JP2021188514A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

To suppress deterioration of a catalyst during PM regeneration.SOLUTION: An exhaust emission control device for an internal combustion engine includes: a filter 20 disposed in an exhaust passage of the internal combustion engine and collecting particulate matters in exhaust gas; a catalyst 23 disposed in the exhaust passage downstream of the filter; and an air-fuel ratio control device controlling an air-fuel ratio of an air-fuel mixture in a combustion chamber 5 of the internal combustion engine to a target air-fuel ratio. The air-fuel ratio control device executes regeneration control for making the target air-fuel ratio leaner than a theoretical air-fuel ratio so that the particulate matters accumulated in the filter are burned, and determines the target air-fuel ratio so that oxygen supplied to the filter completely reacts with the particulate matters on the filter when a temperature of the catalyst is a predetermined temperature or higher during the regeneration control.SELECTED DRAWING: Figure 3

Description

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

Conventionally, it is known that a filter for collecting particulate matter (PM) in exhaust gas and a catalyst for purifying harmful substances (HC, NOx, etc.) in exhaust gas are provided in the exhaust passage of an internal combustion engine. .. In the internal combustion engine described in Patent Document 1, a catalyst is arranged on the downstream side of the filter in the exhaust passage of the internal combustion engine.

Japanese Unexamined Patent Publication No. 2012-177327

In such an internal combustion engine, PM regeneration is performed in which oxygen is supplied to the filter to burn and remove PM in order to reduce clogging of the filter. However, when PM regeneration is performed, high-temperature exhaust gas flows into the catalyst due to the combustion of PM. At this time, if oxygen flowing out of the filter flows into the high-temperature catalyst, the noble metal of the catalyst may generate heat locally and the catalyst may deteriorate.

Therefore, in view of the above problems, an object of the present invention is to suppress deterioration of the catalyst during PM regeneration.

In order to solve the above problems, in the present invention, the filter is arranged in the exhaust passage of the internal combustion engine and collects particulate matter in the exhaust gas, and is arranged in the exhaust passage on the downstream side of the filter. The air-fuel ratio control device includes a catalyst and an air-fuel ratio control device that controls the air-fuel ratio of the air-fuel mixture in the combustion chamber of the internal combustion engine to a target air-fuel ratio, so that the air-fuel ratio control device burns particulate matter deposited on the filter. When the regeneration control that makes the target air-fuel ratio leaner than the theoretical air-fuel ratio is executed and the temperature of the catalyst is equal to or higher than a predetermined temperature in the regeneration control, oxygen supplied to the filter is a particulate substance on the filter. Provided is an internal combustion engine exhaust purification device that determines the target air-fuel ratio so as to completely react with.

According to the present invention, deterioration of the catalyst during PM regeneration can be suppressed.

FIG. 1 is a diagram schematically showing an internal combustion engine provided with an exhaust gas purification device for an internal combustion engine according to an embodiment of the present invention. FIG. 2 is a diagram showing the purification characteristics of the three-way catalyst. FIG. 3 is a time chart of PM accumulation amount and the like when regeneration control is executed. FIG. 4 is a flowchart showing a control routine of PM reproduction processing.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, similar components are given the same reference numbers.

<Explanation of the entire internal combustion engine>
FIG. 1 is a diagram schematically showing an internal combustion engine provided with an exhaust gas purification device for an internal combustion engine according to an embodiment of the present invention. The internal combustion engine shown in FIG. 1 is a spark-ignition type internal combustion engine. The internal combustion engine is mounted on the vehicle.

Referring to FIG. 1, 1 is an engine body, 2 is a cylinder block, 3 is a piston that reciprocates in the cylinder block 2, 4 is a cylinder head fixed on the cylinder block 2, and 5 is a piston 3 and a cylinder head 4. A combustion chamber formed between the two, 6 is an intake valve, 7 is an intake port, 8 is an exhaust valve, and 9 is an exhaust port. The intake valve 6 opens and closes the intake port 7, and the exhaust valve 8 opens and closes the exhaust port 9.

As shown in FIG. 1, the spark plug 10 is arranged in the central portion of the inner wall surface of the cylinder head 4, and the fuel injection valve 11 is arranged in the peripheral portion of the inner wall surface of the cylinder head 4. The spark plug 10 is configured to generate sparks in response to an ignition signal. Further, the fuel injection valve 11 injects a predetermined amount of fuel into the combustion chamber 5 in response to the injection signal. In this embodiment, gasoline having a stoichiometric air-fuel ratio of 14.6 is used as the fuel.

The intake port 7 of each cylinder is connected to the surge tank 14 via the corresponding intake branch pipe 13, and the surge tank 14 is connected to the air cleaner 16 via the intake pipe 15. The intake port 7, the intake branch pipe 13, the surge tank 14, the intake pipe 15, and the like form an intake passage that guides air to the combustion chamber 5. Further, a throttle valve 18 driven by the throttle valve drive actuator 17 is arranged in the intake pipe 15. The throttle valve 18 can be rotated by the throttle valve drive actuator 17, so that the opening area of the intake passage can be changed.

On the other hand, the exhaust port 9 of each cylinder is connected to the exhaust manifold 19. The exhaust manifold 19 has a plurality of branches connected to each exhaust port 9 and an aggregate portion in which these branches are aggregated. The collecting portion of the exhaust manifold 19 is connected to the upstream casing 21 containing the filter 20. The upstream casing 21 is connected to the downstream casing 24 containing the catalyst 23 via the exhaust pipe 22. The exhaust port 9, the exhaust manifold 19, the upstream casing 21, the exhaust pipe 22, the downstream casing 24, and the like form an exhaust passage for discharging the exhaust gas generated by the combustion of the air-fuel mixture in the combustion chamber 5.

Various controls of the internal combustion engine are executed by the electronic control unit (ECU) 31. That is, the ECU 31 functions as a control device for the internal combustion engine. The outputs of various sensors provided in the internal combustion engine are input to the ECU 31, and the ECU 31 controls various actuators of the internal combustion engine based on the outputs of the various sensors and the like.

The ECU 31 is composed of a digital computer, and has a RAM (random access memory) 33, a ROM (read-only memory) 34, a CPU (microprocessor) 35, an input port 36, and an output port connected to each other via a bidirectional bus 32. 37 is provided. In this embodiment, one ECU 31 is provided, but a plurality of ECUs may be provided for each function.

An air flow meter 39 for detecting the flow rate of air flowing in the intake pipe 15 is arranged in the intake pipe 15, and the output of the air flow meter 39 is input to the input port 36 via the corresponding AD converter 38.

Further, an air-fuel ratio sensor 40 for detecting the air-fuel ratio of the exhaust gas discharged from the combustion chamber 5 of the internal combustion engine and flowing into the filter 20 is arranged in the gathering portion of the exhaust manifold 19, that is, the exhaust passage on the upstream side of the filter 20. Will be done. The output of the air-fuel ratio sensor 40 is input to the input port 36 via the corresponding AD converter 38.

Further, a temperature sensor 41 for detecting the temperature (floor temperature) of the catalyst 23 is arranged in the downstream casing 24 in which the catalyst 23 is built. The output of the temperature sensor 41 is input to the input port 36 via the corresponding AD converter 38.

Further, a load sensor 44 that generates an output voltage proportional to the amount of depression of the accelerator pedal 43 is connected to the accelerator pedal 43 provided in the vehicle equipped with the internal combustion engine, and the output voltage of the load sensor 44 is converted to the corresponding AD. It is input to the input port 36 via the device 38. The ECU 31 calculates the engine load based on the output of the load sensor 44.

Further, a crank angle sensor 45 that generates an output pulse each time the crankshaft rotates by a predetermined angle (for example, 10 °) is connected to the input port 36, and this output pulse is input to the input port 36. The ECU 31 calculates the engine speed based on the output of the crank angle sensor 45.

On the other hand, the output port 37 is connected to various actuators of the internal combustion engine via the corresponding drive circuit 46. In the present embodiment, the output port 37 is connected to the spark plug 10, the fuel injection valve 11, and the throttle valve drive actuator 17, and the ECU 31 controls them. Specifically, the ECU 31 controls the ignition timing of the spark plug 10, the injection timing and injection amount of the fuel injection valve, and the opening degree of the throttle valve 18.

The above-mentioned internal combustion engine is a non-supercharged internal combustion engine that uses gasoline as fuel, but the configuration of the internal combustion engine is not limited to the above configuration. Therefore, even if the specific configuration of the internal combustion engine such as the cylinder arrangement, the fuel injection mode, the intake / exhaust system configuration, the valve operating mechanism configuration, and the presence / absence of the supercharger is different from the configuration shown in FIG. good. For example, the fuel injection valve 11 may be arranged so as to inject fuel into the intake port 7. Further, a configuration for recirculating the EGR gas from the exhaust passage to the intake passage may be provided.

<Exhaust purification device for internal combustion engine>
Hereinafter, the exhaust gas purification device for an internal combustion engine (hereinafter, simply referred to as “exhaust gas purification device”) according to the embodiment of the present invention will be described. The exhaust gas purification device includes a filter 20, a catalyst 23, an air-fuel ratio sensor 40, a temperature sensor 41, and an air-fuel ratio control device. In this embodiment, the ECU 31 functions as an air-fuel ratio control device.

The filter 20 is arranged in the exhaust passage of the internal combustion engine and collects particulate matter (PM) in the exhaust gas. The filter 20 is made of, for example, porous ceramics. In the present embodiment, the filter 20 is a gasoline particulate filter (GPF) that collects PM emitted from a gasoline engine.

As shown in FIG. 1, the catalyst 23 is arranged in the exhaust passage on the downstream side of the filter 20. The catalyst 23 is a three-way catalyst capable of occluding oxygen and simultaneously purifying, for example, hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx). The catalyst 23 includes a carrier made of ceramic, a noble metal having a catalytic action (platinum (Pt) or rhodium (Rh) in this embodiment), and an auxiliary catalyst having an oxygen storage capacity (for example, ceria (CeO ₂ )). Has. The noble metal and co-catalyst are supported on the carrier.

FIG. 2 is a diagram showing the purification characteristics of the three-way catalyst. As shown in FIG. 2, the purification rate of HC, CO and NOx by the catalyst 23 is extremely high when the air-fuel ratio of the exhaust gas flowing into the catalyst 23 is in the region near the stoichiometric air-fuel ratio (purification window A in FIG. 2). Will be high. Therefore, the catalyst 23 can effectively purify HC, CO, and NOx when the air-fuel ratio of the exhaust gas is maintained at the stoichiometric air-fuel ratio.

Further, the catalyst 23 occludes or releases oxygen according to the air-fuel ratio of the exhaust gas by the auxiliary catalyst. Specifically, the catalyst 23 occludes excess oxygen in the exhaust gas when the air-fuel ratio of the exhaust gas is leaner than the stoichiometric air-fuel ratio. On the other hand, when the air-fuel ratio of the exhaust gas is richer than the stoichiometric air-fuel ratio, the catalyst 23 releases oxygen that is insufficient to oxidize HC and CO. As a result, even when the air-fuel ratio of the exhaust gas deviates slightly from the stoichiometric air-fuel ratio, the air-fuel ratio on the surface of the catalyst 23 is maintained near the stoichiometric air-fuel ratio, and HC, CO and NOx are effective in the catalyst 23. Purified to.

The air-fuel ratio control device controls the air-fuel ratio of the air-fuel mixture in the combustion chamber 5 of the internal combustion engine to the target air-fuel ratio. Specifically, the air-fuel ratio control device sets the target air-fuel ratio of the air-fuel mixture and controls the amount of fuel supplied to the combustion chamber 5 so that the air-fuel ratio of the air-fuel mixture matches the target air-fuel ratio. For example, the air-fuel ratio control device feedback-controls the amount of fuel supplied to the combustion chamber 5 so that the output air-fuel ratio of the air-fuel ratio sensor 40 matches the target air-fuel ratio. Here, the "output air-fuel ratio" means the air-fuel ratio corresponding to the output value of the air-fuel ratio sensor 40, that is, the air-fuel ratio detected by the air-fuel ratio sensor 40.

The air-fuel ratio control device may control the amount of fuel supplied to the combustion chamber 5 so that the air-fuel ratio of the air-fuel mixture matches the target air-fuel ratio without using the air-fuel ratio sensor 40. In this case, the air-fuel ratio control device is calculated from the intake air amount detected by the air flow meter 39 and the target air-fuel ratio so that the ratio of the fuel supplied to the combustion chamber 5 to the air matches the target air-fuel ratio. The amount of fuel is supplied to the combustion chamber 5. Therefore, the air-fuel ratio sensor 40 may be omitted from the exhaust gas purification device.

In the internal combustion engine as described above, when the exhaust gas containing PM flows into the filter 20, the PM is collected by the filter 20 and the PM is deposited on the filter 20. When the amount of PM deposited on the filter 20 is large, the filter 20 is clogged (clogging). As a result, the exhaust gas discharged through the filter 20 is hindered, and the back pressure rises.

On the other hand, when oxygen is supplied to the filter 20 when the temperature of the filter 20 is high, the PM deposited on the filter 20 is oxidized and burned off. This phenomenon is referred to as regeneration of the filter 20. Regeneration of the filter 20 reduces the amount of PM deposited on the filter 20 and reduces clogging of the filter 20.

In order to supply oxygen to the filter 20 for regeneration of the filter 20, it is necessary to make the air-fuel ratio of the exhaust gas discharged from the engine body 1 leaner than the theoretical air-fuel ratio. Therefore, the air-fuel ratio control device executes regeneration control to make the target air-fuel ratio of the air-fuel mixture leaner than the theoretical air-fuel ratio so that the PM deposited on the filter 20 burns. For example, the air-fuel ratio control device starts regeneration control when the amount of PM deposited on the filter 20 (hereinafter referred to as “PM accumulated amount”) becomes larger than the threshold value.

However, when the regeneration control is executed, the high temperature exhaust gas flows into the catalyst 23 due to the combustion of PM. At this time, if the oxygen flowing out from the filter 20 flows into the high-temperature catalyst 23, the noble metal of the catalyst 23 may generate heat locally and the catalyst 23 may deteriorate. This is particularly remarkable when the noble metal of the catalyst 23 is platinum (Pt) or rhodium (Rh).

Therefore, in the present embodiment, the air-fuel ratio control device mixes the oxygen supplied to the filter 20 so as to completely react with PM on the filter 20 when the temperature of the catalyst 23 is equal to or higher than the predetermined temperature in the regeneration control. Determine the target air-fuel ratio of Qi. In other words, in the air-fuel ratio control device, when the temperature of the catalyst 23 is equal to or higher than a predetermined temperature in the regeneration control, the exhaust gas flowing out of the filter 20 and flowing into the catalyst 23 (hereinafter referred to as “inflow exhaust gas”) is empty. Determine the target air-fuel ratio of the air-fuel mixture so that the fuel ratio becomes the theoretical air-fuel ratio. As a result, the amount of oxygen flowing into the high-temperature catalyst 23 can be reduced, and eventually the deterioration of the catalyst 23 during PM regeneration can be suppressed.

For example, the air-fuel ratio control device calculates the oxygen amount Ona (mg) required for PM regeneration by the following formula (1), and calculates the target air-fuel ratio TAF of the air-fuel mixture by the following formula (2).
Ona = (PMra / PMmw) x Omw ... (1)
TAF = TAFreg + (Ona / Qi) ... (2)
In the above formula (1), PMra is the PM regeneration amount (mg), PMmw is the molecular weight of PM (g / mol), and Omw is the molecular weight of oxygen (g / mol). In the above equation (2), TAFreg is the target air-fuel ratio at the time of normal control, and Qi is the fuel injection amount at the time of normal control.

The PM regeneration amount PMra corresponds to the amount of PM burned and removed per unit time in the regeneration control, and is calculated based on the PM accumulation amount using a map or a calculation formula. The PM regeneration amount PMra decreases as the PM accumulation amount decreases.

The molecular weight PMmw of PM and the molecular weight Omw of oxygen are predetermined constants. The target air-fuel ratio TAFreg during normal control is set according to the operating state of the internal combustion engine, and is set to, for example, the theoretical air-fuel ratio (14.6). The fuel injection amount Qi during normal control is calculated from the intake air amount detected by the air flow meter 39 and the target air-fuel ratio TAFreg during normal control.

On the other hand, when the temperature of the catalyst 23 is lower than the predetermined temperature in the regeneration control, the air-fuel ratio control device sets the target air-fuel ratio of the air-fuel mixture to a lean set air-fuel ratio that is leaner than the theoretical air-fuel ratio. The lean degree of the lean set air-fuel ratio is larger than the lean degree of the target air-fuel ratio of the air-fuel mixture determined when the temperature of the catalyst 23 is equal to or higher than the predetermined temperature. Therefore, in the regeneration control, the air-fuel ratio control device reduces the lean degree of the target air-fuel ratio of the air-fuel mixture when the temperature of the catalyst 23 is equal to or higher than the predetermined temperature as compared with the case where the temperature of the catalyst 23 is lower than the predetermined temperature. do. The degree of lean means the difference between the air-fuel ratio leaner than the stoichiometric air-fuel ratio and the stoichiometric air-fuel ratio.

<Explanation of air-fuel ratio control using time chart>
With reference to FIG. 3, the air-fuel ratio control during PM regeneration will be specifically described. FIG. 3 is a time chart of the amount of PM deposited when the regeneration control is executed, the temperature of the catalyst 23, the target air-fuel ratio of the air-fuel mixture, and the air-fuel ratio of the inflow exhaust gas.

In the illustrated example, at time t0, the temperature of the catalyst 23 is less than the predetermined temperature Tref. Therefore, the target air-fuel ratio of the air-fuel mixture is set to a lean set air-fuel ratio TAFLean that is leaner than the theoretical air-fuel ratio. At this time, the air-fuel ratio of the inflow / exhaust gas becomes leaner than the theoretical air-fuel ratio, but the deterioration of the catalyst 23 is suppressed because the temperature of the catalyst 23 is low.

After time t0, the amount of PM deposited gradually decreases with the regeneration of PM. On the other hand, the temperature of the inflow / exhaust gas gradually rises due to the combustion heat of PM, and as a result, the temperature of the catalyst 23 reaches a predetermined temperature Tref at time t1.

Therefore, after time t1, the target air-fuel ratio of the air-fuel mixture is determined so that the oxygen supplied to the filter 20 completely reacts with PM on the filter 20. As a result, oxygen is consumed on the filter 20, and the air-fuel ratio of the inflow exhaust gas converges to the stoichiometric air-fuel ratio.

As described above, the amount of PM regeneration decreases as the amount of PM deposited decreases. Further, as is clear from the above equations (1) and (2), the smaller the PM regeneration amount PMra, the smaller the lean degree of the target air-fuel ratio TAF of the air-fuel mixture. Therefore, after time t1, as the PM accumulation amount decreases, the lean degree of the target air-fuel ratio of the air-fuel mixture becomes smaller, and the target air-fuel ratio of the air-fuel mixture approaches the theoretical air-fuel ratio.

After time t1, the PM deposit is further reduced, and at time t2, the PM deposit reaches a predetermined value Allef. As a result, the regeneration control is completed, and the target air-fuel ratio of the air-fuel mixture is set to the normal target air-fuel ratio (the theoretical air-fuel ratio in this example).

<PM playback processing>
Hereinafter, the air-fuel ratio control during PM reproduction will be described in detail with reference to the flowchart of FIG. FIG. 4 is a flowchart showing a control routine of PM reproduction processing. This control routine is repeatedly executed by the ECU 31 at predetermined time intervals.

First, in step S101, the air-fuel ratio control device determines whether or not the PM deposit amount is larger than the threshold value. The threshold is predetermined. For example, the air-fuel ratio control device captures PM based on predetermined parameters of the internal combustion engine (for example, intake air amount, engine rotation speed, air-fuel ratio (target air-fuel ratio or air-fuel ratio detected by the air-fuel ratio sensor 40), etc.). The PM accumulation amount is calculated by calculating the collection amount and integrating the collection amount. If it is determined in step S101 that the PM deposit amount is equal to or less than the threshold value, this control routine ends.

On the other hand, if it is determined in step S101 that the amount of PM deposited is greater than the threshold value, the control routine proceeds to step S102. In step S102, the air-fuel ratio control device determines whether or not the temperature of the catalyst 23 is higher than the upper limit threshold value. The upper limit threshold value is set in advance to a temperature (for example, 750 °) capable of suppressing thermal deterioration of the catalyst 23 during regeneration control.

For example, the air-fuel ratio control device determines whether or not the temperature of the catalyst 23 is equal to or higher than the upper limit threshold value based on the output of the temperature sensor 41. The temperature sensor 41 is arranged in the exhaust passage on the upstream side of the catalyst 23 so as to detect the temperature of the inflow exhaust gas, or is located on the downstream side of the catalyst 23 so as to detect the temperature of the exhaust gas flowing out from the catalyst 23. It may be arranged in the exhaust passage. Further, the air-fuel ratio control device may calculate the temperature of the catalyst 23 based on predetermined parameters (for example, intake air amount, engine load, etc.) of the internal combustion engine without using the temperature sensor 41. In this case, the temperature sensor 41 may be omitted from the exhaust gas purification device.

When it is determined in step S102 that the temperature of the catalyst 23 is higher than the upper limit threshold value, this control routine ends. On the other hand, if it is determined in step S102 that the temperature of the catalyst 23 is equal to or lower than the upper limit threshold value, the control routine proceeds to step S103.

In step S103, the air-fuel ratio control device determines whether or not the temperature of the catalyst 23 is below the lower limit threshold value. The lower limit threshold is predetermined and is set to a temperature (for example, 500 °) required for regeneration of the filter 20. If it is determined that the temperature of the catalyst 23 is less than the lower limit threshold value, the control routine proceeds to step S104.

In step S104, the air-fuel ratio control device executes temperature rise control for raising the temperature of the catalyst 23. For example, the air-fuel ratio control device increases the lean degree of the target air-fuel ratio of the air-fuel mixture in the temperature rise control. The air-fuel ratio control device may increase the engine load without changing the target air-fuel ratio of the air-fuel mixture in the temperature rise control.

The temperature rise control in step S104 is continued until the temperature of the catalyst 23 rises and reaches the lower limit threshold value. If it is determined in step S103 that the temperature of the catalyst 23 is equal to or higher than the lower limit threshold value, the control routine proceeds to step S105.

After step S105, reproduction control is executed. That is, in the present embodiment, the regeneration control is executed when the temperature of the catalyst 23 is between the lower limit threshold value and the upper limit threshold value.

In step S105, the air-fuel ratio control device determines whether or not the temperature of the catalyst 23 is equal to or higher than a predetermined temperature. The predetermined temperature is predetermined and is set to a temperature between the lower limit threshold and the upper limit threshold value (for example, 650 °). If it is determined that the temperature of the catalyst 23 is lower than the predetermined temperature, the control routine proceeds to step S106.

In step S106, the air-fuel ratio control device sets the target air-fuel ratio TAF of the air-fuel mixture to a lean set air-fuel ratio TAFlean that is leaner than the theoretical air-fuel ratio. The lean set air-fuel ratio TAFlean is predetermined and is set to, for example, 15 to 17.

After step S106, in step S108, the air-fuel ratio control device determines whether or not the PM deposit amount is equal to or less than a predetermined value. For example, the air-fuel ratio control device calculates the PM regeneration amount based on the PM accumulation amount, and calculates the PM accumulation amount by subtracting the PM regeneration amount. The predetermined value is predetermined and is set to a value smaller than the threshold value in step S101. The predetermined value is zero, and the air-fuel ratio control device may determine whether or not the PM deposit amount is zero.

If it is determined in step S108 that the amount of PM deposited is greater than the predetermined value, the control routine returns to step S105. If it is determined in step S105 that the temperature of the catalyst 23 is equal to or higher than the predetermined temperature, the control routine proceeds to step S107.

In step S107, the air-fuel ratio controller determines the target air-fuel ratio TAF of the air-fuel mixture so that the oxygen supplied to the filter 20 completely reacts with PM on the filter 20. For example, the air-fuel ratio control device calculates the target air-fuel ratio TAF by the above equations (1) and (2).

After step S107, in step S108, the air-fuel ratio control device determines whether or not the PM deposit amount is equal to or less than a predetermined value. When it is determined that the PM deposit amount is equal to or less than a predetermined value, the regeneration control ends and the present control routine ends.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and modifications can be made within the scope of the claims. For example, the filter 20 may have a three-way catalytic function. That is, the filter 20 may be a so-called quaternary catalyst.

Further, the air-fuel ratio control device may periodically execute regeneration control. That is, the air-fuel ratio control device may execute regeneration control at predetermined execution intervals. Further, the air-fuel ratio control device may execute regeneration control when the integrated intake air amount reaches a predetermined value.

5 Combustion chamber 20 Filter 23 Catalyst 31 ECU

Claims (1)

A filter placed in the exhaust passage of an internal combustion engine and collecting particulate matter in the exhaust gas,
With the catalyst arranged in the exhaust passage on the downstream side of the filter,
It is equipped with an air-fuel ratio control device that controls the air-fuel ratio of the air-fuel mixture in the combustion chamber of the internal combustion engine to the target air-fuel ratio.
The air-fuel ratio control device executes regeneration control to make the target air-fuel ratio leaner than the theoretical air-fuel ratio so that the particulate matter deposited on the filter burns, and the temperature of the catalyst is set to a predetermined temperature in the regeneration control. When the above is the case, the exhaust gas purification device of the internal combustion engine determines the target air-fuel ratio so that the oxygen supplied to the filter completely reacts with the particulate matter on the filter.

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