JPH0650132A - Exhaust emission control device of internal combustion engine - Google Patents
Exhaust emission control device of internal combustion engineInfo
- Publication number
- JPH0650132A JPH0650132A JP4203635A JP20363592A JPH0650132A JP H0650132 A JPH0650132 A JP H0650132A JP 4203635 A JP4203635 A JP 4203635A JP 20363592 A JP20363592 A JP 20363592A JP H0650132 A JPH0650132 A JP H0650132A
- Authority
- JP
- Japan
- Prior art keywords
- nox
- absorbent
- exhaust gas
- temperature
- purification rate
- 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.)
- Granted
Links
Landscapes
- Exhaust Gas After Treatment (AREA)
- Combined Controls Of Internal Combustion Engines (AREA)
- Treating Waste Gases (AREA)
Abstract
Description
【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
に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification device for an internal combustion engine.
【０００２】[0002]
【従来の技術】リーン混合気を燃焼せしめるようにした
内燃機関において、流入排気ガスの空燃比がリーンのと
きにはＮＯｘを吸収し、流入排気ガス中の酸素濃度が低
下すると吸収したＮＯｘを放出するＮＯｘ吸収剤を機関
排気通路内に配置し、リーン混合気を燃焼せしめた際に
発生するＮＯｘをＮＯｘ吸収剤により吸収し、ＮＯｘ吸
収剤のＮＯｘ吸収能力が飽和する前にＮＯｘ吸収剤への
流入排気ガスの空燃比を一時的にリッチにしてＮＯｘ吸
収剤からＮＯｘを放出させると共に放出されたＮＯｘを
還元するようにした内燃機関が本出願人により既に提案
されている（特願平３−２８４０９５号参照）。2. Description of the Related Art In an internal combustion engine that burns a lean mixture, NOx absorbs NOx when the air-fuel ratio of the inflowing exhaust gas is lean and releases the absorbed NOx when the oxygen concentration in the inflowing exhaust gas decreases. An absorbent is placed in the engine exhaust passage to absorb NOx generated when a lean air-fuel mixture is burned by the NOx absorbent, and the exhaust gas flowing into the NOx absorbent before the NOx absorbent capacity of the NOx absorbent is saturated. The applicant has already proposed an internal combustion engine in which the air-fuel ratio of the gas is temporarily made rich to release NOx from the NOx absorbent and reduce the released NOx (Japanese Patent Application No. 3-284095). reference).
【０００３】[0003]
【発明が解決しようとする課題】しかしながらこのよう
なＮＯｘ吸収剤はＮＯｘを吸収して保持する能力、即ち
ＮＯｘの浄化率が特定の温度領域においてピークにな
り、ＮＯｘ吸収剤の温度がこの温度領域に対して低くな
っても高くなってもＮＯｘ吸収剤によるＮＯｘ浄化率が
低下する。従ってＮＯｘ浄化率がピークとなる温度領域
でＮＯｘ吸収剤を使用することが必要となるが上述の内
燃機関では複数のＮＯｘ吸収剤を用いた場合に各ＮＯｘ
吸収剤を夫々ＮＯｘ浄化率が高い状態で使用することに
関して何ら示唆していない。However, such an NOx absorbent has the ability to absorb and retain NOx, that is, the purification rate of NOx reaches a peak in a specific temperature range, and the temperature of the NOx absorbent falls within this temperature range. However, the NOx purification rate by the NOx absorbent is reduced regardless of whether the NOx absorbent is low or high. Therefore, it is necessary to use the NOx absorbent in a temperature range where the NOx purification rate reaches its peak. However, in the above-mentioned internal combustion engine, when a plurality of NOx absorbents are used, each NOx absorbent is used.
There is no suggestion as to the use of the absorbents at high NOx purification rates, respectively.
【０００４】[0004]
【課題を解決するための手段】本発明によれば、ＮＯｘ
浄化率がピークとなる温度領域でＮＯｘ吸収剤を使用す
るために流入排気ガスの空燃比がリーンのときにはＮＯ
ｘを吸収し、流入排気ガス中の酸素濃度が低下すると吸
収したＮＯｘを放出するＮＯｘ吸収剤であってＮＯｘ浄
化率がピークとなる温度領域の異なる複数のＮＯｘ吸収
剤を機関排気通路内に配置し、温度の高い排気ガスは温
度が高いときにＮＯｘ浄化率がピークとなるＮＯｘ吸収
剤に送り込むと共に温度の低い排気ガスは温度が低いと
きにＮＯｘ浄化率がピークとなるＮＯｘ吸収剤に送り込
むようにしている。According to the present invention, NOx
When the air-fuel ratio of the inflowing exhaust gas is lean, NO is used because the NOx absorbent is used in the temperature range where the purification rate reaches its peak.
A plurality of NOx absorbents that absorb x and release the absorbed NOx when the oxygen concentration in the inflowing exhaust gas decreases and that have different NOx purification rates in different temperature regions are arranged in the engine exhaust passage. However, the exhaust gas with a high temperature is sent to the NOx absorbent whose NOx purification rate has a peak when the temperature is high, and the exhaust gas with a low temperature is sent to the NOx absorbent whose NOx purification rate has a peak when the temperature is low. I have to.
【０００５】[0005]
【作用】温度の高い排気ガスは温度が高いときにＮＯｘ
浄化率がピークとなるＮＯｘ吸収剤に送り込まれ、温度
の低い排気ガスは温度が低いときにＮＯｘ浄化率がピー
クとなるＮＯｘ吸収剤に送り込まれるので各ＮＯｘ吸収
剤は夫々ＮＯｘ浄化率がピークとなる状態で使用され
る。[Function] Exhaust gas having a high temperature is NOx when the temperature is high.
The exhaust gas having a low purification rate is sent to the NOx absorbent, and the exhaust gas having a low temperature is sent to the NOx absorbent having a peak NOx purification rate when the temperature is low. Therefore, each NOx absorbent has a peak NOx purification rate. Used in the condition.
【０００６】[0006]
【実施例】図１を参照すると、１は機関本体、２はピス
トン、３は燃焼室、４は点火栓、５は吸気弁、６は吸気
ポート、７は排気弁、８は排気ポートを夫々示す。吸気
ポート６は対応する枝管９を介してサージタンク１０に
連結され、各枝管９には夫々吸気ポート６内に向けて燃
料を噴射する燃料噴射弁１１が取付けられる。サージタ
ンク１０は吸気ダクト１２およびエアフローメータ１３
を介してエアクリーナ１４に連結され、吸気ダクト１２
内にはスロットル弁１５が配置される。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, 1 is an engine body, 2 is a piston, 3 is a combustion chamber, 4 is a spark plug, 5 is an intake valve, 6 is an intake port, 7 is an exhaust valve, and 8 is an exhaust port. Show. The intake port 6 is connected to the surge tank 10 via a corresponding branch pipe 9, and each branch pipe 9 is provided with a fuel injection valve 11 for injecting fuel into the intake port 6. The surge tank 10 includes an intake duct 12 and an air flow meter 13
Is connected to the air cleaner 14 through the intake duct 12
A throttle valve 15 is arranged inside.
【０００７】一方、排気ポート８は排気マニホルド１６
を介して第１のＮＯｘ吸収剤１７を内蔵したケーシング
１８に連結され、このケーシング１８は排気管１９を介
して第２のＮＯｘ吸収剤２０を内蔵したケーシング２１
に連結される。更にこのケーシング２１は排気管２２を
介して第３のＮＯｘ吸収剤２３を内蔵したケーシング２
４に連結される。従って排気通路内には排気ガスの流れ
方向において順に第１ＮＯｘ吸収剤１７、第２ＮＯｘ吸
収剤２０、第３ＮＯｘ吸収剤２３が配置されることにな
る。図１に示す内燃機関では燃焼室３内に供給される混
合気の空燃比はリーンとされ、従って燃焼室３内ではリ
ーン混合気が燃焼せしめられることになる。On the other hand, the exhaust port 8 is connected to the exhaust manifold 16
Is connected to a casing 18 containing a first NOx absorbent 17 via a pipe, and the casing 18 is provided with a casing 21 containing a second NOx absorbent 20 via an exhaust pipe 19.
Connected to. Further, this casing 21 is a casing 2 in which a third NOx absorbent 23 is built in via an exhaust pipe 22.
4 is connected. Therefore, the first NOx absorbent 17, the second NOx absorbent 20, and the third NOx absorbent 23 are sequentially arranged in the exhaust passage in the flow direction of the exhaust gas. In the internal combustion engine shown in FIG. 1, the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber 3 is lean, so that the lean air-fuel mixture is burned in the combustion chamber 3.
【０００８】図２は燃焼室３から排出される排気ガス中
の代表的な成分の濃度を概略的に示している。図２から
わかるように燃焼室３から排出される排気ガス中の未燃
ＨＣ，ＣＯの量は燃焼室３内に供給される混合気の空燃
比がリッチになるほど増大し、燃焼室３から排出される
排気ガス中の酸素Ｏ2 の量は燃焼室３内に供給される混
合気の空燃比がリーンになるほど増大する。FIG. 2 schematically shows the concentrations of typical components in the exhaust gas discharged from the combustion chamber 3. As can be seen from FIG. 2, the amount of unburned HC and CO in the exhaust gas discharged from the combustion chamber 3 increases as the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber 3 becomes richer, and is discharged from the combustion chamber 3. The amount of oxygen O 2 in the generated exhaust gas increases as the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber 3 becomes leaner.
【０００９】各ケーシング１８，２１，２４内に収容さ
れている各ＮＯｘ吸収剤１７，２０，２３は例えばアル
ミナを担体とし、この担体上に例えばカリウムＫ、ナト
リウムＮａ、リチウムＬｉ、セシウムＣｓのようなアル
カリ金属、バリウムＢａ、カルシウムＣａ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
類から選ばれた少くとも一つと、白金Ｐｔのような貴金
属と、必要に応じてその他の金属とが担持されている。
機関吸気通路およびＮＯｘ吸収剤１７上流の排気通路内
に供給された空気および燃料の比を各ＮＯｘ吸収剤１
７，２０，２３への流入排気ガスの空燃比と称すると各
ＮＯｘ吸収剤１７，２０，２３は流入排気ガスの空燃比
がリーンのときにはＮＯｘを吸収し、流入排気ガス中の
酸素濃度が低下すると吸収したＮＯｘを放出するＮＯｘ
の吸放出作用を行う。なお、ＮＯｘ吸収剤１７上流の排
気通路内に燃料或いは空気が供給されない場合には流入
排気ガスの空燃比は燃焼室３内に供給される混合気の空
燃比に一致し、従ってこの場合には各ＮＯｘ吸収剤１
７，２０，２３は燃焼室３内に供給される混合気の空燃
比がリーンのときにはＮＯｘを吸収し、燃焼室３内に供
給される混合気中の酸素濃度が低下すると吸収したＮＯ
ｘを放出することになる。Each of the NOx absorbents 17, 20, and 23 contained in each of the casings 18, 21, and 24 uses, for example, alumina as a carrier, on which potassium K, sodium Na, lithium Li, and cesium Cs are formed. At least one selected from the group consisting of alkaline metals, barium Ba, alkaline earths such as calcium Ca, lanthanum La, rare earths such as yttrium Y, precious metals such as platinum Pt, and optionally other metals. Is carried.
The ratio of the air and the fuel supplied into the exhaust passage upstream of the engine intake passage and the NOx absorbent 17 is determined by the NOx absorbent 1
When referred to as the air-fuel ratio of the inflowing exhaust gas to 7, 20, 23, each NOx absorbent 17, 20, 23 absorbs NOx when the air-fuel ratio of the inflowing exhaust gas is lean, and the oxygen concentration in the inflowing exhaust gas decreases. Then, NOx that releases the absorbed NOx
It absorbs and releases. When fuel or air is not supplied into the exhaust passage upstream of the NOx absorbent 17, the air-fuel ratio of the inflowing exhaust gas matches the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber 3, and in this case, Each NOx absorbent 1
7, 20 and 23 absorb NOx when the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber 3 is lean, and absorb NOx when the oxygen concentration in the air-fuel mixture supplied to the combustion chamber 3 decreases.
will emit x.
【００１０】上述の各ＮＯｘ吸収剤１７，２０，２３を
機関排気通路内に配置すれば各ＮＯｘ吸収剤１７，２
０，２３は実際にＮＯｘの吸放出作用を行うがこの吸放
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。しかしながらこの吸放出作用は図３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。次にこ
のメカニズムについて担体上に白金Ｐｔ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。If the above NOx absorbents 17, 20 and 23 are arranged in the engine exhaust passage, the NOx absorbents 17 and 2 will be arranged.
Nos. 0 and 23 actually perform the NOx absorption / release action, but there is a part where the detailed mechanism of this absorption / release action is not clear. However, it is considered that this absorbing and releasing action is performed by the mechanism shown in FIG. Next, this mechanism will be described by taking the case where platinum Pt and barium Ba are supported on the carrier as an example, but the same mechanism can be obtained by using other noble metals, alkali metals, alkaline earths and rare earths.
【００１１】即ち、流入排気ガスがかなりリーンになる
と流入排気ガス中の酸素濃度が大巾に増大し、図３
（Ａ）に示されるようにこれら酸素Ｏ2 がＯ2 - の形で
白金Ｐｔの表面に付着する。一方、流入排気ガス中のＮ
Ｏは白金Ｐｔの表面上でＯ2 - と反応し、ＮＯ2 となる
（２ＮＯ＋Ｏ2 →２ＮＯ2 ）。次いで生成されたＮＯ2
の一部は白金Ｐｔ上で更に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３（Ａ）
に示されるように硝酸イオンＮＯ3 - の形で吸収剤内に
拡散する。このようにしてＮＯｘが各ＮＯｘ吸収剤１
７，２０，２３内に吸収される。That is, when the inflowing exhaust gas becomes considerably lean, the oxygen concentration in the inflowing exhaust gas greatly increases.
As shown in (A), these oxygen O 2 attaches to the surface of platinum Pt in the form of O 2 − . On the other hand, N in the inflowing exhaust gas
O reacts with O 2 − on the surface of platinum Pt to become NO 2 (2NO + O 2 → 2NO 2 ). NO 2 produced next
3A is partially oxidized on the platinum Pt, is absorbed in the absorbent and is bonded to the barium oxide BaO, and FIG.
As shown in ( 3 ), it diffuses into the absorbent in the form of nitrate ion NO 3 − . In this way, NOx is converted to each NOx absorbent 1
Absorbed in 7, 20, 23.
【００１２】流入排気ガス中の酸素濃度が高い限り白金
Ｐｔの表面でＮＯ2 が生成され、吸収剤のＮＯｘ吸収能
力が飽和しない限りＮＯ2 が吸収剤内に吸収されて硝酸
イオンＮＯ3 - が生成される。これに対して流入排気ガ
ス中の酸素濃度が低下してＮＯ2 の生成量が低下すると
反応が逆方向（ＮＯ3 - →ＮＯ2 ）に進み、斯くして吸
収剤内の硝酸イオンＮＯ3 - がＮＯ2 の形で吸収剤から
放出される。即ち、流入排気ガス中の酸素濃度が低下す
ると各ＮＯｘ吸収剤１７，２０，２３からＮＯｘが放出
されることになる。図２に示されるように流入排気ガス
のリーンの度合が低くなれば流入排気ガス中の酸素濃度
が低下し、従って流入排気ガスのリーンの度合を低くす
れば各ＮＯｘ吸収剤１７，２０，２３からＮＯｘが放出
されることになる。NO 2 is produced on the surface of platinum Pt as long as the oxygen concentration in the inflowing exhaust gas is high, and NO 2 is absorbed in the absorbent as long as the NOx absorption capacity of the absorbent is not saturated, and nitrate ions NO 3 − are produced. Is generated. In contrast the reaction with the amount of NO 2 oxygen concentration is lowered in the inflowing exhaust gas is lowered backward (NO 3 - → NO 2) proceeds to, thus nitrate ions to the absorber NO 3 - Are released from the absorbent in the form of NO 2 . That is, when the oxygen concentration in the inflowing exhaust gas decreases, NOx is released from each NOx absorbent 17, 20, 23. As shown in FIG. 2, if the lean degree of the inflowing exhaust gas is low, the oxygen concentration in the inflowing exhaust gas is low. Therefore, if the lean degree of the inflowing exhaust gas is low, each NOx absorbent 17, 20, 23 is reduced. NOx will be released from.
【００１３】一方、このとき流入排気ガスの空燃比をリ
ッチにすると図２に示されるように機関からは多量の未
燃ＨＣ，ＣＯが排出され、これら未燃ＨＣ，ＣＯは白金
Ｐｔ上の酸素Ｏ2 - と反応して酸化せしめられる。ま
た、流入排気ガスの空燃比をリッチにすると流入排気ガ
ス中の酸素濃度が極度に低下するために吸収剤からＮＯ
2 が放出され、このＮＯ2 は図３（Ｂ）に示されるよう
に未燃ＨＣ，ＣＯと反応して還元せしめられる。このよ
うにして白金Ｐｔの表面上にＮＯ2 が存在しなくなると
吸収剤から次から次へとＮＯ2 が放出される。従って流
入排気ガスの空燃比をリッチにすると短時間のうちに各
ＮＯｘ吸収剤１７，２０，２３からＮＯｘが放出される
ことになる。On the other hand, at this time, the air-fuel ratio of the inflowing exhaust gas is
As shown in Fig. 2, a large amount of
Burned HC and CO are discharged, and these unburned HC and CO are platinum
Oxygen O on Pt2 -It reacts with and is oxidized. Well
In addition, when the air-fuel ratio of the inflow exhaust gas is made rich, the inflow exhaust gas
Since the oxygen concentration in the gas is extremely low, NO
2Is released and this NO2As shown in FIG. 3 (B)
It is reduced by reacting with unburned HC and CO. This
Thus NO on the surface of platinum Pt2When no longer exists
Absorbent NO one after another2Is released. Therefore flow
If the air-fuel ratio of the incoming and exhaust gas is made rich, each
NOx is released from the NOx absorbent 17, 20, 23
It will be.
【００１４】このように流入排気ガスの空燃比がリーン
になるとＮＯｘが各ＮＯｘ吸収剤１７，２０，２３に吸
収され、流入排気ガスの空燃比をリッチにするとＮＯｘ
が各ＮＯｘ吸収剤１７，２０，２３から短時間のうちに
放出される。従って図１に示す内燃機関ではリーン混合
気の燃焼期間が一定期間経過したときに機関シリンダ内
に供給される混合気の空燃比を一時的にリッチにして各
ＮＯｘ吸収剤１７，２０，２３からＮＯｘを放出させる
ようにしている。As described above, when the air-fuel ratio of the inflowing exhaust gas becomes lean, NOx is absorbed by the NOx absorbents 17, 20, 23, and when the air-fuel ratio of the inflowing exhaust gas is made rich, NOx.
Is released from each NOx absorbent 17, 20, 23 in a short time. Therefore, in the internal combustion engine shown in FIG. 1, the air-fuel ratio of the air-fuel mixture supplied to the engine cylinder is temporarily made rich when the combustion period of the lean air-fuel mixture has passed for a certain period of time, from each NOx absorbent 17, 20, 23. It is designed to release NOx.
【００１５】ところが各ＮＯｘ吸収剤１７，２０，２３
がＮＯｘを吸収して保持しておく能力、即ちＮＯｘの浄
化率は担体上に担持されている金属の種数によって温度
依存性を有し、これを図４に示す。図４の縦軸はＮＯｘ
浄化率を示しており、図４の横軸は各ＮＯｘ吸収剤１
７，２０，２３の温度を示している。図４からわかるよ
うに白金ＰｔとバリウムＢａの組合せからなるＰｔ−Ｂ
ａ吸収剤は吸収剤の温度が２５０℃から３５０℃の中温
においてＮＯｘの浄化率がピークとなる。これに対して
白金ＰｔとランタンＬａの組合せからなるＰｔ−Ｌａ吸
収剤および白金Ｐｔ、バリウムＢａおよび鉄Ｆｅの組合
せからなるＰｔ−Ｂａ−Ｆｅ吸収剤は２５０℃以下の低
温においてＮＯｘ浄化率がピークとなり、白金Ｐｔとカ
リウムＫとの組合せからなるＰｔ−Ｋ吸収剤、白金Ｐ
ｔ、バリウムＢａおよびニッケルＮｉからなるＰｔ−Ｂ
ａ−Ｎｉ吸収剤、および白金Ｐｔ、バリウムＢａおよび
銅ＣｕからなるＰｔ−Ｂａ−Ｃｕ吸収剤は３５０℃以上
の高温においてＮＯｘ浄化率がピークとなる。However, each NOx absorbent 17, 20, 23
The ability of NOx to absorb and retain NOx, that is, the NOx purification rate, has temperature dependence depending on the number of metals supported on the carrier, which is shown in FIG. The vertical axis of FIG. 4 is NOx
The purification rate is shown, and the horizontal axis of FIG. 4 shows each NOx absorbent 1
The temperatures of 7, 20, and 23 are shown. As can be seen from FIG. 4, Pt-B composed of a combination of platinum Pt and barium Ba
The NOx purification rate of the absorbent a peaks at an intermediate temperature of the absorbent of 250 to 350 ° C. On the other hand, the Pt-La absorbent composed of a combination of platinum Pt and lanthanum La and the Pt-Ba-Fe absorbent composed of a combination of platinum Pt, barium Ba and iron Fe show a peak NOx purification rate at a low temperature of 250 ° C or lower. Pt-K absorbent composed of platinum Pt and potassium K, platinum P
Pt-B composed of t, barium Ba and nickel Ni
The NOx purification rate of the a-Ni absorbent and the Pt-Ba-Cu absorbent composed of platinum Pt, barium Ba, and copper Cu peaks at a high temperature of 350 ° C or higher.
【００１６】例えば図４のＰｔ−Ｂａ吸収剤は低温にな
ると白金Ｐｔの表面上におけるＮＯｘの酸化作用が進ま
なくなり、また吸収剤へのＮＯｘの吸収作用が遅くなる
ためにＮＯｘ浄化率が低下してくる。一方、高温になる
と吸収剤内において硝酸塩が分解されてＮＯｘが放出さ
れるためにＮＯｘ浄化率が低下してくる。ところがこの
ようなＮＯｘの酸化作用や吸収作用および硝酸塩の分解
作用と温度との関係は担体上に担持されている金属の種
数によって異なり、従って図４に示すように担体上に担
持される金属の種類によってＮＯｘ浄化率がピークとな
る温度領域が異なることになる。For example, in the Pt-Ba absorbent shown in FIG. 4, when the temperature is low, the oxidation effect of NOx on the surface of platinum Pt does not proceed, and the absorption effect of NOx on the absorbent is slowed, so that the NOx purification rate decreases. Come on. On the other hand, when the temperature rises, the nitrate is decomposed in the absorbent and NOx is released, so that the NOx purification rate decreases. However, the relationship between the oxidizing action and absorbing action of NOx and the decomposing action of nitrate and the temperature depends on the kind of the metal supported on the carrier. Therefore, as shown in FIG. The temperature range in which the NOx purification rate reaches a peak varies depending on the type.
【００１７】このように担体上に担持される金属の種類
によってＮＯｘ浄化率がピークとなる温度領域が異なる
のでこれを考慮してＮＯｘ吸収剤を使用しなければなら
ない。そこで図１に示す実施例では第１ＮＯｘ吸収剤１
７としてＰｔ−Ｋ吸収剤、Ｐｔ−Ｂａ−Ｎｉ吸収剤、Ｐ
ｔ−Ｂａ−Ｃｕ吸収剤のようにＮＯｘ浄化率が高温でピ
ークとなる吸収剤が用いられ、第２ＮＯｘ吸収剤２０と
してＰｔ−Ｂａ吸収剤のようにＮＯｘ浄化率が中温でピ
ークとなる吸収剤が用いられ、第３ＮＯｘ吸収剤２３と
してＰｔ−Ｂａ−Ｆｅ吸収剤、Ｐｔ−Ｌａ吸収剤のよう
にＮＯｘ浄化率が低温でピークとなる吸収剤が用いられ
ている。As described above, the temperature range in which the NOx purification rate reaches a peak varies depending on the type of metal supported on the carrier, and therefore the NOx absorbent must be used in consideration of this. Therefore, in the embodiment shown in FIG. 1, the first NOx absorbent 1
7, Pt-K absorbent, Pt-Ba-Ni absorbent, P
An absorbent having a high NOx purification rate at a high temperature such as a t-Ba-Cu absorbent is used, and an absorbent having a NOx purification rate peaking at an intermediate temperature, such as a Pt-Ba absorbent, is used as the second NOx absorbent 20. Is used as the third NOx absorbent 23, such as a Pt-Ba-Fe absorbent or a Pt-La absorbent having a NOx purification rate that peaks at a low temperature.
【００１８】図１に示す内燃機関では各ＮＯｘ吸収剤１
７，２０，２３に流入する排気ガス温は下流にいくほど
低くなる。従って上述のようにＮＯｘ浄化率が高温でピ
ークとなる吸収剤を第１ＮＯｘ吸収剤１７として用い、
ＮＯｘ浄化率が低温でピークとなる吸収剤を第２ＮＯｘ
吸収剤２０として用い、ＮＯｘ浄化率が高温でピークと
なる吸収剤を第３ＮＯｘ吸収剤２３として用いることに
よって各吸収剤１７，２０，２３をＮＯｘ浄化率がピー
クとなる温度で使用することができ、斯くしてＮＯｘの
浄化効率を高めることができることになる。In the internal combustion engine shown in FIG. 1, each NOx absorbent 1
The exhaust gas temperature flowing into 7, 20, and 23 becomes lower as it goes downstream. Therefore, as described above, the absorbent having the peak NOx purification rate at a high temperature is used as the first NOx absorbent 17,
When the NOx purification rate reaches a peak at low temperature, the second NOx
By using the absorbent that is used as the absorbent 20 and the NOx purification rate peaks at a high temperature as the third NOx absorbent 23, each of the absorbents 17, 20, and 23 can be used at the temperature where the NOx purification rate peaks. Therefore, the purification efficiency of NOx can be improved.
【００１９】図５は別の実施例を示す。この実施例では
排気マニホルド１６が排気管３０を介して電磁切換弁３
１に連結され、この電磁切換弁３１からは３個の排気管
３２，３３，３４が延びている。排気管３２は第１のＮ
Ｏｘ吸収剤３５を内蔵したケーシング３６に連結され、
排気管３３は第２のＮＯｘ吸収剤３７を内蔵したケーシ
ング３８に連結され、排気管３４は第３のＮＯｘ吸収剤
３９を内蔵したケーシング４０に連結されている。FIG. 5 shows another embodiment. In this embodiment, the exhaust manifold 16 is connected to the electromagnetic switching valve 3 via the exhaust pipe 30.
Three exhaust pipes 32, 33, 34 extend from the electromagnetic switching valve 31. The exhaust pipe 32 is the first N
Connected to a casing 36 containing an Ox absorbent 35,
The exhaust pipe 33 is connected to a casing 38 containing a second NOx absorbent 37, and the exhaust pipe 34 is connected to a casing 40 containing a third NOx absorbent 39.
【００２０】この実施例では第１ＮＯｘ吸収剤３５とし
てＰｔ−Ｋ吸収剤、Ｐｔ−Ｂａ−Ｎｉ吸収剤、Ｐｔ−Ｂ
ａ−Ｃｕ吸収剤のようにＮＯｘ浄化率が高温でピークと
なる吸収剤が用いられ、第２ＮＯｘ吸収剤３７としてＰ
ｔ−Ｂａ吸収剤のようにＮＯｘ浄化率が中温でピークと
なる吸収剤が用いられ、第３ＮＯｘ吸収剤４０としてＰ
ｔ−Ｂａ−Ｆｅ吸収剤、Ｐｔ−Ｌａ吸収剤のようにＮＯ
ｘ浄化率が低温でピークとなる吸収剤が用いられてい
る。In this embodiment, the first NOx absorbent 35 is Pt-K absorbent, Pt-Ba-Ni absorbent, Pt-B.
An absorbent having a NOx purification rate that peaks at a high temperature, such as an a-Cu absorbent, is used, and P is used as the second NOx absorbent 37.
An absorbent whose NOx purification rate has a peak at an intermediate temperature, such as a t-Ba absorbent, is used, and P is used as the third NOx absorbent 40.
NO like t-Ba-Fe absorbent, Pt-La absorbent
An absorbent having an x purification rate that peaks at a low temperature is used.
【００２１】電磁切換弁３１は電子制御ユニット５０の
出力信号により制御される。この電子制御ユニット５０
はディジタルコンピュータからなり、双方向性バス５１
によって相互に接続されたＲＯＭ（リードオンリメモ
リ）５２、ＲＡＭ（ランダムアクセスメモリ（ＲＡＭ）
５３、ＣＰＵ（マイクロプロセッサ）５４、入力ポート
５５および出力ポート５６を具備する。エアフローメー
タ１３は吸入空気量に比例した出力電圧を発生し、この
出力電圧がＡＤ変換器５７を介して入力ポート５５に入
力される。排気管３０には排気ガス温に比例した出力電
圧を発生する温度センサ５８が取付けられ、この温度セ
ンサ５８の出力電圧がＡＤ変換器５９を介して入力ポー
ト５５に入力される。また、入力ポート５５には機関回
転数を表わす出力パルスを発生する回転数センサ６０が
接続される。一方、出力ポート５６は対応する駆動回路
６１を介して夫々点火栓４、燃料噴射弁１１および電磁
切換弁３１に接続される。The electromagnetic switching valve 31 is controlled by the output signal of the electronic control unit 50. This electronic control unit 50
Is a digital computer and has a bidirectional bus 51.
ROM (Read Only Memory) 52, RAM (Random Access Memory (RAM)) mutually connected by
53, a CPU (microprocessor) 54, an input port 55 and an output port 56. The air flow meter 13 generates an output voltage proportional to the intake air amount, and this output voltage is input to the input port 55 via the AD converter 57. A temperature sensor 58 that generates an output voltage proportional to the exhaust gas temperature is attached to the exhaust pipe 30, and the output voltage of the temperature sensor 58 is input to the input port 55 via the AD converter 59. Further, the input port 55 is connected to a rotation speed sensor 60 that generates an output pulse representing the engine rotation speed. On the other hand, the output port 56 is connected to the spark plug 4, the fuel injection valve 11 and the electromagnetic switching valve 31 via the corresponding drive circuit 61, respectively.
【００２２】図６は電磁切換弁３１の制御ルーチンを示
しており、このルーチンは一定時間毎の割込みによって
実行される。図６を参照するとまず初めにステップ７０
において温度センサ５８の出力信号に基いて排気ガス温
Ｔが予め定められた一定値Ｔ1 、例えば２５０℃よりも
低いか否かが判別される。Ｔ≧Ｔ1 のとき、即ち排気ガ
ス温Ｔが低温でないときにはステップ７１に進んで排気
ガス温Ｔが予め定められた一定値Ｔ2 、例えば３５０℃
よりも高いか否かが判別される。Ｔ≦Ｔ2 のとき、即ち
排気ガス温Ｔが高温でないときにはステップ７２に進
む。即ち、排気ガス温Ｔが中温のときにステップ７２に
進む。FIG. 6 shows a control routine for the solenoid operated directional control valve 31, and this routine is executed by interruption at regular time intervals. Referring to FIG. 6, first, step 70
At, it is determined whether the exhaust gas temperature T is lower than a predetermined constant value T 1 , for example, 250 ° C., based on the output signal of the temperature sensor 58. When T ≧ T 1 , that is, when the exhaust gas temperature T is not low, the routine proceeds to step 71, where the exhaust gas temperature T is a predetermined constant value T 2 , for example 350 ° C.
Is higher than the above. When T ≦ T 2 , that is, when the exhaust gas temperature T is not high, the routine proceeds to step 72. That is, when the exhaust gas temperature T is a medium temperature, the routine proceeds to step 72.
【００２３】ステップ７２では排気管３０を排気管３３
に接続するように電磁切換弁３１が切換えられる。従っ
てこのときには排気ガスは第２ＮＯｘ吸収剤３７内に流
入する。このとき排気ガス温Ｔは中温であり、一方第２
ＮＯｘ吸収剤３７のＮＯｘ浄化率は中温のときにピーク
になるので第２ＮＯｘ吸収剤３７のＮＯｘ浄化率はピー
クとなる。斯くしてＮＯｘは第２ＮＯｘ吸収剤３７によ
って良好に浄化されることになる。In step 72, the exhaust pipe 30 is connected to the exhaust pipe 33.
The electromagnetic switching valve 31 is switched so as to be connected to. Therefore, at this time, the exhaust gas flows into the second NOx absorbent 37. At this time, the exhaust gas temperature T is a medium temperature, while the second
Since the NOx purification rate of the NOx absorbent 37 peaks at the medium temperature, the NOx purification rate of the second NOx absorbent 37 peaks. Thus, the NOx is satisfactorily purified by the second NOx absorbent 37.
【００２４】一方、ステップ７０においてＴ＜Ｔ1 であ
ると判断されたとき、即ち排気ガス温Ｔが低温であると
きにはステップ７３に進んで排気管３０を排気管３９に
接続するように電磁切換弁３１が切換えられる。従って
このときには排気ガスは第３ＮＯｘ吸収剤３９内に流入
する。このとき排気ガス温Ｔは低温であり、一方第３Ｎ
Ｏｘ吸収剤３９のＮＯｘ浄化率は低温のときにピークに
なるので第３ＮＯｘ吸収剤３９のＮＯｘ浄化率はピーク
となる。斯くしてＮＯｘは第３ＮＯｘ吸収剤３９によっ
て良好に浄化されることになる。On the other hand, when it is judged at step 70 that T <T 1, that is, when the exhaust gas temperature T is low, the routine proceeds to step 73, where the electromagnetic switching valve is arranged to connect the exhaust pipe 30 to the exhaust pipe 39. 31 is switched. Therefore, at this time, the exhaust gas flows into the third NOx absorbent 39. At this time, the exhaust gas temperature T is low, while the third N
Since the NOx purification rate of the Ox absorbent 39 peaks at a low temperature, the NOx purification rate of the third NOx absorbent 39 peaks. Thus, the NOx will be satisfactorily purified by the third NOx absorbent 39.
【００２５】一方、ステップ７１においてＴ＞Ｔ2 であ
ると判断されたとき、即ち排気ガス温Ｔが高温であると
きにはステップ７４に進んで排気管３０を排気管３２に
接続するように電磁切換弁３１が切換えられる。従って
このときには排気ガスは第１ＮＯｘ吸収剤３５内に流入
する。このとき排気ガス温Ｔは高温であり、一方第１Ｎ
Ｏｘ吸収剤３５のＮＯｘ浄化率は高温のときにピークに
なるので第１ＮＯｘ吸収剤３５のＮＯｘ浄化率はピーク
となる。斯くしてＮＯｘは第１ＮＯｘ吸収剤３５によっ
て良好に浄化されることになる。On the other hand, when it is judged at step 71 that T> T 2, that is, when the exhaust gas temperature T is high, the routine proceeds to step 74, where the electromagnetic switching valve is arranged to connect the exhaust pipe 30 to the exhaust pipe 32. 31 is switched. Therefore, at this time, the exhaust gas flows into the first NOx absorbent 35. At this time, the exhaust gas temperature T is high, while the first N
Since the NOx purification rate of the Ox absorbent 35 peaks at high temperature, the NOx purification rate of the first NOx absorbent 35 peaks. Thus, the NOx is satisfactorily purified by the first NOx absorbent 35.
【００２６】このようにこの実施例では排気ガス温Ｔに
応じてＮＯｘ浄化率がピークとなるＮＯｘ吸収剤を選択
的に使用するようにしているので排気ガス温Ｔにかかわ
らずにＮＯｘを良好に浄化できることになる。なお、こ
の実施例では排気管３０内の排気ガス温Ｔを温度センサ
５８により検出するようにしているが排気管３０内の排
気ガス温Ｔは機関負荷Ｑ／Ｎ（吸入空気量Ｑ／機関回転
数Ｎ）と機関回転数Ｎの関数となる。従って排気管３０
内の排気ガス温Ｔを機関負荷Ｑ／Ｎと機関回転数Ｎの関
数として予め実験により求めておき、これらの関係を図
７に示すようなマップの形で予めＲＯＭ５２内に記憶し
ておいてこのマップから排気ガス温Ｔを求めるようにす
ることもできる。この場合には温度センサ５８を設ける
必要がなくなる。As described above, in this embodiment, the NOx absorbent having the NOx purification rate peaking in accordance with the exhaust gas temperature T is selectively used, so that the NOx is improved regardless of the exhaust gas temperature T. It can be purified. In this embodiment, the exhaust gas temperature T in the exhaust pipe 30 is detected by the temperature sensor 58, but the exhaust gas temperature T in the exhaust pipe 30 is determined by the engine load Q / N (intake air amount Q / engine rotation speed). Number N) and engine speed N. Therefore, the exhaust pipe 30
The exhaust gas temperature T therein is obtained in advance as a function of the engine load Q / N and the engine speed N by experiments, and the relationship between them is stored in advance in the ROM 52 in the form of a map as shown in FIG. It is also possible to obtain the exhaust gas temperature T from this map. In this case, it is not necessary to provide the temperature sensor 58.
【００２７】[0027]
【発明の効果】各ＮＯｘ吸収剤をＮＯｘ浄化率がピーク
となる状態で使用することによって良好なＮＯｘの浄化
作用を行うことができる。EFFECTS OF THE INVENTION By using each NOx absorbent in a state where the NOx purification rate reaches its peak, a good NOx purification action can be performed.
【図１】内燃機関の全体図である。FIG. 1 is an overall view of an internal combustion engine.
【図２】機関から排出される排気ガス中の未燃ＨＣ，Ｃ
Ｏおよび酸素の濃度を概略的に示す線図である。[Fig. 2] Unburned HC and C in exhaust gas discharged from the engine
It is a diagram which shows the concentration of O and oxygen roughly.
【図３】ＮＯｘの吸放出作用を説明するための図であ
る。FIG. 3 is a diagram for explaining the action of NOx absorption and release.
【図４】各ＮＯｘ吸収剤のＮＯｘ浄化率を示す線図であ
る。FIG. 4 is a diagram showing the NOx purification rate of each NOx absorbent.
【図５】内燃機関の別の実施例の全体図である。FIG. 5 is an overall view of another embodiment of the internal combustion engine.
【図６】電磁切換弁を制御するためのフローチャートで
ある。FIG. 6 is a flowchart for controlling an electromagnetic switching valve.
【図７】排気ガス温Ｔのマップを示す図である。FIG. 7 is a diagram showing a map of an exhaust gas temperature T.
１６…排気マニホルド １７，３５…第１ＮＯｘ吸収剤 ２０，３７…第２ＮＯｘ吸収剤 ２３，３９…第３ＮＯｘ吸収剤 16 ... Exhaust manifold 17,35 ... First NOx absorbent 20,37 ... Second NOx absorbent 23, 39 ... Third NOx absorbent
───────────────────────────────────────────────────── フロントページの続き (72)発明者 加藤 健治 愛知県豊田市トヨタ町１番地 トヨタ自動 車株式会社内 (72)発明者 井口 哲 愛知県豊田市トヨタ町１番地 トヨタ自動 車株式会社内 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Kato 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor Satoshi Iguchi 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd.
Claims (1)
はＮＯｘを吸収し、流入排気ガス中の酸素濃度が低下す
ると吸収したＮＯｘを放出するＮＯｘ吸収剤であってＮ
Ｏｘ浄化率がピークとなる温度領域の異なる複数のＮＯ
ｘ吸収剤を機関排気通路内に配置し、温度の高い排気ガ
スは温度が高いときにＮＯｘ浄化率がピークとなるＮＯ
ｘ吸収剤に送り込むと共に温度の低い排気ガスは温度が
低いときにＮＯｘ浄化率がピークとなるＮＯｘ吸収剤に
送り込むようにした内燃機関の排気浄化装置。1. A NOx absorbent that absorbs NOx when the air-fuel ratio of the inflowing exhaust gas is lean and releases the absorbed NOx when the oxygen concentration in the inflowing exhaust gas decreases,
A plurality of NOs in different temperature regions where the Ox purification rate reaches a peak
NOx purification rate is peaked when the temperature of exhaust gas having a high temperature is high by placing the x-absorbent in the engine exhaust passage.
An exhaust gas purification apparatus for an internal combustion engine, which sends exhaust gas having a low temperature to the NOx absorbent, which has a peak NOx purification rate when the temperature is low.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4203635A JP2658754B2 (en) | 1992-07-30 | 1992-07-30 | Exhaust gas purification device for internal combustion engine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4203635A JP2658754B2 (en) | 1992-07-30 | 1992-07-30 | Exhaust gas purification device for internal combustion engine |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0650132A true JPH0650132A (en) | 1994-02-22 |
| JP2658754B2 JP2658754B2 (en) | 1997-09-30 |
Family
ID=16477316
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4203635A Expired - Lifetime JP2658754B2 (en) | 1992-07-30 | 1992-07-30 | Exhaust gas purification device for internal combustion engine |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2658754B2 (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07332396A (en) * | 1994-06-01 | 1995-12-22 | Gkn Viscodrive Gmbh | Viscous coupling |
| US6370869B1 (en) | 1999-07-28 | 2002-04-16 | Toyota Jidosha Kabushiki Kaisha | Exhaust purification device of an engine |
| JP2003536012A (en) * | 2000-06-06 | 2003-12-02 | ジョンソン、マッセイ、パブリック、リミテッド、カンパニー | Diesel exhaust system including NOx trap |
| US6820417B2 (en) * | 2001-11-29 | 2004-11-23 | Analytical Engineering, Inc. | Exhaust aftertreatment system and method for an internal combustion engine |
| EP1609962A1 (en) * | 2004-06-23 | 2005-12-28 | GM Global Technology Operations, Inc. | Exhaust system for improving the NOx reduction efficiency in vehicles |
| JP2015025433A (en) * | 2013-07-29 | 2015-02-05 | 三菱自動車工業株式会社 | Exhaust emission control device for internal combustion engine |
| JP2018021564A (en) * | 2017-10-26 | 2018-02-08 | 三菱自動車工業株式会社 | Exhaust emission control device for internal combustion engine |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4432923B2 (en) | 2006-03-23 | 2010-03-17 | トヨタ自動車株式会社 | Exhaust gas purification device for compression ignition type internal combustion engine |
-
1992
- 1992-07-30 JP JP4203635A patent/JP2658754B2/en not_active Expired - Lifetime
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07332396A (en) * | 1994-06-01 | 1995-12-22 | Gkn Viscodrive Gmbh | Viscous coupling |
| US5791446A (en) * | 1994-06-01 | 1998-08-11 | Gkn Viscodrive Gmbh | Viscous coupling having a toothed hub used as a carrier for the inner |
| US6370869B1 (en) | 1999-07-28 | 2002-04-16 | Toyota Jidosha Kabushiki Kaisha | Exhaust purification device of an engine |
| JP2003536012A (en) * | 2000-06-06 | 2003-12-02 | ジョンソン、マッセイ、パブリック、リミテッド、カンパニー | Diesel exhaust system including NOx trap |
| US6820417B2 (en) * | 2001-11-29 | 2004-11-23 | Analytical Engineering, Inc. | Exhaust aftertreatment system and method for an internal combustion engine |
| EP1609962A1 (en) * | 2004-06-23 | 2005-12-28 | GM Global Technology Operations, Inc. | Exhaust system for improving the NOx reduction efficiency in vehicles |
| JP2015025433A (en) * | 2013-07-29 | 2015-02-05 | 三菱自動車工業株式会社 | Exhaust emission control device for internal combustion engine |
| JP2018021564A (en) * | 2017-10-26 | 2018-02-08 | 三菱自動車工業株式会社 | Exhaust emission control device for internal combustion engine |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2658754B2 (en) | 1997-09-30 |
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