JP2010168905A - Air-fuel ratio learning control device for internal combustion engine - Google Patents

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

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JP2010168905A
JP2010168905A JP2009009560A JP2009009560A JP2010168905A JP 2010168905 A JP2010168905 A JP 2010168905A JP 2009009560 A JP2009009560 A JP 2009009560A JP 2009009560 A JP2009009560 A JP 2009009560A JP 2010168905 A JP2010168905 A JP 2010168905A
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characteristic deviation
air
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JP5051627B2 (en
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Hideaki Ichihara
英明 市原
Koichi Sugiyama
幸一 杉山
Yoshinori Yamashita
義典 山下
Hidekazu Omura
秀和 大村
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Denso Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To learn and correct the displacement of injection characteristics of two fuel injection valves of each cylinder, in an internal combustion engine having two fuel injection valves on the intake side of each cylinder. <P>SOLUTION: While an air-fuel ratio F/B control is performed by injecting both of two fuel injection valves 21 of each cylinder for each fuel injection timing of the cylinder, the displacements (total displacements of injection characteristics) of the injection characteristics of all the fuel injection valves 21 of an engine 11 are learned, based on the corrected amount of the air-fuel ratio F/B. Then, a control to inject a fuel of an injection amount requested by the cylinder to be learned by only one fuel injection valve 21 with the injection of the other fuel injection valve 21 stopped, is performed on only either cylinder (cylinder to be learned) while the air-fuel ratio F/B control is performed while alternately switching between the cylinder to be learned and the injection-stopped fuel injection valve 21. Based on the variation amount of the correction amounts of the air-fuel ratio F/B obtained before and after the stop of the injection of each fuel injection valve 21, the displacement of the injection characteristics of each fuel injection valve 21 of the cylinder to be learned (displacement of individual injection characteristics) is learned individually. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は、内燃機関の各気筒の吸気側にそれぞれ複数の燃料噴射弁を配置した内燃機関の空燃比学習制御装置に関する発明である。   The present invention relates to an air-fuel ratio learning control device for an internal combustion engine in which a plurality of fuel injection valves are arranged on the intake side of each cylinder of the internal combustion engine.

従来の一般的な内燃機関の空燃比制御は、排気通路のうちの触媒の上流側に、排出ガスの空燃比又はリッチ／リーンを検出する排出ガスセンサを配置し、この排出ガスセンサの出力に基づいて空燃比フィードバック補正量を設定して各気筒の燃料噴射弁の燃料噴射量を空燃比フィードバック補正量で補正する空燃比フィードバック制御を実行することで、排出ガスの空燃比を排出ガス浄化効率が高くなる触媒の浄化ウインドウ内（理論空燃比付近）に制御するようにしている。   In the conventional general air-fuel ratio control of an internal combustion engine, an exhaust gas sensor for detecting the air-fuel ratio or rich / lean of exhaust gas is arranged upstream of the catalyst in the exhaust passage, and the output of this exhaust gas sensor is used. By executing air-fuel ratio feedback control that sets the air-fuel ratio feedback correction amount and corrects the fuel injection amount of the fuel injection valve of each cylinder with the air-fuel ratio feedback correction amount, the exhaust gas air-fuel ratio is made higher in exhaust gas purification efficiency. The catalyst is controlled within the purification window (near the theoretical air-fuel ratio).

更に、特許文献１（特開昭６０−９０９４４号公報）に記載されているように、空燃比フィードバック制御実行中に空燃比フィードバック補正量に基づいて全気筒の燃料噴射弁の平均的な噴射特性ずれ（要求噴射量に対する実噴射量のずれによって生じる平均的な空燃比のずれ）を補正するための学習補正量を学習してメモリに記憶しておき、学習完了後は、各気筒の燃料噴射弁の燃料噴射量を空燃比フィードバック補正量と学習補正量で補正して空燃比制御精度を高めるようにしたものがある。   Further, as described in Japanese Patent Application Laid-Open No. 60-90944, the average injection characteristics of the fuel injection valves of all cylinders based on the air-fuel ratio feedback correction amount during execution of the air-fuel ratio feedback control. A learning correction amount for correcting a deviation (an average air-fuel ratio deviation caused by a deviation of the actual injection amount with respect to the required injection amount) is learned and stored in a memory, and after completion of the fuel injection of each cylinder There is a type in which the fuel injection amount of the valve is corrected by the air-fuel ratio feedback correction amount and the learning correction amount to improve the air-fuel ratio control accuracy.

また、特許文献２（特開２００６−２９９９４５号公報）に記載されているように、内燃機関の気筒内での燃料噴霧の微粒化やポートウエット低減（吸気ポート内壁面への燃料付着量低減）等を目的として、内燃機関の各気筒の２つの吸気ポートにそれぞれ燃料噴射弁を配置して、各気筒にそれぞれ２つの燃料噴射弁で燃料を噴射するようにしたものがある。   Further, as described in Patent Document 2 (Japanese Patent Application Laid-Open No. 2006-299945), atomization of fuel spray in the cylinder of the internal combustion engine and port wet reduction (reduction of fuel adhesion to the inner wall surface of the intake port) For the purpose, for example, there are fuel injection valves arranged in two intake ports of each cylinder of an internal combustion engine, and fuel is injected into each cylinder by two fuel injection valves.

特開昭６０−９０９４４号公報JP-A-60-90944 特開２００６−２９９９４５号公報JP 2006-299945 A

ところで、燃料噴射弁の個体差（製造ばらつき）や経時変化等によって燃料噴射弁の噴射特性ずれが発生し、しかも、この噴射特性ずれは、燃料噴射弁毎にずれ量が異なる。そこで、上記特許文献２に記載された各気筒にそれぞれ２本の燃料噴射弁を配置したシステムにおいても、上記特許文献１の空燃比学習制御技術を適用することが考えられるが、上記特許文献１の空燃比学習制御技術は、全気筒の燃料噴射弁の平均的な噴射特性ずれ（平均的な空燃比のずれ）を学習補正量として学習するものであるため、各気筒の２つの燃料噴射弁のそれぞれの噴射特性ずれを個別に補正することはできない。このため、各燃料噴射弁の噴射特性ずれのばらつきにより、気筒間の空燃比ばらつきが発生して気筒間のトルクばらつきが発生したり、排出ガスの浄化効率が低下する等の問題を解決できない。   By the way, due to individual differences (manufacturing variation) of fuel injectors, changes with time, and the like, deviations in the injection characteristics of the fuel injectors occur. Moreover, the deviations in the injection characteristics differ for each fuel injector. Thus, even in a system in which two fuel injection valves are arranged in each cylinder described in Patent Document 2, it is conceivable to apply the air-fuel ratio learning control technique of Patent Document 1 described above. Since the air-fuel ratio learning control technology of this type learns the average injection characteristic deviation (average air-fuel ratio deviation) of the fuel injection valves of all cylinders as a learning correction amount, two fuel injection valves for each cylinder. It is not possible to individually correct each of the injection characteristic deviations. For this reason, problems such as variations in air-fuel ratio between cylinders due to variations in the injection characteristic deviations of the fuel injection valves and variations in torque between the cylinders, and reduction in exhaust gas purification efficiency cannot be solved.

そこで、本発明が解決しようとする課題は、各気筒の吸気側にそれぞれ複数の燃料噴射弁を配置した内燃機関において、各気筒の複数の燃料噴射弁の噴射特性ずれを個別又はグループ別に学習補正できる内燃機関の空燃比学習制御装置を提供することにある。   Therefore, the problem to be solved by the present invention is to correct the learning characteristic correction of the injection characteristics of the plurality of fuel injection valves in each cylinder individually or in a group in an internal combustion engine in which a plurality of fuel injection valves are arranged on the intake side of each cylinder. An object of the present invention is to provide an air-fuel ratio learning control device for an internal combustion engine.

上記課題を解決するために、請求項１に係る発明は、複数の気筒を有する内燃機関の各気筒の吸気側にそれぞれ複数の燃料噴射弁を配置すると共に、排気通路に排出ガスの空燃比又はリッチ／リーンを検出する排出ガスセンサを配置し、前記排出ガスセンサの出力に基づいて空燃比フィードバック補正量を設定して前記各気筒の複数の燃料噴射弁の燃料噴射量を前記空燃比フィードバック補正量で補正する空燃比フィードバック制御を実行する空燃比制御手段を備えた内燃機関の空燃比学習制御装置において、前記各気筒の燃料噴射時期毎に前記各気筒の複数の燃料噴射弁を全て噴射動作させて前記空燃比フィードバック制御を実行しているときに前記空燃比フィードバック補正量に基づいて前記内燃機関全体の燃料噴射弁噴射特性ずれ（以下「全体噴射特性ずれ」という）を学習する全体噴射特性ずれ学習手段と、前記空燃比フィードバック制御を実行しているときにいずれか１つの気筒（以下「学習対象気筒」という）のみでいずれか１つの燃料噴射弁の噴射を停止して他の燃料噴射弁のみで前記学習対象気筒の要求噴射量分の燃料を噴射する制御を、前記学習対象気筒と噴射を停止する燃料噴射弁をそれぞれ順番に切り替えて実施して各燃料噴射弁の噴射停止前後の前記空燃比フィードバック補正量の変化量に基づいて前記学習対象気筒の各燃料噴射弁の噴射特性ずれ（以下「個別噴射特性ずれ」という）を個別に学習する個別噴射特性ずれ学習手段とを備え、前記空燃比制御手段は、前記全体噴射特性ずれの学習値と前記個別噴射特性ずれの学習値とを用いて前記各気筒の複数の燃料噴射弁の燃料噴射量を個別に補正することを特徴とするものである。   In order to solve the above-mentioned problem, the invention according to claim 1 is arranged such that a plurality of fuel injection valves are arranged on the intake side of each cylinder of an internal combustion engine having a plurality of cylinders, and an air-fuel ratio of exhaust gas or An exhaust gas sensor for detecting rich / lean is arranged, an air-fuel ratio feedback correction amount is set based on the output of the exhaust gas sensor, and the fuel injection amounts of the plurality of fuel injection valves of each cylinder are set to the air-fuel ratio feedback correction amount. In an air-fuel ratio learning control device for an internal combustion engine having air-fuel ratio control means for executing air-fuel ratio feedback control to be corrected, the fuel injection valves of each cylinder are all injected at every fuel injection timing of each cylinder. When the air-fuel ratio feedback control is being executed, the fuel injection valve injection characteristic deviation of the whole internal combustion engine (hereinafter referred to as the fuel-air-fuel ratio feedback correction amount) The entire injection characteristic deviation learning means for learning "total injection characteristic deviation" and any one cylinder (hereinafter referred to as "learning target cylinder") when the air-fuel ratio feedback control is being executed. Control is performed to stop the injection of one fuel injection valve and inject the fuel for the required injection amount of the learning target cylinder only with the other fuel injection valve, and the learning target cylinder and the fuel injection valve for stopping the injection in order An injection characteristic deviation of each fuel injection valve of the learning target cylinder (hereinafter referred to as “individual injection characteristic deviation”) is performed based on a change amount of the air-fuel ratio feedback correction amount before and after the injection stop of each fuel injection valve. Individual injection characteristic deviation learning means for individually learning, wherein the air-fuel ratio control means uses the learning value for the overall injection characteristic deviation and the learned value for the individual injection characteristic deviation for each cylinder. It is characterized in that to correct the fuel injection amount of the number of fuel injection valves individually.

この構成では、空燃比フィードバック制御実行中に各気筒の複数の燃料噴射弁を全て噴射動作させて内燃機関全体の燃料噴射弁噴射特性ずれ（全体噴射特性ずれ）を学習すると共に、空燃比フィードバック制御実行中にいずれか１つの気筒（学習対象気筒）のみでいずれか１つの燃料噴射弁の噴射を停止して他の燃料噴射弁のみで学習対象気筒の要求噴射量分の燃料を噴射して各燃料噴射弁の噴射特性ずれ（個別噴射特性ずれ）を個別に学習するため、学習対象気筒に要求噴射量分の燃料を噴射しながら学習対象気筒の各燃料噴射弁の噴射特性ずれ（個別噴射特性ずれ）を個別に学習することができ、学習対象気筒と他の気筒との間の空燃比ばらつきやトルクばらつきを抑えながら個別噴射特性ずれを精度良く学習することができる。そして、全体噴射特性ずれの学習値と個別噴射特性ずれの学習値を用いて各気筒の複数の燃料噴射弁の燃料噴射量を個別に補正するため、各燃料噴射弁の噴射特性ずれを個別に精度良く補正することができて、燃料噴射弁間の噴射特性ずれのばらつきに起因する気筒間の空燃比ばらつきやトルクばらつきを効果的に低減することができる。   In this configuration, during execution of the air-fuel ratio feedback control, all of the fuel injection valves of each cylinder are injected to learn the fuel injection valve injection characteristic deviation (overall injection characteristic deviation) of the entire internal combustion engine, and also the air-fuel ratio feedback control During execution, only one of the cylinders (learning target cylinder) stops injection of any one of the fuel injection valves, and only the other fuel injection valves inject fuel for the required injection amount of the learning target cylinder. In order to learn individually the injection characteristic deviation (individual injection characteristic deviation) of the fuel injection valve, the injection characteristic deviation (individual injection characteristic) of each fuel injection valve of the learning target cylinder while injecting fuel for the required injection amount into the learning target cylinder Deviation) can be individually learned, and the individual injection characteristic deviation can be accurately learned while suppressing variations in air-fuel ratio and torque between the learning target cylinder and other cylinders. Further, in order to individually correct the fuel injection amounts of the plurality of fuel injection valves of each cylinder using the learning value of the overall injection characteristic deviation and the learning value of the individual injection characteristic deviation, the injection characteristic deviation of each fuel injection valve is individually determined. The correction can be performed with high accuracy, and the air-fuel ratio variation and the torque variation between the cylinders due to the variation in the injection characteristic deviation between the fuel injection valves can be effectively reduced.

この場合、請求項２のように、全体噴射特性ずれ学習手段により全体噴射特性ずれの学習が完了した後に、各燃料噴射弁の燃料噴射量を全体噴射特性ずれの学習値で補正した状態で個別噴射特性ずれを学習するようにすると良い。このようにすれば、全体噴射特性ずれを補正した状態で個別噴射特性ずれを学習できるため、個別噴射特性ずれの学習精度を更に向上させることができる。   In this case, as described in claim 2, after learning of the total injection characteristic deviation is completed by the total injection characteristic deviation learning means, the fuel injection amount of each fuel injection valve is individually corrected in a state where the learning value of the total injection characteristic deviation is corrected. It is preferable to learn the injection characteristic deviation. In this way, since the individual injection characteristic deviation can be learned in a state where the overall injection characteristic deviation is corrected, the learning accuracy of the individual injection characteristic deviation can be further improved.

但し、本発明は、各燃料噴射弁の燃料噴射量を全体噴射特性ずれの学習値で補正しない状態で個別噴射特性ずれを学習し、全体噴射特性ずれと個別噴射特性ずれの学習完了後に全体噴射特性ずれの学習値と個別噴射特性ずれの学習値とを用いて各燃料噴射弁の燃料噴射量を個別に補正するようにしても良い。   However, according to the present invention, the individual injection characteristic deviation is learned without correcting the fuel injection amount of each fuel injection valve with the learning value of the total injection characteristic deviation, and the entire injection is performed after the learning of the total injection characteristic deviation and the individual injection characteristic deviation is completed. The fuel injection amount of each fuel injection valve may be individually corrected using the learned value of characteristic deviation and the learned value of individual injection characteristic deviation.

また、請求項３のように、全体噴射特性ずれを学習する全体噴射特性ずれ学習手段の他に、空燃比フィードバック制御を実行しているときに各気筒の複数の燃料噴射弁のうちのいずれか１つの燃料噴射弁からなる燃料噴射弁グループの噴射を停止して他の燃料噴射弁グループのみで各気筒の要求噴射量分の燃料を噴射する制御を、噴射を停止する燃料噴射弁グループを順番に切り替えて実施して燃料噴射弁グループの噴射停止前後の空燃比フィードバック補正量の変化量に基づいて燃料噴射弁グループ別の噴射特性ずれ（以下「グループ別噴射特性ずれ」という）を学習するグループ別噴射特性ずれ学習手段を備え、全体噴射特性ずれの学習値とグループ別噴射特性ずれの学習値とを用いて各気筒の複数の燃料噴射弁の燃料噴射量を燃料噴射弁グループ別に補正するようにしても良い。   In addition to the overall injection characteristic deviation learning means for learning the overall injection characteristic deviation as in claim 3, any one of the plurality of fuel injection valves of each cylinder when the air-fuel ratio feedback control is executed. Control that stops the injection of the fuel injection valve group consisting of one fuel injection valve and injects fuel for the required injection amount of each cylinder only by the other fuel injection valve groups, and in order of the fuel injection valve groups that stop the injection A group that learns an injection characteristic deviation for each fuel injection group (hereinafter referred to as “group-specific injection characteristic deviation”) based on the amount of change in the air-fuel ratio feedback correction amount before and after the injection stop of the fuel injection valve group. A separate injection characteristic deviation learning means is provided, and fuel injection amounts of a plurality of fuel injection valves of each cylinder are injected using the learning value of the overall injection characteristic deviation and the learned value of the individual group injection characteristic deviation. Another to may be corrected group.

この構成では、空燃比フィードバック制御実行中に各気筒の複数の燃料噴射弁を全て噴射動作させて内燃機関全体の燃料噴射弁噴射特性ずれ（全体噴射特性ずれ）を学習すると共に、空燃比フィードバック制御実行中にいずれか１つの燃料噴射弁グループの噴射を停止して他の燃料噴射弁グループのみで各気筒の要求噴射量分の燃料を噴射しながら燃料噴射弁グループ別の噴射特性ずれ（グループ別噴射特性ずれ）を学習するため、各気筒の要求噴射量分の燃料を噴射しながらグループ別噴射特性ずれを学習することができ、気筒間の空燃比ばらつきやトルクばらつきを抑えながらグループ別噴射特性ずれを精度良く学習することができる。そして、全体噴射特性ずれの学習値とグループ別噴射特性ずれの学習値を用いて各気筒の複数の燃料噴射弁の燃料噴射量を燃料噴射弁グループ別に補正するため、各燃料噴射弁グループの噴射特性ずれを精度良く補正することができて、燃料噴射弁グループ間の噴射特性ずれのばらつきに起因する気筒間の空燃比ばらつきやトルクばらつきを低減することができる。   In this configuration, during execution of the air-fuel ratio feedback control, all of the fuel injection valves of each cylinder are injected to learn the fuel injection valve injection characteristic deviation (overall injection characteristic deviation) of the entire internal combustion engine, and also the air-fuel ratio feedback control During the execution, the injection of any one fuel injection valve group is stopped, and only the other fuel injection valve groups inject fuel for the required injection amount of each cylinder. The injection characteristic deviation can be learned while injecting fuel for the required injection amount of each cylinder, and the injection characteristic by group while suppressing air-fuel ratio variation and torque variation between cylinders. The deviation can be learned with high accuracy. Then, in order to correct the fuel injection amount of the plurality of fuel injection valves of each cylinder by the fuel injection valve group using the learning value of the overall injection characteristic deviation and the learning value of the group-specific injection characteristic deviation, the injection of each fuel injection group The characteristic deviation can be corrected with high accuracy, and the air-fuel ratio fluctuation and the torque fluctuation between the cylinders due to the variation in the injection characteristic deviation between the fuel injection valve groups can be reduced.

この場合、請求項４のように、全体噴射特性ずれ学習手段により全体噴射特性ずれの学習が完了した後に、各燃料噴射弁の燃料噴射量を全体噴射特性ずれの学習値で補正した状態でグループ別噴射特性ずれを学習するようにすると良い。このようにすれば、全体噴射特性ずれを補正した状態でグループ別噴射特性ずれを学習できるため、グループ別噴射特性ずれの学習精度を更に向上させることができる。   In this case, as described in claim 4, after learning of the total injection characteristic deviation is completed by the total injection characteristic deviation learning means, the fuel injection amount of each fuel injection valve is corrected with the learning value of the total injection characteristic deviation. It is preferable to learn the different injection characteristic deviation. In this way, since the group-specific injection characteristic deviation can be learned in a state where the overall injection characteristic deviation is corrected, the learning accuracy of the group-specific injection characteristic deviation can be further improved.

但し、本発明は、各燃料噴射弁の燃料噴射量を全体噴射特性ずれの学習値で補正しない状態でグループ別噴射特性ずれを学習し、全体噴射特性ずれとグループ別噴射特性ずれの学習完了後に全体噴射特性ずれの学習値とグループ別噴射特性ずれの学習値とを用いて各燃料噴射弁の燃料噴射量を燃料噴射弁グループ別に補正するようにしても良い。   However, the present invention learns the group-specific injection characteristic deviation in a state where the fuel injection amount of each fuel injection valve is not corrected with the learning value of the total injection characteristic deviation, and after completing the learning of the total injection characteristic deviation and the group-specific injection characteristic deviation The fuel injection amount of each fuel injection valve may be corrected for each fuel injection valve group using the learning value of the overall injection characteristic deviation and the learning value of the group-specific injection characteristic deviation.

更に、請求項５のように、全体噴射特性ずれとグループ別噴射特性ずれと個別噴射特性ずれをそれぞれ学習し、全体噴射特性ずれの学習値とグループ別噴射特性ずれの学習値と個別噴射特性ずれの学習値を用いて各気筒の複数の燃料噴射弁の燃料噴射量を補正するようにしても良い。このようにすれば、燃料噴射弁間の噴射特性ずれのばらつき及び燃料噴射弁グループ間の噴射特性ずれのばらつきに起因する気筒間の空燃比ばらつきやトルクばらつきを低減することができる。   Further, as in claim 5, the overall injection characteristic deviation, the group-specific injection characteristic deviation, and the individual injection characteristic deviation are learned, respectively, and the learning value of the total injection characteristic deviation, the learning value of the group-specific injection characteristic deviation, and the individual injection characteristic deviation The fuel injection amount of the plurality of fuel injection valves of each cylinder may be corrected using the learned value. In this way, it is possible to reduce the variation in air-fuel ratio between cylinders and the variation in torque caused by the variation in the injection characteristic deviation between the fuel injection valves and the variation in the injection characteristic deviation between the fuel injection valve groups.

この場合、請求項６のように、全体噴射特性ずれ学習手段により全体噴射特性ずれの学習が完了し、且つ、グループ別噴射特性ずれ学習手段によりグループ別噴射特性ずれの学習が完了した後、各燃料噴射弁の燃料噴射量を全体噴射特性ずれの学習値及びグループ別噴射特性ずれの学習値で補正した状態で個別噴射特性ずれを学習するようにすると良い。このようにすれば、全体噴射特性ずれとグループ別噴射特性ずれの両方を補正した状態で個別噴射特性ずれを学習できるため、個別噴射特性ずれの学習精度を更に向上させることができる。   In this case, as described in claim 6, after learning of the total injection characteristic deviation is completed by the whole injection characteristic deviation learning unit, and after learning of the group-specific injection characteristic deviation is completed by the group-specific injection characteristic deviation learning unit, The individual injection characteristic deviation may be learned in a state where the fuel injection amount of the fuel injection valve is corrected by the learning value of the overall injection characteristic deviation and the learning value of the group-specific injection characteristic deviation. In this way, since the individual injection characteristic deviation can be learned in a state where both the overall injection characteristic deviation and the group-specific injection characteristic deviation are corrected, the learning accuracy of the individual injection characteristic deviation can be further improved.

また、請求項７のように、内燃機関の停止中でも記憶データを保持する書き換え可能な記憶手段に前記学習値を記憶し、前記記憶手段に前記学習値が記憶されている場合には、前記記憶手段から読み出した前記学習値を用いて各気筒の複数の燃料噴射弁の燃料噴射量を補正するようにすると良い。このようにすれば、記憶手段に学習値が記憶されている場合には、内燃機関の始動時から学習値を用いて各気筒の複数の燃料噴射弁の燃料噴射量を補正することができ、始動性向上や始動時のエミッション低減を実現することができる。   Further, as in claim 7, when the learning value is stored in a rewritable storage means that retains stored data even when the internal combustion engine is stopped, and the learning value is stored in the storage means, the storage It is preferable to correct the fuel injection amounts of the plurality of fuel injection valves of each cylinder using the learned value read from the means. In this way, when the learning value is stored in the storage means, it is possible to correct the fuel injection amounts of the plurality of fuel injection valves of each cylinder using the learning value from the start of the internal combustion engine. Improved startability and reduced emissions at start-up.

また、請求項８のように、前記学習値が所定の許容範囲から外れたときに、燃料噴射弁の異常と判定して運転者に警告する異常判定手段を設けた構成としても良い。このようにすれば、燃料噴射弁の異常が発生したときに、異常な燃料噴射弁を特定したり、異常な燃料噴射弁が属する燃料噴射弁グループを特定することが可能になると共に、燃料噴射弁の異常が発生したことを早期に運転者に知らせて修理・点検を促すことができる。   Further, as in claim 8, there may be provided an abnormality determining means for determining that the fuel injection valve is abnormal and warning the driver when the learned value is out of a predetermined allowable range. In this way, when an abnormality occurs in the fuel injection valve, it becomes possible to specify an abnormal fuel injection valve, or to specify a fuel injection valve group to which the abnormal fuel injection valve belongs. It is possible to promptly notify the driver that a valve abnormality has occurred and prompt repair and inspection.

図１は本発明の実施例１〜３で共通して用いるエンジン制御システム全体の概略構成図である。FIG. 1 is a schematic configuration diagram of an entire engine control system used in common in the first to third embodiments of the present invention. 図２は本発明の実施例１〜３で共通して用いる４気筒エンジンの構成例を説明する図である。FIG. 2 is a diagram illustrating a configuration example of a four-cylinder engine that is commonly used in the first to third embodiments of the present invention. 図３は実施例１の噴射特性ずれ学習補正メインルーチンの処理の流れを示すフローチャートである。FIG. 3 is a flowchart showing the flow of processing of the injection characteristic deviation learning correction main routine of the first embodiment. 図４は実施例１の全体噴射特性ずれ学習ルーチンの処理の流れを示すフローチャートである。FIG. 4 is a flowchart showing the flow of processing of the entire injection characteristic deviation learning routine of the first embodiment. 図５は実施例１の個別噴射特性ずれ学習ルーチンの処理の流れを示すフローチャートである。FIG. 5 is a flowchart showing the flow of processing of the individual injection characteristic deviation learning routine of the first embodiment. 図６は実施例１の学習制御ルーチンの処理の流れを示すフローチャートである。FIG. 6 is a flowchart showing the flow of processing of the learning control routine of the first embodiment. 図７は燃料噴射弁の噴射特性のばらつきを説明する図である。FIG. 7 is a diagram for explaining the variation in the injection characteristics of the fuel injection valve. 図８は実施例２の噴射特性ずれ学習補正メインルーチンの処理の流れを示すフローチャートである。FIG. 8 is a flowchart showing the flow of processing of the injection characteristic deviation learning correction main routine of the second embodiment. 図９は実施例２のグループ別噴射特性ずれ学習ルーチンの処理の流れを示すフローチャートである。FIG. 9 is a flowchart showing the flow of processing of the group-specific injection characteristic deviation learning routine of the second embodiment. 図８は実施例３の噴射特性ずれ学習補正メインルーチンの処理の流れを示すフローチャートである。FIG. 8 is a flowchart showing the flow of processing of the injection characteristic deviation learning correction main routine of the third embodiment.

以下、本発明を実施するための形態を具体化した３つの実施例１〜３を説明する。   Hereinafter, three embodiments 1 to 3 embodying the mode for carrying out the present invention will be described.

本発明の実施例１を図１乃至図７に基づいて説明する。
まず、図１に基づいてエンジン制御システム全体の概略構成を説明する。
内燃機関であるエンジン１１の吸気管１２の最上流部には、エアクリーナ１３が設けられ、このエアクリーナ１３の下流側に、吸入空気量を検出するエアフローメータ１４が設けられている。このエアフローメータ１４の下流側には、モータ１５によって開度調節されるスロットルバルブ１６と、このスロットルバルブ１６の開度（スロットル開度）を検出するスロットル開度センサ１７とが設けられている。 A first embodiment of the present invention will be described with reference to FIGS.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.
An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. A throttle valve 16 whose opening is adjusted by a motor 15 and a throttle opening sensor 17 for detecting the opening (throttle opening) of the throttle valve 16 are provided on the downstream side of the air flow meter 14.

更に、スロットルバルブ１６の下流側には、サージタンク１８が設けられ、このサージタンク１８に、吸気管圧力を検出する吸気管圧力センサ１９が設けられている。また、サージタンク１８とエンジン１１の各気筒の吸気ポート３１との間には、各気筒に空気を導入する吸気マニホールド２０が接続されている。一方、エンジン１１のシリンダヘッドには、各気筒毎に点火プラグ２２が取り付けられ、各点火プラグ２２の火花放電によって筒内の混合気に着火される。   Further, a surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 for detecting the intake pipe pressure is provided in the surge tank 18. An intake manifold 20 that introduces air into each cylinder is connected between the surge tank 18 and the intake port 31 of each cylinder of the engine 11. On the other hand, a spark plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 22.

図２に示すように、エンジン１１の各気筒には、それぞれ２つの吸気ポート３１と２つの排気ポート３２が設けられ、各気筒の２つの吸気ポート３１の付近に、それぞれ吸気ポート３１に向けて燃料を噴射する燃料噴射弁２１が配置され、１気筒当たり２つの燃料噴射弁２１が配置されている。各吸気ポート３１は、それぞれ吸気バルブ３３によって開閉され、各排気ポート３２は、それぞれ排気バルブ３４によって開閉される。   As shown in FIG. 2, each cylinder of the engine 11 is provided with two intake ports 31 and two exhaust ports 32, and in the vicinity of the two intake ports 31 of each cylinder, toward the intake port 31, respectively. A fuel injection valve 21 for injecting fuel is disposed, and two fuel injection valves 21 are disposed per cylinder. Each intake port 31 is opened and closed by an intake valve 33, and each exhaust port 32 is opened and closed by an exhaust valve 34.

一方、図１に示すように、エンジン１１の排気管２３（排気通路）には、排出ガスの空燃比又はリッチ／リーン等を検出する排出ガスセンサ２４（空燃比センサ、酸素センサ等）が設けられ、この排出ガスセンサ２４の下流側に、排出ガスを浄化する三元触媒等の触媒２５が設けられている。   On the other hand, as shown in FIG. 1, the exhaust pipe 23 (exhaust passage) of the engine 11 is provided with an exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting the air-fuel ratio or rich / lean of the exhaust gas. A catalyst 25 such as a three-way catalyst for purifying exhaust gas is provided downstream of the exhaust gas sensor 24.

また、エンジン１１のシリンダブロックには、冷却水温を検出する冷却水温センサ２６や、ノッキング振動を検出するノックセンサ２９が取り付けられている。また、クランク軸２７の外周側には、クランク軸２７が所定クランク角回転する毎にパルス信号を出力するクランク角センサ２８が取り付けられ、このクランク角センサ２８の出力パルス信号に基づいてクランク角やエンジン回転速度が検出される。   A cooling water temperature sensor 26 that detects the cooling water temperature and a knock sensor 29 that detects knocking vibration are attached to the cylinder block of the engine 11. A crank angle sensor 28 that outputs a pulse signal every time the crankshaft 27 rotates by a predetermined crank angle is attached to the outer peripheral side of the crankshaft 27. Based on the output pulse signal of the crank angle sensor 28, the crank angle and The engine speed is detected.

これら各種センサの出力は、エンジン制御回路（以下「ＥＣＵ」と表記する）３０に入力される。このＥＣＵ３０は、マイクロコンピュータを主体として構成され、内蔵されたＲＯＭ（記憶媒体）に記憶された各種のエンジン制御プログラムを実行することで、エンジン運転状態に応じて各気筒の２つの燃料噴射弁２１の燃料噴射弁２１の燃料噴射量や点火プラグ２２の点火時期を制御する。   Outputs of these various sensors are input to an engine control circuit (hereinafter referred to as “ECU”) 30. The ECU 30 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the two fuel injection valves 21 of each cylinder according to the engine operating state. The fuel injection amount of the fuel injection valve 21 and the ignition timing of the spark plug 22 are controlled.

また、ＥＣＵ３０は、所定の空燃比Ｆ／Ｂ制御実行条件が成立したときに、排出ガスセンサ２４の出力に基づいて排出ガスの空燃比を目標空燃比（例えば理論空燃比）に一致させるように空燃比Ｆ／Ｂ補正量を算出し、この空燃比Ｆ／Ｂ補正量を用いて各気筒の２つの燃料噴射弁２１の燃料噴射量を補正する空燃比Ｆ／Ｂ制御を実行する空燃比制御手段として機能する。ここで、「Ｆ／Ｂ」は「フィードバック」を意味する（以下、同様）。   Further, when a predetermined air-fuel ratio F / B control execution condition is satisfied, the ECU 30 makes the air-fuel ratio of the exhaust gas coincide with the target air-fuel ratio (for example, the theoretical air-fuel ratio) based on the output of the exhaust gas sensor 24. Air-fuel ratio control means that calculates an air-fuel ratio F / B correction amount and executes air-fuel ratio F / B control for correcting the fuel injection amount of the two fuel injection valves 21 of each cylinder using the air-fuel ratio F / B correction amount. Function as. Here, “F / B” means “feedback” (hereinafter the same).

ところで、図７に示すように、燃料噴射弁２１の個体差（製造ばらつき）や経時変化等によって燃料噴射弁２１の噴射特性ずれ（要求噴射量に対する実噴射量のずれ）が発生し、しかも、この噴射特性ずれは、燃料噴射弁２１毎にずれ量が異なる。   By the way, as shown in FIG. 7, the injection characteristic deviation (deviation of the actual injection amount with respect to the required injection amount) of the fuel injection valve 21 occurs due to the individual difference (manufacturing variation) of the fuel injection valve 21 and the change with time, and the like. The deviation of the injection characteristic differs for each fuel injection valve 21.

この点を考慮して、ＥＣＵ３０は、後述する図３乃至図６の噴射特性ずれ学習補正用の各ルーチンを実行することで、所定の学習実行条件が成立したときに、エンジン１１全体の燃料噴射弁２１の噴射特性ずれ（以下「全体噴射特性ずれ」という）を学習する全体噴射特性ずれ学習と、各燃料噴射弁２１の噴射特性ずれ（以下「個別噴射特性ずれ」という）を個別に学習する個別噴射特性ずれ学習とを実行し、全体噴射特性ずれの学習値と個別噴射特性ずれの学習値とを用いて各気筒の２つの燃料噴射弁２１の燃料噴射量を個別に補正するようにしている。   In consideration of this point, the ECU 30 executes each routine for correcting the injection characteristic deviation learning shown in FIGS. 3 to 6 described later, and when predetermined learning execution conditions are satisfied, the fuel injection of the entire engine 11 is performed. The overall injection characteristic deviation learning for learning the injection characteristic deviation of the valve 21 (hereinafter referred to as “total injection characteristic deviation”) and the injection characteristic deviation for each fuel injection valve 21 (hereinafter referred to as “individual injection characteristic deviation”) are individually learned. The individual injection characteristic deviation learning is executed, and the fuel injection amounts of the two fuel injection valves 21 of each cylinder are individually corrected using the learning value of the overall injection characteristic deviation and the learned value of the individual injection characteristic deviation. Yes.

ここで、全体噴射特性ずれ学習では、各気筒の燃料噴射時期毎に各気筒の２つの燃料噴射弁２１を全て噴射動作させて空燃比Ｆ／Ｂ制御を実行しているときに空燃比Ｆ／Ｂ補正量に基づいてエンジン１１全体の燃料噴射弁２１の噴射特性ずれ（全体噴射特性ずれ）を学習する。   Here, in the overall injection characteristic deviation learning, the air-fuel ratio F / B is controlled when the air-fuel ratio F / B control is executed by injecting all the two fuel injection valves 21 of each cylinder at every fuel injection timing of each cylinder. Based on the B correction amount, the injection characteristic deviation (total injection characteristic deviation) of the fuel injection valve 21 of the entire engine 11 is learned.

一方、個別噴射特性ずれ学習では、空燃比Ｆ／Ｂ制御の実行中に、いずれか１つの気筒（以下「学習対象気筒」という）のみで片方（例えば左側）の燃料噴射弁２１の噴射を停止して他方（例えば右側）の燃料噴射弁２１のみで学習対象気筒の要求噴射量分の燃料を噴射する制御を、学習対象気筒と噴射を停止する燃料噴射弁２１をそれぞれ順番に切り替えて実施して、各燃料噴射弁２１の噴射停止前後の空燃比Ｆ／Ｂ補正量の変化量に基づいて学習対象気筒の各燃料噴射弁２１の噴射特性ずれ（個別噴射特性ずれ）を個別に学習する。   On the other hand, in the individual injection characteristic deviation learning, during the execution of the air-fuel ratio F / B control, the injection of the fuel injection valve 21 on one side (for example, the left side) is stopped in only one of the cylinders (hereinafter referred to as “learning target cylinder”). Then, the control for injecting the fuel for the required injection amount of the learning target cylinder only by the other (for example, the right side) fuel injection valve 21 is performed by sequentially switching the learning target cylinder and the fuel injection valve 21 for stopping the injection. Thus, the injection characteristic deviation (individual injection characteristic deviation) of each fuel injection valve 21 of the learning target cylinder is individually learned based on the change amount of the air-fuel ratio F / B correction amount before and after the injection stop of each fuel injection valve 21.

以下、ＥＣＵ３０によって実行される図３乃至図６の噴射特性ずれ学習補正用の各ルーチンの処理内容を説明する。以下の説明では、図２に示す４気筒エンジンを例にして説明し、必要に応じて、各気筒の番号を＃１，＃２，＃３，＃４で表し、各気筒＃１〜＃４の２つの燃料噴射弁２１をＡ，Ｂで表す。   Hereinafter, the processing contents of each routine for correcting the injection characteristic deviation learning of FIGS. 3 to 6 executed by the ECU 30 will be described. In the following description, the four-cylinder engine shown in FIG. 2 will be described as an example, and the numbers of the respective cylinders are denoted by # 1, # 2, # 3, and # 4 as necessary, and the respective cylinders # 1 to # 4 are described. These two fuel injection valves 21 are represented by A and B.

［噴射特性ずれ学習補正メインルーチン］
図３の噴射特性ずれ学習補正メインルーチンは、エンジン運転中に周期的に繰り返し実行される。本ルーチンが起動されると、まず、ステップ１０１で、所定の学習実行条件が成立しているか否かを、例えば、[1] 定常運転中（例えばアイドル運転中等）であること、且つ[2] 空燃比Ｆ／Ｂ制御実行中であること等の条件を満たすか否かで判定する。その結果、学習実行条件が成立していないと判定されれば、噴射特性ずれの学習に適した運転条件ではないと判断して、ステップ１０２以降の噴射特性ずれの学習に関する処理を行うことなく、本ルーチンを終了する。 [Injection characteristic deviation learning correction main routine]
The injection characteristic deviation learning correction main routine of FIG. 3 is repeatedly executed periodically during engine operation. When this routine is started, first, in step 101, whether or not a predetermined learning execution condition is satisfied is determined, for example, by [1] being in steady operation (for example, in idle operation) and [2] Judgment is made based on whether a condition such as the execution of air-fuel ratio F / B control is satisfied. As a result, if it is determined that the learning execution condition is not satisfied, it is determined that the operation condition is not suitable for the learning of the injection characteristic deviation, and the processing relating to the learning of the injection characteristic deviation from step 102 onward is performed. This routine ends.

一方、上記ステップ１０１で、学習実行条件が成立していると判定されれば、噴射特性ずれの学習に適した運転条件であると判断して、ステップ１０２以降の噴射特性ずれの学習に関する処理を次のようにして実行する。まず、ステップ１０２で、後述する図４の全体噴射特性ずれ学習ルーチンを実行して、空燃比Ｆ／Ｂ補正量ＡＦＦＢに基づいてエンジン１１全体の燃料噴射弁２１の噴射特性ずれ（全体噴射特性ずれ）を学習する。   On the other hand, if it is determined in step 101 that the learning execution condition is satisfied, it is determined that the operation condition is suitable for learning the injection characteristic deviation, and the processing related to learning of the injection characteristic deviation in step 102 and subsequent steps is performed. Run as follows: First, in step 102, an overall injection characteristic deviation learning routine of FIG. 4 described later is executed, and an injection characteristic deviation (total injection characteristic deviation) of the fuel injection valve 21 of the entire engine 11 is based on the air-fuel ratio F / B correction amount AFFB. ).

この後、ステップ１０３に進み、全体噴射特性ずれ学習が完了したか否か（最終全体噴射特性ずれ学習値Ｇf.all.fin ＝１か否か）を判定し、全体噴射特性ずれ学習が完了するまで、全体噴射特性ずれの学習を継続する。   Thereafter, the process proceeds to step 103, where it is determined whether or not the overall injection characteristic deviation learning has been completed (whether or not the final overall injection characteristic deviation learning value Gf.all.fin = 1), and the overall injection characteristic deviation learning is completed. Until then, the learning of the overall injection characteristic deviation is continued.

その後、全体噴射特性ずれ学習が完了した時点で、ステップ１０４に進み、エンジン停止中でも記憶データを保持する書き換え可能な記憶手段であるバックアップＲＡＭ３８に全体噴射特性ずれ学習値Ｇf.all を更新記憶して、この全体噴射特性ずれ学習値Ｇf.all を空燃比制御に適用する。これにより、空燃比制御実行中に、全気筒の各燃料噴射弁２１の燃料噴射量が一律に全体噴射特性ずれ学習値Ｇf.all で補正される。   Thereafter, when the entire injection characteristic deviation learning is completed, the routine proceeds to step 104 where the entire injection characteristic deviation learned value Gf.all is updated and stored in the backup RAM 38 which is a rewritable storage means for retaining the stored data even when the engine is stopped. The entire injection characteristic deviation learning value Gf.all is applied to the air-fuel ratio control. Thus, during the execution of the air-fuel ratio control, the fuel injection amounts of the fuel injection valves 21 of all the cylinders are uniformly corrected with the total injection characteristic deviation learning value Gf.all.

この後、ステップ１０５に進み、後述する図５の個別噴射特性ずれ学習ルーチンを実行して、学習対象気筒と噴射を停止する燃料噴射弁２１をそれぞれ順番に切り替えて各燃料噴射弁２１の噴射停止前後の空燃比Ｆ／Ｂ補正量の変化量に基づいて学習対象気筒の噴射を停止した燃料噴射弁２１の噴射特性ずれ（個別噴射特性ずれ）を個別に学習する。   Thereafter, the routine proceeds to step 105, where an individual injection characteristic deviation learning routine shown in FIG. 5 to be described later is executed to switch the learning target cylinder and the fuel injection valve 21 for stopping the injection in order, and stop the injection of each fuel injection valve 21. Based on the change amount of the front / rear air-fuel ratio F / B correction amount, the injection characteristic deviation (individual injection characteristic deviation) of the fuel injection valve 21 that stopped the injection of the learning target cylinder is individually learned.

この後、ステップ１０６に進み、個別噴射特性ずれ学習が完了したか否か（燃料噴射弁識別番号ＮＵＭ＝９［最終番号］か否か）を判定し、個別噴射特性ずれ学習が完了するまで、個別噴射特性ずれの学習を継続する。   Thereafter, the process proceeds to step 106, where it is determined whether or not the individual injection characteristic deviation learning is completed (whether or not the fuel injection valve identification number NUM = 9 [final number]), and until the individual injection characteristic deviation learning is completed. Continue learning the individual injection characteristic deviation.

その後、個別噴射特性ずれ学習が完了した時点で、ステップ１０７に進み、個別噴射特性ずれ学習値Ｇf.#1A 〜Ｇf.#4A ，Ｇf.#1B 〜Ｇf.#4B をバックアップＲＡＭ３８に更新記憶して、これらの個別噴射特性ずれ学習値Ｇf.#1A 〜Ｇf.#4A ，Ｇf.#1B 〜Ｇf.#4B を空燃比制御に適用する。これにより、空燃比制御実行中に、各気筒＃１〜＃４の燃料噴射弁Ａ，Ｂの燃料噴射量がそれぞれ該当する個別噴射特性ずれ学習値Ｇf.#1A 〜Ｇf.#4A ，Ｇf.#1B 〜Ｇf.#4B で補正される。ここで、Ｇf.#1A 〜Ｇf.#4A は、それぞれ各気筒＃１〜＃４の一方の燃料噴射弁Ａの燃料噴射量を個別に補正するための個別噴射特性ずれ学習値であり、Ｇf.#1B 〜Ｇf.#4B は、それぞれ各気筒＃１〜＃４の他方の燃料噴射弁Ｂの燃料噴射量を個別に補正するための個別噴射特性ずれ学習値である。   Thereafter, when the individual injection characteristic deviation learning is completed, the routine proceeds to step 107 where the individual injection characteristic deviation learned values Gf. # 1A to Gf. # 4A and Gf. # 1B to Gf. # 4B are updated and stored in the backup RAM 38. These individual injection characteristic deviation learning values Gf. # 1A to Gf. # 4A and Gf. # 1B to Gf. # 4B are applied to the air-fuel ratio control. Thereby, during the execution of the air-fuel ratio control, the individual fuel injection characteristic deviation learning values Gf. # 1A to Gf. # 4A, Gf. Corresponding to the fuel injection amounts of the fuel injection valves A and B of the cylinders # 1 to # 4, respectively. Corrected by # 1B to Gf. # 4B. Here, Gf. # 1A to Gf. # 4A are individual injection characteristic deviation learning values for individually correcting the fuel injection amount of one fuel injection valve A of each of the cylinders # 1 to # 4. . # 1B to Gf. # 4B are individual injection characteristic deviation learning values for individually correcting the fuel injection amount of the other fuel injection valve B of each of the cylinders # 1 to # 4.

［全体噴射特性ずれ学習ルーチン］
図４の全体噴射特性ずれ学習ルーチンは、図３の噴射特性ずれ学習補正メインルーチンのステップ１０２で実行されるサブルーチンであり、特許請求の範囲でいう全体噴射特性ずれ学習手段としての役割を果たす。本ルーチンが起動されると、まず、ステップ２０１で、バックアップＲＡＭ３８から読み出した全体噴射特性ずれ学習値Ｇf.all を空燃比学習値Ｇf にセットする。これにより、全体噴射特性ずれ学習の実行中は、全気筒の各燃料噴射弁２１の燃料噴射量が一律に空燃比学習値Ｇf （全体噴射特性ずれ学習値Ｇf.all ）で補正される。尚、バックアップＲＡＭ３８に全体噴射特性ずれ学習値Ｇf.all が記憶されていない場合は、予め設定された初期値が空燃比学習値Ｇf にセットされる。 [Overall injection characteristic deviation learning routine]
The whole injection characteristic deviation learning routine of FIG. 4 is a subroutine executed in step 102 of the injection characteristic deviation learning correction main routine of FIG. 3 and plays a role as whole injection characteristic deviation learning means in the claims. When this routine is started, first, in step 201, the entire injection characteristic deviation learned value Gf.all read from the backup RAM 38 is set to the air-fuel ratio learned value Gf. As a result, during the execution of the overall injection characteristic deviation learning, the fuel injection amounts of the fuel injection valves 21 of all the cylinders are uniformly corrected with the air-fuel ratio learning value Gf (total injection characteristic deviation learned value Gf.all). If the total injection characteristic deviation learned value Gf.all is not stored in the backup RAM 38, a preset initial value is set as the air-fuel ratio learned value Gf.

この後、ステップ２０２に進み、後述する図６の学習制御ルーチンを実行して空燃比学習値Ｇf を更新した後、ステップ２０３に進み、現時点の空燃比学習値Ｇf を全体噴射特性ずれ学習値Ｇf.all にセットしてバックアップＲＡＭ３８に更新記憶する。   Thereafter, the routine proceeds to step 202, where a learning control routine of FIG. 6 described later is executed to update the air-fuel ratio learned value Gf, and then the routine proceeds to step 203 where the current air-fuel ratio learned value Gf is changed to the entire injection characteristic deviation learned value Gf. Set to .all and update and store in the backup RAM 38.

この後、ステップ２０４に進み、学習が完了したか否か（空燃比Ｆ／Ｂ補正量ＡＦＦＢがほぼ０か否か）を判定し、学習が完了するまで、上記ステップ２０２〜２０４の処理を繰り返す。その後、上記ステップ２０４で、学習完了と判定された時点で、ステップ２０５に進み、最終全体噴射特性ずれ学習値Ｇf.all.fin を「１」にセットして本ルーチンを終了する。   Thereafter, the process proceeds to step 204, in which it is determined whether or not learning is completed (whether the air-fuel ratio F / B correction amount AFFB is substantially 0), and the processes in steps 202 to 204 are repeated until learning is completed. . Thereafter, when it is determined in step 204 that the learning is completed, the process proceeds to step 205 where the final total injection characteristic deviation learned value Gf.all.fin is set to “1”, and this routine is terminated.

尚、全体噴射特性ずれ学習値Ｇf.all を学習（更新記憶）する際に、全体噴射特性ずれ学習値Ｇf.all が予め決められた許容範囲内であるか否かを判定して、全体噴射特性ずれ学習値Ｇf.all が許容範囲から外れた場合は、いずれかの燃料噴射弁２１の異常と判定して、その異常情報をバックアップＲＡＭ３８に記憶すると共に、警告ランプを点灯又は点滅させたり、運転席のインストルメントパネルの表示部に警告表示して運転者に警告するようにしても良い。更に、全体噴射特性ずれ学習値Ｇf.all が予め決められた許容範囲内となるようにガード処理する（全体噴射特性ずれ学習値Ｇf.all の上下限値を所定値以内に制限する）ようにしても良い。   When learning (updating and storing) the total injection characteristic deviation learning value Gf.all, it is determined whether or not the total injection characteristic deviation learning value Gf.all is within a predetermined allowable range. When the characteristic deviation learning value Gf.all is out of the allowable range, it is determined that one of the fuel injection valves 21 is abnormal, and the abnormality information is stored in the backup RAM 38, and a warning lamp is lit or blinked. A warning may be displayed on the display section of the instrument panel on the driver's seat to warn the driver. Further, guard processing is performed so that the total injection characteristic deviation learning value Gf.all falls within a predetermined allowable range (the upper and lower limit values of the total injection characteristic deviation learning value Gf.all are limited to within a predetermined value). May be.

［個別噴射特性ずれ学習ルーチン］
図５の個別噴射特性ずれ学習ルーチンは、図３の噴射特性ずれ学習補正メインルーチンのステップ１０５で実行されるサブルーチンであり、特許請求の範囲でいう個別噴射特性ずれ学習手段としての役割を果たす。本ルーチンが起動されると、まず、ステップ３０１で、本ルーチンの最後のステップ３０６でカウントアップされる燃料噴射弁識別番号ＮＵＭ（＝１〜９）に基づいて以下の（１）〜（８）のいずれに該当するかを判別して、噴射を停止する燃料噴射弁２１を選択する。 [Individual injection characteristic deviation learning routine]
The individual injection characteristic deviation learning routine of FIG. 5 is a subroutine executed in step 105 of the injection characteristic deviation learning correction main routine of FIG. 3, and plays a role as individual injection characteristic deviation learning means in the claims. When this routine is started, first, at step 301, the following (1) to (8) are performed based on the fuel injection valve identification number NUM (= 1 to 9) counted up at the last step 306 of this routine. And the fuel injection valve 21 for stopping the injection is selected.

（１）燃料噴射弁識別番号ＮＵＭ＝１の場合は、気筒＃１が学習対象気筒となり、当該気筒＃１の一方の燃料噴射弁Ａの噴射を停止し、当該気筒＃１の他方の燃料噴射弁Ｂの噴射量を２倍に増大させることで、当該気筒＃１に要求噴射量分の燃料を噴射する。   (1) When the fuel injection valve identification number NUM = 1, the cylinder # 1 becomes a learning target cylinder, the injection of one fuel injection valve A of the cylinder # 1 is stopped, and the other fuel injection of the cylinder # 1 By increasing the injection amount of the valve B by a factor of 2, the required amount of fuel is injected into the cylinder # 1.

（２）燃料噴射弁識別番号ＮＵＭ＝２の場合は、気筒＃１が学習対象気筒となり、当該気筒＃１の他方の燃料噴射弁Ｂの噴射を停止し、当該気筒＃１の一方の燃料噴射弁Ａの噴射量を２倍に増大させることで、当該気筒＃１に要求噴射量分の燃料を噴射する。   (2) When the fuel injection valve identification number NUM = 2, the cylinder # 1 becomes the learning target cylinder, the injection of the other fuel injection valve B of the cylinder # 1 is stopped, and the one fuel injection of the cylinder # 1 By increasing the injection amount of the valve A by a factor of 2, the required amount of fuel is injected into the cylinder # 1.

（３）燃料噴射弁識別番号ＮＵＭ＝３の場合は、気筒＃２が学習対象気筒となり、当該気筒＃２の一方の燃料噴射弁Ａの噴射を停止し、当該気筒＃２の他方の燃料噴射弁Ｂの噴射量を２倍に増大させることで、当該気筒＃２に要求噴射量分の燃料を噴射する。   (3) When the fuel injection valve identification number NUM = 3, the cylinder # 2 becomes the learning target cylinder, the injection of one fuel injection valve A of the cylinder # 2 is stopped, and the other fuel injection of the cylinder # 2 By increasing the injection amount of the valve B by a factor of 2, the required amount of fuel is injected into the cylinder # 2.

（４）燃料噴射弁識別番号ＮＵＭ＝４の場合は、気筒＃２が学習対象気筒となり、当該気筒＃２の他方の燃料噴射弁Ｂの噴射を停止し、当該気筒＃２の一方の燃料噴射弁Ａの噴射量を２倍に増大させることで、当該気筒＃２に要求噴射量分の燃料を噴射する。   (4) When the fuel injection valve identification number NUM = 4, the cylinder # 2 becomes the learning target cylinder, the injection of the other fuel injection valve B of the cylinder # 2 is stopped, and the one fuel injection of the cylinder # 2 is stopped By increasing the injection amount of the valve A by a factor of 2, the required amount of fuel is injected into the cylinder # 2.

（５）燃料噴射弁識別番号ＮＵＭ＝５の場合は、気筒＃３が学習対象気筒となり、当該気筒＃３の一方の燃料噴射弁Ａの噴射を停止し、当該気筒＃３の他方の燃料噴射弁Ｂの噴射量を２倍に増大させることで、当該気筒＃３に要求噴射量分の燃料を噴射する。   (5) When the fuel injection valve identification number NUM = 5, the cylinder # 3 becomes the learning target cylinder, the injection of one fuel injection valve A of the cylinder # 3 is stopped, and the other fuel injection of the cylinder # 3 By increasing the injection amount of the valve B by a factor of 2, the required amount of fuel is injected into the cylinder # 3.

（６）燃料噴射弁識別番号ＮＵＭ＝６の場合は、気筒＃３が学習対象気筒となり、当該気筒＃３の他方の燃料噴射弁Ｂの噴射を停止し、当該気筒＃３の一方の燃料噴射弁Ａの噴射量を２倍に増大させることで、当該気筒＃３に要求噴射量分の燃料を噴射する。   (6) When the fuel injection valve identification number NUM = 6, the cylinder # 3 becomes the learning target cylinder, the injection of the other fuel injection valve B of the cylinder # 3 is stopped, and the one fuel injection of the cylinder # 3 By increasing the injection amount of the valve A by a factor of 2, the required amount of fuel is injected into the cylinder # 3.

（７）燃料噴射弁識別番号ＮＵＭ＝７の場合は、気筒＃４が学習対象気筒となり、当該気筒＃４の一方の燃料噴射弁Ａの噴射を停止し、当該気筒＃４の他方の燃料噴射弁Ｂの噴射量を２倍に増大させることで、当該気筒＃４に要求噴射量分の燃料を噴射する。   (7) When the fuel injection valve identification number NUM = 7, cylinder # 4 becomes the learning target cylinder, the injection of one fuel injection valve A of the cylinder # 4 is stopped, and the other fuel injection of the cylinder # 4 By increasing the injection amount of the valve B by a factor of 2, the required amount of fuel is injected into the cylinder # 4.

（８）燃料噴射弁識別番号ＮＵＭ＝８の場合は、気筒＃４が学習対象気筒となり、当該気筒＃４の他方の燃料噴射弁Ｂの噴射を停止し、当該気筒＃４の一方の燃料噴射弁Ａの噴射量を２倍に増大させることで、当該気筒＃４に要求噴射量分の燃料を噴射する。   (8) When the fuel injection valve identification number NUM = 8, the cylinder # 4 becomes the learning target cylinder, the injection of the other fuel injection valve B of the cylinder # 4 is stopped, and the one fuel injection of the cylinder # 4 By increasing the injection amount of the valve A by a factor of 2, the required amount of fuel is injected into the cylinder # 4.

この後、ステップ３０２に進み、現時点の燃料噴射弁識別番号ＮＵＭに基づいて以下のいずれに該当するかを判別して、現時点の燃料噴射弁識別番号ＮＵＭに対応する個別噴射特性ずれ学習値を空燃比学習値Ｇf にセットする。   Thereafter, the routine proceeds to step 302, where it is determined which of the following applies based on the current fuel injection valve identification number NUM, and the individual injection characteristic deviation learning value corresponding to the current fuel injection valve identification number NUM is empty. Set to the fuel ratio learning value Gf.

燃料噴射弁識別番号ＮＵＭ＝１の場合は、気筒＃１の一方の燃料噴射弁Ａの個別噴射特性ずれ学習値Ｇf.#1A を空燃比学習値Ｇf にセットする。   When the fuel injection valve identification number NUM = 1, the individual injection characteristic deviation learning value Gf. # 1A of one fuel injection valve A of the cylinder # 1 is set to the air-fuel ratio learning value Gf.

燃料噴射弁識別番号ＮＵＭ＝２の場合は、気筒＃１の他方の燃料噴射弁Ｂの個別噴射特性ずれ学習値Ｇf.#1B を空燃比学習値Ｇf にセットする。   When the fuel injection valve identification number NUM = 2, the individual injection characteristic deviation learning value Gf. # 1B of the other fuel injection valve B of the cylinder # 1 is set to the air-fuel ratio learning value Gf.

燃料噴射弁識別番号ＮＵＭ＝３の場合は、気筒＃２の一方の燃料噴射弁Ａの個別噴射特性ずれ学習値Ｇf.#2A を空燃比学習値Ｇf にセットする。   When the fuel injection valve identification number NUM = 3, the individual injection characteristic deviation learning value Gf. # 2A of one fuel injection valve A of the cylinder # 2 is set to the air-fuel ratio learning value Gf.

燃料噴射弁識別番号ＮＵＭ＝４の場合は、気筒＃２の他方の燃料噴射弁Ｂの個別噴射特性ずれ学習値Ｇf.#2B を空燃比学習値Ｇf にセットする。   When the fuel injection valve identification number NUM = 4, the individual fuel injection characteristic deviation learning value Gf. # 2B of the other fuel injection valve B of the cylinder # 2 is set to the air-fuel ratio learning value Gf.

燃料噴射弁識別番号ＮＵＭ＝５の場合は、気筒＃３の一方の燃料噴射弁Ａの個別噴射特性ずれ学習値Ｇf.#3A を空燃比学習値Ｇf にセットする。   When the fuel injection valve identification number NUM = 5, the individual injection characteristic deviation learning value Gf. # 3A of one fuel injection valve A of the cylinder # 3 is set to the air-fuel ratio learning value Gf.

燃料噴射弁識別番号ＮＵＭ＝６の場合は、気筒＃３の他方の燃料噴射弁Ｂの個別噴射特性ずれ学習値Ｇf.#3B を空燃比学習値Ｇf にセットする。   When the fuel injection valve identification number NUM = 6, the individual injection characteristic deviation learning value Gf. # 3B of the other fuel injection valve B of the cylinder # 3 is set to the air-fuel ratio learning value Gf.

燃料噴射弁識別番号ＮＵＭ＝７の場合は、気筒＃４の一方の燃料噴射弁Ａの個別噴射特性ずれ学習値Ｇf.#4A を空燃比学習値Ｇf にセットする。   When the fuel injection valve identification number NUM = 7, the individual injection characteristic deviation learning value Gf. # 4A of one fuel injection valve A of the cylinder # 4 is set to the air-fuel ratio learning value Gf.

燃料噴射弁識別番号ＮＵＭ＝８の場合は、気筒＃４の他方の燃料噴射弁Ｂの個別噴射特性ずれ学習値Ｇf.#4B を空燃比学習値Ｇf にセットする。   In the case of the fuel injection valve identification number NUM = 8, the individual injection characteristic deviation learning value Gf. # 4B of the other fuel injection valve B of the cylinder # 4 is set to the air-fuel ratio learning value Gf.

この後、ステップ３０３に進み、後述する図６の学習制御ルーチンを実行して空燃比学習値Ｇf を更新した後、ステップ３０４に進み、現時点の燃料噴射弁識別番号ＮＵＭに基づいて以下のいずれに該当するかを判別して、現時点の空燃比学習値Ｇf を燃料噴射弁識別番号ＮＵＭに対応する個別噴射特性ずれ学習値にセットする。   Thereafter, the routine proceeds to step 303, where a learning control routine shown in FIG. 6 described later is executed to update the air-fuel ratio learned value Gf, and then the routine proceeds to step 304 where any of the following is performed based on the current fuel injection valve identification number NUM. It is discriminated whether it is true, and the current air-fuel ratio learning value Gf is set to the individual injection characteristic deviation learning value corresponding to the fuel injection valve identification number NUM.

燃料噴射弁識別番号ＮＵＭ＝１の場合は、現時点の空燃比学習値Ｇf を気筒＃１の一方の燃料噴射弁Ａの個別噴射特性ずれ学習値Ｇf.#1A にセットする。   When the fuel injection valve identification number NUM = 1, the current air-fuel ratio learning value Gf is set to the individual injection characteristic deviation learning value Gf. # 1A of one fuel injection valve A of the cylinder # 1.

燃料噴射弁識別番号ＮＵＭ＝２の場合は、現時点の空燃比学習値Ｇf を気筒＃１の他方の燃料噴射弁Ｂの個別噴射特性ずれ学習値Ｇf.#1B にセットする。   When the fuel injection valve identification number NUM = 2, the current air-fuel ratio learning value Gf is set to the individual injection characteristic deviation learning value Gf. # 1B of the other fuel injection valve B of the cylinder # 1.

燃料噴射弁識別番号ＮＵＭ＝３の場合は、現時点の空燃比学習値Ｇf を気筒＃２の一方の燃料噴射弁Ａの個別噴射特性ずれ学習値Ｇf.#2A にセットする。   When the fuel injector identification number NUM = 3, the current air-fuel ratio learned value Gf is set to the individual injection characteristic deviation learned value Gf. # 2A of one fuel injector A of the cylinder # 2.

燃料噴射弁識別番号ＮＵＭ＝４の場合は、現時点の空燃比学習値Ｇf を気筒＃２の他方の燃料噴射弁Ｂの個別噴射特性ずれ学習値Ｇf.#2B にセットする。   When the fuel injector identification number NUM = 4, the current air-fuel ratio learned value Gf is set to the individual injection characteristic deviation learned value Gf. # 2B of the other fuel injector B of the cylinder # 2.

燃料噴射弁識別番号ＮＵＭ＝５の場合は、現時点の空燃比学習値Ｇf を気筒＃３の一方の燃料噴射弁Ａの個別噴射特性ずれ学習値Ｇf.#3A にセットする。   When the fuel injection valve identification number NUM = 5, the current air-fuel ratio learning value Gf is set to the individual injection characteristic deviation learning value Gf. # 3A of one fuel injection valve A of the cylinder # 3.

燃料噴射弁識別番号ＮＵＭ＝６の場合は、現時点の空燃比学習値Ｇf を気筒＃３の他方の燃料噴射弁Ｂの個別噴射特性ずれ学習値Ｇf.#3B にセットする。   When the fuel injector identification number NUM = 6, the current air-fuel ratio learned value Gf is set to the individual injection characteristic deviation learned value Gf. # 3B of the other fuel injector B of the cylinder # 3.

燃料噴射弁識別番号ＮＵＭ＝７の場合は、現時点の空燃比学習値Ｇf を気筒＃４の一方の燃料噴射弁Ａの個別噴射特性ずれ学習値Ｇf.#4A にセットする。   When the fuel injection valve identification number NUM = 7, the current air-fuel ratio learning value Gf is set to the individual injection characteristic deviation learning value Gf. # 4A of one fuel injection valve A of the cylinder # 4.

燃料噴射弁識別番号ＮＵＭ＝８の場合は、現時点の空燃比学習値Ｇf を気筒＃４の他方の燃料噴射弁Ｂの個別噴射特性ずれ学習値Ｇf.#4B にセットする。   When the fuel injection valve identification number NUM = 8, the current air-fuel ratio learning value Gf is set to the individual injection characteristic deviation learning value Gf. # 4B of the other fuel injection valve B of the cylinder # 4.

この後、ステップ３０５に進み、学習が完了したか否か（空燃比Ｆ／Ｂ補正量ＡＦＦＢがほぼ０か否か）を判定し、学習が完了するまで、上記ステップ３０３〜３０５の処理を繰り返す。その後、上記ステップ３０５で、学習完了と判定された時点で、ステップ３０６に進み、燃料噴射弁識別番号ＮＵＭを１だけ増加させて本ルーチンを終了する。   Thereafter, the process proceeds to step 305, where it is determined whether learning is completed (whether the air-fuel ratio F / B correction amount AFFB is substantially 0), and the processing of steps 303 to 305 is repeated until learning is completed. . Thereafter, when it is determined in step 305 that learning is completed, the routine proceeds to step 306, where the fuel injection valve identification number NUM is incremented by 1, and this routine is terminated.

尚、個別噴射特性ずれ学習値Ｇf.#1A 〜Ｇf.#4A ，Ｇf.#1B 〜Ｇf.#4B を学習する際に、それらの個別噴射特性ずれ学習値が予め決められた許容範囲内であるか否かを判定して、いずれかの個別噴射特性ずれ学習値が許容範囲から外れた場合は、許容範囲から外れた燃料噴射弁２１が異常であると判定してその異常情報をバックアップＲＡＭ３８に記憶すると共に、警告ランプを点灯又は点滅させたり、運転席のインストルメントパネルの表示部に警告表示して運転者に警告するようにしても良い。この場合、いずれかの燃料噴射弁２１の異常が発生したときに、異常な燃料噴射弁２１を特定することができる。更に、個別噴射特性ずれ学習値が予め決められた許容範囲内となるようにガード処理する（個別噴射特性ずれ学習値の上下限値を所定値以内に制限する）ようにしても良い。   When learning the individual injection characteristic deviation learning values Gf. # 1A to Gf. # 4A and Gf. # 1B to Gf. # 4B, the individual injection characteristic deviation learning values are within a predetermined allowable range. If any individual injection characteristic deviation learning value is out of the allowable range, it is determined that the fuel injection valve 21 out of the allowable range is abnormal, and the abnormality information is stored in the backup RAM 38. In addition, the warning lamp may be turned on or blinked, or a warning may be displayed on the display section of the driver's instrument panel to warn the driver. In this case, when any one of the fuel injection valves 21 is abnormal, the abnormal fuel injection valve 21 can be specified. Further, guard processing may be performed so that the individual injection characteristic deviation learned value falls within a predetermined allowable range (the upper and lower limit values of the individual injection characteristic deviation learned value are limited to within a predetermined value).

［学習制御ルーチン］
図６の学習制御ルーチンは、図４の全体噴射特性ずれ学習ルーチンのステップ２０２と図５の個別噴射特性ずれ学習ルーチンのステップ３０３で実行されるサブルーチンである。本ルーチンが起動されると、まず、ステップ４０１で、現時点の空燃比学習値Ｇf を前回空燃比学習値Ｇf.o にセットし、次のステップ４０２で、現時点の空燃比Ｆ／Ｂ補正量ＡＦＦＢを前回空燃比Ｆ／Ｂ補正量ＡＦＦＢ.oにセットする。 [Learning control routine]
The learning control routine of FIG. 6 is a subroutine executed in step 202 of the entire injection characteristic deviation learning routine of FIG. 4 and step 303 of the individual injection characteristic deviation learning routine of FIG. When this routine is started, first, at step 401, the current air-fuel ratio learned value Gf is set to the previous air-fuel ratio learned value Gf.o, and at the next step 402, the current air-fuel ratio F / B correction amount AFFB is set. Is set to the previous air-fuel ratio F / B correction amount AFFB.o.

この後、ステップ４０３、４０４の判定処理により、空燃比Ｆ／Ｂ補正量ＡＦＦＢがプラス値、０、マイナス値のいずれであるかを判別して、空燃比Ｆ／Ｂ補正量ＡＦＦＢが０と判定された場合（ステップ４０３、４０４で共に「Ｙｅｓ」と判定された場合）には、ステップ４０５に進み、空燃比学習値更新量ＤＬＧＦを０にセットする。   Thereafter, it is determined whether the air-fuel ratio F / B correction amount AFFB is a positive value, 0, or a negative value by the determination processing in steps 403 and 404, and the air-fuel ratio F / B correction amount AFFB is determined to be 0. If it has been determined (when both the determinations in steps 403 and 404 are “Yes”), the routine proceeds to step 405, where the air-fuel ratio learning value update amount DLGF is set to zero.

また、空燃比Ｆ／Ｂ補正量ＡＦＦＢがマイナス値と判定された場合（ステップ４０３で「Ｎｏ」と判定された場合）には、ステップ４０７に進み、空燃比学習値更新量ＤＬＧＦを予め設定された所定値（マイナス値）にセットする。   When the air-fuel ratio F / B correction amount AFFB is determined to be a negative value (when “No” is determined in step 403), the process proceeds to step 407, where the air-fuel ratio learning value update amount DLGF is set in advance. Set to a predetermined value (negative value).

一方、空燃比Ｆ／Ｂ補正量ＡＦＦＢがプラス値と判定された場合（ステップ４０３で「Ｙｅｓ」、ステップ４０４で「Ｎｏ」と判定された場合）には、ステップ４０６に進み、空燃比学習値更新量ＤＬＧＦを予め設定された所定値（プラス値）にセットする。   On the other hand, if it is determined that the air-fuel ratio F / B correction amount AFFB is a positive value (“Yes” in step 403 and “No” in step 404), the process proceeds to step 406 and the air-fuel ratio learning value is reached. The update amount DLGF is set to a predetermined value (plus value) set in advance.

以上のようにして空燃比学習値更新量ＤＬＧＦをセットした後、ステップ４０８に進み、前回空燃比学習値Ｇf.o に空燃比学習値更新量ＤＬＧＦを加算した値を新たな空燃比学習値Ｇf とする。   After the air-fuel ratio learning value update amount DLGF is set as described above, the routine proceeds to step 408, where the value obtained by adding the air-fuel ratio learning value update amount DLGF to the previous air-fuel ratio learning value Gf.o is set as the new air-fuel ratio learning value Gf. And

この後、ステップ４０９に進み、前回空燃比Ｆ／Ｂ補正量ＡＦＦＢ.oから空燃比学習値更新量ＤＬＧＦを加算した値を新たな空燃比Ｆ／Ｂ補正量ＡＦＦＢとして、本ルーチンを終了する。   Thereafter, the routine proceeds to step 409, where the value obtained by adding the air-fuel ratio learning value update amount DLGF to the previous air-fuel ratio F / B correction amount AFFB.o is set as a new air-fuel ratio F / B correction amount AFFB, and this routine is ended.

以上説明した本実施例１によれば、各気筒の燃料噴射時期毎に各気筒の２つの燃料噴射弁２１を全て噴射動作させて空燃比Ｆ／Ｂ制御を実行しているときに空燃比Ｆ／Ｂ補正量に基づいてエンジン１１全体の燃料噴射弁２１の噴射特性ずれ（全体噴射特性ずれ）を学習した後、空燃比Ｆ／Ｂ制御の実行中にいずれか１つの気筒（学習対象気筒）のみで片方の燃料噴射弁２１の噴射を停止して他方の燃料噴射弁２１のみで学習対象気筒の要求噴射量分の燃料を噴射する制御を、学習対象気筒と噴射を停止する燃料噴射弁２１をそれぞれ順番に切り替えて実施して各燃料噴射弁２１の噴射停止前後の空燃比Ｆ／Ｂ補正量の変化量に基づいて学習対象気筒の各燃料噴射弁２１の噴射特性ずれ（個別噴射特性ずれ）を個別に学習するようにしたので、学習対象気筒に要求噴射量分の燃料を噴射しながら学習対象気筒の各燃料噴射弁２１の噴射特性ずれ（個別噴射特性ずれ）を個別に学習することができ、学習対象気筒と他の気筒との間の空燃比ばらつきやトルクばらつきを抑えながら個別噴射特性ずれを精度良く学習することができる。そして、全体噴射特性ずれの学習値と個別噴射特性ずれの学習値を用いて各気筒の２つの燃料噴射弁２１の燃料噴射量を個別に補正するため、各燃料噴射弁２１の噴射特性ずれを個別に精度良く補正することができて、燃料噴射弁２１間の噴射特性ずれのばらつきに起因する気筒間の空燃比ばらつきやトルクばらつきを効果的に低減することができる。   According to the first embodiment described above, when the air-fuel ratio F / B control is executed by injecting all the two fuel injection valves 21 of each cylinder at every fuel injection timing of each cylinder, the air-fuel ratio F After learning the injection characteristic deviation (total injection characteristic deviation) of the fuel injection valve 21 of the entire engine 11 based on the / B correction amount, any one cylinder (learning target cylinder) during the execution of the air-fuel ratio F / B control Only the other fuel injection valve 21 stops the injection of the fuel injection valve 21 and injects fuel corresponding to the required injection amount of the learning target cylinder, and the fuel injection valve 21 stops the learning target cylinder and the injection. Are switched in order, and the injection characteristic deviation (individual injection characteristic deviation) of each fuel injection valve 21 of the learning target cylinder is based on the change amount of the air-fuel ratio F / B correction amount before and after the injection stop of each fuel injection valve 21. ) To learn individually, The injection characteristic deviation (individual injection characteristic deviation) of each fuel injection valve 21 of the learning target cylinder can be individually learned while injecting fuel for the required injection amount into the learning target cylinder. The individual injection characteristic deviation can be learned with high accuracy while suppressing the air-fuel ratio variation and torque variation between the two. Since the fuel injection amounts of the two fuel injection valves 21 of each cylinder are individually corrected using the learning value of the overall injection characteristic deviation and the learned value of the individual injection characteristic deviation, the injection characteristic deviation of each fuel injection valve 21 is corrected. The correction can be made individually with high accuracy, and the variation in air-fuel ratio between the cylinders and the variation in torque caused by the variation in the injection characteristic deviation between the fuel injection valves 21 can be effectively reduced.

しかも、本実施例１では、全体噴射特性ずれの学習が完了した後に、各燃料噴射弁２１の燃料噴射量を全体噴射特性ずれの学習値で補正した状態で個別噴射特性ずれを学習するようにしたので、全体噴射特性ずれを補正した状態で個別噴射特性ずれを精度良く学習することができ、個別噴射特性ずれの学習精度を更に向上させることができる。   Moreover, in the first embodiment, after learning of the total injection characteristic deviation is completed, the individual injection characteristic deviation is learned in a state where the fuel injection amount of each fuel injection valve 21 is corrected with the learning value of the total injection characteristic deviation. Therefore, the individual injection characteristic deviation can be learned with high accuracy in a state where the overall injection characteristic deviation is corrected, and the learning accuracy of the individual injection characteristic deviation can be further improved.

但し、本発明は、各燃料噴射弁２１の燃料噴射量を全体噴射特性ずれの学習値で補正しない状態で個別噴射特性ずれを学習し、全体噴射特性ずれと個別噴射特性ずれの学習完了後に全体噴射特性ずれの学習値と個別噴射特性ずれの学習値とを用いて各燃料噴射弁２１の燃料噴射量を個別に補正するようにしても良い。   However, in the present invention, the individual injection characteristic deviation is learned in a state where the fuel injection amount of each fuel injection valve 21 is not corrected by the learning value of the total injection characteristic deviation, and the entire injection characteristic deviation and the individual injection characteristic deviation are learned after completing the learning. The fuel injection amount of each fuel injection valve 21 may be individually corrected using the learned value of the injection characteristic deviation and the learned value of the individual injection characteristic deviation.

次に、図８及び図９を用いて本発明の実施例２を説明する。但し、前記実施例１と実質的に同一部分については説明を省略又は簡略化し、主として前記実施例１と異なる部分について説明する。   Next, Embodiment 2 of the present invention will be described with reference to FIGS. However, description of substantially the same parts as those in the first embodiment will be omitted or simplified, and different parts from the first embodiment will be mainly described.

本実施例２では、前記実施例１と同様の方法で全体噴射特性ずれを学習した後に、グループ別噴射特性ずれを学習し、全体噴射特性ずれの学習値とグループ別噴射特性ずれの学習値とを用いて各気筒の２つの燃料噴射弁２１の燃料噴射量を燃料噴射弁グループ別に補正するようにしている。   In the second embodiment, after learning the total injection characteristic deviation by the same method as in the first embodiment, the group-specific injection characteristic deviation is learned, and the learning value of the total injection characteristic deviation and the learning value of the group-specific injection characteristic deviation are The fuel injection amount of the two fuel injection valves 21 of each cylinder is corrected for each fuel injection group.

ここで、グループ別噴射特性ずれの学習では、空燃比Ｆ／Ｂ制御実行中に各気筒の２つの燃料噴射弁２１のうちの一方（例えば左側）の燃料噴射弁２１からなる燃料噴射弁グループの噴射を停止して他方（例えば右側）の燃料噴射弁グループのみで各気筒の要求噴射量分の燃料を噴射する制御を、噴射を停止する燃料噴射弁グループを切り替えて実施して、燃料噴射弁グループの噴射停止前後の空燃比Ｆ／Ｂ補正量の変化量に基づいて燃料噴射弁グループ別の噴射特性ずれ（グループ別噴射特性ずれ）を学習する。
以下、本実施例２で実行される図８及び図９の噴射特性ずれ学習補正用の各ルーチンの処理内容を説明する。 Here, in learning of the injection characteristic deviation by group, during the execution of the air-fuel ratio F / B control, the fuel injection valve group including one (for example, the left side) fuel injection valve 21 of the two fuel injection valves 21 of each cylinder. The fuel injection valve is controlled by switching the fuel injection valve group for stopping the injection and controlling the injection of the fuel for the required injection amount of each cylinder only by the other fuel injection valve group (for example, the right side). A fuel injection valve group-specific injection characteristic deviation (group-specific injection characteristic deviation) is learned based on the amount of change in the air-fuel ratio F / B correction amount before and after stopping the injection of the group.
The processing contents of the routines for correcting the injection characteristic deviation learning in FIGS. 8 and 9 executed in the second embodiment will be described below.

［噴射特性ずれ学習補正メインルーチン］
図８の噴射特性ずれ学習補正メインルーチンは、エンジン運転中に周期的に繰り返し実行される。本ルーチンが起動されると、まず、ステップ５０１〜５０４で、前記実施例１で説明した図３の噴射特性ずれ学習補正メインルーチンのステップ１０１〜１０４と同様の処理により、空燃比Ｆ／Ｂ補正量ＡＦＦＢに基づいてエンジン１１全体の燃料噴射弁２１の噴射特性ずれ（全体噴射特性ずれ）を学習して、全体噴射特性ずれ学習が完了した時点で、バックアップＲＡＭ３８に全体噴射特性ずれ学習値Ｇf.all を更新記憶して、この全体噴射特性ずれ学習値Ｇf.all を空燃比制御に適用する。 [Injection characteristic deviation learning correction main routine]
The injection characteristic deviation learning correction main routine of FIG. 8 is repeatedly executed periodically during engine operation. When this routine is started, first, in steps 501 to 504, air-fuel ratio F / B correction is performed by the same processing as steps 101 to 104 of the injection characteristic deviation learning correction main routine of FIG. 3 described in the first embodiment. The injection characteristic deviation (total injection characteristic deviation) of the fuel injection valve 21 of the entire engine 11 is learned based on the amount AFFB, and when the whole injection characteristic deviation learning is completed, the backup RAM 38 stores the total injection characteristic deviation learned value Gf. All is updated and stored, and this total injection characteristic deviation learning value Gf.all is applied to the air-fuel ratio control.

この後、ステップ５０５に進み、後述する図９のグループ別噴射特性ずれ学習ルーチンを実行して、一方の燃料噴射弁グループの噴射を停止して他方の燃料噴射弁グループのみで各気筒の要求噴射量分の燃料を噴射して、燃料噴射弁グループの噴射停止前後の空燃比Ｆ／Ｂ補正量の変化量に基づいて燃料噴射弁グループ別の噴射特性ずれ（グループ別噴射特性ずれ）を学習する。   Thereafter, the routine proceeds to step 505, where a group-by-group injection characteristic deviation learning routine of FIG. 9 described later is executed to stop the injection of one fuel injection valve group and the required injection of each cylinder only by the other fuel injection valve group. An amount of fuel is injected, and an injection characteristic deviation (group-specific injection characteristic deviation) for each fuel injection valve group is learned based on the change amount of the air-fuel ratio F / B correction amount before and after the injection stop of the fuel injection valve group. .

この後、ステップ５０６に進み、グループ別噴射特性ずれ学習が完了したか否か（グループ識別番号ＧＲＰ＝３［最終番号］か否か）を判定し、グループ別噴射特性ずれ学習が完了するまで、グループ別噴射特性ずれの学習を継続する。   Thereafter, the process proceeds to step 506, where it is determined whether or not the group-specific injection characteristic deviation learning is completed (whether or not the group identification number GRP = 3 [final number]), and until the group-specific injection characteristic deviation learning is completed. Continue learning the injection characteristic deviation by group.

その後、グループ別噴射特性ずれ学習が完了した時点で、ステップ５０７に進み、グループ別噴射特性ずれ学習値Ｇf.A ，Ｇf.B をバックアップＲＡＭ３８に更新記憶して、このグループ別噴射特性ずれ学習値Ｇf.A ，Ｇf.B を空燃比制御に適用する。これにより、空燃比制御実行中に、各気筒＃１，…，＃４の燃料噴射弁Ａ，Ｂの燃料噴射量が燃料噴射弁グループ別にグループ別噴射特性ずれ学習値Ｇf.A ，Ｇf.B で補正される。   Thereafter, when the group-specific injection characteristic deviation learning is completed, the routine proceeds to step 507, where the group-specific injection characteristic deviation learned values Gf.A and Gf.B are updated and stored in the backup RAM 38, and this group-specific injection characteristic deviation learned value is obtained. Gf.A and Gf.B are applied to air-fuel ratio control. Thus, during execution of the air-fuel ratio control, the fuel injection amounts of the fuel injection valves A and B of the cylinders # 1,..., # 4 are group-specific injection characteristic deviation learning values Gf.A and Gf.B for each fuel injection group. It is corrected by.

［グループ別噴射特性ずれ学習ルーチン］
図９のグループ別噴射特性ずれ学習ルーチンは、図８の噴射特性ずれ学習補正メインルーチンのステップ５０５で実行されるサブルーチンであり、特許請求の範囲でいうグループ別噴射特性ずれ学習手段としての役割を果たす。本ルーチンが起動されると、まず、ステップ６０１で、本ルーチンの最後のステップ６０６でカウントアップされるグループ識別番号ＧＲＰに基づいて以下のいずれに該当するかを判別して、噴射を実行する燃料噴射弁グループを選択する。 [Group-specific injection characteristic deviation learning routine]
The group-specific injection characteristic deviation learning routine of FIG. 9 is a subroutine executed in step 505 of the injection characteristic deviation learning correction main routine of FIG. 8 and serves as a group-specific injection characteristic deviation learning means in the claims. Fulfill. When this routine is started, first, in step 601, it is determined which of the following applies based on the group identification number GRP counted up in the last step 606 of this routine, and the fuel for executing the injection Select the injection valve group.

グループ識別番号ＧＲＰ＝１の場合は、一方の燃料噴射弁グループＡ（各気筒＃１〜＃４の一方の燃料噴射弁Ａ）のみで噴射し、他方の燃料噴射弁グループＢ（各気筒＃１〜＃４の他方の燃料噴射弁Ｂ）の噴射を停止する。   When the group identification number GRP = 1, the fuel injection valve group A (one fuel injection valve A of each cylinder # 1 to # 4) is injected only, and the other fuel injection valve group B (each cylinder # 1). Stop injection of the other fuel injection valve B) of # 4.

グループ識別番号ＧＲＰ＝２の場合は、他方の燃料噴射弁グループＢ（各気筒＃１〜＃４の他方の燃料噴射弁Ｂ）のみで噴射し、一方の燃料噴射弁グループＡ（各気筒＃１〜＃４の一方の燃料噴射弁Ａ）の噴射を停止する。   In the case of the group identification number GRP = 2, injection is performed only by the other fuel injection valve group B (the other fuel injection valve B of each cylinder # 1 to # 4), and one fuel injection group A (each cylinder # 1). The injection of one fuel injection valve A) of # 4 is stopped.

この後、ステップ６０２に進み、グループ識別番号ＧＲＰに基づいて以下のいずれに該当するかを判別して、現時点のグループ識別番号ＧＲＰに対応するグループ別噴射特性ずれ学習値を空燃比学習値Ｇf にセットする。   Thereafter, the process proceeds to step 602, where it is determined which of the following applies based on the group identification number GRP, and the group-specific injection characteristic deviation learned value corresponding to the current group identification number GRP is set to the air-fuel ratio learned value Gf. set.

グループ識別番号ＧＲＰ＝１の場合は、一方の燃料噴射弁グループＡのグループ別噴射特性ずれ学習値Ｇf.A を空燃比学習値Ｇf にセットする。
グループ識別番号ＧＲＰ＝２の場合は、他方の燃料噴射弁グループＢのグループ別噴射特性ずれ学習値Ｇf.B を空燃比学習値Ｇf にセットする。 When the group identification number GRP = 1, the group-specific injection characteristic deviation learned value Gf.A of one fuel injection valve group A is set to the air-fuel ratio learned value Gf.
When the group identification number GRP = 2, the group-specific injection characteristic deviation learned value Gf.B of the other fuel injection valve group B is set to the air-fuel ratio learned value Gf.

この後、ステップ６０３に進み、前記実施例１で説明する図６の学習制御ルーチンを実行して空燃比学習値Ｇf を更新した後、ステップ６０４に進み、グループ識別番号ＧＲＰに基づいて以下のいずれに該当するかを判別して、現時点の空燃比学習値Ｇf をグループ識別番号ＧＲＰに対応するグループ別噴射特性ずれ学習値にセットする。   Thereafter, the process proceeds to step 603, the learning control routine of FIG. 6 described in the first embodiment is executed to update the air-fuel ratio learned value Gf, and then the process proceeds to step 604, where any of the following is performed based on the group identification number GRP. And the current air-fuel ratio learning value Gf is set to the group-specific injection characteristic deviation learning value corresponding to the group identification number GRP.

グループ識別番号ＧＲＰ＝１の場合は、現時点の空燃比学習値Ｇf を一方の燃料噴射弁グループＡのグループ別噴射特性ずれ学習値Ｇf.A にセットする。
グループ識別番号ＧＲＰ＝２の場合は、現時点の空燃比学習値Ｇf を他方の燃料噴射弁グループＢのグループ別噴射特性ずれ学習値Ｇf.B にセットする。 When the group identification number GRP = 1, the current air-fuel ratio learned value Gf is set to the group-specific injection characteristic deviation learned value Gf.A of one fuel injection valve group A.
When the group identification number GRP = 2, the current air-fuel ratio learning value Gf is set to the group-specific injection characteristic deviation learning value Gf.B of the other fuel injection valve group B.

この後、ステップ６０５に進み、学習が完了したか否か（空燃比Ｆ／Ｂ補正量ＡＦＦＢがほぼ０か否か）を判定し、学習が完了するまで、上記ステップ６０３〜６０５の処理を繰り返す。その後、上記ステップ６０５で、学習完了と判定された時点で、ステップ６０６に進み、グループ識別番号ＧＲＰを１だけ増加させて本ルーチンを終了する。   Thereafter, the process proceeds to step 605, where it is determined whether learning has been completed (whether the air-fuel ratio F / B correction amount AFFB is substantially zero), and the processing of steps 603-605 is repeated until learning is completed. . Thereafter, when it is determined in step 605 that learning is completed, the process proceeds to step 606, where the group identification number GRP is incremented by 1, and this routine is terminated.

尚、グループ別噴射特性ずれ学習値Ｇf.A ，Ｇf.B を学習する際に、それらのグループ別噴射特性ずれ学習値が予め決められた許容範囲内であるか否かを判定して、いずれかの個別噴射特性ずれ学習値が許容範囲から外れた場合は、許容範囲から外れた燃料噴射弁グループのいずれかの燃料噴射弁２１が異常であると判定して、その異常情報をバックアップＲＡＭ３８に記憶すると共に、警告ランプを点灯又は点滅させたり、運転席のインストルメントパネルの表示部に警告表示して運転者に警告するようにしても良い。この場合、いずれかの燃料噴射弁２１の異常が発生したときに、異常な燃料噴射弁２１が属する燃料噴射弁グループを特定することができる。更に、グループ別噴射特性ずれ学習値が予め決められた許容範囲内となるようにガード処理する（グループ別噴射特性ずれ学習値の上下限値を所定値以内に制限する）ようにしても良い。   When learning the injection characteristic deviation learning values Gf.A and Gf.B for each group, it is determined whether or not the learning characteristic deviation values for each group are within a predetermined allowable range. If the individual injection characteristic deviation learning value is out of the allowable range, it is determined that one of the fuel injection valves 21 in the fuel injection valve group out of the allowable range is abnormal, and the abnormality information is stored in the backup RAM 38. The information may be stored and a warning lamp may be turned on or blinked, or a warning may be displayed on the display unit of the instrument panel of the driver's seat to warn the driver. In this case, when an abnormality occurs in any of the fuel injection valves 21, the fuel injection valve group to which the abnormal fuel injection valve 21 belongs can be specified. Further, guard processing may be performed so that the group-specific injection characteristic deviation learning value falls within a predetermined allowable range (the upper and lower limit values of the group-specific injection characteristic deviation learning value are limited within a predetermined value).

以上説明した本実施例２では、空燃比Ｆ／Ｂ制御実行中に各気筒の２つの燃料噴射弁２１を全て噴射動作させてエンジン１１全体の燃料噴射弁２１の噴射特性ずれ（全体噴射特性ずれ）を学習した後、空燃比Ｆ／Ｂ制御実行中に一方の燃料噴射弁グループの噴射を停止して他方の燃料噴射弁グループのみで各気筒の要求噴射量分の燃料を噴射しながら燃料噴射弁グループ別の噴射特性ずれ（グループ別噴射特性ずれ）を学習するため、各気筒の要求噴射量分の燃料を噴射しながらグループ別噴射特性ずれを学習することができ、気筒間の空燃比ばらつきやトルクばらつきを抑えながらグループ別噴射特性ずれを精度良く学習することができる。そして、全体噴射特性ずれの学習値とグループ別噴射特性ずれの学習値を用いて各気筒の２つの燃料噴射弁２１の燃料噴射量を燃料噴射弁グループ別に補正するため、各燃料噴射弁グループの噴射特性ずれを精度良く補正することができて、燃料噴射弁グループ間の噴射特性ずれのばらつきに起因する気筒間の空燃比ばらつきやトルクばらつきを低減することができる。   In the second embodiment described above, during the execution of the air-fuel ratio F / B control, the two fuel injection valves 21 of each cylinder are all injected to perform the injection characteristic deviation (total injection characteristic deviation) of the engine 11 as a whole. ) Is learned, during the execution of the air-fuel ratio F / B control, the fuel injection is stopped while the fuel injection valve group stops the injection and the fuel injection valve only injects fuel for the required injection amount of each cylinder. In order to learn the injection characteristic deviation for each valve group (injection characteristic deviation for each group), it is possible to learn the injection characteristic deviation for each group while injecting fuel corresponding to the required injection amount of each cylinder. In addition, it is possible to accurately learn the injection characteristic deviation by group while suppressing torque variation. Then, in order to correct the fuel injection amount of the two fuel injection valves 21 of each cylinder by the fuel injection valve group using the learning value of the overall injection characteristic deviation and the learning value of the group-specific injection characteristic deviation, It is possible to correct the injection characteristic deviation with high accuracy, and to reduce the air-fuel ratio fluctuation and the torque fluctuation between the cylinders due to the variation in the injection characteristic deviation between the fuel injection valve groups.

更に、本実施例２では、全体噴射特性ずれの学習が完了した後に、各燃料噴射弁２１の燃料噴射量を全体噴射特性ずれの学習値で補正した状態でグループ別噴射特性ずれを学習するようにしたので、全体噴射特性ずれを補正した状態でグループ別噴射特性ずれを学習することができて、グループ別噴射特性ずれの学習精度を更に向上させることができる。   Further, in the second embodiment, after learning of the total injection characteristic deviation is completed, the group-specific injection characteristic deviation is learned in a state where the fuel injection amount of each fuel injection valve 21 is corrected with the learning value of the total injection characteristic deviation. Therefore, the group-specific injection characteristic deviation can be learned in a state where the overall injection characteristic deviation is corrected, and the learning accuracy of the group-specific injection characteristic deviation can be further improved.

但し、本発明は、各燃料噴射弁２１の燃料噴射量を全体噴射特性ずれの学習値で補正しない状態でグループ別噴射特性ずれを学習し、全体噴射特性ずれとグループ別噴射特性ずれの学習完了後に全体噴射特性ずれの学習値とグループ別噴射特性ずれの学習値とを用いて各燃料噴射弁２１の燃料噴射量を燃料噴射弁グループ別に補正するようにしても良い。   However, the present invention learns the group-specific injection characteristic deviation without correcting the fuel injection amount of each fuel injection valve 21 with the learning value of the total injection characteristic deviation, and completes the learning of the total injection characteristic deviation and the group-specific injection characteristic deviation. Later, the fuel injection amount of each fuel injection valve 21 may be corrected for each fuel injection valve group using the learned value for the overall injection characteristic deviation and the learned value for the group-specific injection characteristic deviation.

本発明の実施例３では、上記実施例１，２で説明した全体噴射特性ずれとグループ別噴射特性ずれと個別噴射特性ずれをそれぞれ学習し、全体噴射特性ずれの学習値とグループ別噴射特性ずれの学習値と個別噴射特性ずれの学習値を用いて各気筒の複数の燃料噴射弁２１の燃料噴射量を補正するようにしている。   In the third embodiment of the present invention, the overall injection characteristic deviation, the group-specific injection characteristic deviation, and the individual injection characteristic deviation described in the first and second embodiments are respectively learned, and the learning value of the total injection characteristic deviation and the group-specific injection characteristic deviation are learned. The fuel injection amount of the plurality of fuel injection valves 21 of each cylinder is corrected using the learned value of this and the learned value of the individual injection characteristic deviation.

本実施例３では、エンジン運転中に図１０の噴射特性ずれ学習補正メインルーチンを周期的に繰り返し実行する。本ルーチンが起動されると、まず、ステップ７０１〜７０４で、前記実施例１で説明した図３の噴射特性ずれ学習補正メインルーチンのステップ１０１〜１０４と同様の処理により、空燃比Ｆ／Ｂ補正量ＡＦＦＢに基づいてエンジン１１全体の燃料噴射弁２１の噴射特性ずれ（全体噴射特性ずれ）を学習して、全体噴射特性ずれ学習が完了した時点で、バックアップＲＡＭ３８に全体噴射特性ずれ学習値Ｇf.all を更新記憶して、この全体噴射特性ずれ学習値Ｇf.all を空燃比制御に適用する。   In the third embodiment, the injection characteristic deviation learning correction main routine of FIG. 10 is periodically and repeatedly executed during engine operation. When this routine is started, first, in steps 701 to 704, the air-fuel ratio F / B correction is performed by the same processing as in steps 101 to 104 of the injection characteristic deviation learning correction main routine of FIG. 3 described in the first embodiment. The injection characteristic deviation (total injection characteristic deviation) of the fuel injection valve 21 of the entire engine 11 is learned based on the amount AFFB, and when the whole injection characteristic deviation learning is completed, the backup RAM 38 stores the total injection characteristic deviation learned value Gf. All is updated and stored, and this total injection characteristic deviation learning value Gf.all is applied to the air-fuel ratio control.

この後、ステップ７０５〜７０７で、前記実施例２で説明した図８の噴射特性ずれ学習補正メインルーチンのステップ５０５〜５０７と同様の処理により、一方の燃料噴射弁グループの噴射を停止して他方の燃料噴射弁グループのみで各気筒の要求噴射量分の燃料を噴射して、燃料噴射弁グループの噴射停止前後の空燃比Ｆ／Ｂ補正量の変化量に基づいて燃料噴射弁グループ別の噴射特性ずれ（グループ別噴射特性ずれ）を学習し、グループ別噴射特性ずれ学習が完了した時点で、グループ別噴射特性ずれ学習値Ｇf.A ，Ｇf.B をバックアップＲＡＭ３８に更新記憶して、グループ別噴射特性ずれ学習値Ｇf.A ，Ｇf.B を空燃比制御に適用する。   Thereafter, in steps 705 to 707, the injection of one fuel injection valve group is stopped by the same processing as in steps 505 to 507 of the injection characteristic deviation learning correction main routine of FIG. The fuel for the required injection amount of each cylinder is injected only by the fuel injection valve group, and the injection for each fuel injection group is performed based on the change amount of the air-fuel ratio F / B correction amount before and after the injection stop of the fuel injection group. When the characteristic deviation (group-specific injection characteristic deviation) is learned and the group-specific injection characteristic deviation learning is completed, the group-specific injection characteristic deviation learned values Gf.A and Gf.B are updated and stored in the backup RAM 38, and the group-specific injection characteristic deviation is learned. The injection characteristic deviation learning values Gf.A and Gf.B are applied to the air-fuel ratio control.

この後、ステップ７０８〜７１０で、前記実施例１で説明した図３の噴射特性ずれ学習補正メインルーチンのステップ１０５〜１０７と同様の処理により、学習対象気筒と噴射を停止する燃料噴射弁２１をそれぞれ順番に切り替えて各燃料噴射弁２１の噴射停止前後の空燃比Ｆ／Ｂ補正量の変化量に基づいて学習対象気筒の各燃料噴射弁２１の噴射特性ずれ（個別噴射特性ずれ）を個別に学習し、個別噴射特性ずれ学習が完了した時点で、個別噴射特性ずれ学習値Ｇf.#1A 〜Ｇf.#4A ，Ｇf.#1B 〜Ｇf.#4B をバックアップＲＡＭ３８に更新記憶して、個別噴射特性ずれ学習値Ｇf.#1A 〜Ｇf.#4A ，Ｇf.#1B 〜Ｇf.#4B を空燃比制御に適用する。   Thereafter, in steps 708 to 710, the learning target cylinder and the fuel injection valve 21 that stops the injection are processed by the same processing as steps 105 to 107 of the injection characteristic deviation learning correction main routine of FIG. 3 described in the first embodiment. The respective injection characteristics deviation (individual injection characteristic deviation) of each fuel injection valve 21 of the learning target cylinder is individually switched based on the change amount of the air-fuel ratio F / B correction amount before and after the injection stop of each fuel injection valve 21. When the individual injection characteristic deviation learning is completed, the individual injection characteristic deviation learned values Gf. # 1A to Gf. # 4A and Gf. # 1B to Gf. # 4B are updated and stored in the backup RAM 38, and the individual injection is performed. The characteristic deviation learning values Gf. # 1A to Gf. # 4A and Gf. # 1B to Gf. # 4B are applied to the air-fuel ratio control.

以上説明した本実施例３によれば、全体噴射特性ずれとグループ別噴射特性ずれと個別噴射特性ずれをそれぞれ学習し、全体噴射特性ずれの学習値とグループ別噴射特性ずれの学習値と個別噴射特性ずれの学習値を用いて各気筒の複数の燃料噴射弁２１の燃料噴射量を補正するようにしたので、燃料噴射弁２１間の噴射特性ずれのばらつき及び燃料噴射弁グループ間の噴射特性ずれのばらつきに起因する気筒間の空燃比ばらつきやトルクばらつきを低減することができる。   According to the third embodiment described above, the overall injection characteristic deviation, the group-specific injection characteristic deviation, and the individual injection characteristic deviation are learned, respectively, and the learning value of the overall injection characteristic deviation, the learning value of the group-specific injection characteristic deviation, and the individual injection Since the fuel injection amount of the plurality of fuel injection valves 21 of each cylinder is corrected using the learned value of the characteristic deviation, the variation in the injection characteristic deviation between the fuel injection valves 21 and the injection characteristic deviation between the fuel injection valve groups. It is possible to reduce air-fuel ratio variations and torque variations between cylinders due to variations in the engine.

しかも、本実施例３では、全体噴射特性ずれの学習が完了した後、各燃料噴射弁２１の燃料噴射量を全体噴射特性ずれの学習値で補正した状態でグループ別噴射特性ずれを学習し、その後、各燃料噴射弁２１の燃料噴射量を全体噴射特性ずれの学習値及びグループ別噴射特性ずれの学習値で補正した状態で個別噴射特性ずれを学習するようにしたので、全体噴射特性ずれとグループ別噴射特性ずれの両方を補正した状態で個別噴射特性ずれを学習することができて、個別噴射特性ずれの学習精度を更に向上させることができる。   Moreover, in the third embodiment, after learning of the total injection characteristic deviation is completed, the group-specific injection characteristic deviation is learned in a state where the fuel injection amount of each fuel injection valve 21 is corrected with the learning value of the total injection characteristic deviation. Thereafter, the individual injection characteristic deviation is learned in a state where the fuel injection amount of each fuel injection valve 21 is corrected by the learning value of the whole injection characteristic deviation and the learning value of the group-specific injection characteristic deviation. The individual injection characteristic deviation can be learned in a state where both the group-specific injection characteristic deviations are corrected, and the learning accuracy of the individual injection characteristic deviation can be further improved.

但し、本発明は、全体噴射特性ずれの学習とグループ別噴射特性ずれの学習と個別噴射特性ずれの学習の順序は適宜変更しても良い。
その他、本発明は、図２に示す４気筒エンジンに限定されず、３気筒以下又は５気筒以上のエンジンに適用したり、各気筒にそれぞれ３つ以上の燃料噴射弁を設けたエンジンに適用しても良い。 However, in the present invention, the order of learning of the overall injection characteristic deviation, learning of the individual-group injection characteristic deviation, and learning of the individual injection characteristic deviation may be appropriately changed.
In addition, the present invention is not limited to the four-cylinder engine shown in FIG. 2, but can be applied to an engine having three or less cylinders or five or more cylinders, or an engine having three or more fuel injection valves in each cylinder. May be.

１１…エンジン（内燃機関）、１２…吸気管、１６…スロットルバルブ、２１…燃料噴射弁、２２…点火プラグ、２３…排気管（排気通路）、２４…排出ガスセンサ、３０…ＥＣＵ（空燃比制御手段，全体噴射特性ずれ学習手段，個別噴射特性ずれ学習手段，グループ別噴射特性ずれ学習手段，異常判定手段）、３１…吸気ポート、３２…排気ポート、３８…バックアップＲＡＭ（記憶手段）   DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 16 ... Throttle valve, 21 ... Fuel injection valve, 22 ... Spark plug, 23 ... Exhaust pipe (exhaust passage), 24 ... Exhaust gas sensor, 30 ... ECU (Air-fuel ratio control) Means, overall injection characteristic deviation learning means, individual injection characteristic deviation learning means, group-specific injection characteristic deviation learning means, abnormality determination means), 31 ... intake port, 32 ... exhaust port, 38 ... backup RAM (storage means).

Claims (8)

複数の気筒を有する内燃機関の各気筒の吸気側にそれぞれ複数の燃料噴射弁を配置すると共に、排気通路に排出ガスの空燃比又はリッチ／リーンを検出する排出ガスセンサを配置し、前記排出ガスセンサの出力に基づいて空燃比フィードバック補正量を設定して前記各気筒の複数の燃料噴射弁の燃料噴射量を前記空燃比フィードバック補正量で補正する空燃比フィードバック制御を実行する空燃比制御手段を備えた内燃機関の空燃比学習制御装置において、
前記各気筒の燃料噴射時期毎に前記各気筒の複数の燃料噴射弁を全て噴射動作させて前記空燃比フィードバック制御を実行しているときに前記空燃比フィードバック補正量に基づいて前記内燃機関全体の燃料噴射弁噴射特性ずれ（以下「全体噴射特性ずれ」という）を学習する全体噴射特性ずれ学習手段と、
前記空燃比フィードバック制御を実行しているときにいずれか１つの気筒（以下「学習対象気筒」という）のみでいずれか１つの燃料噴射弁の噴射を停止して他の燃料噴射弁のみで前記学習対象気筒の要求噴射量分の燃料を噴射する制御を、前記学習対象気筒と噴射を停止する燃料噴射弁をそれぞれ順番に切り替えて実施して各燃料噴射弁の噴射停止前後の前記空燃比フィードバック補正量の変化量に基づいて前記学習対象気筒の各燃料噴射弁の噴射特性ずれ（以下「個別噴射特性ずれ」という）を個別に学習する個別噴射特性ずれ学習手段とを備え、
前記空燃比制御手段は、前記全体噴射特性ずれの学習値と前記個別噴射特性ずれの学習値とを用いて前記各気筒の複数の燃料噴射弁の燃料噴射量を個別に補正することを特徴とする内燃機関の空燃比学習制御装置。 A plurality of fuel injection valves are arranged on the intake side of each cylinder of an internal combustion engine having a plurality of cylinders, and an exhaust gas sensor for detecting the air-fuel ratio or rich / lean of the exhaust gas is arranged in the exhaust passage, and the exhaust gas sensor Air-fuel ratio control means for performing air-fuel ratio feedback control for setting the air-fuel ratio feedback correction amount based on the output and correcting the fuel injection amounts of the plurality of fuel injection valves of each cylinder with the air-fuel ratio feedback correction amount is provided. In an air-fuel ratio learning control device for an internal combustion engine,
The entire internal combustion engine is controlled based on the air-fuel ratio feedback correction amount when the air-fuel ratio feedback control is executed by injecting all of the plurality of fuel injection valves of each cylinder at every fuel injection timing of each cylinder. An overall injection characteristic deviation learning means for learning a fuel injection valve injection characteristic deviation (hereinafter referred to as “total injection characteristic deviation”);
When the air-fuel ratio feedback control is being executed, only one of the cylinders (hereinafter referred to as “learning target cylinder”) stops the injection of any one of the fuel injection valves, and only the other fuel injection valves perform the learning. The control for injecting fuel for the required injection amount of the target cylinder is performed by sequentially switching the learning target cylinder and the fuel injection valve for stopping the injection, and the air-fuel ratio feedback correction before and after the injection stop of each fuel injection valve Individual injection characteristic deviation learning means for individually learning the injection characteristic deviation of each fuel injection valve of the learning target cylinder (hereinafter referred to as “individual injection characteristic deviation”) based on the amount of change in the amount;
The air-fuel ratio control unit individually corrects the fuel injection amounts of the plurality of fuel injection valves of the cylinders using the learning value of the overall injection characteristic deviation and the learned value of the individual injection characteristic deviation. An air-fuel ratio learning control device for an internal combustion engine. 前記個別噴射特性ずれ学習手段は、前記全体噴射特性ずれ学習手段により前記全体噴射特性ずれの学習が完了した後に、前記各燃料噴射弁の燃料噴射量を前記全体噴射特性ずれの学習値で補正した状態で前記個別噴射特性ずれを学習することを特徴とする請求項１に記載の内燃機関の空燃比学習制御装置。   The individual injection characteristic deviation learning means corrects the fuel injection amount of each fuel injection valve with the learning value of the total injection characteristic deviation after the learning of the whole injection characteristic deviation is completed by the whole injection characteristic deviation learning means. The air-fuel ratio learning control device for an internal combustion engine according to claim 1, wherein the individual injection characteristic deviation is learned in a state. 複数の気筒を有する内燃機関の各気筒の吸気側にそれぞれ複数の燃料噴射弁を配置すると共に、排気通路に排出ガスの空燃比又はリッチ／リーンを検出する排出ガスセンサを配置し、前記排出ガスセンサの出力に基づいて空燃比フィードバック補正量を設定して前記各気筒の複数の燃料噴射弁の燃料噴射量を前記空燃比フィードバック補正量で補正する空燃比フィードバック制御を実行する空燃比制御手段を備えた内燃機関の空燃比学習制御装置において、
前記各気筒の燃料噴射時期毎に前記各気筒の複数の燃料噴射弁を全て噴射動作させて前記空燃比フィードバック制御を実行しているときに前記空燃比フィードバック補正量に基づいて前記内燃機関全体の燃料噴射弁噴射特性ずれ（以下「全体噴射特性ずれ」という）を学習する全体噴射特性ずれ学習手段と、
前記空燃比フィードバック制御を実行しているときに前記各気筒の複数の燃料噴射弁のうちのいずれか１つの燃料噴射弁からなる燃料噴射弁グループの噴射を停止して他の燃料噴射弁グループのみで各気筒の要求噴射量分の燃料を噴射する制御を、噴射を停止する燃料噴射弁グループを順番に切り替えて実施して燃料噴射弁グループの噴射停止前後の前記空燃比フィードバック補正量の変化量に基づいて燃料噴射弁グループ別の噴射特性ずれ（以下「グループ別噴射特性ずれ」という）を学習するグループ別噴射特性ずれ学習手段とを備え、
前記空燃比制御手段は、前記全体噴射特性ずれの学習値と前記グループ別噴射特性ずれの学習値とを用いて前記各気筒の複数の燃料噴射弁の燃料噴射量を燃料噴射弁グループ別に補正することを特徴とする内燃機関の空燃比学習制御装置。 A plurality of fuel injection valves are arranged on the intake side of each cylinder of an internal combustion engine having a plurality of cylinders, and an exhaust gas sensor for detecting the air-fuel ratio or rich / lean of the exhaust gas is arranged in the exhaust passage, and the exhaust gas sensor Air-fuel ratio control means for performing air-fuel ratio feedback control for setting the air-fuel ratio feedback correction amount based on the output and correcting the fuel injection amounts of the plurality of fuel injection valves of each cylinder with the air-fuel ratio feedback correction amount is provided. In an air-fuel ratio learning control device for an internal combustion engine,
The entire internal combustion engine is controlled based on the air-fuel ratio feedback correction amount when the air-fuel ratio feedback control is executed by injecting all of the plurality of fuel injection valves of each cylinder at every fuel injection timing of each cylinder. An overall injection characteristic deviation learning means for learning a fuel injection valve injection characteristic deviation (hereinafter referred to as “total injection characteristic deviation”);
When the air-fuel ratio feedback control is being executed, the injection of the fuel injection valve group consisting of any one of the plurality of fuel injection valves of each cylinder is stopped, and only the other fuel injection valve groups The amount of change in the air-fuel ratio feedback correction amount before and after the injection stop of the fuel injection valve group is controlled by sequentially switching the fuel injection valve group that stops the injection to control the injection of the fuel for the required injection amount of each cylinder. And an injection characteristic deviation learning means for each group for learning an injection characteristic deviation for each fuel injection valve group (hereinafter referred to as “group-specific injection characteristic deviation”)
The air-fuel ratio control means corrects the fuel injection amounts of the plurality of fuel injection valves of each cylinder for each fuel injection valve group using the learning value for the overall injection characteristic deviation and the learning value for the group-specific injection characteristic deviation. An air-fuel ratio learning control apparatus for an internal combustion engine, characterized in that: 前記グループ別噴射特性ずれ学習手段は、前記全体噴射特性ずれ学習手段により前記全体噴射特性ずれの学習が完了した後に、前記各燃料噴射弁の燃料噴射量を前記全体噴射特性ずれの学習値で補正した状態で前記グループ別噴射特性ずれを学習することを特徴とする請求項３に記載の内燃機関の空燃比学習制御装置。   The group-specific injection characteristic deviation learning unit corrects the fuel injection amount of each fuel injection valve with the learning value of the total injection characteristic deviation after the total injection characteristic deviation learning unit completes the learning of the total injection characteristic deviation. 4. The air-fuel ratio learning control apparatus for an internal combustion engine according to claim 3, wherein the deviation of the injection characteristics by group is learned in a state of being performed. 前記空燃比フィードバック制御を実行しているときにいずれか１つの気筒（以下「学習対象気筒」という）のみでいずれか１つの燃料噴射弁の噴射を停止して他の燃料噴射弁のみで前記学習対象気筒の要求噴射量分の燃料を噴射する制御を、前記学習対象気筒と噴射を停止する燃料噴射弁をそれぞれ順番に切り替えて実施して各燃料噴射弁の噴射停止前後の前記空燃比フィードバック補正量の変化量に基づいて前記学習対象気筒の各燃料噴射弁の噴射特性ずれ（以下「個別噴射特性ずれ」という）を個別に学習する個別噴射特性ずれ学習手段を備え、
前記空燃比制御手段は、前記全体噴射特性ずれの学習値と前記グループ別噴射特性ずれの学習値と前記個別噴射特性ずれの学習値を用いて前記各気筒の複数の燃料噴射弁の燃料噴射量を補正することを特徴とする請求項３又は４に記載の内燃機関の空燃比学習制御装置。 When the air-fuel ratio feedback control is being executed, only one of the cylinders (hereinafter referred to as “learning target cylinder”) stops the injection of any one of the fuel injection valves, and only the other fuel injection valves perform the learning. The control for injecting fuel for the required injection amount of the target cylinder is performed by sequentially switching the learning target cylinder and the fuel injection valve for stopping the injection, and the air-fuel ratio feedback correction before and after the injection stop of each fuel injection valve An individual injection characteristic deviation learning means for individually learning an injection characteristic deviation of each fuel injection valve of the learning target cylinder (hereinafter referred to as “individual injection characteristic deviation”) based on a change amount of the amount;
The air-fuel ratio control means uses the learned value of the overall injection characteristic deviation, the learned value of the group-specific injection characteristic deviation, and the learned value of the individual injection characteristic deviation, and the fuel injection amounts of the plurality of fuel injection valves of the cylinders The air-fuel ratio learning control apparatus for an internal combustion engine according to claim 3 or 4, wherein 前記個別噴射特性ずれ学習手段は、前記全体噴射特性ずれ学習手段により前記全体噴射特性ずれの学習が完了し、且つ、前記グループ別噴射特性ずれ学習手段により前記グループ別噴射特性ずれの学習が完了した後、前記各燃料噴射弁の燃料噴射量を前記全体噴射特性ずれの学習値及び前記グループ別噴射特性ずれの学習値で補正した状態で前記個別噴射特性ずれを学習することを特徴とする請求項５に記載の内燃機関の空燃比学習制御装置。   The individual injection characteristic deviation learning means has completed learning of the total injection characteristic deviation by the total injection characteristic deviation learning means, and has completed learning of the group-specific injection characteristic deviation by the group-specific injection characteristic deviation learning means. The individual injection characteristic deviation is learned after the fuel injection amount of each fuel injection valve is corrected with the learning value of the overall injection characteristic deviation and the learning value of the group-specific injection characteristic deviation. 6. An air-fuel ratio learning control device for an internal combustion engine according to claim 5. 内燃機関の停止中でも記憶データを保持する書き換え可能な記憶手段に前記学習値を記憶し、
前記空燃比制御手段は、前記記憶手段に前記学習値が記憶されている場合には、前記記憶手段から読み出した前記学習値を用いて前記各気筒の複数の燃料噴射弁の燃料噴射量を補正することを特徴とする請求項１乃至６のいずれかに記載の内燃機関の空燃比学習制御装置。 The learning value is stored in a rewritable storage means that retains stored data even when the internal combustion engine is stopped,
When the learning value is stored in the storage unit, the air-fuel ratio control unit corrects the fuel injection amounts of the plurality of fuel injection valves of the cylinders using the learning value read from the storage unit. The air-fuel ratio learning control apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein 前記学習値が所定の許容範囲から外れたときに前記燃料噴射弁の異常と判定して運転者に警告する異常判定手段を備えていることを特徴とする請求項１乃至７のいずれかに記載の内燃機関の空燃比学習制御装置。   8. An abnormality determining unit that determines that the fuel injection valve is abnormal and warns a driver when the learned value is out of a predetermined allowable range. An air-fuel ratio learning control apparatus for an internal combustion engine.
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