JPH09217658A - Egr control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform no advance processing in a stationary state, and suppress fluctuation of the output of an engine by judging whether an engine is in a stationary state or in a transition state based on engine operating conditions, and executing variable control on advance processing equivalent to the volumetric quantity of a suction system against the objective quantity of EGR in response to the result of judgement. SOLUTION: A control unit 2 inputs sensor signals from a crank angle sensor 3, an acceleration opening sensor 4, a water temperature sensor 5, a vehicle speed sensor 6 and the like, operates an objective EGR rate first based on an engine operating condition, and operates the objective quantity of EGR based on the objective EGR rate and the quantity of intake air. Next, advance processing equivalent to the volumetric quantity of a suction system is performed with respect to the objective quantity of EGR, and variable control on advance processing is executed in response to the result of judging whether EGR is in a stationary state or a transition state based on the engine operating condition. Based on the objective quantity of EGR, and suction and exhaust pressure after advance processing has been over, the opening area of an EGR valve is operated, and the EGR value is drivingly controlled in accordance with the calculated average value of the opening area of the EGR valve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an E connecting an exhaust system and an intake system of an internal combustion engine (particularly a diesel engine).
The present invention relates to an EGR (exhaust gas recirculation) control device that recirculates a part of exhaust gas into intake air via an EGR valve provided in a GR passage.

[0002]

2. Description of the Related Art There are various conventional EGR control devices, but there is a technique as disclosed in Japanese Patent Laid-Open No. 60-192857 that changes the EGR control between a steady state and a transient state. This is the EGR set under the steady condition at the time of transient judgment.
The target value is controlled by subtracting a predetermined value from the rate.

On the other hand, no other control unit controls EGR while considering each dynamics while observing the intake air amount, and no control control during idling is found.

[0004]

However, in the conventional EGR control device, since dynamics calculation is not performed, it is difficult to always set the optimum control value, and EGR When controlling with the intake air amount and the intake pressure, there is a problem that the EGR valve does not operate stably in a steady state due to the influence of the intake pulsation (in particular, the intake pulsation is large in a diesel engine).

In view of the above-mentioned conventional problems, the present invention aims to optimize EGR control by ensuring sufficient transient followability during transients and at the same time obtaining sufficient stability during steady state or idling. To aim.

[0006]

Therefore, in the invention according to claim 1, as shown in FIG. 1, an operating condition detecting means for detecting the operating condition of the engine and an intake air amount detecting for detecting the intake air amount. Means, intake pressure detecting means for detecting intake pressure, exhaust pressure detecting means for detecting exhaust pressure, target EGR rate calculating means for calculating a target EGR rate based on the operating state of the engine, target EGR rate and intake Target EG from air amount
Target EGR amount calculation means for calculating the R amount, advance processing means for performing advance processing corresponding to the intake system capacity for the target EGR amount, and steady / transient determination of a steady state / transient state based on the operating state of the engine. The EGR valve opening area is calculated based on the advancing process variable device for advancing the advancing process according to the judgment result of the judging device and the steady / transient judging device, and the target EGR amount, intake pressure and exhaust pressure after the advancing process. EGR valve opening area calculating means, averaging means for averaging the EGR valve opening area, and EGR valve driving means for driving the EGR valve so that the EGR valve opening area after the averaging processing is provided, An EGR control device for an internal combustion engine is configured.

That is, the steady state / transient state is determined based on the operating state of the engine, and according to the determination result,
By varying the advance process corresponding to the target EGR amount by the intake system capacity, the advance process is not performed in the steady state, and the stability is improved. The invention according to claim 2 is characterized in that, in the invention according to claim 1, the lead processing variable means reduces a lead gain of the lead processing means in a steady state.

That is, in the steady state, the gain of the advance processing means is reduced to improve the stability. In the invention according to claim 3, as shown in FIG. 2, an operating state detecting means for detecting an operating state of the engine, an intake air amount detecting means for detecting an intake air amount, and an intake pressure detecting means for detecting an intake pressure. An exhaust pressure detecting means for detecting the exhaust pressure, a target EGR rate calculating means for calculating a target EGR rate based on the operating state of the engine, and a target EG based on the target EGR amount and the intake air amount.
Target EGR amount calculation means for calculating the R amount, advance processing means for performing advance processing corresponding to the intake system capacity for the target EGR amount, and EGR based on the target EGR amount, intake pressure, and exhaust pressure after the advance processing. EGR valve opening area calculating means for calculating the valve opening area, averaging means for averaging the EGR valve opening area, and EGR valve opening area under at least the idle state based on the operating state of the engine Clamping condition determining means for determining the clamping condition, clamping means for clamping the EGR valve opening area when the clamping condition is satisfied, and EGR valve for driving the EGR valve so that the EGR valve opening area is equal to or after the averaging process. A valve drive means is provided to configure an EGR control device for the internal combustion engine.

That is, the stability of the idle state is improved by clamping the opening area of the EGR valve in the idle state. According to a fourth aspect of the present invention, in the third aspect of the present invention, the clamp determination means determines that the change amounts of the fuel injection amount and the engine speed are each less than or equal to a predetermined value as another condition of the clamp condition. It is characterized by being

That is, even when the fuel injection amount or engine speed fluctuates greatly even in the idle state,
Stop the clamp.

[0011]

According to the first aspect of the present invention, the steady state / transient state is determined based on the operating state of the engine, and the advance process corresponding to the intake system capacity corresponding to the target EGR amount is determined according to the determination result. By varying, it is possible to prevent the advance processing from being performed in the steady state and improve the stability. That is, it is possible to suppress engine output fluctuation in a steady state due to intake pulsation (particularly large intake pulsation in a diesel engine) when controlling the EGR amount using a signal from an air flow meter or the like.

According to the second aspect of the invention, the stability can be improved by reducing the gain of the advance processing means in the steady state. According to the invention of claim 3, the stability in the idle state can be improved by clamping the EGR valve opening area in the idle state. According to the invention of claim 4, even in the idle state, when the fuel injection amount or the engine speed fluctuates greatly, the clamp can be stopped so as not to impair the convergence.

[0013]

Embodiments of the present invention will be described below. FIG. 3 is a system diagram. The EGR valve 1 is provided in an EGR passage that connects the exhaust system and the intake system of the engine, and in response to a signal from the control unit 2, in the case of a negative pressure operation type, a solenoid valve for negative pressure control, a direct acting type. In the case of, it is driven via a step motor or the like to control the EGR amount.

The control unit 2 includes a crank angle sensor 3, an accelerator opening sensor 4, a water temperature sensor 5, a vehicle speed sensor 6, an idle switch 7, an air flow meter 8, an intake pressure sensor 9, and an exhaust pressure as driving state detecting means. A signal is input from the sensor 10 or the like. Here, the control unit 2 drives the EGR valve 1 by performing arithmetic processing by a built-in microcomputer according to the flow of the first embodiment or the flow of the second embodiment described later. [First Embodiment] FIG. 4 is a calculation flow chart of the target EGR valve opening area Aevf. It should be noted that this flow is executed in synchronization with the engine rotation by the crank angle reference signal REF.

In step 1 (denoted as S1 in the figure, the same applies hereinafter), the target EGR amount T is set in accordance with the flow of FIG.
Calculates qek. The details will be described later. In step 2, the intake pressure Pm is read. This portion corresponds to the intake pressure detecting means together with the intake pressure sensor. In step 3, the exhaust pressure Pexh is read. This portion corresponds to the exhaust pressure detecting means together with the exhaust pressure sensor.

In step 4, the exhaust pressure Pexh and the intake pressure P
Based on the pressure difference with m, the EGR flow velocity equivalent value Cqe is calculated by the following equation. Cqe = [K · (Pexh −Pm)] ^1/2 where K is a constant. In step 5, from the target EGR amount Tqek and the EGR flow velocity equivalent value Cqe, E
The GR valve opening area Aev is calculated.

Aev = Tqek / Cqe The equations of Steps 4 and 5 are theoretical equations using Bernoulli's equation. This portion corresponds to the EGR valve opening area calculation means. In step 6, an averaging weight constant (weighted average constant) Nlk for averaging the EGR valve opening area is calculated. Specifically, the averaging weight constant Nlk is obtained by referring to the table as shown in FIG. 12 and searching from the EGR flow velocity equivalent value Cqe.

In step 7, the EGR valve opening area Aev obtained in step 5 is subjected to averaging processing (weighted averaging) according to the following equation, and the result is set as the target EGR valve opening area Aevf, and the processing is terminated. To do. This part corresponds to the averaging means. Aevf = Aev / 2 ^Nlk + (1-1 / 2 ^Nlk ) .Aevf _n-1 where Aevf _n-1 is the Aevf one time before.

In the characteristic example of FIG. 12, when the flow velocity Cqe is small, the averaging weight constant Nlk is large (weighted average emphasizes the old value), and when the flow velocity Cqe is large, the averaging weight constant Nlk is small (new value emphasis). doing. This is because when the flow velocity is small, the required opening area needs to be changed significantly even with a slight change in flow velocity, making it difficult to stabilize. Therefore, the averaging weight constant Nlk is increased and the old value is emphasized in the weighted average. This is to stabilize it. Also, when the flow velocity is high, the opposite phenomenon occurs, and generally the flow velocity increases during the transition (the pressure difference between the intake pressure and the exhaust pressure increases).
For this reason, it is desirable to avoid weighted averaging as much as possible from the followability of transients. Therefore, the averaging weight constant Nlk is made small, and the new value is emphasized in the weighted average to improve the followability. It should be noted that the reason why it has an inversely proportional shape is that the flow velocity has a square root characteristic with respect to the differential pressure as shown in the equation in step 4, and the averaging weight constant is the inverse thereof.

When the target EGR valve opening area Aevf is calculated, the target EGR valve opening area Aevf is converted into an EGR valve drive output signal (lift amount, number of steps, etc.) by a table shown in FIG. 13, for example. To get EGR
The valve is controlled. This portion corresponds to the EGR valve drive means. FIG. 5 is a calculation flow of the target EGR amount Tqek. It should be noted that this flow is executed in step 1 of the flow of FIG.

At step 21, according to the flow of FIG.
The intake fresh air amount Qacn per intake air at the collector inlet is calculated. The details will be described later. In step 22,
The target EGR rate Megr is calculated according to the flow of FIG. The details will be described later. In step 23, the intake fresh air amount Qacn per intake air at the collector inlet and the target E
From the GR rate Megr, the target EGR amount Mqec per intake air at the collector inlet is calculated by the following equation.

Mqec = Qacn.Megr This portion corresponds to the target EGR amount calculation means. Steps
At 24, the intermediate variable Rqec is calculated by the following equation. Rqec = Mqec-KIN-KVOL + Rqec _n-1 ((1
-KIN · KVOL) where KIN is a value equivalent to volumetric efficiency. Also, KVOL
Is (VE / NC) / VM. VE is displacement, NC
Is the number of cylinders, and VM is the intake system volume.

In step 25, according to the flow of FIG.
The lead compensation gain (lead gain) Gkqec is calculated. The details will be described later. In step 26, the target EGR
Quantity Mqec, intermediate variable Rqec, lead compensation gain Gkqec
Using and, advance processing is performed by the following equation, and the result is set as Tqec. Tqec = Gkqec.multidot.Mqec- (Gkqec-1) .multidot.Rqecn _-1 This part corresponds to the advance processing means.

In step 27, the Tqec obtained in step 26 is the target EGR amount per intake air, so this is converted into the target EGR amount Tqek per unit time by the following equation, and the processing is ended. Tqek = (Tqec.Ne) / KCON where Ne is the engine speed and KCON is a constant (for example, 30 for 4 cylinders, 20 for 6 cylinders).

FIG. 6 shows a calculation flow of the intake fresh air amount Qacn per intake air at the collector inlet. This flow is shown in Figure 5.
It is executed in step 21 of the flow. In step 31, the engine speed Ne is read. In step 32,
From the intake air amount Qas0 and the engine speed Ne detected by the flow of FIG.
Calculate the fresh air amount Qac0 per intake air.

Qac0 = (Qas0 / Ne) KCON where KCON is a constant (for example, 30 for 4 cylinders, 20 for 6 cylinders). In step 33, the fresh air amount Qac0 _{n- L} calculated a predetermined number of times (L) before is set as the intake fresh air amount Qacn per intake air at the collector inlet as shown in the following equation, and the processing is ended. Qacn = Qac0 _{nL The} reason why Qac0 before the predetermined number of times is set as the collector inlet value in this way is that there is a transportation delay from the position of the air flow meter as the intake air amount detecting means to the collector inlet.

FIG. 7 is a flow chart for detecting the intake air amount Qas0. It should be noted that this flow is executed in time synchronization such as 4 msec.
In step 41, the output voltage Us of the air flow meter as the intake air amount detecting means is read. In step 42,
The air flow meter output voltage Us is converted into the intake air amount Qas0-d using a characteristic table (voltage-air amount conversion table) of the air flow meter as shown in FIG.

In step 43, the intake air amount Qas0-d is averaged (weighted average), and the result is Qas0-d.
Then, the processing ends. FIG. 8 is a calculation flow of the target EGR rate Megr. This flow is executed in step 22 of the flow shown in FIG. Further, this flow corresponds to the target EGR rate calculation means.

In step 51, the engine speed Ne, the fuel injection amount Qsol, and the engine cooling water temperature Tw are read. In step 52, a basic target EGR rate Megrb is obtained by referring to a map as shown in FIG. 15 and searching from the engine speed Ne and the fuel injection amount Qsol. In step 53, FIG.
Engine cooling water temperature Tw
The water temperature correction coefficient Kegr-tw for correcting the target EGR rate is obtained by searching.

At step 54, the basic target EGR rate Megrb
And the water temperature correction coefficient Kegr-tw, the target EG
Calculate the R rate Megr. Megr = Megrb · Kegr-tw In step 55, it is determined whether the engine is in the complete explosion state or not according to the flow of FIG. The details will be described later.

In step 56, the result in step 55 is judged. If it is judged that the complete explosion is completed, the process is ended. If it is judged that the complete explosion is not completed, the target EGR rate Megr = 0 is set in step 57, The process ends. FIG. 9 is a determination flow of the engine complete explosion. In addition, this flow is the step of FIG.
It is used in 55, but it is executed with time synchronization such as 10 msec.

At step 61, the engine speed Ne is read. In step 62, the engine speed Ne is compared with a predetermined value NRPMK for complete explosion determination, and Ne> NRPMK
If, then go to step 63. In step 63, Ne
> Counter Tmrkb after NRPMK and predetermined time T
Compare with MRKBP, and if Tmrkb> TMRKBP,
The process proceeds to step 64, and the process is terminated as the complete explosion.

When Ne <NRPMK in step 62,
The routine proceeds to step 66, where the counter Tmrkb is cleared, and further proceeds to step 67, where it is determined that the complete explosion has not occurred, and the processing ends. When Tmrkb <TMRKBP in step 63, the routine proceeds to step 65, where the counter Tmrkb is incremented,
Further, the process proceeds to step 67, and the process is terminated because it is not a complete explosion.

In this processing, it is determined that the complete explosion has occurred when the engine speed Ne exceeds a predetermined value (for example, 400 rpm) and a predetermined time has elapsed. FIG. 10 is a calculation flow of the lead compensation gain Gkqec. This flow is executed in step 25 of the flow shown in FIG. In step 71, the accelerator opening degree Cl, the engine speed Ne, the fuel injection amount Qso
Read l.

In step 72, the amount of change dCl = | Cl-Cl _ni | is calculated by taking the difference between the accelerator opening degree Cl and the value Cl _ni before the predetermined number of times (i). In step 73, the difference in engine speed Ne from the value Ne _nj before the predetermined number of times (j) is taken, and the change amount dNe = | Ne-Ne
_{Find nj} |. In step 74, the difference between the fuel injection amount Qsol and the value Qsol _nk before the predetermined number of times (k) is calculated,
The change amount dQsol = | Qsol−Qsol _nk | is calculated.

In step 75, the amount of change d in the accelerator opening is d.
Cl is compared with a predetermined value DCLTR, and if the change amount dCl is small, the routine proceeds to step 76. If the amount of change dCl is large,
When it is determined that the transition is in progress, the process proceeds to step 79, the advance compensation gain Gkqec is set to the predetermined value GKQE (> 1), and the process is terminated. In step 76, the engine speed change amount dNe is compared with a predetermined value DNETR. If the change amount dNe is small, the process proceeds to step 77. If the amount of change dNe is large, it is determined that the transition is in progress, and the routine proceeds to step 79, where the advance compensation gain Gkq
ec is set to a predetermined value GKQE (> 1), and the process ends.

In step 77, the change amount dQ of the fuel injection amount.
sol is compared with a predetermined value DQFTR, and if the change amount dQsol is small, it is determined that it is a steady state, the process proceeds to step 78, the advance compensation gain Gkqec is set to 1, and the process ends. If the amount of change dQsol is large, it is determined that the transition is in progress, and the routine proceeds to step 79, where the advance compensation gain Gkqec is set to a predetermined value GKQE (> 1).
Then, the processing ends.

Here, the steps 71 to 77 correspond to the steady / transient judging means, and the steps 78 and 79 correspond to the advanced processing varying means. In this way, when the advance compensation gain of the target EGR amount is changed between the steady state and the transient state and the advance process is not performed in the steady state, the EGR amount is controlled using a signal from the air flow meter or the like. It is possible to suppress the engine output fluctuation in a steady state due to the intake pulsation (particularly large intake pulsation of a diesel engine). Further, particularly when the intake pulsation is largely generated and the required EGR valve opening area is large, the fluctuation at the time of idling can be suppressed. Further, the unnecessary operation of the EGR valve in the steady state is reduced, the durability of the EGR valve is improved, and the unnecessary reduction of the operation also has the effect of reducing the emission in the steady state. On the other hand, in the transient state, the followability can be secured by sufficient advance processing.

FIG. 11 is a flow chart for calculating the fuel injection amount.
It should be noted that this flow is executed in synchronization with the engine rotation by the crank angle reference signal REF. In step 81, the engine speed Ne is read. In step 82, the accelerator opening degree Cl is read. In step 83, the basic fuel injection amount Mqdrv is obtained by referring to the map as shown in FIG. 17 and searching from the engine speed Ne and the accelerator opening degree Cl.

In step 84, the basic fuel injection amount Mqdrv is subjected to various corrections such as water temperature increase to obtain the final fuel injection amount Qsol, and the process is terminated. [Second Embodiment] FIG. 18 is a calculation flow of the target EGR valve opening area Aevf, which is executed in place of FIG.

FIG. 4 shows steps 1 to 6.
Is the same as In step 7, the EGR valve opening area Aev obtained in step 5 is subjected to an averaging process (weighted average) according to the following equation, and the result is calculated (instead of the target EGR valve opening area Avef). The area Aevs is set and the processing ends. Aevs = Aev / 2 ^Nlk + (1-1 / 2 ^Nlk ) .Aevf _n-1 where Aevf _n-1 is the Aevf one time before.

In step 8, according to the flow of FIG.
It is determined whether or not the opening area is clamped. The details will be described later. In step 9, the result of step 8 is judged, and if clamping is permitted, step
Proceed to step 10, and clamp the previous target EGR valve opening area Aevf _n-1 as the current target EGR valve opening area Aevf. If clamping is not permitted, proceed to step 11 and set the latest target EGR valve opening area Aevs. The processing is ended with the target EGR valve opening area Aevf set this time. The steps 9 and 10 correspond to the clamping means.

When the target EGR valve opening area Aevf is calculated, the target EGR valve opening area Aevf is converted into an EGR valve drive output signal (lift amount, step number, etc.) by a table shown in FIG. 13, for example. To get EGR
The valve is controlled. The calculation flow of the target EGR amount Tqek in FIG. 5 is performed in the same manner, but the calculation of the lead compensation gain Gkqec in step 25 does not depend on the calculation flow of the lead compensation gain Gkqec in FIG. May be a predetermined fixed value. However,
When implementing the first embodiment and the second embodiment in combination, the advance compensation gain Gkqec may be calculated by the calculation flow of FIG.

The calculation flow of the intake fresh air amount Qacn per intake air at the collector inlet of FIG. 6 is similarly performed. Regarding the detection flow of the intake air amount Qas0 in FIG.
The same is done. The calculation flow of the target EGR rate Megr in FIG. 8 is also performed in the same manner. The determination flow of the engine complete explosion in FIG. 9 is performed in the same manner.

The calculation flow of the lead compensation gain Gkqec in FIG. 10 can be omitted, as already described. FIG.
The calculation flow of the fuel injection amount of is similarly performed. FIG. 19 is a determination flow of the EGR valve opening area clamp permission, which is executed as a flow peculiar to the second embodiment.
It should be noted that this flow is executed in synchronization with the engine rotation by the crank angle reference signal REF. Further, this flow corresponds to the clamp determination means.

In step 101, the state of the idle switch (ON / OFF), the engine speed Ne, the fuel injection amount Q
Read sol and vehicle speed Vsp. In step 102, it is determined whether the idle switch is on, and the idle switch =
When it is on, the process proceeds to step 103, and when it is off, the process proceeds to step 111. In step 103, the vehicle speed Vsp and the predetermined value V
Compare with SPID, and if vehicle speed Vsp is low, step 104
When the vehicle speed Vsp is low, the routine proceeds to step 111.

In step 104, the difference in the fuel injection amount Qsol from the value Qsol _{n- i} before the predetermined number of times (i) is taken to obtain the change amount dQsol _i = | Qsol-Qsol _ni |. In step 105, the change amount dQsol _i of the fuel injection amount is compared with the predetermined value DQID, and if the change amount dQsol _{i is} small,
Go to step 106. If the change amount dQsol _{i is} large, the process proceeds to step 111.

In step 106, the difference dNe _i = | Ne-Ne _ni | in the engine speed Ne is calculated from the value Ne _{n- i} before the predetermined number of times (i). Steps
At 107, the change amount dNe _i of the engine speed and the predetermined value D
If the change amount dNe is smaller than the NID, step
Continue to 108. If the change amount dNe _{i is} large, step 111
Proceed to.

In step 108, the clamp timer Ctmri is used.
d is compared with a predetermined value TMR-IDL, and when the clamp timer Ctmrid is large, the process proceeds to step 109, the clamp is permitted (OK), and the process is ended. Clamp timer Ctm
If rid is small, proceed to step 110, and clamp timer C
increment tmrid, go to step 112,
Clamping is prohibited (NG), and the process ends.

In step 111, the clamp timer Ctmri is used.
After d is cleared, the process proceeds to step 112, the clamp is prohibited (NG), and the process ends. In this process, when the idle switch is on, the vehicle is idle at a low vehicle speed, and the clamp permission condition of small fluctuation of the fuel injection amount and small fluctuation of the engine speed is satisfied and the clamp is permitted after a predetermined time has elapsed. Has become.

[Brief description of drawings]

FIG. 1 is a functional block diagram (1) showing the configuration of the present invention.

FIG. 2 is a functional block diagram (2) showing the configuration of the present invention.

FIG. 3 is a system diagram of an embodiment of the present invention.

FIG. 4 is a flowchart of a target EGR valve opening area calculation according to the first embodiment.

FIG. 5 is a flowchart of target EGR amount calculation.

[Fig. 6] Flow chart of intake fresh air amount calculation

FIG. 7 is a flowchart for detecting the intake air amount.

FIG. 8 is a flowchart of target EGR rate calculation.

FIG. 9 is a flow chart of engine complete explosion determination.

FIG. 10 Flowchart of lead compensation gain calculation

[Fig. 11] Flow chart of fuel injection amount calculation

FIG. 12 is a diagram of an EGR valve opening area averaging weight constant table.

FIG. 13 is a diagram of an EGR valve opening area-drive output signal conversion table.

FIG. 14 is a diagram of an air flow meter output voltage-intake air amount conversion table.

FIG. 15 is a diagram of a target EGR rate map

FIG. 16 is a diagram of a target EGR rate water temperature correction coefficient table.

[Fig. 17] Diagram of basic fuel injection amount map

FIG. 18 is a flowchart of a target EGR valve opening area calculation according to the second embodiment.

[Fig. 19] Clamp judgment flowchart

[Explanation of symbols]

 1 EGR valve 2 Control unit 3 Crank angle sensor 4 Accelerator opening sensor 5 Water temperature sensor 6 Vehicle speed sensor 7 Idle switch 8 Air flow meter 9 Intake pressure sensor 10 Exhaust pressure sensor

Claims (4)

[Claims] 1. An E connecting an exhaust system and an intake system of an engine.
An EGR control device for an internal combustion engine, which recirculates a part of exhaust gas into intake air via an EGR valve provided in a GR passage, the operating state detecting means for detecting an operating state of the engine, and an intake air amount. Intake air amount detecting means, intake pressure detecting means for detecting intake pressure, exhaust pressure detecting means for detecting exhaust pressure, target EGR rate calculating means for calculating a target EGR rate based on the operating state of the engine, target Target EGR amount calculation means for calculating a target EGR amount from the EGR rate and intake air amount, advance processing means for performing advance processing corresponding to the intake system capacity for the target EGR amount, and a steady state based on the operating state of the engine -Steady / transient determination means for determining the transient state, advance processing variable means for varying the advance processing according to the determination result of the steady / transient determination means, and the target EGR amount and intake pressure after the advance processing EGR valve opening area calculating means for calculating the EGR valve opening area based on the exhaust pressure, averaging means for averaging the EGR valve opening area, and EGR valve opening area for averaging the EGR valve opening area An EGR control device for an internal combustion engine configured to include an EGR valve drive means for driving the. 2. The EGR control device for an internal combustion engine according to claim 1, wherein the lead processing variable means reduces the lead gain of the lead processing means in a steady state. 3. An E connecting the exhaust system and the intake system of the engine.
An EGR control device for an internal combustion engine, which recirculates a part of exhaust gas into intake air via an EGR valve provided in a GR passage, the operating state detecting means for detecting an operating state of the engine, and an intake air amount. Intake air amount detecting means, intake pressure detecting means for detecting intake pressure, exhaust pressure detecting means for detecting exhaust pressure, target EGR rate calculating means for calculating a target EGR rate based on the operating state of the engine, target Target EGR amount calculation means for calculating the target EGR amount from the EGR amount and intake air amount, advance processing means for performing advance processing corresponding to the intake system capacity with respect to the target EGR amount, and target EGR amount after the advance processing and intake EGR valve opening area calculating means for calculating the EGR valve opening area based on the atmospheric pressure and exhaust pressure, averaging means for averaging the EGR valve opening area, and at least based on the operating state of the engine. Clamping condition determination means for determining the clamping condition of the EGR valve opening area, which is a condition that it is also in an idle state, clamping means for clamping the EGR valve opening area when the clamping condition is satisfied, and after averaging processing or during clamping. And an EGR valve drive means for driving the EGR valve so that the EGR valve opening area of the EGR valve becomes equal to the EGR valve opening area. 4. The clamp determination means determines, as another condition of the clamp condition, that the amount of change in each of the fuel injection amount and the engine speed is less than or equal to a predetermined value. 3. An EGR control device for an internal combustion engine according to item 3.