JP5891734B2 - NOx sensor abnormality diagnosis method, NOx sensor abnormality diagnosis system, and internal combustion engine - Google Patents

NOx sensor abnormality diagnosis method, NOx sensor abnormality diagnosis system, and internal combustion engine Download PDF

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JP5891734B2
JP5891734B2 JP2011253271A JP2011253271A JP5891734B2 JP 5891734 B2 JP5891734 B2 JP 5891734B2 JP 2011253271 A JP2011253271 A JP 2011253271A JP 2011253271 A JP2011253271 A JP 2011253271A JP 5891734 B2 JP5891734 B2 JP 5891734B2
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英和 藤江
英和 藤江
哲史 塙
哲史 塙
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/1446—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being exhaust temperatures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/1448—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an exhaust gas pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/146—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an NOx content or concentration
    • F02D41/1461—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an NOx content or concentration of the exhaust gases emitted by the engine
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/146—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an NOx content or concentration
    • F02D41/1461—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an NOx content or concentration of the exhaust gases emitted by the engine
    • F02D41/1462—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an NOx content or concentration of the exhaust gases emitted by the engine with determination means using an estimation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/18—Circuit arrangements for generating control signals by measuring intake air flow
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/22—Safety or indicating devices for abnormal conditions
    • F02D41/222—Safety or indicating devices for abnormal conditions relating to the failure of sensors or parameter detection devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2067—Urea
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/30—Controlling by gas-analysis apparatus
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/04—Engine intake system parameters
    • F02D2200/0406—Intake manifold pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/04—Engine intake system parameters
    • F02D2200/0414—Air temperature

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Exhaust Gas After Treatment (AREA)
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Description

本発明は、多大な実験工数を掛けることなく、また、連続してＮＯｘセンサの異常を診断できるＮＯｘセンサの異常診断方法、ＮＯｘセンサの異常診断システム、及び内燃機関に関する。   The present invention relates to an NOx sensor abnormality diagnosis method, a NOx sensor abnormality diagnosis system, and an internal combustion engine that can continuously diagnose abnormality of a NOx sensor without taking a large number of experimental steps.

トラックやバス等の車両においては、この車両に搭載された内燃機関から排出されるＮＯｘ（窒素酸化物）の量を減少するために排気ガス浄化処理装置を用いて窒素（Ｎ2）に還元して大気中に放出するようにしている。このＮＯｘ浄化を効率良く行うためには排気ガス中のＮＯｘ濃度及びＮＯｘ量を正確に測定する必要があり、そのために、ＮＯｘセンサが使用されている。 In vehicles such as trucks and buses, in order to reduce the amount of NOx (nitrogen oxides) discharged from the internal combustion engine mounted on the vehicle, it is reduced to nitrogen (N 2 ) using an exhaust gas purification treatment device. In the atmosphere. In order to perform this NOx purification efficiently, it is necessary to accurately measure the NOx concentration and the NOx amount in the exhaust gas. For this purpose, a NOx sensor is used.

このＮＯｘセンサの検出値に基づいて、排気ガス中のＮＯｘを還元するのに必要な尿素等の還元剤を供給しているため、このＮＯｘセンサが正常状態であるか、故障等の異常状態であるかが重要となる。万一、ＮＯｘセンサが異常であると、還元剤の供給量を適正な量にすることができず、還元剤が不十分の場合には、排気ガス中のＮＯｘの還元浄化が不十分になった大気中に基準以上のＮＯｘが放出されてしまい、還元剤が過剰の場合には、ＮＯｘの還元で消費されなかった還元剤が大気中に放出され、還元剤が無駄に消費されることになる。   Since a reducing agent such as urea necessary for reducing NOx in the exhaust gas is supplied based on the detected value of the NOx sensor, the NOx sensor is in a normal state or in an abnormal state such as a failure. It is important whether there is. If the NOx sensor is abnormal, the amount of reducing agent supplied cannot be made appropriate, and if the reducing agent is insufficient, the reduction and purification of NOx in the exhaust gas becomes insufficient. If NOx above the standard is released into the atmosphere and the reducing agent is excessive, the reducing agent that was not consumed by the reduction of NOx is released into the atmosphere and the reducing agent is consumed wastefully. Become.

そのため、ＮＯｘセンサの異常診断が重要であり、例えば、排出ＮＯｘ流量演算記憶手段と検出ＮＯｘ濃度記憶手段を備えて、排出ＮＯｘ流量の経時変化の基準としての基準パターンと、ＮＯｘセンサによって検出される検出ＮＯｘ濃度の経時変化の基準としての追従パターンを規定して、内燃機関が通常運転モードにある場合に排出ＮＯｘ流量が基準パターンに対して所定の関係をもって推移したときに、検出ＮＯｘ濃度が追従パターンに対して所定の関係をもって推移したか否かを判別することによって、ＮＯｘセンサの応答性を判定する故障判定手段を備えたＮＯｘセンサの故障診断装置が提案されている（例えば、特許文献１参照）。   For this reason, abnormality diagnosis of the NOx sensor is important. For example, the NOx sensor is provided with an exhaust NOx flow rate calculation storage means and a detected NOx concentration storage means, and is detected by the NOx sensor with a reference pattern as a reference for the temporal change of the exhaust NOx flow rate. A follow-up pattern is defined as a reference for the temporal change in the detected NOx concentration, and when the internal combustion engine is in the normal operation mode, the detected NOx concentration follows when the exhaust NOx flow changes with a predetermined relationship with respect to the reference pattern. There has been proposed a NOx sensor failure diagnosis device including failure determination means for determining the responsiveness of the NOx sensor by determining whether or not the pattern has changed with a predetermined relationship (for example, Patent Document 1). reference).

このＮＯｘセンサの診断方法では、予め内燃機関から排出されるＮＯｘ流量の経時変化の基準としての基準パターンと、ＮＯｘセンサによって検出される検出ＮＯｘ濃度の経時変化の基準としての追従パターンを予め設定する必要があるが、排出されるＮＯｘの流量は内燃機関の運転状態等の環境条件により大きく変化するため、基準パターンを多数設定する必要があり、多大な工数がかかってしまうという問題がある。   In this NOx sensor diagnosis method, a reference pattern as a reference for the temporal change of the NOx flow rate discharged from the internal combustion engine and a follow-up pattern as a reference for the temporal change of the detected NOx concentration detected by the NOx sensor are set in advance. Although it is necessary, since the flow rate of exhausted NOx varies greatly depending on environmental conditions such as the operating state of the internal combustion engine, it is necessary to set a large number of reference patterns, and there is a problem that it takes a lot of man-hours.

一方、還元触媒の上流側でのＮＯｘ量を算出する上流側ＮＯｘ量演算部とＮＯｘセンサ値検出部と、上流側でのＮＯｘ量の推移に現れたピークに対してＮＯｘセンサが応答しているか否かを判定することによりＮＯｘセンサの合理性を判定する合理性判定部と、内燃機関から排出される排気ガス量を算出する排気ガス量演算部とを備え、合理性診断部は、排気ガス量に応じてピークの発生を認識してＮＯｘセンサの合理性を判断するＮＯｘセンサの合理性診断装置（例えば、特許文献２参照）や内燃機関が予め設定された基準稼働条件になったとき、ＮＯｘセンサの出力値と、前記基準稼働条件に応じて予め設定された基準出力値との偏差に基づき、ＮＯｘセンサの出力を補正する第１補正手段を備えたＮＯｘ補正システム（例えば、特許文献３参照）が提案されている。   On the other hand, whether the NOx sensor is responding to the peak appearing in the transition of the NOx amount on the upstream side, the upstream NOx amount calculating unit and the NOx sensor value detecting unit for calculating the NOx amount on the upstream side of the reduction catalyst A rationality determination unit that determines the rationality of the NOx sensor by determining whether or not, and an exhaust gas amount calculation unit that calculates the amount of exhaust gas discharged from the internal combustion engine. When the NOx sensor rationality diagnosis device (see, for example, Patent Document 2) that recognizes the occurrence of a peak in accordance with the amount and determines the rationality of the NOx sensor or the internal combustion engine reaches a preset reference operating condition, A NOx correction system comprising first correction means for correcting the output of the NOx sensor based on the deviation between the output value of the NOx sensor and a reference output value preset in accordance with the reference operating condition (for example, a patent document) 3 reference) has been proposed.

更に、ＮＯｘセンサに到達する排気ガス中のＮＯｘ濃度を強制的に変動させ、このときにＮＯｘセンサが出力する出力値の変動が当該ＮＯｘセンサが正常であるときに取りうる変動からずれている場合に、ＮＯｘセンサに異常があると判定する故障判定手段を備えたＮＯｘセンサの故障診断装置（例えば、特許文献４参照）や、内燃機関の所定の運転状態における異常判定モード時に、ＮＯｘセンサに到達する排気ガス中のＮＯｘ濃度を、一旦増大させて減少変化させる、ＮＯｘ濃度増減変化手段と、ＮＯｘ濃度が増減変化されたとき、ＮＯｘセンサの所定の第１出力値の出力状態から、ＮＯｘセンサが所定の第２の出力値を出力するまでの経過時間を計測する経過時間計測手段と、計測された経過時間と基準経過時間とに基づき、ＮＯｘセンサの正常又は異常を判定する判定手段を備えた、排気ガス浄化システムが提案されている（例えば、特許文献５参照）。   Further, the NOx concentration in the exhaust gas reaching the NOx sensor is forcibly changed, and the output value output from the NOx sensor at this time deviates from the change that can be taken when the NOx sensor is normal. In addition, a NOx sensor failure diagnosis device (see, for example, Patent Document 4) provided with a failure determination means that determines that the NOx sensor is abnormal or reaches the NOx sensor during an abnormality determination mode in a predetermined operating state of the internal combustion engine. NOx concentration increase / decrease changing means for once increasing and decreasing the NOx concentration in the exhaust gas to be emitted, and when the NOx concentration is increased / decreased, the NOx sensor detects from the output state of the predetermined first output value of the NOx sensor. Based on the elapsed time measuring means for measuring the elapsed time until the predetermined second output value is output, the measured elapsed time and the reference elapsed time, With a determination means for determining normality or abnormality of the support, the exhaust gas purification system has been proposed (e.g., see Patent Document 5).

しかしながら、これらのＮＯｘセンサの異常診断では、内燃機関の運転状態がＮＯｘ濃度のピーク発生時や、強制的にＮＯｘ濃度を変化させて作った特定の状態で行っているので、内燃機関の特別の条件下の状態の時にしか診断できず、連続的に異常診断を行うことができないという問題がある。   However, in the abnormality diagnosis of these NOx sensors, the operation state of the internal combustion engine is performed when the peak of the NOx concentration occurs or in a specific state created by forcibly changing the NOx concentration. There is a problem that diagnosis can be performed only under conditions under conditions, and abnormality diagnosis cannot be performed continuously.

特開２００８−１９０３８３号公報JP 2008-190383 A 特開２０１０−２６５７８１号公報JP 2010-255781 A 特開２００９−１２７５５２号公報JP 2009-127552 A 特開２００３−１２０３９９号公報JP 2003-120399 A 特開２００９−１８０１５０号公報JP 2009-180150 A

本発明は、上記の状況を鑑みてなされたものであり、その目的は、ＮＯｘ濃度の計算値とＮＯｘセンサの検出値を比較することで、ＮＯｘセンサの異常診断を連続的に行うことができるＮＯｘセンサの異常診断方法、ＮＯｘセンサの異常診断システム、及び内燃機関を提供することにある。   The present invention has been made in view of the above-described situation, and an object of the present invention is to continuously perform abnormality diagnosis of the NOx sensor by comparing the calculated value of the NOx concentration with the detected value of the NOx sensor. An object of the present invention is to provide a NOx sensor abnormality diagnosis method, a NOx sensor abnormality diagnosis system, and an internal combustion engine.

上記のような目的を達成するための本発明のＮＯｘセンサの異常診断方法は、内燃機関の排気通路に配置されるＮＯｘセンサの異常診断方法であって、内部ＥＧＲガスの質量流量（ｍ＿ｉｎ＿ｅｇｒ）と外部ＥＧＲガスの質量流量（ｍ＿ｅｘ＿ｅｇｒ）と吸入空気の質量流量（ｍ＿ａｉｒ）と内部ＥＧＲガス中の酸素濃度（Ｏ２＿ｉｎ＿ｅｇｒ）と外部ＥＧＲガス中の酸素濃度（Ｏ２＿ｅｘ＿ｅｇｒ）と大気中の酸素濃度（Ｏ２＿ａｉｒ）とから前記内燃機関のシリンダ内の酸素濃度（Ｏ２＿ｃｙｌ）を算出するステップと、該シリンダ内の酸素濃度（Ｏ２＿ｃｙｌ）から、前記シリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）を算出するステップと、該算出されたＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）と前記ＮＯｘセンサの検出値（ＮＯｘ＿ｍ）とを比較して、前記ＮＯｘセンサが異常であるか否かの診断を行うステップを含み、さらに、このＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）を算出するステップである演算ステップが、前記内燃機関の吸気通路に配置された吸気量センサで検出した吸入空気の質量流量（ｍ＿ａｉｒ）と、前記内燃機関の吸気マニホールドに配置された第１温度センサで検出した温度（Ｔｉ）と前記吸気マニホールドに配置された第１圧力センサで検出した圧力（Ｐｉ）と前記内燃機関の排気マニホールドに配置された第２温度センサで検出した温度（Ｔｅ）と前記排気マニホールドに配置された第２圧力センサで検出した圧力（Ｐｅ）とから算出した外部ＥＧＲガスの質量流量（ｍ＿ｅｘ＿ｅｇｒ）と、前記第２温度センサで検出した温度（Ｔｅ）と前記第２圧力センサで検出した圧力（Ｐｅ）とから算出した内部ＥＧＲガスの質量流量（ｍ＿ｉｎ＿ｅｇｒ）から、（１）式によりシリンダ内の質量流量（ｍ＿ｃｙｌ）を算出する第１演算ステップと、

Figure 0005891734
前記吸気量センサで検出した吸入空気の質量流量（ｍ＿ａｉｒ）と前記燃料噴射量（ｑ）とから、（２）式により、内部ＥＧＲ空気過剰率（λ＿ｉｎ＿ｅｇｒ）を算出する第２演算ステップと、
Figure 0005891734
 前記内部ＥＧＲ空気過剰率（λ＿ｉｎ＿ｅｇｒ）からＥＧＲガスの時間遅れを考慮して算出した外部ＥＧＲ空気過剰率（λ＿ｅｘ＿ｅｇｒ）と大気中の酸素濃度（Ｏ２＿ａｉｒ）と理論空燃比（Ｌ＿ｓｔ）とから、（３）式により外部ＥＧＲガス中の酸素濃度（Ｏ２＿ｅｘ＿ｅｇｒ）を算出する第３演算ステップと、
Figure 0005891734
 前記内部ＥＧＲ空気過剰率（λ＿ｉｎ＿ｅｇｒ）と大気中の酸素濃度（Ｏ２＿ａｉｒ）と理論空燃比（Ｌ＿ｓｔ）とから、（３）式により内部ＥＧＲガス中の酸素濃度（Ｏ２＿ｉｎ＿ｅｇｒ）を算出する第４演算ステップと、
Figure 0005891734
 （５）式より、シリンダ内の酸素濃度（Ｏ２＿ｃｙｌ）を算出する第５演算ステップと、
Figure 0005891734
 定常時のシリンダ内の酸素濃度（Ｏ２＿ｒｅｆ）と定常時のシリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｒｅｆ）と、指数ｉとが予め設定されている（６）式の、シリンダ内の酸素濃度（Ｏ２＿ｃｙｌ）とシリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）の関係から、現在のシリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）を算出する第６演算ステップとを備え、
Figure 0005891734
 前記ＮＯｘセンサが異常であるか否かの診断を行うステップが、前記（６）式から算出された現在のシリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）と前記ＮＯｘセンサの検出値（ＮＯｘ＿ｍ）とを比較して、前記ＮＯｘセンサが異常であるか否かの診断を行う第７演算ステップであることを特徴とする方法である。 The NOx sensor abnormality diagnosis method of the present invention for achieving the above object is a NOx sensor abnormality diagnosis method arranged in an exhaust passage of an internal combustion engine, and includes a mass flow rate (m_in_egr) of internal EGR gas. External EGR gas mass flow rate (m_ex_egr), intake air mass flow rate (m_air), internal EGR gas oxygen concentration (O2_in_egr), external EGR gas oxygen concentration (O2_ex_egr), and atmospheric oxygen concentration (O2_air) Calculating the oxygen concentration (O2_cyl) in the cylinder of the internal combustion engine from the above, calculating the NOx concentration (NOx_cyl) discharged from the cylinder from the oxygen concentration (O2_cyl) in the cylinder, and NOx concentration (NOx_cyl) and the detected value of the NOx sensor (NOx m) and by comparing comprises the step of performing a diagnosis of whether the NOx sensor is abnormal, further calculation step is a step of calculating the NOx concentration (NOx_cyl) is an intake passage of the internal combustion engine The mass flow rate (m_air) of the intake air detected by the intake air amount sensor arranged at the position, the temperature (Ti) detected by the first temperature sensor arranged at the intake manifold of the internal combustion engine, and the first flow rate arranged at the intake manifold. Pressure (Pi) detected by one pressure sensor, temperature (Te) detected by a second temperature sensor arranged in the exhaust manifold of the internal combustion engine, and pressure (Pe) detected by a second pressure sensor arranged in the exhaust manifold ) Calculated from the mass flow rate (m_ex_egr) of the external EGR gas, the temperature (Te) detected by the second temperature sensor, and the second pressure From the mass flow rate of the internal EGR gas calculated from the pressure and (Pe) Detection (M_in_egr) sensor, a first calculation step of calculating a mass flow rate (M_cyl) in the cylinder by (1),
Figure 0005891734
 A second calculation step of calculating an internal EGR excess air ratio (λ_in_egr) from the mass flow rate (m_air) of the intake air detected by the intake air amount sensor and the fuel injection amount (q) by the equation (2);
Figure 0005891734
 From the external EGR excess air ratio (λ_ex_egr) calculated from the internal EGR excess air ratio (λ_in_egr) in consideration of the time delay of EGR gas, the oxygen concentration (O2_air) in the atmosphere, and the theoretical air-fuel ratio (L_st), (3 And a third calculation step of calculating the oxygen concentration (O2_ex_egr) in the external EGR gas by the formula:
Figure 0005891734
 Fourth calculation step of calculating the oxygen concentration (O2_in_egr) in the internal EGR gas from the internal EGR air excess ratio (λ_in_egr), the oxygen concentration (O2_air) in the atmosphere, and the theoretical air-fuel ratio (L_st) by the equation (3) When,
Figure 0005891734
 A fifth calculation step for calculating the oxygen concentration (O2_cyl) in the cylinder from the equation (5);
Figure 0005891734
 The oxygen concentration (O2_ref) in the cylinder in the formula (6) in which the oxygen concentration (O2_ref) in the cylinder at a constant time, the NOx concentration discharged from the cylinder at the normal time (NOx_ref), and the index i are set in advance. A NOx concentration (NOx_cyl) discharged from the cylinder, and a sixth calculation step for calculating the NOx concentration (NOx_cyl) discharged from the current cylinder,
Figure 0005891734
 The step of diagnosing whether or not the NOx sensor is abnormal is based on the NOx concentration (NOx_cyl) discharged from the current cylinder calculated from the equation (6) and the detected value (NOx_m) of the NOx sensor. In comparison , the method is a seventh operation step for diagnosing whether or not the NOx sensor is abnormal .

この方法によれば、排気ガス中のＮＯｘ濃度を計算により求めることで、多大な実験工数を掛けることなくＮＯｘセンサの異常診断を行うことができ、しかも、常時ＮＯｘ濃度を計算しているので、ＮＯｘセンサの異常診断を行う時期を内燃機関の運転状態が特別な条件の時に限定する必要がなく、連続的に行うことができる。また、排気ガス中のＮＯｘ濃度を容易に計算できる。 According to this method, by determining the NOx concentration in the exhaust gas by calculation, the abnormality diagnosis of the NOx sensor can be performed without taking a lot of experiment man-hours, and the NOx concentration is always calculated. It is not necessary to limit the timing for performing abnormality diagnosis of the NOx sensor when the operating state of the internal combustion engine is in a special condition, and it can be performed continuously. Further, the NOx concentration in the exhaust gas can be easily calculated.

この外部ＥＧＲガスは、ＥＧＲ通路を通り吸気通路に戻されるＥＧＲガスであり、内部ＥＧＲガスは、前サイクルの燃焼後のガスが排気ポートに排気されずにシリンダ内（筒内）に残留したガスと、一度排気ポートに排気されるがバルブオーバーラップ時にシリンダ内に戻される排気ガスとからなる。   This external EGR gas is an EGR gas that returns to the intake passage through the EGR passage, and the internal EGR gas is a gas that remains in the cylinder (in-cylinder) without being exhausted by the exhaust gas from the previous cycle to the exhaust port. And exhaust gas once exhausted to the exhaust port but returned to the cylinder when the valve overlaps.

そして、上記の目的を達成するためのＮＯｘセンサの異常診断システムは、内燃機関の排気通路に配置されるＮＯｘセンサの異常診断を行う制御装置を備えたＮＯｘセンサの異常診断システムであって、前記制御装置が、内部ＥＧＲガスの質量流量（ｍ＿ｉｎ＿ｅｇｒ）と外部ＥＧＲガスの質量流量（ｍ＿ｅｘ＿ｅｇｒ）と吸入空気の質量流量（ｍ＿ａｉｒ）と内部ＥＧＲガス中の酸素濃度（Ｏ２＿ｉｎ＿ｅｇｒ）と外部ＥＧＲガス中の酸素濃度（Ｏ２＿ｅｘ＿ｅｇｒ）と大気中の酸素濃度（Ｏ２＿ａｉｒ）とから前記内燃機関のシリンダ内の酸素濃度（Ｏ２＿ｃｙｌ）を算出するとともに、該シリンダ内の酸素濃度（Ｏ２＿ｃｙｌ）から、前記シリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）を算出するＮＯｘ濃度算出手段と、該算出されたＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）と前記ＮＯｘセンサの検出値（ＮＯｘ＿ｍ）とを比較して、前記ＮＯｘセンサが異常であるか否かの診断を行う比較診断手段を備えるとともに、前記ＮＯｘ濃度算出手段が、前記内燃機関の吸気通路に配置された吸気量センサで検出した吸入空気の質量流量（ｍ＿ａｉｒ）と、前記内燃機関の吸気マニホールドに配置された第１温度センサで検出した温度（Ｔｉ）と前記吸気マニホールドに配置された第１圧力センサで検出した圧力（Ｐｉ）と前記内燃機関の排気マニホールドに配置された第２温度センサで検出した温度（Ｔｅ）と前記排気マニホールドに配置された第２圧力センサで検出した圧力（Ｐｅ）とから算出した外部ＥＧＲガスの質量流量（ｍ＿ｅｘ＿ｅｇｒ）と、前記第２温度センサで検出した温度（Ｔｅ）と前記第２圧力センサで検出した圧力（Ｐｅ）とから算出した内部ＥＧＲガスの質量流量（ｍ＿ｉｎ＿ｅｇｒ）から、（１）式によりシリンダ内の質量流量（ｍ＿ｃｙｌ）を算出する第１演算手段と、

Figure 0005891734
前記吸気量センサで検出した吸入空気の質量流量（ｍ＿ａｉｒ）と前記燃料噴射量（ｑ）とから、（２）式により、内部ＥＧＲ空気過剰率（λ＿ｉｎ＿ｅｇｒ）を算出する第２演算手段と、
Figure 0005891734
 前記内部ＥＧＲ空気過剰率（λ＿ｉｎ＿ｅｇｒ）からＥＧＲガスの時間遅れを考慮して算出した外部ＥＧＲ空気過剰率（λ＿ｅｘ＿ｅｇｒ）と大気中の酸素濃度（Ｏ２＿ａｉｒ）と理論空燃比（Ｌ＿ｓｔ）とから、（３）式により外部ＥＧＲガス中の酸素濃度（Ｏ２＿ｅｘ＿ｅｇｒ）を算出する第３演算手段と、
Figure 0005891734
 前記内部ＥＧＲ空気過剰率（λ＿ｉｎ＿ｅｇｒ）から算出した内部ＥＧＲ空気過剰率（λ＿ｉｎ＿ｅｇｒ）と大気中の酸素濃度（Ｏ２＿ａｉｒ）と理論空燃比（Ｌ＿ｓｔ）とから、（４）式により内部ＥＧＲガス中の酸素濃度（Ｏ２＿ｉｎ＿ｅｇｒ）を算出する第４演算手段と、
Figure 0005891734
 （５）式より、シリンダ内の酸素濃度（Ｏ２＿ｃｙｌ）を算出する第５演算手段と、
Figure 0005891734
 定常時のシリンダ内の酸素濃度（Ｏ２＿ｒｅｆ）と定常時のシリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｒｅｆ）と、指数ｉとが予め設定されている（６）式のシリンダ内の酸素濃度（Ｏ２＿ｃｙｌ）とシリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）の関係から、現在のシリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）を算出する第６演算手段とを備え、
Figure 0005891734
 前記比較診断手段が、前記算出された現在のシリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）と前記ＮＯｘセンサの検出値（ＮＯｘ＿ｍ）とを比較して、前記ＮＯｘセンサが異常であるか否かの診断を行う第７演算手段を備えて構成される。 A NOx sensor abnormality diagnosis system for achieving the above object is a NOx sensor abnormality diagnosis system comprising a control device for performing abnormality diagnosis of a NOx sensor disposed in an exhaust passage of an internal combustion engine, The control device is configured to control the mass flow rate of the internal EGR gas (m_in_egr), the mass flow rate of the external EGR gas (m_ex_egr), the mass flow rate of the intake air (m_air), the oxygen concentration in the internal EGR gas (O2_in_egr), and the oxygen in the external EGR gas. The oxygen concentration (O2_cyl) in the cylinder of the internal combustion engine is calculated from the concentration (O2_ex_egr) and the oxygen concentration (O2_air) in the atmosphere, and NOx discharged from the cylinder from the oxygen concentration (O2_cyl) in the cylinder. NOx concentration calculating means for calculating the concentration (NOx_cyl); The NOx concentration calculating means comprises a comparison diagnostic means for comparing the detected NOx concentration (NOx_cyl) with the detected value (NOx_m) of the NOx sensor and diagnosing whether or not the NOx sensor is abnormal. The mass flow rate (m_air) of the intake air detected by the intake air amount sensor arranged in the intake passage of the internal combustion engine, the temperature (Ti) detected by the first temperature sensor arranged in the intake manifold of the internal combustion engine, and the The pressure (Pi) detected by the first pressure sensor arranged in the intake manifold, the temperature (Te) detected by the second temperature sensor arranged in the exhaust manifold of the internal combustion engine, and the second pressure arranged in the exhaust manifold The mass flow rate (m_ex_egr) of the external EGR gas calculated from the pressure (Pe) detected by the sensor and the second temperature sensor The mass flow rate (m_cyl) in the cylinder is calculated from equation (1) from the mass flow rate (m_in_egr) of the internal EGR gas calculated from the measured temperature (Te) and the pressure (Pe) detected by the second pressure sensor. One computing means;
Figure 0005891734
 Second calculating means for calculating an internal EGR excess air ratio (λ_in_egr) from the mass flow rate (m_air) of the intake air detected by the intake air amount sensor and the fuel injection amount (q) according to the equation (2) ;
Figure 0005891734
 From the external EGR excess air ratio (λ_ex_egr) calculated from the internal EGR excess air ratio (λ_in_egr) in consideration of the time delay of EGR gas, the oxygen concentration (O2_air) in the atmosphere, and the theoretical air-fuel ratio (L_st), (3 ) The third computing means for calculating the oxygen concentration (O2_ex_egr) in the external EGR gas by the equation;
Figure 0005891734
 From the internal EGR excess air ratio (λ_in_egr) calculated from the internal EGR excess air ratio (λ_in_egr), the oxygen concentration in the atmosphere (O2_air), and the stoichiometric air-fuel ratio (L_st), the oxygen in the internal EGR gas is expressed by the equation (4). A fourth calculation means for calculating a concentration (O2_in_egr);
Figure 0005891734
 A fifth operation means for calculating the oxygen concentration (O2_cyl) in the cylinder from the equation (5);
Figure 0005891734
 The oxygen concentration (O2_ref) in the cylinder in the equation (6) in which the oxygen concentration (O2_ref) in the cylinder at a constant time, the NOx concentration discharged from the cylinder at the steady state (NOx_ref), and the index i are set in advance. Sixth calculating means for calculating the NOx concentration (NOx_cyl) discharged from the current cylinder from the relationship of the NOx concentration (NOx_cyl) discharged from the cylinder;
Figure 0005891734
 The comparison diagnosis means compares the calculated NOx concentration (NOx_cyl) discharged from the current cylinder with the detected value (NOx_m) of the NOx sensor to diagnose whether the NOx sensor is abnormal. It is comprised including the 7th calculating means which performs .

この構成によれば、排気ガス中のＮＯｘ濃度を計算により求めることで、多大な実験工数を掛けることなくＮＯｘセンサの異常診断を行うことができ、しかも、常時ＮＯｘ濃度を計算しているので、ＮＯｘセンサの異常診断を行う時期を内燃機関の運転状態が特別な条件の時に限定する必要がなく、連続的に行うことができる。また、排気ガス中のＮＯｘ濃度を容易に計算できる。 According to this configuration, by calculating the NOx concentration in the exhaust gas by calculation, the abnormality diagnosis of the NOx sensor can be performed without taking a lot of experiment man-hours, and the NOx concentration is always calculated. It is not necessary to limit the timing for performing abnormality diagnosis of the NOx sensor when the operating state of the internal combustion engine is in a special condition, and it can be performed continuously. Further, the NOx concentration in the exhaust gas can be easily calculated.

そして、上記の目的を達成するための内燃機関は、上記のＮＯｘセンサの異常診断システムを備えて構成され、上記のＮＯｘセンサの異常診断システムと同様の効果を奏することができる。   An internal combustion engine for achieving the above object includes the above NOx sensor abnormality diagnosis system, and can achieve the same effects as the above NOx sensor abnormality diagnosis system.

本発明に係るＮＯｘセンサの異常診断方法、ＮＯｘセンサの異常診断システム、及び内燃機関によれば、排気ガス中のＮＯｘ濃度を計算により求め、この計算されたＮＯｘ濃度とＮＯｘセンサで検出されたＮＯｘ濃度とを比較することで、多大な実験工数をかけることなくＮＯｘセンサの異常診断ができる。また、内燃機関の運転状態が特別な条件下にある状態ではなく、常にＮＯｘ濃度の値を計算して比較できるので、ＮＯｘセンサの異常診断を連続的に行うことができる。   According to the NOx sensor abnormality diagnosis method, the NOx sensor abnormality diagnosis system, and the internal combustion engine according to the present invention, the NOx concentration in the exhaust gas is obtained by calculation, and the calculated NOx concentration and the NOx detected by the NOx sensor are calculated. By comparing the concentration, the abnormality diagnosis of the NOx sensor can be performed without taking a lot of experiment man-hours. In addition, since the operating state of the internal combustion engine is not in a special condition and the value of the NOx concentration can always be calculated and compared, the abnormality diagnosis of the NOx sensor can be performed continuously.

更に、ＥＧＲガスに関して、外部ＥＧＲガスのみならず、内部ＥＧＲガスも考慮しているので、より精度よくＮＯｘセンサの異常診断を行うことができる。   Further, regarding the EGR gas, not only the external EGR gas but also the internal EGR gas is taken into consideration, so that the abnormality diagnosis of the NOx sensor can be performed with higher accuracy.

本発明の実施の形態のＮＯｘセンサの異常診断システム及び内燃機関の構成を示す図である。It is a figure which shows the structure of the abnormality diagnosis system of the NOx sensor of embodiment of this invention, and an internal combustion engine. 本発明の実施の形態のＮＯｘセンサの異常診断システムの制御装置の構成を示す図である。It is a figure which shows the structure of the control apparatus of the abnormality diagnosis system of the NOx sensor of embodiment of this invention.

以下、本発明に係る実施の形態のＮＯｘセンサの異常診断方法、ＮＯｘセンサの異常診断システム、及び内燃機関について、図面を参照しながら説明する。図１に示すように、この内燃機関１０は、エンジン本体１１と、吸気マニホールド１１ａに接続する吸気通路１２と、排気マニホールド１１ｂに接続する排気通路１８を有して構成される。   Hereinafter, an NOx sensor abnormality diagnosis method, a NOx sensor abnormality diagnosis system, and an internal combustion engine according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the internal combustion engine 10 includes an engine body 11, an intake passage 12 connected to the intake manifold 11a, and an exhaust passage 18 connected to the exhaust manifold 11b.

この吸気通路１２には、上流側から順にエアクリーナー１３、ターボチャージャー（ターボ式過給機）１４のコンプレッサー１４ａ、インタークーラー１５、吸気スロットル（吸気弁）１６が設けられている。また、排気通路１８には、ターボチャージャー１４のタービン１４ｂ、排気ガス浄化装置１９が設けられている。   The intake passage 12 is provided with an air cleaner 13, a compressor 14 a of a turbocharger (turbo turbocharger) 14, an intercooler 15, and an intake throttle (intake valve) 16 in order from the upstream side. The exhaust passage 18 is provided with a turbine 14b of the turbocharger 14 and an exhaust gas purification device 19.

なお、図１の構成では、排気ガス浄化装置１９は上流側のＤＰＦ（ディーゼルパティキュレートフィルタ）１９ａと下流側のＳＣＲ触媒（選択的還元型触媒）１９ｂを備えている。このＳＣＲ触媒１９ｂの上流側には、ＮＯｘの還元剤となる尿素水等のアンモニア系溶液（アンモニアを発生する溶液、又はアンモニア水）を排気通路１８中に噴霧する還元剤噴射装置（図示しない）が設けられている。   In the configuration of FIG. 1, the exhaust gas purification device 19 includes an upstream DPF (diesel particulate filter) 19a and a downstream SCR catalyst (selective reduction catalyst) 19b. On the upstream side of the SCR catalyst 19b, a reducing agent injection device (not shown) that sprays an ammonia-based solution (a solution that generates ammonia or ammonia water) such as urea water serving as a NOx reducing agent into the exhaust passage 18. Is provided.

更に、ＥＧＲ（排気再循環）のために、排気通路１８と吸気通路１２とを連通するＥＧＲ通路２０が設けられ、このＥＧＲ通路２０には、ＥＧＲクーラー２１とＥＧＲ弁２２が配設されている。また、ＥＧＲガスＧｅのＥＧＲクーラー２１による過冷却を防止するために、流量調整弁２４を備えた排気戻し通路２３がＥＧＲクーラー２１の出口と排気通路１８とを接続して設けられている。   Further, for EGR (exhaust gas recirculation), an EGR passage 20 that connects the exhaust passage 18 and the intake passage 12 is provided, and an EGR cooler 21 and an EGR valve 22 are provided in the EGR passage 20. . Further, in order to prevent overcooling of the EGR gas Ge by the EGR cooler 21, an exhaust return passage 23 provided with a flow rate adjusting valve 24 is provided connecting the outlet of the EGR cooler 21 and the exhaust passage 18.

そして、空気Ａは、吸気通路１２のエアクリーナー１３で埃等を除去され、コンプレッサー１４ａにより過給されて圧力と温度が上昇した状態となり、インタークーラー１５で冷却された後、吸気スロットル１６で流量を制御され、必要に応じてＥＧＲガスＧｅと混合されて吸気マニホールド１１ａからエンジン本体１１の各シリンダ（気筒）１７内に入る。なお、ＥＧＲガスＧｅは、排気通路１８からＥＧＲ通路２０や排気戻り通路２３に分岐され、適度にＥＧＲクーラー２１で冷却され、また、ＥＧＲ弁２２や流量調整弁２４により流量を調整されて吸気通路１２に供給される。 The air A is dust removed by the air cleaner 13 in the intake passage 12, is supercharged by the compressor 14 a, rises in pressure and temperature, is cooled by the intercooler 15, and is then flowed by the intake throttle 16. It is controlled and mixed with EGR gas Ge as necessary, and enters each cylinder (cylinder) 17 of the engine body 11 from the intake manifold 11a. The EGR gas Ge is branched from the exhaust passage 18 to the EGR passage 20 and the exhaust return passage 23, and is appropriately cooled by the EGR cooler 21, and the flow rate is adjusted by the EGR valve 22 and the flow rate adjusting valve 24, and the intake passage. 12 is supplied.

シリンダ１７内では、燃料噴射弁（図示しない）から噴射された燃料と空気Ａが混合して燃焼して排気ガスＧを発生する。発生した排気ガスＧは排気マニホールド１１ｂから排気通路１８に排出され、タービン１４ｂを駆動した後、ＤＰＦ１９ａでＰＭ（粒子状物質）等を除去されたのち、排気通路１８に供給された還元剤によりＳＣＲ触媒１９ｂでＮＯｘが窒素に還元され、その後、サイレンサー（図示しない）等を通過して大気中に放出される。なお、排気ガスＧの一部はＥＧＲ通路２０に分岐され、ＥＧＲガスＧｅとして再循環される。 In the cylinder 17, the fuel injected from a fuel injection valve (not shown) and air A are mixed and burned to generate exhaust gas G. The generated exhaust gas G is discharged from the exhaust manifold 11 b to the exhaust passage 18, and after driving the turbine 14 b , PM (particulate matter) and the like are removed by the DPF 19 a, and then the SCR is supplied by the reducing agent supplied to the exhaust passage 18. NOx is reduced to nitrogen by the catalyst 19b, and then released into the atmosphere through a silencer (not shown) or the like. A part of the exhaust gas G is branched into the EGR passage 20 and recirculated as the EGR gas Ge.

そして、この内燃機関１０の運転制御やＤＰＦ１９ａの再生制御や、ＳＣＲ触媒１９ｂにおけるＮＯｘ浄化のための還元剤供給制御等を行うために、吸気系では、エアクリーナー１３とコンプレッサー１４ａとの間に吸気量ｍ＿ａｉｒを計測するためのエアフローセンサ（吸気量センサ）３１が、吸気マニホールド１１ａに吸気温度Ｔｉを計測するための第１温度センサ（インテークマニホールド温度センサ）３２と吸気圧Ｐｉを計測するための第１圧力センサ（吸気圧センサ：ブースト圧センサ）３３が配設される。   In order to perform the operation control of the internal combustion engine 10, the regeneration control of the DPF 19a, the reducing agent supply control for NOx purification in the SCR catalyst 19b, etc., in the intake system, the intake air is interposed between the air cleaner 13 and the compressor 14a. An air flow sensor (intake amount sensor) 31 for measuring the amount m_air has a first temperature sensor (intake manifold temperature sensor) 32 for measuring the intake air temperature Ti in the intake manifold 11a and a first air pressure sensor for measuring the intake pressure Pi. 1 pressure sensor (intake pressure sensor: boost pressure sensor) 33 is provided.

また、排気系では、排気マニホールド１１ｂに排気温度Ｔｅを計測するための第２温度センサ（エキゾーストマニホールド温度センサ）３４と排気圧Ｐｅを計測するための第２圧力センサ（排気圧センサ）３５が配設される。また、ＤＰＦ１９ａとＳＣＲ触媒１９ｂとの間にＮＯｘ濃度ＮＯｘ＿ｍ１を計測するＮＯｘセンサ３６が配設される。   In the exhaust system, a second temperature sensor (exhaust manifold temperature sensor) 34 for measuring the exhaust temperature Te and a second pressure sensor (exhaust pressure sensor) 35 for measuring the exhaust pressure Pe are arranged in the exhaust manifold 11b. Established. Further, a NOx sensor 36 that measures the NOx concentration NOx_m1 is disposed between the DPF 19a and the SCR catalyst 19b.

これらのセンサ３１〜３６の検出値を入力して、内燃機関１０の運転制御、ＤＰＦ１９ａの再生制御、ＳＣＲ触媒１９ｂにおけるＮＯｘ浄化のための還元剤供給制御等を行うＥＣＵ（エンジンコントロールユニット）と呼ばれる制御装置（ＥＣＵ）３０が設けられる。   It is called an ECU (engine control unit) that inputs the detection values of these sensors 31 to 36 and performs operation control of the internal combustion engine 10, regeneration control of the DPF 19a, reductant supply control for NOx purification in the SCR catalyst 19b, and the like. A control device (ECU) 30 is provided.

そして、この内燃機関１０の排気通路１８に配置されるＮＯｘセンサ３６の異常診断のために、内燃機関１０にＮＯｘセンサの異常診断システムが備えられ、このＮＯｘセンサの異常診断システムの制御装置４０が制御装置（ＥＣＵ）３０に組み込まれて構成される。   For the abnormality diagnosis of the NOx sensor 36 disposed in the exhaust passage 18 of the internal combustion engine 10, the internal combustion engine 10 is provided with a NOx sensor abnormality diagnosis system, and a control device 40 of this NOx sensor abnormality diagnosis system is provided. A control unit (ECU) 30 is built in and configured.

この制御装置４０は、内部ＥＧＲガスの質量流量ｍ＿ｉｎ＿ｅｇｒと外部ＥＧＲガスの質量流量ｍ＿ｅｘ＿ｅｇｒと吸入空気の質量流量ｍ＿ａｉｒと内部ＥＧＲガス中の酸素濃度Ｏ２＿ｉｎ＿ｅｇｒと外部ＥＧＲガス中の酸素濃度Ｏ２＿ｅｘ＿ｅｇｒと大気中の酸素濃度Ｏ２＿ａｉｒとから内燃機関１０のシリンダ１７内の酸素濃度Ｏ２＿ｃｙｌを算出するとともに、このシリンダ１７内の酸素濃度Ｏ２＿ｃｙｌから、シリンダ１７から排出されるＮＯｘ濃度ＮＯｘ＿ｃｙｌを算出するＮＯｘ濃度算出手段４１と、この算出されたＮＯｘ濃度ＮＯｘ＿ｃｙｌとＮＯｘセンサ３６の検出値ＮＯｘ＿ｍ（＝ＮＯｘ＿ｍｌ、又は、ＮＯｘ＿ｍ２）とを比較して、ＮＯｘセンサ３６が異常であるか否かの診断を行う比較診断手段４２を備えて構成される。 The control device 40 includes an internal EGR gas mass flow rate m_in_egr, an external EGR gas mass flow rate m_ex_egr, an intake air mass flow rate m_air, an internal EGR gas oxygen concentration O2_in_egr, an external EGR gas oxygen concentration O2_ex_egr, and an atmospheric EGR gas flow rate. NOx concentration calculating means 41 for calculating the oxygen concentration O2_cyl in the cylinder 17 of the internal combustion engine 10 from the oxygen concentration O2_air, and calculating the NOx concentration NOx_cyl discharged from the cylinder 17 from the oxygen concentration O2_cyl in the cylinder 17 ; Comparison diagnosis means 42 is provided for comparing the calculated NOx concentration NOx_cyl and the detected value NOx_m (= NOx_ml or NOx_m2) of the NOx sensor 36 to diagnose whether or not the NOx sensor 36 is abnormal. Composed .

このＮＯｘ濃度算出手段４１は、図２に示すように、第１〜第６演算手段４１ａ〜４１ｆを備え、第１演算ステップで、第１演算手段４１ａにより、第１演算ステップで、吸気量センサ３１で検出した吸入空気Ａの質量流量（新規空気流量）ｍ＿ａｉｒと外部ＥＧＲガスＧｅの質量流量ｍ＿ｅｘ＿ｅｇｒと内部ＥＧＲガスＧｅの質量流量ｍ＿ｉｎ＿ｅｇｒとから、（１）式によりシリンダ１７内の質量流量ｍ＿ｃｙｌを算出する。つまり、「（シリンダ内の質量流量ｍ＿ｃｙｌ）＝（吸入空気の質量流量：ｍ＿ａｉｒ）＋（外部ＥＧＲガスの質量流量：ｍ＿ｅｘ＿ｅｇｒ）＋（内部ＥＧＲガスの質量流量：ｍ＿ｉｎ＿ｅｇｒ）」となる。 As shown in FIG. 2, the NOx concentration calculating means 41 includes first to sixth calculating means 41a to 41f . In the first calculating step, the first calculating means 41a sets the intake air amount sensor to the first calculating step. From the mass flow rate (new air flow rate) m_air of the intake air A detected at 31, the mass flow rate m_ex_egr of the external EGR gas Ge, and the mass flow rate m_in_egr of the internal EGR gas Ge, the mass flow rate m_cyl in the cylinder 17 is calculated by the equation (1). calculate. That is, “(mass flow rate in the cylinder m_cyl) = (mass flow rate of intake air: m_air) + (mass flow rate of external EGR gas: m_ex_egr) + (mass flow rate of internal EGR gas: m_in_egr)”.

この外部ＥＧＲガスは、ＥＧＲ通路２０を通り吸気通路１２に戻されるＥＧＲガスＧｅであり、内部ＥＧＲガスは、前サイクルの燃焼後のガスが排気ポートに排気されずにシリンダ１７内（筒内）に残留したガスと、一度排気ポートに排気されるがバルブオーバーラップ時にシリンダ１７内に戻される排気ガスとからなる。   This external EGR gas is an EGR gas Ge that passes through the EGR passage 20 and returns to the intake passage 12, and the internal EGR gas is not exhausted into the exhaust port from the combustion gas in the previous cycle, but in the cylinder 17 (in-cylinder). And the exhaust gas once exhausted to the exhaust port but returned to the cylinder 17 when the valve overlaps.

なお、外部ＥＧＲガスＧｅの質量流量ｍ＿ｅｘ＿ｅｇｒは、第１温度センサ３２で検出した温度Ｔｉと第１圧力センサ３３で検出した圧力Ｐｉと第２温度センサ３４で検出した温度Ｔｅと第２圧力センサ３５で検出した圧力Ｐｅとから算出し、内部ＥＧＲガスの質量流量ｍ＿ｉｎ＿ｅｇｒは、第２温度センサ３４で検出した温度Ｔｅと第２圧力センサ３５で検出した圧力Ｐｅとから算出する。

Figure 0005891734
The mass flow rate m_ex_egr of the external EGR gas Ge includes the temperature Ti detected by the first temperature sensor 32, the pressure Pi detected by the first pressure sensor 33, the temperature Te detected by the second temperature sensor 34, and the second pressure sensor 35. in calculating from the detected pressure Pe, the mass flow rate m_in_egr internal EGR gas is calculated from the temperature Te and the pressure Pe detected by the second pressure sensor 35 detected by the second temperature sensor 34.
Figure 0005891734

ここで、ＥＧＲガスが通過するバルブ有効面積をＡとし、ガス定数をＲとし、比熱比をκとし、シリンダ容積をＶｃｙｌとし、圧縮比をεとすると、外部ＥＧＲ流量ｍ＿ｅｘ＿ｅｇｒは（８）式で算出され、内部ＥＧＲ流量ｍ＿ｉｎ＿ｅｇｒは（９）式で算出される。

Figure 0005891734
Here, when the effective valve area through which EGR gas passes is A, the gas constant is R, the specific heat ratio is κ, the cylinder volume is Vcyl, and the compression ratio is ε, the external EGR flow rate m_ex_egr is expressed by equation (8). The internal EGR flow rate m_in_egr is calculated by the equation (9).
Figure 0005891734

また、第２演算ステップで、第２演算手段４１ｂにより、吸気量センサ３１で検出した吸入空気の質量流量ｍ＿ａｉｒと燃料噴射量ｑとから、（２）式により、内部ＥＧＲ空気過剰率λ＿ｉｎ＿ｅｇｒを算出する。なお、理論空燃比Ｌ＿ｓｔは、燃料によって多少変化するが、ディーゼルエンジンに使用される軽油の場合には、１４．６となり、ガソリンエンジンに使用されるガソリンの場合には、１４．５〜１４．７となる。

Figure 0005891734
Also, in the second calculation step, the internal EGR excess air ratio λ_in_egr is calculated by the second calculation means 41b from the intake air mass flow rate m_air detected by the intake air amount sensor 31 and the fuel injection amount q by the equation (2). To do. The theoretical air-fuel ratio L_st varies slightly depending on the fuel, but is 14.6 in the case of light oil used in a diesel engine, and 14.5 to 14 in the case of gasoline used in a gasoline engine. 7
Figure 0005891734

次に、第３演算ステップで、第３演算手段４１ｃにより、外部ＥＧＲガスＧ＿ｅｘ＿ｅｇｒの酸素濃度Ｏ２＿ｅｘ＿ｅｇｒを計算する。大気中の酸素濃度Ｏ２＿ａｉｒと外部ＥＧＲ空気過剰率λ＿ｅｘ＿ｅｇｒと理論空燃比Ｌ＿ｓｔとから、（３）式により、外部ＥＧＲガスＧｅ中の酸素濃度Ｏ２＿ｅｘ＿ｅｇｒを算出する。この外部ＥＧＲ空気過剰率λ＿ｅｘ＿ｅｇｒには、内部ＥＧＲ空気過剰率λ＿ｉｎ＿ｅｇｒからＥＧＲガスＧｅの時間遅れを考慮した値を用いる。

Figure 0005891734
Next, in the third calculation step, the third calculation means 41c calculates the oxygen concentration O2_ex_egr of the external EGR gas G_ex_egr. From the oxygen concentration O2_air in the atmosphere, the external EGR air excess ratio λ_ex_egr, and the theoretical air-fuel ratio L_st, the oxygen concentration O2_ex_egr in the external EGR gas Ge is calculated by the equation (3). As the external EGR excess air ratio λ_ex_egr , a value taking into account the time delay of the EGR gas Ge from the internal EGR excess air ratio λ_in_egr is used.
Figure 0005891734

次に、第４演算ステップで、第４演算手段４１ｄにより、内部ＥＧＲガスＧ＿ｉｎ＿ｅｇｒの酸素濃度Ｏ２＿ｉｎ＿ｅｇｒを計算する。大気中の酸素濃度Ｏ２＿ａｉｒと内部ＥＧＲ空気過剰率λ＿ｉｎ＿ｅｇｒと理論空燃比Ｌ＿ｓｔとから、（４）式により、内部ＥＧＲガス中の酸素濃度Ｏ２＿ｉｎ＿ｅｇｒを算出する。

Figure 0005891734
Next, in the fourth calculation step, the fourth calculation means 41d calculates the oxygen concentration O2_in_egr of the internal EGR gas G_in_egr. From the oxygen concentration O2_air in the atmosphere, the internal EGR air excess ratio λ_in_egr, and the theoretical air-fuel ratio L_st, the oxygen concentration O2_in_egr in the internal EGR gas is calculated by the equation (4) .
Figure 0005891734

また、第５演算ステップで、第５演算手段４１ｅにより、（５）式より、シリンダ１７内の酸素濃度Ｏ２＿ｃｙｌを算出する。

Figure 0005891734
Further, in the fifth calculation step, the oxygen concentration O2_cyl in the cylinder 17 is calculated from the expression (5) by the fifth calculation means 41e.
Figure 0005891734

また、第６演算ステップで、第６演算手段４１ｆにより、シリンダ１７内の酸素濃度Ｏ２＿ｃｙｌを変換して、シリンダ１７内のＮＯｘ濃度ＮＯｘ＿ｃｙｌを算出する。ここでは、定常時のシリンダ１７内の酸素濃度Ｏ２＿ｒｅｆと定常時のシリンダ１７から排出されるＮＯｘ濃度ＮＯｘ＿ｒｅｆと、指数ｉとが予め設定されている（６）式及び（７）式のシリンダ１７内の酸素濃度Ｏ２＿ｃｙｌとシリンダ１７から排出されるＮＯｘ濃度ＮＯｘ＿ｃｙｌの関係から、現在のシリンダ１７から排出されるＮＯｘ濃度ＮＯｘ＿ｃｙｌを算出する。   In the sixth calculation step, the sixth calculation means 41f converts the oxygen concentration O2_cyl in the cylinder 17 to calculate the NOx concentration NOx_cyl in the cylinder 17. Here, the oxygen concentration O2_ref in the cylinder 17 at the normal time, the NOx concentration NOx_ref discharged from the cylinder 17 at the normal time, and the index i are set in advance in the cylinder 17 of the equations (6) and (7). The NOx concentration NOx_cyl discharged from the current cylinder 17 is calculated from the relationship between the oxygen concentration O2_cyl of NO2 and the NOx concentration NOx_cyl discharged from the cylinder 17.

これらの酸素濃度Ｏ２＿ｒｅｆとＮＯｘ濃度ＮＯｘ＿ｒｅｆと指数ｉは予め定常時のエンジンの実験で求めておき、設定しておく。

Figure 0005891734
Figure 0005891734
 The oxygen concentration O2_ref, the NOx concentration NOx_ref, and the index i are previously determined and set in advance through steady-state engine experiments.
Figure 0005891734
Figure 0005891734

そして、比較診断手段４２には、算出された現在のシリンダ１７から排出されるＮＯｘ濃度ＮＯｘ＿ｃｙｌとＮＯｘセンサ３６の検出値ＮＯｘ＿ｍとを比較して、ＮＯｘセンサ３６が異常であるか否かの診断を行う第７演算手段４２ａを備える。   Then, the comparison diagnosis means 42 compares the calculated NOx concentration NOx_cyl discharged from the current cylinder 17 with the detected value NOx_m of the NOx sensor 36 to diagnose whether the NOx sensor 36 is abnormal. Seventh calculating means 42a is provided.

第７演算ステップでは、この第７演算手段４２ａにより、ＮＯｘセンサ３６が異常であるか否かの診断を行うが、このＮＯｘセンサ３６が異常であるか否かの診断では、ＮＯｘセンサ３６が正常な状態であれば、算出されたＮＯｘ濃度ＮＯｘ＿ｃｙｌとＮＯｘセンサ３６の検出値ＮＯｘ＿ｍと差の絶対値が適正な値に設定された判定値ＮＯｘ＿ｊｕｄ以下となるはずであり、逆にＮＯｘセンサ３６が異常な状態であれば、その差の絶対値が判定値ＮＯｘ＿ｊｕｄを超えるはずである。従って、その差の絶対値が判定値ＮＯｘ＿ｊｕｄを超えた場合にＮＯｘセンサ３６は異常であると判定する。つまり、｜ＮＯｘ＿ｃｙｌ−ＮＯｘ＿ｍ｜≦ＮＯｘ＿ｊｕｄで正常、｜ＮＯｘ＿ｃｙｌ−ＮＯｘ＿ｍ｜＞ＮＯｘ＿ｊｕｄで異常と判定する。これにより、計算されたＮＯｘ濃度ＮＯｘ＿ｃｙｌとＮＯｘセンサ３６の検出値ＮＯｘ＿ｍを比較することで、ＮＯｘセンサ３６の異常診断を行うことができる。 In the seventh calculation step, the seventh calculation means 42a diagnoses whether or not the NOx sensor 36 is abnormal. In the diagnosis of whether or not the NOx sensor 36 is abnormal, the NOx sensor 36 is normal. If this is the case, the absolute value of the difference between the calculated NOx concentration NOx_cyl and the detected value NOx_m of the NOx sensor 36 should be equal to or less than the determination value NOx_jud set to an appropriate value. Conversely, the NOx sensor 36 is abnormal. In such a state, the absolute value of the difference should exceed the determination value NOx_jud. Accordingly, when the absolute value of the difference exceeds the determination value NOx_jud, it is determined that the NOx sensor 36 is abnormal. That is, it is determined that | NOx_cyl-NOx_m | ≦ NOx_jud is normal and | NOx_cyl-NOx_m |> NOx_jud is abnormal. Thus, the NOx sensor 36 can be diagnosed for abnormality by comparing the calculated NOx concentration NOx_cyl with the detected value NOx_m of the NOx sensor 36.

上記のＮＯｘセンサの異常診断方法、ＮＯｘセンサの異常診断システム、及び内燃機関１０によれば、排気ガスＧ中のＮＯｘ濃度ＮＯｘ＿ｃｙｌを計算により求めることで、多大な実験工数を掛けることなくＮＯｘセンサ３６の異常診断を行うことができ、しかも、常時ＮＯｘ濃度ＮＯｘ＿ｃｙｌを計算しているので、ＮＯｘセンサ３６の異常診断を行う時期を内燃機関１０の運転状態が特別な条件の時に限定する必要がなく、連続的に行うことができる。   According to the NOx sensor abnormality diagnosis method, the NOx sensor abnormality diagnosis system, and the internal combustion engine 10 described above, the NOx concentration in the exhaust gas G is determined by calculation, so that the NOx sensor 36 does not require much experimentation. In addition, since the NOx concentration NOx_cyl is constantly calculated, it is not necessary to limit the timing for performing the abnormality diagnosis of the NOx sensor 36 when the operating state of the internal combustion engine 10 is in a special condition. Can be done continuously.

更に、ＥＧＲガスに関して、外部ＥＧＲガスのみならず、内部ＥＧＲガスも考慮しているので、より精度よくＮＯｘセンサの異常診断を行うことができる。   Further, regarding the EGR gas, not only the external EGR gas but also the internal EGR gas is taken into consideration, so that the abnormality diagnosis of the NOx sensor can be performed with higher accuracy.

本発明のＮＯｘセンサの異常診断方法、ＮＯｘセンサの異常診断システム、及び内燃機関によれば、ＮＯｘ濃度の計算値とＮＯｘセンサの検出値を比較することで、ＮＯｘセンサの異常診断を連続的に行うことができるので、車両に搭載するような多くの内燃機関に利用できる。   According to the NOx sensor abnormality diagnosis method, the NOx sensor abnormality diagnosis system, and the internal combustion engine of the present invention, the NOx sensor abnormality diagnosis is continuously performed by comparing the calculated value of the NOx concentration with the detected value of the NOx sensor. This can be used for many internal combustion engines that are mounted on vehicles.

１０ 内燃機関
１１ エンジン本体
１１ａ 吸気マニホールド
１２ 吸気通路
１７ シリンダ（気筒）
１８ 排気通路
１９ 排気ガス浄化装置
１９ａ ＤＰＦ
１９ｂ ＳＣＲ触媒（選択的還元型触媒）
２０ ＥＧＲ通路
３０ 制御装置（ＥＣＵ）
３１ 吸気量センサ（エアフローセンサ）
３２ 第１温度センサ（インテークマニホールド温度センサ）
３３ 第１圧力センサ（吸気圧センサ：ブースト圧センサ）
３４ 第２温度センサ（エキゾーストマニホールド温度センサ）
３５ 第２圧力センサ（排気圧センサ）
３６ ＮＯｘセンサ
４０ 制御装置（ＮＯｘセンサの異常診断システムの制御装置）
４１ ＮＯｘ濃度算出手段
４１ａ 第１演算手段
４１ｂ 第２演算手段
４１ｃ 第３演算手段
４１ｄ 第４演算手段
４１ｅ 第５演算手段
４１ｆ 第６演算手段
４２ 比較診断手段
４２ａ 第７演算手段
Ａ 空気
Ｇ 排気ガス
Ｇｅ 外部ＥＧＲガス
Ｌ＿ｓｔ 理論空燃比
ＮＯｘ＿ｃｙｌ ＮＯｘ濃度の算出値
ＮＯｘ＿ｊｕｄ 判定値
ＮＯｘ＿ｍ ＮＯｘ濃度の計測値
ｍ＿ａｉｒ 吸気量センサの検出値
ｍ＿ｃｙｌ シリンダ内の質量流量
ｍ＿ｅｘ＿ｅｇｒ 外部ＥＧＲガスの質量流量
ｍ＿ｉｎ＿ｅｇｒ 内部ＥＧＲガスの質量流量
Ｏ２＿ａｉｒ 大気中の酸素濃度
Ｏ２＿ｅｘ＿ｅｇｒ 外部ＥＧＲガス中の酸素濃度
Ｏ２＿ｉｎ＿ｅｇｒ 内部ＥＧＲガス中の酸素濃度
Ｐｅ 排気圧
Ｐｉ 吸気圧
Ｔｅ 排気温度
Ｔｉ 吸気温度
λ 排気空気過剰率
λ＿ｅｘ＿ｅｇｒ 外部ＥＧＲガスの空気過剰率
λ＿ｉｎ＿ｅｇｒ 内部ＥＧＲガスの空気過剰率 DESCRIPTION OF SYMBOLS 10 Internal combustion engine 11 Engine main body 11a Intake manifold 12 Intake passage 17 Cylinder
18 Exhaust passage 19 Exhaust gas purification device 19a DPF
19b SCR catalyst (selective reduction catalyst)
20 EGR passage 30 control unit (ECU)
31 Intake air volume sensor (air flow sensor)
32 First temperature sensor (Intake manifold temperature sensor)
33 First pressure sensor (intake pressure sensor: boost pressure sensor)
34 Second temperature sensor (exhaust manifold temperature sensor)
35 Second pressure sensor (exhaust pressure sensor)
36 NOx sensor 40 control device (control device of NOx sensor abnormality diagnosis system)
41 NOx concentration calculating means 41a 1st calculating means 41b 2nd calculating means 41c 3rd calculating means 41d 4th calculating means 41e 5th calculating means 41f 6th calculating means 42 Comparative diagnostic means 42a 7th calculating means A Air G Exhaust gas Ge External EGR gas L_st Theoretical air-fuel ratio NOx_cyl Calculated value of NOx concentration NOx_jud Judgment value NOx_m Measured value of NOx concentration m_air Detected value of intake air sensor m_cyl Mass flow rate in cylinder m_ex_egr Mass flow rate of external EGR gas m_in_egr Mass flow rate of internal EGR gas Oxygen concentration in the atmosphere O2_ex_egr Oxygen concentration in the external EGR gas O2_in_egr Oxygen concentration in the internal EGR gas Pe Exhaust pressure Pi Intake pressure Ti Exhaust temperature Ti Intake temperature λ Exhaust air excess ratio λ_ex_egr Excess air in the external EGR gas Surplus ratio λ_in_egr Excess air ratio of internal EGR gas

Claims (3)

内燃機関の排気通路に配置されるＮＯｘセンサの異常診断方法であって、
内部ＥＧＲガスの質量流量（ｍ＿ｉｎ＿ｅｇｒ）と外部ＥＧＲガスの質量流量（ｍ＿ｅｘ＿ｅｇｒ）と吸入空気の質量流量（ｍ＿ａｉｒ）と内部ＥＧＲガス中の酸素濃度（Ｏ２＿ｉｎ＿ｅｇｒ）と外部ＥＧＲガス中の酸素濃度（Ｏ２＿ｅｘ＿ｅｇｒ）と大気中の酸素濃度（Ｏ２＿ａｉｒ）とから前記内燃機関のシリンダ内の酸素濃度（Ｏ２＿ｃｙｌ）を算出するステップと、
該シリンダ内の酸素濃度（Ｏ２＿ｃｙｌ）から、前記シリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）を算出するステップと、
該算出されたＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）と前記ＮＯｘセンサの検出値（ＮＯｘ＿ｍ）とを比較して、前記ＮＯｘセンサが異常であるか否かの診断を行うステップを含み、
さらに、このＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）を算出するステップである演算ステップが、
前記内燃機関の吸気通路に配置された吸気量センサで検出した吸入空気の質量流量（ｍ＿ａｉｒ）と、前記内燃機関の吸気マニホールドに配置された第１温度センサで検出した温度（Ｔｉ）と前記吸気マニホールドに配置された第１圧力センサで検出した圧力（Ｐｉ）と前記内燃機関の排気マニホールドに配置された第２温度センサで検出した温度（Ｔｅ）と前記排気マニホールドに配置された第２圧力センサで検出した圧力（Ｐｅ）とから算出した外部ＥＧＲガスの質量流量（ｍ＿ｅｘ＿ｅｇｒ）と、前記第２温度センサで検出した温度（Ｔｅ）と前記第２圧力センサで検出した圧力（Ｐｅ）とから算出した内部ＥＧＲガスの質量流量（ｍ＿ｉｎ＿ｅｇｒ）から、（１）式によりシリンダ内の質量流量（ｍ＿ｃｙｌ）を算出する第１演算ステップと、
Figure 0005891734
 前記吸気量センサで検出した吸入空気の質量流量（ｍ＿ａｉｒ）と前記燃料噴射量（ｑ）とから、（２）式により、内部ＥＧＲ空気過剰率（λ＿ｉｎ＿ｅｇｒ）を算出する第２演算ステップと、
Figure 0005891734
 前記内部ＥＧＲ空気過剰率（λ＿ｉｎ＿ｅｇｒ）からＥＧＲガスの時間遅れを考慮して算出した外部ＥＧＲ空気過剰率（λ＿ｅｘ＿ｅｇｒ）と大気中の酸素濃度（Ｏ２＿ａｉｒ）と理論空燃比（Ｌ＿ｓｔ）とから、（３）式により外部ＥＧＲガス中の酸素濃度（Ｏ２＿ｅｘ＿ｅｇｒ）を算出する第３演算ステップと、
Figure 0005891734
 前記内部ＥＧＲ空気過剰率（λ＿ｉｎ＿ｅｇｒ）と大気中の酸素濃度（Ｏ２＿ａｉｒ）と理論空燃比（Ｌ＿ｓｔ）とから、（４）式により内部ＥＧＲガス中の酸素濃度（Ｏ２＿ｉｎ＿ｅｇｒ）を算出する第４演算ステップと、
Figure 0005891734
 （５）式より、シリンダ内の酸素濃度（Ｏ２＿ｃｙｌ）を算出する第５演算ステップと、
Figure 0005891734
 定常時のシリンダ内の酸素濃度（Ｏ２＿ｒｅｆ）と定常時のシリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｒｅｆ）と、指数ｉとが予め設定されている（６）式の、シリンダ内の酸素濃度（Ｏ２＿ｃｙｌ）とシリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）の関係から、現在のシリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）を算出する第６演算ステップとを備え、
Figure 0005891734
 前記ＮＯｘセンサが異常であるか否かの診断を行うステップが、
前記（６）式から算出された現在のシリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）と前記ＮＯｘセンサの検出値（ＮＯｘ＿ｍ）とを比較して、前記ＮＯｘセンサが異常であるか否かの診断を行う第７演算ステップであることを特徴とするＮＯｘセンサの異常診断方法。 An abnormality diagnosis method for a NOx sensor disposed in an exhaust passage of an internal combustion engine,
Internal EGR gas mass flow rate (m_in_egr), external EGR gas mass flow rate (m_ex_egr), intake air mass flow rate (m_air), internal EGR gas oxygen concentration (O2_in_egr), and external EGR gas oxygen concentration (O2_ex_egr) Calculating the oxygen concentration (O2_cyl) in the cylinder of the internal combustion engine from the oxygen concentration in the atmosphere (O2_air);
Calculating a NOx concentration (NOx_cyl) discharged from the cylinder from an oxygen concentration (O2_cyl) in the cylinder;
Comparing the calculated NOx concentration (NOx_cyl) with the detected value (NOx_m) of the NOx sensor to diagnose whether the NOx sensor is abnormal ,
Further, a calculation step which is a step of calculating the NOx concentration (NOx_cyl)
The mass flow rate (m_air) of the intake air detected by the intake air amount sensor arranged in the intake passage of the internal combustion engine, the temperature (Ti) detected by the first temperature sensor arranged in the intake manifold of the internal combustion engine, and the intake air A pressure (Pi) detected by a first pressure sensor arranged on the manifold, a temperature (Te) detected by a second temperature sensor arranged on the exhaust manifold of the internal combustion engine, and a second pressure sensor arranged on the exhaust manifold Calculated from the mass flow rate (m_ex_egr) of the external EGR gas calculated from the pressure (Pe) detected in Step 2, the temperature (Te) detected by the second temperature sensor, and the pressure (Pe) detected by the second pressure sensor The first calculation step for calculating the mass flow rate (m_cyl) in the cylinder from the mass flow rate (m_in_egr) of the internal EGR gas performed by the equation (1). And-up,
Figure 0005891734
 A second calculation step of calculating an internal EGR excess air ratio (λ_in_egr) from the mass flow rate (m_air) of the intake air detected by the intake air amount sensor and the fuel injection amount (q) by the equation (2);
Figure 0005891734
 From the external EGR excess air ratio (λ_ex_egr) calculated from the internal EGR excess air ratio (λ_in_egr) in consideration of the time delay of EGR gas, the oxygen concentration (O2_air) in the atmosphere, and the theoretical air-fuel ratio (L_st), (3 And a third calculation step of calculating the oxygen concentration (O2_ex_egr) in the external EGR gas by the formula:
Figure 0005891734
 Fourth calculation step of calculating the oxygen concentration (O2_in_egr) in the internal EGR gas from the internal EGR air excess ratio (λ_in_egr), the oxygen concentration (O2_air) in the atmosphere, and the theoretical air-fuel ratio (L_st) by the equation (4) When,
Figure 0005891734
 A fifth calculation step for calculating the oxygen concentration (O2_cyl) in the cylinder from the equation (5);
Figure 0005891734
 The oxygen concentration (O2_ref) in the cylinder in the formula (6) in which the oxygen concentration (O2_ref) in the cylinder at a constant time, the NOx concentration discharged from the cylinder at the normal time (NOx_ref), and the index i are set in advance. A NOx concentration (NOx_cyl) discharged from the cylinder, and a sixth calculation step for calculating the NOx concentration (NOx_cyl) discharged from the current cylinder,
Figure 0005891734
 Diagnosing whether the NOx sensor is abnormal,
The NOx concentration (NOx_cyl) discharged from the current cylinder calculated from the equation (6) is compared with the detected value (NOx_m) of the NOx sensor to diagnose whether the NOx sensor is abnormal. An NOx sensor abnormality diagnosis method , comprising: a seventh calculation step to be performed . 内燃機関の排気通路に配置されるＮＯｘセンサの異常診断を行う制御装置を備えたＮＯｘセンサの異常診断システムであって、
前記制御装置が、
内部ＥＧＲガスの質量流量（ｍ＿ｉｎ＿ｅｇｒ）と外部ＥＧＲガスの質量流量（ｍ＿ｅｘ＿ｅｇｒ）と吸入空気の質量流量（ｍ＿ａｉｒ）と内部ＥＧＲガス中の酸素濃度（Ｏ２＿ｉｎ＿ｅｇｒ）と外部ＥＧＲガス中の酸素濃度（Ｏ２＿ｅｘ＿ｅｇｒ）と大気中の酸素濃度（Ｏ２＿ａｉｒ）とから前記内燃機関のシリンダ内の酸素濃度（Ｏ２＿ｃｙｌ）を算出するとともに、該シリンダ内の酸素濃度（Ｏ２＿ｃｙｌ）から、前記シリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）を算出するＮＯｘ濃度算出手段と、
該算出されたＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）と前記ＮＯｘセンサの検出値（ＮＯｘ＿ｍ）とを比較して、前記ＮＯｘセンサが異常であるか否かの診断を行う比較診断手段を備えるとともに、
前記ＮＯｘ濃度算出手段が、
前記内燃機関の吸気通路に配置された吸気量センサで検出した吸入空気の質量流量（ｍ＿ａｉｒ）と、前記内燃機関の吸気マニホールドに配置された第１温度センサで検出した温度（Ｔｉ）と前記吸気マニホールドに配置された第１圧力センサで検出した圧力（Ｐｉ）と前記内燃機関の排気マニホールドに配置された第２温度センサで検出した温度（Ｔｅ）と前記排気マニホールドに配置された第２圧力センサで検出した圧力（Ｐｅ）とから算出した外部ＥＧＲガスの質量流量（ｍ＿ｅｘ＿ｅｇｒ）と、前記第２温度センサで検出した温度（Ｔｅ）と前記第２圧力センサで検出した圧力（Ｐｅ）とから算出した内部ＥＧＲガスの質量流量（ｍ＿ｉｎ＿ｅｇｒ）から、（１）式によりシリンダ内の質量流量（ｍ＿ｃｙｌ）を算出する第１演算手段と、
Figure 0005891734
 前記吸気量センサで検出した吸入空気の質量流量（ｍ＿ａｉｒ）と前記燃料噴射量（ｑ）とから、（２）式により、内部ＥＧＲ空気過剰率（λ＿ｉｎ＿ｅｇｒ）を算出する第２演算手段と、
Figure 0005891734
 前記内部ＥＧＲ空気過剰率（λ＿ｉｎ＿ｅｇｒ）からＥＧＲガスの時間遅れを考慮して算出した外部ＥＧＲ空気過剰率（λ＿ｅｘ＿ｅｇｒ）と大気中の酸素濃度（Ｏ２＿ａｉｒ）と理論空燃比（Ｌ＿ｓｔ）とから、（３）式により外部ＥＧＲガス中の酸素濃度（Ｏ２＿ｅｘ＿ｅｇｒ）を算出する第３演算手段と、
Figure 0005891734
 前記内部ＥＧＲ空気過剰率（λ＿ｉｎ＿ｅｇｒ）から算出した内部ＥＧＲ空気過剰率（λ＿ｉｎ＿ｅｇｒ）と大気中の酸素濃度（Ｏ２＿ａｉｒ）と理論空燃比（Ｌ＿ｓｔ）とから、（４）式により内部ＥＧＲガス中の酸素濃度（Ｏ２＿ｉｎ＿ｅｇｒ）を算出する第４演算手段と、
Figure 0005891734
 （５）式より、シリンダ内の酸素濃度（Ｏ２＿ｃｙｌ）を算出する第５演算手段と、
Figure 0005891734
 定常時のシリンダ内の酸素濃度（Ｏ２＿ｒｅｆ）と定常時のシリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｒｅｆ）と、指数ｉとが予め設定されている（６）式のシリンダ内の酸素濃度（Ｏ２＿ｃｙｌ）とシリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）の関係から、現在のシリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）を算出する第６演算手段とを備え、
Figure 0005891734
 前記比較診断手段が、前記算出された現在のシリンダから排出されるＮＯｘ濃度（ＮＯｘ＿ｃｙｌ）と前記ＮＯｘセンサの検出値（ＮＯｘ＿ｍ）とを比較して、前記ＮＯｘセンサが異常であるか否かの診断を行う第７演算手段を備えていることを特徴とするＮＯｘセンサの異常診断システム。 A NOx sensor abnormality diagnosis system comprising a control device for performing abnormality diagnosis of a NOx sensor disposed in an exhaust passage of an internal combustion engine,
The control device is
Internal EGR gas mass flow rate (m_in_egr), external EGR gas mass flow rate (m_ex_egr), intake air mass flow rate (m_air), internal EGR gas oxygen concentration (O2_in_egr), and external EGR gas oxygen concentration (O2_ex_egr) The oxygen concentration (O2_cyl) in the cylinder of the internal combustion engine is calculated from the oxygen concentration (O2_air) in the atmosphere and the NOx concentration (NOx_cyl) discharged from the cylinder from the oxygen concentration (O2_cyl) in the cylinder. NOx concentration calculating means for calculating
Comparing the calculated NOx concentration (NOx_cyl) with the detected value (NOx_m) of the NOx sensor, a comparison diagnosis means for diagnosing whether or not the NOx sensor is abnormal is provided.
The NOx concentration calculating means
The mass flow rate (m_air) of the intake air detected by the intake air amount sensor arranged in the intake passage of the internal combustion engine, the temperature (Ti) detected by the first temperature sensor arranged in the intake manifold of the internal combustion engine, and the intake air A pressure (Pi) detected by a first pressure sensor arranged on the manifold, a temperature (Te) detected by a second temperature sensor arranged on the exhaust manifold of the internal combustion engine, and a second pressure sensor arranged on the exhaust manifold Calculated from the mass flow rate (m_ex_egr) of the external EGR gas calculated from the pressure (Pe) detected in Step 2, the temperature (Te) detected by the second temperature sensor, and the pressure (Pe) detected by the second pressure sensor The first calculation unit that calculates the mass flow rate (m_cyl) in the cylinder from the mass flow rate (m_in_egr) of the internal EGR gas that has been performed using the equation (1) And,
Figure 0005891734
 Second calculating means for calculating an internal EGR excess air ratio (λ_in_egr) from the mass flow rate (m_air) of the intake air detected by the intake air amount sensor and the fuel injection amount (q) according to the equation (2) ;
Figure 0005891734
 From the external EGR excess air ratio (λ_ex_egr) calculated from the internal EGR excess air ratio (λ_in_egr) in consideration of the time delay of EGR gas, the oxygen concentration (O2_air) in the atmosphere, and the theoretical air-fuel ratio (L_st), (3 ) The third computing means for calculating the oxygen concentration (O2_ex_egr) in the external EGR gas by the equation;
Figure 0005891734
 From the internal EGR excess air ratio (λ_in_egr) calculated from the internal EGR excess air ratio (λ_in_egr), the oxygen concentration in the atmosphere (O2_air), and the stoichiometric air-fuel ratio (L_st), the oxygen in the internal EGR gas is expressed by the equation (4). A fourth calculation means for calculating a concentration (O2_in_egr);
Figure 0005891734
 A fifth operation means for calculating the oxygen concentration (O2_cyl) in the cylinder from the equation (5);
Figure 0005891734
 The oxygen concentration (O2_ref) in the cylinder in the equation (6) in which the oxygen concentration (O2_ref) in the cylinder at a constant time, the NOx concentration discharged from the cylinder at the steady state (NOx_ref), and the index i are set in advance. Sixth calculating means for calculating the NOx concentration (NOx_cyl) discharged from the current cylinder from the relationship of the NOx concentration (NOx_cyl) discharged from the cylinder;
Figure 0005891734
 The comparison diagnosis means compares the calculated NOx concentration (NOx_cyl) discharged from the current cylinder with the detected value (NOx_m) of the NOx sensor to diagnose whether the NOx sensor is abnormal. A NOx sensor abnormality diagnosis system comprising: a seventh calculation means for performing 請求項２に記載のＮＯｘセンサの異常診断システムを備えた内燃機関。 An internal combustion engine comprising the NOx sensor abnormality diagnosis system according to claim 2 .
JP2011253271A 2011-11-18 2011-11-18 NOx sensor abnormality diagnosis method, NOx sensor abnormality diagnosis system, and internal combustion engine Expired - Fee Related JP5891734B2 (en)

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