JPH10213022A - Failure diagnostic device of evapopurge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diagnose a failure at the time of deceleration to prevent a driver from receiving a sense of incongruity by adding a set function of purge ON operation time of a purge valve to a control means based on a detected speed at the time of deceleration. SOLUTION: It is judged whether deceleration is being done or not (step 102). In case of YES, engine speed Ne is compared with diagnosis conducting rotation number No (step 104), and if Ne exceeds No, t1 time for conducting no diagnosis at the time of rapid deceleration is compared with set time Ta after t1 time until fuel cut control conducting rotation number N1 from No is measured (step 106) (step 108). In case of YES, t2 time which is purge ON operation time of a purge valve is determined by t1 time (step 110). After that, suction air pressure change amount absolute value Pevp and judgement level MFevp are compared and judged (step 120). In case of YES, it is diagnosed that an abnormality due to small flow rate in an evapopurge system occurs to inform a driver of the abnormality (step 122).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure diagnosis apparatus for an evaporative purge, and more particularly, to a failure diagnosis by a control means at the time of deceleration, so that there is no fear of giving a driver a sense of incongruity. The present invention relates to a failure diagnosis apparatus for an evaporative purge that can diagnose a failure such as damage and can also diagnose a state in which evaporated fuel leaks to the atmosphere.

[0002]

2. Description of the Related Art Evaporated fuel leaking into the atmosphere from a fuel tank, a float chamber of a vaporizer, etc. contains a large amount of hydrocarbons (HC) and is one of the causes of air pollution. Because of the connection, various techniques for preventing this are known. As a typical example, the fuel vapor in the fuel tank is temporarily adsorbed and held in a canister containing an adsorbent such as activated carbon, and the fuel vapor adsorbed and held in the canister is released (purged) during operation of the internal combustion engine.
There is an evaporation system that supplies the fuel to the internal combustion engine.

As a failure diagnosis apparatus for the evaporative purge, there is one disclosed in Japanese Patent Application Laid-Open No. 4-36056. A failure detection method for an evaporative purge system disclosed in this publication is a failure detection method for an evaporative purge system that adsorbs fuel evaporative gas from a fuel tank to a canister and purges evaporative gas to an intake system during engine operation. A flammable gas sensor is provided in a purge passage between the canister and the intake system to temporarily stop purging of evaporative gas during a predetermined operation after warm-up, and the output of the sensor during the purge stop and the output of the sensor during the purge are output. The presence or absence of an abnormality in the evaporative purge system is determined based on the difference, and a failure in the evaporative purge system is accurately detected.

[0004]

Here, the fault diagnosis method of the purge system in the conventional fault diagnosis apparatus for the evaporative purge is usually such that when the purge is OFF, the purge valve is forcibly turned ON when idling is performed. At that time, the change amount of the engine speed Ne, the change amount of the air-fuel ratio (A / F) feedback (F / B) control amount, the ISC
Speed control) A failure diagnosis of the evaporative purge system is performed by checking whether or not there is a purge flow rate to the internal combustion engine when the purge valve is turned ON by a change amount such as a feedback control amount.

[0005] Conventional failure diagnosis is performed at the time of idling or at the time of high-speed low-speed running.

As a result, when the engine speed Ne during idling is low, the purge valve is forcibly turned ON, the engine speed is reduced, the vibration of the vehicle body is greatly felt by the driver, and the driver feels discomfort. This gives a feeling of anxiety that the vehicle is abnormal, which is disadvantageous in practical use.

Further, at present, for example, when the hose between the purge valve and the canister is disconnected, there is no control measure for diagnosing a failure in the evaporation purge system.
There is an inconvenience that an abnormal part cannot be detected.

Further, when the hose is damaged, if the hose is between the canister and the internal combustion engine, the vapor of the canister is not purged but leaks to the atmosphere, which may lead to deterioration of the environment. There is. If the hose is between the canister and the fuel tank, the vapor in the fuel tank leaks to the atmosphere, which has a disadvantage that the environment may be deteriorated.

Further, even if failure diagnosis is performed at high speed,
Irrespective of the driver's intention, the diagnosis is performed, so that the speed cannot be adjusted as expected, which is inconvenient.

[0010]

In order to eliminate the above-mentioned disadvantages, the present invention provides a purge passage connecting an intake passage of an internal combustion engine to a canister, an evaporating passage connecting a canister and a fuel tank, and In an evaporative purge failure diagnostic device having a purge valve provided in the middle of the purge passage and control means for performing failure diagnosis of an evaporative purge system, a speed at the time of deceleration is detected, and a purge ON operation time of the purge valve is set based on the detected speed. A function of adding the function to the control means.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION
When performing a failure diagnosis of the evaporative purge, the control unit performs a failure diagnosis at the time of deceleration, so that there is no fear that the driver may feel uncomfortable, and a failure such as detachment or damage of the evaporative purge hose is diagnosed. It also diagnoses conditions that leak into the atmosphere.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 to 4 show a first embodiment of the present invention. In FIG. 2, 2 is an internal combustion engine, 4 is an intake passage, 6 is an exhaust passage, and 8 is a fuel tank.

The internal combustion engine 2 is provided with a fuel injection valve (not shown) in the intake passage 4 in a direction toward a combustion chamber (not shown). The fuel injection valve is connected to a fuel tank 8 through a fuel passage (not shown). ing.

The fuel in the fuel tank 8 is supplied to a fuel injection valve via a fuel passage by a fuel pump (not shown), and supplied to a combustion chamber together with air to be burned. The exhaust gas generated by the combustion is discharged through the exhaust passage 6.

A purge passage 14 is provided for connecting the intake passage 4 of the internal combustion engine 2, for example, a downstream side of the throttle valve 10 with a canister 12 for adsorbing and holding evaporated fuel.
An evaporation passage 16 is provided for connecting the canister 12 and the fuel tank 8.

A purge valve 18 as a purge duty valve is provided in the purge passage 14 and a separator 20 is provided in the evaporation passage 16.

A control means (ECU) 22 for diagnosing a failure of the evaporation purge system is provided.

The control means 22 includes an intake air temperature sensor 24 disposed in the intake passage 4 upstream of the throttle valve 12, a throttle opening sensor 26 for detecting the throttle opening of the throttle valve 12, The intake passage 4 downstream of the throttle valve, that is, the surge tank 2
8, an EGR control valve 32, an EGR specifying valve 34, the purge valve 18, an open / close valve (not shown) of the canister 12, and a fuel level gauge 36 of the fuel tank 8.
A water temperature sensor 38 mounted on the internal combustion engine 2 for detecting a cooling water temperature; and a catalyst 40 provided in the exhaust passage 6.
Front O2 sensor 42 disposed upstream of
And a rear O disposed downstream of the catalyst 40.
2 Sensor 44 is connected.

The control means 22 is provided with an atmospheric pressure sensor 46 for detecting the atmospheric pressure.

At this time, the control means 22 is additionally provided with a function of detecting the speed at the time of deceleration and setting the purge ON operation time of the purge valve 18 based on the detected speed.

More specifically, the control means 22 detects the speed at the time of deceleration, that is, sets the diagnosis execution speed N0 and the fuel cut (F / C) control execution speed N1 in advance, and sets the diagnosis execution speed. The time t1 from N0 to the fuel cut control execution speed N1 is measured, and this time t1 is used as the speed at the time of deceleration.

The control means 22 determines the time t2, which is the purge ON operation time of the purge valve 18, based on the measured time t1, and forcibly activates the purge valve 18 for the time t2 during deceleration, that is, during fuel cut control during deceleration. It is controlled to perform the purge ON operation.

In the state where the purge valve 18 is forcibly turned on for the time t2, the control means 22 controls the absolute value of the intake pressure change Pevp1, that is, Pevp1 = | P2-P1 | P1: fuel cut control. The first intake pipe pressure P2 immediately before the purge is turned ON, ie, the first intake pipe pressure P2: the second intake pipe pressure immediately after the elapse of the time t2 from the fuel cut control execution speed N1, ie, immediately before the purge is turned off, becomes smaller than the determination level MFevp. In this case, it is diagnosed that the abnormality is due to a small purge flow rate. At this time, the diagnosis is
It is also performed during deceleration other than fuel cut (F / C) control.

The small purge flow rate is generated when the purge valve 18 fails, when the harness for driving the purge valve 18 is disconnected, or when the connector is disconnected.

As shown in FIG. 4, the determination level MFevp is obtained from a map which is set in advance based on the absolute value Pevp1 of the intake pressure change amount and the first intake pipe pressure P1 at the time of the fuel cut control execution speed N1.

Next, the operation will be described with reference to the control flowchart of the evaporative purge failure diagnostic apparatus shown in FIG.

During the start operation of the internal combustion engine 2, the program of the control flowchart starts (100).
If deceleration is interrupted during diagnosis,
The diagnosis is immediately stopped.

Then, it is determined whether or not the vehicle is decelerating (10).
Perform 2). If this determination (102) is NO, the determination (10) is repeated until the determination (102) becomes YES.
2) is performed, and if the determination (102) is YES, the engine (E / G) rotation speed Ne is changed to the diagnosis execution rotation speed N
The process proceeds to the determination (104) as to whether or not the value exceeds 0.

In this judgment (104), if the engine (E / G) rotation speed Ne is equal to or lower than the diagnosis execution speed N0, that is, if the determination is NO, it is determined whether or not the vehicle is decelerating (10).
Returning to 2), if the engine (E / G) rotation speed Ne exceeds the diagnosis execution speed N0, that is, if YES, the time t1 from the diagnosis execution speed N0 to the fuel cut control execution speed N1 is calculated. Measure (106).

After the measurement of the time t1 (106),
The time t1 is compared with a set time Ta for not performing a diagnosis at the time of rapid deceleration in the first speed, the second speed, etc., and it is determined whether or not t1≥Ta (108).

If the determination (108) is NO, the process returns to the determination (102) as to whether or not the vehicle is decelerating, and the determination (10)
If 8) is YES, the time t2, which is the purge ON operation time of the purge valve 18, is determined based on the measured time t1 (110).

After the determination of the time t2 (110), the purge is performed for the time t2, that is, the control means 22 controls the purge valve 18 to forcibly turn on the purge (11).
2) At the same time, the first intake pipe pressure P1 and the fuel cut control execution speed N1 immediately before the purge ON operation are measured (114).

Further, the second intake pipe pressure P2 immediately before the purge is turned off and the fuel cut (F / C) control end rotation speed N2
Is measured (116), and the third intake pipe pressure P3 when the purge is OFF is measured (118) (see FIG. 3).

Then, the intake pressure change absolute value Pevp1
Is determined (120) as to whether or not it is smaller than the determination level MFevp. If this determination (120) is NO, the process is shifted to the end (124) of the program, and the determination (120) is YES. In this case, an abnormality is diagnosed due to a small flow rate in the evaporative purge system, a notification lamp or the like is turned on to inform the driver (122), and thereafter, the program is shifted to the end (124) of the program.

Thus, a fault diagnosis can be performed during deceleration by the control means 22, and there is no fear that the driver will feel uncomfortable, which is practically advantageous.

In addition, it is possible to diagnose a failure such as detachment or damage of the hose of the evaporation purge system, so that usability can be improved.

Further, the control means 22 can diagnose a state in which the evaporated fuel leaks to the atmosphere, thereby preventing the environment from being deteriorated by the evaporated fuel.

FIGS. 5 and 6 show a second embodiment of the present invention. In the second embodiment, parts that perform the same functions as in the first embodiment will be described with the same reference numerals.

A feature of the second embodiment is that the intake pressure calculation method in the first embodiment is changed.

That is, the change P3-P2 of the intake pressure is
As shown in FIG. 6, it changes depending on the gear position and the running state (up or down).

For this reason, the intake pressure change absolute value Pevp2
Is calculated by the following equation: Pevp1 = | P2− (P1 + P3) / 2 |, and this intake pressure change amount absolute value Pevp2 is used.

In the second embodiment, the control flowchart of FIG. 5 is changed from part A in the control flowchart of FIG. 1 in the first embodiment, so that only the changed part is the failure of the evaporative purge of FIG. A description will be given along a control flowchart of the diagnostic apparatus.

After measuring the third intake pipe pressure P3 when the purge is OFF (118), the absolute value Pevp2 of the intake pressure change is calculated by the following equation: Pevp1 = | P2- (P1 + P3) / 2 |
0), the absolute value of the intake pressure change amount Pevp2 is equal to the judgment level M
It is determined (202) whether or not it is smaller than Fevp.

If the determination (202) is NO, the program shifts to the end (206) of the program. ), For example, by turning on a notification lamp or the like to notify the driver, and then proceeding to the end (206) of the program.

In this case, the failure diagnosis can be performed at the time of deceleration, and the diagnosis accuracy can be improved, so that there is no fear that the driver will feel uncomfortable, which is practically advantageous.

Further, since the failure such as detachment or damage of the evaporation purge system hose can be diagnosed, the usability can be improved as in the case of the first embodiment.

Further, since the state in which the fuel vapor leaks to the atmosphere can be reliably diagnosed, the deterioration of the environment due to the fuel vapor can be prevented as in the first embodiment.

FIGS. 7 and 8 show a third embodiment of the present invention.

The feature of the third embodiment is that the amount of change in the rotation Nevp with respect to the time t1 which is the speed at the time of deceleration is shown.
This is a measure for diagnosing an abnormality in the purge system.

That is, as shown in FIG. 8, a map of the judgment level MNevp is set which includes the time t1 and the rotation change amount Nevp.

In the third embodiment, the control flowchart of FIG. 7 is changed from the part A in the control flowchart of FIG. 1 in the first embodiment to the following. A description will be given along a control flowchart of the diagnostic apparatus.

After measuring the third intake pipe pressure P3 when the purge is OFF (118), it is determined whether or not the rotation change amount Nevp is smaller than the determination level MNevp (30).
Perform 0).

If the judgment (300) is NO, the program shifts to the end (304) of the program. If the judgment (300) is YES, it is diagnosed that the flow rate in the evaporative purge system is small (302). ), For example, by turning on a notification lamp or the like to notify the driver, and then proceeding to the end (304) of the program.

In this case, a fault diagnosis can be performed at the time of deceleration by the control means, and like the first and second embodiments, there is no fear that the driver will feel uncomfortable, which is practically advantageous. is there.

Further, since the failure such as detachment or damage of the evaporation purge system hose can be diagnosed, the usability can be improved as in the first and second embodiments.

Further, since the control means can diagnose the state in which the fuel vapor leaks into the atmosphere, it is possible to prevent the deterioration of the environment due to the fuel vapor, similarly to the first and second embodiments.

FIGS. 9 to 11 show a fourth embodiment of the present invention.

The feature of the fourth embodiment is that, in order to reflect the gear position and the road surface condition as shown in FIG. 6, the intake pressure change absolute value Pevp1 of the first embodiment or the intake pressure change amount of the second embodiment. The pressure change absolute value Pevp2 is corrected by the atmospheric pressure to realize a highly accurate diagnosis.
The function of performing an abnormality diagnosis of the purge system based on the intake pressure change amount Pevp with respect to time is added to the control means.

That is, as shown in FIG. 10, the judgment level MFev consisting of the time t1 and the intake pressure change amount Pevp is determined.
In addition to setting the map of p, the atmospheric pressure correction value Kpa of the atmospheric pressure is calculated using the map of FIG.

In the fourth embodiment, the control flowchart of FIG. 9 is changed from the part A in the control flowchart of FIG. 1 in the first embodiment. A description will be given along a control flowchart of the diagnostic apparatus.

After measuring the third intake pipe pressure P3 when the purge is OFF (118), the intake pressure change absolute value Pevp1
The intake pressure change amount Pevp is calculated by the product of the pressure correction value Kpa and the intake pressure change absolute value Pevp2 and the atmospheric pressure correction value Kpa (400), and the intake pressure change amount Pevp is determined by the determination level MFevp. A determination is made as to whether the value is smaller than the threshold value (402).

If the judgment (402) is NO, the program proceeds to the end of the program (406), and if the judgment (402) is YES, it is diagnosed that the flow rate in the evaporation purge system is small (404). ), For example, by turning on a notification lamp or the like to notify the driver, and then proceeding to the end (406) of the program.

In this case, the control means can perform a fault diagnosis at the time of deceleration, and can realize a highly accurate diagnosis, so that the driver can be operated in the same manner as in the first to third embodiments. There is no fear of giving a sense of incongruity, which is practically advantageous.

Further, since the failure such as detachment or damage of the hose of the evaporation purge system can be diagnosed, the usability can be improved as in the first to third embodiments.

Further, since the control means can diagnose a state in which the fuel vapor leaks to the atmosphere, the deterioration of the environment due to the fuel vapor can be prevented, as in the first to third embodiments.

FIGS. 12 to 15 show a fifth embodiment of the present invention.

The fifth embodiment is characterized in that a diagnosis strategy during deceleration other than fuel cut control and a strategy when the total purge cut time exceeds a predetermined value are set.

That is, at the time of deceleration except during the fuel cut control, when the purge valve is operated to perform the purge ON operation, the minimum value Fmin of the air-fuel ratio feedback control amount during the purge ON operation is set to the value before the purge ON operation. If the value is larger than the value F1, it is diagnosed that air has entered the internal combustion engine due to no vapor in the canister, detachment of the hose or the like, or breakage of the hose. Further, the purge ON operation of the purge valve is controlled so as to be divided into small predetermined time periods, that is, a purge cut time period t3.

In the case where the total Pcut during the purge cut time t3 and t4 is equal to or greater than the predetermined value PCtotal, the control means performs the purge ON operation when the purge valve is purged ON during deceleration. When the minimum value Fmin of the fuel ratio feedback control amount does not become larger than the value F1 before the purge ON operation, control is performed to diagnose that there is an abnormality in the evaporation system due to, for example, hose breakage.

In the fifth embodiment, the control flowchart of FIG. 12 is inserted into the portion B of the control flowchart of FIG. 1 in the first embodiment. Will be described with reference to a control flowchart of the failure diagnosis device.

In the control flowchart shown in FIG. 1, the absolute value Pevp1 of the amount of change in intake pressure is determined by the determination level MFevp.
It is determined whether the value is smaller than (120). If the determination (120) is NO, as shown in FIG. 12, the value F1 is measured before the purge ON operation or immediately after the purge ON operation ( 500), the minimum value Fmin and the maximum value Fmax of the air-fuel ratio feedback control amount during the time t2 'of the purge ON operation are measured (502).

Then, it is determined (504) whether or not the value F1 immediately after the purge ON operation exceeds the minimum value Fmin of the air-fuel ratio feedback control amount (504).
Is NO, the purge cut process (518) is performed until a normal diagnosis, which will be described later, is performed, and the process proceeds to the end (124) of the program, and the determination (504) is YES.
In the case (1), normally, as shown in FIG. 14, the purge ON operation portion is purge-cut for the time t3, that is, the purge is OFF (506).

After the purge cut for the time t3, the purge ON operation is performed only for the time t5 (508), and the value F1 immediately after the purge ON operation becomes the minimum value F of the air-fuel ratio feedback control amount.
The determination (510) of whether or not the time exceeds min is performed again. If the determination (510) is NO, the purge cut processing (518) is performed until a normal diagnosis, which will be described later, is performed. Move to the end (124),
When the judgment (510) is YES, when the purge diagnosis at the time of deceleration is established, the total Pcut for the time t3 and t4, which are the purge cut time during the preceding traveling, is calculated (512).

Further, the total Pcut of the purge cut times t3 and t4 is compared with the predetermined value PCtotal, and it is determined whether the total Pcut is equal to or more than the predetermined value PCtotal (514).
If NO in step 14), the flow returns to the determination (102) of whether or not the vehicle is decelerating in FIG. 1. If the determination in step 514 is YES, the hose of the evaporative purge system is disconnected or the hose is damaged. Diagnosis is made (516) that there is no vapor.

After the diagnosis (516), a purge cut is performed thereafter (518) until a normal diagnosis is made, and the program shifts to the end (124) of the program.

In this case, since the failure diagnosis can be performed at the time of deceleration by the control means, the above-described first to first aspects can be performed.
As in the case of the fourth embodiment, there is no fear that the driver will feel uncomfortable, which is practically advantageous.

Further, since a failure such as detachment or damage of the hose of the evaporation purge system can be diagnosed, the usability can be improved as in the first to fourth embodiments.

Further, since the control means can diagnose the state in which the fuel vapor leaks to the atmosphere, the deterioration of the environment due to the fuel vapor can be prevented as in the first to fourth embodiments.

Further, when the purge valve is operated to perform a purge ON operation during deceleration except during the fuel cut control, the control means sets the minimum value Fmin of the air-fuel ratio feedback control amount during the purge ON operation to a value before the purge ON operation. Is larger than the value F1, the purge ON operation of the purge valve is controlled so as to be divided at every predetermined time, that is, every t3 time, which is a purge cut time, so that there is no vapor in the canister or the hose is disconnected. It can be reliably diagnosed whether the hose has been detached or the hose is broken, which is practically advantageous.

When the total Pcut of the purge cut times t3 and t4 is equal to or greater than the predetermined value PCtotal, the control means may perform the purge ON operation when the purge valve is purged ON during deceleration. When the minimum value Fmin of the fuel ratio feedback control amount does not become larger than the value F1 before the purge ON operation, by performing control to diagnose that there is an abnormality in the evaporation system,
It can reliably diagnose the detachment or breakage of the evaporative hose.

[0082]

As described above in detail, according to the present invention, a purge passage connecting the intake passage of the internal combustion engine and the canister, an evaporative passage connecting the canister and the fuel tank, and a passage provided in the middle of the purge passage are provided. In an evaporative purge failure diagnostic apparatus having a purge valve and control means for performing a failure diagnosis of an evaporative purge system, a function of detecting a speed at the time of deceleration and setting a purge ON operation time of the purge valve based on the detected speed is added to the control means. Since it is provided, the failure can be diagnosed at the time of deceleration by the control means, and there is no fear that the driver will feel uncomfortable, which is practically advantageous. Further, it is possible to diagnose a failure such as detachment or damage of the hose of the evaporation purge system, so that usability can be improved. Furthermore, the control means can diagnose a state in which the fuel vapor leaks to the atmosphere, thereby preventing environmental degradation due to the fuel vapor.

[Brief description of the drawings]

FIG. 1 is a control flowchart of a failure diagnosis apparatus for an evaporative purge according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a failure diagnosis device for an evaporative purge.

FIG. 3 is a time chart of a failure diagnosis device for an evaporative purge.

FIG. 4 is a map of a judgment level MFevp set in advance based on an intake pressure change absolute value Pevp1 and a first intake pipe pressure P1 at a fuel cut control execution speed N1.

FIG. 5 is a control flowchart of an evaporative purge failure diagnostic apparatus according to a second embodiment of the present invention.

FIG. 6 is a diagram showing a relative comparison of a gear position and a road surface.

FIG. 7 is a control flowchart of an evaporative purge failure diagnosis apparatus according to a third embodiment of the present invention.

FIG. 8 is a map of a judgment level MNevp including a time t1 and a rotation change amount Nevp.

FIG. 9 is a control flowchart of an evaporative purge failure diagnostic apparatus according to a fourth embodiment of the present invention.

FIG. 10 is a map of a judgment level MFevp including time t1 and an intake pressure change amount Pevp.

FIG. 11 is a map showing an atmospheric pressure correction value Kpa of the atmospheric pressure.

FIG. 12 is a control flowchart of an evaporative purge failure diagnostic apparatus according to a fifth embodiment of the present invention.

FIG. 13 is a diagram showing a relationship between a purge cut time t3 and an intake air temperature.

FIG. 14 is a time chart of a failure diagnosis device for an evaporative purge.

FIG. 15 is a diagram showing a relationship between a predetermined value PCtotal and an intake air temperature.

[Explanation of symbols]

 2 Internal combustion engine 4 Intake passage 6 Exhaust passage 8 Fuel tank 10 Throttle valve 12 Canister 14 Purge passage 16 Evaporation passage 18 Purge valve 22 Control means (ECU) 24 Intake air temperature sensor 26 Throttle opening sensor 30 Intake pipe pressure sensor 38 Water temperature sensor 40 Catalyst 42 Front O2 sensor 44 Rear O2 sensor 46 Atmospheric pressure sensor

Claims (3)

[Claims] 1. A purge passage connecting an intake passage of an internal combustion engine to a canister, an evaporative passage connecting a canister and a fuel tank, a purge valve provided in the middle of the purge passage, and control for diagnosing a failure of an evaporative purge system. A function of detecting a speed at the time of deceleration and setting a purge ON operation time of the purge valve based on the detected speed is provided to the control means. Fault diagnosis device. 2. The control device according to claim 1, wherein, when decelerating except for fuel cut control, when the purge valve is operated to perform a purge ON operation, the minimum value of the air-fuel ratio feedback control amount during the purge ON operation is a value before the purge ON operation. If it is larger than that, it is diagnosed that air has entered the internal combustion engine,
2. The failure diagnosis device for an evaporative purge according to claim 1, wherein the purge ON operation of the purge valve is controlled so as to be divided into small predetermined time intervals. 3. The controller according to claim 1, wherein, when the total purge cut time is equal to or longer than a predetermined value, the minimum value of the air-fuel ratio feedback control amount during the purge ON operation when the purge valve is purged ON during deceleration. Purge ON
2. The control method according to claim 1, wherein when the value is not larger than the value before the operation, the control is performed to diagnose that there is an abnormality in the evaporation system.
3. The failure diagnosis device for evaporative purge according to claim 1.