JP4056818B2

JP4056818B2 - Leak test method and apparatus

Info

Publication number: JP4056818B2
Application number: JP2002217585A
Authority: JP
Inventors: 透佐々木
Original assignee: Fukuda Co Ltd
Current assignee: Fukuda Co Ltd
Priority date: 2002-07-26
Filing date: 2002-07-26
Publication date: 2008-03-05
Anticipated expiration: 2022-07-26
Also published as: JP2004061201A

Description

【０００１】
【発明の属する技術分野】
この発明は、密封空間を有する検査対象からの漏れを検査するのに好適なリークテスト方法及び装置に関する。
【０００２】
【従来の技術】
一般に、この種のリークテストでは、検査対象を含む第１空間と含まない第２空間とを互いに連通させた状態でこれら空間に圧縮エア等の加圧気体を導入する。そして、第１、第２空間の圧が平衡した後、これら空間を遮断して各々閉鎖系とする。ここで、検査対象の密封状態に不良があったときは、そこからの漏れが第２空間との差圧として検出される。これによって、検査対象の良不良を判定することができる。
【０００３】
【発明が解決しようとする課題】
第１、第２空間に加圧気体を導入すると断熱圧縮により昇温し、この昇温分の放熱によっても圧力変化が起きる。そこで、従来は、このような放熱をはじめとする、漏れ以外の差圧変動要因が十分に収まるまで待って差圧検出を実行していた。そのため、検査に時間がかかっていた。
【０００４】
【課題を解決するための手段】
上記課題を解決するために、本発明に係るリークテスト方法は、検査対象を含む第１空間と含まない第２空間とを互いに連通させた状態でこれら空間に加圧気体を導入した後、これら空間を遮断して各々閉鎖系としてその差圧を検出するリークテスト方法において、加圧気体導入による断熱昇温後の放熱による効果を表す放熱特性項と検査対象での漏れによる効果を表す漏れ特性項とを少なくとも含む差圧の経時変化を示す差圧方程式を予め近似的に設定しておき、上記閉鎖系形成後の上記放熱効果が有効な短い期間における検出差圧データを上記差圧方程式にフィッティングさせて該方程式の各項の係数を確定し、ひいては検出対象の漏れを判定することを特徴とする。これによって、放熱が収まるまで差圧検出を待つ必要が無く、検査時間を大幅に短縮することができる。上記第２空間の容積は、当該第２空間での放熱効果を無視し得る程度に小さいことが望ましい。これによって、差圧方程式を簡単化でき、係数確定を容易化できる。
【０００５】
検査対象の１つ又はそれと同容積で漏れの無いマスタ部材を用いた差圧データの検出を上記放熱有効期間よりも長い期間にわたって１又は複数回行なうことにより上記差圧方程式の漏れ特性項以外の項の係数を事前に確定しておき、その後の検査対象に対する本検査では漏れ特性項の係数のみを確定することにしてもよい。これによって、各々の検査対象に特有の漏れ特性と、それ以外の放熱特性等とを分けて解析することができ、放熱特性等については長期間にわたって１又は複数回行なうことで係数確定の精度を高めることができ、ひいては判定の精度を高めることができる。
上記本検査において、検出差圧データから上記漏れ特性項以外の項の係数をも一時的に求め、それに基づいて上記事前の確定係数を補正し、この補正された事前確定係数と上記検出差圧データとにより上記漏れ特性項の係数を確定することにしてもよい。これによって、検査対象の検査数が１つ増える度に放熱特性等の係数の事前確定値をより精度の高いものに補正することができ、また、周辺温度等の環境特性が経時変化している場合、その変化に適合するように事前確定値を追従させることができ、判定精度を一層高めることができる。
上記事前検査において、上記事前確定係数から得られる理論差圧と実測差圧との差をサンプリングタイムごとに求めておき、上記本検査において、サンプリングタイムごとに検出差圧から上記差を差し引き、この差し引いた値に基づいて漏れ特性項の係数を確定することにしてもよい。これによって、差圧方程式に近似誤差があっても、すなわち放熱や漏れ以外に差圧変化を来たす要因が存在する場合であっても、それを加味した判定を行なうことができ、判定精度を一層高めることができる。
【０００６】
上記判定で用いる差圧方程式に、上記放熱及び漏れ以外の効果を表す１又は複数の特性項を選択的に含ませることができるようにしてもよい。これによって、検出対象の種類、その他の諸要件に合わせて、判定で考慮すべき特性を取捨選択でき、判定精度を高めることができる。この場合、各種特性項を種々組み合わせた差圧方程式（漏れと放熱の各特性項は必ず含む）の候補を複数設けておき、これら候補式の中から１つを選択できるようにして、それを上記判定で用いる差圧方程式としてもよく、各特性項を候補として設定しておき、これら候補項の中から１又は複数を選択できるようにし、選択された項からなる差圧方程式（漏れと放熱の各特性項は必ず含む）を作り、それを上記判定で用いる差圧方程式としてもよい。
【０００７】
本発明に係るリークテスト装置は、検査対象を含む第１空間と含まない第２空間とを互いに連通させた状態でこれら空間に加圧気体を導入した後、これら空間を遮断して各々閉鎖系としてその差圧を検出するリークテスト装置において、加圧気体導入による断熱昇温後の放熱による効果を表す放熱特性項と検査対象での漏れによる効果を表す漏れ特性項とを少なくとも含む差圧の経時変化を示す差圧方程式を近似的に設定する差圧方程式設定部と、上記閉鎖系形成後の上記放熱効果が有効な短い期間における検出差圧データを上記差圧方程式にフィッティングさせて該方程式の各項の係数を確定し、ひいては検出対象の漏れを判定する漏れ判定部とを備えたことを特徴とする。これによって、放熱が収まるまで差圧検出を待つ必要が無く、検査時間を大幅に短縮することができる。
【０００８】
【発明の実施の形態】
以下、本発明の一実施形態を、図面を参照して説明する。
図１は、本発明の一実施形態に係るエアリークテスト装置１の概略構成を示したものである。エアリークテスト装置１は、圧縮エア源１０（加圧気体供給源）と、この圧縮エア源１０から延びる主通路２０と、この主通路２０の中途部から分岐された分岐通路２１とを有している。主通路２０には、上流側から電空レギュレータ１１、テスト圧センサ５１、電磁開閉弁からなる加圧弁３０、フィルタ４０、ボール弁からなるワーク弁３３が順次設けられている。主通路２０の下流端に、コネクタ２９を介してワークＷ（検査対象）の密封された内部空間が接続されるようになっている。フィルタ４０の上流側の主通路２０から排気通路２２が延びている。排気通路２２には、電磁開閉弁からなる排気弁３２が設けられている。排気通路２２の下流端は、排気ポート２２ａを介して大気に開放されている。
【０００９】
加圧弁３０と排気通路２２との間の主通路２０から上記マスタ通路２１が分岐して延びている。分岐通路２１には、ワーク圧センサ５２と、電磁開閉弁からなる平衡弁３１とが上流側から順次設けられている。分岐通路２１の下流端には、小容積（例えば３０ｃｃ）のエアタンク２３が接続されている。分岐通路２１には、差圧検出通路２５が、平衡弁３１をバイパスするようにして設けられている。差圧検出通路２５には、差圧センサ５０が設けられている。
【００１０】
加圧弁３０より下流の主通路２０と、ワークＷの密封空間と、排気弁３２より上流の排気通路２２と、平衡弁３１より上流の分岐通路２１と、差圧センサ５０より上流の差圧検出通路２５とによって、第１空間６１が構成されている。平衡弁３１より下流の分岐通路２１と、エアタンク２３と、差圧センサ５０より下流の差圧検出通路２５とによって、第２空間６２が構成されている。３つの電磁開閉弁３０〜３２を閉じると、第１、第２空間６１，６２が、互いに独立した閉鎖系となる。第２空間６２の容積は、第１空間６１より極めて小さい。
【００１１】
更に、エアリークテスト装置１は、全体を統括する制御手段７０を備えている。制御手段７０には、弁３０〜３２の駆動回路、電空レギュレータ１１の駆動回路、センサ５０〜５２の読み取り回路、これら回路を制御する制御部等（何れも図示せず）の他、差圧方程式設定部７１と、判定部７２が格納されている。設定部７１には後記差圧方程式（１）が設定されている。
【００１２】
上記構成の装置１によるエアリークテスト方法として基本態様と改変態様とを説明する。
〔１〕基本態様
はじめに概略を説明する。ワークＷにはシールを施して内部空間を密封しておく。このワークＷを主通路２０のコネクタ２９に接続する（ワーク接続工程）。ワーク弁３３は開き、排気弁３２は閉じておく。そして、制御手段７０によって加圧弁３０と平衡弁３１を開く。これによって、圧縮エア源１０からの圧縮エアが、第１、第２空間６１，６２に供給される（加圧工程）。このとき、ワーク圧センサ５２の検出圧が設定テスト圧に達した時点で、電空レギュレータ１１によってその二次圧がそれ以上高くならないようにする。続いて、加圧弁３０を閉じる一方、平衡弁３１の開状態を維持する。これによって、第１、第２空間６１，６２の圧力が、共に設定テスト圧になるように均等化される（第１平衡工程）。次に、平衡弁３１を閉じる。これによって、第１、第２空間６１，６２が互いに独立した閉鎖系になる。平衡弁３１の閉操作による乱れが収まるのを待って（例えば２秒程度／第２平衡工程）、差圧センサ５０の検出値を読み取る（検出工程）。この検出差圧に基づいて、判定部７２が差圧方程式（１）の後記係数ａ〜ｃを確定し、ひいてはワークＷの漏れを判定する（判定工程）。判定後、排気弁３２を開いて、第１空間６１を大気開放するとともに、ワークＷを外す（解放工程）。そして、次のワークに対して同様の工程を順次実行する。
【００１３】
上記差圧方程式（１）は、検出工程における差圧の経時変化を関数として近似化したものであり、例えば次式のように設定されている。
Ｙ＝ａｔ＋ｂ（１−ｅ^−ｃｔ） …（式１）
この式（１）をグラフ化すると、図２の実線のようになる。ここで、Ｙは、第２空間６２の圧力から第１空間６１の圧力を差し引いた差圧であり、ｔは、検出工程開始時をゼロとする経過時間である。
なお、第１、第２空間６１，６２間の差圧は、第２平衡工程の開始時（平衡弁弁３１の閉じ時）から生じているが、簡単化のために検出工程開始時の差圧をゼロにリセットしている。
【００１４】
差圧方程式（１）の右辺第１項ａｔは、第１空間６１ひいてはワークＷでの漏れによる効果を表した漏れ特性項である。すなわち、ワークＷでエア漏れが起きていると、第１空間６１の圧力が低下していく。これによって生じる第２空間６２との間の差圧変化を近似的に式化したものである。図２の破線で示すように、この漏れ特性項ａｔは、時間ｔの経過とともに直線状に大きくなっていくものと仮定されている。係数ａは、漏れの度合いを示している。
【００１５】
右辺第２項ｂ（１−ｅ^−ｃｔ）は、第１空間６１での放熱による効果を表す放熱特性項である。すなわち、第１空間６１では加圧工程における断熱圧縮によって昇温する。その後、この昇温分を放熱することにより圧力が低下する。この放熱による圧力低下を指数関数で近似化したものである。指数関数としたのは、一般に放熱量はその時点の温度（周辺との温度差）に比例するからである。係数ｂ，ｃは、放熱の度合いを示している。具体的には、係数ｂは、放熱が収まったときの最終的な圧力低下分（放熱特性の収束点）となり、係数ｃは、放熱が収まる早さ（放熱特性の収束速度）となる。なお、第２空間６２は、容積が極めて小さく、放熱による圧力変動を無視できる。そのため、放熱特性項は、第１空間６１についてのみの式になっている。
【００１６】
図２の二点鎖線で示すように、放熱特性項は、時間ｔ＝０で漏れ特性項より大きな勾配で立ち上がり、時間ｔの経過とともに勾配が次第に緩やかになり、最終的にはほとんどフラットになって係数ｂに収束する。したがって、検出工程の開始から僅かな期間Ｔ_０（例えば１０秒間）だけが、上記放熱に起因する差圧変化を有効に検出できる期間である。この放熱有効期間Ｔ_０を過ぎると、差圧の変化は、ほとんど漏れに起因するものだけとなる。
【００１７】
さて、上記検出工程は、放熱有効期間Ｔ_０内に実行する。すなわち、制御手段７０は、放熱有効期間Ｔ_０の例えば１０秒間に、差圧検出を短時間（例えば１秒）置きに繰り返し実行する。こうして、サンプリングタイムの異なる複数個の検出差圧データがサンプリングされる。そして、上記判定工程では、例えば最小二乗法によって検出差圧データに差圧方程式（１）をフィッティングさせ、各項の係数ａ〜ｃの値を確定する。そして、係数ａの値に基づいてワークＷの漏れの有無を判定する。すなわち、係数ａが所定値を下回っているときは、漏れ無しとして、そのワークＷを良品と判定する。一方、係数ａが所定値以上であるときは、漏れ有りとして、そのワークＷを不良と判定する。
したがって、放熱が収まるまで（図２の放熱特性項がフラットになるまで）差圧検出を待つ必要が無く、検査時間を大幅に短縮することができる。
また、加圧工程で電空レギュレータ１１によって設定テスト圧以上の圧がワークＷに導入されないようにしているので、放熱特性の複雑化を回避でき、係数の確定ひいては判定を容易化することができる。
【００１８】
上記の基本態様のテスト方法でフィッティング精度ひいては判定精度が思わしくない場合、以下の改変態様を適用することができる。
〔２〕改変態様（その１）
実際の検査対象であるワークＷに対する上記基本態様と同様の検査（これを「本検査」という。）に先立ち、事前検査を行なう。事前検査では、図１の仮想線で示すように、マスタ部材Ｍを用意し、これを実際の検査対象のワークＷに代えてコネクタ２９に接続する。マスタ部材Ｍは、漏れ無しと判明している（検査済みの）ワークＷを用いてもよく、ワークＷと同容積で漏れの無い他の部材を用いてもよい。なお、かかるマスタ部材Ｍに代えて、漏れの有無が不明な（未検査の）ワークＷを用いてもよい。このマスタ部材Ｍ又はワークＷに対して、上記と同様の加圧工程、第１平衡工程、第２平衡工程、検出工程を実行する。ただし、検出工程は、短い放熱有効期間Ｔ_０内に留めず、数分〜数十分にわたって長時間実行する。これによって得られた多数のサンプリングデータを差圧方程式（１）にフィッティングさせて、各項の係数ａ〜ｃを求める。上記の各工程を１回でなく、反復して複数回実行し、その平均を取ってもよい。複数回実行する場合には、検出工程の長さを１回だけの場合よりも短くし、例えば数十秒のオーダーにしてもよい。勿論、反復の度に排気弁３２を開けて空間６１，６２を一旦大気開放する。
【００１９】
なお、未検査のワークＷで事前検査を行なう場合は、この検査で得られた漏れ特性項の係数ａの値によって当該ワークＷの漏れ判定を行なうことができるので、当該ワークＷに対する本検査は省略することができる。
マスタ部材Ｍの場合は、漏れが無いので、ａ＝０となることになる。そこで、差圧方程式設定部７１にマスタ部材Ｍ用の下記差圧方程式（２）を追加設定しておき、この式（２）でフィッティングを行なってもよい。
Ｙ＝ｂ（１−ｅ^−ｃｔ） …（式２）
【００２０】
上記事前検査で求められた漏れ特性項以外の項すなわち放熱特性項の係数ｂ，ｃの確定値は、本検査における検査対象のワークＷにも当てはまり得る。そこで、本検査の判定工程では、上記事前検査での放熱特性係数ｂ，ｃの確定値を差圧方程式（１）に代入し、方程式（１）を線形にする。そして、線形最小二乗法等により漏れ特性係数ａのみを確定し、この確定値に基づいてワークＷの漏れの有無を判定する。
この改変態様（その１）によれば、各々のワークＷに特有の漏れ特性と、どのワークＷにも共通に当てはまる傾向の高い放熱特性とを分けて解析することができ、放熱特性については長期間にわたって１又は複数回行なうことで係数確定の精度を高めることができ、ひいては判定の精度を高めることができる。
【００２１】
〔３〕改変態様（その２）
改変態様（その１）と同様の事前検査を行ない、放熱特性係数ｂ，ｃの値を事前確定しておく。その後の本検査の判定工程では、先ず、上記基本態様と同様に、ワークＷの検出差圧データを差圧方程式（１）にフィッティングさせ、各項の係数ａ〜ｃを求める。要するに、当該ワークＷの検出差圧データだけに基づいて係数ｂ，ｃの値を改めて算出する。この算出値に基づいて事前確定値を補正する。すなわち、算出値と事前確定値との加重平均又は移動平均を取り、これを放熱特性係数ｂ，ｃの新たな事前確定値として補正する。この補正された事前確定値と当該ワークＷの検出差圧データとを差圧方程式（１）に代入し、改めて漏れ特性係数ａを算出、確定する。この確定した漏れ特性係数ａの値に基づいて当該ワークＷの漏れの有無を判定する。次のワークＷに対する判定工程では、そのワークＷの検出差圧データだけから算出した放熱特性係数ｂ，ｃの値に基づいて上記補正後の事前確定値を再補正する。なお、ワークＷの検出差圧データだけから算出した漏れ特性係数ａが漏れ有りとされるような大きさのときは、そのワークＷのデータを事前確定値に反映させない（上記補正を行なわない）。
この改変態様（その２）によれば、ワークＷの検査数が１つ増える度に放熱特性係数ｂ，ｃの事前確定値がより精度の高いものに補正されていく。これによって、判定精度を高めることができる。また、周辺温度等の環境特性が経時変化している場合、その変化に適合するように事前確定値を追従させることができる。
【００２２】
〔４〕改変態様（その３）
改変態様（その１）の事前検査において、確定した係数ａ（＝０），ｂ，ｃの値を差圧方程式（１）に代入した理論差圧と、実際の検出差圧すなわち実測差圧との差をサンプリングタイムごとに求めておく。すなわち、各サンプリングタイムを、ｔ_１，ｔ_２，ｔ_３…とする。サンプリングタイムは、期間Ｔ_０内に含まれる必要がある。このサンプリングタイム（ｔ_１，ｔ_２，ｔ_３…）ごとの理論差圧を、Ｙｉ（ｔ_１），Ｙｉ（ｔ_２），Ｙｉ（ｔ_３）…とし、実測差圧をＹｒ（ｔ_１），Ｙｒ（ｔ_２），Ｙｒ（ｔ_３）…とすると、その差、すなわち、
ΔＹ（ｔ_１）＝Ｙｉ（ｔ_１）−Ｙｒ（ｔ_１）
ΔＹ（ｔ_２）＝Ｙｉ（ｔ_２）−Ｙｒ（ｔ_２）
ΔＹ（ｔ_３）＝Ｙｉ（ｔ_３）−Ｙｒ（ｔ_３）
…
を求める。なお、複数回実測した場合には、その平均を実測差圧とする。上記の差ΔＹ（ｔ_１），ΔＹ（ｔ_２），ΔＹ（ｔ_３）…は、近似式としての差圧方程式（１）の近似誤差に相当する。すなわち、放熱や漏れ以外に差圧変化の要因が存在する場合（例えば加圧によってワークＷ自体が変形したり、ワークＷに施したシール部が変形したりし、その後、復元していく場合等）、その要因分の差圧変化（第２空間６２の圧力）−（第１空間６１の圧力）に（−１）をかけたものに相当する。
【００２３】
そして、本検査において、検出差圧から上記差を差し引いて補正差圧を求める。すなわち、本検査におけるサンプリングタイム（ｔ_１，ｔ_２，ｔ_３…）ごとの検出差圧をＹｐ（ｔ_１），Ｙｐ（ｔ_２），Ｙｐ（ｔ_３）…とし、補正差圧をＹｐ’（ｔ_１），Ｙｐ’（ｔ_２），Ｙｐ’（ｔ_３）…とすると、
Ｙｐ’（ｔ_１）＝Ｙｐ（ｔ_１）−ΔＹ（ｔ_１）
Ｙｐ’（ｔ_２）＝Ｙｐ（ｔ_２）−ΔＹ（ｔ_２）
Ｙｐ’（ｔ_３）＝Ｙｐ（ｔ_３）−ΔＹ（ｔ_３）
…
を求める。この補正差圧は、差圧方程式（１）の近似誤差を補正したものであり、放熱や漏れ以外の要因による差圧変化分を加算したものである。この補正差圧Ｙｐ’（ｔ_１），Ｙｐ’（ｔ_２），Ｙｐ’（ｔ_３）…と上記放熱特性項の事前確定係数ｂ，ｃの値とに基づいて直線回帰を行なう。これによって、漏れ特性項の係数ａを確定し、ワークＷの漏れの有無を判定する。
この改変態様（その３）によれば、差圧方程式に近似誤差があっても、すなわち放熱や漏れ以外に差圧変化を来たす要因が存在する場合であっても、それを加味した漏れ特性係数ａを算出することができ、判定精度を高めることができる。
【００２４】
〔５〕改変態様（その４）
制御手段７０の差圧方程式設定部７１に、下記のように、差圧方程式の候補を式（１）だけでなく複数設定しておく。
Ｙ＝ａｔ＋ｂ（１−ｅ^−ｃｔ） …（式１）
Ｙ＝ａｔ＋ｂ_１（１−ｅ^−ｃ１ｔ）＋ｂ_２（１−ｅ^−ｃ２ｔ） …（式３）
Ｙ＝ａｔ＋ｂ_１（１−ｅ^−ｃ１ｔ）＋ｂ_２（１−ｅ^−ｃ２ｔ）＋ｂ_３（１−ｅ^−ｃ３ｔ） …（式４）
…
ここで、式３と式４の右辺第２項は、放熱特性項であり、第３項は、例えばワークＷのシール部の変形による差圧変化を表したシール部変形特性項であり、式４の右辺第４項は、例えばワークＷ自体の変形による差圧変化を表したワーク変形特性項である。その他、周辺温度の変化による差圧変化を表した周辺温度特性項等を含む式を設定してもよい。このように漏れや放熱や以外の特性項をも作り、これらを組み合わせた式を立てておく。各式には、少なくとも漏れ特性項と放熱特性項を含ませる。更に、制御手段７０に、これら候補式の中から１つを選択する式選択部（図示せず）を設けておく。検査作業者は、対象となるワークＷ等に合わせて、上記式選択部によって１つの式を選択する。これによって、判定部７２が、検出差圧データを上記選択された１つの差圧方程式にフィッティングさせて当該式の各項の係数を確定し、その中の漏れ特性係数ａの値に基づいて、ワークＷの漏れの有無を判定する。なお、シール部変形やワーク変形等の各特性項を候補として設定しておき、これら候補項の中から１又は複数を選択できるようにし、選択された候補項と放熱特性項及び漏れ特性項とを組み合わせることによって、上記判定工程で用いる差圧方程式を作ることにしてもよい。
この改変態様（その４）によれば、ワークＷその他の諸要件に合わせて、判定で考慮すべき特性を取捨選択でき、判定精度を高めることができる。
【００２５】
本発明は、上記実施形態に限定されるものではなく、種々の改変を行なうことができる。
例えば、放熱特性項は、上記指数関数ｂ（１−ｅ^−ｃｔ）に代えて累乗関数や対数関数等を用いることも考えられる。
第２平衡工程を短くし、その分だけ放熱有効期間Ｔ_０すなわち検出工程の時間を長くして、差圧データのサンプリング数を増やすのが望ましい。これによって、係数算出の精度を高めることができる。
【００２６】
【発明の効果】
以上説明したように、本発明によれば、放熱をはじめとする漏れ以外の差圧変動要因が収まるまで差圧検出を待つ必要が無く、検査時間を大幅に短縮することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態に係るエアリークテスト装置の概略構成図である。
【図２】上記エアリークテスト装置に設定された差圧方程式とその漏れ特性項及び放熱特性項について差圧の時間変化を示すグラフである。
【符号の説明】
Ｗワーク（検査対象）
Ｍマスタ部材
１エアリークテスト装置
１０圧縮エア源（加圧気体源）
３０加圧弁
３１平衡弁
５０差圧センサ（差圧検出手段）
６１第１空間
６２第２空間
７０制御手段
７１差圧方程式設定部
７２判定部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a leak test method and apparatus suitable for inspecting a leak from an inspection object having a sealed space.
[0002]
[Prior art]
In general, in this type of leak test, a pressurized gas such as compressed air is introduced into these spaces in a state where the first space including the inspection object and the second space not including the inspection object are communicated with each other. And after the pressure of 1st, 2nd space equilibrates, these space is interrupted | blocked and it is set as a closed system, respectively. Here, when there is a defect in the sealed state of the object to be inspected, a leak from there is detected as a differential pressure with respect to the second space. This makes it possible to determine whether the inspection target is good or bad.
[0003]
[Problems to be solved by the invention]
When pressurized gas is introduced into the first and second spaces, the temperature rises due to adiabatic compression, and the pressure change also occurs due to heat dissipation for the temperature rise. Therefore, conventionally, the differential pressure detection is executed after waiting for the differential pressure fluctuation factors other than leakage, such as heat radiation, to be sufficiently reduced. As a result, the inspection took time.
[0004]
[Means for Solving the Problems]
In order to solve the above-described problem, the leak test method according to the present invention introduces a pressurized gas into these spaces in a state where the first space including the inspection object and the second space not including the inspection object communicate with each other. In a leak test method that shuts off these spaces and detects their differential pressure as a closed system, a heat release characteristic term that represents the effect of heat release after adiabatic temperature rise by introducing pressurized gas and a leak that represents the effect of leakage in the test object A differential pressure equation indicating a change with time of the differential pressure including at least a characteristic term is approximately set in advance, and the detected differential pressure data in the short period in which the heat dissipation effect is effective after the closed system is formed is the differential pressure equation. And the coefficient of each term of the equation is determined, and as a result, the leakage of the detection target is determined. As a result, there is no need to wait for differential pressure detection until the heat dissipation is settled, and the inspection time can be greatly shortened. The volume of the second space is desirably small enough to ignore the heat dissipation effect in the second space. This simplifies the differential pressure equation and facilitates coefficient determination.
[0005]
By detecting the differential pressure data using one or the same volume of the inspection target and a master member having no leakage one or more times over a period longer than the effective heat dissipation period, other than the leakage characteristic term of the differential pressure equation The coefficient of the term may be determined in advance, and only the coefficient of the leakage characteristic term may be determined in the subsequent inspection for the inspection object. As a result, it is possible to analyze separately the leakage characteristics peculiar to each inspection object and other heat dissipation characteristics, etc., and for the heat dissipation characteristics, etc., the accuracy of coefficient determination can be improved by performing one or more times over a long period of time. The accuracy of determination can be increased.
In the main inspection, the coefficient of the term other than the leakage characteristic term is also temporarily obtained from the detected differential pressure data, and the prior deterministic coefficient is corrected based on the coefficient, and the corrected prior deterministic coefficient and the detected differential pressure are corrected. The coefficient of the leakage characteristic term may be determined based on the data. As a result, each time the number of inspections to be inspected increases by one, the pre-determined value of the coefficient such as the heat dissipation characteristic can be corrected to a more accurate one, and the environmental characteristics such as the ambient temperature change over time. In this case, the pre-determined value can be made to follow the change, and the determination accuracy can be further improved.
In the preliminary inspection, the difference between the theoretical differential pressure and the actual differential pressure obtained from the prior determination coefficient is obtained for each sampling time, and in the main inspection, the difference is subtracted from the detected differential pressure for each sampling time. The coefficient of the leakage characteristic term may be determined based on the subtracted value. As a result, even if there is an approximation error in the differential pressure equation, that is, even when there is a factor that causes a differential pressure change other than heat dissipation and leakage, it is possible to make a determination that takes this into account, and further improve the determination accuracy. Can be increased.
[0006]
One or more characteristic terms representing effects other than the heat dissipation and leakage may be selectively included in the differential pressure equation used in the determination. Accordingly, the characteristics to be considered in the determination can be selected according to the type of detection target and other various requirements, and the determination accuracy can be improved. In this case, a plurality of candidates for differential pressure equations (each characteristic term for leakage and heat dissipation must be included) with various combinations of various characteristic terms are prepared, and one of these candidate equations can be selected, and It may be a differential pressure equation used in the above determination, and each characteristic term is set as a candidate so that one or more of the candidate terms can be selected, and the differential pressure equation (leakage and heat dissipation) consisting of the selected terms is selected. May be used as the differential pressure equation used in the above determination.
[0007]
The leak test apparatus according to the present invention introduces pressurized gas into these spaces in a state in which the first space including the inspection object and the second space not including the objects to be communicated with each other, and then shuts off these spaces to close each of the closed systems. In the leak test apparatus for detecting the differential pressure, the differential pressure including at least a heat release characteristic term representing the effect of heat release after adiabatic temperature rise by introducing pressurized gas and a leak characteristic term representing the effect due to leak in the inspection object A differential pressure equation setting unit that approximately sets a differential pressure equation indicating a change with time, and a differential pressure equation that fits the detected differential pressure data in a short period of time during which the heat dissipation effect is effective after the closed system is formed. And a leakage determination unit that determines the leakage of the detection target. As a result, there is no need to wait for differential pressure detection until the heat dissipation is settled, and the inspection time can be greatly shortened.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of an air leak test apparatus 1 according to an embodiment of the present invention. The air leak test apparatus 1 includes a compressed air source 10 (a pressurized gas supply source), a main passage 20 extending from the compressed air source 10, and a branch passage 21 branched from a middle portion of the main passage 20. Yes. The main passage 20 is provided with an electropneumatic regulator 11, a test pressure sensor 51, a pressurizing valve 30 composed of an electromagnetic on-off valve, a filter 40, and a work valve 33 composed of a ball valve in that order from the upstream side. A sealed internal space of the workpiece W (inspection target) is connected to the downstream end of the main passage 20 via a connector 29. An exhaust passage 22 extends from the main passage 20 upstream of the filter 40. The exhaust passage 22 is provided with an exhaust valve 32 composed of an electromagnetic on-off valve. The downstream end of the exhaust passage 22 is open to the atmosphere via an exhaust port 22a.
[0009]
The master passage 21 branches and extends from the main passage 20 between the pressurizing valve 30 and the exhaust passage 22. In the branch passage 21, a work pressure sensor 52 and a balance valve 31 including an electromagnetic opening / closing valve are sequentially provided from the upstream side. A small volume (for example, 30 cc) air tank 23 is connected to the downstream end of the branch passage 21. In the branch passage 21, a differential pressure detection passage 25 is provided so as to bypass the balance valve 31. A differential pressure sensor 50 is provided in the differential pressure detection passage 25.
[0010]
The main passage 20 downstream from the pressurizing valve 30, the sealed space of the workpiece W, the exhaust passage 22 upstream from the exhaust valve 32, the branch passage 21 upstream from the balance valve 31, and the differential pressure detection upstream from the differential pressure sensor 50. A first space 61 is constituted by the passage 25. The second space 62 is configured by the branch passage 21 downstream from the balance valve 31, the air tank 23, and the differential pressure detection passage 25 downstream from the differential pressure sensor 50. When the three electromagnetic on-off valves 30 to 32 are closed, the first and second spaces 61 and 62 become a closed system independent of each other. The volume of the second space 62 is extremely smaller than that of the first space 61.
[0011]
Furthermore, the air leak test apparatus 1 includes a control unit 70 that controls the whole. The control means 70 includes a drive circuit for the valves 30 to 32, a drive circuit for the electropneumatic regulator 11, a reading circuit for the sensors 50 to 52, a control unit for controlling these circuits (not shown), and a differential pressure. An equation setting unit 71 and a determination unit 72 are stored. A differential pressure equation (1) described later is set in the setting unit 71.
[0012]
A basic mode and a modified mode will be described as an air leak test method by the apparatus 1 having the above configuration.
[1] Basic aspect First, an outline will be described. The work W is sealed to seal the internal space. This work W is connected to the connector 29 of the main passage 20 (work connection process). The work valve 33 is opened and the exhaust valve 32 is closed. Then, the pressurizing valve 30 and the balance valve 31 are opened by the control means 70. Thereby, the compressed air from the compressed air source 10 is supplied to the first and second spaces 61 and 62 (pressurizing step). At this time, when the detected pressure of the workpiece pressure sensor 52 reaches the set test pressure, the electropneumatic regulator 11 prevents the secondary pressure from becoming higher. Subsequently, the pressurizing valve 30 is closed, while the balance valve 31 is kept open. As a result, the pressures in the first and second spaces 61 and 62 are both equalized to the set test pressure (first balancing step). Next, the balance valve 31 is closed. As a result, the first and second spaces 61 and 62 become a closed system independent of each other. After the disturbance due to the closing operation of the balance valve 31 is settled (for example, about 2 seconds / second equilibrium step), the detection value of the differential pressure sensor 50 is read (detection step). Based on the detected differential pressure, the determination unit 72 determines postscript coefficients a to c of the differential pressure equation (1), and consequently determines the leakage of the workpiece W (determination step). After the determination, the exhaust valve 32 is opened to release the first space 61 to the atmosphere and remove the workpiece W (release process). And the same process is sequentially performed with respect to the following workpiece | work.
[0013]
The differential pressure equation (1) is obtained by approximating the change over time in the differential pressure in the detection process as a function, and is set as the following equation, for example.
Y = at + b (1-e ^−ct ) (Formula 1)
When this equation (1) is graphed, it is as shown by the solid line in FIG. Here, Y is a differential pressure obtained by subtracting the pressure of the first space 61 from the pressure of the second space 62, and t is an elapsed time when the detection process start time is zero.
The differential pressure between the first and second spaces 61 and 62 is generated at the start of the second equilibrium process (when the balance valve valve 31 is closed). The pressure is reset to zero.
[0014]
The first term at on the right side of the differential pressure equation (1) is a leakage characteristic term that represents the effect of leakage in the first space 61 and thus the workpiece W. That is, when air leaks in the workpiece W, the pressure in the first space 61 decreases. This is an approximate expression of the differential pressure change between the second space 62 and the second space 62. As indicated by a broken line in FIG. 2, the leakage characteristic term at is assumed to increase linearly with the passage of time t. The coefficient a indicates the degree of leakage.
[0015]
The second term b (1-e ^−ct ) on the right side is a heat dissipation characteristic term that represents the effect of heat dissipation in the first space 61. That is, the temperature in the first space 61 is increased by adiabatic compression in the pressurizing step. Thereafter, the pressure is reduced by dissipating the temperature rise. This pressure drop due to heat dissipation is approximated by an exponential function. The reason for the exponential function is that the amount of heat release is generally proportional to the temperature at that time (temperature difference from the surroundings). Coefficients b and c indicate the degree of heat dissipation. Specifically, the coefficient b is the final pressure drop when the heat dissipation is stopped (the convergence point of the heat dissipation characteristics), and the coefficient c is the speed at which the heat dissipation is stopped (the convergence speed of the heat dissipation characteristics). Note that the second space 62 has an extremely small volume, and pressure fluctuation due to heat radiation can be ignored. Therefore, the heat dissipation characteristic term is an expression only for the first space 61.
[0016]
As shown by the two-dot chain line in FIG. 2, the heat radiation characteristic term rises at a time t = 0 with a larger gradient than the leakage characteristic term, and the gradient gradually becomes gradually with the lapse of time t and finally becomes almost flat. To converge to the coefficient b. Therefore, only a short period T ₀ (for example, 10 seconds) from the start of the detection process is a period in which the differential pressure change due to the heat dissipation can be detected effectively. After this heat radiation effective period T ₀ , the change in the differential pressure is mostly due to leakage.
[0017]
Now, the detecting step performs heat radiation lifetime T in _0. That is, the control means 70, for example 10 seconds radiator lifetime T _0, repeatedly executes difference pressure detection every short time (e.g. 1 second). Thus, a plurality of detected differential pressure data having different sampling times are sampled. In the determination step, the differential pressure equation (1) is fitted to the detected differential pressure data by, for example, the least square method, and the values of the coefficients a to c of each term are determined. And the presence or absence of the leakage of the workpiece | work W is determined based on the value of the coefficient a. That is, when the coefficient a is less than a predetermined value, it is determined that there is no leakage and the workpiece W is determined as a non-defective product. On the other hand, when the coefficient a is greater than or equal to a predetermined value, it is determined that there is a leak and the workpiece W is determined to be defective.
Therefore, there is no need to wait for differential pressure detection until the heat dissipation is settled (until the heat dissipation characteristic term in FIG. 2 becomes flat), and the inspection time can be greatly shortened.
In addition, since the electropneumatic regulator 11 does not introduce a pressure higher than the set test pressure into the workpiece W in the pressurizing process, it is possible to avoid complication of heat dissipation characteristics and to facilitate determination of the coefficient and determination. .
[0018]
In the case where the fitting accuracy and thus the determination accuracy are not expected in the test method of the above basic mode, the following modified mode can be applied.
[2] Modification (Part 1)
Prior to an inspection similar to the above-described basic mode for the workpiece W that is an actual inspection object (this is referred to as “main inspection”), a preliminary inspection is performed. In the preliminary inspection, as shown by the phantom line in FIG. 1, a master member M is prepared and connected to the connector 29 instead of the actual work W to be inspected. As the master member M, a workpiece W that has been found to have no leakage (inspected) may be used, or another member that has the same volume as the workpiece W and has no leakage may be used. Instead of the master member M, a workpiece W whose leakage is unknown (uninspected) may be used. The same pressurizing process, first equilibration process, second equilibration process, and detection process as described above are performed on the master member M or the workpiece W. However, the detection step is not fastened to the short heat radiation lifetime T in _0, long running over several minutes to several tens of minutes. A large number of sampling data obtained in this way are fitted to the differential pressure equation (1) to obtain the coefficients a to c of each term. Each of the above steps may be repeated several times instead of once and the average may be taken. In the case of executing a plurality of times, the length of the detection process may be made shorter than that in the case of only one time, for example, on the order of several tens of seconds. Of course, the exhaust valve 32 is opened every time the operation is repeated, and the spaces 61 and 62 are once opened to the atmosphere.
[0019]
In addition, when performing a preliminary inspection with an uninspected workpiece W, the leakage determination of the workpiece W can be performed based on the value of the coefficient a of the leakage characteristic term obtained by this inspection. Can be omitted.
In the case of the master member M, since there is no leakage, a = 0. Therefore, the following differential pressure equation (2) for the master member M may be additionally set in the differential pressure equation setting unit 71, and fitting may be performed using this equation (2).
Y = b (1-e ^−ct ) (Formula 2)
[0020]
Terms other than the leakage characteristic term obtained in the preliminary inspection, that is, the definite values of the coefficients b and c of the heat dissipation characteristic term can be applied to the workpiece W to be inspected in this inspection. Therefore, in the determination step of this inspection, the determined values of the heat radiation characteristic coefficients b and c in the preliminary inspection are substituted into the differential pressure equation (1), and the equation (1) is linearized. Then, only the leakage characteristic coefficient a is determined by a linear least square method or the like, and the presence / absence of leakage of the workpiece W is determined based on the determined value.
According to this modified mode (part 1), it is possible to analyze separately the leakage characteristic peculiar to each work W and the heat radiation characteristic that tends to apply to all the works W. By performing one or more times over a period of time, the accuracy of coefficient determination can be increased, and as a result, the accuracy of determination can be increased.
[0021]
[3] Modification mode (part 2)
The same pre-inspection as in the modification mode (part 1) is performed, and the values of the heat dissipation characteristic coefficients b and c are determined in advance. In the subsequent determination step of the main inspection, first, similarly to the basic mode described above, the detected differential pressure data of the workpiece W is fitted to the differential pressure equation (1) to obtain the coefficients a to c of each term. In short, the values of the coefficients b and c are calculated anew based only on the detected differential pressure data of the workpiece W. The pre-determined value is corrected based on the calculated value. That is, a weighted average or a moving average of the calculated value and the predetermined value is taken, and this is corrected as a new predetermined value of the heat radiation characteristic coefficients b and c. The corrected prior fixed value and the detected differential pressure data of the workpiece W are substituted into the differential pressure equation (1), and the leakage characteristic coefficient a is calculated and determined again. The presence or absence of leakage of the workpiece W is determined based on the determined value of the leakage characteristic coefficient a. In the determination process for the next workpiece W, the pre-determined value after correction is recorrected based on the values of the heat radiation characteristic coefficients b and c calculated from only the detected differential pressure data of the workpiece W. If the leakage characteristic coefficient a calculated from only the detected differential pressure data of the workpiece W is large enough to cause leakage, the workpiece W data is not reflected in the pre-determined value (the above correction is not performed). .
According to this modification (No. 2 ), the pre-determined values of the heat radiation characteristic coefficients b and c are corrected to higher accuracy each time the number of inspections of the workpiece W increases by one. Thereby, the determination accuracy can be increased. Moreover, when environmental characteristics, such as ambient temperature, are changing with time, a pre-determined value can be made to follow the change.
[0022]
[4] Modified mode (part 3)
In the preliminary inspection of the modification mode (part 1), the theoretical differential pressure obtained by substituting the values of the determined coefficients a (= 0), b, and c into the differential pressure equation (1), the actual detected differential pressure, that is, the actually measured differential pressure, Is obtained for each sampling time. That is, each sampling _{_{time, t 1, t 2, t}} 3 ... to. Sampling time has to be included within the period T _0. The theoretical differential pressure for each sampling time (t ₁ , t ₂ , t ₃ ...) Is Yi (t ₁ ), Yi (t ₂ ), Yi (t ₃ ), and the measured differential pressure is Yr (t ₁ ). , Yr (t ₂ ), Yr (t ₃ )...
ΔY (t ₁ ) = Yi (t ₁ ) −Yr (t ₁ )
ΔY (t ₂ ) = Yi (t ₂ ) −Yr (t ₂ )
ΔY (t ₃ ) = Yi (t ₃ ) −Yr (t ₃ )
...
Ask for. In addition, when measured several times, the average is made into the measured differential pressure. The above differences ΔY (t ₁ ), ΔY (t ₂ ), ΔY (t ₃ )... Correspond to the approximation error of the differential pressure equation (1) as an approximation formula. That is, when there is a factor of a differential pressure change other than heat dissipation or leakage (for example, when the workpiece W itself is deformed by pressurization or the seal portion applied to the workpiece W is deformed and then restored) ), A difference in pressure difference corresponding to the factor (pressure in the second space 62) − (pressure in the first space 61) multiplied by (−1).
[0023]
In this inspection, the corrected differential pressure is obtained by subtracting the difference from the detected differential pressure. That is, the detected differential pressure at each sampling time (t ₁ , t ₂ , t ₃ ...) In this inspection is Yp (t ₁ ), Yp (t ₂ ), Yp (t ₃ ), and the corrected differential pressure is Yp ′. (T ₁ ), Yp ′ (t ₂ ), Yp ′ (t ₃ )...
Yp ′ (t ₁ ) = Yp (t ₁ ) −ΔY (t ₁ )
Yp ′ (t ₂ ) = Yp (t ₂ ) −ΔY (t ₂ )
Yp ′ (t ₃ ) = Yp (t ₃ ) −ΔY (t ₃ )
...
Ask for. This corrected differential pressure is obtained by correcting the approximation error of the differential pressure equation (1), and is obtained by adding a differential pressure change due to factors other than heat dissipation and leakage. Linear regression is performed on the basis of the corrected differential pressures Yp ′ (t ₁ ), Yp ′ (t ₂ ), Yp ′ (t ₃ ). As a result, the coefficient a of the leakage characteristic term is determined, and the presence or absence of leakage of the workpiece W is determined.
According to this modified mode (No. 3), even if there is an approximation error in the differential pressure equation, that is, even if there is a factor causing the differential pressure change other than heat dissipation and leakage, the leakage characteristic coefficient is taken into account. a can be calculated and the determination accuracy can be increased.
[0024]
[5] Modification mode (4)
In the differential pressure equation setting unit 71 of the control means 70, a plurality of differential pressure equation candidates are set in addition to the equation (1) as follows.
Y = at + b (1-e ^−ct ) (Formula 1)
_{^{Y = at + b 1 (1}} -e -c1t) + b 2 (1-e -c2t) ... ( Equation 3)
_{^{_{^{Y = at + b 1 (1}}}} -e -c1t) + b 2 (1-e -c2t) + b 3 (1-e -c3t) ... ( Equation 4)
...
Here, the second term on the right side of Equation 3 and Equation 4 is a heat dissipation characteristic term, and the third term is a seal portion deformation characteristic term representing a change in differential pressure due to deformation of the seal portion of the workpiece W, for example. The fourth term on the right side of 4 is a workpiece deformation characteristic term representing, for example, a change in differential pressure due to deformation of the workpiece W itself. In addition, an equation including an ambient temperature characteristic term indicating a change in differential pressure due to a change in ambient temperature may be set. In this way, characteristic terms other than leakage, heat dissipation, and the like are also created, and a formula combining them is established. Each expression includes at least a leakage characteristic term and a heat dissipation characteristic term. Further, the control means 70 is provided with an expression selection unit (not shown) for selecting one of these candidate expressions. The inspection operator selects one formula by the formula selection unit in accordance with the target workpiece W or the like. Accordingly, the determination unit 72 fits the detected differential pressure data to the selected differential pressure equation to determine the coefficient of each term of the formula, and based on the value of the leakage characteristic coefficient a therein, The presence or absence of leakage of the workpiece W is determined. It should be noted that each characteristic term such as seal deformation and workpiece deformation is set as a candidate so that one or more of the candidate terms can be selected, and the selected candidate terms, heat dissipation characteristic terms and leakage characteristic terms are selected. May be used to create the differential pressure equation used in the determination step.
According to this modification (No. 4), the characteristics to be considered in the determination can be selected according to the workpiece W and other various requirements, and the determination accuracy can be improved.
[0025]
The present invention is not limited to the above embodiment, and various modifications can be made.
For example, it is also conceivable to use a power function or logarithmic function instead of the exponential function b (1-e ^−ct ) as the heat dissipation characteristic term.
It is desirable to shorten the second equilibration step and increase the effective heat dissipation period T _0, that is, the detection step time, and increase the number of differential pressure data samples. As a result, the accuracy of coefficient calculation can be increased.
[0026]
【The invention's effect】
As described above, according to the present invention, there is no need to wait for the differential pressure detection until the differential pressure fluctuation factors other than leakage including heat dissipation are settled, and the inspection time can be greatly shortened.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an air leak test apparatus according to an embodiment of the present invention.
FIG. 2 is a graph showing a time variation of a differential pressure with respect to a differential pressure equation set in the air leak test apparatus and its leakage characteristic term and heat radiation characteristic term.
[Explanation of symbols]
W Work (inspection object)
M Master member 1 Air leak test device 10 Compressed air source (pressurized gas source)
30 Pressurizing valve 31 Equilibrium valve 50 Differential pressure sensor (Differential pressure detecting means)
61 first space 62 second space 70 control means 71 differential pressure equation setting unit 72 determination unit

Claims

A leak test in which after the pressurized gas is introduced into these spaces in a state where the first space including the test object and the second space not included are in communication with each other, these spaces are blocked and the differential pressure is detected as a closed system. In the method
Preliminarily approximate a differential pressure equation showing the change over time of the differential pressure including at least a heat dissipation characteristic term representing the effect of heat dissipation after adiabatic temperature rise by introducing pressurized gas and a leakage characteristic term representing the effect due to leakage in the inspection object Set it,
A pre-inspection and a main inspection for determining a leak characteristic term coefficient from a detected differential pressure in a short period in which the heat dissipation effect after the closed system formation for the inspection target is effective, and thus determining leakage of the detection target are performed. ,
In the preliminary inspection, differential pressure detection is performed one or more times over a period longer than the heat radiation effective period using one of the inspection targets or a master member having the same volume and no leakage, and detection in the obtained preliminary inspection is performed. By fitting the differential pressure to the differential pressure equation, the coefficient of the term other than the leakage characteristic term of the differential pressure equation is determined in advance as a pre-determined coefficient,
After that, in the main inspection, the coefficient of the term other than the leakage characteristic term is obtained again by fitting the differential pressure equation detected in the heat radiation effective period in the main inspection to the differential pressure equation, and the pre-determined coefficient is corrected based on the coefficient. And a coefficient of the leakage characteristic term is determined by substituting the corrected prior determination coefficient into the differential pressure equation and fitting the detected differential pressure in the main inspection .

A leak test in which after the pressurized gas is introduced into these spaces in a state where the first space including the test object and the second space not included are in communication with each other, these spaces are blocked and the differential pressure is detected as a closed system. In the method
  Preliminarily approximate a differential pressure equation showing the change over time of the differential pressure including at least a heat dissipation characteristic term representing the effect of heat dissipation after adiabatic temperature rise by introducing pressurized gas and a leakage characteristic term representing the effect due to leakage in the inspection object Set it,
  A pre-inspection and a main inspection for determining a leak characteristic term coefficient from a detected differential pressure in a short period in which the heat dissipation effect after the closed system formation for the inspection target is effective, and thus determining leakage of the detection target are performed. ,
  In the preliminary inspection, differential pressure detection is performed one or more times over a period longer than the effective heat dissipation period using one or the same volume of the inspection target and a master member having no leakage, and detection in the obtained preliminary inspection is performed. By fitting the differential pressure to the differential pressure equation above, the coefficients of the terms other than the leakage characteristic term of the differential pressure equation are determined in advance as the pre-determined coefficient, and this pre-determined coefficient is substituted into the differential pressure equation. The difference between the theoretical differential pressure obtained and the detected differential pressure in the actual preliminary inspection is determined for each sampling time,
  Thereafter, in the main inspection, the differential pressure is obtained by subtracting the difference from the detected differential pressure in the main inspection at every sampling time, and the pre-determined coefficient is substituted into the differential pressure equation and the corrected differential pressure is fitted. And determining a coefficient of the leakage characteristic term.

The leak test method according to claim 1 or 2 , wherein the volume of the second space is small enough to ignore the heat dissipation effect in the second space.

A leak test in which after the pressurized gas is introduced into these spaces in a state where the first space including the test object and the second space not included are in communication with each other, these spaces are blocked and the differential pressure is detected as a closed system. In the device
Approximately set the differential pressure equation showing the change over time of the differential pressure including at least the heat dissipation characteristic term representing the effect of heat dissipation after the heat insulation temperature rise by introducing pressurized gas and the leakage characteristic term representing the effect due to leakage in the inspection target A differential pressure equation setting unit,
A pre-inspection and a main inspection for determining a leak characteristic term coefficient from a detected differential pressure in a short period in which the heat dissipation effect after the closed system formation for the inspection target is effective, and thus determining leakage of the detection target are executed. With a leakage judgment unit ,
In the preliminary inspection, the leakage determination unit performs differential pressure detection one or more times over a period longer than the effective heat dissipation period using one or the same volume of the inspection target and a master member that does not leak. By fitting the detected differential pressure in the preliminary inspection to the differential pressure equation, the coefficients of the terms other than the leakage characteristic term of the differential pressure equation are determined in advance as the preliminary determination coefficient. Fitting the detected differential pressure during the heat radiation effective period in the inspection to the differential pressure equation, obtain the coefficient of the term other than the leakage characteristic term again, correct the pre-determined coefficient based on it, and correct the differential pressure equation to the correction this to determine the coefficient of the leakage characteristics claim by fitting the detection pressure difference in the present test with substituting pre determined coefficients Leak testing apparatus according to claim.

A leak test in which after the pressurized gas is introduced into these spaces in a state where the first space including the test object and the second space not included are in communication with each other, these spaces are blocked and the differential pressure is detected as a closed system. In the device
  Approximately set the differential pressure equation showing the change over time of the differential pressure including at least the heat dissipation characteristic term representing the effect of heat dissipation after the heat insulation temperature rise by introducing the pressurized gas and the leakage characteristic term representing the effect due to leakage in the inspection object A differential pressure equation setting unit,
  A pre-inspection and a main inspection for determining a leak characteristic term coefficient from a detected differential pressure in a short period in which the heat dissipation effect after the closed system formation for the inspection target is effective, and thus determining leakage of the detection target are executed. With a leakage judgment unit,
  In the preliminary inspection, the leakage determination unit performs differential pressure detection one or more times over a period longer than the effective heat dissipation period using one or the same volume of the inspection target and a master member that does not leak. By fitting the detected differential pressure in the preliminary inspection to the differential pressure equation, the coefficient of the term other than the leakage characteristic term of the differential pressure equation is determined in advance as the preliminary fixed coefficient, and this preliminary fixed coefficient is The difference between the theoretical differential pressure obtained by substituting in the equation and the detected differential pressure in the actual preliminary inspection is determined at each sampling time, and in the subsequent main inspection, the detected differential pressure in the main inspection is determined at each sampling time. Subtracting the difference to obtain the corrected differential pressure, substituting the pre-determined coefficient into the differential pressure equation and fitting the corrected differential pressure Re leak test apparatus characterized by determining the coefficients of characteristic terms.