JP3412678B2 - Leak diagnosis device for evaporative fuel treatment equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In a conventional vaporized fuel processing apparatus for an internal combustion engine, vaporized fuel generated in a fuel tank or the like is temporarily adsorbed in a canister, and the adsorbed vaporized fuel is released under predetermined engine operating conditions for purging. The purge mixture, which is mixed with air, is sucked into the intake system of the engine while the flow rate is controlled by the purge control valve to prevent the evaporated fuel from evaporating to the outside air (Japanese Patent Laid-Open No. 5-215020, etc.). See).

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

However, it is difficult to make a diagnosis while the engine is operating, and it is difficult to ensure sufficient accuracy when making a diagnosis in a dynamic state. Therefore, a method of performing a leak diagnosis after stopping the engine operation has been considered. For example, the following method is used. That is, after setting the determination level based on the drive current of the electric pump when air is pressure-fed by the electric pump through the reference orifice having the reference diameter, the evaporative fuel is bypassed by the electric pump to bypass the reference orifice. The presence / absence of leak of evaporated fuel is diagnosed by comparing the drive current of the electric pump when air is pressure-fed to the pipe to be subjected to the leak diagnosis of the processing device with the set determination level. Specifically, when the drive current is smaller than the determination level, it is diagnosed that the vaporized fuel is leaking. That is, when a leak amount larger than that when the hole corresponding to the reference orifice is generated is generated, the drive current of the electric pump is reduced from the determination level due to the reduction of the pressure feeding load of air. The presence or absence of leak can be diagnosed.

According to the above method, even if a small amount of leak occurs such as when a small hole is formed in the pipe, it is possible to diagnose with high accuracy.

[0006]

However, in the method of performing the leak diagnosis after the engine is stopped as described above, if the leak diagnosis is executed while the filler cap of the fuel tank is opened and fuel is supplied, the fuel vapor 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 has occurred. Not only the pressurization method using the electric pump, but it seems that it is possible to use the pressure (negative pressure) stored in the accumulator during engine operation, for example .
Therefore, in the main claim, limit the diagnostic method to pressurization.
I stopped it. Please consider. ) Is supplied to the evaporative fuel supply system, and the diagnosis is performed based on the subsequent pressure change, the erroneous diagnosis similarly occurs.

The present invention has been made by paying attention to such a conventional problem, and in an apparatus for diagnosing a leak of evaporated fuel after the engine is stopped, an accurate leak diagnosis can be made every time the vehicle is refueled. An object of the present invention is to provide a leak diagnostic device for an evaporated fuel processing device that can be executed.

[0008]

Therefore, in the invention according to claim 1, as shown in FIG. 1, the evaporated fuel from the fuel tank of the internal combustion engine is temporarily adsorbed by the adsorbing means, and predetermined engine operating conditions are satisfied. While equipped with a leak diagnostic means for diagnosing the presence or absence of a vaporized fuel leak in the vaporized fuel processing device that performs intake treatment on the intake system of the engine after stopping the engine,
Refueling detection means for detecting whether or not the fuel tank is being refueled,
Diagnostic delay means for starting the diagnosis of the presence or absence of a leak of the evaporated fuel after the end of the refueling.

According to this structure, the refueling detection means detects whether or not the fuel tank is being refueled after the engine is stopped, and the diagnosis delay means starts the leak diagnosis of the evaporated fuel after the refueling is completed based on the detection result. Further, the invention according to claim 2 is characterized in that the diagnosis delay means starts the diagnosis when the refueling detection means detects that the refueling is completed.

According to this structure, the detection by the refueling detection means is continued until the end of refueling, and when the end of refueling is detected, the detection by the diagnostic delay means is started. Further, the invention according to claim 3 is characterized in that the diagnosis delay means starts the diagnosis after a predetermined time elapses after the refueling detection means once detects that the fuel is being refueled.

According to this structure, once the refueling detecting means detects that refueling is in progress, the leak diagnosing means performs the leak diagnosis after waiting for a predetermined time sufficient for the refueling to end. Be started. According to a fourth aspect of the present invention, the leak diagnosing means pressurizes the vaporized fuel supply system in a state where the vaporized fuel supply system from the fuel tank to the intake system of the engine is sealed, and leaks at the time of the pressurization. It is characterized in that the presence or absence of a leak is diagnosed by detecting a parameter that changes depending on the presence or absence.

According to this structure, when the vaporized fuel supply system from the fuel tank to the intake system of the engine is hermetically sealed, the vaporized fuel supply system is pressurized. Since the pressure state of is changed, the leak diagnosis means diagnoses the presence or absence of leak based on these parameters. Further, 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 evaporated fuel supply system is pressurized by an electric pump.

According to this structure, the drive current when the electric fuel pump pressurizes the vaporized fuel supply system is reduced when a leak is occurring. Therefore, the leak diagnosis means determines whether or not there is a leak by the drive current. Diagnose. Further, the invention according to claim 6 is characterized in that the refueling detection means detects whether or not refueling is in progress based on a drive current when the electric fuel pump pressurizes the inside of the evaporated fuel supply system.

According to this structure, the drive current when the electric fuel pump pressurizes the evaporated fuel supply system during refueling is greatly reduced as compared with that during non-refueling. Based on this, it is detected whether or not refueling is in progress.

[0015]

According to the first aspect of the present invention, the leak diagnosis that can be performed with high accuracy under static conditions after the engine operation is stopped can be executed after the end of refueling even when refueling is performed, and each time the vehicle is run. Moreover, there is an effect that a highly accurate leak diagnosis can be surely executed. According to the second aspect of the present invention, there is an effect that it is possible to detect the end of refueling by the refueling detection means and simultaneously execute the leak diagnosis.

According to the third aspect of the present invention, the refueling detection means only needs to detect that refueling is being performed only once, which has the effect of reducing the detection load. According to the invention of claim 4, there is an effect that a leak diagnosis can be performed with high accuracy by using a parameter that changes depending on the presence or absence of a leak when pressurizing the evaporated fuel supply system.

According to the invention of claim 5, there is an effect that a highly accurate leak diagnosis can be performed based on the drive current of the electric pump. According to the invention of claim 6, there is an effect that it is possible to reliably detect whether or not refueling is being performed based on the drive current of the electric pump.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. In FIG. 2 showing an embodiment, air is taken into an internal combustion engine 1 via an intake passage 3 provided with a throttle valve 2 which works in conjunction 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 installed at an upstream portion of the intake passage 3, and an electromagnetic flow meter for each cylinder is provided at a downstream portion (manifold portion) of the intake passage 3. A fuel injection valve 5 of a type is provided to inject into the intake passage 3 fuel that is fed under pressure from a fuel pump (not shown) and is controlled to a predetermined pressure by a pressure regulator. The control of the fuel injection amount by the fuel injection valve 5 is performed by a control unit 6 (illustrated by a chain line) with a built-in microcomputer.

Further, the engine 1 is provided with an evaporated fuel processing device. In the evaporated fuel processing device, the evaporated fuel of the fuel generated in the fuel tank 19 is introduced into the evaporated fuel introduction passage 20.
The adsorbent such as activated carbon filled in the canister 21 as the adsorbing means is adsorbed and collected through the adsorbent, and the fuel adsorbed by the adsorbent is admitted to the intake passage 3 on the downstream side of the throttle valve 2 via the purge passage 22. To supply.

An electromagnetically driven purge control valve 23 controlled based on a control signal from the control unit 6 is interposed in the purge passage 22. Further, for the leakage diagnosis of the evaporated fuel in the evaporated fuel processing device,
The following piping system is constructed. That is, a first passage 25 having a reference orifice 24 having a reference diameter of, for example, 0.5 mm, is provided in the air inlet opening at the bottom of the canister 21, and one of the switching valve 26 connected in parallel with the first passage 25. An electric pump 28 is connected via a second passage 27 passing through the port. The air introduction passage 29 connected to the suction port of the electric pump 28 is adapted to introduce air through the 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 whose other port reaches 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 drawing to move to the right in the drawing, the second passage 27 is opened through the one port, and the second passage 27 is opened. Electric pump 28 and canister 21
It is designed to communicate with the air inlet of.

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.
Are provided, and their detection signals are output to the control unit 6. The control unit 6 performs air-fuel ratio feedback control by controlling the fuel injection amount of the fuel injection valve 5 based on signals from the various sensors, and also performs the purge control valve under predetermined operating conditions.
By controlling 23, the process of purging the evaporated fuel into the intake system is performed, and the leakage diagnosis of the evaporated fuel according to the present invention is performed under a predetermined condition.

With this structure, the leak diagnosis routine for the 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 or not a predetermined leak diagnosis start condition, for example, the following condition is satisfied. The engine speed and vehicle speed are both below the specified values, and the engine is stopped.

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

After performing the refueling determination, the process proceeds to step 3 of FIG. 3 to determine the value of the flag FPITN. And
When the value of the flag FPITN is 1, that is, when it is determined that refueling is in progress, the process returns to step 2 to continue the refueling determination,
When the value of N becomes 0 and it is determined that refueling has been completed or that refueling was not originally performed, the routine proceeds to step 4 and subsequent steps to execute leak diagnosis.

First, in step 4, a process of initializing the vaporized fuel purge system atmosphere is performed. Specifically, the purge control valve 23 is opened, the one port of the switching valve 26 is closed, the other port is opened, the electric pump 28 is driven, 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 drive of the electric pump 28 is changed to the first passage.
The gas flows through the canister 21 through the purge passage 22 into the intake passage 3. Further, a part of the air is discharged from the switching valve 26 into 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 residual gas is removed. Next, prior to execution of the leak diagnosis, the leak diagnosis system is self-diagnosed. First, step 5
Then, the purge control valve 23 is closed and the switching valve 26
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. 6, the electric pump 28
The air introduced through the air filter 31 and the air introduction passage 29 by the driving of the above is discharged from the switching valve 26 through the first passage 25 into the atmosphere through the air discharge passage 31 and the air filter 30. . In the above state, after a lapse of a predetermined time, the routine proceeds to step 6, where the drive current of the electric pump 28 is detected and stored as the reference value I PUMP. That is, the electric pump 28 when air flows through the reference orifice 24 having the reference diameter.
Drive current is detected as a reference value for determination of leak diagnosis described later.

In step 7, a leak diagnostic test is executed. 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 drive of the electric pump 28 passes from the fuel tank 19 through the second passage 27 into the canister 21. It flows into the evaporated fuel introduction passage 20 and the purge passage 22 which 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 IPUMPLT detected in step 5 is compared with the reference value IPUMP 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 it is larger, the process proceeds to step 10 and it is diagnosed that there is no leak, and if it is determined that the drive current is below the determination level, the process proceeds to step 11 and it is diagnosed that there is leak.

That is, when the drive current during the leak diagnosis test is smaller than the drive current of the electric pump 28 required for 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 larger than the opening of the reference diameter occurs in the evaporative fuel introduction passage 20 or the purge passage 22 and a leak of a set level or more occurs, otherwise, no leak occurs (normal. ) Is diagnosed.

With this configuration, when refueling is performed after the engine is stopped, the leak diagnosis is performed after the refueling is completed. Therefore, while preventing erroneous diagnosis, highly accurate leak diagnosis can be performed for each running. Can be executed. Next, a second embodiment will be described. In the first embodiment, after the engine operation is stopped, the detection during refueling is continued until the refueling ends, and the leak diagnosis is started after the end detection.
In the second embodiment, once it is detected that refueling is in progress after the engine operation is stopped, the leak diagnosis is executed after waiting a predetermined time sufficient for refueling to end. .

FIG. 8 shows a leak diagnosis routine for evaporated fuel according to the second embodiment. The difference from FIG. 3 is that after the value of the refueling determination flag FPITN is 1 in step 3, it is determined that refueling is in progress, and then in step 12, the predetermined time elapses before proceeding to step 4 to perform a leak diagnosis. That is the point. In this way, it is only necessary to once say that the fuel is being refueled, so the detection load is reduced.

[Brief description of 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 showing a leak diagnosis routine of the first embodiment.

FIG. 4 is a flowchart showing a subroutine of the same leak diagnosis routine.

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

FIG. 6 is a diagram showing an air flow when the determination level is set according to the embodiment.

FIG. 7 is a diagram showing an air flow when a leak diagnosis test is executed according to the above embodiment.

FIG. 8 is a flowchart showing a leak diagnosis routine of the second embodiment.

[Explanation of symbols]

1 Internal combustion engine 6 control unit 19 Fuel tank 20 Evaporative fuel introduction passage 21 canister 22 Purge passage 23 Purge control valve 24 Standard orifice 25 First passage 26 Switching valve 27 Second passage 28 Electric pump 32 Rotation speed sensor

Continuation of front page (58) Fields investigated (Int.Cl. ⁷ , DB name) G01M 3/26 F02D 41/02 301 F02D 45/00 345 F02M 25/08 F02M 25/08 301

Claims (6)

(57) [Claims] Claim: What is claimed is: 1. Evaporative fuel from an internal combustion engine fuel tank is temporarily adsorbed by an adsorbing means, and the presence or absence of leakage of the evaporated fuel in an evaporative fuel processing device for intake treatment into an intake system of the engine under predetermined engine operating conditions is checked. While a leak diagnosis means for diagnosing after the engine operation is stopped is provided, a refueling detection means for detecting whether or not the fuel tank is being refueled after the engine operation is stopped, and a diagnosis for the presence or absence of a leak of the evaporated fuel after the refueling is started. A leak diagnosis apparatus for an evaporated fuel processing apparatus, comprising: a diagnosis delay unit. 2. The leak diagnosis of the fuel vapor processing apparatus according to claim 1, wherein the diagnosis delay means starts the diagnosis when the refueling detection means detects that the refueling is completed. apparatus. 3. The evaporative fuel treatment according to claim 1, wherein the diagnosis delay means starts the diagnosis after a predetermined time has elapsed after the refueling detection means once detected that refueling is being performed. Equipment leak diagnostic device. 4. The leak diagnosing means pressurizes the vaporized fuel supply system from a fuel tank to an intake system of an engine in a sealed state, and changes the parameter depending on whether or not there is a leak at the time of the pressurization. The leak diagnostic device for an evaporated fuel processing device according to claim 1, wherein the leak diagnostic device detects a leak and diagnoses whether or not there is a leak. 5. The evaporative fuel according to claim 4, wherein the leak diagnosing means diagnoses the presence or absence of a leak based on a drive current when the electric fuel pump pressurizes the interior of the evaporative fuel supply system. Leak diagnosis device for processing equipment. 6. The refueling detection means detects whether or not refueling is being performed based on a drive current when the inside of the evaporated fuel supply system is pressurized by an electric pump. Leak diagnosis device for evaporated fuel processing device.