JP2004308612A - Leak diagnostic device for evaporative emisssion purging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent wrong determination of leak by detecting existence of abnormality of a reference pressure detection part when leak diagnosis of an evaporation system with using reference pressure is performed. <P>SOLUTION: After detecting pressure in a reference pressure detection part 37 as a reference pressure by introducing negative pressure to the reference pressure detection part 37 by a vacuum pump 23 under a condition that a passage selector valve 19 is retained at an open air position B, the passage selector valve 19 is switched to a vacuum introduction position A and vacuum is introduced to the evaporation system by the vacuum pump 23 and pressure in the evaporation system is detected, and the reference pressure and the pressure in the evaporation system are compared to perform leak diagnosis is performed. Under these circumstances, the current reference pressure and a reference pressure learned value (for example, previous reference pressure) are compared and existence of abnormality of the reference pressure detection part 37 is determined. When it is determined that abnormality exists, leak diagnosis is stopped or a current leak diagnosis result is made invalid to prevent wrong determination of existence of leak or degree of leak due to abnormality of the reference pressure detection part 37. <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. Thereafter, while the purge control valve is closed and the evaporative system from the purge control valve to the fuel tank is closed, the amount of change in the pressure in the evaporative system (for example, the pressure in the fuel tank) is measured, and the negative pressure is introduced. In some cases, the presence / absence of a leak (leakage) in an evaporative system is determined by comparing a pressure change amount at the time with a leak determination value (for example, a pressure change amount when introducing atmospheric pressure).
[0004]
However, the above-described conventional leak diagnosis has a disadvantage that it is not possible to accurately determine a minute leak or a leak degree (the size of a leak hole).
[0005]
Therefore, for example, as described in Patent Document 2 (Japanese Patent Laid-Open No. 2002-4959), an electric negative pressure pump and a reference hole (a hole having a predetermined diameter corresponding to a minute leak hole) are formed. A pressure detection unit and a switching valve for switching between a path for introducing a negative pressure into the reference pressure detection unit with a negative pressure pump and a path for introducing a negative pressure into the evaporation system with the negative pressure pump are provided. The pressure regulated by the reference hole (reference pressure) is detected by introducing a negative pressure into the detection unit and detecting the pressure in the reference pressure detection unit, and then the negative pressure is detected under the same conditions as when the reference pressure was detected. Some pumps detect negative pressure in the evaporative system by introducing a negative pressure into the evaporative system, and compare the reference pressure with the pressure in the evaporative system to determine minute leaks and the degree of leak. .
[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, when detecting the reference pressure, for example, the reference hole of the reference pressure detection unit is clogged with a foreign substance such as a condensed evaporative component or dust, or an abnormality such as deformation of the reference hole or leakage of the reference pressure detection unit occurs. In such a case, the detected value of the reference pressure deviates from the normal value due to the abnormality (see FIG. 3). However, in the system of Patent Document 2, even if some abnormality occurs in the reference pressure detecting unit and the detected value of the reference pressure deviates from the normal value, there is no means for detecting the abnormality. Leak diagnosis is performed based on an abnormal detection value, and there is a possibility that the leak diagnosis is erroneously determined.
[0008]
The present invention has been made in view of such circumstances, and accordingly, an object thereof is to detect an abnormality of a reference pressure detection unit in a system for performing a leak diagnosis of an evaporative system based on a reference pressure detection value. It is an object of the present invention to provide a leak diagnostic device for an evaporative gas purge system, which can prevent erroneous determination of a leak due to an abnormality in a reference pressure detecting unit.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a leak diagnosis device for an evaporative gas purge system according to claim 1 of the present invention learns a detected value of a reference pressure by a reference pressure learning means, and detects a current detection value of the reference pressure by an abnormality determination means. The reference pressure learning value is compared with the reference pressure learning value to determine whether the reference pressure detection unit is abnormal.
[0010]
If the reference pressure detection unit is normal, the fluctuation amount (variation width) of the reference pressure detected for each leak diagnosis falls within a relatively small fluctuation range (normal fluctuation width) due to changes in atmospheric pressure, temperature, and the like. Should be. Therefore, if the current reference pressure greatly fluctuates beyond the normal fluctuation range with respect to the past reference pressure (the reference pressure learning value), it is determined that an abnormality has occurred in the reference pressure detection unit. Can be. Therefore, if the present reference pressure is compared with the past reference pressure (reference pressure learning value), the fluctuation amount of the present reference pressure with respect to the past reference pressure (reference pressure learning value) falls within the normal fluctuation range. By evaluating whether or not there is an abnormality, it is possible to determine whether or not there is an abnormality in the reference pressure detecting unit. This makes it possible to stop the leak diagnosis using the reference pressure or to invalidate the current leak diagnosis result when it is determined that there is an abnormality in the reference pressure detection unit. It is possible to prevent erroneous determination of the presence / absence of leakage and the degree of leakage due to an abnormality in the part.
[0011]
In this case, the reference pressure learning means may store a previous detected value of the reference pressure or an average value or a smoothed value of a predetermined number of detected values in the past as a reference pressure learned value. . In this way, it is possible to evaluate the fluctuation amount of the current reference pressure with respect to the previous reference pressure or the average reference pressure up to that time, and suddenly between the previous leak diagnosis and the current leak diagnosis. It is possible to accurately detect the abnormality of the generated reference pressure detecting unit (for example, sudden clogging of the reference hole).
[0012]
Alternatively, as in claim 3, the reference pressure learning means detects the first detection value of the reference pressure detected when the reference pressure learning value is not stored or the detection value of a predetermined number of times from the first detection value. The average value or the smoothed value up to may be stored as the reference pressure learning value. In this way, the first reference pressure detected at the time of the first leak diagnosis after the manufacture of the vehicle or the first leak diagnosis after the reference pressure learning value is cleared by battery replacement, or an average reference pressure thereafter. It is possible to evaluate the fluctuation amount of the current reference pressure with respect to the pressure, and to accurately detect the abnormality (for example, the deformation of the reference hole over time) of the reference pressure detection unit which has gradually progressed over a relatively long period of time. it can.
[0013]
In addition, the negative pressure pump, the evaporative communication path connected to the evaporative system, the atmosphere release position for connecting the evaporative communication path to the atmosphere, and the evaporative communication path are connected to the negative pressure pump. And a bypass passage connected between the evaporative communication passage and the negative pressure pump by bypassing the passage switching means. A pressure detector is provided, the passage switching means is switched to the open-to-atmosphere position and the negative pressure pump is operated to introduce a negative pressure into the reference pressure detector to detect the reference pressure, and move the passage switching means to the negative pressure introduction position. By switching and operating the negative pressure pump, a negative pressure may be introduced into the evaporation system to detect the pressure in the evaporation system.
[0014]
In this configuration, since the reference pressure detection unit is provided in the bypass passage connected to the evaporation system communication passage, when a negative pressure is introduced into the reference pressure detection unit, the evaporative gas in the evaporation system passes through the reference pressure detection unit. There is a possibility that the evaporation component (fuel component) condenses and adheres to the reference hole by flowing to the reference hole, and the reference hole may be clogged. However, by applying the present invention, the clogging of the reference hole may be regarded as an abnormality of the reference pressure detection unit. Since detection can be performed, erroneous determination of leak due to clogging of the reference hole can be prevented.
[0015]
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).
[0016]
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.
[0017]
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, the leak check module 17 is connected to a canister communication passage 18 (evaporation communication passage) connected to the canister 13 via an air passage 20 through a passage switching valve 19 (passage switching means). The pressure introduction path 21 is connected. 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.
[0018]
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.
[0019]
A bypass passage 24 bypassing 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 (reference hole) is provided in the bypass passage 24. ing. 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, and the reference pressure detecting unit 37 is provided with a pressure sensor 26. .
[0020]
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.
[0021]
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.
[0022]
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.
[0023]
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.
[0024]
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.
[0025]
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.
[0026]
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. .
[0027]
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.
[0028]
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). .
[0029]
Further, by executing the leak diagnosis program, the ECU 31 functions as leak diagnosis means for diagnosing the presence or absence of a leak in the evaporation system using the reference pressure while the engine is stopped.
[0030]
Here, the leak diagnosis of the evaporation system using the reference pressure will be described. As shown in FIG. 3A, 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 detection process, the negative pressure pump 23 is turned on while the passage switching valve 19 is maintained at the atmosphere opening position B, and a negative pressure is introduced into the reference pressure detection 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.
[0031]
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 reference pressure or a value set to a slightly lower pressure) before a predetermined time has elapsed from the start of the introduction of the negative pressure, there is no leak. If the tank internal pressure is equal to or greater than the leak determination value at a 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.
[0032]
By the way, when detecting the reference pressure, for example, the reference orifice 25 of the reference pressure detector 37 is clogged with foreign matter such as a condensed evaporative component or dust, or the abnormality such as deformation of the reference orifice 25 or leakage of the reference pressure detector 37. Occurs, the pressure in the reference pressure detector 37 (the detected value of the reference pressure) deviates from the normal value and becomes an abnormal value, as shown in FIG. When a leak diagnosis is performed based on such an abnormal reference pressure, there is a problem that an erroneous determination that there is a leak even though there is no actual leak or an erroneous determination of a leak degree (size of a leak hole) occur. .
[0033]
Therefore, the ECU 31 executes the abnormality determination program shown in FIG. 4 to update and store the detected value of the reference pressure in a backup RAM (not shown) as a reference pressure learning value each time the reference pressure is detected. In performing the leak diagnosis of the evaporative system, the reference pressure detected this time is compared with the reference pressure learning value stored in the backup RAM to determine whether the reference pressure detection unit 37 is abnormal. If it is determined that there is an abnormality in the reference pressure detector 37, the evaporative system leak diagnosis using the reference pressure is stopped, or the current leak diagnosis result is invalidated, and the abnormality in the reference pressure detector 37 is determined. Erroneous determination of the presence / absence of leakage and the degree of leakage due to this.
[0034]
Hereinafter, the processing content of the abnormality determination program shown in FIG. 4 executed by the ECU 31 will be described.
[0035]
The abnormality determination program in FIG. 4 is executed, for example, during a reference pressure detection process of leak diagnosis, and plays a role as an abnormality determination unit and a reference pressure learning unit described in the claims. When the program is started, first, in step 101, it is determined whether or not the reference pressure of the current leak diagnosis has been detected. When it is determined that the reference pressure has been detected, the process proceeds to step 102. Then, it is determined whether the reference pressure learning value has been stored.
[0036]
In an initial state in which the reference pressure learning value is not stored (eg, at the time of the first leak diagnosis after the vehicle is manufactured, or at the time of the first leak diagnosis after the reference pressure learning value is cleared by replacing the battery), the process proceeds to step 103. Then, the reference pressure detected in the current leak diagnosis is stored as the reference pressure learning value in the backup RAM, and the program ends.
[0037]
Thereafter, when this program is started at the time of the next leak diagnosis, it is determined in step 102 that the reference pressure learning value has been stored, and the routine proceeds to step 104, where the current reference pressure and the reference pressure learning value (previous reference pressure learning value) are used. It is determined whether or not the absolute value of the difference from the pressure is greater than the abnormality determination value. The abnormality determination value is set in consideration of, for example, the amount of variation (variation width) of the reference pressure due to changes in atmospheric pressure, temperature, and the like.
[0038]
As a result, when it is determined that the absolute value of the difference between the current reference pressure and the reference pressure learning value (previous reference pressure) is equal to or smaller than the abnormality determination value, the process proceeds to step 105 and the reference pressure detection unit 37 After it is determined that there is no abnormality (normal), the process proceeds to step 106, where the reference pressure learning value stored in the backup RAM is updated with the current reference pressure, and the program ends.
[0039]
On the other hand, if it is determined in step 104 that the absolute value of the difference between the current reference pressure and the reference pressure learning value (previous reference pressure) is larger than the abnormality determination value, the process proceeds to step 107. Is determined to be abnormal (clogging of the reference orifice 25, deformation of the reference orifice 25, occurrence of an abnormality such as leakage of the reference pressure detecting unit 37), and a warning provided on the instrument panel of the driver's seat. The lamp 36 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.) is stored in the backup RAM, and is stored in the backup RAM. Exit the program.
[0040]
If it is determined in this program that the reference pressure detection unit 37 is abnormal, the evaporative system leak diagnosis using the reference pressure is stopped, or the current leak diagnosis result is invalidated and the reference pressure This prevents erroneous determination of the presence / absence of leakage and the degree of leakage due to an abnormality of the detection unit 37. Alternatively, when it is determined that the reference pressure detecting unit 37 is abnormal, the leak diagnosis may be performed by a method not using the reference pressure.
[0041]
Further, when it is determined that there is an abnormality in the reference pressure detecting unit 37, an abnormal part may be determined as follows. For example, if the current reference pressure is lower than the reference pressure learning value, it is determined that the reference orifice 25 is clogged, and if the current reference pressure is higher than the reference pressure learning value, the reference orifice 25 is deformed in the expansion direction or the reference It may be determined that the pressure detector 37 is leaking.
[0042]
In the embodiment (1) described above, the difference between the current reference pressure and the reference pressure learning value (previous reference pressure) is compared with the abnormality determination value when performing an evaporative system leak diagnosis using the reference pressure. Then, it is determined whether or not the reference pressure detecting unit 37 is abnormal. Therefore, it is determined whether or not the fluctuation amount of the current reference pressure with respect to the previous reference pressure (the reference pressure learning value) is within a normal fluctuation range. By performing the evaluation, it is possible to determine whether the reference pressure detecting unit 37 is abnormal. Accordingly, when it is determined that the reference pressure detecting unit 37 is abnormal, it is possible to stop the leak diagnosis of the evaporative system using the reference pressure or to invalidate the current leak diagnosis result. In addition, it is possible to prevent the presence or absence of a leak and the erroneous determination of the leak degree due to the abnormality of the reference pressure detecting unit 37, and to improve the reliability of the leak diagnosis.
[0043]
Further, in the present embodiment (1), since the previous reference pressure is used as the reference pressure learning value to be compared with the current reference pressure, the amount of change of the current reference pressure with respect to the previous reference pressure is evaluated. Thus, it is possible to accurately detect an abnormality (for example, a sudden clogging of the reference hole) of the reference pressure detecting unit 37 which has suddenly occurred from the previous leak diagnosis to the current leak diagnosis.
[0044]
As the reference pressure learning value, instead of the previous reference pressure, an average value or a smoothed value of the detected values of the reference pressure in the past predetermined number of times may be stored as the reference pressure learning value. As described above, if the average value or the smoothed value of the reference pressure is set as the reference pressure learning value, the reliability of the reference pressure learning value can be improved.
[0045]
<< Embodiment (2) >>
In the embodiment (1), the previous reference pressure is used as the reference pressure learning value to be compared with the current reference pressure. However, in the embodiment (2) of the present invention shown in FIG. In the initial state where the reference pressure learning value is not stored as the reference pressure learning value to be compared with (in the first leak diagnosis after the vehicle is manufactured, or in the first leak diagnosis after the reference pressure learning value is cleared by battery replacement). Etc.) is used.
[0046]
The abnormality determination program of FIG. 5 executed in this embodiment (2) proceeds to step 202 when it is determined in step 201 that the reference pressure for the current leak diagnosis has been detected, and the reference pressure learning value is calculated. In the initial state where the reference pressure learning value is not stored (at the time of the first leak diagnosis after vehicle manufacture, the first leak after the reference pressure learning value is cleared by battery replacement) At the time of diagnosis or the like), the process proceeds to step 203, where the reference pressure detected in the initial state is stored in the backup RAM as a reference pressure learning value, and the program ends.
[0047]
Thereafter, in the next leak diagnosis, the process proceeds from step 202 to step 204, and the absolute value of the difference between the reference pressure detected in the current leak diagnosis and the reference pressure learning value (the reference pressure detected in the initial state) is determined as the abnormality determination value. It is determined whether it is greater than or equal to. As a result, when it is determined that the absolute value of the difference between the current reference pressure and the reference pressure learning value (the reference pressure in the initial state) is equal to or less than the abnormality determination value, the process proceeds to step 205, where the reference pressure detection unit It is determined that there is no abnormality (normal) in 37, and this program is terminated.
[0048]
On the other hand, if it is determined in step 204 that the absolute value of the difference between the current reference pressure and the reference pressure learning value (the reference pressure in the initial state) is larger than the abnormality determination value, step 207 is performed. To determine that there is an abnormality in the reference pressure detecting unit 37, and turn on a warning lamp 36 provided on an instrument panel in the driver's seat, or warn a warning display unit (not shown) of the instrument panel. The warning is displayed to alert the driver, and the abnormality information (such as the abnormality code) is stored in the backup RAM, and the program is terminated.
[0049]
In the above-described embodiment (2), as the reference pressure learning value to be compared with the current reference pressure, the first leak after the reference pressure learning value is cleared by battery replacement at the time of the first leak diagnosis after the vehicle is manufactured. Since the reference pressure detected in the initial state such as at the time of diagnosis is used, it is possible to evaluate the fluctuation amount of the current reference pressure with respect to the reference pressure in the initial state, and gradually progressed over a relatively long period. An abnormality of the reference pressure detecting section 37 (for example, a temporal deformation of the reference hole) can be detected with high accuracy.
[0050]
In this embodiment (2), the reference pressure initially detected in the initial state is used as the reference pressure learning value, but the reference pressure detected from the first detection in the initial state to the reference pressure detected in the predetermined number of times is used. An average value or an average value may be used.
[0051]
Further, in each of the above embodiments (1) and (2), the present invention is applied to the system that performs the leak diagnosis of the evaporative system using the reference pressure while the engine is stopped. The present invention may be applied to a system that performs a system leak diagnosis.
[0052]
In each of the above embodiments (1) and (2), the negative pressure pump is used when performing the leak diagnosis of the evaporative system using the reference pressure. However, the positive pressure pump that introduces the positive pressure into the evaporative system is used. May be used.
[0053]
In the above embodiments (1) and (2), the pressure sensor 26 detects the reference pressure and the pressure in the evaporative system. However, the pump current is used as substitute information for the reference pressure and the pressure in the evaporative system. It may be used.
[0054]
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. In other words, any system that performs the evaporative leak diagnosis using the reference pressure may be used. It 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 (1) of the present invention. FIG. 2 is a diagram showing a configuration of a leak check module. FIG. FIG. 4B is a time chart showing an example of execution of a diagnosis, and FIG. 4B is a time chart showing an example of execution of a leak diagnosis when the reference pressure detection unit is abnormal. FIG. 4 is a flowchart showing a flow of processing of an abnormality determination program of the embodiment (1). FIG. 5 is a flowchart showing a flow of processing of an abnormality determination program according to the embodiment (2).
11: fuel tank, 12: evaporation passage, 13: canister, 14: purge passage, 15: purge control valve, 17: leak check module, 18: canister communication passage (evaporation communication passage), 19: passage switching valve (passage) Switching means), 20 ... atmosphere communication path, 21 ... negative pressure introduction path, 22 ... check valve, 23 ... negative pressure pump, 24 ... bypass passage, 25 ... reference orifice (reference hole), 26 ... pressure sensor, 31 ... ECU (Leak diagnosis means, abnormality determination means, reference pressure learning means), 37 ... reference pressure detection section.

Claims (4)

The present invention is applied to an evaporative gas purging system for purging evaporative gas generated by evaporating fuel in a fuel tank into an intake system of an internal combustion engine, and introducing a predetermined pressure into a reference pressure detecting unit having a reference hole having a predetermined hole diameter. A process for detecting a pressure regulated by the reference hole (hereinafter referred to as “reference pressure”) and a process for introducing a predetermined pressure into an evaporation system including the fuel tank and detecting a pressure in the evaporation system are executed. And a leak diagnostic device for an evaporative gas purge system including a leak diagnostic means for performing a leak diagnostic of the evaporative system by comparing the reference pressure and the pressure in the evaporative system,
Reference pressure learning means for learning the detection value of the reference pressure,
Abnormality detection means for comparing the current detection value of the reference pressure with the reference pressure learning value learned by the reference pressure learning means to determine the presence or absence of an abnormality in the reference pressure detection section. Diagnostic device for evaporative gas purge system. 2. The reference pressure learning unit according to claim 1, wherein the reference pressure learning unit stores, as the reference pressure learning value, a previous detection value of the reference pressure or an average value or a smoothed value of detection values of a predetermined number of times in the past. Leak diagnosis device for evaporative gas purge system. The reference pressure learning means, as the reference pressure learning value, from the first detection value of the reference pressure detected when the reference pressure learning value is not stored or from the first detection value to a predetermined number of detection values 2. The leak diagnostic apparatus for an evaporative gas purge system according to claim 1, wherein an average value or an average value of the values is stored. A negative pressure pump,
An evaporation system communication path connected to the evaporation system,
A passage switching means operable to switch between an atmosphere release position for communicating the evaporative communication passage with the atmosphere and a negative pressure introduction position for connecting the evaporative communication passage to the negative pressure pump;
A bypass passage that bypasses the passage switching means and is connected between the evaporative communication passage and the negative pressure pump;
Providing the reference pressure detector in the bypass passage,
The leak diagnosis means detects the reference pressure by introducing the negative pressure into the reference pressure detection section by operating the negative pressure pump by switching the passage switching means to the open-to-atmosphere position, and detecting the reference pressure. 4. The pressure in the evaporative system is detected by introducing a negative pressure into the evaporative system by operating the negative pressure pump by switching the pressure to the negative pressure introducing position. A leak diagnostic device for an evaporative gas purge system according to any one of the above.

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