JP5120237B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Exhaust gas purification device for internal combustion engine Download PDF

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JP5120237B2
JP5120237B2 JP2008319058A JP2008319058A JP5120237B2 JP 5120237 B2 JP5120237 B2 JP 5120237B2 JP 2008319058 A JP2008319058 A JP 2008319058A JP 2008319058 A JP2008319058 A JP 2008319058A JP 5120237 B2 JP5120237 B2 JP 5120237B2
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dpf
temperature
dpf regeneration
amount distribution
internal combustion
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JP2010144514A (en
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梨沙 山本
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Nissan Motor Co Ltd
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Description

本発明は、ディーゼルエンジンに代表される内燃機関の排気浄化装置に関し、特に、ＤＰＦの再生技術に関する。 The present invention relates to an exhaust emission control device for an internal combustion engine typified by a diesel engine, and particularly to a DPF regeneration technique.

ディーゼルエンジンでは、排気中のＰＭ（Ｐａｒｔｉｃｕｌａｔｅ Ｍａｔｔｅｒ；粒子状物質）の除去が重要な課題となっており、周知のように、このＰＭを捕集するＤＰＦ（Ｄｉｅｓｅｌ Ｐａｒｔｉｃｕｌａｔｅ Ｆｉｌｔｅｒ；ディーゼルパティキュレートフィルタ）が設けられ、ＤＰＦ再生時には、ＤＰＦを昇温してＤＰＦに堆積するＰＭを燃焼・除去することによって、ＰＭ堆積量を減少させるＤＰＦ再生運転が行われる。   In a diesel engine, removal of PM (Particulate Matter) in the exhaust gas has become an important issue. As is well known, a DPF (Diesel Particulate Filter) that collects PM is known. In the DPF regeneration, a DPF regeneration operation is performed in which the PM deposition amount is reduced by increasing the temperature of the DPF and combusting and removing the PM deposited on the DPF.

特許文献１には、ＤＰＦに捕集される成分には煤（ｓｏｏｔ）等の不溶成分と未燃炭化水素（ＨＣ）等の可溶な有機的留分とが含まれ、これらはそれぞれ燃焼するために必要となる温度が異なる点に着目し、ＤＰＦ再生運転におけるＤＰＦ再生目標温度の設定を二段階に分け、先ず低温側の第１の温度までＤＰＦを昇温させて、ＰＭにおける主に未燃炭化水素（ＨＣ）等を燃焼させ、その後、ＰＭ堆積量が所定量まで低下すると、上記第１の温度よりも高温側の第２の温度までＤＰＦを昇温させて、ＰＭの残りの成分を燃焼させている。
特開２００３−１８４５３６号公報 In Patent Document 1, the components collected in the DPF include insoluble components such as soot and soluble organic fractions such as unburned hydrocarbons (HC), which each burn. Focusing on the difference in the temperature required for this, the setting of the DPF regeneration target temperature in the DPF regeneration operation is divided into two stages. First, the DPF is raised to the first temperature on the low temperature side. When combustion hydrocarbon (HC) or the like is combusted, and then the amount of accumulated PM decreases to a predetermined amount, the DPF is heated to a second temperature higher than the first temperature, and the remaining components of PM Is burning.
JP 2003-184536 A

内燃機関より排出されるＰＭの成分比率，結晶性，燃焼可能温度や燃焼速度などの性状は、機関運転状態に応じて変化する。図８〜図１１は、このような機関運転状態に応じたＰＭの性状を示す特性図である。図８は、ＰＭの燃焼可能温度に応じたＰＭ堆積量のヒストグラムであるＰＭ堆積量分布を示し、内燃機関が低負荷側で運転された場合と内燃機関が高負荷で運転される場合のそれぞれの分布を示している。同図に示すように、ＰＭの燃焼可能温度（あるいは、ＰＭ中の煤（Ｓｏｏｔ）の燃焼可能温度）は、低負荷側で運転されたときに低くなり、高負荷側で運転されたときに高くなる傾向にある。また、図９に示すように、ＤＰＦの温度（以下、床温度あるいはＢＥＤ温度とも呼ぶ）は、ＰＭ燃焼可能温度が高くなるほど高くなり、燃焼速度が大きくなるほど高くなる傾向にある。更に、図１０に示すように、高負荷側で運転されたときには、低負荷側で運転されたときに比して、ＤＰＦのＢＥＤ温度が高くなるまでＰＭ堆積量が低下し難くなる傾向にある。また、図１１に示すように、機関回転数Ｎｅや燃料噴射量（機関負荷）ＱｆｉｎによってもＤＰＦに堆積するＰＭの燃焼可能温度が異なるものとなる。   Properties such as the component ratio, crystallinity, combustible temperature, and combustion speed of PM discharged from the internal combustion engine vary depending on the engine operating state. 8 to 11 are characteristic diagrams showing the properties of PM according to such an engine operating state. FIG. 8 shows a PM accumulation amount distribution, which is a histogram of the PM accumulation amount according to the PM combustible temperature. Each of the case where the internal combustion engine is operated at a low load side and the case where the internal combustion engine is operated at a high load. The distribution of is shown. As shown in the figure, the combustible temperature of PM (or the combustible temperature of soot in PM) becomes low when operated on the low load side, and when operated on the high load side. It tends to be higher. As shown in FIG. 9, the temperature of the DPF (hereinafter also referred to as the bed temperature or the BED temperature) tends to increase as the PM combustible temperature increases and increases as the combustion speed increases. Furthermore, as shown in FIG. 10, when operated on the high load side, the PM deposition amount tends to be less likely to decrease until the BPF temperature of the DPF becomes higher than when operated on the low load side. . Further, as shown in FIG. 11, the combustible temperature of PM deposited on the DPF also differs depending on the engine speed Ne and the fuel injection amount (engine load) Qfin.

従って、上述した従来例のように、単にＤＰＦの温度を二段階に分けて昇温するだけでは、有効にＰＭ堆積量を低減することができず、必要以上にＤＰＦの昇温が行われて排気エミッションや燃費の低下を招いたり、ＤＰＦの昇温が不足して十分なＤＰＦ再生が行われないといった不具合を招くおそれがある。   Therefore, as in the conventional example described above, simply increasing the temperature of the DPF in two stages cannot effectively reduce the amount of accumulated PM, and the DPF is heated more than necessary. There is a risk that exhaust emissions and fuel consumption may be reduced, or that the DPF may not be sufficiently regenerated due to insufficient temperature rise of the DPF.

そこで、本発明では、機関運転状態に基づいて、ＰＭの性状、つまりはＰＭの燃焼特性に応じたＰＭ堆積量のヒストグラムであるＰＭ堆積量分布を予測し、このＰＭ堆積量分布に基づいて、上記ＤＰＦ再生運転におけるＤＰＦ再生目標温度を設定する。そして、ＤＰＦ再生運転中は、上記ＤＰＦの再生温度に基いてＰＭ堆積量分布を更新し、この更新されるＰＭ堆積量分布に応じて再生中のＤＰＦ再生目標温度を更新する。   Therefore, in the present invention, based on the engine operation state, the PM property, that is, the PM accumulation amount distribution which is a histogram of the PM accumulation amount according to the combustion characteristics of the PM is predicted, and based on this PM accumulation amount distribution, A DPF regeneration target temperature in the DPF regeneration operation is set. During the DPF regeneration operation, the PM accumulation amount distribution is updated based on the regeneration temperature of the DPF, and the DPF regeneration target temperature being regenerated is updated according to the updated PM accumulation amount distribution.

本発明によれば、機関運転状態に応じて変化するＰＭの性状に応じたＰＭ堆積量のヒストグラムであるＰＭ堆積量分布を予測し、これに応じてＤＰＦ再生運転におけるＤＰＦ再生目標温度を設定することで、ＤＰＦに堆積するＰＭの性状（燃焼特性）及びその分布に応じた形で適切なＤＰＦ再生目標温度に設定することができ、必要以上にＤＰＦの昇温が行われたりＤＰＦの昇温が不足したりすることを抑制することができる。しかも、ＤＰＦ再生運転中は、上記ＤＰＦの再生温度に基づいてＰＭ堆積量分布を更新し、この更新されるＰＭ堆積量分布に応じて再生中のＰＭ堆積量分布を更新することで、ＤＰＦ再生運転中にも変化するＰＭ堆積量分布を正確に予測し、精度の高いＤＰＦの再生制御を実現することができる。   According to the present invention, the PM accumulation amount distribution, which is a histogram of the PM accumulation amount corresponding to the property of PM that changes according to the engine operating state, is predicted, and the DPF regeneration target temperature in the DPF regeneration operation is set accordingly. As a result, the DPF regeneration target temperature can be set appropriately in accordance with the properties (combustion characteristics) of PM deposited on the DPF and its distribution, and the DPF is heated more than necessary or the DPF is heated. It is possible to suppress the shortage. In addition, during the DPF regeneration operation, the PM deposition amount distribution is updated based on the regeneration temperature of the DPF, and the PM deposition amount distribution being regenerated is updated according to the updated PM deposition amount distribution. It is possible to accurately predict the PM accumulation amount distribution that changes even during operation, and to realize highly accurate DPF regeneration control.

以下、本発明の好ましい実施例を図面に基づいて説明する。図１は本発明の一実施例に係る内燃機関の排気浄化装置を示すシステム図である。内燃機関としての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、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。   Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram showing an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention. An intake passage 2 of a diesel engine 1 as an internal combustion engine is provided with an intake compressor of a variable nozzle type turbocharger 3. The intake air is supercharged by the intake compressor, cooled by an intercooler 4, and passed through an intake throttle valve 5. After that, it flows into the combustion chamber of each cylinder through the collector 6. The fuel is increased in pressure by a common rail fuel injection device, that is, a 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、可変ノズル型のターボチャージャ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、排気浄化のため、排気空燃比がリーンのときに流入する排気中のＮＯｘをトラップし、排気空燃比がリッチのときトラップしたＮＯｘを脱離浄化するＮＯｘトラップ触媒１３を配置してある。また、このＮＯｘトラップ触媒１３には、酸化触媒（貴金属）を担持させて、流入する排気成分（ＨＣ、ＣＯ）を酸化する機能を持たせてある。   Part of the exhaust gas flowing into the exhaust passage 10 is recirculated to the intake side via the EGR valve 12 through the EGR passage 11 as EGR gas. The remainder of the exhaust passes through the exhaust turbine of the variable nozzle type turbocharger 3 and drives it. Here, downstream of the exhaust turbine in the exhaust passage 10, for exhaust purification, NOx in the exhaust flowing in when the exhaust air-fuel ratio is lean is trapped, and when the exhaust air-fuel ratio is rich, the trapped NOx is desorbed and purified. A NOx trap catalyst 13 is disposed. Further, the NOx trap catalyst 13 carries an oxidation catalyst (noble metal) and has a function of oxidizing the exhaust components (HC, CO) flowing in.

更に、このＮＯｘトラップ触媒１３の下流には、排気中のＰＭを捕集するＤＰＦ１４を配置してある。また、このＤＰＦ１４にも、酸化触媒（貴金属）を担持させて、流入する排気成分（ＨＣ、ＣＯ）を酸化する機能を持たせてある。尚、ＮＯｘトラップ触媒１３とＤＰＦ１４とは、逆に配置してもよいし、ＤＰＦにＮＯｘトラップ触媒を担持させて一体に構成してもよい。   Further, a DPF 14 that collects PM in the exhaust gas is disposed downstream of the NOx trap catalyst 13. The DPF 14 also has a function of supporting an oxidation catalyst (noble metal) and oxidizing exhaust components (HC, CO) flowing in. Note that the NOx trap catalyst 13 and the DPF 14 may be disposed in reverse, or may be configured integrally by supporting the NOx trap catalyst on the DPF.

コントロールユニット２０には、エンジン１の制御のため、エンジン回転数Ｎｅ検出用の回転数センサ２１、アクセル開度ＡＰＯ検出用のアクセル開度センサ２２から、信号が入力されている。また、ＮＯｘトラップ触媒１３の温度すなわちＬＮＴ床温度を検出するＬＮＴ温度センサ２３、排気通路１０のＤＰＦ１４入口側にて排気圧力を検出する排気圧力センサ２４、ＤＰＦ１４の温度すなわちＤＰＦ床温度を検出するＤＰＦ温度センサ２５、更に排気通路１０のＤＰＦ１４出口側にて排気空燃比（以下、排気λといい、数値としては空気過剰率で表す）を検出する空燃比センサ２６が設けられ、これらの信号もコントロールユニット２０に入力されている。但し、ＮＯｘトラップ触媒１３の温度やＤＰＦ１４の温度はこれらの下流側に排気温度センサを設けて、排気温度より間接的に検出するようにしてもよい。   In order to control the engine 1, signals are input to the control unit 20 from an engine speed sensor 21 for detecting the engine speed Ne and an accelerator position sensor 22 for detecting the accelerator position APO. Further, an LNT temperature sensor 23 for detecting the temperature of the NOx trap catalyst 13, that is, the LNT floor temperature, an exhaust pressure sensor 24 for detecting the exhaust pressure on the DPF 14 inlet side of the exhaust passage 10, and a DPF for detecting the temperature of the DPF 14, that is, the DPF floor temperature. A temperature sensor 25 and an air / fuel ratio sensor 26 for detecting an exhaust air / fuel ratio (hereinafter referred to as exhaust λ, which is expressed as an excess air ratio) are provided on the outlet side of the DPF 14 in the exhaust passage 10, and these signals are also controlled. Input to the unit 20. However, the temperature of the NOx trap catalyst 13 and the temperature of the DPF 14 may be detected indirectly from the exhaust temperature by providing an exhaust temperature sensor downstream thereof.

コントロールユニット２０は、これらの入力信号に基づいて、燃料噴射弁９による主噴射及び所定の運転条件において主噴射後（膨張行程又は排気行程）に行う後噴射すなわちポスト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への開度指令信号等を出力する。   Based on these input signals, the control unit 20 performs the main injection by the fuel injection valve 9 and the post-injection after the main injection (expansion stroke or exhaust stroke) under predetermined operating conditions, that is, the fuel injection amount and the injection timing of the post injection. A fuel injection command signal to the fuel injection valve 9 for control, an opening command signal to the intake throttle valve 5, an opening command signal to the EGR valve 12, and the like are output.

ここにおいて、コントロールユニット２０では、所定のＤＰＦ再生条件が成立する場合に、ＤＰＦ１４を昇温することによって、ＤＰＦ１４に捕集されて堆積したＰＭの浄化すなわちＤＰＦ再生のための排気浄化制御を、例えば排気中の空気過剰率すなわち排気λの制御により行う。排気λとエンジン１からのＰＭ排出量との関係は、排気λがリッチになるほど増加し、特にストイキ（排気λ＝１．０）よりもリッチ側の場合には、通常運転状態に比べて大幅に増加する。   Here, in the control unit 20, when predetermined DPF regeneration conditions are satisfied, the DPF 14 is heated to purify the PM collected and accumulated in the DPF 14, that is, exhaust purification control for DPF regeneration, for example, This is done by controlling the excess air ratio in the exhaust, that is, the exhaust λ. The relationship between the exhaust λ and the PM emission amount from the engine 1 increases as the exhaust λ becomes richer, particularly when it is richer than the stoichiometric (exhaust λ = 1.0) compared to the normal operation state. To increase.

図２は、本実施例に係るＤＰＦ再生制御の流れを示すフローチャートである。ステップＳ２１では、ＤＰＦ再生運転を行うか否かの実施判断、具体的にはＤＰＦ再生運転フラグＤＰＦ＿ｒｅｇ＿ｒｅｑの設定が行われるとともに、ＰＭ堆積量演算つまりはＰＭ堆積量分布の設定・更新が行われる。ステップＳ２２では、上記ＤＰＦ再生運転フラグＤＰＦ＿ｒｅｇ＿ｒｅｑが１であるかを判定する。このフラグＤＰＦ＿ｒｅｇ＿ｒｅｑは、上記ステップＳ２１において、ＤＰＦ再生運転を行うと判定された場合、１に設定され、ＤＰＦ再生運転を行わないと判定された場合、０に設定される。ＤＰＦ再生運転を行うと判定された場合、ステップＳ２２からステップＳ２３へ進み、ＤＰＦ再生温度設定演算が行われ、ステップＳ２４において、ＤＰＦ再生運転が実施される。このＤＰＦ再生運転では、ＤＰＦ１４の温度を後述するＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔへ向けて昇温するように、例えば燃料噴射量の増量，ポスト噴射，吸気絞り弁５による吸気絞り等が行われる。   FIG. 2 is a flowchart showing the flow of DPF regeneration control according to the present embodiment. In step S21, whether or not to perform the DPF regeneration operation is determined, specifically, the DPF regeneration operation flag DPF_reg_req is set, and the PM accumulation amount calculation, that is, the PM accumulation amount distribution is set / updated. In step S22, it is determined whether the DPF regeneration operation flag DPF_reg_req is 1. This flag DPF_reg_req is set to 1 when it is determined in step S21 that the DPF regeneration operation is performed, and is set to 0 when it is determined that the DPF regeneration operation is not performed. When it is determined that the DPF regeneration operation is to be performed, the process proceeds from step S22 to step S23, the DPF regeneration temperature setting calculation is performed, and the DPF regeneration operation is performed in step S24. In this DPF regeneration operation, for example, an increase in fuel injection amount, post injection, intake throttle by the intake throttle valve 5 and the like are performed so as to raise the temperature of the DPF 14 toward a DPF regeneration target temperature Temp_target described later.

図３は、図２のステップＳ２１のＤＰＦ再生実施判断・ＰＭ堆積量演算の具体的な処理内容を示すサブルーチンである。ステップＳ３１では、ＤＰＦに堆積するＰＭ堆積量ＳＰＭの前回値ＳＰＭｎ−１を読み込む。ＰＭ堆積量ＳＰＭは、後述するＰＭ燃焼可能温度分布におけるＰＭ堆積量の積算値に相当する。ステップＳ３２では、上記ＳＰＭｎ−１等に基づいて、ＤＰＦを昇温することによってＰＭ堆積量を低減するＤＰＦ再生運転を行うか否かを判定する。具体的には、ＤＰＦ再生運転を行うことが可能な機関運転領域（機関負荷，機関回転数等）であり、かつ、ＰＭ堆積量の前回値ＳＰＭｎ−１が所定のＰＭ再生要求値ＰＭ＿ＳＬ以上である場合に、ＤＰＦ再生運転が行われる。また、例えばＤＰＦ再生運転中にＰＭ堆積量が所定値以下まで低下すると、ＤＰＦ再生運転を終了する。   FIG. 3 is a subroutine showing the specific processing contents of the DPF regeneration execution determination / PM accumulation amount calculation in step S21 of FIG. In step S31, the previous value SPMn−1 of the PM deposition amount SPM deposited on the DPF is read. The PM accumulation amount SPM corresponds to an integrated value of the PM accumulation amount in a PM combustible temperature distribution described later. In step S32, based on the above SPMn-1 or the like, it is determined whether or not to perform the DPF regeneration operation for reducing the PM accumulation amount by increasing the temperature of the DPF. Specifically, it is an engine operation region (engine load, engine speed, etc.) in which DPF regeneration operation can be performed, and the previous value SPMn−1 of the PM accumulation amount is equal to or greater than a predetermined PM regeneration request value PM_SL. In some cases, the DPF regeneration operation is performed. Further, for example, when the PM accumulation amount falls below a predetermined value during the DPF regeneration operation, the DPF regeneration operation is terminated.

ステップＳ３２において、ＤＰＦ再生運転を行うと判定された場合、ステップＳ３３へ進み、ＤＰＦ再生運転フラグＤＰＦ＿ｒｅｇ＿ｒｅｑが１に設定され、ＤＰＦ再生運転を行わないと判定された場合、ステップＳ３５へ進み、ＤＰＦ再生運転フラグＤＰＦ＿ｒｅｇ＿ｒｅｑが０に設定される。ＤＰＦ再生運転を行う場合には、ステップＳ３４において、図４に示すＰＭ減算演算を行い、ＤＰＦ再生運転を行わない場合、つまりＤＰＦ再生運転以外の機関運転状態では、ステップＳ３６において、ＰＭ加算演算が行われる。   If it is determined in step S32 that the DPF regeneration operation is to be performed, the process proceeds to step S33, and if the DPF regeneration operation flag DPF_reg_req is set to 1 and it is determined not to perform the DPF regeneration operation, the process proceeds to step S35 to perform the DPF regeneration. The operation flag DPF_reg_req is set to 0. When performing the DPF regeneration operation, the PM subtraction operation shown in FIG. 4 is performed in step S34, and when the DPF regeneration operation is not performed, that is, in the engine operation state other than the DPF regeneration operation, the PM addition operation is performed in step S36. Done.

図４は、図３のステップＳ３４のＰＭ減算演算の具体的な処理内容を示すサブルーチンである。ステップＳ４１では、ＰＭ堆積量分布，ＤＰＦの温度Ｔｅｍｐ＿ＤＰＦ及び図９に示すようなＰＭ燃焼速度のマップ等を読み込む。ＰＭ堆積量分布は、図８及び図１２にも示すように、ＰＭ燃焼可能温度に応じたＰＭ堆積量のヒストグラムであり、図４及び図５のルーチンが所定の短期間（例えば１０ｍｓ毎）に繰り返し行われることで、機関運転中に逐次更新される。   FIG. 4 is a subroutine showing the specific processing contents of the PM subtraction operation in step S34 of FIG. In step S41, a PM accumulation amount distribution, a DPF temperature Temp_DPF, a PM combustion speed map as shown in FIG. As shown in FIGS. 8 and 12, the PM accumulation amount distribution is a histogram of the PM accumulation amount according to the PM combustion possible temperature, and the routines of FIGS. 4 and 5 are performed in a predetermined short period (for example, every 10 ms). Repeatedly, it is updated sequentially during engine operation.

ステップＳ４２では、ＰＭ処理量すなわちＤＰＦからのＰＭの除去量・減算量を演算する。つまり、ＤＰＦ再生運転中には、ＰＭの性状に関連づけてＰＭを減算することによりＰＭ堆積量分布が逐次更新される。具体的には、ＰＭ堆積量分布における各燃焼可能温度毎に、ＰＭ堆積量の減算量（Ｓｔ×ＳＰＭｎ−１）を演算し、これをＰＭ堆積量の前回値ＳＰＭｎ−１から減算することにより、ＰＭ堆積量ｓＰＭｎを更新する。上記のＳｔは、燃焼速度であり、ＰＭ燃焼可能温度及びＤＰＦ温度に基づいて図９のマップを参照することにより求められる。   In step S42, a PM processing amount, that is, a PM removal amount / subtraction amount from the DPF is calculated. That is, during the DPF regeneration operation, the PM accumulation amount distribution is sequentially updated by subtracting PM in association with the property of PM. More specifically, for each combustible temperature in the PM accumulation amount distribution, a subtraction amount (St × SPMn−1) of the PM accumulation amount is calculated, and this is subtracted from the previous value SPMn−1 of the PM accumulation amount. , PM deposition amount sPMn is updated. The above St is the combustion speed, and is obtained by referring to the map of FIG. 9 based on the PM combustible temperature and the DPF temperature.

図５は、図３のステップＳ３６のＰＭ加算演算の具体的な処理内容を示すサブルーチンである。ステップＳ５１では、機関回転数Ｎｅ，燃料噴射量Ｑｆｉｎ，空気流量等を読み込み、これらに基づいて、エンジン出口ＰＭつまり機関から排出されるＰＭ量を演算する。エンジン出口ＰＭは、機関回転数，燃料噴射量（機関負荷），空気流量が大きいほど多くなる。ステップＳ５２では、空気過剰率λがリーン側となるほどエンジン出口ＰＭが小さくなることを考慮して、空気過剰率λによる補正値を算出し、これを用いてエンジン出口ＰＭを補正する。ステップＳ５３では、このようなエンジン出口ＰＭに対し、機関運転状態に対応してＰＭ燃焼可能温度を演算する。図１１に示すように、例えば燃料噴射量（機関負荷）が高くなるほどＰＭ燃焼可能温度を高くする。そしてステップＳ５４では、このＰＭ燃焼可能温度に関連づけてＰＭ堆積量分布にＰＭを加算することによって、ＰＭ堆積量分布を逐次更新する。   FIG. 5 is a subroutine showing the specific processing contents of the PM addition operation in step S36 of FIG. In step S51, the engine speed Ne, the fuel injection amount Qfin, the air flow rate, and the like are read, and based on these, the engine outlet PM, that is, the PM amount discharged from the engine is calculated. The engine outlet PM increases as the engine speed, fuel injection amount (engine load), and air flow rate increase. In step S52, considering that the engine outlet PM becomes smaller as the excess air ratio λ becomes leaner, a correction value based on the excess air ratio λ is calculated and used to correct the engine outlet PM. In step S53, the PM combustion possible temperature is calculated for such an engine outlet PM in accordance with the engine operating state. As shown in FIG. 11, for example, the higher the fuel injection amount (engine load), the higher the PM combustion possible temperature. In step S54, the PM accumulation amount distribution is sequentially updated by adding PM to the PM accumulation amount distribution in association with the PM combustion possible temperature.

図６は、図２のステップＳ２３のＤＰＦ再生温度設定演算の具体的な処理内容を示すサブルーチンである。ステップＳ６１では、ＤＰＦ許容温度Ｔｅｍｐ＿ｍａｘ＿ｄｐｆ（固定値）及びＤＰＦ床温度Ｔｅｍｐ＿ＤＰＦを読み込む。ステップＳ６２では、図１４にも示すように、ＤＰＦを昇温可能な温度差である許可温度差ΔＴ＝Ｔｅｍｐ＿ｍａｘ＿ｄｐｆ−Ｔｅｍｐ＿ＤＰＦを算出する。ステップＳ６３では、許可温度差ΔＴに基づいて、ＤＰＦに堆積するＰＭの低負荷側からの除去量つまりＰＭ除去区間Ｓ１に対応する判定しきい値ＰＭ＿ｔＳＬを決定する。図１４に示すように、判定しきい値ＰＭ＿ｔＳＬは、許可温度差ΔＴが小さくなるほど小さくなり、ＤＰＦ温度Ｔｅｍｐ＿ＤＰＦが高くなるほど小さくなる。本実施例によれば、ＤＰＦ再生運転中にはＤＰＦ温度が徐々に上昇していき、判定しきい値ＰＭ＿ｔＳＬもまた徐々に高くなっていくこととなる。   FIG. 6 is a subroutine showing the specific processing contents of the DPF regeneration temperature setting calculation in step S23 of FIG. In step S61, the DPF allowable temperature Temp_max_dpf (fixed value) and the DPF floor temperature Temp_DPF are read. In step S62, an allowable temperature difference ΔT = Temp_max_dpf−Temp_DPF, which is a temperature difference that can raise the DPF, is calculated as shown in FIG. In step S63, the removal threshold value PM_tSL corresponding to the removal amount of PM accumulated on the DPF from the low load side, that is, the PM removal section S1, is determined based on the allowable temperature difference ΔT. As shown in FIG. 14, the determination threshold value PM_tSL decreases as the allowable temperature difference ΔT decreases, and decreases as the DPF temperature Temp_DPF increases. According to the present embodiment, the DPF temperature gradually increases during the DPF regeneration operation, and the determination threshold value PM_tSL also gradually increases.

ステップＳ６４では、この判定しきい値ＰＭ＿ｔＳＬに基づいてＰＭ堆積量分布を参照して、ＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔを設定する。具体的には図１２に示すように、ＰＭ堆積量分布におけるＰＭ燃焼可能温度の低温側からのＰＭ堆積量の積算値が上記の判定しきい値ＰＭ＿ｔＳＬとなる時点での（最大）温度をＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔとして設定する。なお、図１２において、領域Ｂ，ＤがＰＭ堆積量分布Ａ，Ｃにおける低負荷側からのＰＭ堆積量の積算値が判定しきい値ＰＭ＿ｔＳＬとなる領域である。これにより、ＤＰＦ再生運転の経過・進行に伴って、図１２に示すように、ＰＭ堆積量分布のＰＭ燃焼可能温度の低温側よりＰＭの燃焼が進行していき、図１３にも示すように、ＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔが徐々に上昇していくこととなる。   In step S64, the DPF regeneration target temperature Temp_target is set with reference to the PM accumulation amount distribution based on the determination threshold value PM_tSL. Specifically, as shown in FIG. 12, the (maximum) temperature at the time when the integrated value of the PM deposition amount from the low temperature side of the PM combustion possible temperature in the PM deposition amount distribution becomes the above-described determination threshold value PM_tSL is defined as the DPF. Set as the regeneration target temperature Temp_target. In FIG. 12, regions B and D are regions where the integrated value of the PM deposition amount from the low load side in the PM deposition amount distributions A and C becomes the determination threshold value PM_tSL. As a result, as the DPF regeneration operation progresses and progresses, as shown in FIG. 12, PM combustion proceeds from the low temperature side of the PM combustion possible temperature of the PM accumulation amount distribution, as shown in FIG. The DPF regeneration target temperature Temp_target gradually increases.

図７は、本発明の他の実施例に係る再生温度の設定演算処理の流れを示すフローチャートであり、図６のステップＳ６４以降に実行されるものである。ステップＳ７１では、ＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔ，最低温度Ｔｅｍｐ＿ｍｉｎｉｍｕｍ，ＰＭ堆積量ＳＰＭ，ＤＰＦ温度Ｔｅｍｐ＿ＤＰＦ等を読み込み、これらの値に基づいて、ステップＳ７２ではＰＭ除去区間Ｓ１（図１２参照）におけるＰＭ除去に必要な要求熱量ｔＱを演算する。最低温度Ｔｅｍｐ＿ｍｉｎｉｍｕｍは、区間Ｓ１におけるＰＭ燃焼可能温度の最小値である。ステップＳ７３では、ＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔの補正値Ｈ１を算出する。具体的には、総熱量Ｑｔｏｔａｌに対する要求熱量ｔＱの割合ｔＱ／Ｑｔｏｔａｌを算出し、この割合ｔＱ／Ｑｔｏｔａｌに基づいて図１５のマップを参照して、補正値Ｈ１を求める。総熱量Ｑｔｏｔａｌは、ＤＰＦに残存する全てのＰＭの除去に必要な熱量に相当する。ステップＳ７４では、ＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔに補正値Ｈ１を乗じてＴｅｍｐ＿ｔａｒｇｅｔを補正する。   FIG. 7 is a flowchart showing the flow of the regeneration temperature setting calculation process according to another embodiment of the present invention, which is executed after step S64 in FIG. In step S71, DPF regeneration target temperature Temp_target, minimum temperature Temp_minimum, PM deposition amount SPM, DPF temperature Temp_DPF, and the like are read. Based on these values, in step S72, it is necessary for PM removal in the PM removal section S1 (see FIG. 12). The required heat quantity tQ is calculated. The minimum temperature Temp_minimum is the minimum value of the PM combustible temperature in the section S1. In step S73, a correction value H1 for the DPF regeneration target temperature Temp_target is calculated. Specifically, the ratio tQ / Qtotal of the required heat quantity tQ with respect to the total heat quantity Qtotal is calculated, and the correction value H1 is obtained based on the ratio tQ / Qtotal with reference to the map of FIG. The total heat quantity Qtotal corresponds to the heat quantity necessary for removing all PM remaining in the DPF. In step S74, Temp_target is corrected by multiplying DPF regeneration target temperature Temp_target by correction value H1.

図１５に示すように、総熱量Ｑｔｏｔａｌに対する要求熱量ｔＱの占める割合ｔＱ／Ｑｔｏｔａｌが大きくなるほど、補正値Ｈ１は小さくなり、ＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔが低温側に補正される。このため、ＤＰＦに残存するＰＭの量が少なくなってくると、これに伴って割合ｔＱ／Ｑｔｏｔａｌが大きくなって、ＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔが低温側へ補正されることとなり、ＤＰＦ再生の終了間際に過剰な熱量が与えられてＤＰＦの過度な上昇を招くおそれがない。   As shown in FIG. 15, as the ratio tQ / Qtotal of the required heat quantity tQ with respect to the total heat quantity Qtotal increases, the correction value H1 decreases and the DPF regeneration target temperature Temp_target is corrected to the low temperature side. For this reason, when the amount of PM remaining in the DPF decreases, the ratio tQ / Qtotal increases accordingly, and the DPF regeneration target temperature Temp_target is corrected to the low temperature side, and just before the end of the DPF regeneration. Therefore, there is no possibility that an excessive amount of heat is applied to cause an excessive increase in the DPF.

次に、本発明の特徴的な構成及び作用効果について、上記実施例を参照しつつ列記する。但し、本発明は上記実施例の構成に限定されるものではなく、その趣旨を逸脱しない範囲で、種々の変形・変更を含むものである。   Next, characteristic configurations and operational effects of the present invention will be listed with reference to the above-described embodiments. However, the present invention is not limited to the configuration of the above embodiment, and includes various modifications and changes without departing from the spirit of the present invention.

［１］内燃機関１の排気通路１０中に、流入する排気中のＰＭを捕集するＤＰＦ１４が設けられる。ＤＰＦ再生運転時には、ＤＰＦ１４を昇温することによりＤＰＦ１４に堆積するＰＭ堆積量を低減する（ステップＳ２４）。機関運転状態に基づいて、ＰＭの性状に応じたＰＭ堆積量のヒストグラムであるＰＭ堆積量分布（図１２参照）を予測し（ステップＳ２１）、このＰＭ堆積量分布に基づいて、上記ＤＰＦ再生運転におけるＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔを設定する（ステップＳ２３）。   [1] A DPF 14 is provided in the exhaust passage 10 of the internal combustion engine 1 to collect PM in exhaust gas flowing in. During the DPF regeneration operation, the amount of PM deposited on the DPF 14 is reduced by raising the temperature of the DPF 14 (step S24). Based on the engine operation state, a PM accumulation amount distribution (see FIG. 12) which is a histogram of the PM accumulation amount according to the property of PM is predicted (step S21), and the DPF regeneration operation is performed based on the PM accumulation amount distribution. The DPF regeneration target temperature Temp_target at is set (step S23).

これによって、ＤＰＦに堆積するＰＭの性状（燃焼特性）及びその分布に応じた形でＤＰＦ再生目標温度を適切に設定することができ、必要以上にＤＰＦの昇温が行われたりＤＰＦの昇温が不足したりすることを抑制することができる。   As a result, the DPF regeneration target temperature can be appropriately set in accordance with the properties (combustion characteristics) of PM deposited on the DPF and its distribution, and the DPF is heated more than necessary or the DPF is heated. It is possible to suppress the shortage.

更に、ＤＰＦ再生運転以外の機関運転中には、上記ＰＭの性状に関連づけてＰＭを加算することによりＰＭ堆積量分布を更新し（ステップＳ３６）、ＤＰＦ再生運転中には、ＤＰＦの再生温度に基づいてＰＭ堆積量分布を更新し、具体的には上記ＰＭの性状に関連づけてＰＭを減算することによりＰＭ堆積量分布を更新する（ステップＳ３４）。このように機関運転中にもＰＭ堆積量分布を、所定の短時間毎、あるいは所定クランク角毎に逐次更新することで、機関運転中に変化するＰＭ堆積量分布を瞬時瞬時に正確に予測し、ＤＰＦのＰＭ堆積状況に応じた精度の高い適切なＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔの設定を行うことが可能となる。   Further, during the engine operation other than the DPF regeneration operation, the PM accumulation amount distribution is updated by adding PM in association with the property of the PM (step S36), and during the DPF regeneration operation, the regeneration temperature of the DPF is set. Based on this, the PM accumulation amount distribution is updated. Specifically, the PM accumulation amount distribution is updated by subtracting the PM in association with the property of the PM (step S34). In this way, the PM accumulation amount distribution is updated instantaneously every predetermined short time or every predetermined crank angle even during engine operation, so that the PM accumulation amount distribution that changes during engine operation can be accurately and instantaneously predicted. Therefore, it is possible to set an appropriate DPF regeneration target temperature Temp_target with high accuracy according to the PM deposition state of the DPF.

［２］上記ＰＭの性状とは、典型的には、機関運転状態に応じて変化するＰＭの燃焼可能温度である。このようにＰＭの性状としてＰＭの燃焼可能温度を用いることで、特にＤＰＦ再生運転中におけるＤＰＦからのＰＭの除去量を燃焼可能温度に関連づけて正確に把握でき、ＰＭ堆積量分布を精度良く設定・更新することができる。   [2] The property of PM is typically a combustible temperature of PM that changes according to the engine operating state. Thus, by using the combustible temperature of PM as the property of PM, it is possible to accurately grasp the amount of PM removed from the DPF particularly during the DPF regeneration operation in association with the combustible temperature, and to accurately set the PM deposition amount distribution.・ Can be updated.

［３］図１２及び図１３に示すように、ＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔの設定では、上記ＰＭ堆積量分布における燃焼可能温度の低い側から高い側へとＰＭの除去が進行するように、ＤＰＦ再生運転中におけるＤＰＦ再生目標温度を低い側から高い側へと変化させる。仮に図１３の比較例のようにＤＰＦ再生目標温度を一定とし、ＤＰＦの再生開始直後から高い温度に設定すると、ＤＰＦ再生の開始当初には、ＰＭ燃焼可能温度の低いＰＭのみならずＰＭ燃焼可能温度の高いＰＭまでもが燃焼することとなり、これによってＤＰＦの温度が過度に高くなって、早期にＤＰＦ許容温度を超えてＤＰＦ運転を継続することができず、ＤＰＦのＰＭ浄化率の低下やＤＰＦ再生回数・頻度の増加を招くおそれがある。ＤＰＦ再生頻度が増えると、その都度ＤＰＦの昇温を行う必要があり、燃費や排気エミッションの悪化を避けられない。これに対して本実施例のように、ＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔを低い側から高い側へと変化させることで、ＤＰＦ再生初期には、ＰＭ燃焼可能温度の低いＰＭのみが燃焼・除去されることとなるので、ＤＰＦ温度が過度に高くなることがなく、比較的長い時間にわたって安定してＤＰＦ再生運転を行うことが可能となり、ＤＰＦ再生回数・頻度を低く抑えることができ、ひいては燃費や排気エミッションの悪化を抑制することができる。   [3] As shown in FIG. 12 and FIG. 13, in the setting of the DPF regeneration target temperature Temp_target, the DPF regeneration is performed so that the removal of PM progresses from the low combustible temperature side to the high side in the PM deposition amount distribution. The DPF regeneration target temperature during operation is changed from the low side to the high side. If the DPF regeneration target temperature is set constant as in the comparative example of FIG. 13 and is set to a high temperature immediately after the start of regeneration of the DPF, at the beginning of the DPF regeneration, not only PM having a low PM combustion temperature but also PM combustion is possible. Even PM with a high temperature will burn, and as a result, the temperature of the DPF becomes excessively high, the DPF operation cannot be continued at an early time exceeding the allowable DPF temperature, and the PM purification rate of the DPF is reduced. There is a risk of increasing the number and frequency of DPF regeneration. When the frequency of DPF regeneration increases, it is necessary to raise the temperature of the DPF each time, and deterioration of fuel consumption and exhaust emission is inevitable. On the other hand, as in this embodiment, by changing the DPF regeneration target temperature Temp_target from the low side to the high side, only the PM having a low PM combustible temperature is combusted and removed at the initial stage of the DPF regeneration. Therefore, the DPF temperature does not become excessively high, it is possible to stably perform the DPF regeneration operation over a relatively long time, and the number and frequency of DPF regeneration can be suppressed to a low level. Can be prevented.

［４］より具体的には、図１２に示すように、ＰＭ堆積量分布におけるＰＭ燃焼可能温度の低い側からのＰＭ堆積量の積算値が所定の判定しきい値ＰＭ＿ｔＳＬとなるＰＭ除去区間Ｓ１のＰＭ燃焼可能温度に基づいて、ＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔを設定する。典型的には、ＰＭ除去区間Ｓ１における燃焼可能温度の最大値をＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔとして設定する。これによって、ＤＰＦ再生運転中には、ＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔが徐々に高くなっていき、これに伴って、実際のＤＰＦの温度が徐々に高くなり、ＰＭ燃焼可能温度の低い側から適切にＰＭが除去されていくこととなる。   [4] More specifically, as shown in FIG. 12, the PM removal section S1 in which the integrated value of the PM accumulation amount from the lower PM combustible temperature side in the PM accumulation amount distribution becomes a predetermined determination threshold value PM_tSL. The DPF regeneration target temperature Temp_target is set based on the PM combustible temperature. Typically, the maximum value of the combustible temperature in the PM removal section S1 is set as the DPF regeneration target temperature Temp_target. As a result, during the DPF regeneration operation, the DPF regeneration target temperature Temp_target gradually increases, and accordingly, the actual DPF temperature gradually increases, and the PM combustion temperature is appropriately increased from the low PM combustible temperature side. Will be removed.

［５］図１４にも示すように、ＤＰＦの温度が高くなるほど上記判定しきい値ＰＭ＿ｔＳＬが小さくなるように、ＤＰＦの温度に基づいて判定しきい値ＰＭ＿ｔＳＬを補正している。これによって、ＤＰＦ再生運転中にＤＰＦ温度がＤＰＦ許容温度に近づくと、これに伴って判定しきい値ＰＭ＿ｔＳＬが小さくなって、ＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔが低温側に補正されるために、ＤＰＦ温度がＤＰＦ許容温度を超える事態を招き難い。   [5] As shown in FIG. 14, the determination threshold value PM_tSL is corrected based on the temperature of the DPF so that the determination threshold value PM_tSL decreases as the temperature of the DPF increases. As a result, when the DPF temperature approaches the DPF allowable temperature during the DPF regeneration operation, the determination threshold value PM_tSL decreases accordingly, and the DPF regeneration target temperature Temp_target is corrected to the low temperature side. It is difficult to invite a situation that exceeds the allowable DPF temperature.

［６］上記ＰＭの燃焼可能温度は、例えば図１１に示すように燃料噴射量（機関負荷）Ｑｆｉｎと機関回転数Ｎｅに基づいて求められる。更には、筒内圧情報やＰＭの結晶性等を勘案することにより、より精度良くＰＭの燃焼可能温度を求めることができる。   [6] The combustible temperature of PM is obtained based on the fuel injection amount (engine load) Qfin and the engine speed Ne as shown in FIG. 11, for example. Furthermore, by considering the in-cylinder pressure information and the crystallinity of PM, the combustible temperature of PM can be obtained with higher accuracy.

［７］上記実施例のように機関運転中には極短い演算周期（例えば１０ｍｓ，所定クランク角）で図２〜図７のルーチンを繰り返し実行することによって、瞬時のＰＭ排出量やＰＭ堆積量をＰＭ燃焼可能温度に関連づけて算出し、時々刻々で変化するＰＭ堆積量分布を逐次更新することによって、ＰＭ堆積量分布を精度良く予測することができ、適切なＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔの設定が可能となる。   [7] As in the above embodiment, the routine shown in FIGS. 2 to 7 is repeatedly executed with an extremely short calculation cycle (for example, 10 ms, a predetermined crank angle) during engine operation, so that the instantaneous PM discharge amount and the PM accumulation amount are obtained. Is calculated in association with the PM combustible temperature, and the PM deposition amount distribution that changes from time to time is sequentially updated, so that the PM deposition amount distribution can be accurately predicted, and an appropriate DPF regeneration target temperature Temp_target is set. It becomes possible.

［８］ＤＰＦ再生時においては、図４のステップＳ４２及び図９に示すように、ＤＰＦ床温度とＰＭ堆積量からＰＭ燃焼可能温度毎のＰＭ燃焼速度（Ｓｔ）を算出し、このＰＭ燃焼速度を用いてＰＭ燃焼可能温度毎のＰＭ処理量（除去量・減少量）を精度良く求めることができる。   [8] At the time of DPF regeneration, as shown in step S42 of FIG. 4 and FIG. 9, the PM combustion rate (St) for each PM combustible temperature is calculated from the DPF floor temperature and the PM deposition amount, and this PM combustion rate. The PM processing amount (removal amount / reduction amount) for each PM combustion possible temperature can be obtained with high accuracy.

［９］図７及び図１５に示す他の実施例のように、ＤＰＦ再生が進行し、ＤＰＦに残存するＰＭの量が少なくなってくると、これに応じてＤＰＦ再生目標温度Ｔｅｍｐ＿ｔａｒｇｅｔを低温側へ補正することによって、ＤＰＦ再生の終了間際に過剰な熱量が与えられるてＤＰＦの過度な上昇を招くという事態が生じることを抑制することができる。   [9] As in the other embodiments shown in FIGS. 7 and 15, when the DPF regeneration progresses and the amount of PM remaining in the DPF decreases, the DPF regeneration target temperature Temp_target is decreased accordingly. It is possible to suppress the occurrence of a situation in which an excessive amount of heat is applied just before the end of the DPF regeneration and an excessive increase in the DPF occurs.

本発明の一実施例に係る内燃機関の排気浄化装置を示すシステム図。1 is a system diagram showing an exhaust emission control device for an internal combustion engine according to an embodiment of the present invention. 本実施例の制御の流れを示すフローチャート。The flowchart which shows the flow of control of a present Example. 図２のＤＰＦ再生実施判断・ＰＭ堆積量演算のサブルーチン。FIG. 2 is a subroutine of DPF regeneration execution determination / PM accumulation amount calculation of FIG. 図３のＰＭ減算演算のサブルーチン。FIG. 3 is a subroutine of PM subtraction operation of FIG. 図３のＰＭ加算演算のサブルーチン。FIG. 3 is a subroutine of PM addition calculation of FIG. 図２のＤＰＦ再生温度設定演算のサブルーチン。FIG. 3 is a subroutine of DPF regeneration temperature setting calculation in FIG. 2. FIG. 本発明の他の実施例に係るＤＰＦ再生温度の設定演算処理の流れを示すフローチャート。The flowchart which shows the flow of the setting calculation process of DPF regeneration temperature which concerns on the other Example of this invention. 低負荷運転時及び高負荷運転時におけるＰＭ堆積量分布を示す説明図。Explanatory drawing which shows PM deposition amount distribution at the time of low load operation and high load operation. ＰＭ燃焼可能温度と燃焼速度とＤＰＦの温度との関係を示す説明図。Explanatory drawing which shows the relationship between PM combustion possible temperature, a combustion speed, and the temperature of DPF. 低負荷運転時及び高負荷運転時におけるＤＰＦの温度とＰＭ堆積量との関係を示す説明図。Explanatory drawing which shows the relationship between the temperature of DPF at the time of low load operation and high load operation, and PM deposition amount. 機関回転数及び燃料噴射量に対する燃焼可能温度の関係を示す説明図。Explanatory drawing which shows the relationship of the combustible temperature with respect to engine speed and fuel injection quantity. 本実施例に係るＤＰＦ再生に伴うＰｍ堆積量分布の変化の様子を示す説明図。Explanatory drawing which shows the mode of the change of Pm deposit amount distribution accompanying DPF reproduction | regeneration concerning a present Example. ＤＰＦ再生運転中のＤＰＦ再生目標温度の変化を示す説明図。Explanatory drawing which shows the change of DPF regeneration target temperature during DPF regeneration operation. ＤＰＦ再生運転中の許可温度差ΔＴ及び判定しきい値ＰＭ＿ｔＳＬの変化を示す説明図。Explanatory drawing which shows the change of permissible temperature difference (DELTA) T and determination threshold value PM_tSL during DPF regeneration driving | operation. 熱量割合ｔＱ／Ｑｔｏｔａｌから補正値Ｈ１を求めるための制御マップ。A control map for obtaining the correction value H1 from the heat quantity ratio tQ / Qtotal.

符号の説明Explanation of symbols

１…ディーゼルエンジン（内燃機関）
９…燃料噴射弁
１４…ディーゼルパティキュレートフィルタ（ＤＰＦ）
２０…コントロールユニット
２５…ＤＰＦ温度センサ 1 ... Diesel engine (internal combustion engine)
9 ... Fuel injection valve 14 ... Diesel particulate filter (DPF)
20 ... Control unit 25 ... DPF temperature sensor

Claims (5)

内燃機関の排気通路中に、流入する排気中のＰＭを捕集するＤＰＦが設けられ、ＤＰＦ再生運転時には、ＤＰＦを昇温することによりＤＰＦに堆積するＰＭ堆積量を低減する内燃機関の排気浄化装置において、
機関運転状態に基づいて定まるＰＭの性状毎にＰＭ堆積量をヒストグラム化し、ＰＭの性状毎にＰＭ堆積量分布を予測するＰＭ堆積量分布予測手段と、
このＰＭ堆積量分布に基づいて、ＤＰＦ再生目標温度を設定するＤＰＦ再生目標温度設定手段と、を有し、
上記ＰＭ堆積量分布予測手段は、ＤＰＦ再生運転中は、上記ＤＰＦの再生温度に基いてＰＭ堆積量分布を更新し、
上記ＤＰＦ再生目標温度設定手段は、上記ＰＭ堆積量分布予測手段によって更新されるＰＭ堆積量分布に応じて再生中のＤＰＦ再生目標温度を更新することを特徴とする内燃機関の排気浄化装置。 A DPF for collecting PM in the inflowing exhaust gas is provided in the exhaust passage of the internal combustion engine, and during the DPF regeneration operation, the exhaust purification of the internal combustion engine reduces the amount of PM deposited on the DPF by raising the temperature of the DPF. In the device
PM deposition amount distribution prediction means for making a histogram of the PM deposition amount for each PM property determined based on the engine operating state, and predicting the PM deposition amount distribution for each PM property;
DPF regeneration target temperature setting means for setting the DPF regeneration target temperature based on the PM accumulation amount distribution,
The PM accumulation amount distribution predicting means updates the PM accumulation amount distribution based on the regeneration temperature of the DPF during the DPF regeneration operation,
The DPF regeneration target temperature setting means updates the DPF regeneration target temperature being regenerated according to the PM accumulation amount distribution updated by the PM accumulation amount distribution prediction means. 上記ＰＭの性状は、ＰＭの燃焼可能温度であることを特徴とする請求項１に記載の内燃機関の排気浄化装置。   The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the property of the PM is a combustible temperature of the PM. 上記ＤＰＦ再生目標温度設定手段は、上記ＰＭ堆積量分布における燃焼可能温度の低い側から高い側へとＰＭの除去が進行するように、ＤＰＦ再生運転中におけるＤＰＦ再生目標温度を低い側から高い側へと変化させることを特徴とする請求項２に記載の内燃機関の排気浄化装置。   The DPF regeneration target temperature setting means sets the DPF regeneration target temperature during the DPF regeneration operation from the low side to the high side so that the removal of PM proceeds from the low combustible temperature side to the high side in the PM accumulation amount distribution. The exhaust emission control device for an internal combustion engine according to claim 2, wherein 上記ＤＰＦ再生目標温度設定手段は、上記ＰＭ堆積量分布における燃焼可能温度の低い側からのＰＭ堆積量の積算値が所定の判定しきい値となるＰＭ除去区間の燃焼可能温度に基づいて、上記ＤＰＦ再生目標温度を設定することを特徴とする請求項２又は３に記載の内燃機関の排気浄化装置。   The DPF regeneration target temperature setting means is based on the combustible temperature in the PM removal section in which the integrated value of the PM accumulated amount from the low combustible temperature side in the PM accumulated amount distribution becomes a predetermined determination threshold value. The exhaust gas purification apparatus for an internal combustion engine according to claim 2 or 3, wherein a DPF regeneration target temperature is set. 上記ＤＰＦの温度が高くなるほど上記判定しきい値が小さくなるように、上記ＤＰＦの温度に基づいて上記判定しきい値を補正することを特徴とする請求項４に記載の内燃機関の排気浄化装置。   5. The exhaust gas purification apparatus for an internal combustion engine according to claim 4, wherein the determination threshold value is corrected based on the temperature of the DPF so that the determination threshold value decreases as the temperature of the DPF increases. .
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