JP6708185B2 - Exhaust purification system controller - Google Patents

Exhaust purification system controller Download PDF

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JP6708185B2
JP6708185B2 JP2017160333A JP2017160333A JP6708185B2 JP 6708185 B2 JP6708185 B2 JP 6708185B2 JP 2017160333 A JP2017160333 A JP 2017160333A JP 2017160333 A JP2017160333 A JP 2017160333A JP 6708185 B2 JP6708185 B2 JP 6708185B2
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nox
amount
ozone
ozone supply
catalyst
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JP2019039322A (en
JP2019039322A5 (en
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佑輔 真島
佑輔 真島
樋口　和弘
和弘 樋口
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Denso Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F01N3/208—Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
    • C01B13/10—Preparation of ozone
    • C01B13/11—Preparation of ozone by electric discharge
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0814—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
    • F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
    • F01N3/0842—Nitrogen oxides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N9/00—Electrical control of exhaust gas treating apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2240/00—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
    • F01N2240/38—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being an ozone (O3) generator, e.g. for adding ozone after generation of ozone from air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2550/00—Monitoring or diagnosing the deterioration of exhaust systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
    • F01N2560/026—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting NOx
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/06—Adding substances to exhaust gases the substance being in the gaseous form
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/14—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust gas
    • F01N2900/1402—Exhaust gas composition
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Organic Chemistry (AREA)
  • Toxicology (AREA)
  • Inorganic Chemistry (AREA)
  • Biomedical Technology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
  • Oxygen, Ozone, And Oxides In General (AREA)

Description

本発明は、ＮＯｘ（窒素酸化物）を浄化するＮＯｘ吸蔵還元型の触媒を備える排気浄化システムの制御装置に関するものである。 The present invention relates to a control device for an exhaust gas purification system including a NOx occlusion reduction type catalyst that purifies NOx (nitrogen oxide).

従来、内燃機関の排気浄化システムにおいてＮＯｘ吸蔵還元型触媒を用いてＮＯｘを浄化する技術が知られている。このＮＯｘ吸蔵還元型触媒では、ＮＯ（一酸化窒素）とＮＯ2（二酸化窒素）とで吸蔵効率が異なり、例えば低温状態である場合にＮＯの吸蔵効率が低下する。そこで、内燃機関の排気通路においてＮＯｘ吸蔵還元型触媒よりも上流側にオゾン供給装置によりオゾンを供給し、そのオゾンにより排気中のＮＯをＮＯ2に酸化させる技術が提案されている（例えば特許文献１参照）。 Conventionally, there is known a technique for purifying NOx by using a NOx storage reduction catalyst in an exhaust purification system of an internal combustion engine. In this NOx occlusion reduction type catalyst, NO (nitric oxide) and NO2 (nitrogen dioxide) have different occlusion efficiencies, and the NO occlusion efficiency decreases, for example, in a low temperature state. Therefore, a technique has been proposed in which ozone is supplied by an ozone supply device to the upstream side of the NOx occlusion reduction type catalyst in the exhaust passage of the internal combustion engine, and NO in the exhaust gas is oxidized to NO2 by the ozone (for example, Patent Document 1). reference).

特開２０１６−７９８７２号公報JP, 2016-79872, A

ところで、ＮＯｘ吸蔵還元型触媒の上流側にオゾンを供給する排気浄化システムにおいて、オゾン供給装置により適正量のオゾンが供給されないと、ＮＯｘ吸蔵還元型触媒において所望とするＮＯｘ浄化性能を発揮できなくなることが懸念される。 By the way, in the exhaust gas purification system that supplies ozone to the upstream side of the NOx storage reduction catalyst, unless the ozone supply device supplies a proper amount of ozone, the NOx storage reduction catalyst cannot exhibit the desired NOx purification performance. Is concerned.

本発明は、上記課題に鑑みてなされたものであり、その主たる目的は、オゾン供給を適正に行い、ひいては適正なるＮＯｘ浄化を実現することができる排気浄化システムの制御装置を提供することにある。 The present invention has been made in view of the above problems, and a main object of the present invention is to provide a control device for an exhaust gas purification system, which can appropriately supply ozone, and can thereby realize appropriate NOx purification. ..

以下、上記課題を解決するための手段、及びその作用効果について説明する。 Hereinafter, the means for solving the above problems, and the operation and effect thereof will be described.

本手段における排気浄化システムの制御装置は、
内燃機関（１０）の排気通路に設けられ、排気中のＮＯｘを浄化するＮＯｘ吸蔵還元型の触媒（２１）と、前記排気通路において前記触媒の上流側にオゾンを供給するオゾン供給装置（３２，３３）と、前記触媒の下流側に設けられ、排気中のＮＯｘ量を検出するＮＯｘセンサ（２４）とを備える排気浄化システムに適用され、
前記内燃機関が運転状態あり、かつ前記オゾン供給装置によりオゾンが供給されている状態において前記ＮＯｘセンサにより検出された検出ＮＯｘ量を取得するＮＯｘ量取得部と、
前記ＮＯｘ量取得部により取得された前記検出ＮＯｘ量に基づいて、前記オゾン供給装置によるオゾン供給量制御、及び前記オゾン供給装置の異常診断の少なくともいずれかを実施する制御部と、
を備える。 The control device of the exhaust purification system in this means is
An NOx occlusion reduction type catalyst (21) provided in the exhaust passage of the internal combustion engine (10) for purifying NOx in the exhaust, and an ozone supply device (32, for supplying ozone to the upstream side of the catalyst in the exhaust passage). 33) and a NOx sensor (24) provided downstream of the catalyst for detecting the amount of NOx in the exhaust gas, and is applied to an exhaust gas purification system,
A NOx amount acquisition unit that acquires a detected NOx amount detected by the NOx sensor in a state where the internal combustion engine is in an operating state and ozone is being supplied by the ozone supply device;
A control unit that performs at least one of ozone supply amount control by the ozone supply device and abnormality diagnosis of the ozone supply device, based on the detected NOx amount acquired by the NOx amount acquisition unit,
Equipped with.

上記排気浄化システムでは、内燃機関の排気通路においてＮＯｘ吸蔵還元型触媒の上流側に、オゾン供給装置によりオゾンが供給されることで、排気中のＮＯがＮＯ2に酸化される。これにより、ＮＯｘ吸蔵還元型触媒にＮＯｘ吸蔵能力を高めることが可能となる。かかる場合において、オゾン供給装置により供給されるオゾン量が意図せず低下すると、ＮＯｘ吸蔵還元型触媒のＮＯｘ吸蔵能力が低下し、ひいてはＮＯｘ浄化性能の低下が懸念される。 In the above exhaust gas purification system, NO in the exhaust gas is oxidized to NO2 by supplying ozone by the ozone supply device to the upstream side of the NOx storage reduction catalyst in the exhaust passage of the internal combustion engine. This makes it possible to enhance the NOx storage capacity of the NOx storage reduction catalyst. In such a case, if the amount of ozone supplied by the ozone supply device is unintentionally decreased, the NOx storage reduction type catalyst's NOx storage capacity is reduced, and thus the NOx purification performance may be reduced.

この点、上記構成では、内燃機関が運転状態あり、かつオゾン供給装置によりオゾンが供給されている状態においてＮＯｘセンサにより検出された検出ＮＯｘ量を取得し、その検出ＮＯｘ量に基づいて、オゾン供給装置によるオゾン供給量制御、及びオゾン供給装置の異常診断の少なくともいずれかを実施するようにした。これにより、実際のＮＯｘ浄化率が低下したことを監視しつつ、オゾン供給量制御や異常診断を適正に実施できる。その結果、オゾン供給を適正に行い、ひいては適正なるＮＯｘ浄化を実現することが可能となる。 In this respect, in the above configuration, the detected NOx amount detected by the NOx sensor is acquired while the internal combustion engine is in the operating state and the ozone is supplied by the ozone supply device, and the ozone supply is performed based on the detected NOx amount. At least one of the ozone supply amount control by the device and the abnormality diagnosis of the ozone supply device is performed. As a result, ozone supply amount control and abnormality diagnosis can be appropriately performed while monitoring that the actual NOx purification rate has decreased. As a result, it becomes possible to properly supply ozone and to realize proper NOx purification.

エンジンの排気浄化システムを示す構成図。The block diagram which shows the exhaust gas purification system of an engine. 排気中のＮＯに対するオゾン量と吸蔵効率との関係を示す図。The figure which shows the relationship between the amount of ozone with respect to NO in exhaust gas, and occlusion efficiency. オゾン供給の制御手順を示すフローチャート。The flowchart which shows the control procedure of ozone supply. 各種パラメータと推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）との関係を示す図。The figure which shows the relationship between various parameters and estimated NOx amount (NOx_est). 差ΔＹと補正量との関係を示す図。The figure which shows the relationship between difference (DELTA)Y and correction amount.

以下、実施形態を図面に基づいて説明する。本実施形態では、車載のディーゼルエンジンから排出される排気を浄化する排気浄化システムにおいて、特に触媒上流側にオゾン供給装置からオゾンを添加するものとしている。なお、以下の各実施形態相互において、互いに同一又は均等である部分には、図中、同一符号を付しており、同一符号の部分についてはその説明を援用する。 Embodiments will be described below with reference to the drawings. In the present embodiment, in an exhaust gas purification system for purifying exhaust gas emitted from a vehicle-mounted diesel engine, ozone is added from an ozone supply device, particularly on the upstream side of the catalyst. In each of the following embodiments, the same or equivalent portions are denoted by the same reference numerals in the drawings, and the description of the portions having the same reference numeral is cited.

図１において、エンジン１０は、軽油を燃料とする多気筒ディーゼルエンジンであり、各気筒には吸気管１１及び排気管１２が接続されている。エンジン１０は過給装置１３を備えている。過給装置１３は、吸気管１１に配置された吸気コンプレッサ１４と、排気管１２に配置された排気タービン１５と、それら吸気コンプレッサ１４及び排気タービン１５を連結する回転軸１６とを備えている。排気により排気タービン１５が回転されると、その回転に伴い吸気コンプレッサ１４が回転され、吸気の過給が行われる。なお、吸気管１１には、吸気コンプレッサ１４の下流側に熱交換器としてのインタクーラが配置されているとよい。 In FIG. 1, an engine 10 is a multi-cylinder diesel engine that uses light oil as a fuel, and an intake pipe 11 and an exhaust pipe 12 are connected to each cylinder. The engine 10 includes a supercharging device 13. The supercharging device 13 includes an intake compressor 14 arranged in the intake pipe 11, an exhaust turbine 15 arranged in the exhaust pipe 12, and a rotary shaft 16 connecting the intake compressor 14 and the exhaust turbine 15. When the exhaust turbine 15 is rotated by the exhaust gas, the intake compressor 14 is rotated along with the rotation, and the intake air is supercharged. An intercooler as a heat exchanger may be arranged in the intake pipe 11 downstream of the intake compressor 14.

吸気管１１において吸気コンプレッサ１４の上流側には、吸気管１１を通過する空気量を検出する空気量センサ１８が設けられている。また、エンジン１０の出力軸には、エンジン回転速度を検出する回転速度センサ１９が設けられている。 An air amount sensor 18 for detecting the amount of air passing through the intake pipe 11 is provided on the upstream side of the intake compressor 14 in the intake pipe 11. A rotation speed sensor 19 that detects the engine rotation speed is provided on the output shaft of the engine 10.

排気管１２には、排気管１２内の排気通路を流れる排気中のＮＯｘを浄化するためのＮＯｘ浄化装置として、ＮＯｘ吸蔵還元型の触媒（以下、ＮＯｘ触媒２１という）が設けられている。ＮＯｘ触媒２１は、周知のとおり、リーン燃焼時において排気中に含まれるＮＯｘを吸蔵するとともに、リッチ燃焼時において排気中に含まれるＨＣ、ＣＯといった還元成分を用いて、吸蔵したＮＯｘを還元除去するものである。ＮＯｘ触媒２１は、例えば、担体表面にコーティングされたアルミナに、還元触媒としての銀を担持させた構造を有する。 The exhaust pipe 12 is provided with a NOx occlusion reduction type catalyst (hereinafter referred to as the NOx catalyst 21) as a NOx purification device for purifying NOx in the exhaust flowing through the exhaust passage in the exhaust pipe 12. As is well known, the NOx catalyst 21 stores NOx contained in the exhaust during lean combustion, and reduces and stores the stored NOx using reducing components such as HC and CO contained in the exhaust during rich combustion. It is a thing. The NOx catalyst 21 has, for example, a structure in which silver as a reducing catalyst is supported on alumina coated on the surface of the carrier.

排気管１２においてＮＯｘ触媒２１の上流側には、エンジン１０から排出される排気中のＮＯｘ量を検出するＮＯｘセンサ２２と、排気温度を検出する排気温度センサ２３とが設けられている。なお、これらのセンサ２２，２３は、後述の供給管３１よりも上流側に設けられている。また、ＮＯｘ触媒２１の下流側には、触媒下流側のＮＯｘ量を検出するＮＯｘセンサ２４が設けられている。ＮＯｘ触媒２１には、触媒温度を検出する触媒温度センサ２５が設けられている。ＮＯｘセンサ２２，２４は、例えば固体電解質を構成される限界電流式ガスセンサである。以下の説明では便宜上、触媒上流側のＮＯｘセンサ２２を上流側ＮＯｘセンサ２２、触媒下流側のＮＯｘセンサ２４を下流側ＮＯｘセンサ２４とも言う。なお、触媒温度センサ２５は、ＮＯｘ触媒２１の下流側に設けられていてもよい。 On the upstream side of the NOx catalyst 21 in the exhaust pipe 12, a NOx sensor 22 that detects the NOx amount in the exhaust gas discharged from the engine 10 and an exhaust temperature sensor 23 that detects the exhaust temperature are provided. Note that these sensors 22 and 23 are provided on the upstream side of a supply pipe 31 described later. Further, a NOx sensor 24 that detects the amount of NOx on the downstream side of the catalyst is provided on the downstream side of the NOx catalyst 21. The NOx catalyst 21 is provided with a catalyst temperature sensor 25 that detects the catalyst temperature. The NOx sensors 22 and 24 are limiting current type gas sensors configured of, for example, a solid electrolyte. In the following description, the NOx sensor 22 on the upstream side of the catalyst is also referred to as the upstream NOx sensor 22 and the NOx sensor 24 on the downstream side of the catalyst is also referred to as the downstream NOx sensor 24 for the sake of convenience. The catalyst temperature sensor 25 may be provided on the downstream side of the NOx catalyst 21.

また、本実施形態の排気浄化システムでは、排気管１２においてＮＯｘ触媒２１の上流側にオゾン（Ｏ3）を供給し、そのオゾンにより排気中のＮＯをＮＯ2に酸化することでＮＯｘ触媒２１におけるＮＯｘ吸蔵能力を高めるようにしており、以下にその構成を説明する。 Further, in the exhaust gas purification system of the present embodiment, ozone (O3) is supplied to the upstream side of the NOx catalyst 21 in the exhaust pipe 12, and the NOx stored in the NOx catalyst 21 is oxidized by oxidizing ozone in the exhaust gas to NO2. The ability is enhanced, and the configuration will be described below.

排気管１２においてＮＯｘ触媒２１の上流側には供給管３１が接続されており、その供給管３１には、上流側から順にエアポンプ３２、オゾン生成器３３、開閉弁３４が設けられている。エアポンプ３２は例えば電動ポンプであって、外部から吸入した大気を加圧してオゾン生成器３３に送風する。オゾン生成器３３の構成は周知であるため、図示による詳細な説明は割愛するが、簡単に述べると、オゾン生成器３３において、流通路を形成する容器内には複数の電極が配置されており、その複数の電極間に高電圧が印加されることによりオゾンを生成する。開閉弁３４は、排気管１２からの排気の逆流を抑制する目的で設けられており、排気管１２に対するオゾン供給時には開放され、オゾン供給の停止時には閉鎖される。なお、エアポンプ３２及びオゾン生成器３３がオゾン供給装置に相当する。 In the exhaust pipe 12, a supply pipe 31 is connected to the upstream side of the NOx catalyst 21, and the supply pipe 31 is provided with an air pump 32, an ozone generator 33, and an opening/closing valve 34 in this order from the upstream side. The air pump 32 is, for example, an electric pump and pressurizes the air sucked from the outside to blow the air to the ozone generator 33. Since the configuration of the ozone generator 33 is well known, detailed description thereof will be omitted, but briefly, in the ozone generator 33, a plurality of electrodes are arranged in a container forming a flow passage. , Ozone is generated by applying a high voltage between the plurality of electrodes. The on-off valve 34 is provided for the purpose of suppressing backflow of exhaust gas from the exhaust pipe 12, and is opened when ozone is supplied to the exhaust pipe 12 and closed when ozone supply is stopped. The air pump 32 and the ozone generator 33 correspond to an ozone supply device.

エンジン運転時において排気管１２に対するオゾン供給を行う場合には、オゾン生成器３３における電圧印加によりオゾンが生成される状態下で、エアポンプ３２が駆動され、かつ開閉弁３４が開放される。これにより、オゾン生成器３３を通過する空気と共にオゾンが排気管１２内に流入する。そして、ＮＯｘ触媒２１の上流側においてオゾンによりＮＯからＮＯ2への酸化反応が行われつつ、ＮＯｘ触媒２１においてＮＯ及びＮＯ2が吸蔵され、かつ還元浄化される。 When the ozone is supplied to the exhaust pipe 12 during engine operation, the air pump 32 is driven and the opening/closing valve 34 is opened under the condition that ozone is generated by the voltage application in the ozone generator 33. As a result, ozone flows into the exhaust pipe 12 together with the air passing through the ozone generator 33. Then, while the oxidation reaction of NO to NO2 is performed by ozone on the upstream side of the NOx catalyst 21, NO and NO2 are stored and reduced and purified in the NOx catalyst 21.

ＥＣＵ４０は、ＣＰＵ、ＲＯＭ、ＲＡＭ等よりなるマイクロコンピュータ（以下、マイコンという）を主体として構成された周知の電子制御装置であり、ＲＯＭに記憶された各種の制御プログラムを実行することで、前述した各種センサの検出信号に基づいて、排気浄化に関する各種制御を実施する。ＥＣＵ４０は、オゾン供給装置によるオゾン供給量を所望量に制御するオゾン供給量制御を実施する。この場合、ＥＣＵ４０は、例えば所定量のオゾンを排気管１２に供給すべく、エアポンプ３２やオゾン生成器３３、開閉弁３４の状態を制御する。ＥＣＵ４０は、エンジン１０の運転状態下において、例えばリーン燃焼時にオゾン供給の要求が生じたとして、その要求に応じて排気管１２に対してオゾン供給を実施する。 The ECU 40 is a well-known electronic control device mainly composed of a microcomputer (hereinafter, referred to as a microcomputer) including a CPU, a ROM, a RAM, and the like, and executes the various control programs stored in the ROM, and is described above. Various controls related to exhaust gas purification are performed based on detection signals from various sensors. The ECU 40 executes ozone supply amount control for controlling the ozone supply amount by the ozone supply device to a desired amount. In this case, the ECU 40 controls the states of the air pump 32, the ozone generator 33, and the open/close valve 34 in order to supply a predetermined amount of ozone to the exhaust pipe 12, for example. Under the operating condition of the engine 10, the ECU 40 supplies ozone to the exhaust pipe 12 in response to a request for ozone supply, for example, during lean combustion.

ところで、ＮＯｘ触媒２１においては、排気中に含まれるＮＯｘのうちＮＯとＮＯ2とで吸蔵効率が異なり、比較的低温の状態では、ＮＯの吸蔵効率が非常に低くなる。そのため、低温状態下においてオゾンによりＮＯをＮＯ2に酸化することを目的として、排気管１２に対してオゾンを供給するようにしているが、オゾン供給装置の性能低下によりオゾンが不足すると、触媒上流においてＮＯからＮＯ2への酸化が不十分となることが考えられる。かかる場合、ＮＯｘ中のＮＯの比率が高くなるため、ＮＯｘ触媒２１でのＮＯｘ吸蔵効率が低下することが懸念される。 By the way, in the NOx catalyst 21, NO and NO2 among NOx contained in the exhaust gas have different storage efficiencies, and the storage efficiency of NO becomes very low in a relatively low temperature state. Therefore, ozone is supplied to the exhaust pipe 12 for the purpose of oxidizing NO to NO2 by ozone in a low temperature state. However, when ozone is insufficient due to performance deterioration of the ozone supply device, it is upstream of the catalyst. It is considered that the oxidation of NO to NO2 becomes insufficient. In such a case, since the ratio of NO in NOx is high, there is a concern that the NOx storage efficiency of the NOx catalyst 21 will decrease.

図２は、排気中のＮＯに対するオゾン量と吸蔵効率との関係を示す図である。図２によれば、排気中のＮＯに対するオゾン量が少なくなるほど、ＮＯｘ触媒２１での吸蔵効率が低下することが分かる。 FIG. 2 is a diagram showing the relationship between the amount of ozone with respect to NO in exhaust gas and the storage efficiency. It can be seen from FIG. 2 that the storage efficiency of the NOx catalyst 21 decreases as the amount of ozone with respect to NO in the exhaust gas decreases.

ここで、故障等によりオゾン供給装置から適正量のオゾンが供給されないと、ＮＯｘ触媒２１において所望とするＮＯｘ浄化性能を発揮できなくなる。そこで本実施形態では、エンジン１０が運転状態あり、かつオゾン供給装置によりオゾンが供給されている状態において、下流側ＮＯｘセンサ２４により検出された検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）を取得し、その検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）に基づいて、オゾン供給装置によるオゾン供給量制御とオゾン供給装置の異常診断とを実施することとしている。 Here, unless an appropriate amount of ozone is supplied from the ozone supply device due to a failure or the like, the NOx purification performance desired in the NOx catalyst 21 cannot be exhibited. Therefore, in the present embodiment, the detected NOx amount (NOx_sens) detected by the downstream NOx sensor 24 is acquired in a state where the engine 10 is in the operating state and ozone is being supplied by the ozone supply device, and the detected NOx amount is acquired. Based on (NOx_sens), the ozone supply amount control by the ozone supply device and the abnormality diagnosis of the ozone supply device are performed.

この場合特に、ＥＣＵ４０は、エンジン１０から排出される排気に関する排気情報、及びＮＯｘ触媒２１に関する触媒情報に基づいて、ＮＯｘ触媒２１の下流側に排出されるＮＯｘ量を推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）として算出する。そして、下流側ＮＯｘセンサ２４により検出された検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）と推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）とを比較し、その比較の結果に基づいて、オゾン供給装置によるオゾン供給量制御とオゾン供給装置の異常診断と実施する。 In this case, in particular, the ECU 40 calculates the NOx amount discharged downstream of the NOx catalyst 21 as the estimated NOx amount (NOx_est) based on the exhaust information regarding the exhaust gas emitted from the engine 10 and the catalyst information regarding the NOx catalyst 21. To do. Then, the detected NOx amount (NOx_sens) detected by the downstream NOx sensor 24 is compared with the estimated NOx amount (NOx_est), and based on the result of the comparison, the ozone supply amount control by the ozone supply device and the ozone supply device are performed. Execute abnormality diagnosis.

図３は、オゾン供給の制御手順を示すフローチャートであり、本処理はＥＣＵ４０により所定周期で実施される。 FIG. 3 is a flowchart showing a control procedure of ozone supply, and this processing is executed by the ECU 40 in a predetermined cycle.

図３において、ステップＳ１１では、エンジン１０の運転状態下においてその運転状態が過渡でなく安定しているか否かを判定する。この場合、所定期間内におけるエンジン回転速度及び負荷の変化が所定以下であることに基づいて、エンジン運転状態が安定していることを判定するとよい。また、例えばアクセル操作量に基づいて、車両の運転状態が安定していることを判定する構成であってもよい。ステップＳ１１が否定される場合にはステップＳ１２に進み、ステップＳ１１が肯定される場合にはステップＳ１３に進む。 In FIG. 3, in step S11, it is determined whether the operating state of the engine 10 is stable and not transient under the operating state. In this case, it may be determined that the engine operating state is stable based on the fact that the changes in the engine speed and the load within the predetermined period are equal to or less than a predetermined value. Further, for example, it may be configured to determine that the driving state of the vehicle is stable, based on the accelerator operation amount. When step S11 is denied, it progresses to step S12, and when step S11 is affirmed, it progresses to step S13.

ステップＳ１２では、予め定めた所定量のオゾンを排気管１２に供給すべく、エアポンプ３２やオゾン生成器３３を所定の制御指令値により作動させる。なお、ステップＳ１１が否定される場合には、オゾン供給装置の異常診断は実施されない。 In step S12, the air pump 32 and the ozone generator 33 are operated by a predetermined control command value in order to supply a predetermined amount of ozone to the exhaust pipe 12. In addition, when step S11 is denied, abnormality diagnosis of the ozone supply device is not performed.

また、ステップＳ１３では、供給管３１を介してオゾン生成器３３から排気管１２内に供給されているオゾン量を示すオゾン量情報を取得する。このとき、オゾン量は、オゾン生成器３３の電極に印加する電圧や消費電力から推定されるとよい。なお、エアポンプ３２の送風量を加味してオゾン量が算出されてもよい。 In step S13, ozone amount information indicating the amount of ozone supplied from the ozone generator 33 into the exhaust pipe 12 via the supply pipe 31 is acquired. At this time, the amount of ozone may be estimated from the voltage applied to the electrodes of the ozone generator 33 and the power consumption. The ozone amount may be calculated in consideration of the air blowing amount of the air pump 32.

ステップＳ１４では、エンジン１０から排出される排気に関する排気情報を取得する。排気情報には、例えばエンジン１０から排出されるＮＯｘ量を示す排出ＮＯｘ量や、排気流量、排気温度といった排気パラメータが含まれる。ここで、排出ＮＯｘ量は、上流側ＮＯｘセンサ２２の検出信号により算出され、排気流量は、空気量センサ１８の検出信号により算出され、排気温度は、排気温度センサ２３の検出信号により算出される。なお、予め定められた推定モデルや演算式等を用い、エンジン回転速度やエンジン負荷に基づいて、排出ＮＯｘ量や、排気流量、排気温度を推定することも可能である。 In step S14, exhaust information regarding exhaust emitted from the engine 10 is acquired. The exhaust information includes, for example, the exhausted NOx amount indicating the NOx amount emitted from the engine 10, the exhaust flow rate, and the exhaust parameters such as the exhaust temperature. Here, the exhausted NOx amount is calculated by the detection signal of the upstream NOx sensor 22, the exhaust flow rate is calculated by the detection signal of the air amount sensor 18, and the exhaust temperature is calculated by the detection signal of the exhaust temperature sensor 23. .. Note that it is also possible to estimate the exhausted NOx amount, the exhaust flow rate, and the exhaust temperature based on the engine rotation speed and the engine load using a predetermined estimation model, arithmetic expression, and the like.

ステップＳ１５では、ＮＯｘ触媒２１に関する触媒情報を取得する。触媒情報には、例えばＮＯｘ触媒２１の温度や、ＮＯｘ触媒２１において既に吸蔵されている吸蔵ＮＯｘ量といった触媒パラメータが含まれる。触媒温度は、触媒温度センサ２５の検出信号により算出され、吸蔵ＮＯｘ量は、エンジン１０の運転履歴等から推定により算出される。例えば、リッチ燃焼を行わせた後の燃料噴射回数や燃料噴射量に基づいて吸蔵ＮＯｘ量が推定されるとよい。 In step S15, catalyst information regarding the NOx catalyst 21 is acquired. The catalyst information includes, for example, catalyst parameters such as the temperature of the NOx catalyst 21 and the stored NOx amount that has already been stored in the NOx catalyst 21. The catalyst temperature is calculated by the detection signal of the catalyst temperature sensor 25, and the stored NOx amount is calculated by estimation from the operation history of the engine 10 and the like. For example, the stored NOx amount may be estimated based on the number of fuel injections and the fuel injection amount after performing rich combustion.

その後、ステップＳ１６では、上記ステップＳ１３〜Ｓ１５で取得したオゾン量情報、排気情報、触媒情報に基づいて、ＮＯｘ触媒２１の下流側に排出されるＮＯｘ量を推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）として算出する。ここで、オゾン量情報、排気情報、触媒情報における各種パラメータと推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）との関係について説明する。 Then, in step S16, the NOx amount discharged to the downstream side of the NOx catalyst 21 is calculated as the estimated NOx amount (NOx_est) based on the ozone amount information, the exhaust information, and the catalyst information acquired in steps S13 to S15. Here, the relationship between various parameters in the ozone amount information, exhaust information, and catalyst information and the estimated NOx amount (NOx_est) will be described.

図４（ａ）には、オゾン量情報としてのオゾン量と推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）との関係を示している。ＥＣＵ４０は、オゾン量が小さいほど、推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）として大きい値を算出する。 FIG. 4A shows the relationship between the ozone amount as the ozone amount information and the estimated NOx amount (NOx_est). The ECU 40 calculates a larger value as the estimated NOx amount (NOx_est) as the ozone amount is smaller.

図４（ｂ）には、排気情報としての排出ＮＯｘ量と推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）との関係を示している。ＥＣＵ４０は、排出ＮＯｘ量が大きいほど、推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）として大きい値を算出する。 FIG. 4B shows the relationship between the exhausted NOx amount as the exhaust information and the estimated NOx amount (NOx_est). The ECU 40 calculates a larger value as the estimated NOx amount (NOx_est) as the exhausted NOx amount increases.

図４（ｃ）には、排気情報としての排気流量と推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）との関係を示している。ＥＣＵ４０は、排気流量が大きいほど、推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）として大きい値を算出する。なお、排気流量に代えて排気圧力を排気情報として用いることも可能である。この場合、排気圧力が高いほど、推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）として大きい値を算出する。 FIG. 4C shows the relationship between the exhaust flow rate as the exhaust information and the estimated NOx amount (NOx_est). The ECU 40 calculates a larger value as the estimated NOx amount (NOx_est) as the exhaust flow rate increases. The exhaust pressure may be used as the exhaust information instead of the exhaust flow rate. In this case, the higher the exhaust pressure, the larger the estimated NOx amount (NOx_est) is calculated.

図４（ｄ）には、排気情報としての排気温度と推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）との関係を示している。ＥＣＵ４０は、排気温度が低いほど、推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）として大きい値を算出する。 FIG. 4D shows the relationship between the exhaust temperature as exhaust information and the estimated NOx amount (NOx_est). The ECU 40 calculates a larger value as the estimated NOx amount (NOx_est) as the exhaust temperature is lower.

図４（ｅ）には、触媒情報としての触媒温度と推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）との関係を示している。ＥＣＵ４０は、触媒温度が低いほど、推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）として大きい値を算出する。なお、触媒温度と推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）との関係はオゾン量に依存するため、オゾン量を加味した関係が定められていてもよい。この場合、図４（ｅ）に破線で示すように、オゾン量が小さいほど、推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）を大きくし、かつ触媒温度に対する推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）の傾き（負の傾き）を大きくするとよい。 FIG. 4E shows the relationship between the catalyst temperature as catalyst information and the estimated NOx amount (NOx_est). The ECU 40 calculates a larger value as the estimated NOx amount (NOx_est) as the catalyst temperature is lower. Note that the relationship between the catalyst temperature and the estimated NOx amount (NOx_est) depends on the ozone amount, so a relationship that takes the ozone amount into consideration may be defined. In this case, as indicated by a broken line in FIG. 4E, the estimated NOx amount (NOx_est) increases as the ozone amount decreases, and the slope (negative slope) of the estimated NOx amount (NOx_est) with respect to the catalyst temperature increases. Good to do.

図４（ｆ）には、触媒情報としての吸蔵ＮＯｘ量と推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）との関係を示している。ＥＣＵ４０は、吸蔵ＮＯｘ量が大きいほど、推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）として大きい値を算出する。 FIG. 4F shows the relationship between the stored NOx amount as the catalyst information and the estimated NOx amount (NOx_est). The ECU 40 calculates a larger value as the estimated NOx amount (NOx_est) as the stored NOx amount increases.

上記図４（ａ）〜（ｆ）の関係は、予めマップや数式として定められているとよく、マップや数式に各パラメータの数値を代入することで、推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）が算出されるとよい。 The relationships shown in FIGS. 4A to 4F are preferably defined in advance as maps and mathematical formulas, and the estimated NOx amount (NOx_est) is calculated by substituting the numerical values of the parameters in the maps and mathematical formulas. Good.

なお、排気情報として、排出ＮＯｘ量、排気流量、排気温度のうちいずれか１つ又は２つを用いて推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）を算出してもよい。また、触媒情報として、触媒温度、吸蔵ＮＯｘ量のいずれかを用いて推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）を算出してもよい。さらに、オゾン量情報、排気情報、触媒情報のうちいずれか１つ又は２つを用いて推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）を算出してもよい。 The estimated NOx amount (NOx_est) may be calculated using one or two of the exhausted NOx amount, the exhaust gas flow rate, and the exhaust temperature as the exhaust information. Further, the estimated NOx amount (NOx_est) may be calculated using either the catalyst temperature or the stored NOx amount as the catalyst information. Furthermore, the estimated NOx amount (NOx_est) may be calculated using any one or two of the ozone amount information, the exhaust information, and the catalyst information.

その後、ステップＳ１７では、下流側ＮＯｘセンサ２４により検出された検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）を取得する。この検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）は、ＮＯｘ触媒２１の下流側における実ＮＯｘ量に相当するものである。 Then, in step S17, the detected NOx amount (NOx_sens) detected by the downstream NOx sensor 24 is acquired. The detected NOx amount (NOx_sens) corresponds to the actual NOx amount on the downstream side of the NOx catalyst 21.

ステップＳ１８では、検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）から推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）を減算して求めた差ΔＹ（ΔＹ＝ＮＯｘ＿ｓｅｎｓ−ＮＯｘ＿ｅｓｔ）が所定の閾値ＴＨよりも大きいか否かを判定する。このとき、同ステップＳ１８では、オゾン供給装置から供給されている筈のオゾン量（本来のオゾン量）に対して、触媒下流側のＮＯｘ量が過大になっているか否かが判定される。閾値ＴＨは、ＮＯｘ触媒２１の下流側における許容ＮＯｘ量、すなわち環境基準等に基づいて定められた触媒下流側への流出許容ＮＯｘ量に基づいて定められているとよい。 In step S18, it is determined whether the difference ΔY (ΔY=NOx_sens−NOx_est) obtained by subtracting the estimated NOx amount (NOx_est) from the detected NOx amount (NOx_sens) is larger than a predetermined threshold value TH. At this time, in step S18, it is determined whether or not the NOx amount on the downstream side of the catalyst is excessive with respect to the ozone amount that should be supplied from the ozone supply device (original ozone amount). The threshold value TH may be determined based on the allowable NOx amount on the downstream side of the NOx catalyst 21, that is, the allowable outflow NOx amount to the downstream side of the catalyst, which is determined based on environmental standards or the like.

そして、ΔＹ≦ＴＨであれば、ステップＳ１９に進み、差ΔＹに基づいて、オゾン供給量のフィードバック制御を実施する。この場合、差ΔＹに応じて、オゾン供給量（供給指令値）を増量補正する補正量が設定され、その補正量によりオゾン供給量が更新されるとよい。より具体的には、図５（ａ）に示すように、差ΔＹの０〜閾値ＴＨの範囲内において、差ΔＹが大きいほど、すなわち推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）に対して検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）が大きいほど、補正量として大きい値が設定される。ΔＹ≦０の場合は補正量＝０であるとよい。そして、現在のオゾン供給量に対して補正量が加算されることで、新たなオゾン供給量が算出される。 Then, if ΔY≦TH, the process proceeds to step S19, and feedback control of the ozone supply amount is performed based on the difference ΔY. In this case, a correction amount for increasing and correcting the ozone supply amount (supply command value) is set according to the difference ΔY, and the ozone supply amount may be updated by the correction amount. More specifically, as shown in FIG. 5A, in the range of 0 to the threshold value TH of the difference ΔY, the larger the difference ΔY, that is, the detected NOx amount (NOx_sens) with respect to the estimated NOx amount (NOx_est). Is larger, a larger value is set as the correction amount. When ΔY≦0, it is preferable that the correction amount=0. Then, a new ozone supply amount is calculated by adding the correction amount to the current ozone supply amount.

ただし、補正量は、差ΔＹに応じて可変に設定される以外に、予め定めた一定の増加補正値であってもよい。また、図５（ｂ）の関係を用いて補正量を設定してもよい。図５（ｂ）によれば、差ΔＹが正の場合、すなわちＮＯｘ＿ｓｅｎｓ＞ＮＯｘ＿ｅｓｔの場合には、正の補正量によりオゾン供給量が増加補正され、差ΔＹが負の場合、すなわちＮＯｘ＿ｓｅｎｓ＜ＮＯｘ＿ｅｓｔの場合には、負の補正量によりオゾン供給量が減少補正される。 However, the correction amount may be a predetermined constant increase correction value other than being variably set according to the difference ΔY. Further, the correction amount may be set using the relationship of FIG. According to FIG. 5B, when the difference ΔY is positive, that is, when NOx_sens>NOx_est, the ozone supply amount is increased by the positive correction amount, and when the difference ΔY is negative, that is, when NOx_sens<NOx_est. In this case, the ozone supply amount is reduced and corrected by the negative correction amount.

続くステップＳ２０では、新たに算出されたオゾン供給量について上限ガード処理を実施する。具体的には、新たなオゾン供給量が所定の上限値に達しているか否かを判定し、上限値に達している場合に、オゾン供給量を上限値で制限する。これにより、オゾン供給量は、上限値までの範囲で制限されつつ、都度の差ΔＹに応じてフィードバック制御される。 In a succeeding step S20, an upper limit guard process is performed on the newly calculated ozone supply amount. Specifically, it is determined whether or not the new ozone supply amount has reached a predetermined upper limit value, and if it has reached the upper limit value, the ozone supply amount is limited by the upper limit value. As a result, the ozone supply amount is feedback-controlled according to the difference ΔY at each time while being limited to the range up to the upper limit value.

オゾン供給量を増加する場合、例えばオゾン生成器３３によるオゾン生成量を大きくすべく、印加電圧を大きくするとよい。またこれに加え、エアポンプ３２の送風量を大きくしてもよい。なお、ΔＹ＜ＴＨである場合には、オゾン供給装置が正常である旨が判定されるものとなっている。 When increasing the ozone supply amount, for example, the applied voltage may be increased in order to increase the ozone generation amount by the ozone generator 33. In addition to this, the air flow rate of the air pump 32 may be increased. In addition, when ΔY<TH, it is determined that the ozone supply device is normal.

また、ΔＹ≧ＴＨであれば、ステップＳ２１に進み、オゾン供給装置に異常が生じている旨を判定する。続くステップＳ２２では、オゾン供給装置が異常であることを報知すべく故障警告灯や音声による警告を実施する。また、オゾン供給装置によるオゾン供給を停止する。 If ΔY≧TH, the process proceeds to step S21, and it is determined that an abnormality has occurred in the ozone supply device. In a succeeding step S22, a malfunction warning light or a sound warning is given to notify that the ozone supply device is abnormal. Further, the ozone supply by the ozone supply device is stopped.

以上詳述した本実施形態によれば、以下の優れた効果が得られる。 According to this embodiment described in detail above, the following excellent effects can be obtained.

エンジン１０が運転状態あり、かつオゾン供給装置によりオゾンが供給されている状態において下流側ＮＯｘセンサ２４により検出された検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）を取得し、その検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）に基づいてオゾン供給量制御及び異常診断を実施するようにした。これにより、実際のＮＯｘ浄化率が低下したことを監視しつつ、オゾン供給量制御や異常診断を適正に実施できる。その結果、オゾン供給を適正に行い、ひいては適正なるＮＯｘ浄化を実現することが可能となる。 The detected NOx amount (NOx_sens) detected by the downstream NOx sensor 24 is acquired in a state where the engine 10 is in the operating state and ozone is being supplied by the ozone supply device, and ozone is obtained based on the detected NOx amount (NOx_sens). The supply amount control and the abnormality diagnosis are performed. As a result, ozone supply amount control and abnormality diagnosis can be appropriately performed while monitoring that the actual NOx purification rate has decreased. As a result, it becomes possible to properly supply ozone and to realize proper NOx purification.

オゾン供給装置に異常が生じ、所望のＮＯｘ浄化性能が得られない場合には、警告を発したり、オゾン供給を停止したりすることで、適正な対処が可能となる。 When an abnormality occurs in the ozone supply device and the desired NOx purification performance cannot be obtained, a warning can be issued or the ozone supply can be stopped to take appropriate measures.

エンジン１０の排気情報とＮＯｘ触媒２１に関する触媒情報とに基づいて、触媒下流側のＮＯｘ量を推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）として算出するとともに、その推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）と、下流側ＮＯｘセンサ２４による検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）との比較結果に基づいて、オゾン供給量制御、及びオゾン供給装置の異常診断を実施する構成とした。これにより、エンジン運転状態等に応じて排気やＮＯｘ触媒２１の状態が変化していても、オゾン供給量制御や異常診断を適正に実施することができる。 The NOx amount on the downstream side of the catalyst is calculated as an estimated NOx amount (NOx_est) based on the exhaust information of the engine 10 and the catalyst information on the NOx catalyst 21, and the estimated NOx amount (NOx_est) and the downstream NOx sensor 24 are used. Based on the comparison result with the detected NOx amount (NOx_sens), the ozone supply amount control and the abnormality diagnosis of the ozone supply device are performed. Thereby, even if the state of the exhaust gas or the NOx catalyst 21 changes according to the engine operating state or the like, the ozone supply amount control and the abnormality diagnosis can be properly performed.

エンジン１０からの排出ＮＯｘ量、排気流量、及び排気温度に基づいて推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）を算出する構成にしたため、これらの各パラメータの変化に伴いオゾン供給量制御の精度や異常診断の精度や低下するといった不都合を抑制できる。 Since the estimated NOx amount (NOx_est) is calculated based on the exhausted NOx amount from the engine 10, the exhaust gas flow rate, and the exhaust temperature, the accuracy of ozone supply control and the accuracy of abnormality diagnosis, etc. Inconvenience such as decrease can be suppressed.

ＮＯｘ触媒２１の温度、及びＮＯｘ触媒２１の吸蔵ＮＯｘ量に基づいて推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）を算出する構成にしたため、これらの各パラメータの変化に伴いオゾン供給量制御の精度や異常診断の精度や低下するといった不都合を抑制できる。 Since the estimated NOx amount (NOx_est) is calculated based on the temperature of the NOx catalyst 21 and the stored NOx amount of the NOx catalyst 21, the accuracy of ozone supply amount control and the accuracy of abnormality diagnosis and Inconvenience such as decrease can be suppressed.

排気管１２に供給されているオゾン量を取得し、そのオゾン量に基づいて推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）を算出する構成にしたため、オゾン量の変化に伴いオゾン供給量制御の精度や異常診断の精度や低下するといった不都合を抑制できる。 Since the configuration is such that the amount of ozone supplied to the exhaust pipe 12 is acquired and the estimated NOx amount (NOx_est) is calculated based on the amount of ozone, the accuracy of ozone supply amount control and the accuracy of abnormality diagnosis according to changes in the amount of ozone. It is possible to suppress inconveniences such as deterioration.

検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）と推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）との差ΔＹが閾値ＴＨよりも小さい場合には、差ΔＹに基づいてオゾン供給量制御を実施し、差ΔＹが閾値ＴＨよりも大きい場合には、オゾン供給装置の異常診断を実施する構成とした。これにより、オゾン供給装置について、オゾン供給量制御と異常診断とを必要に応じて適正に実施することができる。この場合、オゾン供給装置が異常と判定される以前には、オゾン供給量制御により、ＮＯｘ触媒２１での安定した浄化性能を得ることが可能となる。 When the difference ΔY between the detected NOx amount (NOx_sens) and the estimated NOx amount (NOx_est) is smaller than the threshold value TH, the ozone supply amount control is performed based on the difference ΔY, and when the difference ΔY is larger than the threshold value TH. Is configured to perform abnormality diagnosis of the ozone supply device. As a result, the ozone supply device can appropriately perform ozone supply amount control and abnormality diagnosis as necessary. In this case, before the ozone supply device is determined to be abnormal, it is possible to obtain stable purification performance of the NOx catalyst 21 by controlling the ozone supply amount.

オゾン供給量が所定の上限値となるまでの範囲内で、オゾン供給量を、検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）に基づいて制御するとともに、オゾン供給量が上限値であることに基づいてオゾン供給装置の異常診断を実施する構成とした。この場合、オゾン供給が可能な制御範囲内において最大限のオゾン供給が実施されるとともに、その最大限のオゾン供給が行われた状態下で、オゾン供給装置の異常診断が実施されるため、オゾン供給を極力行わせつつ適正なる異常診断を実施することができる。 Within a range until the ozone supply amount reaches a predetermined upper limit value, the ozone supply amount is controlled based on the detected NOx amount (NOx_sens), and the ozone supply device is controlled based on the ozone supply amount being the upper limit value. The configuration is such that abnormality diagnosis is performed. In this case, since the maximum ozone supply is performed within the control range in which ozone can be supplied, and the abnormality diagnosis of the ozone supply device is performed under the maximum ozone supply, It is possible to perform appropriate abnormality diagnosis while performing supply as much as possible.

エンジン１０の運転状態が過渡でなく安定していることが満たされる場合に、オゾン供給量制御や異常診断を実施する構成とした。したがって、オゾン供給量制御の制御精度を向上させることができる。また、異常診断での誤診断を抑制し、診断精度を向上させることができる。 When it is satisfied that the operating state of the engine 10 is not transient but stable, ozone supply amount control and abnormality diagnosis are performed. Therefore, the control accuracy of the ozone supply amount control can be improved. In addition, it is possible to suppress erroneous diagnosis in abnormality diagnosis and improve diagnosis accuracy.

（他の実施形態）
上記実施形態を例えば次のように変更してもよい。 (Other embodiments)
The above embodiment may be modified as follows, for example.

・上記実施形態では、ＥＣＵ４０が、オゾン供給量制御と異常診断とを実施する構成としたが、このうち一方のみを実施する構成であってもよい。例えば、ＥＣＵ４０が、検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）と推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）との差ΔＹに基づいて、オゾン供給量制御を実施する。又は、ＥＣＵ４０が、検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）と推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）との差ΔＹに基づいて、オゾン供給装置の異常診断を実施する。 In the above-described embodiment, the ECU 40 is configured to perform the ozone supply amount control and the abnormality diagnosis, but it may be configured to perform only one of them. For example, the ECU 40 executes the ozone supply amount control based on the difference ΔY between the detected NOx amount (NOx_sens) and the estimated NOx amount (NOx_est). Alternatively, the ECU 40 performs abnormality diagnosis of the ozone supply device based on the difference ΔY between the detected NOx amount (NOx_sens) and the estimated NOx amount (NOx_est).

・上記実施形態では、検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）と推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）との差ΔＹに基づいて、オゾン供給量制御や異常診断を実施したが、これを変更し、検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）と推定ＮＯｘ量（ＮＯｘ＿ｅｓｔ）とのうち検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）だけを用いて、オゾン供給量制御や異常診断を実施するようにしてもよい。この場合、オゾン供給装置が一定量のオゾン供給を行う構成とする。そして、ＥＣＵ４０は、検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）に基づいてオゾン供給量を設定することとし、具体的には検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）が大きいほどオゾン供給量を大きくする。また、検出ＮＯｘ量（ＮＯｘ＿ｓｅｎｓ）が所定値以上となる場合、オゾン供給装置に異常が生じている旨を判定する。 In the above embodiment, the ozone supply amount control and the abnormality diagnosis are performed based on the difference ΔY between the detected NOx amount (NOx_sens) and the estimated NOx amount (NOx_est), but this is changed to detect the detected NOx amount (NOx_sens). Of the estimated NOx amount (NOx_est) and the detected NOx amount (NOx_sens), only the ozone supply amount control or the abnormality diagnosis may be performed. In this case, the ozone supply device is configured to supply a constant amount of ozone. Then, the ECU 40 sets the ozone supply amount based on the detected NOx amount (NOx_sens), and specifically increases the ozone supply amount as the detected NOx amount (NOx_sens) increases. Further, when the detected NOx amount (NOx_sens) is equal to or larger than the predetermined value, it is determined that the ozone supply device is abnormal.

・排気浄化システムは、図１に示すものだけに限られず、ＮＯｘ触媒２１の上流側に酸化触媒を有するものや、ＮＯｘ触媒２１の下流側にＤＰＦ、触媒付きＤＰＦを有するものであってもよい。 The exhaust gas purification system is not limited to the one shown in FIG. 1, and may have an oxidation catalyst on the upstream side of the NOx catalyst 21, or a DPF or a DPF with a catalyst on the downstream side of the NOx catalyst 21. ..

・上記実施形態の排気浄化システムを、ディーゼルエンジン以外に、ガソリンエンジン等、他の型式のエンジンに適用することも可能である。また、車両用エンジン以外のエンジンにも適用可能である。 The exhaust gas purification system of the above-described embodiment can be applied to other types of engines such as gasoline engines other than diesel engines. It is also applicable to engines other than vehicle engines.

１０…エンジン（内燃機関）、２１…ＮＯｘ触媒、２４…下流側ＮＯｘセンサ、３２…エアポンプ、３３…オゾン生成器、４０…ＥＣＵ（ＮＯｘ量取得部、制御部）。 10... Engine (internal combustion engine), 21... NOx catalyst, 24... Downstream NOx sensor, 32... Air pump, 33... Ozone generator, 40... ECU (NOx amount acquisition unit, control unit).

Claims (7)

内燃機関（１０）の排気通路に設けられ、排気中のＮＯｘを浄化するＮＯｘ吸蔵還元型の触媒（２１）と、前記排気通路において前記触媒の上流側にオゾンを供給するオゾン供給装置（３２，３３）と、前記触媒の下流側に設けられ、排気中のＮＯｘ量を検出するＮＯｘセンサ（２４）とを備える排気浄化システムに適用され、
前記内燃機関が運転状態であり、かつ前記オゾン供給装置によりオゾンが供給されている状態において前記ＮＯｘセンサにより検出された検出ＮＯｘ量を取得するＮＯｘ量取得部と、
前記内燃機関から排出される排気に関する排気情報、及び前記触媒に関する触媒情報の少なくともいずれかに基づいて、前記触媒の下流側に排出されるＮＯｘ量を推定ＮＯｘ量として算出する算出部と、
前記ＮＯｘ量取得部により取得された検出ＮＯｘ量と、前記算出部により算出された推定ＮＯｘ量とを比較し、その比較の結果に基づいて、前記オゾン供給装置によるオゾン供給量制御、及び前記オゾン供給装置の異常診断の少なくともいずれかを実施する制御部と、
を備える排気浄化システムの制御装置。 An NOx occlusion reduction type catalyst (21) provided in the exhaust passage of the internal combustion engine (10) for purifying NOx in the exhaust, and an ozone supply device (32, for supplying ozone to the upstream side of the catalyst in the exhaust passage). 33) and a NOx sensor (24) that is provided on the downstream side of the catalyst and that detects the amount of NOx in the exhaust gas.
A NOx amount acquisition unit that acquires a detected NOx amount detected by the NOx sensor in a state where the internal combustion engine is in an operating state and ozone is being supplied by the ozone supply device;
A calculation unit that calculates the NOx amount discharged to the downstream side of the catalyst as an estimated NOx amount based on at least one of exhaust information regarding the exhaust discharged from the internal combustion engine and catalyst information regarding the catalyst;
The detected NOx amount acquired by the NOx amount acquisition unit and the estimated NOx amount calculated by the calculation unit are compared, and based on the comparison result , the ozone supply amount control by the ozone supply device and the ozone A control unit that performs at least one of the abnormality diagnosis of the supply device,
A control device for an exhaust gas purification system. 前記算出部は、前記排気情報として、前記内燃機関から排出されるＮＯｘ量、排気流量、及び排気温度の少なくともいずれかである排気パラメータを用い、その排気パラメータに基づいて前記推定ＮＯｘ量を算出する請求項１に記載の排気浄化システムの制御装置。 The calculation unit uses, as the exhaust information, an exhaust parameter that is at least one of a NOx amount discharged from the internal combustion engine, an exhaust flow rate, and an exhaust temperature, and calculates the estimated NOx amount based on the exhaust parameter. The control device for the exhaust gas purification system according to claim 1 . 前記算出部は、前記触媒情報として、前記触媒の温度、及び前記触媒に吸蔵されているＮＯｘ吸蔵量の少なくともいずれかである触媒パラメータを用い、その触媒パラメータに基づいて前記推定ＮＯｘ量を算出する請求項１又は２に記載の排気浄化システムの制御装置。 The calculating unit uses, as the catalyst information, a catalyst parameter that is at least one of the temperature of the catalyst and the NOx storage amount stored in the catalyst, and calculates the estimated NOx amount based on the catalyst parameter. The control device for the exhaust gas purification system according to claim 1 . 前記オゾン供給装置により前記排気通路に供給されているオゾン量を取得するオゾン量取得部を備え、
前記算出部は、前記排気情報及び前記触媒情報の少なくともいずれかと、前記オゾン量取得部により取得されたオゾン量とに基づいて、前記推定ＮＯｘ量を算出する請求項１乃至３のいずれか１項に記載の排気浄化システムの制御装置。 An ozone amount acquisition unit for acquiring the amount of ozone supplied to the exhaust passage by the ozone supply device,
The calculating unit includes at least one of the exhaust information and the catalyst information, on the basis of the acquired amount of ozone by the ozone quantity acquisition unit, any one of claims 1 to 3 for calculating the estimated NOx amount The control device of the exhaust gas purification system according to. 前記制御部は、
前記ＮＯｘ量取得部により取得された検出ＮＯｘ量から、前記算出部により算出された推定ＮＯｘ量を減算した差が所定値よりも小さい場合に、前記オゾン供給装置によるオゾン供給量制御及び前記オゾン供給装置の異常診断のうちオゾン供給量制御を実施し、
前記差が前記所定値よりも大きい場合に、前記オゾン供給装置によるオゾン供給量制御及び前記オゾン供給装置の異常診断のうち異常診断を実施する請求項１乃至４のいずれか１項に記載の排気浄化システムの制御装置。 The control unit is
When the difference obtained by subtracting the estimated NOx amount calculated by the calculation unit from the detected NOx amount acquired by the NOx amount acquisition unit is smaller than a predetermined value, ozone supply amount control and ozone supply by the ozone supply device The ozone supply amount control is carried out in the device abnormality diagnosis,
The exhaust gas according to any one of claims 1 to 4 , wherein when the difference is larger than the predetermined value, the ozone supply amount control by the ozone supply device and the abnormality diagnosis of the ozone supply device are performed. Control device for purification system. 前記制御部は、前記オゾン供給装置によるオゾン供給量が所定の上限値となるまでの範囲内で、当該オゾン供給量を、前記ＮＯｘ量取得部により取得された前記検出ＮＯｘ量に基づいて制御するとともに、前記オゾン供給装置によるオゾン供給量が前記上限値であることに基づいて、前記オゾン供給装置の異常診断を実施する請求項１乃至５のいずれか１項に記載の排気浄化システムの制御装置。 The control unit controls the ozone supply amount based on the detected NOx amount acquired by the NOx amount acquisition unit within a range until the ozone supply amount by the ozone supply device reaches a predetermined upper limit value. At the same time, the control device for the exhaust gas purification system according to any one of claims 1 to 5 , wherein abnormality diagnosis of the ozone supply device is performed based on that the ozone supply amount by the ozone supply device is the upper limit value. . 内燃機関（１０）の排気通路に設けられ、排気中のＮＯｘを浄化するＮＯｘ吸蔵還元型の触媒（２１）と、前記排気通路において前記触媒の上流側にオゾンを供給するオゾン供給装置（３２，３３）と、前記触媒の下流側に設けられ、排気中のＮＯｘ量を検出するＮＯｘセンサ（２４）とを備える排気浄化システムに適用され、
前記内燃機関が運転状態であり、かつ前記オゾン供給装置によりオゾンが供給されている状態において前記ＮＯｘセンサにより検出された検出ＮＯｘ量を取得するＮＯｘ量取得部と、
前記ＮＯｘ量取得部により取得された前記検出ＮＯｘ量に基づいて、前記オゾン供給装置によるオゾン供給量制御、及び前記オゾン供給装置の異常診断の少なくともいずれかを実施する制御部と、
を備え、
前記制御部は、前記オゾン供給装置によるオゾン供給量が所定の上限値となるまでの範囲内で、当該オゾン供給量を、前記ＮＯｘ量取得部により取得された前記検出ＮＯｘ量に基づいて制御するとともに、前記オゾン供給装置によるオゾン供給量が前記上限値であることに基づいて、前記オゾン供給装置の異常診断を実施する排気浄化システムの制御装置。 An NOx occlusion reduction type catalyst (21) provided in the exhaust passage of the internal combustion engine (10) for purifying NOx in the exhaust, and an ozone supply device (32, for supplying ozone to the upstream side of the catalyst in the exhaust passage). 33) and a NOx sensor (24) provided downstream of the catalyst for detecting the amount of NOx in the exhaust gas, and is applied to an exhaust gas purification system,
A NOx amount acquisition unit that acquires a detected NOx amount detected by the NOx sensor in a state where the internal combustion engine is in an operating state and ozone is being supplied by the ozone supply device;
A control unit that performs at least one of ozone supply amount control by the ozone supply device and abnormality diagnosis of the ozone supply device, based on the detected NOx amount acquired by the NOx amount acquisition unit,
Equipped with
The control unit controls the ozone supply amount based on the detected NOx amount acquired by the NOx amount acquisition unit within a range until the ozone supply amount by the ozone supply device reaches a predetermined upper limit value. At the same time, a control device of the exhaust gas purification system that performs abnormality diagnosis of the ozone supply device based on that the ozone supply amount by the ozone supply device is the upper limit value .
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