JP2006316682A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device of an internal combustion engine, capable of performing regeneration processing of a DPF in the proper timing, by accurately calculating a particulate deposit quantity of the DPF. <P>SOLUTION: A basic particulate discharge quantity PMBASE is calculated in response to an engine speed NE and a fuel injection quantity QINJ. The target air excessive ratio λCMD is calculated in response to the engine speed NE and the fuel injection quantity QINJ, and the ratio λRATIO with the actual air excessive ratio λACT is calculated. A correction factor Kλ is calculated in response to the air excessive ratio λRAIO and the fuel injection quantity QINJ, and the basic particulate discharge quantity PMBASE is multiplied by the correction factor Kλ. A particulate discharge quantity PMUT is also calculated by adding and subtracting the other correction term, and a deposit quantity PMACC is calculated by integrating this quantity. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine, and more particularly, to an apparatus having a particulate filter (DPF: Diesel Particulate Filter) for collecting particulates (particulate matter) in the exhaust gas of an internal combustion engine.

  2. Description of the Related Art A technique for providing a DPF that collects particulates in exhaust gas in an exhaust system of a diesel internal combustion engine to reduce the amount of particulate emissions is widely used. Since there is a limit to the amount of particulates that can be collected by the DPF, the amount of particulates accumulated in the DPF is calculated, and the execution timing of the regeneration process for burning the accumulated particulates is commensurate with the calculated amount of particulates accumulated. Determined.

  Patent Document 1 discloses an example of a technique for calculating the amount of DPF particulate accumulation. That is, the particulate discharge amount per unit time is calculated according to the engine speed and the accelerator pedal depression amount, and further corrected according to the engine coolant temperature, and the corrected particulate discharge amount is integrated. Thus, the particulate deposition amount is calculated. Further, according to the technique disclosed in Patent Document 1, when the particulates accumulated in the DPF burn, the regeneration amount per unit time (deposition amount decrease amount) is calculated, and the regeneration amount is subtracted from the particulate deposition amount. The

Japanese Patent Laid-Open No. 5-332125

  In a transient state, such as during acceleration when the accelerator pedal is depressed suddenly, the particulate emissions per unit time calculated according to the engine speed and accelerator pedal depression amount deviate from the actual values. There is a problem that the calculation accuracy of the DPF is lowered, and the execution time of the DPF regeneration process is delayed from the desired time.

  The present invention has been made paying attention to this point, and provides an exhaust emission control device for an internal combustion engine that can more accurately calculate the amount of particulate deposition of DPF and execute DPF regeneration processing at an appropriate time. The purpose is to do.

  In order to achieve the above object, an invention according to claim 1 is directed to an exhaust gas purification apparatus for an internal combustion engine comprising a particulate filter (12) for collecting particulates in the exhaust gas of the internal combustion engine (1). ) In accordance with the operating state of the particulate filter (12), the particulate quantity calculating means (31) for calculating the particulate quantity per unit time (PMBASE), and the mixture combusted in the engine (1) The excess air ratio detection means (21, 33) for detecting the excess air ratio (λACT) of air, the target value (λCMD) of the excess air ratio and the detected excess air ratio (λACT) (λRATIO) ) To correct the particulate quantity (PMBASE), and the corrected particulates. Characterized by comprising an integrating means (41) for calculating accumulated particulate quantity (PMACC) by integrating the amount (PMUT).

  According to a second aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the first aspect, the correction means is configured to determine the parameter based on the comparison result (λRATIO) and a parameter (QINJ) indicating the load of the engine. The curate amount (PMBASE) is corrected.

  According to the first aspect of the present invention, the amount of particulate per unit time accumulated on the particulate filter is calculated according to the operating state of the engine, and the target value of the excess air ratio of the air-fuel mixture combusted in the engine is calculated. The particulate amount is corrected based on the comparison result with the detected excess air ratio, and the particulate accumulation amount is calculated by integrating the corrected particulate amount. For example, in a transient state such as when the engine is accelerating, the increase in intake air is delayed with respect to the increase in fuel, and thus the excess air ratio tends to increase temporarily. It wasn't. Therefore, by correcting the particulate amount based on the comparison result between the target value and the detected value of the excess air ratio, correction according to the deviation from the target value of the excess air ratio is performed, and a more accurate particulate deposition amount. Can be obtained. As a result, the DPF regeneration process can be executed at an appropriate time.

  According to the second aspect of the present invention, the particulate quantity is corrected based on the comparison result between the detected value of the excess air ratio and the target value and the parameter indicating the engine load. Since the influence of the deviation of the excess air ratio increases as the engine load increases, a more accurate particulate accumulation amount can be obtained by performing correction based on the engine load.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing the configuration of an internal combustion engine equipped with an exhaust emission control device according to an embodiment of the present invention and its control device. An internal combustion engine (hereinafter simply referred to as “engine”) 1 is a diesel engine that directly injects fuel into a cylinder, and a fuel injection valve 16 is provided in each cylinder. The fuel injection valve 16 is electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 20, and the valve opening time and valve opening timing of the fuel injection valve 16 are controlled by the ECU 20.

The engine 1 includes an intake pipe 2, an exhaust pipe 4, and a supercharger 8. The supercharger 8 includes a turbine 10 that is driven by exhaust kinetic energy, and a compressor 9 that is rotationally driven by the turbine 10 and compresses intake air.
The turbine 10 includes a plurality of variable vanes (not shown), and is configured to change the turbine rotational speed (rotational speed) by changing the opening degree of the variable vanes. The vane opening degree of the turbine 10 is electromagnetically controlled by the ECU 20.

  An intercooler 5 for cooling the pressurized air and an intake shutter (throttle valve) 3 for controlling the intake air amount are provided in the intake pipe 2 downstream of the compressor 9. The intake shutter 3 is controlled to be opened and closed by the ECU 20 via an actuator (not shown).

  Between the upstream side of the turbine 10 in the exhaust pipe 4 and the downstream side of the intake shutter 5 in the intake pipe 2, an exhaust gas recirculation passage 6 for returning the exhaust gas to the intake pipe 2 is provided. The exhaust gas recirculation passage 6 is provided with an exhaust gas recirculation control valve (hereinafter referred to as “EGR valve”) 7 for controlling the exhaust gas recirculation amount. The EGR valve 7 is an electromagnetic valve having a solenoid, and the valve opening degree is controlled by the ECU 20.

On the downstream side of the turbine 10 of the exhaust pipe 4, a catalytic converter 11 for purifying exhaust and a DPF 12 are provided in this order from the upstream side.
The catalytic converter 11 incorporates an oxidation catalyst for promoting the oxidation of hydrocarbons and carbon monoxide contained in the exhaust gas. Note that the catalytic converter 11 may be added with a NOx adsorbent that adsorbs NOx and a NOx reduction action.

  When the exhaust gas passes through the fine holes in the filter wall, the DPF 12 deposits soot, which is a particulate material mainly composed of carbon (C) in the exhaust gas, on the surface of the filter wall and the holes in the filter wall. Collect by letting. As a constituent material of the filter wall, for example, ceramics such as silicon carbide (SiC) or a porous metal body is used.

  If soot is collected up to the limit of the soot collecting ability of the DPF 12, that is, the accumulation limit, the exhaust pressure rises, so it is necessary to perform a regeneration process for burning the soot in a timely manner. In this regeneration process, post injection is performed in order to raise the temperature of the exhaust gas to the combustion temperature of the soot. Post-injection is fuel injection performed in the exhaust stroke by the fuel injection valve 16. The fuel injected by the post injection is mainly burned by the catalytic converter 11 and raises the temperature of the exhaust gas flowing into the DPF 12.

  Further, a crank angle position sensor 22 that detects the rotation angle of the crankshaft of the engine 1, an intake air flow rate sensor 21 that detects the intake air flow rate GA of the engine 1, and other sensors (not shown) such as the cooling water temperature TW of the engine 1 Cooling water temperature sensor to detect, accelerator sensor to detect accelerator pedal depression amount AP of vehicle driven by engine 1, intake air temperature sensor to detect intake air temperature TA of engine 1, atmospheric pressure sensor to detect atmospheric pressure PA, DPF12 An exhaust temperature sensor for detecting the exhaust temperature TEX immediately upstream is provided, and detection signals from these sensors are supplied to the ECU 20. The rotational speed (rotational speed) NE of the engine 1 is calculated from the output of the crank angle position sensor 22.

  The ECU 20 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, a central processing unit (hereinafter referred to as “CPU”). A storage circuit that stores various calculation programs executed by the CPU, calculation results, and the like, and an output circuit that supplies control signals to the fuel injection valve 16, the EGR valve 7, and the like.

  FIG. 2 is a block diagram showing a configuration of a module for calculating the particulate accumulation amount PMMAC of the DPF 12. As shown in FIG. The function of this module is actually realized by arithmetic processing by the CPU of the ECU 20.

  2 includes a PMBASE calculation unit 31, a λCMD calculation unit 32, a λACT calculation unit 33, a division unit 34, a Kλ calculation unit 35, a multiplication unit 36, a PMCR calculation unit 37, An addition unit 38, a PMRG calculation unit 39, a subtraction unit 40, and an integration unit 41 are provided.

  The PMBASE calculation unit 31 searches a PMBASE map (not shown) corresponding to the detected engine speed NE and the fuel injection amount QINJ, thereby obtaining a basic value of the particulate amount per unit time discharged from the engine 1. The basic particulate emission amount PMBASE is calculated. The PMBASE map is set so that the basic particulate discharge amount PMBASE increases as the engine speed NE increases and the fuel injection amount QINJ increases. The fuel injection amount QINJ is a fuel injection amount per unit time (a fuel amount injected by the fuel injection valve 16) calculated according to the accelerator pedal depression amount AP, and is approximately proportional to the load of the engine 1. .

  The λCMD calculation unit 32 searches a λCMD map (not shown) according to the engine speed NE and the fuel injection amount QINJ, and sets a target value (hereinafter referred to as “target air excess”) of the air excess ratio of the air-fuel mixture combusted in the engine 1. ΛCMD) (referred to as “rate”). The λCMD map is set so that the target excess air ratio λCMD increases as the engine speed NE increases and as the fuel injection amount QINJ increases.

The λACT calculating unit 33 calculates the actual excess air ratio λACT by applying the intake air flow rate GA and the fuel injection amount QINJ to the following equation (1).
λACT = GA / (QINJ × RSTOICH) (1)
Here, RSTOICH is the stoichiometric air-fuel ratio.

The division unit 34 calculates a ratio (hereinafter referred to as “excess air ratio”) λRATIO (= λCMD / λACT) between the target excess air ratio λCMD and the actual excess air ratio λACT.
The Kλ calculator 35 searches the Kλ map shown in FIG. 3 according to the excess air ratio λRATIO and the fuel injection amount QINJ, and calculates the correction coefficient Kλ. The Kλ map is set to a characteristic as shown by, for example, the line L1 in the high load operation state, and is set to a characteristic as shown by, for example, the line L2 in the low load operation state. That is, the Kλ map is set such that the correction coefficient Kλ increases as the excess air ratio λRATIO increases and as the fuel injection amount QINJ (engine load) increases. The Kλ map is set so that the rate of change of the correction coefficient Kλ with respect to the change of the excess air ratio λRATIO increases as the fuel injection amount QINJ increases.

  The multiplier 36 multiplies the basic particulate discharge amount PMBASE by the correction coefficient Kλ. The PMCR calculation unit 37 calculates the correction amount PMCR according to the engine coolant temperature TW, the intake air temperature TA, and the atmospheric pressure PA. The adder 38 adds the correction amount PMCR to the output (PMBASE × Kλ) of the multiplier 36. The PMRG calculating unit 39 calculates the particulate reduction PMRG accumulated in the DPF 12 according to the fuel injection amount QINJ, the intake air flow rate GA, and the exhaust temperature TEX. This is because the exhaust temperature TEX rises during high-load operation of the engine 1 and the particulates accumulated in the DPF 12 are combusted (decreases due to natural regeneration) without performing post-injection. This is in consideration of the decrease in particulates.

By summing up the calculations performed by the multiplier 36, the adder 38, and the subtractor 40, the particulate discharge amount PMUT per unit time is calculated by the following equation (2).
PMUT = PMBASE × Kλ + PMCR−PMRG (2)

The accumulating unit 41 calculates the particulate accumulation amount PMMAC of the DPF 12 by applying and accumulating the particulate discharge amount PMUT to the following equation (3).
PMMAC = PMMAC + PMUT (3)
Here, PMACC on the right side is a calculated value before unit time.

  The ECU 20 executes the regeneration process of the DPF 12 when the particulate accumulation amount PMMAC reaches the predetermined threshold value PMATH.

  FIG. 4 is a time chart for explaining the calculation result of the particulate discharge amount PMUT when the engine 1 is accelerated. (A) shows the transition of the particulate emission amount PMUT, (b) shows the transition of the target excess air ratio λCMD and the actual excess air ratio λACT, and (c) shows the fuel injection amount QINJ and Changes in engine speed NE are shown.

  When the accelerator pedal is depressed at time t0, as shown in FIG. 4C, the fuel injection amount QINJ increases stepwise, and the engine speed NE gradually increases. At this time, the target excess air ratio λCMD gradually increases as shown by the broken line in FIG. 5B, but the actual excess air ratio λACT increases the intake air amount as the fuel injection amount QINJ increases. Since it is delayed, it decreases rapidly immediately after time t0 and then gradually increases. As a result, the basic particulate discharge amount PMBASE changes as shown by a broken line in FIG. 5A, but the particulate discharge amount PMUT corrected by the correction coefficient Kλ is time t0 as shown by a solid line in FIG. Immediately after that, it increases rapidly and then gradually decreases.

  Since the actual particulate discharge amount changes as shown by a solid line in FIG. 4A, the particulate discharge amount PMUT accurately indicates the particulate discharge amount per unit time. Accordingly, by accumulating the particulate discharge amount PMUT, an accurate particulate deposition amount PMMAC can be obtained. In other words, in the conventional method, since the basic particulate discharge amount PMBASE is integrated as it is, the particulate discharge amount is shifted to a value smaller than the actual value. Since the particulate discharge amount PMUT is calculated by the correction, a more accurate particulate discharge amount PMUT can be obtained, and thus a more accurate particulate deposition amount PMMAC can be obtained. As a result, the DPF regeneration process can be executed at an appropriate time.

  In the present embodiment, the intake air flow rate sensor 21 and the ECU 20 constitute an excess air ratio detecting means, and the ECU 20 constitutes a particulate amount calculating means, a correcting means, and an integrating means. Specifically, the λACT calculation unit 33 in FIG. 2 corresponds to a part of the excess air ratio detection unit, the PMBASE calculation unit 31 in FIG. 2 corresponds to the particulate amount calculation unit, and the λCMD calculation unit 32 and the division unit 34. , The Kλ calculating unit 35 and the multiplying unit 36 correspond to a correcting unit, and the integrating unit 41 corresponds to an integrating unit.

  The present invention is not limited to the embodiment described above, and various modifications can be made. FIG. 5 is a block diagram showing a configuration of a modified example of the accumulation amount calculation module shown in FIG. The deposition amount calculation module shown in FIG. 5 includes a Kλ calculator 35a instead of the Kλ calculator 35 shown in FIG. The fuel injection amount QINJ is not input to the Kλ calculator 35a, and the Kλ calculator 35a searches the Kλ table shown in FIG. 6 according to the excess air ratio λRATIO and calculates the correction coefficient Kλ.

  In the modification shown in FIG. 5, the correction coefficient Kλ is calculated according to only the excess air ratio λRATIO using the Kλ table (FIG. 6) corresponding to the average engine load. Thus, when the fuel injection amount QINJ, which is a parameter indicating the engine load, is not used, the particulate emission amount PMUT slightly deviates from the true value when the engine load deviates from the average value. Compared with the conventional example in which the curated discharge amount PMBASE is used as it is, the calculation accuracy of the particulate discharge amount PMUT can be improved.

In the above-described embodiment, the actual excess air ratio λACT is calculated by the equation (1). However, an oxygen concentration sensor may be provided in the exhaust system and may be calculated according to the oxygen concentration sensor output.
In the above-described embodiment, the fuel injection amount QINJ is used as a parameter indicating the engine load. However, the accelerator pedal depression amount AP may be used instead.

  In the above-described embodiment, the correction coefficient Kλ is calculated according to the excess air ratio λRATIO (and the fuel injection amount QINJ), but instead of this, the target excess air ratio λCMD and the actual excess air ratio λACT are calculated. The correction coefficient Kλ may be calculated according to the difference Dλ (= λCMD−λACT). In this case, the Kλ map or the Kλ table is set so that the correction coefficient Kλ increases as the difference Dλ increases.

  The present invention can also be applied to an exhaust purification device such as a marine vessel propulsion engine such as an outboard motor having a vertical crankshaft.

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. It is a block diagram which shows the structure of the module which calculates the amount of particulates accumulate | stored in DPF. It is a figure which shows the map for calculating a correction coefficient (Kλ). It is a time chart for demonstrating transition of the particulate discharge amount at the time of acceleration of an engine. It is a block diagram which shows the modification of the module shown in FIG. It is a figure which shows the table used with the module shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 12 Diesel particulate filter 20 Electronic control unit (Particulate amount calculation means, excess air ratio detection means, correction means, integration means)
21 Intake air flow rate sensor (excess air ratio detection means)

Claims (2)

In an exhaust gas purification apparatus for an internal combustion engine comprising a particulate filter that collects particulates in the exhaust gas of the internal combustion engine,
A particulate amount calculating means for calculating a particulate amount per unit time deposited on the particulate filter in accordance with an operating state of the engine;
An excess air ratio detecting means for detecting an excess air ratio of an air-fuel mixture combusted in the engine;
Correction means for correcting the particulate amount based on a comparison result between the target value of the excess air ratio and the detected excess air ratio;
An exhaust emission control device for an internal combustion engine, comprising: integrating means for calculating a particulate accumulation amount by integrating the corrected particulate amount.   2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the correction unit corrects the particulate amount based on the comparison result and a parameter indicating a load of the engine.

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