JPH11190256A - Failure diagnostic device for fuel evaporative emission processing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a failure diagnostic device capable of determining whether or not a fuel evaporative emission processing system has failed, not only when a vehicle is traveling but also when it is stopped. SOLUTION: When an electronic control unit 20 detects that an external signal ordering the execution of diagnosis on failure is supplied to the electronic control unit 20 from a tester 40 connected to the external signal input terminal 22 of the unit 20, the unit 20 closes a bent solenoid valve 15 and opens a purge solenoid valve 14 to decompress the inside of a fuel tank 5 by means of intake negative pressure. During the decompression or after the decompression is complete, whether or not the seal of the fuel tank is defective is determined according to changes in internal pressure of the tank which are detected by a pressure sensor 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure diagnosis device for a fuel evaporative gas treatment system, and more particularly to a failure diagnosis device that can perform a failure diagnosis not only when a vehicle is running but also when the vehicle is stopped.

[0002]

2. Related Background Art Fuel (hydrocarbon) evaporated in a fuel tank may be released to the atmosphere. Therefore, a vehicle is provided with a fuel evaporative gas treatment system that includes a canister having activated carbon for adsorbing the fuel evaporative gas and that prevents the fuel evaporative gas from diffusing. The canister is provided with an introduction port communicating with the fuel tank, a discharge port communicating with the intake pipe of the engine, and a vent port opened to the atmosphere. The fuel evaporative gas in the fuel tank is introduced into the canister when the engine is stopped and is adsorbed by the activated carbon, 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 engine cylinder Burns in.

[0003] As a failure diagnosis of the fuel evaporative gas treatment system, for example, there is one disclosed in Japanese Patent Application Laid-Open No. Hei 7-127532. This failure diagnosis device opens and closes the canister when the vehicle speed is within a predetermined range and the conditions for starting the leak diagnosis are satisfied, such as when the vehicle speed fluctuation is small, so that the engine output torque does not fluctuate and the exhaust characteristics do not deteriorate. Valve is closed, the purge solenoid valve is duty-driven to put the inside of the fuel tank into a negative pressure state, and when the inside of the fuel tank reaches a predetermined pressure, the purge solenoid valve is closed, and a leak state occurs due to a pressure change after the valve is closed. Is to be detected.

[0004]

However, in order to prevent the exhaust characteristics and drivability from being deteriorated due to the failure diagnosis, the above-mentioned conventional failure diagnosis device satisfies certain predetermined execution conditions while the vehicle is running. It is configured so that failure diagnosis can be performed only when the failure occurs. For this reason, in the case of a vehicle equipped with the conventional device, when performing a failure diagnosis in a reproduction test or a confirmation test at a repair shop, the vehicle must travel in an operating state in which the failure diagnosis execution condition is satisfied. However, it is not practical to run the vehicle every time a reproduction test or a confirmation test is performed.

[0005] It is desirable to perform a failure diagnosis of the fuel evaporative gas treatment system at the time of vehicle shipment on a vehicle production line. It is difficult to perform fault diagnosis. Therefore, an object of the present invention is to provide a failure diagnosis device that can determine the presence or absence of a failure in a fuel evaporative gas treatment system not only during vehicle running but also during vehicle running stop.

[0006]

SUMMARY OF THE INVENTION A failure diagnosis apparatus according to the present invention is directed to a vehicle equipped with a fuel evaporative gas processing system for introducing fuel evaporative gas generated in a fuel tank into an intake pipe via a canister while the vehicle is running. When it is determined that the vehicle is running in an operation state that satisfies the failure diagnosis execution condition,
In addition, the control unit of the failure diagnosis device permits the execution of the failure diagnosis of the fuel evaporative gas processing system both when it is determined that the external signal instructing the execution of the failure diagnosis is supplied.

The failure diagnosis device of the present invention performs the failure diagnosis not only when the conditions for performing the failure diagnosis while the vehicle is running but also when an external signal is applied to the control unit. Unlike the case of failure diagnosis during running of the vehicle, there is little demand in the failure diagnosis in response to an external signal to prevent a decrease in drivability and a deterioration in exhaust characteristics due to the execution of the failure diagnosis. In other words, the failure diagnosis in response to the external signal does not require the running of the vehicle that satisfies the failure diagnosis execution condition as the failure diagnosis execution requirement, but only the application of the external signal to the control unit.
Therefore, even when the vehicle is stopped, the failure diagnosis is performed as long as the external signal is applied to the control unit. here,
For 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.
Thus, 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. Also, unnecessary failure diagnosis is not performed.

Preferably, the failure diagnosis device of the present invention communicates a first opening / closing valve provided in a vent passage of a canister for adsorbing fuel evaporative gas generated in a fuel tank with a canister and an intake pipe of an internal combustion engine. A second on-off valve provided in the purge passage, and a pressure detector for detecting an internal pressure of a closed space formed in the fuel evaporative gas processing system when the first and second on-off valves are closed. The control unit of the failure diagnosis device performs a failure diagnosis based on the internal pressure detected by the pressure detector.

More preferably, at the time of failure diagnosis, the control section 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 performs the second opening / closing operation. The valve is closed, and a failure diagnosis is performed based on a subsequent change in the fuel tank internal pressure. According to the above preferred configuration, an abnormality such as a leak from the fuel tank is 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 determining the supply of the second external signal for instructing the execution of the failure diagnosis at the time of shipment of the vehicle, the control unit performs the second
Allows execution of failure diagnosis in diagnostic mode. The procedure of the fault diagnosis in the first and second diagnosis modes may be the same as that of the fault diagnosis during the running of the vehicle except that the vehicle is kept in a running stopped state. It is preferable to simplify the procedure of the fault diagnosis in the second diagnosis mode more easily than in the first diagnosis mode. The simplification of the failure diagnosis procedure is achieved, for example, by forming a negative pressure for failure diagnosis within a short time.

[0011] According to the preferred apparatus configuration, the failure diagnosis at the time of vehicle repair is performed easily and in a short time, and the failure diagnosis at the time of shipping the vehicle is performed more easily and within a short time.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A failure diagnosis apparatus according to one embodiment of the present invention will be described below with reference to FIG. In FIG. 1, the fuel evaporative gas treatment system equipped with the failure diagnosis device includes a canister 6 containing activated carbon for adsorbing fuel evaporative gas. The canister 6 has 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
It is connected to a port 5 a provided on the upper surface of the fuel tank 5. The discharge port 6b is connected to the intake pipe 2 through the pipe 12.
Is connected to a purge port 2a provided on the pipe wall of the first embodiment. The purge port 2a is provided at a position that is disposed downstream of the throttle valve 3. And the pipe 12
, A normally closed purge solenoid valve 1 as a second on-off valve
4 (second valve means). Vent port 6
c communicates with one port of a normally-open vent solenoid valve 15 as a first on-off valve via a pipe 19,
The other port of the (first valve means) is open to the atmosphere. The electromagnetic valves 14 and 15 are provided by an electronic control unit (ECU)
It is connected to the output side of the ECU 20 and opens and closes under the control of the ECU 20.

In the fuel-evaporated-gas processing system having the above-described configuration, while the operation of the engine 1 is stopped, for example,
The normally-closed purge solenoid valve 14 and the normally-open vent solenoid valve 15 are respectively deenergized, and the purge solenoid valve 14 is closed, while 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 operation of the engine, the intake negative pressure generated in the intake pipe 2 is introduced into the pipe 12. afterwards,
The engine 1 preferably supplies fuel evaporative gas into the intake pipe 2.
When the operation state is such that excessive engine torque fluctuation does not occur even if the engine is inhaled, the purge solenoid valve 14 is energized and opens, 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, and the fuel evaporative gas adsorbed on the activated carbon is separated from the activated carbon by the purge air. And is burned in the cylinder of the engine 1.

In connection with a failure diagnosis process to be described later, the fuel evaporative gas processing system is connected to a throttle sensor 16 for detecting the throttle valve opening θt and a port 5 b provided on the upper surface of the fuel tank 5 through a pipe 18. Pressure sensor 17 (pressure detecting means) for detecting the tank internal pressure
The system includes 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 a 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 an engine speed Ne, an engine water temperature Tw, an intake air amount, etc., a water temperature sensor, an air flow sensor, etc. (All are not shown), and the output side is connected to injectors (one of which is indicated by reference numeral 8 in FIG. 1) provided in each cylinder of the engine 1. 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
The amount of bypass air supplied to the engine 1 via the
A control valve 2c which is adjusted under the control of U20 is provided.

In FIG. 1, reference numeral 40 denotes a multi-user tester (more generally, a special tool for inputting external signals) which can be connected to the judgment signal output terminal 21 and the external signal input terminal 22 of the ECU 20. The determination signal output terminal 21 is used to supply a code signal representing 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 applied from the tester 40 to the ECU 20.

Referring now to FIGS. 2 to 9, the ECU
20 will be described. The failure diagnosis apparatus according to the present embodiment includes a special signal input tool in a repair shop such as a dealer, for example, a tester 40 illustrated in FIG. 1 in addition to a normal failure diagnosis (first failure diagnosis method) performed during traveling of a vehicle. When the first external signal (dealer mode external signal) for instructing the ECU 20 to execute a failure diagnosis at the time of vehicle repair is applied to the ECU 20 or instructing the ECU 20 to execute the failure diagnosis at the time of shipping the vehicle in the shipping process of the vehicle production line. Also, when a second external signal (line-off mode external signal) is applied, the failure diagnosis (second failure diagnosis method) is performed. The first and second external signals may be predetermined code signals.

The failure diagnosis process is started, for example, when an 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 has been completed. Preferably,
It is determined whether or not a predetermined time, for example, 5 seconds, has elapsed from the completion of the engine start. If the start of the engine has not been completed, it is determined that appropriate failure diagnosis cannot be performed, and the control flow returns to "START" in FIG.

When the engine has been started, it is determined whether or not a line-off mode external signal has been supplied to the ECU 20 via, for example, the external signal input terminal 22 (step S).
4) If the signal is not supplied, it is determined whether or not the dealer mode external signal is supplied (step S6). Then, if there is no external signal supply, it is next determined whether or not a failure diagnosis execution condition during running of the vehicle is satisfied (step S8).

The failure diagnosis during the running of the vehicle is performed substantially once, for example, from when the engine 1 starts to when it stops. More specifically, this is performed when the engine 1 is operated for the first time in a specific operating state in which the intake air amount is considerably increased after the engine is started, for example, in an air-fuel ratio feedback range. Therefore, in step S8, EC
With reference to a flag (not shown) stored in the memory of U20, it is first determined whether or not the failure diagnosis during the traveling of the vehicle is completed. If the failure diagnosis is not completed, the failure diagnosis execution condition is satisfied. Is determined. In the present embodiment, a predetermined amount or more of intake air is supplied to the engine 1 in order to prevent the air-fuel ratio of the air-fuel mixture from excessively fluctuating due to the fuel evaporative gas sucked into the engine 1 due to the execution of the failure diagnosis. The failure diagnosis is performed only when the engine 1 is operated in such a specific operation state. For this reason, 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 equal to or less than 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.

Thereafter, when it is determined in step S8 that the conditions for performing the failure diagnosis during running of the vehicle are satisfied, a failure diagnosis in the normal mode (specifically, a subroutine shown in FIGS. 3, 4 and 5) is performed (FIG. 3, FIG. 4, and FIG. 5). Step S10). Prior to the start of the 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 so as not to hinder proper failure diagnosis or to deteriorate exhaust characteristics. The determination is made based on the tank internal pressure change ΔP1 (see FIG. 9) from the start of the diagnosis until the predetermined time T1 elapses.

For this purpose, first, the output of the pressure sensor representing 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 vent solenoid valve 15 is closed (step S102). S
104), 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 reduced as shown in FIG.
Ascend gradually as shown.

Thereafter, at step S108, a predetermined time T1
Is determined, the pressure sensor output representing the tank internal pressure P2 at that time is read (step S11).
0), the pressure change ΔP1 within the predetermined time T1 is calculated by subtracting the tank pressure P1 detected in step S102 from the tank pressure P2 (step S112). Next, it is determined whether or not the 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, if it is determined in step S114 that the pressure change ΔP1 in the fuel tank 5 is within the allowable range, the fuel tank 5 is connected to the intake pipe 2 while the degree of opening of the purge solenoid valve 14 is duty-controlled. To gradually reduce the pressure in the fuel tank by the intake negative pressure. And EC
In U, a purge concentration that provides a maximum flow rate such that the exhaust characteristics do not deteriorate due to enrichment of the air-fuel mixture due to 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 determined 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 processing system, particularly, in the fuel tank. Therefore, the purge solenoid 14a is turned on (step S120), and the timer for measuring the time elapsed from the start of the negative pressure formation is restarted (step S122). Then, a pressure sensor output representing the tank internal pressure P gradually decreasing as the negative pressure is formed is read (step S124), and it is determined whether or not the tank internal pressure P is lower than a predetermined pressure P0 indicating the completion of the negative pressure formation (step S124). Step S126). If the result of this determination is negative, that is, if negative pressure formation is insufficient, it is determined in step S128 whether a 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 discharge port 6b of the canister 6 communicates with the intake pipe 2, and the negative pressure of the intake air acts on the discharge port 6b of the canister 6. Further, the vent port 6c of the canister 6 is closed by the vent solenoid valve 15 in a 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. You.

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

On the other hand, if there is an abnormality such as poor airtightness in the system, the tank internal pressure slowly decreases as shown by the two-dot chain line in FIG. In particular, when there is severe airtight failure, the tank internal pressure P at the time when a predetermined time T2 has elapsed from the start of negative pressure formation becomes higher than the threshold value P0H higher than the predetermined pressure. If there is such an abnormality, the tank internal pressure P at the elapse of the predetermined time T2
Is higher than the threshold value P0H (severe negative pressure formation failure) in step S136, and a failure determination is made in step S138. Specifically, when the failure determination code signal is E
The warning lamp 30 is turned on while writing to the nonvolatile memory of the CU 20. Further, the flag referred to in step S8 is set to a value indicating the completion of the 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 processing ends.

On the other hand, a predetermined time T2 from the start of negative pressure formation
If it is determined in step S136 that the tank internal pressure P at the time point has elapsed is not higher than the threshold value P0H, this relatively slight negative pressure formation failure is due to poor airtightness of the system or due to fuel evaporation. The failure diagnosis process is temporarily suspended because it cannot be immediately determined whether the failure is a failure.
In the present embodiment, the number of interruptions N of the failure diagnosis process is counted (step S142), and when the number reaches a predetermined number Nref (for example, five), the failure is determined (steps S144 and S138). When the failure diagnosis process is interrupted, 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 to perform the failure diagnosis again.

A predetermined time T2 from the start of negative pressure formation
Even if the tank internal pressure P becomes lower than the predetermined pressure P0 before elapse of, but does not become lower than the threshold value P0L and the determination result in step S132 is negative, this slight negative pressure formation failure Is determined to be undetermined, and the failure diagnosis is similarly suspended. On the other hand, the predetermined time T
If the tank internal pressure P becomes lower than the threshold value P0L within 2, it is determined that the negative pressure has been sufficiently formed without detecting any 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 becomes almost equal to the intake negative pressure generated in the intake pipe 2 when the fuel evaporative gas processing system is normal. If the system has a failure, for example, poor airtightness, the absolute value of the negative pressure will be 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 vapor processing system is normal, the fuel tank internal pressure gradually increases as shown by the solid line in FIG. On the other hand, if the processing system has poor airtightness, the air flows into the system, and as shown by a two-dot chain line in FIG.

Therefore, a predetermined time T from the completion of negative pressure formation
It is determined whether or not the increase change ΔP2 of the tank internal pressure until the elapse of 3 is less than the allowable upper limit value ΔP02, that is, whether or not an increase in the internal pressure due to poor airtightness is observed. For this reason, the tank internal pressure P3 at the time when the negative pressure is completed is detected (step S150), and the timer for measuring the elapsed time from the time when the negative pressure is completed 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 negative pressure forming time is detected (step S156), and the tank internal pressure P detected in step S150 is obtained from the tank internal pressure P4.
3, the pressure change ΔP2 is calculated (step S158). Further, this pressure change ΔP2 is equal to the allowable upper limit value Δ
It is determined whether the value is lower than P02 (step S16).
0), if the determination result is affirmative, a normality determination is made (step S162). That is, the normality determination code signal is written in the non-volatile memory of the ECU 20, the off state of the warning lamp 30 is maintained, and the flag related to step S8 is set to a value indicating the completion of the failure diagnosis. on the other hand,
The pressure change ΔP2 that is equal to or greater than the allowable upper limit value ΔP02
If it is determined in 160, an abnormality determination is made in step S164, and the failure diagnosis ends.

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

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

When the engine 1 is started, the ECU 20 executes a failure diagnosis main routine shown in FIG. Then, when the supply of the dealer mode external signal is determined in step S6 after the completion of the engine start, the failure diagnosis in the dealer mode is immediately performed in the vehicle running stopped state (step S14). In detail, in the failure diagnosis subroutine of the dealer mode shown in FIGS. 6 and 7, the rotation speed of the engine 1 which is idling 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 perform the fuel injection in an amount suitable for the failure diagnosis in the dealer mode, and controls the control valve 2c to make the amount of bypass air supplied through the bypass passage 2b appropriate. Drive control. By increasing the engine speed at the time of failure diagnosis in the dealer mode, unintended stoppage of the engine speed can be prevented, but it is not essential to perform the engine speed increase step S200.

In the next step S202, a change ΔP1 in the tank internal pressure from when the vent solenoid valve 15 is closed until a predetermined time T1 has elapsed is detected. Specifically, step S
In step 202, steps S102, S104, S106, S108, and S11 of FIG. 3 related to the failure diagnosis in the normal mode.
0 and the same processing as in S112. In the next step S214 and 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 and simply show the corresponding steps in FIGS.

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 value ΔP01, unlike the normal mode in which the on-duty ratio of the purge solenoid 14a is variably set, the purge solenoid The duty ratio of 14a is fixedly set to a first fixed value, for example, 40% (step S218), and the purge solenoid 14a is turned on (step S22).
0). As a result, the purge solenoid valve 14 is switched to step S218.
Therefore, the pressure in the fuel tank 5 is reduced relatively quickly as compared with the normal mode, and the negative pressure in the fuel tank 5 is formed within a short time. Will be The negative pressure forming time in the dealer mode is reduced to, for example, about one third in the normal mode.

In the next step S226, it is determined whether or not the tank internal pressure P has become lower than the predetermined pressure P0 before a predetermined time T2 has elapsed since the start of the pressure reduction of the fuel tank.
Specifically, in step S226, steps S122, S124, S126, and S1 of FIG.
Thirty 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 in FIG. 4 is performed.
If it is determined in 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. .

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

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

A predetermined time T2 from the start of negative pressure formation
If the tank internal pressure P does not fall below the predetermined pressure P0 before the time elapses (step S226), the predetermined time T
If it is determined in step S236 that the tank internal pressure P has exceeded the threshold value P0H at the time point of step S2, a failure determination is made (step S238). The tank pressure P is equal to the threshold value P0
If the pressure does not exceed H, or if the tank internal pressure P falls below the predetermined pressure P0 but does not fall below the threshold value 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 value larger than that in the normal mode, the failure diagnosis is completed within a relatively short time. The failure diagnosis device according to the present embodiment is also intended to perform failure diagnosis of the fuel vapor processing system in a shipping process of a vehicle production line. By performing failure diagnosis at the time of shipment, for example,
Defective assembly of the fuel evaporative gas treatment system on the 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 the offline mode. An external signal is applied from the tester 20 to the ECU 20. When the engine 1 starts, the ECU 20 executes a failure diagnosis main routine shown in FIG. Then, when the supply of the external signal for the offline mode is determined in step S4 after the engine start is completed, the failure diagnosis in the offline mode is immediately performed while the vehicle is stopped (step S12).

More specifically, in the failure diagnosis subroutine in the offline mode shown in FIG.
The same engine speed increase step S300 as step S200 is performed, and the engine speed is increased to, for example, about 2000 revolutions per minute. Unlike 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 to the elapse of the predetermined time T1 is less than the predetermined value ΔP01 is omitted. Further, the determination as to whether the tank internal pressure P exceeds the threshold value P0H at the elapse of the predetermined time T2 and the failure diagnosis stop processing are also omitted in the offline mode. As described above, the failure diagnosis procedure in the off-line mode is simplified, and the required diagnosis time is greatly reduced as compared with the normal mode and the dealer mode.

In step S301 following step S300, the vent solenoid 15a is turned on and the vent solenoid valve 15 is closed. Next, in step S318 corresponding to step S218 in FIG. 6 relating to the dealer mode, the duty ratio of the purge solenoid 14a is fixedly set to a second fixed value considerably larger than that in the dealer mode, for example, 100%. Is done. 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,
The decompression of the fuel tank 5 is performed at the maximum speed, and the fuel tank 5
Is performed within 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 or not the tank internal pressure P has become lower than the predetermined pressure P0 before a predetermined time T2 has elapsed since the start of the pressure reduction of the fuel tank. Is determined. If the determination result in step S326 is affirmative, that is, if the negative pressure formation is completed within the predetermined time T2, a normality determination is performed (step S362), and if not, a failure determination is performed (step S364). Then, the normality determination step S362 or the failure determination step S364
In step S366 following step S366, the purge solenoid 14a
The vent solenoid 15a is turned off, the purge solenoid valve 14 is closed, and the vent solenoid valve 15 is opened to terminate the failure diagnosis.

As described above, the fault diagnosis in the off-line mode has a considerably simplified diagnosis procedure as compared with the normal mode and the dealer mode, and is completed within a very short time. The failure diagnosis device of the present invention is not limited to the above embodiment. In particular, various diagnostic procedures are known for failure diagnosis during running of the vehicle (normal mode), and these known diagnostic procedures may be applied to the failure diagnostic apparatus of the present invention. Further, in the above embodiment, the failure diagnosis while the vehicle is stopped is performed in two modes (the dealer mode and the offline mode). However, the failure diagnosis when the vehicle is stopped is performed in one of the modes. Well,
Alternatively, a mode other than the above two modes may be additionally set. Further, in the present embodiment, in order to quickly perform the failure diagnosis while the vehicle is stopped, the failure diagnosis while the vehicle is stopped is performed in a procedure different from the procedure of the failure diagnosis while the vehicle is traveling. It is also possible to carry out.

[0050]

The failure diagnosis apparatus of the present invention performs the failure diagnosis of the fuel vapor gas processing system under a predetermined condition while the vehicle is running and when a predetermined external signal for instructing the failure diagnosis is supplied. Since each of the permissible control units is provided, it is possible to increase the chances of failure diagnosis of the fuel evaporative gas processing system. In particular, it is convenient for failure diagnosis at the time of shipping and repair of vehicles, it can reliably and quickly determine the presence or absence of assembly failure of the fuel evaporative gas treatment system on the vehicle production line, and In the case of repair, it is possible to reliably and promptly determine whether or not the repair was properly performed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a failure diagnosis device according to an embodiment of the present invention, together with a fuel evaporative gas processing system provided with the device.

FIG. 2 is a flowchart illustrating a main routine of a failure diagnosis process performed by the electronic control unit of FIG. 1;

FIG. 3 is a flowchart showing a part of a failure diagnosis subroutine in a normal mode shown in FIG. 2;

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

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

FIG. 6 is a flowchart showing a part of a failure diagnosis subroutine in the dealer mode shown in FIG. 2;

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

FIG. 8 is a flowchart showing a failure diagnosis subroutine in an offline mode shown in FIG. 2;

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Intake pipe 5 Fuel tank 6 Canister 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

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mitsuhiro Miyake 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Yoshiki Ohno 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi (72) Inventor Takuya Matsumoto 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation

Claims (1)

[Claims] 1. A fuel evaporator for adsorbing fuel evaporative gas generated in a fuel tank to a canister and then introducing air into the canister to introduce the fuel evaporative gas separated from the canister into an intake pipe of an internal combustion engine. In the gas processing system, when it is determined that the vehicle equipped with the fuel evaporative gas processing system is running in an operating state that satisfies the conditions for performing the fault diagnosis during vehicle running, the failure diagnosis of the fuel evaporative gas processing system is performed. A fuel evaporative gas, comprising: a controller that permits the execution of the failure diagnosis of the fuel evaporative gas processing system when determining that an external signal instructing the execution of the failure diagnosis has been supplied. Failure diagnosis device for processing system.