JPH01244139A - Fuel feed control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve idle stability, by a method wherein an output from an intake air amount detecting means is smoothed to compute a fundamental fuel feed amount, and during idle running or during the starting, by means of a difference between an output from the intake air amount detecting means and a smooth air amount, a target correction factor is decided. CONSTITUTION:An output from an intake air amount detecting means (a), e.g. a heat ray type airflow meter, is smoothed in a primary delay by a smooth value computing means (c) ad a smooth air amount is calculated, and based thereon, a fundamental feed amount of fuel is computed by a feed amount computing means (e). In which case, when the idle time or the starting time of an engine is decided by a running state detecting means (b), a correction factor computing means (d) decides a target correction factor by means of a difference between an output from the intake air amount detecting means and a smooth intake air amount, and according to the target correction factor, a fundamental feed amount is corrected by the computing means (e) to drive a fuel feed means (f). In order to take a countermeasure to cope with a decrease and an increase in rotation during idle running and starting, an injection amount is properly corrected, and idle stability can be improved and starting engine stall can be prevented from occurring.

Description

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

(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, high output, and low fuel consumption to be achieved at a high level. It is in. Further, such a requirement is the same when the vehicle is idling, and it is desired to improve the idling 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,
(For example, see Japanese Patent Publication No. 47-41288).

However, in the conventional device, the capacity of the intake pipe between the installation position of the air flow meter and the installation position of the injection valve (injector), that is, the intake air.

There was a problem in that the injection amount was not calculated appropriately considering the volume, and the 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) By the way, since the device according to the prior application is configured to perform fuel injection using the smooth injection amount AvTp, AvTp is used to stabilize the air-fuel ratio. However, under conditions where sudden drops in rotation occur, such as when idling, the air-fuel ratio is too stable and the rotation cannot be recovered quickly, so there is room for improvement in terms of idle stability. .

In other words, when AvTp is used, it is difficult to immediately richen the air-fuel ratio and increase the rotation speed when the engine speed drops, as is the case with conventional devices (so-called L-Jetro type). Engine stall is more likely to occur.

(Objective of the Invention) Therefore, the present invention aims to improve idling stability and prevent engine stall when starting by correcting the injection amount according to the difference between the output of the air flow meter and the smoothed air amount. .

(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 has an intake air amount detection system that detects the intake air amount of the engine, as shown in FIG. Means a, operating state detecting means for detecting the operating state of the engine, smoothing value calculating means C for calculating a smoothed intake air amount by smoothing the output of the intake air amount detecting means a, and when the engine is in a normal operating state. , calculates a target correction coefficient for correcting the fuel supply amount to reach the target air-fuel ratio based on the operating state at that time, and calculates the output of the intake air amount detection means a and the smoothing value calculation means when the engine is idling or starting. A correction coefficient calculation means d calculates the target correction coefficient based on the difference in the output of C, and a basic supply amount of fuel is calculated based on the smoothed intake air amount calculated by the smoothed value calculation means C. A supply amount calculation means e that corrects the amount according to the target correction coefficient and determines the final supply amount, and a fuel supply means f that supplies fuel to the engine based on the output of the supply amount calculation means e. There is.

(Function) In the present invention, the output of the intake air amount detection means (air flow meter) is smoothed to calculate the smoothed air amount, and the basic supply amount of fuel is calculated based on the intake air amount. Corrected according to the target correction coefficient.

On the other hand, when the engine is idling or starting, the target correction coefficient is determined based on the difference between the output of the intake air amount detection means and the smooth intake air amount.

Therefore, when the engine speed drops during idling, the air-fuel ratio immediately becomes rich and the engine speed recovers, and when the engine speed increases, the air-fuel ratio becomes lean. As a result, idling stability is improved and engine stalling is prevented.

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

2 to 6 are diagrams showing an embodiment of a fuel supply 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. and,
Exhaust gas combusted in the cylinders is introduced into a catalytic converter 6 through an exhaust pipe 5, where harmful components (Co, HC, NOx) in the exhaust gas are purified by a three-way catalyst and discharged.

The intake air flow 1tQa is detected by a hot wire type air flow meter (intake air amount detection means) 7, and is controlled by a throttle valve 8 in the intake pipe 3. The type of air flow meter 7 may be a hot film type, as long as it measures the flow rate of intake air. Therefore, a flap type may be used, but the negative pressure sensor is excluded.

The opening TVO of the throttle valve 8 is detected by a throttle valve opening sensor 9, and the rotation speed N of the engine 1 is detected by a crank angle sensor 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 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 throttle valve opening sensor 9, crank angle sensor 101, water temperature sensor 11, oxygen sensor 12 and idle switch 13
constitutes an operating state detecting means 14, and outputs from the operating state detecting means 14 and the air flow meter 7 are input to a control unit 20.

The control unit) 20 has functions as a smoothing value calculation means, a correction coefficient calculation means, and a supply amount calculation means.
It is composed of a PU 21, a ROM 22, a RAM 23, and an I10 port 24. CPU U21 reads I10 port 2 according to the program written in ROM22.
You can import the external data you need from 4, and also use RA.
While exchanging data with M23, it calculates the smooth intake air amount and processing values necessary for injection control, and outputs the processed data to I10 port 24 as necessary. I
A signal from the sensor group 7.14 is input to the I10 port 24, and an injection signal St is input from the I10 port 24.
is output. The ROM 22 stores calculation programs for the CPU 21, and the RAM 23 stores data used in calculations in the form of a map or the like.

Next, the effect will be explained.

The main program of this embodiment is shown in FIG. 5, and the AvTp calculated in this main program is
is calculated in a subroutine. For convenience of explanation, first
The subroutine for calculating vTp will be explained first.

FIG. 3 shows a subroutine for calculating the smooth injection amount AvTp.

First, the output of the air flow meter 7 is read at P to obtain the intake air IQa. This is for example by table lookup. Next, in P8, the smoothing part basic pulse width T P o is calculated according to the following equation (2).

, N Next, the basic pulse width Tp is calculated by weighted averaging T P o with P. As a result, pulsations based on the output of the air flow meter 7 are smoothed out. In P4, the flat correction basic pulse width TrTp is determined according to the following equation (2).

T r T p = T p X Kflat = ■■
In the equation, Kflat is a flat A/F correction coefficient, which is obtained with interpolation from a map allocated by the rotational speed N and the α-N flow 11Qho.

Note that the α-N flow rate is the air flow rate determined from the throttle valve opening TVO and the rotational speed N, and is already known.

Then, P, sets TrTp to a predetermined maximum limit value T p
Compared to wax, when TrTp>Tpmax, Ph
limit TrTp to T p wax and proceed to P, then T
When rTp≦T p wax, jump P and P
Proceeding to P7, the delay correction pulse width TH3TP as the α-N prefetch correction pulse width is determined. This is α−N
It is determined as the amount of change for each ton of the value TTH3TP, which is looked up from a table with interpolation calculation based on the flow rate Qho. However, if the amount of change is below the correction judgment level,
When TH3TP=0 and the amount of change is negative (-$i speed), the amount of change is multiplied by a predetermined deceleration correction rate. TH3TP is a term that corrects the injection amount with good responsiveness by anticipating changes in the throttle valve 8. Then, P, smooths the injection amount A according to the following formula 〇.
Find vTp (corresponding to smooth intake air volume).

AvTp=TrTpxFLOAD+AvTp−tx (
1-FLOAD)+TH3TP ・・・・・・■ In formula 0, FLOAD is a weighted average coefficient, and FL
OAD=TFLOAD+ given by 2D (deceleration only). Since TFLOAD is a function only of the intake volume, it is determined by a map from the flow path area AA determined by the throttle valve 8 and (displacement amount x rotational speed) NVM. Therefore, the first and second terms of Equation 0 are the weighted average values using FLOAD of the flat corrected basic pulse width TrTp calculated based on the pulsation corrected value of the output of the air flow meter 7, in other words, the first order of TrTp. This corresponds to the part where the delay is calculated (by software). Furthermore, the third term in Equation 0 is a preemptive correction based on the throttle valve opening TvO, and this part is not present in the prior application and is disclosed for the first time in this embodiment.

The effect of adding the third term TH3TP is shown in FIG. In Fig. 4, when acceleration occurs at a certain timing, the basic pulse width 'rp, , Tp changes slightly after the change in the throttle valve opening, and the waveform obtained by correcting Tpo and Tp is expressed as a flat corrected basic pulse width TrTp. Changes as shown in Figure 4.

On the other hand, the α-N flow rate changes stepwise according to the degree of opening of the throttle valve 8, and the delay correction pulse width TH3TP is calculated based on the amount of change in the degree of opening. In addition, smooth injection amount AvT
p is given by the first-order delay of TrTp, and in the case of conventional phase control without TH3TP, the change is shown by the dashed line in the figure, resulting in lack of responsiveness. At this time, the suction negative pressure is shown by a broken line, and is approximately equal to the air flow rate of the injection valve section (injector 4 section), but it does not lag behind (cannot follow) the change in the opening degree of the throttle valve 8. The amount of fuel deposited on the wall of the intake pipe 3 is also affected by the intake volume.

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 0ms advance correction), the response is extremely good and matches the actual air flow rate change. An example of a highland area is also shown.

FIG. 5 is a flowchart showing the main program for calculating the injection amount, and this program is executed once every Ioms, for example.

First, it is determined based on the pH whether the idle switch 13 is on, that is, whether the throttle valve 8 is fully closed. When the idle switch 13 is on, it is determined to be in an idle state, and the difference value A is calculated using the PUSH according to the following equation.

A-TrTp-AvTp ””■ Difference value A is a parameter for determining sudden changes in air flow rate 0 Then, Pl, difference value A is positive (including 0)
If A≧O (positive), the target fuel-air ratio Mfbya is looked up from the first table map at Pl4 based on the magnitude of the difference value A at that time. Also, when A<0, find the absolute value IAI of A with pus,
At Po, the target fuel-air ratio Mfbya is looked up from the second table map based on the magnitude of this absolute value IA1. The reason why the table map is divided into first and second table maps is to correspond to the rise and fall of the rotational speed N, and each map value is set with a tendency as shown in FIG.

On the other hand, when the idle switch 13 is off in step ptt, it is determined at Pl whether or not the elapsed time after the idle switch 13 was turned off is within a predetermined time. If it is within the predetermined time, it is determined that it is time to start from idle, and the PI! Jump to. therefore,
When the vehicle is idling or starting, the steps after ptz are executed.

If it is not within the above predetermined time, it is determined that it is not starting or idling (determined to be normal driving), and the number of revolutions N is determined by PUS.
The target fuel-air ratio Mfbya is looked up from the third table map assigned with and α-N flow rate Qho as parameters.

As described above, Mfbya is looked up using any of the first to third table maps.

Next, in PI9, the target air-fuel ratio Tfbya is determined according to the following formula
(corresponding to the target correction coefficient).

Tfbya=Mfbya+Ktw+Kas+Kh+
+++■ However, KtwH warm-up increase Kas; increase after startup Kh; high water temperature increase 0 In the formula, Ktw, Kas, and Kh are the same correction coefficients as before.

Next, the final injection amount (output pulse width) Ti is calculated according to the following equation (2) by Pz boiling, and the amount of fuel Ti is injected at a predetermined injection timing.

T i= (AvTp+Kathos) XTfby
a×(α+αm)+Ts ・・・・・・In formula 00, K
athos is the wall flow correction pulse width, which has positive and negative values, and is given as a function of the fuel deposition speed Vmf (ms) and the correction factor Ghf (%). α is an air-fuel ratio lambda control correction coefficient based on the output of the oxygen sensor 12, and αm is a mixture ratio learning control correction coefficient. Ts is the invalid pulse width.

In this way, in this embodiment, when idling or starting, the target fuel-air ratio Mfbya is looked up from the first and second tables according to the difference value A, and the final injection amount Ti is appropriately determined based on the MfbyaO value. It is being corrected. Therefore, even if, for example, the rotational speed N suddenly drops during idling, the target fuel-air ratio Mfbya immediately increases, the air-fuel ratio becomes richer, the torque increases, and the rotational speed N quickly decreases. Recover.

Conversely, if the rotational speed N suddenly increases, the target fuel-air ratio Mfb
ya becomes small, the air-fuel ratio becomes lean, the torque decreases, and the rotational speed N becomes stable. On the other hand, at the time of starting, if the rotational speed decreases during clutch engagement at the initial stage of acceleration, the air-fuel ratio becomes rich, effectively preventing the starting engine from stalling.

Note that the target correction coefficient is not limited to Tfbya as in this embodiment, but may take other calculation formats.

(Effects) According to the present invention, since the injection amount is appropriately corrected for rotation drop or increase during idling or starting, it is possible to improve idling stability and prevent engine stalling during starting.

[Brief explanation of the drawing]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 6 are diagrams showing an 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. is a flowchart showing the subroutine for calculating the smooth injection amount, FIG. 4 is a timing chart explaining its operation, FIG. 5 is a flowchart showing the main program for calculating the injection amount, and FIG. 6 is a subroutine for calculating the target fuel-air ratio. It is a figure showing a tendency. 1...Engine, 4...Injector (fuel supply means), -7.
...Air flow meter (intake amount detection means), 14
... Operating state detection means, 20 ... Control unit (smoothing value calculation means, correction coefficient calculation means, supply amount calculation means). Figure 3 Figure 4 Figure 6 True O Correct

Claims (1)

[Scope of Claims] a) intake air amount detection means for detecting the intake air amount of the engine; b) operating state detection means for detecting the operating state of the engine; and c) smoothing by smoothing the output of the intake air amount detection means. a smoothing value calculation means for calculating an intake air amount; d) when the engine is in a normal operating state, calculating a target correction coefficient for correcting the fuel supply amount so as to reach a target air-fuel ratio based on the operating state at that time; correction coefficient calculation means that calculates the target correction coefficient based on the difference between the output of the intake air amount detection means and the output of the smoothed value calculation means when the engine is at idle or when the engine is started; e) correction coefficient calculation means calculated by the smoothed value calculation means; supply amount calculation means for calculating a basic supply amount of fuel based on the smooth intake amount, correcting the basic supply amount according to the target correction coefficient, and determining a final supply amount; f) supply amount calculation means; A fuel supply control device for an internal combustion engine, comprising: a fuel supply means for supplying fuel to the engine based on output; and a fuel supply control device for an internal combustion engine.