JPH06200804A - Air-fuel control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To carry out the air-fuel ratio learning even in a purge execution of a vapored fuel. CONSTITUTION:A vapored fuel generated in a fuel tank 2 is adsorbed to a canister 13, and this vapored fuel is purged to the suction side of an internal combustion engine together with the air through a purge valve 16. And during the normal purge rate control by the purge valve 16, the air-fuel ratio feedback value detected by an oxygen sensor 6 is averaging processed, and by the deflection of the averaging processed value from a logical air-fuel ratio 1, and a purge rate, the density of the vapored fuel sucked in the internal combustion engine through the purge valve 16 is detected. And after a specific time passes from the time to start the purge, the air-fuel ratio learning value is renewed according to the air-fuel ratio feedback value, and the result is stored in a RAM 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control system for an internal combustion engine for sucking vaporized fuel generated in a fuel tank to the intake side of the internal combustion engine and burning it.

[0002]

2. Description of the Related Art Conventionally, a canister purge amount is kept constant in a system in which vaporized fuel generated in a fuel tank is stored in a canister, and the vaporized fuel stored in this canister is discharged together with air to the intake side of an internal combustion engine for combustion. There is a method in which only the value is changed, the concentration of the evaporated fuel sucked from the canister to the intake side of the internal combustion engine is detected based on the change amount of the air-fuel ratio feedback value at that time, and the air-fuel ratio learning value is corrected according to this concentration. (For example, JP-A-2-13024
No. 0).

[0003]

However, in the above-described conventional one, the concentration of the evaporated fuel is high at the beginning of the purge, and the air-fuel ratio due to the influence of the evaporated fuel with respect to the change amount of the air-fuel ratio feedback value to be learned. Since the amount of change in the feedback value becomes larger and the concentration of the evaporated fuel has not yet been accurately detected at the beginning of purge, there is a problem that accurate air-fuel ratio learning cannot be performed sufficiently.

Therefore, an object of the present invention is to satisfactorily learn the air-fuel ratio even during the purge control without being affected by the concentrated fuel vapor. Further, another object is to improve the purge efficiency by continuing the purge control in a specific operating state even during the fuel cut.

[0005]

Therefore, according to the present invention, the vaporized fuel generated in the fuel tank is stored in the canister, and the vaporized fuel stored in the canister is discharged together with air to the intake side of the internal combustion engine. In the air-fuel ratio control device for an internal combustion engine, the air-fuel ratio detecting means for detecting the air-fuel ratio of the internal combustion engine, and the air-fuel ratio control means is supplied to the internal combustion engine according to the air-fuel ratio detected by the air-fuel ratio detecting means. Air-fuel ratio feedback means for feedback-controlling the air-fuel ratio of the air-fuel mixture, and a flow rate control valve for changing the purge rate of air containing evaporated fuel released from the canister to the intake side of the internal combustion engine via the release passage, Purge rate control means for controlling the purge rate by the flow control valve according to the engine state, learning value storage means for storing an air-fuel ratio learning value, and the feedback A learning value updating means for updating the air-fuel ratio learned value based on the air-fuel ratio feedback value by stages,
The fuel amount is corrected so that the air-fuel ratio becomes a predetermined value in accordance with the concentration detecting means for detecting the concentration of the evaporated fuel, the evaporated fuel concentration detected by the concentration detecting means, and the purge rate by the purge rate control means. An air-fuel ratio control apparatus for an internal combustion engine, comprising: purge-responsive fuel amount correction means; and learning prohibition means for prohibiting update of the learned value until a predetermined period elapses after purging by the flow rate control valve is started. Is.

At least one of when the purge rate by the purge rate control means is small and when the internal combustion engine is accelerating and decelerating is detected, and when the purge rate is small or during the accelerating and decelerating, the concentration detection is performed. You may make it further provide the density detection prohibition means which prohibits the density detection by a means. Further, as the learned value storing means, the learned value of the air-fuel ratio is stored according to a plurality of operating regions of the internal combustion engine, and the purge rate is set to 0 while the air-fuel ratio feedback is being executed by the air-fuel ratio feedback means. Uniform learning control means for increasing / decreasing the fuel amount so that the deviation from the reference value detected by the deviation detecting means is less than or equal to a predetermined value, and the deviation being less than or equal to a predetermined value by increasing / decreasing the fuel amount by the uniform learning control means. Uniform learning value updating means for updating learning values in all regions of the learning value storing means based on the fuel increase / decrease amount of the uniform learning control means when the learning value is updated by the uniform learning value updating means. The purge rate control means permits the start of the purge rate control by the purge rate control means, and the purge rate control means controls the purge rate control means. Area-specific learning value updating means for updating the learning value of the learning value storage means for each area based on the air-fuel ratio feedback value by the air-fuel ratio feedback control means when the start of the purge rate control is permitted is further provided. It may be configured.

Further, it is determined whether or not the concentration is being detected by the concentration detecting means or the concentration detected value by the concentration detecting means is stable, and the concentration is not being detected.
Alternatively, it may further include a learning condition determining unit that permits the learning value updating unit to update the learning value when it is determined that the density detection value is stable. Further, a fuel cut state detection means for detecting a fuel cut state of the internal combustion engine, and whether the fuel cut state detection means is in an operating state in which purging by the flow control valve is possible when it is detected that the fuel cut state is in the fuel cut state If it is determined that the operating state is such that purging is possible, the fuel cut purge rate control means for controlling the purge by the flow rate control valve even during the fuel cut may be further provided.

Further, the fuel cut purge rate control means is configured such that the temperature of the internal combustion engine is equal to or higher than a predetermined value, or the elapsed time from the start of purging by the flow rate control valve is equal to or higher than a predetermined value, or the concentration detection means. An operating state determination unit that determines at least one of the detected concentration values according to
The operating state determination means determines whether the temperature of the internal combustion engine is equal to or higher than a predetermined value, the elapsed time after the purge by the flow control valve is started is equal to or more than a predetermined value, and the concentration detection value is equal to or less than a predetermined value. At times, a means for determining that the operating state in which the purging is possible may be included.

[0009]

As a result, the air-fuel ratio learning value of the learning value storage means is updated by the air-fuel ratio learning value updating means based on the air-fuel ratio feedback value of the air-fuel ratio feedback means. Also,
The concentration of the evaporative fuel is detected by the concentration detecting means, and the fuel amount is corrected by the purge responsive fuel amount correcting means so that the air-fuel ratio becomes a predetermined value according to the detected evaporative fuel concentration and the purge rate by the purge rate controlling means. . Then, when the predetermined period has not elapsed since the purge by the flow control valve was started, the learning prohibiting means prohibits the update of the air-fuel ratio learning value.

Further, when the fuel cut state detecting means detects that the fuel is in the fuel cut state, it is judged by the purge rate control means during the fuel cut whether the operating state is such that the purge can be performed by the flow rate control valve, and the purging is possible. When it is determined that the state is in the state, it is possible to control the purge by the flow rate control valve even during the fuel cut.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a vehicle is equipped with a multi-cylinder engine 1, and an intake pipe 2 and an exhaust pipe 3 are connected to the engine 1. An electromagnetic injector 4 is provided at the inner end of the intake pipe 2, and a throttle valve 5 is provided upstream of the electromagnetic injector 4. Further, the exhaust pipe 3 is provided with an oxygen sensor 6 as an air-fuel ratio detecting means, and the sensor 6 outputs a voltage signal according to the oxygen concentration in the exhaust gas.

A fuel supply system for supplying fuel to the injector 4 has a fuel tank 7, a fuel pump 8, a fuel filter 9 and a pressure regulating valve 10. Then, the fuel (gasoline) in the fuel tank 7 is pressure-fed by the fuel pump 8 to the injector 4 of each cylinder through the fuel filter 9, and the fuel supplied to each injector 4 is regulated by the pressure regulating valve 10 to a predetermined pressure. Adjusted to.

A purge pipe 1 extending from the upper portion of the fuel tank 7.
1 is connected to a surge tank 12 of an intake pipe 2, and a canister 1 containing an activated carbon as an adsorbent for adsorbing evaporated fuel generated in a fuel tank is provided in the middle of the purge pipe 11 thereof.
3 are provided. Further, the canister 13 is provided with an atmosphere opening hole 14 for introducing outside air. The purge pipe 11 has a discharge passage 15 on the side closer to the surge tank 12 than the canister 13, and a variable flow solenoid valve 16 (hereinafter referred to as a purge solenoid valve) is provided in the discharge passage 15. In this purge solenoid valve 16, the valve body 17 is always biased by a spring (not shown) in the direction of closing the seat portion 18. However, by exciting the coil 19, the valve body 17 opens the seat portion 18. Has become.
Therefore, the discharge passage 15 is closed by demagnetizing the coil 19 of the purge solenoid valve 16, and the discharge passage 15 is opened by exciting the coil 19. The opening of the purge solenoid valve 16 is adjusted by the CPU 21 described later by the duty ratio control based on the pulse width modulation.

Therefore, the purge solenoid valve 16 has a C
If a control signal is supplied from the PU 21 so that the canister 13 communicates with the intake pipe 2 of the engine 1, new air Qa is introduced from the atmosphere, and this is the canister 1
3 is ventilated and sent from the intake pipe 2 of the engine 1 into the cylinder, and canister purge is performed.
The recovery of the adsorption function of No. 3 will be obtained. Then, the introduction amount Qp (l / _min ) of the fresh air Qa at this time
Is adjusted by changing the duty of the pulse signal supplied from the CPU 21 to the purge solenoid valve 16. FIG. 2 is a characteristic diagram of the purge amount at this time, and shows the relationship between the duty of the purge solenoid valve 16 and the purge amount when the negative pressure in the intake pipe is constant.
As the purge solenoid is increased from 0%,
It can be seen that the purge amount, that is, the amount of air sucked into the engine 1 via the canister 13 increases almost linearly.

The CPU 21 receives a throttle opening signal from a throttle sensor 5a for detecting the opening of the throttle valve 5, an engine speed signal from a speed sensor (not shown) for detecting the speed of the engine 1, and a throttle valve. The intake pressure signal from the intake pressure sensor 5b that detects the pressure of the intake air that has passed through the intake valve 5 (or the intake air amount signal from the intake air amount sensor) and the cooling from the water temperature sensor 5c that detects the temperature of the engine cooling water. A water temperature signal and an intake air temperature signal from an intake air temperature sensor (not shown) that detects the intake air temperature are input.

Further, the CPU 21 inputs a signal (voltage signal) from the oxygen sensor 6 and makes a rich / lean determination of the air-fuel mixture. Then, the CPU 21 changes (skips) the feedback correction coefficient stepwise in order to increase / decrease the fuel injection amount when changing from rich to lean and when changing from lean to rich, and at the time of rich or lean, the feedback correction coefficient is changed. Is gradually increased or decreased. It should be noted that this feedback control is not performed when the engine cooling water temperature is low, and when the vehicle is running under high load and high rotation. Further, the CPU 21 obtains the basic injection time from the engine speed and the intake pressure, corrects the basic injection time with a feedback correction coefficient or the like, and then the final injection time T
AU is obtained, and fuel injection is performed by the injector 4 at a predetermined injection timing.

The ROM 34 stores programs and maps for controlling the operation of the entire engine. RAM
Reference numeral 35 temporarily stores various data, for example, detection data such as the opening of the throttle valve 5 and the engine speed. Then, the CPU 21 controls the operation of the engine based on the program stored in the ROM 34. FIG. 3 shows a full open purge rate map, which is determined by the engine speed Ne and the load (intake pipe pressure this time, other intake air amount or throttle opening may be used). This map shows the ratio of the amount of air flowing through the discharge passage 15 when the duty of the purge solenoid valve 16 is 100% to the total amount of air flowing into the engine 1 through the intake pipe 2, and the ROM 3
It is stored in 4.

This system uses the air-fuel ratio feedback (F
AF) control, purge rate control, evaporated fuel (evaporation) concentration detection, fuel injection amount control, air-fuel ratio learning control, and purge solenoid valve control. Hereinafter, the operation of the embodiment will be described for each control. Air-fuel ratio feedback control Air-fuel ratio feedback control will be described with reference to FIG. This air-fuel ratio feedback control is performed by the CPU 21 about every 4 ms.
It is executed by the base routine of.

First, in step S40, it is determined whether feedback (F / B) control is possible. The F / B condition is mainly when all the following conditions are satisfied.
(1) Not at the start. (2) Fuel is not being cut.
(3) Cooling water temperature (THW) ≧ 40 ° C. (4) TA
U> TAU _min . (5) The oxygen sensor is in an active state.

If the conditions are satisfied, the routine proceeds to step S42, where the oxygen sensor output is compared with the predetermined judgment level, and the air-fuel ratio flag XOXR has a delay time (H · I _msec ).
To operate. For example, when XOXR = 1, rich, XO
Lean when XR = 0. Next, in step S43, the value of FAF is manipulated based on this XOXR. That is, when XOXR changes (0 → 1), (1 → 0), the value of FAF is skipped by a predetermined amount, and integration control of the FAF value is performed while XOXR continues to be 1 or 0. After advancing to the next step S44, the upper and lower limits of the FAF value are checked, and then advancing to step S45
Based on the value, smoothing (averaging) processing is performed for each skip or for every predetermined time to obtain the smoothed value FAFAV. When the F / B control is not established in step S40, the process proceeds to step S46 and the value of FAF is set to 1.0.

Purge Rate Control The main routine of purge rate control is shown in FIG. This routine is also executed by the base routine of the CPU 21 about every 4 _ms . In step S501, it is determined whether purge control is possible. The purge controllable condition is mainly when all the following conditions are satisfied.

(1) Not at the time of starting. (2) Cooling water temperature (T
HW) ≧ 50 ° C. (3) TAU> TAU _min . (4) The oxygen sensor 6 is in the active state. FIG. 1, which will be described later, shows whether the uniform deviation detection is completed in the next step S503.
3 if the uniform deviation detection end flag XICHI is 1 and it is judged that the uniform deviation detection is completed, it is judged in step S504 whether or not the fuel is being cut. If the fuel is being cut, the routine proceeds to step S505. Purge rate (PGR) control during fuel cut is performed. If it is determined in step S504 that the fuel is not being cut, the process proceeds to step S506 to perform the normal purge rate control, and then the purge non-execution flag XIP is executed in step S507 to execute the purge rate control.
Set GR to 0. When the purge rate condition is not satisfied in steps S501 and S503, the process proceeds to step S512 to set the purge rate to 0, and then proceeds to step S513 to set the purge incomplete flag XIPGR to 1.

FIG. 6 shows the normal purge rate control subroutine in step S506 of FIG. First, step S
At 601 it is detected which of the three areas (,,) the FAF value (or FAF smoothed value) is with respect to the reference value 1.0. Here, as shown in FIG. 7A, when the area is within 1.0 ± F% and the area is within 1.0 ± F% or more and within ± G% (where F <G), the area is 1 ．
Indicates the time when it is over 0 ± G%.

If it is in the region, the routine proceeds to step S602, where the purge rate (PGR) is increased by a predetermined value D%. In the case of the area, the process proceeds to step S603 and the PGR is not increased or decreased. If it is in the region, the process proceeds to step S604, and PGR is set to a predetermined value E%.
Gradually decrease. Here, the predetermined values D and E are (b) in FIG.
It is preferable to change the concentration according to the evaporation concentration (FGPG) as shown in. Then, in the next step S605, PG
Check the upper and lower limits of R. Here, the upper limit value is based on various conditions such as the purge start time shown in (c) of FIG. 7, the water temperature shown in (d) of FIG. 7, the operating condition (full open purge rate map) shown in (e) of FIG. It should be the smallest value.

FIG. 8 shows a PGR control subroutine at the time of fuel cut in step S505 of FIG. First, in step S801, it is determined whether the operating state is such that purging is possible even during fuel cut. The purging operation state is such that the internal combustion engine temperature obtained by detecting the exhaust gas temperature or the engine oil temperature is a predetermined value or higher, and even if purging is performed during fuel cut, the exhaust purification catalyst in the exhaust pipe path When the purged evaporated fuel can be purified by (not shown), the purge solenoid valve 1
At least one of the times when it is judged that a sufficiently long time or the number of revolutions of the internal combustion engine has been continued since the purge by 6 was started and the period in which the purge concentration to be purged seems to be sufficiently low has elapsed. What is necessary is just to judge one. Then, when it is determined in step S801 that the operating state is not such that purging is possible, step S802
After proceeding to, the purge stop flag XFGFC is set to 1, and then proceeding to step S803, PGR is set to 0.

When it is determined in step S801 that the operating state is such that purging is possible, the flow advances to step S804 to calculate the purge correction coefficient R. In this step S804, the evaporation concentration FGP is changed as shown in FIG.
According to G, the purge correction coefficient R, which is set in advance so as to have a smaller value as the evaporation concentration increases, is obtained by table lookup. Alternatively, as shown in (b) of FIG. 9, the purge correction coefficient R is set in advance so that the higher the temperature, the larger the value becomes in accordance with the internal combustion engine temperature such as the exhaust gas temperature or the engine oil temperature. It is a look-up request.

The purge correction coefficient calculation step S80
In FIG. 4, the purge correction coefficient R is set to 0 when the evaporation concentration becomes a predetermined value or more or the internal combustion engine temperature becomes a predetermined value or less as shown in (a) and (b) of FIG. Since the purgeable area is also determined in this step, step S801 can be omitted. Then, in the next step S805, the normal PGR of FIG.
Purge rate P previously required in the control subroutine
After multiplying GR by the purge correction coefficient R, step S80
6, the purge stop flag XFGFC is set to 0.

FIG. 10 shows the main routine of the evaporation concentration detection which is executed in the base routine of the CPU 21 about every 4 _ms . First,
If the purge control is started in step S101 and the purge non-execution flag XIPGR is not 1, step S102
When the flag XIPGR is 1 and the purge control has not been started yet, the process proceeds to step S103, where the evaporation concentration FGPG is set to the reference value of 1.0, and the process ends. In step S102, it is determined whether acceleration / deceleration is being performed. Here, the determination as to whether or not the acceleration / deceleration is being performed may be performed by a generally well-known method by detecting an idle switch, a throttle valve opening change, an intake pipe pressure change, a vehicle speed, and the like.

If it is determined in step S102 that the vehicle is accelerating, the process ends. If it is determined that the vehicle is not accelerating, the process proceeds to step S104 to determine whether the first concentration detection end flag XNFGPG is 1, and when it is 1, The process proceeds to the next step S105, and when it is not 1, the process skips step S105 and proceeds to step S106. The initial density detection end flag XNFGPG may be initialized to 0 when the key switch is turned on. When the initial concentration detection is not completed, it is determined in step S105 whether the purge rate PGR is equal to or more than a predetermined value (β%). If not, the process is ended as it is, and if it is above, the process proceeds to the next step S106.

In this step S106, it is judged whether the absolute value of the deviation of FAFAV from the reference value 1 obtained in step S45 of FIG. 4 is a predetermined value (ω%) or more. In step S108, the evaporative concentration is detected. This step S108
Then, the deviation of the FAFAV from the reference value 1 is divided by PGR to be added to the previous evaporation concentration FGPG to obtain the current evaporation concentration FGPG. Therefore, the value of the evaporation concentration FGPG in this embodiment becomes 1 when the evaporation concentration in the discharge passage 15 is 0 (air is 100%), and becomes smaller than 1 as the evaporation concentration in the discharge passage 15 increases. It is set. Here, step S10 of FIG.
It is also possible to replace FAFAV with 1 in 8 and obtain the evaporation concentration by setting the value of FGPG to a value larger than 1 as the evaporation concentration increases.

Then, in the next step S109, it is determined whether or not the first concentration detection end flag XNFPGG is 1, and when it is not 1, the process proceeds to the next step S110, and when it is 1, the steps 110 and S111 are bypassed and the process proceeds to step S112. Then, in step S110, the evaporation concentration FGPG
The change between the previous detection value and the current detection value of is less than or equal to the predetermined value (θ%) three times or more continuously, and it is determined whether the evaporation concentration is stable. When the evaporation concentration is stable, the process proceeds to the next step S111, After setting the density detection end flag XNFPGG to 1, the process proceeds to the next step S112. Also, step S1
If it is determined in 10 that the evaporation concentration is not stable, the process proceeds to step S112. In this step S112, the present evaporation concentration FGPG is subjected to a predetermined averaging for averaging (for example,
1/64 averaging) Calculated, Evaporative concentration average value FGPGA
Find V.

Fuel injection amount control FIG. 11 shows the fuel injection amount control executed in the base routine of the CPU 21 about every 4 _ms . First, step S151
Then, based on the data stored as a map in the ROM 34, the basic fuel injection amount (TP) is obtained from the engine speed and the load (for example, the pressure in the intake pipe), and various basic corrections (cooling water temperature, start-up) are performed in the next step S152. After that, the intake air temperature, etc.) is performed. Next, in step S153 described later with reference to FIG.
After the uniform control fuel correction coefficient KOF is reflected, the process proceeds to step S154. In step S154, the evaporation concentration average value FGPGAV is multiplied by the purge rate PGR to obtain the purge correction coefficient FPG, and then in step S156, F
AF, FPG, the air-fuel ratio learning value (KGj) for each engine operating region,

[0033]

[Equation 1] 1+ (FAF-1) + (KGj-1) + FPG Calculated as a correction coefficient, fuel injection amount TAU
To reflect. Purge Solenoid Valve Control FIG. 12 shows a purge solenoid valve control routine executed by the CPU 21 by interrupting every 100 _ms .
In step S161, the purge non-execution flag XIPGR is 1
Alternatively, in step S162, the purge stop flag XFGFC
Is 1, the duty of the purge solenoid valve 16 is set to 0 in step S163. Otherwise, the process proceeds to step S164, and if the drive cycle of the purge solenoid valve 16 is 100 _ms ,

[0034]

## EQU2 ## Duty = (PGR / PGR _fo ) × (100 _ms
The duty of the purge solenoid valve 16 is calculated by the equation −P _V ) × P _Pa + P _V. Here, PGR is the purge rate obtained in FIGS. 6 and 8, PGR _fo is the purge rate in each operating state when the purge solenoid valve 16 is fully open (see FIG. 3), and P _V is the voltage with respect to changes in the battery voltage. The correction value, P _Pa, is an atmospheric pressure correction value for variations in atmospheric pressure.

Air-Fuel Ratio Learning Control Next, FIG. 13 shows an air-fuel ratio learning control routine executed every time the FAF value is skipped. First, step S1
In step 31, it is determined whether the uniform deviation detection end flag XICHI is 1, and when it is 1, the process proceeds to step S132, and the uniform control fuel correction coefficient KOF is set to the reference value 1. here,
The uniform deviation detection end flag XICHI may be initialized to 0 when the key switch is turned on.
Further, in step S131, the uniform deviation detection end flag XI is set.
If it is determined that CHI is not 1, the process proceeds to step S133 and it is determined whether a uniform shift can be detected.

Here, in this step S133, during the air-fuel ratio feedback, the cooling water temperature THW is 50 ° C. or higher, the increase after start is 0, the increase in warm-up is 0, and the battery voltage is 11.5V.
When all of the above basic conditions are satisfied, it is determined that the uniform deviation can be detected, and the process proceeds to step S134 to set these conditions to 1
If any one is not satisfied, it ends as it is. Then, in step S134, it is determined whether the deviation of FAFAV from the reference value 1 is less than or equal to a predetermined value (a%). If not, the process proceeds to step S135 to set the uniform control fuel correction coefficient KOF,
After increasing / decreasing by a predetermined amount b in accordance with the deviation of the FAF value from the reference value 1 with respect to the previous uniform control fuel correction coefficient KOF, the process proceeds to step S136.

As a result of the increase / decrease in the uniform control fuel correction coefficient KOF in step S135, the deviation from the reference value 1 of FAFAV in step S134 becomes a predetermined value (a%) or less due to the air-fuel ratio feedback control in FIG. If it is determined that the FAF value has skipped three times or more, the process ends if it does not skip three times or more, and if it skips three times or more, the process proceeds to the next step S138 and a uniform deviation occurs. After setting the detection end flag XICHI to 1, the process proceeds to step S139 to check the operating region at that time, and then the process proceeds to step S136.

In step S136, it is determined whether the uniform deviation detection end flag XICHI has changed from 0 to 1.
If it has not changed, the processing is ended as it is, and if it has changed, the routine proceeds to step S140, and the air-fuel ratio learning value KG _{0 of} each region is shifted by the deviation from the reference value 1 of the uniform control fuel correction coefficient KOF.
After updating KG ₇ , the uniform control fuel correction coefficient KOF is returned to the reference value 1. Here, the air-fuel ratio learning values KG _{0 to} KG in each region
The update amount of ₇ may be changed by a preset value centering on the area at the time of area check in step S139. In addition, steps S140 and S1
After the end of 32, the process proceeds to step S141 to update the learning value for each area.

Next, FIG. 14 shows an area-specific learning value update subroutine of step S141 of FIG. First, in step S1701, it is determined whether or not the initial concentration detection end flag XNFPGG is 1, and when it is not 1, the process ends as it is. The amount of increase is 0, the amount of warm-up is 0, and FA
F value skipped 5 times or more, battery voltage is 11.5
Step S1 that all basic conditions of V or higher are satisfied
If it is judged at 702 that one of the basic conditions is not satisfied, the process is ended, and if all are satisfied, the next step S
Proceed to 1716.

In step S1716, the operation of the internal combustion engine is continued for a sufficiently long time or the number of revolutions after the purge solenoid valve 16 starts the purge operation.
It is judged whether or not the period Xt (for example, 60 seconds) in which the purged evaporative emission concentration is considered to be sufficiently small has elapsed, and when it has not elapsed, the process ends as it is, and when it has elapsed, learning control for each region is performed. .

The learning control is FAFA in step S1703.
After reading the value of V, it is performed separately for idle time KG ₀ (step S1708) and traveling (step S1710) according to the determination result of whether it is idle in step S1705. ) Is divided into a predetermined number (for example, seven) of areas KG _{1 to} KG ₇ . Further, when the engine speed is within the predetermined engine speed in steps S1706 and S1709 (600 to 1 at idle).
000 _rpm , 1000-3200 _rpm when running, only
The learning value is updated. Further, at the time of idling, the intake pipe pressure PM is 173 m in step S1707.
The learning value is updated when mHg or more.

The updating method of the learning values KG _{0 to} KG ₇ of each area is such that when the difference between the FAF smoothed value FAFAV and the reference value 1.0 is larger than a predetermined value (for example, 2%), the learning value of the area. This is performed by increasing / decreasing KG _{0 to} KG ₇ by a predetermined value (K%, L%) (steps S1711-S171).
4). Finally, the upper and lower limits of KGj are checked (step S1715). Here, the upper limit value of KGj is, for example, 1.
2, the lower limit value is set to 0.8, and the upper and lower limit values can be set for each engine operating region. Note that the learned values KG _{0 to} KG ₇ of each area are backed up by the power source so that the learned values KG _{0 to} KG ₇ are retained even after the key switch is turned off.
Needless to say, it is stored in M35 (learning value storage means).

A time chart of the embodiment described above is shown in FIG. (A) shows the uniform control fuel correction coefficient KOF, (b) shows the purge rate PGR, (c) shows the detected evaporation concentration value FGPG and its smoothed value FGPGAV, and (d) shows the fuel reduction correction coefficient FPG. And (e) shows the FAF value. Then, first, in the state where the purge rate is set to 0 during the air-fuel ratio feedback, the uniform control fuel correction coefficient KOF is increased / decreased to detect the uniform deviation of the air-fuel ratio, thereby updating the air-fuel ratio learning values in all regions. , The purge rate control is started to detect the first-time evaporative emission concentration, and then the evaporative emission concentration FGP is reflected by updating the evaporative emission concentration and reflecting the fuel reduction correction coefficient FPG according to the purge control.
The air-fuel ratio learning value in each region is individually updated after G has stabilized and a sufficiently large period has elapsed since the purge was started.

Further, in the above-described embodiment, the uniform control fuel correction coefficient KOF is increased or decreased to detect the uniform deviation of the air-fuel ratio, thereby updating the air-fuel ratio learning value in each region. A uniform learning value for the entire range is stored in the RAM separately from the learning value for the air-fuel ratio, and the single uniform learning value for the entire range is updated by increasing or decreasing the uniform control fuel correction coefficient KOF to detect the uniform deviation of the air-fuel ratio. You may do it.

In the embodiment described above, FIG.
In step S1716, the purge solenoid valve 1
Although the learning control for each region is started when the time or the number of engine revolutions exceeds a predetermined value from the start of the purge by 6, the internal combustion is performed via the discharge passage 15 after the purge solenoid valve 16 starts the purge. If the purge flow rate of the evaporation discharged to the intake passage side of the engine is integrated, and the learning for each region is started when the integrated purge flow rate becomes equal to or greater than a predetermined value, the air-fuel ratio learning will be performed better. be able to.

An embodiment in which the purge flow rate is integrated in this case will be described with reference to FIG. FIG. 16 shows a step S16 in the purge solenoid valve control routine of FIG.
When it is determined that XIPGR is 1 in step 1, the integrated value PFI of the purge flow rate is reset to 0 in step S165.
Further, after step S164, the fuel injection amount TAU, the engine speed NE, and the purge rate PGR are multiplied to obtain the purge flow rate PF discharged to the intake passage side of the internal combustion engine through the discharge passage 15. In addition to adding step S166, the purge flow rate PF is added after step S166.
Is calculated to obtain the integrated purge flow rate PFI Step S1
67 is added.

Instead of step S1716 of FIG. 14, as shown in FIG. 17, the cumulative purge flow rate PFI is compared with a predetermined value PFIt, and if the cumulative purge flow rate PFI is less than or equal to the predetermined value PFIt, learning for each region is performed. If the integrated purge flow rate PFI is greater than the predetermined value PFIt without executing the process, the purge execution period of the evaporation is not less than the predetermined integrated purge flow rate at which the evaporation concentration is sufficiently low after the purge is started. Therefore, the learning control for each area is executed.

[0048]

As described above, according to the present invention, the air-fuel ratio learning value of the learning value storage means is updated by the air-fuel ratio learning value updating means based on the air-fuel ratio feedback value by the air-fuel ratio feedback means, and the concentration detecting means is also used. The concentration of the evaporative fuel is detected by, and the fuel amount is corrected by the purge responsive fuel amount correcting device so that the air-fuel ratio becomes a predetermined value according to the detected evaporative fuel concentration and the purge ratio by the purge ratio controlling device. When the predetermined period has not elapsed since the purge by the flow rate control valve has started, the learning prohibition means prohibits the update of the air-fuel ratio learning value, so that the purge control is in progress without being affected by the concentrated fuel vapor. Also has the excellent effect that the air-fuel ratio can be learned satisfactorily.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram of the purge solenoid valve in the above embodiment.

FIG. 3 is a full open purge rate map in the above embodiment.

FIG. 4 is a flowchart of air-fuel ratio feedback control in the above embodiment.

FIG. 5 is a flowchart of purge rate control in the above embodiment.

FIG. 6 is a flowchart of a normal purge rate control subroutine in the above embodiment.

7 (a) to 7 (e) are various characteristic diagrams used in a normal purge rate control subroutine in the above-described embodiment.

FIG. 8 is a flowchart of a fuel cut purge rate control subroutine in the above embodiment.

9 (a) and 9 (b) are various characteristic diagrams used in the fuel cut purge rate control subroutine in the above embodiment.

FIG. 10 is a flowchart of evaporation concentration detection in the above embodiment.

FIG. 11 is a flowchart of fuel injection amount control in the above embodiment.

FIG. 12 is a flowchart of purge solenoid valve control in the above embodiment.

FIG. 13 is a flowchart of air-fuel ratio learning control in the above embodiment.

FIG. 14 is a flowchart of a learning value updating subroutine for each area in the above-described embodiment.

FIG. 15 is a time chart showing waveforms at various points in the above-described embodiment.

FIG. 16 is a flowchart showing another embodiment of purge solenoid valve control.

FIG. 17 is a flowchart of a main part in another embodiment of FIG.

[Explanation of symbols]

 1 Multi-cylinder engine 2 Intake pipe 5 Throttle valve 5a Throttle sensor 5b Intake pressure sensor 6 Oxygen sensor 7 Fuel tank 13 Canister 15 Release passage 16 Purge solenoid valve 21 CPU

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location F02D 45/00 312 Q 7536-3G 340 D 7536-3G 358 Z 7536-3G 364 K 7536-3G F02M 25/08 301 J 7314-3G (72) Inventor Junya Morikawa 1-1-1, Showa-cho, Kariya city, Aichi prefecture Nihon Denso Co., Ltd.

Claims (10)

[Claims] 1. An air-fuel ratio control of an internal combustion engine in which vaporized fuel generated in a fuel tank is stored in a canister, and the vaporized fuel stored in the canister is discharged together with air to an intake side of the internal combustion engine through a discharge passage. The device is an air-fuel ratio detecting means for detecting an air-fuel ratio of the internal combustion engine, and an air-fuel ratio feedback-controlling air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine according to the air-fuel ratio detected by the air-fuel ratio detecting means. Fuel ratio feedback means, a flow rate control valve that changes a purge rate of air containing evaporated fuel that is released from the canister to the intake side of the internal combustion engine through the release passage, and a purge rate by the flow rate control valve Purging rate control means for controlling the air-fuel ratio, learning value storage means for storing the air-fuel ratio learning value, and air-fuel ratio feedback value by the feedback means. A learning value updating means for updating the air-fuel ratio learning value based on the above, a concentration detecting means for detecting the concentration of the evaporated fuel, an evaporated fuel concentration detected by the concentration detecting means, and a purge rate by the purge rate control means. Accordingly, a purge responsive fuel amount correcting means for correcting the fuel amount so that the air-fuel ratio becomes a predetermined value, and learning for prohibiting update of the learning value until a predetermined period has elapsed after the purge by the flow control valve is started An air-fuel ratio control device for an internal combustion engine, comprising: prohibiting means. 2. When the purge rate by the purge rate control means is small, and at least one of when the internal combustion engine is accelerating and decelerating is detected, and when the purge rate is small or during the accelerating and decelerating, the concentration detection is performed. The air-fuel ratio control device for an internal combustion engine according to claim 1, further comprising concentration detection prohibiting means for prohibiting concentration detection by the means. 3. An averaging means for averaging the feedback value of the air-fuel ratio by the air-fuel ratio feedback means, and a reference value of the output of the averaging means when the purge rate is controlled by the purge rate control means. Deviation detection means for detecting a deviation from the reference value detected by the deviation detection means and the purge rate of the purge rate control means to detect the concentration of the evaporated fuel. 3. An air-fuel ratio control system for an internal combustion engine according to claim 1, further comprising: 4. The learned value storage means stores learned values of an air-fuel ratio according to a plurality of operating regions of an internal combustion engine, and the purge rate is set during execution of air-fuel ratio feedback by the air-fuel ratio feedback means. A uniform learning control means for increasing or decreasing the fuel amount so that the deviation from the reference value detected by the deviation detecting means becomes a predetermined value or less, and the deviation due to the increase or decrease of the fuel amount by the uniform learning control means. Uniform learning value updating means for updating the learning values of all areas of the learning value storing means based on the fuel increase / decrease amount of the uniform learning control means when is less than or equal to a predetermined value, and the uniform learning value updating means. The purge start permission means for permitting the purge rate control means to start the purge rate control after the learning value is updated by the purge rate control means, and the purge rate by the purge start permission means. A learning value updating means for each area for updating the learning value of the learning value storage means for each area based on the air-fuel ratio feedback value by the air-fuel ratio feedback control means in a state where the start of the purge rate control by the controlling means is permitted. The air-fuel ratio control device for an internal combustion engine according to claim 3, further comprising: 5. The at least one of whether the initial concentration is being detected by the concentration detecting means or the concentration detected value by the concentration detecting means is stable, and the initial concentration is not being detected, or the concentration detected value is not detected. The air-fuel ratio control apparatus for an internal combustion engine according to claim 4, further comprising learning condition determination means for permitting updating of the learned value by the region-based learned value updating means when it is determined to be stable. 6. A fuel cut state detecting means for detecting a fuel cut state of an internal combustion engine, and an operating state in which purging by the flow control valve is possible when the fuel cut state detecting means detects that the fuel cut state is present. 6. The fuel cut purge rate control means for controlling the purge by the flow rate control valve even during the fuel cut when it is determined that the operating state is such that purging is possible. An air-fuel ratio control device for an internal combustion engine as set forth in. 7. The fuel cut purge rate control means comprises:
At least one of whether the temperature of the internal combustion engine is equal to or higher than a predetermined value, the elapsed time after the purge by the flow rate control valve is started is a predetermined value or more, and the concentration detection value by the concentration detecting means is a predetermined value or less is determined. Operating condition determining means, the temperature of the internal combustion engine is equal to or higher than a predetermined value by the operating condition determining means, a period elapsed from the start of purging by the flow control valve is a predetermined value or more, and the concentration detection value is a predetermined value or less. 7. The air-fuel ratio control system for an internal combustion engine according to claim 6, further comprising means for determining that the operating state is such that the purge is possible when any of the above is determined. 8. The fuel cut purge rate control means comprises:
8. The air-fuel ratio control device for an internal combustion engine according to claim 7, further comprising means for changing the purge rate by the flow rate control valve according to the engine temperature or the detected concentration value determined by the operating state determination means. 9. The purge responsive fuel correction means is a means for blunting the concentration of the evaporated fuel detected by the concentration detecting means, and an air-fuel ratio is set in accordance with the circulated evaporated fuel concentration and the purge rate. 9. The air-fuel ratio control device for an internal combustion engine according to claim 1, further comprising means for correcting the fuel amount so as to have a predetermined value. 10. The learning inhibiting means integrates the purge flow rate of the evaporated fuel released to the intake passage side of the internal combustion engine through the release passage after the purge by the flow control valve is started. And a means for canceling prohibition of updating the learning value when the purge flow rate of the evaporated fuel accumulated by the accumulating means exceeds a predetermined value.
10. An air-fuel ratio control device for an internal combustion engine according to any one of 9 to 10.