JP4501622B2 - EGR amount control device for internal combustion engine - Google Patents

Description

  The present invention relates to an EGR amount control device for an internal combustion engine, in which an EGR valve is provided in an EGR (exhaust gas recirculation) passage for recirculating a part of exhaust gas from an exhaust system to an intake system, and the EGR amount is controlled by the EGR valve. The present invention relates to an EGR control device for avoiding deterioration of torque fluctuation.

  In Patent Document 1, a surge level index value calculating means for calculating a surge level index value for detecting a surge generated in the engine based on engine crank angular speed information is compared with the surge level index value and the determination threshold. And a surge level determination means for determining the surge level, and the opening of the EGR valve is controlled based on the change of the surge level and the surge level.

When controlling the opening degree of the EGR valve, particularly the step motor type EGR valve, the basic EGR amount based on the engine speed and the engine load is based on the change in the surge level and the target value that is increased or decreased based on the surge level. The EGR amount is calculated by multiplying the limit value, the motor target position of the step motor type EGR valve is obtained based on the EGR amount, and the step motor type is calculated according to the comparison result between the motor target position and the current motor position. The EGR valve is driven.
JP 2002-48011 A

  However, in Patent Document 1, when the feedback correction value of the current motor position (EGR valve opening) is reflected so as to determine the deterioration of the surge and converge the surge, the pressure difference between the intake system and the exhaust system depends on the operating state. May increase, and in this case, the EGR amount changes abruptly. As a result, a torque step due to a change in the intake air amount or a change in the ignition timing occurs, and the drivability deteriorates.

  The present invention has been made in view of the above problems, and an object of the present invention is to suppress a torque step due to a rapid change in the EGR amount and ensure stable drivability.

Therefore, in the present invention, an EGR valve is provided in an EGR passage that recirculates part of the exhaust gas from the exhaust system to the intake system, and an EGR amount control device for an internal combustion engine that controls the EGR amount by the EGR valve is based on engine rotation fluctuations. The surge deterioration index value is calculated and the surge deterioration index value is compared with the determination threshold value to determine the presence or absence of surge deterioration, while the estimated EGR amount is calculated and the target EGR amount is calculated based on the determination of the presence or absence of surge deterioration. It calculates a correction amount, the amount of change in the estimated EGR quantity to allow correction of the target EGR quantity in the case of less than the first predetermined value, corrects the target EGR amount using the compensation amount.

  According to the present invention, since the target EGR amount is corrected in accordance with the permission determination of the correction of the target EGR amount based on the change amount of the estimated EGR amount, the torque step generated when the EGR amount changes abruptly is set to a level where there is no problem. This has the effect of being able to suppress and ensure stable drivability.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing an overall configuration of an internal combustion engine of the present invention.
Air is sucked into the combustion chamber of each cylinder of the engine 1 from the air cleaner 2 through the intake duct 3, the throttle valve 4, and the intake manifold 5. Each branch portion of the intake manifold 5 is provided with a fuel injection valve 6 for each cylinder. However, the fuel injection valve 6 may be arranged to directly face the combustion chamber.

  The fuel injection valve 6 is an electromagnetic fuel injection valve (injector) that opens when energized by a solenoid and closes when energization is stopped, and from an engine control unit (hereinafter referred to as “ECU”) 12 described later. The valve is energized by the drive pulse signal to open the valve, and the fuel supplied from the fuel pump (not shown) and adjusted to a predetermined pressure by the pressure regulator is injected and supplied.

Each combustion chamber of the engine 1 is provided with a spark plug 7, which sparks and ignites and burns the air-fuel mixture. The ignition timing of the spark plug 7 is also controlled by the ECU 12.
Exhaust gas from each combustion chamber of the engine 1 is discharged through an exhaust manifold 8. Further, an EGR passage 9 is led out from the exhaust manifold 8, whereby a part of the exhaust is recirculated to the intake manifold 5 via the EGR valve 10. The opening degree of the EGR valve 10 is also controlled by the ECU 12.

The ECU 12 includes a microcomputer including a CUP, a ROM, a RAM, an A / D converter, an input / output interface, and the like, receives input signals from various sensors, and based on these, the fuel injection valve 6, the ignition The operation of the plug 7 and the EGR valve 10 is controlled.
The various sensors include a crank that generates a reference crank angle signal (REF signal) at every 180 ° crank angle in the case of four cylinders in synchronization with the crankshaft rotation of the engine 1 and can detect the engine speed from the cycle. An angle sensor 13, an air flow meter 14 for detecting the intake air amount Qa in the intake duct 3, a throttle sensor 15 for detecting the opening TVO of the throttle valve 4, a water temperature sensor 16 for detecting the cooling water temperature Tw of the engine 1, and a vehicle speed VSP. A vehicle speed sensor 17 to be detected, an ignition switch 18 and the like are provided.

The output shaft of the engine 1 is connected to an automatic transmission (not shown) having a torque converter with a lock-up clutch, and is referred to as a control unit for automatic transmission control (hereinafter referred to as “A / T-CU”). ) 20 and ECU 12 are connected by a communication line, and gear position information and lockup information are input to ECU 12 from A / T-CU 20.
Control of the EGR valve 10 by the ECU 12 is performed as follows. A target EGR amount (EGR rate) set based on the operating conditions of the engine 1 is converted into a target EGR valve opening area, the target EGR valve opening area is converted into an EGR valve opening, and the EGR valve 10 is converted based on this. To control. When the EGR valve 10 is driven by a step motor, the target EGR amount (rate) is converted into a target step number, and the EGR valve is controlled based on this.

  Here, in the present invention, a surge deterioration index value is calculated based on engine rotation fluctuation, and the presence or absence of surge deterioration is determined by comparing the surge deterioration index value with a determination threshold value, while calculating an estimated EGR amount, A correction amount for the target EGR amount (target EGR valve opening area or target step number) is calculated based on the determination of whether or not the surge has deteriorated, and it is determined whether correction of the target EGR amount is permitted based on the change amount of the estimated EGR amount Then, the deterioration of the surge is avoided by correcting the target EGR amount using the correction amount based on the permission determination.

Next, specific control will be described with reference to the flowchart of FIG.
FIG. 2 is a flowchart of an EGR control (target step number) correction routine executed by the ECU 12 every 10 ms in time synchronization.
In step 1 (shown as “S1” in the figure, the same applies hereinafter), a surge deterioration index value FILD per unit time is calculated based on the rotational fluctuation of the engine 1.

Specifically, the cycle TREF (ms) of the REF signal is measured by another routine executed in rotation synchronization (REF signal interruption), and the engine speed (rpm) = 30 / TREF ( (In the case of a four-cylinder engine). Then, the fluctuation amount of the engine speed Ne is calculated, and this is set as the surge deterioration index value FILD.
However, since the engine rotation fluctuation includes a noise component irrelevant to the combustion stability, the noise component is removed by a technique as disclosed in JP-A-7-259627. That is, whether the combustion stability is good or bad is reflected in the frequency characteristics of the rotational fluctuation, so that the rotational fluctuation of the engine is detected. From the detected rotational fluctuation components, the first BPF normalized by the engine rotational frequency is detected. (Band-pass filter) and first BRF (band-reject filter) remove noise components caused by processing errors of the crank angle sensor 13, detect the gear ratio, and set the coefficient accordingly. The noise component caused by the distortion of the vehicle drive system is removed by the BRF of 2, and the rotational fluctuation component (frequency component) that gives an unpleasant vibration to the human is extracted and obtained by the second BPF in time synchronization. An execution value calculation is performed on the received signal, and a surge deterioration index value FILD is calculated.

In step 2, the target EGR amount (rate) TGEGR is calculated from the engine speed and the load. The target EGR rate is calculated from the difference (current calculation value−previous calculation value) or ratio (current calculation value / previous calculation value) between the previous calculation value and the current calculation value of the target EGR amount.
In step 3, an estimated EGR amount (rate) ESTMEGR is calculated based on the intake pressure PMANI and the target EGR valve opening area TAEGR as shown in the following equation (see Japanese Patent Application Laid-Open No. 2004-108272). This corresponds to estimated EGR amount calculation means.

ESTMEGR = TAEGR * (PMANI) ^ (1 / SHEATR) / (REX * TEX) * sqrt [2 * SHEATR * REX * TEX / (SHEATR-1) * (1-PMANI) ^ {(SHEATR-1) / SHEATR }]
Here, REX is a gas constant of the exhaust gas, and a target equivalent ratio (= 14.7 / target air-fuel ratio) of the exhaust gas is calculated and calculated based on this value. TEX is the gas temperature of the exhaust gas. SHEATR is an exhaust gas specific heat ratio, and calculates a target equivalent ratio and an in-cylinder temperature when the exhaust valve is closed, and calculates based on these calculated values. sqrt is the square root (√).

As shown in the following equation, the estimated EGR amount ESTMEGR may be calculated from the square root of the pressure ratio (PEXMANI / PMANI) between the intake pressure PMANI and the exhaust pressure PEXMANI and the EGR valve opening area TAEGR.
ESTMEGR = EGR valve opening area × √ (PEXMANI / PMANI)
When the estimated EGR amount ESTMEGR is calculated in this way, the same result can be obtained by approximating the exhaust pressure PEXMANI with the atmospheric pressure instead of calculating the intake pressure PMANI and the exhaust pressure PEXMANI.

Further, since the intake pressure PMANI has a correlation with the intake air amount Qa, the estimated EGR amount ESTMEGR can be calculated by substituting the intake air amount Qa for the ratio (PEXMANI / PMANI) of the intake pressure PMANI and the exhaust pressure PEXMANI. Good.
In step 4, as shown in the following equation, a deviation (change amount) is obtained by subtracting a calculated value (previous calculated value, initial value is 0) 10 ms before from the latest value (current calculated value) of the estimated EGR amount ESTMEGR. ) Calculate DEGR.

DEGR = ESTMEGR (latest value) −ESTMEGR (calculated value 10 ms before)
The deviation DEGR of the estimated EGR amount ESTMEGR may be calculated as a ratio between the latest value and the calculated value 10 ms before (latest value / 10 calculated value before 10 ms).
In step 5, it is determined whether or not the vehicle is in a stable state. Here, whether or not the vehicle is in a stable state is determined based on whether or not all of the following conditions (1) to (6) are satisfied.

(1) EGR region (EGRQ> 0). That is, it is a condition that EGR is being executed.
(2) The difference between the target EGR rate and the actual EGR rate is equal to or less than a predetermined value. That is, the condition is that EGR control converges and is not in a transient state.
(3) The gear position is the same continuously for a predetermined opening. In other words, the condition is that the gear is not being changed.

(4) The basic fuel injection amount Tp calculated based on the cylinder intake air amount is within a predetermined range.
(5) The absolute value of the deviation (change amount) DEGR of the estimated EGR amount ESTMEGR is less than the first predetermined value (| DEGR | <DEGR1 #). Thus, determining whether to permit correction of the target EGR amount TGEGR corresponds to target EGR amount correction permission determining means. That is, if | DEGR | <DEGR1 #, correction of the target EGR amount TGEGR is permitted. The first predetermined value DEGR1 # is the maximum value for the correction permission determination.

(6) The vehicle is in steady driving (# FCNST2 = 1).
Here, # FCNST2 is calculated according to the following conditions (6-1) to (6-3).
(6-1) Vehicle Speed Change (DVSP) Determination Continue for a predetermined number of times, when DVSP <predetermined value, set # FDVLLC = 1.
Continue for a predetermined number of times, and when DVSP ≧ predetermined value, set # FDVLLC = 0.

(6-2) Rotational Change (DNe) Determination Continue for a predetermined number of times, and when DNe <predetermined value, set # FDNLLC = 1.
If DNe ≧ predetermined value continues for a predetermined number of times, # FDNLLC = 0.
(6-3) Steady state determination When # FDVLLC = 1 (small vehicle speed change) continues for a predetermined time in the non-lock-up state, or when # FDNLLC = 1 (small rotation change) in the lock-up state. When the state continues for a predetermined time, # FCNST2 = 1 (steady state).

When in the non-lock-up state, the state of # FDVLLC = 0 (large vehicle speed change) continues for a predetermined time, or in the lock-up state, the state of # FDNLLC = 0 (large rotation change) continues for a predetermined time. # FCNST2 = 0 (unsteady).
As a result of the determination, if the vehicle is not in a stable state, that is, if any one of the conditions (1) to (6) is not satisfied, the process proceeds to step 6 and step 7, and the surge deterioration index value (integrated value) SFILD Is set to 0, the integration time TIME is set to 0, and the process proceeds to step 22 described later while maintaining the current target step number correction value ELCFB (initial value is 0). In particular, when correction of the target EGR amount TGEGR is not permitted (| DEGR | ≧ DEGR1 #), unnecessary correction of the target EGR amount TGEGR is not performed.

On the other hand, as a result of the determination, if the vehicle is in a stable state, that is, if all the conditions (1) to (6) are satisfied, the process proceeds to step 8 to perform the process described later. In particular, when the correction of the target EGR amount TGEGR is permitted (| DEGR | <DEGR1 #), the necessary minimum correction of the target EGR amount TGEGR is performed.
In step 8, the latest surge deterioration index value FILD per unit time is added to the previous surge deterioration index value (integrated value) SFILD as in the following equation. This corresponds to surge deterioration index value calculation means.

SFILD = SFILD (previous value) + FILD
In step 9, the execution time interval Δt of this routine is added to the accumulated time TIME as in the following equation.
TIME = TIME (previous value) + Δt
In step 10, it is determined whether or not the accumulated time TIME has reached a predetermined sampling time TIME0 (for example, 2 seconds).

If not reached (TIME <TIME0), the process proceeds to step 22 to be described later as it is, that is, while maintaining the current target step number correction value ELCFB (initial value is 0).
If reached (TIME ≧ TIME0), the process proceeds to step 11 and thereafter.
In step 11, the accumulated time TIME is cleared (TIME = 0).
In step 12, a judgment threshold value ELSL for judgment of surge deterioration is calculated from a map of engine speed and engine load for each gear position.

In step 13, the surge deterioration index value (integrated value) SFILD is compared with the determination threshold ELSL to determine whether SFILD ≧ ELSL (surge deterioration state). This corresponds to the surge deterioration determining means.
If SFILD <ELSL and the surge is not deteriorated, the process proceeds to step 21 described later while maintaining the current target step number correction value ELCFB (initial value is 0).

If SFILD ≧ ELSL and the surge is worse, the process proceeds to step 14.
In step 14, it is determined whether or not the deviation DEGR of the estimated EGR amount ESTMEGR is greater than or equal to a second predetermined value (DEGR ≧ DEGR2 #). If the deviation DEGR is less than the second predetermined value (DEGR <DEGR2 #), the process proceeds to step 15, and the target step number correction gain GTGEGR is set to 1.0 and the process proceeds to step 17. Note that the second predetermined value DEGR2 # of the deviation DEGR is smaller than the first predetermined value DEGR1 # described above (step 5).

  In step 16, the target step number correction gain GTGEGR is calculated by referring to the target step number correction gain calculation table in FIG. The target step number correction gain calculation table shows the deviation DEGR on the horizontal axis and the target step number correction gain GTGEGR on the vertical axis. As the deviation amount DEGR increases, the target step number correction gain GTGEGR also increases. Thus, the target EGR correction amount ELCFB is corrected so that the opening degree of the EGR valve 10 is decreased, and is reflected in the target EGR amount (target EGR valve opening area or target step number).

In step 17, a predetermined value ΔS is added to the previous target step number correction value ELCFB as in the following equation.
ELCFB = ELCFB (previous calculation value) + ΔS
Here, the initial value of the target step number correction value ELCFB is 0, and is initially set when the ignition is turned off.

Further, the predetermined value ΔS is the minimum number of steps, but switching between 1-phase excitation and 2-phase excitation is possible, and when it can be driven by 0.5 steps by 1-phase excitation (weak excitation), for example, 0. 5
In step 18, the current target step number correction value is calculated by multiplying the target step number correction value ELCFB calculated in step 17 by the target step number correction gain GTGEGR, as in the following equation. This corresponds to the target EGR amount correction amount calculation means.

ELCFB = ELCFB × GTGEGR
In step 19, the target step number correction value ELCFB is compared with a predetermined maximum value ELCFBMX to determine whether ELCFB> ELCFBMX. If NO, the process proceeds directly to step 21. If YES, step 19 is performed. 20, ELCFB = ELCFBMX (limiter).

In step 21, the surge deterioration index value (integrated value) SFILD is cleared for the next calculation (SFILD = 0).
In step 22, the final target step number is obtained by subtracting the target step number correction value ELCFB from the reference target step number (reference target EGR amount) determined from the engine speed and the engine load as in the following equation. Ask for.

Target step number = reference target step number−ELCFB
When the target number of steps is determined in this way, a command signal is output to the step motor for EGR valve control drive. This corresponds to the target EGR amount correction means.
FIG. 4 is a time chart of EGR control. When the surge level deteriorates and the surge deterioration index value (integrated value) SFILD exceeds the determination threshold value ELSL, the target step number correction value ELCFB is predetermined from the initial value (0). This indicates that the value ΔS is increased, and the target step number is corrected to the reduction side accordingly.

FIG. 5 shows the relationship between the number of steps and the EGR flow rate. With respect to the design median value (target EGR amount after correction), the flow rate increases due to a sudden increase in the differential pressure between the intake system and the exhaust system or component variations. When the state becomes the side, the surge deterioration is detected, and the target step number is offset-corrected. As a result, the EGR flow rate characteristic can be returned to the design median value.
According to this embodiment, an EGR valve 10 is provided in an EGR passage 9 for recirculating a part of exhaust gas from an exhaust system to an intake system, and an EGR amount control device for an internal combustion engine that controls the EGR amount by the EGR valve 10 includes: Surge deterioration index value calculation means (step 8) for calculating the surge deterioration index value SFILD based on the rotational fluctuation of 1, and surge deterioration for comparing the surge deterioration index value SFILD and the determination threshold value ELSL to determine the presence or absence of surge deterioration A determination means (step 13), an estimated EGR amount calculation means (step 3) for calculating an estimated EGR amount ESTMEGR, and a target EGR amount correction for calculating a correction amount ELCFB for the target EGR amount TGEGR based on the determination of the presence or absence of surge deterioration Based on the amount calculation means (step 18) and the change amount DEGR of the estimated EGR amount ESTMEGR, the target EGR amount T Target EGR amount correction permission determination means (step 5) for determining whether to permit correction of EGR, and target EGR amount TGEGR for correcting the target EGR amount TGEGR using the correction amount ELCFB based on the permission determination of correction of the target EGR amount TGEGR Quantity correction means (step 22). For this reason, since the target EGR amount TGEGR is corrected according to the permission determination of the correction of the target EGR amount TGEGR based on the estimated amount of change EGR of the estimated EGR amount ESTMEGR, there is no problem with a torque level difference caused by a sudden change in the EGR amount. And stable driving performance can be secured.

In addition, according to the present embodiment, the target EGR amount correction permission determining means determines that the target EGR amount TGEGR is the target EGR amount TGEGR when the change amount DEGR of the estimated EGR amount ESTMEGR is less than the first predetermined value DEGR1 # (| DEGR | <DEGR1 #). Correction is permitted (step 5). For this reason, correction can be permitted only when the correction permission determination is less than the maximum value.
Further, according to the present embodiment, when the target EGR amount correcting means determines to permit correction of the target EGR amount TGEGR (step 5), the target EGR amount TGEGR is added to or subtracted from the target EGR amount TGEGR. Is corrected (step 22). For this reason, by performing addition / subtraction correction, that is, offset correction, for the surge deterioration due to the deviation of the opening area of the EGR valve 10, the correction value can be correctly reflected, and fuel consumption and drivability can be improved.

  Further, according to the present embodiment, the target EGR amount correcting means (step 22) determines the target EGR amount TGEGR as the EGR valve when the change amount DEGR of the estimated EGR amount ESTMEGR is equal to or larger than the second predetermined value (DEGR ≧ DEGR2 #). Correction is performed so that the opening degree of 10 decreases. For this reason, even when the estimated EGR amount ESTMEGR changes greatly, it is possible to suppress the occurrence of surge and suppress the torque step due to the intake air amount change and the ignition timing change, thereby preventing the drivability from deteriorating.

Further, according to the present embodiment, the target EGR amount correction amount calculating means determines the correction amount for the target EGR amount TGEGR based on the change amount DEGR of the estimated EGR amount ESTMEGR when it is determined that the surge has deteriorated (step 13). ELCFB is calculated (step 18).
Further, according to the present embodiment, the estimated EGR amount ESTMEGR is calculated from the pressure ratio (PEXMANI / PMANI) between the intake system and the exhaust system and the EGR valve opening area TAEGR (step 3). For this reason, the estimated EGR amount can be calculated more easily.

According to the present embodiment, the exhaust system pressure PEXMANI is set to atmospheric pressure (step 3). For this reason, the estimated EGR amount ESTMEGR can be easily calculated, and it is not necessary to provide a sensor for detecting the exhaust pressure PEXMANI, thereby reducing the cost.
Further, according to the present embodiment, the intake air amount is substituted for the pressure ratio (PEXMANI / PMANI) between the intake system and the exhaust system. Therefore, the estimated EGR amount ESTMEGR can be easily calculated.

Further, according to the present embodiment, the change amount DEGR of the estimated EGR amount ESTMEGR is calculated based on the previous calculated value and the current calculated value of the estimated EGR amount ESTMEGR (step 4). For this reason, it is possible to appropriately calculate the change amount DEGR in accordance with the change state of the estimated EGR amount ESTMEGR.
Further, according to the present embodiment, the change amount DEGR of the estimated EGR amount ESTMEGR is calculated by the difference between the previous calculated value and the current calculated value of the estimated EGR amount ESTMEGR (current calculated value−previous calculated value) (step 4). For this reason, it is possible to calculate an appropriate change amount DEGR corresponding to a change with time.

Further, according to the present embodiment, the change amount DEGR of the estimated EGR amount ESTMEGR is calculated by the ratio (current calculated value / previous calculated value) between the previous calculated value and the current calculated value of the estimated EGR amount ESTMEGR (step 4). For this reason, even when the estimated target amount ESTMEGR fluctuates rapidly, an appropriate change amount DEGR can be calculated.
Until now, the estimated EGR amount (rate) ESTMEGR is calculated based on the intake pressure PMANI and the target EGR valve opening area TAEGR, or the pressure ratio of the intake pressure PMANI and the exhaust pressure PEXMANI (PEXMANI / PMANI) Although the calculation based on the square root and the EGR valve opening area TAEGR has been described, the present invention is not limited to this.

That is, in the flowchart of FIG. 2 described above, the target EGR rate is calculated in step 2, while the estimated EGR rate is calculated in step 3, and the change amount DEGR of the estimated EGR amount ESTMEGR is calculated based on these in step 4. You may make it calculate.
In this case, the change amount DEGR of the estimated EGR amount ESTMEGR is calculated from the difference between the target EGR rate and the estimated EGR rate.

  Further, the change amount DEGR of the estimated EGR amount ESTMEGR may be calculated by the ratio of the target EGR rate and the estimated EGR rate (target EGR rate / estimated EGR rate).

Engine system diagram showing an embodiment of the present invention Flowchart of EGR control (target step number) correction routine Target step number correction gain calculation table Time chart A diagram showing the relationship between the number of steps and the EGR flow rate

Explanation of symbols

1 Engine 5 Intake Manifold 6 Fuel Injection Valve 7 Spark Plug 8 Exhaust Manifold 9 EGR Passage 10 EGR Valve 12 ECU
13 Crank angle sensor

Claims (13)

In an EGR amount control device for an internal combustion engine that includes an EGR valve in an EGR passage that recirculates part of the exhaust gas from the exhaust system to the intake system, and controls the EGR amount by the EGR valve,
A surge deterioration index value calculating means for calculating a surge deterioration index value based on the rotational fluctuation of the engine;
Surge deterioration determination means for determining the presence or absence of surge deterioration by comparing the surge deterioration index value and the determination threshold,
An estimated EGR amount calculating means for calculating an estimated EGR amount;
A target EGR amount correction amount calculating means for calculating a correction amount for the target EGR amount based on the determination of the presence or absence of the surge deterioration;
Target EGR amount correction permission determining means for determining whether to permit correction of the target EGR amount based on the amount of change in the estimated EGR amount;
Target EGR amount correction means for correcting the target EGR amount using the correction amount based on permission determination for correction of the target EGR amount;
I have a,
The target EGR amount correction permission determining means permits the correction of the target EGR amount when the change amount of the estimated EGR amount is less than a first predetermined value . 2. The target EGR amount correcting means corrects the target EGR amount by adding / subtracting the correction amount to / from the target EGR amount when it is determined that correction of the target EGR amount is permitted. EGR amount control device for internal combustion engine. The target EGR amount correction means, wherein when the amount of change in the estimated EGR quantity is equal to or greater than the second predetermined value, according to claim 2, wherein the opening of the EGR valve target EGR amount and correcting to decrease EGR amount control device for internal combustion engine. The target EGR amount correction amount calculating means calculates a correction amount for the target EGR amount based on a change amount of the estimated EGR amount when it is determined that the surge has deteriorated . The EGR amount control device for an internal combustion engine according to claim 3. 5. The estimated EGR amount calculating means calculates the estimated EGR amount from a pressure ratio between an intake system and an exhaust system and an EGR valve opening area. 6. An EGR amount control device for an internal combustion engine. 6. The EGR amount control device for an internal combustion engine according to claim 5 , wherein the pressure of the exhaust system is an atmospheric pressure . 7. The EGR amount control apparatus for an internal combustion engine according to claim 5, wherein the pressure ratio of the intake system and the exhaust system is substituted by an intake air amount . The variation of the estimated EGR quantity, an internal combustion engine according to any one of claims 1 to 7, characterized in that calculated on the basis of the previously calculated value and the current calculated value of the estimated EGR quantity EGR amount control device. 9. The EGR amount control apparatus for an internal combustion engine according to claim 8 , wherein the change amount of the estimated EGR amount is calculated by a difference between a previous calculated value and a current calculated value of the estimated EGR amount . 9. The EGR amount control device for an internal combustion engine according to claim 8 , wherein the change amount of the estimated EGR amount is calculated by a ratio between a previous calculated value and a current calculated value of the estimated EGR amount. The EGR amount control apparatus for an internal combustion engine according to any one of claims 1 to 7, wherein the change amount of the estimated EGR amount is calculated based on a target EGR rate and an estimated EGR rate . 12. The EGR amount control apparatus for an internal combustion engine according to claim 11 , wherein the change amount of the estimated EGR amount is calculated from a difference between the target EGR rate and the estimated EGR rate . 12. The EGR amount control device for an internal combustion engine according to claim 11 , wherein the change amount of the estimated EGR amount is calculated by a ratio between the target EGR rate and the estimated EGR rate.