JP4161024B2

JP4161024B2 - Grinding method for inner diameter of small diameter pipe

Info

Publication number: JP4161024B2
Application number: JP2003009963A
Authority: JP
Inventors: 宗勝古堅; 忠裕植松
Original assignee: Usui Co Ltd
Current assignee: Usui Co Ltd
Priority date: 2002-03-01
Filing date: 2003-01-17
Publication date: 2008-10-08
Anticipated expiration: 2023-01-17
Also published as: JP2004154923A

Description

【０００１】
【産業上の利用分野】
本発明は、内周面の平滑度が要求される細径管の内周面を切削する方法に係り、特にディーゼル機関等の燃料噴射管の製造における熱間製管時あるいは途中工程の伸管時に発生した管内面の酸化スケール疵（微細クラック）や皺を除去する細径管内周面研削方法に関する。
【０００２】
【従来の技術】
ディーゼル機関の燃料噴射管に用いられる細径管では、管内の通過抵抗の減少と噴射ノズルの閉塞防止のために管内面の平滑度が高いことが要求されると共に、高圧力の繰返し疲労に耐えるため管内周面の欠陥、特に微細クラックや皺を減少させることが要求される。
【０００３】
この燃料噴射管に用いられる細径管の微細クラックや皺を除去する方法としては、例えば▲１▼機械的切削による方法（特許第３０８５７６２号等参照）、▲２▼サンドブラスト処理による方法（特開昭６１−１２６３６８号公報、特公昭４９−４０７７３号公報等参照）が知られている。
しかしながら、従来の▲１▼機械的切削による方法は、偏肉、偏芯のある被加工パイプであっても熱間圧延時の黒皮層を完全に除去でき、さらに例え初期内削後の被加工パイプの伸管加工時に新たに微細クラックなどが発生してもこれを確実に除去し、高い内圧繰返し圧力が得られ高品質の細径管を得ることができるという効果を奏するが、非能率的でかつコストが高くつくこと、機械切削では管体の長さに制限があり短尺の管体にしか適用できないこと、またそのために後工程の伸管の本数が増加するという難点があった。
また、▲２▼サンドブラスト処理による方法は、機械的切削による方法に比べ能率的でコストも高くつくことがなく、また比較的長尺の管体にも適用できるという利点はあるが、従来のサンドブラスト処理による方法は、いずれも直管の状態でブラスト処理（平行噴射）を施すため研削能が小さく、管軸方向および円周方向の均一研削には限界があり、また管体中央部を目標値まで研削するには長時間要するという欠点がある。さらに、管軸方向および円周方向に研削量が異なるため必然的に管体の肉厚も変動し、後工程の伸管加工において管体中央部と両管端付近の加工度の差を生ずるという問題がある。
【０００４】
【発明が解決しようとする課題】
本発明は、上記した従来技術、特にサンドブラスト処理による方法の問題点に鑑みなされたもので、サンドブラスト処理により管軸方向および円周方向に均一に研削することができる細径管内周面研削方法を提案することを目的とするものである。
【０００５】
【課題を解決するための手段】
前記目的を達成するために、本発明は、細径管の内周面をサンドブラスト処理によって研削する方法において、第１発明は、被研削細径管を弾性限界以下または弾性限界以上の内部応力で単一、または連続して複数個所湾曲させ、かつ管軸芯周りに回転を与えた状態でサンドブラスト処理を施すことを特徴とし、第２発明は、被研削細径管を弾性限界以下または弾性限界以上の内部応力で湾曲させ、かつ管軸芯周りに回転を与えた状態で当該被研削細径管の一端部を固定し、他端部を湾曲方向に変位させてサンドブラスト処理を施すことを特徴とし、第３発明は、前記第２発明において、被研削細径管の両端部を湾曲方向に交互に変位させてサンドブラスト処理を施すことを特徴とし、第４発明は、前記サンドブラスト処理後、当該被研削細径管を矯正工程で直線状に伸管することを特徴とし、第５発明は、前記サンドブラスト処理後、回転を付与し続けた状態で直線状に戻すことを特徴とするものである。
なお、前記サンドブラスト処理は、被研削細径管の両管端より交互に実施するのが好ましい。
【０００６】
本発明において、被研削細径管を内部応力が弾性限界以下または弾性限界以上であるように単一、または連続して複数箇所湾曲させ、この湾曲した状態でサンドブラスト処理を施すのは、管体の軸芯方向中央部と端部の研削量の均一化をはかるためである。
すなわち、直管（平行噴射）では前記したように管内面の研削能が小さいため管体の軸芯方向中央部と端部とでは必然的に研削量が異なる。しかるに、管体を湾曲させた状態で研削材を噴射した場合には、いわゆる傾斜噴射相当となるため研削能は平行噴射よりも大きくなる。つまり、管体を湾曲させると軸方向の各位置で傾斜噴射となるため管軸方向の均一研削に近い研削が可能となる。さらに、管体を湾曲させた状態で当該管体を管軸を中心に回転させながら研削材を噴射すると、管円周方向の均一研削も可能となる。
したがって、管体を単一、または連続して複数箇所湾曲させた状態で管軸を中心に回転させながらサンドブラストを実施した場合には、管軸方向および円周方向の均一研削が可能となり、管体の肉厚が変動することが少ないため、後工程の伸管加工において管体中央部と両管端付近の加工度の差を生ずることがあまりない。また、管軸方向での研削量の均一化効果は、管のたわみ量が大きい程増大することが判明している。さらに、傾斜噴射は平行噴射に比べ研削能が大きいため管内面を目標値まで研削するのに長時間要することもない。
【０００７】
なお、管長が比較的短い被研削細径管の場合は、管体を弓状のように単一に湾曲させた状態でサンドブラスト処理を行うが、管長が例えば５ｍ〜３０ｍ程度の長い管体の場合は、単一に湾曲させる方式では曲げのたわみ量の絶対値が大きくなり装置が過大になる。このため、本発明では当該管体を波状（蛇行状やサインカーブ状）のように連続して湾曲させてサンドブラスト処理を行う方法を採用することとした。すなわち、管体を連続して湾曲させた場合においても、軸方向の各位置で傾斜噴射となるため管軸方向の均一研削に近い研削が可能となるとともに、管円周方向の均一研削も可能となる。
【０００８】
また、本発明において、弓状に湾曲させた被研削細径管の一端部を固定し、他端部を湾曲方向に変位させてサンドブラスト処理を施すのは、被研削細径管の曲率の最大点が軸方向にずれることにより、曲率ほぼ零の点が固定されないために管体全長にわたり研削量をほぼ均一にできるためである。さらに、被研削細径管の片側端部だけでなく、両管端部を湾曲方向に交互に変位させても同様の作用効果が得られることはいうまでもない。
【０００９】
また、サンドブラスト処理後に伸管すると管内面粗さが向上することも判明している。これは、サンドブラスト処理することにより、原管内面に均一微細な梨地肌が形成され、それが潤滑油の保持効果を上げて良好な潤滑状態のもとで伸管加工が行われるからであると考えられる。
【００１０】
なお、被研削細径管を円弧状、放物線状、楕円状等に単一に、あるいは連続して複数箇所湾曲させる方法としては、当該管体の両端を把持した状態で当該管体中間部に、好ましくは複数個所に集中荷重を付与する方法、あるいは管体の両端を把持した状態で当該管体に曲げモーメントを付与する方法等がある。
【００１１】
【実施例】
以下、本発明の実施例を図面を参照して説明する。図１〜図５は本発明方法を実施するための装置例を示す概略図で、図１〜図３は管長が比較的短い（１ｍ〜５ｍ程度）被研削細径管用の装置例を、図４〜図５は管長が例えば５ｍ〜３０ｍ程度の長い被研削細径管用の装置例をそれぞれ示す。図中、１１ａは短尺の被研削細径管、１１ｂは長尺の被研削細径管、１２は管保持台、１３は管曲げ付与装置、１４は管回転装置、１５は管曲げモーメント付与装置、１６は研削材噴射ノズルである。
【００１２】
被研削細径管１１ａ、１１ｂは伸管加工等の冷間絞り加工で成形されたものが一般的であり、この細径管は材質が例えばＪＩＳＧ３４５５ＳＴＳ３７０材で、外径がφ８〜φ２７ｍｍ、内径がφ４〜φ１９ｍｍ、長さは短尺の被研削細径管１１ａの場合は１，０００〜５，０００ｍｍ、長尺の被研削細径管１１ｂの場合は例えば５，０００ｍｍ〜３０，０００ｍｍである。
【００１３】
図１〜図５に示す装置における管保持台１２は、例えば管の端部を着脱可能、回転保持可能にクランプする機構を備えたものを用いるとともに、一方の管保持台１２には管回転装置１４が設けられ、管軸を中心に管に回転を付与できるように構成されている。この両側の管保持台１２は、管を湾曲させる際必然的に間隔が狭くなるので、管の湾曲動作に追従できるように可動に設置されていることはいうまでもない。
管回転装置１４は、管の端部をクランプした状態で当該クランプ装置をモータ等の動力により回転させる機構を備えたものを用いることができる。
管曲げ付与装置１３としては、エアーシリンダーや油圧シリンダー等の流体圧シリンダーを用いるのが一般的である。すなわち、流体圧シリンダー１３−１のロッド先端にローラを有した押圧治具１３−２を取着し、該流体圧シリンダー１３−１にて被研削細径管１１ａ、１１ｂを押圧して円弧状等に湾曲させて回転可能に保持する。
【００１４】
図１に示す装置は管曲げ付与装置１３が１台の場合、図２に示す装置は管曲げ付与装置１３が３台の場合（多点押し）をそれぞれ示す。図３に示す装置は前記の管曲げ付与装置１３を用いずに、両管端部の管保持台１２を回動させて管を円弧状等に湾曲させる方式の管曲げモーメント付与装置１５を用いた例で、例えば管保持台１２、管回転装置１４をターンテーブル等の回転台上に設置し、管の端部を保持した状態で該回転台１５をモータや流体圧シリンダー等の動力で回動させて管を円弧状等に湾曲させる方式である。図４に示す装置は管体を波状（蛇行状やサインカーブ状）のように連続して湾曲させてサンドブラスト処理を施す方法を採用したもので、この装置の場合は管曲げ付与装置１３を管軸方向に複数台配置するとともに、各管曲げ付与装置１３は管軸方向に可動に設置する。図５に示す装置は前記図３に示す装置の管曲げモーメント付与装置１５を湾曲方向にも可動に設置し、該管曲げモーメント付与装置１５により管を円弧状等に湾曲させた状態で、さらに該管曲げモーメント付与装置１５を湾曲方向に変位させてサンドブラスト処理を施す方式である。
【００１５】
上記図１、図２に示す装置により被研削細径管１１ａにサンドブラスト処理を施す場合は、当該管の両端部を管保持台１２にてクランプした状態で管曲げ付与装置１３により管中央部に集中荷重を付与して円弧状等に湾曲させる。この時の管中央部のたわみ量σは管曲げ付与装置１３により集中荷重を加減して設定する。サンドブラストを行う際は、被研削細径管１１ａを図のように湾曲させた状態で、管回転装置１４を駆動して管軸を中心に管に回転を付与しながら、被研削細径管１１ａの開口端に配置した研削材噴射ノズル１６を介して研削材を当該管内に噴射する。このサンドブラスト処理は、被研削細径管１１ａの両管端より交互に実施する。
【００１６】
図３に示す装置により被研削細径管１１ａにサンドブラスト処理を施す場合は、当該管の両端部を管保持台１２にてクランプした状態で管曲げモーメント付与装置１５により当該管を湾曲させた後、前記と同様に管回転装置１４を駆動して管軸を中心に管に回転を付与しながら、被研削細径管１１ａの開口端に配置した研削材噴射ノズル１６を介して研削材を当該管内に噴射する。この場合もサンドブラスト処理は、被研削細径管の両管端より交互に実施する。
【００１７】
図３に示す装置により被研削細径管１１ａにサンドブラスト処理を施した場合には、前記したごとく、管軸方向および円周方向の均一研削が可能となり、後工程の伸管加工において管体中央部と両管端付近の加工度の差を生ずることがない。また、管軸方向での研削量の均一化効果は、管のたわみ量が大きい程増大し、さらに、傾斜噴射は平行噴射に比べ研削能が大きいため管内面を目標値まで研削するのに長時間要することもない。
【００１８】
次に、図４に示す装置により被研削細径管１１ｂにサンドブラスト処理を施す場合は、当該管の両端部を管保持台１２にてクランプした状態で複数台の管曲げ付与装置１３により管体を波状（蛇行状やサインカーブ状）のように連続して湾曲させる。管曲げ付与装置１３は、矢印で示すように管長手方向および管湾曲方向に移動可能に設置されている。サンドブラストを行う際は、被研削細径管１１ｂを管曲げ付与装置１３により図のように波状（蛇行状やサインカーブ状）に湾曲させた状態で、管回転装置１４を駆動して管軸を中心に管に回転を付与しながら、被研削細径管１１ｂの開口端に配置した研削材噴射ノズル１６を介して研削材を当該管内に噴射する。この研削材噴射中に、曲げを与える支点を管長手方向に適当量ずらすことにより、曲率ほぼ零の点が固定されないために研削材の当たる軸方向位置が変わり管体全長にわたり研削量をほぼ均一にできる。この装置の場合もサンドブラスト処理は、被研削細径管の両管端より交互に実施する。
【００１９】
また、図５に示す装置により被研削細径管１１ｂにサンドブラスト処理を施す場合は、当該管の両端部を管保持台１２にてクランプした状態で管曲げモーメント付与装置１５により当該管を湾曲させた後、前記と同様に管回転装置１４を駆動して管軸を中心に管に回転を付与しながら、被研削細径管１１ｂの開口端に配置した研削材噴射ノズル１６を介して研削材を当該管内に噴射するとともに、この研削材噴射中に管曲げモーメント付与装置１５を矢印イのように湾曲方向にずらすことにより、曲率ほぼ零の点が固定されないために研削材の当たる軸方向位置が変わり管体全長にわたり研削量をほぼ均一にできる。この装置の場合もサンドブラスト処理は、被研削細径管の両管端より交互に実施する。
なお、ここでは管体の片側端部を固定し、他端部を矢印イのようにずらせるように可動に設けた例を示したが、片側端部だけでなく両側の管端部を矢印イのようにずらせるように可動に設け、両側の管端部を矢印イ、ロのように交互にずらしながらサンドブラスト処理を施すことも可能である。
【００２０】
なお、被研削細径管を円弧状、放物線状、楕円状等に湾曲させる方法としては、当該管体の両端を把持した状態で当該管体中央部や任意個所に集中荷重を付与する方法、あるいは管体の両端を把持した状態で当該管体に曲げモーメントを付与する方法等があるが、被研削細径管を弾性限界以下または弾性限界以上の内部応力で湾曲させた場合の残留たわみ量は、以下のように説明される。
すなわち、被研削細径管に曲げを与えた場合、全長弾性変形の管については、当然のことながら曲げを除去すれば残量たわみはなくなり、真直な状態となる。一方、曲げで塑性変形を発生した管については、当該管の回転を止めて曲げを除去すれば残留たわみ量σｒを生じるため、この残留曲がりを小さくする必要がある。その方法としては、管に回転を与えながら曲げを徐々に除去すればよい。この方法では、曲げ除去動作開始から曲げ除去が終わる間に管が回転した回数をＮｓとした場合、Ｎｓの増大により残留たわみ量σｒは小さくなる。これは繰返し回転曲げによる矯正作用が働いたことによる。
なお、残留たわみを小さくする他の方法としては、サンドブラスト処理後にプレス矯正機やロータリー矯正機を使う方法等がある。
図１〜図５では、先に管を湾曲させてから回転させる方式を示したが、先に管を回転させてから湾曲させてもよい。
【００２１】
【実施例】
実施例１
被研削細径管として、材質ＪＩＳＧ３４５５ＳＴＳ３７０で、表１に示す各種サイズおよびたわみ量の管を用い、前記図２に示す管内面研削装置により管を湾曲させかつ回転させながらサンドブラスト処理を実施した。本実施例における研削材、研削材噴射圧力、研削時間を表２に、処理後の細径管の内面形状を図６に、それぞれ示す。なお、図６には比較のため、表１に示す真直な被研削細径管（従来例）を回転させながらサンドブラスト処理を実施した場合の従来法による結果を併せて示した。
図６に示す結果より明らかなごとく、本発明法は被研削細径管を真っ直ぐのままサンドブラスト処理を施した従来法に比べ、管軸方向および管円周方向での研削量の均一化がはかられ、またその効果は管のたわみ量σが大きいほど増大することがわかる。
なお、同一たわみ量でも研削量に若干の差が生じているのは、管内径の大きさによる圧力損失等が影響しているものと考えられる。
【００２２】
【表１】

【００２３】
【表２】

【００２４】
実施例２
実施例１における供試Ｎｏ１〜２のサンドブラスト処理管（原管）をそれぞれ伸管工程で所定の製品寸法に仕上げた場合の各製品の内表面粗さを、同一寸法の真直な被研削細径管の内面を機械的切削処理して仕上げた製品の内表面粗さと比較して表３に示す。
表３の結果より明らかなごとく、本発明のサンドブラスト処理した製品の内表面粗さは、従来法の機械的切削処理の製品に比べて粗さが低減している。これはサンドブラスト処理することにより、原管内面に均一微細な梨地肌が形成され、それが潤滑油の保持効果を上げて良好な潤滑状態のもとで伸管加工が行われるからであると考えられる。
【００２５】
【表３】

【００２６】
なお、ここでは図２に示す管内面研削装置により短尺管の内面を研削した場合の実施例のみを示したが、図４あるいは図５に示す管内面研削装置により長尺管の内面を研削した場合も同様の効果が得られることはいうまでもない。また、前記実施例は自動車のディーゼル機関の燃料噴射管に使用される細径管に適用した場合を説明したが、この他にも例えば建設機械用、船舶用等のディーゼル機関に使用される厚肉細径管をはじめ種々の管に適用しても同様の効果が得られることはいうまでもない。
【００２７】
【発明の効果】
以上詳細に説明したように、本発明法によれば、管体の長短にかかわらずサンドブラスト処理により管軸方向および円周方向に均一に研削することができるので、管体の肉厚の均一化がはかられるばかりでなく、熱間製管時あるいは途中工程の伸管時に発生した管内面の酸化スケール疵（微細クラック）や皺を完全に除去することができ、また傾斜噴射は平行噴射に比べ研削能が大きいため管内面を目標値まで研削するのに長時間要することもないため、内周面が高品質でかつ眞円度、均一性に優れた細径管を低コストで製造することができるという優れた効果を奏する。
【図面の簡単な説明】
【図１】本発明法を実施するための装置の第１実施例を示す概略図である。
【図２】本発明法を実施するための装置の第２実施例を示す概略図である。
【図３】本発明法を実施するための装置の第３実施例を示す概略図である。
【図４】本発明法を実施するための装置の第４実施例を示す概略図である。
【図５】本発明法を実施するための装置の第５実施例を示す概略図である。
【図６】本発明の実施例おけるサンドブラスト処理後の細径管の内面形状を示す図である。
【符号の説明】
１１ａ短尺の被研削細径管
１１ｂ長尺の被研削細径管
１２管保持台
１３管曲げ付与装置
１４管回転装置
１５管曲げモーメント付与装置
１６研削材噴射ノズル[0001]
[Industrial application fields]
The present invention relates to a method for cutting an inner peripheral surface of a small-diameter pipe that requires smoothness of the inner peripheral surface, and in particular, during the hot pipe production in the production of a fuel injection pipe of a diesel engine, etc. The present invention relates to a method for grinding an inner peripheral surface of a small-diameter pipe that removes oxide scale wrinkles (fine cracks) and wrinkles generated on the inner surface of the pipe.
[0002]
[Prior art]
Small diameter pipes used for fuel injection pipes of diesel engines require high smoothness of the pipe inner surface to reduce the passage resistance in the pipe and prevent the injection nozzle from clogging, and withstand repeated fatigue under high pressure. Therefore, it is required to reduce defects on the inner peripheral surface of the pipe, particularly fine cracks and wrinkles.
[0003]
As a method for removing fine cracks and soot in the small-diameter pipe used in this fuel injection pipe, for example, (1) a method by mechanical cutting (see Japanese Patent No. 3085762, etc.), and (2) a method by sandblasting (Japanese Patent Laid-Open No. Japanese Patent Publication No. 61-126368, Japanese Patent Publication No. 49-40773, etc.) are known.
However, the conventional method (1) by mechanical cutting can completely remove the black skin layer during hot rolling even for pipes with uneven thickness and eccentricity. Even if new microcracks are generated during pipe expansion, they can be removed reliably, resulting in high internal pressure repetition pressure and high quality thin pipes. In addition, the cost is high, the length of the tubular body is limited by mechanical cutting, and it can only be applied to a short tubular body. In addition, there are problems that the number of drawn tubes in the subsequent process increases.
In addition, the method (2) by sandblasting is advantageous in that it is more efficient and less expensive than the method by mechanical cutting, and can be applied to relatively long pipes. All processing methods have a low grinding ability because they are blasted (parallel injection) in a straight pipe state, and there is a limit to uniform grinding in the tube axis direction and the circumferential direction. There is a disadvantage that it takes a long time to grind. Furthermore, since the grinding amount differs in the tube axis direction and the circumferential direction, the thickness of the tube body inevitably fluctuates, resulting in a difference in the workability between the tube center and the ends of both tubes in the subsequent tube drawing process. There is a problem.
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of the problems of the above-described prior art, particularly the method by sandblasting, and provides a method for grinding an inner peripheral surface of a small-diameter pipe that can be uniformly ground in the pipe axis direction and the circumferential direction by sandblasting. The purpose is to propose.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a method for grinding an inner peripheral surface of a small-diameter pipe by sandblasting, and the first invention provides that the thin-diameter pipe to be ground is subjected to an internal stress that is less than or equal to the elastic limit. The second invention is characterized in that sandblasting is performed in a state where a single portion or a plurality of portions are continuously bent and rotated around the tube axis, and the second invention is characterized in that the thin pipe to be ground is below the elastic limit or below the elastic limit. It is curved with the above internal stress and fixed at one end of the fine pipe to be ground while being rotated around the tube axis, and is subjected to sandblasting by displacing the other end in the bending direction. The third invention is characterized in that, in the second invention, the sandblasting treatment is performed by alternately displacing both ends of the fine pipe to be ground in the bending direction. Fine to be ground And characterized in that Shinkan straight tubes in straightening step, the fifth invention, after the sandblasting, and is characterized in that the back straight in a state of continuing to impart rotation.
In addition, it is preferable to perform the said sandblasting process alternately from the both pipe ends of a to-be-ground small diameter pipe | tube.
[0006]
In the present invention, it is a tube body to bend a small-diameter pipe to be ground in a single or continuous plural places so that the internal stress is below the elastic limit or above the elastic limit, and to perform the sandblast treatment in this curved state. This is because the amount of grinding at the center part and the end part in the axial direction of the core is made uniform.
That is, in the straight pipe (parallel injection), as described above, the grinding ability of the inner surface of the pipe is small, so that the grinding amount is inevitably different between the central part and the end part in the axial direction of the pipe body. However, when the abrasive is jetted in a state where the tube is curved, the grinding ability is larger than that of parallel jet because it corresponds to so-called inclined jet. That is, when the tube is bent, the inclined jet is produced at each position in the axial direction, so that grinding close to uniform grinding in the tube axis direction is possible. Furthermore, uniform grinding in the pipe circumferential direction is also possible by injecting the abrasive while rotating the pipe body around the pipe axis in a curved state.
Therefore, when sandblasting is performed while rotating the tube body around the tube axis in a state where the tube body is bent single or continuously, the tube axis direction and the circumferential direction can be uniformly ground. Since the thickness of the body rarely fluctuates, there is not much difference in the degree of processing between the central part of the pipe body and the vicinity of both pipe ends in the subsequent pipe drawing process. Further, it has been found that the effect of equalizing the grinding amount in the tube axis direction increases as the deflection amount of the tube increases. Furthermore, since the inclined jet has a higher grinding ability than the parallel jet, it does not take a long time to grind the inner surface of the pipe to the target value.
[0007]
In addition, in the case of a to-be-ground small diameter pipe having a relatively short pipe length, the sand blasting process is performed in a state where the pipe body is bent in a single shape like an arcuate shape, but the pipe length is, for example, about 5 m to 30 m. In such a case, the single bending method increases the absolute value of the bending deflection, resulting in an excessive apparatus. For this reason, in the present invention, a method is adopted in which the tube body is continuously bent like a wave shape (meandering shape or sine curve shape) and sandblasting is performed. In other words, even when the tube is bent continuously, it is possible to perform grinding close to uniform grinding in the tube axis direction and uniform grinding in the tube circumferential direction because of the inclined jet at each axial position. It becomes.
[0008]
In the present invention, the one end of the thin pipe to be ground curved in an arcuate shape is fixed, and the other end is displaced in the bending direction to perform the sand blasting process. This is because when the point is shifted in the axial direction, the point with substantially zero curvature is not fixed, so that the grinding amount can be made substantially uniform over the entire length of the tube. Furthermore, it goes without saying that the same effects can be obtained by alternately displacing not only one end portion of the thin pipe to be ground but also both tube end portions in the bending direction.
[0009]
It has also been found that the pipe inner surface roughness improves when the pipe is drawn after sandblasting. This is because, by sandblasting, a uniform fine textured surface is formed on the inner surface of the original tube, which increases the retention effect of the lubricating oil and the tube is drawn under good lubrication conditions. Conceivable.
[0010]
In addition, as a method of bending a small-diameter pipe to be ground in a circular shape, a parabolic shape, an elliptical shape, or the like in a single portion or continuously, a plurality of portions are continuously bent in the middle portion of the tubular body while holding both ends of the tubular body. Preferably, there are a method of applying a concentrated load to a plurality of locations, a method of applying a bending moment to the tube body while holding both ends of the tube body, and the like.
[0011]
【Example】
Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 are schematic views showing examples of apparatuses for carrying out the method of the present invention, and FIGS. 1 to 3 show examples of apparatuses for small diameter pipes to be ground having a relatively short pipe length (about 1 to 5 m). 4 to 5 show examples of apparatuses for long-diameter thin pipes having a pipe length of about 5 to 30 m, for example. In the figure, 11a is a short to-be-ground small diameter pipe, 11b is a long to-be-ground small diameter pipe, 12 is a tube holding table, 13 is a tube bending applying device, 14 is a tube rotating device, and 15 is a tube bending moment applying device. , 16 is an abrasive spray nozzle.
[0012]
The to-be-ground

thin tubes

11a and 11b are generally formed by cold drawing such as tube drawing, and the thin tube is made of, for example, JIS G3455 STS370 material and has an outer diameter of φ8 to φ27 mm. The inner diameter is φ4 to φ19 mm, and the length is 1,000 to 5,000 mm in the case of a short to-be-ground thin pipe 11a, and is 5,000 mm to 30,000 mm in the case of a long to-be-ground pipe 11b. .
[0013]
The tube holding table 12 in the apparatus shown in FIGS. 1 to 5 is, for example, one having a mechanism that clamps the end of the tube so that it can be attached and detached and rotated and held. 14 is provided so that rotation can be imparted to the tube around the tube axis. The pipe holding bases 12 on both sides inevitably have a narrow interval when the pipe is bent, so it goes without saying that the pipe holding bases 12 are movably installed so as to follow the bending operation of the pipe.
As the tube rotating device 14, a device provided with a mechanism for rotating the clamping device with power such as a motor in a state where the end portion of the tube is clamped can be used.
As the tube bending imparting device 13, a fluid pressure cylinder such as an air cylinder or a hydraulic cylinder is generally used. That is, a pressing jig 13-2 having a roller is attached to the tip of the rod of the fluid pressure cylinder 13-1, and the

narrow pipes

11a and 11b to be ground are pressed by the fluid pressure cylinder 13-1 to form an arc. It is curved to be held in a rotatable manner.
[0014]
The apparatus shown in FIG. 1 shows the case where there is one tube bending imparting device 13, and the apparatus shown in FIG. 2 shows the case where there are three tube bending imparting devices 13 (multi-point pressing). The apparatus shown in FIG. 3 uses a tube bending moment applying device 15 of a type in which the tube holding base 12 at both ends of the tube is rotated to bend the tube in an arc shape or the like without using the tube bending applying device 13 described above. In this example, for example, the tube holding table 12 and the tube rotating device 14 are installed on a rotating table such as a turntable, and the rotating table 15 is rotated by power such as a motor or a hydraulic cylinder while holding the end of the tube. This is a system in which the tube is bent in an arc shape or the like. The apparatus shown in FIG. 4 employs a method in which the pipe body is continuously bent like a wavy shape (meandering or sine curve) and subjected to sandblasting. A plurality of units are arranged in the axial direction, and each of the tube bending imparting devices 13 is movably installed in the direction of the tube axis. In the apparatus shown in FIG. 5, the tube bending moment applying device 15 of the apparatus shown in FIG. 3 is movably installed in the bending direction, and the tube is bent in an arc shape by the tube bending moment applying device 15. In this method, the pipe bending moment applying device 15 is displaced in the bending direction to perform sandblasting.
[0015]
When sandblasting is applied to the small diameter pipe 11a to be ground by the apparatus shown in FIGS. 1 and 2, the pipe bend imparting apparatus 13 puts both ends of the pipe into the center of the pipe with the pipe holding table 12 clamped. A concentrated load is applied and curved in an arc shape or the like. The deflection amount σ at the center of the tube at this time is set by adjusting the concentrated load by the tube bending imparting device 13. When sandblasting is performed, while the thin pipe 11a to be ground is bent as shown in the drawing, the pipe rotating device 14 is driven to apply rotation to the pipe around the pipe axis, while the thin pipe 11a to be ground is applied. The abrasive is injected into the pipe through the abrasive injection nozzle 16 disposed at the opening end of the pipe. This sand blasting process is alternately performed from both ends of the thin pipe 11a to be ground.
[0016]
When sandblasting is performed on the thin pipe 11a to be ground by the apparatus shown in FIG. 3, the pipe is bent by the pipe bending moment applying device 15 with both ends of the pipe clamped by the pipe holding base 12. In the same manner as described above, while the tube rotating device 14 is driven to impart rotation to the tube around the tube axis, the abrasive is applied via the abrasive injection nozzle 16 disposed at the opening end of the small diameter tube 11a to be ground. Inject into the tube. Also in this case, the sandblasting process is alternately performed from both ends of the fine pipe to be ground.
[0017]
When sandblasting is performed on the thin pipe 11a to be ground by the apparatus shown in FIG. 3, as described above, uniform grinding in the pipe axis direction and the circumferential direction is possible. There is no difference in the degree of processing between the end of the pipe and the ends of both pipes. Also, the effect of equalizing the grinding amount in the pipe axis direction increases as the pipe deflection increases, and the inclined jet has a higher grinding ability than the parallel jet, so it is long for grinding the pipe inner surface to the target value. It does not take time.
[0018]
Next, when sand blasting is performed on the thin pipe 11b to be ground by the apparatus shown in FIG. 4, the pipe body is provided by a plurality of pipe bending imparting apparatuses 13 with both ends of the pipe clamped by the pipe holding base 12. Is continuously curved like a wave (meandering or sine curve). The tube bending imparting device 13 is installed so as to be movable in the tube longitudinal direction and the tube bending direction as indicated by arrows. When sandblasting is performed, the tube rotating device 14 is driven to turn the tube shaft in a state in which the to-be-ground small diameter tube 11b is bent in a wave shape (meandering or sine curve) as shown in the figure by the tube bending imparting device 13. While imparting rotation to the tube at the center, the abrasive is injected into the tube through the abrasive injection nozzle 16 disposed at the opening end of the thin pipe 11b to be ground. During the injection of the abrasive, the fulcrum to bend is shifted by an appropriate amount in the longitudinal direction of the pipe, so that the point of almost zero curvature is not fixed, the axial position where the abrasive hits changes, and the grinding amount is almost uniform over the entire length of the tube Can be. Also in this apparatus, sandblasting is performed alternately from both ends of the thin pipe to be ground.
[0019]
Further, when sandblasting is performed on the thin pipe 11b to be ground using the apparatus shown in FIG. 5, the pipe is bent by the pipe bending moment applying device 15 with both ends of the pipe clamped by the pipe holding base 12. After that, the abrasive material is driven through the abrasive material injection nozzle 16 disposed at the open end of the thin pipe 11b to be ground while driving the tube rotating device 14 in the same manner as described above to rotate the tube around the tube axis. And the pipe bending moment applying device 15 is shifted in the bending direction as indicated by an arrow A during the injection of the abrasive, so that the point of almost zero curvature is not fixed. Changes and the grinding amount can be made almost uniform over the entire length of the tube. Also in this apparatus, sandblasting is performed alternately from both ends of the thin pipe to be ground.
In this example, one end of the tube body is fixed and the other end is movably provided so as to be displaced as indicated by arrow A. However, not only the one end but also the tube ends on both sides are indicated by arrows. It is also possible to movably displace it like a and to perform sandblasting while alternately shifting the pipe ends on both sides as shown by arrows a and b.
[0020]
In addition, as a method of curving the to-be-ground small diameter tube in an arc shape, a parabola shape, an elliptical shape, etc., a method of applying a concentrated load to the tube body central portion or an arbitrary place in a state where both ends of the tube body are gripped, Alternatively, there is a method of applying a bending moment to the tube while holding both ends of the tube, but the amount of residual deflection when the to-be-ground thin tube is bent with internal stress below the elastic limit or above the elastic limit Is described as follows.
In other words, when the thin pipe to be ground is bent, the pipe of the full length elastic deformation is naturally straightened if the bending is removed so that the remaining amount of deflection is eliminated. On the other hand, for a pipe that has undergone plastic deformation due to bending, if the bending is removed by stopping the rotation of the pipe, a residual deflection amount σr is generated, and thus it is necessary to reduce this residual bending. As the method, the bending may be gradually removed while rotating the tube. In this method, when the number of rotations of the tube between the start of the bending removal operation and the end of the bending removal is Ns, the remaining deflection amount σr is reduced by increasing Ns. This is due to the fact that corrective action by repeated rotating bending worked.
As another method for reducing the residual deflection, there is a method of using a press straightener or a rotary straightener after sandblasting.
Although FIGS. 1 to 5 show a method in which the tube is first rotated and then rotated, the tube may be first rotated and then bent.
[0021]
【Example】
Example 1
As the thin pipe to be ground, the material JIS G3455 STS370 was used, and pipes of various sizes and deflection amounts shown in Table 1 were used, and the sandblasting was performed while the pipe was curved and rotated by the pipe inner surface grinding apparatus shown in FIG. . Table 2 shows the grinding material, grinding material injection pressure, and grinding time in this example, and FIG. 6 shows the inner surface shape of the small-diameter pipe after processing. For comparison, FIG. 6 also shows the results obtained by the conventional method when the sand blasting process was performed while rotating the straight pipe to be ground shown in Table 1 (conventional example).
As is apparent from the results shown in FIG. 6, the method of the present invention is more uniform in the grinding amount in the pipe axis direction and the pipe circumferential direction than the conventional method in which the thin pipe to be ground is straightened and sandblasted. It can be seen that the effect increases as the tube deflection σ increases.
A slight difference in the grinding amount even with the same amount of deflection is considered to be due to the pressure loss due to the size of the inner diameter of the tube.
[0022]
[Table 1]

[0023]
[Table 2]

[0024]
Example 2
The inner surface roughness of each product when the sandblasted pipes (original pipes) of test Nos. 1 and 2 in Example 1 are finished to the predetermined product dimensions in the drawing process, and the straight ground fine diameter of the same dimensions. Table 3 compares the inner surface roughness of the product finished by mechanically cutting the inner surface of the tube.
As is apparent from the results in Table 3, the inner surface roughness of the sandblasted product of the present invention is less than that of the conventional mechanical cutting product. This is thought to be because the sandblasting process forms a uniform fine textured surface on the inner surface of the original tube, which increases the retention effect of the lubricating oil and allows the tube to be drawn under good lubrication conditions. It is done.
[0025]
[Table 3]

[0026]
Here, only the embodiment in which the inner surface of the short pipe is ground by the pipe inner surface grinding apparatus shown in FIG. 2 is shown, but the inner face of the long pipe is ground by the pipe inner surface grinding apparatus shown in FIG. 4 or FIG. Needless to say, the same effect can be obtained in this case. Moreover, although the said Example demonstrated the case where it applied to the thin diameter pipe | tube used for the fuel-injection pipe | tube of the diesel engine of a motor vehicle, the thickness used for diesel engines, such as for construction machines and ships, is also used for this. It goes without saying that the same effect can be obtained even if it is applied to various pipes including a thin-walled pipe.
[0027]
【The invention's effect】
As described in detail above, according to the method of the present invention, the pipe body can be uniformly ground by sandblasting regardless of the length of the pipe body, so that the thickness of the pipe body can be made uniform. In addition to being peeled off, it is possible to completely remove oxide scale soot (fine cracks) and soot from the inner surface of the pipe that has been generated during hot pipe making or during the extension of the intermediate process. Compared with the high grinding ability, it does not take a long time to grind the inner surface of the pipe to the target value, so that a small diameter pipe with high quality, roundness and uniformity can be manufactured at a low cost. There is an excellent effect of being able to.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a first embodiment of an apparatus for carrying out the method of the present invention.
FIG. 2 is a schematic view showing a second embodiment of an apparatus for carrying out the method of the present invention.
FIG. 3 is a schematic view showing a third embodiment of an apparatus for carrying out the method of the present invention.
FIG. 4 is a schematic view showing a fourth embodiment of an apparatus for carrying out the method of the present invention.
FIG. 5 is a schematic view showing a fifth embodiment of an apparatus for carrying out the method of the present invention.
FIG. 6 is a view showing an inner surface shape of a small-diameter pipe after sandblasting in an example of the present invention.
[Explanation of symbols]
11a Short to-be-ground small diameter pipe 11b Long to-be-ground small diameter pipe 12 Tube holding base 13 Tube bending imparting device 14 Tube rotating device 15 Tube bending moment imparting device 16 Grinding material injection nozzle

Claims

In a method of grinding the inner peripheral surface of a small diameter pipe by sandblasting, the thin diameter pipe to be ground is bent at a single point or a plurality of points continuously with an internal stress below the elastic limit or above the elastic limit, and around the tube axis. A method for grinding an inner peripheral surface of a small-diameter pipe, wherein sandblasting is performed in a state where rotation is applied to the inner surface of the pipe.

In the method of grinding the inner peripheral surface of a small-diameter pipe by sandblasting, the thin-diameter pipe to be ground is bent with an internal stress below the elastic limit or above the elastic limit and is rotated around the axis of the pipe. A method for grinding an inner peripheral surface of a small-diameter pipe, characterized in that one end of a grinding fine-diameter pipe is fixed and the other end is displaced in a bending direction to perform sandblasting.

3. The method for grinding an inner peripheral surface of a thin pipe according to claim 2, wherein sandblasting is performed by alternately displacing both ends of the thin pipe to be ground in the bending direction.

In the method of grinding the inner peripheral surface of a small diameter pipe by sandblasting, the thin diameter pipe to be ground is bent single or continuously with an internal stress below the elastic limit or above the elastic limit and rotated around the pipe axis. A method for grinding an inner peripheral surface of a small-diameter pipe, which is subjected to a sandblasting treatment in a given state and, after the treatment, is straightened in a straightening process.

In a method of grinding the inner peripheral surface of a small diameter pipe by sandblasting, the thin diameter pipe to be ground is bent at a single point or a plurality of points continuously with an internal stress below the elastic limit or above the elastic limit, and around the tube axis. A method for grinding an inner peripheral surface of a small-diameter pipe, which is subjected to a sandblasting process in a state where rotation is applied to the tube, and is then returned to a straight line in a state in which the rotation is continuously applied.

6. The method for grinding an inner peripheral surface of a small-diameter pipe according to any one of claims 1 to 5, wherein the sand blasting process is alternately performed from both pipe ends of the fine pipe to be ground.