JPH06117332A - Failure diagnosis device for evaporative purge system - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to an apparatus for diagnosing a failure of an evaporation purge system that discharges (purges) evaporated fuel (vapor) of an internal combustion engine to an intake system and burns it, and erroneous detection due to a change in atmospheric pressure. The purpose is to prevent. [Structure] In step 101, an altitude (atmospheric pressure) is calculated by a HAC sensor and stored as HAC. Further, in step 103, the altitude change (atmospheric pressure change) ΔHAC is calculated from the difference between the previous and present HACs. Advanced HA in step 102
It is determined that C is less than the predetermined value a, and Δ is determined in step 105.
Only when it is determined that the absolute value of HAC is less than the predetermined value b,
The judgment value β is calculated (step 107). This determination value β is a value that is inversely proportional to HAC, and is used in the fault diagnosis by comparing the magnitude with the pressure value of the evaporation system when a negative pressure is introduced into the evaporation system for a predetermined time.

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 evaporation purge system that discharges (purge) to an intake system of an engine and burns it.

[0002]

2. Description of the Related Art In order to prevent vaporized fuel (vapor) from being released into the atmosphere in a fuel tank, each part is hermetically sealed and the vapor is once adsorbed by an adsorbent in a canister.
In an internal combustion engine equipped with an evaporative purge system that causes fuel adsorbed while the vehicle is running to be sucked into the intake system and burned, if the vapor passage is damaged or the pipes are disconnected for some reason, the vapor is released to the atmosphere. If it is discharged and the purge passage to the intake system is closed, the vapor in the canister overflows and the vapor leaks to the atmosphere from the canister atmosphere introduction port. Therefore, it is necessary to diagnose whether or not such a failure of the evaporative purge system has occurred.

Therefore, the present applicant has provided a bypass passage between a vapor introduction hole of a canister and a purge passage as a failure diagnosis device for an evaporation purge system, and an intake passage of an internal combustion engine via a throttle provided in the bypass passage. Negative pressure is introduced to the fuel tank, the negative pressure is detected by the pressure sensor provided in the path from the vapor introduction hole of the canister to the fuel tank, and if it does not reach the predetermined negative pressure within the predetermined time, it is judged as a failure. A device (Japanese Patent Application No. 3-323364) is proposed.

[0004]

According to the failure diagnosis apparatus proposed by the applicant of the present invention, since the negative pressure of the purge passage is introduced into the fuel tank with the atmosphere hole of the canister being opened, the ventilation of the canister is performed. The resistance and the resistance of the piping of the vapor passage and the purge passage determine the negative pressure of the purge passage, and the maximum negative pressure level applied to the fuel tank.

The negative pressure in the purge passage is determined by the negative pressure in the intake pipe of the internal combustion engine. However, it is known that the negative pressure of the intake pipe generally decreases as negative pressure when the altitude of the vehicle equipped with the internal combustion engine increases (atmospheric pressure decreases). Since the intake pipe is communicated with the purge passage via the purge control valve, when the intake pipe negative pressure becomes small, the negative pressure in the purge passage becomes small, whereby the maximum negative pressure level applied to the fuel tank also becomes small.

On the other hand, in the failure diagnosis device proposed by the present applicant, even if a negative pressure is introduced into the fuel tank when there is a leak in the evaporative system, air flows in from the leaked portion and the pressure is reduced by that amount. Since the detected negative pressure value of the sensor becomes small, the decrease in the detected negative pressure value may be due to the leak in the evaporative system, or there is no leak in the evaporative system, and when the above atmospheric pressure drops (the altitude becomes higher. It is not possible to distinguish whether it is due to a negative pressure drop (in some cases), and an erroneous judgment is made.

The present invention has been made in view of the above points,
An object of the present invention is to provide a failure diagnosis device for an evaporation purge system that solves the above-mentioned problems by determining whether or not to execute failure diagnosis according to atmospheric pressure, or by changing a judgment value or the like.

[0008]

FIG. 1 is a block diagram showing the principle of the present invention for achieving the above object. As shown in the figure, according to the present invention, the evaporated fuel from the fuel tank 10 is adsorbed to the adsorbent in the canister 12 through the vapor passage 11, and the adsorbed fuel in the canister 12 is passed through the purge passage 13 to the internal combustion engine 9 during a predetermined operation. In an apparatus for diagnosing a failure of an evaporation purge system for purging the intake passage 14, an atmospheric pressure detecting means 16 for detecting atmospheric pressure, a pressure introducing means 17, and a pressure in an evaporation system 15 from a purge passage 13 to a fuel tank 10. The pressure detection means 18 for detecting the pressure, the determination means 19 and the control means 20 are provided.

Here, the pressure introducing means 17 introduces a negative pressure in the intake passage 14 into the evaporation system 15 from the purge passage 13 to the fuel tank 10. Further, the pressure detecting means 18 detects the pressure in the evaporation system 15. Further, the judging means 19 measures the degree of change in the pressure inside the evaporation system 15 based on the pressure value detected by the pressure detecting means 18 when the negative pressure is introduced into the evaporation system 15 by the pressure introducing means 17, The presence or absence of a failure in the evaporative purge system is determined based on the result of comparison between the measured value and the determined value. Further, the control means 20 controls the determination means 19 according to the atmospheric pressure detected by the atmospheric pressure detection means 16.

[0010]

In the present invention, the control means 20 varies the judgment value of the judgment means 19 or corrects the detected pressure value according to the atmospheric pressure detected by the atmospheric pressure detection means 16. The influence of atmospheric pressure can be excluded from the pressure value.

Further, the control means 20 is an atmospheric pressure detecting means 16
When the atmospheric pressure detected by the device is below a predetermined value or when the change in the detected atmospheric pressure is above a predetermined value, the determination operation of the determination means 20 is prohibited, so that a negative pressure above a predetermined level is introduced into the evaporation system 15. If the negative pressure is stable, the evaporative system 1
The determination operation by the determination means 19 can be performed only when the determination operation is introduced in FIG.

[0012]

First, each embodiment of the system configuration of the present invention will be described. FIG. 2 shows a system configuration diagram of the first embodiment of the present invention. This embodiment is an example applied to an automobile engine as the internal combustion engine 9, and the operation of each part is controlled by the microcomputer 21. 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 then the intake pipe 24
The flow rate is controlled by the throttle valve 25 inside the surge tank 26, the intake manifold 27,
(The intake passage 14 is formed together with the intake pipe 24) and the intake valve 28 flow into the combustion chamber 29 of the engine (corresponding to the internal combustion engine 9) while the intake valve 28 is open.

The fuel tank 30 is the fuel tank 10 described above.
Corresponding to, and contains the fuel 42. Reference numeral 31 denotes a fuel tank internal pressure control valve, which is a mechanical control valve for connecting (opening) or shutting off between the vapor passages 32a and 32c and 32d, and when the tank internal pressure is a value in the positive pressure direction from the set pressure of the spring 31a, The diaphragm 31b is positioned as shown in the drawing to communicate between the vapor passages 32a, 32c and 32d, and when the tank internal pressure is a value in the negative pressure direction from the set pressure of the spring 31a, the diaphragm 31b moves downward to move the vapor passage 32a. And between 32c and 32d.
As a result, the tank internal pressure of the fuel tank 30 is maintained at the positive set pressure, and the vapor generation utilization is suppressed as low as possible. In addition, 31c is an atmospheric opening.

Further, one end of the vapor passage 32a is
Together with the vapor passage 32b, it communicates with the vapor introduction port 33a of the canister 33. This canister 33 (corresponding to the canister 12) is of a type in which a vapor introduction port 33a and a purge port 33b are communicated in the same space, and inside is filled with activated carbon 33c as an adsorbent, and partly An atmosphere introduction hole 33d is provided.

Further, in the present embodiment, at the time of failure diagnosis, the tank internal pressure control by the fuel tank internal pressure control valve 31 is prohibited and the negative pressure is introduced into the fuel tank 30. Vapor passage 32 between the exits
A tank internal pressure switching valve (VSV) 34 is provided to bypass (b) and 32c and to conduct (open) or shut off between the vapor passages 32b and 32c. The tank internal pressure switching valve 34 is an electromagnetic valve that is turned on or off by an output control signal from the microcomputer 21.
Further, the vapor passage 32c is provided with a throttle (orifice) 36.

Further, the purge port 33 of the canister 33
b is communicated with the purge-side VSV 38 via the purge passage 37. One end of the purge side VSV 38 is connected to the surge tank 26, for example, and the other end of the purge passage 39 and the other end of the purge passage 37 are connected to the microcomputer 2
It is a solenoid valve that conducts or shuts off based on a control signal from 1.

The pressure sensor 40 is provided in the middle of the vapor passage 32d, and is provided to detect the pressure in the vapor passage 32d to substantially detect the internal pressure of the fuel tank 30, and the pressure detecting means 18 is provided. Are configured.
The warning lamp 41 is provided to notify the driver of the abnormality when the microcomputer 21 detects the abnormality.

An intake air temperature sensor 43 for detecting the intake air temperature is attached near the air flow meter 23. The throttle position sensor 44 is attached to the throttle body and has a structure for detecting the movement of the throttle valve 25 by various contacts. When the throttle valve 25 is in the fully closed state (idle position), its IDL contact is turned on. In addition, bypassing the throttle valve 25, the downstream side of the air flow meter 23 and the surge tank 26
A bypass passage 45 that communicates with and is provided.

Further, the bypass path 45 has the bypass path 4
An idle speed control valve (ISCV) 46 for increasing or decreasing the amount of air flowing through 5 is provided. Further, a fuel injection valve 47 is provided for each cylinder so that a part thereof projects into the intake manifold 27. The fuel injection valve 47 injects the fuel 42 in the fuel tank 30 into the air flow passing through the intake manifold 27 for a time instructed by the microcomputer 21. Furthermore, H
The AC sensor 48 is an altitude compensation sensor mounted at a predetermined position of the vehicle and detects atmospheric pressure (absolute pressure) as an electric signal. The HAC sensor 48 constitutes the atmospheric pressure detecting means 16.

The microcomputer 21 controls the pressure introducing means 17, the judging means 19 and the control means 20 to the V
This is an electronic control device that is realized by software processing together with the SV 34, 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 includes a central processing unit (CPU) 50 and a read only memory (ROM) storing a processing program.
51, random access used as work area
A memory (RAM) 52, a backup RAM 53 that holds data even after the engine is stopped, an input interface circuit 54 with a multiplexer, an A / D converter 56, an input / output interface circuit 55, and the like,
They are connected via a bidirectional bus 57.

The input interface circuit 54 receives an intake air amount detection signal from the air flow meter 23, a detection signal from the throttle position sensor 44, a pressure detection signal from the pressure sensor 40, an output detection signal from the intake air temperature sensor 43, and H.
Atmospheric pressure detection signals from the AC sensor 48 are sequentially switched and combined in time series, and the combined signal is supplied to a single A / D converter 56 for analog / digital conversion, and then sequentially sent to the bus 57. Let

The input / output interface circuit 55 receives a detection signal from the throttle position sensor 44, inputs it to the CPU 50 via the bus 57, and at the same time processes each signal input from the bus 57 appropriately to inject fuel. Valve 47, tank internal pressure switching valve 34, purge side VSV
38, the warning lamp 41 and the ISCV 46 are selectively sent to control them.

Next, the evaporative purge operation of the system configuration will be described. The evaporative purge is performed by the microcomputer 21 according to a purge control routine. The purge control routine is executed, for example, as part of the main routine, and it is determined whether the engine has been warmed up, the air-fuel ratio feedback (F / B) is being executed, or whether the engine is idling based on the output of the throttle position sensor 44. ,
If even one of these conditions is not met, the purge side V
When the SV 38 is shut off and all of these conditions are satisfied, the purge side VSV 38 is opened. The tank internal pressure switching valve 34 is always closed. This allows
Purge is not executed unless the operating condition satisfies all of the above three conditions, and the purge is executable when the operating condition satisfies all three conditions. Note that purging is not executed during failure diagnosis.

That is, the tank internal pressure in the fuel tank 30 increases in accordance with the purge generation amount, but when the internal pressure of the fuel tank 30 is equal to or lower than the positive pressure set by the fuel tank internal pressure control valve 31, the fuel tank internal pressure control valve 31 is shut off. Therefore, the vapor is not supplied to the canister 33. When the amount of vapor generated in the fuel tank 30 becomes large and the tank internal pressure becomes higher than the pressure set by the fuel tank internal pressure control valve 31, the fuel tank internal pressure control valve 31 is opened, so that the vapor in the fuel tank can be transferred to the vapor passage 32d. , Sent to the canister 33 through the fuel tank internal pressure control valve 31 and the vapor passage 32a,
It is adsorbed by the activated carbon 33c and prevented from being released into the atmosphere.

By sending the vapor to the canister 33,
When the tank internal pressure in the fuel tank 30 becomes equal to or lower than the set pressure of the fuel tank internal pressure control valve 31, the fuel tank internal pressure control valve 31
Is cut off again. By repeating the above operation, the pressure in the fuel tank 30 is maintained at the set pressure of the fuel tank internal pressure control valve 31.

On the other hand, in the vapor adsorbed on the activated carbon 33c in the canister 33, the negative pressure of the intake system in the predetermined operating state is introduced into the canister 33 through the purge passage 39, the purge side VSV 38 and the purge passage 37, whereby Atmosphere is introduced into the canister 33 through the air introduction hole 33d.
Sent in.

Then, the fuel adsorbed on the activated carbon 33c is desorbed, and the fuel is sucked into the surge tank 26 from the purge port 33b through the purge passage 37, the purge side VSV 38 and the purge passage 39. In addition, the activated carbon 33c is regenerated by the above desorption and prepared for the next adsorption of vapor.

At the time of failure diagnosis, the tank internal pressure switching valve 34
Is opened (valve open) and the VSV 38 on the purge side is opened (valve open), and the intake pipe negative pressure generated by the ventilation resistance of the canister 33 is bypassed to the fuel tank internal pressure control valve 31 to the fuel tank 30. Call.

FIG. 4 shows a system configuration diagram of the second embodiment of the present invention. 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 the second embodiment shown in FIG. 4, by connecting the vapor passage 32c to the purge passage 37 via the tank internal pressure switching valve 34 and the bypass passage 49,
The feature is that the canister 33 is bypassed.

In this embodiment, since the tank internal pressure switching valve 34 is shut off (closed) during normal purging, the vapor passage 3
2c and the purge passage 37 do not communicate with each other and are independent of each other, and the same evaporation system as in the first embodiment is configured, and the tank internal pressure of the fuel tank 30 is controlled to the set pressure of the fuel tank internal pressure control valve 31. At the same time, the vapor generated in the fuel tank 30 is adsorbed by the activated carbon 33c in the canister 33.

At the time of failure diagnosis, the tank internal pressure switching valve 34 is opened, so that the vapor passage 32c is connected to the purge passage 37 via the bypass passage 49. As a result, the negative pressure of the surge tank 26 is maintained by the purge passage 39, the purge VSV 38, the purge passage 37, when the purge VSV 38 is opened.
Bypass passage 49, tank internal pressure switching valve 34, throttle 36,
It is introduced into the fuel tank 30 through the vapor passages 32c and 32d.

At this time, since the diameter of the throttle 36 is set to be quite small, the large air flow resistance of the throttle 36 makes the upstream side (fuel tank 30 side) of the throttle 36 a substantially static system, and the throttle 36 Upstream vapor passages 32c, 32
When there is no leak in d, the negative pressure is introduced to the upstream side of the throttle 36, whereas when there is a leak, the negative pressure can be prevented from being applied at all, thereby improving the detection accuracy of the pressure sensor 40. You can

Next, a first embodiment of the fault diagnosis routine of the present invention will be described. The first embodiment of the failure diagnosis routine comprises the high altitude detection routine of FIG. 5 and the leak detection routine of FIG. When the highland detection routine of FIG. 5 is activated, for example, in a cycle of 1 second, the altitude is first calculated from the output value of the HAC sensor 48 and stored in the RAM 52 as a variable HAC (step 101). For example, a pressure of 1 atm is enclosed in the HAC sensor 48, and by taking the pressure difference between the pressure of 1 atm and the atmospheric pressure, the change of the atmospheric pressure with respect to 1 atm can be seen, and the altitude is estimated from the change of the atmospheric pressure. be able to.

Then, it is determined whether HAC is higher than a predetermined altitude a (step 102). If it is high, the intake pipe negative pressure is equal to or lower than the predetermined value, and it is determined that the maximum negative pressure level applied to the fuel tank 30 is too small to perform reliable fault diagnosis, and the highland execution prohibition flag is set to "1". (Step
108) and terminates this routine. HAC is a predetermined altitude a
When it is less than the above, it is judged that the intake pipe negative pressure is sufficiently obtained, and the routine proceeds to the next step 103, from the previous output value HAC _OLD of the HAC sensor 48 to the output value HAC of the HAC sensor 48 of this time.
Is subtracted to calculate the change in altitude (change in atmospheric pressure) ΔHAC.

Next, in order to enable the next processing, the current output value HAC of the HAC sensor 48 is substituted into HAC _OLD and stored in the RAM 52 (step 104). continue,
Change in altitude (change in atmospheric pressure) It is judged whether the absolute value of ΔHAC is a predetermined change amount b or more (step 105). If it is b or more, the negative pressure is introduced because the change in intake pipe negative pressure is the predetermined value or more. It is determined that the reliable failure diagnosis cannot be performed by the above, and the highland execution prohibition flag is set to "1" (step 108).
), And ends this routine.

On the other hand, when | ΔHAC | <b, the change in the intake pipe negative pressure is less than a predetermined value and is substantially stable. Therefore, it is determined that a reliable fault diagnosis is possible, and the highland execution prohibition flag is cleared. (Step 106), the table as shown in FIG. 7 stored in advance in the ROM 51 is calculated, and the altitude (atmospheric pressure) H is calculated.
The determination value β is calculated with reference to AC (step 107), and this routine is ended.

Here, the table shown in FIG. 7 is the advanced HAC.
The negative value of the intake pipe becomes smaller as the pressure rises (as the atmospheric pressure lowers), and the maximum value of the negative pressure applied to the fuel tank 30 lowers. Therefore, as the HAC becomes larger, the determination value β becomes smaller. Shows. Further, as described in step 102, when the HAC is a or more, the determination value β is not calculated and the determination is prohibited.

Next, the leak detection routine of FIG. 6 will be described. When this leak detection routine is activated, for example, in a cycle of 65 ms, it is first determined whether or not the execution flag is set to "1" (step 201). This execution flag is set to "1" in step 218, which will be described later, only when this leak detection routine is executed. Since the initial value is set to "0" by the initial routine, the execution flag is initially set. If not, the process proceeds to step 202.

In step 202, it is judged whether or not the highland execution prohibition flag is set to "1". The highland execution prohibition flag is a flag which is set only in step 108 of FIG. 5 and is cleared in step 106. If it is set, the leak detection is not performed and this routine is terminated. 203 Perform the following leak detection.

At step 203, the negative pressure introduction flag is "1".
It is determined whether or not is set. Since this negative pressure introduction flag is cleared by the initial routine, it is determined that it is cleared when this step 203 is first executed, and the routine proceeds to step 204, where the purge flow rate is calculated. This purge flow rate is calculated from the duty ratio of the drive signal of the purge side VSV 38 and the intake pipe negative pressure when the purge side VSV 38 is duty ratio controlled.

That is, when the intake pipe negative pressure is the same, the purge flow rate is larger as the duty ratio is larger (the opening degree of the purge side VSV 38 is larger), and when the duty ratio is the same, the intake pipe negative pressure is in the negative pressure direction. The larger the flow rate, the higher the purge flow rate. When the purge side VSV 38 is on / off controlled, the purge flow rate increases as the intake pipe negative pressure increases in the negative pressure direction.

Next, at step 205, it is judged whether or not the calculated purge flow rate is equal to or larger than the predetermined value Y. If it is less than the predetermined value Y, it is judged that reliable leak detection cannot be performed because a sufficient purge flow rate cannot be obtained. , Step 206: VSV3 on the purge side
8 and the tank internal pressure switching valve 34 are closed (shut off), and this routine ends. On the other hand, when it is determined in step 205 that the purge flow rate is equal to or greater than the predetermined value Y, the purge side VSV 38 and the tank internal pressure switching valve 34 are opened to introduce the intake pipe negative pressure into the evaporation system (step 207), and then the negative pressure is introduced. After setting the flag to "1" (step 208), the leak determination timer is added (step 209).

The above steps 201 to 203, 209 and 210 are repeated until the value of the leak determination timer after the addition shows the value X seconds after the start of the introduction of the first negative pressure in step 207. The introduction is continuously performed, and when it is determined in step 210 that X seconds have elapsed, the process proceeds to step 211, and the substantial tank internal pressure is read from the output value of the pressure sensor 40.

Then, it is judged whether or not the tank internal pressure is a value on the negative pressure side of the judgment value β (step 212). When it is on the negative pressure side, it is judged that there is no leakage in the evaporation system and the warning lamp 41 Is turned off (step 213), and the leak failure fail code is cleared (step 214). On the other hand, when it is determined in step 212 that the tank internal pressure is on the positive pressure side of the determination value β, it is determined that there is a leak in the evaporation system, and the warning lamp 41 is turned on (step
215) Then, the driver stores the leak failure fail code in, for example, the backup RAM 53 after notifying the failure occurrence of the evaporative purge system (step 216). This leak failure fail code is read from the backup RAM 53 at the time of subsequent repair and informs that the evaporative purge system has a failure.

When the presence or absence of a failure in the evaporative purge system is determined as described above, the leak determination timer and the negative pressure introduction flag are each cleared in step 217, and the execution flag is set to "1" in the next step 218. Is set to end this routine. After that, even if this leak detection routine is started, the execution flag is judged to be "1" in step 201, so this leak detection routine is not executed until it is restarted thereafter. According to this embodiment, the judgment value β
Is varied according to the altitude (that is, the atmospheric pressure) as shown in FIG. 7, and therefore the influence of the atmospheric pressure is removed from the relationship between the tank internal pressure and the determination value β after the elapse of a predetermined time X seconds after the introduction of the negative pressure. Accurate failure judgment is possible. Further, since the failure diagnosis is performed when the purge flow rate is the predetermined value Y or more, the altitude is the predetermined altitude a or more, and the altitude change is less than the predetermined value b, the failure is accurate based on the stable and sufficient purge flow rate. Can diagnose.

Next, a second embodiment of the fault diagnosis routine of the present invention will be described. This embodiment comprises the highland detection routine of FIG. 8 and the leak detection routine of FIG. First, the highland detection routine of FIG. 8 will be described. In FIG. 8, the same processing steps as those in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 8, when the highland execution prohibition flag is cleared in step 106, the altitude HAC calculated in step 101 is stored in the ROM 51 in advance.
The tank internal pressure altitude correction value γ is calculated by referring to the table of 0 and stored in the RAM 52 (step 150). This Figure 1
The table shown by 0 shows the characteristic that the tank internal pressure altitude correction value γ becomes larger as the altitude HAC becomes higher (the atmospheric pressure becomes lower).

Next, the leak detection routine of FIG. 9 will be described. In the figure, the same processing steps as those in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted. In FIG. 9, step 21
When it is determined that 0 seconds have passed since the introduction of the negative pressure at 0, the step
The routine proceeds to 250, where the tank internal pressure is read, and then the correction value γ is added to the tank internal pressure.

Subsequently, the routine proceeds to step 251, where the tank internal pressure after addition and the fixed judgment value β'are compared in magnitude, and when the tank internal pressure is on the negative pressure side of the fixed judgment value β ', it is normal, and on the positive pressure side. Is determined to be abnormal. In the present embodiment, the determination value β ′ is fixed, but the correction value γ is added to the detection tank internal pressure, so that the influence of atmospheric pressure is removed during the comparison determination with β ′.

[0050]

As described above, according to the present invention, when the failure diagnosis is performed based on the magnitude comparison result of the pressure value and the judgment value when the intake pipe negative pressure is introduced into the evaporative system for a predetermined time, the judgment value Since the influence of atmospheric pressure can be eliminated when comparing with the pressure value, accurate and highly reliable fault diagnosis not affected by atmospheric pressure can be performed. Further, since the failure diagnosis is performed when a negative pressure equal to or higher than a predetermined level or a stable negative pressure is introduced into the evaporation system, it is possible to prevent an erroneous diagnosis.

[Brief description of drawings]

FIG. 1 is a principle configuration 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 the microcomputer in FIG.

FIG. 4 is a system configuration diagram of a second embodiment of the present invention.

FIG. 5 is a flowchart of a first embodiment of a highland detection routine.

FIG. 6 is a flowchart of a first embodiment of a leak detection routine.

FIG. 7 is a diagram showing a determination value calculation table in the highland detection routine of FIG.

FIG. 8 is a flowchart of a second embodiment of a highland detection routine.

FIG. 9 is a flowchart of a second embodiment of a leak detection routine.

10 is a diagram showing a correction value calculation table in the highland detection routine of FIG.

[Explanation of symbols]

 9 Internal Combustion Engine 10 Fuel Tank 11, 32a to 32d Vapor Passage 12, 33 Canister 13, 37, 39 Purge Passage 14 Intake Passage 15 Evaporative System 16 Atmospheric Pressure Detecting Means 17 Pressure Introducing Means 18 Pressure Detecting Means 19 Judging Means 20 Control Means 21 Microcomputer 31 Fuel tank internal pressure control valve 34 Tank internal pressure switching valve 36 Throttle (orifice) 40 Pressure sensor 41 Warning lamp 48 HAC sensor 49 Bypass passage

Claims (5)

[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 atmospheric pressure detecting means for detecting atmospheric pressure, and the evaporation system from the purge passage to the fuel tank,
Based on the pressure value detected by the pressure introducing unit for introducing the negative pressure of the intake passage, the pressure detecting unit for detecting the pressure in the evaporation system, and the pressure value detected by the pressure detecting unit, the change in the pressure in the evaporation system is detected. Determining means for measuring the degree and determining the presence or absence of a failure of the evaporative purge system from the result of comparison between the measured value and the determining value, and controlling the determining means according to the atmospheric pressure detected by the atmospheric pressure detecting means. A failure diagnosis device for an evaporative purge system, comprising: a control unit. 2. The failure diagnosing device for an evaporative purge system according to claim 1, wherein the control means is means for varying the judgment value according to the detected atmospheric pressure. 3. The failure diagnosing device for an evaporative purge system according to claim 1, wherein the control means is means for correcting the pressure value detected by the pressure detecting means in accordance with the detected atmospheric pressure. 4. The failure diagnosis device for an evaporative purge system according to claim 1, wherein the control means is means for prohibiting the determination by the determination means when the detected atmospheric pressure is equal to or lower than a predetermined value. . 5. The failure diagnosis device for an evaporative purge system, wherein the control means is means for prohibiting the determination by the determination means when the change in the detected atmospheric pressure is equal to or more than a predetermined value.