JP2745966B2 - 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, when the vapor passage is damaged or the pipe is disconnected for any reason, the vapor is released to the atmosphere, and when the purge passage to the intake system is blocked,
The vapor in the canister overflows, and the vapor leaks from the canister air inlet to the atmosphere. 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,
An evaporative purge system that waits for a predetermined negative pressure, closes the first control valve, closes for a predetermined time, holds the negative pressure, and diagnoses the occurrence of a failure based on the degree of change in the pressure at that time. Proposed a failure diagnosis device.

[0004]

However, in the above-described proposed device, when a failure is diagnosed, a negative pressure is introduced into the fuel tank by connecting the canister and the fuel tank to the intake pipe without requesting the engine. Unnecessary vapor is inhaled, and the air-fuel ratio becomes rich, and the exhaust emission deteriorates. In addition, the application of the negative pressure lowers the boiling point of the fuel in the fuel tank and generates vapor, which causes a change in pressure. The present invention has been made in view of the above points, and has as its object to provide a failure diagnosis device for an evaporative purge system that solves the above-described problems by introducing a positive pressure into a fuel tank and performing a failure diagnosis. .

[0005]

In order to achieve the above object, the present invention has a principle configuration as shown in FIG.
That is, according to the present invention, the evaporated fuel from the fuel tank 11 is adsorbed by the adsorbent in the canister 13 through the vapor passage 12, and the adsorbed fuel in the canister 13 is purged to the intake passage 15 of the internal combustion engine 10 through the purge passage 14 during a predetermined operation. In a device for diagnosing a malfunction of an evaporative purge system, a fuel tank 11, a vapor passage 12, a canister 1
Positive pressure introducing means 16 for introducing a positive pressure into the evaporative system of the third and purge passages 14, evaporative system internal pressure detecting means 17 for substantially detecting the internal pressure in the evaporative system, and positive pressure introducing means 16
And a determining means 18 for determining whether or not there is an abnormality in the evaporative system based on the detection result of the evaporative system internal pressure detecting means 17 when the positive pressure is introduced into the evaporative system.

[0006]

According to the present invention, positive pressure is introduced into the purge passage 14, the canister 13, the vapor passage 12 and the fuel tank 11 by the positive pressure introducing means 16, and the internal pressure in the evaporative system where the positive pressure is introduced at that time is reduced. The abnormality of the evaporation system is determined by the determination means 18 based on the determination. By setting the introduction pressure to a positive pressure, the vapor is not sucked out from the evaporative system, and the vapor does not adversely affect the engine. Fuel tank 11
Because the generation of vapor is suppressed by the positive pressure introduced into
Pressure change of the tank internal pressure can be reduced. Further, since the pressure in the vapor passage 12 is higher than that in the intake passage 15, the intake passage 1
5 can be prevented from flowing.

[0007]

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 atmosphere 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 29 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 28 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 30. Further, a fuel injection valve 31 is provided for each cylinder so that a part thereof projects into the intake manifold 27. The fuel injection valve 31 injects the fuel 33 in the fuel tank 32 into the airflow passing through the intake manifold 27 for a time specified by the microcomputer 21.

The fuel tank 32 is provided with the fuel tank 11 described above.
And the fuel 33 is accommodated therein, and the evaporative fuel (vapor) generated inside is sent to a canister 35 (corresponding to the canister 13) through a vapor passage 34 (corresponding to the vapor passage 12). The canister 35 is filled with an adsorbent such as activated carbon, and has an air hole 36 in a part thereof.

The air hole 36 is provided with an air passage 37a and a canister air hole vacuum switching valve (V).
SV) 38 to the atmosphere passage 37b.
The canister air vent VSV38 is a microcomputer 2
This is a control valve that communicates or shuts off between the air passages 37a and 37b based on the control signal of (1).

The canister 35 is connected to a purge passage 39a.
And 39b are connected to the purge side VSV 40. One end of the purge side VSV 40 has a throttle valve 25.
Passage 3 communicating with the intake passage 24 downstream of the
A control valve that communicates or shuts off the purge passage 9c and the purge passage 39b based on a control signal from the microcomputer 21.

Further, the purge passages 39a and 39b are connected to the secondary air side VSV 41 via respective passages 39d. The purge passage 39c is connected to the AC through a passage 39e.
It is connected to one end of the V VSV 42. Secondary air side V
SV41 is connected to the existing secondary air system.

The secondary air system includes air pumps 43, 2
It comprises a secondary air control valve (ACV) 44, a VSV for ACV 42, and secondary air passages 45a to 45d communicating between them. The air pump 43 pumps air by an electric or mechanical pump. When the air pump 43 is mechanical, it is driven by the engine.

When the secondary air is required, the ACV 44 conducts the secondary air passages 45a and 45b, and introduces the air from the air pump 43 to the exhaust manifold 46 through the secondary air passage 45b. The conduction of this ACV44 is AC
The VSV 42 for V is opened, and the intake pipe negative pressure is supplied to the passage 39e and the AC
Introduced into ACV44 via VVSV42 for V and ACV4
This is performed by pulling the diaphragm No. 4 rightward in the figure.

When the secondary air is unnecessary, the ACV VSV 42
Is closed so that the negative pressure of the intake pipe does not act on the ACV 44, so that A is established between the secondary air passages 45a and 45b.
CV 44 shuts off and secondary air passages 45a and 45c
Is made to conduct. As a result, the air from the air inlet is pressure-fed by the air pump 43 and the secondary air passage 45
a, one end is relieved to a secondary air passage 45d connected to the air cleaner 22 via the ACV 44, the secondary air passage 45c, and the secondary air side VSV 41 in the off state.

The pressure sensor 47 is provided in the middle of the vapor passage 34, and is provided for substantially detecting the internal pressure of the evaporative system including the fuel tank 32 by detecting the pressure of the vapor passage 34. Evaporation system internal pressure detecting means 17
Is composed. The warning lamp 48 is provided to notify the driver of the abnormality when the microcomputer 21 detects the abnormality.

In such a configuration, the vapor generated in the fuel tank 32 is adsorbed by the activated carbon in the canister 35 through the vapor passage 34 and is prevented from being released to the atmosphere. Normally, the canister air vent VSV 38 is open, and when the evaporative purge system is activated, the purge side VSV 38 is opened.
V40 is also open. Thereby, the atmosphere is introduced into the canister 35 from the atmosphere passage 37b through the canister atmosphere hole VSV38, the atmosphere passage 37a and the atmosphere hole 36 by utilizing the negative pressure of the intake manifold 27 during operation.

Then, the fuel adsorbed on the activated carbon is desorbed, and the fuel is sucked into the intake pipe 24 through the purge passages 39a and 39b, the purge VSV 40 and the purge passage 39c, respectively. The activated carbon is regenerated by the above desorption, and prepares for the next vapor adsorption.

The microcomputer 21 is a control device for realizing a part of the positive pressure introducing means 16 and the determining means 18 by software processing, and has a known hardware configuration as shown in FIG. 2, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. In FIG. 3, a microcomputer 21 includes a central processing unit (CP).
U) 50, a read-only file storing the processing program
A memory (ROM) 51, a random access memory (RAM) 52 used as a work area, a backup RAM 53 for holding data even after the engine is stopped, an input interface circuit 54 having a multiplexer, an A / D
It is composed of a converter 56, an input / output interface circuit 55, and the like, which are connected via a bus 57.

The input interface circuit 54 receives, in parallel, an intake air amount detection signal from the air flow meter 23, a detection signal from the throttle position sensor 30, a pressure detection signal from the pressure sensor 47, and the like. The serial signal is converted into a serially synthesized signal and supplied to a single A / D converter 56, where the serial signal is converted from analog to digital and transmitted to a bus 57 in sequence.

The input / output interface circuit 55 receives a detection signal from the throttle position sensor 30 and inputs the detection signal to the CPU 50 via the bus 57, while processing each signal input from the bus 57 to process the fuel injection valve 31. ,
Canister air vent VSV 38, purge side VSV 40, 2
They are selectively sent to the next air side VSV 41, the ACV VSV 42, and the warning lamp 48 to control them.

The CPU 50 of the microcomputer 21 configured as described above executes the processing of the flowchart described below in accordance with the program stored in the ROM 51. FIG. 4 is a flowchart for explaining the operation of the first embodiment of the main part of the present invention, which is started, for example, 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 has been cleared (the value is "0") by the initial routine at the time of starting the engine, it is not set at first, and the process proceeds to the next step 102.

In step 102, it is checked whether or not 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 103
Proceed to. In step 103, the canister air hole VSV3
8 is turned off (closed), and in a subsequent step 104, the purge side VSV 40 is turned off (closed).

The canister air hole VSV in step 103
Assuming that the shutoff at 38 has been performed at time t ₁ as schematically shown in FIG.
The interruption of the SV 40 is also performed at time t as schematically shown in FIG.
Performed in ₁ . Thereby, the purge side V shown in FIG.
SV40, purge passages 39b, 39a, canister 3
5. The inside of the evaporation system of the vapor passage 34 and the fuel tank 32 is closed.

Subsequently, in step 105 of FIG. 4, the ACV VSV 42 is turned off at time t _{1 as} schematically shown in FIG. 5C. By shutting off the ACV VSV 42, the ACV 44 is not exposed to the negative pressure of the intake pipe, and the secondary air passages 45 a and 45 shown in FIG.
c.

[0026] then proceeds to step 106 of FIG. 4, secondary air side VSV41 is turned on as shown schematically in FIG. 5 (D) in the above time t _1. As a result, the secondary air passage 45c and the purge passage 39d communicate with each other via the secondary air side VSV 41, and the air pressurized by the air pump 43
Secondary air passage 45a, ACV44, secondary air passage 45c,
The fuel is fed into the evaporative system in the above-mentioned closed state through the secondary air side VSV 41, respectively, and a positive pressure is introduced into the fuel tank 32 through the canister 35 and the vapor passage 34.

Therefore, after time t ₁ , the internal pressure of the fuel tank 32 increases from a certain value to a larger positive pressure value as shown in FIG. Then, step 1 in FIG.
At 07, it is determined whether or not the tank internal pressure is equal to or lower than X (Pa) based on the detection signal of the pressure sensor 47. When the pressure is equal to or lower than X (Pa), the positive pressure is being set, and this routine is ended. Steps 101 to 107 are repeatedly executed every 65 ms until the tank internal pressure becomes larger than X (Pa) on the positive pressure side. Then, the tank internal pressure at the time t ₂ is X (P
a) If it is determined in step 107 that the pressure has become larger on the positive pressure side, the process proceeds to the next step 108 and the secondary air side V
The SV 41 is turned off as schematically shown in FIG. 5D, and the introduction of the positive pressure to the fuel tank 32 is stopped.

When the process of step 106 in FIG. 4 is completed, it is subsequently determined whether or not the leak determination timer is "0" (step 109). Since the leak determination timer has been cleared to “0” by the above-described initial routine, when the determination in step 109 is performed first,
It is determined to be "0" and the routine proceeds to step 110, where the current detection value of the pressure sensor 47 is used as the diagnosis start pressure value P _S in the RAM
52.

Subsequently, the value of the leak determination timer is added by a predetermined value (step 111), the leak determination flag is set to "1" (step 112), and this routine ends.
Then, when this routine is started again, it is determined in step 102 that the leak is being determined.
The program jumps from 3 to 107, and reaches step 109 via step 108.

Since it is determined in step 109 that the leak determination timer is not "0", it is determined whether the value of the leak determination timer is a value corresponding to the diagnosis time (leak determination time) α (step 109). 113) If the time has not reached α, this routine is terminated via steps 111 and 112.

In this way, steps 101 and 10
The processing of 2, 108, 109, 113, 111 and 112 is repeated every 65 ms, and when the value of the leak determination timer becomes a value corresponding to the leak determination time α at time t ₃ , the detection value of the pressure sensor 47 at that time As the diagnosis end pressure value P _E
It is stored in the AM 52 (step 114). And RA
Pressure value P _S read from the M52, on the basis of the P _E,
The rate of change in pressure is calculated from the equation (P _E -P _S ) / α (second) (step 115). This pressure change rate is shown in FIG.
Shows the rate of change per unit time in the tank internal pressure from the time t ₂ shown in (E) up to t _3.

Subsequently, for example, referring to a map of the determination value β corresponding to the fuel amount stored in the backup RAM 53 and reading the determination value β, it is determined whether or not the calculated pressure change rate is equal to or greater than the above determination value β. A determination is made (step 116). When the pressure change rate is equal to or greater than β, the pressure change is large, so that it is determined that the leakage is large and abnormal, and the warning lamp 48
Is turned on (step 117), and after the driver is notified of the occurrence of a failure in the evaporative purge system, the leak failure code is stored, for example, in the backup RAM 53 (step 118), and the routine proceeds to step 119. 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 pressure change rate per unit time is less than β, since the degree of change of the leak is equal to or less than the specified value, it is determined that the leak is normal, and the steps 117 and 118 are jumped to the step 119. . In step 119, the canister atmosphere hole VSV38 is set to the open state (valve open).
Subsequently, the leak determination timer is cleared (step 12).
0), and set the execution flag to "1" (step 12).
1) Further, the leak determination flag is cleared to "0" (step 122), and the failure diagnosis processing ends. Thereafter, even if this routine is started, the execution flag is determined to be "1" in step 101, so that this routine will not be executed until restarted.

As described above, according to the present embodiment, the positive pressure introducing means 16 is realized by the steps 103 to 107 and the secondary air system, and the determining means 18 is realized by the steps 108 to 116. Therefore, the pressure change rate can be calculated in a state where the pressure change in the tank is small, so that accurate failure diagnosis can be always performed without fear of erroneous diagnosis. In addition, there is no increase in hydrocarbons (HC) and nitrogen monoxide (NO) in the exhaust gas.

Next, a second embodiment of the present invention will be described. FIG. 6 is a flowchart for explaining the operation of the second embodiment of the main part of the present invention. In the figure, the same reference numerals are given to the same processing steps as in FIG. 4, and the description thereof will be omitted. In the flowchart of the failure diagnosis processing routine of the evaporative purge system shown in FIG. 6, when this routine is first started, the routine proceeds to step 201 via steps 101 and 102. In step 201, it is determined whether or not the positive pressure setting flag is "1". Since the positive pressure setting flag has been cleared by the initial routine, the positive pressure setting flag is initially "0", and therefore, the process proceeds to step 202 through the next steps 103 to 106, and determines whether or not the timer A is 0 seconds. Is determined. Since this timer A is also cleared to 0 second by the initial routine executed after the engine is started, when this step 202 is first executed, step 203 is executed.
Then, the sensor value P _S1 of the pressure sensor 47 at that time is stored in the RAM 52 of FIG.
The value of the timer A in the PU 50 is added by a predetermined value, and this routine is once ended.

Thereafter, until timer A reaches γ seconds, 65
Steps 101, 102, 201, 103-1 every ms
06,202,205,204 are repeated, the timer A is stored sensor value P _E1 of the pressure sensor 47 to the RAM52 at t ₄ when it is determined in step 205 to have reached the γ seconds (step 206). Then, from the stored sensor values P _S1 and P _E1 and the known time γ (second), (P _E1
−PS ₁ ) / γ to calculate the rate of change (step 2)
07), it is determined whether or not the calculated change rate is equal to or greater than a predetermined set value δ (step 208).

Here, the time after the time t ₁ is a period during which the positive pressure is introduced from the secondary air system into the system, and the pressure value in the system at the time t _{4 when} γ seconds have passed after the introduction of the positive pressure. The rate of change is equal to or greater than the set value δ because the pressure in the system greatly changes in the positive pressure direction when there is not much leakage in the system. On the other hand, when the leakage in the system is relatively large, the pressure in the system in the time from the time t _{1 to the} time t ₄ changes very slowly in the positive pressure direction. Is less than the set value δ.

Accordingly, when the rate of change is equal to or greater than the set value δ, it is roughly determined that there is no relatively large failure in the evaporative purge system, and the positive pressure setting flag is set to “1” (step 209). After the positive pressure setting flag is set in step 209, the introduction of the positive pressure is stopped while the evaporative system is kept closed, and the pressure change rate per unit time in α seconds is determined in the same manner as in the routine of FIG. Then, the presence or absence of a failure is determined from the result of the comparison between the measured value and the determination value β (steps 107 to 116).

On the other hand, if it is determined in step 208 that the pressure change rate per unit time during the positive pressure introduction period of γ seconds is less than the set value δ, it is determined that there is a leak in the evaporative system, and the flow advances to step 117. Warning lamp 48
Lights up. Thereafter, as in the first embodiment, storage of the leak failure code, opening of the canister vent hole VSV 38, clearing of the leak determination timer and the leak determination flag, and setting of the execution flag are performed (steps 117 to 1).
19, 121, 210, and 211), and the timer A and the positive pressure setting flag are also cleared (steps 210 and 210).
211).

As described above, according to the present embodiment, the failure diagnosis of the evaporative purge system can be performed from the pressure change rate per unit time during the positive pressure introduction period. At this time, since the positive pressure is introduced into the fuel tank 32, generation of vapor in the tank can be suppressed, and accurate failure diagnosis can be performed.

FIG. 7 shows a system configuration diagram of a second embodiment of the present invention. 2, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. The system shown in FIG. 7 is a system having a supercharging system (turbo, supercharger) in which a positive pressure from the supercharging system is introduced into the fuel tank 32 at the time of failure diagnosis of the evaporative purge system.

In FIG. 7, a compressor 63 is provided at a portion where the intake passages 61 and 62 communicate with each other. Since the compressor 63 is coaxially fixed to the turbine 64 and the shaft, the compressor 63 and the turbine 64 rotate integrally. The intake passage 62 communicates with the surge tank 26.

The engine combustion chamber 29 is connected to the exhaust manifold 46 through an exhaust valve 65 and an exhaust passage 66, respectively.
Is communicated to. A turbine 64 is provided at a portion where the exhaust passage 66 communicates with the exhaust manifold 46. Further, a pressure sensor 67 is attached to the surge tank 26.

In the supercharging system having such a configuration, when the exhaust gas flows from the exhaust manifold 46 to rotate the turbine 64, the compressor 63 rotates in accordance with the rotation, and the compressor 63 passes through the intake passage 61.
The compressed air is supplied to the combustion chamber 29 and compressed to be sent out to the intake passage 62, whereby a high-density air-fuel mixture is sucked into the combustion chamber 29 to increase the output.

Here, in this embodiment, the purge side VSV4
0 is provided at a position where communication between the surge tank 26 and the vapor passage 39a is established or interrupted.
The fuel is purged from the canister 35, or the air pumped by the supercharging system is introduced from the surge tank 26 into the purge passage 39a.

Next, a failure diagnosis of the evaporative purge system of the internal combustion engine having such a supercharging system will be described with reference to FIGS. FIG. 8 is a flowchart for explaining the operation of the third embodiment of the main part of the present invention. The same reference numerals are given to the same processing steps as in FIG. 4, and the description thereof will be omitted. The failure diagnosis processing routine of the evaporative purge system shown in FIG.
When activated once every 5 ms, it is checked in step 301 via step 101 whether supercharging is in progress. Whether or not supercharging is being performed is determined by a pressure sensor 67 that monitors the supercharging pressure.
Is determined from the output signal of.

If it is determined that the fuel is not being supercharged, the routine proceeds to step 302, where it is checked whether or not a leak determination flag, which will be described later, is set. judge. When the leak determination is not being performed, the canister air vent VSV 38 is opened (opened) (step 303), and the purge side VSV 40 is set to a state where the purge of the fuel from the canister 35 can be executed, and this routine is temporarily terminated.

On the other hand, if it is determined in step 301 that the supercharging is being performed, and if it is determined in step 102 that the leakage is not being determined, the canister air vent VSV 38 is shut off (step 103), and the purge side VSV 40 is turned off. An open state is set (step 304). Opened 9 of blocking and purge side VSV40 of the canister atmospheric hole VSV38 (A), assuming that was done at time t ₁₀ as shown respectively schematic (B), the pressurized by supercharging system Air is supplied from the surge tank 26 to the fuel tank 32 through the purge side VSV 40, the purge passage 39a, the canister 35, and the vapor passage 34, respectively.

As a result, the internal pressure of the fuel tank 32 is reduced as shown in FIG.
As (C), the positive pressure from the time t ₁₀ X (Pa)
Start to rise in the direction. Then, when it is determined in step 107 that the tank internal pressure has reached X (Pa) based on the output signal of the pressure sensor 37 (time t ₁₁ ), the process proceeds to step 305 in FIG. 8 and proceeds to FIG. The purge-side VSV 40 is shut off as schematically shown. Thereby, the purge side V
Since both the SV 40 and the canister air vent VSV 38 were shut off, the purge passage 39a, the canister 3
5. The system of the vapor passage 34 and the fuel tank 32 is closed, and the state where the positive pressure introduced immediately before is maintained.

When the process of step 305 in FIG. 8 is completed, the rate of change in pressure per unit time in α seconds is measured in the same manner as in the above-described embodiments, and the magnitude of the measured value is compared with the judgment value β. From the result, it is determined whether there is a failure (steps 109 to 109).
116) If it is determined that a failure has occurred, the warning lamp 4
8 and the storage of the leak failure code (steps 117 and 118). Thereafter, the canister air vent VSV 38 is opened to release the closed state of the system (step 119), and the leak is determined in the same manner as when it is determined to be normal. The timer and the leak determination flag are cleared, and the execution flag is set (steps 120 to 122).

[0051] In FIG. 5, the time t ₁₂ is determined to have passed the time α seconds, the time t ₁₂ after the canister large pores VSV3
8 is opened, the tank internal pressure decreases in the atmospheric pressure direction as shown in FIG. Step 302
Or, when it is determined in step 102 that the leak is being determined,
The processing after step 305 is executed without performing the positive pressure introducing operation.

In this embodiment, steps 103, 304, and 10
7 and the supercharging system to realize the positive pressure introducing means 16 and the steps 305 and 109 to 116 to realize the determining means 18 so that an accurate diagnosis can be made as in the above-described embodiments to cause deterioration of exhaust emission. It has the feature that it can be eliminated.

It should be noted that the present invention is not limited to the above-described embodiment.
The evaporative purge system may be diagnosed based on the positive pressure change rate during the positive pressure introduction period. In this case, utilizing the fact that the canister 35 acts as a passage resistance, the canister air hole V
The SV 38 need not be provided. However, when the canister air vent VSV 38 is not provided, it is necessary to confirm that no vapor remains in the canister at the start of the determination. Further, in each of the above embodiments, an existing secondary air supply system or supercharging system is used as the positive pressure introducing means. However, it goes without saying that a dedicated positive pressure introducing means may be provided.

[0054]

As described above, according to the present invention, since the pressure introduced into the fuel tank is a positive pressure, the generation of vapor in the fuel tank is suppressed, so that the change in the pressure in the tank is introduced into the negative pressure. It is possible to reduce the possibility of erroneous diagnosis, and to prevent the vapor from flowing into the intake passage at the time of failure diagnosis. It has features such as being able to be improved.

[Brief description of the 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 a microcomputer in FIG. 2;

FIG. 4 is a flowchart showing a failure diagnosis routine of a first embodiment of the main part of the present invention.

FIG. 5 is a time chart for explaining the operation of each unit in FIG. 4;

FIG. 6 is a flowchart showing a failure diagnosis routine according to a second embodiment of the main part of the present invention.

FIG. 7 is a system configuration diagram of a second embodiment of the present invention.

FIG. 8 is a flowchart illustrating a failure diagnosis routine according to a third embodiment of the present invention.

FIG. 9 is a time chart for explaining the operation of each unit in FIG. 8;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 11, 32 Fuel tank 12, 34 Vapor passage 13, 35 Canister 14, 39a-39d Purge passage 15 Intake passage 16 Positive pressure introducing means 17 Evaporation system internal pressure detecting means 18 Judgment means 21 Microcomputer 38 Canister air hole vacuum Switching valve (VSV) 40 Vacuum switching valve on purge side (V
SV) 41 Secondary air side vacuum switching valve (VSV) 42 ACV vacuum switching valve (V
SV) 43 Air pump 44 Secondary air control valve (ACV) 48 Warning lamp 63 Compressor 63 Turbine

Claims (3)

(57) [Claims] 1. A failure of an evaporative purge system for adsorbing fuel vapor from a fuel tank to an adsorbent in a canister through a vapor passage and purging the adsorbed fuel in the canister to a suction passage of an internal combustion engine through a purge passage during a predetermined operation. A positive pressure introducing means for introducing a positive pressure into an evaporative system of the fuel tank, the vapor passage, the canister and the purge passage; and an evaporative system internal pressure detecting means for substantially detecting an internal pressure in the evaporative system. And determining means for determining the presence or absence of an abnormality in the evaporation system based on a detection result of the evaporation system internal pressure detecting means when a positive pressure is introduced into the evaporation system by the positive pressure introducing means. A failure diagnosis device for the evaporative purge system. 2. The method according to claim 1, wherein said positive pressure introducing means introduces a positive pressure into said evaporative system in a closed state, and said judging means sets a positive pressure within a positive pressure introduction stop period after said introduced positive pressure reaches a predetermined value. 2. The method according to claim 1, further comprising: measuring a degree of change in the pressure in the evaporative system at a predetermined time, and determining whether there is an abnormality in the evaporative system based on a magnitude comparison result between the measurement result and a determination value.
A failure diagnosis device for the evaporative purge system described in the above. 3. The determination means measures the degree of change in pressure in the evaporative system during a predetermined positive pressure introduction period from the start of positive pressure introduction by the positive pressure introduction means, and determines whether the measurement result is larger or smaller than the determination value. 3. The failure diagnosis device for an evaporative purge system according to claim 1, wherein the presence or absence of an abnormality in the evaporative system is determined from the comparison result.