JP2722982B2 - Exhaust gas purification system for an internal combustion engine - Google Patents

Exhaust gas purification system for an internal combustion engine

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Publication number
JP2722982B2
JP2722982B2 JP4526993A JP4526993A JP2722982B2 JP 2722982 B2 JP2722982 B2 JP 2722982B2 JP 4526993 A JP4526993 A JP 4526993A JP 4526993 A JP4526993 A JP 4526993A JP 2722982 B2 JP2722982 B2 JP 2722982B2
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reducing agent
exhaust
exhaust gas
internal combustion
combustion engine
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JP4526993A
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JPH06257426A (en )
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信也 広田
康 荒木
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トヨタ自動車株式会社
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【発明の詳細な説明】 DETAILED DESCRIPTION OF THE INVENTION

【0001】 [0001]

【産業上の利用分野】本発明は、内燃機関の排気浄化装置に関し、詳細には、内燃機関の排気中のNO Xを効果的に除去可能な排気浄化装置に関する。 BACKGROUND OF THE INVENTION This invention relates to an exhaust purifying apparatus for an internal combustion engine, in particular, to effectively removable exhaust purification apparatus NO X in the exhaust gas of an internal combustion engine.

【0002】 [0002]

【従来の技術】この種の排気浄化装置の例としては、例えば特開昭62─106826号公報に開示されたものがある。 Examples of the Related Art This kind of exhaust purification device, is disclosed in JP Sho 62─106826. 同公報の装置は、ディーゼル機関の排気通路に酸素の存在下でNO Xを吸収する吸収剤(触媒)を収容した容器を接続し、このNO X吸収剤に排気中のNO X The apparatus of this publication is to connect a vessel containing an absorbent (catalyst) for absorbing NO X in the presence of oxygen in an exhaust passage of a diesel engine, NO X in the exhaust gas to the the NO X absorbent
を吸収させ、該吸収剤のNO X吸収効率が低下した時に容器への排気の流入を遮断して容器内に気体状の還元剤を供給することにより還元雰囲気を生成して吸収剤からNO Xを放出させるとともに、放出されたNO Xを還元浄化するものである。 To absorb, NO from the absorbent to produce a reducing atmosphere by NO X absorption efficiency of the absorbent is supplied gaseous reducing agent into the container to block the flow of exhaust gas to the container when dropped X together to release, it is to reduce and purify the released NO X.

【0003】 [0003]

【発明が解決しようとする課題】上記特開昭62─10 The object of the invention is to be Solved by the above-mentioned JP-A-62─10
6826号公報の装置は、NO X吸収剤を収容する容器上流側に設けた遮断弁を用いて容器への排気の流入を遮断して、排気中に含まれる酸素が流入することを防止してから容器内に還元剤を供給することにより、容器内を還元雰囲気にしてNO X吸収剤のNO X放出、還元浄化(以下、「再生」という)を行っている。 6826 JP devices, shut off the flow of exhaust gas into the vessel using a shut-off valve provided in the container upstream housing the the NO X absorbent, thereby preventing the oxygen contained in the exhaust gas flowing by supplying the reducing agent into the container from, and the inside of the container to a reducing atmosphere the NO X absorbent of the NO X emission reduction purification (hereinafter, referred to as "regeneration") is performed. このため、上記公報の装置ではエンジン運転中にNO X吸収剤の再生操作を行う場合、排気をNO X吸収剤容器をバイパスして流す必要が生じ、排気中のNO Xが浄化されずに大気に放出される問題が生じる。 Therefore, the apparatus of the above publication when reproducing operation of the NO X absorbent during the engine operation, the exhaust must have caused to flow by bypassing the the NO X absorbent vessel, air in the NO X in the exhaust gas without being purified there is a problem that is released.

【0004】また、これを防止するためには、NO X吸収剤を収容した複数の容器をエンジン排気通路に並列に接続して、1つのNO X吸収剤の再生操作実行中でも他のNO X吸収剤を通して排気を浄化することができるようにする必要があり、複数の容器を設けるために装置が大型化し、車両用エンジンに使用するような場合には搭載性が悪化する問題がある。 [0004] In order to prevent this, a plurality of containers accommodating the the NO X absorbent are connected in parallel to the engine exhaust passage, the other of the NO X absorbent even during the regenerating operation of one of the NO X absorbent You need to be able to purify the exhaust through agent, bulky device for providing a plurality of containers, if such use in vehicle engine has a problem that mountability becomes worse.

【0005】また、NO X吸収剤の容器への排気流入を止める前記遮断弁は比較的長時間開弁保持された後、上記再生操作時にのみ短時間閉弁作動する間欠作動状態になるため、排気中の微粒子や油分等により可動部分がスティックして作動不良を生じやすい問題がある。 Further, after the shut-off valve is a relatively long period of time is the open-valve state hold stop exhaust flowing into the container of the NO X absorbent, to become intermittent operation state only briefly closed operation during the reproduction operation, moving parts by fine particles or oil or the like in the exhaust gas is a problem-prone malfunction and stick. 一方、 on the other hand
前記の装置大型化の問題を回避するために、例えばNO To avoid the problem of device size of the, for example, NO
X吸収剤に流入する排気を完全に遮断するのではなく、 Rather than completely block the exhaust gas flowing into the X absorbent,
流入する排気の流量を所定流量まで低減して還元剤を供給することにより、単一のNO X吸収剤容器を用いながら再生操作時にもエンジン排気の流れを確保するようにした構成も可能である。 By the flow rate of the exhaust gas flowing by reducing to a predetermined flow rate to supply the reducing agent, it is also possible configurations so as to ensure the flow of the engine exhaust even during reproduction operation while using a single of the NO X absorbent container .

【0006】しかし、この場合にはNO X吸収剤の再生操作時に、排気通路に設けた絞り弁等によりエンジンの排気流量全体を絞る必要が生じるためエンジンの出力が急激に低下し、車両走行中に運転性が悪化する問題がある。 However, during the regenerating operation of the NO X absorbent in this case, the output of the engine for it is necessary to narrow the entire exhaust flow of an engine by a diaphragm valve or the like provided in the exhaust passage decreases rapidly, while the vehicle is traveling there is a problem that operability is deteriorated. 本発明は、上記問題に鑑み、装置の小型化が可能であり、しかも車両の運転性への影響や可動部分のスティックが生じることを防止可能な内燃機関の排気浄化装置を提供することを目的としている。 The present invention is the view of the problems, it is possible to reduce the size of the apparatus, moreover aims to provide an exhaust purification device capable of preventing an internal combustion engine that stick effects and moving parts of the vehicle drivability occurs It is set to.

【0007】 [0007]

【課題を解決するための手段】本発明によれば、機関排気通路に配置され流入排気の空燃比がリーンのときにN According to the present invention SUMMARY OF], when the air-fuel ratio of the inflowing exhaust is disposed to the engine exhaust passage is lean N
Xを吸収し流入排気の酸素濃度が低下したときに吸収したNO Xを放出するNO X吸収剤と、前記NO X吸収剤への排気の流入を遮断してNO X吸収剤に還元剤を供給しNO X吸収剤から吸収したNO Xを放出させるとともに放出されたNO Xを還元浄化する還元剤導入手段とを備えた内燃機関の排気浄化装置において、前記NO X And the NO X absorbent concentration of oxygen absorbs O X inflow exhaust emits the absorbed NO X when reduced, a reducing agent to the NO X absorbent by blocking the flow of exhaust gas into the the NO X absorbent in the exhaust purification apparatus for an internal combustion engine having a reducing agent introduction means for reducing and purifying the released NO X with the release of NO X absorbed from the supply to the NO X absorbent, the NO X
吸収剤は排気が通過する複数の独立した流路を有する担体のそれぞれの流路壁面に担持され、それぞれの流路を通過する排気中のNO Xの吸収をおこない、前記還元剤導入手段は前記担体の前記複数の排気流路のうち一時に一部の流路ずつ排気の流入の遮断及び還元剤の供給を行うことにより順次全部の排気流路の壁面のNO X吸収剤からのNO Xの放出と還元浄化とを行うことを特徴とする内燃機関の排気浄化装置が提供される。 Absorber is supported on each of the channel wall surface of the carrier having a plurality of independent flow path through the exhaust performs absorption of the NO X in the exhaust gas passing through the flow paths, the reducing agent introducing means the of the NO X from the NO X absorbent wall of said plurality of exhaust flow path exhaust passage temporarily sequentially whole by performing blocking and supply of the reducing agent flowing into the exhaust by a portion of the flow path of the carrier exhaust purifying apparatus for an internal combustion engine and performs release and the reduction purification is provided.

【0008】 [0008]

【作用】還元剤導入手段は、NO X吸収剤担体の複数の流路のうち一時に一部の流路のみについて排気の流入の遮断と還元剤の供給を行う。 [Action] reducing agent introducing means, for supplying blocking and reducing agent temporarily exhaust the only part of the channel inlet of the plurality of channels of the NO X absorbent carrier. NO X吸収剤の全部の流路が同時に遮断されることがないため、排気は遮断されていない他の流路を通って流れ、流路壁面のNO X吸収剤により排気中のNO Xが浄化される。 Because all of the flow path of the NO X absorbent is prevented from being cut off at the same time, the exhaust flows through the other flow path is not blocked, NO X in the exhaust gas by the NO X absorbent in the passage walls clean It is. また、還元剤導入手段は一時に一部の流路ずつ順次排気の遮断と還元剤の供給を行うので、一定の時間が経過すると全部の流路壁面のNO X吸収剤の再生が完了する。 The reducing agent introducing means since the supply of blocking and reducing agent temporarily sequential exhaust by part of the flow passage, the regeneration of the NO X absorbent of all the flow path walls after a certain amount of time to complete.

【0009】 [0009]

【実施例】以下、添付図面を用いて本発明の実施例について説明する。 EXAMPLES The following examples of the present invention will be described with reference to the accompanying drawings. 図1から図3は本発明の排気浄化装置の一実施例を示し、図において3は図示しないエンジンの排気管、5はNO X吸収剤の担体を示す。 Figures 1 to 3 show an embodiment of an exhaust gas purifying apparatus of the present invention, an exhaust pipe of an engine 3 is not shown in FIG, 5 shows the carrier of the NO X absorbent. 本実施例ではNO X吸収剤担体5は金属、セラミック等の耐熱材料を円筒形状に成形し、軸線方向に多数の細い排気流路5b The NO X absorbent carrier 5 in this embodiment is formed of metal, a heat-resistant material such as ceramic in a cylindrical shape, many fine exhaust passage 5b in the axial direction
を設けた、通常の触媒のモノリス担体と同様な構造とされており、それぞれの排気流路5bの壁面には後述するNO X吸収剤が担持されている。 Was provided, which is a monolithic carrier and a similar structure of the conventional catalysts, the NO X absorbent to be described later to the wall surface of the respective exhaust passage 5b is supported. また、本実施例ではN Further, in the present embodiment N
X吸収剤担体5は排気管3内に軸線回りに回転可能に保持され、排気管壁を貫通する駆動軸7により回転駆動されるようになっている。 O X absorbent carrier 5 is rotatably held about an axis in the exhaust pipe 3, and is rotated by a driving shaft 7 passing through the exhaust pipe wall.

【0010】また、8で示すのは、駆動軸7に接続された直流サーボモータ等の適宜な形式の可変速度モータであり、後述するエンジン制御回路(ECU)20からの制御信号に応じた回転速度で駆動軸7及びNO X吸収剤担体5を回転駆動するようになっている。 [0010] Shown in 8 is a variable speed motor suitable form such as a DC servo motor connected to the drive shaft 7, rotated in response to a control signal from an engine control circuit (ECU) 20 to be described later It adapted to rotate the drive shaft 7 and the NO X absorbent carrier 5 at a rate. 11で示すのは、NO X吸収剤担体5に還元剤を供給する還元剤供給装置である。 Shown 11 is a reducing agent supply device supplying a reducing agent to the NO X absorbent carrier 5. 還元剤供給装置11は排気管3内面にに対して固定された還元剤供給部12と、還元剤供給源13 The reducing agent supply device 11 and a fixed reducing agent supply unit 12 with respect to the exhaust pipe 3 inside surface, the reducing agent supply source 13
及び流量制御弁14とを備えている。 And a flow control valve 14. 本実施例では還元剤として水素、一酸化炭素等の還元性気体、プロパン、 Reducing gas, propane hydrogen, carbon monoxide as the reducing agent in this embodiment,
プロピレン、ブタン等の液体又は気体の炭化水素等が使用可能であり、還元剤は加圧容器等の還元剤供給源13 Propylene, hydrocarbons such as liquid or gas such as butane is available and reducing agent, such as a pressurized vessel reducing agent supply source 13
からECU20の制御信号に応じて作動する流量制御弁14により流量調整されて供給部12に供給される。 Is the flow rate adjusted by the flow rate control valve 14 that operates in accordance with a control signal ECU20 from being supplied to the supply portion 12.

【0011】図1に示すように還元剤供給部12はNO [0011] reducing agent supply unit 12 as shown in FIG. 1 is NO
X吸収剤担体5の上流側端面5aの一部分を覆う扇形をしており、図3にその断面を示すようにNO X吸収剤担体5に対向する部分には縁部12aと、この縁部12a Has a sector covering a portion of the upstream-side end face 5a of the X absorbent carrier 5, and the edge portion 12a at a portion facing the NO X absorbent carrier 5 as shown in the cross section in FIG. 3, the edge 12a
により周囲を囲まれた凹部12bが形成されており、還元剤は固定配管15を介して凹部12b内に注入される。 A recess 12b which is surrounded is formed by, the reducing agent is injected into the recess 12b through the fixed pipe 15. また、縁部12aはNO X吸収剤担体5の上流側端面5aと微小な間隙を保って配置されており、凹部12 Also, the edge 12a is disposed while maintaining the upstream-side end surface 5a with a small gap of the NO X absorbent carrier 5, the recess 12
b内への排気ガスの侵入と凹部12b内の還元剤の排気管3内への流出を実質的に阻止している。 It is substantially prevented from flowing out to the reducing agent the exhaust pipe 3 in the invasion and the recess 12b of the exhaust gas into the b.

【0012】従って、還元剤供給部12に覆われた部分の担体5の流路5bには排気の流入が遮断されるとともに凹部12aから還元剤が供給される。 Accordingly, the reducing agent is supplied from the recessed portion 12a together with the inflow of the exhaust gas is blocked in the flow path 5b of the support 5 of the portion covered by the reducing agent supply unit 12. また、担体5が回転すると還元剤供給部12は流路5bを順次覆って行き、担体5が一回転する間に全部の流路5bの排気流入の遮断と還元剤の供給が行われる。 The reducing agent supply unit 12 and the carrier 5 is rotated went sequentially over the flow path 5b, the supply of blocking a reducing agent in the exhaust flow of the whole of the flow path 5b while the carrier 5 makes one rotation is performed. 図2に16で示すのは、NO X吸収剤担体5の下流側に配置された排気温度検出用の排気温度センサである。 Shown in FIG. 2 to 16, an exhaust temperature sensor for exhaust gas temperature detection which is disposed on the downstream side of the NO X absorbent carrier 5.

【0013】また、図2に20で示すのはエンジンの制御回路(ECU)である。 [0013] Shown at 20 in FIG. 2 is a control circuit of the engine (ECU). ECU20はCPU、RA ECU20 is CPU, RA
M、ROM、及び入力ポート、出力ポートを相互に双方向バスで接続した構成の公知のディジタルコンピュータからなり、エンジンの燃料噴射量制御等の基本制御を行うほか、本実施例では可変速度モータ8の速度制御と還元剤供給装置11の流量制御弁14の開度制御等のNO M, ROM, and an input port, mutually consist known digital computer configuration connected by a bidirectional bus output port, in addition to performing the basic control such as fuel injection amount control of the engine, in this embodiment a variable speed motor 8 NO speed control of the opening degree control of the flow control valve 14 of the reducing agent supply device 11
X吸収剤再生操作の制御を行っている。 It is doing the control of X absorbent playback operation. これらの制御のため、ECU20の入力ポートには排気温度センサ16 For these controls, the input port of the ECU20 exhaust temperature sensor 16
から排気温度信号が入力されている他、エンジン回転数、アクセル開度等の信号がそれぞれ図示しないセンサから入力されている。 Other that exhaust temperature signal is inputted from the engine speed, the signal of an accelerator opening degree is inputted from a sensor (not shown), respectively.

【0014】次に、本発明に使用するNO X吸収剤のN [0014] Next, N of the NO X absorbent for use in the present invention
X吸放出作用について説明する。 O X absorbing and releasing the operation will be explained. NO X吸収剤は例えばアルミナ等の担持層を使用し、この担持層に例えばカリウムK,ナトリウムNa ,リチウムLi ,セシウムC The NO X absorbent is used a supported layer, for example alumina or the like, the carrier layer, for example, potassium K, sodium Na, lithium Li, cesium C
s のようなアルカリ金属、バリウムBa , カルシウムC Alkali metals such as s, barium Ba, calcium C
a のようなアルカリ土類、ランタンLa ,イットリウムYのような希土類から選ばれた少なくとも一つと、白金Pt のような貴金属とが担持されている。 Alkaline earth such as a, lanthanum La, at least the one selected from rare earth such as yttrium Y, and a noble metal such as platinum Pt are carried. 本実施例では、担体5のそれぞれの流路5bの壁面には上記成分を担持したアルミナ等の担持層がコーティングされており、NO X吸収剤層を形成している。 In this embodiment, the wall surface of the flow paths 5b of the support 5 is supported layer such as alumina carrying the component is coated, to form a the NO X absorbent layer. このNO X吸収剤は流入する排気の空燃比がリーンの場合にはNO Xを吸収し、酸素濃度が低下するとNO Xを放出するNO Xの吸放出作用を行う。 This the NO X absorbent absorbs NO X in the case the air-fuel ratio of the exhaust gas flowing is lean, the oxygen concentration is carried out to absorbing and releasing action of the NO X that releases NO X when lowered.

【0015】なお、上述の排気空燃比とは、ここではN [0015] Note that the exhaust air-fuel ratio described above, where N
X吸収剤の上流側の排気通路やエンジン燃焼室、吸気通路等にそれぞれ供給された空気量の合計と燃料の合計の比を意味するものとする。 O X absorbent upstream side of the exhaust passage and the engine combustion chamber is intended to mean the ratio of the total sum and the fuel respectively supplied amount of air in the intake passage or the like. 従って、NO X吸収剤の上流側排気通路に燃料、還元剤または空気が供給されない場合には排気空燃比はエンジンの運転空燃比(エンジン燃焼室内の燃焼における空燃比)と等しくなる。 Therefore, the fuel in the upstream side exhaust passage of the NO X absorbent, the exhaust air-fuel ratio in the case of the reducing agent or air is not supplied is equal to the operating air-fuel ratio of the engine (air-fuel ratio in the combustion in the engine combustion chamber).

【0016】上記吸放出作用の詳細なメカニズムについては明らかでない部分もある。 [0016] there is also a part not clear about the detailed mechanism of the absorption and release action. しかし、この吸放出作用は図4に示すようなメカニズムで行われているものと考えられる。 However, this absorbing and releasing action is considered to be performed by the mechanism shown in FIG. 次にこのメカニズムについて担体上に白金P Next platinum P This mechanism on the support
t およびバリウムBa を担持させた場合を例にとって説明するが他の貴金属、アルカリ金属、アルカリ土類、希土類を用いても同様なメカニズムとなる。 Although will be described as an example case of carrying t and barium Ba other noble metals, alkali metals, alkaline earth, a similar mechanism may be used with rare earth.

【0017】すなわち、流入排気がかなりリーンになると流入排気中の酸素濃度が大幅に増大し、図4(A) に示されるようにこれら酸素O 2がO 2 -またはO 2-の形で白金Pt の表面に付着する。 [0017] That is, the oxygen concentration in the inflowing exhaust gas and the inflow exhaust gas becomes considerably lean, greatly increased, these oxygen O 2 is O 2 as shown in FIG. 4 (A) - platinum or O 2- in the form adhere to the Pt surface. 一方、流入排気中のNOは白金Pt の表面上でこのO 2 On the other hand, NO in the inflowing exhaust gas is the O 2 on the surface of the platinum Pt -またはO 2-と反応し、N - or it reacts with O 2-, N
2となる(2NO+O 2 →2NO 2 ) 。 O 2 and made (2NO + O 2 → 2NO 2 ). 次いで生成されたNO 2の一部は白金Pt上で酸化されつつ吸収剤内に吸収されて酸化バリウムBaOと結合しながら、図4 Then part of the produced NO 2 while bonding with the barium oxide BaO is absorbed into the absorbent while being oxidized on the platinum Pt, 4
(A) に示されるように硝酸イオンNO 3 -の形で吸収剤内に拡散する。 Nitrate ions NO as shown in (A) 3 - is diffused in the absorbent in the form of. このようにしてNO XがNO X吸収剤内に吸収される。 In this way, NO X is absorbed in the NO X absorbent.

【0018】従って、流入排気中の酸素濃度が高い限り白金Pt の表面でNO 2が生成され、吸収剤のNO X吸収能力が飽和しない限りNO 2が吸収剤内に吸収されて硝酸イオンNO 3 -が生成される。 [0018] Thus, NO 2 is produced on the surface of the platinum Pt so long as the oxygen concentration is high in the inflowing exhaust gas, so long as NO 2 to NO X absorbing capacity of the absorbent is not saturated is absorbed in the absorbent and nitrate ions NO 3 - is generated. これに対して流入排気中の酸素濃度が低下してNO 2の生成量が減少すると反応が逆方向(NO 3 - →NO 2 )に進み、こうして吸収剤内の硝酸イオンNO 3 -がNO 2の形で吸収剤から放出される。 In contrast the oxygen concentration decreases and the amount of NO 2 is reduced by reaction backward in the inflowing exhaust gas (NO 3 - → NO 2) proceeds to thus of the absorbent and nitrate ions NO 3 - is NO 2 It is in the form of release from the absorbent. すなわち、流入排気中の酸素濃度が低下するとNO X吸収剤からNO Xが放出されることになる。 That is, the oxygen concentration in the inflowing exhaust gas is NO X is released from the NO X absorbent when lowered.

【0019】一方、流入排気中にHC、CO等の還元成分が存在すると、これらの成分は白金Pt 上の酸素O 2 Meanwhile, HC in the inflowing exhaust, if reducing components such as CO are present, these components oxygen O 2 on the platinum Pt
-またはO 2-と反応して酸化され、排気中の酸素を消費して排気中の酸素濃度を低下させる。 - or is reacted with oxide and O 2-, lowering the oxygen concentration in the exhaust to consume oxygen in the exhaust. また、排気中の酸素濃度低下によりNO X吸収剤から放出されたNO 2は図4(B) に示すようにHC,COと反応して還元される。 Further, NO 2 released from the NO X absorbent is reduced by reacting HC, and CO as shown in FIG. 4 (B) by the oxygen concentration decreases in the exhaust gas. このようにして白金Pt の表面上にNO 2が存在しなくなると吸収剤から次から次へとNO 2が放出される。 Such is NO 2 on the surface of the platinum Pt, the NO 2 is successively released from the absorbent longer exists Next the following.

【0020】すなわち、流入排気中のHC,COは、まず白金Pt 上のO 2 -またはO 2-とただちに反応して酸化され、次いで白金Pt 上のO 2 -またはO 2-が消費されてもまだHC,COが残っていればこのHC,COによって吸収剤から放出されたNO Xが還元される。 [0020] That is, HC in the inflowing exhaust gas, CO, first O 2 on the platinum Pt - immediately react with oxidized or O 2-, and then on the platinum Pt O 2 - or O 2- is consumed the HC, NO X released from the absorbent by CO is reduced even yet HC, any remaining CO is. 本実施例では、リーン空燃比の燃焼を行うエンジンが使用されているため、通常運転時にNO X吸収剤担体5の流路5bを通過する排気の空燃比はリーンであり、流路5b In this embodiment, since the engine for combustion of lean air-fuel ratio is used, the air-fuel ratio of the normal passing through the flow path 5b of the NO X absorbent carrier 5 during operation exhaust is lean, the passage 5b
壁面のNO X吸収剤は排気中のNO Xを吸収する。 NO X absorbent of the wall to absorb the NO X in the exhaust gas.

【0021】次いで、NO X吸収剤担体5がモータ8により回転され、流路5bの入口が還元剤供給部12により覆われる位置に来ると流路5bへ流入する排気は還元剤供給部12により遮断され、凹部12b内に供給された還元剤が流路5b内に流入する。 [0021] Then, NO X absorbent carrier 5 is rotated by the motor 8, the exhaust gas inlet of the flow path 5b flows into the flow path 5b come to the position covered by the reducing agent supply unit 12 by the reducing agent supplying unit 12 blocked, the reducing agent supplied into the concave portion 12b flows into the flow path 5b. このため、流路5b For this reason, the flow path 5b
内の排気は入口側から還元剤に置換されて行き、流路5 Exhaust inner went displaced from the inlet side to the reducing agent, the flow path 5
b内には大幅にリッチな雰囲気が形成されて行く。 Is in the b go is greatly rich atmosphere is formed. 流路5b壁面のNO X吸収剤はこのリッチ雰囲気下で吸収したNO Xを放出し、NO X吸収剤の再生が行われる。 The NO X absorbent in the passage 5b wall releases NO X absorbed under the rich atmosphere, regeneration of the NO X absorbent is carried out.

【0022】NO X吸収剤担体5が更に回転して流路5 [0022] rotates and the NO X absorbent carrier 5 further flow path 5
bの入口が還元剤供給部12の外に出ると流路5b内には再び排気が流入し、流路5b内の還元剤を流路出口から押し出すので流路5b内はリーン雰囲気になりNO X b inlet exhaust flows again in the reducing agent outside exits the flow path 5b of the supply portion 12, flow passage 5b since extruding a reducing agent in the flow path 5b from the channel outlet becomes lean atmosphere NO X
吸収剤は再生された状態で再びNO Xの吸収を開始する。 Absorbent starts to absorb again NO X in a state of being reproduced. 本実施例では、NO X吸収剤担体5の回転速度と還元剤供給部12への還元剤供給量はエンジンのNO X排出量に比例した値に設定される。 In this embodiment, the rotational speed and the reducing agent supply amount to the reducing agent supply portion 12 of the NO X absorbent carrier 5 is set to a value proportional to the NO X emissions engine. すなわち、前述のEC In other words, the above-mentioned EC
U20は単位時間当たりのエンジンからのNO Xの排出量を予めエンジン負荷(アクセル開度)とエンジン回転数の関数としてROMに記憶しており、アクセル開度と回転数とから上記関数によりNO X排出量を算出し、これにそれぞれ一定の係数を乗じたものをNO X吸収剤担体5の回転数と還元剤供給装置11からの還元剤供給量として設定するとともに、この設定値を得るように可変速度モータ8の速度と流量制御弁14の開度とを調整する。 U20 is stored emissions of the NO X from the engine per unit time in advance the engine load (accelerator opening) in the ROM as a function of engine speed, NO X by the function of the accelerator opening and the rotational speed calculating the emissions, respectively are multiplied by certain coefficients and sets as the reducing agent supply amount from the rotational speed and the reducing agent supply device 11 of the NO X absorbent carrier 5 in this so as to obtain the set value adjusting the opening speed and the flow control valve 14 of the variable speed motor 8.

【0023】上記のように、エンジンのNO X排出量に比例した速度でNO X吸収剤担体5を回転させることにより再生操作が開始されるまでに流路5b壁面のNO X [0023] As described above, the flow path 5b wall until regenerating operation is initiated by rotating the the NO X absorbent carrier 5 at a rate proportional to the NO X emissions the engine NO X
吸収剤が吸収するNO X量は運転条件にかかわらず略一定になる。 The amount of NO X absorbent absorbs becomes substantially constant regardless of the operating conditions. また、還元剤供給量をエンジンのNO X排出量に比例した値(すなわちNO X吸収剤担体5の回転速度に比例した値)とすることにより再生操作時に流路5 Further, the flow path 5 at the time of reproduction operation by a value proportional to the reducing agent supply amount to the NO X emissions the engine (i.e., a value proportional to the rotational speed of the NO X absorbent carrier 5)
b壁面のNO X吸収剤に供給される還元剤の量も運転条件にかかわらず略一定になり、NO X吸収剤のNO X吸収量、還元剤供給量等の再生条件が運転条件にかかわらず一定の最適値に保持される。 The amount of reducing agent supplied to the NO X absorbent in b wall becomes substantially constant regardless of the operating conditions, NO X absorption of the NO X absorbent, regardless of the playback condition is the operating condition such as the reducing agent supply amount It is maintained at a constant optimum value.

【0024】本実施例では、原則としてエンジン稼働中は常時NO X吸収剤担体5の回転と還元剤の供給とを行う。 [0024] In this embodiment, it performs during engine operation and the rotation of the constantly the NO X absorbent carrier 5 and the supply of the reducing agent in principle. また、ECU20は排気温度センサ16の出力により排気温度を監視し、排気温度が所定値以下、すなわちNO X吸収剤温度が活性温度以下になっていると判断される排気温度以下になった場合にはNO X吸収剤への還元剤供給を停止し、余剰還元剤の大気放出を防止する。 Further, ECU 20 is an exhaust temperature is monitored by the output of the exhaust gas temperature sensor 16, the exhaust gas temperature is below a predetermined value, i.e., when the NO X absorbent temperature is below the exhaust temperature is determined to be equal to or less than the activation temperature stops the reducing agent supply to the NO X absorbent to prevent atmospheric discharge of excess reducing agent.

【0025】このため、NO X吸収剤担体等の可動部分は常時作動しており、従来の遮断弁等のように長い間隔の間欠作動を行う部材が存在しないので可動部分のスティック等により作動不良等の問題が発生することが防止される。 [0025] Thus, the movable portions such as the NO X absorbent carriers are always active, operation failure due stick of the moving part because member for intermittent operation of a long distance as in such a conventional shut-off valve is not present thereby preventing the problems such as occur. なお、本実施例ではNO X吸収剤担体5は連続回転を行うが、NO X吸収剤担体5を連続回転させる代わりに一定回転角ずつ比較的短い間隔で間欠的に回転させるようにしてもよい。 In the the NO X absorbent carrier 5 in this embodiment performs continuous rotation, but may be caused to intermittently rotate at relatively short intervals by a constant rotation angle instead of continuously rotating the the NO X absorbent carrier 5 .

【0026】また、本実施例ではNO X吸収剤担体5の流路全体のうち、常に一定の比率の流路が排気管3内に開口しておりNO X吸収剤の再生に伴って排気流路面積が変動することがないため、従来NO X吸収剤再生時の遮断弁の開閉や排気絞り等により生じていたエンジン出力の変動によるトルクショックの発生が防止される。 Further, of the total flow path of the NO X absorbent carrier 5 in this embodiment, always an exhaust stream with the playback of the NO X absorbent is open to the flow path in the exhaust pipe 3 to scale since the road area does not vary, the occurrence of torque shock due to fluctuation of the engine output has been caused by the conventional the nO X absorbent opening and closing the exhaust throttle like shut-off valve at the time of reproduction can be prevented.

【0027】更に、本実施例では、上述のようにNO X Furthermore, in this embodiment, as described above NO X
吸収剤の再生操作がエンジン出力に影響を及ぼさないためNO X吸収剤担体5の回転速度を全体的に大きく設定して短い周期でNO X吸収剤の吸収再生サイクルを繰り返すことが可能となる。 Regenerating operation of the absorbent becomes possible to repeat the absorption regeneration cycle of the NO X absorbent at short intervals by setting overall increase the rotational speed of the NO X absorbent carrier 5 because it does not affect the engine output. 一般にNO X吸収剤はNO X吸収量が大きい場合には再生に長時間を必要とし、再生後のNO X吸収能力も充分に回復しない傾向があるが、上記のように短い周期で再生操作を行うようにすることにより、NO X吸収量が少ない段階で早期にNO Generally the NO X absorbent requires a long time to play. If NO X absorption amount is large, NO X absorption ability after regeneration also tend not recovered sufficiently, but the playback operation at a short period as described above by so performing, early NO in step NO X absorption is small X吸収剤の再生を行うことができるため短時間で完全な再生を行いNO X吸収剤の吸収能力を完全に回復させることが可能となる。 The absorption capacity of the NO X absorbent perform complete regeneration within a short time it is possible to reproduce the X absorbent becomes fully possible to recover.

【0028】更に上記以外にも、短い周期でNO X吸収剤の再生を行うことはNO X吸収剤の硫黄被毒の防止の上で大きな効果がある。 Furthermore in addition to the above, to perform the regeneration of the NO X absorbent at a short period there is a great effect in the prevention of sulfur poisoning of the NO X absorbent. 比較的硫黄成分の含有量が多い軽油などの燃料を使用するエンジンでは排気中に硫黄酸化物が多く含まれるが、この硫黄酸化物は、前述のNO Relatively While the engine using a fuel, such as high content diesel fuel sulfur components contain many sulfur oxides in the exhaust, the sulfur oxides, the above-described NO
Xの場合と全く同じメカニズムでNO X吸収剤に吸収されてBaOと結合してBaSO 4を生成する。 For X and be absorbed at all in the NO X absorbent by the same mechanism to produce a BaSO 4 in combination with BaO. このBa The Ba
SO 4は比較的安定した化合物であるため一旦生成されると分解されにくく、NO X吸収剤中のBaSO 4が増大するとNO Xの吸収能力が低下してしまう問題が生じる。 SO 4 is relatively stable compounds and are temporarily less likely to be degraded to be produced for the problem of the BaSO 4 in the NO X absorbent increases the absorption capacity of the NO X decreases occurs. この硫黄被毒の発生を防止するためには、NO X吸収剤に吸収された硫酸イオンがBaOと結合して安定なBaSO 4を生成する前にNO X吸収剤の再生操作を行い、前述のNO Xの場合と同様なメカニズムで硫黄酸化物をNO X吸収剤から放出させる必要がある。 To prevent the occurrence of sulfur poisoning performs reproduction operation of the NO X absorbent before absorbed sulfate ions to the NO X absorbent is combined with BaO to produce the stable BaSO 4, described above the sulfur oxides in the case of the NO X similar mechanisms need to be released from the NO X absorbent. 本実施例では上述のように短い周期でNO X吸収剤の再生を行うことができるため、NO X吸収剤の硫黄被毒の発生を有効に防止することができる。 In this embodiment it is possible to reproduce of the NO X absorbent at a short period as described above, it is possible to effectively prevent the occurrence of sulfur poisoning of the NO X absorbent.

【0029】以上に本発明の一実施例について説明したが、本発明は上記実施例に限定されるわけではなく、本発明の技術的範囲から逸脱することなく種々の改変が可能である。 [0029] been described with reference to preferred embodiments of the present invention above, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the scope of the present invention. 例えば、上述の実施例では可変速度モータ8 For example, in the above embodiment the variable speed motor 8
によりNO X吸収剤担体5を回転駆動しているが、可変速度モータを使用せずにエンジンの出力軸からギア、ベルト等を介してエンジン回転数に比例する速度でNO X The NO X and the absorbent carrier 5 driven to rotate, but the gear from the output shaft of the engine without using a variable speed motor, NO X via a belt or the like at a rate proportional to the engine speed
吸収剤担体5を回転駆動する構成も可能である。 Configuration for rotating the absorbent carrier 5 is also possible.

【0030】また、上述の実施例では還元剤供給部12 Further, in the above embodiment the reducing agent supply unit 12
を固定してNO X吸収剤担体5を回転させているが、同様にNO X吸収剤担体5を排気管3内に固定して還元剤供給部12をNO X吸収剤担体5に対して回転させるようにした構成も可能である。 While rotating the the NO X absorbent carrier 5 by fixing the similarly rotated by fixing the the NO X absorbent carrier 5 into the exhaust pipe 3 to a reducing agent supply unit 12 with respect to the NO X absorbent carrier 5 configuration so as to be possible. この場合、例えば、図5に示すように還元剤供給部12を駆動軸7を用いて回転駆動し、駆動軸内に設けた還元剤供給通路18から還元剤を凹部12bに供給するようにするとともに、駆動軸の周囲に摺接する環状の部材19を設け、固定配管からこの部材19と駆動軸7内の半径方向入口ポート22を介して還元剤供給通路18に還元剤を供給することができる。 In this case, for example, to rotate driven by the drive shaft 7 to the reducing agent supply unit 12 as shown in FIG. 5, so as to supply the reducing agent to the recess 12b from the reducing agent supply passage 18 provided in the drive shaft with the sliding contact annular member 19 around the drive shaft is provided, it is possible to supply the reducing agent to the reducing agent supply passage 18 through the radial inlet port 22 of the drive shaft within 7 from the fixed piping this member 19 .

【0031】 [0031]

【発明の効果】本発明の排気浄化装置は、上述のようにNO X吸収剤担体の流路の一部ずつについて排気の遮断と還元剤の供給を順次行うようにしたことによりNO X Exhaust purification apparatus of the present invention exhibits, NO by which it is adapted sequentially to supply the blocking and reducing agent in the exhaust for each part of the flow path of the NO X absorbent carrier as described above X
吸収剤の再生操作時のエンジン出力の変動や可動部材のスティックの発生の問題を防止することが可能となる。 It is possible to prevent the absorbent regenerating operation during the engine output fluctuations and the movable member sticks occur problems become.
また、単一のNO X吸収剤担体を用いて連続的にNO X Further, continuously NO X using a single of the NO X absorbent carrier
吸収剤の再生操作を行うことができるため、装置の小型化が可能となり、車両への搭載製が向上する効果がある。 It is possible to perform the regenerating operation of the absorber, it is possible to miniaturize the device, made mounted on the vehicle can be improved.

【図面の簡単な説明】 BRIEF DESCRIPTION OF THE DRAWINGS

【図1】本発明の一実施例を示す図である。 1 is a diagram showing an embodiment of the present invention.

【図2】本発明の一実施例を示す断面図である。 2 is a sectional view showing an embodiment of the present invention.

【図3】図2のA部の拡大図である。 3 is an enlarged view of part A of FIG.

【図4】本発明のNO X吸収剤のNO X吸放出作用を説明する図である。 4 is a diagram illustrating a NO X absorbing and releasing action of the NO X absorbent of the present invention.

【図5】本発明の別の実施例を説明する図である。 5 is a diagram for explaining another embodiment of the present invention.

【符号の説明】 DESCRIPTION OF SYMBOLS

3…排気管 5…NO X吸収剤 5a…上流側端面 5b…排気流路 7…駆動軸 8…モータ 11…還元剤供給装置 12…還元剤供給部 13…還元剤供給源 14…流量制御弁 16…排気温度センサ 20…エンジン制御回路(ECU) 3 ... exhaust pipe 5 ... NO X absorbent 5a ... upstream end surface 5b ... exhaust passage 7 ... drive shaft 8 ... motor 11 ... reducing agent supply device 12 ... reducing agent supply unit 13 ... reducing agent supply 14 ... flow control valve 16 ... exhaust gas temperature sensor 20: engine control circuit (ECU)

Claims (1)

    (57)【特許請求の範囲】 (57) [the claims]
  1. 【請求項1】 機関排気通路に配置され流入排気の空燃比がリーンのときにNO Xを吸収し流入排気の酸素濃度が低下したときに吸収したNO Xを放出するNO X吸収剤と、前記NO X吸収剤への排気の流入を遮断してNO 1. A and the NO X absorbent when the air-fuel ratio of the disposed engine exhaust passage inflow exhaust gas oxygen concentration of the inflowing exhaust absorbs NO X when the lean releases the absorbed NO X when lowered, the shut off the flow of exhaust gas into the NO X absorbent NO
    X吸収剤に還元剤を供給しNO X吸収剤から吸収したN N absorbed from supplying reducing agent to the X absorbent the NO X absorbent
    Xを放出させるとともに放出されたNO Xを還元浄化する還元剤導入手段とを備えた内燃機関の排気浄化装置において、前記NO X吸収剤は排気が通過する複数の独立した流路を有する担体のそれぞれの流路壁面に担持され、それぞれの流路を通過する排気中のNO Xの吸収をおこない、前記還元剤導入手段は前記担体の前記複数の排気流路のうち一時に一部の流路ずつ排気の流入の遮断及び還元剤の供給を行うことにより順次全部の排気流路の壁面のNO X吸収剤からのNO Xの放出と還元浄化とを行うことを特徴とする内燃機関の排気浄化装置。 In the exhaust purification apparatus for an internal combustion engine having a reducing agent introduction means for reducing and purifying the released NO X with the release of O X, wherein the NO X absorbent carrier having a plurality of independent flow paths exhaust passes each is carried on the flow path wall surface, subjected to absorption of the NO X in the exhaust gas passing through the respective flow path, wherein the reducing agent introducing means part of the flow to a temporary out of the plurality of exhaust flow path of the carrier the exhaust gas of the internal combustion engine, characterized by performing the release of the NO X from the NO X absorbent sequential whole of the wall surface of the exhaust passage by performing blocking and supply of the reducing agent flowing into the exhaust by the road and reduce and purify purifying device.
JP4526993A 1993-03-05 1993-03-05 Exhaust gas purification system for an internal combustion engine Expired - Lifetime JP2722982B2 (en)

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