JPH10115259A - Egr flow amount diagnostic device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diagnose a recirculation amount of EGR during control of the EGR. SOLUTION: In an internal combustion engine system having an exhaust gas recirculating device EGR, a valve control means 103 of the EGR, a detection means 102 of an internal combustion engine condition parameter and an estimation means 101 are set, an actual intake pressure at EGR time is detected, here, an intake pressure at the time with no EGR applied is estimated. A difference between output values of these means represents an EGR partial pressure value. In a condition that an EGR valve opening is almost fully closed, so as to make the EGR partial pressure value zero, a gain of the estimation means 101 of the internal combustion engine parameter is adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate diagnosis of an EGR system installed for reducing NOx of an internal combustion engine.

[0002]

2. Description of the Related Art A three-way catalyst is installed in an exhaust system of an internal combustion engine,
A technology for purifying hydrocarbons HC, carbon monoxide CO, and nitric oxide NOx in exhaust gas. In order to control the actual air-fuel ratio centering on the stoichiometric air-fuel ratio at which the purification performance of the three-way catalyst becomes efficient, It is a known technique to provide a fuel ratio detecting means in an exhaust system upstream of a three-way catalyst and feed back an oxygen concentration in exhaust gas to an internal combustion engine control device. In addition, when the mixture gas is appropriately mixed with exhaust gas containing CO ₂ gas having a larger heat capacity than N ₂ in the air, the combustion temperature is higher than when no exhaust gas is mixed even if the same calorific value is burned. And generation of NOx can be suppressed. This is known as exhaust gas recirculation (hereinafter referred to as EGR). As a known technique for EGR flow rate diagnosis, Japanese Patent Laid-Open Publication No. Hei 6-31571 discloses a method for performing EGR flow rate diagnosis based on operating conditions before and after the EGR valve is closed and opened. .

[0003]

[Problems to be Solved by the Invention] Air Resour in California, USA
On-Board Diagnosis Phase proposed by ces Board
According to II, the vehicle equipped with the EGR device is required to monitor the EGR recirculation amount. An object of the present invention is to provide a means for detecting the EGR flow rate corresponding to this.

[0004]

A combustion state detecting apparatus for an internal combustion engine according to the present invention for solving the above-mentioned problems is basically provided in an internal combustion engine system having an exhaust gas recirculation device EGR. An internal combustion engine state parameter detecting means, an internal combustion engine state parameter estimating means, an internal combustion engine state parameter comparing means for comparing the detected and estimated internal combustion engine state parameters, and an EGR flow rate judging from the comparison value. There is provided a flow rate determining means and an internal combustion engine state parameter correcting means for correcting the internal combustion engine state parameter estimating means.

[0005] The actual intake pressure when EGR is applied is detected by an internal combustion engine state parameter detecting means.
The intake pressure when GR is not applied is estimated from the internal combustion engine state parameter estimating means. The difference between the output values of the above means is
This shows the EGR partial pressure value. At this time, in order to improve the accuracy of the internal combustion engine state parameter estimating means, the gain of the internal combustion engine state parameter estimating means is adjusted so that the EGR partial pressure value becomes zero when the EGR valve opening is almost fully closed. adjust.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an EGR flow rate diagnosing apparatus for an internal combustion engine according to an embodiment of the present invention;

FIG. 1 shows a block diagram of the present invention. As shown in the figure, the intake pressure is estimated by the internal combustion engine state parameter estimating means in block 101, and the intake pressure is detected by the internal combustion engine state parameter detecting means in block 102. And
EG is controlled by the EGR valve control means in block 103.
The R valve is controlled, and the EGR partial pressure is detected by the internal combustion engine state parameter comparison means in block 104. At this time,
The gain of the internal combustion engine state parameter estimating means is adjusted by the internal combustion engine state parameter correcting means in block 105. Finally, the EGR flow rate determination means in block 106
It is determined whether the EGR flow is equal to or more than a predetermined value.

FIG. 2 shows an internal combustion engine system to which the present invention is applied. The engine includes an internal combustion engine, an intake system, and an exhaust system. The internal combustion engine is provided with an ignition device 201, a fuel injection device 202, and a rotation speed detecting means 203. The intake system includes an air cleaner, intake temperature detecting means, and flow rate detecting means 20.
4, and an exhaust system is provided with an air-fuel ratio sensor 205 and a three-way catalyst 206. The internal combustion engine control device 207 uses the output signal Qa of the flow rate detection means 204 and the rotation speed detection means 203 to generate a ring gear or plate 208.
, The fuel injection amount Ti is calculated, and the injection amount of the fuel injection device is controlled. Further, the internal combustion engine control device 207 uses the air-fuel ratio sensor 205
The air-fuel ratio feedback control for correcting the fuel injection amount Ti so that the air-fuel ratio in the internal combustion engine becomes the stoichiometric air-fuel ratio is performed.

Further, when an exhaust gas containing CO ₂ gas having a larger heat capacity than N ₂ in the air is appropriately mixed into the air-fuel mixture, even if the same calorific value is burned, no exhaust gas is mixed. As a result, the combustion temperature decreases, and the generation of NOx can be suppressed. This is called exhaust gas recirculation (EGR), and the internal combustion engine control device 207 controls the EGR valve 209 to realize this. The present invention relates to the diagnosis of the EGR recirculation amount.

The EGR is a device for circulating a part of the exhaust gas to the intake system to reduce NOx. The ratio between the EGR flow rate and the intake air amount is generally called an EGR rate, and is defined by the following equation (1).

[0011]

(Equation 1)

Here, Q _EGR : recirculation amount by EGR, Pe: EGR partial pressure, Q
a: intake air amount, Pa: actual intake pressure, L: load, Ne: rotation speed, K1: constant Here, when rearranging equation (1), equation (2) is obtained.
It can be seen that the GR reflux amount Q _EGR is proportional to the product of Pe and Ne.

[0013]

## EQU2 ## Q _EGR = K1 · Pe · Ne (Equation 2) This is the desired rotational speed Na and the EGR partial pressure P at that time.
This shows that the product of en is equal to the product of the rotational speed Ne at the time of measurement and the EGR partial pressure Pe at that time. Therefore, Equation 3 holds,

[0014]

[Equation 3] Pen · Na = Pe · Ne (Equation 3) where Na: normalized rotation speed, Pen: normalized EGR partial pressure From the expression 3, Pen at the desired rotation speed Na can be detected.

Next, a method for detecting Pe will be described. In order to obtain Pe, the intake pressure Pa when EGR is actually applied is measured, and the intake pressure P0 when EGR is not applied at that time is estimated. Differential pressure is EGR
The EGR partial pressure Pe thus increased. That is, Equation 4
Holds, and it is important to estimate P0.

[0016]

(Equation 4) Pe = Pa−P0 (Equation 4) In order to obtain the above P0, consider the intake system model shown in FIG. This model indicates that the measured air amount Qa stays due to the intake manifold charge phenomenon, and then becomes the air amount Qc flowing into each cylinder. Here, assuming that the calculated intake pressure is P0, Equations 5 and 6 hold.

[0017]

(Equation 5)

[0018]

(Equation 6)

Equation (6) consists of parameters determined by the structure of the intake system, and can be set in advance by a map of the rotational speed Ne and the estimated intake pressure P0. Since the estimated intake pressure P0 is not affected by all the bypass systems of the intake system, EGR
It shows the value when EGR is not applied even if it is applied. FIG. 4 shows an intake pressure estimation block diagram that can be created from Equations 5 and 6. The relationship between the estimated intake pressure P0 and the air amount Qa can be considered as a kind of low-pass filter whose cutoff frequency changes depending on the rotation speed Ne. As described above, by measuring the actual intake pressure Pa from the intake pressure sensor and obtaining the estimated intake pressure P0 from Equations 5 and 6, the differential pressure can be used as the EGR partial pressure Pe.

FIG. 5 shows the estimated intake pressure and the actual intake pressure. EG
When R is not applied, the actual intake pressure Pa and the estimated intake pressure P0 are almost the same, but when EGR is applied, the actual intake pressure Pa becomes higher than the estimated intake pressure P0, and the differential pressure becomes equal to the EGR. The partial pressure becomes Pe.

With the above method, Pen can be detected. However, in this system, when the EGR valve is fully closed, P
It is assumed that a and Pen are equal and the differential pressure is always zero. However, actually, the estimation accuracy of the estimated intake pressure P0 decreases due to the influence of the pulsation of Qa, the influence of the temperature, the influence of the atmospheric pressure, and the like, and even if the EGR valve is fully closed, the differential pressure Pe does not always become zero ( In FIG. 5, it is almost zero). Therefore, the present invention sets a predetermined gain in the above-described intake pressure estimation method, and when the EGR is equal to or less than a predetermined value 1 (almost fully closed), the differential pressure between the actual intake pressure Pa and the estimated intake pressure P0 becomes zero. Adjust the gain to. Then, when the EGR valve becomes equal to or more than a predetermined value 2 (the predetermined value 2 is larger than the predetermined value 1), the actual intake pressure Pa is measured, and the estimated intake pressure P with the above-mentioned gain adjustment is measured.
The normalized EGR partial pressure Pen is detected by using Expression 3 from 0. When the normalized EGR partial pressure Pen is larger than a predetermined value, the normal judgment is made, and in the following cases, the abnormality judgment is made.

FIG. 6 shows this process. In step 601, the air amount Qa is measured and filtered. The filtering is for improving the transient response of Qa. In step 602, the rotational speed Ne is measured. Next, in step 603, a change in the estimated intake pressure P0 is obtained. Then, in step 604, the estimated intake pressure P0 is obtained by integrating the variation of the estimated intake pressure P0. Here, K in step 603 is K = R.Tm / Vm, and initial values are given to Qc and P0old. Step 60
In step 5, an average value P0m of the estimated intake pressure P0 is obtained, and in step 606, a predetermined gain a is applied to the estimated average intake pressure P0m. After confirming in step 607 that there is no fluctuation of the bypass system outside the EGR, in step 608, the EGR
Check the valve opening. Normally, the EGR opening is a map value of the rotation speed and the load, and the value changes depending on the operation state. If the EGR valve opening is equal to or less than a predetermined value 1,
In step 616, the actual intake pressure pa is measured, and the average value
Ask for. In step 617, a difference ΔP between the actual average intake pressure Pam and the corrected estimated average intake pressure P0ma is determined. If ΔP is within a predetermined range (ε0−ε1) in step 618, ΔP is regarded as substantially zero, and in step 619, ΔP
Is smaller than ε0, in step 620, the gain a
And if ΔP is greater than ε1, step 6
At 21, the gain a is increased. Here, the unit amount (Δa) for increasing and decreasing the gain a is given as a constant or a function of the intake air temperature. Then, step 622
Then, the gain a is shifted by one sampling to back up.

If it is determined in step 608 that the EGR valve opening is in the range of the predetermined value 1 to the predetermined value 2, nothing is performed. Is measured, and an average value pam is obtained. In step 610, a difference Pe between the actual average intake pressure Pam and the corrected estimated average intake pressure Poma is determined. Step 611
Then, in order to obtain Pen at the desired rotation speed, Pe is multiplied by the ratio of the rotation speed Ne at the measurement and the desired rotation speed Na.
In step 612, a determination value is retrieved from the atmospheric pressure table. In step 613, if Pen is larger than the determination value, normality is determined in step 614. If Pen is equal to or less than the determination value, abnormality determination is performed in step 615. I do.

Finally, at step 623, a map search is performed for the cylinder inflow air amount Qc from the rotational speed Ne and the estimated intake pressure P,
In step 624, the estimated intake pressure P is backed up by shifting one sampling.

As another mode, a method of diagnosing from the ratio between the actual intake pressure Pa and the estimated intake pressure P0 when EGR is applied can be considered. EGR flow rate diagnosis PA in this case
Fig. D is shown in Fig. 7. The difference from FIG.
0, 617, respectively, which are steps 710, 7
It will be changed to 17. In step 710, the actual average intake pressure P
am and the corrected estimated average intake pressure P0ma are determined,
Used as a diagnostic value. In step 717, a ratio between the actual average intake pressure Pam and the corrected estimated average intake pressure P0ma is obtained and used for updating the gain a. Other steps have the same functions as in FIG.

As described above, when the EGR valve is almost fully closed, the estimated intake pressure is corrected to match the actual intake pressure, and the EGR flow can be diagnosed during the EGR control.

[0027]

The recirculation amount of EGR can be diagnosed during the EGR control.

[Brief description of the drawings]

FIG. 1 is a block diagram of the present invention.

FIG. 2 is a block diagram of an internal combustion engine system to which the present invention is applied.

FIG. 3 is an explanatory diagram of an intake manifold pressure estimation model.

FIG. 4 is a block diagram of intake manifold pressure estimation.

FIG. 5 is an explanatory diagram of a difference between an estimated intake manifold pressure and an actual intake manifold pressure when EGR is applied.

FIG. 6 is a PAD diagram of the present invention.

FIG. 7 is a PAD diagram of the present invention.

[Explanation of symbols]

101: internal combustion engine state parameter estimating means, 102: internal combustion engine state parameter detecting means, 103: EGR valve control means, 104: internal combustion engine state parameter comparing means,
105 ... internal combustion engine state parameter correction means, 106 ... E
GR flow rate determining means.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Takanobu Ichihara 2520 Ojitakaba, Hitachinaka City, Ibaraki Prefecture Inside the Automotive Equipment Division, Hitachi, Ltd. (72) Inventor Yuji Ikeda 2477 Takaba, Hitachinaka City, Ibaraki Prefecture Within Hitachi Car Engineering

Claims (16)

[Claims] In an internal combustion engine system having an EGR of an exhaust gas recirculation device, the EGR valve control means includes:
Internal-combustion-engine state parameter detecting means, internal-combustion-engine state parameter estimating means, internal-combustion-engine state parameter comparing means for comparing the detected and estimated internal-combustion-engine state parameters, and EGR flow rate determination from the comparison values; Means for correcting internal combustion engine state parameter estimation means for correcting the internal combustion engine state parameter estimation means. 2. The system according to claim 1, wherein the internal combustion engine state parameter is an intake pressure, the means for detecting the internal combustion engine state parameter is a means for measuring the intake pressure, and the means for estimating the internal combustion engine state parameter is an intake pressure. An EGR flow rate diagnostic device for an internal combustion engine, which is means for estimating an atmospheric pressure. 3. The EG of an internal combustion engine according to claim 1, wherein the means for estimating the intake pressure is obtained from a rotational speed and an air amount and is not affected by any bypass system of the intake system.
R flow rate diagnostic device. 4. The apparatus according to claim 1, wherein said means for estimating the intake pressure is provided even when EGR is applied.
An EGR flow rate diagnostic device for an internal combustion engine that estimates intake pressure when EGR is not applied. 5. An internal combustion engine EG according to claim 1, wherein said internal combustion engine state parameter correcting means adjusts a gain of said internal combustion engine state parameter estimating means.
R flow rate diagnostic device. 6. The method of claim 1, 2, 3, 4, or 5,
An internal combustion engine EGR flow rate diagnostic device for adjusting a gain such that the estimated value of the internal combustion engine state parameter estimating means matches the detected value of the internal combustion engine state parameter detecting means. 7. The internal combustion engine state parameter correcting means,
The gain of the internal combustion engine state parameter estimating means is increased when the detected value of the internal combustion engine state parameter detecting means is larger than the estimated value of the internal combustion engine state parameter estimating means, and is decreased when the detected value is smaller. 3,
7. The apparatus for diagnosing EGR flow of an internal combustion engine according to 4, 5, or 6. 8. The EGR flow rate of an internal combustion engine according to claim 1, wherein the gain increase / decrease of said internal combustion engine state parameter correcting means is a constant or a function of an intake air temperature. Diagnostic device. 9. The method according to claim 1, wherein said gain adjustment is performed when a ratio between an intake air amount and a flow rate of a bypass system is equal to or less than a predetermined value. An EGR flow rate diagnostic device for an internal combustion engine according to any one of the preceding claims. 10. The gain control according to claim 1, wherein said gain adjustment is performed when an opening of said bypass valve is equal to or less than a predetermined value.
10. The EGR flow rate diagnostic device for an internal combustion engine according to 2, 3, 4, 5, 6, 7, 8, or 9. 11. The gain adjustment is performed when the EGR valve opening is equal to or less than a predetermined value.
The apparatus for diagnosing EGR flow of an internal combustion engine according to any one of 3, 4, 5, 6, 7, 8, 9 and 10. 12. The condition under which the gain adjustment is not performed is as follows.
The EGR valve opening is equal to or greater than a predetermined value, and the EGR flow rate is determined when the condition is satisfied.
The EGR flow rate diagnostic device for an internal combustion engine according to any one of 4, 5, 6, 7, 8, 9, 10 and 11. 13. The diagnostic value calculated for determining the EGR flow rate is a difference or a ratio between a detected value of the means for detecting the intake pressure and an estimated value of the means for estimating the intake pressure. Claims 1,2,3,4,5,6,7,8,9,1
13. The apparatus for diagnosing EGR flow of an internal combustion engine according to 0, 11 or 12. 14. A diagnostic value calculated for determining the EGR flow rate is obtained by rotating a difference or a ratio between a detected value of the intake pressure detecting means and an estimated value of the intake pressure estimating means. A value normalized by a number.
An EGR flow rate diagnostic device for an internal combustion engine according to any one of 5, 6, 7, 8, 9, 10, 11, 12 and 13. 15. The judgment value to be compared with the diagnosis value is a function of the atmospheric pressure.
The EGR flow rate diagnostic device for an internal combustion engine according to any one of 9, 10, 11, 12, 13 and 14. 16. An EGR flow rate diagnosis is not performed when a flow rate of a bypass system other than the EGR changes.
3,4,5,6,7,8,9,10,11,12,1
16. The EGR flow rate diagnostic device for an internal combustion engine according to 3, 14, or 15.