JPH0211839A - Fuel injection controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the flatness of the air-fuel ratio by correcting the synchronous injection quantity by the transition correction quantity and shortage correction quantity, besides the transition correction quantity, when an engine shifts to a prescribed transition state. CONSTITUTION:In a transition judging means 6, the variation quantity of the engine load is obtained from the operation state of an engine, and it is judged that the engine is in a prescribed transition state. A synchronous injection quantity calculating means (c) calculates the synchronous injection quantity in each revolution on the basis of the engine operation state, and when the transition to a prescribed transition state is performed, the synchronous injection quantity is corrected according to the transition correction quantity and corrected with the transition correction quantity and the shortage portion accompanied with the correction is corrected by the shortage correction quantity. Since a fuel injection means (g) jets fuel on the basis of the output of the synchronous injection calculating means (c), the correction for the synchronous injection quantity in transition is made proper, and the flatness of the air-fuel ratio is improved, and the emission characteristic can be improved.

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 improves the flatness of the air-fuel ratio during transient operation.

(Prior art) When the required output for the engine of a vehicle such as an automobile changes, it is necessary to control the fuel supply amount with good responsiveness according to the degree of the request. This affects driving performance such as drive feeling and exhaust composition.

Generally, the deviation of the air-fuel ratio from the target air-fuel ratio during engine acceleration/deceleration is caused by the intake manifold of the intake system or the intake bow I-
This is due to changes in the amount of adhering fuel and floating fuel attached to the engine, and the amount of adhering and floating fuel varies greatly depending on the operating condition of the engine.

Specifically, the fuel injection amount during acceleration/deceleration is the change amount Δ of the throttle valve opening.
Although it was corrected by TVO, etc., ΔTV○ has no correlation with air volume or wall flow, and (weak) flatness of the air-fuel ratio (A/F) is poor. Therefore, improvements should be made to exhaust emissions, slow acceleration drivability, etc. There were few.

Furthermore, in a low intermediate temperature region of the cooling water where there is a lot of wall flow, the amount of fuel that enters the combustion chamber during acceleration decreases, so it is necessary to constantly increase the amount of fuel injection to achieve lynch, which does not improve fuel efficiency.

As a fuel injection control device for an internal combustion engine that eliminates the above-mentioned drawbacks, there is, for example, one described in Japanese Patent Laid-Open No. 58-6238. This device focuses on the fact that the amount of fuel adhering to the wall and the amount of fuel adhering to the wall carried away to the combustion chamber during intake changes depending on the amount of injected fuel. At the same time as the estimated calculation, the calculated value is integrated, and the amount of fuel taken away is estimated from the integrated result. Then, the amount obtained by subtracting the amount of fuel carried away from the calculated amount of fuel adhering to the wall surface is added to the synchronous injection amount to determine the effective synchronous injection amount. That is, when the amount of fuel adhering to the wall surface is large, the synchronous injection amount is increased, and when the amount of fuel carried away is large, the synchronous injection amount is decreased to suppress air-fuel ratio fluctuations.

(Problem to be Solved by the Invention) However, in such a conventional fuel injection control device for an internal combustion engine, the behavior of the wall flow that changes with a relatively slow time constant is called the low frequency component. ), but the correction for things that change with a relatively fast time constant (hereinafter referred to as high-frequency bones) is not taken into consideration, and in this respect, the following problems arise. It was occurring.

That is, during slow acceleration that does not reach interrupt injection, the air-fuel ratio (A/F) at the first intake at the beginning of acceleration may become slightly lean. It turns out that this is because when the injection timing is just before the intake stroke, there is a high proportion of wall flow even if the amount is increased. Furthermore, even if the injection timing is too early, the injection will be performed using an old air amount signal, resulting in a slightly lean result.

(Purpose of the Invention) Therefore, the present invention corrects the flatness of the air-fuel ratio by correcting the synchronous injection amount using the transient correction amount and the excess/deficiency correction amount in addition to the transient correction amount when the engine shifts to a predetermined transient state. The purpose is to increase 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, a transient determination means for determining the amount of change in engine load from the operating state of the engine, and determining whether the engine is in a predetermined transient state based on the amount of change in engine load; After calculating the synchronous injection amount for each rotation and moving to a predetermined transient state, the synchronous injection amount is corrected according to the transient correction amount, and also corrected by the transient correction amount, and the excess or deficiency caused by the correction is corrected. synchronous injection amount calculation means C that corrects with an insufficient correction amount; transient correction amount calculation means d that calculates the transient correction amount based on the amount of change in the engine load when the engine shifts to a predetermined transient state; a correction amount calculation means e which calculates the transient correction amount based on the timing of the synchronous injection when the transition to a predetermined transient state; It includes an excess/deficiency correction amount calculating means f for calculating, and a fuel injection means g for injecting fuel based on the output of the synchronous injection amount calculating means C.

(Function) In the present invention, when the engine shifts to a predetermined transient state, the synchronous injection amount is corrected by the transient correction amount based on the synchronous injection timing and the excess/deficiency correction amount that corrects the correction error in addition to the transient correction amount. Ru.

Therefore, the correction of the synchronous injection amount at the time of transition becomes appropriate, the air-fuel ratio becomes more flat, and the emission characteristics are improved.

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

2 to 8 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. The exhaust gas combusted in the cylinder is introduced into the catalytic converter 6 through the exhaust pipe 5, where the harmful components (C(l)-1(, NOx) in the exhaust gas are purified by a three-way catalyst and then discharged. be done.

The intake air flow rate Qa is detected by a hot wire type air flow meter 7 and controlled by a throttle valve 8 in the intake pipe 3. Note that the type of air flow make 7 may be a hot film type, and in short, any type that measures the flow rate of intake air may be used.

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

The opening degree TVO of the throttle valve 8 is detected by the opening degree sensor 9, and the rotation speed N of the engine 1 is detected by the crank angle sensor 10. 180°) at a predetermined position before compression top dead center (TDC) of each cylinder, for example
Reference signal Ca that becomes a pulse of CH) level at DC 70°
In addition to outputting the unit angle of the crank angle (for example, 2
A unit signal C1, which becomes a [H] level pulse, is output for each [H] level pulse. Note that the engine rotation speed N can be determined by calculating the pulses of the reference signal Ca as a coefficient.

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. As the oxygen sensor 12, for example, a sensor capable of detecting from rich to lean as disclosed in Japanese Patent Laid-Open No. 61-24.1434 is used.

Furthermore, the operation of the starter motor is controlled by the start switch 13.
Detected by

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 includes a transient discrimination means, a synchronous injection calculation means, a transient correction amount calculation means,
It has functions as a correction amount calculation means and an excess/deficiency correction amount calculation means, and is composed of a CPU 21, a ROM 22, a RAM 23, and an I10 board 24. CPU21 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 correspondingly processed data is output to the I10 port 24. I10
A signal from the operating state detection means 14 is input to the port 24, and an injection signal Si 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 after. Avt calculated in the program of FIG.
p is calculated in a subroutine.

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

a T p o = X K ・・・・・・■
Next, in P3, the basic pulse width Tp is obtained by weighted averaging of Tpo.
Calculate. As a result, pulsations based on the output of the airflow metaph are smoothed out. In P4, the flat correction basic pulse width TrTp is determined according to the following equation (2).

TrTp=TpxKflat −・---−■ In the formula, Kflat is a flat A/F correction coefficient,
It is calculated with interpolation from a map allocated by the rotational speed N and the α-N flow rate Qho. Note that the α-N flow rate is the amount of air determined from the throttle valve opening TVO and the rotational speed N, and is already known.

Next, in P5, TrTp is set to a predetermined maximum limit value T p
max, and when Tr T p > Tpmax, limit TrTp to Tpmax in P6, proceed to P7, and set Tp.
When rTp≦Tpmax, jump to P6 and proceed to P7. In P7, the delay correction pulse width TH3TP is determined as the α-N prefetch correction pulse width. 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 judgment level, TH3
If TP=O and the amount of change is negative (deceleration), the amount of change is multiplied by a predetermined deceleration correction rate. TH3TP 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 amount Avtp is calculated according to the following formula (■).
(corresponding to smooth intake air volume).

Avtp=TrTpXFLOAD+Avtl)X (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 area AA determined by the throttle valve 8 and (displacement amount x rotational speed) NVM. Therefore, the first and second terms of equation (2) are the weighted average value using FLOAD of the flat corrected basic pulse width TrTp calculated based on the pulsation corrected value of the output of the airflow meter 7, in other words, the first order of TrTp. This corresponds to the part that calculates the delay by calculation (using software). Furthermore, the third term in equation (2) is a preemptive correction based on the throttle valve opening degree TV○, and this part is not found 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 Figure 4, when accelerating at a certain timing, the basic pulse width Tpo is slightly delayed from the throttle valve change.
, Tp change, and the waveform obtained by correcting Tpo and Tp changes as a flat corrected basic pulse width TrTp as shown in FIG.

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, the 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 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, in Avtp of this embodiment, as shown by the solid line in the figure, the correction term consisting of TH3TP is αN preemptive correction (
Since it is added as a preemption correction of 10ms,
It has extremely good responsiveness and matches actual changes in air flow rate. Note that known examples are also illustrated.

FIG. 5 shows the wall flow correction amount (transient correction amount) Ch for each cylinder.

This is a flowchart showing a program to obtain sn.
It is executed every predetermined period. First, the amount of change ΔAvtpn (where n is the cylinder number) in the smooth injection amount Avtp (corresponding to the smooth intake air amount) is determined based on the pH according to the following equation. ΔA
vtpn corresponds to the amount of change in engine load.

ΔAvtpn=Avtp −Avtpoint −■ However, Avtpoint is the value at the time of previous fuel injection (Avtp
-+) and corresponds to the n-th cylinder.

Next, in P and □, the injection timing correction factor Gzit is set using the injection timing T as a parameter. This Gzit looked up from the table is the wall flow correction amount Chos for each cylinder, which will be described later.
This is to correct the calculation of n and the cylinder-specific increase correction amount E racin based on the injection timing.

Next, PI3 determines whether the amount of change ΔAvtp>Q. That is, by determining the sign of ΔAvtpn, the acceleration state or deceleration state of the engine 1 is determined. When the amount of change is negative (ΔAvtpn<O), it is determined that the system is in a deceleration state, and the cylinder-by-cylinder wall flow correction amount (transient correction amount) amount Chosn during deceleration is determined in accordance with the following equation 〇 in PI4.

Chosn-ΔAvtpnX GztwmX Gzit
-■ However, Gztwn: Water temperature correction coefficient during deceleration. Next, in PI5, according to the following formula
Excess/deficiency correction amount) EriLm is calculated and the current routine ends.

Er1tn−ΔAvtpnX GztwmX (Gzi
t -E RA CP H) ・・・=・・■However, ER
ACPH: Wall flow high frequency separation correction amount basic value On the other hand, when the amount of change is positive (ΔAvtpn>O), it is judged that the state is in acceleration, and PI3 calculates the wall flow correction amount for each cylinder during acceleration (transient Amount of correction) Find Chosn.

Chosn =ΔAvtpnX GztwpX (Gz
it -E RA CP H) --■ However, Gztw
p: Water temperature correction coefficient during acceleration Next, in PI3, according to the following formula 〇, increase correction amount for each cylinder during acceleration (excess/deficiency correction amount) Er
1tn is obtained and the current routine is ended.

Er1tn−ΔAvtpn X GztwpX (Gz
it-ERACPH)-・”■ In this case, G z twp
may be the same as Gztw, which will be described later, for interrupt injection. Also, if you want to make it slightly richer due to sudden acceleration and interrupt injection, you may want to find it from a separate table (if heavy gasoline is taken into account, you may want to make it slightly richer).

FIG. 6 is a flowchart showing a synchronous injection program, and this program is executed in synchronization with engine rotation. First, in P21, the cylinder is discriminated, and this is done by reading the cylinder discrimination signal output from the crank angle sensor 10 provided in each cylinder. Next, in P2□, the synchronous injection amount Tin corresponding to the cylinder is calculated according to the following equation [phase], and the injection signal Si is output from the I10 boat 24 to the injector 4.

Tin-(Avtp +Kathos)XTfbyaX
(α-+-7m)+Chosn-old Eracin→-
TS・・・・・・[phase] However, Kathos:
It is a wall flow correction bone (low frequency component) that changes with a relatively slow time constant (transient correction amount), has positive and negative values, and is a function of the fuel deposition speed mf (ms) and correction factor Ghf [%]. is given by

Tfbya: Target air-fuel ratio α: A λ control correction coefficient for the air-fuel ratio based on the output of the oxygen sensor 12.

αm = Mixture ratio learning control correction coefficient Old Eracin: Previous increase correction amount for each cylinder TS: Dead time correction coefficient for injector 4 Then, at PN2, the injection signal Si causes injector 4 to
is driven for a predetermined period of time and fuel is injected. Next, the current smooth injection amount Avtpi used in the [phase] formula in PX3 is set as the previous smooth injection amount Avtpoin (Avtpi→A
vtpoint) Store in the RAM 23 and use pzs to obtain the cylinder-specific increase correction amount Er1tn obtained from the above PI5 or PI7.
E rac when calculating the next synchronous injection amount Tin
Store it in the RAM 23 as in. Next, in P26, the wall flow rate Mf is calculated according to the following equation 0, and the value is stored in RAM2.
3 and end this routine.

Mf - Old Mf + Vmf ...@However, old Mf
: Previous wall flow calculation value Vmf: Adhesion speed The adhesion speed Vmf is the flow rate of fuel taken up by the wall flow, and is determined as the flow rate per rotation.

The actual operation by executing each of the above programs is shown in the timing chart of FIG. FIG. 7 is an example showing a change in the synchronous injection pulse of a specific cylinder when the engine 1 is slowly accelerated. The first synchronous injection 1i immediately after Ensifun 1 transitions to a slow acceleration state
Tin is increased by the cylinder-specific wall flow correction amount Chosn, and the next Tin is corrected by the amount of increase (excess or deficiency) due to Chosn by the cylinder-specific increase correction amount Eracin. Thereafter, as the wall flow rate increases, the amount of fuel carried away into the combustion chamber during the intake stroke also increases, so the correction amount is reduced accordingly.

Therefore, as shown in FIG. 8, which shows the behavior of the air amount, injection amount, and air-fuel ratio in the conventional case and this embodiment, the conventional method for correcting the injection amount in response to stepwise changes in the air amount Since the effective injection time TAU-Tp was corrected in minutes K a thos, the injection amount was corrected as shown in the shaded area,
There was a delay in control with respect to the peak value of the air amount, and more fuel was flowing into the wall, causing the air-fuel ratio to fluctuate significantly toward the lean side.

On the other hand, in this embodiment, the injection amount immediately after the air amount change is K.
In addition to a Lhos, the cylinder-specific wall flow correction amount Chosn and the cylinder-specific increase correction amount Eracin are corrected by the injection timing correction factor Gzit, so control responsiveness is improved and injection is performed in accordance with the peak value of the air amount. The amount is corrected to increase, and lynching after the amount is corrected is also suppressed. As a result, as shown by the broken line in the figure, air-fuel ratio fluctuations during transient times are extremely small and become almost flat. Thereby, emission characteristics can be improved. In addition, during deceleration, the synchronous injection amount immediately after the transition to the deceleration state is reduced according to the amount of air change, and after the reduction is corrected, the amount is increased, suppressing lean after correction, and the same effect is obtained. Of course.

Although synchronous injection has been described in this embodiment, if interrupt injection is required such as during acceleration after restart, the interrupt injection amount 1nj is determined according to the following formulas 〇 and 0.
A similar effect can be obtained by calculating sten and the cylinder-specific increase correction amount Eracin.

Injstcn-ΔAvtpion X Gztw
Gzcyn 4-1”s...@ However, ΔAvtpoin: Previous value Gztw: Water temperature correction factor for cylinder-specific asynchronous injection Gzcy
n: Injection timing correction factor during non-synchronization E racin =
E racin' +ΔAvtpoinX Gz
twX (G zcyn -E racp) --
@However, Eracin': Previous value Eracp
: Asynchronous injection transition standard correction factor By using these @ and 0 formulas, the flatness of the air-fuel ratio during asynchronous injection can be improved.

(Effects of the Invention) According to the present invention, when the engine shifts to a predetermined transient state, the synchronous injection amount is corrected by the transient correction amount and the excess/deficiency correction amount in addition to the transient correction amount. By setting an appropriate amount of synchronous injection, it is possible to improve the flatness of the air-fuel ratio and improve the emission characteristics.

[Brief explanation of the drawing]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 8 are diagrams showing an embodiment of a fuel injection control device for an internal combustion engine according to the present invention, FIG. 2 is an overall configuration diagram thereof, and FIG. Flowchart 1-1 4th shows the subroutine that calculates the smooth injection amount.
The figure is a timing chart explaining the effect based on the smooth injection amount, FIG. 5 is a flowchart showing the program for calculating wall flow correction amount for each cylinder, FIG. 6 is a flowchart showing the synchronous injection program, and FIG. The timing chart of the synchronous injection pulse, FIG. 8, is a timing chart explaining the action of the synchronous injection. 1...Engine, 4...Injector (fuel injection means), 14.
... Operating state detection means, 20 ... Control unit (transient discrimination means, synchronous injection amount calculation means, transient correction amount calculation means, correction amount calculation means, excess/deficiency correction amount calculation 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 based on the amount of change in engine load, the engine detects a predetermined transient state. c) calculates a synchronous injection amount for each rotation based on the operating state of the engine, and when a transition to a predetermined transient state occurs, calculates the synchronous injection amount according to the transient correction amount; d) when the engine shifts to a predetermined transient state, the engine load e) a correction amount calculation unit that calculates the transient correction amount based on the timing of synchronous injection when the engine shifts to a predetermined transient state; means; f) excess/deficiency correction amount calculation means for calculating the current excess/deficiency correction amount based on the transient correction amount in the previous synchronous injection; and g) injecting fuel based on the output of the synchronous injection amount calculation means. A fuel injection control device for an internal combustion engine, comprising: a fuel injection means;