JP2009127472A - Exhaust emission control device - Google Patents

Exhaust emission control device Download PDF

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JP2009127472A
JP2009127472A JP2007301757A JP2007301757A JP2009127472A JP 2009127472 A JP2009127472 A JP 2009127472A JP 2007301757 A JP2007301757 A JP 2007301757A JP 2007301757 A JP2007301757 A JP 2007301757A JP 2009127472 A JP2009127472 A JP 2009127472A
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exhaust
temperature
additive
supply
reducing agent
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JP4445000B2 (en
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Osamu Shimomura
修 下村
Ataru Ichikawa
中 市川
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Denso Corp
Soken Inc
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Denso Corp
Nippon Soken Inc
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Application filed by Denso Corp, Nippon Soken Inc filed Critical Denso Corp
Priority to JP2007301757A priority Critical patent/JP4445000B2/en
Priority to DE102008043895.2A priority patent/DE102008043895B4/en
Priority to US12/274,724 priority patent/US20090133389A1/en
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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
    • 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
    • F01N2250/00—Combinations of different methods of purification
    • F01N2250/02—Combinations of different methods of purification filtering and catalytic conversion
    • 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
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/06—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being a temperature sensor
    • 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
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
    • 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
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
    • F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters
    • 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
    • Y02T10/12—Improving ICE efficiencies
    • 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)
  • Toxicology (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To surely reduce (purify) nitrogen oxides, while preventing an additive such as urea from being uselessly consumed. <P>SOLUTION: When an exhaust temperature is lower than an ammonia generating temperature T1, the supply of the urea is stopped. When an exhaust temperature is from the ammonia generating temperature T1 to a supply stopping temperature T2 or until a supply stopping time passes from a time when the exhaust temperature reaches the ammonia generating temperature T1 or higher, the urea of a quantity larger than an ordinary quantity is supplied. When an exhaust temperature reaches the supply stopping temperature T2 or higher or when the supply stopping time passes, a supply quantity of the urea is also reduced to the ordinary quantity. Thus, while preventing the urea from being uselessly consumed, the nitrogen oxides can be surely reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、ディーゼルエンジン等の内燃機関の排気中に含まれる窒素酸化物を還元するための排気浄化装置に関するものであり、車両に適用して有効である。   The present invention relates to an exhaust emission control device for reducing nitrogen oxides contained in exhaust gas from an internal combustion engine such as a diesel engine, and is effective when applied to a vehicle.

ディーゼルエンジン等の内燃機関の排気中に含まれる窒素酸化物（ＮＯｘ）を還元するための排気浄化装置として、例えば特許文献１に記載の発明では、排気管に還元反応を促進する触媒を設けるとともに、触媒に流れ込む排気中に尿素水溶液等の添加剤を噴射することにより、窒素酸化物を浄化（還元）している。   As an exhaust purification device for reducing nitrogen oxide (NOx) contained in exhaust gas from an internal combustion engine such as a diesel engine, for example, in the invention described in Patent Document 1, a catalyst for promoting a reduction reaction is provided in an exhaust pipe. The nitrogen oxides are purified (reduced) by injecting an additive such as an aqueous urea solution into the exhaust gas flowing into the catalyst.

すなわち、排気中に噴射された尿素（ＣＯ(ＮＨ2)2）を排気熱にて加水分解して（ＣＯ(ＮＨ2)2＋Ｈ2Ｏ）→２ＮＨ3＋ＣＯ2）、還元剤であるアンモニア（ＮＨ3）を生成し、触媒を介して窒素酸化物とアンモニアとを反応させて窒素酸化物を還元している。
特開２００３−２９３７３９号公報 That is, urea (CO (NH 2 ) 2 ) injected into exhaust gas is hydrolyzed with exhaust heat (CO (NH 2 ) 2 + H 2 O) → 2NH 3 + CO 2 ), and ammonia (reducing agent) ( NH 3 ) is generated, and nitrogen oxides and ammonia are reacted via a catalyst to reduce the nitrogen oxides.
JP 2003-293739 A

ところで、尿素を排気熱により加水分解するには、排気温度を１７０℃〜１７５℃以上の温度（以下、この温度アンモニア生成温度という。）とする必要があので、排気温度がアンモニア生成温度未満のときに尿素を排気中に添加しても、窒素酸化物をアンモニアにて還元することができないばかりか、尿素が加水分解されずにそのまま大気中に放出され、尿素が無駄に消費されてしまうという問題が発生する。   By the way, in order to hydrolyze urea with exhaust heat, it is necessary to set the exhaust temperature to a temperature of 170 ° C. to 175 ° C. or higher (hereinafter referred to as this temperature ammonia generation temperature). Even when urea is added to the exhaust gas, not only the nitrogen oxides cannot be reduced with ammonia, but also urea is released into the atmosphere as it is not hydrolyzed, and urea is consumed wastefully. A problem occurs.

本発明は、上記点に鑑み、尿素等の添加剤が無駄に消費されてしまうことを防止しつつ、窒素酸化物を確実に還元（浄化）することを目的とする。   In view of the above points, an object of the present invention is to reliably reduce (purify) nitrogen oxides while preventing additives such as urea from being wasted.

本発明は、上記目的を達成するために、請求項１に記載の発明では、内燃機関（１）から排出される排気の熱を利用して添加剤から還元剤を生成するとともに、排気中に含まれる窒素酸化物を還元剤にて還元する排気浄化装置であって、内燃機関から排出される排気の通路を構成する排気管（２）と、排気管（２）に設けられ、排気中の窒素酸化物の還元反応を促進する触媒（３）と、添加剤を触媒（３）より排気流れ上流側に供給する供給手段（５）と、排気管（２）を流通する排気の温度を検出する温度検出手段（８）と、供給手段（５）の作動を制御することにより、排気管（２）に供給される添加剤の供給量を調整する制御手段（１０）とを備え、制御手段（１０）は、温度検出手段（８）が検出した排気温度が、添加剤から還元剤を生成するに必要な生成温度未満の場合には、添加剤の供給を停止し、一方、排気温度が生成温度以上の場合には、添加剤を供給し、さらに、制御手段（１０）は、添加剤の供給を開始した時から所定時間が経過した場合に、所定時間が経過する前の供給量に比べて、添加剤の供給量を低減することを特徴とする。   In order to achieve the above object, according to the present invention, the invention according to claim 1 generates the reducing agent from the additive using the heat of the exhaust discharged from the internal combustion engine (1), and in the exhaust. An exhaust purification device that reduces contained nitrogen oxides with a reducing agent, provided in an exhaust pipe (2) constituting an exhaust passage exhausted from an internal combustion engine, and an exhaust pipe (2), Detects the temperature of the exhaust gas flowing through the exhaust pipe (2), the catalyst (3) for promoting the reduction reaction of nitrogen oxides, the supply means (5) for supplying the additive to the upstream side of the exhaust flow from the catalyst (3) Temperature control means (8) for controlling, and control means (10) for adjusting the supply amount of the additive supplied to the exhaust pipe (2) by controlling the operation of the supply means (5). (10) is that the exhaust temperature detected by the temperature detecting means (8) is changed from the additive to the reducing agent. When the production temperature is lower than the production temperature necessary for production, the supply of the additive is stopped. On the other hand, when the exhaust temperature is equal to or higher than the production temperature, the additive is supplied, and the control means (10) further adds When a predetermined time has elapsed from the start of the supply of the agent, the supply amount of the additive is reduced compared to the supply amount before the predetermined time has elapsed.

これにより、請求項１に記載の発明では、排気温度が生成温度未満の場合には、添加剤の供給を停止するので、添加剤が無駄に消費されてしまうことを防止できる。
また、排気温度が生成温度以上の場合には、添加剤を供給して添加剤から生成された還元剤にて窒素酸化物を還元（浄化）するとともに、生成された還元剤の一部が触媒（３）に吸着される。そして、排気温度が生成温度未満となり、添加剤の供給が停止した場合には、この触媒（３）に吸着されている還元剤にて窒素酸化物が還元される。 Thereby, in invention of Claim 1, since supply of an additive is stopped when exhaust temperature is less than production | generation temperature, it can prevent that an additive is consumed wastefully.
In addition, when the exhaust temperature is equal to or higher than the generation temperature, the additive is supplied to reduce (purify) nitrogen oxides with the reducing agent generated from the additive, and a part of the generated reducing agent is a catalyst. Adsorbed on (3). When the exhaust temperature becomes lower than the generation temperature and supply of the additive is stopped, nitrogen oxides are reduced by the reducing agent adsorbed on the catalyst (3).

ところで、排気温度が生成温度以上の場合には、前述したように、生成された還元剤の一部は、還元に用いられることなく触媒（３）に吸着され、排気温度が生成温度未満のときに還元に用いられるが、生成される還元剤の量が、触媒（３）で吸着可能な量を超えると、生成された還元剤は、窒素酸化物の還元に用いられることなく排出されてしまうので、添加剤が無駄に消費されてしまう。   By the way, when the exhaust temperature is equal to or higher than the generation temperature, as described above, a part of the generated reducing agent is adsorbed to the catalyst (3) without being used for reduction, and the exhaust temperature is lower than the generation temperature. However, if the amount of the reducing agent produced exceeds the amount that can be adsorbed by the catalyst (3), the produced reducing agent will be discharged without being used for the reduction of nitrogen oxides. As a result, the additive is wasted.

これに対して、請求項１に記載の発明では、添加剤の供給を開始した時から所定時間が経過した場合には、所定時間が経過する前の供給量に比べて、添加剤の供給量を低減するので、生成される還元剤の量が触媒（３）で吸着可能な量を超えてしまうことを未然に防止することが可能となる。   On the other hand, in the invention according to claim 1, when a predetermined time has elapsed since the start of the supply of the additive, the supply amount of the additive compared to the supply amount before the predetermined time has elapsed. Therefore, it is possible to prevent the amount of the reducing agent produced from exceeding the amount that can be adsorbed by the catalyst (3).

なお、上記の説明からも明らかなように、「所定時間」とは、「生成される還元剤の量が触媒（３）で吸着可能な量を超えてしまう時間以下の時間」をいう。
以上のように、請求項１に記載の発明では、添加剤が無駄に消費されてしまうことを防止しつつ、窒素酸化物を確実に還元（浄化）することができる。 As is clear from the above description, the “predetermined time” refers to “a time equal to or less than the time during which the amount of the reducing agent produced exceeds the amount that can be adsorbed by the catalyst (3)”.
As described above, according to the first aspect of the present invention, it is possible to reliably reduce (purify) nitrogen oxide while preventing the additive from being wasted.

請求項２に記載の発明では、内燃機関（１）から排出される排気の熱を利用して添加剤から還元剤を生成するとともに、排気中に含まれる窒素酸化物を還元剤にて還元する排気浄化装置であって、内燃機関から排出される排気の通路を構成する排気管（２）と、排気管（２）に設けられ、排気中の窒素酸化物の還元反応を促進する触媒（３）と、添加剤を触媒（３）より排気流れ上流側に供給する供給手段（５）と、排気管（２）を流通する排気の温度を検出する温度検出手段（８）と、触媒（３）より排気流れ下流側に設けられ、還元剤を検出する還元剤検出手段（１１）と、供給手段（５）の作動を制御することにより、排気管（２）に供給される添加剤の供給量を調整する制御手段（１０）とを備え、制御手段（１０）は、温度検出手段（８）が検出した排気温度が、添加剤から還元剤を生成するに必要な生成温度未満の場合には、添加剤の供給を停止し、一方、排気温度が生成温度以上の場合には、添加剤を供給し、さらに、制御手段（１０）は、添加剤の供給を開始した時以降であって、還元剤検出手段（１１）により所定値以上の還元剤が検出された場合に、還元剤が検出される前の供給量に比べて、添加剤の供給量を低減することを特徴とする。   In the second aspect of the invention, the reducing agent is generated from the additive using the heat of the exhaust discharged from the internal combustion engine (1), and the nitrogen oxide contained in the exhaust is reduced by the reducing agent. An exhaust purification device, which is provided in an exhaust pipe (2) constituting an exhaust passage exhausted from an internal combustion engine, and a catalyst (3) for promoting a reduction reaction of nitrogen oxides in the exhaust. ), Supply means (5) for supplying the additive upstream of the catalyst (3), temperature detection means (8) for detecting the temperature of the exhaust gas flowing through the exhaust pipe (2), and catalyst (3 ) Supply of the additive supplied to the exhaust pipe (2) by controlling the operation of the reducing agent detection means (11) for detecting the reducing agent and the supply means (5) provided downstream of the exhaust flow. Control means (10) for adjusting the amount, and the control means (10) When the exhaust temperature detected by (8) is lower than the generation temperature necessary for generating the reducing agent from the additive, the supply of the additive is stopped, while when the exhaust temperature is equal to or higher than the generation temperature, The additive is supplied, and further, the control means (10) starts the supply of the additive, and when the reducing agent detecting means (11) detects a reducing agent of a predetermined value or more, the control means (10) The supply amount of the additive is reduced as compared with the supply amount before the agent is detected.

これにより、請求項２に記載の発明においても、請求項１に記載の発明と同様に、排気温度が生成温度未満の場合には、添加剤の供給が停止されるとともに、触媒（３）に吸着されている還元剤にて窒素酸化物が還元されるので、添加剤が無駄に消費されてしまうことを防止できる。   As a result, in the invention according to claim 2, as in the invention according to claim 1, when the exhaust gas temperature is lower than the generation temperature, the supply of the additive is stopped and the catalyst (3) Since nitrogen oxides are reduced by the adsorbed reducing agent, it is possible to prevent the additive from being consumed wastefully.

また、排気温度が生成温度以上の場合には、添加剤を供給して添加剤から生成された還元剤にて窒素酸化物を還元（浄化）するとともに、生成された還元剤の一部が触媒（３）に吸着される。   In addition, when the exhaust temperature is equal to or higher than the generation temperature, the additive is supplied to reduce (purify) nitrogen oxides with the reducing agent generated from the additive, and a part of the generated reducing agent is a catalyst. Adsorbed on (3).

そして、添加剤の供給を開始した時以降であって、還元剤検出手段（１１）により還元剤が検出された場合には、還元剤が検出される前の供給量に比べて、添加剤の供給量を低減するので、生成される還元剤の量が触媒（３）で吸着可能な量を超えてしまうことを未然に防止することが可能となる。   Then, after the start of the supply of the additive and when the reducing agent is detected by the reducing agent detection means (11), the amount of the additive is compared with the supply amount before the reducing agent is detected. Since the supply amount is reduced, it is possible to prevent the amount of the reducing agent produced from exceeding the amount that can be adsorbed by the catalyst (3).

したがって、請求項２に記載の発明においても、添加剤が無駄に消費されてしまうことを防止しつつ、窒素酸化物を確実に還元（浄化）することができる。
請求項３に記載の発明では、内燃機関（１）から排出される排気の熱を利用して添加剤から還元剤を生成するとともに、排気中に含まれる窒素酸化物を還元剤にて還元する排気浄化装置であって、内燃機関から排出される排気の通路を構成する排気管（２）と、排気管（２）に設けられ、排気中の窒素酸化物の還元反応を促進する触媒（３）と、添加剤を触媒（３）より排気流れ上流側に供給する供給手段（５）と、排気管（２）を流通する排気の温度を検出する温度検出手段（８）と、供給手段（５）の作動を制御することにより、排気管（２）に供給される添加剤の供給量を調整する制御手段（１０）とを備え、制御手段（１０）は、温度検出手段（８）が検出した排気温度が、添加剤から還元剤を生成するに必要な生成温度未満の場合には、添加剤の供給を停止し、一方、排気温度が生成温度以上の場合には、添加剤を供給し、さらに、制御手段（１０）は、排気温度が生成温度より高い所定温度以上の場合には、排気温度が生成温度以上、前記所定温度未満のときの供給量に比べて、添加剤の供給量を低減することを特徴とする。 Therefore, also in the invention described in claim 2, it is possible to reliably reduce (purify) the nitrogen oxide while preventing the additive from being wasted.
In the third aspect of the present invention, the reducing agent is generated from the additive using the heat of the exhaust discharged from the internal combustion engine (1), and the nitrogen oxides contained in the exhaust are reduced by the reducing agent. An exhaust purification device, which is provided in an exhaust pipe (2) constituting an exhaust passage exhausted from an internal combustion engine, and a catalyst (3) for promoting a reduction reaction of nitrogen oxides in the exhaust. ), Supply means (5) for supplying the additive upstream of the catalyst (3), temperature detection means (8) for detecting the temperature of the exhaust gas flowing through the exhaust pipe (2), and supply means ( And a control means (10) for adjusting the supply amount of the additive supplied to the exhaust pipe (2) by controlling the operation of 5). The control means (10) includes a temperature detection means (8). When the detected exhaust temperature is lower than the production temperature required to produce the reducing agent from the additive Stops supplying the additive, while if the exhaust temperature is higher than the generation temperature, the additive is supplied, and the control means (10) further controls the exhaust temperature to be higher than a predetermined temperature higher than the generation temperature. Is characterized in that the supply amount of the additive is reduced compared to the supply amount when the exhaust temperature is equal to or higher than the generation temperature and lower than the predetermined temperature.

これにより、請求項３に記載の発明では、請求項１に記載の発明と同様に、排気温度が生成温度未満の場合には、添加剤の供給が停止されるとともに、触媒（３）に吸着されている還元剤にて窒素酸化物が還元されるので、添加剤が無駄に消費されてしまうことを防止できる。   Thereby, in the invention of claim 3, as in the invention of claim 1, when the exhaust gas temperature is lower than the generation temperature, the supply of the additive is stopped and the catalyst (3) is adsorbed. Since nitrogen oxides are reduced by the reducing agent being used, it is possible to prevent wasteful consumption of the additive.

また、排気温度が生成温度以上の場合には、添加剤を供給して添加剤から生成された還元剤にて窒素酸化物を還元（浄化）するとともに、生成された還元剤の一部が触媒（３）に吸着される。   In addition, when the exhaust temperature is equal to or higher than the generation temperature, the additive is supplied to reduce (purify) nitrogen oxides with the reducing agent generated from the additive, and a part of the generated reducing agent is a catalyst. Adsorbed on (3).

そして、排気温度が生成温度より高い所定温度以上の場合には、排気温度が生成温度以上、前記所定温度未満の場合の供給量に比べて、添加剤の供給量を低減するので、生成される還元剤の量が触媒（３）で吸着可能な量を超えてしまうことを未然に防止することが可能となる。   When the exhaust temperature is equal to or higher than the predetermined temperature higher than the generation temperature, the amount of additive supplied is reduced compared to the supply amount when the exhaust temperature is equal to or higher than the generation temperature and lower than the predetermined temperature. It is possible to prevent the amount of the reducing agent from exceeding the amount that can be adsorbed by the catalyst (3).

つまり、添加剤から還元剤を生成し続けると、その時間の経過に伴い排気温度が次第上昇していく。そこで、排気温度が、例えば請求項１に記載の所定時間が経過したときの排気温度相当に到達したときに、添加剤の供給量を低減すれば、生成される還元剤の量が触媒（３）で吸着可能な量を超えてしまうことを未然に防止できる。   That is, if the reducing agent is continuously generated from the additive, the exhaust temperature gradually increases with the passage of time. Therefore, for example, when the exhaust gas temperature reaches the exhaust gas temperature equivalent to the exhaust gas temperature when the predetermined time according to claim 1 has elapsed, the amount of reducing agent produced can be reduced by reducing the amount of additive supplied. ) Can be prevented from exceeding the amount that can be adsorbed.

以上のように、請求項３に記載の発明においても、添加剤が無駄に消費されてしまうことを防止しつつ、窒素酸化物を確実に還元（浄化）することができる。
請求項４に記載の発明では、内燃機関（１）から排出される排気の熱を利用して添加剤から還元剤を生成するとともに、排気中に含まれる窒素酸化物を還元剤にて還元する排気浄化装置であって、内燃機関から排出される排気の通路を構成する排気管（２）と、排気管（２）に設けられ、排気中の窒素酸化物の還元反応を促進する触媒（３）と、添加剤を触媒（３）より排気流れ上流側に供給する供給手段（５）と、排気管（２）を流通する排気の温度を検出する温度検出手段（８）と、供給手段（５）の作動を制御することにより、排気管（２）に供給される添加剤の供給量を調整する制御手段（１０）とを備え、制御手段（１０）は、温度検出手段（８）が検出した排気温度が、添加剤から還元剤を生成するに必要な生成温度未満の場合には、添加剤の供給を停止し、一方、排気温度が生成温度以上の場合には、添加剤を供給し、さらに、制御手段（１０）は、排気温度が生成温度より高い所定温度以上となった場合、及び添加剤の供給を開始した時から所定時間が経過した場合のうち少なくとも一方の条件が成立した場合には、いずれかの条件が成立する以前に供給していた供給量に比べて、添加剤の供給量を低減することを特徴とすることを特徴とする。 As described above, also in the invention according to the third aspect, it is possible to reliably reduce (purify) the nitrogen oxide while preventing the additive from being wasted.
In the invention according to claim 4, the reducing agent is generated from the additive using the heat of the exhaust discharged from the internal combustion engine (1), and the nitrogen oxide contained in the exhaust is reduced by the reducing agent. An exhaust purification device, which is provided in an exhaust pipe (2) constituting an exhaust passage exhausted from an internal combustion engine, and a catalyst (3) for promoting a reduction reaction of nitrogen oxides in the exhaust. ), Supply means (5) for supplying the additive upstream of the catalyst (3), temperature detection means (8) for detecting the temperature of the exhaust gas flowing through the exhaust pipe (2), and supply means ( 5) by controlling the operation of 5) to adjust the supply amount of the additive supplied to the exhaust pipe (2). The control means (10) includes a temperature detection means (8). When the detected exhaust temperature is lower than the production temperature required to produce the reducing agent from the additive Stops supplying the additive, while when the exhaust temperature is higher than the generation temperature, the additive is supplied, and the control means (10) further increases the exhaust temperature to a predetermined temperature higher than the generation temperature. And when at least one of the conditions is satisfied when a predetermined time has elapsed since the start of the supply of the additive, compared with the supply amount supplied before any of the conditions is satisfied. , Characterized in that the supply amount of the additive is reduced.

これにより、請求項４に記載の発明では、請求項１と請求項３とを組み合わせた発明となるので、添加剤が無駄に消費されてしまうことを防止しつつ、窒素酸化物を確実に還元（浄化）することができる。   As a result, the invention according to claim 4 is an invention combining claim 1 and claim 3, so that nitrogen oxides are reliably reduced while preventing the additive from being wasted. (Purification) can be done.

因みに、上記各手段等の括弧内の符号は、後述する実施形態に記載の具体的手段等との対応関係を示す一例であり、本発明は上記各手段等の括弧内の符号に示された具体的手段に限定されるものではない。   Incidentally, the reference numerals in parentheses for each of the above means are examples showing the correspondence with the specific means described in the embodiments described later, and the present invention is indicated by the reference numerals in the parentheses of the above respective means. It is not limited to specific means.

本実施形態は、本発明に係る排気浄化装置を車両用ディーゼルエンジンの尿素ＳＣＲ（選択還元：Selective catalytic reduction）システムに適用したものであり、以下に本発明の実施形態を図面と共に説明する。   In the present embodiment, the exhaust gas purification apparatus according to the present invention is applied to a urea SCR (Selective Catalytic Reduction) system of a vehicle diesel engine, and the embodiment of the present invention will be described below with reference to the drawings.

（第１実施形態）
１．図面の説明
図１は本実施形態に係る排気浄化装置の模式図であり、図２は本実施形態に係る排気浄化装置の特徴的作動を示すフローチャートであり、図３は添加剤（尿素）の噴射量と排気温度及び時間との関係を示すグラフであり、図４は添加剤（尿素）の噴射量と排気温度との関係を示す図表である。 (First embodiment)
1. DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of an exhaust purification apparatus according to the present embodiment, FIG. 2 is a flowchart showing characteristic operations of the exhaust purification apparatus according to the present embodiment, and FIG. 3 shows an additive (urea). FIG. 4 is a graph showing the relationship between the injection amount and the exhaust temperature and time, and FIG. 4 is a chart showing the relationship between the injection amount of the additive (urea) and the exhaust temperature.

２．排気浄化装置の構成（図１参照）
排気管２は、ディーゼル式の内燃機関１から排出される排気の通路を構成するものであり、この排気管２には、排気中の窒素酸化物の還元反応を促進するＳＣＲ触媒３（以下、触媒３と略す。）、及び排気に含まれるすす等の粒子状物質を捕捉するＤＰＦ（ディーゼル微粒子除去装置：Diesel Particulate Filter）４等が設けられている。なお、ＤＰＦ４は、触媒３より排気流れ上流側（内燃機関側）に設けられている。 2. Configuration of exhaust purification system (see Fig. 1)
The exhaust pipe 2 constitutes a passage of exhaust discharged from the diesel internal combustion engine 1, and the exhaust pipe 2 includes an SCR catalyst 3 (hereinafter referred to as “reduced nitrogen oxide”) that promotes a reduction reaction of nitrogen oxides in the exhaust. And a DPF (diesel particulate filter: Diesel Particulate Filter) 4 that captures particulate matter such as soot contained in the exhaust. The DPF 4 is provided on the upstream side (internal combustion engine side) of the exhaust gas flow from the catalyst 3.

また、供給弁５は、還元反応に用いる添加剤（本実施形態では、尿素水溶液）を触媒３より排気流れ上流側の排気管２に供給する供給手段であり、添加剤タンク６は排気管２に供給される添加剤を蓄えるタンク手段である。   The supply valve 5 is a supply means for supplying an additive used in the reduction reaction (in this embodiment, an aqueous urea solution) to the exhaust pipe 2 on the upstream side of the exhaust flow from the catalyst 3, and the additive tank 6 is an exhaust pipe 2. Tank means for storing the additive to be supplied to the tank.

添加剤ポンプ７は、添加剤タンク６に蓄えられている添加剤を供給弁５に送るポンプ手段であり、排気温度センサ８は、内燃機関１から排出される排気の温度を検出する温度検出手段であり、ＮＯｘセンサ９は触媒３を通過した排気中に含まれる窒素酸化物を検出するＮＯｘ検出手段である。   The additive pump 7 is a pump unit that sends the additive stored in the additive tank 6 to the supply valve 5, and the exhaust temperature sensor 8 is a temperature detection unit that detects the temperature of the exhaust discharged from the internal combustion engine 1. The NOx sensor 9 is NOx detection means for detecting nitrogen oxides contained in the exhaust gas that has passed through the catalyst 3.

なお、本実施形態では。触媒３の入口近傍で排気温度を検出し、触媒３の出口近傍で窒素酸化物を検出している。
そして、排気温度センサ８及びＮＯｘセンサ９の検出信号は、電子制御装置（以下、ＥＣＵと記す。）１０に入力されており、ＥＣＵ１０は、これらセンサ８、９の検出信号等に基づいて供給弁５及び添加剤ポンプ７の作動を制御する。 In the present embodiment. The exhaust temperature is detected in the vicinity of the inlet of the catalyst 3, and nitrogen oxides are detected in the vicinity of the outlet of the catalyst 3.
The detection signals of the exhaust temperature sensor 8 and the NOx sensor 9 are input to an electronic control unit (hereinafter referred to as ECU) 10, and the ECU 10 supplies the supply valve based on the detection signals of these sensors 8 and 9. 5 and the operation of the additive pump 7 are controlled.

なお、ＥＣＵ１０は、ＣＰＵ１０Ａ、ＲＡＭ１０Ｂ及びＲＯＭ１０Ｃ、時間を計時するタイマ１０Ｄ等からなる周知のマイクロコンピュータにて構成されたものであり、供給弁５等を制御するためのプログラムは、ＲＯＭ１０Ｃに記憶されている。   The ECU 10 is constituted by a known microcomputer including a CPU 10A, a RAM 10B and a ROM 10C, a timer 10D for measuring time, and the like. A program for controlling the supply valve 5 and the like is stored in the ROM 10C. Yes.

３．排気浄化装置の基本的作動
排気浄化装置は、排気中に噴射された添加剤である尿素（ＣＯ(ＮＨ2)2）を排気熱にて加水分解して（ＣＯ(ＮＨ2)2＋Ｈ2Ｏ）→２ＮＨ3＋ＣＯ2）、還元剤であるアンモニア（ＮＨ3）を生成し、触媒３を介して窒素酸化物とアンモニアとを反応させて窒素酸化物を浄化（還元）する。 3. Basic operation of exhaust gas purification device The exhaust gas purification device hydrolyzes urea (CO (NH 2 ) 2 ), which is an additive injected into exhaust gas, with exhaust heat (CO (NH 2 ) 2 + H 2 O ) → 2NH 3 + CO 2 ), ammonia (NH 3 ) as a reducing agent is generated, and nitrogen oxide and ammonia are reacted through the catalyst 3 to purify (reducing) the nitrogen oxide.

このとき、排気温度を１７０℃〜１７５℃以上の温度（以下、この温度アンモニア生成温度という。）とすると、尿素を加水分解してアンモニアを生成することができるが、排気温度がアンモニア生成温度より低い場合には、尿素が加水分解されずにそのまま大気中に放出され、尿素が無駄に消費されてしまう。   At this time, if the exhaust temperature is set to a temperature of 170 ° C. to 175 ° C. or higher (hereinafter referred to as this temperature ammonia generation temperature), urea can be hydrolyzed to generate ammonia, but the exhaust temperature is higher than the ammonia generation temperature. When it is low, urea is released into the atmosphere as it is without being hydrolyzed, and urea is wasted.

４．排気浄化装置の特徴的作動（図２参照）
排気浄化装置（供給弁５及び添加剤ポンプ７）は、内燃機関１の始動と同時に開始され、供給される添加剤の量は、通常、内燃機関１から排出される排気の温度（排気温度センサ８の検出温度）及び排気中に含まれる窒素酸化物の量（ＮＯｘセンサ９の検出値）等に基づいて制御（以下、この制御を、通常制御という。）される。 4). Characteristic operation of exhaust purification system (see Fig. 2)
The exhaust purification device (supply valve 5 and additive pump 7) is started simultaneously with the start of the internal combustion engine 1, and the amount of additive supplied is usually the temperature of exhaust discharged from the internal combustion engine 1 (exhaust temperature sensor). 8) and the amount of nitrogen oxides contained in the exhaust (the detected value of the NOx sensor 9), etc. (hereinafter, this control is referred to as normal control).

そして、図２に示す制御（以下、この制御を還元剤スリップ抑制制御という。）は、通常制御と同時に開始されて通常制御と独立して作動するものであり、その概要は、以下の通りである。   The control shown in FIG. 2 (hereinafter, this control is referred to as reducing agent slip suppression control) starts simultaneously with the normal control and operates independently of the normal control. The outline of the control is as follows. is there.

すなわち、排気温度センサ８が検出した排気温度が、アンモニア生成温度未満の場合には、排気管２への添加剤（尿素）の供給を停止し、一方、排気温度がアンモニア生成温度以上の場合には、排気管２へ添加剤を供給する。   That is, when the exhaust temperature detected by the exhaust temperature sensor 8 is lower than the ammonia generation temperature, the supply of the additive (urea) to the exhaust pipe 2 is stopped, while when the exhaust temperature is equal to or higher than the ammonia generation temperature. Supplies an additive to the exhaust pipe 2.

そして、排気管２に供給する添加剤の量は、内燃機関１から排出される排気中に含まれる窒素酸化物の全て還元するために必要な還元剤の量よりも多量の還元剤が生成されるような量とする。   The amount of additive supplied to the exhaust pipe 2 is such that a larger amount of reducing agent is generated than the amount of reducing agent required to reduce all of the nitrogen oxides contained in the exhaust discharged from the internal combustion engine 1. The amount is as follows.

このとき、加水分解により生成された還元剤は触媒３に吸着された後、触媒３を介して窒素酸化物と還元反応するが、余分に生成された還元剤は触媒３に吸着され続け、排気温度がアンモニア生成温度未満まで低下して添加剤の供給が停止すると、余分に生成されて触媒３の吸着されていた還元剤が還元反応に消費されて窒素酸化物が浄化される。   At this time, after the reducing agent produced by hydrolysis is adsorbed by the catalyst 3, it undergoes a reduction reaction with the nitrogen oxide via the catalyst 3, but the extra reducing agent produced continues to be adsorbed by the catalyst 3 and exhausted. When the temperature drops below the ammonia generation temperature and the supply of the additive is stopped, the reducing agent that has been generated and adsorbed on the catalyst 3 is consumed in the reduction reaction, and the nitrogen oxides are purified.

しかし、排気温度がアンモニア生成温度以上となる状態が長時間に渡って継続すると、生成された還元剤の総量が、触媒３が吸着することができる限界値を超えてしまい、生成された還元剤が還元反応に用いられることなく、放出されてしまう。   However, if the state where the exhaust gas temperature is equal to or higher than the ammonia generation temperature continues for a long time, the total amount of generated reducing agent exceeds the limit value that the catalyst 3 can adsorb, and the generated reducing agent Are released without being used in the reduction reaction.

そこで、本実施形態では、排気温度がアンモニア生成温度より高い所定温度（以下、この温度を供給停止温度という。）以上となった場合、及び添加剤の供給を開始した時から所定時間（以下、この時間を供給停止時間という。）が経過した場合のうち少なくとも一方の場合には、いずれかの条件が成立する以前に、排気管２に供給していた添加剤の供給量に比べて、添加剤の供給量を低減することを特徴としている。   Therefore, in the present embodiment, when the exhaust gas temperature is equal to or higher than a predetermined temperature higher than the ammonia generation temperature (hereinafter, this temperature is referred to as supply stop temperature) and when the additive supply is started, the predetermined time (hereinafter, This time is referred to as supply stop time.) In at least one of the cases where the supply stop time has elapsed, the amount of additive is compared with the amount of additive supplied to the exhaust pipe 2 before any of the conditions is satisfied. It is characterized by reducing the supply amount of the agent.

ところで、前記のいずれかの条件が成立する以前とは、排気温度がアンモニア生成温度以上、供給温度停止温度未満のとき、又は排気温度がアンモニア生成温度以上となった時から供給停止時間が経過する以前のときであるので、いずれかの条件が成立する以前に排気管２に供給していた添加剤の供給量とは、前述したように、内燃機関１から排出される排気中に含まれる窒素酸化物の全て還元するために必要な還元剤の量よりも多量の還元剤が生成されるような量である。   By the way, before any of the above conditions is satisfied, the supply stop time elapses when the exhaust temperature is equal to or higher than the ammonia generation temperature and lower than the supply temperature stop temperature, or when the exhaust temperature becomes equal to or higher than the ammonia generation temperature. Since the previous time, the supply amount of the additive supplied to the exhaust pipe 2 before any of the conditions is satisfied is the nitrogen contained in the exhaust discharged from the internal combustion engine 1 as described above. The amount is such that a larger amount of reducing agent is produced than the amount of reducing agent required to reduce all of the oxide.

そこで、以下、排気中に含まれる窒素酸化物の全て還元するために必要な還元剤の量を生成することが可能な添加剤の供給量を通常量と呼び、前記のいずれかの条件が成立する以前に供給される添加剤の供給量を通常量より多い量と呼ぶ。   Therefore, hereinafter, the supply amount of the additive capable of generating the amount of reducing agent necessary for reducing all of the nitrogen oxides contained in the exhaust is referred to as a normal amount, and any of the above conditions is established. The supply amount of the additive supplied before the operation is referred to as an amount larger than the normal amount.

以下、図２に示すフローチャートに基づいて、上記作動の詳細を説明する。
還元剤スリップ抑制制御が起動されると、排気温度センサ８の検出温度（以下、排気温度という。）がアンモニア生成温度Ｔ１未満であるか否かが判定される（Ｓ１）。 The details of the above operation will be described below based on the flowchart shown in FIG.
When the reducing agent slip suppression control is activated, it is determined whether or not the detected temperature of the exhaust temperature sensor 8 (hereinafter referred to as exhaust temperature) is lower than the ammonia generation temperature T1 (S1).

そして、排気温度がアンモニア生成温度Ｔ１未満であると判定された場合には（Ｓ１：ＹＥＳ）、還元剤の供給（噴射）が停止されるとともに、タイマ１０Ｄの計時時間が初期化された後（Ｓ２）、タイマ１０Ｄによる時間の計時が開始又は継続される（Ｓ７）。   When it is determined that the exhaust temperature is lower than the ammonia generation temperature T1 (S1: YES), the supply (injection) of the reducing agent is stopped and the time count of the timer 10D is initialized ( S2) Time measurement by the timer 10D is started or continued (S7).

一方、排気温度がアンモニア生成温度Ｔ１未満でない、つまり排気温度がアンモニア生成温度Ｔ１以上であると判定された場合には（Ｓ１：ＮＯ）、タイマ１０Ｄによる計時時間が供給停止時間以上であるか否かが判定され（Ｓ３）、計時時間が供給停止時間以上であると判定された場合には（Ｓ３：ＹＥＳ）、通常量の添加剤が排気管２に供給された後（Ｓ５）、タイマ１０Ｄによる時間の計時が開始又は継続される（Ｓ７）。   On the other hand, when it is determined that the exhaust temperature is not lower than the ammonia generation temperature T1, that is, the exhaust temperature is equal to or higher than the ammonia generation temperature T1 (S1: NO), whether or not the time measured by the timer 10D is equal to or longer than the supply stop time. Is determined (S3), and when it is determined that the measured time is equal to or longer than the supply stop time (S3: YES), after the normal amount of additive is supplied to the exhaust pipe 2 (S5), the timer 10D The time measurement by is started or continued (S7).

また、計時時間が供給停止時間以上でないと判定された場合には（Ｓ３：ＮＯ）、排気温度が供給停止温度Ｔ２以上であるか否かが判定され（Ｓ４）、排気温度が供給停止温度Ｔ２以上であると判定された場合には（Ｓ４：ＹＥＳ）、通常量の添加剤が排気管２に供給された後（Ｓ５）、タイマ１０Ｄによる時間の計時が開始又は継続される（Ｓ７）。   If it is determined that the time measured is not equal to or longer than the supply stop time (S3: NO), it is determined whether the exhaust temperature is equal to or higher than the supply stop temperature T2 (S4), and the exhaust temperature is determined to be the supply stop temperature T2. When it is determined that it is above (S4: YES), after the normal amount of additive is supplied to the exhaust pipe 2 (S5), the time measurement by the timer 10D is started or continued (S7).

一方、排気温度が供給停止温度Ｔ２以上でないと判定された場合には（Ｓ４：ＮＯ）、通常量より多い添加剤が排気管２に供給された後（Ｓ６）、タイマ１０Ｄによる時間の計時が開始又は継続される（Ｓ７）。そして、Ｓ７が実行されると、再び、Ｓ１が実行される。   On the other hand, when it is determined that the exhaust temperature is not equal to or higher than the supply stop temperature T2 (S4: NO), after the additive amount larger than the normal amount is supplied to the exhaust pipe 2 (S6), the time is counted by the timer 10D Start or continue (S7). When S7 is executed, S1 is executed again.

５．排気浄化装置の特徴
本実施形態では、排気温度がアンモニア生成温度Ｔ１未満の場合には、図３又は図４に示すように、添加剤の供給を停止するので、添加剤が無駄に消費されてしまうことを防止できる。 5). In the present embodiment, when the exhaust gas temperature is lower than the ammonia generation temperature T1, the supply of the additive is stopped as shown in FIG. 3 or FIG. Can be prevented.

また、排気温度がアンモニア生成温度Ｔ１以上の場合には、通常量より多い添加剤を供給するので、添加剤から生成された還元剤にて窒素酸化物が還元（浄化）されるとともに、生成された還元剤の一部が触媒３に吸着される。そして、排気温度がアンモニア生成温度Ｔ１未満となり、添加剤の供給が停止した場合には、この触媒３に吸着されている還元剤にて窒素酸化物が還元される。   Further, when the exhaust temperature is equal to or higher than the ammonia generation temperature T1, an additive larger than the normal amount is supplied, so that the nitrogen oxide is reduced (purified) by the reducing agent generated from the additive and is generated. A part of the reducing agent is adsorbed on the catalyst 3. When the exhaust gas temperature becomes lower than the ammonia generation temperature T1 and the supply of the additive is stopped, the nitrogen oxide is reduced by the reducing agent adsorbed on the catalyst 3.

ところで、排気温度がアンモニア生成温度Ｔ１以上の場合には、前述したように、生成された還元剤の一部は、還元に用いられることなく触媒３に吸着され、排気温度がアンモニア生成温度Ｔ１未満のときに還元に用いられるが、生成される還元剤の量が、触媒３で吸着可能な量を超えると、生成された還元剤は、窒素酸化物の還元に用いられることなく排出されてしまうので、添加剤が無駄に消費されてしまう。   By the way, when the exhaust temperature is equal to or higher than the ammonia generation temperature T1, as described above, a part of the generated reducing agent is adsorbed on the catalyst 3 without being used for reduction, and the exhaust temperature is lower than the ammonia generation temperature T1. In this case, when the amount of the reducing agent produced exceeds the amount that can be adsorbed by the catalyst 3, the produced reducing agent is discharged without being used for the reduction of nitrogen oxides. As a result, the additive is wasted.

これに対して、本実施形態では、図３に示すように、添加剤の供給を開始した時から供給停止時間が経過した場合には、所定時間が経過する前の供給量に比べて、添加剤の供給量を低減するので、生成される還元剤の量が触媒３で吸着可能な量を超えてしまうことを未然に防止することが可能となる。   On the other hand, in this embodiment, as shown in FIG. 3, when the supply stop time has elapsed from the time when the supply of the additive has started, the addition amount is larger than the supply amount before the predetermined time has elapsed. Since the supply amount of the agent is reduced, it is possible to prevent the amount of the reducing agent produced from exceeding the amount that can be adsorbed by the catalyst 3.

また、添加剤から還元剤を生成し続けると、その時間の経過に伴い排気温度が次第上昇していくので、排気温度が供給停止温度Ｔ２以上となったときに、添加剤の供給量を低減すれば、生成される還元剤の量が触媒３で吸着可能な量を超えてしまうことを未然に防止できる。   Further, if the reducing agent is continuously generated from the additive, the exhaust temperature gradually increases with the passage of time, so when the exhaust temperature becomes equal to or higher than the supply stop temperature T2, the supply amount of the additive is reduced. By doing so, it is possible to prevent the amount of the reducing agent produced from exceeding the amount that can be adsorbed by the catalyst 3.

なお、上記の説明からも明らかなように、供給停止温度とは、例えばアンモニア生成温度Ｔ１から供給停止時間が経過したときの排気温度相当する温度であり、供給停止時間及び供給停止温度Ｔ２は、触媒３の仕様や内燃機関１の仕様等に基づいて適宜決定されるものである。   As apparent from the above description, the supply stop temperature is, for example, a temperature corresponding to the exhaust temperature when the supply stop time has elapsed from the ammonia generation temperature T1, and the supply stop time and the supply stop temperature T2 are: This is appropriately determined based on the specifications of the catalyst 3 and the specifications of the internal combustion engine 1.

以上のように、本実施形態では、添加剤が無駄に消費されてしまうことを防止しつつ、窒素酸化物を確実に還元（浄化）することができる。
６．発明特定事項と実施形態との対応関係
本実施形態では、供給弁５が特許請求の範囲に記載された供給手段に相当し、排気温度センサ８が特許請求の範囲に記載された温度検出手段に相当し、ＥＣＵ１０が特許請求の範囲に記載された制御手段に相当する。 As described above, in the present embodiment, nitrogen oxides can be reliably reduced (purified) while preventing the additive from being consumed wastefully.
6). Correspondence between Invention Specific Items and Embodiment In this embodiment, the supply valve 5 corresponds to the supply means described in the claims, and the exhaust temperature sensor 8 corresponds to the temperature detection means described in the claims. The ECU 10 corresponds to the control means described in the claims.

（第２実施形態）
１．本実施形態に係る排気浄化装置の概要
本実施形態は、図５に示すように、触媒３の排気流れ下流側に、還元剤であるアンモニアを検出するアンモニアセンサ１１を設けるとともに、排気温度がアンモニア生成温度Ｔ１以上となった時以降、アンモニアセンサ１１にて所定値以上のアンモニアを検出するまでは、通常量より多い量の添加剤を供給し、アンモニアセンサ１１にてアンモニアを検出した後、排気温度がアンモニア生成温度Ｔ１未満となるまでは、通常量の添加剤を供給するものである。 (Second Embodiment)
1. Outline of Exhaust Gas Purifying Device According to this Embodiment As shown in FIG. 5, this embodiment is provided with an ammonia sensor 11 for detecting ammonia as a reducing agent on the downstream side of the exhaust flow of the catalyst 3, and the exhaust temperature is ammonia. After the generation temperature T1 or higher, the ammonia sensor 11 supplies more additive than the normal amount until ammonia is detected by the ammonia sensor 11, and after the ammonia is detected by the ammonia sensor 11, the exhaust gas is exhausted. Until the temperature falls below the ammonia production temperature T1, a normal amount of additive is supplied.

なお、図５は本実施形態に係る排気浄化装置の模式図であり、図６は本実施形態に係る排気浄化装置の特徴的作動を示すフローチャートである。以下、図６に基づいて、上記作動の詳細を説明する。   FIG. 5 is a schematic diagram of the exhaust purification apparatus according to the present embodiment, and FIG. 6 is a flowchart showing characteristic operations of the exhaust purification apparatus according to the present embodiment. The details of the operation will be described below with reference to FIG.

２．本実施形態に係る排気浄化装置の特徴的作動
還元剤スリップ抑制制御が起動されると、先ず、排気温度がアンモニア生成温度Ｔ１未満であるか否かが判定される（Ｓ１１）。 2. Characteristic Operation of the Exhaust Gas Purification Device According to the Present Embodiment When the reducing agent slip suppression control is activated, it is first determined whether or not the exhaust gas temperature is lower than the ammonia production temperature T1 (S11).

そして、排気温度がアンモニア生成温度Ｔ１未満であると判定された場合には（Ｓ１１：ＹＥＳ１）、還元剤の供給（噴射）が停止されるとともに、タイマ１０Ｄの計時時間が初期化された後（Ｓ１２）、タイマ１０Ｄによる時間の計時が開始又は継続されて、一定時間が経過したときに（Ｓ１６）、再び、Ｓ１１が実行される。   When it is determined that the exhaust temperature is lower than the ammonia generation temperature T1 (S11: YES1), the supply (injection) of the reducing agent is stopped and the time measured by the timer 10D is initialized ( S12) When the time measurement by the timer 10D is started or continued and a certain time has elapsed (S16), S11 is executed again.

一方、排気温度がアンモニア生成温度Ｔ１未満でない、つまり排気温度がアンモニア生成温度Ｔ１以上であると判定された場合には（Ｓ１１：ＮＯ）、アンモニアセンサ１１により所定値以上のアンモニアが検出されたか否かが判定され（Ｓ１３）、所定値以上のアンモニアが検出されたと判定された場合には（Ｓ１３：ＹＥＳ）、通常量の添加剤が排気管２に供給された後（Ｓ１４）、一定時間が経過したときに（Ｓ１６）、再び、Ｓ１１が実行される。   On the other hand, if it is determined that the exhaust temperature is not lower than the ammonia generation temperature T1, that is, the exhaust temperature is equal to or higher than the ammonia generation temperature T1 (S11: NO), whether or not ammonia greater than a predetermined value is detected by the ammonia sensor 11. Is determined (S13), and when it is determined that more than a predetermined value of ammonia has been detected (S13: YES), after a normal amount of additive has been supplied to the exhaust pipe 2 (S14), a certain time When the time has elapsed (S16), S11 is executed again.

一方、所定値以上のアンモニアが検出されていないと判定された場合には（Ｓ１３：ＮＯ）、通常量より多い添加剤が排気管２に供給された後（Ｓ１５）、一定時間が経過したときに（Ｓ１６）、再び、Ｓ１１が実行される。   On the other hand, when it is determined that ammonia of a predetermined value or more is not detected (S13: NO), after a certain amount of time has elapsed after an additive larger than the normal amount is supplied to the exhaust pipe 2 (S15) (S16), S11 is executed again.

３．本実施形態に係る排気浄化装置の特徴
本実施形態においても、上述の実施形態と同様に、排気温度がアンモニア生成温度Ｔ１未満の場合には、添加剤の供給が停止されるとともに、触媒３に吸着されている還元剤にて窒素酸化物が還元されるので、添加剤が無駄に消費されてしまうことを防止できる。 3. Features of the Exhaust Gas Purifying Device According to this Embodiment Also in this embodiment, when the exhaust gas temperature is lower than the ammonia generation temperature T1, the supply of the additive is stopped and the catalyst 3 is added to the catalyst 3 as in the above embodiment. Since nitrogen oxides are reduced by the adsorbed reducing agent, it is possible to prevent the additive from being consumed wastefully.

また、排気温度がアンモニア生成温度Ｔ１以上の場合には、添加剤を供給して添加剤から生成された還元剤にて窒素酸化物を還元（浄化）するとともに、生成された還元剤の一部が触媒３に吸着される。   When the exhaust temperature is equal to or higher than the ammonia generation temperature T1, the additive is supplied to reduce (purify) nitrogen oxides with the reducing agent generated from the additive, and a part of the generated reducing agent. Is adsorbed by the catalyst 3.

そして、添加剤の供給を開始した時以降であって、アンモニアセンサ１１により還元剤であるアンモニアが所定値以上検出された場合には、還元剤が検出される前の供給量に比べて、添加剤の供給量を低減するので、生成される還元剤の量が触媒３で吸着可能な量を超えてしまうことを未然に防止することが可能となる。   Then, after the start of the supply of the additive, when the ammonia sensor 11 detects ammonia as the reducing agent at a predetermined value or more, it is added compared to the supply amount before the reducing agent is detected. Since the supply amount of the agent is reduced, it is possible to prevent the amount of the reducing agent produced from exceeding the amount that can be adsorbed by the catalyst 3.

したがって、本実施形態においても、添加剤が無駄に消費されてしまうことを防止しつつ、窒素酸化物を確実に還元（浄化）することができる。
４．発明特定事項と実施形態との対応関係
本実施形態では、アンモニアセンサ１１が特許請求の範囲に記載された還元剤検出手段に相当する。 Therefore, also in this embodiment, it is possible to reliably reduce (purify) the nitrogen oxide while preventing the additive from being consumed wastefully.
4). Correspondence Relationship between Invention Specific Items and Embodiments In this embodiment, the ammonia sensor 11 corresponds to a reducing agent detecting means described in the claims.

（その他の実施形態）
上述の実施形態では、添加剤として尿素を用いたが、本発明はこれに限定されるものではなく、アンモニア以外の還元剤又はこの還元剤を生成可能な添加剤を用いてもよい。 (Other embodiments)
In the above-described embodiment, urea is used as an additive. However, the present invention is not limited to this, and a reducing agent other than ammonia or an additive capable of generating this reducing agent may be used.

また、本発明は、第１実施形態と第２実施形態とを組み合わせてもよい。
また、本発明は、特許請求の範囲に記載された発明の趣旨に合致するものであればよく、上述の実施形態に限定されるものではない。 Further, the present invention may combine the first embodiment and the second embodiment.
Further, the present invention is not limited to the above-described embodiment as long as it matches the gist of the invention described in the claims.

本発明の第１実施形態に係る排気浄化装置の模式図である。1 is a schematic diagram of an exhaust emission control device according to a first embodiment of the present invention. 本発明の第１実施形態に係る排気浄化装置の特徴的作動を示すフローチャートThe flowchart which shows the characteristic action | operation of the exhaust gas purification apparatus which concerns on 1st Embodiment of this invention. 添加剤（尿素）の噴射量と排気温度及び時間との関係を示すグラフである。It is a graph which shows the relationship between the injection quantity of an additive (urea), exhaust temperature, and time. 添加剤（尿素）の噴射量と排気温度との関係を示す図表である。It is a graph which shows the relationship between the injection quantity of an additive (urea), and exhaust temperature. 本発明の第２実施形態に係る排気浄化装置の模式図である。It is a schematic diagram of the exhaust gas purification apparatus according to a second embodiment of the present invention. 本発明の第２実施形態に係る排気浄化装置の特徴的作動を示すフローチャートThe flowchart which shows the characteristic action | operation of the exhaust gas purification apparatus which concerns on 2nd Embodiment of this invention.

符号の説明Explanation of symbols

１…内燃機関、２…排気管、３…触媒、５…供給弁、６…添加剤タンク、
７…添加剤ポンプ、８…排気温度センサ、９…ＮＯｘセンサ、１０…ＥＣＵ。 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Exhaust pipe, 3 ... Catalyst, 5 ... Supply valve, 6 ... Additive tank,
7 ... Additive pump, 8 ... Exhaust temperature sensor, 9 ... NOx sensor, 10 ... ECU.

Claims (4)

内燃機関から排出される排気の熱を利用して添加剤から還元剤を生成するとともに、排気中に含まれる窒素酸化物を前記還元剤にて還元する排気浄化装置であって、
前記内燃機関から排出される排気の通路を構成する排気管と、
前記排気管に設けられ、排気中の窒素酸化物の還元反応を促進する触媒と、
前記添加剤を前記触媒より排気流れ上流側に供給する供給手段と、
前記排気管を流通する排気の温度を検出する温度検出手段と、
前記供給手段の作動を制御することにより、前記排気管に供給される前記添加剤の供給量を調整する制御手段とを備え、
前記制御手段は、前記温度検出手段が検出した排気温度が、前記添加剤から還元剤を生成するに必要な生成温度未満の場合には、前記添加剤の供給を停止し、一方、前記排気温度が前記生成温度以上の場合には、前記添加剤を供給し、
さらに、前記制御手段は、前記添加剤の供給を開始した時から所定時間が経過した場合に、前記所定時間が経過する前の供給量に比べて、前記添加剤の供給量を低減することを特徴とする排気浄化装置。 An exhaust emission control device that generates a reducing agent from an additive using heat of exhaust gas discharged from an internal combustion engine and reduces nitrogen oxides contained in the exhaust gas with the reducing agent,
An exhaust pipe constituting a passage of exhaust discharged from the internal combustion engine;
A catalyst that is provided in the exhaust pipe and promotes a reduction reaction of nitrogen oxides in the exhaust;
Supply means for supplying the additive to the upstream side of the exhaust flow from the catalyst;
Temperature detecting means for detecting the temperature of the exhaust gas flowing through the exhaust pipe;
Control means for adjusting the supply amount of the additive supplied to the exhaust pipe by controlling the operation of the supply means,
The control means stops the supply of the additive when the exhaust temperature detected by the temperature detection means is lower than the generation temperature necessary for generating the reducing agent from the additive, while the exhaust temperature Is above the production temperature, supply the additive,
Further, the control means reduces the supply amount of the additive when a predetermined time has elapsed from the start of the supply of the additive, compared to the supply amount before the predetermined time has elapsed. A featured exhaust purification device. 内燃機関から排出される排気の熱を利用して添加剤から還元剤を生成するとともに、排気中に含まれる窒素酸化物を前記還元剤にて還元する排気浄化装置であって、
前記内燃機関から排出される排気の通路を構成する排気管と、
前記排気管に設けられ、排気中の窒素酸化物の還元反応を促進する触媒と、
前記添加剤を前記触媒より排気流れ上流側に供給する供給手段と、
前記排気管を流通する排気の温度を検出する温度検出手段と、
前記触媒より排気流れ下流側に設けられ、前記還元剤を検出する還元剤検出手段と、
前記供給手段の作動を制御することにより、前記排気管に供給される前記添加剤の供給量を調整する制御手段とを備え、
前記制御手段は、前記温度検出手段が検出した排気温度が、前記添加剤から還元剤を生成するに必要な生成温度未満の場合には、前記添加剤の供給を停止し、一方、前記排気温度が前記生成温度以上の場合には、前記添加剤を供給し、
さらに、前記制御手段は、前記添加剤の供給を開始した時以降であって、前記還元剤検出手段により所定値以上の前記還元剤が検出された場合に、前記還元剤が検出される前の供給量に比べて、前記添加剤の供給量を低減することを特徴とする排気浄化装置。 An exhaust emission control device that generates a reducing agent from an additive using heat of exhaust gas discharged from an internal combustion engine and reduces nitrogen oxides contained in the exhaust gas with the reducing agent,
An exhaust pipe constituting a passage of exhaust discharged from the internal combustion engine;
A catalyst that is provided in the exhaust pipe and promotes a reduction reaction of nitrogen oxides in the exhaust;
Supply means for supplying the additive to the upstream side of the exhaust flow from the catalyst;
Temperature detecting means for detecting the temperature of the exhaust gas flowing through the exhaust pipe;
A reducing agent detecting means provided on the downstream side of the exhaust flow from the catalyst for detecting the reducing agent;
Control means for adjusting the supply amount of the additive supplied to the exhaust pipe by controlling the operation of the supply means,
The control means stops the supply of the additive when the exhaust temperature detected by the temperature detection means is lower than the generation temperature necessary for generating the reducing agent from the additive, while the exhaust temperature Is above the production temperature, supply the additive,
Further, the control means is after the start of the supply of the additive and before the reducing agent is detected when the reducing agent detecting means detects the reducing agent of a predetermined value or more. An exhaust emission control device that reduces the supply amount of the additive compared to the supply amount. 内燃機関から排出される排気の熱を利用して添加剤から還元剤を生成するとともに、排気中に含まれる窒素酸化物を前記還元剤にて還元する排気浄化装置であって、
前記内燃機関から排出される排気の通路を構成する排気管と、
前記排気管に設けられ、排気中の窒素酸化物の還元反応を促進する触媒と、
前記添加剤を前記触媒より排気流れ上流側に供給する供給手段と、
前記排気管を流通する排気の温度を検出する温度検出手段と、
前記供給手段の作動を制御することにより、前記排気管に供給される前記添加剤の供給量を調整する制御手段とを備え、
前記制御手段は、前記温度検出手段が検出した排気温度が、前記添加剤から還元剤を生成するに必要な生成温度未満の場合には、前記添加剤の供給を停止し、一方、前記排気温度が前記生成温度以上の場合には、前記添加剤を供給し、
さらに、前記制御手段は、前記排気温度が前記生成温度より高い所定温度以上の場合には、前記排気温度が前記生成温度以上、前記所定温度未満のときの供給量に比べて、前記添加剤の供給量を低減することを特徴とする排気浄化装置。 An exhaust emission control device that generates a reducing agent from an additive using heat of exhaust gas discharged from an internal combustion engine and reduces nitrogen oxides contained in the exhaust gas with the reducing agent,
An exhaust pipe constituting a passage of exhaust discharged from the internal combustion engine;
A catalyst that is provided in the exhaust pipe and promotes a reduction reaction of nitrogen oxides in the exhaust;
Supply means for supplying the additive to the upstream side of the exhaust flow from the catalyst;
Temperature detecting means for detecting the temperature of the exhaust gas flowing through the exhaust pipe;
Control means for adjusting the supply amount of the additive supplied to the exhaust pipe by controlling the operation of the supply means,
The control means stops the supply of the additive when the exhaust temperature detected by the temperature detection means is lower than the generation temperature necessary for generating the reducing agent from the additive, while the exhaust temperature Is above the production temperature, supply the additive,
Further, the control means, when the exhaust temperature is equal to or higher than a predetermined temperature higher than the generation temperature, compared with the supply amount when the exhaust temperature is equal to or higher than the generation temperature and lower than the predetermined temperature. An exhaust emission control device characterized by reducing a supply amount. 内燃機関から排出される排気の熱を利用して添加剤から還元剤を生成するとともに、排気中に含まれる窒素酸化物を前記還元剤にて還元する排気浄化装置であって、
前記内燃機関から排出される排気の通路を構成する排気管と、
前記排気管に設けられ、排気中の窒素酸化物の還元反応を促進する触媒と、
前記添加剤を前記触媒より排気流れ上流側に供給する供給手段と、
前記排気管を流通する排気の温度を検出する温度検出手段と、
前記供給手段の作動を制御することにより、前記排気管に供給される前記添加剤の供給量を調整する制御手段とを備え、
前記制御手段は、前記温度検出手段が検出した排気温度が、前記添加剤から還元剤を生成するに必要な生成温度未満の場合には、前記添加剤の供給を停止し、一方、前記排気温度が前記生成温度以上の場合には、前記添加剤を供給し、
さらに、前記制御手段は、前記排気温度が前記生成温度より高い所定温度以上となった場合、及び前記添加剤の供給を開始した時から所定時間が経過した場合のうち少なくとも一方の条件が成立した場合には、いずれかの条件が成立する以前に供給していた供給量に比べて、前記添加剤の供給量を低減することを特徴とする排気浄化装置。 An exhaust emission control device that generates a reducing agent from an additive using heat of exhaust gas discharged from an internal combustion engine and reduces nitrogen oxides contained in the exhaust gas with the reducing agent,
An exhaust pipe constituting a passage of exhaust discharged from the internal combustion engine;
A catalyst that is provided in the exhaust pipe and promotes a reduction reaction of nitrogen oxides in the exhaust;
Supply means for supplying the additive to the upstream side of the exhaust flow from the catalyst;
Temperature detecting means for detecting the temperature of the exhaust gas flowing through the exhaust pipe;
Control means for adjusting the supply amount of the additive supplied to the exhaust pipe by controlling the operation of the supply means,
The control means stops the supply of the additive when the exhaust temperature detected by the temperature detection means is lower than the generation temperature necessary for generating the reducing agent from the additive, while the exhaust temperature Is above the production temperature, supply the additive,
Further, the control means satisfies at least one of a condition in which the exhaust temperature is equal to or higher than a predetermined temperature higher than the generation temperature and a predetermined time has elapsed since the start of the supply of the additive. In this case, the exhaust emission control device is characterized in that the supply amount of the additive is reduced as compared with the supply amount supplied before any of the conditions is satisfied.
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DE112010005468T5 (en) 2010-04-09 2013-01-24 Ud Trucks Corp. Emission control device for a motor

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