JP3501207B2 - Failure diagnosis device for fuel evaporative gas treatment 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 diagnosing apparatus for a fuel evaporative gas treatment system, and more particularly to a failure diagnosing apparatus capable of diagnosing a failure not only while the vehicle is running but also when the vehicle is stopped.

[0002]

Related Background Art Fuel (hydrocarbons) vaporized in a fuel tank may be released to the atmosphere. Therefore, a vehicle is equipped with a fuel evaporative gas treatment system that includes a canister having activated carbon for adsorbing the fuel evaporative gas to prevent the emission of the fuel evaporative gas. The canister is provided with an introduction port that communicates with the fuel tank, an exhaust port that communicates with the intake pipe of the engine, and a vent port that opens to the atmosphere. The fuel evaporative gas in the fuel tank is introduced into the canister when the engine is stopped and adsorbed by the activated carbon, and is separated from the activated carbon by the purge air introduced from the vent port during the subsequent engine operation and is sucked into the intake pipe together with the purge air, and the cylinder of the engine. Burns inside.

As a failure diagnosis of the fuel evaporative gas treatment system, there is, for example, the one disclosed in Japanese Patent Application Laid-Open No. 7-127532. This failure diagnosis device opens and closes the canister to the atmosphere when the vehicle speed is within a predetermined range and the conditions for leak diagnosis start such as small vehicle speed fluctuations are met so that the output torque of the engine does not fluctuate and the exhaust characteristics do not deteriorate. Valve is closed, the purge solenoid valve is duty driven to bring the inside of the fuel tank into a negative pressure state, the purge solenoid valve is closed when the inside of the fuel tank reaches a predetermined pressure, and the leak state is caused by the pressure change after closing. I am trying to detect.

[0004]

However, the above-mentioned conventional failure diagnosis device satisfies certain predetermined execution conditions while the vehicle is running in order to prevent deterioration of exhaust characteristics and drivability accompanying the execution of the failure diagnosis. It is configured so that the failure diagnosis can be performed only when the failure occurs. Therefore, in the case of a vehicle equipped with a conventional device, when a failure diagnosis is performed in a reproduction test or a confirmation test at a repair shop, it is essential to drive the vehicle in an operating state where the failure diagnosis execution condition is satisfied. However, it is not practical to drive the vehicle every time the reproduction test or the confirmation test is performed.

Further, it is desirable to carry out a failure diagnosis of the fuel evaporative gas treatment system at the time of shipping the vehicle on the vehicle production line, but for the same reason as in the case of the failure diagnosis at the time of repairing the vehicle, the total number of the shipped vehicles is reduced. It is difficult to carry out a failure diagnosis. Therefore, an object of the present invention is to provide a failure diagnosis device capable of determining whether or not there is a failure in the fuel evaporative gas treatment system not only while the vehicle is traveling but also when the vehicle is stopped.

[0006]

According to the failure diagnosis apparatus of the present invention, a vehicle equipped with a fuel evaporative gas treatment system for introducing fuel evaporative gas generated in a fuel tank into an intake pipe through a canister is running. When it is determined that the vehicle is traveling in an operating state that satisfies the condition for performing the fault diagnosis of
And, when it is determined that the external signal for instructing the failure diagnosis is supplied, the controller of the failure diagnosis device allows the failure diagnosis of the fuel evaporative gas treatment system to be executed , and the external signal Vehicle failure diagnosis according to
The failure diagnosis procedure according to the establishment of the failure diagnosis execution condition
The feature is that the procedure is simpler .

In the failure diagnosis apparatus of the present invention, the failure diagnosis is carried out not only when the conditions for carrying out the failure diagnosis while the vehicle is traveling are satisfied, but also when an external signal is applied to the control section. Unlike the case of failure diagnosis while the vehicle is running, in the case of failure diagnosis responding to an external signal, there are few requests to prevent deterioration of drivability and deterioration of exhaust characteristics accompanying the execution of failure diagnosis. In other words, the failure diagnosis responding to the external signal does not require the vehicle running that satisfies the failure diagnosis execution condition to be the failure diagnosis execution requirement, and only the application of the external signal to the control unit is the execution requirement.
Therefore, even when the vehicle travel is stopped, the failure diagnosis can be performed as long as the external signal is applied to the control unit. here,
For the application of the external signal, for example, a special tool usually provided in a shipping process of a production line or a repair shop is used.
As a result, even when the vehicle is shipped or repaired, the failure diagnosis of the fuel evaporative gas treatment system can be performed while the vehicle is stopped. Moreover, unnecessary failure diagnosis is not performed.

When the control section determines the supply of the external signal,
Fault diagnosis is simpler than the fault diagnosis procedure while the vehicle is running.
Implement disconnection. Preferably, the failure diagnosis device of the present invention is
A first opening / closing valve provided in a vent passage of the canister for adsorbing fuel evaporative gas generated in the fuel tank; a second opening / closing valve provided in a purge passage communicating between the canister and the intake pipe of the internal combustion engine; And a pressure detector for detecting an internal pressure of a closed space formed in the fuel evaporative gas treatment system when the first and second opening / closing valves are closed. The control unit of the failure diagnosis device performs failure diagnosis based on the internal pressure detected by the pressure detector.

More preferably, in the failure diagnosis, the control unit closes the first opening / closing valve and opens the second opening / closing valve during operation of the internal combustion engine to form a negative pressure in the fuel tank, and then the second opening / closing. The valve is closed, and the failure diagnosis is performed based on the subsequent change in the fuel tank internal pressure. According to the above-described preferable device configuration, an abnormality such as a leak from the fuel tank can be reliably detected.

In the present invention, preferably, when the supply of the first external signal for instructing the execution of the failure diagnosis at the time of vehicle repair is determined, the control unit permits the execution of the failure diagnosis in the first diagnosis mode. When the supply of the second external signal for instructing the execution of the failure diagnosis at the time of shipping the vehicle is determined, the control unit determines that the second
Allows fault diagnostics to be performed in diagnostic mode . The procedure of failure diagnosis in the first diagnostic mode simplified than that of the failure diagnosis in the vehicle running, it is preferable to simplify than in the procedure of the failure diagnosis in the second diagnostic mode the first diagnostic mode . The simplification of the failure diagnosis procedure is achieved, for example, by forming a negative pressure for the failure diagnosis within a short time.

According to the above-described preferable apparatus configuration, the failure diagnosis at the time of repairing the vehicle can be easily performed in a short time, and the failure diagnosis at the time of shipping the vehicle can be performed more easily within a short time.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A failure diagnosis apparatus according to an embodiment of the present invention will be described below with reference to FIG. In FIG. 1, a fuel evaporative emission gas treatment system equipped with a failure diagnosis device includes a canister 6 containing activated carbon for adsorbing the fuel evaporative emission gas. The canister 6 is an introduction port 6 for introducing the fuel evaporative gas in the fuel tank 5.
a, a discharge port 6b for discharging the fuel evaporative gas to the intake pipe 2 of the engine 1, and a vent port 6c for introducing the atmosphere.

The introduction port 6a is connected via a pipe 11 to
It is connected to a port 5 a provided on the upper surface of the fuel tank 5. The exhaust port 6b is connected to the intake pipe 2 via the pipe 12.
It is connected to the purge port 2a provided on the pipe wall. The purge port 2a is provided at a position arranged downstream of the throttle valve 3. And the pipe 12
The normally closed purge solenoid valve 1 as the second on-off valve
4 (second valve means) is arranged. Vent port 6
c communicates with one port of the normally open type vent solenoid valve 15 as the first opening / closing valve through the pipe 19, and the solenoid valve 15
The other port of the (first valve means) is open to the atmosphere. The solenoid valves 14 and 15 are electronic control units (ECU)
It is connected to the output side of the ECU 20 and is opened and closed under the control of the ECU 20.

In the fuel evaporative gas treatment system having the above structure, while the engine 1 is stopped, for example,
The normally-closed purge solenoid valve 14 and the normally-open vent solenoid valve 15 are deenergized so that the purge solenoid valve 14 is closed and the vent solenoid valve 15 is opened. Then, the fuel evaporative gas in the fuel tank 5 flows into the canister 6 and is adsorbed on the activated carbon.

During the subsequent engine operation, the intake negative pressure generated in the intake pipe 2 is introduced into the pipe 12. afterwards,
The engine 1 preferably supplies the fuel evaporative gas to the intake pipe 2
When the operating state is such that excessive engine torque fluctuation does not occur even if the intake valve is inhaled, the purge solenoid valve 14 is urged to open and the intake negative pressure acts on the canister 6. As a result, when the internal pressure of the canister 6 becomes lower than the atmospheric pressure, the atmosphere (purge air) flows into the canister 6, the fuel evaporative gas adsorbed by the activated carbon is separated from the activated carbon by the purge air, and the inside of the intake pipe 2 together with the purge air. And is burned in the cylinder of the engine 1.

In connection with the failure diagnosis process described later, the fuel evaporative gas treatment system includes a throttle sensor 16 for detecting the throttle valve opening θt, and a pipe 18 to a port 5b provided on the upper surface of the fuel tank 5. A pressure sensor 17 (pressure detection means) that communicates with each other to detect the tank internal pressure,
It is provided with an ECU 20 that performs a failure diagnosis process, and a warning lamp 30 that notifies that there is a failure in the system. The sensors 16 and 17 are connected to the input side of the ECU 20, and the warning lamp 30 is connected to the output side of the ECU 20.

The ECU 20 includes a processor, a memory, an interface circuit, a timer and the like, and has various control functions such as a fuel injection amount control function and a bypass air amount control function in addition to the failure diagnosis function. In connection with the fuel injection amount control, on the input side of the ECU 20, in addition to the throttle sensor 16, an engine speed sensor for detecting engine speed Ne, engine water temperature Tw, intake air amount, a water temperature sensor, an air flow sensor, etc. (Both not shown) are connected, and injectors (one of which is shown by reference numeral 8 in FIG. 1) provided in each cylinder of the engine 1 are connected to the output side. The ECU 20
A fuel injection amount suitable for the engine operating state determined based on the detection signals input from these sensors is calculated, and the injector is driven to open for a valve opening time corresponding to the fuel injection amount. In connection with the bypass air amount control, the bypass passage 2b and the bypass passage 2b
EC of the amount of bypass air supplied to the engine 1 via the
A control valve 2c for adjusting under the control of U20 is provided.

In FIG. 1, reference numeral 40 represents a multi-user tester (more generally, a special tool for external signal input) that can be connected to the determination signal output terminal 21 and the external signal input terminal 22 of the ECU 20. The determination signal output terminal 21 is used for supplying a code signal indicating a failure diagnosis result (normality determination or abnormality determination) from the ECU 20 to the tester 40, and the external signal input terminal 22 is an external signal for instructing execution of the failure diagnosis. Is used to apply from the tester 40 to the ECU 20.

The ECU will now be described with reference to FIGS. 2 to 9.
The failure diagnosis process by 20 will be described. In addition to the normal failure diagnosis (first failure diagnosis method) performed while the vehicle is running, the failure diagnosis apparatus of the present embodiment has a special signal input tool in a repair shop such as a dealer, such as the tester 40 illustrated in FIG. When a first external signal (external signal for dealer mode) for instructing execution of failure diagnosis during vehicle repair is applied from the ECU to the ECU 20, or for execution of failure diagnosis during vehicle shipment in the shipping process of the vehicle production line The failure diagnosis (second failure diagnosis method) is executed even when the second external signal (external signal for line-off mode) is applied. The first and second external signals may be predetermined code signals.

The failure diagnosis process is started, for example, when the ignition key is turned on to start the engine. First, in step S2 of FIG. 2, it is determined whether or not the start of the engine 1 is completed. Preferably,
It is determined whether or not a predetermined time, for example, 5 seconds has elapsed from the time when the engine start was completed. If the start of the engine is not completed, it is determined that proper failure diagnosis cannot be performed, and the control flow returns to "start" in FIG.

When the engine start is completed, it is judged whether or not a line-off mode external signal is supplied to the ECU 20 via the external signal input terminal 22 (step S).
4) If the signal is not supplied, it is determined whether the dealer mode external signal is supplied (step S6). Then, if no external signal is supplied, it is next determined whether or not the condition for carrying out the failure diagnosis while the vehicle is traveling is satisfied (step S8).

The failure diagnosis while the vehicle is traveling is substantially performed once, for example, after the engine 1 is started and stopped. More specifically, it is performed when the engine 1 is first operated after the engine is started, for example, in a specific operating state in which the intake air amount increases to a considerable extent, for example, in the air-fuel ratio feedback region. Therefore, in step S8, EC
By referring to a flag (not shown) stored in the memory of U20, it is first judged whether or not the failure diagnosis while the vehicle is running is completed. If the failure diagnosis is not completed, the failure diagnosis execution condition is satisfied. Is determined. In this embodiment, in order to prevent the air-fuel ratio of the air-fuel mixture from fluctuating excessively due to the fuel vaporized gas sucked into the engine 1 in accordance with the execution of the failure diagnosis, the engine 1 is supplied with intake air of a predetermined amount or more. The failure diagnosis is executed only when the engine 1 is operated in such a specific operation state as described above. Therefore, an air flow sensor (A
Based on the FS) output, it is determined whether or not the current engine operating state is suitable for performing the failure diagnosis. That is, if the AFS output is less than or equal to the predetermined value, it is determined that the engine 1 is not in the specific operation state, and the control flow returns to "start" in FIG.

After that, when it is determined in step S8 that the condition for carrying out the failure diagnosis while the vehicle is running is determined, the failure diagnosis in the normal mode (specifically, the subroutine shown in FIGS. 3, 4 and 5) is carried out ( Step S10). Prior to the start of substantial failure diagnosis, in the present embodiment, it is determined whether or not the degree of fuel evaporation in the fuel tank 5 is suppressed to the extent that it does not hinder proper failure diagnosis or deteriorate exhaust characteristics. The determination is made based on the tank internal pressure change ΔP1 (see FIG. 9) from the start of diagnosis until the predetermined time T1 elapses.

Therefore, first, the pressure sensor output indicating the fuel tank internal pressure P1 at the start of the failure diagnosis is read (step S102), the vent solenoid 15a is turned on and the normally open type vent solenoid valve 15 is closed (step S102). S
104), and is started after the timer for measuring the elapsed time from the time when the vent solenoid valve 15 is closed is reset.
That is, the timer is restarted (step S10).
6). At this time, the normally closed purge solenoid valve 14 is closed, the inside of the fuel tank 5 communicating with the atmosphere via the vent solenoid valve 15 is shut off from the outside, and the tank internal pressure is as shown in FIG.
It gradually rises as shown in.

Then, in step S108, a predetermined time T1
When the progress of is judged, the pressure sensor output representing the tank internal pressure P2 at that time is read (step S11).
0), the tank internal pressure P1 detected in step S102 is subtracted from the tank internal pressure P2 to calculate the pressure change ΔP1 within the predetermined time T1 (step S112). Next, it is determined whether or not this pressure change ΔP1 is smaller than the allowable pressure change ΔP01 (step S114). If the pressure change is excessive, the vent solenoid 15a is turned off to stop the failure diagnosis process (step S116). ), The control flow returns to "start" in FIG.

On the other hand, when it is determined in step S114 that the pressure change ΔP1 in the fuel tank 5 is within the allowable range, the intake pipe 2 is connected to the fuel tank 5 while duty-controlling the opening degree of the purge solenoid valve 14. And the inside of the fuel tank is gradually decompressed by the negative pressure of intake air. And EC
In U, the purge concentration that maximizes the flow rate so that the exhaust characteristics are not deteriorated due to the enrichment of the air-fuel mixture due to the pressure reduction is calculated, and the on-duty ratio of the purge solenoid 14a is determined based on the result (step S118). . Therefore, there is an effect that the failure diagnosis start timing is advanced and the total failure diagnosis time can be shortened.

Next, it is judged whether or not the negative pressure formation in the fuel tank 5 is completed within a predetermined time T2, that is, whether or not there is a leak in the fuel evaporative gas treatment system, especially in the fuel tank. Therefore, the purge solenoid 14a is turned on (step S120), and the timer for measuring the elapsed time from the start of negative pressure formation is restarted (step S122). Then, the pressure sensor output indicating the tank internal pressure P that gradually decreases as the negative pressure is formed is read (step S124), and it is determined whether or not the tank internal pressure P becomes lower than the predetermined pressure P0 indicating the completion of the negative pressure formation ( Step S126). If the determination result is negative, that is, if negative pressure formation is insufficient, it is determined in step S128 whether or not the predetermined time T2 has elapsed. If the predetermined time T2 has not elapsed, the control flow moves to step S124.

When the purge solenoid 14a is turned on and the purge solenoid valve 14 is opened in step S120, the exhaust port 6b of the canister 6 communicates with the intake pipe 2, and the intake negative pressure acts on the exhaust port 6b of the canister 6. Further, the vent port 6c of the canister 6 is closed by the vent solenoid valve 15 in the closed state, the fuel tank 5 communicates with the intake pipe 2 via the canister 6, and the exhaust of the fuel tank 5 by the intake negative pressure is started. It

Normally, as the exhaust of the fuel tank 5 progresses, the fuel tank internal pressure P sufficiently decreases before the predetermined time T2 elapses, as shown by the solid line in FIG. Therefore, the determination result in step S126 becomes affirmative and the determination result in step S130 becomes negative. In this case, it is further determined whether or not the tank internal pressure P becomes lower than the threshold value P0L lower than the predetermined pressure P0 within the predetermined time T2 (step S132).

On the other hand, if the system has an abnormality such as airtightness, the tank internal pressure gradually decreases as shown by the chain double-dashed line in FIG. If there is a particularly severe airtightness, the tank internal pressure P becomes higher than a threshold value P0H that is higher than the predetermined pressure when the predetermined time T2 has elapsed from the start of negative pressure formation. When there is such an abnormality, the tank internal pressure P after the elapse of the predetermined time T2
Is higher than the threshold value P0H (severe negative pressure formation failure) is determined in step S136, and a failure determination is performed in step S138. Specifically, the failure determination code signal is E
The warning lamp 30 is turned on while being written in the nonvolatile memory of the CU 20. Further, the flag referred to in step S8 is set to a value indicating completion of failure diagnosis. In the next step S140, the purge solenoid 14a is turned off, the purge solenoid valve 14 is closed, and the failure diagnosis process ends.

On the other hand, a predetermined time T2 has passed since the start of negative pressure formation.
When it is determined in step S136 that the tank internal pressure P is not higher than the threshold value P0H at the time when has elapsed, this relatively slight negative pressure formation failure is due to the system airtightness failure or fuel evaporation. If it is impossible to immediately determine whether or not the failure, the failure diagnosis process is temporarily stopped.
In the present embodiment, the number N of times of failure diagnosis processing interruption is counted (step S142), and when the number of times N reaches a predetermined number Nref (for example, 5 times), the failure determination is performed (steps S144 and S138). In addition, when interrupting the failure diagnosis process, after the purge solenoid 14a is turned off and the purge solenoid valve 14 is closed in step S146,
The process proceeds to step S102 and the failure diagnosis is performed again.

It should be noted that a predetermined time T2 has passed since the start of negative pressure formation.
Even if the tank internal pressure P becomes lower than the predetermined pressure P0 before the time elapses, but is not lower than the threshold value P0L and the determination result in step S132 is negative, this slight negative pressure formation defect is caused. The cause of is determined to be undetermined, and the failure diagnosis is similarly interrupted. On the other hand, the predetermined time T
When the tank internal pressure P becomes lower than the threshold value P0L within 2, it is determined that the negative pressure is sufficiently formed without detecting the abnormality, and the purge solenoid 14a is turned off to complete the negative pressure formation. (Step S134), the purge solenoid valve 14 is closed.

The negative pressure stored in the canister 6 and the fuel tank 5 as described above is substantially equal to the negative intake pressure generated in the intake pipe 2 if the fuel evaporative gas treatment system is normal. If the system is out of order, for example, if there is airtightness, the absolute value of the negative pressure becomes smaller than the absolute value of the intake negative pressure. When a negative pressure is formed in the fuel tank 6, the fuel in the fuel tank 6 evaporates. When the fuel evaporative gas treatment system is normal, the internal pressure of the fuel tank gradually rises as shown by the solid line in FIG. On the other hand, if the processing system has poor airtightness, the atmosphere flows into the system, and the tank internal pressure increase speed increases as compared with the normal system, as shown by the chain double-dashed line in FIG.

Therefore, a predetermined time T has passed since the completion of negative pressure formation.
It is determined whether or not the increase change ΔP2 in the tank internal pressure before the lapse of 3 falls below the allowable upper limit value ΔP02, that is, whether or not the internal pressure rise due to poor airtightness is not observed. Therefore, the tank internal pressure P3 at the time of completion of negative pressure formation is detected (step S150), and the timer for measuring the elapsed time from the time of completion of negative pressure formation is restarted (step S1).
52). Then, the tank internal pressure P4 at the time when it is determined in step S154 that the predetermined time T3 has elapsed from the time of forming the negative pressure is detected (step S156), and the tank internal pressure P4 is detected from this tank internal pressure P4 in step S150.
3 is subtracted and the pressure change ΔP2 is calculated (step S158). Furthermore, this pressure change ΔP2 is the allowable upper limit value Δ
It is determined whether or not it falls below P02 (step S16).
0), if this determination result is affirmative, a normal determination is made (step S162). That is, the normality determination code signal is written in the non-volatile memory of the ECU 20, the warning lamp 30 is maintained in the off state, and the flag related to step S8 is set to a value indicating the completion of failure diagnosis. on the other hand,
The pressure change ΔP2 of the allowable upper limit value ΔP02 or more is the step S.
When the determination is made in 160, an abnormality determination is made in step S164 and the failure diagnosis is ended.

When the above abnormality determination is made, the warning lamp 30
When a warning is given by illuminating, the driver often requests a dealer to inspect and repair the vehicle. According to the failure diagnosis apparatus of the present embodiment, the dealer side can easily perform a reproduction test or the like for reconfirming the abnormality of the fuel evaporative gas treatment system mounted on the vehicle without running the vehicle.

That is, when a vehicle equipped with the fuel evaporative gas treatment system for which an abnormality has been determined is brought in, the operator connects the connection terminal of the tester 40 shown in FIG. 1 to the determination signal output terminal 21 of the ECU 20. It is confirmed whether or not the abnormality determination code signal is stored in the nonvolatile memory of the ECU 20. When the abnormality determination code signal representing the abnormality of the fuel evaporative emission gas processing system is confirmed by the tester 40, the worker connects the connection terminal of the tester 40 to the external signal input terminal 22 of the ECU 20 in order to perform the system abnormality reproduction test. After that, the engine 1 of the vehicle is started, and then the tester 40 is operated to output an external signal for dealer mode from the tester 20 to the EC.
Apply to U20.

When the engine 1 is started, the ECU 20 executes the failure diagnosis main routine shown in FIG. When the supply of the dealer mode external signal is determined in step S6 after the engine start is completed, the failure diagnosis in the dealer mode is immediately performed in the vehicle traveling stopped state (step S14). More specifically, in the failure diagnosis subroutine of the dealer mode shown in FIGS. 6 and 7, the rotation speed of the engine 1 which is idle after the engine is started is increased to a predetermined rotation speed suitable for the failure diagnosis, for example, about 2000 rotations per minute. (Step S200). Specifically, E
The CU 20 controls the valve opening time of the fuel injection valve 8 so as to inject an amount of fuel suitable for failure diagnosis in the dealer mode, and at the same time, the control valve 2c to make the amount of bypass air supplied through the bypass passage 2b proper. Drive control. Although it is possible to prevent the involuntary stop of the engine rotation by increasing the engine rotation speed in the failure diagnosis in the dealer mode, it is not essential to carry out the engine rotation increasing step S200.

In the next step S202, the tank internal pressure change ΔP1 from when the vent solenoid valve 15 is closed to when a predetermined time T1 has elapsed is detected. Specifically, step S
In 202, steps S102, S104, S106, S108 and S11 of FIG. 3 relating to the failure diagnosis in the normal mode.
The same processing as 0 and S112 is performed. In the next step S214 and the subsequent steps, substantially the same processing as in the case of the failure diagnosis in the normal mode is executed. However,
6 and 7 collectively show the corresponding steps in FIGS. 3 to 5 collectively.

When it is determined in step S214 that the internal pressure change ΔP1 within the predetermined time T1 is smaller than the allowable upper limit ΔP01, unlike the normal mode in which the on-duty ratio of the purge solenoid 14a is variably set, the purge solenoid is different. The duty ratio of 14a is fixedly set to a first fixed value, such as 40% (step S218), and the purge solenoid 14a is turned on (step S22).
0). As a result, the purge solenoid valve 14 is set in step S218.
The ON operation is performed at the duty ratio of 40% set in step 3. Therefore, the decompression of the fuel tank 5 is performed relatively quickly as compared with the case of the normal mode, and the negative pressure is formed in the fuel tank 5 within a short time. Be seen. The negative pressure forming time in the dealer mode is shortened to, for example, about one-third in the normal mode.

At the next step S226, it is judged if the tank internal pressure P has become lower than the predetermined pressure P0 before the predetermined time T2 has elapsed from the time when the pressure reduction of the fuel tank started.
Specifically, in step S226, steps S122, S124, S126 and S1 of FIG. 4 relating to the normal mode are performed.
30 processes are performed. When the tank internal pressure P becomes lower than the predetermined pressure P0 within the predetermined time T2, the same determination step S232 as step S132 of FIG. 4 is performed.
When it is determined in this step S232 that the tank internal pressure P has become lower than the threshold value P0L within the predetermined time T2, the purge solenoid 14a is turned off in step S234 and the pressure reduction (negative pressure formation) of the fuel tank is completed. .

Then, a predetermined time T has passed since the completion of negative pressure formation.
The tank internal pressure change ΔP2 until 3 has elapsed is detected (step S250). In this step S250, steps S150, S152, S of FIG.
The processing in 154, S156, and S158 is performed. Then, if it is determined in step S260 that the pressure change ΔP2 is smaller than the allowable upper limit value ΔP02, the normal determination is performed (step S262), and if not, the failure determination is performed (step S264).

On the other hand, the internal pressure change ΔP1 within a predetermined time T1 after the vent solenoid valve 15 is closed to check the degree of fuel evaporation in the fuel tank 5 at the time of failure diagnosis is the allowable upper limit value Δ.
If it is determined in step S214 that it is P01 or more, the failure diagnosis is interrupted (step S216). When the failure diagnosis interruption count N reaches the upper limit count Nref (steps S242 and S244), step S238.
In step S240, the purge solenoid 14a is turned off to complete the failure diagnosis.

Further, a predetermined time T2 has passed since the start of negative pressure formation.
When the tank internal pressure P does not drop below the predetermined pressure P0 by the time (step S226), the predetermined time T
When it is determined in step S236 that the tank internal pressure P has exceeded the threshold value P0H when 2 has elapsed, a failure determination is performed (step S238). The tank pressure P is the threshold P0
When it does not exceed H, or when the tank internal pressure P falls below the predetermined pressure P0 but does not fall below the threshold P0L within the predetermined time T2, the failure diagnosis is interrupted.

As described above, the failure diagnosis in the dealer mode is performed in substantially the same manner as in the normal mode. However, by fixing the on-duty ratio of the purge solenoid 14a to a larger value than in the normal mode, the failure diagnosis is completed within a relatively short time. The failure diagnosis apparatus according to the present embodiment is also planned to perform failure diagnosis of the fuel evaporative gas treatment system in the shipping process of the vehicle production line. By carrying out a failure diagnosis at the time of shipment, for example,
Defective assembly of fuel evaporative gas treatment system on production line can be found.

When performing a failure diagnosis in the shipping process, the operator starts the engine 1 of the vehicle, connects the connection terminal of the tester 40 to the external signal input terminal 22 of the ECU 20, and operates the tester 40 to operate in the offline mode. An external signal is applied from the tester 20 to the ECU 20. When the engine 1 is started, the ECU 20 executes the failure diagnosis main routine shown in FIG. If the supply of the external signal for the offline mode is determined in step S4 after the completion of the engine start, the failure diagnosis in the offline mode is immediately performed with the vehicle traveling stopped state (step S12).

More specifically, in the failure diagnosis subroutine of the off-line mode shown in FIG.
The engine speed increasing step S300, which is the same as step S200, is performed, and the engine speed is increased to, for example, about 2000 rpm. Unlike the case of the normal mode and the dealer mode, in the offline mode, the determination as to whether or not the tank internal pressure change ΔP1 from the closing of the vent solenoid valve 15 until the elapse of the predetermined time T1 falls below the predetermined value ΔP01 is omitted. Further, the determination as to whether or not the tank internal pressure P exceeds the threshold value P0H at the time when the predetermined time T2 has elapsed, and the failure diagnosis stop processing are also omitted in the offline mode. As described above, the failure diagnosis procedure in the offline mode is simplified, and the required diagnosis time is significantly shortened as compared with the normal mode and the dealer mode.

In step S301 following step S300 for increasing the engine speed, the vent solenoid 15a is turned on and the vent solenoid valve 15 is closed. Next, in step S318 corresponding to step S218 of FIG. 6 relating to the dealer mode, the duty ratio of the purge solenoid 14a is fixedly set to a second fixed value, for example 100%, which is considerably larger than that in the dealer mode. To be done. Then, when the purge solenoid 14a is turned on in the next step S320, the purge solenoid valve 14 is turned on at the duty ratio of 100% set in step S318, that is, the purge solenoid valve 14 is maintained in the open state, Therefore,
Decompression of the fuel tank 5 is performed at the maximum speed,
Negative pressure formation in is performed in the shortest time.

Next, in step S326 which is the same as step S226 in FIG. 6 relating to the dealer mode, it is determined whether the tank internal pressure P has become lower than the predetermined pressure P0 before the predetermined time T2 has elapsed from the time when the pressure reduction of the fuel tank started. Is determined. If the determination result in step S326 is positive, that is, if the negative pressure formation is completed within the predetermined time T2, the normality determination is performed (step S362), and otherwise the failure determination is performed (step S364). Then, the normality determination step S362 or the failure determination step S364
In step S366 subsequent to the step S366, the purge solenoid 14a
Both the vent solenoid 15a and the vent solenoid 15a are turned off to close the purge solenoid valve 14 and open the vent solenoid valve 15 to complete the failure diagnosis.

As described above, the failure diagnosis in the off-line mode is completed in an extremely short time because the diagnosis procedure is considerably simplified as compared with the case of the normal mode and the dealer mode. The failure diagnosis device of the present invention is not limited to that according to the above embodiment. In particular, various diagnosis procedures are known for failure diagnosis while the vehicle is traveling (normal mode), and these known diagnosis procedures may be applied to the failure diagnosis apparatus of the present invention. Further, in the above embodiment, the failure diagnosis while the vehicle is stopped is performed in two modes (dealer mode and offline mode). However, the failure diagnosis is performed in any one of the modes while the vehicle is stopped. Good,
Alternatively, modes other than the above two modes may be additionally set .

[0050]

The failure diagnosis apparatus of the present invention performs the failure diagnosis of the fuel evaporative gas treatment system under a predetermined condition while the vehicle is traveling and when a predetermined external signal for instructing the failure diagnosis is supplied. Allowance and failure according to external signal
Since the control unit that performs the diagnosis in a simple procedure is provided, it is possible to increase the chances of failure diagnosis of the fuel evaporative gas treatment system. In particular, it is convenient for failure diagnosis at the time of shipping or repairing the vehicle, it can reliably and quickly determine whether there is a defective assembly of the fuel evaporative gas treatment system in the vehicle production line, and the system that has an abnormality can be detected. In the case of repair, it can be surely and quickly determined whether or not the repair was properly performed.

[Brief description of drawings]

FIG. 1 is a schematic view showing a failure diagnosis device according to an embodiment of the present invention together with a fuel evaporative gas treatment system equipped with the device.

FIG. 2 is a flowchart showing a main routine of a failure diagnosis process executed by the electronic control unit of FIG.

3 is a flowchart showing a part of a normal mode failure diagnosis subroutine shown in FIG.

FIG. 4 is a flowchart showing another part of the normal mode failure diagnosis subroutine.

FIG. 5 is a flowchart showing the rest of the normal mode failure diagnosis subroutine.

FIG. 6 is a flowchart showing a part of a dealer mode failure diagnosis subroutine shown in FIG.

FIG. 7 is a flowchart showing the rest of the dealer mode failure diagnosis subroutine.

FIG. 8 is a flowchart showing a failure diagnosis subroutine in the offline mode shown in FIG.

FIG. 9 is a graph showing changes in the internal pressure of the fuel tank with the passage of time during execution of the failure diagnosis process in the normal mode, together with changes in operating states of the vent solenoid valve and the purge solenoid valve.

[Explanation of symbols]

1 engine 2 intake pipe 5 fuel tank 6 canisters 14 Purge solenoid valve 14a Purge solenoid 15 Vent solenoid valve 15a Vent solenoid 17 Pressure sensor 20 Electronic control unit 21 Judgment signal output terminal 22 External signal input terminal 30 warning lamp 40 tester

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Mitsuhiro Miyake 5-3-8, Shiba, Minato-ku, Tokyo Within Mitsubishi Motors Corporation (72) Inventor Yoshinori Ono 5-3-8, Shiba, Minato-ku, Tokyo Mitsubishi Motors Co., Ltd. (72) Inventor Takuya Matsumoto 5-3-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Co., Ltd. (56) Reference JP-A-9-317573 (JP, A) JP 5-240118 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F02M 25/08 F02D 45/00 364

Claims (2)

(57) [Claims] 1. A fuel evaporation system in which a fuel evaporative gas generated in a fuel tank is adsorbed to a canister, and then the atmosphere is introduced into the canister to separate the fuel evaporative gas from the canister into an intake pipe of an internal combustion engine. In the gas treatment system, when it is determined that a vehicle equipped with the fuel evaporative emission treatment system is traveling in an operating state that satisfies a condition for performing a fault diagnosis while the vehicle is traveling, a failure diagnosis of the fuel evaporative emission treatment system is performed. A control unit is provided which permits the execution of a failure diagnosis of the fuel evaporative gas treatment system when it is determined that an external signal for instructing the execution of the failure diagnosis is supplied, and the control unit includes the external signal. According to
For failure diagnosis, the conditions for performing failure diagnosis while the vehicle is running are met.
This <br/> and characterized, the trouble diagnosis device for the fuel evaporative emission treatment system carried out by a simple procedure than the failure diagnosis procedure in accordance with the. 2. The control unit instructs execution of the failure diagnosis.
When it is determined that an external signal to
Immediately carry out a failure diagnosis of the evaporative gas treatment system
The fuel evaporative emission gas treatment system according to claim 1,
Failure diagnostic device.