JP2000205053A - Egr control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent EGR control systems for the control of an intake air quantity from opening and closing EGR valves excessively in a transient phase. SOLUTION: The deviation gndlt of an actual intake air quantity gn obtained in S304 from a target intake air quantity gntrg computed in S305 is calculated in S307, before S311 determines whether its absolute value exceeds a preset value A. If S311 is acceptable or finds it larger, a correction level iefb calculated in S310 depending upon the intake air quantity deviation gndlt is set to zero in S312, so that a final EGR valve opening iefin computed in S313 through the addition of a basic EGR valve opening iebse set in S306 and the intake-air- quantity-deviation-dependent correction level iefb does not include the correction level iefb. This control prevents excessive opening and closing of EGR valves.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an EGR control device, and more particularly to an EGR control device for performing feedback control of an intake air amount to a target value.

[0002]

2. Description of the Related Art An EGR device is an effective means for reducing NOx and is currently mounted on most vehicles. However, with the tightening of exhaust gas regulations, more precise control is required. Therefore, there is known an EGR device which obtains a difference between a target intake air amount and an actual intake air amount, that is, a deviation of the intake air amount, and corrects the EGR amount based on the difference. There is a device described in the above.

The EGR system has been developed for reducing NOx as described above. However, the EGR system may be used for controlling the amount of intake air. Used for control of That is, when the actual intake air amount is excessive, the EGR amount is increased so that the actual intake air amount decreases, and when the actual intake air amount is insufficient, the EGR amount is decreased so that the actual intake air amount increases. In order to make the EGR valve open, a correction amount for the basic EGR valve opening is calculated based on the intake air amount deviation, and the EGR valve opening is obtained by correcting the basic EGR valve opening with a correction amount based on the intake air amount deviation. Control the opening degree.

[0004]

However, when the intake air amount is controlled as described above, the following problems occur due to a delay in change of the air amount during a transition. For example, when the actual intake air amount is significantly short of the target intake air amount during acceleration, the EGR control device excessively reduces the opening of the EGR valve to rapidly increase the actual intake air amount. This leads to an increase in NOx. Conversely, when the actual intake air amount becomes significantly excessive with respect to the target intake air amount during deceleration, the EGR control device excessively increases the opening degree of the EGR valve so as to rapidly decrease the actual intake air amount. As a result, smoke is increased.

[0005] In view of the above problems, the present invention provides an EGR control device used for controlling the intake air amount, which is used in a transient state.
An object of the present invention is to prevent the EGR valve from being opened and closed excessively and to control the EGR amount to an appropriate value.

[0006]

According to the first aspect of the present invention, target intake air amount calculating means for calculating a target intake air amount according to operating conditions, and a basic EGR valve opening degree according to operating conditions are calculated. A basic EGR valve opening calculating means, an actual intake air amount detecting means for detecting an actual intake air amount, an intake air amount deviation calculating means for calculating a deviation of the actual intake air amount from a target intake air amount, and a basic EGR An EG for controlling the EGR valve opening so that the EGR valve opening is obtained by correcting the valve opening by the correction amount.
The R valve control means increases the EGR amount so as to decrease the actual intake air amount when the actual intake air amount is excessive, and increases the actual intake air amount when the actual intake air amount is insufficient. A correction amount calculating means for calculating a correction amount of the EGR valve opening based on the intake air amount deviation to reduce the EGR amount; and whether or not the deviation of the intake air amount exceeds a predetermined value. And a prohibition of the correction based on the correction amount calculated by the correction amount calculating means corresponding to the intake air amount deviation when the deviation of the intake air amount exceeds a predetermined value. EG comprising means
An R control device is provided.

According to the invention described in claim 2, according to claim 1
In the invention, further, a steady-state intake pressure calculating means for calculating a steady-state intake pressure which is a steady-state intake pressure under each operating condition, an actual intake-pressure detecting means for detecting an actual intake pressure, and an actual intake pressure An intake pressure deviation calculating means for calculating a deviation of the air pressure; and an intake pressure deviation corresponding correction amount calculating means for calculating a correction amount of the EGR valve opening based on the intake pressure deviation, wherein the deviation of the intake air amount is predetermined. If the correction value exceeds the predetermined value, the correction of the basic EGR valve opening by the correction amount calculated by the intake air amount deviation correction amount calculating means is prohibited, and the basic amount is corrected by the correction amount calculated by the intake pressure deviation correction amount calculating means. EG
An EGR control device for correcting an R valve opening is provided.

According to the invention described in claim 3, according to claim 2
In the invention, when the fuel injection amount is equal to or less than a predetermined value and the deviation of the intake air amount exceeds a predetermined value, the opening of the EGR valve is maintained at a predetermined intermediate opening. An EGR control device is provided.

Here, referring to FIG.
The operation of the third invention will be described. FIG. 2A shows the intake air amount in the case of rapid acceleration after rapid deceleration, and the broken line shows the target intake air amount set for the engine speed and the fuel injection amount. The solid line indicates the actual intake air amount, and an intake air amount deviation occurs. FIG. 2B shows the problem of the prior art, and the broken line shows the basic E set for the engine speed and the fuel injection amount.
The GR valve opening, indicated by a solid line, is the EGR valve opening obtained by correcting the basic EGR valve opening with a correction amount corresponding to the intake air amount deviation based on the intake air amount deviation. Then, the EGR valve opening is excessively corrected by this correction. As a result, on the deceleration side, the EGR amount becomes too large, and smoke is generated. On the acceleration side, the EGR amount becomes too small, and NOx increases. Indicates that a problem has occurred.

FIG. 2C illustrates the operation of the first aspect of the present invention. In FIG. 2A, when the intake air amount deviation is equal to or more than a predetermined value, that is, on the time axis. At T1
In the period indicated by and the period indicated by T2, the correction based on the intake air amount deviation correction amount is not performed, and the basic EGR valve opening indicated by the broken line is set. As a result, an excessive increase or an excessive decrease in the EGR amount can be prevented.

However, when there is an intake air amount deviation, the return to the basic EGR valve opening is an excessive return. Therefore, it is an invention of claim 2 to perform a correction based on a deviation between the actual intake pressure and the intake pressure in a steady state, that is, an intake pressure deviation so as not to return too much, and FIG. The effect is shown.

In the second aspect, when the deviation of the intake air amount is large, the correction is performed based on the deviation of the intake pressure as described above for the following reason. Although the intake pressure deviation is not proportional to the intake air amount deviation, if the actual intake air amount is larger than the target intake air amount, the actual intake pressure also becomes larger than the steady-state intake pressure. When the amount is smaller than the target intake air amount, the actual intake pressure also becomes smaller than the steady-state intake pressure, and the tendency of the mutual deviation is the same. If one reverses from positive to negative, the other reverses from positive to negative. To reverse.
Further, for example, when reducing the EGR valve opening so as to increase the intake air amount, it is considered that the actual intake air amount is more likely to increase when the pressure in the intake pipe is high than when the pressure in the intake pipe is low. Therefore, the method of reducing the EGR valve opening may be small, but such correction is also possible. Therefore,
The correction based on the intake pressure deviation is performed.

Next, the operation of the invention of claim 3 will be described. When the correction based on the intake air amount deviation correction amount is stopped as in the first aspect of the present invention, it is not known at which position in the entire stroke the EGR valve stops. In the case of rapid deceleration and rapid acceleration, the EGR valve must be fully opened to rapidly reduce the intake air amount, and then the EGR valve must be fully closed to rapidly increase the intake air amount. . Therefore, it takes time to move from the fully open state to the fully closed state, and the reduction of the EGR amount is not executed immediately, which causes generation of smoke.

Therefore, in the invention of claim 3, in such a case, that is, when the fuel injection amount is equal to or less than a predetermined value and the intake air amount deviation is larger than the predetermined deviation determination value, As shown by the two-dot chain line, the opening of the EGR valve is fixed at a predetermined intermediate opening,
The required amount of movement of the R valve is reduced, and the above-described problem due to a response delay of the valve is solved. FIG. 2 (E) is a diagram for explaining this control. In the period T1 on the time axis, the opening of the EGR valve is predetermined because the fuel injection amount has become equal to or less than a predetermined value. As shown by the dashed line in FIG.
(D) performs the same control as that of the second embodiment. The intermediate opening of the EGR valve shown by the two-dot chain line in FIG. 2E is larger than the basic opening shown in FIG. 2C. It changes according to the size of the basic opening.

[0015]

FIG. 1 is a diagram showing a configuration common to each embodiment of the present invention. In FIG. 1, an engine 1 is a diesel engine, and an engine 1 includes an intake pipe 2.
And an exhaust pipe 3. An EGR pipe 4 for recirculating a part of the exhaust gas passing through the exhaust pipe 3 to the intake pipe 2 is disposed so as to communicate the intake pipe 2 and the exhaust pipe 3. An EGR control valve 5 for controlling the amount of the recirculated gas (hereinafter, referred to as EGR gas) is provided in the middle of 4.

The EGR control valve 5 is connected to a diaphragm chamber 5a and a diaphragm (not shown) provided in the diaphragm chamber 5a, and has a valve body 5b which moves and adjusts a passage area of the EGR gas. The diaphragm chamber 5a of the EGR control valve 5 is communicated with a vacuum pump 7 via a vacuum regulating valve (hereinafter, referred to as VRV) 6, and controls the VRV 6 by a signal from an engine control unit (hereinafter, referred to as ECU) 50. , And controls the EGR gas amount.

The intake pipe 2 has an air cleaner 9 for filtering air taken in from the upstream side, an air flow meter 10 for detecting the amount of air taken in, a turbocharger 11 for pressurizing the air taken in, and a pressurized air. An intercooler 12 for cooling air, a diesel throttle valve 13, and a pressure sensor 14 for detecting intake pressure are provided. The pressure sensor 14 is mounted via a switching valve 14 ', and can detect atmospheric pressure by switching the conduction of the switching valve 14'.

The fuel injection pump 15 pumps fuel to the fuel injection valve 16 of the engine 1. The fuel injection pump 15 is directly driven by the engine 1 and is provided with an engine speed sensor 17 for detecting the engine speed NE. I have. An accelerator opening sensor 19 is provided near the accelerator pedal 18 and detects an amount of depression of the accelerator pedal 18 (hereinafter referred to as an accelerator opening APA). The signal of each sensor is sent to the ECU 50, and the ECU 50 sends a signal for operating the EGR control valve 5 to the VRV 6 based on the signals of these sensors and data stored in an internal storage device as described later.

Next, the control of each embodiment configured as described above will be described in detail with reference to flowcharts. FIG. 3 is a flowchart of the first embodiment. In step 301, the engine speed NE is calculated based on a signal from the engine speed sensor 17.
In step 302, the accelerator opening sensor 19
The accelerator opening APA is calculated based on the signals from the ECUs. In step 303, the fuel injection amount Q set for the engine speed NE and the accelerator opening APA is calculated from the first map (see FIG. 6). .

In step 304, the air flow meter 10
The intake air amount gn is calculated based on the signal from
At 05, the engine speed NE was obtained from the second map (see FIG. 7).
And the target intake air amount set for the fuel injection amount Q
gntrg is calculated, and in step 306, the third map (FIG. 8)
), The basic EGR valve opening degree iebse set for the engine speed NE and the fuel injection amount Q is calculated. In step 307, the target intake air calculated in step 306 is calculated from the intake air amount gn calculated in step 305. The intake air amount deviation gndlt is calculated by subtracting the amount gntrg.

In step 308, a proportional term iefbpt of the correction amount iefb corresponding to the intake air amount deviation is calculated by multiplying the intake air amount deviation gndlt calculated in step 307 by the proportional gain Gp.
In step 309, a constant Ci is added to the previous value to obtain an integral term.
iefbi is calculated, and in step 310, the proportional term iefbpt calculated in step 308 and the integral term iefbi calculated in step 309 are added to calculate an intake air amount deviation corresponding correction amount iefb.

Here, the proportional term iefbpt and the integral term of the correction amount iefb corresponding to the intake air amount deviation will be described. This is based on the same concept as that used for the feedback control of the air-fuel ratio, and its outline is as shown in FIG. And the proportional term iefbp is the intake air amount deviation gndl
Stop by multiplying t by the proportional gain Gp. In the present embodiment, the proportional gain Gp is a fixed value, but the intake air amount deviation
A different value may be set according to the sign of gndlt, a map value corresponding to the intake air amount deviation gndlt, or a proportional term iefbp may be used as a map value corresponding to the intake air amount deviation gndlt. . On the other hand, the integral term iefbi is
It is the result of adding the constant Ci to its previous value. That is, iefbi = iefbi + Ci. Here, in the present embodiment, the constant Ci is a fixed value, but may be another value depending on the sign of the intake air amount deviation gndlt, or may be a map value corresponding to the intake air amount deviation gndlt. .

In step 311, it is determined whether or not the absolute value of the intake air amount deviation gndlt calculated in step 304 is larger than a predetermined determination value A. If an affirmative determination is made in step 311, the process proceeds to step 312, in which the intake air amount deviation corresponding correction amount iefb is set to 0 (zero), and step 313 is performed.
Proceeds to step 313 if a negative determination is made
Proceed to. Then, in step 313, step 306
The final EGR valve operation amount iefin is calculated by adding the EGR correction amount iefb corresponding to the intake air amount deviation to the basic EGR valve opening degree iebse calculated in the above.

Therefore, if the absolute value of the intake air amount deviation gndlt is larger than the predetermined determination value A, step 31
Since the process proceeds from 1 to 312 to 313, the basic EGR valve opening degree is set. If the absolute value of the intake air amount deviation gndlt is smaller than a predetermined determination value A, the process proceeds to step 311 to 313 and the correction amount iefb corresponding to the intake air amount deviation corresponds. The opening is added to the basic EGR valve opening iebse, and the operation shown in FIG. 2D can be realized.

Next, FIG. 4 is a flowchart of the control according to the second embodiment. Steps 401 to 410
Are the same as steps 301 to 310 in the flowchart of the first embodiment of FIG. Step 4
At 11, the actual intake pressure based on the signal from the pressure sensor 14
In step 412, a steady-state intake pressure pmst set for the engine speed NE and the fuel injection amount Q is calculated from the fourth map (see FIG. 9).
In step 3, the intake air pressure pmst in the steady state calculated in step 412 is subtracted from the actual intake pressure pm calculated in step 411 to calculate the air suction pressure deviation pmdlt. In step 414, the engine pressure is calculated from the fifth map (see FIG. 10). Engine speed NE and fuel injection amount Q
Is calculated for the correction gradient iesb set for.

In step 415, the intake pressure deviation pmdlt calculated in step 413 is multiplied by the correction gradient iesb calculated in step 414 to calculate a correction amount iepm corresponding to the intake pressure deviation. In step 416, the absolute value of the intake air amount deviation gndlt calculated in step 407 is set to a predetermined determination value A.
It is determined whether it is greater than.

If an affirmative determination is made in step 416, the flow proceeds to step 417, in which the EGR valve feedback control operation amount iefb is set to 0 (zero), and the flow proceeds to step 419. If a negative determination is made, the flow proceeds to step 417, in which the intake pressure deviation is determined. The corresponding EGR correction amount iepm is set to 0 (zero), and step 419 is performed.
Proceed to. Then, in step 419, step 406
The final EGR valve opening degree iefin is calculated by adding the intake air amount deviation corresponding correction amount iefb and the intake pressure deviation corresponding EGR correction amount iepm to the basic EGR valve opening degree iebse calculated in (1).

Therefore, if the absolute value of the intake air amount deviation gndlt is larger than the predetermined determination value A, step 41
In step 418, when only the intake pressure deviation correction amount iepm is set as the EGR valve opening added to the basic EGR valve opening iebse, and the absolute value of the intake air amount deviation gndlt is smaller than the predetermined determination value A, the process proceeds to step 418. EGR corresponding to intake air amount deviation
Only the correction amount iefb is the EGR valve opening added to the basic EGR valve opening iebse, and the operation shown in FIG. 2D can be realized.

Next, FIG. 5 is a flowchart of the control according to the third embodiment. Steps 501 to 515
Are the same as steps 401 to 415 in the flowchart of the second embodiment in FIG. Step 5
At 16, the intake air amount deviation gndlt is equal to the predetermined judgment value −A.
It is determined whether it is smaller than. If an affirmative determination is made in step 516, the process proceeds to step 519, where the EGR correction amount iefb corresponding to the intake air amount deviation is set to 0 (zero), and step 5 is performed.
Proceed to 23.

If a negative determination is made in step 516,
Proceeding to step 517, it is determined whether the intake air amount deviation gndlt is smaller than a predetermined determination value A. Step 5
If a negative determination is made in step 17, the process proceeds to step 520, where the intake pressure deviation correspondence correction amount iepm is set to 0 (zero), and the process proceeds to step 523. If an affirmative determination is made in step 517, the process proceeds to step 518, where the fuel injection amount Q is 0 (zero).
It is determined whether or not this is the case. If an affirmative determination is made in step 518, the process proceeds to step 521, where the intake air amount deviation corresponding correction amount iefb is set to 0 (zero), and step 523 is performed.
Proceed to. If a negative determination is made in step 519, the process proceeds to step 524.

When the routine proceeds to step 523, the correction amount iefb corresponding to the intake air amount deviation and the correction amount iepm corresponding to the intake pressure deviation are added to the basic EGR valve opening degree iebse calculated in step 506 to finally open the EGR valve. Calculate the degree iefin and return. When the process proceeds to step 524, the process returns after setting the EGR valve opening to the predetermined intermediate opening B.

Therefore, the vehicle is rapidly decelerated to the target intake air amount.
If the actual intake air amount gn is larger than a predetermined value A with respect to gntrg and the fuel injection amount is 0 (zero),
Steps 516 → 517 → 518 → 524 proceed to EGR
The valve opening is set to a predetermined intermediate opening B. Suddenly decelerated,
If the fuel injection amount is not 0 (zero) even if the actual intake air amount gn is greater than the predetermined intake air amount gn with respect to the target intake air amount gntrg, steps 516 → 517 →
518 → 521 → 523, the correction amount corresponding to the intake pressure deviation
EGR added only to basic EGR valve opening iebse
The valve opening is assumed. Target intake air amount gntrg and actual intake air amount
If the difference of gn is between a predetermined value -A and A,
Steps 516 → 517 → 520 → 523 are advanced and only the correction amount iefb corresponding to the intake air amount deviation is the basic EGR valve opening degree iebse.
The EGR valve opening is added to the EGR valve opening. Therefore, FIG.
(E) can be realized.

[0033]

According to the invention described in each claim, the basic E
The GR valve opening is corrected by an intake air amount deviation correction amount corresponding to the intake air amount deviation between the target intake air amount and the actual intake air amount, but the intake amount between the target intake air amount and the actual intake air amount is corrected. When the air amount deviation is large, the correction with the correction amount corresponding to the intake air amount deviation is prohibited, so that the excessive operation of the EGR valve to prevent the intake air amount from increasing and decreasing more than necessary is prevented, and the generation of smoke and NOx Can be prevented from increasing. In particular, when the intake air amount deviation between the target intake air amount and the actual intake air amount is large, the intake pressure corresponding to the intake pressure deviation between the steady-state intake pressure and the actual intake air pressure. Since the correction is performed using the correction amount corresponding to the atmospheric pressure deviation, it is possible to approach the EGR valve opening more appropriately than the basic EGR opening. In particular, according to the third aspect, when the fuel injection amount is equal to or less than a predetermined value, the EGR valve opening can be set to a predetermined intermediate opening.
The R valve is prevented from moving its full stroke (from fully open to fully closed), and a delay in the operation of the EGR valve prevents a delay in the increase in the intake air amount and the occurrence of smoke.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a time chart illustrating control.

FIG. 3 is a flowchart of control according to the first embodiment.

FIG. 4 is a flowchart of control according to the second embodiment.

FIG. 5 is a flowchart of control according to a third embodiment.

FIG. 6 is a map of a fuel injection amount Q set with respect to an engine speed NE and an accelerator opening APA.

FIG. 7 is a map of a target intake air amount gntrg set for the engine speed NE and the fuel injection amount Q;

FIG. 8 is a map of an EGR valve basic opening degree iebse set for the engine speed NE and the fuel injection amount Q;

FIG. 9 is a map of an intake pressure pmst in a steady state set for the engine speed NE and the fuel injection amount Q;

FIG. 10 is a map of a correction gradient iesb for calculating an intake pressure deviation correspondence correction amount iepm set for the engine speed NE and the fuel injection amount Q;

FIG. 11 is a proportional term iefb of a correction amount iefb corresponding to an intake air amount deviation.
It is a figure explaining p and integral term iefbi.

[Explanation of symbols]

 5 EGR control valve 6 Vacuum regulating valve (VRV) 7 Vacuum pump 10 Air flow meter 11 Turbocharger 12 Intercooler 15 Fuel injection pump 17 Engine speed sensor 19 Accelerator opening sensor

Claims (3)

[Claims] 1. A target intake air amount calculating means for calculating a target intake air amount according to operating conditions, and a basic EG for calculating a basic EGR valve opening degree according to operating conditions.
R valve opening calculating means, actual intake air amount detecting means for detecting actual intake air amount, intake air amount deviation calculating means for calculating deviation of actual intake air amount from target intake air amount, basic EGR valve opening EGR valve control means for controlling the EGR valve opening so that the EGR valve opening is corrected by the correction amount, and the EGR amount such that the actual intake air amount is reduced when the actual intake air amount is excessive. If the actual intake air amount is too small, the EGR amount is reduced so that the actual intake air amount is increased, and the correction amount of the EGR valve opening based on the intake air amount deviation is calculated. Correction amount calculating means; determining means for determining whether the deviation of the intake air amount exceeds a predetermined value; and determining the deviation of the intake air amount if the deviation of the intake air amount exceeds the predetermined value. Correction amount calculated by the corresponding correction amount calculation means EG, comprising: a correction prohibition unit corresponding to an intake air amount deviation for prohibiting correction by the EG.
R control device. 2. A steady-state intake pressure calculating means for calculating a steady-state intake pressure which is a steady-state intake pressure under each operating condition; an actual intake-pressure detecting means for detecting an actual intake pressure; An intake pressure deviation calculating means for calculating a deviation of the intake pressure; and an intake pressure deviation corresponding correction amount calculating means for calculating a correction amount of the EGR valve opening based on the intake pressure deviation, wherein the deviation of the intake air amount is predetermined. If the correction value exceeds the predetermined value, the correction of the basic EGR valve opening based on the correction amount calculated by the correction amount calculating means corresponding to the intake air amount deviation is prohibited, and the correction amount calculated by the correction amount calculating means corresponding to the intake pressure deviation. Basic E
2. The GR valve opening is corrected.
2. The EGR control device according to claim 1. 3. The fuel injection amount is equal to or less than a predetermined value.
3. The EGR control device according to claim 2, wherein when the deviation of the intake air amount exceeds a predetermined value, the EGR valve opening is maintained at a predetermined intermediate opening.