JP2004293438A - Leak diagnosing device of evaporation gas purging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an evaporation gas from being emitted to the atmosphere by surely executing the leak diagnosis of an evaporation gas purge system with a sufficient frequency and executing leak diagnosis during an interruption of an engine. <P>SOLUTION: When the engine is operated, the leak diagnosis is executed by introducing a negative pressure from an engine intake system into an evaporation system ranging from a fuel tank 11 to a purge control valve 15 every time when a specified leak diagnosis execution condition is established. On the other hand, while the engine is not operated, the leak diagnosis is executed by introducing a negative pressure into the evaporation system by a negative pressure pump installed in a leak check module 17 when a predetermined time elapses after an IG switch 33 is turned off, but the leak diagnosis is inhibited when the concentration of the evaporation gas within the evaporation system is high during an interruption of the engine. Thus, while the evaporation gas of a high concentration is prevented from being emitted to the atmosphere during the interruption of the engine, the leak diagnosis both during the operation of the engine and during the interruption of the engine is executed so that the leak diagnosis can be executed with a sufficient frequency. <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. Immediately after the internal combustion engine is stopped, the fuel filler cap of the fuel tank may be opened for fuel supply, and when the fuel filler is opened, the pressure in the evaporation system changes.
[0008]
Therefore, in order to ensure the diagnostic accuracy of the leak diagnosis while the internal combustion engine is stopped, the internal combustion engine must be controlled so as not to be affected by the change in the amount of evaporative gas generated after the internal combustion engine is stopped or the pressure change in the evaporative system due to the opening of the refueling port. It is necessary to start the leak diagnosis after a predetermined time (for example, several hours or more) has elapsed from the stop of the operation of the engine. Therefore, if the internal combustion engine is frequently restarted before the start time of the leak diagnosis while the internal combustion engine is stopped, the number of times that the leak diagnosis is executed while the internal combustion engine is stopped is reduced, and the leak diagnosis is not performed. Execution frequency may not be secured.
[0009]
Further, during the stop of the internal combustion engine, the purge control for purging the evaporative gas adsorbed in the canister into the intake system of the internal combustion engine is not performed, so that the adsorbed amount of the evaporative component in the canister is in a saturated state or a state close to the saturated state. When the internal combustion engine is stopped, the evaporative gas concentration in the evaporative system may become considerably high while the internal combustion engine is stopped.
[0010]
When the electric pump is operated while the internal combustion engine is stopped to make the inside of the evaporation system a negative pressure, the gas in the evaporation system is discharged into the atmosphere through the canister. At this time, if the concentration of the evaporative gas in the evaporative system is high, even if the gas in the evaporative system is discharged through the canister, the evaporative component in the gas may not be completely adsorbed by the canister and may be released to the atmosphere. In addition, when leak diagnosis is performed by pressurizing the inside of the evaporative system to a positive pressure with an electric pump while the internal combustion engine is stopped, if the evaporative gas concentration in the evaporative system is high, the air opening / closing valve is opened after the end of the leak diagnosis to evaporate. Even if the gas in the system is discharged into the atmosphere through the canister, there is a possibility that the evaporative component in the gas cannot be completely adsorbed by the canister and is discharged into the atmosphere.
[0011]
As a countermeasure, in a system that performs a leak diagnosis while the internal combustion engine is stopped, the leak diagnosis when the internal combustion engine is stopped is performed only when the evaporative gas concentration in the evaporation system is low while the internal combustion engine is stopped. The number of times that the leak diagnosis is performed while the engine is stopped is reduced, and the execution frequency of the leak diagnosis may not be secured.
[0012]
The present invention has been made in view of such circumstances, and accordingly, an object of the present invention is to prevent a high concentration of evaporative gas from being released into the atmosphere by performing a leak diagnosis while the internal combustion engine is stopped. It is an object of the present invention to provide a leak diagnostic device for an evaporative gas purge system capable of reliably ensuring an execution frequency.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, a leak diagnostic device for an evaporative gas purge system according to claim 1 of the present invention uses a leak diagnostic means to introduce a predetermined pressure into the evaporative system during operation of the internal combustion engine to seal the evaporative system. Diagnosis of leaks in the evaporative system based on the pressure in the evaporative system based on the pressure in the evaporative system while the engine is running, and sealing of the evaporative system by introducing a predetermined pressure into the evaporative system while the internal combustion engine is stopped In the state where the evaporative gas concentration in the evaporative system is high while the internal combustion engine is stopped, the diagnosis is performed while the internal combustion engine is stopped. In the Japanese Patent Application Laid-Open No. H11-260, the leak diagnosis during stoppage of the internal combustion engine is prohibited.
[0014]
With this configuration, it is possible to execute the leak diagnosis during the stop of the internal combustion engine only when the evaporative gas concentration in the evaporative system is low during the stop of the internal combustion engine. Can be prevented from being released into the atmosphere. In addition, since both the leak diagnosis during the operation of the internal combustion engine and the leak diagnosis during the stop of the internal combustion engine can be executed, the internal combustion engine is restarted before the start of the leak diagnosis during the stop of the internal combustion engine, Even if the concentration of evaporative gas in the evaporative system increases while the internal combustion engine is stopped, the number of times leak diagnosis is performed while the internal combustion engine is stopped decreases, but the shortfall can be compensated for by the leak diagnosis during operation of the internal combustion engine. As a result, it is possible to increase the number of executions of the leak diagnosis as compared with a system that performs only the leak diagnosis while the internal combustion engine is stopped, and it is possible to detect an evaporative system leak (leak) at an early stage.
[0015]
According to a second aspect of the present invention, a negative pressure pump for introducing a negative pressure into the evaporative system is provided as the pressure introducing means, and the negative pressure pump is operated when performing a leak diagnosis while the internal combustion engine is stopped. Then, it is preferable to introduce a negative pressure into the evaporation system. If the leak diagnosis is performed with the negative pressure in the evaporative system, even if a leak hole is opened in the evaporative system, during the leak diagnosis, only the air is sucked into the evaporative system from the leak hole, During the leak diagnosis, the evaporative gas in the evaporative system can be prevented from leaking into the atmosphere from the leak hole.
[0016]
By the way, the leak diagnosis during the stop of the internal combustion engine has the advantage that the diagnosis accuracy is higher than the leak diagnosis during the operation of the internal combustion engine. There is no problem even if the frequency of executing the leak diagnosis during the operation of the engine is low (or not at all). Further, if it is not necessary to perform the leak diagnosis during the operation of the internal combustion engine, the influence on the drivability and the like due to the leak diagnosis during the operation of the internal combustion engine can be avoided.
[0017]
Therefore, it may be determined whether the execution of the leak diagnosis during the operation of the internal combustion engine is based on the execution history of the leak diagnosis during the stop of the internal combustion engine. With this configuration, if the execution frequency of the leak diagnosis during the stop of the internal combustion engine is sufficiently ensured, the execution frequency of the leak diagnosis during the operation of the internal combustion engine can be reduced (or even if the execution is not performed). ), The influence on the drivability and the like due to the leak diagnosis during the operation of the internal combustion engine can be avoided. In addition, when the frequency of executing the leak diagnosis during the stop of the internal combustion engine is insufficient, the shortage can be compensated for by the leak diagnosis during the operation of the internal combustion engine.
[0018]
In this case, the execution of the leak diagnosis during the operation of the internal combustion engine may be determined based on the number of times of travel since the previous execution of the leak diagnosis during the stop of the internal combustion engine. With this configuration, it is possible to execute the leak diagnosis during the operation of the internal combustion engine when the state in which the leak diagnosis during the stop of the internal combustion engine is not executed continues several times.
[0019]
Also, it may be determined whether or not to execute the leak diagnosis while the internal combustion engine is stopped, based on the execution history of the leak diagnosis while the internal combustion engine is operating. In this case, regardless of the execution history of the leak diagnosis while the internal combustion engine is stopped, the leak diagnosis is performed during the operation of the internal combustion engine. This is supplemented by a leak diagnosis while the internal combustion engine is stopped. With this configuration, the number of executions of the leak diagnosis while the internal combustion engine is stopped is reduced as compared to the case where the leak diagnosis is executed while the internal combustion engine is stopped, regardless of the execution history of the leak diagnosis during the operation of the internal combustion engine. It is possible to improve the durability and life of the pressure introducing means such as a negative pressure pump that is operated while the internal combustion engine is stopped, and to reduce the battery power consumption while the internal combustion engine is stopped. Lifespan can be extended.
[0020]
Also, it may be determined whether to execute the leak diagnosis while the internal combustion engine is stopped based on the execution history of the leak diagnosis while the internal combustion engine is stopped. With this configuration, for example, the leak diagnosis is performed at an appropriate interval, such as performing the leak diagnosis once during the stop of the internal combustion engine per N times of running (N ≧ 2). As in the case of the fifth aspect, the life of the pressure introducing means and the life of the battery can be extended.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
<< Embodiment (1) >>
Hereinafter, an embodiment (1) of the present invention will be described with reference to FIGS. 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).
[0022]
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.
[0023]
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 provided in the middle of the atmosphere communication path 20 via a check valve 22 and an electric negative pressure pump 23 (pressure introduction means). It is connected to the. 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.
[0024]
The passage switching valve 19 can switch 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 is composed of a simple solenoid valve.
[0025]
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). A pressure sensor 26 (pressure detecting means) for detecting the pressure in the bypass passage 24 is provided in a passage of the bypass passage 24 which is connected from the reference orifice 25 to the negative pressure introduction passage 21.
[0026]
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 bypass passage 24 is connected to the negative pressure introducing passage 21 and the canister. Since the pressure in the bypass passage 24 is detected by the pressure sensor 26 to communicate with the inside of the evaporation system via the communication passage 18, the pressure in the fuel tank 11, which is representative data of the pressure in the evaporation system (hereinafter referred to as “the pressure in the evaporation system”). Tank internal pressure ”).
[0027]
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.
[0028]
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, since the inside of the bypass passage 24 is opened to the atmosphere through the atmosphere communication passage 20, the pressure sensor 26 The atmospheric pressure can be detected by detecting the pressure in the passage 24.
[0029]
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 passage from the reference orifice 25 to the negative pressure pump 23 in the bypass passage 24 has a negative pressure. At this time, by detecting the pressure on the side of the negative pressure pump 23 in the bypass passage 24 by the pressure sensor 26, the reference pressure corresponding to the reference leak hole diameter of the reference orifice 25 can be detected.
[0030]
Further, as shown in FIG. 1, a fuel level sensor 27 for detecting the remaining fuel amount 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.
[0031]
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.
[0032]
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. .
[0033]
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.
[0034]
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). .
[0035]
Further, the ECU 31 functions as a leak diagnosis unit by executing each of the leak diagnosis programs shown in FIGS. 3 to 6 described below, and performs both the leak diagnosis while the engine is running and the leak diagnosis while the engine is stopped. If the evaporative gas concentration in the evaporative system is high while the engine is stopped, prohibit the leak diagnosis while the engine is stopped, and secure the execution frequency of the leak diagnosis. Prevents evaporative gas from being released into the atmosphere.
[0036]
Here, the leak diagnosis during the operation of the engine and the leak diagnosis during the stop of the engine performed in the embodiment (1) will be described.
As shown in FIG. 7, the leak diagnosis during the engine operation is performed by switching the passage switching valve 19 to the negative pressure introducing position A at the time t1 when the condition for executing the leak diagnosis during the engine operation is satisfied, and closing the evaporation system. The purge control valve 15 is opened to introduce a negative pressure from the engine intake system into the evaporation system. This function serves as a pressure introducing means at the time of leak diagnosis during operation of the engine.
[0037]
At the time t2 when the tank internal pressure detected by the pressure sensor 26 decreases to the predetermined negative pressure due to the introduction of the negative pressure, the purge control valve 15 is closed to stop the introduction of the negative pressure, and the evaporation system is closed again. At a time point t3 when a predetermined time has elapsed from the stop of the introduction of the negative pressure, the change amount ΔP in the tank pressure within the predetermined time period is calculated. If the change amount ΔP in the tank pressure is equal to or less than the leak determination value, it is determined that there is no leak. If the change amount ΔP is larger than the leak determination value, it is determined that there is a leak.
[0038]
On the other hand, as shown in FIG. 8, the leak diagnosis during the stop of the engine is performed when the evaporative gas concentration in the evaporative system is low at time t4 when a predetermined time (for example, 3 to 5 hours) has elapsed from the stop of the engine operation. The negative pressure pump 23 is turned on while maintaining the pressure 19 at the atmospheric release position B, and a negative pressure is introduced into the bypass passage 24 on the negative pressure pump 23 side from the reference orifice 25, and the negative pressure corresponds to the reference orifice 25. At time t5 when the pressure becomes stable around the reference pressure, the negative pressure in the bypass passage 24 detected by the pressure sensor 26 is stored in the memory of the ECU 31 as the reference pressure.
[0039]
After the detection of the reference pressure, the passage 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 is introduced into the evaporation system. If the tank internal pressure detected by the pressure sensor 26 becomes lower than the leak determination value before a predetermined time has elapsed from the start of the negative pressure introduction, it is determined that there is no leak, and at a time t7 when the predetermined time has elapsed from the start of the negative pressure introduction. If the tank internal pressure is equal to or greater than the leak determination value, 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.
Hereinafter, the processing contents of each program for leak diagnosis shown in FIGS. 3 to 6 executed by the ECU 31 will be described.
[0040]
[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 there is, the process proceeds to step 102, and a later-described leak diagnosis program during engine operation shown in FIG. 5 is executed.
[0041]
Thereafter, after the IG switch 33 is switched from ON to OFF, every time this routine is started, “No” is determined in step 101, and the process proceeds to step 103, where the main relay control program of FIG. I do.
[0042]
[Main relay control]
When the main relay control program of FIG. 4 is started in step 103, first, in step 201, a leak diagnosis period during engine stoppage is performed based on the measurement time of the soak timer 35 (elapsed time after the IG switch 33 is turned off). It is determined whether it is within. Here, the leak diagnosis period while the engine is stopped is a time period after the predetermined time during which the IG switch 33 is turned off (this predetermined time is a time required for the tank internal pressure to stabilize, for example, 3 to 5 hours). It is set to the period until it ends.
[0043]
Immediately after the IG switch 33 is turned off, in step 201, it is determined that the current time is not within the leak diagnosis period while the engine is stopped, and the process proceeds to step 202, where the main relay 32 is turned off, and the ECU 31, the purge control valve 15, the passage The power supply to the 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 the battery from being consumed.
[0044]
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 supply to operate the drive circuit of the main relay control terminal of the ECU 31 to turn on the main relay 32, and to perform a leak diagnosis. The power supply voltage is supplied to necessary parts (ECU 31, purge control valve 15, passage switching valve 19, negative pressure pump 23, pressure sensor 26, fuel level sensor 27, etc.).
[0045]
Accordingly, the main routine of the leak diagnosis shown in FIG. 3 is started. In step 103, the main relay control program shown in FIG. 4 is started. In step 201, it is determined that the engine is within the leak diagnosis period while the engine is stopped. In step 203, 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 components necessary for the leak diagnosis (ECU 31, purge control valve 15, passage switching) Power supply to the valve 19, the negative pressure pump 23, the pressure sensor 26, the fuel level sensor 27, etc.) is continued.
[0046]
Thereafter, the routine proceeds to step 204, where a leak diagnosis program for stopping the engine shown in FIG. Thereafter, when the leak diagnosis while the engine is stopped is completed, “No” is determined in step 201, the process proceeds to step 202, 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.
[0047]
[Diagnosis of leaks during engine operation]
When the leak diagnosis program during engine operation in FIG. 5 is started in step 102 of the leak diagnosis main control program in FIG. 3, first, in step 301, it is determined whether or not the leak diagnosis execution condition during engine operation is satisfied. Is determined. Here, the leak diagnosis execution condition during the operation of the engine is, for example, to satisfy both of the following conditions (1) and (2).
[0048]
(1) The intake pipe pressure is equal to or lower than a predetermined value (that is, a stable operation state such as an idle operation state or a low-speed operation state).
(2) Low evaporative gas concentration in the evaporative system
The condition (2) may be determined by one or more of the following methods (1) to (3).
[0049]
(1) Since the amount of evaporative gas purged into the engine intake system changes according to the evaporative gas concentration and the purge flow rate during the purge control and the air-fuel ratio feedback correction amount changes, the purge flow rate and the air-fuel ratio feedback correction during the purge control The amount is learned, the evaporative gas concentration is calculated based on these learned values, and it is determined whether the evaporative gas concentration is lower than a predetermined value.
[0050]
(2) Since the tank internal pressure changes according to the evaporative gas concentration in the evaporative system, it is determined whether or not the evaporative gas concentration is lower than a predetermined value based on the tank internal pressure.
(3) Since the amount of evaporative gas generated changes in accordance with the fuel temperature and the outside air temperature and the evaporative gas concentration in the evaporative system changes, it is determined whether the evaporative gas concentration is lower than a predetermined value based on the fuel temperature and the outside air temperature. judge.
[0051]
If both of the above conditions (1) and (2) are satisfied, the leak diagnosis execution condition during engine operation is satisfied, but there is a condition that does not satisfy either one of the above conditions (1) and (2). For example, the condition for executing the leak diagnosis during the operation of the engine is not satisfied. If it is determined that the condition for executing the leak diagnosis during the operation of the engine is not satisfied, the program is terminated without executing the processing related to the leak diagnosis during the operation of the engine after step 302.
[0052]
On the other hand, when it is determined in step 301 that the conditions for executing the leak diagnosis during the operation of the engine are satisfied, the processes related to the leak diagnosis during the operation of the engine after step 302 are executed as follows. First, in step 302, the passage switching valve 19 is switched to the negative pressure introduction position A to seal the evaporation system.
[0053]
Thereafter, the process proceeds to step 303, where it is determined whether or not the tank internal pressure detected by the pressure sensor 26 has decreased below a predetermined negative pressure (for example, -1.33 kPa). If the tank internal pressure has not decreased below the predetermined negative pressure, Proceeding to step 304, the process of opening the purge control valve 15 and introducing a negative pressure from the engine intake system into the evaporation system is continued.
[0054]
Thereafter, when it is determined in step 303 that the tank internal pressure has dropped below the predetermined negative pressure, the routine proceeds to step 305, where the purge control valve 15 is closed to stop the introduction of negative pressure from the engine intake system, and the The system is closed again. Then, in the next step 306, it is determined whether or not a predetermined time has elapsed since the stop of the introduction of the negative pressure. If the predetermined time has not elapsed, the present program is terminated as it is.
[0055]
As a result, the evaporative system is maintained in a sealed state until a predetermined time has elapsed from the stop of the introduction of the negative pressure. Then, when a predetermined time has elapsed from the stop of the introduction of the negative pressure, the process proceeds to step 307, and the amount of change ΔP in the tank internal pressure within the predetermined time is calculated. Thereafter, the routine proceeds to step 308, where the tank internal pressure change amount ΔP is compared with a predetermined leak determination value. As a result, when it is determined that the tank internal pressure change amount ΔP is equal to or smaller than the leak determination value, the process proceeds to step 309, and it is determined that the tank is normal (no leak).
[0056]
On the other hand, when it is determined in step 308 that the tank internal pressure change amount ΔP is larger than the leak determination value, the process proceeds to step 310, where it is determined that there is an abnormality (there is a leak), and the A warning lamp 36 provided on the panel is turned on, or a warning is displayed on a warning display section (not shown) of the instrument panel to warn the driver, and the abnormality information (abnormal code etc.) It is stored in a backup RAM (not shown).
Thereafter, the routine proceeds to step 311, where the passage switching valve 19 is switched to the atmosphere opening position B, and the program is terminated.
[0057]
[Leak diagnosis during engine stop]
When the leak diagnostic program for stopping the engine shown in FIG. 6 is started in step 204 of the main relay control program shown in FIG. 4, first, in step 401, it is determined whether or not the evaporative gas concentration in the evaporative system is higher than a predetermined value. The determination may be made by one or more of the following methods (1) to (3).
[0058]
(1) The purge flow rate during the purge control and the air-fuel ratio feedback correction amount are learned during the engine operation, and the evaporative gas concentration is calculated based on these learned values (for example, the learned value immediately before the engine is stopped). It is determined whether or not the evaporative gas concentration is higher than a predetermined value.
[0059]
(2) Since the tank internal pressure changes according to the evaporation gas concentration in the evaporation system, it is determined whether or not the evaporation gas concentration is higher than a predetermined value based on the tank internal pressure.
(3) Since the amount of evaporative gas generated changes in accordance with the fuel temperature and the outside air temperature and the evaporative gas concentration in the evaporative system changes, it is determined whether or not the evaporative gas concentration is higher than a predetermined value based on the fuel temperature and the outside air temperature. judge.
[0060]
If it is determined in step 401 that the evaporative gas concentration in the evaporative system is higher than a predetermined value (that is, the amount of evaporative gas adsorbed in the canister 13 is in a saturated state or a state close thereto), the evaporative system in the evaporative system Even if the gas is discharged to the atmosphere through the canister 13, it is determined that there is a possibility that a high concentration of the evaporative gas in the evaporative system may be released to the atmosphere, and the processing related to the leak diagnosis during the stop of the engine after step 402 This program is terminated without executing.
[0061]
On the other hand, if it is determined in step 401 that the concentration of the evaporative gas in the evaporative system is low, the processing related to the leak diagnosis during engine stop after step 402 is executed as follows. First, in step 402, it is determined whether or not the reference pressure detection flag is set to "1" which means that the reference pressure has been detected. If the reference pressure has not been detected yet, the reference in steps 403 to 407 is determined. The pressure detection processing is executed as follows.
[0062]
First, in step 403, while the passage switching valve 19 is maintained at the atmosphere opening position B, the process proceeds to step 404, in which the negative pressure pump 23 is turned on so that the bypass passage 24 is located closer to the negative pressure pump 23 than the reference orifice 25. Introduce negative pressure. Thereafter, the process proceeds to step 405, where it is determined whether or not the speed of change of the pressure in the bypass passage 24 detected by the pressure sensor 26 is lower than a predetermined speed (for example, 0.133 kPa / sec). If it is equal to or higher than the speed, it is determined that it is still necessary to introduce a negative pressure, and this program is terminated as it is.
[0063]
Thereafter, at step 405, when it is determined that the pressure change speed is lower than the predetermined speed, it is determined that the negative pressure in the bypass passage 24 has stabilized near the reference pressure corresponding to the reference leak hole diameter of the reference orifice 25. The routine proceeds to step 406, where the negative pressure in the bypass passage 24 detected by the pressure sensor 26 is stored in the memory of the ECU 31 as a reference pressure.
[0064]
Thereafter, the process proceeds to step 407, in which the passage 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.
[0065]
Thereafter, the process proceeds to step 408, 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, the reference pressure -0.655 kPa). If the tank internal pressure is equal to or greater than the leak determination value, the process proceeds to step 409, where it is determined whether or not a predetermined time (for example, 10 minutes) has elapsed from the start of the negative pressure introduction. If there is, the process proceeds to step 410, where the reference pressure detection flag is set to "1" which means that the reference pressure has been detected, and the program ends.
[0066]
Thereafter, if it is determined in step 408 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 411 and determines that the pressure is normal (no leak).
[0067]
On the other hand, if it is determined in Step 408 that the predetermined time has elapsed from the start of the introduction of the negative pressure without being determined in Step 408 that the tank internal pressure is lower than the leak determination value, the process proceeds to Step 412. 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.
[0068]
Thereafter, in step 413, the negative pressure pump 23 is turned off, and in the next step 414, the passage switching valve 19 is switched to the atmosphere opening position B, and then the process proceeds to step 415, where the reference pressure detection flag is reset to "0". And terminate this program.
[0069]
In the embodiment (1) described above, when the evaporative gas concentration in the evaporative system is high while the engine is stopped, the leak diagnosis during the stop of the engine is prohibited, and only when the evaporative gas concentration is low, the leak during the stop of the engine is stopped. Since the diagnosis is performed, it is possible to prevent a high concentration of evaporative gas from being released into the atmosphere by the leak diagnosis during the stop of the engine.
[0070]
In addition, since both the leak diagnosis during the engine operation and the leak diagnosis during the engine stop are executed, the engine is restarted before the start of the leak diagnosis during the engine stop or during the engine stop. Even if the concentration of evaporative gas in the evaporative system becomes high and the number of leak diagnoses performed while the engine is stopped decreases, this can be compensated for by the leak diagnosis while the engine is running. It is possible to increase the number of executions of the leak diagnosis as compared to a system that performs only the leak, and it is possible to detect an evaporative leak at an early stage.
[0071]
Further, in the present embodiment (1), when performing a leak diagnosis while the engine is stopped, a negative pressure is applied to the inside of the evaporative system by the negative pressure pump 23, so that a leak hole is opened in the evaporative system. Even during the leak diagnosis, only the air is sucked into the evaporative system from the leak hole, and it is possible to prevent the evaporative gas in the evaporative system from leaking into the atmosphere from the leak hole during the leak diagnostic. There is also an advantage.
[0072]
<< Embodiment (2) >>
By the way, leak diagnosis during engine stoppage has the advantage of higher diagnostic accuracy than leak diagnosis during engine operation.If the frequency of execution of leak diagnosis during engine stoppage is sufficiently ensured, it is Even if the leak diagnosis is performed less frequently (or not at all), there is no problem. Further, if it is not necessary to perform the leak diagnosis during the operation of the engine, the influence on the drivability and the like due to the leak diagnosis during the operation of the engine can be avoided.
[0073]
Therefore, in the embodiment (2) of the present invention, by executing a leak diagnosis main control program of FIG. 9 described later, it is determined whether or not to execute the leak diagnosis during the engine operation based on the execution history of the leak diagnosis while the engine is stopped. By judging, if the frequency of executing the leak diagnosis while the engine is stopped is insufficient, the shortage is compensated for by the leak diagnosis during the operation of the engine.
[0074]
The leak diagnosis main control program of FIG. 9 executed in the present embodiment (2) includes the processing of step 102a between steps 101 and 102 of the leak diagnosis main control program of FIG. Are added, and the other steps are the same as those in FIG.
[0075]
In this program, when it is determined in step 101 that the engine is operating (IG switch ON), the process proceeds to step 102a, and it is determined whether or not the leak diagnosis was performed during the previous stop of the engine.
[0076]
As a result, if the leak diagnosis has been executed during the previous engine stop, it is determined that the frequency of execution of the leak diagnosis can be secured without executing the leak diagnosis during the engine operation, and step 102 (FIG. 5). This program is terminated without executing the engine running leak diagnosis program). As a result, during the current engine operation, the leak diagnosis during the engine operation is not performed.
[0077]
On the other hand, if it is determined in step 102a that the leak diagnosis has not been executed during the previous engine stop, the process proceeds to step 102, and the above-described leak diagnosis program during engine operation in FIG. 5 is executed. Thus, when the leak diagnosis execution condition is satisfied during the current engine operation, the leak diagnosis during the engine operation is performed.
[0078]
In this program, the leak diagnosis during the engine operation is performed when the leak diagnosis has not been performed during the previous engine stop. It may be determined whether or not to execute the leak diagnosis during the operation of the engine based on With this configuration, it is possible to execute the leak diagnosis during the operation of the engine when the state in which the leak diagnosis during the stop of the engine is not executed continues several times.
[0079]
In the above-described embodiment (2), whether to execute the leak diagnosis during the engine operation is determined based on the execution history of the leak diagnosis while the engine is stopped. Sufficiently secured means that the frequency of execution of leak diagnosis during engine operation can be reduced (or need not be performed), and the influence of leak diagnosis during engine operation on drivability is also avoided. it can. In addition, when the frequency of executing the leak diagnosis while the engine is stopped is insufficient, the shortfall can be compensated for by the leak diagnosis during the operation of the engine.
[0080]
It should be noted that whether or not to execute the leak diagnosis during the engine operation may be determined based on the accumulated traveling distance, the accumulated operation time, and the like from the previous execution of the leak diagnosis while the engine is stopped. The same effect as (2) can be obtained.
[0081]
<< Embodiment (3) >>
In the above embodiment (2), whether or not to execute the leak diagnosis during the engine operation is determined based on the execution history of the leak diagnosis while the engine is stopped. It may be determined whether or not to execute the leak diagnosis while the engine is stopped based on the execution history. Hereinafter, an embodiment (3) of the present invention that embodies this will be described.
[0082]
In the present embodiment (3), by executing the leak diagnosis main control program shown in FIG. 10, it is determined whether or not to execute the leak diagnosis while the engine is stopped according to the execution history of the leak diagnosis during the operation of the engine. In this case, regardless of the execution history of the leak diagnosis while the engine is stopped, the leak diagnosis during the engine operation is performed. This is supplemented by a leak diagnosis.
[0083]
The leak diagnosis main control program of FIG. 10 is obtained by adding the processing of step 102b between steps 101 and 103 of the leak diagnosis main control program of FIG. 3 described in the above embodiment (1). Are the same as those in FIG.
[0084]
In this program, if it is determined in step 101 that the engine is running (IG switch ON), the process proceeds to step 102, and the engine running leak diagnosis program of FIG. 5 described in the embodiment (1) is executed. Then, when the condition for executing the leak diagnosis during the engine operation is satisfied, the leak diagnosis during the engine operation is executed.
[0085]
On the other hand, if it is determined in step 101 that the engine is stopped (the IG switch is OFF), the process proceeds to step 102b, and it is determined whether the leak diagnosis was performed during the previous engine operation.
[0086]
As a result, if the leak diagnosis has been executed during the previous engine operation, it is determined that the frequency of the leak diagnosis can be secured without executing the leak diagnosis while the engine is stopped. This program ends without executing the main relay control program). As a result, during the current engine stop, the leak diagnosis during the engine stop is not performed.
[0087]
On the other hand, if it is determined in step 102b that the leak diagnosis has not been performed during the previous engine operation, the process proceeds to step 103, and the above-described main relay control program of FIG. 4 is executed. Thereby, if the evaporative gas concentration is not high during the current engine stop, a leak diagnosis during the engine stop is executed.
[0088]
In this program, when the leak diagnosis was not executed during the previous engine operation, the leak diagnosis during the stop of the engine is executed. It may be determined whether or not to execute the leak diagnosis while the engine is stopped based on With this configuration, it is possible to execute the leak diagnosis while the engine is stopped when the vehicle is running several times without performing the leak diagnosis while the engine is running.
[0089]
In the above-described embodiment (3), whether to execute the leak diagnosis while the engine is stopped is determined based on the execution history of the leak diagnosis while the engine is running. Regardless, the number of times of performing the leak diagnosis while the engine is stopped can be reduced as compared with the case where the leak diagnosis is performed while the engine is stopped. The durability and life of the battery 17 can be improved, the power consumption of the battery while the engine is stopped can be reduced, and the life of the battery can be extended.
[0090]
It should be noted that it may be determined whether or not to execute the leak diagnosis while the engine is stopped, based on the accumulated traveling distance and the accumulated operation time from the previous execution of the leak diagnosis while the engine is running. The same effect as (3) can be obtained.
[0091]
Further, it may be determined whether or not to execute the leak diagnosis while the engine is stopped based on the execution history of the leak diagnosis while the engine is stopped. In this way, for example, a leak diagnosis while the engine is stopped can be performed at an appropriate interval, for example, once per engine N times (N ≧ 2), a leak diagnosis while the engine is stopped can be performed. Thus, the same effect as that of the embodiment (3) can be obtained.
[0092]
In each of the embodiments (1) to (3) described above, when performing the leak diagnosis while the engine is stopped, the inside of the evaporative system is set to the negative pressure by using the negative pressure pump 23. However, the positive pressure pump is used. May be used to pressurize the inside of the evaporation system to a positive pressure. Further, when performing a leak diagnosis during engine operation, a negative pressure or a positive pressure pump may be used to introduce a negative pressure or a positive pressure into the evaporation system, or a negative pressure pump and an intake pipe negative pressure may be introduced. A negative pressure may be introduced into the evaporation system by using the pressure together.
[0093]
In addition, according to the present invention, the configuration of the leak diagnosis system such as the evaporative gas purge system and the leak check module 17 may be appropriately changed, and the specific method of determining the leak diagnosis may be appropriately changed.
[0094]
In short, the present invention can be widely applied to a system that performs both a leak diagnosis during engine stop and a leak diagnosis during engine operation, regardless of the system configuration or a specific method of determining leak diagnosis.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an evaporative gas purge system according to an embodiment (1) 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 according to the embodiment (1).
FIG. 4 is a flowchart showing a processing flow of a main relay control program according to the embodiment (1).
FIG. 5 is a flowchart showing a flow of processing of a leak diagnosis program during engine operation according to the embodiment (1).
FIG. 6 is a flowchart showing a processing flow of a leak diagnosis program during engine stop according to the embodiment (1).
FIG. 7 is a time chart showing an example of execution of a leak diagnosis during engine operation.
FIG. 8 is a time chart showing an example of executing a leak diagnosis while the engine is stopped.
FIG. 9 is a flowchart showing a flow of processing of a leak diagnosis main control program according to the embodiment (2).
FIG. 10 is a flowchart showing a flow of processing of a leak diagnosis main control program according to the embodiment (3).
[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 (pressure introduction means), 24 .. bypass passage, 25... Reference orifice, 26... Pressure sensor (pressure detection means), 31. , 32 ... main relay, 33 ... IG switch, 35 ... soak timer.

Claims (6)

In an evaporative gas purge system for purging evaporative gas generated by evaporating fuel in a fuel tank into an intake system of an internal combustion engine,
Pressure introducing means for introducing a predetermined pressure into an evaporation system including the fuel tank,
Pressure detection means for detecting the pressure in the evaporation system,
During operation of the internal combustion engine, a predetermined pressure is introduced into the evaporation system during operation of the internal combustion engine to diagnose the presence or absence of a leak in the evaporation system based on the pressure in the evaporation system while the evaporation system is sealed. Leak diagnosis and internal combustion that diagnoses the presence or absence of a leak in the evaporative system based on the pressure in the evaporative system while the evaporative system is closed by introducing a predetermined pressure into the evaporative system while the internal combustion engine is stopped. Leak diagnosis means for performing a leak diagnosis while the engine is stopped,
A leak diagnostic device for an evaporative gas purge system, wherein the leak diagnostic means prohibits a leak diagnostic while the internal combustion engine is stopped when the evaporative gas concentration in the evaporative system is high while the internal combustion engine is stopped. As the pressure introducing means, a negative pressure pump for introducing a negative pressure into the evaporation system is provided,
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. The evaporative gas purge system according to claim 1, wherein the leak diagnosis unit determines whether or not to execute the leak diagnosis during the operation of the internal combustion engine based on a history of execution of the leak diagnosis while the internal combustion engine is stopped. Leak diagnostic equipment. 4. The leak diagnosis device according to claim 3, wherein the leak diagnosis unit determines whether to execute the leak diagnosis during the operation of the internal combustion engine based on the number of times of travel since a previous execution of the leak diagnosis during the stop of the internal combustion engine. 5. Leak diagnostic device for evaporative gas purge system. The evaporative gas purge system according to claim 1, wherein the leak diagnosis unit determines whether or not to execute the leak diagnosis while the internal combustion engine is stopped based on an execution history of the leak diagnosis while the internal combustion engine is operating. Leak diagnostic equipment. 6. The leak diagnosis unit according to claim 1, wherein the leak diagnosis unit determines whether to execute the leak diagnosis while the internal combustion engine is stopped based on a history of the leak diagnosis while the internal combustion engine is stopped. Leak diagnostic device for evaporative gas purge system.

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