JP2003042009A - Leak diagnosis device for evaporating gas purging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the frequency of leak diagnosis in spite of a longer leak diagnosis time for detecting minor leak in an evaporating gas purging system. SOLUTION: When the operation of an engine is stopped during leak diagnosis, power supply is continued for parts required for the continuation of the leak diagnosis to completely execute the leak diagnosis and the power supply is shut off right after the completion of the leak diagnosis. In this case, when the leak diagnosis is not completed even after the passage of a preset time since the operation stop of the engine, the power supply is shut off to terminate the leak diagnosis for preventing the consumption of a battery. In a system for introducing predetermined pressure (negative pressure, atmospheric pressure or positive pressure) into an evaporating system at starting the leak diagnosis to close the evaporating system and for measuring a subsequent pressure change in the evaporating system for determining the presence or not of leak, when the operation of the engine is stopped during introducing the predetermined pressure into the evaporating system, the power supply is shut off to terminate the leak diagnosis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative gas purge system for performing leak diagnosis of an evaporative gas purging system for purging (releasing) evaporative gas (fuel evaporative gas) produced by evaporation of fuel in a fuel tank to an intake system of an internal combustion engine. The present invention relates to a leak diagnostic device for a system.

[0002]

2. Description of the Related Art Conventionally, in an evaporative gas purging system, in order to prevent evaporative gas generated in a fuel tank from leaking to the atmosphere, the evaporative gas in the fuel tank is adsorbed in a canister through an evaporative passage and By installing a purge control valve in the middle of the purge passage that purges the evaporative gas adsorbed in the canister to the intake system of the internal combustion engine, and controlling the opening and closing of the purge control valve according to the operating state of the internal combustion engine The purge flow rate of evaporative gas to be purged into the system is controlled. In order to prevent the evaporative gas from leaking from the evaporative gas purging system to the atmosphere for a long period of time, it is necessary to detect the evaporative gas leakage at an early stage.

Therefore, a pressure sensor for detecting the pressure in the fuel tank (hereinafter referred to as "tank pressure") is provided, the purge control valve is opened to introduce a negative pressure from the intake system into the fuel tank, and then the purge is performed. By closing the control valve and sealing the evaporative system from the purge control valve to the fuel tank, by measuring the amount of change in the tank internal pressure and comparing the amount of change in the tank internal pressure with the leak determination value, Evaporative leaks
There is one that is designed to diagnose the presence or absence of. In this case, if there is no leak in the evaporative system, the amount of change in tank internal pressure will be a value according to the amount of evaporative gas generated, and will be smaller than the leak judgment value. It becomes larger by the amount and becomes the leak judgment value or more.

[0004]

In recent years, it has been required to be able to detect even a small amount of leak in order to comply with increasingly stringent environmental regulations. The smaller the leak, the smaller the change in the tank internal pressure. Therefore, in order to accurately detect the small leak, it is necessary to set the measurement time of the tank internal pressure change amount to a considerably long time. In general, leak diagnosis is performed under stable operating conditions such as idle operation and low-speed running so that it is not affected by changes in the operating conditions of the internal combustion engine. If set, even if the leak diagnosis is started during operation of the internal combustion engine, the leak diagnosis is canceled during the leak diagnosis because the operating conditions of the internal combustion engine change or the operation of the internal combustion engine is stopped. Therefore, the number of times the leak diagnosis is performed to the end during the operation of the internal combustion engine is extremely reduced.
As a result, even if a leak actually occurs, the detection of the leak is delayed, and it is not possible to detect both a small amount of leak (long leak diagnosis time) and early detection of the leak. .

The present invention has been made in view of the above circumstances, and therefore an object thereof is to increase the frequency of leak diagnosis even if the leak diagnosis time is lengthened to detect a small amount of leak. Therefore, it is another object of the present invention to provide a leak diagnostic apparatus for an evaporative gas purge system that can achieve both small leak detection and early leak detection.

[0006]

In order to achieve the above object, a leak diagnostic apparatus for an evaporative gas purge system according to claim 1 of the present invention is designed to prevent a leak when an internal combustion engine is stopped during a leak diagnostic. The diagnosis means continues the power supply to the components necessary for the continuation of the leak diagnosis and executes the leak diagnosis to the end. In this way, by increasing the leak diagnosis time in order to detect a small amount of leak, even if the frequency of stopping the operation of the internal combustion engine increases in the middle of the leak diagnosis, the leak diagnosis can be used to operate the internal combustion engine. The presence / absence of a leak can be determined by continuing the execution after the stop, the frequency of leak diagnosis can be increased, and the detection of a small amount of leak and the early detection of a leak can be compatible.

In this case, when the leak diagnosis is continued until after the operation of the internal combustion engine is stopped as in claim 2, it is preferable to cut off the power supply immediately after the end of the leak diagnosis. With this configuration, it is possible to prevent the on-vehicle battery from being consumed due to continuing power supply even after the leak diagnosis is completed while the internal combustion engine is stopped.

Further, as in claim 3, when the leak diagnosis does not end even after a lapse of a predetermined period from the stop of the operation of the internal combustion engine, it is preferable to cut off the power supply to stop the leak diagnosis. This makes it possible to limit the period (predetermined period) during which the leakage diagnosis can be performed after the internal combustion engine is stopped to an appropriate length so that the battery performance does not deteriorate, and the battery runs out or the battery voltage drops. It is possible to prevent the startability from being deteriorated.

Further, at the start of the leak diagnosis, a predetermined pressure (negative pressure, atmospheric pressure, positive pressure) is introduced into the evaporative system to seal the evaporative system, and thereafter the pressure change in the evaporative system is measured. In the system for determining the presence / absence of leak, when the operation of the internal combustion engine is stopped while the predetermined pressure is being introduced into the evaporative system as in claim 4, the power supply is cut off and the leak diagnosis is stopped. You may do it. In other words, the leak diagnosis is substantially started after first introducing a predetermined pressure into the evaporative system to seal the evaporative system, and therefore when the internal combustion engine is stopped before that. If the leak diagnosis is continued, the power must be supplied for a considerably long time before the leak diagnosis ends, which increases the load on the battery and may cause deterioration of startability due to battery exhaustion or battery voltage drop. There is a nature. Furthermore, in a system that introduces intake pipe negative pressure or positive pressure into the evaporative system at the time of leak diagnosis, if the operation of the internal combustion engine is stopped during the introduction of pressure into the evaporative system, the pressure source (intake pipe negative pressure or (Air pump, etc.)
Since the pressure of [2] disappears and the pressure cannot be introduced into the evaporation system, it is meaningless to continue the leak diagnosis. Therefore, when the operation of the internal combustion engine is stopped while the predetermined pressure is being introduced into the evaporative system, it is possible to avoid the exhaustion of the vehicle-mounted battery by shutting off the power supply and stopping the leak diagnosis. .

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. First, the configuration of the evaporative gas purge system will be described with reference to FIG. A canister 13 is connected to the fuel tank 11 via an evaporation passage 12. In this canister 13, an adsorbent (not shown) such as activated carbon that adsorbs evaporative gas (fuel evaporative gas) is housed. An atmosphere opening / closing valve 14 is attached to the atmosphere communication hole on the bottom surface of the canister 13.

The atmosphere opening / closing valve 14 is composed of a normally open solenoid valve. When the energization is off, the atmosphere opening / closing valve 14 is held in the open state and the atmosphere communication hole of the canister 13 is opened to the atmosphere. Kept in. The atmosphere opening / closing valve 14 closes when energized, and the atmosphere communication hole of the canister 13 is closed.

On the other hand, a purge passage 15 is provided between the canister 13 and the engine intake system for purging (releasing) the evaporative gas adsorbed by the adsorbent in the canister 22 to the engine intake system. A purge control valve 16 that controls the purge flow rate is provided in the middle of the passage 15. The purge control valve 16 is composed of a normally-closed solenoid valve, and is configured to control the purge flow rate of the evaporation gas from the canister 13 to the engine intake system by duty-controlling the energization.

Further, the fuel tank 11 is provided with a tank internal pressure sensor 17 for detecting the internal pressure thereof. When the evaporation system from the fuel tank 11 to the purge control valve 16 is sealed, the internal pressure of the fuel tank 11 and the internal pressure of other parts of the evaporation system match, so the tank internal pressure sensor 17
By detecting the internal pressure of the fuel tank 11, the internal pressure of the evaporation system can be detected.

A fuel level sensor 18 for detecting the remaining amount of fuel is provided in the fuel tank 11. Besides, a water temperature sensor 19 for detecting the engine cooling water temperature, an intake air temperature sensor 20 for detecting the intake air temperature, a crank angle sensor 26 for outputting a pulse signal having a frequency corresponding to the engine speed, and an intake pipe pressure sensor for detecting the intake pipe pressure. 27, various sensors such as a vehicle speed sensor 28 for detecting the vehicle speed are provided.

The outputs of these various sensors are output to the control circuit 2.
Input to 1. A power supply voltage is supplied to the power supply terminal of the control circuit 21 via the main relay 22. In addition, the power supply voltage is also supplied to the atmosphere opening / closing valve 14, the purge control valve 16, the tank internal pressure sensor 17, and the fuel level sensor 18 via the main relay 22. The relay drive coil 22b that drives the relay contact 22a of the main relay 22 is connected to the main relay control terminal of the control circuit 21, and by energizing the relay drive coil 22b, the relay contact 22a is turned on. Power supply voltage is supplied to the control circuit 21, the atmosphere opening / closing valve 14, the purge control valve 16, the tank internal pressure sensor 17, and the fuel level sensor 18. Then, by turning off the power supply to the relay drive coil 22b, the relay contact 22a is turned off.
Then, the power supply to the control circuit 21 and the like is turned off. The ON / OFF signal of the ignition switch 23 is input to the key SW terminal of the control circuit 21. In addition, the control circuit 21 includes a backup power supply 24 and a soak timer 25 which operates by using the backup power supply 24 as a power supply.
Is built in. The soak timer 25 starts the time counting operation after the engine is stopped (after the ignition switch 23 is turned off) and measures the elapsed time after the engine is stopped.

The control circuit 21 is mainly composed of a microcomputer, and executes a fuel injection control program, an ignition control program, and a purge control program stored in a ROM (storage medium) of the microcomputer, thereby performing fuel injection control and ignition control. And purge control. Further, the control circuit 21 executes the routines shown in FIGS. 2 and 3 stored in the ROM to start the leak diagnosis when a predetermined leak diagnosis execution condition is satisfied during engine operation, When the operation of the engine is stopped in the middle of the leak diagnosis, the main relay 22 is continuously maintained in the ON state, and the components (control circuit 21,
Power supply to the atmosphere opening / closing valve 14, the purge control valve 16, and the tank internal pressure sensor 17) is continued, and the leak diagnosis is executed to the end. This function plays a role corresponding to the leak diagnosis means in the claims. The processing contents of each routine shown in FIGS. 2 and 3 will be described below.

[Leak Diagnosis Routine] The leak diagnosis routine of FIG. 2 is executed every predetermined time (for example, every 20 msec), and the leak diagnosis is executed as follows. When this routine is started, first, at step 101, it is judged if the leak diagnosis execution condition is satisfied. The leak diagnosis execution conditions include, for example, that a predetermined time has elapsed since the engine was started, that the cooling water temperature is a predetermined temperature (for example, 70 ° C.) or higher, and the intake air temperature (outside air temperature).
Is lower than a predetermined temperature (for example, 50 ° C.), a predetermined operating condition such as idling or low speed running, and the leak diagnosis execution condition is satisfied when all of these conditions are satisfied, If any of the conditions are not met,
The leak diagnosis execution condition is not satisfied.

When the leak diagnosis execution condition is not satisfied, this routine is terminated without performing the leak diagnosis. Then, at the time point t1 (see FIG. 4) when the leak diagnosis execution condition is satisfied, the leak diagnosis is executed as follows by the processing of step 102 and the following steps. First, in step 102,
The atmosphere opening / closing valve 14 is closed, and the purge control valve 16 is closed to close the evaporation system. Thereafter, the routine proceeds to step 103, where it is determined whether the internal pressure of the fuel tank 11 detected by the tank internal pressure sensor 17 (hereinafter referred to as "tank internal pressure") is lower than a predetermined negative pressure, and it is lower than the predetermined negative pressure. If not, the routine proceeds to step 104, where the purge control valve 16 is opened to introduce the negative pressure from the engine intake system into the evaporation system.

Thereafter, at time t2 (see FIG. 4) when the tank internal pressure has dropped to a predetermined negative pressure, the routine proceeds to step 105, where the purge control valve 16 is closed to terminate the introduction of negative pressure, and the evaporation system is closed again. . Then, in the next step 106, it is determined whether or not a predetermined time (for example, 1 to 3 minutes) has elapsed from the completion of the introduction of the negative pressure. If the predetermined time has not elapsed, this routine is ended as it is.

As a result, the evaporative system is maintained in a closed state until a predetermined time elapses after the introduction of the negative pressure. Then, at a time point t4 (see FIG. 4) after a lapse of a predetermined time from the completion of the introduction of the negative pressure, the process proceeds to step 107, the tank internal pressure change amount ΔP within the predetermined time is calculated, and the next step 108 is performed.
Then, the tank internal pressure change amount ΔP is compared with a predetermined leak determination value, and if the tank internal pressure change amount ΔP is less than or equal to the leak determination value, it is determined that there is no leak (normal), and this routine ends.

If the tank pressure change amount ΔP is larger than the leak determination value, it is determined that a leak has occurred (abnormal), and
In step 109, a warning lamp (not shown) is turned on to warn the driver and an error code is output to the control circuit 2.
1 is stored in the backup RAM (not shown),
In the next step 110, the atmosphere opening / closing valve 14 is opened, and this routine is ended.

In this case, considering that the tank internal pressure change amount ΔP changes depending on the remaining fuel amount in the fuel tank 11, the leak determination value is made variable according to the remaining fuel amount detected by the fuel level sensor 18. May be.

[Main Relay Control Routine] The main relay control routine shown in FIG. 3 is executed every predetermined time (for example, 20 ms).
ec)) and the main relay 22
Control ON / OFF of. When this routine is started, first in step 201, it is determined whether or not an ignition switch (hereinafter referred to as "IG switch") 23 is turned on, that is, whether or not the engine is operating, and the IG switch 23 Is on (engine is operating), the process proceeds to step 207, and the main relay 22 is turned on.
The power supply voltage is supplied to the control circuit 21, the atmosphere opening / closing valve 14, the purge control valve 16, the tank internal pressure sensor 17, and the fuel level sensor 18 while maintaining the N state.

After that, the IG switch 23 is turned on and turned off.
At the time point t3 (see FIG. 4) when the mode is switched to F, it is determined as "No" in step 201, and the process proceeds to step 202,
It is determined whether or not the leak diagnosis is being executed by the leak diagnosis routine of FIG. 2, and if the leak diagnosis is not being executed, the routine proceeds to step 206, the main relay 22 is turned off, and the control circuit 21 , On-off valve 14,
Power supply to the purge control valve 16, the tank internal pressure sensor 17, and the fuel level sensor 18 is shut off.

On the other hand, if it is determined in step 202 that the leak diagnosis is being executed, step 20 is executed.
In order to limit the power supply time after the IG switch 23 is turned off from the viewpoint of battery protection, it is determined whether or not a predetermined time has elapsed after the IG switch 23 is turned off (after the engine operation is stopped). If the predetermined time has already passed, the routine proceeds to step 206, and the main relay 22 is turned off even during the leak diagnosis, and the control circuit 2
1. The power supply to the atmosphere opening / closing valve 14 and the like is cut off to stop the leak diagnosis and prevent the battery from being consumed.

On the other hand, if the predetermined time has not elapsed after the IG switch 23 was turned off, the routine proceeds to step 204, where it is determined whether or not the power supply voltage is higher than a predetermined voltage capable of ensuring engine startability. Is below a predetermined voltage,
Going to step 206, even during the leak diagnosis,
The main relay 22 is turned off to cut off the power supply to the control circuit 21, the atmosphere opening / closing valve 14 and the like to stop the leak diagnosis and prevent the consumption of the battery.

If the power supply voltage is higher than the predetermined voltage, the routine proceeds to step 205, where it is judged whether or not the negative pressure is being introduced from the engine intake system into the evaporation system.
If the negative pressure is being introduced, the routine proceeds to step 206, the main relay 22 is turned off, and the control circuit 21 and the atmosphere opening / closing valve 14 are turned on.
Shut off the power supply to etc. and stop the leak diagnosis. This is because if the operation of the engine is stopped while the negative pressure is being introduced into the evaporative system, the pressure in the intake pipe rises to atmospheric pressure and the negative pressure cannot be introduced into the evaporative system. Because is meaningless.

On the other hand, if the introduction of the negative pressure into the evaporation system has been completed, the routine proceeds to step 207, where the IG switch 2
Even after 3 is turned off (after engine operation is stopped), the main relay 22 is maintained in the on state to supply power to the components (control circuit 21, atmospheric on-off valve 14, etc.) necessary for continuing the leak diagnosis. continue. As a result, even when the operation of the engine is stopped in the middle of the leak diagnosis, the leak diagnosis can be continuously executed after the engine operation is stopped to determine the presence or absence of the leak, and the frequency of the leak diagnosis can be increased. Therefore, it is possible to achieve both small leak detection and early leak detection.

Then, at time t when the leak diagnosis is completed.
4 (see FIG. 4), it is determined to be “No” in step 202, the process proceeds to step 206, and the main relay 22 is turned off.
After that, the power supply to the control circuit 21, the atmosphere opening / closing valve 14 and the like is cut off.

In this embodiment, when the leakage diagnosis is continued after the engine operation is stopped, the fuel level sensor 18 is also supplied with power, but the fuel level sensor 18 is not supplied with power. You may do it. In short, the parts that continue to supply power after the engine is stopped may be the minimum necessary parts (control circuit 21, atmosphere opening / closing valve 14, purge control valve 16, tank internal pressure sensor 17) to continue the leak diagnosis. .

Further, in the present embodiment, the negative pressure is introduced from the engine intake system into the evaporation system at the start of the leak diagnosis, but a positive pressure may be introduced into the evaporation system by an air pump or the like. Alternatively, atmospheric pressure may be introduced into the evaporative system. Needless to say, the leak diagnosis method may be appropriately changed.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an evaporative gas purge system according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a processing flow of a leak diagnosis routine.

FIG. 3 is a flowchart showing a processing flow of a main relay control routine.

FIG. 4 is a time chart showing an example of leak diagnosis.

[Explanation of symbols]

11 ... Fuel tank, 12 ... Evaporation passage, 13 ... Canister, 14 ... Atmosphere opening / closing valve, 15 ... Purge passage, 16 ... Purge control valve, 17 ... Tank internal pressure sensor, 18 ... Fuel level sensor, 19 ... Water temperature sensor, 20 ... Intake air temperature sensor, 21
... control circuit (leak diagnostic means), 22 ... main relay,
23 ... Ignition switch, 24 ... Backup power supply, 25 ... Soak timer.

Claims (4)

[Claims] 1. A leak diagnostic device for an evaporative gas purge system, comprising: leak diagnostic means for performing leak diagnostics of an evaporative gas purge system for purging evaporative gas produced by evaporation of fuel in a fuel tank into an intake system. Is a leak in the evaporative gas purge system characterized by continuing to supply power to the components necessary for continuing the leak diagnosis and executing the leak diagnosis to the end when the operation of the internal combustion engine is stopped during the leak diagnosis. Diagnostic device. 2. The leak diagnosing means shuts off the power supply immediately after the end of the leak diagnosis when the leak diagnosis is continued until after the operation of the internal combustion engine is stopped. Leak diagnostic device for evaporative gas purge system. 3. The leak diagnosing means interrupts the leak diagnosis by shutting off the power supply when the leak diagnosis does not end even after a lapse of a predetermined period from the operation stop of the internal combustion engine. The leak diagnosis device for the evaporative gas purge system according to claim 1. 4. The leak diagnosing means introduces a predetermined pressure into the evaporative system including the fuel tank at the start of the leak diagnosing to seal the evaporative system, and thereafter measures a pressure change in the evaporative system. To determine the presence or absence of a leak,
4. The leak diagnosis is stopped by interrupting the power supply when the operation of the internal combustion engine is stopped while the predetermined pressure is being introduced into the evaporative system. A leak diagnostic device for the evaporative gas purge system described.