JPH0658213A - Failure diagnosis device for evapo-purge system - Google Patents

Abstract

PURPOSE:To prevent fluctuation of an air-fuel ratio at the introducing time of negative pressure in a device which judges failure of an evapo-purge system for purging evaporated fuel (vapor) in an internal combustion engine to an intake system for the purpose of combustion. CONSTITUTION:In order to diagnose occurrence of failure, an inner tank pressure switching valve 34 and a canistor atmosphere port VSV 36 are respectively closed first, and a purging side VSV 38 is opened. Negative pressure is introduced from the purging side VSV 38 to vapor passages 32a, 32b, and adsorption fuel in a canistor 33 is suctioned into an intake passage. After a specified time, the inner tank pressure switching valve 34 is opened, and the negative pressure in the intake passage is introduced into an evapo system to a fuel tank 30.

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 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 leaks into the atmosphere through the canister air inlet. Therefore,
It is necessary to diagnose whether such an evaporative purge system has a failure.

Therefore, the present applicant previously filed Japanese Patent Application No. 3-138.
No. 002 has a first control valve that opens and closes a purge passage that purges the evaporated fuel stored in the canister into the intake system of the internal combustion engine, and a second control valve that opens and closes the atmospheric hole of the canister. After closing the second control valve during failure diagnosis,
Failure diagnosis of the evaporative purge system in which the first control valve is closed after a predetermined negative pressure is reached, the airtightness is maintained for a predetermined time, and whether or not a failure has occurred is diagnosed based on the degree of change in pressure at that time. Proposed a device.

[0004]

However, in the failure diagnosis device proposed by the applicant of the present invention, after the atmospheric hole of the canister is shut off by the second control valve for the purpose of failure diagnosis,
Since the first control valve is opened to introduce the negative pressure of the intake passage into the system, negative pressure is applied to the entire evaporation system from the first control valve to the fuel tank at one time. Both the vapor generated in the fuel tank and the vapor desorbed from the activated carbon in the canister are sucked into the intake passage at the same time, resulting in a rough air-fuel ratio, deteriorating drivability and exhaust emission. Will end up.

The present invention has been made in view of the above points,
An object of the present invention is to provide a failure diagnostic device for an evaporative purge system that solves the above problems by introducing a negative pressure stepwise.

[0006]

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 11 is transferred to the vapor passage 12
In the device for diagnosing the failure of the evaporative purge system in which the adsorbent in the canister 13 is adsorbed by the adsorbent in the canister 13 and the adsorbed fuel in the canister 13 is purged into the intake passage 15 of the internal combustion engine 10 through the purge passage 14 in a predetermined operation, the pressure introducing means 17 And a pressure detecting means 18 for detecting the pressure in the evaporation system 16 from the purge passage 14 to the fuel tank 11.
And the determination means 19 is provided.

Here, the pressure introducing means 17 first introduces a negative pressure in the intake passage 15 to at least a part of the evaporation system 16 from the purge passage 14 to the fuel tank 11 that does not include the fuel tank 11. After that, the negative pressure is introduced stepwise so that the negative pressure is introduced into the entire evaporation system 16.

The pressure detecting means 18 detects the pressure in the evaporation system 16. Further, when the negative pressure is introduced into the entire evaporation system by the pressure introducing means 17, the determining means 19
Based on the negative pressure value detected by the pressure detecting means 18, the degree of change in the pressure in the evaporation system 16 is measured, and it is determined whether or not there is a failure in the evaporation purge system from the comparison result of the measured value and the determination value. .

[0009]

In the failure diagnosis, the negative pressure of the intake air is introduced by the pressure introducing means 17 into a part of the evaporation system 16 and then into the entire evaporation system 16 including the fuel tank 11. Therefore, in the present invention, the amount of vapor sucked from the purge passage 14 into the intake passage 15 with a single negative pressure introduction can be made smaller than in the conventional case.

[0010]

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

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

The fuel tank 30 is the fuel tank 11 described above.
Corresponding to, and contains the fuel 45. 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 a positive pressure, and the amount of vapor generation 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 (corresponding to the canister 13) is of a type in which a vapor introduction port 33a and a purge port 33b are communicated in the same space, the inside thereof is filled with activated carbon 33c as an adsorbent, and part of the atmosphere An 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 in order to introduce a negative pressure into the fuel tank 30, the inlet and the guide of the fuel tank internal pressure control valve 31 are introduced. 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.

The atmosphere introducing hole 33d of the canister 33 is communicated with a canister atmosphere hole vacuum switching valve (VSV) 36 through an atmosphere passage 35. The canister atmosphere hole VSV36 is a microcomputer 21.
Based on the control signal of the
It is a control valve that connects or disconnects between and.

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 control 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.

The microcomputer 21 is a control device which realizes the pressure introducing means 17 and the judging means 19 together with the VSVs 34 and 36 by software processing, as shown in FIG.
It 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, the microcomputer 21
Is a central processing unit (CPU) 50, a read only memory (ROM) 51 storing a processing program, a random access memory (RA) used as a work area.
M) 52, a backup RAM 53 that retains 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, etc., which are connected via a bidirectional bus 57. It is connected.

The input interface circuit 54 sequentially switches the intake air amount detection signal from the air flow meter 23, the detection signal from the throttle position sensor 28, the pressure detection signal from the pressure sensor 40, etc., and synthesizes them in time series. The signal is supplied to a single A / D converter 56 for analog-to-digital conversion, and then sequentially sent to the bus 57.

The input / output interface circuit 55 receives a detection signal from the throttle position sensor 28 and 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. The valve 29, the tank internal pressure switching valve 34, the canister atmosphere hole VSV 36, the purge side VSV 38, and the warning lamp 41 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 the purge control routine of FIG. The purge control routine is executed, for example, as a part of the main routine, and whether the engine cooling water temperature THW of the internal combustion engine has warmed up to a predetermined value A or more by the output of a water temperature sensor (not shown) (step 101), or the air-fuel ratio feedback (F /
B) Whether it is being executed (step 102) or idling based on the output of the throttle position sensor 28 (step 103) is determined, and if any one of these cases is not satisfied, the purge side VSV 38 is shut off. If all of these conditions are satisfied (step 104), the purge side VSV 38 is opened (step 105).

When step 104 or 105 is processed, subsequently, the canister atmosphere hole VSV36 is opened (step 106). The tank internal pressure switching valve 34 is always closed. As a result, the above step 101
Purge is not executed unless the operating condition satisfies all of the three conditions determined in ~ 103, and the purge is executable when the operating condition satisfies all the three conditions.

That is, the tank internal pressure in the fuel tank 30 increases according to the amount of vapor generated, 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 above-mentioned 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 the atmosphere is released. Canister atmosphere hole VSV3 from the inlet 36a
6, the atmosphere is sent into the canister 33 through the atmosphere passage 35 and the atmosphere introduction hole 33d.

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.

Next, the failure diagnosis of the evaporative purge system that performs the above operation will be described. In this case, the CPU 50 of the microcomputer 21 activates the failure diagnosis routine shown in FIGS. 5 and 6 every 65 ms, for example, according to the program stored in the ROM 51. In the figure, first, it is checked whether the execution flag is set (the value is "1") (step 201). Since the execution flag is cleared (the value is "0") by the initial routine at the time of starting the engine, it is not initially set, so the next step 202
Go to.

In step 202, it is checked whether or not the tank side pressure release is in progress by checking whether or not the tank side pressure release flag is set. Since the tank side depressurizing flag has been cleared by the initial routine, it is initially determined that the tank side depressurizing is not in progress, that is, the purging system for introducing the negative pressure to the fuel tank 30 is not depressurized, and the next step 203 Go to.

In step 203, it is checked whether a leak determination flag, which will be described later, is set. Since the leak determination flag is also cleared by the initial routine, it is not initially set, and the tank internal pressure switching valve 34 is initially set.
Is released (step 204), the first timer is added (step 205), and it is determined whether or not the value is a value after γ minutes have passed (step 206). If γ minutes has not elapsed, this routine is once ended.

[0030] When made as schematically shown in FIG. 7 (B) opening of the tank internal pressure switching valve 34 in step 204 at time t _1, at time t ₁ as shown in FIG. (C) the canister atmospheric hole VSV36 Is in an open state and the purge side VSV 38 is in a closed (shut off) state. Therefore, the fuel tank 30 has vapor passages 32d and 32c, a tank internal pressure switching valve 34, a vapor passage 32b, a canister 33 and a canister atmosphere hole VSV3.
6 will be communicated with the atmosphere inlet 36a,
The tank internal pressure of the fuel tank 30 which has been controlled to the set pressure by the fuel tank internal pressure control valve 31 until then is shown in FIG.
As shown in (A), the pressure changes from the positive pressure to the atmospheric pressure from time t ₁ .

Thereafter, the failure diagnosis routine of FIGS. 5 and 6 is started several times, and it is determined from the value of the first timer that a predetermined time γ has elapsed after the tank internal pressure switching valve 34 was opened. Then (step 206), step 20 in FIG.
At 7 the positive pressure Y (Pa) is determined based on the detection signal of the pressure sensor 40, and the tank internal pressure is determined as the introduction pressure of the negative pressure.
It is determined whether or not

When the tank internal pressure is more positive than Y (Pa), the fuel vapor generation amount is large, it is estimated that there is no leakage, and accurate failure diagnosis is impossible, so failure diagnosis is performed until the next starting opportunity. Canister atmosphere hole VSV
Open 36 (step 228), shut off the tank pressure switching valve 34 (step 229), clear various timers (step 229).
230) and set the execution flag (step
231) and clear the leak determination flag (step 232
), And ends this routine.

In step 207, when the tank internal pressure is equal to or lower than Y (Pa), that is, when the tank internal pressure is an atmospheric pressure or a negative pressure side value than Y (Pa), the amount of vapor generated is small, and it is judged that accurate failure diagnosis is possible and the negative pressure is determined. Start setting.

First, the tank internal pressure switching valve 34 and the canister atmosphere hole VSV36 are shut off (steps 208 and 209), and the purge side VSV38 is opened (step 210). As a result, the negative pressure of the surge tank 26 passes through the purge passage 39, the purge-side VSV 38, and the purge passage 37, and the canister 3 is discharged.
3 and further to the vapor passages 32a and 32b. Here, the negative pressure introduced into the vapor passage 32a closes the fuel tank internal pressure control valve 31, and the negative pressure introduced into the vapor passage 32b is blocked by the tank internal pressure switching valve 34 in step 208. Negative pressure is fuel tank 3
It is never introduced to zero.

Therefore, in this embodiment, the purge side VSV 38 is used.
Of the evaporative system from the fuel tank to the fuel tank 30, the purge side V
First, the negative pressure is introduced into only a part of the evaporation system from the SV 38 to the vapor passages 32a and 32b. As a result, the vapor adsorbed on the activated carbon 33c in the canister 33 is desorbed at this time, and the purge passage 37 and the purge side VSV 38 are removed.
And the intake passage 27 is drawn into the intake manifold 27 from the surge tank 26 through the purge passage 39.
The vapor in 0 is not sucked.

Tank internal pressure switching valve 3 in step 208 above
4 shut off, step 209 canister vent VSV36
Assuming that the shut-off of the valve and the opening of the purge-side VSV 38 in step 210 are performed at time t _{2 as} schematically shown in FIGS. 7 (B), (C) and (D), then in step 211 of FIG. The second timer is added, and in step 212 it is determined whether the value of the second timer after addition is less than or equal to η minutes.

Time t₂From η minutes to step
The process from 208 to 212 is repeated and a part of the above evaporative system
By continuing to introduce the negative pressure to the canister 33
The inner vapor is made almost empty. When η minutes have passed,
Time t determined in step 212 ₃Then, as shown in FIG.
As shown, the tank internal pressure switching valve 34 is opened (step 213
 ), This allows the tank pressure to be cut off from the purge side VSV38.
Exchange valve 34, vapor passages 32c and 32d, and fuel tank 3
Negative pressure is introduced into the entire evaporative system including zero.

Therefore, after the time t ₃ , the vapor in the fuel tank 30 is sucked from the surge tank 26 to the intake manifold 27 while a part of the vapor is adsorbed by the activated carbon 33c in the canister 33. As shown in FIG. 7 (A), when there is no leak in the evaporation system, the pressure changes in the negative pressure direction. The above steps 208 to 213 together with the VSVs 34, 36 and 38 are the pressure introducing means 17
Are configured.

Subsequently, in step 214 of FIG. 6, the tank internal pressure is set to the diagnostic start pressure X based on the detection signal of the pressure sensor 40.
It is determined whether or not (Pa) or less, and when the tank internal pressure is a value on the atmospheric pressure side of the negative pressure X (Pa), the negative pressure setting is further continued, so after setting the tank side pressure releasing flag (step 215). ), And once ends this routine. 65ms until the tank internal pressure becomes larger than X (Pa) on the negative pressure side
The above steps 201, 202, 214, and 215 are repeatedly executed every time. When it is determined in step 214 that the tank internal pressure has become larger than X (Pa) on the negative pressure side, the tank side pressure releasing flag is cleared (step 216) and then the purge side VSV 38 is shut off (step 217).

VSV38 on the purge side in step 217
7D is assumed to be performed at time t ₄ as schematically shown in FIG. 7D, since both VSVs 36 and 38 are closed, the pressure in the evaporation system from the purge side VSV 38 to the fuel tank 30 is reduced. When the system has no failure, it is kept airtight and gradually drops to the atmospheric pressure side. When the purge-side VSV 38 is shut off in step 217, the processing of the determination means 19 is realized by the following steps 218 to 225.

That is, first, it is determined whether or not the leak determination timer is "0" (step 218). Since the leak determination timer has been cleared to "0" by the initial routine described above, when the determination at step 218 is first made, it is determined as "0" and the routine proceeds to step 219, where the pressure sensor 40 The current detection value of the diagnostic start pressure value P
_It is stored in the RAM 52 as _S.

Subsequently, a predetermined value is added to the value of the leak determination timer (step 220), the leak determining flag is set to "1" (step 221), and this routine is ended. Then, when this routine is started again next time, since it is determined in step 203 in FIG. 5 that the leakage is being determined, step 20 is executed.
Jump from 4 to 216, and further through step 217 to step 218.

This time, it is determined in step 218 that the leak determination timer is not "0", so it is determined whether the value of the leak determination timer is equal to the diagnostic time (leak determination time) α (step 222), and when the time α has not yet come, this routine is ended via steps 220 and 221.

In this way, steps 201 to 203, 21
Processing of 7, 218, 222, 220, and 221 is repeated every 65 ms.
And the value of the leak determination timer corresponds to the leak determination time α.
When it reaches a value, the detected value of the pressure sensor 40 at that time is diagnosed.
End pressure value P_EStored in the RAM 52 as (step
223). The pressure value read from the RAM 52
P _S, P_EBased on (P_E-P_S) / Α (seconds)
The rate of change of pressure is calculated from the equation (step 224).

Subsequently, it is judged whether or not the calculated change rate is equal to or larger than a predetermined threshold value β (step 225). When it is equal to or larger than β, it is judged that the leakage is large and abnormal because the pressure change is large. Then, turn on the warning lamp 41 (step 22
6) After notifying the driver of the occurrence of a failure in the evaporative purge system, the leak failure fail code is stored in, for example, the backup RAM 53 (step 227) and the process proceeds to step 228. The leak failure fail code is read from the backup RAM 53 at the time of subsequent repair, and informs the cause of failure of the evaporative purge system. On the other hand, the calculated rate of change is β
If it is judged to be less than the specified value, it is judged to be normal because the leakage is below the specified value, and steps 226 and 227 are jumped to step 228.

When the presence or absence of a failure in the evaporative purge system is determined as described above, subsequently, the canister atmosphere hole VSV36 is opened (step 228) to release the negative pressure closed state of the evaporative system, and the fuel tank is further opened. In order to make the operation of the internal pressure control valve 31 effective, the tank internal pressure switching valve 34
Is cut off (step 229).

As a result, the atmosphere is introduced into the system from the atmosphere introduction port 36a of FIG. 2 through the canister atmosphere hole VSV36 and the canister 33, so that the tank internal pressure is a positive pressure depending on the state of vapor generation via atmospheric pressure in a short time. Changes to.

Thereafter, the various timers and the leak determination timer are cleared (step 230), the execution flag is set to "1" (step 231), and the leak determination flag is cleared to "0" (step 232). Then, the failure diagnosis process ends. After that, even if this routine is started, step 201
Since the execution flag is determined to be "1" in step 1, this routine is not executed until it is restarted thereafter.

As described above, according to this embodiment, when the negative pressure of the intake system is introduced into the evaporative system at the time of failure diagnosis,
First, from the purge-side VSV 38 to the vapor passages 32a and 32
The negative pressure is introduced only to part of the evaporative system that does not include the fuel tank 30 up to b so that the adsorption vapor in the canister 33 is sucked into the surge tank 26, and then the evaporative system that includes the fuel tank 30. Since the negative pressure is introduced into the entire tank so that the vapor in the fuel tank 30 is sucked into the surge tank 26, the vapor pressure in the negative pressure is introduced at the time of introducing the negative pressure at the time of failure diagnosis as compared with the apparatus proposed by the applicant. Since it is possible to reduce the amount of vapor suction, the roughness of the air-fuel ratio is suppressed to a small level,
Therefore, deterioration of exhaust emission can be significantly reduced.

8 and 9 are flowcharts showing a second embodiment of the failure diagnosis routine of the essential part of the present invention.
The same processing steps as those in FIGS. 5 and 6 are designated by the same reference numerals,
The description is omitted. In FIG. 8, in step 212, η
When it is determined that the minutes have elapsed, the VSV 38 on the purge side is shut off (step 301), the negative pressure is held in the canister 33, and then the tank internal pressure switching valve 34 is opened to open the canister 33.
The negative pressure is introduced into the fuel tank 30 (step 302).

Subsequently, the third timer is added (step
303), and it is determined whether or not the value of the third timer after addition is equal to or less than θ minutes (step 304). Purge side VSV38
9 is shut off and the state where the tank internal pressure switching valve 34 is opened has elapsed by θ minutes, the routine proceeds to step 214 in FIG. 9, and the same processing as in FIG. 6 is executed thereafter.

In this embodiment, after the negative pressure of the surge tank 26 is temporarily stored in the canister 33, the negative pressure is introduced into the fuel tank 30 by using the canister 33 as a negative pressure source so that the tank internal pressure becomes X.
Step until the pressure becomes larger on the negative pressure side than (Pa)
The processes of 208 to 212 and 301 to 304 are repeated. This embodiment also has the same effect as the first embodiment.

The present invention is not limited to the above embodiment, and for example, the canister may be of a type in which the vapor introduction port and the purge port do not communicate in the same space. Further, the pressure sensor 43 may be directly attached to the fuel tank 30, or the vapor purging portion may be an intake passage portion near the throttle valve 25.

[0054]

As described above, according to the present invention, when the negative pressure is introduced, the negative pressure is introduced stepwise into the evaporative system. Therefore, the amount of vapor introduced into the intake passage can be controlled at every introduction of the negative pressure. It has a feature that it can be reduced compared to the applicant's previous proposed device, thus preventing the air-fuel ratio from becoming rough when introducing negative pressure, and preventing deterioration of drivability and exhaust emission.

[Brief description of drawings]

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

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

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

FIG. 4 is a flowchart showing a purge control routine.

FIG. 5 is a flow chart (No. 1) showing a first embodiment of a failure diagnosis routine which is an essential part of the present invention.

FIG. 6 is a flowchart (No. 2) showing the first embodiment of the failure diagnosis routine which is the main part of the present invention.

FIG. 7 is a time chart for explaining the operation of FIGS. 5 and 6.

FIG. 8 is a flowchart (No. 1) showing a second embodiment of the failure diagnosis routine which is the main part of the present invention.

FIG. 9 is a flowchart (No. 2) showing a second embodiment of the failure diagnosis routine which is the main part of the present invention.

[Explanation of symbols]

10 Internal Combustion Engine 11,30 Fuel Tank 12,32a to 32d Vapor Passage 13,33 Canister 14,37,39 Purge Passage 15 Intake Passage 17 Pressure Introducing Means 18 Pressure Detecting Means 19 Judgment Means 21 Microcomputer 31 Fuel Tank Internal Pressure Control Valve 34 Tank internal pressure switching valve (VSV) 35 Atmosphere passage 36 Canister Atmosphere hole Vacuum switching valve (VSV) 38 Purge side vacuum switching valve (V
SV) 40 Pressure sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akinori Nagauchi 1st Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (1)

[Claims] 1. A failure of an evaporation purge system for adsorbing evaporated fuel from a fuel tank to an adsorbent in a canister through a vapor passage and purging the adsorbed fuel in the canister through a purge passage into an intake passage of an internal combustion engine during a predetermined operation. In the device for diagnosing, the negative pressure of the intake passage is first introduced into a part of the evaporative system that does not include at least the fuel tank in the evaporative system from the purge passage to the fuel tank, and then the entire evaporative system is introduced. Pressure introducing means for introducing the negative pressure stepwise so as to introduce the negative pressure, pressure detecting means for detecting the pressure in the evaporation system, and introducing the negative pressure to the entire evaporation system by the pressure introducing means. At this time, based on the negative pressure value detected by the pressure detection means, measure the degree of change in pressure in the evaporative system, between the measured value and the judgment value. A failure diagnosis device for an evaporative purge system, comprising: a determination unit that determines whether or not there is a failure in the evaporative purge system based on a comparison result.