JP2008121573A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology capable of more precisely determining quantity of particulate matter accumulated on a particulate filter in an exhaust emission control device for an internal combustion engine. <P>SOLUTION: This exhaust emission control device is provided with an accumulation quantity estimation means S114 estimating quantity of particulate matter accumulated on the particulate filter by assuming that increase rate of accumulation quantity of particulate matter after reduction of increase rate of differential pressure gets higher as increase rate of accumulation quantity of particulate matter before reduction of increase rate of differential pressure gets higher when increase rate of differential pressure between before and after a filter reduces although quantity of particulate matter accumulated on the particulate filter increases further after a process that differential pressure between before and after filter increases as quantity of particulate matter accumulated on the particulate filter increases. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine.

  By providing a particulate filter (hereinafter referred to as a filter) in the exhaust passage, particulate matter (hereinafter referred to as PM) in the exhaust can be collected. When the amount of PM collected by this filter increases, exhaust resistance increases, resulting in deterioration of fuel consumption and the like. Therefore, it is necessary to regenerate a so-called filter that removes the PM collected by the filter. It is desirable to regenerate the filter when the amount of PM trapped in the filter is an appropriate amount. For this purpose, it is necessary to accurately grasp the amount of PM collected by the filter.

  Here, if the relationship between the pressure difference between the upstream side and the downstream side of the filter (hereinafter referred to as the differential pressure before and after the filter) and the PM accumulation amount is obtained in advance, the differential pressure before and after the filter is measured. The amount of PM deposition can be estimated. However, there is a case where the relationship between the actually accumulated PM amount and the differential pressure before and after the filter is interrupted halfway (here, for the sake of convenience, hereinafter referred to as a saturated state). Therefore, when the PM exceeds a certain accumulation amount, it becomes difficult to detect the accurate PM accumulation amount based on the differential pressure across the filter.

  The reason will be described below. PM deposited in the pores inside the partition walls of the filter is relatively easily oxidized by the catalytic action. However, PM deposited on the surface of the partition wall away from the catalyst is oxidized relatively easily at the portion in contact with the surface of the partition wall, but is not easily oxidized at the portion not in contact with the surface of the partition wall. As a result, spaces such as cavities and cracks are generated in the deposited PM layer. Since an infinite number of such spaces are formed in the deposited PM layer, the exhaust gas flowing into the filter passes through the deposited PM layer and passes through the pores. Therefore, even if the PM deposition amount increases, it is considered that the differential pressure before and after the filter hardly increases.

  That is, while PM remains in a state where the pores are clogged, the differential pressure across the filter increases almost in proportion to the amount of PM deposited. However, when the amount of PM in the exhaust gas increases, PM begins to deposit on the partition wall even if a part of the PM deposited in the pores is oxidized. Then, as described above, the differential pressure before and after the filter becomes saturated, and the differential pressure before and after the filter does not increase even though PM deposition further proceeds on the partition wall surface.

Here, when the amount of PM deposited on the filter is small, the amount of PM deposited is estimated according to the differential pressure across the filter, and the amount of PM deposited on the filter is large and is in the saturated state. In this case, a technique is known in which the amount of accumulated PM is estimated in consideration of the amount of PM generated per unit time or the operating state of the internal combustion engine (see, for example, Patent Document 1).
JP 2004-76589 A Japanese Patent No. 3757853

However, when estimating the PM estimated amount based on the operating state of the internal combustion engine or the like, the estimation is performed based on the PM emission amount obtained in advance through experiments or the like. In this case, the amount of PM emission changes due to variations in the production of fuel injection valves, EGR valves, throttles, etc. of the internal combustion engine, and variations in the properties of fuel distributed in the market. More PM emissions are estimated. For this reason, the interval at which the filter is regenerated is shortened, and there is a risk that the fuel consumption will deteriorate.

  The present invention has been made in view of the above-described problems, and in an exhaust gas purification apparatus for an internal combustion engine, a technique that can more accurately determine the amount of particulate matter deposited on a particulate filter. The purpose is to provide.

In order to achieve the above object, an exhaust gas purification apparatus for an internal combustion engine according to the present invention comprises:
A particulate filter that collects particulate matter in the exhaust of the internal combustion engine;
Differential pressure detecting means for detecting a differential pressure between the upstream side and the downstream side of the particulate filter;
Particulate matter deposited on the particulate filter after passing through a process in which the differential pressure detected by the differential pressure detecting means increases as the amount of particulate matter deposited on the particulate filter increases. In the case where the rate of increase in the differential pressure detected by the differential pressure detecting means decreases even though the amount of the pressure increases further, the rate of increase in the amount of particulate matter deposited before the rate of increase in the differential pressure decreases The amount of particulate matter deposited on the particulate filter as the rate of increase in the amount of particulate matter deposited after the rate of increase in the differential pressure has decreased,
It is characterized by providing.

  Before the differential pressure before and after the filter reaches saturation, the differential pressure before and after the filter increases with the increase in the amount of particulate matter, but this relationship is obtained as including the manufacturing variation of the components constituting the internal combustion engine. Can do. Even if the differential pressure before and after the filter is saturated, the particulate matter discharged from the internal combustion engine does not change. Therefore, the particulate matter is deposited after the saturation state as before the saturation state. Should do.

  That is, if the increasing rate of the particulate matter deposition amount is obtained before the differential pressure before and after the filter becomes saturated, the increasing rate of the particulate matter deposition amount after becoming saturated can also be obtained. Based on this rate of increase, the amount of particulate matter deposited on the particulate filter can be determined. The “increase rate” may be an increase amount per unit time.

In order to achieve the above object, an exhaust emission control device for an internal combustion engine according to the present invention includes:
A particulate filter that collects particulate matter in the exhaust of the internal combustion engine;
Differential pressure detecting means for detecting a differential pressure between the upstream side and the downstream side of the particulate filter;
Storage means for storing in advance the amount of particulate matter flowing into the particulate filter;
Based on the differential pressure detected by the differential pressure means during the process of increasing the differential pressure detected by the differential pressure detection means as the amount of particulate matter deposited on the particulate filter increases. A deposit amount increase rate calculating means for calculating an increase rate of the deposit amount of the particulate matter;
Correction means for correcting the amount of particulate matter stored in the storage means based on the increase rate of the particulate matter accumulation amount obtained by the deposition amount increase rate calculating means;
Particulate matter deposited on the particulate filter after passing through a process in which the differential pressure detected by the differential pressure detecting means increases as the amount of particulate matter deposited on the particulate filter increases. When the rate of increase in the differential pressure detected by the differential pressure detecting means decreases despite the further increase in the amount of the particulate filter, the particulate filter is based on the amount of particulate matter corrected by the correcting means. Deposit amount estimation means for estimating the amount of particulate matter deposited on the
It is good also as providing.

  The amount of particulate matter discharged from the internal combustion engine can be obtained in advance as an experimental value. However, since it is difficult to perform an experiment in all the internal combustion engines, values obtained in other internal combustion engines are used. Therefore, an error due to manufacturing variation or the like can occur. Therefore, the correction means determines how much the increase rate of the actual particulate matter deposition amount obtained by the deposition amount increase rate calculation means is compared with the amount of particulate matter stored in the maintenance particulate matter characteristic storage means. Calculate whether or not there is a deviation, and correct that amount.

  And even if the differential pressure before and after the filter is saturated, the amount of particulate matter discharged from the internal combustion engine does not change, so the correction value obtained before the saturated state remains unchanged even after the saturated state is reached. Can be used.

  That is, after the differential pressure before and after the filter is saturated, the amount of particulate matter stored in the storage means is corrected by the correction means, so that the amount of particulate matter flowing into the particulate filter can be more accurately determined. Can be requested.

  In the present invention, the particulate matter is removed when the combustion state in the internal combustion engine changes, and the accumulated amount of the particulate matter is estimated from the subsequent increasing process of the differential pressure detected by the differential pressure means. it can.

  “When the combustion state in the internal combustion engine changes” means, for example, that the combustion state changes even if the engine speed and the engine load are the same, and the amount of particulate matter discharged per unit time from the internal combustion engine changes. It means to do. In such a case, since the relationship between the increase in the differential pressure before and after the filter and the increase in the amount of collected particulate matter changes, the accumulation of particulate matter after the differential pressure before and after the filter becomes saturated The amount estimate needs to be changed accordingly. That is, in estimating the increase rate of the particulate matter deposition amount after the combustion state changes, it is not necessary to consider the increase rate of the particulate matter deposition amount before the combustion state changes. In addition, by removing the particulate matter collected so far, it takes more time to reach the saturation state, so that it is possible to improve the estimation accuracy of the rate of increase in the amount of particulate matter deposited.

  In the present invention, the particulate matter can be removed when the fuel of the internal combustion engine is newly replenished.

  When fuels having different properties are replenished, the combustion state of the internal combustion engine may change. Therefore, the amount of particulate matter discharged from the internal combustion engine may also change. On the other hand, if the particulate matter that has accumulated on the particulate filter is removed after the fuel is replenished, the particulate matter is deposited considering only the amount of particulate matter discharged after the fuel property has changed. The rate of increase in quantity can be estimated. Thereby, the estimation precision of the increase rate of the amount of particulate matter can be improved.

  In the present invention, the particulate matter can be removed when the lubricating oil of the internal combustion engine is replaced.

  When the lubricating oil is replaced, the viscosity of the lubricating oil may change, which may change the combustion state of the internal combustion engine. Therefore, the amount of particulate matter discharged from the internal combustion engine may also change. On the other hand, if the particulate matter accumulated on the particulate filter is removed after the lubricating oil is replaced, only the amount of particulate matter discharged after the lubricating oil is replaced is taken into account. The rate of increase in the amount of deposition can be estimated. Thereby, the estimation accuracy of the rate of increase in the amount of particulate matter deposited can be increased.

In addition, the combustion state may change when a part constituting the internal combustion engine or a part attached to the internal combustion engine is replaced, or when the atmospheric pressure or the air temperature changes more than a threshold value.

  According to the present invention, the amount of particulate matter deposited on the particulate filter can be determined more accurately in the exhaust gas purification apparatus for an internal combustion engine.

  Hereinafter, specific embodiments of an exhaust emission control device for an internal combustion engine according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a schematic configuration of an internal combustion engine 1 to which an exhaust gas purification apparatus for an internal combustion engine according to an embodiment is applied, and an intake system and an exhaust system thereof. The internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine. The internal combustion engine 1 is provided with a fuel injection valve 11 for supplying fuel into the cylinder of the internal combustion engine 1.

  An intake passage 2 and an exhaust passage 3 are connected to the internal combustion engine 1. A throttle 4 is provided in the middle of the intake passage 2. The throttle 4 is opened and closed by an electric actuator. An air flow meter 5 that outputs a signal corresponding to the flow rate of the intake air flowing through the intake passage 2 is provided in the intake passage 2 upstream of the throttle 4. The air flow meter 5 measures the amount of fresh intake air in the internal combustion engine 1.

On the other hand, a particulate filter 6 (hereinafter referred to as a filter 6) carrying an NOx storage reduction catalyst 61 (hereinafter referred to as NOx catalyst 61) is provided in the middle of the exhaust passage 3. The NOx catalyst 61 has a function of storing NOx in the exhaust when the oxygen concentration of the inflowing exhaust gas is high, and reducing the stored NOx when the oxygen concentration of the inflowing exhaust gas is reduced and a reducing agent is present. Have. The filter 6 collects PM contained in the exhaust.

Further, in this embodiment, a fuel addition valve 7 is provided for adding fuel (light oil) as a reducing agent into the exhaust gas flowing through the exhaust passage 3 upstream from the NOx catalyst 61. Here, the fuel addition valve 7 is opened by a signal from the ECU 20 described later to inject fuel. The fuel injected from the fuel addition valve 7 into the exhaust passage 3 enriches the air-fuel ratio of the exhaust flowing from the upstream of the exhaust passage 3 and reduces the NOx stored in the NOx catalyst 61. .

When the fuel injected from the fuel addition valve 7 reacts with the NOx catalyst 61, the temperature of the filter 6 is raised by the reaction heat. When the fuel injection from the fuel addition valve 7 is stopped after the temperature of the filter 6 has risen to a temperature required for PM oxidation, the filter 6 becomes a lean atmosphere and is collected by the filter 6. PM is oxidized. That is, the filter 6 can be regenerated. Thus, when raising the temperature of the filter 6, the amount of fuel injected from the fuel addition valve 7 is determined so that the temperature of the filter 6 becomes the target temperature.

  Further, a differential pressure sensor 8 that detects a pressure difference between the upstream side and the downstream side of the filter 6 (hereinafter referred to as a differential pressure across the filter) is attached to the exhaust passage 3. In this embodiment, the differential pressure sensor 8 corresponds to the differential pressure detection means in the present invention.

A temperature sensor 9 that outputs a signal corresponding to the temperature of the exhaust gas flowing through the exhaust passage 3 is attached to the exhaust passage 3 upstream of the filter 6. Based on the output signal of the temperature sensor 9, the temperatures of the filter 6 and the NOx catalyst 61 can be detected. Further, an air-fuel ratio sensor 10 that outputs a signal corresponding to the air-fuel ratio of the exhaust gas flowing through the exhaust passage 3 is attached to the exhaust passage 3 downstream of the filter 6.

  The internal combustion engine 1 configured as described above is provided with an ECU 20 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 20 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

  In addition to the above sensors, the ECU 20 outputs an electric signal corresponding to the amount of depression of the accelerator pedal 12 by the driver to detect the engine load, and an accelerator position sensor 13 that detects the engine speed and a crank position sensor that detects the engine speed. 14 are connected via electric wiring, and the output signals of these various sensors are input to the ECU 20. On the other hand, the fuel injection valve 11 and the fuel addition valve 7 are connected to the ECU 20 via electric wiring, and the ECU 20 controls the opening and closing timing of the fuel injection valve 11 and the fuel addition valve 7.

  Here, until the PM accumulation amount in the filter 6 reaches a predetermined amount, the differential pressure before and after the filter detected by the differential pressure sensor 8 and the PM accumulation amount of the filter 6 are in a substantially proportional relationship. However, if PM deposition on the filter 6 continues beyond a predetermined amount, the relationship between the two is not proportional, and even if the PM deposition amount increases, the differential pressure may not increase any more.

  On the other hand, in the present embodiment, the amount of PM deposited on the filter 6 after being saturated is estimated based on the rate of increase of the differential pressure before and after the filter before saturation.

  Here, FIG. 2 is a time chart showing the transition of the differential pressure across the filter. Since the differential pressure before and after the filter is affected by the amount of intake air and the temperature of the exhaust, correction according to the amount of intake air and the temperature of the exhaust is made so as to cancel the influence. As a result, even if the engine speed and the engine load change, the change in the differential pressure across the filter is not affected. And the pressure increase rate is so high that it becomes the solid line shown by (2) from the dashed-dotted line shown by (1), and also the dotted line shown by (3). That is, the amount of PM emission per unit time is increasing.

  Next, FIG. 3 is a diagram showing the relationship between the amount of PM flowing into the filter 6 (incoming gas PM amount) and the differential pressure across the filter. Instead of the input PM amount, the PM amount discharged from the internal combustion engine 1 may be used. The differential pressure before and after the filter is corrected according to the amount of intake air and the temperature of the exhaust as in the case of FIG. Also, the points indicated by (1), (2), and (3) in FIG. 3 correspond to the lines indicated by the same reference numerals in FIG.

  That is, the higher the pressure increase rate before the filter differential pressure before and after saturation is, the greater the amount of PM flowing into the filter 6 per unit time (hereinafter referred to as the input PM amount). It is considered that the amount of the input gas PM does not change even after the differential pressure before and after the filter is saturated. For this reason, the amount of PM collected by the filter 6 after the differential pressure across the filter is saturated can be obtained. Furthermore, the total amount of PM accumulated on the filter 6 can be obtained by adding the amount of collected PM obtained based on the differential pressure sensor 8 before the differential pressure before and after the filter is saturated.

  Therefore, in this embodiment, the amount of PM discharged from the internal combustion engine 1 is obtained in advance and mapped. Then, this map is corrected before the differential pressure before and after the filter becomes saturated, and the PM amount discharged from the internal combustion engine 1 is obtained using the corrected map after becoming saturated. Based on the amount of PM discharged from the internal combustion engine 1, the amount of PM deposited on the filter 6 is obtained. Note that the amount of PM accumulated in the filter 6 before the filter differential pressure before and after the filter becomes saturated can be obtained based on the filter differential pressure before and after.

Next, a flow for obtaining the regeneration time of the filter 6 in this embodiment will be described. FIG. 4 is a flowchart showing a flow for obtaining the regeneration time of the filter 6 in this embodiment. This routine is repeatedly executed every unit time.

  In step S101, the PM accumulation amount (X (i), X (i-1), Y (i), Y (i-1)) is initialized to zero. The PM deposition amount (X (i), X (i-1), Y (i), Y (i-1)) will be described later. Note that (i) indicates the value of the current routine, and (i-1) indicates the value of the previous routine.

  In step S102, the intake air amount G, the exhaust temperature T, and the filter differential pressure ΔP are read. The intake air amount G can be obtained from the air flow meter 5, the exhaust temperature T can be obtained from the temperature sensor 9, and the filter differential pressure ΔP can be obtained from the differential pressure sensor 8. The intake air amount G is obtained as a substitute for the flow rate of the exhaust gas passing through the filter 6, and the exhaust gas temperature T is obtained as a substitute for the temperature of the filter 6.

In step S103, the filter front-rear differential pressure ΔP is corrected by the intake air amount G and the exhaust temperature T, and the filter front-rear differential pressure A (i) according to the reference engine operating state is calculated. That is, the filter front-rear differential pressure ΔP changes according to the intake air amount G and the exhaust gas temperature T, so that this effect is removed to obtain the filter front-rear differential pressure in the reference operation state. The corrected differential pressure A (i) before and after the filter is obtained by the following equation.
A (i) = ΔP / (G / T ^1/2 )
The corrected differential pressure A (i) before and after the filter is stored in the ECU 20.

  In step S104, the PM accumulation amount X (i) of the filter 6 is calculated based on the corrected filter front-rear differential pressure A (i). The relationship between the corrected filter front-rear differential pressure A (i) and the PM accumulation amount X (i) of the filter 6 is obtained in advance through experiments or the like and mapped.

  In step S105, the fuel injection amount Q, the engine speed Ne, and the PM accumulation amount X (i-1) obtained in the previous routine are read.

In step S106, the increase ΔX in the PM accumulation amount X (i) of the filter 6 from the previous routine to the current routine and the increase ΔA in the corrected filter front-rear differential pressure A (i) are calculated by the following equations. . These are calculated as values per unit time.
ΔA = A (i) −A (i−1)
ΔX = X (i) −X (i−1)

  In step S107, the engine exhaust PM amount PMe, the first PM collection efficiency K1, the second PM collection efficiency K2, and the oxidized PM amount PMd are calculated.

  The engine exhaust PM amount PMe is an estimated value of the PM amount discharged from the internal combustion engine 1 per unit time, and is calculated based on the fuel injection amount Q and the engine speed Ne. The relationship between the engine speed Ne, the fuel injection amount Q, and the engine exhaust PM amount PMe is obtained in advance through experiments or the like, mapped, and stored in the ECU 20. Hereinafter, this map is referred to as an input gas PM map. In this embodiment, the ECU 20 storing the input gas PM map corresponds to the storage means in the present invention.

  Here, not all PM discharged from the internal combustion engine 1 is collected by the filter 6. That is, the collection efficiency of the filter 6 is not always 100%. The collection efficiency of the filter 6 decreases as the flow rate of the exhaust gas passing through the filter 6 increases. The flow rate of the exhaust gas has a correlation with the amount of gas discharged from the internal combustion engine 1 per unit time, and this gas amount has a correlation with the intake air amount G and the engine speed Ne of the internal combustion engine 1.

  Therefore, the first PM collection efficiency K1 is calculated based on the intake air amount G and the engine speed Ne. The relationship between the intake air amount G and the engine speed Ne and the first PM collection efficiency K1 is obtained in advance through experiments or the like and mapped and stored in the ECU 20.

  Further, the collection efficiency of the filter 6 also varies depending on the amount of PM collected by the filter 6. As the amount of PM collected by the filter 6 increases, the passage area of the exhaust gas in the filter 6 decreases, so that the collection efficiency increases.

  Therefore, the second PM collection efficiency K2 is calculated based on the PM accumulation amount X (i-1) obtained in the previous routine. The relationship between the PM accumulation amount X (i-1) and the second PM collection efficiency K2 is obtained in advance through experiments or the like and mapped and stored in the ECU 20.

  The oxidized PM amount PMd is the amount of PM oxidized by the filter 6 per unit time. The PM deposited on the filter 6 is oxidized according to the temperature of the filter 6 without performing the regeneration process of the filter 6. That is, as the temperature of the filter 6 increases, the oxidized PM amount PMd increases. Further, as the amount of exhaust gas passing through the filter 6 increases, the oxidized PM amount PMd increases. The amount of exhaust gas passing through the filter 6 is correlated with the intake air amount G of the internal combustion engine 1 and the engine speed Ne.

  Therefore, the oxidized PM amount PMd is calculated based on the intake air amount G, the engine speed Ne, and the exhaust temperature T. The relationship between the intake air amount G, the engine speed Ne, the exhaust temperature T, and the oxidized PM amount is obtained in advance through experiments or the like, mapped, and stored in the ECU 20.

  In step S108, the actual PM amount (actual input gas PM amount PMer) flowing into the filter 6 from the previous routine to the current routine is calculated.

Here, the increment ΔX of the PM deposition amount X (i) is obtained by subtracting the oxidized PM amount from the newly deposited PM amount. This is equal to a value obtained by subtracting the oxidized PM amount PMd from the value obtained by multiplying the actual input gas PM amount PMer by the first PM collection efficiency K1 and the second PM collection efficiency K2. That means
ΔX = PMer × K1 × K2-PMd
It can be. When this equation is transformed, PMer = (ΔX + PMd) / (K1 × K2)
It becomes. In this embodiment, the ECU 20 that executes the process of step S108 corresponds to the accumulation amount increase rate calculating means in the present invention.

In step S109, a correction coefficient K3 for correcting the input gas PM map is obtained, and the input gas PM map is corrected. The correction coefficient K3 is calculated by the following equation.
K3 = PMer / PMe
By this correction coefficient K3, how much the engine exhaust PM amount PMe deviates from a value obtained in advance through experiments or the like is obtained, and the input gas PM map is corrected. That is, the engine exhaust PM amount PMe until the differential pressure across the filter is saturated is corrected. Here, since the engine exhaust PM amount PMe is calculated based on the fuel injection amount Q and the engine speed Ne, the ECU 20 stores the relationship between the engine speed Ne and the fuel injection amount Q and the correction coefficient K3. . Based on this map, the engine exhaust PM amount PMe after the differential pressure across the filter is saturated is corrected. In this embodiment, the ECU 20 that executes the process of step S109 corresponds to the correcting means in the present invention.

In step S110, it is determined whether or not the increased amount ΔA of the corrected differential pressure A (i) before and after the filter is smaller than a predetermined amount.

  In this step, it is determined whether or not the differential pressure across the filter is saturated. Therefore, the predetermined amount may be substantially zero.

  If an affirmative determination is made in step S110, the process proceeds to step S111, whereas if a negative determination is made, the process returns to step S102.

  In step S111, the PM deposition amount (saturated PM deposition amount Xt) when the differential pressure across the filter is saturated is calculated. The PM accumulation amount X (i) of the filter 6 calculated in step S104 is substituted for the saturation PM accumulation amount Xt.

  In step S112, the fuel injection amount Q, the intake air amount G, the engine speed Ne, and the exhaust temperature T are read.

  In step S113, the engine exhaust PM amount PMe, the first PM collection efficiency K1, the second PM collection efficiency K2, the correction coefficient K3, and the oxidation PM amount PMd are calculated. Here, it is calculated in the same manner as in step S107. The value obtained in step S109 is used as the correction coefficient K3.

  In step S114, the amount of PM newly deposited on the filter 6 after the filter front-rear differential pressure is saturated (PM deposition amount Y (i) after saturation) is calculated.

The post-saturation PM deposition amount Y (i) is added to the post-saturation PM deposition amount Y (i-1) obtained in the previous routine by adding the PM amount newly accumulated between the previous routine and the current routine. It is obtained by subtracting the amount of PM oxidized between the previous routine and the current routine. That is, the post-saturation PM deposition amount Y (i) can be calculated by the following equation.
Y (i) = Y (i-1) + PMe * K1 * K2 * K3-PMd

  In step S115, it is determined whether the amount of PM deposited on the filter 6 is greater than a predetermined value Z. In this step, it is determined whether the regeneration process of the filter 6 is necessary. That is, the predetermined value Z can be an upper limit value of the PM accumulation amount that does not require regeneration of the filter 6 yet. The amount of PM deposited on the filter 6 can be calculated as a sum of the PM deposition amount Xt at saturation and the PM deposition amount Y (i) after saturation.

  In this embodiment, the ECU 20 that executes the process of step S114 corresponds to the accumulation amount estimating means in the present invention.

  If an affirmative determination is made in step S115, the process proceeds to step S116, whereas if a negative determination is made, the process returns to step S112.

  In step S116, the filter regeneration flag is turned ON. When this filter regeneration flag is set to ON, the filter 6 is regenerated when the operating state of the internal combustion engine 1 is suitable for the regeneration of the filter 6.

  In this way, the preset inlet gas PM map can be corrected based on the change in the amount of deposition before the filter differential pressure before and after the saturation state. It can be calculated more accurately. Thereby, the regeneration of the filter 6 can be performed at an appropriate time.

  In the present embodiment, the filter 6 is forcibly regenerated when the fuel of the internal combustion engine 1 is newly supplied or when the lubricating oil of the internal combustion engine 1 is replaced. Then, the amount of PM deposited on the filter 6 is obtained in the same manner as in the first embodiment.

  That is, when the fuel is replenished or the lubricating oil is replaced, the combustion state of the internal combustion engine 1 can change, so the amount of PM discharged from the internal combustion engine 1 per unit time can also change. Therefore, before and after the change of the combustion state, the relationship shown in FIG. 2, that is, the rate of increase of the differential pressure across the filter also changes. For this reason, the rate of increase of the differential pressure across the filter does not become constant, making it difficult to estimate the amount of inflow PM after the differential pressure across the filter is saturated.

  Even in such a case, since the relationship of FIG. 2 is reset by regenerating the filter 6, it is possible to easily estimate the inflow PM amount.

  Note that the filter 6 may be forcibly regenerated even when the combustion state of the internal combustion engine 1 changes.

1 is a diagram illustrating a schematic configuration of an internal combustion engine to which an exhaust gas purification apparatus for an internal combustion engine according to an embodiment is applied, and an intake system and an exhaust system thereof. It is a time chart which showed transition of differential pressure before and behind a filter. It is the figure which showed the relationship between the quantity of PM (inflow gas PM quantity) which flows into a filter, and filter differential pressure. It is the flowchart which showed the flow which calculates | requires the regeneration time of the filter in an Example.

Explanation of symbols

1 Internal combustion engine 2 Intake passage 3 Exhaust passage 4 Throttle 5 Air flow meter 6 Particulate filter 7 Fuel addition valve 8 Differential pressure sensor 9 Temperature sensor 10 Air-fuel ratio sensor 11 Fuel injection valve 12 Accelerator pedal 13 Accelerator opening sensor 14 Crank position sensor 20 ECU
61 NOx storage reduction catalyst

Claims (5)

A particulate filter that collects particulate matter in the exhaust of the internal combustion engine;
Differential pressure detecting means for detecting a differential pressure between the upstream side and the downstream side of the particulate filter;
Particulate matter deposited on the particulate filter after passing through a process in which the differential pressure detected by the differential pressure detecting means increases as the amount of particulate matter deposited on the particulate filter increases. In the case where the rate of increase in the differential pressure detected by the differential pressure detecting means decreases even though the amount of the pressure increases further, the rate of increase in the amount of particulate matter deposited before the rate of increase in the differential pressure decreases The amount of particulate matter deposited on the particulate filter as the rate of increase in the amount of particulate matter deposited after the rate of increase in the differential pressure has decreased,
An exhaust emission control device for an internal combustion engine, comprising: A particulate filter that collects particulate matter in the exhaust of the internal combustion engine;
Differential pressure detecting means for detecting a differential pressure between the upstream side and the downstream side of the particulate filter;
Storage means for storing in advance the amount of particulate matter flowing into the particulate filter;
Based on the differential pressure detected by the differential pressure means during the process of increasing the differential pressure detected by the differential pressure detection means as the amount of particulate matter deposited on the particulate filter increases. A deposit amount increase rate calculating means for calculating an increase rate of the deposit amount of the particulate matter;
Correction means for correcting the amount of particulate matter stored in the storage means based on the increase rate of the particulate matter accumulation amount obtained by the deposition amount increase rate calculating means;
Particulate matter deposited on the particulate filter after passing through a process in which the differential pressure detected by the differential pressure detecting means increases as the amount of particulate matter deposited on the particulate filter increases. When the rate of increase in the differential pressure detected by the differential pressure detecting means decreases despite the further increase in the amount of the particulate filter, the particulate filter is based on the amount of particulate matter corrected by the correcting means. Deposit amount estimation means for estimating the amount of particulate matter deposited on the
An exhaust emission control device for an internal combustion engine, comprising:   The particulate matter is removed when the combustion state in the internal combustion engine changes, and the amount of particulate matter deposited is estimated from the subsequent process of increasing the differential pressure detected by the differential pressure means. 3. An exhaust emission control device for an internal combustion engine according to 1 or 2.   The exhaust gas purification apparatus for an internal combustion engine according to claim 3, wherein the particulate matter is removed when the fuel for the internal combustion engine is newly replenished.   The exhaust emission control device for an internal combustion engine according to claim 3, wherein particulate matter is removed when the lubricating oil of the internal combustion engine is replaced.

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