JPS6338533B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control method that detects an air-fuel ratio based on exhaust gas components of an internal combustion engine and feedback-controls the air-fuel ratio of a mixture supplied to the internal combustion engine based on the detection signal. .

The conventional air-fuel ratio control method is simply integral control based on the output of the air-fuel ratio sensor, and detects a transient state and performs acceleration increase, deceleration decrease, etc., regardless of the output of the air-fuel ratio sensor. For this reason, during transient periods such as acceleration and deceleration of the internal combustion engine, the stoichiometric air-fuel ratio is not met, resulting in deterioration of exhaust gas.

In view of the above problems, the present invention proposes an air-fuel ratio control method that can improve exhaust gas purification by keeping the air-fuel ratio as close to the stoichiometric air-fuel ratio as possible even when the feedback control is stopped and during transitions such as acceleration and deceleration of the internal combustion engine. It is something.

The method of the present invention is characterized by an air-fuel ratio sensor that detects the air-fuel ratio based on the exhaust gas components of the internal combustion engine, and a value for transient fuel correction corresponding to at least the magnitude of the transient state of the engine. This method has a rewritable non-volatile memory that is always stored regardless of whether the engine is running or stopped, and controls the amount of fuel supplied to the engine during a transient period regardless of execution of feedback control or stoppage. By rewriting the value of the non-volatile memory during feedback control execution according to the sensor signal, the feedback period of the air-fuel ratio sensor is prevented from becoming longer, that is, the fuel amount is controlled to the target air-fuel ratio even during a transient period. The purpose is to prevent the deterioration of exhaust gas.

The present invention will be explained below with reference to embodiments shown in the drawings. FIG. 1 shows an embodiment of the present invention, in which an internal combustion engine 1 is a known four-stroke spark ignition internal combustion engine installed in an automobile, and fuel air is supplied to an air cleaner 2, an intake passage 3, a throttle valve 4, Inhale through the intake pipe 9. Further, fuel is supplied from a fuel system (not shown) to electromagnetic fuel injection valves 5 provided corresponding to each cylinder.
Supplied via. Exhaust gas after combustion is passed through the exhaust manifold 6, exhaust pipe 7, and three-way catalytic converter 8.
It is then released into the atmosphere. Further, a pressure sensor 11 for detecting intake pipe pressure is connected to the intake pipe 9 via a conduit 10.
It is connected to and generates an output corresponding to the amount of intake air. Further, a thermistor-type intake temperature sensor 12 is installed that detects the temperature of air taken into the engine 1 and outputs an analog voltage according to the intake temperature.

In addition, the engine 1 is equipped with a thermistor-type water temperature sensor 13 that detects the cooling water temperature and outputs an analog voltage according to the cooling water temperature, and the exhaust manifold 6 is further equipped with a thermistor-type water temperature sensor 13 that detects the air-fuel ratio from the oxygen concentration in the exhaust gas. An air-fuel ratio sensor 14 is installed which outputs a voltage of about 1 volt (high level) when the air-fuel ratio is smaller than the stoichiometric air-fuel ratio (rich) and about 0.1 volt (low level) when it is larger than the stoichiometric air-fuel ratio (lean). ing.

The rotation sensor 15 detects the rotation speed of the crankshaft of the engine 1 and outputs a pulse signal with a frequency corresponding to the rotation speed. 16 is a power source that generates a DC voltage obtained by stabilizing the voltage from the battery 16-1. The control circuit 20 calculates the fuel injection amount based on the detection signals of the sensors 11 to 16, and adjusts the fuel injection amount by controlling the opening time of the electromagnetic fuel injection valve 5.

Figure 2 A, B, C, and D are the intake pipe pressure P and the difference value of the intake pipe pressure P [(pn-pn-1)/(Tn-Tn-1)], respectively, during the transient period of the internal combustion engine, and the transient correction The acceleration increase ratio as a value and the output of the air-fuel ratio sensor are shown with elapsed time as the horizontal axis.

In the case of characteristic a with a small increase ratio in FIG. 2C for the difference value of intake pipe pressure as shown in FIG. 2B, the output of the air-fuel ratio sensor becomes characteristic aa in FIG. Indicates a state in which the increase in fuel quantity is insufficient, and in the case of an increase ratio like characteristic b, the output of the air-fuel ratio sensor becomes an output like characteristic bb, as in the steady state, and the adaptive value of the fuel increase is well within the stoichiometric air-fuel ratio. Indicates the state of fit.

In the present invention, the air-fuel ratio sensor output always outputs a characteristic bb in any transient state, and by matching the air-fuel ratio to the stoichiometric air-fuel ratio, the purification rate of the three-way catalyst is always kept at its best and the exhaust gas is purified. It is.

Now, when accelerating, it is generally necessary to increase the amount due to the sensor's delayed response, etc., but when decelerating, it is also necessary to decrease it due to the sensor's delayed response, etc., and Figure 3 A, B, C, and D show the intake pipe pressure at that time. P, difference value of intake pipe pressure P [(pn-pn-1)/
(Tn−Tn−1)], reduction ratio as transient correction value,
and the air-fuel ratio sensor output are shown with elapsed time as the horizontal axis.

In the case of a reduction ratio of characteristic C in Fig. 3C, the output of the air-fuel ratio sensor becomes an output as shown in characteristic CC in Fig. 3D, indicating a state in which the fuel reduction is still insufficient.
By further reducing the amount of fuel to bring it to a characteristic like the characteristic d, the air-fuel ratio sensor output becomes an output like the characteristic dd, indicating a state in which the value of the fuel reduction matches well with the stoichiometric air-fuel ratio.

Next, the control circuit 20 will be explained in detail with reference to FIG. 70 is a CPU (central processing unit) that performs calculations and control, and uses a microprocessor. 71
is the system bus, which includes the data bus, address bus,
Consists of a control bus. The CPU 70 sends and receives data to and from each of the other circuit units 72 to 77 through the system bus 71. The timer section 72
In addition to supplying the operating clock to the CPU 70,
A clock is also supplied to the interrupt control section 73, input interface section 74, and fuel injection control section 77, respectively.

The interrupt control unit 73 receives a timer interrupt request signal at fixed time intervals (approximately 8 to 50 ms) based on the signal from the timer unit 72, and receives an ignition interrupt request signal based on the ignition pulse signal from the rotation sensor 15. and reset each interrupt request signal.
do. The input interface section 74 is a section that converts signals from each sensor into a form that can be used by the CPU 70, and includes a pressure sensor 11 that detects intake pipe pressure, an intake air temperature sensor 12, and a cooling water temperature sensor 1.
3. Each analog signal PM from the battery terminal,
Convert THA, THW, and V _B to digital data using an A/D converter. Furthermore, the air-fuel ratio sensor 14
The comparator determines whether the current air-fuel ratio is above the stoichiometric air-fuel ratio (lean) or below (rich) based on the signal λ from the CPU 70 . Also, using the clock signal from the timer section 72, the interval between adjacent ignition pulse signals from the rotation sensor 15 is stored, and the data is stored in the CPU 7.
0 and calculate the rotation speed as described below.

Reference numeral 75 denotes a read-only memory unit (ROM) that stores programs and optimum control data for each engine condition, and 76 indicates a temporary memory unit (RAM) used during program operation. 78 is a non-volatile RAM that stores the transient correction map even when the engine is stopped. Reference numeral 77 denotes a fuel injection control section which converts the injection time data transferred from the CPU 70 into a valve opening time pulse width using a clock supplied from the timer section 72, and opens the injector (electromagnetic fuel injection valve) 5 during this time.

In other words, the injector 5, which is opened by the IG pulse signal whose frequency is divided by 2, is connected to the CPU.
The valve is opened for the injection time data transferred from 70. Note that this embodiment employs a six-cylinder synchronous injection system, and the injectors of each cylinder are connected in parallel. The CPU 70 inputs the input signals from each sensor through the input interface section 74 according to the program stored in the ROM 75, calculates the optimum injection amount according to the engine condition at that time, and sends the input signal to the fuel injection control section 77. Output data.

FIG. 5 shows a more detailed circuit diagram of the fuel injection control section 77. The operation will be explained below with reference to timing charts shown in FIGS. 7A and 7B. 71
0 indicates a data bus, which is the system bus 7 in FIG.
It is one component of 1. The high voltage pulse of the primary coil generated by the rotation sensor 15 each time ignition is waveform-shaped by an interface circuit 74 shown in FIG. 4, and when the frequency is divided by two, it becomes an IG pulse signal as shown in FIG. 7A. This IG pulse, which is generated once every two ignitions, sets the Q output of the injection control flip-flop (I.FF) 702 to "1" (output to "0") through the terminal 720 in FIG. At the same time, the IG pulse is applied to the G terminal of the injection time register (IR) 700 and the L terminal of the down counter (DC) 701, and the injection time data E, which was previously set in I.R 700 by the CPU 70, passes through the path 711 to the D .C7
Transferred to 01. When I.FF702 is set,
The Q output connected to the E terminal of the D.C701 becomes "1" and a down count is started. DC
The data transferred to the timer section 701 is counted down by the 8 μs clock supplied from the timer section 72 until it becomes "zero" (the ZD terminal is "1").

When the Zero Deteet (ZD) terminal of DC701 becomes "1", "1" is input to the R terminal of I.FF702, and I.
The FF 702 is reset (Q output is "0", output is "1"). At the same time, the E terminal of the D.C 701 becomes "0" again and the down count ends. Therefore, the output signal of I.FF 702 (injector valve opening drive signal) becomes as shown in FIG. 7B.
The output of I.FF702 is connected to the first stage transistor 731 of the power amplifier circuit 730 through a resistor.
Further, its emitter is connected to transistors 732 and 733 forming a pair of Darlington transistors. The collector of the transistor 733 is connected to one terminal of the six drive coils of the injector 5 through the output terminal 723.
The other terminal of the drive coil is connected to the positive side (V _B ) of the battery through a resistor.
Therefore, while the output of IFF 702 is "0", transistors 731 to 733 are all turned on, and current flows through the drive coil of injector 5.
Injector 5 is opened. That is, as shown in Fig. 7A and B, each time an IG pulse is generated,
The injector 5 starts injection, and injects fuel for an amount corresponding to the injection time data calculated by the CPU 70 and set in the I.R 700.

FIG. 6 shows a detailed circuit diagram of the air-fuel ratio sensor input circuit of the input interface section 74. The operation will be explained below with reference to timing charts shown in FIGS. 7C and 7D. Air fuel ratio sensor 14
The output voltage (in this example, the main component is ZrO ₂ ) (FIG. 7C) is connected to the inverting input terminal (-) of the first comparator 750 through an input terminal 725 and a resistor 760. On the other hand, comparator 75
The non-inverting input terminal (+) of 0 is the voltage dividing resistor 761,
It is fixed at 0.45V by 762. Therefore, when the output voltage of the air-fuel ratio sensor 14 is 0.45V or less (lean), the output of the comparator 750 becomes "1", and when it is 0.45V or more (rich), the output becomes "0". The output of comparator 750 is resistor 764,7
67 and is input to the inverting input terminal of the second comparator 751. The resistor 764 and the capacitor 765 constitute an integrating circuit when the air-fuel ratio is reversed from lean to rich, and the resistors 763, 764 and the capacitor 765 constitute an integral circuit when the air-fuel ratio is reversed from rich to lean. This is to correct chattering in the air-fuel ratio sensor output signal caused by variations in the air-fuel ratio between cylinders, ignition noise, and the like. The non-inverting input terminal of the comparator 751 is the first
Similarly to the comparator 750, the voltage dividing resistor 768,
769 inputs a reference voltage of about 0.45V, but the reference voltage value is slightly larger than 0.45V when the output of the comparator 751 is "1" due to the positive feedback resistor 771, and is slightly smaller when the output is "0". By providing hysteresis in the comparator 751, the output of the comparator 751 becomes "0" when the output of the comparator 750 is "1" (1ean), and becomes "1" when the output of the comparator 750 is "0" (rich). Therefore, with respect to the air-fuel ratio sensor output voltage signal shown in FIG. 7C, the output of the comparator 751 becomes "0" when lean and "1" when rich, as shown in (h). The output of the comparator 751 is connected to the input port of the CPU 70 through a terminal 726, and the CPU 70 calculates the feedback control amount of the air-fuel ratio by accessing this input port at fixed time intervals using a timer interrupt to be described later.

Next, the programs stored in the ROM 75 will be described in detail. The program can be divided into three levels: main routine, timer interrupt handling program, and injection interrupt program. The explanations will be given below. First, regarding the main routine, it is the program with the lowest execution priority, and if any of the other two interrupts occur while this program is being executed, that execution will take priority and the main routine will be temporarily suspended. It will be resumed after the interrupt program ends.

Next, the processing in the main routine is shown in FIG. The main routine starts processing when the power of the control circuit 20 is turned OFF and then ON, and first proceeds to step 1001 to execute initialization processing. In the initialization process, the control circuit 20 is initialized, for example.
Clearing the RAM 76, setting initial data, enabling interrupts, etc. are executed. Next, the process proceeds to step 1002, where the engine coolant temperature THW is calculated based on the signal from the water temperature sensor 13, and step 1003
Find the water temperature increase coefficient K _THW using a known method.
Similarly, step 100 is performed by the intake air temperature sensor 12.
Step 4 calculates the intake air temperature THA, and step 1005 calculates the intake air temperature correction coefficient K _THA . Next, step 100
At step 6, the battery voltage _VB is calculated based on the signal from the battery 16-1, and at step 1007, the invalid injection time _τNB is calculated from _VB . τ _NB is τ _NB
=−C ₁・V _B +C ₂ ...Formula (1) (however, τ _NB ≧C ₃ ,
C ₁ , C ₂ , C ₃ are constants). Next, in step 1008, the air-fuel ratio sensor determines whether the conditions for opening (stopping) the air-fuel ratio feedback control (for example, cooling water temperature, rotational speed, etc.) are met, and the conditions for holding (holding) the air-fuel ratio feedback control (for example, when the fuel injection The determination is made based on whether or not the engine is stopped (in other words, the fuel is being cut). Thereafter, the process returns to step 1002 and the above process is repeated.

Next, the timer interrupt whose execution priority is the next highest after the injection interrupt will be explained with reference to FIGS. 9 to 11. This is an interrupt that is activated at fixed time intervals (for example, 8 ms) based on a signal from the timer section 72. In response to an interrupt request signal from the interrupt control section 73, when the injection interrupt program is not being executed, step 1101 is executed immediately when the injection interrupt program is not being executed, or after the execution is completed when the injection interrupt program is being executed, and the timer request interrupt signal is reset. Next, proceed to step 1102,
The intake pipe pressure PM is calculated based on the signal from the intake pipe pressure sensor 11. If it is determined to open the feedback in the main routine described above, the determination in step 1103 is YES and the process proceeds to step 111.
0, and the feedback coefficient Kf=1 is set as the feedback control amount. If hold is determined, YES is determined in step 1104, and Kf ends the interrupt processing while maintaining the previous state.

Next, in step 1105, the transient state (acceleration,
(deceleration, etc.) and reset the judgment flag, f _LC = 0.
shall be. In step 1106, the input signal from the air-fuel ratio sensor 14, which is converted into a logical signal through the air-fuel ratio sensor input circuit shown in FIG. 6 and input to the input port of the CPU 70, is input into the CPU ₇₀ and stored in O . As shown in Figure 7
Inside the CPU 70, "lean" corresponds to "0" and "rich" corresponds to "1".

Next, condition judgment step 11 shown in FIG.
Proceed to step 20. At step 1120, the process branches to each step based on the state of both O _XR stored at step 1106 and O _XR ', the value of O _XR 8 ms ago. First, O _XR = 1 (rich),
When O×R'=0 (lean), that is, when the signal from the air-fuel ratio sensor 14 changes from lean to rich, the processes from step 1130 to step 1133 are executed.

First, in step 1130, the feedback coefficient Kf is decreased by Δskip as the feedback control amount, as in normal feedback control. That is, the following equation (2) is executed to calculate the proportional term of the coefficient Kf.

Kf = Kf - ΔSkip (2) Next, in step 1131, the time obtained by multiplying the past lean duration average T _L by K is compared with the lean duration time t _L before the change from lean to rich. . In other words, compared to the past average value, the lean time becomes longer than the set value (K・T _{L )} .
< _tR ) is a transient time (for example, during acceleration), and the determination flag _fLC is set to "1" in step 1132 in order to increase the fuel correction value, which will be described later. If it is shorter than the set value, step 1132 is skipped. Next, in step 1133, the following equation (3) is executed in order to average the lean time t _L found this time.

T _L = (T _L +t _L )/2 ...(3) Next, O _XR = 0 (lean), O _XR ′ = 1 (rich),
In other words, if the rich state is reversed to the lean state, steps 1138 to 1141 are executed. In step 1138, the feedback coefficient is
Increase Kf by Δskip. That is, the proportional term of the feedback coefficient Kf is calculated using the following equation (4).

Kf=Kf+ΔSkip...(4) Next, in step 1139, similarly to step 1131, calculate the time obtained by multiplying the average value T _R of past rich duration times by K and the rich duration time t _R before the change from rich to lean. compare. In other words, when the rich time becomes longer than the set value (K・T _R ) compared to the past average value (when K・T _R <t _R ), it is during a transient period (for example, during deceleration) that the rich time becomes longer than the set value (K・T R ). In order to reduce the correction value, the determination flag _fLC is set to "-1" in step 1140. If it is shorter than the set value, step 1140 is skipped. Next step 11
In step 41, the following equation (5) is executed in order to average the rich time t _R found this time.

T _R =(T _R +t _R )/2 (5) Next, when O×R=0 (lean) and O×R'=0 (lean), steps 1134 and 1135 are executed. In step 1134, the feedback coefficient Kf
Add the integral constant Δi to . That is, the following equation (6) is executed to calculate the integral term of the coefficient Kf.

Kf=Kf+Δi (6) In step 1135, the lean duration time _tL is increased by "1" to count.

Further, when O×R=1 (rich) and O×R'=1 (rich), steps 1136 and 1137 are executed. In step 1136, the feedback coefficient Kf
Subtract the integral constant Δi from . That is, the following equation (7) is executed.

Kf=Kf-Δi (7) In step 1137, the rich duration time _tR is incremented by "1" in order to count it.

After the above processing is completed, in step 1142, the current signal value O.times.R of the air-fuel ratio sensor 14 is transferred to O.times.R'.

This method compares the lean and rich times in the transient state with the previous feedback period to determine a flag _fLC for correction.

As another method, as shown in FIG. 10B, the lean and rich times in the transient state are arbitrarily compared with set times to determine the flag _fLC for correction. Similar to FIG. 10A, a change in the air-fuel ratio sensor 14 is detected in step 1170, and when the lean to rich condition is reversed, in step 1171, the change in the air-fuel ratio sensor 14 is detected.
kf, and in step 1172, if the lean duration time _tL is longer than the predetermined value _KL , it is determined that it is a transient period (for example, during acceleration), and the process proceeds to step 1173, where the flag _fLC is set to "1" to increase the amount of fuel. ”.
Also, when changing from rich to lean, step 117
0, proceed to step 1188, and proceed to step 118.
At step 8, set Kf+Δskip→Kf, and step 11
If the rich continuation time t _R is longer than the predetermined value K _R at step 89, it is determined that a transition is occurring (for example, during deceleration), and the process proceeds to step 1190, where a flag f _LC is set to reduce the fuel.
is set to "-1". Further, when the air-fuel ratio does not change, that is, steps 1174 to 1177 and step 1191 are the same as steps 1134 to 1137 and step 1142 in FIG. 10A, so a description thereof will be omitted.

Next, in Fig. 11, the transient correction coefficient as a transient correction value is determined depending on the state of the transient judgment flag _fLC .
The process for determining K _TR is shown by steps 1150 to 1164. First step 115
For 0, take out the intake pipe pressure PM 24ms ago and use it as PM'. In step 1151, the difference PM-PM' between PM' and the current intake pipe pressure PM is calculated, and the result is stored in A.

Next, in step 1152, acceleration/deceleration is determined. At this time, if A≧0, that is, acceleration, step 1153 is executed, and if A<0, that is, deceleration, step 1154 is executed. In step 1153, the increase ratio for the acceleration correction map TMAP1 is calculated according to the value of A according to the characteristic diagram in FIG.
Store in Δα. Also, in step 1154, the first
According to the characteristic diagram in FIG. 5, the reduction ratio for the deceleration correction map TMAP2 is calculated according to the value of A and stored in Δα. Subsequently, in step 1155, the absolute value of A is taken and used as the transient pressure change amount _PTR .

Next, in step 1156, the process branches into three processing steps depending on the state of the transient determination flag _fLC described above. When f _LC = 1, it is determined that the output of the air-fuel ratio sensor is in a lean state, and in step 1157, a transient correction map described later is used.
Let R=Δα as a coefficient for rewriting TMAP1 and TMAP2. When f _LC =-1, it is determined that the output of the air-fuel ratio sensor is in a transition period when it is in a rich state, and in step 1158, R=-Δα is set as a coefficient similar to step 1154. If f _LC =0, that is, in a steady state, skip to step 1162. Acceleration correction map in steps 1159 to 1161
Rewrite the current operating status points in TMAP1 and deceleration correction map TMAP2.

The rewriting method is as follows. At step 1159, if A≧0, that is, when the vehicle is being accelerated, the process advances to step 1160. Acceleration correction map TMAP1
As shown in FIG. 16, is a conventionally known two-dimensional map of the rotational speed Ne and the transient pressure change amount P _TR , and is always prepared in the non-volatile RAM. For example, the rotation speed at the map grid point closest to the current operating condition is Nec, and the amount of pressure change is P _TRC.
and the map value of that grid point is TMAP1
(Nec, P _TRC ) is corrected according to the following equation (8).

TMAP1 (Nec, P _TRC ) = TMAP1 (Nec, P _TRC ) + R ... (8) R; Amount of correction found in steps 1157 and 1158 Also, when A < 0, that is, when decelerating, proceed to step 1161, The deceleration correction map TMAP2 is corrected in the same manner as in step 1160.

Thereafter, the process proceeds to step 1162 in FIG. 12, where it is determined whether the state is accelerated or decelerated. If A≧0, that is, at the time of acceleration, the process advances to step 1163. Furthermore, if it is determined in step 1163 that A≧150 mmHg, that is, sudden acceleration, the process proceeds to step 1164, where the acceleration water temperature correction coefficient K _ACC is calculated according to the characteristic diagram shown in FIG. Also, in this step 1163, A<
When the temperature is 150 mmHg, K _ACC is set to 1 in step 1165. Next, the process proceeds to step 1166, where A is obtained by performing a known interpolation calculation from the acceleration correction map TMAP1 (Ne, P _TR ), and in step 1167, _A
Calculate K _ACC to calculate transient correction coefficient K _TR .

If it is determined in step 1162 that A<0, that is, deceleration occurs, the process advances to step 1168, where the deceleration correction map is
Interpolation is performed on TMAP2 (Ne, P _TR ) in the same way as in step 1166 to calculate the transient correction coefficient K _TR .

This completes the timer interrupt.

Next, injection interruption will be explained with reference to FIG. The injection interrupt is an interrupt with the highest priority level, and if an injection interrupt request signal is generated by the IG signal from the rotation sensor 15 even while the main routine or timer interrupt program is being executed, the processing of the currently executing program is temporarily stopped and the injection interrupt program is executed. Execute. While the injection interrupt program is being executed, other interrupt request signals will not interrupt the processing. First, in step 1201, the injection interrupt request signal is canceled, and then the process moves to step 1202 to calculate the rotational speed Ne. The rotation speed Ne is determined by the following equation (9) by measuring the time interval T _IG between adjacent IG pulse signals using the timer section 72, for example.

Ne=K _IG /T _IG ...(9) K _IG ; constant (determined by the number of cylinders and the frequency of the measurement clock) Next, in step 1203, the intake pipe pressure PM is determined based on the signal from the intake pipe pressure sensor 11. Calculated. From this Ne and PM, the basic injection amount τ _BASE is determined in step 1204 by interpolation from a two-dimensional map of (Ne, PM).

Next, in step 1205, a correction coefficient K _ACC included in the injection amount τ _SYNC is calculated from the transient correction coefficient K _TR determined by the timer interrupt. That is,
Normally, K _ACC =K _TR , but if K _ACC >0, that is, when acceleration is being increased, the amount is decreased by ΔK _ACC (one ignition attenuation amount) for each ignition, and this continues until K _ACC =0.

Next, in step 1206, the synchronous injection amount τ _SYNC
is calculated, for example, using the following equation (10).

τ _SYNC =K _THW ×K _THA ×Kf ×K _ACC ×τ _BASE +τ _NB ...(10) K _THW : Water temperature correction coefficient K _THA : Intake temperature correction coefficient Kf: Air-fuel ratio sensor feedback coefficient τ _NB : Ineffective injection Time K _ACC : Transient correction coefficient Next, in step 1207 , it is set in the calculation injection register 700 by the Set command from the CPU 70 applied to the terminal 721 . When the injection interrupt processing is finished, the interrupted main routine or timer interrupt processing is restarted.

With this, the processing in the program ends.

In this embodiment, a fuel injection device using an intake pipe pressure sensor as a basic sensor for the intake air amount has been described, but the present invention can be similarly applied to an intake air amount sensor that directly detects the air amount.

As described above, according to the method of the present invention, even when the feedback control by the air-fuel ratio sensor is stopped, the air-fuel ratio can be sufficiently adjusted to the stoichiometric air-fuel ratio even during transient periods such as acceleration and deceleration of the internal combustion engine, as well as during steady-state conditions. This has the excellent effect of making exhaust gas purification even better. In addition, among the various correction values that correct the basic fuel amount, the transient correction value is updated especially during a transient period, so this update does not affect the fuel supply other than during a transient period. There is also the effect that state-optimal air-fuel ratio correction can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an apparatus for explaining the method of the present invention, FIGS. 2A to D, and FIGS. 3A
~D is an explanatory diagram showing changes in intake pipe pressure, pressure difference value, increase ratio, and air-fuel ratio sensor output during acceleration and deceleration of the internal combustion engine, Figure 4 is a block diagram of the control circuit, and Figure 5 is a diagram showing changes in the air-fuel ratio sensor output. A detailed circuit diagram of the injection control section, FIG. 6 is a detailed circuit diagram of the input interface section, FIGS. 7A to D are time charts for explaining the circuit operation shown in FIGS. 5 and 6, and FIG. ~13th
The figure is a flowchart showing the operation of the CPU, number 14.
The figure shows the calculation characteristics of the increase ratio of the acceleration correction map.
FIG. 5 is a characteristic diagram for calculating the reduction ratio of the deceleration correction map, FIG. 16 is a configuration diagram of the transient correction map, and FIG. 17 is a characteristic diagram showing the water temperature correction coefficient during acceleration. DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 14... Air-fuel ratio sensor, 20... Control circuit, 75... ROM, 76... RAM, 78... Non-volatile RAM.

Claims (1)

[Claims] 1. An air-fuel ratio sensor that detects an air-fuel ratio based on exhaust gas components of an internal combustion engine, and under a predetermined condition determined in advance based on the engine cooling water temperature, etc. An air-fuel ratio control method that performs feedback control to a target air-fuel ratio by correcting the amount of fuel supplied to the engine using a feedback control value obtained by using a transient correction value for correcting the amount of fuel in transient states such as acceleration or deceleration of the engine. is stored in a rewritable memory, and when a transient state of the engine occurs, the basic fuel amount to the engine is corrected based on the transient correction value, regardless of whether feedback control is executed or stopped based on the feedback control value. is supplied to the engine, and in this transient state, if feedback control based on the feedback control value is being executed, the transient correction value in the memory is corrected according to the signal from the air-fuel ratio sensor; An air-fuel ratio control method comprising controlling the amount of fuel to the engine to the target air-fuel ratio even in a transient state of the engine. 2. The transient correction value is corrected only when the signal of the air-fuel ratio sensor continues to be richer or leaner than the target air-fuel ratio for a certain period of time or more, and the setting period is the same as the previous one. 2. The air-fuel ratio control method according to claim 1, wherein the air-fuel ratio control method is determined from an average value of the duration of the signal of the air-fuel ratio sensor. 3. A plurality of the transient correction values in the memory are stored according to the magnitude of the change in the intake air amount, intake pressure, etc., and among the plurality of transient correction values, the transient correction value is Claim 1 or 2, wherein the basic fuel amount is corrected with a corresponding transient correction value, and the transient correction value is modified.
The air-fuel ratio control method described in .