JP2000234541A - Fuel injection control device for internal combustion engine - Google Patents

Fuel injection control device for internal combustion engine

Info

Publication number
JP2000234541A
JP2000234541A JP11035834A JP3583499A JP2000234541A JP 2000234541 A JP2000234541 A JP 2000234541A JP 11035834 A JP11035834 A JP 11035834A JP 3583499 A JP3583499 A JP 3583499A JP 2000234541 A JP2000234541 A JP 2000234541A
Authority
JP
Japan
Prior art keywords
engine
air
fuel ratio
fuel injection
fuel
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
Application number
JP11035834A
Other languages
Japanese (ja)
Other versions
JP3680245B2 (en
Inventor
Junichi Kako
純一 加古
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toyota Motor Corp
Original Assignee
Toyota Motor Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Toyota Motor Corp filed Critical Toyota Motor Corp
Priority to JP03583499A priority Critical patent/JP3680245B2/en
Publication of JP2000234541A publication Critical patent/JP2000234541A/en
Application granted granted Critical
Publication of JP3680245B2 publication Critical patent/JP3680245B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Landscapes

  • Exhaust Gas After Treatment (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

Abstract

PROBLEM TO BE SOLVED: To shorten the time to reach a rich air-fuel ratio in rich spike operation. SOLUTION: An NOx occulsion reduction catalyst 7 is arranged in an exhaust passage 2 of an internal combustion engine 1 having inner cylinder injection valves 111 to 114. NOx in the exhaust gas is absorbed by the catalyst 7 by operating the engine under a lean air-fuel ratio stratification combustion mode. Then the engine is operated under a rich air-fuel ratio even mixture combustion mode. By this rich-spike operation, NOx absorbed by the catalyst 7 is reduced and purified. An electronic control unit(ECU) 30 sets an engine fuel injection amount under the rich air-fuel ratio even mixture combustion mode during rich-spike operation, based on an intaken air amount and an engine speed. Since the fuel injection amount is set according to the actual intake amount, it is possible to vary the engine air-fuel ratio to a specified rich value in a short time irrespective of variation retarding of the intake amount at the time of changeover of the modes.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【発明の属する技術分野】本発明は、要求機関負荷に応
じて内燃機関の燃焼空燃比を制御する内燃機関の燃料噴
射制御装置に関する。The present invention relates to a fuel injection control device for an internal combustion engine that controls a combustion air-fuel ratio of the internal combustion engine according to a required engine load.

【０００２】[0002]

【従来の技術】機関の各気筒内に直接燃料を噴射する筒
内燃料噴射弁を備え、必要に応じて機関の運転空燃比を
リーン空燃比とリッチ空燃比とに制御するとともに、機
関燃焼モードをリーン空燃比成層燃焼と均質混合気燃焼
とに切り換える内燃機関が知られている。2. Description of the Related Art An in-cylinder fuel injection valve for directly injecting fuel into each cylinder of an engine is provided. The operating air-fuel ratio of the engine is controlled to a lean air-fuel ratio and a rich air-fuel ratio as required. There is known an internal combustion engine that switches between a lean air-fuel ratio stratified combustion and a homogeneous mixture combustion.

【０００３】このような筒内噴射式内燃機関では、例え
ば機関の軽中負荷運転時等には各気筒の圧縮行程に筒内
燃料噴射弁から燃料噴射を行い、可燃混合気を点火プラ
グ付近に成層させることにより全体として極めてリーン
な空燃比で機関を運転することを可能としている。ま
た、これらの機関では高負荷運転時には各気筒の吸気行
程に燃料噴射を行い燃焼室全体に均質な可燃空燃比の混
合気を形成する均質混合気燃焼を行うことにより機関出
力の増大を可能としている。すなわち、これらの筒内燃
料噴射機関では、機関負荷条件に応じて機関の運転モー
ドがリーン空燃比の成層燃焼モードと均質混合気燃焼モ
ードとの間で切り換えられる。[0003] In such a direct injection internal combustion engine, for example, when the engine is operating at light or medium load, fuel is injected from the direct fuel injection valve during the compression stroke of each cylinder, and a combustible air-fuel mixture is supplied to the vicinity of the ignition plug. The stratification makes it possible to operate the engine with an extremely lean air-fuel ratio as a whole. In addition, these engines can increase the engine output by performing fuel injection during the intake stroke of each cylinder during high-load operation and performing homogeneous mixture combustion to form a homogeneous mixture with a combustible air-fuel ratio throughout the combustion chamber. I have. That is, in these in-cylinder fuel injection engines, the operation mode of the engine is switched between a stratified combustion mode having a lean air-fuel ratio and a homogeneous mixture combustion mode in accordance with the engine load condition.

【０００４】一方、リーン空燃比の排気中のＮＯX を浄
化するＮＯX 吸蔵還元触媒を備えた排気浄化装置が知ら
れている。ＮＯX 吸蔵還元触媒は流入する排気の空燃比
がリーンのときに排気中のＮＯX を吸収し、流入する排
気の空燃比が理論空燃比、またはそれ以下のリッチ空燃
比になると吸収したＮＯX を放出し、還元浄化する性質
を有する。このようなＮＯX 吸蔵還元触媒を用いた排気
浄化装置では、リーン空燃比での運転を続けた後、機関
に要求される負荷とは無関係に機関をリッチ空燃比で運
転してＮＯX 吸蔵還元触媒から吸収したＮＯX を放出さ
せ、還元浄化する必要がある。[0004] On the other hand, there is known an exhaust gas purifying apparatus provided with a NO X storage reduction catalyst for purifying NO X in exhaust gas having a lean air-fuel ratio. The NO X storage reduction catalyst absorbs NO X in the exhaust gas when the air-fuel ratio of the exhaust gas flowing is lean, the air-fuel ratio is the stoichiometric air-fuel ratio of the exhaust gas flowing NO X to or absorbed to become rich air-fuel ratio of the following, And has the property of reducing and purifying. In such an exhaust gas purification apparatus using the NO X storage reduction catalyst, after operating at a lean air-fuel ratio, the engine is operated at a rich air-fuel ratio regardless of the load required for the engine, and the NO X storage reduction is performed. to release NO X absorbed from the catalyst, it is necessary to reduce and purify.

【０００５】この種の筒内燃料噴射式内燃機関の例とし
ては、例えば特開平７−３３２０７１号公報に記載され
たものがある。同公報の機関は排気通路にＮＯX 吸蔵還
元触媒を備えており、極めてリーンな空燃比の成層燃焼
からリッチ空燃比の均質混合気燃焼まで機関運転状態に
応じて広い空燃比範囲で運転される。また、同公報の機
関はリーン空燃比運転中にＮＯ X 吸蔵還元触媒に吸収さ
れたＮＯX を放出、還元浄化するために、リーン空燃比
運転がある程度の時間継続すると機関に要求される負荷
（機関運転状態）とは無関係に所定時間だけ機関運転モ
ードをリッチ空燃比の均質混合気燃焼モードに切り換え
るリッチスパイク操作を行う。[0005] As an example of this kind of in-cylinder fuel injection type internal combustion engine,
For example, Japanese Patent Application Laid-Open No. 7-332071 describes
There are things. The engine of the publication discloses NO in the exhaust passage.XOcclusion return
Stratified combustion with extremely lean air-fuel ratio
Engine operation from combustion to homogeneous air / fuel mixture with rich air-fuel ratio
It is operated in a wide air-fuel ratio range accordingly. In addition, the
Seki is NO during lean air-fuel ratio operation XAbsorbed by storage reduction catalyst
NOXTo reduce and purify the lean air-fuel ratio
Load required by the engine when operation continues for some time
Engine operation mode for a predetermined time regardless of (engine operation state).
Mode to rich air-fuel ratio homogeneous mixture combustion mode
Perform a rich spike operation.

【０００６】ところで、同公報の機関は運転者のアクセ
ルペダル操作とは独立して作動する電子制御スロットル
弁を備えており、機関の成層燃焼モードではスロットル
弁開度はほぼ全開に近い開度に維持される。このため、
同公報の機関は成層燃焼モードでは機関運転状態を制御
する制御量（例えば点火時期、燃料噴射量、燃料噴射時
期、スロットル弁開度等）を運転者のアクセルペダル踏
込み量（アクセル開度）と機関回転数とを用いて予め定
めた関係に基づいて設定し機関の運転状態を制御してい
る。また、リッチスパイク時には、リーン空燃比の成層
燃焼モードからリッチ空燃比の均質混合気燃焼モードに
急激に運転モードを切り換えると燃焼モードの相違と空
燃比の変化とにより機関出力トルクの急変が生じる場合
がある。このため、同公報の機関ではトルク変動が発生
することを防止するために、リッチスパイク操作時には
リッチ空燃比均質燃焼モードに移行後も含めて成層燃焼
モードと同様にアクセル開度と機関回転数とに基づいて
上記制御量を設定するとともに、成層燃焼モード時の値
からリッチ空燃比均質混合気燃焼モードの値まで上記制
御量を徐々に変化させるようにしている。The engine disclosed in this publication has an electronically controlled throttle valve that operates independently of the driver's operation of the accelerator pedal. In the stratified combustion mode of the engine, the throttle valve opening is set to an almost full opening. Will be maintained. For this reason,
In the engine disclosed in the publication, in the stratified combustion mode, a control amount (for example, ignition timing, fuel injection amount, fuel injection timing, throttle valve opening, etc.) for controlling the engine operating state is determined by a driver's accelerator pedal depression amount (accelerator opening). The operating state of the engine is controlled by setting the relationship based on a predetermined relationship using the engine speed. Also, during a rich spike, when the operation mode is suddenly switched from the stratified combustion mode having a lean air-fuel ratio to the homogeneous air-fuel mixture combustion mode having a rich air-fuel ratio, a sudden change in engine output torque occurs due to a difference in the combustion mode and a change in the air-fuel ratio. There is. For this reason, in the engine of the publication, in order to prevent the torque fluctuation from occurring, the accelerator opening and the engine speed are set at the same time as in the stratified charge combustion mode even after shifting to the rich air-fuel ratio homogeneous combustion mode during the rich spike operation. And the control amount is gradually changed from a value in the stratified combustion mode to a value in the rich air-fuel ratio homogeneous mixture combustion mode.

【０００７】[0007]

【発明が解決しようとする課題】ところが、上記前記特
開平７−３３２０７１号公報の機関ではリッチスパイク
操作時に機関の制御量、特に燃料噴射量をアクセル開度
と機関回転数とに基づいて設定しているため問題が生じ
る場合がある。すなわち、同公報ではリッチスパイク操
作時の燃料噴射量、スロットル弁開度等を含めた機関の
制御量はアクセル開度と機関回転数とに基づいて予め準
備された数値マップから決定される。また、この制御量
決定に使用する数値マップとしてはリーン空燃比成層燃
焼モード用マップとリッチ空燃比均質混合気燃焼モード
用マップ、及び中間の空燃比での運転モード用マップが
準備されており、空燃比切り換え時には順次使用するマ
ップを切り換えることにより制御量を時間とともに変化
させてリーン空燃比成層燃焼モードからリッチ空燃比均
質混合気燃焼モードに移行するようにしている。However, in the engine disclosed in Japanese Patent Application Laid-Open No. 7-332071, the control amount of the engine, particularly the fuel injection amount, is set based on the accelerator opening and the engine speed during the rich spike operation. May cause problems. That is, in the publication, the control amount of the engine including the fuel injection amount and the throttle valve opening during the rich spike operation is determined from a numerical map prepared in advance based on the accelerator opening and the engine speed. In addition, as a numerical map used for this control amount determination, a map for a lean air-fuel ratio stratified combustion mode, a map for a rich air-fuel ratio homogeneous mixture combustion mode, and a map for an operation mode at an intermediate air-fuel ratio are prepared. When the air-fuel ratio is switched, the control amount is changed with time by sequentially switching the map to be used, so that the mode shifts from the lean air-fuel ratio stratified combustion mode to the rich air-fuel ratio homogeneous mixture combustion mode.

【０００８】このため、例えば機関がリーン空燃比運転
からリッチ空燃比均質混合気燃焼モードに移行したとき
にはスロットル弁開度と燃料噴射量とはリッチ空燃比均
質混合気燃焼モード用の数値マップからアクセル開度と
機関回転数とに基づいて決定される値に直ちに変更され
ることになる。ところが、実際の運転ではスロットル弁
開度は比較的急速に変化して短時間で設定値になるが、
実際に機関に吸入される空気量はスロットル弁開度の変
化に対して遅れるためスロットル弁開度変化直後は機関
吸入空気量はスロットル弁開度に対応した値になってい
ない場合がある。例えば、リーン空燃比運転からリッチ
空燃比均質混合気燃焼モードに運転が切り換わるとスロ
ットル弁開度はアクセル開度と機関回転数とに基づいて
リッチ空燃比均質混合気燃モード用マップから定まる値
まで低減され、同様に燃料噴射量はマップに基づいて増
量されて所定のリッチ空燃比が達成される。しかし、切
り換え直後は実際の機関吸入空気量は変化後のスロット
ル弁開度に対応した値まで充分に低下していない場合が
あり、切り換え直後はマップから定まる燃料噴射量では
所定のリッチ空燃比を得ることはできず、一時的に機関
の実際の燃焼空燃比が理論空燃比近傍のリーン空燃比に
なってしまう場合が生じる。ＮＯX 吸蔵還元触媒は、リ
ーン空燃比領域では排気空燃比が理論空燃比に近づくほ
どＮＯX の吸蔵能力が低下するため、リッチスパイク操
作時のリッチ空燃比均質混合気燃焼モード移行直後に上
記のように一時的に機関空燃比が理論空燃比近傍のリー
ン空燃比で運転される状態が生じると吸収されていたＮ
ＯX の一部が浄化されないまま放出されてしまう場合が
ある。For this reason, for example, when the engine shifts from the lean air-fuel ratio operation to the rich air-fuel ratio homogeneous mixture combustion mode, the throttle valve opening and the fuel injection amount are obtained from the numerical map for the rich air-fuel ratio homogeneous mixture combustion mode. The value is immediately changed to a value determined based on the opening and the engine speed. However, in actual operation, the throttle valve opening changes relatively quickly and reaches a set value in a short time.
Since the amount of air actually taken into the engine is delayed with respect to the change in the throttle valve opening, the engine intake air amount may not be a value corresponding to the throttle valve opening immediately after the change in the throttle valve opening. For example, when the operation is switched from the lean air-fuel ratio operation to the rich air-fuel ratio homogeneous mixture combustion mode, the throttle valve opening is a value determined from the rich air-fuel ratio homogeneous mixture air-fuel mode map based on the accelerator opening and the engine speed. And the fuel injection amount is similarly increased based on the map to achieve a predetermined rich air-fuel ratio. However, immediately after the switching, the actual engine intake air amount may not be sufficiently reduced to a value corresponding to the throttle valve opening after the change, and immediately after the switching, the fuel injection amount determined from the map may not satisfy the predetermined rich air-fuel ratio. It cannot be obtained, and the actual combustion air-fuel ratio of the engine may temporarily become a lean air-fuel ratio near the stoichiometric air-fuel ratio. The NO X storage reduction catalyst, the exhaust air-fuel ratio is a lean air-fuel ratio range to lower the storage capacity of more NO X approaches the stoichiometric air-fuel ratio immediately after the rich air-fuel ratio uniform mixture combustion mode transition during the rich spike operation above As described above, when the state where the engine air-fuel ratio is temporarily operated at the lean air-fuel ratio near the stoichiometric air-fuel ratio occurs, the absorbed N
Some of O X is in some cases been released without being purified.

【０００９】このため、上記公報の機関ではリッチスパ
イク操作実施毎に未浄化のＮＯX が大気に放出され排気
性状が悪化する問題が生じる。また、上記公報の機関で
は、リッチスパイク操作時に成層燃焼モードと均質混合
気燃焼モードとの間で機関運転モードを切り換えている
が、機関運転モードの切り換えを伴わないリッチスパイ
ク操作（例えばリーン空燃比運転時に機関が均質混合気
燃焼モードで運転されている場合）においても機関燃焼
空燃比がリッチ空燃比に変化したときにアクセル開度と
機関回転数とに基づいて燃料噴射量を決定していると同
様に機関吸入空気量の変化遅れによる排気性状の悪化等
の問題が生じる。For this reason, in the engine disclosed in the above publication, unpurified NO X is released into the atmosphere every time the rich spike operation is performed, and there is a problem that the exhaust properties deteriorate. Further, in the engine of the above publication, the engine operation mode is switched between the stratified combustion mode and the homogeneous mixture combustion mode during the rich spike operation, but the rich spike operation without switching the engine operation mode (for example, the lean air-fuel ratio). Even when the engine is operated in the homogeneous mixture combustion mode during operation), the fuel injection amount is determined based on the accelerator opening and the engine speed when the engine combustion air-fuel ratio changes to the rich air-fuel ratio. In the same manner as described above, problems such as deterioration of exhaust characteristics due to a delay in change of the engine intake air amount occur.

【００１０】また、機関のリッチスパイク操作はＮＯX
吸蔵還元触媒からＮＯX を放出させるべきとき以外に
も、後述するブレーキ作動負圧確保の必要がある場合に
も実行されるため、この場合にもＮＯX 吸蔵還元触媒に
は理論空燃比近傍のリーン空燃比排気が流入し未浄化の
ＮＯX が大気に放出されるようになるおそれがある。本
発明は上記問題に鑑み、リッチスパイク操作時に短時間
で実際の機関燃焼空燃比をリッチ空燃比に移行させＮＯ
X 吸蔵還元触媒を使用した場合にも排気性状の悪化を防
止可能な内燃機関の燃料噴射制御装置を提供することを
目的としている。[0010] Further, the rich spike operation of the engine is NO X
From storage reduction catalyst in addition to when to emit NO X, to be executed when there is a need for a brake actuation vacuum retention that will be described later, the stoichiometric air-fuel ratio of the vicinity to the NO X occluding and reducing catalyst in this case lean air-fuel ratio exhaust gas flows unpurified NO X may become to be discharged to the atmosphere. SUMMARY OF THE INVENTION In view of the above-described problems, the present invention shifts the actual engine combustion air-fuel ratio to the rich air-fuel ratio in a short
It is an object of the present invention to provide a fuel injection control device for an internal combustion engine that can prevent deterioration of exhaust characteristics even when an X storage reduction catalyst is used.

【００１１】[0011]

【課題を解決するための手段】請求項１に記載の発明に
よれば、要求機関負荷に応じて機関燃焼空燃比を制御す
る内燃機関の燃料噴射制御装置であって、機関の燃料噴
射を機関吸入空気量と機関回転数とに基づいて制御する
第１の燃料噴射制御手段と、機関の燃料噴射を要求機関
負荷と機関回転数とに基づいて設定する第２の燃料噴射
制御手段とを備え、機関がリーン空燃比で運転されてい
るときに、要求機関負荷とは無関係に機関補機の要求に
より機関をリッチ空燃比で運転するリッチスパイク操作
を行い、前記リッチスパイク操作における空燃比の切り
換え時に、機関燃焼空燃比がリーンである間は前記第２
の燃料噴射制御手段により機関燃料噴射を制御し、機関
がリッチ空燃比で運転される間は前記第１の燃料噴射制
御手段により機関の燃料噴射を制御する内燃機関の燃料
噴射制御装置が提供される。According to the first aspect of the present invention, there is provided a fuel injection control device for an internal combustion engine for controlling an engine combustion air-fuel ratio in accordance with a required engine load. The first fuel injection control means controls the fuel injection of the engine based on the intake air amount and the engine speed, and the second fuel injection control means sets the fuel injection of the engine based on the required engine load and the engine speed. When the engine is operating at a lean air-fuel ratio, the engine performs a rich spike operation to operate the engine at a rich air-fuel ratio at the request of an engine accessory regardless of the required engine load, and switches the air-fuel ratio in the rich spike operation. Sometimes, while the engine combustion air-fuel ratio is lean, the second
A fuel injection control device for an internal combustion engine, wherein the fuel injection control means controls the engine fuel injection by the fuel injection control means and controls the fuel injection of the engine by the first fuel injection control means while the engine is operated at the rich air-fuel ratio. You.

【００１２】すなわち、請求項１の発明ではリッチスパ
イク操作実施時には機関空燃比がリーンである間は従来
と同様に機関燃料噴射は要求機関負荷（例えばアクセル
開度）と機関回転数とに基づいて制御されるが、機関の
燃焼空燃比がリッチ空燃比に切り換えられると機関の燃
料噴射は吸入空気量と機関回転数とに基づいて制御され
るようになる。このため、リッチ空燃比運転に移行後は
機関燃料噴射量も実際の吸入空気量に応じて設定される
ようになる。従って、リッチ空燃比均質混合気燃焼モー
ドに移行直後で実際の機関吸入空気量がスロットル弁開
度に対応した値になっていない場合にも燃料噴射量は実
際の吸入空気量に基づいて機関燃焼空燃比を所定のリッ
チ空燃比にする値に設定されるようになり、機関燃焼空
燃比をリッチ空燃比に切り換え直後から所定のリッチ空
燃比を得ることができる。That is, in the first aspect of the present invention, when the rich spike operation is performed, as long as the engine air-fuel ratio is lean, the engine fuel injection is performed based on the required engine load (eg, the accelerator opening) and the engine speed as in the related art. Control is performed, but when the combustion air-fuel ratio of the engine is switched to the rich air-fuel ratio, the fuel injection of the engine is controlled based on the intake air amount and the engine speed. For this reason, after shifting to the rich air-fuel ratio operation, the engine fuel injection amount is also set according to the actual intake air amount. Therefore, even if the actual engine intake air amount is not a value corresponding to the throttle valve opening immediately after the transition to the rich air-fuel ratio homogeneous mixture combustion mode, the fuel injection amount is determined based on the actual intake air amount. The air-fuel ratio is set to a value that sets the predetermined rich air-fuel ratio, and the predetermined rich air-fuel ratio can be obtained immediately after switching the engine combustion air-fuel ratio to the rich air-fuel ratio.

【００１３】請求項２に記載の発明によれば、筒内に直
接燃料を噴射する筒内燃料噴射弁を備え、各気筒の圧縮
行程中に燃料を噴射してリーン空燃比成層燃焼を行う成
層燃焼モードと、各気筒の吸気行程中に燃料を噴射して
均質混合気燃焼を行う均質混合気燃焼モードとを切り換
えて運転する内燃機関の燃料噴射制御装置であって、機
関の燃料噴射を機関吸入空気量と機関回転数とに基づい
て制御する第１の燃料噴射制御手段と、機関の燃料噴射
を要求機関負荷と機関回転数とに基づいて設定する第２
の燃料噴射制御手段とを備え、要求機関負荷に応じて前
記成層燃焼モードと前記均質混合気燃焼モードとの運転
切り換えを行うとともに、要求機関負荷とは無関係に機
関補機の要求によりリッチ空燃比の均質混合気燃焼モー
ドで機関を運転するリッチスパイク操作を行い、機関が
リーン空燃比成層燃焼モードで運転されているときの前
記リッチスパイク操作実施中には、機関燃焼空燃比がリ
ーンである間は前記第２の燃料噴射制御手段により機関
燃料噴射を制御し、機関がリッチ空燃比の均質混合気燃
焼モードで運転される間は前記第１の燃料噴射制御手段
により機関の燃料噴射を制御する内燃機関の燃料噴射制
御装置が提供される。According to the second aspect of the present invention, a stratified fuel injection valve for directly injecting fuel into the cylinder is provided, and the fuel is injected during the compression stroke of each cylinder to perform stratified combustion with a lean air-fuel ratio. A fuel injection control device for an internal combustion engine that operates by switching between a combustion mode and a homogeneous mixture combustion mode in which fuel is injected during an intake stroke of each cylinder to perform homogeneous mixture combustion. First fuel injection control means for controlling based on the intake air amount and the engine speed, and second control for setting the fuel injection of the engine based on the required engine load and the engine speed.
Fuel injection control means for switching the operation between the stratified combustion mode and the homogeneous mixture combustion mode according to the required engine load, and irrespective of the required engine load, the rich air-fuel ratio During the rich spike operation when the engine is operated in the lean air-fuel ratio stratified combustion mode, while the engine is operating in the lean air-fuel ratio stratified combustion mode, while the engine combustion air-fuel ratio is lean, Controls the engine fuel injection by the second fuel injection control means, and controls the fuel injection of the engine by the first fuel injection control means while the engine is operated in the rich air-fuel ratio homogeneous mixture combustion mode. A fuel injection control device for an internal combustion engine is provided.

【００１４】すなわち、請求項２の発明ではリッチスパ
イク操作実施時には機関空燃比がリーンである間は従来
と同様に機関燃料噴射は要求機関負荷（例えばアクセル
開度）と機関回転数とに基づいて制御されるが、機関の
運転がリッチ空燃比均質混合気燃焼モードに切り換えら
れると機関の燃料噴射は吸入空気量と機関回転数とに基
づいて制御されるようになる。このため、リッチ空燃比
均質混合気燃焼モードに移行後は機関燃料噴射量も実際
の吸入空気量に応じて設定されるようになる。従って、
リッチ空燃比均質混合気燃焼モードに移行直後で実際の
機関吸入空気量がスロットル弁開度に対応した値になっ
ていない場合にも燃料噴射量は実際の吸入空気量に基づ
いて機関燃焼空燃比を所定のリッチ空燃比にする値に設
定されるようになり、リッチ空燃比均質燃焼モード切り
換え直後から所定のリッチ空燃比を得ることができる。In other words, according to the second aspect of the present invention, during the execution of the rich spike operation, as long as the engine air-fuel ratio is lean, the engine fuel injection is performed based on the required engine load (for example, the accelerator opening) and the engine speed as in the prior art. Although the control is performed, when the operation of the engine is switched to the rich air-fuel ratio homogeneous mixture combustion mode, the fuel injection of the engine is controlled based on the intake air amount and the engine speed. For this reason, after shifting to the rich air-fuel ratio homogeneous mixture combustion mode, the engine fuel injection amount is also set according to the actual intake air amount. Therefore,
Even when the actual engine intake air amount does not correspond to the throttle valve opening immediately after the transition to the rich air-fuel ratio homogeneous mixture combustion mode, the fuel injection amount is determined based on the actual intake air amount based on the actual engine intake air amount. Is set to a value that sets a predetermined rich air-fuel ratio, and a predetermined rich air-fuel ratio can be obtained immediately after switching to the rich air-fuel ratio homogeneous combustion mode.

【００１５】請求項３に記載の発明によれば、前記機関
補機は、機関排気通路に配置され流入する排気空燃比が
リーンの時に排気中のＮＯX を吸収し流入する排気空燃
比がリッチになったときに吸収したＮＯX を放出、還元
浄化するＮＯX 吸蔵還元触媒であり、前記リッチスパイ
ク操作はＮＯX 吸蔵還元触媒から吸収したＮＯX を放出
させ、還元浄化するときに実行される請求項１または請
求項２に記載の内燃機関の燃料噴射制御装置が提供され
る。According to the invention described in claim 3, wherein the engine accessory is an exhaust air-fuel ratio of the exhaust air-fuel ratio flowing disposed engine exhaust passage flows to absorb NO X in the exhaust gas when the lean-rich the absorbed NO X when it is released, a the NO X storage reduction catalyst for purifying the rich spike operation to release NO X absorbed from the NO X storage reduction catalyst, is executed when the reduction and purification A fuel injection control device for an internal combustion engine according to claim 1 or 2 is provided.

【００１６】すなわち、請求項３の発明ではＮＯX 吸蔵
還元触媒から吸収したＮＯX を放出させるためにリッチ
スパイク操作を行う場合にも、リッチ空燃比均質混合気
燃焼モードへの切り換え直後から実際の機関燃焼空燃比
が所定のリッチ空燃比となるため、理論空燃比近傍のリ
ーン空燃比排気がＮＯX 吸蔵還元触媒に流入することが
なくなり未浄化のＮＯX の大気への放出が防止される。That is, according to the third aspect of the invention, even when the rich spike operation is performed to release the NO X absorbed from the NO X storage reduction catalyst, the actual operation is performed immediately after switching to the rich air-fuel ratio homogeneous mixture combustion mode. Since the engine combustion air-fuel ratio becomes a predetermined rich air-fuel ratio, lean air-fuel ratio exhaust near the stoichiometric air-fuel ratio does not flow into the NO X storage reduction catalyst, and the emission of unpurified NO X to the atmosphere is prevented.

【００１７】請求項４に記載の発明によれば、更に、機
関排気通路に配置され排気の空燃比を検出する空燃比セ
ンサを備え、前記リッチスパイク操作時に前記空燃比セ
ンサ出力に基づいて機関燃焼空燃比を予め定めた空燃比
に制御する請求項１または請求項２に記載の内燃機関の
燃料噴射制御装置が提供される。すなわち、請求項４の
発明ではリッチスパイク操作時に排気空燃比センサで検
出された実際の排気空燃比（機関燃焼空燃比）に基づい
て機関の燃焼空燃比が制御されるため、リッチスパイク
操作時の空燃比制御の精度が向上する。According to the fourth aspect of the present invention, there is further provided an air-fuel ratio sensor disposed in the engine exhaust passage for detecting the air-fuel ratio of the exhaust gas, and the engine combustion is performed based on the air-fuel ratio sensor output during the rich spike operation. A fuel injection control device for an internal combustion engine according to claim 1 or 2, wherein the air-fuel ratio is controlled to a predetermined air-fuel ratio. That is, in the invention of claim 4, the combustion air-fuel ratio of the engine is controlled based on the actual exhaust air-fuel ratio (engine combustion air-fuel ratio) detected by the exhaust air-fuel ratio sensor during the rich spike operation. The accuracy of air-fuel ratio control is improved.

【００１８】[0018]

【発明の実施の形態】以下、添付図面を用いて本発明の
実施形態について説明する。図１は本発明を自動車用内
燃機関に適用した場合の実施形態の概略構成を示す図で
ある。図１において、１は自動車用内燃機関を示す。本
実施形態では、機関１は＃１から＃４の４つの気筒を備
えた４気筒ガソリン機関とされ、各気筒には気筒内に直
接燃料を噴射する筒内燃料噴射弁１１１から１１４が設
けられている。後述するように、本実施形態の内燃機関
１は、理論空燃比より高い（リーン）空燃比から理論空
燃比より低い（リッチ）空燃比までの広い範囲の空燃比
で運転可能な機関とされている。Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a schematic configuration of an embodiment when the present invention is applied to an internal combustion engine for a vehicle. In FIG. 1, reference numeral 1 denotes an automobile internal combustion engine. In the present embodiment, the engine 1 is a four-cylinder gasoline engine having four cylinders # 1 to # 4, and each cylinder is provided with in-cylinder fuel injection valves 111 to 114 for directly injecting fuel into the cylinder. ing. As will be described later, the internal combustion engine 1 of the present embodiment is an engine capable of operating in a wide range of air-fuel ratios from an air-fuel ratio higher than the stoichiometric air-fuel ratio (lean) to an air-fuel ratio lower than the stoichiometric air-fuel ratio (rich). I have.

【００１９】また、本実施形態では＃１から＃４の気筒
は互いに点火時期が連続しない２つの気筒からなる２つ
の気筒群にグループ分けされている。（例えば、図１の
実施形態では、気筒点火順序は１−３−４−２であり、
＃１、＃４の気筒と＃２、＃３の気筒とがそれぞれ気筒
群を構成している。）また、各気筒の排気ポートは気筒
群毎に排気マニホルドに接続され、気筒群毎の排気通路
に接続されている。図１において、２１ａは＃１、＃４
気筒からなる気筒群の排気ポートを個別排気通路２ａに
接続する排気マニホルド、２１ｂは＃２、＃４気筒から
なる気筒群の排気ポートを個別排気通路２ｂに接続する
排気マニホルドである。本実施形態では、個別排気通路
２ａ、２ｂ上には、公知の三元触媒からなるスタートキ
ャタリスト（以下「ＳＣ」と呼ぶ）５ａと５ｂがそれぞ
れ配置されている。また、個別排気通路２ａ、２ｂはＳ
Ｃ下流側で共通の排気通路２に合流している。In this embodiment, the cylinders # 1 to # 4 are grouped into two cylinder groups each including two cylinders whose ignition timings are not continuous. (For example, in the embodiment of FIG. 1, the cylinder ignition order is 1-3-4-2,
The cylinders # 1 and # 4 and the cylinders # 2 and # 3 each constitute a cylinder group. The exhaust port of each cylinder is connected to an exhaust manifold for each cylinder group, and is connected to an exhaust passage for each cylinder group. In FIG. 1, 21a is # 1, # 4
The exhaust manifold 21b connects the exhaust ports of the cylinder group consisting of cylinders to the individual exhaust passages 2a, and the exhaust manifold 21b connects the exhaust ports of the cylinder group consisting of # 2 and # 4 cylinders to the individual exhaust passage 2b. In the present embodiment, start catalysts (hereinafter, referred to as "SC") 5a and 5b made of a known three-way catalyst are arranged on the individual exhaust passages 2a and 2b, respectively. The individual exhaust passages 2a and 2b are S
It joins the common exhaust passage 2 on the downstream side of C.

【００２０】共通排気通路２上には、後述するＮＯX 吸
蔵還元触媒７が配置されている。図１に２９ａ、２９ｂ
で示すのは、個別排気通路２ａ、２ｂのスタートキャタ
リスト５ａ、５ｂ上流側に配置された空燃比センサ、３
１で示すのは、排気通路２のＮＯX 吸蔵還元触媒７下流
側に配置された空燃比センサである。空燃比センサ２９
ａ、２９ｂ及び３１は、広い空燃比範囲で排気空燃比に
対応する電圧信号を出力する、いわゆるリニア空燃比セ
ンサとされている。On the common exhaust passage 2, a NO X storage reduction catalyst 7 described later is arranged. FIG. 1 shows 29a and 29b.
Indicate the air-fuel ratio sensors 3 and 3 arranged upstream of the start catalysts 5a and 5b of the individual exhaust passages 2a and 2b.
Reference numeral 1 denotes an air-fuel ratio sensor disposed downstream of the NO X storage reduction catalyst 7 in the exhaust passage 2. Air-fuel ratio sensor 29
Reference numerals a, 29b, and 31 denote so-called linear air-fuel ratio sensors that output voltage signals corresponding to the exhaust air-fuel ratio in a wide air-fuel ratio range.

【００２１】図１に１０ｂで示すのは機関各気筒の吸気
ポートを吸気通路１０に接続する吸気マニホルド、１０
ａは吸気通路１０に設けられたサージタンクである。ま
た、本実施形態では＃２、＃３気筒の個別排気通路２ｂ
のＳＣ５ｂ上流側と機関吸気通路１０のサージタンク１
０ａとはＥＧＲ通路４３で接続されている。更に、ＥＧ
Ｒ通路４３上にはＥＧＲ通路を通って排気通路２ｂから
吸気通路１０に還流する排気流量を制御する流量制御弁
からなるＥＧＲ弁４１が設けられている。ＥＧＲ弁４１
は後述するＥＣＵ３０からの制御信号に応じて作動する
ステッパモータ、負圧アクチュエータ等の適宜な形式の
アクチュエータ４１ａを備え、ＥＣＵ３０からの制御信
号に応じた開度をとる。In FIG. 1, reference numeral 10b denotes an intake manifold for connecting the intake port of each cylinder of the engine to an intake passage 10.
a is a surge tank provided in the intake passage 10. In this embodiment, the individual exhaust passages 2b of the # 2 and # 3 cylinders are used.
Tank 5 in the upstream of SC5b and engine intake passage 10
0a is connected with the EGR passage 43. Further, EG
Provided on the R passage 43 is an EGR valve 41, which is a flow control valve for controlling the flow rate of exhaust gas flowing from the exhaust passage 2b to the intake passage 10 through the EGR passage. EGR valve 41
Is provided with an actuator 41a of an appropriate type such as a stepper motor or a negative pressure actuator that operates in accordance with a control signal from the ECU 30, which will be described later.

【００２２】更に、本実施形態では吸気通路１０上には
スロットル弁１５が設けられている。本実施形態のスロ
ットル弁１５はいわゆる電子制御スロットル弁とされて
おり、ステッパモータ等の適宜な形式のアクチュエータ
１５ａにより駆動され後述するＥＣＵ３０からの制御信
号に応じた開度をとる。図１に３０で示すのは機関１の
電子制御ユニット（ＥＣＵ）である。ＥＣＵ３０は、本
実施形態ではＲＡＭ、ＲＯＭ、ＣＰＵを備えた公知の構
成のマイクロコンピュータとされ、機関１の点火時期制
御や燃料噴射制御等の基本制御を行なっている。また、
本実施形態では、ＥＣＵ３０は上記の基本制御を行う他
に、後述するように機関運転状態に応じて筒内噴射弁１
１１から１１４の燃料噴射モードを変更し機関の運転空
燃比を変更する制御を行なうとともに、更にＮＯX 吸蔵
還元触媒７からのＮＯX 放出操作やブレーキ負圧確保の
ために機関のリーン空燃比運転中に運転空燃比をリッチ
空燃比に切り換えるリッチスパイク操作を行なってい
る。Further, in this embodiment, a throttle valve 15 is provided on the intake passage 10. The throttle valve 15 of the present embodiment is a so-called electronically-controlled throttle valve, and is driven by an appropriate type of actuator 15a such as a stepper motor or the like, and has an opening in accordance with a control signal from an ECU 30 described later. Reference numeral 30 in FIG. 1 denotes an electronic control unit (ECU) of the engine 1. In the present embodiment, the ECU 30 is a microcomputer having a known configuration including a RAM, a ROM, and a CPU, and performs basic control such as ignition timing control and fuel injection control of the engine 1. Also,
In the present embodiment, in addition to performing the above-described basic control, the ECU 30 performs the in-cylinder injection valve 1 according to the engine operating state as described later.
Performs a control to change the operating air-fuel ratio changes to the engine fuel injection mode from 11 to 114, further lean air-fuel ratio operation of the engine in order of the NO X release operation or the brake vacuum retention from the NO X storage reduction catalyst 7 A rich spike operation is performed during which the operating air-fuel ratio is switched to the rich air-fuel ratio.

【００２３】ＥＣＵ３０の入力ポートには、空燃比セン
サ２９ａ、２９ｂからスタートキャタリスト５ａ、５ｂ
入口における排気空燃比を表す信号と、空燃比センサ３
１からＮＯX 吸蔵還元触媒７出口における排気空燃比を
表す信号が、また、図示しない機関吸気マニホルドに設
けられた吸気圧センサ３５から機関の吸気管圧力に対応
する信号がそれぞれ入力されている他、機関クランク軸
（図示せず）近傍に配置された回転数センサ３３から機
関クランク軸一定回転角毎にパルス信号が入力されてい
る。更に、本実施形態では、ＥＣＵ３０の入力ポートに
は機関１のアクセルペダル（図示せず）近傍に配置した
アクセル開度センサ３７から運転者のアクセルペダル踏
込み量（アクセル開度）を表す信号が入力されている。
ＥＣＵ３０は、所定間隔毎に吸気圧センサ３５出力とア
クセル開度センサ３７出力とをＡＤ変換して吸気管圧力
ＰＭとアクセル開度ＡＣＣＰとしてＥＣＵ３０のＲＡＭ
の所定領域に格納するとともに、回転数センサ３３から
のパルス信号の間隔から機関回転数ＮＥを算出し、ＲＡ
Ｍの所定の領域に格納している。また、ＥＣＵ３０の出
力ポートは、各気筒への燃料噴射量及び燃料噴射時期を
制御するために、図示しない燃料噴射回路を介して各気
筒の燃料噴射弁１１１から１１４に接続されている他、
スロットル弁１５のアクチュエータ１５ｂに図示しない
駆動回路を介して接続されスロットル弁１５の開度を制
御している。The input ports of the ECU 30 are provided with the start catalysts 5a, 5b from the air-fuel ratio sensors 29a, 29b.
A signal representing the exhaust air-fuel ratio at the inlet and an air-fuel ratio sensor 3
1 to a signal representing the exhaust air-fuel ratio at the outlet of the NO X storage reduction catalyst 7, and a signal corresponding to the intake pipe pressure of the engine from an intake pressure sensor 35 provided in an engine intake manifold (not shown). A pulse signal is input from the rotation speed sensor 33 disposed near the engine crankshaft (not shown) at every constant rotation angle of the engine crankshaft. Further, in the present embodiment, a signal indicating the accelerator pedal depression amount (accelerator opening) of the driver is input to an input port of the ECU 30 from an accelerator opening sensor 37 arranged near an accelerator pedal (not shown) of the engine 1. Have been.
The ECU 30 performs AD conversion on the output of the intake pressure sensor 35 and the output of the accelerator opening sensor 37 at predetermined intervals to obtain the intake pipe pressure PM and the accelerator opening ACCP in the RAM of the ECU 30.
And the engine speed NE is calculated from the interval of the pulse signal from the speed sensor 33,
M in a predetermined area. The output port of the ECU 30 is connected to the fuel injection valves 111 to 114 of the respective cylinders via a fuel injection circuit (not shown) in order to control the amount and timing of fuel injection into each cylinder.
The throttle valve 15 is connected to an actuator 15b of the throttle valve 15 via a drive circuit (not shown) to control the opening of the throttle valve 15.

【００２４】また、ＥＣＵ３０はＥＧＲ弁４１のアクチ
ュエータ４１ａに図示しない駆動回路介して接続されＥ
ＧＲ弁４１開度を制御して、機関運転状態に応じて排気
通路２ｂの排気の一部を吸気通路１０に還流するＥＧＲ
操作を実施する。本実施形態では、機関１の通常の運転
時（後述するリッチスパイク操作が実施されていない
時）にはＥＣＵ３０は運転条件に応じて機関１を以下の
５つのモードのいずれかで運転する。The ECU 30 is connected to an actuator 41a of the EGR valve 41 via a drive circuit (not shown).
EGR that controls a degree of opening of the GR valve 41 and recirculates a part of the exhaust gas from the exhaust passage 2 b to the intake passage 10 according to the engine operating state.
Perform the operation. In the present embodiment, during normal operation of the engine 1 (when a later-described rich spike operation is not performed), the ECU 30 operates the engine 1 in one of the following five modes according to operating conditions.

【００２５】 リーン空燃比成層燃焼（圧縮行程１回
噴射） リーン空燃比弱成層燃焼（吸気行程／圧縮行程２回
噴射） リーン空燃比均質混合気燃焼（吸気行程１回噴射） 理論空燃比均質混合気燃焼（吸気行程１回噴射） リッチ空燃比均質混合気燃焼（吸気行程１回噴射） すなわち、機関１の軽負荷運転領域では、上記モード
のリーン空燃比成層燃焼が行なわれる。機関１は気筒内
に吸入空気のスワール（旋回流）を生じさせるスワール
ポートを有する吸気弁と通常のストレートポートを有す
る吸気弁との２つの吸気弁を備えており、ストレートポ
ートに連通する吸気通路に設けられたスワールコントロ
ールバルブ（ＳＣＶ）（図示せず）の開度を調節するこ
とによりスワールポートから気筒内に流入する吸気量を
制御することが可能となっている。成層燃焼を行なう場
合には、ＳＣＶ開度は全閉とされスワールポートからの
吸気量を増大し、気筒内に強いスワールを生成させる。
また、この状態では筒内燃料噴射は各気筒の圧縮行程後
半に１回のみ行なわれ、噴射された燃料は気筒点火プラ
グ近傍に可燃混合気の層を形成する。また、この運転状
態での燃料噴射量は極めて少なく、気筒内の全体として
の空燃比は２５から３０程度もしくはそれ以上になる。Lean air-fuel ratio stratified combustion (compression stroke single injection) Lean air-fuel ratio weak stratified combustion (intake stroke / compression stroke twice injection) Lean air-fuel ratio homogeneous mixture combustion (intake stroke single injection) Stoichiometric air-fuel ratio homogeneous mixing Air Combustion (Single-Injection Injection Injection) Rich Air-Fuel Ratio Homogeneous Mixture Combustion (Single-Intake Injection Injection) That is, in the light load operation region of the engine 1, the lean air-fuel ratio stratified combustion in the above mode is performed. The engine 1 includes two intake valves, an intake valve having a swirl port for generating a swirl (swirl flow) of intake air in a cylinder, and an intake valve having a normal straight port, and an intake passage communicating with the straight port. By adjusting the opening of a swirl control valve (SCV) (not shown) provided in the cylinder, it is possible to control the amount of intake air flowing into the cylinder from the swirl port. When performing stratified charge combustion, the SCV opening is fully closed to increase the amount of intake air from the swirl port and generate strong swirl in the cylinder.
In this state, in-cylinder fuel injection is performed only once in the latter half of the compression stroke of each cylinder, and the injected fuel forms a combustible mixture layer near the cylinder ignition plug. Further, the fuel injection amount in this operating state is extremely small, and the air-fuel ratio as a whole in the cylinder becomes about 25 to 30 or more.

【００２６】また、上記モードの状態から負荷が増大
して低負荷運転領域になると、上記モードのリーン空
燃比弱成層燃焼が行なわれる。機関負荷が増大するにつ
れて気筒内に噴射する燃料は増量されるが、この負荷領
域では圧縮行程後半の燃料噴射に加えて、予め吸気行程
前半に燃料を噴射することにより目標量の燃料を気筒に
供給するようにしている。吸気行程前半に気筒内に噴射
された燃料は着火時までに極めてリーンな均質混合気を
生成する。圧縮行程後半ではこの極めてリーンな均質混
合気中に更に燃料が噴射され点火プラグ近傍に着火可能
な可燃混合気の層が生成される。着火時にはこの可燃混
合気層が燃焼を開始し周囲の希薄な混合気層に火炎が伝
播するため安定した燃焼が行なわれるようになる。この
状態では吸気行程と圧縮行程での噴射により供給される
燃料量はモードより増量されるが、全体としての空燃
比はやや低いリーン（例えば空燃比で２０から３０程
度）になる。Further, when the load increases from the state of the above-mentioned mode to enter a low-load operation range, the lean air-fuel ratio weak stratified combustion in the above-mentioned mode is performed. As the engine load increases, the amount of fuel injected into the cylinder increases.However, in this load region, in addition to the fuel injection in the latter half of the compression stroke, the target amount of fuel is previously injected into the cylinder by injecting fuel in the first half of the intake stroke. I am trying to supply. The fuel injected into the cylinder in the first half of the intake stroke produces an extremely lean homogeneous mixture by the time of ignition. In the latter half of the compression stroke, fuel is further injected into this extremely lean homogeneous mixture to form a layer of ignitable combustible mixture near the spark plug. At the time of ignition, the combustible air-fuel mixture layer starts burning, and the flame propagates to the surrounding lean air-fuel mixture layer, so that stable combustion is performed. In this state, the amount of fuel supplied by the injection in the intake stroke and the compression stroke is increased from the mode, but the air-fuel ratio as a whole becomes slightly lower (for example, about 20 to 30 in air-fuel ratio).

【００２７】更に機関負荷が増大すると、機関１では上
記モードのリーン空燃比均質混合気燃焼が行なわれ
る。この状態ではＳＣＶは全開とされ吸気の大部分はス
トレートポートから気筒内に流入する。また、この状態
では燃料噴射は吸気行程前半に１回のみ実行され、燃料
噴射量は上記モードより更に増量される。この状態で
気筒内に生成される均質混合気は理論空燃比に比較的近
いリーン空燃比（例えば空燃比で１５から２５程度）と
なる。When the engine load further increases, the engine 1 performs the lean air-fuel ratio homogeneous mixture combustion in the above mode. In this state, the SCV is fully opened, and most of the intake air flows into the cylinder from the straight port. In this state, the fuel injection is performed only once in the first half of the intake stroke, and the fuel injection amount is further increased from the above mode. In this state, the homogeneous mixture generated in the cylinder has a lean air-fuel ratio relatively close to the stoichiometric air-fuel ratio (for example, an air-fuel ratio of about 15 to 25).

【００２８】更に機関負荷が増大して機関高負荷運転領
域になると、モードの状態から更に燃料が増量され、
上記モードの理論空燃比均質混合気運転が行なわれ
る。この状態では、気筒内には理論空燃比の均質な混合
気が生成されるようになり、機関出力が増大する。ま
た、更に機関負荷が増大して機関の全負荷運転になる
と、モードの状態から燃料噴射量が更に増量されモー
ドのリッチ空燃比均質混合気運転が行なわれる。この
状態では、気筒内に生成される均質混合気の空燃比はリ
ッチ（例えば空燃比で１２から１４程度）になる。When the engine load further increases and enters the engine high load operation region, the fuel is further increased from the mode state,
The stoichiometric air-fuel ratio homogeneous mixture operation in the above mode is performed. In this state, a homogeneous air-fuel mixture having a stoichiometric air-fuel ratio is generated in the cylinder, and the engine output increases. Further, when the engine load further increases and the engine becomes full load operation, the fuel injection amount is further increased from the mode state, and the rich air-fuel ratio homogeneous mixture operation in the mode is performed. In this state, the air-fuel ratio of the homogeneous mixture generated in the cylinder becomes rich (for example, about 12 to 14 in air-fuel ratio).

【００２９】本実施形態では、アクセル開度（運転者の
アクセルペダル踏込み量）と機関回転数とに応じて予め
実験等に基づいて最適な運転モード（上記から）が
設定されており、ＥＣＵ３０のＲＯＭにアクセル開度と
機関回転数とを用いたマップとして格納してある。機関
１の運転中、ＥＣＵ３０はアクセル開度センサ３７で検
出したアクセル開度と機関回転数とに基づいて、現在上
記からのいずれの運転モードを選択すべきかを決定
し、それぞれのモードに応じて燃料噴射量、燃料噴射時
期及び回数、点火時期、スロットル弁開度、ＥＧＲ量
（ＥＧＲ弁開度）等の機関の運転状態を制御する制御量
を決定する。In the present embodiment, the optimal operation mode (from the above) is set in advance based on experiments and the like according to the accelerator opening (the amount of depression of the accelerator pedal by the driver) and the engine speed. The map is stored in the ROM using the accelerator opening and the engine speed. During operation of the engine 1, the ECU 30 determines which of the above operation modes should be currently selected based on the accelerator opening detected by the accelerator opening sensor 37 and the engine speed, and according to each mode. A control amount for controlling an operating state of the engine, such as a fuel injection amount, a fuel injection timing and the number of times, an ignition timing, a throttle valve opening, an EGR amount (EGR valve opening), is determined.

【００３０】また、モード（理論空燃比均質混合気燃
焼）が選択された場合には、ＥＣＵ３０は更に上記によ
り算出した燃料噴射量を、機関排気空燃比が理論空燃比
となるように空燃比センサ２９ａ、２９ｂの出力に基づ
いてフィードバック補正する空燃比制御を行なう。より
詳細には、上記からのモード（リーン空燃比燃焼）
が選択された場合、ＥＣＵ３０は上記からのモード
毎に予め準備されたマップに基づいて、アクセル開度と
機関回転数とから燃料噴射量、燃料噴射時期、スロット
ル開度、ＥＧＲ量及び点火時期等の制御量を決定する。
アクセル開度は運転者の要求する機関負荷を表してい
る。従って、モードからでは燃料噴射量等の各制御
量の値は要求機関負荷と機関回転数とに基づいて設定さ
れる。When the mode (stoichiometric air-fuel ratio homogeneous mixture combustion) is selected, the ECU 30 further uses the fuel injection amount calculated above as an air-fuel ratio sensor so that the engine exhaust air-fuel ratio becomes the stoichiometric air-fuel ratio. Air-fuel ratio control for performing feedback correction based on the outputs of 29a and 29b is performed. More specifically, the mode from above (lean air-fuel ratio combustion)
Is selected, the ECU 30 calculates the fuel injection amount, the fuel injection timing, the throttle opening, the EGR amount, the ignition timing, etc. from the accelerator opening and the engine speed based on the maps prepared in advance for each mode from the above. Is determined.
The accelerator opening represents the engine load required by the driver. Therefore, in the mode, the values of the control amounts such as the fuel injection amount are set based on the required engine load and the engine speed.

【００３１】また、上記とのモード（理論空燃比ま
たはリッチ空燃比均質混合気燃焼）が選択された場合に
は、ＥＣＵ３０は上記とのモード毎に予め準備され
たマップに基づいて、スロットル弁開度と機関回転数、
及び吸気圧センサ３５で検出した吸気管圧力とに基づい
て燃料噴射量等の制御量を設定する。一般に、機関吸入
空気量は機関回転数と吸気管負圧との関数として表され
る。また、機関吸入空気量と機関回転数とは機関負荷状
態を表すパラメータとして使用される。このため、モー
ドととでは、燃料噴射量等の各制御量は機関回転数
と吸気管負圧とから定まる機関吸入空気量に更に機関回
転数を考慮して所望の空燃比を得るのに必要な値に設定
される。すなわち、本実施形態ではモード、の均質
混合気燃焼運転では燃料噴射量等の各制御量の値は機関
吸入空気量と機関回転数とに基づいて設定される。When the above mode (stoichiometric air-fuel ratio or rich air-fuel ratio homogeneous mixture combustion) is selected, the ECU 30 opens the throttle valve based on a map prepared for each mode. Degree and engine speed,
And a control amount such as a fuel injection amount based on the intake pipe pressure detected by the intake pressure sensor 35. Generally, the engine intake air amount is expressed as a function of the engine speed and the intake pipe negative pressure. The engine intake air amount and the engine speed are used as parameters representing the engine load state. For this reason, in the mode, each control amount such as the fuel injection amount is necessary to obtain a desired air-fuel ratio in consideration of the engine speed in addition to the engine intake air amount determined from the engine speed and the intake pipe negative pressure. Is set to an appropriate value. That is, in the present embodiment, in the mode of the homogeneous mixture combustion operation, the values of the respective control amounts such as the fuel injection amount are set based on the engine intake air amount and the engine speed.

【００３２】また、スロットル弁１５開度はモードか
らでは全開に近い領域でアクセル開度に応じて制御さ
れる。この領域ではアクセル開度が低下するとスロット
ル弁開度も低減されるが、スロットル弁全開相当の領域
であるためスロットル弁開度が変化しても吸気管圧力は
略一定になり、ほとんど吸気絞りは生じない。一方モー
ド、ではスロットル弁開度はアクセル開度に略等し
い開度に制御される。すなわち、アクセル開度（アクセ
ルペダル踏込み量）が０のときにはスロットル開度も０
（全閉）に、アクセル開度が１００パーセントのとき
（アクセルペダルがいっぱいに踏み込まれたとき）には
スロットル開度も１００パーセント（全開）にセットさ
れる。In the mode, the opening of the throttle valve 15 is controlled in accordance with the accelerator opening in a region close to full opening. In this region, when the accelerator opening decreases, the throttle valve opening also decreases.However, since this is a region equivalent to the throttle valve being fully opened, the intake pipe pressure becomes substantially constant even when the throttle valve opening changes, and the intake throttle is almost completely closed. Does not occur. On the other hand, in the mode, the throttle valve opening is controlled to an opening substantially equal to the accelerator opening. That is, when the accelerator opening (accelerator pedal depression amount) is 0, the throttle opening is also 0
At (fully closed), when the accelerator opening is 100% (when the accelerator pedal is fully depressed), the throttle opening is also set to 100% (fully open).

【００３３】また、ＥＧＲ弁４１開度は、モードでは
比較的多量のＥＧＲガスを還流させるように設定され、
モードからになるにつれてＥＧＲガス量が低下する
ように制御される。また、モード、ではＥＧＲはほ
ぼ停止される。次に、本実施形態のＮＯX 吸蔵還元触媒
７について説明する。本実施形態のＮＯX 吸蔵還元触媒
７は、例えばアルミナを担体とし、この担体上に例えば
カリウムＫ、ナトリウムＮa 、リチウムＬi 、セシウム
Ｃs のようなアルカリ金属、バリウムＢa 、カルシウム
Ｃa のようなアルカリ土類、ランタンＬa 、セリウムＣ
ｅ、イットリウムＹのような希土類から選ばれた少なく
とも一つの成分と、白金Ｐｔのような貴金属とを担持し
たものである。ＮＯX 吸蔵還元触媒は流入する排気ガス
の空燃比がリーンのときに、排気中のＮＯX （ＮＯ2 、
ＮＯ）を硝酸イオンＮＯ3 - の形で吸収し、流入排気ガ
スがリッチになると吸収したＮＯX を放出するＮＯX の
吸放出作用を行う。The opening of the EGR valve 41 is set so that a relatively large amount of EGR gas is recirculated in the mode.
Control is performed so that the EGR gas amount decreases as the mode is changed. In the mode, EGR is almost stopped. Next, the NO X storage reduction catalyst 7 of the present embodiment will be described. The NO X storage-reduction catalyst 7 of this embodiment uses, for example, alumina as a carrier, and on this carrier, for example, an alkali metal such as potassium K, sodium Na, lithium Li, or cesium Cs, or an alkaline earth such as barium Ba or calcium Ca. , Lanthanum La, cerium C
e, carrying at least one component selected from rare earths such as yttrium Y and a noble metal such as platinum Pt. When the air-fuel ratio of the inflowing exhaust gas is lean, the NO X storage-reduction catalyst reduces the NO X (NO 2 ,
The NO) nitrate ions NO 3 - is absorbed in the form of inflow exhaust gas is performed to absorbing and releasing action of the NO X that releases NO X absorbed and becomes rich.

【００３４】本実施形態では、リーン空燃比運転可能な
機関１が使用されており、機関１がリーン空燃比で運転
されているときにはＮＯX 吸蔵還元触媒は流入する排気
中のＮＯX を吸収する。また、機関１がリッチ空燃比で
運転されると、ＮＯX 吸蔵還元触媒７は吸収したＮＯX
を放出し、リッチ空燃比の排気中のＨＣ、ＣＯ成分を用
いて放出したＮＯX を還元浄化する。本実施形態では、
リーン空燃比運転中にＮＯX 吸蔵還元触媒７に吸収され
たＮＯX 量が増大すると、短時間機関空燃比をリーン空
燃比からリッチ空燃比に切り換えるリッチスパイク運転
を行い、ＮＯX吸蔵還元触媒からのＮＯX の放出と還元
浄化とを行なうようにしている。In this embodiment, the engine 1 capable of operating at a lean air-fuel ratio is used. When the engine 1 is operating at a lean air-fuel ratio, the NO X storage reduction catalyst absorbs NO X in the exhaust gas flowing into the engine. . Further, when the engine 1 is operated at a rich air-fuel ratio, NO X occluding and reducing catalyst 7 is absorbed NO X
Releases, it reduces and purifies the released was NO X with HC, CO components in the exhaust gas of a rich air-fuel ratio. In this embodiment,
When the lean air-fuel ratio the amount of NO X absorbed in the NO X occluding and reducing catalyst 7 during operation increases, performs the rich spike operation for switching to a rich air-fuel ratio for a short time the engine air-fuel ratio from a lean air-fuel ratio from the NO X storage reduction catalyst release that to perform the reduction and purification of NO X.

【００３５】次に、本実施形態の機関１のリッチスパイ
ク操作について説明する。本実施形態では、ＥＣＵ３０
はＮＯX カウンタの値を増減することによりＮＯ X 吸蔵
還元触媒７が吸収保持しているＮＯX 量を推定する。Ｎ
ＯX 吸蔵還元触媒７に単位時間当たりに吸収されるＮＯ
X の量はＮＯX 吸蔵還元触媒に単位時間当たりに流入す
る排気中のＮＯX 量、すなわち機関１で単位時間当たり
に生成されるＮＯX 量に比例している。一方、機関で単
位時間当たりに発生するＮＯX の量は機関への燃料供給
量、空燃比、排気流量等によって定まるため、機関運転
条件が定まればＮＯX 吸蔵還元触媒に吸収されるＮＯX
量を知ることができる。本実施形態では、予め機関運転
条件（アクセル開度、機関回転数、吸入空気量、吸気管
圧力、空燃比、燃料供給量、ＥＧＲ量など）を変えて機
関が単位時間当たりに発生するＮＯX 量を実測し、ＮＯ
X 吸蔵還元触媒７に単位時間当たりに吸収されるＮＯX
量を、例えば機関負荷（燃料噴射量）と機関回転数とを
用いた数値マップの形でＥＣＵ３０のＲＯＭに格納して
いる。ＥＣＵ３０は一定時間毎（上記の単位時間毎）に
機関負荷（燃料噴射量）と機関回転数とからこのマップ
を用いて単位時間当たりにＮＯX 吸蔵還元触媒に吸収さ
れたＮＯX 量を算出し、ＮＯX カウンタをこのＮＯX 吸
収量だけ増大させる。これによりＮＯX カウンタの値は
常にＮＯX 吸蔵還元触媒７に吸収されたＮＯX の量を表
すようになる。ＥＣＵ３０は、機関のリーン空燃比運転
中に、上記ＮＯX カウンタの値が所定値以上に増大した
ときに、短時間機関を前述ののモード（リッチ空燃比
均質混合気燃焼）で運転するリッチスパイク操作を行な
う。これにより、ＮＯX 吸蔵還元触媒から吸収したＮＯ
X が放出され、還元浄化される。なお、機関がリッチ空
燃比運転されると排気中のＨＣ、ＣＯの量が増大し、Ｎ
ＯX 吸蔵還元触媒からはＮＯX が放出され、排気中のＨ
Ｃ、ＣＯにより還元される。ここで、単位時間当たりに
ＮＯX吸蔵還元触媒から放出されて排気中のＨＣ、ＣＯ
により還元されるＮＯX の量は、排気の空燃比（排気中
のＨＣ、ＣＯ量）、排気流量により定まる。本実施形態
では、予め機関運転条件（アクセル開度、機関回転数、
吸入空気量、吸気管圧力、空燃比、燃料供給量、ＥＧＲ
量など）を変えて機関をリッチ空燃比で運転し、ＮＯX
吸蔵還元触媒７から単位時間当たりに放出、還元浄化さ
れるＮＯX 量を実測し、機関のリッチ空燃比運転時にＮ
ＯX 吸蔵還元触媒７から単位時間当たり放出されるＮＯ
X 量を、例えば機関負荷（燃料噴射量）と機関回転数と
を用いた数値マップの形でＥＣＵ３０のＲＯＭに格納し
ている。ＥＣＵ３０は機関のリッチ空燃比運転時に一定
時間毎（上記の単位時間毎）に機関負荷（燃料噴射量）
と機関回転数とからこのマップを用いて単位時間当たり
にＮＯX 吸蔵還元触媒から放出されるＮＯX 量を算出
し、ＮＯX カウンタをこのＮＯX 吸収量だけ減少させ
る。そして、リッチスパイク操作時には、このＮＯX カ
ウンタの値が０になった時にリッチスパイク操作を終了
する。Next, the rich spy of the engine 1 of this embodiment is described.
A description will be given of the lock operation. In the present embodiment, the ECU 30
Is NOXNO by increasing or decreasing the counter value XOcclusion
NO retained by the reduction catalyst 7XEstimate the amount. N
OXNO absorbed by the storage reduction catalyst 7 per unit time
XNOXFlows into the storage reduction catalyst per unit time
NO in exhaustXQuantity, ie per unit time at institution 1
NO generated inXIt is proportional to the quantity. On the other hand,
NO generated per unit timeXAmount of fuel to the engine
Engine operation because it is determined by the amount, air-fuel ratio, exhaust flow
NO if conditions are determinedXNO absorbed by the storage reduction catalystX
You can know the quantity. In this embodiment, the engine operation is performed in advance.
Conditions (accelerator opening, engine speed, intake air amount, intake pipe
Pressure, air-fuel ratio, fuel supply, EGR, etc.)
NO generated per unit timeXMeasure the amount, NO
XNO absorbed by the storage reduction catalyst 7 per unit timeX
The engine load (fuel injection amount) and the engine speed.
Stored in the ROM of the ECU 30 in the form of the numerical map used
I have. The ECU 30 operates at regular intervals (each of the above unit times).
This map is based on engine load (fuel injection amount) and engine speed.
NO per unit time usingXAbsorbed by storage reduction catalyst
NOXCalculate the quantity, NOXSet the counter to this NOXSucking
Increase by yield. This makes NOXThe counter value is
Always NOXNO absorbed by storage reduction catalyst 7XTable of quantity
I will be. The ECU 30 performs a lean air-fuel ratio operation of the engine.
In the above NOXThe counter value has increased beyond the specified value
When the short-time engine is in the aforementioned mode (rich air-fuel ratio
Perform rich spike operation that operates with homogeneous mixture combustion).
U. Thereby, NOXNO absorbed from the storage reduction catalyst
XIs released and reduced and purified. In addition, the engine is rich empty
When the fuel-ratio operation is performed, the amounts of HC and CO in the exhaust gas increase, and N
OXNO from the storage reduction catalystXIs released and H in the exhaust
It is reduced by C and CO. Here, per unit time
NOXHC and CO in exhaust gas released from the storage reduction catalyst
NO reduced byXIs determined by the air-fuel ratio of the exhaust
HC and CO amounts) and the exhaust flow rate. This embodiment
Then, the engine operating conditions (accelerator opening, engine speed,
Intake air amount, intake pipe pressure, air-fuel ratio, fuel supply amount, EGR
The engine is operated at a rich air-fuel ratioX
Released from the storage reduction catalyst 7 per unit time, reduced and purified
NOXMeasured during operation of the engine at rich air-fuel ratio
OXNO released per unit time from the storage reduction catalyst 7
XFor example, the engine load (fuel injection amount) and the engine speed
Stored in the ROM of the ECU 30 in the form of a numerical map using
ing. ECU 30 is constant during rich air-fuel ratio operation of the engine
Engine load (fuel injection amount) every time (each unit time above)
Per unit time using this map from the
NOXNO released from the storage reduction catalystXCalculate quantity
And NOXSet the counter to this NOXReduce the amount absorbed
You. At the time of the rich spike operation, this NOXMosquito
Ends rich spike operation when counter value reaches 0
I do.

【００３６】すなわち、本実施形態では機関１のリーン
空燃比運転が続きＮＯX 吸蔵還元触媒７に吸蔵されたＮ
ＯX 量が所定量まで増大すると機関運転状態から要求さ
れる機関負荷とは無関係に機関をリッチ空燃比で運転す
るリッチスパイク操作が行われる。また、リッチスパイ
ク操作はＮＯX 吸蔵還元触媒の吸蔵したＮＯX 量とは別
に行われる場合がある。すなわち、本実施形態の機関で
はモードからのリーン空燃比運転ではスロットル弁
１５は全開に近い開度とされているため吸気管の負圧が
低く（絶対圧力が高く）なっている。一方、車両ブレー
キに負圧を用いた倍力装置を使用するような場合には、
常に倍力装置作動用の負圧を確保しておく必要がある
が、リーン空燃比運転中は吸気管負圧が低くなっている
ためスロットル弁下流側の吸気通路から倍力装置に負圧
を導入することができない。そこで、本実施形態では倍
力装置に負圧タンクを設け、リーン空燃比運転中はこの
負圧タンクに蓄えた負圧を用いて倍力装置を作動させる
ようにしている。また、倍力装置の作動により負圧タン
ク内の圧力が上昇（負圧が低下）した場合には上記と同
様なリッチスパイク操作を行う。リーン空燃比運転が行
われる負荷領域でリッチスパイク操作が行われるとスロ
ットル弁１５開度は低下しスロットル弁１５下流側に大
きな負圧が発生するようになる。本実施形態では倍力装
置に負圧を供給する負圧タンク等の負圧が低下した場合
にも機関の要求負荷とは無関係にリッチスパイク操作が
行われる。通常の運転中にモードのリーン空燃比成層
燃焼運転から加速等で機関負荷が増大する場合にはある
程度の時間をかけて機関運転モードがから、、
のモードを経てのリッチ空燃比モードに切り換えられ
る。リッチスパイク操作時にはできるだけ早く空燃比を
リッチに切り換えることが必要とされるが、モードの
リーン空燃比成層燃焼運転から直接モードのリッチ空
燃比均質混合気燃焼に切り換えると、燃焼モードの変化
（成層燃焼から均質混合気燃焼）と空燃比の変化（リー
ン空燃比からリッチ空燃比）との両方が同時に生じるた
め機関の出力トルクが大きく変動してしまう。そこで、
通常、リーン空燃比成層燃焼運転（モード）からのリ
ッチスパイク操作時にもリッチ空燃比均質混合気燃焼運
転（モード）に至るまでにモード、で機関数回転
程度の運転を行って徐々に空燃比と運転モードとを切り
換えるようにしている。また、前述したように通常運転
時のモード（リッチ空燃比均質混合気燃焼）では機関
の燃料噴射量等の制御量は機関吸入空気量と機関回転数
（機関吸気管負圧と機関回転数）とに基づいて設定され
ているが、通常リッチスパイク操作時のモードの運転
時間は短いため、リッチスパイク操作時のモード運転
では、モードからと同様に要求機関負荷と機関回転
数（アクセル開度と機関回転数）とに基づいて設定する
ようにして制御の簡素化が図られている。すなわち、従
来はリッチスパイク操作時のモード（リーン空燃比均
質混合気空燃比燃焼）用に別途数値マップが準備されて
おり、リッチスパイク中にモードからモードへの切
り換えが行われると引き続き要求機関負荷と機関回転数
（アクセル開度と機関回転数）とに基づいて燃料噴射量
をはじめとする各制御量が決定されていた。That is, in this embodiment, the lean air-fuel ratio operation of the engine 1 continues, and the NO stored in the NO X storage reduction catalyst 7 continues.
O X amount rich spike operation is performed to operate independently of the engine at a rich air-fuel ratio and increasing the engine load required from the engine operating condition to a predetermined amount. Moreover, the rich spike operation is sometimes separately performed from the occluded amount of NO X in the NO X storage reduction catalyst. That is, in the engine of the present embodiment, the negative pressure of the intake pipe is low (absolute pressure is high) in the lean air-fuel ratio operation from the mode, since the throttle valve 15 has an opening close to full open. On the other hand, when using a booster using negative pressure for vehicle braking,
It is necessary to always maintain a negative pressure for booster operation.However, during lean air-fuel ratio operation, negative pressure is supplied from the intake passage downstream of the throttle valve to the booster because the intake pipe negative pressure is low. Can not be introduced. Therefore, in the present embodiment, the booster is provided with a negative pressure tank, and the booster is operated using the negative pressure stored in the negative pressure tank during the lean air-fuel ratio operation. When the pressure in the negative pressure tank increases (negative pressure decreases) due to the operation of the booster, the same rich spike operation as described above is performed. When the rich spike operation is performed in the load region where the lean air-fuel ratio operation is performed, the opening of the throttle valve 15 decreases, and a large negative pressure is generated downstream of the throttle valve 15. In the present embodiment, even when the negative pressure of the negative pressure tank or the like that supplies the negative pressure to the booster drops, the rich spike operation is performed irrespective of the required load of the engine. If the engine load increases due to acceleration or the like from the lean air-fuel ratio stratified combustion operation mode during normal operation, the engine operation mode takes a certain time from the engine operation mode,
Mode is switched to the rich air-fuel ratio mode. At the time of the rich spike operation, it is necessary to switch the air-fuel ratio to rich as soon as possible. However, when the mode is switched from the lean air-fuel ratio stratified combustion operation to the direct mode rich air-fuel ratio homogeneous mixture combustion, the combustion mode changes (stratified combustion). Therefore, both the change in the air-fuel ratio and the change in the air-fuel ratio (from the lean air-fuel ratio to the rich air-fuel ratio) occur at the same time, so that the output torque of the engine greatly varies. Therefore,
Normally, even during the rich spike operation from the lean air-fuel ratio stratified combustion operation (mode), the mode is changed to the rich air-fuel ratio homogeneous mixture combustion operation (mode), and the operation is performed at about the number of revolutions of the engine to gradually increase the air-fuel ratio. The operation mode is switched. As described above, in the normal operation mode (rich air-fuel ratio homogeneous mixture combustion), the control amount such as the fuel injection amount of the engine is the engine intake air amount and the engine speed (the engine intake pipe negative pressure and the engine speed). However, since the operation time of the mode during the rich spike operation is usually short, the mode engine operation during the rich spike operation requires the required engine load and the engine speed (the accelerator opening and the (Engine speed) to simplify the control. That is, conventionally, a numerical map is separately prepared for the mode during the rich spike operation (lean air-fuel ratio homogeneous mixture air-fuel ratio combustion), and when the mode is switched from the mode to the rich spike mode, the required engine load continues. Each control amount including the fuel injection amount has been determined based on the engine speed and the engine speed (accelerator opening and engine speed).

【００３７】ところが、この場合燃料噴射量とスロット
ル弁開度とは要求機関負荷と機関回転数とに基づいて予
め準備された数値マップから決定される値に直ちに変化
することになるが、実際に機関に吸入される空気量はス
ロットル弁開度変化より遅れて変化するので変化後のス
ロットル弁開度に対応した値になるまでに多少の時間遅
れが生じることになる。このため、モードへの切り換
え時にはスロットル弁開度は直ちに低下しても実際の機
関吸入空気量は直ちには低下しない。一方、燃料噴射量
はモードへの切り換え直後からスロットル弁開度に対
応した値に変更されるため、切り換え直後は燃料噴射量
より実際の機関吸入空気量が多くなってしまい実際の機
関空燃比が目標値（リッチ空燃比）よりリーン側にずれ
る問題が生じる。In this case, however, the fuel injection amount and the throttle valve opening immediately change to values determined from a numerical map prepared in advance based on the required engine load and the engine speed. Since the amount of air taken into the engine changes later than the change in the throttle valve opening, a slight time delay occurs until the air amount reaches a value corresponding to the changed throttle valve opening. Therefore, when switching to the mode, the actual engine intake air amount does not immediately decrease even if the throttle valve opening immediately decreases. On the other hand, the fuel injection amount is changed to a value corresponding to the throttle valve opening immediately after switching to the mode, so immediately after the switching, the actual engine intake air amount becomes larger than the fuel injection amount, and the actual engine air-fuel ratio becomes smaller. There is a problem that the target value (rich air-fuel ratio) is shifted to the lean side.

【００３８】このため、従来リッチスパイク操作時に機
関空燃比がリッチ空燃比（モード）に切り換えられた
直後に機関空燃比が理論空燃比近傍のリーン空燃比領域
（例えば空燃比で２０以下）で運転され、ＮＯX 吸蔵還
元触媒の吸蔵能力低下のために未浄化のＮＯX が大気に
放出される場合が生じていた。本実施形態では、リッチ
スパイク操作時のリッチ空燃比均質混合気燃焼モード時
には燃料噴射量を機関吸入空気量と機関回転数とに基づ
いて設定することによりこの問題を解決している。すな
わち、本実施形態ではリッチスパイク操作時に機関運転
モードがモードのリッチ空燃比均質混合気燃焼モード
に切り換えられると燃料噴射量が吸気圧センサで検出さ
れた吸気管圧力と機関回転数とから定まる実際の機関吸
入空気量と機関回転数とに基づいて所定のリッチ空燃比
（例えば空燃比で１２から１４）を得る値に設定され
る。このため、機関運転モードがリッチ空燃比均質混合
気燃焼モードに切り換えられた直後から燃料噴射量は実
際の機関吸入空気量に対して所定のリッチ空燃比が得ら
れる値に設定されるようになり、切り換え直後から安定
したリッチ空燃比が得られるようになる。For this reason, the engine is operated in a lean air-fuel ratio region (for example, an air-fuel ratio of 20 or less) near the stoichiometric air-fuel ratio immediately after the engine air-fuel ratio is switched to the rich air-fuel ratio (mode) during the conventional rich spike operation. In some cases, unpurified NO X is released to the atmosphere due to a decrease in the storage capacity of the NO X storage reduction catalyst. In the present embodiment, this problem is solved by setting the fuel injection amount based on the engine intake air amount and the engine speed in the rich air-fuel ratio homogeneous mixture combustion mode during the rich spike operation. That is, in the present embodiment, when the engine operation mode is switched to the rich air-fuel ratio homogeneous mixture combustion mode during the rich spike operation, the actual fuel injection amount is determined from the intake pipe pressure detected by the intake pressure sensor and the engine speed. Is set to a value to obtain a predetermined rich air-fuel ratio (for example, an air-fuel ratio of 12 to 14) based on the engine intake air amount and the engine speed. For this reason, immediately after the engine operation mode is switched to the rich air-fuel ratio homogeneous mixture combustion mode, the fuel injection amount is set to a value at which a predetermined rich air-fuel ratio is obtained with respect to the actual engine intake air amount. Thus, a stable rich air-fuel ratio can be obtained immediately after the switching.

【００３９】図２は、本実施形態のリッチスパイク操作
時のスロットル弁開度ＴＡ、吸気管圧力ＰＭ、燃料噴射
量ＱＩＮＪ及び機関燃焼空燃比Ａ／Ｆの変化を示すタイ
ミング図である。図２に示すようにモード（リーン空
燃比成層燃焼）の状態からリッチスパイク操作が開始さ
れると、運転モードはモード、モードを経てモード
に切り換えられる。このときスロットル弁開度ＴＡは
モード、モードに切り換わったときにリッチスパイ
ク操作時のそれぞれの運転モード用の数値マップに基づ
いてアクセル開度と機関回転数（要求機関負荷と機関回
転数）とから定まる値に切り換えられる。この場合図２
に示すように吸入空気量（吸気管圧力ＰＭ）はスロット
ル弁開度ＴＡが変化しても直ちに変化後のスロットル弁
開度に対応した値にはならず比較的緩やかに変化して、
モードの定常状態における空気量に到達する。FIG. 2 is a timing chart showing changes in the throttle valve opening TA, the intake pipe pressure PM, the fuel injection amount QINJ, and the engine combustion air-fuel ratio A / F during the rich spike operation of this embodiment. As shown in FIG. 2, when the rich spike operation is started from the mode (lean air-fuel ratio stratified combustion), the operation mode is switched to the mode via the mode. At this time, the throttle valve opening TA is set to the mode, the accelerator opening and the engine speed (required engine load and engine speed) based on the numerical map for each operation mode at the time of rich spike operation when the mode is switched to the mode. Can be switched to a value determined from. In this case, FIG.
As shown in (2), even if the throttle valve opening TA changes, the intake air amount (intake pipe pressure PM) does not immediately become a value corresponding to the changed throttle valve opening, but changes relatively slowly.
The air volume in the steady state of the mode is reached.

【００４０】また、本実施形態にもおいても燃料噴射量
ＱＩＮＪはモードからではアクセル開度と機関回転
数とに基づいて設定されるため、図２に示すように運転
モードが、に切り換えられる毎にスロットル弁開度
ＴＡと同様にステップ状に変化する。しかし、本実施形
態ではモードからモードに運転状態が切り換えられ
ると燃料噴射量ＱＩＮＪは機関吸入空気量と機関回転数
（吸気管負圧と機関回転数）とに応じて設定されるよう
になるため、モード切り換え直後は実際の吸入空気量
に応じた値まで一旦急増し、その後吸入空気量（ＰＭ）
の低下に合わせて減少する。このため、機関燃焼空燃比
Ａ／Ｆはモードからモードに運転モードが切り換え
られると直ちに所定のリッチ空燃比（１２から１４程
度）に変化するようになる。Also in this embodiment, since the fuel injection amount QINJ is set based on the accelerator opening and the engine speed from the mode, the operation mode is switched to the operation mode as shown in FIG. Every time, it changes stepwise similarly to the throttle valve opening TA. However, in this embodiment, when the operation state is switched from the mode to the mode, the fuel injection amount QINJ is set according to the engine intake air amount and the engine speed (the intake pipe negative pressure and the engine speed). Immediately after the mode switching, the value temporarily increases to a value corresponding to the actual intake air amount, and then the intake air amount (PM)
Decrease in accordance with the decrease of For this reason, the engine combustion air-fuel ratio A / F immediately changes to a predetermined rich air-fuel ratio (about 12 to 14) when the operation mode is switched from the mode to the mode.

【００４１】一方、図２の点線は従来のようにリッチス
パイク時のモードでの運転時に要求機関負荷と機関回
転数とに基づいて燃料噴射量を設定した場合のモード
開始直後における燃料噴射量ＱＩＮＪと機関空燃比Ａ／
Ｆとの変化を示している。この場合には図２に点線で示
すように、モードからに切り換えが行われると燃料
噴射量ＱＩＮＪはスロットル弁開度ＴＡの変化に応じて
ステップ状に変化しモードの運転の間一定値に維持さ
れる。ところが、前述したように実際には機関吸入空気
量はスロットル弁開度ＴＡの変化に対して遅れて変化す
るため、モードの運転開始直後は充分に吸入空気量が
減少していない。このため、燃料噴射量に対して吸入空
気量が過大となり、吸入空気量が充分に低減してスロッ
トル弁開度に対応した値になるまでの間機関空燃比Ａ／
Ｆは充分なリッチ空燃比にならない。このため、機関空
燃比が理論空燃比近傍のリーン空燃比領域にとどまる時
間が長くなり、ＮＯX 吸蔵還元触媒から未浄化のＮＯX
が放出されるようになる。On the other hand, the dotted line in FIG. 2 indicates the fuel injection amount QINJ immediately after the start of the mode when the fuel injection amount is set based on the required engine load and the engine speed during the operation in the mode at the time of the rich spike as in the prior art. And engine air-fuel ratio A /
The change from F is shown. In this case, as shown by the dotted line in FIG. 2, when the mode is switched to the mode, the fuel injection amount QINJ changes stepwise according to the change in the throttle valve opening TA and is maintained at a constant value during the operation of the mode. Is done. However, as described above, since the engine intake air amount actually changes with a delay with respect to the change in the throttle valve opening TA, the intake air amount is not sufficiently reduced immediately after the start of the mode operation. For this reason, the intake air amount becomes excessive with respect to the fuel injection amount, and the engine air-fuel ratio A / A is maintained until the intake air amount is sufficiently reduced to a value corresponding to the throttle valve opening.
F does not have a sufficient rich air-fuel ratio. Therefore, the time the engine air-fuel ratio remains in the lean air-fuel ratio range of the near stoichiometric air-fuel ratio is increased, unpurified from the NO X storage reduction catalyst NO X
Will be released.

【００４２】図３は上述した燃料噴射量ＱＩＮＪの算出
操作を示すフローチャートである。本操作はＥＣＵ３０
により一定時間毎に実行されるルーチンとして行われ
る。図３において、ステップ３０１では現在の機関の運
転モード（モード〜）が読み込まれる。そして、ス
テップ３０３ではステップ３０１で読み込まれた現在の
運転モードが通常運転時（リッチスパイク操作実行時以
外の運転時）のモード（理論空燃比均質混合気燃焼）
かモード（リッチ空燃比均質混合気燃焼）のいずれか
であるか否かが判定され、いずれでもない場合には次に
ステップ３０５で現在のモードがリッチスパイク操作中
のモード（リッチ空燃比均質混合気燃焼）であるか否
かが判定される。FIG. 3 is a flowchart showing the operation for calculating the above-described fuel injection amount QINJ. This operation is performed by the ECU 30
Is performed as a routine executed at regular intervals. In FIG. 3, in step 301, the current operation mode (mode to) of the engine is read. Then, in step 303, the current operation mode read in step 301 is the mode (normal stoichiometric air-fuel ratio homogeneous air-fuel mixture combustion) in the normal operation (operation other than the execution of the rich spike operation).
Or the mode (rich air-fuel ratio homogeneous mixture combustion) is determined. If neither is the case, then in step 305, the current mode is changed to the mode during rich spike operation (rich air-fuel ratio homogeneous mixture). Is determined.

【００４３】ステップ３０３で現在の機関運転モードが
通常運転時のモードまたは、またはステップ３０５
で現在の運転モードがリッチスパイク操作中のモード
であった場合にはステップ３０７が実行され、燃料噴射
量ＱＩＮＪの値が吸気圧センサ３５（図１）で検出され
た吸気管圧力ＰＭと機関回転数ＮＥとに基づいて予め準
備された数値マップから決定される。これにより、燃料
噴射量ＱＩＮＪは実際の機関回転数と実際の機関吸入空
気量とに基づいて所定のリッチ空燃比を得ることができ
る値に設定され、機関空燃比は直ちに所定のリッチ空燃
比に変化する。In step 303, the current engine operation mode is the normal operation mode or step 305.
If the current operation mode is the mode during the rich spike operation, step 307 is executed, and the value of the fuel injection amount QINJ is determined by the intake pipe pressure PM detected by the intake pressure sensor 35 (FIG. 1) and the engine speed. It is determined from a numerical map prepared in advance based on the number NE. As a result, the fuel injection amount QINJ is set to a value at which a predetermined rich air-fuel ratio can be obtained based on the actual engine speed and the actual engine intake air amount, and the engine air-fuel ratio immediately becomes the predetermined rich air-fuel ratio. Change.

【００４４】一方、ステップ３０３、３０５で現在の機
関運転モードが通常運転時のモード、及びリッチス
パイク操作中のモードのいずれでもない場合には、ス
テップ３０９が実行され、燃料噴射量ＱＩＮＪはアクセ
ル開度センサ３７で検出されたアクセル開度ＡＣＣＰと
機関回転数とに基づいて設定される。これにより、モー
ドからでは常に燃料噴射量ＱＩＮＪは要求機関負荷
と機関回転数とに応じた値に設定されるようになる。On the other hand, if the current engine operation mode is neither the normal operation mode nor the rich spike operation mode in steps 303 and 305, step 309 is executed, and the fuel injection amount QINJ is set to the accelerator open state. It is set based on the accelerator opening ACCP detected by the degree sensor 37 and the engine speed. Thus, in the mode, the fuel injection amount QINJ is always set to a value corresponding to the required engine load and the engine speed.

【００４５】本実施形態では、上述したようにリッチス
パイク操作時にモードの運転が行われると直ちに機関
空燃比は所定のリッチ空燃比に変化するため、ＮＯX 吸
蔵還元触媒から未浄化のＮＯX が放出されることが防止
される。また、例えばＮＯX吸蔵還元触媒の劣化は、Ｎ
ＯX 吸蔵還元触媒に流入する排気空燃比がリーンからリ
ッチに変化した時からＮＯX 吸蔵還元触媒出口での排気
空燃比がリッチに変化するまでに要する時間に基づいて
判定することができる。すなわち、リッチスパイク操作
時にＮＯX 吸蔵還元触媒から吸収したＮＯX が放出され
ると排気中のＨＣ、ＣＯ成分が放出されたＮＯX により
酸化されるため、ＮＯX 吸蔵還元触媒出口での排気空燃
比は直ちにはリッチ空燃比に変化せず、ＮＯX 吸蔵還元
触媒からのＮＯX 放出が生じている間は理論空燃比近傍
に維持され、ＮＯX の放出が完了すると同時にリッチ空
燃比に変化する。このため、リッチスパイク操作時に機
関空燃比がリーンからリッチに切り換えられた時から、
ＮＯX 吸蔵還元触媒７下流側の空燃比センサ３１で検出
された排気空燃比がリッチ空燃比に変化するまでの時間
を測定することにより、ＮＯX 吸蔵還元触媒に吸収され
たＮＯX 量を算出することができ、更に算出したＮＯX
吸蔵還元触媒の吸収ＮＯX 量が所定値より低下した場合
にはＮＯX 吸蔵還元触媒のＮＯX 吸蔵能力が低下、すな
わちＮＯX 吸蔵還元触媒が劣化したと判定することがで
きる。[0045] In this embodiment, since immediately the engine air-fuel ratio when the operation mode is performed at the time of the rich-spike operation as described above which changes to a predetermined rich air-fuel ratio, NO X from storage reduction catalyst unpurified NO X is Release is prevented. Further, for example, deterioration of the NO X occluding and reducing catalyst, N
The determination can be made based on the time required from the time when the exhaust air-fuel ratio flowing into the O X storage reduction catalyst changes from lean to rich to the time when the exhaust air-fuel ratio at the NO X storage reduction catalyst outlet changes to rich. That is, since the HC in the exhaust gas and NO X absorbed from the NO X storage reduction catalyst during the rich spike operation is released, CO components are oxidized by the released NO X, the exhaust air in the NO X storage reduction catalyst outlet The fuel ratio does not immediately change to the rich air-fuel ratio, but is maintained near the stoichiometric air-fuel ratio while NO X is being released from the NO X storage reduction catalyst, and changes to the rich air-fuel ratio at the same time as the release of NO X is completed. . Therefore, when the engine air-fuel ratio is switched from lean to rich during the rich spike operation,
By the NO X storage reduction catalyst 7 exhaust gas air-fuel ratio detected by the air-fuel ratio sensor 31 on the downstream side to measure the time until the change to the rich air-fuel ratio, calculated amount of NO X absorbed in the NO X occluding and reducing catalyst And the calculated NO X
Absorbed amount of NO X in the storage reduction catalyst is reduced the NO X storage ability of the NO X occluding and reducing catalyst when lower than the predetermined value, i.e., it can be determined that the NO X storage reduction catalyst has degraded.

【００４６】ところが、従来のようにリッチスパイク操
作時に全て要求機関負荷と機関回転数とに基づいて燃料
噴射量を設定していると、機関の運転モードがリッチ空
燃比均質混合気燃焼モードに切り換えられても直ちには
実際の空燃比はリッチ空燃比に変化せず、ＮＯX 吸蔵還
元触媒に流入する排気の空燃比にばらつきを生じるよう
になる。このため、上記の方法でＮＯX 吸蔵還元触媒の
劣化を判定していると劣化の判定に誤差を生じる問題が
ある。However, if the fuel injection amount is set based on the required engine load and the engine speed during the rich spike operation as in the prior art, the operation mode of the engine is switched to the rich air-fuel ratio homogeneous mixture combustion mode. Even if it is, the actual air-fuel ratio does not immediately change to the rich air-fuel ratio, and the air-fuel ratio of the exhaust gas flowing into the NO X storage reduction catalyst varies. For this reason, there is a problem that when the deterioration of the NO X storage reduction catalyst is determined by the above method, an error is caused in the determination of the deterioration.

【００４７】これに対して、本実施形態ではリッチスパ
イク操作中のリッチ空燃比均質混合気運転時に直ちにＮ
ＯX 吸蔵還元触媒に流入する排気空燃比が安定したリッ
チ空燃比に変化するため上記劣化判定の誤差を防止する
ことが可能となっている。なお、本実施形態では実際の
機関吸入空気量を吸気管圧力と機関回転数とに基づいて
求めているが、例えば吸気通路にエアフローメータを有
する場合には、エアフローメータで直接検出した吸入空
気量と機関回転数とに基づいてリッチスパイク操作中の
リッチ空燃比均質混合気燃焼運転時の燃料噴射量を決定
するようにしてもよい。On the other hand, in the present embodiment, when the rich air-fuel ratio homogeneous mixture operation is performed during the rich spike operation, N
O X occluding air-fuel ratio of the exhaust gas flowing into the reduction catalyst it is possible to prevent the error of the deterioration determination for changing a stable rich air-fuel ratio. In the present embodiment, the actual engine intake air amount is obtained based on the intake pipe pressure and the engine speed. For example, when an air flow meter is provided in the intake passage, the intake air amount directly detected by the air flow meter is obtained. The fuel injection amount during the rich air-fuel ratio homogeneous mixture combustion operation during the rich spike operation may be determined based on the engine speed and the engine speed.

【００４８】また、本実施形態ではリッチスパイク操作
中のリッチ空燃比均質混合気燃焼時には燃料噴射量は機
関吸入空気量と機関回転数とに基づいて設定されるが、
ＮＯ X 吸蔵還元触媒７上流側の排気通路の空燃比センサ
２９ａ、２９ｂで検出した排気空燃比が所定のリッチ空
燃比になるように、機関吸入空気量と機関回転数とに基
づいて設定された燃料噴射量を更に空燃比センサ２９
ａ、２９ｂの出力に基づいて補正するようにすれば、リ
ッチスパイク操作時に空燃比を正確に所定のリッチ空燃
比に制御することが可能となる。In this embodiment, the rich spike operation is performed.
During the combustion of a homogeneous rich air-fuel mixture, the fuel injection
It is set based on the intake air amount and the engine speed.
NO XAir-fuel ratio sensor in the exhaust passage upstream of the storage reduction catalyst 7
The exhaust air-fuel ratio detected at 29a, 29b is a predetermined rich air
Based on the engine intake air amount and the engine speed, the fuel
The fuel injection amount set based on the air-fuel ratio sensor 29
If the correction is made based on the outputs of a and 29b,
The air-fuel ratio is accurately specified during the switch spike operation.
The ratio can be controlled.

【００４９】上述のように、上記実施形態ではリッチス
パイク操作中のリッチ空燃比均質混合気燃焼時に燃料噴
射量を機関吸入空気量と機関回転数とに基づいて設定す
ることにより、リーン空燃比からリッチ空燃比への切り
換え時に機関空燃比が所定のリッチ空燃比に変化する時
間を短縮している。しかし、従来のように要求機関負荷
と機関回転数とに基づいて燃料噴射量を設定しながら、
上記時間を短縮することも可能である。As described above, in the above-described embodiment, the fuel injection amount is set based on the engine intake air amount and the engine speed during the combustion of the rich air-fuel ratio homogeneous mixture during the rich spike operation. The time during which the engine air-fuel ratio changes to a predetermined rich air-fuel ratio when switching to the rich air-fuel ratio is reduced. However, while setting the fuel injection amount based on the required engine load and the engine speed as in the past,
It is also possible to shorten the time.

【００５０】前述したようにリーン空燃比からリッチ空
燃比への切り換え時に所定のリッチ空燃比への到達が遅
れる原因はスロットル弁開度変化に対して実際の機関吸
入空気量変化の追従が遅れることによっている。このた
め、例えばリッチスパイク操作中のスロットル弁開度変
化時（モードからへの切り換え時）にスロットル弁
開度の変化速度に応じて燃料を増量するようにしてもよ
い。この場合、例えばスロットル弁開度の変化速度（減
少速度）が大きい場合には変化直後の実際の吸入空気量
とスロットル弁開度に対応した吸入空気量との差が大き
くなるため、スロットル弁開度の変化速度が大きいほど
燃料を増量するようにすればよい。As described above, when switching from the lean air-fuel ratio to the rich air-fuel ratio, the delay in reaching the predetermined rich air-fuel ratio is caused by the delay in following the change in the actual engine intake air amount with respect to the change in the throttle valve opening. Depending on. Therefore, for example, when the throttle valve opening changes during the rich spike operation (when switching from the mode), the fuel may be increased according to the changing speed of the throttle valve opening. In this case, for example, when the change speed (decrease speed) of the throttle valve opening is large, the difference between the actual intake air amount immediately after the change and the intake air amount corresponding to the throttle valve opening becomes large. The fuel may be increased as the rate of change of the degree increases.

【００５１】図４は、スロットル弁開度変化速度に応じ
た燃料の増量補正を行う場合の燃料噴射量補正操作を説
明するフローチャートである。本操作はＥＣＵ３０によ
り一定時間毎に実行される。図４において操作がスター
トすると、ステップ４０１ではスロットル弁開度ＴＡ、
機関回転数ＮＥ及び現在の機関運転モード（モードか
ら）が読み込まれ、ステップ４０３ではステップ４０
１で読み込まれた現在の機関運転モードがリッチスパイ
ク操作中のモード（リッチ空燃比均質混合気燃焼モー
ド）か否かが判定される。現在リッチスパイク操作中の
のモードで運転が行われている場合には次にステップ
４０５に進み現在のスロットル弁開度ＴＡの前回操作実
行時からの変化量ΔＴＡが、ΔＴＡ＝ＴＡ−ＴＡOLD と
して算出される。ＴＡOLD は前回操作実行時にステップ
４０１で読み込んだスロットル弁開度である。そして、
ステップ４０７では燃料噴射量の増量係数ｆｄｌｔａが
ΔＴＡと機関回転数ＮＥとに基づいて予め準備した数値
マップから設定され、ステップ４１９ではアクセル開度
と機関回転数とから定まる燃料噴射量ＱＩＮＪに増量係
数ｆｄｌｔａを乗じた値が新たにＱＩＮＪとして設定さ
れる。前述したように、増量係数ｆｄｌｔａはΔＴＡが
負の大きな値になるほど大きな正の値かつｆｄｌｔａ＞
１となるように設定される。また、ΔＴＡが同一であれ
ばｆｄｌｔａの値は機関回転数が高い程大きな値とな
る。FIG. 4 is a flow chart for explaining the fuel injection amount correction operation in the case of performing the fuel increase correction in accordance with the throttle valve opening change speed. This operation is executed by the ECU 30 at regular intervals. When the operation starts in FIG. 4, in step 401, the throttle valve opening degree TA,
The engine speed NE and the current engine operation mode (from the mode) are read.
It is determined whether or not the current engine operation mode read in 1 is a mode during a rich spike operation (a rich air-fuel ratio homogeneous mixture combustion mode). If the operation is being performed in the mode in which the rich spike operation is currently being performed, the process proceeds to step 405, where the change amount ΔTA of the current throttle valve opening TA from the previous operation execution time is set as ΔTA = TA−TA OLD. Is calculated. TA OLD is the throttle valve opening read in step 401 during the previous execution of the operation. And
In step 407, the fuel injection amount increase coefficient fdlta is set from a numerical map prepared in advance based on ΔTA and the engine speed NE. In step 419, the fuel injection amount QINJ is determined by the accelerator opening and the engine speed. The value multiplied by fdlta is newly set as QINJ. As described above, the increase coefficient fdlta becomes larger as ΔTA becomes a larger negative value, and fdlta>
It is set to be 1. If ΔTA is the same, the value of fdlta increases as the engine speed increases.

【００５２】上記によりＱＩＮＪを補正後、ステップ４
１１では現在のＴＡの値を用いてＴＡOLD の値を更新し
て操作を終了する。図４の操作を行うことにより、リッ
チスパイク操作中にリッチ空燃比均質混合気燃焼モード
になりスロットル弁開度ＴＡが絞られると燃料噴射量が
増量されるため、実際の機関吸入空気量が充分に減少し
ていない場合でも機関の実際の空燃比は直ちにリッチ空
燃比に変化するようになり、ＮＯX 吸蔵還元触媒から未
浄化のＮＯX が放出されることが防止される。After correcting QINJ as described above, step 4
At 11, the value of TA OLD is updated using the current value of TA, and the operation is terminated. By performing the operation in FIG. 4, the rich air-fuel ratio homogeneous mixture combustion mode is set during the rich spike operation, and the fuel injection amount is increased when the throttle valve opening TA is reduced, so that the actual engine intake air amount is sufficient. The actual air-fuel ratio of the engine immediately changes to the rich air-fuel ratio even if it has not been reduced to a low value, and the emission of unpurified NO X from the NO X storage reduction catalyst is prevented.

【００５３】なお、上記のようにスロットル弁開度変化
量ΔＴＡに応じて燃料を増量する代りにリッチスパイク
操作中に運転モードがリッチ空燃比均質混合気燃焼モー
ドに切り換えられた直後所定時間だけ目標空燃比を更に
リッチ側に設定するようにしてもよい。リッチ空燃比均
質混合気燃焼モード変化直後の所定時間目標空燃比を更
にリッチに設定することにより、吸入空気量変化が充分
に低下しない間も機関空燃比が理論空燃比近傍のリーン
空燃比になることが防止されるため、ＮＯX 吸蔵還元触
媒から未浄化のＮＯX が放出されることが防止される。Instead of increasing the fuel in accordance with the throttle valve opening change amount ΔTA as described above, the target mode is set for a predetermined time immediately after the operation mode is switched to the rich air-fuel ratio homogeneous mixture combustion mode during the rich spike operation. The air-fuel ratio may be set further to the rich side. Rich air-fuel ratio By setting the target air-fuel ratio further rich for a predetermined time immediately after the change of the homogeneous air-fuel mixture combustion mode, the engine air-fuel ratio becomes a lean air-fuel ratio near the stoichiometric air-fuel ratio even when the intake air amount change does not sufficiently decrease. since it is possible to prevent, that the NO X unpurified from the NO X storage reduction catalyst is released is prevented.

【００５４】[0054]

【発明の効果】各請求項に記載の発明によれば、リッチ
スパイク操作時に短時間で機関空燃比をリーン空燃比か
らリッチ空燃比に変化させることが可能となるため、Ｎ
ＯX 吸蔵還元触媒を用いた場合にもリッチスパイク操作
初期に未浄化のＮＯX が大気に放出されることを防止す
ることが可能となる。According to the invention described in each claim, the engine air-fuel ratio can be changed from the lean air-fuel ratio to the rich air-fuel ratio in a short time during the rich spike operation.
O X occluding and reducing catalyst to NO X unpurified rich spike operation early even when used it becomes possible to prevent from being released into the atmosphere.

【図面の簡単な説明】[Brief description of the drawings]

【図１】本発明を自動車用筒内噴射式内燃機関に適用し
た実施形態の概略構成を説明する図である。FIG. 1 is a diagram illustrating a schematic configuration of an embodiment in which the present invention is applied to a direct injection type internal combustion engine for a vehicle.

【図２】本発明のリッチスパイク操作の一例を説明する
タイミング図である。FIG. 2 is a timing chart illustrating an example of a rich spike operation of the present invention.

【図３】図２のリッチスパイク操作を説明するフローチ
ャートである。FIG. 3 is a flowchart illustrating a rich spike operation in FIG. 2;

【図４】リッチスパイク操作の他の例を説明するフロー
チャートである。FIG. 4 is a flowchart illustrating another example of a rich spike operation.

【符号の説明】[Explanation of symbols]

１…内燃機関 ２…排気通路 ７…ＮＯX 吸蔵還元触媒 １５…電子制御スロットル弁 １１１〜１１４…筒内噴射弁1 ... internal combustion engine 2 ... exhaust passage 7 ... NO X occluding and reducing catalyst 15 ... electronic control throttle valve 111 to 114 ... cylinder injection valve

───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.7 識別記号 ＦＩ テーマコート゛(参考） Ｆ０２Ｄ 41/34 Ｆ０２Ｄ 41/34 Ｅ Ｆターム(参考） 3G091 AA02 AA11 AA12 AA17 AA24 AA28 AB03 AB06 BA14 BA33 CB02 CB03 DA04 DC01 EA00 EA01 EA03 EA05 EA06 EA07 EA34 FB10 FB12 GB02W GB03W GB06W GB17X HA11 HA12 HA36 3G301 HA01 HA04 HA09 HA16 HA17 JA00 JA25 JB09 MA01 MA13 MA19 MA26 NC02 ND01 NE02 NE13 NE23 PA01Z PA07Z PA12Z PA17Z PD01Z PD04A PD04Z PE01Z PF03Z PF05Z──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. 7 Identification code FI Theme coat ゛ (Reference) F02D 41/34 F02D 41/34 EF Term (Reference) 3G091 AA02 AA11 AA12 AA17 AA24 AA28 AB03 AB06 BA14 BA33 CB02 CB03 DA04 DC01 EA00 EA01 EA03 EA05 EA06 EA07 EA34 FB10 FB12 GB02W GB03W GB06W GB17X HA11 HA12 HA36 3G301 HA01 HA04 HA09 HA16 HA17 JA00 JA25 JB09 MA01 MA13 MA19 MA26 NC02 ND01 NE02 NE13 NE23 PA01ZPA07ZPZ PDZZ

Claims (4)

【特許請求の範囲】[Claims] 【請求項１】 要求機関負荷に応じて機関燃焼空燃比を
制御する内燃機関の燃料噴射制御装置であって、 機関の燃料噴射を機関吸入空気量と機関回転数とに基づ
いて制御する第１の燃料噴射制御手段と、機関の燃料噴
射を要求機関負荷と機関回転数とに基づいて設定する第
２の燃料噴射制御手段とを備え、 機関がリーン空燃比で運転されているときに、要求機関
負荷とは無関係に機関補機の要求により機関をリッチ空
燃比で運転するリッチスパイク操作を行い、 前記リッチスパイク操作における空燃比の切り換え時
に、機関燃焼空燃比がリーンである間は前記第２の燃料
噴射制御手段により機関燃料噴射を制御し、機関がリッ
チ空燃比で運転される間は前記第１の燃料噴射制御手段
により機関の燃料噴射を制御する内燃機関の燃料噴射制
御装置。1. A fuel injection control device for an internal combustion engine that controls an engine combustion air-fuel ratio according to a required engine load, wherein a first fuel injection control device controls an engine fuel injection based on an engine intake air amount and an engine speed. Fuel injection control means, and second fuel injection control means for setting the fuel injection of the engine based on the required engine load and the engine speed. When the engine is operated at a lean air-fuel ratio, A rich spike operation for operating the engine at a rich air-fuel ratio in response to a request from an engine accessory regardless of an engine load is performed. At the time of switching the air-fuel ratio in the rich spike operation, the second spike operation is performed while the engine combustion air-fuel ratio is lean. The fuel injection control device of the internal combustion engine controls the fuel injection of the engine by the fuel injection control means, and controls the fuel injection of the engine by the first fuel injection control means while the engine is operated at the rich air-fuel ratio. Place. 【請求項２】 筒内に直接燃料を噴射する筒内燃料噴射
弁を備え、各気筒の圧縮行程中に燃料を噴射してリーン
空燃比成層燃焼を行う成層燃焼モードと、各気筒の吸気
行程中に燃料を噴射して均質混合気燃焼を行う均質混合
気燃焼モードとを切り換えて運転する内燃機関の燃料噴
射制御装置であって、 機関の燃料噴射を機関吸入空気量と機関回転数とに基づ
いて制御する第１の燃料噴射制御手段と、機関の燃料噴
射を要求機関負荷と機関回転数とに基づいて設定する第
２の燃料噴射制御手段とを備え、 要求機関負荷に応じて前記成層燃焼モードと前記均質混
合気燃焼モードとの運転切り換えを行うとともに、要求
機関負荷とは無関係に機関補機の要求によりリッチ空燃
比の均質混合気燃焼モードで機関を運転するリッチスパ
イク操作を行い、 機関がリーン空燃比成層燃焼モードで運転されていると
きの前記リッチスパイク操作実施中には、機関燃焼空燃
比がリーンである間は前記第２の燃料噴射制御手段によ
り機関燃料噴射を制御し、機関がリッチ空燃比の均質混
合気燃焼モードで運転される間は前記第１の燃料噴射制
御手段により機関の燃料噴射を制御する内燃機関の燃料
噴射制御装置。2. A stratified combustion mode including a direct fuel injection valve for injecting fuel directly into a cylinder, injecting fuel during a compression stroke of each cylinder to perform a lean air-fuel ratio stratified combustion, and an intake stroke of each cylinder. A fuel injection control device for an internal combustion engine that operates by switching between a homogeneous mixture combustion mode in which fuel is injected and a homogeneous mixture combustion is performed, wherein fuel injection of the engine is controlled by an engine intake air amount and an engine speed. First fuel injection control means for controlling the fuel injection of the engine based on the required engine load and the engine speed, and the second fuel injection control means for setting the fuel injection of the engine based on the required engine load and the engine speed. While performing operation switching between the combustion mode and the homogeneous mixture combustion mode, perform a rich spike operation of operating the engine in the homogeneous mixture combustion mode with a rich air-fuel ratio at the request of the engine auxiliary machine regardless of the required engine load, During the execution of the rich spike operation when the engine is operated in the lean air-fuel ratio stratified combustion mode, while the engine combustion air-fuel ratio is lean, the engine fuel injection is controlled by the second fuel injection control means, A fuel injection control device for an internal combustion engine, wherein the first fuel injection control means controls fuel injection of the engine while the engine is operated in a homogeneous air / fuel mixture combustion mode with a rich air-fuel ratio. 【請求項３】 前記機関補機は、機関排気通路に配置さ
れ流入する排気空燃比がリーンの時に排気中のＮＯX を
吸収し流入する排気空燃比がリッチになったときに吸収
したＮＯX を放出、還元浄化するＮＯX 吸蔵還元触媒で
あり、前記リッチスパイク操作はＮＯX 吸蔵還元触媒か
ら吸収したＮＯX を放出させ、還元浄化するときに実行
される請求項１または請求項２に記載の内燃機関の燃料
噴射制御装置。Wherein said engine accessory is, NO X exhaust air-fuel ratio of the exhaust air-fuel ratio flowing disposed engine exhaust passage flows to absorb NO X in the exhaust gas when the lean absorbed when they become rich releasing, the NO X storage reduction catalyst for purifying the rich spike operation to release NO X absorbed from the NO X storage reduction catalyst, according to claim 1 or claim 2 is performed when the reduction and purification A fuel injection control device for an internal combustion engine. 【請求項４】 更に、機関排気通路に配置され排気の空
燃比を検出する空燃比センサを備え、前記リッチスパイ
ク操作時に前記空燃比センサ出力に基づいて機関燃焼空
燃比を予め定めた空燃比に制御する請求項１または請求
項２に記載の内燃機関の燃料噴射制御装置。4. An air-fuel ratio sensor disposed in an engine exhaust passage and detecting an air-fuel ratio of exhaust gas, wherein the engine combustion air-fuel ratio is set to a predetermined air-fuel ratio based on the air-fuel ratio sensor output during the rich spike operation. 3. The fuel injection control device for an internal combustion engine according to claim 1, wherein the control is performed.
JP03583499A 1999-02-15 1999-02-15 Fuel injection control device for internal combustion engine Expired - Lifetime JP3680245B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP03583499A JP3680245B2 (en) 1999-02-15 1999-02-15 Fuel injection control device for internal combustion engine

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP03583499A JP3680245B2 (en) 1999-02-15 1999-02-15 Fuel injection control device for internal combustion engine

Publications (2)

Publication Number Publication Date
JP2000234541A true JP2000234541A (en) 2000-08-29
JP3680245B2 JP3680245B2 (en) 2005-08-10

Family

ID=12453010

Family Applications (1)

Application Number Title Priority Date Filing Date
JP03583499A Expired - Lifetime JP3680245B2 (en) 1999-02-15 1999-02-15 Fuel injection control device for internal combustion engine

Country Status (1)

Country Link
JP (1) JP3680245B2 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002115581A (en) * 2000-10-10 2002-04-19 Denso Corp Air-fuel ratio control device for internal combustion engine
JP2012215134A (en) * 2011-03-31 2012-11-08 Honda Motor Co Ltd Air fuel ratio controlling apparatus

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002115581A (en) * 2000-10-10 2002-04-19 Denso Corp Air-fuel ratio control device for internal combustion engine
JP4608758B2 (en) * 2000-10-10 2011-01-12 株式会社デンソー Air-fuel ratio control device for internal combustion engine
JP2012215134A (en) * 2011-03-31 2012-11-08 Honda Motor Co Ltd Air fuel ratio controlling apparatus

Also Published As

Publication number Publication date
JP3680245B2 (en) 2005-08-10

Similar Documents

Publication Publication Date Title
US6708668B2 (en) Control system and method for direct-injection spark-ignition engine
US6289672B1 (en) Exhaust gas purification device for an internal combustion engine
EP0974747B1 (en) A control system for an internal combustion engine
EP1028243B1 (en) Control apparatus for direct injection engine
JP4208012B2 (en) Exhaust gas purification device for internal combustion engine
EP2591222B1 (en) Fuel injection control of an internal combustion engine
JP3324039B2 (en) Method for reducing harmful exhaust emissions of gasoline engines operated with lean fuel-air mixtures
US6758034B1 (en) Method for operating an internal combustion engine
US6755185B2 (en) Method and electronic control unit for controlling the regeneration of a fuel vapor accumulator in internal combustion engines
JP3873537B2 (en) Exhaust gas purification device for internal combustion engine
JP3680245B2 (en) Fuel injection control device for internal combustion engine
JP3680241B2 (en) Exhaust gas purification device for internal combustion engine
JP3633312B2 (en) Exhaust gas purification device for internal combustion engine
JP3624702B2 (en) Control device for internal combustion engine
JP3680237B2 (en) Exhaust gas purification device for internal combustion engine
JP4339599B2 (en) In-cylinder injection internal combustion engine control device
JP3622290B2 (en) Control device for internal combustion engine
JP3478135B2 (en) Exhaust gas purification device for internal combustion engine
JP3633295B2 (en) Exhaust gas purification device for lean combustion internal combustion engine
JP2004346917A (en) Internal combustion engine control device
JP2000080914A (en) Internal combustion engine
JP3890775B2 (en) Air-fuel ratio control device for internal combustion engine
JP3123438B2 (en) Exhaust gas purification device for internal combustion engine
JP2000192833A (en) Controller for cylinder injection type internal combustion engine
JP3646586B2 (en) Control device for internal combustion engine

Legal Events

Date Code Title Description
A977 Report on retrieval

Free format text: JAPANESE INTERMEDIATE CODE: A971007

Effective date: 20040122

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20040127

A521 Written amendment

Free format text: JAPANESE INTERMEDIATE CODE: A523

Effective date: 20040323

TRDD Decision of grant or rejection written
A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

Effective date: 20050419

A61 First payment of annual fees (during grant procedure)

Free format text: JAPANESE INTERMEDIATE CODE: A61

Effective date: 20050502

R150 Certificate of patent or registration of utility model

Free format text: JAPANESE INTERMEDIATE CODE: R150

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20080527

Year of fee payment: 3

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20090527

Year of fee payment: 4

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20100527

Year of fee payment: 5

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20110527

Year of fee payment: 6

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20110527

Year of fee payment: 6

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20120527

Year of fee payment: 7

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20120527

Year of fee payment: 7

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20130527

Year of fee payment: 8

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20140527

Year of fee payment: 9

EXPY Cancellation because of completion of term