JP2004170137A

JP2004170137A - Insulation detecting device for non-grounded power source

Info

Publication number: JP2004170137A
Application number: JP2002333934A
Authority: JP
Inventors: Yoshihiro Kawamura; 佳浩河村; Kazutomo Hasegawa; 千倫長谷川
Original assignee: Yazaki Corp
Current assignee: Yazaki Corp
Priority date: 2002-11-18
Filing date: 2002-11-18
Publication date: 2004-06-17

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulation detecting device for a non-grounded power source improved in accuracy of estimated power source voltage. <P>SOLUTION: This insulation detecting device for a non-grounded power source is formed of first switching means S1 and S2 for connecting a capacitor 9 to a direct current power source 3, which is insulated from a grounded potential part 7, for the first set time, second switching means S1 and S4 for connecting a positive terminal of the power source 3 to the grounded potential part 7 for the second set time, third switching means S2 and S3 for connecting the grounding potential part 7 to a negative terminal of the power source 3 for the second set time, fourth switching means S3 and S4 for connecting a detecting means 11 for detecting voltage of the capacitor 9, a computing means 11 for obtaining insulation resistances Rp and Rn in relation to the grounding potential part 7 of the power source 3 on the basis of the power source voltage of the power source 3 based on the detecting means after cutting the first switching means and each of the voltage detected by the detecting means 11 after cutting the second and the third switching means, and a correcting means 11 for correcting the power source voltage on the basis of the already-known reference power source and the already-known reference resistance corresponding to the insulation resistances Rp and Rn. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、非接地電源の絶縁検出装置に係り、特に、電気による推進力を利用する車両に搭載された非接地の直流電源に好適な絶縁検出装置に関する。
【０００２】
【従来の技術】
非接地電源の絶縁検出装置は、非接地の直流電源の正及び負端子に接続され、接地電位部からは絶縁された正及び負側の主回路配線の接地電位部に対する絶縁抵抗つまり地絡抵抗を検出することで、接地電位部に対する絶縁や地絡状態を検出するものである（例えば、特許文献１参照）。このような従来の絶縁検出装置では、非接地の直流電源の正端子と接地電位部との間にコンデンサを直列に設定時間の間接続するスイッチング手段、非接地の電源の負端子と接地電位部との間にコンデンサを直列に設定時間の間接続するスイッチング手段、各スイッチング手段の遮断後にコンデンサの両端子間の電圧を検出する検出手段を接続する検出用のスイッチング手段、検出手段で検出した各スイッチング手段の遮断後のコンデンサの両端子間電圧とコンデンサを完全に充電することによって予め算出しておいた電源電圧とに基づいて電源の接地電位部に対する絶縁抵抗つまり地絡抵抗を求める演算手段などを備えており、演算手段で演算された地絡抵抗の値から絶縁状態の検出や判定などを行っている。
【０００３】
このような絶縁検出装置では、地絡抵抗の値を算出する際、コンデンサの容量などを定数として含む式を用いるが、定数として用いるコンデンサの容量などには、製品間における容量などのばらつきや温度変化による容量のばらつきなどが存在し、さらに容量などの経時変化などが生じる場合もある。このように定数として用いる値にばらつきや変化がある場合、算出した地絡抵抗の値と実際の地絡抵抗の値との間の計測誤差が増大するため、絶縁状態の検出精度が低下してしまう。したがって、コンデンサの容量など地絡抵抗を算出する際の定数となる値にばらつきや変化などがあっても、地絡抵抗の計測誤差をできるだけ低減し、絶縁状態の検出精度を向上することが望まれている。
【０００４】
これに対して、絶縁状態の検出精度を向上するため、本願の発明者らは、正端子側及び負端子側の配線が接地電位部から絶縁された直流電源にコンデンサを直列に第１の設定時間の間接続する第１のスイッチング手段と、電源の正端子と接地電位部との間にコンデンサを直列に第２の設定時間の間接続する第２のスイッチング手段と、接地電位部と電源の負端子との間にコンデンサを直列に第２の設定時間の間接続する第３のスイッチング手段と、第１、第２及び第３の各スイッチング手段の遮断後にコンデンサの両端子間の電圧を検出する検出手段を接続する第４のスイッチング手段と、第１のスイッチング手段を遮断後の検出手段での検出電圧に基づいて電源電圧を推定し、この推定した電源電圧と第２及び第３のスイッチング手段を遮断後の検出手段での各検出電圧とに基づいて電源の接地電位部に対する絶縁抵抗を求める演算手段とを備えた構成の絶縁検出装置を考えている。
【０００５】
このような絶縁検出装置とすれば、コンデンサを完全に充電するのに要する時間よりも短い時間に第１の設定時間を設定し、この第１の設定時間の間、第１のスイッチング手段によって直流電源と接地電位部との間にコンデンサが直流に接続されて充電され、このときのコンデンサの両端端子間の電圧を第４のスイッチング手段によって接続された検出手段で検出することにより、この検出した電圧からコンデンサの容量などを定数として含む電源電圧を算出するための式により演算手段が電源電圧を推定することができる。そして、この推定した電源電圧と、第２及び第３のスイッチング手段遮断後の検出手段での検出電圧とに基づいてコンデンサの容量などを定数として含む絶縁抵抗を算出するための式により絶縁抵抗を演算することで、絶縁抵抗の計測誤差を低減し、絶縁状態の検出精度を向上できる。
【特許文献１】
特開平８−２２６９５０号公報（第４−７頁、第１図）
【０００６】
【発明が解決しようとする課題】
ところで、電源電圧が定められた範囲を超えた値となった場合、この電源から電力を供給される機器や装置類、例えば車両などで不具合などが発生するのを防ぐため、電源電圧の異常を判断するための判定値を設け、この判定値と電源電圧とを比較して電源電圧の異常を判断する場合がある。これに対して、電源が上記のような本願の発明者らが考えている構成の絶縁検出装置を備えている場合、この絶縁検出装置で推定した電源電圧から電源電圧の異常を判定すれば、電源電圧の異常を検出するための装置や機器類を別個に電源に設ける必要が無くなる。
【０００７】
ところが、上記のような本願の発明者らが考えている構成の絶縁検出装置では、コンデンサの両端子間電圧から電源電圧を推定するため、電源電圧を推定する式には、コンデンサの容量などを定数として含んでいる。このため、コンデンサの容量などが製品間でばらつくことにより、定数となる数値にばらつきが生じることになる。したがって、本願の発明者らが考えている構成の絶縁検出装置で推定した電源電圧は、実際の電源電圧に対してこの定数となる数値のばらつきに応じた誤差を含むことになる。
【０００８】
この結果、本願の発明者らが考えている構成の絶縁検出装置を電源電圧の異常の検出に用いるとき、電源電圧の異常を判断するための判定値を、実際の電源電圧に基づいて決定すると、推定した電源電圧の実際の電源電圧に対する誤差が大きくなるに連れ、例えば実際には電源電圧が正常であるにも係わらず、絶縁検出装置で推定した電源電圧が判定値を越えた値を示し、電源異常と判断されてしまうといった問題が生じる可能性が大きくなる。一方、電源電圧の異常を判断するための判定値を、推定した電源電圧が実際の電源電圧に対して誤差に対応するマージンを実際の電源電圧に加えて決定すると、推定した電源電圧の実際の電源電圧に対する誤差が大きくなるに連れてマージンが大きくなるため、例えば実際の電源電圧は判定値を越えており異常であるにも係わらず、絶縁検出装置で推定した電源電圧が判定値よりも低い値を示し、電源異常を検出できなくなるといった問題が生じる可能性が大きくなる。
【０００９】
したがって、本願の発明者らが考えている構成の絶縁検出装置を電源電圧の異常の検出に用いるためには、実際の電源電圧に対する推定した電源電圧の誤差をできるだけ小さくする、すなわち推定した電源電圧の精度を向上する必要がある。
【００１０】
本発明の課題は、推定した電源電圧の精度を向上することにある。
【００１１】
【課題を解決するための手段】
本発明の絶縁検出装置は、正端子側及び負端子側の配線が接地電位部から絶縁された直流電源にコンデンサを直列に、このコンデンサが完全に充電される時間よりも短い第１の設定時間の間接続する第１のスイッチング手段と、電源の正端子と接地電位部との間にコンデンサを直列に第２の設定時間の間接続する第２のスイッチング手段と、接地電位部と電源の負端子との間にコンデンサを直列に第２の設定時間の間接続する第３のスイッチング手段と、第１、第２及び第３の各スイッチング手段の遮断後に前記コンデンサの両端子間の電圧を検出する検出手段を接続する第４のスイッチング手段と、第１のスイッチング手段を遮断後の前記検出手段での検出電圧に基づいて電源の電源電圧を推定し、この推定した電源電圧と第２及び第３のスイッチング手段を遮断後の検出手段での各検出電圧とに基づいて電源の接地電位部に対する絶縁抵抗を求める演算手段と、電源に変えて電源電圧が既知の基準電源を、電源の接地電位部に対する絶縁抵抗に対応させて抵抗値が既知の基準抵抗を接続した状態で、第１のスイッチング手段を遮断後の検出手段での検出電圧に基づいて基準電源の電源電圧を演算手段で推定し、この推定した基準電源の電源電圧と基準電源の既知の電源電圧とに基づいて、演算手段で推定した電源の電源電圧を補正する補正手段とを備えた構成とする。
【００１２】
このような構成とすれば、予め基準電源の電源電圧を演算させておくことにより、実際に電源の接地電位部に対する絶縁抵抗を演算する際に、補正手段が、演算手段で演算して推定した電源電圧を補正する。このため、コンデンサの容量などの製品間でのばらつきなどによって生じる実際の電源電圧に対する推定した電源電圧の誤差を小さくできる。したがって、推定した電源電圧の精度を向上できる。
【００１３】
また、上記の絶縁検出装置として、第１のスイッチング手段が、電源の正端子に接続された第１のスイッチ部と、電源の負端子に接続された第２のスイッチ部とを含み、第３のスイッチング手段が、第２のスイッチ部と、第１のスイッチに直列に接続された第３のスイッチ部とを含み、第２のスイッチング手段が、第１のスイッチ部と、第２のスイッチ部に直列に接続された第４のスイッチ部とを含み、第１のスイッチ部と第３のスイッチ部との間と、第２のスイッチ部と第４のスイッチ部との間とに、正側から負側に向かう方向に整流する第１のダイオード、第１の抵抗及びコンデンサが直列に接続され、第１のダイオード及び第１の抵抗に並列に、この第１ダイオードと逆方向に整流する第２のダイオード及び第２の抵抗が直列に接続されており、検出手段が、第３のスイッチ部と第４のスイッチ部との間に接続され、検出手段と第４のスイッチ部との間が接地電位部に接地されている回路構成とする。
【００１４】
さらに、演算手段は、この演算手段で求めた補正した電源電圧と第２及び第３のスイッチング手段を遮断後の検出手段での各検出電圧とに基づいて基準抵抗の抵抗値を求め、補正手段は、演算手段で求めた基準抵抗の抵抗値と基準抵抗の既知の抵抗値とに基づいて、演算手段で求めた電源の接地電位部に対する絶縁抵抗の値を補正する構成とする。
【００１５】
このような構成とすれば、電源の接地電位部に対する絶縁抵抗の演算に、電源の推定した電源電圧を用いることによって絶縁抵抗の計測誤差を低減できるのに加え、補正手段で、演算手段で演算した電源の接地電位部に対する絶縁抵抗の値を補正することによっても絶縁抵抗の計測誤差を低減できるため、絶縁状態の検出精度を一層向上できる。
【００１６】
さらに、検出手段、演算手段、及び補正手段が１つのマイクロコンピュータで形成され、マイクロコンピュータに設けられた補正モードポートには、この補正モードポートに印加される電圧を変える補正モード用スイッチング手段が接続され、この補正モード用スイッチング手段により補正モードポートに印加される電圧が変わることにより、マイクロコンピュータが補正手段として作動する補正モードに切り換えられる構成とする。このような構成とすれば、補正手段を備えた絶縁検出装置の構成を簡素化できる。
【００１７】
また、閉路したときに第２の抵抗をバイパスする経路を形成する第５のスイッチ部を含むバイパス手段を備えた構成とすれば、第４のスイッチング手段が閉路している状態でバイパス手段の第５のスイッチ部が閉路すると、コンデンサの放電時間を短縮できるため、絶縁状態の検出に要する時間を短縮できるので好ましい。
【００１８】
【発明の実施の形態】
以下、本発明を適用してなる絶縁検出装置の一実施形態について図１乃至図４を参照して説明する。図１は、本発明を適用してなる絶縁検出装置の概略構成を示す図である。図２は、本発明を適用してなる絶縁検出装置の絶縁抵抗の算出動作を示すフロー図である。図３は、各スイッチ部の動作に対するコンデンサの充放電状態と電圧の読み込みタイミングを示すタイムチャートである。図４は、絶縁抵抗の値に対する各電源電圧の計測時間で検出した絶縁抵抗の値の検出誤差を示す図である。図５は、本発明を適用してなる絶縁検出装置の補正モードにおける動作を示すフロー図である。
【００１９】
本実施形態の絶縁検出装置１は、図１に示すように、例えば電力を利用して推進力を得る電気推進車両などの電力源となる直流電源３に対して適用したものである。電源３は、複数の蓄電池などを直列接続したものや燃料電池などであり、電源３の正端子側の正側主回路配線５ａと負端子側の負側主回路配線５ｂとが、各々、接地電位部７、例えば車体などから絶縁されており、電源３は非接地電源となっている。絶縁検出装置１は、第１スイッチＳ１、第２スイッチＳ２、第３スイッチＳ３、第４スイッチＳ４、コンデンサ９、補正手段や検出手段及び演算手段などを兼ねると共に絶縁状態を判定するマイコン１１、そして各スイッチを設定された時間に応じて開閉制御する図示していないスイッチング制御回路などで構成されている。なお、図示していないスイッチング制御回路をマイコン１１に一体に含めるなど、検出手段、演算手段及びスイッチング制御回路などは、別体または一体に適宜形成できる。また、図１で示した第１スイッチＳ１、第２スイッチＳ２、第３スイッチＳ３、第４スイッチＳ４は、例えばリレーや半導体スイッチといった様々なスイッチ機能を有する部品からなるスイッチ部を接点として模式的に示したものである。
【００２０】
電源３の正側端子には、この正側端子から第１スイッチＳ１及び第３スイッチＳ３が順次直列に接続され、電源３の負側端子には、この負端子側から第２スイッチＳ２、第４スイッチＳ４及び第４抵抗Ｒ４が順次直列に接続されている。第１スイッチＳ１と第３スイッチＳ３との間から第２スイッチＳ２と第４スイッチＳ４との間には、第１ダイオードＤ１、第１抵抗Ｒ１及びコンデンサ９が順次直列に接続されている。第１抵抗Ｒ１とコンデンサ９との間から第１スイッチＳ１と第３スイッチＳ３との間には、第２ダイオードＤ２及び第２抵抗Ｒ２が順次直列に接続されている。すなわち、第１ダイオードＤ１及び第１抵抗Ｒ１と、第２ダイオードＤ２及び第２抵抗Ｒ２とは並列に接続されている。また、第２ダイオードＤ２と第２抵抗Ｒ２との間の部位から接地電位部７に、バイパス手段として、第５スイッチＳ５、そして第２抵抗Ｒ２よりも抵抗が低い第５抵抗Ｒ５が順次直列に接続されている。なお、第１ダイオードＤ１は、正側から負側に向かう方向に整流するものであり、第２ダイオードＤ２は、第１ダイオードＤ１と逆方向に整流するものである。
【００２１】
第３スイッチＳ３と第４抵抗Ｒ４間には、第３スイッチＳ３と第４抵抗Ｒ４に対して直列に第３抵抗Ｒ３が接続されており、第３スイッチＳ３と第３抵抗Ｒ３との間の部位には、直列に順次接続された第６スイッチＳ６と第６抵抗Ｒ６とを介してマイコン１１が、マイコン１１のアナログ／デジタル変換ポートつまりＡ／Ｄポートで接続されている。マイコン１１の補正モードポートには、一方の端子側が接地電位部７に設置された第７スイッチＳ７が接続されている。なお、マイコン１１のＡ／Ｄポートと第６抵抗Ｒ６との間の部位には、マイコン１１のＡ／Ｄポートに負電位が印加されるのを抑制するためのショットキーダイオードＳＤ１のカソードと、マイコン１１のＡ／Ｄポートに過剰な正電位が印加されるのを抑制するためのショットキーダイオードＳＤ２のアノードとが接続されている。ショットキーダイオードＳＤ１のアノードは、接地電位部７に設置され、ショットキーダイオードＳＤ２のカソードは、電源３の正側端子側に接続されている。また、第３抵抗Ｒ３と第４抵抗Ｒ４との間の部位は、接地電位部７に接地されている。
【００２２】
なお、本実施形態では、電源３にコンデンサ９を直列に第１の設定時間の間接続する第１のスイッチング手段は、第１スイッチＳ１、第２スイッチＳ２及び図示していないスイッチング制御回路などで形成されている。電源３の正端子と接地電位部７との間にコンデンサ９を直列に第２の設定時間の間接続する第２のスイッチング手段は、第１スイッチＳ１、第４スイッチＳ４及び図示していないスイッチング制御回路などで形成されている。接地電位部７と電源３の負端子との間にコンデンサ９を直列に第２の設定時間の間接続する第３のスイッチング手段は、第２スイッチＳ２、第３スイッチＳ３及び図示していないスイッチング制御回路などで形成されている。第４のスイッチング手段は、第３スイッチＳ３、第４スイッチＳ４及び図示していないスイッチング制御回路などで形成されている。さらに、マイコン１１の補正機能を作動させてマイコン１１を補正モードに切り換える補正モード用スイッチング手段は、第７スイッチＳ７及び図示していないスイッチング制御回路などで形成されている。また、コンデンサ９には、例えば数μＦといった比較的高容量のものが用いられ、第１抵抗Ｒ１と第２抵抗Ｒ２には、例えば数百ｋΩといった比較的高い抵抗値のものが用いられている。
【００２３】
このような構成の絶縁検出装置の動作と本発明の特徴部について説明する。絶縁検出装置１による接地電位部７に対する絶縁状態の検出動作において、絶縁検出装置１は、図２及び図３に示すように、絶縁状態の検出を開始すると、図示していないスイッチング制御回路が第１スイッチＳ１及び第２スイッチＳ２を第１の設定時間である第１閉路時間Ｔ１の間、閉路する（ステップ１０１）。すなわち、第１のスイッチング手段により、接地電位部７を介さずに電源３にコンデンサ９を直列に接続する回路が形成され、第１閉路時間Ｔ１の間、コンデンサ９への充電が行われ、コンデンサ９の両端子間の電圧ＶＣが上昇する。なお、第１閉路時間Ｔ１は、コンデンサ９を完全に充電するのに必要な時間よりも短い時間に設定されており、例えばコンデンサ９を完全に充電するのに必要な時間の１／５〜１／１０といったような短い時間となっており、第１閉路時間Ｔ１は、必要とされる絶縁抵抗の計測誤差範囲によって選択されたものである。
【００２４】
ステップ１０１において第１閉路時間Ｔ１が経過すると、第１スイッチＳ１及び第２スイッチＳ２が開路つまり遮断され、第１閉路時間Ｔ１よりも短い所定時間ｔｗ１経過後、第３スイッチＳ３及び第４スイッチＳ４が閉路される（ステップ１０３）。すなわち、第４のスイッチング手段により、コンデンサ９の両端子間の電圧を検出するマイコン１１が接続された回路が形成されると共に、第２抵抗Ｒ２、第３抵抗Ｒ３、そして第４抵抗Ｒ４を含むコンデンサ９からの放電回路が形成される。第３スイッチＳ３及び第４スイッチＳ４が閉路されてから第１閉路時間Ｔ１よりも短い所定時間ｔｗ２経過後、マイコン１１は、Ａ／Ｄポートを介してＡ／Ｄ変換データ、つまりコンデンサ９の両端子間の電圧ＶＣを読み込む（ステップ１０５）。このときのコンデンサ９の両端子間電圧ＶＣの値つまり検出電圧Ｖ０により、次式（１）から推定の電源電圧Ｖ０ｓを算出する（ステップ１０７）。
Ｖ０ｓ＝〔Ｖ０／｛１−ＥＸＰ（−Ｔ１／Ｃ・Ｒ１）｝〕・ａ …（１）
ただし、式（１）において、Ｔ１は第１スイッチＳ１及び第２スイッチＳ２の閉路時間、Ｃはコンデンサ９の容量、Ｒ１は第１抵抗Ｒ１の抵抗値、ａは後述する補正値である。
【００２５】
一方、図示していないスイッチング制御回路は、ステップ１０５でコンデンサ９の両端子間の電圧ＶＣを検出した後、第３スイッチＳ３及び第４スイッチＳ４が閉路された状態で、第５スイッチＳ５を閉路して第２抵抗Ｒ２をバイパスさせる。これにより、第２抵抗Ｒ２よりも抵抗値が低い第５抵抗Ｒ５を介して放電されるため、コンデンサ９からの放電量が増大してコンデンサ９の両端子間の電圧ＶＣの降下割合が増大し、コンデンサ９からの放電に要する時間を短縮できる。第５スイッチＳ５を閉路して、第１閉路時間Ｔ１よりも短い所定時間ｔｄ１経過後、第５スイッチＳ５を開路つまり遮断した後、マイコン１１は、Ａ／Ｄポートを介してＡ／Ｄ変換データ、つまりコンデンサ９の両端子間の電圧ＶＣを読み込む（ステップ１０９）。
【００２６】
ステップ１０９で電圧ＶＣが０Ｖであることが確認されたら、図示していないスイッチング制御回路は、第３スイッチＳ３を開路し、所定時間ｔｗ１経過後に第１スイッチＳ１を閉路する。そして、第１スイッチＳ１及び第４スイッチＳ４を第２の設定時間である第２閉路時間Ｔ２の間、閉路する（ステップ１１１）。すなわち、第２のスイッチング手段により、電源３の正端子と接地電位部７との間にコンデンサ９を直列に接続した回路、つまり、図１に示すように、正側主回路配線５ａ、第１スイッチＳ１、第１ダイオードＤ１、第１抵抗Ｒ１、コンデンサ９、第４スイッチＳ４、第４抵抗Ｒ４、接地電位部７、そして図１において点線で示すような位置に仮定される負端子側の地絡抵抗Ｒｎ、負側主回路配線５ｂを順次直列に電源３に接続した回路が形成される。これにより、第２閉路時間Ｔ２の間、コンデンサ９への充電が行われ、図３に示すように、地絡抵抗Ｒｎの値に応じてコンデンサ９の両端子間の電圧ＶＣが上昇する。なお、第２の設定時間である第２閉路時間Ｔ２も、第１閉路時間Ｔ１と同様に、コンデンサ９を完全に充電するのに必要な時間よりも短く、所定時間ｔｗ１、ｔｗ２、ｔｄ１よりも長い時間に設定されている。
【００２７】
ステップ１１１において第２閉路時間Ｔ２が経過すると、図２及び図３に示すように、第１スイッチＳ１が開路つまり遮断され、所定時間ｔｗ１経過後、第３スイッチＳ３が閉路され、第３スイッチＳ３及び第４スイッチＳ４が閉路された状態となる。すなわち、第４のスイッチング手段により、コンデンサ９の両端子間の電圧を検出するマイコン１１が接続された回路が形成されると共に、第２抵抗Ｒ２、第３抵抗Ｒ３、そして第４抵抗Ｒ４を含むコンデンサ９からの放電回路が形成される。この状態で、マイコン１１は、Ａ／Ｄポートを介してＡ／Ｄ変換データ、つまりコンデンサ９の両端子間の電圧ＶＣを読み込む（ステップ１１３）。このときのコンデンサ９の両端子間電圧ＶＣの値を検出電圧ＶＣＮとする。
【００２８】
一方、図示していないスイッチング制御回路は、ステップ１１５でコンデンサ９の両端子間の電圧ＶＣを検出した後、第３スイッチＳ３及び第４スイッチＳ４が閉路された状態で、第５スイッチＳ５を閉路して第２抵抗Ｒ２をバイパスさせ、コンデンサ９からの放電に要する時間を短縮する。第５スイッチＳ５を閉路して、第２閉路時間Ｔ２よりも短い所定時間ｔｄ２経過後、第５スイッチＳ５を開路つまり遮断した後、マイコン１１は、Ａ／Ｄポートを介してＡ／Ｄ変換データ、つまりコンデンサ９の両端子間の電圧ＶＣを読み込む（ステップ１１５）。
【００２９】
ステップ１１５で電圧ＶＣが０Ｖであることが確認されたら、図示していないスイッチング制御回路は、第４スイッチＳ４を開路し、所定時間ｔｗ１経過後、第２スイッチＳ２を閉路する。そして、第２スイッチＳ２及び第３スイッチＳ３を第２の設定時間である第２閉路時間Ｔ２の間、閉路する（ステップ１１７）。すなわち、第３のスイッチング手段により、接地電位部７と電源３の負端子との間にコンデンサ９を直列に接続した回路、つまり、図１に示すように、正側主回路配線５ａ、図１において点線で示すような位置に仮定される正端子側の地絡抵抗Ｒｐ、接地電位部７、第３抵抗Ｒ３、第３スイッチＳ３、第１ダイオードＤ１、第１抵抗Ｒ１、コンデンサ９、第２スイッチＳ２、そして負側主回路配線５ｂを順次直列に電源３に接続した回路が形成される。これにより、第２閉路時間Ｔ２の間、コンデンサ９への充電が行われ、図３に示すように、地絡抵抗Ｒｐの値に応じてコンデンサ９の両端子間の電圧ＶＣが上昇する。
【００３０】
なお、ステップ１１７で第２スイッチＳ２及び第３スイッチＳ３を第２の設定時間である第２閉路時間Ｔ２の間閉路する際、第６スイッチＳ６を開路つまり遮断する。第６スイッチＳ６は、通常は閉路されており、マイコン１１のＡ／Ｄポートには、第３スイッチＳ３と第３抵抗Ｒ３との間の部位の電圧が印可される状態となっている。しかし、第６スイッチＳ６は、第２スイッチＳ２及び第３スイッチＳ３が閉路する間は遮断され、マイコン１１のＡ／Ｄポートには、第３スイッチＳ３と第３抵抗Ｒ３との間の部位の電圧が印可されない状態となる。すなわち、第２スイッチＳ２及び第３スイッチＳ３が閉路している間、第３スイッチＳ３と第３抵抗Ｒ３との間の部位は、負電位となるが、第６スイッチＳ６が第２スイッチＳ２及び第３スイッチＳ３が閉路する間遮断されることにより、この負電位がマイコン１１のＡ／Ｄポートに印可されるのを防いでいる。
【００３１】
ステップ１１７において第２閉路時間Ｔ２が経過すると、図２及び図３に示すように、第２スイッチＳ２が開路つまり遮断され、所定時間ｔｗ１経過後、第４スイッチＳ４が閉路され、第３スイッチＳ３及び第４スイッチＳ４が閉路された状態となる。すなわち、第４のスイッチング手段により、コンデンサ９の両端子間の電圧を検出するマイコン１１が接続された回路が形成されると共に、第２抵抗Ｒ２、第３抵抗Ｒ３、そして第４抵抗Ｒ４を含むコンデンサ９からの放電回路が形成される。そして、第４スイッチＳ４が閉路されてから所定時間ｔｗ２経過後、マイコン１１は、Ａ／Ｄポートを介してＡ／Ｄ変換データ、つまりコンデンサ９の両端子間の電圧ＶＣを読み込む（ステップ１１９）。このときのコンデンサ９の両端子間電圧ＶＣの値を検出電圧ＶＣＰとする。
【００３２】
ここで、マイコン１１は、ステップ１１３、１１９で検出したＶＣＮ、ＶＣＰを用いて、以下の式（２）から、電源３の接地電位部７となる車体などに対する絶縁抵抗、すなわち地絡抵抗Ｒｎ、Ｒｐを代表する地絡抵抗値ＲＬを算出する（ステップ１２１）。
ＲＬ＝〔−Ｒ１−Ｔ２／Ｃ・ｌｎ｛１−（ＶＣＰ＋ＶＣＮ）／Ｖ０ｓ｝〕・ｂ…（２）
ただし、式（２）において、Ｔ２は第２閉路時間、Ｃはコンデンサ９の容量、Ｒ１は第１抵抗Ｒ１の抵抗値、Ｖ０ｓはステップ１２１で推定した電源電圧、ｂは後述する補正値である。
【００３３】
一方、図示していないスイッチング制御回路は、ステップ１１９でコンデンサ９の両端子間の電圧ＶＣを検出した後、第３スイッチＳ３及び第４スイッチＳ４が閉路された状態で、第５スイッチＳ５を閉路して第２抵抗Ｒ２をバイパスさせ、コンデンサ９からの放電に要する時間を短縮する。第５スイッチＳ５を閉路して所定時間ｔｄ２経過後、第５スイッチＳ５を開路つまり遮断した後、マイコン１１は、Ａ／Ｄポートを介してＡ／Ｄ変換データ、つまりコンデンサ９の両端子間の電圧ＶＣを読み込む（ステップ１２３）。そして、ステップ１２５で電圧ＶＣが０Ｖであることが確認された時点で、１回の絶縁状態の検出サイクルを終了する。また、絶縁状態の検出を行う間、ステップ１０１からステップ１２３までの絶縁状態の検出サイクルを繰り返す。
【００３４】
マイコン１１は、１回の絶縁状態の検出サイクルで求めた地絡抵抗値ＲＬから絶縁状態を判定する。例えば、地絡抵抗値ＲＬと、予め絶縁状態を判定するために定めた基準となる地絡抵抗の値つまり基準抵抗値とを比較し、地絡抵抗値ＲＬが基準抵抗値以下になっている場合には、絶縁不良が生じていると判定する。
【００３５】
ところで、式（２）などからわかるように、コンデンサ９の容量Ｃ、さらに第１抵抗Ｒ１の抵抗値Ｒ１が製品間差や温度変化などによりばらつくと、地絡抵抗値ＲＬの計測精度に影響し、検出した地絡抵抗値ＲＬの精度が低下してしまう。したがって、絶縁状態の検出精度が低下してしまうことになる。特にコンデンサ９は、浮遊容量を考慮すると数μＦといった比較的大きな値のものが必要となるため、例えば製品間差において±５％程度のばらつきがあるとすると、これに温度変化を考慮すると±１０％程度のばらつきが生じる場合があり、このようなコンデンサ９の容量のばらつきが絶縁状態の検出精度を低下させてしまうことになる。加えて、経時変化による部品定数の変化によって生じるばらつきなども絶縁状態の検出精度を低下させてしまうことになる。
【００３６】
しかし、本実施形態の絶縁検出装置１では、絶縁検出のサイクルの最初の段階で第１スイッチＳ１と第２スイッチＳ２を、コンデンサ９を完全に充電するのに要する時間よりも短い第１閉路時間Ｔ１の間閉路することにより、電源３の電源電圧を推定している。第１スイッチＳ１と第２スイッチＳ２を短時間閉路してコンデンサ９を充電する場合は、実際のコンデンサ９の容量と抵抗Ｒ１の抵抗値とで決定される時定数Ｃ・Ｒ１で充電されるときの充電到達電圧を推定する方式であるため、推定した電源電圧Ｖ０ｓは、実際の電源３の電源電圧ではなく、コンデンサ９と抵抗Ｒ１の容量及び抵抗値の誤差、つまりばらつきを含んだ値となる。そして、このばらつきを含む推定した電源電圧Ｖ０ｓを、絶縁検出のサイクルにおける以降に続くステップ１２１で行う地絡抵抗値ＲＬの演算に用いることで、コンデンサ９の容量のばらつきに対する補正が行われ、コンデンサ９の容量のばらつきによって生じる実際の地絡抵抗の値と、算出した地絡抵抗値ＲＬとの誤差を低減することができる。したがって、絶縁状態の検出精度を向上できる。
【００３７】
ここで、本実施形態の絶縁検出装置１によって計測した地絡抵抗値ＲＬと、実際の地絡抵抗の値との誤差をある所定の規格容量を有するコンデンサ９、そしてある所定の規格抵抗値を有する第１抵抗Ｒ１を用いた場合を想定して計算した結果を図４に示す。なお、コンデンサ９は、製品間差と温度変化を考慮して±１０％程度の容量のばらつきが、第１抵抗Ｒ１は、製品間差と温度変化を考慮して±２％程度の容量のばらつきがあるものとする。図４において、Ｖ０計測時間は、第１閉路時間を意味し、したがって、図４では、第１閉路時間Ｔ１をｔ秒、２ｔ秒、そして３ｔ秒、ただしｔ＜２ｔ＜３ｔとした場合の計測誤差を示している。なお、図４は、縦軸を検出精度つまり検出誤差、横軸を地絡抵抗の値として計算結果をグラフ化したものである。
【００３８】
図４からわかるように、従来の絶縁検出装置で検出した場合、つまり推定した電源電圧を用いていない場合に比べて、本実施形態の絶縁検出装置１で検出した場合、つまり推定した電源電圧を用いた場合の方が各地絡抵抗値に対して計測誤差が低減されている。さらに、Ｖ０計測時間つまり第１閉路時間Ｔ１の設定によって計測誤差の低減度合いが異なっており、第１閉路時間Ｔ１がｔ秒のときには、地絡抵抗が小さくなるにしたがって誤差が大きくなるが、地絡抵抗が大きくなるにしたがって誤差が小さくなっている。第１閉路時間Ｔ１が２ｔ秒のときには、地絡抵抗が大きい場合には、第１閉路時間Ｔ１がｔ秒のときよりも誤差が大きくなるが、各地絡抵抗にわたって平均的に誤差が小さくなっている。第１閉路時間Ｔ１が３ｔ秒のときにも各地絡抵抗にわたって平均的に誤差が小さくなっているが、誤差は、第１閉路時間Ｔ１が２ｔ秒のときよりも大きい。
【００３９】
したがって、絶縁不良を判定するための基準抵抗値の設定を比較的大きな値とする場合には、第１閉路時間Ｔ１をｔ秒とするのが好ましく、絶縁不良を判定するための基準抵抗値の設定を比較的小さな値とする場合には、第１閉路時間Ｔ１を２ｔ秒とするのが好ましい。このように、第１閉路時間Ｔ１つまり第１の設定時間は、基準抵抗値周辺で計測誤差が小さくなるように選択するのが好ましい。例えば、図４において基準抵抗値をＲΩに設定したとすれば、第１閉路時間Ｔ１として２ｔ秒を選択するのが好ましく、このとき、従来の絶縁検出装置では±１０％以上の計測誤差があるのに対し、本実施形態の絶縁検出装置１では、±２％以下の計測誤差となり、絶縁状態の検出精度を向上できることになる。
【００４０】
一方、本実施形態の絶縁検出装置１では、式（１）に定数としてコンデンサ９の容量Ｃ、さらに第１抵抗Ｒ１の抵抗値Ｒ１が含まれていることなどからわかるように、コンデンサ９の容量Ｃ、さらに第１抵抗Ｒ１の抵抗値Ｒ１に製品間差などによりばらつきがあると、絶縁検出装置１で推定した電源３の電源電圧に誤差が生じることとなる。このため、本実施形態の絶縁検出装置１では、例えば工場での生産過程や車両への組み付け前、さらに車両の定期検査時などに、マイコン１１で推定した電源電圧を補正するための補正作業を行うことができる。
【００４１】
絶縁検出装置１の補正作業を行う場合、図５に示すように、既知の電源電圧を有する基準電源と、既知の抵抗値を有する基準抵抗とを絶縁検出装置１に接続する。このとき、基準電源は、図１における電源３に相当する位置に、基準抵抗は、図１における正端子側の地絡抵抗Ｒｐ及び負端子側の地絡抵抗Ｒｎに対応させた位置に接続する（ステップ２０１）。
【００４２】
ステップ２０１で基準電源と基準抵抗とを絶縁検出装置１に接続した後、図５に示すように、補正手段となるマイコン１１の補正モードポートに接続された第７スイッチＳ７を閉路つまりオンする（ステップ２０３）。第７スイッチＳ７が開路つまり遮断された状態では、補正モードポートに所定の正電位が印加されているが、第７スイッチＳ７をオンすることによって補正モードポートの印加電位が０Ｖとなり、マイコン１１は、これを補正モードの開始指令としている。したがって、第７スイッチＳ７をオンすることで、マイコン１１の補正機能つまり補正プログラムがスタートする。ステップ２０３で補正機能がスタートすると、図２に示す絶縁状態の検出動作の内、ステップ１０１からステップ１０９を行い、前述の式（１）から電源電圧Ｖ０ｓを推定する。そして、推定した電源電圧Ｖ０ｓと予めマイコン１１に入力されている基準電源の既知の電源電圧とに差がないか比較する（ステップ２０５）。なお、ステップ２０５において前述の式（１）で最初に電源電圧Ｖ０ｓを推定する場合、式（１）の補正値ａは、１としており、最初に推定した電源電圧Ｖ０ｓは補正されていない状態となっている。
【００４３】
ステップ２０５において、推定した電源電圧Ｖ０ｓと基準電源の既知の電源電圧とに差がある場合には、例えば基準電源の既知の電源電圧に対する推定した電源電圧Ｖ０ｓの比率などから補正値ａを算出する（ステップ２０７）。ステップ２０７の後、ステップ２０５に戻り、ステップ２０７で算出した補正値ａを用いて前述の式（１）から補正した電源電圧Ｖ０ｓを算出し、この補正した電源電圧Ｖ０ｓと、予めマイコン１１に入力されている基準電源の既知の電源電圧とに差がないか再度比較する。このように、補正した電源電圧Ｖ０ｓと、予めマイコン１１に入力されている基準電源の既知の電源電圧との差がなくなるまで、ステップ２０５とステップ２０７が繰り返される。
【００４４】
一方、ステップ２０５において、推定した電源電圧Ｖ０ｓと予めマイコン１１に入力されている基準電源の既知の電源電圧とに差がない場合、またはステップ２０７で算出した補正値ａで補正した電源電圧Ｖ０ｓと予めマイコン１１に入力されている基準電源の既知の電源電圧とに差がなくなった場合には、図２に示す絶縁状態の検出動作の内、ステップ１１１からステップ１２３を行い、前述の式（２）から地絡抵抗値ＲＬを算出する。そして、算出した地絡抵抗値ＲＬと予めマイコン１１に入力されている基準抵抗の既知の抵抗値とに差がないか比較する（ステップ２０９）。なお、ステップ２０９において前述の式（２）で最初に地絡抵抗値ＲＬを算出する場合、式（２）の補正値ｂは、１としており、最初に算出した地絡抵抗ＲＬは補正されていない状態となっている。
【００４５】
ステップ２０９において、算出した地絡抵抗値ＲＬと基準抵抗の既知の抵抗値とに差がある場合には、例えば基準抵抗の既知の抵抗値に対する算出した地絡抵抗値ＲＬの比率などから補正値ｂを算出する（ステップ２１１）。ステップ２１１の後、ステップ２０９に戻り、ステップ２１１で算出した補正値ｂを用いて前述の式（２）から補正した地絡抵抗値ＲＬを算出し、この補正した地絡抵抗値ＲＬと、予めマイコン１１に入力されている基準抵抗の既知の抵抗値とに差がないか再度比較する。このように、補正した地絡抵抗値ＲＬと、予めマイコン１１に入力されている基準抵抗の既知の抵抗値との差がなくなるまで、ステップ２０９とステップ２１１が繰り返される。
【００４６】
一方、ステップ２１１において、ステップ２０９で算出した地絡抵抗値ＲＬと予めマイコン１１に入力されている基準抵抗の既知の抵抗値とに差がない場合、またはステップ２１１で算出した補正値ｂで補正した地絡抵抗値ＲＬと予めマイコン１１に入力されている基準抵抗の既知の抵抗値とに差がなくなった場合には、補正モードを終了するため、補正機能を果たすプログラムを終了し（ステップ２１３）、補正作業を終了する。
【００４７】
そして、実際に絶縁状態の検出動作を行うとき、マイコン１１は、図２に示すような電源３の電源電圧を推定するステップ１０７において、前述の式（１）の補正値ａとして、この補正モードで算出した補正値ａを、前述の式（２）の補正値ｂとして、この補正モードで算出した補正値ｂを用いて、各々推定した電源電圧Ｖ０ｓ及び地絡抵抗値ＲＬを算出する。
【００４８】
なお、本実施形態の絶縁検出装置１では、コンデンサ９の容量Ｃや第１抵抗Ｒ１の抵抗値Ｒ１などの製品間のばらつきにより生じる、実際の電源３の電源電圧に対する推定した電源電圧の誤差を低減することができる。しかし、実際の電源３の電源電圧に対する推定した電源電圧の誤差を生じるもう一つの要因として、絶縁検出装置１の周囲の温度変化によるコンデンサ９の容量Ｃや第１抵抗Ｒ１の抵抗値Ｒ１などの変化がある。したがって、絶縁検出装置１の周囲の温度変化により生じる実際の電源３の電源電圧に対する推定した電源電圧の誤差が、コンデンサ９の容量Ｃや第１抵抗Ｒ１の抵抗値Ｒ１などの製品間のばらつきにより生じる誤差よりも大きなものである場合には、マイコン１１に温度センサポートを設け、この温度センサポートに絶縁検出装置１周囲の温度を検出する温度センサ、例えばサーミスタなどの感温素子などを接続する。そして、複数の温度条件、例えば高温条件と低温条件といった２点の温度条件に絶縁検出装置１を置いた状態で、各々補正モードの動作を行うことにより、温度補償を考慮した補正値ａ、ｂを算出することができる。
【００４９】
このように本実施形態の絶縁検出装置１では、マイコン１１が補正機能を有しており、補正手段となるため、絶縁検出装置１に電圧が既知の基準電源と抵抗値が既知の基準抵抗を接続した状態で絶縁状態の検出動作を行うことで、電源３の推定した電源電圧を補正するための補正値ａを算出するができる。そして、実際に絶縁検出装置１で電源３の絶縁状態の検出を行う際に、この補正値ａにより推定した電源電圧Ｖ０ｓの算出時に値を補正することで、コンデンサ９の容量Ｃや第１抵抗Ｒ１の抵抗値Ｒ１などの製品間でのばらつきなどによって生じる電源３の実際の電源電圧に対する推定した電源電圧Ｖ０ｓの誤差を小さくできる。したがって、推定した電源電圧の精度を向上できる。
【００５０】
さらに、推定した電源電圧の精度を向上できることにより、電源電圧の異常を検出するための判定値を、実際の電源電圧の値に近づける、言い換えればマージンを小さくできるため、電源電圧の異常を正確に検出できないといった問題を生じ難くできる。したがって、本実施形態の絶縁検出装置１は、値絡抵抗の測定や絶縁状態の検出だけでなく、電源電圧の異常を判定するための電源電圧の検出装置としても用いることができ、またこれにより、絶縁検出装置の用途を広げることができる。加えて、経時的に補正モードを実施して補正値ａを更新することで、コンデンサ９や第１抵抗Ｒ１の経時的劣化により容量Ｃや抵抗値Ｒ１に変化が生じても、電源電圧の推定精度を維持できる。さらに、コンデンサ９や第１抵抗Ｒ１に容量Ｃや抵抗値Ｒ１のばらつきが比較的大きい精度の低い部品を使用しても、電源電圧の推定精度を向上できる。
【００５１】
さらに、本実施形態の絶縁検出装置１では、マイコン１１の補正機能が、算出した地絡抵抗値ＲＬを補正するための補正値ｂを算出する機能も有している。したがって、実際に絶縁検出装置１で電源３の絶縁状態の検出を行う際に、この補正値ｂにより地絡抵抗値ＲＬの算出時に算出した値の補正を行うことで、コンデンサ９の容量Ｃや第１抵抗Ｒ１の抵抗値Ｒ１などの製品間でのばらつきなどによって生じる電源３の実際の地絡抵抗に対する算出した地絡抵抗値ＲＬの誤差を小さくできる。したがって、推定した電源電圧Ｖ０ｓを用いることによって地絡抵抗の計測誤差を低減できるのに加え、マイコン１１で、地絡抵抗値ＲＬを補正することによっても地絡抵抗値ＲＬの計測誤差を低減できるため、絶縁状態の検出精度を一層向上できる。ただし、推定した電源電圧の精度の向上のみを目的とする場合には、補正値ｂによる地絡抵抗値ＲＬの補正を行わない構成にすることもできる。
【００５２】
ところで、本実施形態の絶縁検出装置１では、第２スイッチＳ２及び第３スイッチＳ３が閉路している間、第３スイッチＳ３と第３抵抗Ｒ３との間の部位は、負電位となる。このため、第２スイッチＳ２及び第３スイッチＳ３が閉路している間、負電位がマイコン１１のＡ／Ｄポートに印可され、マイコン１１が破損する可能性がある。このような負電位がマイコン１１のＡ／Ｄポートに印可されるのを抑制するめに、ショットキーダイオードＳＤ１が設けられている。しかし、絶縁検出装置１の周囲温度によってショットキーダイオードＳＤ１の特性は変化するため、絶縁検出装置１の周囲温度によってショットキーダイオードＳＤ１のマイコン１１のＡ／Ｄポートへの負電位の印可の抑制能力は変化してしまう。したがって、ショットキーダイオードＳＤ１では、マイコン１１のＡ／Ｄポートへの負電位の印可を防げずマイコン１１が破損する場合がある。
【００５３】
これに対して、本実施形態の絶縁検出装置１では、第３スイッチＳ３と第３抵抗Ｒ３との間の部位とマイコン１１のＡ／Ｄポートとの間に第６スイッチＳ６を設け、少なくとも第２スイッチＳ２及び第３スイッチＳ３が閉路し、マイコン１１がＡ／Ｄポートを介してＡ／Ｄ変換データを読み込むときに第６スイッチＳ６を開路する構成としている。これにより、マイコン１１のＡ／Ｄポートに負電位が印可される可能性がある場合に、マイコン１１のＡ／Ｄポートへの通電を遮断できるので、マイコン１１の破損を防ぐことができる。なお、第６スイッチＳ６を設けた場合、ショットキーダイオードＳＤ１がマイコン１１の破損の抑制のみに用いられているものであれば、ショットキーダイオードＳＤ１を設けていない構成にすることもできる。
【００５４】
さらに、本実施形態の絶縁検出装置１では、閉路したときに第２抵抗Ｒ２をバイパスする経路を形成する第５スイッチＳ５を含むバイパス手段を備えているため、マイコン１１によるコンデンサ９の両端子間の電圧の検出後に第５スイッチＳ５を閉路することで、コンデンサ９からの放電時間を短縮することができる。したがって、絶縁検出のための１サイクルに要する時間を短縮することができ、単位時間当たりの絶縁検出の回数を増やし、絶縁検出の精度をさらに向上できる。
【００５５】
なお、第５スイッチＳ５を含むバイパス手段としては、本実施形態の構成に限らず、バイパス手段は、図６に示すように、第２抵抗Ｒ２の両端子間に、第２抵抗Ｒ２と並列に第５スイッチＳ５が接続されている構成にすることもできる。また、絶縁検出のための１サイクルに要する時間の短縮などの必要性がない場合などには、第５スイッチＳ５を含むバイパス手段を設けない構成にすることもできる。
【００５６】
また、本実施形態では、電源３の正端子側の地絡抵抗Ｒｐと負端子側の地絡抵抗Ｒｎを代表する地絡抵抗値ＲＬを算出している。しかし、個別の式により電源電圧Ｖ０ｓと検出電圧ＶＣＰ、ＶＣＮなどとに基づいて電源３の正端子側の地絡抵抗Ｒｐと負端子側の地絡抵抗Ｒｎを個々に推定し、絶縁不良の部位も検出できるようにすることもできる。
【００５７】
また、本実施形態の絶縁検出装置１では、演算手段となるマイコン１１によって式（１）や式（２）によって推定した電源電圧Ｖ０ｓや地絡抵抗値ＲＬを演算している。しかし、これらの式（１）や式（２）といった複雑な関数式の演算にかかる時間を短縮するため、マイコン１１の記憶手段となるメモリなどにアドレスに対応させて推定した電源電圧Ｖ０ｓや地絡抵抗値ＲＬなどを記憶した電源電圧用データテーブルや地絡抵抗値用データテーブルなどを準備し、演算手段であるマイコン１１で各々のデータテーブルに対応したアドレスを演算する構成にすることもできる。このとき、演算手段であるマイコン１１は、電源電圧を推定するために検出したコンデンサ９の両端子間電圧ＶＣの値つまり検出電圧Ｖ０、推定した電源電圧Ｖ０ｓ及び地絡抵抗値ＲＬを求めるために検出したコンデンサ９の両端子間電圧ＶＣの値つまり検出電圧ＶＣＮ、ＶＣＰなどから、式（１）や式（２）よりも簡単なアドレスの演算式により、各々電源電圧用データテーブルのアドレス、地絡抵抗値用データテーブルのアドレスを算出し、この算出した各々のアドレスから推定した電源電圧Ｖ０ｓや地絡抵抗値ＲＬを決定する。
【００５８】
なお、このような電源電圧用データテーブルや地絡抵抗値用データテーブルを用いて推定した電源電圧Ｖ０ｓや地絡抵抗値ＲＬを求める構成の絶縁検出装置に本願発明を適用する場合のマイコン１１の補正モードの動作について以下に説明する。ここでは、図５に示した動作と同じ動作を行うステップには同じ符号を付して説明を省略し、図５と異なる動作のみを説明する。推定した電源電圧の補正では、図７に示すように、ステップ２０３でマイコンを補正モードにした後、電源電圧用データテーブルに対するアドレスを算出する。そして、この電源電圧用データテーブルに対するアドレスにより電源電圧用データテーブルから電源電圧Ｖ０ｓを求め、この電源電圧用データテーブルから求めた電源電圧Ｖ０ｓと基準電源の既知の電源電圧とを比較する（ステップ２１５）。
【００５９】
ステップ２１５において電源電圧用データテーブルから求めた電源電圧Ｖ０ｓと基準電源の既知の電源電圧とに差がある場合には、ステップ２１５で算出した電源電圧用データテーブルに対するアドレスをシフトする（ステップ２１７）。ステップ２１７の後、ステップ２１５に戻り、ステップ２１７でシフトした電源電圧用データテーブルに対するアドレスにより電源電圧用データテーブルから補正した電源電圧Ｖ０ｓを求め、この補正した電源電圧Ｖ０ｓと、予めマイコン１１に入力されている基準電源の既知の電源電圧とに差がないか再度比較する。このように、補正した電源電圧Ｖ０ｓと、予めマイコン１１に入力されている基準電源の既知の電源電圧との差がなくなるまで、ステップ２１７で電源電圧用データテーブルに対するアドレスをシフトし、ステップ２１５で補正した電源電圧Ｖ０ｓを求める動作が繰り返される。
【００６０】
一方、地絡抵抗値の補正では、地絡抵抗値用データテーブルに対するアドレスを算出する。そして、この地絡抵抗値用データテーブルに対するアドレスにより地絡抵抗値用データテーブルから地絡抵抗値ＲＬを求め、この地絡抵抗値用データテーブルから求めた地絡抵抗値ＲＬと基準抵抗の既知の抵抗値とを比較する（ステップ２１９）。ステップ２１９において地絡抵抗値用データテーブルから求めた地絡抵抗値ＲＬと基準抵抗の既知の抵抗値とに差がある場合には、ステップ２１９で算出した地絡抵抗値用データテーブルに対するアドレスをシフトする（ステップ２２１）。
【００６１】
ステップ２２１の後、ステップ２１９に戻り、ステップ２２１でシフトした地絡抵抗値用データテーブルに対するアドレスにより地絡抵抗値用データテーブルから補正した地絡抵抗値ＲＬを求め、この補正した地絡抵抗値ＲＬと、予めマイコン１１に入力されている基準抵抗の既知の抵抗値とに差がないか再度比較する。このように、補正した地絡抵抗値ＲＬと、予めマイコン１１に入力されている基準抵抗の既知の抵抗値との差がなくなるまで、ステップ２２１で地絡抵抗値用データテーブルに対するアドレスをシフトし、ステップ２１９で補正した地絡抵抗値ＲＬを求める動作が繰り返される。
【００６２】
また、本実施形態の絶縁検出装置１では、第６スイッチＳ６は、通常は閉路されており、マイコン１１のＡ／Ｄポートに第３スイッチＳ３と第３抵抗Ｒ３との間の部位の電圧が印可される状態となっているが、第２スイッチＳ２及び第３スイッチＳ３が閉路する間は遮断され、マイコン１１のＡ／Ｄポートに第３スイッチＳ３と第３抵抗Ｒ３との間の部位の電圧が印可されない状態とする。しかし、第６スイッチＳ６は、図８に示すように、通常は開路され、第３スイッチＳ３と第４スイッチＳ４とが閉路された状態で、マイコン１１がＡ／Ｄポートを介してＡ／Ｄ変換データを読み込むときにのみ閉路され、マイコン１１のＡ／Ｄポートに第３スイッチＳ３と第３抵抗Ｒ３との間の部位の電圧が印可される構成にすることもできる。このような構成とすれば、マイコン１１のＡ／Ｄポートへの負電位の印可を防ぐだけでなく、マイコン１１のＡ／Ｄポートへ不要なノイズやその他のストレスが印可されるのを抑制することもできる。
【００６３】
また、本発明は、本実施形態において示した回路構成に限らず、正端子側及び負端子側の配線が接地電位部から絶縁された直流電源にコンデンサを直列に第１の設定時間の間接続する第１のスイッチング手段、電源の正端子と接地電位部との間に前記コンデンサを直列に第２の設定時間の間接続する第２のスイッチング手段、電源の負端子と接地電位部との間にコンデンサを直列に第２の設定時間の間接続する第３のスイッチング手段、第１、第２及び第３の各スイッチング手段の遮断後にコンデンサの両端子間の電圧を検出する検出手段を接続する第４のスイッチング手段などをそなえていれば様々な回路構成の絶縁検出装置に適用することができる。
【００６４】
【発明の効果】
本発明によれば、推定した電源電圧の精度を向上できる。
【図面の簡単な説明】
【図１】本発明を適用してなる絶縁検出装置の一実施形態の概略構成を示す図である。
【図２】本発明を適用してなる絶縁検出装置の一実施形態における絶縁抵抗の算出動作を示すフロー図である。
【図３】各スイッチ部の動作に対するコンデンサの充放電状態と電圧の読み込みタイミングを示すタイムチャートである。
【図４】絶縁抵抗の値に対する各電源電圧の計測時間で検出した絶縁抵抗の値の検出誤差を示す図である。
【図５】本発明を適用してなる絶縁検出装置の一実施形態における補正モードの動作を示すフロー図である。
【図６】本発明を適用してなる絶縁検出装置の変形例の概略構成を示す図である。
【図７】本発明を適用してなる絶縁検出装置の変形例における補正モードの動作を示すフロー図である。
【図８】本発明を適用してなる絶縁検出装置の変形例における各スイッチ部の動作に対するコンデンサの充放電状態と電圧の読み込みタイミングを示すタイムチャートである。
【符号の説明】
１絶縁検出装置
３電源
５ａ正側主回路配線
５ｂ負側主回路配線
７接地電位部
９コンデンサ
１１マイコン
Ｓ１第１スイッチ
Ｓ２第２スイッチ
Ｓ３第３スイッチ
Ｓ４第４スイッチ
Ｓ５第５スイッチ
Ｓ６第６スイッチ
Ｓ７第７スイッチ
Ｒｐ正端子側地絡抵抗
Ｒｎ負端子側地絡抵抗[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an insulation detection device for an ungrounded power supply, and more particularly to an insulation detection device suitable for an ungrounded DC power supply mounted on a vehicle that uses electric propulsion.
[0002]
[Prior art]
The insulation detection device of the ungrounded power supply is connected to the positive and negative terminals of the ungrounded DC power supply, and is insulated from the ground potential part by the insulation resistance to the ground potential part of the main circuit wiring on the positive and negative sides, that is, the ground fault resistance. Is detected to detect insulation with respect to the ground potential portion and a ground fault state (for example, see Patent Document 1). In such a conventional insulation detection device, switching means for connecting a capacitor in series between a positive terminal of an ungrounded DC power supply and a ground potential section for a set time, a negative terminal of an ungrounded power supply and a ground potential section A switching means for connecting a capacitor in series for a set time, a switching means for detection connecting a detection means for detecting a voltage between both terminals of the capacitor after each switching means is cut off, Calculation means for obtaining an insulation resistance to a ground potential portion of a power supply, that is, a ground fault resistance, based on a voltage between both terminals of the capacitor after the switching means is cut off and a power supply voltage previously calculated by fully charging the capacitor. And detects and determines the insulation state from the value of the ground fault resistance calculated by the calculation means.
[0003]
When calculating the value of the ground fault resistance, such an insulation detection device uses an equation that includes the capacitance of the capacitor as a constant. However, the capacitance of the capacitor used as a constant includes variations in capacitance between products and temperature. There is a variation in capacitance due to the change, and further, a change over time in the capacitance and the like may occur. If there is a variation or change in the value used as the constant in this way, the measurement error between the calculated ground fault resistance value and the actual ground fault resistance value increases, and the insulation state detection accuracy decreases. I will. Therefore, even if there is a variation or change in the value used as the constant for calculating the ground fault resistance such as the capacitance of the capacitor, it is desirable to reduce the measurement error of the ground fault resistance as much as possible and to improve the detection accuracy of the insulation state. It is rare.
[0004]
On the other hand, in order to improve the detection accuracy of the insulation state, the inventors of the present application set a capacitor in series with a DC power supply in which the wiring on the positive terminal side and the wiring on the negative terminal side are insulated from the ground potential part. First switching means for connecting for a time, second switching means for connecting a capacitor in series between the positive terminal of the power supply and the ground potential for a second set time, A third switching means for connecting a capacitor in series with the negative terminal for a second set time, and detecting a voltage between both terminals of the capacitor after the first, second and third switching means are cut off; A power supply voltage is estimated on the basis of a voltage detected by the fourth switching means for connecting the detecting means to be switched on and the detecting means after the first switching means is cut off, and the estimated power supply voltage is connected to the second and third switching means. Block means Contemplates insulation detecting device of the configuration and an arithmetic means for obtaining the insulation resistance to ground potential of the power on the basis of the respective detection voltage after the detection means.
[0005]
According to such an insulation detecting device, the first set time is set to a time shorter than the time required to completely charge the capacitor, and during the first set time, the DC is set by the first switching means. The capacitor is connected and charged between the power supply and the ground potential section by direct current, and the voltage between both terminals of the capacitor at this time is detected by the detecting means connected by the fourth switching means, thereby detecting the voltage. The calculating means can estimate the power supply voltage from an equation for calculating the power supply voltage including the capacity of the capacitor as a constant from the voltage. Then, based on the estimated power supply voltage and the voltage detected by the detection means after the second and third switching means are cut off, the insulation resistance is calculated by an equation for calculating the insulation resistance including the capacitance of the capacitor as a constant. The calculation can reduce the measurement error of the insulation resistance and improve the detection accuracy of the insulation state.
[Patent Document 1]
JP-A-8-226950 (page 4-7, FIG. 1)
[0006]
[Problems to be solved by the invention]
By the way, when the power supply voltage exceeds a predetermined range, an abnormality in the power supply voltage is performed in order to prevent a failure or the like from occurring in a device or equipment to which power is supplied from the power supply, for example, a vehicle. There is a case where a determination value for determination is provided, and this determination value is compared with the power supply voltage to determine whether the power supply voltage is abnormal. On the other hand, if the power supply is provided with the insulation detection device having the configuration considered by the inventors of the present application as described above, if it is determined that the power supply voltage is abnormal from the power supply voltage estimated by the insulation detection device, It is not necessary to separately provide a device and a device for detecting an abnormality in the power supply voltage in the power supply.
[0007]
However, in the insulation detection device having the configuration considered by the inventors of the present invention as described above, the power supply voltage is estimated from the voltage between both terminals of the capacitor. Included as a constant. For this reason, when the capacitance of the capacitor or the like varies between products, a constant numerical value varies. Therefore, the power supply voltage estimated by the insulation detection device having the configuration considered by the inventors of the present application includes an error corresponding to the variation of the numerical value that is this constant with respect to the actual power supply voltage.
[0008]
As a result, when the insulation detection device having the configuration considered by the inventors of the present application is used to detect an abnormality in the power supply voltage, the determination value for determining the abnormality in the power supply voltage is determined based on the actual power supply voltage. As the error of the estimated power supply voltage with respect to the actual power supply voltage increases, for example, the power supply voltage estimated by the insulation detection device exceeds the determination value despite the fact that the power supply voltage is actually normal. Thus, there is a greater possibility that a problem such as a power supply abnormality being determined will occur. On the other hand, when the determination value for determining the abnormality of the power supply voltage is determined by adding a margin corresponding to an error between the estimated power supply voltage and the actual power supply voltage to the actual power supply voltage, the actual value of the estimated power supply voltage is determined. Since the margin increases as the error with respect to the power supply voltage increases, for example, the power supply voltage estimated by the insulation detection device is lower than the determination value even though the actual power supply voltage exceeds the determination value and is abnormal. Value, and the possibility that a power supply abnormality cannot be detected increases.
[0009]
Therefore, in order to use the insulation detection device having the configuration considered by the inventors of the present application for detecting an abnormality in the power supply voltage, the error of the estimated power supply voltage with respect to the actual power supply voltage should be minimized, that is, the estimated power supply voltage. It is necessary to improve the accuracy of.
[0010]
An object of the present invention is to improve the accuracy of an estimated power supply voltage.
[0011]
[Means for Solving the Problems]
The insulation detection device of the present invention includes a capacitor connected in series to a DC power supply in which the wiring on the positive terminal side and the wiring on the negative terminal side are insulated from the ground potential, and a first set time shorter than the time required for the capacitor to be completely charged. A second switching means for connecting a capacitor in series between a positive terminal of the power supply and the ground potential section for a second set time; a first switching means connected between the ground potential section and the power supply. A third switching means for connecting a capacitor in series with the terminal for a second set time, and detecting a voltage between both terminals of the capacitor after the first, second and third switching means are shut off; And a power supply voltage of a power supply is estimated based on a voltage detected by the detection means after the first switching means is turned off and a fourth switching means for connecting the detection means. Three Calculating means for obtaining an insulation resistance with respect to a ground potential portion of the power supply based on each detection voltage of the detection means after the switching off of the switching means; and a reference power supply having a known power supply voltage in place of the power supply, In a state where a reference resistance having a known resistance value is connected in correspondence with the insulation resistance, the power supply voltage of the reference power supply is estimated by the calculation means based on the detection voltage of the detection means after the first switching means is cut off. A correction means is provided for correcting the power supply voltage of the power supply estimated by the calculating means based on the estimated power supply voltage of the reference power supply and the known power supply voltage of the reference power supply.
[0012]
With such a configuration, by calculating the power supply voltage of the reference power supply in advance, when actually calculating the insulation resistance of the power supply with respect to the ground potential portion, the correction means calculates and estimates the calculation using the calculation means. Correct the power supply voltage. For this reason, it is possible to reduce the error of the estimated power supply voltage with respect to the actual power supply voltage caused by variations between products such as the capacitance of the capacitor. Therefore, the accuracy of the estimated power supply voltage can be improved.
[0013]
Further, as the above insulation detection device, the first switching means includes a first switch unit connected to a positive terminal of the power supply, and a second switch unit connected to a negative terminal of the power supply, Switching means includes a second switch section and a third switch section connected in series to the first switch, and the second switching means includes a first switch section and a second switch section. And a fourth switch unit connected in series with the first switch unit and the third switch unit, and between the second switch unit and the fourth switch unit on the positive side. A first diode, a first resistor, and a capacitor rectifying in a direction from the first diode to the negative side are connected in series, and a first diode rectifying in a direction opposite to the first diode in parallel with the first diode and the first resistor. Two diodes and a second resistor are connected in series. And the detection means is connected between the third switch part and the fourth switch unit, between the detecting means and the fourth switching unit is a circuit configuration which is grounded to the ground potential portion.
[0014]
Further, the calculating means obtains the resistance value of the reference resistor based on the corrected power supply voltage obtained by the calculating means and the respective detected voltages at the detecting means after the second and third switching means are cut off. Is configured to correct the value of the insulation resistance with respect to the ground potential portion of the power supply obtained by the calculating means based on the resistance value of the reference resistor obtained by the calculating means and the known resistance value of the reference resistance.
[0015]
With such a configuration, it is possible to reduce the measurement error of the insulation resistance by using the power supply voltage estimated by the power supply for the calculation of the insulation resistance with respect to the ground potential portion of the power supply. By correcting the value of the insulation resistance with respect to the ground potential portion of the power supply, the measurement error of the insulation resistance can be reduced, so that the detection accuracy of the insulation state can be further improved.
[0016]
Further, the detection means, the calculation means, and the correction means are formed by one microcomputer, and a correction mode switching means for changing a voltage applied to the correction mode port is connected to a correction mode port provided in the microcomputer. When the voltage applied to the correction mode port is changed by the correction mode switching means, the microcomputer is switched to the correction mode in which the microcomputer operates as the correction means. With such a configuration, the configuration of the insulation detection device including the correction unit can be simplified.
[0017]
Further, if the bypass means including the fifth switch unit which forms a path for bypassing the second resistor when the circuit is closed is provided, the fourth switching means may be closed while the fourth switching means is closed. When the switch unit 5 is closed, the discharging time of the capacitor can be shortened, so that the time required for detecting the insulation state can be shortened, which is preferable.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an insulation detection device to which the present invention is applied will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of an insulation detection device to which the present invention is applied. FIG. 2 is a flowchart showing the operation of calculating the insulation resistance of the insulation detection device according to the present invention. FIG. 3 is a time chart showing the charging / discharging state of the capacitor and the voltage reading timing with respect to the operation of each switch unit. FIG. 4 is a diagram illustrating a detection error of the value of the insulation resistance detected during the measurement time of each power supply voltage with respect to the value of the insulation resistance. FIG. 5 is a flowchart showing an operation in a correction mode of the insulation detection device to which the present invention is applied.
[0019]
As shown in FIG. 1, the insulation detection device 1 of the present embodiment is applied to a DC power supply 3 serving as a power source of, for example, an electric propulsion vehicle that obtains propulsion using electric power. The power supply 3 is a battery in which a plurality of storage batteries are connected in series, a fuel cell, or the like. The positive main circuit wiring 5a on the positive terminal side and the negative main circuit wiring 5b on the negative terminal side of the power supply 3 are grounded. The power supply 3 is a non-grounded power supply, being insulated from the potential unit 7, for example, a vehicle body. The insulation detection device 1 includes a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a capacitor 9, a microcomputer 11, which also serves as a correction unit, a detection unit, and a calculation unit, and determines an insulation state, and It is composed of a switching control circuit (not shown) for opening and closing each switch according to a set time. Note that the detection unit, the calculation unit, the switching control circuit, and the like can be formed separately or integrally as appropriate, for example, a switching control circuit (not shown) is integrally included in the microcomputer 11. Further, the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 shown in FIG. 1 are typically formed by using, for example, a switch unit composed of components having various switch functions such as a relay and a semiconductor switch as a contact. This is shown in FIG.
[0020]
A first switch S1 and a third switch S3 are sequentially connected in series to the positive terminal of the power supply 3 from the positive terminal, and a second switch S2 and a second switch S2 are connected to the negative terminal of the power supply 3 from the negative terminal. The four switches S4 and the fourth resistor R4 are sequentially connected in series. A first diode D1, a first resistor R1, and a capacitor 9 are sequentially connected in series between the first switch S1 and the third switch S3 and between the second switch S2 and the fourth switch S4. A second diode D2 and a second resistor R2 are sequentially connected in series between the first resistor R1 and the capacitor 9 and between the first switch S1 and the third switch S3. That is, the first diode D1 and the first resistor R1, and the second diode D2 and the second resistor R2 are connected in parallel. As a bypass means, a fifth switch S5 and a fifth resistor R5 having a lower resistance than the second resistor R2 are sequentially connected in series from a portion between the second diode D2 and the second resistor R2 to the ground potential section 7. It is connected. The first diode D1 rectifies in the direction from the positive side to the negative side, and the second diode D2 rectifies in the direction opposite to the first diode D1.
[0021]
A third resistor R3 is connected between the third switch S3 and the fourth resistor R4 in series with respect to the third switch S3 and the fourth resistor R4, and is connected between the third switch S3 and the third resistor R3. The microcomputer 11 is connected to the portion via a sixth switch S6 and a sixth resistor R6, which are sequentially connected in series, via an analog / digital conversion port of the microcomputer 11, that is, an A / D port. The correction mode port of the microcomputer 11 is connected to a seventh switch S7 whose one terminal side is provided in the ground potential unit 7. A cathode of a Schottky diode SD1 for suppressing a negative potential from being applied to the A / D port of the microcomputer 11 is provided between the A / D port of the microcomputer 11 and the sixth resistor R6. The anode of a Schottky diode SD2 for suppressing an excessive positive potential from being applied to the A / D port of the microcomputer 11 is connected. The anode of Schottky diode SD1 is installed at ground potential section 7, and the cathode of Schottky diode SD2 is connected to the positive terminal side of power supply 3. Further, a portion between the third resistor R3 and the fourth resistor R4 is grounded to the ground potential section 7.
[0022]
In the present embodiment, the first switching means for connecting the capacitor 9 in series with the power supply 3 for the first set time is a first switch S1, a second switch S2, a switching control circuit (not shown), and the like. Is formed. The second switching means for connecting a capacitor 9 in series between the positive terminal of the power supply 3 and the ground potential unit 7 for a second set time includes a first switch S1, a fourth switch S4, and a switching switch (not shown). It is formed by a control circuit and the like. The third switching means for connecting a capacitor 9 in series between the ground potential unit 7 and the negative terminal of the power supply 3 for a second set time includes a second switch S2, a third switch S3, and a switching switch (not shown). It is formed by a control circuit and the like. The fourth switching means includes a third switch S3, a fourth switch S4, a switching control circuit (not shown), and the like. Further, the correction mode switching means for activating the correction function of the microcomputer 11 to switch the microcomputer 11 to the correction mode is formed by a seventh switch S7 and a switching control circuit (not shown). The capacitor 9 has a relatively high capacitance of, for example, several μF, and the first resistor R1 and the second resistor R2 have a relatively high resistance of, for example, several hundred kΩ. .
[0023]
The operation of the insulation detecting device having such a configuration and the features of the present invention will be described. In the operation of detecting the insulation state with respect to the ground potential unit 7 by the insulation detection device 1, as shown in FIGS. 2 and 3, when the insulation detection device 1 starts detecting the insulation state, a switching control circuit (not shown) The first switch S1 and the second switch S2 are closed for a first closing time T1, which is a first set time (step 101). That is, the first switching means forms a circuit for connecting the capacitor 9 in series to the power supply 3 without passing through the ground potential unit 7, and the capacitor 9 is charged during the first closed time T1, and the capacitor 9 is charged. 9, the voltage VC between both terminals increases. The first closing time T1 is set to a time shorter than the time required to completely charge the capacitor 9, and is, for example, 1/5 to 1 to 1 times the time required to completely charge the capacitor 9. / 10, and the first closing time T1 is selected according to the required measurement error range of the insulation resistance.
[0024]
In step 101, when the first closing time T1 elapses, the first switch S1 and the second switch S2 are opened or cut off, and after the lapse of a predetermined time tw1 shorter than the first closing time T1, the third switch S3 and the fourth switch S4. Is closed (step 103). That is, the fourth switching means forms a circuit to which the microcomputer 11 for detecting the voltage between both terminals of the capacitor 9 is connected, and includes the second resistor R2, the third resistor R3, and the fourth resistor R4. A discharge circuit from the capacitor 9 is formed. After a lapse of a predetermined time tw2 shorter than the first closing time T1 from the closing of the third switch S3 and the fourth switch S4, the microcomputer 11 outputs the A / D conversion data, that is, both ends of the capacitor 9, through the A / D port. The voltage VC between the slaves is read (step 105). From the value of the voltage VC between both terminals of the capacitor 9 at this time, that is, the detected voltage V0, the estimated power supply voltage V0s is calculated from the following equation (1) (step 107).
V0s = [V0 / {1-EXP (-T1 / C · R1)}] · a (1)
In the equation (1), T1 is the closing time of the first switch S1 and the second switch S2, C is the capacitance of the capacitor 9, R1 is the resistance value of the first resistor R1, and a is the correction value described later.
[0025]
On the other hand, the switching control circuit (not shown) detects the voltage VC between both terminals of the capacitor 9 in step 105, and then closes the fifth switch S5 with the third switch S3 and the fourth switch S4 closed. To bypass the second resistor R2. This discharges through the fifth resistor R5 having a lower resistance value than the second resistor R2, so that the amount of discharge from the capacitor 9 increases and the rate of drop of the voltage VC between both terminals of the capacitor 9 increases. In addition, the time required for discharging from the capacitor 9 can be reduced. After the fifth switch S5 is closed and a predetermined time td1 shorter than the first closed time T1 has elapsed, the fifth switch S5 is opened or shut off, and then the microcomputer 11 outputs the A / D converted data via the A / D port. That is, the voltage VC between both terminals of the capacitor 9 is read (step 109).
[0026]
When it is confirmed in step 109 that the voltage VC is 0 V, a switching control circuit (not shown) opens the third switch S3 and closes the first switch S1 after a lapse of a predetermined time tw1. Then, the first switch S1 and the fourth switch S4 are closed for a second closing time T2, which is a second set time (step 111). That is, a circuit in which the capacitor 9 is connected in series between the positive terminal of the power supply 3 and the ground potential unit 7 by the second switching means, that is, as shown in FIG. The switch S1, the first diode D1, the first resistor R1, the capacitor 9, the fourth switch S4, the fourth resistor R4, the ground potential unit 7, and the ground on the negative terminal side assumed at a position shown by a dotted line in FIG. A circuit is formed in which the short-circuit resistance Rn and the negative-side main circuit wiring 5b are sequentially connected in series to the power supply 3. Thereby, the capacitor 9 is charged during the second closing time T2, and as shown in FIG. 3, the voltage VC between both terminals of the capacitor 9 increases according to the value of the ground fault resistance Rn. The second closing time T2, which is the second set time, is also shorter than the time required to completely charge the capacitor 9, similarly to the first closing time T1, and is shorter than the predetermined times tw1, tw2, and td1. Set for a long time.
[0027]
When the second closing time T2 elapses in step 111, as shown in FIGS. 2 and 3, the first switch S1 is opened or shut off, and after the elapse of a predetermined time tw1, the third switch S3 is closed and the third switch S3 is opened. And the fourth switch S4 is closed. That is, the fourth switching means forms a circuit to which the microcomputer 11 for detecting the voltage between both terminals of the capacitor 9 is connected, and includes the second resistor R2, the third resistor R3, and the fourth resistor R4. A discharge circuit from the capacitor 9 is formed. In this state, the microcomputer 11 reads the A / D conversion data via the A / D port, that is, the voltage VC between both terminals of the capacitor 9 (step 113). The value of the voltage VC between both terminals of the capacitor 9 at this time is defined as a detection voltage VCN.
[0028]
On the other hand, the switching control circuit (not shown) detects the voltage VC between both terminals of the capacitor 9 in step 115, and then closes the fifth switch S5 with the third switch S3 and the fourth switch S4 closed. Thus, the second resistor R2 is bypassed, and the time required for discharging from the capacitor 9 is reduced. After the fifth switch S5 is closed and a predetermined time td2 shorter than the second closing time T2 has elapsed, the fifth switch S5 is opened or shut off, and then the microcomputer 11 outputs the A / D converted data via the A / D port. That is, the voltage VC between both terminals of the capacitor 9 is read (step 115).
[0029]
If it is confirmed in step 115 that the voltage VC is 0 V, a switching control circuit (not shown) opens the fourth switch S4 and closes the second switch S2 after a predetermined time tw1 has elapsed. Then, the second switch S2 and the third switch S3 are closed for a second closing time T2, which is a second set time (step 117). That is, a circuit in which the capacitor 9 is connected in series between the ground potential section 7 and the negative terminal of the power supply 3 by the third switching means, that is, as shown in FIG. , A ground fault resistor Rp on the positive terminal side assumed at a position indicated by a dotted line, a ground potential portion 7, a third resistor R3, a third switch S3, a first diode D1, a first resistor R1, a capacitor 9, and a second A circuit is formed in which the switch S2 and the negative-side main circuit wiring 5b are sequentially connected in series to the power supply 3. Thereby, the capacitor 9 is charged during the second closing time T2, and as shown in FIG. 3, the voltage VC between both terminals of the capacitor 9 increases according to the value of the ground fault resistance Rp.
[0030]
In step 117, when the second switch S2 and the third switch S3 are closed for the second closing time T2, which is the second set time, the sixth switch S6 is opened or shut off. The sixth switch S6 is normally closed, and the voltage of the portion between the third switch S3 and the third resistor R3 is applied to the A / D port of the microcomputer 11. However, the sixth switch S6 is shut off while the second switch S2 and the third switch S3 are closed, and the A / D port of the microcomputer 11 is connected to a portion between the third switch S3 and the third resistor R3. No voltage is applied. That is, while the second switch S2 and the third switch S3 are closed, the portion between the third switch S3 and the third resistor R3 is at a negative potential, but the sixth switch S6 is connected to the second switch S2 and the third switch R3. This negative potential is prevented from being applied to the A / D port of the microcomputer 11 by being shut off while the third switch S3 is closed.
[0031]
When the second closing time T2 elapses in step 117, as shown in FIGS. 2 and 3, the second switch S2 is opened or shut off, and after the elapse of the predetermined time tw1, the fourth switch S4 is closed and the third switch S3 is opened. And the fourth switch S4 is closed. That is, the fourth switching means forms a circuit to which the microcomputer 11 for detecting the voltage between both terminals of the capacitor 9 is connected, and includes the second resistor R2, the third resistor R3, and the fourth resistor R4. A discharge circuit from the capacitor 9 is formed. Then, after a lapse of a predetermined time tw2 since the fourth switch S4 is closed, the microcomputer 11 reads the A / D conversion data via the A / D port, that is, the voltage VC between both terminals of the capacitor 9 (step 119). . The value of the voltage VC between both terminals of the capacitor 9 at this time is defined as a detection voltage VCP.
[0032]
Here, the microcomputer 11 uses the VCN and VCP detected in steps 113 and 119 to obtain the insulation resistance to the vehicle body or the like serving as the ground potential section 7 of the power supply 3, that is, the ground fault resistance Rn from the following equation (2). A ground fault resistance value RL representing Rp is calculated (step 121).
RL = [− R1-T2 / C · ln {1- (VCP + VCN) / V0s}] · b (2)
In the equation (2), T2 is the second closing time, C is the capacitance of the capacitor 9, R1 is the resistance value of the first resistor R1, V0s is the power supply voltage estimated in step 121, and b is a correction value described later. .
[0033]
On the other hand, the switching control circuit (not shown) detects the voltage VC between both terminals of the capacitor 9 in step 119, and then closes the fifth switch S5 with the third switch S3 and the fourth switch S4 closed. Thus, the second resistor R2 is bypassed, and the time required for discharging from the capacitor 9 is reduced. After a lapse of a predetermined time td2 after closing the fifth switch S5, and after opening or shutting off the fifth switch S5, the microcomputer 11 outputs A / D conversion data, that is, between the two terminals of the capacitor 9 through the A / D port. The voltage VC is read (step 123). Then, when it is confirmed in step 125 that the voltage VC is 0 V, one insulation state detection cycle ends. In addition, while detecting the insulation state, the insulation state detection cycle from step 101 to step 123 is repeated.
[0034]
The microcomputer 11 determines the insulation state from the ground fault resistance value RL obtained in one insulation state detection cycle. For example, the ground fault resistance value RL is compared with a value of a ground fault resistance which is a reference for determining an insulation state in advance, that is, a reference resistance value, and the ground fault resistance value RL is equal to or less than the reference resistance value. In such a case, it is determined that insulation failure has occurred.
[0035]
By the way, as can be seen from the equation (2), if the capacitance C of the capacitor 9 and the resistance value R1 of the first resistor R1 vary due to a difference between products or a temperature change, the accuracy of measuring the ground fault resistance value RL is affected. As a result, the accuracy of the detected ground fault resistance value RL decreases. Therefore, the detection accuracy of the insulation state is reduced. In particular, since the capacitor 9 needs to have a relatively large value of several μF in consideration of the stray capacitance, for example, if there is a variation of about ± 5% in the difference between products, it is ± 10% in consideration of a temperature change. % In some cases, and such variation in the capacitance of the capacitor 9 reduces the detection accuracy of the insulation state. In addition, variations caused by changes in component constants due to changes over time also lower the detection accuracy of the insulation state.
[0036]
However, in the insulation detection device 1 of the present embodiment, the first switch S1 and the second switch S2 are set to the first closing time shorter than the time required to completely charge the capacitor 9 in the first stage of the insulation detection cycle. By closing the circuit during T1, the power supply voltage of the power supply 3 is estimated. When charging the capacitor 9 by closing the first switch S1 and the second switch S2 for a short time, when charging is performed with a time constant C · R1 determined by the actual capacitance of the capacitor 9 and the resistance value of the resistor R1. The estimated power supply voltage V0s is not an actual power supply voltage of the power supply 3 but a value including an error between the capacitance and resistance value of the capacitor 9 and the resistor R1, that is, a value including variation. . Then, by using the estimated power supply voltage V0s including this variation in the calculation of the ground fault resistance value RL performed in the subsequent step 121 in the insulation detection cycle, the variation in the capacitance of the capacitor 9 is corrected, 9 can reduce an error between the actual ground fault resistance value caused by the variation in capacitance and the calculated ground fault resistance value RL. Therefore, the detection accuracy of the insulation state can be improved.
[0037]
Here, an error between the ground fault resistance value RL measured by the insulation detection device 1 of the present embodiment and the actual ground fault resistance value is calculated by using a capacitor 9 having a predetermined standard capacitance and a predetermined standard resistance value. FIG. 4 shows a calculation result assuming the case where the first resistor R1 having the above-described configuration is used. The capacitor 9 has a capacitance variation of about ± 10% in consideration of the difference between products and the temperature change, and the first resistor R1 has a capacitance variation of about ± 2% in consideration of the difference between products and the temperature change. It is assumed that there is. In FIG. 4, the V0 measurement time means the first closing time. Therefore, in FIG. 4, the measurement is performed when the first closing time T1 is t seconds, 2t seconds, and 3t seconds, where t <2t <3t. The error is shown. FIG. 4 is a graph in which the calculation results are plotted with the vertical axis representing the detection accuracy, that is, the detection error, and the horizontal axis representing the ground fault resistance value.
[0038]
As can be seen from FIG. 4, the case where the detection is performed by the insulation detection device 1 of the present embodiment, that is, the estimated power supply voltage is compared with the case where the detection is performed by the conventional insulation detection device, that is, the case where the estimated power supply voltage is not used. In the case of using, the measurement error is reduced with respect to the short-circuit resistance value in each place. Further, the degree of reduction of the measurement error varies depending on the setting of the V0 measurement time, that is, the setting of the first closing time T1, and when the first closing time T1 is t seconds, the error increases as the ground fault resistance decreases. The error decreases as the resistance increases. When the first closing time T1 is 2t seconds, when the ground fault resistance is large, the error becomes larger than when the first closing time T1 is t seconds, but the error becomes smaller on average over the short-circuit resistance in each place. I have. Even when the first closing time T1 is 3 t seconds, the error is smaller on average across the short-circuit resistance, but the error is larger than when the first closing time T1 is 2 t seconds.
[0039]
Therefore, when setting the reference resistance value for determining the insulation failure to be a relatively large value, the first closing time T1 is preferably set to t seconds, and the reference resistance value for determining the insulation failure is preferably set to t seconds. When the setting is a relatively small value, the first closing time T1 is preferably set to 2t seconds. As described above, it is preferable that the first closing time T1, that is, the first set time is selected so that the measurement error becomes small around the reference resistance value. For example, if the reference resistance value is set to RΩ in FIG. 4, it is preferable to select 2t seconds as the first closing time T1, and at this time, the conventional insulation detecting device has a measurement error of ± 10% or more. On the other hand, in the insulation detection device 1 of the present embodiment, the measurement error is ± 2% or less, and the detection accuracy of the insulation state can be improved.
[0040]
On the other hand, in the insulation detection device 1 of the present embodiment, as can be seen from the fact that the capacitance C of the capacitor 9 and the resistance value R1 of the first resistor R1 are included in the equation (1) as a constant, the capacitance of the capacitor 9 is C, if the resistance value R1 of the first resistor R1 varies due to a product difference or the like, an error occurs in the power supply voltage of the power supply 3 estimated by the insulation detection device 1. For this reason, in the insulation detection device 1 of the present embodiment, a correction operation for correcting the power supply voltage estimated by the microcomputer 11 is performed, for example, during a production process in a factory, before assembling to a vehicle, and during a regular inspection of the vehicle. It can be carried out.
[0041]
When performing the correction work of the insulation detection device 1, as shown in FIG. 5, a reference power supply having a known power supply voltage and a reference resistor having a known resistance value are connected to the insulation detection device 1. At this time, the reference power supply is connected to a position corresponding to the power supply 3 in FIG. 1, and the reference resistance is connected to a position corresponding to the ground fault resistance Rp on the positive terminal side and the ground fault resistance Rn on the negative terminal side in FIG. (Step 201).
[0042]
After connecting the reference power supply and the reference resistance to the insulation detecting device 1 in step 201, as shown in FIG. 5, the seventh switch S7 connected to the correction mode port of the microcomputer 11 serving as the correction means is closed, that is, turned on ( Step 203). In the state where the seventh switch S7 is open or cut off, a predetermined positive potential is applied to the correction mode port. However, when the seventh switch S7 is turned on, the applied potential of the correction mode port becomes 0 V, and the microcomputer 11 This is a correction mode start command. Therefore, turning on the seventh switch S7 starts the correction function of the microcomputer 11, that is, the correction program. When the correction function starts in step 203, steps 101 to 109 are performed in the insulating state detection operation shown in FIG. 2, and the power supply voltage V0s is estimated from the above-described equation (1). Then, a comparison is made as to whether there is a difference between the estimated power supply voltage V0s and a known power supply voltage of the reference power supply previously input to the microcomputer 11 (step 205). In the case where the power supply voltage V0s is first estimated in the above equation (1) in step 205, the correction value a in the equation (1) is set to 1, and the initially estimated power supply voltage V0s is not corrected. Has become.
[0043]
In step 205, when there is a difference between the estimated power supply voltage V0s and the known power supply voltage of the reference power supply, the correction value a is calculated from, for example, the ratio of the estimated power supply voltage V0s to the known power supply voltage of the reference power supply. (Step 207). After step 207, the process returns to step 205, where the corrected power supply voltage V0s is calculated from the above equation (1) using the correction value a calculated in step 207, and the corrected power supply voltage V0s is input to the microcomputer 11 in advance. The known power supply voltage of the reference power supply is compared again for a difference. Steps 205 and 207 are repeated until there is no difference between the corrected power supply voltage V0s and the known power supply voltage of the reference power supply input to the microcomputer 11 in advance.
[0044]
On the other hand, in step 205, if there is no difference between the estimated power supply voltage V0s and the known power supply voltage of the reference power supply previously input to the microcomputer 11, or the power supply voltage V0s corrected by the correction value a calculated in step 207 When there is no difference between the reference power supply voltage and the known power supply voltage of the reference power supply input to the microcomputer 11 in advance, steps 111 to 123 are performed in the insulation state detection operation shown in FIG. ) To calculate the ground fault resistance value RL. Then, it is compared whether there is a difference between the calculated ground fault resistance value RL and a known resistance value of the reference resistance previously input to the microcomputer 11 (step 209). In the case where the ground fault resistance value RL is first calculated in the above equation (2) in step 209, the correction value b in the equation (2) is set to 1, and the first calculated ground fault resistance RL is corrected. There is no state.
[0045]
In step 209, when there is a difference between the calculated ground fault resistance value RL and the known resistance value of the reference resistance, the correction value is obtained from, for example, the ratio of the calculated ground fault resistance value RL to the known resistance value of the reference resistance. b is calculated (step 211). After step 211, the process returns to step 209 to calculate a ground fault resistance value RL corrected from the above-described equation (2) using the correction value b calculated in step 211. A comparison is again made to see if there is any difference between the reference resistance and the known resistance value input to the microcomputer 11. Steps 209 and 211 are repeated until the difference between the corrected ground fault resistance value RL and the known resistance value of the reference resistance input in advance to the microcomputer 11 disappears.
[0046]
On the other hand, in step 211, when there is no difference between the ground fault resistance value RL calculated in step 209 and the known resistance value of the reference resistance previously input to the microcomputer 11, or the correction is performed using the correction value b calculated in step 211. When the difference between the ground fault resistance value RL and the known resistance value of the reference resistance previously input to the microcomputer 11 disappears, the program that performs the correction function is ended in order to end the correction mode (step 213). ), End the correction work.
[0047]
Then, when actually performing the insulation state detection operation, the microcomputer 11 determines the correction value a of the above-described equation (1) in step 107 for estimating the power supply voltage of the power supply 3 as shown in FIG. The estimated power supply voltage V0s and the ground fault resistance value RL are calculated using the correction value a calculated in the above as the correction value b of the above-described equation (2) and the correction value b calculated in this correction mode.
[0048]
In addition, in the insulation detection device 1 of the present embodiment, the error of the estimated power supply voltage with respect to the actual power supply voltage of the power supply 3 caused by variations between products such as the capacitance C of the capacitor 9 and the resistance value R1 of the first resistor R1 is calculated. Can be reduced. However, another factor that causes an error in the estimated power supply voltage with respect to the actual power supply voltage of the power supply 3 is, for example, the capacitance C of the capacitor 9 or the resistance value R1 of the first resistor R1 due to a temperature change around the insulation detection device 1. There is change. Therefore, an error in the estimated power supply voltage with respect to the actual power supply voltage of the power supply 3 caused by a change in temperature around the insulation detection device 1 is caused by variations between products such as the capacitance C of the capacitor 9 and the resistance value R1 of the first resistor R1. If the error is larger than the generated error, a temperature sensor port is provided in the microcomputer 11, and a temperature sensor for detecting the temperature around the insulation detection device 1, for example, a temperature-sensitive element such as a thermistor is connected to the temperature sensor port. . Then, in a state where the insulation detection device 1 is placed under a plurality of temperature conditions, for example, two temperature conditions such as a high-temperature condition and a low-temperature condition, the operation of the correction mode is performed so that the correction values a and b taking the temperature compensation into consideration. Can be calculated.
[0049]
As described above, in the insulation detection device 1 of the present embodiment, the microcomputer 11 has a correction function and serves as a correction unit. Therefore, the insulation detection device 1 is provided with a reference power supply having a known voltage and a reference resistance having a known resistance value. By performing the insulation state detection operation in the connected state, the correction value a for correcting the power supply voltage estimated by the power supply 3 can be calculated. When the insulation detection device 1 actually detects the insulation state of the power supply 3, the capacitance C of the capacitor 9 and the first resistance are corrected by correcting the value when calculating the power supply voltage V0s estimated by the correction value a. The error of the estimated power supply voltage V0s with respect to the actual power supply voltage of the power supply 3 caused by variations between products such as the resistance value R1 of R1 can be reduced. Therefore, the accuracy of the estimated power supply voltage can be improved.
[0050]
Furthermore, since the accuracy of the estimated power supply voltage can be improved, the determination value for detecting the power supply voltage abnormality can be made closer to the actual power supply voltage value, in other words, the margin can be reduced, so that the power supply voltage abnormality can be accurately detected. The problem that detection is impossible can be prevented. Therefore, the insulation detection device 1 according to the present embodiment can be used not only for measuring the value of the short-circuit resistance and detecting the insulation state, but also as a power supply voltage detection device for determining an abnormality in the power supply voltage. The use of the insulation detection device can be expanded. In addition, by executing the correction mode over time and updating the correction value a, even when the capacitance C and the resistance value R1 change due to the deterioration over time of the capacitor 9 and the first resistor R1, the estimation of the power supply voltage is performed. Accuracy can be maintained. Furthermore, even if the capacitor 9 and the first resistor R1 use low precision components having relatively large variations in the capacitance C and the resistance value R1, the estimation accuracy of the power supply voltage can be improved.
[0051]
Further, in the insulation detection device 1 of the present embodiment, the correction function of the microcomputer 11 has a function of calculating a correction value b for correcting the calculated ground fault resistance value RL. Therefore, when the insulation detection device 1 actually detects the insulation state of the power supply 3, the correction value b is used to correct the value calculated when the ground fault resistance value RL is calculated. The error of the calculated ground fault resistance value RL with respect to the actual ground fault resistance of the power supply 3 caused by variations between the products such as the resistance value R1 of the first resistor R1 can be reduced. Therefore, in addition to reducing the measurement error of the ground fault resistance by using the estimated power supply voltage V0s, the measurement error of the ground fault resistance value RL can also be reduced by correcting the ground fault resistance value RL in the microcomputer 11. Therefore, the detection accuracy of the insulation state can be further improved. However, when the purpose is only to improve the accuracy of the estimated power supply voltage, a configuration in which the ground fault resistance value RL is not corrected by the correction value b may be adopted.
[0052]
By the way, in the insulation detection device 1 of the present embodiment, while the second switch S2 and the third switch S3 are closed, a portion between the third switch S3 and the third resistor R3 has a negative potential. For this reason, while the second switch S2 and the third switch S3 are closed, a negative potential is applied to the A / D port of the microcomputer 11, and the microcomputer 11 may be damaged. In order to prevent such a negative potential from being applied to the A / D port of the microcomputer 11, a Schottky diode SD1 is provided. However, since the characteristics of the Schottky diode SD1 change depending on the ambient temperature of the insulation detection device 1, the ability of the Schottky diode SD1 to suppress application of a negative potential to the A / D port of the microcomputer 11 depending on the ambient temperature of the insulation detection device 1. Changes. Therefore, with the Schottky diode SD1, the application of the negative potential to the A / D port of the microcomputer 11 cannot be prevented, and the microcomputer 11 may be damaged.
[0053]
On the other hand, in the insulation detection device 1 of the present embodiment, the sixth switch S6 is provided between the portion between the third switch S3 and the third resistor R3 and the A / D port of the microcomputer 11, and at least the sixth switch S6 is provided. The second switch S2 and the third switch S3 are closed, and the sixth switch S6 is opened when the microcomputer 11 reads the A / D conversion data via the A / D port. Thus, when there is a possibility that a negative potential may be applied to the A / D port of the microcomputer 11, the power supply to the A / D port of the microcomputer 11 can be cut off, so that damage to the microcomputer 11 can be prevented. When the sixth switch S6 is provided, the configuration without the Schottky diode SD1 can be adopted as long as the Schottky diode SD1 is used only for suppressing damage to the microcomputer 11.
[0054]
Furthermore, the insulation detecting device 1 of the present embodiment includes bypass means including the fifth switch S5 that forms a path that bypasses the second resistor R2 when the circuit is closed. By closing the fifth switch S5 after the detection of the voltage, the discharge time from the capacitor 9 can be shortened. Therefore, the time required for one cycle for insulation detection can be reduced, the number of insulation detections per unit time can be increased, and the accuracy of insulation detection can be further improved.
[0055]
Note that the bypass unit including the fifth switch S5 is not limited to the configuration of the present embodiment, and the bypass unit is provided between the two terminals of the second resistor R2 in parallel with the second resistor R2, as shown in FIG. A configuration in which the fifth switch S5 is connected may be employed. Further, when there is no need to shorten the time required for one cycle for insulation detection or the like, a configuration without the bypass unit including the fifth switch S5 can be adopted.
[0056]
Further, in the present embodiment, the ground fault resistance RL representing the ground fault resistance Rp on the positive terminal side and the ground fault resistance Rn on the negative terminal side of the power supply 3 is calculated. However, the ground fault resistance Rp on the positive terminal side and the ground fault resistance Rn on the negative terminal side of the power supply 3 are individually estimated based on the power supply voltage V0s and the detection voltages VCP, VCN, etc., using an individual formula, and Can also be detected.
[0057]
Further, in the insulation detection device 1 of the present embodiment, the power supply voltage V0s and the ground fault resistance value RL estimated by the equations (1) and (2) are calculated by the microcomputer 11 as the calculating means. However, in order to reduce the time required for calculating the complex function formulas such as the formulas (1) and (2), the power supply voltage V0s estimated based on the address in the memory or the like serving as the storage means of the microcomputer 11 and the ground voltage are calculated. It is also possible to prepare a power supply voltage data table or a ground fault resistance value data table or the like in which the ground resistance value RL or the like is stored, and to calculate the address corresponding to each data table by the microcomputer 11 as the calculating means. . At this time, the microcomputer 11 which is a calculating means calculates the value of the voltage VC between both terminals of the capacitor 9 detected for estimating the power supply voltage, that is, the detected voltage V0, the estimated power supply voltage V0s, and the ground fault resistance value RL. From the detected value of the voltage VC between both terminals of the capacitor 9, that is, the detected voltages VCN and VCP, the address and the ground of the power supply voltage data table are calculated by an arithmetic expression of an address simpler than the equations (1) and (2). The address of the ground resistance data table is calculated, and the power supply voltage V0s and the ground resistance RL estimated from each of the calculated addresses are determined.
[0058]
It should be noted that the microcomputer 11 in the case where the present invention is applied to an insulation detection device configured to obtain the power supply voltage V0s and the ground fault resistance RL estimated using such a power supply voltage data table and a ground fault resistance data table. The operation in the correction mode will be described below. Here, steps for performing the same operations as the operations illustrated in FIG. 5 are denoted by the same reference numerals, description thereof will be omitted, and only operations different from those in FIG. 5 will be described. In the correction of the estimated power supply voltage, as shown in FIG. 7, after setting the microcomputer in the correction mode in step 203, the address for the power supply voltage data table is calculated. Then, the power supply voltage V0s is obtained from the power supply voltage data table based on the address for the power supply voltage data table, and the power supply voltage V0s obtained from the power supply voltage data table is compared with a known power supply voltage of the reference power supply (step 215). ).
[0059]
If there is a difference between the power supply voltage V0s obtained from the power supply voltage data table and the known power supply voltage of the reference power supply in step 215, the address for the power supply voltage data table calculated in step 215 is shifted (step 217). . After step 217, the process returns to step 215, in which the corrected power supply voltage V0s is obtained from the power supply voltage data table using the address of the power supply voltage data table shifted in step 217, and the corrected power supply voltage V0s is input to the microcomputer 11 in advance. The known power supply voltage of the reference power supply is compared again for a difference. The address for the power supply voltage data table is shifted in step 217 until the difference between the corrected power supply voltage V0s and the known power supply voltage of the reference power supply previously input to the microcomputer 11 disappears in step 217. The operation of obtaining the corrected power supply voltage V0s is repeated.
[0060]
On the other hand, in the correction of the ground fault resistance value, an address for the ground fault resistance data table is calculated. Then, the ground fault resistance value RL is obtained from the ground fault resistance data table based on the address to the ground fault resistance data table, and the ground fault resistance value RL obtained from the ground fault resistance data table and the known resistance of the reference resistance are determined. (Step 219). If there is a difference between the ground fault resistance value RL obtained from the ground fault resistance data table and the known resistance value of the reference resistance in step 219, the address for the ground fault resistance data table calculated in step 219 is set. Shift (step 221).
[0061]
After step 221, the process returns to step 219 to obtain a corrected ground fault resistance value RL from the ground fault resistance data table based on the address of the ground fault resistance data table shifted in step 221, and obtains the corrected ground fault resistance value. RL is compared again with a known resistance value of the reference resistance input to the microcomputer 11 in advance. In step 221, the address for the ground fault resistance data table is shifted until the difference between the corrected ground fault resistance value RL and the known resistance value of the reference resistance previously input to the microcomputer 11 disappears. The operation for obtaining the ground fault resistance value RL corrected in step 219 is repeated.
[0062]
In the insulation detection device 1 of the present embodiment, the sixth switch S6 is normally closed, and the voltage of the portion between the third switch S3 and the third resistor R3 is applied to the A / D port of the microcomputer 11. Although it is in a state of being applied, it is shut off while the second switch S2 and the third switch S3 are closed, and the A / D port of the microcomputer 11 is connected to a portion between the third switch S3 and the third resistor R3. A state where no voltage is applied is set. However, as shown in FIG. 8, the sixth switch S6 is normally open, and the microcomputer 11 is connected to the A / D port via the A / D port while the third switch S3 and the fourth switch S4 are closed. It is also possible to adopt a configuration in which the circuit is closed only when the conversion data is read, and the voltage of the portion between the third switch S3 and the third resistor R3 is applied to the A / D port of the microcomputer 11. With such a configuration, not only the application of a negative potential to the A / D port of the microcomputer 11 but also the suppression of the application of unnecessary noise and other stress to the A / D port of the microcomputer 11 is suppressed. You can also.
[0063]
In addition, the present invention is not limited to the circuit configuration shown in the present embodiment, and a capacitor is connected in series to a DC power supply whose positive terminal side and negative terminal side wiring are insulated from the ground potential portion for a first set time. First switching means, second switching means for connecting the capacitor in series between the positive terminal of the power supply and the ground potential section for a second set time, and between the negative terminal of the power supply and the ground potential section A third switching means for connecting a capacitor in series for a second set time, and a detecting means for detecting a voltage between both terminals of the capacitor after the first, second and third switching means are cut off. If it has the fourth switching means and the like, it can be applied to insulation detection devices having various circuit configurations.
[0064]
【The invention's effect】
According to the present invention, the accuracy of the estimated power supply voltage can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an embodiment of an insulation detection device to which the present invention is applied.
FIG. 2 is a flowchart showing an operation of calculating an insulation resistance in one embodiment of an insulation detection device to which the present invention is applied.
FIG. 3 is a time chart showing a charge / discharge state of a capacitor and a voltage reading timing with respect to an operation of each switch unit.
FIG. 4 is a diagram illustrating a detection error of an insulation resistance value detected during a measurement time of each power supply voltage with respect to the insulation resistance value.
FIG. 5 is a flowchart showing an operation in a correction mode in one embodiment of the insulation detection device to which the present invention is applied.
FIG. 6 is a diagram showing a schematic configuration of a modified example of the insulation detection device to which the present invention is applied.
FIG. 7 is a flowchart showing an operation in a correction mode in a modification of the insulation detection device to which the present invention is applied.
FIG. 8 is a time chart showing a charging / discharging state of a capacitor and a voltage reading timing with respect to an operation of each switch unit in a modification of the insulation detection device to which the present invention is applied.
[Explanation of symbols]
1 Insulation detection device
3 power supply
5a Positive main circuit wiring
5b Negative main circuit wiring
7 Ground potential section
9 Capacitor
11 microcomputer
S1 First switch
S2 Second switch
S3 3rd switch
S4 4th switch
S5 Fifth switch
S6 6th switch
S7 7th switch
Rp Positive terminal side ground fault resistance
Rn Negative terminal side ground fault resistance

Claims

First switching in which a capacitor is connected in series to a DC power supply whose wiring on the positive terminal side and the negative terminal side are insulated from the ground potential portion for a first set time shorter than the time when the capacitor is completely charged Means,
Second switching means for connecting the capacitor in series between a positive terminal of the power supply and the ground potential portion for a second set time;
Third switching means for connecting the capacitor in series between the ground potential section and the negative terminal of the power supply for a second set time;
Fourth switching means for connecting a detecting means for detecting a voltage between both terminals of the capacitor after the first, second and third switching means are cut off;
A power supply voltage of the power supply is estimated based on a voltage detected by the detection means after the first switching means is cut off, and the estimated power supply voltage of the power supply and the power supply voltage after the second and third switching means are cut off. Calculating means for determining an insulation resistance of the power supply with respect to the ground potential portion based on each detection voltage at the detection means,
After disconnecting the first switching means in a state where a reference power supply having a known power supply voltage is connected in place of the power supply, and a reference resistance having a known resistance value is connected in correspondence with the insulation resistance of the power supply with respect to the ground potential portion, Estimating the power supply voltage of the reference power supply by the calculation means based on the voltage detected by the detection means, and calculating the power supply voltage based on the estimated power supply voltage of the reference power supply and the known power supply voltage of the reference power supply. And a correction unit for correcting the power supply voltage of the power supply estimated in step (a).

The first switching unit includes a first switch unit connected to a positive terminal of the power supply, and a second switch unit connected to a negative terminal of the power supply, wherein the third switching unit includes: The second switch unit; and a third switch unit connected in series to the first switch, wherein the second switching unit includes the first switch unit and the second switch unit. A fourth switch unit connected in series with the first switch unit, wherein the fourth switching unit includes the third switch unit and the fourth switch unit, and wherein the first switch unit and the fourth switch unit are connected to each other. 3, a first diode, a first resistor, and a first resistor that rectify in a direction from the positive side to the negative side between the second switch unit and the fourth switch unit. A capacitor is connected in series and the first A second diode and a second resistor, which rectify in the opposite direction to the first diode, are connected in series with the diode and the first resistor in parallel, and the detecting means includes: The insulation detection device according to claim 1, wherein the insulation detection device is connected between the fourth switch unit and the detection unit and the fourth switch unit are grounded to the ground potential unit. .

The calculating means obtains a resistance value of the reference resistor based on the corrected power supply voltage obtained by the calculating means and each detection voltage of the detecting means after the second and third switching means are cut off, The correction means corrects the value of the insulation resistance of the power supply with respect to the ground potential portion of the power supply obtained by the calculation means, based on the resistance value of the reference resistor obtained by the calculation means and the known resistance value of the reference resistance. The insulation detection device according to claim 1 or 2, wherein the insulation detection is performed.

The detection means, the calculation means, and the correction means are formed of one microcomputer, and a correction mode switching means for changing a voltage applied to the correction mode port is provided in a correction mode port provided in the microcomputer. The microcomputer is switched to a correction mode in which the microcomputer is operated as the correction means by changing the voltage applied to the correction mode port by the correction mode switching means. 4. The insulation detecting device according to any one of items 3 to 5.