JP2677130B2 - Exhaust gas purification device for internal combustion engine - Google Patents
Exhaust gas purification device for internal combustion engineInfo
- Publication number
- JP2677130B2 JP2677130B2 JP25830892A JP25830892A JP2677130B2 JP 2677130 B2 JP2677130 B2 JP 2677130B2 JP 25830892 A JP25830892 A JP 25830892A JP 25830892 A JP25830892 A JP 25830892A JP 2677130 B2 JP2677130 B2 JP 2677130B2
- Authority
- JP
- Japan
- Prior art keywords
- nox
- exhaust gas
- catalyst
- intake
- release
- 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 - Lifetime
Links
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- Exhaust Gas After Treatment (AREA)
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 purifying apparatus 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吸放出触媒を
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吸放出触媒により吸収し、
ＮＯｘ吸放出触媒のＮＯｘ吸収能力が飽和する前にＮＯ
ｘ吸放出触媒への流入排気ガスの空燃比を一時的にリッ
チにしてＮＯｘ吸放出触媒からＮＯｘを放出させると共
に放出されたＮＯｘを還元して浄化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 is absorbed when the air-fuel ratio of the inflowing exhaust gas is lean, and is released when the oxygen concentration in the inflowing exhaust gas is low. The intake / release catalyst is arranged in the engine exhaust passage, and NOx generated when the lean air-fuel mixture is burned is absorbed by the NOx intake / release catalyst,
Before the NOx absorption capacity of the NOx absorption / release catalyst becomes saturated, NO
The applicant has already proposed an internal combustion engine that temporarily enriches the air-fuel ratio of the exhaust gas flowing into the x-adsorption catalyst to release NOx from the NOx-adsorption catalyst and reduce and purify the released NOx. Proposed (Japanese Patent Application No. 3-
284095).
【０００３】[0003]
【発明が解決しようとする課題】ところでNOx 吸放出触
媒はNOx 吸放出触媒の温度が一定温度範囲内にあるとき
にNOx の吸収量が最大となる、即ちNOx 浄化率が最大と
なる。従って高いNOx 浄化率を確保するためにはNOx 吸
放出触媒の温度をNOx 浄化率が最大となる温度範囲内に
維持する必要がある。しかしながら上述の内燃機関では
機関負荷が高くなって排気ガス温が上昇したときにNOx
吸放出触媒の温度が最大NOx 浄化率の得られる温度を越
えてしまい、斯くして機関負荷が高くなったときに良好
なNOx 浄化率を確保することができないという問題があ
る。 [Problems to be solved by the invention] By the way,
The medium is when the temperature of the NOx absorbing / releasing catalyst is within a certain temperature range.
The maximum amount of NOx absorbed, that is, the maximum NOx purification rate
Become. Therefore, in order to secure a high NOx purification rate, NOx absorption
Keep the temperature of the release catalyst within the temperature range that maximizes the NOx purification rate.
Need to maintain. However, in the above-mentioned internal combustion engine
NOx when engine load increases and exhaust gas temperature rises
The temperature of the intake / release catalyst exceeds the temperature at which the maximum NOx purification rate is obtained.
Good when the engine load becomes high.
There is a problem that it is not possible to secure a high NOx purification rate.
You.
【０００４】[0004]
【課題を解決するための手段】上記問題点を解決するた
め本発明によれば、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の空燃比がストイキま
たはリッチのときには吸収したNOx を放出すると共に放
出されたNOx を還元する一対のNOx 吸放出触媒を機関排
気通路内に並列配置し、機関負荷が予め定められた負荷
よりも低いときには機関から排出された排気ガスをいず
れか一方のNOx 吸放出触媒のみに流入させ続けると共に
他方のNOx 吸放出触媒への排気ガスの流入を停止し続
け、機関負荷が予め定められた負荷よりも高いときには
機関から排出された排気ガスを一対のNOx 吸放出触媒に
交互に流入させるようにしている。 To solve the above problems, according to the present invention, NOx is absorbed when the air-fuel ratio of the inflowing exhaust gas is lean and it is absorbed when the air-fuel ratio of the inflowing exhaust gas is stoichiometric or rich. A pair of NOx intake / release catalysts that release NOx and reduce the released NOx are arranged in parallel in the engine exhaust passage, and the engine load is a predetermined load.
Exhaust gas emitted from the engine when it is lower than
While continuing to flow into only one of the NOx absorption and release catalysts
Stop the inflow of exhaust gas to the other NOx absorption / release catalyst and continue.
When the engine load is higher than the predetermined load,
Exhaust gas emitted from the engine is used as a pair of NOx absorption and release catalysts.
It is made to flow in alternately.
【０００５】[0005]
【作用】機関負荷が高く排気ガス温が高いときには排気
ガスが一対のNOx 吸放出触媒に交互に送り込まれる。そ
の結果、各NOx 吸放出触媒の温度は最大NOx 浄化率の得
られる温度を越えることなく最大NOx 浄化率が得られる
温度範囲内に維持される。 [Operation] Exhaust when engine load is high and exhaust gas temperature is high
The gas is alternately sent to the pair of NOx absorbing and releasing catalysts. So
As a result, the temperature of each NOx absorption / release catalyst is the maximum NOx purification rate.
Maximum NOx purification rate can be obtained without exceeding the required temperature
Maintained within temperature range.
【０００６】[0006]
【実施例】図１を参照すると、２は希薄燃焼可能な内燃
機関の本体、３は吸気通路、４は排気通路、５は吸気通
路３内に設けられたスロットル弁である。排気通路４は
主排気通路６と副排気通路８に分岐した後再び合流す
る。主排気通路６には主ＮＯｘ吸放出触媒１０が配置さ
れ、副排気通路８には副ＮＯｘ吸放出触媒１２が配置さ
れる。副ＮＯｘ吸放出触媒１２の容量は主ＮＯｘ吸放出
触媒１０の容量よりも小さくされている。主ＮＯｘ吸放
出触媒１０より上流の主排気通路６には第１開閉弁１４
が配置され、副ＮＯｘ吸放出触媒１２より上流の副排気
通路８には第２開閉弁１６が配置される。第１および第
２開閉弁１４，１６は連動して駆動せしめられ、第１開
閉弁１４が全開のときには第２開閉弁１６は全閉であ
り、第１開閉弁１４が全閉のときには第２開閉弁１６は
全開である。第１および第２開閉弁１４，１６はアクチ
ュエータ１８によって駆動され、アクチュエータ１８は
電子制御ユニット（ＥＣＵ）によって制御される。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, reference numeral 2 is a main body of an internal combustion engine capable of lean combustion, 3 is an intake passage, 4 is an exhaust passage, and 5 is a throttle valve provided in the intake passage 3. The exhaust passage 4 branches into a main exhaust passage 6 and a sub exhaust passage 8 and then joins again. A main NOx intake / release catalyst 10 is arranged in the main exhaust passage 6, and a sub-NOx intake / release catalyst 12 is arranged in the auxiliary exhaust passage 8. The capacity of the auxiliary NOx intake / release catalyst 12 is smaller than the capacity of the main NOx intake / release catalyst 10. A first opening / closing valve 14 is provided in the main exhaust passage 6 upstream of the main NOx intake / release catalyst 10.
The second opening / closing valve 16 is arranged in the auxiliary exhaust passage 8 upstream of the auxiliary NOx intake / release catalyst 12. The first and second opening / closing valves 14 and 16 are driven in conjunction with each other, the second opening / closing valve 16 is fully closed when the first opening / closing valve 14 is fully open, and the second opening / closing valve 16 is fully closed when the first opening / closing valve 14 is fully closed. The on-off valve 16 is fully open. The first and second on-off valves 14 and 16 are driven by an actuator 18, and the actuator 18 is controlled by an electronic control unit (ECU).
【０００７】スロットル弁５の開度を検出するスロット
ル弁開度センサ２２はＥＣＵ２０に接続される。図２は
機関燃焼室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
室から排出される排気ガス中の未燃ＨＣ，ＣＯの量は燃
焼室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、燃焼室から排出される排気ガス中の酸素Ｏ2 の
量は燃焼室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。A throttle valve opening sensor 22 for detecting the opening of the throttle valve 5 is connected to the ECU 20. FIG. 2 schematically shows the concentrations of typical components in the exhaust gas discharged from the engine combustion chamber. As can be seen from FIG. 2, the amount of unburned HC and CO in the exhaust gas discharged from the combustion chamber increases as the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber becomes rich, and the exhaust gas discharged from the combustion chamber increases. The amount of oxygen O 2 therein increases as the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber becomes leaner.
【０００８】主ＮＯｘ吸放出触媒１０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。機関吸気通路３および排気通路４
内に供給された空気および燃料の比を主ＮＯｘ吸放出触
媒１０への流入排気ガスの空燃比と称するとこの主ＮＯ
ｘ吸放出触媒１０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、主ＮＯｘ吸放出触媒１０上流の排気通路
４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主ＮＯｘ吸放出触媒１０は
燃焼室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ＮＯｘを放出することにな
る。The main NOx absorbing / releasing catalyst 10 uses, for example, alumina as a carrier, on which potassium K, sodium Na, lithium Li, an alkali metal such as cesium Cs, an alkaline earth such as barium Ba, calcium Ca, At least one selected from rare earths such as lanthanum La and yttrium Y and a noble metal such as platinum Pt are supported. Engine intake passage 3 and exhaust passage 4
The ratio of the air and the fuel supplied into the main NOx intake / release catalyst 10 is called the air-fuel ratio of the exhaust gas flowing into the main NOx intake / release catalyst 10.
The x absorption / release catalyst 10 absorbs NOx when the air-fuel ratio of the inflowing exhaust gas is lean, and releases and absorbs the absorbed NOx when the oxygen concentration in the inflowing exhaust gas decreases. When fuel or air is not supplied into the exhaust passage 4 upstream of the main NOx intake / release catalyst 10, the air-fuel ratio of the inflowing exhaust gas coincides with the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber. The main NOx intake / release catalyst 10 absorbs NOx when the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber is lean, and releases the absorbed NOx when the oxygen concentration in the air-fuel mixture supplied to the combustion chamber decreases. become.
【０００９】上述の主ＮＯｘ吸放出触媒１０を機関排気
通路内に配置すればこの主ＮＯｘ吸放出触媒１０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-mentioned main NOx intake / release catalyst 10 is arranged in the engine exhaust passage, the main NOx intake / release catalyst 10 actually performs the NOx intake / release operation, but the detailed mechanism of this intake / release operation is not clear. There are also parts. However, it is considered that this absorption / release action is performed by a mechanism as shown in FIG. Next, this mechanism will be described by taking as an example a case where platinum Pt and barium Ba are supported on a carrier, but the same mechanism can be obtained by using other noble metals, alkali metals, alkaline earths and rare earths.
【００１０】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触媒内に吸収さ
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が主ＮＯｘ吸放出触媒１
０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 oxygens O 2 adhere to the surface of platinum Pt in the form of O 2 − . On the other hand, N
O is O 2 on the surface of the platinum Pt - reacted with, and NO 2 (2NO + O 2 → 2NO 2). NO 2 generated
Part of Pt is further oxidized on platinum Pt, absorbed in the catalyst and bound to barium oxide BaO, and diffused into the absorbent in the form of nitrate ion NO 3 − as shown in FIG. 3 (A). . In this way, NOx is the main NOx intake / release catalyst 1
It is absorbed within 0.
【００１１】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、触媒のＮＯｘ吸収能力
が飽和しない限りＮＯ2 が触媒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、斯くして触媒内
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主
ＮＯｘ吸放出触媒１０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
い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いを低くすれば主ＮＯ
ｘ吸放出触媒１０からＮＯｘが放出されることになる。[0011] to flow in the oxygen concentration in the exhaust gas is NO 2 with high long as the surface of the platinum Pt generation, as long as NO 2 to the catalyst of the NOx absorption capacity is not saturated is absorbed in the catalyst nitrate ions NO 3 - are produced It On the other hand, when the oxygen concentration in the inflowing exhaust gas decreases and the amount of NO 2 produced decreases, the reaction proceeds in the opposite direction (NO 3 − → NO 2 ), and thus the nitrate ion NO 3 − in the catalyst is It is 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 the main NOx intake / release catalyst 10. As shown in FIG. 2, when the lean degree of the inflowing exhaust gas is low, the oxygen concentration in the inflowing exhaust gas is low, and therefore when the leanness of the inflowing exhaust gas is low, the main NO
NOx is released from the x-suction / release catalyst 10.
【００１２】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と反応して還元浄化せしめられる。こ
のようにして白金Ｐｔの表面上にＮＯ2 が存在しなくな
ると触媒から次から次へと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
主ＮＯｘ吸放出触媒１０からＮＯｘが放出されて還元浄
化されることになる。On the other hand, at this time, the air-fuel ratio of the inflowing exhaust gas is reset.
As shown in Fig. 2, a large amount of
Fuel HC and CO are discharged, and these unburned HC and CO are converted to platinum.
Oxygen O on PtTwo -And oxidize. Ma
When the air-fuel ratio of the inflow exhaust gas is made rich, the inflow exhaust gas
NOx from the absorbent because the oxygen concentration in the
TwoIs released and this NOTwoIs as shown in FIG.
Then, it reacts with unburned HC and CO to be reduced and purified. This
NO on the surface of platinum PtTwoNo longer exists
Then NO from catalyst to catalystTwoIs released. Therefore
If the air-fuel ratio of the incoming exhaust gas is made rich, it will
NOx is released from the main NOx absorption / release catalyst 10 to reduce and purify it.
Will be realized.
【００１３】このように流入排気ガスの空燃比がリーン
になるとＮＯｘが主ＮＯｘ吸放出触媒１０に吸収され、
流入排気ガスの空燃比をリッチにするとＮＯｘが主ＮＯ
ｘ吸放出触媒１０から短時間のうちに放出されて還元浄
化される。副ＮＯｘ吸放出触媒１２も主ＮＯｘ吸放出触
媒１０と同様の触媒であり同様の作用効果を奏する。Thus, when the air-fuel ratio of the inflowing exhaust gas becomes lean, NOx is absorbed by the main NOx intake / release catalyst 10,
When the air-fuel ratio of the inflowing exhaust gas is made rich, NOx is the main NO
The x-absorbing / releasing catalyst 10 is released in a short time and is reduced and purified. The auxiliary NOx intake / release catalyst 12 is also a catalyst similar to the main NOx intake / release catalyst 10 and has the same operation effect.
【００１４】本実施例では機関高負荷運転時以外の場合
には、主ＮＯｘ吸放出触媒１０のみに排気ガスが流入せ
しめられる。ＮＯｘ吸放出触媒は、所定温度範囲、例え
ば３００℃前後の範囲内で高いＮＯｘ浄化率を示す。高
負荷運転時以外の場合においては、排気ガスの温度が比
較的低いために、主ＮＯｘ吸放出触媒１０のみに排気ガ
スを流入せしめ、これによって、主ＮＯｘ吸放出触媒１
０は所定温度範囲内に維持せしめられて高いＮＯｘ浄化
率を維持することができる。In this embodiment, the exhaust gas is made to flow into only the main NOx intake / release catalyst 10 except when the engine is under high load operation. The NOx absorption / release catalyst exhibits a high NOx purification rate in a predetermined temperature range, for example, in the range of around 300 ° C. Except during high load operation, the temperature of the exhaust gas is relatively low, so that the exhaust gas is caused to flow into the main NOx intake / release catalyst 10 only, whereby the main NOx intake / release catalyst 1
When 0 is maintained within the predetermined temperature range, a high NOx purification rate can be maintained.
【００１５】一方、高負荷運転時においては、主ＮＯｘ
吸放出触媒１０および副ＮＯｘ吸放出触媒１２に所定時
間ずつ交互に排気ガスが流入せしめられる。高負荷運転
時においては排気ガスの温度が高いため、主ＮＯｘ吸放
出触媒１０および副ＮＯｘ吸放出触媒１２に排気ガスを
交互に流すことによって、各ＮＯｘ吸放出触媒１０，１
２の温度を所定温度範囲内に維持してＮＯｘ浄化率を高
めることができる。On the other hand, during high load operation, the main NOx
The exhaust gas is caused to flow into the intake / release catalyst 10 and the auxiliary NOx intake / release catalyst 12 alternately for a predetermined time. Since the temperature of the exhaust gas is high during the high load operation, the exhaust gas is alternately flown to the main NOx intake / release catalyst 10 and the auxiliary NOx intake / release catalyst 12, so that each of the NOx intake / release catalysts 10, 1 is discharged.
The NOx purification rate can be increased by maintaining the temperature of 2 within the predetermined temperature range.
【００１６】本出願の発明者は、ＮＯｘ吸放出触媒は昇
温時においてＮＯｘ浄化率が高められることを見い出し
た。本実施例では、主ＮＯｘ吸放出触媒１０および副Ｎ
Ｏｘ吸放出触媒１２に交互に排気ガスが流入せしめられ
るため、主ＮＯｘ吸放出触媒１０または副ＮＯｘ吸放出
触媒１２に排気ガスが流入開始されるときに、主ＮＯｘ
吸放出触媒１０または副ＮＯｘ吸放出触媒１２に昇温過
程が強制的に作り出され、このため、ＮＯｘ浄化率を高
めることができる。The inventor of the present application has found that the NOx absorption / release catalyst has an increased NOx purification rate at a temperature rise. In the present embodiment, the main NOx intake / release catalyst 10 and the auxiliary N 2
Since the exhaust gas is caused to flow into the Ox intake / release catalyst 12 alternately, when the exhaust gas starts to flow into the main NOx intake / release catalyst 10 or the auxiliary NOx intake / release catalyst 12, the main NOx is released.
A temperature raising process is forcibly created in the intake / release catalyst 10 or the auxiliary NOx intake / release catalyst 12, and thus the NOx purification rate can be increased.
【００１７】図４には第１および第２開閉弁１４，１６
を制御するためのルーチンを示す。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４を参照する
と、まず、ステップ４０で機関負荷としてスロットル弁
開度ＴＡが読込まれる。ステップ４２ではスロットル弁
開度ＴＡに基づいて、機関負荷が高負荷か否か判定され
る。高負荷でないと判定された場合には、ステップ４４
に進み第１開閉弁開カウンタＣｏが１とされる。次い
で、ステップ４６で第１開閉弁閉カウンタＣｓが０とさ
れる。次いでステップ４８で第１開閉弁１４が全開され
かつ第２開閉弁１６が全閉され、これによって、主ＮＯ
ｘ吸放出触媒１０のみに排気ガスが流入せしめられる。FIG. 4 shows the first and second on-off valves 14, 16
Is shown below. This routine is executed by interruption every predetermined time. Referring to FIG. 4, first, at step 40, the throttle valve opening TA is read as the engine load. In step 42, it is determined based on the throttle valve opening degree TA whether the engine load is high. If it is determined that the load is not high, step 44
Then, the first open / close valve open counter Co is set to 1. Next, at step 46, the first on-off valve close counter Cs is set to zero. Next, at step 48, the first opening / closing valve 14 is fully opened and the second opening / closing valve 16 is fully closed, whereby the main NO
Exhaust gas is allowed to flow into only the x absorption / release catalyst 10.
【００１８】一方、ステップ４２で高負荷運転と判定さ
れた場合には、ステップ５０に進み、第１開閉弁開カウ
ンタＣｏが０より大きいか否か判定される。最初Ｃｏ＝
１であるからステップ５２に進み、Ｃｏが１だけインク
リメントされる。ステップ５４では、Ｃｏが所定値αよ
り大きいか否か判定される。最初Ｃｏはαより小さいた
め、否定判定されてステップ４６およびステップ４８に
進む。ステップ５４でＣｏ＞αと判定されると、ステッ
プ５６に進んでＣｏが０とされ、次いでステップ５８で
第１開閉弁１４が全閉されかつ第２開閉弁１６が全開さ
れる。これによって、主ＮＯｘ吸放出触媒１０への排気
ガスの流入が停止せしめられかつ副ＮＯｘ吸放出触媒１
２に排気ガスが流入せしめられる。On the other hand, if it is judged at step 42 that the engine is operating under high load, the routine proceeds to step 50, where it is judged if the first on-off valve opening counter Co is greater than zero. First Co =
Since it is 1, the routine proceeds to step 52, where Co is incremented by 1. In step 54, it is determined whether Co is larger than the predetermined value α. Initially, Co is smaller than α, so a negative determination is made and the process proceeds to step 46 and step 48. If it is determined in step 54 that Co> α, the routine proceeds to step 56, where Co is set to 0, then, in step 58, the first opening / closing valve 14 is fully closed and the second opening / closing valve 16 is fully opened. As a result, the inflow of exhaust gas into the main NOx intake / release catalyst 10 is stopped and the auxiliary NOx intake / release catalyst 1 is
Exhaust gas is allowed to flow into 2.
【００１９】ステップ５６でＣｏが０とされたため、次
の処理サイクルにおけるステップ５０で否定判定され
て、ステップ６０に進み、第１開閉弁閉カウンタＣｓが
１だけインクリメントされる。次いで、ステップ６２
で、Ｃｓが所定値βより大きいか否か判定される。最初
Ｃｓはβより小さいために、否定判定されてステップ５
６およびステップ５８に進む。一方、Ｃｓ＞βと判定さ
れると、ステップ６４に進み、Ｃｏが１とされた後、ス
テップ４６およびステップ４８に進む。このように、機
関高負荷運転時には、主ＮＯｘ吸放出触媒１０および副
ＮＯｘ吸放出触媒１２に所定時間ずつ交互に排気ガスが
流入せしめられる。これによって、主ＮＯｘ吸放出触媒
１０および副ＮＯｘ吸放出触媒１２は昇温および降温せ
しめられるが、主ＮＯｘ吸放出触媒１０および副ＮＯｘ
吸放出触媒１２の温度は、ＮＯｘ吸放出触媒が触媒活性
を示す温度領域内となるように制御される。なんとなれ
ば、ＮＯｘ吸放出触媒の温度が触媒活性を示す温度領域
外の温度になると、ＮＯｘを浄化することができなくな
るためである。Since Co is set to 0 at step 56, a negative determination is made at step 50 in the next processing cycle, and the routine proceeds to step 60, where the first on-off valve closing counter Cs is incremented by 1. Then, step 62
Then, it is determined whether or not Cs is larger than the predetermined value β. Initially, Cs is smaller than β, so a negative determination is made and step 5
6 and step 58. On the other hand, if it is determined that Cs> β, the process proceeds to step 64, Co is set to 1, and then the process proceeds to step 46 and step 48. In this way, during engine high load operation, the exhaust gas is caused to flow into the main NOx intake / release catalyst 10 and the auxiliary NOx intake / release catalyst 12 alternately for a predetermined time. As a result, the temperature of the main NOx intake / release catalyst 10 and the auxiliary NOx intake / release catalyst 12 is raised and lowered, but the main NOx intake / release catalyst 10 and the auxiliary NOx are released.
The temperature of the adsorption / desorption catalyst 12 is controlled so that the NOx adsorption / desorption catalyst is in a temperature range where the NOx adsorption / desorption catalyst exhibits catalytic activity. This is because NOx cannot be purified when the temperature of the NOx absorption / release catalyst falls outside the temperature range in which the catalyst activity is exhibited.
【００２０】[0020]
【発明の効果】ＮＯｘ浄化率を高めることができる。The NOx purification rate can be increased.
【図１】本発明の実施例の内燃機関の全体図である。FIG. 1 is an overall view of an internal combustion engine according to an embodiment of the present invention.
【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 shows unburned HC and C in exhaust gas discharged from an engine.
FIG. 3 is a diagram schematically showing the concentrations of O and oxygen.
【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 an absorption / release effect of NOx.
【図４】第１、第２開閉弁の制御を実行するためのフロ
ーチャートである。FIG. 4 is a flow chart for executing control of first and second opening / closing valves.
１０…主ＮＯｘ吸放出触媒 １２…副ＮＯｘ吸放出触媒 １４…第１開閉弁 １６…第２開閉弁 10 ... Main NOx intake / release catalyst 12 ... Sub NOx intake / release catalyst 14 ... First on-off valve 16 ... Second on-off valve
Claims (1)
はNOx を吸収し流入排気ガスの空燃比がストイキまたは
リッチのときには吸収したNOx を放出すると共に放出さ
れたNOx を還元する一対のNOx 吸放出触媒を機関排気通
路内に並列配置し、機関負荷が予め定められた負荷より
も低いときには機関から排出された排気ガスをいずれか
一方のNOx 吸放出触媒のみに流入させ続けると共に他方
のNOx 吸放出触媒への排気ガスの流入を停止し続け、機
関負荷が上記予め定められた負荷よりも高いときには機
関から排出された排気ガスを一対のNOx 吸放出触媒に交
互に流入させるようにした内燃機関の排気浄化装置。1. A pair of NOx absorbing / releasing which absorbs NOx when the air-fuel ratio of the inflowing exhaust gas is lean, releases the absorbed NOx when the air-fuel ratio of the inflowing exhaust gas is stoichiometric or rich, and reduces the released NOx. The catalyst is placed in parallel in the engine exhaust passage so that the engine load is lower than the predetermined load.
Exhaust gas emitted from the engine when either is low
Continue to flow into only one NOx absorption and release catalyst and the other
The exhaust gas flow to the NOx absorption / release catalyst of the
If the customs load is higher than the predetermined load,
Exhaust gas emitted from Seki is exchanged with a pair of NOx absorbing and releasing catalysts.
An exhaust gas purification device for an internal combustion engine that allows the two to flow into each other .
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25830892A JP2677130B2 (en) | 1992-09-28 | 1992-09-28 | Exhaust gas purification device for internal combustion engine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25830892A JP2677130B2 (en) | 1992-09-28 | 1992-09-28 | Exhaust gas purification device for internal combustion engine |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH06108834A JPH06108834A (en) | 1994-04-19 |
| JP2677130B2 true JP2677130B2 (en) | 1997-11-17 |
Family
ID=17318450
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP25830892A Expired - Lifetime JP2677130B2 (en) | 1992-09-28 | 1992-09-28 | Exhaust gas purification device for internal combustion engine |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2677130B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3440654B2 (en) * | 1994-11-25 | 2003-08-25 | トヨタ自動車株式会社 | Exhaust gas purification device |
-
1992
- 1992-09-28 JP JP25830892A patent/JP2677130B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH06108834A (en) | 1994-04-19 |
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