JP3417401B2 - Air-fuel ratio control device for internal combustion engine - Google Patents

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-mentioned prior art, the ratio of the air containing the evaporated fuel discharged during the acceleration / deceleration of the internal combustion engine or to the intake side of the internal combustion engine to the intake air (purge rate) is small. Sometimes, there is a problem that the accurate fuel vapor concentration cannot be detected.

Therefore, the object of the present invention is to accurately detect the concentration of evaporated fuel.

[0005]

Therefore, in the invention according to claim 1, the concentration detecting means for detecting the concentration of the evaporated fuel and the concentration detecting means for prohibiting the concentration detection during the acceleration / deceleration of the internal combustion engine are prohibited. An air-fuel ratio control device for an internal combustion engine, which comprises a concentration detection inhibiting means.

As a result, the concentration detection of the evaporated fuel is prohibited during the acceleration / deceleration of the internal combustion engine, so that the inaccurate concentration detection can be prevented and the concentration detection accuracy can be improved as a result.

Further, in the invention according to claim 2,
A concentration detecting means for detecting the concentration of the evaporated fuel; and a concentration detection suppressing means for prohibiting the concentration detection by the concentration detecting means when the purge rate set by the purge rate controlling means is equal to or less than a predetermined value. The present invention provides an air-fuel ratio control device for an internal combustion engine.

As a result, when the purge rate is equal to or lower than a predetermined value, that is, when the ratio of the air containing the evaporated fuel to the intake air is small, the concentration detection of the evaporated fuel is prohibited. The detection accuracy can be improved.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. As shown in Figure 1,
The vehicle is equipped with a multi-cylinder engine 1.
An intake pipe 2 and an exhaust pipe 3 are connected to. Intake pipe 2
An electromagnetic injector 4 is provided at the inner end of the valve, and a throttle valve 5 is provided at the upstream side thereof. 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.

The 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 includes a throttle opening signal from a throttle sensor 5a for detecting the opening of the throttle valve 5, an engine rotation speed signal from a rotation speed sensor (not shown) for detecting the rotation 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> TAUmin. (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 XO has a delay time (H · Imsec).
Operate the XR. For example, when XOXR = 1, rich,
Lean when XOXR = 0. Next in step S43
Then, the value of FAF is manipulated based on this XOXR. That is, XOXR changes (0 → 1), (1 → 0)
Then, the FAF value is skipped by a predetermined amount, and the FAF value integration control 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 F value, smoothing (averaging) processing is performed at every skip or every predetermined time to obtain a 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 FIG. 5 shows the main routine of the purge rate control. 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> TAUmin. (4) The oxygen sensor 6 is in the active state. In the next step S503, it is judged whether the uniform deviation detection is completed or not by a uniform deviation detection end flag XICHI in FIG. 13 which will be described later. If it is judged that the uniform deviation detection is completed, it is determined in step S504 whether the fuel is being cut. If it is during the fuel cut, the routine proceeds to step S505, where the fuel cut purge rate (PGR) control 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 (a) of FIG.
Within 0 ± F%, the area is within 1.0 ± F% or more and within ± G% (where F <G), and the area is within 1.0 ± 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 to decrease PGR by a predetermined value E%. Here, it is preferable that the predetermined values D and E are changed according to the evaporation concentration (FGPG) as shown in FIG. 7B. Then, in the next step S605, the upper and lower limits of PGR are checked. Here, the upper limit is (c) in FIG.
7, the purge start time, the water temperature shown in FIG.
The smallest value among various conditions such as the operating condition (full open purge rate map) shown in (e) of FIG.

FIG. 8 shows the 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 equal to or higher than a predetermined value, and even if purging is performed during the fuel cut, the exhaust purification catalyst in the exhaust pipe path is used. When the purged evaporated fuel can be purified by (not shown), the internal combustion engine is purged while the operation of the internal combustion engine is continued for a sufficiently large time or the number of revolutions after the purge solenoid valve 16 starts the purge. It suffices to judge at least one of the cases when it is judged that the period in which the evaporation concentration seems to be sufficiently small has passed. Then, if it is determined in step S801 that the purge is not in an operable state, the flow advances to step S802 to set the purge stop flag XFGFC to 1, and then to step S803 to set PGR to 0.

If it is determined in step S801 that the engine is in the purging-enabled operating state, 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 for the evaporation concentration detection, which is executed in the base routine of the evaporation concentration detection 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 S1
If 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. That is, since the concentration cannot be accurately detected during acceleration / deceleration of the internal combustion engine, the concentration detection is prohibited. On the other hand, if it is determined in step S102 that acceleration is not being performed, the process proceeds to step S104, it is determined whether the first concentration detection end flag XNFGPG is 1, and if it is 1, the process proceeds to next step S105, and if it is not 1, the process skips step S105. It proceeds to step S106. The initial density detection end flag XNFGPG may be initialized to 0 when the key switch is turned on. Then, when the initial concentration detection is not completed, it is determined in step S105 whether the purge rate PGR is a predetermined value (β%) or more. That is, when the purge rate is small, accurate concentration detection cannot be performed, so concentration detection is prohibited. On the other hand, when the purge rate is equal to or higher than the predetermined value, 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 initial 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 S15
In step 1, the basic fuel injection amount (TP) is calculated from the engine speed and load (for example, intake pipe pressure) based on the data stored as a map in the ROM 34, and in step S152, various basic corrections (cooling water temperature, After starting, perform intake air temperature, etc.). 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,

[0032]

[Equation 1] 1+ (FAF-1) + (KGj-1) + FPG Calculated as a correction coefficient, fuel injection amount TAU
To reflect.

FIG. 12 shows a purge solenoid valve control routine executed by the purge solenoid valve control CPU 21 by interrupting the time every 100 ms. In step S161, the purge non-execution flag XIPGR
Is 1 or the purge stop flag XFG is determined in step S162.
When FC is 1, the routine proceeds to step S163, where the duty of the purge solenoid valve 16 is set to 0. Otherwise, the process proceeds to step S164 and the purge solenoid valve 1
If the driving cycle of 6 is 100 ms,

[0034]

[Equation 2] Duty = (PGR / PGRfo) × (100
The duty of the purge solenoid valve 16 is calculated by the following equation: ms−PV) × PPa + PV. Here, PGR is the purge rate obtained in FIGS. 6 and 8, PGRfo is the purge rate in each operating state when the purge solenoid valve 16 is fully open (see FIG. 3), and PV is the voltage correction value for fluctuations in the battery voltage. , PPa are atmospheric pressure correction values 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 values KG0 to 0
After updating KG7, the uniform control fuel correction coefficient KOF is returned to the reference value 1. Here, the air-fuel ratio learning values KG0 to KG in each region
The update amount of 7 may be changed by a preset value centered 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 divided into idle KG0 (step S1708) and traveling (step S1710) according to the determination result of whether or not it is idle in step S1705, and the load (for example, intake pipe pressure) during traveling is performed. Is divided into a predetermined number (for example, seven) of areas KG1 to KG7. Further, when the engine speed is within the predetermined engine speed in steps S1706 and S1709 (600 to 1 at idle).
The learning value is updated only at 000 rpm, and 1000 to 3200 rpm when running. Further, at the time of idling, the intake pipe pressure PM becomes 17 by step S1707.
The learning value is updated when it is 3 mmHg or more.

The updating method of the learning values KG0 to KG7 of each area is as follows. When the difference between the FAF smoothing value FAFAV and the reference value 1.0 is larger than a predetermined value (for example, 2%), the learning values KG0 to KG0 of the area. This is done by increasing / decreasing KG7 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. The learning values KG0 to KG7 of the respective areas are backed up by the power source so that the memory values are retained even after the key switch is turned off.
Of course, it is stored in the AM 35 (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.

[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

Front page continuation (51) Int.Cl. ⁷ Identification symbol FI F02D 41/14 F02D 41/14 310P 43/00 301 43/00 301H 301M 45/00 301 45/00 301L 368 368F (72) Inventor Junya Morikawa 1-chome, Showa-cho, Kariya city, Aichi, Japan DENSO CORPORATION (56) References JP-A-2-130240 (JP, A) JP-A-4-72453 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02M 25/08 301 F02D 41/02 330 F02D 41/14 310 F02D 43/00 301 F02D 45/00 301 F02D 45/00 368

Claims (2)

(57) [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. A fuel ratio feedback means, a flow control valve for purging evaporated fuel from the canister to the intake side of the internal combustion engine via the discharge passage, a learning value storage means for storing an air-fuel ratio learning value, and an air-fuel ratio by the feedback means A learning value updating means for updating the air-fuel ratio learning value based on a feedback value; a concentration detecting means for detecting the concentration of the evaporated fuel; Air-fuel ratio control system for an internal combustion engine, characterized in that it comprises a concentration detection inhibiting means for inhibiting the density detection by the density detecting means during acceleration and deceleration of the function. 2. An air-fuel ratio control of an internal combustion engine, wherein evaporated fuel generated in a fuel tank is stored in a canister, and the evaporated 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, and a concentration detecting means for detecting the concentration when the purge rate set by the purge rate controlling means is equal to or less than a predetermined value. An air-fuel ratio control device for an internal combustion engine, comprising: a concentration detection suppressing means for prohibiting concentration detection by the means.