JP2005291086A - Exhaust emission control device for engine - Google Patents

Exhaust emission control device for engine Download PDF

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JP2005291086A
JP2005291086A JP2004107181A JP2004107181A JP2005291086A JP 2005291086 A JP2005291086 A JP 2005291086A JP 2004107181 A JP2004107181 A JP 2004107181A JP 2004107181 A JP2004107181 A JP 2004107181A JP 2005291086 A JP2005291086 A JP 2005291086A
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fuel
storage unit
reducing agent
heat medium
engine
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JP4087350B2 (en
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Yasushi Osaku
靖司 尾作
Toshio Kondo
俊男 近藤
Kiyoshi Fukuda
喜代史 福田
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UD Trucks Corp
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UD Trucks 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
    • F01N3/206—Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents
    • F01N3/2066—Selective catalytic reduction [SCR]
    • 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
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/10—Adding substances to exhaust gases the substance being heated, e.g. by heating tank or supply line of the added substance
    • 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
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • F01N2610/1406—Storage means for substances, e.g. tanks or reservoirs
    • 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

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To economically and safely thaw a liquid reducing agent frozen in a tank. <P>SOLUTION: The tank 2 is partitioned in three layers arranged in series, by two partition walls 1. Fuel is stored in one of the layers located outside, a urea water solution used in an NOx reduction catalyst 7 is stored in the other, and an antifreezing solution is stored in the middle layer. Return piping 14 for returning excess fuel from a fuel injection device 12 for pressurizing fuel to directly inject it into a combustion chamber of an engine 5, is allowed to pass through the inside of a heat medium storage part 2c, and a heat exchanger pipe 15 for performing heat exchange between the excess fuel and the antifreezing solution is interposed at the part located in the heat medium storage part 2c, of the return piping 14. The urea water solution in a reducing agent storage part 2b can thereby be indirectly heated using the excess fuel of high temperature from the fuel injection device 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、液体還元剤を用いて、排気中の窒素酸化物（ＮＯｘ）を還元除去するエンジンの排気浄化装置（以下「排気浄化装置」という）に関し、特に、タンク内で凍結した液体還元剤を解凍する技術に関する。   The present invention relates to an exhaust purification device for an engine (hereinafter referred to as “exhaust purification device”) for reducing and removing nitrogen oxide (NOx) in exhaust gas by using a liquid reducing agent, and in particular, a liquid reducing agent frozen in a tank. It is related with the technique which defrosts.

エンジンから排出される排気中のＮＯｘを浄化する排気浄化装置として、特開２０００−２７６２７号公報（特許文献１）に開示されるような排気浄化装置が提案されている。
かかる排気浄化装置は、エンジンの排気通路にＮＯｘ還元触媒を介装し、ＮＯｘ還元触媒の上流側に還元剤を噴射供給することにより、排気中のＮＯｘと還元剤とを触媒還元反応させ、ＮＯｘを無害成分に浄化処理するものである。 As an exhaust gas purification device that purifies NOx in exhaust gas discharged from an engine, an exhaust gas purification device as disclosed in Japanese Patent Laid-Open No. 2000-27627 (Patent Document 1) has been proposed.
Such an exhaust purification device includes a NOx reduction catalyst in the exhaust passage of an engine, and injects and supplies a reducing agent upstream of the NOx reduction catalyst, thereby causing NOx and reducing agent in the exhaust to undergo a catalytic reduction reaction. Is purified to harmless components.

還元反応は、ＮＯｘと反応性のよいアンモニアを用いるもので、還元剤としては、加水分解してアンモニアを容易に発生する尿素水溶液が用いられる。更に、タンクに貯蔵した尿素水溶液が、寒冷期に凍結しないように、タンク内に電気ヒータが設けられている。
特開２０００−２７６２７号公報 The reduction reaction uses ammonia that is highly reactive with NOx, and as the reducing agent, an aqueous urea solution that is easily hydrolyzed to generate ammonia is used. Furthermore, an electric heater is provided in the tank so that the urea aqueous solution stored in the tank does not freeze in the cold season.
JP 2000-27627 A

しかしながら、このような排気浄化装置では、タンクに貯蔵した尿素水溶液等の液体還元剤を加熱するために、電気ヒータにおいて電力が消費されてしまう。このため、電気ヒータの駆動源であるバッテリ及び発電機の容量を増加させる必要があり、コストの上昇や、設置スペースの増大を招いてしまう恐れがあった。
そこで、本発明は以上のような従来の問題点に鑑み、エンジンの燃焼室内へ燃料を直接噴射する燃料噴射装置からの高温の余剰燃料を利用して、タンク内の液体還元剤を間接的に加熱することにより、凍結した液体還元剤を電力を消費せずに解凍できる排気浄化装置を提供することを目的とする。 However, in such an exhaust gas purification apparatus, electric power is consumed in the electric heater to heat the liquid reducing agent such as urea aqueous solution stored in the tank. For this reason, it is necessary to increase the capacity of the battery and the generator that are the drive source of the electric heater, which may increase the cost and increase the installation space.
Therefore, in view of the above-described conventional problems, the present invention indirectly uses liquid surplus fuel in the tank by using high-temperature surplus fuel from a fuel injection device that directly injects fuel into the combustion chamber of the engine. An object of the present invention is to provide an exhaust emission control device capable of thawing a frozen liquid reducing agent without consuming electric power by heating.

このため、請求項１記載の発明は、２枚の隔壁により、内部が直列に並ぶ３つの層に仕切られ、外側に位置する層の一方が燃料を貯蔵する燃料貯蔵部となり、他方が液体還元剤を貯蔵する還元剤貯蔵部となるとともに、中間層が熱媒体を貯蔵する熱媒体貯蔵部となるタンクと、エンジンの排気通路に配設され、前記還元剤貯蔵部に貯蔵される液体還元剤を使用して窒素酸化物を還元浄化する還元触媒と、前記燃料貯蔵部に貯蔵された燃料を加圧して前記エンジンの燃焼室内に直接噴射する燃料噴射装置からの余剰燃料を、前記熱媒体貯蔵部内を経由して前記燃料貯蔵部に戻す戻り配管と、前記戻り配管の前記熱媒体貯蔵部内に位置する部位に介装され、前記余剰燃料と前記熱媒体との間で熱交換を行う熱交換器と、を含んでエンジンの排気浄化装置が構成されることを特徴とする。   Therefore, according to the first aspect of the present invention, the inner wall is divided into three layers arranged in series by the two partition walls, and one of the outer layers is a fuel storage section for storing fuel, and the other is liquid reduction. A liquid reducing agent that is disposed in the exhaust passage of the engine and that is stored in the reducing agent storage unit, the tank being a reducing agent storage unit that stores the agent and an intermediate layer serving as a heating medium storage unit that stores the heat medium A reduction catalyst for reducing and purifying nitrogen oxides using the catalyst, and surplus fuel from a fuel injection device that pressurizes the fuel stored in the fuel storage unit and directly injects the fuel into the combustion chamber of the engine. A return pipe that returns to the fuel storage part via the inside, and a heat exchange that is interposed in a portion of the return pipe that is located in the heat medium storage part and performs heat exchange between the surplus fuel and the heat medium And exhaust gas purification of the engine including Device characterized in that it is configured.

請求項２記載の発明は、前記熱媒体貯蔵部の底部に開閉可能な開口部が備えられたことを特徴とする。
請求項３記載の発明は、前記熱交換器の上流側の戻り配管と前記燃料貯蔵部とを連通する連通路と、前記余剰燃料が、前記熱交換器または前記連通路のいずれか一方に導入されるように、前記余剰燃料の流路を切り換える切換バルブと、を備えたことを特徴とする。 The invention according to claim 2 is characterized in that an opening that can be opened and closed is provided at the bottom of the heat medium storage unit.
According to a third aspect of the present invention, there is provided a communication path that connects the upstream return pipe of the heat exchanger and the fuel storage section, and the surplus fuel is introduced into either the heat exchanger or the communication path. As described above, a switching valve for switching the flow path of the surplus fuel is provided.

請求項４記載の発明は、前記還元剤貯蔵部に貯蔵された液体還元剤の温度を検出する温度センサと、前記温度センサにより検出された液体還元剤の温度が所定値以下であるときのみ、前記余剰燃料が前記熱交換器に導入されるように、前記切換バルブを制御する流路制御手段と、を備えたことを特徴とする。
請求項５記載の発明は、前記熱交換器に、熱交換を促進するフィンを備えたことを特徴とする。 The invention according to claim 4 is a temperature sensor that detects the temperature of the liquid reducing agent stored in the reducing agent storage unit, and only when the temperature of the liquid reducing agent detected by the temperature sensor is a predetermined value or less. And a flow path control means for controlling the switching valve so that the surplus fuel is introduced into the heat exchanger.
The invention according to claim 5 is characterized in that the heat exchanger is provided with fins for promoting heat exchange.

請求項１記載の発明によれば、燃料噴射装置により加圧され高温となっている余剰燃料が戻り配管により熱媒体貯蔵部内に設けられた熱交換器に導入される。これにより、熱媒体貯蔵部内の熱媒体が熱交換器を介して加熱されその温度が上昇する。そして、熱媒体は隔壁を介して還元剤貯蔵部内の液体還元剤と接しているので、熱媒体の温度が上昇することによりこの液体還元剤が間接的に加熱される。従って、還元剤貯蔵部内の液体還元剤が凍結していても、解凍させることができる。   According to the first aspect of the present invention, surplus fuel pressurized by the fuel injection device and having a high temperature is introduced into the heat exchanger provided in the heat medium storage unit by the return pipe. Thereby, the heat medium in a heat medium storage part is heated via a heat exchanger, and the temperature rises. Since the heat medium is in contact with the liquid reducing agent in the reducing agent storage section via the partition wall, the liquid reducing agent is indirectly heated when the temperature of the heat medium rises. Therefore, even if the liquid reducing agent in the reducing agent reservoir is frozen, it can be thawed.

請求項２記載の発明によれば、開口部を開き、熱媒体貯蔵部内の熱媒体を排出させることにより、熱媒体貯蔵部内の熱媒体が大気と入れ替わる。大気は熱媒体より熱伝導性が劣るので、燃料貯蔵部内の燃料から還元剤貯蔵部内の液体還元剤への伝熱が抑制される。そして、液体還元剤が凍結していないときに、開口部を開くことによって、還元剤貯蔵部内の液体還元剤が必要以上に加熱されることを抑制できる。   According to the second aspect of the present invention, the heat medium in the heat medium storage unit is replaced with the atmosphere by opening the opening and discharging the heat medium in the heat medium storage unit. Since the air has lower thermal conductivity than the heat medium, heat transfer from the fuel in the fuel storage unit to the liquid reducing agent in the reducing agent storage unit is suppressed. And when the liquid reducing agent is not frozen, it can suppress that the liquid reducing agent in a reducing agent storage part is heated more than needed by opening an opening part.

請求項３記載の発明によれば、切換バルブを切り換えることにより余剰燃料を熱交換器に導入させずに連通路を通って燃料貯蔵部に戻すことができる。これにより、余剰燃料によって熱媒体を加熱することが防止され、必要がないときに還元剤貯蔵部内の液体還元剤が加熱されることを防止できる。
請求項４記載の発明によれば、還元剤貯蔵部に貯蔵された液体還元剤の温度が所定値以下であるときのみ、余剰燃料が熱交換器に導入されるように切換バルブが自動的に切り換わるので、切換バルブの切換えミスを防止できる。 According to the third aspect of the present invention, by switching the switching valve, it is possible to return the surplus fuel to the fuel storage section through the communication path without introducing it into the heat exchanger. Thereby, it is possible to prevent the heating medium from being heated by the surplus fuel, and it is possible to prevent the liquid reducing agent in the reducing agent storage unit from being heated when it is not necessary.
According to the fourth aspect of the invention, the switching valve is automatically set so that the surplus fuel is introduced into the heat exchanger only when the temperature of the liquid reducing agent stored in the reducing agent storage section is equal to or lower than a predetermined value. Since switching is performed, switching errors of the switching valve can be prevented.

請求項５記載の発明によれば、熱交換器内に導入された余剰燃料によって熱媒体が効率よく加熱されて温度上昇するので、液体還元剤を効率よく加熱することができる。   According to the fifth aspect of the present invention, since the heat medium is efficiently heated by the surplus fuel introduced into the heat exchanger and the temperature rises, the liquid reducing agent can be efficiently heated.

以下、添付された図面を参照して本発明を詳述する。
本発明の排気浄化装置には、図１に示すように、２枚の隔壁１により、内部が直列に並ぶ３つの層に仕切られたタンク２が備えられている。タンク２内の３つの層のうち、外側に位置する層の一方が燃料を貯蔵する燃料貯蔵部２ａとなるとともに、他方が液体還元剤を貯蔵する還元剤貯蔵部２ｂとなる。また、中間層は熱媒体としての不凍液を貯蔵する熱媒体貯蔵部２ｃとなる。還元剤貯蔵部２ｂと熱媒体貯蔵部２ｃとを仕切る隔壁１ａは、燃料貯蔵部２ａと熱媒体貯蔵部２ｃとを仕切る隔壁１ｂより熱伝導性が優れている。更に、熱媒体貯蔵部２ｃの底部には、着脱可能なプラグ３により閉塞された開口部４が設けられている。 Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
As shown in FIG. 1, the exhaust purification apparatus of the present invention includes a tank 2 that is partitioned into three layers that are arranged in series by two partition walls 1. Of the three layers in the tank 2, one of the outer layers is a fuel storage unit 2a for storing fuel, and the other is a reducing agent storage unit 2b for storing a liquid reducing agent. The intermediate layer serves as a heat medium storage unit 2c that stores an antifreeze liquid as a heat medium. The partition wall 1a that partitions the reducing agent storage unit 2b and the heat medium storage unit 2c is more thermally conductive than the partition wall 1b that partitions the fuel storage unit 2a and the heat medium storage unit 2c. Furthermore, the opening part 4 obstruct | occluded with the plug 3 which can be attached or detached is provided in the bottom part of the heat-medium storage part 2c.

エンジン５の排気通路である排気管６には、ＮＯｘを還元浄化するＮＯｘ還元触媒７が配設されている。ＮＯｘ還元触媒７の排気上流には、排気管６内に開口した噴孔から液体還元剤としての尿素水溶液を噴射供給する噴射ノズル８が配設されている。なお、液体還元剤は、尿素水溶液の他にアンモニア水溶液等でもよい。
噴射ノズル８には、還元剤供給装置９によって、尿素水溶液が圧縮空気とともに供給される。還元剤供給装置９には、供給配管１０を介して還元剤貯蔵部２ｂに貯蔵された尿素水溶液が供給される。また、還元剤供給装置９にて排気管６内に噴射供給されなかった余剰の尿素水溶液は戻り配管１１を介して還元剤貯蔵部２ｂ内に戻される。還元剤供給装置９は、図示しないコントローラによってエンジン５の運転状態に基づいて作動制御される。 An exhaust pipe 6 that is an exhaust passage of the engine 5 is provided with a NOx reduction catalyst 7 that reduces and purifies NOx. An injection nozzle 8 for injecting and supplying an aqueous urea solution as a liquid reducing agent from an injection hole opened in the exhaust pipe 6 is disposed upstream of the NOx reduction catalyst 7. The liquid reducing agent may be an aqueous ammonia solution in addition to the aqueous urea solution.
An aqueous urea solution is supplied to the injection nozzle 8 together with compressed air by a reducing agent supply device 9. The reducing agent supply device 9 is supplied with the urea aqueous solution stored in the reducing agent storage unit 2b through the supply pipe 10. Further, the excess urea aqueous solution that has not been injected and supplied into the exhaust pipe 6 by the reducing agent supply device 9 is returned to the reducing agent storage unit 2 b via the return pipe 11. The reducing agent supply device 9 is controlled to operate based on the operating state of the engine 5 by a controller (not shown).

排気管６内に噴射供給された尿素水溶液は、排気熱及び排気中の水蒸気により加水分解され、アンモニアが生成される。生成されたアンモニアは、ＮＯｘ還元触媒７において、排気中のＮＯｘと反応し、水及び無害なガスに浄化される。
エンジン５には、燃料を加圧して燃焼室内に直接噴射する燃料噴射装置１２が設けられている。燃料噴射装置１２には、供給配管１３を介して燃料貯蔵部２ａに貯蔵された燃料が供給される。 The aqueous urea solution injected and supplied into the exhaust pipe 6 is hydrolyzed by the exhaust heat and the water vapor in the exhaust to produce ammonia. The produced ammonia reacts with NOx in the exhaust gas in the NOx reduction catalyst 7 and is purified into water and harmless gas.
The engine 5 is provided with a fuel injection device 12 that pressurizes the fuel and injects it directly into the combustion chamber. The fuel stored in the fuel storage unit 2 a is supplied to the fuel injection device 12 via the supply pipe 13.

燃料噴射装置１２において加圧された燃料のうち、燃焼室内に噴射されなかった余剰燃料を、燃料噴射装置１２から熱媒体貯蔵部２ｃ内を経由して燃料貯蔵部２ａに戻す戻り配管１４が設けられている。
戻り配管１４の熱媒体貯蔵部２ｃ内に位置する部位には、熱交換パイプ１５（熱交換器）が介装されている。熱交換パイプ１５は、内部を通過する燃料と熱媒体貯蔵部２ｃ内の不凍液との間で熱交換させる。 A return pipe 14 is provided for returning surplus fuel that has not been injected into the combustion chamber out of the pressurized fuel in the fuel injection device 12 from the fuel injection device 12 to the fuel storage portion 2a via the heat medium storage portion 2c. It has been.
A heat exchange pipe 15 (heat exchanger) is interposed in a portion of the return pipe 14 located in the heat medium storage unit 2c. The heat exchange pipe 15 exchanges heat between the fuel passing through the inside and the antifreeze liquid in the heat medium storage unit 2c.

また、熱交換パイプ１５の上流側の戻り配管１４と燃料貯蔵部２ａとを連通する連通路１６が設けられている。燃料噴射装置１２からの余剰燃料（以下、戻り燃料という）が、熱交換パイプ１５または連通路１６のいずれか一方に導入されるように、戻り配管１４と連通路１６との分岐部には、戻り燃料の流路を切り換える切換バルブ１７が設けられる。
還元剤貯蔵部２ｂには、その内部に貯蔵された尿素水溶液の温度を検出する温度センサ１８が設けられている。更に、温度センサ１８からの尿素水溶液の温度を入力し、切換バルブ１７の作動制御を行うコントローラ１９が設けられている。コントローラ１９は、還元剤貯蔵部２ｂ内の尿素水溶液の温度が所定値以下であるときのみ、戻り燃料が熱交換パイプ１５に導入されるように切換バルブ１７を制御する。なお、所定値は尿素水溶液の凍結温度より若干高い温度に設定されている。 In addition, a communication path 16 is provided that communicates the return pipe 14 upstream of the heat exchange pipe 15 and the fuel storage unit 2a. In a branch portion between the return pipe 14 and the communication path 16, so that surplus fuel from the fuel injection device 12 (hereinafter referred to as return fuel) is introduced into either the heat exchange pipe 15 or the communication path 16, A switching valve 17 for switching the return fuel flow path is provided.
The reducing agent storage unit 2b is provided with a temperature sensor 18 for detecting the temperature of the urea aqueous solution stored therein. Further, a controller 19 is provided that inputs the temperature of the urea aqueous solution from the temperature sensor 18 and controls the operation of the switching valve 17. The controller 19 controls the switching valve 17 so that the return fuel is introduced into the heat exchange pipe 15 only when the temperature of the aqueous urea solution in the reducing agent storage unit 2b is equal to or lower than a predetermined value. The predetermined value is set to a temperature slightly higher than the freezing temperature of the urea aqueous solution.

以上のような構成によれば、還元剤貯蔵部２ｂ内の尿素水溶液の温度が所定値以下であるときは、戻り燃料が、熱交換パイプ１５に導入される。このとき、燃料噴射装置１２により加圧されることによって戻り燃料は高温になっているので、熱媒体貯蔵部２ｃ内の不凍液は熱交換パイプ１５を介して加熱されその温度が上昇する。そして、不凍液は隔壁１を介して還元剤貯蔵部２ｂ内の尿素水溶液及び燃料貯蔵部２ａ内の燃料に夫々接しているとともに、還元剤貯蔵部２ｂと熱媒体貯蔵部２ｃとを仕切る隔壁１ａが燃料貯蔵部２ａと熱媒体貯蔵部２ｃとを仕切る隔壁１ｂより熱伝導性が優れているので、尿素水溶液が間接的にかつ優先して加熱される。これにより、還元剤貯蔵部２ｂ内の尿素水溶液が凍結していても、解凍させることができる。   According to the above configuration, the return fuel is introduced into the heat exchange pipe 15 when the temperature of the urea aqueous solution in the reducing agent storage unit 2b is equal to or lower than a predetermined value. At this time, since the return fuel becomes high temperature by being pressurized by the fuel injection device 12, the antifreeze liquid in the heat medium storage unit 2c is heated via the heat exchange pipe 15, and the temperature rises. The antifreeze liquid is in contact with the urea aqueous solution in the reducing agent storage unit 2b and the fuel in the fuel storage unit 2a through the partition wall 1, and the partition wall 1a partitioning the reducing agent storage unit 2b and the heat medium storage unit 2c is provided. Since the thermal conductivity is superior to the partition wall 1b that partitions the fuel storage unit 2a and the heat medium storage unit 2c, the aqueous urea solution is indirectly and preferentially heated. Thereby, even if the urea aqueous solution in the reducing agent storage part 2b is frozen, it can be thawed.

また、熱交換パイプ１５における熱交換によって戻り燃料が冷却されるので、燃料貯蔵部２ａ内の燃料の温度上昇を抑制できる。これにより、エンジン５の燃焼室内に噴射される燃料の温度上昇が抑制されるので、燃費を向上させることができる。
還元剤貯蔵部２ｂ内の尿素水溶液の温度が所定値より高いときには、戻り燃料は連通路１６に導入されるので、戻り燃料によって還元剤貯蔵部２ｂ内の尿素水溶液が所定値以上の温度となるまで加熱されることを防止できる。所定値は、尿素水溶液の凍結温度より若干高い温度に設定されているので、解凍されている尿素水溶液を加熱することがなく、必要以上に尿素水溶液が加熱されることを抑制できる。 In addition, since the return fuel is cooled by heat exchange in the heat exchange pipe 15, an increase in the temperature of the fuel in the fuel storage unit 2a can be suppressed. Thereby, since the temperature rise of the fuel injected into the combustion chamber of the engine 5 is suppressed, fuel consumption can be improved.
When the temperature of the urea aqueous solution in the reducing agent storage unit 2b is higher than a predetermined value, the return fuel is introduced into the communication path 16, so that the urea aqueous solution in the reducing agent storage unit 2b becomes a temperature equal to or higher than the predetermined value by the return fuel. Can be prevented from being heated. Since the predetermined value is set to a temperature slightly higher than the freezing temperature of the urea aqueous solution, it is possible to prevent the urea aqueous solution from being heated more than necessary without heating the thawed urea aqueous solution.

なお、本実施形態では、切換バルブ１７を尿素水溶液の温度に基づいて自動的に切り換えるが、手動で切換バルブ１７を切り換えてもよい。
また、尿素水溶液が凍結していないときには、熱媒体貯蔵部２ｃ内の不凍液を開口部４から排出させるとよい。これにより、熱媒体貯蔵部２ｃ内の不凍液が大気と入れ替わる。大気は不凍液より熱伝導性が劣るので、燃料貯蔵部２ａ内の燃料から還元剤貯蔵部２ｂ内の尿素水溶液への伝熱が抑制され、還元剤貯蔵部２ｂ内の尿素水溶液が必要以上に加熱されることを更に抑制できる。 In this embodiment, the switching valve 17 is automatically switched based on the temperature of the urea aqueous solution, but the switching valve 17 may be switched manually.
In addition, when the urea aqueous solution is not frozen, the antifreeze liquid in the heat medium storage unit 2 c may be discharged from the opening 4. Thereby, the antifreeze in the heat medium storage unit 2c is replaced with the atmosphere. Since the air has lower thermal conductivity than the antifreeze, heat transfer from the fuel in the fuel storage unit 2a to the urea aqueous solution in the reducing agent storage unit 2b is suppressed, and the urea aqueous solution in the reducing agent storage unit 2b is heated more than necessary. This can be further suppressed.

更に、熱交換パイプ１５に熱交換を促進させるフィンを設けるとよい。これにより、不凍液が戻り燃料によって効率よく加熱されて温度上昇するので、尿素水溶液を効率よく加熱することができる。   Furthermore, it is good to provide the heat exchange pipe 15 with the fin which accelerates | stimulates heat exchange. As a result, the antifreeze is efficiently heated by the return fuel and the temperature rises, so that the aqueous urea solution can be efficiently heated.

本発明の排気浄化装置の構成図Configuration diagram of the exhaust emission control device of the present invention

符号の説明Explanation of symbols

１ 隔壁
２ タンク
２ａ 燃料貯蔵部
２ｂ 還元剤貯蔵部
２ｃ 熱媒体貯蔵部
４ 開口部
５ エンジン
６ 排気管
７ ＮＯｘ還元触媒
８ 噴射ノズル
９ 還元剤供給装置
１２ 燃料噴射装置
１４ 戻り配管
１５ 熱交換パイプ
１６ 連通路
１７ 切換バルブ
１８ 温度センサ
１９ コントローラ DESCRIPTION OF SYMBOLS 1 Partition 2 Tank 2a Fuel storage part 2b Reductant storage part 2c Heat medium storage part 4 Opening part 5 Engine 6 Exhaust pipe 7 NOx reduction catalyst 8 Injection nozzle 9 Reductant supply apparatus 12 Fuel injection apparatus 14 Return piping 15 Heat exchange pipe 16 Communication path 17 Switching valve 18 Temperature sensor 19 Controller

Claims (5)

２枚の隔壁により、内部が直列に並ぶ３つの層に仕切られ、外側に位置する層の一方が燃料を貯蔵する燃料貯蔵部となり、他方が液体還元剤を貯蔵する還元剤貯蔵部となるとともに、中間層が熱媒体を貯蔵する熱媒体貯蔵部となるタンクと、
エンジンの排気通路に配設され、前記還元剤貯蔵部に貯蔵される液体還元剤を使用して窒素酸化物を還元浄化する還元触媒と、
前記燃料貯蔵部に貯蔵された燃料を加圧して前記エンジンの燃焼室内に直接噴射する燃料噴射装置からの余剰燃料を、前記熱媒体貯蔵部内を経由して前記燃料貯蔵部に戻す戻り配管と、
前記戻り配管の前記熱媒体貯蔵部内に位置する部位に介装され、前記余剰燃料と前記熱媒体との間で熱交換を行う熱交換器と、
を含んで構成されることを特徴とするエンジンの排気浄化装置。 The two partition walls are divided into three layers arranged in series, and one of the outer layers serves as a fuel storage unit for storing fuel, and the other serves as a reducing agent storage unit for storing a liquid reducing agent. A tank serving as a heat medium storage unit in which the intermediate layer stores the heat medium;
A reduction catalyst that is disposed in the exhaust passage of the engine and that reduces and purifies nitrogen oxides using a liquid reducing agent stored in the reducing agent storage unit;
A return pipe for returning surplus fuel from a fuel injection device that pressurizes the fuel stored in the fuel storage unit and directly injects the fuel into the combustion chamber of the engine to the fuel storage unit via the heat medium storage unit;
A heat exchanger that is interposed in a portion of the return pipe located in the heat medium storage unit, and performs heat exchange between the surplus fuel and the heat medium;
An exhaust emission control device for an engine characterized by comprising: 前記熱媒体貯蔵部の底部に開閉可能な開口部が備えられたことを特徴とする請求項１に記載のエンジンの排気浄化装置。   The engine exhaust gas purification apparatus according to claim 1, wherein an opening that can be opened and closed is provided at a bottom of the heat medium storage unit. 前記熱交換器の上流側の戻り配管と前記燃料貯蔵部とを連通する連通路と、
前記余剰燃料が、前記熱交換器または前記連通路のいずれか一方に導入されるように、前記余剰燃料の流路を切り換える切換バルブと、
を備えたことを特徴とする請求項１または２に記載のエンジンの排気浄化装置。 A communication path communicating the return pipe upstream of the heat exchanger and the fuel storage unit;
A switching valve for switching the flow path of the surplus fuel so that the surplus fuel is introduced into either the heat exchanger or the communication path;
The exhaust emission control device for an engine according to claim 1 or 2, further comprising: 前記還元剤貯蔵部に貯蔵された液体還元剤の温度を検出する温度センサと、
前記温度センサにより検出された液体還元剤の温度が所定値以下であるときのみ、前記余剰燃料が前記熱交換器に導入されるように、前記切換バルブを制御する流路制御手段と、
を備えたことを特徴とする請求項３に記載のエンジンの排気浄化装置。 A temperature sensor for detecting the temperature of the liquid reducing agent stored in the reducing agent storage unit;
A flow path control means for controlling the switching valve so that the surplus fuel is introduced into the heat exchanger only when the temperature of the liquid reducing agent detected by the temperature sensor is equal to or lower than a predetermined value;
The exhaust emission control device for an engine according to claim 3, comprising: 前記熱交換器に、熱交換を促進するフィンを備えたことを特徴とする請求項１〜４のいずれか１つに記載のエンジンの排気浄化装置。   The engine exhaust gas purification apparatus according to any one of claims 1 to 4, wherein the heat exchanger includes a fin for promoting heat exchange.
JP2004107181A 2004-03-31 2004-03-31 Engine exhaust purification system Expired - Fee Related JP4087350B2 (en)

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US8857160B2 (en) 2009-01-09 2014-10-14 Robert Bosch Gmbh Reservoir for accommodating an aqueous solution
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