JP6881247B2 - Internal combustion engine control device - Google Patents

Internal combustion engine control device Download PDF

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JP6881247B2
JP6881247B2 JP2017215924A JP2017215924A JP6881247B2 JP 6881247 B2 JP6881247 B2 JP 6881247B2 JP 2017215924 A JP2017215924 A JP 2017215924A JP 2017215924 A JP2017215924 A JP 2017215924A JP 6881247 B2 JP6881247 B2 JP 6881247B2
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fuel ratio
value
cylinders
combustion engine
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啓一 明城
啓一 明城
勇喜 野瀬
勇喜 野瀬
美紗子 伴
美紗子 伴
英二 生田
英二 生田
良行 正源寺
良行 正源寺
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Toyota Motor Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
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    • Y02T10/40—Engine management systems

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Description

本発明は、複数の気筒から排出された排気を浄化する排気浄化装置と、前記複数の気筒毎に設けられた燃料噴射弁と、を備える内燃機関を制御対象とする内燃機関の制御装置に関する。 The present invention relates to an internal combustion engine control device for controlling an internal combustion engine including an exhaust gas purification device for purifying exhaust gas discharged from a plurality of cylinders and a fuel injection valve provided for each of the plurality of cylinders.

たとえば特許文献１には、排気浄化触媒（排気浄化装置）の昇温要求がある場合、一部の気筒を、空燃比が理論空燃比よりもリッチであるリッチ燃焼気筒とし、残りの気筒を、空燃比が理論空燃比よりもリーンであるリーン燃焼気筒とするディザ制御処理を実行する制御装置が記載されている。 For example, in Patent Document 1, when there is a request for raising the temperature of an exhaust purification catalyst (exhaust purification device), some cylinders are designated as rich combustion cylinders having an air-fuel ratio richer than the stoichiometric air-fuel ratio, and the remaining cylinders are defined as rich combustion cylinders. A control device that executes a dither control process for a lean combustion cylinder whose air-fuel ratio is leaner than the stoichiometric air-fuel ratio is described.

特開２０１６−１６９６６５号公報Japanese Unexamined Patent Publication No. 2016-169665

ディザ制御による排気浄化装置の昇温性能は、リッチ燃焼気筒の空燃比とリーン燃焼気筒の空燃比との差の絶対値が大きいほど大きい。一方、同絶対値が大きいほど回転変動が大きくなりやすい。このため、ディザ制御では、回転変動がドライバビリティの低下を招くことがない範囲で、昇温性能を確保する上で必要な上記絶対値を設定することとなる。ただし、たとえば燃料噴射弁の経年劣化や内燃機関の圧縮比の個体差等に起因して、回転変動が想定以上に大きくなり、これによりドライバビリティの低下を招くおそれがある。しかし、ドライバビリティの改善を図るべく上記絶対値を小さくする場合、昇温性能が低下し、排気浄化装置の浄化能力の低下を招くおそれがある。 The temperature rise performance of the exhaust gas purification device by dither control increases as the absolute value of the difference between the air-fuel ratio of the rich combustion cylinder and the air-fuel ratio of the lean combustion cylinder increases. On the other hand, the larger the absolute value, the larger the rotation fluctuation tends to be. Therefore, in the dither control, the above absolute value necessary for ensuring the temperature rising performance is set within a range in which the rotational fluctuation does not cause a decrease in drivability. However, for example, due to aged deterioration of the fuel injection valve, individual differences in the compression ratio of the internal combustion engine, and the like, the rotational fluctuation becomes larger than expected, which may lead to a decrease in drivability. However, if the absolute value is reduced in order to improve drivability, the temperature rising performance may be deteriorated, which may lead to a decrease in the purification capacity of the exhaust gas purification device.

上記課題を解決すべく、内燃機関の制御装置は、複数の気筒から排出された排気を浄化する排気浄化装置と、前記複数の気筒毎に設けられた燃料噴射弁と、を備える内燃機関を制御対象とし、前記複数の気筒のうちの一部の気筒を、空燃比が理論空燃比よりもリッチであるリッチ燃焼気筒とし、前記複数の気筒のうちの前記一部の気筒とは別の気筒を、空燃比が理論空燃比よりもリーンであるリーン燃焼気筒とすべく、前記燃料噴射弁を操作するディザ制御処理と、前記内燃機関の制御量の制御に所定以上の異常が生じていると判定する場合、該異常が生じていないと判定する場合と比較して前記リッチ燃焼気筒の空燃比と前記リーン燃焼気筒の空燃比との差の絶対値を小さくする部品保護処理と、前記所定以上の異常が生じていないと判定される場合であって前記内燃機関のクランク軸の回転変動が所定以上であると判定する場合、前記リッチ燃焼気筒の空燃比と前記リーン燃焼気筒の空燃比との差の絶対値を小さくする振動抑制処理と、を実行し、前記部品保護処理では、前記振動抑制処理よりも前記リッチ燃焼気筒の空燃比と前記リーン燃焼気筒の空燃比との差の絶対値を小さくする。 In order to solve the above problems, the control device of the internal combustion engine controls the internal combustion engine including an exhaust purification device for purifying the exhaust discharged from the plurality of cylinders and a fuel injection valve provided for each of the plurality of cylinders. Target, some of the plurality of cylinders are rich combustion cylinders having an air-fuel ratio richer than the stoichiometric air-fuel ratio, and cylinders other than the part of the plurality of cylinders are used. , It is determined that an abnormality of a predetermined value or more has occurred in the dither control process for operating the fuel injection valve and the control amount of the internal combustion engine so that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio. In this case, the component protection treatment for reducing the absolute value of the difference between the air-fuel ratio of the rich combustion cylinder and the air-fuel ratio of the lean combustion cylinder as compared with the case where it is determined that the abnormality has not occurred, and the predetermined or higher When it is determined that no abnormality has occurred and it is determined that the rotation fluctuation of the crank shaft of the internal combustion engine is equal to or more than a predetermined value, the difference between the air-fuel ratio of the rich combustion cylinder and the air-fuel ratio of the lean combustion cylinder. In the component protection process, the absolute value of the difference between the air-fuel ratio of the rich combustion cylinder and the air-fuel ratio of the lean combustion cylinder is smaller than that of the vibration suppression process. To do.

ディザ制御では、ディザ制御によってリッチ燃焼気筒とリーン燃焼気筒との空燃比を異ならせることから、全ての気筒の燃焼状態を最も安定な状態に制御することが困難であり、燃焼が悪化しやすい傾向を有する。一方、内燃機関の制御量の制御に所定以上の異常が生じている場合、燃焼制御に異常がある可能性が高い。そのため、上記異常が生じると、ディザ制御による燃焼が悪化しやすい傾向が顕在化し、内燃機関の部品の劣化が促進されるおそれがある。そこで上記構成では、部品保護処理によって、リッチ燃焼気筒の空燃比とリーン燃焼気筒の空燃比との差の絶対値を小さくすることにより、部品を保護する。一方、所定以上の異常が生じていないと判定される場合であって回転変動が所定以上である場合には、リッチ燃焼気筒の空燃比とリーン燃焼気筒の空燃比との差の絶対値を小さくしつつも部品保護処理時よりも大きい値とする。これにより、排気成分の悪化を抑制しつつもドライバビリティの悪化を極力改善することができる。 In dither control, the air-fuel ratios of the rich combustion cylinder and the lean combustion cylinder are made different by dither control, so it is difficult to control the combustion state of all cylinders to the most stable state, and combustion tends to deteriorate. Has. On the other hand, when the control amount of the internal combustion engine is abnormal more than a predetermined value, there is a high possibility that the combustion control is abnormal. Therefore, when the above abnormality occurs, there is a possibility that the combustion due to dither control tends to be deteriorated and the deterioration of the parts of the internal combustion engine is promoted. Therefore, in the above configuration, the parts are protected by reducing the absolute value of the difference between the air-fuel ratio of the rich combustion cylinder and the air-fuel ratio of the lean combustion cylinder by the parts protection treatment. On the other hand, when it is determined that no abnormality of the predetermined value or more has occurred and the rotational fluctuation is the predetermined value or more, the absolute value of the difference between the air-fuel ratio of the rich combustion cylinder and the air-fuel ratio of the lean combustion cylinder is made small. However, the value should be larger than that at the time of component protection processing. As a result, it is possible to improve the deterioration of drivability as much as possible while suppressing the deterioration of the exhaust component.

一実施形態にかかる制御装置および内燃機関を示す図。The figure which shows the control device and the internal combustion engine which concerns on one Embodiment. 同実施形態にかかる制御装置が実行する処理の手順を示す流れ図。The flow chart which shows the procedure of the process executed by the control device which concerns on the same embodiment.

以下、内燃機関の制御装置にかかる一実施形態について図面を参照しつつ説明する。
図１に示す内燃機関１０は、車両に搭載される。内燃機関１０において、吸気通路１２から吸入された空気は、過給機１４を介して各気筒の燃焼室１６に流入する。燃焼室１６には、燃料を噴射する燃料噴射弁１８と、火花放電を生じさせる点火装置２０とが設けられている。燃焼室１６において、空気と燃料との混合気は、燃焼に供され、燃焼に供された混合気は、排気として、排気通路２２に排出される。排気通路２２のうちの過給機１４の下流には、酸素吸蔵能力を有した三元触媒２４が設けられている。 Hereinafter, an embodiment of a control device for an internal combustion engine will be described with reference to the drawings.
The internal combustion engine 10 shown in FIG. 1 is mounted on a vehicle. In the internal combustion engine 10, the air sucked from the intake passage 12 flows into the combustion chamber 16 of each cylinder via the supercharger 14. The combustion chamber 16 is provided with a fuel injection valve 18 for injecting fuel and an ignition device 20 for generating spark discharge. In the combustion chamber 16, the air-fuel mixture is subjected to combustion, and the combustion-exposed air-fuel mixture is discharged to the exhaust passage 22 as exhaust gas. A three-way catalyst 24 having an oxygen storage capacity is provided downstream of the supercharger 14 in the exhaust passage 22.

制御装置３０は、内燃機関１０を制御対象とし、その制御量（トルク、排気成分等）を制御するために、燃料噴射弁１８や点火装置２０等の内燃機関１０の操作部を操作する。この際、制御装置３０は、三元触媒２４の上流側の空燃比センサ４０によって検出される空燃比Ａｆや、クランク角センサ４４の出力信号Ｓｃｒ、エアフローメータ４６によって検出される吸入空気量Ｇａを参照する。制御装置３０は、ＣＰＵ３２、ＲＯＭ３４、およびＲＡＭ３６を備えており、ＲＯＭ３４に記憶されたプログラムをＣＰＵ３２が実行することにより上記制御量の制御を実行する。 The control device 30 controls the internal combustion engine 10, and operates the operation unit of the internal combustion engine 10 such as the fuel injection valve 18 and the ignition device 20 in order to control the controlled amount (torque, exhaust component, etc.). At this time, the control device 30 determines the air-fuel ratio Af detected by the air-fuel ratio sensor 40 on the upstream side of the three-way catalyst 24, the output signal Scr of the crank angle sensor 44, and the intake air amount Ga detected by the air flow meter 46. refer. The control device 30 includes a CPU 32, a ROM 34, and a RAM 36, and the CPU 32 executes a program stored in the ROM 34 to control the control amount.

図２に、制御装置３０が実行する処理の１つを示す。図２に示す処理は、ＲＯＭ３４に記憶されたプログラムをＣＰＵ３２がたとえば所定周期で繰り返し実行することにより実現される。なお、以下では、先頭に「Ｓ」が付与された数字によって、ステップ番号を表現する。 FIG. 2 shows one of the processes executed by the control device 30. The process shown in FIG. 2 is realized by the CPU 32 repeatedly executing the program stored in the ROM 34, for example, at a predetermined cycle. In the following, the step number is represented by a number prefixed with "S".

図２に示す一連の処理において、ＣＰＵ３２は、空燃比を目標空燃比に制御するうえで燃料噴射弁１８が噴射すべき噴射量である要求噴射量Ｑｄを算出する（Ｓ１０）。詳しくはＣＰＵ３２は、まず、回転速度ＮＥと吸入空気量Ｇａとに基づきベース噴射量Ｑｂを算出する。ベース噴射量Ｑｂは、燃焼室１６における混合気の空燃比を目標空燃比に開ループ制御するための操作量である開ループ操作量である。次にＣＰＵ３２は、フィードバック制御量である空燃比Ａｆを目標値Ａｆ＊にフィードバック制御するための操作量であるフィードバック操作量ＫＡＦを算出する。詳しくはＣＰＵ３２は、目標値Ａｆ＊と空燃比Ａｆとの差Δを入力とする比例要素、積分要素、および微分要素の各出力値の和を、ベース噴射量Ｑｂの補正比率δとし、フィードバック操作量ＫＡＦを、「１＋δ」とする。そして、ＣＰＵ３２は、ベース噴射量Ｑｂにフィードバック操作量ＫＡＦを乗算した値を、要求噴射量Ｑｄに代入する。なお、回転速度ＮＥは、ＣＰＵ３２により、クランク角センサ４４の出力信号Ｓｃｒに基づき、図２に示す処理とは別の処理によって算出される。 In the series of processes shown in FIG. 2, the CPU 32 calculates the required injection amount Qd, which is the injection amount to be injected by the fuel injection valve 18 in order to control the air-fuel ratio to the target air-fuel ratio (S10). Specifically, the CPU 32 first calculates the base injection amount Qb based on the rotation speed NE and the intake air amount Ga. The base injection amount Qb is an open loop operation amount which is an operation amount for controlling the air-fuel ratio of the air-fuel mixture in the combustion chamber 16 to the target air-fuel ratio in an open loop. Next, the CPU 32 calculates the feedback manipulated variable KAF, which is the manipulated variable for feedback-controlling the air-fuel ratio Af, which is the feedback controlled variable, to the target value Af *. Specifically, the CPU 32 sets the sum of the output values of the proportional element, the integrating element, and the differential element, which input the difference Δ between the target value Af * and the air-fuel ratio Af, as the correction ratio δ of the base injection amount Qb, and performs a feedback operation. The amount KAF is set to "1 + δ". Then, the CPU 32 substitutes the value obtained by multiplying the base injection amount Qb by the feedback operation amount KAF into the required injection amount Qd. The rotation speed NE is calculated by the CPU 32 based on the output signal Scr of the crank angle sensor 44 by a process different from the process shown in FIG.

次に、ＣＰＵ３２は、三元触媒２４の昇温要求があるか否かを判定する（Ｓ１２）。本実施形態では、三元触媒２４の暖機要求が生じていることと、硫黄被毒回復処理の実行要求が生じていることとの論理和が真である場合に、昇温要求があると判定する。ここで、三元触媒２４の暖機要求は、内燃機関１０の始動からの吸入空気量Ｇａの積算値ＩｎＧａが第１規定値Ｉｎｔｈ１以上である旨の条件（ア）と、積算値ＩｎＧａが第２規定値Ｉｎｔｈ２以下である旨の条件（イ）との論理積が真である場合に生じるものとする。ここで、第２規定値Ｉｎｔｈ２は、第１規定値Ｉｎｔｈ１よりも大きい。なお、条件（ア）は、三元触媒２４の上流側の端部の温度が活性温度となっていると判定される条件である。また、条件（イ）は、三元触媒２４の全体が未だ活性状態となっていないと判定される条件である。一方、硫黄被毒回復処理の実行要求は、硫黄被毒量が所定量以上となる場合に生じるものとする。ここで、ＣＰＵ３２は、図２とは別の処理で、要求噴射量Ｑｄの積算値に基づき硫黄被毒量を算出する。 Next, the CPU 32 determines whether or not there is a request for raising the temperature of the three-way catalyst 24 (S12). In the present embodiment, when the logical sum of the request for warming up the three-way catalyst 24 and the request for executing the sulfur poisoning recovery treatment are true, there is a request for temperature rise. judge. Here, the warm-up request for the three-way catalyst 24 is a condition (a) that the integrated value InGa of the intake air amount Ga from the start of the internal combustion engine 10 is equal to or higher than the first specified value Inth1 and the integrated value InGa is the first. 2 It shall occur when the logical product with the condition (a) that the specified value is Inth2 or less is true. Here, the second specified value Inth2 is larger than the first specified value Inth1. The condition (a) is a condition for determining that the temperature at the upstream end of the three-way catalyst 24 is the active temperature. Further, the condition (a) is a condition for determining that the entire three-way catalyst 24 is not yet in the active state. On the other hand, the request for execution of the sulfur poisoning recovery treatment shall occur when the amount of sulfur poisoning exceeds a predetermined amount. Here, the CPU 32 calculates the sulfur poisoning amount based on the integrated value of the required injection amount Qd by a process different from that of FIG.

ＣＰＵ３２は、昇温要求がないと判定する場合（Ｓ１２：ＮＯ）、噴射量指令値Ｑ＊に要求噴射量Ｑｄを代入する（Ｓ１４）。そしてＣＰＵ３２は、燃料噴射弁１８から噴射量指令値Ｑ＊に応じた量の燃料を噴射すべく、燃料噴射弁１８に操作信号ＭＳ２を出力する（Ｓ１６）。 When the CPU 32 determines that there is no temperature rise request (S12: NO), the CPU 32 substitutes the required injection amount Qd into the injection amount command value Q * (S14). Then, the CPU 32 outputs an operation signal MS2 to the fuel injection valve 18 in order to inject a fuel amount corresponding to the injection amount command value Q * from the fuel injection valve 18 (S16).

これに対し、ＣＰＵ３２は、昇温要求があると判定する場合（Ｓ１２：ＹＥＳ）、要求噴射量Ｑｄの補正要求値（噴射量補正要求値α）のベース値（ベース要求値α０）を算出する（Ｓ１８）。噴射量補正要求値αは、内燃機関１０の気筒＃１〜＃４のそれぞれから排出される排気全体の成分を、気筒＃１〜＃４の全てで燃焼対象とする混合気の空燃比を目標空燃比とした場合と同等としつつも、燃焼対象とする混合気の空燃比を気筒間で異ならせるディザ制御によって要求される要求噴射量Ｑｄの補正量である。ここで、本実施形態にかかるディザ制御では、第１の気筒＃１〜第４の気筒＃４のうちの１つの気筒を、混合気の空燃比を理論空燃比よりもリッチとするリッチ燃焼気筒とし、残りの３つの気筒を、混合気の空燃比を理論空燃比よりもリーンとするリーン燃焼気筒とする。そして、リッチ燃焼気筒における噴射量を、上記要求噴射量Ｑｄの「１＋α」倍とし、リーン燃焼気筒における噴射量を、要求噴射量Ｑｄの「１−（α／３）」倍とする。リーン燃焼気筒とリッチ燃焼気筒との上記噴射量の設定によれば、気筒＃１〜＃４のそれぞれに充填される空気量が同一であるなら、内燃機関１０の各気筒＃１〜＃４から排出される排気全体の成分を、気筒＃１〜＃４の全てで燃焼対象とする混合気の空燃比を目標空燃比とした場合と同等とすることができる。なお、上記噴射量の設定によれば、気筒＃１〜＃４のそれぞれに充填される空気量が同一であるなら、各気筒において燃焼対象とされる混合気の燃空比の平均値の逆数が目標空燃比となる。なお、燃空比とは、空燃比の逆数のことである。 On the other hand, when it is determined that there is a temperature rise request (S12: YES), the CPU 32 calculates the base value (base request value α0) of the correction request value (injection amount correction request value α) of the required injection amount Qd. (S18). The injection amount correction required value α targets the air-fuel ratio of the air-fuel mixture in which the components of the entire exhaust gas discharged from each of the cylinders # 1 to # 4 of the internal combustion engine 10 are to be burned in all the cylinders # 1 to # 4. It is a correction amount of the required injection amount Qd required by the dither control that makes the air-fuel ratio of the air-fuel mixture to be burned different between the cylinders while being the same as the case where the air-fuel ratio is used. Here, in the dither control according to the present embodiment, one of the first cylinders # 1 to the fourth cylinder # 4 is a rich combustion cylinder in which the air-fuel ratio of the air-fuel mixture is richer than the stoichiometric air-fuel ratio. Then, the remaining three cylinders are lean combustion cylinders in which the air-fuel ratio of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio. Then, the injection amount in the rich combustion cylinder is set to "1 + α" times the required injection amount Qd, and the injection amount in the lean combustion cylinder is set to "1- (α/3)" times the required injection amount Qd. According to the setting of the injection amount of the lean combustion cylinder and the rich combustion cylinder, if the amount of air filled in each of the cylinders # 1 to # 4 is the same, the cylinders # 1 to # 4 of the internal combustion engine 10 The components of the entire exhaust gas can be made equivalent to the case where the air-fuel ratio of the air-fuel mixture to be burned in all the cylinders # 1 to # 4 is set as the target air-fuel ratio. According to the above injection amount setting, if the amount of air filled in each of the cylinders # 1 to # 4 is the same, the reciprocal of the average value of the fuel-air ratio of the air-fuel mixture to be burned in each cylinder. Is the target air-fuel ratio. The fuel-air ratio is the reciprocal of the air-fuel ratio.

詳しくは、ＣＰＵ３２は、内燃機関１０の動作点を規定する回転速度ＮＥおよび負荷率ＫＬに基づき、ベース要求値α０を可変設定する。なお、本実施形態では、硫黄被毒回復処理と触媒暖機処理とで、ベース要求値α０がゼロよりも大きくなる動作点が異なっている。ここで、負荷率ＫＬは、燃焼室１６内に充填される空気量を示すパラメータであり、ＣＰＵ３２により、吸入空気量Ｇａに基づき算出される。負荷率ＫＬは、基準流入空気量に対する、１気筒の１燃焼サイクル当たりの流入空気量の比である。ちなみに、基準流入空気量は、回転速度ＮＥに応じて可変設定される量としてもよい。 Specifically, the CPU 32 variably sets the base required value α0 based on the rotation speed NE and the load factor KL that define the operating point of the internal combustion engine 10. In the present embodiment, the operating point at which the base required value α0 becomes larger than zero is different between the sulfur poisoning recovery treatment and the catalyst warm-up treatment. Here, the load factor KL is a parameter indicating the amount of air filled in the combustion chamber 16, and is calculated by the CPU 32 based on the intake air amount Ga. The load factor KL is the ratio of the inflow air amount per combustion cycle of one cylinder to the reference inflow air amount. Incidentally, the reference inflow air amount may be an amount variably set according to the rotation speed NE.

次にＣＰＵ３２は、ベース要求値α０がゼロよりも大きいか否かを判定する（Ｓ２０）。そしてＣＰＵ３２は、ゼロであると判定する場合（Ｓ２０：ＮＯ）、Ｓ１４の処理に移行する。一方、ＣＰＵ３２は、ゼロよりも大きいと判定する場合（Ｓ２０：ＹＥＳ）、内燃機関１０の部品を保護する要求があるか否かを判定する（Ｓ２２）。この処理は、内燃機関１０の制御量の制御に所定以上の異常が生じているか否かの判定処理となる。すなわち、内燃機関１０の制御量の制御に所定以上の異常が生じている場合、想定した制御が正常になされないため、内燃機関１０の部品の劣化を招くおそれがあるとして、部品を保護する要求があると判定する。具体的には、たとえば、クランク角センサ４４の出力信号Ｓｃｒに基づき把握されるクランク軸の回転変動量Δωの絶対値が規定値ΔｔｈＨ以上となることを検知した場合や、空燃比Ａｆを目標値にフィードバック制御する積分要素の出力値の絶対値が所定以上の状態が継続したりする場合に、制御量の制御に所定以上の異常が生じていると判定する。なお、回転変動量Δωは、燃焼の悪化度合いを定量化するパラメータであり、圧縮上死点を１回のみ含む所定角度間隔の回転速度（瞬時回転速度ω）を、圧縮上死点の出現タイミングが時系列的に隣り合う一対の気筒のうちの先に圧縮上死点が出現する気筒における値から後に圧縮上死点が出現する気筒における値を減算した値である。燃焼が悪化してトルクが低下する場合、回転変動量Δωは、負で絶対値が大きい値となる。 Next, the CPU 32 determines whether or not the base request value α0 is larger than zero (S20). Then, when the CPU 32 determines that the value is zero (S20: NO), the CPU 32 shifts to the process of S14. On the other hand, when the CPU 32 determines that it is larger than zero (S20: YES), it determines whether or not there is a request to protect the parts of the internal combustion engine 10 (S22). This process is a process for determining whether or not an abnormality of a predetermined value or more has occurred in the control of the controlled amount of the internal combustion engine 10. That is, if an abnormality of a predetermined value or more occurs in the control of the control amount of the internal combustion engine 10, the assumed control is not performed normally, which may lead to deterioration of the parts of the internal combustion engine 10, and a request for protecting the parts. It is determined that there is. Specifically, for example, when it is detected that the absolute value of the rotation fluctuation amount Δω of the crankshaft grasped based on the output signal Scr of the crank angle sensor 44 becomes the specified value ΔthH or more, or when the air-fuel ratio Af is set as the target value. When the absolute value of the output value of the integrating element to be feedback-controlled continues to be equal to or higher than a predetermined value, it is determined that an abnormality of a predetermined value or higher has occurred in the control of the control amount. The rotation fluctuation amount Δω is a parameter for quantifying the degree of deterioration of combustion, and the rotation speed (instantaneous rotation speed ω) at predetermined angular intervals including the compression top dead center only once is set as the appearance timing of the compression top dead center. Is the value obtained by subtracting the value in the cylinder in which the compression top dead center appears later from the value in the cylinder in which the compression top dead center appears first among the pair of adjacent cylinders in chronological order. When the combustion deteriorates and the torque decreases, the rotational fluctuation amount Δω is negative and has a large absolute value.

ＣＰＵ３２は、部品保護要求がないと判定する場合（Ｓ２２：ＮＯ）、クランク軸の回転変動量Δωの絶対値が上記規定値ΔｔｈＨよりも小さい所定値ΔｔｈＬ以上であるか否かを判定する（Ｓ２４）。この処理は、制御量の制御に所定以上の異常が生じているわけではないものの、ドライバビリティの悪化をもたらすか否かを判定するものである。なお、ベース要求値α０は、ドライバビリティを許容範囲内に保つ値に適合されている。しかし、燃料噴射弁１８の個体差や経年劣化、内燃機関１０の圧縮比の個体差やデポジット付着等に起因した経年変化に起因して、ベース要求値α０がドライバビリティが許容範囲から外れる事態が生じえ、Ｓ２４の処理は、この事態を検知する処理である。 When it is determined that there is no component protection request (S22: NO), the CPU 32 determines whether or not the absolute value of the rotation fluctuation amount Δω of the crankshaft is equal to or greater than a predetermined value ΔthL smaller than the above-mentioned specified value ΔthH (S24). ). In this process, although the control amount control does not have an abnormality more than a predetermined value, it is determined whether or not the drivability is deteriorated. The base requirement value α0 is adapted to a value that keeps drivability within an allowable range. However, due to individual differences in the fuel injection valve 18, deterioration over time, individual differences in the compression ratio of the internal combustion engine 10, changes over time due to deposit adhesion, etc., the drivability of the base required value α0 may be out of the permissible range. The process of S24 may occur, and the process of S24 is a process of detecting this situation.

ＣＰＵ３２は、所定値ΔｔｈＬ未満であると判定する場合（Ｓ２４：ＮＯ）、噴射量補正要求値αに、ベース要求値α０を代入する（Ｓ２６）。そして、ＣＰＵ３２は、燃料噴射の対象となる気筒がリッチ燃焼気筒であるか否かを判定する（Ｓ２８）。ＣＰＵ３２は、リッチ燃焼気筒であると判定する場合（Ｓ２８：ＹＥＳ）、噴射量指令値Ｑ＊に、「Ｑｄ・（１＋α）」を代入し（Ｓ３０）、Ｓ１６の処理に移行する。これに対し、ＣＰＵ３２は、リーン燃焼気筒であると判定する場合（Ｓ２８：ＮＯ）、噴射量指令値Ｑ＊に、「Ｑｄ・｛１−（α／３）｝」を代入し（Ｓ３２）、Ｓ１６の処理に移行する。 When the CPU 32 determines that the value is less than the predetermined value ΔthL (S24: NO), the CPU 32 substitutes the base request value α0 for the injection amount correction request value α (S26). Then, the CPU 32 determines whether or not the cylinder to be fuel-injected is a rich combustion cylinder (S28). When the CPU 32 determines that the cylinder is a rich combustion cylinder (S28: YES), the CPU 32 substitutes "Qd · (1 + α)" for the injection amount command value Q * (S30), and proceeds to the process of S16. On the other hand, when the CPU 32 determines that the cylinder is a lean burn cylinder (S28: NO), the CPU 32 substitutes "Qd · {1- (α / 3)}" for the injection amount command value Q * (S32). The process proceeds to S16.

一方、ＣＰＵ３２は、所定値ΔｔｈＬ以上であると判定する場合（Ｓ２４：ＹＥＳ）、ベース要求値α０が、前回の噴射量補正要求値α（ｎ−１）から所定量Δαを減算した値よりも大きいか否かを判定する（Ｓ３４）。ＣＰＵ３２は、減算した値以下であると判定する場合（Ｓ３４：ＮＯ）、Ｓ２６の処理に移行する。一方、ＣＰＵ３２は、減算した値よりも大きいと判定する場合（Ｓ３４：ＹＥＳ）、前回の噴射量補正要求値α（ｎ−１）から所定量Δαを減算した値を、噴射量補正要求値αに代入する（Ｓ３６）。次にＣＰＵ３２は、噴射量補正要求値αが、通常時下限値αｔｈＨよりも小さいか否かを判定する（Ｓ３８）。ここで、ＣＰＵ３２は、通常時下限値αｔｈＨを、触媒暖機処理時と硫黄被毒回復処理時とで各別に設定している。触媒暖機処理時においては、通常時下限値αｔｈＨは、排気成分の悪化を所定以下に抑制できる下限値とされている。また、硫黄被毒回復処理時においては、通常時下限値αｔｈＨは、硫黄被毒回復処理を実行可能な下限値に設定されている。そしてＣＰＵ３２は、通常時下限値αｔｈＨよりも小さいと判定する場合（Ｓ３８：ＹＥＳ）、噴射量補正要求値αに、通常時下限値αｔｈＨを代入する（Ｓ４０）。 On the other hand, when the CPU 32 determines that the predetermined value is ΔthL or more (S24: YES), the base request value α0 is larger than the value obtained by subtracting the predetermined amount Δα from the previous injection amount correction request value α (n-1). It is determined whether or not it is large (S34). When the CPU 32 determines that the value is equal to or less than the subtracted value (S34: NO), the CPU 32 shifts to the process of S26. On the other hand, when the CPU 32 determines that the value is larger than the subtracted value (S34: YES), the CPU 32 subtracts the predetermined amount Δα from the previous injection amount correction request value α (n-1) to obtain the injection amount correction request value α. Substitute in (S36). Next, the CPU 32 determines whether or not the injection amount correction request value α is smaller than the normal lower limit value αthH (S38). Here, the CPU 32 sets the lower limit value αthH at the normal time separately for the catalyst warm-up treatment and the sulfur poisoning recovery treatment. At the time of the catalyst warm-up treatment, the lower limit value αthH at normal time is set to the lower limit value capable of suppressing the deterioration of the exhaust component to a predetermined value or less. Further, during the sulfur poisoning recovery treatment, the normal lower limit value αthH is set to a lower limit value at which the sulfur poisoning recovery treatment can be executed. Then, when the CPU 32 determines that it is smaller than the normal time lower limit value αthH (S38: YES), the CPU 32 substitutes the normal time lower limit value αthH into the injection amount correction request value α (S40).

これに対し、ＣＰＵ３２は、部品保護要求があると判定する場合（Ｓ２２：ＹＥＳ）、ベース要求値α０がフェールセーフ時上限値αｔｈＬよりも大きいか否かを判定する（Ｓ４２）。フェールセーフ時上限値αｔｈＬは、通常時下限値αｔｈＨよりも小さい値であり、部品を保護する上での噴射量補正要求値αの上限値である。そして、ＣＰＵ３２は、フェールセーフ時上限値αｔｈＬよりも大きいと判定する場合（Ｓ４２：ＹＥＳ）、噴射量補正要求値αに、フェールセーフ時上限値αｔｈＬを代入する（Ｓ４４）。一方、ＣＰＵ３２は、フェールセーフ時上限値αｔｈＬ以下であると判定する場合（Ｓ４２：ＮＯ）、噴射量補正要求値αに、ベース要求値α０を代入する（Ｓ４６）。 On the other hand, when the CPU 32 determines that there is a component protection request (S22: YES), the CPU 32 determines whether or not the base request value α0 is larger than the fail-safe upper limit value αthL (S42). The fail-safe upper limit value αthL is a value smaller than the normal time lower limit value αthH, and is an upper limit value of the injection amount correction required value α for protecting the component. Then, when the CPU 32 determines that it is larger than the fail-safe upper limit value αthL (S42: YES), the CPU 32 substitutes the fail-safe upper limit value αthL for the injection amount correction request value α (S44). On the other hand, when the CPU 32 determines that the fail-safe upper limit value αthL or less (S42: NO), the CPU 32 substitutes the base request value α0 for the injection amount correction request value α (S46).

ＣＰＵ３２は、Ｓ２６，Ｓ４０，Ｓ４４，Ｓ４６の処理が完了する場合や、Ｓ３８の処理において否定判定する場合、Ｓ２８の処理に移行する。なお、ＣＰＵ３２は、Ｓ１６の処理が完了する場合には、図２に示す一連の処理を一旦終了する。 When the processing of S26, S40, S44, and S46 is completed, or when a negative determination is made in the processing of S38, the CPU 32 shifts to the processing of S28. When the processing of S16 is completed, the CPU 32 temporarily ends the series of processing shown in FIG.

以下、本実施形態の作用および効果について説明する。
ＣＰＵ３２は、ディザ制御の実行時に、回転変動量Δωの絶対値が規定値ΔｔｈＨ以上とまではいかないものの、所定値ΔｔｈＬ以上となると判定する場合、ドライバビリティを改善すべく、通常時上限値αｔｈＬ以上とする条件下、噴射量補正要求値αを減少補正する。これにより、三元触媒２４の下流の排気成分の悪化を抑制しつつも、ドライバビリティを極力改善できる。 Hereinafter, the action and effect of this embodiment will be described.
When the CPU 32 determines that the absolute value of the rotation fluctuation amount Δω does not exceed the specified value ΔthH when executing dither control, but determines that it becomes the predetermined value ΔthL or more, the CPU 32 usually has an upper limit value αthL or more in order to improve drivability. Under the condition of, the injection amount correction request value α is reduced and corrected. As a result, drivability can be improved as much as possible while suppressing deterioration of the exhaust component downstream of the three-way catalyst 24.

一方、ＣＰＵ３２は、部品保護要求が生じる場合、噴射量補正要求値αを、フェールセーフ時上限値αｔｈＬ以下とする。すなわち、内燃機関１０の制御量の制御に所定以上の異常が生じている場合、ディザ制御によるリッチ燃焼気筒の空燃比やリーン燃焼気筒の空燃比が理論空燃比からずれるために燃焼が悪化しやすい傾向が顕在化し、内燃機関１０の燃料噴射弁１８や点火装置２０、三元触媒２４等の部品の劣化を促進するおそれがある。このため、それら部品を保護すべく、噴射量補正要求値αを回転変動量Δωの絶対値が所定値ΔｔｈＬ以上となる場合よりも小さい値に制限する。 On the other hand, when a component protection request occurs, the CPU 32 sets the injection amount correction request value α to be equal to or less than the fail-safe upper limit value αthL. That is, when an abnormality of a predetermined value or more occurs in the control of the control amount of the internal combustion engine 10, the air-fuel ratio of the rich combustion cylinder and the air-fuel ratio of the lean combustion cylinder by the dither control deviate from the stoichiometric air-fuel ratio, so that the combustion tends to deteriorate. The tendency becomes apparent, and there is a risk of accelerating the deterioration of parts such as the fuel injection valve 18 of the internal combustion engine 10, the ignition device 20, and the three-way catalyst 24. Therefore, in order to protect those parts, the injection amount correction request value α is limited to a value smaller than the case where the absolute value of the rotation fluctuation amount Δω is equal to or more than the predetermined value ΔthL.

＜対応関係＞
上記実施形態における事項と、上記「課題を解決するための手段」の欄に記載した事項との対応関係は、次の通りである。ディザ制御処理は、Ｓ１８，Ｓ２６〜Ｓ３２，Ｓ１６の処理に対応し、部品保護処理は、Ｓ４２〜Ｓ４６の処理に対応し、振動抑制処理は、Ｓ２４，Ｓ３４〜Ｓ４０の処理に対応する。 <Correspondence>
The correspondence between the matters in the above-described embodiment and the matters described in the above-mentioned "means for solving the problem" column is as follows. The dither control process corresponds to the processes of S18, S26 to S32, S16, the component protection process corresponds to the process of S42 to S46, and the vibration suppression process corresponds to the process of S24, S34 to S40.

＜その他の実施形態＞
なお、本実施形態は、以下のように変更して実施することができる。本実施形態および以下の変更例は、技術的に矛盾しない範囲で互いに組み合わせて実施することができる。 <Other Embodiments>
In addition, this embodiment can be implemented by changing as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

・内燃機関１０の制御に所定以上の異常が生じているか否かの判定処理としては上記実施形態で例示したものに限らない。たとえば、排気温度が所定温度以上となる場合に所定以上の異常が生じていると判定してもよい。 -The processing for determining whether or not an abnormality of a predetermined value or more has occurred in the control of the internal combustion engine 10 is not limited to that illustrated in the above embodiment. For example, when the exhaust temperature is equal to or higher than a predetermined temperature, it may be determined that an abnormality of a predetermined temperature or higher has occurred.

・内燃機関としては、４気筒の内燃機関に限らない。また、燃料噴射弁としては、燃焼室１６に燃料を噴射するものに限らず、吸気通路１２に燃料を噴射するものであってもよい。 -The internal combustion engine is not limited to a 4-cylinder internal combustion engine. Further, the fuel injection valve is not limited to the one that injects fuel into the combustion chamber 16, and may be one that injects fuel into the intake passage 12.

１０…内燃機関、１２…吸気通路、１４…過給機、１６…燃焼室、１８…燃料噴射弁、２０…点火装置、２２…排気通路、２４…三元触媒、３０…制御装置、３２…ＣＰＵ、３４…ＲＯＭ、３６…ＲＡＭ、４０…空燃比センサ、４４…クランク角センサ、４６…エアフローメータ。 10 ... Internal combustion engine, 12 ... Intake passage, 14 ... Supercharger, 16 ... Combustion chamber, 18 ... Fuel injection valve, 20 ... Ignition device, 22 ... Exhaust passage, 24 ... Three-way catalyst, 30 ... Control device, 32 ... CPU, 34 ... ROM, 36 ... RAM, 40 ... air-fuel ratio sensor, 44 ... crank angle sensor, 46 ... air flow meter.

Claims (1)

複数の気筒から排出された排気を浄化する排気浄化装置と、前記複数の気筒毎に設けられた燃料噴射弁と、を備える内燃機関を制御対象とし、
前記複数の気筒のうちの一部の気筒を、空燃比が理論空燃比よりもリッチであるリッチ燃焼気筒とし、前記複数の気筒のうちの前記一部の気筒とは別の気筒を、空燃比が理論空燃比よりもリーンであるリーン燃焼気筒とすべく、前記燃料噴射弁を操作するディザ制御処理と、
前記内燃機関の制御量の制御に所定以上の異常が生じていると判定する場合、該異常が生じていないと判定する場合と比較して前記リッチ燃焼気筒の空燃比と前記リーン燃焼気筒の空燃比との差の絶対値を小さくする部品保護処理と、
前記所定以上の異常が生じていないと判定される場合であって前記内燃機関のクランク軸の回転変動が所定以上であると判定する場合、前記リッチ燃焼気筒の空燃比と前記リーン燃焼気筒の空燃比との差の絶対値を小さくする振動抑制処理と、を実行し、
前記部品保護処理では、前記振動抑制処理よりも前記リッチ燃焼気筒の空燃比と前記リーン燃焼気筒の空燃比との差の絶対値を小さくする内燃機関の制御装置。 An internal combustion engine including an exhaust gas purification device for purifying exhaust gas discharged from a plurality of cylinders and a fuel injection valve provided for each of the plurality of cylinders is controlled.
Some of the plurality of cylinders are rich combustion cylinders whose air-fuel ratio is richer than the stoichiometric air-fuel ratio, and cylinders other than some of the plurality of cylinders are air-fuel ratios. Is a dither control process that operates the fuel injection valve so that the lean combustion cylinder is leaner than the stoichiometric air-fuel ratio.
When it is determined that an abnormality of a predetermined value or more has occurred in the control of the control amount of the internal combustion engine, the air-fuel ratio of the rich combustion cylinder and the emptyness of the lean combustion cylinder are compared with the case where it is determined that the abnormality has not occurred. Parts protection treatment that reduces the absolute value of the difference from the fuel ratio,
When it is determined that no abnormality of the predetermined value or more has occurred and it is determined that the rotational fluctuation of the crankshaft of the internal combustion engine is equal to or more than the predetermined value, the air-fuel ratio of the rich combustion cylinder and the emptyness of the lean combustion cylinder are determined. Execute vibration suppression processing to reduce the absolute value of the difference from the fuel ratio,
In the component protection process, an internal combustion engine control device that makes the absolute value of the difference between the air-fuel ratio of the rich combustion cylinder and the air-fuel ratio of the lean combustion cylinder smaller than that of the vibration suppression process.
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