JP3590248B2

JP3590248B2 - Overheating prevention device for injection molding machine

Info

Publication number: JP3590248B2
Application number: JP31662497A
Authority: JP
Inventors: 秀樹小山
Original assignee: FANUC Corp
Current assignee: FANUC Corp
Priority date: 1997-11-04
Filing date: 1997-11-04
Publication date: 2004-11-17
Anticipated expiration: 2017-11-04
Also published as: JPH11129309A

Description

【０００１】
【発明の属する技術分野】
本発明は、射出成形機の過昇温防止装置の改良に関する。
【０００２】
【従来の技術】
射出成形機の加熱部材、例えば、射出シリンダのバレルやノズルまたは金型等にヒータと熱電対とを設け、この熱電対によって検出される温度に基いてヒータのＯＮ／ＯＦＦ制御を行って加熱部材の温度を設定値に保持するようにした射出成形機の過昇温防止装置が公知である。
【０００３】
ヒータのＯＮ／ＯＦＦ制御にはＳＳＲ（ＳｏｌｉｄＳｔａｔｅＲｅｌａｙ）または電磁接触器等が用いられるが、ＳＳＲがショートして破損したり電磁接触器の接点が溶着してしまったりすると、制御装置からのＯＮ／ＯＦＦ指令に関わりなくヒータに電力が供給され続けることになり、バレルやノズルまたは金型等の加熱部材の温度が必要以上に上昇してしまうといった問題が発生する。
【０００４】
また、温度検出手段である熱電対がバレルやノズルまたは金型等の加熱部材から外れてしまったり断線が生じたりした場合には、熱電対による加熱部材の温度検出が行われなくなるため、制御装置の側には常に低い温度検出情報が与えられる結果となってヒータの常ＯＮ制御が実施され、前記と同様、バレルやノズルまたは金型等の加熱部材の過昇温やヒータの断線といった障害が発生してしまう。
【０００５】
これらの問題を解消するための手段として、温度を制御するための制御装置とは別に専用のアラーム検出装置を設け、温度制御用の熱電対とは独立した別の熱電対をこのアラーム検出装置に接続して加熱部材の異常昇温を検出し、ヒータへの電力の供給を停止するようにした射出成形機が提案されている。
【０００６】
しかし、このような構造を適用しても、アラーム検出装置の熱電対がバレルやノズルまたは金型等の加熱部材から外れてしまったり断線したりすると、アラーム検出装置の過昇温検出機能は機能しなくなり、前記と同様、加熱部材の過昇温といった問題が発生する場合がある。また、加熱部材の昇温目標温度の設定を変更する度にそれに合わせてアラーム検出装置の設定温度も変更しなければならず、設定作業が煩わしくなる。
【０００７】
更に、温度制御用の熱電対に加えてアラーム検出装置の熱電対をバレルやノズルまたは金型等の加熱部材に配備するため、加熱部材に複雑な加工を施したり、あるいは、２対式の熱電対等を利用したりする必要が生じ、製造コストが増大するといった欠点がある。
【０００８】
【発明が解決しようとする課題】
本発明の課題は、前記従来技術の欠点を解消し、ヒータのＯＮ／ＯＦＦ制御に用いられるＳＳＲや電磁接触器にショートや溶着が発生した場合、更には、加熱部材から熱電対が外れてしまったような場合でも加熱部材の過昇温を防止することができ、しかも、加熱部材に対する複雑な加工も必要のない射出成形機の過昇温防止装置を提供することにある。
【０００９】
【課題を解決するための手段】
本発明は、射出成形機の加熱部材にヒータと温度センサとを設け、前記温度センサによって検出される温度に基いて、前記ヒータをＯＮ／ＯＦＦ制御し、前記加熱部材の温度をフィードバック制御する射出成形機の過昇温防止装置であって、ＯＮ／ＯＦＦ周期の全周期にわたってＯＮ指令ではないときに、検出される温度上昇率が許容設定値を上回るとアラームを出力する。
【００１０】
これによってヒータに電源を接続するスイッチング手段がショートしたり溶着した時等の異常を検出する。
【００１１】
さらに、具体的には、第１及び第２の許容設定値を設定記憶する記憶手段と、所定異常検出周期毎に前記温度センサで検出される温度とＯＮ／ＯＦＦの全周期にわたってＯＮ指令であるか否かを検出する検出手段と、
前記検出手段でＯＮ／ＯＦＦの全周期にわたってＯＮ指令であることが検出され、かつ異常検出周期の今周期で検出された温度と前周期で検出された温度との差が前記第１の許容設定値を下回るとき、及び前記検出手段でＯＮ／ＯＦＦの全周期にわたってＯＮ指令でないことが検出され、かつ異常検出周期の今周期で検出された温度と前周期で検出された温度との差が前記第２の許容設定値を上回るとき、アラームを出力するアラーム出力手段とを設けて、スイッチング手段や温度センサの異常を検出する。
【００１２】
【発明の実施の形態】
以下、図面を参照して本発明の実施形態を説明する。図１は本発明を適用した一実施形態の射出成形機における過昇温防止装置の構成の要部を示すブロック図である。
【００１３】
図１において、符号１は射出成形機の加熱部材、例えば、シリンダのバレルやノズルまたは金型等の加熱部材に取り付けられたヒータである。ヒータ１は、そのＯＮ／ＯＦＦ制御を行うＳＳＲ（ＳｏｌｉｄＳｔａｔｅＲｅｌａｙ）のスイッチング部２と、電磁リレーＭＣＣのスイッチＳＷ１とを介して三相交流電源の２相の端子に接続されている。
【００１４】
なお、ＱＦ１およびＦＵＳＥは回路保護のためのブレーカもしくはヒューズである。
【００１５】
符号ＴＨはヒータ１で昇温される加熱部材のフィードバック制御および異常昇温等の検出処理に用いられる温度センサとしての熱電対であり、前述した加熱部材、つまり、シリンダのバレルやノズルまたは金型等に内嵌して取り付けられ、過昇温防止装置の主要部を構成する温度調整計３の温度アンプ４とＡ／Ｄ変換器とを介して該温度調整計３のプロセッサ５に接続されている。
【００１６】
温度調整計３のメモリ６は、ヒータ１によって加熱される加熱部材の昇温目標温度、および、後述する第１，第２の設定許容値を記憶するためのもので、不揮発性メモリによって構成されている。
【００１７】
プロセッサ５は、熱電対ＴＨによって検出される加熱部材の現在温度とメモリ６に設定された加熱部材の昇温目標温度との偏差に基いて、Ｉ／Ｏボード７、および、その出力端子ＤＯ２を介してＳＳＲをＯＮ／ＯＦＦ制御する。
【００１８】
つまり、熱電対ＴＨによって検出される加熱部材の現在温度がメモリ６に設定された加熱部材の昇温目標温度よりも低ければ、ＳＳＲのスイッチング部２をＯＮの状態としてヒータ１に通電し、また、熱電対ＴＨによって検出される加熱部材の現在温度がメモリ６に設定された加熱部材の昇温目標温度よりも高ければ、ＳＳＲのスイッチング部２をＯＦＦの状態としてヒータ１への通電を停止するといった処理を行う。
【００１９】
なお、温度調整計３の出力バッファ８にＳＳＲへのＯＮ指令やＯＦＦ指令を所定周期毎に書き込み、射出成形機を駆動制御するＣＮＣ装置９側のプロセッサによって出力バッファ８の状態を検出して、ＣＮＣ装置９側のプロセッサによりＩ／Ｏボード７を介してＳＳＲをＯＮ／ＯＦＦ制御するようにしてもよい。
【００２０】
また、温度調整計３のプロセッサ５が熱電対ＴＨを介して加熱部材の異常昇温や熱電対ＴＨの異常等を検出した場合には、Ｉ／Ｏボード７、および、その出力端子ＤＯ１を介して電磁リレーＭＣＣが駆動され、ヒータ１への電源投入直後から常ＯＮ状態となっているスイッチＳＷ１が開かれて、ＳＳＲのスイッチング部２よりも電源側の位置でヒータ１への電力供給が遮断される。前記と同様、ＣＮＣ装置９側のプロセッサによってこの処理を行うことも可能である。
【００２１】
メモリ６に対する昇温目標温度および後述の第１，第２の設定許容値の設定作業は、ＣＮＣ装置９側のキーボード操作等により、Ｉ／Ｏボード７，入力バッファ１０，プロセッサ５を介して行われる。
【００２２】
ヒータ１による昇温作業が正常に行われた場合の加熱部材の温度変化の例を図３に実線で示す。
【００２３】
例えば、図３に示すように、昇温目標温度が２００度、また、室温が２０度であるとする。
【００２４】
まず、ヒータ１への電源投入直後の段階では加熱部材の温度は概ね室温と等しく２０度程度であるから、熱電対ＴＨによって検出される加熱部材の現在温度はメモリ６に設定された加熱部材の昇温目標温度２００度よりも低い。従って、ＳＳＲのスイッチング部２はＯＮの状態に保持され、ヒータ１が通電されて加熱部材の温度、つまり、熱電対ＴＨによって検出される温度が図３に示すように線形的に上昇することになる。
【００２５】
このような状態は、図３におけるＡの区間のように、熱電対ＴＨによって検出される温度がメモリ６に設定された加熱部材の昇温目標温度２００度に達するまで続く。このままＳＳＲのスイッチング部２がＯＮの状態に保持されると加熱部材の温度がそのまま上昇を続けるので、結果的に、熱電対ＴＨによって検出される加熱部材の現在温度がメモリ６に設定された加熱部材の昇温目標温度２００度よりも高くなり、これを検出した温度調整計３のプロセッサ５からの指令によりＳＳＲ２がＯＦＦの状態に切り替えられてヒータ１への通電が断たれ、加熱部材の温度が徐々に下降を開始する。
【００２６】
そして、熱電対ＴＨによって検出される加熱部材の現在温度がメモリ６に設定された昇温目標温度２００度を下回ると、これを検出した温度調整計３のプロセッサ５からの指令によりＳＳＲのスイッチング部２が再びＯＮの状態に切り替えられ、ヒータ１が通電されて加熱部材の温度が再び上昇を開始する。
【００２７】
以下、前記と同様の処理操作が繰り返し実行される結果、加熱部材の現在温度は、図３のＢの区間に示すように、ＯＮ／ＯＦＦ制御による温度フィードバック制御が行われ、メモリ６に設定された昇温目標温度２００度の近傍に、ある程度の許容幅を有して安定的に保持されることになる。
【００２８】
しかし、ＳＳＲのスイッチング部２がショートしたり溶着等の故障が生じると、熱電対ＴＨが加熱部材の過昇温を検知していたとしてもプロセッサ５からの指令によってＳＳＲのスイッチング部２を開路することはできなくなる。従って、過昇温状態であってもヒータ１への通電状態がそのまま保持されることになり、加熱部材の温度が、図３に示す通り、メモリ６に設定された昇温目標温度２００度を超えて限界点まで線形的に上昇してしまうといった問題が生じることがあり、成形不良等が発生する他、ヒータ１自体の断線の危険もある。
【００２９】
また、熱電対ＴＨが加熱部材から外れてしまった場合や熱電対ＴＨに断線が生じた場合には、この熱電対ＴＨが常に室温を検出し続けるか、または、断線によってプロセッサ５への信号入力が断たれるため、プロセッサ５は、常に加熱部材の現在温度がメモリ６の昇温目標温度よりも低いと認識し続けることになる。この結果、プロセッサ５がＳＳＲのスイッチング部２を常にＯＮの状態に保持し続けることになり、ＳＳＲのスイッチング部２がショートしたり溶着した場合と同様、ヒータ１への通電状態がそのまま維持され、回路に異常が生じるとか加熱部材の温度が図３に示すように限界点まで線形的に上昇してしまうといった問題が起きる場合がある。
【００３０】
そこで、本実施形態においては、前述したような通常のＯＮ／ＯＦＦ制御によるフィードバック温度制御に加え、図２に示すような異常検出処理をプロセッサ５に所定周期毎に繰り返し実行させ、ＳＳＲのスイッチング部２のショートや溶着および熱電対ＴＨの外れや断線に関連する事故を未然に防止するようにしている。
【００３１】
以下、ＳＳＲによるヒータ１のＯＮ／ＯＦＦ制御は従来と同様にして実施されるものとして、本実施形態における異常検出処理の詳細について説明する。
【００３２】
所定異常検出周期毎の異常検出処理を開始したプロセッサ５は、まず、ヒータ１が連続ＯＮ指令の状態になっているか否か、つまり、温度制御のＯＮ／ＯＦＦ周期の全周期にわたってＯＮ指令が出力されているか否かを判断する（ステップＳ１）。加熱部材の昇温過程である図３のＡに相当する区間内では全周期ＯＮ指令である。連続ＯＮの状態になっている場合、プロセッサ５は、熱電対ＴＨを介して加熱部材の現在温度ｔを読み込み、その値から、前周期の異常検出処理において検出された加熱部材の温度ｔ０（なおｔ０は初期設定で最初は０にセットされている）を減じて異常検出処理の１処理周期分に対する加熱部材の温度の上昇量（上昇率）を求め、その値が第１の許容設定値ａよりも小さいか否かを判別する（ステップＳ２）。
【００３３】
第１の許容設定値ａは、図３に示されるような区間Ａにおける加熱部材の温度の上昇特性に基いて決められる正の値であり、例えば、異常検出処理の１処理周期の時間がΔＴであるとすれば、図３における温度の上昇量（上昇率）ａ′が許容設定値ａに相当する値となる。
【００３４】
しかし、実際には、室温の高低等によっても加熱部材の温度の上昇特性には変化が生じるので、実際の許容設定値ａの値は、室温が低いために加熱部材の温度上昇が鈍くなったような場合であっても、これを熱電対ＴＨの外れや断線等の異常として検出することがないように、ａ′よりも低めの値を設定する必要がある。許容設定値ａの大きさは、実際には、熱電対脱落時における室温の上昇等によって熱電対ＴＨに生じる温度上昇等と、ヒータ１の加熱による加熱部材の強制的な温度上昇とを区別できる程度の大きさであれば十分である。従って、昇温目標温度の設定変更等に伴って許容設定値ａの大きさを再検討するといった必要性もない。
【００３５】
そして、ステップＳ２の判別結果が真となった場合、つまり、異常検出処理１処理周期分に対する加熱部材の温度の上昇量（上昇率）が許容設定値ａに満たない場合は、連続ＯＮ指令であるから温度の上昇率は許容設定値ａ以上になるはずなのに許容設定値ａに満たないから、プロセッサ５は、熱電対ＴＨが加熱部材から外れているか、もしくは、熱電対ＴＨに断線が生じているものと判断し、出力バッファ８およびＩ／Ｏボード７を介してＣＮＣ装置９に異常検出信号を出力し、ＣＮＣ装置９側のブザーもしくはモニタ表示等によって作業者に異常を知らせると共に、電磁リレーＭＭＣを作動させてスイッチＳＷ１を開き、ＳＳＲのスイッチング部２よりも電源側の位置でヒータ１への電力供給を遮断する（ステップＳ３）。
【００３６】
従って、熱電対ＴＨが加熱部材から外れたり断線したりした場合は、ヒータ１に対する通電開始直後の段階で電源が遮断されることになる。また、図３のＢの区間のように設定値まで温度が上昇し、温度制御によりＳＳＲのスイッチング部２がＯＮ／ＯＦＦしている状態において、熱電対ＴＨが加熱部材から外れたり断線したりした場合においても、熱電対ＴＨで検出される温度が低下するから、温度制御によりＯＮ／ＯＦＦ周期の全周期にわたってＯＮ指令が出力されることになる。このときもステップＳ２で温度上昇がないことが検出されるから、ステップＳ３でアラームが出力されることになる。
【００３７】
熱電対ＴＨが加熱部材の真の温度を検出しないことを原因として従来生じていた加熱部材の過昇温やヒータ１の断線といった問題は完全に解消される。
【００３８】
また、ステップＳ２の判別結果が偽となって熱電対ＴＨの温度上昇がヒータ１による強制加熱に起因するものであることが明らかになった場合、つまり、熱電対ＴＨの取り付け状態やリード線の接続が適切であることが判明した場合には、ステップＳ３の処理はスキップされ、スイッチＳＷ１はそのままＯＮの状態に保持され、ステップＳ６に移行し、ステップＳ２の処理で読み込んだ加熱部材の現在温度ｔを前周期の加熱部材の温度ｔ０として更新記憶し、当該処理周期の異常検出処理を終了する。
【００３９】
熱電対ＴＨによって検出される加熱部材の温度が昇温目標値に達するまでの間、前記と同様の処理が繰り返し実行され、熱電対ＴＨに異常がなければ、ヒータ１に対する電力供給はそのまま許容され、熱電対ＴＨによって検出される加熱部材の温度が昇温目標温度に到達する。そして、加熱部材の温度が昇温目標温度に達すると、ＳＳＲには温度フィードバック制御によって決まるＯＮ／ＯＦＦ周期のデューティー比によるＯＮ／ＯＦＦ指令が出力されることになる。その結果、ステップＳ１でＯＮ／ＯＦＦ周期の全周期にわたってＯＮ指令が出力されていないことが検出されることになる。すなわち図３のＢの区間に入りＯＮ／ＯＦＦ周期内でＯＮ区間の指令とＯＦＦ区間の指令があり、ＳＳＲにＯＮ／ＯＦＦが出されているとき、ステップＳ１からステップＳ４に移行し、プロセッサ５は、加熱部材の現在温度ｔを読み込み、その値から、前周期の異常検出処理において検出された加熱部材の温度ｔ０を減じて異常検出処理１処理周期分に対する加熱部材の温度の上昇量（上昇率）を求め、その値が第２の許容設定値ｂよりも大きいか否かを判別する（ステップＳ４）。
【００４０】
第２の許容設定値ｂは、図３に示されるような区間Ｂにおいて昇温目標温度保持のためにヒータ１が正常にＯＮ／ＯＦＦされているとき生じる最大の変化量に基いて決められる値である（最大の変化量よりも少し大きな値）。
【００４１】
そして、ステップＳ４の判別結果が真となった場合、つまり、異常検出処理１処理周期分に対する加熱部材の温度の上昇量（上昇率）が許容設定値ｂを超えている場合、プロセッサ５は、ＳＳＲのスイッチング部２にショートや溶着が生じている状態にあるものと判断し、出力バッファ８およびＩ／Ｏボード７を介してＣＮＣ装置９に異常検出信号を出力し、ＣＮＣ装置９側のブザーもしくはモニタ表示等によって作業者に異常を知らせると共に、電磁リレーＭＭＣを作動させてスイッチＳＷ１を開き、ＳＳＲのスイッチング部２よりも電源側の位置でヒータ１への電力供給を遮断する（ステップＳ５）。
【００４２】
従って、ＳＳＲのスイッチング部２にショートや溶着が生じた場合、ヒータ１に対する電力の供給は直ちに遮断されることになり、ＳＳＲスイッチング部２のショートや溶着に起因して従来生じていた加熱部材の過昇温やヒータ１の断線といった問題が完全に解消される。
【００４３】
また、ステップＳ４の判別結果が偽となり、ＳＳＲのスイッチング部２へのＯＦＦ指令によってＳＳＲが正常に作動し、加熱部材の温度を昇温目標温度に保持するためのＯＮ／ＯＦＦ制御が正常に行われていると判明した場合には、ステップＳ５の処理はスキップされ、スイッチＳＷ１はそのままＯＮの状態に保持される。
【００４４】
次いで、プロセッサ５は、ステップＳ４の処理で読み込んだ加熱部材の現在温度ｔを前周期の加熱部材の温度ｔ０として更新記憶し（ステップＳ６）、当該処理周期の異常検出処理を終了する。
【００４５】
以下、昇温目標温度保持のためのＳＳＲのスイッチング部２のＯＮ／ＯＦＦ制御が正常に行われる間、前記と同様の処理が繰り返し実行され、また、ＳＳＲのスイッチング部２にショートや溶着が生じた場合にはステップＳ４の処理によってその異常が検出され、スイッチＳＷ１が開路されてヒータ１に対する電力供給が遮断されることになる。
【００４６】
以上、一実施形態として、温度調整計３のプロセッサ５によってＳＳＲのスイッチング部２のショートや溶着等の異常検出、および、熱電対ＴＨの外れや断線といった異常検出を行って加熱部材の異常昇温を防止する場合の例について述べたが、温度調整計３からＩ／Ｏボード７を介してＣＮＣ装置９側のプロセッサに熱電対ＴＨの温度検出データやメモリ６の各種設定値を転送するようにすれば、ＣＮＣ装置９側のプロセッサによって前記と同様の処理を行うことができ、また、ＣＮＣ装置９側のメモリに昇温目標温度や許容設定値ａ，ｂを記憶させてＣＮＣ装置９側のプロセッサのみによって前記と同様の処理を行わせることも可能である。
【００４７】
更に、温度調整計３のプロセッサ５とＣＮＣ装置９側のプロセッサとにより前記の処理を重複して実行させてダブルチェックを行うことも可能である。
【００４８】
【発明の効果】
本発明によれば、格別の熱電対を設けなくても、加熱部材の温度制御に用いられる熱電対をそのまま利用してヒータ制御用のＳＳＲ（ＳｏｌｉｄＳｔａｔｅＲｅｌａｙ）や電磁接触器のショートおよび溶着を検出し、加熱部材の過昇温を防止することができる。従って、射出成形機の加熱部材に複雑な加工を施す必要もなく、安価で信頼性の高い過昇温防止装置を提供することができる。
【００４９】
また、熱電対が外れたり断線したりして正常な温度検出が行われなくなった場合には、ヒータへの電力供給が自動的に停止されるので、熱電対自体の脱落や損傷による加熱部材の過昇温も防止することができる。
【図面の簡単な説明】
【図１】本発明を適用した一実施形態の射出成形機における過昇温防止装置の要部を示すブロック図である。
【図２】同実施形態における過昇温防止方法を実施するための処理の概略を示すフローチャートである。
【図３】加熱部材の正常な温度上昇と異常発生時の温度上昇の状態を概略で示す線図である。
【符号の説明】
１ヒータ
２ＳＳＲ（ＳｏｌｉｄＳｔａｔｅＲｅｌａｙ）のスイツチング部
３温度調整計
４温度アンプ
５プロセッサ
６メモリ
７Ｉ／Ｏボード
８出力バッファ
９ＣＮＣ装置
１０入力バッファ
ＭＣＣ電磁リレー
ＳＷ１スイッチ
ＴＨ熱電対
ＱＦ１ブレーカまたはヒューズ
ＦＵＳＥブレーカまたはヒューズ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement in an excessive temperature rise prevention device for an injection molding machine.
[0002]
[Prior art]
A heater and a thermocouple are provided on a heating member of an injection molding machine, for example, a barrel, a nozzle, a mold, or the like of an injection cylinder, and ON / OFF control of the heater is performed based on a temperature detected by the thermocouple to heat the heating member. An apparatus for preventing an excessive rise in temperature of an injection molding machine in which the temperature of the injection molding machine is maintained at a set value is known.
[0003]
For the ON / OFF control of the heater, an SSR (Solid State Relay) or an electromagnetic contactor is used, but if the SSR is short-circuited and damaged or the contact of the electromagnetic contactor is welded, the ON / OFF from the control device is performed. Electric power is continuously supplied to the heater regardless of the / OFF command, which causes a problem that the temperature of a heating member such as a barrel, a nozzle or a mold rises more than necessary.
[0004]
Further, when the thermocouple serving as the temperature detecting means is detached from the heating member such as a barrel, a nozzle or a mold or is disconnected, the temperature of the heating member is not detected by the thermocouple. As a result, always ON control of the heater is performed as a result of giving low temperature detection information to the side of the heater, and similarly to the above, failures such as excessive heating of the heating member such as a barrel, a nozzle or a mold, and disconnection of the heater are caused. Will occur.
[0005]
As a means for solving these problems, a dedicated alarm detection device is provided separately from the control device for controlling temperature, and another thermocouple independent of the thermocouple for temperature control is used for this alarm detection device. There has been proposed an injection molding machine which is connected to detect an abnormal temperature rise of a heating member and stop supplying power to the heater.
[0006]
However, even if such a structure is applied, if the thermocouple of the alarm detection device comes off from or disconnects from the heating member such as the barrel, nozzle or mold, the overheating detection function of the alarm detection device will function. As in the case described above, a problem such as excessive heating of the heating member may occur. Further, every time the setting of the heating target temperature of the heating member is changed, the set temperature of the alarm detection device must be changed accordingly, which makes the setting operation cumbersome.
[0007]
Furthermore, in addition to a thermocouple for temperature control, a thermocouple of an alarm detection device is provided on a heating member such as a barrel, a nozzle or a mold, so that the heating member is subjected to complicated processing or a two-pair thermocouple. There is a drawback that it is necessary to use equality and the manufacturing cost increases.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned disadvantages of the related art, and when a short circuit or welding occurs in an SSR or an electromagnetic contactor used for ON / OFF control of a heater, a thermocouple further comes off from a heating member. even it is possible to prevent the excessive rise in temperature of the heating member when the like, moreover, is to provide an excessive Yutakabo TomeSo location of complex processing is also unnecessary injection molding machine to the heating element.
[0009]
[Means for Solving the Problems]
The present invention provides an injection molding machine in which a heating member is provided with a heater and a temperature sensor, and the heater is turned on / off based on a temperature detected by the temperature sensor, and the temperature of the heating member is feedback-controlled. An excessive temperature rise prevention device for a molding machine , which outputs an alarm when a detected temperature rise rate exceeds an allowable set value when an ON command is not issued over the entire ON / OFF cycle .
[0010]
Switching means by Re this connecting power to the heater when detecting an abnormality such as a time obtained by welding or short.
[0011]
More specifically, a storage means for setting and storing the first and second allowable set values, and an ON command for the temperature detected by the temperature sensor at every predetermined abnormality detection cycle and the ON / OFF cycle. Detection means for detecting whether or not
The detection means detects that the ON command is issued over the entire ON / OFF cycle, and the difference between the temperature detected in the current cycle of the abnormality detection cycle and the temperature detected in the previous cycle is the first allowable setting. When the value is lower than the value, and when the detection means detects that the ON command is not the ON command for the entire ON / OFF cycle, the difference between the temperature detected in the current cycle of the abnormality detection cycle and the temperature detected in the previous cycle is the same as the above. An alarm output means for outputting an alarm when the value exceeds the second allowable set value is provided to detect an abnormality of the switching means or the temperature sensor.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a main part of a configuration of an overheating prevention device in an injection molding machine according to an embodiment to which the present invention is applied.
[0013]
In FIG. 1, reference numeral 1 denotes a heater attached to a heating member of an injection molding machine, for example, a heating member such as a barrel of a cylinder, a nozzle or a mold. The heater 1 is connected to two-phase terminals of a three-phase AC power supply via a switching unit 2 of an SSR (Solid State Relay) for performing ON / OFF control thereof and a switch SW1 of an electromagnetic relay MCC.
[0014]
Note that QF1 and FUSE are breakers or fuses for circuit protection.
[0015]
Reference symbol TH denotes a thermocouple as a temperature sensor used for feedback control of a heating member heated by the heater 1 and detection processing of abnormal heating, etc., and the above-mentioned heating member, that is, a cylinder barrel, a nozzle or a mold. And connected to the processor 5 of the temperature controller 3 via the temperature amplifier 4 and the A / D converter of the temperature controller 3 constituting a main part of the excessive temperature rise prevention device. I have.
[0016]
The memory 6 of the temperature controller 3 stores a target temperature of a heating member to be heated by the heater 1 and first and second set permissible values to be described later, and is constituted by a nonvolatile memory. ing.
[0017]
The processor 5 sets the I / O board 7 and its output terminal DO2 based on the deviation between the current temperature of the heating member detected by the thermocouple TH and the target temperature of the heating member set in the memory 6. ON / OFF control of the SSR via the CPU.
[0018]
That is, if the current temperature of the heating member detected by the thermocouple TH is lower than the target temperature of the heating member set in the memory 6, the switching unit 2 of the SSR is turned on and the heater 1 is energized. If the current temperature of the heating member detected by the thermocouple TH is higher than the target temperature of the heating member set in the memory 6, the switching unit 2 of the SSR is turned off and the power supply to the heater 1 is stopped. Is performed.
[0019]
The ON command and the OFF command to the SSR are written into the output buffer 8 of the temperature controller 3 at predetermined intervals, and the state of the output buffer 8 is detected by the processor of the CNC device 9 which controls the driving of the injection molding machine. The SSR may be ON / OFF controlled by the processor of the CNC device 9 via the I / O board 7.
[0020]
Further, when the processor 5 of the temperature controller 3 detects an abnormal temperature rise of the heating member or an abnormality of the thermocouple TH via the thermocouple TH, the processor 5 of the temperature controller 3 outputs the abnormality via the I / O board 7 and its output terminal DO1. The electromagnetic relay MCC is driven, and the switch SW1, which is normally ON immediately after the power supply to the heater 1 is turned on, is opened, and the power supply to the heater 1 is cut off at a position closer to the power supply than the switching unit 2 of the SSR. Is done. As described above, this processing can be performed by the processor on the CNC device 9 side.
[0021]
The operation of setting the target temperature to be heated and the first and second allowable setting values for the memory 6 is performed via the I / O board 7, the input buffer 10, and the processor 5 by a keyboard operation or the like on the CNC device 9 side. Is
[0022]
An example of a temperature change of the heating member when the temperature raising operation by the heater 1 is normally performed is shown by a solid line in FIG.
[0023]
For example, as shown in FIG. 3, it is assumed that the target temperature is 200 degrees and the room temperature is 20 degrees.
[0024]
First, at the stage immediately after the power supply to the heater 1 is turned on, the temperature of the heating member is approximately equal to room temperature and about 20 ° C. Therefore, the current temperature of the heating member detected by the thermocouple TH is the temperature of the heating member set in the memory 6. It is lower than the target temperature of 200 ° C. Therefore, the switching unit 2 of the SSR is kept in the ON state, the heater 1 is energized, and the temperature of the heating member, that is, the temperature detected by the thermocouple TH rises linearly as shown in FIG. Become.
[0025]
Such a state continues until the temperature detected by the thermocouple TH reaches the target temperature 200 ° C. of the heating member set in the memory 6, as shown in section A in FIG. If the switching unit 2 of the SSR is kept ON in this state, the temperature of the heating member continues to rise as it is. As a result, the current temperature of the heating member detected by the thermocouple TH is set in the memory 6. The temperature rise target temperature of the member becomes higher than 200 degrees, and the SSR 2 is switched to the OFF state by a command from the processor 5 of the temperature controller 3 that detects the temperature rise, the power supply to the heater 1 is cut off, and the temperature of the heating member is increased. Begins to descend gradually.
[0026]
When the current temperature of the heating member detected by the thermocouple TH falls below the target temperature of 200 ° C. set in the memory 6, the switching unit of the SSR is operated in response to a command from the processor 5 of the temperature controller 3 detecting the temperature. 2 is turned on again, the heater 1 is energized, and the temperature of the heating member starts to rise again.
[0027]
Hereinafter, as a result of repeatedly executing the same processing operation as described above, the current temperature of the heating member is set in the memory 6 by performing temperature feedback control by ON / OFF control as shown in the section B of FIG. In the vicinity of the target temperature of 200 ° C., the temperature is stably maintained with a certain allowable width.
[0028]
However, if the switching unit 2 of the SSR is short-circuited or a failure such as welding occurs, the switching unit 2 of the SSR is opened by a command from the processor 5 even if the thermocouple TH detects excessive heating of the heating member. You will not be able to do it. Therefore, even if the temperature is excessively high, the energized state of the heater 1 is maintained as it is, and the temperature of the heating member is reduced to the target temperature 200 ° C. set in the memory 6 as shown in FIG. There may be a problem that the temperature rises linearly to the limit point beyond the limit. In addition to the occurrence of molding failure, there is a risk of disconnection of the heater 1 itself.
[0029]
Further, when the thermocouple TH is detached from the heating member or when the thermocouple TH is disconnected, the thermocouple TH always detects the room temperature, or a signal input to the processor 5 due to the disconnection. Is cut off, the processor 5 always keeps recognizing that the current temperature of the heating member is lower than the temperature increase target temperature of the memory 6. As a result, the processor 5 always keeps the SSR switching unit 2 in the ON state, and the energized state to the heater 1 is maintained as in the case where the SSR switching unit 2 is short-circuited or welded, There may be a problem that an abnormality occurs in the circuit or that the temperature of the heating member linearly rises to a limit point as shown in FIG.
[0030]
Therefore, in the present embodiment, in addition to the feedback temperature control by the normal ON / OFF control as described above, the processor 5 repeatedly executes the abnormality detection processing as shown in FIG. In this way, accidents related to short-circuiting, welding, disconnection or disconnection of the thermocouple TH are prevented beforehand.
[0031]
Hereinafter, assuming that the ON / OFF control of the heater 1 by the SSR is performed in the same manner as in the related art, the details of the abnormality detection processing in the present embodiment will be described.
[0032]
The processor 5 that has started the abnormality detection processing for each predetermined abnormality detection cycle first determines whether or not the heater 1 is in a continuous ON instruction state, that is, outputs an ON instruction over the entire ON / OFF cycle of the temperature control. It is determined whether or not it has been performed (step S1). In the section corresponding to A in FIG. 3 in the heating process of the heating member, the full cycle ON command is issued. In the case of the continuous ON state, the processor 5 reads the current temperature t of the heating member via the thermocouple TH, and from the value reads the temperature t0 of the heating member detected in the abnormality detection processing of the previous cycle (note that (t0 is initially set to 0 in the initial setting) to obtain the amount of increase (rate of increase) in the temperature of the heating member for one processing cycle of the abnormality detection processing, and that value is the first allowable set value a It is determined whether it is smaller than (Step S2).
[0033]
The first allowable set value a is a positive value determined based on the temperature rise characteristic of the heating member in the section A as shown in FIG. 3, and for example, the time of one processing cycle of the abnormality detection processing is ΔT In this case, the temperature rise amount (rise rate) a 'in FIG. 3 is a value corresponding to the allowable set value a.
[0034]
However, in practice, the temperature rise characteristic of the heating member changes depending on the level of the room temperature, etc., so that the actual allowable set value a has a slower temperature rise of the heating member because the room temperature is low. Even in such a case, it is necessary to set a value lower than a 'so as not to detect this as an abnormality such as disconnection or disconnection of the thermocouple TH. In practice, the magnitude of the allowable set value a can be distinguished from a temperature rise or the like generated in the thermocouple TH due to a rise in room temperature when the thermocouple falls off, and a forced temperature rise of the heating member due to the heating of the heater 1. Sufficient size is sufficient. Accordingly, there is no need to reconsider the magnitude of the allowable set value a with a change in the setting of the temperature increase target temperature.
[0035]
If the determination result of step S2 is true, that is, if the amount of increase in the temperature of the heating member (increase rate) for one processing cycle of the abnormality detection processing is less than the allowable set value a, a continuous ON command is issued. Since the temperature rise rate should be equal to or higher than the allowable set value a, the processor 5 does not satisfy the allowable set value a. Therefore, the processor 5 determines that the thermocouple TH has come off the heating member or the thermocouple TH has been disconnected. And outputs an abnormality detection signal to the CNC device 9 via the output buffer 8 and the I / O board 7 to notify the operator of the abnormality by means of a buzzer or a monitor display on the CNC device 9 side, and to notify the operator of the electromagnetic relay. The switch SW1 is opened by operating the MMC, and the power supply to the heater 1 is cut off at a position closer to the power supply than the switching unit 2 of the SSR (step S3).
[0036]
Therefore, when the thermocouple TH is detached from the heating member or is disconnected, the power is cut off immediately after the power supply to the heater 1 is started. Further, in a state where the temperature rises to the set value as in the section B of FIG. 3 and the switching unit 2 of the SSR is turned on / off by the temperature control, the thermocouple TH is detached from the heating member or disconnected. Also in this case, since the temperature detected by the thermocouple TH decreases, the ON command is output over the entire ON / OFF cycle by the temperature control. At this time, since no temperature rise is detected in step S2, an alarm is output in step S3.
[0037]
Problems caused by the thermocouple TH not detecting the true temperature of the heating member, such as excessive heating of the heating member and disconnection of the heater 1, which have conventionally occurred, are completely eliminated.
[0038]
Further, when the determination result of step S2 is false and it becomes clear that the temperature rise of the thermocouple TH is caused by the forced heating by the heater 1, that is, the mounting state of the thermocouple TH or the lead wire If it is determined that the connection is appropriate, the process of step S3 is skipped, the switch SW1 is kept in the ON state, the process proceeds to step S6, and the current temperature of the heating member read in the process of step S2 is read. t is updated and stored as the temperature t0 of the heating member in the previous cycle, and the abnormality detection processing in the processing cycle ends.
[0039]
Until the temperature of the heating member detected by the thermocouple TH reaches the target temperature increase value, the same processing as described above is repeatedly performed. If there is no abnormality in the thermocouple TH, power supply to the heater 1 is allowed as it is. , The temperature of the heating member detected by the thermocouple TH reaches the temperature increase target temperature. When the temperature of the heating member reaches the target temperature, the ON / OFF command is output to the SSR based on the duty ratio of the ON / OFF cycle determined by the temperature feedback control. As a result, it is detected in step S1 that the ON command has not been output over the entire ON / OFF cycle. That is, when there is an ON section command and an OFF section command in the ON / OFF cycle in the section B of FIG. 3 and ON / OFF is output to the SSR, the process proceeds from step S1 to step S4, and the processor 5 Reads the current temperature t of the heating member, subtracts the temperature t0 of the heating member detected in the abnormality detection processing in the previous cycle from the value, and calculates the amount of increase (increase) in the temperature of the heating member for one processing cycle of the abnormality detection processing. Rate) is determined, and it is determined whether the value is greater than a second allowable set value b (step S4).
[0040]
The second allowable set value b is a value determined based on the maximum amount of change that occurs when the heater 1 is normally turned on / off for maintaining the temperature increase target temperature in the section B as shown in FIG. (A value slightly larger than the maximum change amount).
[0041]
If the determination result of step S4 is true, that is, if the amount of increase in the temperature of the heating member (the increase rate) for one processing cycle of the abnormality detection processing exceeds the allowable set value b, the processor 5 It is determined that a short circuit or welding has occurred in the switching unit 2 of the SSR, an abnormality detection signal is output to the CNC device 9 via the output buffer 8 and the I / O board 7, and a buzzer on the CNC device 9 side is output. Alternatively, the operator is notified of the abnormality by a monitor display or the like, and at the same time, the switch SW1 is opened by operating the electromagnetic relay MMC, and the power supply to the heater 1 is cut off at a position closer to the power supply than the switching unit 2 of the SSR (step S5). .
[0042]
Therefore, when a short circuit or welding occurs in the switching unit 2 of the SSR, the supply of power to the heater 1 is immediately shut off, and the heating member which has conventionally occurred due to the short circuit or the welding of the SSR switching unit 2 is generated. Problems such as excessive temperature rise and disconnection of the heater 1 are completely eliminated.
[0043]
In addition, the determination result of step S4 becomes false, and the SSR operates normally by the OFF command to the switching unit 2 of the SSR, and the ON / OFF control for maintaining the temperature of the heating member at the target temperature is performed normally. If it is determined that the switch SW1 has been turned on, the process of step S5 is skipped, and the switch SW1 is kept in the ON state.
[0044]
Next, the processor 5 updates and stores the current temperature t of the heating member read in the processing of step S4 as the temperature t0 of the heating member in the previous cycle (step S6), and ends the abnormality detection processing in the processing cycle.
[0045]
Hereinafter, while the ON / OFF control of the switching unit 2 of the SSR for maintaining the temperature increase target temperature is normally performed, the same processing as described above is repeatedly performed, and a short circuit or welding occurs in the switching unit 2 of the SSR. In this case, the abnormality is detected by the processing in step S4, the switch SW1 is opened, and the power supply to the heater 1 is cut off.
[0046]
As described above, as one embodiment, the processor 5 of the temperature controller 3 detects an abnormality such as short-circuit or welding of the switching unit 2 of the SSR and an abnormality such as disconnection or disconnection of the thermocouple TH to abnormally increase the temperature of the heating member. In the above description, the temperature controller 3 transfers the temperature detection data of the thermocouple TH and various setting values of the memory 6 from the temperature controller 3 to the processor of the CNC device 9 via the I / O board 7. Then, the same processing as described above can be performed by the processor on the CNC device 9 side, and the temperature increase target temperature and the allowable set values a and b are stored in the memory on the CNC device 9 side, and the CNC device 9 side The same processing as described above can be performed only by the processor.
[0047]
Further, it is also possible to perform the double check by causing the processor 5 of the temperature controller 3 and the processor of the CNC device 9 to execute the above processing redundantly.
[0048]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, even if it does not provide a special thermocouple, SSR (Solid State Relay) for heater control and short-circuit and welding of an electromagnetic contactor are detected using the thermocouple used for temperature control of a heating member as it is. In addition, the temperature of the heating member can be prevented from rising excessively. Therefore, there is no need to perform complicated processing on the heating member of the injection molding machine, and an inexpensive and highly reliable overheating prevention device can be provided.
[0049]
In addition, when normal temperature detection is not possible due to disconnection or disconnection of the thermocouple, power supply to the heater is automatically stopped, and the heating member may be dropped due to the thermocouple itself or being damaged. Excessive temperature rise can also be prevented.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a main part of an excessive temperature rise prevention device in an injection molding machine according to an embodiment of the present invention.
FIG. 2 is a flowchart showing an outline of a process for implementing an excessive temperature rise prevention method in the embodiment.
FIG. 3 is a diagram schematically illustrating a normal temperature rise of a heating member and a temperature rise when an abnormality occurs.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heater 2 Switching part of SSR (Solid State Relay) 3 Temperature controller 4 Temperature amplifier 5 Processor 6 Memory 7 I / O board 8 Output buffer 9 CNC device 10 Input buffer MCC Electromagnetic relay SW1 Switch TH Thermocouple QF1 Breaker or fuse FUSE Breaker or fuse

Claims

The heating member of the injection molding machine is provided with a heater and a temperature sensor, and the temperature of the heating member is controlled based on the temperature detected by the temperature sensor. A temperature rise prevention device which outputs an alarm when a detected temperature rise rate exceeds an allowable set value when an ON command is not issued over the entire ON / OFF cycle. Temperature rise prevention device.

The heating member of the injection molding machine is provided with a heater and a temperature sensor, and the temperature of the heating member is controlled based on the temperature detected by the temperature sensor. A temperature rise prevention device, which outputs an alarm when a temperature rise rate detected when an ON command is issued over an entire ON / OFF cycle falls below a first allowable set value, and outputs an alarm over the entire ON / OFF cycle. An excessive temperature rise prevention device for an injection molding machine, which outputs an alarm when a temperature rise rate detected when the command is not an ON command exceeds a second allowable set value.

A heater and a temperature sensor are provided on a heating member of the injection molding machine, and the temperature of the heating member is feedback-controlled by controlling ON / OFF of the heater based on a temperature detected by the temperature sensor. A temperature rise prevention device,
Storage means for setting and storing the first and second allowable setting values;
Detecting means for detecting whether the temperature is detected by the temperature sensor at every predetermined abnormality detection cycle and whether or not the ON command is issued over the entire ON / OFF cycle;
The detection means detects that the ON command is issued over the entire ON / OFF cycle, and the difference between the temperature detected in the current cycle of the abnormality detection cycle and the temperature detected in the previous cycle is the first allowable setting. When the value is lower than the value, and when the detection means detects that the ON command is not the ON command for the entire ON / OFF cycle, the difference between the temperature detected in the current cycle of the abnormality detection cycle and the temperature detected in the previous cycle is the same as the above. And an alarm output means for outputting an alarm when the value exceeds a second allowable set value.