JP2830628B2 - Failure diagnosis device for evaporation purge system - Google Patents

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 system, and more particularly to a method for adsorbing fuel vapor (vapor) of an internal combustion engine into an adsorbent in a canister and subjecting the adsorbed fuel to internal combustion under predetermined operating conditions. The present invention relates to a device for diagnosing a failure of an evaporative purge system that discharges (purges) an intake system of an engine and burns the engine.

[0002]

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

Therefore, the present applicant has previously filed Japanese Patent Application No. 3-138.
No. 002, a first control valve for opening and closing a purge passage for purging evaporative fuel stored in a canister to an intake system of an internal combustion engine, and a second control valve for opening and closing an atmospheric hole of the canister, At the time of failure diagnosis, after closing the second control valve,
The first control valve is closed after waiting for a predetermined negative pressure, and the hermetic seal is maintained for a predetermined time, and the occurrence of a failure is diagnosed based on the degree of change in the pressure detected by the relative pressure sensor at that time. A failure diagnosis device for the evaporative purge system was proposed.

[0004]

In order to introduce a negative pressure into the fuel tank at the time of the above-described failure diagnosis, high-concentration vapor in the fuel tank is purged into the intake passage at the time of introducing the negative pressure.
The air-fuel ratio fluctuates. Therefore, the above-described failure diagnosis is performed in an operation state in which the amount of intake air is large, that is, in a state in which the vehicle speed is somewhat high so that the fluctuation of the air-fuel ratio due to the purge becomes small.

[0005] By the way, on a slope with a 5% gradient, 90 km / h
/ H, there is an altitude difference of 75 m per minute.
Here, there is an atmospheric pressure change of 1333 Pa at an altitude difference of 100 m.
A pressure change of Pa occurs.

On the other hand, a pressure change of about 638 Pa per minute occurs in a hole having a diameter of 0.4 mm generated in a vapor supply passage for detecting a failure. If the atmospheric pressure changes in the process of evaporative leak determination in a closed system using a relative pressure sensor that detects the differential pressure from the atmospheric pressure, the pressure in the closed system is not affected by the atmospheric pressure change However, there is a difference in the influence of the change in the atmospheric pressure between the atmosphere side and the inside of the closed system, so that the above-described leak determination cannot be performed accurately, and an accurate failure diagnosis cannot be performed. The present invention has been made in view of the above points, by correcting the detected pressure or determination value in the evaporation system according to the atmospheric pressure,
An object of the present invention is to provide a failure diagnosis device for an evaporative purge system that prevents erroneous diagnosis due to a change in atmospheric pressure and improves reliability.

[0007]

According to the failure diagnosis apparatus for an evaporative purge system of the present invention, as shown in FIG. 1, the evaporated fuel from a fuel tank 11 is adsorbed on an adsorbent in a canister 13 through a vapor passage 12. , The canister 1
The adsorbed fuel in the internal combustion engine 3 is passed through a purge passage 14
An evaporative purge system for purging the intake passage 15 of the
It has an evaporative system pressure detecting means 16 for detecting a pressure in a closed space of the evaporative system from the purge passage 14 to the fuel tank 11, and generates a negative pressure in the evaporative system.
Introduced, then a trouble diagnosis device for the evaporative emission control system as compared with the determination value of change in the detected pressure of the fuel vapor purge system within the pressure detecting means 16 in the determination unit 17 performs the leakage detection of the evaporative emission control system, large having an atmospheric pressure detecting means 18 for detecting the atmospheric pressure, depending on the atmospheric pressure detected by the atmospheric pressure detecting means 18, and a correction means 19 for correcting the detected pressure of the fuel vapor purge system pressure force detection means 16. Also correct
Means 19 is a discriminating means instead of the pressure detected by the pressure detecting means 16.
The determination value of step 17 is corrected.

[0008]

According to the present invention, the evaporative purge system adsorbs the fuel vapor from the fuel tank 11 to the adsorbent in the canister 13 through the vapor passage 12, and adsorbs the fuel in the canister 13 through the purge passage 14.
Purge into the intake passage 15 of zero.

[0009] evaporative system internal pressure detecting means 16, the par
The pressure in a closed space of the evaporation system from the passage 14 to the fuel tank 11 is detected.

The discriminating means 17 introduces a negative pressure into the evaporation system.
After that, a change in the detected pressure of the evaporative system pressure detecting means 16 is compared with a judgment value to detect a leak in the evaporative purge system.

The atmospheric pressure detecting means 18 detects the atmospheric pressure.

The correcting means 19 comprises the atmospheric pressure detecting means 18
By correcting the pressure detected by the evaporative system pressure detecting means 16 or the judgment value of the discriminating means 17 in accordance with the atmospheric pressure detected in the above step, a change in the atmospheric pressure when leak detection is performed.
Accurate leak detection without being affected by
Can be.

[0013]

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

The opening of the throttle valve 25 is controlled in conjunction with an accelerator pedal (not shown), and the opening is detected by a 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 specified by the microcomputer 21.

The fuel tank 30 includes the fuel tank 11 described above.
, Which contains the fuel 31 and sends out the evaporated fuel (vapor) generated inside to the canister 33 (corresponding to the above-described canister 13) through the vapor passage 32 (corresponding to the vapor passage 12). The canister 33 is filled with an adsorbent such as activated carbon, and has an air hole 34 in a part thereof.

The air hole 34 is connected to a canister air hole vacuum switching valve (VSV) 36 through an air passage 35. Canister air hole V
The SV 36 is a control valve for communicating or shutting off the connection between the air introduction hole 36a and the air passage 35 based on a control signal of the microcomputer 21.

The canister 33 is connected to a purge VSV 38 via a purge passage 37. The purge side VSV 38 is a control valve that communicates or shuts off the other end of the purge passage 39 having one end communicating with the surge tank 26 and the other end of the purge passage 37 based on a control signal from the microcomputer 21.

A pressure sensor 40 (corresponding to the above-mentioned evaporative system internal pressure means 16) is provided in the middle of the vapor passage 32,
The internal pressure of the fuel tank 30 is substantially detected by detecting the pressure (relative pressure) of the vapor passage 32.

An atmospheric pressure sensor 41 (corresponding to the above-mentioned atmospheric pressure detecting means) is provided for detecting the atmospheric pressure.
The warning lamp 42 is provided to notify the driver of the abnormality when the microcomputer 21 detects the abnormality.

In this configuration, the vapor generated in the fuel tank 30 is adsorbed by the activated carbon in the canister 33 via the vapor passage 32, and is prevented from being released to the atmosphere. Normally, the canister air vent VSV36 is open, and when the evaporative purge system is activated, the purge side VSV is opened.
V38 is also open. As a result, during operation, the negative pressure of the intake manifold 27 is used to release the air inlet 36a.
The air 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 supplied to the purge passage 37, the purge side VSV3.
8 and into the surge tank 26 through the purge passage 39 respectively. The activated carbon is regenerated by the above desorption, and prepares for the next vapor adsorption.

The microcomputer 21 has a known hardware configuration as shown in FIG. In FIG.
The same components as those described above are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 3, a microcomputer 21 includes a central processing unit (CPU) 50, a read-only memory (ROM) 51 storing a processing program, a random access memory (RAM) 52 used as a work area,
Backup RAM that retains data even after the engine stops
53, an input interface circuit 54, an A / D converter 56 with a multiplexer, an input / output interface circuit 55, and the like, which are connected via a bus 57.

The A / D converter 56 sequentially receives an intake air amount detection signal from the air flow meter 23, a detection signal from the throttle position sensor 28, a pressure detection signal from the pressure sensor 40, a pressure detection signal from the atmospheric pressure sensor 41, and the like through the input interface circuit 54. The data is switched and fetched, converted from analog to digital, and sequentially transmitted to the bus 57.

The input / output interface circuit 55 receives a detection signal from the throttle position sensor 28 and inputs the detection signal to the CPU 50 via the bus 57, and also converts the signals input from the bus 57 to the fuel injection valve 29 and the canister The air holes VSV 36, the purge side VSV 38, and the warning lamp 42 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 in accordance with the program stored in the ROM 51.

The diagnostic processing routine of FIG.
This is a part of a main routine executed every ec, and is started under the condition that the catalyst temperature is equal to or higher than a predetermined value and the intake air amount is equal to or higher than a predetermined value. First, it is checked whether the execution flag is set (the value is "1") (step 100). Since the execution flag has been cleared (the value is "0") by the initial routine at the time of starting the engine, the execution flag is not set at first, and the process proceeds to the next step 101.

In step 101, it is determined whether a leak determination flag described later is set. Since this leak determination flag is also cleared by the initial routine,
Initially, it is not set, and initially the next step 102
Proceed to. In step 102, the canister air hole VSV3
Then, the purge side VSV 38 is opened (opened) in step 103.

The valve closing of the canister atmosphere hole VSV 36 is performed at time t ₁ as shown in FIG. 5B, and the valve opening of the purge side VSV 38 is substantially the same time t as shown in FIG. ₁ , the negative pressure to the engine combustion chamber is reduced by the purge passage 39 and the purge side VSV shown in FIG.
38, purge passage 37, canister 33, vapor passage 3
2 to the fuel tank 30. Thus, the internal pressure of the fuel tank 30 (tank pressure), as shown in FIG. 5 (C), rapidly rises (negative pressure decreases) the time t ₁ after the negative direction.

Subsequently, in step 104 of FIG. 4, the tank internal pressure is increased to a predetermined value XP based on the detection signal of the pressure sensor 40.
It is determined whether or not the pressure is equal to or less than a. When the pressure is equal to or less than XPa, the negative pressure is being set, and thus this routine ends. The above steps 100 to 104 are repeatedly executed every 65 ms until the tank internal pressure becomes larger on the negative pressure side than XPa. When the tank pressure is determined in step 104 that a large negative pressure side than X Pa, to cut off the purge side VSV38 at time t ₂ as shown in FIG. 5 (A) (Step 1
05).

Next, it is determined whether or not the leak determination timer is "0".
Is performed (step 106). Initial luch mentioned above
This leak determination timer is cleared to “0” by the
Therefore, the determination in step 106 is performed first.
Is determined to be “0” and the process proceeds to step 200.
The current detection value of the pressure sensor 40 is used as the diagnosis start pressure value P.
_SIs stored in the RAM 52 as the
Diagnosis start of the detection value of the present atmospheric pressure sensor 41_SHWhen
And stores it in the RAM 52.

Subsequently, the value of the leak determination timer is incremented by a predetermined value (step 202), the leak determination flag is set to "1" (step 203), and the routine ends. Then, when this routine is started again, it is determined in step 101 that the leak is being determined, so that steps 102 to 104 are jumped, and the process proceeds to step 106 via step 105.

Since it is determined that the leak determination timer is not "0" at step 106, it is determined whether the value of the leak determination timer is equal to the diagnosis time (leak determination time) α (step 106). 107 ) If the time has not reached α, this routine is terminated via steps 202 and 203.

In this way, steps 100 and 10
Processing of 1,105-107,202,203 is 65ms
It repeats every time, and the value of the leak determination timer becomes the leak determination time α
Comes to the corresponding value for the process proceeds to step 108, and stored in the RAM52 a detection value of the pressure sensor 40 at that time as a diagnosis end pressure value P _E, the RAM52 the detected value of the atmospheric pressure sensor 41 as a diagnostic completion atmospheric pressure P _EH It is stored (step 109). Then, the pressure value P is read out from the RAM 52 and
_{From S} , P _E and atmospheric pressures P _SH , P _EH (P _E -P _S )-
From the equation (P _EH -P _SH ), the pressure change of the fuel tank 30 from which the influence of the atmospheric pressure change is removed is calculated (step 11).
0 ), the change in pressure is divided by α seconds to calculate the conversion rate (step 111 ).

Subsequently, it is determined whether or not the calculated rate of change is equal to or greater than a predetermined threshold value β (step 112). When the rate of change is equal to or greater than β, it is determined that the leak is large and abnormal due to a large change in pressure. Then, the warning lamp 42 is turned on (step 113), and after notifying the driver of the occurrence of a failure in the evaporative purge system, the leak failure code is stored in, for example, the backup RAM 53 (step 114), and the routine proceeds to step 115. The leak failure code is read out from the backup RAM 53 at the time of subsequent repair to notify the cause of the 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 leak is normal because the leak is equal to or less than the specified value, and the routine jumps to steps 115 and 114, and proceeds to step 115. In step 115, the canister atmosphere hole VSV36 is opened (valve opened). Subsequently, the leak determination timer is cleared (step 116), the execution flag is set to "1" (step 117), and the leak determination flag is set to "0".
(Step 118), and the failure diagnosis process ends. Thereafter, even if this routine is started, step 1
Since the execution flag is determined to be "1" at 01, this routine will not be executed until restarting thereafter.

At step 115 , the canister air hole VSV
Assuming that the time when the valve 36 is opened is t ₃ , FIG.
As shown in (C), the tank internal pressure reaches the atmospheric pressure in a short time due to the atmosphere introduced from the atmosphere inlet 36a.

If there is no change in the atmospheric pressure, the tank internal pressure changes as shown by the solid line in FIG. At time t ₂ ,
The increase in the tank internal pressure during t ₃ is due to the generation of vapor.

In the downhill running state as shown by the broken line in FIG. 5 (E), the atmospheric pressure as shown by the broken line in FIG. 5 (D) increases. The increase increases between t ₂ and t ₃ as shown by the broken line in FIG.

In the uphill running condition as shown by the one-dot chain line in FIG. 5E, the atmospheric pressure as shown by the one-dot chain line in FIG. The rise becomes smaller between the times t ₂ and t ₃ as shown by the dashed line in FIG. 5C. However, in the above embodiment, the pressure change is obtained by subtracting the change in the atmospheric pressure (P _EH -P _SH ) from the change in the tank internal pressure (P _E -P _S ) in step 110, and using this, the change rate is used in step 111. Therefore, the rate of change of the tank internal pressure shown by the solid line in FIG. 5C can be obtained regardless of whether the vehicle is going downhill or uphill, and thereby accurate leak determination can be performed, thereby improving the reliability of failure diagnosis.

FIG. 6 shows a system configuration diagram of a second embodiment of the present invention. 2, the same parts as those of FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. In FIG. 6, the vapor passage 3
A check valve 60 is provided between the second canister 33 and the pressure sensor 40. The check valve 60 communicates with the canister 33 through the vapor passage 61, and the VSV
36 is removed, and the air hole 34 is open to the atmosphere. The check valve 60 is opened only when the pressure on the fuel tank 30 side is higher than the pressure on the canister 33 by a predetermined value or more.

In the embodiment of FIG. 2, a failure between the fuel tank 30, the vapor passage 32, the canister 33, and the purge passage 37 is diagnosed, whereas in the embodiment of FIG.
This is a simple type that diagnoses a failure between the vapor passages 32.

The engine stopping fuel tank 30 at the time of the vapor passage 32, check valve 60, the vapor passage 61, since it is open to the atmosphere through the canister 33 large pores 34, the pressure within the tank is a P ₀ of about P ₀ atmospheric pressure .

When the engine is started, the fuel 3
Since 1 is pumped up by the pump, the volume of the upper space of the fuel tank 30 increases, and the pressure in the tank decreases to negative pressure. Thereafter, when the high-temperature fuel is returned, the fuel temperature in the fuel tank 30 increases, the generation of vapor increases, and the pressure in the tank increases to a positive pressure.

The microcomputer 21 has the configuration shown in FIG. 3, and executes the diagnostic processing shown in FIGS.

The atmospheric pressure reading routine shown in FIG. 7 is, for example, an interruption routine every one minute. First, in step 300, the current detection value of the atmospheric pressure sensor 41 is set as the atmospheric pressure P _AH and R
Store it in AM52.

Next, at step 302, it is determined whether or not the engine has been started. When the ignition switch is turned on, the routine proceeds to step 304, where the atmospheric pressure P _AH is transferred to the previous atmospheric pressure P _AHO and stored in the RAM 52. in step 306 subtracts the previous atmospheric pressure P _{AH O} from atmospheric pressure P _AH atmospheric pressure change Δ
P _AH is calculated and this routine ends.

If the engine has not been started, the routine proceeds from step 302 to step 308, where the atmospheric pressure P _{AH is changed} to the previous atmospheric pressure P _AH.
After calculating the atmospheric pressure change ΔP _AH by subtracting _AHO , at step 310, the atmospheric pressure P _AH is transferred to the previous atmospheric pressure P _AHO and R
This is stored in the AM 52 and this routine is terminated.

The diagnosis processing routine shown in FIG.
The normal flag is reset (the value is "0") by an initial routine at the time of engine start, which is a part of a main routine executed every time.

First, at step 320, it is determined whether or not a predetermined time has elapsed after the start. The predetermined time is, for example, about 10 minutes. If the predetermined time has not elapsed after the start, the process proceeds to step 322, where the atmospheric pressure change ΔP _AH is used to refer to the maps shown in FIGS. 9A and 9B to determine the pressure determination values a and b, respectively. Is calculated. The pressure determination value a is a value for determining normal when the tank internal pressure becomes higher than this, and the pressure determination value b is a value for determining normal when the tank internal pressure becomes lower than this.

The map of FIG. 9A shows that the larger the change in atmospheric pressure ΔP _AH, that is, the higher the rate of increase in atmospheric pressure, the lower the positive pressure pressure judgment value a becomes. The map indicates that as the change in atmospheric pressure ΔP _AH increases, the negative pressure determination value b decreases.

Next, at step 324, the pressure P in the tank, which is the value detected by the pressure sensor 40, is read.
At 328, the tank internal pressure P is compared with each of the pressure determination values a and b. If the tank pressure P is equal to or greater than the pressure determination value a in step 326, or if the tank pressure P is equal to or less than the pressure determination value b in step 328, the normal flag is set to a value "1" in step 330 and the routine is terminated. If b <P <a in steps 326 and 328, this routine ends.

On the other hand, when a predetermined time has elapsed after the start, the process proceeds from step 320 to step 332, where it is determined whether or not the normal flag is set to a value "1". If the normal flag has been set, the routine proceeds to step 334, in which the warning lamp 42 is turned off. If the normal flag has not been set, the routine proceeds to step 336, in which the warning lamp 42 is turned on.

When the atmospheric pressure change ΔPa is zero, the pressure judgment values a and b are a ₁ and b ₁ , respectively. Fuel tank 3
If 0 and there is no record mode the vapor passage 32, after the tank pressure P is the engine start (t _0), decreases as indicated by a solid line Ia in Fig. 10 rises after a pressure determination value b less than ₁ Pressure it exceeds the judgment value a _1. Therefore, the normal flag is set, and the warning lamp 42 remains off. Also, if a small motor les to the fuel tank 30, tank pressure P is warning lamp 42 is not set correctly flag remained between b ₁ from the pressure judgment value a ₁ as shown in broken line Ib lights, fuel if there is a large mode Les tank 30, the pressure P in the tank warning lamp 42 is not set normal flag hardly changes from the pressure P ₀ as shown in two-dot chain line Ic is turned on.

Next, when the atmospheric pressure change ΔPa is negative as shown in FIG. 11B, the pressure judgment values a and b are respectively a ₁ and b ₁
It further rises to a ₁ and b ₁ . Without les mode to the fuel tank 30 and the vapor passage 32, after the tank pressure P is the engine start (t _0), although the pressure judgment value b ₁ or more drops as shown by a solid line IIa shown in FIG. 11 (A) After it becomes less than b ₂ , it rises and exceeds the pressure judgment value a ₂ . Therefore, the normal flag is set, and the warning lamp 42 remains off. Also, if a small motor les to the fuel tank 30, tank pressure P is not set normal flag but exceeds the pressure judgment value a ₁ as shown in broken line IIb remained between b ₂ from the pressure judgment value a ₂ warning lamp 42 is lit, if there is a large mode-les in the fuel tank 30, the pressure P in the tank warning lamp 42 is not set normal flag hardly changes from the pressure P ₀ as shown in two-dot chain line IIc is turned .

When the change in atmospheric pressure ΔPa is positive as shown in FIG. 12B, the pressure judgment values a and b are a ₁ and b _{1, respectively.}
The values are further reduced to a ₃ and b ₃ . Without les mode to the fuel tank 30 and the vapor passage 32, it is the pressure P in the tank after the engine start (t _0), and decreased to less than the pressure determination value b ₃ as shown in solid lines III a shown in FIG. 12 (A) elevated exceeds the pressure determination value a ₃ by after. Therefore, the normal flag is set, and the warning lamp 42 remains off. Also, if a small motor les to the fuel tank 30, tank pressure P is normal flag becomes a pressure determination value a less than ₁ as shown in broken lines III b remained between b ₃ from the pressure determination value a ₃ is set The warning lamp 42 lights up and the fuel tank 30
If there is a large mode Le, the tank pressure P is a two-dot chain line III
As shown in FIG. 3C, the warning flag 42 is turned on without substantially changing from the pressure P ₀ and without setting the normal flag.

[0056] Thus atmospheric pressure change [Delta] P _AH pressure judgment value a according to, by varying the b, it is prevented that diagnosed erroneously as normal when there is a small motor-les in the fuel tank 30, an accurate diagnosis Can be performed.

It should be noted that in the flowchart of FIG. 7, step 310 may be deleted to obtain the atmospheric pressure change ΔP _{AH based} on the atmospheric pressure at the time of starting, and the pressure determination values a and b may be calculated.

Further, a method of calculating the differential pressure between the minimum value and the maximum value of the tank internal pressure within a predetermined time after the start and determining that the pressure is normal when the differential pressure exceeds the determination value, is also possible in the first embodiment. As described above, by correcting the minimum value and the maximum value of the tank internal pressure with the atmospheric pressure and calculating the differential pressure, erroneous diagnosis can be prevented.

[0059]

As described above, according to the failure diagnosing apparatus for an evaporative purge system of the present invention, erroneous diagnosis due to a change in atmospheric pressure can be prevented, reliability can be improved, and it is extremely useful in practical use.

[Brief description of the drawings]

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

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

FIG. 3 is a configuration diagram of an example of hardware of a microcomputer in FIG. 2;

FIG. 4 is a flowchart for explaining the operation of the diagnostic processing of the present invention.

FIG. 5 is a time chart for explaining the operation of the present invention.

FIG. 6 is a system configuration diagram of a second embodiment of the present invention.

FIG. 7 is a flowchart for explaining the operation of the diagnostic processing of the present invention.

FIG. 8 is a flowchart for explaining the operation of the diagnostic processing of the present invention.

FIG. 9 is a diagram showing a map of pressure determination values.

FIG. 10 is a time chart for explaining the operation of the present invention.

FIG. 11 is a time chart for explaining the operation of the present invention.

FIG. 12 is a time chart for explaining the operation of the present invention.

[Explanation of symbols]

11, 30 Fuel tank 12, 32, 61 Vapor passage 13, 33 Canister 14, 37, 39 Purge passage 15 Intake passage 16 Evaporation system internal pressure detection means 17 Judgment means 18 Atmospheric pressure detection means 19 Correction means 20 Judgment means 21 Microcomputer 36 Vacuum switching valve (VSV) for canister air hole 38 Vacuum-side vacuum switching valve (V
SV) 40 Pressure sensor 41 Atmospheric pressure sensor 42 Warning lamp 60 Check valve

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F02M 25/08 G01M 15/00

Claims (2)

(57) [Claims] 1. A fuel vapor from the fuel tank is adsorbed by the adsorbent in the canister through the vapor passage, at evaporation purge system for purging the adsorbed fuel in the canister through the purge passage to the intake passage of an internal combustion engine, said purge passage A pressure detecting means for detecting a pressure in a closed space out of the evaporative system from the fuel tank to the fuel tank , introducing a negative pressure into the evaporative system, and thereafter detecting the evaporative system internal pressure A failure diagnostic device for an evaporative purge system that detects leakage of the evaporative purge system from a change in detected pressure of the means, wherein the atmospheric pressure detecting means detects an atmospheric pressure, and the atmospheric pressure detecting means detects an atmospheric pressure detected by the atmospheric pressure detecting means. Te, failure diagnosis of the evaporative emission control system characterized by comprising a correction means for correcting the detected pressure of the evaporation system the pressure detecting means instrumentation Place. 2. A vapor passage for evaporating fuel from a fuel tank.
Through the canister to adsorb the adsorbent inside the canister.
Intake of the internal combustion engine through the purge passage through the adsorbed fuel in the star
An evaporative purge system that purges to the passage, from within the evaporative system from the purge passage to the fuel tank
Pressure inside the evaporative system that detects the pressure inside the enclosed space
Detecting means for introducing a negative pressure into the evaporative system;
The change in the pressure detected by the internal pressure detection means
Evaporator that detects leaks in the evaporation purge system
A failure diagnosis device for the system, wherein the atmospheric pressure detection means for detecting the atmospheric pressure, and the determination based on the atmospheric pressure detected by the atmospheric pressure detection means.
Correction means for correcting the constant value.
Failure diagnosis device for vapor purge system.