JPH10299459A - Exhaust gas purifying device for internal combustion engine - Google Patents
Exhaust gas purifying device for internal combustion engineInfo
- Publication number
- JPH10299459A JPH10299459A JP9107267A JP10726797A JPH10299459A JP H10299459 A JPH10299459 A JP H10299459A JP 9107267 A JP9107267 A JP 9107267A JP 10726797 A JP10726797 A JP 10726797A JP H10299459 A JPH10299459 A JP H10299459A
- Authority
- JP
- Japan
- Prior art keywords
- deterioration
- catalyst
- smoke
- combustion
- determination value
- 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
Classifications
-
- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
Landscapes
- Exhaust Gas After Treatment (AREA)
- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
- Combined Controls Of Internal Combustion Engines (AREA)
Abstract
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
化装置に関し、詳しくは、排気浄化用の触媒のスモーク
による劣化を診断し、また、スモーク劣化発生時に触媒
の転化性能の回復を図る技術に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, and more particularly, to a technique for diagnosing deterioration of an exhaust gas purifying catalyst due to smoke and recovering the conversion performance of the catalyst when smoke deterioration occurs. About.
【0002】[0002]
【従来の技術】近年、シリンダ内に燃料を直接噴射する
直噴式内燃機関(筒内噴射式内燃機関)の開発が進めら
れている。該直噴式内燃機関においては、低負荷,低回
転領域で成層燃焼を行わせて超希薄空燃比(例えば空燃
比25〜50程度)での燃焼を可能にしているが、該成層リ
ーン燃焼時には、点火栓周りに濃い混合気が形成される
ためにスモークが出やすく、また、直接シリンダ内に燃
料を噴射するためピストンや燃焼室壁面に燃料が付着し
やすく、この付着燃料が拡散燃焼してしまうことにより
芯が残ってスモークとして排出されるため、均質燃焼時
によりもスモークの排出量が多くなるという傾向があっ
た。2. Description of the Related Art In recent years, a direct injection type internal combustion engine (in-cylinder injection type internal combustion engine) for directly injecting fuel into a cylinder has been developed. In the direct injection type internal combustion engine, stratified combustion is performed in a low-load, low-speed region to enable combustion at an ultra-lean air-fuel ratio (for example, an air-fuel ratio of about 25 to 50). Smoke is likely to be produced due to the formation of a rich mixture around the spark plug.Fuel is also likely to adhere to the piston and the combustion chamber wall surface because the fuel is directly injected into the cylinder, and the deposited fuel will diffuse and burn. As a result, the wick remains and is discharged as smoke, so that there is a tendency that the amount of smoke discharged is larger than in homogeneous combustion.
【0003】前記成層燃焼時に排出されるスモークは排
気浄化用触媒に堆積することになるが、高負荷,高回転
側に移行して均質燃焼により排気温度が高くなれば、前
記触媒に堆積していたスモークは脱離,焼失される。し
かし、低負荷,低回転域での成層燃焼が長時間継続され
ると、スモークの堆積量が多くなり、該スモーク被毒に
よって触媒の転化性能が低下し、排気エミッションが悪
化することになってしまう。そこで、従来では、成層燃
焼が所定時間以上継続したときには、成層燃焼を禁止し
て均質燃焼を強制的に実行させることにより、成層燃焼
時に生成されたスモーク(カーボン)を焼失させるよう
にしていた(特開昭63−138120号公報)。[0003] The smoke discharged during the stratified combustion accumulates on the exhaust gas purifying catalyst. However, when the exhaust gas temperature increases due to the high-load, high-speed side and homogeneous combustion, the exhaust gas accumulates on the catalyst. The smoke is detached and burned. However, if stratified combustion at a low load and a low engine speed is continued for a long time, the amount of smoke deposited increases, and the conversion of the catalyst is reduced due to the poisoning of the smoke, and the exhaust emission is deteriorated. I will. Therefore, conventionally, when stratified combustion continues for a predetermined time or longer, the smoke (carbon) generated during the stratified combustion is burned off by inhibiting the stratified combustion and forcibly executing the homogeneous combustion ( JP-A-63-138120).
【0004】[0004]
【発明が解決しようとする課題】しかし、前記成層燃焼
時の触媒に対するスモークの堆積は、一定割合で進行す
るのではなく、排気温度(触媒入口温度)が低いほど堆
積が進行しやすい。従って、成層燃焼が所定時間以上継
続すれば転化性能が悪化するほどのスモークが触媒に堆
積するとは限らず、上記のように成層燃焼が所定時間以
上継続したことをもって強制的に均質燃焼に切り換える
構成では、スモークの堆積量が少なく充分な転化性能を
発揮できる状態であるにも関わらず、均質燃焼への強制
的な切り換えが行われ、燃費悪化や排気エミッションの
悪化を招く可能性がある。However, the deposition of smoke on the catalyst during the stratified combustion does not proceed at a constant rate, but the deposition tends to proceed as the exhaust gas temperature (catalyst inlet temperature) is lower. Therefore, if the stratified combustion continues for a predetermined time or more, smoke that deteriorates the conversion performance does not always accumulate on the catalyst, and as described above, when the stratified combustion is continued for a predetermined time or more, the combustion is forcibly switched to the homogeneous combustion. In this case, although the amount of smoke deposited is small and sufficient conversion performance can be exhibited, forcible switching to homogeneous combustion is performed, which may lead to deterioration of fuel consumption and deterioration of exhaust emission.
【0005】また、無用に均質燃焼へ切り換えられるこ
とを回避すべく、成層燃焼の継続を許容する時間を長く
すると、触媒の転化性能を低下させるだけのスモークが
堆積しているのに、この状態が放置されて排気エミッシ
ョンを悪化させる可能性があった。本発明は上記問題点
に鑑みなされたものであり、触媒のスモークによる劣化
状態を診断でき、また、スモークによる劣化が判定され
たときに、触媒の転化性能の回復を図れる排気浄化装置
を提供することを目的とする。[0005] Further, if the time allowed for the continuation of stratified combustion is lengthened in order to avoid unnecessary switching to homogeneous combustion, smoke is accumulated to reduce the conversion performance of the catalyst. Could be left unchecked and degrade exhaust emissions. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides an exhaust gas purifying apparatus capable of diagnosing a state of deterioration of a catalyst due to smoke and recovering the conversion performance of the catalyst when deterioration due to smoke is determined. The purpose is to:
【0006】[0006]
【課題を解決するための手段】そのため請求項1に係る
内燃機関の排気浄化装置は、図1に示すように構成され
る。図1において、触媒は内燃機関の排気系に設置され
て排気を浄化するものである。An exhaust gas purifying apparatus for an internal combustion engine according to the present invention is configured as shown in FIG. In FIG. 1, a catalyst is provided in an exhaust system of an internal combustion engine to purify exhaust gas.
【0007】劣化判定値記憶手段は、前記触媒のスモー
クによる劣化度合いを示す判定値を予め機関の運転条件
毎に記憶しており、運転条件検出手段は前記機関の運転
条件を検出する。そして、判定値積算手段は、劣化判定
値記憶手段から運転条件検出手段で検出された運転条件
に応じて検索した前記判定値を積算する。The deterioration judgment value storage means stores in advance a judgment value indicating the degree of deterioration of the catalyst due to smoke for each operating condition of the engine, and the operating condition detecting means detects the operating condition of the engine. Then, the judgment value accumulating means accumulates the judgment value retrieved from the deterioration judgment value storage means according to the operating condition detected by the operating condition detecting means.
【0008】ここで、スモーク劣化診断手段は、判定値
積算手段で積算された判定値に基づいて前記触媒のスモ
ークによる劣化状態を診断する。スモークによる劣化度
合い(スモーク堆積量)は運転条件によって異なるか
ら、予め運転条件毎の劣化度合いを求めてこれを判定値
として記憶させておき、運転条件毎の劣化度合いが積み
重なっていくものとして運転条件毎の判定値を積算し、
該積算結果が許容レベルを越えた時点で、転化性能を低
下させるだけのスモークが触媒に堆積しているものと推
定するものである。Here, the smoke deterioration diagnosis means diagnoses the deterioration state of the catalyst due to smoke based on the judgment value integrated by the judgment value accumulation means. Since the degree of deterioration due to smoke (the amount of smoke deposition) differs depending on the operating conditions, the degree of deterioration for each operating condition is determined in advance and stored as a determination value. Integrate the judgment value of each
When the integration result exceeds an allowable level, it is estimated that smoke enough to lower the conversion performance is deposited on the catalyst.
【0009】請求項2記載の発明では、前記劣化判定値
記憶手段が、前記運転条件としての機関負荷と機関回転
速度とによって複数に区分される運転領域毎に前記劣化
度合いを示す判定値が割り付けられたマップを記憶する
構成とした。触媒に対するスモークの堆積度合いは排気
温度に相関し、低排温時ほど堆積し易くなるから、排気
温度に相関する機関負荷及び機関回転速度に応じて判定
値を記憶させるものである。In the invention according to the second aspect, the deterioration determination value storage means allocates a determination value indicating the degree of deterioration for each of a plurality of operating regions classified according to an engine load and an engine rotation speed as the operating conditions. The stored map is configured to be stored. The degree of smoke deposition on the catalyst correlates with the exhaust gas temperature, and the lower the temperature of the exhaust gas, the easier the deposition. Therefore, the determination value is stored in accordance with the engine load and the engine speed correlated with the exhaust gas temperature.
【0010】請求項3記載の発明では、前記判定値が、
低回転,低負荷時ほど劣化度合いが大きいことを示す値
に設定される構成とした。低回転,低負荷時ほど排気温
度が低くなり、スモークの堆積が多くなるので、かかる
傾向に合わせて判定値を記憶させるものである。請求項
4記載の発明では、前記機関の燃焼方式が、成層燃焼と
均質燃焼とに切り換えられる構成であり、前記劣化判定
値記憶手段が、前記機関負荷と機関回転速度とに応じた
判定値のマップとして、前記成層リーン燃焼時用の判定
値マップと、前記均質リーン燃焼時用の判定値マップと
を記憶し、判定値積算手段が、前記燃焼方式に応じて参
照するマップを選択して前記判定値を検索する構成とし
た。In the invention according to claim 3, the judgment value is:
The configuration is set such that the lower the rotation speed and the lower the load, the greater the degree of deterioration. Since the exhaust temperature becomes lower and the amount of smoke increases as the rotation speed and the load decrease, the judgment value is stored in accordance with the tendency. In the invention according to claim 4, the combustion system of the engine is switched between stratified combustion and homogeneous combustion, and the deterioration determination value storage means stores a determination value according to the engine load and the engine speed. As the map, the determination value map for stratified lean combustion and the determination value map for homogeneous lean combustion are stored, and the determination value integrating means selects a map to be referred to according to the combustion method, and It is configured to search the judgment value.
【0011】均質リーン燃焼と成層リーン燃焼とによっ
てスモーク劣化度合いが異なるので、それぞれの燃焼方
式毎に判定値を参照するマップを備え、そのときの燃焼
方式に対応するマップを参照して判定値を検索させる。
請求項5記載の発明では、前記劣化判定値記憶手段が、
前記運転条件としての触媒入口排気温度に応じて前記劣
化度合いを示す判定値を記憶する構成とした。Since the degree of smoke deterioration differs between homogeneous lean combustion and stratified lean combustion, a map for referencing a judgment value is provided for each combustion method, and the judgment value is determined with reference to a map corresponding to the combustion method at that time. Let me search.
In the invention according to claim 5, the deterioration determination value storage means includes:
A determination value indicating the degree of deterioration is stored according to a catalyst inlet exhaust temperature as the operating condition.
【0012】前述のように、触媒に対するスモークの堆
積は、排気温度、特に、触媒入口での排気温度に大きく
影響されるから、触媒入口排気温度に応じて予め判定値
を記憶させ、そのときの入口温度に対応して判定値が設
定されるようにした。請求項6記載の発明では、図1点
線示のように、前記触媒の上流側及び下流側にそれぞれ
設けられて排気中の酸素濃度を検出する第1,第2の酸
素センサと、前記第1の酸素センサで検出される酸素濃
度の変動周波数と前記第2の酸素センサで検出される酸
素濃度の変動周波数とに基づいて前記触媒の劣化状態を
診断する触媒劣化診断手段と、を備え、前記触媒劣化診
断手段で前記触媒の劣化状態が判定されていることを前
提条件として、前記スモーク劣化診断手段が前記触媒の
スモークによる劣化状態を診断する構成とした。As described above, since the deposition of smoke on the catalyst is greatly affected by the exhaust gas temperature, particularly, the exhaust gas temperature at the catalyst inlet, the judgment value is stored in advance in accordance with the catalyst inlet exhaust temperature, The judgment value is set according to the inlet temperature. In the invention according to claim 6, as shown by the dotted line in FIG. 1, first and second oxygen sensors provided respectively on the upstream side and the downstream side of the catalyst to detect the oxygen concentration in the exhaust gas, A catalyst deterioration diagnosing means for diagnosing the deterioration state of the catalyst based on the fluctuation frequency of the oxygen concentration detected by the oxygen sensor and the fluctuation frequency of the oxygen concentration detected by the second oxygen sensor, The smoke deterioration diagnosing means diagnoses the deterioration state of the catalyst due to smoke on the premise that the catalyst deterioration state is determined by the catalyst deterioration diagnosing means.
【0013】触媒の転化性能の劣化は、酸素ストレージ
能力の低下として判断でき、該酸素ストレージ能力によ
って触媒上流側での酸素濃度の変動に対して下流側の変
動が応答遅れを生じ、酸素ストレージ能力が低下する
と、前記応答遅れが小さくなる。そこで、触媒上下流そ
れぞれにおける酸素濃度の変動周波数を求めてこれを比
較することで、触媒の酸素ストレージ能力低下、引いて
は、転化性能を低下を診断するものであり、これによっ
て転化性能の低下が診断されたときに、前記判定値に基
づいてその原因がスモークの堆積によるものであるか否
かを判断させるものである。The deterioration of the conversion performance of the catalyst can be judged as a decrease in the oxygen storage capacity, and the fluctuation in the oxygen concentration on the upstream side of the catalyst causes a response delay due to the fluctuation in the oxygen concentration on the upstream side of the catalyst. Decreases, the response delay decreases. Therefore, by determining the variation frequency of the oxygen concentration in each of the upstream and downstream of the catalyst and comparing this, the decrease in the oxygen storage capacity of the catalyst and, consequently, the decrease in the conversion performance are diagnosed. Is diagnosed on the basis of the determination value as to whether or not the cause is due to the accumulation of smoke.
【0014】請求項7記載の発明では、図1点線示のよ
うに、前記スモーク劣化診断手段により前記触媒のスモ
ークによる劣化状態が判定されたときに、所定値以下の
空燃比での燃焼を強制的に行わせる触媒劣化回復手段を
設ける構成とした。スモークの堆積による触媒劣化が判
定されたときには、スモークの脱離・焼失を図れる空燃
比での燃焼を強制的に行わせ、触媒の転化性能の回復を
図るものである。According to the seventh aspect of the present invention, as shown by a dotted line in FIG. 1, when the smoke deterioration diagnosis means determines that the catalyst has deteriorated due to smoke, combustion at an air-fuel ratio equal to or lower than a predetermined value is forcibly performed. In this case, the catalyst deterioration recovery means is provided for the purpose. When it is determined that the catalyst has deteriorated due to the accumulation of smoke, the combustion is forcibly performed at an air-fuel ratio at which the smoke can be desorbed and burned, thereby recovering the conversion performance of the catalyst.
【0015】請求項8記載の発明では、前記機関の燃焼
方式が、成層燃焼と均質燃焼とに切り換えられる構成で
あり、前記触媒劣化回復手段が、理論空燃比以下の空燃
比での均質燃焼を強制的に行わせる構成とした。かかる
構成では、触媒のスモークによる劣化が判定されると、
成層燃焼が禁止されると共に、均質リーン燃焼も禁止さ
れ、均質燃焼でかつ理論空燃比以下の空燃比での燃焼を
行わせて、触媒に堆積したスモークの脱離・焼失を図
る。According to the present invention, the combustion system of the engine is switched between stratified combustion and homogeneous combustion, and the catalyst deterioration recovery means performs homogeneous combustion at an air-fuel ratio equal to or lower than the stoichiometric air-fuel ratio. The configuration was made to force it. In such a configuration, when deterioration due to smoke of the catalyst is determined,
The stratified combustion is prohibited, and the homogeneous lean combustion is also prohibited. The homogeneous combustion is performed at an air-fuel ratio equal to or lower than the stoichiometric air-fuel ratio, so that the smoke deposited on the catalyst is desorbed and burned.
【0016】[0016]
【発明の効果】請求項1記載の発明によると、触媒に対
するスモークの堆積による劣化状態を、運転条件による
劣化度合いの違いに対応して精度良く診断できるという
効果がある。請求項2及び請求項3記載の発明による
と、機関負荷,機関回転速度から排気温度が低くスモー
クが堆積し易い条件であるか否かを判断して、触媒のス
モークによる劣化を診断できるという効果がある。According to the first aspect of the present invention, there is an effect that the deterioration state due to the accumulation of smoke on the catalyst can be accurately diagnosed in accordance with the difference in the degree of deterioration depending on the operating conditions. According to the second and third aspects of the present invention, it is possible to determine whether the exhaust gas temperature is low and smoke is easily deposited based on the engine load and the engine rotational speed, thereby diagnosing deterioration of the catalyst due to smoke. There is.
【0017】請求項4記載の発明によると、均質リーン
燃焼と成層リーン燃焼とによる劣化度合いの違いに対応
して、触媒のスモークによる劣化を精度良く診断するこ
とができるという効果がある。請求項5記載の発明によ
ると、触媒入口排気温度からスモークの堆積し易い条件
を判断して、触媒のスモークによる劣化を高精度に診断
できるという効果がある。According to the fourth aspect of the present invention, there is an effect that it is possible to accurately diagnose the deterioration of the catalyst due to smoke in accordance with the difference in the degree of deterioration between the homogeneous lean combustion and the stratified lean combustion. According to the fifth aspect of the present invention, it is possible to determine a condition under which smoke is likely to accumulate from the exhaust gas temperature at the catalyst inlet and diagnose the deterioration of the catalyst due to smoke with high accuracy.
【0018】請求項6記載の発明によると、触媒の酸素
ストレージ能力の低下として転化性能の低下状態を診断
した上で、その原因がスモークの堆積によるものである
か否かを診断させることができ、実際に転化性能(酸素
ストレージ能力)の低下が発生していない状態でスモー
ク劣化を誤診断することを回避できるという効果があ
る。According to the sixth aspect of the present invention, it is possible to diagnose whether the conversion performance is low as the oxygen storage capacity of the catalyst is low and then to determine whether the cause is due to the accumulation of smoke. This has the effect of avoiding erroneous diagnosis of smoke deterioration in a state where the conversion performance (oxygen storage capacity) has not actually decreased.
【0019】請求項7及び請求項8記載の発明による
と、スモーク堆積による触媒劣化を精度良く診断し、か
つ、スモーク劣化が発生したときに、リーン空燃比での
燃焼を禁止して排気温度の上昇を図るから、触媒のスモ
ーク劣化を的確に回復させることができるという効果が
ある。According to the seventh and eighth aspects of the present invention, catalyst deterioration due to smoke accumulation is diagnosed accurately, and when smoke deterioration occurs, combustion at a lean air-fuel ratio is prohibited to reduce exhaust gas temperature. Since the increase is intended, there is an effect that the smoke deterioration of the catalyst can be accurately recovered.
【0020】[0020]
【発明の実施の形態】以下に本発明の実施の形態を説明
する。図2は、本発明に係る排気浄化装置が適用される
内燃機関のシステム構成図であり、内燃機関1の各気筒
には、燃焼室内に直接燃料を噴射する電磁式の燃料噴射
弁2がそれぞれに設けられ、該燃料噴射弁2から噴射さ
れた燃料によってシリンダ内に混合気が形成される。即
ち、本実施の形態における機関1は、所謂直噴式内燃機
関(筒内噴射式内燃機関)である。Embodiments of the present invention will be described below. FIG. 2 is a system configuration diagram of an internal combustion engine to which the exhaust emission control device according to the present invention is applied. In each cylinder of the internal combustion engine 1, an electromagnetic fuel injection valve 2 for directly injecting fuel into a combustion chamber is provided. And an air-fuel mixture is formed in the cylinder by the fuel injected from the fuel injection valve 2. That is, the engine 1 in the present embodiment is a so-called direct injection internal combustion engine (in-cylinder injection internal combustion engine).
【0021】前記燃料噴射弁2は、コントロールユニッ
ト3からの噴射制御信号に応じて燃料を噴射する。機関
1の排気通路9には、排気中のHC,COの酸化と、N
Oxの還元とを同時に行う三元触媒4(排気浄化用の触
媒)が配置され、該三元触媒4の上流側と下流側とには
それぞれ排気中の酸素濃度を検出する第1,第2酸素セ
ンサ5,6が配置されている。The fuel injection valve 2 injects fuel according to an injection control signal from the control unit 3. In the exhaust passage 9 of the engine 1, oxidation of HC and CO in exhaust gas and N
A three-way catalyst 4 (catalyst for purifying exhaust gas) for simultaneously performing the reduction of Ox is disposed, and a first and a second sensor for detecting the oxygen concentration in the exhaust gas are respectively provided upstream and downstream of the three-way catalyst 4. Oxygen sensors 5 and 6 are arranged.
【0022】前記コントロールユニット3には、前記第
1,第2酸素センサ5,6からの検出信号が入力される
一方、運転条件検出手段としての機関の冷却水温度を検
出する水温センサ10,吸気通路8に介装されたスロット
ル弁11の上流側で吸入空気流量を検出するエアフローメ
ータ12,機関の回転速度を検出する回転数センサ13等か
らの検出信号も入力されるようになっている。The control unit 3 receives the detection signals from the first and second oxygen sensors 5 and 6, and receives a water temperature sensor 10 for detecting a cooling water temperature of the engine as operating condition detecting means. Detection signals from an air flow meter 12 for detecting an intake air flow rate on the upstream side of a throttle valve 11 interposed in the passage 8, a rotation speed sensor 13 for detecting a rotation speed of the engine, and the like are also input.
【0023】そして、前記コントロールユニット3は、
図3に示すような目標空燃比マップを参照してそのとき
の目標トルクTq及び機関回転速度Neに対応する目標
空燃比を設定すると共に、低負荷,低回転域では成層燃
焼を行わせ、それ以外の運転領域では均質燃焼域を行わ
せる。均質燃焼域では、目標空燃比がリーン、ストイキ
(理論空燃比),リッチに制御され、ストイキ(理論空
燃比)を目標空燃比とする場合には、前記第1酸素セン
サ5の検出信号に基づいて実際の空燃比を理論空燃比に
一致させるべく燃料噴射量をフィードバック補正する空
燃比フィードバック制御を実行する。The control unit 3
Referring to a target air-fuel ratio map as shown in FIG. 3, a target air-fuel ratio corresponding to the target torque Tq and the engine speed Ne at that time is set, and stratified combustion is performed in a low load and low speed range. In other operating regions, a homogeneous combustion region is performed. In the homogeneous combustion region, the target air-fuel ratio is controlled to be lean, stoichiometric (stoichiometric air-fuel ratio), and rich. When the stoichiometric (stoichiometric air-fuel ratio) is set to the target air-fuel ratio, the target air-fuel ratio is determined based on the detection signal of the first oxygen sensor 5. Then, the air-fuel ratio feedback control for performing the feedback correction of the fuel injection amount so as to make the actual air-fuel ratio coincide with the stoichiometric air-fuel ratio is executed.
【0024】ところで、リーン燃焼特に成層運転による
リーン燃焼時にスモークが発生し易く、このスモークが
三元触媒4に堆積して転化性能を一時的に低下させるこ
とがあるので、本実施の形態では、図4〜図8のフロー
チャートに示すようにして、前記スモークによる触媒劣
化を診断し、かつ、スモーク劣化が発生したときに触媒
の転化性能の回復を図るようになっている。In the meantime, smoke is likely to be generated during lean combustion, particularly during lean combustion in stratified operation, and this smoke may accumulate on the three-way catalyst 4 and temporarily lower the conversion performance. As shown in the flowcharts of FIGS. 4 to 8, the catalyst deterioration due to the smoke is diagnosed, and when the smoke deterioration occurs, the conversion performance of the catalyst is restored.
【0025】図4のフローチャートはメインルーチンを
示し、まず、S1では、前記第1,第2酸素センサ5,
6を用い、三元触媒4の酸素ストレージ能力が低下して
いるか否かを診断することで、触媒劣化を診断させる。
このS1の部分が触媒劣化診断手段に相当する。S2で
は、前記診断結果を判別し、三元触媒4の劣化が診断さ
れているときには、該触媒劣化がスモークの堆積による
ものであるか否かを判別させるために、S3へ進んでス
モーク劣化判定値の設定及び該判定値の積算を行わせ、
次のS4では、前記スモーク劣化判定値の積算値Reに
基づいてスモークによる劣化の診断を行う。FIG. 4 is a flowchart showing a main routine. First, in S1, the first and second oxygen sensors 5 and 5 are used.
By using 6 to diagnose whether or not the oxygen storage capacity of the three-way catalyst 4 has decreased, catalyst deterioration is diagnosed.
This step S1 corresponds to catalyst deterioration diagnosis means. In S2, the result of the diagnosis is determined, and if the deterioration of the three-way catalyst 4 has been diagnosed, the process proceeds to S3 to determine whether the catalyst deterioration is due to the accumulation of smoke. Setting the value and integrating the judgment value,
In the next S4, a diagnosis of deterioration due to smoke is made based on the integrated value Re of the smoke deterioration determination value.
【0026】上記S3の部分が判定値記憶手段に相当
し、S4の部分がスモーク劣化診断手段に相当する。ま
た、後述するように、コントロールユニット3には、予
め劣化判定値を検索するためのマップが記憶されてお
り、コントロールユニット3のメモリが劣化判定値記憶
手段に相当することになる。尚、便宜上、S2で劣化判
断されたときにのみS3に進むように記載したが、実際
上は、劣化度合い判定値の設定及び積算は、S2におけ
る判別の如何に関わらず実行されるものとする。The step S3 corresponds to the judgment value storage means, and the step S4 corresponds to the smoke deterioration diagnosis means. As will be described later, a map for searching for a deterioration determination value is stored in the control unit 3 in advance, and the memory of the control unit 3 corresponds to a deterioration determination value storage unit. Note that, for convenience, the process proceeds to S3 only when the deterioration is determined in S2, but in practice, the setting and integration of the deterioration degree determination value are performed regardless of the determination in S2. .
【0027】S5では、スモーク劣化の診断結果を判別
し、スモーク劣化の発生が診断されたときには、S6へ
進み、三元触媒4に堆積しているスモークの脱離,焼失
を図るべく、排気温度が低い成層燃焼,均質リーン燃焼
を禁止し、ストイキ又はリッチ空燃比での均質燃焼のみ
を強制的に行わせるようにする。上記S6の部分が、触
媒劣化回復手段に相当する。At S5, the result of the diagnosis of the smoke deterioration is determined. When the occurrence of the smoke deterioration is diagnosed, the routine proceeds to S6, where the exhaust gas temperature is determined so as to remove and burn out the smoke deposited on the three-way catalyst 4. Is prohibited, stratified combustion and homogeneous lean combustion are prohibited, and only homogeneous combustion at a stoichiometric or rich air-fuel ratio is forcibly performed. Step S6 corresponds to a catalyst deterioration recovery unit.
【0028】スモークによる三元触媒4の劣化,回復
は、触媒入口温度に対して、図9及び図10に示すような
相関を示し、触媒入口温度が低いと触媒のスモークによ
る劣化が進み、逆に、触媒入口温度が高いとスモークに
よる劣化は進行せずに、逆に、それまでに堆積したスモ
ークの脱離,焼失が図られることで、触媒性能の回復が
図れる。そこで、スモーク劣化の診断がなされたときに
は、高い触媒入口温度を確保すべく、成層燃焼及びリー
ン均質燃焼を禁止し、触媒性能の回復を図るものであ
る。The deterioration and recovery of the three-way catalyst 4 due to the smoke show a correlation as shown in FIGS. 9 and 10 with respect to the catalyst inlet temperature. When the catalyst inlet temperature is low, the deterioration due to the smoke of the catalyst proceeds, and If the catalyst inlet temperature is high, the deterioration due to smoke does not progress, and conversely, the smoke deposited up to that time is desorbed and burned, so that the catalyst performance can be recovered. Therefore, when a diagnosis of smoke deterioration is made, stratified combustion and lean homogeneous combustion are prohibited in order to secure a high catalyst inlet temperature, and the catalyst performance is restored.
【0029】S7では、前記成層燃焼及びリーン均質燃
焼の禁止によって実際に三元触媒4の転化性能が回復し
たか否かを、前記S1と同様に、第1,第2酸素センサ
5,6を用いて診断し、回復が認められたきとには、S
8へ進んで、劣化フラグ,前記積算値Reをリセット
し、S9では成層燃焼及びリーン均質燃焼の禁止を解除
して通常の制御状態に復帰させる。In S7, it is determined whether the conversion performance of the three-way catalyst 4 has actually been recovered by the prohibition of the stratified combustion and the lean homogeneous combustion. Diagnosis is made by using
Proceeding to 8, the deterioration flag and the integrated value Re are reset, and in S9, the prohibition of the stratified combustion and the lean homogeneous combustion is released, and the normal control state is returned.
【0030】図5のフローチャートは、前記S1の内容
を詳細に示すものであり、S11では冷却水温度TWを読
み込む。S12では、前記読み込んだ冷却水温度TWが所
定温度T1以上であるか否かを判別し、所定温度T1以
上であればS13へ進む。S13では、空燃比フィードバッ
ク制御領域であるか否かを判別する。前記空燃比フィー
ドバック制御領域とは目標空燃比が理論空燃比(ストイ
キ)である運転領域である。The flowchart of FIG. 5 shows the details of the above S1. In S11, the cooling water temperature TW is read. In S12, it is determined whether or not the read cooling water temperature TW is equal to or higher than a predetermined temperature T1, and if it is equal to or higher than the predetermined temperature T1, the process proceeds to S13. In S13, it is determined whether or not the current state is in the air-fuel ratio feedback control region. The air-fuel ratio feedback control region is an operation region where the target air-fuel ratio is the stoichiometric air-fuel ratio (stoichiometric).
【0031】そして、空燃比フィードバック制御中であ
るときには、S14へ進み、第1酸素センサ5の反転周波
数f1を読み込み、S15では、第2酸素センサ6の反転
周波数f2を読み込む。前記反転周波数f1,f2は、
前記空燃比フィードバック制御に基づいて目標空燃比を
中心にリッチ・リーン状態を繰り返すことによって生じ
る酸素濃度変動を示すものである。When the air-fuel ratio feedback control is being performed, the process proceeds to S14, where the inversion frequency f1 of the first oxygen sensor 5 is read, and in S15, the inversion frequency f2 of the second oxygen sensor 6 is read. The inversion frequencies f1 and f2 are:
The graph shows the oxygen concentration fluctuation caused by repeating the rich / lean state around the target air-fuel ratio based on the air-fuel ratio feedback control.
【0032】S16では前記読み込んだ反転周波数f1,
f2に基づいて反転周波数比fr=f2,f1を算出す
る。S17では、前記反転周波数比frが所定値fra以
上であるか否かを判別し、前記反転周波数比frが所定
値fra以上であれば触媒劣化と見做し、S18へ進んで
劣化判定フラグF1に1をセットし、前記反転周波数比
frが所定値fra未満であれば触媒劣化はないものと
見做し、S19へ進んで前記劣化判定フラグF1に0をセ
ットする。At S16, the read inversion frequencies f1,
The inversion frequency ratio fr = f2, f1 is calculated based on f2. In S17, it is determined whether or not the inversion frequency ratio fr is equal to or more than a predetermined value fra. If the inversion frequency ratio fr is equal to or more than the predetermined value fra, it is determined that the catalyst has deteriorated. Is set to 1. If the inversion frequency ratio fr is less than the predetermined value fra, it is considered that the catalyst has not deteriorated, and the routine proceeds to S19, where 0 is set to the deterioration determination flag F1.
【0033】前記S2では、前記劣化判定フラグF1の
判別によって、三元触媒4が劣化しているか否かを判別
する。三元触媒4の転化性能が低下しているときには、
酸素ストレージ能力が低下しており、酸素ストレージ能
力が低下すると、触媒4上流側での酸素濃度の変動周波
数に対して下流側の酸素濃度の変動周波数が近づくか
ら、前記反転周波数比frは劣化が進むほど大きな値と
なる(図11参照)。そこで、前記反転周波数比frが所
定値fra以上であるときには、前記酸素ストレージ能
力の低下が発生しているものと判断し、以て、三元触媒
4の劣化を判定するものである。At S2, it is determined whether or not the three-way catalyst 4 has deteriorated, based on the determination of the deterioration determination flag F1. When the conversion performance of the three-way catalyst 4 is reduced,
When the oxygen storage capacity is reduced and the oxygen storage capacity is reduced, the fluctuation frequency of the oxygen concentration on the downstream side approaches the fluctuation frequency of the oxygen concentration on the upstream side of the catalyst 4, so that the reversal frequency ratio fr deteriorates. The value increases as the process proceeds (see FIG. 11). Therefore, when the reversal frequency ratio fr is equal to or greater than the predetermined value fra, it is determined that the oxygen storage capacity has decreased, and thus the deterioration of the three-way catalyst 4 is determined.
【0034】但し、上記の診断によって三元触媒4の劣
化が判定されても、その原因は、スモークの堆積とは限
らない。そこで、図6及び図7のフローチャートに示す
ようにして、現在の触媒劣化状態がスモーク堆積による
ものであるか否かを判断するものである。図6のフロー
チャートは、前記S3の内容を詳細に示すものであり、
まず、S31では、前回までの劣化度合い積算値Reを読
み込み、S32では、成層運転中であるか否かを判別す
る。However, even if deterioration of the three-way catalyst 4 is determined by the above-mentioned diagnosis, the cause is not limited to the accumulation of smoke. Therefore, as shown in the flowcharts of FIGS. 6 and 7, it is determined whether or not the current catalyst deterioration state is due to smoke accumulation. The flowchart of FIG. 6 shows the details of S3 in detail.
First, in S31, the deterioration degree integrated value Re up to the previous time is read, and in S32, it is determined whether or not the stratified operation is being performed.
【0035】そして、成層運転中であるときには、S33
へ進んで、予め成層運転中(成層リーン燃焼)に対応し
て記憶されている劣化度合い判定値Srmn のマップを参
照し、現在の運転条件に対応する劣化度合い判定値Srm
n を検索する。次のS34では、前回までの積算値Reに
S33で求めた劣化度合い判定値Srmnを加算し、該加算
結果を積算値Reにセットすることで、順次劣化度合い
判定値を積算する。If the vehicle is in stratified operation, S33
Then, referring to the map of the deterioration degree determination value Srmn stored in advance corresponding to during the stratification operation (stratified lean combustion), the deterioration degree determination value Srm corresponding to the current operation condition is obtained.
Search for n. In the next S34, the deterioration degree determination value Srmn obtained in S33 is added to the integrated value Re up to the previous time, and the addition result is set in the integrated value Re, thereby sequentially integrating the deterioration degree determination values.
【0036】一方、S32で成層運転中でないと判別さ
れ、均質燃焼中であるときには、S35へ進み、均質リー
ン運転中であるか、均質ストイキ・リッチ運転中である
かを判別する。そして、均質リーン運転中であるときに
はS36へ進み、予め均質リーン運転中に対応して記憶さ
れている劣化度合い判定値Hrmn のマップを参照し、現
在の運転条件に対応する劣化度合い判定値Hrmn を検索
する。On the other hand, if it is determined in step S32 that the stratified operation is not being performed, and if the homogeneous combustion is being performed, the process proceeds to step S35, and it is determined whether the homogeneous lean operation or the homogeneous stoichiometric rich operation is being performed. When the homogeneous lean operation is being performed, the process proceeds to S36, and the deterioration degree determination value Hrmn corresponding to the current operating condition is determined by referring to a map of the deterioration degree determination value Hrmn stored in advance corresponding to the homogeneous lean operation. Search for.
【0037】次のS37では、前回までの積算値ReにS
36で求めた劣化度合い判定値Hrmnを加算し、該加算結
果を積算値Reにセットすることで、順次劣化度合い判
定値を積算する。また、S35で均質ストイキ・リッチ運
転中であると判別されたときには、スモーク発生はない
ものは判断し、S38へ進み、前回までの積算値Reをそ
のまま今回値としてセットする。In the next step S37, S is added to the integrated value Re up to the previous time.
The deterioration degree determination values Hrmn obtained in 36 are added, and the addition result is set in the integrated value Re, whereby the deterioration degree determination values are sequentially integrated. If it is determined in S35 that the vehicle is in the homogeneous stoichiometric / rich operation, it is determined that no smoke has occurred, and the process proceeds to S38, where the integrated value Re up to the previous time is set as the current value.
【0038】前記S33,S36で参照する判定値Srmn ,
Hrmn のマップは、図12及び図13に示すように機関負荷
を代表する基本燃料噴射量Tpと機関回転速度Neとに
よって複数に区分される領域毎に判定値Srmn ,Hrmn
が予め記憶されたものであり、図9に示すように、触媒
入口温度が低いときほど触媒劣化度合いが大きくなるこ
とに対応して、排気温度が低くなる低負荷,低回転時ほ
ど大きな値(より劣化度合いが大きいことを示す値)に
設定されている。The judgment values Srmn, referred to in S33 and S36,
As shown in FIGS. 12 and 13, the map of Hrmn is used to determine the judgment values Srmn, Hrmn for each of a plurality of regions divided by the basic fuel injection amount Tp representing the engine load and the engine speed Ne.
Is stored in advance. As shown in FIG. 9, the lower the catalyst inlet temperature, the greater the degree of catalyst deterioration. (A value indicating that the degree of deterioration is greater).
【0039】また、均質ストイキ・リッチ運転中である
ときには、排気温度が高く図9に示すように、触媒劣化
度合いが充分に小さい(スモークの堆積が進行しない)
ので、積算値Reの更新を行わない。図7のフローチャ
ートは、前記S4の内容を詳細に示すものであり、前記
図6のフローチャートで算出される積算値Reに基づい
てスモーク劣化が生じているか否かを診断するものであ
り、まず、S41では、前記積算値Reを読み込み、S42
では、前記積算値Reが所定値Rea以上であるか否か
を判別する。Further, during the homogeneous stoichiometric rich operation, the exhaust gas temperature is high and the degree of catalyst deterioration is sufficiently small as shown in FIG. 9 (smoke accumulation does not proceed).
Therefore, the integrated value Re is not updated. The flowchart of FIG. 7 shows the details of S4 in detail, and diagnoses whether or not smoke deterioration has occurred based on the integrated value Re calculated in the flowchart of FIG. In S41, the integrated value Re is read, and in S42
Then, it is determined whether or not the integrated value Re is equal to or greater than a predetermined value Rea.
【0040】そして、前記積算値Reが所定値Rea以
上であるときには、スモークの堆積が進んで触媒劣化が
生じているものと見做して、S43へ進み、スモーク劣化
フラグF2に1をセットする。また、前記積算値Reが
所定値Rea未満であるときには、スモークの堆積が充
分に少なく、三元触媒4は劣化はスモーク以外の要因に
よるものであると見做して、前記スモーク劣化フラグF
2に0をセットする。If the integrated value Re is equal to or greater than the predetermined value Rea, it is considered that the accumulation of smoke has progressed and the catalyst has deteriorated, and the process proceeds to S43, where 1 is set to the smoke deterioration flag F2. . On the other hand, when the integrated value Re is less than the predetermined value Rea, it is considered that the accumulation of smoke is sufficiently small, and the deterioration of the three-way catalyst 4 is caused by factors other than the smoke.
Set 0 to 2.
【0041】前記S5では、前記スモーク劣化フラグF
2の判別によって、三元触媒4の劣化がスモークの堆積
によるものであるか否かを判別する。そして、スモーク
劣化フラグF2に1がセットされていて、触媒に対する
スモークの堆積により転化性能の低下が発生していると
判断されると、成層リーン燃焼,均質リーン燃焼を禁止
し、本来成層リーン燃焼,均質リーン燃焼を行う領域で
均質ストイキ燃焼又は均質リッチ燃焼を行わせること
で、排気温度の上昇を図り、成層リーン燃焼,均質リー
ン燃焼時に触媒4に堆積したスモークの脱離・焼失を図
り、以て、触媒のスモーク被毒状態を解消して転化性能
を回復させる。In S5, the smoke deterioration flag F
By the determination of 2, it is determined whether or not the deterioration of the three-way catalyst 4 is due to the accumulation of smoke. If the smoke deterioration flag F2 is set to 1 and it is determined that the conversion performance has deteriorated due to the accumulation of smoke on the catalyst, the stratified lean combustion and the homogeneous lean combustion are prohibited, and the stratified lean combustion is originally performed. , By performing the homogeneous stoichiometric combustion or the homogeneous rich combustion in the region where the homogeneous lean combustion is performed, the exhaust temperature is increased, and the smoke deposited on the catalyst 4 during the stratified lean combustion and the homogeneous lean combustion is desorbed / burned out. Thus, the smoke poisoning state of the catalyst is eliminated and the conversion performance is restored.
【0042】図8のフローチャートは、前記S7の内容
を詳細に示すものであり、成層リーン燃焼,均質リーン
燃焼を禁止した結果、触媒の転化性能が回復したか否か
をこのルーチンによって判断する。まず、S71では、空
燃比フィードバック制御領域であるか否かを判別し、空
燃比フィードバック制御中であれば、S72へ進む。The flowchart of FIG. 8 shows the details of the above S7. In this routine, it is determined whether or not the conversion performance of the catalyst has recovered as a result of prohibiting stratified lean combustion and homogeneous lean combustion. First, in S71, it is determined whether or not it is in the air-fuel ratio feedback control region. If the air-fuel ratio feedback control is being performed, the process proceeds to S72.
【0043】S72では、上流側の第1酸素センサ5の反
転周波数f1を読み込み、次のS73では、下流側の第2
酸素センサ6の反転周波数f2を読み込む。そして、S
74では、反転周波数比fr=f2/f1を算出し、S75
では、前記反転周波数比frが所定値frb以下である
か否かを判別する。前記反転周波数比frは劣化が進む
ほど大きな値になるから(図11参照)、前記反転周波数
比frが所定値frb以下であるときには、三元触媒4
における転化性能が回復したものと判断できる。In S72, the reversal frequency f1 of the upstream first oxygen sensor 5 is read, and in the next S73, the downstream second oxygen sensor 5 is read.
The reversal frequency f2 of the oxygen sensor 6 is read. And S
At 74, the inversion frequency ratio fr = f2 / f1 is calculated, and at S75
Then, it is determined whether or not the inversion frequency ratio fr is equal to or less than a predetermined value frb. Since the inversion frequency ratio fr increases as the deterioration proceeds (see FIG. 11), when the inversion frequency ratio fr is equal to or less than the predetermined value frb, the three-way catalyst 4
It can be determined that the conversion performance in has recovered.
【0044】従って、前記S75で前記反転周波数比fr
が所定値frb以下であると判断されたときには、S8
へ進んで、劣化判定フラグF1,スモーク劣化フラグF
2,積算値Reをリセットし、S9では成層リーン燃
焼,均質リーン燃焼の禁止をキャンセルして、通常制御
状態に復帰させる。上記構成によると、前記反転周波数
比frに基づいて触媒劣化が発生していることが確認さ
れている状態で、機関負荷,機関回転速度によるスモー
ク劣化度合いの違いを考慮してスモーク劣化の有無を診
断することで、スモーク堆積による触媒劣化を精度良く
診断できるものであり、かかる診断結果に基づいて成層
リーン燃焼,均質リーン燃焼を禁止して転化性能の回復
を図る制御を実行させれば、回復処理が必要なときに確
実に回復処理を実行させることができ、無用にリーン燃
焼が制限されたり、スモーク劣化状態が放置されること
を防止できる。Therefore, in S75, the inversion frequency ratio fr
Is determined to be equal to or less than the predetermined value frb, S8
To the deterioration determination flag F1 and the smoke deterioration flag F
2. The integrated value Re is reset, and in S9, the prohibition of the stratified lean combustion and the homogeneous lean combustion is canceled, and the normal control state is returned. According to the above configuration, in a state where it is confirmed that catalyst deterioration has occurred based on the reversal frequency ratio fr, the presence or absence of smoke deterioration is determined in consideration of the difference in the degree of smoke deterioration depending on the engine load and the engine rotation speed. By diagnosing, it is possible to accurately diagnose the deterioration of the catalyst due to smoke accumulation. Based on the result of the diagnosis, if the control for inhibiting the stratified lean combustion and the homogeneous lean combustion and recovering the conversion performance is executed, the recovery can be performed. When the processing is required, the recovery processing can be reliably executed, and it is possible to prevent the lean combustion from being unnecessarily limited and the smoke deterioration state from being left unnecessarily.
【0045】ところで、上記実施の形態では、機関負荷
と機関回転速度とから排気温度を推定できることから、
機関負荷,機関回転速度をパラメータとして劣化度合い
判定値を求める構成としたが、触媒のスモーク被毒度合
いに最も相関するのは、触媒入口排気温度であるので、
より高精度にスモーク劣化の度合いを診断するために、
前記三元触媒4の上流側に触媒入口排気温度を検出する
排温センサ7が配置し、この排温センサ7で検出された
触媒入口排気温度に基づいて前記劣化度合い判定値を求
め、この判定値を積算した値Reに基づいてスモーク劣
化を診断させる構成としても良い。In the above embodiment, since the exhaust gas temperature can be estimated from the engine load and the engine speed,
Although the deterioration degree determination value is obtained by using the engine load and the engine speed as parameters, the catalyst inlet exhaust temperature is most correlated with the degree of smoke poisoning of the catalyst.
In order to diagnose the degree of smoke deterioration with higher accuracy,
An exhaust temperature sensor 7 for detecting a catalyst inlet exhaust temperature is disposed upstream of the three-way catalyst 4, and the deterioration degree determination value is obtained based on the catalyst inlet exhaust temperature detected by the exhaust temperature sensor 7. The smoke deterioration may be diagnosed based on the value Re obtained by integrating the values.
【0046】図14のフローチャートは、上記のように触
媒入口排気温度に応じて劣化度合い判定値Ornを求め
る第2の実施の形態を示すものであり、前記図6のフロ
ーチャートに代えて、前記図4のフローチャートのS3
の内容を示すものである。この図14のフローチャートに
おいて、S301 では、前回までの積算値Reを読み込
み、次のS302 では、前記排温センサ7で検出された触
媒入口排気温度を読み込む。The flowchart of FIG. 14 shows a second embodiment for obtaining the deterioration degree judgment value Orn in accordance with the catalyst inlet exhaust gas temperature as described above. Instead of the flowchart of FIG. S3 of the flowchart of 4
It shows the contents of. In the flowchart of FIG. 14, in S301, the integrated value Re up to the previous time is read, and in the next S302, the catalyst inlet exhaust gas temperature detected by the exhaust temperature sensor 7 is read.
【0047】そして、S303 では、図15に示すように、
予め触媒入口排気温度に対応して劣化度合い判定値Or
nを記憶したテーブルを参照し、現在の触媒入口排気温
度に対応する判定値Ornを検索する。ここで、前記触
媒入口排気温度が高くなると、図10に示したように、触
媒に堆積したいたスモークの脱離・焼失が図られて触媒
性能が回復するので、図16に示すように、前記触媒性能
の回復が図られる温度範囲においては、前記判定値Or
nがマイナスの値に設定されて、積算値Reが回復分に
見合って減少変化するよう構成すると良い。Then, in S303, as shown in FIG.
Deterioration degree judgment value Or corresponding to catalyst exhaust gas temperature in advance
With reference to a table storing n, a determination value Orn corresponding to the current catalyst inlet exhaust gas temperature is searched. Here, when the catalyst inlet exhaust gas temperature is increased, as shown in FIG. 10, the smoke deposited on the catalyst is desorbed and burned off, and the catalyst performance is restored.As shown in FIG. In the temperature range in which the recovery of the catalyst performance is achieved, the determination value Or
It is preferable that n is set to a negative value and the integrated value Re is reduced and changed in proportion to the recovery amount.
【0048】S304 では、前記S303 で求めた判定値O
rnを前回までの積算値Reに加算し、該加算結果を新
たに積算値Reにセットする。S305 では、前記更新さ
れた積算値Reを記憶する。上記のように、触媒入口排
気温度を直接検出し、該検出された触媒入口排気温度に
基づいて劣化度合い判定値Ornを設定する構成であれ
ば、機関負荷,機関回転速度及び燃焼方式から排気温度
を推定して劣化度合い判定値を設定する第1の実施の形
態に比べてより高精度にスモーク劣化を診断できる。但
し、第1の実施の形態の場合には、前記排温センサ7を
必要としないという利点がある。At S304, the judgment value O obtained at S303 is obtained.
rn is added to the integrated value Re up to the previous time, and the added result is newly set as the integrated value Re. In S305, the updated integrated value Re is stored. As described above, if the catalyst inlet exhaust temperature is directly detected and the deterioration degree determination value Orn is set based on the detected catalyst inlet exhaust temperature, the exhaust gas temperature is determined based on the engine load, the engine rotation speed, and the combustion method. Can be diagnosed more accurately than in the first embodiment in which the deterioration degree is estimated and the deterioration degree determination value is set. However, in the case of the first embodiment, there is an advantage that the exhaust temperature sensor 7 is not required.
【0049】ところで、前記図4のフローチャートのS
5で、スモーク劣化でないと判別されたときには、前記
三元触媒4が白金を主成分とする白金系触媒であれば、
白金が高温リーン排気雰囲気に晒されたことによる酸化
によって一時的な劣化が生じている可能性がある。前記
白金の酸化による一時劣化は、高温リーン排気雰囲気に
晒されることで進行し、高温リッチ排気雰囲気に晒され
ることで回復する特性がある。そこで、前記S5でスモ
ーク劣化でないと判別されたときには、前記白金の酸化
による一時劣化であるものと推定し、触媒を高温リッチ
排気雰囲気に晒すようにして劣化の回復を図るようにし
ても良い。Incidentally, S in the flowchart of FIG.
If it is determined that the three-way catalyst 4 is not a smoke deterioration, the three-way catalyst 4 is a platinum-based catalyst containing platinum as a main component.
Oxidation of platinum by exposure to a high temperature lean exhaust atmosphere may have caused temporary degradation. The temporary deterioration due to the oxidation of platinum progresses by being exposed to a high-temperature lean exhaust atmosphere, and recovers by being exposed to a high-temperature rich exhaust atmosphere. Therefore, when it is determined in S5 that the deterioration is not the smoke deterioration, the deterioration may be recovered by estimating the temporary deterioration due to the oxidation of the platinum and exposing the catalyst to a high-temperature rich exhaust atmosphere.
【0050】ここで、本来リーン燃焼を行わせる低負
荷,低回転側で空燃比をリッチにしても触媒が低温リッ
チ排気雰囲気に晒されることになり、劣化回復が遅れる
ばかりか、燃費悪化や排気エミッションの悪化を招く。
そこで、前記反転周波数比frに基づいて劣化度合い判
定値Rmを設定し、該判定値Rmに応じて劣化回復を行
わせる目標排気温度を設定する。そして、ストイキ燃焼
を行った場合に排気温度が前記目標排気温度以上になる
高負荷,高回転領域を回復処理領域として特定する一
方、前記ストイキ燃焼を行った場合の排気温度と、前記
回復処理領域において通常制御のリッチ空燃比で燃焼さ
せた場合の排気温度と、前記目標排気温度とに基づい
て、前記回復処理領域内で最小のリーン補正によって目
標排気温度を得られる空燃比補正係数を前記回復処理領
域内の各領域別に設定し、該空燃比補正係数による補正
を行わせることで前記目標とする温度のリッチ排気雰囲
気に触媒を晒すようにする。Here, even if the air-fuel ratio is rich on the low-load, low-rotation side where the lean combustion is originally performed, the catalyst is exposed to the low-temperature rich exhaust atmosphere. It causes emission deterioration.
Therefore, a deterioration degree determination value Rm is set based on the inversion frequency ratio fr, and a target exhaust temperature at which deterioration recovery is performed is set according to the determination value Rm. Then, a high-load, high-speed region in which the exhaust gas temperature becomes equal to or higher than the target exhaust gas temperature when the stoichiometric combustion is performed is specified as a recovery processing region, while the exhaust temperature when the stoichiometric combustion is performed and the recovery processing region are determined. The air-fuel ratio correction coefficient for obtaining the target exhaust temperature by the minimum lean correction within the recovery processing region based on the exhaust temperature when the combustion is performed at the rich air-fuel ratio under the normal control and the target exhaust temperature. The catalyst is exposed to the rich exhaust atmosphere at the target temperature by setting each region in the processing region and performing correction by the air-fuel ratio correction coefficient.
【0051】空燃比と排気温度との相関は、一般に、理
論空燃比よりも所定値だけリーン側の空燃比において排
気温度が最高温度になる一方、空燃比を排気温度が最高
となる温度からリッチ側に移行させるほど排気温度が低
下する特性がある。そこで、リッチ空燃比で燃焼させる
高負荷,高回転域で、触媒回復に必要な排気温度を確保
するために必要最小限のリーン化を施し(但し、理論空
燃比よりもリッチ側の空燃比)、触媒回復に必要な高温
リッチ雰囲気を積極的に生成するようにし、該高温リッ
チ雰囲気に触媒を晒して白金の酸化による一時劣化の状
態を回復させるようにするものである。In general, the correlation between the air-fuel ratio and the exhaust gas temperature is such that the exhaust gas temperature becomes the highest at the air-fuel ratio leaner than the stoichiometric air-fuel ratio by a predetermined value, and the air-fuel ratio is changed from the temperature at which the exhaust gas temperature becomes the highest. There is a characteristic that the exhaust gas temperature decreases as it moves to the side. Therefore, in the high-load, high-speed range where combustion is performed at a rich air-fuel ratio, a minimum necessary lean operation is performed to secure the exhaust gas temperature necessary for catalyst recovery (however, the air-fuel ratio on the rich side of the stoichiometric air-fuel ratio). A high-temperature rich atmosphere required for catalyst recovery is positively generated, and the catalyst is exposed to the high-temperature rich atmosphere to recover the state of temporary deterioration due to oxidation of platinum.
【0052】尚、上記の白金の酸化による一時劣化を回
復させる場合も、前記反転周波数比frに基づいて触媒
性能の回復が判定されたときには、前記空燃比補正をキ
ャンセルし、通常制御に復帰させるようにする。In the case where the above-mentioned temporary deterioration due to the oxidation of platinum is recovered, when the recovery of the catalyst performance is determined based on the inversion frequency ratio fr, the correction of the air-fuel ratio is canceled and the control is returned to the normal control. To do.
【図1】本発明に係る排気浄化装置の基本構成を示すブ
ロック図。FIG. 1 is a block diagram showing a basic configuration of an exhaust gas purification device according to the present invention.
【図2】実施の形態における内燃機関の構成を示すシス
テム図。FIG. 2 is a system diagram showing a configuration of an internal combustion engine in the embodiment.
【図3】上記実施の形態の機関における運転条件毎の空
燃比と燃焼方式とを示す線図。FIG. 3 is a diagram showing an air-fuel ratio and a combustion method for each operating condition in the engine of the embodiment.
【図4】上記実施の形態における触媒劣化診断及び触媒
回復処理を示すフローチャート。FIG. 4 is a flowchart showing catalyst deterioration diagnosis and catalyst recovery processing in the embodiment.
【図5】上記実施の形態における酸素濃度の変動周波数
に基づく劣化診断の様子を示すフローチャート。FIG. 5 is a flowchart showing a state of a deterioration diagnosis based on the variation frequency of the oxygen concentration in the embodiment.
【図6】上記実施の形態における劣化度合い判定値の設
定の様子を示すフローチャート。FIG. 6 is a flowchart showing how a deterioration degree determination value is set in the embodiment.
【図7】上記実施の形態におけるスモーク劣化診断の様
子を示すフローチャート。FIG. 7 is a flowchart showing a state of smoke deterioration diagnosis in the embodiment.
【図8】上記実施の形態における触媒性能の回復診断の
様子を示すフローチャート。FIG. 8 is a flowchart showing a state of a catalyst performance recovery diagnosis in the embodiment.
【図9】触媒入口温度と触媒劣化度合いとの相関を示す
線図。FIG. 9 is a diagram showing a correlation between a catalyst inlet temperature and a degree of catalyst deterioration.
【図10】触媒入口温度と触媒回復度合いとの相関を示す
線図。FIG. 10 is a diagram showing a correlation between a catalyst inlet temperature and a catalyst recovery degree.
【図11】反転周波数比と触媒劣化度との相関を示す線
図。FIG. 11 is a diagram showing a correlation between an inversion frequency ratio and a degree of catalyst deterioration.
【図12】上記実施の形態における成層燃焼時用の劣化度
合い判定値のマップを示す図。FIG. 12 is a diagram showing a map of a deterioration degree determination value for stratified combustion in the embodiment.
【図13】上記実施の形態における均質リーン燃焼時用の
劣化度合い判定値のマップを示す図。FIG. 13 is a diagram showing a map of a deterioration degree determination value for homogeneous lean combustion in the embodiment.
【図14】劣化度合い判定値を触媒入口温度に基づいて設
定する第2の実施の形態を示すフローチャート。FIG. 14 is a flowchart illustrating a second embodiment in which a deterioration degree determination value is set based on a catalyst inlet temperature.
【図15】上記第2の実施の形態における触媒入口温度に
応じた劣化度合い判定値のテーブルを示す図。FIG. 15 is a view showing a table of a deterioration degree determination value according to a catalyst inlet temperature in the second embodiment.
【図16】上記第2の実施の形態における触媒入口温度と
劣化度合い判定値との相関を示す線図。FIG. 16 is a diagram showing a correlation between a catalyst inlet temperature and a deterioration degree determination value in the second embodiment.
1 内燃機関 2 燃料噴射弁 3 コントロールユニット 4 三元触媒 5 第1酸素センサ 6 第2酸素センサ 7 排温センサ 8 吸気通路 9 排気通路 10 水温センサ 11 スロットル弁 12 エアフローメータ 13 回転数センサ Reference Signs List 1 internal combustion engine 2 fuel injection valve 3 control unit 4 three-way catalyst 5 first oxygen sensor 6 second oxygen sensor 7 exhaust temperature sensor 8 intake passage 9 exhaust passage 10 water temperature sensor 11 throttle valve 12 air flow meter 13 rotation speed sensor
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 FI F02D 45/00 301 F02D 45/00 301G 368 368F ──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. 6 Identification code FI F02D 45/00 301 F02D 45/00 301G 368 368F
Claims (8)
の触媒と、 前記触媒のスモークによる劣化度合いを示す判定値を予
め機関の運転条件毎に記憶した劣化判定値記憶手段と、 前記機関の運転条件を検出する運転条件検出手段と、 前記劣化判定値記憶手段から前記運転条件検出手段で検
出された運転条件に応じて検索した前記判定値を積算す
る判定値積算手段と、 該判定値積算手段で積算された判定値に基づいて前記触
媒のスモークによる劣化状態を診断するスモーク劣化診
断手段と、 を含んで構成されたことを特徴とする内燃機関の排気浄
化装置。An exhaust purification catalyst installed in an exhaust system of an internal combustion engine; a degradation determination value storage means for storing in advance a determination value indicating a degree of degradation of the catalyst due to smoke for each operating condition of the engine; Operating condition detecting means for detecting an operating condition of the engine; determining value integrating means for integrating the determination values retrieved from the deterioration determination value storage means in accordance with the operating conditions detected by the operating condition detecting means; An exhaust gas purification apparatus for an internal combustion engine, comprising: smoke deterioration diagnosis means for diagnosing a state of deterioration of the catalyst due to smoke based on the determination value integrated by the value integration means.
としての機関負荷と機関回転速度とによって複数に区分
される運転領域毎に前記劣化度合いを示す判定値が割り
付けられたマップを記憶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 deterioration determination value storage means stores a map in which a determination value indicating the degree of deterioration is assigned to each of a plurality of operating regions classified according to an engine load and an engine rotation speed as the operating conditions. 2. The method according to claim 1, wherein
An exhaust gas purifying apparatus for an internal combustion engine according to claim 1.
度合いが大きいことを示す値に設定されることを特徴と
する請求項2記載の内燃機関の排気浄化装置。3. The exhaust gas purifying apparatus for an internal combustion engine according to claim 2, wherein the determination value is set to a value indicating that the degree of deterioration is larger at a lower rotation speed and a lower load.
焼とに切り換えられる構成であり、前記劣化判定値記憶
手段が、前記機関負荷と機関回転速度とに応じた判定値
のマップとして、前記成層燃焼時用の判定値マップと、
前記均質リーン燃焼時用の判定値マップとを記憶し、判
定値積算手段が、前記燃焼方式に応じて参照するマップ
を選択して前記判定値を検索することを特徴とする請求
項2又は3に記載の内燃機関の排気浄化装置。4. The engine according to claim 1, wherein the combustion mode is switched between stratified combustion and homogeneous combustion. The deterioration determination value storage means stores a map of determination values according to the engine load and the engine speed. A determination value map for the stratified combustion,
4. The storage device according to claim 2, wherein the determination value map for the homogeneous lean combustion is stored, and the determination value integrating means selects a map to be referred to in accordance with the combustion method and searches for the determination value. An exhaust gas purifying apparatus for an internal combustion engine according to claim 1.
としての触媒入口排気温度に応じて前記劣化度合いを示
す判定値を記憶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。5. The exhaust gas purification system according to claim 1, wherein said deterioration determination value storage means stores a determination value indicating said degree of deterioration according to a catalyst inlet exhaust temperature as said operating condition. apparatus.
けられて排気中の酸素濃度を検出する第1,第2の酸素
センサと、 前記第1の酸素センサで検出される酸素濃度の変動周波
数と前記第2の酸素センサで検出される酸素濃度の変動
周波数とに基づいて前記触媒の劣化状態を診断する触媒
劣化診断手段と、 を備え、 前記触媒劣化診断手段で前記触媒の劣化状態が判定され
ていることを前提条件として、前記スモーク劣化診断手
段が前記触媒のスモークによる劣化状態を診断すること
を特徴とする請求項1〜5のいずれか1つに記載の内燃
機関の排気浄化装置。6. A first and a second oxygen sensor provided respectively on the upstream side and the downstream side of the catalyst for detecting an oxygen concentration in exhaust gas, and a variation in an oxygen concentration detected by the first oxygen sensor. A catalyst deterioration diagnosing means for diagnosing the deterioration state of the catalyst based on a frequency and a fluctuation frequency of the oxygen concentration detected by the second oxygen sensor. The exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein the smoke deterioration diagnosing means diagnoses a deterioration state of the catalyst due to smoke on the precondition that the determination is made. .
のスモークによる劣化状態が判定されたときに、所定値
以下の空燃比での燃焼を強制的に行わせる触媒劣化回復
手段を設けたことを特徴とする請求項1〜6のいずれか
1つに記載の内燃機関の排気浄化装置。7. A catalyst deterioration recovery means for forcibly performing combustion at an air-fuel ratio equal to or lower than a predetermined value when the smoke deterioration diagnosis means determines the deterioration state of the catalyst due to smoke. The exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 6.
焼とに切り換えられる構成であり、前記触媒劣化回復手
段が、理論空燃比以下の空燃比での均質燃焼を強制的に
行わせることを特徴とする請求項7記載の内燃機関の排
気浄化装置。8. A combustion system of the engine is switched between stratified combustion and homogeneous combustion, and the catalyst deterioration recovery means forcibly performs homogeneous combustion at an air-fuel ratio equal to or lower than a stoichiometric air-fuel ratio. The exhaust gas purifying apparatus for an internal combustion engine according to claim 7, characterized in that:
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP10726797A JP3444139B2 (en) | 1997-04-24 | 1997-04-24 | Exhaust gas purification device for internal combustion engine |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP10726797A JP3444139B2 (en) | 1997-04-24 | 1997-04-24 | Exhaust gas purification device for internal combustion engine |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH10299459A true JPH10299459A (en) | 1998-11-10 |
JP3444139B2 JP3444139B2 (en) | 2003-09-08 |
Family
ID=14454733
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JP10726797A Expired - Lifetime JP3444139B2 (en) | 1997-04-24 | 1997-04-24 | Exhaust gas purification device for internal combustion engine |
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JP (1) | JP3444139B2 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2012012011A (en) * | 2010-07-02 | 2012-01-19 | Robert Bosch Gmbh | Method of diagnosing and/or controlling at least one system of device |
JP2017194019A (en) * | 2016-04-21 | 2017-10-26 | トヨタ自動車株式会社 | Internal combustion device |
-
1997
- 1997-04-24 JP JP10726797A patent/JP3444139B2/en not_active Expired - Lifetime
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2012012011A (en) * | 2010-07-02 | 2012-01-19 | Robert Bosch Gmbh | Method of diagnosing and/or controlling at least one system of device |
JP2017194019A (en) * | 2016-04-21 | 2017-10-26 | トヨタ自動車株式会社 | Internal combustion device |
Also Published As
Publication number | Publication date |
---|---|
JP3444139B2 (en) | 2003-09-08 |
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