JPH0227134A - Device for controlling air-fuel ratio of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the converging degree of learning by reducingly setting the weighing with respect to the previous learning correction factor in a weight mean operation by a learning correction factor setting means at the time of high load as compared to at the time of low load and reducingly correcting the weighing in an initial stage steady operating condition after a transient operation. CONSTITUTION:A fuel injection quantity operating means H operates a fuel injection quantity based on a fundamental fuel injection quantity, a feedback correction factor and a learning correction factor which are set by each setting means B, F, G. A fuel injecting means I is operated by a driving pulse signal corresponding to the fuel injection quantity. A weighing variably setting means J reducingly sets the weighing for the previous learning correction factor in the operation of weight mean by the learning correction factor setting means G at the time of low load as compared to at the time of high load, and carrying out weighing according to a newly set feedback correction factor at the time of high load to increase learning speed. Also, in an initial-stage steady operating condition after a transient operation, the weighing is reducingly corrected, to avoid the effect of variation in air-fuel ratio at the time of the transient operation.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an air-fuel ratio control device for an internal combustion engine having an electronically controlled fuel injection device. The present invention relates to an air-fuel ratio control device configured to feedback control the fuel injection amount based on the detection result.

<Prior Art> An electronically controlled fuel injection system for an internal combustion engine is equipped with an electromagnetic fuel injection valve in the engine intake system, and is configured to control engine operating state parameters related to the amount of air taken into the engine (e.g. engine intake air flow rate and engine Set the basic fuel injection amount based on the
The final fuel injection amount is obtained by multiplying this by a feedback correction coefficient for air-fuel ratio feedback control, and the drive pulse signal in the pulse corresponding to this fuel injection amount is applied at a predetermined timing synchronized with the engine rotation. By outputting to the fuel injection valve, the fuel injection amount is controlled and the optimal amount of fuel is injected and supplied to the engine.

Regarding air-fuel ratio feedbank control, an oxygen sensor is installed in the engine exhaust system, and the air-fuel ratio of the engine intake air-fuel mixture, which is closely related to the oxygen concentration in the engine exhaust, is detected through the oxygen concentration in the engine exhaust detected by the oxygen sensor. , compares the detected air-fuel ratio with the stoichiometric air-fuel ratio, which is the target air-fuel ratio, determines whether it is rich or lean, and changes the feedback correction coefficient based on this to feedback-control the air-fuel ratio to the stoichiometric air-fuel ratio. There is.

Specifically, as shown in Figure 7, the output voltage of the oxygen sensor is compared with the slice level voltage corresponding to the stoichiometric air-fuel ratio, which is the target air-fuel ratio, and when the output voltage is large, it is rich, and when the output voltage is small, it is rich. Based on this determination result, a feedback correction coefficient is set and controlled by proportional-integral (PI) control. For example, when the engine is rich (lean), the feedback correction coefficient is first decreased (increased) by a proportional constant of 2 minutes, and then decreased (increased) by an integral constant of 1 minute in time synchronization or rotation synchronization to bring the air-fuel ratio to the theoretical value. Control to bring the air-fuel ratio close to
(Refer to the publication number, etc.)

<Problems to be Solved by the Invention> By the way, the responsiveness of oxygen sensors is generally poor, so when the output voltage of the oxygen sensor crosses the slice level voltage, the actual air-fuel ratio tends to be richer or leaner than the target air-fuel ratio. A lot has changed. As a result, the amount of overshoot and undershoot becomes large, resulting in large fluctuations in the air-fuel ratio and poor convergence to the target air-fuel ratio (as a result, drivability deteriorates due to surge torque and There is a risk that the amount of emissions of Co, HC, NOx, etc. will increase.

In order to solve such problems, the applicant first calculated the deviation of the detected air-fuel ratio (oxygen sensor output voltage) from the target air-fuel ratio (slice level voltage) and the detected air-fuel ratio (oxygen sensor output voltage). ) proposed an air-fuel ratio control device configured to predict the trend of the air-fuel ratio and set a feedback correction coefficient based on the differential value of
(See issue 07).

By the way, in order to match the base air-fuel ratio obtained by the fuel injection amount calculated without the feedback correction coefficient to the target air-fuel ratio, the learning correction coefficient is determined by learning the deviation from the reference value of the feedback correction coefficient. It has been conventionally practiced to correct the fuel injection amount using a correction coefficient.

However, when proportional/integral control of the feedback correction coefficient is performed only by rich/lean judgment for the target air-fuel ratio, there is no problem with the above conventional learning correction coefficient setting, but as mentioned above, the deviation and differential value of the air-fuel ratio If the configuration is such that the feedback correction coefficient is set based on As a result, the deviation of the feedback correction coefficient from the reference value varies, and as shown in FIG. 8, there is a problem that the convergence of the learning correction coefficient is poor.

The present invention has been made in view of the above problems, and is configured to set a feedback correction coefficient based on the deviation of the air-fuel ratio from the target air-fuel ratio and the differential value of the change in the air-fuel ratio. It is an object of the present invention to improve the learning convergence degree even in an operating state where the learning frequency is low without being affected by air-fuel ratio fluctuations during transient operation.

Means for Solving the Problems> Therefore, in the present invention, as shown in FIG.
An air-fuel ratio control device for an internal combustion engine includes the means.

(8) Engine operating state detection means for detecting the engine operating state (B) Basic fuel injection amount setting means for setting the basic fuel injection amount based on the engine operating state detected by the engine operating state detection means (C) Engine exhaust Air-fuel ratio detection means (D) that detects the air-fuel ratio of the air-fuel mixture taken into the engine by detecting the components; Deviation calculation means (E) that calculates the deviation of the detected air-fuel ratio from the target air-fuel ratio; Differential value calculating means (F) for calculating a differential value of the air-fuel ratio; Feedback correction coefficient setting means (G) for setting a feedback correction coefficient for feedback correcting the basic fuel injection amount based on the deviation and the differential value. learning correction coefficient setting means (H) for setting a new learning correction coefficient by weighted averaging of the feedback correction coefficient set by the feedback correction coefficient setting means and the previous learning correction coefficient; set by the basic fuel injection amount setting means; fuel injection amount calculation means (I) calculation for calculating the fuel injection amount based on the basic fuel injection amount, the feedback correction coefficient set by the feedback correction coefficient setting means, and the learning correction coefficient set by the learning correction coefficient setting means; In addition to the above-mentioned configuration, the learning correction coefficient setting means G performs the previous learning correction in the weighted average calculation of the learning correction coefficient setting means G. A variable weight setting means J is provided to set the weight for the coefficient to be reduced at high load compared to low load, and to correct the weight to decrease in the initial steady state of operation after transient operation.

<Operation> Based on the engine operating state detected by the engine operating state detecting means A, the basic fuel injection amount setting means B sets a basic fuel injection amount that substantially corresponds to the target air-fuel ratio.

On the other hand, the air-fuel ratio is detected by the air-fuel ratio detection means C, the deviation calculation means calculates the deviation of the air-fuel ratio from the target air-fuel ratio, and the differential value calculation means E calculates the differential value (change rate) of the detected air-fuel ratio. Calculate.

Since the trend of the air-fuel ratio can be predicted based on these deviations and the differential value, the feedback correction coefficient setting means F sets the feedback correction coefficient based on these deviations and the differential value.

The learning correction coefficient setting means G takes a weighted average of the feedback correction coefficient set by the feedback correction coefficient setting means F and the previous learning correction coefficient, and sets a new learning correction coefficient.

The fuel injection amount calculation means H calculates the fuel injection amount based on the basic fuel injection amount, feedback correction coefficient, and learning correction coefficient set by each of the setting means BF and G. Then, the fuel injection means (2) is activated by a drive pulse signal corresponding to this fuel injection amount.

Further, the variable weight setting means J sets the weight for the previous learning correction coefficient in the weighted average calculation of the learning correction coefficient setting means G to be reduced at high loads compared to low loads, and sets a new weight at high loads. The learning speed is accelerated by weighting using the feedback correction coefficient, and the weighting is corrected to decrease in the initial steady state of operation after the transient operation to avoid the influence of air-fuel ratio fluctuations during the transient operation.

<Example> The present invention will be explained in detail below.

In FIG. 2, an engine 1 is connected to an air cleaner 2 through an intake duct 3. Air is taken in via the throttle valve 4 and the intake manifold 5. A branch portion of the intake manifold 5 is provided with a fuel injection valve 6 as a fuel injection means for each cylinder. The fuel injection valve 6 is an electromagnetic fuel injection valve that opens when the solenoid is energized and closes when the energization is stopped. Fuel is injected and supplied by a pump and adjusted to a predetermined pressure by a pressure regulator.

Although this example is a multi-point injection system, it may also be a single-point injection system in which a single fuel injection valve is provided in common to all cylinders, such as upstream of the throttle valve 4.

An ignition plug 7 is provided in the combustion chamber of the engine 1, which ignites a spark to ignite and burn the air-fuel mixture.

From engine 1, exhaust manifold 8° exhaust duct 9. Exhaust gas is discharged via a three-way catalyst 10 and a muffler 11. The three-way catalyst 10 is an exhaust purification device that oxidizes Co and HC in the exhaust components and reduces NOx to convert it into other harmless substances, and its conversion efficiency is closely related to the air-fuel ratio of the intake air-fuel mixture. There is a relationship.

The control unit 12 includes a CPU, ROMRAM,
It is equipped with a microcomputer including an A/D converter and a human input interface, receives input signals from various sensors, performs arithmetic processing as described below, and controls the operation of the fuel injection valve 6.

As the various sensors described above, a hot wire type air flow meter 13 is provided in the intake duct 3, and outputs a voltage signal according to the intake air flow rate Q.

Further, a crank angle sensor 14 is provided, and in the case of a four-cylinder engine, outputs a reference signal for every 180 degrees of crank angle and a unit signal for every 1 degree or 2 degrees of crank angle. Here, the engine rotational speed N can be calculated by measuring the period of the reference signal or the number of unit signals generated within a predetermined time.

Further, a water temperature sensor 15 is provided in the water jacket of the engine 1 to detect the cooling water temperature Tw.

These air flow meters 13. The crank angle sensor 14 and the like correspond to the engine operating state detection means.

Further, an oxygen sensor 16 as an air-fuel pressure detecting means is provided at a gathering part of the exhaust manifold 8, and detects the air-fuel ratio of the intake air-fuel mixture via the oxygen concentration in the exhaust gas.

The oxygen sensor 16 is made of, for example, a zirconia (ZrOz) tube, which is an oxygen ion conductor used as a solid electrolyte for concentration batteries, and has a cylindrical shape with a bottom and a closed end facing the exhaust gas. It generates an electromotive force depending on the ratio of oxygen concentrations.

A platinum catalyst layer is provided on the outer surface of the zirconia tube by vapor-depositing platinum that functions as an oxidation catalyst. By combining unburned components such as CO and reducing the outside oxygen concentration to almost zero, the ratio of inside and outside oxygen concentrations is increased and a large electromotive force is generated.However, in a lean mixture, the difference in oxygen concentration is small and almost no voltage is generated. This is a well-known method in which the electromotive force does not occur and the electromotive force suddenly changes near the stoichiometric air-fuel ratio as shown in FIG.

Furthermore, the throttle valve 4 has an opening degree TV of the throttle valve 4.
A throttle sensor 17 is attached to detect O using a potentiometer.

Here, the CPU of the microcomputer built into the control unit 12 performs arithmetic processing according to the program on the ROM shown as the flowcharts of FIGS. 4 to 6, and controls fuel injection. In this embodiment, the control unit 12 includes basic fuel injection amount setting means, fuel injection amount calculation means, and feedback correction coefficient setting means.

The functions of the deviation calculating means, the differential value calculating means, and the learning correction coefficient setting means as variable setting means are provided in software as shown in the flowchart.

The routine shown in the flowchart of FIG. 4 is an air-fuel ratio feedback control routine, which is executed at predetermined minute intervals (for example, every 10 m5).

First, in step 1, the output voltage V from the oxygen sensor 16
oz is input, and in the next step 2, the output voltage ■ is input.

The differential value ΔE of 2 is calculated based on the following formula.

Here, VO2-", VO2-", and VO2-lo are the output voltages V of the oxygen sensor 16 before 30 m5, before 20 m5, and before 10 m5, respectively. It is 2. In this way, the output voltage (■) was determined at three different gate times: 30m5, 20+ns, and 10m5. By averaging the amount of change (differential value ΔE) of 2 to finally obtain the differential value E, even if the output voltage V oZ is disturbed due to the influence of noise or fuel distribution, the disturbance will be the differential value. This can avoid a large influence on the value ΔE.

Then, in step 3, it is determined whether the differential value ΔE calculated in step 2 is a positive value or a negative value. If it is determined that 2 indicates an increasing tendency, the process proceeds to step 4, where it is determined whether the flag is positive or negative. The first time the differential value ΔE is determined to be positive, the flag is negative as will be described later, so the process goes to step 5 and calculates the minimum value ■ according to the weighted average calculation of the formula below. Set 2MIN.

Next time, even if E is positive for the differential value, jump to step 5 and get the minimum value ■. Prevent the calculation of 2MIN from being performed. That is, the output voltage ■. 2 reverses from a downward trend to an upward trend, and when the differential value ΔE is determined to be positive for the first time, the output voltage V is reached. 2. Determine that it is the peak of the valley of change and set it to the minimum value V. 2MIN is calculated.

In this way, when the differential value ΔE is reversed to negative from the state in which the weighted average calculation in step 5 is performed and the flag is set to positive, that is, the minimum value V. When 2 is at its peak, from an upward trend to a downward trend, the process proceeds from step 3 to step 7, and if the flag is determined to be positive, the process proceeds to step 8. In step 8, the weighted average of the following formula is calculated. Maximum value V according to the calculation. , MAX are set, and in the next step 9, the flag is set to negative.

If the differential value ΔE continues to be negative, it is determined in step 7 that the flag is negative, and step 8
Maximum value at■. ! No MAX operation is performed.

Further, when the differential value ΔE is reversed from negative to positive in this way, step 3 goes to step 4, and further,
By proceeding from step 4 to step 5, the output voltage ■.

The peak of the valley of 2 is detected and the minimum value ■. An operation to obtain 2 is performed.

In this way, the output voltage ■ by weighted average calculation. Maximum value of 2■. ZMAX and minimum value■. If we calculate 2MIN, the output voltage ■. Even if a disturbance unrelated to the air-fuel ratio occurs in 2, the maximum value of this disturbance is ■. ZMAX and minimum value■
. It can be avoided that the calculation of 2MIN is affected.

Furthermore, the output voltage of the oxygen sensor 16 is ■. 2. Since the changes in the characteristics are gradual, the maximum value ■ is obtained by calculating the weighted average every minute time as described above. ZMAX and minimum value■. 2 Maximum value V, 2 MAX and minimum value ■ only at the initial stage of restart without determining the old N. 2MIN is determined, and while the engine is running, the average value SL is set based on the value determined at the initial stage of startup, and the maximum value SL is set each time the engine is stopped. ZMAX and minimum value■. , MIN
Alternatively, the maximum value V may be cleared at the initial stage of startup as described above. 2MAχ and minimum value ■. Weighted average calculation may also be performed when calculating 2MIN.

Then, in step 10, the output voltage of the oxygen sensor 16 is determined as described above. Maximum value of 2■. ZMAX and minimum value■. Find the simple average value SL with 2MIN.

Therefore, the average value SL found here is
6 output voltage V. 2.Characteristics change and compared to the initial value, for example, the maximum value■. When ZMAX decreases, it changes according to the change.

In the next step 11, the maximum value ■ obtained in each initial state of the engine is determined. ZMAX, average value SL, and current maximum value ■. Based on ZMAX and the average value SL, a correction coefficient Rr a ti on the air-fuel ratio rich side of the differential value ΔE of the output of the oxygen sensor 16. 7 is calculated based on the following formula.

The minimum value V obtained for each. 2MIN and average value SL,
Current minimum value■. Based on 2MIN and the average value SL, the oxygen sensor 16 output voltage ■. Correction coefficient L rati of the differential value ΔE of 2 on the lean side of the air-fuel ratio. Calculate ゎ based on the following formula.

In this way, the output voltage V of the oxygen sensor 16. If the differential value ΔE is corrected based on the change from the initial state of the engine in the two characteristics, for example, the output voltage will change from the initial state to ■. Even if the slope (change speed) with respect to the air-fuel ratio change in No. 2 becomes slow, the degree of convergence to the target air-fuel ratio can be determined with high accuracy from the differential value ΔE.

Then, in step 13, the average value SL calculated in step 10 and the output voltage (■) of the oxygen sensor 16 read in step 1 are calculated. 2 to determine whether the current air-fuel ratio of the intake air-fuel mixture is richer or leaner than the target air-fuel ratio defined by the average value SL.

In step 13, if it is determined that VO2>SL and the air-fuel ratio is rich with respect to the target air-fuel ratio, the process proceeds to step 14, where the current output voltage ■ is determined. The deviation E (←V, 2-3L) between 2 and the average value SL is calculated. In the next step 15, as shown in the formula below, the ratio of the actual deviation E to the current maximum rich-side deviation is determined, and this ratio is set as the R-fuzzy quantity U representing the rich-side deviation with respect to the target air-fuel ratio. .

R-fuzzy quantity U← (V, 2MAχ -SL) That is, the R-fuzzy quantity U is 1 when the deviation E is maximum, and the rich side deviation quantity is small (it is indeed a value approaching zero).

Here, the average (JS
L is the current maximum value V in step 10 described above. 2MAX
and the minimum value■. Since the calculation is based on zMIN, the oxygen sensor 6 deteriorates and its output voltage ■. 2. Even if the overall characteristics decrease or the rate of change near the stoichiometric air-fuel ratio changes, the rich/lean determination is performed correctly, and the R facy amount U approximately correctly indicates the air-fuel ratio enrichment tendency. become.

That is, the maximum value VO2 in the initial state of the oxygen sensor 16
MAX and minimum value■. If the average SL with 2 MIN is used as the slice level voltage and the slice level voltage is used to determine the deviation E even after the oxygen sensor 16 has deteriorated, the output voltage (2) will be obtained, for example. 2 has decreased overall, it will be judged as lean in the original rich state, and at 17A during the Su/Sochi judgment, it will be erroneously judged as if the gap in the air-fuel ratio on the rich side has decreased, and the target air-fuel ratio ( The air-fuel ratio will be controlled more than the stoichiometric air-fuel ratio.

However, in this embodiment, the output voltage of the oxygen sensor 16 is . 2 Changes in characteristics, namely output voltage■. Maximum value of □■.

2MAX and minimum value■. , MIN, and calculate the average value SL as the rich/lean judgment level and the R-fuzzy quantity U.
Since it is used as the standard for calculation, it is possible to approximately accurately capture the tendency of the leakage, and as a result, even if the output voltage of the oxygen sensor 16 is □ Even if there is a change in characteristics, feedback control can be performed for a long time to converge around the target air-fuel ratio.

In addition, in the next step 16, the correction coefficient Rr a calculated in step 11 is added to the differential value ΔE calculated in step 2.
Ti. . is multiplied and corrected to set the final differential value ΔE.

Here, the maximum value ■ than the initial state. When 2MAX-3L becomes smaller, the output voltage becomes ■. 2 is in a state where the range of change is smaller, the differential value ΔE is corrected to be larger than in the initial state to cope with the decrease in the range of change, and conversely, the maximum value ∆ is smaller than that in the initial state. 2MAX-S
When L is large, that is, when the change 1 in the output voltage VO2 becomes large, the differential value ΔE is corrected to decrease so that it appears to be changing slowly, in order to cope with the increase in the range of change.

When it is determined that it is rich in step 13, the above-mentioned processing is performed, but in step 13, ■. 2. Similar processing is also performed when it is determined to be SL and the air-fuel ratio is lean.

That is, if it is determined that the air-fuel ratio is lean, step 1
Proceed to step 7 and calculate the output voltage ■ from the average value SL. 2 to find the deviation E, while in step 18 step 15
In the same way, L represents the deviation on the lean side from the target air-fuel ratio.
Compute the fuzzy quantity U.

In addition, in the next step 19, the correction coefficient L ratio calculated in step 12 is used to
Perform the correction calculation for the differential value ΔE in the same manner as in step 6 to obtain the final value ΔE.
”, and corresponds to changes occurring due to deterioration of the oxygen sensor 16.

Meanwhile, ■ in step 13. If it is Nasaki SL and it is determined that the current air-fuel ratio is approximately the target air-fuel ratio, proceed to step 20 and set the differential value ΔE calculated in step 2 as the final value as E'', and In the next step 21, the deviation E is set to zero.

Average value SL and output voltage V. Based on the air-fuel ratio determination by comparison with 2, the fuzzy quantity U and the differential value ΔE' are
Once set, the process proceeds to the next step 22, where the feedback correction coefficient α is set.

In step 22, first, the differential value ΔE' is calculated from the maximum positive value PB, the positive intermediate value PM, the positive minimum value PS Z, the negative minimum (iNs, the negative intermediate value NM, and the negative maximum value NB). While converting to 7-level values, step 15 or step 1
7 in the range of 1 to 0 to 1 for the fuzzy quantity U obtained in 9.
Based on these step values (degree of convergence and deviation of air-fuel ratio), set the step value of the feedback correction coefficient α from a preset map, and calculate the current feedback correction coefficient α from this step value. Set.

Here, for example, when the step value is zero, the feedback correction coefficient α is set to 1 (reference value), and the feedback correction coefficient α is set by increasing or subtracting from 1 according to the positive/negative and magnitude of the step value.

In the next step 23, a new learning correction coefficient KBLRC is set by weighting the feedback correction coefficient α obtained in step 22 this time and the previous learning correction coefficient KBLRC according to the following formula.

The learning correction coefficient KBLRC is used to calculate the basic fuel injection amount Tp by using the learning correction coefficient KB when calculating the fuel injection amount Ti.
This is to make the base air-fuel ratio obtained by the fuel injection amount Ti, which is corrected by LRC and calculated without the feedback correction coefficient α, coincide with the target air-fuel ratio, but the reference value of the feedback correction coefficient α ( 1) Instead of learning the deviation from 1), the learning correction coefficient KBL is determined by the weighted average of the previous learning correction coefficient KBLRC and the newly set feedback correction coefficient α as described above.
With a configuration that calculates RC, it is possible to improve the convergence of the learning correction coefficient KBLRC.

That is, as already explained in the above steps, in this embodiment, the feedback correction coefficient α is set from the air-fuel ratio deviation E and the differential value ΔE, and the oxygen sensor 16
is the output voltage ■ around the stoichiometric air-fuel ratio, which is the target air-fuel ratio. 2 is a characteristic that changes suddenly, the feedback correction coefficient α will fluctuate minutely when the air-fuel ratio is reversed, and the deviation of the feedback correction coefficient α from the reference value will vary. With the configuration in which the correction coefficient KBLRC is set, it is possible to prevent the learning correction coefficient KBLRC from being influenced by small fluctuations in the feedback correction coefficient α. Therefore, in the case of this embodiment, the convergence of the learning correction coefficient KBLRC increases as shown in FIG. 8, and accordingly, the feedback correction coefficient α also becomes stable with good convergence.

Further, in step 24, the output voltage ■ inputted this time is used for calculating the differential value ΔE next time. 2 to 10m
Data V from 5 days ago. Set as 2-10, this time 10m5
Previous data V. Data from 20m5 ago is treated as 2-10■. Set it as 2-20, and furthermore, this time 20
Data V before m5. 2-20 is treated as 30
Data before m5■. Set as 2-30.

The weight constant X in the weighted average formula in step 23 is set according to the routine shown in the flowchart of FIG.

This routine is executed every predetermined minute time (for example, 10 m5), and first, in step 31, the opening degree TVO of the throttle valve 4 detected by the throttle sensor 17 is input, and in the next step 32, the previous input is input. By comparing with the value, the opening change rate Δ per execution cycle of this routine is determined.
Calculate TVO.

Then, in step 33, it is determined whether or not the opening change rate ΔTVO calculated in step 32 exceeds a predetermined value (for example, 1 degree). Proceed to step 34.

In step 34, the weighting is a correction coefficient X rat of a constant
A countdown timer value Tm for setting iQ is set to a predetermined time (for example, 500 m5), and in the next step 35, the correction coefficient X r l t i is set. Let be zero.

On the other hand, if it is determined in step 33 that the opening change rate ΔTVO is less than a predetermined value (for example, 1°) and the engine is in a steady operating state, the process proceeds to step 36, where the timer value T
A new timer value Tm is set by subtracting m by the execution cycle (10 ms) of this routine. Next step 37
Then, in step 36, it is determined whether or not the timer value Tm resulting from the subtraction is less than or equal to zero, and if it is less than zero, the process proceeds to step 38 and the timer value Tm is set to zero, but if it is determined that it exceeds zero. Sometimes, the process skips step 38 and proceeds to step 39.

In step 39, the correction coefficient X ratio is searched from the map based on the timer value Tm. here,
When the timer value Tm is the predetermined value set in step 34, the correction coefficient The correction coefficient xr□,0 is set to 1 when Tm becomes zero.

Therefore, in a stable steady state of operation, the correction coefficient
rat=. is 1, but when transitioning from such a state to transient operation, the correction coefficient X r a t i. is set to zero and this correction factor X ra ti. The weighting corrected by setting the constant X to zero allows the latest feedback correction coefficient α to be used as the learning correction coefficient KBLRC to speed up the learning speed. Then, when returning from transient operation to steady operation, the influence of the air-fuel ratio (wall flow) fluctuation during transient operation remains, so the correction coefficient X r II is immediately adjusted.
Instead of setting tio to 1 for steady operation, the correction coefficient
By reducing and correcting the data, more weight is given to the latest data.

In the next step 40, weights set for each of a plurality of operating states divided by the basic fuel injection amount Tp and engine speed N, which are set as described later, map the basic value XBASE of the constant In step 41, the correction coefficient χra is added to this basic value xIlA3E.
tio is multiplied and a constant X is set for weighting. The weight set in this manner is such that the constant X is used in the weighted average calculation in step 23 described above.

Here, in the map of basic values XBA and E that are set corresponding to the basic fuel injection amount TP and engine rotational speed N, it is important to set a small value when the learning frequency is low and the load is high. This allows the learning speed to be ensured even in high-load operating conditions where learning frequency is low.

The routine shown in the flowchart of FIG. 6 is a fuel injection amount setting routine that is executed every predetermined minute period (for example, 10 m5). First, in step 51, the intake air flow rate Q detected by the air flow meter 13 is inputted, In the next step 52, the basic fuel injection amount Tp (←KXQ/N; K is a constant) is determined based on the engine rotational speed N detected by the crank angle sensor 14 and the intake air flow rate Q.
Calculate.

In addition to calculating the basic fuel injection amount Tp based on the intake air flow rate Q detected by the air flow meter 13 as described above, the intake pressure PB is calculated instead of the air flow meter 13.
A basic fuel injection amount T is provided based on the intake pressure PB detected by the intake pressure sensor.
Alternatively, p may be calculated.

That is, in step 53, the intake pressure PB detected by the intake pressure sensor is input. In the next step 54, first,
Based on the intake pressure PB, the basic volumetric efficiency K is calculated from the map.
In addition to searching and setting PB, the current PB and N are stored in advance from a map that stores minute correction coefficients KFLAT for each operating state classified by intake pressure PB and engine speed N.
Based on this, the corresponding minute correction coefficient KFLAT is searched and set, and the basic volumetric efficiency KPg is multiplied by the minute correction coefficient KFLAT to determine the volumetric efficiency Q of fresh air. Find 7L.

Then, in the next step 55, the basic fuel injection amount Tp is calculated according to the following formula.

T p'-KcoNX Qcv+, X KTAX P
B Here, K COW is a constant, and KTA is an intake air temperature correction coefficient that is set to increase as the intake air temperature decreases.

As described above, when the basic fuel injection amount Tp is calculated based on the intake air flow rate Q detected by the air flow meter 13 or the intake pressure PB detected by the intake pressure sensor, in the next step 56, this basic fuel injection amount is calculated using the following equation. A final fuel injection amount Ti is calculated by correcting Tp.

Ti+-TpX (α+KBLRC) XC0EF+T
sHere, C0EF is various correction coefficients based on engine operating conditions such as engine cooling water temperature, and Ts is a correction factor based on battery voltage.

A drive pulse signal having a pulse width corresponding to the fuel injection amount Ti calculated as described above is output to the fuel injection valve 6 at a predetermined injection timing, and fuel corresponding to Ti is injected and supplied to the engine 1.

<Effects of the Invention> As explained above, according to the present invention, in a device that sets an air-fuel ratio feedback correction coefficient based on a differential value and a deviation of a detected air-fuel ratio from a target air-fuel ratio, a learning correction coefficient can be quickly set. It is possible to converge to
This has the effect that the degree of learning convergence can be improved even in operating conditions where the learning frequency is low, without being affected by air-fuel ratio fluctuations during transient operation.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of the present invention, Fig. 2 is a system schematic diagram showing an embodiment of the present invention, and Fig. 3 shows the output characteristics of the oxygen sensor as the air-fuel ratio detection means in the same embodiment. 4 to 6 are flowcharts showing the control routine in the above embodiment, FIG. 7 is a time chart for explaining conventional feedback control characteristics, and FIG. 8 is a flowchart showing problems in conventional control and 3 is a time chart for explaining the invention in detail. 1... Engine 6... Fuel injection valve 12... Control unit 13... Air flow meter 1
4...Crank angle sensor 15...Water temperature sensor 1
6...Oxygen sensor patent applicant Japan Electronics Co., Ltd. Agent Patent attorney Fujio Sasashima O

Claims (2)

[Claims] (1) An engine operating state detection means for detecting an engine operating state; a basic fuel injection amount setting means for setting a basic fuel injection amount based on the engine operating state detected by the engine operating state detection means; air-fuel ratio detection means for detecting and thereby detecting the air-fuel ratio of the air-fuel mixture taken into the engine; deviation calculation means for calculating the deviation of the detected air-fuel ratio from a target air-fuel ratio; and differentiation of the detected air-fuel ratio. a differential value calculating means for calculating a value; a feedback correction coefficient setting means for setting a feedback correction coefficient for feedback correcting the basic fuel injection amount based on the deviation and the differential value; and the feedback correction coefficient setting means learning correction coefficient setting means for setting a new learning correction coefficient by weighted averaging of the feedback correction coefficient set in and the previous learning correction coefficient; and the basic fuel injection amount set by the basic fuel injection amount setting means and the fuel injection amount calculation means for calculating the fuel injection amount based on the feedback correction coefficient set by the feedback correction coefficient setting means and the learning correction coefficient set by the learning correction coefficient setting means; An air-fuel ratio control device for an internal combustion engine, comprising: a fuel injection means for injecting and supplying fuel to the engine on and off based on a drive pulse signal; (2) The weighting of the previous learning correction coefficient in the weighted average calculation of the learning correction coefficient setting means is set to be decreased at high load compared to low load, and the weighting is decreased in the initial steady operation state after transient operation. 2. The air-fuel ratio control device for an internal combustion engine according to claim 1, further comprising variable weight setting means.