JPH11336620A - Leak diagnosis device for vapor fuel treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent erroneous leak diagnosis of a vapor fuel treatment device. SOLUTION: A pressure condition of vapor fuel is sensed after a leak diagnosis condition is effected and initilizing is performed post to stopping of engine operation (S1 to S3). When the vapor fuel pressure is a specified level or higher, that is, when FVAPER=1, leak diagnosis is suspended. When the pressure is determined to be less than the specified value, that is, when FVAPER=0, leak diagnosis is started (S4, S5...). It is thus possible to avoid erroneous diagnosis that no leak is determined due to high pressure of vapor fuel.

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 by pressurizing the inside of the evaporated fuel supply system 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 leak diagnosis system that pressurizes the inside of the fuel vapor supply system,
When the fuel temperature is high, the amount of vapor (fuel vapor) generated increases, the fuel vapor pressure in the fuel tank increases, and holes and the like that are actually diagnosed as leaks are generated. Even in such a case, there is a possibility that the drive current of the electric pump increases due to the effect of the increase in the evaporative fuel pressure, thereby erroneously diagnosing no leak.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a leak diagnosis apparatus for an evaporative fuel treatment apparatus capable of preventing erroneous leak diagnosis due to evaporative fuel pressure. And

[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 supply system, the evaporative fuel supply system, which performs suction processing to the intake system of the engine, determines whether or not the evaporative fuel leaks in the evaporative fuel supply system from the fuel tank to the intake system of the engine after the operation of the engine is stopped. Pressure diagnosis means for diagnosing by pressurizing and detecting a parameter which varies depending on the presence or absence of a leak at the time of pressurization, and evaporative fuel pressure state detection means for detecting an evaporative fuel pressure state before the start of the diagnosis Diagnostic delay / stop means for delaying or stopping the diagnosis when a state in which the fuel vapor pressure is higher than a predetermined level is detected by the fuel vapor pressure state detecting means; Characterized by being configured to include.

According to this configuration, after the engine operation is stopped, before the leak diagnosis condition is satisfied and the diagnosis is started, the fuel vapor pressure state is detected by the fuel vapor pressure state detecting means, and the fuel vapor pressure is equal to or higher than a predetermined level. When a high state is detected, the leak diagnosis is delayed or completely stopped by the diagnosis delay / stop means until the fuel vapor pressure is reduced.

Further, in the invention according to claim 2, the pressurization in the evaporative fuel supply system is performed by pressure-feeding air into the evaporative fuel supply system by an electric pump, and the evaporative fuel pressure state detecting means includes: While the driving of the electric pump is stopped, an electromotive force state of the electric pump caused by reversing the electric pump by the evaporative fuel pressure is detected, and the evaporative fuel pressure state is detected based on the electromotive force state. I do.

With this configuration, when the pressure of the evaporative fuel in the evaporative fuel supply system increases while the drive of the electric pump for pressurizing the evaporative fuel supply system for leak diagnosis is stopped, the evaporative fuel flows back to the electric pump. To reverse the electric pump,
An electromotive force is generated in the electric pump. Since the magnitude of the electromotive force is correlated with the reverse flow rate of the fuel vapor to the electric pump, and thus with the magnitude of the fuel vapor pressure, the fuel vapor pressure state can be detected based on the electromotive force state.

According to a third aspect of the present invention, the evaporative fuel pressure state detecting means permits the evacuation of the evaporative fuel after a predetermined time has elapsed while preventing the evaporative fuel from flowing back to the electric pump before the start of the leak diagnosis. The evaporative fuel pressure state is detected based on the electromotive force state of the electric pump at that time. According to such a configuration, before the start of the leak diagnosis, the backflow of the evaporated fuel to the electric pump is prevented, and after elapse of a predetermined time, the evaporated fuel pressure in the evaporated fuel supply system is increased, and then the backflow is allowed. A fuel vapor pressure state based on the electromotive force state of the pump is detected.

Further, the invention according to claim 4 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 the electric pump. . According to such a configuration, the drive current when the inside of the evaporative fuel supply system is pressurized by the electric pump decreases when a leak occurs, so that the leak diagnosis unit diagnoses the presence or absence of the leak based on the drive current.

[0014]

According to the first aspect of the present invention, when the fuel vapor pressure in the fuel vapor supply system before the start of the leak diagnosis is higher than a predetermined level, the leak diagnosis is delayed or stopped, so that the fuel vapor pressure is reduced. When the value is high, there is an effect that it is possible to prevent erroneous diagnosis such as diagnosing that there is no leak even if there is a leak.

According to the second aspect of the present invention, it is possible to detect the fuel vapor pressure state by using the electric pump used for leak diagnosis, and it is not necessary to provide a pressure sensor or a fuel temperature sensor. There is an advantageous effect. According to the third aspect of the present invention, even if the amount of generated vapor is the same level, by waiting for a predetermined time to elapse,
Since the pressure in the evaporative fuel supply system is sufficiently increased to increase the reverse flow and the electromotive force of the electric pump is detected, there is an effect that the evaporative fuel pressure state can be detected with high accuracy.

According to the invention of claim 4, there is an effect that the leak diagnosis can be performed with high accuracy based on the drive current of the electric pump.

[0017]

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. Further, in a situation in which the evaporative fuel pressure state is detected, and the pressure is high and an erroneous diagnosis is made that the gas is leaking but not leaking, the leak diagnosis is postponed or stopped for a predetermined time. Here, the leak diagnosis means, the evaporative fuel pressure state detection means, and the diagnosis delay / stop means in the present invention are provided by a later-described software function of the control unit 6.

A routine for diagnosing a leak of evaporated fuel 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 separately executed for the purge control valve 23, it is diagnosed that there is no failure. When it is determined in step 1 that the leak diagnosis condition is satisfied, the process proceeds to step 2, where a process for initializing the evaporated fuel purge system atmosphere 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.
The air introduced through the air filter 31 and the air introduction passage 29 by the driving of the canister flows through the canister through the first passage 25.
The gas flows through the purge passage 22 and flows into the intake passage 3. 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, in step 3, the fuel vapor pressure state (the amount of generated vapor) is detected. FIG.
The subroutine for detecting the fuel vapor pressure state will be described. Explaining based on the drawing, first, the power supply of the electric pump 28 is turned off.
To stop driving. Here, the electric pump 28 is provided with a check pin for locking the rotation, and the rotation of the electric pump 28 is locked by the check pin at the same time when the power is turned off, whereby the backflow of the evaporated fuel to the electric pump 28 is performed. Is prevented (S21). Alternatively, an on-off valve may be provided downstream of the electric pump 28, and the on-off valve may be closed. Next, the purge control valve 23 is fully closed (S22), the switching valve 26 is set to the second passage 27 opening side (S23), and the settings are set so that the fuel vapor pressure in the fuel vapor supply system is balanced. After a lapse of the predetermined time, the rotation lock of the electric pump 28 by the check pin is released, and the reverse flow of the evaporative fuel generated by this causes the electric pump 28 to reverse and generate an electromotive force, so that the electromotive force (current) IPUMPRV is Measure (S
24, S25). And the measured current IPUMP
The RV is compared with a reference value IPUMPRV0 for determination (S26). If the reference value IPUMPRV0 is greater than or equal to the reference value IPUMPRV0, it is determined that the fuel vapor pressure is high enough to cause a false diagnosis in the leak diagnosis, and the flag FVAPER is set to 1. Set (S27) and set the reference value IPUMPRV
If it is less than 0, it is determined that no erroneous diagnosis will occur, and the flag FVAPER is reset to 0 (S28).

After the determination of the fuel vapor pressure state, the value of the flag FVAPER is determined in step 4 of FIG. If the flag FVAPER is 0,
Since the fuel pressure is low and no misdiagnosis occurs,
The process proceeds to step 5 and thereafter to start the leak diagnosis. When the flag FVAPER is 1, the fuel vapor pressure is high,
Return to step 2 because there is a possibility of erroneous diagnosis.
After the initialization is performed again, the evaporative fuel pressure state is determined, and after waiting for the evaporative fuel pressure to drop and the flag FVAPER to be reset to 0, the routine proceeds to step 5, where the leak diagnosis is started.

In step 5, the purge control valve 23 is closed, 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. . In this case, as shown in FIG.
Is introduced from the switching valve 26 through the first passage 25 to the atmosphere through the air discharge passage 31 and the air filter 30.

In step 6, the electric pump is operated in the above state.
The drive current of No. 28 is detected, and the current value is set as a judgment level IPUMP. That is, the drive current of the electric pump 28 when the air flows through the reference orifice 24 having the reference diameter is detected. 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.
The air introduced through the air filter 31 and the air introduction passage 29 by the driving of the canister flows through the canister through the second passage 27.
The fuel flows into the evaporative fuel introduction passage 20 and the purge passage 22 from the fuel tank 19 to the purge control valve 23 through the inside 21. In step 8, the drive current IPU
Detect MPLT.

In step 9, the drive current I PUMPLT detected in step 8 is compared with the determination level I PUMPLT set in step 6 to perform a fuel oil leak diagnosis. Specifically, when it is determined that the drive current is equal to or lower than the determination level, the process proceeds to step 10 to diagnose that a leak has occurred, and when it is determined that the drive current is greater than the determination level DLSL, the process proceeds to step 11. Proceed to diagnose no leak.

That is, basically, the electric pump 28 required for air to flow through the reference orifice 24 having the reference diameter is used.
When the drive current at the time of the leak diagnosis test is smaller than the drive current of the electric motor 28, that is, when the drive load of the electric pump 28 is reduced, a hole larger than the reference diameter is provided in the evaporated fuel introduction passage 20 or the purge passage 22. It is diagnosed that a leak equal to or more than the opening level occurs and a leak exceeding a set level occurs, otherwise, it is diagnosed that no leak has occurred (normal).

With this configuration, when the fuel vapor pressure is higher than a predetermined level, the start of the leak diagnosis is delayed, and the leak diagnosis is performed after the fuel vapor pressure becomes low. It is possible to prevent erroneous diagnosis that no leak has occurred even though a leak has occurred, and to perform correct leak diagnosis. Further, the evaporative fuel pressure state can be detected by using the electric pump 28 used for leak diagnosis, and there is no need to provide a pressure sensor or a fuel temperature sensor, which is advantageous in terms of cost. By detecting the evaporative fuel pressure state after elapse of a predetermined time in the drive stop state, the pressure in the evaporative fuel supply system is sufficiently increased to increase the reverse flow rate, thereby detecting the electromotive force of the electric pump. In addition, as another embodiment, when the evaporative fuel pressure is determined to be equal to or higher than a predetermined level in the evaporative fuel pressure state detection in step 3 of FIG. May be configured to end the routine and stop the leak diagnosis.

[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 an embodiment of the present invention.

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

FIG. 4 is a flowchart showing a subroutine for detecting an evaporated fuel pressure state in the leak diagnosis routine of the above.

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.

[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 (4)

[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. Diagnosis is made by pressurizing 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 closed after the operation of the engine is stopped, and detecting a parameter that changes depending on the presence or absence of a leak during the pressurization. The fuel vapor pressure state detecting means detects the fuel vapor pressure state before the start of the diagnosis, and the fuel vapor pressure state detecting means determines that the fuel vapor pressure is higher than a predetermined level. A diagnosis delay / stop means for delaying or stopping the diagnosis when detected; and a leak diagnosis of the evaporative fuel treatment apparatus, characterized by comprising: Location. 2. The method according to claim 2, wherein the pressurization of the fuel vapor supply system is performed by feeding air into the fuel vapor supply system by an electric pump. The method according to claim 1, wherein an electromotive force state of the electric pump caused by reversing the electric pump by the fuel vapor pressure is detected, and the fuel vapor pressure state is detected based on the electromotive force state. Leak diagnosis device for fuel processor. 3. The fuel vapor pressure state detecting means according to claim 1, wherein a predetermined time has elapsed while preventing the fuel vapor from flowing back to the electric pump before the start of the leak diagnosis. The leak diagnosis device for an evaporative fuel processing apparatus according to claim 2, wherein the evaporative fuel pressure state is detected based on the electromotive force state. 4. The leak diagnostic means according to claim 2, wherein the presence or absence of a leak is diagnosed based on a drive current when the inside of the evaporative fuel supply system is pressurized by the electric pump.
3. A leak diagnostic device for an evaporative fuel treatment device according to claim 1.