JP5088306B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a technical field of a control device for an internal combustion engine including a turbocharger and an EGR device.

  This type of technique is proposed in Patent Document 1, for example. Patent Document 1 proposes a technique for determining a backflow state in which EGR gas flows back from the intake side to the exhaust side. Specifically, based on the intake pressure, the exhaust pressure, and the EGR flow rate, the forward flow state and the reverse flow state of the EGR gas are determined, and the EGR valve is closed when the EGR flow rate decreases due to the reverse flow. Have been described.

JP 2008-101498 A

  However, with the technique described in Patent Document 1, it is possible to detect the forward flow state and the reverse flow state of the EGR gas, but it is difficult to appropriately determine the blow-in of the intake air to the exhaust side due to the reverse flow of the EGR gas. there were. For this reason, there is a possibility that emission may be deteriorated.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a control device for an internal combustion engine that can appropriately determine the blow-by due to the backflow of intake air through the EGR passage. To do.

In one aspect of the present invention, a control device for an internal combustion engine that is applied to an internal combustion engine that includes a turbocharger and an EGR device having an EGR passage and an EGR valve has a differential pressure between the intake pressure and the exhaust pressure. Whether or not a reverse flow of the intake air from the intake side to the exhaust side occurs through the EGR passage based on the pulsation width of the intake pressure during a predetermined period when the EGR valve is open below the predetermined value Backflow determination means for determining whether or not the backflow occurs using a variation rate defined by an average value of the intake pressure and a standard deviation of the intake pressure during the predetermined period. It is determined whether or not.
The above control device for an internal combustion engine is preferably applied to an internal combustion engine including a turbocharger and an EGR device. The reverse flow determination means is configured to perform EGR based on the pulsation width (in other words, the amplitude value) of the intake pressure in a predetermined period when the differential pressure between the intake pressure and the exhaust pressure is less than a predetermined value and the EGR valve is open. It is determined whether or not a reverse flow of the intake air from the intake side to the exhaust side occurs through the passage. As a result, it is possible to appropriately determine whether the intake air is blown from the intake side to the exhaust side due to the backflow of gas in the EGR passage.
Further, the reverse flow determination means determines whether or not a reverse flow has occurred using a variation rate defined by the average value of the intake pressure and the standard deviation of the intake pressure during a predetermined period. Thereby, it is possible to accurately determine the backflow of the intake air from the intake side to the exhaust side.

In another aspect of the present invention, a control device for an internal combustion engine applied to an internal combustion engine provided with a turbocharger and an EGR device having an EGR passage and an EGR valve has a differential pressure between the intake pressure and the exhaust pressure. Whether or not a reverse flow of the intake air from the intake side to the exhaust side occurs through the EGR passage based on the pulsation width of the intake pressure during a predetermined period when the EGR valve is open below the predetermined value A reverse flow determining means for determining whether or not the reverse flow is determined by the reverse flow determining means, and correcting the air-fuel ratio in the cylinder by correcting the fuel injection amount. and means, the. Thereby, the emission deterioration resulting from a backflow mentioned above can be suppressed appropriately.

  Preferably, the air-fuel ratio correcting means is defined by the fluctuation rate obtained when the backflow determining means determines that the backflow is occurring and the intake pressure when the intake air is not backflowing. Based on the result of comparison with the reference fluctuation rate, the air-fuel ratio is corrected. As a result, the air-fuel ratio can be corrected with higher accuracy.

In another aspect of the present invention, a control device for an internal combustion engine applied to an internal combustion engine provided with a turbocharger and an EGR device having an EGR passage and an EGR valve has a differential pressure between the intake pressure and the exhaust pressure. Whether or not a reverse flow of the intake air from the intake side to the exhaust side occurs through the EGR passage based on the pulsation width of the intake pressure during a predetermined period when the EGR valve is open below the predetermined value a backflow determining section for performing Kano determination, if the back flow by the back flow determining means is determined to have occurred, and a EGR valve control means for controlling to reduce the opening degree of the EGR valve. Also by this, it is possible to appropriately suppress the emission deterioration caused by the backflow described above.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

[Device configuration]
FIG. 1 is a configuration diagram showing the configuration of an internal combustion engine to which the control device for an internal combustion engine of the present invention is applied. In FIG. 1, solid arrows indicate an example of a gas (intake and exhaust) flow, and broken arrows indicate a signal flow.

  The internal combustion engine (engine) is mounted as a driving power source in a vehicle such as an automobile, and mainly includes a plurality of cylinders 10, an intake passage 3 and an exhaust passage 4 connected to each cylinder 10, an intake passage 3, And a turbocharger 5 provided in the exhaust passage 4. In FIG. 1, only one cylinder 10 is displayed. The turbocharger 5 includes a compressor 5a provided in the intake passage 3 and a turbine 5b provided in the exhaust passage 4, and these are configured to rotate integrally.

  In the intake passage (intake pipe) 3, an air cleaner 9, an air flow meter (AFM) 41, an air bypass valve 31, a compressor 5a of the turbocharger 5, an intercooler 6, a throttle valve 32, and intake air are taken. A storable surge tank 7 is provided. The AFM 41 detects the amount of intake air (intake amount) taken from outside, and transmits a detection signal S41 corresponding to the detected intake amount to the ECU 50. The air bypass valve 31 is provided in the bypass passage 3 a that connects the upstream side and the downstream side of the compressor 5 a in the intake passage 3. The air bypass valve 31 is for adjusting the amount of intake air passing through the bypass passage 3a, and is controlled by a control signal from the ECU 50. For example, when the throttle valve 32 is suddenly closed, the ECU 50 opens the air bypass valve 31 to prevent the intake pressure in the intake passage 3 from rising suddenly, and the intake air compressed by the compressor 5a. Is released from the bypass passage 3a. The throttle valve 32 is for adjusting the amount of intake air in the intake passage 3 and is controlled by a control signal from the ECU 50.

  The intake passage 3 is provided with an intake air temperature sensor 42 and intake pressure sensors 43 and 44. The intake air temperature sensor 42 detects the temperature of intake air (intake air temperature) in the intake passage 3 and transmits a detection signal S42 corresponding to the detected intake air temperature to the ECU 50. The intake pressure sensors 43 and 44 detect intake pressure in the intake passage 3 (meaning intake pipe pressure; the same applies hereinafter) and transmit detection signals S43 and S44 corresponding to the detected intake pressure to the ECU 50.

  An intake passage 3 and an exhaust passage 4 are connected to the combustion chamber 10a of the cylinder 10, and a fuel injection valve 11 for injecting fuel into the combustion chamber 10a, and fuel in the combustion chamber 10a are ignited. A spark plug 12 is provided. The fuel injection valve 11 and the spark plug 12 are controlled by a control signal from the ECU 50. The cylinder 10 is provided with an intake valve 13 and an exhaust valve 14. The intake valve 13 controls conduction / interruption between the intake passage 3 and the combustion chamber 10a by opening and closing. The exhaust valve 14 controls opening / closing of the exhaust passage 4 and the combustion chamber 10a by opening and closing. When the intake valve 13 is opened, intake air is introduced from the intake passage 3 into the combustion chamber 10a. The intake air introduced into the combustion chamber 10a is mixed with the fuel injected from the fuel injection valve 11, and then burned when the spark plug 12 is ignited. Exhaust gas generated by the combustion is discharged to the exhaust passage 4 when the exhaust valve 14 is opened. When fuel and intake air are burned in the combustion chamber 10a, a force is generated that pushes down the piston 15 to the bottom dead center. The force that pushes down the piston 15 to the bottom dead center is transmitted to the crankshaft 17 through the connecting rod 16, and the crankshaft 17 rotates. Here, a crank angle sensor 45 is provided in the vicinity of the crankshaft 17. The crank angle sensor 45 detects the rotation angle (crank angle) of the crankshaft 17 and transmits a detection signal S45 corresponding to the detected crank angle to the ECU 50. Further, a water temperature sensor 48 is attached to the side surface of the cylinder 10 to detect the coolant temperature in the water jacket (not shown) of the cylinder 10 and send a detection signal S48 corresponding to the detected water temperature to the ECU 50. Send.

  In the exhaust passage 4, a turbine 5 b of the turbocharger 5, a waste gate valve 36, and a catalyst 8 are provided. The waste gate valve 36 is provided in the bypass passage 4 a that connects the upstream side and the downstream side of the turbine 5 b in the exhaust passage 4. The waste gate valve 36 is for adjusting the exhaust amount passing through the bypass passage 4a, and is controlled by a control signal from the ECU 50. The catalyst 8 is a three-way catalyst, for example, and has a function of purifying hydrocarbons, carbon monoxide, nitrogen oxides, and the like. Instead of the catalyst 8, an exhaust purification device that combines a particulate filter that collects particulate matter in the exhaust gas and the catalyst may be used.

  The exhaust passage 4 is provided with an air-fuel ratio sensor (A / F sensor) 46. The A / F sensor 46 detects the air-fuel ratio of the exhaust gas in the exhaust passage 4, and transmits a detection signal S46 corresponding to the detected air-fuel ratio to the ECU 50. Specifically, the A / F sensor 46 is an oxygen concentration sensor. Since the oxygen concentration sensor has a large temperature dependence of its output voltage, it is necessary to keep the element temperature at an appropriate temperature (active temperature) in order to maintain a good detection accuracy of the oxygen concentration. Therefore, a heater is attached to the oxygen concentration sensor. The ECU 50 controls energization of the heater so as to keep the element temperature at the activation temperature (for example, about 700 ° C. or higher) by the heat generated by the heater.

  In the internal combustion engine according to the present embodiment, an EGR device 20 for recirculating exhaust gas (EGR gas) to the intake side is provided. The EGR device 20 mainly includes an EGR passage 21 through which EGR gas passes, an EGR catalyst 22 configured to purify the EGR gas, an EGR cooler 23 that cools the EGR gas, and an amount of EGR gas that is recirculated to the intake side. The EGR valve 33 is configured to be adjustable. One end of the EGR passage 21 is connected to the exhaust passage 4 upstream of the turbine 5 b and the other end is connected to the intake passage 3 downstream of the throttle valve 32. Specifically, the EGR passage 21 includes two passages 21a and 21b, and EGR gas is introduced through these passages 21a and 21b. That is, EGR gas is taken out from the two exhaust systems. The EGR valve 33 is controlled by a control signal S33 supplied from the ECU 50.

  Here, with reference to FIG. 2, a specific configuration of the EGR device 20 described above will be described. FIG. 2 is a schematic diagram showing the configuration of the EGR device 20. Here, as an example, a configuration of an internal combustion engine including four cylinders 10a, 10b, 10c, and 10d is shown. In FIG. 2, the difference between the exhaust passages 4 a and 4 d is represented by hatching, and the connection portion of the passage is represented by a black circle. The same components as those shown in FIG. 1 are denoted by the same reference numerals.

  As illustrated, an exhaust passage 4a is connected to the cylinders 10a and 10d, and an exhaust passage 4b is connected to the cylinders 10b and 10c. Then, the passage 21a in the EGR passage 21 is connected to the exhaust passage 4a, the passage 21b in the EGR passage 21 is connected to the exhaust passage 4b, and EGR gas is introduced from these passages 21a and 21b. The turbocharger 5 is configured such that exhaust gas is supplied to the turbine 5b from the exhaust passages 4a and 4b, that is, configured as a twin entry turbocharger.

  Returning to FIG. The ECU (Electronic Control Unit) 50 has a CPU, ROM, RAM, A / D converter, input / output interface, etc. (not shown), and detects the operating state of the internal combustion engine based on detection signals S41 to S46 from various sensors. Then, the internal combustion engine is controlled based on the detected operating state. In the present embodiment, the ECU 50 mainly determines whether or not a reverse flow of the intake air from the intake side to the exhaust side occurs through the EGR passage 21 based on the intake pressure detected by the intake pressure sensor 44. Then, the ECU 50 controls the fuel injection valve 11 and the EGR valve 33 based on the determination result. Thus, the ECU 50 functions as a control device for the internal combustion engine in the present invention, and operates as a backflow determination means, an air-fuel ratio correction means, and an EGR valve control means.

[Backflow judgment method]
Next, a method for determining the backflow of the intake air (fresh air) from the intake side to the exhaust side performed in the present embodiment will be described. In the present embodiment, the ECU 50 determines whether or not a reverse flow of the intake air from the intake side to the exhaust side occurs through the EGR passage 21 based on the intake pressure detected by the intake pressure sensor 44. That is, it determines whether the intake air has blown from the intake side to the exhaust side due to the backflow of gas in the EGR passage 21.

  Here, the reason for performing such determination will be described. When the intake air flows backward to the exhaust side through the EGR passage 21, the emission deterioration may occur due to the deviation of the in-cylinder air-fuel ratio (detected value of the air flow meter 41). Further, the catalyst 8 may be melted (oxygen reacts on the catalyst 8), in other words, the condition that the bed temperature of the catalyst 8 rises abnormally may be satisfied. On the other hand, when the supercharging pressure on the low speed side is high as in a twin entry turbocharger, there is a tendency that the condition that the average intake pressure is higher than the average back pressure. In this case, since the ignition timing on the low speed side shifts to the retard side due to knocking, it can be said that it is desirable to introduce the EGR gas and advance the ignition timing. If the EGR gas introduction possible range is clearly determined, the EGR valve 33 can be appropriately controlled by a map adapted in advance. However, such an introduction possible range can be determined by the wastegate valve 36 or the ignition delay angle by the knock strength. It can be said that it is difficult to determine uniquely.

  Therefore, in the present embodiment, it is determined whether or not the backflow of the intake air from the intake side to the exhaust side occurs through the EGR passage 21. Specifically, when the differential pressure between the intake pressure and the exhaust pressure is equal to or less than a predetermined value (for example, in a high load range) and the EGR valve 33 is open, the ECU 50 Based on the pulsation width, it is determined whether or not a reverse flow of the intake air from the intake side to the exhaust side occurs through the EGR passage 21. In other words, the ECU 50 determines whether or not the backflow has occurred based on the magnitude of the amplitude value of the intake pressure during the predetermined period.

  FIG. 3 is a diagram for explaining the basic concept of the backflow determination method in the present embodiment. FIG. 3 shows the crank angle on the horizontal axis and the intake pressure (intake pipe pressure) on the vertical axis. A solid line A1 indicates a change in intake pressure during normal time (that is, when no backflow occurs), and a broken line A2 indicates a change in intake pressure when a backflow occurs. The intake pressure indicated by the solid line A1 and the intake pressure indicated by the broken line A2 are obtained by setting the same flow rate.

  As can be seen from FIG. 3, when the backflow is generated, the pulsation width of the intake pressure is smaller than that in the normal state. This is presumably because the influence of exhaust pressure is reduced when backflow occurs. Specifically, it is considered that the backflow tends to occur when the intake pressure is higher than the exhaust pressure. In this case, if the amplitude value (≈standard deviation) of the exhaust pulsation decreases while the intake gate pressure 36 is maintained by opening the waste gate valve 36 or the like, the pulsation width of the intake pressure when the EGR gas is introduced decreases. It can be said that there is a tendency to. Conversely, if the intake pressure increases while maintaining the exhaust pressure amplitude, it can be said that the same phenomenon tends to occur.

  From the above, in the present embodiment, when the differential pressure between the intake pressure and the exhaust pressure is equal to or less than a predetermined value and the EGR valve 33 is open, based on the pulsation width of the intake pressure during a predetermined period, It is determined whether or not a reverse flow of the intake air from the intake side to the exhaust side occurs through the passage 21. For example, the ECU 50 determines that the backflow has occurred when the pulsation width of the intake pressure is equal to or less than a predetermined value. As an example, the ECU 50 measures the pulsation width of the intake pressure based on the difference value between the average value of the intake pressure during the predetermined period and the maximum value of the intake pressure. Note that since the minimum value of the intake pressure is difficult to obtain at the minimum location, an average value is used.

  Here, when the backflow is determined by directly measuring the pulsation width of the intake pressure as described above, it can be said that an erroneous determination may occur due to, for example, an increase in standard deviation due to noise. Therefore, in the present embodiment, the ECU 50 does not directly measure the pulsation width of the intake pressure, but uses the fluctuation rate defined by the average value of the intake pressure and the standard deviation of the intake pressure during a predetermined period, thereby By indirectly determining the pulsation width of the atmospheric pressure, it is determined whether or not the intake air is flowing backward to the exhaust side through the EGR passage 21. Specifically, assuming that the average value of the intake pressure in the predetermined period is “Ave.P” and the standard deviation of the intake pressure in the predetermined period is “Std.P”, the fluctuation rate ΔP is expressed by the following equation (1). Is done.

ΔP = Std. P / Ave. P Formula (1)
The variation rate ΔP in the equation (1) is a value corresponding to the relative standard deviation (variation coefficient) of the intake pressure in a predetermined period. The average value and the standard deviation of the intake pressure are obtained from the intake pressure measured at a predetermined crank angle or a predetermined time. For example, 720 (CA) can be used as the predetermined crank angle, and 10 (sec) can be used as the predetermined time.

  Further, in the present embodiment, the ECU 50 is a variation rate obtained from the equation (1) and a variation rate defined by the intake pressure when the intake air is not flowing backward (a variation rate obtained in advance by adaptation, Hereinafter, the degree of intake backflow is defined by a deviation rate (%). This divergence rate is expressed by equation (2).

Deviation rate = (reference rate of change-current rate of change) / reference rate of change x 100 (2)
As shown in the equation (2), as the deviation rate increases, the amount of intake air that flows back to the exhaust side through the EGR passage 21 tends to increase, that is, the amount of intake air that blows through to the exhaust side tends to increase. The ECU 50 performs control for correcting the air-fuel ratio (air-fuel ratio correction control) and control for the EGR valve 33 based on such a deviation rate. Specifically, the air-fuel ratio in the cylinder is converged to the target air-fuel ratio by performing control to reduce the fuel injection amount in accordance with the deviation rate (for example, the fuel injection amount is reduced as the deviation rate increases). The reason for this is to suppress the deterioration of the emission caused by the fact that the intake air blows through to the exhaust side and not all the intake air corresponding to the intake air amount detected by the air flow meter 41 flows into the cylinder.

  Further, the ECU 50 performs control to reduce the opening degree of the EGR valve 33 when the deviation rate is equal to or greater than a predetermined value. For example, the ECU 50 performs control to reduce the opening degree of the EGR valve 33 so that the deviation rate is less than a predetermined value (or the fluctuation rate is less than a predetermined value). This is because the amount of intake air flowing backward to the exhaust side through the EGR passage 21 is reduced to suppress the deterioration of the emission due to the melting loss of the catalyst 8 or the like. The predetermined value used for the deviation rate to determine whether or not to reduce the opening of the EGR valve 33 is set in consideration of an error (noise) of the deviation rate. For example, the opening of the EGR valve 33 is determined. The divergence rate is set such that the degree needs to be reduced.

  Here, with reference to FIG.4 and FIG.5, the control method which concerns on this embodiment is demonstrated concretely.

  FIG. 4 shows an example of a time chart when the control according to the present embodiment is performed. FIG. 4 shows the control execution flag on / off, the deviation rate, and the opening degree of the EGR valve 33 in order from the top. The control execution flag is a flag indicating whether or not a condition for causing a reverse flow of the intake air is satisfied. The differential pressure between the intake air pressure and the exhaust air pressure is equal to or less than a predetermined value, and the EGR valve 33 is opened. Turns on when the condition is met. For example, the control execution flag is turned on when the upstream pressure of the throttle valve 32 is equal to or higher than a predetermined value and the EGR control is being executed.

  In this case, the control execution flag is turned on from off at time t1. Thereafter, at time t2, the deviation rate becomes equal to or greater than the predetermined value B1. At this time, the ECU 50 performs control to reduce the opening degree of the EGR valve 33. Thereby, at the time t3, the deviation rate becomes less than the predetermined value B1. Therefore, at time t3, the ECU 50 ends the control for reducing the opening degree of the EGR valve 33.

  FIG. 5 is a diagram for explaining an example of a method for reducing the fuel injection amount in accordance with the deviation rate. In FIG. 5, the horizontal axis indicates the deviation rate (%), and the vertical axis indicates the fuel injection amount increase coefficient. When a value equal to or smaller than “1” is used as the increase coefficient, the fuel injection amount is reduced.

  As shown in FIG. 5, when the deviation rate is less than “25 (%)”, the increase coefficient is decreased according to the deviation rate. When the deviation rate is “25 (%)” or more, the increase coefficient is not related to the deviation rate. It becomes a constant value (0.8). The ECU 50 obtains an increase coefficient corresponding to the deviation rate obtained from the equations (1) and (2) based on the relationship between the deviation rate and the increase coefficient of the fuel injection amount. Then, the ECU 50 corrects (decreases) the fuel injection amount in accordance with the obtained increase coefficient. For example, an amount obtained by multiplying the original fuel injection amount by an increase coefficient is set as the corrected fuel injection amount.

[Control processing]
Next, a control process according to the present embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing a control process according to the present embodiment. This process is repeatedly executed by the ECU 50 at a predetermined cycle.

  First, in step S101, the ECU 50 determines whether or not the upstream pressure of the throttle valve 32 (throttle upstream pressure) is greater than or equal to a predetermined value. The ECU 50 makes a determination based on the pressure obtained from the intake pressure sensor 43. If the upstream pressure of the throttle valve 32 is greater than or equal to a predetermined value (step S101; Yes), the process proceeds to step S102. If the upstream pressure of the throttle valve 32 is less than the predetermined value (step S101; No), the process ends. To do.

  In step S102, the ECU 50 determines whether or not EGR control is being executed. In other words, it is determined whether or not the EGR valve 33 is open. Note that, by performing the determinations in steps S101 and S102, it is determined whether or not a condition that causes a backflow of intake air is satisfied. If the EGR control is being executed (step S102; Yes), the process proceeds to step S103. If the EGR control is not being executed (step S102; No), the process ends.

  In step S103, the ECU 50 acquires the intake pressure between predetermined crank angles. Specifically, the intake pressure between 720 (CA) is measured. The ECU 50 acquires the intake pressure from the intake pressure sensor 44. Then, the process proceeds to step S104.

  In step S104, the ECU 50 calculates the variation rate from the intake pressure acquired in step S103. Specifically, the fluctuation rate is calculated by substituting the average value (Ave.P) of the intake pressure between 720 (CA) and the standard deviation (Std.P) of the intake pressure into Equation (1). . Then, the process proceeds to step S105.

  In step S105, the ECU 50 executes air-fuel ratio correction control based on the variation rate calculated in step S104. Specifically, the ECU 50 calculates the deviation rate by substituting the obtained variation rate into the equation (2), and performs control to reduce the fuel injection amount based on the deviation rate. For example, the ECU 50 obtains an increase coefficient corresponding to the variation rate calculated in step S104 in accordance with the relationship between the predetermined deviation rate and the increase coefficient as shown in FIG. 5, and performs fuel injection based on the increase coefficient. Reduce the amount. Thereby, the air-fuel ratio in the cylinder is converged to the target air-fuel ratio. When the above process ends, the process proceeds to step S106.

  In step S106, the ECU 50 determines whether or not the deviation rate is a predetermined value or more. Here, it is determined whether or not the opening degree of the EGR valve 33 needs to be reduced. The predetermined value used for the determination is set in consideration of an error (noise) of the deviation rate and the like, and is set to a deviation rate that needs to reduce the opening of the EGR valve 33, for example. As an example, the predetermined value is set to “20 (%)”.

  If the deviation rate is equal to or greater than the predetermined value (step S106; Yes), the process proceeds to step S107. In this case, the ECU 50 performs control to reduce the opening degree of the EGR valve 33 (step S107). For example, the ECU 50 performs control by setting the opening degree of the EGR valve 33 so that the deviation rate is less than a predetermined value (or the fluctuation rate is less than a predetermined value). Then, the process ends. On the other hand, when the deviation rate is less than the predetermined value (step S106; No), the process ends.

  According to the control process described above, by using the fluctuation rate in the intake pressure, it is possible to appropriately determine the blow-by due to the backflow of the intake air to the exhaust side through the EGR passage 21. Further, by performing the air-fuel ratio correction based on the fluctuation rate (specifically, the deviation rate), it is possible to appropriately suppress the emission deterioration caused by the backflow.

1 is a configuration diagram showing a configuration of an internal combustion engine according to an embodiment of the present invention. It is the schematic which shows the structure of an EGR apparatus. It is a figure for demonstrating the basic concept of the backflow determination method in this embodiment. An example of the time chart at the time of performing control concerning this embodiment is shown. It is a figure for demonstrating an example of the method of correct | amending a fuel injection amount according to a deviation rate. It is a flowchart which shows the control processing which concerns on this embodiment.

Explanation of symbols

3 Intake passage 4 Exhaust passage 5 Turbocharger 8 Catalyst 10 Cylinder 20 EGR device 21 EGR passage 32 Throttle valve 33 EGR valve 41 Air flow meter 43, 44 Intake pressure sensor 50 ECU

Claims (4)

A control device for an internal combustion engine applied to an internal combustion engine having a turbocharger and an EGR device having an EGR passage and an EGR valve,
When the differential pressure between the intake pressure and the exhaust pressure is equal to or less than a predetermined value and the EGR valve is open, from the intake side to the exhaust side through the EGR passage based on the pulsation width of the intake pressure during a predetermined period. A reverse flow determination means for determining whether or not the reverse flow of the intake air is occurring,
Said backflow determining means, characterized in that said using the average value and variation rate defined by the standard deviation of those intake pressure of the intake pressure in a predetermined period, it is determined whether the check ring is occurring A control device for an internal combustion engine. A control device for an internal combustion engine applied to an internal combustion engine having a turbocharger and an EGR device having an EGR passage and an EGR valve,
When the differential pressure between the intake pressure and the exhaust pressure is equal to or less than a predetermined value and the EGR valve is open, from the intake side to the exhaust side through the EGR passage based on the pulsation width of the intake pressure during a predetermined period. Backflow determination means for determining whether or not the backflow of the intake air is occurring,
When the reverse flow by the back flow determining means is determined to have occurred, by correcting the fuel injection amount, characterized by comprising air-fuel ratio correction means for correcting the air-fuel ratio in the cylinder, the Control device for internal combustion engine. The air-fuel ratio correction means includes a reference fluctuation rate defined by the fluctuation rate obtained when the reverse flow determination means determines that the reverse flow is generated, and the intake pressure when the intake air is not backflowing. The control apparatus for an internal combustion engine according to claim 2 , wherein correction for the air-fuel ratio is performed based on a result of comparison with. A control device for an internal combustion engine applied to an internal combustion engine having a turbocharger and an EGR device having an EGR passage and an EGR valve,
When the differential pressure between the intake pressure and the exhaust pressure is equal to or less than a predetermined value and the EGR valve is open, from the intake side to the exhaust side through the EGR passage based on the pulsation width of the intake pressure during a predetermined period. Backflow determination means for determining whether or not the backflow of the intake air is occurring,
The backflow when the backflow is determined to have occurred by determining means, the control apparatus for an internal combustion engine, characterized in that it comprises, an EGR valve control means for controlling to reduce the opening degree of the EGR valve.

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