JP2004278409A - Leak diagnostic device for evaporated gas purge system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent lowering of leak diagnostic accuracy due to refueling, while maintaining performance frequency of leak diagnoses during engine stop and fulfilling demand of battery electric power consumption reduction. <P>SOLUTION: The leak diagnostic device determines whether a fuel tank 11 has been refueled or not based on the change in the remaining fuel amount detected by a fuel level sensor 27 after each engine stop. When it is determined that the tank is refueled, a leak diagnosis after engine stop is inhibited. Lowering of leak diagnosis accuracy due to refueling is thereby prevented, and when it is determined that the tank has been refueled, supplying of electric power to each part necessary for a leak diagnosis is cut off, so that electric power consumption during engine stop can be reduced. Because it is unnecessary to lengthen the waiting period of a leak diagnosis, the increase of the number of times of engine restart can be prevented before start of leak diagnosis, and the performance frequency of leak diagnoses during engine stop can be maintained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a leak diagnosis device for an evaporative gas purge system that performs a leak diagnosis of an evaporative gas purge system that purges (discharges) evaporative gas (fuel evaporative gas) generated by evaporating fuel in a fuel tank into an intake system of an internal combustion engine. It is.
[0002]
[Prior art]
Conventionally, in an evaporative gas purge system, in order to prevent evaporative gas generated from the fuel tank from leaking into the atmosphere, the evaporative gas generated from the fuel tank is adsorbed in the canister, and the canister and the intake air of the internal combustion engine are sucked. By opening a purge control valve provided in a purge passage communicating with the system, the negative pressure of the intake system is used to purge the evaporative gas adsorbed in the canister to the intake system. In order to prevent a state in which the evaporative gas leaks from the evaporative gas purge system into the atmosphere for a long time, it is necessary to detect the evaporative gas leak at an early stage.
[0003]
Therefore, for example, as described in Patent Document 1 (Japanese Patent Application Laid-Open No. 5-125997), the purge control valve is opened during operation of the internal combustion engine to introduce a negative pressure from the intake system into the fuel tank. After that, while the purge control valve is closed and the evaporative system from the purge control valve to the fuel tank is sealed, the pressure in the evaporative system (for example, the pressure in the fuel tank) is monitored by a pressure sensor, and the evaporative system leaks. (Leakage) is diagnosed.
[0004]
In order to ensure the diagnostic accuracy of the leak diagnosis during the operation of the internal combustion engine, a predetermined value must be set so as not to be affected by the fluctuation of the fuel in the fuel tank or the pressure change in the fuel tank due to the atmospheric pressure change during uphill or downhill traveling. In addition, it is necessary to perform a leak diagnosis during a period when the operation state is stable (for example, an idling operation state), and it is necessary to set a time for measuring a pressure change in the evaporation system to a relatively long time. For this reason, depending on the driving method of the vehicle, the running pattern, etc., even if the leak diagnosis is started, the operating state of the internal combustion engine changes or the operation of the internal combustion engine is stopped during the leak diagnosis. The number of times the diagnosis is stopped may increase, and the execution frequency of the leak diagnosis may not be secured.
[0005]
Therefore, when performing a leak diagnosis, a technique for introducing a negative pressure or a positive pressure into an evaporative system using an electric pump (for example, see Patent Document 2) is not affected by a change in the operating state of the internal combustion engine. It has been proposed to perform a leak diagnosis of the evaporative system by introducing a negative pressure or a positive pressure into the evaporative system using an electric pump while the internal combustion engine is stopped, thereby ensuring the frequency of performing the leak diagnostics.
[0006]
[Patent Document 1]
JP-A-5-125997 (page 2, etc.)
[Patent Document 2]
JP-A-2002-4959 (page 2, etc.)
[0007]
[Problems to be solved by the invention]
By the way, for a while after the stop of the operation of the internal combustion engine, the pressure in the evaporation system increases due to the evaporation gas generated in the fuel tank, and thereafter, the pressure in the evaporation system decreases as the fuel temperature decreases.
[0008]
Therefore, the present invention provides a method of performing a leak diagnosis while the internal combustion engine is stopped, in order to prevent the influence of a change in the amount of evaporative gas generated after the internal combustion engine is stopped, from a predetermined time after the internal combustion engine is stopped. We are developing a system to execute leak diagnosis after a certain waiting time (for example, several hours or more) has elapsed.
[0009]
However, when fuel is supplied to the fuel tank after the internal combustion engine is stopped, the amount of evaporative gas generated by the newly refueled fuel increases, so the time required for the pressure behavior in the evaporative system to stabilize is longer than usual. become longer. For this reason, when refueling is performed after the internal combustion engine is stopped, there is a possibility that a leak diagnosis wait time elapses and the leak diagnosis is started before the pressure behavior in the evaporative system is stabilized. There is a concern that accuracy will be reduced.
[0010]
As a countermeasure, the waiting time from the stop of the operation of the internal combustion engine to the start of the leak diagnosis (hereinafter referred to as the “leak diagnosis waiting time”) is increased to wait for the pressure behavior in the evaporation system to stabilize even during refueling. It is conceivable to make it possible to execute a leak diagnosis. However, if the waiting time of the leak diagnosis is increased, the chances of the internal combustion engine being restarted before the start of the leak diagnosis are increased, and the frequency of executing the leak diagnosis while the internal combustion engine is stopped is reduced, or the waiting time of the leak diagnosis is reduced. There is a concern that the battery power consumption during the operation will increase and the battery consumption will be accelerated.
[0011]
SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object thereof is to provide a system for performing a leak diagnosis while the internal combustion engine is stopped, to secure the execution frequency of the leak diagnosis while the internal combustion engine is stopped and to reduce the battery power consumption. It is an object of the present invention to provide a leak diagnostic device for an evaporative gas purge system that can prevent a decrease in leak diagnostic accuracy due to fuel supply while satisfying a demand for an amount reduction.
[0012]
[Means for Solving the Problems]
To achieve the above object, a leak diagnostic apparatus for an evaporative gas purge system according to claim 1 of the present invention determines whether or not fuel is supplied to a fuel tank while the internal combustion engine is stopped by a refueling determining means, After it is determined that fuel has been supplied to the fuel tank during the stop, the leak diagnosis during the stop of the internal combustion engine is prohibited by the leak diagnosis prohibiting means.
[0013]
In this way, it is possible to prevent a decrease in leak diagnosis accuracy due to fuel supply beforehand, and to ensure reliability of leak diagnosis. Moreover, since it is not necessary to increase the waiting time for the leak diagnosis as a measure for refueling, it is possible to avoid an increase in the opportunity of restarting the internal combustion engine before the start of the leak diagnosis, and to execute the leak diagnosis while the internal combustion engine is stopped. Frequency can be secured. Moreover, if it is not necessary to lengthen the waiting time for the leak diagnosis, it is possible to avoid an increase in battery power consumption during the waiting time, and to immediately supply power to the components required for the leak diagnosis when it is determined that refueling is required. Can be cut off, the power consumption of the battery while the internal combustion engine is stopped can be reduced, and the life of the battery can be extended.
[0014]
Further, a negative pressure pump for introducing a negative pressure into the evaporative system is provided, and when performing a leak diagnosis while the internal combustion engine is stopped, the negative pressure pump is operated to reduce the negative pressure into the evaporative system. It is good to introduce. In a system that performs a leak diagnosis with a negative pressure in the evaporative system, even if a leak hole is opened in the evaporative system, only air is sucked into the evaporative system from the leak hole during the leak diagnosis. Further, there is an advantage that the evaporative gas in the evaporative system can be prevented from leaking into the atmosphere from the leak hole during the leak diagnosis.
[0015]
However, on the other hand, in a negative pressure type leak diagnosis system that introduces negative pressure into the evaporative system to perform leak diagnosis, if a large amount of evaporative gas is generated by refueling the fuel, the pressure change due to the evaporative system leak and the generation of evaporative gas There is a disadvantage that it is difficult to determine the pressure change due to the leak diagnosis accuracy decreases, but by applying the present invention, the leak diagnosis can be prohibited at the time of refueling, so even in a negative pressure type leak diagnosis system, It is possible to reliably prevent a decrease in leak diagnosis accuracy due to fuel supply.
[0016]
The determination as to whether or not fuel has been supplied to the fuel tank may be made based on, for example, whether or not the filler cap of the fuel tank has been opened. In this case, if the filler cap is opened. Even when the fuel is not actually supplied (that is, when the accuracy of the leak diagnosis does not decrease due to the supply of the fuel), it is determined that the fuel has been supplied, and the leak diagnosis is prohibited. I will. In addition, it is necessary to newly provide a sensor switch for detecting opening and closing of the filler cap, which cannot meet the demand for cost reduction.
[0017]
Therefore, it is preferable to determine whether fuel has been supplied to the fuel tank based on a change in the remaining fuel amount detected by the remaining fuel amount detecting means. This makes it possible to accurately determine whether or not fuel has been supplied to the fuel tank, and to prohibit the leak diagnosis only when fuel is actually supplied. In addition, since the fuel remaining amount detecting means can use the fuel level sensor generally provided in the fuel tank, there is no need to provide a new sensor switch, and it is possible to satisfy the demand for cost reduction.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, the configuration of the evaporation 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. The canister 13 contains an adsorbent (not shown) such as activated carbon for adsorbing evaporative gas (fuel evaporative gas).
[0019]
On the other hand, between the canister 13 and the engine intake system, a purge passage 14 for purging (releasing) the evaporative gas adsorbed by the adsorbent in the canister 13 to the engine intake system is provided. A purge control valve 15 for controlling the purge flow rate is provided on the way. The purge control valve 15 is constituted by a normally-closed solenoid valve, and controls the purge flow rate of evaporative gas from the canister 13 to the engine intake system by duty control of energization.
[0020]
A leak check module 17 is attached to the atmosphere communication passage 16 of the canister 13 in order to diagnose a leak in the evaporation system from the fuel tank 11 to the purge control valve 15. As shown in FIG. 2, in the leak check module 17, an atmosphere communication path 20 and a negative pressure introduction path 21 are connected to a canister communication path 18 connected to the canister 13 via a path switching valve 19. The atmosphere communication path 20 is provided so as to directly communicate with the atmosphere side, and the negative pressure introduction path 21 is connected in the middle of the atmosphere communication path 20 via a check valve 22 and an electric negative pressure pump 23. . During operation of the negative pressure pump 23, the check valve 22 is opened to discharge gas from the negative pressure introduction passage 21 to the atmosphere communication passage 20. When the negative pressure pump 23 is stopped, the check valve 22 is closed and air communication is performed. The backflow of the atmosphere from the passage 20 to the negative pressure introduction passage 21 is prevented.
[0021]
The passage switching valve 19 performs a switching operation between an atmosphere opening position B connecting the canister communication passage 18 and the atmosphere communication passage 20 and a negative pressure introduction position A connecting the canister communication passage 18 and the negative pressure introduction passage 21. It consists of a possible solenoid valve.
[0022]
Further, a bypass passage 24 that bypasses the passage switching valve 19 is connected between the canister communication passage 18 and the negative pressure introduction passage 21, and a reference orifice 25 is provided in the middle of the bypass passage 24. The reference orifice 25 is formed so that the inside diameter of the passage is narrowed significantly from the inside diameter of the passage at the other part of the bypass passage 24 and becomes the reference leak hole diameter (for example, 0.5 mm in diameter). The reference orifice 25 and a passage 24a of the bypass passage 24 that connects the reference orifice 25 to the negative pressure introduction passage 21 constitute a reference pressure detecting unit 37. The reference pressure detecting unit 37 is provided with a pressure sensor 26. I have.
[0023]
When the passage switching valve 19 is switched to the negative pressure introducing position A when the purge control valve 15 is closed, the evaporative system is closed and the peripheral portion of the pressure sensor 26 of the reference pressure detecting unit 37 is connected to the negative pressure introducing passage 21. The pressure sensor 26 detects the pressure in the reference pressure detecting unit 37 to communicate with the evaporative system via the canister communication passage 18 so that the representative data of the pressure in the fuel tank 11 in the evaporative system can be obtained. Pressure (hereinafter referred to as “tank internal pressure”) can be detected.
[0024]
When the negative pressure pump 23 is driven in a state where the passage switching valve 19 is switched to the negative pressure introducing position A and the evaporative system is closed, the gas in the evaporative system is discharged to the atmosphere through the canister 13. Then, a negative pressure is introduced into the evaporation system.
[0025]
On the other hand, when the passage switching valve 19 is switched to the atmosphere opening position B when the purge control valve 15 is closed, the inside of the bypass passage 24 (the inside of the reference pressure detecting unit 37) is opened to the atmosphere via the atmosphere communication passage 20. Therefore, the atmospheric pressure can be detected by detecting the pressure in the reference pressure detector 37 by the pressure sensor 26.
[0026]
When the negative pressure pump 23 is driven in a state where the passage switching valve 19 is switched to the atmosphere opening position B and the inside of the evaporation system is opened to the atmosphere through the atmosphere communication passage 20, the reference orifice 25 exists. The inside of the reference pressure detector 37 becomes negative pressure. At this time, by detecting the pressure in the reference pressure detecting unit 37 by the pressure sensor 26, the reference pressure corresponding to the reference leak hole diameter of the reference orifice 25 can be detected.
[0027]
Further, as shown in FIG. 1, a fuel level sensor 27 (fuel remaining amount detecting means) for detecting the remaining amount of fuel is provided in the fuel tank 11. In addition, various sensors such as a crank angle sensor 28 that outputs a crank angle signal for each predetermined crank angle, an intake pipe pressure sensor 29 that detects an intake pipe pressure, and a vehicle speed sensor 30 that detects a vehicle speed are provided.
[0028]
Outputs of these various sensors are input to a control circuit (hereinafter referred to as “ECU”) 31. A power supply terminal of the ECU 31 is supplied with a power supply voltage from a vehicle-mounted battery (not shown) via a main relay 32. In addition, a power supply voltage is also supplied to the purge control valve 15, the passage switching valve 19, the negative pressure pump 23, the pressure sensor 26, the fuel level sensor 27, and the like via the main relay 32. A relay drive coil 32b for driving a relay contact 32a of the main relay 32 is connected to a main relay control terminal of the ECU 31. When the relay drive coil 32b is energized, the relay contact 32a is turned on, and the ECU 31 and the like are turned on. Is supplied with a power supply voltage. Then, by turning off the power supply to the relay drive coil 32b, the relay contact 32a is turned off, and the power supply to the ECU 31 and the like is turned off.
[0029]
An ON / OFF signal of an ignition switch (hereinafter, referred to as an “IG switch”) 33 is input to a key SW terminal of the ECU 31. When the IG switch 33 is turned on, the main relay 32 is turned on and power supply to the ECU 31 and the like is started. When the IG switch 33 is turned off, the main relay 32 is turned off and the power supply to the ECU 31 and the like is turned off. .
[0030]
Further, the ECU 31 has a backup power supply 34 and a soak timer 35 that operates to measure time using the backup power supply 34 as a power supply. The soak timer 35 starts a timing operation after the engine stops (after the IG switch 33 is turned off) and measures the elapsed time after the engine stops. As described above, when the IG switch 33 is turned off, the main relay 32 is turned off and the power supply to the ECU 31 and the like is turned off. However, in order to perform a leak diagnosis while the engine is stopped, the measurement time of the soak timer 35 (engine When the elapsed time after the stop reaches a predetermined time (for example, 3 to 5 hours), the drive circuit of the main relay control terminal of the ECU 31 is operated by using the backup power supply 34 of the ECU 31 as a power source, and the main relay 32 is turned on. The power supply voltage is supplied to the purge control valve 15, the passage switching valve 19, the negative pressure pump 23, the pressure sensor 26, the fuel level sensor 27, and the like.
[0031]
The ECU 31 is mainly configured by a microcomputer, and performs fuel injection control, ignition control, and purge control by executing a fuel injection control program, an ignition control program, and a purge control program stored in its ROM (storage medium). .
[0032]
Further, the ECU 31 executes the respective programs for leak diagnosis shown in FIGS. 3 to 5 described later, so that a predetermined time (for example, 3 to 5 hours) has elapsed since the engine operation was stopped (the IG switch 33 was turned off). The leak diagnosis is performed when the engine is stopped, but it is determined whether or not fuel is supplied to the fuel tank 11 immediately after the engine is stopped. After it is determined that the fuel is supplied, the leak diagnosis is performed while the engine is stopped. Thus, the power consumption during engine stop is reduced to reduce the load on the battery, and the accuracy of leak diagnosis due to fuel supply is prevented from lowering.
[0033]
Here, the leak diagnosis during the stop of the engine, which is executed in the present embodiment, will be described. As shown in FIG. 6, the reference pressure detection process is started at a time point t1 when a predetermined time (for example, 3 to 5 hours) has elapsed since the engine operation was stopped (the IG switch 33 was turned off). In the reference pressure start process, the negative pressure pump 23 is turned on while the passage switching valve 19 is maintained at the atmospheric opening position B, and a negative pressure is introduced into the reference pressure detecting unit 37. At a time point t2 at which the pressure becomes stable near the corresponding reference pressure, the negative pressure in the reference pressure detection unit 37 detected by the pressure sensor 26 is stored in the memory of the ECU 31 as the reference pressure.
[0034]
After the detection of the reference pressure, the passage switching valve 19 is switched to the negative pressure introducing position A while the negative pressure pump 23 is maintained in the ON state, and the negative pressure is introduced into the evaporation system by the negative pressure pump 23. If the tank internal pressure detected by the pressure sensor 26 becomes lower than a leak determination value (for example, a value set to a pressure slightly lower than the reference pressure) before a predetermined time has elapsed from the start of negative pressure introduction, it is determined that there is no leak. If the tank internal pressure is equal to or greater than the leak determination value at time t4 when a predetermined time has elapsed from the start of the introduction of the negative pressure, it is determined that there is a leak. At this time, if the tank internal pressure converges around the reference pressure, it is determined that the reference orifice 25 has a leak hole equivalent to the reference leak hole diameter (for example, 0.5 mm in diameter). If the tank internal pressure is larger than the reference pressure, the reference orifice 25 It is determined that the leak hole is larger than the reference leak hole diameter of 25.
[0035]
Hereinafter, the processing contents of each program for leak diagnosis shown in FIGS. 3 to 5 which are executed by the ECU 31 will be described.
[0036]
[Leak diagnosis main control]
The leak diagnosis main control program shown in FIG. 3 is executed every predetermined time (for example, every 20 msec) while the main relay 32 is ON. When the program is started, first, in step 101, it is determined whether or not the IG switch 33 is turned off, that is, whether or not the engine is stopped. If so, the program ends.
[0037]
After that, after the IG switch 33 is switched from ON to OFF, every time the routine is started, “Yes” is determined in step 101, and the process proceeds to step 102, in which the fuel is supplied to the fuel tank 11. The determination is made based on, for example, whether the remaining fuel amount detected by the fuel level sensor 27 has changed by a predetermined amount or more. The processing of step 102 plays a role as a refueling determination means referred to in the claims.
[0038]
Thereafter, the process proceeds to step 103, where it is determined whether or not a predetermined time (for example, several minutes to 10 minutes) required for refueling determination has elapsed since the IG switch 33 was turned off. Terminate this program. As a result, the main relay 32 is maintained in the ON state until a predetermined time has elapsed since the IG switch 33 was turned off, and during that time, the refueling determination is performed.
[0039]
Thereafter, at step 103, when it is determined that a predetermined time (refueling determination time) has elapsed since the IG switch 33 was turned off, the routine proceeds to step 104, where a main relay control program of FIG.
[0040]
[Main relay control]
When the main relay control program in FIG. 4 is started in step 104, first, in step 201, it is determined whether or not fuel has been supplied to the fuel tank 11 based on the determination result in step 102 in FIG. As a result, when it is determined that the fuel has not been supplied, the process proceeds to step 202, and based on the measurement time of the soak timer 35 (elapsed time after the IG switch 33 is turned off), during the leak diagnosis period during which the engine is stopped. Is determined. Here, during the leak diagnosis period while the engine is stopped, the leakage is started after a predetermined time has elapsed since the IG switch 33 was turned off (this predetermined time is a time required for the tank internal pressure to stabilize, for example, 3 to 5 hours). The period is set until the diagnosis is completed.
[0041]
When the refueling determination time immediately after the IG switch 33 is turned off has elapsed, it is determined in step 202 that the current time is not within the leak diagnosis period while the engine is stopped, and the routine proceeds to step 203, where the main relay 32 is turned off, and the ECU 31, The power supply to the purge control valve 15, the passage switching valve 19, the negative pressure pump 23, the pressure sensor 26, the fuel level sensor 27, and the like is cut off to prevent battery consumption.
[0042]
Thereafter, when the measurement time of the soak timer 35 reaches a predetermined time while the engine is stopped, the backup power supply 34 of the ECU 31 is used as a power source to operate the drive circuit of the main relay control terminal of the ECU 31 to turn on the main relay 32, and the ECU 31 The power supply voltage is supplied to the control valve 15, the passage switching valve 19, the negative pressure pump 23, the pressure sensor 26, the fuel level sensor 27, and the like.
[0043]
As a result, the main routine of the leak diagnosis shown in FIG. 3 is started. In step 104, when the main relay control program shown in FIG. 4 is started, it is determined in step 202 that the engine is within the leak diagnosis period while the engine is stopped. In step 204, even after the IG switch 33 is turned off (after the engine is stopped), the main relay 32 is maintained in the ON state, and the ECU 31, the purge control valve 15, the passage switching valve 19, the negative pressure pump 23 , The power supply to the pressure sensor 26, the fuel level sensor 27, and the like is continued.
[0044]
Thereafter, the routine proceeds to step 205, where a later-described engine-stopped leak diagnosis program of FIG. 5 is executed. Thereafter, when the leak diagnosis while the engine is stopped is completed, "No" is determined in step 202, the process proceeds to step 203, the main relay 32 is turned off, and the ECU 31, the purge control valve 15, the passage switching valve 19, the negative pressure The power supply to the pump 23, the pressure sensor 26, the fuel level sensor 27 and the like is cut off.
[0045]
On the other hand, if it is determined in step 201 that fuel has been supplied to the fuel tank 11, the process proceeds to step 206, in which the soak timer 35 is turned off, the main relay 32 is turned off, and the ECU 31, the purge control valve 15. The power supply to the passage switching valve 19, the negative pressure pump 23, the pressure sensor 26, the fuel level sensor 27 and the like is cut off. As a result, the leak diagnosis program during engine stop of FIG. 5 is not executed, and the leak diagnosis during engine stop is prohibited. The processing of step 206 plays a role as a leak diagnosis prohibiting means referred to in the claims.
[0046]
When the measurement time of the soak timer 35 is used in another control, the soak timer 35 may not be turned off (maintained in the ON state) in step 206.
[0047]
[Leak diagnosis during engine stop]
5 is started in step 205 of the main relay control program in FIG. 4 and plays a role as a leak diagnosis means in the claims. When the program is started, first, in step 301, it is determined whether or not the reference pressure detection flag is set to “1” which means that the reference pressure has been detected, and the reference pressure has not been detected yet. For example, the reference pressure detection processing of steps 302 to 306 is executed as follows.
[0048]
First, in step 302, the process proceeds to step 303 while maintaining the passage switching valve 19 at the atmosphere opening position B, and turns on the negative pressure pump 23 to introduce a negative pressure into the reference pressure detecting unit 37. Thereafter, the process proceeds to step 304, where it is determined whether or not the speed of change of the pressure in the reference pressure detecting unit 37 detected by the pressure sensor 26 is lower than a predetermined speed (for example, 0.1 kPa / sec). If the speed is equal to or higher than the predetermined speed, it is determined that it is still necessary to introduce a negative pressure, and this program is terminated.
[0049]
Thereafter, when it is determined in step 304 that the pressure change speed is lower than the predetermined speed, it is determined that the negative pressure in the reference pressure detection unit 37 has stabilized near the reference pressure corresponding to the reference leak hole diameter of the reference orifice 25. Then, the process proceeds to a step 305, wherein the negative pressure in the reference pressure detector 37 detected by the pressure sensor 26 is stored in the memory of the ECU 31 as a reference pressure.
[0050]
Thereafter, the routine proceeds to step 306, where the path switching valve 19 is switched to the negative pressure introduction position A while the negative pressure pump 23 is maintained in the ON state, and the negative pressure pump 23 introduces a negative pressure into the evaporation system.
[0051]
Thereafter, the process proceeds to step 307, where it is determined whether or not the tank internal pressure detected by the pressure sensor 26 is lower than a leak determination value (for example, a reference pressure -0.5 kPa). If the tank internal pressure is equal to or greater than the leak determination value, the process proceeds to step 308, where it is determined whether or not a predetermined time (for example, 10 minutes) has elapsed from the start of the introduction of the negative pressure. If there is, the process proceeds to step 309, where the reference pressure detection flag is set to "1" which means that the reference pressure has been detected, and the program ends.
[0052]
Thereafter, if it is determined in step 307 that the tank internal pressure is lower than the leak determination value before a predetermined time has elapsed from the start of the introduction of the negative pressure, the process proceeds to step 310 and determines that the tank is normal (no leak).
[0053]
On the other hand, if it is determined in step 307 that the predetermined time has elapsed from the start of the introduction of the negative pressure without being determined in step 307 that the tank internal pressure is lower than the leak determination value, the process proceeds to step 311. Then, it is determined that there is an abnormality (there is a leak), and the warning lamp 36 provided on the instrument panel of the driver's seat is turned on, or a warning is displayed on a warning display section (not shown) of the instrument panel to drive the vehicle. The warning is given to the user, and the abnormality information (error code etc.) is stored in the backup RAM (not shown) of the ECU 31.
[0054]
Thereafter, in step 312, the negative pressure pump 23 is turned off. In step 313, the passage switching valve 19 is switched to the atmosphere opening position B. Then, the process proceeds to step 314, and the reference pressure detection flag is reset to "0". And terminate this program.
[0055]
In the present embodiment described above, it is determined whether or not fuel has been supplied to the fuel tank 11 every time the engine is stopped. If it is determined that fuel has been supplied, the leak diagnosis during the subsequent stop of the engine is prohibited. Therefore, it is possible to prevent a decrease in leak diagnosis accuracy due to fuel supply beforehand, and to ensure reliability of leak diagnosis. Moreover, since it is not necessary to increase the waiting time for leak diagnosis as a measure for refueling, it is possible to avoid an increase in the number of opportunities for the engine to be restarted before the start of leak diagnosis. Can be secured. In addition, if it is not necessary to lengthen the waiting time for the leak diagnosis, it is possible to avoid an increase in the power consumption of the soak timer 35 and the like during the waiting time. The power supply to the soak timer 35, the ECU 31, the passage switching valve 19, the negative pressure pump 23, the pressure sensor 26, etc.) can be cut off, the power consumption of the battery when the engine is stopped can be reduced, and the life of the battery can be reduced. Can be extended.
[0056]
Further, in the present embodiment, the negative pressure is introduced into the evaporative system by the negative pressure pump 23 when performing the leak diagnosis while the engine is stopped. Therefore, even if the leak hole is opened in the evaporative system. The advantage is that only air is sucked into the evaporative system from the leak hole during the leak diagnosis, and it is possible to prevent evaporative gas in the evaporative system from leaking from the leak hole into the atmosphere during the leak diagnosis. There is.
[0057]
Moreover, in a system in which a negative pressure is introduced into the evaporative system to perform a leak diagnosis, when a large amount of evaporative gas is generated by refueling, it becomes difficult to distinguish between a pressure increase due to the evaporative system leak and a pressure increase due to the evaporative gas generation. However, in the present embodiment, the leak diagnosis can be prohibited when the fuel is supplied, so that the decrease in the leak diagnosis accuracy due to the fuel supply can be surely prevented.
[0058]
In the present embodiment, it is determined whether or not fuel has been supplied to the fuel tank 11 based on a change in the remaining fuel amount detected by the fuel level sensor 27. It is possible to accurately determine whether or not the leak is detected, and the leak diagnosis can be prohibited only when the fuel is actually supplied. In addition, since the fuel level sensor 27 generally provided in the fuel tank 11 can be used, there is no need to provide a new sensor switch, and it is possible to satisfy the demand for cost reduction.
[0059]
However, a sensor for detecting the opening and closing of the filler cap of the fuel tank 11 may be provided to determine whether or not fuel has been supplied to the fuel tank 11 based on whether or not the filler cap of the fuel tank 11 has been opened. good.
[0060]
Further, in the above-described embodiment, the negative pressure pump 23 is used when performing the leak diagnosis while the engine is stopped. However, a positive pressure pump for introducing a positive pressure into the evaporation system may be provided. Alternatively, the configuration may be such that no pump is provided, and the leak diagnosis may be performed without forcing a predetermined pressure into the evaporation system.
[0061]
In addition, the present invention may appropriately change the configuration of the leak diagnosis system such as the evaporative gas purge system and the leak check module 17, and may appropriately change the specific method of determining the leak diagnosis. Any system that performs a leak diagnosis can be implemented by applying the present invention.
[Brief description of the 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 diagram showing a configuration of a leak check module.
FIG. 3 is a flowchart showing a processing flow of a leak diagnosis main control program;
FIG. 4 is a flowchart showing a flow of processing of a main relay control program.
FIG. 5 is a flowchart showing a flow of processing of a leak diagnosis program when the engine is stopped.
FIG. 6 is a time chart showing an example of execution of a leak diagnosis during engine operation.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... fuel tank, 12 ... evaporation passage, 13 ... canister, 14 ... purge passage, 15 ... purge control valve, 17 ... leak check module, 18 ... canister communication passage, 19 ... passage switching valve, 20 ... atmosphere communication passage, 21 ... Negative pressure introduction path, 22 ... Check valve, 23 ... Negative pressure pump, 24 ... Bypass passage, 25 ... Reference orifice, 26 ... Pressure sensor, 27 ... Fuel level sensor (fuel remaining amount detecting means), 31 ... ECU (Leakage) Diagnostic means, refueling determining means, leak diagnostic inhibiting means), 32: main relay, 33: IG switch, 35: soak timer, 37: reference pressure detecting section.

Claims (3)

The present invention is applied to an evaporative gas purging system for purging an evaporative gas generated by evaporating fuel in a fuel tank into an intake system of an internal combustion engine. A leak diagnostic device of an evaporative gas purge system including a leak diagnostic unit that performs a leak diagnostic while the internal combustion engine is stopped to diagnose the presence or absence of a leak.
Refueling determining means for determining whether fuel has been supplied to the fuel tank while the internal combustion engine is stopped,
After the refueling determination means determines that fuel has been supplied to the fuel tank while the internal combustion engine is stopped, a leak diagnosis prohibition means for prohibiting a leak diagnosis while the internal combustion engine is stopped is provided. Diagnostic device for evaporative gas purge system. A negative pressure pump for introducing a negative pressure into the evaporation system,
2. The evaporative gas purge according to claim 1, wherein the leak diagnosing means operates the negative pressure pump to introduce a negative pressure into the evaporative system when performing the leak diagnosis while the internal combustion engine is stopped. 3. System leak diagnostic device. A fuel remaining amount detecting unit for detecting a remaining amount of fuel in the fuel tank,
3. The fuel supply system according to claim 1, wherein the refueling determination unit determines whether fuel is supplied to the fuel tank based on a change in the remaining fuel amount detected by the remaining fuel amount detection unit. 4. Leak diagnosis device for evaporative gas purge system.

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