JPS6239257B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electronic engine control device that detects the operating state of an engine using various sensors and controls the air-fuel ratio and the like to an appropriate state. As interest in environmental conservation by preventing air pollution and energy depletion increases, control devices that comprehensively control the operating conditions of automobile gasoline engines to improve exhaust gas conditions and improve fuel ratios are being developed. Therefore, microcomputers are used to capture signals from sensors that provide various data that indicate the operating status of the engine, such as a cooling water temperature sensor and an O ₂ sensor that provides the oxygen concentration in exhaust gas. Electronic engine control devices (EEC) have come into use, which control the amount of fuel supplied, ignition timing, etc. to ensure optimal engine operating conditions at all times. An example of a system in which such EEC is applied to an engine equipped with a carburetor type air-fuel mixture supply means is shown in FIGS. 1 to 6. Figure 1 is a cross-sectional view of the engine's throttle chamber (located in the carburetor), which is constructed so that the amount of fuel and bypass air is controlled by solenoid valves 16 to 22 provided around the engine. It is something that An accelerator pedal (not shown) controls the opening of a low-speed throttle valve 12, thereby controlling the amount of air supplied from an air cleaner (not shown) to each cylinder of the engine. The opening of this low-speed throttle valve becomes larger,
When the amount of air passing through the low-speed bench lily 34 increases, the negative pressure of the low-speed bench lily causes a diaphragm (not shown) to be used to increase the speed of the high-speed throttle 14.
Open. This reduces the increase in air resistance caused by an increase in the amount of intake air. In this way, the throttle valves 12, 14
The air flow rate controlled by and supplied to the engine is
It is taken in as an analog quantity by a negative pressure sensor (not shown). Based on this analog quantity and other signals from sensors to be described later, the opening degree of each solenoid valve 16, 18, 20, 22 shown in FIG. 1 is controlled. On the other hand, the fuel led from the fuel tank is transferred to the conduit 24.
from the main jet 26 to a conduit 28. Additionally, fuel in conduit 24 is also directed to conduit 28 via main solenoid valve 18. Therefore, the larger the opening of the main solenoid valve 18, the more fuel will be introduced into the conduit 28, and these fuels will be further mixed with air in the main emulsion tube 30 and will be sent to the vent lily 34 through the main nozzle 32. Supplied. When the high-speed throttle 14 is opened, fuel is also sucked out from the nozzle 36 communicating with the main nozzle 32 to the vent lily 38. On the other hand, the slow solenoid valve 16 is also controlled simultaneously with the main solenoid valve 18, and when the slow solenoid valve 16 opens, air via the air cleaner is supplied to the conduit 42 through the opening 40. Fuel from conduit 28, on the other hand, is supplied to conduit 42 via slow emulsion tube 44. Therefore, the amount of fuel in conduit 42 decreases as the amount of air from slow solenoid valve 16 increases. This mixture of fuel and air in conduit 42 is supplied to the throttle chamber through a slow hole 46. The fuel solenoid valve 20 is a valve for increasing the amount of fuel, and is used for increasing the starting amount, increasing the amount for warming up, etc. Fuel introduced through hole 48 communicating with conduit 24 is directed to conduit 50 leading to the throttle chamber, depending on the opening amount of fuel solenoid valve 20. The air solenoid valve 22 is a valve that controls the amount of air supplied to the engine, and air from the air cleaner is supplied to the air solenoid valve 22 through an opening 52, and is communicated to the throttle chamber according to the opening. is led to a conduit 54 where it is located. The slow solenoid valve 16 and main solenoid valve 18 shown in FIG. 1 control the air/fuel ratio (A/F), and the fuel solenoid valve 20 increases the amount of fuel.
In addition, slow solenoid valve 16, main solenoid valve 18, and air solenoid valve 22 control engine speed at idle. FIG. 2 shows an ignition system in which a pulsed current is supplied to a power transistor 64 through an amplifier 62, which turns the transistor 64 on. As a result, the ignition coil 68 from the battery 66
Primary coil current flows to. When the input pulse current falls, the transistor 64 is cut off, and
A high voltage is generated in the secondary coil of the ignition coil 68. This high voltage is distributed via a power distributor 70 to each spark plug 72 in each cylinder of the engine in synchronization with engine rotation. FIG. 3 is for explaining an exhaust gas recirculation (hereinafter referred to as EGR) system, in which constant negative pressure from a negative pressure source 80 is applied to a control valve 86 via a pressure control valve 84. The pressure control valve 84 controls the ratio of the negative pressure of the constant negative pressure source to the atmosphere 88 according to the ON duty ratio of the repeated pulses applied to the transistor 90, and controls the state of application of the negative pressure to the control valve 86. Therefore, the negative pressure applied to the control valve 86 is determined by the ON duty ratio of the transistor 90. Due to the controlled negative pressure of the pressure control valve 84, the exhaust pipe 92
The amount of EGR flowing from the engine to the intake pipe 82 is controlled. FIG. 4 is an overall configuration diagram of a control system using a microcomputer. It is composed of a central processing unit 102 (hereinafter referred to as CPU), a read-only memory 104 (hereinafter referred to as ROM), a random access memory 106 (hereinafter referred to as RAM), and an input/output circuit 108. . The CPU 102 calculates input data from the input/output circuit 108 using various programs stored in the ROM 104, and returns the calculation results to the input/output circuit 108 again. RAM 106 is used for intermediate storage necessary for these operations. CPU10
2, ROM104, RAM106, input/output circuit 10
Exchange of various data between the 8 is performed by a bus line 110 consisting of a data bus, a control bus, and an address bus. The input/output circuit 108 includes a first analog-digital converter 122 (hereinafter referred to as ADC1) and a second analog-digital converter 124.
(hereinafter referred to as ADC2) and angle signal processing circuit 126
It waits for input means to the discrete input/output circuit 128 (hereinafter referred to as DIO) for inputting and outputting 1-bit information. ADC1 includes a battery voltage detection sensor 132 (hereinafter referred to as VBS) and a cooling water temperature sensor 134 (hereinafter referred to as VBS).
TWS), atmospheric temperature sensor 136 (hereinafter referred to as AS), adjustment voltage generator 138 (hereinafter referred to as VRS), throttle angle sensor 140 (hereinafter referred to as θTHS),
) and O ₂ sensor 142 for λ control (hereinafter referred to as O ₂ S
) is applied to a multiplexer 162 (hereinafter referred to as MPX), which selects one of them and converts it into an analog/digital signal.
The signal is input to a conversion circuit 164 (hereinafter referred to as ADC). The digital value that is the output of the ADC 164 is held in a register 166 (hereinafter referred to as REG). In addition, the negative pressure sensor 144 (hereinafter referred to as VCS)
It is input to ADC2, 124, converted to digital via analog-to-digital conversion circuit 172 (hereinafter referred to as ADC), and converted into a register 124 (hereinafter referred to as ADC).
REG). The angle sensor 146 (hereinafter referred to as ANGS) outputs a signal indicating a reference crank angle, for example, 180 degrees crank angle (hereinafter referred to as REF), and a signal indicating a minute angle, for example, 1 degree crank angle (hereinafter referred to as POS). The signal is applied to the angle signal processing circuit 126, where the waveform is shaped. The DIO 128 includes an idle switch 148 (hereinafter referred to as IDLE-SW), a top gear switch 150 (hereinafter referred to as TOP-SW), and a starter switch.
A switch 152 (hereinafter referred to as START-SW) is input. Next, a pulse output circuit and a controlled object based on the calculation results of the CPU 102 will be explained. In this embodiment, an air-fuel ratio control device 165 (hereinafter referred to as CABC) controls the slow solenoid 16 and the main solenoid 18 by changing the pulse duty. By increasing the on-duty of CABC 165, main solenoid 18 tends to reduce its fuel supply, which is applied via inverter 163. On the other hand, the amount of fuel supplied to the slow solenoid 16 increases as the on-duty of CABC increases. CABC165
A register (hereinafter referred to as CABP) for setting the repetition pulse period and a register (hereinafter referred to as CABD) for setting the on-duty are provided, and these data are set by the CPU 102, respectively. The ignition pulse generation circuit 168 (hereinafter referred to as IGNC) has a register (hereinafter referred to as ADV) for setting ignition timing data and a register (hereinafter referred to as DWL) for controlling the ignition coil primary current conduction time. Data is set by CPU 102. This output pulse of IGNC 168 is applied to ignition device 170. The details of the igniter 170 are shown in FIG. 2, and the output pulses are applied to the amplifier 62 of FIG. The fuel increase pulse generation circuit 176 (hereinafter referred to as FSC) controls the on-duty of the pulse to control the fuel solenoid 20 shown in FIG.
FSCP) and a register for setting the on time (hereinafter referred to as FSCD). Additionally, a STATUS register 198 is provided,
This allows you to investigate the cause of IRQ,
IRQ is prohibited by MASK register 200. EGR amount control pulse generation circuit 178 (hereinafter referred to as EGRC)
) contains a register for setting pulse repetition period data (hereinafter referred to as EGRP) and a register for setting on-time data (hereinafter referred to as EGRP).
EGRD) is provided and repetitive pulses are applied to air solenoid valve 22 via AND date 184. The signal from the output DIO1 of the DIO 128 is applied to this AND gate 184, and when this DIO1 signal is at L level, the AND gate 184 is activated and the air solenoid
Valve 22 is controlled. On the other hand, when DIO1 is at H level, AND gate 18
6 becomes operational and controls the EGR device 188. The basics of the EGR device 188 are as already explained in FIG. As mentioned above, DIO 128 is a 1-bit signal input/output circuit, and is a register (hereinafter referred to as DDR) 1 that holds data for determining input or output.
It has a register 194 (hereinafter referred to as DOUT) for holding data to output 92.
This DIO 128 outputs a signal DIO0 for controlling the fuel pump 190. FIG. 5 shows a program system for the control circuit shown in FIG. When the power is turned on by a key switch (not shown), the CPU 102 enters a start mode and executes an initialization program (INITIALIZ) 204. Next, execute the monitoring program (MONIT) 206 and execute the BACK GROUND JOB 2.
Execute 08. This background job includes, for example, the EGR amount calculation task (hereinafter referred to as EGR
CAL TASK) and fuel solenoid valve and air solenoid valve calculation tasks (hereinafter referred to as FISC). this
During execution of TASK, when an interrupt factor (hereinafter referred to as IRQ) occurs, an IRQ factor analysis program 224 (hereinafter referred to as IRQ ANAL) is executed from an IRQ disclosure step 222. This IRQ ANAL program further includes ADC1 end interrupt processing (hereinafter referred to as ADC1END).
IRQ) program 226, ADC2 end interrupt processing (hereinafter referred to as ADC2END IRQ) program 228, and certain period elapsed interrupt processing (hereinafter INTV)
IRQ) program 230 and engine stop interrupt processing (hereinafter referred to as ENST IRQ) program 2
32, and issues an activation request (hereinafter referred to as QUEUE) to each task that requires activation, which will be described later. Each program ADC1END IRQ226 and ADC2END IRQ in this IRQ ANAL program 224
228 and INTV IRQ230 programs
Each task to which a QUEUE is issued is a level zero task group 252, a level 1 task group 254, a level 2 task group 256, a level 3 task group 258, or a task constituting each task group. Also, according to ENST IRQ program 232
The task that generates QUEUE is the engine stop processing task 262 (hereinafter referred to as ENST TASK). When this ENST TASK 262 is executed, the control system enters the start mode again and returns to the starting point 202. The task scheduler 242 determines the execution order of the task groups so that they are executed starting from the task group in which QUEUE is occurring or the task group with the highest level among the task groups whose execution has been interrupted (here, level zero is the highest). do. When the execution of the task group is completed, the completion report program 260 (hereinafter referred to as EXIT)
Completion is reported by Based on this completion report, the task group with the highest level among the task groups waiting for execution is executed next. When there are no more suspended tasks or QUEUE tasks, the task scheduler 242
The program then moves on to executing the back ground job 208 again. Furthermore, if an IRQ occurs while any of the level 0 task group to level 3 task group is being executed, the process returns to the starting point 222 of the IRQ processing program.

【table】

[Table] Table 1 above shows the activation of each task and its function. In this Table 1, IRQ ANAL is a program for managing the control system shown in Figure 5.
There are programs, TASK SCHDULER, and EXIT. These programs (hereinafter referred to as OS) are held at addresses A000 to A300 of the ROM 104 as shown in FIG. Furthermore, as a level zero program
There are AD1IN, AD1ST, AD2IN, AD2ST, and RPMIN programs, and usually INTV IRQ 10 [m
SEC]. There are CARBC, IGNCAL, and DWLCAL programs as level 1 programs, which are activated every 20 [mSEC] of INTV IRQ. A level 2 program is the LAMBDA program, which is activated every 40 [mSEC] of INTV IRQ and performs closed-loop control of the air-fuel ratio (referred to as A/F). As a level 3 program
There is a HOSEI program and INTV IRQ's 100 [m
SEC]. There are also EGRCAL and FISC programs as background jobs. The above level zero program is PROG
1 and are stored at addresses A700 to AAFF of the ROM 104 in FIG. 6, respectively. Level 1 program is ROM104 as PROG2
are stored from address AB00 to ABFF. Level 2 program as PROG3
It is stored in the ROM 104 from address AE00 to AEFF. The level 3 program is stored as PROG4 in addresses AF00 to AFFF of the ROM 104. Also, background job programs are held in B000 to B1FF. From the above program PROG1
A list of start addresses (hereinafter referred to as SETMR) for each program up to PROG4 is held from B200 to B2FF, and from PROG1 to PROG
Values representing each program startup cycle up to 4 (see below)
TTM) is stored at addresses B300 to B3FF. Other data is stored at addresses B400 to B4FF of the ROM in FIG. 6 as necessary. Following that, data ADV.MAP and AF for calculation.
MAP and EGR.MAP are memorized respectively. Note that detailed explanations of other programs will be omitted. Thus, according to the EEC mentioned above,
Almost all controls related to the engine, such as A/F control, can be properly performed, and it is possible to satisfactorily meet strict exhaust gas regulations, and to obtain an engine with a good fuel ratio. By the way, in such an EEC, closed loop control of the A/F is performed using the O ₂ sensor 142 as described above, but this O ₂ sensor has characteristics as shown in FIG. 7, for example. Mainly used. In the figure, the horizontal axis is A/
When F is the stoichiometric air-fuel ratio, it is indicated as 1 (this is called λ = 1), and the vertical axis is the output voltage V _S of the O ₂ sensor.
As is clear from this, O ₂
The output voltage from the sensor 142 does not change approximately proportionally (or inversely proportionally) to changes in A/F, but changes to a high voltage state when A/F reaches a certain value, for example, when λ=1. It changes such that it switches between H and low voltage state L. Therefore, the O ₂ sensor 14 exhibiting such a change
In order to loop-control the A/F using the output voltage V _S of 2, the above-mentioned EEC employs a control method as shown in FIG. In the figure, I is
The output voltage V _S of the O ₂ sensor 142 is shown, and B shows the A/F control. As is clear from this figure, the output voltage V _S of the O ₂ sensor when λ=1 is
The slice level S/L corresponding to 1 is set, and when the output voltage V _S is in the state a higher than S/L, the A/F is increased sequentially as time passes as shown by e in the figure. Yuki, output voltage V _S is S/L
While in the lower b state, the A/F is controlled to gradually decrease over time as shown by f in the figure, and the output voltage V _S of the O ₂ sensor is reduced to S/L. When the A/F changes as indicated by c or d, the A/F is controlled to be rapidly decreased as shown in g in the figure, or increased as shown in h in the figure. At this time, parts e and f are integrally controlled according to the characteristics shown in Fig. 8B, and g and h are
This part is called proportional control, and by performing such control, the average value of A/F becomes λ=1. Note that the reason for performing proportional control as shown in parts g and h is that the control loop system includes the system from the engine's fuel supply system to the output of the O ₂ sensor, and the digital signal processing system. This is to compensate for the delay in response due to the presence of a motor, and by providing this proportional control, the response can be significantly improved. However, in the EEC mentioned above,
Closed-loop control of the A/F is assigned as a level 3 task and is activated only at a cycle of 40 [mSEC], which does not provide sufficient responsiveness to A/F fluctuations and The drawback was that sufficient improvement could not be obtained. On the other hand, in order to improve the responsiveness of this A/F closed-loop control, it is possible to shorten its activation cycle, but this would require more time for this A/F closed-loop control task, which would result in more time being spent on other tasks. The drawback was that it resulted in a wasteful program structure with a lot of pressure. Additionally, related devices of this type include:
For example, the disclosure of JP-A-54-58116 can be mentioned. An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide an A/
An object of the present invention is to provide an EEC A/F control device that can improve the exhaust gas condition by increasing the responsiveness of F closed loop control. To achieve this objective, the present invention divides an A/F closed-loop control program by a microcomputer into a proportional control task and an integral control task, and sets the activation period of the proportional control task to be longer than the activation period of the integral control task. It is characterized by being short. Embodiments of the A/F control device according to the present invention will be described below with reference to FIGS. 9 to 11 of the drawings. Note that the following explanations are all embodiments in which the present invention is embodied by the EEC described in FIGS. 1 to 8. Now, FIG. 9 is a program system diagram showing one embodiment of the present invention. In the program system diagram of FIG. 5, the level 1 task group 254 and the level 2 task group 254 are
The contents of the task group 256 are different, and the task group 256
The difference is that only some of the tasks of A/F closed loop control included in , that is, tasks related to proportional control are taken out and moved to task group 254 and programmed as A/F control (1). There is. Therefore, in this embodiment, as is clear from Table 1 above, the activation period T 1 of the A/F close rape control (1) included in the level 1 task group 254, that is, the proportional control task ₂₆₄ becomes 20 [mSEC],
The activation period T 2 of the A/F closed loop control (2) remaining in the level 2 task group 256, that is, the integral control task group ₂₆₆ , is 40 [mSEC] as before. Next, these tasks 264 and 266 will be described. FIG. 10 is a flowchart showing an embodiment of the proportional control task 264. When the task is started every 20 [mSEC] activation period _T1 via the task scheduler 242, it first starts at S10 (step 10, the same applies hereafter). ), it is checked whether closed-loop control of the A/F is permitted. The permission for A/F closed loop control will be described later, but in short, A/F closed loop control will not be performed unless the engine temperature has reached a predetermined value or higher and the _O2 sensor is also activated. This is to prevent this from happening. Therefore, as long as the result in S10 is NO, even if the process is started, the process directly proceeds to EXIT 260, and no substantial task is performed here. Now, when the result was YES in S10,
At step S11, it is checked whether the output voltage V _S of the O ₂ sensor 142 is higher than a predetermined level S/L, that is, H. The result in S11 is NO, that is, the O ₂ sensor 142
When the output voltage V _S is L lower than the level S/L, that is, when the A/F is weak,
Proceeding to S12, it is checked whether or not the diluted state is displayed. If the result is NO, that is, if the diluted state is not displayed, the process remains as is.
This task group ends towards EXIT260. However, when the result in S12 is YES, the process proceeds to the next step S13, where proportional correction is performed in the direction of enriching the A/F. Subsequently, in S14, the dilute state is displayed, and in S15, proportional correction is displayed, and this task is completed. Also, if the result in S11 is YES, that is, the A/F is rich, the process goes to S16, where it is checked whether there is a lean status display, and if the result is NO, the process goes directly to EXIT 260 and executes this task. The process ends, but when the result in S16 is YES, the process proceeds to S17. Then, in S17, A/F dilution proportional correction is performed, in the next S18, rich state display is performed, and finally, in S19, proportional correction display is performed, and this task is completed. Next, the results of the operations according to S11 to S19 will be explained. First, when the result is NO in S11, O ₂
The output voltage V _S of the sensor 142 is at part b in Fig. 8A.
It shows that there is. So in the next S12,
When I checked the concentration status display by S18, it was
If NO, when this task is executed by starting immediately before this starting timing, the output voltage V
_S is in part b lower than level S/L, meaning that S18 was not executed. Therefore, at this time, the process simply proceeds to EXIT 260 without doing anything. However, if the result is YES in S12,
That is, at the startup timing before that, S18 is executed and the rich state is displayed, and at the startup timing after that, the output voltage V _S is at part a,
After that, it means that it changed to part b for the first time.
In other words, at this time, the point immediately after point c in FIG. 8A is detected. Therefore, if YES is obtained in S12, the A/F concentration proportional amount correction is performed in S13, that is, the part g in Figure 8 B.
control will be carried out. Similarly, when the result is YES in S11,
This shows that the output voltage V _S of the O ₂ sensor 142 is at part a in FIG. 8A. Therefore, proceed to the next step S16, and if the result of checking the lean state display in S14 is NO, that is, there is no lean state display, the output voltage V _S is higher than the level S/L even at the startup timing immediately before this startup timing. It means that it met a. Therefore, at this time, leave it as is.
Head to EXIT260. On the other hand, if the result in S16 is YES, it means that S14 was executed at the previous startup timing and the diluted state was displayed, and at the subsequent startup timing, the output voltage V _S was in part b, and then , which means that the output voltage V _S exceeds S/L and moves to part a for the first time. In other words, at this time, the area immediately after point d in FIG. 8A has been detected. Therefore, if the result in S16 is YES, the process proceeds to S17, where the A/F dilution proportional correction shown in part h in FIG. 8B is performed. According to the embodiment shown in FIG. 10,
Detecting points c and d at which the output voltage V _S of the O ₂ sensor 142 crosses the level S/L is performed by a relatively short activation cycle T ₁ in the level 1 task group 254,
As a result, proportional portion control of A/F closed loop control is performed, so the detection delay at points c and d is reduced, and control with good responsiveness is possible. Next, FIG. 11 is a flowchart showing an embodiment of the integral control task 266, in which the activation period T ₂ of 40 [mSEC] is
It is started every time, and when it starts and starts executing this task, first the A/F is turned on in S20.
It is checked whether closed-loop control of is allowed. If the result in S20 is NO, proceed to S21, check whether the cooling water temperature is above the specified value based on the signal from the water temperature sensor 134 (Fig. 4), and if this is NO.
If so, proceed to S22 and check whether there is a failure indication of the water temperature sensor 142. If this is also NO, close loop control is performed in S23 without entering closed loop control, and the result is set in the control system in S24 and EXIT2 is executed.
60 and finish this task. Also, if the result is YES in S21 or S22,
Proceeding to S25, it is checked whether the O ₂ sensor 142 is activated or not. If the result is NO, it is determined in the next S26 whether or not there is a failure indication for the O ₂ sensor 142, and the result is also NO. If so, proceed to S23 and do not enter closed-loop control. On the other hand, if the result in S25 or S26 is YES, the process advances to S27, and a display indicating permission to execute closed loop control is made. Therefore, after this S27 is executed, this task group 266 performs S21 to S23, and S25 to S25 until the engine is stopped.
Step S27 will no longer be executed. Note that S22 and S26 are provided here for the following reason. That is, the water temperature sensor 134 and
If there is a failure in the signal detection system such as the O ₂ sensor 142, the result in S21 or S26 will not become YES no matter how long it takes. Therefore, S22 or S26
If there is no S27, S27 will not be executed forever, and therefore the A/F control will not shift to closed loop control forever. Therefore, when conditions such as a certain period of time have passed after the engine starts operating, the water temperature sensor 134 and O ₂ sensor 142 are tested.
This is provided in order to immediately start angle closed loop control and improve the A/F control even a little by displaying a display to that effect when a malfunction is found. Therefore, these steps S22 and S26 need to be removed if the system is not configured to test such sensors. Note that even in this case, there is no problem because the operation of the present invention is performed in exactly the same way. Now, the result of S20 is YES at the startup timing of _T2
Then proceed to S28. In this S28, it is checked whether or not the sparse state display, which is the result of S14 in FIG. 11, is being performed.
When the result of S28 is NO, the A/F dilution integral correction is performed in S29, that is, the control shown in part e of Fig. The integral correction, that is, the control shown in part f in FIG. 8B is performed. After that, proceed to S31, and then S15 or S19 in Figure 11.
It is checked whether there is a proportional correction display or not, and if this is NO, proceed directly to S24, set the control result, and then proceed to EXIT 260, but if the result in S31 is YES, proceed to S32,
First, reset the proportional correction display. Then S33
Now, A/F based on the data obtained in S29 or S30.
Rewriting of the control data is prohibited, and in the following S24, the control result is performed using the previous data, and this task is ended. Next, the operations obtained by executing these steps S28 to S32 will be explained. First, the reason why the result is NO in S28 is that the proportional control task in Fig. 10 is executed, and at that time point d in Fig. 8 A is detected, the rich state is displayed in S18, and then the O ₂ sensor means that the output voltage V _S is still in the state of part a. Therefore, in this case, the integral correction in the A/F dilution direction shown in part e in FIG. 8B is performed in S29. Also, if the result in S28 is YES, it means that point c in Figure 8A has been detected and task 264
The dilute state is indicated by S14, and then O ₂
This means that the output voltage V _S of the sensor is still in the state of part b. Therefore, at this time S30
Then, the integral correction in the A/F concentration direction shown in part f in FIG. 8B is performed. Next, the reason why the result becomes YES in S31 is that the activation timing of T1 occurs during the execution of this task ₂₆₆ at the activation timing of _T2 , and the A/F by the proportional control task 264 shown in FIG. This means that either the enrichment proportional correction of A/F or the dilution proportional correction of A/F is performed, and the display in S15 or S19 is made. Therefore, at this time,
First, in S32, the display of this proportional correction is reset, and then in S33, rewriting of the control data using the integral correction data obtained in S29 or S30 is prohibited. In other words, at this time, S29 or S30
This discards the data obtained and prevents it from being reflected in A/F control. As a result, according to the embodiment shown in FIG. 11, the response delay characteristics of the control system are corrected, and the A/F control characteristics can be further improved. That is, when the activation timing T ₂ occurs immediately before time t in FIG. 8 and the integral control task 266 is being executed, the activation timing T ₁ occurs at time t, and the proportional control task 264 is started. Assume that point d happens to be detected when execution begins. In this case, due to the delay characteristics of the control system including the digital signal processing system, the data obtained in S29 or S30 of the integral control task group 266, which was executed at the startup timing of _T2 immediately before time t, It is set as a control result at t,
A control as shown by part f' is added, and the subsequent control by proportional correction becomes like part h' shown by a broken line, and the A/F control deviates from the predetermined value. However, according to the embodiment shown in FIG. 11, in such a case, rewriting of the data is prohibited by S33, and the addition of the portion f' indicated by the broken line in FIG. 8 (b) is prevented. Therefore, A/F control can always be kept in an appropriate state. As described above, in the embodiment of the present invention shown in FIG. 9, the proportional control task 264 and the integral control task group 266 are executed at different startup timings, and closed-loop control of the A/F is performed. . Therefore, according to the embodiment shown in FIG.
Since the timing to perform the proportional control shown at points c and d in Figure 8A is detected in a relatively short startup period called SEC], the response delay of the control system can be reduced, and the response Since the integral control, which is less affected by delay, has a relatively long startup cycle of 40 [mSEC], the load on the microcomputer does not increase much. In addition, when control tasks are performed at different timings, out-of-control operations that occur due to response delays in the control system can be prevented with a simple method of prohibiting data rewriting based on correction results. This effect can be obtained. In the above embodiment, the activation period T ₁ of the proportional control task was 20 [mSEC], and the activation period T ₂ of the integral control task was 40 [mSEC], but these activation periods T ₁ and T ₂ were It may be set to any period as long as the condition (T ₁ <T ₂ ) is satisfied. As explained above, according to the present invention, the responsiveness of A/F closed loop control can be made faster without significantly increasing the load on the microcomputer, and there is no accompanying out-of-control operation. It is possible to provide an EEC A/F control device that can sufficiently improve exhaust gas while eliminating the drawbacks of the prior art.

[Brief explanation of the drawing]

Figures 1 to 6 are diagrams showing an example of an electronic engine control system (EEC), in which Figure 1 is a sectional view of the engine throttle chamber, Figure 2 is a schematic diagram of the ignition system, and Figure 3 is a schematic diagram of the ignition system. 4 is a block diagram of the overall configuration of the control system, FIG. 5 is a diagram of its program system, FIG. 6 is a memory configuration diagram showing program contents stored in ROM, and FIG. 7 is a system diagram of the exhaust gas recirculation device. is a characteristic diagram of an O ₂ sensor, FIG. 8 is an explanatory diagram showing an example of air-fuel ratio control using an O ₂ sensor, FIG. 9 is a program system diagram showing an example of an air-fuel ratio control device according to the present invention, and FIG. 10 is a flowchart showing the contents of the proportional control task, and FIG. 11 is a flowchart showing the contents of the integral control task. 264... Proportional control task, 266... Integral control task.

Claims (1)

[Scope of Claims] 1. In an air-fuel ratio control device for an internal combustion engine that controls a supplied air-fuel ratio according to a signal from a means for detecting an output air-fuel ratio in exhaust gas, the signal changes across a predetermined level. means for performing, by a first activation timing period, a task of detecting the signal and a proportional control task of the air-fuel ratio to be performed when the signal changes across a predetermined level; means for performing an integral control task of the air-fuel ratio to be performed when the condition is high and when the condition is low, in a second activation timing period, wherein the first activation timing period is the second activation timing period. An air-fuel ratio control device characterized by being configured to be shorter. 2. The air-fuel ratio system according to claim 1, further comprising means for prohibiting the air-fuel ratio control by the integral control task when the proportional control task is entered and the air-fuel ratio correction control is performed. Fuel ratio control device.