JPH01290939A - Fuel supply control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To provide enhanced accuracy of the fuel supply control and responsiveness even though there is response delay in an air flow meter at transient or ripple error by correcting the smoothing supply amount with a prefetch correction amount computed on the basis of the change amount of the air flow amount. CONSTITUTION:In a control unit 30, the fundamental fuel supply amount is calculated on the basis of the suction air amount sensed by an air flow meter 7 and the number of revolutions sensed by a crank angle sensor 10. This fundamental supply amount is smoothened, and the smoothened supply amount is computed. The suction air amount is calculated from the degree of opening of a throttle valve 8 sensed by a throttle opening sensor 9 and the number of revolutions of an engine 1, and the prefetch correction amount is computed on the basis of the change amount of the suction air amount. The smoothing supply amount is corrected with this prefetch correction amount, and the final fuel supply amount is calculated. This allows smoothing the fundamental pulse width of an injector 4 with high accuracy and good response, and the pulse width corresponding to the flow rate in the injector 4 part can be corrected properly with the prefetch correction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel supply control device for an internal combustion engine such as an automobile, and more particularly to a fuel supply control device that calculates a fuel supply amount based on an intake air amount.

(Prior art) In recent years, demands on internal combustion engines such as automobiles have become more sophisticated, and there is a tendency for mutually contradictory issues such as reduction of harmful exhaust gas, descendant output, and low fuel consumption to be achieved at the descendant level. It is in. Further, the requirements like 24.2 are the same when accelerating. It is desired to improve the accuracy of acceleration stability.

In this type of conventional fuel supply control device, the required load per unit revolution of the engine is determined from the output of an air flow meter provided upstream of the throttle valve, and the fuel injection amount is calculated from this. In addition, by correcting the fuel injection amount during transient periods,
I'm dealing with it.

However, with conventional devices, appropriate injection amount calculation (especially wall flow correction) takes into consideration the capacity of the intake pipe between the installation position of the air flow meter and the intake position of the injection valve (injector), that is, the intake volume. There was a problem that injection characteristics during transient times were delayed from the required characteristics of the engine, resulting in poor driving performance.

In order to solve this problem, the present applicant has previously proposed a fuel supply control device (see Japanese Patent Laid-Open No. 162066/1983). In the device related to this prior application, in order to accurately determine the amount of air flowing through the injection valve, the output of the air flow meter is smoothed by a first-order lag, and based on the smoothed air amount, the amount of fuel injection (hereinafter simply referred to as smoothed injection amount) is calculated. ; AvTp) is calculated. Note that AvTp is calculated as a pulse width equivalent to the cylinder air amount, and the calculation method is the same as in the embodiment described later, and will be described in detail later.

(Problem to be Solved by the Invention) Incidentally, in such a device related to the prior order, since the fuel injection is performed using smooth injection 11AvTp, AvTp does not contribute to stabilizing the air-fuel ratio. However, since the smoothing accuracy was not necessarily sufficient, the air-fuel ratio may deviate from the target value (for example, λ=1) during a transient period. In addition, A v T p is sensitive to the influence of response delay and pulsation error of the air flow meter depending on the acceleration state (see Fig. 13 (B)).
A certain delay may occur as shown in C).

In that case, as shown in FIG. 6(D), the air-fuel ratio may become lean at times, leading to deterioration in drivability such as lean misfire or drop in lean torque. In any case, when the air-fuel ratio deviates from λ-1 during a transient period, the conversion rate of the three-way catalyst decreases, and the exhaust emission characteristics deteriorate.

(Purpose of the Invention) Therefore, the present invention calculates a smooth supply amount by smoothing the basic supply amount, and also calculates a preemptive correction amount based on the amount of change in the intake air amount obtained from the throttle valve opening and the engine rotation speed. By calculating the final supply amount by preemptively correcting the smooth supply amount using the preemption correction amount, the accuracy of fuel supply control and Improving responsiveness and eliminating deviations in air-fuel ratio,
The purpose is to improve drivability and exhaust emission characteristics.

(Means for Solving the Problems) In order to achieve the above object, the fuel supply control device for an internal combustion engine according to the present invention includes an intake air amount detection means a for detecting the intake air amount of the engine, and a rotation speed for detecting the engine rotation speed. The detecting means includes an opening detecting means C for detecting the opening of the throttle valve, an air amount calculating means d for calculating the intake air amount of the engine from the opening of the throttle valve and the engine rotational speed, and an air amount calculating means d for calculating the intake air amount of the engine from the opening of the throttle valve and the engine rotation speed. smooth supply amount calculation means e which calculates the basic supply amount of fuel based on the amount and rotational speed and smoothes the basic supply amount to calculate a smooth supply amount; and the intake air amount calculated by the air amount calculation means. a correction amount calculation means f for calculating a preemptive correction amount for preemptively correcting the smooth supply amount based on the amount of change; and a final supply amount of fuel based on the output of the smooth supply amount calculation means and the output of the correction amount calculation means. supply amount calculation means g that calculates
and a fuel supply means for supplying fuel to the engine based on the output of the supply amount calculation means.

(Operation) In the present invention, the smooth supply amount is calculated by smoothing the basic supply amount, and the intake air amount is calculated from the throttle valve opening and the engine rotation speed. Then, a preemptive correction amount is calculated based on the amount of change in the intake air amount, and the smooth supply amount is preemptively corrected using the preemptive correction amount to calculate the final supply amount. Therefore, even if there is a response delay or pulsation error of the air flow meter during a transient period, the accuracy and responsiveness of fuel supply control are improved, and deviations in the air-fuel ratio are eliminated. As a result, drivability and exhaust emission characteristics are improved.

(Example) Hereinafter, the present invention will be explained based on the drawings.

2 to 10 are diagrams showing a first embodiment of an air-fuel ratio control device for an internal combustion engine according to the present invention. First, the configuration will be explained.

FIG. 2 is a diagram showing the overall configuration of this device. In Fig. 2, 1 is an engine, and intake air is supplied to an air cleaner 2.
The fuel passes through the intake pipe 3 and is injected from the injector (fuel supply means) 4 based on the injection signal Si. Then, the exhaust gas combusted in the cylinder is introduced into the catalytic converter 6 through the exhaust pipe 5, where the harmful components (Co, HCSNo.chi.) in the exhaust gas are purified by a three-way catalyst, and the exhaust gas is discharged.

The intake air flow iQa is detected by a hot wire type air flow meter (intake air amount detection means) 7 and controlled by a throttle valve 8 in the intake pipe 3. In addition, air flow meter 7
The type may be a hot film, and in short, any type that measures the flow rate of intake air may be used. Therefore, a flap type may be used, but the negative pressure sensor is excluded.

The opening TVO of the throttle valve 8 is determined by the throttle valve opening sensor (opening detection means).
9, and the engine 10 rotation speed N is detected by a crank angle sensor (rotation speed detection means) 10. Further, the temperature Tw of the cooling water flowing through the water jacket is detected by a water temperature sensor 11, and the oxygen concentration in the exhaust gas is detected by an oxygen sensor (air-fuel ratio detection means) 12. The oxygen sensor 12 used has a characteristic that its output Vs changes suddenly at the stoichiometric air-fuel ratio. Further, the idle state of the engine 1 is detected by an idle switch 13.

The air flow meter 7, throttle valve opening sensor 9, crank angle sensor lO1, and water temperature sensor 11 constitute the operating state detecting means 14, and the outputs from the operating state detecting means 14, oxygen sensor 12, and idle switch 13 are controlled. input to unit 20.

The control unit) 20 has functions as an air 7 calculation means, a smooth supply amount calculation means, a correction amount calculation means, and a supply amount calculation means, and includes a CPU 21, a ROM 22, and a RAM 22.
23 and I10 port 24. CPU
21 according to the program written in ROM22,
While importing necessary external data from the I10 boat 24 and exchanging data with the RAM 23, it calculates and processes the processing values necessary for smooth intake air amount and air-fuel ratio control, and performs processing as necessary. The processed data is output to the I10 port 24. I10 boat 24 sensor group 7.
The signals from 9.10.11.12.13 are input, and the I10 boat 24 outputs the injection signal Si.

The ROM 22 stores calculation programs for the CPU 21, and the RAM 23 stores data in the form of data maps used in calculations.

Next, the effect will be explained.

The main program of this embodiment is shown in FIG. 5, and the T I(
S T P is calculated in a subroutine.

For convenience of explanation, the subroutine for determining TH3TP will be described first.

FIG. 3 is a subroutine for calculating the prefetch correction pulse width T) ISTP.

First, at P, based on the α-N flow rate Qho, a prefetched correction pulse width table value TT is obtained from the table map shown in FIG.
Look up H3TP, and calculate the difference (amount of change) A for each predetermined time (for example, 10 ms) according to the following equation (2) in P2. Note that the α-N flow rate is the air flow rate determined from the throttle valve opening TVO and the engine rotational speed N, and is already known.

A=TTH3TP-Old TTH3TP...■Next, use Pl to set the absolute value of the amount of change A to a predetermined correction judgment level L
It is compared with ADTP#, and when l A l >LADTP#, it is determined that a predetermined transition is occurring, and the sign or negative of the amount of change is determined in P4. When A≧0, it is determined that the process is accelerating, and at P, the change iA is preemptively corrected pulse width TH3TP (as TH3TP=A), and the process proceeds to P8, and when Ago, the amount of change is negative (that is, during deceleration). It is determined that T HS T P is calculated according to the following equation (2).

T H S T P = A x A D T P G
# -・----■ However, ADTPG#: Deceleration correction rate On the other hand, P: l T: I A I ≦LADTP# (7
), it is determined that the engine is in a slow acceleration or steady state and is not in a transient state, and as a countermeasure against fluctuations, THSTP is set to 0 at P7 and the process proceeds to P. P, then the TTH that I looked up this time.
3TP is stored in a predetermined memory and this routine ends.

Figure 5 shows the pulse width equivalent to the flow rate of the injection valve (smooth injection blood) Av
This is a flowchart showing a program for calculating Tp, and this program is executed once every 10 ms, for example. First, Pli calculates the basic pulse width Tpo before smoothing according to the following formula (■), and Tpo is calculated according to the following formula (Fran) A
/F correction and calculate the basic pulse width Tp.

N However, K; Constant Tp = Tpo

(Tpo in the conventional example) from the map to which ρ1 is added, with interpolation calculation. In other words, the H/W (hot wire air flow meter) output pulsation error is caused by the cylinder.
＼ is highly dependent on the volumetric flow rate and is easily affected by atmospheric pressure changes, intake temperature changes, etc. Therefore, in this example, α-N flow 1Q
Tp with Kflat assigned by ho and rotation speed N
By correcting o, the pulsation error is reduced as shown by the solid line in FIG. 6(B). Next, WOT (Wid
In order to minimize the pulse width fluctuation at full speed), the TPO pulsation is smoothed by 1/2" swapping weighted average to obtain the corrected basic pulse width TrTP of the flora l-A/F. Here, ND is the pulsation smoothing index, and as shown in Fig. 6 (C), it can be used for WOT (ND = 3'), for steady (or idle) (ND = 1:l, and for transient (ND = 0) depending on the operating condition. ). Therefore, during transient periods, weighted averaging is not performed and TrTp is used as is to ensure responsiveness, and during WOT, appropriate weighted averaging is performed to The width pulsation is smoothed.Next, at P+3, α-N flow Q is calculated from the throttle valve opening TVO and the engine speed N.
ho (see FIG. 6(D)), and at P+4, the prefetch correction pulse width T H is determined by the 2 subroutine shown in FIG. 3.
STP is calculated (see the hatched part in FIG. 6 (E)), and this TH3TP is a term that anticipates changes in the throttle valve 8 and corrects the injection amount with good response.Next, I) 1. According to the following formula (■), the pulse width A, V corresponds to the air amount at the injection valve part.
Calculate T p.

AvTp=TrTpXF1oad+AvTp−B@sX
(1-Fload) +TH3TP-- ■However, A
v T p −+oas: In the previous AvTp■2, F 1oad is a weighted average coefficient, and F ]oa
Given by d=Tfload+K2D (deceleration only). Since Tfload is a function only of the intake volume, the flow area AA determined by the throttle valve 8
(Rotational speed x displacement) NMV is calculated from the map shown in Fig. 7. Therefore, the first and second terms of equation 0 are the francs calculated based on the pulsation-corrected value of the output of the air flow meter 7. Regarding the A/F correction basic pulse width TrTp, it corresponds to the part where the weighted average value using F 1oad, in other words, the first-order delay of TrTp is calculated (by software). Furthermore, the third term in Equation 0 is a preemptive correction based on the throttle valve opening T■0, and this part is not found in the prior application and is disclosed for the first time in this embodiment.

Next, AvTp is limited to the AvTp maximum limit value Tpmax at P(b, and the current routine ends.

T pmax is the table value T tpmax obtained with interpolation calculation from the map assigned by the rotation speed N. After multiplying the air density learning coefficient Adenst, the allowance is YUTOR
■Add # to find. Also, Adenst is T at WOT.
Let it be the ratio of P and table T pmax value. In this case T
pmax is expressed by the following formula (■).

Tpmax=Tp+YUTORI# at WOT...
・■ The effect of such 1゛p smoothing and addition of THSTP is shown in FIG. In Fig. 6, when acceleration occurs at a certain timing, the basic pulse widths Tpo and Tp change slightly after the change in the throttle valve opening, and the waveform obtained by correcting Tpo and Tp is a flat A/F corrected basic pulse width TrT.
p changes as shown in the same figure (C). On the other hand, α−N
? fLitQho changes in a stepwise manner as shown in FIG.
P is calculated. In addition, the pulse width equivalent to the injection valve part flow rate (smooth injection ff1) A V Tp is given by the first-order lag of TrTp, and in the case of conventional phase control without 'r HS T P, the change is shown by the dashed-dotted line in the figure. Lacks responsiveness. At this time, the suction negative pressure is shown by a broken line and is approximately equal to the airflow of the injection valve section (injector 4 section), but this cannot follow the change in the opening degree of the throttle valve 8 without delay. In addition, the intake volume also affects the amount of fuel deposited on the wall surface of the intake pipe 3.

On the other hand, in AvTp of this embodiment, as shown by the solid line in the figure, the correction term TH3TP is α-N prefetch correction (1
Since it is added as a 0'ms advance correction), it has extremely good responsiveness and is able to match actual air flow rate changes. An example of a highland area is also shown.

Incidentally, in this embodiment, the preemption correction is made to be a preemption correction amount whose phase is 10m5 ahead of the intake negative pressure (intake pipe internal pressure), but it is of course not limited to this, and it may be determined as appropriate depending on the distance between the intake valve and the injection valve. A value is set. For example, in the case of an intake valve and an injection valve as shown in Fig. 8 (A), if the distance between them is i, - In an EGi engine used for boat fishing, the spray arrival time (injector injection delay) is as shown in Fig. 8. It is shown as (B). Therefore, if the spray arrival time is taken into consideration and the preemptive correction is performed using a signal with a waveform that is 5 to 15 m5 ahead of the suction force negative pressure, it is possible to eliminate fluctuations in the air-fuel ratio due to the delay in the arrival of the spray.

FIG. 9 is a flowchart showing a program for calculating the final injection amount Ti.
Executed once every s. In PZI, the final injection amount Ti is calculated according to the following equation (2), and this routine ends.

T i= (AvTp+Kathos)XTfbya
Xα+Ts ・・・・・・■ However,
K a thos: Wall flow correction pulse width (transient correction amount) Tfbya: Target fuel-air ratio α: Air-air-fuel ratio feed bank corrector S: Invalid pulse width (voltage correction amount) Here, Kat and hos are the amount of fuel to the intake system This is a delay correction amount corresponding to the delay in fuel flowing into the cylinder due to the influence of adhesion, floating fuel, etc., and has a positive or negative value, and the fuel adhesion speed Vm
It is given by a function of f (ms) and correction factor Ghf (%). α is the air-fuel ratio λ based on the output of the oxygen sensor 12
These are control correction coefficients, and Ts is each correction coefficient for correcting the basic fuel injection amount, but since it has little relation to the present invention, detailed explanation will be omitted. Then, the final injection amount Ti is set to I10 boat 2.
T1 is stored as a voltage pulse width having a predetermined duty value in the output register of T1 at a predetermined crank angle.
outputs an injection signal Si corresponding to the injector 4 to the injector 4.

As described above, in this embodiment, smoothing of the basic pulse width is performed with high precision and good responsiveness, and the α-N flow rate Qh
The injector flow rate equivalent pulse width AvTp is appropriately corrected by the advance correction T HS T P based on o. Therefore, even during acceleration as shown in Fig. 10 (A), the suction negative pressure (-injection valve flow rate) remains as shown by the solid line in Fig. 10 (B).
A look-ahead correction is performed that goes 10m5 ahead of the current position, eliminating the negative effects of the injector delay and spray delay. the result,
As shown in the same figure (C), the flatness of the air-fuel ratio increases,
Drivability and exhaust emission characteristics can be significantly improved.

FIG. 11.12 is a diagram showing a second embodiment of the present invention,
The hardware configuration of this embodiment is the same as that of the first embodiment, so its explanation will be omitted. This example is TplIla
This is an example of finding A, v T p after x restriction.

FIG. 11 is a flowchart showing a program for calculating AvTp. Steps that perform the same processing as the program in FIG. 5 of the first embodiment are given the same numbers and explanations are omitted, and different steps are The contents of the steps are explained by marking the step numbers with ('').

In the program shown in FIG. 11, first, in P31, the output of the air flow meter 7 is read to determine the intake air interval Qa, and in P3□, the pre-smoothing basic pulse width Tpo is calculated. Next, after passing through P and □, T r Tp is compared with a predetermined maximum limit value Tpmax at P'J3, and TrTp>Tpmax
When x, P! 4, limit TrTp to Tpmax and proceed to Pl4, and if TrTp≦T pmax, then P
34 and proceed to Pl4. After passing through ePI4, Pl
, AvTp is calculated according to the zeroth equation.

In formula 0, Flood is a weighted average coefficient, and the first
It is obtained from the table map shown in Figure 2.

Therefore, in this embodiment, the same effects as in the first embodiment can be obtained.

(Effects) According to the present invention, the smooth supply amount is calculated by smoothing the basic supply amount, and the preemptive correction amount is calculated based on the amount of change in the air flow rate obtained from the throttle valve opening and the engine speed. The final supply amount is calculated by preemptively correcting the smooth supply amount using the preemption correction amount, so even if there is a response delay or pulsation error of the air flow meter during transient periods, the accuracy and responsiveness of the supplied fuel can be improved. It is possible to improve driveability and exhaust emission characteristics by eliminating deviations in air-fuel ratio.

[Brief explanation of the drawing]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 10 are diagrams showing a first embodiment of a fuel supply control device for an internal combustion engine according to the present invention, FIG. 2 is an overall configuration diagram thereof, and FIG. The figure is a flowchart showing the subroutine for calculating the preemption correction pulse width TH3TP, Figure 4 is a table map showing the preemption correction pulse width table value TTH3TP, and Figure 5 is the main flowchart for calculating the injection valve flow rate equivalent pulse width AvTp Flowchart showing the program, FIG. 6 is a timing chart to explain its action, FIG. 7 is a table map showing its weighted average coefficient F1oad, FIG. 8 is a diagram to explain its spray arrival time, FIG. 9 is a flowchart showing a program for calculating the final injection amount Ti, FIG. 10 is a timing chart for explaining its effect, and FIGS. 1, FIG. 11 is a flowchart showing a program for calculating the pulse width AvTp corresponding to the flow rate of the injection valve, FIG. 12 is a flowchart showing the weighted average coefficient F1oad, and FIG. 1 is a timing chart for explaining problems of a conventional fuel supply control device for an internal combustion engine. 1...Engine, 4...Injector (fuel supply means), 7...
...Air flow meter (intake air amount detection means), 9...
... Throttle valve opening sensor (opening detection means), 10...
...Crank angle sensor (rotation speed detection means), 20...
... Control unit (air amount calculation means, smooth supply amount calculation means, correction amount calculation means, supply amount calculation means).

Claims (1)

[Claims] a) intake air amount detection means for detecting the intake air amount of the engine; b) rotation speed detection means for detecting the engine rotation speed; and c) opening degree detection means for detecting the opening degree of the throttle valve. d) air amount calculation means for calculating the intake air amount of the engine from the opening degree of the throttle valve and the engine speed; e) calculating the basic supply amount of fuel based on the engine intake air amount and the engine speed. and smoothing supply amount calculation means for smoothing the basic supply amount to calculate a smooth supply amount; f) Preemptively correcting the smooth supply amount based on the amount of change in the intake air amount calculated by the air amount calculation means. g) supply amount calculation means for calculating the final supply amount of fuel based on the output of the smooth supply amount calculation means and the output of the correction amount calculation means; h) supply amount calculation means A fuel supply control device for an internal combustion engine, comprising: fuel supply means for supplying fuel to the engine based on the output of the quantity calculation means.