JPH08109844A - Air-fuel ratio control device for internal combustion engine - Google Patents
Air-fuel ratio control device for internal combustion engineInfo
- Publication number
- JPH08109844A JPH08109844A JP24735794A JP24735794A JPH08109844A JP H08109844 A JPH08109844 A JP H08109844A JP 24735794 A JP24735794 A JP 24735794A JP 24735794 A JP24735794 A JP 24735794A JP H08109844 A JPH08109844 A JP H08109844A
- Authority
- JP
- Japan
- Prior art keywords
- air
- fuel ratio
- purge gas
- correction coefficient
- 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
Landscapes
- Supplying Secondary Fuel Or The Like To Fuel, Air Or Fuel-Air Mixtures (AREA)
- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
- Combined Controls Of Internal Combustion Engines (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、内燃機関の空燃比制御
装置に関し、特に、キャニスタに吸着した蒸発燃料を所
定の運転条件下で機関に導入するパージガス制御手段を
備えた内燃機関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 system for an internal combustion engine, and more particularly to an air-fuel ratio control system for an internal combustion engine equipped with purge gas control means for introducing evaporated fuel adsorbed in a canister into the engine under predetermined operating conditions. Regarding the control device.
【０００２】[0002]
【従来の技術】一般に、自動車の内燃機関では、燃料タ
ンク内で発生した蒸発燃料（ベーパ）を一時的に貯蔵す
るキャニスタを設け、このキャニスタで吸着した燃料を
所定の運転条件下で機関吸気系に導入している。ここ
で、パージガス導入時には、このパージガスの有する燃
料成分が燃料噴射弁から噴射される燃料に加算されて、
機関に供給される燃料量が増大する。このため、排気ガ
ス中の空燃比（Ａ／Ｆ）を検出する空燃比センサ（酸素
センサ）の検出信号に基づく疑似的な比例積分制御によ
って、空燃比フィードバック補正係数を小さくし、燃料
噴射弁からの燃料噴射量を減量調整している（例えば特
開昭６３−７１５３６号公報、特開平４−１１２９５９
号公報等参照）。2. Description of the Related Art Generally, an internal combustion engine of an automobile is provided with a canister for temporarily storing evaporated fuel (vapor) generated in a fuel tank, and the fuel adsorbed by the canister is sucked into the engine intake system under a predetermined operating condition. Have been introduced to. Here, when the purge gas is introduced, the fuel component of the purge gas is added to the fuel injected from the fuel injection valve,
The amount of fuel supplied to the engine increases. Therefore, the air-fuel ratio feedback correction coefficient is reduced by the pseudo proportional-plus-integral control based on the detection signal of the air-fuel ratio sensor (oxygen sensor) that detects the air-fuel ratio (A / F) in the exhaust gas, and the The fuel injection amount is adjusted to decrease (for example, JP-A-63-71536 and JP-A-4-112959).
No.
【０００３】そこで、図１３〜図１８に基づいて従来技
術による内燃機関の空燃比制御装置を説明する。A conventional air-fuel ratio control system for an internal combustion engine will be described with reference to FIGS.
【０００４】例えば４気筒等の複数の気筒（図示せず）
を有する機関本体１には、吸気通路２と排気通路３とが
設けられている。この吸気通路２は、その上流側が図外
のエアフローメータを介してエアフィルタに接続され、
その下流側は各気筒に対応して分岐している。一方、排
気通路３は、その上流側が各気筒に対応して分岐し、そ
の下流側は三元触媒等からなる触媒コンバータ４を介し
て図外のマフラに接続されている。A plurality of cylinders such as four cylinders (not shown)
An intake passage 2 and an exhaust passage 3 are provided in the engine body 1 having the. The intake passage 2 has its upstream side connected to an air filter via an air flow meter (not shown),
The downstream side is branched corresponding to each cylinder. On the other hand, the exhaust passage 3 has its upstream side branched corresponding to each cylinder, and its downstream side is connected to a muffler (not shown) via a catalytic converter 4 including a three-way catalyst or the like.
【０００５】キャニスタ５は、吸気通路２と燃料タンク
６との間に設けられている。このキャニスタ５は、ケー
シング５Ａと、このケーシング５Ａ内に画成され、内部
に活性炭等の吸着剤５Ｂを収容した吸着室５Ｃと、外部
の新気（大気）を吸着室５Ｃ内に取り入れるべくケーシ
ング５Ａの底部に形成された新気導入口５Ｄと、ケーシ
ング５Ａの上部に形成され、蒸発燃料通路７を介して燃
料タンク６の上部に接続された蒸発燃料導入口５Ｅと、
ケーシング５Ａの上部に形成され、パージ通路８を介し
て吸気通路２のスロットルバルブ９下流側に接続された
パージガス導出口５Ｆと、新気導入口５Ｄに設けられた
エアフィルタ５Ｇとを備えて構成されている。The canister 5 is provided between the intake passage 2 and the fuel tank 6. The canister 5 includes a casing 5A, an adsorption chamber 5C defined in the casing 5A and containing an adsorbent 5B such as activated carbon inside, and a casing for taking in fresh air (atmosphere) outside into the adsorption chamber 5C. A fresh air inlet 5D formed at the bottom of 5A, and an evaporated fuel inlet 5E formed at the upper part of the casing 5A and connected to the upper part of the fuel tank 6 via the evaporated fuel passage 7.
A purge gas outlet 5F formed in the upper part of the casing 5A and connected to the downstream side of the throttle valve 9 of the intake passage 2 via the purge passage 8 and an air filter 5G provided in the fresh air inlet 5D are configured. Has been done.
【０００６】また、パージ通路８の途中には、後述する
コントロールユニット１２からの制御信号によってデユ
ーテイ制御されるパージ制御弁１０と、吸気通路２のス
ロットルバルブ９近傍の吸入負圧によって開閉するパー
ジカット弁１１とが設けられている。In the middle of the purge passage 8, a purge control valve 10 which is duty-controlled by a control signal from a control unit 12 which will be described later, and a purge cut which opens and closes by a suction negative pressure in the vicinity of the throttle valve 9 of the intake passage 2. A valve 11 is provided.
【０００７】機関を電気的に集中制御するコントロール
ユニット１２は、ＣＰＵ等の演算処理回路、ＲＯＭ，Ｒ
ＡＭ等の記憶回路、入出力回路等を含んだマイクロコン
ピュータシステムとして構成され、パージ制御弁１０を
デユーテイ制御するパージガス制御手段１２Ａと、燃料
噴射量を調整することにより排気ガス中の空燃比が理論
空燃比近傍となるように制御する空燃比制御手段１２Ｂ
とを備えている。そして、このコントロールユニット１
２の入力側には、クランク角センサ１３、空燃比センサ
１４、スロットルセンサ１５及び図示せぬ水温センサや
エアフローメータ等が接続され、コントロールユニット
１２の出力側には、パージ制御弁１０と、各気筒毎に設
けられた燃料噴射弁１６等が接続されている。ここで、
クランク角センサ１３、空燃比センサ１４、スロットル
センサ１５及びエアフローメータ等の各種センサは、コ
ントロールユニット１２の入出力回路に入力され、この
入出力回路からパージガス制御手段１２Ａ及び空燃比制
御手段１２Ｂに供給されるようになっている。The control unit 12 for electrically centrally controlling the engine includes an arithmetic processing circuit such as a CPU, ROM, and R.
It is configured as a microcomputer system including a memory circuit such as AM, an input / output circuit, and the like, and has a purge gas control means 12A for performing duty control of the purge control valve 10 and an air-fuel ratio in the exhaust gas by adjusting the fuel injection amount. Air-fuel ratio control means 12B for controlling so as to be close to the air-fuel ratio
It has and. And this control unit 1
A crank angle sensor 13, an air-fuel ratio sensor 14, a throttle sensor 15, a water temperature sensor (not shown), an air flow meter, and the like are connected to the input side of 2, and the purge control valve 10 and each of the purge control valve 10 are connected to the output side of the control unit 12. The fuel injection valve 16 and the like provided for each cylinder are connected. here,
Various sensors such as the crank angle sensor 13, the air-fuel ratio sensor 14, the throttle sensor 15 and the air flow meter are input to the input / output circuit of the control unit 12 and supplied from the input / output circuit to the purge gas control means 12A and the air-fuel ratio control means 12B. It is supposed to be done.
【０００８】なお、１７は、パージ通路８の途中に設け
られた逆止弁を示し、この逆止弁１７は、燃料タンク６
からの蒸発燃料がキャニスタ５に向けて流入するのを許
し、逆向きの流れを阻止するものである。Reference numeral 17 denotes a check valve provided in the middle of the purge passage 8. The check valve 17 is a check valve.
The fuel vapor from the above is allowed to flow into the canister 5, and the reverse flow is blocked.
【０００９】従来技術による内燃機関の空燃比制御装置
は、上述の如き構成を有するもので、例えば機関本体１
の停止後等に、燃料タンク６内で蒸発燃料が発生する
と、この蒸発燃料は蒸発燃料通路７を介してキャニスタ
５に導かれ、吸着室５Ｃ内の吸着剤５Ｂに一時的に吸着
される。An air-fuel ratio control system for an internal combustion engine according to the prior art has the above-mentioned construction, and is, for example, an engine body 1.
When the evaporated fuel is generated in the fuel tank 6 after the stop, etc., the evaporated fuel is guided to the canister 5 via the evaporated fuel passage 7 and is temporarily adsorbed by the adsorbent 5B in the adsorption chamber 5C.
【００１０】次に、機関本体１が定速走行域等の所定の
運転条件に達すると、パージガス制御手段１２Ａからの
制御信号によりパージ制御弁１０が開弁し、吸気通路２
内の吸入負圧がキャニスタ５に作用して、新気が吸着室
５Ｃ内に吸い込まれる。これにより、吸着されていた燃
料は、吸着剤５Ｂから離脱して所謂パージガスとなり、
このパージガスは、パージガス導出口５Ｆからパージ通
路８を介してスロットルバルブ９の下流側で吸気通路２
内に導入される。そして、蒸発燃料が離脱した吸着剤５
Ｂは、再び吸着可能状態に復活する。Next, when the engine body 1 reaches a predetermined operating condition such as a constant speed traveling range, the purge control valve 10 is opened by a control signal from the purge gas control means 12A, and the intake passage 2 is opened.
The suction negative pressure therein acts on the canister 5, and fresh air is sucked into the adsorption chamber 5C. As a result, the adsorbed fuel is separated from the adsorbent 5B and becomes so-called purge gas,
This purge gas passes from the purge gas outlet 5F through the purge passage 8 to the intake passage 2 downstream of the throttle valve 9.
Introduced within. Then, the adsorbent 5 from which the evaporated fuel has separated
B is restored to the adsorbable state again.
【００１１】一方、機関がアイドリング等の所定の低負
荷域になった場合は、スロットルバルブ９の弁開度が小
さくなり、パージカット弁１１の圧力室に吸入負圧が導
入されないため、該パージカット弁１１は閉弁（全閉）
する。これにより、万が一、パージ制御弁１０が開弁し
たまま故障した場合でも、アイドリング時等には、パー
ジカット弁１１によってパージガスの流通が自動的に遮
断され、多量のパージガスが機関本体１に供給されてア
イドル回転数が過渡に上昇するという、いわゆるハイア
イドル状態が生じるのを未然に防止している。On the other hand, when the engine is in a predetermined low load region such as idling, the valve opening of the throttle valve 9 becomes small and the suction negative pressure is not introduced into the pressure chamber of the purge cut valve 11, so that the purge is performed. Cut valve 11 is closed (fully closed)
To do. As a result, even if the purge control valve 10 malfunctions with the valve open, the purge cut valve 11 automatically shuts off the flow of the purge gas at a time of idling, and a large amount of the purge gas is supplied to the engine body 1. This prevents the occurrence of a so-called high idle state in which the idle speed transiently rises.
【００１２】ここで、コントロールユニット１２の空燃
比制御手段１２Ｂは、下記数１に示す如く、機関本体１
の運転条件に応じて燃料噴射量Ｔiを演算している。Here, the air-fuel ratio control means 12B of the control unit 12 uses the engine body 1 as shown in the following formula 1.
The fuel injection amount T i is calculated according to the operating conditions of.
【００１３】[0013]
【数１】Ｔi＝ＴP×Ｃoef×α＋ＴＳ 但し、ＴＰ：基本噴射量（吸入空気量Ｑ／機関回転数
Ｎ） Ｃoef：各種補正係数（水温増量、混合比割付増量等） α ：空燃比フィードバック補正係数 ＴS：無効噴射パルス 前記数１中に示す空燃比フィードバック補正係数αは、
目標値たる理論空燃比と空燃比センサ１４が検出した排
気ガス中の実際の空燃比との偏差を解消するためのもの
で、理論空燃比に相当する所定のスライスレベルで比較
された空燃比センサ１４の検出信号のリッチ側、リーン
側への反転に基づいた疑似的な比例積分制御によって求
められる。そして、排気ガス中の空燃比が理論空燃比よ
りも濃いリッチ状態では、αの値が１（１００％）より
も小さくなって燃料噴射量Ｔiが減少し、排気ガス中の
空燃比が理論空燃比よりも薄いリーン状態になると、α
の値が１よりも大きくなって燃料噴射量Ｔiが増大する
ようになっている。なお、機関冷却水温が低い冷間始動
時や高速高負荷時等には、αの値はクランプされ、これ
により通常の燃料噴射量制御を行うようになっている。[ Formula 1] T i = T P × C oef × α + T S However, T P : basic injection amount (intake air amount Q / engine speed N) C oef : various correction factors (water temperature increase, mixture ratio allocation increase, etc.) α: Air-fuel ratio feedback correction coefficient T S : Invalid injection pulse The air-fuel ratio feedback correction coefficient α shown in the above equation 1 is
The air-fuel ratio sensor is for eliminating the deviation between the target theoretical air-fuel ratio and the actual air-fuel ratio in the exhaust gas detected by the air-fuel ratio sensor 14, and is compared at a predetermined slice level corresponding to the theoretical air-fuel ratio. It is obtained by pseudo proportional-plus-integral control based on the inversion of the detection signal of 14 to the rich side and the lean side. Then, in the rich state where the air-fuel ratio in the exhaust gas is richer than the theoretical air-fuel ratio, the value of α becomes smaller than 1 (100%), the fuel injection amount T i decreases, and the air-fuel ratio in the exhaust gas becomes theoretical. When leaner than the air-fuel ratio,
Is larger than 1 and the fuel injection amount T i is increased. It should be noted that the value of α is clamped at the time of cold start when the engine cooling water temperature is low or at the time of high speed and high load, whereby the normal fuel injection amount control is performed.
【００１４】パージガスを吸気通路２に導入しない場
合、図１４に示す如く、空燃比フィードバック補正係数
αは、その目標値が理論空燃比に応じた１００％に設定
されて疑似的に比例積分（ＰＩ）制御されている。即
ち、排気ガス中の空燃比Ａ／Ｆが薄くなってリーン状態
になると、燃料噴射量Ｔiを増量して理論空燃比に近づ
けるべく、αを、リーン時比例制御分ＰLによってある
程度まで上昇させた後に、リーン時積分制御分ＩLによ
って徐々に増大させる。これとは逆に、排気ガス中の空
燃比Ａ／Ｆが濃くなってリッチ状態になると、燃料噴射
量Ｔiを減量して理論空燃比に近づけるべく、αを、リ
ッチ時比例制御分ＰRによってある程度まで下降させた
後に、リッチ時積分制御分ＩRによって徐々に減少させ
る。When the purge gas is not introduced into the intake passage 2, the target value of the air-fuel ratio feedback correction coefficient α is set to 100% according to the stoichiometric air-fuel ratio and the pseudo integral proportional (PI) as shown in FIG. ) It is controlled. That is, when the air-fuel ratio A / F in the exhaust gas becomes thin and becomes lean, in order to increase the fuel injection amount T i to approach the stoichiometric air-fuel ratio, α is increased to some extent by the lean proportional control amount P L. After that, the lean time integral control amount I L is gradually increased. On the contrary, when the air-fuel ratio A / F in the exhaust gas becomes rich and becomes rich, in order to reduce the fuel injection amount T i and bring it closer to the stoichiometric air-fuel ratio, α is set to the rich proportional control P R After being lowered to a certain extent by, it is gradually reduced by the rich time integral control component I R.
【００１５】これにより、排気ガス中の空燃比Ａ／Ｆの
平均値（図中では「平均Ａ／Ｆ」と示す）は、理論空燃
比近傍に収束する。なお、各制御分ＰL，ＰRは、基本噴
射量ＴPと機関回転数Ｎとにより定まる機関の運転条件
に従って、図示せぬマップから読み出されるようになっ
ている。As a result, the average value of the air-fuel ratio A / F in the exhaust gas (shown as "average A / F" in the figure) converges near the theoretical air-fuel ratio. The control amounts P L and P R are read from a map (not shown) according to the engine operating conditions determined by the basic injection amount T P and the engine speed N.
【００１６】次に、図１５に示す如く、パージガスを吸
気通路２に導入した場合、パージガスが有する燃料成分
だけ、機関本体１に供給される燃料の総量が増大するた
め、空燃比がリッチ状態となる。従って、リッチ時積分
制御分ＩRの作動時間の方がリーン時積分制御ＩLの作動
時間よりも長くなるため、空燃比フィードバック補正係
数αは、その目標値が徐々に小さくなっていき（この移
行過程は図１５中に示されていない）、理論空燃比に対
応した１００％よりも小さい値（図中では約９１％であ
る）を目標値として変化する。Next, as shown in FIG. 15, when the purge gas is introduced into the intake passage 2, the total amount of fuel supplied to the engine body 1 is increased by the fuel component of the purge gas, so that the air-fuel ratio becomes rich. Become. Therefore, since the operating time of the rich integration control I R is longer than the operating time of the lean integration control I L , the target value of the air-fuel ratio feedback correction coefficient α is gradually reduced ( The transition process is not shown in FIG. 15), and changes with a value smaller than 100% corresponding to the theoretical air-fuel ratio (about 91% in the figure) as the target value.
【００１７】つまり、図１６に示す如く、パージガス導
入時には、空燃比フィードバック補正係数αが、パージ
ガスを導入しないときの値（１００％）よりも所定量Δ
αだけ小さくなるため（図１５の例では約９％であ
る）、機関本体１が要求する燃料の量に対して各燃料噴
射弁１６から噴射される燃料噴射量Ｔiが占める割合が
低下する。That is, as shown in FIG. 16, when the purge gas is introduced, the air-fuel ratio feedback correction coefficient α is a predetermined amount Δ more than the value (100%) when the purge gas is not introduced.
Since it becomes smaller by α (about 9% in the example of FIG. 15), the ratio of the fuel injection amount T i injected from each fuel injection valve 16 to the amount of fuel required by the engine body 1 decreases. .
【００１８】[0018]
【発明が解決しようとする課題】ところで、上述した従
来技術では、空燃比制御手段１２Ｂが、空燃比センサ１
４からの検出信号に基づいて空燃比フィードバック補正
係数αの値を比例積分制御することにより、排気ガス中
の空燃比の平均値を理論空燃比近傍に維持しているた
め、三元触媒等の触媒コンバータ４によって、排気ガス
中のＮＯx、ＣＯ、ＨＣを効率よく転化（浄化）するこ
とができる。By the way, in the above-mentioned prior art, the air-fuel ratio control means 12B is constituted by the air-fuel ratio sensor 1
Since the average value of the air-fuel ratio in the exhaust gas is maintained in the vicinity of the theoretical air-fuel ratio by controlling the value of the air-fuel ratio feedback correction coefficient α based on the detection signal from 4, the average value of the air-fuel ratio in the exhaust gas is maintained near the theoretical air-fuel ratio. The catalytic converter 4 can efficiently convert (purify) NO x , CO, and HC in the exhaust gas.
【００１９】しかし、パージガスの導入量が増大する
と、各燃料噴射弁１６から噴射される燃料の割合が相対
的に減少して、リーン側からリッチ側に移行するよりも
（リッチ側への補正）、リッチ側からリーン側に移行す
る方（リーン側への補正）が応答性が高くなるため、排
気ガス中の空燃比の平均値が理論空燃比に収束せず、図
１５に示す如く、リーン側にずれ易くなる。However, when the introduction amount of the purge gas is increased, the ratio of the fuel injected from each fuel injection valve 16 is relatively decreased, and the lean side is shifted to the rich side (correction to the rich side). Since the response from the rich side to the lean side (correction to the lean side) becomes higher, the average value of the air-fuel ratio in the exhaust gas does not converge to the theoretical air-fuel ratio, and as shown in FIG. It is easy to shift to the side.
【００２０】即ち、各燃料噴射弁１６からの噴射燃料は
液体のため、噴射燃料の全てが吸入空気に乗って直ちに
燃焼室内に供給される訳ではなく、その一部は吸気通路
２の内壁や吸気ポートを開閉する吸気弁（図示せず）に
付着して壁流となり、壁流の状態で燃焼室内に流入す
る。従って、空燃比をリーン側からリッチ側に補正すべ
く、空燃比フィードバック補正係数αを大きくして燃料
噴射量Ｔiを増大させても、壁流と化す分だけ燃焼室へ
の供給に時間遅れが生じるため、図１７中の点線に示す
如く、パージガス導入時にリーン側からリッチ側へ移行
するのに要する時間ＴLonは、図１７中の実線に示すパ
ージガスを導入しないときの同時間ＴLoffよりも長くな
る。That is, since the fuel injected from each fuel injection valve 16 is liquid, not all of the injected fuel is immediately supplied to the combustion chamber by riding on the intake air. It adheres to an intake valve (not shown) that opens and closes the intake port to form a wall flow, which flows into the combustion chamber in a wall flow state. Therefore, even if the air-fuel ratio feedback correction coefficient α is increased to increase the fuel injection amount T i in order to correct the air-fuel ratio from the lean side to the rich side, there is a time delay in the supply to the combustion chamber by the amount of the wall flow. Therefore, as shown by the dotted line in FIG. 17, the time T Lon required to shift from the lean side to the rich side at the time of introducing the purge gas is longer than the time T Loff shown in the solid line in FIG. 17 when the purge gas is not introduced. Also becomes longer.
【００２１】これとは逆に、空燃比をリッチ側からリー
ン側に補正すべく、空燃比フィードバック補正係数αを
小さくして燃料噴射弁１６からの燃料噴射量Ｔiを減少
させた場合、壁流と化す分だけ燃焼室内に直ちに供給さ
れる噴射燃料の量が少なくなるため、パージガス導入時
のリーン側への移行時間ＴRonは、パージガスを導入し
ないときの同時間ＴRoffよりも短くなる。On the contrary, when the fuel injection amount T i from the fuel injection valve 16 is reduced by reducing the air-fuel ratio feedback correction coefficient α in order to correct the air-fuel ratio from the rich side to the lean side, the wall Since the amount of the injected fuel immediately supplied into the combustion chamber is reduced by the amount of the flow, the transition time TRon to the lean side at the time of introducing the purge gas is shorter than the same time TRoff when the purge gas is not introduced.
【００２２】また、パージガス中の燃料成分は液体燃料
よりも薄く、軽質であるため、パージガスの流量が多い
ということは、燃焼室内に供給される燃料が元々全体的
に軽質傾向になり易いということを意味する。Further, since the fuel component in the purge gas is thinner and lighter than the liquid fuel, the fact that the flow rate of the purge gas is high means that the fuel supplied into the combustion chamber tends to tend to be lighter as a whole. Means
【００２３】従って、機関本体１に供給される燃料が全
体的に軽質傾向にある中で、リッチ側へ補正するときの
応答時間が長くなる一方、リーン側に補正するときの応
答時間が短くなるため、空燃比の平均値は、図１５中に
示す如く、理論空燃比よりもリーン側にずれ易い。そし
て、図１８に示す如く、触媒コンバータ４は、理論空燃
比近傍のある限られた領域（ウインドウ）で、その転化
性能を十分に発揮するため、排気ガスの空燃比がリーン
側にずれてウインドウの外に出ると、ＮＯxの転化性能
が急激に低下する。特に、機関回転数が低いほど、吸入
空気量に占めるパージガスの割合が相対的に上昇するた
め、平均空燃比が理論空燃比近傍からリーン側にずれ易
くなる。Therefore, while the fuel supplied to the engine body 1 tends to be light overall, the response time when correcting to the rich side becomes long, while the response time when correcting to the lean side becomes short. Therefore, the average value of the air-fuel ratio tends to shift to the lean side of the stoichiometric air-fuel ratio, as shown in FIG. Then, as shown in FIG. 18, the catalytic converter 4 fully exhibits its conversion performance in a limited region (window) near the theoretical air-fuel ratio, so that the air-fuel ratio of the exhaust gas shifts to the lean side and becomes the window. If it goes out of the temperature range, the conversion performance of NO x sharply deteriorates. Particularly, as the engine speed is lower, the ratio of the purge gas to the intake air amount is relatively increased, so that the average air-fuel ratio is likely to shift from near the stoichiometric air-fuel ratio to the lean side.
【００２４】本発明は、かかる従来技術の問題点に鑑み
てなされたもので、その目的は、パージガスの導入時で
も速やかに空燃比を理論空燃比近傍に制御することがで
きるようにした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 the problems of the prior art, and an object thereof is to make it possible to quickly control the air-fuel ratio to near the stoichiometric air-fuel ratio even when the purge gas is introduced. To provide an air-fuel ratio control device of
【００２５】[0025]
【課題を解決するための手段】そこで、本発明は、パー
ジガス導入時とパージガス非導入時とにおける空燃比フ
ィードバック補正係数αの偏差に応じて、平均空燃比が
理論空燃比近傍からリーン側にずれることに着目し、空
燃比フィードバック補正係数αを、それ自身の変化量
（偏差）に応じて自動的に修正することとした。即ち、
本発明に係る内燃機関の空燃比制御装置は、キャニスタ
に吸着させた燃料を所定の運転条件下でパージガスとし
て吸気通路に導入するパージガス制御手段と、排気通路
に設けられた空燃比センサの検出信号に基づいて空燃比
のフィードバック制御を行う空燃比制御手段と、を備え
た内燃機関において、パージガス導入時に、理論空燃比
近傍における空燃比フィードバック補正係数の値とパー
ジガス導入後における空燃比フィードバック補正係数の
値との偏差に基づいて、空燃比がリッチ側方向にシフト
するように空燃比フィードバック補正係数を修正する空
燃比フィードバック補正係数修正手段を設けたことを特
徴とする。Therefore, in the present invention, the average air-fuel ratio deviates from the vicinity of the stoichiometric air-fuel ratio to the lean side depending on the deviation of the air-fuel ratio feedback correction coefficient α when the purge gas is introduced and when the purge gas is not introduced. Focusing on this point, the air-fuel ratio feedback correction coefficient α is automatically corrected according to its own variation (deviation). That is,
An air-fuel ratio control system for an internal combustion engine according to the present invention is a detection signal of an air-fuel ratio sensor installed in an exhaust passage and a purge gas control means for introducing fuel adsorbed in a canister as purge gas into a suction passage under predetermined operating conditions. In an internal combustion engine equipped with an air-fuel ratio control means for performing feedback control of the air-fuel ratio based on, at the time of introducing the purge gas, the value of the air-fuel ratio feedback correction coefficient near the theoretical air-fuel ratio and the air-fuel ratio feedback correction coefficient after introducing the purge gas An air-fuel ratio feedback correction coefficient correction means for correcting the air-fuel ratio feedback correction coefficient is provided so that the air-fuel ratio shifts toward the rich side based on the deviation from the value.
【００２６】また、前記空燃比フィードバック補正係数
修正手段は、パージガス導入時に、理論空燃比近傍にお
ける空燃比フィードバック補正係数の値とパージガス導
入後における空燃比フィードバック補正係数の値との偏
差に基づいて修正値を設定し、空燃比がリッチ側方向に
シフトするように前記修正値によって空燃比フィードバ
ック補正係数を修正するのが好ましい。Further, the air-fuel ratio feedback correction coefficient correction means corrects, when introducing the purge gas, based on the deviation between the value of the air-fuel ratio feedback correction coefficient near the theoretical air-fuel ratio and the value of the air-fuel ratio feedback correction coefficient after introducing the purge gas. It is preferable to set a value and correct the air-fuel ratio feedback correction coefficient by the correction value so that the air-fuel ratio shifts toward the rich side.
【００２７】さらに、前記パージガス制御手段は、所定
の運転条件下で略ステップ状にパージガスを吸気通路に
導入し、パージガスを前回導入したときに得られた前記
空燃比フィードバック補正係数の値を記憶する記憶手段
を設け、前記空燃比フィードバック補正係数修正手段
は、この記憶手段が記憶した空燃比フィードバック補正
係数の値と理論空燃比近傍における空燃比フィードバッ
ク補正係数の値との偏差に基づいて前記修正値を設定し
てもよい。Further, the purge gas control means introduces the purge gas into the intake passage in a substantially stepwise manner under a predetermined operating condition, and stores the value of the air-fuel ratio feedback correction coefficient obtained when the purge gas was previously introduced. A storage means is provided, and the air-fuel ratio feedback correction coefficient correction means is a correction value based on a deviation between the value of the air-fuel ratio feedback correction coefficient stored by the storage means and the value of the air-fuel ratio feedback correction coefficient in the vicinity of the theoretical air-fuel ratio. May be set.
【００２８】[0028]
【作用】パージガスの導入時に、理論空燃比近傍におけ
る空燃比フィードバック補正係数の値とパージガス導入
後における空燃比フィードバック補正係数の値との偏差
に基づいて、空燃比がリッチ側方向にシフトするように
空燃比フィードバック補正係数を修正すれば、リーン側
にずれ易いパージガス導入時の空燃比を理論空燃比近傍
に収束させることができる。When the purge gas is introduced, the air-fuel ratio is shifted toward the rich side based on the deviation between the value of the air-fuel ratio feedback correction coefficient near the theoretical air-fuel ratio and the value of the air-fuel ratio feedback correction coefficient after the introduction of the purge gas. By correcting the air-fuel ratio feedback correction coefficient, the air-fuel ratio at the time of introducing the purge gas, which tends to shift to the lean side, can be converged to near the stoichiometric air-fuel ratio.
【００２９】また、パージガスの導入時に、理論空燃比
近傍における空燃比フィードバック補正係数の値とパー
ジガス導入後における空燃比フィードバック補正係数の
値との偏差に基づいて修正値を設定し、空燃比がリッチ
側方向にシフトするように前記修正値によって空燃比フ
ィードバック補正係数を修正すれば、パージガス導入時
におけるリーン側へのずれ量に応じて、該空燃比を理論
空燃比近傍にシフトさせることができる。Further, when the purge gas is introduced, a correction value is set based on the deviation between the value of the air-fuel ratio feedback correction coefficient near the stoichiometric air-fuel ratio and the value of the air-fuel ratio feedback correction coefficient after the introduction of the purge gas, and the air-fuel ratio becomes rich. If the air-fuel ratio feedback correction coefficient is corrected by the correction value so as to shift in the lateral direction, the air-fuel ratio can be shifted to the vicinity of the stoichiometric air-fuel ratio according to the amount of deviation to the lean side when the purge gas is introduced.
【００３０】さらに、前記パージガス制御手段は、所定
の運転条件下で略ステップ状にパージガスを吸気通路に
導入し、パージガスを前回導入したときに得られた前記
空燃比フィードバック補正係数の値を記憶する記憶手段
を設け、前記空燃比フィードバック補正係数修正手段
が、この記憶手段が記憶した空燃比フィードバック補正
係数の値と理論空燃比近傍における空燃比フィードバッ
ク補正係数との偏差に基づいて前記修正値を設定すれ
ば、空燃比変動の不安定要因であるパージガスの導入時
間を短縮しつつ、より正確かつ速やかに空燃比を理論空
燃比近傍に維持することができる。Further, the purge gas control means introduces the purge gas into the intake passage in a substantially stepwise manner under a predetermined operating condition, and stores the value of the air-fuel ratio feedback correction coefficient obtained when the purge gas was previously introduced. A storage means is provided, and the air-fuel ratio feedback correction coefficient correction means sets the correction value based on a deviation between the value of the air-fuel ratio feedback correction coefficient stored by the storage means and the air-fuel ratio feedback correction coefficient near the theoretical air-fuel ratio. By doing so, it is possible to more accurately and promptly maintain the air-fuel ratio near the stoichiometric air-fuel ratio while shortening the introduction time of the purge gas, which is a cause of unstable air-fuel ratio fluctuations.
【００３１】[0031]
【実施例】以下、本発明の実施例を図１〜図１２に基づ
いて詳細に説明する。なお、以下の各実施例では上述し
た従来技術と同一の構成要素に同一の符号を付し、その
説明を省略するものとする。Embodiments of the present invention will now be described in detail with reference to FIGS. In addition, in each of the following embodiments, the same components as those in the above-described related art are designated by the same reference numerals, and the description thereof will be omitted.
【００３２】まず、図１〜図８は本発明の第１の実施例
に係り、図１は、本発明の第１の実施例に係る内燃機関
の空燃比制御装置の全体を示す説明図であって、本実施
例によるコントロールユニット２１は、従来技術で述べ
たコントロールユニット１２と同様にマイクロコンピュ
ータシステムとして構成され、パージ制御弁８のデユー
テイ制御を行うパージガス制御手段２１Ａと、空燃比フ
ィードバック補正係数αに基づいて各燃料噴射弁１６に
印加する噴射信号を制御する空燃比制御手段２１Ｂとを
備えている。First, FIGS. 1 to 8 relate to a first embodiment of the present invention, and FIG. 1 is an explanatory view showing the whole air-fuel ratio control system for an internal combustion engine according to the first embodiment of the present invention. Therefore, the control unit 21 according to the present embodiment is configured as a microcomputer system similarly to the control unit 12 described in the related art, and has the purge gas control means 21A for performing the duty control of the purge control valve 8 and the air-fuel ratio feedback correction coefficient. Air-fuel ratio control means 21B for controlling the injection signal applied to each fuel injection valve 16 based on α is provided.
【００３３】但し、このコントロールユニット２１は、
これらに加えて、後述の如く、パージガス導入時に、空
燃比フィードバック補正係数αの偏差Δαに基づいて、
排気ガス中の空燃比がリッチ側方向に向けてシフトする
ように、空燃比フィードバック補正係数αを修正する空
燃比フィードバック補正係数修正手段２１Ｃ（図中では
「α修正」と示す）も備えている。However, the control unit 21 is
In addition to these, at the time of introducing the purge gas, based on the deviation Δα of the air-fuel ratio feedback correction coefficient α,
Air-fuel ratio feedback correction coefficient correction means 21C (shown as "alpha correction" in the figure) for correcting the air-fuel ratio feedback correction coefficient α is also provided so that the air-fuel ratio in the exhaust gas shifts toward the rich side. .
【００３４】次に、図２〜図８を参照しつつ本実施例の
作用を説明する。図２は、空燃比フィードバック補正係
数修正手段２１Ｃによる修正処理を示すフローチャート
であって、ステップ１では、基本噴射量ＴPと機関回転
数Ｎとを読込む。なお、エアフローメータからの吸入空
気量Ｑと回転数Ｎとを読込む構成としてもよい。Next, the operation of this embodiment will be described with reference to FIGS. FIG. 2 is a flowchart showing the correction processing by the air-fuel ratio feedback correction coefficient correction means 21C. In step 1, the basic injection amount T P and the engine speed N are read. Note that the intake air amount Q and the rotation speed N from the air flow meter may be read.
【００３５】そして、ステップ２では、空燃比制御手段
２１Ｂの状態から空燃比フィードバック補正係数αを用
いた空燃比制御を行っているか否かを判定する。このス
テップ２で「ＮＯ」と判定したときは、例えば冷間始動
時等の如く、空燃比フィードバック補正係数αがクラン
プされて空燃比制御を行っていない場合のため、処理を
終了する。一方、前記ステップ２で「ＹＥＳ」と判定し
たときは、ステップ３に移り、パージガス制御手段２１
Ａの状態に基づいて、パージガスを吸気通路２に導入し
ているか否かを判定する。Then, in step 2, it is determined whether the air-fuel ratio control means 21B is performing the air-fuel ratio control using the air-fuel ratio feedback correction coefficient α. If "NO" is determined in this step 2, since the air-fuel ratio feedback correction coefficient α is clamped and the air-fuel ratio control is not being performed, such as during cold start, the process ends. On the other hand, when it is determined to be “YES” in step 2, the process proceeds to step 3 and the purge gas control means 21
Based on the state of A, it is determined whether the purge gas is being introduced into the intake passage 2.
【００３６】このステップ３で「ＮＯ」と判定したとき
は、吸気通路２にパージガスの導入を行っていない場合
であるから、ステップ４に移り、図３，図４にそれぞれ
示す比例制御分マップから現在の機関の運転条件（基本
噴射量ＴP，Ｎ）に応じた比例制御分ＰLmap，Ｐ
Rmap（比例ゲイン）を読み出し、これらの値をＰL，ＰR
にそれぞれセットする。If "NO" is determined in step 3, it means that the purge gas is not introduced into the intake passage 2. Therefore, the process proceeds to step 4 and the proportional control map shown in FIGS. 3 and 4 is used. Proportional control components P Lmap , P corresponding to the current engine operating conditions (basic injection amount T P , N)
Rmap (proportional gain) is read and these values are set to P L and P R
Set each to.
【００３７】一方、前記ステップ３で「ＹＥＳ」と判定
したときは、パージガスの導入を開始した場合のため、
ステップ５に移って、パージガス導入後における空燃比
フィードバック補正係数αの平均値αAを求める。On the other hand, if "YES" is determined in step 3, it means that the introduction of the purge gas is started.
Moving to step 5, the average value α A of the air-fuel ratio feedback correction coefficient α after introducing the purge gas is obtained.
【００３８】ここで、この平均値αAは、図５に示す如
く、空燃比フィードバック補正係数αの反転毎のピーク
値（α1，α2，α3，…）を加重平均することにより、
下記数２に従って求められるもので、プログラムサイク
ル毎に更新される。Here, as shown in FIG. 5, this average value α A is obtained by weighted averaging the peak values (α 1 , α 2 , α 3 , ...) At each inversion of the air-fuel ratio feedback correction coefficient α.
It is obtained according to the following equation 2, and is updated every program cycle.
【００３９】[0039]
【数２】αA(n)＝β・α(n)＋（１−β）・αA(n-1) 但し、β：係数 次に、ステップ６では、下記数３に示す如く、前記ステ
ップ５で求めたパージガス導入後における空燃比フィー
ドバック補正係数αの平均値αAと理論空燃比近傍にお
ける空燃比フィードバック補正係数αの値であるＣとを
比較して、両者の偏差Δαを求める。ここで、通常、こ
の値Ｃは１００％であり、パージガス導入中の平均値α
Aは１００％よりも小さいため、偏差Δαは負の値とな
る。## EQU00002 ## .alpha.A (n) =. Beta..alpha. (N) + (1-.beta.). Alpha.A (n-1) However, .beta .: coefficient Next, in step 6, as shown in the following equation 3, The average value α A of the air-fuel ratio feedback correction coefficient α after introducing the purge gas obtained in step 5 is compared with C, which is the value of the air-fuel ratio feedback correction coefficient α in the vicinity of the stoichiometric air-fuel ratio, to obtain the deviation Δα between the two. Here, normally, this value C is 100%, and the average value α during the introduction of the purge gas α
Since A is smaller than 100%, the deviation Δα has a negative value.
【００４０】[0040]
【数３】Δα＝αA−Ｃ そして、ステップ７では、図６に示す修正値マップから
前記ステップ６で求めた偏差Δαに基づいて、現在の偏
差Δαに対応した修正値ｄｐを読み出す。ここで、図６
に示す修正値マップについて説明すると、この修正値マ
ップは、Δαの値が小さくなるほど、即ち、平均値αA
と理論空燃比近傍における空燃比フィードバック係数α
の値Ｃとの差が大きくなるほど、修正値ｄｐが大きくな
るように設定されている。また、加速や減速等の運転条
件によって空燃比フィードバック補正係数αは変動する
ため、偏差Δαが所定のスライスレベルΔαLを越えて
小さくなった場合のみ、修正値ｄｐを読み出せるように
なっている。ここで、パージガス導入時における空燃比
のリーン側へのずれ（シフト量）は、キャニスタ５に蓄
積された蒸発燃料の量、吸気通路２に導入されたパージ
ガス量、燃料噴射弁１６の形式及び取付位置等によって
変化するため、この修正値マップは、機関の形式毎に予
め実験等によって求められるものである。Equation 3] [Delta] [alpha] = alpha A -C Then, in step 7, based on the deviation [Delta] [alpha] obtained in Step 6 from the modified value map shown in FIG. 6, reads out the correction value dp corresponding to the current deviation [Delta] [alpha]. Here, FIG.
The correction value map shown in FIG. 2 will be described. This correction value map shows that the smaller the value of Δα, that is, the average value α A
And the air-fuel ratio feedback coefficient α near the stoichiometric air-fuel ratio
The correction value dp is set to be larger as the difference from the value C of is larger. Further, since the air-fuel ratio feedback correction coefficient α changes depending on operating conditions such as acceleration and deceleration, the correction value dp can be read only when the deviation Δα becomes smaller than the predetermined slice level Δα L. . Here, the deviation (shift amount) of the air-fuel ratio to the lean side at the time of introducing the purge gas is the amount of evaporated fuel accumulated in the canister 5, the amount of purge gas introduced into the intake passage 2, the type and attachment of the fuel injection valve 16. Since the map changes depending on the position and the like, this correction value map is obtained in advance by experiments or the like for each engine type.
【００４１】最後に、ステップ８では、前記ステップ７
で読み出した修正値ｄｐにより、機関の運転条件に応じ
て比例制御分マップから読み出される各比例制御ＰL，
ＰRをそれぞれ修正し、空燃比をリッチ側方向にシフト
させる。Finally, in step 8, step 7
With the correction value dp read in step 1, each proportional control P L , which is read from the proportional control component map according to the operating conditions of the engine,
Each P R is corrected to shift the air-fuel ratio toward the rich side.
【００４２】具体的には、図７に示す如く、リーン時比
例制御分ＰL（＝ＰLmap）に修正値ｄｐを加算すると共
に、リッチ時比例制御分ＰR（＝ＰRmap）から修正値ｄ
ｐを減算する。これにより、空燃比フィードバック補正
係数αが大きくなって、燃料噴射量Ｔiが増加するた
め、排気ガス中の空燃比Ａ／Ｆはリッチ側に向けて移行
し、その平均空燃比が理論空燃比近傍に収束する。な
お、ここで、図８に示す如く、パージ制御弁１０は、徐
々に開弁時間が増大するようにデユーテイ制御されるた
め、これに応じて、空燃比フィードバック補正係数αは
徐々に小さくなっていく。Specifically, as shown in FIG. 7, the correction value dp is added to the lean proportional control amount P L (= P Lmap ) and the correction value is changed from the rich proportional control amount P R (= P Rmap ). d
Subtract p. As a result, the air-fuel ratio feedback correction coefficient α increases and the fuel injection amount T i increases, so the air-fuel ratio A / F in the exhaust gas shifts toward the rich side, and the average air-fuel ratio becomes the stoichiometric air-fuel ratio. It converges to the neighborhood. Here, as shown in FIG. 8, the purge control valve 10 is duty-controlled so that the valve opening time gradually increases, and accordingly, the air-fuel ratio feedback correction coefficient α gradually decreases. Go.
【００４３】このように構成される本実施例によれば、
以下の効果を奏する。According to the present embodiment configured as described above,
The following effects are obtained.
【００４４】第１に、パージガス制御手段２１Ａによっ
てパージガスが導入されると、空燃比フィードバック補
正係数修正手段２１Ｃは、パージガス導入の前後で変化
する空燃比フィードバック補正係数αの偏差Δαを求
め、この偏差Δαに基づいて、空燃比センサ１４が検出
する空燃比がリッチ側方向にシフトするように、空燃比
フィードバック補正係数αを修正する構成としたため、
機関要求燃料に占める燃料噴射量の割合が相対的に低下
するパージガス導入中でも、リーン側にシフトする空燃
比を速やかに理論空燃比近傍に収束させることができ、
ＮＯxの排出を抑制することができる。First, when the purge gas is introduced by the purge gas control means 21A, the air-fuel ratio feedback correction coefficient correction means 21C finds the deviation Δα of the air-fuel ratio feedback correction coefficient α which changes before and after the introduction of the purge gas. Since the air-fuel ratio feedback correction coefficient α is modified based on Δα so that the air-fuel ratio detected by the air-fuel ratio sensor 14 shifts toward the rich side,
Even during the introduction of purge gas in which the ratio of the fuel injection amount to the engine required fuel decreases relatively, the air-fuel ratio shifting to the lean side can be promptly converged to near the stoichiometric air-fuel ratio,
It is possible to suppress the emission of NO x .
【００４５】第２に、偏差Δαに基づいて修正値マップ
から修正値ｄｐを読み出し、この読み出された修正値ｄ
ｐによって空燃比フィードバック補正係数αを修正する
構成としたため、空燃比補正係数αの変動（偏差Δα）
に応じた修正値ｄｐを速やかに得ることができる。Secondly, the correction value dp is read from the correction value map based on the deviation Δα, and the read correction value d is read.
Since the air-fuel ratio feedback correction coefficient α is modified by p, the fluctuation of the air-fuel ratio correction coefficient α (deviation Δα)
It is possible to promptly obtain the correction value dp corresponding to.
【００４６】第３に、パージガス導入が空燃比に与える
影響を、空燃比フィードバック補正係数αの偏差Δαに
よって検出する構成のため、全体構造を簡素化しつつ空
燃比制御を行うことができる。Thirdly, since the influence of the introduction of the purge gas on the air-fuel ratio is detected by the deviation Δα of the air-fuel ratio feedback correction coefficient α, the overall structure can be simplified and the air-fuel ratio control can be performed.
【００４７】第４に、本実施例では、修正値マップに所
定のスライスレベルΔαLを設定し、偏差Δαがスライ
スレベルΔαLを越えて小さくなったときに、修正値ｄ
ｐを読み出せる構成としたため、加減速等によって空燃
比フィードバック補正係数αが変動した場合でも、これ
による空燃比フィードバック補正係数αの誤修正を未然
に防止することができる。Fourthly, in the present embodiment, a predetermined slice level Δα L is set in the correction value map, and when the deviation Δα becomes smaller than the slice level Δα L , the correction value d
Since p can be read, even if the air-fuel ratio feedback correction coefficient α changes due to acceleration / deceleration or the like, it is possible to prevent erroneous correction of the air-fuel ratio feedback correction coefficient α due to this.
【００４８】次に、図９〜図１１に基づいて本発明の第
２の実施例を説明する。なお、本実施例では、上述した
第１の実施例と同一の構成要素に同一の符号を付し、そ
の説明を省略するものとする。本実施例の特徴は、パー
ジガスを短時間で吸気通路２内に導入すると共に、パー
ジガスの導入初期には前回のパージガス導入時における
最終平均値αAに基づいて空燃比フィードバック補正係
数αを修正するようにした点にある。Next, a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, the same components as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted. The feature of this embodiment is that the purge gas is introduced into the intake passage 2 in a short time, and the air-fuel ratio feedback correction coefficient α is corrected based on the final average value α A at the time of the introduction of the purge gas at the beginning of the introduction of the purge gas. There is a point in doing so.
【００４９】即ち、本実施例によるコントロールユニッ
ト３１は、第１の実施例で述べたコントロールユニット
２１と同様に、パージガスの導入量を制御するパージガ
ス制御手段３１Ａと、前記数１に基づいて燃料噴射量を
制御する空燃比制御手段３１Ｂと、パージガス導入前後
の空燃比フィードバック補正係数αの偏差Δαに基づい
て空燃比フィードバック補正係数αを修正する空燃比フ
ィードバック補正係数修正手段３１Ｃとを備えている。
しかし、本実施例によるコントロールユニット３１で
は、図１１に示す如く、パージガス制御手段３１Ａによ
って略ステップ状にパージガスを導出すると共に、前回
の偏差Δα等を記憶する記憶手段３１Ｄを備えている点
で第１の実施例と相違する。That is, the control unit 31 according to the present embodiment, similar to the control unit 21 described in the first embodiment, has the purge gas control means 31A for controlling the introduction amount of the purge gas, and the fuel injection based on the equation (1). The air-fuel ratio control means 31B for controlling the amount and the air-fuel ratio feedback correction coefficient correction means 31C for correcting the air-fuel ratio feedback correction coefficient α based on the deviation Δα of the air-fuel ratio feedback correction coefficient α before and after introducing the purge gas are provided.
However, in the control unit 31 according to the present embodiment, as shown in FIG. 11, the purge gas is controlled in a stepwise manner by the purge gas control means 31A and the storage means 31D for storing the previous deviation Δα and the like is provided. This is different from the first embodiment.
【００５０】次に、本実施例の作用について図１０に示
すフローチャートを参照しつつ説明する。Next, the operation of this embodiment will be described with reference to the flowchart shown in FIG.
【００５１】まず、ステップ１１〜１４は、第１の実施
例で述べた図２に示すステップ１〜４と同様の処理を行
うもので、ステップ１１では、基本噴射量ＴP及び機関
回転数Ｎを読込み、ステップ１２では、空燃比制御手段
３１Ｂの状態に基づいて空燃比制御を行っているか否か
を判定し、このステップ１２で「ＹＥＳ」と判定したと
きは、ステップ１３によりパージガス導入中であるか否
かを判定する。そして、このステップ１３で「ＮＯ」と
判定したときは、ステップ１４に移って、図３及び図４
に示す比例制御分マップから機関の運転条件に応じた値
を各比例制御分ＰL，ＰRにそれぞれセットする。First, in steps 11 to 14, the same processing as steps 1 to 4 shown in FIG. 2 described in the first embodiment is performed. In step 11, the basic injection amount T P and the engine speed N are set. In step 12, it is determined whether or not the air-fuel ratio control is being performed based on the state of the air-fuel ratio control means 31B. When it is determined "YES" in this step 12, the purge gas is being introduced in step 13. Determine if there is. When it is determined to be "NO" in step 13, the process proceeds to step 14,
To set each value corresponding to the operating condition of the engine from the proportional control amount map each proportional control amount P L, the P R shown.
【００５２】次に、ステップ１５では、パージガス制御
手段３１Ａによるパージガスの導入が初期状態にあるか
否かを判定する。即ち、本実施例では、パージガスを略
ステップ状に、オンオフ的に吸気通路２に導入するた
め、パージガス導入直後の空燃比フィードバック補正係
数αの平均値αAを正確に求めるべく、このステップ１
５では、パージガス導入の立ち上がりを検出している。Next, at step 15, it is judged whether or not the introduction of the purge gas by the purge gas control means 31A is in the initial state. That is, in the present embodiment, since the purge gas is introduced into the intake passage 2 in a substantially step-like manner into the intake passage 2, in order to accurately obtain the average value α A of the air-fuel ratio feedback correction coefficient α immediately after the introduction of the purge gas, this step 1
In 5, the rising of the introduction of purge gas is detected.
【００５３】そして、ステップ１６では、後述のステッ
プ２０で記憶した平均値αA，偏差Δαを記憶手段３１
Ｄから読み出し、ステップ１７では、この記憶値に基づ
いて図２に示すステップ８と同様に、各比例制御分
ＰL，ＰRを修正する。つまり、前記ステップ１５でも説
明した通り、本実施例では、図１１に示す如く、オンオ
フ的にパージガスを導入するため、空燃比フィードバッ
ク補正係数αも略ステップ状に変化する。従って、第１
の実施例の如く、直前の平均値αA(n-1)を使用して数２
によりパージガス導入直後の平均値αAを求めると誤差
が大きくなる。このため、図１１中に示す通り、パージ
ガス導入直後には、前回のパージガス導入時の最後に得
られた平均値αAを用いて偏差Δαを演算し、これによ
り修正値ｄｐを設定して空燃比フィードバック補正係数
αを修正するようになっている。Then, in step 16, the average value α A and the deviation Δα stored in step 20 described later are stored in the storage means 31.
The data is read from D, and in step 17, the proportional control components P L and P R are corrected based on this stored value as in step 8 shown in FIG. That is, as described in step 15, in the present embodiment, as shown in FIG. 11, the purge gas is introduced on and off, so the air-fuel ratio feedback correction coefficient α also changes in a substantially stepwise manner. Therefore, the first
As in the embodiment of the above, using the immediately preceding average value α A (n-1) ,
Therefore, the error increases when the average value α A immediately after the introduction of the purge gas is obtained. Therefore, as shown in FIG. 11, immediately after the introduction of the purge gas, the deviation Δα is calculated using the average value α A obtained at the last time of the introduction of the purge gas, and the correction value dp is set to the empty value. The fuel ratio feedback correction coefficient α is modified.
【００５４】次に、ステップ１８では、パージガス導入
直後の過渡期が終了したため、前記数２に従って新たな
平均値αAを求め、さらに、ステップ１９では、この現
在のパージガス導入における定常状態での平均値αAに
基づいて、理論空燃比近傍における空燃比フィードバッ
ク補正係数αの値Ｃとの偏差Δαを求めると共に、図６
に示す修正値マップから偏差Δαに応じた修正値ｄｐを
読み出す。即ち、本実施例では、パージガス導入初期
（導入直後）のみ記憶値に基づいて修正値ｄｐを設定
し、その後は、第１の実施例で述べたと同様に、実際の
平均値αAと値Ｃとの偏差Δαを算出して修正値ｄｐを
求めるようになっている。Next, at step 18, since the transitional period immediately after the introduction of the purge gas is completed, a new average value α A is obtained according to the above-mentioned equation 2, and at step 19, the average value in the steady state at the present introduction of the purge gas is obtained. Based on the value α A , the deviation Δα from the value C of the air-fuel ratio feedback correction coefficient α in the vicinity of the theoretical air-fuel ratio is calculated, and
The correction value dp corresponding to the deviation Δα is read from the correction value map shown in FIG. That is, in this embodiment, the correction value dp is set based on the stored value only at the initial stage (immediately after the introduction) of the purge gas, and thereafter, the actual average value α A and the value C are set in the same manner as described in the first embodiment. The deviation Δα from the calculated value is calculated to obtain the correction value dp.
【００５５】そして、ステップ２０では、前記ステップ
１８で求めた最新の平均値αAを前記数２中に示す直前
の平均値αA(n-1)として記憶手段３１Ｄに記憶し、次回
のパージガス導入に備える。Then, in step 20, the latest average value α A obtained in step 18 is stored in the storage means 31D as the immediately preceding average value α A (n-1) shown in the equation 2, and the next purge gas is stored. Prepare for introduction.
【００５６】なお、本実施例では、プログラムサイクル
毎に、平均値αAを更新記憶する場合を例に挙げて説明
したが、これに限らず、例えばパージガス制御手段３１
Ａの状態に基づいてパージガス導入の停止を検出し、導
入停止と判定した場合に平均値αAを記憶する構成とし
てもよい。また、前回記憶した平均値αAをそのまま次
回のパージガス導入初期に用いる場合を説明したが、こ
れに限らず、例えばパージガス導入回数、インターバル
期間、機関の運転条件等のパラメータと関連付けて平均
値αAを記憶しておき、学習補正した値を用いてもよ
い。In the present embodiment, the case where the average value α A is updated and stored for each program cycle has been described as an example, but the present invention is not limited to this, and for example, the purge gas control means 31.
It may be configured to detect the stop of the purge gas introduction based on the state of A and store the average value α A when it is determined that the introduction of the purge gas is stopped. Further, the case where the previously stored average value α A is used as it is at the initial stage of the next purge gas introduction has been described, but the present invention is not limited to this, and the average value α A is associated with parameters such as the number of purge gas introduction times, an interval period, and engine operating conditions, A may be stored and the value corrected by learning may be used.
【００５７】このように構成される本実施例でも、前記
第１の実施例で述べたと同様の効果を得ることができ
る。また、これに加えて以下の効果を奏する。Also in this embodiment having such a configuration, the same effect as that described in the first embodiment can be obtained. In addition to this, the following effects are achieved.
【００５８】第１に、図１１に示す如く、略ステップ状
に（オンオフ的に）、パージガスを導入するため、パー
ジガスの導入時間を短縮することができる。First, as shown in FIG. 11, since the purge gas is introduced in a stepwise manner (on / off manner), the introduction time of the purge gas can be shortened.
【００５９】第２に、前回のパージガス導入の最後に得
られた空燃比フィードバック補正係数αの平均値αAを
数２中におけるαA(n-1)として記憶手段３１Ｄで記憶し
ておき、この記憶した平均値αAを用いて次回のパージ
ガス導入直後の平均値αAを求める構成としたため、パ
ージガスの導入が略ステップ状に変化した場合でも、導
入初期の偏差Δα及び修正値ｄｐを比較的正確に求める
ことができ、速やかに空燃比を理論空燃比近傍に収束さ
せることができる。Secondly, the average value α A of the air-fuel ratio feedback correction coefficient α obtained at the end of the previous introduction of the purge gas is stored in the storage means 31D as α A (n-1) in the equation 2, Since the stored average value α A is used to calculate the average value α A immediately after the introduction of the purge gas next time, even if the introduction of the purge gas changes in a substantially stepwise manner, the deviation Δα at the initial introduction and the correction value dp are compared. The air-fuel ratio can be promptly converged to near the stoichiometric air-fuel ratio.
【００６０】なお、前記各実施例では、各比例制御分Ｐ
L，ＰRを修正値ｄｐによって調整することにより、空燃
比がリッチ側方向に向けてシフトするように空燃比フィ
ードバック補正係数αを修正する場合を例示したが、本
発明は、これに限らず、例えば、図１２に示す変形例の
ように、リーン時積分制御分ＩLの傾きを角度θだけ大
きくすると共に、リッチ時積分制御分ＩRの傾きを角度
θだけ小さくすることにより、空燃比フィードバック補
正係数αをリッチ側方向に向けて修正する構成としても
よい。また、リッチ側及びリーン側の制御分を同時に調
整する必要は必ずしもないため、リーン側の制御分
ＰL，ＩLのみを強めてもよい。In each of the above embodiments, each proportional control component P
The case where the air-fuel ratio feedback correction coefficient α is corrected so that the air-fuel ratio shifts toward the rich side by adjusting L and P R by the correction value dp has been illustrated, but the present invention is not limited to this. For example, as in the modification shown in FIG. 12, by increasing the inclination of the lean integration control amount I L by the angle θ and decreasing the inclination of the rich integration control component I R by the angle θ, the air-fuel ratio The feedback correction coefficient α may be modified toward the rich side. Further, since it is not always necessary to adjust the control amounts on the rich side and the lean side at the same time, only the control amounts P L and I L on the lean side may be strengthened.
【００６１】[0061]
【発明の効果】以上詳述した如く、本発明によれば、パ
ージガスの導入時に、理論空燃比近傍における空燃比フ
ィードバック補正係数の値とパージガス導入後における
空燃比フィードバック補正係数の値との偏差に基づい
て、空燃比がリッチ側方向にシフトするように空燃比フ
ィードバック補正係数を修正したため、リーン側にずれ
易いパージガス導入時の空燃比を理論空燃比近傍に収束
させることができ、パージガス導入時のＮＯxの排出を
低減することができる。As described above in detail, according to the present invention, when the purge gas is introduced, the deviation between the value of the air-fuel ratio feedback correction coefficient near the stoichiometric air-fuel ratio and the value of the air-fuel ratio feedback correction coefficient after the introduction of the purge gas is calculated. Based on this, since the air-fuel ratio feedback correction coefficient is modified so that the air-fuel ratio shifts toward the rich side, it is possible to converge the air-fuel ratio when introducing purge gas that tends to shift to the lean side to near the theoretical air-fuel ratio, and when introducing purge gas. The emission of NO x can be reduced.
【００６２】また、空燃比フィードバック補正係数の偏
差に基づいて修正値を設定し、空燃比がリッチ側方向に
シフトするように前記修正値によって空燃比フィードバ
ック補正係数を修正したため、パージガス導入時におけ
る空燃比のリーン側へのずれ量に応じて、該空燃比を理
論空燃比近傍にシフトさせることができる。Further, the correction value is set based on the deviation of the air-fuel ratio feedback correction coefficient, and the air-fuel ratio feedback correction coefficient is corrected by the correction value so that the air-fuel ratio shifts toward the rich side. The air-fuel ratio can be shifted to near the stoichiometric air-fuel ratio according to the amount of deviation of the fuel ratio to the lean side.
【００６３】さらに、パージガス制御手段は、所定の運
転条件下で略ステップ状にパージガスを吸気通路に導入
し、パージガスを前回導入したときに得られた空燃比フ
ィードバック補正係数の値を記憶する記憶手段を設け、
この記憶手段が記憶した空燃比フィードバック補正係数
の値と理論空燃比近傍における空燃比フィードバック補
正係数との偏差に基づいて修正値を設定し、この修正値
により、空燃比フィードバック補正係数を修正したた
め、空燃比変動の不安定要因であるパージガスの導入時
間を短縮しつつ、より正確かつ速やかに空燃比を理論空
燃比近傍に維持することができる。Further, the purge gas control means introduces the purge gas into the intake passage in a substantially stepwise manner under predetermined operating conditions, and stores the value of the air-fuel ratio feedback correction coefficient obtained when the purge gas was previously introduced. Is provided
A correction value is set based on the deviation between the value of the air-fuel ratio feedback correction coefficient stored by this storage means and the air-fuel ratio feedback correction coefficient in the vicinity of the theoretical air-fuel ratio, and the correction value is used to correct the air-fuel ratio feedback correction coefficient. It is possible to more accurately and promptly maintain the air-fuel ratio near the stoichiometric air-fuel ratio while shortening the introduction time of the purge gas, which is an unstable factor of the air-fuel ratio fluctuation.
【図１】本発明の第１の実施例に係る空燃比制御装置の
全体構成を示す説明図。FIG. 1 is an explanatory diagram showing an overall configuration of an air-fuel ratio control device according to a first embodiment of the present invention.
【図２】空燃比フィードバック補正係数の修正処理を示
すフローチャート。FIG. 2 is a flowchart showing correction processing of an air-fuel ratio feedback correction coefficient.
【図３】リーン時の比例制御分ＰLを読み出すためのマ
ップを示す説明図。FIG. 3 is an explanatory diagram showing a map for reading a proportional control amount P L at the time of leaning.
【図４】リッチ時の比例制御分ＰRを読み出すためのマ
ップを示す説明図。FIG. 4 is an explanatory view showing a map for reading a proportional control amount P R at the time of rich.
【図５】空燃比の平均値を求めるための説明図。FIG. 5 is an explanatory diagram for obtaining an average value of an air-fuel ratio.
【図６】偏差Δαと修正値ｄｐとの関係を記憶した修正
値マップを示す説明図。FIG. 6 is an explanatory diagram showing a correction value map storing a relationship between a deviation Δα and a correction value dp.
【図７】修正値ｄｐによる空燃比フィードバック補正係
数の修正方法を示す説明図。FIG. 7 is an explanatory diagram showing a method of correcting an air-fuel ratio feedback correction coefficient with a correction value dp.
【図８】パージガス導入と空燃比フィードバック補正係
数との関係を示す特性図。FIG. 8 is a characteristic diagram showing a relationship between introduction of purge gas and an air-fuel ratio feedback correction coefficient.
【図９】本発明の第２の実施例に係る空燃比制御装置の
全体構成を示す説明図。FIG. 9 is an explanatory diagram showing an overall configuration of an air-fuel ratio control device according to a second embodiment of the present invention.
【図１０】空燃比フィードバック補正係数の修正処理を
示すフローチャート。FIG. 10 is a flowchart showing correction processing of an air-fuel ratio feedback correction coefficient.
【図１１】パージガス導入と空燃比フィードバック補正
係数との関係を示す特性図。FIG. 11 is a characteristic diagram showing a relationship between introduction of purge gas and an air-fuel ratio feedback correction coefficient.
【図１２】本発明の変形例に係る他の修正方法を示す説
明図。FIG. 12 is an explanatory diagram showing another correction method according to the modification of the present invention.
【図１３】従来技術による空燃比制御装置の全体構成を
示す説明図。FIG. 13 is an explanatory diagram showing an overall configuration of an air-fuel ratio control device according to a conventional technique.
【図１４】パージガス非導入時における空燃比フィード
バック補正係数と空燃比等との関係を示す説明図。FIG. 14 is an explanatory diagram showing a relationship between an air-fuel ratio feedback correction coefficient and an air-fuel ratio when a purge gas is not introduced.
【図１５】パージガス導入時における空燃比フィードバ
ック補正係数と空燃比等との関係を示す説明図。FIG. 15 is an explanatory diagram showing a relationship between an air-fuel ratio feedback correction coefficient and an air-fuel ratio when introducing purge gas.
【図１６】パージガス導入の前後で機関要求燃料に占め
る燃料噴射量の割合が変化すること示す説明図。FIG. 16 is an explanatory diagram showing that the ratio of the fuel injection amount to the engine required fuel changes before and after the introduction of purge gas.
【図１７】パージガス導入の前後で、リッチ側及びリー
ン側への応答時間が変化する状態を示す説明図。FIG. 17 is an explanatory diagram showing a state in which the response times to the rich side and the lean side change before and after introducing the purge gas.
【図１８】触媒コンバータの転化性能を示す特性図。FIG. 18 is a characteristic diagram showing conversion performance of a catalytic converter.
１…機関本体 ２…吸気通路 ３…排気通路 ５…キャニスタ １４…空燃比センサ ２１，３１…コントロールユニット ２１Ａ，３１Ａ…パージガス制御手段 ２１Ｂ，３１Ｂ…空燃比制御手段 ２１Ｃ，３１Ｃ…空燃比フィードバック補正係数修正手
段 ３１Ｄ…記憶手段DESCRIPTION OF SYMBOLS 1 ... Engine main body 2 ... Intake passage 3 ... Exhaust passage 5 ... Canister 14 ... Air-fuel ratio sensor 21, 31 ... Control unit 21A, 31A ... Purge gas control means 21B, 31B ... Air-fuel ratio control means 21C, 31C ... Air-fuel ratio feedback correction coefficient Correction means 31D ... Storage means
Claims (3)
転条件下でパージガスとして吸気通路に導入するパージ
ガス制御手段と、排気通路に設けられた空燃比センサの
検出信号に基づいて空燃比のフィードバック制御を行う
空燃比制御手段と、を備えた内燃機関において、 パージガス導入時に、理論空燃比近傍における空燃比フ
ィードバック補正係数の値とパージガス導入後における
空燃比フィードバック補正係数の値との偏差に基づい
て、空燃比がリッチ側方向にシフトするように空燃比フ
ィードバック補正係数を修正する空燃比フィードバック
補正係数修正手段を設けたことを特徴とする内燃機関の
空燃比制御装置。1. A feedback control of an air-fuel ratio based on a purge gas control means for introducing a fuel adsorbed in a canister as a purge gas into an intake passage under a predetermined operating condition, and a detection signal of an air-fuel ratio sensor provided in an exhaust passage. In the internal combustion engine equipped with the air-fuel ratio control means for performing, when introducing the purge gas, based on the deviation between the value of the air-fuel ratio feedback correction coefficient near the theoretical air-fuel ratio and the value of the air-fuel ratio feedback correction coefficient after introducing the purge gas, An air-fuel ratio control device for an internal combustion engine, comprising air-fuel ratio feedback correction coefficient correction means for correcting the air-fuel ratio feedback correction coefficient so that the air-fuel ratio shifts toward the rich side.
手段は、パージガス導入時に、理論空燃比近傍における
空燃比フィードバック補正係数の値とパージガス導入後
における空燃比フィードバック補正係数の値との偏差に
基づいて修正値を設定し、空燃比がリッチ側方向にシフ
トするように前記修正値によって空燃比フィードバック
補正係数を修正することを特徴とする請求項１に記載の
内燃機関の空燃比制御装置。2. The air-fuel ratio feedback correction coefficient correction means corrects, based on the deviation between the value of the air-fuel ratio feedback correction coefficient near the stoichiometric air-fuel ratio and the value of the air-fuel ratio feedback correction coefficient after introduction of the purge gas, when the purge gas is introduced. The air-fuel ratio control device for an internal combustion engine according to claim 1, wherein a value is set, and the air-fuel ratio feedback correction coefficient is corrected by the correction value so that the air-fuel ratio shifts toward the rich side.
条件下で略ステップ状にパージガスを吸気通路に導入
し、 パージガスを前回導入したときに得られた前記空燃比フ
ィードバック補正係数の値を記憶する記憶手段を設け、 前記空燃比フィードバック補正係数修正手段は、この記
憶手段が記憶した空燃比フィードバック補正係数の値と
理論空燃比近傍における空燃比フィードバック補正係数
の値との偏差に基づいて前記修正値を設定することを特
徴とする請求項２に記載の内燃機関の空燃比制御装置。3. The purge gas control means introduces the purge gas into the intake passage in a substantially stepwise manner under predetermined operating conditions, and stores the value of the air-fuel ratio feedback correction coefficient obtained when the purge gas was introduced last time. Storage means is provided, the air-fuel ratio feedback correction coefficient correction means, the correction value based on the deviation between the value of the air-fuel ratio feedback correction coefficient stored by the storage means and the value of the air-fuel ratio feedback correction coefficient in the vicinity of the theoretical air-fuel ratio. The air-fuel ratio control device for an internal combustion engine according to claim 2, wherein
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24735794A JP3517985B2 (en) | 1994-10-13 | 1994-10-13 | Air-fuel ratio control device for internal combustion engine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24735794A JP3517985B2 (en) | 1994-10-13 | 1994-10-13 | Air-fuel ratio control device for internal combustion engine |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08109844A true JPH08109844A (en) | 1996-04-30 |
| JP3517985B2 JP3517985B2 (en) | 2004-04-12 |
Family
ID=17162222
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP24735794A Expired - Fee Related JP3517985B2 (en) | 1994-10-13 | 1994-10-13 | Air-fuel ratio control device for internal combustion engine |
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| Country | Link |
|---|---|
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6343467B1 (en) | 1997-07-28 | 2002-02-05 | Denso Corporation | Air-fuel ratio control apparatus and method for internal combustion engine |
-
1994
- 1994-10-13 JP JP24735794A patent/JP3517985B2/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6343467B1 (en) | 1997-07-28 | 2002-02-05 | Denso Corporation | Air-fuel ratio control apparatus and method for internal combustion engine |
| DE19833938B4 (en) * | 1997-07-28 | 2006-07-13 | Denso Corp., Kariya | Air / fuel ratio control device and associated method for an internal combustion engine |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3517985B2 (en) | 2004-04-12 |
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