JPH10196463A - Exhaust gas recirculation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent exhaust gas from being excessively recirculated when the abnormality of opening valve fixing is generated on an exhaust gas recirculation valve, concerning an exhaust gas recirculation device for partially reciculating exhaust gas of an internal combustion engine to an intake passage. SOLUTION: An exhaust gas recirculation valve 80 is interposed in an exhaust gas recirculation passage 78 for communicating an exhaust passage 68 and an intake passage 52 with each other. An intake throttle valve 58 is provided inside of the intake passage 52. An exhaust turbine 70 of a variable capacity turbocharger 62 is communicated with the exhaust passage 68. When the actual opening of the exhaust gas recirculation valve 80 is larger than the target opening, it is judged that the abnormality of opening valve fixing is generated. When abnormality of opening valve fixing is detected, the intake throttle valve 58 is full opened regardless of the operating state of an internal combustion engine 10, and the variable capacity turbocharger 62 is so controlled that the flowing resistance of the exhaust turbine 70 may be minimum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation device, and more particularly to an exhaust gas recirculation device for recirculating a part of exhaust gas to an intake passage in an internal combustion engine mounted on a vehicle.

[0002]

2. Description of the Related Art Conventionally, Japanese Patent Application Laid-Open No. 55-1233, for example,
As disclosed in No. 45, there is known an exhaust gas recirculation device that recirculates a part of exhaust gas of an internal combustion engine to an intake passage. Exhaust gas contains a large amount of inert gas such as H ₂ O, CO ₂ , and N ₂ . Therefore, when the exhaust gas is recirculated to the intake passage, the maximum combustion temperature generated in the combustion chamber decreases due to the heat capacity of the inert gas, and as a result, NOx contained in the exhaust gas decreases. Therefore, by returning the exhaust gas to the intake passage, the exhaust emission can be purified.

On the other hand, if the exhaust gas is excessively supplied into the intake passage, the combustion in the combustion chamber becomes unstable. in this case,
As the output of the internal combustion engine decreases, unburned components such as HC and CO increase and exhaust emission may worsen. Therefore, when the exhaust gas is recirculated to the intake passage, it is necessary to control the recirculation amount to an appropriate amount.

The conventional exhaust gas recirculation device includes an exhaust gas recirculation passage communicating the exhaust gas passage and the intake gas passage, and an exhaust gas recirculation valve interposed therein. The exhaust gas recirculation valve
Control is performed so that an appropriate amount of exhaust gas is recirculated from the exhaust passage toward the intake passage in accordance with the operation state of the internal combustion engine.
Therefore, according to the above-described conventional exhaust gas recirculation device, it is possible to appropriately purify exhaust emissions.

[0005] Further, the above-mentioned conventional exhaust gas recirculation device has:
A mechanism for detecting the actual opening of the exhaust gas recirculation valve is provided, and if the measured actual opening of the exhaust gas recirculating valve is significantly different from the target opening, an abnormality has occurred in the exhaust gas recirculating valve. It has a function to recognize Therefore, according to the above-described conventional exhaust gas recirculation device, when a situation occurs in which the flow rate of the recirculated exhaust gas cannot be properly controlled, the state can be reliably recognized as abnormal.

[0006]

In some cases, an internal combustion engine incorporates a variable capacity turbocharger having a variable nozzle in an exhaust turbine. Further, an internal combustion engine (diesel engine) may be provided with an intake throttle valve in an intake passage.

The variable capacity turbocharger changes the angle of the variable nozzle so that the capacity of the turbine becomes an appropriate value according to the operation state of the internal combustion engine. According to the variable capacity turbocharger, high load
Excellent responsiveness and high efficiency can always be obtained up to the high rotation range.

[0008] The intake throttle valve in a diesel engine is controlled to an opening degree according to the operating state of the internal combustion engine. When there is no need to recirculate exhaust gas from the exhaust passage to the intake passage, the intake throttle valve is controlled to be almost fully open. In this case, the diesel engine can smoothly inhale a large amount of air without a large load. When it is necessary to recirculate the exhaust gas from the exhaust passage to the intake passage, the intake throttle valve is controlled to an appropriate opening according to the operating state of the internal combustion engine. In this case, the pressure in the intake passage (hereinafter, referred to as
(Referred to as intake pressure) becomes a negative pressure, and a large differential pressure occurs before and after the exhaust gas recirculation passage. As a result, a stable flow rate of exhaust gas flows from the exhaust passage toward the intake passage.

The above-described variable capacity turbocharger and intake throttle valve are controlled independently of the exhaust gas recirculation valve. For this reason, when an abnormality occurs in which the exhaust gas recirculation valve is stuck in the open state (hereinafter, referred to as valve opening stuck abnormality), even if the abnormality is detected, the variable displacement turbocharger or the intake throttle valve will The control is performed according to the operating state of the internal combustion engine in the same manner as in the case where no valve opening sticking abnormality occurs.

When the variable nozzle of the variable capacity turbocharger operates in a direction to reduce the effective area of the exhaust gas flow path, the pressure in the exhaust passage (hereinafter, referred to as exhaust pressure) increases. Therefore, if the variable nozzle is controlled as described above in an environment in which the exhaust gas recirculation valve has a valve opening sticking abnormality, an excessive amount of exhaust gas may flow from the exhaust passage into the intake passage. Similarly, when the intake throttle valve is operated in the valve closing direction in an environment where the exhaust gas recirculation valve has a valve opening sticking abnormality, an excessive amount of exhaust gas is discharged from the exhaust passage due to a decrease in intake pressure. A situation occurs in which the air flows into the intake passage.
As described above, when the conventional exhaust gas recirculation device is used in combination with the variable capacity turbocharger or the intake throttle valve, the exhaust gas is excessively recirculated in an environment where the exhaust gas recirculation valve has a valve opening sticking abnormality. Could not be prevented.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is possible to prevent the exhaust gas from being excessively recirculated when the exhaust gas recirculation valve has a valve opening fixation abnormality. It is an object to provide a recirculation device.

[0012]

The above object is achieved by the present invention.
In an exhaust gas recirculation device that recirculates exhaust gas from an exhaust passage of an internal combustion engine to an intake passage, an exhaust gas recirculation passage that connects the exhaust passage and the intake passage, and an exhaust gas recirculation device that is interposed in the exhaust gas recirculation passage. A valve, opening control means for controlling the opening of the exhaust gas recirculation valve to a target opening corresponding to the operating state of the internal combustion engine, actual opening detecting means for detecting the actual opening of the exhaust gas recirculating valve, Pressure adjusting means for changing the differential pressure generated on both sides of the exhaust gas recirculation valve in accordance with the operating state of the engine, and when the actual opening is larger than the target opening,
This is achieved by an exhaust gas recirculation apparatus including: a differential pressure reducing unit that controls the pressure adjusting unit so that a differential pressure generated on both sides of the exhaust gas recirculation valve is reduced.

In the present invention, the exhaust gas recirculation valve is controlled to a target opening corresponding to the operating state of the internal combustion engine. When the exhaust gas recirculation valve opens, the differential pressure across the exhaust gas recirculation valve, that is,
Exhaust gas having a flow rate corresponding to the differential pressure between the exhaust pressure and the intake pressure adjusted by the pressure adjusting means and the opening degree of the exhaust recirculation valve is recirculated from the exhaust passage to the intake passage. If the exhaust gas recirculation valve is stuck abnormally, the exhaust gas is likely to be excessively recirculated. On the other hand, when the valve opening sticking abnormality occurs in the exhaust gas recirculation valve, the actual opening of the exhaust gas recirculation valve becomes larger than its target opening. In this case, since the pressure difference before and after the exhaust gas recirculation valve is reduced by the pressure adjusting means, excessive recirculation of the exhaust gas is prevented.

In the present invention, when "the actual opening degree of the exhaust gas recirculation valve is larger than its target opening degree", the two are compared and the actual opening degree is larger than the target opening degree. Other
If the actual opening exceeds the predetermined value and is larger than the target opening,
Also, a case is included in which the ratio between the actual opening and the target opening is larger than a predetermined value.

[0015] The object of the present invention is as described in claim 2.
2. The exhaust gas recirculation device according to claim 1, wherein the pressure adjusting unit includes a variable capacity turbocharger having a variable nozzle in an exhaust turbine, and the actual opening is larger than the target opening. 3. In addition, the present invention is also achieved by an exhaust gas recirculation device that changes the opening degree of the variable nozzle so that the effective area of the passage through which the exhaust gas flows in the exhaust turbine increases.

In the present invention, a variable capacity turbocharger is mounted on the internal combustion engine. The variable-capacity turbocharger is variable in the exhaust turbine to ensure excellent responsiveness and high efficiency in a wide operating range from low load / low speed to high load / high speed depending on the operating condition of the internal combustion engine. Activate the nozzle. Specifically, the variable nozzle of the variable capacity turbocharger has a
The variable nozzle is operated such that the effective area of the passage through which the exhaust gas flows in the exhaust turbine is reduced. In this case, a high exhaust pressure is easily generated in the exhaust passage. On the other hand, the variable nozzle of the variable capacity turbocharger operates the variable nozzle such that the effective area of the passage through which the exhaust gas flows in the exhaust turbine increases in a high-load and high-rotation region.
In this case, a situation is formed in which the exhaust pressure in the exhaust passage is difficult to increase.

In the present invention, when the exhaust gas recirculation valve is stuck abnormally, the variable capacity turbocharger is designed to increase the effective area of the passage of the exhaust gas in the exhaust turbine, that is, to increase the effective area of the exhaust passage. The opening degree of the variable nozzle is changed so that a situation in which the pressure is hard to increase is formed. If the opening degree of the variable nozzle changes in this way, it is difficult for a differential pressure to be generated on both sides of the exhaust gas recirculation valve. Is prevented.

According to a third aspect of the present invention, in the exhaust gas recirculation apparatus according to the first aspect, the pressure adjusting means includes an intake throttle valve provided in an intake passage. When the actual opening is larger than the target opening, the differential pressure reducing unit is also achieved by an exhaust gas recirculation device that increases the opening of the intake throttle valve.

In the present invention, an intake throttle valve is mounted on the internal combustion engine. The opening degree of the intake throttle valve is appropriately adjusted according to the operating state of the internal combustion engine. When the intake throttle valve is opened, the flow resistance in the intake passage decreases, so that the intake loss can be reduced. On the other hand, when the intake throttle valve is closed, a negative pressure is generated in the intake passage, so that the exhaust gas is easily circulated.

In the present invention, if the exhaust gas recirculation valve is stuck in the open state, the intake throttle valve operates in the valve opening direction regardless of the operating state of the internal combustion engine. When the intake throttle valve is opened as described above, a differential pressure is less likely to be generated on both sides of the exhaust gas recirculation valve.
Excessive recirculation of exhaust gas is prevented.

[0021]

FIG. 1 is a system configuration diagram of an internal combustion engine 10 equipped with an exhaust gas recirculation device according to a first embodiment of the present invention. In the present embodiment, the internal combustion engine 10
Is an electronic control unit 12 (hereinafter, referred to as ECU 12)
Is controlled by

The internal combustion engine 10 has a cylinder block 14. A water jacket 16 is formed in the wall of the cylinder block 14. The piston 18, the connecting rod 20, and the crankshaft 22 are housed inside the cylinder block 14.

A water temperature sensor 24 for detecting the temperature of the cooling water flowing inside the water jacket 16 and a crank angle sensor 26 for detecting the rotation angle of the crankshaft 22 are provided on the wall surface of the cylinder block 14. Have been. The output signal of the water temperature sensor 24 and the output signal of the crank angle sensor 26 are both supplied to the ECU 12. The ECU 12 detects the temperature THW of the cooling water and the crank angle CA based on these output signals.

An oil pan 28 is fixed below the cylinder block 14. Engine oil 30 is stored inside the oil pan 28. A cylinder head 32 is fixed to an upper portion of the cylinder block 14. A main combustion chamber 33 is formed between the cylinder head 32 and the piston 18. Inside the cylinder head 32, an intake port 34, a sub-combustion chamber 36, and an exhaust port 38 communicating with the main combustion chamber 33 are formed.

The cylinder head 36 is provided with a fuel injection valve 40 whose tip is exposed to the auxiliary combustion chamber 36 and a glow plug 42 whose tip is similarly exposed to the auxiliary combustion chamber 36. The cylinder head 36 is provided with an intake valve (not shown) for opening and closing the intake port 34 and an exhaust valve 44 for opening and closing the exhaust port 38.

A fuel injection pump 46 is connected to the fuel injection valve 40 via a fuel pipe (not shown). The fuel injection pump 46 is a pump that operates using the output torque of the internal combustion engine 10 as a driving force, and supplies high-pressure fuel to fuel injection valves disposed in each cylinder of the internal combustion engine 10 at appropriate timing. The fuel injection valves disposed in the respective cylinders, when receiving a supply of high-pressure fuel from the fuel pump 46,
Fuel is injected into the sub-combustion chamber 36.

The fuel injection valve 40 has an NE sensor 48 for detecting the rotational speed NE of the internal combustion engine 10 and a fuel temperature THF.
And a fuel temperature sensor 50 for detecting the temperature. The output signal of the NE sensor 48 and the output signal of the fuel temperature sensor 50 are both supplied to the ECU 12. ECU12
Detects the engine speed NE and the fuel temperature THF based on these output signals.

An intake passage 52 communicates with an intake port 34 of the internal combustion engine 10. The intake passage 52 is provided with an intake pressure sensor 54 for detecting the internal pressure of the intake passage 52, that is, the intake pressure PM, and an intake temperature sensor 56 for detecting the temperature inside the intake passage 52, that is, the intake temperature THA. ing. The output signal of the intake pressure sensor 54 and the output signal of the intake temperature sensor 56 are both supplied to the ECU 12. The ECU 12 performs the following based on these output signals.
The intake pressure PM and the intake temperature THA are detected.

Inside the intake passage 52, an intake pressure sensor 5 is provided.
An intake throttle valve 58 is disposed on the upstream side of the fourth throttle valve 4. The drive device 60 is connected to the intake throttle valve 58. The drive device 60 drives the intake throttle valve 58 according to a control signal supplied from the ECU 12. The ECU 12
The drive device 60 is controlled so that the opening degree of the intake throttle valve 58 becomes an appropriate opening degree according to the operating state of the internal combustion engine 10.

A compressor 64 of a variable capacity turbocharger 62 communicates with the intake passage 52. An air filter (not shown) communicates with the compressor 64 of the variable capacity turbocharger 62. The variable capacity turbocharger 62 supercharges the air filtered by the air filter from the compressor 64 to the intake passage 52 during operation of the internal combustion engine 10. A waste gate valve 66 for preventing the supercharging pressure from becoming an excessive value is incorporated in the compressor 64.

An exhaust passage 68 communicates with an exhaust port 38 of the internal combustion engine 10. An exhaust turbine 70 of the variable capacity turbocharger 62 communicates with the exhaust passage 68. Further, a catalytic converter and a muffler (not shown) communicate with the exhaust turbine 70. Compressor 64
Uses the energy of the exhaust gas flowing inside the exhaust turbine 70 to supercharge the air guided from the air filter into the intake passage 52. In the exhaust passage 68, the exhaust gas that has flowed into the exhaust turbine 70 passes through a flow path formed inside the exhaust turbine 70 toward the catalytic converter.

When the flow path formed inside the exhaust turbine 70 has a large effective area, a large amount of exhaust flow is required to obtain an appropriate supercharging pressure by the compressor 64. Therefore, when the internal combustion engine 10 is operating in a low load / low rotation range, the effective area of the circulation path inside the exhaust turbine 70 is small in order to obtain a sufficient supercharging pressure with excellent responsiveness. It is desirable.

On the other hand, when the effective area of the flow path inside the exhaust turbine 70 is small, the exhaust pressure is increased to an unreasonably high pressure in an environment where a large amount of exhaust gas flows into the exhaust turbine 70, that is, A state where the exhaust loss increases and the output of the internal combustion engine 10 decreases is realized. Therefore, under a situation where a large amount of exhaust gas is generated, that is, the internal combustion engine 1
When 0 is operating in a high-load / high-rotation region, it is desirable that the flow path formed inside the exhaust turbine 70 has a large effective area.

The exhaust turbine 70 of the variable capacity turbocharger 62 is provided with a plurality of variable nozzles 72 for changing the effective area of a flow path formed therein. These variable nozzles 72 have negative pressure actuators 74 and 76 for driving the variable nozzles 72 in one direction or the other direction, respectively, using a negative pressure supplied from a vacuum pump (not shown) (not shown) as a power source. Are connected. The negative pressure actuators 74 and 76 are
The angle of the variable nozzle 72 is changed according to the control signal supplied from the control unit 12. The ECU 12 controls the negative pressure actuators 74 and 76 appropriately so that the angle of the variable nozzle 72 becomes an appropriate angle according to the operation state of the internal combustion engine 10.

The internal combustion engine 10 has an exhaust gas recirculation passage 78 that connects the exhaust passage 68 and the intake passage 52. An EGRV 80 is interposed in the exhaust gas recirculation passage 78. E
The GRV 80 is connected to a negative pressure actuator 82 that drives the EGRV 80 using a negative pressure supplied from a V / P (not shown) as a driving source.

The negative pressure actuator 82 includes an EGRV 80
To the valve opening direction. Also, EGRV
A biasing force due to a differential pressure generated on both sides, that is, a differential pressure between the exhaust pressure and the intake pressure acts on 80. Therefore, the opening of the EGRV 80 is controlled to an opening in accordance with the urging force generated by the negative pressure actuator 82 and the differential pressure generated on both sides of the EGRV 80.

The ECU 12 supplies a drive signal having an appropriate duty ratio to the negative pressure actuator 12 so that the opening of the EGRV 80 becomes an appropriate opening according to the operating state of the internal combustion engine 10. Negative pressure actuator 1
2 generates an urging force according to the duty ratio of the supplied drive signal. As a result, the opening of the EGRV 80 is controlled to an appropriate opening according to the operating state of the internal combustion engine 10.

In the vicinity of the EGRV 80, a lift sensor 84 for detecting the actual opening of the EGRV 80 is provided.
The output signal of the lift sensor 84 is supplied to the ECU 12. The ECU 12 detects the actual opening of the EGRV 80 based on the output signal of the lift sensor 84.

An accelerator opening sensor 88 for detecting the opening AACC of the accelerator pedal 86 is connected to the ECU 12. The ECU 12 is connected to a vehicle speed sensor 90 that generates a pulse signal at a cycle corresponding to the vehicle speed SPD. The ECU 12 controls the accelerator opening degree sensor 88
Accelerator opening AACC and vehicle speed SPD are detected based on an output signal from vehicle speed sensor 90 and the output signal.

In the internal combustion engine 10, when the EGRV 80 is operating properly, an appropriate amount of exhaust gas is returned from the exhaust passage 68 to the intake passage 52 according to the operating state of the internal combustion engine 10. In this case, the maximum combustion temperature of the fuel in the main combustion chamber 33 can be suppressed to an appropriate temperature, and as a result, clean exhaust emissions can be obtained.

On the other hand, when the EGRV 80 is stuck in the open state in the internal combustion engine 10, that is, when the valve sticking abnormality occurs, the flow rate of the recirculated exhaust gas is changed according to the operating state of the internal combustion engine 10. Cannot be controlled to an appropriate value. In particular, in such a situation, if a small effective area is given to the flow path inside the exhaust turbine 70 or if a small opening is given to the intake throttle valve 58, the EGRV8
A large differential pressure is generated on both sides of the exhaust gas 68, and exhaust gas is excessively recirculated from the exhaust passage 68 to the intake passage 52.

The system according to the present embodiment is characterized in that it is possible to prevent the occurrence of excessive recirculation of exhaust gas in the event that the EGRV 80 has a valve opening sticking abnormality.
Hereinafter, with reference to FIG. 2, a characteristic portion of the system of the present embodiment will be described. FIG. 2 shows an example of an EC for realizing the above functions.
9 shows a flowchart of an example of a control routine executed by U12. The routine shown in FIG. 2 is a periodic interrupt routine that is started every predetermined time. When the routine shown in FIG. 2 is started, first, the process of step 100 is executed.

In step 100, based on the output signals of various sensors provided in the internal combustion engine 10, the engine speed NE,
Fuel temperature THF, accelerator opening AACC, vehicle speed SPD,
Intake temperature THA and intake pressure PM are calculated. EC
U12 determines the operating state of the internal combustion engine 10 based on these calculated values.

In step 102, an opening to be given to the EGRV 80 is calculated as a target opening TGA based on the operating state of the internal combustion engine 10. The target opening degree TGA is an opening degree for recirculating an appropriate amount of exhaust gas corresponding to the operation state of the internal combustion engine 10. In this embodiment, the target opening T
GA is calculated with reference to a map stored in the ECU 12.

In step 104, the above target opening TG
The drive duty Duty for realizing A, that is, the duty ratio of the drive signal supplied to the negative pressure actuator 82 is calculated. In the present embodiment, the drive duty Du
ty is calculated by referring to a map stored in the ECU 12 based on the target opening TGA and the differential pressure generated on both sides of the EGRV 80. In addition, EGRV80
Is obtained as a differential pressure between the exhaust pressure calculated based on the operating state of the internal combustion engine 10 and the intake pressure PM detected by the intake pressure sensor 56.

In step 106, the actual opening 80 of the EGRV 80 is detected based on the output signal of the lift sensor 84. In step 108, a ratio "a = (actual opening) / (target opening)" between the actual opening and the target opening is calculated.

In step 110, it is determined whether or not the calculated value a is equal to or larger than a predetermined value 1.1. If a ≧ 1.1 holds, it can be determined that the actual opening of the EGRV 80 is unduly large as compared to the target opening. in this case,
The ECU 12 determines that the EGRV 80 has the valve opening fixation abnormality, and then executes the process of step 112.

In step 112, a process for setting the drive duty of the EGRV 80 to "0" is executed. When the drive duty is set to “0”, the negative pressure actuator 84
However, the urging force generated in the direction to open the EGRV 80 disappears. If the fixation of the EGRV 80 is loose, the fixation may be released by the disappearance of the urging force of the negative pressure actuator 84. When the fixation of the EGRV 80 is released by the processing in step 112, normal control is resumed again after the next processing cycle. When the process of step 112 is completed, the process proceeds to step 11
4 is executed.

In step 114, the process of fully closing the variable nozzle 72 (VN) of the variable capacity turbocharger 62, that is, the process of maximizing the effective area of the flow path formed inside the exhaust turbine 70 is executed. You. After the process of step 114 is performed, the characteristics of the variable capacity turbocharger 62 are changed to characteristics that achieve both excellent responsiveness and high efficiency in a high-load and high-speed region, similarly to a normal turbocharger. Fixed. For this reason, low load
Responsivity in the low rotation region is impaired compared to normal operation.

However, when the processing of step 114 is performed, the flow resistance when the exhaust gas flows through the exhaust turbine 70 is always suppressed to a small value.
That is, a situation where high exhaust pressure is unlikely to be generated can be formed. When the exhaust pressure is suppressed to a low value, the differential pressure generated on both sides of the exhaust gas recirculation valve 80 in which the valve opening sticking abnormality has occurred can be suppressed to a small value. Also, the exhaust gas recirculation valve 8
If the differential pressure generated on both sides of 0 can be suppressed to a small value, even under the situation where the valve opening fixation abnormality occurs,
The amount of exhaust gas recirculation can be suppressed to a small amount. Therefore, according to the system of the present embodiment, the exhaust gas is excessively recirculated when the EGRV 80 has a valve opening sticking abnormality despite the fact that the variable displacement turbocharger 62 is incorporated in the internal combustion engine 10. Can be prevented. When the process of step 114 is completed, the process proceeds to step 1
Sixteen processes are executed.

In step 116, the check engine lamp is turned on, and the EGRV8
A process for notifying that 0 is abnormal is executed. When the process of step 116 ends, the current routine ends. In the routine shown in FIG.
If it is determined in step 110 that the condition a ≧ 1.1 is not satisfied, the process of step 118 is executed next.

In step 118, it is determined whether or not the calculated value a is equal to or less than a predetermined value 0.9. If a ≦ 0.9 holds, it can be determined that the actual opening of the EGRV 80 is unduly small as compared to the target opening. in this case,
The ECU 12 determines that the EGRV 80 is stuck in the valve closed state, that is, the EGRV 80 has a valve closing stuck abnormality.

If the abnormality that has occurred in the EGRV 80 is a valve-closing abnormality, the exhaust gas will not be excessively recirculated even if no processing is performed. For this reason, if it is determined in step 118 that a ≦ 0.9 is satisfied, then the process of step 116, that is, only the process of displaying an abnormality to the driver of the vehicle, is executed. This routine ends.

On the other hand, in step 118, a ≦ 0.9
Is determined not to be established, it can be determined that the EGRV 80 is appropriately controlled in the vicinity of the target opening. In this case, without any further processing,
This routine is immediately terminated.

As described above, according to the internal combustion engine 10, the EG
When the RV 80 is functioning normally, the function of the variable capacity turbocharger 62 can provide excellent responsiveness and excellent output characteristics over a wide operating range. Further, when the EGRV 80 has a valve opening sticking abnormality, it is possible to inform the driver of the abnormality and to prevent the exhaust gas from being excessively recirculated. Furthermore,
When the EGRV 80 has a valve-closed sticking abnormality, the driver can be notified of the occurrence of the abnormality while maintaining the function of the variable capacity turbocharger 62.

In the above embodiment, the variable capacity turbocharger 62 corresponds to the "pressure adjusting means" of the first aspect, and the ECU 12 executes the processing of steps 102 and 104. Accordingly, the “opening degree control means” according to claim 1 can execute step 1
By executing the processing of step 06, the “actual opening detection means” according to claim 1 can execute the steps 110 and 11 described above.
The "differential pressure reducing means" according to the first and second aspects is realized by executing the processing of the fourth aspect.

Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment of the present invention corresponds to FIG.
In the system configuration shown in FIG.
This is realized by executing a control routine shown in FIG. 3 instead of the control routine shown in FIG.

FIG. 3 shows an example of the system according to the present embodiment.
4 shows a flowchart of a control routine executed by the CU 12. In FIG. 3, steps that execute the same processing as the steps in the routine shown in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted. The routine shown in FIG. 3 is a regular interruption routine started at predetermined time intervals, similarly to the routine shown in FIG. When the routine shown in FIG. 3 is started, first, the process of step 120 is executed.

In step 120, based on the output signals of various sensors provided in the internal combustion engine 10, the engine speed NE,
Fuel temperature THF, accelerator opening AACC, vehicle speed SPD,
And the intake air temperature THA is calculated. The ECU 12 determines the operating state of the internal combustion engine 10 based on these calculated values.

In step 122, the target opening of the intake throttle valve 58 is calculated. The target opening degree of the intake throttle valve 58 is calculated to a value for realizing the intake pressure PM to be generated in order to set the recirculation amount of the exhaust gas to a flow rate corresponding to the operation state of the internal combustion engine 10. The target opening of the intake throttle valve 58 is
Specifically, based on the operating state of the internal combustion engine 10, EC
The calculation is performed with reference to the map stored in U12.

When the processing in step 122 is completed,
Thereafter, the processing of steps 102 to 110 is sequentially performed. If it is determined in step 110 that a ≧ 1.1 does not hold, the same processing as in the first embodiment is performed. On the other hand, in step 110, a ≧ 1.
If it is determined that “1” is established, the process proceeds to step 11
After the drive duty of the EGRV 80 is set to "0" in step 2, the process of step 124 is executed.

In step 124, a process for fully closing the intake throttle valve 58 is executed. As described above, it is determined in step 110 that a ≧ 1.1 holds because EG
This is the case where the valve closing fixation abnormality of the RV 80 has occurred. When the process of step 124 is performed in such a situation, the intake pressure is thereafter maintained at a value near the atmospheric pressure, and the differential pressure generated on both sides of the EGRV 80 is suppressed to a small value. it can.

Further, in the present embodiment, after the processing in step 124 is completed, the variable nozzle 72 of the variable capacity turbocharger 62 is then fully opened in step 11.
4 is executed. For this reason, according to the system of the present embodiment, despite having both the variable capacity turbocharger 62 and the intake throttle valve 58, the EGR
EGRV8 when a valve opening sticking abnormality occurs in V80
The differential pressure generated on both sides of zero can be maintained at a sufficiently small value. Therefore, according to the system of the present embodiment,
The flow rate of the recirculated exhaust gas when the EGRV 80 has the valve opening sticking abnormality can be suppressed to a smaller amount as compared with the case of the above-described first embodiment.

In the above-described embodiment, the variable displacement turbocharger 62 and the intake throttle valve 58 correspond to the "pressure adjusting means" of the first embodiment.
The CU 12 performs steps 110, 114 and 124 described above.
By executing the above processing, the "differential pressure reducing means" according to the first and third aspects is realized.

Next, a third embodiment of the present invention will be described with reference to FIGS. In the third embodiment of the present invention, in the system configuration shown in FIG.
Then, it is realized by executing the control routine shown in FIGS. 4 and 5 instead of the control routine shown in FIG.

FIGS. 4 and 5 show a flowchart of a control routine executed by the ECU 12 in the system of this embodiment. 4 and FIG.
Steps that execute the same processes as those in the routine shown in FIG. 3 or in the routine shown in FIG. 3 are given the same reference numerals, and descriptions thereof are omitted.

The routine shown in FIGS. 4 and 5 is a regular interruption routine started at predetermined time intervals, similarly to the routine shown in FIG. 2 or FIG. 4 and 5
When the routine shown in FIG.
After the processes of 0, 122, and 102 to 108 are sequentially performed, the process of step 130 is performed.

In step 130, the counter n is set to "0".
Is performed. When the processing in step 130 is completed, then in step 110, a ≧ a
It is determined whether 1.1 is satisfied. In this routine, if it is determined in step 110 that the condition of a ≧ 1.1 is satisfied, then the process of step 132 is executed. On the other hand, if it is determined that a ≧ 1.1 does not hold, the process of step 118 is executed next, as in the first and second embodiments.

In step 132, a process for reducing the drive duty of the EGRV 80 by 5% and a process for incrementing the counter n are executed. When the process of step 132 is completed, the process of step 134 is executed next. Assuming that the condition of step 110 is temporarily satisfied simply due to a control error, the actual opening should approach the target opening by executing the process of step 132. On the other hand, actually EGRV8
If there is a valve opening sticking abnormality at 0,
Even if the process of 32 is executed, the actual opening does not approach the target opening.

In step 134, it is determined whether or not the coefficient value of the counter n has reached "5", that is, after it is determined that the condition of a ≧ 1.1 is satisfied, whether or not the process of step 132 has been repeated five times Is determined. If it is determined in step 134 that n ≧ 5 is satisfied, it can be determined that the EGRV 80 has actually caused the valve-opening sticking abnormality. Therefore, in this case, the EGRV8
In order to cope with the valve opening sticking abnormality of 0, the processing after step 112 is executed.

When it is determined that a ≧ 1.1 is satisfied even though the EGRV 80 does not have the valve sticking abnormality, and after the EGRV 80 has the valve sticking error,
If the fixation is released while the processing of step 132 is repeatedly executed, n ≧ n in step 134
Before it is determined that 5 is established, it is determined in step 110 that a ≧ 1.1 is not established. Therefore, in such a case, processing for dealing with the valve opening sticking abnormality, that is, steps 112, 124, 114 and 116
Is not executed.

In this embodiment, if it is determined in step 118 that a ≦ 0.9 is satisfied, then the processing of step 136 is executed. On the other hand, if it is determined that a ≦ 0.9 is not established, the current routine is terminated without any further processing, as in the first and second embodiments.

At step 136, a process for increasing the drive duty of the EGRV 80 by 5% and a process for incrementing the counter n are executed. When the process of step 136 is completed, the process of step 138 is executed next. If the condition in step 118 is satisfied simply due to a control error,
The actual opening should approach the target opening by executing the process of 36. On the other hand, if the EGRV 80 actually has the valve-closing abnormality, the actual opening does not approach the target opening even if the process of step 136 is executed.

At step 138, after it is determined whether the coefficient value of the counter n has reached "5", that is, after it is determined that the condition of a≤0.9 is satisfied, it is determined whether or not the process at step 136 is repeated five times. Is determined. If it is determined in step 138 that n ≧ 5 is satisfied, it can be determined that the EGRV 80 is actually having the valve-closed sticking abnormality. Therefore, in this case, the EGRV8
In order to cope with the valve closing sticking abnormality of 0, the process of step 116 is executed.

When it is determined that a ≦ 0.9 is satisfied even though the EGRV 80 does not have the valve-closing abnormality, and after the EGRV 80 has the valve-closing abnormality,
If the fixation is released while the processing of step 136 is repeatedly executed, n ≧ n in step 138.
Before it is determined that 5 is established, it is determined in step 118 that a ≦ 0.9 is not established. Therefore, in such a case, the processing for coping with the valve-closed sticking abnormality, that is, the processing of step 116 is not executed.

As described above, according to the system of the present embodiment, only when the EGRV 80 actually has the valve-opening abnormality or the valve-closing abnormality, the processing for coping with them is executed. Can be. Therefore, according to the system of the present embodiment, higher control reliability can be obtained as compared with the system of the first embodiment or the system of the second embodiment.

[0077]

As described above, according to the first aspect of the present invention, despite the provision of the mechanism for changing the differential pressure generated on both sides of the exhaust gas recirculation valve in accordance with the operation state of the internal combustion engine, Excessive recirculation of exhaust gas can be effectively prevented when an exhaust valve reopening valve abnormality occurs.

According to the second aspect of the invention, when the variable-capacity turbocharger is mounted on the internal combustion engine and the exhaust gas recirculation valve is stuck in the open state, the exhaust gas is prevented from being excessively recirculated. can do. According to the third aspect of the present invention, it is possible to prevent the exhaust gas from being excessively recirculated when the exhaust gas recirculation valve has a valve opening fixation abnormality while the intake throttle valve is mounted on the internal combustion engine. .

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of an internal combustion engine equipped with an exhaust gas recirculation device according to one embodiment of the present invention.

FIG. 2 is a flowchart of an example of a control routine executed by the system according to the first embodiment of the present invention.

FIG. 3 is a flowchart of an example of a control routine executed in a system according to a second embodiment of the present invention.

FIG. 4 is a flowchart (part 1) of an example of a control routine executed by a system according to a third embodiment of the present invention;
It is.

FIG. 5 is a flowchart (part 2) of an example of a control routine executed by the system according to the third embodiment of the present invention;
It is.

[Explanation of symbols]

 Reference Signs List 10 internal combustion engine 12 electronic control unit (ECU) 52 intake passage 58 intake throttle valve 62 variable capacity turbocharger 68 exhaust passage 70 exhaust turbine 72 variable nozzle 78 exhaust recirculation passage 80 exhaust recirculation valve (EGRV)

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁶ Identification code FI F02D 9/02 F02D 21/08 311B 21/08 311 23/00 J 23/00 43/00 301K 43/00 301 301N 301R F02B 37 / 12 301N

Claims (3)

[Claims] 1. An exhaust gas recirculation system for recirculating exhaust gas from an exhaust passage of an internal combustion engine to an intake passage, wherein the exhaust gas recirculation passage communicates the exhaust passage and the intake passage, and the exhaust gas recirculation is provided in the exhaust gas recirculation passage. A valve; opening control means for controlling the opening of the exhaust gas recirculation valve to a target opening corresponding to the operating state of the internal combustion engine; actual opening detecting means for detecting the actual opening of the exhaust gas recirculation valve; Pressure adjusting means for changing a differential pressure generated on both sides of the exhaust gas recirculation valve in accordance with an operation state of the engine; and when the actual opening is larger than the target opening, the pressure adjusting means is provided on both sides of the exhaust gas recirculation valve. An exhaust gas recirculation device comprising: a pressure reducing unit that controls the pressure adjusting unit so that a generated differential pressure is reduced. 2. The exhaust gas recirculation device according to claim 1, wherein the pressure adjusting means includes a variable capacity turbocharger having a variable nozzle in an exhaust turbine, and the actual opening is smaller than the target opening. And the differential pressure reducing means changes the opening degree of the variable nozzle so as to increase the effective area of the path through which the exhaust gas flows in the exhaust turbine. apparatus. 3. The exhaust gas recirculation device according to claim 1, wherein the pressure adjusting means includes an intake throttle valve provided in an intake passage, and the actual opening is larger than the target opening. The exhaust gas recirculation device, wherein the differential pressure reducing unit increases the opening of the intake throttle valve.