JPH0444096B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an air-fuel ratio control device, and more particularly, to an air-fuel ratio control device that highly accurately controls the air-fuel ratio to a target air-fuel ratio during transient operating conditions of an automobile engine that performs fuel injection. This invention relates to a fuel ratio control device.

(Prior art) Generally, during transient operation of an automobile, it is necessary to increase or decrease the amount of fuel in response to the transient operating state to ensure good driving performance, and also to compensate for fluctuations in the air-fuel ratio during the transient operation. It is necessary to quickly attenuate and control the air-fuel ratio to the target air-fuel ratio.

Examples of such conventional air-fuel ratio control devices include, for example, Japanese Patent Application Laid-open No. 144631/1983;
144632 and Japanese Patent Application Laid-Open No. 144639 are known, and these air-fuel ratio control devices control the amount of change in throttle valve opening or intake pipe negative pressure every predetermined time. Using the corresponding integrated value as a correction coefficient, the amount of acceleration is increased and the amount of deceleration is decreased in accordance with the throttle valve opening or the rate of increase/decrease in intake pipe pressure. Furthermore, Japanese Patent Application Laid-Open No. 58-144634 and Japanese Patent Application Laid-Open No. 58-144640 disclose that increasing or decreasing a correction coefficient during a transient period, and then recovering at a predetermined recovery speed to increase or decrease the amount of acceleration or deceleration. At the same time, the recovery speed is switched to a low speed in the middle of recovery, that is, the recovery speed is changed to 2.
An air-fuel ratio control device that performs stepwise correction is described.

(Problem to be Solved by the Invention) However, in such conventional air-fuel ratio control devices, the correction coefficient is determined only based on the throttle valve opening or the rate of increase or decrease in intake pipe pressure. The air-fuel ratio was controlled by correcting the fuel injection amount during transient operation by restoring the correction coefficient linearly at a predetermined recovery speed or switching to a low speed during recovery, which caused fluctuations in the air-fuel ratio during transient operation. The air-fuel ratio cannot be quickly controlled to the target air-fuel ratio, and the air-fuel ratio is overshot and damped oscillations are repeated to achieve the target air-fuel ratio. Particularly in cold weather, the amount of fuel adhering to the intake passage is large, and the amount varies greatly depending on the operating conditions, so the air-fuel ratio varies greatly from the target air-fuel ratio. As a result, there were problems such as sluggishness and torque fluctuations, deteriorating driving performance, and increasing exhaust emissions such as CO. In particular, in the lean combustion method that has recently been adopted to improve fuel efficiency, deviations in the air-fuel ratio from the target air-fuel ratio cause large fluctuations in torque. There was a problem in that it was not possible to set the engine to a very lean setting, and it was not possible to sufficiently improve fuel efficiency.

(Objective of the Invention) Therefore, an object of the present invention is to improve driving performance during transient operation and improve fuel efficiency by accurately controlling the air-fuel ratio during transient to a target air-fuel ratio.

(Means for Solving the Problems) The air-fuel ratio control device of the present invention, as its overall configuration diagram is shown in FIG. ) basic injection amount calculation means for calculating a basic injection amount of fuel corresponding to the target air-fuel ratio based on the operating state; (c) at least a warm-up signal, a load signal, and a rotation among the detection signals of the operating state detection means (d) change amount calculating means for calculating the amount by which the predetermined values assigned corresponding to the three parameters of the signal change per predetermined period; (d) calculating the amount of transient correction by adding the amount of change for each predetermined period; (e) attenuation coefficient calculation means for calculating a damping coefficient for determining an increase/decrease rate of the transient correction amount based on the transient correction amount and the operating state; (f) attenuation coefficient calculation means for attenuating the transient correction amount. (g) a final injection amount calculation means that corrects the basic injection amount based on the transient correction amount after the attenuation correction and calculates a final injection amount; (h) an engine. and fuel injection means for supplying a final injection amount of fuel to the fuel injection device, and accurately controls the air-fuel ratio to the target air-fuel ratio.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

2 to 12 are diagrams showing an embodiment of the present invention.

First, to explain the configuration, in Figure 2, 1
is a multi-cylinder engine, and intake air is supplied to each cylinder of the engine 1 through an intake pipe 2. A fuel injection valve 3 as a fuel injection means for injecting fuel to each cylinder is attached to the intake pipe 2, and the flow rate of intake air supplied to the engine 1 is controlled by the intake pipe 2.
The throttle valve 4 is controlled by a throttle valve 4 provided at the collecting part. The throttle valve 4 is linked with the accelerator pedal of the vehicle, and the valve opening Cv of the throttle valve 4 is detected by a throttle opening sensor 5. The flow rate of intake air (hereinafter referred to as intake air amount) Qa is detected by the air flow meter 6. Further, the engine rotation speed N is detected by a crank angle sensor 7, which is connected to a signal disc plate 7a attached to the crankshaft of the engine and provided with a protrusion on the outer periphery, and a protrusion on the signal disc plate 7a. magnetic deck 7b that detects
It has . Further, the temperature Tw of the cooling water flowing through the water jacket is detected by the water temperature sensor 8 as a warm-up signal. The above throttle opening sensor 5, air flow meter 6, crank angle sensor 7
The water temperature sensor 8 constitutes an operating state detecting means 9, and a signal from the operating state detecting means 9 is input to a control unit 10.

The control unit 10 has functions as a basic injection amount calculation means, a change amount calculation means, a transient correction amount calculation means, a damping coefficient calculation means, a damping correction means, and a final injection amount calculation means.
ROM12, RAM13, and I/O port 1
It is composed of 4. The CPU 11 takes in necessary external data through the I/O port 14 according to the program written in the ROM 12, performs arithmetic processing while exchanging data with the RAM 13, and performs arithmetic processing as necessary. The processed data is output to the I/O port 14. ROM
Reference numeral 12 stores a program for controlling the CPU 11. For example, it is constituted by a non-volatile memory, stores data used in calculations in the form of a map, etc., and retains the stored contents even after the engine 1 is stopped. The I/O port 14 receives signals from the throttle opening sensor 5, air flow meter 6, crank angle sensor 7, and water temperature sensor 8, as well as signals from an air-fuel ratio sensor (not shown), an ignition switch, etc. The input signal is converted to digital. Further, an injection signal Si is outputted from the I/O port 14 to the fuel injection valve 3.

Next, the action will be explained.

Generally, the amount of fuel injected into an engine using a fuel injection valve is controlled by changing the duty value of an injection signal output to the fuel injection valve.

In the case of this embodiment, the duty value of this injection signal Si is calculated by the control unit 10.
That is, the control unit 10 controls the intake air amount Q
First, the basic injection amount Tp is calculated based on
Calculate. Then, the injection signal Si with the duty value corresponding to this final injection amount Ta is sent to the I/O port 1.
4 to the fuel injection valve 3. And that program is ROM1 of control unit 10.
It is written in 2.

FIG. 3 is a flowchart showing a main program for calculating the fuel injection amount, which is executed at predetermined intervals, for example, every 10 msec. In addition, in the figure, P ₁ ~
P ₁₉ shows each step of the flow.

First, the data required in step _P1 , i.e.
Data such as throttle valve opening Cv, intake air amount Qa, engine speed N, cooling water temperature Tw, air-fuel ratio sensor and ignition switch are read, and in step _P2 , a new basic injection amount (new basic injection amount) based on the data from the current execution is read. Injection amount) NTp is calculated using the following formula.

NTp=K・Qa/N (1) However, K: coefficient determined by the characteristics of the fuel injection valve 3 and the value of the target air-fuel ratio.

Next, in step _P3 , the pulse width of the basic injection amount (old basic injection amount) Tp when this program was executed last time is compared with 5ms, and if Tp≦5ms, the new basic injection amount NTp is set in step _P4 . When Tp > 5ms, the basic injection amount Tp is the sum of 1/4 of the new basic injection amount NTp and 3/4 of the old basic injection amount Tp in step _P5 . Set and perform smoothing processing. This smoothing process prevents the basic injection amount Tp from changing suddenly. That is, during transient operation, the amount of air actually taken into each cylinder of the engine 1 is:
The intake air amount Qa detected by the air flow meter 6 is not the same as the intake air amount Qa detected by the air flow meter 6, but increases by the amount of air required to change the pressure for the volume of the intake pipe 2. The intake air amount Qa detected by the air flow meter 6 increases with acceleration and decreases with deceleration. do. Therefore, smoothing processing is performed to suppress fluctuations in the basic injection amount Tp due to the overshoot of the intake air amount Qa. Next, in step _P6 , the maximum basic injection amount TpMAX at the engine speed N is calculated based on the engine speed N, and in step _P7 , the basic injection amount Tp is compared with the maximum basic injection amount TpMAX. In step _P7 , when Tp>TpMAX, the maximum basic injection amount TpMAX is determined in step _P8 .
is adopted as the basic injection amount Tp, and the process proceeds to step _P9 . When Tp≦TpMAX, the process directly proceeds to step _P9 . In this way, the maximum basic injection amount
The reason for setting TpMAX is to limit the basic injection amount Tp to the maximum injection amount TpMAX when the basic injection amount Tp becomes too large despite the smoothing process during transient operation. It should be noted that from step _P1 to step _P8 described above, it functions as a basic injection amount calculation means. In step _P9 , it is determined whether the count value Ct of the counter (displaying the number of program repetitions) built into the control unit 10 has reached 5, that is, whether this main program has been repeated 5 times. , if Ct<5, add 1 to the count value Ct of the counter at step _P10 and proceed to step _P11 , and if Ct=5 at step _P9 , proceed to step P10.
At step _P12 , the count value Ct is reset, and at step _P13 , a transient calculation described later is performed. That is, since this program is executed every 10ms, transient calculation is performed once every 50ms. In step _P11 , various increase correction coefficients COEF are calculated for various known increase corrections such as water temperature increase correction, increase correction after moving and starting, increase correction after idling, and throttle valve full-open increase correction, and in step _P14 , the basic injection amount Tp is calculated. and the amount of transient correction described later.
The added value of Tf (Tp+Tf) is compared with the minimum injection amount Tmin. In step P ₁₄ , if Tp + Tf < Tmin, the minimum injection amount is set as the injection amount Po in step P ₁₅ .
Tmin is adopted, and when Tp+Tf≧Tmin, in step _P16 , the added value (Tp+Tf) of the basic injection amount Tp and the transient correction amount Tf is compared with the maximum injection amount Tmax.
When Tp+Tf≦Tmax in step _P16 , the sum of the basic injection amount Tp and the transient correction amount Tf is adopted as the injection amount To in step _P17 , and Tp+Tf>Tmax is determined.
In this case, the maximum injection amount Tmax is adopted as the injection amount To in step _P18 . In addition, the maximum injection amount above
Tmax is to prevent overriching due to the correction by the transient correction amount Tf during acceleration, and the minimum injection amount Tmin is to prevent over-richness due to the correction by the transient correction amount Tf when accelerating and returning to idle. This prevents the engine from stalling. Then, in step _P19 , a final injection amount Ta is calculated using the following equation, and an injection signal Si having a duty value corresponding to this final injection amount Ta is output to the fuel injection valve 3.

Ta = To × COEF × α + Ts ... (2) However, α: Feedback correction coefficient based on the air-fuel ratio sensor output, Ts: Voltage correction amount that corrects the operation delay of the fuel injector 3 with respect to the injection signal Si. ₁₁ and steps _P14 to _P19 function as final injection amount calculation means.

Next, the transient calculation in step _P13 above is
This will be explained based on the flowchart of the transient calculation subroutine shown in FIG. In addition, in FIG. 4, P ₁₀₁ to _{P 106} indicate each step of the flow.

First, in step P ₁₀₁ , a new F value is calculated based on the operating state at the time of the current transient calculation, and in step P ₁₀₂ , this new F value is compared with the new F value (old F value) from the previous time the transient calculation was performed. Difference (amount of change) dF (dF=
New F value - old F value) is calculated. This new F value is calculated based on numerical values set in advance for each driving state of the vehicle, and this calculation will be described later. Therefore, the amount of change dF indicates the rate of change in the operating state each time the transient calculation is executed. In step _P103 , the new F value is set as the old F value. In steps P ₁₀₁ to P ₁₀₃ , the amount of change per predetermined period in the predetermined values assigned to at least three parameters, the warm-up signal, the load signal, and the rotation signal, among the detection signals of the operating state detection means 9 is determined. It functions as a change amount calculating means for calculating . Next, in step _P104 , the transient correction amount Tf
is obtained by adding the change amount dF to the transient correction amount Tf at the previous execution, and step _P104 functions as a transient correction coefficient calculation means. Then, in step _P105 , a damping coefficient Gk that determines the attenuation ratio of the transient correction amount Tf is calculated, and in step _P106 , the transient correction amount Tf obtained in step _P104 is multiplied by the damping coefficient Gk to determine the transient correction amount. Tf
is being calculated. The damping coefficient Gk is calculated based on the transient correction amount Tf and the operating state, and this calculation will be described later. Note that the step _P105 functions as a damping coefficient calculation means, and the step _P106 functions as a damping correction means for attenuating the transient correction amount Tf based on the damping correction coefficient Gk.

The calculation of the new F value in step _P101 is performed in 5 steps.
The explanation will be based on the flowchart shown in the figure. Note that P ₂₀₁ to _{P 214} in FIG. 5 indicate each step of the flow.

In step P ₂₀₁ , set the cooling water temperature Tw to 80
℃, when Tw≧80℃, the step
At _P202 , a numerical value FH previously written in the ROM 12 in the form of a data table is looked up using the engine speed N and the basic injection amount Tp as parameters, as shown in FIG. 6, for example. numerical value
FH indicates the F value after warming up the engine, and this value
FH is adopted as the new F value in step _P203 . When Tw＜80℃ at step P ₂₀₁ , step
In P ₂₀₄ , the water temperature Tw is compared with 40℃, and when Tw≧40℃, that is, when the water temperature Tw is between 80℃ and 40℃, in step P ₂₀₅ , as in step P ₂₀₂ , the numerical value FH is set. Then, in step _P206 , the engine speed N and basic injection amount Tp are used as parameters, and as shown in FIG.
Look up the numerical value FC1 written in.
The numerical value FC1 indicates the F value when the cooling water temperature Tw is 40°C. Then, in step _P207 , a new F value is calculated by interpolation according to the following equation.

New F value = FC1 - (FC1 - FH) × (Tw - 40) / 40 ... (3) In step P ₂₀₄ , when Tw < 40℃,
In step P ₂₀₈ , the water temperature Tw is compared with 0℃, and Tw≧
When the temperature is 0°C, that is, when the water temperature Tw is between 40°C and 0°C, step P ₂₀₉ is executed.
Similarly to P ₂₀₆ , the numerical value FC1 is looked up, and further, in step P ₂₁₀ , the numerical value previously written in the ROM 12 in the form of a data table is retrieved using the engine speed N and the basic injection amount Tp as parameters.
Look up FC2. This numerical value FC2 indicates the F value when the cooling water temperature Tw is 0° C., and is given in the same way as the numerical value FC1 shown in FIG. 7, but is given as a larger value than the numerical value FC1. And step P ₂₁₁
The new F value is calculated by interpolation using the following formula.

New F value = FC2 - (FC2 - FC1) × (Tw / 40) ... (4) In step P ₂₀₈ , when Tw < 0℃,
In step P ₂₁₂ , as in step P ₂₁₀ , the number FC2
In step _P213 , a numerical value FC3 written in advance in the ROM 12 in the form of a data table is looked up using the engine speed N and the basic injection amount Tp as parameters. this number
FC3 indicates the F value when the cooling water temperature Tw is -20℃,
It is given as a value larger than the numerical value FC2. Then, in step _P214 , a new F value is calculated by interpolation using the following equation.

New F value = FC3 - (FC3 - FC2) × (Tw + 20) / 20 ... (5) The new F value is the operating condition, that is, engine speed N, cooling water temperature Tw, and basic injection amount.
Detailed settings are made according to Tp. Therefore, the transient correction amount Tf is carefully designed in response to the operating state and changes in the operating state, and the fuel injection amount is corrected to an injection amount appropriate for the transient operating state. As a result, fluctuations in the air-fuel ratio at the initial stage of transient operation can be controlled to be small.

Next, the calculation of the damping coefficient Gk in step _P105 of the flowchart shown in FIG. 4 will be explained based on the flowchart shown in FIG. In addition, P ₃₀₁ in Figure 8
~P ₃₁₄ shows each step of the flow.

In step P ₃₀₁ , compare the cooling water temperature Tw with 80℃,
When Tw≧80°C, in step _P302 , the engine speed N and the transient correction amount Tf are used as parameters,
For example, as shown in Figure 9, numerical values are written in advance in the ROM 12 in the form of a data table.
Look up GH. This numerical value GH indicates the attenuation rate of the transient correction amount Tf after engine warm-up,
At step _P103 , the damping coefficient GK is calculated using the following equation.

GK=1−GH...(6) When Tw＜80℃ at step _P301 , step
In P ₃₀₄ , the water temperature Tw is compared with 40°C, and when Tw≧40°C, that is, when the water temperature Tw is between 80°C and 40°C, the attenuation rate GH is determined in step P ₃₀₅ , as in step P ₃₀₂ . Further, in step _P306 , the engine speed N and the transient correction amount Tf are used as parameters, and the data is stored in the ROM 12 in advance in the form of a data table, for example, as shown in FIG.
Look up the attenuation factor GC1 written in. This attenuation rate GC1 indicates the attenuation rate when the cooling water temperature Tw is 40°C. And step P ₃₀₇
Then, calculate the low damping coefficient GK by interpolation using the following formula.

GK=1-{GC1+(GH-GC1)×(Tw-40)/
40} ...(7) In step P ₃₀₄ , when Tw<40℃,
In step P ₃₀₈ , the water temperature Tw is compared with 0℃, and Tw≧
When the temperature is 0°C, that is, when the water temperature Tw is between 40°C and 0°C, step P ₃₀₉ is executed.
Similarly to P ₃₀₆ , the damping factor GC1 is looked up, and further, in step P ₃₁₀ , the damping factor written in advance in the ROM 12 in the form of a data table is retrieved using the engine speed N and the transient correction amount Tf as parameters.
Look up GC2. This attenuation rate GC2 indicates the attenuation rate when the cooling water temperature Tw is 0°C, and the 10th
It is given in the same way as the damping rate GC1 shown in the figure, but it is given as a smaller value than the damping rate GC1 for the same engine speed N and the same transient correction amount Tf. Then, in step _P311 , the damping coefficient GK is calculated by interpolation using the following equation.

GK=1-{GC+(GC-GC2)×(Tw/40)}
...(8) In step P ₃₀₈ , when Tw<0℃,
In step P ₃₁₂ , as in step P ₃₁₀ , the damping factor
GC2 is looked up, and at step _P313 , the attenuation factor GC3, which has been written in advance in the ROM 12 in the form of a data table, is looked up using the engine speed N and the transient correction amount Tf as parameters. This attenuation rate GC3 indicates the attenuation rate when the cooling water temperature Tw is -20°C, and is given as a smaller value than the attenuation rate GC2. Then, in step _P314 , the damping coefficient GK is calculated by interpolation using the following equation.

GK=1-{GC3+(GC2-GC3)×(Tw+20)/20}...
(9) In this way, the damping coefficient GK that determines the attenuation rate of the transient correction amount Tf is precisely determined in accordance with the transient correction amount Tf and the operating state. Therefore,
The air-fuel ratio can be quickly controlled to the target air-fuel ratio while preventing overshoot due to excessive correction of fluctuations in the air-fuel ratio at the initial stage of transient operation.

As mentioned above, it is possible to quickly correct the fuel injection amount to the optimal injection amount during transient operation, suppress fluctuations in the air-fuel ratio at the beginning of transient operation, and quickly bring the air-fuel ratio to the target air-fuel ratio. Since it can be controlled, it is possible to prevent the occurrence of so-called breathing problems, and it is possible to improve driving performance during transient operation. Additionally, since the range of fluctuation in the air-fuel ratio at the initial stage of transient operation can be reduced, the air-fuel ratio can be set to a leaner air-fuel ratio than before even during warm-up operation, making it possible to further reduce fuel consumption. .

This situation will be explained based on FIG. 11. When the accelerator pedal is depressed and the state shifts to acceleration, if the above-mentioned transient correction is not performed, the first
As shown in FIG. 1b, the air-fuel ratio fluctuates greatly and it takes a long time to control the air-fuel ratio to the target air-fuel ratio. In FIG. 11b, the broken line indicates the case of a D-Jetronic system engine that calculates the intake air amount based on the intake pipe pressure and engine speed to calculate the fuel injection amount, and the solid line indicates the case of this embodiment. , detects the intake air amount with an air flow meter and calculates the fuel injection amount. This shows the case of an L-Jetronic type engine. Therefore, as shown in FIG. 11c, the linear correction shown by the broken line explained in the conventional example, the two-step correction shown by the dashed-dotted line, and the transient correction of this embodiment shown by the solid line are applied to the L-Jetrnic engine. As shown in Figure 11d, when linear correction is performed (dashed line) and when two-step correction is performed (dotted-dash line), the air-fuel ratio changes at the beginning of acceleration (initial transient operation). is large, and even after that, damped oscillations are repeated due to overshoot, and the target air-fuel ratio is controlled. However, in the case of this example (solid line), fluctuations in the air-fuel ratio at the beginning of acceleration (in the beginning of transient operation) are suppressed to a small level. In addition, the air-fuel ratio after the change is quickly controlled to the target air-fuel ratio. Note that FIG. 11a shows changes in intake pipe pressure, and FIG. 11e shows elapsed time from the start of acceleration.

In addition, when the engine speed is changed, comparing the conventional two-step correction and the transient correction of this embodiment, the 12th
The result is as shown in Figure b. That is, in the conventional case, there is a large variation in the controlled air-fuel ratio between when the engine rotation is high and when the engine rotation is low, and the range of variation is large as shown by diagonal lines.
On the other hand, when performing the transient correction of this embodiment, as described above, the transient correction amount Tf and damping coefficient GK are calculated in accordance with the engine speed, so changes in the engine speed Regardless of the situation, stable air-fuel ratio control can be performed at all times, improving driving performance and fuel efficiency. Note that FIG. 12a shows the change in intake pipe pressure, and FIG. 12c shows the elapsed time from the start of acceleration.

In the above embodiments, the case of the L-Jetronic system has been described, but it can be similarly applied to the D-Jetronic system, and can also be applied during deceleration.

(Effects of the Invention) According to the present invention, fluctuations in the air-fuel ratio during transient operation can be suppressed to a small value in any operating state, and the air-fuel ratio can be quickly controlled to the target air-fuel ratio. It is possible to improve driving performance and further reduce fuel consumption.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of the present invention. FIG. 2 to FIG. 12 are diagrams showing one embodiment of the present invention,
Figure 2 is a schematic diagram of its configuration, Figure 3 is a flowchart of the main program for calculating the fuel injection amount,
Figure 4 is a flowchart of the subroutine for calculating the transient correction coefficient, Figure 5 is a flowchart of the subroutine for calculating the new F value, and Figures 6 and 7 are the flowchart of the subroutine for calculating the new F value. Figure 8 is a flowchart of the subroutine for calculating the damping coefficient; Figures 9 and 10 are diagrams showing the data table of the damping coefficient for calculating the damping coefficient; Figure 11 is the operation. In the explanatory diagram, the 11th
Figure a is the intake pipe pressure, Figure 11b is the air-fuel ratio without transient correction, Figure 11c is the correction amount, and Figure 11c is the amount of correction.
FIG. 11(d) shows the air-fuel ratio after transient correction, and FIG. 11(e) shows the elapsed time of the transient operation. FIG. 12 is an explanatory diagram of the effect when the engine speed is changed. FIG. 12a shows the intake pipe pressure, FIG. 12b shows the air-fuel ratio, and FIG. 12c shows the elapsed time of the transient operation. 3...Fuel injection valve (fuel injection means), 9...Operating state detection means, 10...Control unit (basic injection amount calculation means, change amount calculation means, transient correction amount calculation means, damping coefficient calculation means, damping correction) means, final injection amount calculation means).

Claims (1)

[Scope of Claims] 1 (a) Operating state detection means for detecting the operating state of the vehicle; (b) Basic injection amount calculation means for calculating the basic injection amount of fuel corresponding to the target air-fuel ratio based on the operating state. and (c) calculating the amount by which a predetermined value assigned to at least three parameters, a warm-up signal, a load signal, and a rotation signal among the detection signals of the operating state detection means, changes per predetermined period. (d) Transient correction amount calculation means for calculating a transient correction amount by adding the change amount at predetermined intervals; (e) Calculating the transient correction amount based on the transient correction amount and the operating state. (f) attenuation correction means for attenuating the transient correction amount based on the attenuation coefficient; (g) attenuation correction means for attenuating the transient correction amount based on the attenuation coefficient; An air-fuel ratio control characterized by comprising: final injection amount calculation means for correcting based on the correction amount and calculating the final injection amount; and (h) fuel injection means for supplying the final injection amount of fuel to the engine. Device.