JP4425003B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine that purifies NOx in exhaust gas with a catalyst and controls an exhaust gas recirculation flow rate that circulates from an exhaust system to an intake system.

  As a conventional control device for this type of internal combustion engine, for example, one disclosed in Patent Document 1 is known. In this control device, the reference exhaust gas recirculation flow rate (hereinafter referred to as “reference EGR amount”) to be recirculated to the intake pipe is set according to the rotational speed of the internal combustion engine and the pressure in the intake pipe, and when the catalyst is deteriorated, The reference EGR amount is corrected to the increase side. Specifically, when the travel distance of a vehicle equipped with an internal combustion engine is greater than a predetermined value and the difference between the NOx concentration discharged from the catalyst and the reference NOx concentration is greater than a predetermined value, the catalyst deteriorates. It is determined that When it is determined that the catalyst has deteriorated, the reference EGR amount is corrected to the increase side, and the EGR valve is controlled so that the corrected reference EGR amount is obtained. Thus, the amount of NOx discharged into the atmosphere is reduced by lowering the combustion temperature and reducing the amount of NOx produced.

  However, in the conventional control device for an internal combustion engine, as described above, when the reference EGR amount is corrected to the increase side, only the EGR valve is controlled, and the desired EGR amount may not be obtained. . That is, since the exhaust gas recirculation operation is performed using the differential pressure between the upstream side and the downstream side of the EGR valve, the actual EGR amount is not changed in the intake pipe even if the valve opening of the EGR valve is constant. Varies depending on the pressure. For this reason, for example, when the differential pressure between the upstream side and the downstream side of the EGR valve is small and the required EGR amount to be circulated is large, the EGR valve is fully opened only by controlling the opening degree of the EGR valve. At this point, the EGR amount reaches the upper limit, and it becomes difficult to secure the required EGR amount. For this reason, in this case, the effect of suppressing the combustion temperature by EGR cannot be sufficiently obtained, and the amount of NOx produced cannot be sufficiently reduced, so that NOx in the exhaust gas exceeding the purification performance of the catalyst flows into the catalyst. As a result, a large amount of NOx that could not be treated with the catalyst may be discharged into the atmosphere.

  Further, in this control device, whether or not the catalyst is deteriorated is determined according to a comparison result between the difference between the actual NOx concentration and the reference NOx concentration and a predetermined value, and it is determined that the catalyst is deteriorated. In addition, the reference EGR amount is simply increased. For this reason, the EGR amount is set so that the amount of NOx discharged does not exceed the regulation value in both the state where the catalyst is determined to be deteriorated and the state where it is not determined that the catalyst is deteriorated. It must be set on the safe side, that is, higher. For this reason, the combustion state tends to become unstable, and the particulates discharged from the internal combustion engine increase.

  The present invention has been made to solve such a problem. When the catalyst is deteriorated, a sufficient exhaust gas flow rate can be secured, thereby reliably reducing the amount of NOx emissions. An object of the present invention is to provide a control device for an internal combustion engine.

JP-A-5-113157

In order to achieve this object, the invention according to claim 1 purifies NOx in exhaust gas with a catalyst (NOx catalyst 14 in the embodiment (hereinafter the same in this section)) and exhaust system (exhaust pipe 10). A control device 1 for the internal combustion engine 3 that controls the exhaust gas recirculation flow rate (target EGR amount MEGR) that circulates from the intake system (intake pipe 8) to the intake system (intake pipe 8). Crank angle sensor 20, accelerator opening 28), intake air amount control means (ECU 2, throttle valve 9a) for controlling the intake air amount (intake air amount GTH) flowing through the intake system according to the detected operating state, catalyst The deterioration state detection means (ECU 2, first LAF sensor 25, second LAF sensor 26, steps 3 and 4 in FIG. 3) for detecting the deterioration state of the exhaust gas when the deterioration of the catalyst is detected Exhaust gas recirculation amount compensation means for correcting the flow rate increasing side and (ECU 2, EGR control valve 6a, step 8,9 of FIG. 3), in accordance with the corrected exhaust gas recirculation amount, the more the exhaust gas recirculation amount is large, the intake air amount control intake air quantity correcting means for correcting the amount of intake air is controlled by means more to the decrease side (ECU 2, a throttle valve 9a, step 10 of FIG. 3), characterized in that it comprises a.

According to this configuration, the operating state of the internal combustion engine is detected by the operating state detection unit, and the intake air amount flowing through the intake system is controlled by the intake air amount control unit according to the operating state. Further, when the deterioration of the catalyst is detected by the deterioration state detection means, the exhaust gas circulation flow rate correction means corrects the exhaust gas circulation flow rate to the increase side. Further, according to the corrected exhaust gas recirculation flow rate, the intake air amount correction unit corrects the intake air amount to a lower side as the exhaust gas recirculation flow rate is larger . Therefore, by correcting the intake air amount to the decreasing side according to the exhaust gas flow rate, the negative pressure of the intake system can be increased, and the differential pressure between the exhaust system and the intake system can be increased, and the exhaust gas is taken into the intake air. The system can be sufficiently refluxed. As a result, a sufficient exhaust gas flow rate can be ensured, whereby the amount of NOx emission can be reliably reduced.

  The invention according to claim 2 is the control apparatus 1 for the internal combustion engine 3 according to claim 1, wherein the deterioration state detection means detects deterioration degree detection means (ECU 2, first LAF sensor 25, The exhaust gas recirculation flow rate correction means corrects the exhaust gas recirculation flow rate according to the detected degree of deterioration of the catalyst (steps 8 and 9 in FIG. 3). It is characterized by that.

  According to this configuration, the degree of deterioration of the catalyst is detected by the degree of deterioration detection means, and the exhaust gas recirculation flow rate is corrected to increase according to this deterioration degree. Therefore, the exhaust gas recirculation flow amount is determined according to the actual deterioration degree of the catalyst. It can be set to an appropriate amount without excess or deficiency. Thereby, not only the NOx emission amount but also the particulate emission amount can be suppressed.

It is a figure showing a schematic structure of an internal-combustion engine to which a control device by an embodiment of the present invention is applied. It is a figure which shows the control apparatus of FIG. 1 schematically. It is a flowchart which shows the process which controls the amount of EGR. It is an example of the map used by the process of FIG. It is an example of the map used by the process of FIG.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of an internal combustion engine according to an embodiment of the present invention, and FIG. 2 shows a schematic configuration of a control device 1. The internal combustion engine (hereinafter referred to as “engine”) 3 is, for example, an in-line 4-cylinder (only one shown) diesel engine mounted on a vehicle (not shown).

  As shown in the figure, the engine 3 includes a piston 3a and a cylinder head 3b for each cylinder, and a combustion chamber 3c is formed by the piston 3a and the cylinder head 3b. An intake pipe 8 (intake system) and an exhaust pipe 10 (exhaust system) are connected to the cylinder head 3b, and a fuel injection valve (hereinafter referred to as "injector") 4 is attached so as to face the combustion chamber 3c. Yes.

  The injector 4 is disposed in the center of the top wall of the combustion chamber 3c, and is connected to the high-pressure pump 4a via the fuel pipe 4b. The fuel is boosted from a fuel tank (not shown) to a high pressure by the high-pressure pump 4 a and then supplied to the injector 4 in a state of being regulated by a regulator (not shown) and injected through the injector 4. Is done. Further, the injector 4 is controlled by a drive signal from the ECU 2 to be described later for a fuel injection time and a fuel injection timing (a valve opening timing and a valve closing timing) that are valve opening times.

  A magnet rotor 20 a is attached to the crankshaft 3 d of the engine 3. The magnet rotor 20a constitutes the crank angle sensor 20 together with the MRE pickup 20b. The crank angle sensor 20 (operating state detection means) outputs a CRK signal and a TDC signal, which are pulse signals, with the rotation of the crankshaft 3d.

  The CRK signal is output every predetermined crank angle (for example, 30 °). The ECU 2 obtains the rotational speed NE (hereinafter referred to as “engine rotational speed”) NE of the engine 3 based on the CRK signal. The TDC signal is a signal indicating that the piston 3a of each cylinder is at a predetermined crank angle position near the TDC (top dead center) at the start of the intake stroke, and in this example of the 4-cylinder type, every crank angle of 180 °. Is output.

  The intake pipe 8 is provided with an air flow sensor 21 and a throttle valve mechanism 9 in order from the upstream side. The air flow sensor 21 detects an intake air amount GTH (intake amount) passing through the throttle valve 9 a of the throttle valve mechanism 9 and outputs a detection signal to the ECU 2.

  A supercharging pressure control mechanism 5 is disposed downstream of the airflow sensor 21 in the intake pipe 8. The supercharging pressure control mechanism 5 includes a supercharger 5a attached to the intake pipe 8 and the exhaust pipe 10, an actuator 5b connected to the supercharger 5a, and a vane opening control valve 5c connected to the actuator 5b. Etc. The supercharger 5a is a so-called turbocharger, and includes a turbine rotor 5d and a housing 5e. The turbine rotor 5d is an assembly of compressor blades and turbine blades (both not shown) and the like, and is built in a housing 5e that constitutes the intake pipe 8 and the exhaust pipe 10, and is rotatably attached thereto. ing. When the turbine blade of the turbine rotor 5d is rotationally driven by the exhaust gas in the exhaust pipe 10, the supercharger 5a adds the intake air in the intake pipe 8 by rotationally driving the compressor blade integrated therewith. Perform supercharging operation.

  The supercharger 5a includes a plurality of variable vanes 5f (only two shown). These variable vanes 5f are for changing the supercharging pressure generated by the supercharger 5a, and are rotatably attached to the wall of the portion of the housing 5e that houses the turbine blades. Each variable vane 5f is mechanically connected to the actuator 5b, and its opening degree (hereinafter referred to as “vane opening degree”) is changed by being driven by the actuator 5b.

  On the other hand, the actuator 5 b is a diaphragm type that operates by negative pressure, and is connected to the negative pressure pump 12 via the negative pressure pipe 11. In the middle of the negative pressure pipe 11, the vane opening degree control valve 5c is provided. The negative pressure pump 12 is connected to a drive shaft (not shown) of the engine 3, generates a negative pressure when driven by the engine 3 during operation of the engine 3, and supplies the negative pressure to the vane opening control valve 5 c. To do. The vane opening degree control valve 5c is composed of an electromagnetic valve, and the negative pressure supplied to the actuator 5b changes when the valve opening degree VL changes according to the drive signal from the ECU 2. The supercharging pressure is controlled by changing the vane opening degree of the variable vane 5f through the actuator 5b in accordance with the change in the negative pressure. More specifically, when the vane opening degree of the variable vane 5f is changed to the closing side, the flow rate of exhaust gas flowing into the turbine blade increases, thereby increasing the intake air amount GTH flowing downstream from the compressor blade. The supercharging pressure increases. Further, a supercharging pressure sensor 22 is attached to the intake pipe 8 downstream of the supercharging pressure control mechanism 5, and the supercharging pressure sensor 22 detects the supercharging pressure PACT in the intake pipe 8. The detection signal is output to the ECU 2.

  The throttle valve mechanism 9 includes a throttle valve 9a and an actuator 9b that opens and closes the throttle valve 9a. The throttle valve 9a (intake air amount control means and intake air amount correction means) is rotatably provided in the middle of the intake pipe 8, and the intake air amount GTH is controlled according to the opening. The actuator 9b is a combination of a motor connected to the ECU 2 and a gear mechanism (both not shown). The actuator 9b is driven by a drive signal from the ECU 2, thereby opening the throttle valve 9a (hereinafter referred to as "throttle valve"). TH) is controlled.

  Further, the portion of the intake pipe 8 on the downstream side of the throttle valve 9a is an intake manifold 8a including one collecting portion and four branch portions branched therefrom. Further, the intake manifold 8a is divided into a swirl line 8b and a bypass line 8c from the collecting part to each branch part, and these lines 8b and 8c each burn through two intake ports. It communicates with the chamber 3c.

  A swirl control mechanism 7 is provided in the bypass line 8c. The swirl control mechanism 7 includes a swirl valve 7a, an actuator 7b that drives to open and close the swirl valve 7a, a swirl control valve 7c, and the like. The swirl control mechanism 7 generates a swirl in the combustion chamber 3c by changing the opening of the swirl valve 7a, and the air-fuel mixture in the combustion chamber 3c is agitated by this swirl. The actuator 7b and the swirl control valve 7c are provided in the middle of the negative pressure pipe 11, and these are configured similarly to the actuator 5b and the vane opening control valve 5c of the supercharging pressure control mechanism 5, respectively. That is, the swirl control valve 7c is constituted by an electromagnetic valve, and the valve opening VLS changes according to the drive signal from the ECU 2, and the negative pressure supplied to the diaphragm actuator 7b changes accordingly. By doing so, the opening degree of the swirl valve 7a is controlled.

  An EGR pipe 6 is connected between the intake pipe 8 and the exhaust pipe 10. One end of the EGR pipe 6 is connected to the upstream side of the supercharger 5a of the exhaust pipe 10, and the other end is connected to a swirl line 8b of the intake manifold 8a. An EGR control valve 6 a is attached to the EGR pipe 6. The EGR control valve 6a (exhaust gas flow rate correcting means) is configured by a linear electromagnetic valve, and the valve lift amount linearly changes in accordance with a drive signal from the ECU 2. The ECU 2 controls the opening degree of the EGR pipe 6, that is, the EGR amount by controlling the valve lift amount of the EGR control valve 6 a according to the operating state of the engine 3. The EGR control valve 6a is provided with a valve lift amount sensor 24. The valve lift amount sensor 24 detects the valve lift amount LACT of the EGR control valve 6a and outputs a detection signal to the ECU 2. .

  The exhaust pipe 10 is provided with a catalyst device 13 on the downstream side of the supercharging pressure control mechanism 5. This catalyst device 13 is a combination of a NOx catalyst 14 and a three-way catalyst (not shown). The NOx catalyst 14 (catalyst) has an air / fuel ratio of the air-fuel mixture supplied to the engine 3 that is higher than the stoichiometric air / fuel ratio. In the case of lean, it is purified by adsorbing NOx in the exhaust gas, and when the air-fuel ratio is richer than the stoichiometric air-fuel ratio, the adsorbed NOx is reduced. The three-way catalyst purifies CO, HC and NOx in the exhaust gas by an oxidation-reduction action.

  Further, the exhaust pipe 10 is provided with a first LAF sensor 25 on the upstream side of the NOx catalyst 14 and a second LAF sensor 26 on the downstream side. The first and second LAF sensors 25 and 26 (degradation state detection means and deterioration degree detection means) are configured to detect oxygen concentration in exhaust gas in a wide range of air-fuel ratios from a rich region richer than the stoichiometric air-fuel ratio to an extremely lean region. Are detected linearly, and detection signals OACT1 and OACT2 representing them are output to the ECU 2, respectively.

  A throttle valve opening sensor 23, an intake pipe absolute pressure sensor 27, and an accelerator opening sensor 28 are connected to the ECU 2. The throttle valve opening sensor 23 detects the throttle valve opening TH and outputs a detection signal to the ECU 2. The intake pipe absolute pressure sensor 27 detects the intake pipe absolute pressure PBA, which is the absolute pressure in the intake pipe 8, and outputs a detection signal to the ECU 2. The accelerator opening sensor 28 (operating state detecting means) detects an accelerator opening AP, which is an operation amount of an accelerator pedal (not shown), and outputs a detection signal to the ECU 2.

  In the present embodiment, the ECU 2 constitutes an operation state detection means, an intake air amount control means, a deterioration state detection means, a deterioration degree detection means, an exhaust gas recirculation flow rate correction means, and an intake air amount correction means, and includes an I / O interface, The microcomputer is composed of a CPU, RAM, ROM and the like. The detection signals of the various sensors 20 to 28 are input to the CPU via the I / O interface.

  Based on these detection signals, the CPU determines the operating state of the engine 3 according to a program stored in the ROM and the like, and controls the intake air amount GTH supplied to the engine 3 based on the determined operating state. . Specifically, the intake air amount GTH is controlled by setting the throttle valve opening TH according to the engine speed NE and the accelerator opening AP. Further, the deterioration state of the NOx catalyst 14 is detected, and the EGR amount is controlled according to the detected deterioration state.

  FIG. 3 is a flowchart showing a process for detecting the deterioration state of the NOx catalyst 14 and controlling the EGR amount and the like according to the detected deterioration state. This process is executed in synchronization with the generation of the TDC signal. In this process, first, in step 1 (illustrated as “S1”, the same applies hereinafter), the map shown in FIG. 4 is searched according to the engine speed NE and the intake pipe absolute pressure PBA, whereby the EGR amount is not deteriorated. A time map value EGRMAP is obtained and set as the target EGR amount MEGR (step 2). This map defines the amount of EGR to be recirculated when the NOx catalyst 14 is not deteriorated. The map value EGRMAP for non-deterioration is such that the larger the engine speed NE is, the more the intake pipe absolute pressure PBA is. A larger value is set to a larger value. This is because the higher the engine speed NE and the higher the intake pipe absolute pressure PBA, the more the NOx generation amount tends to increase due to the increase in the combustion temperature.

  Returning to FIG. 3, in step 3 following step 2, a deterioration degree parameter NOXC is calculated. This deterioration degree parameter NOXC is downstream of the oxygen concentration OACT1 detected by the first LAF sensor 25 disposed upstream of the NOx catalyst 14 when the air-fuel ratio is changed from the lean side to the rich side with respect to the stoichiometric air-fuel ratio. This is calculated as a response delay of the oxygen concentration OACT2 detected by the second LAF sensor 26 arranged on the side. That is, the greater the degree of deterioration of the NOx catalyst 14, the more difficult NOx is adsorbed to the NOx catalyst 14, and the reduction time due to enrichment is shortened, so that the response time of the downstream oxygen concentration OACT2 becomes faster. The parameter NOXC represents that the degree of deterioration of the NOx catalyst 14 is larger as the value is smaller.

  Next, it is determined whether or not the deterioration degree parameter NOXC is larger than a predetermined determination value NOJUD (step 4). When the determination result is YES and NOXC> NOJUD, it is assumed that the NOx catalyst 14 has sufficiently adsorbed NOx and the NOx catalyst 14 has not deteriorated, and the target EGR amount MEGR obtained in step 2 above is obtained. Accordingly, the valve lift amount of the EGR control valve 6a is determined (step 5), and this process is terminated.

  When the determination result of step 4 is NO and NOXC ≦ NOJUD, it is determined that the NOx catalyst 14 has deteriorated, and a map value ZEGR for deterioration of the EGR amount is obtained by searching the map shown in FIG. 6) The deterioration EGR amount MZEGR is set (step 7).

  This map defines the EGR amount to be recirculated when the NOx catalyst 14 is deteriorated at a very high predetermined deterioration degree. As in FIG. 4, the deterioration map value ZEGR is set to a larger value as the engine speed NE and the intake pipe absolute pressure PBA are larger. Further, the deterioration map value ZEGR is set to a value larger than the non-deterioration map value EGRMAP in FIG. 4 in the entire region of the engine speed NE and the intake pipe absolute pressure PBA. This is because the NOx emission amount is suppressed by increasing the EGR amount in accordance with the decrease in the purification performance accompanying the deterioration of the NOx catalyst 14.

  Next, the target EGR amount MEGR is set according to the deterioration degree parameter NOXC calculated in Step 3 (Step 8). The target EGR amount MEGR is obtained by performing an interpolation operation according to the deterioration degree parameter NOXC using the target EGR amount MEGR obtained in step 2 and the deterioration-time EGR amount MZEGR obtained in step 7.

  Next, in steps 9 to 11, the following control is executed according to the target EGR amount MEGR obtained in step 8. First, the valve lift amount of the EGR control valve 6a is determined according to the target EGR amount MEGR (step 9). Next, a throttle valve opening TH is determined by searching a table (not shown) (step 10). In this table, the throttle valve opening TH is set to a smaller value as the target EGR amount MEGR is larger. As described above, when the NOx catalyst 14 is deteriorated, the throttle valve opening TH is controlled to be decreased according to the target EGR amount MEGR, and the negative pressure in the intake pipe 8 is increased, whereby the exhaust pipe The pressure difference between the intake pipe 10 and the intake pipe 8 can be further increased, so that a sufficient amount of EGR can be ensured.

  Next, the target supercharging pressure and the valve opening VLS of the swirl control valve 7c of the swirl control mechanism 7 are determined according to the target EGR amount MEGR (step 11). Specifically, the target supercharging pressure is set to a larger value as the target EGR amount MEGR is larger, and the valve opening degree VLS of the swirl control valve 7c is set to a smaller value. This is due to the following reason. As the throttle valve opening TH is controlled to decrease in step 10, the charging efficiency tends to decrease and the intake air amount GTH tends to be insufficient. In such a case, the combustion state becomes unstable. . Further, when the target EGR amount MEGR increases, the exhaust gas flowing into the supercharger 5a becomes insufficient, and the supercharging pressure decreases. For this reason, the minimum intake air amount GTH necessary for combustion can be secured by setting the target supercharging pressure to the increase side according to the target EGR amount MEGR, thereby maintaining a stable combustion state. Can do. Further, when the target EGR amount MEGR increases, the NOx emission amount tends to decrease while the particulate emission amount tends to increase. Therefore, by setting the valve opening VLS of the swirl control valve 7c to the decreasing side, the swirl valve 7a is controlled to the closed side, and the swirl generated in the combustion chamber 3c is strengthened, thereby homogenizing the air-fuel mixture. Accordingly, the amount of particulates discharged can be reduced.

  As described above, according to the present embodiment, the deterioration degree parameter NOXC is calculated based on the oxygen concentrations OACT1 and OACT2 detected by the first and second LAF sensors 25 and 26, and this value is smaller than the determination value NOJUD. In (NOXC ≦ NOJUD), assuming that the NOx catalyst 14 is deteriorated, the target EGR amount MEGR is set to a larger value than when the NOx catalyst 14 is not deteriorated (steps 2, 7, and 8). Further, the throttle valve opening TH is determined according to the target EGR amount MEGR (step 10), and the intake air amount GTH is corrected to the decreasing side. Therefore, when the NOx catalyst 14 is deteriorated, the negative air pressure in the intake pipe 8 is increased by correcting the intake air amount GTH to the decrease side according to the target EGR amount MEGR, and the exhaust pipe 10 and the intake pipe The differential pressure with respect to the pipe 8 can be increased, and the exhaust gas can be sufficiently circulated through the intake pipe 8. As a result, a sufficient EGR amount can be ensured, and thereby the NOx emission amount can be reliably reduced.

  Furthermore, since the target EGR amount MEGR is calculated according to the calculated deterioration degree parameter NOXC, the target EGR amount MEGR can be set to an appropriate amount that does not exceed the shortage according to the actual deterioration degree of the NOx catalyst 14. Thereby, not only the NOx emission amount but also the particulate emission amount can be suppressed.

  In addition, this invention can be implemented in a various aspect, without being limited to embodiment described. For example, in the described embodiment, the deterioration degree parameter NOXC is calculated using the oxygen concentrations OACT1 and OACT2 detected by the first and second LAF sensors 25 and 26 disposed on the upstream and downstream sides of the NOx catalyst 14. You may obtain | require by the other suitable method. For example, a LAF sensor or an O2 sensor is provided downstream of the NOx catalyst 14, and the deterioration degree of the NOx catalyst 14 is calculated according to the response time of the sensor when the air-fuel ratio is set to be leaner than the stoichiometric air-fuel ratio. Also good. Alternatively, a NOx sensor may be provided on the downstream side of the NOx catalyst 14, the downstream NOx concentration may be directly detected, and the deterioration degree of the NOx catalyst 14 may be calculated according to the detection result.

  Moreover, although this embodiment is an example which applied this invention to the diesel engine, you may apply not only to this but to a gasoline engine. The supercharger is not limited to a turbocharger, and may be a mechanical supercharger such as a supercharger. The present invention is not limited to an internal combustion engine mounted on a vehicle, but is applied to various industrial internal combustion engines including a marine vessel propulsion engine such as an outboard motor having a crankshaft arranged in a vertical direction. It is possible. In addition, the detailed configuration can be changed as appropriate within the scope of the gist of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control apparatus 2 ECU (Operating state detection means, intake air amount control means, deterioration state detection means,
Deterioration degree detection means, exhaust gas recirculation flow correction means and intake air amount correction means)
3 Engine 6a EGR control valve 8 Intake pipe 9a Throttle valve 10 Exhaust pipe 14 NOx catalyst 20 Crank angle sensor 25 First LAF sensor 26 Second LAF sensor 28 Accelerator opening sensor NE Engine speed AP Accelerator opening GTH Intake air amount TH Throttle valve Opening degree OACT1 Oxygen concentration OACT2 Oxygen concentration NOXC Degradation degree parameter MEGR Target EGR amount

Claims (2)

A control device for an internal combustion engine that purifies NOx in exhaust gas with a catalyst and controls an exhaust gas recirculation flow rate that circulates from an exhaust system to an intake system,
Operating state detecting means for detecting the operating state of the internal combustion engine;
Intake amount control means for controlling the amount of intake air flowing through the intake system according to the detected operating state;
A deterioration state detecting means for detecting a deterioration state of the catalyst;
Exhaust gas flow rate correction means for correcting the exhaust gas flow rate to the increase side when deterioration of the catalyst is detected;
In accordance with the corrected exhaust gas recirculation flow rate, as the exhaust gas recirculation flow rate is larger, an intake air amount correction unit that corrects the intake air amount controlled by the intake air amount control unit to a decreasing side;
A control device for an internal combustion engine, comprising: The deterioration state detecting means includes a deterioration degree detecting means for detecting a deterioration degree of the catalyst,
The control apparatus for an internal combustion engine according to claim 1, wherein the exhaust gas recirculation flow rate correcting means corrects the exhaust gas recirculation flow rate in accordance with the detected degree of deterioration of the catalyst.

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