JPH01305144A - Fuel injection controller of internal combustion engine - Google Patents

Abstract

PURPOSE:To enhance flatness of air fuel ratio per cylinder so as to improve emission characteristics by switching the correction of the next time synchronous injection quantity depending on whether the present asynchronous injection timing is sooner or later than the synchronous injection corresponding to the next time intake stroke. CONSTITUTION:Asynchronous injection is judged by a means (b) on the basis of the running condition of an engine detected by a means (a), namely an amount of engine load variation, and also calculation is carried out by a means (c) so that the next time synchronous injection quantity may be corrected depending upon a synchronously transferring correction quantity. Also calculation is carried out by a means (d) so that an asynchronous injection quantity may be corrected according to an injection timing correction factor during the asynchronous injection process. Further, the injection timing correction factor is set up by a means (e) according to the timing of the asynchronous injection. On the other hand, the synchronously transferring correction quantity is set up by a means (f) depending upon whether the timing of the asynchronous injection is sooner or later than the synchronous injection corresponding to the next time intake stroke, during the asynchronous injection process. And fuel is injected by a means (g) on the basis of the output from each of means (c) and (d).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection control device for an internal combustion engine such as an automobile, and more particularly to a device that performs interrupt injection during acceleration.

(Prior art) Generally, when the required output for the engine changes,
It is necessary to control the amount of fuel supplied with good responsiveness according to the degree of demand, and this affects the air-fuel ratio particularly during excessive driving, and influences driving performance such as drive feeling and exhaust composition.

Conventional fuel injection control devices for this type of internal combustion engine include:
For example, there is one described in JP-A-59-101556. This device calculates the basic injection amount Tp based on the intake air amount and the engine speed, and also detects the opening degree of the throttle valve, and when the rate of increase exceeds a certain value, the fuel injection amount is increased independently of the basic injection amount. Immediately performs temporary addition and increases the amount according to the degree of acceleration, and also performs interrupt injection that is determined according to the movement of the throttle valve to compensate for the shortfall in the basic injection amount Tp due to a delay in the response of the intake air amount during sudden acceleration. It is supplemented by

However, in the conventional device described above, the fuel injected during or immediately after the intake stroke enters only a small amount during the intake stroke, and is inhaled in large quantities during the next intake stroke, so the benefits of asynchronous injection cannot be fully utilized. There was a drawback. On the other hand, if the pulse width of asynchronous injection is increased for this purpose, 2
The feeling of inhaling for the first time is too rich, which is still inconvenient.

Therefore, the applicant of the present invention has previously proposed a device that corrects the asynchronous injection amount for each cylinder according to the cycle position at that time when it is determined that asynchronous injection is to be performed (
(Refer to Japanese Patent Application No. 156121/1982), this device makes it possible to improve the air-fuel ratio dispersion (- times, cylinder by cylinder) caused by the difference in waiting time between asynchronous injection and the immediately following intake stroke. This ensures good drivability and exhaust performance with no misfires or loss of torque.

(Problem to be Solved by the Invention) By the way, in the device according to the above-mentioned prior application, the air-fuel ratio is prevented from becoming rich by supplying less fuel in the next synchronous injection to compensate for the excess amount caused by the asynchronous injection. However, if you look at each cylinder, the air-fuel ratio may become rich or lean, and so-called whiskers may appear in the emission characteristics (the air-fuel ratio is not flat). It turns out that there is room for improvement.

(Objective of the Invention) Therefore, the present invention aims to improve the flatness of the air-fuel ratio for each cylinder by switching the correction amount to be reflected in the next synchronous injection depending on whether the asynchronous injection is earlier or later than the synchronous injection corresponding to the next intake stroke. The purpose is to increase the emission characteristics and improve the emission characteristics.

(Means for Solving the Problems) In order to achieve the above object, the fuel injection control device for an internal combustion engine according to the present invention has an operating state detection means for detecting the operating state of the engine, as a basic conceptual diagram thereof is shown in FIG. (a) and determining means for determining the amount of change in engine load from the operating state of the engine and determining whether or not to perform asynchronous injection separately from synchronous injection for each revolution based on the amount of change in engine load. Synchronous injection calculation means C calculates the synchronous injection amount for each rotation based on the operating state, and if there is an asynchronous injection, corrects the next synchronous injection amount according to the synchronous transition correction amount, and it is determined that the asynchronous injection is to be performed. an asynchronous injection calculating means d which calculates an asynchronous injection amount for each cylinder based on the amount of change in the engine load and corrects the asynchronous injection amount according to an injection timing correction factor; A correction factor setting means e for setting an injection timing correction factor; and a correction factor setting means e for setting an injection timing correction factor; It is provided with a transition correction amount setting means f for setting the synchronous transition correction amount accordingly, and a fuel injection means g for injecting fuel based on the outputs of the synchronous injection calculation means C and the asynchronous injection calculation means d.

(Operation) In the present invention, when it is determined to perform asynchronous injection,
A synchronous transition correction amount for correcting the next synchronous injection amount is set for each cylinder depending on whether the timing of the asynchronous injection is earlier or later than the synchronous injection corresponding to the next intake stroke.

Therefore, the asynchronous and next synchronous injection amounts are appropriate for each cylinder, resulting in a more flat air-fuel ratio and improved emission characteristics.

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

2 to 10 are diagrams showing an embodiment of a fuel injection 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, intake air passes through an air cleaner 2 and an intake pipe 3, and fuel is injected from an injector (fuel injection means) 4 based on an 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, HC, NOx) in the exhaust gas are purified by a three-way catalyst and then discharged.

The intake air flow 11Qa is detected by a hot wire airflow meter and controlled by a throttle valve 8 in the intake pipe 3. Note that the type of airflow meter may be a hot film type, and in short, any type that measures the flow rate of intake air may be used.

Therefore, although the second flap may be used, the negative pressure sensor is omitted in this embodiment. Note that the present invention may be applied to any system using a negative pressure sensor.

The opening TVO of the throttle valve 8 is detected by an 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. oxygen sensor 1
As the sensor 2, for example, a sensor that can detect from rich to lean as disclosed in Japanese Patent Application Laid-Open No. 61-241434 is used. Furthermore, the operation of the starter motor is detected by the start switch 13.

The air flow meter 7, the opening sensor 9, the crank angle sensor 10, the water temperature sensor 11, the oxygen sensor 12, and the start switch 13 constitute an operating state detecting means 14, and the output from the operating state detecting means 14 is sent to a control unit 20. is input. The control unit 20 has functions as a determination means, a synchronous injection calculation means, an asynchronous injection calculation means, a correction factor setting means, and a transition correction amount setting means, and includes a CPU 21, a ROM 22, a RAM 23, and an Ilo
, +5-to 24. CPU U21 is RO
According to the program written in the M22, necessary external data is taken in from the I10 boat 24, and while data is exchanged with the RAM 23, the processing values necessary for injection amount control are calculated, and the necessary The data processed accordingly is output to the I10 boat 24. I10
A signal from the operating state detection means 14 is manually input to the boat 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 as shown in FIG. 5 and thereafter.
p is calculated in a subroutine.

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

FIG. 3 is a subroutine for calculating smooth injection 1AvTp.

First, the output of the air flow meter is read at Pl to determine the intake air amount Qa. This is for example by table lookup. Next, in P2, the smoothing part basic pulse width Tpo is calculated according to the formula 0.

Next, the basic pulse width Tp is obtained by weighted averaging Tpo by P.
Calculate. As a result, pulsations based on the output of the airflow meter are smoothed out. In P4, the flat corrected basic pulse width TrTp is determined according to the following equation.

T r T p = T p X Kflat --・
...In formula 00, Kflat is a flat A/F correction coefficient, which is obtained with interpolation from a map assigned by the rotational speed N and the α-N flow rate Qho. In addition, α
The -N flow rate is the amount of air 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
max, when T r T p > Tpmax, limit T r T p to Tpmax at P6 and proceed to P, and when 7rTp≦Tpmax, jump from P6 and proceed to P7. P, the delay correction pulse width T HS T P as the α-N preemption correction pulse width is determined. This is determined as the amount of change every 10 m5 in the value TH3TP looked up from the table with interpolation calculation based on the α-N flow rate Qho. However, if the amount of change is below the correction determination level, TH3TP=O, and if the amount of change is negative (deceleration), the amount of change is multiplied by a predetermined deceleration correction rate. THS
TP is a term that anticipates changes in the throttle valve 8 and corrects the injection amount with good responsiveness. Next, in P8, the smooth injection 1AvTp (corresponding to the smooth intake air amount) is determined according to the following equation (2).

AvTp=TrTpxFLOAD+AvTp-+X (
1-Fl, 0AD) + 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 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 airflow meter, 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 found in the prior application (but is disclosed for the first time in this embodiment).

The effect of adding the third term THSTP is shown in FIG. In Fig. 4, 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 shown as a flat corrected basic pulse width TrTp in Fig. 4. It changes like this.

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. Also, smooth jet Av
T p is given by the first-order delay of TrTp, and T HS
In the case of conventional phase control without TP, the change is shown by the dashed line in the figure, and responsiveness is lacking. 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 this cannot follow the change in the opening degree of the throttle valve 8 without delay. In addition, the amount of combustion adhering to the wall surface of the intake pipe 3 is also influenced by the intake volume.

On the other hand, the AVTp of this embodiment is T! as shown by the solid line in the figure. Since a correction term of 13 TP is added as a pre-preparation correction of α-N (pre-preparation correction of 10 mS), the response is excellent and it is massed to actual air flow rate changes. An example of a highland area is also shown.

FIG. 5 is a flowchart showing a program for interrupt injection. First, it is determined whether the star l-switch 13 is on based on the pH, and if the start switch 13 is on, it is determined that cranking is in progress, and the current routine is ended. On the other hand, when the start switch 13 is not ON, it is determined that the startup is complete and the process proceeds to steps after P1□.In P1□, the amount of change in AVTp ΔAvT according to the following formula ■
Find pn (where n is the cylinder number). ΔAvTp
n corresponds to the amount of change in engine load.

ΔAvTp=AvTp−AVTpozn +++++++
■However, A v T point is the previous value (A v T point
T p-〇 corresponds to the n-th cylinder.

Next, at PI3, the amount of change ΔAvTpn is compared with the interrupt injection determination value LASN I. ΔA v T p n <
When LASN I, it is determined that there is no need to perform interrupt injection, and at PI4, the interrupt injection amount (corresponding to cylinder-specific asynchronous injection pulse width) IN and JsETn are set to "0" and jump to PN2. On the other hand, ΔA V T p n≧LASNI
In this case, it is determined that it is necessary to perform an interrupt injection, and then the PI5 determines whether or not there is sudden acceleration.

When there is sudden acceleration, the injection timing correction factor GZCYL for asynchronous injection is looked up from the table for sudden acceleration using PI6, and when the acceleration is not sudden, the injection timing correction factor GZCLS is looked up from the table for slow acceleration using P. GZCYL,
GZCLS is for correcting the fuel injection amount during asynchronous injection timing. Then, interrupt injection 1 at pH 1
1NJsETn is calculated according to the following equation (2).

rNJSETn=ΔAvTp nXGZTwXGZCY
n+Ts...In formula 00, GZTw is the water temperature correction factor for asynchronous injection by air, and the cooling water temperature is adjusted in step P31 of the bank ground job shown in Fig. 7 based on the table map shown in Fig. 6. It is determined by lookup using 'rW as a parameter. In addition, GZCYn in the formula (■) is the injection timing correction rate GZCYL and G
It represents ZCLS in general, and TS is the dead time correction coefficient of the injector 4.

Next, at Pl'l, it is determined whether the timing of the current asynchronous injection is between the synchronous injection and the intake stroke (hereinafter, this section will be referred to as section B). Note that when the timing of asynchronous injection is between the intake stroke and synchronous injection, it is expressed as being in section A, and the section between Δ and 8 is shown as shown in FIG.

When it is in section B, that is, when there is a No branch at pH 9, the correction amount (which is the asynchronous transition pulse width and corresponds to the synchronous transition correction amount in the claims) is set at P2° according to the following formula 〇. calculate.

ERACI n =ΔAvTp nXGZTwx (G
ZCYn-ERACPH) 10ERACI n' ・・・・・・■However, ERA
Crn': Previous value 0 In the equation, ERACPH is the asynchronous injection transition standard correction factor, and is a magnification for covering only the wall flow portion taken by the wall flow. Therefore, for example, GZCYn is E RA
If it is larger than CPH, ERACIn becomes positive, and the next synchronous injection is reduced by ERACIn by the magnification of the difference. This is because the next synchronous injection will be enough to compensate for the increase in air amount corresponding to the increase in load, so only the wall flow is corrected. Note that ERACI n ′ corresponds to a wall flow correction component that changes with a relatively fast time constant, a so-called high frequency component.

On the other hand, when the pH is 9 and not in the B section, the increase correction rate ERACI n is calculated at PH 1 according to the following equation (2).

ERACIn=ΔAvTp nXGZTwx (GZC
Yn-ERACP) +ERACI n' --------1 ■Here, ERA
Unlike ERACPH, CP is an asynchronous injection transition standard correction factor that also adds an increase in air to the perfect flow. Since this is the section where the next intake synchronous injection has finished, the increase in air volume must also be compensated for, and even if the increased air volume is injected, the next synchronous injection (the next Inhalation feeling)
This is because there is no need to reduce ERACP, and therefore ERACP is set larger than ERACPH.

Therefore, in formula 0, ERACP is also the asynchronous injection transition standard correction factor, but in this case, the increase in air amount from synchronous injection must also be added to the interruption, so the total increase in amount for interruption injection and synchronous injection is The relationship is as follows: total increase - wall flow + air increase - ERACP XGZTw x ΔAvTp. Next, this AV'rp on P2□
is set as Taue AvTpoint, and it is determined whether or not all 6 cylinders have finished in PX3. If it is not completed, the pH returns to 2, and when it is completed, the interrupt injection 1rNJSETn is sent to the output port at pH 4, and the interrupt injection is executed.

FIG. 8 is a flowchart showing a synchronous injection program, and this program is executed in synchronization with engine rotation. First, in P41, the synchronous injection amount Ti is calculated according to the following equation (2).

Ti-(AvTpxαm+Kathos)xα+Ts
+ (Chos n-ERAC1n) ・・・・・・
・■ In formula 0, ) (athos is the wall flow correction component (so-called low frequency component) that changes with a relatively slow time constant, has positive and negative values, and is dependent on the fuel deposition speed V [ms] and the correction factor. Ghf
It is given as a function of (%).

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. In addition, Chosn is the wall flow correction amount for each cylinder, and Chosn=ΔAvTpnXGZTWP (or G
ZTWM)...[phase] is given by the formula. However, GZTWP is the water temperature correction coefficient during acceleration, GZT
WM is a water temperature correction coefficient during deceleration. Next, at P4□, the synchronous injection iTi is sent to the output port, and synchronous injection is executed.

After that, Pd2 resets ERACIn=Q, and P4
In step 4, the current AVTp is set as the Taue AvTpoin and the routine ends.

The actual injection situation resulting from the execution of each of the above programs is shown in the timing chart of FIG.

Taking as an example the case where the engine load (that is, the air amount equivalent to AVTp) changes at timing L and the case where it changes at timing t2, consider timing 1. Then, the interrupt injection is performed in the B section, and at timing L2, the interrupt injection is performed in the A section.

-4h -9*11 people in (a)) At this time, the change in air volume due to the increase in load (
Δair amount) is included in the AVTp of the next synchronous injection, so it is only necessary to perform interrupt injection of the wall flow, and the injection fft
I N J S T n is calculated using the 0 formula. In addition,
The relationship between the injection time correction factors CZCYL and CZCLS and the injection timing is shown in FIG.

For example, if GZCYn of the interrupt injection is larger than ERACPH, the synchronous injection is considered to be over-injected and reduced by ERACI n. The synchronous injection is executed by the program shown in FIG. Therefore, in the synchronous injection, the ninth
The part shown by hunting in Figure (a) is the increase correction amount ERAC.
It is reduced as I n. Note that the wall flow portion resulting from the interruption injection gradually decreases with each subsequent intake stroke, as shown in the figure.

Therefore, GZ determined by the timing of interrupt injection
If CYn also includes air increment, ERAC
This amount is greater than the PH, and the amount of air increase will be reduced from the next synchronous injection. If the timing of synchronous injection is just before intake air, only a small proportion of the synchronous injection will be inhaled into the intake air, so it would be better to inject the air increase earlier with interrupt injection to prevent the next lean. It is possible to prevent the subsequent intake air from becoming richer.

There is little need for this if the synchronous injection timing is well in advance of the intake stroke.

In any case, ERACPH(times)XGZTW(times) becomes the total correction magnification including the interrupt injection and the next reduction.

Include 1 sub-include 1u rg & 9E b (')
-Field W- At this time, the change in air amount due to the increase in load is added to the current interrupt injection by 1m. That is, the increase in air amount since the previous synchronous injection is also reflected in the interrupt injection amount, and ERACI n is calculated according to the above formula 0. In this case, ERACI n is B RA
The ER value is larger than that of CP II by the amount of air increase.
Calculated based on ACP. Therefore, the reduction ERAcIn of the next synchronous injection is Jffi only for the excessive increase in wall flow due to the interrupt injection. Therefore, in the next synchronous injection, the pulse width is calculated such that only the hunting portion shown in the figure becomes smaller. In other words, the amount during the next synchronous injection is corrected to be reduced. Therefore, there is never a situation where the amount of asynchronous injection V becomes insufficient (also, since the amount is appropriately reduced between synchronous injections, the air-fuel ratio becomes optimal for each cylinder, and the flatness of the air-fuel ratio is ensured.

Note that in step P2゜ in FIG.
ACI n may also be calculated.

ERACI n-ΔAvTpxGZTwx (G Z
C'/n-ERACPH)-ΔAvTp+
ERACI n'...0 In the 0 formula, the AAvTp term is subtracted as the air amount change, but this is only in the case of Fig. 9 (b), and in the case of (A), -ΔAvTp is necessary. do not have.

Based on the above, fuel injection will be finely corrected for each cylinder depending on the timing of asynchronous injection.
Unlike the example of the prior application, the air-fuel ratio does not lynch or lean for each cylinder, ensuring flatness and preventing deviations in emission characteristics.

As a result, the conversion efficiency of the three-way catalyst in particular can be increased.

(Effects of the Invention) According to the present invention, since the correction of the next synchronous injection amount is switched depending on whether the timing of the asynchronous injection is earlier or later than the synchronous injection corresponding to the next intake stroke, the amount of the asynchronous injection is changed for each cylinder. Furthermore, by setting the next synchronous injection amount to an appropriate value, it is possible to improve the flatness of the air-fuel ratio, and it is possible to prevent emisocidine characteristics. As a result, in an engine to which this device is applied, the conversion efficiency of the three-way catalyst can be increased.

[Brief explanation of the drawing]

Figure 1 is a basic conceptual diagram of the present invention, Figures 2 to io are diagrams showing an embodiment of the fuel injection control device for an internal combustion engine according to the present invention, Figure 2 is an overall configuration diagram thereof, and Figure 3 is a diagram showing an embodiment of the fuel injection control device for an internal combustion engine according to the present invention. 4 is a flowchart showing a subroutine for calculating the smooth injection amount.
The figure is a timing chart explaining the effect based on the smooth injection amount, Figure 5 is a flowchart showing the interrupt injection program, Figure 6 is a diagram showing the characteristics of the water temperature correction factor, and Figure 7 is the water temperature correction factor. FIG. 8 is a flowchart showing the look amplification subroutine, FIG. 8 is a flowchart showing the synchronous injection program, FIG. 9 is a timing chart explaining the effect of the interrupt injection, and FIG. 10 is a diagram showing the characteristics of the various correction amounts. be. 1...Engine, 4...Injector (fuel injection means), 14
... Operating state detection means, 20 ... Control unit (determination means, synchronous injection calculation means, asynchronous injection calculation means, correction rate setting means, transition correction amount setting means).

Claims (1)

[Scope of Claims] a) Operating state detection means for detecting the operating state of the engine; b) Determining the amount of change in engine load from the operating state of the engine, and performing synchronous injection for each revolution based on the amount of change in engine load. c) Calculates the synchronous injection amount for each revolution based on the operating state of the engine, and if there is an asynchronous injection, transfers the next synchronous injection amount to synchronous. d) when it is determined to perform asynchronous injection, calculates an asynchronous injection amount for each cylinder based on the amount of change in the engine load, and injects the asynchronous injection amount; Asynchronous injection calculation means for correcting according to the timing correction factor; e) correction factor setting means for setting the injection timing correction factor according to the timing of the asynchronous injection; and f) when it is determined to perform the asynchronous injection, the asynchronous injection is performed. g) transition correction amount setting means for setting the synchronous transition correction amount according to whether the timing of the synchronous injection corresponding to the next intake stroke is earlier or later than the synchronous injection corresponding to the next intake stroke; 1. A fuel injection control device for an internal combustion engine, comprising: a fuel injection means for injecting fuel based on the fuel injection means;