JPH06193519A - Failure diagnostic device of evaporative purge system - Google Patents

Abstract

PURPOSE:To obviate the necessity for correcting a detection value and specify a failure generation part by using a single pressure detecting means. CONSTITUTION:A first valve means M10 is provided in an evaporation passage between a canister M3 and a fuel tank M1, and the means M10 is communicated from the fuel tank M1 in a canister M3 direction when tank inner pressure of the fuel tank M1 is a first specific value or more, and the means M10 is communicated from the canister M3 in the fuel tank M1 direction when tank inner pressure is a second specific value or less. A second valve means M11 is communicated from the atmosphere in the canister M3 direction when inner pressure of the canister M3 is a third specific value or less, and the second valve means M11 is communicated from the canister M3 in the atmosphere when inner pressure of the canister M3 is a fourth specific value or more.

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 failure diagnostic device for an evaporative purge system that discharges (purge) to an intake system of an engine and burns it.

[0002]

2. Description of the Related Art Fuel (vapor) evaporated in a fuel tank
In order to prevent air from being released to the atmosphere, each part is hermetically sealed, and the vapor is once adsorbed by the adsorbent in the canister, and the fuel adsorbed while the vehicle is running is sucked into the intake system and burned by evaporative purging. In an internal combustion engine equipped with a system, if the vapor passage is damaged for some reason or if the pipe is disconnected, the vapor is released to the atmosphere, and if the purge passage to the intake system is blocked,
The vapor in the canister overflows, and the vapor leaks into the atmosphere through the air hole in the canister. Therefore, it is necessary to diagnose whether or not such a failure of the evaporative purge system has occurred.

The applicant of the present application has proposed Japanese Patent Application No. 3-138002, Japanese Patent Application No. 3-323364, etc. as a failure diagnostic device for the evaporative purge system.

The one disclosed in Japanese Patent Application No. 3-138002 discloses a purge negative pressure introduced into the evaporation passage system and held for a certain period of time, and a failure in the evaporation passage system is diagnosed by a change in pressure in the evaporation passage system during that period. To do.

In Japanese Patent Application No. 3-323364, a vapor passage communicating the fuel tank and the canister and a purge passage communicating the canister and the intake passage are communicated with each other, and the vapor passage or the purge passage is connected to the vapor passage. The pressure sensor provided detects the pressure at the time of purging and compares the detected pressure with a predetermined pressure to diagnose a failure of the evaporation system.

[0006]

In the above conventional device,
Although it was possible to determine that a failure occurred in the evaporative system, it was not possible to identify which part of the evaporative system failed. Further, since the purge negative pressure varies depending on the operating state of the engine, there is a problem that it is necessary to correct the detected pressure change amount or the detected pressure in order to prevent erroneous diagnosis.

The present invention has been made in view of the above points,
By performing communication in both directions between the fuel tank and the canister with predetermined set values, and by communicating in both directions between the canister and the atmosphere with predetermined set values, it is not necessary to correct the detection value An object of the present invention is to provide a failure diagnostic device for an evaporative purge system that can identify a part where a failure has occurred by using a pressure detection means.

[0008]

FIG. 1 shows the principle of the present invention.

As shown in FIG. 1, the failure diagnosis apparatus for the evaporative purge system according to the present invention causes the evaporated fuel from the fuel tank M1 to be adsorbed by the adsorbent in the canister M3 through the vapor passage M2, and the adsorbed fuel in the canister M3 described above. In the intake passage M6 of the internal combustion engine M5 through the purge passage M4. The evaporation purge system in which the pressure detection means M7 detects the pressure of the evaporation path in the evaporation purge system and the determination means M8 diagnoses the failure. In the failure diagnosing device, the fuel tank M1 is provided in an evaporation path between the fuel tank M1 and the fuel tank M1, and communicates in the direction from the fuel tank M1 to the canister M3 when the tank internal pressure of the fuel tank M1 is equal to or higher than a first predetermined value. When the tank internal pressure is equal to or lower than the second predetermined value, the canister M3 communicates with the fuel tank M1. The first valve means M10 and the canister M3 are provided in the atmosphere opening path, and when the internal pressure of the canister M3 is equal to or lower than a third predetermined value, the internal pressure of the canister M3 is communicated from the atmosphere in the direction of the canister M3. A second valve means M11 communicating with the canister M3 in the atmosphere direction when the fourth predetermined value or more is provided, and the pressure detecting means M7 is provided in the evaporation path on the fuel tank M1 side of the first valve means M10; Based on the output value of the pressure detecting means M7, the failure diagnosis of the evaporative purge system is performed.

[0010]

In the present invention, the first valve means M10 is provided in the evaporation path between the canister M3 and the fuel tank M1, and when the tank internal pressure of the fuel tank M1 is the first predetermined value or more, the fuel tank M1 From the canister M3 direction to the fuel tank M1 direction when the tank internal pressure is equal to or lower than a second predetermined value, and the second valve means M11 connects the canister M3 to the third predetermined value. In the following, the atmosphere is communicated in the direction of the canister M3, and when the internal pressure of the canister M3 is a fourth predetermined value or more, the canister M3 is communicated in the direction of the atmosphere, and in the evaporation path on the fuel tank M1 side from the first valve means M10. The failure diagnosis is performed without correcting the detection value detected by the pressure detection means M7 provided in the above, and the failure occurrence portion is specified.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows the system configuration of the device of the present invention.
In the figure, the fuel tank 21 comprises a main tank 21a and a sub tank 21b. The sub tank 21b is inside the main tank 21a, communicates with the main tank 21a, and has the fuel pump 22 arranged therein. Also,
A rollover valve 23 is provided above the fuel tank 21. The rollover valve 23 is provided to prevent fuel from flowing outside when the vehicle rolls over.

The fuel pump 22 is connected to a fuel injection valve 26 via a pipe 24 and a pressure regulator 25, respectively. The pressure regulator 25 is provided to keep the fuel pressure constant, and the fuel injector 26
The surplus fuel that is not injected in is returned to the sub tank 21b through the return pipe 27.

The upper portion of the fuel tank 21 has a vapor passage 28a, an internal pressure control valve 29, and a vapor passage 28b.
Through the canister 30. The internal pressure control valve 29 includes a tank positive pressure relief valve 29c including a diaphragm 29a and a spring 29b, and a back purge check valve 29f including a check ball 29d and a spring 29e. The tank internal pressure relief valve 29c opens when the tank internal pressure becomes equal to or higher than a set value A (for example, 150 mmAq) from the atmospheric pressure from the air introduction hole 29g. The check valve 29f has a set value B (for example, -50 mmAq) when the tank internal pressure is higher than the internal pressure of the canister 30.
The valve will open when:

A pressure sensor 31 is provided in the vapor passage 28a. The pressure sensor 31 is a kind of strain gauge that detects the strain of the silicon wafer with a bridge circuit, and measures the difference between the pressure in the space formed by the fuel tank 21 and the internal pressure control valve 29 and the atmospheric pressure.

The canister 30 includes a first chamber 30a and a second chamber 3
It is classified as 0b, and has activated carbon 30c as an adsorbent inside. The first chamber 30a has a vapor passage 28b.
The internal pressure control valve 29 is communicated with the intake passage 36 via a purge passage 32 and a purge control valve 33 which is an electromagnetic valve (VSV), and the intake passage 36 is communicated with a position downstream of the throttle valve 35.

In the second chamber 30b, a canister negative pressure maintaining check valve 30f composed of a check ball 30d and a spring 30e, and a check ball 3 provided in parallel therewith.
0g and a canister positive pressure maintaining check valve 30i composed of a spring 30h communicate with the atmosphere introducing hole 30j. The negative pressure maintaining check valve 30f is the canister 3
The internal pressure of 0 is the set value C with respect to the atmospheric pressure (for example, -100 m
When it becomes less than mAq), the valve is opened. The positive pressure check valve 30i opens when the internal pressure of the canister 30 becomes equal to or higher than a set value D (for example, 350 mmAq) with respect to the atmospheric pressure. Note that each of 30k, 30m, and 30n is a filter.

An air cleaner (AC) 3 for filtering air to remove dust is provided upstream of the throttle valve 35.
4 are provided.

The throttle valve 35 is a valve whose opening is controlled by the amount of depression of an accelerator pedal operated by the driver.
Detected by 7. Further, the fuel temperature sensor 40 detects the fuel temperature of the main tank 21a in the fuel tank 21,
The intake air temperature sensor 41 detects the intake air temperature in the intake passage 36, and the water temperature sensor 42 detects the temperature of the engine cooling water and supplies respective detection signals to the microcomputer 38.

The microcomputer 38 is an electronic control unit for controlling the evaporative purge system. When an abnormality is determined, a warning lamp 39 is turned on to inform the driver of the occurrence of the abnormality.

The microcomputer 38 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 38 includes a central processing unit (CPU) 50, a read only memory (ROM) 51 storing a processing program, and a random access memory (RAM) 5 used as a work area.
2. Backup R that retains data even after the engine is stopped
The AM 53, an input interface circuit 54 with a multiplexer, an input / output interface circuit 55, an A / D converter 56, and the like are connected to each other via a bidirectional bus 57.

The A / D converter 56 receives the pressure detection signal from the pressure sensor 31, the detection signal from the throttle position sensor 37, the fuel temperature sensor 40, and the intake air temperature sensor 4.
1. The detection signals of the water temperature sensor 42 are sequentially switched and fetched through the input interface circuit 54, converted into analog / digital, and sequentially transmitted to the bus 57. The input / output interface circuit 55 sends a signal from the throttle position sensor 37 and an air-fuel ratio feedback correction coefficient from a microcomputer which controls the fuel injection coming from the terminal 45 to the bus 57, while the fuel injection valve 26 and the purge Control signals are selectively sent to the control valve 33, the warning light 39, and the bypass control valve 45 to control them.

Next, the operation of the normal evaporative purge of the system shown in FIG. 2 will be described. When an ignition switch (not shown) is turned on, the fuel pump 22 shown in FIG.
The fuel in the sub-tank 21b is activated by the operation of
Is discharged to the pressure regulator 25 through the pressure regulator 25 and is sent to the fuel injection valve 26 at a constant pressure there. The fuel injection time from the microcomputer 38, the fuel injection valve 26
Is injected into the intake passage 36 from. The surplus fuel is returned to the sub tank 21b via the return pipe 27.

On the other hand, the evaporated fuel (vapor) generated in the fuel tank 21 reaches the internal pressure control valve 29 through the vapor passage 28 because the bypass control valve 45 is open. Here, when the tank internal pressure is smaller than the set value A set by the internal pressure control valve 29, the check ball 29a is in the position shown in the figure by the spring force of the spring 29b and blocks the vapor passage 28, so that the vaporized fuel canister 30 To be blocked.

For example, when the engine is cold-started, the tank internal pressure is near atmospheric pressure, and immediately after that, the fuel volume is reduced due to fuel consumption by the fuel injection valve 26, so the tank internal pressure temporarily decreases to a negative pressure. However, thereafter, the fuel temperature gradually rises due to the exhaust heat, the amount of vaporized fuel generated increases, the tank internal pressure rises in the positive pressure direction, and reaches the set pressure by the tank internal pressure relief valve 29c of the internal pressure control valve 29.

When vaporized fuel is further generated and the tank internal pressure becomes equal to or higher than the set pressure, the vaporized fuel is vaporized into the vapor passage 28.
And, it is sent into the canister 30 through the internal pressure control valve 29 and adsorbed to the activated carbon 30c inside. When the evaporated fuel is sent to the canister 30, the tank internal pressure decreases, and when the tank internal pressure becomes equal to or lower than the set value B, the tank internal pressure relief valve 29c is closed again.

As described above, when there is no leakage in the vapor passage 28 or the fuel tank 21, the evaporated fuel is adsorbed by the activated carbon 30a in the canister 30 through the internal pressure control valve 29 as described above. Immediately after the engine is started, the purge control valve 33 is closed because the purge control condition is not satisfied.

The purge control conditions are those that can minimize adverse effects on operability and exhaust emission even if the air-fuel ratio becomes rough due to purging. For example, the cooling water temperature is equal to or higher than a predetermined temperature, and the air-fuel ratio is the target value. The microcomputer 38 determines that the purge control conditions are satisfied when the intake air amount is equal to or more than a predetermined value and the fuel cut is not performed during the injection feedback control.

If it is determined that the purge control condition is satisfied, the microcomputer 38 opens the purge control valve 33. Then, due to the negative pressure in the intake passage 36, the negative pressure maintaining check valve 30f is opened and the atmosphere is introduced into the canister 30 through the atmosphere inlet 30j, and the fuel adsorbed on the activated carbon 30a is desorbed and purged. Passage 3
2 and the purge control valve 33, respectively, and the evaporated fuel is sucked into the intake passage 36. In addition, the activated carbon 30a is regenerated by the above desorption and prepared for the next vapor adsorption. As a result, the purge flow rate gradually increases.

Next, the failure diagnosis processing executed by the microcomputer 38 in the above system will be described. Figure 4
5 and 6 show a flowchart of the first embodiment of the failure diagnosis routine.

The routine of FIG. 4 is, for example, an interrupt routine every 64 msec. In the figure, in step S10, it is determined whether or not the engine is stopped, and if the engine is operating, the starting routine shown in FIG. 5 is executed in step S12, and then 20 minutes after the start in step S14. Or not.

If 20 minutes have not elapsed after the start, it is judged in step S16 whether the absolute value of the tank internal pressure P detected by the pressure sensor 31 is within a predetermined value β (for example, 50 mmAq), and | P | ≧ β That is, only when the tank internal pressure is equal to or higher than the predetermined value β or equal to or lower than −β, it is determined that the fuel tank 21 does not leak, and the tank normal flag is set to 1 in step S18. Next, in step S20, it is determined whether or not the increase rate of the tank internal pressure P exceeds the predetermined value and is large, and only when it is large, the flag XPUP is set to 1 in step S22. The above-mentioned tank normal flag and the flag XPUP are reset to 0 at the time of starting. Further, step S24
It is determined whether the tank internal pressure P has experienced the state of the set value A of the tank positive pressure relief valve 29c for 5 minutes. If it has been experienced for 5 minutes, it is determined that the generation of vapor is large and the step S2 is performed.
In step 6, the flag XPA is set to 1, and if it has not been experienced for 5 minutes, it is determined that the occurrence of vapor is small, and in step S28 the flag XPA is set to 0 and the processing cycle is ended.

If it is determined in step S14 that 20 minutes have elapsed after the start, it is determined in step S30 whether or not the tank normal flag is 1, and if the tank normal flag is 1, the process proceeds to step S20. If the tank normal flag is 0, the tank internal pressure has not changed to a positive pressure or a negative pressure even after 20 minutes have elapsed from the start, and therefore it is determined that there is a leak in the fuel tank 21, and the warning lamp 39 is turned on in step S32. Illuminates to indicate an abnormality and ends the processing cycle.

On the other hand, if it is determined in step S10 that the engine has stopped, the purge control valve 33 is closed in step S34, and it is determined in step S36 whether or not 10 minutes have elapsed after the engine was stopped. If not, it is determined in step S38 whether the flag XPUP is 1 or not. When XPUP = 1, it is determined in step S40 whether the flag XPA is 1 or not,
When XPA = 1, it is determined in step S42 whether the tank internal pressure P is higher than the set value A or not. When the tank internal pressure P is A or less, the processing cycle is ended, and the tank internal pressure P is set to the set value A.
In the case of a larger value, even if vapor is generated due to the rise in fuel temperature due to engine stoppage and the tank positive pressure relief valve 29c is opened, the tank internal pressure still rises above the set value A. , It is determined that there is no leakage in the path closed by the valve 29 and the valve 30, and the warning light 3 is generated in step S44.
After turning off 9 and displaying normal, the power supply of the microcomputer 38 is turned off in step S46, and the diagnostic process ends.

When the flag XPUP = 0 or XPA = 0, the increase rate of the tank internal pressure is small or the generation of vapor is small, so that the routine proceeds to step S46, the power is turned off and the diagnosis processing is ended.

When both the flags XPUP and XPA are 1 and the tank internal pressure remains at the set value A or is smaller than A for 10 minutes after the engine is stopped, the tank is generated despite the large generation of vapor. The internal pressure does not exceed the set value A because the purge control valve 33, the valve 29, and the valve 30
There is a leak in the route closed by and
At 48, the warning lamp 39 is turned on to display the abnormality, and then the process proceeds to step S46, the power is turned off, and the diagnosis process is ended.

In the starting routine shown in FIG. 5, step S
At 50, it is determined whether or not it is within 2 seconds after the start, and if it is within 2 seconds, whether or not the cooling water temperature detected by the water temperature sensor 42 in steps S52 and S54 is substantially equal to the intake air temperature detected by the intake air temperature sensor 41, It is determined whether the intake air temperature is lower than 30 ° C. Step S
At the time of cold start satisfying 50 to S54, step S56
To determine whether the high pressure memory flag is set,
If this is set, it is determined in step S60 whether the tank internal pressure P is smaller than the set value B of the check valve 29f. When the engine was operated last time, the amount of vapor was large, the high-pressure memory flag was set, and when the next cold start is performed, the vapor is liquefied and the tank internal pressure P drops below the set value B. When the decrease is large, the value is decreased to the set value C of the check valve 30f. Therefore, if the tank internal pressure P is smaller than the set value B in step S60, the warning lamp 39 is turned off in step S62 to display normal, and the processing cycle is ended.

If the tank internal pressure P is equal to or higher than the set value B in step S60, it is determined in step S64 whether the tank internal pressure P is equal to the set value B. If they are equal, there is no leakage in the fuel tank 21, Assuming that the canister 30 is leaking and the tank internal pressure P does not become smaller than the set value B, the warning lamp 39 is turned on in step S66 to display the abnormality, and the processing cycle is ended. If the tank internal pressure P exceeds the set value B, it is determined that there is a leak in the fuel tank 21 and the step S
At 68, the warning light 39 is turned on to end the processing cycle.

On the other hand, if it is determined in step S50 that 2 seconds have elapsed after the start, the cooling water temperature is set to 8 in step S80.
It is determined whether or not the temperature exceeds 0 ° C. If the temperature exceeds 0 ° C, it is determined in step S82 whether the tank internal pressure has experienced the state of the set value A for 5 minutes. It is determined that the generation is large and the tank internal pressure is high (that is, the gas density in the tank is low), the high pressure storage flag is set in step S84, and the processing cycle is ended. The cooling water temperature is 80
If the temperature is less than 0 ° C. or the tank internal pressure has not been in the set value A for 5 minutes, it is determined that the generation of vapor is small and the tank internal pressure is low, and the high pressure storage flag is cleared in step S86, and the processing cycle ends.

6 to 8 are flowcharts of the second embodiment of the failure diagnosis routine.

The routine of FIG. 6 is, for example, an interrupt routine every 64 msec. In the figure, in step S110, it is determined whether or not the engine is stopped, and if the engine is operating, the startup routine shown in FIG. 5 is executed in step S112. Next, in step S114, it is determined whether or not the tank internal pressure P is larger than the set value A, and if P≤A, the step S
At 116, it is determined whether the fuel temperature detected by the fuel temperature sensor 40 is higher than a predetermined value α (for example, 35 ° C.).

If the fuel temperature is equal to or lower than the predetermined value α, the processing cycle is ended. If the fuel temperature is greater than the predetermined value α, it is determined in step S118 whether or not 20 minutes have elapsed after the start. The absolute value of the tank internal pressure P detected by the pressure sensor 31 in step S120 is a predetermined value β (for example, 50 mm
Aq) or not, and only if | P | ≧ β, that is, the tank internal pressure is equal to or more than a predetermined value β or less than −β, it is determined that there is no leak in the fuel tank 21, and the tank normal flag is set to 1 in step S122. To do. Next, in step S124, it is determined whether or not the increase rate of the tank internal pressure P exceeds the predetermined value and is large. Only when the increase rate is large, the flag XPUP is set to 1 in step S126. The above-mentioned tank normal flag and the flag XPUP are reset to 0 at the time of starting. Further, in step S128, it is determined whether or not the tank internal pressure P has experienced the state of the set value A of the tank positive pressure relief valve 29c for 5 minutes. Set flag XPA to 1. If it has not been experienced for 5 minutes, it is determined that the generation of vapor is small, and in step S132, the flag XPA is set to 0 and the processing cycle is ended.

If it is determined in step S118 that 20 minutes have elapsed after the start, it is determined in step S134 whether the tank normal flag is 1 and the tank normal flag is 1.
If the tank normal flag is 0, the tank internal pressure has not changed to a positive pressure or a negative pressure even after 20 minutes have passed since the start.
In step S136, the warning lamp 39 is turned on to display an abnormality, and the processing cycle is terminated.

After executing step S130, it is determined in step S140 of FIG. 7 whether the diagnosis flag is 0. If the diagnosis flag is 0, the diagnosis flag is set to 1 in step S141. This diagnostic flag is set to 0 at the time of starting. After this, in step S142, the purge control valve 33
Is closed to perform purge cut, and it is determined in step S144 whether the value of the air-fuel ratio feedback correction coefficient FAF has increased. The increase in FAF means that the vapor is sufficiently supplied from the fuel tank 21 to the canister 30. In this case, it is determined in step S146 whether one minute has elapsed from the start of the purge cut. .

When one minute has passed from the purge cut, it is judged in step S148 whether the tank internal pressure P is larger than the set value A. If P≤A, the tank internal pressure is generated even though vapor is sufficiently generated. Is low, it is determined that there is a leak in the fuel tank 21. In step S150, the warning lamp 39 is turned on to display an abnormality, and the processing cycle is ended.

If the tank internal pressure P is larger than the set value A in step S114 of FIG. 6 or step S148 of FIG. 7, the warning lamp 39 is turned off to display that it is normal in step S152, and the processing cycle is executed. finish. If the diagnostic flag is 1 in each of steps S140, S144, and S146, or if FAF does not increase, or if one minute has not elapsed after the purge cut, the processing cycle ends.

On the other hand, if it is determined in step S110 in FIG. 6 that the engine has stopped, the purge control valve 33 is closed in step S160, and it is determined in step S162 whether 10 minutes have elapsed after the engine stopped. If not, it is determined in step S164 whether the flag XPUP is 1 or not. X
When PUP = 1, the flag XPA is 1 in step S166.
If XPA = 1, it is determined in step S168 whether the fuel temperature is higher than the predetermined value α. If it is higher than the predetermined value α, in step S170 the tank internal pressure P is higher than the set value A. Or not.

Here, when the tank internal pressure P is higher than the set value A, even if the tank positive pressure relief valve 29c is opened due to the vapor generated due to the increase in the fuel temperature due to the engine stop, the tank internal pressure P is still set value A. Rises above the purge control valve 3
3, the valve 29, and the path closed by the valve 30 are not leaked, the warning lamp 39 is turned off in step S172 to display normal, and the microcomputer 38 is powered off in step S174 to perform a diagnostic process. finish. If P ≦ A, it is determined that there is a leak in the fuel tank 21 and step S17 is performed.
After the warning light 39 is turned on to display the abnormality in step 6, the process proceeds to step S174, the power is turned off, and the diagnosis process ends.

If the flag XPUP = 0, XPA = 0, or the fuel temperature is less than or equal to α, the increase rate of the tank internal pressure is small or the generation of vapor is small.
Proceeding to 74, the power is turned off and the diagnosis processing is ended.

Further, if it is determined in step S162 that 10 minutes have elapsed after the engine is stopped, it is determined in step S180 whether the engine is started. If it is restarted, the process proceeds to step S114 in FIG. If not, step S
At 174, the power is turned off and the diagnosis process ends.

Since the relief valve 29c and the check valves 29f, 30f, and 30i have different set values, the single pressure sensor 31 identifies and detects the failure of the fuel tank 21 and the canister 30, respectively. It is possible to diagnose the entire evaporative system.

Further, each of the above valves 29c, 29f, 30
Since the determination level is defined by the setting values of f and 30i, various corrections are not required.

Further, since the internal pressure of the canister 30 is maintained at a high pressure, it is possible to prevent the evaporation from being released from the canister 30 to the atmosphere and to reduce the volume of the canister 30.
Further, the tank internal pressure can be set to a low pressure (set value A) according to the regulation during traveling, and can be set to a high pressure (set value D) during stop to prevent over-injection of fuel. Also, check valve 3
0f and 30i are smaller than the solenoid valve (VSV) and can be built in the canister 30.

[0053]

As described above, the present invention has been made in view of the above points. Communication between the fuel tank and the canister in both directions is performed at a predetermined set value, and communication between the canister and the atmosphere is performed in both directions. By performing each with a predetermined set value, it is not necessary to correct the detected value, and it is possible to specify the part where the failure has occurred using a single pressure detecting means, which is extremely useful in practice.

[Brief description of drawings]

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

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

FIG. 3 is a configuration diagram of hardware of a microcomputer.

FIG. 4 is a flowchart of a failure diagnosis routine of the present invention.

FIG. 5 is a flowchart of a failure diagnosis routine of the present invention.

FIG. 6 is a flowchart of a failure diagnosis routine of the present invention.

FIG. 7 is a flowchart of a failure diagnosis routine of the present invention.

FIG. 8 is a flowchart of a failure diagnosis routine of the present invention.

[Explanation of symbols]

 M1,21 Fuel tank M2,28 Vapor passage M3,30 Canister M4,32 Purge passage M6,36 Intake passage M7 Pressure detection means M8 Determination means M10 First valve means M11 Second valve means 26 Fuel injection valve 29 Internal pressure control Valve 29c Tank positive pressure relief valve 29f Check valve 30 Canister 30f Canister Positive pressure holding check valve 30i Canister negative pressure holding check valve 31 Pressure sensor 33 Purge control valve 38 Microcomputer 39 Warning light 40 Fuel temperature sensor 42 Water temperature sensor

Claims (1)

[Claims] 1. An evaporation purging 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 into an intake passage of an internal combustion engine through a purge passage. In a failure diagnostic device for an evaporative purge system, which detects a pressure in an evaporative path in a purge system by a pressure detecting means, a failure diagnostic device for an evaporative purge system is provided in an evaporative path between the canister and a fuel tank, and the tank internal pressure of the fuel tank is First valve means communicating from the fuel tank in the direction of the canister when the value is equal to or more than a first predetermined value, and communicating from the canister in the direction of the fuel tank when the tank internal pressure is equal to or less than the second value, and an atmosphere opening path of the canister. When the internal pressure of the canister is equal to or lower than a third predetermined value, the canister is connected in the direction of the canister from the atmosphere. And a second valve means communicating with the canister in the direction of the atmosphere when the internal pressure of the canister is equal to or higher than a fourth predetermined value, and the pressure detecting means is connected to the evaporation path on the fuel tank side of the first valve means. A failure diagnosis apparatus for an evaporative purge system, wherein the failure diagnosis apparatus is provided for performing a failure diagnosis of the evaporative purge system based on an output value of the pressure detecting means.