JP2002322932A - Air fuel ratio control device for engine - Google Patents
Air fuel ratio control device for engineInfo
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- JP2002322932A JP2002322932A JP2001130051A JP2001130051A JP2002322932A JP 2002322932 A JP2002322932 A JP 2002322932A JP 2001130051 A JP2001130051 A JP 2001130051A JP 2001130051 A JP2001130051 A JP 2001130051A JP 2002322932 A JP2002322932 A JP 2002322932A
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- air
- fuel ratio
- fuel
- boundary point
- ratio
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- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
- Combined Controls Of Internal Combustion Engines (AREA)
- Exhaust Gas After Treatment (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、触媒の前後に配設
した空燃比検出手段で取得した空燃比情報に基づいて空
燃比フィードバック制御を行うエンジンの空燃比制御装
置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device for an engine that performs air-fuel ratio feedback control based on air-fuel ratio information obtained by air-fuel ratio detection means disposed before and after a catalyst.
【０００２】[0002]
【従来の技術】従来、エンジンの排気通路に、触媒を配
設し、この触媒の上流側と下流側とに広域空燃比センサ
或いはＯ2センサ等の空燃比センサを配し、２つのセン
サで得られた空燃比情報に基づいて、燃料噴射量をフィ
ードバック制御する空燃比制御装置が知られている。2. Description of the Related Art Conventionally, a catalyst is disposed in an exhaust passage of an engine, and a wide-range air-fuel ratio sensor or an air-fuel ratio sensor such as an O2 sensor is disposed upstream and downstream of the catalyst. 2. Description of the Related Art There is known an air-fuel ratio control device that performs feedback control of a fuel injection amount based on obtained air-fuel ratio information.
【０００３】例えば、特開２０００-９７０８１号公報
には、触媒の上流に排ガス中の酸素濃度に応じて空燃比
をリニアに検出する空燃比センサを配設し、下流に排ガ
ス中の酸素濃度により空燃比のリッチ/リーンを検出す
る酸素濃度（Ｏ2）センサを配設し、下流側のＯ2センサ
で得られた空燃比情報に基づいて上流側の目標空燃比を
算出し、この目標空燃比と上流側の空燃比センサで得ら
れた空燃比情報とに基づいて、燃料噴射量を補正する上
流側空燃比フィードバック補正量を算出する技術が開示
されている。For example, in Japanese Patent Application Laid-Open No. 2000-97081, an air-fuel ratio sensor that linearly detects an air-fuel ratio in accordance with the oxygen concentration in exhaust gas is provided upstream of the catalyst, and the air-fuel ratio sensor is provided downstream in accordance with the oxygen concentration in exhaust gas. An oxygen concentration (O2) sensor for detecting rich / lean air-fuel ratios is provided, and an upstream target air-fuel ratio is calculated based on air-fuel ratio information obtained by a downstream O2 sensor. There is disclosed a technique of calculating an upstream air-fuel ratio feedback correction amount for correcting a fuel injection amount based on air-fuel ratio information obtained by an upstream air-fuel ratio sensor.
【０００４】この先行技術では、下流側のＯ2センサで
得られた空燃比情報に基づき設定した目標空燃比を上流
側の空燃比センサで得られた空燃比情報に基づいて補正
することで、下流側の空燃比が一定となるようにフィー
ドバック制御している。In this prior art, the target air-fuel ratio set based on the air-fuel ratio information obtained by the downstream O2 sensor is corrected based on the air-fuel ratio information obtained by the upstream air-fuel ratio sensor, so that the downstream air-fuel ratio is corrected. Feedback control is performed so that the air-fuel ratio on the side becomes constant.
【０００５】[0005]
【発明が解決しようとする課題】しかし、下流側の空燃
比は、キャニスタに吸着されている燃料粒子を吸気系へ
供給して燃焼させるエバポパージシステムから供給され
た燃料粒子等の外乱に起因して、空燃比が目標空燃比か
ら一時的に大きくずれた後に、それに対するフィードバ
ック補正量が設定されるため、下流側空燃比が目標空燃
比に対し大きく振られ易くなり、目標空燃比に収束する
までに時間がかかってしまう。However, the air-fuel ratio on the downstream side is caused by disturbance of fuel particles and the like supplied from an evaporative purge system for supplying the fuel particles adsorbed to the canister to an intake system and burning the same. Then, after the air-fuel ratio temporarily deviates from the target air-fuel ratio temporarily, the feedback correction amount for the air-fuel ratio is set. It will take some time.
【０００６】目標空燃比に収束する時間が長くなると、
その間、排気エミッションの悪化やドライバビリティの
低下を招いてしまうばかりでなく、近年、益々厳しくな
る排ガス規制に十分に対応しきれなくなる可能性があ
る。When the time required to converge on the target air-fuel ratio becomes longer,
In the meantime, not only may the exhaust emission deteriorate or the drivability deteriorate, but also it may not be possible to fully cope with the increasingly strict exhaust gas regulations in recent years.
【０００７】本発明は、上記事情に鑑み、触媒下流の空
燃比を外乱の影響をほとんど受けることなく目標空燃比
に収束させることが可能で、空燃比制御性が向上し、触
媒の浄化能力を最大限活用させることで排気エミッショ
ンの大幅な改善、及びドライバビリティの向上を図るこ
とのできるエンジンの空燃比制御装置を提供することを
目的とする。In view of the above circumstances, the present invention makes it possible to make the air-fuel ratio downstream of the catalyst converge to the target air-fuel ratio almost without being affected by disturbance, to improve the air-fuel ratio controllability, and to improve the purification performance of the catalyst. It is an object of the present invention to provide an air-fuel ratio control device for an engine capable of achieving a significant improvement in exhaust emission and an improvement in drivability by making maximum use.
【０００８】[0008]
【課題を解決するための手段】上記目的を達成するため
請求項１記載の発明は、エンジンの排気系に介装した触
媒の前後に前側空燃比検出手段と後側空燃比検出手段と
を各々設け、該両空燃比検出手段で取得した空燃比情報
に基づいて燃料噴射量を補正するエンジンの空燃比制御
装置において、上記触媒を浄化能力を最大限活用可能な
上流領域と該上流領域で浄化しきれなかった未浄化成分
を浄化する下流領域とに区分する境界点を設定する触媒
境界点設定手段と、上記境界点の実空燃比を上記両空燃
比検出手段で取得した空燃比情報に基づいて設定する境
界点実空燃比設定手段と、上記実空燃比に基づき燃料噴
射量を補正する燃料補正量を設定する補正量設定手段と
を備えることを特徴とする。According to a first aspect of the present invention, a front air-fuel ratio detecting means and a rear air-fuel ratio detecting means are provided before and after a catalyst interposed in an exhaust system of an engine. An air-fuel ratio control device for an engine that corrects a fuel injection amount based on air-fuel ratio information obtained by the air-fuel ratio detection means. A catalyst boundary point setting means for setting a boundary point for dividing the unpurified component into a downstream region for purifying the unpurified component, and an actual air-fuel ratio at the boundary point based on the air-fuel ratio information obtained by the air-fuel ratio detection means. And a correction amount setting unit for setting a fuel correction amount for correcting the fuel injection amount based on the actual air-fuel ratio.
【０００９】すなわち、請求項１記載の発明では、触媒
を浄化能力を最大限活用可能な上流領域と、この上流領
域で浄化しきれなかった未浄化成分を浄化する下流領域
とに区分する境界点を設定し、この境界点での実空燃比
を触媒の前後に配設した両空燃比検出手段で取得した空
燃比情報に基づいて設定し、この境界点での実空燃比に
基づき燃料噴射量を補正する燃料補正量を設定する。In other words, according to the first aspect of the present invention, the boundary point for dividing the catalyst into an upstream region in which the purifying ability can be utilized to the maximum and a downstream region in which unpurified components that cannot be completely purified in the upstream region are purified. The actual air-fuel ratio at this boundary point is set based on the air-fuel ratio information obtained by the air-fuel ratio detecting means disposed before and after the catalyst, and the fuel injection amount is set based on the actual air-fuel ratio at this boundary point. Set the fuel correction amount to correct.
【００１０】この場合、好ましくは、請求項２記載の発
明のように、境界点における目標空燃比を設定し、この
目標空燃比と実空燃比とに基づき境界点の空燃比誤差を
設定し、この空燃比誤差に基づき実空燃比を目標空燃比
に収束させる燃料補正量を設定する。又、このときの境
界点を、請求項３の記載の発明のように、空気流量に基
づいて設定する。更に、目標空燃比を、請求項４記載の
発明のように、触媒の前後に配設した両空燃比検出手段
で各々取得した空燃比情報に基づいて設定する。In this case, preferably, a target air-fuel ratio at the boundary point is set, and an air-fuel ratio error at the boundary point is set based on the target air-fuel ratio and the actual air-fuel ratio. Based on the air-fuel ratio error, a fuel correction amount for converging the actual air-fuel ratio to the target air-fuel ratio is set. Further, the boundary point at this time is set based on the air flow rate, as in the third aspect of the present invention. Further, the target air-fuel ratio is set based on the air-fuel ratio information respectively obtained by the air-fuel ratio detecting means disposed before and after the catalyst.
【００１１】[0011]
【発明の実施の形態】以下、図面に基づいて本発明の一
実施の形態を説明する。図１に空燃比制御システムの概
略構成図を示す。同図の符号１はエンジンで、このエン
ジン１の吸気ポート１ａに吸気マニホルド２を介して吸
気管３が連通され、この吸気管３の最上流にエアクリー
ナ（図示せず）が設けられている。又、吸気管３の中途
にスロットル弁４が介装され、このスロットル弁４の下
流に、吸気マニホルド２の集合部に接続するエアチャン
バ５が形成されている。更に、吸気マニホルド２に噴射
方向を吸気ポート１ａ側へ指向されたインジェクタ６が
固設されている。一方、エンジン１の排気ポート１ｂに
排気管７が連通され、この排気管７の中途に、排ガス中
の有害成分（ＣＯ，ＨＣ，ＮＯｘ）を浄化する三元触媒
８が介装されて、図示しないマフラに連通されている。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration diagram of the air-fuel ratio control system. In FIG. 1, reference numeral 1 denotes an engine. An intake pipe 3 communicates with an intake port 1a of the engine 1 via an intake manifold 2, and an air cleaner (not shown) is provided at the most upstream side of the intake pipe 3. In addition, a throttle valve 4 is interposed in the middle of the intake pipe 3, and an air chamber 5 connected to a collection portion of the intake manifold 2 is formed downstream of the throttle valve 4. Further, an injector 6 whose injection direction is directed toward the intake port 1a is fixed to the intake manifold 2. On the other hand, an exhaust pipe 7 is communicated with an exhaust port 1b of the engine 1, and a three-way catalyst 8 for purifying harmful components (CO, HC, NOx) in exhaust gas is interposed in the middle of the exhaust pipe 7, and is shown in the drawing. Not connected to the muffler.
【００１２】又、吸気管３に形成されたエアチャンバ５
に、スロットル弁４下流の吸気管圧力Ｐｍを検出する吸
気管圧力センサ９が配設されている。一方、排気管７の
三元触媒８の上流側に、前側空燃比検出手段の一例であ
り排ガス中の空燃比に比例した電圧を出力する広域空燃
比センサ(以下「ＬＡＦセンサ」)１０が配設され、下流
側に、後側空燃比検出手段の一例であり排ガス中の空燃
比のリッチ/リーンを検出して電圧値を反転させるＯ2セ
ンサ１１が配設されている。又、図示しないが、クラン
ク軸に、このクランク軸の回転に応じて所定クランク角
毎にクランクパルスを出力するクランク角センサが配設
されている。尚、符号１２は点火プラグである。An air chamber 5 formed in the intake pipe 3
An intake pipe pressure sensor 9 for detecting an intake pipe pressure Pm downstream of the throttle valve 4 is provided. On the other hand, on the upstream side of the three-way catalyst 8 of the exhaust pipe 7, a wide-range air-fuel ratio sensor (hereinafter referred to as "LAF sensor") 10, which is an example of a front air-fuel ratio detecting means and outputs a voltage proportional to the air-fuel ratio in exhaust gas, is arranged. An O2 sensor 11, which is an example of a rear air-fuel ratio detecting means and detects rich / lean air-fuel ratios in exhaust gas and inverts the voltage value, is disposed downstream. Although not shown, a crank angle sensor that outputs a crank pulse at predetermined crank angles in accordance with the rotation of the crank shaft is provided on the crank shaft. Reference numeral 12 denotes a spark plug.
【００１３】又、符号２０はマイクロコンピュータ等か
らなる電子制御装置（ＥＣＵ）で、各センサ・スイッチ
類から出力される情報に基づき空燃比制御、点火時期制
御等の各種制御を行なう。空燃比制御では、三元触媒８
の上流と下流とに設けられているＬＡＦセンサ１０とＯ
2センサ１１とで取得した触媒前空燃比ＦA/Fと触媒後空
燃比ＲA/Fとに基づき、空燃比をフィードバック制御す
る。この場合、本形態では、図２に示すように、三元触
媒８内を、浄化能力を最大限活用可能な上流領域Ａと、
上流領域Ａで浄化しきれなかった排ガス中の未浄化成分
(ＣＯ，ＨＣ，ＮＯｘ)を浄化することの可能な下流領域
Ｂとに仮想的に区分し、その両領域Ａ，Ｂの境界点Ｐｂ
における実際の空燃比（以下「境界点実空燃比」）αを
推定し、この境界点実空燃比αとエンジン運転状態に基
づいて設定した目標空燃比αｏとの差に基づいて、触媒
下流の空燃比が目標空燃比αｏに素早く収束するように
空燃比フィードバック制御を行う。Reference numeral 20 denotes an electronic control unit (ECU) including a microcomputer or the like, which performs various controls such as air-fuel ratio control and ignition timing control based on information output from each sensor and switch. In the air-fuel ratio control, the three-way catalyst 8
Sensors 10 and O provided upstream and downstream of
Based on the pre-catalyst air-fuel ratio FA / F and the post-catalyst air-fuel ratio RA / F acquired by the two sensors 11, the air-fuel ratio is feedback-controlled. In this case, in the present embodiment, as shown in FIG. 2, the inside of the three-way catalyst 8 is divided into an upstream region A where the purifying ability can be maximized,
Unpurified components in exhaust gas that could not be purified in upstream area A
(CO, HC, NOx) is virtually divided into a downstream region B that can be purified, and a boundary point Pb between the two regions A and B.
The actual air-fuel ratio (hereinafter referred to as “boundary point actual air-fuel ratio”) α is estimated based on the difference between the boundary point actual air-fuel ratio α and the target air-fuel ratio αo set based on the engine operating state. The air-fuel ratio feedback control is performed so that the air-fuel ratio quickly converges to the target air-fuel ratio αo.
【００１４】このＥＣＵ２０で処理される空燃比制御機
能は、基本燃料噴射量設定部２１、触媒境界点設定部２
２、空燃比分布推定部２３、境界点実空燃比設定部２
４、燃料噴射量設定部２５等で構成されている。The air-fuel ratio control function processed by the ECU 20 includes a basic fuel injection amount setting unit 21 and a catalyst boundary point setting unit 2
2. Air-fuel ratio distribution estimating unit 23, boundary point actual air-fuel ratio setting unit 2
4. It comprises a fuel injection amount setting unit 25 and the like.
【００１５】基本燃料噴射量設定部２１は、クランク角
センサから出力されるクランクパルスに基づいて算出し
たエンジン回転数Ｎｅと、吸気管圧力センサ９で検出し
たスロットル弁４下流の吸気管圧力Ｐｍとに基づき、基
本燃料噴射量マップ（図示せず）を補間計算付きで参照
して基本燃料噴射量Ｔｐを設定する。The basic fuel injection amount setting unit 21 calculates the engine speed Ne calculated based on the crank pulse output from the crank angle sensor, the intake pipe pressure Pm downstream of the throttle valve 4 detected by the intake pipe pressure sensor 9, and the like. , The basic fuel injection amount Tp is set by referring to a basic fuel injection amount map (not shown) with interpolation calculation.
【００１６】触媒境界点設定部２２は、吸気管圧力Ｐｍ
から演算により求め、或いは吸入空気量センサ（図示せ
ず）で検出した吸入空気質量流量に基づいて算出した単
位時間当たりの空気質量（以下「空気流量」）Ｇａに基
づき、図４に示す容積比率マップを補間計算付きで参照
して、三元触媒８全体の容積に対する下流領域Ｂの必要
容積を示す容積比率ε（ε＝Ｂ／(Ａ＋Ｂ)）を決定し、
この容積比率εに基づき境界点Ｐｂの位置を逐次算出す
る。The catalyst boundary point setting section 22 determines the intake pipe pressure Pm
Based on the air mass per unit time (hereinafter referred to as "air flow rate") Ga calculated from the following formula or calculated based on the intake air mass flow rate detected by an intake air mass sensor (not shown), the volume ratio shown in FIG. Referring to the map with interpolation calculation, a volume ratio ε (ε = B / (A + B)) indicating the required volume of the downstream region B with respect to the entire volume of the three-way catalyst 8 is determined,
The position of the boundary point Pb is sequentially calculated based on the volume ratio ε.
【００１７】容積比率マップは、空気流量Ｇａの増加に
対して下流領域Ｂの容積が増加する正の相関を示す特性
を有している。すなわち、定常運転においては、上流領
域Ａにて排ガス成分のほとんどが浄化されると仮定し、
燃料カット状態から復帰した時等において、境界点実空
燃比αが目標空燃比αｏから一時的にずれた場合、上流
領域Ａから漏出した排ガス中の未浄化成分の量は、 ｛（αｏ−α）／αｏ｝・Ｇａ に比例する。ここで、｛（αｏ−α）／αｏ｝が、エン
ジンの運転状態によらず、ある範囲の値を取ると仮定し
た場合、下流領域Ｂが上流領域Ａから漏出した未浄化成
分を全て浄化するために必要な容積は、空気流量Ｇａに
のみ依存することになる。そのため、空気流量Ｇａに基
づいて下流領域Ｂの容積を決定することで、上流領域Ａ
と下流領域Ｂとの境界点Ｐｂを求めることができる。
尚、容積比率マップの特性は三元触媒８の種類、容積、
搭載するエンジンの排気量等により相違するため、予め
機種毎に実験などから求めておく。The volume ratio map has a characteristic showing a positive correlation that the volume of the downstream region B increases with an increase in the air flow rate Ga. That is, in the steady operation, it is assumed that most of the exhaust gas components are purified in the upstream region A,
When the actual air-fuel ratio α at the boundary point temporarily deviates from the target air-fuel ratio αo, for example, when returning from the fuel cut state, the amount of the unpurified component in the exhaust gas leaked from the upstream area A becomes ｛(αo−α ) / Αo｝ · Ga. Here, assuming that {(αo−α) / αo} takes a value within a certain range regardless of the operating state of the engine, the downstream region B purifies all unpurified components leaked from the upstream region A. The volume required for this depends only on the air flow rate Ga. Therefore, by determining the volume of the downstream area B based on the air flow rate Ga, the upstream area A is determined.
Point Pb between the image and the downstream area B can be obtained.
The characteristics of the volume ratio map include the type, volume,
Since it differs depending on the displacement of the engine to be mounted, it is determined in advance for each model from experiments and the like.
【００１８】空燃比分布推定部２３は、ＬＡＦセンサ１
０で検出した触媒前空燃比ＦA/Fと、Ｏ2センサ１１で検
出した触媒後空燃比ＲA/Fとに基づき、触媒内の空燃比
分布を推定する。触媒後空燃比ＲA/Fは触媒前空燃比ＦA
/Fに比べ緩慢に変化する。従って、図５に示すように、
触媒前空燃比ＦA/F、境界点実空燃比α、触媒後空燃比
ＲA/Fは、単調増加（或いは単調減少）するため、三元
触媒８内での空燃比分布を、触媒前空燃比ＦA/Fと触媒
後空燃比ＲA/Fとに基づき線形補間計算により推定す
る。The air-fuel ratio distribution estimating section 23 is provided with the LAF sensor 1
The air-fuel ratio distribution in the catalyst is estimated based on the air-fuel ratio FA / F before the catalyst detected at 0 and the air-fuel ratio RA / F after the catalyst detected by the O2 sensor 11. The air-fuel ratio RA / F after the catalyst is the air-fuel ratio FA before the catalyst.
It changes more slowly than / F. Therefore, as shown in FIG.
Since the before-catalyst air-fuel ratio FA / F, the boundary point actual air-fuel ratio α, and the post-catalyst air-fuel ratio RA / F monotonically increase (or monotonically decrease), the air-fuel ratio distribution in the three-way catalyst 8 is represented by It is estimated by a linear interpolation calculation based on FA / F and the air-fuel ratio after catalyst RA / F.
【００１９】境界点実空燃比設定部２４は、推定された
三元触媒８内の空燃比分布に基づき、触媒境界点設定部
２２で設定した境界点Ｐｂでの実際の空燃比(以下「境
界点実空燃比」)αを、次式から算出する。 α＝ε・ＦA/F＋(１−ε)・ＲA/FThe boundary point actual air-fuel ratio setting unit 24 determines the actual air-fuel ratio at the boundary point Pb set by the catalyst boundary point setting unit 22 based on the estimated air-fuel ratio distribution in the three-way catalyst 8 (hereinafter referred to as “boundary air-fuel ratio”). The point actual air-fuel ratio is calculated from the following equation. α = ε · FA / F + (1-ε) · RA / F
【００２０】燃料噴射量設定部２５は、先ず、エンジン
回転数Ｎｅと吸気管圧力Ｐｍとに基づき、図６に示す目
標空燃比マップを補間計算付きで参照して、目標空燃比
αｏを設定する。この目標空燃比マップは、吸気管圧力
Ｐｍとエンジン回転数Ｎｅとに基づき、予め実験などに
より求めた値が格納されている。尚、この目標空燃比α
ｏは、目標空燃比がエンジン運転領域毎に大きく変動し
ない場合は固定値であっても良い。The fuel injection amount setting unit 25 first sets the target air-fuel ratio αo based on the engine speed Ne and the intake pipe pressure Pm by referring to the target air-fuel ratio map shown in FIG. 6 with interpolation calculation. . In this target air-fuel ratio map, a value previously obtained by an experiment or the like based on the intake pipe pressure Pm and the engine speed Ne is stored. Note that this target air-fuel ratio α
o may be a fixed value when the target air-fuel ratio does not greatly change for each engine operation region.
【００２１】次いで、目標空燃比αｏと境界点実空燃比
αとの差から、境界点空燃比誤差Δαを算出し(Δα＝
αｏ−α)、この境界点空燃比誤差Δαに基づき、境界
点実空燃比αを目標空燃比αｏに収束させるための燃料
補正量λを逐次算出する。Next, a boundary point air-fuel ratio error Δα is calculated from the difference between the target air-fuel ratio αo and the boundary point actual air-fuel ratio α (Δα =
αo−α), based on the boundary point air-fuel ratio error Δα, sequentially calculates a fuel correction amount λ for converging the boundary point actual air-fuel ratio α to the target air-fuel ratio αo.
【００２２】そして、基本燃料噴射量設定部２１で設定
した基本燃料噴射量Ｔｐを、燃料補正量λで補正し、燃
料噴射量Ｔｉを設定する。その結果、境界点実空燃比α
が目標空燃比αｏに収束する方向へ空燃比フィードバッ
ク制御される。Then, the basic fuel injection amount Tp set by the basic fuel injection amount setting section 21 is corrected by the fuel correction amount λ to set the fuel injection amount Ti. As a result, the boundary point actual air-fuel ratio α
Is subjected to air-fuel ratio feedback control in a direction converging to the target air-fuel ratio αo.
【００２３】このように、本形態では、境界点Ｐｂの境
界点空燃比誤差Δαに基づいて、空燃比をフィードバッ
ク制御するようにしたので、三元触媒８の上流領域Ａで
の排気ガス浄化性能を最大限に発揮させることができ
る。又、下流領域Ｂの必要容積を、上流領域Ａから漏出
した排ガス中の未浄化成分量と正の相関を有する空気流
量Ｇａに基づいて設定するようにしたので、上流領域Ａ
から漏出した排気ガス中の未浄化成分を下流領域Ｂでほ
とんど浄化させることができる。As described above, in this embodiment, the air-fuel ratio is feedback-controlled based on the air-fuel ratio error Δα at the boundary point Pb, so that the exhaust gas purification performance in the upstream region A of the three-way catalyst 8 is improved. Can be maximized. Further, the required volume of the downstream region B is set based on the air flow rate Ga having a positive correlation with the amount of unpurified components in the exhaust gas leaked from the upstream region A.
Unpurified components in the exhaust gas leaked from the exhaust gas can be substantially purified in the downstream region B.
【００２４】その結果、外乱等の影響を受けて触媒前空
燃比ＦA/Fが目標空燃比αｏから一時的に大きくずれた
場合であっても、三元触媒８の上流領域Ａから漏出した
排気ガス中の未浄化成分は、下流領域Ｂにて浄化される
ため、触媒後空燃比ＲA/Fを外乱の影響を受けることな
く、常に一定に制御することができ、良好な排ガス浄化
性能を得ることができる。As a result, even if the pre-catalyst air-fuel ratio FA / F temporarily deviates significantly from the target air-fuel ratio αo due to the influence of disturbance or the like, the exhaust gas leaked from the upstream area A of the three-way catalyst 8 Since the unpurified components in the gas are purified in the downstream region B, the post-catalyst air-fuel ratio RA / F can be constantly controlled without being affected by disturbance, and a good exhaust gas purification performance is obtained. be able to.
【００２５】次に、図３に示すフローチャートに従い、
本形態による空燃比制御ルーチンについて説明する。Next, according to the flowchart shown in FIG.
An air-fuel ratio control routine according to the present embodiment will be described.
【００２６】このルーチンは、エンジン始動後、所定周
期で起動され、先ず、ステップＳ１で、燃料増量、或い
は燃料カット中か否か等のエンジン運転状態に基づき空
燃比フィードバック制御条件が成立しているか否かを調
べ、燃料増量或いは燃料カット中等のときは空燃比フィ
ードバック制御条件不成立と判断し、ステップＳ２へ分
岐し、システムを初期化してルーチンを抜ける。This routine is started at a predetermined cycle after the engine is started. First, in step S1, whether the air-fuel ratio feedback control condition is satisfied based on the engine operating state such as whether the fuel is being increased or the fuel is being cut or not. It is determined whether the air-fuel ratio feedback control condition is not satisfied when the fuel is being increased or the fuel is being cut, and the flow branches to step S2 to initialize the system and exit from the routine.
【００２７】一方、ステップＳ１で、空燃比フィードバ
ック条件が成立していると判断されると、ステップＳ３
へ進み、空気流量Ｇａに基づき、図４に示す容積比率マ
ップを補間計算付きで参照して、三元触媒８全体の容積
に対する下流領域Ｂの容積比率εを設定する。そして、
この容積比率εに基づき、三元触媒８の上流領域Ａと下
流領域Ｂとを区分する境界点Ｐｂの位置を決定する。On the other hand, if it is determined in step S1 that the air-fuel ratio feedback condition is satisfied, step S3
Then, based on the air flow rate Ga, the volume ratio ε of the downstream region B with respect to the entire volume of the three-way catalyst 8 is set with reference to the volume ratio map shown in FIG. And
Based on the volume ratio ε, the position of the boundary point Pb that separates the upstream area A and the downstream area B of the three-way catalyst 8 is determined.
【００２８】その後、ステップＳ４へ進み、三元触媒８
の前後に配設されているＬＡＦセンサ１０とＯ2センサ
１１とで、各々検出した触媒前空燃比ＦA/Fと触媒後空
燃比ＲA/Fとに基づき、線形補間計算により境界点Ｐｂ
の実際の空燃比(境界点実空燃比)αを算出する。Thereafter, the process proceeds to step S4, where the three-way catalyst 8
The boundary point Pb is calculated by a linear interpolation calculation based on the before-catalyst air-fuel ratio FA / F and the post-catalyst air-fuel ratio RA / F detected by the LAF sensor 10 and the O2 sensor 11 disposed before and after, respectively.
The actual air-fuel ratio (boundary point actual air-fuel ratio) α is calculated.
【００２９】次いで、ステップＳ５へ進み、エンジン回
転数Ｎｅと吸気管圧力Ｐｍとに基づき、図６に示す目標
空燃比マップを補間計算付きで参照して、目標空燃比α
ｏを設定する。Then, the process proceeds to a step S5, wherein the target air-fuel ratio α is referenced based on the engine speed Ne and the intake pipe pressure Pm with reference to the target air-fuel ratio map shown in FIG.
Set o.
【００３０】その後、ステップＳ６へ進み、目標空燃比
αｏと境界点実空燃比αとの差から、境界点空燃比誤差
Δαを算出し(Δα＝αｏ−α)、ステップＳ７へ進み、
この境界点空燃比誤差Δαに基づき、境界点実空燃比α
を目標空燃比αｏに収束させるための燃料補正量λを設
定し、ルーチンを抜ける。Thereafter, the process proceeds to step S6, where a boundary-point air-fuel ratio error Δα is calculated from the difference between the target air-fuel ratio αo and the boundary-point actual air-fuel ratio α (Δα = αo−α), and the process proceeds to step S7.
Based on the boundary point air-fuel ratio error Δα, the boundary point actual air-fuel ratio α
Is set to converge to the target air-fuel ratio αo, and the routine exits.
【００３１】この燃料補正量λは、燃料噴射制御処理に
おいて読込まれ、エンジン回転数Ｎｅと吸気管圧力Ｐｍ
とに基づいて設定した基本燃料噴射量Ｔｐを燃料補正量
λで補正して、インジェクタ６から噴射される燃料噴射
量Ｔｉが設定される。The fuel correction amount λ is read in the fuel injection control process, and the engine speed Ne and the intake pipe pressure Pm
Is corrected by the fuel correction amount λ, and the fuel injection amount Ti injected from the injector 6 is set.
【００３２】次に、図７に示す燃料カット状態から復帰
したときの空燃比挙動特性図を参照して、従来の空燃比
フィードバック制御による空燃比挙動と、本形態による
空燃比フィードバック制御時の空燃比挙動とを比較す
る。Next, with reference to the air-fuel ratio behavior characteristic when returning from the fuel cut state shown in FIG. 7, the air-fuel ratio behavior by the conventional air-fuel ratio feedback control and the air-fuel ratio behavior during the air-fuel ratio feedback control according to the present embodiment will be described. Compare with fuel ratio behavior.
【００３３】触媒下流の空燃比挙動は触媒上流に比べて
緩慢なため、同図（ａ）に示す従来例のように、触媒下
流で検出した空燃比(触媒後Ａ／Ｆ)に基づいて、触媒上
流の目標空燃比を算出し、触媒上流で検出した空燃比
(触媒前Ａ／Ｆ)が目標空燃比(目標Ａ／Ｆ)に収束するよ
うに空燃比フィードバック制御を行うと、燃料補正量λ
が過大となってしまい、空燃比がリッチ／リーン側へ大
きく振れて、触媒後Ａ／Ｆが目標Ａ／Ｆに収束するまで
に比較的長い時間がかかる傾向となる。Since the air-fuel ratio behavior downstream of the catalyst is slower than that upstream of the catalyst, the air-fuel ratio behavior based on the air-fuel ratio (A / F after the catalyst) detected downstream of the catalyst, as in the conventional example shown in FIG. Calculates the target air-fuel ratio upstream of the catalyst, and detects the air-fuel ratio detected upstream of the catalyst.
When the air-fuel ratio feedback control is performed so that (the A / F before the catalyst) converges to the target air-fuel ratio (target A / F), the fuel correction amount λ
Becomes excessively large, the air-fuel ratio greatly swings toward the rich / lean side, and it tends to take a relatively long time for the post-catalyst A / F to converge to the target A / F.
【００３４】これに対し、同図(ｂ)に示すように、本形
態によれば、境界点Ｐｂにおける空燃比(境界点Ａ／Ｆ)
の応答が触媒後Ａ／Ｆよりも早く、しかも境界点Ａ／Ｆ
は触媒後Ａ／Ｆの予測情報を含んでいるので、適切な燃
料補正量λを算出することができ、触媒後Ａ／Ｆを素早
く目標Ａ／Ｆに収束させることができる。そのため、外
乱等に対する触媒後Ａ／Ｆの空燃比制御性が向上し、排
気エミッションを低減することができると共に、良好な
ドライバビリティを得ることができる。On the other hand, as shown in FIG. 3B, according to the present embodiment, the air-fuel ratio at the boundary point Pb (boundary point A / F)
Response is faster than the post-catalyst A / F, and the boundary point A / F
Contains prediction information of the post-catalyst A / F, so that an appropriate fuel correction amount λ can be calculated, and the post-catalyst A / F can quickly converge to the target A / F. Therefore, the controllability of the air-fuel ratio of the post-catalyst A / F with respect to disturbances and the like is improved, the exhaust emissions can be reduced, and good drivability can be obtained.
【００３５】[0035]
【発明の効果】以上、説明したように本発明によれば、
触媒を浄化能力を最大限活用可能な上流領域と、この上
流領域で浄化しきれなかった排ガスの未浄化成分を浄化
する下流領域とに区分し、その境界点の実空燃比が目標
空燃比に収束するように空燃比制御するので、結果的に
触媒下流の空燃比を外乱の影響をほとんど受けることな
く目標空燃比に素早く収束させることが可能となり、空
燃比制御性が向上し、排気エミッションの大幅な改善、
及びドライバビリティの向上を図ることができる。As described above, according to the present invention,
The catalyst is divided into an upstream area where the purification capacity can be fully utilized and a downstream area where the unpurified components of exhaust gas that cannot be purified in this upstream area are purified, and the actual air-fuel ratio at the boundary point is set to the target air-fuel ratio. Since the air-fuel ratio is controlled so as to converge, the air-fuel ratio downstream of the catalyst can be quickly converged to the target air-fuel ratio almost without being affected by disturbances.As a result, the air-fuel ratio controllability is improved and the exhaust emission is improved. Significant improvements,
In addition, the drivability can be improved.
【図１】空燃比制御システムの概略構成図FIG. 1 is a schematic configuration diagram of an air-fuel ratio control system.
【図２】三元触媒を上流領域と下流領域とに仮想的区分
したときの境界点を示す概念図FIG. 2 is a conceptual diagram showing boundary points when a three-way catalyst is virtually divided into an upstream region and a downstream region.
【図３】空燃比制御ルーチンを示すフローチャートFIG. 3 is a flowchart showing an air-fuel ratio control routine.
【図４】触媒全体に対する下流領域の容積比率を設定す
るマップの概念図FIG. 4 is a conceptual diagram of a map for setting a volume ratio of a downstream region to the entire catalyst.
【図５】触媒内の空燃比分布を示す説明図FIG. 5 is an explanatory diagram showing an air-fuel ratio distribution in a catalyst.
【図６】目標空燃比マップの概念図FIG. 6 is a conceptual diagram of a target air-fuel ratio map.
【図７】燃料カット状態からの復帰時における、(ａ)従
来の空燃比制御時の空燃比挙動を示す特性図、(ｂ)本形
態による空燃比制御時の空燃比挙動を示す特性図7A is a characteristic diagram showing the air-fuel ratio behavior during the conventional air-fuel ratio control when returning from the fuel cut state, and FIG. 7B is a characteristic diagram showing the air-fuel ratio behavior during the air-fuel ratio control according to the present embodiment.
１ エンジン ８ 三元触媒 １０ 広域空燃比センサ(前側空燃比検出手段) １１ Ｏ2センサ(後側空燃比検出手段) ２２ 触媒境界点設定部 ２３ 空燃比分布推定部 ２４ 境界点実空燃比設定部 ２５ 燃料噴射量設定部 Ａ 上流領域 Ｂ 下流領域 Ｇａ 空気流量 Ｐｂ 境界点 Ｔｉ 燃料噴射量 α 境界点実空燃比 αｏ 目標空燃比 Δα 境界点空燃比誤差 λ 燃料補正量 Reference Signs List 1 engine 8 three-way catalyst 10 wide-range air-fuel ratio sensor (front air-fuel ratio detecting means) 11 O2 sensor (rear air-fuel ratio detecting means) 22 catalyst boundary point setting unit 23 air-fuel ratio distribution estimating unit 24 boundary point actual air-fuel ratio setting unit 25 Fuel injection amount setting section A Upstream region B Downstream region Ga Air flow rate Pb Boundary point Ti Fuel injection amount α Boundary point actual air-fuel ratio αo Target air-fuel ratio Δα Boundary point air-fuel ratio error λ Fuel correction amount
───────────────────────────────────────────────────── フロントページの続き Ｆターム(参考） 3G084 BA13 BA17 BA24 DA04 DA10 EB12 FA07 FA11 FA26 FA30 FA33 3G091 AA17 AA23 AA28 AB03 BA01 CB02 CB05 DA01 DA02 DB07 DB08 DB11 DC01 EA01 EA05 EA06 EA31 EA34 FA05 FA17 FA18 FA19 FB10 FB11 FB12 GA06 HA36 HA37 3G301 HA01 JA03 JA11 JA21 KA21 KA27 LB01 MA01 NA06 ND01 PA01Z PA07Z PD09Z PE01Z PE03Z ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 3G084 BA13 BA17 BA24 DA04 DA10 EB12 FA07 FA11 FA26 FA30 FA33 3G091 AA17 AA23 AA28 AB03 BA01 CB02 CB05 DA01 DA02 DB07 DB08 DB11 DC01 EA01 EA05 EA06 EA31 EA34 FA05 FA10 FB11 GA06 HA36 HA37 3G301 HA01 JA03 JA11 JA21 KA21 KA27 LB01 MA01 NA06 ND01 PA01Z PA07Z PD09Z PE01Z PE03Z
Claims (4)
前側空燃比検出手段と後側空燃比検出手段とを各々設
け、該両空燃比検出手段で取得した空燃比情報に基づい
て燃料噴射量を補正するエンジンの空燃比制御装置にお
いて、 上記触媒を浄化能力を最大限活用可能な上流領域と該上
流領域で浄化しきれなかった未浄化成分を浄化する下流
領域とに区分する境界点を設定する触媒境界点設定手段
と、 上記境界点の実空燃比を上記両空燃比検出手段で取得し
た空燃比情報に基づいて設定する境界点実空燃比設定手
段と、 上記実空燃比に基づき燃料噴射量を補正する燃料補正量
を設定する補正量設定手段とを備えることを特徴とする
エンジンの空燃比制御装置。A front air-fuel ratio detecting means and a rear air-fuel ratio detecting means are respectively provided before and after a catalyst interposed in an exhaust system of an engine, and fuel is detected based on air-fuel ratio information obtained by the two air-fuel ratio detecting means. In an air-fuel ratio control device for an engine that corrects an injection amount, a boundary point that divides the catalyst into an upstream region capable of maximizing the purifying ability and a downstream region purifying unpurified components that cannot be purified in the upstream region. A boundary point actual air-fuel ratio setting means for setting the actual air-fuel ratio of the boundary point based on the air-fuel ratio information obtained by the air-fuel ratio detecting means; and An air-fuel ratio control device for an engine, comprising: a correction amount setting means for setting a fuel correction amount for correcting a fuel injection amount.
目標空燃比設定手段と、 上記目標空燃比と上記実空燃比とに基づき上記境界点の
空燃比誤差を設定する境界点空燃比誤差設定手段と、 上記空燃比誤差に基づき上記実空燃比を上記目標空燃比
に収束させる燃料補正量を設定する補正量設定手段とを
備えることを特徴とする請求項１記載のエンジンの空燃
比制御装置。2. A target air-fuel ratio setting means for setting a target air-fuel ratio at the boundary point, and a boundary-point air-fuel ratio error setting for setting an air-fuel ratio error at the boundary point based on the target air-fuel ratio and the actual air-fuel ratio. 2. An air-fuel ratio control apparatus for an engine according to claim 1, further comprising: a correction amount setting unit configured to set a fuel correction amount for converging the actual air-fuel ratio to the target air-fuel ratio based on the air-fuel ratio error. .
ことを特徴とする請求項１或いは２記載のエンジンの空
燃比制御装置。3. An air-fuel ratio control device for an engine according to claim 1, wherein said boundary point is set based on an air flow rate.
各々取得した空燃比情報に基づいて設定することを特徴
とする請求項２或いは３記載のエンジンの空燃比制御装
置。4. An air-fuel ratio control device for an engine according to claim 2, wherein said target air-fuel ratio is set based on air-fuel ratio information respectively obtained by said air-fuel ratio detecting means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001130051A JP2002322932A (en) | 2001-04-26 | 2001-04-26 | Air fuel ratio control device for engine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001130051A JP2002322932A (en) | 2001-04-26 | 2001-04-26 | Air fuel ratio control device for engine |
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| Publication Number | Publication Date |
|---|---|
| JP2002322932A true JP2002322932A (en) | 2002-11-08 |
Family
ID=18978491
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000097081A (en) * | 1998-09-24 | 2000-04-04 | Denso Corp | Air-fuel ratio control device of internal-combustion engine |
| JP2002195080A (en) * | 2000-12-26 | 2002-07-10 | Toyota Motor Corp | Air-fuel ratio control device of internal-combustion engine |
-
2001
- 2001-04-26 JP JP2001130051A patent/JP2002322932A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000097081A (en) * | 1998-09-24 | 2000-04-04 | Denso Corp | Air-fuel ratio control device of internal-combustion engine |
| JP2002195080A (en) * | 2000-12-26 | 2002-07-10 | Toyota Motor Corp | Air-fuel ratio control device of internal-combustion engine |
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