JP2021143666A - Control device of internal combustion engine - Google Patents

Abstract

To suppress the deterioration of exhaust emission at the regeneration of a filter.SOLUTION: When regenerating a first filter 30 and a second filter 40, a control device 200 of an internal combustion engine 100 alternately performs control for combusting an air-fuel mixture whose air excess rate is higher than 1 in a cylinder 11 of a first cylinder group 10a, and combusting an air-fuel mixture whose air excess rate is lower than 1 in the cylinder 11 of a second cylinder group 10b so that an air-fuel ratio of exhaust emission flowing into a three-dimensional catalyst 52 reaches a theoretical air-fuel ratio, and control for combusting the air-fuel mixture whose air excess rate is lower than 1 in the cylinder 11 of the first cylinder group 10a, and combusting the air-fuel mixture whose air excess rate is higher than 1 in the cylinder 11 of the second cylinder group 10b.SELECTED DRAWING: Figure 1

Description

The present invention relates to a control device for an internal combustion engine.

Patent Document 1 describes, as a conventional internal combustion engine, a three-way catalyst for purifying unburned gas (carbon monoxide (CO) and hydrocarbon (HC)) and nitrogen oxides (NOx) in the exhaust gas, and a three-way catalyst in the exhaust gas. A filter for collecting particulate matter (Particulate Matter; hereinafter referred to as "PM") and a filter provided in the exhaust passage are disclosed. Further, in Patent Document 1, as a control device for controlling this conventional internal combustion engine, the amount of NOx emitted from the engine body differs depending on the air-fuel ratio, and the air-fuel ratio is changed from the stoichiometric air-fuel ratio to the lean limit (lean capable of normal combustion). Since the NOx emission tends to decrease as it approaches the limit of the air-fuel ratio on the side), the air-fuel ratio is in the air-fuel ratio range on the lean side of the theoretical air-fuel ratio at which the NOx emission is less than a predetermined amount during filter regeneration. Those configured to control the internal combustion engine so as to fit within (eg 19-23) are disclosed.

Japanese Unexamined Patent Publication No. 2018-178981

However, in the case of the conventional internal combustion engine control device described above, the air-fuel ratio is leaner than the theoretical air-fuel ratio, although the air-fuel ratio is controlled so that the NOx emission from the engine body is equal to or less than a predetermined amount during filter regeneration. It is said to be the air-fuel ratio on the side. Therefore, the NOx purification rate of the three-way catalyst is lowered, and the NOx cannot be sufficiently purified by the three-way catalyst, and NOx is discharged to the outside air, which deteriorates the exhaust emission during filter regeneration. There was a problem.

The present invention has been made by paying attention to such a problem, and an object of the present invention is to suppress deterioration of exhaust emissions during filter regeneration.

In order to solve the above problems, the internal combustion engine 100 according to an embodiment of the present invention includes an engine body including a first cylinder group having at least one cylinder, a second cylinder group having at least one cylinder, and a first cylinder. The first exhaust passage where the exhaust generated in the group is discharged, the second exhaust passage where the exhaust generated in the second cylinder group is discharged, and the first exhaust passage are provided to collect the particulate matter in the exhaust. 1st filter, 2nd filter provided in the 2nd exhaust passage to collect particulate matter in the exhaust, and 1st filter to join the exhausts of the 1st exhaust passage and the 2nd exhaust passage, respectively. It also includes a collective exhaust passage formed by assembling the first exhaust passage and the second exhaust passage on the downstream side in the exhaust flow direction with respect to the second filter, and a three-way catalyst provided in the collective exhaust passage. When the first filter and the second filter are regenerated, the control device of the internal combustion engine has an excess air ratio in the cylinders of the first cylinder group so that the air-fuel ratio of the exhaust flowing into the three-way catalyst becomes the stoichiometric air-fuel ratio. The stoichiometric air-fuel ratio is the control that burns the air-fuel mixture that is greater than 1 and burns the air-fuel mixture that has an excess air ratio of less than 1 in the cylinders of the second cylinder group, and the air-fuel ratio of the exhaust that flows into the three-way catalyst. As described above, the control of burning the air-fuel mixture having an excess air-fuel ratio of less than 1 in the cylinders of the first cylinder group and burning the air-fuel ratio having an excess air-fuel ratio of more than 1 in the cylinders of the second cylinder group is alternately performed. Configured to carry out.

According to this aspect of the present invention, deterioration of exhaust emissions during filter regeneration can be suppressed.

FIG. 1 is a schematic configuration diagram of an internal combustion engine according to an embodiment of the present invention and an electronic control unit that controls the internal combustion engine. FIG. 2 is a diagram showing the relationship between the air-fuel ratio and the purification rate of the three-way catalyst. FIG. 3 is a flowchart illustrating filter regeneration control according to an embodiment of the present invention. FIG. 4 is a time chart illustrating the operation of filter regeneration control according to the embodiment of the present invention.

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.

FIG. 1 is a schematic configuration diagram of an internal combustion engine 100 according to an embodiment of the present invention and an electronic control unit 200 that controls the internal combustion engine 100.

The internal combustion engine 100 according to the present embodiment is a spark-ignition type gasoline engine, and includes an engine main body 10 and an exhaust device 20. The type of the internal combustion engine 100 is not particularly limited, and may be a premixed compression ignition type gasoline engine or a diesel engine.

The engine body 10 includes a first bank 10a and a second bank 10b, each having three cylinders 11. The engine body 10 generates power for driving, for example, a vehicle by burning the fuel injected from the fuel injection valve 12 provided in each cylinder 11 inside each cylinder 11. In FIG. 1, the description of the intake device, the spark plug, and the like is omitted in order to prevent the drawings from being complicated. Further, the fuel injection method is not limited to the in-cylinder direct injection type, and may be a port injection type. Further, although three cylinders 11 are formed in each of the banks 10a and 10b, at least one cylinder 11 may be formed.

The exhaust device 20 is a device for purifying the exhaust (combustion gas) generated inside each cylinder 11 and discharging it to the outside air, and is a first exhaust passage 21, a second exhaust passage 22, and a collective exhaust passage. 23, a first PM collecting device 30, a second PM collecting device 40, and a catalyst device 50 are provided.

The first exhaust passage 21 is a passage through which the exhaust gas discharged from each cylinder 11 formed in the first bank 10a flows.

The second exhaust passage 22 is a passage through which the exhaust gas discharged from each cylinder 11 formed in the second bank 10b flows.

The collective exhaust passage 23 is a passage in which the first exhaust passage and the second exhaust passage are aggregated into one. The exhausts of the first exhaust passage 21 and the second exhaust passage 22 are merged in the collective exhaust passage 23, respectively, and finally discharged to the outside air.

Exhaust gas contains harmful substances such as unburned gas (carbon monoxide (CO) and hydrocarbon (HC)), nitrogen oxides (NOx), and particulate matter (PM; Particular Matter). Therefore, in the present embodiment, the above-mentioned first PM collecting device 30, second PM collecting device 40, and catalyst device 50 are provided as an exhaust aftertreatment device for removing harmful substances in the exhaust.

The first PM collecting device 30 is provided in the first exhaust passage 21. The first PM collecting device 30 includes a casing 31 and a wall flow type filter 32 held in the casing 31, and the filter 32 collects PM in the exhaust gas that has flowed into the inside. A first differential pressure sensor 201 for detecting the front-rear differential pressure of the filter 32 is attached to the casing 31.

The second PM collecting device 40 is provided in the second exhaust passage 22. The second PM collecting device 40 includes a casing 41 and a filter 42 like the first PM collecting device 30, and the filter 42 collects the PM in the exhaust gas that has flowed into the inside. A second differential pressure sensor 202 for detecting the front-rear differential pressure of the filter 42 is attached to the casing 41.

In the present embodiment, the estimated value of the PM accumulation amount of the filter 32 (hereinafter referred to as “first estimated PM accumulation amount”) Qpm1 is calculated based on the front-rear differential pressure of the filter 32 detected by the first differential pressure sensor 201. Then, based on the front-rear differential pressure of the filter 42 detected by the second differential pressure sensor 202, the estimated value of the PM accumulation amount of the filter 42 (hereinafter referred to as “the second estimated PM accumulation amount”) Qpm2 is calculated. .. However, the estimation of the PM deposition amount is not limited to such a method, and may be estimated by appropriately selecting from various known methods such as estimation according to the engine operating state. ..

The PM collecting devices 30 and 40 are called GPF (Gasoline Particulate Filter) when the internal combustion engine 100 is a gasoline engine, and DPF (Diesel Particulate Filter) when the internal combustion engine 100 is a diesel engine. Sometimes called.

The catalyst device 50 is provided in the collective exhaust passage 23. The catalyst device 50 includes a casing 51 and a three-way catalyst 52 supported on a honeycomb-shaped carrier made of cordilite (ceramic) held in the casing 51, and flows into the inside by the three-way catalyst 52. Purify unburned gas (CO and HC) and NOx in the exhaust gas.

In the first exhaust passage 21 on the upstream side in the exhaust flow direction from the first PM collecting device 30, the air-fuel ratio of the exhaust gas discharged from each cylinder 11 formed in the first bank 10a (hereinafter, "first exhaust air-fuel ratio"). The first air-fuel ratio sensor 204 for detecting) is attached. Further, in the second exhaust passage 22 on the upstream side in the exhaust flow direction from the second PM collecting device 40, the air-fuel ratio of the exhaust discharged from each cylinder 11 formed in the second bank 10b (hereinafter, "second exhaust empty"). A second air-fuel ratio sensor 205 for detecting (referred to as "fuel ratio") is attached.

The electronic control unit 200 includes a central arithmetic unit (CPU) connected to each other by a bidirectional bus, various memories such as a read-only memory (ROM) and a random access memory (RAM), an input port, and an output port. It is a microcomputer.

In the electronic control unit 200, in addition to the first differential pressure sensor 201, the second differential pressure sensor 202, the first air fuel ratio sensor 204, and the second air fuel ratio sensor 205 described above, the load of the engine body 10 (engine load) The load sensor 211 that generates an output voltage proportional to the amount of depression of the accelerator pedal 220 corresponding to the above, and every time the crank shaft (not shown) of the engine body 10 rotates by, for example, 15 ° as a signal for calculating the engine rotation speed and the like. Output signals from various sensors such as the crank angle sensor 212 that generates an output pulse are input to the sensor.

The electronic control unit 200 controls the internal combustion engine 100 based on the input output signals of various sensors and the like.

Specifically, in the electronic control unit 200, the engine output torque is normally applied to the engine load while feedback-controlling the injection amount of the fuel injection valve 12 so that the first exhaust air-fuel ratio and the second exhaust air-fuel ratio become the target air-fuel ratio. The injection amount of the fuel injection valve 12 is controlled so as to obtain the target torque according to the above. In the present embodiment, the electronic control unit 200 basically sets the target air-fuel ratio to the theoretical air-fuel ratio, and the excess air ratio λ in each cylinder 11 is set so that the engine output torque becomes the target torque according to the engine load. The internal combustion engine 100 is operated by burning the air-fuel mixture of 1.

Further, in the electronic control unit 200, since the filters 32 and 42 of the PM collecting devices 30 and 40 cause clogging when PM is continuously collected, each filter before the filters 32 and 42 are clogged. Filter regeneration control is performed to regenerate the filters 32 and 42 by burning and removing the PM collected in the filters 32 and 42.

Here, when an air-fuel mixture (stoichi air-fuel mixture or rich air-fuel mixture) having an excess air ratio λ of 1 or less is being burned in each cylinder 11 of each bank 10a and 10b, oxygen discharged from each cylinder 11 is used. Exhaust gas that is not included will flow into the PM collecting devices 30 and 40, respectively. In this way, when the exhaust gas containing no oxygen flows into the PM collecting devices 30 and 40, oxygen does not exist in the PM collecting devices 30 and 40, so that the PM collecting devices 30 and 40 The PM does not react with oxygen and burns inside, and the PM in the exhaust gas flowing into the PM collecting devices 30 and 40 continues to be collected by the filters 32 and 42.

On the other hand, when an air-fuel mixture (lean air-fuel mixture) having an excess air ratio λ larger than 1 is burned in each cylinder 11 of each bank 10a and 10b, the exhaust gas containing oxygen discharged from each cylinder 11 captures each PM. It will flow into the collectors 30 and 40. When the exhaust gas containing oxygen flows into the PM collecting devices 30 and 40, the temperature of the filters 32 and 42 (hereinafter referred to as "filter temperature") is set to a predetermined PM combustion temperature (for example, 500 to 600 [° C.]. ]) If it is more than the above, the PM deposited on the filters 32 and 42 reacts with oxygen in the PM collecting devices 30 and 40 and burns, and is removed from the filters 32 and 42.

Therefore, in order to regenerate the filters 32 and 42, the target air-fuel ratio is set to a lean air-fuel ratio that is leaner than the theoretical air-fuel ratio, and the excess air ratio λ is greater than 1 in each cylinder 11 of each bank 10a and 10b. It is necessary to burn a large air-fuel mixture (lean air-fuel mixture).

However, if the air-fuel mixture (lean air-fuel mixture) having an excess air ratio λ larger than 1 is burned in each cylinder 11 of each of the banks 10a and 10b, it flows into the catalyst device 50 provided in the collective exhaust passage 23. The air-fuel ratio of the exhaust becomes the lean air-fuel ratio.

Here, as shown in FIG. 2, the three-way catalyst 52 in the catalyst device 50 has unburned gas (HC,) when the exhaust air-fuel ratio is in a predetermined region near the stoichiometric air-fuel ratio, that is, within the range of the purification window A. The purification rate of CO) and NOx tends to be high, and the leaner the exhaust air-fuel ratio tends to be, the lower the purification rate of NOx. Therefore, in order to regenerate the filters 32 and 42, if an air-fuel mixture (lean air-fuel mixture) having an excess air ratio λ larger than 1 is burned in each cylinder 11 of each bank 10a and 10b, a three-way catalyst is used. The NOx purification rate at 52 is lowered, NOx cannot be sufficiently purified, and NOx is discharged to the outside air, which may deteriorate the exhaust emission during filter regeneration.

Therefore, in the present embodiment, when the filters 32 and 42 are regenerated, the air-fuel ratios of the exhaust gas flowing into the catalyst device 50 provided in the collective exhaust passage 23 are the stoichiometric air-fuel ratios of the banks 10a and 10b. An air-fuel mixture (lean air-fuel mixture) having an excess air-fuel ratio λ greater than 1 is burned in each cylinder 11 of one of the banks, and an air-fuel mixture having an excess air-fuel ratio λ of less than 1 is burned in each cylinder 11 of the other bank. It was decided to alternately control the combustion of (rich air-fuel mixture).

As a result, when the air-fuel mixture (lean air-fuel mixture) having an excess air ratio λ larger than 1 is burned in each cylinder 11 of the first bank 10a, the filter 32 of the first collection device 30 is regenerated. Can be done.

At this time, the lean air-fuel ratio exhaust is discharged to the first exhaust passage 21, while the rich air-fuel ratio exhaust is discharged to the second exhaust passage 22, so that the collective exhaust passage 23 is discharged. , The exhaust of the stoichiometric air-fuel ratio where these exhausts merge will flow. That is, since the exhaust gas having a stoichiometric air-fuel ratio can flow into the catalyst device 50, the three-way catalyst 52 in the catalyst device 50 can purify unburned gas (HC, CO) and NOx with a high purification rate. ..

Then, the air-fuel mixture (lean air-fuel mixture) having an excess air ratio λ greater than 1 is burned in each cylinder 11 of the first bank 10a, and the excess air ratio λ is less than 1 in each cylinder 11 of the second bank 10b. From the state in which the air-fuel mixture (rich air-fuel mixture) is being burned, the air-fuel mixture (rich air-fuel mixture) having an excess air ratio λ of less than 1 is burned in each cylinder 11 of the first bank 10a, and each of the second banks 10b is burned. By switching to a state in which the air-fuel mixture (lean air-fuel mixture) having an excess air ratio λ larger than 1 is being burned in the cylinder 11, the filter 42 of the second collection device 30 can be regenerated next.

At this time as well, the exhaust gas having a theoretical air-fuel ratio at which the exhaust gases of the first exhaust passage 21 and the second exhaust passage 22 are merged flows through the collective exhaust passage 23, so that the three-way catalyst 52 in the catalyst device 50 is used. , Unburned gas (HC, CO) and NOx can be purified with a high purification rate.

Hereinafter, the filter regeneration control according to the present embodiment will be described with reference to FIG. FIG. 3 is a flowchart illustrating filter regeneration control according to the present embodiment. The electronic control unit 200 repeatedly executes this routine at a predetermined calculation cycle during engine operation.

In step S1, the electronic control unit 200 refers to a table or the like created in advance by an experiment or the like, and based on the front-rear differential pressure of the filter 32 detected by the first differential pressure sensor 201, the first estimated PM accumulation amount Qpm1 Is calculated, and the second estimated PM accumulation amount Qpm2 is calculated based on the front-rear differential pressure of the filter 42 detected by the second differential pressure sensor 202. The estimated PM deposits Qpm1 and Qpm2 basically tend to increase as the anteroposterior differential pressure of each of the filters 32 and 42 increases.

In step S2, in the electronic control unit 200, the total value (hereinafter referred to as “estimated total PM accumulation amount”) Qpm of the first estimated PM accumulation amount Qpm1 and the second estimated PM accumulation amount Qpm2 has a predetermined regeneration start threshold value Qthr1. Judge whether or not it is the above. If the estimated total PM accumulation amount Qpm is equal to or higher than the regeneration start threshold value Qthr1, the electronic control unit 200 determines that the filters 32 and 42 need to be regenerated, and proceeds to the process of step S3. On the other hand, if the estimated total PM accumulation amount Qpm is less than the regeneration start threshold value Qthr1, the electronic control unit 200 determines that it is not necessary to regenerate the filters 32 and 42, and ends the present process.

In step S3, the electronic control unit 200 calculates the estimated temperature (hereinafter referred to as “estimated filter temperature”) Tfil of each of the filters 32 and 42. In the present embodiment, the electronic control unit 200 reads the detection values of various estimation parameters for estimating the filter temperature during engine operation, and calculates the estimation filter temperature Tfil based on the detection values of the estimation parameters. Since the filter temperature during engine operation changes mainly under the influence of exhaust heat, one or more parameters that affect the amount of heat energy of the exhaust, such as engine speed, engine load, engine water temperature, and intake amount, are used. Parameters can be appropriately selected and used as estimation parameters. The calculation of the estimated filter temperature Tfil is not limited to such a method, and may be estimated by appropriately selecting from various known methods. Further, in the present embodiment, it is assumed that the temperatures of the filters 32 and 42 are the same.

In step S4, the electronic control unit 200 determines whether or not the estimated filter temperature Tfil is equal to or higher than a predetermined PM combustion temperature (for example, 500 to 600 [° C.]) Tthr. If the estimated filter temperature Tfil is equal to or higher than the PM combustion temperature Tthr, the electronic control unit 200 introduces oxygen-containing exhaust gas into the PM collecting devices 30 and 40 to collect PM accumulated in the filters 32 and 42. Since it can be burned and removed by reacting with oxygen in each of the PM collecting devices 30 and 40, the process proceeds to step S5. On the other hand, if the estimated filter temperature Tfil is lower than the PM combustion temperature Tthr, the electronic control unit 200 cannot burn and remove the PM even if the exhaust containing oxygen is introduced into the PM collecting devices 30 and 40. This process ends.

In step S5, the electronic control unit 200 sets the target air-fuel ratio of the first exhaust air-fuel ratio (hereinafter referred to as “first target air-fuel ratio”) to a predetermined lean air-fuel ratio (for example, 15.6), and sets the second exhaust. The target air-fuel ratio of the air-fuel ratio (hereinafter referred to as “second target air-fuel ratio”) is set to a predetermined rich air-fuel ratio (for example, 13.6), and the excess air ratio λ is 1 in each cylinder 11 of the first bank 10a. A larger air-fuel mixture (lean air-fuel mixture) is burned, and an air-fuel ratio λ of less than 1 is burned in each cylinder 11 of the second bank 10b (rich air-fuel mixture). As a result, the filter 32 of the first collection device 30 is regenerated.

In step S6, the electronic control unit 200 sets the first target air-fuel ratio to the lean air-fuel ratio, and the elapsed time te1 from setting the second target air-fuel ratio to the rich air-fuel ratio becomes equal to or greater than the predetermined switching time treg. Determine if it is. If the elapsed time t is equal to or longer than the switching time treg, the electronic control unit 200 proceeds to the process of step S7. On the other hand, if the elapsed time te1 is less than the switching time treg, the electronic control unit 200 performs the process of step S6 again after a predetermined time has passed.

In step S7, the electronic control unit 200 sets the first target air-fuel ratio to the rich air-fuel ratio (for example, 13.6), sets the second target air-fuel ratio to the lean air-fuel ratio (for example, 15.6), and sets the first target air-fuel ratio. An air-fuel mixture (rich air-fuel mixture) having an excess air-fuel ratio λ of less than 1 is burned in each cylinder 11 of the bank 10a, and an air-fuel ratio (lean) having an excess air-fuel ratio λ greater than 1 in each cylinder 11 of the second bank 10b. Air-fuel mixture) is burned. As a result, the filter 42 of the second collection device 40 is regenerated.

In step S8, the electronic control unit 200 sets the first target air-fuel ratio to the rich air-fuel ratio, and the elapsed time te2 from setting the second target air-fuel ratio to the lean air-fuel ratio becomes equal to or greater than the predetermined switching time treg. Determine if it is. If the elapsed time te2 is equal to or longer than the switching time treg, the electronic control unit 200 proceeds to the process of step S9. On the other hand, if the elapsed time te2 is less than the switching time treg, the electronic control unit 200 performs the process of step S8 again after a predetermined time has passed.

In step S9, the electronic control unit 200 calculates the first estimated PM deposition amount Qpm1 and the second estimated PM deposition amount Qpm2 in the same manner as in step S1.

In step S10, in the electronic control unit 200, the estimated total PM accumulation amount Qpm (the total value of the first estimated PM accumulation amount Qpm1 and the second estimated PM accumulation amount Qpm2 calculated in step S9) is set to a predetermined regeneration end threshold value Qthr2. It is determined whether or not it is (<Qthr1) or less. If the estimated total PM accumulation amount Qpm is equal to or less than the regeneration start threshold value Qthr2, the electronic control unit 200 proceeds to the process of step S11 in order to end the filter regeneration control. On the other hand, the electronic control unit 200 returns to the process of step S5 if the estimated total PM accumulation amount Qpm is larger than the regeneration start threshold value Qthr2.

In step S11, the electronic control unit 200 returns the first target air-fuel ratio and the second target air-fuel ratio to the stoichiometric air-fuel ratio, respectively, and ends the filter regeneration control.

FIG. 4 is a time chart illustrating the operation of the filter reproduction control according to the present embodiment.

When it is determined at time t1 that the estimated total PM accumulation amount Qpm is equal to or higher than the regeneration start threshold value Qthr1, the filter regeneration control is started. Specifically, the first target air-fuel ratio is set to a predetermined lean air-fuel ratio, and the second target air-fuel ratio is set to a predetermined rich air-fuel ratio. The difference value between the theoretical air-fuel ratio and the predetermined lean air-fuel ratio is substantially the same as the difference value between the theoretical air-fuel ratio and the predetermined rich air-fuel ratio.

As a result, the air-fuel mixture (lean air-fuel mixture) having an excess air ratio λ larger than 1 can be burned in each cylinder 11 of the first bank 10a to introduce an exhaust gas containing oxygen into the first collection device 30. Therefore, the filter 32 of the first collection device 30 can be regenerated. Therefore, after time t1, the amount of PM deposited in the filter 32 (corresponding to Qpm1 in FIG. 4) has decreased.

Further, since the air-fuel mixture (lean air-fuel mixture) having an excess air ratio λ larger than 1 is burned in each cylinder 11 of the first bank 10a, the NOx concentration is relatively high in the first exhaust passage 21. Exhaust is discharged. Since this exhaust gas joins and flows into the collective exhaust passage 23, the NOx concentration on the inlet side of the catalyst device 50 becomes high. On the other hand, since the air-fuel mixture (rich air-fuel mixture) having an excess air ratio λ of less than 1 is burned in each cylinder 11 of the second bank 10b, the second exhaust passage 22 is relatively unburned gas. Exhaust gas containing a large amount of gas is discharged. This exhaust also joins and flows into the collective exhaust passage 23. As a result, exhaust gas having a stoichiometric air-fuel ratio in which these exhaust gases are merged flows through the collective exhaust passage 23. That is, since the exhaust gas having a stoichiometric air-fuel ratio can flow into the catalyst device 50, the three-way catalyst 52 in the catalyst device 50 can purify unburned gas (HC, CO) and NOx with a high purification rate. , The NOx concentration on the outlet side of the catalyst device 50 can be made almost zero.

When the predetermined switching time treg elapses from the time t1, the first target air-fuel ratio is set to the predetermined rich fuel ratio, the second target air-fuel ratio is set to the predetermined lean air-fuel ratio, and the estimated total PM is set. This control is alternately repeated until the accumulated amount Qpm becomes equal to or less than the regeneration end threshold Qthr2.

That is, at the time t3 when the predetermined switching time treg elapses from the time t2, the first target air-fuel ratio is set to the predetermined lean air-fuel ratio again, and the second target air-fuel ratio is set to the predetermined rich air-fuel ratio. At the time t4 when the predetermined switching time treg elapses from the time t3, the first target air-fuel ratio is set to the predetermined rich fuel ratio again, and the second target air-fuel ratio is set to the predetermined lean air-fuel ratio. Then, at time t5, when the estimated total PM accumulation amount Qpm becomes equal to or less than the regeneration end threshold value Qthr2, the filter regeneration control is terminated, and the first target air-fuel ratio and the second target air-fuel ratio are returned to the theoretical air-fuel ratios, respectively.

The internal combustion engine 100 according to the present embodiment described above includes an engine having a first bank 10a (first cylinder group) having at least one cylinder 11 and a second bank 10b (second cylinder group) having at least one cylinder. The main body 10, the first exhaust passage 21 from which the exhaust generated in the first bank 10a is discharged, the second exhaust passage 22 from which the exhaust generated in the second bank 10b is discharged, and the first exhaust passage 21 are provided. The first PM collecting device 30 (first filter) that collects the particulate matter in the exhaust gas, and the second PM collecting device 40 (the second PM collecting device 40) that is provided in the second exhaust passage 22 and collects the particulate matter in the exhaust gas. In order to merge the second filter) with the exhausts of the first exhaust passage 21 and the second exhaust passage 22, the first exhaust is downstream from the first PM collecting device 30 and the second PM collecting device 40 in the exhaust flow direction. It includes a collective exhaust passage 23 formed by assembling the passage 21 and the second exhaust passage 22, and a three-way catalyst 52 provided in the collective exhaust passage 23.

Then, the electronic control unit 200 (control device) for controlling the internal combustion engine has an air-fuel ratio of the exhaust flowing into the three-way catalyst 52 when the first PM collecting device 30 and the second PM collecting device 40 are regenerated. Combusts an air-fuel mixture having an excess air ratio of more than 1 in the cylinder 11 of the first bank 10a and an air-fuel mixture having an excess air ratio of less than 1 in the cylinder 11 of the second bank 10b so that The air-fuel mixture having an excess air ratio of less than 1 is burned in the cylinder 11 of the first bank 10a so that the combustion control and the air-fuel ratio of the exhaust flowing into the three-way catalyst 52 become the stoichiometric air-fuel ratio, and the second bank 10b The control for burning the air-fuel mixture having an excess air ratio of more than 1 in the cylinder 11 of the above is alternately performed.

As a result, when the air-fuel mixture (lean air-fuel mixture) having an excess air ratio λ larger than 1 is burned in each cylinder 11 of the first bank 10a, the filter 32 of the first collection device 30 is regenerated. Can be done.

At this time, the lean air-fuel ratio exhaust is discharged to the first exhaust passage 21, while the rich air-fuel ratio exhaust is discharged to the second exhaust passage 22, so that the collective exhaust passage 23 is discharged. , The exhaust of the stoichiometric air-fuel ratio where these exhausts merge will flow. That is, since the exhaust gas having a stoichiometric air-fuel ratio can flow into the catalyst device 50, the three-way catalyst 52 in the catalyst device 50 can purify unburned gas (HC, CO) and NOx with a high purification rate. ..

Then, the air-fuel mixture (lean air-fuel mixture) having an excess air ratio λ greater than 1 is burned in each cylinder 11 of the first bank 10a, and the excess air ratio λ is less than 1 in each cylinder 11 of the second bank 10b. From the state in which the air-fuel mixture (rich air-fuel mixture) is being burned, the air-fuel mixture (rich air-fuel mixture) having an excess air ratio λ of less than 1 is burned in each cylinder 11 of the first bank 10a, and each of the second banks 10b is burned. By switching to a state in which the air-fuel mixture (lean air-fuel mixture) having an excess air ratio λ larger than 1 is being burned in the cylinder 11, the filter 42 of the second collection device 30 can be regenerated next.

At this time as well, the exhaust gas having a theoretical air-fuel ratio at which the exhaust gases of the first exhaust passage 21 and the second exhaust passage 22 are merged flows through the collective exhaust passage 23, so that the three-way catalyst 52 in the catalyst device 50 is used. , Unburned gas (HC, CO) and NOx can be purified with a high purification rate.

Therefore, according to the present embodiment, it is possible to suppress deterioration of exhaust emissions during filter regeneration.

Although the embodiments of the present invention have been described above, the above embodiments are only a part of the application examples of the present invention, and the technical scope of the present invention is limited to the specific configurations of the above embodiments. No.

10 Engine body 10a 1st bank (1st cylinder group)
10b 2nd bank (2nd cylinder group)
21 1st exhaust passage 22 2nd exhaust passage 23 Collective exhaust passage 30 1st PM collecting device (1st filter)
40 2nd PM collector (2nd filter)
52 Three-way catalyst 100 Internal combustion engine 200 Electronic control unit (control device)

Claims (1)

An engine body including a first cylinder group having at least one cylinder and a second cylinder group having at least one cylinder,
The first exhaust passage through which the exhaust generated in the first cylinder group is discharged, and
A second exhaust passage through which the exhaust generated in the second cylinder group is discharged, and
A first filter provided in the first exhaust passage and collecting particulate matter in the exhaust,
A second filter provided in the second exhaust passage and collecting particulate matter in the exhaust,
In order to merge the exhausts of the first exhaust passage and the second exhaust passage, the first exhaust passage and the second exhaust passage are assembled on the downstream side in the exhaust flow direction from the first filter and the second filter. The collective exhaust passage formed by letting
The three-way catalyst provided in the collective exhaust passage and
An internal combustion engine control device for controlling an internal combustion engine.
When the first filter and the second filter are regenerated, the excess air ratio in the cylinders of the first cylinder group is set to 1 so that the air-fuel ratio of the exhaust flowing into the three-way catalyst becomes the stoichiometric air-fuel ratio. The stoichiometric air-fuel ratio is the control of burning a large air-fuel mixture and burning the air-fuel mixture having an excess air ratio of less than 1 in the cylinders of the second cylinder group, and the air-fuel ratio of the exhaust flowing into the three-way catalyst. As described above, the control is such that the air-fuel mixture having an excess air ratio of less than 1 is burned in the cylinders of the first cylinder group and the air-fuel ratio having an excess air ratio of more than 1 is burned in the cylinders of the second cylinder group. , Are configured to be performed alternately,
Internal combustion engine control device.

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