JP4811333B2 - Exhaust gas purification system for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust purification system for an internal combustion engine including two or more catalysts arranged in series in an exhaust passage of the internal combustion engine.

  In an exhaust gas purification system for an internal combustion engine, the temperature of the catalyst may be raised by supplying a reducing agent to a catalyst having an oxidation function provided in an exhaust passage. By raising the temperature of the catalyst in this way, it is possible to recover the exhaust purification capability of the exhaust purification device provided on the downstream side of the catalyst or the catalyst.

  Patent Document 1 discloses a technique for estimating the activity of an oxidation catalyst provided in an exhaust passage of an internal combustion engine based on the temperature of exhaust flowing into the oxidation catalyst and the flow rate of exhaust passing through the oxidation catalyst. Yes.

Patent Document 2 discloses that the activity of the oxidation catalyst provided in the exhaust passage of the internal combustion engine decreases when the flow rate of the exhaust gas is large.
JP 2004-251230 A JP 2005-330870 A

  In the configuration in which the first and second catalysts having an oxidation function are provided in series in the exhaust passage of the internal combustion engine in order from the upstream side, the upstream side is provided to raise the temperature of the second catalyst provided on the downstream side to the target temperature. In some cases, the reducing agent is supplied into the exhaust gas that flows through the exhaust passage further upstream than the first catalyst provided in the exhaust gas. In this case, a part of the reducing agent is oxidized in the first catalyst, and the reducing agent that has not been oxidized in the first catalyst is supplied to the second catalyst and oxidized in the second catalyst.

  Therefore, the temperature of the second catalyst is increased by the amount of heat generated by oxidizing the reducing agent in the first catalyst and the amount of heat generated by oxidizing the reducing agent in the second catalyst itself.

  At this time, part of the heat generated by oxidizing the reducing agent in the first catalyst may be lost due to heat dissipation until the exhaust reaches the second catalyst. Even if the amount of reducing agent supplied into the exhaust gas is the same, if the amount of heat dissipated from the exhaust gas between the first catalyst and the second catalyst (hereinafter referred to as inter-catalyst heat dissipation amount) changes, The temperature reached when the two catalysts rise in temperature also changes.

  The present invention has been made in view of the above problem, and in the case where the first and second catalysts having an oxidation function are provided in series in the exhaust passage of the internal combustion engine in order from the upstream side, the first catalyst Another object of the present invention is to provide a technique capable of controlling the temperature of the second catalyst to the target temperature with higher accuracy when the temperature of the second catalyst is raised by supplying a reducing agent into the exhaust gas flowing upstream. To do.

  The present invention releases heat from the exhaust between the first catalyst and the second catalyst when the temperature of the second catalyst is raised by supplying a reducing agent into the exhaust flowing upstream from the first catalyst. The greater the amount of heat released, the greater the amount of reducing agent supplied.

More specifically, the exhaust gas purification system for an internal combustion engine according to the present invention is:
A first catalyst having an oxidation function provided in an exhaust passage of an internal combustion engine;
A second catalyst having an oxidation function provided in the exhaust passage downstream of the first catalyst;
Reducing agent supply means for supplying a reducing agent into the exhaust gas flowing in the exhaust passage upstream of the first catalyst;
The temperature raising control is executed to supply the reducing agent to the first and second catalysts by supplying the reducing agent into the exhaust gas by the reducing agent supply means, thereby executing the temperature raising control for raising the temperature of the second catalyst. Means,
A heat release amount calculating means for calculating a heat release amount radiated from the exhaust between the first catalyst and the second catalyst when the temperature increase control is executed by the temperature increase control execution means,
The supply amount of the reducing agent from the reducing agent supply unit during the temperature increase control by the temperature increase control execution unit is increased as the heat release amount calculated by the heat release amount calculation unit increases.

  When the amount of reducing agent supplied from the reducing agent supply means increases, the amount of reducing agent supplied to the second catalyst without being oxidized in the first catalyst increases. Therefore, the calorific value generated by oxidizing the reducing agent in the second catalyst increases.

  According to the present invention, the amount of heat generated by oxidation of the reducing agent in the second catalyst increases as the amount of heat released between the catalysts increases. Therefore, the temperature of the second catalyst can be controlled to the target temperature with higher accuracy when the temperature increase control is executed.

  In the present invention, the heat release amount calculation means has a heat generation amount calculation means for calculating a heat generation amount generated by oxidizing the reducing agent in the first catalyst when the temperature increase control is executed by the temperature increase control execution means. May be. In this case, the heat release amount calculation means calculates the heat release amount between the catalysts based on the heat generation amount in the first catalyst calculated by the heat generation amount calculation means and the intake air amount of the internal combustion engine.

  The amount of heat generated by oxidizing the reducing agent in the first catalyst increases as the temperature of the first catalyst increases when the reducing agent is supplied. Further, the smaller the intake air amount of the internal combustion engine when the reducing agent is supplied, the smaller the flow rate of the exhaust gas. Therefore, the calorific value calculation means may calculate the calorific value generated by oxidizing the reducing agent in the first catalyst based on the temperature of the first catalyst and the intake air amount of the internal combustion engine.

  The greater the temperature difference between the temperature of the exhaust gas flowing out from the first catalyst and the outside of the exhaust passage, the greater the heat release amount between the catalysts. Therefore, the greater the amount of heat generated by the first catalyst, the greater the amount of heat released between the catalysts. Further, the smaller the intake air amount of the internal combustion engine (that is, the smaller the exhaust gas flow rate), the longer it takes for the exhaust gas flowing out from the first catalyst to reach the second catalyst. Therefore, the smaller the intake air amount of the internal combustion engine, the greater the heat release amount between the catalysts. Thus, the heat release amount between the catalysts can be calculated based on the heat generation amount in the first catalyst and the intake air amount of the internal combustion engine.

  In the present invention, the reference value for the amount of reducing agent supplied from the reducing agent supply means based on the difference between the temperature of the second catalyst and the target temperature when the temperature increase control execution means starts executing the temperature increase control. There may be provided a reference supply amount calculating means for calculating the reference supply amount. In this case, when the temperature increase control is performed, the reference supply amount of the reducing agent calculated by the reference supply amount calculation unit is supplied from the reducing agent supply unit, and then the reduction is performed based on the heat release amount calculated by the heat dissipation amount calculation unit. The supply amount of the reducing agent from the agent supply means may be corrected.

  According to this, the temperature of the second catalyst can be controlled to the target temperature with higher accuracy.

  According to the present invention, when the first and second catalysts having an oxidation function are provided in series in the exhaust passage of the internal combustion engine in order from the upstream side, the reducing agent is present in the exhaust flowing upstream from the first catalyst. The temperature of the second catalyst can be controlled to the target temperature with higher accuracy when the temperature of the second catalyst is raised.

  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.

<Example 1>
<Schematic configuration of intake and exhaust system of internal combustion engine>
Here, a 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 intake / exhaust system of an internal combustion engine according to the present embodiment. The internal combustion engine 1 is a diesel engine for driving a vehicle. An intake passage 2 and an exhaust passage 3 are connected to the internal combustion engine 1.

  A compressor housing 15 a of a turbocharger 15 is installed in the intake passage 2. An air flow meter 4 is provided in the intake passage 2 upstream of the compressor housing 15a. A throttle valve 5 is provided in the intake passage 2 downstream of the compressor housing 15a.

  A turbine housing 15 b of the turbocharger 15 is installed in the exhaust passage 3. A first oxidation catalyst 6 is provided in the exhaust passage 3 downstream of the turbine housing 15b. In the exhaust passage 3 on the downstream side of the first oxidation catalyst 6, a second dioxide catalyst 7 and a particulate filter (hereinafter simply referred to as a filter) 8 are provided close to each other in order from the upstream side.

  The first oxidation catalyst 6 is a catalyst having a smaller heat capacity than the first dioxide catalyst 7. The filter 8 collects particulate matter (hereinafter referred to as PM) in the exhaust gas. The filter 8 carries an NOx storage reduction catalyst (hereinafter simply referred to as NOx catalyst) 9.

  In this embodiment, the first oxidation catalyst 6 and the second dioxide catalyst 7 correspond to the first catalyst and the second catalyst according to the present invention, respectively. The first oxidation catalyst 6 and the second dioxide catalyst 7 may be replaced with a catalyst having an oxidation function other than the oxidation catalyst.

  A fuel addition valve 10 is provided upstream of the turbine housing 15b in the exhaust passage 3 to add fuel as a reducing agent into the exhaust. In this embodiment, the fuel addition valve 10 corresponds to the reducing agent supply means according to the present invention.

  Furthermore, a first temperature sensor 11 that detects the temperature of the exhaust gas flowing into the first oxidation catalyst 6 is provided in the exhaust passage 3 downstream of the turbine housing 15 b and immediately upstream of the first oxidation catalyst 6. A second temperature sensor 12 for detecting the temperature of the exhaust gas flowing into the second dioxide catalyst 7 is provided downstream of the first oxidation catalyst 6 in the exhaust passage 3 and immediately upstream of the second dioxide catalyst 7. .

The internal combustion engine 1 is provided with an electronic control unit (ECU) 20. The air flow meter 4, the first temperature sensor 11, and the second temperature sensor 12 are electrically connected to the ECU 20. Further, the ECU 20 is electrically connected to a crank position sensor 13 that detects a crank angle of the internal combustion engine 1 and an accelerator opening sensor 14 that detects an accelerator opening of a vehicle on which the internal combustion engine 1 is mounted. These output signals are input to the ECU 20.

  The ECU 20 calculates the engine speed of the internal combustion engine 1 based on the output signal of the crank position sensor 13, and calculates the engine load of the internal combustion engine 1 based on the output signal of the accelerator opening sensor 14.

  The ECU 20 is electrically connected to a fuel injection valve for injecting fuel into the cylinder of the internal combustion engine 1, a throttle valve 5, and a fuel addition valve 10. These are controlled by the ECU 20.

<Temperature control>
When removing PM collected by the filter 8 or when reducing SOx stored in the NOx catalyst 9, it is necessary to raise the temperature of the filter 8. In this embodiment, when the temperature of the filter 8 is raised, the fuel is supplied to the first and second dioxide catalysts 6 and 7 by adding fuel into the exhaust gas from the fuel addition valve 10, thereby Perform temperature rise control to raise the temperature. The temperature of the exhaust gas flowing into the filter 8 rises as the temperature of the second dioxide catalyst 7 rises. Thereby, the temperature of the filter 8 rises. In this embodiment, the second dioxide catalyst 7 and the filter 8 are installed close to each other. Therefore, heat radiation from the exhaust between the second dioxide catalyst 7 and the filter 8 is suppressed.

  In the temperature increase control, the temperature of the second dioxide catalyst 7 is controlled to the target temperature by controlling the amount of fuel added from the fuel addition valve 10. The target temperature is determined in advance according to the purpose of executing the temperature increase control. That is, when the temperature increase control is executed in order to remove the PM collected by the filter 8, the target temperature is a value that allows the temperature of the filter 8 to be a temperature at which PM can be oxidized. When the temperature raising control is executed to reduce the SOx stored in the NOx catalyst 9, the target temperature is set to the temperature at which the filter 8 (that is, the temperature of the NOx catalyst 9) can reduce SOx. It is a value that can be.

  In the present embodiment, the fuel added to the exhaust gas from the fuel addition valve 10 is first supplied to the first oxidation catalyst 6. The first dioxide catalyst 7 is supplied with the amount of heat generated by oxidizing the fuel in the first oxidation catalyst 6 together with the fuel that has not been oxidized in the first oxidation catalyst 6.

  At this time, part of the heat generated by the oxidation of the fuel in the first oxidation catalyst 6 is lost due to heat dissipation until the exhaust reaches the second dioxide catalyst 7. Therefore, even when the fuel addition amount from the fuel addition valve 10 is the same when the temperature increase control is executed, the catalyst is a heat release amount radiated from the exhaust between the first oxidation catalyst 6 and the second dioxide catalyst 7. The greater the amount of heat released during heating, the lower the temperature reached by raising the temperature of the second dioxide catalyst 7.

  Therefore, in this embodiment, when the temperature increase control is performed, the amount of fuel added from the fuel addition valve 10 is increased as the amount of heat released from the catalyst increases. When the amount of fuel added from the fuel addition valve 10 increases, the amount of fuel supplied to the first dioxide catalyst 7 without being oxidized in the first oxidation catalyst 6 increases. For this reason, the amount of heat generated by the oxidation of the fuel in the second dioxide catalyst 7 increases.

  Here, the routine of temperature increase 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 20 and is repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1. In this embodiment, the ECU 20 that executes this routine corresponds to the temperature increase control execution means according to the present invention.

In this routine, the ECU 20 first determines in S101 whether or not an execution condition for the temperature increase control is satisfied. Here, the execution conditions of the temperature increase control are, that is, the execution conditions of the filter regeneration control for removing the PM collected by the filter 8 and the execution of the SOx poisoning recovery control for reducing the SOx stored in the NOx catalyst 9. Conditions. If an affirmative determination is made in S101, the ECU 20 proceeds to S102, and if a negative determination is made, the ECU 20 once ends the execution of this routine.

  In S102, the ECU 20 calculates a reference value Qfaddbase of the fuel addition amount from the fuel addition valve 10. The reference value Qfaddbase is calculated based on the difference between the current temperature of the second dioxide catalyst 7 and the target temperature targeted in the temperature increase control. As described above, the target temperature is determined in advance according to the purpose of the temperature increase control. The temperature of the second dioxide catalyst 7 can be calculated based on the detection value of the second temperature sensor 12, the operating state of the internal combustion engine 1, and the like. In the present embodiment, the ECU 20 that executes S102 corresponds to the reference supply amount calculating means according to the present invention.

  Next, the ECU 20 proceeds to S103, sets the fuel addition amount Qfadd to the reference value Qfaddbase, and executes fuel addition from the fuel addition valve 10.

  Next, the ECU 20 proceeds to S104 and calculates the temperature Tc1 of the first oxidation catalyst 6. The temperature Tc1 of the first oxidation catalyst 6 can be calculated based on the detection value of the first temperature sensor 11 and the reference value Qfaddbase of the fuel addition amount.

  Next, the ECU 20 proceeds to S105 and calculates the inter-catalyst heat release amount Qhr based on the difference between the temperature Tc1 of the first oxidation catalyst 6 and the detected value Ts2 of the second temperature sensor 12. In the present embodiment, the ECU 20 that executes S105 corresponds to a heat radiation amount calculating means according to the present invention.

  Next, the ECU 20 proceeds to S106 and corrects the fuel addition amount Qfadd from the fuel addition valve 10 based on the inter-catalyst heat release amount Qhr. At this time, the ECU 20 increases the fuel addition amount Qfadd from the fuel addition valve 10 as the inter-catalyst heat release amount Δhr increases. Thereafter, the ECU 20 once ends the execution of this routine.

  According to this embodiment, the fuel supplied to the second dioxide catalyst 7 increases by the amount corresponding to the heat release amount between the catalysts. Therefore, the amount of heat corresponding to the amount of heat dissipated between the catalysts is supplemented by an increase in the amount of heat generated by the oxidation of fuel in the second dioxide catalyst 7. Accordingly, the temperature of the second dioxide catalyst 7 can be controlled to the target temperature with higher accuracy when the temperature increase control is executed.

<Example 2>
FIG. 3 is a diagram showing a schematic configuration of the intake and exhaust system of the internal combustion engine according to the present embodiment. In the present embodiment, the first and second temperature sensors 11 and 12 according to the first embodiment are not provided in the exhaust passage 3. Since the configuration other than this point is the same as that of the first embodiment, the same reference numeral is given to the same configuration, and the description thereof is omitted.

<Temperature control>
Also in the present embodiment, when the temperature of the filter 8 is increased, the temperature increase control similar to that in the first embodiment is performed. Here, the relationship between the fuel addition amount Qfadd from the fuel addition valve 10 during the temperature increase control, the heat generation amount Qh1 in the first oxidation catalyst 6, and the heat generation amount Qh2 in the second dioxide catalyst 7 will be described based on FIG. To do. FIG. 4 is a graph showing the ratio of the heat generation amount Qh1 at the first oxidation catalyst 6 and the heat generation amount Qh2 at the second dioxide catalyst 7 to the fuel addition amount Qfadd from the fuel addition valve 10. In FIG. 4, Qhr represents the heat release amount between the catalysts, Qhs represents the amount of heat supplied to the second dioxide catalyst 7, and Qfs represents the fuel supplied to the second dioxide catalyst 7. FIG. 4A shows a case where the amount of oxidation of the fuel in the first oxidation catalyst 6 is relatively large.
(B) shows a case where the oxidation amount of the fuel in the first oxidation catalyst 6 is relatively small.

  As shown in FIG. 4, the fuel amount Qfs that is not oxidized in the first oxidation catalyst 6 out of the fuel addition amount Qadd from the fuel addition valve 10 is supplied to the second dioxide catalyst 7. Then, the fuel corresponding to the fuel amount Qfs is oxidized in the first dioxide catalyst 7 and becomes a calorific value in the second dioxide catalyst 7. In addition, a calorific value Qhs obtained by subtracting the inter-catalyst heat dissipation amount Qhr from the calorific value Qh <b> 1 generated when the fuel is oxidized in the first oxidation catalyst 6 is supplied to the second dioxide catalyst 7. That is, the sum of the amount of fuel Qfs supplied to the second dioxide catalyst 7 and the amount of heat corresponding to the amount of heat Qhs supplied to the second dioxide catalyst 7 is the calorific value Qh2 of the first dioxide catalyst 7.

  As the amount of fuel oxidized in the first oxidation catalyst 6 increases, the amount of heat generated Qh1 in the first oxidation catalyst 6 increases. The temperature of the exhaust gas flowing out from the first oxidation catalyst 6 increases as the calorific value Qh1 at the first oxidation catalyst 6 increases. The greater the temperature difference between the temperature of the exhaust gas flowing out from the first oxidation catalyst 6 and the outside of the exhaust passage 3, the greater the inter-catalyst heat release amount Qhr. Therefore, the greater the heat generation amount Qh1 at the first oxidation catalyst 6, the greater the inter-catalyst heat release amount Qhr.

  Further, the smaller the intake air amount Ga of the internal combustion engine 1, the smaller the flow rate of exhaust gas in the exhaust passage 3. The smaller the exhaust gas flow rate, the longer the time it takes for the exhaust gas flowing out from the first oxidation catalyst 6 to reach the second dioxide catalyst 7, so the inter-catalyst heat release amount Qhr increases.

  Therefore, in this embodiment, the inter-catalyst heat release amount Qhr when the temperature increase control is executed is calculated based on the heat generation amount Qh1 in the first oxidation catalyst 6 and the intake air amount Ga of the internal combustion engine 1. As in the first embodiment, the fuel addition amount Qfadd from the fuel addition valve 10 is increased as the inter-catalyst heat release amount Qhr is increased.

  Hereinafter, the routine of temperature increase 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 20 and is repeatedly executed at predetermined intervals during the operation of the internal combustion engine 1. This routine is obtained by replacing S104 and S105 of the routine shown in FIG. 2 with S204 and S205. Therefore, only S204 and S205 will be described, and description of other steps will be omitted. In this embodiment, the ECU 20 that executes this routine corresponds to the temperature increase control execution means according to the present invention.

  In this routine, the ECU 20 proceeds to S204 after S103. In S204, the ECU 20 calculates a heat generation amount Qh1 in the first oxidation catalyst 6. The calorific value Qh1 at the first oxidation catalyst 6 increases as the temperature of the first oxidation catalyst 6 when the fuel is supplied increases, that is, as the temperature of the exhaust gas discharged from the internal combustion engine 1 increases. Further, the calorific value Qh1 at the first oxidation catalyst 6 increases as the flow rate of the exhaust when the fuel is supplied is smaller, that is, as the intake air amount Ga of the internal combustion engine 1 is smaller. Accordingly, the heat generation amount Qh1 in the first oxidation catalyst 6 can be calculated based on the operating state of the internal combustion engine 1 and the reference value Qfaddbase of the fuel addition amount. In the present embodiment, the ECU 20 that executes S204 corresponds to the calorific value calculation means according to the present invention.

  Next, the ECU 20 proceeds to S205, and calculates the inter-catalyst heat release amount Qhr based on the heat generation amount Qh1 at the first oxidation catalyst 6 and the intake air amount Ga of the internal combustion engine 1. The relationship between the heat generation amount Qh1 at the first oxidation catalyst 6 and the intake air amount Ga of the internal combustion engine 1 and the inter-catalyst heat release amount Qhr is obtained by experiments or the like and stored in advance in the ECU 20 as a map. Thereafter, the ECU 20 proceeds to S106.

Also in this embodiment, the fuel supplied to the second dioxide catalyst 7 increases by an amount corresponding to the inter-catalyst heat release amount Qhr. Therefore, the amount of heat corresponding to the inter-catalyst heat release amount Qhr is supplemented by the increase in the heat generation amount Qh <b> 2 generated when the fuel is oxidized in the second dioxide catalyst 7. Accordingly, the temperature of the second dioxide catalyst 7 can be controlled to the target temperature with higher accuracy when the temperature increase control is executed.

<Modification>
FIG. 6 is a diagram showing a schematic configuration of an intake / exhaust system of an internal combustion engine according to a modification of the present embodiment. In the present embodiment, an O ₂ sensor 16 that detects the oxygen concentration of the exhaust gas is provided downstream of the first oxidation catalyst 6 and upstream of the second dioxide catalyst 7 in the exhaust passage 3. Since the configuration other than this point is the same as the schematic configuration diagram shown in FIG.

  In the present modification as well, temperature increase control similar to the above is performed, but the method of calculating the calorific value Qh1 in the first oxidation catalyst 6 at that time is different from the above. Hereinafter, a method for calculating the calorific value Qh1 in the first oxidation catalyst 6 according to this modification will be described.

When the fuel is oxidized in the first oxidation catalyst 6, the O ₂ concentration of the exhaust gas flowing out from the first oxidation catalyst 6 decreases. That is, it can be determined that the lower the O ₂ concentration of the exhaust gas flowing out from the first oxidation catalyst 6, the greater the calorific value Qh 1 generated when the fuel is oxidized in the first oxidation catalyst 6. Therefore, in the present modification, the heat generation amount Qh1 in the first oxidation catalyst 6 is calculated based on the detected value of the O ₂ sensor 16 and the intake air amount Ga of the internal combustion engine 1 when the temperature increase control is executed.

  In the first and second embodiments, the first oxidation catalyst 6 may be provided in the exhaust passage 3 upstream of the turbine housing 15 b of the turbocharger 15. In this case, the turbine housing 15 b is located between the first oxidation catalyst 6 and the second dioxide catalyst 7. As the exhaust gas passes through the turbine housing 15b, the amount of heat released from the catalyst increases. Even in such a case, according to the first and second embodiments, the fuel addition amount from the fuel addition valve 10 is corrected based on the heat release amount between the catalysts when the temperature increase control is executed. 7 can be controlled to the target temperature with higher accuracy.

  In the first and second embodiments, the first oxidation catalyst 6 may be provided at the curved portion of the exhaust passage 3. In the curved portion of the exhaust passage 3, the exhaust flow rate increases (the exhaust flow rate increases). Even in such a case, according to the first and second embodiments, the fuel addition amount from the fuel addition valve 10 is corrected based on the heat release amount between the catalysts when the temperature increase control is executed. 7 can be controlled to the target temperature with higher accuracy.

  In the first and second embodiments, the temperature increase control is performed as a control for increasing the temperature of the filter 8 to the target temperature by supplying fuel to the first oxidation catalyst 6 and the NOx catalyst 9 without providing the second dioxide catalyst 7. Also good. In such a case, the heat release amount between the catalysts is calculated as the heat release amount radiated from the exhaust between the first oxidation catalyst 6 and the filter 8. When the temperature increase control is executed, the fuel addition amount from the fuel addition valve 10 is corrected based on the heat release amount between the catalysts, whereby the temperature of the filter 8 can be controlled to the target temperature with higher accuracy.

  In the first and second embodiments, instead of adding fuel from the fuel addition valve 10, fuel can be supplied into the exhaust gas by performing sub fuel injection at a time after the main fuel injection in the internal combustion engine 1. Good.

1 is a diagram showing a schematic configuration of an intake / exhaust system of an internal combustion engine according to Embodiment 1. FIG. 3 is a flowchart illustrating a routine for temperature increase control according to the first embodiment. FIG. 4 is a diagram illustrating a schematic configuration of an intake / exhaust system of an internal combustion engine according to a second embodiment. The figure which shows the ratio of the emitted-heat amount in a 1st oxidation catalyst with respect to the amount of fuel addition from a fuel addition valve, and the emitted-heat amount in a 2nd dioxide catalyst. FIG. 4 (a) shows a case where the amount of oxidation of the fuel at the first oxidation catalyst is relatively large, and FIG. 4 (b) shows a case where the amount of oxidation of the fuel at the first oxidation catalyst is relatively small. Show. 9 is a flowchart illustrating a routine for temperature increase control according to the second embodiment. FIG. 6 is a diagram showing a schematic configuration of an intake / exhaust system of an internal combustion engine according to a modification of the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Intake passage 3 ... Exhaust passage 4 ... Air flow meter 5 ... Throttle valve 6 ... First oxidation catalyst 7 ... Second dioxide catalyst 8 ... Patty filter 9 ... NOx storage reduction catalyst 10 ... fuel addition valve 11 .. first temperature sensor 12 ... second temperature sensor 16 · _{O 2} sensor 20 ... ECU

Claims (2)

A first catalyst having an oxidation function provided in an exhaust passage of an internal combustion engine;
A second catalyst having an oxidation function provided in the exhaust passage downstream of the first catalyst;
Reducing agent supply means for supplying a reducing agent into the exhaust gas flowing in the exhaust passage upstream of the first catalyst;
The temperature raising control is executed to supply the reducing agent to the first and second catalysts by supplying the reducing agent into the exhaust gas by the reducing agent supply means, thereby executing the temperature raising control for raising the temperature of the second catalyst. Means,
A heat release amount calculating means for calculating a heat release amount radiated from the exhaust between the first catalyst and the second catalyst when the temperature increase control is executed by the temperature increase control execution means,
The heat dissipation amount calculating means
A calorific value calculating means for calculating a calorific value generated by oxidizing the reducing agent in the first catalyst when the temperature raising control is executed by the temperature raising control executing means;
Calculating a heat release amount based on a heat generation amount of the first catalyst calculated by the heat generation amount calculation means and an intake air amount of the internal combustion engine;
An internal combustion engine characterized in that the amount of reducing agent supplied from the reducing agent supply means when the temperature raising control execution means is executed is increased as the heat release amount calculated by the heat release amount calculation means increases. Engine exhaust purification system. The temperature rise control execution means is
Reference supply for calculating a reference supply amount that is a reference value of the supply amount of the reducing agent from the reducing agent supply means based on the difference between the temperature of the second catalyst and the target temperature when starting the temperature increase control Having a quantity calculating means,
When the temperature increase control is performed, the reference supply amount of the reducing agent calculated by the reference supply amount calculation unit is supplied from the reducing agent supply unit, and then, based on the heat release amount calculated by the heat release amount calculation unit. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the supply amount of the reducing agent from the reducing agent supply means is corrected.

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