JP2004042100A - Method for discriminating short circuit in arc welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correctly discriminate short circuit without detecting welding voltage between a power feeding tip and a base metal in consumable electrode type arc welding in which a welding wire is fed at a feeding rate corresponding to a previously decided current set value and a short circuit period Ts and an arc period Ta are repeated. <P>SOLUTION: A welding current iw during welding is detected, and a welding current smoothened value ia obtained by smoothening the detected value of the welding current with a time constant of several tens to several hundreds of milliseconds is detected. A previously decided current increase value is added to the welding current smoothened value, and short circuit discrimination values iat are momentarily calculated. The occurrence of a short circuit is discriminated when the welding current detected value reaches or surpasses the short circuit discrimination value iat during the arc period Ta (time t11). Subsequently, when the welding current detected value becomes smaller than the short circuit discrimination value iat during the short circuit period Ts (time t21), it is discriminated that the short circuit is released and an arc is reproduced. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、アーク期間と短絡期間とを繰り返す消耗電極式アーク溶接の短絡判別方法に関し、特に、給電チップ・母材間の電圧ｗｐ検出することなく正確に短絡を判別することができる方法に関する。
【０００２】
【従来の技術】
図８は、消耗電極式アーク溶接装置の構成図である。以下、同図を参照して説明する。
制御装置ＰＬＣは、溶接電源装置ＰＳ、図示していないポジショナ等の動作を制御し、溶接電源装置ＰＳには電圧設定信号Ｖｒ、電流設定信号Ｉｒ等の制御信号を送出する。溶接電源装置ＰＳは、上記の電圧設定信号Ｖｒに対応した溶接電圧ｖｗ及び溶接電流ｉｗを出力すると共に、上記の電流設定信号Ｉｒに対応した送給速度で溶接ワイヤ１を送給するための送給制御信号Ｆｃを出力する。送給モータＷＭは、上記の送給制御信号Ｆｃに従って送給ロール５を回転させて溶接ワイヤ１を送給する。溶接ワイヤ１は、溶接トーチ４を通って母材２へ送給されると共に、溶接トーチ４の先端部に取り付けられた給電チップ４ａから給電されて、母材２との間にアーク３が発生する。溶接電源装置ＰＳの出力端子と溶接トーチ４及び母材２との間はケーブル６で接続されている。上記の溶接電圧ｖｗは給電チップ４ａと母材２との間の電圧であり、端子電圧ｖｔは溶接電源装置ＰＳの出力端子間の電圧である。上記のケーブル６が往復で５ｍ程度以下と非常に短い場合には、上記の溶接電圧ｖｗと上記の端子電圧ｖｔとは略等しくなる。しかし、ケーブル６の長さが往復で１０ｍ程度を超えるとケーブル６の抵抗値及びインダクランス値の影響が大きくなるために、上記の溶接電圧ｖｗと上記の端子電圧ｖｔとは大きく異なった値となる。
【０００３】
図９は、アーク期間と短絡期間とを繰り返すアーク溶接の電流・電圧波形図であり、同図（Ａ）は溶接電流ｉｗの時間変化を示し、同図（Ｂ）は溶接電圧ｖｗの時間変化を示す。アーク期間Ｔａと短絡期間Ｔｓとを繰り返すアーク溶接には、短絡移行溶接、グロビュール移行溶接、スプレー移行溶接等があるが、同図はその典型である短絡移行溶接のときの波形である。以下、同図を参照して説明する。
【０００４】
▲１▼　時刻ｔ１〜ｔ２の期間（短絡期間Ｔｓ）
時刻ｔ１〜ｔ２の短絡期間Ｔｓ中は、溶接ワイヤと母材との短絡によって負荷が非常に小さくなるために、同図（Ａ）に示すように、溶接電流ｉｗは時間経過とともに増加し、同図（Ｂ）に示すように、溶接電圧ｖｗは小さな値となる。このように電流が増加すると短絡部の溶滴に働く電磁的ピンチ力が増大するために、溶滴の母材への移行が加速されて短時間で短絡が解除されてアークが再発生する。しかしながら、この電流の増加率があまり大きすぎると、アーク再発生時に大粒のスパッタが多く発生し、また、ビード外観も悪くなるために、不良な溶接品質になる。これを防止するために、短絡期間中の電圧設定値をアーク期間中よりも小さくすることによって短絡期間中の電流の増加率を適正化する制御を行っている。この短絡電流制御を行うためには、短絡期間Ｔｓとアーク期間Ｔａとを判別する必要がある。この一般的な方法としては、同図（Ｂ）に示すように、基準電圧値Ｖｔｈを予め設定し、溶接電圧ｖｗがこの基準電圧値Ｖｔｈ以下のときを短絡期間Ｔｓと判別する方法が使用される。
【０００５】
▲２▼　時刻ｔ２〜ｔ３の期間（アーク期間Ｔａ）
時刻ｔ２において短絡が解除してアークが再発生すると、負荷が大きくなるために、同図（Ａ）に示すように、溶接電流ｉｗは時間経過とともに減少した後に定常値になり、同図（Ｂ）に示すように、溶接電圧ｖｗは数十Ｖのアーク電圧値に大きくなる。このアーク電圧値とアーク長とは略比例関係にあるので、適正なアーク長に設定するためにはアーク電圧値を適正値に設定すればよく、図８で上述した電圧設定信号Ｖｒは、このアーク電圧値を設定している。同図のＸ１及びＸ２で示すように、アーク期間Ｔａ中の溶接電流ｉｗ及び溶接電圧ｖｗは一定値ではなく大きく変動することが多い。これは、送給速度の変動、トーチ高さの変動、母材表面状態の変動、シールドガスによるシールド状態の変動等の種々の要因によってアーク負荷状態が刻々と変化するためである。
【０００６】
【発明が解決しようとする課題】
上記のように、給電チップ・母材間の電圧である溶接電圧ｖｗを検出することができれば短絡を判別することができる。ところで、実際の溶接ラインにおいては多数の加工用装置の配置上の制約から溶接電源装置と母材ワークとが相当に離れた場所に配置されることが多くある。このような場合には、図８で上述したケーブル６の長さが往復で２０〜５０ｍと長くなることも多くある。このときに給電チップ・母材間の溶接電圧ｖｗを検出するためには、溶接電源装置と溶接トーチ又は母材との間に専用の検出線を配線する必要がある。しかし、▲１▼この配線には手間とコストがかかること、▲２▼溶接トーチは溶接ロボット等に搭載されて激しく移動するために検出線の断線が発生しやすいこと、▲３▼母材ワークが自動車フレーム、橋梁、鉄骨等のように大型構造物である場合には溶接個所近くに上記の検出線を接続することが困難であること等の種々の原因から上記の検出線が使用されていない。そして、溶接電圧ｖｗの代りに端子電圧ｖｔを検出するのが一般的である。
【０００７】
図１０は、ケーブルが長いときの端子電圧ｖｔの波形図である。上述したように、ケーブルの抵抗値及びインダクランス値が大きいために、溶接電流の変化によってノイズが重畳して同図のような波形となる。上述したように、この端子電圧ｖｔと基準電圧値Ｖｔｈを比較して短絡期間Ｔｓを判別すると、Ｘ３に示すようにアーク期間Ｔａを短絡と判別したり、Ｘ４に示すように短絡機関Ｔｓをアークと判別する誤検出が発生する。このために、端子電圧ｖｔを大きな時定数で平滑して誤検出を防止している。しかし、大きな時定数で平滑すると短絡判別のタイミングが大きく遅れることになり、遅れなしに正確に短絡期間Ｔｓを判別することはできない。この結果、短絡電流の増加率の適正化が不十分となり、スパッタの増加、ビード外観の悪化等によって溶接品質が悪くなる。
【０００８】
また、上記以外の短絡判別方法として溶接電流ｉｗの増加率（微分値ｉｂ＝ｄｉ／ｄｔ）による方法がある。図１１は、この方法を示す波形図であり、同図（Ａ）は溶接電流ｉｗの時間変化を示し、同図（Ｂ）は溶接電流ｉｗの増加分の微分値ｉｂ＝ｄｉｗ／ｄｔの時間変化を示す。同図（Ａ）に示すように、時刻ｔ１において短絡が発生すると電流は増加するので、同図（Ｂ）のＸ５に示すように、微分値ｉｂも大きくなる。この微分値ｉｂが予め定めた微分基準値Ｂｔｈを超えると短絡と判別する。この方法では、溶接電流ｉｗを検出して微分値ｉｂを算出するので、溶接電源装置内の電流検出器によって検出することができる。したがって、ケーブルが長い場合でも検出線を追加・配線する必要はない。しかし、同図（Ａ）に示すように、アーク期間Ｔａ中の溶接電流ｉｗは上述したように種々の要因によるアーク負荷の変動に伴い大きく変動する。この変動を微分すると、同図（Ｂ）のＸ６に示すように、微分値ｉｂは大きくなり微分基準値Ｂｔｈを超えて短絡を誤検出する場合が生じる。したがって、この電流増加率によっても正確に短絡を判別することはできない。
【０００９】
そこで、本発明では、ケーブルの長さに影響されることなく検出線も不要な短絡判別方法を提供することを目的とする。
【００１０】
【課題を解決するための手段】
請求項１の発明は、予め定めた電流設定値に対応した送給速度で溶接ワイヤを送給し短絡期間とアーク期間とを繰り返すアーク溶接の短絡判別方法において、溶接中の溶接電流を検出しこの溶接電流検出値を数十ｍｓ〜数百ｍｓの時定数で平滑した溶接電流平滑値を検出しこの溶接電流平滑値に予め定めた増加電流値を加算して短絡判別値を刻々と演算し、上記アーク期間中に上記溶接電流検出値が上記短絡判別値以上になったことを判別して短絡発生を判別し、続けて上記短絡期間中に上記溶接電流検出値が上記短絡判別値未満になったことを判別して短絡が解除してアークが再発生したことを判別することを特徴とするアーク溶接の短絡判別方法である。
【００１１】
請求項２の発明は、上記短絡判別値を、溶接電流平滑値が電流設定値以下のときには上記電流設定値に予め定めた増加電流値を加算した値として刻々と演算する請求項１記載のアーク溶接の短絡判別方法である。
【００１２】
請求項３の発明は、上記短絡解除の判別を、短絡期間中に溶接電流検出値がこの短絡期間中の最大値から予め定めた減少電流値だけ小さくなったことを判別することによって行う請求項１又は請求項２記載のアーク溶接の短絡判別方法である。
【００１３】
【発明の実施の形態】
以下、本発明の実施の形態について図面を参照して説明する。本発明は、以下の実施の形態に限定されるものではない。
【００１４】
［実施の形態１］
本発明の実施の形態１は、溶接電流ｉｗを平滑した溶接電流平滑値ｉａに予め定めた増加電流値ΔＩａを加算して短絡判別値ｉａｔ＝ｉａ＋ΔＩａを刻々と演算し、アーク期間中に溶接電流ｉｗがこの短絡判別値ｉａｔ以上になったときに短絡発生を判別し、続けて短絡期間中に溶接電流ｉｗがこの時点での短絡判別値ｉａｔ未満になったときに短絡解除と判別する方法である。以下、図面を参照して説明する。
【００１５】
図１は、実施の形態１における短絡判別方法を示す波形図であり、同図（Ａ）は溶接電流ｉｗの時間変化を示し、同図（Ｂ）は短絡判別信号Ｓｄの時間変化を示す。同図（Ａ）に示すように、溶接電流ｉｗを数十ｍｓ〜数百ｍｓの時定数で平滑した溶接電流平滑値ｉａを検出する。この溶接電流平滑値ｉａに予め定めた増加電流値ΔＩａを加算して短絡判別値ｉａｔ＝ｉａ＋ΔＩａを刻々と演算する。同図（Ａ）に示すように、時刻ｔ１において短絡が発生すると電流が増加して時刻ｔ１１において溶接電流ｉｗが短絡判別値ｉａｔ以上になったことを判別すると、同図（Ｂ）に示すように、短絡判別信号ＳｄがＨｉｇｈレベル（短絡）に変化する。続いて、時刻ｔ２において短絡が解除されてアークが再発生すると電流が減少して時刻ｔ２１において溶接電流ｉｗがこの時点での短絡判別値ｉａｔ未満になったことを判別すると、同図（Ｂ）に示すように、短絡判別信号ＳｄはＬｏｗレベル（アーク）に変化する。短絡が発生した時刻ｔ１と短絡判別信号ＳｄがＨｉｇｈレベルに変化する時刻ｔ１１との間には少しの遅れがあるが、短時間であるので短絡電流の制御には影響はない。また、時刻ｔ２の短絡解除時も同様である。上記の溶接電流平滑値ｉａの時定数をどの値に設定するかは重要である。すなわち、この時定数は１回のアーク期間中の溶接電流ｉｗの急激な変動を平滑することができる値である数十ｍｓ以上である必要がある。他方、この時定数は、送給速度、トーチ高さ等の変動による数十回の短絡／アークの繰り返し期間にわたる緩やかで大きな変化幅である溶接電流ｉｗの変動は平滑しないために数百ｍｓ以下の値である必要がある。これにより、溶接電流ｉｗの急激な変動は平滑して影響をなくし、かつ、緩やかで大きな変動に対しては平滑せずに短絡判別値ｉａｔに反映させることによって、誤検出なしに正確に短絡を判別することが可能となる。短絡移行溶接時における上記の時定数は１００ｍｓ程度であり、上記の増加電流値ΔＩａは５０Ａ程度である。
【００１６】
図２は、実施の形態１に係る溶接電源装置ＰＳのブロック図である。以下、同図を参照して各回路について説明する。
【００１７】
出力制御回路ＩＮＶは、交流商用電源（３相２００Ｖ等）を入力として、後述する電圧誤差増幅信号Ｅｖに従ってインバータ制御、サイリスタ位相制御等の出力制御を行い溶接に適した溶接電圧ｖｗ及び溶接電流ｉｗを出力する。外部に設けられた制御装置ＰＬＣから電圧設定信号Ｖｒ及び電流設定信号Ｉｒが入力される。送給制御回路ＦＣは、上記の電流設定信号Ｉｒに対応した送給速度で溶接ワイヤ１を送給するための送給制御信号Ｆｃを出力する。送給モータＷＭは、上記の送給制御信号Ｆｃに従って送給ロール５を回転させて溶接ワイヤ１を送給する。溶接ワイヤ１は、溶接トーチ４を通って母材２へ送給されてアーク３が発生する。
【００１８】
電流検出回路ＩＤは、上記の溶接電流ｉｗを検出して電流検出信号ｉｄを出力する。電流平滑回路ＩＡは、上記の電流検出信号ｉｄを上述したように数十ｍｓ〜数百ｍｓの時定数で平滑して溶接電流平滑信号ｉａを出力する。短絡判別値演算回路ＩＡＴは、上記の溶接電流平滑信号ｉａに予め定めた増加電流値ΔＩａを加算して短絡電流判別値信号ｉａｔを出力する。比較回路ＣＭは、上記の電流検出信号ｉｄと上記の短絡判別値信号ｉａｔとを比較して、ｉｄ≧ｉａｔのときにＨｉｇｈレベルとなり、ｉｄ＜ｉａｔのときにＬｏｗレベルとなる短絡判別信号Ｓｄを出力する。
【００１９】
短絡電圧設定回路ＶＲＳは、短絡期間中の溶接電流の増加率を適正化するための短絡電圧設定信号Ｖｒｓを出力する。電圧設定切換回路ＳＶは、上記の短絡判別信号ＳｄがＨｉｇｈレベル（短絡）のときにはａ側に切り換わり上記の短絡電圧設定信号Ｖｒｓを電圧制御設定信号Ｖｒｃとして出力し、上記の短絡判別信号ＳｄがＬｏｗレベル（アーク）のときにはｂ側に切り換わり上記の外部からの電圧設定信号Ｖｒを電圧制御設定信号Ｖｒｃとして出力する。電圧検出回路ＶＤは、端子電圧ｖｔを検出して電圧検出信号ｖｄを出力する。電圧誤差増幅回路ＥＶは、上記の電圧制御設定信号Ｖｒｃと上記の電圧検出信号ｖｄとの誤差を増幅して電圧誤差増幅信号Ｅｖを出力する。この電圧誤差増幅回路ＥＶによって溶接電源装置ＰＳは定電圧制御される。
【００２０】
［実施の形態２］
本発明の実施の形態２は、上述した実施の形態１において、上記の短絡判別値ｉａｔを、溶接電流平滑値ｉａが電流設定値Ｉｒ以下のときには電流設定値Ｉｒに予め定めた増加電流値ΔＩａを加算した値（Ｉｒ＋ΔＩａ）として刻々と演算するアーク溶接の短絡判別方法である。溶接継手形状の制約、ワイヤ溶着量の増大等からトーチ高さ（ワイヤ突出し長さ）を通常の適正範囲よりも長く設定して溶接する場合がある。一般的にワイヤ突出し長さが適正範囲よりも長くなると、アーク発生状態がやや不安定になる。このために、アーク期間中の溶接電流ｉｗの変動がさらに大きくなり、溶接電流平滑値ｉａの変動も大きくなるために、実施の形態１の方法では短絡発生を誤検出する可能性がある。ところで、電流設定値Ｉｒは、ワイヤ突出し長さが適正範囲のときの溶接電流平滑値ｉａと略等しくなる。溶接電流平滑値ｉａはワイヤ突出し長さと反比例の関係にあるので、ワイヤ突出し長さが長くなると溶接電流平滑値ｉａは小さくなる。したがって、溶接電流平滑値ｉａが電流設定値Ｉｒ以下のときはワイヤ突出し長さが適正範囲よりも長いときであり、このときには上記のようにアーク発生状態がやや不安定になり、溶接電流平滑値ｉａの変動も大きくなる。実施の形態２では、このような場合には誤検出を防止するために、変動が大きな溶接電流平滑値ｉａに代えて電流設定値Ｉｒを使用して短絡判別値ｉａｔ＝Ｉｒ＋ΔＩａを演算する方法である。この方法では、短絡発生の判別タイミングが若干遅くなるが、誤検出を防止することができる。以下、図面を参照して説明する。
【００２１】
図３は、実施の形態２における短絡判別方法を示す波形図であり、同図（Ａ）は溶接電流ｉｗの時間変化を示し、同図（Ｂ）は短絡判別信号Ｓｄの時間変化を示す。同図は、ワイヤ突出し長さが適正範囲よりも長い場合である。
【００２２】
同図（Ａ）に示すように、溶接電流平滑値ｉａは電流設定値Ｉｒ以下であるために、短絡判別値ｉａｔは電流設定値Ｉｒ及び予め定めた増加電流値ΔＩａによってｉａｔ＝Ｉｒ＋ΔＩａとして演算される。これ以後の動作は上述した図１のときと同様に、溶接電流ｉｗと上記の短絡判別値ｉａｔとを比較して、同図（Ｂ）に示すように、ｉｗ≧ｉａｔの期間（時刻１１〜ｔ２１）を短絡期間（Ｈｉｇｈレベル）と判別する。
【００２３】
図４は、実施の形態２に係る溶接電源装置ＰＳのブロック図である。同図において上述した図２と同一の回路には同一符号を付してそれらの説明は省略する。以下、図２とは異なる点線で示す回路について説明する。第２の短絡判別値演算回路ＩＡＴ２は、溶接電流平滑信号ｉａ、電流設定信号Ｉｒ及び増加電流値ΔＩａを入力として、ｉａ＞Ｉｒのときには短絡判別値信号ｉａｔ＝ｉａ＋ΔＩａを演算して出力し、ｉａ≦Ｉｒのときには短絡判別値信号ｉａｔ＝Ｉｒ＋ΔＩａを演算して出力する。
【００２４】
［実施の形態３］
本発明の実施の形態３は、上述した実施の形態１及び２において、短絡発生の判別は上記のままで、短絡解除の判別を短絡期間中に溶接電流ｉｗがこの短絡期間中の最大値Ｉｐｈから予め定めた減少電流値ΔＩｐだけ小さくなったことを判別することによって行う短絡判別方法である。この目的は、短絡解除の判別の遅れを短くすることにある。すなわち、実施の形態１及び２においては、短絡が解除されてアークが再発生し、溶接電流ｉｗが短絡判別値ｉａｔまで減少するまでは短絡期間と判別する。しかし、短絡解除時の電流値が実際の短絡期間中の最大値Ｉｐｈとなるので、実施の形態３では、この最大値Ｉｐｈから予め定めた減少電流値ΔＩｐを減算した短絡解除判別値Ｉｐｔ＝Ｉｐｈ−ΔＩｐを求め、溶接電流ｉｗ＜Ｉｐｔになったときに短絡が解除されたと判別する。通常、短絡判別値ｉａｔ＜短絡解除判別値Ｉｐｔなので、短絡解除の判別の遅れを短くすることができる。以下、図面を参照して説明する。
【００２５】
図５は、実施の形態３における短絡判別方法を示す波形図であり、同図（Ａ）は溶接電流ｉｗの時間変化を示し、同図（Ｂ）は短絡判別信号Ｓｄの時間変化を示す。同図（Ａ）に示す溶接電流ｉｗの波形は、図１と同一のときであり、したがって短絡判別値ｉａｔ＝ｉａ＋ΔＩａの場合である。
【００２６】
同図（Ａ）に示すように、時刻ｔ１１において溶接電流ｉｗが短絡判別値ｉａｔ以上になると短絡発生と判別する。続いて、短絡期間中の溶接電流ｉｗの最大値Ｉｐｈをサンプル・ホールドして短絡解除判別値Ｉｐｔ＝Ｉｐｈ−ΔＩｐ（定数）を演算し、時刻２２において溶接電流ｉｗがこの短絡解除判別値Ｉｐｔ未満になったときに短絡解除と判別する。上記の減少電流値ΔＩｐは例えば５０Ａに設定される。したがって、同図（Ｂ）に示すように、時刻ｔ１１〜ｔ２２の期間を短絡期間（Ｈｉｇｈレベル）として判別する。図１及び図３と同図とを比較すると明らかなように、短絡解除の判別の遅れが時刻ｔ２１から時刻ｔ２２へと短くなっている。
【００２７】
同図は、図１の溶接電流波形の場合であるが、図３の溶接電流波形の場合も同様である。このときの説明は省略する。
【００２８】
図６は、実施の形態３に係る溶接電源装置ＰＳのブロック図である。同図は、実施の形態１に本短絡解除の判別方法を加味した場合である。同図において上述した図２と同一の回路には同一符号を付してそれらの説明は省略する。以下、図２とは異なる点線で示す回路について説明する。
【００２９】
短絡電流最大値保持回路ＩＰＨは、電流検出信号ｉｄを入力として短絡期間中の最大値をサンプル・ホールドして短絡電流最大値信号Ｉｐｈを出力する。短絡解除判別値演算回路ＩＰＴは、上記の短絡電流最大値信号Ｉｐｈから予め定めた減少電流値ΔＩｐを減算して短絡解除判別値信号Ｉｐｔを出力する。第２の比較回路ＣＭ２は、上記の電流検出信号ｉｄと上記の短絡解除判別値信号Ｉｐｔとを比較してｉｄ≧ＩｐｔのときにＨｉｇｈレベルとなり、ｉｄ＜ＩｐｔのときにＬｏｗレベルとなるリセット信号Ｒｓを出力する。比較回路ＣＭは、上記の電流検出信号ｉｄと短絡判別値信号ｉａｔとを比較して、ｉｄ≧ｉａｔのときにＨｉｇｈレベルとなり、ｉｄ＜ｉａｔのときにＬｏｗレベルとなるセット信号Ｓｅｔを出力する。フリップフロップ回路ＦＦは、上記のセット信号ＳｅｔがＨｉｇｈレベルに変化すると短絡判別信号ＳｄはＨｉｇｈレベルとなり、上記のリセット信号ＲｓがＬｏｗレベルに変化すると短絡判別信号ＳｄはＬｏｗレベルになる。以降の動作は図２と同一である。
【００３０】
図７は、実施の形態２の図４に上記の図６を加味した溶接電源装置ＰＳのブロック図である。同図において上述した図４及び図６と同一の回路には同一符号を付してそれらの回路の説明は省略する。
【００３１】
【発明の効果】
請求項１記載のアーク溶接の短絡判別方法によれば、溶接電源装置と母材又は溶接トーチとの間のケーブルが長い場合でも溶接電圧を検出するための検出線を使用することなく溶接電流の検出のみで正確に短絡を判別することができるので、短絡電流の増加率を適正値に制御して常に良好な溶接品質を得ることができる。さらには、検出線の配線に要する手間とコストを無くすことができ、検出線の断線によるトラブルを無くすことができる。
請求項２記載のアーク溶接の短絡判別方法によれば、上記の効果に加えて、ワイヤ突出し長さが長い場合でも溶接電流の変動によって短絡期間を誤検出することがないので、ワイヤ突出し長さが長い場合でも良好な溶接品質を得ることができる。
請求項３記載のアーク溶接の短絡判別方法によれば、上記の効果に加えて、短絡解除の判別の遅れを短くすることができるので、実際の短絡解除直後から遅れることなくアーク電流を適正化することができ、ビード外観がさらに良好になる。
【図面の簡単な説明】
【図１】本発明の実施の形態１に係る短絡判別方法を示す溶接電流ｉｗの波形図である。
【図２】実施の形態１に係る溶接電源装置のブロック図である。
【図３】実施の形態２に係る短絡判別方法を示す溶接電流ｉｗの波形図である。
【図４】実施の形態２に係る溶接電源装置のブロック図である。
【図５】実施の形態３に係る短絡判別方法を示す溶接電流ｉｗの波形図である。
【図６】実施の形態３に係る溶接電源装置のブロック図である。
【図７】実施の形態３に係るもう１つの溶接電源装置のブロック図である。
【図８】従来のアーク溶接装置の構成図である。
【図９】従来技術における溶接電流ｉｗ及び溶接電圧ｖｗの波形図である。
【図１０】従来技術１の短絡判別方法の課題を説明するための溶接電源装置の端子電圧ｖｔの波形図である。
【図１１】従来技術２の短絡判別方法の課題を説明するための溶接電流ｉｗ及び溶接電圧ｖｗの波形図である。
【符号の説明】
１　溶接ワイヤ
２　母材
３　アーク
４　溶接トーチ
４ａ　給電チップ
５　送給ロール
６　ケーブル
Ｂｔｈ　基準微分値
ＣＭ　比較回路
ＣＭ２　第２の比較回路
ＥＶ　電圧誤差増幅回路
Ｅｖ　電圧誤差増幅信号
ＦＣ　送給制御回路
Ｆｃ　送給制御信号
ＦＦ　フリップフロップ回路
ＩＡ　電流平滑回路
ｉａ　溶接電流平滑（値／信号）
ＩＡＴ　短絡判別値演算回路
ｉａｔ　短絡判別値（信号）
ＩＡＴ２　第２の短絡判別値演算回路
ｉｂ　（電流）微分値
ＩＤ　電流検出回路
ｉｄ　電流検出信号
ＩＮＶ　出力制御回路
ＩＰＨ　短絡電流最大値保持回路
Ｉｐｈ　短絡電流最大値（信号）
ＩＰＴ　短絡解除判別値演算回路
Ｉｐｔ　短絡解除判別値（信号）
Ｉｒ　電流設定（値／信号）
ｉｗ　溶接電流
ＰＬＣ　制御装置
ＰＳ　溶接電源装置
Ｒｓ　リセット信号
Ｓｄ　短絡判別信号
Ｓｅｔ　セット信号
ＳＶ　電圧設定切換回路
Ｔａ　アーク期間
Ｔｓ　短絡期間
Ｖｒ　電圧設定（値／信号）
Ｖｒｃ　電圧制御設定信号
ＶＲＳ　短絡電圧設定回路
Ｖｒｓ　短絡電圧設定信号
ｖｔ　端子電圧
Ｖｔｈ　基準電圧値
ｖｗ　溶接電圧
ＷＭ　送給モータ
ΔＩａ　増加電流値
ΔＩｐ　減少電流値[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for determining a short circuit in consumable electrode arc welding in which an arc period and a short circuit period are repeated, and more particularly to a method for accurately determining a short circuit without detecting a voltage wp between a power supply tip and a base material.
[0002]
[Prior art]
FIG. 8 is a configuration diagram of a consumable electrode type arc welding apparatus. Hereinafter, description will be made with reference to FIG.
The control device PLC controls operations of the welding power supply device PS and a positioner (not shown), and sends control signals such as a voltage setting signal Vr and a current setting signal Ir to the welding power supply device PS. The welding power supply device PS outputs the welding voltage vw and the welding current iw corresponding to the voltage setting signal Vr, and sends the welding wire 1 at a feeding speed corresponding to the current setting signal Ir. It outputs a supply control signal Fc. The feed motor WM feeds the welding wire 1 by rotating the feed roll 5 according to the feed control signal Fc. The welding wire 1 is fed to the base material 2 through the welding torch 4, and is supplied with power from a power supply tip 4 a attached to the tip of the welding torch 4 to generate an arc 3 between the welding wire 1 and the base material 2. I do. The cable 6 is connected between the output terminal of the welding power supply PS and the welding torch 4 and the base material 2. The welding voltage vw is a voltage between the power supply tip 4a and the base material 2, and the terminal voltage vt is a voltage between the output terminals of the welding power supply device PS. When the above-mentioned cable 6 is very short, such as about 5 m or less in reciprocation, the welding voltage vw is substantially equal to the terminal voltage vt. However, if the length of the cable 6 exceeds about 10 m in a round trip, the influence of the resistance value and the inductance value of the cable 6 increases, so that the welding voltage vw differs greatly from the terminal voltage vt. Become.
[0003]
9A and 9B are current / voltage waveform diagrams of arc welding in which an arc period and a short circuit period are repeated. FIG. 9A shows a time change of the welding current iw, and FIG. 9B shows a time change of the welding voltage vw. Is shown. The arc welding in which the arc period Ta and the short-circuit period Ts are repeated includes short-circuit transfer welding, globule transfer welding, spray transfer welding, and the like. FIG. Hereinafter, description will be made with reference to FIG.
[0004]
{Circle around (1)} Time period from time t1 to t2 (short circuit period Ts)
During the short-circuit period Ts from time t1 to t2, the load becomes very small due to the short-circuit between the welding wire and the base material, so that the welding current iw increases with time, as shown in FIG. As shown in FIG. (B), the welding voltage vw has a small value. When the current increases in this manner, the electromagnetic pinch force acting on the droplet at the short-circuit portion increases, so that the transition of the droplet to the base material is accelerated, the short circuit is released in a short time, and an arc is generated again. However, if the rate of increase of the current is too large, large spatters are generated at the time of arc re-generation, and the bead appearance also deteriorates, resulting in poor welding quality. In order to prevent this, the voltage set value during the short-circuit period is made smaller than that during the arc period, thereby performing control to optimize the current increase rate during the short-circuit period. In order to perform the short-circuit current control, it is necessary to determine the short-circuit period Ts and the arc period Ta. As a general method, a method is used in which a reference voltage value Vth is set in advance and a time when the welding voltage vw is equal to or less than the reference voltage value Vth is determined as a short-circuit period Ts, as shown in FIG. You.
[0005]
(2) Period from time t2 to t3 (arc period Ta)
When the short circuit is released at time t2 and the arc re-occurs, the load increases, so that the welding current iw decreases with time and then becomes a steady value, as shown in FIG. ), The welding voltage vw increases to an arc voltage value of several tens of volts. Since the arc voltage value and the arc length are substantially proportional, the arc voltage value may be set to an appropriate value in order to set the arc length to an appropriate value. The voltage setting signal Vr described above with reference to FIG. The arc voltage value is set. As indicated by X1 and X2 in the figure, the welding current iw and the welding voltage vw during the arc period Ta often fluctuate rather than have constant values. This is because the state of the arc load changes every moment due to various factors such as a change in the feeding speed, a change in the torch height, a change in the surface condition of the base material, and a change in the shield state due to the shield gas.
[0006]
[Problems to be solved by the invention]
As described above, if the welding voltage vw, which is the voltage between the power supply tip and the base material, can be detected, a short circuit can be determined. By the way, in an actual welding line, there are many cases where a welding power supply device and a base material work are arranged at a considerably distant place due to restrictions on arrangement of a large number of processing apparatuses. In such a case, the length of the cable 6 described above with reference to FIG. At this time, in order to detect the welding voltage vw between the power supply tip and the base material, it is necessary to wire a dedicated detection line between the welding power supply device and the welding torch or the base material. However, (1) this wiring is troublesome and costly, (2) the welding torch is mounted on a welding robot or the like and moves violently, so that the detection wire is easily broken, and (3) the base material work. In the case of a large structure such as an automobile frame, a bridge, a steel frame, etc., the above-described detection line is used for various reasons such as difficulty in connecting the above-described detection line near a welding point. Absent. In general, a terminal voltage vt is detected instead of the welding voltage vw.
[0007]
FIG. 10 is a waveform diagram of the terminal voltage vt when the cable is long. As described above, since the resistance value and the inductance value of the cable are large, noise is superimposed due to a change in the welding current, resulting in a waveform as shown in FIG. As described above, when the short-circuit period Ts is determined by comparing the terminal voltage vt with the reference voltage value Vth, the arc period Ta is determined to be short-circuited as indicated by X3, or the short-circuit engine Ts is arced as indicated by X4. Is erroneously detected. For this reason, the terminal voltage vt is smoothed with a large time constant to prevent erroneous detection. However, if the smoothing is performed with a large time constant, the timing of the short circuit determination is greatly delayed, and the short circuit period Ts cannot be accurately determined without a delay. As a result, the increase rate of the short-circuit current is not properly adjusted, and the welding quality is deteriorated due to an increase in spatter, deterioration of the bead appearance, and the like.
[0008]
As a short-circuit determination method other than the above, there is a method based on an increase rate of the welding current iw (differential value ib = di / dt). FIGS. 11A and 11B are waveform diagrams showing this method. FIG. 11A shows the time change of the welding current iw, and FIG. 11B shows the time of the differential value ib = diw / dt of the increase in the welding current iw. Indicates a change. As shown in FIG. 7A, when a short circuit occurs at time t1, the current increases, and the differential value ib also increases as shown by X5 in FIG. If the differential value ib exceeds a predetermined differential reference value Bth, it is determined that a short circuit has occurred. In this method, since the differential value ib is calculated by detecting the welding current iw, it can be detected by the current detector in the welding power supply device. Therefore, even if the cable is long, there is no need to add and wire a detection line. However, as shown in FIG. 5A, the welding current iw during the arc period Ta fluctuates greatly with the fluctuation of the arc load due to various factors as described above. When this variation is differentiated, the differential value ib increases and exceeds the differential reference value Bth, as shown by X6 in FIG. 7B, and a short circuit may be erroneously detected. Therefore, it is not possible to accurately determine a short circuit even from this current increase rate.
[0009]
Accordingly, an object of the present invention is to provide a short-circuit determination method that does not require a detection line without being affected by the length of a cable.
[0010]
[Means for Solving the Problems]
The invention according to claim 1 is a method for determining a short circuit in arc welding in which a welding wire is fed at a feed rate corresponding to a predetermined current set value and a short circuit period and an arc period are repeated, wherein a welding current during welding is detected. A welding current smoothed value obtained by smoothing the welding current detection value with a time constant of several tens to several hundreds of ms is detected, and a predetermined increasing current value is added to the welding current smoothed value to calculate a short circuit determination value every moment. During the arc period, it is determined that the welding current detection value is equal to or greater than the short-circuit determination value to determine the occurrence of a short-circuit. Subsequently, during the short-circuit period, the welding current detection value is less than the short-circuit determination value. It is a method of determining a short circuit in arc welding, wherein it is determined that the short circuit has occurred and the short circuit has been released and the arc has been regenerated.
[0011]
According to a second aspect of the present invention, the short-circuit determination value is calculated every moment as a value obtained by adding a predetermined increased current value to the current set value when the welding current smoothed value is equal to or less than the current set value. This is a welding short-circuit determination method.
[0012]
According to a third aspect of the present invention, the determination of the release of the short circuit is performed by determining that the welding current detection value during the short circuit period has decreased from the maximum value during the short circuit period by a predetermined reduced current value. A method for determining a short circuit in arc welding according to claim 1 or 2.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments.
[0014]
[Embodiment 1]
According to the first embodiment of the present invention, a short-circuit determination value iat = ia + ΔIa is calculated every moment by adding a predetermined increase current value ΔIa to a welding current smooth value ia obtained by smoothing the welding current iw, and the welding current during the arc period is calculated. When iw is equal to or greater than the short-circuit determination value iat, it is determined that a short-circuit has occurred. When the welding current iw falls below the short-circuit determination value iat at this time during the short-circuit period, it is determined that the short-circuit has been released. is there. Hereinafter, description will be made with reference to the drawings.
[0015]
FIGS. 1A and 1B are waveform diagrams illustrating a short-circuit determination method according to the first embodiment. FIG. 1A illustrates a change over time of the welding current iw, and FIG. 1B illustrates a change over time of the short-circuit determination signal Sd. As shown in FIG. 3A, a welding current smoothed value ia obtained by smoothing the welding current iw with a time constant of several tens to several hundreds of ms is detected. A short circuit determination value iat = ia + ΔIa is calculated every moment by adding a predetermined increased current value ΔIa to the welding current smooth value ia. As shown in FIG. 5A, when a short circuit occurs at time t1, the current increases. At time t11, when it is determined that the welding current iw has become equal to or greater than the short circuit determination value iat, as shown in FIG. Then, the short-circuit determination signal Sd changes to a high level (short-circuit). Subsequently, when the short circuit is released at time t2 and the arc re-occurs, the current decreases, and it is determined at time t21 that the welding current iw has become less than the short circuit determination value iat at this time. As shown in (1), the short-circuit determination signal Sd changes to a low level (arc). Although there is a slight delay between the time t1 at which the short circuit occurs and the time t11 at which the short circuit determination signal Sd changes to the High level, the short time does not affect the control of the short circuit current. The same applies when the short circuit is released at time t2. It is important to set the time constant of the above welding current smooth value ia to which value. That is, the time constant needs to be several tens ms or more, which is a value capable of smoothing a sudden change in the welding current iw during one arc period. On the other hand, the time constant is several hundred ms or less because the fluctuation of the welding current iw, which is a gradual and large change width over the repetition period of several tens of short circuits / arcs due to the fluctuation of the feeding speed, the torch height, etc., is not smoothed. Must be the value of As a result, a sharp change in the welding current iw is smoothed and eliminated, and a gentle and large change is reflected in the short-circuit determination value iat without smoothing, whereby a short-circuit is accurately detected without erroneous detection. It is possible to determine. The above time constant at the time of short-circuit transfer welding is about 100 ms, and the above-mentioned increased current value ΔIa is about 50 A.
[0016]
FIG. 2 is a block diagram of welding power supply device PS according to Embodiment 1. Hereinafter, each circuit will be described with reference to FIG.
[0017]
The output control circuit INV receives an AC commercial power supply (three-phase 200 V or the like) as input and performs output control such as inverter control and thyristor phase control in accordance with a voltage error amplification signal Ev described later, and performs welding voltage vw and welding current iw suitable for welding. Is output. A voltage setting signal Vr and a current setting signal Ir are input from a control device PLC provided outside. The feed control circuit FC outputs a feed control signal Fc for feeding the welding wire 1 at a feed speed corresponding to the current setting signal Ir. The feed motor WM feeds the welding wire 1 by rotating the feed roll 5 according to the feed control signal Fc. The welding wire 1 is fed to the base material 2 through the welding torch 4 and an arc 3 is generated.
[0018]
The current detection circuit ID detects the above welding current iw and outputs a current detection signal id. The current smoothing circuit IA smoothes the current detection signal id with a time constant of several tens ms to several hundred ms as described above, and outputs a welding current smooth signal ia. The short circuit determination value calculation circuit IAT adds a predetermined increase current value ΔIa to the welding current smoothing signal ia to output a short circuit current determination value signal iat. The comparison circuit CM compares the current detection signal id with the short-circuit determination value signal iat, and determines a short-circuit determination signal Sd that is high when id ≧ iat and low when id <iat. Output.
[0019]
The short-circuit voltage setting circuit VRS outputs a short-circuit voltage setting signal Vrs for optimizing the increase rate of the welding current during the short-circuit period. When the short-circuit determination signal Sd is at a high level (short-circuit), the voltage setting switching circuit SV switches to the a side and outputs the short-circuit voltage setting signal Vrs as a voltage control setting signal Vrc. At the time of a low level (arc), the voltage is switched to the side b and the above-mentioned external voltage setting signal Vr is output as a voltage control setting signal Vrc. The voltage detection circuit VD detects the terminal voltage vt and outputs a voltage detection signal vd. The voltage error amplifier EV amplifies the error between the voltage control setting signal Vrc and the voltage detection signal vd and outputs a voltage error amplified signal Ev. The voltage error amplifier circuit EV controls the welding power supply PS at a constant voltage.
[0020]
[Embodiment 2]
The second embodiment of the present invention is different from the first embodiment in that the short-circuit discrimination value ia is set to the increased current value ΔIa which is set in advance to the current set value Ir when the welding current smooth value ia is equal to or smaller than the current set value Ir. Is a method of determining short circuit of arc welding, which is calculated every moment as a value (Ir + ΔIa) obtained by adding the following. Due to restrictions on the shape of the weld joint, an increase in the amount of wire welding, and the like, welding may be performed with the torch height (wire projection length) set longer than a normal appropriate range. In general, if the wire protrusion length is longer than an appropriate range, the arc generation state becomes slightly unstable. For this reason, the fluctuation of the welding current iw during the arc period further increases, and the fluctuation of the welding current smooth value ia also increases. Therefore, the method of the first embodiment may erroneously detect the occurrence of a short circuit. By the way, the current set value Ir is substantially equal to the welding current smooth value ia when the wire protrusion length is in the appropriate range. Since the welding current smooth value ia is inversely proportional to the wire protrusion length, the welding current smooth value ia decreases as the wire protrusion length increases. Therefore, when the welding current smooth value ia is equal to or less than the current setting value Ir, the wire protrusion length is longer than the appropriate range. At this time, the arc generation state becomes somewhat unstable as described above, and the welding current smooth value The fluctuation of ia also increases. In the second embodiment, in such a case, in order to prevent erroneous detection, a method of calculating the short-circuit determination value iat = Ir + ΔIa using the current setting value Ir instead of the welding current smooth value ia having large fluctuations. is there. In this method, the timing of determining the occurrence of a short circuit is slightly delayed, but erroneous detection can be prevented. Hereinafter, description will be made with reference to the drawings.
[0021]
3A and 3B are waveform diagrams illustrating a short-circuit determination method according to the second embodiment. FIG. 3A illustrates a change over time of the welding current iw, and FIG. 3B illustrates a change over time of the short-circuit determination signal Sd. The figure shows a case where the wire protrusion length is longer than an appropriate range.
[0022]
As shown in FIG. 3A, since the welding current smooth value ia is equal to or smaller than the current set value Ir, the short-circuit determination value iat is calculated as ia = Ir + ΔIa by the current set value Ir and a predetermined increased current value ΔIa. You. In the subsequent operation, the welding current iw is compared with the short-circuit determination value iat as in the case of FIG. 1 described above, and as shown in FIG. t21) is determined as the short-circuit period (High level).
[0023]
FIG. 4 is a block diagram of welding power supply device PS according to Embodiment 2. In this figure, the same circuits as those in FIG. Hereinafter, a circuit indicated by a dotted line different from FIG. 2 will be described. The second short circuit determination value calculation circuit IAT2 receives the welding current smoothing signal ia, the current setting signal Ir, and the increase current value ΔIa, and calculates and outputs a short circuit determination value signal iat = ia + ΔIa when ia> Ir. When ≦ Ir, the short circuit determination value signal iat = Ir + ΔIa is calculated and output.
[0024]
[Embodiment 3]
In the third embodiment of the present invention, in the first and second embodiments described above, the determination of the occurrence of the short circuit is performed as described above, and the determination of the release of the short circuit is performed while the welding current iw is set to the maximum value Iph during the short circuit period. This is a short-circuit determination method performed by determining that the current value has become smaller by a predetermined reduced current value ΔIp. An object of the present invention is to reduce a delay in determining whether to release a short circuit. That is, in the first and second embodiments, the short circuit period is determined until the short circuit is released, the arc is regenerated, and the welding current iw decreases to the short circuit determination value iat. However, since the current value at the time of short circuit release becomes the maximum value Iph during the actual short circuit period, in the third embodiment, the short circuit release determination value Ipt = Iph obtained by subtracting a predetermined reduced current value ΔIp from this maximum value Iph. -ΔIp is determined, and when the welding current iw <Ipt, it is determined that the short circuit has been released. Normally, since the short-circuit determination value iat <the short-circuit release determination value Ipt, the delay of the short-circuit release determination can be shortened. Hereinafter, description will be made with reference to the drawings.
[0025]
FIGS. 5A and 5B are waveform diagrams illustrating a short-circuit determination method according to the third embodiment. FIG. 5A illustrates a change over time of the welding current iw, and FIG. 5B illustrates a change over time of the short-circuit determination signal Sd. The waveform of the welding current iw shown in FIG. 7A is the same as that of FIG. 1, and therefore is the case of the short circuit determination value iat = ia + ΔIa.
[0026]
As shown in FIG. 9A, when the welding current iw becomes equal to or more than the short-circuit determination value iat at time t11, it is determined that a short-circuit has occurred. Subsequently, the maximum value Iph of the welding current iw during the short circuit period is sampled and held, and a short circuit release determination value Ipt = Iph−ΔIp (constant) is calculated. At time 22, the welding current iw is less than the short circuit release determination value Ipt. When it becomes, it is determined that the short circuit is released. The reduced current value ΔIp is set to, for example, 50A. Therefore, as shown in FIG. 7B, the period from time t11 to t22 is determined as the short-circuit period (High level). As is clear from the comparison between FIGS. 1 and 3 and FIG. 3, the delay in the determination of the release of the short circuit is reduced from time t21 to time t22.
[0027]
FIG. 3 shows the case of the welding current waveform of FIG. 1, but the same applies to the case of the welding current waveform of FIG. The description at this time is omitted.
[0028]
FIG. 6 is a block diagram of welding power supply device PS according to Embodiment 3. FIG. 9 shows a case where the method of determining the termination of the short circuit is added to the first embodiment. In this figure, the same circuits as those in FIG. Hereinafter, a circuit indicated by a dotted line different from FIG. 2 will be described.
[0029]
The short-circuit current maximum value holding circuit IPH receives the current detection signal id as an input, samples and holds the maximum value during the short-circuit period, and outputs a short-circuit current maximum value signal Iph. The short-circuit release determination value calculation circuit IPT outputs a short-circuit release determination value signal Ipt by subtracting a predetermined decrease current value ΔIp from the short-circuit current maximum value signal Iph. The second comparison circuit CM2 compares the current detection signal id with the short-circuit release determination value signal Ipt, and sets a high level when id ≧ Ipt, and a low level when id <Ipt. Output Rs. The comparison circuit CM compares the current detection signal id with the short-circuit determination value signal iat, and outputs a set signal Set that becomes a high level when id ≧ iat and becomes a low level when id <iat. In the flip-flop circuit FF, when the set signal Set changes to the high level, the short circuit determination signal Sd changes to the high level, and when the reset signal Rs changes to the low level, the short circuit determination signal Sd changes to the low level. The subsequent operation is the same as in FIG.
[0030]
FIG. 7 is a block diagram of a welding power supply device PS obtained by adding FIG. 6 to FIG. 4 of the second embodiment. In this figure, the same circuits as those in FIGS. 4 and 6 described above are denoted by the same reference numerals, and description of those circuits will be omitted.
[0031]
【The invention's effect】
According to the method for determining a short circuit of arc welding according to claim 1, even when the cable between the welding power supply device and the base material or the welding torch is long, the welding current can be detected without using the detection line for detecting the welding voltage. Since short-circuiting can be accurately determined only by detection, the rate of increase in short-circuit current can be controlled to an appropriate value to always obtain good welding quality. Further, the labor and cost required for wiring the detection lines can be eliminated, and troubles due to disconnection of the detection lines can be eliminated.
According to the method for determining a short circuit in arc welding according to the present invention, in addition to the above-described effects, even when the wire protrusion length is long, a short circuit period is not erroneously detected due to a change in welding current. Good welding quality can be obtained even when the welding time is long.
According to the method for determining a short circuit in arc welding according to the third aspect, in addition to the above effects, the delay in the determination of the short circuit can be shortened, so that the arc current can be optimized without delay immediately after the actual short circuit is released. And the bead appearance is further improved.
[Brief description of the drawings]
FIG. 1 is a waveform diagram of a welding current iw showing a short circuit determination method according to Embodiment 1 of the present invention.
FIG. 2 is a block diagram of the welding power supply device according to Embodiment 1.
FIG. 3 is a waveform diagram of a welding current iw showing a short circuit determination method according to a second embodiment.
FIG. 4 is a block diagram of a welding power supply device according to Embodiment 2.
FIG. 5 is a waveform diagram of a welding current iw showing a short circuit determination method according to a third embodiment.
FIG. 6 is a block diagram of a welding power supply device according to Embodiment 3.
FIG. 7 is a block diagram of another welding power supply device according to Embodiment 3.
FIG. 8 is a configuration diagram of a conventional arc welding apparatus.
FIG. 9 is a waveform diagram of a welding current iw and a welding voltage vw in a conventional technique.
FIG. 10 is a waveform diagram of a terminal voltage vt of the welding power supply device for describing a problem of the short circuit determination method according to Prior Art 1.
FIG. 11 is a waveform diagram of a welding current iw and a welding voltage vw for explaining a problem of the short circuit determination method according to the conventional technique 2.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 welding wire 2 base material 3 arc 4 welding torch 4 a feeding tip 5 feeding roll 6 cable Bth reference differential value CM comparing circuit CM2 second comparing circuit EV voltage error amplifier Ev voltage error amplifier signal FC transmission control circuit Fc transmission Supply control signal FF Flip-flop circuit IA Current smoothing circuit ia Welding current smoothing (value / signal)
IAT short circuit judgment value calculation circuit iat short circuit judgment value (signal)
IAT2 Second short circuit determination value calculation circuit ib (current) differential value ID Current detection circuit id Current detection signal INV Output control circuit IPH Short circuit current maximum value holding circuit Iph Short circuit current maximum value (signal)
IPT short circuit release determination value calculation circuit Ipt short circuit release determination value (signal)
Ir current setting (value / signal)
iw Welding current PLC controller PS Welding power supply Rs Reset signal Sd Short circuit discrimination signal Set Set signal SV Voltage setting switching circuit Ta Arc period Ts Short circuit period Vr Voltage setting (value / signal)
Vrc Voltage control setting signal VRS Short circuit voltage setting circuit Vrs Short circuit voltage setting signal vt Terminal voltage Vth Reference voltage value vw Welding voltage WM Feed motor ΔIa Increasing current value ΔIp Decreasing current value

Claims (3)

予め定めた電流設定値に対応した送給速度で溶接ワイヤを送給し短絡期間とアーク期間とを繰り返すアーク溶接の短絡判別方法において、
溶接中の溶接電流を検出しこの溶接電流検出値を数十ｍｓ〜数百ｍｓの時定数で平滑した溶接電流平滑値を検出しこの溶接電流平滑値に予め定めた増加電流値を加算して短絡判別値を刻々と演算し、前記アーク期間中に前記溶接電流検出値が前記短絡判別値以上になったことを判別して短絡発生を判別し、続けて前記短絡期間中に前記溶接電流検出値が前記短絡判別値未満になったことを判別して短絡が解除してアークが再発生したことを判別することを特徴とするアーク溶接の短絡判別方法。In a method for determining a short circuit in arc welding, in which a welding wire is fed at a feed speed corresponding to a predetermined current set value and a short circuit period and an arc period are repeated.
A welding current during welding is detected, a welding current smoothed value obtained by smoothing the welding current detection value with a time constant of several tens to several hundreds of ms is detected, and a predetermined increasing current value is added to the welding current smoothed value. A short-circuit determination value is calculated every moment, and it is determined that the welding current detection value has become equal to or greater than the short-circuit determination value during the arc period to determine the occurrence of a short-circuit. Subsequently, the welding current detection is performed during the short-circuit period. A method for determining a short circuit in arc welding, comprising determining that the value has become less than the short circuit determination value and determining that the short circuit has been released and an arc has reoccurred. 前記短絡判別値を、溶接電流平滑値が電流設定値以下のときには前記電流設定値に予め定めた増加電流値を加算した値として刻々と演算する請求項１記載のアーク溶接の短絡判別方法。The method according to claim 1, wherein the short-circuit determination value is calculated every moment as a value obtained by adding a predetermined increased current value to the current set value when the welding current smoothed value is equal to or less than the current set value. 前記短絡解除の判別を、短絡期間中に溶接電流検出値がこの短絡期間中の最大値から予め定めた減少電流値だけ小さくなったことを判別することによって行う請求項１又は請求項２記載のアーク溶接の短絡判別方法。3. The method according to claim 1, wherein the determination of the release of the short circuit is performed by determining that a welding current detection value during the short circuit period has decreased from a maximum value during the short circuit period by a predetermined reduced current value. A method for determining short circuits in arc welding.

Images