WO2016194984A1

WO2016194984A1 - Device for controlling water purification system

Info

Publication number: WO2016194984A1
Application number: PCT/JP2016/066304
Authority: WO
Inventors: 紀靖小橋; 角岡　卓; 大塚　孝之; 橋本　浩成
Original assignee: トヨタ自動車株式会社
Priority date: 2015-06-02
Filing date: 2016-06-01
Publication date: 2016-12-08

Abstract

The present invention addresses the problem of suppressing the execution of a filter regeneration process in conditions that could induce an excessive temperature increase in a particulate filter, when there is a discrepancy between the amount of PM sediment determined by an ECU and the actual amount of PM sediment, as a result of an action such as replacing the ECU or the particulate filter. In order to overcome this problem, it is assumed in the present invention that a value measured by a differential pressure sensor is a value for when only PM has accumulated in a particulate filter when the difference between an estimated amount of PM sediment estimated from the operation history for an internal combustion engine and the amount of PM sediment calculated from the value measured by the differential pressure sensor is equal to or greater than a threshold value. If the measured value is equal to or less than a prescribed upper limit value, a first regeneration process is executed, which is a process of oxidizing and removing PM accumulated in the particulate filter, and if the measured value is greater than the prescribed upper limit value, a second regeneration process is executed without executing the first regeneration process.

Description

Control device for exhaust purification system

The present invention relates to a control device for an exhaust purification system, and more particularly to a control device applied to an exhaust purification system including a particulate filter disposed in an exhaust passage of an internal combustion engine.

In an exhaust purification system in which a particulate filter is disposed in an exhaust passage of an internal combustion engine, a PM (Particulate Matter) accumulation amount or an ash accumulation amount of the particulate filter is calculated from an operation history of the internal combustion engine, and the PM accumulation amount is a certain threshold value A technique for executing a filter regeneration process for oxidizing and removing PM trapped in the particulate filter is known (for example, see Patent Document 1).

JP 2008-057443 A US Pat. No. 6,405,528

By the way, during the use of a vehicle equipped with the exhaust purification system described above, a control device (for example, ECU (Electronic Control Unit)) for calculating the PM accumulation amount and the ash accumulation amount of the particulate filter is replaced, The curate filter may be replaced. When the control device is replaced, there is a possibility that the PM deposition amount or the ash deposition amount calculated by the replaced control device may deviate from the actual PM deposition amount or the ash deposition amount. For example, when the control device is replaced, the ash deposition amount and the PM deposition amount held in the replaced control device are reset to zero. Therefore, when the control device is replaced while PM or ash is accumulated on the particulate filter, the PM accumulation amount calculated by the replaced control device and the actual PM accumulation amount of the particulate filter may be different. There is sex.

Further, even when the particulate filter is replaced, the PM deposition amount and the ash deposition amount calculated by the control device may deviate from the actual PM deposition amount and the ash deposition amount of the particulate filter after replacement. . For example, when the particulate filter is replaced, there is a possibility that the amount of ash deposited in the control device and the amount of ash deposited on the particulate filter after replacement are different. As a result, the PM deposition amount calculated based on the ash deposition amount held in the control device may deviate from the actual PM deposition amount of the particulate filter.

As described above, when the PM accumulation amount or the ash accumulation amount calculated by the control device deviates from the actual PM accumulation amount or the ash accumulation amount, the filter regeneration process is executed in a state where the actual PM accumulation amount is excessively large. There is a possibility. In such a case, the particulate filter may be overheated during the filter regeneration process.

The present invention has been made in view of the above-described circumstances, and the purpose of the present invention is to determine the PM accumulation amount calculated by the control device and the particulate filter due to replacement of the control device and the particulate filter. The present invention provides a technique capable of suppressing the filter regeneration process from being performed in a state where there is a possibility of causing an excessive temperature rise of the particulate filter when the actual PM accumulation amount deviates.

In order to solve the above-described problem, the present invention has a predetermined threshold value or more between the estimated PM accumulation amount estimated from the operation history of the internal combustion engine and the PM accumulation amount calculated from the measured value of the differential pressure sensor. When the difference occurs, it is assumed that the measured value of the differential pressure sensor is a value in a state where only PM is deposited on the particulate filter, and if the measured value is not more than a predetermined upper limit value, the particulates If the first regeneration process, which is a process for oxidizing and removing PM accumulated on the filter, is performed and the measured value is larger than the predetermined upper limit value, the first regeneration process is not performed and the second regeneration process is performed. The playback process was executed.

Specifically, an exhaust purification system control device according to the present invention includes a particulate filter disposed in an exhaust passage of an internal combustion engine, an exhaust pressure upstream of the particulate filter, and an exhaust pressure downstream of the particulate filter. And a differential pressure sensor that measures a differential pressure across the front and rear, which is a difference between the two. Then, the control device, based on the operation history of the internal combustion engine, a first calculation means for calculating an ash accumulation amount that is an amount of ash accumulated on the particulate filter, a measured value of the differential pressure sensor, Based on the ash accumulation amount calculated by the first calculation means, second calculation means for calculating a PM accumulation amount, which is the amount of PM accumulated on the particulate filter, and the operation history of the internal combustion engine Based on the estimation means for estimating the estimated PM accumulation amount, which is an estimated value of the PM amount accumulated on the particulate filter, and the PM accumulation amount calculated by the second calculation means and the estimation means When the difference from the estimated PM accumulation amount is equal to or greater than a predetermined threshold, and the measured value of the differential pressure sensor is equal to or smaller than a predetermined upper limit value, the particulate filter is installed The first regeneration process, which is a process for oxidizing and removing the PM deposited on the particulate filter by raising the temperature to the first regeneration temperature, is performed, and the measured value of the differential pressure sensor is the predetermined upper limit. If greater than the value, the first regeneration process is not performed, and the particulate filter is heated to a second regeneration temperature that is lower than the predetermined first regeneration temperature and is a temperature at which PM can be oxidized. And a control means for executing a second reproduction process.

Here, the “predetermined threshold value” is the second calculating means when the difference between the PM accumulation amount calculated by the second calculating means and the estimated PM accumulation amount estimated by the estimating means is equal to or greater than the predetermined threshold value. When at least one of the PM accumulation amount calculated by the above and the PM accumulation amount estimated by the estimation means deviates from the actual PM accumulation amount, and the first regeneration process is executed in that state, the particulate filter It is a value that may cause an excessive temperature rise. This “predetermined threshold value” is obtained in advance by an adaptation operation using an experiment or the like. Further, the “predetermined upper limit value” is obtained when the first regeneration process is executed when only PM is accumulated in the particulate filter and the differential pressure across the particulate filter is equal to or lower than the predetermined upper limit value. The differential pressure before and after the particulate filter is considered not to overheat. In other words, if the differential pressure across the particulate filter is less than or equal to a predetermined upper limit value, even if only PM is deposited on the particulate filter, This is the maximum differential pressure before and after one regeneration process can be performed. This “predetermined upper limit value” is obtained experimentally in advance. Note that the differential pressure across the particulate filter changes in accordance with the flow rate of the exhaust gas passing through the particulate filter. Therefore, the predetermined upper limit value may be changed so as to be a value corresponding to the exhaust flow rate at the time when the differential pressure sensor measures the differential pressure across the particulate filter. Further, instead of changing the predetermined upper limit value, the measured value of the differential pressure sensor may be corrected.

If there is a divergence between the ash deposition amount calculated by the first calculation means and the actual ash deposition amount due to replacement of the control device or the particulate filter, the calculation is performed by the second calculation means. There is a possibility that at least one of the PM deposition amount and the PM deposition amount estimated by the estimation means is different from the actual PM deposition amount. In such a state, when it is determined whether or not the first regeneration process can be performed based on the PM accumulation amount calculated by the second calculation means or the PM accumulation amount estimated by the estimation means, the actual PM accumulation amount There is a possibility that the first regeneration process is performed in an excessively small state, or the first regeneration process is performed in an excessively large amount of actual PM deposition. Here, when the first regeneration process is performed in a state where the actual PM deposition amount is excessively small, the possibility that the particulate filter is excessively heated is low, but in the state where the actual PM deposition amount is excessively large. When the first regeneration process is performed, there is a high possibility that the temperature of the particulate filter is excessively increased. Therefore, it is necessary to avoid a situation in which the first regeneration process is executed in a state where the actual PM accumulation amount is excessively large.

On the other hand, when the difference between the PM accumulation amount calculated by the second calculation means and the estimated PM accumulation amount estimated by the estimation means exceeds a predetermined threshold, the control device for the exhaust purification system of the present invention Assuming a state in which the amount of PM collected in the filter is the largest, it is determined whether or not the first regeneration process can be performed. Specifically, when the difference between the PM accumulation amount calculated by the second calculation means and the estimated PM accumulation amount estimated by the estimation means is equal to or greater than a predetermined threshold, the control device for the exhaust purification system of the present invention provides: Assume that no ash is deposited on the particulate filter and only PM is deposited. Under such an assumption, the measured value of the differential pressure sensor can be regarded as being correlated with the amount of PM deposited on the particulate filter.

Here, when it is considered that the measured value of the differential pressure sensor indicates the differential pressure before and after the PM is deposited on the particulate filter, the PM deposition amount correlated with the measured value is expressed as “maximum PM deposition”. When the amount is defined as “amount”, the maximum PM deposition amount is an estimated amount that is larger than the actual PM deposition amount. When it is assumed that only PM is deposited on the particulate filter and the differential pressure across the particulate filter is equal to the predetermined upper limit value, the PM accumulation amount correlated with the predetermined upper limit value is expressed as “limit”. When “PM deposition amount” is defined, the actual PM deposition amount when the measured value of the differential pressure sensor is not more than the predetermined upper limit value (when the maximum PM deposition amount is not more than the limit PM deposition amount) is the limit PM deposition. Less than the amount. The limit PM deposition amount (predetermined upper limit value) at that time is the maximum value of the PM deposition amount (differential pressure before and after) that can perform the first regeneration process without excessively raising the temperature of the particulate filter, as described above. Therefore, when the first regeneration process is executed when the actual PM deposition amount is equal to or less than the limit PM deposition amount, the particulate filter is trapped by the particulate filter while suppressing excessive temperature rise of the particulate filter. The PM that is present can be oxidized and removed. On the other hand, when the measured value of the differential pressure sensor is larger than the predetermined upper limit value (when the maximum PM deposition amount is larger than the limit PM deposition amount), the actual PM deposition amount may be larger than the limit PM deposition amount. If the first regeneration process is executed in such a state, the particulate filter may overheat. However, the control device for the exhaust gas purification system of the present invention does not execute the first regeneration process when the measured value of the differential pressure sensor is larger than the predetermined upper limit value, and therefore prevents excessive temperature rise of the particulate filter. Can do.

In the control device for the exhaust gas purification system of the present invention, the control means has a difference between the PM accumulation amount calculated by the second calculation means and the estimated PM accumulation amount estimated by the estimation means equal to or greater than a predetermined threshold value. In this case, the maximum PM deposition amount may be calculated from the measured value of the differential pressure sensor. In that case, the control means executes a first regeneration process if the maximum PM deposition amount is equal to or less than the limit PM deposition amount, and performs the first regeneration process if the maximum PM deposition amount is larger than the limit PM deposition amount. Don't do it. According to such a configuration, an effect similar to the method of comparing the measured value of the differential pressure sensor with the predetermined upper limit value can be obtained.

Incidentally, the difference between the PM accumulation amount calculated by the second calculation means and the estimated PM accumulation amount estimated by the estimation means is equal to or larger than a predetermined threshold value, and the measured value of the differential pressure sensor is larger than the predetermined upper limit value. In some cases, if the state where the first regeneration process is not performed continues, the pressure loss of the particulate filter may become excessively large, and the state where the accurate PM accumulation amount of the particulate filter cannot be grasped continues. . Therefore, the difference between the PM accumulation amount calculated by the second calculation means and the estimated PM accumulation amount estimated by the estimation means is greater than or equal to a predetermined threshold value, and the measured value of the differential pressure sensor is greater than the predetermined upper limit value. In this case, it is desirable to oxidize and remove PM deposited on the particulate filter by a method different from the first regeneration process described above.

Therefore, the control means has a difference between the PM accumulation amount calculated by the second calculation means and the estimated PM accumulation amount estimated by the estimation means equal to or greater than a predetermined threshold, and a measured value of the differential pressure sensor. Is greater than a predetermined upper limit value, the second regeneration process is a process of raising the temperature of the particulate filter to a second regeneration temperature that is lower than the predetermined first regeneration temperature and at which PM can be oxidized. I tried to run. When such a second regeneration process is executed, the amount of PM oxidized per unit time in the particulate filter can be reduced compared to when the first regeneration process is executed. The PM deposited on the particulate filter can be oxidized and removed while suppressing the excessive temperature rise. In addition, when the measured value of the differential pressure sensor decreases below the predetermined upper limit value by executing the second regeneration process, the second regeneration process may be switched to the first regeneration process.

Further, as the first regeneration process, when a fuel cut operation request of the internal combustion engine is generated, the fuel cut operation is performed for a predetermined first regeneration period, whereby the PM accumulated on the particulate filter is oxidized and oxidized. In the exhaust purification system in which the removal process is performed, the control means is estimated by the estimation means and the PM accumulation amount calculated by the second calculation means when a fuel cut operation request for the internal combustion engine is generated. A method of performing a fuel cut operation in a second regeneration period shorter than the first regeneration period if the difference from the estimated PM accumulation amount is equal to or greater than a predetermined threshold and the measured value of the differential pressure sensor is greater than a predetermined upper limit value Thus, the second reproduction process may be executed. According to such a configuration, when the second regeneration process is performed, the fuel cut operation period is shorter than when the first regeneration process is performed. Therefore, the oxidation is performed in the particulate filter during the fuel cut operation period. The amount of PM to be reduced can be reduced. As a result, it is possible to oxidize and remove PM deposited on the particulate filter while suppressing excessive temperature rise of the particulate filter.

Further, the control means may determine the actual ash deposition amount from the measured value of the differential pressure sensor when the first regeneration process is completed. The control means may correct the ash accumulation amount calculated by the first calculation means based on the actual ash accumulation amount. When the ash accumulation amount is updated in this way, it is possible to eliminate the deviation between the calculated value of the ash accumulation amount and the actual ash accumulation amount due to the replacement of the control device or the particulate filter. As a result, it is possible to eliminate the deviation between the PM accumulation amount calculated by the second calculation means and the actual PM accumulation amount.

According to the present invention, when the PM deposition amount calculated by the control device deviates from the actual PM deposition amount of the particulate filter due to replacement of the control device or the particulate filter, the particulate filter It is possible to suppress the first regeneration process from being performed in a state where there is a possibility of causing an excessive temperature rise.

It is a figure which shows schematic structure of the internal combustion engine to which this invention is applied, and its exhaust system. The figure which shows the relationship between actual PM deposition amount (SIGMA) PM0, PM deposition amount (SIGMA) PM1 calculated | required from the measured value of a differential pressure sensor, and PM deposition amount (SIGMA) PM2 estimated from the operation history of an internal combustion engine when ECU is replaced | exchanged. It is. When the particulate filter is replaced, the relationship between the actual PM accumulation amount ΣPM0, the PM accumulation amount ΣPM1 obtained from the measured value of the differential pressure sensor, and the PM accumulation amount ΣPM2 estimated from the operation history of the internal combustion engine FIG. It is a figure which shows the example of a setting of predetermined | prescribed upper limit value (DELTA) Plmt. It is a timing chart which shows the execution method of the 2nd reproduction processing. It is a flowchart which shows the process routine which ECU performs when oxidizing and removing PM currently collected by the particulate filter. In another embodiment, it is a flowchart which shows the process routine which ECU performs when oxidizing and removing PM collected by the particulate filter. It is a flowchart which shows the processing routine performed by ECU when switching on and off of a permission flag.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied and its exhaust system. An internal combustion engine 1 shown in FIG. 1 is a compression ignition type internal combustion engine (diesel engine) having a plurality of cylinders. The internal combustion engine 1 includes a fuel injection valve 2 that injects fuel into a cylinder (not shown). The internal combustion engine 1 is connected to an exhaust pipe 3 having a passage through which gas (exhaust gas) combusted in the cylinder flows. A filter casing 4 is arranged in the middle of the exhaust pipe 3. The filter casing 4 contains a particulate filter in a cylindrical casing. The particulate filter is a filter for collecting PM contained in the exhaust gas. More specifically, the particulate filter alternately has a passage in which the upstream end is closed by a plug and a passage in which the downstream end is closed by a plug. This is a wall flow type filter arranged. In this particulate filter, a catalyst having an oxidation function (for example, a three-way catalyst, a storage reduction type catalyst (NSR (NO _X Storage Reduction) catalyst), or an oxidation catalyst, hereinafter referred to as “oxidation catalyst”) is used. It is supported. The oxidation catalyst may be accommodated in a catalyst casing disposed in the exhaust pipe 3 upstream from the filter casing 4.

The filter casing 4 is provided with a differential pressure sensor 5 for measuring a difference (a differential pressure between the front and rear) between the exhaust pressure upstream of the particulate filter and the exhaust pressure downstream of the particulate filter. The differential pressure sensor 5 may be configured to measure the difference between the pressure in the exhaust pipe 3 upstream from the filter casing 4 and the pressure in the exhaust pipe 3 downstream from the filter casing 4. In addition, a pressure sensor for measuring the exhaust pressure upstream of the particulate filter and a pressure sensor for measuring the exhaust pressure downstream of the particulate filter are attached to the filter casing 4 or the exhaust pipe 3, and the difference between them is described later in the ECU 8. May calculate the differential pressure across the front and rear.

The exhaust pipe 3 downstream of the filter casing 4 is provided with an exhaust temperature sensor 6 for measuring the temperature of the exhaust gas flowing out from the filter casing 4. Further, a fuel addition valve 7 for adding fuel to the exhaust gas flowing in the exhaust pipe 3 is attached to the exhaust pipe 3 upstream of the filter casing 4. When the above-described oxidation catalyst is disposed in the exhaust pipe 3 upstream from the filter casing 4, the fuel addition valve 7 is disposed in the exhaust pipe 3 upstream from the oxidation catalyst.

The internal combustion engine 1 configured as described above is provided with an ECU 8 as a control device according to the present invention. The ECU 8 is an electronic control unit that includes a CPU, ROM, RAM, backup RAM, and the like. The ECU 8 is electrically connected to various sensors such as an accelerator position sensor 10 and a crank position sensor 11 in addition to the above-described differential pressure sensor 5 and exhaust temperature sensor 6. The accelerator position sensor 10 is a sensor that measures an operation amount (accelerator opening) of the accelerator pedal 9. The crank position sensor 11 is a sensor that measures the rotational position of the crankshaft.

Further, the ECU 8 is electrically connected to various devices such as the fuel injection valve 2 and the fuel addition valve 7, and controls various devices based on the measurement values of the various sensors described above. For example, the ECU 8 calculates a fuel amount (target fuel injection amount) to be injected into the cylinder per cycle using the measured values of the accelerator position sensor 10 and the crank position sensor 11 as parameters, and fuel according to the target fuel injection amount. The injection valve 2 is controlled. Further, the ECU 8 executes a first regeneration process for oxidizing and removing the PM accumulated on the particulate filter when the PM accumulation amount of the particulate filter exceeds a predetermined regeneration threshold. As used herein, the “regeneration threshold” means that if the amount of PM actually deposited on the particulate filter is less than or equal to the predetermined regeneration threshold, the first regeneration process is performed without causing excessive temperature rise of the particulate filter. This is an amount obtained by subtracting a margin from the maximum value of the PM deposition amount that can be executed.

Here, the execution procedure of the first reproduction process will be described. First, the ECU 8 calculates the PM accumulation amount of the particulate filter based on the measured value (front-rear differential pressure) of the differential pressure sensor 5. There is a correlation between the pressure loss (front-rear differential pressure) of the particulate filter and the PM accumulation amount, that the front-rear differential pressure increases as the PM accumulation amount of the particulate filter increases. Therefore, if the correlation between the differential pressure before and after the particulate filter and the PM accumulation amount is obtained in advance, the PM accumulation amount can be obtained using the measured value of the differential pressure sensor 5 as an argument. However, the differential pressure across the particulate filter also varies depending on the exhaust flow rate passing through the particulate filter. Therefore, it is preferable to obtain the correlation between the front-rear differential pressure, the exhaust flow rate, and the PM deposition amount in advance, and to obtain the PM deposition amount using the measured value of the differential pressure sensor 5 and the exhaust flow rate as arguments. The exhaust flow rate passing through the particulate filter correlates with the sum of the intake air amount and the fuel injection amount of the internal combustion engine 1. Therefore, by adding the intake air amount measured by a sensor such as an air flow meter and the fuel injection amount, the exhaust gas flow rate passing through the particulate filter can be obtained.

Note that the exhaust gas from the internal combustion engine 1 may contain ash, which is a nonflammable substance derived from the components of additives contained in the lubricating oil. The ash in the exhaust gas is collected and deposited on the particulate filter in the same manner as PM. Therefore, the differential pressure across the particulate filter varies depending on the ash deposition amount in addition to the PM deposition amount and the exhaust gas flow rate described above. Therefore, in order to accurately obtain the PM accumulation amount of the particulate filter, the total accumulation amount of PM and ash accumulated on the particulate filter is obtained by using the measured value of the differential pressure sensor 5 and the exhaust gas flow rate as arguments. It is necessary to subtract the ash deposition amount from the total deposition amount.

The ash accumulation amount of the particulate filter correlates with the operation history of the internal combustion engine 1 (for example, the cumulative operation time of the internal combustion engine 1, the cumulative travel distance of the vehicle on which the internal combustion engine 1 is mounted, or the integrated value of the fuel injection amount). . Therefore, the ash accumulation amount of the particulate filter can be obtained based on the operation history of the internal combustion engine 1. Further, immediately after the end of the first regeneration process, it can be considered that PM has been removed from the particulate filter. Therefore, the actual ash deposition amount can be obtained using the measured value of the differential pressure sensor 5 and the exhaust gas flow rate immediately after the end of the first regeneration process as parameters. Then, the ash accumulation amount of the particulate filter is reduced by correcting the ash accumulation amount obtained from the operation history of the internal combustion engine 1 based on the actual ash accumulation amount obtained each time the first regeneration process is performed. It can be obtained with high accuracy. It should be noted that the “first calculation means” according to the present invention is realized by the ECU 8 obtaining the ash accumulation amount by the above-described method. Further, the “second calculating means” according to the present invention is realized when the ECU 8 obtains the PM accumulation amount by the method of subtracting the ash accumulation amount from the total accumulation amount.

The process for obtaining the PM accumulation amount by the above-described method is repeatedly executed during the operation period of the internal combustion engine 1. Then, when the PM accumulation amount exceeds a predetermined regeneration threshold value, the ECU 8 executes the first regeneration process. Specifically, the ECU 8 adds fuel to the exhaust gas from the fuel addition valve 7 and deposits on the particulate filter using reaction heat generated when the added fuel is oxidized by the oxidation catalyst. The particulate filter is heated to a target temperature (corresponding to the “first regeneration temperature” in the present invention) that is assumed to be efficiently oxidized. During execution of the first regeneration process, the ECU 8 calculates the temperature of the particulate filter from the measured value of the exhaust temperature sensor 6, and is added from the fuel addition valve 7 so that the calculated value converges to the target temperature. The amount of fuel to be controlled may be feedback controlled. When the amount of fuel added from the fuel addition valve 7 is feedback-controlled in this way, the PM deposited on the particulate filter can be efficiently oxidized and removed.

Note that the PM accumulation amount of the particulate filter may be estimated based on the operation history of the internal combustion engine 1. For example, the ECU 8 calculates the amount of PM discharged from the internal combustion engine 1 per unit time (PM discharge amount) using the fuel injection amount, the intake air amount, the engine speed, and the like as parameters. Then, the ECU 8 may integrate the PM discharge amount and use the integrated value as the PM accumulation amount (estimated PM accumulation amount) of the particulate filter. Further, from the viewpoint that PM discharged from the internal combustion engine 1 is collected by the particulate filter at a predetermined ratio, a coefficient corresponding to the predetermined ratio (hereinafter referred to as “collection coefficient”) is defined as PM. The accumulated amount of the calculation result may be used as the estimated PM accumulation amount by multiplying the discharge amount. In this case, the predetermined ratio may be a fixed value, or may be a variable value that is changed according to the exhaust flow rate (for example, a value that decreases as the exhaust flow rate increases). As described above, the ECU 8 calculates the PM accumulation amount based on the operation history of the internal combustion engine 1, thereby realizing the “estimating means” according to the present invention.

Incidentally, there is a possibility that the filter casing 4 or the ECU 8 may be replaced during the use of the vehicle on which the internal combustion engine 1 is mounted. When the filter casing 4 or the ECU 8 is replaced, there is a possibility that the PM accumulation amount obtained by the ECU 8 after the replacement is different from the actual PM accumulation amount. For example, when the ECU 8 is replaced, the ash accumulation amount and the PM accumulation amount held in the replaced ECU 8 are reset to zero. Therefore, when the ECU 8 is replaced while PM and ash are accumulated on the particulate filter, the PM accumulation amount obtained by the ECU 8 after the replacement may deviate from the actual PM accumulation amount.

Here, when the ECU 8 is replaced in a state where PM and ash are accumulated on the particulate filter, the measured value (front-rear differential pressure) of the differential pressure sensor 5 and the PM accumulation amount obtained by the ECU 8 after replacement The relationship is shown in FIG. ΣPM0 in FIG. 2 indicates the actual PM deposition amount of the particulate filter. ΣPM1 in FIG. 2 indicates a PM deposition amount (hereinafter referred to as “first PM deposition amount”) that the ECU 8 after replacement obtains based on the front-rear differential pressure and the ash deposition amount (zero). ΣPM2 in FIG. 2 indicates an estimated PM accumulation amount (hereinafter referred to as “second PM accumulation amount”) that the ECU 8 after replacement obtains based on the operation history of the internal combustion engine 1. Moreover, the solid line in FIG. 2 shows the correlation between the differential pressure before and after and the PM accumulation amount recognized by the ECU 8 after replacement. On the other hand, the alternate long and short dash line in FIG. 2 shows the correlation between the differential pressure before and after and the actual PM deposition amount.

When the ECU 8 is replaced, the first PM accumulation amount ΣPM1 obtained by the replaced ECU 8 is obtained on the assumption that the ash accumulation amount is zero. Therefore, the first PM accumulation amount ΣPM1 obtained by the replaced ECU 8 is larger than the actual PM accumulation amount ΣPM0 as shown in FIG. Further, the second PM accumulation amount ΣPM2 obtained by the replaced ECU 8 becomes zero, which is smaller than the actual PM accumulation amount ΣPM0. As described above, when the ECU 8 is replaced, both the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 obtained by the replaced ECU 8 are different from the actual PM accumulation amount ΣPM0. Furthermore, a divergence also occurs between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 obtained by the ECU 8 after replacement. Here, in the example shown in FIG. 2, when the ECU 8 after replacement determines whether or not the first regeneration process can be performed based on the second PM accumulation amount ΣPM2, the actual PM accumulation amount becomes the predetermined regeneration described above. There is a possibility that the first reproduction process is executed in a state where the number is larger than the threshold value. As a result, the temperature of the particulate filter may be excessively increased during the execution of the first regeneration process.

Further, when the filter casing 4 is replaced with a used filter casing 4, the amount of ash accumulated in the ECU 8 is different from the amount of ash deposited on the replaced particulate filter. For example, the ash deposition amount of the particulate filter after replacement is smaller than the ash deposition amount of the particulate filter before replacement, and the PM deposition amount of the particulate filter after replacement is larger than the PM deposition amount of the particulate filter before replacement. In this case, the first PM accumulation amount ΣPM1 and the second PM accumulation amount obtained by the ECU 8 may be smaller than the actual PM accumulation amount.

Here, the ash deposition amount of the particulate filter after replacement is less than the ash deposition amount of the particulate filter before replacement, and the PM deposition amount of the particulate filter after replacement is more than the PM deposition amount of the particulate filter before replacement. The relationship between the measured value of the differential pressure sensor 5 (front-rear differential pressure) and the PM deposition amount obtained by the ECU 8 after replacement of the particulate filter when the particulate filter is replaced under many conditions 3 shows. The solid line in FIG. 3 shows the correlation between the differential pressure before and after recognized by the ECU 8 and the PM accumulation amount of the particulate filter after replacement. On the other hand, the alternate long and short dash line in FIG. 2 shows the correlation between the differential pressure before and after and the actual PM deposition amount of the particulate filter after replacement.

When the particulate filter is replaced, the first PM accumulation amount ΣPM1 obtained by the ECU 8 is obtained on the assumption that the ash accumulation amount of the particulate filter after replacement is equal to the ash accumulation amount of the particulate filter before replacement. It is done. Therefore, the first PM accumulation amount ΣPM1 obtained by the ECU 8 is smaller than the actual PM accumulation amount ΣPM0 of the particulate filter after replacement. Further, the second PM accumulation amount ΣPM2 estimated from the operation history of the internal combustion engine 1 is a value assuming a particulate filter before replacement. Therefore, the second PM accumulation amount ΣPM2 estimated by the ECU 8 is also smaller than the actual PM accumulation amount ΣPM0 of the particulate filter after replacement. Furthermore, a divergence also occurs between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2. Here, in the example shown in FIG. 3, when it is determined whether or not the first regeneration process can be performed based on the first PM accumulation amount ΣPM1 or the second PM accumulation amount ΣPM2, the actual PM accumulation amount is There is a possibility that the first reproduction process is executed in a state where the number is larger than the predetermined reproduction threshold. As a result, the temperature of the particulate filter may be excessively increased during the execution of the first regeneration process. Although FIG. 3 shows an example in which the first PM deposition amount ΣPM1 is smaller than the second PM deposition amount ΣPM2, the first PM deposition amount ΣPM1 may be larger than the second PM deposition amount ΣPM2. Even in such a case, if the first PM deposition amount ΣPM1 and the second PM deposition amount ΣPM2 are less than the actual PM deposition amount ΣPM0, the same problem as in the example shown in FIG. 3 occurs.

Considering the tendency shown in FIGS. 2 and 3, the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 are actually caused by the replacement of the ECU 8 or the particulate filter. If there is a deviation from the PM accumulation amount, it is considered that a deviation also occurs between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2. Therefore, in the present embodiment, when a divergence greater than or equal to a predetermined threshold ΔΣPMthr occurs between the first PM deposition amount ΣPM1 and the second PM deposition amount ΣPM2, the first PM deposition amount ΣPM1 and the second PM deposition amount ΣPM2 It is determined that at least one of these may deviate from the actual PM accumulation amount. When it is determined that at least one of the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 may deviate from the actual PM accumulation amount, the ECU 8 One of ΣPM1 and ΣPM2 is compared with the regeneration threshold value, and the process for determining whether or not to execute the first regeneration process is not performed. That is, in the present embodiment, when a difference of a predetermined threshold ΔΣPMthr or more occurs between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2, the measured value of the differential pressure sensor 5 and the predetermined upper limit value ΔPlmt To determine whether or not to execute the first reproduction process.

The “predetermined threshold ΔΣPMthre” referred to here is caused by replacement of the ECU 8 or the particulate filter when the difference ΔΣPM between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 is equal to or greater than the predetermined threshold ΔΣPMthre. Further, at least one of the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 is a value that can be regarded as deviating from the actual PM accumulation amount, and the first regeneration process is executed in that state. And a value that may cause excessive temperature rise of the particulate filter. Such a predetermined threshold is a value obtained in advance by an adaptation operation using an experiment or the like. The “predetermined upper limit value ΔPlmt” is an excess of the particulate filter even if only PM is accumulated on the particulate filter if the differential pressure across the particulate filter is equal to or lower than the predetermined upper limit value ΔPlmt. This corresponds to the maximum value of the differential pressure before and after the first regeneration process can be performed while suppressing the temperature rise. Specifically, as shown in FIG. 4, the difference between before and after of the particulate filter when the ash accumulation amount of the particulate filter is zero and the PM accumulation amount of the particulate filter is equal to a predetermined limit PM accumulation amount ΣPMlmt. The pressure may be set to the predetermined upper limit value ΔPlmt. As used herein, the “limit PM accumulation amount” means that if the PM accumulation amount of the particulate filter is equal to or less than the limit PM accumulation amount ΣPMlmt, the first regeneration process can be performed while suppressing excessive temperature rise of the particulate filter. This is the maximum value of the PM deposition amount that can be generated, for example, an amount equal to the above-described regeneration threshold. By the way, since the differential pressure across the particulate filter also changes depending on the exhaust flow rate passing through the particulate filter as described above, the predetermined upper limit ΔPlmt may be changed depending on the exhaust flow rate passing through the particulate filter. Alternatively, the measured value of the differential pressure sensor 5 may be corrected by the exhaust gas flow rate passing through the particulate filter.

Here, if the measured value of the differential pressure sensor 5 is equal to or less than the predetermined upper limit value ΔPlmt, it is obtained from the measured value of the differential pressure sensor 5 under the assumption that only PM is deposited on the particulate filter. The PM deposition amount (maximum PM deposition amount) is the PM deposition amount (limit PM deposition amount) when only PM is deposited on the particulate filter and the differential pressure across the particulate filter is equal to the predetermined upper limit value ΔPlmt. ) It becomes the following. Here, since the maximum PM deposition amount is an amount estimated to be equal to or larger than the actual PM deposition amount, the maximum PM deposition amount is equal to or less than the limit PM deposition amount (measured value of the differential pressure sensor 5). Is equal to or less than the predetermined upper limit value ΔPlmt), the actual PM deposition amount of the particulate filter is equal to or less than the maximum PM deposition amount. Therefore, if the measured value of the differential pressure sensor 5 is equal to or less than the predetermined upper limit value ΔPlmt, it can be said that the first regeneration process can be performed without excessively raising the temperature of the particulate filter. Therefore, in the present embodiment, when the difference between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 is equal to or greater than the predetermined threshold value ΔΣPMthre, the measured value of the differential pressure sensor 5 is equal to or less than the predetermined upper limit value ΔPlmt. Then, the first reproduction process is performed.

On the other hand, if the difference between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 is equal to or greater than the predetermined threshold ΔΣPMthre, if the measured value of the differential pressure sensor 5 is greater than the predetermined upper limit ΔPlmt, the actual There is a possibility that the PM deposition amount is larger than the limit PM deposition amount. When the first regeneration process is executed in such a state, there is a possibility that the temperature of the particulate filter will be excessively increased. Therefore, in the present embodiment, when the difference between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 is equal to or greater than the predetermined threshold value ΔΣPMthr, the measured value of the differential pressure sensor 5 is greater than the predetermined upper limit value ΔPlmt. If it is larger, the first regeneration process is not performed.

As described above, when the difference between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 is equal to or greater than the predetermined threshold value ΔΣPMthr, the measured value of the differential pressure sensor 5 is compared with the predetermined upper limit value ΔPlmt. When it is determined whether or not the first regeneration process can be performed by the method, the first regeneration process is suppressed from being executed in a state where there is a possibility of excessive temperature rise of the particulate filter. In addition, when the difference between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 is equal to or larger than the predetermined threshold ΔΣPMthre and the measured value of the differential pressure sensor 5 is larger than the predetermined upper limit ΔPlmt, If the state in which the regeneration process is not performed continues, the pressure loss of the particulate filter becomes excessively large, which may increase the back pressure of the internal combustion engine 1. Therefore, when the difference between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 is equal to or greater than the predetermined threshold value ΔΣPMthre and the measured value of the differential pressure sensor 5 is greater than the predetermined upper limit value ΔPlmt, By raising the temperature of the particulate filter to a temperature lower than the target temperature at the time of the regeneration process and capable of oxidizing PM (corresponding to the “second regeneration temperature” in the present invention), per unit time A process (second regeneration process) for oxidizing and removing the PM deposited on the particulate filter is performed while suppressing the amount of PM to be oxidized. Such a second regeneration process may be executed until all of the PM deposited on the particulate filter is oxidized and removed, but as shown in FIG. The first regeneration process may be performed by performing the process until the temperature drops below a predetermined upper limit value ΔPlmt and then raising the temperature of the particulate filter to the first regeneration temperature. As described above, when the second regeneration process and the first regeneration process are executed in combination, the amount of PM deposited on the particulate filter is oxidized and removed more quickly while suppressing excessive temperature rise of the particulate filter. be able to.

In addition, when the difference between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 is equal to or greater than the predetermined threshold ΔΣPMthre, the first regeneration process or the second regeneration process is performed, so that the particulate filter is deposited. When all of the PM being oxidized is oxidized and removed, the ECU 8 finishes the first regeneration process or the second regeneration process, and updates the ash accumulation amount held in the ECU 8. That is, the ECU 8 obtains the amount of ash actually deposited on the particulate filter using the measured value of the differential pressure sensor 5 and the exhaust flow rate immediately after the end of the first regeneration process as parameters, and the actual ash accumulation amount Based on this, the ash accumulation amount held in the ECU 8 is corrected. Thus, when the ash accumulation amount held in the ECU 8 is updated, the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 obtained by the ECU 8 after the update are approximated to the actual PM accumulation amount. Therefore, even if it is determined whether or not the first regeneration process can be performed by comparing one of the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 with the regeneration threshold value, the particulate filter excess The first regeneration process can be performed while suppressing the temperature rise.

Hereinafter, the procedure for oxidizing and removing the PM collected in the particulate filter in the present embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing a processing routine executed by the ECU 8 when oxidizing and removing the PM collected by the particulate filter. This processing routine is stored in advance in the ROM of the ECU 8 and is repeatedly executed by the ECU 8 during the operation period of the internal combustion engine 1.

In the processing routine of FIG. 6, the ECU 8 first calculates the first PM deposition amount ΣPM1 from the measured value of the differential pressure sensor 5 and the ash deposition amount held in the ECU 8 in the processing of S101. Specifically, as described above, the ECU 8 uses the measured value of the differential pressure sensor 5 and the exhaust flow rate (the sum of the intake air amount and the fuel injection amount) as arguments, and the PM accumulated in the particulate filter. A first PM accumulation amount ΣPM1 is calculated by obtaining a total accumulation amount of ash and subtracting the ash accumulation amount from the total accumulation amount. The ash accumulation amount used in this calculation is updated based on the measured value of the differential pressure sensor 5 and the exhaust flow rate immediately after the previous end of the first regeneration process or the second regeneration process, and is a value held in the ECU 8. It is. Further, the ECU 8 calculates the second PM accumulation amount ΣPM2 from the operation history of the internal combustion engine 1 in the process of S101. Specifically, as described above, the ECU 8 calculates the second PM accumulation amount ΣPM2 by integrating the PM discharge amount calculated using the fuel injection amount, the intake air amount, the engine speed, and the like as parameters. . The ECU 8 may calculate the second PM accumulation amount ΣPM2 by a method of multiplying the PM emission amount by the above-described collection coefficient and integrating the calculation results.

In the process of S102, the ECU 8 determines whether or not the absolute value of the difference between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 calculated in the process of S101 is equal to or greater than the predetermined threshold value ΔΣPMthre described above. To do. If the determination in S102 is affirmative, at least one of the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 may deviate from the actual PM accumulation amount. In such a case, the ECU 8 proceeds to the process of S103.

In the process of S103, the ECU 8 reads a measured value (front-rear differential pressure) ΔP of the differential pressure sensor 5. Subsequently, the ECU 8 proceeds to the process of S104, and determines whether or not the front-rear differential pressure ΔP read in the process of S103 is equal to or less than the predetermined upper limit value ΔPlmt described above. When an affirmative determination is made in the process of S104, it can be considered that the amount of PM actually deposited on the particulate filter is equal to or less than the aforementioned limit PM accumulation amount ΣPMlmt. Therefore, when the front-rear differential pressure ΔP is equal to or less than the predetermined upper limit value ΔPlmt, it can be considered that the first regeneration process can be executed without excessively raising the temperature of the particulate filter. Therefore, the ECU 8 proceeds to the process of S105 and executes the first regeneration process. Specifically, the ECU 8 adds fuel into the exhaust gas from the fuel addition valve 7. The fuel added from the fuel addition valve 7 is oxidized by an oxidation catalyst carried on the particulate filter or an oxidation catalyst arranged upstream of the filter casing 4 to generate reaction heat. As a result, the particulate filter is heated by the reaction heat of the added fuel. At that time, the ECU 8 calculates the temperature of the particulate filter from the measured value of the exhaust temperature sensor 6, and feedback-controls the amount of fuel added from the fuel addition valve 7 so that the temperature becomes the first regeneration temperature. . When the first regeneration process is performed in this way, PM deposited on the particulate filter is oxidized and removed.

The ECU 8 proceeds to the process of S106 after executing the process of S105. In the process of S106, the ECU 8 determines whether or not all PM deposited on the particulate filter has been oxidized. Specifically, the ECU 8 determines that all PM accumulated in the particulate filter has been oxidized and removed if the amount of change in the measured value of the differential pressure sensor 5 per unit time is equal to or less than a predetermined determination value. To do. As an alternative method, it may be determined whether or not all PM deposited on the particulate filter has been oxidized and removed using the execution time of the first regeneration process as a parameter. That is, the time required for oxidizing and removing all PM deposited on the particulate filter (required regeneration time) correlates with the PM deposition amount at the time when the first regeneration process is started. Therefore, if the correlation between the PM deposition amount and the required regeneration time is obtained in advance, the required regeneration time corresponding to the maximum PM deposition amount can be obtained from the correlation. Then, when the execution time of the first regeneration process reaches the required regeneration time, it may be determined that all of the PM deposited on the particulate filter has been oxidized and removed. If a negative determination is made in the process of S106, the ECU 8 returns to the process of S105 and continues to execute the first regeneration process. On the other hand, if an affirmative determination is made in the process of S106, the ECU 8 proceeds to the process of S107.

In the process of S107, the ECU 8 ends the first regeneration process by stopping the fuel addition from the fuel addition valve 7 into the exhaust. Subsequently, the ECU 8 proceeds to the process of S108 and updates the ash accumulation amount held in the ECU 8. Specifically, the ECU 8 reads the measured value of the differential pressure sensor 5 immediately after the completion of the first regeneration process, and at the time, the exhaust flow rate (sum of the intake air amount and the fuel injection amount) passing through the particulate filter. ) Is calculated. Then, the ECU 8 calculates the total accumulation amount of PM and ash accumulated on the particulate filter as the measured value of the differential pressure sensor 5, the exhaust gas flow rate, and the parameters. Note that immediately after the end of the first regeneration process, the PM accumulation amount of the particulate filter can be considered to be zero, so that the total accumulation amount can be regarded as being equal to the actual ash accumulation amount. Therefore, the ECU 8 regards the total accumulation amount as the actual ash accumulation amount, and updates the value of the ash accumulation amount held in the ECU 8. In this way, when the ash accumulation amount held in the ECU 8 is updated, the accuracy of the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 obtained by the ECU 8 thereafter can be improved.

When a negative determination is made in the process of S104, there is a possibility that the amount of PM actually deposited on the particulate filter is larger than the aforementioned limit PM accumulation amount ΣPMlmt. That is, when a negative determination is made in the process of S104, there is a possibility that the temperature of the particulate filter is excessively increased due to the execution of the first regeneration process. Therefore, the ECU 8 proceeds to the process of S109 and executes the second regeneration process. Specifically, the ECU 8 controls the amount of fuel added from the fuel addition valve 7 so that the temperature of the particulate filter is raised to a second regeneration temperature that is lower than the first regeneration temperature. When the second regeneration process is executed in this way, the PM deposited on the particulate filter is oxidized and removed. At that time, the PM oxidation rate (PM oxidized per unit time) Amount) is slower than when the first regeneration process is executed. As a result, PM deposited on the particulate filter is gradually oxidized. Therefore, it is possible to oxidize and remove PM deposited on the particulate filter while suppressing excessive temperature rise of the particulate filter.

The ECU 8 proceeds to the process of S110 after executing the process of S109. In the process of S110, the ECU 8 determines whether or not all PM deposited on the particulate filter has been oxidized. Specifically, the ECU 8 determines whether or not all the PM deposited on the particulate filter has been oxidized by using the same method as the process of S106 described above. If a negative determination is made in the process of S110, the ECU 8 returns to the process of S109 and continues to execute the second regeneration process. On the other hand, if an affirmative determination is made in the processing of S110, the ECU 8 proceeds to the processing of S111.

In the process of S111, the ECU 8 ends the second regeneration process by stopping the fuel addition from the fuel addition valve 7 into the exhaust. Then, the ECU 8 proceeds to the process of S108, and updates the ash accumulation amount held in the ECU 8. When the measured value (front-rear differential pressure) ΔP of the differential pressure sensor 5 falls below the predetermined upper limit value ΔPlmt during execution of the second regeneration process, the ECU 8 changes from the second regeneration process to the first regeneration process at that time. You may move to.

Further, when a negative determination is made in the process of S102, it can be considered that the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 are not deviated from the actual PM accumulation amount. The playback process is executed. That is, if a negative determination is made in S102, the ECU 8 proceeds to S112, and determines whether or not the first PM accumulation amount ΣPM1 obtained in S101 is greater than the predetermined regeneration threshold ΣPMreg. Determine. When a negative determination is made in the process of S112, the ECU 8 ends the execution of this process routine. On the other hand, if an affirmative determination is made in the process of S112, the ECU 8 proceeds to the process of S105 and executes the first regeneration process.

As described above, the “control means” according to the present invention is realized by the ECU 8 executing the processing routine of FIG. 6. Therefore, when at least one of the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 deviates from the actual PM accumulation amount due to replacement of the ECU 8 or the particulate filter, the particulate filter is excessively elevated. The PM deposited on the particulate filter can be oxidized and removed without heating. Further, the actual ash deposition amount is obtained based on the measured value of the differential pressure sensor 5 when all the PM deposited on the particulate filter is oxidized and removed, whereby the ash deposition amount held in the ECU 8 is obtained. Therefore, it is possible to improve the accuracy of the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 obtained by the ECU 8 thereafter.

<Other embodiments>
In the above-described embodiment, the example in which the present invention is applied to a compression ignition type internal combustion engine (diesel engine) has been described. However, the present invention can also be applied to a spark ignition type internal combustion engine (gasoline engine). Since the exhaust temperature of a spark ignition internal combustion engine is higher than the exhaust temperature of a compression ignition internal combustion engine, the temperature of the particulate filter rises to the oxidizable temperature of PM during the operation of the spark ignition internal combustion engine. There are many opportunities to do. Therefore, the first regeneration process in the spark ignition type internal combustion engine performs the fuel cut operation when the temperature of the particulate filter is a temperature at which PM can be oxidized and a fuel cut operation request such as during deceleration operation occurs. This is performed by a method of executing for a predetermined period (stopping fuel injection for a predetermined period). When the first regeneration process is performed by such a method, the particulate filter is exposed to an oxidizing atmosphere, so that PM deposited on the particulate filter is oxidized and removed. Here, the “predetermined period” means that if the execution period of the fuel cut operation is equal to or shorter than the predetermined period, the PM deposited on the particulate filter is oxidized and oxidized without excessively raising the temperature of the particulate filter. This is a period that can be removed, and corresponds to the “first regeneration period” of the present invention.

In the spark ignition internal combustion engine in which the first regeneration process is performed by the above-described method, at least one of the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 is caused by replacement of the ECU 8 or the particulate filter. When deviating from the actual PM accumulation amount, as in the case of the compression ignition type internal combustion engine described above, a deviation also occurs between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2. Therefore, when the difference between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 is equal to or greater than a predetermined threshold value ΔΣPMthre, the measured value (front-rear differential pressure) ΔP of the differential pressure sensor 5 is equal to or less than the predetermined upper limit value ΔPlmt. If so, the first regeneration process is performed by the above-described method, and if the measured value (front-rear differential pressure) ΔP of the differential pressure sensor 5 is larger than the predetermined upper limit value ΔPlmt, the first regeneration process by the above-described method is performed. If not. The difference between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 is equal to or greater than a predetermined threshold value ΔΣPMthre, and the measured value (front-rear differential pressure) ΔP of the differential pressure sensor 5 is greater than the predetermined upper limit value ΔPlmt. In this case, the amount of PM oxidized during the fuel cut operation period can be reduced by executing the second regeneration process by performing the fuel cut operation in the second regeneration period shorter than the first regeneration period. That's fine. The second regeneration period may be set to a shorter period as the measured value (front / rear differential pressure) ΔP of the differential pressure sensor 5 increases and the temperature of the particulate filter increases. When the second regeneration period is thus determined, it is possible to more reliably suppress the particulate filter from being excessively heated during execution of the second regeneration process.

Here, a procedure for oxidizing and removing PM deposited on the particulate filter in the spark ignition type internal combustion engine will be described with reference to FIG. FIG. 7 is a processing routine executed by the ECU 8 triggered by the start of the fuel cut operation of the internal combustion engine 1. This processing routine is assumed to be stored in advance in the ROM of the ECU 8 or the like.

In the processing routine of FIG. 7, the ECU 8 first calculates the temperature of the particulate filter from the measured value of the exhaust temperature sensor 6 in the processing of S201, and determines whether or not the temperature is equal to or higher than a predetermined temperature. The predetermined temperature here is the lowest temperature at which PM deposited on the particulate filter can be oxidized. If a negative determination is made in the processing of S201, the ECU 8 ends the execution of this processing routine. On the other hand, if a positive determination is made in the process of S201, the ECU 8 proceeds to the process of S202.

In the process of S202, the ECU 8 determines whether or not the permission flag is on. Here, the permission flag indicates that the difference between the first PM deposition amount ΣPM1 and the second PM deposition amount ΣPM2 is less than a predetermined threshold ΔΣPMthre, and the difference between the first PM deposition amount ΣPM1 and the second PM deposition amount ΣPM2. Is a flag that is turned on when the value is equal to or greater than a predetermined threshold value ΔΣPMthre and the measured value (front-rear differential pressure) ΔP of the differential pressure sensor 5 is equal to or less than a predetermined upper limit value ΔPlmt. Note that the difference between the first PM accumulation amount ΣPM1 and the second PM accumulation amount ΣPM2 is equal to or greater than a predetermined threshold value ΔΣPMthre, and the measured value (front-rear differential pressure) ΔP of the differential pressure sensor 5 is greater than a predetermined upper limit value ΔPlmt. In this case, the permission flag is turned off. The procedure for switching the permission flag on and off will be described later.

If an affirmative determination is made in the process of S202, it can be considered that the particulate filter does not overheat even if the fuel cut operation is performed over the first regeneration period. Therefore, the ECU 8 proceeds to the process of S203 and determines whether or not the first regeneration period has elapsed since the fuel cut operation was started. When a negative determination is made in the process of S203, the ECU 8 repeatedly executes the process of S203. On the other hand, if an affirmative determination is made in the process of S203, the ECU 8 proceeds to the process of S205 and ends the fuel cut operation.

If a negative determination is made in the process of S202, it can be considered that the particulate filter may overheat if the fuel cut operation is performed over the first regeneration period. Therefore, the ECU 8 proceeds to the process of S204, and determines whether or not the second regeneration period has elapsed since the fuel cut operation was started. If a negative determination is made in the process of S204, the ECU 8 repeatedly executes the process of S204. On the other hand, when an affirmative determination is made in the process of S204, the ECU 8 proceeds to the process of S205 and ends the fuel cut operation.

If the fuel cut operation of the internal combustion engine 1 is terminated before the process of S205 is performed during the process routine of FIG. 7, the ECU 8 terminates the execution of this process routine. And

Next, the procedure for switching the permission flag on and off will be described with reference to FIG. FIG. 8 is a flowchart showing a processing routine executed by the ECU 8 when the permission flag is switched on and off. This processing routine is stored in advance in the ROM of the ECU 8 and is repeatedly executed by the ECU 8 during the operation period of the internal combustion engine 1. In the processing routine of FIG. 8, the same reference numerals are given to the processing similar to the processing routine of FIG. 6 described above.

In the processing routine of FIG. 8, the processing of S301 to S302 is executed instead of the processing of S105 to S112 of the processing routine of FIG. In the processing routine of FIG. 6 described above, when a negative determination is made in the processing of S102, the processing of S112 is executed. In the processing routine of FIG. 8, when a negative determination is made in the processing of S102, S301 is executed. The process is executed.

Specifically, in the processing routine of FIG. 8, when a negative determination is made in the processing of S102 and when a positive determination is made in the processing of S104, the ECU 8 proceeds to the processing of S301 and turns on the above-described permission flag. . On the other hand, if a negative determination is made in the process of S104, the ECU 8 proceeds to the process of S302 and turns off the permission flag described above.

According to the procedure described above, in the spark ignition type internal combustion engine, when the ECU 8 or the particulate filter is replaced, the PM accumulated on the particulate filter is increased without excessively raising the temperature of the particulate filter. It can be oxidized and removed. Further, the actual ash deposition amount is obtained based on the measured value of the differential pressure sensor 5 when all the PM deposited on the particulate filter is oxidized and removed, whereby the ash deposition amount held in the ECU 8 is obtained. Can also be updated.

1 Internal combustion engine 2 Fuel injection valve 3 Exhaust pipe 4 Filter casing 5 Differential pressure sensor 6 Exhaust temperature sensor 7 Fuel addition valve 8 ECU

Claims

A particulate filter disposed in the exhaust passage of the internal combustion engine;
A differential pressure sensor for measuring a differential pressure before and after that is a difference between an exhaust pressure upstream of the particulate filter and an exhaust pressure downstream of the particulate filter;
A control device applied to an exhaust purification system comprising:
First calculation means for calculating an ash accumulation amount that is an amount of ash accumulated on the particulate filter based on an operation history of the internal combustion engine;
Second computing means for computing a PM deposition amount, which is the amount of PM deposited on the particulate filter, based on the measured value of the differential pressure sensor and the ash deposition amount computed by the first computing means; ,
Estimating means for estimating an estimated PM accumulation amount which is an estimated value of the PM amount accumulated on the particulate filter based on an operation history of the internal combustion engine;
When the difference between the PM accumulation amount calculated by the second calculation means and the estimated PM accumulation amount estimated by the estimation means is equal to or greater than a predetermined threshold value, the measured value of the differential pressure sensor is equal to or less than a predetermined upper limit value. If so, the first regeneration process, which is a process for oxidizing and removing PM deposited on the particulate filter by increasing the temperature of the particulate filter to a predetermined first regeneration temperature, is performed, and the difference If the measured value of the pressure sensor is greater than the predetermined upper limit value, the particulate filter is set to a temperature at which the particulate filter is lower than the predetermined first regeneration temperature and PM can be oxidized without executing the first regeneration process. Control means for executing a second regeneration process which is a process for raising the temperature to the second regeneration temperature;
An exhaust purification system control apparatus comprising:
The first regeneration process oxidizes and removes PM deposited on the particulate filter by executing a fuel cut operation for a predetermined first regeneration period when a fuel cut operation request for the internal combustion engine is generated. Process
In the second regeneration process, when the difference between the PM accumulation amount calculated by the second calculation means and the estimated PM accumulation amount estimated by the estimation means is equal to or greater than the predetermined threshold value, the differential pressure sensor The process according to claim 1, wherein if the measured value is larger than the predetermined upper limit value, the fuel cut operation is executed for a second regeneration period shorter than the first regeneration period when a fuel cut operation request of the internal combustion engine is generated. The control apparatus of the exhaust gas purification system described.
The control means calculates the amount of ash actually deposited on the particulate filter from the measured value of the differential pressure sensor when the first regeneration process is finished, and based on the amount of ash, The exhaust purification system control device according to claim 1 or 2, wherein the ash accumulation amount calculated by one calculation means is corrected.