JP2007023959A - Pm accumulation-quantity estimation device - Google Patents

Pm accumulation-quantity estimation device Download PDF

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JP2007023959A
JP2007023959A JP2005209790A JP2005209790A JP2007023959A JP 2007023959 A JP2007023959 A JP 2007023959A JP 2005209790 A JP2005209790 A JP 2005209790A JP 2005209790 A JP2005209790 A JP 2005209790A JP 2007023959 A JP2007023959 A JP 2007023959A
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excess air
air ratio
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ratio
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JP4622719B2 (en
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Kosuke Yasuhara
功祐 安原
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Nissan Motor Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To improve estimation accuracy of PM accumulation quantity of DPF. <P>SOLUTION: A base value of PM emission quantity is calculated from engine rotation speed Ne and fuel injection quantity Qf. Target excess air factor tλ and error rate Δλ=(actual excess air factor rλ - target excess air factor tλ)/(actual excess air factor rλ) are used as a first parameter A and a second parameter B respectively, and PM emission quantity correction factor is calculated according to the same. The base value of PM emission quantity is corrected by multiplying the same by the correction factor and PM emission quantity after correction is integrated to PM emission quantity is estimated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、内燃機関の排気通路に配置されて排気中のＰＭ（Particulate Matter；粒子状物質）を捕集するフィルタの再生時期の判断のため、前記フィルタのＰＭ堆積量を推定する装置に関する。   The present invention relates to an apparatus for estimating a PM accumulation amount of a filter for determining a regeneration time of a filter that is disposed in an exhaust passage of an internal combustion engine and collects PM (Particulate Matter) in exhaust gas.

従来のＰＭ堆積量推定装置としては、特許文献１に記載されているように、１）圧力センサによりフィルタの前後差圧を検出し、これに基づいてＰＭ堆積量を推定するものと、２）機関の運転状態（燃料噴射量、機関回転数、ＥＧＲ率など）に応じてＰＭ排出量を算出し、これを積算してＰＭ堆積量を推定するものとが知られている。尚、特許文献１に記載の発明では、両方の推定を実施し、より信頼性の高い方の推定データを選択して、再生時期の判断に用いている。
特開２００４−１３２３５８号公報 As a conventional PM accumulation amount estimation device, as described in Patent Document 1, 1) a pressure sensor detects a differential pressure across a filter and estimates the PM accumulation amount based on this, and 2) It is known that the PM emission amount is calculated according to the engine operating state (fuel injection amount, engine speed, EGR rate, etc.), and this is integrated to estimate the PM accumulation amount. In the invention described in Patent Document 1, both estimations are performed, and the more reliable estimation data is selected and used for judging the reproduction time.
JP 2004-132358 A

ところで、機関の運転状態に応じてＰＭ排出量を算出し、これを積算してＰＭ堆積量を推定する場合、予め実験で求めた機関の運転状態に対するＰＭ排出量のデータを用いるが、これは定常条件でのデータであり、過渡条件において増大するＰＭ排出量については考慮していないため、ＰＭ堆積量の推定値が実際値より少なくなり、フィルタの再生時期の判断を誤るおそれがある。   By the way, when calculating the PM emission amount according to the operating state of the engine and estimating the PM accumulation amount by integrating the PM emission amount, the PM emission amount data with respect to the operating state of the engine obtained in advance by experiment is used. Since it is data in a steady condition and does not consider the PM emission amount that increases in the transient condition, the estimated value of the PM accumulation amount becomes smaller than the actual value, and there is a possibility that the judgment of the regeneration timing of the filter is erroneous.

そのため、実験で求めたデータを何倍かにして用いることにより、ＰＭ堆積量の推定値を底上げする方法もあるが、このようにすると、フィルタ再生サイクルが一律に短くなり、燃費の悪化の原因となる。
本発明は、このような実状に鑑み、機関の運転状態に応じてＰＭ排出量を算出し、これを積算してＰＭ堆積量を推定する場合に、その推定精度を大幅に向上させることを目的とする。 For this reason, there is a method of raising the estimated value of the PM accumulation amount by using the data obtained by the experiment several times. However, in this case, the filter regeneration cycle is uniformly shortened, and the cause of deterioration in fuel consumption is caused. It becomes.
In view of such a situation, the present invention aims to greatly improve the estimation accuracy when calculating the PM emission amount according to the operating state of the engine and integrating the PM emission amount to estimate the PM accumulation amount. And

このため、本発明は、機関の運転状態に応じて算出したＰＭ排出量を空気過剰率に応じて補正し、補正後のＰＭ排出量を積算してフィルタのＰＭ堆積量を算出する構成とする。   Therefore, the present invention is configured to correct the PM emission amount calculated according to the operating state of the engine according to the excess air ratio, and to calculate the PM accumulation amount of the filter by integrating the corrected PM emission amount. .

本発明によれば、過渡条件において空気過剰率が変動することに着目し、ＰＭ排出量を空気過剰率に応じて補正することで、過渡条件でのＰＭ排出量の増大を考慮に入れることができ、これによりＰＭ堆積量の推定精度を向上させることができる。   According to the present invention, attention is paid to the fact that the excess air ratio fluctuates under transient conditions, and the increase in PM emissions under transient conditions can be taken into account by correcting the PM emissions according to the excess air ratio. This can improve the estimation accuracy of the PM accumulation amount.

以下に本発明の実施の形態を図面に基づいて説明する。
図１は本発明の一実施形態を示す内燃機関（具体的にはディーゼルエンジン）のシステム図である。
ディーゼルエンジン１の吸気通路２には可変ノズル型の過給機（ターボチャージャ）３の吸気コンプレッサが備えられ、吸入空気は吸気コンプレッサによって過給され、インタークーラ４で冷却され、吸気絞り弁５を通過した後、コレクタ６を経て、各気筒の燃焼室内へ流入する。燃料は、コモンレール式燃料噴射装置により、すなわち、高圧燃料ポンプ７により高圧化されてコモンレール８に送られ、各気筒の燃料噴射弁９から燃焼室内へ直接噴射される。燃焼室内に流入した空気と噴射された燃料はここで圧縮着火により燃焼し、排気は排気通路１０へ流出する。 Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a system diagram of an internal combustion engine (specifically, a diesel engine) showing an embodiment of the present invention.
The intake passage 2 of the diesel engine 1 is provided with an intake compressor of a variable nozzle type supercharger (turbocharger) 3. The intake air is supercharged by the intake compressor and cooled by the intercooler 4. After passing, it flows through the collector 6 and into the combustion chamber of each cylinder. The fuel is increased in pressure by the common rail type fuel injection device, that is, by the high pressure fuel pump 7, sent to the common rail 8, and directly injected from the fuel injection valve 9 of each cylinder into the combustion chamber. The air that has flowed into the combustion chamber and the injected fuel are combusted by compression ignition, and the exhaust gas flows out to the exhaust passage 10.

排気通路１０へ流出した排気の一部は、ＥＧＲガスとして、ＥＧＲ装置により、すなわち、ＥＧＲ通路１１によりＥＧＲ弁１２を介して、吸気側へ還流される。排気の残りは、可変ノズル型の過給機３の排気タービンを通り、これを駆動する。
ここで、排気通路１０の排気タービン下流には、ディーゼル・パティキュレート・フィルタ（以下「ＤＰＦ」という）１３を設け、これにより排気中のＰＭを捕集する。この他、酸化触媒やＮＯｘトラップ触媒なども設けるが、図示は省略した。 A part of the exhaust gas flowing into the exhaust passage 10 is recirculated as EGR gas to the intake side by the EGR device, that is, through the EGR valve 12 through the EGR valve 11. The remainder of the exhaust passes through the exhaust turbine of the variable nozzle type supercharger 3 and drives it.
Here, a diesel particulate filter (hereinafter referred to as “DPF”) 13 is provided downstream of the exhaust turbine in the exhaust passage 10 to collect PM in the exhaust. In addition, although an oxidation catalyst, a NOx trap catalyst, and the like are provided, the illustration is omitted.

エンジンコントロールユニット（以下「ＥＣＵ」という）２０には、エンジン１の制御のため、アクセル開度ＡＰＯ検出用のアクセル開度センサ２１、エンジン回転数Ｎｅ検出用の回転数センサ２２、吸入空気量Ｑａ検出用のエアフローメータ２３、排気通路１０にてエンジン１からの排気成分濃度を検出することにより空燃比を検出可能な空燃比センサ２４などから、信号が入力されている。   In order to control the engine 1, an engine control unit (hereinafter referred to as “ECU”) 20 includes an accelerator opening sensor 21 for detecting an accelerator opening APO, a rotation speed sensor 22 for detecting an engine rotation speed Ne, and an intake air amount Qa. A signal is input from an air flow meter 23 for detection, an air-fuel ratio sensor 24 that can detect an air-fuel ratio by detecting an exhaust component concentration from the engine 1 in the exhaust passage 10 and the like.

ＥＣＵ２０は、これらの入力信号に基づいて、燃料噴射弁９による燃料噴射の燃料噴射量及び噴射時期制御のための燃料噴射弁９への燃料噴射指令信号、吸気絞り弁５への開度指令信号、ＥＧＲ弁１２への開度指令信号、過給機３の可変ノズル機構１５へのノズル開度指令信号等を出力する。
ここにおいて、ＥＣＵ２０では、ＤＰＦ１３でのＰＭの捕集によりＰＭ堆積量が増加すると、排気抵抗が増加して、運転性が悪化することから、ＰＭ堆積量を推定し、これが所定のしきい値を超えたときに再生時期と判断し、燃料噴射時期の遅角（あるいはポスト噴射）などにより排気温度を上昇させて、再生処理（ＰＭの燃焼除去）を行う。 Based on these input signals, the ECU 20 controls the fuel injection amount of the fuel injection by the fuel injection valve 9 and the fuel injection command signal to the fuel injection valve 9 for injection timing control, and the opening degree command signal to the intake throttle valve 5. , An opening command signal to the EGR valve 12, a nozzle opening command signal to the variable nozzle mechanism 15 of the supercharger 3, and the like are output.
Here, the ECU 20 estimates the PM accumulation amount because the exhaust resistance increases and the drivability deteriorates when the PM accumulation amount increases due to the collection of PM by the DPF 13. When it exceeds, the regeneration time is determined, and the exhaust temperature is increased by delaying the fuel injection timing (or post injection) or the like, and regeneration processing (PM combustion removal) is performed.

次に、本発明でのＰＭ堆積量の推定について説明する。
図２はＰＭ堆積量推定の概要を示すブロック図である。
ＰＭ排出量（基本値）マップ１０１は、予め定常実験により、エンジンの運転状態、詳しくはエンジン回転数Ｎｅと負荷（例えば燃料噴射量）Ｑｆとに応じ、ＰＭ排出量を求めて、記憶させたもので、このマップを参照して、エンジン回転数Ｎｅと負荷（燃料噴射量）Ｑｆとから、ＰＭ排出量（単位時間当たりのＰＭ排出量）を算出する。尚、負荷としては、燃料噴射量の他、トルク等を用いてもよい。 Next, estimation of the PM accumulation amount in the present invention will be described.
FIG. 2 is a block diagram showing an outline of PM accumulation amount estimation.
The PM emission amount (basic value) map 101 was previously determined and memorized in accordance with the engine operating state, specifically, the engine speed Ne and the load (for example, fuel injection amount) Qf by a steady experiment. Therefore, referring to this map, the PM emission amount (PM emission amount per unit time) is calculated from the engine speed Ne and the load (fuel injection amount) Qf. In addition to the fuel injection amount, torque or the like may be used as the load.

ＰＭ排出量補正係数マップ１０２は、空気過剰率に応じて、補正係数を算出するためのもので、空気過剰率としては、目標空気過剰率と実空気過剰率との両方を用いる。
より具体的には、第１パラメータＡとして、目標空気過剰率ｔλを用い、第２パラメータＢとして、実空気過剰率ｒλと目標空気過剰率ｔλとの差（ｒλ−ｔλ）、又は、比（ｒλ／ｔλ）を用いる。 The PM emission amount correction coefficient map 102 is used to calculate a correction coefficient in accordance with the excess air ratio, and both the target excess air ratio and the actual excess air ratio are used as the excess air ratio.
More specifically, the target excess air ratio tλ is used as the first parameter A, and the difference between the actual excess air ratio rλ and the target excess air ratio tλ (rλ−tλ) or the ratio ( rλ / tλ) is used.

また、第２パラメータＢとして、実空気過剰率ｒλと目標空気過剰率ｔλとの差（誤差；ｒλ―ｔλ）を用いる場合は、これを、実空気過剰率ｒλ又は目標空気過剰率ｔλに対する比に変換した値（誤差率）を用いるとよい。
この場合、Ｂ＝（ｒλ−ｔλ）／ｔλ 又は、Ｂ＝（ｒλ−ｔλ）／ｒλ となる。
乗算部１０３は、マップ１０１から求めたＰＭ排出量（基本値）に、マップ１０２から求めたＰＭ排出量補正係数を乗じて、ＰＭ排出量（＝基本値×補正係数）を算出する。 When the difference (error; rλ−tλ) between the actual excess air ratio rλ and the target excess air ratio tλ is used as the second parameter B, this is expressed as a ratio to the actual excess air ratio rλ or the target excess air ratio tλ. The value (error rate) converted to is preferably used.
In this case, B = (rλ−tλ) / tλ or B = (rλ−tλ) / rλ.
The multiplier 103 multiplies the PM emission amount (basic value) obtained from the map 101 by the PM emission amount correction coefficient obtained from the map 102 to calculate the PM emission amount (= basic value × correction coefficient).

積算部１０４は、補正後のＰＭ排出量を積算することにより、ＤＰＦのＰＭ堆積量を推定する。
次に目標空気過剰率ｔλ、実空気過剰率ｒλの求め方について説明する。
目標空気過剰率ｔλは、目標空気量ｔＱａと、実燃料噴射量Ｑｆとから、次式により算出する。 The integrating unit 104 estimates the PM accumulation amount of the DPF by integrating the corrected PM discharge amount.
Next, how to obtain the target excess air ratio tλ and the actual excess air ratio rλ will be described.
The target excess air ratio tλ is calculated from the target air amount tQa and the actual fuel injection amount Qf by the following equation.

目標空気過剰率ｔλ＝目標空気量ｔＱａ／（実燃料噴射量Ｑｆ×１４．６）
尚、実燃料噴射量Ｑｆは、ＥＣＵによる燃料噴射量の指令値でよく、これはアクセル開度ＡＰＯとエンジン回転数Ｎｅとから算出される。目標空気量ｔＱａは、ＥＣＵにて燃料噴射量Ｑｆとエンジン回転数Ｎｅとに基づいて算出される値とする。
実空気過剰率ｒλは、実空気量ｒＱａと、実燃料噴射量Ｑｆとから、次式により算出する。 Target excess air ratio tλ = target air amount tQa / (actual fuel injection amount Qf × 14.6)
The actual fuel injection amount Qf may be a command value for the fuel injection amount by the ECU, and is calculated from the accelerator opening APO and the engine speed Ne. The target air amount tQa is a value calculated by the ECU based on the fuel injection amount Qf and the engine speed Ne.
The actual excess air ratio rλ is calculated from the actual air amount rQa and the actual fuel injection amount Qf by the following equation.

実空気過剰率ｒλ＝実空気量ｒＱａ／（実燃料噴射量Ｑｆ×１４．６）
尚、実空気量ｒＱａは、エアフローメータ出力に基づく検出値とする。
目標空気過剰率ｔλに対する実空気過剰率ｒλの誤差を学習し、該学習に基づく学習値（学習補正係数）Ｋで空気量を補正制御する学習制御手段を備える場合、実空気量と実燃料噴射量とに基づいて算出した実空気過剰率ｒλは、前記学習値Ｋで補正するとよい。 Actual excess air ratio rλ = actual air amount rQa / (actual fuel injection amount Qf × 14.6)
The actual air amount rQa is a detected value based on the air flow meter output.
When learning control means for learning an error of the actual excess air ratio rλ with respect to the target excess air ratio tλ and correcting and controlling the air amount with a learning value (learning correction coefficient) K based on the learning is provided, the actual air amount and the actual fuel injection The actual excess air ratio rλ calculated based on the amount may be corrected with the learning value K.

この場合、実空気過剰率のｒλの計算式は、次式のごとくとなる。
実空気過剰率ｒλ＝〔実空気量ｒＱａ／（実燃料噴射量Ｑｆ×１４．６）〕／Ｋ
また、実空気過剰率ｒλは、上記の計算式による計算値とする他、空燃比センサによる検出値としてもよい。
図３はＰＭ堆積量推定のフローチャートである。 In this case, the equation for calculating the actual excess air ratio rλ is as follows.
Actual excess air ratio rλ = [actual air amount rQa / (actual fuel injection amount Qf × 14.6)] / K
Further, the actual excess air ratio rλ may be a value detected by the air-fuel ratio sensor in addition to the value calculated by the above formula.
FIG. 3 is a flowchart of PM accumulation amount estimation.

Ｓ１では、エンジン回転数Ｎｅ、燃料噴射量Ｑｆを読込む。
Ｓ２では、図４のマップを参照し、エンジン回転数Ｎｅと燃料噴射量ＱｆとからＰＭ排出量基本値を検索する。図４のマップからわかるように、エンジン回転数Ｎｅが高いほど、また燃料噴射量Ｑｆが多いほど、ＰＭ排出量基本値は大となる。
Ｓ３では、目標空気量ｔＱａ、実空気量ｒＱａを読込む。目標空気量ｔＱａはＥＣＵでの計算値、実空気量ｔＱａはエアフローメータによる検出値である。 In S1, the engine speed Ne and the fuel injection amount Qf are read.
In S2, the PM emission basic value is searched from the engine speed Ne and the fuel injection amount Qf with reference to the map of FIG. As can be seen from the map of FIG. 4, the PM emission basic value increases as the engine speed Ne increases and the fuel injection amount Qf increases.
In S3, the target air amount tQa and the actual air amount rQa are read. The target air amount tQa is a value calculated by the ECU, and the actual air amount tQa is a value detected by an air flow meter.

Ｓ４では、目標空気量ｔＱａと燃料噴射量Ｑｆとから、次式により、目標空気過剰率ｔλを算出する。
ｔλ＝ｔＱａ／（Ｑｆ×１４．６）
Ｓ５では、実空気量ｒＱａと燃料噴射量Ｑｆとから、次式により、実空気過剰率ｒλを算出する。 In S4, the target excess air ratio tλ is calculated from the target air amount tQa and the fuel injection amount Qf by the following equation.
tλ = tQa / (Qf × 14.6)
In S5, the actual excess air ratio rλ is calculated from the actual air amount rQa and the fuel injection amount Qf by the following equation.

ｒλ＝ｒＱａ／（Ｑｆ×１４．６）
Ｓ６では、目標空気過剰率に対する実空気過剰率の誤差を学習し、該学習に基づく学習値（学習補正係数）Ｋで空気量を補正制御する学習制御手段を備える場合に、学習値Ｋを読込み、Ｓ５で算出した実空気過剰率ｒλを学習値Ｋで割ることにより、実空気過剰率ｒλを補正する。 rλ = rQa / (Qf × 14.6)
In S6, the learning value K is read when learning the error of the actual excess air ratio with respect to the target excess air ratio and learning control means for correcting and controlling the air amount with the learning value (learning correction coefficient) K based on the learning. The actual excess air ratio rλ is corrected by dividing the actual excess air ratio rλ calculated in S5 by the learning value K.

ｒλ＝ｒλ／Ｋ
Ｓ７では、実空気過剰率ｒλと目標空気過剰率ｔλとの差を、実空気過剰率ｒλで割ることにより、誤差率Δλを算出する。
Δλ＝（ｒλ−ｔλ）／ｒλ
又は、実空気過剰率ｒλと目標空気過剰率ｔλとの差を、目標空気過剰率ｔλで割ることにより、誤差率Δλ＝（ｒλ−ｔλ）／ｔλを算出するようにしてもよい。 rλ = rλ / K
In S7, the error rate Δλ is calculated by dividing the difference between the actual excess air ratio rλ and the target excess air ratio tλ by the actual excess air ratio rλ.
Δλ = (rλ−tλ) / rλ
Alternatively, the error rate Δλ = (rλ−tλ) / tλ may be calculated by dividing the difference between the actual excess air ratio rλ and the target excess air ratio tλ by the target excess air ratio tλ.

Ｓ８では、図５のマップを参照し、目標空気過剰率ｔλと誤差率Δλとから、ＰＭ排出量補正係数を検索する。図５からわかるように、空気過剰率の誤差率Δλがリッチ側に大きくなるほど、ＰＭ排出量補正係数は大となり、更に、目標空気過剰率ｔλがリッチ側になるほど、ＰＭ排出量補正係数は更に大となる。尚、誤差率Δλがリーン側のとき、ＰＭ排出量補正係数は１（補正なし）となる。   In S8, the PM exhaust amount correction coefficient is searched from the target excess air rate tλ and the error rate Δλ with reference to the map of FIG. As can be seen from FIG. 5, the PM exhaust amount correction coefficient increases as the error rate Δλ of the excess air ratio increases toward the rich side, and further, the PM exhaust amount correction coefficient further increases as the target excess air ratio tλ increases toward the rich side. Become big. When the error rate Δλ is on the lean side, the PM emission amount correction coefficient is 1 (no correction).

尚、図６の特性ａは、空気過剰率λと、ＰＭ排出量との一般的な関係を示している。特性ｂは、特性ａでのλ＝１．３でのＰＭ排出量を基準値として、各λでのＰＭ排出量の基準値に対する比を算出することにより、空気過剰率λと、ＰＭ排出量の基準値に対する比との関係を示している。図５のマップは、このような特性をもとに作成される。
Ｓ９では、Ｓ２で求めたＰＭ排出量（基本値）に、Ｓ８で求めたＰＭ排出量補正係数を乗じて、ＰＭ排出量（＝基本値×補正係数）を算出する。 The characteristic a in FIG. 6 shows a general relationship between the excess air ratio λ and the PM emission amount. The characteristic b is calculated by calculating the ratio of the PM discharge amount at each λ to the reference value by using the PM discharge amount at λ = 1.3 in the characteristic a as a reference value. The relationship with the ratio with respect to the reference value is shown. The map of FIG. 5 is created based on such characteristics.
In S9, the PM emission amount (= basic value × correction coefficient) is calculated by multiplying the PM emission amount (basic value) obtained in S2 by the PM emission amount correction coefficient obtained in S8.

Ｓ１０では、補正後のＰＭ排出量を積算することにより、ＰＭ堆積量（＝ΣＰＭ排出量）を推定する。
図７は実空気過剰率を空燃比センサにより検出する場合のフローチャートである。
異なる部分についてのみ説明すると、Ｓ３では、目標空気量ｔＱａのみを読込む。
Ｓ５では、空燃比センサ信号により、実空気過剰率ｒλを検出する。従って、図６のＳ６のような補正の必要はなくなる。他は同じである。 In S10, the PM accumulation amount (= ΣPM emission amount) is estimated by integrating the corrected PM emission amount.
FIG. 7 is a flowchart in the case where the actual excess air ratio is detected by the air-fuel ratio sensor.
To explain only the different parts, only the target air amount tQa is read in S3.
In S5, the actual excess air ratio rλ is detected from the air-fuel ratio sensor signal. Accordingly, there is no need for correction as in S6 of FIG. Others are the same.

本実施形態によれば、過渡条件において空気過剰率が変動することに着目し、定常条件での運転状態に応じて算出したＰＭ排出量を空気過剰率に応じて補正することで、過渡条件でのＰＭ排出量の増大を考慮に入れることができ、これによりＰＭ堆積量の推定精度を向上させることができる。
また、本実施形態によれば、目標空気過剰率、及び、実空気過剰率に応じて、補正することにより、過渡条件で実、目標空気過剰率が誤差を持つ場合に増大するＰＭ排出量を運転状態に応じたＰＭ排出特性を変えずに推定することができ、適合範囲も少なくてすむ。 According to the present embodiment, paying attention to the fact that the excess air ratio fluctuates under transient conditions, by correcting the PM emission amount calculated according to the operating state under steady conditions according to the excess air ratio, The increase in the PM emission amount can be taken into consideration, and this can improve the estimation accuracy of the PM deposition amount.
Further, according to the present embodiment, by correcting according to the target excess air ratio and the actual excess air ratio, the PM emission amount that increases when the target excess air ratio has an error in the transient condition is actually increased. It is possible to estimate without changing the PM emission characteristic according to the operating state, and it is possible to reduce the conforming range.

また、本実施形態によれば、第１パラメータとして、目標空気過剰率、第２パラメータとして、実空気過剰率と目標空気過剰率との差（ｒλ−ｔλ）又は比（ｒλ／ｔλ）を用い、これらに応じて補正することにより、過渡条件で実空気過剰率が目標空気過剰率よりも過濃になることで、予測よりも多くのＰＭを発生させているという状況等を補償することができる。   Further, according to the present embodiment, the target excess air ratio is used as the first parameter, and the difference (rλ−tλ) or ratio (rλ / tλ) between the actual excess air ratio and the target excess air ratio is used as the second parameter. By correcting according to these, it is possible to compensate for a situation in which the actual excess air ratio becomes excessively higher than the target excess air ratio under transient conditions, thereby generating more PM than expected. it can.

また、本実施形態によれば、前記第２パラメータとして、実空気過剰率と目標空気過剰率との差（ｒλ−ｔλ）を用いる場合に、これを実空気過剰率ｔλ又は目標空気過剰率ｔλに対する比に変換した値を用いることにより、実空気過剰率と目標空気過剰率の誤差に対して、誤差の絶対値は同じでも、もとの空気過剰率に応じて実際には感度が違うのを、的確に反映して、補償することができる。   According to the present embodiment, when the difference (rλ−tλ) between the actual excess air ratio and the target excess air ratio is used as the second parameter, this is used as the actual excess air ratio tλ or the target excess air ratio tλ. By using the value converted to the ratio to the actual excess air ratio and the target excess air ratio error, the sensitivity is actually different depending on the original excess air ratio even though the absolute value of the error is the same. Can be accurately reflected and compensated.

この場合、特に、分母の空気過剰率として、実空気過剰率ｒλを用いることにより、すなわち、ＰＭ発生に最も影響の大きい実空気過剰率の感度を考慮することで、図７に示すような実際の空気過剰率とＰＭ発生量の特性から直接求めた比を係数として、補正係数マップに適用することができる。
分母の空気過剰率として、目標空気過剰率ｔλを用いる場合は、実空気過剰率との誤差分だけ適合が余分に必要となるが、補償目的は満足させることができる。 In this case, in particular, by using the actual excess air ratio rλ as the excess air ratio of the denominator, that is, by considering the sensitivity of the actual excess air ratio that has the greatest influence on the PM generation, the actual excess air ratio as shown in FIG. The ratio directly obtained from the characteristics of the excess air ratio and the amount of PM generated can be applied to the correction coefficient map as a coefficient.
When the target excess air ratio tλ is used as the excess air ratio of the denominator, an extra adaptation is required by an error from the actual excess air ratio, but the compensation purpose can be satisfied.

また、本実施形態によれば、目標空気過剰率は、目標空気量と実燃料噴射量とに基づいて算出することにより、スモーク限界にかかるような運転が実施された場合に、実空気過剰率との誤差が小さくなってしまったり、補正係数マップの第１パラメータＡが過濃になってしまったりすることを防止できる。
また、本実施形態によれば、実空気過剰率は、実空気量と実燃料噴射量とに基づいて算出するが、これは、空気量のバラツキが空気過剰率に及ぼす影響が大きいからであり、また空気過剰率を直接検出する手段（空燃比センサ）がない場合に特に有効である。 Further, according to the present embodiment, the target excess air ratio is calculated based on the target air amount and the actual fuel injection amount. And the first parameter A of the correction coefficient map can be prevented from becoming excessively dark.
Further, according to the present embodiment, the actual excess air ratio is calculated based on the actual air amount and the actual fuel injection amount, because the variation in the air amount greatly affects the excess air ratio. This is particularly effective when there is no means (air-fuel ratio sensor) for directly detecting the excess air ratio.

また、本実施形態によれば、目標空気過剰率に対する実空気過剰率の誤差を学習し、該学習に基づく学習値Ｋで空気量を補正制御する学習制御手段を備える場合に、実空気量と実燃料噴射量とに基づいて算出した実空気過剰率を、前記学習値Ｋで補正することにより、実空気過剰率と目標空気過剰率とを空気量で補正して一致させる制御を行った場合に、実空気過剰率が過補正となり、実空気過剰率と目標空気過剰率の誤差が収束しないのを防止できる。   In addition, according to the present embodiment, when the learning control means for learning the error of the actual excess air ratio with respect to the target excess air ratio and correcting and controlling the air amount with the learning value K based on the learning is provided, When the actual excess air ratio calculated based on the actual fuel injection amount is corrected with the learned value K, thereby correcting the actual excess air ratio and the target excess air ratio with the air amount so as to match. In addition, the actual excess air ratio is overcorrected, and it is possible to prevent the error between the actual excess air ratio and the target excess air ratio from converging.

また、本実施形態によれば、排気系に空燃比センサを備える場合に、そのセンサ信号に基づいて、実空気過剰率を検出することにより、実空気過剰率をより正確にかつ簡易にとらえることができる。
尚、本発明では、エンジンからのＰＭ排出量を算出・補正し、これを積算してＤＰＦのＰＭ堆積量を算出しているが、ここでいう「ＰＭ排出量」をエンジンからの純然たるＰＭ排出量ととらえて、ＰＭ堆積量の算出に際して、ＰＭ捕集効率を考慮してもよいし、「ＰＭ排出量」を単位時間当たりのＤＰＦでのＰＭ堆積量ととらえるようにしてもよい。 Further, according to the present embodiment, when the air-fuel ratio sensor is provided in the exhaust system, the actual excess air ratio can be more accurately and easily detected by detecting the actual excess air ratio based on the sensor signal. Can do.
In the present invention, the PM emission amount from the engine is calculated and corrected, and this is integrated to calculate the PM accumulation amount of the DPF. However, the “PM emission amount” here is the pure PM from the engine. When calculating the PM deposition amount, the PM collection efficiency may be taken into consideration, or “PM emission amount” may be regarded as the PM deposition amount in the DPF per unit time.

本発明の一実施形態を示すディーゼルエンジンのシステム図The system diagram of the diesel engine which shows one Embodiment of this invention ＰＭ堆積量推定の概要を示すブロック図Block diagram showing the outline of PM accumulation estimation ＰＭ堆積量推定のフローチャートFlow chart of PM accumulation amount estimation ＰＭ排出量基本値マップを示す図The figure which shows the PM emission basic value map ＰＭ排出量補正係数マップを示す図The figure which shows PM emission amount correction coefficient map 空気過剰率に対するＰＭ排出量の特性図Characteristic chart of PM emissions against excess air ratio 実空気過剰率を空燃比センサにより検出する場合のフローチャートFlowchart when the actual excess air ratio is detected by an air-fuel ratio sensor

符号の説明Explanation of symbols

１ ディーゼルエンジン
２ 吸気通路
３ 過給機
４ インタークーラ
５ 吸気絞り弁
６ コレクタ
７ 高圧燃料ポンプ
８ コモンレール
９ 燃料噴射弁
１０ 排気通路
１１ ＥＧＲ通路
１２ ＥＧＲ弁
１３ ＤＰＦ
１５ 可変ノズル機構
２０ ＥＣＵ
２１ アクセル開度センサ
２２ 回転数センサ
２３ エアフローメータ
２４ 空燃比センサ DESCRIPTION OF SYMBOLS 1 Diesel engine 2 Intake passage 3 Supercharger 4 Intercooler 5 Intake throttle valve 6 Collector 7 High pressure fuel pump 8 Common rail 9 Fuel injection valve 10 Exhaust passage 11 EGR passage 12 EGR valve 13 DPF
15 Variable nozzle mechanism 20 ECU
21 Accelerator opening sensor 22 Rotation speed sensor 23 Air flow meter 24 Air-fuel ratio sensor

Claims (11)

排気通路に排気中のＰＭを捕集するフィルタを備える内燃機関において、
機関の運転状態に応じてＰＭ排出量を算出するＰＭ排出量算出手段と、
前記ＰＭ排出量を空気過剰率に応じて補正する補正手段と、
前記補正後のＰＭ排出量を積算して前記フィルタのＰＭ堆積量を算出するＰＭ堆積量算出手段と、
を含んで構成されるＰＭ堆積量推定装置。 In an internal combustion engine having a filter for collecting PM in exhaust gas in an exhaust passage,
PM emission amount calculating means for calculating the PM emission amount according to the operating state of the engine;
Correction means for correcting the PM emission amount according to the excess air ratio;
PM accumulation amount calculating means for calculating the PM accumulation amount of the filter by integrating the corrected PM discharge amount;
PM accumulation amount estimation device comprising: 前記補正手段は、目標空気過剰率、及び、実空気過剰率に応じて、補正することを特徴とする請求項１記載のＰＭ堆積量推定装置。   The PM accumulation amount estimation apparatus according to claim 1, wherein the correction unit corrects according to a target excess air ratio and an actual excess air ratio. 前記補正手段は、第１パラメータとして、目標空気過剰率、第２パラメータとして、実空気過剰率と目標空気過剰率との差を用い、これらに応じて補正することを特徴とする請求項２記載のＰＭ堆積量推定装置。   The correction means uses a target excess air ratio as a first parameter and a difference between an actual excess air ratio and a target excess air ratio as a second parameter, and corrects the correction accordingly. PM deposition amount estimation device. 前記補正手段は、第１パラメータとして、目標空気過剰率、第２パラメータとして、実空気過剰率と目標空気過剰率との比を用い、これらに応じて補正することを特徴とする請求項２記載のＰＭ堆積量推定装置。   The correction means uses a target excess air ratio as a first parameter and a ratio between an actual excess air ratio and a target excess air ratio as a second parameter, and corrects the ratio accordingly. PM deposition amount estimation device. 前記補正手段は、前記第２パラメータとして、実空気過剰率と目標空気過剰率との差を、実空気過剰率に対する比に変換した値を用いることを特徴とする請求項３記載のＰＭ堆積量推定装置。   The PM accumulation amount according to claim 3, wherein the correction means uses, as the second parameter, a value obtained by converting a difference between the actual excess air ratio and the target excess air ratio into a ratio to the actual excess air ratio. Estimating device. 前記補正手段は、前記第２パラメータとして、実空気過剰率と目標空気過剰率との差を、目標空気過剰率に対する比に変換した値を用いることを特徴とする請求項３記載のＰＭ堆積量推定装置。   The PM accumulation amount according to claim 3, wherein the correction means uses, as the second parameter, a value obtained by converting a difference between the actual excess air ratio and the target excess air ratio into a ratio to the target excess air ratio. Estimating device. 前記目標空気過剰率は、目標空気量と実燃料噴射量とに基づいて算出することを特徴とする請求項２〜請求項６のいずれか１つに記載のＰＭ堆積量推定装置。   The PM accumulation amount estimation device according to any one of claims 2 to 6, wherein the target air excess ratio is calculated based on a target air amount and an actual fuel injection amount. 前記実空気過剰率は、実空気量と実燃料噴射量とに基づいて算出することを特徴とする請求項２〜請求項７のいずれか１つに記載のＰＭ堆積量推定装置。   8. The PM accumulation amount estimation device according to claim 2, wherein the actual excess air ratio is calculated based on an actual air amount and an actual fuel injection amount. 目標空気過剰率に対する実空気過剰率の誤差を学習し、該学習に基づく学習値で空気量を補正制御する学習制御手段を備える場合に、
実空気量と実燃料噴射量とに基づいて算出した実空気過剰率を、前記学習値で補正することを特徴とする請求項８記載のＰＭ堆積量推定装置。 When learning error of the actual excess air ratio with respect to the target excess air ratio, and having learning control means for correcting and controlling the air amount with the learning value based on the learning,
9. The PM accumulation amount estimation device according to claim 8, wherein an actual excess air ratio calculated based on an actual air amount and an actual fuel injection amount is corrected by the learned value. 前記実空気過剰率は、空燃比センサにより検出することを特徴とする請求項２〜請求項７のいずれか１つに記載のＰＭ堆積量推定装置。   The PM accumulation amount estimation apparatus according to any one of claims 2 to 7, wherein the actual excess air ratio is detected by an air-fuel ratio sensor. 前記ＰＭ排出量算出手段は、機関回転数及び負荷に応じてＰＭ排出量を算出することを特徴とする請求項１〜請求項１０のいずれか１つに記載のＰＭ堆積量推定装置。   The PM accumulation amount estimation device according to any one of claims 1 to 10, wherein the PM emission amount calculation means calculates a PM emission amount according to an engine speed and a load.
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