JPS6341634A - Air-fuel ratio controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To secure a good air-fuel ratio all the time, by discriminating whether a transient correction compensation value is of any fuel among plural types of fuel differing in a time constant each, and operating a learning value of the transient compensation value on the discriminated fuel on the basis of the desired air-fuel ratio and the actual air-fuel ratio. CONSTITUTION:In this controller, there are provided with both operational devices 2 and 3 consisting of operational devices 2A and 3A operating an equilibrium sticking quantity on each fuel to be varied by a relatively speedy time constant and a relatively late time constant among suction system fuels, operational devices 2B and 3B operating a sticking speed (transient compensation value) on the basis of a deflection between this equilibrium sticking quantity and another sticking quantity to be varied by a first-order lag to the said sticking quantity and operational devices 2C and 3C operating this time sticking quantity from the sticking speed. And, whether it is the transient compensation value of any fuel or not is discriminating by a discriminating device 7, and a learning value of the discriminated transient compensation value is operated by an operational device 8 on the basis of the desired air-fuel ratio out of an operational device 5 and the actual air-fuel ratio out of a detecting device 6, thereby utilizing it for operation of a final injection quantity.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an air-fuel ratio control device for an internal combustion engine.

(Prior Art) Electronically controlled fuel injection engines are actually widely adopted due to their high fuel metering accuracy, and when controlling the injection amount supplied from the injection valve to the engine intake system, the engine load (for example, intake air ff1Qa) and the engine speed N, the basic fuel injection amount (basic pulse width) T11 (= -Qa/N,
However, K is a constant. ) is corrected according to other operating variables, and the injection amount (injection pulse width) Ti is calculated based on the following equation (1). Engineering” Volume 34 No. 11 No. 2
(See page 8, etc.)

Ti=TpXCOEFXLMBDA+Ts...(1
) However, C0EF: Sum of various correction coefficients LAMBDA:
Air-fuel ratio correction coefficient Ts: Invalid pulse width.

(Problems to be Solved by the Invention) By the way, in a system in which one or more fuel injection valves are installed in a gathering part of the intake passage far from the engine cylinder (hereinafter referred to as "5PIVc installation"), , some of the injected fuel adheres to the inner wall of the intake pipe or intake boat before reaching the cylinder, or the amount of fuel that is floating in the intake pipe without being inhaled (this amount of fuel is hereinafter referred to as the "adhered amount"). ) occurs as a fuel delay during transient periods, which greatly affects the accuracy of air-fuel ratio control.

Therefore, based on the deviation between the intake system fuel adhesion amount under steady operating conditions (this adhesion amount is hereinafter referred to as the "equilibrium adhesion amount") and the calculated value of the adhesion amount that changes with a first-order lag with respect to this equilibrium adhesion amount, (This amount of adhesion per unit cycle is hereinafter referred to as "adhesion rate.")
The applicant has previously proposed a device in which the amount of fuel to be supplied is corrected based on this deposition speed, and this device can detect factors related to the amount of fuel deposited in the intake system. Instead, the amount of adhering fuel in the intake system is handled directly, making it possible to obtain air-fuel ratio characteristics with better responsiveness than before, regardless of acceleration or deceleration.

However, when conducting experiments, it was found that the behavior of intake system fuel is not uniform, and can be roughly divided into fuel that changes with a relatively fast time constant and fuel that changes with a relatively slow time constant. In other words, the intake system fuel is divided into those that change with a relatively fast time constant and those that change with a relatively slow time constant, and matching is performed for each fuel with different behavior. An experiment was conducted based on the obtained deposition rate, and it matched well with reality.

Therefore, there is no problem at the time of setting, but if there are differences in fuel properties or changes over time after setting, the set transient correction amount will no longer match the actual value due to matching, and this difference will cause the target air-fuel ratio to change. It is possible that you will not be able to obtain it. For example, if the actual air-fuel ratio deviates from the target air-fuel ratio, it will lead to poor drivability and an increase in harmful emissions, so make sure that the target air-fuel ratio can be obtained even if error factors occur after setting. is desirable.

The present invention has been made in view of these conventional problems, and provides an air-fuel ratio control device that provides a learning fi function for calculating transient correction amounts for a plurality of intake system fuels having different time constants. The purpose is to

(Means for Solving the Problems) In the present invention, as shown in FIG. Transient correction amounts KATHO8l , KATI(O
82, and transient correction amounts KATHO3+ and KAT for these plurality of fuels.
T-1082 assumes an air-fuel ratio control device for an internal combustion engine comprising means 4 for correcting the basic injection amount Tp, means 5 for calculating the target air-fuel ratio, and means 6 for detecting the actual air-fuel ratio. , a means 7 for determining whether or not the transient correction amount is equal to 4 for any of the fuels, and a learned value KBT of the transient correction amount for the determined fuel.
Means 8 for calculating LRCI and KBTLRC2 based on the target air-fuel ratio and the actual air-fuel ratio is additionally provided.

Note that the configurations of the plurality of means 2 and 3 are the same, so to discuss only the fuel having a fast time constant, there is a means 2A for calculating the equilibrium adhesion amount MFH1 of intake system fuel according to the operating state. , this equilibrium adhesion amount MFHI and the calculated value of the adhesion amount that changes with a first order lag with respect to this equilibrium adhesion amount (
means 2B for calculating the adhesion speed VMFI based on the deviation from MFI-+), and means 2C for calculating the current adhesion amount MF by adding the adhesion speed VMF to the previously calculated adhesion amount MFI1. It consists of Basically, this adhesion speed VMFI is the transient correction amount KATHOSl.

For convenience of explanation, the subscript "1" is used for fuels with fast time constants, and the subscript "1" is used for fuels with slow time constants.
2” is added. In addition, in the calculation of the transient correction amount, etc., which is executed every control cycle, the current calculated value is less than the calculated value based on the previous calculated value, so the subscript "-1" indicating the previous calculated value is used. to distinguish them.

(Function) With this configuration, it is determined which of the multiple fuels with different time constants is the transient correction amount, and the learned value calculating means 8 determines whether the actual air-fuel ratio deviates from the target air-fuel ratio for the determined fuel. The learned values KBTLRCI and KBTLRC2 are rewritten so as not to deviate from the target air-fuel ratio during the next injection.

As a result, these learned values KBTLRCI, KBTLRC
21 The iron transient correction amount has been slightly adjusted, and even if this causes differences in fuel properties, atmospheric pressure, and intake temperature, which are the cause of errors since the time of revision, a good result is obtained regardless of these differences. The air-fuel ratio can be adjusted to improve drivability and exhaust emissions.

This will be explained below using examples.

(Example) In FIG. 2, one fuel injection valve 24 that serves all cylinders is provided in the intake passage 22 upstream of the intake throttle valve 21 (SPI device).
In addition, it represents the mechanical configuration when the present invention is applied to an engine in which the throttle valve opening α (also referred to as TVO) is used as the engine load signal instead of the air amount in order to simplify the device.

Therefore, in this example, the injection pulse width is controlled using α and N as basic variables (hereinafter, this will be referred to as the α-N method).

For this reason, an air amount sensor is not provided, but instead a wrinkled valve opening sensor 25 is provided.

In addition, two idle-up solenoid valves (referred to as S■) 26 and 27 are installed in parallel in the passage 23 that bypasses the throttle valve 21 in order to enhance control at the time of starting, while a swirl valve is installed in the intake boat. A control valve 28 is provided.

The engine speed N is detected by a crank angle sensor 32 built into the distributor 31, the cooling water temperature TIII is detected by a water temperature sensor 33, and an oxygen sensor 34 is provided as a sensor for detecting the actual air-fuel ratio. Instead, these crank angle signals (reference signal and angle signal)
, the water temperature signal, and the actual air-fuel ratio signal are input to the control unit 35 together with the two-marked valve opening signal, and the optimal fuel injection pulse width Ti is calculated in the control unit 35 based on these signals. Ru.

Next, the calculation contents of the injection pulse width Ti are shown in FIG. 3 (consisting of FIG. 3(A) to FIG. 3(C).

) to FIG. 10, the parts related to the present invention will be explained first, and then the system as a whole will be outlined. In other words, the control contents shown in these figures constitute one air-fuel ratio control system as a whole, and the breakdown of these is as follows: Figure 3 is the main routine for calculating the injection pulse width, and Figures 4 to 17 are the main routines. Variables used in the routine (transient correction amount K
AT HOS, feedback correction amount LAMBDA
, target air-fuel ratio TFBYA, intake temperature correction coefficient KTA), and FIGS. 8 to 10 are routines showing the learning content and rewriting of the learning values.

The numbers in the figure represent processing numbers. Note that such control can be easily performed by configuring the control unit 35 with a microcomputer. In this case, the calculation of each variable is executed in the control cycle shown in the table below.

Now, the feature of this invention is to determine which of the plurality of fuels with different time constants is the transient correction amount, and to set the learned value of the transient correction amount for the determined fuel to the target air-fuel ratio. The point is that the calculation is based on the actual air-fuel ratio. That is, a learning routine shown in FIG. 8 was provided to execute these steps. Then, a plurality of learning coefficients KBTLRCI, KB calculated in the learning routine
Based on TLRC2, the main injection control routine shown in FIG. 3 is executed, and the injection pulse width Ti of synchronous injection, which will be described later, is calculated.

Ti=(TpXKBLRC +ΣKATHO8kXKBTLRCk)k=1 X L A M B D A 10T s... (4-
8) Here, the first term is a steady term, the second term is a transient term, and LA
MBDA is air-fuel ratio feedback correction coefficient, KBLRC
is the basic injection amount learning correction coefficient.

Learning correction coefficient (hereinafter simply referred to as "learning coefficient") KBTLRCl for multiple fuels shown in equation (4-8).

The introduction of KBTLRC2 is the main part of this invention,
This will be explained below.

First, the purpose of determining which fuel is the transient correction amount is to clarify the learning target. Note that since the transient correction amount is basically equivalent to the adhesion speed VMF, the adhesion speed VMF is targeted in this embodiment. That is, during a transient period, the adhesion speed VMFI (solid line) of multiple fuels with different time constants is shown in FIG. 11, 11MF2
(dashed line), as shown in the figure,
At the beginning of the transient, fuel with a fast time constant is dominant;
In the latter half of the transition, instead of this, fuel with a slow time constant becomes dominant. In addition, the adhesion speed VMF for the entire fuel
is given by the sum of these VMFI and VMF2. Therefore, in order to determine which of the plurality of fuels is used, it is preferable to set the reference value TVMF at an appropriate position and to distinguish between cases in which the fuel exceeds the reference value and cases in which it falls below the reference value.

Therefore, in this example, each adhesion speed VMF1. “t7MF2
and the reference value TvMF, VMFI > TV M
F KakV M F 2 > T V M F Tea'
-) It is determined that this is a transient correction amount for fuel that changes with a very fast time constant, and VMFI ≦TVMP and V
Since MF2>TVMP, it is determined that the fuel changes with a slow time constant (steps 133 to 13).
6).

Next, for the transient correction amount for the determined fuel, each learning coefficient KBTLRC,
, KBTLRC2.

Here, even if there are multiple fuels, the learning content is the same, so for the convenience of the following explanation, we will basically talk about fuels that change with a slow time constant, and only when they are different, we will talk about fuels that change with a slow time constant. Refer to the fuel used. Further, for convenience of explanation, "old" before the symbol indicates the value from the previous calculation, and "new" indicates the value from the current calculation. Furthermore, since the fuel-air ratio and the air-fuel ratio have a reciprocal relationship, the fuel-air ratio can also be controlled in the same way. For this reason, although the fuel-air ratio is adopted in this embodiment, it will be explained as the air-fuel ratio. Therefore, the air-fuel ratio in the explanation of the following mathematical expressions may mean the fuel-air ratio.

The purpose of learning is to change the actual air-fuel ratio AFBYA to the target air-fuel ratio TFBY.
It is important not to deviate from A.

Therefore, it is sufficient to incorporate the ratio or deviation between the target air-fuel ratio and the actual air-fuel ratio into the learning calculation. Therefore, in this example, this ratio is adopted to define the shortage rate R1 in the steady state and the shortage rate RTR in the transient state using the following formula (steps 137 and 140).
, 138, 141).

R=(TFBYA/AFBYA) XLAMBDA...(98) RTR=iR(Tp+KATHO8)-Tpl/KAT
HO8...(9B) However, Tp is the basic pulse width, and KATHO3 is the sum of the transient correction amounts for each of multiple fuels (ΣK A T
HOS k).

First, to explain the steady state, since the transient correction amount KATHO8 is almost equal to zero in the steady state, by setting the transient correction amount KATHO8 to zero in curve formation (4-Δ), Te (old Te) at the previous calculation can be Seek.

Note that Te=Ti−Ts.

Old Te=TpX Old K B I-RCX Old LAMBDA・
...(9C) As a result, the actual air-fuel ratio AFBYA is AFBYA=Qa
/old Te (however, Qa is the air flow rate), so substitute equation (9C) into this equation and rearrange in terms of Qa.

Qa=-AFBYAXTPX old KBLRC x old LAMB
DA...(9D) Also, the target air-fuel ratio TFBYA at the time of calculation this time is TFBYA = (TpX new KBL
RCX new LAMBDA)/Qa (However, this time, assuming that the air-fuel ratio has reached the target value, new LAMBDA = 1.0.) Therefore, by transforming this formula, new K B L R,
C is obtained.

New KBLRC=QaXTFBYA/Tp...(9E) If we delete Qa from equations (9D) and (9E), we get
New KBLRC = old KBLRCX (TFBYA x old LAMBDA/AFBYA) = old KBLRCXR = (9F). That is, since R=new KBLRC/old KBLRC, R has a meaning as a learning coefficient shortage rate. For example, if R=1.0, it means that it matches the target value. The learning value is rewritten so that R=1.0 after all.

Next, when talking about the transition period, since it is a transition period this time, the shortage rate R is R = new Te / old Te - (9, 1
). However, new Te = new T p
9K) Old 1'e-Old Tl)X Old K A T HOS + Old K A
T HOS X old KBTLRC, +... (9L).

Transform these equations (9K) and (9L) to create the new KBTLR
Let's organize C1.

New KBTLRC+ = (R (old T1) x old KBLRC 10 old KATHO8X old KBTLRCI) - new Tp x new KBLRCI / new KAT HOS... (9M)
The learning coefficient shortage rate RTR during transient is RTR-New KBTL
Since it is RC+/old KBTLRCI, the formula (9
Substitute H).

RTR=IR (old Tp x old KBLRC 10 old KATHO8
...(9N) Here, basic pulse width Tp + steady state learning coefficient KBLR
C. Regarding the transient correction amount KATHO3, the following equation (9P) is obtained assuming that the new and old values are approximately equal.

RTR = lR (old Tp x old KBLRC + old KAT HOS X old KBTLRCI) - old Tp x old KBI-RC1 / (old KAT HOS
-(9P) Therefore, this formula (9P) is a strict formula for RTR, and it is best to use this formula to find R and TR. However, in practice, the old K
BL RC, old KBT I-RC+ almost 1.0
Therefore, it is safe to say that RTR of practical soil
The following equation (9Q) is obtained as the calculation equation.

RTR = (R (old T 11 + old KATHO3) - old Tp
)/(Former KAT HOS)...(9Q) The transient correction $RTR was calculated as described above.

Then, the learning value is rewritten based on this RTR (steps 139, 142). FIG. 9 shows the content of this rewriting, in which the learning coefficient KBT L RC+ is rewritten according to the following formula (9-B) (step 153)
.

KBTLRC,=KBTLRC,-.

Xil + (RTR1,)XX KA Tl... (1
0-a) Here, what this formula (10-a) means is (R
T R-1) indicates the shortfall, and this shortfall X K A
This means that it is rewritten by a factor of T (a constant between O and 1). Also, g>exchange rate XKAT is 1°0 (100
% rewriting) will cause overshoot and hunting, so this value (for example, 50%) is introduced to avoid this. The rewriting method itself is well known, and as shown in Fig. 9, the engine speed N at that time is
Select the address corresponding to the air amount QCYL flowing into the engine sill, read the data at that address as old data (KBTLRC+ -+), calculate new data (KBTLRC+) using this old data, and Store data at the address (step 151
~154).

The same applies to fuel that changes with a slow time constant (step 142 in Fig. 8, step 161 in Fig. 10).
~164), the old data (KBTLRC2-1) is calculated using the following formula (
10-b), it is rewritten with new data (KBTL RC2) (step 163).

KBTLRC2=KBTLRC2-1 Xll + (RTR, 1)XX KA Tl... (i
o-b) Also, as in the conventional example, the feedback correction coefficient LAMBD
Considering the change characteristics of A, the average value R of R and RTR is actually
, RTR is adopted.

Next, the operation when configured in this way will be explained with reference to FIG. Initially, the transient correction amount (MF+) for fuel that changes with a fast time constant is dominant, so the deviation from the target air-fuel ratio TFBYA is learned for this transient correction amount, and then the deviation for fuel that changes with a slow time constant is learned. When the transient correction amount (VMF2) becomes dominant, this transient correction amount is learned. That is, since there are multiple fuels with different time constants, it is necessary to calculate a learning coefficient for each fuel.

As a result, if the actual air-fuel ratio AFBYA during a transient period deviates from the target air-fuel ratio TFBYA as shown in the figure, this is incorporated into the average value RTR, and the next interrupt injection is learned so that no deviation from the target air-fuel ratio occurs. (steps 139, 142, steps 151 to 15 in FIG. 9)
4. Steps 161 to 164 in FIG. 10). for example,
If the air-fuel ratio is leaner than the target air-fuel ratio, the shortage rate R (or RT
R) > 1, the injection pulse width Ti increases and the amount of fuel is increased, and conversely, when the air-fuel ratio becomes richer than the target air-fuel ratio, the fuel is reduced (note that the target air-fuel ratio and the actual air-fuel ratio are Since the reciprocals of these (target fuel-air ratio, actual fuel-air ratio) are adopted, the positions of TFBYA and AFBYA are interchanged with one numerator in the denominator.)

That is, injection pulse width Ti T 1=(Tpx K B L RC 10ΣKATHO8kXKBTLRCk)X L A
M B D A + T s
-・-(9-8), learning coefficient KB
TLRCI and KBTLRC2 have different fuel properties, so when the actual air-fuel ratio deviates from the target air-fuel ratio, they change slightly to bring the actual air-fuel ratio closer to the target air-fuel ratio.

As a result, even if there are differences in fuel properties, atmospheric pressure, intake temperature, etc. that have caused errors since the time of revision, a good air-fuel ratio can be obtained regardless of these differences to improve drivability and exhaust emissions. Emissions can be improved.

On the other hand, even in the conventional example, when setting, the actual air-fuel ratio is matched to match the target air-fuel ratio, so unless there is a change over time or a difference in fuel properties, stable air-fuel ratio characteristics cannot be obtained. can. However, since it does not have a learning function, it cannot deal with error factors in the air-fuel ratio that occur after the revision. For example, even if the injection pulse width itself is the same, the actual amount of fuel changes depending on the environment in which it is used, so the difference in fuel used for matching will result in a difference in the air-fuel ratio. . Therefore, it can be said that if there were differences in atmospheric pressure or intake temperature caused by differences in fuel properties or differences between highlands and lowlands, the air-fuel ratio would inevitably fluctuate.

Next, to outline the entire system, the routine in FIG. 3 is the part that finally calculates the injection pulse width Ti using the following equation (4-^).

Here, in the SPI device, the amount of air flowing into the shilling QC
There are differences in that YL and the amount of air passing through the injection valve QAINJ do not necessarily match, and there is a supply delay for the fuel injected from the injection valve to reach the cylinder. Two points are taken into consideration. However, these are calculated independently for each (QAINJ is calculated for the air amount, and the transient correction amount KAT HOS is calculated for the fuel delay). This is to simplify the concept and clarify whether the control error is due to the air amount metering error or the fuel delay. This greatly improves the accuracy during setting. Furthermore, changes over time after the time of setting and differences in fuel properties can also cause a decrease in accuracy, so a learning function is provided for these factors.

Expressing this mathematically, the effective pulse width Te is calculated by the following formula (4
) (step 70). Note that, assuming that the invalid pulse width is Ts, the sum with Te is T i (" T e + Ts
) (step 69.70).

Te=(TpX K B L RC ten ΣKATHO8k
XKBTLRCk) Correction coefficient KBLRC: Steady-state learning coefficient KBTLRC+: Transient learning coefficient for fuel that changes with a fast time constant KBTLRC2: Transient learning coefficient for fuel that changes with a slow time constant. Here, Tp is used as the basic pulse width, but its content is calculated by the following equation (5), unlike the L-Jetronitter method.

Tll”QA I N J c XTFBYAXK・(
5) However, QAINJG: Injection valve air amount (mg) T
FBYA: Target air-fuel ratio: A constant (+ns/mg) based on the injection valve characteristics.

First, the air in the injection valve section is fiQA+NJ, but since it is difficult to directly determine this in this embodiment which does not have an air amount sensor, it is determined based on QcYL. In other words, QAINJ is QcyL and its variation dQ c
Considering that it can be approximately determined from Y L / dt using the following formula (3)% formula%, the following formula group (6^
) to (6F).

QA I N J G = QA I N J cXKT
A - (6^) QA + NJc = QcytXVcyt + DCM ... (6B) Q c Y L: Q +1 X K 2 + QCYL
-I
CM””(QCYL QCYL-f)XKMAN I
0XTref-・(6E)KTA=KTAOXKTA
Q cy L...(6F) However, QAINJG: Injection valve air amount/Schilling (m FI) QA+N, +c: Injection valve air amount/Schilling (cc) Air amount to QCYL Niji ring/Schilling volume (%) V CY L Nijiring volume (cc) DCM: Manifold air change amount (cc) KTA: Intake temperature correction coefficient (
rI1g/cc) QH: Equilibrium air volume/Schilling volume (%
) K2: QCYL change rate/calculation Qno: Linearization air amount/Schilling volume (%) KFLAT Nearat air-fuel ratio coefficient (%) KMAN IO
: Manifold coefficient Tref: Period of Ref signal (,175) KTAO: Basic intake temperature correction coefficient (og/cc) KTAQCYL: Load correction factor (%) for intake temperature correction.

These second groups (6^) to (6F) have become complicated due to various corrections and standardizations (converted to per cylinder, shilling volume per tooth, etc.), but basically they are teeth,
QA+N and +c are determined by the sum of a steady term (QCYLXVcyc) and a transient term (DCM).

However, since this value QA+NJc is in volume units, it can change due to changes in intake air temperature, so it is converted to mass units using KTA as a correction factor (steps 61 to 63).
.

Also, set 2 to QcYLli' as a smoothing constant, Q) +
Weighting using 1QCYL-1 as a variable and K2 as a weight is determined by the average value (steps 55 to 57 in Fig. 3 (B)
).

Next, variables such as Quo and KFLAT are determined from the flow path area of the intake system and the engine speed. This is because the air amount sensor is eliminated from the intake system to reduce costs and facilitate maintenance.

Therefore, the flow path area is determined by the following equations (6G) and (611) (steps 41 to 52).

AADNV=AAXTref/V CYI---(a
c) AA=ATVO+A I 10AAC...(611
) However, AADNV: flow path area/(rotation speed x cylinder volume) (cm2/rpm' cc) AA: total flow path surface f
jt (0m2) ATVO: Throttle valve flow path area (c'n2) AI: 5V26
The flow path area (0 m2) of AAC:5V27 is (c"112).

In other words, this system uses the valve opening T as a load signal.
Although the flow path area ATVO based on VO is adopted, if there is a passage 23 that bypasses the throttle valve 21,
These areas AI and AAC must also be taken into account. Therefore, the total flow area AA is determined by the flow area ATVO based on the throttle valve opening and the flow area of the bypass passage (AI or AA).
C) (steps 41 to 49).

Note that these 5V26 and 27 are two-position valves. This is to reduce costs by performing four-stage control instead of using a duty control solenoid valve.

In addition, in actual control, the value AA/N obtained by dividing the total flow path area AA by the rotation speed N (AA X T r
This corresponds to the ef part. ) is adopted.

If AA is used as it is, it will have a region that changes suddenly as N changes, so if this is used as a parameter,
Accuracy decreases in this sudden change region. however,
For example, increasing the map lattice and α in order to improve accuracy will also lengthen the computation time. Therefore,
By adopting AA/N, these control problems have been solved.

Therefore, this A A D N V (= A A
The linearizing air amount Quo is determined using (X T ref/VCYL) (step 53). In addition, the flat air-fuel ratio coefficient K F L A T is obtained from the map using QHolN as a parameter, and the throttle valve flow path area ATVO is obtained from the TV
It is determined from the table using O as a parameter (step 54.42).

In addition, the basic intake temperature correction coefficient KTAO and the intake temperature load correction coefficient KTAQ CY L are also calculated based on the intake temperature TA.
IQCYL is searched as a parameter, and KTA is determined by the product of these (steps 81 to 8 in Figure 7).
3).

Since the air amount QAINJ of the injection valve section has been determined by the above calculation, the next step is to determine the correction amount for the fuel delay that occurs during the transient period. This correction amount is KATHO8i (i=1.2) used in step 66, and is specifically calculated in the routine shown in FIG.

In this example, transient correction for multiple fuels with different time constants is performed based on the deviation between the equilibrium adhesion amount MFH of intake system fuel and the calculated value of the adhesion amount that changes with a first-order lag with respect to changes in this equilibrium adhesion amount. Find the quantity.

Expressing this numerically, it is given by the following group of equations (7^-a) to (7E).

KATHO8i=VMF1 XGHF ・=(7^
-a) VMFi=(MFHi-MFi-+)X K
MFi-(7B-a)MFI
=MFi −1+VMFi −(7C-a)KMFi
= CK MF A T i 10K MF ”11 M
F i )X K M F N i ... (7D-a) G HF = G HF Q c Y L X G
HF F B Y A... (7E) However, KATHO8i: Transient correction it (/'s) VM
Fi: Adhesion speed (μS/injection) MFHi: Equilibrium adhesion amount (μS) MFi: Adhesion amount at the time of current calculation (μS) KMFi: Quantity ratio (%) K M F A T i : Basic amount ratio (%) K M
F V M Fi : Adhesion speed correction factor of quantity ratio (
%) KMFNi: Rotation correction rate of quantity ratio (%) G HF:
Correction factor (%) GHFQ CY L: Deceleration correction factor (%) GHFFBY
A: Air-fuel ratio correction factor (%).

That is, the adhesion speed V M F i is the equilibrium adhesion amount MFH
1 and the calculated value of the adhesion amount that changes with a first-order lag with respect to this equilibrium adhesion amount (MFHi-MFi-1). It is obtained by multiplying the coefficient K M F i representing whether the ratio approaches each other (steps 3-03, 10
4).

Here, the equilibrium adhesion amount MFH (MFHi) is calculated based on the amount of air passing through the injection valve, the engine speed N, and the cooling water temperature Tu+, by a combination of a three-dimensional map search and linear approximation interpolation calculation. Calculated.

In other words, six different reference temperatures TLI are set in advance within the range of temperature changes that can actually be taken by the cooling water temperature Tu+.
For each IO-Tu+5 (TIIIO>...>Tus), the reference temperature Tu+n(
Twelve pieces of equilibrium adhesion amount data for providing the equilibrium adhesion iMFHiTwn (n=0 to 5) are prepared by actual measurement. Then, the reference temperature TllIn, T above and below the actual water temperature TW
Equilibrium adhesion amount MFHiTu+n at uu++1, MF
Using HiTuu++l, T 1111 T 1lIn
M F Hi is finally determined by interpolation calculation using +T uo+10+ (step 101).

In addition, high accuracy can be obtained using a method based on a three-dimensional map and interpolation calculation 1, but if you want to increase the calculation speed even though the accuracy is moderate, there is also a method that uses two tables, which can be calculated using the following formula. (7F).

MFHiTwn=MFHiQnXMFHiNn...(
7F) However, the coefficient based on MFHiQn:QAI N J is a coefficient based on MFHiNn:N, and MFHiQnl:l:QAI N J is
HiNn is determined by table search using N as a parameter.

Note that when TIII>Tll1o and TIII<
Since interpolation calculations cannot be performed during Turn,
Let MFHi−MFHiTu+o. Furthermore, during fuel cut, MFHi=FCMFHi (constant value).

On the other hand, the adhesion amount M Fi calculated this time is the adhesion speed calculated this time M Fi - 1, which is the adhesion amount calculated last time.
(steps 106 and 107).

Next, the quantity ratio K M F i may be a constant value, but in this example, the basic value K M F A T i is determined by map search using AADNV and TW as parameters, and further correction is performed based on VM Fi and N. . That is, the correction coefficients for the basic value KMF A Ti are two coefficients KMF VMF i , KMF N
i, and these are introduced so that the air-fuel ratio at the initial stage of the transient has a flat characteristic. That is, there is a slight lack of correction during slow acceleration, and errors occur due to differences in rotational speed, and when conducting experiments, slight deviations occur, and these are attempted to be resolved individually.

In addition, the adhesion speed correction factor KMFVMFi of the amount ratio is VM
The rotation correction factor KMFNi of the quantity ratio is obtained by searching a table using Fi-1 as a parameter and N as a parameter.

Next, the correction factor GHF is a value that takes into account differences in fuel properties and the like. This is due to the fact that highly volatile fuel rapidly vaporizes and is inhaled into the engine due to the development of suction negative pressure during deceleration. becomes less. Therefore, when decelerating, it is necessary to underestimate the amount of adhesion, and conversely, the correction coefficient (G
HF QCYL) may be assigned a small value. That is, during acceleration (when VMFi is positive)
is not corrected (GHFQ CY L =1..0
), and during deceleration (when M F i is negative), a value of 1 or less is used. Furthermore, the target air-fuel ratio TFBYA
The deceleration correction factor GHF
Q CY L l;tQ cy 1-, and the air-fuel ratio correction factor GHFFBYA is obtained by table search using TFBYA as a parameter.

Using the thus obtained V M F i and GHF, the transient correction amount KATHO8i is finally obtained (steps 109 and 110).

Next, the air-fuel ratio correction coefficient LAMBDA and the target air-fuel ratio TFBYA used in steps 68 and 64 in FIG. 3(C) are calculated in the conventional example, and their routines are shown in FIGS. 5 and 6, respectively. It is.

That is, LAMBDA is a correction coefficient in air-fuel ratio feedback control. Figure 5 is an example of PID control, where the actual air-fuel ratio (specifically, the oxygen sensor output Ip) and the target value of the air-fuel ratio (specifically, the sensor output equivalent of the target value tiT
+p) Proportional amount (P) obtained based on the deviation ER from
The following equation (8A) that adds the integral (■) and differential (D)
LAMBDA is obtained in (8D) (step 11
1-118).

LAMBDA=P1110D...(88)
P=KP-ER...(8B) I=I-+ 1+-ER-(8C)D=KD
・(ER-ER-+) ...(8D) However,
KP: proportional gain Kl: integral gain KD: differential gain.

The deviation ER is given by the following equation (8E) (step 114).

ER=Ip T+ p-(n+I) ・=
(8E) Here, the second term of the interval (8E) indicates the sensor output Ip when the Ref signal was input (n+1) times ago (where n is the number of cylinders). This is done in consideration of the fact that there is a time delay until the result of the air-fuel ratio set in the intake system is detected by the sensor 34 provided in the exhaust system.

In addition, the target air-fuel ratio TFBYA is T”r Q c y +
-+N is calculated as a parameter (steps 91 to 95 in FIG. 6). Note that step 95 in the same figure is TFBY
A is provided with an upper limit value and a lower limit value, and is given the function of 7-else-7.

Next, there are a plurality of learning coefficients KBLRC and KBTLRCi used in steps 65 and 67 in FIG. 3(C). In this example, the air amount (QAINJ) and fuel delay correction amount (KATHO3) Along with the fact that they are determined separately, learning correction is also performed separately and independently. In other words, the learning coefficient KBLR during steady state
C is calculated in the calculation routine of the air-fuel ratio correction coefficient LAMBDA, and the transient learning coefficient KBTLRCi is calculated in the calculation routine of the transient correction amount KATHO8 (steps 1.19 and 120 in Fig. 5). , Figures 8 to 10).

Learning correction basically adds a control amount based on the deviation from the target value in advance to prevent deviation from occurring during the next calculation.KBL RCli LA
M B D A 1m, KBTLRCil:l:,:
L A M B D A and further the actual air fuel ratio AFBYA
is calculated based on the target air-fuel ratio TFBYA, etc. (steps 119 and 120, FIGS. 8 to 10).

Of these, the transient learning coefficient KBTLRCzKBTLRC
2 is the essential part of this invention, and has been described above.

In addition, by comparing the adhesion speed V M-F with the reference value L l , it is determined that the steady state (VMF<Ll) is the transient state (VMF
≧L+), and learning for K B L and RC is performed only during steady state (
step 119).

(Effects of the Invention) As explained above, in the present invention, it is determined which of multiple fuels with different time constants is the transient correction amount, and the transient correction amount for the determined fuel is learned. Since the value is calculated based on the target air-fuel ratio and the actual air-fuel ratio, if the actual air-fuel ratio deviates from the target air-fuel ratio during a transient period, a deviation will occur during the next transient period, and learning is performed to avoid this. As a result, even if there are differences in fuel properties, atmospheric pressure, intake temperature, etc. that are the cause of errors after setting, regardless of these differences, operation will be performed with a good air-fuel ratio. performance and exhaust emissions.

[Brief explanation of drawings]

FIG. 1 is a conceptual configuration diagram of the present invention, FIG. 2 is a schematic diagram showing the mechanical configuration of an embodiment of the present invention applied to an SP device, and FIGS. 3 to 10 are the same as those in FIG. FIG. 11 is a flowchart illustrating the contents of the 4J operation executed in the control unit, and a waveform diagram illustrating the characteristics of the learning coefficients K BTL RC1 and KBTLRC2 for multiple fuels in this embodiment. DESCRIPTION OF SYMBOLS 1... Basic injection amount calculation means, 2, 3... A plurality of transient correction amount calculation means, 4... Injection amount correction calculation means, 5...
・Target air-fuel ratio calculation means, 6...Actual air-fuel ratio detection means, 7
...Discrimination means, 8...Learned value calculation means, 21...
Intake throttle valve, 22... Intake passage, 23... Bypass passage, 24... Fuel injection valve, 25... Throttle valve opening sensor, 34... Oxygen sensor (air-fuel ratio sensor), 35・
··control unit. (1 other person) Figure 3 (8) Figure 5 Figure 6 Figure 7 Figure 9 Figure 10

Claims (1)

[Claims] Means for calculating the basic fuel injection amount according to operating conditions, equilibrium adhesion amount and this equilibrium adhesion amount for intake system fuel that changes with a relatively fast time constant and fuel that changes with a relatively slow time constant. a plurality of means each calculating a transient correction amount based on a deviation from a calculated value of the adhesion amount that changes with a first-order lag; and a means for correcting and calculating the basic injection amount using the transient correction amount for the plurality of fuels. An air-fuel ratio control device for an internal combustion engine, comprising means for calculating a target air-fuel ratio, means for detecting an actual air-fuel ratio, means for determining whether the transient correction amount is for any of the fuels, and determining. 1. An air-fuel ratio control device for an internal combustion engine, comprising means for calculating a learned value of a transient correction amount for the fuel that has been adjusted based on the target air-fuel ratio and the actual air-fuel ratio.