JP3667380B2

JP3667380B2 - Sewing skip detection device

Info

Publication number: JP3667380B2
Application number: JP08044495A
Authority: JP
Inventors: 実小作; 正人小沢
Original assignee: ジューキ株式会社
Priority date: 1995-04-05
Filing date: 1995-04-05
Publication date: 2005-07-06
Anticipated expiration: 2020-07-06
Also published as: JPH08276088A

Description

【０００１】
【産業上の利用分野】
この発明は、１針毎の針糸の移動量を接触音により測定して目飛びあるいは糸切れを検出するミシンの目飛び検出装置に関するものである。
【０００２】
【従来の技術】
図１１に示すように、ミシンの針糸１は針糸調子２、３、天秤４、糸案内５、６を経て針７に供給され、針７の上下と針板の下方に設けられた釜（図示せず）の回転運動との組み合わせにより布を貫通し、かつ下糸と絡み合いつつ縫い目を形成する。
【０００３】
しかしミシンによる縫製中、正常な縫い目の途中で縫い目が１目あるいは数目にわたって形成されていない目飛びと呼ばれる異常な縫い目が発生する場合がある（図１２（ａ）、（ｂ）参照）。このような目飛びが生じる原因としては、使用する糸や布の品質上の不完全、つまり、糸よりや布厚さなどにむらがありミシン動作に適合しないこと、あるいはミシン自体の機構の不備、たとえば針と釜のセットゲージの不良、針上下動と釜回転のタイミング不一致などが考えられる。そしていずれにしても、目飛びが生じた場合は、速やかにミシンの作動を停止して縫い目が形成されなかった部分の修正を行う必要がある。
【０００４】
従来このような目飛びを検出する手段として、圧電素子を用いた音検知センサを針糸に接触させて針糸走行時の接触音を監視し、接触音の発生時間の変化により目飛びあるいは糸切れを検出するようにした検出装置がある（特開平４―１０２４９９号公報参照）。
【０００５】
また、他の目飛び検出装置としては、歪みゲージを用いた張力センサで針糸の張力を監視し、針糸の張力異常を検出することによって目飛びあるいは糸切れをを検出するようにしたものがある（特開昭５０―５４４５７号公報）。
【０００６】
【発明が解決しようとする課題】
しかしながら、針糸走行時の接触音により目飛びを検出する方式では、正常な縫い目形成時と目飛び発生時の接触音の極わずかな差を検知しなければならないため、極めて高感度の音検知センサが必要となる。また、接触音のわずかな変化によって目飛びを検出するため、正常な縫い目形成時でも音の発生時間のばらつきが大きい場合には目飛びとして誤検出される問題がある。
【０００７】
また、張力センサにより張力変動を検知する場合においても正常な縫い目形成時と目飛び発生時の張力変化は極わずかであるため、極めて高感度の張力センサが必要である。この場合も１針１針毎の縫いのばらつきなどによる針糸張力の変動が大きいと誤検出が多く発生し、極めて信頼性の低い検出装置しか実現できない。
【０００８】
本発明は、以上のような事情の下に創案されたもので、誤検出を防止して確実に目飛びあるいは糸切れを検出できるミシンの目飛び検出装置を提供することを目的とする。
【０００９】
【課題を解決するための手段】
上記目的を達成するために本発明に係る目飛び検出装置は、針と釜との協働により縫い目を形成するミシンの糸供給源と針との間の針糸経路上に配置され、縫い目形成による上記針糸の移動にともなう音の発生を検知して検出信号を発生する音検知センサを有し、該検出信号の発生時間により糸切れまたは目飛びの発生を検出する検出装置を前提とし、前記音検知センサを、ミシンの天秤の上流側近傍および下流側近傍に配置される糸案内と針糸との摩擦音を検出すべく当該糸案内と一体に設けたことを特徴としている（請求項１）。
【００１０】
請求項１に記載された目飛び検出装置はさらに、前記音検知センサが一体に設けられた前記糸案内と前記天秤との間に配置した補助糸調子と、前記音検知センサと、当該音検知センサの出力に基づいてミシンが１回転動作する毎の前記摩擦音の発生時間を測定する時間測定手段と、当該時間測定手段による前回の測定値と今回の測定値とを比較して糸移動量差を求める糸移動量差検出手段と、当該糸移動量差検出手段の出力値に応じて目飛び検出信号を発生する目飛び検出信号発生手段とを備えてなることが望ましい（請求項２）。
【００１１】
また、請求項１に記載された目飛び検出装置はさらに、ミシンの回転速度に応じた適正な糸移動量のデータを予め記憶した記憶手段と、ミシンの回転速度を検出する回転検出手段と、この回転検出手段による検出速度に応じて前記記憶手段から糸移動量のデータを読み出して前記音検知センサの信号と比較する比較手段と、この比較手段による比較結果に応じて目飛び検出信号を発生する手段とを備えてなることが望ましい（請求項３）。
【００１２】
また、本発明に係る目飛び検出装置は、針と釜との協働により縫い目を形成するミシンの糸供給源と針との間の針糸経路上に配置され、縫い目形成による上記針糸の移動にともなう音の発生を検知して信号を発生する音検知センサを有し、該検出信号の発生時間により糸切れまたは目飛びの発生を検出する検出装置を前提とし、ミシンの天秤の上流側近傍および下流側近傍に配置される糸案内と針糸との摩擦音を検出すべく当該糸案内と一体に設けた音検知センサと、ミシンの回転速度に応じた適正な糸移動量のデータを予め記憶した記憶手段と、ミシンの回転速度を検出する回転検出手段と、この回転検出手段による検出速度に応じて前記記憶手段からデータを読み出して前記音検知センサの信号と比較する比較手段と、この比較手段による比較結果に応じて目飛び検出信号を発生する手段とを備えてなることを特徴とする（請求項４）。
【００１３】
請求項２に記載された目飛び検出装置はさらに、ミシンの回転速度を検出する回転検出手段と、当該回転検出手段により検出される回転速度の変化が予め設定された値以上になったとき前記目飛び検出信号の発生を停止させる信号制御手段を備えてなることが望ましい（請求項５）。
【００１４】
請求項３、４に記載された目飛び検出装置はさらに、前記回転検出手段により検出される回転速度の変化が予め設定された値以上になったとき前記目飛び検出信号の発生を停止させる信号制御手段を備えていることが望ましい（請求項６）。
【００１５】
請求項１〜６に記載された目飛び検出装置は、前記ミシンが複数の針と各針に応じた針糸を有する場合において、前記音検知センサが各針糸経路上に各別に配置され、上記複数の音検知センサの各別の検出信号に基づいて目飛び検出信号を発生することが望ましい（請求項７）。
【００１６】
請求項１〜７に記載された目飛び検出装置はさらに、前記音検知センサの信号を増幅するための増幅器の増幅率を調節する増幅率調節手段を備えていることが望ましい（請求項８）。
【００１７】
請求項２に記載された目飛び検出装置はさらに、前記時間測定手段による時間測定値を増減させる時間補正手段を備えていることが望ましい（請求項９）。
【００１８】
請求項２〜７に記載された目飛び検出装置はさらに、前記目飛び検出信号の発生を選択的に停止させるための検出停止手段を備えていることが望ましい。
【００１９】
【作用】
請求項１及び請求項４に記載された目飛び検出装置によれば、前記釜により針糸が捕捉されたときと捕捉されないときとの糸移動量の差が顕著となる位置である天秤の上流側近傍および下流側近傍に配置される一対の糸案内の少なくとも一方と針糸との摩擦音を、当該糸案内と一体に設けた音検知センサで検出することにより、高感度のセンサを使用することなく目飛び発生時に生じる摩擦音の特徴的な変化を確実に検出できる。
【００２０】
請求項２に記載された目飛び検出装置によれば、前記音検知センサが一体に設けられた糸案内と天秤との間に配置した補助糸調子は、目飛びが発生して針糸が弛んだ場合に糸案内の糸通過部を通過して逆行するのを防止する働きをもつことにより、目飛びが発生した場合に弛んだ針糸の糸案内を通過する下方向への移動を防止し、弛みによる針糸の移動量変化を正確に検知できる。
そして、前記音検知センサで検出される摩擦音の発生時間を前記時間測定手段が１針毎に測定し、前記時間測定手段による前回の測定値と今回の測定値とを前記糸移動量差検出手段が比較して糸移動量差を求め、その値に応じて目飛び検出信号発生手段が目飛び検出信号を発生させることにより、正常な縫い目形成時における摩擦音の発生時間のばらつきが大きい場合でもこれを誤検出することなく目飛びの発生を確実に検知できる。
【００２１】
請求項３及び４に記載された目飛び検出装置によれば、ミシンの回転速度に応じた適正な糸移動量データを予め記憶手段に記憶しておき、前記回転検出手段によってミシンの回転速度が検出される度に前記比較手段が前記記憶手段から糸移動量のデータを読み出して前記検出信号と比較し、その値に応じて目飛び検出信号を発生させることにより、正常な縫い目形成時における摩擦音の発生時間のばらつきが大きい場合でもこれを誤検出することなく目飛びの発生を確実に検知できる。
【００２２】
請求項５及び６に記載された目飛び検出装置によれば、ミシンの回転速度の変化が予め設定された値以上になったとき前記目飛び検出信号の発生を停止させるので、例えばミシン起動直後や停止直前など回転速度の変化が必然的に生じる場合における摩擦音発生時間の変化を異常として目飛び検出信号が発生されるのを防止することができる。
【００２３】
請求項７に記載された目飛び検出装置によれば、ミシンが複数の針と各針に応じた針糸を有する場合においても、各針糸経路上に各別に配置された音検知センサの各別の検出信号に基づいて糸の異常を判別することができる。
【００２４】
請求項８に記載された目飛び検出装置によれば、摩擦音の大きさに応じて前記増幅器の増幅率を調節することにより、音検知センサによる検出信号の強度を適切に調節できるので、摩擦音の検出ミスを防止して目飛びの発生を確実に検知できる。
【００２５】
請求項９に記載された目飛び検出装置によれば、縫いピッチなどにより摩擦音の発生時間が変化する場合でも、前記時間測定手段による時間測定値を増減させることにより摩擦音の発生時間が一定になるように補正できるので、摩擦音発生時間の変化を異常として誤検出することなく、目飛びの発生を確実に検知できる。
【００２６】
請求項１０に記載された目飛び検出装置によれば、目飛びを検知する必要がない場合には前記検出停止手段によって前記目飛び検出信号の発生を停止させることができる。したがって不必要に目飛び検出信号が発生され、その度にミシンが停止されるなどの不都合をなくすことができる。
【００２７】
【実施例】
次に本発明の実施例について図面を参照して説明する。
【００２８】
図１は本発明に係る目飛び検出装置を備えてなる本縫いミシンの針糸経路を示す部分正面図である。同図に示すように針糸１は、針糸調子３、糸取りばね２４、糸案内５´（図３参照）、補助糸調子８、天秤４、及び糸案内６を順に経て針７に供給される。
【００２９】
天秤４は、ミシンの回転に伴って１針毎に矢印Ａで示す方向に上下運動する。そして天秤４の上下運動により針糸１は、糸案内５´および糸案内６の糸通過部９、１０に案内されつつ１針毎に往復移動を繰り返す。そして針糸１が移動する間、糸案内５´および糸案内６の糸通過部９、１０に摩擦抵抗が加わり、摩擦音が発生する。
【００３０】
ミシンが一回転駆動する間には、糸案内５´および糸案内６に摩擦抵抗が加わるときと加わらないときがあり、その位相および強度は、正常な縫い目形成時においてミシン回転数が一定であればほぼ一定である。そして、目飛びが発生すると、天秤４の運動により図２に示すように針糸１が弛むため、その間は糸案内５´および糸案内６に摩擦抵抗は加わらなくなる。
【００３１】
目飛び発生時の弛みによる針糸移動量の変化は、正常な縫い目形成時における移動量のばらつきよりも遥かに大きい。例えば最も一般的な本縫い一本針小釜ミシンにおいて、図１および図２の糸案内５´の位置で針糸１の移動量を測定した場合、正常な縫い目形成時と目飛び発生時の針糸移動量の差は、約８０ｍｍである。ミシン１針当りの全体の針糸移動量が約１１０ｍｍであることを考えるとき、その変化量は約７３％にもなる。このことは天秤４の下流側の糸案内６においてもほぼ同様である。
【００３２】
したがって天秤４の前後に設けられた糸案内５´と糸案内６のいずれか一方と針糸１との摩擦音を監視することにより、目飛び発生時に生じる摩擦音の特徴的な変化を確実に検出することができる。
【００３３】
図１および図２は、天秤４の上流側の糸案内５´と針糸１との摩擦音を検出できるようにした場合の装置構成を例示したものである。
【００３４】
糸案内５´は、図３に示すようにその先端部に糸通過部９を有する筒状の案内部材１３と、この案内部材１３をミシンにねじ１５（図１参照）で固定するための取付部材１４とからなる。糸通過部９は、案内部材１３の筒状部の先端に突設された突片３７の先端部に、針糸１が通過する糸孔１２を形成してなる。そしてこの糸案内５´は、針糸１との摩擦音（振動）を検出するための圧電素子からなる音検知センサ１１を案内部材１３に内蔵することにより音検知センサユニット１７を構成している。
【００３５】
この糸案内５´と天秤４との間に設けられた補助糸調子８は、目飛びが発生して針糸１が弛んだ場合に、針糸１の弛み分が糸案内５´の糸通過部９を通過して逆行するのを防止する働きをもつものである。すなわち、目飛びが発生した場合には針糸１は釜の周囲を回る必要がないため消費されず、弛んだ針糸１が糸通過部９を通過して図２中矢印Ｂ方向に移動する可能性があるが、補助糸調子８を設けることで針糸１のＢ方向への移動を防止し、弛みによる針糸１の移動量の変化の正確な検知を可能にする。
【００３６】
図４には、本実施例のミシンにおける制御ブロック図が示されている。本実施例のミシンの制御部は、中央処理装置（ＣＰＵ）４０と記憶装置（メモリ）４１とで主に構成される。ＣＰＵ４０は、メモリ４１内に予め記憶されたプログラムに従って演算制御動作する。ＣＰＵ４０は、速度設定スイッチの速度設定信号及びスタートストップスイッチのオン信号に応じて、モータ駆動回路４４に制御信号を出力し、モータＭを前記設定された速度で駆動及び停止制御させるとともに、所定のタイミングで送り量のデータをメモリ４１から読み出して、制御信号として布送り機構駆動回路４５に出力し、布送り機構４６を動作制御して１ステッチ毎に布送り機構４６による送り量を決定する。
【００３７】
ＣＰＵ４０には、目飛び検出回路４７が接続されている。目飛び検出回路４７は、前記音検知センサ１１からの検出信号と、ミシンの上軸に取り付けられたエンコーダ（回転検出センサ）４２からの信号とに基づいて目飛び検出信号をＣＰＵ４０に出力する。ＣＰＵ４０は、目飛び検出信号を受けると直ちにモータ駆動回路４４に停止指令信号を出力する。
【００３８】
また、ＣＰＵ４０には、目飛び検出機能のオン／オフやセンサ信号の増幅率を設定・変更、あるいはミシンの駆動条件の設定・変更のための各種データの入力操作を行うためのキーやスイッチ類を配設してなる入力装置４８、ミシンの異常をブザー音やランプの点灯によって報知する警報装置４９、及びミシンの運転状態や入力装置４８による入力情報を表示するための表示装置５０が接続されている。
【００３９】
図５には、上記目飛び検出回路４７の構成例がブロック図で示されている。同図に示す目飛び検出回路４７は、前記音検知センサ１１からの信号に基づいて前記摩擦音の発生時間を１針毎に検出するための時間測定手段５１と、前記回転検出センサ４２から信号（図７（ａ）参照）が発せられる度に、ミシンの回転速度を検出するためのタイミング信号（図７（ｂ）参照）を発生するタイミング発生回路５２と、時間測定手段５１からの信号（図７（ｄ）参照）に基づいて前回の測定値と今回との糸移動量差を求める糸移動量差検出手段５３と、前記タイミング発生回路５２からのタイミング信号に基づいて前回の回転数測定値と今回の回転数測定値から糸移動量差を求める糸移動量差検出手段５４と、前記糸量差検出手段５３の出力値と糸移動量差検出手段５４の出力値とを比較してその差が予め設定された値よりも大きいときに目飛び検出信号を発生する目飛び検出信号発生手段５５とからなる。
【００４０】
時間測定手段５１は、音検知センサ１１からの摩擦音検出信号を増幅する増幅器５６と、増幅された摩擦音検出信号のうちの必要な周波数の信号のみを通過させるバンドパスフィルタ５７と、これを通過した信号の波形を時間測定が可能な波形（図７（ｃ）参照）に整形する波形整形回路５８と、前記タイミング発生回路５２と、このタイミング発生回路５２からのクロック信号を前記波形整形回路５８から信号が送出されている間のみ通過させる時間測定回路５９とからなる。前記増幅器５６の増幅率は、前記入力装置４８からのキー入力によりＣＰＵ４０を介して設定・変更できるようになっている。
【００４１】
糸移動量差検出手段５３は、時間測定回路５９を通過してくるクロック信号の数を１針毎に記憶する時間データ一時記憶装置６０と、この時間データ一時記憶装置６０に記憶された前回の時間データ（クロック信号数）と時間測定回路５９から送られてくる今回の時間データ（クロック信号数）とを比較して前回と今回との時間差を求める比較回路６１と、この比較回路６１からの出力値に基づいて前回と今回との糸移動量差を演算して順次出力する演算回路６２とからなる。
【００４２】
糸移動量差検出手段５４は、前記タイミング発生回路５２から送られてくるクロック信号を回転数検出器４３で変換し回転数データとして１針毎に記憶する回転数データ一時記憶装置６３と、この回転数データ一時記憶装置６３に記憶された前回の回転数データと前記回転数検出器４３から送られてくる今回の回転数データとを比較して前回と今回との回転数差を求める比較回路６４と、回転数差に対応させて回転数のばらつきによる幅を持たせた糸移動量差データを予め記憶し、比較回路６４の出力値に対応する糸移動量差データを出力する糸移動量差データ発生回路（ＲＯＭ）６５とからなる。比較回路６４の出力値は検出ＯＮ／ＯＦＦ信号として直接ＣＰＵ４０にも入力され、その値が予め設定された設定値以上の場合ＣＰＵ４０によって前記警報装置５０の警報機能が停止されるようになっている。この設定値はミシンの起動直後や停止寸前など回転数の変化が急激であるときの回転数差に基づき設定される。
【００４３】
目飛び検出信号発生手段５５は、前記演算回路６２からの糸移動量差データと前記糸移動量差データ発生回路６５からの糸移動量差データとを比較してその差を出力する比較回路６６と、この比較回路６６からの出力値が予め回転数のばらつきを考慮して設定された値よりも大きいときに検出信号を出力する検出信号発生回路６７とからなる。ここでの設定値は、ミシン回転数のばらつきに起因して変動する糸移動量差程度に設定される。
【００４４】
以上の構成によれば、針糸供給時、天秤４の上下運動により針糸１が引っ張られると、針糸１と糸案内５´の孔部９とが擦れて摩擦音が発生し、この摩擦音が音検知センサ１１によって検出される。音検知センサ１１で検出された摩擦音信号は、増幅器５６で増幅され、増幅された摩擦音検出信号のうちの必要な周波数帯域の信号のみがバンドパスフィルタ５７を通過し、波形整形回路５８で時間測定が可能な波形の信号（図７（ｃ）参照）に整形される。また、回転検出センサ４２からのタイミングによってタイミング発生回路５２からクロック信号（図７（ｂ）参照）が発生し、これが時間測定手段５１の時間測定回路５９と糸移動量差検出手段５４の回転数データ一時記憶装置６３および比較回路６４とに入力される。時間測定回路５９に入力されたクロック信号は波形整形回路５８から信号が送られてくる間のみ通過され、糸移動量差検出手段５３に入力される。
【００４５】
糸移動量差検出手段５３においては、時間測定回路５９を通過してきたクロック信号（図７（ｄ）参照）が時間データとして時間データ一時記憶装置６０に記憶される。時間データ一時記憶装置６０は、時間測定回路５９から１針分の時間データが到来する度にそれまで記憶していた前回の時間データを出力する。そして、この時間データ一時記憶装置６０からの前回の時間データと時間測定回路５９からの今回の時間データとが比較回路６１に入力される。そして比較回路６１で求められた前回と今回との時間差データが演算回路６２に入力されることにより、演算回路６２によって前回と今回との糸移動量差が演算され、その糸移動量差データが目飛び検出信号発生手段５５の比較回路６６に入力される。
【００４６】
一方、糸移動量差検出手段５４においては、回転数検出器４３から１針分の回転数データが到来する度に回転数データ一時記憶装置６３がそれまで記憶していた前回の回転数データを出力する。そして、この前回の回転数データとタイミング発生回路５２からの信号を回転数検出器４３により変換された今回の回転数データとが比較回路６４に入力される。そして比較回路６４で求められた回転数差データが糸移動量差データ発生装置６５に入力されることにより、当該回転数差データに対応する糸移動量差データが糸移動量差データ発生装置（ＲＯＭ）６５より出力され、目飛び検出信号発生手段５５の比較回路６６に入力される。またこの糸移動量差検出手段５４の比較回路６４の回転数差データはＣＰＵ４０にも入力される。この回転数差データが予め設定された設定値以上の場合ＣＰＵ４０は前記警報装置４９の警報機能を停止させる。
【００４７】
そして目飛び検出信号発生手段５５においては、前記演算回路６２からの糸移動量差データと前記糸移動量差データ発生回路６５からの糸移動量差データとが比較回路６６によって比較され、その差が検出信号発生回路６７に与えられる。そして比較回路６６からの出力値が予め設定された値よりも大きいときには検出信号発生回路６７よりＣＰＵ４０に目飛び検出信号が出力される。ＣＰＵ４０は目飛び検出信号を受けると直ちに警報装置４９のブザーを鳴らし、ランプを点灯させて作業者に異常の発生を知らせるとともに、モータ駆動回路４４に停止指令信号を出力してモータＭの駆動を停止させる。
【００４８】
上記のように、音検知センサ１１によって針糸１の摩擦音を検出し、次々に送られてくる１針毎の摩擦音の発生時間を比較して、前回と今回との摩擦音の発生時間差に基づく糸移動量差を求めるとともに、回転検出センサ４２によってミシンの回転数を検出し、次々に送られてくる１針毎の回転数（回転速度）を比較して、前回と今回との回転数差に基づく糸移動量差を求め、前記摩擦音の発生時間差に基づく糸移動量差と前記回転数差に基づく糸移動量差との比較結果に基づいて目飛びを判別することにより、ミシン回転数の変化に起因して摩擦音の発生時間のばらつきが大きい場合でもこれを誤検出することなく目飛びの発生を確実に検知できる。
【００４９】
図６には、他の実施例の目飛び検出装置における目飛び検出回路のブロック図が示されている。同図に示す目飛び検出回路４７´は、前記音検知センサ１１からの信号に基づいて前記摩擦音の発生時間を１針毎に検出するための時間測定手段５１と、前記回転検出センサ４２から信号（図７（ａ）参照）が発せられる度に、ミシンの回転速度を検出するためのタイミング信号（図７（ｂ）参照）を発生するタイミング発生回路５２と、時間測定手段５１からの信号（図７（ｄ）参照）に基づいて糸移動量を求める第１の糸移動量検出手段６８と、前記タイミング発生回路５２からの信号を回転数検出器４３により変換しその回転数データに基づいて推定糸移動量を求める第２の糸移動量検出手段６９と、前記第１の糸移動量検出手段６８の出力値と第２の糸移動量検出手段６９の出力値とを比較してその差が予め設定された値よりも大きいときに検出信号を発生する目飛び検出信号発生手段７０とからなる。
【００５０】
時間測定手段５１は、音検知センサ１１からの摩擦音検出信号を増幅する増幅器５６と、増幅された摩擦音検出信号のうちの必要な周波数の信号のみを通過させるバンドパスフィルタ５７と、これを通過した信号の波形を時間測定が可能な波形（図５（ｃ）参照）に整形する波形整形回路５８と、タイミング発生回路５２からのクロック信号を前記波形整形回路５８から信号が送出されている間のみ通過させる時間測定回路５９とからなる。前記増幅器５６の増幅率は、前記入力装置４８からのキー入力によりＣＰＵ４０を介して設定・変更できるようになっている。
【００５１】
第１の糸移動量検出手段６８は、時間測定回路５９を通過してくるクロック信号を１針毎の時間データとして順次出力する一時記憶バッファ７５と、一時記憶バッファ７５からの時間データに基づいて１針毎の糸移動量を演算して順次出力する演算回路７１とからなる。
【００５２】
第２の糸移動量検出手段６９は、前記タイミング発生回路５２から送られてくるクロック信号を回転数検出器４３により回転数データに変換さし１針毎に記憶し順次出力する回転数データ一時記憶装置７２と、この回転数データ一時記憶装置７２に記憶された前回の回転数データと前記タイミング発生回路５２からの信号を回転数検知器４３にて変換して得られた回転数データとを比較して前回と今回との回転数差を求める比較回路７３と、回転数データに対応し回転数のばらつきによる幅を持たせた適正な糸移動量データを予め記憶し、回転数データ一時記憶装置７２から回転数データが出力されるとその回転数データに対応する糸移動量データを出力する糸移動量データ発生回路（ＲＯＭ）７４とからなる。比較回路７３の出力データは、検出ＯＮ／ＯＦＦ信号としてＣＰＵ４０に入力され、その値が予め設定された設定値以上の場合ＣＰＵ４０によって前記警報装置４９の警報機能が停止されるようになっている。この設定値はミシンの起動時や停止寸前など回転数の変化が急激であるときの回転数差に基づき設定される。
【００５３】
目飛び検出信号発生手段７０は、前記演算回路７１からの糸移動量データと前記糸移動量データ発生回路７４からの糸移動量データとを比較してその差を出力する比較回路７６と、この比較回路７６からの出力値が予め回転数のばらつきを考慮し設定された値よりも大きいときに目飛び検出信号を出力する検出信号発生回路７７とからなる。ここでの設定値は、ミシン回転数のばらつきに起因して変動する糸移動量程度に設定される。
【００５４】
図６の構成によれば、針糸供給時、天秤４の上下運動により針糸１が引っ張られると、針糸１と糸案内５´の孔部９とが擦れて摩擦音が発生し、この摩擦音が音検知センサ１１によって検出される。音検知センサ１１で検出された摩擦音信号は、図５の場合と同様時間測定手段５１の増幅器５６、バンドパスフィルタ５７、波形整形回路５８及び時間測定回路５９で順次処理され、時間測定回路５９を通過したクロック信号が第１の糸移動量検出手段６８に入力される。
【００５５】
第１の糸移動量検出手段６８においては、時間測定回路５９を通過してきたクロック信号が一時記憶バッファ７５に入力される。そして演算回路７１は、一時記憶バッファ７５を介して送られてくる時間データに基づいて糸移動量を演算し、得られた糸移動量データを目飛び検出信号発生手段７０の比較回路７６に出力する。
【００５６】
一方、第２の糸移動量検出手段６９においては、回転数検出器４３から出力された回転数データが回転数データ一時記憶装置７２と比較回路７３とに入力される。回転数データ一時記憶装置７２は、１針分の回転数データが到来する度に前回の１針分の回転数データを比較回路７３と糸移動量データ発生回路７４とに出力する。糸移動量データ発生回路７４は回転数データが入力される度に当該回転数データに対応する適正な糸移動量データを目飛び検出信号発生手段７０の比較回路７６に出力する。また、第２の糸移動量検出手段６９の比較回路７３は、回転数データ一時記憶装置７２からの前回の１針分の回転数データと回転数検出器４３からの今回の１針分の回転数データとを比較し、その差を検出ＯＮ／ＯＦＦ信号としてＣＰＵ４０に出力する。そして検出ＯＮ／ＯＦＦ信号が設定値以上の場合、ＣＰＵ４０は前記警報装置５０の警報機能を停止させる。
【００５７】
目飛び検出信号発生手段７０においては、前記演算回路７１からの糸移動量データと前記糸移動量データ発生回路７４からの糸移動量データとが比較回路７６によって比較され、その差が検出信号発生回路７７に出力される。そして比較回路７６からの出力値が予め設定された値よりも大きいときには検出信号発生回路７７が目飛び検出信号をＣＰＵ４０に出力する。ＣＰＵ４０は目飛び検出信号を受けると直ちに警報装置４９のブザーを鳴らし、ランプを点灯させて作業者に異常の発生を知らせるとともに、モータ駆動回路４４に停止指令信号を出力してモータＭの駆動を停止させる。
【００５８】
上記のように、音検知センサ１１によって針糸１の摩擦音を検出し、次々に送られてくる１針毎の摩擦音の発生時間から糸移動量を算出するとともに、回転検出センサ４２によってミシンの回転数を検出し、糸移動量データ発生回路７４に予め記憶させたデータから当該回転数に対応する適正な糸移動量を求め、前記摩擦音の発生時間に基づく糸移動量と予め記憶しておいた適正な糸移動量との比較結果に基づいて目飛びを判別することにより、ミシン回転数の変化に起因して摩擦音の発生時間のばらつきが大きい場合でもこれを誤検出することなく目飛びの発生を確実に検知できる。
【００５９】
以上、本実施例の目飛び検出装置によれば、天秤４の上流側の糸案内５´に音検知センサ１１を設けて、目飛び発生時に生じる摩擦音の顕著な変化を検出するようにしたので、さほど高感度の音検知センサ１１を使用することなく、目飛び発生時における摩擦音の変化を確実に検出することができる。
【００６０】
また本実施例では、比較器６４、７３によって検出されるミシンの回転数の変化がが予め設定された設定値以上になったときＣＰＵ４０によって目飛び検出信号の発生が停止されるので、例えばミシン起動直後や停止直前など回転速度の変化が必然的に生じる場合における摩擦音発生時間の変化を異常と判断し目飛び検出信号が発生されるのを防止することができる。
【００６１】
また、摩擦音の大きさに応じて増幅器５６の増幅率を調節することにより、音検知セン１１サによる検出信号の強度を適切に調節できるので、摩擦音の検出ミスを防止して目飛びの発生を確実に検知できる。
【００６２】
また、時間測定手段５１による時間測定値を入力装置４８からのキー入力操作などにより増減できるようにしておけば、縫いピッチなどにより摩擦音の発生時間が変化する場合でも摩擦音の検出時間が一定になるように補正できるので、縫いピッチの違いによる誤検出を防止できる。
【００６３】
なお、上記実施例では天秤４の上流側の糸案内５´と針糸１との摩擦音を検出できるようにした場合の装置構成について説明したが、図８に示すように天秤４の下流側に補助糸調子８´および音検知センサユニット１７´を設けても上記実施例と同様の効果が得られる。
【００６４】
また、音検知センサ１１の設置場所は、糸案内５´、６´に限定されず、例えば天秤４の糸孔と針糸１との摩擦音を検出できるように天秤４に音検知センサ１１を取り付けてもよい。また、糸取りばね２４と針糸１との摩擦音を検出するようにしてもよい。要するに、音検知センサ１１の設置場所は、釜により針糸が捕捉されたときと捕捉されないときとの糸移動量の差が顕著となる針糸経路位置であればどこでもよい。
【００６５】
また、上記実施例では糸案内５´と天秤４との間に補助糸調子８を設けることにより、針糸１の弛み分が糸案内５´の糸通過部９を通過して逆行するのを防止するようになしたが、仮にこの補助調子８が設けられておらず、目飛び発生時に針糸１が逆行したとしても、そのときの針糸１の張力は正常な縫い目形成時よりも著しく低下するため、これに伴う摩擦音の特徴的な変化を検出することにより目飛びを検知することができる。ただし、正常な縫い目形成時における針糸移動量と目飛び発生時における針糸移動量との差によって目飛びの発生を検知するようになした本発明の目飛び検出装置にあっては、上記の如く補助糸調子８を設けるなどして針糸１の逆行を防止し、目飛び発生時に糸移動量の急激な変化が確実に創出されるようにしておくことが望ましい。
【００６６】
上記針糸１の逆行は、針糸１に僅かな摩擦抵抗を付加するだけで防ぐことができる。したがって例えば図９、図１０に示すように、案内部材１３の突片３７を上方に屈曲させ、かつ突片３７の糸孔１２の数を増やすなどして、針糸１に摩擦抵抗を付加する機能を糸案内５´自体に持たせておけば、上記補助糸調子８は必要なくなる。
【００６７】
また一般的には１本の針糸に対し１つの音検知センサを使用するため多本針ミシンの場合には複数の音検知センサを必要とする。
【００６８】
また、本発明の目飛び検出装置は、環縫いミシン用の目飛び検出装置としても適用可能である。その場合、本縫いミシンの糸案内（図１２中、符号５、６）に相当する部品に音検知センサ１１を装着あるいは内蔵させることにより、本縫いの場合と同様目飛びを検知することができる。ただし、環縫いミシンは本縫いミシンよりも針糸１の消費量が多く、目飛びが発生した際の糸移動量の変化も大きいため、天秤（針棒２５と兼用）の動きと直接関係のない位置、例えば針糸ボビン近傍の糸案内に音検知センサ１１を設けても目飛びの検知が可能である。
【００６９】
さらに、本発明の目飛び検出装置は、目飛び検出の場合と同様の原理で糸切れを検知することもできる。
【００７０】
【発明の効果】
以上要するに本発明によれば、以下のような優れた効果を発揮できる。
【００７１】
請求項１及び請求項４に記載された目飛び検出装置によれば、前記釜により針糸が捕捉されたときと捕捉されないときとの糸移動量の差が顕著となる位置である天秤の上流側近傍および下流側近傍に配置される糸案内と針糸との摩擦音を、当該糸案内と一体に設けた音検知センサで検出することにより、高感度のセンサを使用することなく目飛び発生時に生じる摩擦音の特徴的な変化を確実に検出できるので、正常な縫い目形成時における摩擦音の発生時間のばらつきが大きい場合でもこれを誤検出することなく目飛びの発生を確実に検知できる。
【００７２】
請求項２に記載された目飛び検出装置によれば、前記音検知センサが一体に設けられた糸案内と天秤との間に配置した補助糸調子は、目飛びが発生して針糸が弛んだ場合に糸案内の糸通過部を通過して逆行するのを防止する働きをもつことにより、目飛びが発生した場合に弛んだ針糸の糸案内を通過する下方向への移動を防止し、弛みによる針糸の移動量変化を正確に検知できる。
そして、前記音検知センサで検出される摩擦音の発生時間を前記時間測定手段が１針毎に測定し、前記時間測定手段による前回の測定値と今回の測定値とを前記糸移動量差検出手段が比較して糸移動量差を求め、その値に応じて目飛び検出信号発生手段が目飛び検出信号を発生させることにより、正常な縫い目形成時における摩擦音の発生時間のばらつきが大きい場合でもこれを誤検出することなく目飛びの発生を確実に検知できる。
【００７３】
請求項３及び４に記載された目飛び検出装置によれば、ミシンの回転速度に応じた適正な糸移動量をデータを予め記憶手段に記憶しておき、前記回転検出手段によってミシンの回転速度が検出される度に前記比較手段が前記記憶手段から糸移動量のデータを読み出して音検知センサによる検出信号と比較し、その比較結果に応じて目飛び検出信号を発生させることにより、ミシン回転数のばらつきに起因して摩擦音の発生時間に変動が生じた場合でもこれを目飛びの発生として誤検出するのを防止して目飛びの発生をより確実に検知できる。
【００７４】
請求項５及び６に記載された目飛び検出装置によれば、ミシンの回転速度の変化が予め設定された値以上になったとき目飛び検出信号の発生を停止させるので、ミシンの回転速度の変化が急な場合における摩擦音発生時間の変化を異常とは判断して目飛び検出信号が発生されるのを防止することができる。
【００７５】
請求項７に記載された目飛び検出装置によれば、ミシンが複数の針と各針に応じた針糸を有する場合においても、各針糸経路上に各別に配置された音検知センサの各別の検出信号に基づいて糸の異常を判別することができる。
【００７６】
請求項８に記載された目飛び検出装置によれば、摩擦音の大きさに応じて音検知センサの増幅器の増幅率を調節することにより音検知センサの検出信号強度を適切に調節できるので、摩擦音の検出ミスを防止して目飛びの発生を確実に検知できる。
【００７７】
請求項９に記載された目飛び検出装置によれば、縫いピッチなどにより摩擦音の発生時間が変化する場合でも、前記時間測定手段による時間測定値を増減させることにより摩擦音の発生時間が一定になるように補正できるので、摩擦音発生時間の変化を異常として誤検出することなく、目飛びの発生を確実に検知できる。
【００７８】
請求項１０に記載された目飛び検出装置によれば、目飛び検出信号の発生を必要に応じて停止させることができる。
【図面の簡単な説明】
【図１】本発明の目飛び検出装置を本縫いミシンに適用した場合の針糸の状態を示す部分正面図である。
【図２】同じく針糸の状態を示す部分正面図である。
【図３】音検知センサを内蔵してなる糸案内の一実施例を示す斜視図である。
【図４】本発明の目飛び検出装置を備えた一実施例のミシンにおける制御ブロック図である。
【図５】図４のミシンの目飛び検出回路の一構成例を示すブロック図である。
【図６】図４のミシンの目飛び検出回路の別の構成例を示すブロック図である。
【図７】図５および図６の各部の信号波形図である。
【図８】本発明の目飛び検出装置を本縫いミシンに適用した場合の他の実施例を示す部分正面図である。
【図９】糸案内の他の実施例を示す斜視図である。
【図１０】糸案内の他の実施例を示す斜視図である。
【図１１】一般的な本縫いミシンにおける針糸の供給経路を示す部分斜視図である。
【図１２】（ａ）正常な縫い目を示す側断面図、（ｂ）は目飛び発生時の縫い目を示す側断面図である。
【符号の説明】
１針糸
４天秤
５´ 糸案内
６糸案内
８補助糸調子
８´ 補助糸調子
９糸通過部
１１音検知センサ
１２糸孔
１３案内部材
４０ＣＰＵ（信号制御手段）
４２エンコーダ（回転検出センサ、回転検出手段、時間補正手段）
４３回転数検出器
４７目飛び検出回路
５１時間測定手段
５３糸移動量差検出手段
５４糸移動量差検出手段
５５目飛び検出信号発生手段
５６増幅器
６６比較回路（比較手段）
６７検出信号発生回路
６８糸移動量検出手段
６９糸移動量検出手段
７０目飛び検出信号発生手段
７４糸移動量差データ発生回路（記憶手段）
７６比較回路（比較手段）
７７検出信号発生回路[0001]
[Industrial application fields]
The present invention relates to a stitch skip detection device for a sewing machine that detects a stitch skip or a thread break by measuring a movement amount of a needle thread for each needle using a contact sound.
[0002]
[Prior art]
As shown in FIG. 11, the needle thread 1 of the sewing machine is supplied to the needle 7 through the needle thread tensions 2 and 3, the balance 4, the thread guides 5 and 6, and the hooks provided above and below the needle 7 and below the needle plate. A seam is formed while penetrating the cloth and intertwining with the lower thread by a combination with a rotational movement (not shown).
[0003]
However, during sewing with a sewing machine, an abnormal seam called a stitch skip in which a seam is not formed over one or several stitches in the middle of a normal seam may occur (see FIGS. 12A and 12B). The cause of such skipping is imperfection in the quality of the yarn or cloth used, that is, unevenness in the thickness of the yarn or cloth, and incompatibility with the sewing machine operation, or inadequate mechanism of the sewing machine itself. For example, it is conceivable that the set gauge of the needle and the hook is defective, or the timing of the vertical movement of the needle and the timing of the hook rotation are not matched. In any case, when stitch skipping occurs, it is necessary to immediately stop the operation of the sewing machine and correct the portion where the seam is not formed.
[0004]
Conventionally, as means for detecting such skipping, a sound detection sensor using a piezoelectric element is brought into contact with the needle thread to monitor the contact sound when the needle thread is running, and the skipping or thread is detected depending on the change in the generation time of the contact sound. There is a detection device that detects a break (see Japanese Patent Application Laid-Open No. 4-102499).
[0005]
As another stitch skip detection device, the tension of a needle thread is monitored by a tension sensor using a strain gauge, and a stitch skip or thread breakage is detected by detecting an abnormal tension of the needle thread. (Japanese Patent Laid-Open No. 50-54457).
[0006]
[Problems to be solved by the invention]
However, in the method of detecting stitch skipping with the contact sound during needle thread traveling, it is necessary to detect a very small difference between the contact sound at the time of normal stitch formation and the occurrence of stitch skipping. A sensor is required. In addition, since the skip is detected by a slight change in the contact sound, there is a problem that the skip is erroneously detected when the variation in sound generation time is large even during normal seam formation.
[0007]
In addition, when detecting a variation in tension with a tension sensor, a tension change with a very high sensitivity is required because a change in tension when a normal seam is formed and when a stitch skip occurs is very small. Also in this case, if the variation in the needle thread tension due to the variation in stitches for each stitch is large, many false detections occur, and only a detection device with extremely low reliability can be realized.
[0008]
The present invention has been made under the circumstances as described above, and it is an object of the present invention to provide a stitch skip detection device for a sewing machine that can prevent erroneous detection and reliably detect stitch skipping or yarn breakage.
[0009]
[Means for Solving the Problems]
  In order to achieve the above object, a stitch skip detection device according to the present invention is arranged on a needle thread path between a thread supply source of a sewing machine that forms a seam by cooperation of a needle and a shuttle and a needle, and forms a seam. Assuming a detection device that detects the occurrence of a sound accompanying the movement of the needle thread due to the above and a detection device that generates a detection signal, and detects the occurrence of thread breakage or skipping according to the generation time of the detection signal, The sound detection sensor;Provided integrally with the thread guide to detect frictional noise between the thread guide and the needle thread located near the upstream and downstream of the sewing machine balance.(Claim 1).
[0010]
  The skipping detection device according to claim 1 further includes:An auxiliary thread tension disposed between the thread guide and the balance, in which the sound detection sensor is provided integrally;A sound detection sensor, time measuring means for measuring the generation time of the frictional sound every time the sewing machine makes one rotation based on the output of the sound detection sensor, a previous measurement value and a current measurement value by the time measurement means; And a yarn movement amount difference detecting means for obtaining a yarn movement amount difference detecting means, and a stitch detection signal generating means for generating a stitch detection signal in accordance with the output value of the yarn movement amount difference detecting means. (Claim 2).
[0011]
In addition, the stitch skip detection device according to claim 1 further includes a storage unit that stores in advance data of an appropriate yarn movement amount corresponding to the rotation speed of the sewing machine, a rotation detection unit that detects the rotation speed of the sewing machine, Comparing means for reading the yarn movement amount data from the storage means according to the detection speed by the rotation detecting means and comparing it with the signal of the sound detection sensor, and generating a skip detection signal according to the comparison result by the comparing means It is desirable to comprise a means to do (claim 3).
[0012]
  Also,According to the present inventionThe stitch skip detection device is arranged on the needle thread path between the thread supply source of the sewing machine that forms the seam and the needle by the cooperation of the needle and the shuttle, and generates a sound accompanying the movement of the needle thread due to the formation of the seam. Assuming a detection device that has a sound detection sensor that detects a signal and detects the occurrence of yarn breakage or skipping according to the generation time of the detection signal,A sound detection sensor provided integrally with the thread guide to detect frictional noise between the thread guide and the needle thread disposed in the vicinity of the upstream side and the downstream side of the balance of the sewing machine;A storage unit that stores in advance data of an appropriate yarn movement amount according to the rotational speed of the sewing machine, a rotation detection unit that detects the rotational speed of the sewing machine, and data from the storage unit according to the detection speed by the rotation detection unit. Comparing means for reading out and comparing with the signal of the sound detection sensor, and means for generating a skip detection signal in accordance with the comparison result by the comparing means (claim 4).
[0013]
The stitch skip detection device according to claim 2 further includes a rotation detection means for detecting a rotation speed of the sewing machine, and a change in the rotation speed detected by the rotation detection means when the change is greater than or equal to a preset value. It is desirable to provide signal control means for stopping the generation of the skip detection signal.
[0014]
5. The skip detection device according to claim 3, further comprising: a signal for stopping the generation of the skip detection signal when a change in rotational speed detected by the rotation detection means is equal to or greater than a preset value. It is desirable to have a control means (Claim 6).
[0015]
When the sewing machine has a plurality of needles and a needle thread corresponding to each needle, the sound detection sensor is arranged separately on each needle thread path. It is desirable to generate a skip detection signal based on the separate detection signals of the plurality of sound detection sensors.
[0016]
It is desirable that the skip detection device according to any one of claims 1 to 7 further includes amplification factor adjusting means for adjusting an amplification factor of an amplifier for amplifying a signal of the sound detection sensor. .
[0017]
It is desirable that the skipping detection device described in claim 2 further includes time correction means for increasing or decreasing the time measurement value by the time measurement means (claim 9).
[0018]
It is preferable that the skip detection device according to any one of claims 2 to 7 further includes a detection stop means for selectively stopping the generation of the skip detection signal.
[0019]
[Action]
  Claim 1And claim 4According to the stitch skip detection device described in the above, there is a difference in yarn movement amount between when the needle thread is captured by the hook and when it is not captured.Detecting a frictional sound between at least one of a pair of thread guides arranged near the upstream side and downstream side of the balance, which is a prominent position, and the needle thread with a sound detection sensor provided integrally with the thread guide.ByWithout using highly sensitive sensorsIt is possible to reliably detect a characteristic change in the frictional sound that occurs when skipping occurs.
[0020]
  According to the skipping detection device according to claim 2,The auxiliary thread tension disposed between the thread guide and the balance, which are integrally provided with the sound detection sensor, goes backward through the thread passage section of the thread guide when the stitch skips and the needle thread is loosened. By preventing the needle thread from moving, it is possible to prevent the needle thread that has slackened from moving downward passing through the thread guide when skipping occurs, and to accurately detect changes in the amount of movement of the needle thread due to slack.
  Then, the time measuring means measures the generation time of the friction sound detected by the sound detection sensor for each needle, and the previous measured value and the current measured value by the time measuring means are detected by the yarn movement amount difference detecting means. Are compared to determine the yarn movement amount difference, and the stitch skip detection signal generating means generates the stitch skip detection signal according to the difference, so that even if there is a large variation in the generation time of the friction noise during normal stitch formation, The occurrence of skipping can be reliably detected without erroneously detecting.
[0021]
According to the stitch skip detection device described in claims 3 and 4, appropriate yarn movement amount data corresponding to the rotational speed of the sewing machine is stored in advance in the storage means, and the rotational speed of the sewing machine is determined by the rotation detection means. Each time the detecting means detects the frictional sound during normal seam formation by reading out the data of the yarn movement amount from the storage means and comparing it with the detection signal and generating a skip detection signal according to the value. Even when there is a large variation in the occurrence time, occurrence of skipping can be reliably detected without erroneously detecting this.
[0022]
According to the skipping detection device according to claims 5 and 6, since the generation of the skipping detection signal is stopped when the change in the rotational speed of the sewing machine exceeds a preset value, for example, immediately after starting the sewing machine. It is possible to prevent a skip detection signal from being generated with an abnormal change in the frictional sound generation time when a change in rotational speed inevitably occurs, such as immediately before stopping.
[0023]
According to the stitch skip detection device of the seventh aspect, even when the sewing machine has a plurality of needles and a needle thread corresponding to each needle, each of the sound detection sensors arranged separately on each needle thread path. A yarn abnormality can be determined based on another detection signal.
[0024]
According to the skip detection device according to the eighth aspect, the intensity of the detection signal by the sound detection sensor can be appropriately adjusted by adjusting the amplification factor of the amplifier according to the magnitude of the frictional sound. It is possible to reliably detect the occurrence of skipping by preventing detection errors.
[0025]
According to the stitch skip detection device of the ninth aspect, even when the generation time of the frictional sound changes due to the sewing pitch or the like, the generation time of the frictional sound becomes constant by increasing or decreasing the time measurement value by the time measuring means. Therefore, the occurrence of skipping can be reliably detected without erroneously detecting a change in the frictional sound generation time as an abnormality.
[0026]
According to the skipping detection device of the tenth aspect, the generation of the skipping detection signal can be stopped by the detection stop means when it is not necessary to detect the skipping. Therefore, it is possible to eliminate the inconvenience that a skip detection signal is generated unnecessarily and the sewing machine is stopped each time.
[0027]
【Example】
Next, embodiments of the present invention will be described with reference to the drawings.
[0028]
FIG. 1 is a partial front view showing a needle thread path of a lock stitch sewing machine provided with a stitch skip detection device according to the present invention. As shown in the figure, the needle thread 1 is supplied to the needle 7 through the needle thread tension 3, the thread take-up spring 24, the thread guide 5 '(see FIG. 3), the auxiliary thread tension 8, the balance 4, and the thread guide 6. The
[0029]
The balance 4 moves up and down in the direction indicated by the arrow A for each needle as the sewing machine rotates. The needle thread 1 repeats reciprocation for each needle while being guided by the thread guides 9 ′ and 10 of the thread guide 5 ′ by the vertical movement of the balance 4. While the needle thread 1 moves, a frictional resistance is applied to the thread passage portions 9 and 10 of the thread guide 5 'and the thread guide 6 to generate a frictional sound.
[0030]
While the sewing machine is driven for one rotation, friction resistance may or may not be applied to the thread guide 5 'and the thread guide 6, and the phase and strength of the sewing machine may be constant when the sewing machine forms a normal seam. Almost constant. When skipping occurs, the needle thread 1 is loosened as shown in FIG. 2 due to the movement of the balance 4, so that no frictional resistance is applied to the thread guide 5 ′ and the thread guide 6 during that time.
[0031]
The change in the amount of movement of the needle thread due to the loosening at the time of occurrence of stitch skipping is far greater than the variation in the amount of movement during normal seam formation. For example, when the movement amount of the needle thread 1 is measured at the position of the thread guide 5 ′ in FIGS. 1 and 2 in the most general main stitch single needle hook shuttle sewing machine, The difference in the amount of movement of the needle thread is about 80 mm. When considering that the total needle thread movement amount per sewing machine needle is about 110 mm, the amount of change is about 73%. The same applies to the yarn guide 6 on the downstream side of the balance 4.
[0032]
Therefore, by monitoring the frictional sound between the thread guide 5 ′ and the thread guide 6 provided before and after the balance 4 and the needle thread 1, it is possible to reliably detect the characteristic change of the frictional sound that occurs when the stitch skip occurs. be able to.
[0033]
FIG. 1 and FIG. 2 exemplify the configuration of the apparatus when it is possible to detect frictional noise between the thread guide 5 ′ on the upstream side of the balance 4 and the needle thread 1.
[0034]
As shown in FIG. 3, the thread guide 5 'has a cylindrical guide member 13 having a thread passage portion 9 at its tip, and an attachment for fixing the guide member 13 to the sewing machine with a screw 15 (see FIG. 1). Member 14. The thread passage portion 9 is formed by forming a thread hole 12 through which the needle thread 1 passes at the distal end portion of a projecting piece 37 projecting from the distal end of the cylindrical portion of the guide member 13. The thread guide 5 ′ constitutes a sound detection sensor unit 17 by incorporating a sound detection sensor 11 made of a piezoelectric element for detecting a frictional sound (vibration) with the needle thread 1 in the guide member 13.
[0035]
The auxiliary thread tension 8 provided between the thread guide 5 'and the balance 4 allows the slack of the needle thread 1 to pass through the thread guide 5' when the stitch thread 1 is loosened and the needle thread 1 is slack. It has a function of preventing going backward through the section 9. That is, when skipping occurs, the needle thread 1 is not consumed because it does not need to go around the hook, and the slackened needle thread 1 moves in the direction of arrow B in FIG. Although there is a possibility, the auxiliary thread tension 8 is provided to prevent the needle thread 1 from moving in the B direction, and it is possible to accurately detect a change in the amount of movement of the needle thread 1 due to the slack.
[0036]
FIG. 4 shows a control block diagram of the sewing machine of this embodiment. The control unit of the sewing machine according to the present embodiment mainly includes a central processing unit (CPU) 40 and a storage device (memory) 41. The CPU 40 performs an arithmetic control operation according to a program stored in the memory 41 in advance. The CPU 40 outputs a control signal to the motor drive circuit 44 in response to the speed setting signal of the speed setting switch and the ON signal of the start / stop switch, controls the motor M to be driven and stopped at the set speed, The feed amount data is read from the memory 41 at the timing, and is output as a control signal to the cloth feed mechanism drive circuit 45, and the cloth feed mechanism 46 is controlled to determine the feed amount by the cloth feed mechanism 46 for each stitch.
[0037]
A skip detection circuit 47 is connected to the CPU 40. The skip detection circuit 47 outputs a skip detection signal to the CPU 40 based on the detection signal from the sound detection sensor 11 and the signal from the encoder (rotation detection sensor) 42 attached to the upper shaft of the sewing machine. When the CPU 40 receives the skip detection signal, it immediately outputs a stop command signal to the motor drive circuit 44.
[0038]
Further, the CPU 40 has keys and switches for setting / changing the skip detection function, setting / changing the amplification factor of the sensor signal, or inputting various data for setting / changing the driving condition of the sewing machine. Are connected, an alarm device 49 for notifying a sewing machine abnormality by a buzzer sound or lighting of a lamp, and a display device 50 for displaying the operating state of the sewing machine and input information by the input device 48. ing.
[0039]
FIG. 5 is a block diagram showing a configuration example of the skip detection circuit 47. The skip detection circuit 47 shown in the figure includes a time measuring means 51 for detecting the generation time of the frictional sound for each needle based on a signal from the sound detection sensor 11 and a signal ( A timing generation circuit 52 that generates a timing signal (see FIG. 7B) for detecting the rotational speed of the sewing machine each time a reference is issued, and a signal (see FIG. 7 (d)), the yarn movement amount difference detecting means 53 for obtaining the yarn movement amount difference between the previous measurement value and the current measurement value, and the previous rotation speed measurement value based on the timing signal from the timing generation circuit 52. And the yarn movement amount difference detection means 54 for obtaining the yarn movement amount difference from the rotation speed measurement value this time, and the output value of the yarn amount difference detection means 53 and the output value of the yarn movement amount difference detection means 54 are compared. Difference is greater than a preset value Consisting stitch skipping detection signal generating means 55 for generating a stitch skipping detection signal when high.
[0040]
The time measuring means 51 passes through the amplifier 56 that amplifies the frictional sound detection signal from the sound detection sensor 11, the band-pass filter 57 that passes only the signal of the necessary frequency among the amplified frictional sound detection signal, and this. A waveform shaping circuit 58 for shaping the waveform of the signal into a waveform capable of time measurement (see FIG. 7C), the timing generation circuit 52, and a clock signal from the timing generation circuit 52 from the waveform shaping circuit 58. It consists of a time measuring circuit 59 that passes only while the signal is being transmitted. The amplification factor of the amplifier 56 can be set and changed via the CPU 40 by key input from the input device 48.
[0041]
The yarn movement amount difference detecting means 53 stores a time data temporary storage device 60 that stores the number of clock signals passing through the time measurement circuit 59 for each stitch, and the previous time data stored in the time data temporary storage device 60. A comparison circuit 61 that compares the time data (number of clock signals) with the current time data (number of clock signals) sent from the time measurement circuit 59 to obtain a time difference between the previous time and the current time, and from the comparison circuit 61 It comprises an arithmetic circuit 62 that calculates the yarn movement amount difference between the previous time and the current time based on the output value and sequentially outputs it.
[0042]
The yarn movement amount difference detecting means 54 converts the clock signal sent from the timing generating circuit 52 by the rotation number detector 43 and stores the rotation number data temporarily as a rotation number data 63 for each stitch, and this Comparing circuit for comparing the previous rotational speed data stored in the rotational speed data temporary storage device 63 with the current rotational speed data sent from the rotational speed detector 43 to determine the rotational speed difference between the previous time and the current time. 64 and yarn movement amount difference data corresponding to the rotation speed difference and having a width due to variations in the rotation number are stored in advance, and yarn movement amount difference data corresponding to the output value of the comparison circuit 64 is output. A difference data generation circuit (ROM) 65 is included. The output value of the comparison circuit 64 is also directly input to the CPU 40 as a detection ON / OFF signal. When the value is equal to or higher than a preset set value, the alarm function of the alarm device 50 is stopped by the CPU 40. . This set value is set based on the rotational speed difference when the rotational speed changes rapidly, such as immediately after starting the sewing machine or just before stopping.
[0043]
The skip detection signal generating means 55 compares the yarn movement amount difference data from the arithmetic circuit 62 with the yarn movement amount difference data from the yarn movement amount difference data generation circuit 65 and outputs the difference. And a detection signal generation circuit 67 that outputs a detection signal when the output value from the comparison circuit 66 is larger than a value set in consideration of variations in the rotational speed. The set value here is set to about the yarn movement amount difference that fluctuates due to variations in the number of rotations of the sewing machine.
[0044]
According to the above configuration, when the needle thread 1 is pulled by the vertical movement of the balance 4 when the needle thread is supplied, the needle thread 1 and the hole 9 of the thread guide 5 ′ are rubbed to generate a frictional sound. It is detected by the sound detection sensor 11. The frictional sound signal detected by the sound detection sensor 11 is amplified by the amplifier 56, and only a signal in a necessary frequency band among the amplified frictional sound detection signals passes through the bandpass filter 57 and is time-measured by the waveform shaping circuit 58. Can be shaped into a waveform signal (see FIG. 7C). Further, a clock signal (see FIG. 7B) is generated from the timing generation circuit 52 according to the timing from the rotation detection sensor 42, and this is the number of rotations of the time measurement circuit 59 of the time measurement means 51 and the yarn movement amount difference detection means 54. The data is input to the temporary data storage device 63 and the comparison circuit 64. The clock signal inputted to the time measuring circuit 59 is passed only while the signal is sent from the waveform shaping circuit 58 and inputted to the yarn movement amount difference detecting means 53.
[0045]
In the yarn movement amount difference detecting means 53, the clock signal (see FIG. 7D) that has passed through the time measuring circuit 59 is stored in the time data temporary storage device 60 as time data. The time data temporary storage device 60 outputs the previous time data stored so far every time time data for one stitch arrives from the time measurement circuit 59. The previous time data from the time data temporary storage device 60 and the current time data from the time measurement circuit 59 are input to the comparison circuit 61. Then, the time difference data between the previous time and the current time obtained by the comparison circuit 61 is input to the arithmetic circuit 62, whereby the arithmetic circuit 62 calculates the yarn movement amount difference between the previous time and the current time. This is input to the comparison circuit 66 of the skip detection signal generating means 55.
[0046]
On the other hand, in the yarn movement amount difference detecting means 54, every time the rotational speed data for one stitch arrives from the rotational speed detector 43, the rotational speed data temporary storage device 63 stores the previous rotational speed data so far. Output. The previous rotation speed data and the current rotation speed data obtained by converting the signal from the timing generation circuit 52 by the rotation speed detector 43 are input to the comparison circuit 64. The rotation speed difference data obtained by the comparison circuit 64 is input to the yarn movement amount difference data generation device 65, whereby the yarn movement amount difference data corresponding to the rotation speed difference data is converted into the yarn movement amount difference data generation device ( ROM) 65 and input to the comparison circuit 66 of the skip detection signal generating means 55. Further, the rotational speed difference data of the comparison circuit 64 of the yarn movement amount difference detecting means 54 is also input to the CPU 40. When the rotation speed difference data is equal to or greater than a preset value, the CPU 40 stops the alarm function of the alarm device 49.
[0047]
In the stitch skip detection signal generation means 55, the yarn movement amount difference data from the arithmetic circuit 62 and the yarn movement amount difference data from the yarn movement amount difference data generation circuit 65 are compared by the comparison circuit 66, and the difference therebetween. Is supplied to the detection signal generation circuit 67. When the output value from the comparison circuit 66 is greater than a preset value, the detection signal generation circuit 67 outputs a skip detection signal to the CPU 40. When the CPU 40 receives the skip detection signal, it immediately sounds the buzzer of the alarm device 49 to turn on the lamp to notify the operator of the occurrence of abnormality, and outputs a stop command signal to the motor drive circuit 44 to drive the motor M. Stop.
[0048]
As described above, the frictional sound of the needle thread 1 is detected by the sound detection sensor 11, and the generation time of the frictional sound for each needle that is sent one after another is compared. In addition to obtaining the movement amount difference, the rotation detection sensor 42 detects the number of rotations of the sewing machine, and compares the number of rotations (rotation speed) for each needle that is sent one after another. A change in the number of rotations of the sewing machine is determined by determining a skip based on a comparison result between a difference in the amount of movement of the yarn based on the difference in generation time of the frictional sound and a difference in the amount of movement of the yarn based on the difference in the number of rotations. Even when there is a large variation in the generation time of the frictional noise due to the occurrence of this, the occurrence of skipping can be reliably detected without erroneously detecting this.
[0049]
FIG. 6 shows a block diagram of a skip detection circuit in a skip detection device of another embodiment. The skip detection circuit 47 ′ shown in the figure is based on a signal from the sound detection sensor 11, a time measuring means 51 for detecting the generation time of the friction sound for each needle, and a signal from the rotation detection sensor 42. Each time (see FIG. 7A) is issued, a timing generation circuit 52 that generates a timing signal (see FIG. 7B) for detecting the rotational speed of the sewing machine, and a signal ( The first yarn movement amount detecting means 68 for obtaining the yarn movement amount based on FIG. 7D) and the signal from the timing generation circuit 52 are converted by the rotation number detector 43 and based on the rotation number data. The difference between the output value of the second yarn movement amount detection means 69 for obtaining the estimated yarn movement amount, the output value of the first yarn movement amount detection means 68 and the output value of the second yarn movement amount detection means 69 is compared. Is greater than the preset value Consisting stitch skipping detection signal generating means 70. for generating a detection signal when.
[0050]
The time measuring means 51 passes through the amplifier 56 that amplifies the frictional sound detection signal from the sound detection sensor 11, the band-pass filter 57 that passes only the signal of the necessary frequency among the amplified frictional sound detection signal, and this. A waveform shaping circuit 58 that shapes the waveform of the signal into a waveform capable of time measurement (see FIG. 5C), and a clock signal from the timing generation circuit 52 only while the signal is sent from the waveform shaping circuit 58. And a time measuring circuit 59 for passing through. The amplification factor of the amplifier 56 can be set and changed via the CPU 40 by key input from the input device 48.
[0051]
The first yarn movement amount detection means 68 is based on the temporary storage buffer 75 that sequentially outputs the clock signal passing through the time measurement circuit 59 as time data for each stitch, and the time data from the temporary storage buffer 75. An arithmetic circuit 71 that calculates and sequentially outputs the yarn movement amount for each stitch.
[0052]
The second yarn movement amount detecting means 69 converts the clock signal sent from the timing generation circuit 52 into the rotation number data by the rotation number detector 43, stores it for each stitch, and sequentially outputs the rotation number data. The storage device 72, the previous rotation number data stored in the rotation number data temporary storage device 72, and the rotation number data obtained by converting the signal from the timing generation circuit 52 by the rotation number detector 43. A comparison circuit 73 for comparing the rotation speed data with the previous time and the current rotation speed by comparison, and appropriate yarn movement amount data corresponding to the rotation speed data and having a width due to variations in the rotation speed are stored in advance, and the rotation speed data is temporarily stored. When the rotational speed data is output from the device 72, it comprises a yarn movement amount data generating circuit (ROM) 74 for outputting the yarn movement amount data corresponding to the rotation speed data. The output data of the comparison circuit 73 is input to the CPU 40 as a detection ON / OFF signal, and the alarm function of the alarm device 49 is stopped by the CPU 40 when the value is equal to or higher than a preset set value. This set value is set based on the difference in the number of revolutions when the change in the number of revolutions is abrupt, such as when the sewing machine is started or just before stopping.
[0053]
The stitch skip detection signal generation means 70 compares the yarn movement amount data from the arithmetic circuit 71 with the yarn movement amount data from the yarn movement amount data generation circuit 74, and outputs a difference between the comparison circuit 76 and the comparison circuit 76. It comprises a detection signal generation circuit 77 that outputs a skip detection signal when the output value from the comparison circuit 76 is larger than a value set in advance in consideration of variations in the rotational speed. The set value here is set to about the yarn movement amount that fluctuates due to variations in the number of rotations of the sewing machine.
[0054]
According to the configuration of FIG. 6, when the needle thread 1 is pulled by the vertical movement of the balance 4 when the needle thread is supplied, the needle thread 1 and the hole 9 of the thread guide 5 ′ are rubbed to generate a frictional sound. Is detected by the sound detection sensor 11. The frictional sound signal detected by the sound detection sensor 11 is sequentially processed by the amplifier 56, the band pass filter 57, the waveform shaping circuit 58 and the time measuring circuit 59 of the time measuring means 51 as in the case of FIG. The passed clock signal is input to the first yarn movement amount detection means 68.
[0055]
In the first yarn movement amount detection means 68, the clock signal that has passed through the time measurement circuit 59 is input to the temporary storage buffer 75. Then, the arithmetic circuit 71 calculates the yarn movement amount based on the time data sent via the temporary storage buffer 75 and outputs the obtained yarn movement amount data to the comparison circuit 76 of the skip detection signal generating means 70. To do.
[0056]
On the other hand, in the second yarn movement amount detection means 69, the rotational speed data output from the rotational speed detector 43 is input to the rotational speed data temporary storage device 72 and the comparison circuit 73. The rotational speed data temporary storage device 72 outputs the previous rotational speed data for one stitch to the comparison circuit 73 and the yarn movement amount data generation circuit 74 each time the rotational speed data for one stitch arrives. The yarn movement amount data generation circuit 74 outputs appropriate yarn movement amount data corresponding to the rotation number data to the comparison circuit 76 of the skip detection signal generation means 70 every time rotation number data is input. Further, the comparison circuit 73 of the second yarn movement amount detecting means 69 has the previous rotation speed data for one stitch from the rotation speed data temporary storage device 72 and the current rotation for one stitch from the rotation speed detector 43. The numerical data is compared, and the difference is output to the CPU 40 as a detection ON / OFF signal. When the detection ON / OFF signal is equal to or higher than the set value, the CPU 40 stops the alarm function of the alarm device 50.
[0057]
In the skip detection signal generating means 70, the yarn movement amount data from the arithmetic circuit 71 and the yarn movement amount data from the yarn movement amount data generation circuit 74 are compared by the comparison circuit 76, and the difference is detected signal generation. It is output to the circuit 77. When the output value from the comparison circuit 76 is larger than a preset value, the detection signal generation circuit 77 outputs a skip detection signal to the CPU 40. When the CPU 40 receives the skip detection signal, it immediately sounds the buzzer of the alarm device 49 to turn on the lamp to notify the operator of the occurrence of abnormality, and outputs a stop command signal to the motor drive circuit 44 to drive the motor M. Stop.
[0058]
As described above, the sound detection sensor 11 detects the frictional sound of the needle thread 1, calculates the thread movement amount from the generation time of the frictional sound for each needle that is successively sent, and the rotation detection sensor 42 rotates the sewing machine. The number is detected, an appropriate yarn movement amount corresponding to the rotation number is obtained from the data stored in advance in the yarn movement amount data generation circuit 74, and the yarn movement amount based on the generation time of the friction sound is stored in advance. By determining the skipping based on the comparison result with the appropriate amount of yarn movement, even if there is a large variation in the generation time of frictional noise due to changes in the number of rotations of the sewing machine, it is possible to generate skipping without erroneous detection. Can be detected reliably.
[0059]
As described above, according to the skipping detection device of the present embodiment, the sound detection sensor 11 is provided in the yarn guide 5 ′ on the upstream side of the balance 4 so as to detect a significant change in the frictional sound generated when the skipping occurs. The change in the frictional sound at the time of skipping can be reliably detected without using the highly sensitive sound detection sensor 11.
[0060]
In this embodiment, when the change in the rotational speed of the sewing machine detected by the comparators 64 and 73 becomes equal to or higher than a preset value, the generation of the skip detection signal is stopped by the CPU 40. It is possible to prevent a skip detection signal from being generated by determining that a change in the frictional sound generation time is abnormal when a change in rotational speed inevitably occurs immediately after startup or immediately before stopping.
[0061]
Further, by adjusting the amplification factor of the amplifier 56 in accordance with the magnitude of the frictional sound, the intensity of the detection signal from the sound detection sensor 11 can be adjusted appropriately. It can be detected reliably.
[0062]
Further, if the time measurement value by the time measuring means 51 can be increased or decreased by a key input operation from the input device 48, the detection time of the frictional sound becomes constant even when the generation time of the frictional sound changes due to the sewing pitch or the like. Therefore, it is possible to prevent erroneous detection due to a difference in the sewing pitch.
[0063]
In the above-described embodiment, the apparatus configuration in the case where the frictional sound between the thread guide 5 'on the upstream side of the balance 4 and the needle thread 1 can be detected has been described. However, as shown in FIG. Even if the auxiliary thread tension 8 'and the sound detection sensor unit 17' are provided, the same effect as in the above embodiment can be obtained.
[0064]
The installation location of the sound detection sensor 11 is not limited to the thread guides 5 ′ and 6 ′. For example, the sound detection sensor 11 is attached to the balance 4 so that the frictional sound between the thread hole of the balance 4 and the needle thread 1 can be detected. May be. Further, a friction sound between the thread take-up spring 24 and the needle thread 1 may be detected. In short, the sound detection sensor 11 may be installed anywhere as long as the needle thread path position where the difference in the amount of thread movement between when the needle thread is captured by the hook and when it is not captured is significant.
[0065]
In the above embodiment, the auxiliary thread tension 8 is provided between the thread guide 5 'and the balance 4, so that the slack of the needle thread 1 passes back through the thread passage 9 of the thread guide 5'. Although this auxiliary tone 8 is not provided, even if the needle thread 1 goes backward when the stitch skips, the tension of the needle thread 1 at that time is significantly higher than that at the time of normal seam formation. Therefore, the skipping can be detected by detecting the characteristic change of the frictional sound. However, in the stitch skip detection device of the present invention which detects the occurrence of stitch skipping by the difference between the needle thread movement amount at the time of normal stitch formation and the stitch thread movement amount at the time of stitch skip occurrence, It is desirable to prevent the needle thread 1 from going backward by providing the auxiliary thread tension 8 as described above, and to ensure that a sudden change in the amount of thread movement is reliably created when stitch skipping occurs.
[0066]
The backward movement of the needle thread 1 can be prevented by adding a slight frictional resistance to the needle thread 1. Therefore, for example, as shown in FIGS. 9 and 10, the frictional resistance is added to the needle thread 1 by bending the protruding pieces 37 of the guide member 13 upward and increasing the number of thread holes 12 of the protruding pieces 37. If the thread guide 5 'itself has a function, the auxiliary thread tension 8 is not necessary.
[0067]
In general, since one sound detection sensor is used for one needle thread, in the case of a multi-needle sewing machine, a plurality of sound detection sensors are required.
[0068]
The stitch skip detection device of the present invention is also applicable as a stitch skip detection device for a chain stitch sewing machine. In that case, by skipping or incorporating the sound detection sensor 11 into a part corresponding to the thread guide (reference numerals 5 and 6 in FIG. 12) of the main sewing machine, it is possible to detect skipping as in the case of the main sewing. . However, the chain stitch sewing machine consumes more needle thread 1 than the main stitch sewing machine, and the change in the amount of thread movement when the stitch skips is large, which is directly related to the movement of the balance (also used as the needle bar 25). Even if the sound detection sensor 11 is provided at a position where there is no needle, for example, in the vicinity of the needle thread bobbin, the skipping can be detected.
[0069]
Furthermore, the stitch skip detection device of the present invention can also detect yarn breakage based on the same principle as in the case of stitch skip detection.
[0070]
【The invention's effect】
In short, according to the present invention, the following excellent effects can be exhibited.
[0071]
  Claim 1And claim 4According to the stitch skip detection device described in the above, there is a difference in yarn movement amount between when the needle thread is captured by the hook and when it is not captured.Detecting the frictional sound between the thread guide and needle thread arranged near the upstream side and downstream side of the balance, which is a prominent position, with a sound detection sensor provided integrally with the thread guideByWithout using highly sensitive sensorsSince it is possible to reliably detect characteristic changes in the frictional sound that occurs when a skip occurs, even if there is a large variation in the generation time of the frictional sound during normal seam formation, it is possible to reliably detect the occurrence of a skip without erroneous detection. .
[0072]
  According to the skipping detection device according to claim 2,The auxiliary thread tension disposed between the thread guide and the balance, which are integrally provided with the sound detection sensor, goes backward through the thread passage section of the thread guide when the stitch skips and the needle thread is loosened. By preventing the needle thread from moving, it is possible to prevent the needle thread that has slackened from moving downward passing through the thread guide when skipping occurs, and to accurately detect changes in the amount of movement of the needle thread due to slack.
  Then, the time measuring means measures the generation time of the friction sound detected by the sound detection sensor for each needle, and the previous measured value and the current measured value by the time measuring means are detected by the yarn movement amount difference detecting means. Are compared to determine the yarn movement amount difference, and according to the value, the skip detection signal generating means generates a skip detection signal,Even when there is a large variation in the generation time of frictional noise during normal seam formation, the occurrence of stitch skipping can be reliably detected without erroneously detecting this.
[0073]
According to the stitch skip detection device described in claims 3 and 4, the appropriate yarn movement amount corresponding to the rotational speed of the sewing machine is stored in advance in the storage means, and the rotational speed of the sewing machine is detected by the rotation detection means. When the comparison means reads the yarn movement amount data from the storage means and compares it with the detection signal from the sound detection sensor, and generates a skip detection signal according to the comparison result, the sewing machine rotation Even if the frictional sound generation time varies due to the variation in the number, it is possible to prevent erroneous detection of this as a skipping occurrence and to detect the occurrence of the skipping more reliably.
[0074]
According to the stitch skip detection device of the fifth and sixth aspects, since the generation of the stitch skip detection signal is stopped when the change in the rotational speed of the sewing machine exceeds a preset value, the rotation speed of the sewing machine It is possible to prevent the occurrence of the skip detection signal by judging that the change in the frictional sound generation time when the change is abrupt is abnormal.
[0075]
According to the stitch skip detection device of the seventh aspect, even when the sewing machine has a plurality of needles and a needle thread corresponding to each needle, each of the sound detection sensors arranged separately on each needle thread path. A yarn abnormality can be determined based on another detection signal.
[0076]
According to the skip detection device according to the eighth aspect of the invention, the detection signal intensity of the sound detection sensor can be appropriately adjusted by adjusting the amplification factor of the amplifier of the sound detection sensor according to the magnitude of the friction sound. It is possible to reliably detect the occurrence of skipping by preventing erroneous detection.
[0077]
According to the stitch skip detection device of the ninth aspect, even when the generation time of the frictional sound changes due to the sewing pitch or the like, the generation time of the frictional sound becomes constant by increasing or decreasing the time measurement value by the time measuring means. Therefore, the occurrence of skipping can be reliably detected without erroneously detecting a change in the frictional sound generation time as an abnormality.
[0078]
According to the skipping detection device of the tenth aspect, the generation of the skipping detection signal can be stopped as necessary.
[Brief description of the drawings]
FIG. 1 is a partial front view showing a state of a needle thread when a stitch skip detection device of the present invention is applied to a lockstitch sewing machine.
FIG. 2 is a partial front view showing the state of the needle thread.
FIG. 3 is a perspective view showing an embodiment of a yarn guide incorporating a sound detection sensor.
FIG. 4 is a control block diagram of a sewing machine according to an embodiment equipped with a skip detection device of the present invention.
5 is a block diagram showing an example of the configuration of a stitch skip detection circuit of the sewing machine in FIG. 4;
6 is a block diagram showing another configuration example of the stitch skip detection circuit of FIG. 4; FIG.
7 is a signal waveform diagram of each part of FIGS. 5 and 6. FIG.
FIG. 8 is a partial front view showing another embodiment when the stitch skip detection device of the present invention is applied to a lockstitch sewing machine.
FIG. 9 is a perspective view showing another embodiment of the yarn guide.
FIG. 10 is a perspective view showing another embodiment of the yarn guide.
FIG. 11 is a partial perspective view showing a needle thread supply path in a general lockstitch sewing machine.
12A is a side cross-sectional view showing a normal seam, and FIG. 12B is a side cross-sectional view showing a seam when a stitch skip occurs.
[Explanation of symbols]
1 Needle thread
4 Balance
5 'thread guide
6 Thread guide
8 Auxiliary thread tension
8 'Auxiliary thread tension
9 Yarn passage
11 Sound detection sensor
12 thread hole
13 Guide members
40 CPU (signal control means)
42 Encoder (Rotation detection sensor, rotation detection means, time correction means)
43 Speed detector
47 Skip detection circuit
51 Time measurement means
53 Yarn movement amount difference detection means
54 Yarn movement amount difference detection means
55 Skip detection signal generating means
56 Amplifier
66 Comparison circuit (comparison means)
67 Detection signal generation circuit
68 Yarn movement amount detection means
69 Yarn movement amount detection means
70 Skip detection signal generating means
74 Yarn movement amount difference data generation circuit (storage means)
76 Comparison circuit (comparison means)
77 Detection signal generator

Claims

A detection signal is detected by detecting the occurrence of noise accompanying the movement of the needle thread due to the formation of the seam, which is arranged on the needle thread path between the thread supply source of the sewing machine that forms the seam by the cooperation of the needle and the shuttle. A detection device for detecting occurrence of yarn breakage or skipping according to the generation time of the detection signal,
A stitch skip of a sewing machine characterized in that the sound detection sensor is provided integrally with the thread guide so as to detect a friction sound between a thread guide and a needle thread disposed in the vicinity of the upstream side and the downstream side of the balance of the sewing machine. Detection device.

An auxiliary thread tension disposed between the thread guide and the balance, in which the sound detection sensor is provided integrally;
And time measuring means for the sewing machine to measure the frictional sound generation time of each rotation operation 1 based on the output of the sound sensor,
A yarn movement amount difference detecting means for comparing the previous measurement value by the time measurement means and the current measurement value to obtain a yarn movement amount difference;
2. The stitch skip detection device for a sewing machine according to claim 1, further comprising stitch skip detection signal generating means for generating a stitch skip detection signal in accordance with an output value of the yarn movement amount difference detection means.

Storage means for storing in advance data of an appropriate yarn movement amount according to the rotational speed of the sewing machine;
Rotation detection means for detecting the rotation speed of the sewing machine;
Comparison means for reading out data from the storage means according to the detection speed by the rotation detection means and comparing it with the signal of the sound detection sensor;
The apparatus according to claim 1, further comprising means for generating a skip detection signal in accordance with a comparison result by the comparison means.

It is arranged on the needle thread path between the thread supply source of the sewing machine that forms the seam and the needle by the cooperation of the needle and the shuttle, and detects the generation of the sound caused by the movement of the needle thread due to the formation of the seam and outputs a signal. A detection device that has a sound detection sensor that generates and detects the occurrence of yarn breakage or skipping according to the generation time of the detection signal,
A sound detection sensor provided integrally with the thread guide to detect frictional noise between the thread guide and the needle thread disposed in the vicinity of the upstream side and the downstream side of the balance of the sewing machine;
Storage means for storing in advance data of an appropriate yarn movement amount according to the rotational speed of the sewing machine;
Rotation detection means for detecting the rotation speed of the sewing machine;
Comparison means for reading out data from the storage means according to the detection speed by the rotation detection means and comparing it with the signal of the sound detection sensor;
And a means for generating a skip detection signal in accordance with the comparison result of the comparison means.

Rotation detection means for detecting the rotation speed of the sewing machine;
3. The sewing machine according to claim 2, further comprising signal control means for stopping the generation of the skip detection signal when a change in rotational speed detected by the rotation detection means becomes a preset value or more. Skip detection device.

5. The signal control means for stopping the generation of the skipping detection signal when a change in rotational speed detected by the rotation detection means becomes a preset value or more. Sewing machine skip detection device.

The sewing machine has a plurality of needles and a needle thread corresponding to each needle,
The sound detection sensors are individually arranged on each needle thread path,
7. The stitch skip detection device according to claim 1, wherein a skip detection signal is generated based on the detection signals of the plurality of sound detection sensors.

8. The stitch skip detection device according to claim 1, wherein an amplification factor of an amplifier for amplifying a signal of the sound detection sensor is adjustable.

4. The sewing machine skip detection device according to claim 2, further comprising time correction means for increasing or decreasing a time measurement value by said time measurement means.

6. The stitch skip detection device according to claim 2, further comprising detection stop means for selectively stopping generation of the skip detection signal.