JPS61272431A - Method of feedback-controlling air-fuel ratio of internal-combustion engine - Google Patents

Abstract

PURPOSE:To enable common use of an electronic control unit, by a method wherein a correction value, applicable to feedback control of an air-fuel ratio, is corrected by means of a correction value responding to a set value fed from a varying voltage generating means. CONSTITUTION:After an output signal from each sensor is corrected to a given voltage level by a level correcting circuit 504, the output signals are orderly fed to an A/D converter 506 through a multiplexer 505. A VPRO regulator 511 comprises a varying voltage circuit, and a voltage, determining a proportional item correcting value, is fed to an A/D converter 506 through a multiplexer 505. A CPU 503 computes the fuel injection time of a fuel injection valve 6 to feed the result to a driving circuit 509 through a data bass 510. This enables the common use of an electronic control unit and decreases a cost.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to an air-fuel ratio feedhack control method for an internal combustion engine, and in particular to a feedback control method that facilitates sharing of an electronic control unit when changing engine specifications. be.

(Technical background of the invention and its problems) The valve opening time of the fuel injection device of an internal combustion engine, especially a gasoline engine, can be determined in immediate response to the output signal level of an exhaust concentration detector, such as an 02 sensor, installed in the exhaust system of the engine. The applicant has previously proposed an air-fuel ratio feedback control method for an internal combustion engine that can improve exhaust gas characteristics and driving performance by accurately controlling the air-fuel ratio to obtain the stoichiometric air-fuel ratio (Patent Application No. (Sho 57-188743).

The air-fuel ratio feedback control method according to this proposal compares the detected voltage value of the 02 sensor with a predetermined reference voltage value, and based on the comparison result, the air-fuel ratio of the air-fuel mixture supplied to the engine is set to the target air-fuel ratio, e.g. When it is determined that the stoichiometric air-fuel ratio is changing only on the rich side or lean side,
Integral term control (one term control) is performed to increase or decrease the 02 feed bank coefficient by a constant value according to the engine speed,
Also, when it is determined that the air-fuel ratio of the mixture has changed from the rich side to the lean side, or from the lean side to the rich side based on the above comparison results, a constant value corresponding to the engine speed is set as in integral term control. This is to control the average air-fuel ratio to match the target air-fuel ratio over the entire feedback control region by performing proportional term control (P-term control) in which the 02 feedback coefficient is increased or decreased at once.

By the way, there are two types of vehicles: vehicles equipped with automatic transmissions (hereinafter referred to as AT vehicles) and vehicles equipped with manual transmissions (hereinafter referred to as MT vehicles).
When compared with MT cars, the average air-fuel ratio (average A/F) is changed to the stoichiometric air-fuel ratio (1
The fuel supply system is set to be leaner than 4 and 7). On the other hand, in the case of an AT vehicle, since HC and Co emissions during gear changes are small, NOx emissions tend to increase due to leaner average air-fuel ratios. Additionally, AT cars generally emit more NOx than MT cars. In this way, even with the same engine, AT cars and M
Because the emission rates of Co, HC, and NOx differ between T-cars, the contents of the memory (ROM), which is built into the electronic control unit and stores various correction coefficients and correction variables necessary for fuel supply control, must be changed. It is necessary to rewrite it.

However, when the memory is particularly a mask ROM,
In order to change the memory contents, it goes without saying that the ROM itself must be replaced, but it is also necessary to change the mask pattern used when manufacturing the ROM, which takes at least 2 to 3 months and costs a lot of money to change. becomes.

Therefore, the engine used for AT cars is designed with a cam curve specifically designed for AT cars to change the pulp timing.
The electronic control unit is shared between T cars and MT cars.

However, if the electronic control unit is simply shared, the proportional term control during 02 feedback control,
The correction values for the P term, 1 term, etc. used for integral term control are for AT vehicles,
Even if the specifications of a manual transmission vehicle are changed, the same specifications will remain the same, so changing the design of the engine cam curve alone will not be able to handle engines with multiple specifications, and if the pulp timing changes, the combustion state will also change, resulting in a decrease in output. Furthermore, there is a problem that the number of engine models increases due to the design change of the cam curve.

(Object of the Invention) The present invention has been made in view of the above-mentioned points, and an object of the present invention is to make the electronic control unit common and applicable to engines with various specifications.

(Summary of the Invention) In order to achieve the above object, the present invention compares an exhaust concentration detection value detected by an exhaust concentration detector disposed in the exhaust system of an internal combustion engine with a predetermined reference value, and The air-fuel ratio of the air-fuel mixture is increased or decreased by a first correction value when the detected exhaust gas concentration value changes from the rich side to the lean side or from the lean side to the rich side with respect to the predetermined reference value. When the detected exhaust gas concentration value is on the lean side or the rich side with respect to the predetermined reference value, the target air pressure is set by at least one of integral control, which increases or decreases the air-fuel ratio at predetermined intervals using second correction values. In the air-fuel ratio feedback control method for an internal combustion engine that performs feedback control on the fuel ratio, the correction value applied to at least one of the controls is based on a correction value corresponding to a set voltage supplied from an adjustable variable voltage forming means. An air-fuel ratio feedback control method for an internal combustion engine is provided.

(Example of the invention) An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram of a fuel supply control device to which the present invention is applied, in which a throttle valve opening sensor 4 is connected to a throttle valve 3 provided in the middle of an intake pipe 2 of an engine 1. , outputs an electric signal corresponding to the opening degree of the throttle valve 3 and supplies it to an electronic control unit (hereinafter referred to as ECU) 5.

A fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 3 and slightly upstream of an intake valve (not shown) in the intake pipe 2, and each injection valve is connected to a fuel pump (not shown). It is also electrically connected to the ECU 3, and the valve opening time for fuel injection is controlled by a signal from the ECU 3.

On the other hand, an absolute pressure sensor 8 is provided immediately downstream of the throttle valve 3 via a pipe 7, and an absolute pressure signal converted into an electrical signal by the absolute pressure sensor 8 is supplied to the ECU 3. Further, an intake air temperature sensor 9 is installed downstream of the intake air temperature sensor 9 to detect the intake air temperature and output a corresponding electric signal to be supplied to the ECU 3.

A water temperature sensor 10 mounted on the main body of the engine 1 is composed of a thermistor or the like, detects the engine cooling water temperature, outputs a corresponding temperature signal, and supplies the signal to the ECU 3. The engine rotational angular position sensor 11 and the cylinder discrimination sensor 12 are installed around the camshaft or crankshaft (not shown) of the engine 1, and the engine rotational angular position sensor 11 detects a predetermined crankshaft every 180 degree rotation of the engine crankshaft. A pulse (hereinafter referred to as a TDC signal) is output at an angular position, and the cylinder discrimination sensor 12 outputs a pulse at a predetermined crank angle position of a specific cylinder, and each of these pulse signals is supplied to the ECU 3.

The three-way catalyst 14 is disposed in the exhaust pipe 13 of the engine 1, and purifies components such as HC, CO, and NOx in the exhaust gas. The 02 sensor is installed on the upstream side of the three-way catalyst 14 in the exhaust pipe 13, detects the oxygen concentration in the exhaust gas, outputs a signal corresponding to the output value, and supplies the signal to the ECU 3. E
An atmospheric pressure sensor 16 that detects atmospheric pressure and an engine starter switch 17 are connected to the CU 3, and a signal from the atmospheric pressure sensor 16 and a signal indicating the on/off state of the starter switch 17 are supplied. Furthermore, ECU3 has batch 1
8 is connected and the operating voltage of the ECU is supplied.

FIG. 2 is a block diagram showing the circuit configuration inside the ECU 3 shown in FIG. 1, in which the output signal from the engine rotation angle position sensor 11 shown in FIG.
The TDC signal is supplied to the central processing unit (hereinafter referred to as CPU) 503 and also to the Me counter 502. The Me counter 502 indicates the current TDC signal from the time when the previous TDC signal was input from the engine rotation angle position sensor 11.
It measures the time interval until the input of the DC signal, and its count Me is proportional to the reciprocal of the engine rotation speed Ne.

The Me counter 502 transfers this count value Me to the data bus 51.
0 to the CPU 303.

The output signals from each sensor such as the throttle valve opening sensor 4, the intake pipe absolute pressure sensor 8, and the engine water temperature sensor 10 in FIG. Sequential A-
The signal is supplied to a D converter 506. Further, a Vn open rectifier 511 is connected to the multiplexer 505. The voltage regulator 511 is composed of a variable voltage circuit composed of, for example, a voltage dividing resistor connected to a constant voltage circuit (not shown).
A voltage vmx that determines a proportional term correction value PL, which will be described later and is applicable in a specific operating range of the engine, is supplied to an A-D converter 506 via a multiplexer 505. The A-D converter 506 connects each of the above-mentioned sensors and the VPRO regulator 511.
The analog output voltages from the CP tJ503 are sequentially converted into digital signals and supplied to the CP tJ503 via the data bus 510.

The CP 0503 is further connected to a read-only memory (hereinafter referred to as ROM) 507, a random access memory (hereinafter referred to as RAM) 508, and a drive circuit 509 via a data bus 510.RAM2O3 temporarily stores the calculation results in the CPU 303. memorize it, R
The OM 507 stores a control program executed by the CPU 303, a basic injection time Ti map of the fuel injection valve 6 to be read based on the absolute pressure in the intake pipe and the engine speed, a correction coefficient map, etc.

The CPU 303 calculates the fuel injection time TOUT of the fuel injection valve 6 according to the aforementioned various engine parameter signals and injection time correction parameter signals according to the control program stored in the ROM2O3, and sends these calculated values via the data bus 510. and is supplied to the drive circuit 509. The drive circuit 509 supplies the fuel injection valve 6 with a control signal to open the fuel injection valve 6 according to the calculated value.

TOUT=T 1xKo2 xK+ +2...
(1) Here, Ti indicates the basic fuel injection time of the fuel injection valve 6, and this basic injection time is, for example, the absolute pressure in the intake pipe PBA.
and the engine rotation speed Ne. Ko2 is an 02 feedback correction coefficient which will be described later. K1 and K2 are a correction coefficient and a correction variable respectively calculated according to various engine parameter signals, and are set to required values to optimize fuel consumption characteristics, exhaust gas characteristics, etc. according to engine operating conditions. Ru.

FIG. 3 shows the set voltage (output voltage) of the Vn regulator 511.
(9) X represents a table for setting the proportional term correction value PLFm mentioned above, and the setting voltage VPROM can be changed from Ov to 50% depending on the combination of resistance values, for example, as shown in
Up to v is set divided into 25\i floors, and a value VPRO is associated with each stage. The present invention provides a set voltage V in order to obtain the optimum air-fuel ratio for the engine using a single voltage forming means.
A proportional term correction value PL■ is set to a value corresponding to pzx.

The table shown in Fig. 3 shows the proportional term (hereinafter referred to as P term) correction value PLPRO for AT cars and MT cars, the horizontal column shows the P term correction value PLPl'li ~PLPRO5 for AT cars, and the vertical column shows the P term correction value PLPRO5 for AT cars. Represents the P-term correction value PLIY [N to PLn5 for MT cars, and the two-term correction value PLF for these AT cars and MT cars.
Each value of mi~PL■5 is VR1i1~Vn+5, which will be described later.
．． . . , is uniquely set by one value among VPRO5+ to VPRO55. In other words, if the (9) value is set to, for example, V%34, the correction value for AT cars is P.
The correction value for MT cars that is set to L mg is PLPRO.
To 3. Also, for example, the correction value for AT cars may be PLPRO2,
When setting the correction value for MT vehicles to PL3, the Vq value may be set to VFR]32.

Setting value VPRO4+~VPRO+5. ”', VPR
O51 to VPm55 and the set voltage (9)X are expressed in the relationship as shown in FIG. That is, the set values VPRDi1 to Vp vary with respect to the change in the set voltage VFROX from Ov to IV.
It changes by a value equal to five steps of mi';. Similarly, set voltage (2) X's 1v~2V12■~3V13v~4v
The setting value is VF1111δ for changes from 14v to 5■
~Vf121, VF1131~Vnz, Vn<s ~V
pma, VFR051 to VFR[155, each changing by a value equal to five steps. Therefore, a desired value among the set values VRII to VFl'1055 can be easily set using the set voltage vFgJx. That is, each correction value PLl'm for AT cars and MT cars is determined by the set voltage V1gx.
can be easily set to the optimum value to suit the engine specifications.

Furthermore, even if the adjusted value deviates somewhat when adjusting the set voltage V FR[l X, the correction value PLPRO does not deviate significantly. Incidentally, in order to prevent the once set correction value PLPFII from going out of order, the set voltage VFmX is given a predetermined allowable width Δ■. The table is stored in the ROM2O3 shown in FIG.

These correction values PL■ are used to adjust the set voltage VF of the Vnm regulator 5l1 during the assembly process of incorporating the fuel supply control device into the engine to which the method of the present invention is applied, or during periodic maintenance.
By adjusting alX, it is set to the optimum value.

FIG. 5 shows a flowchart showing the procedure for determining the correction value pL(6) for an AT or MT vehicle. When the ignition switch is turned on, the ECU 3 shown in FIG.
is initialized, and at the same time, the set value v is read into the CPU 503 (step 10). Next, it is determined whether or not it is an AT vehicle (step 11), and if the determination answer is affirmative (Yes), the process proceeds to step 12, where the set value V(9) read in step 10 and the determination result that it is an AT vehicle are determined. Based on this, the P-term correction value PLPRO for AT vehicles is determined from the table shown in FIG. If the answer to step 11 is negative (No), that is, if the vehicle is an MT vehicle, the process proceeds to step 13, and based on the set value VPRO read in step 10 and the determination result that it is an MT vehicle, The P-term correction value PLPRO for MT vehicles is determined from the table shown in the figure. Furthermore, AT in step 11
Discrimination between a car and an MT car is made, for example, by the presence or absence of a jumper wire connected to the ECU 3.

Returning to FIG. 1, the output of the 02 sensor 15 fluctuates during engine operation, and the fluctuation period T changes depending on the engine speed Ne, becoming shorter at high speeds. The 02 sensor 15 outputs a rich signal when the detected concentration value exceeds the reference value Vr, and outputs a lean signal when the detected concentration value falls below the reference value Vr. Both signals represent that the air-fuel mixture is richer and leaner than the stoichiometric air-fuel ratio, respectively.

In this embodiment, the air-fuel ratio in the area adjacent to the high-load open area in the feedback control area is controlled to be richer than the target air-fuel ratio, for example, the stoichiometric air-fuel ratio, and the low-load side area in this feedback control area is Then, control is performed to achieve the target air-fuel ratio. Therefore, in this embodiment, the rotation speed Ne is taken as a parameter corresponding to the magnitude of the engine load, and the proportional term correction value PL when the output of the 02 sensor 15 changes from the rich side to the lean side, and the The proportional term correction value PR when the change is made to the Ne-PL child table Ne- in FIG. 6(a) is
As shown in the PR child table (b) in the same figure, the value of PL is set to be larger than the value of PR by the required amount.

In the low load side region of the feedback control region, the proportional term correction value PL when the output of the 02 sensor 15 changes from a rich signal to a lean signal is the same as the proportional term correction value PR when the output changes vice versa. using the value of
When the output of the 02 sensor 15 changes from a rich signal to a lean signal, PL is applied to increase the 02 feedbank correction coefficient KO2, and when the output changes from a lean signal to a rich signal, PR is used to decrease it. On the other hand, 02 sensor 1
If the output of 5 is on the rich side without being inverted, the integral term correction value Δ
k (FIG. 6(C)) is applied to decrease the 02 feedback coefficient Ko2 at predetermined intervals, and on the lean side, the coefficient value Ko2 is similarly increased at predetermined intervals using this integral correction value Δk. As a result, the average value π of the coefficient value Ko2
Under τ, the air-fuel ratio is corrected and controlled to a value that allows the target air-fuel ratio to be obtained.

On the other hand, in the feedback control region adjacent to the high load open region, when the output of the 02 sensor 15 changes from a rich signal to a lean signal, a proportional term correction value PL with a large value corresponding to the engine speed Ne at that time is applied. Then, the 02 feedback correction coefficient KO2 is corrected to increase, and when the signal changes from a lean signal to a rich signal, correction is performed by applying a proportional term correction value PR having a smaller value than the above value. on the other hand,
If the o2 sensor output is not inverted, the integral term correction is performed using the integral term correction value Δk in the same manner as described above. As a result,
Below the average value of the coefficient value Ko2, τ is a value larger than the above-mentioned average value. Therefore, the coefficient value Ko2 is 02
When used as a feedback control signal, the air-fuel ratio in the feedback control area adjacent to the high-load open area will deviate to a larger value on the fuel-rich side than the stoichiometric air-fuel ratio due to the contribution of the increase in the average value as described above. be done. The magnitude of this deviation, and therefore the air-fuel ratio of the mixture, is determined by the proportional term correction value P.
It is set to a required value by appropriately setting the degree of difference between L and PR.

In the above case, only the proportional term correction value was set to PL > PR to increase the average value of the coefficient value Ko2 by τ, but
The value of the integral term correction value Δ is set to be more than when it is on the rich side.
By setting the required amount to be larger when it is on the lean side and by making the degree of increase correspond to the engine speed Ne, the average value πo of the coefficient value Ko2 can be increased.
2 can be increased. This correction value increase setting may be performed by increasing either the proportional term correction value PL or the integral term correction value Δ, or both positive values PL.

It is also possible to set Δk to increase at the same time.

FIG. 7 shows a flowchart of a subroutine for calculating the 02 feed bank correction coefficient Ko2.

First, it is determined whether activation of the 02 sensor 15 has been completed (step 15). That is, the internal resistance detection method of the 02 sensor 15 detects whether or not the output voltage of the 02 sensor 15 has reached the activation starting point Vx (for example, 0.6 V), and when it reaches Vx, it is determined that it is activated. do.

If the answer is negative (No), the coefficient value Ko2 is set to 1 (step 16). On the other hand, the answer is affirmative (Y
es), it is determined whether the engine is in the open loop control region (step 17). This open control region includes a high load operation region, a low rotation region, an idle region, a high rotation region, a lean mixture region, etc. The high load operation region includes, for example, T when the fuel injection time TOUT is a predetermined value.
This is an area set to a value larger than wot. Here, Twot is a constant and is the lower limit of the amount of fuel supplied necessary to enrich the air-fuel mixture during high-load operation such as when the throttle valve is fully opened.

In the low rotation region, the engine rotation speed Ne is a predetermined value NLOI) (
(for example, 700 rpm) or less, and the intake pipe absolute pressure PB
A is a region where A is greater than or equal to L (for example, 360 mmHg) than the predetermined value Pa. The idle region is a region in which the engine rotation speed Ne is lower than a predetermined rotation speed NxoL (for example, 11000 rpm) and the absolute pressure PBA is lower than the predetermined pressure PB.
is a region where the predetermined rotational speed N is larger than L (for example, 3000 rpm). The air-fuel mixture lean region is a region in which the intake pipe absolute pressure PBA is smaller than the discrimination value PBLS, which is set to a larger value as the engine speed Ne increases. When the engine is in any of the above regions, it is determined that the engine is being operated in the open loop control region, and in this case, the process proceeds to step 16, where Ko2 is set to 1.

On the other hand, if the answer to Stellaf 17 is negative (No), the engine is determined to be in the feedback region and shifts to closed loop control, and the output level of 02 sensor 15 is reversed between the previous input of the TDC signal and the current input. In step 18), if the answer is affirmative (Yes), proportional term (P term) control is performed. That is, the output level of the 02 sensor 15 is at a low level (lean signal) with respect to the reference value.
If the answer is affirmative (Yes), the ROM 5 is updated to pass the correction value PL.
Figure 6 (a) Ne-PL child table stored in 07
)), a correction value PL corresponding to the engine speed Ne at that time is determined (step 20). Next, in step 21, this correction value PL is added to the previous value of the coefficient value KO2.

On the other hand, in step 19, the output Vo of the 02 sensor 15
2 is determined to be at a high level (rich signal) with respect to the reference value Vr, the correction value PR should be applied (Ne-PR child table Fig. 6 (b)), which corresponds to the engine rotation speed Ne detected this time. Find the corrected value PR (step 22)
. Then, in step 23, this correction value PR is subtracted from the coefficient value Ko2 at the previous loop. Next, the integral term (one term) control from step 24 onwards is performed as follows. First, in step 18, if the output level Vo2 of the 02 sensor 15 is on the same level side as in the previous loop with respect to the reference level Vr, the process advances to step 24, and the 02
It is determined whether the output of the sensor 15 is on the low level side. If the answer is affirmative (Yes), add 1 to the value of the TDC signal pulse count number NXL (step 25
), the count number NxR is a predetermined value Nx (for example, 4
) is reached (step 26). As a result of this determination, if the count number NIL has not yet reached Nx, the coefficient value Ko2 is maintained at the value at the previous loop (step 27), and if the count number N and IL have reached Nx, Ko2 is set to a predetermined value. Δk (for example, about 0.3% of Ko2)
(step 28), and at the same time set the number of pulses counted so far Nx to 0 (step 29).
A predetermined value Δk is added to KO2 every time NIL reaches NI. On the other hand, if the answer in step 24 is negative (N
O), 1 is added to the pulse count number N of the TDC signal (step 30), and the count number N
Step 3
1), if the answer is negative (No), the value of the coefficient value Ko2 is maintained at the value at the previous loop (step 32), and if the answer is affirmative (Yes), the predetermined value Δ is changed from the coefficient value Ko2.
k is subtracted (step 33), the counted pulse number NxH is reset to O (step 34), and a predetermined value Δk is subtracted from Ko2 every time NxH reaches Nx, as described above. According to the above embodiment,
02 Feedback correction coefficient value Ko2 proportional term correction value P
L, is set to a value according to the engine speed Ne, and 02
A correction value PL that is set when the output of the sensor 15 changes from the rich side to the lean side is set to be a larger value than a correction value PR that is set when the output changes from the lean side to the rich side, 02 corrected with such a correction value
By feedback-controlling the air-fuel ratio of the air-fuel mixture using the feedback coefficient Ko2, the target air-fuel ratio can be set to a richer value as the engine in the feedback control region approaches the high-load open region.

Therefore, the engine output can be increased as the high-load operating region approaches, and drivability can be further improved.

Furthermore, since there is less change in the air-fuel ratio when transitioning from the feedback control region to the high load open region, drivability during the transition is further improved.

In the above embodiment, the correction value PL of the P term has been described, but the present invention is not limited to this, and it goes without saying that other correction values such as the correction value ΔK of the first term can also be applied.

(Effects of the Invention) As explained above, according to the present invention, the detected exhaust gas concentration detected by the exhaust concentration detector disposed in the exhaust system of the internal combustion engine is compared with a predetermined reference value, and the The air-fuel ratio of the air-fuel mixture is increased or decreased by a first correction value when the detected exhaust gas concentration value changes from the rich side to the lean side or from the lean side to the rich side with respect to the predetermined reference value. When the detected exhaust gas concentration value is on the lean side or the rich side with respect to the predetermined reference value, the target air pressure is set by at least one of integral control, which increases or decreases the air-fuel ratio at predetermined intervals using second correction values. In an air-fuel ratio feedback control method for an internal combustion engine that performs feedback control on a fuel ratio, the correction value applied to at least one of the controls is corrected by a correction value corresponding to a set voltage supplied from an adjustable variable voltage forming means. As a result, the electronic control unit can be used with engines of various specifications such as AT cars and MT cars, and therefore the electronic control unit can be shared, and as a result, the cam curve of the engine etc. There is no need to make any design changes, and costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a fuel supply control device for implementing the fuel supply control method for an internal combustion engine according to the present invention, and FIG. 2 is an implementation of the internal configuration of the electronic control unit shown in FIG. 1. FIG. 3 is a block diagram showing an example, and FIG. 3 is a table showing an example of the relationship between correction coefficients, correction variables, and set values according to the control method of the present invention. FIG. 4 is a graph showing the relationship in FIG. Figure 5 shows the correction value P from the table in Figure 3.
Flowchart showing the procedure for determining LP RO, No. 6
The figure is a graph showing changes in the correction value with respect to the engine rotation speed in the 02 feedback control, and FIG. 7 is a flowchart showing the procedure for calculating the 02 feedback correction coefficient Ko2. 1... Engine, 2... Intake rod, 3... Throttle valve, 5... ECU, 6... Fuel injection valve, 4.8~
12.16...sensor, 13...exhaust pipe, 14...
・Three-way catalyst, 15...O2 sensor, 18...Battery', 503...CPU, 507...ROM, 5
11...v issue regulator. 3 figures

Claims (1)

[Claims] 1. Compare the detected exhaust concentration value detected by the exhaust concentration detector placed in the exhaust system of the internal combustion engine with a predetermined reference value, and determine the air-fuel ratio of the air-fuel mixture supplied to the engine when the detected exhaust concentration value is Proportional control that increases or decreases the air-fuel ratio by a first correction value when the air-fuel ratio changes from a rich side to a lean side or from a lean side to a rich side with respect to a predetermined reference value, and the detected exhaust concentration value is changed with respect to the predetermined reference value. In an air-fuel ratio feedback control method for an internal combustion engine, the air-fuel ratio is feedback-controlled to a target air-fuel ratio by at least one of integral control that increases or decreases the air-fuel ratio at predetermined intervals using second correction values when the air-fuel ratio is on the lean side or the rich side. An air-fuel ratio feedback control method for an internal combustion engine, characterized in that the correction value applied to at least one of the controls is corrected by a correction value corresponding to a set voltage supplied from an adjustable variable voltage forming means.