JP2006118400A - Exhaust gas purification system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more efficiently oxidize PM deposited on a filter in an exhaust gas purification system for an internal combustion engine provided with a filter provided in an exhaust passage of the internal combustion engine while suppressing an excessive temperature rise of the filter. • Provide technology that can be removed.
In an exhaust gas purification apparatus for an internal combustion engine, when filter regeneration control is performed by supplying a reducing agent to a filter carrying a catalyst having an oxidation function from the upstream side of the filter (S101), the filter When the temperature on the upstream side of the filter becomes equal to or higher than the specified upper limit temperature (S104), control for suppressing the temperature rise of the filter is executed. The lower the temperature on the downstream side of the filter, the higher the specified upper limit temperature. A value is set (S103).
[Selection] Figure 4

Description

  The present invention relates to an exhaust gas purification system for an internal combustion engine, and more particularly to an exhaust gas purification system for an internal combustion engine provided with a particulate filter that is provided in an exhaust passage of the internal combustion engine and collects particulate matter in the exhaust gas.

In the case where the exhaust passage of the internal combustion engine is provided with a particulate filter (hereinafter simply referred to as PM) that collects particulate matter (hereinafter referred to as PM) in the exhaust, the temperature from the downstream side of the filter When the value obtained by subtracting the temperature on the upstream side of the filter is equal to or greater than the threshold value ΔT1, it is determined that rapid combustion of the filter has occurred, and the flow rate of exhaust gas flowing into the filter (hereinafter simply referred to as exhaust flow rate) is increased. A technique is known (for example, refer to Patent Document 1).
JP 2004-68804 A Japanese Patent No. 2630024 Japanese Unexamined Patent Publication No. Sho 63-1001009 Japanese Patent Laid-Open No. 03-202611

  Some filters provided in an exhaust passage of an internal combustion engine carry a catalyst having an oxidation function. In an exhaust gas purification system for an internal combustion engine having such a filter, a filter regeneration control for raising the temperature of the filter to a target temperature by supplying a reducing agent to the filter in order to oxidize and remove the PM accumulated on the filter. Is done.

  When such filter regeneration control is executed, the temperature of the filter rises above the target temperature due to variations in the amount of reducing agent supplied to the filter, changes in the operating state of the internal combustion engine, and the filter eventually overheats. There is a case. Therefore, when it is determined that there is a possibility that the temperature of the filter may be excessively increased during the execution of the filter regeneration control, the filter temperature increase suppression control is executed to suppress the temperature increase of the filter.

  However, if the filter temperature rise control is executed and the filter temperature falls below the target temperature, it is necessary to raise the filter temperature to the target temperature again in order to continue the oxidation and removal of PM. . Therefore, when the temperature rise of the filter is excessively suppressed, the efficiency of the filter regeneration control may be reduced.

  The present invention has been made in view of the above problems, and in an exhaust gas purification system for an internal combustion engine provided with a filter provided in an exhaust passage of the internal combustion engine, the filter is prevented from overheating. It is an object of the present invention to provide a technique capable of oxidizing and removing the PM deposited on the substrate more efficiently.

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, wherein filter regeneration control is performed by supplying a reducing agent from an upstream side of the filter to a filter carrying a catalyst having an oxidation function. When the temperature of the filter becomes equal to or higher than the specified upper limit temperature, the control for suppressing the temperature rise of the filter is executed, and the lower the temperature on the downstream side of the filter, the higher the specified upper limit temperature is set. is there.

More specifically, the exhaust gas purification system for an internal combustion engine according to the present invention is:
A particulate filter that is provided in an exhaust passage of the internal combustion engine, collects particulate matter in the exhaust, and carries a catalyst having an oxidation function;
Reducing agent supply means for supplying a reducing agent to the particulate filter from the upstream side of the particulate filter;
Filter regeneration for supplying a reducing agent to the particulate filter by the reducing agent supply means to raise the temperature of the particulate filter to a target temperature, thereby oxidizing and removing particulate matter deposited on the particulate filter Filter regeneration control execution means for executing control;
Filter upstream temperature detection means for detecting the upstream temperature in the particulate filter;
Filter downstream temperature detecting means for detecting the downstream temperature of the particulate filter;
When the filter regeneration control is being executed by the filter regeneration control executing means, if the upstream temperature in the particulate filter detected by the filter upstream temperature detecting means is equal to or higher than a specified upper limit temperature, the particulates Filter temperature increase suppression control execution means for executing filter temperature increase suppression control for suppressing temperature increase of the curate filter;
Specified upper limit temperature setting means for setting the specified upper limit temperature to a higher value as the downstream temperature in the particulate filter detected by the filter downstream temperature detecting means is lower;
It is characterized by providing.

  In the filter regeneration control according to the present invention, the reducing agent is supplied to the filter from the upstream side of the filter. When the reducing agent is supplied to the filter, the reducing agent is oxidized by the catalyst supported on the filter, and the temperature of the filter rises due to oxidation heat generated at that time.

  In the filter regeneration control, the temperature of the filter is controlled to the target temperature by adjusting the supply amount of the reducing agent. Here, the target temperature is a temperature at which PM deposited on the filter can be oxidized and removed, and a temperature at which excessive temperature rise of the filter can be suppressed.

  However, during the execution of the filter regeneration control, the temperature of the filter becomes higher than the target temperature due to a change in the exhaust gas flow rate or a variation in the supply amount of the reducing agent, and as a result, there is a possibility of causing an excessive temperature rise of the filter. Therefore, when there is a possibility that the temperature of the filter is excessively increased, it is necessary to suppress the temperature increase of the filter.

  Therefore, in the present invention, when the filter regeneration control is being executed, when the filter upstream temperature becomes equal to or higher than the specified upper limit temperature, the filter temperature increase suppression execution means suppresses the temperature increase of the filter. Perform suppression control. Here, the specified upper limit temperature is higher than the target temperature.

  And in this invention, the regulation upper limit temperature used as the threshold value which performs filter temperature increase suppression control is changed according to filter downstream side temperature.

In the present invention, when the filter regeneration control is executed, the reducing agent is supplied to the filter from the upstream side. Therefore, in the filter, the oxidation of PM is promoted more upstream than downstream. Since the filter has a certain heat capacity, there may be a temperature difference between the upstream side and the downstream side of the filter during execution of the filter regeneration control. That is, the downstream temperature in the filter (hereinafter simply referred to as the filter downstream temperature) may be lower than the upstream temperature in the filter (hereinafter simply referred to as the filter upstream temperature).

  In such a case, when the temperature of the entire filter becomes equal to or higher than that temperature, even if the temperature on the upstream side of the filter rises above the temperature at which it can be determined that there is a risk that the filter will overheat, the temperature on the downstream side of the filter If it is low to some extent, the upstream heat in the filter is absorbed downstream, and therefore the temperature on the upstream side of the filter decreases in a short time. Therefore, the excessive temperature rise of the filter is suppressed without executing the filter temperature rise suppression control.

  Therefore, in the present invention, the specified upper limit temperature is set to a higher value as the filter downstream side temperature is lower.

  The lower the temperature on the downstream side of the filter, the more the heat on the upstream side in the filter can be absorbed on the downstream side. That is, even when the temperature on the upstream side of the filter is higher, if the temperature on the downstream side of the filter is sufficiently low, the excessive temperature increase of the filter is suppressed without executing the filter temperature increase suppression control. Therefore, the specified upper limit temperature, which is a threshold value for executing the filter temperature increase suppression control, can be set to a higher value as the filter downstream temperature is lower.

  According to the present invention, it is possible to suppress unnecessary execution of filter temperature increase suppression control during execution of filter regeneration control. Therefore, it is possible to more efficiently oxidize and remove PM deposited on the filter while suppressing the temperature of the filter from excessively rising.

  In the present invention, when the exhaust flow rate detecting means for detecting the exhaust flow rate is further provided, the specified upper limit temperature may be set based on the exhaust flow rate detected by the exhaust flow rate detecting means.

  The amount of heat transmitted from the upstream side to the downstream side in the filter (hereinafter referred to as propagation heat amount) and the amount of heat removed from the filter by the exhaust (hereinafter referred to as removal heat amount) vary depending on the exhaust flow rate. That is, the amount of propagation heat and the amount of heat taken away increase as the exhaust flow rate increases.

  Since the downstream filter temperature is less likely to increase as the amount of propagation heat is smaller, more heat on the upstream side of the filter is absorbed on the downstream side. Therefore, the specified upper limit temperature can be set to a higher value as the amount of propagation heat is smaller. On the other hand, as the amount of heat taken away increases, the temperature of the entire filter is less likely to rise. Therefore, even if the temperature on the upstream side of the filter rises to a higher temperature, it is difficult for the filter to overheat. Therefore, the specified upper limit temperature can be set to a higher value.

  Therefore, it is possible to set the specified upper limit temperature based on the exhaust gas flow rate in consideration of the amount of heat transferred and the amount of heat taken away. By setting the specified upper limit temperature in this way, unnecessary execution of the filter temperature increase suppression control during execution of the filter regeneration control can be further suppressed.

  In the present invention, when the downstream PM accumulation amount detecting means for detecting the downstream PM accumulation amount (hereinafter referred to as the downstream PM accumulation amount) in the filter is further provided, the smaller the downstream PM accumulation amount, the more the regulation. The upper limit temperature may be set to a high value.

  The smaller the downstream PM accumulation amount, the less the filter downstream temperature rises. Therefore, more heat on the upstream side in the filter is absorbed on the downstream side.

  Therefore, as described above, the specified upper limit temperature can be set to a higher value as the downstream PM accumulation amount is smaller. By setting the specified upper limit temperature in this way, unnecessary execution of the filter temperature increase suppression control during execution of the filter regeneration control can be further suppressed.

  In the present invention, in the case of further comprising an oxidizing ability detecting means for detecting the oxidizing ability of the catalyst supported on the filter, the specified upper limit temperature may be set to a higher value as the oxidizing ability of the catalyst is lower.

  The lower the oxidation capacity of the catalyst, the more difficult the oxidation of PM is, so the temperature of the filter is less likely to rise. Therefore, when the oxidation capacity of the catalyst is relatively low, the temperature of the filter is difficult to overheat even if the temperature on the upstream side of the filter is relatively high.

  Therefore, as described above, the specified upper limit temperature can be set to a higher value as the oxidation ability of the catalyst is lower. By setting the specified upper limit temperature in this way, unnecessary execution of the filter temperature increase suppression control during execution of the filter regeneration control can be further suppressed.

  According to the present invention, in an exhaust gas purification system for an internal combustion engine provided with a filter provided in an exhaust passage of the internal combustion engine, the PM deposited on the filter is more efficiently oxidized and suppressed while suppressing excessive temperature rise of the filter. Can be removed.

  Hereinafter, specific embodiments of an exhaust gas purification system for an internal combustion engine according to the present invention will be described with reference to the drawings.

<Schematic configuration of internal combustion engine and intake / exhaust system thereof>
Here, the case where the present invention is applied to a diesel engine for driving a vehicle will be described as an example. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its intake / exhaust system according to the present embodiment.

  The internal combustion engine 1 is a diesel engine for driving a vehicle. An intake passage 4 and an exhaust passage 2 are connected to the internal combustion engine 1. The intake passage 4 is provided with an air flow meter 9 and a throttle valve 8 for outputting an electrical signal corresponding to the amount of intake air. On the other hand, the exhaust passage 2 is provided with a particulate filter 3 (hereinafter simply referred to as a filter 3) for collecting PM in the exhaust. The filter 3 carries an oxidation catalyst. The catalyst supported on the filter 3 only needs to have an oxidation function, and may be an NOx storage reduction catalyst, for example.

  An upstream exhaust temperature sensor 6 and a downstream exhaust temperature sensor 7 for outputting an electrical signal corresponding to the exhaust temperature are provided in the vicinity of the filter 3 in the exhaust passage 2 and upstream and downstream of the filter 3. Each is provided. A fuel addition valve 5 for adding fuel to the exhaust is provided in the exhaust passage 2 upstream of the upstream exhaust temperature sensor 6.

  The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU) 10 for controlling the internal combustion engine 1. The ECU 10 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver. The ECU 10 is electrically connected to various sensors such as the air flow meter 9, the upstream side exhaust temperature sensor 6, and the downstream side exhaust temperature sensor 7. These output signals are input to the ECU 10. The ECU 10 is electrically connected to the throttle valve 8 and the fuel addition valve 5. These are controlled by the ECU 10.

<Filter regeneration control>
In the present embodiment, when the specified condition is satisfied, the ECU 10 executes filter regeneration control to oxidize and remove PM accumulated on the filter 3. As the specified condition, the accumulated value of the operating time of the internal combustion engine 1 is defined when the PM accumulated amount in the filter 3 estimated from the accumulated value of the fuel injection amount in the internal combustion engine 1 is equal to or more than the prescribed PM accumulated amount. When it becomes more than time, the case where the integrated value of the travel distance of the vehicle carrying the internal combustion engine 1 becomes more than a specified distance can be illustrated.

  In the filter regeneration control according to the present embodiment, fuel is added from the fuel addition valve 5 into the exhaust. This added fuel is supplied to the filter 3 as a reducing agent, and is oxidized by the oxidation catalyst supported on the filter 3. The temperature of the filter 3 rises due to the oxidation heat generated at this time. Then, the temperature of the filter 3 is controlled to the target temperature by adjusting the amount of fuel added from the fuel addition valve 5.

  Here, the target temperature is a temperature at which PM deposited on the filter 3 can be oxidized and removed and an excessive temperature rise of the filter 3 can be suppressed. This target temperature is determined in advance by experiments or the like.

<Filter temperature rise suppression control>
When the filter regeneration control is executed, the temperature of the filter 3 may rise beyond the target temperature due to a variation in the amount of fuel added from the fuel addition valve 5 or a change in the exhaust flow rate accompanying a change in the intake air amount. When the temperature of the filter 3 rises beyond the target temperature to some extent, there is a possibility that the oxidation of PM is rapidly promoted and the filter 3 is excessively heated.

  Therefore, in this embodiment, when the filter regeneration control is being executed, if the filter upstream temperature becomes equal to or higher than the specified upper limit temperature Tlimit higher than the target temperature, the filter 3 is controlled to suppress the temperature increase of the filter 3. Temperature rise suppression control is executed.

  In the filter temperature increase suppression control according to the present embodiment, fuel addition from the fuel addition valve 5 is stopped, and the exhaust flow rate is increased by increasing the opening of the throttle valve 8. By increasing the exhaust flow rate, the amount of heat taken away from the filter 3 increases, so that the temperature rise of the filter 3 can be suppressed.

  As other filter temperature rise suppression control, for example, when an EGR passage that communicates the intake passage 4 and the exhaust passage 2 and an EGR valve that controls the amount of EGR gas are provided, the EGR valve is closed. In addition, control for reducing the oxygen concentration of the exhaust gas flowing into the filter 3 can be mentioned. Alternatively, a bypass passage that bypasses the filter 3 may be provided in the exhaust passage 2, and the temperature of the filter 3 may be suppressed by shutting off the supply of oxygen to the catalyst by flowing the exhaust through the bypass passage.

<Specified upper limit temperature setting method>
Next, a method for setting the specified upper limit temperature Tlimit according to the present embodiment will be described.

  FIG. 2 is a diagram illustrating changes in the filter upstream temperature Tf and the filter downstream temperature Tr when the filter regeneration control is executed. In FIG. 2, the vertical axis represents temperature, and the horizontal axis represents time. The solid line represents the filter upstream temperature Tf, and the alternate long and short dash line represents the filter downstream temperature Tr.

When the filter regeneration control is executed at the time indicated by A in FIG. 2, the filter upstream temperature Tf starts to rise toward the target temperature Tt. However, in the filter regeneration control according to the present embodiment, fuel is supplied to the filter 3 from the upstream side of the filter 3, and the filter 3 has a certain heat capacity. Therefore, as shown in FIG. The temperature Tr rises later than the filter upstream temperature Tf. As a result, a temperature difference is generated between the filter upstream temperature Tf and the filter downstream temperature Tr. Hereinafter, a value obtained by subtracting the filter downstream temperature Tr from the filter upstream temperature Tf is referred to as a filter temperature difference ΔT.

  Here, the change in the filter upstream temperature Tf when the filter upstream temperature Tf rises above the target temperature Tt during the filter regeneration control will be described with reference to FIG. In FIG. 3, as in FIG. 2, the vertical axis and the horizontal axis represent temperature and time, respectively, and the solid line and the alternate long and short dash line represent the filter upstream temperature Tf and the filter downstream temperature Tr, respectively.

  As described above, during execution of the filter regeneration control, there may be a temperature difference between the filter upstream temperature Tf and the filter downstream temperature Tr. Therefore, even when the filter upstream temperature Tf exceeds the target temperature Tt as shown in FIG. 3 due to variations in the amount of fuel added from the fuel addition valve 5 or changes in the operating state of the internal combustion engine 1, The filter downstream temperature Tr may be lower than the target temperature Tt.

  If the downstream temperature Tr of the filter at this time is low to some extent, that is, if the filter temperature difference ΔT at this time is large to some extent, the heat on the upstream side is absorbed downstream in the filter 3, as shown in FIG. The filter upstream temperature Tf once increased to the target temperature Tt or higher is reduced in a short time.

  Therefore, even if the filter upstream temperature Tf rises above the temperature at which it can be determined that there is a risk of overheating of the filter 3 when the temperature of the entire filter 3 exceeds that temperature, the filter downstream temperature Tr If the temperature is low to some extent, the upstream temperature Tf of the filter decreases in a short time. Therefore, the excessive temperature increase of the filter 3 is suppressed without executing the filter temperature increase suppression control.

As the downstream temperature Tr of the filter is lower, more heat on the upstream side in the filter 3 can be absorbed on the downstream side. Therefore, in this embodiment, the specified upper limit temperature Tlimit, which is a threshold value for executing the filter temperature increase suppression control, is set to a higher value as the filter downstream temperature Tr is lower.

<Filter temperature rise suppression control routine>
Here, the control routine of the filter temperature rise suppression control according to the present embodiment will be described based on the flowchart shown in FIG. This routine is stored in advance in the ECU 10 and is executed every time the crankshaft rotates by a specified angle during the operation of the internal combustion engine 1.

  In this routine, the ECU 10 first determines in S101 whether or not the filter regeneration control is being executed. When an affirmative determination is made in S101, the ECU 10 proceeds to S102, and when a negative determination is made, the ECU 10 once ends the execution of this routine.

  In S102, the ECU 10 detects the filter upstream temperature Tf and the filter downstream temperature Tr. In the present embodiment, the ECU 10 estimates the filter upstream temperature Tf from the output value of the upstream side exhaust temperature sensor 6 and estimates the filter downstream side temperature Tr from the output value of the downstream side exhaust temperature sensor 7. The filter upstream temperature Tf and the filter downstream temperature Tr may be estimated from the engine load and engine speed of the internal combustion engine 1, the heat capacity of the filter 3, and the like.

  Next, the ECU 10 proceeds to S103 and sets the specified upper limit temperature Tlimit based on the filter downstream temperature Tr. At this time, the specified upper limit temperature Tlimit is set to a higher value as the filter downstream temperature Tr is lower. The relationship between the filter downstream temperature Tr and the specified upper limit temperature Tlimit may be determined in advance by experiments or the like, and these relationships may be stored in the ECU 10 as a map.

  Next, the ECU 10 proceeds to S104, and determines whether or not the filter upstream temperature Tf is equal to or higher than the specified upper limit temperature Tlimit. If an affirmative determination is made in S104, the ECU 10 proceeds to S105, and if a negative determination is made, the ECU 10 once ends the execution of this routine.

  In S105, the ECU 10 executes the filter temperature increase suppression control and temporarily ends the execution of this routine.

  According to the control routine, the filter temperature increase suppression control is executed when the filter upstream temperature Tf is equal to or higher than the specified upper limit temperature Tlimit during the filter regeneration control. The specified upper limit temperature Tlimit is set to a higher value as the filter downstream temperature Tr is lower.

  Therefore, according to the present embodiment, it is possible to suppress the unnecessary execution of the filter temperature increase suppression control during the execution of the filter regeneration control. Therefore, it is possible to more efficiently oxidize and remove PM deposited on the filter 3 while suppressing the temperature of the filter 3 from excessively rising. As a result, it becomes possible to suppress exhaust emission and deterioration of fuel consumption.

  Since the schematic configuration of the internal combustion engine and the intake / exhaust system thereof according to the present embodiment is the same as that of the first embodiment, the description thereof is omitted. Also in this embodiment, the same filter regeneration control and filter temperature rise suppression control as those in the first embodiment are performed.

<Filter temperature rise suppression control routine>
Here, the control routine of the filter temperature raising control according to the present embodiment will be described based on the flowchart shown in FIG. In this routine, S201 to S203 are added to the control routine shown in FIG. 4 described above, and S103 is replaced with S204. For this reason, the same steps as those in the control routine shown in FIG. This routine is stored in advance in the ECU 10 and is executed every time the crankshaft rotates by a specified angle during the operation of the internal combustion engine 1.

  In this routine, if an affirmative determination is made in S103, the ECU 10 proceeds to S201. In S201, the ECU 10 detects the current exhaust gas flow rate. Here, the exhaust flow rate is estimated based on the intake air amount detected by the air flow meter 9.

  Next, the ECU 10 proceeds to S202, and detects the downstream PM accumulation amount in the filter 3 at the present time. In this embodiment, the integrated value of the fuel injection amount of the internal combustion engine 1 since the end of the previous filter regeneration control, the elapsed time from the start of the execution of the current filter regeneration control, the filter upstream temperature Tf, the filter downstream temperature Tr, etc. Based on the above, the upstream PM accumulation amount and the downstream PM accumulation amount are estimated separately.

  Next, the ECU 10 proceeds to S203 and detects the current oxidation capability of the oxidation catalyst carried on the filter 3. In this embodiment, the oxidation capacity of the oxidation catalyst is estimated based on the integrated value of the travel distance of the vehicle up to the present time, the integrated value of the exhaust flow rate, the difference in exhaust temperature before and after the filter 3 when the filter regeneration control is executed, and the like.

  Next, the ECU 10 proceeds to S204, and sets the specified upper limit temperature Tlimit based on the filter downstream temperature Tf, the exhaust flow rate, the downstream PM accumulation amount, and the oxidation ability of the oxidation catalyst.

  Here, as in the first embodiment, the specified upper limit temperature Tlimit is set to a higher value as the filter downstream temperature Tr is lower.

  Further, the specified upper limit temperature Tlimit is set based on the exhaust flow rate in consideration of the propagation heat amount and the carry heat amount.

  Furthermore, the specified upper limit temperature Tlimit is set to a higher value as the downstream PM accumulation amount is smaller and the oxidation ability of the oxidation catalyst is lower.

  Following S204, the ECU 10 proceeds to S104.

  According to the routine described above, the specified upper limit temperature Tlimit can be set as high as possible within a range in which excessive temperature rise of the filter 3 can be suppressed.

  Therefore, according to the present embodiment, unnecessary execution of the filter temperature increase suppression control during the execution of the filter regeneration control can be further suppressed.

The figure which shows schematic structure of the internal combustion engine which concerns on the Example of this invention, and its intake / exhaust system. The figure which shows the change of the filter upstream temperature and filter downstream temperature at the time of filter regeneration control execution. The figure which shows the change of filter upstream temperature and filter downstream temperature when filter upstream temperature rises exceeding target temperature at the time of filter regeneration control execution. The flowchart which shows the control routine of the filter temperature increase suppression control which concerns on Example 1 of this invention. The flowchart which shows the control routine of the filter temperature increase suppression control which concerns on Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Exhaust passage 3 ... Particulate filter 5 ... Fuel addition valve
6 ... Upstream exhaust temperature sensor 7 ... Downstream exhaust temperature sensor 8 ... Throttle valve 9 ... Air flow meter 10 ... ECU

Claims (4)

A particulate filter that is provided in an exhaust passage of the internal combustion engine, collects particulate matter in the exhaust, and carries a catalyst having an oxidation function;
Reducing agent supply means for supplying a reducing agent to the particulate filter from the upstream side of the particulate filter;
Filter regeneration for supplying a reducing agent to the particulate filter by the reducing agent supply means to raise the temperature of the particulate filter to a target temperature, thereby oxidizing and removing particulate matter deposited on the particulate filter Filter regeneration control execution means for executing control;
Filter upstream temperature detection means for detecting the upstream temperature in the particulate filter;
Filter downstream temperature detecting means for detecting the downstream temperature of the particulate filter;
When the filter regeneration control is being executed by the filter regeneration control executing means, if the upstream temperature in the particulate filter detected by the filter upstream temperature detecting means is equal to or higher than a specified upper limit temperature, the particulates Filter temperature increase suppression control execution means for executing filter temperature increase suppression control for suppressing temperature increase of the curate filter;
Specified upper limit temperature setting means for setting the specified upper limit temperature to a higher value as the downstream temperature in the particulate filter detected by the filter downstream temperature detecting means is lower;
An exhaust gas purification system for an internal combustion engine, comprising: An exhaust flow rate detecting means for detecting the flow rate of the exhaust gas flowing into the particulate filter,
2. The exhaust purification system for an internal combustion engine according to claim 1, wherein the specified upper limit temperature setting means sets the specified upper limit temperature based on an exhaust flow rate detected by the exhaust flow rate detecting means. Further comprising a downstream PM accumulation amount detection means for detecting the accumulation amount of the downstream particulate matter in the particulate filter,
The prescribed upper limit temperature setting means sets the prescribed upper limit temperature to a higher value as the downstream particulate matter accumulation amount in the particulate filter detected by the downstream PM accumulation amount detection means is smaller. The exhaust gas purification system for an internal combustion engine according to claim 1 or 2. It further comprises an oxidation capacity detection means for detecting the oxidation capacity of the catalyst,
4. The prescribed upper limit temperature setting means sets the prescribed upper limit temperature to a higher value as the oxidation ability of the catalyst detected by the oxidation ability detection means is lower. 2. An exhaust gas purification system for an internal combustion engine according to 1.

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