JP5001492B2

JP5001492B2 - Coating film thickness prediction apparatus and coating film thickness prediction method in electrodeposition coating

Info

Publication number: JP5001492B2
Application number: JP2001195063A
Authority: JP
Inventors: 顕彰吉田; 雅夫石鍋; 秀範古川
Original assignee: Kansai Paint Co Ltd; Toyota Motor Corp
Current assignee: Kansai Paint Co Ltd; Toyota Motor Corp
Priority date: 2001-06-27
Filing date: 2001-06-27
Publication date: 2012-08-15
Anticipated expiration: 2021-06-27
Also published as: JP2003013288A

Description

【０００１】
【発明の属する技術分野】
本発明は、特に被塗物への電着塗装の前に実測可能な印加電圧により予め塗膜量を予測する電着塗装における塗膜厚み予測装置及び塗膜厚み予測方法に関する。
【０００２】
【従来の技術】
従来より、例えば自動車等の被塗物に塗装を行う方法として、静電塗装方法、スプレー塗装方法、エアーレス塗装方法、浸漬塗装方法、電着塗装方法が用いられてきた。
【０００３】
特に、電着塗装方法は、複雑な形状のものに対しても均一に塗装でき、塗料の使用効率が高く、電着塗装時の溶媒が水であるために火災に対して安全であり、また公害対策も有利であるという点で、上記他の塗装方法に比べ優れた特徴を有する。
【０００４】
一般に、電着塗装方法には、アニオン型とカチオン型がある。そして、その析出機構は現象的には同一であり、水性電着塗料中に浸漬された金属被塗物を陽極又は陰極として対極との間に直流電流を流し、電気泳動現象と水の電界を利用して、電着成分を被塗物表面に塗膜として析出させる方法である。通常、アニオン型電着塗装方法では被塗物を陽極とし、一方カチオン型電着塗装方法では被塗物を陰極として通電させて、被塗物に塗膜を析出させる。
【０００５】
上記アニオン型及びカチオン型のいずれの電着塗装方法においても、電着塗装中に供給される電着槽内のクーロン量と、被塗物に析出する塗膜量（すなわち、電着成分析出量、塗膜厚み）とは相関性があることが見出されている。また、上記クーロン量と、電着塗装時に被塗物に流れる電流の電流密度の間にも相関関係があることが見出されている。
【０００６】
そこで、電着塗装時に被塗物に流れる電流を調整することによって、塗膜量を制御することが考えられるが、実際に被塗物に流れている電流量を、塗装中に測定することは不可能であるために、塗膜量を制御することは困難であった。
【０００７】
近年、塗膜量を予測して制御する方法が提案されている。例えば、特開平５−５９５９３号公報の「電着塗装方法」には、自動車などの被塗物の袋構造部を想定したミニチュアボックス（模擬袋構造）を、実際の被塗物と同時に電着塗装を行うことにより、ミニチュアボックスの穴の径を変化させ穴面積／袋構造部の内部面積との比と、電着塗装により形成された袋構造部内面の塗装膜厚との関係を調べ、この関係より、実際の自動車などの被塗物の袋構造部内の塗装膜厚を予測する方法が提案されている。
【０００８】
また、特開平５−９７９３号公報の「電着塗装方法及び装置」には、電着槽内の固形物含有量とクーロン量とを用いて複数のクーロン効率（ｍｇ／Ｃ）を演算により求めるとともに、それらのクーロン効率により得られる塗膜膜厚を予め測定しておき、更に互いに異なるクローン効率を有する２つの電着塗料により形成される２つの塗膜膜厚ｄ１，ｄ２から予め係数ｋ（ｋ＝ｄ１／ｄ２）を複数個求める方法が提案されている。この方法によれば、実際の電着塗装時のクーロン効率と所望の塗膜膜厚を得るために、係数ｋを求めたのち、この係数ｋを用いて、目標電圧Ｖ１＝実際の印加電圧Ｖ×ｋの式より、目標電圧Ｖ１を求めている。
【０００９】
【発明が解決しようとする課題】
しかしながら、上記特開平５−５９５９３号公報の「電着塗装方法」は、主に電着塗料種、塗装条件などの変更を行った場合や自動車のモデルチェンジによる袋構造部の変化によって、塗膜膜厚が変化していないかどうか、塗装された自動車を解体し塗膜厚みを調べる煩雑さを解消するために、同一条件で同時に実際の被塗物と模擬構造物とを電着塗装し、そののち模擬構造物の塗膜膜厚を測定し、この模擬構造物の塗膜膜厚から実際の被塗物の塗膜膜厚を予測する方法である。従って、上記方法では、被塗物に所望の塗膜膜厚を得るための電着塗装条件を得ることはできなかった。
【００１０】
また、上記特開平５−９７９３号公報の「電着塗装方法及び装置」は、電着槽内のクーロン効率を求め、更に上述したように異なる電着塗料に対して複数の係数ｋを求めておく必要があり、作業が煩雑であるとともに、上記目標電圧Ｖ１を求める演算も煩雑であった。更に、どの係数ｋを用いるかにより目標電圧Ｖ１が異なるため、係数ｋの選択が難しく、その結果、緻密な塗膜膜厚の制御が困難となるおそれがあった。
【００１１】
そこで、本発明は上記課題に鑑みてなされたものであり、その目的は、試験用被塗物を用いて予備試験を行い、電着塗装時の印加電圧の経時変化と試験用被塗物の塗膜量との関係を求め、実際の被塗物への電着塗装時の塗膜量を予測する電着塗装における塗膜厚み予測装置及び塗膜厚み予測方法を提供することである。
【００１２】
【課題を解決するための手段】
上記目的を達成するために、本発明の電着塗装における塗膜厚み予測方法は、以下の特徴を有する。
【００１３】
（１）電着塗料が収容された電着槽内に電極を配置し、前記電着槽に試験用被塗物を浸漬し、更に電着塗装時における前記試験用被塗物の電流密度を測定するために単位面積当たりの電流量を測定する電流計と、単位面積当たりのクーロン量を測定するクーロン量測定器とを前記試験用被塗物に装着し、さらに前記試験用被塗物に析出する塗膜の塗膜量を塗膜量測定器により測定し、前記電極と前記試験用被塗物との間に電圧を印加する電着塗装における塗膜厚み予測方法であって、電圧印加時間における印加電圧と、そのときの前記電流密度の経時変化とを計測し、使用する電着塗料固有の［電流密度／印加電圧］に対する［電圧・時間積分値］の関係を求め、電着塗装時における前記試験用被塗物の単位面積当たりのクーロン量と前記電着塗料の塗膜量とを測定し、単位面積当たりのクーロン量と塗膜量との関係を求め、電圧印加時間における前記電流密度を印加電圧で除した値に前記電圧・時間積分値を乗じて得られた値と、電圧印加時間における単位面積当たりのクーロン量の値とが相関性を有することに基づき、［電流密度／印加電圧］に［電圧・時間積分値］を乗じた値と［塗膜量］との関係を求め、印加する印加電圧の電圧印加時間に応じて、使用する電着塗料固有の［電流密度／印加電圧］に対する［電圧・時間積分値］の関係から電流密度を求め、［電流密度／印加電圧］に［電圧・時間積分値］を乗じた値と［塗膜量］との関係から、印加する印加電圧の電圧印加時間に応じた各電着塗料固有の予測塗膜量を求める塗膜厚み予測方法である。
【００１４】
上記試験用被塗物の電着塗装予備試験により、実測可能な印加電圧と予測塗膜量との関係を得ることができる。一方、通常、電着塗装では電圧を管理して行っている。従って、この予備試験により得られた印加電圧の経時変化と予測塗膜量との関係を用い、実際の被塗物への電着塗装時の印加電圧を調整することによって、所望の塗膜量を得ることができる。また、実際に調節可能な印加電圧により塗膜量を管理するため、より緻密な塗膜量の管理を行うことができる。
【００１６】
上述の電流密度を印加電圧で除した値を前記電圧・時間積分値に乗じて得られた値の単位は、単位面積当たりのクーロン量の単位と同じである。従って、この乗じて得られた値と塗膜量との関係を求めることができ、その結果、印加電圧の経時変化と予測塗膜量との関係を得ることができる。従って、上述同様、上記予備試験により求められた印加電圧の経時変化と予測塗膜量との関係を用いて、実際の被塗物への電着塗装時の印加電圧を調整して、所望の塗膜量を得ることができる。
【００１８】
電着塗料種が異なる場合、電着塗装時の塗膜析出量も異なることから、予め実際に被塗物に電着塗装する際に用いる電着塗料毎に、印加電圧の経時変化と予測塗膜量との関係を求めておくことが好ましい。これにより、実際の電着塗装時における被塗物の塗膜量をより正確に予測することができる。
【００１９】
また、本発明の電着塗装における塗膜厚み予測装置は、以下の特徴を有する。
【００２０】
（１）電着塗料が収容された電着槽と、前記電着槽内に配置された電極と、前記電着槽に浸漬された試験用被塗物と、前記電極と前記試験用被塗物との間に電圧を印加する電源と、前記電源の印加電圧を検出する電圧計と、前記試験用被塗物に配置され電着塗装時の電流密度を測定するために単位面積当たりの電流量を測定する電流計と、電圧印加時間を測定するタイマーと、電圧印加時間における印加電圧と電流密度との経時変化の関係を記憶する第１の記憶装置と、電着塗装時の前記試験用被塗物における単位面積当たりのクーロン量を測定するクーロン量測定器と、前記試験用被塗物における前記単位面積当たりの塗膜量を測定する塗膜量測定器と、前記単位面積当たりのクーロン量と塗膜量との関係を記憶する第２の記憶装置と、前記第１の記憶装置に記憶された電圧印加時間における印加電圧と電流密度の経時変化を基に、使用する電着塗料固有の前記電流密度を印加電圧で除した値［電流密度／印加電圧］に対する前記印加電圧と印加時間を乗じた［電圧・時間積分値］の関係を求める第１の演算装置と、印加する印加電圧の電圧印加時間に応じて、前記第１の演算装置で求めた使用する電着塗料固有の［電流密度／印加電圧］に対する［電圧・時間積分値］の関係から電流密度を求め、電圧印加時間における前記［電流密度／印加電圧］に前記［電圧・時間積分値］を乗じて得られた値と、電圧印加時間における前記第２の記憶装置に記憶されている前記単位面積当たりのクーロン量と塗膜量との関係における単位面積当たりのクーロン量の値とが相関性を有することに基づき、［電流密度／印加電圧］に［電圧・時間積分値］を乗じた値と［塗膜量］との関係から、印加する印加電圧の電圧印加時間に応じた各電着塗料固有の予測塗膜量を求める第２の演算装置と、を有する塗膜厚み予測装置である。
【００２１】
上述の構成により、試験用被塗物における印加電圧の経時変化から予測塗膜量が演算できるため、実際の被塗物への電着塗装における印加電圧を調整することにより、所望の塗膜量を得ることができ、更に緻密な塗膜量の管理を行うことができる。
【００２３】
上述したように、電流密度を印加電圧で除した値を前記電圧・時間積分値に乗じて得られた値の単位は、単位面積当たりのクーロン量の単位と同じである。従って、この乗じて得られた値と塗膜量との関係を求めることができ、その結果、印加電圧の経時変化と予測塗膜量との関係を第２の演算装置により求めることができる。従って、上記演算装置により得られた印加電圧の経時変化と予測塗膜量との関係を用いて、実際の被塗物への電着塗装時の印加電圧を調整して、所望の塗膜量を得ることができる。
【００２４】
【発明の実施の形態】
以下、本発明の好適な実施形態を説明する。
【００２５】
図１には、本実施の形態の電着塗装における塗膜厚みの予測装置の構成の一例が示されている。
【００２６】
塗膜厚みの予測装置１０の電着槽１２内には、電着塗料１４が収容され、電着塗料１４に浸漬するように、電極１６と試験用被塗物１８とが配置されている。そして、電極１６と試験用被塗物１８との間に電圧を印加する電源２２が設けられ、更に電源２２から印加される電圧を測定する電圧計２４が、電極１６と試験用被塗物１８と電源２２とからなる回路内に配置されている。また、試験用被塗物１８には、試験用被塗物１８に流れる電流の電流密度を測定する電流計２０が装着されている。
【００２７】
また、電着塗装がアニオン型電着である場合には、試験用被塗物１８は陽極として、一方カチオン型である場合には、試験用被塗物１８は陰極として通電させる。これにより、試験用被塗物１８に塗膜３０が析出形成される。
【００２８】
更に、上述の塗膜厚み予測装置１０において、電流計２０に替えクーロン量測定器を装着して、電着予備試験を行うことによって、単位面積当たりのクーロン量をクーロン量測定器で測定するとともに、そのときの析出する塗膜の塗膜量を塗膜量測定器により測定する。なお、本実施の形態では、電着塗料において塗膜量と塗膜厚みとは相関関係があることから、塗膜量を例に取って以下説明する。
【００２９】
更に詳説すると、図２に示すように、本実施の形態の装置において、電流計２０と電圧計２４と電圧印加時間を測定するタイマー２６とからの出力は、第１の記憶装置３４に送られ、第１の記憶装置３４は、電圧印加時間における印加電圧と電流密度との経時変化とを関連づけて記憶する。また、上述したクーロン量測定器２８と塗膜量測定器３２とからの出力は、第２の記憶装置３６に送信され、第２の記憶装置３６は、単位面積当たりのクローン量と塗膜量とを関連付けて記憶する。更に、第１の記憶装置３４に記憶された電圧印加時間における印加電圧と電流密度との経時変化の情報は、演算装置４０内の第１の演算装置４２に出力され、第１の演算装置４２は、上記情報に基づき、電流密度を印加電圧で除した値（以下「塗膜電気抵抗値の逆数」という）と、印加電圧に印加時間を乗じた電圧・時間積分値とを求め、両者の関係を求める。また、第２の演算装置４４は、第１の演算装置４２から出力される塗膜電気抵抗値の逆数と電圧・時間積分値とを乗じた値が、第２の記憶装置３６に記憶されている単位面クーロン量と相関性を有することから、その相関性に基づき、印加電圧の経時変化と塗膜量との関係を求める。
【００３０】
これにより、実測可能な印加電圧に基づいて、被塗物に対する塗膜量を予測することができる。
【００３１】
更に、電着塗料により電着塗装時の塗膜析出度合いが異なるため、電着塗装を行う電着塗料毎に、上記装置により印加電圧の経時変化と予想塗膜量との関係を求めておくのが好ましい。また、被塗物の材質によって電着塗装時の塗膜析出度合いが異なるため、実際に電着塗装を行う被塗物と同一の材質の試験用被塗物を用いて予備電着塗装試験を行うことが好ましい。
【００３２】
次に、本実施の形態の電着塗装における塗膜厚みの予想方法について、図１〜図５を用いて説明する。なお、図３〜図５において、矢印方向に向かってグラフの軸の値は大きくなっている。
【００３３】
まず、図１の装置１０を用いて、図３に示すように、電圧計２４で計測しながら、一定電圧における電流密度の経時変化を測定するために電流計２０により単位面積当たりの電流量を測定し、更に上記タイマー２６を用いて印加時間を計測して、複数電圧における電流密度の経時変化を測定しておく。ここで、図３において、例えばＡ電圧は２５０Ｖ、Ｂ電圧は１００Ｖ、Ｃ電圧は５０Ｖの順で電圧が低くなっている。また、電着塗装では、塗料粒子の析出と同時に水素ガス（カチオン型電着の場合）又は酸素ガス（アニオン型電着の場合）が発生するため、電圧印加初期では、塗膜内にこれらのガスの流通路が点在しており、電流が流れやすい。従って、図３のように、電圧が高いほど初期の電流密度は高い。一方、電着塗料の析出が促進されるにしたがって、塗膜厚みが増大するとともに、ガスの流通路内への析出も促進されるため、ガスの流通路の径が小さくなる。その結果、ガスの放出が困難になり、電極反応が阻害され塗膜電気抵抗が増大することによって、ジュール熱により析出塗膜中の電着塗料が融合し流通路を塞ぐため、連続膜を形成するができる。このように、電圧印加時間が経過するにしたがって、電極反応が阻害されるため、図３に示すように、電流密度が低くなっていく。
【００３４】
次に、図３に示す複数の電圧における電流密度の経時変化に基づき、図４に示すように、［電流密度／印加電圧］（すなわち、塗膜電気抵抗値の逆数）に対する［電圧・時間積分値］との関係を求める。この関係は、電着塗料固有のマスターカーブとして表される。通常、電着塗装の予備試験では、例えば被塗物１４０ｃｍ²の一枚板を試験用被塗物として用いるため、本実施の形態では、電流密度の単位を［Ａ／ｍｍ²］と表すこととする。また、電圧の単位は［Ｖ］、印加時間は、秒［ｓ］で表すこととする。
【００３５】
従って、図４に示す［電流密度／印加電圧］の単位は「Ａ／ｍｍ²・Ｖ」となり、［電圧・時間積分値］の単位は「Ｖ・ｓ」となる。この［電流密度／印加電圧］の値に［電圧・時間積分値］を乗ずると、その単位は「Ａ・ｓ／ｍｍ²」となる。一方、「Ａ・ｓ」が「Ｃ」（クーロン）であることから、上記「Ａ・ｓ／ｍｍ²」の単位は、後述する［単位面積当たりのクーロン量］の単位「Ｃ／ｍｍ²」に相当する。
【００３６】
更に、図１の装置１０の電流計２０に替えてクーロン量測定器２８を用いて、更に塗膜量を塗膜量測定器３２により計測して、図５に示すような［単位面積当たりのクーロン量］と［塗膜量］との関係を求めておく。
【００３７】
そして、上述した［電流密度／印加電圧］に［電圧・時間積分値］を乗じた値と、［単位面積当たりのクーロン量］との相関に基づき、図４，５より、［電流密度／印加電圧］に［電圧・時間積分値］を乗じた値と［塗膜量］（単位：ｍｇ）との関係が求められ、この関係に基づき、所望の塗膜量に対して、図４に示すマスターカーブ上のいくつかの点が選択される。この選択されたいくつかの点に対して印加する電圧値を決めることによって、図３のグラフに基づき、電圧印加時間を求めることができる。これらより、電着塗装における印加電圧の経時変化と塗膜量との関係を求めることができる。
【００３８】
このように、本実施の形態の塗膜厚みの予測方法によれば、実測可能な印加電圧に基づいて、塗膜量を予測し、実際の被塗物への塗膜量を緻密に制御することができる。
【００３９】
【発明の効果】
以上の通り、本発明の塗膜厚み予測装置及び予測方法によれば、実測可能な印加電圧を用いて、試験用被塗物により予め電着塗装時の印加電圧の経時変化と塗膜量との関係を求めているので、実際の被塗物に対する電着塗装時の印加させる電圧における塗膜量を予測することができる。これにより、より精度の高い塗膜量、すなわち塗膜厚みの制御を行うことができる。
【図面の簡単な説明】
【図１】本発明の電着塗装における塗膜厚み予測装置の構造の概略を示す模式図である。
【図２】本発明における塗膜厚み予測装置の処理回路の概略構成図である。
【図３】電着塗装において印加電圧一定条件下での電圧印加時間と電流密度との関係を示す図である。
【図４】電圧・時間積分値と電流密度／印加電圧との関係を示す図である。
【図５】電着塗装時の単位面積当たりのクーロン量と塗膜量との関係を示す図である。
【符号の説明】
１０塗膜厚みの予測装置、１２電着槽、１４電着塗料、１６電極、１８試験用被塗物、２０電流密度計、２２電源、２４電圧計、２６タイマー、２８クーロン量測定器、３０塗膜、３２塗膜量測定器、３４第１の記憶装置、３６第２の記憶装置、４０演算装置、４２第１の演算装置、４４第２の演算装置。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coating film thickness prediction apparatus and a coating film thickness prediction method in electrodeposition coating, in which the coating amount is predicted in advance based on an applied voltage that can be actually measured before electrodeposition coating on an object to be coated.
[0002]
[Prior art]
Conventionally, for example, electrostatic coating methods, spray coating methods, airless coating methods, immersion coating methods, and electrodeposition coating methods have been used as methods for coating an object such as an automobile.
[0003]
In particular, the electrodeposition coating method can apply even to complex shapes evenly, the paint usage efficiency is high, and since the solvent during electrodeposition coating is water, it is safe from fire. Compared to the above other coating methods, it has superior characteristics in that pollution control is also advantageous.
[0004]
Generally, electrodeposition coating methods include an anionic type and a cationic type. The precipitation mechanism is the same in terms of phenomenon. A direct current is passed between the metal coating immersed in the water-based electrodeposition paint as the anode or cathode and the counter electrode, and the electrophoretic phenomenon and the electric field of water are reduced. This is a method in which an electrodeposition component is deposited as a coating film on the surface of an object to be coated. Usually, in the anionic electrodeposition coating method, the coating object is used as an anode, while in the cationic electrodeposition coating method, the coating object is applied as a cathode to deposit a coating film on the coating object.
[0005]
In both the anionic and cationic electrodeposition coating methods, the amount of coulomb in the electrodeposition tank supplied during electrodeposition coating and the amount of coating deposited on the object to be coated (that is, electrodeposition component deposition) Amount, coating thickness) has been found to be correlated. It has also been found that there is a correlation between the amount of coulomb and the current density of the current flowing through the workpiece during electrodeposition coating.
[0006]
Therefore, it is conceivable to control the amount of coating film by adjusting the current flowing through the object during electrodeposition coating, but it is possible to measure the amount of current actually flowing through the object during coating. Since it was impossible, it was difficult to control the coating amount.
[0007]
In recent years, methods for predicting and controlling the coating amount have been proposed. For example, in “Electrodeposition Coating Method” of Japanese Patent Application Laid-Open No. 5-59593, a miniature box (simulated bag structure) that assumes a bag structure portion of an object to be coated such as an automobile is electrodeposited simultaneously with the actual object to be coated. By coating, the diameter of the hole in the miniature box was changed to investigate the relationship between the ratio of the hole area / inner area of the bag structure and the coating film thickness on the inner surface of the bag structure formed by electrodeposition coating, From this relationship, a method for predicting the coating film thickness in the bag structure portion of an actual article such as an automobile has been proposed.
[0008]
Further, in “Electrodeposition coating method and apparatus” of JP-A-5-9793, a plurality of coulomb efficiencies (mg / C) are obtained by calculation using the solid content and coulomb amount in the electrodeposition tank. In addition, the coating film thickness obtained by the Coulomb efficiency is measured in advance, and the coefficient k (2) is previously calculated from the two coating film thicknesses d1 and d2 formed by the two electrodeposition coating materials having different clone efficiencies. A method for obtaining a plurality of k = d1 / d2) has been proposed. According to this method, in order to obtain the coulomb efficiency and the desired coating film thickness during actual electrodeposition coating, the coefficient k is obtained, and then the target voltage V1 = the actual applied voltage V is obtained using this coefficient k. The target voltage V1 is obtained from the formula xk.
[0009]
[Problems to be solved by the invention]
However, the “electrodeposition coating method” of the above-mentioned Japanese Patent Application Laid-Open No. 5-59593 is based on the change in the structure of the bag due to changes in the electrodeposition paint type, coating conditions, etc. In order to eliminate the trouble of disassembling the painted car and checking the coating thickness to see if the film thickness has changed, the actual coating object and the simulated structure are electrodeposited simultaneously under the same conditions, Thereafter, the coating film thickness of the simulated structure is measured, and the actual coating film thickness of the object to be coated is predicted from the coating film thickness of the simulated structure. Therefore, in the above method, electrodeposition coating conditions for obtaining a desired coating film thickness on an object to be coated could not be obtained.
[0010]
In addition, “Electrodeposition coating method and apparatus” of JP-A-5-9793 calculates the coulomb efficiency in an electrodeposition tank, and further calculates a plurality of coefficients k for different electrodeposition paints as described above. The operation is complicated, and the calculation for obtaining the target voltage V1 is also complicated. Furthermore, since the target voltage V1 differs depending on which coefficient k is used, it is difficult to select the coefficient k, and as a result, there is a possibility that it is difficult to control the precise coating film thickness.
[0011]
Therefore, the present invention has been made in view of the above problems, and the purpose of the present invention is to perform a preliminary test using a test coating, and to determine the change in applied voltage with time during electrodeposition coating and the test coating. An object of the present invention is to provide a coating thickness prediction apparatus and coating thickness prediction method in electrodeposition coating for obtaining the relationship with the coating amount and predicting the coating amount at the time of electrodeposition coating on an actual object to be coated.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the coating thickness prediction method in electrodeposition coating of the present invention has the following characteristics.
[0013]
(1) An electrode is placed in an electrodeposition tank in which an electrodeposition paint is accommodated, the test object is immersed in the electrodeposition tank, and the current density of the test object at the time of electrodeposition coating is further determined. In order to measure, an ammeter that measures the amount of current per unit area and a coulomb amount measuring device that measures the amount of coulomb per unit area are attached to the test object, and further to the test object the coating amount of the precipitated coating film was measured by coating weight meter, a thickness of the coating film prediction method in the applied electrodeposition coating a voltage between the electrode and the object to be coated for the test, the voltage applied and the applied voltage at time, measure the temporal change of the current density at this time, we obtain the relationship of the voltage-time integral] electrodeposition coating specific for the [current density / voltage applied] to use electrodeposition The amount of coulomb per unit area of the test object during coating and the electric power Measure the coating film amount of the paint, determine the relationship between the amount of coulomb per unit area and the coating amount, and multiply the value obtained by dividing the current density at the voltage application time by the applied voltage by the voltage / time integral value. and the resulting value, based on that the value of the Coulomb per unit area of the voltage application time to have a correlation, the value obtained by multiplying the voltage-time integral value] to [current density / voltage applied] [ The amount of current density is determined from the relationship of [Voltage / time integral value] to [Current density / Applied voltage] specific to the electrodeposition paint used, depending on the voltage application time of the applied voltage to be applied. From the relationship between [Current density / Applied voltage] multiplied by [Voltage / time integral value] and [Coating amount], the prediction specific to each electrodeposition paint according to the voltage application time of the applied voltage to be applied This is a method for predicting the thickness of a coating film to determine the amount of coating film.
[0014]
By the electrodeposition coating preliminary test of the test object, the relationship between the actually measured applied voltage and the predicted coating amount can be obtained. On the other hand, voltage is usually controlled in electrodeposition coating. Therefore, by using the relationship between the change over time of the applied voltage obtained by this preliminary test and the predicted coating amount, and adjusting the applied voltage at the time of electrodeposition coating on the actual object to be coated, the desired coating amount Can be obtained. In addition, since the coating amount is managed by the actually adjustable applied voltage, a more precise coating amount can be managed.
[0016]
The unit of the value obtained by multiplying the voltage / time integrated value by the value obtained by dividing the current density by the applied voltage is the same as the unit of coulomb amount per unit area. Therefore, the relationship between the value obtained by the multiplication and the coating amount can be obtained, and as a result, the relationship between the change in applied voltage with time and the predicted coating amount can be obtained. Therefore, as described above, the applied voltage at the time of electrodeposition coating on the actual object to be coated is adjusted by using the relationship between the change with time of the applied voltage obtained by the preliminary test and the predicted coating amount, and the desired voltage is applied. The coating amount can be obtained.
[0018]
When the type of electrodeposition paint is different, the amount of coating deposited at the time of electrodeposition coating is also different, so the change in applied voltage over time and the predicted coating are different for each electrodeposition paint used in actual electrodeposition coating on the object. It is preferable to obtain a relationship with the film amount. Thereby, the coating-film amount of the to-be-coated object at the time of actual electrodeposition coating can be estimated more correctly.
[0019]
Moreover, the coating-film thickness prediction apparatus in the electrodeposition coating of this invention has the following characteristics.
[0020]
(1) An electrodeposition tank in which an electrodeposition paint is accommodated, an electrode disposed in the electrodeposition tank, a test coating immersed in the electrodeposition tank, the electrode and the test coating A power source for applying a voltage between the power source, a voltmeter for detecting the applied voltage of the power source, and a current per unit area for measuring the current density at the time of electrodeposition coating placed on the test object. An ammeter for measuring the amount, a timer for measuring the voltage application time, a first storage device for storing the relationship of changes over time in the applied voltage and current density in the voltage application time, and for the test at the time of electrodeposition coating A coulomb measuring device for measuring the amount of coulomb per unit area in the object to be coated, a coating amount measuring device for measuring the amount of film per unit area in the test object, and the coulomb per unit area A second storage device for storing the relationship between the amount and the coating amount; Based on the temporal change of the applied voltage and the current density at a voltage application time stored in the first storage device, divided by the electrodeposition coating specific of the current density the applied voltage to use [current density / voltage applied] A first computing device that obtains a relationship of [voltage / time integral value] obtained by multiplying the applied voltage and the application time with respect to the voltage, and a use obtained by the first computing device according to the voltage application time of the applied voltage to be applied The current density is obtained from the relationship of [voltage / time integrated value] with respect to [current density / applied voltage] specific to the electrodeposition paint to be applied, and the [voltage / time integrated value] is added to [current density / applied voltage] in the voltage application time. a value obtained by multiplying the Coulomb quantity value and the correlation of per unit area in relation to the amount of coulombs and coating amount per unit area which is stored in the second storage device in the voltage application time Yes child sex From the relationship between [Current density / Applied voltage] multiplied by [Voltage / time integral value] and [Coating amount], it is specific to each electrodeposition paint depending on the voltage application time of the applied voltage to be applied. And a second arithmetic unit that calculates a predicted coating amount.
[0021]
With the above-described configuration, the predicted coating amount can be calculated from the change over time of the applied voltage on the test coating, so the desired coating amount can be adjusted by adjusting the applied voltage in the electrodeposition coating on the actual coating. Can be obtained, and more precise control of the coating amount can be performed.
[0023]
As described above, the unit of the value obtained by multiplying the voltage / time integrated value by the value obtained by dividing the current density by the applied voltage is the same as the unit of the coulomb amount per unit area. Therefore, the relationship between the value obtained by multiplication and the coating amount can be obtained, and as a result, the relationship between the change in applied voltage with time and the predicted coating amount can be obtained by the second arithmetic unit. Therefore, using the relationship between the change in the applied voltage with time obtained by the above arithmetic unit and the predicted coating amount, the applied voltage at the time of electrodeposition coating on the actual object to be coated is adjusted to obtain the desired coating amount. Can be obtained.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described.
[0025]
FIG. 1 shows an example of the configuration of a coating thickness predicting device in the electrodeposition coating of the present embodiment.
[0026]
An electrodeposition paint 14 is accommodated in the electrodeposition tank 12 of the coating thickness prediction apparatus 10, and an electrode 16 and a test object 18 are arranged so as to be immersed in the electrodeposition paint 14. A power source 22 for applying a voltage is provided between the electrode 16 and the test object 18, and a voltmeter 24 for measuring a voltage applied from the power source 22 is further connected to the electrode 16 and the test object 18. And a power source 22. In addition, the test object to be coated 18, conductive Nagarekei 20 for measuring the current density of the current flowing through the test object to be coated 18 is mounted.
[0027]
When the electrodeposition coating is anionic electrodeposition, the test object 18 is energized as an anode, and when it is cationic, the test object 18 is energized as a cathode. As a result, the coating film 30 is deposited on the test object 18.
[0028]
Further, the coating film thickness predicting apparatus 10 described above, wearing the Coulomb measuring instrument instead of electrostatic Nagarekei 20, by performing the electrodeposition preliminary test to measure the amount of coulombs per unit area in the Coulomb measuring instrument At the same time, the coating amount of the coating film deposited at that time is measured by a coating amount meter. In the present embodiment, since there is a correlation between the coating amount and the coating thickness in the electrodeposition coating, the following description will be given by taking the coating amount as an example.
[0029]
More detail, as shown in FIG. 2, the output from the apparatus of the present embodiment, electrostatic Nagarekei 20 and voltmeter 24 and a timer 26 for measuring the voltage application time is sent to the first storage device 34 The first storage device 34 stores the applied voltage and the current density with time in the voltage application time in association with each other. The outputs from the above-described coulomb amount measuring device 28 and coating film amount measuring device 32 are transmitted to the second storage device 36, and the second storage device 36 stores the clone amount and the coating amount per unit area. Are stored in association with each other. Further, the information on the change over time of the applied voltage and the current density in the voltage application time stored in the first storage device 34 is output to the first arithmetic device 42 in the arithmetic device 40, and the first arithmetic device 42. Based on the above information, the value obtained by dividing the current density by the applied voltage (hereinafter referred to as “reciprocal of the coating electrical resistance value”) and the voltage / time integral value obtained by multiplying the applied voltage by the application time are obtained. Seeking a relationship. The second arithmetic unit 44 stores a value obtained by multiplying the reciprocal of the coating film electrical resistance value output from the first arithmetic unit 42 by the voltage / time integral value in the second storage unit 36. Since there is a correlation with the unit surface coulomb amount, the relationship between the change in applied voltage with time and the coating amount is obtained based on the correlation.
[0030]
Thereby, the coating-film amount with respect to a to-be-coated object can be estimated based on the applied voltage which can be measured.
[0031]
Furthermore, since the degree of coating deposition during electrodeposition varies depending on the electrodeposition paint, the relationship between the change in applied voltage with time and the expected amount of film is obtained for each electrodeposition paint subjected to electrodeposition coating by the above apparatus. Is preferred. In addition, since the degree of coating deposition during electrodeposition varies depending on the material of the object to be coated, a preliminary electrodeposition coating test is performed using the same test material as the object to be electrodeposited. Preferably it is done.
[0032]
Next, the prediction method of the coating film thickness in the electrodeposition coating of this Embodiment is demonstrated using FIGS. 3 to 5, the value of the axis of the graph increases in the direction of the arrow.
[0033]
First, using the apparatus 10 of FIG. 1, as shown in FIG. 3, while measuring by the voltmeter 24, a current amount per unit area by electrodeposition Nagarekei 20 to measure the time course of the current density at a constant voltage It was measured, further measuring the application time using the timer 26 in advance by measuring the time course of the current density at a plurality voltage. Here, in FIG. 3, for example, the A voltage is 250 V, the B voltage is 100 V, and the C voltage is 50 V in this order. In addition, in electrodeposition coating, hydrogen gas (in the case of cationic electrodeposition) or oxygen gas (in the case of anion type electrodeposition) is generated at the same time as the coating particles are deposited. Gas flow passages are scattered and current flows easily. Therefore, as shown in FIG. 3, the higher the voltage, the higher the initial current density. On the other hand, as the deposition of the electrodeposition paint is promoted, the thickness of the coating film increases and the deposition of the gas into the flow path is also promoted, so that the diameter of the gas flow path is reduced. As a result, it becomes difficult to release gas, and the electrode reaction is hindered and the electrical resistance of the paint film increases, so that the electrodeposition paint in the deposited paint film is fused by Joule heat to close the flow path, thus forming a continuous film. I can do it. Thus, since the electrode reaction is inhibited as the voltage application time elapses, the current density decreases as shown in FIG.
[0034]
Next, based on the change with time of the current density at a plurality of voltages shown in FIG. 3, as shown in FIG. 4, the [Voltage and time integration] with respect to [Current density / Applied voltage] (that is, the reciprocal of the coating film electrical resistance value) Value]. This relationship is expressed as a master curve unique to the electrodeposition paint. Usually, in the preliminary test of electrodeposition coating, for example, a single plate of 140 cm ² to be coated is used as the test coating, and therefore, in this embodiment, the unit of current density is expressed as [A / mm ² ]. And The unit of voltage is [V], and the application time is expressed in seconds [s].
[0035]
Therefore, the unit of [current density / applied voltage] shown in FIG. 4 is “A / mm ² · V”, and the unit of [voltage / time integral value] is “V · s”. When the value of [current density / applied voltage] is multiplied by [voltage / time integral value], the unit is “A · s / mm ² ”. On the other hand, since “A · s” is “C” (Coulomb), the unit of “A · s / mm ² ” is the unit “C / mm ² ” of [Coulomb amount per unit area] described later. It corresponds to.
[0036]
Furthermore, by using the Coulomb measuring device 28 in place of the electrostatic Nagarekei 20 of the apparatus 10 of FIG. 1, further by measuring the coating amount by coating weight measuring device 32, [per unit area as shown in FIG. 5 The relationship between [coulomb amount] and [coating amount] is obtained in advance.
[0037]
Based on the correlation between the value obtained by multiplying the above-mentioned [current density / applied voltage] by [voltage / time integral value] and [coulomb amount per unit area], from FIG. The relationship between the value obtained by multiplying [Voltage] by [Voltage / time integral value] and [Coating amount] (unit: mg) is obtained. Based on this relationship, the desired coating amount is shown in FIG. Several points on the master curve are selected. By determining the voltage value to be applied to the selected points, the voltage application time can be obtained based on the graph of FIG. From these, the relationship between the change over time of the applied voltage and the coating amount in electrodeposition coating can be determined.
[0038]
Thus, according to the coating film thickness prediction method of the present embodiment, the coating amount is predicted based on the actually measured applied voltage, and the actual coating amount on the object is precisely controlled. be able to.
[0039]
【Effect of the invention】
As described above, according to the coating film thickness prediction apparatus and the prediction method of the present invention, using the actually measured applied voltage, the change over time in the applied voltage and the coating amount in the electrodeposition coating in advance by the test object. Therefore, it is possible to predict the amount of coating film at a voltage to be applied at the time of electrodeposition coating on an actual object to be coated. Thereby, the coating amount with higher accuracy, that is, the coating thickness can be controlled.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an outline of the structure of a coating film thickness prediction apparatus in electrodeposition coating according to the present invention.
FIG. 2 is a schematic configuration diagram of a processing circuit of a coating film thickness prediction apparatus according to the present invention.
FIG. 3 is a diagram showing the relationship between voltage application time and current density under constant applied voltage conditions in electrodeposition coating.
FIG. 4 is a diagram showing a relationship between a voltage / time integral value and a current density / applied voltage.
FIG. 5 is a diagram showing the relationship between the amount of coulomb per unit area and the amount of coating film during electrodeposition coating.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Coating thickness prediction apparatus, 12 Electrodeposition tank, 14 Electrodeposition paint, 16 Electrodes, 18 Test object, 20 Current density meter, 22 Power source, 24 Voltmeter, 26 Timer, 28 Coulomb meter, 30 Coating film, 32 Coating film amount measuring device, 34 First storage device, 36 Second storage device, 40 Arithmetic device, 42 First arithmetic device, 44 Second arithmetic device.

Claims

In order to measure the current density of the test object during electrodeposition coating by placing an electrode in the electrodeposition tank containing the electrodeposition paint, immersing the test object in the electrodeposition tank An ammeter for measuring the amount of current per unit area and a coulomb amount measuring device for measuring the amount of coulomb per unit area are attached to the test object, and further deposited on the test object. A method for predicting a coating film thickness in an electrodeposition coating by measuring a coating amount of a film with a coating amount measuring device and applying a voltage between the electrode and the test object,
And applied voltage in the voltage application time, to measure the time course of the current density at this time, we obtain the relationship of the voltage-time integral value] for electrodeposition coating specific [current density / voltage applied] to use,
Measure the amount of coulomb per unit area of the test object at the time of electrodeposition coating and the amount of coating film of the electrodeposition paint, and determine the relationship between the amount of coulomb per unit area and the amount of coating,
That a value obtained by multiplying the voltage-time integral value to the value obtained by dividing the current density at an applied voltage in the voltage application time, and the value of the Coulomb per unit area of the voltage application time to have a correlation Based on the above, the relationship between the value obtained by multiplying the [current density / applied voltage] by the [voltage / time integral value] and the [coating amount]
According to the voltage application time of the applied voltage to be applied, the current density is obtained from the relationship of [voltage / time integral value] with respect to [current density / applied voltage] specific to the electrodeposition paint to be used. From the relationship between the value obtained by multiplying the [voltage / time integral value] and the [coating amount], a predicted coating amount specific to each electrodeposition coating material corresponding to the voltage application time of the applied voltage is obtained. Coating thickness prediction method.

An electrodeposition tank containing an electrodeposition paint; and
An electrode disposed in the electrodeposition bath;
A test article immersed in the electrodeposition bath; and
A power supply for applying a voltage between the electrode and the test object;
A voltmeter for detecting an applied voltage of the power source;
An ammeter that measures the amount of current per unit area in order to measure the current density during electrodeposition coating placed on the test object;
A timer for measuring the voltage application time;
A first storage device for storing a relationship of change over time in applied voltage and current density during voltage application time;
A coulomb amount measuring device for measuring the coulomb amount per unit area in the test object during electrodeposition coating;
A coating amount measuring device for measuring the coating amount per unit area in the test object;
A second storage device for storing the relationship between the coulomb amount per unit area and the coating amount;
It said first value based on the time course of the applied voltage and the current density in the stored voltage application time, obtained by dividing the electrodeposition coating specific of the current density used in the applied voltage to the memory device [current density / voltage applied A first arithmetic unit for obtaining a relation of [voltage / time integral value] obtained by multiplying the applied voltage and the application time with respect to
In accordance with the voltage application time of the applied voltage to be applied, the current density is obtained from the relationship of [voltage / time integral value] with respect to [current density / applied voltage] specific to the electrodeposition paint to be used obtained by the first arithmetic unit. A value obtained by multiplying the [current density / applied voltage] in the voltage application time by the [voltage / time integrated value], and the unit area stored in the second storage device in the voltage application time. based on the value of the Coulomb per unit area in relation to the amount of coulombs and coating amount of to have a correlation, the value obtained by multiplying the voltage-time integral value] to [current density / voltage applied] From the relationship with [amount of coating film], a second arithmetic unit for obtaining a predicted coating amount specific to each electrodeposition paint according to the voltage application time of the applied voltage to be applied;
A coating thickness predicting device characterized by comprising: