JP2004170103A - Insulation detector for non-grounded power supply - Google Patents

Insulation detector for non-grounded power supply Download PDF

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JP2004170103A
JP2004170103A JP2002333310A JP2002333310A JP2004170103A JP 2004170103 A JP2004170103 A JP 2004170103A JP 2002333310 A JP2002333310 A JP 2002333310A JP 2002333310 A JP2002333310 A JP 2002333310A JP 2004170103 A JP2004170103 A JP 2004170103A
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switch
capacitor
power supply
switching
time
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JP3962990B2 (en
Inventor
Kazutoshi Oshiro
和俊 大城
Yoshihiro Kawamura
佳浩 河村
Toshihiro Sone
利浩 曽根
Tadashi Shimada
正 嶋田
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Yazaki Corp
矢崎総業株式会社
Honda Motor Co Ltd
本田技研工業株式会社
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulation detector for a non-grounded power supply with enhanced detection accuracy. <P>SOLUTION: A combination of first and second switches S1 and S2 as a first switching means for performing connection for a first set period, a combination of the first and fourth switches S1 and S4 as a second switching means for performing connection for a second set period, a combination of the second and third switches S2 and S3 as a third switching means for likewise performing connection for the second set period, and a combination of the third and fourth switches S3 and S4 as a fourth switching means for thereto connecting a microcomputer 11 for detecting the terminal voltage of a capacitor 9, are prepared for a series circuit comprising a DC power supply 3 and the capacitor 9. These switching means of four kinds are used successively to calculate insulation resistance by means of the microcomputer 11. <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、演算手段で求めた地絡抵抗から絶縁状態の検出や判定などを行っている。
【0003】
【特許文献1】
特開平8−226950号公報(第4−7頁、第1図)
【発明が解決しようとする課題】
上記のような絶縁検出装置では、地絡抵抗を求める際、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、求め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求め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】
本発明の課題は、絶縁状態の検出精度を向上することにある。
【0005】
【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とすることにより上記課題を解決する。
【0006】
このような構成とすることにより、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の設定時間を設定すれば、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絶縁抵抗を求めることで、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。
【0007】
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。
【0008】
さらに、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。
【0009】
【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。
【0010】
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、検出手段と演算手段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。
【0011】
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。
【0012】
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抵抗R2の両端子間には、第2抵抗R2と並列に第5スイッチS5が接続されている。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。
【0013】
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との間には、検出手段と演算手段を兼ねるマイコン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ポートを介して接続されている。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。
【0014】
したがって、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、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、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、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。なお、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。
【0015】
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。
【0016】
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、コンデンサ9の両端子間の電圧VCが降下する。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)。
V0=V0s(1−EXP(−T1/C・R1)) …(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の抵抗値である。
【0017】
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とで、第2抵抗R2の抵抗値を下げた状態とし、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)。
【0018】
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。
【0019】
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、コンデンサ9の両端子間の電圧VCが降下する。そして、第3スイッチS3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113)。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VCNにより、次式(2)から電源3の負端子側の接地電位部7となる車体などに対する絶縁抵抗、すなわち負端子側の地絡抵抗Rnを算出する(ステップ115)。
Rn=−R1−T2/C・ln(1−VCN/V0s) …(2)
ただし、式(2)において、T2は第1スイッチS1及び第4スイッチS4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、V0sはステップ107で推定した電源電圧である。
【0020】
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をバイパスさせることで、第2抵抗R2の抵抗値を下げた状態とし、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117)。
【0021】
ステップ117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119)。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。
【0022】
ステップ119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、コンデンサ9の両端子間の電圧VCが降下する。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121)。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VCPにより、次式(3)から電源3の正端子側の接地電位部7となる車体などに対する絶縁抵抗、すなわち正端子側の地絡抵抗Rpを算出する(ステップ123)。
Rp=−R1−T2/C・ln(1−VCP/V0s) …(3)
ただし、式(3)において、T2は第2スイッチS2及び第3スイッチS3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、V0sはステップ107で推定した電源電圧である。
【0023】
一方、図示していないスイッチング制御回路は、ステップ123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とで、第2抵抗R2の抵抗値を下げた状態とし、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125)。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125までの絶縁状態の検出サイクルを繰り返す。
【0024】
マイコン11は、1回の絶縁状態の検出サイクルで求めた電源3の正端子側の地絡抵抗Rpと、負端子側の地絡抵抗Rnの値から絶縁状態を判定する。例えば、電源3の正端子側の地絡抵抗Rpと、予め定められた基準抵抗値とを比較し、地絡抵抗Rp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。
【0025】
ところで、式(2)、(3)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、電源3の正端子側の地絡抵抗Rp、負端子側の地絡抵抗Rnの計測精度に影響し、検出した地絡抵抗Rp、Rnの値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。
【0026】
これに対して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、ステップ115及びステップ123で行う正端子側の地絡抵抗Rp、負端子側の地絡抵抗Rnの演算に用いることで、コンデンサ9の容量や抵抗R1の抵抗値のばらつきに対する補正が行われ、これらのばらつきによって生じる、実際の正端子側地絡抵抗Rp及び負端子側地絡抵抗Rnの値と、算出した正端子側地絡抵抗Rp及び負端子側地絡抵抗Rnの値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。
【0027】
このような本実施形態の絶縁検出装置1によって計測した正端子側の地絡抵抗Rp及び負端子側の地絡抵抗Rnの値と、実際の正端子側の地絡抵抗Rp及び負端子側の地絡抵抗Rn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。
【0028】
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、つまり補正無しの場合に比べて、本実施形態の絶縁検出装置1で検出した場合、つまり補正ありの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。
【0029】
したがって、絶縁不良を判定する地絡抵抗の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地絡抵抗の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、絶縁不良を判定する地絡抵抗の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において絶縁不良を判定する地絡抵抗の値を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。
【0030】
さらに、本実施形態の絶縁検出装置1では、コンデンサ9などの容量のばらつきによる絶縁状態の検出への影響を低減できるので、製品間差のばらつきがより少ない高品位、高精度の部品を用いる必要がなく、絶縁検出精度を向上するためのコストの増大を抑えることができる。
【0031】
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。
【0032】
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5に示すように、第2ダイオードD2と第2抵抗R2との間から接地電位部7に第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を直列に接続した構成などにするこもできる。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。
【0033】
また、本実施形態では、正端子側の地絡抵抗Rpと負端子側の地絡抵抗Rnを個別に算出し、これにより絶縁不良の部位も検出できるようにしている。しかし、絶縁不良の部位を検出せず絶縁不良の発生のみを判定する場合などには、推定した電源電圧V0sと検出電圧VCP、VCNなどとに基づいて正端子側の地絡抵抗Rpと負端子側の地絡抵抗Rnとを代表する地絡抵抗値などを算出する別の式を用いることもできる。
【0034】
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。
【0035】
【発明の効果】
本発明によれば、絶縁状態の検出精度を向上できる。
【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変形例を示す図である。
【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
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 performs detection and determination of the insulation state from the ground fault resistance obtained by the calculation means.
[0003]
[Patent Document 1]
JP-A-8-226950 (page 4-7, FIG. 1)
[Problems to be solved by the invention]
In the insulation detection device as described above, when calculating the ground fault resistance, an expression including the capacitance of the capacitor as a constant is used, but the capacitance of the capacitor to be used as a constant depends on variations in capacitance between products and temperature changes. There may be variations in capacitance and the like, and there may be a change with time in the capacitance and the like. If the values used as constants vary or change in this way, the measurement error between the obtained ground fault resistance value and the actual ground fault resistance value increases, and the insulation state detection accuracy decreases. I will. Therefore, 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, even if there are variations or changes in the values used as constants for obtaining the ground fault resistance such as the capacitance of the capacitor. ing.
[0004]
An object of the present invention is to improve the detection accuracy of an insulation state.
[0005]
[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 cut off. A power supply voltage is estimated based on a voltage detected by the fourth switching means for connecting the detection means and the detection means after the first switching means is cut off, and the estimated power supply voltage and the second and third switching means are estimated. The solution to the problem by calculating means for obtaining the insulation resistance to ground potential of the power on the basis of the respective detection voltage by the detection means after blocking the configuration with.
[0006]
With such a configuration, if the first set time is set to a time shorter than the time required to completely charge the capacitor, the DC power is supplied by the first switching means during the first set time. 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 calculation means can estimate the power supply voltage from the voltage. Then, an insulation resistance is obtained based on the estimated power supply voltage and a voltage detected by the detection unit after the second and third switching units are cut off, thereby reducing a measurement error of the insulation resistance and detecting the insulation state. Accuracy can be improved.
[0007]
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.
[0008]
Further, when the bypass means including the fifth switch section that 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 reduced, and the time required for detecting the insulation state can be reduced, which is preferable.
[0009]
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.
[0010]
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 or the like are connected in series or a fuel cell. 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 each connected to the ground potential. The power supply 3 is a non-grounded power supply. The insulation detecting 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 detecting means and calculating means and determines an insulation state, and sets each switch. And a switching control circuit (not shown) that performs opening and closing control according to the set time.
[0011]
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.
[0012]
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. A fifth switch S5 is connected between both terminals of the second resistor R2 in parallel with the second resistor R2. 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.
[0013]
A third resistor R3 is connected between the third switch S3 and the fourth resistor R4 in series with the third switch S3 and the fourth resistor R4, and is connected between the third switch S3 and the third resistor R3. Is connected to the microcomputer 11 via an analog / digital conversion port of the microcomputer 11, that is, an A / D port. Further, a portion between the third resistor R3 and the fourth resistor R4 is grounded to the ground potential section 7.
[0014]
Accordingly, 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. A second switching means for connecting a capacitor 9 in series between the terminal and the ground potential unit 7 for a second set time includes a first switch S1, a fourth switch S4, a switching control circuit (not shown), 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 not shown. In a switching control circuit or the like, the fourth switching means is formed by a third switch S3, a fourth switch S4, a switching control circuit (not shown), and the like. 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. .
[0015]
The operation of the insulation detecting device having such a configuration and the features of the present invention will be described. When the insulation detection device 1 starts detecting the insulation state as shown in FIGS. 2 and 3, a switching control circuit (not shown) sets the first switch S1 and the second switch S2 to a first set time. The circuit is closed for one closing time T1 (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.
[0016]
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, and the voltage VC between both terminals of the capacitor 9 drops. 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).
V0 = V0s (1−EXP (−T1 / C · R1)) (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, and R1 is the resistance value of the first resistor R1.
[0017]
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. By bypassing the second resistor R2, the resistance value of the second resistor R2 is reduced, and the time required for discharging from the capacitor 9 is 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).
[0018]
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.
[0019]
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, and the voltage VC between both terminals of the capacitor 9 drops. Then, after a lapse of a predetermined time tw2 since the third switch S3 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 113). . Based on the value of the voltage VC between both terminals of the capacitor 9 at this time, that is, the detection voltage VCN, the insulation resistance with respect to the vehicle body or the like which becomes the ground potential portion 7 on the negative terminal side of the power supply 3 from the following equation (2), that is, the ground on the negative terminal side The short-circuit resistance Rn is calculated (step 115).
Rn = -R1-T2 / C.ln (1-VCN / V0s) (2)
In the equation (2), T2 is the closing time of the first switch S1 and the fourth switch S4, C is the capacitance of the capacitor 9, R1 is the resistance value of the first resistor R1, and V0s is the power supply voltage estimated in step 107. is there.
[0020]
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. By bypassing the second resistor R2, the resistance value of the second resistor R2 is reduced, 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 117).
[0021]
When it is confirmed in step 117 that the voltage VC is 0 V, a switching control circuit (not shown) opens the fourth switch S4, and after a predetermined time tw1, closes the second switch S2. 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 119). 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.
[0022]
When the second closing time T2 elapses in step 119, as shown in FIGS. 2 and 3, the second switch S2 is opened or cut off, and after the elapse of a 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, and the voltage VC between both terminals of the capacitor 9 drops. Then, after a predetermined time tw2 has elapsed since the fourth switch S4 was 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 121). . Based on the value of the voltage VC between both terminals of the capacitor 9 at this time, that is, the detection voltage VCP, the insulation resistance to the vehicle body or the like which becomes the ground potential portion 7 on the positive terminal side of the power supply 3 from the following equation (3), that is, the ground on the positive terminal side The short-circuit resistance Rp is calculated (step 123).
Rp = -R1-T2 / C.ln (1-VCP / V0s) (3)
In the equation (3), T2 is the closing time of the second switch S2 and the third switch S3, C is the capacitance of the capacitor 9, R1 is the resistance value of the first resistor R1, and V0s is the power supply voltage estimated in step 107. is there.
[0023]
On the other hand, the switching control circuit (not shown) closes the fifth switch S5 with the third switch S3 and the fourth switch S4 closed after detecting the voltage VC between both terminals of the capacitor 9 in step 123. By bypassing the second resistor R2, the resistance value of the second resistor R2 is reduced, 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 125). 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 125 is repeated.
[0024]
The microcomputer 11 determines the insulation state from the value of the ground fault resistance Rp on the positive terminal side of the power supply 3 and the value of the ground fault resistance Rn on the negative terminal side obtained in one insulation state detection cycle. For example, the ground fault resistance Rp on the positive terminal side of the power supply 3 is compared with a predetermined reference resistance value. If the ground fault resistance Rp is equal to or less than the reference resistance value, insulation failure has occurred. Is determined.
[0025]
By the way, as can be seen from the equations (2) and (3), 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 positive terminal side of the power supply 3 is changed. The measurement accuracy of the ground fault resistance Rp and the ground fault resistance Rn on the negative terminal side is affected, and the accuracy of the detected ground fault resistances Rp and Rn is reduced. 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.
[0026]
On the other hand, in the insulation detection device 1 of the present embodiment, the first switch S1 and the second switch S2 in the first stage of the insulation detection cycle are set to the first switch S1 and the second switch S2, which are shorter than the time required to completely charge the capacitor 9. By closing the circuit for the closing time 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, the estimated power supply voltage V0s including the variation is used in the calculation of the ground fault resistance Rp on the positive terminal side and the ground fault resistance Rn on the negative terminal side performed in steps 115 and 123, so that the capacitance and the resistance of the capacitor 9 are obtained. Corrections are made for variations in the resistance value of R1, and the actual values of the positive terminal side ground fault resistance Rp and the negative terminal side ground fault resistance Rn, and the calculated positive terminal side ground fault resistance Rp and negative An error with the value of the terminal-side ground fault resistance Rn can be reduced. Therefore, the detection accuracy of the insulation state can be improved.
[0027]
The values of the ground fault resistance Rp on the positive terminal side and the ground fault resistance Rn on the negative terminal side measured by the insulation detection device 1 of the present embodiment and the actual ground fault resistance Rp on the positive terminal side and the actual ground fault resistance Rp on the negative terminal side are measured. FIG. 4 shows the result of calculating the error from the value of the ground fault resistance Rn on the assumption that the capacitor 9 having a certain predetermined standard capacity and the first resistor R1 having a certain predetermined standard resistance value are 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.
[0028]
As can be seen from FIG. 4, the case where detection is performed by the insulation detection device 1 of the present embodiment, that is, the case where correction is performed, is greater than the case where detection is performed by the conventional insulation detection device, that is, without correction. The measurement error is reduced with respect to the value. 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.
[0029]
Therefore, when the value of the ground fault resistance for determining the insulation failure is set to a relatively large value, the first closing time T1 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 such that the measurement error becomes small around the value of the ground fault resistance for determining the insulation failure. For example, if the value of the ground fault resistance for judging insulation failure is set to RΩ in FIG. 4, it is preferable to select 2t seconds as the first closing time T1, and at this time, ± 10 %, Whereas the insulation detection device 1 of the present embodiment has a measurement error of ± 2% or less, and the insulation state detection accuracy can be improved.
[0030]
Furthermore, in the insulation detection device 1 of the present embodiment, it is possible to reduce the influence on the detection of the insulation state due to the variation in the capacitance of the capacitor 9 or the like. Therefore, an increase in cost for improving insulation detection accuracy can be suppressed.
[0031]
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.
[0032]
Note that the bypass unit including the fifth switch S5 is not limited to the configuration of the present embodiment, and the bypass unit includes a ground potential unit 7 between the second diode D2 and the second resistor R2 as shown in FIG. Alternatively, a configuration may be adopted in which a fifth switch S5 and a fifth resistor R5 having a lower resistance than the second resistor R2 are connected in series. 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.
[0033]
Further, in the present embodiment, the ground fault resistance Rp on the positive terminal side and the ground fault resistance Rn on the negative terminal side are individually calculated, so that a portion having insulation failure can be detected. However, in the case where only the occurrence of insulation failure is determined without detecting the location of insulation failure, for example, the ground fault resistance Rp on the positive terminal side and the negative terminal on the basis of the estimated power supply voltage V0s and the detection voltages VCP, VCN, etc. Another formula for calculating a ground fault resistance value or the like representing the ground fault resistance Rn on the side can also be used.
[0034]
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.
[0035]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the detection precision of an insulation state 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 diagram showing 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
Rp Positive terminal side ground fault resistance
Rn Negative terminal side ground fault resistance

Claims (3)

  1. 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、該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、
    前記電源の正端子と前記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と、
    前記接地電位部と前記電源の負端子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3のスイッチング手段と、
    前記第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、
    前記第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前記電源の電源電圧を推定し、該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前記検出手段での各検出電圧とに基づいて前記電源の前記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非接地電源の絶縁検出装置。
    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;
    Estimating a power supply voltage of the power supply based on a voltage detected by the detecting means after the first switching means is cut off, and detecting the estimated power supply voltage and the detecting means after the second and third switching means are cut off Calculating means for calculating an insulation resistance of the power supply with respect to the ground potential portion based on each of the detection voltages obtained in the step (a).
  2. 前記第1のスイッチング手段が、前記電源の正端子に接続された第1のスイッチ部と、前記電源の負端子に接続された第2のスイッチ部とを含み、前記第3のスイッチング手段が、前記第2のスイッチ部と、前記第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、前記第2のスイッチング手段が、前記第1のスイッチ部と、前記第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、前記第4のスイッチング手段が、前記第3のスイッチ部と、前記第4のスイッチ部とを含み、前記第1のスイッチ部と前記第3のスイッチ部との間と、前記第2のスイッチ部と前記第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の抵抗及び前記コンデンサが直列に接続され、前記第1のダイオード及び前記第1の抵抗に並列に、該第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、前記検出手段が、前記第3のスイッチ部と前記第4のスイッチ部との間に接続され、前記検出手段と前記第4のスイッチ部との間が前記接地電位部に接地されていることを特徴とする請求項1に記載の絶縁検出装置。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. .
  3. 閉路したときに前記第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ことを特徴とする請求項1または2に記載の絶縁検出装置。3. The insulation detecting device according to claim 1, further comprising a bypass unit including a fifth switch unit that forms a path that bypasses the second resistor when the circuit is closed.
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