JP3331660B2 - 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 a self-diagnosis device in a fuel evaporative gas diffusion preventing device, and more particularly to a self-diagnosis device for preventing the diffusion of fuel evaporative gas generated in a fuel supply system of an automobile. The present invention relates to a device for self-diagnosing a supply abnormality.

[0002]

2. Description of the Related Art As one of the prior arts of a self-diagnosis method in a fuel evaporative gas diffusion preventing device, a negative pressure is introduced into a fuel tank by forcibly opening a purge control valve within a fixed time during idling. There is a method of detecting the occurrence of a leak in the fuel evaporative gas supply passage by measuring the pressure in the fuel tank by measuring the state of the sealed negative pressure change with time in the fuel tank.

[0003]

However, the concentration of the fuel evaporative gas greatly changes depending on the temperature, fuel properties, remaining amount in the fuel tank, and the like. For example, immediately after supplying highly volatile gasoline in a very high temperature state, a highly concentrated evaporative gas is generated, and by opening the purge control valve at the time of idling according to the above-described self-diagnosis method, the highly concentrated evaporative gas is immediately blown into the cylinder. There is a problem that the air-fuel ratio becomes excessively rich due to inflow into the engine, leading to engine stall.

In view of the above problems, the present invention stops the self-diagnosis of the evaporative fuel adsorbing device when the fuel evaporative gas concentration is equal to or higher than the set value, thereby preventing idling of the engine stall and ensuring reliable operation. The purpose is to enable self-diagnosis.

[0005]

Accordingly, the present invention provides a purge control valve in an evaporative fuel purge passage connecting an evaporative fuel adsorber and an intake passage of an internal combustion engine, and a purge control valve disposed in an exhaust passage of the internal combustion engine. In an air-fuel ratio control device for an internal combustion engine configured to feedback-control the air-fuel ratio of the air-fuel mixture of the internal combustion engine based on the output signal of the exhaust gas sensor, at least the air-fuel ratio of the air-fuel mixture is feedback-controlled.
Concentration detecting means for detecting a fuel evaporative gas concentration in the fuel purge passage based on an air-fuel ratio correction coefficient and a load of the internal combustion engine for detecting a failure of the evaporated fuel adsorbing device. And a failure detection stopping means for stopping execution of the failure detection by the failure detecting means when the concentration of the evaporative gas detected by the concentration detecting means is equal to or higher than a predetermined value. It is to provide a fuel ratio control device.

[0006]

According to this, at least the air-fuel ratio of the air-fuel mixture is adjusted.
Air-fuel ratio correction coefficient for feedback control and internal combustion engine
When the concentration of the fuel evaporative gas detected by the concentration detecting means based on the load is equal to or higher than the set value, the failure detecting means stops the failure detection of the evaporated fuel adsorbing device by the failure detection stopping means.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration diagram around an engine mounted on an automobile. An intake pipe 2 and an exhaust pipe 3 are connected to the engine 1. An air cleaner 4 for filtering air is arranged upstream of the intake pipe 2, and air is sucked into the intake pipe 2 via the air cleaner 4. A throttle valve 6 that opens and closes in conjunction with an accelerator pedal 5 is provided in the intake pipe 2. A bypass passage 7 is provided so as to bypass the throttle valve 6, and a rotation speed control valve 8 is arranged in the middle of the bypass passage 7. By adjusting the opening of the rotation speed control valve 8, the amount of intake air when the engine 1 is idling can be adjusted to change the engine rotation speed.

[0008] Air from the intake pipe 2 is supplied to a combustion chamber 10 through an intake valve 9. Further, the exhaust gas in the combustion chamber 10 is exhausted to the exhaust pipe 3 via the exhaust valve 11. The exhaust pipe 3 is provided with an O ₂ sensor 12 as air-fuel ratio detecting means.

On the other hand, a fuel tank 13 containing a liquid fuel
Is connected to a fuel pump 14, and the fuel in the fuel tank 13 is transported by the fuel pump 14 in a pressurized state. The fuel from the fuel pump 14 is supplied to a fuel injection valve 15 provided in the intake pipe 2, and the fuel is injected by opening and closing the fuel injection valve 15. The fuel tank 13 is connected to the communication pipe 1.
The canister 6 is connected to a canister 17 as an evaporative fuel adsorbing device, and an adsorbent 19 for adsorbing fuel evaporative gas, for example, activated carbon is accommodated in the canister body 18. As a result, the fuel evaporative gas generated in the fuel tank 13 is transferred to the adsorbent 19 of the canister 17 through the communication pipe 16.
Is to be adsorbed. Also, the canister body 1
8, an air opening hole 20 opened to the atmosphere is formed,
Air can be sucked into the interior.

Further, a hose connection portion 21 is formed in the canister body 18, and one end of a supply pipe 22 is inserted into the hose connection portion 21. The other end of the supply pipe 22 is connected to a purge control valve 23. This purge control valve 23
Is connected to one end of a supply pipe 24, and the other end of the supply pipe 24 is connected to the intake pipe 2. Therefore, both supply pipes 22 and 2
4, a purge control valve 23 is interposed, so that the intake pipe 2 and the canister 17 can communicate with each other via the supply pipe 22, the purge control valve 23, and the supply pipe 24. In this communication state, the fuel vapor adsorbed by the adsorbent 19 of the canister 17 can be guided into the intake pipe 2 by the negative pressure generated in the intake pipe 2 of the engine 1. The opening of the purge control valve 23 can be adjusted, and the purge flow rate passing through the supply pipes 22 and 24 is changed according to the opening. Also, supply pipes 22, 24
Is generally formed of a flexible material such as a rubber hose or a nylon hose.

The electronic control circuit 25 as purge flow rate control means, idle speed control means, air-fuel ratio control means, opening degree change amount calculation means, abnormality determination means, concentration detection means, failure detection means, failure detection stop means, CPU 26 and ROM 27
, A RAM 28, and an input / output circuit 29, and are mutually connected via a common bus 30. A control program and data for the CPU 26 are stored in the ROM 27 in advance, and the RAM 28 is readable and writable. CPU2
Numeral 6 inputs various signals through the input / output circuit 29. That is, a signal from the O ₂ sensor 12, a signal from the water temperature sensor 31 for detecting the temperature of the engine cooling water, a signal from the throttle opening sensor 39 for detecting the opening of the throttle valve 6, and the on / off state of the car air conditioner. A signal from an air conditioner switch 32 for detecting an OFF operation, a signal from a headlight switch 33 for detecting a headlight lighting operation, a signal from a heater blower switch 34, and ON when the accelerator pedal 5 is not depressed. And a vehicle speed sensor 36
And a signal from a speed sensor 37 for detecting the engine speed.

Then, the CPU 26 outputs these signals, R
The drive of the fuel injection valve 15, the purge control valve 23, and the rotation speed control valve 8 is controlled via an input / output circuit 29 based on programs and data in the OM 27 and the RAM 28.

That is, the CPU 26 adjusts the opening of the purge control valve 23 in accordance with the operating state of the engine 1 and
Control the purge flow rates of 2, 24. That is, the opening degree of the purge control valve is calculated and controlled by the CPU 26 so that the purge flow rate becomes a predetermined ratio with respect to the intake air amount by an intake air amount sensor (not shown). Further, the CPU 26 controls the intake air amount by adjusting the opening of the rotation speed control valve 8 so that the target rotation speed is achieved during the idling operation of the engine 1.
The air-fuel ratio of the air-fuel mixture to the engine 1 detected by the _two sensors 12 is controlled to be constant. That is, CP
U26 calculates the basic injection time from the engine speed by the speed sensor 37 and the intake air amount by the intake air amount sensor (not shown), and calculates a feedback correction coefficient FA for the basic injection time.
The final injection time is obtained by performing correction by F or the like, and fuel injection is performed by the fuel injection valve 15 at a predetermined injection timing.

A warning lamp 38 is provided on the instrument panel of the vehicle as warning means, and is connected to the CPU 26 via an input / output circuit 29. Next, the operation of the self-diagnosis device in the fuel evaporative gas diffusion prevention device thus configured will be described.

First, the feedback control of the air-fuel ratio is shown in FIG.
It will be described based on. This process is executed every predetermined time. As shown in FIG. 3, the CPU 26 compares the output voltage of the O ₂ sensor 12 with the comparison voltage Vref to determine whether the mixture is rich or lean. Then, in step 100, the CPU 26 determines whether or not a condition for feedback control is satisfied. It is determined that the conditions are satisfied when the engine water temperature detected by the water temperature sensor 31 is 40 ° C. or higher and the throttle opening detected by the throttle opening sensor 39 is 70 ° or lower. If the condition is not satisfied, the CPU 26 sets a feedback correction coefficient FAF = 1.0 in step 101.

When the feedback control condition is satisfied, the CPU 26 determines whether or not the air-fuel ratio is rich in step 102 based on a signal from the O ₂ sensor 12. Then, it is determined whether or not lean has been inverted from rich to rich.
When the CPU 26 reverses from lean to rich, in step 104 the feedback correction coefficient FAF-α (α is the skip amount) is used as a new feedback correction coefficient FAF.
In step 05, the feedback correction coefficient FAF-β (β is an integral amount, α> β) is set as a new feedback correction coefficient FAF.

In step 102, in the case of a lean condition, the CPU 26 compares the result of the previous detection with the result of the previous detection in step 106 to determine whether or not the condition has been changed from rich to lean. When the CPU 26 inverts from rich to lean, the feedback correction coefficient FAF + α (α is the skip amount) is used as a new feedback correction coefficient FAF in step 107, and when there is no inversion from rich to lean, the feedback correction coefficient FAF + β (β Is an integral amount) as a new feedback correction coefficient FAF.

Therefore, if there is a reversal between rich and lean due to the processing of steps 102 to 108, the feedback correction coefficient FAF is changed (skipped) stepwise to increase or decrease the fuel injection amount, and the rich or lean state is changed. At times, the feedback correction coefficient FAF is gradually increased or decreased.

FIG. 4 shows a target idle speed control processing routine executed every predetermined time. The CPU 26 determines in step 200 whether or not the vehicle is idling. this is,
When the idle switch 35 is turned on and the vehicle speed detected by the vehicle speed sensor 36 is 2 Km / h or less, it is determined that the vehicle is idling. When idling, the CPU 26 detects the operation state of the air conditioner switch 32 and the alternator load state (the operation state of the headlight switch 33 and the heater blower switch 34) in step 201, and detects the engine temperature by the water temperature sensor 31 in step 202. Read the cooling water temperature. The CPU 26 proceeds to step 20
At 3, the target rotational speed NT is determined. This is to determine the target rotation speed NT based on the load state (no load, alternator load applied, air conditioner on) corresponding to the engine cooling water temperature using the map of FIG.

Next, the CPU 26 calculates a deviation ΔNE (= NT−NE) between the target engine speed NT and the actual engine engine speed NE by the engine speed sensor 37 at step 204, and at step 205, sets the deviation of the engine control valve 8. The control opening amount Q is calculated. The calculation of the control opening Q is to obtain the control opening Q corresponding to the rotational speed deviation ΔNE using the map shown in FIG. Further, the CPU 26 determines in step 206
In the opening theta _i of the previous speed control valve of a value obtained by adding the controlled opening degree Q in opening theta _i-1 of the 8 time speed control valve 8, the rotational speed so that the opening theta _i The control valve 8 is controlled.

Referring to the flowchart of FIG. 11, a description will be given of a routine for calculating the concentration of evaporative gas, which is executed every predetermined time.
First, at step 401, the intake air amount Q of the engine and the engine speed Ne are read, and it is determined whether or not the conditions for purging control are satisfied (step 402). If if purge conditions, the process proceeds to step 403, it reads in the fuel injection quantity q at that time as q _0, reads the air-fuel ratio feedback correction amount FAF at that time as FAF _0.
FAF ₀ may be an average value of FAF for a predetermined time.

Next, at step 404, the purge control valve 23 is closed to stop purging for a predetermined time, and after the air-fuel ratio feedback correction amount FAF is stabilized, the value FAF is set to FAF _1.
It reads the fuel injection quantity q at that time as q ₁ reads in the (step 405). Next, step 406
, Purge control is started as usual, and
In step 07, the evaporative gas concentration α is calculated. The value of α is calculated by a calculation method described later.

Next, at step 408, the value of α is equal to or more than a predetermined value (evaporation gas concentration at which, for example, 30% higher than λ = 1.0 (λ = 0.7) when idling). In the case of, the process proceeds to step 409, and the abnormality detection processing of the evaporative gas diffusion prevention device is prohibited. On the other hand, when the value of α is equal to or less than the predetermined value, the process proceeds to step 410 to execute the abnormality detection processing.

Here, the method of calculating the vaporized gas concentration α in step 407 will be described. Q: Step 40
Intake air amount read at 1, q ₀ , q ₁ : Step 40
Fuel injection amount read at 3,405, Ne: Step 4
01: engine speed read at 01, ΔQ: purge flow rate passing through the purge control valve, α: evaporative gas concentration, P: purge control valve opening (%), FAF ₀ : read at step 403 during purge control Air-fuel ratio feedback control correction amount, FAF ₁ : Assuming that the air-fuel ratio feedback control correction amount read in step 405 when the purge control is stopped, ΔQ is Q, Ne, P previously described as a map as shown in FIG. (%).

Further, the fuel injection amounts q ₀ and q ₁ are obtained by calculating from the command value for driving the fuel injection valve 15. Since the air-fuel ratio is fed back to λ = 1.0 (stoichiometric air-fuel ratio) by the O ₂ sensor 12, the following relationship is established.

[0026]

Q / (q ₁ · FAF ₁ ) = (Q + ΔQ) / (q
₀ · FAF ₀ + αΔQ) By transforming the above equation, the evaporating gas concentration α is obtained by the following equation.

[0027]

Α = ｛[(Q + ΔQ) × q ₁ × FAF ₁ ] / Q
-Q ₀ · FAF ₀ ｝ / ΔQ FIGS. 7 to 9 show an abnormality detection processing routine executed at predetermined time intervals in step 410 of FIG. Hereinafter, this processing will be described with reference to the time chart of FIG.

First, at the timing of t1 in FIG. 10, the CPU 26 executes steps 300, 301, 302, 3
At 03, it is determined whether or not an abnormality can be detected. That is,
In step 300, it is confirmed that there is no external load (air conditioner load and alternator load by operating the headlights and the blower motor) which is a factor that changes the intake air amount during idling. After confirming that number control is being performed, step 302
It is confirmed that feedback control is being performed by the O ₂ sensor 12 for controlling the air-fuel ratio to be constant at
In step 303, it is determined whether or not the engine cooling water temperature is equal to or lower than 70 ° C.

The CPU 26 determines in steps 300 and 30
If the conditions 1, 302 and 303 are not satisfied, the flags F1, F2 and F3 are all set to "0" in step 304. If all the conditions for executing the abnormality detection processing are satisfied, the CPU 26 determines in steps 306, 307, and 308 that the flag F
It is determined whether F1, F2, and F3 are "1". Initially, F1, F2, and F3 = 0 through the initialization or the processing of step 304, and the purge control valve 23 is fully closed in step 309.
Then, the CPU 26 corrects the correction coefficient F in the air-fuel ratio feedback control by the O ₂ sensor 12 in step 310 of FIG.
It is checked whether AF is within the range of 0.95 to 1.05, that is, whether the air-fuel ratio is near the target air-fuel ratio. If the feedback correction coefficient FAF falls within the range of 0.95 to 1.05, the CPU 26 proceeds to step 3.
In step 11, it is checked whether the engine speed is near the target speed (650 to 750 rpm) by the idle speed feedback control.

When the engine speed is close to the target engine speed, the CPU 26 determines whether or not 5 seconds have elapsed since the purge control valve 23 was fully closed in step 312, that is, the stable state was maintained for a predetermined period (5 seconds). ) It is determined whether or not it is continuous, and if 5 seconds have not elapsed, a flag F1 is set in step 313.
Set to "1".

In the next processing, step 300 → 3
01 → 302 → 303 → 306
06, since F1 = 1 at this time, step 310 → 311
→ 312 → 313, and such processing is repeated. Then, in step 312, the purge control valve 2
After 5 seconds have passed since 3 was fully closed (t in FIG. 10).
2), the opening degree θ1 of the rotation speed control valve 8 at that time is stored in step 314. That is, the opening degree θ1 of the rotation speed control valve 8 is read as the intake air amount in the bypass passage 7 when the purge control valve 23 is fully closed (opening degree 0%).

Thereafter, the CPU 26 sets the flag F1 to "0" in step 315, and adds a value obtained by adding 0.2% to the previous opening degree _Pi-1 of the purge control valve 23 in step 316. as opening P _i, the purge control valve 23
Is opened by 0.2%. Then, the CPU 26 determines in step 317 whether or not the opening degree of the purge control valve 23 has reached 20%.
At step 18, the flag F2 is set to "1".

In the next processing, step 300 → 3
01 → 302 → 303 → 306 → 307, and at step 307, since F2 = 1 at this time, step 316
→ 317 → 318, the purge control valve 23 is gradually opened, and when the opening reaches 20% in step 317 (FIG. 1).
1 at time t3), the flag F2
To “0”. Further, the CPU 26 determines in step 320 of FIG. 9 whether the correction coefficient FAF in the air-fuel ratio feedback control by the O ₂ sensor 12 is in the range of 0.95 to 1.05, that is, the air-fuel ratio is equal to the target air-fuel ratio. Check if it is nearby. When the feedback correction coefficient FAF is in the range of 0.95 to 1.05, the CPU 26 determines in step 321 that the engine speed is close to the target speed (650 to 7) by the idle speed feedback control.
Check if it is at 50 rpm).

When the engine speed is near the target speed, the CPU 26 determines whether or not 5 seconds have elapsed since the opening degree of the purge control valve 23 was set to 20% in step 322, that is, a stable state is maintained for a predetermined period ( 5 seconds) or more, and if not, the flag F is set at step 323.
Set 3 to “1”.

In the next processing, step 300 → 3
The process moves from 01 to 302 to 303 to 306 to 307 to 308, and at step 308, since F3 = 1 at this time, steps 320 to 321 to 322 to 323 are performed, and such processing is repeated. Then, the CPU 26 proceeds to step 3
At 22, when 5 seconds have elapsed since the opening degree of the purge control valve 23 was set to 20% (timing t4 in FIG. 10)
At step 324, the opening θ of the rotation speed control valve 8 at that time
2 is stored. That is, the opening degree θ2 of the rotation speed control valve 8 is read as the intake air amount in the bypass passage 7 at the opening degree of the purge control valve 23 of 20%.

Then, the CPU 26 sets the flag F3 to "0" in step 325. Further, the CPU 26 changes the opening degree (the amount of intake air in the bypass passage) of the rotation speed control valve 8 when the opening degree of the purge control valve 23 is changed from 0% (fully closed) to 20% in step 326 (Δθ). = Θ1-θ2). In step 327, the CPU 26 determines whether Δθ is within a predetermined range (10 to 15%). That is, although the opening of the purge control valve 23 is changed from 0% (fully closed) to 20%, the opening of the rotation speed control valve 8 (the amount of intake air in the bypass passage) is small. This indicates that the suction resistance of the system piping and the purge control valve 23 has increased (clogging, broken piping), and a flow rate characteristic defect is detected. In addition, when the opening degree of the rotation speed control valve 8 (the amount of intake air in the bypass passage) changes greatly, the suction resistance of the purge system piping and the purge control valve decreases (the piping disconnects, the pipe cracks occur, the purge control valve (A full-open failure) has occurred, and a flow characteristic failure is detected.

If a failure in the flow characteristics is detected in step 327, the CPU 26 sets an abnormal mode in step 328 and turns on the warning lamp 38. If no flow characteristic failure is detected, a normal mode is set in step 329, and the process ends.

As described above, in this embodiment, the electronic control circuit 2
5 (purge flow rate control means, idle speed control means, air-fuel ratio control means, opening change amount calculation means, abnormality determination means) adjusts the opening of the purge control valve 23 in accordance with the operating state of the engine 1 and supplies it. In addition to controlling the purge flow rates of the pipes 22 and 24 (supply passages), the intake air amount is controlled by adjusting the opening of the rotation speed control valve 8 so that the target rotation speed is attained during idling operation of the engine 1. , O ₂ sensor 1
2 (air-fuel ratio detecting means) to control the air-fuel ratio of the air-fuel mixture to the engine 1 to be constant. Electronic control circuit 2
5 is during air-fuel ratio control and during rotation speed control.
The purge control valve 23 is forcibly changed between a fully closed state (opening 0%) and a predetermined opening state (opening 20%), and a change amount Δθ of the opening of the rotation speed control valve 8 at that time is obtained. , The amount of change Δθ of the opening of the rotation speed control valve 8 is within a predetermined allowable range (10 to 1).
5%), it is determined that an abnormal supply of fuel evaporative gas to the supply pipe 2 has occurred due to an abnormality in at least one of the supply pipes 22, 24 and the purge control valve 23, and a warning lamp 38 (warning Means) to light the warning. In other words, although the purge flow rate changes with the change in the opening degree of the purge control valve 23, the air-fuel ratio changes. However, the air-fuel ratio is always maintained at a constant value by the air-fuel ratio control. Since the opening degree of the number control valve 8 changes according to the change in the purge flow rate by the purge control valve 23, the opening degree of the rotation speed control valve 8 that changes with the change in the opening degree of the purge control valve 23 changes according to the change in the purge flow rate. This indicates the amount, and an abnormality can be detected by this change.

As a result, the pipes 22 and 24 connecting the canister 17 and the intake pipe 2 and the fuel gas supply path of the purge control valve 23 are not affected by the concentration of the fuel evaporative gas purged from the canister 17 to the intake pipe 2. Thus, it is possible to detect a decrease in the purge performance of the purge system by detecting the flow rate characteristic failure of the purge system.

In the above embodiment, the opening degree of the purge control valve 23 is changed from fully closed to 20%, and the supply amount of the fuel evaporative gas to the intake pipe 2 is determined based on the change amount Δθ of the rotation speed control valve 8 at this time. The abnormality is determined, but is not limited thereto. For example, the opening degree of the purge control valve 23 is changed from 5% to 25%, or
The supply abnormality may be determined from the above-mentioned change amount Δθ when changing from 0% to fully closed.

The present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, the idle speed control is performed by the bypass air system. May be performed. or,
In the above embodiment, the warning lamp 38 is used as the warning means. However, a warning buzzer may be used as the warning means, and a warning sound may be emitted when an abnormality is detected.

In the above-described embodiment, as the means for detecting the evaporative gas concentration, the evaporative gas concentration is obtained by calculating from the change in the air-fuel ratio feedback control amount FAF when the purge control valve 23 is turned on / off. The same effect as that of the present invention can be obtained by using the detecting means. For example, an HC concentration sensor may be provided in the supply path of the evaporated gas.

[0043]

As described in detail above, according to the present invention,
When the fuel evaporative gas concentration is equal to or higher than the set value, the self-diagnosis of the evaporative fuel adsorbing device is stopped. An excellent effect that the self-diagnosis can be surely executed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration around an engine according to an embodiment.

FIG. 2 is a flowchart for explaining the operation of the embodiment.

FIG. 3 is a time chart for explaining an air-fuel ratio process.

FIG. 4 is a flowchart illustrating an operation.

FIG. 5 is a map for obtaining a target rotation speed with respect to a cooling water temperature.

FIG. 6 is a map for obtaining a control opening amount corresponding to a deviation of the rotational speed.

FIG. 7 is a flowchart for explaining an operation.

FIG. 8 is a flowchart for explaining the operation.

FIG. 9 is a flowchart for explaining the operation.

FIG. 10 is a time chart showing various processes.

FIG. 11 is a flowchart illustrating an operation.

FIG. 12 is a map for obtaining a purge flow rate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Engine (internal combustion engine) 2 Intake pipe 8 Speed control valve 12 O ₂ sensor as air-fuel ratio detecting means 13 Fuel tank 17 Canister as evaporative fuel adsorbing device 19 Adsorbent 22 Supply pipe constituting supply passage 23 Purge control valve 24 supply pipe constituting a supply passage 25 purge flow rate control means, idle speed control means,
Air-fuel ratio control means, opening degree change amount calculation means, abnormality determination means,
Electronic control circuit as concentration detection means, failure detection means, failure detection stop means 38 Warning lamp as warning means

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F02D 45/00345 F02D 45 / 00345K (56) References JP-A-4-143452 (JP, A) JP-A-4-12157 (JP, A) JP-A-4-5462 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02M 25/08 F02M 25/08 301 F02D 41/08 315 F02D 41/16 F02D 45/00 301 F02D 45/00 345

Claims (1)

(57) [Claims] 1. A purge control valve is provided in an evaporative fuel purge passage connecting an evaporative fuel adsorber and an adsorption passage of an internal combustion engine, and an output signal of an exhaust gas sensor disposed in an exhaust passage of the internal combustion engine is provided. An air-fuel ratio control device for an internal combustion engine configured to feedback-control the air-fuel ratio of the air-fuel mixture of the internal combustion engine based on the feedback control of at least the air-fuel ratio of the air-fuel mixture
Concentration detecting means for detecting a fuel evaporative gas concentration in the fuel purge passage based on an air-fuel ratio correction coefficient and a load on the internal combustion engine, a failure detecting means for detecting a failure of the evaporated fuel adsorbing device, and the concentration detection An air-fuel ratio control device for an internal combustion engine, comprising: a failure detection stopping means for stopping execution of the failure detection by the failure detecting means when the evaporative gas concentration detected by the means is equal to or more than a predetermined value.