JP2007023888A - Control device of internal combustion engine - Google Patents

Control device of internal combustion engine Download PDF

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JP2007023888A
JP2007023888A JP2005207107A JP2005207107A JP2007023888A JP 2007023888 A JP2007023888 A JP 2007023888A JP 2005207107 A JP2005207107 A JP 2005207107A JP 2005207107 A JP2005207107 A JP 2005207107A JP 2007023888 A JP2007023888 A JP 2007023888A
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egr
injection
post
cylinder
injection amount
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Michihiro Hatake
道博 畠
Tokuyuki Koga
▲徳▼幸 古賀
Masatoshi Taniguchi
雅俊 谷口
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Mitsubishi Motors Corp
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Mitsubishi Motors Corp
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  • Exhaust-Gas Circulating Devices (AREA)
  • Output Control And Ontrol Of Special Type Engine (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of preventing inconvenience such as a torque fluctuation, fouling and the deterioration in an EGR system and an intake system by restraining a phenomenon of recirculation of unburnt fuel discharged by post-injection to the intake side in response to EGR control. <P>SOLUTION: This control device of the internal combustion engine is constituted so that only exhaust gas of a # 4 cylinder is recirculated to the intake side as EGR gas. In EGR recirculation, when performing the post-injection for purging NOx of an NOx catalyst 10, HC and CO are secured by controlling #1 to #3 cylinders in the rich air-fuel ratio, and the #4 cylinder is controlled in the lean air-fuel ratio, and the unburnt fuel recirculated to the intake side together with the EGR gas is restrained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は排ガスの一部を吸気側に還流させるＥＧＲ装置を備えると共に、メイン噴射後にポスト噴射を実行可能な内燃機関（以下、エンジンと称する）の制御装置に関するものである。   The present invention relates to a control device for an internal combustion engine (hereinafter referred to as an engine) that includes an EGR device that recirculates part of exhaust gas to the intake side and that can perform post injection after main injection.

例えばリーンバーンエンジンやディーゼルエンジンなどの排気系には、排ガス中のＮＯx（窒素酸化物）を吸蔵する吸蔵型ＮＯx触媒や排ガス中のＰＭ（パティキュレートマター）を捕集するＤＰＦ（ディーゼルパティキュレートフィルタ）などの排気浄化装置が設けられている。これらの排気浄化装置ではＮＯx吸蔵量やＰＭ捕集量が飽和限界に達する以前にＮＯxやＰＭを処理する必要があり、例えばＮＯx触媒では、エンジンの排気空燃比のリッチ化によりＮＯx触媒上に還元剤としてＨＣやＣＯを供給してＮＯxを放出還元浄化するＮＯxパージを実行しており、ＤＰＦでは、排気昇温による排ガスの熱、或いはＤＰＦの上流側の前段酸化触媒上に供給したＨＣやＣＯを酸化反応させたときの反応熱を利用して、ＤＰＦ上のＰＭを強制的に燃焼させる強制再生を実行している。   For example, in exhaust systems such as lean burn engines and diesel engines, a storage type NOx catalyst that stores NOx (nitrogen oxide) in exhaust gas and a DPF (diesel particulate filter) that collects PM (particulate matter) in exhaust gas are collected. ) Etc. are provided. In these exhaust purification devices, it is necessary to treat NOx and PM before the NOx occlusion amount and PM trapped amount reach the saturation limit. For example, in the case of a NOx catalyst, it is reduced on the NOx catalyst by enriching the exhaust air / fuel ratio of the engine. NOx purge is performed to release and reduce NOx by supplying HC or CO as an agent. In the DPF, the heat of exhaust gas due to the temperature rise of the exhaust, or the HC or CO supplied on the upstream oxidation catalyst upstream of the DPF Forcible regeneration is performed in which the PM on the DPF is forcibly burned by utilizing the heat of reaction when the is oxidized.

上記排気空燃比のリッチ化、排気昇温、ＨＣやＣＯ供給などのための有効な手法としてポスト噴射が広く行われている。当該ポスト噴射はトルク発生のためのメイン噴射後の膨張行程や排気行程で実行され、燃焼途中或いは燃焼前の筒内ガスを排ガスとして排出して上記リッチ化、排気昇温、ＨＣやＣＯ供給を実現している。
一方、上記排気浄化装置の効率的な再生を目的として種々の提案がなされている（例えば、特許文献１参照）。当該特許文献１に開示された技術はＮＯx触媒に対するＮＯxパージに関するものであり、吸気側に排ガスを還流させるためのＥＧＲ通路に特定気筒のみを連通させた上で、ＮＯxパージ時には他の全ての気筒をリーン運転を継続させたまま特定気筒のみをリッチ空燃比に制御し、特定気筒から未燃状態で排出されるＨＣやＣＯによりＮＯx触媒からＮＯxを放出還元浄化している。
特許第３４６２４４５号明細書 As an effective method for enriching the exhaust air-fuel ratio, raising the temperature of exhaust gas, supplying HC and CO, post injection is widely performed. The post-injection is executed in the expansion stroke and exhaust stroke after the main injection for generating torque, and the in-cylinder gas before or during combustion is discharged as exhaust gas, and the above enrichment, exhaust temperature rise, HC and CO supply are performed. Realized.
On the other hand, various proposals have been made for the purpose of efficient regeneration of the exhaust purification device (for example, see Patent Document 1). The technique disclosed in Patent Document 1 relates to NOx purging for the NOx catalyst. Only the specific cylinder is connected to the EGR passage for recirculating exhaust gas to the intake side, and all other cylinders are used during NOx purging. While the lean operation is continued, only the specific cylinder is controlled to a rich air-fuel ratio, and NOx is released and reduced and purified by the NOx catalyst by HC and CO discharged from the specific cylinder in an unburned state.
Japanese Patent No. 3462445

ところで、上記ポスト噴射は排気空燃比のリッチ化、排気昇温、ＨＣやＣＯの供給の何れの場合でも未燃燃料の排出を伴うことになるが、このときにＥＧＲ制御が実行されていると、未燃燃料が吸気側に還流されてエンジンのトルク変動やＥＧＲ系及び吸気系の汚損・劣化などの問題を生じる。
即ち、ＥＧＲ制御の有無に関わらず、ポスト噴射による噴射燃料は一部がエンジンの筒内で燃焼されてトルク増加と排気空燃比のリッチ化および排気昇温に寄与する一方、筒内で燃焼されないトルク増加に寄与しない分は排気空燃比のリッチ化や排気昇温に貢献しており、図８はこのときのポスト噴射によるトルク増加状況を示している。ＥＧＲ制御が実行されない場合のポスト噴射によるトルク増加は、図中にハッチングで示すようにエンジンの運転状態に関わらずポスト噴射時期などによって一義的に定まることから、ポスト噴射時期などから求めたトルク寄与率（全ポスト噴射量に対するトルク発生に寄与したポスト噴射量の割合）をポスト噴射量に乗算した値だけメイン噴射量を減少補正すれば、ポスト噴射に起因するトルク増加を抑制できる。 By the way, the post-injection is accompanied by discharge of unburned fuel in any of the cases of exhaust gas air-fuel ratio enrichment, exhaust gas temperature increase, and HC and CO supply. At this time, EGR control is executed. The unburned fuel is recirculated to the intake side, causing problems such as engine torque fluctuations and contamination / deterioration of the EGR system and intake system.
That is, regardless of the presence or absence of EGR control, part of the fuel injected by post-injection is burned in the cylinder of the engine, contributing to torque increase, exhaust air-fuel ratio enrichment, and exhaust temperature rise, but not burned in the cylinder. The portion that does not contribute to the torque increase contributes to the enrichment of the exhaust air-fuel ratio and the exhaust gas temperature rise, and FIG. 8 shows the torque increase situation due to post injection at this time. The torque increase due to post-injection when EGR control is not executed is uniquely determined by the post-injection time, etc., regardless of the engine operating state, as shown by hatching in the figure, so the torque contribution obtained from the post-injection time, etc. If the main injection amount is corrected to decrease by a value obtained by multiplying the post injection amount by the ratio (the ratio of the post injection amount contributing to the torque generation with respect to the total post injection amount), the torque increase caused by the post injection can be suppressed.

ところが、ＥＧＲ制御の実行時には、ポスト噴射により排出された未燃燃料が吸気側に還流されて燃焼するため、トルク増加を引き起こす現象が生じる。図８にクロスハッチングで示すように、このときの新気量は還流未燃燃料量と共にポスト噴射の実行中に常に変動し続けるため、未燃燃料の還流に起因するトルク寄与率を的確に算出するには制御が複雑化し、現実的に困難であり、トルク変動により車両のドライバビリティを悪化させてしまうという問題を生じた。   However, when EGR control is executed, unburnt fuel discharged by post-injection is recirculated to the intake side and burned, resulting in a phenomenon that causes an increase in torque. As shown by cross-hatching in FIG. 8, the amount of fresh air at this time always fluctuates during the post injection with the amount of recirculated unburned fuel, so the torque contribution rate due to recirculation of unburned fuel is accurately calculated. Therefore, the control is complicated and practically difficult, and the drivability of the vehicle deteriorates due to torque fluctuation.

また、吸気側に還流された未燃燃料は、ＥＧＲ系や吸気系（例えばＥＧＲクーラやＥＧＲバルブ、吸気通路など）を汚損・劣化を促進させる要因となる。ＥＧＲ通路に設けたＥＧＲ触媒上で還流された未燃燃料を燃焼させる対策も考えられるが、例えばＮＯx触媒に対するＮＯxパージのように、ポスト噴射の実行中には排気空燃比がリッチ側に制御されている場合が大半のため、酸素不足により未燃燃料の燃焼は期待できず、この対策は適用できなかった。   Further, the unburned fuel recirculated to the intake side causes the EGR system and the intake system (for example, an EGR cooler, an EGR valve, an intake passage, etc.) to promote fouling and deterioration. Although measures to combust unburned fuel recirculated on the EGR catalyst provided in the EGR passage are also conceivable, the exhaust air-fuel ratio is controlled to the rich side during post injection, for example, NOx purge for the NOx catalyst. In most cases, the combustion of unburned fuel could not be expected due to lack of oxygen, and this measure could not be applied.

上記特許文献１の技術では、ＮＯxパージ時にＥＧＲ通路と連通する特定気筒の排気空燃比をリッチ側に制御しているため、必然的に吸気側への未燃燃料の還流を抑制できず、上記問題の対策とはなり得なかった。
本発明はこのような問題点を解決するためになされたもので、その目的とするところは、ポスト噴射により排出された未燃燃料がＥＧＲ制御に伴って吸気側に還流する現象を抑制して、これによるトルク変動やＥＧＲ系及び吸気系の汚損・劣化などの不具合を未然に防止することができる内燃機関の制御装置を提供することにある。 In the technique of Patent Document 1 described above, since the exhaust air-fuel ratio of the specific cylinder communicating with the EGR passage is controlled to the rich side during NOx purge, the recirculation of unburned fuel to the intake side cannot necessarily be suppressed. It could not be a countermeasure for the problem.
The present invention has been made to solve such problems, and the object of the present invention is to suppress the phenomenon that unburned fuel discharged by post-injection recirculates to the intake side in accordance with EGR control. Another object of the present invention is to provide a control device for an internal combustion engine that can prevent problems such as torque fluctuations and fouling / deterioration of the EGR system and intake system.

上記目的を達成するため、請求項１の発明は、内燃機関の特定気筒のみを該内燃機関の排気側と連通させるＥＧＲ通路、及びＥＧＲ通路の開度を調整可能なＥＧＲバルブから構成され、特定気筒の排ガスをＥＧＲガスとして吸気側に還流するＥＧＲ手段と、内燃機関の各気筒に対してメイン噴射後にポスト噴射を実行するポスト噴射制御手段と、ＥＧＲ手段によるＥＧＲガスの還流時にポスト噴射制御手段によりポスト噴射が実行されたときに、特定気筒に対するポスト噴射量を他気筒に対するポスト噴射量より減少補正するポスト噴射量補正手段とを備えたものである。   In order to achieve the above object, the invention of claim 1 comprises an EGR passage that allows only a specific cylinder of the internal combustion engine to communicate with the exhaust side of the internal combustion engine, and an EGR valve that can adjust the opening of the EGR passage. EGR means for recirculating exhaust gas from the cylinders as EGR gas to the intake side, post injection control means for executing post injection after main injection for each cylinder of the internal combustion engine, and post injection control means when the EGR gas is recirculated by the EGR means When the post injection is executed by the above, post injection amount correction means for correcting the post injection amount for the specific cylinder to be smaller than the post injection amount for the other cylinders is provided.

従って、ＥＧＲ手段によるＥＧＲガスの還流時において、例えば内燃機関の排気通路に設けた排気浄化装置の昇温による早期活性化、或いは排気浄化装置へのＨＣやＣＯの供給を目的としてポスト噴射制御手段によりポスト噴射が実行されるときには、他気筒に対するポスト噴射量に比較して特定気筒に対するポスト噴射量が減少補正される。これにより特定気筒の排ガスに含まれる未燃燃料、即ち、ＥＧＲ手段によりＥＧＲガスと共に内燃機関の排気側に還流される未燃燃料が減少するため、還流された未燃燃料の燃焼に起因するトルク増加が抑制されると共に、未燃燃料によるＥＧＲ系や吸気系の汚損・劣化が未然に防止される。   Accordingly, when the EGR gas is recirculated by the EGR means, for example, the post-injection control means for the purpose of early activation by raising the temperature of the exhaust purification device provided in the exhaust passage of the internal combustion engine or the supply of HC or CO to the exhaust purification device Thus, when post injection is executed, the post injection amount for the specific cylinder is corrected to be smaller than the post injection amount for the other cylinders. As a result, unburned fuel contained in the exhaust gas of the specific cylinder, that is, unburned fuel recirculated to the exhaust side of the internal combustion engine together with EGR gas by the EGR means is reduced, so that torque caused by combustion of the recirculated unburned fuel is reduced. The increase is suppressed, and contamination and deterioration of the EGR system and the intake system due to unburned fuel are prevented.

請求項２の発明は、請求項１において、ポスト噴射量補正手段が、特定気筒に対するポスト噴射量を０に補正するものである。
従って、特定気筒に対するポスト噴射量が０に補正されてポスト噴射が中止されるため、排ガス中に未燃燃料が存在しなくなり、吸気側への未燃燃料の還流を完全に抑制可能となる。 According to a second aspect of the present invention, in the first aspect, the post injection amount correcting means corrects the post injection amount for the specific cylinder to zero.
Therefore, since the post injection amount for the specific cylinder is corrected to 0 and the post injection is stopped, there is no unburned fuel in the exhaust gas, and the recirculation of the unburned fuel to the intake side can be completely suppressed.

請求項３の発明は、請求項１または２において、ＥＧＲ手段のＥＧＲ通路にＥＧＲガス中の未燃燃料を燃焼させるＥＧＲ触媒が備えられたものである。
従って、特定気筒の排ガス中に残存する未燃燃料がＥＧＲ触媒により燃焼されるため、吸気側への未燃燃料の還流をより確実に抑制可能となる。
請求項４の発明は、請求項３において、ポスト噴射量補正手段が、特定気筒の排気空燃比がリーン側となるように特定気筒に対するポスト噴射量を補正するものである。 According to a third aspect of the present invention, in the first or second aspect, the EGR passage of the EGR means is provided with an EGR catalyst for burning unburned fuel in the EGR gas.
Therefore, since the unburned fuel remaining in the exhaust gas of the specific cylinder is burned by the EGR catalyst, the recirculation of the unburned fuel to the intake side can be more reliably suppressed.
According to a fourth aspect of the present invention, in the third aspect, the post injection amount correcting means corrects the post injection amount for the specific cylinder so that the exhaust air-fuel ratio of the specific cylinder is on the lean side.

従って、特定気筒の排気空燃比がリーン側に制御されることで排ガス中に酸素が存在し、この酸素を利用してＥＧＲ触媒による未燃燃料の燃焼作用が確実に得られる。
請求項５の発明は、請求項１乃至４において、特定気筒と他気筒とのポスト噴射量の相違によるトルク格差を縮小する方向に、特定気筒または他気筒の少なくとも一方のメイン噴射量を補正するメイン噴射量補正手段を備えたものである。 Therefore, oxygen is present in the exhaust gas by controlling the exhaust air-fuel ratio of the specific cylinder to the lean side, and the combustion action of unburned fuel by the EGR catalyst can be reliably obtained using this oxygen.
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the main injection amount of at least one of the specific cylinder or the other cylinder is corrected so as to reduce a torque difference due to a difference in post injection amount between the specific cylinder and the other cylinder. Main injection amount correction means is provided.

従って、特定気筒または他気筒の少なくとも一方のメイン噴射量が補正されることでトルク格差が縮小され、ポスト噴射量の相違に起因して発生するトルク変動の弊害が未然に回避される。   Accordingly, the torque difference is reduced by correcting the main injection amount of at least one of the specific cylinder and the other cylinders, and the adverse effect of torque fluctuations caused by the difference in the post injection amount is avoided.

以上説明したように請求項１の発明の内燃機関の制御装置によれば、ポスト噴射量を減少させた特定気筒の排ガスをＥＧＲガスとして吸気側に還流させることにより、ＥＧＲガスと共に未燃燃料が吸気側に還流される現象を抑制し、これによるトルク変動やＥＧＲ系及び吸気系の汚損・劣化などの不具合を未然に防止することができる。
請求項２の発明の内燃機関の制御装置によれば、請求項１に加えて、特定気筒に対するポスト噴射を中止して吸気側への未燃燃料の還流を完全に抑制でき、未燃燃料の還流による不具合を一層確実に防止することができる。 As described above, according to the control device for an internal combustion engine of the first aspect of the present invention, the exhaust gas of the specific cylinder whose post-injection amount is reduced is recirculated to the intake side as EGR gas, so that the unburned fuel is combined with the EGR gas. It is possible to suppress the phenomenon of recirculation to the intake side and prevent problems such as torque fluctuation and contamination / deterioration of the EGR system and intake system.
According to the control device for an internal combustion engine of the invention of claim 2, in addition to claim 1, post-injection to the specific cylinder can be stopped to completely suppress the recirculation of unburned fuel to the intake side. Problems due to reflux can be prevented more reliably.

請求項３，４の発明の内燃機関の制御装置によれば、請求項１及び２に加えて、ＥＧＲ触媒の未燃燃料の燃焼作用により吸気側への未燃燃料の還流をより確実に抑制でき、未燃燃料の還流による不具合を一層確実に防止することができる。
請求項５の発明の内燃機関の制御装置によれば、請求項１乃至４に加えて、気筒間のトルク格差を縮小する方向にメイン噴射量を補正し、ポスト噴射量の相違に起因して発生するトルク変動の弊害を未然に回避することができる。 According to the control apparatus for an internal combustion engine of the third and fourth aspects of the invention, in addition to the first and second aspects, the recirculation of the unburned fuel to the intake side is more reliably suppressed by the combustion action of the unburned fuel of the EGR catalyst. It is possible to more reliably prevent problems caused by recirculation of unburned fuel.
According to the control apparatus for an internal combustion engine of the fifth aspect of the invention, in addition to the first to fourth aspects, the main injection amount is corrected in a direction to reduce the torque difference between the cylinders, and due to the difference in the post injection amount. It is possible to avoid the adverse effects of torque fluctuations that occur.

［第１実施形態］
以下、本発明を吸蔵型ＮＯx触媒を備えたディーゼルエンジンの制御装置に具体化した一実施形態を説明する。
図は本実施形態のディーゼルエンジンの制御装置を示す全体構成図である。エンジン１は直列４気筒機関として構成され、各気筒に設けられた燃料噴射ノズル２には図示しないコモンレールから加圧燃料が供給され、燃料噴射ノズル２の開弁に伴って各気筒の筒内に燃料が噴射される。各気筒の吸気側には吸気マニホールド３を介して共通のサージタンク４が接続され、サージタンク４には吸気絞り弁５を備えた吸気通路６が接続されている。各気筒の排気側には排気マニホールド７及びターボチャージャ８を介して共通の排気通路９が接続され、排気通路９にはＮＯx触媒１０が設けられている。なお、図ではターボチャージャ８の設置状態を略しているが、実際にはターボチャージャ８は吸気通路６とも接続されて吸入空気を過給し得る。 [First Embodiment]
Hereinafter, an embodiment in which the present invention is embodied in a control device for a diesel engine equipped with an occlusion-type NOx catalyst will be described.
FIG. 1 is an overall configuration diagram showing a control device for a diesel engine according to the present embodiment. The engine 1 is configured as an in-line four-cylinder engine. A fuel injection nozzle 2 provided in each cylinder is supplied with pressurized fuel from a common rail (not shown), and the fuel injection nozzle 2 opens into the cylinder of each cylinder. Fuel is injected. A common surge tank 4 is connected to the intake side of each cylinder via an intake manifold 3, and an intake passage 6 having an intake throttle valve 5 is connected to the surge tank 4. A common exhaust passage 9 is connected to the exhaust side of each cylinder via an exhaust manifold 7 and a turbocharger 8, and a NOx catalyst 10 is provided in the exhaust passage 9. In the figure, the installation state of the turbocharger 8 is omitted, but actually, the turbocharger 8 can be connected to the intake passage 6 to supercharge intake air.

ＮＯｘ触媒１０は、例えば、白金（Ｐｔ）、パラジウム（Ｐｄ），ロジウム（Ｒｈ）等の貴金属と、バリウム（Ｂａ）、カリウム（Ｋ）、ナトリウム（Ｎａ）等のアルカリ金属、アルカリ土類金属のＮＯｘトラップ剤とを含み、エンジン１の排気空燃比がリーンのときに排ガス中のＮＯｘを硝酸塩Ｘ−ＮＯ3として吸蔵する一方、排気空燃比がリッチのときに吸蔵しているＮＯｘを放出して窒素（Ｎ２）等に還元浄化する機能を有する。なお、排気浄化装置の構成はこれに限らず、例えばＮＯx触媒１０に加えて酸化触媒を設けてもよい。 The NOx catalyst 10 includes, for example, noble metals such as platinum (Pt), palladium (Pd), and rhodium (Rh), alkali metals such as barium (Ba), potassium (K), and sodium (Na), and alkaline earth metals. NOx in the exhaust gas is stored as nitrate X-NO 3 when the exhaust air-fuel ratio of the engine 1 is lean, and the stored NOx is released when the exhaust air-fuel ratio is rich. It has a function of reducing and purifying to nitrogen (N 2 ) or the like. The configuration of the exhaust purification device is not limited to this, and for example, an oxidation catalyst may be provided in addition to the NOx catalyst 10.

そして、吸気通路６には図示しないエアクリーナを介して吸入空気が導入され、吸入空気はターボチャージャ８により過給された後にサージタンク４及び吸気マニホールド３を経て各気筒の筒内に分配され、筒内では燃料噴射ノズル２からの噴射燃料が圧縮着火されてエンジントルクを発生する。燃焼後の排ガスは排気マニホールド７を経てターボチャージャ８を回転駆動した後に排気通路９及びＮＯx触媒１０を経て外部に排出され、その際に上記のように排ガス中のＮＯxがＮＯx触媒１０に吸蔵される。   Then, intake air is introduced into the intake passage 6 via an air cleaner (not shown), and the intake air is supercharged by the turbocharger 8 and then distributed to the cylinders of each cylinder through the surge tank 4 and the intake manifold 3. Inside, the fuel injected from the fuel injection nozzle 2 is compressed and ignited to generate engine torque. The exhaust gas after combustion rotates the turbocharger 8 through the exhaust manifold 7 and then is discharged to the outside through the exhaust passage 9 and the NOx catalyst 10. At this time, NOx in the exhaust gas is occluded in the NOx catalyst 10 as described above. The

本実施形態のエンジン１に備えられたＥＧＲ装置は一般的なものとは構成を異にしており、＃４気筒の排ガスのみをＥＧＲガスとして吸気側に還流するように構成されている。即ち、＃１〜＃３気筒の排気マニホールド７はＥＧＲ装置とは関係なく独立して設けられ、＃４気筒の排気マニホールド７のみにＥＧＲ通路１１（ＥＧＲ手段）の一端が接続され、ＥＧＲ通路１１の他端が吸気通路６に接続されている。ＥＧＲ通路１１には排気マニホールド７側よりＥＧＲ触媒１２、ＥＧＲクーラ１３、ＥＧＲバルブ１４（ＥＧＲ手段）が設けられ、ＥＧＲバルブ１４によりＥＧＲ通路１１の開度が調整され、それに応じて＃４気筒から排出された排ガスの一部がＥＧＲ通路１１を経てＥＧＲガスとして吸気通路６に還流される。   The EGR device provided in the engine 1 of the present embodiment has a different configuration from a general one, and is configured to recirculate only the exhaust gas of the # 4 cylinder to the intake side as EGR gas. That is, the exhaust manifold 7 for the # 1 to # 3 cylinders is provided independently of the EGR device, and one end of the EGR passage 11 (EGR means) is connected only to the exhaust manifold 7 for the # 4 cylinder, and the EGR passage 11 Is connected to the intake passage 6. The EGR passage 11 is provided with an EGR catalyst 12, an EGR cooler 13, and an EGR valve 14 (EGR means) from the exhaust manifold 7 side, and the opening degree of the EGR passage 11 is adjusted by the EGR valve 14, and from the # 4 cylinder accordingly Part of the discharged exhaust gas is recirculated to the intake passage 6 as EGR gas through the EGR passage 11.

一方、車室内には、図示しない入出力装置、制御プログラムや制御マップ等の記憶に供される記憶装置（ＲＯＭ，ＲＡＭ等）、中央処理装置（ＣＰＵ）、タイマカウンタ等を備えたＥＣＵ（エンジン制御ユニット）２１が設置されており、エンジン１の総合的な制御を行う。ＥＣＵ２１の入力側には、エンジン１の回転速度Ｎeを検出する回転速度センサ２２、アクセル操作量θaccを検出するアクセルセンサ２３などの各種センサ類が接続され、ＥＣＵ２１の出力側には、上記燃料噴射ノズル２、ＥＧＲバルブ１４などの各種デバイス類が接続されている。   On the other hand, an input / output device (not shown), a storage device (ROM, RAM, etc.) used for storing control programs and control maps, a central processing unit (CPU), a timer counter, etc. Control unit) 21 is installed and performs overall control of the engine 1. Various sensors such as a rotational speed sensor 22 for detecting the rotational speed Ne of the engine 1 and an accelerator sensor 23 for detecting the accelerator operation amount θacc are connected to the input side of the ECU 21, and the fuel injection is connected to the output side of the ECU 21. Various devices such as the nozzle 2 and the EGR valve 14 are connected.

ＥＣＵ２１はエンジン回転速度Ｎe及びアクセル操作量θaccに基づき、図示しないマップから燃料噴射量を設定し、エンジン回転速度Ｎe及び燃料噴射量に基づき、図示しないマップから燃料噴射時期を設定すると共に、ポスト噴射などを実行する場合には、同様の手順でポスト噴射の燃料噴射量及び燃料噴射時期も設定し、これらの設定に基づいて燃料噴射ノズル２を駆動制御して各気筒に対する燃料噴射を実行する。   The ECU 21 sets the fuel injection amount from a map (not shown) based on the engine rotation speed Ne and the accelerator operation amount θacc, sets the fuel injection timing from a map (not shown) based on the engine rotation speed Ne and the fuel injection amount, and performs post injection. For example, the post-injection fuel injection amount and the fuel injection timing are set in the same procedure, and the fuel injection nozzle 2 is driven and controlled based on these settings to execute the fuel injection for each cylinder.

また、エンジン１の運転中において排ガスに含まれるＮＯxはＮＯx触媒１０に吸蔵されるが、ＥＣＵ２１はＮＯx触媒１０が飽和限界付近に達したときにポスト噴射を行って排気空燃比をリッチ側に制御し、ＮＯx触媒１０に吸蔵されているＮＯxを放出還元するＮＯxパージを実行する（ポスト噴射制御手段）。なお、ＮＯxパージの開始時期は、エンジン１の運転状態から推定したＮＯx排出量の積算値が飽和限界に相当する所定値に達したとき、或いはＮＯx触媒１０の下流側に設けた図示しないＮＯxセンサにより検出されるＮＯx量が所定値を越えたときを目安として判定する。   Further, during operation of the engine 1, NOx contained in the exhaust gas is occluded in the NOx catalyst 10, but the ECU 21 performs post injection when the NOx catalyst 10 reaches the saturation limit and controls the exhaust air-fuel ratio to the rich side. Then, NOx purge for releasing and reducing NOx stored in the NOx catalyst 10 is executed (post injection control means). The NOx purge start timing is determined when the integrated value of the NOx emission amount estimated from the operating state of the engine 1 reaches a predetermined value corresponding to the saturation limit, or a NOx sensor (not shown) provided on the downstream side of the NOx catalyst 10. When the amount of NOx detected by the above exceeds a predetermined value, the determination is made as a guide.

一方、ＥＣＵ２１はエンジン回転速度Ｎe及び燃料噴射量に基づき、図示しないマップから目標空気過剰率tgtλを算出し、この目標空気過剰率tgtλと実際の空気過剰率λとからＥＧＲ弁２１の開度（即ち、ＥＧＲ率）をフィードバックして目標空気過剰率tgtλを達成するＥＧＲ制御を実行する。例えば実空気過剰率λは、ＥＧＲガス中の残存酸素量の推定値に図示しないエアフローセンサ出力から求まる吸入空気量を加算した新気量と燃料噴射量とから算出するか、或いは排気通路９に設けたリニア空燃比センサの出力から算出する。   On the other hand, the ECU 21 calculates a target excess air ratio tgtλ from a map (not shown) based on the engine speed Ne and the fuel injection amount, and the opening degree of the EGR valve 21 (from the target excess air ratio tgtλ and the actual excess air ratio λ). That is, the EGR control is performed to achieve the target excess air ratio tgtλ by feeding back the EGR rate. For example, the actual excess air ratio λ is calculated from a fresh air amount obtained by adding an intake air amount obtained from an air flow sensor output (not shown) to an estimated value of the residual oxygen amount in the EGR gas and a fuel injection amount, or in the exhaust passage 9. It calculates from the output of the provided linear air-fuel ratio sensor.

図２はＥＧＲ還流による効果を示した説明図であり、破線で示すＥＧＲガスを還流させない場合に比較して実線で示すＥＧＲガスを還流させた場合には、図中の下段に示すように、不活性なＥＧＲガスの還流により筒内燃焼温度を低下させてエンジンアウトのＮＯx排出量を低減できると共に、ＥＧＲ還流分だけ吸気絞り弁５による吸気制限を緩和できることから、図中の上段に示すように吸気負圧が上昇（大気圧に接近）してスロットルロスの軽減により燃費向上でき、さらに、図中の中段に示すように新気量が低下することから、例えばＮＯx触媒１０のＮＯxパージ時に排気空燃比のリッチ化に要するポスト噴射量を減少させて燃費向上できることが判る。   FIG. 2 is an explanatory diagram showing the effect of EGR recirculation, and when the EGR gas indicated by the solid line is recirculated compared to the case where the EGR gas indicated by the broken line is not recirculated, as shown in the lower part of the figure, The in-cylinder combustion temperature can be lowered by the recirculation of the inert EGR gas to reduce the NOx emission amount of the engine-out, and the intake restriction by the intake throttle valve 5 can be relaxed by the EGR recirculation amount. As the intake negative pressure rises (approaching atmospheric pressure) and the throttle loss is reduced, fuel efficiency can be improved. Further, as shown in the middle part of the figure, the amount of fresh air decreases, so for example during NOx purge of the NOx catalyst 10 It can be seen that the fuel consumption can be improved by reducing the post injection amount required for enriching the exhaust air-fuel ratio.

一方、上記燃料噴射制御は、基本的に全ての気筒に対して共通の噴射量及び噴射時期を適用して実行するが、ＥＧＲ還流とＮＯxパージとが重なった運転領域では、排気空燃比のリッチ化による未燃燃料が吸気側に還流されたときの不具合を防止すべく、＃１〜＃３気筒と＃４気筒とに対して異なる燃料噴射制御を実行しており、以下、当該燃料噴射制御について詳述する。   On the other hand, the fuel injection control is basically executed by applying a common injection amount and injection timing to all the cylinders. However, in the operation region where EGR recirculation and NOx purge overlap, the exhaust air-fuel ratio is rich. In order to prevent problems when the unburned fuel is recirculated to the intake side due to the conversion, different fuel injection control is executed for the # 1 to # 3 cylinders and the # 4 cylinders. Will be described in detail.

図３はＥＧＲ還流時に実行されるＮＯxパージの燃料噴射制御状況を示すタイムチャート、図４は同じくＥＧＲ還流時に実行されるＮＯxパージのポスト噴射によるトルク増加状況を示すタイムチャートである。これらの図に示すように、本実施形態では＃４気筒を含めた全気筒に対してポスト噴射を実行しており、当該ポスト噴射はメイン噴射の燃焼のほぼ終了後に実行されて、噴射燃料の燃焼を抑制してＮＯx触媒１０に還元剤としてＨＣやＣＯを供給するように配慮されている。   FIG. 3 is a time chart showing the fuel injection control status of NOx purge executed at the time of EGR recirculation, and FIG. 4 is a time chart showing the torque increase status due to the post injection of NOx purge executed at the same time of EGR recirculation. As shown in these figures, in this embodiment, post-injection is executed for all cylinders including the # 4 cylinder, and the post-injection is executed almost after completion of combustion of the main injection, and the injected fuel Consideration is given to supply HC and CO as a reducing agent to the NOx catalyst 10 while suppressing combustion.

ここで、ＥＧＲガスとして利用される＃４気筒の排ガスは吸気側への未燃燃料の還流を防止すべくリーン空燃比に制御する必要があり、一方、ＮＯx触媒１０上でのＮＯxパージに利用されるＨＣやＣＯを確保するために、全気筒の排ガスが合流した後の空燃比（以下、トータル空燃比と称する）は所定のリッチ側に制御する必要がある。
そこで、図３に示すように＃４気筒に対するポスト噴射は＃１〜＃３気筒に比較して噴射量（噴射ノズル２の開弁期間）を減少させており、これにより図４に示すようにＮＯxパージ中において＃４気筒は理論空燃比（λ＝1.0）よりリーン側の空燃比に制御される（ポスト噴射量補正手段）。また、このような＃４気筒に対する空燃比制御の影響を受けてトータル空燃比はリーン側に偏るため、その影響を補償すべく＃１〜＃３気筒はＮＯxパージのための最適空燃比に対して若干リッチ側の空燃比となるようにポスト噴射の噴射量が制御され、結果としてトータル空燃比は理論空燃比より僅かにリッチ側のＮＯxパージに対して最適空燃比に保持される。 Here, the exhaust gas from the # 4 cylinder used as the EGR gas needs to be controlled to a lean air-fuel ratio in order to prevent recirculation of unburned fuel to the intake side, while being used for NOx purge on the NOx catalyst 10. In order to secure HC and CO, the air-fuel ratio (hereinafter referred to as the total air-fuel ratio) after the exhaust gases from all the cylinders have joined needs to be controlled to a predetermined rich side.
Therefore, as shown in FIG. 3, the post-injection for the # 4 cylinder reduces the injection amount (the valve opening period of the injection nozzle 2) compared to the # 1 to # 3 cylinders, and as shown in FIG. During the NOx purge, the # 4 cylinder is controlled to a leaner air-fuel ratio than the stoichiometric air-fuel ratio (λ = 1.0) (post injection amount correcting means). Further, since the total air-fuel ratio is biased toward the lean side due to the influence of the air-fuel ratio control for the # 4 cylinder, the # 1- # 3 cylinders are compensated for the optimum air-fuel ratio for NOx purge to compensate for the influence. As a result, the post-injection injection amount is controlled so that the air-fuel ratio becomes slightly richer. As a result, the total air-fuel ratio is maintained at the optimum air-fuel ratio with respect to the NOx purge slightly richer than the stoichiometric air-fuel ratio.

＃１〜＃３気筒に対して＃４気筒に対するポスト噴射は噴射時期についても別個に設定されており、ＥＧＲガスとしての還流を考慮した上で、排ガス中の未燃燃料を抑制し、かつＥＧＲ系の耐熱温度を越える温度上昇を抑制するために好適な値に設定される。そして、リーン空燃比による運転で＃４気筒の排ガス中の未燃燃料が大幅に減少しているため、ＥＧＲガスに含まれて吸気側に還流される未燃燃料も大幅に減少し、それに応じて図４にクロスハッチングで示すようにＥＧＲ還流に起因するトルク増加分がごく僅かなものとなる。しかも、リーン空燃比下では排ガス中に酸素が存在するため、排ガス中に残存する未燃燃料はこの酸素を利用してＥＧＲ触媒１２上で燃焼され、結果として吸気側への未燃燃料の還流が未然に防止されて、クロスハッチングのトルク増加分もほとんど発生しなくなる。   The post-injection for the # 4 cylinder is set separately for the # 1 to # 3 cylinders with respect to the injection timing, and the unburned fuel in the exhaust gas is suppressed in consideration of the recirculation as the EGR gas, and the EGR It is set to a suitable value in order to suppress a temperature rise exceeding the heat resistance temperature of the system. And since the unburned fuel in the exhaust gas of the # 4 cylinder is greatly reduced by the operation with the lean air-fuel ratio, the unburned fuel contained in the EGR gas and recirculated to the intake side is also greatly reduced. Thus, as shown by cross hatching in FIG. 4, the torque increase due to the EGR recirculation is very slight. Moreover, since oxygen exists in the exhaust gas under a lean air-fuel ratio, the unburned fuel remaining in the exhaust gas is burned on the EGR catalyst 12 using this oxygen, and as a result, the unburned fuel returns to the intake side. Is prevented, and the increase in cross-hatching torque hardly occurs.

従って、吸気側に還流された未燃燃料の燃焼に起因してエンジントルクが増加する現象が生じなくなり、ＮＯxパージ中のトルク増加は、図４にハッチングで示すポスト噴射の噴射燃料の燃焼に起因するものとなり、ＮＯxパージのポスト噴射では燃料の大半が燃焼せずにＨＣやＣＯの供給に利用されるため、このポスト噴射によるトルク増加は無視できる程度でトルク抑制の必要はほとんどない。また、仮にトルク増加が顕著なものであったとしても、ポスト噴射時期などから求めたトルク寄与率をポスト噴射量に乗算した値だけメイン噴射量を減少補正することで容易にトルク抑制できる。よって、ＮＯxパージ中の未燃燃料の還流に起因するエンジントルクの増加を抑制でき、もってトルク変動により車両のドライバビリティが悪化する事態を未然に防止することができる。   Accordingly, the phenomenon that the engine torque increases due to the combustion of the unburned fuel recirculated to the intake side does not occur, and the torque increase during the NOx purge is caused by the combustion of the injected fuel of the post injection shown by hatching in FIG. In the post-injection of the NOx purge, most of the fuel is used for the supply of HC and CO without being combusted. Therefore, the torque increase due to this post-injection is negligible and there is almost no need for torque suppression. Even if the torque increase is remarkable, the torque can be easily suppressed by correcting the decrease in the main injection amount by a value obtained by multiplying the post injection amount by the torque contribution rate obtained from the post injection timing or the like. Therefore, it is possible to suppress an increase in engine torque due to the recirculation of unburned fuel during the NOx purge, thereby preventing a situation in which the drivability of the vehicle is deteriorated due to torque fluctuation.

更に、吸気側への未燃燃料の還流を防止することで、未燃燃料によりＥＧＲ系や吸気系が汚損・劣化する現象も防止でき、もってエンジン１の耐久性を向上できるという効果も得られる。
加えて、未燃燃料の還流による不具合を防止しながらＮＯxパージ中にもＥＧＲ制御を継続できるため、図２に基づいて説明したＥＧＲ還流による種々の効果をＮＯxパージ中にも得ることができる。 Further, by preventing the unburned fuel from flowing back to the intake side, it is possible to prevent the EGR system and the intake system from being polluted and deteriorated by the unburned fuel, and the durability of the engine 1 can be improved. .
In addition, since the EGR control can be continued even during the NOx purge while preventing problems due to the recirculation of unburned fuel, various effects by the EGR recirculation described with reference to FIG. 2 can be obtained even during the NOx purge.

ところで、本実施形態では＃４気筒を含めた全気筒に対してポスト噴射を実行したが、例えば＃１〜＃３気筒に対するポスト噴射のみでＮＯxパージに必要なＨＣ及びＣＯを確保可能なときには、必ずしも＃４気筒に対するポスト噴射を実行する必要はない。よって、図５に示すようにＮＯxパージ時に＃１〜＃３気筒に対してポスト噴射を行い、＃４気筒についてはポスト噴射を中止してもよい。   By the way, in this embodiment, post-injection is executed for all cylinders including the # 4 cylinder. However, for example, when HC and CO necessary for NOx purge can be secured only by post-injection for the # 1 to # 3 cylinders, It is not always necessary to perform post injection for the # 4 cylinder. Therefore, as shown in FIG. 5, post-injection may be performed for the # 1 to # 3 cylinders during NOx purge, and post-injection may be stopped for the # 4 cylinders.

この場合には＃４気筒の排ガス中に未燃燃料が存在しないことから、吸気側への未燃燃料の還流を完全に抑制してこれに起因する不具合を確実に防止できると共に、ＥＧＲガス中の未燃燃料を処理するためのＥＧＲ触媒１２を省略できるという効果も得られる。
［第２実施形態］
次に、本発明をＤＰＦを備えたディーゼルエンジンの制御装置に具体化した一実施形態を説明する。本実施形態は、第１実施形態のＮＯx触媒１０をＤＰＦ及び前段酸化触媒に置換した上で燃料噴射制御の内容を変更したものであり、他の構成は第１実施形態と共通である。従って、同一構成の個所の説明は省略し、相違点を重点的に説明する。 In this case, since there is no unburned fuel in the exhaust gas of the # 4 cylinder, the recirculation of unburned fuel to the intake side can be completely suppressed, and the trouble caused by this can be surely prevented, and in the EGR gas The effect that the EGR catalyst 12 for processing the unburned fuel can be omitted is also obtained.
[Second Embodiment]
Next, an embodiment in which the present invention is embodied in a control device for a diesel engine equipped with a DPF will be described. In the present embodiment, the content of the fuel injection control is changed after the NOx catalyst 10 of the first embodiment is replaced with a DPF and a pre-stage oxidation catalyst, and other configurations are the same as those in the first embodiment. Therefore, the description of the parts having the same configuration is omitted, and the differences will be mainly described.

図６は本実施形態のディーゼルエンジンの制御装置を示す部分構成図であり、この図では排気浄化装置の個所のみを示しているが、他の構成は第１実施形態と同一である。
排気通路９に設けられた排気浄化装置は、排気上流側の前段酸化触媒３１と下流側のＤＰＦ３２とから構成されている。ＤＰＦ３２はハニカム型のセラミック担体からなるウォールフロー式のフィルタであり、排気通路９を経て排出される各気筒の排ガス中のＰＭ（パティキュレートマター）がＤＰＦ３２に捕集される。なお、排気浄化装置の構成はこれに限らず、例えば前段酸化触媒３１を省略する代わりにＤＰＦ３２上に酸化触媒を担持させてもよい。 FIG. 6 is a partial configuration diagram showing a control device for a diesel engine according to the present embodiment. In FIG. 6, only the location of the exhaust purification device is shown, but the other configuration is the same as that of the first embodiment.
The exhaust gas purification device provided in the exhaust passage 9 includes a upstream oxidation catalyst 31 on the upstream side of the exhaust gas and a DPF 32 on the downstream side. The DPF 32 is a wall flow type filter made of a honeycomb type ceramic carrier, and PM (particulate matter) in the exhaust gas of each cylinder discharged through the exhaust passage 9 is collected by the DPF 32. The configuration of the exhaust purification device is not limited to this, and for example, an oxidation catalyst may be supported on the DPF 32 instead of omitting the front-stage oxidation catalyst 31.

ＤＰＦ３２に捕集されたＰＭは、主にエンジン１の高回転高負荷域において連続的に焼却除去されるが（連続再生）、連続再生が望めない運転領域が続いてＤＰＦ３２が飽和限界に達する場合もあり、このような状況ではＥＣＵ２１の制御によりＰＭが強制的に焼却除去される（強制再生）。なお、強制再生の開始時期は、例えばエンジン１の運転状態から推定したＰＭ排出量の積算値が飽和限界に相当する所定値に達したときを目安として判定する。   PM collected in the DPF 32 is continuously incinerated and removed mainly in the high rotation and high load region of the engine 1 (continuous regeneration), but the operation region where continuous regeneration cannot be expected continues and the DPF 32 reaches the saturation limit. In such a situation, PM is forcibly removed by incineration under the control of the ECU 21 (forced regeneration). Note that the forced regeneration start timing is determined, for example, when the integrated value of the PM emission amount estimated from the operating state of the engine 1 reaches a predetermined value corresponding to the saturation limit.

強制再生はポスト噴射により実行され（ポスト噴射制御手段）、まず、メイン噴射後の膨張行程でポスト噴射を行うことで燃焼途中の排ガスを排出する排気昇温により前段酸化触媒３１を昇温し、その後に排気行程のポスト噴射を追加して前段酸化触媒３１にＨＣやＣＯを供給し、これらのＨＣやＣＯが前段酸化触媒３１上で酸化反応したときの反応熱を利用してＤＰＦ３２上のＰＭを燃焼する。勿論、ポスト噴射時期は、膨張行程のみ或いは排気行程のみに限ることなく、それぞれの昇温作用が得られる範囲内で任意に変更できる。   Forced regeneration is performed by post-injection (post-injection control means). First, the temperature of the front-stage oxidation catalyst 31 is increased by exhaust gas temperature increase by exhausting exhaust gas during combustion by performing post-injection in the expansion stroke after main injection, After that, post-injection of the exhaust stroke is added to supply HC and CO to the pre-stage oxidation catalyst 31, and PM on the DPF 32 is utilized using reaction heat when these HC and CO are oxidized on the pre-stage oxidation catalyst 31. To burn. Of course, the post-injection timing is not limited to only the expansion stroke or only the exhaust stroke, and can be arbitrarily changed within a range in which the respective temperature raising actions can be obtained.

そして、この強制再生では上記ＮＯｘパージとは異なり、排気昇温や前段酸化触媒３１での酸化反応のためにトータル空燃比をリーン側に制御しているものの、燃焼途中の排ガスの排出やＨＣ，ＣＯの供給により排ガス中には未燃燃料が存在することから、ＮＯxパージの場合と同じく吸気側への未燃燃料の還流を防止するための燃料噴射制御が必要となり、以下、当該燃料噴射制御について詳述する。   In this forced regeneration, unlike the NOx purge, although the total air-fuel ratio is controlled to the lean side for the exhaust gas temperature rise and the oxidation reaction in the pre-stage oxidation catalyst 31, the exhaust gas exhaust during combustion and HC, Since unburned fuel is present in the exhaust gas due to the supply of CO, fuel injection control is required to prevent the return of unburned fuel to the intake side as in the case of the NOx purge. Will be described in detail.

図７はＥＧＲ還流時に実行されるＤＰＦ強制再生の燃料噴射制御状況を示すタイムチャートであり、強制再生開始当初の排気昇温の段階で、＃１〜＃３気筒に比較して＃４気筒のポスト噴射は別個に設定された噴射量及び噴射時期により実行される。例えば＃１〜＃３気筒に対するポスト噴射の噴射量及び噴射時期は排気昇温を目的として設定される一方、＃４気筒に対するポスト噴射は上記ＮＯxパージの場合と同様にＥＧＲガスとしての還流を考慮して、排ガス中の未燃燃料の抑制、及びＥＧＲ系の耐熱温度を越える温度上昇の抑制を達成可能な好適な値に設定される。特に排気昇温では排ガス温度の上昇によりＥＧＲ系に与えるダメージが懸念されるが、＃４気筒のポスト噴射では噴射量の減少により発熱量を低減するなどの配慮がなされる（ポスト噴射量補正手段）。   FIG. 7 is a time chart showing the fuel injection control status of DPF forced regeneration executed at the time of EGR recirculation, and at the stage of exhaust gas temperature increase at the beginning of forced regeneration, the # 4 cylinder is compared with the # 1 to # 3 cylinders. Post-injection is executed with an injection amount and injection timing set separately. For example, the injection amount and injection timing of post-injection for cylinders # 1 to # 3 are set for the purpose of raising the exhaust gas temperature, while post-injection for cylinder # 4 considers recirculation as EGR gas as in the case of the NOx purge. Thus, it is set to a suitable value that can achieve suppression of unburned fuel in the exhaust gas and suppression of temperature rise exceeding the heat resistance temperature of the EGR system. In particular, when the exhaust gas temperature rises, there is a concern about damage to the EGR system due to an increase in the exhaust gas temperature. However, in the post injection of the # 4 cylinder, consideration is given to reducing the heat generation amount by reducing the injection amount (post injection amount correction means). ).

また、排気昇温を目的としたポスト噴射では燃料の一部が燃焼してトルク発生に寄与することから、上記のようにＥＧＲ系の熱対策として＃４気筒のポスト噴射量を減少した場合、当該＃４気筒が発生するトルクが他気筒より減少して気筒間のトルク格差が発生する。このときのポスト噴射のトルク寄与率はポスト噴射時期などから特定可能なため、図７にハッチングで示すように＃４気筒に対してはポスト噴射のトルク不足分だけメイン噴射量を増加補正している（メイン噴射量補正手段）。これにより各気筒の発生トルクを均等化できるため、ポスト噴射の相違に起因して発生するトルク変動の弊害を未然に回避できる。なお、＃４気筒に対するメイン噴射量を増加補正する代わりに、＃１〜＃３気筒に対するメイン噴射量を減少補正してもよい。   In addition, in post-injection aimed at raising the temperature of exhaust gas, part of the fuel burns and contributes to torque generation. Therefore, when the post-injection amount of the # 4 cylinder is reduced as a countermeasure against EGR heat as described above, The torque generated by the # 4 cylinder is reduced from that of the other cylinders, resulting in a torque difference between the cylinders. Since the post-injection torque contribution ratio at this time can be specified from the post-injection timing and the like, as shown by hatching in FIG. (Main injection amount correction means). As a result, the generated torque of each cylinder can be equalized, so that adverse effects of torque fluctuations caused by the difference in post-injection can be avoided. Instead of increasing the main injection amount for the # 4 cylinder, the main injection amount for the # 1 to # 3 cylinders may be corrected to decrease.

そして、＃４気筒に対する噴射量の減少設定により、ＥＧＲガスに含まれて吸気側に還流される未燃燃料は大幅に減少し、図３にクロスハッチングで示したようにＥＧＲ還流に起因するトルク増加分も大幅に減少し、しかも、このとき＃４気筒の排気空燃比はリーン側に制御されているためＥＧＲガス中の未燃燃料がＥＧＲ触媒１２上で燃焼され、吸気側への未燃燃料の還流が未然に防止される。   The unburned fuel contained in the EGR gas and recirculated to the intake side is greatly reduced by the setting of the injection amount reduction for the # 4 cylinder, and the torque caused by the EGR recirculation as shown by cross hatching in FIG. The increase is also greatly reduced. Moreover, since the exhaust air-fuel ratio of the # 4 cylinder is controlled to the lean side at this time, the unburned fuel in the EGR gas is burned on the EGR catalyst 12 and unburned to the intake side. Fuel recirculation is prevented in advance.

一方、以上の排気昇温により前段酸化触媒３１が活性温度に達すると、ＥＣＵ２１はポスト噴射を継続した状態で、図７に破線で示すように＃１〜＃３気筒に対してＨＣ及びＣＯの供給を目的としたポスト噴射を追加する。当該ポスト噴射の噴射時期は、噴射燃料の燃焼防止のために排気昇温のポスト噴射の燃焼終了後に設定され、ポスト噴射の噴射量は、前段酸化触媒３１上で適切な酸化反応を生起可能な過不足のないＨＣ及びＣＯが供給されるように設定される。これに対して＃４気筒はポスト噴射が追加されずに上記排気昇温時と同一運転状態のため、この段階においても吸気側への未燃燃料の還流が防止されている。   On the other hand, when the pre-stage oxidation catalyst 31 reaches the activation temperature due to the above exhaust gas temperature increase, the ECU 21 continues the post injection, and the HC and CO of the # 1 to # 3 cylinders are shown in FIG. Add post-injection for supply purposes. The injection timing of the post-injection is set after completion of the post-injection combustion of the exhaust gas temperature to prevent combustion of the injected fuel, and the injection amount of the post-injection can cause an appropriate oxidation reaction on the pre-stage oxidation catalyst 31. It is set so that HC and CO without excess and deficiency are supplied. On the other hand, the # 4 cylinder is not operated with post-injection and is in the same operating state as when the exhaust gas temperature is raised, so that unburned fuel is prevented from returning to the intake side even at this stage.

よって、強制再生中の未燃燃料の還流に起因するエンジントルクの増加を抑制して、トルク変動により車両のドライバビリティが悪化する事態を未然に防止できると共に、未燃燃料によりＥＧＲ系や吸気系が汚損・劣化する現象も防止でき、さらに強制再生中にもＥＧＲ制御を継続できるため、ＥＧＲ還流による種々の効果を強制再生中にも得ることができる。   Therefore, it is possible to suppress an increase in engine torque due to the recirculation of unburned fuel during forced regeneration and prevent a situation in which vehicle drivability deteriorates due to torque fluctuations. As a result, the EGR control can be continued even during forced regeneration, so that various effects of EGR reflux can be obtained even during forced regeneration.

なお、図５に基づくＮＯxパージの説明と同様に、この強制再生でも＃１〜＃３気筒に対するポスト噴射のみで排気昇温を達成可能であれば、＃４気筒についてはポスト噴射を中止してもよい。また、前段酸化触媒３１が活性温度に達した時点で、全気筒に対する排気昇温用のポスト噴射を中止して、＃１〜＃３気筒に対するＨＣ及びＣＯ供給のためのポスト噴射のみを実行するようにしてもよい。   Similarly to the explanation of the NOx purge based on FIG. 5, if the exhaust gas temperature can be increased only by the post injection for the # 1 to # 3 cylinders even in this forced regeneration, the post injection is stopped for the # 4 cylinder. Also good. Further, when the pre-stage oxidation catalyst 31 reaches the activation temperature, the post-injection for exhaust gas temperature raising for all the cylinders is stopped, and only the post-injection for supplying HC and CO to the # 1 to # 3 cylinders is executed. You may do it.

以上で実施形態の説明を終えるが、本発明の態様はこの実施形態に限定されるものではない。例えば上記各実施形態では、吸蔵型ＮＯx触媒１０やＤＰＦ３２を備えたディーゼルエンジン１の制御装置に具体化したが、内燃機関の種別はこれに限ることはなく、例えばガソリンエンジンに適用してもよい。
また、上記第１実施形態ではＮＯx触媒１０に対するＮＯxパージを目的としてポスト噴射を実行し、第２実施形態ではＤＰＦ３２に対する強制再生を目的としてポスト噴射を実行したが、これらの場合に限ることはなく、例えば上記ＮＯx触媒１０に吸蔵されたＳＯx（硫黄成分の酸化物）を強制的に除去するためのＳパージを目的としてポスト噴射を実行したり、或いは冷態始動時の三元触媒の早期活性化を目的として本実施形態のポスト噴射を実行したりしてもよい。 This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in each of the embodiments described above, the control device for the diesel engine 1 including the storage-type NOx catalyst 10 and the DPF 32 is embodied. However, the type of the internal combustion engine is not limited to this, and may be applied to, for example, a gasoline engine. .
In the first embodiment, post injection is executed for the purpose of NOx purge for the NOx catalyst 10, and post injection is executed for the purpose of forced regeneration for the DPF 32 in the second embodiment. However, the present invention is not limited to these cases. For example, post injection is performed for the purpose of S purge for forcibly removing SOx (sulfur component oxide) occluded in the NOx catalyst 10, or early activation of the three-way catalyst at the time of cold start The post-injection of the present embodiment may be executed for the purpose of making it easier.

さらに、上記各実施形態では＃４気筒を特定気筒としたが、特定気筒として設定する気筒はいずれの気筒でもよいし、その数も１気筒に限らず複数気筒であってもよい。   Further, in the above embodiments, the # 4 cylinder is the specific cylinder, but the cylinder set as the specific cylinder may be any cylinder, and the number is not limited to one, and may be a plurality of cylinders.

第１実施形態のＮＯx触媒を備えたディーゼルエンジンの制御装置を示す全体構成図である。It is a whole block diagram which shows the control apparatus of the diesel engine provided with the NOx catalyst of 1st Embodiment. ＥＧＲ還流による効果を示した説明図である。It is explanatory drawing which showed the effect by EGR recirculation | reflux. ＥＧＲ還流時に実行されるＮＯxパージの燃料噴射制御状況を示すタイムチャートである。It is a time chart which shows the fuel-injection control condition of NOx purge performed at the time of EGR recirculation | reflux. 同じくＥＧＲ還流時に実行されるＮＯxパージのポスト噴射によるトルク増加状況を示すタイムチャートである。It is a time chart which shows the torque increase condition by the post injection of NOx purge similarly performed at the time of EGR recirculation | reflux. ＥＧＲ還流時に実行されるＮＯxパージの燃料噴射制御状況の別例を示すタイムチャートである。It is a time chart which shows another example of the fuel injection control situation of NOx purge performed at the time of EGR recirculation. 第２実施形態のＤＰＦを備えたディーゼルエンジンの制御装置を示す部分構成図である。It is a partial block diagram which shows the control apparatus of the diesel engine provided with DPF of 2nd Embodiment. ＥＧＲ還流時に実行されるＤＰＦ強制再生の燃料噴射制御状況を示すタイムチャートである。It is a time chart which shows the fuel injection control condition of DPF forced regeneration performed at the time of EGR recirculation. 従来技術のＥＧＲ還流時に実行されるポスト噴射によるトルク増加状況を示すタイムチャートである。It is a time chart which shows the torque increase condition by the post injection performed at the time of EGR recirculation of a prior art.

符号の説明Explanation of symbols

１ エンジン（内燃機関）
１１ ＥＧＲ通路（ＥＧＲ手段）
１４ ＥＧＲバルブ（ＥＧＲ手段）
２１ ＥＣＵ（ポスト噴射制御手段、ポスト噴射量補正手段、メイン噴射量補正手段） 1 engine (internal combustion engine)
11 EGR passage (EGR means)
14 EGR valve (EGR means)
21 ECU (post injection control means, post injection amount correction means, main injection amount correction means)

Claims (5)

内燃機関の特定気筒のみを該内燃機関の排気側と連通させるＥＧＲ通路、及び該ＥＧＲ通路の開度を調整可能なＥＧＲバルブから構成され、上記特定気筒の排ガスをＥＧＲガスとして吸気側に還流するＥＧＲ手段と、
上記内燃機関の各気筒に対してメイン噴射後にポスト噴射を実行するポスト噴射制御手段と、
上記ＥＧＲ手段によるＥＧＲガスの還流時に上記ポスト噴射制御手段によりポスト噴射が実行されたときに、上記特定気筒に対するポスト噴射量を他気筒に対するポスト噴射量より減少補正するポスト噴射量補正手段と
を備えたことを特徴とする内燃機関の制御装置。 An EGR passage that allows only a specific cylinder of the internal combustion engine to communicate with the exhaust side of the internal combustion engine, and an EGR valve that can adjust the opening of the EGR passage, and recirculates the exhaust gas of the specific cylinder to the intake side as EGR gas EGR means;
Post injection control means for executing post injection after main injection for each cylinder of the internal combustion engine;
Post injection amount correcting means for correcting the post injection amount for the specific cylinder to be smaller than the post injection amount for the other cylinders when post injection is executed by the post injection control means when the EGR gas is recirculated by the EGR means. A control apparatus for an internal combustion engine, characterized by comprising: 上記ポスト噴射量補正手段は、上記特定気筒に対するポスト噴射量を０に補正することを特徴とする請求項１記載の内燃機関の制御装置。   2. The control apparatus for an internal combustion engine according to claim 1, wherein the post injection amount correcting means corrects the post injection amount for the specific cylinder to zero. 上記ＥＧＲ手段のＥＧＲ通路には、上記ＥＧＲガス中の未燃燃料を燃焼させるＥＧＲ触媒が備えられたことを特徴とする請求項１または２記載の内燃機関の制御装置。   3. The control apparatus for an internal combustion engine according to claim 1, wherein an EGR catalyst for burning unburned fuel in the EGR gas is provided in the EGR passage of the EGR means. 上記ポスト噴射量補正手段は、上記特定気筒の排気空燃比がリーン側となるように該特定気筒に対するポスト噴射量を補正することを特徴とする請求項３記載の内燃機関の制御装置。   4. The control apparatus for an internal combustion engine according to claim 3, wherein the post injection amount correcting means corrects the post injection amount for the specific cylinder so that the exhaust air-fuel ratio of the specific cylinder is on the lean side. 上記特定気筒と他気筒とのポスト噴射量の相違によるトルク格差を縮小する方向に、上記特定気筒または他気筒の少なくとも一方のメイン噴射量を補正するメイン噴射量補正手段を備えたことを特徴とする請求項１乃至４のいずれかに記載の内燃機関の制御装置。   And a main injection amount correcting means for correcting a main injection amount of at least one of the specific cylinder and the other cylinder in a direction to reduce a torque difference due to a difference in post injection amount between the specific cylinder and the other cylinder. The control apparatus for an internal combustion engine according to any one of claims 1 to 4.
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