JP2010174818A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suitably perform, in an internal combustion engine mounted with an exhaust recirculation mechanism, exhaust temperature control for suppressing a temperature rise of a catalyst, while reflecting a delay amount from basic ignition timing in the internal combustion engine. <P>SOLUTION: An ECU 35 includes a condition determination section operating the exhaust recirculation device 40 when a predetermined EGR performance condition is met, a catalyst temperature rise detection section detecting a temperature rise of a predetermined value or higher of the catalyst 20 when the exhaust recirculation device 40 is operated, and an exhaust temperature falling control section for reducing exhaust temperature when a temperature rise of the predetermined value or higher of the catalyst 20 is detected. The catalyst temperature rise detection section detects a temperature rise of the predetermined value or higher of the catalyst 20 when a delay amount from the basic ignition timing exceeds a predetermined value preset according to an engine load and when a catalyst temperature estimated based on the engine load and an engine rotation speed exceeds a predetermined temperature. The exhaust temperature falling control section increases a recirculation amount of exhaust gas in the exhaust recirculation device 40. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to control of an internal combustion engine equipped with an exhaust gas recirculation mechanism.

  An engine system equipped with an exhaust gas recirculation device that lowers the combustion temperature in the internal combustion engine to suppress a rise in exhaust temperature and improve fuel efficiency by recirculating a part of the exhaust gas of the internal combustion engine to the intake system of the internal combustion engine Is installed.

  In Japanese Patent Laying-Open No. 2006-266221 (Patent Document 1), in a temperature increase control device of an aftertreatment device including an exhaust purification catalyst and a diesel particulate filter, in order to prevent an excessive temperature increase of the catalyst after completion of the temperature increase control. Further, there is disclosed a catalyst cooling promoting means for promoting cooling of the exhaust purification catalyst until the temperature of the exhaust purification catalyst becomes equal to or lower than a threshold value after the temperature raising control is completed. The catalyst cooling promoting means is configured to maintain the exhaust gas flow rate until the temperature of the exhaust purification catalyst becomes equal to or lower than the threshold value.

  Japanese Patent Laid-Open No. 2007-198277 (Patent Document 2) discloses an exhaust gas recirculation device for an internal combustion engine, which includes a turbocharger provided with a turbine in an exhaust passage and a compressor in an intake passage, and an exhaust passage downstream of the turbine. And a low pressure EGR passage connecting the intake passage upstream of the compressor, a high pressure EGR passage connecting the exhaust passage upstream of the turbine and the intake passage downstream of the compressor, and a low pressure EGR downstream of the turbine and low pressure EGR EGR gas amount change for simultaneously changing the amount of EGR gas flowing through the low pressure EGR passage and the high pressure EGR passage so that the temperature of the exhaust purification catalyst provided in the exhaust passage upstream of the passage is within the target range A configuration comprising means is disclosed.

JP 2006-266221 A JP 2007-198277 A

  Here, when considering an acceleration transition from a low-load operation state such as an idle operation, the temperature of the catalyst provided in the exhaust system as the exhaust temperature increases due to the internal combustion engine shifting to the high-load operation state Rises.

  On the other hand, in an internal combustion engine, one that performs knock control system control is known as an example of ignition timing control that controls the ignition timing of a spark plug (ignition plug). In this control, the knock sensor detects the occurrence of knocking, and if it is determined that knocking has occurred, the ignition timing is retarded from the basic ignition timing determined according to the operating state of the internal combustion engine. At this time, by retarding the ignition timing to retard the combustion timing, combustion is also performed during the exhaust process, so the temperature of the catalyst rises. In particular, at the time of transition to the above-described high-load operation state, knocking is likely to occur, so the ignition timing is changed to the retard side. Therefore, the temperature of the exhaust gas is promoted, and there is a possibility that the temperature of the catalyst increases more than a predetermined value. Therefore, it is necessary to accurately detect such a temperature rise of the catalyst and appropriately execute exhaust gas temperature control for suppressing the catalyst temperature rise.

  The present invention has been made in order to solve such problems, and an object of the present invention is to control the exhaust temperature for suppressing the temperature rise of the catalyst and to reduce the retard amount from the basic ignition timing in the internal combustion engine. It is to reflect and execute appropriately.

  An internal combustion engine control apparatus according to the present invention is an internal combustion engine control apparatus equipped with an exhaust gas recirculation device that recirculates part of the exhaust gas of the internal combustion engine to the intake system of the internal combustion engine, and the exhaust gas by the exhaust gas recirculation device. A condition determination unit for operating the exhaust gas recirculation device when a predetermined condition capable of executing recirculation is established, and a catalyst provided in the exhaust system of the internal combustion engine when the exhaust gas recirculation device is operating And a catalyst temperature rise detection unit for detecting a temperature rise of a predetermined level or more, and an exhaust temperature lowering control unit for lowering the exhaust temperature when a temperature rise of the catalyst level is detected by the temperature rise detection unit. . The catalyst temperature rise detection unit includes a retard amount obtaining unit that obtains a retard amount from the basic ignition timing in the internal combustion engine, and a catalyst temperature estimation unit that estimates the temperature of the catalyst based on the load and output speed of the internal combustion engine. And when the retard amount acquired by the retard amount acquiring means exceeds a predetermined value set in advance according to the load of the internal combustion engine, and the temperature of the catalyst estimated by the catalyst temperature estimating means is Detecting means for detecting an increase in temperature of the catalyst above a predetermined level when the temperature exceeds the predetermined temperature. The exhaust temperature lowering control unit increases the recirculation amount of the exhaust gas by the exhaust gas recirculation device in accordance with the load and retard amount of the internal combustion engine.

  According to this invention, the exhaust gas temperature control for suppressing the temperature rise of the catalyst can be appropriately executed by reflecting the retard amount from the basic ignition timing in the internal combustion engine.

It is the schematic which shows the structure of the engine system controlled by the control apparatus of the internal combustion engine by embodiment of this invention. It is a functional block diagram which shows the control structure of the exhaust gas temperature control of the internal combustion engine by this Embodiment. It is a flowchart which shows the process sequence for implement | achieving exhaust gas temperature control according to the functional block diagram shown in FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 shows a schematic configuration of an engine system controlled by a control device for an internal combustion engine according to an embodiment of the present invention.

  As an example, the engine 10 includes four cylinders 2 and a fuel injection valve 3 that injects fuel into an intake port (not shown). In FIG. 1, the inline four-cylinder engine is described only as an example, and in the present invention, the number of cylinders and the arrangement of the cylinders are not specifically limited.

  The fuel injection valve 3 is opened when a drive voltage is applied, and as a result, fuel is injected from the fuel injection valve 3. Further, the engine 10 is provided with a crank position sensor 33 that detects a rotational position of a crankshaft (not shown) that receives a rotational force by fuel combustion in each cylinder 2. For example, the crank position sensor 33 generates a pulse signal NE every time the crankshaft rotates by a predetermined angle.

  An intake manifold 8 is connected to the intake side of the engine 10, and each branch of the intake manifold 8 communicates with a combustion chamber of each cylinder 2 via an intake port (not shown). The intake manifold 8 is connected to the intake pipe 9, and a throttle valve 13 that adjusts the amount of intake air flowing through the intake pipe 9 is provided at a portion of the intake pipe 9 located immediately upstream of the intake manifold 8.

  A throttle actuator 14 that opens and closes the throttle valve 13 composed of a stepper motor or the like is attached to the throttle valve 13. In addition, a throttle position sensor 15 that outputs an electrical signal proportional to the opening of the throttle valve 13 is disposed in the vicinity of the throttle actuator 14. Further, an air flow meter 51 that outputs an electrical signal corresponding to the amount of air sucked into the engine 10 (intake amount) is disposed in the intake pipe 9.

  On the other hand, an exhaust manifold 18 is connected to the exhaust side of the engine 10, and each branch of the exhaust manifold 18 communicates with the combustion chamber of each cylinder 2 via an exhaust port (not shown). The exhaust manifold 18 is connected to an exhaust pipe 19, and a catalyst 20 (typically a three-way catalyst) for purifying HC, CO, NOx and the like in the exhaust is provided in the middle of the exhaust pipe 19. ing.

  Further, the exhaust pipe 19 upstream of the catalyst 20 has an air-fuel ratio sensor 23 that outputs an electric signal corresponding to the air-fuel ratio of the exhaust flowing in the exhaust pipe 19, and the temperature of the exhaust flowing in the exhaust pipe 19. An exhaust temperature sensor 24 for outputting a corresponding electric signal is arranged. Furthermore, a water temperature sensor 52 that outputs an electrical signal corresponding to the temperature of the cooling water circulating through the cooling water path of the engine 10 (cooling water temperature Tw) is arranged.

  Further, the engine 10 is provided with an exhaust gas recirculation device 40 that recirculates a part of the exhaust gas discharged from the engine 10 and flowing through the exhaust manifold 18 to the intake manifold 8.

  The exhaust gas recirculation device 40 is configured by an EGR passage 25 formed so as to reach from the exhaust manifold 18 through the cylinder head to the collecting portion of the intake manifold 8, and an electromagnetic valve or the like, and flows in the EGR passage 25. An EGR valve 26 that adjusts the flow rate of exhaust gas (EGR gas) according to the magnitude of the applied voltage, and an EGR cooler 27 that is provided in the EGR valve 26 and an upstream EGR passage and cools the EGR gas flowing through the EGR passage. Including.

  In the exhaust gas recirculation device 40 configured as described above, when the EGR valve 26 is opened, a part of the exhaust gas flowing in the exhaust manifold 18 is cooled by the EGR cooler 27 via the EGR passage 25. After that, it flows into the collecting portion of the intake manifold 8. The EGR gas that has flowed into the intake manifold 8 is distributed to the combustion chambers of the respective cylinders 2 while being mixed with fresh air that has flowed in from the upstream of the intake manifold 8, and burns together with the fuel injected from the fuel injection valve 3.

Here, the EGR gas contains an inert gas component that does not burn itself and has endothermic properties, such as water (H ₂ O) and carbon dioxide (CO ₂ ). . Therefore, when the EGR gas is contained in the air-fuel mixture, the combustion temperature of the air-fuel mixture becomes low, and the amount of nitrogen oxide (NOx) generated is suppressed. Further, when the operating state of the engine 10 is in a region of a high load and a high rotational speed, an increase in the temperature of the exhaust gas from the engine 10 can be suppressed by including EGR gas in the air-fuel mixture.

  The engine 10 configured as described above has an electronic control unit (ECU) for controlling the engine 10 in response to a driver's request detected by an output signal (accelerator opening) of the accelerator position sensor 36 or the like. ) 35 is attached.

  The ECU 35 performs arithmetic processing by a CPU (Central Processing Unit) based on signals transmitted from various sensors, a map and a program stored in a storage device such as a ROM (Read Only Memory) (not shown), and the engine 10 performs desired processing. Devices (actuators) are controlled so as to be in an operating state. In FIG. 1, the illustrated throttle position sensor 15, air-fuel ratio sensor 23, exhaust temperature sensor 24, crank position sensor 33, accelerator position sensor 36, and air flow meter 51 are illustrated, and the fuel injection valve 3, as the actuator, The throttle actuator 14 and the EGR valve 26 are exemplified.

  Next, regarding the exhaust gas temperature control executed when suppressing the temperature rise of the exhaust system (typically, the catalyst 20) in the engine system shown in FIG. 1, the functional block diagram of FIG. 2 and the flowchart of FIG. Will be described.

  Each functional block shown in FIG. 2 indicates a functional unit realized by the ECU 35, and may be configured by a circuit (hardware) having a function corresponding to the block, or may be set in advance. It may be realized by executing software processing according to the program.

  Referring to FIG. 2, engine speed calculation unit 170 calculates the rotation speed (engine speed) Ne of the crankshaft of engine 10 based on signal NE from crank position sensor 33. Further, the volumetric efficiency calculation unit 160 calculates the volumetric efficiency VE of the engine 10 by correcting the intake air amount detected by the air flow meter 51 with detected values such as temperature, humidity, pulsation, and atmospheric pressure.

  The catalyst temperature estimating unit 100 is typically based on the engine speed Ne and the engine load LDe (corresponding to the volumetric efficiency VE) calculated by the engine speed calculating unit 170 based on the operating state parameter of the engine 10. Estimate the catalyst temperature. Specifically, the temperature change amount of the catalyst 20 is sequentially estimated from the exhaust gas temperature (exhaust temperature) and the heat capacity of the catalyst 20 which are sequentially calculated based on the engine speed Ne and the engine load LDe, and this estimation is performed. By integrating the amount of temperature change, the estimated temperature (catalyst temperature) Tctl of the catalyst 20 can be calculated. Alternatively, the catalyst temperature Tctl may be obtained by a method different from the above, for example, by providing a temperature sensor in the catalyst 20.

  The catalyst OT determination unit 110 acquires the catalyst temperature Tctl estimated by the catalyst temperature estimation unit 100, acquires the retard amount Qrtd from the basic ignition timing from an ignition timing control system (not shown), and the EGR execution condition determination unit A flag FEGR indicating whether or not exhaust gas recirculation can be executed is acquired from 140. When the flag FEGR is turned on (when exhaust gas recirculation can be executed), the catalyst OT determination unit 110 performs a method described later on the basis of the catalyst temperature Tctl and the ignition timing retard amount Qrtd. Then, it is determined whether or not the exhaust gas temperature lowering control is required to suppress the increase in the exhaust gas temperature, and a signal JD indicating the determination result is output. The catalyst temperature estimation unit 100 and the catalyst OT determination unit 110 constitute a “catalyst temperature rise detection unit”.

  In the ignition timing control system described above, for example, it is determined whether or not knocking has occurred based on the output signal of the knock sensor, and if it is determined that knocking has occurred, the engine 10 is in an operating state. A so-called knock control system that retards the ignition timing from the basic ignition timing determined accordingly is included. Then, the ignition timing control system retards the ignition timing to retard the combustion timing, so that the combustion is also performed during the exhaust process, and thus the temperature of the catalyst 20 rises.

  The EGR execution condition determination unit 140 determines whether or not a predetermined EGR execution condition for executing exhaust gas recirculation by the exhaust gas recirculation device 40 is satisfied. For example, the EGR execution conditions are: (1) a predetermined time has elapsed after engine start or fuel cut return, (2) volumetric efficiency VE is greater than or equal to a predetermined value, and (3) idle off. (4) The vehicle is traveling (vehicle speed> 0), (5) the cooling water temperature Tw is equal to or higher than a predetermined temperature, (6) the vehicle is not decelerating, and the like.

  When all of these EGR predetermined conditions are satisfied and the exhaust gas recirculation can be executed, the EGR execution condition determining unit 140 turns on the flag FEGR, and otherwise turns off the flag FEGR.

  When the flag FEGR is turned on, the EGR control unit 200 determines the opening (EGR opening) of the EGR valve 26 based on the operating state parameters of the engine 10 (typically, the engine speed Ne and the volumetric efficiency VE). Degree), that is, the exhaust gas recirculation amount (EGR amount) is controlled. Specifically, the EGR control unit 200 obtains the EGR opening degree by referring to the opening degree map 210. The opening degree map 210 is stored in a ROM or the like in the ECU 35, for example. Note that the map value of the opening degree map 210 is preliminarily adapted to the EGR opening degree corresponding to the parameter values (engine speed, volume efficiency) indicating the operating state of the engine 10 based on the experimental results and the like.

  Further, the EGR control unit 200 obtains an increase in the exhaust gas recirculation amount (hereinafter also referred to as an added EGR amount) for lowering the exhaust gas temperature when the catalyst temperature is increased by referring to the exhaust gas recirculation amount increase map 220. . By increasing the exhaust gas recirculation amount and reducing the ratio of fresh air introduced into the intake system, the oxygen concentration of the combusted air-fuel mixture decreases, so that the exhaust temperature can be lowered.

  Note that the map value of the exhaust gas recirculation amount increase map 220 is preliminarily adapted to the optimum value corresponding to the operating state parameters (volumetric efficiency, ignition timing retardation amount) of the engine 10 based on experimental results and the like. . The EGR control unit 200 guards with a predetermined increase in the exhaust gas recirculation amount. This is to prevent unnecessary output reduction due to an excessive increase in the exhaust gas recirculation amount.

  The EGR control unit 200 adds the increased amount set by the exhaust gas recirculation amount increase map to the basic exhaust gas recirculation amount obtained by referring to the opening degree map 210, thereby obtaining the final exhaust gas recirculation amount. Decide. Then, the EGR opening degree is controlled according to the determined exhaust gas recirculation amount.

  The exhaust temperature lowering control unit 150 performs exhaust temperature lowering control based on the signal JD from the catalyst OT determination unit 110. Specifically, when the catalyst OT determination unit 110 determines that the exhaust gas temperature reduction control is necessary to suppress the increase in the catalyst temperature, the exhaust gas temperature is decreased by operating the EGR control unit 200. Let

  Specifically, the exhaust temperature lowering control unit 150 operates the EGR control unit 200 to lower the exhaust temperature by exhaust recirculation amount increase control. At this time, the EGR control unit 200 determines an appropriate opening degree of the EGR valve 26 (that is, an exhaust gas recirculation amount) by referring to the opening degree map 210 in accordance with the engine speed Ne and the volumetric efficiency VE at that time. At the same time, by referring to the exhaust gas recirculation amount increase map 220, the increase amount of the exhaust gas recirculation amount is determined according to the volumetric efficiency VE and the retard amount Qrtd of the ignition timing at that time. Then, the final exhaust gas recirculation amount is determined by adding the increased exhaust gas recirculation amount to the basic exhaust gas recirculation amount.

  The exhaust temperature control according to the functional block diagram shown in FIG. 2 can also be realized by the ECU 35 executing a program for executing the processing shown in the flowchart described in FIG. The above program is activated every predetermined control cycle to execute a series of processes.

  Referring to FIG. 3, ECU 35 determines in step S01 whether or not an EGR execution condition is satisfied. That is, the process of step S01 corresponds to the function of the EGR execution condition determination unit 140 shown in FIG.

  Since the ECU 35 cannot execute exhaust gas recirculation when the EGR execution condition is not satisfied (NO in S01), the ECU 35 advances the process to step S07 and does not execute exhaust gas recirculation. As a result, the EGR valve 26 is maintained in the closed state (EGR opening = 0), and the exhaust gas circulation amount increase control for decreasing the exhaust temperature is not executed (that is, the added EGR amount = 0).

  On the other hand, when the EGR execution condition is satisfied (when YES is determined in S01) and exhaust gas recirculation can be executed, the exhaust gas temperature lowering control is required by executing the following steps S02 to S05. It is determined whether or not a temperature increase (catalyst OT) of the catalyst 20 has occurred. That is, the processes of S02 to S05 correspond to the function of the catalyst OT determination unit 110 shown in FIG.

  Specifically, the ECU 35 acquires the retard amount Qrtd of the ignition timing in step S02. The process of step S02 can be realized, for example, when the catalyst OT determination unit 110 shown in FIG. 2 acquires the ignition timing retard amount Qrtd from the ignition timing control system.

  Furthermore, ECU35 acquires the temperature (catalyst temperature Tctl) of the catalyst 20 by step S03. The process of step S03 can be realized by, for example, an estimation calculation by the catalyst temperature estimation unit 100 shown in FIG.

  Next, in step S04, the ECU 35 determines whether or not the retardation amount Qrtd of the ignition timing acquired in step S04 is larger than a predetermined retardation amount A. The predetermined retardation amount A is set to an appropriate retardation amount for maintaining the catalyst temperature within a predetermined allowable range, for example, by referring to a retardation amount map (not shown) according to the volumetric efficiency VE at that time. The The map value of the retard amount map is preliminarily adapted to the retard amount corresponding to the volumetric efficiency over the use load range of the engine 10 based on experimental results and the like.

  When the retard amount Qrtd of the ignition timing is equal to or less than the predetermined retard amount A (NO determination in S04), the ECU 35 determines that the exhaust temperature lowering control is unnecessary (the catalyst OT is not generated). Therefore, the ECU 35 advances the process to S07, and the exhaust gas circulation amount increase control for decreasing the exhaust temperature is not executed (added EGR amount = 0).

  On the other hand, when the retard amount Qrtd of the ignition timing exceeds the predetermined retard amount A (when YES is determined in S04), the ECU 35 further determines that the catalyst temperature Tctl acquired in S03 is a predetermined value in step S05. It is determined whether or not the temperature is higher than the determination temperature B. The predetermined determination temperature B is set, for example, in a predetermined high temperature range that may reduce the exhaust purification performance of the catalyst 20.

  When the catalyst temperature Tctl is higher than the predetermined determination temperature B (YES determination in S05), the ECU 35 determines that exhaust temperature lowering control is necessary (catalyst OT generation). Then, the process proceeds to step S06, and the exhaust gas temperature is lowered by the exhaust gas recirculation amount increase control.

  In step S06, as described with reference to FIG. 2, by referring to the exhaust gas recirculation amount increase map 220, the increase amount (addition) of the exhaust gas recirculation amount is added according to the volumetric efficiency VE and the ignition timing retard amount Qrtd at that time. EGR amount) is determined. That is, the process in step S06 corresponds to the function of the EGR control unit 200 shown in FIG.

  On the other hand, when the catalyst temperature Tctl is equal to or lower than the predetermined determination temperature B (NO determination in S05), the ECU 35 determines that the exhaust temperature lowering control is unnecessary (catalyst OT is not generated), and the process proceeds to step S07. In this case, in step S07, the exhaust gas recirculation amount increase control for lowering the exhaust temperature is not executed (added EGR amount = 0), and normal EGR control is executed. That is, by referring to the opening degree map 210 shown in FIG. 2, the EGR opening degree of the exhaust gas recirculation device 40 is set according to the engine speed Ne and the volumetric efficiency VE at that time.

  As described above, according to the control device for an internal combustion engine according to the present embodiment, in the engine equipped with the exhaust gas recirculation device, an increase in the temperature of the catalyst is detected based on the retard amount from the basic ignition timing, Further, by comparing the catalyst temperature estimated from the operating state of the engine with a predetermined determination temperature, it is detected that the temperature increase of the catalyst may reduce the purification ability of the catalyst. Thereby, it is possible to accurately detect the occurrence of a catalyst temperature increase (catalyst OT) that requires exhaust gas temperature decrease control.

  Further, when the catalyst OT is generated, the exhaust gas recirculation amount increase control is performed as the exhaust gas temperature decrease control, so that the internal combustion engine is compared with the conventional control configuration in which the exhaust temperature is decreased by increasing the fuel injection amount. It is possible to improve the fuel efficiency of vehicles equipped with

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  2 cylinder, 3 fuel injection valve, 8 intake manifold, 9 intake pipe, 10 engine, 13 throttle valve, 14 throttle actuator, 15 throttle position sensor, 18 exhaust manifold, 19 exhaust pipe, 20 catalyst, 23 air-fuel ratio sensor, 24 exhaust temperature sensor, 25 EGR passage, 26 EGR valve, 27 EGR cooler, 33 crank position sensor, 36 accelerator position sensor, 40 exhaust recirculation device, 51 air flow meter, 52 water temperature sensor, 100 catalyst temperature estimation unit, 110 catalyst OT Determination unit, 140 EGR execution condition determination unit, 150 exhaust temperature decrease control unit, 160 volumetric efficiency calculation unit, 170 engine speed calculation unit, 200 EGR control unit, 210 opening degree map, 220 exhaust recirculation amount increase map.

Claims (1)

A control device for an internal combustion engine equipped with an exhaust gas recirculation device that recirculates part of the exhaust gas of the internal combustion engine to the intake system of the internal combustion engine,
A condition determination unit that operates the exhaust gas recirculation device when a predetermined condition is established in which exhaust gas recirculation by the exhaust gas recirculation device is executable;
When the exhaust gas recirculation device is in operation, a catalyst temperature rise detection unit that detects a temperature rise of a predetermined or higher temperature of the catalyst provided in the exhaust system of the internal combustion engine;
An exhaust temperature lowering control unit for lowering the exhaust temperature when the temperature increase detecting unit detects a temperature increase of the catalyst above a predetermined level,
The catalyst temperature rise detection unit
A retard amount obtaining means for obtaining a retard amount from a basic ignition timing in the internal combustion engine;
Catalyst temperature estimating means for estimating the temperature of the catalyst based on the load and output speed of the internal combustion engine;
The catalyst estimated by the catalyst temperature estimating means when the retard amount acquired by the retard amount acquiring means exceeds a predetermined value set in advance according to the load of the internal combustion engine. When the temperature of the catalyst exceeds a predetermined temperature, the detection means for detecting a temperature rise of the catalyst more than a predetermined,
The exhaust gas temperature reduction control unit executes an increase in the exhaust gas recirculation amount by the exhaust gas recirculation device in accordance with a load of the internal combustion engine and the retardation amount.

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