JPH021973B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio feedback control device for electronically feedback controlling the air-fuel ratio of an air-fuel mixture supplied to an internal combustion engine, and particularly to an air-fuel ratio feedback control device that electronically controls the air-fuel ratio of an air-fuel mixture supplied to an internal combustion engine. Related to an electronic air-fuel ratio feedback control device that improves engine operating performance and promotes exhaust gas purification by increasing or decreasing a value according to the engine rotational speed to perform accurate and responsive air-fuel ratio control. .

The valve opening time of the fuel injection device of an internal combustion engine, especially a gasoline engine, is set to a reference value depending on the engine speed and the absolute pressure inside the intake pipe, and the specifications representing the operating state of the engine, such as the engine speed and the inside of the intake pipe. Constants and/or coefficients are added by electronic means depending on the absolute pressure of the engine, engine water temperature, throttle valve opening, exhaust concentration (oxygen concentration), etc.
The present applicant has proposed a fuel supply device that determines the amount of fuel by multiplying the amount of fuel and controls the fuel injection amount, thereby controlling the air-fuel ratio of the air-fuel mixture supplied to the engine.

According to the fuel supply device according to this proposal, the valve opening time of the fuel injection device is controlled in feedback according to the output voltage of the exhaust gas concentration detector (O ₂ sensor) placed in the exhaust system, so that the air-fuel ratio can be close to the stoichiometric air-fuel ratio. This system aims to improve driving performance and purify exhaust gas emissions. For specific operating conditions of the engine (for example, when the _O2 sensor is inactive, idle range, partial lean range, throttle valve fully open range, and deceleration range), preset coefficients are applied to determine the best fit for each specific operating state. Open-loop control is performed to obtain respectively adapted predetermined air-fuel ratios.

On the other hand, under normal engine operating conditions, the valve opening time of the fuel injection system is controlled by closed-loop control.
Settings must be made to obtain an accurate air-fuel ratio in immediate response to the output signal level of the _O2 sensor.

According to the present invention, during closed loop control
Proportional control (P-term control) or integral control (I-term control) is selectively performed according to changes in the output voltage of the O ₂ sensor. In other words, if the output voltage of the O ₂ sensor changes only on the high level side or low level side with respect to the reference voltage, integral control is performed by increasing or decreasing the O ₂ feedback coefficient Ko ₂ with a time constant according to the engine speed (Ne). Also, when the O ₂ sensor output voltage changes from a high level side to a low level side or from a low level side to a high level side with respect to the reference voltage, a value according to the engine rotation speed is set as in integral control. By performing proportional control by increasing or decreasing the coefficient Ko ₂ at once, it is possible to perform accurate and quick control according to engine rotation, and to obtain stability in engine operating performance and exhaust gas emissions. The present invention provides an electronic air-fuel ratio feedback control device with a function to

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram of the device of the present invention,
Reference numeral 1 indicates, for example, a four-cylinder internal combustion engine, and the engine 1 is of a type consisting of four main combustion chambers and an auxiliary combustion chamber (both not shown) communicating with the main combustion chambers. An intake pipe 2 is connected to the engine 1, and the intake pipe 2 includes a main intake pipe communicating with each main combustion chamber and a sub-intake pipe (both not shown) communicating with each sub-combustion chamber. A throttle body 3 is provided in the middle of the intake pipe 2, and a main throttle valve and a sub-throttle valve (both not shown) disposed inside the main intake pipe and a sub-intake pipe, respectively, are provided in conjunction with each other. A throttle valve opening sensor 4 is connected to the main throttle valve to convert the valve opening of the main throttle valve into an electrical signal and send it to an electronic control unit (hereinafter referred to as "ECU") 5.

A fuel injection device 6 is provided in the intake pipe 2 between the engine 1 and the throttle body 3. This fuel injection device 6 consists of a main injector and a sub-injector (both not shown).The main injector is located in the main intake pipe slightly upstream of the intake valve (not shown) for each cylinder, and the sub-injector is located in the sub-intake pipe. These throttle valves are common to each cylinder and are provided slightly downstream of the sub-throttle valve. The fuel injection device 6 is connected to a fuel pump (not shown). Main injector and sub injector are ECU5
The fuel injection valve opening time is controlled by a signal from the ECU 5.

On the other hand, an absolute pressure sensor 8 is provided immediately downstream of the main throttle valve of the throttle body 3 via a pipe 7, and an absolute pressure signal converted into an electrical signal by the absolute pressure sensor 8 is sent to the ECU 5.
sent to. Also, downstream of it is an intake air temperature sensor 9.
is installed, and this intake air temperature sensor 9 also converts the intake air temperature into an electrical signal and sends it to the ECU 5.

An engine water temperature sensor 10 is provided in the main body of the engine 1. This sensor 10 is made of a thermistor, etc., and is inserted into the circumferential wall of the engine cylinder filled with cooling water, and supplies its detected temperature signal to the ECU 5.

An engine rotation speed sensor (hereinafter referred to as "Ne sensor") 11 and a cylinder discrimination sensor 12 are installed around the camshaft or crankshaft (not shown) of the engine, and the former 11 receives a TDC signal, that is, 180 degrees of the engine crankshaft. The latter 12 outputs one pulse each at a predetermined crank angle position of a specific cylinder at a predetermined crank angle position for each rotation, and these pulses are sent to the ECU 5.

A three-way catalyst 14 is disposed in the exhaust pipe 13 of the engine 1 and performs the action of purifying HC, CO, and NO _x components in the exhaust gas. On the upstream side of this three-way catalyst 14,
An O ₂ sensor 15 is inserted into the exhaust pipe 13 , and this sensor 15 detects the oxygen concentration in the exhaust gas and supplies the detected value signal to the ECU 5 .

Furthermore, the ECU 5 includes a sensor 1 that detects atmospheric pressure.
6 and an engine starter switch 17 are connected, and the ECU 5 is supplied with a detected value signal from the sensor 16 and a starter switch ON/OFF state signal.

Next, details of the air-fuel ratio control operation of the electronic air-fuel ratio feedback control device of the present invention having the above-described configuration will be explained with reference to FIG. 1 and FIGS. 2 to 10 described above.

First, FIG. 2 shows the air-fuel ratio control of the present invention, that is,
This is a block diagram showing the overall program configuration of the control contents of the main and sub-injector valve opening times T _OUTM and T _OUTS in the ECU 5. It consists of a main program 1 and a sub-program 2, and the main program 1 is based on the engine speed Ne.
The subprogram 2 performs control in synchronization with the TDC signal and consists of a starting control subroutine 3 and a basic control program 4. On the other hand, the subprogram 2 consists of an asynchronous control subroutine 5 when not synchronized with the TDC signal.

The basic calculation formula in the starting control subroutine 3 is expressed as T _OUTM = Ti _CRM ×K _Ne + (T _V +ΔT _V ) (1) T _OUTS = Ti _CRS × K _Ne + T _V (2). Here, Ti _CRM and Ti _CRS are reference values for the valve opening times of the main and sub-injectors, respectively, and are determined by _TiCRM and _TiCRS tables 6 and 7, respectively. K _Ne is a correction coefficient at the time of starting specified by the rotational speed Ne, and is determined by the K _Ne table 8. T _V is a constant for adjusting the valve opening time to increase or decrease according to changes in battery voltage.
It is determined from the _TV table, and ΔT _V is added to the TV for the sub-injector for the main injector according to the operating characteristics of the injector due _to the difference in structure.

Also, the basic calculation formula in basic control program 4 is T _OUTM = (Ti _M − T _DEC ) × K _TA・K _TW・K _AFC・K _PA
・K _AST・K _WOT・K _O2・K _LS ) +T _ACC ×(K _TA・K _TWT・K _AFC・K _PA・K _AST )+
(T _V +ΔT _V )……(3) T _OUTS = (Ti _S − T _DEC ) × (K _TA・K _TW・K _AST・K _P
A ) + T _V ......(4) Here, Ti _M and Ti _S are reference values for the valve opening times of the main and sub-injectors, respectively, and are calculated from the basic Ti map 10, respectively. T _DEC and T _ACC are constants during deceleration and acceleration, respectively, and are determined by the acceleration and deceleration subroutine 11. Various coefficients such as K _TA , K _TW . . . are calculated by respective tables and subroutines 12. K _TA is the intake air temperature correction coefficient calculated from the table based on the actual intake air temperature, K _TW is the fuel increase coefficient calculated from the table based on the actual engine water temperature T _W , and K _AFC is the fuel cut calculated by the subroutine. After fuel increase factor, K _PA
is the atmospheric pressure correction coefficient determined from the table based on the actual atmospheric pressure, K _AST is the post-start fuel increase coefficient determined by the subroutine, and K _WOT is a constant that is the enrichment coefficient of the mixture when the throttle valve is fully opened. , K _O2 is an O ₂ feedback correction coefficient determined by a subroutine according to the actual oxygen concentration in exhaust gas, and K _LS is a constant that is a lean coefficient of the air-fuel mixture during lean/stoichiometric operation. Stoichiometric is an abbreviation for Stoichiometric, which indicates stoichiometry, that is, the theoretical air-fuel ratio. Also, it is a fuel increase constant during acceleration determined by the _TACC subroutine and is determined from a predetermined table.

On the other hand, the formula for calculating the asynchronous control subroutine 5 of the main injector opening time T _MA that is not synchronized with the TDC signal is T _MA = Ti _A ×K _TWT × K _AST + (T _V +ΔT _V ) ……(5 ). Here, Ti _A is a fuel increase reference value during acceleration control that is asynchronous during acceleration, that is, not synchronized with the TDC signal, and is determined from the Ti _A table 13. K _TWT is the water temperature increase coefficient K _TW shown in Table 1.
Synchronous acceleration obtained from 4 and calculated based on it,
This is the fuel increase coefficient after acceleration and during asynchronous acceleration.

Figure 3 shows the cylinder discrimination signal and TDC signal input to the ECU 5, and the main signal and TDC signal output from the ECU 5.
This is a timing chart showing the relationship between the sub-injector drive signal and the pulse of the cylinder discrimination signal _S1 .
S ₁ a is inputted once every 720° of the engine crank angle, and in parallel, pulses S _{2 a} - S _{2 e of the TDC signal S 2} are inputted once every 180° of the engine crank angle.
Each cylinder's main injector drive signal S ₃ − is inputted pulse by pulse, and the relationship between these two signals is
The output timing of _S6 is set.

That is, the main injector drive signal S ₃ for the first cylinder is output with the first TDC signal pulse S ₂ a,
The second TDC signal pulse S ₂ b outputs the main injector drive signal S ₄ for the third cylinder, the third pulse S _2C outputs the fourth cylinder drive signal S ₅ , and the fourth pulse S ₂ d The drive signal _S6 for the second cylinder is sequentially output. Further, the sub-injector drive signal _S7 is generated one pulse each time each TDC signal pulse is input, that is, every 180 degrees of crank angle. In addition, the TDC signal pulses S ₂ a, S ₂ b... are set to occur 60 degrees earlier than the top dead center of the piston in the cylinder, and there is a delay due to the calculation time in the ECU 5, and the pulses before the top dead center. The time lag between when the air-fuel mixture is generated by the opening of the intake valve and the operation of the injector until the air-fuel mixture is sucked into the cylinder is absorbed in advance.

FIG. 4 shows a flowchart of the main program 1 when the valve opening time is controlled in synchronization with the TDC signal in the ECU 5, and the program as a whole consists of an input signal processing block, a basic control block, and a starting control block. First, in the input signal processing block, when the engine ignition switch is turned on, the CPU in the ECU 5 is initialized (step 1), and when the engine is started, a TDC signal is input (step 2). Then all the basic analog values are atmospheric pressure P _A , absolute pressure P _B , from each sensor.
Engine water temperature T _W , atmospheric temperature T _A , battery voltage V,
The throttle valve opening θth, the output voltage value V of the O ₂ sensor, the on/off state of the starter switch 17, etc. are read into the ECU 5 and the necessary values are stored (step 3). Next, the elapsed time from the first TDC signal to the next TDC signal is counted, and based on that value, the engine rotation speed Ne is calculated and stored in the ECU 5 (step 4). Next, in the basic control block, it is determined based on the calculated value of Ne whether the engine speed is less than or equal to the cranking speed (starting speed) (step 5). If the answer is affirmative (Yes), it is sent to the startup control subroutine of the startup control block.
Ti _CRM and Ti _CRS are determined based on the engine cooling water temperature T _W using the Ti _CRM table and Ti _CRS table (step 6), and the correction coefficient K _Ne of Ne is determined using the K _Ne table (step 7). And _T.V.
The battery voltage correction constant T _V is determined from the table (step 8), and each value is inserted into the above equations (1) and (2) to calculate T _OUTM and T _OUTS (step 9).

Also, if the answer in step 5 is negative ( _NO )
If so, it is determined whether or not the engine is in a state that requires a fuel cut (step 10), and if the answer is affirmative (Yes), the values of T _OUTM and T _OUTS are both set to zero and a fuel cut is performed ( Step 11).

On the other hand, if the answer is determined to be no ( _NO ) in step 10, each correction coefficient K _TA , K _TW , K _AFC ,
K _PA , K _AST , K _WOT , K _O2 , K _LS , K _TWT, etc. and _correction constants T _DEC , T _ACC , TV , ΔT _V are calculated (step 12). These correction coefficients and constants are subroutines,
These are determined by a table or the like.

Next, a predetermined corresponding map is selected according to each data such as the rotation speed Ne, absolute pressure P _B, etc., and Ti _M and Ti _S are determined based on the map (step 13). Therefore, based on the correction coefficient value, correction constant value, and reference value obtained in steps 12 and 13 above, the previous formula (3),
Calculate T _OUTM and T _OUTS using (4) (step 14).
Then, the main and sub-injectors are operated respectively based on the values of T _OUTM and T _OUTS obtained in this way (step 15).

As mentioned above, in addition to controlling the valve opening times of the main and sub-injectors in synchronization with the TDC signal, the main injector is controlled in synchronization with a pulse train that is not synchronized with the TDC signal but has a fixed time interval. Asynchronous control is performed, but detailed explanation will be omitted.

Next, a subroutine for calculating the correction coefficient K _O2 during _O2 feedback control in the above-mentioned valve opening time control will be explained. FIG. 5 shows a flowchart of the K _O2 calculation subroutine.

First, it is determined whether activation of the O ₂ sensor has been completed (step 1). That is, the internal resistance detection method of the O ₂ sensor detects whether the output voltage of the O ₂ sensor has reached _the activation starting point _V occurs,
The active daybreak timer detects whether a predetermined time (for example, 60 seconds) has elapsed since the generation of this signal, and also determines whether the water temperature increase coefficient K _TW and the post-start increase coefficient K _AST are both 1. However, if both conditions are satisfied, it is determined that it is activated. If the answer is no ( _NO ), then K _O2
is the average value in the previous O ₂ feedback control
Set to K _REF (Step 2). On the other hand, if the answer is affirmative (Yes), it is determined whether the throttle valve is fully open (step 3). As a result, if the engine is fully open, K _O2 is set to the above K _REF in the same way as described above (step 2). If the engine is not fully opened, it is determined whether the engine is in an idle state (step 4);
The rotational speed Ne is smaller than the predetermined rotational speed N _IDL (e.g. 100 rpm), and the absolute pressure P _B is also smaller than the predetermined pressure P _BIDL (e.g.
360 mmHg), it is assumed that the engine is in an idle state and K _O2 is set to K _REF via step 2. If it is determined that the engine is not in an idling state, it is determined whether or not the engine is in a deceleration state (step 5). In other words, check whether the fuel cut is established and whether the absolute pressure P _B is equal to the predetermined pressure P _BDEC (e.g.
200Hg), it is determined that the vehicle is in a deceleration state and K _O2 is set to the above K _REF (Step 2).
On the other hand, if it is determined that the vehicle is not in the deceleration state, it is determined whether the lean coefficient _KLS during lean/stoichiometric operation is 1 (step 6), and if the answer is no ( _NO ), sets K _O2 to the above K _REF (step 2), and if the answer is yes, the process moves to the closed loop control described below.

First, it is determined whether the output level of the O ₂ sensor has reversed (step 7), and the answer is affirmative (Yes).
In this case, it is determined whether the previous loop was an open loop (step 8). Then, if it is determined that the previous loop is not an open loop, proportional control (P-term control) is performed. Figure 6 shows Ne−Pi for determining the correction value Pi for correcting the coefficient K _O2 .
It is a table, and the rotation speed Ne is, for example, 1500 rpm ~
Five stages of N _FB 1 to 5 are set in the range up to 3500 rpm, and correspondingly Pi is set to P1 to 6, which is added to or subtracted from the coefficient K _O2 when the output level of the O ₂ sensor is reversed. A correction value Pi is determined based on the engine speed Ne (step 9).

Next, it is determined whether the output level of the O ₂ sensor is _low (step 10), and if the answer is affirmative (Yes), the Pi value obtained from the table is added to K _{O 2} (step 10). 11). In addition, if the answer is no ( _NO ), the above Pi value is subtracted from K _O2 (step
12). Next, the average value K _REF is calculated based on the K _O2 thus obtained (step 13). If the answer is _NO in step 7, i.e.
If the O ₂ sensor output level is maintained at the same level, or if the answer in step 8 is affirmative (Yes), that is, if the previous loop was an open loop, proportional control (term control) is performed. That is, first, it is determined whether the output level of the O ₂ sensor _{is low} or not (step 14), and the answer is affirmative (Yes).
In this case, the number of pulses of the TDC signal is counted (step 15), and the counted number N _LL is equal to the predetermined value N _I
(for example, 30 pulses) (step 16), and if it has not reached it yet, keep K _O2 at the previous value (step 17), and if N _IL reaches N _I For K _O2 , set a predetermined value Δk (for example, 0.3 of K _O2
%) (step 18). At the same time, the number of pulses N _IL counted up to that point is reset to 0 (step 19), and a predetermined value Δk is added to K _O2 every time N _IL reaches N _I. On the other hand, the step
If the answer is NO ( _NO ) in step 14, the number of pulses of the TDC signal is used as a counter (step 20), and it is determined whether the counted number N _IH has reached a predetermined value N _I (step 20). 21), if the answer is no (N _O ), then K _O2
The value of is maintained at the previous value (step 22), and if the answer is affirmative (Yes), a predetermined value Δk is subtracted from K _O2 (step 23), and the number of pulses counted is
N _IH is reset to 0 (step 24), and a predetermined value Δk is subtracted from K _O2 every time N _IH reaches N _I in the same way as described above.

That is, the O ₂ feedback control according to the present invention (i) performs integral control by increasing or decreasing the control amount of the air-fuel ratio by a constant value for each predetermined number of angular position signals, regardless of the engine speed; ii) Proportional control is performed by increasing or decreasing the control amount using a variable value that increases as the engine speed increases each time an angular position signal is input.

The integral control in (i) above is based on the following reasons.

(1) Feedback control of the air-fuel ratio of the air-fuel mixture, etc. was originally based on the current result (O ₂ sensor output value) and the number of TDCs.
It is assumed that there is a time difference between the signal (angular position signal) and the previous cause (actual fuel supply amount).

As is generally recognized, the proportional term used in feedback control is set to restore the controlled variable that has exceeded the target value all at once, and the integral term is set to gradually bring the controlled variable closer to the target value. be done. Therefore, it can be said that the smaller the integral term is, the better, if control delays are ignored.

By the way, in a control circuit that performs feedback control, the minimum value (1LSB) of the integral term for the total control amount width is determined by the circuit's ability, and as long as the ability of the circuit is fixed, the larger the control amount width is, the smaller the minimum value (1LSB) will be. also becomes larger. For example, in the case of a circuit with an 8-bit capacity, the minimum value (1LSB) is equal to the total control amount width divided by 1/256.

(2) When controlling using the minimum value (1LSB), which has a limit to setting it small like this, each
If integral control is performed every time the TDC signal is generated, the control speed (control gain) will become excessive, and the fluctuation range of the air-fuel ratio will increase, resulting in a decrease in control accuracy.

(3) Furthermore, when a digital control circuit with a central processing unit is used as a control circuit as in the present invention, reading correction values from a table and performing interpolation calculations is much easier than simple addition using an analog control circuit in the processing flow. If these are performed in the same circuit, the total computation time performed by the circuit will become longer, so it is preferable not to perform integral control computations if possible at high engine speeds where the TDC signal generation interval becomes short.

(4) In the present invention, air-fuel ratio control is executed every time each TDC signal is generated. In this case, if the integral term is a variable value as a function of engine speed, each TDC signal is
Since the signal generation interval itself is a function of the engine speed, the integral term becomes a quadratic function value of the engine speed and does not simply represent a delay in control.

Therefore, for reasons (1), (2), and (4) above, in the present invention, integral control is performed every several TDC signals (angular position signals), and by using a fixed value, more precision can be achieved. This achieves control, and also makes it possible to shorten the total calculation time of the control circuit (CPU) mentioned in (3) above.

Next, regarding the proportional control in (ii) above, the higher the engine speed, the more integral control terms are generated per unit time, and as a result, the actual air-fuel ratio tends to deviate greatly from the target air-fuel ratio. Therefore, in the present invention, the higher the engine speed, the larger the value of the proportional control term Pi is set. This allows the actual air-fuel ratio to be quickly adjusted to the target air-fuel ratio when the output of the exhaust concentration detector is reversed, especially in the high engine speed range, that is, when the detector output changes from the lean side to the rich side or vice versa with respect to the reference value. It is possible to improve the responsiveness of the control by converging to the fuel ratio, and to suppress the fluctuation range of the air-fuel ratio to a small extent, thereby further improving the control accuracy.

7 to 10 are circuit diagrams of the internal configuration of the ECU 5 used in the air-fuel ratio feedback control system of the present invention described above, and particularly show circuit diagrams of calculation blocks for the correction coefficients K _O2 and K _REF .

First, FIG. 7 shows the entire internal configuration of the ECU 5, particularly showing the calculation blocks of the correction coefficients K _O2 and K _REF , and the TDC signal of the engine rotation speed sensor 11 in FIG. The signal is supplied to a one-shot circuit 501 which together with a circuit 502 constitutes a waveform shaping circuit. The one-shot circuit 501 generates an output signal S _O for each TDC signal, and the signal S _O operates a sequence clock generation circuit 502 to sequentially generate clock signals C _O -6. The clock signal CP _O is supplied to the rotational speed NE value register 503 and the reference clock generator 5
The immediately preceding count value of the rotation number counter 504 that counts the reference clock pulses from 09 is set in the NE value register 503. Clock signal CP _I is then supplied to revolution counter 504 to reset the previous count value of the counter to signal 0. Therefore, the engine speed Ne is measured as the number counted between the pulses of the TDC signal,
The number of measurements Ne is the number of revolutions NE value register 50.
Stored in 3. Further, the clock signal CPO _- 6 is supplied to the circuit of FIG. 9, which will be described later.

In parallel with this, the throttle valve opening sensor 4,
The output signals of the absolute pressure sensor 8 and the engine coolant temperature sensor 10 are supplied to the A/D converter 505 and converted into digital signals, and then are respectively stored in the slot valve opening degree θ _TH value register 506, the absolute pressure P _B value register 507, and the engine water temperature T _W value register 508, and the stored value of the register is supplied to the basic Ti calculation control circuit 521 and the specific operating state detection circuit 510 together with the stored value of the engine rotation speed register 503 mentioned above. The stored values of the P _B value register 507 and the NE value register 503 are also supplied to the lean operation detection circuit 593.
Corresponding to these stored values, the circuit 593 sends a correction coefficient _KLS value signal during lean operation to the specific operating state detection circuit 510. Furthermore, the stored values of the NE value register 503, P _B value register 57 and T _W value register 508 are stored in the fuel cut detection circuit 5.
94, and the circuit 594 sends a binary signal indicating the fuel cut state to the specific operating state detection circuit 510 in accordance with these stored values. Basic Ti
The calculation control circuit includes each of the registers 503, 506-
A coefficient calculation process is performed based on the input values from 508, and the basic injection time Ti is determined based on these calculated values. Further, the specific operating state detection circuit 510 is further inputted with the output of the O ₂ sensor 15, and is shown in FIG.
On the condition that the activation of the O ₂ sensor 15 is completed, the engine operates in a specific operating state (e.g., throttle valve fully open range, idle range, deceleration range, or lean operation range), and when the conditions for this specific operating state are met, the output terminal 51
Output = 1 is output from output terminal 510a as an open-loop signal, while when any of the conditions of the specific operating state is not satisfied, that is, when the engine is in the air-fuel ratio feedback operation state by the O ₂ sensor, a closed loop is output from the output terminal 510a. Outputs output=1 as a signal. These output terminals 510
Output = 1 from a, 510b is an AND circuit 511,
512 is supplied to each one input terminal. AND
The other input terminal of each of the circuits 511 and 512 has a first
Predetermined value memory 513 and second predetermined value memory 51
4 store values are provided respectively. The first predetermined value memory 513 stores coefficients (for example, K _WOT = 1.0, K _LS = 1.0) that are applied when the specific operating state condition is not satisfied, that is, during O ₂ feedback control, and the second predetermined value memory 514 contains coefficients that are applied when the specific operating state condition is not met. Coefficients (for example,
In the throttle valve full opening range, K _WOT = 1.2, K _LS = 1.0,
K _WOT = 1.0, K LS = 0.8 in the lean operating range, K WOT = 1.0, K _LS = 0.8 in the deceleration range, and K _WOT = 1.0, K _LS = 0.8 in the idle range.
Both K _WOT and K _LS (1.0) are memorized.
AND circuits 511 and 512 output from the specific operating state detection circuit 510 to one of the input terminals = 1.
are supplied to the memory 513, respectively.
The stored value from 514 is supplied as a second coefficient to a multiplication circuit 524, which will be described later, via an OR circuit 515.

On the other hand, the output of the O ₂ sensor 15 in FIG. 1 is input to the lean/rich comparison circuit 516 in FIG.
At 6, the output level of the O ₂ sensor is low _and high.
It is determined whether or not this is the case, and this determination signal is supplied to the K _O2 calculation circuit 517. K _O2 calculation circuit 517
is further the output terminal 5 of the specific operating state detection circuit 510.
The closed loop signal from 10a is input,
As described later, the circuit 517 calculates the value of K _O2 according to the value of the discrimination signal, and ANDs the calculated K _O2 value.
One input terminal of circuit 518 is supplied. AND
The closed loop signal = 1 from the output terminal 510a of the specific operating state detection circuit 510 is supplied to the other input terminal of the circuit 518, and during O ₂ feedback control other than the specific operating state, an AND circuit is supplied. 518 is the K _O2 calculation circuit 51
The calculated K _O2 value signal from 7 is supplied to one input terminal of a first multiplier circuit 523 as a first coefficient b via an OR circuit 520. The basic value Ti from the basic Ti calculation control circuit 521 is input as input a to the other input terminal of the first multiplier circuit 523, and this Ti value a is multiplied by the above calculated K _O2 value b, and the multiplied value signal is a×b=Ti×K _O2 is supplied to one input terminal of the second multiplier circuit 524 as input c. As mentioned above, the other input terminal of this second multiplier circuit 524 receives the coefficients K _WOT and K _LS (both 1.0) during the closed loop.
is input as input d, and the circuit 524 receives the multiplication value signal a×b=Ti×K _O2 and the coefficient K _WOT ,
Multiply by K _LS to obtain the reference value T _OUT (actually the same as the output multiplication value of the first multiplier circuit 523).
Provides to T _OUT value register 525. And T _OUT
In the value control circuit 526, the other _correction coefficients K _TA ,
K _AFC , K _PA , K _AST , etc., constants T _ACC , T _DEC , _TV , etc. are added and/or multiplied as appropriate to perform arithmetic processing according to the basic formula described above, and a predetermined drive output is supplied to the main injector. .

AND in the above O ₂ feedback control
The output of the circuit 518 is also supplied to an average value calculation circuit 519, which calculates the average value K _REF based on the calculated K _O2 value that is sequentially input during O ₂ feedback control, and uses this K _REF value signal is supplied to one input terminal of the AND circuit 522.

Next, the specific operating state of the engine is detected by the detection circuit 5.
10, the open loop signal = 1 is supplied from the output terminal 510b of the circuit 510 to the other input terminal of the AND circuit 522, so that the calculated K _REF value signal of the average value calculation circuit 519 corresponds to the corresponding value.
It is supplied as a first coefficient to a first multiplier circuit 523 via an AND circuit 522 and an OR circuit 520.

The first multiplier circuit 523 uses the basic value Ti as described above.
The signal of the value obtained by multiplying this calculated K _REF by the second
The signal is supplied to a multiplication circuit 524. During the open loop, the coefficients (K _WOT , K _LS ) of the second predetermined value memory 514 described above are input to the AND circuit 512 and the OR circuit 51.
5 to the second multiplier circuit 524 as the second coefficient, and the circuit 524 is input to the first multiplier circuit 52 as the second coefficient.
The multiplication value from 3 is multiplied by this second coefficient, and the signal of the multiplication value is supplied to the T _OUT value register 525. From this point on, the T _OUT value register 525 and
The T _OUT value control circuit 526 performs valve opening time control similar to the closed loop operation described above.

FIG. 8 is a circuit diagram showing an example of the internal configuration of the specific operating state circuit 510 and lean/rich comparison circuit 516 of FIG. 7. Lean/rich comparison circuit 51
6 is a comparator that receives the output of the _O2 sensor 15 at its inverting input terminal and the reference voltage _E1 at its non-inverting input terminal.
The comparator COMP ₁ outputs High output = 1 when the output of the O ₂ sensor is lower than the reference voltage E ₁ , that is _, when the air-fuel mixture is in a lean state, and when it is high, that is, when the air-fuel mixture is in a rich state. outputs _LOW output = 0, respectively, and the K _O2 calculation circuit 517 in Fig. 7
supply to. Further, the output of the O ₂ sensor 15 is also supplied to the comparator COMP ₂ of the O ₂ sensor activation determination section of the specific driving state detection circuit 510. As the O ₂ sensor becomes activated, its internal resistance decreases and the output voltage drops, but the comparator COMP ₂ uses the O ₂ sensor output, which is input to the inverting input terminal, as the reference voltage E ₂ , which is input to the non-inverting input terminal. (for example, 0.6V), the output = 1 is output and the RS flip-flop 52
It is applied to the set input terminal S of No.7. When the RS flip-flop 527 starts the engine, an initial reset signal is supplied to the reset input terminal R to set the output of the Q output terminal to 0, but the comparator COMP ₂
When the output = 1 is given from the Q output terminal, the AND circuit 52 outputs the output = 1 as an activation signal.
8 is supplied to one input terminal of 8.

Furthermore, there is a memory for storing predetermined values that serve as criteria for determining each specific operating state, that is, a θ _WOT value memory 529 and a N _IDL value memory for determining the throttle valve fully open range, idle range, deceleration range, and lean operation range, respectively. 530, P _BIDL value memory 531, P _BDEC value memory 5
32, K _LS =1.0 memories 533 are connected to corresponding comparison circuits 534-538, respectively. As described below, these comparison circuits 534-538 output == when the conditions of each specific operating state are not satisfied.
1 is output for each.

First, in the comparison circuit 534, when a predetermined value θ _WOT (for example, 50°)≧the actual throttle valve opening θ, that is, when A ₁ ≧B ₁ in the figure, an output=1 is outputted, and the output is supplied to the AND circuit 528. The comparison circuit 535 performs a predetermined number of times.
N _IDL (For example, 1000 rpm) If the input A ₂ corresponding to the actual rotation speed Ne, that is, the predetermined rotation speed, and the time count value input B ₂ between TDC for the actual rotation speed are A ₂ ≧
When B ₂ , output = 1. In terms of engine rotation speed, the predetermined rotation speed (1000 rpm) is the actual rotation speed. In addition, in the N _IDL memory 530, the rotation speed Ne
is a value obtained by counting the reference clock pulses between TDC signal pulses.
N The reciprocal of _{the IDL} value is stored. In addition, the comparison circuit 536 outputs a predetermined absolute pressure P _BIDL (for example, 360 mmHg).
Output=1 when the actual absolute pressure P _B , that is, A ₃ B ₃ . When the output of either of the comparators 535 and 536 = 1, the output is sent to the OR circuit 539.
is supplied to the AND circuit 528 via.

The comparator circuit 537 outputs an output of 1 when the predetermined absolute pressure P _BDEL is the actual absolute pressure P _B , that is, A ₄ B ₄ ,
It is supplied to one input terminal of the AND circuit 540.
The AND circuit 540 supplies an output =1 to the AND circuit 528, which receives this output =1 and the binary signal =1 when the fuel cut is not established which is input to the other input terminal. Furthermore, in the comparator 538, when the actual correction coefficient K _LS = 1.0, that is, A ₅ = B ₅ , the output =
1 is output and supplied to the AND circuit 528. AND
The circuit 528 outputs an output of 1 as a closed loop signal from the output terminal 510a when all outputs of the comparison circuits 534 to 538 are inputted with the O ₂ sensor activation signal of 1.
Also, when the O ₂ activation signal = 1 is not input, or when the output of any one of the comparison circuits 534 to 536 is 0, the AND circuit 528
The output of is 0, and in this case, this output = 0
The output is inverted to 1 by an inverter 541 connected to the output side of the AND circuit 528, and output as an open loop signal via the output terminal 510b.

FIG. 9 is a circuit diagram showing an example of the internal configuration of the K _O2 calculation circuit shown in FIG. 7. The closed loop signal = 1 from the specific operating state detection circuit 510 in FIG.
It is supplied to the D input terminal of 1D flip-flop 542.

This flip-flop 542 outputs a flag signal indicating the current operating state, and outputs an output of 1 during a closed loop and an output of 0 during an open loop. That is, when the closed loop signal = 1 is input, an output = 1 is output to the Q output terminal at the input timing of clock pulse CP ₁ from the sequence clock generation circuit 502 in FIG. 7, and the AND circuits 544, 545, 5
46. 1D flip-flop 542
A 2D flip-flop 543 is connected to the 2D flip-flop 543, and this flip-flop 543 outputs a flag signal indicating the previous operating state.
If the previous time was a closed loop signal, output = 1 to the output terminal, and if it was an open loop, output = 1.
0 is output for each.

Here, assuming that the previous circuit was a closed loop, the output = 1 is output from the 2D flip-flop 543, and this output = 1 is sent directly to the AND circuit 544 and then to the AND circuit via the inverter 547.
are respectively supplied to circuits 545.

On the other hand, the Loreen/Rich discrimination signal from the Lean/Rich comparator circuit 516 shown in detail in FIG.
It is input to the D input terminal of the 3D flip-flop 548. This 3D flip-flop 548 outputs the current club signal of the _Q2 sensor output, and when the lean state signal = 1 is input from the lean/rich comparison circuit 516, it outputs the club signal to the Q output terminal.
When rich state signal = 0 is inputted to 1, output = 0
are output at the input timing of clock pulse _CP1 . This 3D flip-flop 54
A fourth D flip-flop 549 is connected to 8, and this flip-flop 549 outputs a flag signal of the previous O ₂ sensor output.
If the previous O ₂ sensor output indicates a lean state, an output = 1 is output to the Q output terminal, and if the previous O 2 sensor output indicates a rich state, an output = 0 is output. Therefore, the lean/
If the lean/rich determination signal of the rich comparison circuit 516 is inverted, the third and fourth D flip-flops 5
The outputs of 48 and 549 are different from each other, for example, one is 1 and the other is 0. Both flip-flops 54
The outputs of flip-flops 548 and 549 are input to an exclusive OR circuit 550, but when the lean/rich determination signal is inverted, the outputs of both flip-flops 548 and 549 are different from each other, so the exclusive OR circuit 550 outputs an output of 1. This output = 1 directly corresponds to the AND circuit 5 mentioned above.
44,545 and also via the inverter 551.
It is supplied to AND circuit 546.

Returning to the assumption that the current time is a closed loop and the previous time is a closed loop as described above, if the lean/rich determination signal is reversed between the previous time and this time, the AND circuit 544
has flip-flop 5 on all its input terminals.
Since output = 1 is input from both 42, 543 and exclusive OR circuit 550, AND circuit 5
44 outputs output=1. This output is used as a proportional (P term) control command signal as described below.
Proportional control of the air-fuel ratio is performed.

Note that in this assumption, the AND circuits 545, 54
6, the output = 0 is input to one of the input terminals by the action of the inverters 547 and 551, respectively, so the output of the OR circuit 552 connected to the output side of both the AND circuits 545 and 546 is 1
When , the integral (I term, used as a control command signal) is 0, and no integral control is performed.

Here, if the lean/rich discrimination signal does not invert between the previous time and this time, contrary to the above, AND
The output of the circuit 544 becomes 0 and no P-term control is performed, while the output of the AND circuit 546 becomes 1,
An I-term control command signal is outputted via the OR circuit 552, and I-term control is performed.

Also, when the previous time was an open loop,
The output of the AND circuit 544 becomes 0, while the output of the flip-flop 543 becomes 0, so the output =
AND which inputs 0 via inverter 547
The output of the circuit 545 becomes 1, and I-term control is performed.

All of the above-mentioned operations apply when the current time is a closed loop, but when the current time is an open loop, the 1D
The output of flip-flop 542 becomes 0, and therefore, this output = 0 is input to each input terminal of all AND circuits 544, 545, and 546, so neither P-term nor I-term control is performed.

Furthermore, at the end of this cycle, the second and second
The 4D flip-flops 543 and 549 are reset by the clock pulse _CP6 to output the current operating status and the _O2 sensor output plug signals, respectively.

Next, a case where I-term control is performed in the circuit of FIG. 9 will be described. The aforementioned OR circuit 552
The output of 1 is input to one input terminal of each of AND circuits 553 and 554. Here, if the level of the lean/rich discrimination signal of the lean/rich comparison circuit 516 in FIGS.
directly input to another input terminal of the AND circuit 553,
Output=0 is input to the other AND circuit 554 via an inverter 555. Therefore, when the _Q2 sensor output indicates a lean mixture, the AND
Circuit 553 is activated. The AND circuit 553 outputs a single pulse every time the clock pulse CP ₂ is input in the state where both of the above outputs = 1 are input _.
The counter 556 counts the number of pulses and applies the count value to a comparator circuit 557 as input B ₆ . Comparison circuit 55
7 is this count value B ₆ and the predetermined N _I value memory 558
When A ₆ = _{B 6 ,} an output of 1 is supplied to the D input terminal of the fifth D flip _- flop 559. At this time, the 5D flip-flop 559 is in a state reset by the clock pulse CP ₁ , but at the input timing of the clock pulse CP ₃ , it outputs an output = 1 to the Q output terminal, and Δk
It is supplied to one of the three input terminals of the AND circuit 561 as a value addition command symbol. This AND circuit 56
The I term control command signal = 1 from the above-mentioned OR circuit 552 is input to another input terminal of 1.
The AND circuit 561 is inputted to the last input terminal on the condition that these two signals=1 are inputted, and is the amount of change for one time to be added to K _O2 . The Δk value signal of the memory 562 that stores the Δk value
Input Y to adder circuit 564 via OR circuit 563
Supply as. The previous K _O2 value is input to this adder circuit 564 as input X;
The sum value X+Y _{of the K O2 value} Set in register 566, K _O2
The value is updated. This K _O2 value is input to the addition circuit 564 to be used as the previous K _O2 value X in the next control cycle. At the same time, the clock pulse CP ₅ is applied to the other input terminal of the AND circuit 560, which has one input terminal receiving the Δk value addition command signal from the flip-flop 559, so that the AND circuit 560 ORs the single pulse. A reset signal is applied to the N _IL counter 556 via the circuit 567, and the count value is set to O. Note that when the input count value _B6 of the comparator 557 does not reach the predetermined store value N _L value _A6 , the Δk value addition command signal is not generated.
The input value Y of the adder circuit 564 is 0, so the K _O2 value auxiliary register 565 and the K _O2 value register 5
Even if clock pulses CP ₄ and CP ₅ are input to 66, the stored values of these registers do not change and maintain the previous K _O2 value.

Note that the above clock pulse CP ₅ is applied exclusively to one input terminal when the lean/rich discrimination signal is inverted.
Output = 1 is input from OR circuit 550
is input to the other input terminal of the AND circuit 568,
AND circuit 568 outputs a single pulse to reset _NIL counter 556 via OR circuit 567.

On the other hand, the lean/rich determination signal from the lean/rich comparator circuit 516 representing the O ₂ sensor output is
When the air-fuel mixture is _low , that is, when the air-fuel mixture is rich, this output = 0 is input to the AND circuit 553.
The output of the AND circuit 553 becomes 0 and the above-mentioned Δk
While the value addition operation is not performed, the above output = 0 is inverted to output = 1 by the inverter 555.
It is input to one input terminal of the AND circuit 554. Another input terminal of this AND circuit 554 has the above-mentioned OR
Since output = 1 is input from the circuit 552,
AND circuit 554 outputs a single pulse every time clock pulse CP ₂ is input to the last input terminal.
N is applied to _{the IH} counter 569. After this, a Δk value subtraction operation similar to the Δk value addition operation described above is performed. That is, when the count value A ₇ of the single pulse reaches the predetermined value B ₇ from the N _I value memory 558 (where A ₆ and B ₇ are A ₆ =B ₇ ), the comparator 570 outputs = 1 to the 6th D flip-flop 571 (reset by clock pulse CP ₁ )
and the output = 1 becomes Δk at the input timing of clock pulse _CP3 from the flip-flop 571.
It is supplied to the AND circuit 572 as a value subtraction command signal and the value memory (value = 2's complement of Δk) 573
The stored value is AND circuit 572, OR circuit 56
3 to the adder circuit 564. This value Y is added to _the previous K _O2 value to K _O2 value auxiliary register 565 and K _O2
clock pulses in each value register 566.
It is set at the input timing of CP ₄ and CP ₅ , and an updated K _O2 value is obtained. Similar to the Δk value addition operation described above, the N _IH value counter 569 is reset to 0 via the AND circuit 574 and the OR circuit 575 by this clock pulse CP ₅ .

The operations other than those described above are the same as the Δk value addition operations described above, so the explanation will be omitted.

Next, to explain the case where P-term control is performed, as mentioned above, if there is a closed loop in the previous time as well as in this time, and the O ₂ sensor output is reversed between the previous time and this time, the AND circuit 544 Output=1 is supplied to one input terminal of AND circuits 576 and 578 as a P-term control command signal. Immediately after the air-fuel mixture changes from rich to lean, an output of 1 is input from the lean/rich comparator circuit 516 of FIG. 8 to another input terminal of the AND circuit 576. Therefore, AND circuit 576
supplies a correction value Pi from a Pi value memory 577 to be described later, which is input to the last input terminal while these outputs = 1 are being input, to the addition circuit 564 as input Y via the OR circuit 563. After this, in the same way as the Δk value addition/subtraction operation in the I-term control described above, the adding circuit 564 converts this Pi value to the previous value.
It is added to the K _O2 value and set in the auxiliary register 565 and the K _O2 value register 566, respectively, to update the K _O2 value.

On the other hand, immediately after the air-fuel mixture changes from lean to rich, the lean/rich comparator circuit 516 outputs an output = 0, and this output = 0 is the output of the inverter 5.
55 inverts the output to 1 and outputs it to AND circuit 57
8 further input terminals. The P-term control command signal = 1 is input to the one input terminal of this AND circuit 578, and while these outputs = 1 are being input, the AND circuit 578 receives a value, which will be described later, which is input to the last input terminal. The correction value from memory 579 is supplied as input Y to adder circuit 564 via OR circuit 563. This is the two's complement of the above Pi, so in the adder circuit 564, the previous K _O2
effectively subtracting the Pi value from the value and setting the subtracted value in registers 565 and 566 in the same manner as described above;
K _O2 is updated.

FIG. 10 shows details of the Pi value memory 577 and value memory 579 in the circuit of FIG. 9, and the method of obtaining the Pi value and the value using the circuit of FIG. 10 will be described below. As explained with reference to FIG. 6, the correction values Pi and are determined according to the output value Ne from the engine rotation speed sensor 11, for example.
The range from 1500rpm to 3500rpm is divided into 5 stages.
N _FB1 (=value corresponding to 1500rpm), N _FB2 (=
value corresponding to 2000 rpm), ......, N _FB5 (=
The value corresponding to 3500rpm) is N _FB1~5 value memory 5
80a to 580e, and Pi values corresponding to the respective rotational speeds NFB1 _{to 5} are stored in P1 _{to 6} value memories 581a to 581f. or,
P _{1 to 6} values 2's complement values _{1 to 6} are _{1 to 6} value memory 582a
~582f. The Pi value memory 5
Each of 81a to 581f is an AND circuit 585
The output terminals of the AND circuits 585a to 585f are connected to the input terminal of an OR circuit 586. Similarly, value memories 582a to 5
Each output terminal of 82f is an AND circuit 587
The output terminals of the AND circuits 587a to 587f are connected to the input terminal of an OR circuit 588.

The N _E value signal corresponding to the output signal from the engine speed sensor 11 (proportional to the reciprocal of the engine speed Ne value. Therefore, the higher the engine speed, the smaller the N _E value) is compared. Circuits 583a to 583
The respective inputs A _{10 to 14} are applied to one input terminal of e, and the inputs B _{10 to 14} are applied to each other input terminal.
The N _{FB1 to 5} values stored in the N _{FB1 to 5} value memory are respectively applied.

One output terminal of the comparison circuit 583a is connected to the above-mentioned
A comparison circuit 583 is connected to the other input terminal of each of the AND circuits 585a and 587a, and when the relationship A ₁₀ ≧B ₁₀ holds, output=1 is supplied to the AND circuits 585a and 587a.
The other output terminal of a is connected to one input terminal of the AND circuit 584a, and when the relationship A ₁₀ <B ₁₀ is established, the output to the AND circuit 584a is
1 is supplied. Similarly, comparison circuits 583b to 58
One output terminal of each of the circuits 3e is connected to the other input terminal of the AND circuit 584a and the AND circuit 584b,
It is connected to one input terminal of each of 584c and 584d, and when the relationship of N _E value (A _{11 to 14} ) ≧ N _FB value (B _{11 to 14} ) is established, each AND
Output=1 is provided to circuits 584a-584d. Further, the other output terminals of each of the comparison circuits 583b to 583e are connected to AND circuits 584b to 584d.
It is also connected to the other input terminal of each of AND circuits 585f and 587f, and when the relationship of N _E value (A _{11 to 14} ) < N _FB value (B _{11 to 14} ) is established, each AND circuit 584b to Output=1 is supplied to 584d and AND circuits 585f and 587f. The AND circuit 584a has input terminals of the other of the AND circuits 585b and 587b.
The AND circuit 584b connects the AND circuit 5 to the other input terminal of the AND circuits 585c and 587c.
84c is the aforementioned AND circuit 585d and 587d
The AND circuit 584d is connected to the other input terminal of the AND circuits 585e and 587e, respectively. When output=1 is simultaneously input to two input terminals of each of the AND circuits 584a to 584d, output=1 is supplied to the corresponding input terminal of the AND circuit.

The current output value Ne from the engine speed sensor 11
=1750 rpm as an example, the comparison circuit 58
In 3a, the value corresponding to 1750 rpm is input to A ₁₀ , and the value corresponding to 1500 rpm is input to B ₁₀ , so A ₁₀ <
B ₁₀ is established, and output = 0 to AND circuit 585a.
An output of 1 is supplied to each input terminal of the AND circuit 584a. A ₁₁ in comparison circuit 583b
has a value corresponding to 1750rpm, B ₁₁ has a value corresponding to 2000rpm
Since a value corresponding to is inputted, A ₁₁ ≧B ₁₁ is established, and the AND circuit 584a is supplied with an output of 1, and the AND circuit 584b is supplied with an output of 0 to their respective input terminals. Similarly, comparison circuits 583c to 583
AND circuits 584b to 584d, 585f from e
And output=1 or 0 is input to 587f. In this example, only the AND circuit 584a receives an output of 1 from its two input terminals, so as a result, an output of 1 is output from the output terminal of the AND circuit 584a.
Output=1 is input to the input terminals of AND circuits 585b and 587b, and other AND circuits 585a and 587b
85c-585f, 587a and 587c-58
Output=0 is input to 7f. AND circuit 58
The _P2 value stored in the _P2 value memory described above is input to the other input terminal of 5b, and while the output = 1 from the AND circuit 584a is input, the OR
The _P2 value is input to circuit 586. Similarly, _two values are input from the AND circuit 587b to the OR circuit 588. The P ₂ values and ₂ values from the above OR circuits 586 and 588 are respectively output from the AND circuits 576 and 57 in FIG.
8. The same applies to other rotational speeds Ne, so the explanation will be omitted.

Regarding the case where the above-mentioned I-term control is performed,
An example of performing I-term control proportional to engine speed Ne by increasing/decreasing Δk to a coefficient K _{O2 every} time N TDC pulses N I has been explained based on the flowchart in Fig. 5, but other application examples , I-term control uses the same method as described for P-term control, that is, the coefficient
The correction value for correcting K _O2 may be selected and determined from a plurality of predetermined values i _c that are preset according to the rotational speed Ne.

As detailed above, according to the present invention, the coefficient K _O2 applied in the air-fuel ratio feedback control performed in accordance with the output value of the _O2 sensor disposed in the exhaust system of the internal combustion engine is In P-term and I-term control that increases or decreases the value, that is, P-term control, when the O ₂ sensor output signal is reversed, a constant value P _i corresponding to the engine rotation speed Ne is increased or decreased to a coefficient K _O2 in the direction of correcting this. In I-term control, when the O ₂ sensor output signal continues at the same level, the constant value Δk is increased or decreased by the coefficient K _{O 2} every N _I TDC pulses in the direction of correcting this, thereby changing the engine rotation. It is possible to perform control according to the requirements, and it is possible to perform accurate and responsive control.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the entire air-fuel ratio feedback control system of the present invention, and Fig. 2 is a main block diagram of the ECU of Fig. 1. Sub-injector opening time T _OUTM ,
A block diagram of the overall program configuration of the T _OUTS control contents, Figure 3 is a timing chart showing the relationship between the cylinder discrimination signal and TDC signal input to the ECU, and the main and sub-injector drive signals output from the ECU. Fig. 4 is a flowchart of the main program for calculating the basic valve opening times T _OUTM and T _OUTS , Fig. 5 is a flowchart of the subroutine for calculating the _O2 feedback correction coefficient K _O2 , and Fig. 6 is a flowchart of the subroutine for calculating the O2 feedback correction coefficient K _O2 . Ne-Pi table for determining correction value Pi, Figure 7 shows correction coefficient K _O2
Figures 8 and 9 are detailed diagrams of the lean/rich comparison circuit, specific operating state detection circuit, and K _O2 calculation circuit in Figure 7, respectively, and Figure 10 is a circuit diagram of the entire ECU internal configuration showing the calculation block in detail. The figure is a detailed explanatory diagram of the Pi value, the circuit for selecting the value, the Pi value memory, and the value memory when performing the P-term control of FIG. 9. 1...Internal combustion engine, 5...ECU, 8...Absolute pressure sensor, 11...Engine speed sensor, 1
3... Exhaust pipe, 15... O ₂ sensor, 510...
Specific operating state detection circuit, 516... Lean/rich comparison circuit, 517... K _O2 calculation circuit.

Claims (1)

[Claims] 1 An electronic air-fuel ratio feedback control device that controls the air-fuel ratio of the air-fuel mixture supplied to the engine to a target air-fuel ratio according to the output of an exhaust gas concentration detector disposed in the exhaust system of an internal combustion engine, which An angular position detector that outputs a signal at the rotational position, a comparator that outputs a binary signal by comparing the output of the detector with a reference value, and an engine rotational speed detector that outputs a rotational speed signal according to the engine rotational speed. means, and the angular position signal, the binary signal, and the rotation speed signal are arranged to be inputtable, and the binary signal is discriminated every time the angular position signal is input, and when the detector output changes across a reference value. An electronic type including a digital control circuit that performs proportional control by selectively performing integral control as long as it changes only on one side with respect to the reference value, and determines the control amount of the air-fuel ratio so that the air-fuel ratio becomes the target air-fuel ratio. In the air-fuel ratio feedback control device, the control circuit performs the proportional control by reading from a memory a proportional term set to increase as the engine speed indicated by the rotation speed signal increases each time the angular position signal is input. , the control amount is increased or decreased based on the read proportional term, and the integral control is performed by increasing or decreasing the control amount by a constant value every predetermined number of angular position signals regardless of the rotational speed signal. An electronic air-fuel ratio feedback control device for an internal combustion engine, characterized in that: