JP4036626B2

JP4036626B2 - Ultrasonic cleaning method and ultrasonic cleaning apparatus

Info

Publication number: JP4036626B2
Application number: JP2001295312A
Authority: JP
Inventors: 茂上野
Original assignee: Sharp Corp
Current assignee: Sharp Corp
Priority date: 2001-09-27
Filing date: 2001-09-27
Publication date: 2008-01-23
Anticipated expiration: 2021-09-27
Also published as: JP2003093983A

Description

【０００１】
【発明の属する技術分野】
本発明は、浸漬超音波洗浄に関し、特に、真空下で行う浸漬超音波洗浄に関する。
【０００２】
【従来の技術】
洗浄対象物を溶剤に浸漬した状態で溶剤に超音波を加えることにより対象物を洗浄する浸漬超音波洗浄は、金属、プラスチック加工部品等の洗浄に広く採用されてきた。環境保護のためにフロンが全廃されて以来、代替溶剤を用いる洗浄方法が種々提案されているが、中でもハロゲンを全く含まず乾燥も容易な炭化水素系の溶剤を用いた洗浄方法が注目されている。炭化水素系の溶剤を用いる場合も浸漬超音波洗浄は有用であり、大気圧下で行うことのほか、真空下で行うことも提案されている。
【０００３】
大気圧下で浸漬超音波洗浄を行う場合、洗浄対象物であるワークが表面に袋穴や溝等の微細構造を有すると、溶媒が入り込まなくなって、部分的に十分な洗浄ができないことがある。また、ワークの表面が平滑であっても、ワーク同士が接触していると、そこに溶媒が入り込まなくなって、やはり洗浄が不十分になることがある。
【０００４】
浸漬超音波洗浄はキャビテーション作用を利用したものであるが、液体にキャビテーションを発生させるためには、液体中の音圧を一定の閾値以上にする必要があることが知られている（最新洗浄技術総覧、第３章、第３節、１９３−１９６頁）。ここで、空気が飽和した液体に比べて脱気した液体の方が閾値が高く、したがって、真空度を増すほど脱気の度合いが高まって、閾値も高くなる。
【０００５】
また、溶剤の閾値が高いほど、キャビテーションが発生したときにはその作用が強くなって、洗浄力も高くなる。これが、真空下で浸漬超音波洗浄を行う主な理由である。
【０００６】
従来の浸漬超音波洗浄方法における洗浄処理の工程と洗浄槽内の圧力の関係を図５に示す。まず、洗浄槽に溶剤を入れ、これにワークを浸す。このときの洗浄槽内の圧力は大気圧すなわち約十万Ｐａ（７６０torr）である。次いで、洗浄槽から空気を排出して、洗浄槽内を所定の真空度、例えば数千Ｐａ（数十torr）とする。そして、この真空度を保った状態で溶剤に超音波を加えてワークを洗浄する。所定時間の洗浄後、超音波を止め、洗浄槽内を大気圧に戻して、ワークを洗浄槽から取り出す。これで洗浄が終了する。
【０００７】
このように、真空下で浸漬超音波洗浄を行うと、常圧下で行うときよりも洗浄力が高まり、ワーク表面の微細構造の汚れやワーク同士が接触している部分の汚れを、より良好に除去することができる。また、洗浄時間も短縮される。
【０００８】
【発明が解決しようとする課題】
しかし、真空にすることにより、溶剤の閾値が高くなりすぎて、装置に備えた超音波発生器の発する超音波の強度を超えることもある。その場合、キャビテーションは発生せず、真空による溶媒の浸透と振動だけによる洗浄となってしまい、真空下で超音波洗浄を行うことによる本来の洗浄力は得られない。また、発振強度の低い超音波発生器を備えた洗浄装置の場合は、溶剤の脱気の度合いが低い状態つまり真空度の低い状態でしかキャビテーションを発生させることができなくなり、発生したキャビテーションの作用が弱く、高い洗浄力は得られない。
【０００９】
真空下での超音波洗浄では、キャビテーション発生のための閾値が溶剤に実際に加える超音波の音圧よりも僅かに低くなるように、真空度を設定するのが理想的である。しかし、その理想的な真空度は超音波発生器の能力や溶剤の種類によって変動するため、常に確実に理想的な真空度とすることは難しい。
【００１０】
内部を真空にする洗浄槽には、当然、耐圧性が要求される。ここで、洗浄槽を真空度の高い状態に長時間耐え得るようにしようとすると、装置のコスト増を招き、また、構造や大きさに制約が生じて、一度に洗浄できるワークの量が限られてしまう。
【００１１】
本発明は、このような問題点に鑑みてなされたもので、高い洗浄力を確実に発揮し、しかも洗浄槽への圧力付加が軽減される超音波洗浄方法および超音波洗浄装置を提供することを目的とする。
【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、本発明では、洗浄槽内で洗浄の対象物を溶剤に浸し、溶剤に超音波を加えることにより対象物を洗浄する超音波洗浄方法において、洗浄槽を真空にした状態で溶剤に超音波を加える真空洗浄工程と、洗浄槽を大気圧にした状態で溶剤に超音波を加える常圧洗浄工程と、を含む超音波洗浄方法であって、真空度が異なる少なくとも２段階の真空洗浄工程と、常圧洗浄工程と、を真空度の高い順に行う。
【００１３】
この方法では、浸漬超音波洗浄を真空下と常圧下で行う。最初の真空洗浄工程では、溶剤が脱気されてキャビテーション発生のための閾値が高くなり、高い洗浄力が得られる。次の常圧洗浄工程では洗浄槽内は大気圧に戻されるが、洗浄槽への空気の導入を静かに行うことにより、溶剤をある程度脱気した状態に保つことが可能である。したがって、常圧洗浄工程でも高い洗浄力が得られる。また、真空洗浄工程を洗浄槽の真空度を２段階以上に設定して行うため、真空洗浄工程の途中でキャビテーション発生のための閾値を変えることが可能である。これにより、溶剤に加える超音波の音圧を一定にする場合でも、閾値がその音圧よりも低くなり易く、キャビテーションを発生させて高い洗浄力を得ることが容易になる。また、洗浄槽内を高い真空度に保つ時間が短くなって、洗浄槽に必要な耐圧性を低減することができる。
【００１４】
ここで、真空洗浄工程と常圧洗浄工程とを１サイクルとして、複数サイクルを行うようにしてもよい。対象物をより良好に洗浄することが可能になる。
【００１５】
その場合、真空洗浄工程での洗浄槽の真空度をサイクルごとに変化させるとよい。このようにすると、真空洗浄工程でキャビテーションを発生させて高い洗浄力を得ることがより確実にできるようになる。また、対象物の洗浄の進行の程度に応じて各サイクルの洗浄力を変えることができ、洗浄槽の真空度を必要以上に高めるという無駄も避けられる。
【００１６】
溶剤としては炭化水素系のものを使用するとよい。高い洗浄力の確保と環境の保護を両立させることが可能になる。
【００１７】
上記目的を達成するために、本発明ではまた、超音波洗浄装置は、対象物を出し入れするための開閉可能な蓋を有する洗浄槽と、洗浄槽内に超音波を発生させる超音波発生器と、洗浄槽を真空にする真空ポンプと、洗浄槽に大気を導き入れるバルブとを備え、上記のいずれかの超音波洗浄方法によって対象物を洗浄するものとする。
【００１８】
真空洗浄工程から常圧洗浄工程に移行する際にはバルブを介して空気を洗浄槽内に導入することが可能であり、洗浄槽の蓋は、洗浄開始前に対象物を洗浄槽に入れるときと洗浄終了後に対象物を洗浄槽から取り出すとき以外、開く必要がない。したがって、工程の移行を能率よく行うことができる。また、バルブの開き具合によって洗浄槽に導入する空気の量を調節することが可能であり、真空洗浄工程における洗浄槽の真空度の設定も容易である。
【００１９】
【発明の実施の形態】
以下、本発明の一実施形態の超音波洗浄装置について図面を参照しながら説明する。本実施形態の超音波洗浄装置１の構成を図１に模式的に示す。超音波洗浄装置１は、開閉可能な蓋１２を有する洗浄槽１１、超音波振動子１３、超音波発振器１４、ポンプ１５、加温タンク１６、濾過器１７、真空ポンプ１８、セパレータ１９、２つの空気バルブ２０、２１、および圧力計２２を備えている。
【００２０】
洗浄槽１１は溶剤Ｓおよび洗浄対象物であるワークＷを収容する。洗浄槽１１と蓋１２の接触部にはパッキングが設けられており、蓋１２を閉じることより洗浄槽１１は密閉される。超音波振動子１３は洗浄槽１１内の下部に配設されており、洗浄槽１１に収容された溶剤Ｓに超音波を加える。超音波発振器１４は、所定周波数の信号を超音波振動子１３に与えて振動させ、超音波振動子１３に超音波を発生させる。
【００２１】
ポンプ１５はパイプを介して洗浄槽１１の下部に接続されており、自己と洗浄槽１１の間で溶剤Ｓを循環させる。加温タンク１６と濾過器１７は、洗浄槽１１とポンプ１５を接続するパイプの途中、つまり、溶剤Ｓの循環路上に配置されている。加温タンク１６はヒータ１６ａを有しており、溶剤Ｓを加温する。濾過器１７は内部にフィルタ１７ａを有しており、溶剤Ｓに含まれる異物を除去する。
【００２２】
真空ポンプ１８は水封式であり、パイプを介して洗浄槽１１の上部に接続されている。真空ポンプ１８は洗浄槽１１の空気を吸引して外部に排出し、洗浄槽１１を真空にする。セパレータ１９は真空ポンプ１８を水封するためのもので、これにより、真空ポンプ１８によって得られる真空度は数千Ｐａ（数十torr）となる。
【００２３】
バルブ２０は洗浄槽１１と真空ポンプ１８を接続するパイプの途中に設けられており、洗浄槽１１からの空気の排出路を開閉する。バルブ２１は、洗浄槽１１の上部に空気の導入路として設けられたパイプに設けられており、導入路を開閉する。圧力計２２は、洗浄槽１１と真空ポンプ１８を接続するパイプのうち、洗浄槽１１とバルブ２０の間の部位に取り付けられており、洗浄槽１１内の気圧を検出する。
【００２４】
超音波洗浄装置１では、溶剤Ｓを洗浄槽１１に入れて溶剤ＳにワークＷを浸し、超音波振動子１３から溶剤Ｓに超音波を加えて溶剤Ｓにキャビテーションを発生させることにより、ワークＷの洗浄を行う。ワークＷを洗浄している間ポンプ１５によって溶剤Ｓを循環させることにより、ワークＷから分離し溶剤Ｓに含まれるようになった汚れは異物として濾過器１７によって除去され、溶剤Ｓの清浄度は略一定に保たれる。また、加熱タンク１６において循環する溶剤Ｓを加熱することにより、洗浄槽１１内の溶剤の温度を略一定にすることもできる。
【００２５】
このような構成の超音波洗浄装置１では、洗浄時の洗浄槽１１内（溶剤Ｓの上の空間）の真空度を、真空ポンプ１８の能力の範囲内で任意に設定することができる。洗浄槽１１内を真空にして洗浄を行うときには蓋１２、バルブ２０、２１を閉じておき、常圧で洗浄を行うときは、バルブ２１を開け、蓋１２、バルブ２０を閉じておく。なお、溶剤Ｓは、ワークＷや汚れの種類に応じて選択すればよいが、金属、プラスチック加工部品等を洗浄するときは炭化水素系の溶剤を用いるとよい。
【００２６】
超音波洗浄装置１で実施する本発明の洗浄方法について説明する。本発明では、洗浄槽１１を真空にした状態で溶剤Ｓに超音波を加える真空洗浄工程と、洗浄槽１１を大気圧にした状態で溶剤Ｓに超音波を加える常圧洗浄工程とを続けて行う。また、真空洗浄工程では、洗浄槽１１の真空度を２段階以上にして、各段階の真空度で溶剤Ｓに超音波を加える。真空洗浄工程の開始から常圧洗浄工程の終了まで、洗浄槽１１の蓋１２は閉じたままにしておき、真空度の調節は、バルブ２１の開閉と真空ポンプ１８の駆動によって行う。
【００２７】
洗浄処理の工程と洗浄槽１１内の圧力の関係を示す図２を参照して、洗浄処理の流れを説明する。これは真空洗浄工程での真空度を２段階とする場合の例である。なお、洗浄に先立ち、洗浄槽１１に清浄な溶剤Ｓを入れておき、全体が浸るようにワークＷを溶剤Ｓ中に入れて、蓋１２を閉じておく。また、ポンプ１５による溶剤Ｓの循環を開始しておき、洗浄槽１１内の溶剤Ｓが所定の温度に保たれるように、加熱タンク１６による溶剤Ｓの加熱も開始しておく。真空ポンプ１８も駆動して、いつでも減圧可能なようにしておく。
【００２８】
まず、バルブ２１を閉じたままバルブ２０を開いて、洗浄槽１１から排気する（減圧工程）。圧力計２２によって検出される洗浄槽１１内の圧力が数千Ｐａ（数十torr）に定めた第１の所定値ＰＡになった時点で、バルブ２０を閉じる。次いで、超音波振動子１３より溶剤Ｓに超音波を加えて、ワークＷを洗浄する（真空洗浄工程Ａ）。
【００２９】
所定時間経過後、溶剤Ｓに超音波を加えることを休止し、バルブ２１を少し開いて洗浄槽１１に空気を徐々に導き入れる（加圧工程）。洗浄槽１１内の圧力が数千Ｐａないし数万Ｐａ（数百torr）に定めた第２の所定値ＰＢになった時点で、バルブ２１を閉じる。そして、溶剤Ｓに超音波を加えることを再開し、ワークＷを洗浄する（真空洗浄工程Ｂ）。
【００３０】
所定時間経過後、溶剤Ｓに超音波を加えることを休止し、バルブ２１を少し開いて真空槽１１に空気を徐々に導き入れる（加圧工程）。洗浄槽１１内の圧力が大気圧（約十万Ｐａ）に戻った時点で、バルブ２１を閉じる。そして、溶剤Ｓに超音波を加えることを再開し、ワークＷを洗浄する（常圧洗浄工程）。所定時間経過後、溶剤Ｓに超音波を加えることを止めて洗浄を終了し、蓋１２を開けてワークＷを取り出す。取り出したワークＷは、真空乾燥等の適当な方法で乾燥する。
【００３１】
減圧工程で洗浄槽１１内を真空にすることにより溶剤Ｓは高度に脱気され、その状態で真空洗浄工程が行われる。ここで、溶剤Ｓに生じるキャビテーションの作用が強くなるようにキャビテーション発生の閾値を高くするのが望ましく、そのためには洗浄槽１１内の真空度はできるだけ高くするのがよい。しかし、その一方で、溶剤Ｓの脱気の度合いをあまりに高めると、キャビテーション発生の閾値が超音波振動子１３から溶剤Ｓに加える超音波の音圧を超えるおそれがあり、洗浄槽１１内の真空度を高くしすぎるとキャビテーションを発生させることができなくなる。したがって、真空洗浄工程における真空度を最適に設定するのは難しく、そのためには超音波振動子１３の能力、溶剤の種類、温度等も考慮する必要がある。
【００３２】
しかし、真空洗浄工程を２段階以上の真空度で行うことで、溶剤Ｓの脱気の度合いを変化させることが可能であり、これにより、ほぼ確実に溶剤Ｓにキャビテーションを発生させることができる。特に、洗浄槽１１内の圧力を数万Ｐａとする場合は、超音波振動子１３として特に高出力のものを用いなくても、炭化水素系の溶剤に確実にキャビテーションを発生させることができる。
【００３３】
図２に示した例では、仮に最初の真空洗浄工程Ａでキャビテーションが発生しなかったとしても、次の真空洗浄工程Ｂにおいて確実にキャビテーションが発生する。また、真空洗浄工程Ａでキャビテーションが発生すれば、その作用は強いから、より高い洗浄力が得られることになる。
【００３４】
常圧洗浄工程は真空洗浄工程に続いて行われ、しかも、常圧に戻すための真空槽１１への空気の導入は徐々になされて溶剤Ｓに乱れを生じさせないため、常圧洗浄工程でも溶剤Ｓの脱気度はある程度以上に保たれる。したがって、常圧洗浄工程においても、発生したキャビテーションの作用は強く、高い洗浄力が得られる。
【００３５】
洗浄槽１１は、最も高い真空度に耐え得るだけの耐圧性を有しなければならないが、洗浄中常に最も高い真空度とされるわけではないので、特殊な構造とする必要はない。したがって、洗浄槽１１は比較的低コストとなり、また、大型化も容易である。洗浄槽１１を大型化すると、一度に洗浄できるワークＷの量が増して、洗浄効率が向上する。
【００３６】
なお、図２に示した例では、最初の真空洗浄工程Ａの真空度を高くし、これに続く真空洗浄工程Ｂの真空度を低下させているが、逆にしてもかまわない。ただし、最初の真空洗浄工程Ａの真空度を高くする方が、制御が容易である。また、ここでは、工程と工程の間の期間は溶剤Ｓに超音波を加えるのを休止しているが、工程間の期間に超音波を加えるようにしてもかまわない。
【００３７】
真空洗浄工程と常圧洗浄工程とを１サイクルとし、蓋１２を開くことなく、複数サイクルを続けて行うようにしてもよい。ワークＷを一層良好に洗浄することが可能になる。この例を図３に示す。これは、各サイクルの真空洗浄工程の真空度を、図２の例と同様に、２段階に設定するとともに、最初のサイクルの真空洗浄工程Ａ、Ｂと次のサイクルの真空洗浄工程Ｃ、Ｄの真空度を異ならせたときのものである。
【００３８】
真空洗浄工程の２段階以上の真空度をサイクル間で同じに設定してもよい。しかし、図３に示した例のように、真空洗浄工程での真空度をサイクル間で相違させるようにすると、溶剤Ｓを種類の異なるものに替えるときでも、確実にキャビテーションを発生させて高い洗浄力を得ることができる。また、ワークＷの洗浄の進行の程度に応じて各サイクルの洗浄力を変えることも可能になって、洗浄槽の真空度を必要以上に高めるという無駄を避けることもできる。さらに、洗浄槽１１に最高の圧力が加わる時間を短くすることも可能になる。
【００３９】
真空洗浄工程および常圧洗浄工程の時間は任意に定めることができる。例えば、溶剤Ｓとして炭化水素系のものを用いて、金属製やプラスチック製のワークＷを洗浄する場合、真空洗浄工程と常圧洗浄工程をそれぞれ２分行えば、従来よりも短い時間でより良好な洗浄結果を得ることが可能である。真空洗浄工程の全時間の各真空度の工程への配分も任意に定めてよい。例えば、図２のように真空洗浄工程の真空度を２段階として、真空洗浄工程Ａ、Ｂの時間の和を２分とする場合、真空洗浄工程Ａ、Ｂをそれぞれ１分とすることもできるし、真空洗浄工程Ａを３０秒、真空洗浄工程Ｂを１分３０秒とすることもできる。
【００４０】
真空洗浄工程に続いて常圧洗浄工程を行うことの有用性を確認するために、次の試験を行った。ワークＷとしては、Ｍ５×Ｌ５０のキャップボルトを平ワッシャ２０枚に通し、ワッシャを２つのナットで両側から挟んで締め付けたものを用いた。ワークＷは、個々の構成部品を、脱脂洗浄した後ＪＩＳ１種１号品の油に一定時間浸し、次いで一定時間油切りを行って、上記のように組み合わせることにより調製した。
【００４１】
溶剤ＳとしてはＨＣ−２５０を用い、溶剤Ｓの温度は３５℃とした。また、超音波振動子１３が発する超音波の周波数は４０ｋＨｚとした。真空洗浄工程での洗浄槽１１内の圧力は９３３０Ｐａ（７０torr）とし、真空洗浄工程の時間は１分、常圧洗浄工程の時間は４分とした。試験における工程と洗浄槽１１内の真空度の関係を図４に示す。洗浄後、ワークＷを乾燥し、フーリエ変換赤外（ＦＴ−ＩＲ）分光光度計によって、ワークＷに残存している油の量を測定して、洗浄による除去率を算出した。
【００４２】
比較のために、同一条件で調製したワークＷを従来の２通りの洗浄方法で洗浄して、同様に除去率を算出した。比較例１では、洗浄槽１１を真空にすることなく、したがって、溶剤Ｓを脱気することなく、常圧で５分間洗浄した。比較例２では、洗浄槽１１内の圧力を９３３０Ｐａとし、５分間洗浄した。溶剤Ｓの種類、温度、溶剤Ｓに加える超音波等の他の条件は、上記の試験例と同じ設定である。
【００４３】
結果をまとめて表に示す。

【００４４】
比較例１と比較例２より明らかなように、真空洗浄では、脱気を行わない常圧洗浄に比べて、はるかに高い清浄力が得られる。また、比較例２と試験例より判るように、真空洗浄に続いて常圧洗浄を行うと、一層高い洗浄力が得られる。しかも、試験例での真空洗浄工程の時間は１分のみであり、試験例の洗浄力は、主として、溶剤Ｓから脱気した状態での常圧洗浄工程で発揮されたことが判る。この試験例では真空洗浄工程の真空度を１段階のみとしているが、真空洗浄工程の真空度を２段階以上とすると、各真空度ごとに固有の洗浄力が定まり、しかもそれらの洗浄力は常圧洗浄工程での洗浄力以上であるから、さらに高い洗浄力が得られることになる。
【００４５】
なお、本実施形態で示した装置構成や真空度等の具体的な値は例にすぎず、他の構成や値とすることも可能である。特に、真空洗浄工程における真空度およびその段階数ならびに各工程の時間は、使用する溶剤Ｓに応じて設定するのが好ましい。
【００４６】
【発明の効果】
洗浄槽を真空にした状態で溶剤に超音波を加える真空洗浄工程と、洗浄槽を大気圧にした状態で溶剤に超音波を加える常圧洗浄工程と、を含む超音波洗浄方法であって、真空度が異なる少なくとも２段階の真空洗浄工程と、常圧洗浄工程と、を真空度の高い順に行うようにした本発明の超音波洗浄方法では、真空洗浄工程だけでなくこれに続く常圧洗浄工程も溶剤を脱気した状態で洗浄を行うことができるため、高い洗浄力が得られる。また、真空洗浄工程を洗浄槽の真空度を２段階以上に設定して行うから、真空洗浄工程の途中でキャビテーション発生のための閾値を変えることが可能であり、溶剤に加える超音波の音圧を一定にする場合でも、キャビテーションを発生させて高い洗浄力を得ることが容易になる。
【００４７】
しかも、洗浄槽内を高い真空度に保つ時間を短くすることが可能であり、洗浄槽にあまり高度な耐圧性が必要でなくなる。したがって、低コストで実施することが可能であり、また、洗浄槽を大きくして一度に洗浄できる対象物の量を増すことも容易になる。
【００４８】
真空洗浄工程と常圧洗浄工程とを１サイクルとして、複数サイクルを行うようにすると、対象物をより良好に洗浄することができる。
【００４９】
その際、真空洗浄工程での洗浄槽の真空度をサイクルごとに変化させるようにすると、キャビテーションを発生させて高い洗浄力を得ることがより確実にできるようになる上、対象物の洗浄の進行の程度に応じて各サイクルの洗浄力を変えることができて、洗浄槽の真空度を必要以上に高めるという無駄も避けられる。
【００５０】
炭化水素系の溶剤を使用すると、高い洗浄力の確保と環境の保護を両立させることができる。
【００５１】
対象物を出し入れするための開閉可能な蓋を有する洗浄槽と、洗浄槽内に超音波を発生させる超音波発生器と、洗浄槽を真空にする真空ポンプと、洗浄槽に大気を導き入れるバルブとを備え、上記のいずれかの超音波洗浄方法によって対象物を洗浄するようにした本発明の超音波洗浄装置では、対象物を良好にかつ能率よく洗浄することが可能である。また、洗浄槽にあまり高度な耐圧性が必要でないから、低コストで実現することができ、洗浄槽を大型化して一度に多量の対象物を洗浄することも可能になる。
【図面の簡単な説明】
【図１】本発明の一実施形態の超音波洗浄装置の構成を模式的に示す図。
【図２】上記超音波洗浄装置での洗浄処理の工程と洗浄槽の真空度の関係の例を示す図。
【図３】上記超音波洗浄装置での洗浄処理の工程と洗浄槽の真空度の関係の他の例を示す図。
【図４】上記超音波洗浄装置で試験に採用した洗浄処理の工程と洗浄槽の真空度の関係を示す図。
【図５】従来の洗浄処理の工程と洗浄槽の真空度の関係の例を示す図。
【符号の説明】
１超音波洗浄装置
１１洗浄槽
１２蓋
１３超音波振動子
１４超音波発振器
１５ポンプ
１６加温タンク
１６ａヒータ
１７濾過器
１７ａフィルタ
１８真空ポンプ
１９セパレータ
２０バルブ
２１バルブ
２２圧力計
Ｓ溶剤
Ｗワーク[0001]
BACKGROUND OF THE INVENTION
The present invention relates to immersion ultrasonic cleaning, and more particularly to immersion ultrasonic cleaning performed under vacuum.
[0002]
[Prior art]
Immersion ultrasonic cleaning, in which an object is cleaned by applying ultrasonic waves to the solvent while the object to be cleaned is immersed in a solvent, has been widely adopted for cleaning metal and plastic processed parts. Since the abolition of CFCs for environmental protection, various cleaning methods using alternative solvents have been proposed. Among them, cleaning methods using hydrocarbon solvents that do not contain any halogen and are easy to dry are attracting attention. Yes. In the case of using a hydrocarbon-based solvent, immersion ultrasonic cleaning is also useful, and it has been proposed to perform under vacuum as well as under atmospheric pressure.
[0003]
When performing immersion ultrasonic cleaning under atmospheric pressure, if the workpiece that is the object to be cleaned has a fine structure such as a bag hole or groove on the surface, the solvent may not enter and partial cleaning may not be possible. . Even if the surfaces of the workpieces are smooth, if the workpieces are in contact with each other, the solvent may not enter the workpieces, and cleaning may be insufficient.
[0004]
Immersion ultrasonic cleaning uses cavitation, but it is known that the sound pressure in the liquid must be above a certain threshold in order to generate cavitation in the liquid (the latest cleaning technology). Overview, Chapter 3, Section 3, pp. 193-196). Here, the threshold value is higher for the degassed liquid than for the liquid saturated with air. Therefore, as the degree of vacuum increases, the degree of deaeration increases and the threshold value also increases.
[0005]
Also, the higher the solvent threshold, the stronger the action when cavitation occurs, and the higher the cleaning power. This is the main reason for performing immersion ultrasonic cleaning under vacuum.
[0006]
FIG. 5 shows the relationship between the cleaning process in the conventional immersion ultrasonic cleaning method and the pressure in the cleaning tank. First, a solvent is put into the cleaning tank, and the work is immersed in this. The pressure in the washing tank at this time is atmospheric pressure, that is, about 100,000 Pa (760 torr). Next, air is discharged from the cleaning tank, and the inside of the cleaning tank is set to a predetermined degree of vacuum, for example, several thousand Pa (several tens of torr). Then, the workpiece is cleaned by applying ultrasonic waves to the solvent while maintaining the degree of vacuum. After cleaning for a predetermined time, the ultrasonic wave is stopped, the inside of the cleaning tank is returned to atmospheric pressure, and the work is taken out from the cleaning tank. This completes the cleaning.
[0007]
In this way, when ultrasonic cleaning is performed under vacuum, the cleaning power is higher than when performed under normal pressure, and the fine structure of the workpiece surface and dirt on the parts where the workpieces are in contact are better. Can be removed. Also, the cleaning time is shortened.
[0008]
[Problems to be solved by the invention]
However, by applying a vacuum, the solvent threshold may become too high, exceeding the intensity of the ultrasonic waves emitted by the ultrasonic generator provided in the apparatus. In this case, cavitation does not occur, and the cleaning is performed only by the permeation and vibration of the solvent by vacuum, and the original cleaning power by performing ultrasonic cleaning under vacuum cannot be obtained. In addition, in the case of a cleaning device equipped with an ultrasonic generator with low oscillation intensity, cavitation can be generated only when the degree of degassing of the solvent is low, that is, when the degree of vacuum is low. However, high detergency cannot be obtained.
[0009]
In ultrasonic cleaning under vacuum, it is ideal to set the degree of vacuum so that the threshold for cavitation generation is slightly lower than the sound pressure of ultrasonic waves actually applied to the solvent. However, since the ideal degree of vacuum varies depending on the capability of the ultrasonic generator and the type of solvent, it is difficult to always ensure the ideal degree of vacuum.
[0010]
Naturally, pressure resistance is required for a cleaning tank that evacuates the interior. Here, if the cleaning tank can withstand a high degree of vacuum for a long time, the cost of the apparatus is increased, and the structure and size are limited, so that the amount of work that can be cleaned at one time is limited. It will be.
[0011]
The present invention has been made in view of such problems, and provides an ultrasonic cleaning method and an ultrasonic cleaning apparatus that reliably exhibit high cleaning power and reduce pressure applied to a cleaning tank. With the goal.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, in an ultrasonic cleaning method for cleaning an object by immersing the object to be cleaned in a solvent in a cleaning tank and applying ultrasonic waves to the solvent, the cleaning tank is evacuated. An ultrasonic cleaning method comprising: a vacuum cleaning step of applying ultrasonic waves to the solvent in a state; and an atmospheric pressure cleaning step of applying ultrasonic waves to the solvent in a state where the cleaning tank is at atmospheric pressure. The vacuum cleaning process in steps and the normal pressure cleaning process are performed in order of increasing vacuum .
[0013]
In this method, immersion ultrasonic cleaning is performed under vacuum and normal pressure. In the first vacuum cleaning step, the solvent is degassed, the threshold value for generating cavitation is increased, and high cleaning power is obtained. In the next normal pressure washing step, the inside of the washing tank is returned to the atmospheric pressure, but by introducing air gently into the washing tank, it is possible to keep the solvent deaerated to some extent. Therefore, a high cleaning power can be obtained even in the normal pressure cleaning process. Further, since the vacuum cleaning process is performed by setting the vacuum degree of the cleaning tank to two or more stages, it is possible to change the threshold value for generating cavitation during the vacuum cleaning process. As a result, even when the sound pressure of the ultrasonic wave applied to the solvent is kept constant, the threshold value tends to be lower than the sound pressure, and it becomes easy to generate cavitation and obtain a high cleaning power. Further, the time for keeping the inside of the cleaning tank at a high degree of vacuum is shortened, and the pressure resistance required for the cleaning tank can be reduced.
[0014]
Here, a plurality of cycles may be performed by setting the vacuum cleaning step and the normal pressure cleaning step as one cycle. The object can be cleaned better.
[0015]
In that case, it is good to change the vacuum degree of the washing tank in a vacuum washing process for every cycle. In this way, it is possible to more reliably obtain a high cleaning power by generating cavitation in the vacuum cleaning process. Further, the cleaning power of each cycle can be changed according to the progress of the cleaning of the object, and the waste of increasing the vacuum degree of the cleaning tank more than necessary can be avoided.
[0016]
A hydrocarbon-based solvent may be used as the solvent. It is possible to achieve both high detergency and environmental protection.
[0017]
In order to achieve the above object, according to the present invention, an ultrasonic cleaning apparatus includes a cleaning tank having an openable / closable lid for taking in and out an object, and an ultrasonic generator for generating ultrasonic waves in the cleaning tank. A vacuum pump that evacuates the cleaning tank and a valve that introduces air into the cleaning tank are provided, and the object is cleaned by any of the ultrasonic cleaning methods described above.
[0018]
When moving from the vacuum cleaning process to the normal pressure cleaning process, it is possible to introduce air into the cleaning tank through a valve, and the cover of the cleaning tank is used to put an object into the cleaning tank before the start of cleaning. And it is not necessary to open it except when the object is taken out from the washing tank after washing. Therefore, the process can be transferred efficiently. In addition, the amount of air introduced into the cleaning tank can be adjusted by opening the valve, and the degree of vacuum of the cleaning tank in the vacuum cleaning process can be easily set.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an ultrasonic cleaning apparatus according to an embodiment of the present invention will be described with reference to the drawings. The configuration of the ultrasonic cleaning apparatus 1 of the present embodiment is schematically shown in FIG. The ultrasonic cleaning apparatus 1 includes a cleaning tank 11 having an openable / closable lid 12, an ultrasonic vibrator 13, an ultrasonic oscillator 14, a pump 15, a heating tank 16, a filter 17, a vacuum pump 18, a separator 19,

Air valves

20 and 21 and a pressure gauge 22 are provided.
[0020]
The cleaning tank 11 accommodates the solvent S and the workpiece W that is the object to be cleaned. Packing is provided at the contact portion between the cleaning tank 11 and the lid 12, and the cleaning tank 11 is sealed by closing the lid 12. The ultrasonic vibrator 13 is disposed in the lower part of the cleaning tank 11 and applies ultrasonic waves to the solvent S accommodated in the cleaning tank 11. The ultrasonic oscillator 14 applies a signal having a predetermined frequency to the ultrasonic vibrator 13 to vibrate, and causes the ultrasonic vibrator 13 to generate an ultrasonic wave.
[0021]
The pump 15 is connected to the lower part of the cleaning tank 11 through a pipe, and circulates the solvent S between itself and the cleaning tank 11. The heating tank 16 and the filter 17 are arranged in the middle of the pipe connecting the cleaning tank 11 and the pump 15, that is, on the circulation path of the solvent S. The heating tank 16 has a heater 16a and warms the solvent S. The filter 17 has a filter 17a inside, and removes foreign matters contained in the solvent S.
[0022]
The vacuum pump 18 is water-sealed and is connected to the upper part of the cleaning tank 11 through a pipe. The vacuum pump 18 sucks the air in the cleaning tank 11 and discharges it to the outside to make the cleaning tank 11 vacuum. The separator 19 is used to seal the vacuum pump 18 with water, whereby the degree of vacuum obtained by the vacuum pump 18 is several thousand Pa (several tens of torr).
[0023]
The valve 20 is provided in the middle of the pipe connecting the cleaning tank 11 and the vacuum pump 18, and opens and closes the air discharge path from the cleaning tank 11. The valve 21 is provided in a pipe provided as an air introduction path in the upper part of the cleaning tank 11 and opens and closes the introduction path. The pressure gauge 22 is attached to a portion between the cleaning tank 11 and the valve 20 among the pipes connecting the cleaning tank 11 and the vacuum pump 18, and detects the atmospheric pressure in the cleaning tank 11.
[0024]
In the ultrasonic cleaning apparatus 1, the solvent W is placed in the cleaning tank 11, the work W is immersed in the solvent S, and ultrasonic waves are applied to the solvent S from the ultrasonic vibrator 13 to generate cavitation in the solvent S, thereby Perform cleaning. By circulating the solvent S by the pump 15 while washing the workpiece W, the dirt separated from the workpiece W and contained in the solvent S is removed as foreign matter by the filter 17, and the cleanliness of the solvent S is It is kept almost constant. Further, by heating the solvent S circulating in the heating tank 16, the temperature of the solvent in the cleaning tank 11 can be made substantially constant.
[0025]
In the ultrasonic cleaning apparatus 1 having such a configuration, the degree of vacuum in the cleaning tank 11 (the space above the solvent S) at the time of cleaning can be arbitrarily set within the range of the capability of the vacuum pump 18. The lid 12 and the

valves

20 and 21 are closed when cleaning the inside of the cleaning tank 11 in a vacuum, and the valve 21 is opened and the lid 12 and the valve 20 are closed when cleaning at normal pressure. The solvent S may be selected according to the workpiece W and the type of dirt, but a hydrocarbon-based solvent may be used when cleaning metal, plastic processed parts and the like.
[0026]
The cleaning method of the present invention performed by the ultrasonic cleaning apparatus 1 will be described. In the present invention, a vacuum cleaning process in which ultrasonic waves are applied to the solvent S in a state where the cleaning tank 11 is evacuated, and a normal pressure cleaning process in which ultrasonic waves are applied to the solvent S in a state where the cleaning tank 11 is set to atmospheric pressure. Do. In the vacuum cleaning process, the degree of vacuum of the cleaning tank 11 is set to two or more levels, and ultrasonic waves are applied to the solvent S at the vacuum level of each level. The lid 12 of the cleaning tank 11 is kept closed from the start of the vacuum cleaning process to the end of the normal pressure cleaning process, and the degree of vacuum is adjusted by opening and closing the valve 21 and driving the vacuum pump 18.
[0027]
The flow of the cleaning process will be described with reference to FIG. 2 showing the relationship between the cleaning process and the pressure in the cleaning tank 11. This is an example in which the degree of vacuum in the vacuum cleaning process is two stages. Prior to cleaning, a clean solvent S is put in the cleaning tank 11, and the workpiece W is put in the solvent S so that the whole is immersed, and the lid 12 is closed. Further, the circulation of the solvent S by the pump 15 is started, and the heating of the solvent S by the heating tank 16 is also started so that the solvent S in the cleaning tank 11 is maintained at a predetermined temperature. The vacuum pump 18 is also driven so that the pressure can be reduced at any time.
[0028]
First, the valve 20 is opened while the valve 21 is closed, and the cleaning tank 11 is evacuated (decompression step). When the pressure in the cleaning tank 11 detected by the pressure gauge 22 reaches a first predetermined value PA set at several thousand Pa (several tens of torr), the valve 20 is closed. Next, ultrasonic waves are applied to the solvent S from the ultrasonic vibrator 13 to clean the workpiece W (vacuum cleaning step A).
[0029]
After a predetermined time has elapsed, the application of ultrasonic waves to the solvent S is stopped, the valve 21 is opened a little, and air is gradually introduced into the cleaning tank 11 (pressurization step). When the pressure in the cleaning tank 11 reaches a second predetermined value PB determined to be several thousand Pa to several tens of thousands Pa (several hundred torr), the valve 21 is closed. Then, the application of ultrasonic waves to the solvent S is resumed, and the workpiece W is cleaned (vacuum cleaning step B).
[0030]
After a predetermined time has elapsed, the application of ultrasonic waves to the solvent S is stopped, the valve 21 is opened a little, and air is gradually introduced into the vacuum chamber 11 (pressure process). When the pressure in the cleaning tank 11 returns to atmospheric pressure (about 100,000 Pa), the valve 21 is closed. And it restarts applying an ultrasonic wave to the solvent S, and wash | cleans the workpiece | work W (atmospheric pressure washing | cleaning process). After a predetermined time has elapsed, the ultrasonic wave is stopped from being applied to the solvent S to finish the cleaning, the lid 12 is opened, and the workpiece W is taken out. The taken out work W is dried by an appropriate method such as vacuum drying.
[0031]
The solvent S is highly degassed by evacuating the cleaning tank 11 in the decompression step, and the vacuum cleaning step is performed in this state. Here, it is desirable to raise the cavitation threshold so that the action of cavitation generated in the solvent S becomes strong. For this purpose, the degree of vacuum in the cleaning tank 11 should be as high as possible. However, on the other hand, if the degree of degassing of the solvent S is increased too much, the threshold for cavitation generation may exceed the sound pressure of the ultrasonic wave applied to the solvent S from the ultrasonic vibrator 13, and the vacuum in the cleaning tank 11 If the degree is too high, cavitation cannot be generated. Therefore, it is difficult to optimally set the degree of vacuum in the vacuum cleaning process. For this purpose, it is necessary to consider the ability of the ultrasonic vibrator 13, the type of solvent, the temperature, and the like.
[0032]
However, it is possible to change the degree of degassing of the solvent S by performing the vacuum cleaning process at two or more degrees of vacuum, whereby cavitation can be generated in the solvent S almost certainly. In particular, when the pressure in the cleaning tank 11 is set to several tens of thousands of Pa, cavitation can be reliably generated in the hydrocarbon solvent without using an ultrasonic vibrator 13 having a particularly high output.
[0033]
In the example shown in FIG. 2, even if cavitation does not occur in the first vacuum cleaning step A, cavitation surely occurs in the next vacuum cleaning step B. Further, if cavitation occurs in the vacuum cleaning step A, its action is strong, and thus higher cleaning power can be obtained.
[0034]
The normal pressure cleaning process is performed following the vacuum cleaning process, and air is gradually introduced into the vacuum chamber 11 to return to the normal pressure so that the solvent S is not disturbed. The degree of deaeration of S is kept above a certain level. Therefore, even in the normal pressure cleaning process, the generated cavitation has a strong action and a high cleaning power can be obtained.
[0035]
The cleaning tank 11 must have a pressure resistance that can withstand the highest degree of vacuum. However, the cleaning tank 11 does not always have the highest degree of vacuum during cleaning, and thus does not need to have a special structure. Therefore, the cleaning tank 11 is relatively low cost and can be easily enlarged. When the cleaning tank 11 is enlarged, the amount of workpieces W that can be cleaned at a time increases, and the cleaning efficiency improves.
[0036]
In the example shown in FIG. 2, the degree of vacuum in the first vacuum cleaning step A is increased and the degree of vacuum in the subsequent vacuum cleaning step B is reduced, but this may be reversed. However, control is easier if the degree of vacuum in the first vacuum cleaning step A is increased. Here, the application of ultrasonic waves to the solvent S is suspended during the period between the processes, but the ultrasonic waves may be applied during the period between the processes.
[0037]
The vacuum cleaning step and the normal pressure cleaning step may be one cycle, and a plurality of cycles may be continuously performed without opening the lid 12. The workpiece W can be cleaned more satisfactorily. An example of this is shown in FIG. This is because the degree of vacuum in the vacuum cleaning process of each cycle is set to two stages, as in the example of FIG. 2, and the vacuum cleaning processes A and B in the first cycle and the vacuum cleaning processes C and D in the next cycle are performed. When the degree of vacuum is different.
[0038]
The degree of vacuum in two or more stages of the vacuum cleaning process may be set to be the same between cycles. However, as in the example shown in FIG. 3, if the degree of vacuum in the vacuum cleaning process is made different between cycles, even when the solvent S is changed to a different type, cavitation is surely generated and high cleaning is performed. You can gain power. Moreover, it becomes possible to change the cleaning power of each cycle according to the progress of the cleaning of the workpiece W, and it is possible to avoid waste of increasing the vacuum degree of the cleaning tank more than necessary. Furthermore, it is possible to shorten the time during which the highest pressure is applied to the cleaning tank 11.
[0039]
The time of the vacuum cleaning step and the normal pressure cleaning step can be arbitrarily determined. For example, when a metal or plastic workpiece W is cleaned using a hydrocarbon solvent as the solvent S, if the vacuum cleaning step and the normal pressure cleaning step are performed for 2 minutes each, it is better in a shorter time than before. It is possible to obtain a cleaning result. The distribution of the degree of vacuum over the entire time of the vacuum cleaning process may be arbitrarily determined. For example, as shown in FIG. 2, when the vacuum degree of the vacuum cleaning process is two steps and the sum of the times of the vacuum cleaning processes A and B is 2 minutes, the vacuum cleaning processes A and B can each be 1 minute. The vacuum cleaning step A can be 30 seconds, and the vacuum cleaning step B can be 1 minute 30 seconds.
[0040]
In order to confirm the usefulness of performing the normal pressure cleaning step following the vacuum cleaning step, the following test was performed. As the workpiece W, an M5 × L50 cap bolt was passed through 20 flat washers, and the washer was clamped between two sides with two nuts. The workpiece W was prepared by degreasing and washing the individual components and then immersing them in JIS Class 1 No. 1 oil for a certain period of time, followed by degreasing for a certain period of time and combining them as described above.
[0041]
As the solvent S, HC-250 was used, and the temperature of the solvent S was set to 35 ° C. Further, the frequency of the ultrasonic wave emitted from the ultrasonic vibrator 13 was set to 40 kHz. The pressure in the cleaning tank 11 in the vacuum cleaning process was 9330 Pa (70 torr), the time of the vacuum cleaning process was 1 minute, and the time of the normal pressure cleaning process was 4 minutes. The relationship between the process in the test and the degree of vacuum in the cleaning tank 11 is shown in FIG. After washing, the workpiece W was dried, and the amount of oil remaining on the workpiece W was measured by a Fourier transform infrared (FT-IR) spectrophotometer, and the removal rate by washing was calculated.
[0042]
For comparison, the workpiece W prepared under the same conditions was cleaned by two conventional cleaning methods, and the removal rate was calculated in the same manner. In Comparative Example 1, cleaning was performed at normal pressure for 5 minutes without evacuating the cleaning tank 11 and therefore without degassing the solvent S. In Comparative Example 2, the pressure in the cleaning tank 11 was 9330 Pa, and cleaning was performed for 5 minutes. Other conditions such as the type of solvent S, temperature, and ultrasonic waves applied to the solvent S are the same as those in the above test example.
[0043]
The results are summarized in the table.

[0044]
As is clear from Comparative Example 1 and Comparative Example 2, the vacuum cleaning can provide much higher cleaning power than the normal pressure cleaning without degassing. Further, as can be seen from Comparative Example 2 and the test example, when the normal pressure cleaning is performed after the vacuum cleaning, a higher cleaning power can be obtained. Moreover, the time of the vacuum cleaning process in the test example is only 1 minute, and it can be seen that the cleaning power of the test example was mainly exhibited in the atmospheric pressure cleaning process in a state where the solvent S was degassed. In this test example, the degree of vacuum in the vacuum cleaning process is only one stage. However, if the degree of vacuum in the vacuum cleaning process is two or more stages, the specific cleaning power is determined for each degree of vacuum, and the cleaning power is always normal. Since it is more than the detergency in the pressure washing process, a higher detergency can be obtained.
[0045]
Note that the specific values such as the device configuration and the degree of vacuum shown in the present embodiment are merely examples, and other configurations and values may be used. In particular, the degree of vacuum and the number of stages in the vacuum cleaning process and the time of each process are preferably set according to the solvent S to be used.
[0046]
【The invention's effect】
An ultrasonic cleaning method comprising: a vacuum cleaning step in which ultrasonic waves are applied to the solvent in a state where the cleaning tank is evacuated; and an atmospheric pressure cleaning step in which ultrasonic waves are applied to the solvent in a state where the cleaning tank is at atmospheric pressure , In the ultrasonic cleaning method of the present invention in which the vacuum cleaning process of at least two stages having different vacuum levels and the normal pressure cleaning process are performed in descending order of the vacuum level , not only the vacuum cleaning process but also the subsequent normal pressure cleaning is performed. Since the cleaning can be performed in a state where the solvent is degassed, a high cleaning power can be obtained. Moreover, since the vacuum cleaning process is performed by setting the vacuum degree of the cleaning tank to two or more stages, it is possible to change the threshold for cavitation generation during the vacuum cleaning process, and the sound pressure of the ultrasonic wave applied to the solvent Even in the case of keeping constant, it becomes easy to generate cavitation and obtain a high detergency.
[0047]
In addition, it is possible to shorten the time during which the inside of the cleaning tank is maintained at a high degree of vacuum, and the cleaning tank does not require a very high pressure resistance. Therefore, it can be carried out at a low cost, and it becomes easy to increase the amount of objects that can be cleaned at a time by enlarging the cleaning tank.
[0048]
If the vacuum cleaning step and the normal pressure cleaning step are set as one cycle and a plurality of cycles are performed, the object can be cleaned better.
[0049]
At that time, if the degree of vacuum of the cleaning tank in the vacuum cleaning process is changed for each cycle, it becomes possible to generate cavitation and obtain a high cleaning power more reliably, and the progress of the cleaning of the target object The cleaning power of each cycle can be changed according to the degree of the above, and the waste of increasing the vacuum degree of the cleaning tank more than necessary can be avoided.
[0050]
When a hydrocarbon solvent is used, it is possible to achieve both high detergency and environmental protection.
[0051]
A cleaning tank having an openable / closable lid for taking in and out the object, an ultrasonic generator for generating ultrasonic waves in the cleaning tank, a vacuum pump for evacuating the cleaning tank, and a valve for introducing air into the cleaning tank In the ultrasonic cleaning apparatus of the present invention in which the object is cleaned by any one of the ultrasonic cleaning methods described above, the object can be cleaned well and efficiently. In addition, since the cleaning tank does not require a high degree of pressure resistance, it can be realized at a low cost, and the cleaning tank can be enlarged to clean a large amount of objects at once.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing the configuration of an ultrasonic cleaning apparatus according to an embodiment of the present invention.
FIG. 2 is a view showing an example of a relationship between a cleaning process in the ultrasonic cleaning apparatus and a vacuum degree of a cleaning tank.
FIG. 3 is a view showing another example of the relationship between the cleaning process in the ultrasonic cleaning apparatus and the vacuum degree of the cleaning tank.
FIG. 4 is a diagram showing the relationship between the cleaning process employed in the test by the ultrasonic cleaning apparatus and the degree of vacuum in the cleaning tank.
FIG. 5 is a diagram showing an example of the relationship between a conventional cleaning process and the degree of vacuum of a cleaning tank.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ultrasonic cleaning apparatus 11 Cleaning tank 12 Cover 13 Ultrasonic vibrator 14 Ultrasonic oscillator 15 Pump 16 Heating tank 16a Heater 17 Filter 17a Filter 18 Vacuum pump 19 Separator 20 Valve 21 Valve 22 Pressure gauge S Solvent W Workpiece

Claims

In the ultrasonic cleaning method of cleaning an object by immersing the object to be cleaned in a solvent in a cleaning tank and applying ultrasonic waves to the solvent,
An ultrasonic cleaning method comprising: a vacuum cleaning step in which ultrasonic waves are applied to the solvent in a state where the cleaning tank is evacuated; and an atmospheric pressure cleaning step in which ultrasonic waves are applied to the solvent in a state where the cleaning tank is at atmospheric pressure,
A vacuum cleaning process vacuum of at least two different stages, and atmospheric pressure washing process, have rows in descending order of the degree of vacuum, and, a vacuum cleaning step and atmospheric pressure washing process as one cycle, performs a plurality of cycles, An ultrasonic cleaning method, wherein the degree of vacuum of a cleaning tank in a vacuum cleaning step is changed for each cycle .

In the ultrasonic cleaning method of cleaning an object by immersing the object to be cleaned in a solvent in a cleaning tank and applying ultrasonic waves to the solvent,
A vacuum cleaning process in which ultrasonic waves are applied to the solvent in a state where the cleaning tank is evacuated and an atmospheric pressure cleaning process in which ultrasonic waves are applied to the solvent in a state where the cleaning tank is at atmospheric pressure are performed in this order. The vacuum level of the cleaning tank is set to at least two stages, and the vacuum cleaning process and the normal pressure cleaning process are set as one cycle, and multiple cycles are performed, and the vacuum level of the cleaning tank in the vacuum cleaning process is changed for each cycle. An ultrasonic cleaning method, characterized by comprising:

Ultrasonic cleaning method according to any one of claims 1 or claim 2, characterized by using a hydrocarbon solvent.

A cleaning tank having an openable / closable lid for taking in and out an object, an ultrasonic generator for generating ultrasonic waves in the cleaning tank, a vacuum pump for evacuating the cleaning tank, and a valve for introducing air into the cleaning tank An ultrasonic cleaning apparatus, wherein the object is cleaned by the ultrasonic cleaning method according to any one of claims 1 to 3 .