JP3334632B2 - Exhaust gas purification device for internal combustion engine - Google Patents
Exhaust gas purification device for internal combustion engineInfo
- Publication number
- JP3334632B2 JP3334632B2 JP22217698A JP22217698A JP3334632B2 JP 3334632 B2 JP3334632 B2 JP 3334632B2 JP 22217698 A JP22217698 A JP 22217698A JP 22217698 A JP22217698 A JP 22217698A JP 3334632 B2 JP3334632 B2 JP 3334632B2
- Authority
- JP
- Japan
- Prior art keywords
- sulfur component
- fuel
- storage
- amount
- catalyst
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D2200/00—Input parameters for engine control
- F02D2200/02—Input parameters for engine control the parameters being related to the engine
- F02D2200/08—Exhaust gas treatment apparatus parameters
- F02D2200/0818—SOx storage amount, e.g. for SOx trap or NOx trap
-
- 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
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
-
- 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
- Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
- Y02C20/00—Capture or disposal of greenhouse gases
- Y02C20/10—Capture or disposal of greenhouse gases of nitrous oxide (N2O)
Landscapes
- Exhaust Gas After Treatment (AREA)
- Treating Waste Gases (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Description
【0001】[0001]
【発明の属する技術分野】本発明は、内燃機関の排気浄
化装置に係り、詳しくは、吸蔵型NOx触媒に吸蔵され
た硫黄酸化物(SOx)を除去する技術に関する。The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, and more particularly to a technique for removing sulfur oxides (SOx) stored in a storage type NOx catalyst.
【0002】[0002]
【関連する背景技術】内燃機関において、空燃比をリー
ン空燃比とすると、酸素が過剰に存在し、従来の三元触
媒ではその浄化特性から排ガス中のNOx(窒素酸化
物)を充分に浄化できないという問題があり、最近で
は、酸素過剰雰囲気においてもNOxを浄化できる吸蔵
型NOx触媒が開発され実用化されている。2. Related Art In an internal combustion engine, if the air-fuel ratio is set to a lean air-fuel ratio, oxygen is excessively present, and the conventional three-way catalyst cannot sufficiently purify NOx (nitrogen oxide) in exhaust gas due to its purification characteristics. Recently, a storage NOx catalyst capable of purifying NOx even in an oxygen-excess atmosphere has been developed and put into practical use.
【0003】吸蔵型NOx触媒は、酸素過剰状態(酸化
雰囲気)において排ガス中のNOxを硝酸塩X−NO 3 と
して吸蔵し、該吸蔵したNOxをCO(一酸化炭素)過
剰状態(還元雰囲気)でN 2 (窒素)に還元させる特性
(同時に炭酸塩X−CO 3 が生成される)を有した触媒
として構成されている。筒内噴射型内燃機関に関してい
えば、例えば、吸蔵型NOx触媒のNOx吸蔵量が飽和す
る前に空燃比を理論空燃比またはその近傍値に制御する
ような吸気行程でのリッチ空燃比運転に定期的に切換え
(これをリッチスパイクという)、これにより、COの
多い還元雰囲気を生成し、吸蔵したNOxを浄化還元
(NOxパージ)して吸蔵型NOx触媒の再生を図るよう
にしている。[0003] occlusion-type NOx catalyst occludes NOx in the exhaust gas in an oxygen excess state (oxidation atmosphere), as the nitrate X-NO 3, N of NOx was suction built with CO (carbon monoxide) over state (reduction atmosphere) It is configured as a catalyst having the property of reducing to 2 (nitrogen) (carbonate X-CO 3 is generated at the same time). Speaking of the in-cylinder injection type internal combustion engine, for example, the air-fuel ratio is controlled to the stoichiometric air-fuel ratio or a value close to the stoichiometric air-fuel ratio before the NOx storage amount of the storage NOx catalyst is saturated. (This is referred to as a rich spike), thereby generating a CO-rich reducing atmosphere, purifying and reducing the stored NOx (NOx purge), and regenerating the stored NOx catalyst.
【0004】ところで、燃料中にはS(サルファ)成分
(硫黄成分)が含まれており、このS成分は酸素と反応
してSOx(硫黄酸化物)となり、該SOxは硫酸塩X−
SO 4としてNOxの代わりに吸蔵型NOx触媒に吸蔵さ
れる。つまり、吸蔵型NOx触媒には、硝酸塩と硫酸塩
とが吸蔵されることになる。ところが、硫酸塩は硝酸塩
よりも塩としての安定度が高く、空燃比がリッチ状態
(酸素濃度が低下した還元雰囲気)になってもその一部
しか分解されず、吸蔵型NOx触媒に残留する硫酸塩の
量は時間とともに増加する。このように硫酸塩の量が増
加すると、吸蔵型NOx触媒の吸蔵能力が時間とともに
低下し、吸蔵型NOx触媒としての性能が悪化すること
になり好ましいことではない(S被毒)。By the way, S (sulfur) component is contained in fuel.
(Sulfur component), and this S component reacts with oxygen
To form SOx (sulfur oxide), which is converted to sulfate X-
SO FourAs a storage NOx catalyst instead of NOx
It is. In other words, the storage NOx catalyst contains nitrate and sulfate
Will be occluded. However, sulfates are nitrates
Higher salt stability and rich air-fuel ratio
(Reducing atmosphere with reduced oxygen concentration)
Of the sulfate remaining on the NOx storage catalyst
The amount increases with time. Thus, the amount of sulfate increased.
Increases, the storage capacity of the storage NOx catalyst increases over time.
And the performance as a storage NOx catalyst deteriorates.
Is unfavorable (S poisoning).
【0005】しかしながら、このように吸蔵されたSO
xは、空燃比をリッチ状態にするとともに、触媒を高温
状態にすることで除去(Sパージ)されることが分かっ
ており、例えばSOxの吸蔵量を推定するようにし該推
定値が所定量に達したと判定すると空燃比をリッチ化す
るとともに点火時期のリタードにより排気昇温させ触媒
を高温状態にする技術が特開平7−217474号公報
等に開示されている。[0005] However, the thus stored SO 2
It is known that x is removed (S purge) by setting the air-fuel ratio to a rich state and setting the catalyst to a high temperature state. For example, the storage amount of SOx is estimated, and the estimated value becomes a predetermined amount. Japanese Unexamined Patent Publication No. Hei 7-217474 discloses a technique for enriching the air-fuel ratio when it is determined that the temperature has reached and raising the temperature of the exhaust gas by retarding the ignition timing to bring the catalyst to a high temperature state.
【0006】[0006]
【発明が解決しようとする課題】ところが、上記公報に
開示された技術では、SOxの吸蔵量を例えば燃料噴射
時間と機関回転速度とにのみ基づいて推定するようにし
ており、該推定値が所定量に達したか否かの判定が必ず
しも適正な判定とならない場合があり好ましいことでは
ない。However, in the technique disclosed in the above publication, the amount of occluded SOx is estimated based only on the fuel injection time and the engine speed, for example. It is not preferable that the determination as to whether or not the amount has been reached is not always an appropriate determination.
【0007】つまり、燃焼によって発生するSOx量は
空燃比や燃料性状(燃料中の硫黄成分含有量)等によっ
て大きく左右されるものであり、SOxの吸蔵量の推定
値が所定量に達したと判定されたとき、これら空燃比や
燃料性状等の状況によっては実際のSOx吸蔵量が既に
飽和状態に至っており、NOxが吸蔵型NOx触媒に吸蔵
されることなく不用意にそのまま排出されてしまう場合
があるのである。That is, the amount of SOx generated by combustion largely depends on the air-fuel ratio, fuel properties (sulfur component content in fuel), etc., and the estimated value of the SOx storage amount has reached a predetermined amount. When the determination is made, the actual SOx storage amount has already reached a saturated state depending on the conditions such as the air-fuel ratio and the fuel property, and the NOx is inadvertently discharged as it is without being stored in the storage NOx catalyst. There is.
【0008】また逆に、SOxの吸蔵量の推定値が所定
量に達したと判定されたとき、空燃比や燃料性状等の状
況によっては実際のSOx吸蔵量が少ない場合があり、
このような状況で空燃比をリッチ空燃比状態としSパー
ジを繰り返し行うと、燃費を悪化させる要因となり好ま
しいことではない。本発明はこのような問題点を解決す
るためになされたもので、その目的とするところは、吸
蔵型NOx触媒に吸蔵されるSOxの吸蔵量を正確に推定
し、吸蔵されたSOxを効率よく除去可能な内燃機関の
排気浄化装置を提供することにある。Conversely, when it is determined that the estimated value of the amount of stored SOx has reached a predetermined amount, the actual amount of stored SOx may be small depending on conditions such as the air-fuel ratio and fuel properties.
In such a situation, if the air-fuel ratio is set to the rich air-fuel ratio state and the S purge is repeatedly performed, the fuel efficiency is deteriorated, which is not preferable. The present invention has been made in order to solve such a problem, and an object of the present invention is to accurately estimate the amount of SOx stored in a storage NOx catalyst and efficiently store the stored SOx. It is an object of the present invention to provide a removable exhaust gas purification device for an internal combustion engine.
【0009】[0009]
【課題を解決するための手段】上記した目的を達成する
ために、請求項1の発明によれば、硫黄成分吸蔵度合演
算手段によって吸蔵型NOx触媒への硫黄成分の吸蔵度
合が空燃比に応じた度合となるよう演算されるようにさ
れており、吸蔵型NOx触媒に吸蔵される硫黄成分の堆
積量は、燃料噴射量相関値演算手段により演算される燃
料噴射量相関値と上記硫黄成分吸蔵度合演算手段により
演算される硫黄成分の吸蔵度合とに基づいて推定され
る。To achieve the above object SUMMARY OF THE INVENTION According to the first aspect of the present invention, occlusion degree of sulfur components to occlusion-type NOx catalyst by the sulfur component storage degree calculation means in the air-fuel ratio The amount of sulfur component stored in the storage NOx catalyst is calculated based on the fuel injection amount correlation value calculated by the fuel injection amount correlation value calculation means and the sulfur component. It is estimated based on the storage degree of the sulfur component calculated by the storage degree calculating means.
【0010】従って、吸蔵型NOx触媒に吸蔵される硫
黄成分(S成分)、即ち硫黄酸化物(SOx)の堆積量
が空燃比に応じて変化する吸蔵度合を考慮して推定され
ることになり、SOxの堆積量が実際に即した適正な値
とされる。故に、硫黄成分除去手段による硫黄成分の除
去、即ちSOxの除去つまりSパージの実施タイミング
が極めて適正なものとされ、Sパージの実施インターバ
ルが長くなってNOxが不用意に排出されてしまうよう
なことがなくなり、またSパージが頻繁に行われて燃費
が悪化するようなことが好適に防止される。また、請求
項2の発明によれば、吸蔵型NOx触媒への硫黄成分の
吸蔵度合が、さらに触媒温度に応じた度合となるよう演
算されるようにされており、吸蔵型NOx触媒に吸蔵さ
れる硫黄酸化物(SOx)の堆積量が触媒温度に応じて
変化する吸蔵度合を考慮して推定され、SOxの堆積量
がさらに実際に即した適正な値とされる。 また、請求項
3の発明によれば、吸蔵型NOx触媒への硫黄成分の吸
蔵度合が、さらに燃料性状に応じた度合となるよう演算
されるようにされており、吸蔵型NOx触媒に吸蔵され
る硫黄酸化物(SOx)の堆積量が燃料性状に応じて変
化する吸蔵度合を考慮して推定され、SOxの堆積量が
さらに実際に即した適正な値とされる。 また、請求項4
の発明によれば、上記燃料性状はノックセンサからの出
力情報に基づき容易に検出される。 Accordingly, sulfur component occluded in the occlusion-type NOx catalyst (S component), i.e., that the amount of deposition of sulfur oxides (SOx) are estimated taking into account the occlusion degree that varies depending on the air-fuel ratio That is, the SOx deposition amount is set to an appropriate value that actually matches. Therefore, the removal timing of the sulfur component by the sulfur component removal means, that is, the removal timing of SOx, that is, the execution timing of the S purge is made extremely appropriate, and the execution interval of the S purge becomes long, so that the NOx is inadvertently discharged. In addition, it is possible to preferably prevent the fuel consumption from being deteriorated due to frequent S purge. Also, billing
According to the invention of the item 2, the sulfur component is stored in the NOx storage catalyst.
The degree of occlusion is further adjusted according to the catalyst temperature.
Is stored in the storage NOx catalyst.
Amount of sulfur oxide (SOx) deposited depends on catalyst temperature
Estimated taking into account the changing degree of occlusion, the amount of SOx deposited
Is further set to an appropriate value according to the actual situation. Claims
According to the third aspect of the present invention, the sulfur component is absorbed into the storage NOx catalyst.
Calculated so that the degree of storage is more in accordance with the fuel properties
Is stored in the storage NOx catalyst.
Changes in the amount of sulfur oxide (SOx) deposited
Is estimated in consideration of the degree of occlusion,
Further, it is set to an appropriate value according to the actual situation. Claim 4
According to the invention, the fuel property is output from the knock sensor.
It is easily detected based on force information.
【0011】[0011]
【発明の実施の形態】以下、本発明の一実施形態を添付
図面に基づき説明する。図1を参照すると、車両に搭載
された本発明に係る内燃機関の排気浄化装置の概略構成
図が示されており、以下同図に基づいて本発明に係る排
気浄化装置の構成を説明する。DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the accompanying drawings. Referring to FIG. 1, there is shown a schematic configuration diagram of an exhaust gas purifying apparatus for an internal combustion engine according to the present invention mounted on a vehicle. Hereinafter, the configuration of the exhaust gas purifying apparatus according to the present invention will be described with reference to FIG.
【0012】機関本体(以下、単にエンジンという)1
は、例えば、燃料噴射モード(運転モード)を切換える
ことで吸気行程での燃料噴射(吸気行程噴射モード)ま
たは圧縮行程での燃料噴射(圧縮行程噴射モード)を実
施可能な筒内噴射型火花点火式直列4気筒ガソリンエン
ジンとされている。そして、この筒内噴射型のエンジン
1は、容易にして理論空燃比(ストイキ)での運転やリ
ッチ空燃比での運転(リッチ空燃比運転)の他、リーン
空燃比での運転(リーン空燃比運転)が実現可能とされ
ており、特に圧縮行程噴射モードでは、超リーン空燃比
での運転が可能とされている。Engine body (hereinafter simply referred to as engine) 1
For example, in-cylinder injection spark ignition capable of performing fuel injection in an intake stroke (intake stroke injection mode) or fuel injection in a compression stroke (compression stroke injection mode) by switching a fuel injection mode (operation mode), for example. It is an inline 4-cylinder gasoline engine. The in-cylinder injection type engine 1 can be easily operated at a stoichiometric air-fuel ratio (stoichiometric ratio), at a rich air-fuel ratio (rich air-fuel ratio operation), or at a lean air-fuel ratio (lean air-fuel ratio). In particular, in the compression stroke injection mode, it is possible to operate at a super lean air-fuel ratio.
【0013】同図に示すように、エンジン1のシリンダ
ヘッド2には、各気筒毎に点火プラグ4とともに電磁式
の燃料噴射弁6が取り付けられており、これにより、燃
焼室8内に燃料を直接噴射可能とされている。そして、
燃料噴射弁6には、燃料パイプを介して燃料タンクを擁
した燃料供給装置(共に図示せず)が接続されている。As shown in FIG. 1, the cylinder head 2 of the engine 1 is provided with an electromagnetic fuel injection valve 6 together with a spark plug 4 for each cylinder, whereby fuel is injected into the combustion chamber 8. Direct injection is possible. And
A fuel supply device (both not shown) having a fuel tank is connected to the fuel injection valve 6 via a fuel pipe.
【0014】さらに、シリンダヘッド2には、各気筒毎
に略直立方向に吸気ポートが形成されており、各吸気ポ
ートと連通するようにして吸気マニホールド10の一端
がそれぞれ接続されている。そして、吸気マニホールド
10の他端にはスロットル弁11が接続されており、該
スロットル弁11にはスロットル開度θthを検出するス
ロットルセンサ11aが設けられている。Further, an intake port is formed in the cylinder head 2 in a substantially upright direction for each cylinder, and one end of an intake manifold 10 is connected to communicate with each intake port. A throttle valve 11 is connected to the other end of the intake manifold 10. The throttle valve 11 is provided with a throttle sensor 11a for detecting a throttle opening θth.
【0015】また、シリンダヘッド2には、各気筒毎に
略水平方向に排気ポートが形成されており、各排気ポー
トと連通するようにして排気マニホールド12の一端が
それぞれ接続されている。なお、図中符号13は、クラ
ンク角を検出するクランク角センサであり、該クランク
角センサ13はエンジン回転速度Neを検出可能とされ
ている。また、符号18は、例えばエンジン1の振動変
化を検出してノッキングを検出するノックセンサであ
る。An exhaust port is formed in the cylinder head 2 in a substantially horizontal direction for each cylinder, and one end of an exhaust manifold 12 is connected to communicate with each exhaust port. Reference numeral 13 in the figure denotes a crank angle sensor for detecting a crank angle, and the crank angle sensor 13 is capable of detecting an engine rotation speed Ne. Reference numeral 18 denotes a knock sensor that detects knocking by detecting a change in vibration of the engine 1, for example.
【0016】同図に示すように、排気マニホールド12
には排気管(排気通路)14が接続されており、この排
気管14にはエンジン1に近接した小型の近接三元触媒
20及び排気浄化触媒装置30を介してマフラー(図示
せず)が接続されている。また、排気管14には排気温
度を検出する高温センサ16が設けられている。排気浄
化触媒装置30は、吸蔵型NOx触媒30aと三元触媒
30bとの2つの触媒を備えて構成されており、三元触
媒30bの方が吸蔵型NOx触媒30aよりも下流側に
配設されている。As shown in FIG.
An exhaust pipe (exhaust passage) 14 is connected to the exhaust pipe 14. A muffler (not shown) is connected to the exhaust pipe 14 via a small proximity three-way catalyst 20 close to the engine 1 and an exhaust purification catalyst device 30. Have been. The exhaust pipe 14 is provided with a high temperature sensor 16 for detecting the exhaust gas temperature. The exhaust purification catalyst device 30 includes two catalysts, a storage NOx catalyst 30a and a three-way catalyst 30b, and the three-way catalyst 30b is disposed downstream of the storage NOx catalyst 30a. ing.
【0017】吸蔵型NOx触媒30aは、酸化雰囲気に
おいてNOxを一旦吸蔵させ、主としてCOの存在する
還元雰囲気中においてNOxをN2(窒素)等に還元させ
る機能を持つものである。詳しくは、吸蔵型NOx触媒
30aは、貴金属として白金(Pt),ロジウム(R
h)等を有した触媒として構成されており、吸蔵材とし
てはバリウム(Ba)等のアルカリ金属、アルカリ土類
金属が採用されている。The storage type NOx catalyst 30a has a function of temporarily storing NOx in an oxidizing atmosphere and reducing NOx to N 2 (nitrogen) or the like mainly in a reducing atmosphere where CO is present. More specifically, the storage NOx catalyst 30a uses platinum (Pt) and rhodium (R) as noble metals.
h) and the like, and an alkali metal such as barium (Ba) or an alkaline earth metal is employed as the storage material.
【0018】また、吸蔵型NOx触媒30aと三元触媒
30bとの間にはNOx濃度を検出するNOxセンサ32
が設けられている。さらに、入出力装置、記憶装置(R
OM、RAM、不揮発性RAM等)、中央処理装置(C
PU)、タイマカウンタ等を備えたECU(電子コント
ロールユニット)40が設置されており、このECU4
0により、本発明に係る内燃機関の排気浄化装置の総合
的な制御が行われる。ECU40の入力側には、上述し
た高温センサ16、ノックセンサ18やNOxセンサ3
2等の各種センサ類が接続されており、これらセンサ類
からの検出情報が入力する。A NOx sensor 32 for detecting the NOx concentration is provided between the storage type NOx catalyst 30a and the three-way catalyst 30b.
Is provided. Further, an input / output device, a storage device (R
OM, RAM, nonvolatile RAM, etc.), central processing unit (C
PU), an ECU (electronic control unit) 40 including a timer counter and the like.
With 0, comprehensive control of the exhaust gas purification device for an internal combustion engine according to the present invention is performed. On the input side of the ECU 40, the above-described high temperature sensor 16, knock sensor 18, NOx sensor 3
2 and the like are connected, and detection information from these sensors is input.
【0019】一方、ECU40の出力側には、点火コイ
ルを介して上述した点火プラグ4や燃料噴射弁6等が接
続されており、これら点火コイル、燃料噴射弁6等に
は、各種センサ類からの検出情報に基づき演算された燃
料噴射量や点火時期等の最適値がそれぞれ出力される。
これにより、燃料噴射弁6から適正量の燃料が適正なタ
イミングで噴射され、点火プラグ4によって適正なタイ
ミングで点火が実施される。On the other hand, the output side of the ECU 40 is connected to the above-described ignition plug 4 and the fuel injection valve 6 via an ignition coil. The ignition coil, the fuel injection valve 6 and the like are connected to various sensors. The optimum values such as the fuel injection amount and the ignition timing calculated based on the detection information are output.
As a result, an appropriate amount of fuel is injected from the fuel injection valve 6 at an appropriate timing, and ignition is performed by the spark plug 4 at an appropriate timing.
【0020】実際には、ECU40では、スロットルセ
ンサ11aからのスロットル開度情報θthとクランク角
センサ13からのエンジン回転速度情報Neとに基づい
てエンジン負荷に対応する目標筒内圧、即ち目標平均有
効圧Peを求めるようにされており、さらに、当該目標
平均有効圧Peとエンジン回転速度情報Neとに応じてマ
ップ(図示せず)より燃料噴射モードを設定するように
されている。例えば、目標平均有効圧Peとエンジン回
転速度Neとが共に小さいときには、燃料噴射モードは
圧縮行程噴射モードとされ、燃料は圧縮行程で噴射さ
れ、一方、目標平均有効圧Peが大きくなり或いはエン
ジン回転速度Neが大きくなると燃料噴射モードは吸気
行程噴射モードとされ、燃料は吸気行程で噴射される。In practice, the ECU 40 determines the target in-cylinder pressure corresponding to the engine load, that is, the target average effective pressure, based on the throttle opening information θth from the throttle sensor 11a and the engine rotation speed information Ne from the crank angle sensor 13. Pe is determined, and the fuel injection mode is set from a map (not shown) according to the target average effective pressure Pe and the engine rotation speed information Ne. For example, when the target average effective pressure Pe and the engine rotation speed Ne are both low, the fuel injection mode is the compression stroke injection mode, and fuel is injected in the compression stroke, while the target average effective pressure Pe increases or the engine rotation speed increases. When the speed Ne increases, the fuel injection mode is set to the intake stroke injection mode, and fuel is injected during the intake stroke.
【0021】そして、目標平均有効圧Peとエンジン回
転速度Neとから制御目標となる目標空燃比(目標A/
F)が設定され、上記適正量の燃料噴射量は該目標A/
Fに基づいて決定される。上記高温センサ16により検
出された排気温度情報からは触媒温度Tcatが推定され
る。詳しくは、高温センサ16を吸蔵型NOx触媒30
aに直接設置できないことに起因して発生する誤差を補
正するために、目標平均有効圧Peとエンジン回転速度
情報Neとに応じて予め実験等により温度差マップ(図
示せず)が設定されており、故に触媒温度Tcatは、目
標平均有効圧Peとエンジン回転速度情報Neとが決まる
と一義に推定されるようにされている。The target air-fuel ratio (target A / A) is set as a control target based on the target average effective pressure Pe and the engine speed Ne.
F) is set, and the appropriate amount of fuel injection is set to the target A /
It is determined based on F. The catalyst temperature Tcat is estimated from the exhaust gas temperature information detected by the high temperature sensor 16. Specifically, the high temperature sensor 16 is connected to the storage NOx catalyst 30.
A temperature difference map (not shown) is set in advance by an experiment or the like in accordance with the target average effective pressure Pe and the engine rotation speed information Ne in order to correct an error that occurs due to the inability to directly install the apparatus in the area a. Therefore, the catalyst temperature Tcat is uniquely estimated when the target average effective pressure Pe and the engine speed information Ne are determined.
【0022】以下、このように構成された排気浄化装置
の本発明に係る作用について説明する。つまり、吸蔵型
NOx触媒30aには、上述したようにSOxも吸蔵され
てしまい、当該SOxを除去する必要があるのである
が、ここでは、当該SOxの吸蔵量(被毒S量Qs)の推
定方法、即ち吸蔵型NOx触媒30aのS(サルファ)
劣化判定方法について説明する。Hereinafter, the operation of the exhaust gas purifying apparatus thus configured according to the present invention will be described. In other words, SOx is also stored in the storage NOx catalyst 30a as described above, and it is necessary to remove the SOx. Here, however, the estimation of the storage amount of the SOx (poisoned S amount Qs) is performed. Method, ie, S (sulfur) of the storage NOx catalyst 30a
A method for determining deterioration will be described.
【0023】被毒S量Qsは、基本的には燃料噴射積算
量Qfに基づき設定されるものであり、燃料噴射制御ル
ーチン(図示せず)の実行周期毎に次式により演算され
る(硫黄成分堆積量推定手段)。 Qs=Qs(n-1)+ΔQf・K−Rs …(1) ここに、Qs(n-1)は被毒S量の前回値であり、ΔQfは
実行周期当たりの燃料噴射積算量(燃料噴射量相関
値)、Kは補正係数(吸蔵度合)、Rsは実行周期当た
りの再生S量を示している。The poisoning S amount Qs is basically set based on the integrated fuel injection amount Qf, and is calculated by the following equation at each execution cycle of a fuel injection control routine (not shown) (Sulfur Component accumulation amount estimation means). Qs = Qs (n−1) + ΔQf · K−Rs (1) Here, Qs (n−1) is the previous value of the poisoning S amount, and ΔQf is the integrated fuel injection amount per execution cycle (fuel injection (Amount correlation value), K is a correction coefficient (degree of occlusion), and Rs is a regeneration S amount per execution cycle.
【0024】つまり、現在の被毒S量Qsは、燃料噴射
制御ルーチンの実行周期当たりの燃料噴射積算量ΔQf
を補正係数Kで補正して積算するとともに、該積算値か
ら実行周期当たりの再生S量Rsを減算することで求め
られる。ここに、燃料噴射積算量ΔQfは、上述したよ
うに目標A/Fに基づいて決定された燃料噴射量により
算出される(燃料噴射量相関値演算手段)。That is, the current poisoning S amount Qs is determined by the fuel injection integrated amount ΔQf per execution cycle of the fuel injection control routine.
Is corrected by the correction coefficient K and integrated, and the reproduction S amount Rs per execution cycle is subtracted from the integrated value. Here, the integrated fuel injection amount ΔQf is calculated based on the fuel injection amount determined based on the target A / F as described above (fuel injection amount correlation value calculating means).
【0025】ところで、補正係数Kは、次式(2)に示す
ように、空燃比A/Fに応じたS被毒係数K1、S含有
量(燃料性状)に応じたS被毒係数K2及び触媒温度Tc
atに応じたS被毒係数K3の3つの補正係数の積からな
っている(硫黄成分吸蔵度合演算手段)。 K=K1・K2・K3 …(2) 空燃比A/Fに応じたS被毒係数K1は、図2(a)に
示すように、実験データに基づき、リッチ空燃比では小
さな値とされ、リーン空燃比で大きな値をとるようにさ
れている(例えば、リーン空燃比時に対し、リッチ空燃
比時は1/4、ストイキオ時には2/3)。即ち、目標
A/Fがリッチ空燃比とされエンジン1がリッチ空燃比
運転しているような場合には、SOxが吸蔵型NOx触媒
30aに吸蔵され難いとみなし、一方目標A/Fがリー
ン空燃比とされエンジン1がリーン空燃比運転している
場合には、燃料量に応じて略一定量のSOxが吸蔵型N
Ox触媒30aに吸蔵されるとみなすのである。Incidentally, as shown in the following equation (2), the correction coefficient K is an S poisoning coefficient K1 corresponding to the air-fuel ratio A / F, an S poisoning coefficient K2 corresponding to the S content (fuel property), and Catalyst temperature Tc
It consists of the product of three correction coefficients of the S poisoning coefficient K3 according to at (sulfur component occlusion degree calculating means). K = K1, K2, K3 (2) As shown in FIG. 2A, the S poisoning coefficient K1 corresponding to the air-fuel ratio A / F is set to a small value in the rich air-fuel ratio based on the experimental data. The lean air-fuel ratio takes a large value (for example, 1/4 at the rich air-fuel ratio and 2/3 at the stoichiometric ratio with respect to the lean air-fuel ratio). That is, when the target A / F is set to the rich air-fuel ratio and the engine 1 is operating at the rich air-fuel ratio, it is assumed that SOx is hardly stored in the storage NOx catalyst 30a, while the target A / F is set to the lean air-fuel ratio. When the engine 1 is operating at a lean air-fuel ratio as the fuel ratio, a substantially constant amount of SOx is stored in the storage type N in accordance with the fuel amount.
That is, it is assumed that the oxygen is stored in the Ox catalyst 30a.
【0026】また、S含有量(燃料性状)に応じたS被
毒係数K2は、図2(b)に実線で示すように、実験デ
ータに基づき、燃料中のS含有量が大きくなるほど大き
な値をとるようにされている(例えば、比例関係)。即
ち、SOxの発生量は燃料中に含まれるS(サルファ)
成分によって左右されるため、当該S成分の含有量に応
じて補正を行うのである。As shown by the solid line in FIG. 2 (b), the S poisoning coefficient K2 according to the S content (fuel property) increases as the S content in the fuel increases, based on experimental data. (For example, a proportional relationship). That is, the amount of SOx generated is S (sulfur) contained in the fuel.
Since it depends on the component, the correction is performed according to the content of the S component.
【0027】ところで、S含有量を燃料補給毎に測定す
ることは実際には不可能であるため、これに代えて、燃
焼時に発生するノッキングをノックセンサ18により検
出して現在使用している燃料中のS含有量を推定する。
これは、一般に低オクタン価の低質な燃料ではS含有量
が多く、高オクタン価の高質な燃料ではS含有量が少な
いことに基づくものである。つまり、例えばノックセン
サからの情報によりノッキングが発生し易い燃焼状態の
とき、即ちノッキングのために点火時期をあまり進角で
きないとき(点火時期進角補正値が小のとき)には低オ
クタン価でS含有量が多いと判断でき、一方ノッキング
が発生し難いとき、即ち点火時期を多く進角できるとき
(点火時期進角補正値が大のとき)には高オクタン価で
S含有量が少ないと判断できるのである。Incidentally, since it is actually impossible to measure the S content every fuel replenishment, the knocking sensor 18 detects the knocking generated at the time of combustion and detects the currently used fuel. The S content in the medium is estimated.
This is based on the fact that a low-octane-number low-quality fuel generally has a high S content, and a high-octane-number high-quality fuel has a low S content. That is, for example, in a combustion state in which knocking is likely to occur due to information from the knock sensor, that is, when the ignition timing cannot be advanced so much due to knocking (when the ignition timing advance correction value is small), the octane number is low. When it can be determined that the content is large, and when knocking is unlikely to occur, that is, when the ignition timing can be advanced a lot (when the ignition timing advance correction value is large), it can be determined that the S content is small with a high octane number. It is.
【0028】なお、日本国内では、レギュラガソリンと
プレミアムガソリンのようにそれぞれ品質が一定に保持
された2種類の燃料が販売されているが、このような場
合には、図2(b)中に破線で示すように、S含有量は
階段状に2段階に区別される。つまり、プレミアムガソ
リンであれば良質でS含有量が非常に少ないと判断して
S被毒係数K2は0近傍値とされ、レギュラガソリンで
あれば大きな値とされる。In Japan, two types of fuels, such as regular gasoline and premium gasoline, whose quality is kept constant, are sold. In such a case, FIG. As shown by the broken line, the S content is divided into two steps in a stepwise manner. That is, it is determined that the quality is high and the S content is very small in the case of premium gasoline, and the S poisoning coefficient K2 is set to a value close to 0, and is set to a large value in the case of regular gasoline.
【0029】また、触媒温度に応じたS被毒係数K3
は、図2(c)に示すように、実験データに基づき、触
媒温度Tcatが中程度の温度(例えば、300〜500
℃程度)のときに大きな値をとるようにされている。即
ち、触媒温度Tcatが低いときには活性度合が低く、触
媒温度Tcatが高いときにはSOxはパージされる方向な
ので、吸蔵型NOx触媒30aに吸蔵されるSOxの量は
比較的少ないと判断するのである。Also, the S poisoning coefficient K3 according to the catalyst temperature
As shown in FIG. 2C, based on the experimental data, the catalyst temperature Tcat is a medium temperature (for example, 300 to 500
(About ° C). That is, when the catalyst temperature Tcat is low, the degree of activity is low, and when the catalyst temperature Tcat is high, the SOx is in the purging direction. Therefore, it is determined that the amount of SOx stored in the storage NOx catalyst 30a is relatively small.
【0030】これにより、実行周期当たりの被毒S量Δ
Qsがより一層正確に推定されることになる。また、実
行周期当たりの再生S量Rsは次式(3)から演算される。 Rs=α・R1・R2・dT …(3) ここに、αは単位時間当たりの再生率(設定値)であ
り、dTは燃料噴射制御ルーチンの実行周期を示してお
り、R1及びR2はそれぞれ触媒温度Tcatに応じた再生
能力係数及び空燃比A/Fに応じた再生能力係数を示し
ている。Thus, the amount of poisoning S per execution cycle Δ
Qs will be more accurately estimated. The reproduction S amount Rs per execution cycle is calculated from the following equation (3). Rs = α · R1 · R2 · dT (3) where α is a regeneration rate (set value) per unit time, dT indicates an execution cycle of the fuel injection control routine, and R1 and R2 are respectively A regeneration capacity coefficient according to the catalyst temperature Tcat and a regeneration capacity coefficient according to the air-fuel ratio A / F are shown.
【0031】触媒温度Tcatに応じた再生能力係数R1
は、図3(a)に示すように、実験データに基づき、触
媒温度Tcatが大きくなるにつれて指数関数的に増大す
るようにされている。つまり、SOxは触媒温度Tcatが
大きくなるほど指数関数的に急速に吸蔵型NOx触媒3
0aから除去され易くなる傾向にあり、故に再生能力係
数R1はこれに応じて増加するようにされている。The regeneration capacity coefficient R1 according to the catalyst temperature Tcat
As shown in FIG. 3A, based on experimental data, is set to increase exponentially as the catalyst temperature Tcat increases. That is, the SOx increases exponentially rapidly as the catalyst temperature Tcat increases.
0a tends to be easily removed, and therefore the reproduction capability coefficient R1 is increased accordingly.
【0032】空燃比A/Fに応じた再生能力係数R2
は、図3(b)に示すように、実験データに基づき、空
燃比A/Fがリッチ空燃比では大きく略一定値とされ、
超リーン空燃比となるほど減少するようにされている。
つまり、SOxは、上述したように、リッチ空燃比であ
る還元雰囲気中では良好に除去される一方、空燃比がリ
ーン空燃比となると逆に吸蔵型NOx触媒30aに吸蔵
されるようになり、再生能力係数R2はこれに応じて設
定されている。Regeneration capacity coefficient R2 according to air-fuel ratio A / F
As shown in FIG. 3 (b), based on the experimental data, the air-fuel ratio A / F is made substantially constant at a rich air-fuel ratio,
It is designed to decrease as the air-fuel ratio becomes extremely lean.
That is, as described above, SOx is favorably removed in a reducing atmosphere having a rich air-fuel ratio, whereas when the air-fuel ratio becomes a lean air-fuel ratio, it is occluded by the occlusion type NOx catalyst 30a. The performance coefficient R2 is set accordingly.
【0033】つまり、SOxは触媒温度Tcatが高温に加
熱され空燃比A/Fがリッチ空燃比になると還元除去さ
れることになるのであるが、これら図3(a)及び
(b)に基いて触媒温度Tcat、空燃比A/Fに対応す
る再生能力係数R1,R2を求めることで、実行周期当た
りの再生S量Rsを適正に演算するようにでき、故に、
現在の被毒S量Qsをより一層正確に求めることが可能
とされる。That is, SOx is reduced and removed when the catalyst temperature Tcat is heated to a high temperature and the air-fuel ratio A / F becomes a rich air-fuel ratio. Based on these FIGS. 3 (a) and 3 (b), SOx is reduced. By obtaining the regeneration capacity coefficients R1 and R2 corresponding to the catalyst temperature Tcat and the air-fuel ratio A / F, the regeneration S amount Rs per execution cycle can be properly calculated.
The current poisoning S amount Qs can be obtained more accurately.
【0034】そして、当該被毒S量Qsが所定量、即ち
S劣化判定閾値に達したと判定されると、吸蔵型NOx
触媒30aからのSOxの除去、即ちSパージが開始さ
れる。この際、上述の如く被毒S量Qsの推定が正確で
あるため、当該判定は極めて適正なのものとされる。つ
まり、本発明によれば、Sパージの実施インターバルが
長くなってNOxが不用意に排出されてしまうようなこ
ともなく、またSパージが頻繁に行われて燃費が悪化す
るようなこともなく、効率よくSパージが実施されるこ
とになる。When it is determined that the poisoning S amount Qs has reached a predetermined amount, that is, the S deterioration determination threshold value, the storage NOx
Removal of SOx from the catalyst 30a, that is, S purge is started. At this time, since the estimation of the poisoning S amount Qs is accurate as described above, the determination is extremely appropriate. That is, according to the present invention, there is no possibility that the execution interval of the S purge becomes long and NOx is inadvertently discharged, and that the fuel efficiency is not deteriorated due to the frequent S purge being performed. Thus, the S purge is performed efficiently.
【0035】Sパージが開始されると、目標A/Fがリ
ッチ空燃比とされるとともに、例えば2段噴射或いは点
火時期リタードが実施されて排気昇温が行われる(硫黄
成分除去手段)。2段噴射は、燃料噴射を2回に分割
し、主噴射を圧縮行程或いは吸気行程で行うとともに副
噴射を膨張行程で行うようなものであり、膨張行程で副
噴射する燃料を排気通路内で燃焼させて排気昇温を行う
ようなものである。また、点火時期リタードは、燃焼を
緩慢にし、排気後においても燃焼を継続させることで排
気昇温を行うようなものである。なお、ここでは、これ
ら2段噴射及び点火時期リタードの制御内容の詳細につ
いては説明を省略する。When the S purge is started, the target A / F is set to the rich air-fuel ratio, and, for example, the two-stage injection or the ignition timing retard is performed to raise the exhaust gas temperature (sulfur component removing means). The two-stage injection is such that the fuel injection is divided into two times, and the main injection is performed in the compression stroke or the intake stroke and the sub-injection is performed in the expansion stroke. It is like burning and raising the temperature of exhaust gas. Further, the ignition timing retard is such that the exhaust gas temperature is increased by slowing down the combustion and continuing the combustion even after the exhaust gas. Here, the details of the control contents of these two-stage injection and ignition timing retard are omitted.
【0036】これにより、吸蔵型NOx触媒30a内が
還元雰囲気とされるとともに良好に昇温されて所定の高
温(例えば、650℃)とされ、SOxが良好に除去さ
れることとなる。そして、Sパージが開始された後、例
えば、上記式(1)により演算される被毒S量Qsが再生S
量Rsの増加により所定値(例えば、値0または値0近
傍値)以下にまで減少したと判定されると、Sパージは
終了させられる。As a result, the inside of the storage NOx catalyst 30a is set to a reducing atmosphere, and the temperature is satisfactorily raised to a predetermined high temperature (for example, 650 ° C.), so that SOx is removed satisfactorily. After the start of the S purge, for example, the poisoning S amount Qs calculated by the above equation (1) becomes equal to the regeneration S amount.
If it is determined that the amount has decreased to a predetermined value (for example, a value 0 or a value near the value 0) or less due to an increase in the amount Rs, the S purge is terminated.
【0037】ところで、以上のようにして吸蔵型NOx
触媒30aに吸蔵されたSOxの吸蔵量、即ち被毒S量
Qsが正確に推定され、SOxが良好に除去されるのであ
るが、通常、吸蔵型NOx触媒30aは熱劣化等により
経時劣化しSOxによる被毒に関係なくNOxの吸蔵能力
が低下するものである。つまり、時間経過とともに吸蔵
型NOx触媒30aに吸蔵可能なNOxの量が低下するこ
とになる。By the way, as described above, the storage NOx
The storage amount of SOx stored in the catalyst 30a, that is, the poisoning S amount Qs is accurately estimated, and SOx is removed satisfactorily. However, the storage NOx catalyst 30a usually deteriorates with time due to thermal deterioration or the like, and SOx is deteriorated. NOx storage capacity is reduced irrespective of the poisoning caused by NOx. That is, the amount of NOx that can be stored in the storage-type NOx catalyst 30a decreases with time.
【0038】故に、このような場合にはNOxの吸蔵能
力の低下に伴いSOxを極力吸蔵させないようにするの
がよく、ここでは、Sパージの実施回数を重ねる毎にS
劣化判定閾値を小さくし、つまり早期にSパージが実施
されるようにし、これによりNOxの吸蔵能力を常に良
好に確保可能にしている。つまり、図4を参照すると、
被毒S量Qsの時間変化が示されているが、詳しくは、
このように1回目のSパージでは値Qs1であったS劣化
判定閾値を2回目は値Qs2と小さくし、3回目では値Q
s3とさらに小さくするようにする。これにより、吸蔵型
NOx触媒30aの経時劣化に対応してSパージが早期
に実施されることになり、吸蔵型NOx触媒30aはN
Oxを常に良好に吸蔵可能な状態に維持される。Therefore, in such a case, it is preferable that the SOx is not absorbed as much as possible with the decrease in the NOx storage capacity.
The deterioration determination threshold value is reduced, that is, the S purge is performed early, so that the NOx occlusion capacity can always be sufficiently ensured. That is, referring to FIG.
The time change of the poisoning S amount Qs is shown.
As described above, the S deterioration determination threshold value, which was the value Qs1 in the first S purge, is reduced to the value Qs2 in the second time, and the value Q is reduced in the third time.
Make it even smaller with s3. As a result, the S purge is performed at an early stage in response to the aging of the storage NOx catalyst 30a, and the storage NOx catalyst 30a
Ox is always kept in a state in which it can be occluded well.
【0039】なお、図4中、被毒S量Qsは鋸歯状に増
減を繰り返しながら増加しているが、これは、通常の運
転時であってもSパージが行われることを示している。
つまり、車両が登坂路を走行するような場合には目標A
/Fがリッチ空燃比とされる場合が多いのであるが、こ
のような場合に還元雰囲気が形成されて吸蔵型NOx触
媒30aが上記所定の高温(例えば、650℃)を超え
て加熱され、Sパージが好ましく自然に実施されること
を示している。In FIG. 4, the poisoning S amount Qs increases while repeatedly increasing and decreasing in a sawtooth manner, which indicates that the S purge is performed even during a normal operation.
That is, when the vehicle travels on an uphill road, the target A
/ F is often set to a rich air-fuel ratio. In such a case, a reducing atmosphere is formed and the storage NOx catalyst 30a is heated above the predetermined high temperature (for example, 650 ° C.), and S / S This shows that the purge is preferably performed spontaneously.
【0040】なお、上記実施形態では、燃料噴射積算量
Qfに基づいて被毒S量Qsを算出するようにしたが、燃
料噴射積算量Qfに代えて燃料噴射量と相関する車両の
走行距離から被毒S量Qsを推定するようにしてもよ
い。この場合、被毒S量Qsは上記式(1)に代えて次式
(4)から求められる。 Qs=Qs(n-1)+(V・dT)・K−Rs …(4) ここに、Vは車速であり、(V・dT)が燃料噴射制御
ルーチンの実行周期当たりの走行距離(燃料噴射量相関
値)である(燃料噴射量相関値演算手段)。In the above embodiment, the poisoning S amount Qs is calculated based on the integrated fuel injection amount Qf. However, instead of the integrated fuel injection amount Qf, the poisoning S amount Qs is calculated based on the travel distance of the vehicle correlated with the fuel injection amount. The poisoning S amount Qs may be estimated. In this case, the poisoning S amount Qs is obtained by the following equation instead of the above equation (1).
Required from (4). Qs = Qs (n−1) + (V · dT) · K−Rs (4) where V is the vehicle speed, and (V · dT) is the mileage (fuel) per execution cycle of the fuel injection control routine. (Fuel injection amount correlation value calculation means).
【0041】また、例えば、バッテリが一旦外されると
ECU40の記憶装置に記憶された被毒S量Qsの演算
データが途中でリセットされ消去されてしまうことにな
るが、このような場合には、上記S劣化判定に拘わら
ず、Sパージを強制的に実施するようにする。または、
被毒S量Qsの初期値をS劣化判定閾値に近い十分大き
な値とし、1回目のSパージを早期に実施するようにす
る。これにより、実際の被毒S量Qsが多いままで走行
が続けられることなく、被毒S量Qsの演算値と実際の
SOx吸蔵量とが常に一致することになり、以降、被毒
S量Qsの推定が継続して適正なものとされる。Further, for example, once the battery is removed, the calculation data of the poisoning S amount Qs stored in the storage device of the ECU 40 is reset and erased halfway, but in such a case, Accordingly, the S purge is forcibly performed regardless of the S deterioration determination. Or
The initial value of the poisoning S amount Qs is set to a sufficiently large value close to the S deterioration determination threshold, so that the first S purge is performed early. As a result, the calculated value of the poisoning S amount Qs always coincides with the actual SOx occlusion amount without traveling while the actual poisoning S amount Qs is large. The estimation of Qs continues to be appropriate.
【0042】また、上記実施形態では、被毒S量Qsが
所定値(例えば、値0または値0近傍値)以下にまで減
少したと判定されたらSパージを終了するようにした
が、簡略化して、予め設定した所定時間に亘ってSパー
ジを行うようにし、該所定時間が経過したときにSパー
ジを終了するようにしてもよい。In the above-described embodiment, the S purge is terminated when it is determined that the poisoning S amount Qs has decreased to a predetermined value (for example, a value 0 or a value near the value 0). Thus, the S purge may be performed for a predetermined time set in advance, and the S purge may be terminated when the predetermined time has elapsed.
【0043】[0043]
【発明の効果】以上詳細に説明したように、本発明の請
求項1の内燃機関の排気浄化装置によれば、吸蔵型NO
x触媒への硫黄成分の吸蔵度合を空燃比に応じた度合と
なるよう演算するようにしており、吸蔵型NOx触媒に
吸蔵される硫黄成分の堆積量を燃料噴射量に相当する燃
料噴射量相関値と上記硫黄成分の吸蔵度合とに基づいて
推定するようにしている。As described above in detail, according to the exhaust gas purifying apparatus for an internal combustion engine of the first aspect of the present invention, the storage NO
degree and corresponding occlusion degree of sulfur components in the x catalyst air-fuel ratio
The amount of sulfur component stored in the storage NOx catalyst is estimated based on the fuel injection amount correlation value corresponding to the fuel injection amount and the degree of storage of the sulfur component. I have.
【0044】従って、吸蔵型NOx触媒に吸蔵される硫
黄成分(S成分)、即ち硫黄酸化物(SOx)の堆積量
を空燃比に応じて変化する吸蔵度合を考慮して推定で
き、SOxの堆積量を実際に即した適正な値にできる。
故に、硫黄成分除去手段による硫黄成分の除去、即ちS
Oxの除去つまりSパージの実施タイミングを極めて適
正なものにでき、Sパージの実施インターバルが長くな
ってNOxが不用意に排出されてしまうことを抑止で
き、Sパージが頻繁に行われて燃費が悪化するようなこ
とを好適に防止することができる。また、請求項2の内
燃機関の排気浄化装置によれば、吸蔵型NOx触媒に吸
蔵される硫黄酸化物(SOx)の堆積量を触媒温度に応
じて変化する吸蔵度合を考慮して推定でき、SOxの堆
積量をさらに実際に即した適正な値にできる。 また、請
求項3、4の内燃機関の排気浄化装置によれば、吸蔵型
NOx触媒に吸蔵される硫黄酸化物(SOx)の堆積量を
燃料性状に応じて変化する吸蔵度合を考慮して推定で
き、SOxの堆積量をさらに実際に即した適正な値にで
きる。 [0044] Thus, the sulfur component occluded in the occlusion-type NOx catalyst (S component), i.e. sulfur oxide deposition amount (SOx) can be estimated by considering the occlusion degree that varies depending on the air-fuel ratio, the SOx The deposition amount can be set to an appropriate value according to the actual situation.
Therefore, the removal of the sulfur component by the sulfur component removing means, that is, S
The removal timing of Ox, that is, the execution timing of the S purge can be made extremely appropriate, and the execution interval of the S purge can be prevented from being extended to prevent careless emission of NOx. Deterioration can be suitably prevented. Claim 2
According to the exhaust gas purification device for a fuel engine, the storage NOx catalyst
The amount of stored sulfur oxides (SOx) depends on the catalyst temperature.
Can be estimated by taking into account the degree of storage that changes
The volume can be set to an appropriate value based on the actual situation. In addition,
According to the exhaust gas purifying apparatus for an internal combustion engine according to claims 3 and 4, the occlusion type
The amount of sulfur oxide (SOx) stored in the NOx catalyst
Estimation taking into account the degree of occlusion that changes depending on the fuel properties
The amount of SOx deposition to a more appropriate value
Wear.
【図1】本発明に係る内燃機関の排気浄化装置を示す概
略構成図である。FIG. 1 is a schematic configuration diagram showing an exhaust gas purification device for an internal combustion engine according to the present invention.
【図2】被毒S量Qsの補正係数を示す図であって、空
燃比A/Fに応じたS被毒係数K1の空燃比A/との関
係(a)、S含有量に応じたS被毒係数K2のS含有量
との関係(b)及び触媒温度Tcatに応じたS被毒係数
K3の触媒温度Tcatとの関係(c)を示す図である。FIG. 2 is a diagram showing a correction coefficient of the poisoning S amount Qs, which shows the relationship between the S poisoning coefficient K1 and the air-fuel ratio A / according to the air-fuel ratio A / F (a), and the S-content It is a figure which shows the relationship (b) with the S content of the S poisoning coefficient K2 and the catalyst temperature Tcat of the S poisoning coefficient K3 according to the catalyst temperature Tcat.
【図3】再生S量Rsの演算に使用する触媒温度Tcatに
応じた再生能力係数R1の触媒温度Tcatとの関係(a)
及び空燃比A/Fに応じた再生能力係数R2の空燃比A
/Fとの関係(b)を示す図である。FIG. 3 shows the relationship between the regeneration capacity coefficient R1 and the catalyst temperature Tcat according to the catalyst temperature Tcat used for calculating the regeneration S amount Rs (a).
And the air-fuel ratio A of the regeneration capacity coefficient R2 according to the air-fuel ratio A / F
FIG. 10 is a diagram showing a relationship (b) with / F.
【図4】Sパージを行った場合の被毒S量Qsの時間変
化を示すタイムチャートである。FIG. 4 is a time chart showing a time change of a poisoning S amount Qs when an S purge is performed.
1 エンジン(内燃機関) 4 点火プラグ 6 燃料噴射弁 11 スロットル弁 11a スロットルセンサ 13 クランク角センサ 16 高温センサ 18 ノックセンサ 30a 吸蔵型NOx触媒 40 電子制御ユニット(ECU) DESCRIPTION OF SYMBOLS 1 Engine (internal combustion engine) 4 Spark plug 6 Fuel injection valve 11 Throttle valve 11a Throttle sensor 13 Crank angle sensor 16 High temperature sensor 18 Knock sensor 30a Storage type NOx catalyst 40 Electronic control unit (ECU)
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平9−317447(JP,A) 特開 平7−217474(JP,A) (58)調査した分野(Int.Cl.7,DB名) B01D 53/86 F01N 3/08 B01D 53/34 B01D 53/81 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-9-317447 (JP, A) JP-A-7-217474 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) B01D 53/86 F01N 3/08 B01D 53/34 B01D 53/81
Claims (4)
燃機関がリーン空燃比運転状態にあるとき排気中のNO
xを吸蔵させ、理論空燃比運転またはリッチ空燃比運転
状態にあるとき前記吸蔵させたNOxを還元する吸蔵型
NOx触媒と、 燃料噴射量に相当する燃料噴射量相関値を演算する燃料
噴射量相関値演算手段と、 燃料中に含まれ前記排気通路に排出される硫黄成分の前
記吸蔵型NOx触媒への吸蔵度合を空燃比に応じた度合
となるよう演算する硫黄成分吸蔵度合演算手段と、 前記燃料噴射量相関値演算手段により演算される燃料噴
射量相関値と前記硫黄成分吸蔵度合演算手段により演算
される硫黄成分の吸蔵度合とに基づいて前記吸蔵型NO
x触媒に吸蔵される硫黄成分の堆積量を推定する硫黄成
分堆積量推定手段と、 前記硫黄成分堆積量推定手段により推定された硫黄成分
の堆積量に基づき前記吸蔵型NOx触媒に吸蔵された硫
黄成分を除去する硫黄成分除去手段と、 を備えたことを特徴とする内燃機関の排気浄化装置。1. An exhaust passage provided in an exhaust passage of an internal combustion engine, the NO in the exhaust when the internal combustion engine is in a lean air-fuel ratio operating state.
a storage type NOx catalyst that stores x and reduces the stored NOx when in a stoichiometric air-fuel ratio operation or a rich air-fuel ratio operation state, and a fuel injection amount correlation that calculates a fuel injection amount correlation value corresponding to the fuel injection amount. degree corresponding value calculation means, said storage extent to occlusion-type NOx catalyst of the sulfur component contained in the fuel is discharged into the exhaust passage to the air-fuel ratio
Sulfur component occlusion degree calculating means that calculates so as to obtain the fuel injection amount correlation value calculated by the fuel injection amount correlation value calculating means and the sulfur component occlusion degree calculated by the sulfur component occlusion degree calculating means. The storage type NO
x sulfur component accumulation amount estimating means for estimating the accumulation amount of sulfur component occluded in the x catalyst, and sulfur occluded by the occlusion type NOx catalyst based on the sulfur component accumulation amount estimated by the sulfur component accumulation amount estimating means. An exhaust gas purifying apparatus for an internal combustion engine, comprising: a sulfur component removing means for removing a component.
に触媒温度に応じた度合となるよう前記排気通路に排出
される硫黄成分の前記吸蔵型NOx触媒への吸蔵度合を
演算することを特徴とする、請求項1記載の内燃機関の
排気浄化装置。 2. The method according to claim 1, wherein said sulfur component occlusion degree calculating means further comprises:
To the exhaust passage to a degree corresponding to the catalyst temperature
Storage degree of the sulfur component to be stored in the storage NOx catalyst
2. The internal combustion engine according to claim 1, wherein the operation is performed.
Exhaust gas purification device.
に燃料性状に応じた度合となるよう前記排気通路に排出
される硫黄成分の前記吸蔵型NOx触媒への吸蔵度合を
演算することを特徴とする、請求項1または2記載の内
燃機関の排気浄化装置。 3. The method according to claim 2, wherein the sulfur component occlusion degree calculating means further comprises:
Discharged to the exhaust passage to a degree according to the fuel properties
Storage degree of the sulfur component to be stored in the storage NOx catalyst
3. The method according to claim 1, wherein the calculation is performed.
Exhaust purification device for fuel engine.
機関のノッキングを検出するノックセンサを含み、該ノ
ックセンサからの出力情報に基づき前記燃料性状を検出
することを特徴とする、請求項3記載の内燃機関の排気
浄化装置。 4. The method according to claim 1, wherein the sulfur component occlusion degree calculating means is an internal combustion engine.
A knock sensor for detecting knocking of the engine;
Fuel properties are detected based on output information from the
4. The exhaust of an internal combustion engine according to claim 3, wherein
Purification device.
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