JP2009092002A - Air-fuel ratio control device for internal combustion engine - Google Patents

Air-fuel ratio control device for internal combustion engine Download PDF

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JP2009092002A
JP2009092002A JP2007264013A JP2007264013A JP2009092002A JP 2009092002 A JP2009092002 A JP 2009092002A JP 2007264013 A JP2007264013 A JP 2007264013A JP 2007264013 A JP2007264013 A JP 2007264013A JP 2009092002 A JP2009092002 A JP 2009092002A
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fuel ratio
catalyst
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Hideo Ikegaya
英男 池ヶ谷
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Denso Corp
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Denso Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To improve emission from a system feedback-controlling air-fuel ratio based on output of an exhaust gas sensor (oxygen sensor) at a catalyst downstream side. <P>SOLUTION: When it is judged that there is no deterioration of a catalyst, first air-fuel ratio feedback control in which behavior of air-fuel ratio correction quantity is unsymmetrical in a rich side and a lean side by making correction gain at the rich side and correction gain at the lean side different is executed. When it is judged that there is deterioration of the catalyst, second air-fuel ratio feedback control in which behavior of air-fuel ratio correction quantity is symmetrical in the rich side and the lean side by making difference between the correction gain at the rich side and the correction gain at the lean side smaller than that during the first air-fuel ratio feedback control or zero is executed. Response is increased by setting the correction gain to a large gain (high response gain) when it is judged that there is no deterioration of the catalyst, and response is retarded by setting the correction gain to a small gain (low response gain) when it is judged that there is deterioration of the catalyst. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、排気浄化用の触媒の下流側に設置した排気センサの出力に基づいて内燃機関に供給する混合気の空燃比をフィードバック制御する内燃機関の空燃比制御装置に関する発明である。   The present invention relates to an air-fuel ratio control apparatus for an internal combustion engine that feedback-controls the air-fuel ratio of an air-fuel mixture supplied to the internal combustion engine based on the output of an exhaust sensor installed downstream of an exhaust purification catalyst.

近年の電子制御化が進んだ自動車は、内燃機関の空燃比制御や触媒の劣化診断を行うために、排気通路に排気センサ（酸素センサや空燃比センサ等）を設置している。一般に、空燃比制御と触媒の劣化診断の両方を行う場合は、触媒の上流側と下流側にそれぞれ排気センサを設置し、上流側の排気センサ（又は上下両側の排気センサ）の出力に基づいて、触媒上流側の排気ガスの空燃比が触媒の浄化ウインド（排気浄化率が高い空燃比範囲）に収まるように内燃機関の供給空燃比（燃料噴射量）をフィードバック制御し、触媒を通過した排気ガスの浄化状態（リッチ／リーン）に応じて出力が変化する下流側の排気センサの出力に基づいて触媒の劣化診断を行うようにしたものが多い。   2. Description of the Related Art In recent years, automobiles that have become electronically controlled have installed exhaust sensors (oxygen sensors, air-fuel ratio sensors, etc.) in the exhaust passage in order to perform air-fuel ratio control of internal combustion engines and diagnosis of catalyst deterioration. In general, when performing both air-fuel ratio control and catalyst deterioration diagnosis, exhaust sensors are installed on the upstream side and downstream side of the catalyst, respectively, and based on the outputs of the upstream exhaust sensors (or the exhaust sensors on both the upper and lower sides). The exhaust gas that has passed through the catalyst is feedback controlled so that the air-fuel ratio of the exhaust gas upstream of the catalyst falls within the catalyst purification window (the air-fuel ratio range in which the exhaust purification rate is high). In many cases, the deterioration diagnosis of the catalyst is performed based on the output of the exhaust sensor on the downstream side where the output changes according to the gas purification state (rich / lean).

しかし、上記構成では、触媒の上流側と下流側にそれぞれ排気センサを設ける必要があるため、高価なシステム構成となる欠点がある。
そこで、安価なシステム構成とするために、触媒の下流側のみに排気センサを設けて、この下流側の排気センサの出力に基づいて空燃比を制御する技術が幾つか提案されている（下流側の排気センサがあれば触媒の劣化診断も可能である）。 However, the above configuration has a drawback that an expensive system configuration is required because it is necessary to provide exhaust sensors on the upstream side and the downstream side of the catalyst, respectively.
Therefore, in order to obtain an inexpensive system configuration, several technologies have been proposed in which an exhaust sensor is provided only on the downstream side of the catalyst, and the air-fuel ratio is controlled based on the output of the downstream exhaust sensor (downstream side). If you have an exhaust sensor, you can diagnose the deterioration of the catalyst).

例えば、特許文献１（特開昭６４−６６４４１号公報）では、下流側の排気センサの出力の平均値を演算し、この出力の平均値に基づいて空燃比ディザ制御の中心値を変化させるようにしている。ここで、空燃比ディザ制御では、空燃比補正係数ＦＡＦを所定周期でリッチ側とリーン側とに交互に振幅させるようにしている（特許文献１の３Ｂ図参照）。   For example, in Patent Document 1 (Japanese Patent Laid-Open No. 64-66441), an average value of the output of the downstream exhaust sensor is calculated, and the center value of the air-fuel ratio dither control is changed based on the average value of the output. I have to. Here, in the air-fuel ratio dither control, the air-fuel ratio correction coefficient FAF is alternately amplified between the rich side and the lean side in a predetermined cycle (see FIG. 3B of Patent Document 1).

この空燃比制御方法では、触媒上流側の排気ガスの空燃比が触媒の浄化ウインド内に制御されている条件下では、触媒のストレージ効果による下流側の排気センサの応答遅れの影響で、実際には空燃比を補正する必要がない制御状態になっていても空燃比を補正してしまい、却ってエミッションを悪化させてしまう場合がある。   In this air-fuel ratio control method, under the condition that the air-fuel ratio of the exhaust gas upstream of the catalyst is controlled in the catalyst purification window, it is actually caused by the response delay of the exhaust sensor on the downstream side due to the storage effect of the catalyst. In some cases, the air-fuel ratio is corrected even in a control state where it is not necessary to correct the air-fuel ratio, and the emission may be worsened.

このような問題を解決するために、特許文献２（特開平２−２３０９３６号公報）に記載されているように、触媒上流側の排気ガスの空燃比が触媒の浄化ウインド内に制御されているか否かを下流側の排気センサの出力の反転周期に基づいて判定し、排気センサの出力の反転周期が所定値以下になった時点で、空燃比が触媒の浄化ウインド内に制御されていると判断して、スキップ量を固定（ホールド）して空燃比の過補正を防止するようにしたものがある。   In order to solve such a problem, as described in Patent Document 2 (Japanese Patent Laid-Open No. 2-230936), is the air-fuel ratio of the exhaust gas upstream of the catalyst controlled in the purification window of the catalyst? Is determined based on the inversion period of the downstream exhaust sensor output, and the air-fuel ratio is controlled in the purification window of the catalyst when the inversion period of the exhaust sensor output becomes a predetermined value or less. In some cases, the skip amount is fixed (held) to prevent overcorrection of the air-fuel ratio.

また、特許文献３（特許第２６６６５２８号公報）に記載されているように、下流側の排気センサの出力に基づいて触媒の劣化の有無を判定し、触媒の劣化無しと判定される場合は、排気センサの出力の反転周期が所定値以下になった時点で、空燃比が触媒の浄化ウインド内に制御されていると判断して、空燃比補正量の積分制御を禁止し、触媒の劣化無しと判定される場合は、排気センサの出力のリッチ・リーンデューティ比が所定値となった時点で、空燃比が触媒の浄化ウインド内に制御されていると判断して、空燃比補正量の積分制御を禁止するようにしたものがある。
特開昭６４−６６４４１号公報 特開平２−２３０９３６号公報 特許第２６６６５２８号公報 Further, as described in Patent Document 3 (Japanese Patent No. 2666528), the presence or absence of catalyst deterioration is determined based on the output of the downstream exhaust sensor, and when it is determined that there is no catalyst deterioration, When the reversal cycle of the output of the exhaust sensor falls below a predetermined value, it is judged that the air-fuel ratio is controlled in the catalyst purification window, and integral control of the air-fuel ratio correction amount is prohibited, and there is no catalyst deterioration. If the rich / lean duty ratio of the exhaust sensor output reaches a predetermined value, it is determined that the air-fuel ratio is controlled in the catalyst purification window, and the air-fuel ratio correction amount is integrated. There is something that prohibits the control.
JP-A 64-66441 JP-A-2-230936 Japanese Patent No. 2666528

しかしながら、空燃比が触媒の浄化ウインド内に制御されているか否かは、内燃機関の運転条件によって逐次変化するため、上記特許文献２，３のように、触媒のストレージ効果によって応答性が遅くなっている下流側の排気センサの出力の反転周期やリッチ・リーンデューティ比に基づいて空燃比が触媒の浄化ウインド内に制御されているか否かを判定すると、実際の空燃比制御状態に対して補正の切り換えタイミングが遅れてしまい、結果的にエミッション悪化につながるという問題がある。   However, whether or not the air-fuel ratio is controlled in the catalyst purification window changes sequentially depending on the operating conditions of the internal combustion engine. Therefore, as in Patent Documents 2 and 3, the responsiveness is delayed due to the storage effect of the catalyst. If the air-fuel ratio is controlled in the purification window of the catalyst based on the inversion cycle of the downstream exhaust sensor output or the rich / lean duty ratio, the actual air-fuel ratio control state is corrected. There is a problem in that the timing of switching is delayed, resulting in worsening of emissions.

本発明はこのような事情を考慮してなされたものであり、従ってその目的は、触媒下流側の排気センサの出力に基づいて空燃比をフィードバック制御するシステムにおけるエミッションを従来より改善することができる内燃機関の空燃比制御装置を提供することにある。   The present invention has been made in view of such circumstances. Therefore, the object of the present invention is to improve the emission in the system that feedback-controls the air-fuel ratio based on the output of the exhaust sensor downstream of the catalyst. An object is to provide an air-fuel ratio control apparatus for an internal combustion engine.

上記目的を達成するために、請求項１に係る発明は、内燃機関の排気通路に排気浄化用の触媒を設置すると共に、前記触媒の下流側に排気センサを設置した内燃機関の空燃比制御装置において、前記排気センサの出力に基づいて前記内燃機関に供給する混合気の空燃比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空燃比制御手段と、前記排気センサの出力に基づいて前記触媒の劣化の有無を判定する触媒劣化判定手段とを備え、前記空燃比制御手段は、前記触媒劣化判定手段により前記触媒の劣化無しと判定されている場合はリッチ側の補正ゲインとリーン側の補正ゲインとを異ならせて空燃比補正量の挙動がリッチ側とリーン側とで非対称となる第１の空燃比フィードバック制御を実行し、前記触媒の劣化有りと判定されている場合はリッチ側の補正ゲインとリーン側の補正ゲインとの差を前記第１の空燃比フィードバック制御の場合よりも小さく又は０にして前記空燃比補正量の挙動がリッチ側とリーン側とで対称となる第２の空燃比フィードバック制御を実行するようにしたものである。   In order to achieve the above object, an invention according to claim 1 is an air-fuel ratio control apparatus for an internal combustion engine in which an exhaust purification catalyst is installed in an exhaust passage of the internal combustion engine, and an exhaust sensor is installed downstream of the catalyst. The air-fuel ratio control means for performing feedback correction of the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine based on the output of the exhaust sensor, and the deterioration of the catalyst based on the output of the exhaust sensor Catalyst deterioration determining means for determining the presence or absence of the catalyst, and the air-fuel ratio control means includes a rich correction gain and a lean correction gain when the catalyst deterioration determination means determines that there is no deterioration of the catalyst. And the first air-fuel ratio feedback control in which the behavior of the air-fuel ratio correction amount becomes asymmetric between the rich side and the lean side is executed, and it is determined that the catalyst has deteriorated. The difference between the rich side correction gain and the lean side correction gain is made smaller or 0 than in the case of the first air-fuel ratio feedback control, and the behavior of the air-fuel ratio correction amount differs between the rich side and the lean side. The second air-fuel ratio feedback control that is symmetric is executed.

一般に、触媒上流側の排気ガスの空燃比が触媒の浄化ウインド内に制御されている条件下で、下流側の排気センサの出力に基づいて空燃比フィードバック制御を行った場合に、エミッションを悪化させる要因となるものは、主に新品触媒（劣化無しの触媒）におけるＮＯｘであり、ＨＣやＣＯ等のリッチ成分によるエミッション悪化は少ない。これは、新品触媒の酸素ストレージ量が多いためと考えられる。   In general, when air-fuel ratio feedback control is performed based on the output of the exhaust sensor on the downstream side under the condition that the air-fuel ratio of the exhaust gas upstream of the catalyst is controlled in the catalyst purification window, the emission is deteriorated. The factor is mainly NOx in a new catalyst (a catalyst without deterioration), and the emission deterioration due to rich components such as HC and CO is small. This is probably because the amount of oxygen storage of the new catalyst is large.

従って、本発明のように、触媒の劣化無しと判定されている場合は、リッチ側の補正ゲインとリーン側の補正ゲインとを異ならせて空燃比補正量の挙動がリッチ側とリーン側とで非対称となる第１の空燃比フィードバック制御を実行すれば、劣化無しの触媒（新品触媒）の場合は、例えば、ＨＣやＣＯ等のリッチ成分の浄化能力を確保できる範囲内で、空燃比を少しだけリッチ側にずらしてＮＯｘの排出量を低減するように制御することが可能となり、劣化無しの触媒（新品触媒）の場合のＮＯｘ等のエミッションを従来より改善することができる。   Therefore, as in the present invention, when it is determined that the catalyst is not deteriorated, the rich-side correction gain and the lean-side correction gain are made different so that the behavior of the air-fuel ratio correction amount differs between the rich side and the lean side. When the first air-fuel ratio feedback control that is asymmetric is executed, in the case of a non-degraded catalyst (new catalyst), for example, the air-fuel ratio is slightly reduced within a range in which the purification ability of rich components such as HC and CO can be secured. Therefore, it is possible to control to reduce the NOx emission amount by shifting to the rich side only, and it is possible to improve the emission of NOx and the like in the case of a catalyst without deterioration (new catalyst).

一方、劣化した触媒は、酸素ストレージ量が少なくなるため、空燃比が触媒の浄化ウインドを外れたときには、ＨＣやＣＯ等のリッチ成分に関しても、ＮＯｘと同様に、浄化能力の低下が顕著に現れる。   On the other hand, since the deteriorated catalyst has a small oxygen storage amount, when the air-fuel ratio deviates from the catalyst purification window, a reduction in the purification capability also appears remarkably with respect to rich components such as HC and CO, as with NOx. .

従って、本発明のように、触媒の劣化有りと判定されている場合は、リッチ側の補正ゲインとリーン側の補正ゲインとの差を第１の空燃比フィードバック制御の場合よりも小さく又は０にして空燃比補正量の挙動がリッチ側とリーン側とで対称となる第２の空燃比フィードバック制御を実行するようにすれば、ＨＣやＣＯ等のリッチ成分とＮＯｘとをほぼ均等に浄化するように空燃比を制御することが可能となり、劣化した触媒の場合のエミッション悪化を防止することができる。   Accordingly, when it is determined that the catalyst has deteriorated as in the present invention, the difference between the rich correction gain and the lean correction gain is set to be smaller or zero than in the first air-fuel ratio feedback control. If the second air-fuel ratio feedback control in which the behavior of the air-fuel ratio correction amount is symmetric between the rich side and the lean side is executed, the rich components such as HC and CO and NOx are purified almost uniformly. In addition, the air-fuel ratio can be controlled, and emission deterioration in the case of a deteriorated catalyst can be prevented.

また、請求項２のように、触媒の劣化無しと判定されている場合と触媒の劣化有りと判定されている場合とで空燃比フィードバック制御の補正ゲインを変更するようにしても良い。例えば、触媒の劣化無しと判定されている場合は、補正ゲインを大きなゲイン（高応答ゲイン）に設定して応答性を速めれば、新品触媒（劣化無しの触媒）の場合に、ＮＯｘ排出量が増加し始めたときに、応答良く空燃比をリッチ側に補正してＮＯｘ排出量の増加を抑制することができる。また、触媒の劣化有りと判定されている場合は、補正ゲインを小さなゲイン（低応答ゲイン）に変更して応答性を遅くすれば、空燃比の過補正を防止でき、劣化した触媒の場合のエミッション悪化を防止することができる。   Further, the correction gain of the air-fuel ratio feedback control may be changed between when it is determined that there is no catalyst deterioration and when it is determined that there is catalyst deterioration. For example, if it is determined that the catalyst is not deteriorated, the NOx emission amount can be increased in the case of a new catalyst (catalyst without deterioration) by setting the correction gain to a large gain (high response gain) to speed up the response. When the fuel gas starts to increase, the air-fuel ratio can be corrected to the rich side with good response to suppress an increase in the NOx emission amount. If it is determined that the catalyst has deteriorated, overcorrection of the air-fuel ratio can be prevented by changing the correction gain to a small gain (low response gain) and slowing down the response. Emission deterioration can be prevented.

上記請求項１に係る発明と請求項２に係る発明とを組み合わせて実施すれば（請求項３）、触媒の劣化の有無に応じたより適切な空燃比制御を行うことができる。   If the invention according to claim 1 is combined with the invention according to claim 2 (claim 3), more appropriate air-fuel ratio control can be performed according to the presence or absence of catalyst deterioration.

また、請求項４のように、前記補正ゲインをスキップ量ゲインと積分量ゲインとを用いて算出し、前記スキップ量ゲイン及び／又は前記積分量ゲインを前記触媒の劣化の有無に応じて変更するようにすれば良い。このようにすれば、一般的な空燃比フィードバック制御システムに本発明を適用する場合に、スキップ量ゲインや積分量ゲインを触媒の劣化の有無に応じて変更するだけで良く、本発明を容易に実施することができる。   According to a fourth aspect of the present invention, the correction gain is calculated using a skip amount gain and an integral amount gain, and the skip amount gain and / or the integral amount gain is changed according to the presence or absence of deterioration of the catalyst. You can do that. In this way, when the present invention is applied to a general air-fuel ratio feedback control system, it is only necessary to change the skip amount gain or the integral amount gain in accordance with the presence or absence of deterioration of the catalyst. Can be implemented.

以下、本発明を実施するための最良の形態を具体化した一実施例を説明する。
まず、図１に基づいてエンジン制御システム全体の概略構成を説明する。
内燃機関であるエンジン１１の吸気管１２の最上流部には、エアクリーナ１３が設けられ、このエアクリーナ１３の下流側には、スロットルバルブ１５が設けられている。更に、スロットルバルブ１５の下流側には、サージタンク１７が設けられ、このサージタンク１７に、吸気管圧力を検出する吸気管圧力センサ１８が設けられている。この吸気管圧力センサ１８によって吸気管圧力を検出すると共に、この吸気管圧力検出値から吸入空気量を演算する。尚、スロットルバルブ１５の上流側に吸入空気量を計測するエアフロメータを設けても良い。 Hereinafter, an embodiment embodying the best mode for carrying out the present invention will be described.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.
An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and a throttle valve 15 is provided downstream of the air cleaner 13. Further, a surge tank 17 is provided on the downstream side of the throttle valve 15, and an intake pipe pressure sensor 18 for detecting the intake pipe pressure is provided in the surge tank 17. The intake pipe pressure sensor 18 detects the intake pipe pressure, and calculates the intake air amount from the intake pipe pressure detection value. An air flow meter that measures the intake air amount may be provided upstream of the throttle valve 15.

また、サージタンク１７には、エンジン１１の各気筒に空気を導入する吸気マニホールド１９が設けられ、各気筒の吸気マニホールド１９の吸気ポート近傍に、燃料を噴射する燃料噴射弁２０が取り付けられている。   The surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 19 of each cylinder. .

一方、エンジン１１の排気管２１（排気通路）の途中には、排出ガス中のＣＯ，ＨＣ，ＮＯｘ等を低減させる三元触媒等の触媒２２が設置され、この触媒２２の下流側には、排気ガスのリッチ／リーンに応じて出力が反転する酸素センサ２３（排気センサ）が設置されている。尚、酸素センサ２３の代わりに、排気ガスの空燃比に応じたリニアな空燃比信号を出力する空燃比センサ（リニアＡ／Ｆセンサ）を設置しても良い。   On the other hand, a catalyst 22 such as a three-way catalyst for reducing CO, HC, NOx, etc. in the exhaust gas is installed in the middle of the exhaust pipe 21 (exhaust passage) of the engine 11. An oxygen sensor 23 (exhaust sensor) whose output is inverted according to rich / lean exhaust gas is provided. Instead of the oxygen sensor 23, an air-fuel ratio sensor (linear A / F sensor) that outputs a linear air-fuel ratio signal corresponding to the air-fuel ratio of the exhaust gas may be installed.

また、エンジン１１のシリンダブロックには、冷却水温を検出する冷却水温センサ２７や、エンジン回転速度を検出するクランク角センサ２８等が取り付けられている。
これら各種のセンサ２３，２７，２８の出力は、エンジン制御回路（以下「ＥＣＵ」と表記する）２９に入力される。このＥＣＵ２９は、マイクロコンピュータを主体として構成され、内蔵されたＲＯＭ（記憶媒体）に記憶されたエンジン制御用の各ルーチンを実行することで、燃料噴射弁２０の燃料噴射量や点火プラグ２４の点火時期等を制御する。 A cooling water temperature sensor 27 for detecting the cooling water temperature, a crank angle sensor 28 for detecting the engine rotation speed, and the like are attached to the cylinder block of the engine 11.
The outputs of these various sensors 23, 27 and 28 are input to an engine control circuit (hereinafter referred to as “ECU”) 29. The ECU 29 is mainly composed of a microcomputer, and executes each routine for engine control stored in a built-in ROM (storage medium), so that the fuel injection amount of the fuel injection valve 20 and the ignition of the ignition plug 24 are performed. Control time etc.

更に、ＥＣＵ２９は、後述する図２の空燃比フィードバック補正ゲイン算出ルーチンを実行することで、触媒２２の下流側の酸素センサ２３の出力に基づいて空燃比フィードバック制御の補正ゲイン（フィードバック補正係数）を算出し、図３に示すように、一定の振幅且つ一定の周期で空燃比補正量をリッチ側とリーン側とに交互に振幅させる空燃比ディザ制御を実行する際に、ディザ波形状の空燃比補正量の中心値を補正ゲインに応じてオフセットさせる空燃比フィードバック制御を実行する。更に、ＥＣＵ２９は、酸素センサ２３の出力に基づいて触媒２２の劣化の有無を判定する機能も備えている。   Further, the ECU 29 executes an air-fuel ratio feedback correction gain calculation routine of FIG. 2 described later, thereby obtaining a correction gain (feedback correction coefficient) for air-fuel ratio feedback control based on the output of the oxygen sensor 23 on the downstream side of the catalyst 22. As shown in FIG. 3, when performing air-fuel ratio dither control in which the air-fuel ratio correction amount is alternately amplified between the rich side and the lean side with a constant amplitude and a constant period, an air-fuel ratio in the form of a dither wave Air-fuel ratio feedback control for offsetting the center value of the correction amount according to the correction gain is executed. Further, the ECU 29 has a function of determining whether the catalyst 22 has deteriorated based on the output of the oxygen sensor 23.

ところで、触媒２２上流側の排気ガスの空燃比が触媒２２の浄化ウインド内に制御されている条件下で、下流側の酸素センサ２３の出力に基づいて空燃比フィードバック制御を行った場合に、エミッションを悪化させる要因となるものは、主に新品触媒（劣化無しの触媒）におけるＮＯｘであり、ＨＣやＣＯ等のリッチ成分によるエミッション悪化は少ない。これは、新品触媒の酸素ストレージ量が多いためと考えられる。   By the way, when the air-fuel ratio feedback control is performed based on the output of the downstream oxygen sensor 23 under the condition that the air-fuel ratio of the exhaust gas upstream of the catalyst 22 is controlled in the purification window of the catalyst 22, the emission The cause of worsening the NO is mainly NOx in a new catalyst (a catalyst without deterioration), and the emission deterioration due to rich components such as HC and CO is small. This is probably because the amount of oxygen storage of the new catalyst is large.

そこで、本実施例では、図３（ａ）に示すように、触媒２２が劣化していない場合は、リッチ側の補正ゲインとリーン側の補正ゲインとを異ならせて空燃比補正量の挙動がリッチ側とリーン側とで非対称となる第１の空燃比フィードバック制御を実行する。具体的には、触媒２２が劣化無しの触媒（新品触媒）の場合は、ＨＣやＣＯ等のリッチ成分の浄化能力を確保できる範囲内で、空燃比を少しだけリッチ側にずらしてＮＯｘの排出量を低減するように制御する。   Therefore, in the present embodiment, as shown in FIG. 3A, when the catalyst 22 is not deteriorated, the rich-side correction gain and the lean-side correction gain are made different so that the behavior of the air-fuel ratio correction amount is changed. First air-fuel ratio feedback control that is asymmetric between the rich side and the lean side is executed. Specifically, when the catalyst 22 is a catalyst with no deterioration (new catalyst), the NOx emission is made by slightly shifting the air-fuel ratio to the rich side within a range in which the purification ability of rich components such as HC and CO can be secured. Control to reduce the amount.

一方、触媒２２が劣化している場合は、酸素ストレージ量が少なくなるため、空燃比が触媒の浄化ウインドを外れたときには、ＨＣやＣＯ等のリッチ成分に関しても、ＮＯｘと同様に、浄化能力の低下が顕著に現れる。   On the other hand, when the catalyst 22 is deteriorated, the amount of oxygen storage is reduced. Therefore, when the air-fuel ratio deviates from the purification window of the catalyst, the rich components such as HC and CO also have a purification capacity similar to NOx. The decrease is noticeable.

そこで、本実施例では、図３（ｂ）に示すように、触媒２２が劣化している場合は、リッチ側の補正ゲインとリーン側の補正ゲインとの差を第１の空燃比フィードバック制御の場合よりも小さく又は０にして空燃比補正量の挙動がリッチ側とリーン側とで対称となる第２の空燃比フィードバック制御を実行する。これにより、ＨＣやＣＯ等のリッチ成分とＮＯｘとをほぼ均等に浄化するように空燃比を制御することが可能となる。   Therefore, in this embodiment, as shown in FIG. 3B, when the catalyst 22 is deteriorated, the difference between the rich-side correction gain and the lean-side correction gain is determined by the first air-fuel ratio feedback control. The second air-fuel ratio feedback control is executed such that the behavior of the air-fuel ratio correction amount is made smaller or smaller than the case and the behavior of the air-fuel ratio correction amount is symmetric between the rich side and the lean side. This makes it possible to control the air-fuel ratio so as to purify rich components such as HC and CO and NOx substantially evenly.

更に、本実施例では、触媒２２の劣化無しと判定されている場合と触媒２２の劣化有りと判定されている場合とで空燃比フィードバック制御の補正ゲインを変更するようにしている。具体的には、触媒２２の劣化無しと判定されている場合は、補正ゲインを大きなゲイン（高応答ゲイン）に設定して応答性を速めることで、触媒２２の劣化が無い場合に、ＮＯｘ排出量が増加し始めたときに、応答良く空燃比をリッチ側に補正してＮＯｘ排出量の増加を抑制する。また、触媒２２の劣化有りと判定されている場合は、補正ゲインを小さなゲイン（低応答ゲイン）に変更して応答性を遅くすることで、空燃比の過補正を防止して、触媒２２の劣化時のエミッション悪化を防止する。   Further, in this embodiment, the correction gain of the air-fuel ratio feedback control is changed between the case where it is determined that the catalyst 22 is not deteriorated and the case where it is determined that the catalyst 22 is deteriorated. Specifically, when it is determined that the catalyst 22 is not deteriorated, NOx emission is performed when the catalyst 22 is not deteriorated by setting the correction gain to a large gain (high response gain) to speed up the response. When the amount starts to increase, the air-fuel ratio is corrected to the rich side with good response to suppress an increase in the NOx emission amount. If it is determined that the catalyst 22 has deteriorated, the correction gain is changed to a small gain (low response gain) to slow down the responsiveness, so that overcorrection of the air-fuel ratio is prevented. Prevents deterioration of emissions during deterioration.

更に、本実施例では、補正ゲインをスキップ量ＳＫＩＰと積分量ＡＢＳとを用いて算出し、スキップ量ゲインＳＫＩＰと積分量ゲインＡＢＳの両方を触媒２２の劣化の有無に応じて変更するようにしている。   Further, in this embodiment, the correction gain is calculated using the skip amount SKIP and the integral amount ABS, and both the skip amount gain SKIP and the integral amount gain ABS are changed according to the presence or absence of deterioration of the catalyst 22. Yes.

以上説明した本実施例の空燃比フィードバック制御に対する補正ゲインの設定は、ＥＣＵ２９によって図２の空燃比フィードバック補正ゲイン算出ルーチンに従って次のように実行される。   The correction gain setting for the air-fuel ratio feedback control of the present embodiment described above is executed by the ECU 29 as follows according to the air-fuel ratio feedback correction gain calculation routine of FIG.

図２の空燃比フィードバック制御ルーチンは、エンジン運転中に所定周期で繰り返し実行され、特許請求の範囲でいう空燃比制御手段としての役割を果たす。本ルーチンが起動されると、まずステップ１０１で、触媒劣化判定処理ルーチン（図示せず）を実行して、酸素センサ２３の出力に基づいて触媒２２の劣化の有無を判定する。   The air-fuel ratio feedback control routine of FIG. 2 is repeatedly executed at a predetermined period during engine operation, and serves as air-fuel ratio control means in the claims. When this routine is started, first, in step 101, a catalyst deterioration determination processing routine (not shown) is executed, and the presence or absence of deterioration of the catalyst 22 is determined based on the output of the oxygen sensor 23.

一般に、触媒２２が劣化すると、下流側の酸素センサ２３の出力の振幅と周波数が増加することから、例えば、次の［１］〜［５］のいずれかの方法で触媒２２の劣化の有無を判定すれば良い。   Generally, when the catalyst 22 deteriorates, the amplitude and frequency of the output of the downstream oxygen sensor 23 increase. For example, the presence or absence of deterioration of the catalyst 22 is checked by any one of the following methods [1] to [5]. Judgment is sufficient.

［１］酸素センサ２３の出力の軌跡長を用いる方法
触媒２２が劣化すると、下流側の酸素センサ２３の出力の振幅と周波数が増加して、酸素センサ２３の出力の軌跡長が増加する特性を利用して、触媒２２の劣化の有無を判定する。 [1] Method Using Trajectory Length of Output of Oxygen Sensor 23 When the catalyst 22 deteriorates, the amplitude and frequency of the output of the oxygen sensor 23 on the downstream side increase, and the trajectory length of the output of the oxygen sensor 23 increases. Utilizing it, the presence or absence of deterioration of the catalyst 22 is determined.

［２］酸素センサ２３の出力の面積（出力と目標値との差の積算値）を用いる方法
触媒２２の劣化により、酸素センサ２３の出力の振幅と周波数が増加すると、酸素センサ２３の出力の面積（出力と目標値との差の積算値）が増加する特性を利用して、触媒２２の劣化の有無を判定する。 [2] Method Using Area of Output of Oxygen Sensor 23 (Integrated Value of Difference between Output and Target Value) When the amplitude and frequency of the output of oxygen sensor 23 increase due to deterioration of catalyst 22, the output of oxygen sensor 23 The presence / absence of deterioration of the catalyst 22 is determined using the characteristic that the area (the integrated value of the difference between the output and the target value) increases.

［３］酸素センサ２３の出力のリッチ／リーンの反転回数（周波数、周期）を用いる方法
触媒２２が劣化すると、酸素センサ２３の出力の周波数（リッチ／リーンの反転回数）が増加し、周期が短くなる特性を利用して、触媒２２の劣化の有無を判定する。 [3] Method of using the number of times of rich / lean reversal (frequency, cycle) of the output of the oxygen sensor 23 When the catalyst 22 deteriorates, the frequency of the output of the oxygen sensor 23 (number of times of rich / lean reversal) increases and the cycle becomes longer. The presence / absence of deterioration of the catalyst 22 is determined using the shortening characteristic.

［４］酸素センサ２３の出力の振幅を用いる方法
触媒２２が劣化すると、酸素センサ２３の出力の振幅が増加する特性を利用して、触媒２２の劣化の有無を判定する。 [4] Method Using Output Sensor Amplitude of Oxygen Sensor 23 When the catalyst 22 deteriorates, the presence or absence of deterioration of the catalyst 22 is determined using the characteristic that the output amplitude of the oxygen sensor 23 increases.

［５］酸素センサ２３の応答遅れ時間を用いる方法
触媒２２が劣化すると、触媒２２のストレージ量（排出ガス成分の飽和吸着量）が減少するため、触媒２２で浄化されずに通り抜ける排気ガス成分が増加する。この関係で、目標空燃比のリッチ／リーンを反転させてから酸素センサ２３の出力のリッチ／リーンが反転するまでの応答遅れ時間は、触媒２２が劣化すると短くなる。従って、酸素センサ２３の応答遅れ時間が所定の判定値以下であるか否かで、触媒２２の劣化の有無を判定することができる。このステップ１０１の処理が特許請求の範囲でいう触媒劣化判定手段としての役割を果たす。 [5] Method Using Response Delay Time of Oxygen Sensor 23 When the catalyst 22 deteriorates, the storage amount of the catalyst 22 (saturated adsorption amount of exhaust gas components) decreases, so that exhaust gas components that pass through without being purified by the catalyst 22 are reduced. To increase. In this relationship, the response delay time from when the rich / lean of the target air-fuel ratio is reversed until the rich / lean of the output of the oxygen sensor 23 is reversed becomes shorter when the catalyst 22 deteriorates. Therefore, the presence or absence of deterioration of the catalyst 22 can be determined based on whether or not the response delay time of the oxygen sensor 23 is equal to or less than a predetermined determination value. The process of step 101 plays a role as catalyst deterioration determination means in the claims.

触媒劣化判定処理後に、ステップ１０２に進み、上記ステップ１０１の触媒劣化判定処理結果に基づいて触媒２２が劣化しているか否かを判定し、触媒２２が劣化していると判定されれば、ステップ１０３に進み、補正ゲインフラグＸＳＧＡＩＮを低応答ゲイン（Ｌｏｗ）を意味する「１」にセットし、触媒２２が劣化していないと判定されれば、ステップ１０４に進み、補正ゲインフラグＸＳＧＡＩＮを高応答ゲイン（Ｈｉｇｈ）を意味する「０」にセットする。   After the catalyst deterioration determination process, the process proceeds to step 102, where it is determined whether the catalyst 22 is deteriorated based on the result of the catalyst deterioration determination process in step 101. The process proceeds to 103, the correction gain flag XSGAIN is set to “1” which means a low response gain (Low), and if it is determined that the catalyst 22 has not deteriorated, the process proceeds to step 104 and the correction gain flag XSGAIN is set to a high response. It is set to “0” which means gain (High).

この後、ステップ１０５に進み、酸素センサ２３の出力のリッチ／リーンが前回の状態から反転したか否かを判定し、リッチ／リーンが反転していなければ、ステップ１１１に進み、スキップ量ゲインＳＫＩＰを「０」にセットし、次のステップ１１２で、積分量ゲインＡＢＳも「０」にセットする。   Thereafter, the process proceeds to step 105, where it is determined whether the rich / lean output of the oxygen sensor 23 has been reversed from the previous state. If the rich / lean has not reversed, the process proceeds to step 111, where the skip amount gain SKIP is determined. Is set to “0”, and in the next step 112, the integral gain ABS is also set to “0”.

上記ステップ１０５で、酸素センサ２３の出力のリッチ／リーンが前回の状態から反転したと判定されれば、ステップ１０６に進み、補正ゲインフラグＸＳＧＡＩＮが１（低応答ゲイン）であるか否かを判定し、補正ゲインフラグＸＳＧＡＩＮが１（低応答ゲイン）であれば、ステップ１０７に進み、スキップ量ゲインＳＫＩＰを低応答ゲイン「１」にセットし、次のステップ１０８で、積分量ゲインＡＢＳも低応答ゲイン「０．１」にセットする。   If it is determined in step 105 that the rich / lean output of the oxygen sensor 23 has been reversed from the previous state, the process proceeds to step 106 to determine whether or not the correction gain flag XSGAIN is 1 (low response gain). If the correction gain flag XSGAIN is 1 (low response gain), the process proceeds to step 107, the skip amount gain SKIP is set to the low response gain “1”, and in the next step 108, the integral amount gain ABS is also low response. Set the gain to “0.1”.

上記ステップ１０６で、補正ゲインフラグＸＳＧＡＩＮが１（低応答ゲイン）ではなく、０（高応答ゲイン）であると判定されれば、ステップ１０９に進み、スキップ量ゲインＳＫＩＰを高応答ゲイン「２」にセットし、次のステップ１１０で、積分量ゲインＡＢＳも高応答ゲイン「０．２」にセットする。   If it is determined in step 106 that the correction gain flag XSGAIN is not 1 (low response gain) but 0 (high response gain), the process proceeds to step 109 and the skip amount gain SKIP is set to the high response gain “2”. In step 110, the integral gain ABS is also set to a high response gain “0.2”.

以上のようにして、スキップ量ゲインＳＫＩＰと積分量ゲインＡＢＳをセットした後、ステップ１１３に進み、現在の酸素センサ２３の出力がリーンであるか否かを判定し、現在の酸素センサ２３の出力がリーンであれば、ステップ１１４に進み、前回の補正ゲインＳＧＡＩＮ(i-1) から今回のスキップ量ゲインＳＫＩＰと積分量ゲインＡＢＳを差し引いて今回の補正ゲインＳＧＡＩＮを求める。
ＳＧＡＩＮ＝ＳＧＡＩＮ(i-1) −ＳＫＩＰ−ＡＢＳ After the skip amount gain SKIP and the integral amount gain ABS are set as described above, the process proceeds to step 113, where it is determined whether or not the current output of the oxygen sensor 23 is lean, and the current output of the oxygen sensor 23 is determined. If it is lean, the routine proceeds to step 114, where the current correction gain SGAIN is obtained by subtracting the current skip amount gain SKIP and the integral amount gain ABS from the previous correction gain SGAIN (i-1).
SGAIN = SGAIN (i-1) -SKIP-ABS

これに対して、上記ステップ１１３で、現在の酸素センサ２３の出力がリーンではなく、リッチであると判定されれば、ステップ１１５に進み、補正ゲインフラグＸＳＧＡＩＮが１（低応答ゲイン）であるか否かを判定し、補正ゲインフラグＸＳＧＡＩＮが１（低応答ゲイン）であれば、ステップ１１６に進み、前回の補正ゲインＳＧＡＩＮ(i-1) に今回のスキップ量ゲインＳＫＩＰと積分量ゲインＡＢＳを加算して今回の補正ゲインＳＧＡＩＮを求める。
ＳＧＡＩＮ＝ＳＧＡＩＮ(i-1) ＋ＳＫＩＰ＋ＡＢＳ On the other hand, if it is determined in step 113 that the current output of the oxygen sensor 23 is not lean but rich, the process proceeds to step 115 where the correction gain flag XSGAIN is 1 (low response gain). If the correction gain flag XSGAIN is 1 (low response gain), the process proceeds to step 116, and the current skip amount gain SKIP and integral amount gain ABS are added to the previous correction gain SGAIN (i-1). The current correction gain SGAIN is obtained.
SGAIN = SGAIN (i-1) + SKIP + ABS

一方、上記ステップ１１５で、補正ゲインフラグＸＳＧＡＩＮが１（低応答ゲイン）ではなく、０（高応答ゲイン）であると判定されれば、ステップ１１７に進み、前回の補正ゲインＳＧＡＩＮ(i-1) に今回のスキップ量ゲインＳＫＩＰと積分量ゲインＡＢＳのそれぞれの２倍のゲインを加算して今回の補正ゲインＳＧＡＩＮを求める。
ＳＧＡＩＮ＝ＳＧＡＩＮ(i-1) ＋（ＳＫＩＰ＋ＡＢＳ）×２ On the other hand, if it is determined in step 115 that the correction gain flag XSGAIN is not 1 (low response gain) but 0 (high response gain), the process proceeds to step 117 and the previous correction gain SGAIN (i-1). The current correction gain SGAIN is obtained by adding twice the gains of the skip amount gain SKIP and the integral amount gain ABS.
SGAIN = SGAIN (i-1) + (SKIP + ABS) × 2

尚、「ＳＫＩＰ＋ＡＢＳ」の例えば１．５倍、２、５倍、３倍等の値を前回の補正ゲインＳＧＡＩＮ(i-1) に加算して今回の補正ゲインＳＧＡＩＮを求めるようにしても良い。     The current correction gain SGAIN may be obtained by adding a value of “SKIP + ABS”, for example, 1.5 times, 2, 5 times, 3 times, etc. to the previous correction gain SGAIN (i−1).

以上説明した図２の空燃比フィードバック補正ゲイン算出ルーチンによって補正ゲインを算出した後、図３に示すように、空燃比ディザ制御における一定の振幅且つ一定の周期で振幅するディザ波形状の空燃比補正量の中心値に補正ゲインを反映させて、該空燃比補正量の中心値を補正ゲインに応じてオフセットさせる。   After the correction gain is calculated by the air-fuel ratio feedback correction gain calculation routine of FIG. 2 described above, as shown in FIG. 3, the air-fuel ratio correction in the dither wave shape that has a constant amplitude and a constant period in the air-fuel ratio dither control is performed. The correction gain is reflected on the center value of the amount, and the center value of the air-fuel ratio correction amount is offset according to the correction gain.

この場合、図３（ａ）に示すように、触媒２２が劣化していない場合は、リッチ側の補正ゲインとリーン側の補正ゲインとを異ならせて空燃比補正量の挙動がリッチ側とリーン側とで非対称となる第１の空燃比フィードバック制御を実行するようにしたので、触媒２２が劣化無しの触媒（新品触媒）の場合は、例えば、ＨＣやＣＯ等のリッチ成分の浄化能力を確保できる範囲内で、空燃比を少しだけリッチ側にずらしてＮＯｘの排出量を低減するように制御することが可能となり、劣化無しの触媒（新品触媒）の場合のＮＯｘ等のエミッションを従来より改善することができる。   In this case, as shown in FIG. 3A, when the catalyst 22 is not deteriorated, the rich-side correction gain and the lean-side correction gain are made different so that the behavior of the air-fuel ratio correction amount is different from that of the rich side and the lean side. Since the first air-fuel ratio feedback control that is asymmetrical with respect to the catalyst side is executed, when the catalyst 22 is a catalyst with no deterioration (new catalyst), for example, the ability to purify rich components such as HC and CO is secured. Within the possible range, the air-fuel ratio can be shifted slightly to the rich side to control NOx emissions, improving NOx emissions in the case of a non-degraded catalyst (new catalyst). can do.

一方、図３（ｂ）に示すように、触媒２２の劣化有りと判定されている場合は、リッチ側の補正ゲインとリーン側の補正ゲインとの差を第１の空燃比フィードバック制御の場合よりも小さく又は０にして空燃比補正量の挙動がリッチ側とリーン側とで対称となる第２の空燃比フィードバック制御を実行するようにしたので、ＨＣやＣＯ等のリッチ成分とＮＯｘとをほぼ均等に浄化するように空燃比を制御することが可能となり、触媒２２が劣化した場合のエミッション悪化を防止することができる。   On the other hand, as shown in FIG. 3B, when it is determined that the catalyst 22 has deteriorated, the difference between the rich correction gain and the lean correction gain is set to be greater than that in the first air-fuel ratio feedback control. Since the second air-fuel ratio feedback control is performed so that the behavior of the air-fuel ratio correction amount is symmetric between the rich side and the lean side, the rich component such as HC and CO and NOx are substantially reduced. It becomes possible to control the air-fuel ratio so as to purify evenly, and it is possible to prevent emission deterioration when the catalyst 22 deteriorates.

更に、本実施例では、触媒２２の劣化無しと判定されている場合は、補正ゲインを大きなゲイン（高応答ゲイン）に設定して応答性を速めるようにしているので、触媒２２が新品触媒（劣化無しの触媒）の場合に、ＮＯｘ排出量が増加し始めたときに、応答良く空燃比をリッチ側に補正してＮＯｘ排出量の増加を抑制することができる。また、触媒２２が劣化有りと判定されている場合は、補正ゲインを小さなゲイン（低応答ゲイン）に変更して応答性を遅くするようにしたので、空燃比の過補正を防止でき、触媒２２が劣化している場合のエミッション悪化を防止することができる。   Furthermore, in this embodiment, when it is determined that the catalyst 22 is not deteriorated, the correction gain is set to a large gain (high response gain) so as to speed up the response. In the case of a non-degraded catalyst), when the NOx emission starts to increase, the increase in the NOx emission can be suppressed by correcting the air-fuel ratio to the rich side with good response. In addition, when it is determined that the catalyst 22 is deteriorated, the correction gain is changed to a small gain (low response gain) to slow down the response, so that overcorrection of the air-fuel ratio can be prevented, and the catalyst 22 can be prevented. It is possible to prevent the emission deterioration when the is deteriorated.

尚、本実施例では、スキップ量ゲインＳＫＩＰと積分量ゲインＡＢＳの両方を触媒２２の劣化の有無に応じて変更するようにしたが、スキップ量ゲインＳＫＩＰと積分量ゲインＡＢＳのいずれか一方のみを触媒２２の劣化の有無に応じて変更するようにしても良い。   In this embodiment, both the skip amount gain SKIP and the integral amount gain ABS are changed depending on whether the catalyst 22 is deteriorated, but only one of the skip amount gain SKIP and the integral amount gain ABS is changed. You may make it change according to the presence or absence of deterioration of the catalyst 22. FIG.

その他、本発明は、図１に示すような吸気ポート噴射エンジンに限定されず、筒内噴射エンジンにも適用して実施できる。   In addition, the present invention is not limited to the intake port injection engine as shown in FIG. 1 but can be applied to a cylinder injection engine.

本発明の一実施例を示すエンジン制御システム全体の概略構成図である。1 is a schematic configuration diagram of an entire engine control system showing an embodiment of the present invention. 空燃比フィードバック補正ゲイン算出ルーチンの処理の流れを示すフローチャートである。It is a flowchart which shows the flow of a process of an air fuel ratio feedback correction gain calculation routine. （ａ）は触媒劣化無し時の酸素センサ出力と補正ゲインと空燃比補正量の挙動の一例を示すタイムチャートであり、（ｂ）は触媒劣化時の酸素センサ出力と補正ゲインと空燃比補正量の挙動の一例を示すタイムチャートである。(A) is a time chart showing an example of the behavior of the oxygen sensor output, correction gain, and air-fuel ratio correction amount when there is no catalyst deterioration, and (b) is the oxygen sensor output, correction gain, and air-fuel ratio correction amount when the catalyst deteriorates. It is a time chart which shows an example of behavior of this.

符号の説明Explanation of symbols

１１…エンジン（内燃機関）、１２…吸気管、２０…燃料噴射弁、２１…排気管（排気通路）、２２…触媒、２３…酸素センサ（排気センサ）、２９…ＥＣＵ（空燃比制御手段，触媒劣化判定手段）   DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 20 ... Fuel injection valve, 21 ... Exhaust pipe (exhaust passage), 22 ... Catalyst, 23 ... Oxygen sensor (exhaust sensor), 29 ... ECU (Air-fuel ratio control means, Catalyst degradation judgment means)

Claims (4)

内燃機関の排気通路に排気浄化用の触媒を設置すると共に、前記触媒の下流側に排気センサを設置した内燃機関の空燃比制御装置において、
前記排気センサの出力に基づいて前記内燃機関に供給する混合気の空燃比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空燃比制御手段と、
前記排気センサの出力に基づいて前記触媒の劣化の有無を判定する触媒劣化判定手段とを備え、
前記空燃比制御手段は、前記触媒劣化判定手段により前記触媒の劣化無しと判定されている場合はリッチ側の補正ゲインとリーン側の補正ゲインとを異ならせて空燃比補正量の挙動がリッチ側とリーン側とで非対称となる第１の空燃比フィードバック制御を実行し、前記触媒の劣化有りと判定されている場合はリッチ側の補正ゲインとリーン側の補正ゲインとの差を前記第１の空燃比フィードバック制御の場合よりも小さく又は０にして前記空燃比補正量の挙動がリッチ側とリーン側とで対称となる第２の空燃比フィードバック制御を実行することを特徴とする内燃機関の空燃比制御装置。 In an air-fuel ratio control apparatus for an internal combustion engine in which an exhaust purification catalyst is installed in an exhaust passage of the internal combustion engine, and an exhaust sensor is installed downstream of the catalyst,
Air-fuel ratio control means for performing air-fuel ratio feedback control for feedback correction of the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine based on the output of the exhaust sensor;
Catalyst deterioration determination means for determining the presence or absence of deterioration of the catalyst based on the output of the exhaust sensor;
When the catalyst deterioration determining means determines that the catalyst is not deteriorated, the air-fuel ratio control means changes the rich-side correction gain and the lean-side correction gain so that the behavior of the air-fuel ratio correction amount is rich. The first air-fuel ratio feedback control that is asymmetric between the lean side and the lean side is executed, and when it is determined that the catalyst has deteriorated, the difference between the rich side correction gain and the lean side correction gain is calculated as the first side. The second air-fuel ratio feedback control is executed, wherein the second air-fuel ratio feedback control is executed so that the behavior of the air-fuel ratio correction amount is symmetric between the rich side and the lean side. Fuel ratio control device. 内燃機関の排気通路に排気浄化用の触媒を設置すると共に、前記触媒の下流側に排気センサを設置した内燃機関の空燃比制御装置において、
前記排気センサの出力に基づいて前記内燃機関に供給する混合気の空燃比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空燃比制御手段と、
前記排気センサの出力に基づいて前記触媒の劣化の有無を判定する触媒劣化判定手段とを備え、
前記空燃比制御手段は、前記触媒劣化判定手段により前記触媒の劣化無しと判定されている場合と前記触媒の劣化有りと判定されている場合とで前記空燃比フィードバック制御の補正ゲインを変更することを特徴とする内燃機関の空燃比制御装置。 In an air-fuel ratio control apparatus for an internal combustion engine in which an exhaust purification catalyst is installed in an exhaust passage of the internal combustion engine, and an exhaust sensor is installed downstream of the catalyst,
Air-fuel ratio control means for performing air-fuel ratio feedback control for feedback correction of the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine based on the output of the exhaust sensor;
Catalyst deterioration determination means for determining the presence or absence of deterioration of the catalyst based on the output of the exhaust sensor;
The air-fuel ratio control means changes the correction gain of the air-fuel ratio feedback control between the case where the catalyst deterioration determining means determines that the catalyst is not deteriorated and the case where it is determined that the catalyst is deteriorated. An air-fuel ratio control apparatus for an internal combustion engine characterized by the above. 前記空燃比制御手段は、前記触媒劣化判定手段により前記触媒の劣化無しと判定されている場合と前記触媒の劣化有りと判定されている場合とでリッチ側の補正ゲインとリーン側の補正ゲインを個別に変更する手段を備えていることを特徴とする請求項２に記載の内燃機関の空燃比制御装置。   The air-fuel ratio control means calculates a rich correction gain and a lean correction gain when the catalyst deterioration determining means determines that the catalyst is not deteriorated and when the catalyst is determined to be deteriorated. The air-fuel ratio control apparatus for an internal combustion engine according to claim 2, further comprising means for individually changing. 前記空燃比制御手段は、前記補正ゲインをスキップ量ゲインと積分量ゲインとを用いて算出し、前記スキップ量ゲイン及び／又は前記積分量ゲインを前記触媒の劣化の有無に応じて変更することを特徴とする請求項１ないし３のいずれかに記載の内燃機関の空燃比制御装置。   The air-fuel ratio control means calculates the correction gain using a skip amount gain and an integral amount gain, and changes the skip amount gain and / or the integral amount gain according to the presence or absence of deterioration of the catalyst. The air-fuel ratio control apparatus for an internal combustion engine according to any one of claims 1 to 3,
JP2007264013A 2007-10-10 2007-10-10 Air-fuel ratio control device for internal combustion engine Pending JP2009092002A (en)

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JP2013510779A (en) * 2009-11-20 2013-03-28 アクテガ ディエス ゲーエムベーハー Sealing polymer formulations for use with fat-containing fillers
US8471247B2 (en) 2009-08-24 2013-06-25 E I Du Pont De Nemours And Company Organic light-emitting diode luminaires
JP2014199042A (en) * 2013-03-29 2014-10-23 本田技研工業株式会社 Engine exhaust emission control device
JP2016070227A (en) * 2014-09-30 2016-05-09 日産自動車株式会社 Internal combustion engine air-fuel ratio control device

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JPH02283834A (en) * 1989-04-24 1990-11-21 Toyota Motor Corp Air-fuel ratio control device for internal combustion engine

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8471247B2 (en) 2009-08-24 2013-06-25 E I Du Pont De Nemours And Company Organic light-emitting diode luminaires
JP2013510779A (en) * 2009-11-20 2013-03-28 アクテガ ディエス ゲーエムベーハー Sealing polymer formulations for use with fat-containing fillers
JP2014199042A (en) * 2013-03-29 2014-10-23 本田技研工業株式会社 Engine exhaust emission control device
JP2016070227A (en) * 2014-09-30 2016-05-09 日産自動車株式会社 Internal combustion engine air-fuel ratio control device

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