JP2015010474A - Control device of internal combustion engine - Google Patents

Control device of internal combustion engine Download PDF

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JP2015010474A
JP2015010474A JP2013134027A JP2013134027A JP2015010474A JP 2015010474 A JP2015010474 A JP 2015010474A JP 2013134027 A JP2013134027 A JP 2013134027A JP 2013134027 A JP2013134027 A JP 2013134027A JP 2015010474 A JP2015010474 A JP 2015010474A
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air
fuel ratio
fuel
control
lean
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毅 園田
Takeshi Sonoda
毅 園田
智弘 八木
Tomohiro Yagi
智弘 八木
浩策 太田
Kosaku Ota
浩策 太田
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Daihatsu Motor Co Ltd
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Abstract

PROBLEM TO BE SOLVED: To solve a problem that a fuel injection amount is excessively corrected to a lean side during port wet remains immediately after air-fuel ratio rich control is finished immediately after a return from fuel cut.SOLUTION: When a rotation number of an internal combustion engine exceeds a prescribed rotation number and an accelerator operation amount goes below a prescribed threshold, a fuel cut is performed. When a prescribed fuel cut finish condition is established, control for finishing the fuel cut is performed. Immediately after a return from the fuel cut, air-fuel ratio rich control for setting an air-fuel ratio to a rich side is performed. A guide is applied to a correction coefficient at a lean side of first air-fuel ratio feedback control after the finish of the air-fuel ratio rich control, and the air-fuel ratio is controlled to the lean side while lowering a speed of an increase of a correction amount of the air-fuel ratio more than that at a normal time for a prescribed period of time.

Description

本発明は、吸気ポートに燃料を噴射し、点火プラグを介した火花点火により混合気に着火する構成を有する内燃機関に用いられ、空燃比センサの出力信号に基づき空燃比のフィードバック制御を行う内燃機関の制御装置に関する。   The present invention is used in an internal combustion engine having a configuration in which fuel is injected into an intake port and an air-fuel mixture is ignited by spark ignition via an ignition plug, and an internal combustion engine that performs air-fuel ratio feedback control based on an output signal of an air-fuel ratio sensor The present invention relates to an engine control device.

従来より、空燃比を理論空燃比近傍に保つべく、排気通路に空燃比センサを設け、この空燃比センサの出力信号に基づき空燃比のフィードバック制御を行う内燃機関の制御装置が知られている。このフィードバック制御としては、空燃比センサの出力信号が示す空燃比がリーンからリッチに切り替わった際に、燃料噴射量の補正係数を所定のスキップ値だけ減少させ、さらに所定時間あたりリーン積分値だけ逓減させるようにする一方、空燃比センサの出力信号が示す空燃比がリッチからリーンに切り替わった際に、燃料噴射量の補正係数を所定のスキップ値だけ増加させ、さらに所定時間あたりリッチ積分値だけ逓増させるようにする制御が広く用いられている。   2. Description of the Related Art Conventionally, there has been known an internal combustion engine control device in which an air-fuel ratio sensor is provided in an exhaust passage and an air-fuel ratio feedback control is performed based on an output signal of the air-fuel ratio sensor in order to keep the air-fuel ratio close to the theoretical air-fuel ratio. In this feedback control, when the air-fuel ratio indicated by the output signal of the air-fuel ratio sensor switches from lean to rich, the fuel injection amount correction coefficient is decreased by a predetermined skip value and further decreased by a lean integral value per predetermined time. On the other hand, when the air-fuel ratio indicated by the output signal of the air-fuel ratio sensor switches from rich to lean, the fuel injection amount correction coefficient is increased by a predetermined skip value and further increased by a rich integral value per predetermined time. The control to make it happen is widely used.

一方、内燃機関の回転数が所定回転数を上回りかつアクセル操作量が所定の閾値を下回る場合に燃料カットを行うとともに、所定の燃料カット終了条件が成立したときには、燃料カットを終了する制御も従来より知られている。この制御に伴い燃料カットを終了した直後においては、触媒が空気に触れたことにより触媒に過剰量の酸素が吸着されており、この状態を解消すべく空燃比を理論空燃比よりもリッチ側に制御することが行われている。しかして、この空燃比リッチ制御が終了し、空燃比のフィードバック制御を開始する時点では、吸気ポート近傍に付着した燃料（以下、ポートウェットと称する）が残存しているため、燃料噴射量が本来の要求量よりもさらにリーン側に補正される。その後、ポートウェットがなくなり空燃比センサの出力信号が示す空燃比がリッチからリーンに切り替わると、上述したように燃料噴射量の補正係数を増加させる制御が行われるが、ポートウェットが残存している期間に過度にリーン側に補正されていることにより、燃料噴射量の補正係数を増加させてもなお燃料噴射量の補正係数が理論空燃比よりもリーン側であることがあるという問題が存在する。   On the other hand, when the rotational speed of the internal combustion engine exceeds a predetermined rotational speed and the accelerator operation amount falls below a predetermined threshold value, the fuel cut is performed, and when the predetermined fuel cut end condition is satisfied, the fuel cut end control is also conventionally performed. More known. Immediately after the fuel cut is completed in accordance with this control, the catalyst is in contact with air, so that an excessive amount of oxygen is adsorbed on the catalyst, and the air-fuel ratio is made richer than the stoichiometric air-fuel ratio in order to eliminate this state. To be controlled. Therefore, when the air-fuel ratio rich control is finished and the air-fuel ratio feedback control is started, the fuel adhering to the vicinity of the intake port (hereinafter referred to as port wet) remains, so that the fuel injection amount is originally It is corrected further to the lean side than the required amount. After that, when there is no port wet and the air-fuel ratio indicated by the output signal of the air-fuel ratio sensor switches from rich to lean, control is performed to increase the fuel injection amount correction coefficient as described above, but port wet remains. Due to excessive correction to the lean side during the period, there is a problem that even if the fuel injection amount correction factor is increased, the fuel injection amount correction factor may be leaner than the stoichiometric air-fuel ratio. .

特開昭６２−１２９５４３号公報Japanese Patent Laid-Open No. 62-129543

本発明は以上の点に着目し、燃料カットからの復帰直後の空燃比リッチ制御が終了した直後のポートウェットが残存している期間に、燃料噴射量が過度にリーン側に補正されることによる不具合を解消することを目的とする。   The present invention pays attention to the above points, and the fuel injection amount is excessively corrected to the lean side in the period in which the port wet remains immediately after the air-fuel ratio rich control immediately after the return from the fuel cut ends. The purpose is to solve the problem.

以上の課題を解決すべく、本発明に係る内燃機関の制御装置は、以下に述べるような構成を有する。すなわち本発明に係る内燃機関の制御装置は、吸気ポートに燃料を噴射し、点火プラグを介した火花点火により混合気に着火する構成の内燃機関の制御を行うとともに、空燃比センサの出力信号に基づき空燃比のフィードバック制御を行うものであって、内燃機関の回転数が所定回転数を上回りかつアクセル操作量が所定の閾値を下回る場合に燃料カットを行うとともに、所定の燃料カット終了条件が成立したときには、燃料カットを終了する制御を行い、燃料カットからの復帰直後には空燃比をリッチ側に設定する空燃比リッチ制御を行い、この空燃比リッチ制御終了後の最初の空燃比フィードバック制御のリーン側の補正係数にガードを掛け、所定期間、通常のよりも空燃比の補正量の増大の速度を小さくしつつ空燃比をリーン側に制御する。   In order to solve the above problems, a control device for an internal combustion engine according to the present invention has a configuration as described below. That is, the control apparatus for an internal combustion engine according to the present invention controls an internal combustion engine configured to inject fuel into an intake port and ignite an air-fuel mixture by spark ignition through an ignition plug, and to output an air-fuel ratio sensor output signal. Based on the feedback control of the air-fuel ratio, the fuel cut is performed when the rotational speed of the internal combustion engine exceeds the predetermined rotational speed and the accelerator operation amount falls below the predetermined threshold, and the predetermined fuel cut end condition is satisfied. When the fuel cut is performed, the control for terminating the fuel cut is performed. Immediately after the return from the fuel cut, the air / fuel ratio rich control for setting the air / fuel ratio to the rich side is performed. Applying a guard to the lean correction factor and controlling the air / fuel ratio to the lean side while reducing the rate of increase of the air / fuel ratio correction amount over the specified period. That.

このようなものであれば、燃料カットからの復帰直後の空燃比リッチ制御が終了した直後のポートウェットが残存している期間においては、空燃比をリーン側に制御する際の空燃比の補正量の増大の速度を小さくしているので、燃料噴射量が過度にリーン側に補正され、空燃比がリッチからリーンに切り替わった際に燃料噴射量の補正係数を増加させてもなお燃料噴射量の補正係数が理論空燃比よりもリーン側となる不具合の発生を抑制できる。   If this is the case, during the period in which the port wet remains immediately after the air-fuel ratio rich control immediately after returning from the fuel cut, the air-fuel ratio correction amount for controlling the air-fuel ratio to the lean side Therefore, even if the fuel injection amount correction factor is increased when the fuel injection amount is excessively corrected to the lean side and the air-fuel ratio is switched from rich to lean, the fuel injection amount still increases. Occurrence of a problem that the correction coefficient is leaner than the theoretical air-fuel ratio can be suppressed.

本発明によれば、燃料カットからの復帰直後の空燃比リッチ制御が終了した直後のポートウェットが残存している期間に、燃料噴射量が過度にリーン側に補正されることによる不具合を解消することができる。   According to the present invention, inconvenience due to excessive correction of the fuel injection amount to the lean side during a period in which the port wet remains immediately after the air-fuel ratio rich control immediately after the return from the fuel cut ends. be able to.

本発明の一実施形態に係る内燃機関及び制御装置の概略構成図。1 is a schematic configuration diagram of an internal combustion engine and a control device according to an embodiment of the present invention. フロントＯ2センサの出力を参照した空燃比フィードバック制御の模様を示すタイミング図。Timing diagram illustrating the pattern of the air-fuel ratio feedback control with reference to the output of the front O 2 sensor. 制御中心補正量ＦＡＣＦと遅延時間ＴＤＲ、ＴＤＬとの関係を例示するグラフ。The graph which illustrates the relationship between control center correction amount FACF and delay time TDR, TDL. リアＯ2センサの出力を参照した空燃比フィードバック制御の模様を示すタイミング図。Timing diagram illustrating the pattern of the air-fuel ratio feedback control with reference to the output of the rear O 2 sensor. 同実施形態の制御装置が実行する処理の手順例を示すフローチャート。The flowchart which shows the example of a procedure of the process which the control apparatus of the embodiment performs. 同実施形態の制御装置が実行する処理の作用を示すタイミング図。The timing diagram which shows the effect | action of the process which the control apparatus of the embodiment performs. 従来の車両の制御装置が実行する処理の作用を示すタイミング図。The timing diagram which shows the effect | action of the process which the conventional vehicle control apparatus performs.

本発明の一実施形態を、図１〜図７を参照して説明する。   An embodiment of the present invention will be described with reference to FIGS.

図１に、本実施形態における車両用内燃機関の概要を示す。本実施形態における内燃機関は、火花点火式ガソリンエンジンであり、複数の気筒１（図１には、そのうち一つを図示している）を具備している。各気筒１の吸気ポート近傍には、燃料を噴射するインジェクタ１１を設けている。また、各気筒１の燃焼室の天井部に、点火プラグ１２を取り付けてある。点火プラグ１２は、点火コイルにて発生した誘導電圧の印加を受けて、中心電極と接地電極との間で火花放電を惹起するものである。点火コイルは、半導体スイッチング素子であるイグナイタとともに、コイルケースに一体的に内蔵される。   FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. The internal combustion engine in the present embodiment is a spark ignition gasoline engine and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel is provided. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives spark voltage generated by the ignition coil and causes spark discharge between the center electrode and the ground electrode. The ignition coil is integrally incorporated in a coil case together with an igniter that is a semiconductor switching element.

吸気を供給するための吸気通路３は、外部から空気を取り入れて各気筒１の吸気ポートへと導く。吸気通路３上には、エアクリーナ３１、電子スロットルバルブ３２、サージタンク３３、吸気マニホルド３４を、上流からこの順序に配置している。   The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream.

排気を排出するための排気通路４は、気筒１内で燃料を燃焼させたことで生じる排気を各気筒１の排気ポートから外部へと導く。この排気通路４上には、排気マニホルド４２及び排気浄化用の三元触媒４１を配置している。   The exhaust passage 4 for discharging the exhaust guides the exhaust generated by burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4.

排気通路４における触媒４１の上流及び／または下流には、排気通路を流通する排気ガスの空燃比を検出するための空燃比センサ４３、４４を設置する。空燃比センサ４３、４４はそれぞれ、排気ガスの空燃比に対して非線形な出力特性を有するＯ2センサであって
もよく、排気ガスの空燃比に比例した出力特性を有するリニアＡ／Ｆセンサであってもよい。本実施形態では、触媒４１の上流側及び下流側の各空燃比センサ４３、４４について、排気ガス中の酸素濃度に応じた電圧信号を出力するＯ2センサを想定している。Ｏ2センサ４３、４４の出力特性は、ウィンドウの範囲では空燃比に対する出力の変化率が大きく急峻な傾きを示し、それよりも空燃比が大きいリーン領域では低位飽和値に漸近し、空燃比が小さいリッチ領域では高位飽和値に漸近する、いわゆるＺ特性曲線を描く。 Air-fuel ratio sensors 43 and 44 for detecting the air-fuel ratio of the exhaust gas flowing through the exhaust passage are installed upstream and / or downstream of the catalyst 41 in the exhaust passage 4. Each of the air-fuel ratio sensors 43 and 44 may be an O 2 sensor having a non-linear output characteristic with respect to the air-fuel ratio of the exhaust gas, or a linear A / F sensor having an output characteristic proportional to the air-fuel ratio of the exhaust gas. There may be. In the present embodiment, an O 2 sensor that outputs a voltage signal corresponding to the oxygen concentration in the exhaust gas is assumed for each of the upstream and downstream air-fuel ratio sensors 43 and 44 of the catalyst 41. The output characteristics of the O 2 sensors 43 and 44 show a large and steep slope of the output change rate with respect to the air-fuel ratio in the window range, and asymptotically approach the low saturation value in the lean region where the air-fuel ratio is larger than that. In a small rich region, a so-called Z characteristic curve that draws an asymptotic approach to a high saturation value is drawn.

本実施形態の内燃機関の制御装置たるＥＣＵ０は、プロセッサ、メモリ、入力インタフェース、出力インタフェース等を有したマイクロコンピュータシステムである。   The ECU 0 as the control device for the internal combustion engine of the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

入力インタフェースには、車両の実車速を検出する車速センサから出力される車速信号ａ、クランクシャフトの回転角度及びエンジン回転数を検出するエンジン回転センサから出力されるクランク角信号ｂ、アクセルペダルの踏込量またはスロットルバルブ３２の開度をアクセル開度（いわば、要求負荷）として検出するセンサから出力されるアクセル開度信号ｃ、吸気通路３（特に、サージタンク３３）内の吸気温及び吸気圧を検出する温度・圧力センサから出力される吸気温・吸気圧信号ｄ、機関の冷却水温を検出する水温センサから出力される冷却水温信号ｅ、触媒４１の上流側における排気ガスの空燃比を検出する空燃比センサ４３から出力される空燃比信号ｆ、触媒４１の下流側における排気ガスの空燃比を検出する空燃比センサ４４から出力される空燃比信号ｇ、吸気カムシャフトまたは排気カムシャフトの複数のカム角にてカム角センサから出力されるカム角信号ｈ等が入力される。   The input interface includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from an engine rotation sensor that detects the rotation angle and engine speed of the crankshaft, and depression of an accelerator pedal. The accelerator opening signal c output from a sensor that detects the amount or the opening of the throttle valve 32 as an accelerator opening (so-called required load), the intake air temperature and the intake pressure in the intake passage 3 (particularly, the surge tank 33). The intake air temperature / intake pressure signal d output from the temperature / pressure sensor to be detected, the coolant temperature signal e output from the water temperature sensor to detect the coolant temperature of the engine, and the air-fuel ratio of the exhaust gas upstream of the catalyst 41 are detected. An air-fuel ratio signal f output from the air-fuel ratio sensor 43 and an air-fuel ratio sensor for detecting the air-fuel ratio of the exhaust gas downstream of the catalyst 41 The air-fuel ratio signal g outputted from the 4, the cam angle signal h or the like to be output from the cam angle sensor is input in a plurality of cam angle of the intake camshaft or an exhaust camshaft.

出力インタフェースからは、点火プラグ１２のイグナイタに対して点火信号ｉ、インジェクタ１１に対して燃料噴射信号ｊ、スロットルバルブ３２に対して開度操作信号ｋ等を出力する。   From the output interface, an ignition signal i is output to the igniter of the spark plug 12, a fuel injection signal j is output to the injector 11, an opening operation signal k is output to the throttle valve 32, and the like.

ＥＣＵ０のプロセッサは、予めメモリに格納されているプログラムを解釈、実行し、運転パラメータを演算して内燃機関の運転を制御する。ＥＣＵ０は、内燃機関の運転制御に必要な各種情報ａ、ｂ、ｃ、ｄ、ｅ、ｆ、ｇ、ｈを入力インタフェースを介して取得し、要求される燃料噴射量、燃料噴射タイミング（一度の燃焼に対する燃料噴射の回数を含む）、燃料噴射圧、点火タイミング等といった運転パラメータを決定する。運転パラメータの決定手法自体は、既知のものを採用することが可能である。しかして、ＥＣＵ０は、運転パラメータに対応した各種制御信号ｉ、ｊ、ｋを出力インタフェースを介して印加する。   The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, h necessary for operation control of the internal combustion engine via the input interface, and requests the required fuel injection amount, fuel injection timing (once Operating parameters such as fuel injection pressure, ignition timing, etc.). As the operation parameter determination method itself, a known method can be adopted. Accordingly, the ECU 0 applies various control signals i, j, k corresponding to the operation parameters via the output interface.

本実施形態のＥＣＵ０は、気筒１に充填される混合気の空燃比、ひいては気筒１から排出され三元触媒４１へと導かれる排気ガスの空燃比をフィードバック制御する。ＥＣＵ０は、まず、吸気圧及び吸気温、エンジン回転数、要求ＥＧＲ率等から、気筒１に充填される新気の量を算出し、これに見合った基本噴射量ＴＰを決定する。次いで、この基本噴射量ＴＰを、触媒４１の上流側の空燃比に応じて定まるフィードバック補正係数ＦＡＦで補正し、さらには内燃機関の状況に応じて定まる各種補正係数Ｋやインジェクタ３６の無効噴射時間ＴＡＵＶをも加味して、最終的な燃料噴射時間（インジェクタ１１に対する通電時間）Ｔを算定する。燃料噴射時間Ｔは、
Ｔ＝ＴＰ×ＦＡＦ×Ｋ＋ＴＡＵＶ （１）
となる。そして、燃料噴射時間Ｔだけインジェクタ１１に信号ｊを入力、インジェクタ１１を開弁して燃料を噴射させる。 The ECU 0 of the present embodiment performs feedback control of the air-fuel ratio of the air-fuel mixture charged in the cylinder 1 and, consequently, the air-fuel ratio of the exhaust gas discharged from the cylinder 1 and led to the three-way catalyst 41. The ECU 0 first calculates the amount of fresh air charged into the cylinder 1 from the intake pressure and intake temperature, the engine speed, the required EGR rate, etc., and determines the basic injection amount TP corresponding to this. Next, the basic injection amount TP is corrected with a feedback correction coefficient FAF determined according to the air-fuel ratio on the upstream side of the catalyst 41. Further, various correction coefficients K determined according to the state of the internal combustion engine and the invalid injection time of the injector 36 The final fuel injection time (energization time for the injector 11) T is calculated in consideration of TAUV. The fuel injection time T is
T = TP × FAF × K + TAUV (1)
It becomes. Then, the signal j is input to the injector 11 for the fuel injection time T, and the injector 11 is opened to inject fuel.

触媒４１の上流側の空燃比信号ｆを参照したフィードバック制御は、例えば、内燃機関の冷却水温が所定温度以上であり、燃料カット中でなく、パワー増量中でなく、内燃機関の始動から所定時間が経過し、触媒４１の上流側の空燃比センサ４３が活性中、吸気圧が正常である、等の諸条件が全て成立している場合に行う。   The feedback control with reference to the air-fuel ratio signal f on the upstream side of the catalyst 41 is performed, for example, when the cooling water temperature of the internal combustion engine is equal to or higher than a predetermined temperature, the fuel is not cut, the power is not increased, and the predetermined time has elapsed from the start of the internal combustion engine. This is performed when all of the conditions such as the air-fuel ratio sensor 43 upstream of the catalyst 41 is active and the intake pressure is normal are satisfied.

図２に示すように、ＥＣＵ０は、触媒４１の上流側のガスの空燃比を検出するセンサであるフロントＯ2センサ４３の出力電圧ｆを、目標空燃比に相当する電圧値（鎖線で表す
）と比較して、その目標電圧値よりも高ければリッチ、その目標電圧値よりも低ければリーンと判定する。そして、センサ出力ｆがリーンからリッチに切り替わったときには、リッチ判定遅延時間ＴＤＲの経過を待って、フィードバック補正係数ＦＡＦをスキップ値ＲＳＭだけ減少させる。その後、補正係数ＦＡＦを所定時間あたりリーン積分値ＫＩＭだけ逓減させる。補正係数ＦＡＦの減少に伴い、燃料噴射量が絞られて、混合気の空燃比がリーンへと向かう。 As shown in FIG. 2, the ECU 0 sets the output voltage f of the front O 2 sensor 43 that is a sensor for detecting the air-fuel ratio of the gas upstream of the catalyst 41 to a voltage value (represented by a chain line) corresponding to the target air-fuel ratio. As compared with the above, it is determined that the value is rich if the value is higher than the target voltage value, and the value is lean if the value is lower than the target voltage value. When the sensor output f is switched from lean to rich, the feedback correction coefficient FAF is decreased by the skip value RSM after the rich determination delay time TDR has elapsed. Thereafter, the correction coefficient FAF is decreased by a lean integral value KIM per predetermined time. As the correction coefficient FAF decreases, the fuel injection amount is reduced, and the air-fuel ratio of the air-fuel mixture moves toward lean.

あるいは、センサ出力ｆがリッチからリーンに切り替わったときには、リーン判定遅延時間ＴＤＬの経過を待って、フィードバック補正係数ＦＡＦをスキップ値ＲＳＰだけ増加させる。その後、補正係数ＦＡＦを所定時間あたりリッチ積分値ＫＩＰだけ逓増させる。補正係数ＦＡＦの増加に伴い、燃料噴射量が上積みされて、混合気の空燃比がリッチへと向かう。   Alternatively, when the sensor output f is switched from rich to lean, the feedback correction coefficient FAF is increased by the skip value RSP after the lean determination delay time TDL has elapsed. Thereafter, the correction coefficient FAF is increased by the rich integral value KIP per predetermined time. As the correction coefficient FAF increases, the fuel injection amount is increased and the air-fuel ratio of the air-fuel mixture becomes richer.

遅延時間ＴＤＲ、ＴＤＬは、制御中心補正量ＦＡＣＦに応じて増減する。図３に、補正量ＦＡＣＦと遅延時間ＴＤＲ、ＴＤＬとの関係を例示する。補正量ＦＡＣＦが大きくなるほど、リッチ判定遅延時間ＴＤＲ（実線で表す）は延長され、リーン判定遅延時間ＴＤＬ（破線で表す）は短縮される。さすれば、フィードバック補正係数ＦＡＦが増加から減少に転じる時期が遅れ、減少から増加に転じる時期が早まる。結果、燃料噴射量が平均的に増すこととなり、空燃比フィードバック制御の制御中心がリッチ側に変位する。   The delay times TDR and TDL increase or decrease according to the control center correction amount FACF. FIG. 3 illustrates the relationship between the correction amount FACF and the delay times TDR and TDL. As the correction amount FACF increases, the rich determination delay time TDR (represented by a solid line) is extended, and the lean determination delay time TDL (represented by a broken line) is shortened. In this case, the time when the feedback correction coefficient FAF starts to decrease is delayed, and the time when the feedback correction coefficient FAF starts to increase increases. As a result, the fuel injection amount increases on average, and the control center of the air-fuel ratio feedback control is displaced to the rich side.

他方、補正量ＦＡＣＦが小さくなるほど、リッチ判定遅延時間ＴＤＲは短縮され、リーン判定遅延時間ＴＤＬは延長される。さすれば、フィードバック補正係数ＦＡＦが増加から減少に転じる時期が早まり、減少から増加に転じる時期が遅れる。結果、燃料噴射量が平均的に減ることとなり、空燃比フィードバック制御の制御中心がリーン側に変位する。   On the other hand, the smaller the correction amount FACF, the shorter the rich determination delay time TDR and the lean determination delay time TDL. Then, the time when the feedback correction coefficient FAF starts to decrease from the increase is advanced, and the time when the feedback correction coefficient FAF starts to increase is delayed. As a result, the fuel injection amount decreases on average, and the control center of the air-fuel ratio feedback control is displaced to the lean side.

ＥＣＵ０は、空燃比のフィードバック制御中、上記の制御中心補正量ＦＡＣＦをも算出する。原則として、ＦＡＣＦは、触媒４１の下流側の空燃比に応じて定まる。触媒４１の下流側の空燃比信号ｇを参照したフィードバック制御は、例えば、冷却水温が所定温度以上であり、空燃比フィードバック制御の開始から所定時間が経過し、フロントＯ2センサ
４３が活性してから所定時間が経過し、過渡期の燃料補正量が所定値を下回り、アイドル状態で車速が０若しくは０に近い所定値以下であるかまたは非アイドル状態で所定の運転領域にある、等の諸条件が全て成立している場合に行う。 The ECU 0 also calculates the control center correction amount FACF during the air-fuel ratio feedback control. In principle, the FACF is determined according to the air-fuel ratio on the downstream side of the catalyst 41. In the feedback control with reference to the air-fuel ratio signal g on the downstream side of the catalyst 41, for example, the cooling water temperature is equal to or higher than a predetermined temperature, a predetermined time has elapsed from the start of the air-fuel ratio feedback control, and the front O 2 sensor 43 is activated. The fuel correction amount in the transition period is below a predetermined value, the vehicle speed is 0 or less than a predetermined value close to 0 in the idle state, or is in the predetermined operating range in the non-idle state, etc. Performed when all the conditions are met.

図４に示すように、ＥＣＵ０は、触媒４１の下流側のガスの空燃比を検出するセンサであるリアＯ2センサ４４の出力電圧ｇを、目標空燃比に相当する電圧値（鎖線で表す。こ
の電圧値は、フロントＯ2センサ４３の出力信号ｆの目標電圧値とは一致しないことがあ
る）と比較して、その目標電圧値よりも高ければリッチ、その目標電圧値よりも低ければリーンと判定する。そして、センサ出力ｇがリッチである間は、制御中心補正量ＦＡＣＦを所定時間あたりリーン積分値ＦＡＣＦＫＩＭだけ逓減させる。既に述べたように、補正
量ＦＡＣＦの減少に伴い、空燃比制御中心はリーンへと向かう。 As shown in FIG. 4, the ECU 0 represents the output voltage g of the rear O 2 sensor 44 that is a sensor for detecting the air-fuel ratio of the gas downstream of the catalyst 41 by a voltage value (a chain line) corresponding to the target air-fuel ratio. This voltage value may not match the target voltage value of the output signal f of the front O 2 sensor 43), and is rich if it is higher than the target voltage value, and lean if it is lower than the target voltage value. Is determined. Then, while the sensor output g is rich, the control center correction amount FACF is decreased by a lean integral value FACFKIM per predetermined time. As described above, the air-fuel ratio control center moves toward lean as the correction amount FACF decreases.

逆に、センサ出力ｇがリーンである間は、制御中心補正量ＦＡＣＦを所定時間あたりリッチ積分値ＦＡＣＦＫＩＰだけ逓増させる。補正量ＦＡＣＦの増加に伴い、空燃比制御中心はリッチへと向かう。   On the contrary, while the sensor output g is lean, the control center correction amount FACF is increased by the rich integral value FACFKIP per predetermined time. As the correction amount FACF increases, the air-fuel ratio control center moves toward rich.

また、本実施形態では、内燃機関の回転数が所定回転数を上回りかつアクセル操作量が所定の閾値を下回る場合に燃料カットを行うとともに、所定の燃料カット終了条件が成立したときには、燃料カットを終了する制御をおこなう。これら燃料カット制御及び燃料カット終了制御は、従来行われているものとして周知のものと同様の手法により行うようにしているので、詳細な説明は省略する。   Further, in the present embodiment, the fuel cut is performed when the rotation speed of the internal combustion engine exceeds a predetermined rotation speed and the accelerator operation amount falls below a predetermined threshold value, and when the predetermined fuel cut end condition is satisfied, the fuel cut is performed. Control to end. The fuel cut control and the fuel cut end control are performed by a method similar to that known in the art and will not be described in detail.

しかして本実施形態では、燃料カットからの復帰直後には空燃比をリッチ側に設定する空燃比リッチ制御を行うとともに、この空燃比リッチ制御終了後の最初の空燃比フィードバック制御のリーン側の補正係数にガードを掛け、所定期間、通常のよりも空燃比の補正量の増大の速度を小さくしつつ空燃比をリーン側に制御するようにしている。   Therefore, in the present embodiment, the air-fuel ratio rich control is performed to set the air-fuel ratio to the rich side immediately after the return from the fuel cut, and the correction on the lean side of the first air-fuel ratio feedback control after the completion of the air-fuel ratio rich control is performed. The coefficient is guarded, and the air-fuel ratio is controlled to the lean side while reducing the rate of increase of the air-fuel ratio correction amount over the predetermined period.

詳述すると、燃料カット終了条件が成立した際には、まず、所定期間の間、燃料噴射量を基本噴射量ＴＰよりも所定割合だけ増量する燃料リッチ制御を行う。次いで、前記所定期間が終了すると、燃料噴射量の空燃比フィードバック制御を開始する。このとき、気筒内の混合気は理論空燃比（Ａ／Ｆ）0よりもリッチ側であるので、空燃比をリーン側に補正する制御が行われる。ここで、ポートウェットの影響が残存していることにより、燃料噴射量が本来の要求量よりもさらにリーン側に補正されることとなるが、このことの影響を逓減すべく、空燃比がリーン側に転じるまで、より具体的にはリアＯ2センサ４４から空燃比がリーンであることを示す空燃比信号ｇが出力されるまでは、前記スキップ値ＲＳＭ及び所定時間あたりリーン積分値ＫＩＭに１よりも小さい正のガード係数Ｇを乗算した値だけ変化させるようにしている。 More specifically, when the fuel cut end condition is satisfied, first, fuel rich control is performed in which the fuel injection amount is increased by a predetermined ratio from the basic injection amount TP during a predetermined period. Next, when the predetermined period ends, air-fuel ratio feedback control of the fuel injection amount is started. At this time, since the air-fuel mixture in the cylinder is richer than the stoichiometric air-fuel ratio (A / F) 0, control is performed to correct the air-fuel ratio to the lean side. Here, since the influence of the port wet remains, the fuel injection amount is corrected further to the lean side than the original required amount. In order to reduce this influence, the air-fuel ratio becomes lean. Until the air-fuel ratio signal g indicating that the air-fuel ratio is lean is output from the rear O 2 sensor 44, more specifically, the skip value RSM and the lean integrated value KIM per predetermined time are set to 1. Only a value obtained by multiplying a smaller positive guard coefficient G is changed.

以下、この空燃比制御プログラムによる制御の手順についてフローチャートである図５を参照しつつ以下に述べる。   Hereinafter, the control procedure by the air-fuel ratio control program will be described with reference to FIG. 5 which is a flowchart.

まず、燃料カット終了条件が成立した後、所定期間の間、燃料噴射量を基本噴射量ＴＰよりも所定割合だけ増量する燃料リッチ制御を行う（ステップＳ１）。前記所定期間が終了すると、空燃比フィードバック制御に移行する。まず、式（１）のフィードバック補正係数ＦＡＦを、初期値である１から前記スキップ値ＲＳＭに前記ガード係数Ｇを乗算した値だけ減少させる（ステップＳ２）。それから、リアＯ2センサ４４から空燃比がリーンであることを示す空燃比信号ｇが出力されるまで（ステップＳ３）、補正係数ＦＡＦを所定時間あたり前記リーン積分値ＫＩＭに前記ガード係数Ｇを乗算した値だけ逓減させる（ステップＳ４）。そして、リアＯ2センサ４４から空燃比がリーンであることを示す空燃比信号ｇが出力された後は、通常の空燃比フィードバック制御に移行する（ステップＳ５）。 First, after the fuel cut end condition is satisfied, fuel rich control is performed to increase the fuel injection amount by a predetermined ratio from the basic injection amount TP for a predetermined period (step S1). When the predetermined period ends, the routine proceeds to air-fuel ratio feedback control. First, the feedback correction coefficient FAF of Expression (1) is decreased from an initial value of 1 by a value obtained by multiplying the skip value RSM by the guard coefficient G (step S2). Then, until the air-fuel ratio signal g indicating that the air-fuel ratio is lean is output from the rear O 2 sensor 44 (step S3), the lean integral value KIM is multiplied by the guard coefficient G per predetermined time with the correction coefficient FAF. The value is decreased by the determined value (step S4). Then, after the air-fuel ratio signal g indicating that the air-fuel ratio is lean is output from the rear O 2 sensor 44, the routine proceeds to normal air-fuel ratio feedback control (step S5).

すなわち、このような制御によれば、図６に示すように、時刻ｔ1に燃料カット終了条件が成立すると、時刻ｔ2まで燃料リッチ制御が行われ、この燃料リッチ制御が終了した直後は、空燃比がリーンであることを示す空燃比信号ｇが出力されるまで、すなわち時刻ｔ3まで、通常よりも緩やかに燃料噴射量を減少させる制御が行われる。ここで、従来の制御を行った場合は、図７に示すように、空燃比がリーンであることを示す空燃比信号ｇが出力されるまで、すなわち時刻ｔ3まで、通常と同じ割合で燃料噴射量を減少させる制御を行うので、時刻ｔ3で空燃比がリーンに転じたことを反映してフィードバック補正係数ＦＡＦをスキップ値ＲＳＰだけ増加させた場合でも、該フィードバック補正係数ＦＡＦが１を下回ったままであり、空燃比が過剰にリーン側となる。これに対して、本実施形態の制御では、前段で述べたような制御を行うことにより、時刻ｔ3での前記フィードバック補正係数ＦＡＦが大きく、空燃比がリーンに転じたことを反映してフィードバック補正係数ＦＡＦをスキップ値ＲＳＰだけ増加させることにより、該フィードバック補正係数ＦＡＦが１を上回る、換言すれば空燃比が直ちにリッチ側に転じるように燃料噴射量を増加させることができる。 That is, according to such control, as shown in FIG. 6, when the fuel cut end condition is satisfied at time t 1 , the fuel rich control is performed until time t 2 , and immediately after the fuel rich control ends, Until the air-fuel ratio signal g indicating that the air-fuel ratio is lean is output, that is, until time t 3 , control is performed to decrease the fuel injection amount more slowly than usual. Here, when the conventional control is performed, as shown in FIG. 7, the fuel is supplied at the same rate as usual until the air-fuel ratio signal g indicating that the air-fuel ratio is lean is output, that is, until time t 3. Since control is performed to reduce the injection amount, even when the feedback correction coefficient FAF is increased by the skip value RSP to reflect that the air-fuel ratio has changed to lean at time t 3 , the feedback correction coefficient FAF is less than 1. The air-fuel ratio becomes excessively lean. On the other hand, in the control of the present embodiment, the feedback control coefficient FAF at time t 3 is large by performing the control described in the previous stage, and the feedback reflects that the air-fuel ratio has changed to lean. By increasing the correction coefficient FAF by the skip value RSP, the fuel injection amount can be increased so that the feedback correction coefficient FAF exceeds 1, that is, the air-fuel ratio immediately turns to the rich side.

すなわち、本実施形態によれば、燃料カットからの復帰直後の空燃比リッチ制御が終了した直後のポートウェットが残存している期間に、燃料噴射量が過度にリーン側に補正されることによる不具合を解消することができる。   That is, according to the present embodiment, the fuel injection amount is excessively corrected to the lean side during the period in which the port wet remains immediately after the air-fuel ratio rich control immediately after the return from the fuel cut ends. Can be eliminated.

なお、本発明は以上に述べた実施形態に限らない。   The present invention is not limited to the embodiment described above.

例えば、上述した実施形態では、燃料カット終了条件成立後の増量補正が終了してから、リアＯ2センサ４４から空燃比がリーンであることを示す空燃比信号が出力されるまでの期間、リーン積分値ＫＩＭにガード係数Ｇを乗算するようにしているが、燃料カット終了条件成立後の増量補正が終了してから所定の長さの期間が経過するまでの間、リーン積分値ＫＩＭにガード係数Ｇを乗算する制御を行うようにしてもよい。この場合において、前記所定時間は、燃料が揮発しにくくなるにつれて長くなるように設定する。具体的には、燃料が揮発しにくいものである場合、始動時の回転数の上昇の速度が遅くなることに着目して、始動時に所定の回転数に達するまでの時間が長くなるほど前記リーン積分値ＫＩＭにガード係数Ｇを乗算する期間の長さも長くする制御を行う。 For example, in the above-described embodiment, the lean period from when the increase correction after the fuel cut end condition is satisfied to when the air-fuel ratio signal indicating that the air-fuel ratio is lean is output from the rear O 2 sensor 44 is lean. The integral value KIM is multiplied by the guard coefficient G. The lean integral value KIM is multiplied by the guard coefficient until the predetermined length of time elapses after the increase correction after the fuel cut end condition is satisfied. You may make it perform control which multiplies G. In this case, the predetermined time is set to be longer as the fuel is less likely to volatilize. Specifically, when the fuel is difficult to volatilize, paying attention to the fact that the speed of increase in the rotational speed at the time of starting becomes slow, the lean integration becomes longer as the time until reaching the predetermined rotational speed at the time of starting becomes longer. Control is performed to increase the length of the period in which the value KIM is multiplied by the guard coefficient G.

その他、本発明の趣旨を損ねない範囲で種々に変更してよい。   In addition, you may change variously in the range which does not impair the meaning of this invention.

０…制御装置（ＥＣＵ）
１１…燃料噴射弁（インジェクタ）
１２…点火プラグ
４３…空燃比センサ（フロントＯ2センサ）
４４…空燃比センサ（リアＯ2センサ） 0 ... Control unit (ECU)
11 ... Fuel injection valve (injector)
12 ... the spark plug 43 ... the air-fuel ratio sensor (front O 2 sensor)
44 ... Air-fuel ratio sensor (rear O 2 sensor)

Claims (1)

吸気ポートに燃料を噴射し、点火プラグを介した火花点火により混合気に着火する構成の内燃機関の制御を行うとともに、空燃比センサの出力信号に基づき空燃比のフィードバック制御を行う内燃機関の制御装置であって、
内燃機関の回転数が所定回転数を上回りかつアクセル操作量が所定の閾値を下回る場合に燃料カットを行うとともに、所定の燃料カット終了条件が成立したときには、燃料カットを終了する制御を行い、
燃料カットからの復帰直後には空燃比をリッチ側に設定する空燃比リッチ制御を行い、この空燃比リッチ制御終了後の最初の空燃比フィードバック制御のリーン側の補正係数にガードを掛け、所定期間、通常のよりも空燃比の補正量の増大の速度を小さくしつつ空燃比をリーン側に制御することを特徴とする内燃機関の制御装置。 Control of an internal combustion engine configured to inject fuel into an intake port and ignite an air-fuel mixture by spark ignition through an ignition plug, and control of the internal combustion engine to perform air-fuel ratio feedback control based on an output signal of the air-fuel ratio sensor A device,
When the rotational speed of the internal combustion engine exceeds a predetermined rotational speed and the accelerator operation amount is below a predetermined threshold, the fuel cut is performed, and when a predetermined fuel cut end condition is satisfied, a control to end the fuel cut is performed,
Immediately after the return from the fuel cut, air-fuel ratio rich control is performed to set the air-fuel ratio to the rich side, and the lean-side correction coefficient of the first air-fuel ratio feedback control after the air-fuel ratio rich control is finished is guarded, for a predetermined period. A control apparatus for an internal combustion engine, characterized in that the air-fuel ratio is controlled to the lean side while the rate of increase of the correction amount of the air-fuel ratio is made smaller than usual.
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JP2008202563A (en) * 2007-02-22 2008-09-04 Toyota Motor Corp Air/fuel ratio control device for internal combustion engine

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Publication number Priority date Publication date Assignee Title
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