to the paper surface in FIG. 13).
[0048]
The movable plate 25 is provided with drive members 29 and 29 for driving the third pressure punch members 27 and 27, and a fourth pressure punch for pressing the pair of seam constituting wall portions 5a and 5b. A member 30 is provided. Tapered portions 29a, 29a are formed inside the lower portions of the drive members 29, 29, and tapered portions 27a, 27a that engage with the tapered portions 29a, 29a are formed outside the upper portions of the third pressure punch members 27, 27. ing.
[0049]
As a third processing step, the secondary intermediate molded product 14 is first set in the facing space 28 of the third pressure punch members 27 and 27 so that the bottom wall portion 2 faces downward (FIG. 13). When the upper mold 23 is lowered from this state as indicated by an arrow A1, the taper portions 29a and 29a of the drive members 29 and 29 engage with the taper portions 27a and 27a of the third pressure punch members 27 and 27, and The three pressure punch members 27 and 27 are driven in a direction approaching each other against the biasing force of the spring member (FIG. 14). As a result, the punch surfaces 27b, 27b of the third pressure punch members 27, 27 come into contact with the bent portions 31a, 31b that form the boundary between the side wall portions 3, 4 and the seam-constituting wall portions 5a, 5b. , 4 are pressed in a direction approaching each other by an external force applied by the punch surfaces 27b, 27b.
[0050]
When the third pressurizing punch members 27 and 27 are further driven in a direction approaching each other, the end surfaces 5c and 5d approach and finally come into close contact with each other while the curvature of the bottom wall 2 is removed, and the upper wall 5 Is formed (FIG. 15). Further, at this time, the protrusions 27 c have protrusions 3 a and 4 a at locations close to the bottom wall portion 2 of the side wall portions 3 and 4 (at least at locations below the center in the height direction of the side wall portions 3 and 4). It is formed.
[0051]
Subsequently, when the upper die 23 is further lowered as the fourth processing step, the engagement between the tapered portions 27a, 27a of the third pressure punch members 27, 27 and the tapered portions 29a, 29a of the drive members 29, 29 is released. Then, the third pressure punch members 27, 27 are stopped at that position. When the upper mold 23 is lowered in this state (that is, with the pressure applied to the side walls 3 and 4 maintained), the fourth pressure punch member 30 abuts on the upper wall 5 and the upper wall 5 is applied. Is pressed (FIG. 16). Although the upper wall portion 5 and the bottom wall portion 2 can be more reliably flattened by the pressurization of the fourth pressure punch member 30, this fourth processing step is not necessarily essential.
[0052]
Then, when the upper die 23 is raised and separated from the lower die 22, the third pressure punch members 27 and 27 move again in the direction away from each other, and the completed pipe body 1 is obtained.
[0053]
FIG. 17 is an explanatory view of the pipe body manufactured as described above, and FIG. 18 is an explanatory view of a pipe body having no convex portion shown for comparison. The pipe body 1 ′ shown in FIG. 18 is manufactured in the same manner as the pipe body 1 shown in FIG. 17 except that no projection is formed in the third processing step, and corresponds to the pipe body 1 of the pipe body 1 ′. The same reference numerals as those of the pipe body 1 are attached to the parts to be performed.
[0054]
In general, when a workpiece is deformed by pressing (bending), a springback (a phenomenon in which the deformation is slightly restored by the elasticity of the workpiece after the machining force is removed) occurs. Each bottom wall 2 of 1 ′ tends to return to the curved surface as shown by a chain line in FIG. 18 due to the stress (spring back force) generated with the spring back. That is, after the external force by the third pressurizing punch members 27, 27 is removed, the end surfaces 5c, 5d of the seam-constituting wall portions 5a, 5b tend to be separated from each other. Therefore, the pipe body 1 ′ shown in FIG. It is difficult to reliably prevent the gap between the end faces 5c and 5d without performing the above process.
[0055]
On the other hand, the pipe body 1 shown in FIG. 17 manufactured by the method according to the present embodiment is formed with convex portions 3a, 4a, and the portions of the convex portions 3a, 4a have a springback force as shown in FIG. Since f1 is generated, the spring back force f1 cancels the spring back force generated on the bottom wall 2 or acts to close the seam 5e with a larger magnitude, so that the end surface is not welded. The gaps can be prevented by closely contacting 5c and 5d. Specifically, the amount of opening between the end surfaces 5c and 5d by only the springback force generated in the bottom wall portion 2 is δ1 (see FIG. 19A), and the amount of closing between the end surfaces 5c and 5d by only the springback force f1. (Note that the end faces 5c and 5d can move freely without interfering with each other. See FIG. 19B.) When δ1 ≦ δ2, the end faces 5c and 5d are in close contact with each other.
[0056]
Further, since the convex portions 3a and 4a are provided near the bottom wall portion 2, that is, on the side far from the joint 5e, as shown in FIG. 20, near the joint constituting wall portion 5, that is, near the joint 5e. A force in the direction of closing the end surfaces 5c and 5d can be applied more efficiently than when provided on the side. Furthermore, since the convex portions 3a and 4a are in a symmetrical position with respect to the joint 5e, the force in the direction in which the end surfaces 5c and 5d are closed can be applied in a balanced manner.
[0057]
Since the pipe body manufacturing apparatus according to this embodiment can be configured only by providing the protrusions 27c and 27c in a general-purpose press machine that has been used conventionally, the existing equipment is used effectively and capital investment is made. The accuracy of the product can be improved while suppressing the above. Note that in the press forming apparatus 21 of the pipe body manufacturing apparatus, convex portions are formed on a surface (side wall portions 3 and 4) different from the upper wall portion 5 composed of the seam constituting wall portions 5a and 5b. A situation in which the seam-constituting wall portions 5a, 5b are shifted due to the influence of the pressure applied to form the portion and the upper wall portion 5 is not formed well is prevented.
[0058]
In the above example, the seam 5e is formed at the center of the upper wall portion 5. However, as shown in FIG. 21, in the vicinity of the boundary between the upper wall portion 5 and the side wall portion 3, which is near one vertex of the cross section. A seam 5e may be formed. Further, the convex portion may be provided on the bottom wall portion 2 instead of being provided on the side wall portions 3 and 4. In such a case, for example, as shown in FIG. 22, a protrusion is provided on the fixed plate 22 (protrusion 22 a) instead of the third pressure punch members 27, 27, and the fourth pressure punch member 30 is viewed from above. What is necessary is just to form the convex part 2a in the center of the bottom wall part 2, when pressing. Further, the plurality of convex portions 3 a and 4 a are not provided in the form of dots as shown in FIG. 1, but a smaller number (or one) of linear convex portions is provided along the longitudinal direction of the pipe body 1. It does not matter if it is provided.
[0059]
[Manufacture of pipes with other polygonal cross sections]
23 shows a method of manufacturing a pipe body having a triangular cross section, FIG. 24 shows a method of manufacturing a pipe body having a pentagonal cross section, FIG. 25 shows a method of manufacturing a pipe body having a hexagonal cross section, and FIG. The manufacturing method of an octagon-shaped pipe body is shown, respectively. In each of these drawings, (a) shows a state in which a secondary intermediate molded product is set in a press molding apparatus, (b) shows a state in which a convex portion is formed by pressing with a third pressure punch member, (c) ) Indicates a completed polygonal pipe body, and each symbol in the drawing corresponds to each element in the production of the pipe body having the above-mentioned quadrilateral (rectangular) cross section. That is, 1 is a pipe body, 2 is a surface that is curved at the stage of the secondary intermediate molded product 14, 3 and 4 are surfaces on which convex portions 3a and 4a are formed, 5a and 5b are seam-constituting wall portions, and 5c. 5d is an end surface, 5 is a surface having a seam 5e, 24 is a third fixing plate, 27 is a third pressure punch member, 27c is a projection, and 5 'is 2, 3, 3 of the pipe body. The other surface than the surface represented by 4 and 5 is shown. Each pipe body 1 is bilaterally symmetrical including the convex portions 3a and 4a and the joint 5e, and the end surfaces 5c and 5d are in close contact with each other by the springback force generated in the convex portions 3a and 4a.
[0060]
[Usage example of manufactured pipe body]
For example, as shown in FIGS. 27A and 27B, the pipe body 1 manufactured as described above is used for a frame (support member) of a facsimile / copier as an image forming apparatus. That is, a mounting frame 39 is attached to the pipe body 1 to form a cantilevered frame body 38 as a frame, and a scanner unit or the like (not shown) is mounted on the mounting frame 39. Thus, by using the pipe body 1 for the cantilevered frame body 38, the frame of the copying machine can be manufactured at low cost, high quality and high accuracy.
[0061]
【The invention's effect】
  As explained above,According to the invention of claim 1, claim 3, claim 4, claim 9, claim 10, claim 12, claim 14, and claim 15,Even when the pipe body is manufactured without processing and welding the metal plate by press forming, the pair of sides of the metal plate are brought into close contact with each other by the springback force generated when elastically recovering. It is possible to manufacture a pipe body that is stable and not conspicuous in the gaps during mass production.
[0062]
  Also,According to any one of claims 1 to 4, claim 7 to claim 10, and claim 12 to claim 15,When the joint part of the pair of sides of the metal plate is formed on one side of the polygon, the convex part is provided on the surface corresponding to the side different from the side on which the joint part is formed. Can be formed by pressing from the outside of the polygon, such that the pair of sides are displaced due to the influence of the applied pressure, causing a problem in joining. Above allAccording to the invention of claim 2, claim 8 or claim 13,For a pipe body having a quadrangular cross section, a convex portion is provided on the surface corresponding to the side adjacent to the side where the joint is formed, and near the surface corresponding to the side opposite to the side where the joint is formed. Since it is provided, the effect that the pair of sides of the metal plate can be efficiently brought into close contact with each other by the springback force generated in the convex portion is also obtained.
[0063]
  further,According to the invention of claim 5, claim 6 or claim 11,Forming an intermediate molded product having a curved surface so as to be convex toward the inside of the polygon and having a pair of sides separated from each other, and removing the curved surface from the pair of sides Since the pipe body is manufactured by applying an external force so as to be joined, the flatness of each surface of the manufactured pipe body can be easily ensured without performing a significant correction process afterwards.
  According to the sixteenth aspect of the present invention, an image forming apparatus having a low-cost, high-quality, and high-accuracy frame can be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a pipe body according to the present invention.
FIG. 2 is a front view showing the pipe body of FIG. 1;
3 is a plan view showing a metal plate used for manufacturing the pipe body of FIGS. 1 and 2. FIG.
FIG. 4 is a front view showing a primary intermediate molded product.
5A and 5B show a pressing device used for forming the primary intermediate molded product of FIG. 4, in which FIG. 5A is an explanatory view showing a state where a metal plate is placed on a movable plate, and FIG. 5B is a state where the metal plate is pressurized. It is explanatory drawing of.
FIG. 6 is a front view showing a secondary intermediate molded product, (a) is an overall view thereof, and (b) is a partially enlarged view.
7 is a perspective view showing the secondary intermediate molded product of FIG. 6. FIG.
FIGS. 8A and 8B show a pressing device used for forming the secondary intermediate molded product of FIGS. 6 and 7, wherein FIG. 8A is an explanatory view showing a state in which the primary intermediate molded product is placed on a movable plate, and FIG. It is explanatory drawing of the state which pressurized the intermediate molded product.
FIG. 9 is an explanatory view showing another example of a secondary intermediate molded product and a press device used for the molding.
FIG. 10 is a front view showing another example of a pipe body according to the present invention.
FIG. 11 is an explanatory view showing still another example of a press device used for forming a secondary intermediate molded product.
12 is a front view showing a secondary intermediate molded product formed by the pressing device of FIG. 11. FIG.
FIG. 13 is an explanatory view showing a state in which the secondary intermediate molded product of FIGS. 6 and 7 is set in a press molding apparatus.
FIG. 14 is an explanatory view showing a state in which a third pressure punch member is in contact with a bent portion of a secondary intermediate molded product set in a press molding apparatus.
FIG. 15 is an explanatory view showing a state where driving of the third pressure punch member is completed in the press molding apparatus.
FIG. 16 is an explanatory view showing a state where a fourth pressure punch member presses the upper wall portion in the press molding apparatus.
17 is a schematic diagram for explaining a spring back generated in the pipe body of FIGS. 1 and 2. FIG.
FIG. 18 is a schematic diagram for explaining a spring back generated in a pipe body having no convex portion.
FIG. 19 shows the effect of springback force separated and emphasized for the pipe body of FIG. 17, (a) is a schematic diagram showing the effect of springback force generated on the bottom wall, and (b) is It is a schematic diagram which shows the influence of the springback force which arises in a convex part.
FIG. 20 is a schematic diagram for explaining a spring back generated in a pipe body having a convex portion near an upper wall portion.
FIG. 21 is a front view showing still another example of the pipe body according to the present invention.
FIG. 22 is an explanatory view showing a manufacturing example of a pipe body when a convex portion is formed on a bottom wall portion.
FIGS. 23A and 23B show a method for manufacturing a pipe body having a triangular cross section, wherein FIG. 23A shows a state in which a secondary intermediate molded product is set in a press molding apparatus, and FIG. (C) is explanatory drawing which shows the completed pipe body in the state which forms the part.
24A and 24B show a method for manufacturing a pentagonal pipe body, where FIG. 24A shows a state where a secondary intermediate molded product is set in a press molding apparatus, and FIG. (C) is explanatory drawing which shows the completed pipe body in the state which forms the part.
FIG. 25 shows a method for manufacturing a pipe body having a hexagonal cross section, in which (a) shows a state where a secondary intermediate molded product is set in a press molding apparatus, and (b) shows a state where pressure is applied by a third pressure punch member. (C) is explanatory drawing which shows the completed pipe body in the state which forms the convex part.
FIG. 26 shows a manufacturing method of a pipe body having an octagonal cross section, where (a) shows a state where a secondary intermediate molded product is set in a press molding apparatus, and (b) shows a state where pressure is applied by a third pressure punch member. (C) is explanatory drawing which shows the completed pipe body in the state which forms the convex part.
FIG. 27 shows a frame of a copying machine according to the present invention, in which (a) is a perspective view thereof and (b) is a side view thereof.
[Explanation of symbols]
1 Pipe body
2 Bottom wall (surface corresponding to the side opposite to the side where the joint is formed)
3, 4 Side wall (surface corresponding to the side adjacent to the side where the joint is formed)
3a, 4a Convex part
5 Upper wall (surface corresponding to the side where the joint is formed)
5e seam (joint)
6 Metal plate
6c, 6d Bending line (straight line)
6e, 6e A pair of sides
8 Primary intermediate product
14 Secondary intermediate product (intermediate product)
21 Press molding equipment (working equipment body)
27 Third pressure punch member (punch member)
27c Projection (projection forming means)
30 Fourth pressure punch member (internal pressure punch member)
38 Cantilever frame (frame)
f1 Springback force

Claims

Manufactures a pipe body in which a metal plate having a pair of sides parallel to each other is bent at a plurality of locations along a straight line parallel to the pair of sides and the pair of sides are joined to form one side having a square cross section A pipe body manufacturing method,
Providing a convex portion inwardly on a surface corresponding to a side adjacent to the side where the joint portion is formed, and bringing the pair of sides into close contact with each other by a springback force generated in the convex portion A manufacturing method of a pipe body.

2. The method of manufacturing a pipe body according to claim 1 , wherein the convex portion is provided in the vicinity of a surface corresponding to a side opposite to a side where the joint portion is formed.

Manufactures a pipe body in which a metal plate having a pair of sides parallel to each other is bent at a plurality of locations along a straight line parallel to the pair of sides and the pair of sides are joined to form one side having a square cross section A pipe body manufacturing method,
Providing a convex portion so as to be convex inward on a surface corresponding to a side opposite to the side where the joint portion is formed, and bringing the pair of sides into close contact with each other by a springback force generated in the convex portion A manufacturing method of a pipe body.

A metal plate having a pair of sides parallel to each other is bent at a plurality of locations along a straight line parallel to the pair of sides, and the pair of sides is joined to each other so that the cross section is triangular, pentagonal, hexagonal, octagonal A pipe body manufacturing method for manufacturing a pipe body in which one side of any of the squares is formed,
A convex portion is provided on the surface corresponding to any side other than the side where the joint portion is formed so as to be convex toward the inside, and the pair of sides are brought into close contact with each other by a springback force generated in the convex portion. A manufacturing method of a pipe body characterized by the above .

In the manufacturing method of the pipe body according to any one of claims 1 to 4 ,
The metal plate is bent along the straight line according to the angle of each vertex of the polygon, and a surface corresponding to any side other than the side where the joint is formed is directed toward the inside of the polygon. Form an intermediate molded product by curving it to be convex,
By applying an external force to a surface other than the curved surface of the intermediate molded product and corresponding to a side other than the side on which the joint portion is formed, the pair of sides is removed while removing the curvature of the curved surface. And manufacturing the pipe body characterized by forming the convex portion.

In the manufacturing method of the pipe body according to claim 5 ,
The metal plate is bent in accordance with the angles of some vertices of the polygon to have a concave cross section, and an internal pressure punch member that pressurizes the metal plate is inserted into the concave shape, and the internal pressure punch member The intermediate molded product is formed by forming a curved surface, bending the metal plate in accordance with the angle of the remaining vertex of the polygon, and pulling out the internal pressure punch member through the pair of sides. A manufacturing method of a pipe body characterized by the above.

By bending a metal plate having a pair of sides parallel to each other at a plurality of locations along a straight line parallel to the pair of sides and joining the pair of sides, a pipe body in which one side of a square is formed is formed. An apparatus for manufacturing a pipe body to be manufactured,
A spring back force generated in the convex portion, comprising convex portion forming means for forming a convex portion on the surface corresponding to the side adjacent to the side on which the joint portion is formed to be convex toward the inside of the polygon. The pipe body manufacturing apparatus, wherein the pair of sides are brought into close contact with each other.

8. The pipe body manufacturing apparatus according to claim 7 , wherein the convex portion forming means forms the convex portion near a surface corresponding to a side opposite to a side where the joint portion is formed. Body manufacturing equipment.

By bending a metal plate having a pair of sides parallel to each other at a plurality of locations along a straight line parallel to the pair of sides and joining the pair of sides, a pipe body in which one side of a square is formed is formed. An apparatus for manufacturing a pipe body to be manufactured,
A spring back force generated in the convex portion, comprising convex portion forming means for forming a convex portion on the surface corresponding to the side opposite to the side where the joint portion is formed so as to be convex toward the inside of the polygon. The pipe body manufacturing apparatus , wherein the pair of sides are brought into close contact with each other .

A metal plate having a pair of sides parallel to each other is bent at a plurality of locations along a straight line parallel to the pair of sides, and the pair of sides are joined together to form a triangle, pentagon, hexagon, or octagon. A pipe body manufacturing apparatus for manufacturing a pipe body in which one side of any of the squares is formed,
Protruding portion forming means for providing a protruding portion so as to protrude inward on a surface corresponding to any side other than the side where the joint portion is formed, and the pair of springs by the springback force generated in the protruding portion. An apparatus for manufacturing a pipe body, wherein the sides of the pipes are brought into close contact with each other .

In the pipe body manufacturing apparatus according to any one of claims 7 to 10 ,
The metal plate is bent along the straight line according to the angle of each vertex of the polygon, and a surface corresponding to any side other than the side where the joint is formed protrudes toward the inside of the polygon. A processing apparatus main body on which an intermediate molded product that is curved to be set is set, and a side other than the curved surface of the intermediate molded product set on the processing apparatus main body, on which the joint portion is formed A punch member that applies an external force to a surface corresponding to the other side, and the convex portion forming means is provided on the punch member, and the punch member joins the pair of sides while removing the curvature of the curved surface. And forming the convex portion on the surface to which the external force is applied by the convex portion forming means.

A metal plate having a pair of sides parallel to each other was bent at a plurality of locations along a straight line parallel to the pair of sides, and a pair of sides were joined to form a square side. A pipe body,
A convex portion is provided so as to be convex inward on a surface corresponding to a side adjacent to the side where the joint portion is formed, and the pair of sides are brought into close contact with each other by a springback force generated in the convex portion. A pipe body characterized by being.

13. The pipe body according to claim 12 , wherein the convex portion is provided near a surface corresponding to a side facing the side on which the joint portion is formed.

A metal plate having a pair of sides parallel to each other is bent at a plurality of locations along a straight line parallel to the pair of sides, and the pair of sides is joined to form a square side. A pipe body,
A convex portion is provided so as to be convex toward the inside on a surface corresponding to the side opposite to the side on which the joint portion is formed, and the pair of sides are brought into close contact with each other by a springback force generated in the convex portion. A pipe body characterized by being.

A metal plate having a pair of sides parallel to each other is bent at a plurality of locations along a straight line parallel to the pair of sides, and the pair of sides is joined to each other so that the cross section is triangular, pentagonal, hexagonal, octagonal A pipe body in which one side of the square is formed,
A convex portion is provided on the surface corresponding to any side other than the side where the joint portion is formed so as to be convex inward, and the pair of sides are brought into close contact with each other by a springback force generated in the convex portion. A pipe body characterized by being .

An image forming apparatus having the pipe body according to any one of claims 12 to 15.