JPH11326110A - Device for diagnosing leak from evaporated-fuel treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit highly accurate leak diagnosis for every traveling while preventing error diagnosis, by detecting whether a fuel tank is being fueled or not after the stop of an engine, and performing leak diagnosis after the completion of the fueling. SOLUTION: After conditions for leak diagnosis such as the state of an engine stop are met, a purge control valve 23 is closed, a switching valve 26 is turned to the open side of the second passage 27, and the completion of fuelling is determined at the time when the driving current of an electric pump 28 is equal to a threshold value or more. After the determination, initialization processing is performed to remove the residual pressure, etc., of a purge passage 22. Next, the purge control valve 23, the switching valve 26, and the electric pump 28 are brought to the same states as at the time of the determination of fuelling. and introduced air is discharged to the air from an air filter 30, and the value of the driving current detected after predetermined time is taken as a reference value IPUMP. Next, the port of the switching valve 26 is reversed to flow air introduced from the air filter 30 into an evaporated-fuel introducing passage 20 and the purge passage 22 between a fuel tank 10 and the purge control valve 23, and the value of the driving current detected after predetermined time is taken as a leak test value IPUMPLT. When it is greater (smaller) than the reference value, the absence (presence) of the occurrence of leak is diagnosed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leak diagnosis device for an evaporative fuel treatment system for an internal combustion engine, and more particularly to a technique for preventing erroneous diagnosis.

[0002]

2. Description of the Related Art In a conventional evaporative fuel processing apparatus for an internal combustion engine, evaporative fuel generated in a fuel tank or the like is temporarily adsorbed to a canister, and the adsorbed evaporative fuel is released under predetermined engine operating conditions for purging. A purge mixture mixed with air is suctioned into the intake system of the engine while controlling the flow rate with a purge control valve, thereby preventing evaporation of the evaporated fuel into the outside air (Japanese Patent Laid-Open No. 5-215020, etc.). See).

By the way, in the above-mentioned apparatus, if a crack is generated in the middle of the fuel vapor pipe or a sealing failure occurs at the joint of the fuel vapor pipe, the fuel vapor is radiated from the leak portion to the atmosphere. As a result, the original effect of preventing radiation cannot be sufficiently exhibited. Therefore,
Various devices for diagnosing the presence or absence of the leak of the evaporative fuel have been proposed.For example, after supplying an intake negative pressure generated by engine operation to a sealed evaporative fuel supply system, based on a pressure change in the system, There is one that diagnoses the presence or absence of a leak (hereinafter referred to as leak diagnosis as appropriate).

[0004] However, there is a restriction in making a diagnosis during operation of the engine, and it is also difficult to ensure sufficient accuracy in making a diagnosis in a dynamic state. Therefore, a method of performing a leak diagnosis after stopping the operation of the engine has been considered. For example, the following method is used. That is, after setting a determination level based on the drive current of the electric pump when air is pumped through the reference orifice having the reference diameter by the electric pump, the evaporative fuel is bypassed by the electric pump to bypass the reference orifice. The present invention compares the drive current of the electric pump when the air is pressure-fed to the pipe to be subjected to the leak diagnosis of the processing apparatus with the set determination level to diagnose whether or not the fuel vapor leaks. Specifically, when the drive current is smaller than the determination level, it is diagnosed that the fuel vapor leak has occurred. That is, when a leak amount larger than the leak amount when the hole corresponding to the reference orifice is generated, the drive current of the electric pump decreases from the determination level due to a decrease in the air pumping load. It can diagnose the presence or absence of a leak.

[0005] According to the above method, even when a small amount of leaks occur, such as when a fine hole is formed in a pipe, diagnosis can be performed with high accuracy.

[0006]

However, in such a system in which the leak diagnosis is performed after the operation of the engine is stopped, if the leak diagnosis is performed while the filler cap of the fuel tank is opened and refueling is performed, the evaporative fuel is removed. Since the inside of the supply system is opened to the atmospheric pressure, the drive current of the electric pump is reduced, and it may be erroneously diagnosed that a leak is occurring. In addition to the pressurization method using the electric pump, it seems possible to use the pressure (negative pressure) stored in the accumulator during engine operation, for example .
So, the main claim is to limit the diagnostic method to pressurization.
I stopped. Please consider. ) Is supplied into the evaporative fuel supply system, and a diagnosis based on a subsequent pressure change also causes erroneous diagnosis.

The present invention has been made in view of such a conventional problem. An apparatus for performing a leak diagnosis of evaporative fuel after stopping the operation of an engine performs an accurate leak diagnosis for each traveling even if refueling is performed. An object of the present invention is to provide a leak diagnostic device for an evaporative fuel treatment device that can be executed.

[0008]

Therefore, according to the first aspect of the present invention, as shown in FIG. 1, fuel vapor from a fuel tank of an internal combustion engine is temporarily adsorbed by an adsorbing means, and a predetermined engine operating condition is obtained. In the evaporative fuel processing device that performs suction processing to the intake system of the engine at, while equipped with leak diagnostic means for diagnosing the presence or absence of evaporative fuel after engine operation is stopped, after the engine operation is stopped,
Refueling detecting means for detecting whether or not the fuel tank is being refueled;
Diagnostic delay means for starting diagnosis of the presence or absence of leakage of the evaporated fuel after the refueling is completed.

With this configuration, the refueling detecting means detects whether or not the fuel tank is being refueled after the engine operation is stopped, and based on the detection result, the diagnosis delay means starts the fuel vapor leak diagnosis after the refueling is completed. The invention according to claim 2 is characterized in that the diagnosis delay unit starts the diagnosis when the refueling detection unit detects that the refueling has been completed.

With this configuration, the detection by the refueling detecting means is continued until the refueling is completed, and when the refueling is detected, the detection by the diagnosis delay means is started. Further, the invention according to claim 3 is characterized in that the diagnosis delay unit starts the diagnosis after a predetermined time has elapsed after the refueling detection unit once detects that refueling is being performed.

With this configuration, once the refueling is detected by the refueling detecting means, after a predetermined time sufficient for the refueling to be completed has elapsed, the leak diagnosis by the leak diagnosing means is performed. Be started. Further, in the invention according to claim 4, the leak diagnosis means pressurizes the inside of the evaporative fuel supply system in a state where the evaporative fuel supply system from the fuel tank to the intake system of the engine is sealed, It is characterized by detecting a parameter that changes depending on the presence or absence and diagnosing the presence or absence of a leak.

According to this configuration, when the inside of the fuel vapor supply system is pressurized in a state where the fuel vapor supply system from the fuel tank to the intake system of the engine is closed, for example, depending on the presence or absence of a leak, the pressurizing load or the pressure after pressurization is determined. The leak diagnostic means diagnoses the presence or absence of a leak based on these parameters. The invention according to claim 5 is characterized in that the leak diagnosis means diagnoses the presence or absence of a leak based on a drive current when the inside of the evaporative fuel supply system is pressurized by an electric pump.

According to this structure, the drive current when the electric fuel pump pressurizes the inside of the evaporative fuel supply system decreases when a leak occurs, so that the leak diagnosis means determines whether or not there is a leak by the drive current. Diagnose. The invention according to claim 6 is characterized in that the refueling detecting means detects whether or not refueling is being performed based on a drive current when the inside of the evaporative fuel supply system is pressurized by an electric pump.

With this configuration, the drive current when the evaporative fuel supply system is pressurized by the electric pump during refueling is greatly reduced as compared to during non-refueling. It is detected whether or not refueling is in progress.

[0015]

According to the first aspect of the present invention, a leak diagnosis that can be performed with high accuracy under static conditions after the engine operation is stopped can be executed even after refueling has been performed after refueling has been completed. Therefore, there is an effect that highly accurate leak diagnosis can be reliably performed. According to the second aspect of the present invention, there is an effect that the leak diagnosis can be executed at the same time when the refueling is detected by the refueling detecting means.

According to the third aspect of the present invention, the refueling detecting means only needs to detect that the fuel is being supplied only once, which has the effect of reducing the detection load. According to the fourth aspect of the invention, there is an effect that accurate leak diagnosis can be performed using a parameter that changes depending on the presence or absence of a leak when pressurizing the evaporative fuel supply system.

According to the fifth aspect of the invention, there is an effect that leak diagnosis can be performed with high accuracy based on the drive current of the electric pump. According to the invention according to claim 6, there is an effect that whether or not fueling is being performed can be reliably detected based on the drive current of the electric pump.

[0018]

Embodiments of the present invention will be described below. In FIG. 2 showing one embodiment, air is sucked into an internal combustion engine 1 through an intake passage 3 provided with a throttle valve 2 interlocked with an accelerator pedal (not shown). An air flow meter 4 for detecting an intake air flow rate controlled by the throttle valve 2 is mounted at an upstream portion of the intake passage 3, and an electromagnetic flow meter (manifold portion) at a downstream portion of the intake passage 3 is provided for each cylinder. A fuel injection valve 5 of a type is provided and injects fuel supplied from a fuel pump (not shown) and controlled to a predetermined pressure by a pressure regulator into the intake passage 3. The control of the fuel injection amount by the fuel injection valve 5 is performed by a control unit 6 (shown by a dashed line) built in a microcomputer.

The engine 1 is provided with a fuel vapor treatment device. The evaporative fuel processing device converts the evaporative fuel of the fuel generated in the fuel tank 19 into the evaporative fuel introduction passage 20.
The fuel adsorbed by the adsorbent is adsorbed and collected by an adsorbent such as activated carbon filled in a canister 21 serving as an adsorbing means, and the fuel adsorbed by the adsorbent is supplied to an intake passage 3 downstream of the throttle valve 2 via a purge passage 22. Supply.

The purge passage 22 is provided with an electromagnetically driven purge control valve 23 which is controlled based on a control signal from the control unit 6. Further, for the fuel vapor leak diagnosis in the fuel vapor processing apparatus,
The following piping system is configured. That is, a first passage 25 provided with a reference orifice 24 having a reference diameter of, for example, 0.5 mm in the air inlet opening at the bottom of the canister 21, and one of a switching valve 26 connected in parallel to the first passage 25. And an electric pump 28 is connected via a second passage 27 passing through the port. An air introduction passage 29 connected to a suction port of the electric pump 28 introduces air through an air filter 30. An air discharge passage 31 is connected to the other port of the switching valve 26. In the state shown in the drawing, the switching valve 26 communicates with the second passage 27 that connects the other port to the air introduction port of the canister 21, and allows the air discharged from the air discharge passage 31 to enter the atmosphere through the air filter 30. When the switching valve 26 is switched from the state shown in the figure to the right side in the figure, the second passage 27 is opened through the one port, and is discharged through the second passage 27. Electric pump 28 and canister 21
With the air inlet of the air conditioner.

A rotation speed sensor 32 for detecting the engine rotation speed N, a water temperature sensor 33 for detecting the water temperature Tw, and an air-fuel ratio sensor 34 for detecting the air-fuel ratio based on the oxygen concentration in the exhaust gas and the like.
The detection signals are output to the control unit 6. The control unit 6 performs an air-fuel ratio feedback control by controlling a fuel injection amount by the fuel injection valve 5 based on signals from the various sensors, and performs the purge control valve under a predetermined operating condition.
By controlling 23, a process of purging the evaporated fuel into the intake system is performed, and a leak diagnosis of the evaporated fuel according to the present invention is performed under predetermined conditions.

With this configuration, a routine for diagnosing a leak of evaporated fuel according to the first embodiment by the control unit 6 will be described with reference to the flowchart of FIG. In step 1 (abbreviated as S1 in the figure, the same applies hereinafter), it is determined whether a predetermined leak diagnosis start condition, for example, the following condition is satisfied. The engine speed and the vehicle speed are each lower than a predetermined value, and the engine is stopped.

In the failure diagnosis routine executed separately for the purge control valve 23, it is diagnosed that there is no failure. If it is determined in step 1 that the above-described leak diagnosis condition is satisfied, the process proceeds to step 2 and a refueling determination is performed.
The refueling determination subroutine will be described with reference to the flowchart of FIG. 4. When the purge control valve 23 is fully closed (step
21) The switching valve 26 is set to the second passage 27 opening side (step
22) After a lapse of a predetermined time, the drive current IPU of the electric pump 28 is
MP0 is measured and read (steps 23 and 24), and the drive current IPUMP0 is compared with a threshold value IPUMPCP for determining whether the filler cap is open (step 25). Is determined to be in the middle and flag FPIT
N is set to 1 (step 26), and when it exceeds the threshold value, it is determined that refueling is not being performed, and the flag FPITN is reset to 0 (step 27). That is, when the fuel is not being supplied, when the electric pump 28 is driven to pump the air into the closed evaporative fuel supply system by closing the valves, the drive current increases because the pressure in the system increases. On the other hand, when the filler cap is opened for refueling, the pressure in the system does not rise even if air is pumped, so the drive current remains small, so the drive current is compared with a threshold value. This makes it possible to reliably determine whether or not the fuel is being supplied. When a leak occurs, the pressure in the system decreases, but the pressure rises to a sufficiently high pressure as compared with the pressure when the filler cap is open during refueling, so there is no erroneous determination. The predetermined time is set to a time required for the pressure in the system to equilibrate after the driving of the electric pump 28 (determined by the volume of the system and the pump discharge amount) + α.

After the refueling determination is made, the routine proceeds to step 3 in FIG. 3, where the value of the flag FPITN is determined. And
If the value of the flag FPITN is 1, that is, it is determined that refueling is being performed, the flow returns to step 2 to continue refueling determination, and the flag FPITN is determined.
When the value of N becomes 0 and it is determined that refueling has been completed or that refueling has not been performed originally, the routine proceeds to step 4 and thereafter to execute a leak diagnosis.

First, in step 4, a process for initializing the atmosphere of the fuel vapor purge system is performed. Specifically, the purge control valve 23 is opened, the one port of the switching valve 26 is closed, and the other port is opened to drive the electric pump 28, and this state is maintained for a predetermined time. At this time, as shown in FIG. 5, the air introduced through the air filter 31 and the air introduction passage 29 by the driving of the electric pump 28 is supplied to the first passage.
The gas flows through the canister 21 through the purge passage 22 and flows into the intake passage 3 through the passage 25. Part of the air is released from the switching valve 26 to the atmosphere via the air discharge passage 31 and the air filter 30.

As a result, the residual pressure (negative pressure) in the purge passage 22
And the residual gas is removed. Next, the self-diagnosis of the leak diagnosis system is performed prior to the execution of the leak diagnosis. First, step 5
Then, the purge control valve 23 is closed, and the switching valve 26 is closed.
The one port is closed and the other port is opened to drive the electric pump 28, and this state is maintained for a predetermined time.

At this time, as shown in FIG.
The air introduced through the air filter 31 and the air introduction passage 29 by the driving of the air is discharged from the switching valve 26 through the first passage 25 to the atmosphere through the air discharge passage 31 and the air filter 30. . After a lapse of a predetermined time in the above state, the process proceeds to step 6, where the drive current of the electric pump 28 is detected and stored as a reference value IPUMP. That is, when the air flows through the reference orifice 24 having the reference diameter, the electric pump 28
Is detected as a reference value for determination of leak diagnosis described later.

In step 7, a leak diagnosis test is performed. Specifically, the purge control valve 23 is closed, the other port of the switching valve 26 is closed, and one port is opened to drive the electric pump 28, and this state is maintained for a predetermined time. At this time, as shown in FIG. 7, the air introduced through the air filter 31 and the air introduction passage 29 by the driving of the electric pump 28 passes through the canister 21 through the second passage 27 and is discharged from the fuel tank 19. The fuel flows into the evaporated fuel introduction passage 20 and the purge passage 22 that reach the purge control valve 23.

After the lapse of the predetermined time in the above state, the routine proceeds to step 8, where the drive current of the electric pump 28 is detected and stored as the leak test value IPUMPLT. In step 9, the leak test value I PUMPLT detected in step 5 is compared with the reference value I PUMP stored in step 6. Then, in step 9, the leak test value IPUMPLT is changed to the reference value IPUMPLT.
If it is determined that the current is larger than the threshold, the process proceeds to step 10 to diagnose that no leakage has occurred. If it is determined that the drive current is equal to or lower than the determination level, the process proceeds to step 11 to diagnose that the leak has occurred.

That is, when the drive current at the time of the leak diagnosis test is smaller than the drive current of the electric pump 28 required for the air to flow through the reference orifice 24 having the reference diameter, that is, the drive of the electric pump 28 If the load decreases,
It is diagnosed that a leak equal to or more than a set level occurs due to the occurrence of a failure equivalent to the opening of a hole larger than the reference diameter in the evaporative fuel introduction passage 20 or the purge passage 22, and if not, there is no leak (normal ) Is diagnosed.

According to this configuration, when refueling is performed after the engine operation is stopped, the leak diagnosis is performed after the refueling is completed. Can be performed. Next, a second embodiment will be described. In the first embodiment, after the engine operation is stopped, the detection of refueling is continued until the refueling is completed, and the leak diagnosis is started after the completion of the refueling is detected.
In the second embodiment, once it is detected that refueling is being performed after the engine operation is stopped, a leak diagnosis is executed after a predetermined time sufficient for refueling has elapsed thereafter. .

FIG. 8 shows a fuel vapor leak diagnosis routine according to the second embodiment. The difference from FIG. 3 is that after it is determined in step 3 that the value of the refueling determination flag FPITN is 1, that is, the fuel is being supplied, the flow proceeds to step 12 after the predetermined time has elapsed, and the flow proceeds to step 4 to perform the leak diagnosis. It is a point that was made. With this configuration, it is only necessary to perform the refueling operation once, so that the detection load is reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a diagram showing a system configuration according to the embodiment of the present invention.

FIG. 3 is a flowchart illustrating a leak diagnosis routine according to the first embodiment;

FIG. 4 is a flowchart showing a subroutine of the above-mentioned leak diagnosis routine.

FIG. 5 is a diagram showing a flow of air when an initialization process is performed in the embodiment.

FIG. 6 is a diagram showing the flow of air when a determination level is set in the embodiment.

FIG. 7 is a diagram showing the flow of air when a leak diagnostic test according to the embodiment is performed.

FIG. 8 is a flowchart illustrating a leak diagnosis routine according to the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 6 Control unit 19 Fuel tank 20 Evaporated fuel introduction passage 21 Canister 22 Purge passage 23 Purge control valve 24 Reference orifice 25 First passage 26 Switching valve 27 Second passage 28 Electric pump 32 Rotation speed sensor

Claims (6)

[Claims] An evaporative fuel processing apparatus for temporarily adsorbing fuel vapor from a fuel tank of an internal combustion engine to an adsorbing means and performing suction processing on an intake system of the engine under predetermined engine operating conditions determines whether or not there is a leak of vapor fuel. A fuel supply means for detecting whether or not the fuel tank is being refueled after stopping the operation of the engine; and starting a diagnosis of whether or not the fuel vapor leaks after the refueling is completed. A leak diagnosis device for an evaporative fuel treatment device, comprising: diagnosis delay means; 2. The leak diagnosis according to claim 1, wherein the diagnosis delay unit starts the diagnosis when the refueling detection unit detects that the refueling is completed. apparatus. 3. The fuel vapor processing according to claim 1, wherein the diagnosis delay means starts the diagnosis after a predetermined time has elapsed after the fueling detection means once detects that the fuel is being supplied. Equipment leak diagnostic device. 4. The leak diagnostic means pressurizes the inside of the fuel vapor supply system in a state in which the fuel vapor supply system from the fuel tank to the intake system of the engine is sealed, and a parameter which varies depending on the presence or absence of a leak at the time of pressurization. 2. The leak diagnostic device for an evaporative fuel treatment apparatus according to claim 1, wherein the device diagnoses the presence or absence of a leak by detecting a leak. 5. The evaporative fuel according to claim 4, wherein the leak diagnostic means diagnoses whether or not there is a leak based on a drive current when the inside of the evaporative fuel supply system is pressurized by an electric pump. Leak diagnosis device for processing equipment. 6. The fuel supply system according to claim 5, wherein the fuel supply detection means detects whether or not fuel is being supplied based on a drive current when the inside of the fuel vapor supply system is pressurized by an electric pump. Leak diagnosis device for evaporative fuel processing equipment.