JP2002256988A - Failure diagnosis device for evaporation purge system - Google Patents

Abstract

(57) [Summary] [Problem] An evaporative purge system that can prevent erroneous determination due to opening of a cap at the time of refueling, can continue refueling even when refueling during failure diagnosis, and reduce cost. To provide a failure diagnosis device. SOLUTION: A fuel vapor in a fuel tank is adsorbed on a canister and purge-controlled to an intake system, the system is closed in a negative pressure state, and the pressure increased in the same space during a failure diagnosis for the presence or absence of leakage. In the failure diagnosis device of the evaporative purge system having no path for escaping, when it is determined that the vehicle is stopped (YES in step S110), and when it is determined that the pressure in the fuel tank has exceeded the determination value (YES in step S130), The failure diagnosis is stopped (step S140).
Since the evaporative purge system, which is a closed space, is opened and the increased pressure escapes and the pressure in the system decreases, refueling can be continued.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure diagnosis apparatus for an evaporative purge system which adsorbs fuel vapor generated in a fuel tank to a caster and purges the vapor to an intake system of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as an evaporative purge system mounted on a vehicle or the like, for example, there is a technology disclosed in Japanese Patent Application Laid-Open No. 10-103169. This evaporative purge system includes a canister for adsorbing fuel vapor (evaporation) generated in a fuel tank with activated carbon, an evaporative passage communicating the fuel tank with the canister, and a purge passage communicating the canister with an intake passage of the internal combustion engine. And The canister is provided with an atmosphere valve having two diaphragms. When the pressure in the canister becomes a positive pressure equal to or higher than a predetermined value, one of the diaphragms is opened and the air in the canister is discharged to the atmosphere. Further, when the pressure in the canister becomes smaller than a predetermined negative pressure (when the absolute value becomes larger), the other diaphragm is opened, and the atmosphere is sucked into the canister. The evaporative purge system is configured to adsorb fuel vapor generated in a fuel tank to a canister and purge the adsorbed fuel vapor from the canister to an intake passage of an internal combustion engine.

Further, the above-mentioned evaporative purge system is provided with a failure diagnostic device which diagnoses whether or not fuel vapor is leaking due to a hole or a tear in the evaporative passage and the purge passage. In this failure diagnosis device, the purge control valve provided in the purge passage is opened to make the inside of the evaporative purge system a negative pressure state, then the inside of the system is closed, and the leakage or the like is performed based on a pressure change in the closed space. Diagnose the presence or absence of

[0004]

According to the above-mentioned prior art, when fuel is supplied during the failure diagnosis processing for diagnosing the presence of leakage or the like, the pressure in the fuel tank rises due to the refueling and the pressure in the canister becomes a predetermined value. It becomes positive pressure more than the value. In this case, even if the pressure becomes a positive pressure equal to or higher than a predetermined value, one of the diaphragms of the atmospheric valve opens to discharge the air in the canister to the atmosphere, so that refueling can be continued without any trouble. By the way, in the evaporative purge system as in the above-mentioned prior art, it is also possible to make a change such that the atmosphere valve is eliminated and an atmosphere introduction control valve composed of a solenoid valve is provided at the atmosphere inlet / outlet of the canister. This air introduction control valve is closed when a failure is diagnosed, and is opened otherwise.

[0005] In the failure diagnosis apparatus for an evaporative purge system in which such a change is added to the above-described prior art, when performing a failure diagnosis, the air introduction control valve is closed to shut off the air inlet / outlet of the canister. Is a closed space. When refueling is performed during the failure diagnosis in this way, the pressure in the closed space increases due to refueling,
Since the air inlet / outlet is shut off, there is no route for the pressure to escape. Therefore, there arises a problem that it becomes impossible to continue refueling any more.

Further, in the above-mentioned prior art, if a failure diagnosis process is performed during refueling, no attempt is made to set a negative pressure in the system because the cap is open. Since such a phenomenon occurs when a large hole is formed in a passage or the like in the system, there is a possibility that a failure diagnosis may be erroneously determined. Therefore, in the above-described related art, when the opening operation of the lid opener is detected based on the detection signal of the opening sensor and it is determined that refueling is being performed, the failure diagnosis processing is prohibited. However, in this conventional technique, it is necessary to provide a special opening sensor for detecting the opening operation of the lid opener, and there is a problem that the number of parts increases and the cost increases accordingly.

The present invention has been made in view of the above circumstances, and an object thereof is to prevent erroneous determination due to opening of a cap at the time of refueling, and to continue refueling even when refueling during failure diagnosis. It is an object of the present invention to provide a failure diagnosis apparatus for an evaporative purge system, which enables the reduction and the cost.

[0008]

The means for solving the above problems and the operation and effects thereof will be described below. The invention according to claim 1 is an evaporative purge system for adsorbing fuel vapor generated in a fuel tank to a canister and performing purge control to an intake system of an internal combustion engine. In a failure diagnosis device for an evaporative purge system having no path for releasing the pressure that has risen in the enclosed space during the failure diagnosis for the presence or absence of leakage or the like in the space, a stop determination unit that determines whether the vehicle is stopped or not. The tank internal pressure determining means for determining whether the pressure in the fuel tank has exceeded a determination value, and the stop determining means determining that the vehicle is stopped, and the tank internal pressure determining means determining the pressure in the fuel tank. A failure diagnosis control unit for stopping the failure diagnosis when it is determined that the value exceeds the value.

According to this configuration, when it is determined that the vehicle is stopped and the pressure in the fuel tank exceeds the determination value, it can be determined that the pressure has increased due to refueling.
Abort the fault diagnosis. In this manner, the fuel is supplied during the failure diagnosis processing, whereby the evaporative purge system, which is a closed space, is opened, the increased pressure escapes, and the pressure in the system decreases, so that the oil supply can be continued.
Further, it is possible to prevent erroneous determination of failure diagnosis due to refueling during failure diagnosis. Further, since it is determined whether or not to stop the failure diagnosis processing based on the pressure in the fuel tank detected by the pressure sensor normally provided in the evaporative purge system, the opening operation of the lid opener as in the above-described prior art is performed. It is not necessary to provide a special open sensor for detecting the pressure. Therefore, it is possible to prevent erroneous determination due to opening of the cap during refueling, to continue refueling even when refueling during failure diagnosis, and to reduce costs.

According to a second aspect of the present invention, in the failure diagnosis apparatus for an evaporative purge system according to the first aspect, the failure diagnosis control means determines that the failure has occurred when the stop determination means determines that the vehicle is not stopped. The feature is that diagnosis is permitted.

According to this configuration, since refueling is performed only when the vehicle is stopped, when it is determined that the vehicle is not stopped, it is determined that refueling is not performed and the failure diagnosis is permitted. Therefore, if a determination result that the vehicle is not stopped based on only the output signal of the idle switch or the like is obtained, the failure diagnosis can be permitted.

According to a third aspect of the present invention, in the failure diagnosis apparatus for an evaporative purge system according to the first aspect, the failure diagnosis control means determines that the vehicle is stopped by the stop determination means, and the tank internal pressure When the determination means determines that the pressure in the fuel tank is lower than a determination value, the failure diagnosis is permitted.

According to this configuration, even when the vehicle is stopped, if the pressure in the fuel tank is lower than the determination value, it is determined that refueling is not being performed or refueling is being performed but there is no problem with refueling. Since it can be done, the system allows the failure diagnosis. Therefore, even when the vehicle is stopped, the failure diagnosis can be continued as long as the pressure in the fuel tank is lower than the determination value.

According to a fourth aspect of the present invention, in the failure diagnosis apparatus for an evaporative purge system according to any one of the first to third aspects, the failure diagnosis control means stops the failure diagnosis after stopping the failure diagnosis. When the determination means determines that the vehicle is not stopped, the failure diagnosis is restarted.

According to this configuration, after the failure diagnosis is stopped because the pressure in the evaporative purge system has risen due to refueling, when it is determined that the vehicle is not stopped, the refueling has been terminated. Can be resumed.

According to a fifth aspect of the present invention, in the failure diagnosis device for an evaporative purge system according to the first aspect, when the failure diagnosis control means suspends the failure diagnosis, the internal combustion engine continues after the suspension. During the operation, the failure diagnosis is not restarted irrespective of the determination results of the two determination means.

According to this configuration, immediately after new fuel is charged, the fuel evaporates violently, and there is a high possibility of erroneous determination. Therefore, the pressure in the evaporation purge system increases due to refueling during the failure diagnosis processing. If the process is stopped, the failure diagnosis process is not performed during the trip. That is, after the suspension, while the internal combustion engine is continuously operated, the failure diagnosis processing is not restarted. Therefore,
It is possible to prevent erroneous determination of failure diagnosis due to refueling, and improve the reliability of failure diagnosis. Here, “trip” refers to a period during which the ignition switch is turned on and the internal combustion engine is continuously operated.

According to a sixth aspect of the present invention, in the failure diagnosis apparatus for an evaporative purge system according to any one of the first to fifth aspects, the fuel tank and the canister communicate with each other via an evaporative passage having a throttle. The evaporative passage is provided with an internal pressure valve that opens when the pressure in the fuel tank becomes a positive pressure equal to or higher than a predetermined value and communicates the fuel tank and the canister without passing through the throttle. It is characterized by.

According to this configuration, the fuel tank and the canister communicate with each other through the throttle until the pressure in the fuel tank becomes a positive pressure equal to or higher than a predetermined value. During normal operation, the pressure is substantially near the atmospheric pressure, and the pressure becomes a positive pressure only during refueling. Therefore, when the pressure in the epoch purge system exceeds the determination value during the failure diagnosis processing, it can be reliably determined that the pressure has increased due to refueling.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a failure diagnosis apparatus for an evaporation purge system mounted on a vehicle or the like embodying the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an evaporative purge system and a failure diagnostic device according to the present embodiment.
In FIG. 1, reference numeral 11 denotes an intake manifold (intake system) of an engine (not shown), and reference numeral 12 denotes an intake passage. A throttle valve 13 is provided in the intake passage 12. An air cleaner 14 is provided upstream of the throttle valve 13 in the intake passage 12. The throttle valve 13 is provided with a throttle opening sensor (not shown) having an idle switch 15. The idle switch 15 outputs an idle signal “ON” when the opening of the throttle valve 13 is “0”.

The evaporative purge system 20 shown in FIG.
A canister 22 which constitutes a part of the engine and adsorbs fuel vapor generated in the fuel tank 21, an evaporative passage 23 which communicates the fuel tank 21 with the canister 22,
A purge passage 24 is provided for communicating the canister 22 with the intake manifold 11. Further, the evaporative purge system 20 includes an air introduction passage 25 for introducing the air into the canister 22.

The fuel tank 21 is provided with a refueling pipe 26 for refueling. A cap 27 is attached to an oil supply port of the oil supply pipe 26, and a check valve 28 is provided at an outlet thereof. Further, a circulation path 29 is provided in the fuel supply pipe 26 in a branched manner, and an open end of the circulation path 29 is opened in an upper space of the fuel tank 21.

A circulation path 29 is provided on the upper wall of the fuel tank 21.
In addition, a pressure sensor 30 that detects the pressure in the fuel tank 21 and outputs an electric signal corresponding to the detected pressure, and one end of the evaporation passage 23 are provided. The same end is branched into two passages, one of which is provided with a float valve 1.
6, a liquid reservoir 31, and a throttle 32 are provided in this order from the opening end side of the passage. In the other passage, the float valve 17 and the liquid reservoir 33 are sequentially provided from the opening end side of the passage.

In the vicinity of the canister 22 in the evaporation passage 23, an internal pressure valve 34 and a throttle 35 are provided. The internal pressure valve 34 and the throttle 35 operate while the pressure in the fuel tank 21 is lower than the opening pressure of the internal pressure valve 34 (the internal pressure valve opening pressure shown in FIG. 4).
The diaphragm of the internal pressure valve 34 is at the valve closing position, and the fuel tank 21 and the canister 22 communicate with each other through the throttle 35.

On the other hand, the pressure in the fuel tank 21 is
4 reaches the valve opening pressure, the diaphragm of the internal pressure valve 34 is displaced to the valve opening position against the urging force, and the fuel vapor generated in the fuel tank 21 passes through the evaporation passage 23 without passing through the throttle 35. It is sent to the canister 22. In the present example, the diaphragm of the internal pressure valve 34 is urged by a spring (not shown) and the atmospheric pressure acts on the diaphragm. With such a configuration, until the pressure in the fuel tank 21 reaches the opening pressure of the internal pressure valve 34,
The fuel vapor generated in the fuel tank 21 is supplied to the evaporation passage 2
It is sent to the canister 22 via the aperture 3 and the throttle 35. For this reason, the pressure in the canister 22 is near the atmospheric pressure during traveling or while the engine is running and the vehicle is stopped, except during refueling when the pressure in the fuel tank 21 increases.

The canister 22 is provided with an adsorbent therein, and the fuel vapor from the fuel tank 21 is adsorbed by the adsorbent, temporarily stored therein, and then, when placed under negative pressure, adsorbed by the adsorbent. It is configured so that the fuel vapor can be released again. The interior of the canister 22 is partitioned into two adsorbent chambers 46 and 47 by a partition plate 45. Both adsorbent chambers 4
6 and 47 are each filled with an adsorbent and communicate with each other via a gas permeable filter 48. The adsorbent chamber 46 communicates with the fuel tank 21 via the evaporation passage 23 and communicates with the intake manifold 11 via the purge passage 24. On the other hand, the adsorbent chamber 47
It communicates with the air introduction passage 25. In addition, canister 2
2 is provided with a guide member 49 for guiding the adsorbed fuel vapor to the purge passage 24.

A purge control valve 40 comprising an electromagnetic valve is provided in the middle of the purge passage 24.
Is opened, the intake negative pressure in the intake manifold 11 is introduced into the canister 22 through the purge passage 24.

On the other hand, the air introduction passage 25 communicates between an inlet 18 provided in an oil supply opening which is opened and closed by a fuel lid (not shown) and an air intake / exhaust port (not shown) of the canister 22. Atmosphere entering from the mouth 18 is introduced into the canister 22. This atmosphere introduction passage 2
An air introduction control valve 41 composed of a solenoid valve is provided at a connection portion between the air inlet 5 and the air intake / exhaust port of the canister 22.

Further, in the middle of the air introduction passage 25, an air dust filter 42, an air drain valve 43, and a filter bypass passage 44 for bypassing the air dust filter 42 are provided. The atmosphere drain valve 43 is connected to the atmosphere introduction passage 2.
When the pressure in the passage 25a on the side of the air introduction control valve 41 becomes a positive pressure equal to or greater than a predetermined value, the diaphragm is displaced to the valve opening position against the urging force, and the diaphragm 25a and the filter bypass passage 44 are displaced. Communicate. The reason why the pressure in the passage portion 25a becomes a positive pressure equal to or higher than the predetermined value is that the pressure in the fuel tank 21 increases at the time of refueling and the pressure in the canister 22 reaches the positive pressure equal to or higher than the predetermined value. This is when the valve 41 is opened.

At this time, as described above, the atmospheric drain valve 43
Is opened and the passage portion 25a and the filter bypass passage 44 communicate with each other, the pressure in the canister 22 becomes lower than the atmospheric introduction control valve 4.
1. The passage portion 25a, the filter bypass passage 44, and the passage portion 25b of the air introduction passage 25 on the intake manifold 11 side escape from the inlet port 18 to the atmosphere. Thus, even when the excess air in the canister 22 is exhausted to the atmosphere, the fuel vapor remaining in the gas in the canister 22 passes through the adsorbent chambers 46 and 47 to the adsorbent therein. It is adsorbed so that the fuel vapor does not leak to the outside air.

The atmospheric drain valve 43 is also opened when the atmospheric dust filter 42 is clogged and the pressure in the filter bypass passage 44 becomes a positive pressure equal to or higher than a predetermined value, and the filter bypass passage 44 and the passage portion 25a are opened. Is to be communicated. As a result, even if the air dust filter 42 is clogged, the air is not purified, but the air remains in the canister 22.
Introduced within.

In the evaporative purge system 20 configured as described above, the fuel vapor generated in the fuel tank 21 is sent to the canister 22 through the evaporative passage 23 and is adsorbed by the canister 22. When the purge control valve 40 is opened, the negative pressure in the intake manifold 11 is supplied to the canister 22 via the purge passage 24. At this time, the atmosphere is introduced into the canister 22 via the atmosphere introduction passage 25, the atmosphere dust filter 42, and the atmosphere introduction control valve 41. By introducing the atmosphere in this manner, the adsorbed fuel vapor is purged (released) from the canister 22 to the intake manifold 11.

Also, as described above, the intake manifold 1
1 is supplied to the canister 22 through the purge passage 24, and the purge control valve 40 and the air introduction control valve 41 are closed.
That is, the inside of the fuel vapor path (in the evaporative purge system) of the system becomes a negative pressure and becomes a closed space. Here, the “fuel vapor path” of the evaporative purge system 20 includes the fuel tank 21, the evaporative passage 23, and the canister 2.
2 and a path including a passage between the canister 22 and the control valve 40 in the purge passage 24. In this manner, a failure diagnosis process to be described later is performed in a state where the inside of the “fuel vapor path” of the evaporation purge system 20 is in a negative pressure state and the inside of the path is a closed space.

In the engine, the evaporative purge system 20 and the failure diagnostic device configured as described above, the outputs of various sensors such as the idle switch 15 and the pressure sensor 30 function as a control system of the engine and serve as a failure diagnostic device. It is input to a functioning electronic control unit (hereinafter referred to as ECU) 50. The ECU 50 controls the driving of the fuel injection valve, the fuel pump, the purge control valve 40, the atmosphere introduction control valve 41, and the like, and executes a failure diagnosis process regarding the presence or absence of leakage in the fuel vapor path.

FIG. 2 shows an outline of the hardware configuration of the ECU 50. The internal configuration of the ECU 50 will be described with reference to FIG. The ECU 50 is a CPU 51a that executes various processes related to engine control and failure diagnosis, a ROM 51b that is a read-only storage medium, a RAM 51c that is a readable and writable volatile storage medium, and is readable and writable. The microcomputer 51 mainly includes a backup RAM 51d, which is a non-volatile storage medium that is backed up by a battery and stores the stored contents even after the engine is stopped.

The input port of the microcomputer 51 is connected to various sensors required for controlling the operation of the engine, such as a rotation speed sensor and a cylinder discrimination sensor, in addition to the idle switch 15 and the pressure sensor 30.

A drive circuit for driving the fuel injection valve 52, the fuel pump 53, the purge control valve 40, and the atmosphere introduction valve 41 is connected to an output port of the microcomputer 51. The ECU 50 controls the output of various sensors taken into the microcomputer 51,
In addition to performing various controls related to the operation of the engine such as fuel injection, the purge control valve 40 and the atmosphere introduction control valve 41 are opened and closed to perform the purge control of the evaporation purge system 20 and the failure diagnosis processing.

Next, an outline of an operation mode relating to the purge control of the evaporation purge system 20 will be described. Fuel vapor generated in the fuel tank 21 during operation of the engine flows into the canister 22 through the evaporation passage 23.

The fuel vapor flowing into the canister 22 is
It is once adsorbed by the adsorbent filled in the canister 22. Thereafter, when the purge control valve 40 and the atmosphere introduction control valve 41 are opened by a control signal from the ECU 50,
Since the intake negative pressure is introduced into the canister 22 from the intake manifold 11 through the purge passage 24, the canister 2 is introduced through the air introduction passage 25 and the air dust filter 42.
Atmosphere is introduced into 2. The introduction of the negative pressure and the atmosphere into the canister 22 in this way allows the canister 22
Is released, and the released fuel vapor is purged to the intake manifold 11 through the purge passage 24.

Next, a failure diagnosis process of the evaporation purge system executed by the ECU 50 will be described. When performing the failure diagnosis processing of the evaporative purge system 20, the EC
According to the control command of U50, the air introduction control valve 41 is closed and the purge control valve 40 is opened. Thus, the interior of the canister 22 is shut off from the atmosphere, and a negative pressure is introduced into the canister 22 from the intake manifold 11 via the purge passage 24. Thus, the fuel vapor path of the evaporative purge system 20, that is, the fuel tank 21, the evaporative passage 23, the canister 2
2, and the entirety of the purge passage 24 including the passage between the canister 22 and the control valve 40 is in a negative pressure state.

When the purge control valve 40 is closed in this state, the inside of the fuel evaporation path is hermetically closed while maintaining a negative pressure state.
An enclosed space is formed. In the state where the inside of the fuel vapor path is a negative pressure state and the inside of the fuel vapor path is a closed space, a failure diagnosis process described later is performed. During this process, the internal pressure of the fuel vapor path is detected by a pressure sensor 30 provided in the fuel tank 21.

If there is no abnormality (leakage of fuel vapor) in the fuel vapor path, the fuel in the fuel tank 21 evaporates, and the pressure in the fuel vapor path becomes equilibrium with the air and fuel vapor remaining in the path. Will gradually approach the pressure at which the pressure reached. On the other hand, if there is a leak in the fuel vapor path, the pressure in the path rapidly approaches the outside pressure (atmospheric pressure). Based on the change in the pressure in the fuel vapor path, the ECU 50 executes the evaporative purge system 2
0, that is, the evaporation passage 23 and the purge passage 24
During the operation of the vehicle, it is determined whether or not there is a failure such as a leak in the fuel vapor path.

As a part of such a failure diagnosis process or as a process independent of the failure diagnosis process, the process shown in FIG. 3 is executed at predetermined time intervals during engine operation. First, in step S110 shown in the figure, it is determined whether or not the vehicle is stopped, that is, whether or not the vehicle speed is 0 km / h. When the opening of the throttle valve 13 is not “0” and the output signal of the idle switch 15 is “OFF” (from the time point t1 to the time point t2 in FIG. 4), step S12 is performed.
The process proceeds to 0, and the fault diagnosis process (evaporation OBD) is permitted.
At this time, for example, the “failure diagnosis permission flag” is set to “1”. The reason for this permission is that it can be determined that fuel is not being supplied when the vehicle is not stopped, and that there is no pressure increase in the fuel tank 21 due to fueling. In this way, if the failure diagnosis processing is being executed, the processing is continued, and if not, the processing is started. In order to start the failure diagnosis process, it is necessary that the “failure diagnosis permission flag” is set to “1” and other conditions are satisfied. Thereafter, the processing shown in FIG. 3 is temporarily terminated.

On the other hand, if the decision result in step S110 is YE
In the case of S, that is, the opening of the throttle valve 13 is “0”, and the output signal of the idle switch 15 is “ON”.
(At time t2 in FIG. 4), step S13
Go to 0. In this step S130, the pressure sensor 30
Then, it is determined whether or not the pressure in the fuel tank 21 detected at the time exceeds a predetermined determination value shown in FIG. This determination value is set to a value lower than the valve opening pressure of the internal pressure valve 34 (the internal pressure valve opening pressure shown in FIG. 4).

If the pressure in the fuel tank 21 has not reached the above determination value (from time t2 to time t4 in FIG. 4), the process proceeds to step S120, and the failure diagnosis process is permitted. This is because the vehicle is stopped but not refueling, or refueling is started while the vehicle is stopped (time t3 in FIG. 4).
However, this is because the pressure in the fuel tank 21 is not high enough to hinder refueling, and there is no hindrance to the failure diagnosis processing.

On the other hand, if the pressure in the fuel tank 21 (tank pressure) is equal to or greater than the above-mentioned determination value (at time 4 in FIG. 4), the process proceeds to step S140, and the failure diagnosis process (evaporation OBD) is stopped. I do. At this time, the “failure diagnosis processing flag” is set to “0” and the air introduction control valve 4
1 is opened to release the pressure in the fuel vapor path (in the evaporative purge system) from the air inlet / outlet of the canister 22 to the atmosphere.

The reason for this is that it is possible to determine that the pressure in the fuel tank 21 has become equal to or higher than the above-mentioned determination value because refueling was performed during the failure diagnosis processing. This is because the above cannot be continued. In this way, when the pressure in the fuel tank 21 becomes equal to or higher than the above-described determination value due to refueling, the failure diagnosis processing is stopped, the closed fuel vapor path is opened to release the pressure in the same path, and refueling is continued. I can do it.

When the air introduction control valve 41 is opened in this manner, the pressure in the passage portion 25a of the air introduction passage 25 on the side of the air introduction control valve 41 becomes a positive pressure equal to or higher than a predetermined value. The valve is opened, and the passage portion 25a and the filter bypass passage 44 communicate with each other. As a result, the pressure in the canister 22 passes through the air introduction control valve 41, the passage 25 a, the filter bypass passage 44, and the passage 25 b of the air introduction passage 25 without passing through the air dust filter 42, and flows from the inlet port 18 to the atmosphere. Run away. As a result, refueling can be continued.

After the end of step S140, the process shown in FIG. 3 is temporarily ended. After stopping the failure diagnosis processing in step S140, if it is determined in step S110 that the vehicle is not stopped, the process proceeds to step S120, and the failure diagnosis processing is permitted. At this time, the “failure diagnosis processing flag” is set to “1”, and if other conditions for performing the failure diagnosis processing are met, the once stopped failure diagnosis processing is restarted. Thereafter, the processing shown in FIG.

After the failure diagnosis process is stopped in step S140, when the process proceeds to step S130,
When the pressure in the fuel tank 21 is lower than the determination value, the process proceeds to step S120, and the failure diagnosis processing is permitted. At this time, the “failure diagnosis processing flag” is set to “1”, and if other conditions for performing the failure diagnosis processing are met, the once stopped failure diagnosis processing is restarted. Thereafter, the processing shown in FIG.

The stop determining means for determining whether or not the vehicle is stopped corresponds to step S110. Also,
The tank internal pressure determining means for determining whether the pressure in the fuel tank 21 has exceeded the determination value corresponds to step S130. When the stop determination unit determines that the vehicle is stopped and the tank internal pressure determination unit determines that the pressure in the fuel tank 21 exceeds the determination value, the failure diagnosis control unit that stops the failure diagnosis corresponds to the step S140. . When the stop determination unit determines that the vehicle is not stopped, the failure diagnosis control unit that permits the failure diagnosis corresponds to step S120.

As described above, according to the present embodiment, the following operational effects can be obtained. (1) It is determined that the vehicle is stopped (YE in step S110)
S) When it is determined that the pressure in the fuel tank has exceeded the determination value (YES in step S130), it can be determined that the pressure has increased due to refueling, and the failure diagnosis is stopped. In this manner, the fuel is supplied during the failure diagnosis processing, whereby the evaporative purge system, which is a closed space, is opened, the increased pressure escapes, and the pressure in the system decreases, so that the oil supply can be continued. Further, it is possible to prevent erroneous determination of failure diagnosis due to refueling during failure diagnosis. Further, since it is determined whether or not to stop the failure diagnosis processing based on the pressure in the fuel tank detected by the pressure sensor normally provided in the evaporative purge system, the opening operation of the lid opener as in the above-described prior art is performed. It is not necessary to provide a special open sensor for detecting the pressure. Therefore, it is possible to prevent erroneous determination due to opening of the cap during refueling, to continue refueling even when refueling during failure diagnosis, and to reduce costs.

(2) Since refueling is performed only when the vehicle is stopped,
When it is determined that the vehicle is not stopped (NO in step S110), it is determined that refueling has not been performed, and a failure diagnosis is permitted. Therefore, if a determination result that the vehicle is not stopped is obtained based only on the output signal of the idle switch 15, the failure diagnosis can be permitted.

(3) Even if the vehicle is stopped, if the pressure in the fuel tank is lower than the determination value (NO in step S130), refueling is not performed or refueling is being performed, but there is no problem in refueling. Since it can be determined that there is no failure, the failure diagnosis is permitted. Therefore, even when the vehicle is stopped, the failure diagnosis can be continued as long as the pressure in the fuel tank is lower than the determination value.

(4) When it is determined that the vehicle is not stopped after the failure diagnosis is stopped because the pressure in the evaporation purge system has increased due to refueling (NO in step S110).
Since the refueling has been completed, the stopped failure diagnosis can be restarted.

(5) The internal pressure of the internal pressure valve 3
Until the valve opening pressure of 4 (positive pressure equal to or higher than a predetermined value) is reached, the fuel tank 21 and the canister 22 are in communication with each other via the throttle 35. Inside it is near atmospheric pressure, and the pressure becomes positive pressure only when refueling. Therefore, when the pressure in the epoch purge system 20, which is the closed space, exceeds the determination value during the failure diagnosis process (step S
(YES at 130), it can be reliably determined that the pressure has increased due to refueling.

[Modifications] One embodiment of the present invention has been described above. However, the above-described embodiment can be implemented by changing its configuration as described below.

In the above embodiment, the pressure sensor 30
Although it is provided on the upper wall of the fuel tank 21, it may be provided anywhere in the passage of the evaporative passage 23 or the purge passage 24, the inner wall of the canister 22, etc. as long as the pressure in the above-mentioned fuel passage can be detected. .

In the above embodiment, the air introduction control valve 41 composed of a solenoid valve is provided at the connection between the air introduction passage 25 and the air intake / exhaust port of the canister 22, but the present invention is not limited to such a configuration. . That is, the failure diagnosis apparatus of the present invention can be applied to any structure as long as the evaporation purge system has no path for releasing the increased pressure in the evaporation purge system 20 which is closed when the failure is diagnosed. it can.

In the above-described embodiment, the failure diagnosis as to whether or not there is a failure such as a leak in the fuel vapor path is performed based on the pressure transition in the evaporative purge system 20 that has become the closed space, that is, in the fuel vapor path. However, the present invention is not limited to such a configuration. For example, the failure diagnosis device of the present invention can be applied to an evaporative purge system that performs a failure diagnosis based on a temperature change in the canister 22 that forms a part of the fuel vapor path that has become the closed space.

In the above embodiment, the above step S
When the failure diagnosis is stopped at 140, after the stop, while the engine is continuously operated, that is, during the “trip”, the failure diagnosis is not restarted regardless of the determination results of steps S110 and S130. It may be. That is, when the failure diagnosis is stopped, during the trip, even if the determination result of step S110 is NO and the determination result of step S130 is NO, the failure diagnosis is not restarted.

In this way, immediately after the new fuel is charged, the fuel evaporates violently and the possibility of erroneous determination is high. Therefore, the pressure in the evaporation purge system rises due to refueling during the failure diagnosis processing, and the processing is stopped. If so, the failure diagnosis process is not performed during the trip. That is, after its suspension,
While the internal combustion engine is continuously operated, the failure diagnosis processing is not restarted. With this configuration, erroneous determination of failure diagnosis due to refueling can be prevented, and reliability of failure diagnosis can be improved.

In the above embodiment, the air introduction passage 25
Communicates between an inlet port 18 provided in a fuel supply opening that is opened and closed by a fuel lid and an air intake / exhaust port of a canister 22 so that air entering from the port 18 is introduced into the canister 22. However, the present invention is not limited to such a configuration. The atmosphere introduced into the canister 22 may be introduced from a location other than the refueling opening.

In the above-described embodiment, the diaphragm of the internal pressure valve 34 is urged by a spring and the atmospheric pressure is applied to the diaphragm.
The pressure in the passage portion of the evaporation passage 23 between the throttle 35 and the canister 22 may be applied instead of the atmospheric pressure.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a failure diagnosis device for an evaporation purge system according to the present invention.

FIG. 2 is an electronic control unit (ECU) used in the device.
FIG. 2 is a block diagram showing an electrical configuration of the embodiment.

FIG. 3 is a flowchart showing the operation of the apparatus.

FIG. 4 is a timing chart for explaining the operation of the apparatus.

[Explanation of symbols]

11: intake manifold (intake system), 12: intake passage (intake system), 13: throttle valve, 15: idle switch, 20: evaporative purge system, 21: fuel tank, 22: canister, 23: evaporative passage, 24 ... Purge passage, 25: atmosphere introduction passage, 30: pressure sensor, 3
4 ... internal pressure valve, 35 ... throttle, 40 ... purge control valve, 41 ...
Atmospheric introduction control valve, 50: Electronic control unit (ECU) as a failure diagnosis device.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hideki Miyahara 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 2G087 AA19 BB25 CC11 DD07 EE21 FF23 3G044 BA22 CA16 DA03 EA32 EA40 EA55 FA04 GA03

Claims (6)

[Claims] 1. An evaporative purge system for adsorbing fuel vapor generated in a fuel tank to a canister and performing purge control on an intake system of an internal combustion engine. In a failure diagnosis device for an evaporative purge system having no path for releasing the pressure that has risen in the enclosed space during the failure diagnosis for the presence or absence of the fuel tank, a stop determination unit that determines whether or not the vehicle is stopped, the fuel tank Tank internal pressure determining means for determining whether or not the pressure in the fuel tank has exceeded a determination value, and that the stop determination means has determined that the vehicle is stopped, and that the pressure in the fuel tank has exceeded the determination value by the tank internal pressure determination means. And a failure diagnosis control means for stopping the failure diagnosis when the determination is made. 2. The failure diagnosis of the evaporative purge system according to claim 1, wherein the failure diagnosis control means permits the failure diagnosis when the stop determination means determines that the vehicle is not stopped. apparatus. 3. The failure diagnosis control means, when the vehicle stop determination means determines that the vehicle is stopped, and when the tank internal pressure determination means determines that the pressure in the fuel tank is lower than a determination value, The failure diagnosis device for an evaporative purge system according to claim 1, wherein failure diagnosis is permitted. 4. The failure diagnosis control unit restarts the failure diagnosis when the stop determination unit determines that the vehicle is not stopped after stopping the failure diagnosis. The failure diagnosis device for an evaporative purge system according to any one of the preceding claims. 5. The failure diagnosis control means, when the failure diagnosis is stopped, after the suspension, while the internal combustion engine is continuously operated, irrespective of the determination results of the two determination means. 2. The method according to claim 1, wherein the process is not restarted.
A failure diagnostic device for an evaporative purge system according to claim 1. 6. The fuel tank and the canister communicate with each other through an evaporative passage having a throttle, and the evaporative passage opens when the pressure in the fuel tank becomes a positive pressure equal to or higher than a predetermined value. The failure diagnosis device for an evaporative purge system according to any one of claims 1 to 5, further comprising an internal pressure valve for communicating the fuel tank and the canister without passing through the throttle.