JPH05180099A - Trouble diagnostic device for evaporation purge system - Google Patents

Abstract

PURPOSE:To prevent a wrong diagnosis, relating to a device for diagnosing a trouble of an evaporation purge system in which vaporized fuel (vapor) of an internal combustion engine is absorbed to an absorbent in a canister to release (purge) the absorbed fuel, to an intake system of the internal combustion engine under a predetermined operational condition, to be burned. CONSTITUTION:After commanding to close both a vacuum switching valve(VSV) in a purge side and a canister atmospheric hole VSV (step 103, 106), a tank internal pressure reaches a predetermined pressure Y (Pa) to judge a pressure in a system generated in a value approximate to a stable condition (step 107), and then based on this time pressure sensor value PS and a pressure sensor value PE after a predetermined time alpha, a change rate is calculated (step 109 to 111, 112 to 114). When the calculated change rate is a threshold value betaor more, a trouble is judged because of leakage the specified value or more, to perform lighting or the like of a warning lamp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure diagnosing device for an evaporative purge system, and more particularly, to adsorbing evaporated fuel (vapor) of an internal combustion engine to an adsorbent in a canister, and adsorbing the adsorbed fuel to an internal combustion engine under a predetermined operating condition. The present invention relates to a device for diagnosing a failure of an evaporative purge system that discharges (purges) and burns the intake air of an engine.

[0002]

2. Description of the Related Art Fuel evaporated in a fuel tank (vapor)
In order to prevent air from being released to the atmosphere, each part is hermetically sealed, and the vapor is once adsorbed by the adsorbent in the canister, and the fuel adsorbed while the vehicle is running is sucked into the intake system and burned by evaporative purging. In an internal combustion engine equipped with a system, the vapor supply passage is damaged for some reason,
If the pipe is disconnected, vapor is released from the canister to the atmosphere, and if the purge passage to the intake system is blocked, the vapor in the canister overflows and vapor is released from the canister atmosphere inlet to the atmosphere. It will leak. Therefore, it is necessary to diagnose whether such a failure of the evaporative purge system has occurred.

Therefore, the present applicant previously filed Japanese Patent Application No. 3-138.
No. 002 has a first control valve that opens and closes a purge passage that purges the evaporated fuel stored in the canister into the intake system of the internal combustion engine, and a second control valve that opens and closes an atmospheric hole of the canister. After closing the second control valve during failure diagnosis,
Failure diagnosis of the evaporative purge system that waits until a predetermined negative pressure is reached, closes the first control valve, maintains the airtightness for a predetermined time, and diagnoses the occurrence of a failure based on the degree of change in pressure at that time. Proposed a device.

[0004]

However, in the device proposed by the applicant of the present invention, the pressure is not stable for a while after the second control valve is closed due to the passage resistance in the system. Since the pressure is not equalized in the system, the detected pressure immediately after the first control valve is closed is not reliable as the diagnosis start set pressure, and therefore immediately after the first control valve is closed. If the diagnosis is started from, there is a possibility of misdiagnosis.

Further, when the second control valve is closed, the negative pressure of the engine intake passage is applied to the fuel tank, so the boiling point of the fuel is lowered at the time of closing the valve to generate fuel vapor, and the first control is performed. When the valve is closed, the negative pressure drops rapidly as if there was a large leak in the evaporative purge system. Furthermore, if a pressure sensor is installed in the vapor passage for pressure measurement for the failure diagnosis, a difference from the internal pressure of the fuel tank occurs due to the passage resistance of the vapor passage, and the fuel tank is closed at the moment when the first control valve is closed. It is the same as the internal pressure. Also from the above, according to the proposed device of the present applicant, there is a possibility of erroneous diagnosis. The present invention has been made in view of the above points, and an object of the present invention is to provide a failure diagnostic device for an evaporative purge system that solves the above problems by waiting for the negative pressure to stabilize before starting diagnosis.

[0006]

FIG. 1 is a block diagram showing the principle of the present invention. In the figure, the failure diagnosis apparatus of the present invention causes the evaporated fuel from the fuel tank 11 to be adsorbed by the adsorbent in the canister 13 through the vapor passage 12 and the adsorbed fuel in the canister 13 through the purge passage 14 during a predetermined operation. In the failure diagnosis device for purging the intake passage 15 of 10, the first control valve 16, the second control valve 17, the valve control means 18, the detection means 19 and the determination means 20 are provided.

The first control valve 16 connects or disconnects the purge passage 14. The second control valve 17 opens and closes the atmosphere hole of the canister 13. The valve control means 18 closes the second control valve 17 and opens the first control valve 16 to open the intake passage 1
After the pressure of 5 is introduced into the system from the purge passage 14 to the fuel tank 11, the first control valve 16 is closed after the pressure reaches a predetermined value.

The detection means 19 is controlled by the valve control means 18
Also, it is substantially detected that the pressures in the system after both the second control valves 16 and 17 receive the valve closing command are substantially stable.
The determination means 20 measures the degree of change of the pressure in the system for a set time from the time when the pressure in the system is detected to be substantially stable by the detection means 19, and determines whether or not the evaporative purge system has failed from the measurement result. To judge.

[0009]

In the present invention, the point that the first control valve 16 is closed after the second control valve 17 is closed and the pressure in the system reaches a predetermined value is the same as the above-mentioned apparatus proposed by the applicant. Similar, but
Unlike the device proposed by the applicant, the first and second control valves 1
The measurement of the degree of change in the system pressure for diagnosis is not started immediately after both 6 and 17 are closed, but the system pressure is detected after the detection means 19 detects that the pressure in the system is substantially stable. The measurement of the degree of change of is started. Therefore,
In the present invention, the means 2 for judging the presence or absence of a failure of the evaporative purge system is based on the measurement result of the pressure in the system in a substantially stable state.
It can be determined by 0.

[0010]

FIG. 2 shows a system configuration diagram of an embodiment of the present invention. In the figure, the air from which dust and dust in the atmosphere have been removed by the air cleaner 22 has its intake air amount measured by an air flow meter 23, and its flow rate is controlled by a throttle valve 25 in an intake pipe 24. Further, it flows through a surge tank 26 and an intake manifold 27 (which constitutes the intake passage 15 together with the intake pipe 24) into a combustion chamber (both not shown) of an internal combustion engine during a period in which an intake valve is open.

The opening of throttle valve 25 is controlled in conjunction with an accelerator pedal (not shown), and the opening is detected by throttle position sensor 28. Further, a fuel injection valve 29 is provided for each cylinder so that a part thereof projects into the intake manifold 27. The fuel injection valve 29 injects the fuel 31 in the fuel tank 30 into the air flow passing through the intake manifold 27 for a time designated by the microcomputer 21.

The fuel tank 30 is the fuel tank 11 described above.
The fuel 31 is accommodated and the evaporated fuel (vapor) generated inside is sent to the canister 33 (corresponding to the canister 13 described above) through the vapor passage 32 (corresponding to the vapor passage 12). The canister 33 is filled with an adsorbent such as activated carbon inside and a part of the canister 33 is provided with an atmosphere hole 34.

The atmosphere hole 34 is communicated with a canister atmosphere hole vacuum switching valve (VSV) 36 through an atmosphere passage 35. Canister vent V
The SV 36 is a control valve that connects or disconnects the atmosphere introducing hole 36 a and the atmosphere passage 35 based on a control signal from the microcomputer 21, and constitutes the second control valve 17.
Further, the canister 33 communicates with the purge-side VSV 38 via the purge passage 37. The purge-side VSV 38 is a control valve that connects or shuts off the other end of the purge passage 39, one end of which communicates with the surge tank 26, and the other end of the purge passage 37, based on a control signal from the microcomputer 21. The first control valve 16 is configured.

The pressure sensor 40 is provided in the middle of the vapor passage 32, and is provided to detect the pressure in the vapor passage 32 to substantially detect the internal pressure of the fuel tank 30. The warning lamp 41 is provided to notify the driver of the abnormality when the microcomputer 21 detects the abnormality.

In such a structure, the vapor generated in the fuel tank 30 is adsorbed by the activated carbon in the canister 33 through the vapor passage 32 and prevented from being released into the atmosphere. Normally, the canister atmosphere hole VSV36 is opened, and when the evaporative purge system is operating, the purge side VS
V38 is also open. As a result, the negative pressure of the intake manifold 27 is used during operation, and the air inlet 36a
The atmosphere is introduced into the canister 33 through the canister atmosphere hole VSV 36, the atmosphere passage 35, and the atmosphere hole 34.

Then, the fuel adsorbed on the activated carbon is desorbed, and the fuel is purged by the purge passage 37 and the purge side VSV3.
8 and the purge passage 39, respectively, to be sucked into the surge tank 26. In addition, the activated carbon is regenerated by the above desorption and prepared for the next adsorption of vapor.

The microcomputer 21 is a control device for realizing the above-mentioned valve control means 18, detection means 19 and determination means 20 by software processing, and has a known hardware configuration as shown in FIG. 2, those parts which are the same as those corresponding parts in FIG. 2 are designated by the same reference numerals, and a description thereof will be omitted.
In FIG. 3, a microcomputer 21 is a central processing unit (CPU) 50, and a read program storing a processing program.
Only memory (ROM) 51, random access memory (RAM) 52 used as a work area, backup RAM 5 that retains data even after the engine is stopped
3, input interface circuit 54, multiplexer-equipped A / D converter 56, and input / output interface circuit 5
5, etc., which are connected via a bus 57.

The A / D converter 56 sequentially fetches the intake air amount detection signal from the air flow meter 23, the detection signal from the throttle position sensor 28, the pressure detection signal from the pressure sensor 40, etc. through the input interface circuit 54 and fetches it. Are converted from analog to digital and are sequentially transmitted to the bus 57.

The input / output interface circuit 55 receives the detection signal from the throttle position sensor 28 and inputs the detection signal to the CPU 50 via the bus 57, while the signals input from the bus 57 are supplied to the fuel injection valve 29 and the canister. The porosity VSV 36, the purge side VSV 38, and the warning lamp 41 are selectively sent to control them.

The CPU 50 of the microcomputer 21 having the above configuration executes the processing of the flowchart described below according to the program stored in the ROM 51. FIG. 4 is a flow chart for explaining the operation of the first embodiment of the essential part of the present invention, for example, interrupt activation is performed every 65 ms. In the figure, first, it is checked whether the execution flag is set (the value is "1") (step 101). Since the execution flag is cleared (the value is "0") by the initial routine at the time of starting the engine, it is not initially set, so the routine proceeds to the next step 102.

In step 102, it is checked whether a leak determination flag, which will be described later, is set. Since this leak determination flag is also cleared by the initial routine,
Initially it is not set, then the next step 103
Go to. In step 103, the canister atmospheric hole VSV3
6 is shut off (valve closed), and in the following step 104, the purge side VSV 38 is opened (valve open).

The canister atmosphere hole VSV36 is closed at time t ₁ as shown in FIG. 5 (B), and the purge side VSV 38 is opened at substantially the same time t as shown in FIG. 5 (A). _If it is performed at ₁ , the negative pressure to the engine combustion chamber is the purge passage 39, the purge side VSV shown in FIG.
38, purge passage 37, canister 33, vapor passage 3
2 to the fuel tank 30. As a result, the internal pressure of the fuel tank 30 (tank internal pressure) rapidly increases in the negative direction after time t ₁ (the negative pressure decreases), as shown in FIG. 5C.

Subsequently, in step 105 of FIG. 4, it is judged whether the tank internal pressure is X Pa or less based on the detection signal of the pressure sensor 40. When it is X Pa or less, the negative pressure is being set, and this routine is finished. To do. Tank pressure is X
The above steps 101 to 105 are repeatedly executed every 65 ms until the pressure becomes larger than Pa on the negative pressure side. And
When it is determined in step 105 that the tank internal pressure has become larger than X Pa on the negative pressure side, the purge side VSV 38 is set as shown in FIG.
After interruption at time t ₂ as shown in (A) (step 10
6), the tank internal pressure is a pressure Y P on the atmospheric pressure side of X Pa.
It is determined whether or not it is a or more (step 107).

Since the two VSVs 36 and 38 are both closed at the time t ₂ , the pressure in the system from the purge side VSV 38 to the fuel tank 30 is maintained when the system has no failure and is extremely gentle. It decreases to the atmospheric pressure side. However, immediately after time t ₂ , the pressure in the system acts so as to be equalized, and the pressure detected by the pressure sensor 40 changes to a relatively large pressure. Steps 103-10 above
6 is a process for realizing the valve control means 18, and step 107 is a process for realizing the detection means 19.

Y Pa in step 107 above
Is preset to the leak determination start negative pressure at which the pressure in the system after the time t ₂ can be considered to be stable. Step 10
When it is determined in 7 that the pressure detected by the pressure sensor 40 (tank internal pressure) has not yet dropped to Y Pa,
This routine is completed, and again after 65 ms, step 10
The processes 1 to 107 are performed.

After that, the processing of the judging means 20 is realized by steps 108 to 115. That is, FIG.
If the tank pressure at time t ₃ is determined to be less than Y Pa as shown in (C) (step 107), leakage determination timer is determined whether "0" (step 108). Since the leak determination timer has been cleared to "0" by the above-mentioned initial routine, the first step 1
When the determination of 08 is made, it is determined as "0" and the routine proceeds to step 109, where the current detection value of the pressure sensor 40 is stored in the RAM 52 as the diagnosis start pressure value P _S.

Subsequently, a predetermined value is added to the value of the leak determination timer (step 110), the leak determination flag is set to "1" (step 111), and this routine is ended.
Then, when this routine is started again next time, since it is determined in step 102 that the leakage determination is in progress, step 10
Jump from 3 to 105, and further steps 106 and 107
To reach step 108.

This time, it is determined in step 108 that the leak determination timer is not "0", so it is determined whether the value of the leak determination timer is equal to the diagnostic time (leak determination time) α (step 112), when the time α has not yet come, this routine is ended via steps 110 and 111.

In this way, steps 101 and 10
When the values of the leak determination timer reach a value corresponding to the leak determination time α, the process of 2, 106 to 108, 112, 110, 111 is repeated every 65 ms, and the detected value of the pressure sensor 40 at that time is set to the diagnostic end pressure. The value P _E is stored in the RAM 52 (step 113). Then, based on the pressure values P _S and P _E read from the RAM 52, (P _E −
The rate of change in pressure is calculated from the equation P _S ) / α (seconds) (step 114).

Then, it is judged whether or not the calculated change rate is equal to or larger than a predetermined threshold value β (step 115). When it is equal to or larger than β, it is judged that the leakage is large and abnormal because the change in pressure is large. Then, the warning lamp 41 is turned on (step 116), the driver is notified of the failure occurrence of the evaporative purge system, the leak failure fail code is stored in, for example, the backup RAM 53 (step 117), and the routine proceeds to step 118. The leakage failure fail code is read out from the backup RAM 53 at the time of subsequent repair and informs the cause of failure of the evaporative purge system.

On the other hand, when it is determined that the calculated change rate is less than β, it is determined that the leakage is normal because the leakage is less than the specified value, and steps 116 and 117 are jumped to step 118. In step 118, the canister atmosphere hole VSV36 is opened (opened). Then, the leak determination timer is cleared (step 119), the execution flag is set to "1" (step 120), the leak determination flag is further cleared to "0" (step 121), and the failure diagnosis process is ended. To do. After that, even if this routine is started, step 10
Since the execution flag is determined to be "1" at 1, this routine is not executed until it is restarted thereafter.

In step 118, the canister atmosphere hole VSV
When time 36 is opened it is assumed to be t _4, 5
As shown in (C), the tank internal pressure reaches atmospheric pressure in a short time due to the atmosphere introduced from the atmosphere inlet 36a.

As described above, according to this embodiment, two V
After both the SVs 36 and 38 are closed, the time α leak is determined after the tank internal pressure reaches the negative pressure Y Pa that is close to a stable state, and the presence or absence of a failure is determined based on the pressure change rate in the stable pressure state. You can make an accurate decision.

The pressure sensor 40 is directly connected to the fuel tank 3
Although the tank internal pressure may be measured by mounting the pressure sensor in the vapor passage 32 as shown in FIG. 2, the pressure in the vapor passage 32 detected by the pressure sensor 40 varies depending on the magnitude of the passage resistance. Figure 6 in the process of applying pressure
As shown by the broken line in (C), the negative pressure is larger than the tank internal pressure shown by the solid line.

Therefore, the purge side VSV shown in FIG.
When the pressure in the vapor passage 32 reaches Z Pa, which is a negative pressure larger than X Pa, when 38 is in the valve open state and the canister atmosphere hole VSV 36 shown in FIG. By switching the VSV 38 to the valve closed state as shown in FIG. 6 (A), the pressure in the vapor passage 32 instantly becomes a negative pressure of about the same level as the tank internal pressure, and the diagnosis can be performed by the routine of FIG.

FIG. 7 is a flow chart for explaining the operation of the second embodiment of the essential part of the present invention. In the figure, the same steps as those in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted. Figure 7
In the flowchart of the failure diagnosis processing routine of the evaporation purge system of (time t ₁₁ in to FIG. 8 (A)) canister large pores VSV36 is closed in step 103, also purged side VSV38 is opened in step 104 (FIG. 8 (B) at time t ₁₂ ) and then at time t ₁₂ when the tank internal pressure becomes higher than X Pa on the negative pressure side (step 105),
The purge side VSV 38 is closed as shown in FIG. 8B (step 106).

The process up to this point is the same as that of the first embodiment shown in FIG. 4, but in this embodiment, after the delay timer is added next (step 201), it is determined whether the value of the delay timer is A seconds or less. The determination is made (step 202). The value of this A second is 2
Time t when both VSVs 36 and 38 are closed
It is set in advance from ₁₂ to the constant time required for the tank internal pressure to reach a pressure close to a stable state.

When the value of the delay timer is equal to or less than A seconds, this routine is ended, and then this routine is waited for starting. In this way, every time this routine is started, for example, every 65 ms, the above steps 101 to 10 are performed.
6, 201 and 202 are performed, and when the value of the delay timer becomes longer than A seconds (time t _{13 in} FIG. 8), the failure diagnosis start process from step 202 to steps 108 to 111 is performed.

Then, at time t _{14 when} α seconds have elapsed, the tank internal pressure P _S shown in FIG. 8C at the failure diagnosis start time t ₁₃ is shown.
And the tank internal pressure P _{E at the} failure diagnosis end time t ₁₄ , the change rate (= (P _E −P _S ) / α) is calculated (steps 112 to 114), and the change rate is larger than the predetermined threshold β. It is determined whether or not (step 115), and whether or not the leakage is large.

When the rate of change in tank internal pressure is small as shown in FIG. 8C, the evaporative purge system is judged to be normal,
When the rate of change in tank pressure is β or more, it is determined to be abnormal, and a warning lamp is lit and a leak failure fail code is stored. After that, the canister atmosphere hole VSV36 is opened (step 118), the delay timer and the leak determination timer are cleared (step 203), the execution flag is set (step 120), and the leak determination flag is cleared (step 1).
21) etc. are performed and the failure diagnosis routine is ended.

In this embodiment, it is estimated that the pressure in the system from the purge passage 37 to the fuel tank 30 has reached a pressure close to a stable state after a lapse of a predetermined time A seconds, and after the lapse of the A seconds, the tank Since the internal pressure is measured and the rate of change in the tank internal pressure for the failure diagnosis of the evaporative purge system is calculated, the accurate diagnosis can be performed as in the first embodiment.

Next, the operation of the third embodiment of the essential part of the present invention will be described with reference to the flowchart of FIG. In the figure,
The same processing steps as those in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted. In the flowchart of the failure diagnosis processing routine of the evaporation purge system of FIG.
If it is determined that the leak determination flag is not set to "1", it is determined whether the negative pressure stability flag is "1" (step 301).

Since the initial value of this negative pressure stability flag is "0", when this routine is first activated, the routine proceeds from step 301 to steps 103 and 104, where the canister atmosphere hole VSV36 is closed and purged. The valve opening of the VSV 38 is performed at time t ₂₁ as shown in FIGS. 10 (A) and 10 (B), respectively. As a result, the negative pressure of the intake manifold 27 is introduced into the canister 33 and the fuel tank 30, and the tank internal pressure rapidly increases in the negative pressure direction as shown in FIG. 10 (C).

When the pressure sensor 40 detects that the tank internal pressure has increased in the negative pressure direction up to the initial set negative pressure X Pa (step 105), the negative pressure stability flag is "1".
(Step 302) ,. After that, when this routine is started again, it is determined in step 301 that the negative pressure stability flag is set to "1".
Proceeding from step 301 to step 303, VSV38 on the purge side
Is closed (shut off) at time t ₂₂ as shown in FIG. 10 (B).

Subsequently, the value of the delay timer is added (step 304), and it is determined whether the value after the addition is B seconds or less (step 305). When it is B seconds or less, this routine is terminated and B seconds is passed. When the time has elapsed, it is determined from the pressure detected by the pressure sensor 40 whether the tank internal pressure is W Pa or less (step 306).

Immediately after time t ₂₂ when both the VSVs 36 and 38 are closed, the pressure is not stabilized due to the passage resistance in the system, so the tank internal pressure is initially set at the stage when the set time B seconds has elapsed. The pressure is greatly reduced to the atmospheric pressure side from the negative pressure X Pa and is lower than the threshold value WPa. On the other hand, when the tank internal pressure is higher than W Pa in the negative pressure direction even after B seconds have elapsed, it can be considered that the pressure in the system is substantially stable.

Therefore, in this embodiment, two VSVs 36 and
And t when both valve 38 and valve 38 are closed. _{twenty two}To negative pressure for B seconds
Stop applying fuel to the fuel tank 30
Is monitored and the tank internal pressure is greatly reduced to below W Pa
When it decreases in the pressure direction, the pressure in the system is still stable.
If not, reset the negative pressure stability flag value to "0"
After that (step 307), the purge-side VSV 38 is turned on again.
Open the valve (step 104) and apply negative pressure to the fuel tank 30.
Over time, monitor whether the tank internal pressure becomes higher than XPa
(Step 105), the tank internal pressure becomes higher than XPa.
The negative pressure stability flag is set to "1" again when
(Step 302).

Thereafter, the purge side VSV 38 is closed (step 303), and it is judged whether or not B seconds have elapsed from the valve closing time (steps 304 and 305). At the time when B seconds have elapsed, the tank internal pressure at that time is W. It is determined whether Pa or less (step 306).

Thus, in this embodiment, the initial set negative pressure X
When the tank internal pressure reaches Pa, the negative pressure is stopped from being applied to the fuel tank for a certain time B seconds, and it is checked if the tank internal pressure is lower than the determination start negative pressure W Pa during that time, Repeats applying negative pressure again, and when the tank internal pressure does not fall below the judgment start negative pressure W Pa within the negative pressure introduction stop period B seconds into the fuel tank 30, the pressure in the system is close to a stable state. If it is determined that the failure has occurred, the failure diagnosis is started (steps 306, 108 to 111).

The failure diagnosis method is the same as in the first and second embodiments, and as shown in FIG. 10C, the tank internal pressure at time t ₂₃ when the tank internal pressure does not drop below the judgment start negative pressure W Pa. It is determined whether the rate of change between P _S and the tank internal pressure P _E at time t ₂₄ , which is α seconds after time t _{23, is} larger than a predetermined threshold value β (steps 112 to 115).

Canister atmosphere hole V after normal or abnormal judgment
The SV36 is opened (step 118), the delay timer and the leak determination timer are cleared (step 308), the execution flag is set (step 309), and the leak determination in-progress flag and the negative pressure stability flag are cleared (step 310). ),
This routine ends.

As described above, this embodiment also has two VSVs 36.
After closing both valves 38 and 38, the tank internal pressure is measured after it is determined that the pressure in the system has reached a substantially stable state, and the failure diagnosis of the evaporative purge system is performed based on the measurement result. An accurate diagnosis can be made as in the first and second embodiments.

The present invention is not limited to the above embodiment, and for example, the evaporated fuel may be purged near the throttle valve 25.

[0054]

As described above, according to the present invention, after the first control valve for connecting or disconnecting the purge passage and the second control valve for opening / closing the atmospheric hole of the canister are both closed, Since the diagnosis is started by measuring the tank internal pressure after detecting that the negative pressure in the system has entered a substantially stable state, the reliability of the diagnosis start set pressure is higher than that of the device previously proposed by the applicant. It has features such as high cost and accurate diagnosis.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a system configuration diagram of an embodiment of the present invention.

FIG. 3 is a configuration diagram of an example of hardware of the microcomputer in FIG.

FIG. 4 is a flowchart for explaining the operation of the first embodiment of the essential parts of the present invention.

5 is a time chart explaining the operation of each part of FIG. 4. FIG.

FIG. 6 is a time chart explaining the operation of each part of the modified example of FIG.

FIG. 7 is a time chart for explaining the operation of the second embodiment of the main part of the present invention.

FIG. 8 is a time chart explaining the operation of each part of FIG.

FIG. 9 is a time chart for explaining the operation of the third embodiment of the essential part of the present invention.

FIG. 10 is a time chart illustrating the operation of each part of FIG.

[Explanation of symbols]

11, 30 Fuel tank 12, 32 Vapor passage 13, 33 Canister 14, 37, 39 Purge passage 15 Intake passage 16 First control valve 17 Second control valve 18 Valve control means 19 Detecting means 20 Judging means 21 Microcomputer 36 Canister atmosphere hole vacuum switching valve (VSV) 38 Vapor side vacuum switching valve (V
SV) 40 pressure sensor

Claims (1)

[Claims] 1. A failure of an evaporation purge system for adsorbing evaporated fuel from a fuel tank to an adsorbent in a canister through a vapor passage and purging the adsorbed fuel in the canister through a purge passage into an intake passage of an internal combustion engine during a predetermined operation. In the device for diagnosing, the first control valve that connects or disconnects the purge passage, the second control valve that opens and closes the atmospheric hole of the canister, and the second control valve that is closed and Valve control means for opening the first control valve, introducing the pressure in the intake passage into the system from the purge passage to the fuel tank, and then closing the first control valve after reaching a predetermined pressure value. A detection unit that substantially detects that the pressure in the system is substantially stable after both the first and second control valves receive a closing command by the valve control unit; And a determination unit that determines the presence or absence of a failure of the evaporative purge system by measuring the degree of change in the pressure in the system for a set time from the time when it is detected that the internal pressure is substantially stable. A failure diagnostic device for the evaporative purge system.