JPH10184408A - Intake control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform high-precise control of an intake air amount and an EGR gas amount of an engine. SOLUTION: A target opening area tAtotal of an intake system is computed based on a target intake air amount tQair, a target EGR gas amount tQegr, and an engine rotation speed Ne. A computing result is allotted to a target throttle valve opening area tAair and a target EGR valve opening area tAegr, and the target throttle valve opening area tAair and the target EGR opening area tAegr are corrected by a pressure in a spot situated upper stream from a throttle valve and a pressure in a spot situated upper stream from an EGR valve. Further, second target throttle valve opening area tAegr 2 is corrected by an exhaust pressure to form a second EGR valve opening area tAegr 2. A target throttle valve opening TPS corresponding to the tAair 2 and a target EGR valve opening tEGR corresponding to the tAegr 2 are computed. A throttle valve is controlled by a throttle valve control device 10 so that a throttle valve opening is adjusted to the target throttle valve opening tTPS and an EGR valve is controlled by an EGR valve control device 24 so that an EGR valve opening is adjusted to the target EGR valve opening tEGR.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake control system for an engine, and more particularly to an engine control technology having an electronically controlled throttle valve control system and an EGR control system.

[0002]

2. Description of the Related Art Conventionally, as a control device of an intake air amount of an engine provided with an electronically controlled throttle valve control device, there is a device disclosed in, for example, JP-A-62-110536.

[0003]

However, in such a conventional control method of the intake air amount, the target throttle valve opening is directly searched from the target engine torque and the engine rotation speed. There is a problem that it cannot be applied to an engine equipped with an exhaust gas recirculation device.

That is, the target throttle valve opening corresponding to the target intake air amount is set on the premise that EGR is not performed. However, if EGR is performed, the intake pressure changes, and even if the throttle valve opening is the same, the intake air is changed. The amount changes. Therefore, it is necessary to control the throttle valve opening and the EGR valve opening in association with each other.

[0005] Further, when the atmospheric pressure changes or the exhaust pressure changes when traveling at high altitude or the like, the ratio between the amount of intake air and the amount of EGR gas deviates from the setting. Further, in an engine equipped with a supercharging device, the pressure upstream of the throttle valve and the EGR
Since the pressure upstream of the valve varies widely, the amount of intake air and E
The ratio with the GR gas amount deviates from the setting. .

The present invention has been made in view of such conventional problems, and controls the throttle valve and the EGR valve in cooperation with each other, and collectively controls the pressure upstream of the throttle valve (atmospheric pressure or supercharging pressure). To provide an engine intake control device capable of controlling the intake air amount and the EGR gas amount to respective target values with high accuracy by controlling in consideration of the pressure (exhaust pressure) upstream of the EGR valve. With the goal.

[0007]

Therefore, according to the present invention, as shown in FIG. 1, a throttle valve control device for controlling an opening degree of a throttle valve interposed in an intake system to a target value is provided. E interposed in the EGR passage connecting the exhaust system and the intake system
An EGR control device for controlling the opening of the GR valve to a target value, wherein the engine intake control device controls the amount of air passing through the throttle valve and the amount of EGR gas passing through the EGR valve; Operating state detecting means for detecting an operating state including a speed; target intake air amount calculating means for calculating a target intake air amount via the throttle valve;
Target EGR gas amount calculating means for calculating a target EGR gas amount via the EGR valve; a sum of the calculated target intake air amount and target EGR gas amount; and an engine detected by the operating state detecting means. A target opening area calculating means for calculating a target opening area of the intake system from the rotation speed, and a ratio between the target intake air amount and the target EGR gas amount,
Target opening area distributing means for distributing the target opening area of the intake system into a target throttle valve opening area and a target EGR valve opening area; first pressure detecting means for detecting a pressure upstream of the throttle valve; and a pressure upstream of the EGR valve. Second to detect
Pressure detection means, and either or both of the target throttle valve opening area and the target EGR valve opening area,
Target throttle valve opening area correction calculating means and / or target EGR valve opening area correction means for correcting one or both of the pressure upstream of the throttle valve and the pressure upstream of the EGR valve; The throttle valve control device is driven so that the opening degree at which the corrected and calculated second target throttle valve opening area is obtained is set so that the opening degree at which the corrected and calculated second target EGR valve opening area is obtained. It is characterized by driving the EGR control device.

(Action / Effect) Target intake air amount and target EGR
After calculating the gas amount, the target opening area of the intake system required to obtain the total intake amount obtained by summing them is obtained, and then the target opening area is obtained as the target intake air amount and the target EGR gas amount, respectively. To the target throttle valve opening area and the target EGR valve opening area.

Further, the allocated target throttle valve opening area is corrected by the atmospheric pressure, and the target EGR valve opening area is corrected by the exhaust pressure, so that the second target throttle valve opening area and the second target EGR valve opening area are corrected. Is calculated, and the throttle valve and the EGR valve are cooperatively controlled so that the corrected and calculated second target opening areas are obtained.

Therefore, by performing EGR, the intake air amount does not shift, and as a result, the EGR gas amount does not shift, and the throttle valve with respect to the change between the pressure upstream of the throttle valve and the pressure upstream of the EGR valve does not change. By correcting the valve opening area and the opening area of the EGR valve,
The target intake air amount and the target EGR gas amount can be controlled with high accuracy, so that compatibility between engine performance and exhaust purification performance can be improved.

According to a second aspect of the present invention, the target throttle valve opening area correction calculating means corrects the target throttle valve opening area based on the square root of the ratio between the first reference pressure and the pressure upstream of the throttle valve. The target EGR valve opening area correction calculating means corrects the target EGR valve opening area based on the square root of the ratio between the second reference pressure and the pressure upstream of the EGR valve. Then, the second target EGR valve opening area is calculated.

(Operation / Effect) Since the flow rate of the gas passing through the throttle by the throttle valve or the EGR valve is proportional to the square root of the pressure, the opening area is set to the square root of the ratio between the first reference pressure and the pressure upstream of the throttle valve. The intake air amount and the EGR gas amount can be controlled with high accuracy by making corrections using the square root of the second reference pressure and the pressure upstream of the EGR valve.

According to a third aspect of the present invention, the target throttle valve opening area correction calculating means calculates the target throttle valve opening area based on the square root of the ratio of the pressure upstream of the EGR valve to the pressure upstream of the throttle valve. The second target throttle valve opening area is calculated after the correction. (Function / Effect) Correcting the EGR rate (EGR gas amount / intake air amount) by correcting the target throttle valve opening area with the square root of the ratio of the pressure upstream of the EGR valve to the pressure upstream of the throttle valve. Can be.

The invention according to a fourth aspect is characterized in that the target E
The GR valve opening area correction calculating means calculates the second target throttle valve opening area by correcting the target EGR valve opening area based on the square root of the ratio between the pressure upstream of the throttle valve and the pressure upstream of the EGR valve. Features. (Operation / Effect) Correcting the EGR rate (EGR gas amount / intake air amount) by correcting the target EGR valve opening area by the square root of the ratio of the pressure upstream of the throttle valve to the pressure upstream of the EGR valve. Can be.

Further, the invention according to claim 5 is characterized in that the first pressure detecting means directly detects the pressure upstream of the throttle valve by a sensor. (Operation / Effect) By providing the sensor, the pressure upstream of the throttle valve can be accurately detected.

The invention according to claim 6 is characterized in that the first pressure detecting means detects the pressure upstream of the throttle valve based on the operating state of the engine detected based on the operating state detecting means. It is a feature. (Operation / Effect) Since the pressure upstream of the throttle valve is estimated and detected from the detected values of other operating states without providing a sensor for directly detecting the pressure upstream of the throttle valve, the cost can be reduced.

Further, the invention according to claim 7 is characterized in that the second pressure detecting means directly detects the pressure upstream of the EGR valve by a sensor. (Operation / Effect) By providing the sensor, the pressure upstream of the EGR valve can be accurately detected.

The invention according to claim 8 is characterized in that the second pressure detecting means detects the pressure upstream of the EGR valve based on the operating state of the engine detected based on the operating state detecting means. And (Operation / Effect) Without providing a sensor for directly detecting the pressure upstream of the EGR valve, the EGR valve detects the EGR valve from the detected values in other operating states.
Since the pressure upstream of the valve is estimated and detected, the cost can be reduced.

The invention according to claim 9 is configured to include a target engine torque calculating means for calculating a target engine torque, wherein the target intake air amount calculating means includes the calculated target engine torque and the detected target engine torque. The target intake air amount is calculated based on the determined engine rotation speed.

(Operation / Effect) Since the target engine torque is calculated and the target intake air amount is calculated and the intake air amount is controlled so as to obtain the target engine torque, good driving performance can be ensured. . The invention according to claim 10 is configured to include accelerator operation amount detection means for detecting an accelerator operation amount, and calculate a target engine torque based on the detected accelerator operation amount and the engine rotation speed. Features.

(Operation / Effect) By calculating the target engine torque based on the accelerator operation amount and the engine rotation speed according to the driver's intention, it is possible to obtain good vehicle running performance. Further, according to the invention according to claim 11, the target air-fuel ratio is variably set based on the detected engine operating state, and the target intake air amount calculating means outputs the calculated target engine torque and the detected engine torque. A target intake air amount is calculated based on a target fuel supply amount calculated in accordance with the rotation speed and the target air-fuel ratio.

(Operation / Effect) Since the target air-fuel ratio and the target engine torque are simultaneously satisfied, the required engine torque is obtained while improving the exhaust purification performance and the fuel efficiency by promoting the lean air-fuel ratio, thereby achieving good operation. Performance can be ensured. The invention according to claim 12 is characterized in that the target EGR gas amount calculating means calculates a target EGR gas amount based on the calculated target intake air amount and a set target EGR rate. .

(Operation / Effect) Since the ratio of the EGR gas amount to the intake air amount is controlled to be a desired ratio, it is possible to satisfy the compatibility between the engine performance and the exhaust gas purification performance by EGR.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows a system configuration according to an embodiment of the present invention. An accelerator operation amount sensor 1 as an accelerator operation amount detecting means detects an operation amount of an accelerator pedal depressed by a driver.

A crank angle sensor 2, which is one of the operation state detecting means, generates a position signal for each unit crank angle and a reference signal for each cylinder stroke phase difference, and counts the number of the position signals generated per unit time. By doing so, or by measuring the reference signal generation cycle, the engine speed can be detected. An air flow meter 3, which is also one of the operation state detecting means, detects the amount of intake air to the engine 4 (the amount of intake air per unit time).

A water temperature sensor 5, which is one of the operating state detecting means, detects the temperature of the cooling water of the engine. The engine 4 is provided with a fuel injection valve 6 which is driven by a fuel injection signal and injects fuel directly into the combustion chamber, and an ignition plug 7 which is mounted in the combustion chamber and ignites. By the direct injection method into the combustion chamber, leaning by stratified combustion becomes possible, and the air-fuel ratio can be variably controlled over a wide range. A throttle valve 9 is interposed in the intake passage 8 of the engine 4, and a throttle valve control device 10 for electronically controlling the opening of the throttle valve 9 by a DC motor or the like is provided.

Further, a vehicle speed sensor 11 is provided as vehicle speed detecting means for detecting the vehicle speed. Detection signals from the various sensors are input to a control unit 12, and the control unit 12 controls a throttle through the throttle valve control device 10 in accordance with an operation state detected based on a signal from the sensors. The opening degree of the valve 9 is controlled, the fuel injection valve 6 is driven to control the fuel injection amount (fuel supply amount), the ignition timing is set, and the ignition plug 7 is ignited at the ignition timing. .

An EGR valve 23 is interposed in an EGR passage 22 connecting the exhaust passage 21 and the intake passage 8 of the engine 1,
An EGR control device 24 for electronically controlling the opening of the EGR valve 23 by a step motor or the like is provided. The engine speed Ne is controlled by the control unit 12.
EGR is performed in a predetermined region represented by the engine load (represented by a fuel injection amount or the like) and a target EGR rate (EGR
Gas amount / intake air flow rate).
A drive signal is output to the control device to control the opening of the EGR valve 23.

The exhaust passage 21 is provided with an air-fuel ratio sensor 25 for detecting the concentration of a specific component in the exhaust gas, for example, oxygen to detect the air-fuel ratio of the air-fuel mixture. Further, a first pressure sensor 26 for detecting a pressure upstream of the throttle valve which is an atmospheric pressure or a supercharging pressure, and a second pressure sensor 26 for detecting a pressure (exhaust pressure) upstream of the EGR valve.
A pressure sensor 27 is provided, and their detection signals are input to the control unit 12 and used for controlling the opening of the throttle valve 9 and the opening of the EGR valve 23.

FIG. 3 shows a functional configuration of the present embodiment. The target opening area calculation unit A includes a target intake air amount tQair.
, The target EGR gas amount tQegr, and the engine rotation speed Ne, and the target opening area tAtotal is calculated based on these values. Here, the target EGR gas amount tQegr can be replaced with a target EGR rate.

The target opening area distribution section B has a target opening area tAtot calculated by the target opening area calculation section A.
al, a target intake air amount tQair, and a target EGR gas amount tQegr are input, and a target throttle valve opening area tAair and a target EGR valve opening area tAegr are calculated based on these values. The target throttle valve opening area correction calculation unit C calculates the target throttle valve opening area according to the first reference pressure and the pressure upstream of the throttle valve, or according to the pressure upstream of the EGR valve and the pressure upstream of the throttle valve. A second target throttle valve opening area tAair2 in which tAair is corrected is calculated.

[0032] The target EGR valve opening area correction calculation unit D calculates the target pressure according to the second reference pressure and the pressure upstream of the EGR valve, or
A second target EGR valve opening area tAegr2 obtained by correcting the target EGR valve opening area tAegr is calculated according to the pressure upstream of the throttle valve and the pressure upstream of the EGR valve. Here, simply, only one of the target throttle valve opening area correction calculation unit C and the target EGR valve opening area correction calculation unit D is provided, and the target throttle valve opening area tA is provided.
A configuration may be adopted in which only one of the air and the target EGR valve opening area tAegr is corrected. However, even in such a case, for convenience, step 8 in FIG.
Or one of the target throttle valve opening area tAair and the target EGR valve opening area tAegr as it is, the second target throttle valve opening area tAair2 or the second target EGR valve opening area tAeg.
r2, the target throttle valve opening area t
Even when any of Aair and the target EGR valve opening area tAegr are not substantially corrected, they are treated as the second target throttle valve opening area tAair2 and the second target EGR valve opening area tAegr2.

The target throttle valve opening correction calculating section E calculates a target throttle valve opening tTPS according to the second target throttle valve opening area tAair2. Target EGR
The valve opening calculator F calculates the second target EGR valve opening area tA.
The target EGR valve opening degree tEGR according to egr2 is calculated. The throttle valve control device 10 drives the throttle valve 9 so that the opening of the throttle valve 9 matches the target throttle valve opening tTPS.

The EGR control device 24 controls the EGR so that the opening of the EGR valve 23 coincides with the target EGR valve opening tEGR.
The valve 23 is driven. Next, the throttle valve 9 and the EGR valve 23 are controlled by the control unit 12 having the arithmetic function.
Will be described with reference to the flowcharts of FIGS.

In step 1, the accelerator operation amount APS detected by the accelerator operation amount sensor 1 and the engine rotation speed N detected by the crank angle sensor 2 are determined.
Based on e, a target engine torque tTe required to obtain the target driving force of the vehicle is calculated. The function of step 1 constitutes a target engine torque calculating means. In step 2, a target engine torque tT of the engine is set.
Based on e and the engine rotation speed Ne calculated based on the detection signal from the crank angle sensor 2, a target fuel amount tQf is calculated by a search from a map as shown in FIG.

In step 3, based on the target engine torque tTe and the engine speed Ne, a target air-fuel ratio tA / F is obtained by searching a map as shown in FIG.
Is calculated. In step 4, the target fuel amount tQf
And the target air-fuel ratio tA / F to calculate a target intake air amount tQair for each intake stroke drawn into the cylinder. The functions of steps 1 to 4 constitute the target intake air amount calculation means.

In step 5, the target intake air amount tQ
the target EGR rate tRgr (EGR
EGR gas amount tQ to obtain (gas amount / intake air amount)
Egr is calculated by the following equation. The function of step 5 constitutes a target EGR gas amount calculating means. tQegr = tQair × tRegr In step 6, the calculated target intake air amount tQa
ir and the target intake air amount (tQair + tQegr) obtained by summing the target EGR gas amount tQegr, and the engine rotation speed N
e, the target opening area tAtotal of the intake system
Is calculated. The function of step 6 constitutes a target opening area calculating means.

In step 7, the target opening area tAtotal of the intake system and the target intake air amount tQair
And the target EGR gas amount tQegr and the target throttle valve opening area tAair and the target E
The GR valve opening area tAegr is calculated. The function of Step 7 constitutes a target opening area distribution unit. tAair = tAtotal × tQair / (tQair + tQegr) tAegr = tAtotal × tQegr / (tQair + tQegr) Here, the target throttle valve opening area tAair and the target intake air amount tQair and the engine rotational speed NEGR from the target intake air amount tQair and the engine rotation area NQRir. Aegr is the target EGR gas amount tQe
The calculation is not performed individually from the gr and the engine rotation speed Ne.

That is, between the intake air amount and the EGR gas amount, if the intake air amount changes, the intake pressure changes and the same E
The EGR gas amount at the GR valve opening also changes.
This is because if the R gas amount changes, the intake pressure also changes and the intake air amount at the same throttle valve opening also changes. Therefore, once the target opening area tAtotal of the intake system is calculated from the sum of the target intake air amount tQair and the target EGR gas amount tQegr and the engine rotational speed Ne, the target opening area tAtotal is distributed according to the above equation and the target throttle area. It is necessary to calculate the valve opening area tAair and the target EGR valve opening area tAegr.

In step 8, the target throttle valve opening area tAair is corrected in accordance with the atmospheric pressure detected by the first pressure sensor 26, and the second target throttle valve opening area tAair is corrected.
Aair2 is calculated, and the target EGR valve opening area tAegr is corrected in accordance with the exhaust pressure detected by the second pressure sensor 27, and the second target EGR valve opening area tAegr is calculated.
2 is calculated. Here, since the flow rate of the gas passing through the throttle of the throttle valve or the EGR valve is proportional to the square root of the pressure,
The second target throttle valve opening area tAair2 and the second target EGR valve opening area t in accordance with the following formula and formula, or formula and formula, or formula and formula:
Aegr2 can be calculated.

TAair2 = tAair × (P1 / Pa) ^1/2 ··· tAegr2 = tAegr × (P2 / Pe) ^1/2 ··· or tAair2 = tAair ··· tAegr2 = tAegr × (Pa / Pe) ^1/2 ... or tAair2 = tAair * (Pe / Pa) ^1/2 ... tAegr2 = tAegr where P1: first reference pressure, P2: second reference pressure, Pa:
Pressure upstream of the throttle valve, Pe: pressure upstream of the EGR valve. If the pressure Pa upstream of the throttle valve and the pressure Pe upstream of the EGR valve use values directly detected by the first pressure sensor 26 or the second pressure sensor 27, highly accurate correction can be performed using a highly accurate detection value. However, an estimated value estimated based on the detected value of the operating state used for another engine control may be used, and in this case, the cost can be reduced.

In step 9, the second correction-calculated second
A target throttle valve opening tTPS is calculated according to the target throttle valve opening area tAair2. In step 10,
The corrected target second target EGR valve opening area tAeg
The target EGR valve opening tEGR corresponding to r2 is calculated. In step 11, the throttle valve controller 10 is driven to perform feedback control so that the opening of the throttle valve 9 becomes the target throttle valve opening tTPS.

In step 12, the EGR control device 24 is driven to set the opening of the EGR valve 23 to the target EGR valve opening t.
Feedback control is performed to achieve EGR. As described above, according to the present embodiment, the electronically controlled throttle valve and the EGR valve are cooperatively controlled, and the opening of the throttle valve is corrected by the pressure upstream of the EGR valve and the pressure upstream of the throttle valve. By controlling and controlling the opening degree of the EGR valve with the pressure upstream of the throttle valve and the pressure upstream of the EGR valve, the intake air amount and the EGR gas amount can be simultaneously controlled with high accuracy. As a result, the compatibility between the engine output performance and the exhaust purification performance can be improved.

Although the operation of the target engine torque is calculated as in the present embodiment, the transient operation performance can be further improved. However, the present invention is sufficiently effective even if the present invention is applied to a system in which the target engine torque is not calculated. It is. Further, in the case where the target air-fuel ratio is variably controlled, particularly in the case where the air-fuel ratio is variably controlled by a direct fuel injection system, the actual air-fuel ratio can follow the variable target air-fuel ratio with high accuracy. Although it is particularly advantageous, it is sufficiently effective when applied to a device having a limited air-fuel ratio control range.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a diagram showing a system configuration according to an embodiment of the present invention.

FIG. 3 is a block diagram showing a functional configuration of the embodiment.

FIG. 4 is a flowchart showing a first stage of a control routine of a throttle valve and an EGR valve according to the embodiment;

FIG. 5 is a flowchart showing a latter part of the routine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Accelerator operation amount sensor 2 Crank angle sensor 4 Engine 6 Fuel injection valve 7 Control unit 8 Intake passage 9 Throttle valve 10 Throttle valve control device 11 Vehicle speed sensor 12 Control unit 21 Exhaust passage 22 EGR passage 23 EGR valve 24 EGR control device 26 1 pressure sensor 27 2nd pressure sensor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 43/00 301 F02D 43/00 301N F02M 25/07 550 F02M 25/07 550R 550F

Claims (12)

[Claims] A throttle valve control device for controlling an opening degree of a throttle valve interposed in an intake system to a target value; and an opening degree of an EGR valve interposed in an EGR passage connecting an exhaust system and an intake system. An EGR control device that controls the amount of air passing through the throttle valve and the amount of EGR gas that passes through the EGR valve. Operating state detecting means for detecting, target intake air amount calculating means for calculating a target intake air amount via the throttle valve, and target EGR gas amount calculating means for calculating a target EGR gas amount via the EGR valve A target opening area for calculating a target opening area of the intake system from the sum of the calculated target intake air amount and the target EGR gas amount, and the engine speed detected by the operating state detecting means. Opening area calculation means; and a target opening area distribution for distributing a target opening area of the intake system into a target throttle valve opening area and a target EGR valve opening area corresponding to a ratio of the target intake air amount and the target EGR gas amount. Means, first pressure detecting means for detecting pressure upstream of the throttle valve, second pressure detecting means for detecting pressure upstream of the EGR valve, and one of the target throttle valve opening area and the target EGR valve opening area Or a target throttle valve opening area correction calculation unit and / or a target EGR valve opening area correction unit that corrects either or both of the pressure upstream of the throttle valve and the pressure upstream of the EGR valve, The throttle valve control device is driven so that the throttle valve has an opening degree at which the corrected target second target throttle valve opening area is obtained. The correction calculation intake air control device for an engine, wherein a second target EGR valve opening area to drive the EGR control device such that the opening is obtained. 2. The target throttle valve opening area correction calculating means corrects the target throttle valve opening area based on the square root of the ratio between the first reference pressure and the pressure upstream of the throttle valve and corrects the second target throttle valve opening area. The target EGR valve opening area correction calculating means corrects the target EGR valve opening area based on the square root of the ratio between the second reference pressure and the pressure upstream of the EGR valve, and calculates the target EGR valve opening area. The engine intake control device according to claim 1, wherein the area is calculated. 3. The target throttle valve opening area correction calculating means corrects the target throttle valve opening area based on the square root of the ratio between the pressure upstream of the EGR valve and the pressure upstream of the throttle valve, and calculates the second target throttle valve opening area. 2. The intake control device for an engine according to claim 1, wherein an opening area is calculated. 4. The target EGR valve opening area correction calculating means corrects the target EGR valve opening area based on the square root of the ratio of the pressure upstream of the throttle valve to the pressure upstream of the EGR valve, and calculates the second target EGR valve. The intake control device for an engine according to claim 1 or 3, wherein the opening area is calculated. 5. The intake control device for an engine according to claim 1, wherein said first pressure detecting means directly detects a pressure upstream of a throttle valve by a sensor. 6. The system according to claim 1, wherein said first pressure detecting means detects a pressure upstream of a throttle valve based on an operating state of the engine detected by said operating state detecting means. The intake control device for an engine according to any one of claims 1 to 4. 7. The intake control device for an engine according to claim 1, wherein the second pressure detecting means directly detects a pressure upstream of an EGR valve by a sensor. 8. The system according to claim 1, wherein said second pressure detecting means detects a pressure upstream of an EGR valve based on an operating state of the engine detected by said operating state detecting means. 7. The intake control device for an engine according to any one of 6. 9. A target engine torque calculating means for calculating a target engine torque, wherein the target intake air amount calculating means is based on the calculated target engine torque and the detected engine speed. The intake control device for an engine according to any one of claims 1 to 8, wherein the target intake air amount is calculated by using the following method. 10. An accelerator operation amount detecting means for detecting an accelerator operation amount, wherein a target engine torque is calculated based on the detected accelerator operation amount and an engine rotation speed. An intake control device for an engine according to claim 9. 11. A target air-fuel ratio is variably set based on the detected engine operating state, and the target intake air amount calculating means corresponds to the calculated target engine torque and the detected engine speed. The intake air for an engine according to any one of claims 1 to 10, wherein a target intake air amount is calculated based on the target fuel supply amount calculated and the target air-fuel ratio. Control device. 12. The target EGR gas amount calculating means calculates a target EGR gas amount based on the calculated target intake air amount and a set target EGR rate. Item 12. The engine intake control device according to any one of items 11.