JP2004093400A

JP2004093400A - Nox sensor and simulator simulating operation of oxygen sensor

Info

Publication number: JP2004093400A
Application number: JP2002255680A
Authority: JP
Inventors: Shinji Kumazawa; 熊澤　真治; Akihiro Kobayashi; 小林　章弘; Yoshinori Inoue; 井上　義規; Yuji Oi; 大井　雄二; Norikazu Ieda; 家田　典和
Original assignee: NGK Spark Plug Co Ltd
Current assignee: Niterra Co Ltd
Priority date: 2002-08-30
Filing date: 2002-08-30
Publication date: 2004-03-25
Anticipated expiration: 2022-08-30
Also published as: JP4045148B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor simulator capable of easily simulating the operation of a sensor, particularly, simulating the operation of an all area air-fuel ratio sensor or an NOx sensor among oxygen sensors. <P>SOLUTION: This NOx sensor simulator comprises an altering means 30 outputting a control signal indicating the control target of a first oxygen pump current, a current generating means 37 outputting, based on a signal indicating a partial pressure of oxygen, a signal simulating the first oxygen pump current, a comparing means 31 comparing the control signal outputted by the altering means 30 with the signal simulating the first oxygen pump current outputted by the first oxygen pump current generating means 37 and indicating the compared results, a frequency characteristic set means 32 setting the frequency characteristics of the output signal from the comparing means 31, and an oxygen partial pressure signal generating means 34 outputting, based on the signal having frequency characteristics set by the frequency characteristic set means 32, the signal indicating the partial pressure of oxygen. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、センサのシミュレータに関し、特に、酸素センサ、中でも、全領域空燃比センサ（ＵＥＧＯ）、或いはＮＯｘセンサの動作を模擬することができるセンサのシミュレータに関する。
【０００２】
【従来の技術】
従来、センサの制御回路を検査する場合、実際のセンサ素子を用いて、制御回路の検査を行っている。
【０００３】
【発明が解決しようとする課題】
しかしながら、センサの制御回路の検査において、実際のセンサ素子を用いた場合、使用によるセンサ素子の変化により、複数の制御回路の検査に亘って、均一な条件で検査を行うことが困難であるという問題がある。また、目標通りにセンサ素子の状態を維持することが困難であるという問題点がある。
【０００４】
本発明の目的は、センサの動作を簡単に模擬することができるセンサのシミュレータ、特に、酸素センサ、中でも、全領域空燃比センサ、或いはＮＯｘセンサの動作を模擬することができるセンサのシミュレータを提供することである。
【０００５】
【課題を解決するための手段】
本発明は第１の視点において、第１拡散抵抗を介して被検ガスが導入される第１測定室と、前記第１測定室の内側と外側に設けられた一対の電極を備え、該一対の電極間の電位差に基づいて前記第１測定室内における被検ガス中の酸素分圧を検出する酸素分圧検知セルと、前記第１測定室の内側と外側に設けられた一対の電極を備え、前記第１測定室の内側から外側へ又は外側から内側へ該一対の電極を介して酸素を汲み出すことにより、被検ガス中の酸素分圧に応じた電流（以下「第１酸素ポンプ電流」という）が流れる第１酸素ポンプセルと、前記第１測定室から第２拡散抵抗を介してガスが導入される第２測定室と、前記第２測定室の内側と外側に設けられた一対の電極を備え、前記第２測定室内の窒素酸化物を分解し、解離した酸素が移動することによりＮＯｘ濃度に応じた電流（以下「第２酸素ポンプ電流」という）が該一対の電極間に流れる第２酸素ポンプセルと、を備えるＮＯｘセンサの動作をシミュレートする装置であって、前記第１酸素ポンプ電流の制御目標を示す制御信号を出力する変更手段と、酸素分圧を示す信号に基づいて、前記第１酸素ポンプ電流を模擬した信号を出力する第１酸素ポンプ電流生成手段と、前記変更手段が出力する前記制御信号と前記第１酸素ポンプ電流生成手段が出力する前記第１酸素ポンプ電流を模擬した信号とを比較して比較結果を示す信号を出力する比較手段と、前記比較手段の出力信号の周波数特性を設定する周波数特性設定手段と、前記周波数特性設定手段によって周波数特性が設定された信号に基づいて、前記酸素分圧を示す信号を出力する酸素分圧信号生成手段とを有するＮＯｘセンサのシミュレータを提供する。
【０００６】
本発明は第２の視点において、拡散抵抗を通じて測定室に導入されるガスの酸素分圧を検出する酸素濃淡電池セルと、前記酸素濃淡電池セルにより検出される酸素分圧に応じて、前記酸素濃淡電池セルの酸素濃淡起電力が一定となるよう前記測定室内から外へ或いは該測定室外から内へ酸素を汲み出す酸素ポンピングセルと、を有し、前記酸素ポンピングセルに流れる酸素ポンピング電流に基づいて被測定ガス中の酸素濃度を測定する酸素センサの動作をシミュレートする装置であって、前記酸素ポンピング電流の制御目標を示す制御信号を出力する変更手段と、酸素分圧を示す信号に基づいて、前記酸素ポンピング電流を模擬した信号を出力する酸素ポンピング電流生成手段と、前記変更手段が出力する前記制御信号と前記酸素ポンピング電流生成手段が出力する前記酸素ポンピング電流を模擬した信号とを比較して比較結果を示す信号を出力する比較手段と、前記比較手段の出力信号の周波数特性を設定する周波数特性設定手段と、前記周波数特性設定手段によって周波数特性が設定された信号に基づいて、前記酸素分圧を示す信号を出力する酸素分圧信号生成手段とを有する酸素センサのシミュレータを提供する。
【０００７】
本発明は第３の視点において、酸素分圧を検出する酸素濃淡電池セルと、前記酸素濃淡電池セルにより検出される酸素分圧に応じて酸素を汲み出す酸素ポンピングセルと、を有し、前記酸素ポンピングセルに流れる酸素ポンピング電流に基づいて被測定ガス中の所定ガス濃度を測定するセンサの動作をシミュレートする装置であって、前記酸素ポンピング電流の制御目標を示す制御信号を出力する変更手段と、酸素分圧を示す信号に基づいて、前記酸素ポンピング電流を模擬した信号を出力する酸素ポンピング電流生成手段と、前記変更手段が出力する前記制御信号と前記酸素ポンピング電流生成手段が出力する前記酸素ポンピング電流を模擬した信号とを比較して比較結果を示す信号を出力する比較手段と、前記比較手段の出力信号の周波数特性を設定する周波数特性設定手段と、前記周波数特性設定手段によって周波数特性が設定された信号に基づいて、前記酸素分圧を示す信号を出力する酸素分圧信号生成手段と、を有するセンサのシミュレータを提供する。
【０００８】
【発明の実施の形態】
本発明の好ましい実施の形態に係るセンサのシミュレータは、酸素ポンピングセルと酸素濃淡電池セルの組合せからなるセンサ、特に、酸素センサ、中でも、全領域空燃比センサ（ＵＥＧＯ）又はＮＯｘセンサの動作を模擬するために用いられる。
【０００９】
本発明の好ましい実施の形態に係るＮＯｘセンサのシミュレータは、図２を参照して、第１酸素ポンプ電流の制御目標を示す制御信号を出力する変更手段３０と、酸素分圧を示す信号に基づいて、前記第１酸素ポンプ電流を模擬した信号を出力する第１酸素ポンプ電流生成手段３７と、変更手段３０が出力する前記制御信号と第１酸素ポンプ電流生成手段３７が出力する前記第１酸素ポンプ電流を模擬した信号とを比較して比較結果を示す信号を出力する比較手段３１と、比較手段３１の出力信号の周波数特性を設定する周波数特性設定手段３２と、周波数特性設定手段３２によって周波数特性が設定された信号に基づいて、酸素分圧を示す信号を出力する酸素分圧信号生成手段３４とを有するＮＯｘセンサのシミュレータを提供する。
【００１０】
本発明の好ましい実施の形態に係る酸素センサのシミュレータは、図２を参照して、拡散抵抗を通じて測定室に導入されるガスの酸素分圧を検出する酸素濃淡電池セル（図１の３）と、前記酸素濃淡電池セルにより検出される酸素分圧に応じて、前記酸素濃淡電池セルの酸素濃淡起電力が一定となるよう前記測定室内から外へ或いは該測定室外から内へ酸素を汲み出す酸素ポンピングセル（図１の１）と、を有し、前記酸素ポンピングセルに流れる酸素ポンピング電流に基づいて被測定ガス中の酸素濃度を測定する酸素センサの動作をシミュレートする装置であって、前記酸素ポンピング電流の制御目標を示す制御信号を出力する変更手段３０と、酸素分圧を示す信号に基づいて、前記酸素ポンピング電流を模擬した信号を出力する酸素ポンピング電流生成手段３７と、変更手段３０が出力する前記制御信号と酸素ポンピング電流生成手段３７が出力する前記酸素ポンピング電流を模擬した信号とを比較して比較結果を示す信号を出力する比較手段３１と、比較手段３１の出力信号の周波数特性を設定する周波数特性設定手段３２と、周波数特性設定手段３２によって周波数特性が設定された信号に基づいて、前記酸素分圧を示す信号を出力する酸素分圧信号生成手段３４とを有する酸素センサのシミュレータを提供する。
【００１１】
本発明の好ましい実施の形態に係るセンサのシミュレータは、図１を参照して、酸素分圧を検出する酸素濃淡電池セル３と、酸素濃淡電池セル３により検出される酸素分圧に応じて酸素を汲み出す酸素ポンピングセル１と、を有し、酸素ポンピングセル１に流れる酸素ポンピング電流に基づいて被測定ガス中の所定ガス濃度を測定するセンサの動作をシミュレートする装置であって、図２を参照して、前記酸素ポンピング電流の制御目標を示す制御信号を出力する変更手段３０と、酸素分圧を示す信号に基づいて、前記酸素ポンピング電流を模擬した信号を出力する酸素ポンピング電流生成手段３７と、変更手段３０が出力する前記制御信号と酸素ポンピング電流生成手段３７が出力する前記酸素ポンピング電流を模擬した信号とを比較して比較結果を示す信号を出力する比較手段３１と、比較手段３１の出力信号の周波数特性を設定する周波数特性設定手段３２と、周波数特性設定手段３２によって周波数特性が設定された信号に基づいて、前記酸素分圧を示す信号を出力する酸素分圧信号生成手段３４とを有する。
【００１２】
本発明の好ましい実施の形態に係るセンサのシミュレータは、、酸素分圧信号生成手段（図２の３４）に接続され、酸素分圧検知セル（図１の３）の内部抵抗に対応する抵抗値を設定する酸素分圧検知セルの素子抵抗設定手段を有する。
【００１３】
【実施例】
以上説明した本発明の好ましい実施の形態をさらに明確化するために、以下図面を参照して、本発明の一実施例を説明する。
【００１４】
図１（Ａ）〜図１（Ｄ）は、本発明の一実施例に係る検査装置によって検査されるＮＯｘセンサの構成要素であるＮＯｘセンサ素子の構成及び測定原理を説明するための図である。
【００１５】
図１（Ａ）を参照すると、ＮＯｘセンサ素子は、主として、第１酸素ポンプセル１、第２酸素ポンプセル２及び酸素分圧検知セル３、さらにＮＯｘセンサ素子を所定の作動温度に加熱するヒータ４から構成されている。第１酸素ポンプセル１と酸素分圧検知セル３の間には、第１測定室５が形成されている。第１測定室５には、第１拡散孔７を介して、被検ガスが導入される。第１測定室５は、第２拡散孔８を通じて、第２測定室６と連通している。
【００１６】
第１酸素イオンポンプセル１は、ジルコニアのような酸素イオン伝導性を有する固体電解質と、固体電解質上に形成された一対の電極９，１０から構成されている。電極１０は第１測定室５に面して配置され、電極９は外部に面して配置されている。電極１０上で第１測定室５内の酸素等が解離され生成された酸素イオンが固体電解質を通って電極９上から外部へ導出され、このとき該固体電解質を通じて流れる電流が第１酸素ポンプ電流Ｉｐ１である。
【００１７】
第２酸素イオンポンプセル２は、ジルコニアのような酸素イオン伝導性を有する固体電解質と、固体電解質上に形成された一対の電極１３，１４から構成されている。電極１３は第２測定室６に面して配置され、電極１４は第２測定室６外に配置されると共に酸素濃度が安定した雰囲気に晒されている。電極１３上で第２測定室６内のＮＯｘ等が解離され生成された酸素イオンが固体電解質を通って電極１４上から外部へ導出され、このとき固体電解質を通じて流れる電流が第２酸素ポンプ電流Ｉｐ２である。通常の測定モードにおいて、電極１３と電極１４間には一定の電圧が印加される。
【００１８】
酸素分圧検知セル（酸素濃淡電池セル）３は、ジルコニアのような酸素イオン伝導性を有する固体電解質と、固体電解質上に形成された一対の電極１１，１２から構成されている。電極１１は第１測定室５に面して配置され、電極１２は酸素濃度が安定した雰囲気に晒されている。したがって、電極１１と電極１２の間に発生する電位差に基づいて、第１測定室５内の酸素濃度、結局、被検ガス中の酸素濃度を検出することができる。
【００１９】
図１（Ａ）を参照すると、センサ制御手段３０（図２参照）は、酸素分圧検知セルに現れる第１測定室５内の酸素濃度を検出すると共に、第１測定室５外に設けられた電極１２上の酸素濃度を制御する酸素分圧セル制御手段２１と、酸素分圧検知セル３の検出出力に基づいて第１酸素ポンプ電流Ｉｐ１を制御することにより、第１測定室５内の酸素濃度を可及的に一定に制御する第１酸素ポンプセル制御手段２０と、第２酸素ポンプセル２に可及的に一定な所定の電圧を印加することにより、ＮＯｘ濃度に応じた第２酸素ポンプ電流Ｉｐ２が流れるように第２酸素ポンプセル２を制御する第２酸素ポンプセル制御手段２２と、を含んで構成される。
【００２０】
以上説明したＮＯｘセンサ素子及びその制御手段を用いたＮＯｘ測定原理については、図１（Ｂ）〜図１（Ｄ）に示すとおりであるから、これらを参照することとする。
【００２１】
また、酸素センサ、中でも、全領域空燃比センサ（ＵＥＧＯ）は、、図１（Ａ）〜図１（Ｄ）に示したＮＯｘセンサから、第２酸素ポンプセル２を除いて構成することができる。
【００２２】
次に、以上説明したＮＯｘセンサ及び全領域空燃比センサ（ＵＥＧＯ）の動作を選択的にシミュレートすることができる本発明の一実施例に係るセンサのシミュレータについて説明する。
【００２３】
図２は、本発明の一実施例に係る、ＵＥＧＯ又はＮＯｘセンサのシミュレータを説明するための図である。
【００２４】
図２を参照すると、本発明の一実施例に係るシミュレータは、第１酸素ポンプ電流の制御目標を示す制御信号、例えば、第１酸素ポンプセル１（図１参照）のような酸素ポンピングセルに印加される電圧Ｖ１を変更させるためのＩｐ制御信号を主力するＶ１変更手段３０と、酸素分圧を示す信号に基づいて第１酸素ポンプ電流Ｉｐ１を模擬した信号を出力する第１酸素ポンプ電流生成手段３７と、Ｖ１変更手段３０が出力する前記制御信号と第１酸素ポンプ電流生成手段３７が出力する第１酸素ポンプ電流Ｉｐ１を模擬した信号とを比較して比較結果を示す信号を出力する比較手段３１と、比較手段３１の出力信号の周波数特性を設定する周波数特性設定手段３２と、周波数特性設定手段３２によって周波数特性が設定された信号に基づいて、酸素分圧を示す信号を出力する酸素分圧信号生成手段３４と、酸素分圧検知セル３（図１参照）のような酸素濃淡電池セルの素子抵抗（特に、高周波インピーダンス）を模擬する信号を出力するＲｐｖｓ変更手段３５とを有している。
【００２５】
Ｖ１変更手段３０の出力信号は、比較手段３１の反転入力端子に入力される。比較手段３１の非反転入力端子には、生成された検出電圧Ｖｓ、すなわち、酸素分圧に追随して変動制御される第１酸素ポンプ電流Ｉｐ１を模擬した信号が入力される。
【００２６】
比較手段３１は、目標値を示すＩｐ制御信号と、生成された検出電圧信号とに基づいて、第１酸素ポンプセル（酸素ポンピング）のドライブする信号を出力する。
【００２７】
周波数特性設定手段３２には、比較手段３１の出力信号が入力され、例えば、ＣＲ回路の時定数を変更することにより、第１酸素ポンプセル１の周波数特性を模擬した信号を出力する。
【００２８】
酸素分圧信号生成手段３４は、周波数特性設定手段３２によって周波数特性が設定された信号に基づいて、Ｖｓリミッタ３３によってレベルが制限された、酸素分圧を示す信号を出力する。
【００２９】
Ｒｐｖｓ変更手段３５は、酸素分圧信号生成手段３４の出力端子に接続される。Ｒｐｖｓ変更手段３５によって酸素分圧検知セル（酸素濃淡電池セル）３の素子抵抗の変動が模擬されることにより、第１酸素ポンプセル（酸素ポンピングセル）に流れる第１酸素ポンプ電流（酸素ポンピング電流）Ｉｐ１の特性等が変動し、また、酸素分圧検知セル３の素子抵抗に基づいて、センサを所定の作動温度に加温するためにセンサに付設されるヒータ４（図１参照）に供給される電力の制御が変更される。
【００３０】
酸素分圧信号生成手段３４の参照電圧端子ＲＥＦには、オペアンプ３６の出力端子が接続され、オペアンプ３６の非反転入力端子には抵抗３９が接続され、抵抗３９の両端には第１酸素ポンプ電流生成手段３７の反転入力端子と非反転入力端子がそれぞれ接続され、第１酸素ポンプ電流生成手段３７の出力端子は比較手段３１の非反転入力端子に接続されている。オペアンプ３６の非反転入力端子と、抵抗３９の第１酸素ポンプ電流生成手段３７の非反転入力端子側との間の節点には、抵抗３８が接続されている。抵抗３９に流れる電流から、例えば、スイッチ４７の両端に電流計（抵抗）を挿入することにより、酸素ポンピング電流Ｉｐ１を検出することができる。酸素分圧検知セル３のマイナス側（コモン側）電位Ｖｓ−は、抵抗３８に流れる電流から、例えば、スイッチ４５の両端に電流計（抵抗）を挿入することにより、測定することができる。
【００３１】
オペアンプ３４の参照電圧端子ＲＥＦとオペアンプ３６の出力端子との間の節点に接続されるスイッチ４３の両端に挿入される抵抗から、ＮＯｘ測定時、第２酸素ポンプセル２（図１参照）に流れる第２酸素ポンプ電流Ｉｐ２を検出することができる。なお、スイッチ４３の両端に挿入される抵抗の値を変えることにより第２酸素ポンプ電流Ｉｐ２を可変に設定することができる。
【００３２】
酸素濃淡電池セルのプラス側電位Ｖｓ＋は、Ｒｐｖｓ変更手段３５に接続されスイッチ４１に並行に挿入される抵抗を用いて測定することができる。
【００３３】
なお、スイッチ４０、４２、４４、４６は、シミュレート対象であるＮＯｘセンサ、ＵＥＧＯセンサを選択するためのスイッチである。
【００３４】
【発明の効果】
本発明によれば、センサの動作を簡単に模擬することができるセンサのシミュレータ、特に、酸素センサ、中でも、全領域空燃比センサ、或いはＮＯｘセンサの動作を模擬することができるセンサのシミュレータが提供される。
【図面の簡単な説明】
【図１】（Ａ）〜（Ｄ）は、本発明の一実施例に係るセンサのシミュレータが模擬可能なＮＯｘセンサを説明するための図である。
【図２】本発明の一実施例に係るセンサのシミュレータを説明するための図である。
【符号の説明】
１　第１酸素ポンプセル
２　第２酸素ポンプセル
３　酸素分圧検知セル
４　ヒータ
５　第１測定室
６　第２測定室
７　第１拡散孔
８　第２拡散孔
９　電極
１０　電極
１１　電極
１２　電極
１３　電極
１４　電極
２０　第１酸素ポンプセル制御手段（Ｉｐ１ドライブ）
２０ａ　検出抵抗
２１　酸素分圧検知セル制御手段（Ｖｓドライブ）
２２　第２酸素ポンプセル制御手段（Ｉｐ２ドライブ）
２２ａ　検出抵抗
３０　Ｖ１変更手段（変更手段）
３１　比較手段（酸素ポンピングセル駆動手段）
３２　周波数特性設定手段
３３　Ｖｓリミッタ
３４　酸素分圧信号生成手段（オペアンプ）
３５　Ｒｐｖｓ変更手段（酸素分圧検知セルの素子抵抗設定手段）
３６　オペアンプ
３７　第１酸素ポンプ電流生成手段（オペアンプ）
３８　抵抗
３９　抵抗
４０　スイッチ
４１　スイッチ
４２　スイッチ
４３　スイッチ
４４　スイッチ
４５　スイッチ
４６　スイッチ
４７　スイッチ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sensor simulator, and more particularly to a sensor simulator capable of simulating the operation of an oxygen sensor, particularly, a full-range air-fuel ratio sensor (UEGO) or a NOx sensor.
[0002]
[Prior art]
Conventionally, when testing a control circuit of a sensor, the control circuit is tested using an actual sensor element.
[0003]
[Problems to be solved by the invention]
However, when an actual sensor element is used in an inspection of a sensor control circuit, it is difficult to perform an inspection under uniform conditions over an inspection of a plurality of control circuits due to a change in the sensor element due to use. There's a problem. There is also a problem that it is difficult to maintain the state of the sensor element as intended.
[0004]
An object of the present invention is to provide a sensor simulator that can easily simulate the operation of a sensor, and in particular, a sensor simulator that can simulate the operation of an oxygen sensor, particularly, an all-range air-fuel ratio sensor or a NOx sensor. It is to be.
[0005]
[Means for Solving the Problems]
According to a first aspect, the present invention includes a first measurement chamber into which a test gas is introduced via a first diffusion resistor, and a pair of electrodes provided inside and outside the first measurement chamber. An oxygen partial pressure detection cell for detecting the oxygen partial pressure in the test gas in the first measurement chamber based on the potential difference between the electrodes, and a pair of electrodes provided inside and outside the first measurement chamber. By pumping oxygen through the pair of electrodes from the inside to the outside or from the outside to the inside of the first measurement chamber, a current corresponding to the oxygen partial pressure in the test gas (hereinafter referred to as “first oxygen pump current )), A second measurement chamber into which gas is introduced from the first measurement chamber via a second diffusion resistor, and a pair of inner and outer sides of the second measurement chamber. An electrode, and oxygen that decomposes nitrogen oxide in the second measurement chamber and dissociates it. A second oxygen pump cell that moves between the pair of electrodes so that a current according to the NOx concentration (hereinafter, referred to as “second oxygen pump current”) moves, the device simulating the operation of a NOx sensor, Changing means for outputting a control signal indicating a control target of the first oxygen pump current, and first oxygen pump current generating means for outputting a signal simulating the first oxygen pump current based on a signal indicating an oxygen partial pressure A comparing unit that compares the control signal output by the changing unit with a signal simulating the first oxygen pump current output by the first oxygen pump current generating unit and outputs a signal indicating a comparison result; Frequency characteristic setting means for setting the frequency characteristic of the output signal of the comparing means; and the oxygen partial pressure based on the signal whose frequency characteristic is set by the frequency characteristic setting means. Providing a simulator of the NOx sensor having the oxygen partial pressure signal generating means for outputting a signal indicative.
[0006]
In a second aspect, the present invention provides, in a second aspect, an oxygen concentration battery cell for detecting an oxygen partial pressure of a gas introduced into a measurement chamber through a diffusion resistor, and the oxygen concentration cell detected according to the oxygen partial pressure detected by the oxygen concentration battery cell. An oxygen pumping cell that pumps oxygen in or out of the measurement chamber so that the oxygen concentration electromotive force of the concentration battery cell is constant, based on an oxygen pumping current flowing through the oxygen pumping cell. A device for simulating the operation of an oxygen sensor for measuring the oxygen concentration in the gas to be measured, comprising: a changing unit that outputs a control signal indicating a control target of the oxygen pumping current; and a signal indicating an oxygen partial pressure. Oxygen pumping current generating means for outputting a signal simulating the oxygen pumping current; the control signal output from the changing means; and the oxygen pumping current. A comparison unit that compares a signal simulating the oxygen pumping current output by the flow generation unit and outputs a signal indicating a comparison result; a frequency characteristic setting unit that sets a frequency characteristic of an output signal of the comparison unit; An oxygen sensor simulator comprising: an oxygen partial pressure signal generation unit that outputs a signal indicating the oxygen partial pressure based on a signal whose frequency characteristic is set by a frequency characteristic setting unit.
[0007]
In a third aspect, the present invention includes, in a third aspect, an oxygen concentration battery cell for detecting an oxygen partial pressure, and an oxygen pumping cell for pumping oxygen in accordance with the oxygen partial pressure detected by the oxygen concentration battery cell, An apparatus for simulating an operation of a sensor for measuring a predetermined gas concentration in a gas to be measured based on an oxygen pumping current flowing through an oxygen pumping cell, wherein the changing means outputs a control signal indicating a control target of the oxygen pumping current. An oxygen pumping current generating unit that outputs a signal simulating the oxygen pumping current based on a signal indicating an oxygen partial pressure; and the control signal output by the changing unit and the oxygen pumping current generating unit output by the oxygen pumping current generating unit. Comparing means for comparing a signal simulating the oxygen pumping current and outputting a signal indicating a comparison result; and a frequency of an output signal of the comparing means. A sensor simulator comprising: frequency characteristic setting means for setting characteristics; and oxygen partial pressure signal generating means for outputting a signal indicating the oxygen partial pressure based on a signal whose frequency characteristic has been set by the frequency characteristic setting means. I will provide a.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The sensor simulator according to the preferred embodiment of the present invention simulates the operation of a sensor composed of a combination of an oxygen pumping cell and an oxygen concentration cell, particularly an oxygen sensor, especially a full area air-fuel ratio sensor (UEGO) or a NOx sensor. Used to
[0009]
Referring to FIG. 2, the NOx sensor simulator according to the preferred embodiment of the present invention is configured based on a changing unit 30 that outputs a control signal indicating a control target of the first oxygen pump current, and a signal indicating an oxygen partial pressure. A first oxygen pump current generating unit 37 that outputs a signal simulating the first oxygen pump current; a control signal output by the changing unit 30 and the first oxygen pump current generated by the first oxygen pump current generating unit 37. A comparing means 31 for comparing the signal simulating the pump current and outputting a signal indicating a comparison result; a frequency characteristic setting means 32 for setting a frequency characteristic of an output signal of the comparing means 31; A NOx sensor simulator having an oxygen partial pressure signal generation unit that outputs a signal indicating an oxygen partial pressure based on a signal whose characteristics are set.
[0010]
Referring to FIG. 2, the oxygen sensor simulator according to the preferred embodiment of the present invention includes an oxygen concentration battery cell (3 in FIG. 1) for detecting the oxygen partial pressure of the gas introduced into the measurement chamber through the diffusion resistance. Oxygen that pumps oxygen out of the measurement chamber or into and out of the measurement chamber so that the oxygen concentration electromotive force of the oxygen concentration battery cell becomes constant in accordance with the oxygen partial pressure detected by the oxygen concentration battery cell. A pumping cell (1 in FIG. 1) for simulating an operation of an oxygen sensor for measuring an oxygen concentration in a gas to be measured based on an oxygen pumping current flowing through the oxygen pumping cell, Changing means 30 for outputting a control signal indicating a control target of the oxygen pumping current; and an oxygen pump for outputting a signal simulating the oxygen pumping current based on a signal indicating the oxygen partial pressure. Comparing means 31 for comparing the control signal output from the changing means 30 with the signal simulating the oxygen pumping current output from the oxygen pumping current generating means 37 and outputting a signal indicating a comparison result. A frequency characteristic setting unit 32 for setting a frequency characteristic of an output signal of the comparison unit 31; and an oxygen component for outputting a signal indicating the oxygen partial pressure based on the signal whose frequency characteristic is set by the frequency characteristic setting unit 32. An oxygen sensor simulator having the pressure signal generating means 34 is provided.
[0011]
Referring to FIG. 1, a sensor simulator according to a preferred embodiment of the present invention includes an oxygen concentration battery cell 3 for detecting an oxygen partial pressure, and an oxygen simulator based on the oxygen partial pressure detected by the oxygen concentration battery cell 3. And an oxygen pumping cell 1 that pumps out gas, and simulates an operation of a sensor that measures a predetermined gas concentration in a gas to be measured based on an oxygen pumping current flowing through the oxygen pumping cell 1, and FIG. A changing means 30 for outputting a control signal indicating a control target of the oxygen pumping current; and an oxygen pumping current generating means for outputting a signal simulating the oxygen pumping current based on a signal indicating an oxygen partial pressure. 37, the control signal output by the changing means 30 and a signal simulating the oxygen pumping current output by the oxygen pumping current generating means 37 are compared. A comparison unit 31 that outputs a signal indicating a comparison result; a frequency characteristic setting unit 32 that sets a frequency characteristic of an output signal of the comparison unit 31; and a signal whose frequency characteristic is set by the frequency characteristic setting unit 32. An oxygen partial pressure signal generating means 34 for outputting a signal indicating the oxygen partial pressure.
[0012]
The simulator of the sensor according to the preferred embodiment of the present invention is connected to the oxygen partial pressure signal generating means (34 in FIG. 2) and has a resistance value corresponding to the internal resistance of the oxygen partial pressure detection cell (3 in FIG. 1). For setting the element resistance of the oxygen partial pressure detection cell.
[0013]
【Example】
In order to further clarify the preferred embodiments of the present invention described above, an embodiment of the present invention will be described below with reference to the drawings.
[0014]
FIGS. 1A to 1D are diagrams for explaining the configuration and measurement principle of a NOx sensor element that is a component of a NOx sensor inspected by an inspection apparatus according to an embodiment of the present invention. .
[0015]
Referring to FIG. 1A, the NOx sensor element mainly includes a first oxygen pump cell 1, a second oxygen pump cell 2, an oxygen partial pressure detection cell 3, and a heater 4 for heating the NOx sensor element to a predetermined operating temperature. It is configured. A first measurement chamber 5 is formed between the first oxygen pump cell 1 and the oxygen partial pressure detection cell 3. A test gas is introduced into the first measurement chamber 5 through the first diffusion hole 7. The first measurement chamber 5 is in communication with the second measurement chamber 6 through the second diffusion holes 8.
[0016]
The first oxygen ion pump cell 1 is composed of a solid electrolyte having oxygen ion conductivity such as zirconia, and a pair of electrodes 9 and 10 formed on the solid electrolyte. The electrode 10 is arranged facing the first measurement chamber 5, and the electrode 9 is arranged facing the outside. Oxygen ions generated by dissociation of oxygen and the like in the first measurement chamber 5 on the electrode 10 are led out of the electrode 9 through the solid electrolyte through the solid electrolyte. At this time, a current flowing through the solid electrolyte is a first oxygen pump current. Ip1.
[0017]
The second oxygen ion pump cell 2 includes a solid electrolyte having oxygen ion conductivity such as zirconia, and a pair of electrodes 13 and 14 formed on the solid electrolyte. The electrode 13 is arranged facing the second measurement chamber 6, and the electrode 14 is arranged outside the second measurement chamber 6 and is exposed to an atmosphere having a stable oxygen concentration. Oxygen ions generated by dissociation of NOx and the like in the second measurement chamber 6 on the electrode 13 are led out of the electrode 14 through the solid electrolyte through the solid electrolyte, and the current flowing through the solid electrolyte at this time is the second oxygen pump current Ip2. It is. In the normal measurement mode, a constant voltage is applied between the electrodes 13 and 14.
[0018]
The oxygen partial pressure detection cell (oxygen concentration battery cell) 3 is composed of a solid electrolyte having oxygen ion conductivity such as zirconia, and a pair of electrodes 11 and 12 formed on the solid electrolyte. The electrode 11 is arranged facing the first measurement chamber 5, and the electrode 12 is exposed to an atmosphere having a stable oxygen concentration. Therefore, the oxygen concentration in the first measurement chamber 5, that is, the oxygen concentration in the test gas can be detected based on the potential difference generated between the electrode 11 and the electrode 12.
[0019]
Referring to FIG. 1A, the sensor control means 30 (see FIG. 2) detects the oxygen concentration in the first measurement chamber 5 that appears in the oxygen partial pressure detection cell and is provided outside the first measurement chamber 5. By controlling the first oxygen pump current Ip1 based on the detection output of the oxygen partial pressure detection cell 3 and the oxygen partial pressure cell control means 21 for controlling the oxygen concentration on the electrode 12, the inside of the first measurement chamber 5 is controlled. A first oxygen pump cell control means 20 for controlling the oxygen concentration as constant as possible, and a second oxygen pump according to the NOx concentration by applying a predetermined constant voltage to the second oxygen pump cell 2. And a second oxygen pump cell control means 22 for controlling the second oxygen pump cell 2 so that the current Ip2 flows.
[0020]
The principle of NOx measurement using the above-described NOx sensor element and its control means is as shown in FIGS. 1B to 1D, and therefore, reference is made thereto.
[0021]
Further, an oxygen sensor, in particular, a full-range air-fuel ratio sensor (UEGO) can be configured by removing the second oxygen pump cell 2 from the NOx sensor shown in FIGS. 1 (A) to 1 (D).
[0022]
Next, a description will be given of a sensor simulator according to one embodiment of the present invention, which can selectively simulate the operations of the NOx sensor and the full area air-fuel ratio sensor (UEGO) described above.
[0023]
FIG. 2 is a diagram illustrating a UEGO or NOx sensor simulator according to an embodiment of the present invention.
[0024]
Referring to FIG. 2, the simulator according to one embodiment of the present invention includes a control signal indicating a control target of a first oxygen pump current, for example, applied to an oxygen pumping cell such as the first oxygen pump cell 1 (see FIG. 1). V1 changing means 30 for mainly controlling an Ip control signal for changing the applied voltage V1, and first oxygen pump current generating means for outputting a signal simulating the first oxygen pump current Ip1 based on a signal indicating the oxygen partial pressure. 37, a comparing means for comparing the control signal output from the V1 changing means 30 with a signal simulating the first oxygen pump current Ip1 output from the first oxygen pump current generating means 37, and outputting a signal indicating a comparison result. 31, frequency characteristic setting means 32 for setting the frequency characteristic of the output signal of the comparison means 31, and a signal whose frequency characteristic has been set by the frequency characteristic setting means 32. An oxygen partial pressure signal generating means 34 that outputs a signal indicating the oxygen partial pressure, and a signal that simulates the element resistance (particularly, high-frequency impedance) of the oxygen concentration cell such as the oxygen partial pressure detection cell 3 (see FIG. 1). Rpvs changing means 35 for outputting.
[0025]
The output signal of the V1 changing means 30 is input to the inverting input terminal of the comparing means 31. The non-inverting input terminal of the comparison means 31 receives the generated detection voltage Vs, that is, a signal simulating the first oxygen pump current Ip1 that is variably controlled to follow the oxygen partial pressure.
[0026]
The comparing means 31 outputs a signal for driving the first oxygen pump cell (oxygen pumping) based on the Ip control signal indicating the target value and the generated detection voltage signal.
[0027]
The output signal of the comparison means 31 is input to the frequency characteristic setting means 32, and a signal simulating the frequency characteristic of the first oxygen pump cell 1 is output by, for example, changing the time constant of the CR circuit.
[0028]
The oxygen partial pressure signal generating means 34 outputs a signal indicating the oxygen partial pressure, the level of which is limited by the Vs limiter 33, based on the signal whose frequency characteristic has been set by the frequency characteristic setting means 32.
[0029]
The Rpvs changing means 35 is connected to the output terminal of the oxygen partial pressure signal generating means 34. By simulating the fluctuation of the element resistance of the oxygen partial pressure detection cell (oxygen concentration cell) 3 by the Rpvs changing means 35, the first oxygen pump current (oxygen pumping current) flowing through the first oxygen pump cell (oxygen pumping cell) The characteristics and the like of Ip1 fluctuate, and are supplied to a heater 4 (see FIG. 1) attached to the sensor for heating the sensor to a predetermined operating temperature based on the element resistance of the oxygen partial pressure detection cell 3. Power control is changed.
[0030]
An output terminal of an operational amplifier 36 is connected to the reference voltage terminal REF of the oxygen partial pressure signal generating means 34, a resistor 39 is connected to a non-inverting input terminal of the operational amplifier 36, and a first oxygen pump current is connected to both ends of the resistor 39. The inverting input terminal and the non-inverting input terminal of the generating means 37 are connected to each other, and the output terminal of the first oxygen pump current generating means 37 is connected to the non-inverting input terminal of the comparing means 31. The resistor 38 is connected to a node between the non-inverting input terminal of the operational amplifier 36 and the non-inverting input terminal of the first oxygen pump current generating means 37 of the resistor 39. From the current flowing through the resistor 39, for example, by inserting an ammeter (resistance) at both ends of the switch 47, the oxygen pumping current Ip1 can be detected. The negative (common) potential Vs− of the oxygen partial pressure detection cell 3 can be measured from the current flowing through the resistor 38 by, for example, inserting an ammeter (resistance) at both ends of the switch 45.
[0031]
When NOx is measured from the resistor inserted at both ends of the switch 43 connected to the node between the reference voltage terminal REF of the operational amplifier 34 and the output terminal of the operational amplifier 36, the second current flowing through the second oxygen pump cell 2 (see FIG. 1). 2 The oxygen pump current Ip2 can be detected. The second oxygen pump current Ip2 can be variably set by changing the value of a resistor inserted between both ends of the switch 43.
[0032]
The positive potential Vs + of the oxygen concentration battery cell can be measured using a resistor connected to the Rpvs changing unit 35 and inserted in parallel with the switch 41.
[0033]
The switches 40, 42, 44, and 46 are switches for selecting a NOx sensor and a UEGO sensor to be simulated.
[0034]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the simulator of a sensor which can simulate the operation | movement of a sensor easily, especially the simulator of a sensor which can simulate the operation | movement of an oxygen sensor, especially a full area air-fuel ratio sensor or a NOx sensor is provided. Is done.
[Brief description of the drawings]
FIGS. 1A to 1D are diagrams illustrating a NOx sensor that can be simulated by a sensor simulator according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a sensor simulator according to one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st oxygen pump cell 2 2nd oxygen pump cell 3 Oxygen partial pressure detection cell 4 Heater 5 1st measurement room 6 2nd measurement room 7 1st diffusion hole 8 2nd diffusion hole 9 electrode 10 electrode 11 electrode 12 electrode 13 electrode 14 electrode 20 First oxygen pump cell control means (Ip1 drive)
20a detection resistor 21 oxygen partial pressure detection cell control means (Vs drive)
22 Second oxygen pump cell control means (Ip2 drive)
22a detecting resistor 30 V1 changing means (changing means)
31 Comparison means (Oxygen pumping cell driving means)
32 Frequency characteristic setting means 33 Vs limiter 34 Oxygen partial pressure signal generating means (operational amplifier)
35 Rpvs change means (element resistance setting means of oxygen partial pressure detection cell)
36 Operational amplifier 37 First oxygen pump current generating means (op-amp)
38 resistor 39 resistor 40 switch 41 switch 42 switch 43 switch 44 switch 45 switch 46 switch 47 switch

Claims

A first measurement chamber into which a test gas is introduced via a first diffusion resistance; and a pair of electrodes provided inside and outside the first measurement chamber, wherein the first and second electrodes are provided based on a potential difference between the pair of electrodes. An oxygen partial pressure detection cell for detecting the oxygen partial pressure in the test gas in the first measurement chamber, and a pair of electrodes provided inside and outside the first measurement chamber, from the inside of the first measurement chamber A first oxygen pump cell in which a current (hereinafter, referred to as a “first oxygen pump current”) according to an oxygen partial pressure in a test gas flows by pumping oxygen to the outside or from the outside to the inside through the pair of electrodes; A second measurement chamber into which gas is introduced from the first measurement chamber via a second diffusion resistance; and a pair of electrodes provided inside and outside the second measurement chamber, NOx concentration by decomposing nitrogen oxides Depending current (hereinafter referred to as "the second oxygen pump current") is a device that simulates the operation of a NOx sensor and a second oxygen pumping cell flowing between the pair of electrodes,
Changing means for outputting a control signal indicating a control target of the first oxygen pump current;
First oxygen pump current generation means for outputting a signal simulating the first oxygen pump current based on a signal indicating the oxygen partial pressure;
A comparing unit that compares the control signal output by the changing unit with a signal simulating the first oxygen pump current output by the first oxygen pump current generating unit and outputs a signal indicating a comparison result;
Frequency characteristic setting means for setting the frequency characteristic of the output signal of the comparing means,
Oxygen partial pressure signal generating means for outputting a signal indicating the oxygen partial pressure based on the signal whose frequency characteristic is set by the frequency characteristic setting means,
A simulator for a NOx sensor, comprising:

2. The device according to claim 1, further comprising an element resistance setting unit of the oxygen partial pressure detection cell connected to the oxygen partial pressure signal generation unit and configured to set a resistance value corresponding to an internal resistance of the oxygen partial pressure detection cell. Simulator.

An oxygen concentration battery cell for detecting the oxygen partial pressure of the gas introduced into the measurement chamber through the diffusion resistance, and the oxygen concentration electromotive force of the oxygen concentration battery cell according to the oxygen partial pressure detected by the oxygen concentration battery cell. An oxygen pumping cell for pumping oxygen from the measurement chamber to the outside or from the outside of the measurement chamber so as to be constant, the oxygen concentration in the gas to be measured based on the oxygen pumping current flowing through the oxygen pumping cell. An apparatus for simulating the operation of an oxygen sensor for measuring,
Changing means for outputting a control signal indicating a control target of the oxygen pumping current,
Oxygen pumping current generating means for outputting a signal simulating the oxygen pumping current based on a signal indicating the oxygen partial pressure,
A comparison unit that outputs a signal indicating a comparison result by comparing the control signal output by the change unit and a signal simulating the oxygen pumping current output by the oxygen pumping current generation unit,
Frequency characteristic setting means for setting the frequency characteristic of the output signal of the comparing means,
Oxygen partial pressure signal generating means for outputting a signal indicating the oxygen partial pressure based on the signal whose frequency characteristic is set by the frequency characteristic setting means,
A simulator for an oxygen sensor, comprising:

4. The device according to claim 3, further comprising an element resistance setting unit of the oxygen partial pressure detection cell connected to the oxygen partial pressure signal generation unit and configured to set a resistance value corresponding to an internal resistance of the oxygen partial pressure detection cell. Simulator.

An oxygen concentration battery cell that detects oxygen partial pressure, and an oxygen pumping cell that pumps oxygen in accordance with the oxygen partial pressure detected by the oxygen concentration battery cell, comprising an oxygen pumping current flowing through the oxygen pumping cell. A device that simulates the operation of a sensor that measures a predetermined gas concentration in a measured gas based on
Changing means for outputting a control signal indicating a control target of the oxygen pumping current,
Oxygen pumping current generating means for outputting a signal simulating the oxygen pumping current based on a signal indicating the oxygen partial pressure,
A comparison unit that outputs a signal indicating a comparison result by comparing the control signal output by the change unit and a signal simulating the oxygen pumping current output by the oxygen pumping current generation unit,
Frequency characteristic setting means for setting the frequency characteristic of the output signal of the comparing means,
Oxygen partial pressure signal generating means for outputting a signal indicating the oxygen partial pressure based on the signal whose frequency characteristic is set by the frequency characteristic setting means,
A simulator for a sensor, comprising: