JP2677130B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Exhaust gas purification device for internal combustion engine

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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
Application number
JP25830892A
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Japanese (ja)
Other versions
JPH06108834A (en
Inventor
健治 加藤
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toyota Motor Corp
Original Assignee
Toyota Motor Corp
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Filing date
Publication date
Application filed by Toyota Motor Corp filed Critical Toyota Motor Corp
Priority to JP25830892A priority Critical patent/JP2677130B2/en
Publication of JPH06108834A publication Critical patent/JPH06108834A/en
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Publication of JP2677130B2 publication Critical patent/JP2677130B2/en
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Expired - Lifetime legal-status Critical Current

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Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【0001】[0001]

【産業上の利用分野】本発明は内燃機関の排気浄化装置
に関する。
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
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.

【図面の簡単な説明】[Brief description of the drawings]

【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.

【符号の説明】[Explanation of symbols]

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)

(57)【特許請求の範囲】(57) [Claims] 【請求項1】 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 .
JP25830892A 1992-09-28 1992-09-28 Exhaust gas purification device for internal combustion engine Expired - Lifetime JP2677130B2 (en)

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)

* Cited by examiner, † Cited by third party
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

Also Published As

Publication number Publication date
JPH06108834A (en) 1994-04-19

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