JP4390656B2 - Exhaust gas purification system for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas purification system for an internal combustion engine.

  The exhaust gas of the internal combustion engine contains particulate matter mainly composed of carbon. A technique for providing a particulate filter (hereinafter referred to as “filter”) for collecting particulate matter in an exhaust system of an internal combustion engine is known in order to prevent such particulate matter from being released into the atmosphere.

  In such a filter, when the amount of collected particulate matter increases, the back pressure in the exhaust increases due to clogging of the filter, and the engine performance decreases. On the other hand, by raising the temperature of the filter, the collected particulate matter is oxidized and removed to regenerate the exhaust purification performance of the filter (hereinafter referred to as “filter regeneration process”).

  Here, as a method for raising the temperature of the filter in the regeneration process, an oxidation catalyst having an oxidation ability is carried on the filter or an oxidation catalyst having an oxidation ability is disposed on the upstream side of the filter. A method of supplying a fuel as a reducing agent to a catalyst is known. As a result, the oxidation reaction of the fuel can occur in the oxidation catalyst, and the temperature of the filter can be raised.

  And in order to maintain the temperature of said filter at the temperature suitable for a regeneration process, control of the addition amount of the said reducing agent is needed. Therefore, for example, the supply amount of the reducing agent per unit time is basically set on the basis of the intake air amount to the internal combustion engine and the filter inlet temperature, and the relationship between the filter inlet temperature and the filter outlet temperature. Based on this, there has been proposed a technique in which the supply amount of the reducing agent is corrected to decrease (see, for example, Patent Document 1).

However, also in the above technique, when the internal combustion engine is accelerated during the regeneration process of the filter, the reducing agent supplied to the filter during the acceleration may complete the oxidation reaction during the acceleration. Occasionally, oxidation may occur after completion of acceleration, and the temperature of the filter may rise excessively after completion of acceleration. As a result, it may be difficult to accurately control the temperature of the filter.
Japanese Patent Laid-Open No. 05-222916 Japanese Patent Laid-Open No. 05-044434 JP 09-004437 A Japanese Patent Application Laid-Open No. 11-062561

  An object of the present invention is to provide an exhaust gas purification system for an internal combustion engine that raises the temperature of a filter by supplying a reducing agent to an oxidation catalyst and performs the regeneration process of the filter, during the regeneration process of the filter. The present invention provides a technique capable of controlling the temperature of the filter to a target temperature more accurately even when the internal combustion engine is accelerated.

In order to achieve the above object, the present invention provides an exhaust gas purification system for an internal combustion engine that performs a regeneration process by supplying a reducing agent from a reducing agent supply means to a filter that carries an oxidation catalyst or has a separate body.
The amount of unburned reducing agent that has not been oxidized in the filter during acceleration of the internal combustion engine during the regeneration process is calculated, and after the acceleration of the internal combustion engine during the regeneration process, the temperature of the filter is originally targeted. The greatest feature is that an amount of reducing agent obtained by subtracting the amount of unburned reducing agent from the amount of basic reducing agent supplied to control the temperature is supplied from the reducing agent supply means to the filter.

More specifically, a filter that is provided in the exhaust passage of the internal combustion engine and collects particulate matter in the exhaust of the internal combustion engine, and carries an oxidation catalyst or has a separate body,
A reducing agent supply means for supplying a reducing agent to the filter from the upstream side of the filter in the exhaust passage,
In the regeneration process for removing the particulate matter deposited on the filter by oxidation, in the exhaust gas purification system for an internal combustion engine that raises the temperature of the filter by supplying the reducing agent to the filter from the reducing agent supply means,
Filter temperature detecting means for detecting the temperature of the filter;
A basic reducing agent amount to be supplied from the reducing agent supply means to the filter based on a difference between a target temperature at which the filter is to be controlled during the regeneration process and a filter temperature detected by the filter temperature detection means. A basic reducing agent amount calculating means for calculating
During acceleration of the internal combustion engine during the regeneration process, based on the difference between the target temperature at which the filter is to be controlled and the temperature of the filter detected by the filter temperature detecting means, in the filter during acceleration An unburned reducing agent amount calculating means for calculating an unburned reducing agent amount;
Further comprising
After acceleration of the internal combustion engine during the regeneration process, an amount obtained by subtracting the unburned reducing agent amount calculated by the unburned reducing agent amount calculating unit from the basic reducing agent amount calculated by the basic reducing agent amount calculating unit. The reducing agent is supplied to the filter from the reducing agent supply means.

  Here, when the filter regeneration process is performed, the basic reducing agent supplied from the reducing agent supply means to the filter based on the difference between the filter temperature at that time and the target temperature of the filter to be controlled in the regeneration process. A quantity is calculated. An amount of reducing agent corresponding to the basic reducing agent amount is supplied from the reducing agent supply means to the filter.

  However, when the internal combustion engine is accelerated during the regeneration process of the filter, the reducing agent supplied in a large amount to the filter may not be oxidized during the acceleration and become unburned fuel. In that case, the oxidation temperature of the unburned fuel occurs after the acceleration of the internal combustion engine is finished, so that the temperature of the filter may increase excessively after the acceleration is finished. This sometimes makes it difficult to accurately control the temperature of the filter.

  Therefore, in the present invention, when the internal combustion engine is accelerated during the filter regeneration process, the filter uses the filter among the basic reducing agent amount from the difference between the target temperature of the filter during acceleration and the actual filter temperature. The amount of unburned reducing agent, which is the amount of reducing agent that has not yet been oxidized, is calculated. Then, after the acceleration of the internal combustion engine is completed during the filter regeneration process, an amount of reducing agent obtained by subtracting the amount of unburned reducing agent from the amount of basic reducing agent is supplied to the filter. Then, when the reducing agent not oxidized by the filter during the acceleration is oxidized by the filter after the acceleration of the internal combustion engine, a total amount of the reducing agent corresponding to the basic reducing agent amount is oxidized by the filter. Can do. As a result, the filter temperature after acceleration of the internal combustion engine can be controlled to the target temperature with higher accuracy.

  Then, even when the internal combustion engine is accelerated during the filter regeneration process, it is possible to suppress the filter temperature from greatly deviating from the target temperature after the acceleration is completed, and the filter regeneration process can be performed more reliably.

  In the present invention, during acceleration of the internal combustion engine during the regeneration process, a difference between a target temperature at which the filter is to be controlled and a temperature of the filter detected by the filter temperature detecting means is greater than a predetermined value. If larger, the basic reducing agent amount of reducing agent may be supplied from the reducing agent supply means to the filter even after acceleration of the internal combustion engine during the regeneration process.

  Here, the predetermined value is the difference between the target temperature at which the filter is to be controlled and the filter temperature detected by the filter temperature detecting means during acceleration of the internal combustion engine during the regeneration process. If it is larger, the temperature difference is set as a threshold value at which it is possible to determine that the temperature of the filter has not yet reached the steady state because the temperature of the filter is being raised at the beginning of the regeneration process.

  Then, when the difference between the target temperature and the temperature of the filter is larger than the predetermined value, the filter temperature is being raised during the regeneration process and may not yet reach a steady state. Judgment is high. In such a case, it is considered that it is difficult to bring the temperature of the filter close to the target temperature even if the above-described control during and after acceleration of the internal combustion engine is performed. Therefore, in such a case, the basic reducing agent amount of the reducing agent is supplied to the filter as usual even after the acceleration of the internal combustion engine, thereby promoting the steady state of the temperature of the filter.

  In this way, only when it is really effective, after the acceleration of the internal combustion engine is completed, the amount of reducing agent obtained by subtracting the amount of unburned reducing agent from the amount of basic reducing agent can be supplied to the filter. Can be prevented from being controlled. In addition, when the filter is being heated and has not reached a steady state, by supplying a reducing agent in an amount other than the basic reducing agent amount to the filter, the time for the filter temperature to reach a steady state is reversed. It can suppress delaying.

  In the present invention, after the acceleration of the internal combustion engine during the regeneration process, the unburned reducing agent amount calculating means is calculated from the basic reducing agent amount calculated by the basic reducing agent amount calculating means. Reduce the amount of reducing agent by dividing it into a plurality of times, and reduce the amount of reducing agent by dividing the amount of unburned reducing agent from the basic reducing agent amount by the number of times corresponding to the number of divisions. You may make it supply to the said filter from a supply means.

  That is, when the control according to the present invention is not performed, unburned fuel that has not caused an oxidation reaction during acceleration of the internal combustion engine causes an oxidation reaction after acceleration of the internal combustion engine, so that the temperature of the filter is increased. In some cases, the temperature rises excessively, but even in this case, the unburned reducing agent does not cause an oxidation reaction at once, and the reaction time varies. Therefore, the temperature of the filter does not rise instantaneously but rises and falls with a predetermined time width.

  Therefore, also in the case of performing the control in the present invention, not all the unburned reducing agent amount calculated during acceleration of the internal combustion engine is reduced from the basic reducing agent amount at once, but the unburned reducing agent amount is reduced. The amount of unburned reducing agent is divided as appropriate, and the amount of reducing agent obtained by subtracting the amount of unburned reducing agent from the basic reducing agent amount is supplied to the filter over the number of times corresponding to the number of divisions.

  Then, after the acceleration of the internal combustion engine, the unburned reducing agent amount can be subtracted from the basic reducing agent amount with a distribution closer to the time distribution when the unburned reducing agent causes an oxidation reaction, so that the temperature of the filter Can be brought closer to the target temperature with higher accuracy. Further, it is possible to suppress the amount of the supplied reducing agent from being extremely reduced only when the reducing agent is supplied once, and it is possible to improve the convergence of the filter temperature to the target temperature.

Further, in the present invention, after the acceleration of the internal combustion engine during the regeneration process, the unburned reducing agent calculated by the unburned reducing agent amount calculating means from the basic reducing agent amount calculated by the basic reducing agent amount calculating means. When the internal combustion engine is re-accelerated by the time when the reducing agent amount reduced in amount is completely supplied from the reducing agent supply means to the filter, the unburned reducing agent amount is erased and The amount of unburned reducing agent during the reacceleration may be newly calculated by the fuel reducing agent amount calculating means.

  That is, after the acceleration of the internal combustion engine during the filter regeneration process, control is performed to supply the filter with an amount of reducing agent calculated by subtracting the amount of unburned reducing agent calculated during acceleration of the internal combustion engine from the basic reducing agent amount. If the internal combustion engine re-accelerates during the process, the unburned reducing agent amount calculated during the previous acceleration is cleared, and a new unburned reducing agent amount is calculated during the re-acceleration. I did it.

  Then, in each acceleration operation of the internal combustion engine, the amount of the unburned reducing agent can be calculated independently.After the acceleration is completed, the unburned reducing agent is not affected by the previous acceleration. Only the amount of unburned reducing agent in can be subtracted from the basic reducing agent amount. As a result, even if the acceleration state of the internal combustion engine changes in a complicated manner during the filter regeneration process, the temperature of the filter can be more accurately controlled to the target temperature by a simple flow.

  Further, in the present invention, when the unburned reducing agent amount calculated by the unburned reducing agent amount calculation means during acceleration of the internal combustion engine during the regeneration process is larger than a predetermined amount, the predetermined amount The unburned reducing agent amount calculated by the unburned reducing agent amount calculating means may be used.

  That is, if the amount of unburned reducing agent during acceleration of the internal combustion engine becomes excessive, the amount of reducing agent subtracted from the basic reducing agent amount after acceleration of the internal combustion engine may increase abnormally. In the present invention, considering that the control for subtracting the unburned reducing agent amount from the basic reducing agent amount is correction for the temperature of the filter, it is desirable to provide a certain upper limit for the value handled as the unburned reducing agent amount. In other words, if the amount of unburned reducing agent as the correction amount increases beyond the upper limit, it may be difficult to appropriately control the filter temperature to the target temperature.

  Therefore, in the present invention, when the unburned reducing agent amount calculated by the unburned reducing agent amount calculating means is greater than a predetermined amount during acceleration of the internal combustion engine during the regeneration process, The amount of unburned reducing agent was determined by quantification.

  If it does so, control which subtracts the unburned reducing agent amount from the basic reducing agent amount can be performed only within a range in which the temperature of the filter can be appropriately controlled to the target temperature. As a result, the temperature of the filter can be controlled to the target temperature more accurately.

  The means for solving the problems in the present invention can be used in combination as much as possible.

  According to the present invention, in the exhaust gas purification system for an internal combustion engine that raises the temperature of the filter by supplying a reducing agent to the oxidation catalyst and performs the regeneration process of the filter, the internal combustion engine during the regeneration process of the filter Even when the temperature of the filter is accelerated, the temperature of the filter can be controlled to the target temperature more accurately.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine according to the present embodiment and its exhaust system and control system. An internal combustion engine 1 shown in FIG. 1 is a diesel engine. In FIG. 1, the inside of the internal combustion engine 1 and its intake system are omitted.

  In FIG. 1, an exhaust pipe 5 through which exhaust gas discharged from the internal combustion engine 1 flows is connected to the internal combustion engine 1, and this exhaust pipe 5 is connected downstream to a muffler (not shown). A filter 10 that purifies particulate matter (for example, soot) in the exhaust is disposed in the middle of the exhaust pipe 5.

  The filter 10 in this embodiment is one in which an oxidation catalyst is supported on a wall flow type particulate filter made of a porous base material. However, the filter 10 may not necessarily carry an oxidation catalyst. In that case, for example, an oxidation catalyst may be provided independently on the upstream side of the exhaust purification device 10 in the exhaust pipe 5.

  On the upstream side of the filter 10 in the exhaust pipe 5, a fuel addition valve 12 that supplies fuel as a reducing agent to the filter 10 when the filter 10 is regenerated is disposed. The fuel added from the fuel addition valve 12 causes an oxidation reaction in the oxidation catalyst carried on the filter 10 together with the exhaust from the internal combustion engine 1. As a result, the temperature of the filter 10 increases. The fuel addition valve 12 constitutes a reducing agent supply means in the present embodiment.

  A filter temperature sensor 17 that detects the temperature of the exhaust gas discharged from the filter 10 is provided in the exhaust pipe 5 on the downstream side of the filter 10. Here, since the temperature of the exhaust gas discharged from the filter 10 detected by the filter temperature sensor 17 is substantially the same as the temperature of the filter 10, this can be used as the temperature of the filter 10. Here, the filter temperature detection means in the present embodiment includes the filter temperature sensor 17.

The internal combustion engine 1 configured as described above and its exhaust system are provided with an electronic control unit (ECU) 20 for controlling the internal combustion engine 1 and the exhaust system. 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 driver's request, and performs control related to the exhaust gas purification device 10 of the internal combustion engine 1.

  The ECU 20 includes a crank position sensor (not shown), an accelerator position sensor, sensors related to control of the operating state of the internal combustion engine 1 such as an air flow meter for detecting the intake air amount, and a filter temperature sensor 17 in the present embodiment. An output signal is input to the ECU 20 through electrical wiring. On the other hand, a fuel injection valve (not shown) in the internal combustion engine 1 is connected to the ECU 20 via an electrical wiring, and the fuel addition valve 12 in this embodiment is connected via an electrical wiring and is controlled by the ECU 20. It is like that.

  The ECU 20 includes a CPU, a ROM, a RAM, and the like. The ROM stores a program for performing various controls of the internal combustion engine 1 and a map storing data. A regeneration processing routine for reducing back pressure in the filter 10 by oxidizing and removing particulate matter from the filter 10 (not shown), and a filter regeneration fuel addition routine in the present invention, which will be described later, are also stored in the ROM of the ECU 20. One of the stored programs.

  Here, in the internal combustion engine 1, as described above, exhaust gas purification is performed by collecting particulate matter in the exhaust gas using the filter 10. However, when the accumulation amount of the particulate matter collected in the filter 10 increases, the filter 10 is clogged. As a result, the back pressure of the internal combustion engine 1 increases, and the operation performance may be deteriorated.

  Therefore, in the internal combustion engine 1, every time a predetermined period or every time when it is detected that a predetermined amount or more of the particulate matter has been collected in the filter 10, a regeneration process for oxidizing and removing the particulate matter in the filter 10 is performed. Done.

  In this regeneration process, fuel as a reducing agent is supplied from the fuel addition valve 12 to the oxidation catalyst on the filter 10. As a result, the oxidation reaction of the fuel occurs in the oxidation catalyst, the temperature of the oxidation catalyst and the filter 10 carrying the oxidation catalyst also rises, and the temperature of the filter 10 becomes equal to or higher than the ignition temperature of the particulate matter. Thereby, the particulate matter in the filter 10 can be oxidized and removed.

  In the regeneration process, a target temperature at which the temperature of the filter 10 is to be controlled is set. The basic fuel amount supplied from the fuel addition valve 12 to the filter 10 is determined based on the difference ΔT between the actual temperature of the filter 10 obtained from the output of the filter temperature detection sensor 17 and the target temperature. . The relationship between the basic fuel amount and ΔT is obtained experimentally and mapped in advance. Therefore, the basic fuel amount is determined by reading the basic fuel amount value corresponding to the difference ΔT between the target temperature and the actual temperature of the filter 10 from this map. Here, the basic reducing agent amount calculating means in the present embodiment is constituted by the ECU 20. In this embodiment, since fuel is used as the reducing agent to be supplied to the filter 10, the basic fuel amount here means the basic reducing agent amount.

  Next, the relationship between the acceleration state during the regeneration process of the internal combustion engine 1 and the temperature of the filter 10 will be described with reference to FIG. FIG. 2 shows the relationship between the engine speed of the internal combustion engine 1 during the regeneration process of the filter 10 in the internal combustion engine 1, the accompanying fuel supply amount from the fuel addition valve 12, and the temperature of the filter 10.

  Before the time t1 in FIG. 2, the engine speed is stable at a relatively small value. In this case, the temperature of the filter 10 is controlled to the target temperature indicated by the broken line in FIG. 2 by adding the fuel corresponding to the basic fuel amount calculated by the ECU 20 as the basic reducing agent amount calculating means from the fuel addition valve 12. ing.

  Next, let us consider a case where the engine speed rapidly increases due to acceleration of the internal combustion engine 1 at time t1. In this case, since the intake air amount and the exhaust gas flow rate increase rapidly, the amount of heat removed by the exhaust gas from the filter 10 increases, and the temperature of the filter 10 becomes lower than the target temperature. Then, the ECU 20 that is the basic reducing agent amount calculating means increases the basic fuel amount based on the difference between the actual temperature of the filter 10 detected by the filter temperature sensor 17 and the target temperature. As a result, the fuel supply amount increases.

  Since a large amount of fuel is added from the fuel addition valve 12 in a short period between the time point t1 and the time point t2, a part of the fuel is added on the filter 10 between the time points t1 and t2. The oxidation reaction may not end and may remain unburned. In that case, after the engine speed is stabilized after the time t2, the fuel remaining on the filter 10 without being burned is oxidized, so that the temperature of the filter 10 is compared with the target temperature after the time t2. Rise to a high temperature.

As described above, when the fuel addition amount from the fuel addition valve 12 is determined based only on the basic reducing agent amount calculated by the ECU 20 which is the basic reducing agent amount calculating means, the internal combustion engine 1 is in the process of regenerating the filter 10. When accelerating, the temperature of the filter 10 becomes unstable, and it may be difficult to accurately control the target temperature, particularly after acceleration.

  Therefore, in the present invention, of the fuel supplied from the fuel addition valve 12 to the filter 10 between time t1 and time t2 in FIG. 2, the amount of unburned fuel that was not oxidized between time t1 and time t2. The amount of unburned fuel described above is subtracted from the amount of basic fuel supplied from the fuel addition valve 12 to the filter 10 after time t2. In this embodiment, since fuel is used as the reducing agent supplied to the filter 10, the unburned fuel amount here means the unburned reducing agent amount. Further, the unburned reducing agent amount calculating means in the present embodiment is configured by the ECU 20.

  FIG. 3 shows a flow chart of the filter regeneration fuel addition routine in this embodiment. This routine is a program stored in the ROM in the ECU 20, and is a routine that is executed at predetermined intervals during the regeneration process of the filter 10.

  When this routine is executed, first, in S101, a difference ΔT between the target temperature during the regeneration process of the filter 10 and the actual temperature of the filter 10 at that time is detected. Specifically, the output signal of the filter temperature sensor 17 is read by the ECU 20 and is detected by subtracting it from the target temperature read from a map prepared in advance.

  Next, proceeding to S102, the basic fuel amount FB is calculated by the ECU 20, which is a basic reducing agent amount calculating means. Specifically, it is calculated by reading the basic fuel amount FB corresponding to ΔT detected in S101 from the above-mentioned map storing the relationship between ΔT and the basic fuel amount FB.

  Next, the process proceeds to S103, and it is determined whether or not ΔT detected in S101 is larger than T0. Here, when the difference ΔT between the target temperature of the filter 10 and the actual temperature of the filter 10 is larger than T0, it is determined that the filter 10 is being heated in the initial stage of the regeneration process. It is a temperature difference as a threshold, and may be defined between 30 ° C. and 50 ° C., for example. That is, in the regeneration process of the filter 10, if the filter 10 is warming and has not yet reached a steady state, the filter 10 temperature is set to the target temperature even if the filter regeneration fuel addition routine in this embodiment is executed. Therefore, in this case, the control according to this routine is not applied.

  Therefore, if it is determined in S103 that ΔT is larger than T0, the present routine is once terminated. When it is determined that ΔT is equal to or less than T0, the process proceeds to S104.

  In S104, it is determined whether or not the internal combustion engine 1 to which the control according to this routine is applied is being accelerated. Specifically, determination may be made based on the output of an air flow meter (not shown) based on whether the change in the intake air amount is a predetermined amount or more, or whether the output of an accelerator position sensor (not shown) is a predetermined value or more.

  If it is determined in S104 that the internal combustion engine 1 is accelerating, the process proceeds to S109 to calculate the amount of unburned fuel among the fuel added to the filter 10 from the fuel addition valve 12 during acceleration. On the other hand, if it is determined that the vehicle is not accelerating, it can be determined that the acceleration of the internal combustion engine 1 has ended or is in a steady operation state, and thus the process proceeds to S105.

In S109, the difference ΔT between the target temperature of the filter 10 and the actual temperature of the filter 10 at this time is detected again based on the output of the filter temperature sensor 17. Then, the process proceeds to S110, and the fuel addition valve 1 is calculated from ΔT obtained in S109 and the intake air amount Ga at this time.
Among the fuels added to the filter 10 from 2, the unburned fuel amount Q that has not been oxidized by the filter 10 is calculated.

  Here, it is considered that the unburned fuel amount Q increases as the difference ΔT between the target temperature of the filter 10 and the actual temperature of the filter 10 increases. Further, as the intake air amount Ga at this time increases, the amount of fuel supplied from the fuel addition valve 12 in order to equalize the A / F ratio increases. Therefore, in S110, the unburned fuel amount Q at the time of execution of this process can be calculated by the following calculation formula.

  Unburnt fuel amount Q = (target temperature−actual temperature of filter 10) × α × Ga (1)

  In the above formula, α is a proportionality constant and is experimentally obtained in advance. If the unburned fuel amount Q at the time of execution of this process is calculated in S110, the process proceeds to S111.

  In S111, a total unburned fuel amount QT, which is a total value of the unburned fuel amount Q, is calculated so as to integrate the unburned fuel amount Q calculated in S110 at the time of execution of S110 over the acceleration period. Specifically, the unburned fuel amount Q calculated at the time of execution of S110 of the present routine is added to the total unburned fuel amount QT at the previous execution of the routine, and a new total unburned fuel amount QT is obtained. Is calculated. When the process of S111 ends, the process proceeds to S112.

  In S112, it is determined whether or not the calculated total unburned fuel amount QT is equal to or less than QMAX, which is the maximum value that can be handled as the unburned fuel amount in this routine. If QT is equal to or less than QMAX, the process proceeds to S113, and QT is stored as it is as the value of QT. On the other hand, if QT is larger than QMAX, the process proceeds to S114, where the value of QMAX is substituted into QT and stored. Here, QMAX is the sum of the threshold values that do not cause the control to become unstable when a value obtained by subtracting the total unburned fuel amount QT from the basic fuel amount FB is added from the fuel addition valve 12 in the processing described later in this routine. The amount of fuel may be used.

  Here, the description returns to S104. If it is determined in S104 that the vehicle is not accelerating, the process proceeds to S105. In S105, it is determined whether or not acceleration is determined in S104 at the time of the previous execution of this routine. In other words, it is determined whether or not the current execution of this routine is executed immediately after the acceleration of the internal combustion engine 1 ends. If it is determined that the previous acceleration was being performed, the process proceeds to S108. Then, from the basic fuel amount FB, the total unburned fuel amount QT at the time of execution of this routine last time, in other words, at the time of execution of the last routine during acceleration is subtracted. Then, the process proceeds to S107, and an amount of fuel obtained by subtracting the total unburned fuel amount QT at the time of the last execution during acceleration from the basic fuel amount FB is added from the fuel addition valve 12, and this routine is once ended.

  Thus, by subtracting the total unburned fuel amount QT during acceleration from the basic fuel amount FB, the temperature of the filter 10 after acceleration increases excessively due to oxidation of unburned fuel, and can be accurately controlled to the target temperature. It can be suppressed from disappearing.

  On the other hand, if it is determined in S105 that the previous acceleration was not being performed, in other words, if it is determined that the current execution of this routine was performed during steady operation, the process proceeds to S106 and the value of QT is cleared. Then, the process proceeds to S107, and the fuel of the basic fuel amount FB calculated in S102 is added from the fuel addition valve 12. When the processing of S107 is executed, this routine is once terminated.

As described above, in the filter regeneration fuel addition routine according to the present embodiment, the unburned fuel amount at each time point during acceleration of the internal combustion engine 1 is integrated to calculate the total unburned fuel amount. The amount is subtracted from the basic fuel amount calculated by the ECU 20 which is the basic reducing agent amount calculating means and added to the filter 10. Thereby, it is possible to suppress the unburned fuel during the acceleration of the internal combustion engine 1 from being oxidized in the filter 10 after the acceleration and excessively increasing the temperature of the filter 10. As a result, after the internal combustion engine 1 is accelerated, the filter 10 can be controlled more accurately so that the temperature of the filter 10 becomes the target temperature.

  Further, in this embodiment, when the difference between the target temperature of the filter 10 and the actual temperature is larger than a predetermined value (T0), the fuel corresponding to the basic fuel amount is not calculated without calculating the unburned fuel amount. Add from addition valve 12. Therefore, when the temperature of the filter 10 is largely deviated from the target temperature without causing the acceleration of the internal combustion engine 1 such as during the temperature increase in the initial stage of the regeneration process, the basic fuel amount of fuel is used as it is. The fuel was added from the fuel addition valve 12. As a result, only when there is a real effect, after the acceleration of the internal combustion engine 1 is completed, an amount of fuel obtained by subtracting the total amount of unburned fuel from the basic fuel amount can be supplied to the filter 10, and wasteful complicated control can be performed. It can be suppressed. In addition, when the temperature of the filter 10 is increasing and the steady state has not been reached, by supplying an amount of fuel different from the basic fuel amount to the filter 10, the time for the filter temperature to reach the steady state is delayed. Can be suppressed.

  Furthermore, in this embodiment, when the total unburned fuel amount accumulated during acceleration of the internal combustion engine 1 is larger than the maximum value (QMAX) that can be handled as the unburned fuel amount in this routine, An amount of fuel obtained by subtracting the maximum value (QMAX) that can be handled as an unburned fuel amount in this routine from the fuel amount is added from the fuel injection valve 12. If it does so, it can control that the correction amount of the fuel addition amount after acceleration becomes excessive, and control becomes unstable.

  Next, a second embodiment of the present invention will be described. The hardware configuration of the internal combustion engine 1 and its exhaust system and control system in the present embodiment is the same as that described in the first embodiment, and therefore the description thereof is omitted. In the filter regeneration fuel addition routine in this embodiment, when the internal combustion engine 1 is accelerated during the regeneration process of the filter 10, the total unburned fuel amount QT is decremented from the basic fuel amount FB when the routine is executed for the first time after acceleration. In this example, the basic fuel amount is calculated based on the total unburned fuel amount QT accumulated during the acceleration after the internal combustion engine 1 has accelerated once. In this example, when the internal combustion engine 1 re-accelerates before the correction of FB is completed, the total unburned fuel amount QT calculated and integrated during the previous acceleration is cleared.

  FIG. 4 is a flowchart for the filter regeneration fuel addition routine in this embodiment. This routine is a program stored in the ROM of the ECU 20, and is repeatedly executed by the ECU 20 at predetermined intervals during the regeneration process of the filter 10.

  When this routine is executed, the processing from S101 to S103 is first executed. Since these processing are the same as the processing in the first embodiment, description thereof is omitted here. Next, in S201, it is determined whether or not the fuel addition amount correction period after acceleration of the internal combustion engine 1 is in progress. Here, the fuel addition amount correction period refers to a period in which the fuel addition amount is corrected by subtracting the total unburned fuel amount QT from the basic fuel amount FB after the acceleration of the internal combustion engine 1. That is, in this routine, as described above, when the internal combustion engine 1 is accelerated during the regeneration processing of the filter 10, the total unburned fuel amount QT is reduced from the basic fuel amount FB when the routine is executed for the first time after acceleration. Since the subtraction is divided into a plurality of times instead of subtracting once, correction is performed so that a part of the total unburned fuel amount QT is subtracted from the basic fuel amount FB over several executions of this routine after completion of acceleration. . In S201, it is determined whether or not such correction is to be performed in the current execution of this routine.

Specifically, for example, it may be determined whether the value of the total unburned fuel amount QT at this time point is smaller than the total unburned fuel amount QT at the start of execution of the previous routine and greater than zero. . This is because, during the fuel addition amount correction period after acceleration of the internal combustion engine 1, the total unburned fuel amount QT should be reduced by the processing of S209 described later each time this routine is executed. And based on the judgment that the bag is not 0.

  If it is determined in S201 that the fuel addition amount correction period after acceleration is in progress, the process proceeds to S204. In S204, it is determined whether the internal combustion engine 1 is accelerating. Here, the determination may be made by the same method as the process of S104 in the first embodiment. When it is determined in S204 that the internal combustion engine 1 is accelerating, it is determined that the acceleration is re-accelerated during the fuel addition amount correction period after acceleration. In this case, the process proceeds to S205 and the total unburned fuel amount QT is once cleared. Then, in the processing of S109 to S114, integration of the total unburned fuel amount QT during the reacceleration is newly started. Here, the contents of the processing of S109 to S114 are the same as those described in the first embodiment, and therefore description thereof is omitted.

  On the other hand, if it is determined in S204 that the vehicle is not accelerating, that is, if it is determined that the vehicle has not been accelerated during the fuel addition amount correction period after acceleration, the process proceeds to S206. The contents of the process of S206 will be described later. If it is determined in S201 that the fuel addition amount correction period after acceleration is not in progress, the process proceeds to S202. Also in S202, it is determined whether the internal combustion engine 1 is accelerating. Again, the determination method may be the same as S104 in the first embodiment.

  When it is determined in S202 that acceleration is in progress, the process proceeds to S109 to S114. That is, this case corresponds to a case where the internal combustion engine 1 is re-accelerated in a period that is not the fuel addition amount correction period after acceleration. In this case, since the total unburned fuel amount QT is 0 without being cleared, the process proceeds to S109 instead of S205, and the integration of the total unburned fuel amount QT in the current acceleration is newly started. .

  On the other hand, if it is determined in S202 that the vehicle is not accelerating, the process proceeds to S203. In S203, it is determined whether or not the total unburned fuel amount QT is greater than zero. If it is determined that the total unburned fuel amount QT is greater than 0, the process proceeds to S206 as in the case where it is determined in S204 that the vehicle is not accelerating.

  In S206, it is determined whether or not the divided unburned fuel amount QT / A obtained by dividing the total unburned fuel amount QT by the predetermined value A is larger than the threshold value C. Here, A is a value that determines how much the total unburned fuel amount QT is divided and then the fuel supply amount is corrected. In this embodiment, A = 2, for example. Further, the threshold value C is calculated by dividing the total unburned fuel amount QT and correcting it little by little. If the remaining amount of the total unburned fuel amount QT is, the total unburned fuel amount is not divided. It is a value that determines whether or not the remaining amount of QT is corrected all at once.

  When it is determined in S206 that the divided unburned fuel amount QT / A is larger than the threshold value C, the process proceeds to S207, and the divided divided unburned fuel amount QT / A is calculated from the basic fuel amount FB calculated in S102. Then, the process proceeds to S209, and a value obtained by subtracting the divided unburned fuel amount QT / A from the total unburned fuel amount QT is used as a new total unburned fuel amount QT. Then, the process proceeds to S107, and the fuel amount FB calculated in S207 from the fuel addition valve 12 is added.

  On the other hand, if it is determined in S206 that the divided unburned fuel amount QT / A is equal to or less than the threshold value C, it is determined that the remaining amount of the total unburned fuel amount QT may be corrected at once. Then, the remaining amount QT of the total unburned fuel amount is subtracted from the basic fuel amount FB. Then, the process proceeds to S210 and the value of the total unburned fuel amount TQ is cleared. Then, the process proceeds to S107, and the fuel amount FB calculated in S208 is added from the fuel addition valve 12.

  Further, if it is determined in S203 that the total unburned fuel amount QT = 0, it is determined that the fuel addition amount correction period after acceleration has ended, so the process proceeds to S107 and the basic fuel calculated in S102 is reached. The amount FB is added as it is from the fuel addition valve 12.

  As described above, in the filter regeneration fuel addition routine in this embodiment, the divided unburned fuel amount obtained by dividing the total unburned fuel amount calculated during acceleration is subtracted from the basic fuel amount, and the basic fuel amount is calculated. By adding an amount of fuel obtained by subtracting the divided unburned fuel amount from the fuel addition valve 12, the fuel addition amount is corrected little by little. Therefore, it is easier to stabilize the temperature of the filter 10 at the target temperature than when correcting by subtracting the total unburned fuel amount at once from the basic fuel amount. In the case of further acceleration during the fuel addition amount correction period after acceleration, since the remaining amount of the total unburned fuel amount is cleared and the accumulation of the unburned fuel amount is newly started, the internal combustion engine The amount of unburned fuel can be corrected independently for each acceleration operation. As a result, even if the acceleration state of the internal combustion engine 1 changes complicatedly during the regeneration process of the filter 10, the temperature of the filter 10 can be more accurately controlled to the target temperature by a simple flow.

  In the above description, the ECU 20 as the basic reducing agent amount calculating means calculates the basic fuel amount (basic reducing agent amount) FB based on the difference ΔT between the target temperature and the actual temperature of the filter 10. The method of calculating the amount (basic reducing agent amount) FB is not limited to this method. For example, it may be calculated based on the intake air amount Ga and the temperature near the inlet of the filter 10.

  In the second embodiment, the divided unburned fuel amount is defined by the mathematical formula QT / A. During the fuel addition amount correction period after acceleration, the fuel amount to be subtracted from the basic fuel amount FB is determined by the fuel regeneration routine in the filter regeneration. Changed from run to run. However, the definition of the amount of divided unburned fuel is not limited to this. For example, the total unburned fuel amount QT at the end of acceleration may be simply divided into equal amounts, or may be corrected by subtracting a certain amount of fuel from the basic fuel amount FB regardless of the total unburned fuel amount QT. Also good.

It is a figure which shows schematic structure of the internal combustion engine which concerns on the Example of this invention, its exhaust system, and a control system. It is a graph which shows the engine rotation speed of the internal combustion engine which concerns on the Example of this invention, the fuel supply amount accompanying the change of engine rotation speed, and the change of filter temperature. It is a flowchart which shows the fuel addition routine at the time of filter regeneration which concerns on Example 1 of this invention. It is a flowchart which shows the fuel addition routine at the time of filter regeneration which concerns on Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 5 ... Exhaust pipe 10 ... Filter 12 ... Fuel addition valve 17 ... Filter temperature sensor 20 ... ECU

Claims (5)

A filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust of the internal combustion engine and carrying an oxidation catalyst or having a separate body;
A reducing agent supply means for supplying a reducing agent to the filter from the upstream side of the filter in the exhaust passage,
In the regeneration process for removing the particulate matter deposited on the filter by oxidation, in the exhaust gas purification system for an internal combustion engine that raises the temperature of the filter by supplying the reducing agent to the filter from the reducing agent supply means,
Filter temperature detecting means for detecting the temperature of the filter;
A basic reducing agent amount to be supplied from the reducing agent supply means to the filter based on a difference between a target temperature at which the filter is to be controlled during the regeneration process and a filter temperature detected by the filter temperature detection means. A basic reducing agent amount calculating means for calculating
During acceleration of the internal combustion engine during the regeneration process, based on the difference between the target temperature at which the filter is to be controlled and the temperature of the filter detected by the filter temperature detecting means, in the filter during acceleration An unburned reducing agent amount calculating means for calculating an unburned reducing agent amount;
Further comprising
After acceleration of the internal combustion engine during the regeneration process, an amount obtained by subtracting the unburned reducing agent amount calculated by the unburned reducing agent amount calculating unit from the basic reducing agent amount calculated by the basic reducing agent amount calculating unit. An exhaust gas purification system for an internal combustion engine, wherein the reducing agent is supplied from the reducing agent supply means to the filter.   If the difference between the target temperature at which the filter is to be controlled and the filter temperature detected by the filter temperature detecting means is greater than a predetermined value during acceleration of the internal combustion engine during the regeneration process, the regeneration is performed. The exhaust purification system of an internal combustion engine according to claim 1, wherein the basic reducing agent amount of reducing agent is supplied from the reducing agent supply means to the filter even after acceleration of the internal combustion engine during processing.   After the acceleration of the internal combustion engine during the regeneration process, the unburned reducing agent amount calculated by the unburned reducing agent amount calculating unit is set to a plurality of times from the basic reducing agent amount calculated by the basic reducing agent amount calculating unit. The amount of reducing agent obtained by dividing and subtracting and subtracting the amount of unburned reducing agent from the basic reducing agent amount is supplied from the reducing agent supply means to the filter for the number of times corresponding to the number of divisions. The exhaust gas purification system for an internal combustion engine according to claim 1.   After acceleration of the internal combustion engine during the regeneration process, an amount obtained by subtracting the unburned reducing agent amount calculated by the unburned reducing agent amount calculating unit from the basic reducing agent amount calculated by the basic reducing agent amount calculating unit. When the internal combustion engine re-accelerates before supplying the reducing agent from the reducing agent supply unit to the filter, the unburned reducing agent amount is calculated by the unburned reducing agent amount calculating unit after erasing the unburned reducing agent amount. The exhaust gas purification system for an internal combustion engine according to claim 1 or 3, wherein the amount of unburned reducing agent during the reacceleration is newly calculated.   When the unburned reducing agent amount calculated by the unburned reducing agent amount calculating means during acceleration of the internal combustion engine during the regeneration process is larger than a predetermined amount, the unburned reducing agent is used with the predetermined amount. 5. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the unburned reducing agent amount is calculated by an amount calculating means.

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