JP2001342914A - Abnormality diagnostic device for fuel vapor purge system for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid an erroneous judgment at an abnormality diagnosis of valve in a fuel vapor purge system for vehicle. SOLUTION: A purge control valve 11 of a passage 8 for connecting an engine suction passage 9 and a canister 2 is opened to make a reduced pressure intake circumstance of the canister 2 and a valve-closing command is given against a by-path control valve 42 of a by-path passage 41 for connecting the canister 2 and a fuel tank 1. Under this circumstance, a variation of internal pressure of the canister 2 and internal pressure of the fuel tank 1 is monitored. An existence of abnormality of the by-path control valve 42 is judged based on a relationship between both internal pressures. However, in the case where a differential pressure valve 5 provided on a breather circuit 7 in parallel to the by-path passage 41 is possible to open by itself caused by a turn traveling of the vehicle, a judgment regarding the existence of abnormality of the by-path control valve 42 is reserved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel tank, a canister, a purge control valve provided in a passage for purging fuel vapor from the canister to an engine intake passage,
A fuel vapor for a vehicle, comprising: a bypass control valve provided in a bypass passage connecting the canister and the fuel tank; and a differential pressure valve provided in a passage parallel to the bypass passage between the canister and the fuel tank. Regarding the purge system. In particular, the present invention relates to an abnormality diagnosis device for diagnosing the presence or absence of an abnormality in the bypass control valve.

[0002]

2. Description of the Related Art Generally, a vehicle provided with a tank for volatile liquid fuel employs a so-called fuel vapor purge system. According to a typical charcoal canister type purge system, fuel vapor generated in the fuel tank is once collected in the canister, and the collected fuel vapor is appropriately
Purged (discharged) into the intake passage of the engine. In addition, in order to ensure the reliability of the fuel vapor purge system, the system often incorporates an abnormality diagnosis device for detecting leaks due to holes, tears, and the like. This abnormality diagnosis device includes, for example, a pressure sensor for detecting an internal pressure in a fuel tank and an area communicating with the fuel tank, and a bypass control valve (a negative pressure introduction passage) for opening and closing a bypass passage (a negative pressure introduction passage) connecting the fuel tank and the canister. Valve). Further, a diagnostic program for finding an abnormality (malfunction) of each device component such as the pressure sensor and the control valve is incorporated in the abnormality diagnosis device, thereby further ensuring the reliability of the purge system. ing.

[0003] One of the applicants for the present patent application is a prior application (Japanese Patent Application No.
No. 00-59314), a valve abnormality diagnosis apparatus of a new type which can perform abnormality diagnosis of a bypass control valve provided in the bypass passage relatively frequently without having to satisfy strict preconditions. Has been proposed. The new diagnostic method is to apply a suction negative pressure to the purge system and issue a valve closing command to the bypass control valve.
When significant follow-up (or correlation) of the fuel tank internal pressure is statistically recognized with respect to a sufficient change in the canister internal pressure, the bypass control valve interposed in the passage connecting the fuel tank and the canister is stuck open. It is determined that an abnormality (opening abnormality) has occurred.

[0004]

SUMMARY OF THE INVENTION The present invention relates to an improvement for further improving the degree of perfection of an abnormality diagnosis apparatus employing the above-mentioned new diagnosis method, and relates to an improvement from the following viewpoint.

That is, in an actual vehicle fuel vapor purge system, for example, a breather passage is provided in parallel between the fuel tank and the canister in addition to the bypass passage, and the breather passage has an autonomous operation type. A differential pressure valve is provided. That is, there is a possibility that the fuel tank and the canister communicate with each other in two systems, that is, a passage that passes through a bypass control valve of the other control type and a passage that passes through a differential pressure valve of the autonomous operation type. In such an environment, in order to determine the presence or absence of an abnormal opening of the bypass control valve based on the new diagnostic method, it is necessary that the differential pressure valve be closed at least during the diagnosis. If the differential pressure valve opens on its own during the valve abnormality diagnosis, the fuel tank communicates with the canister, and it follows that the internal pressure of the fuel tank follows the change in the internal pressure of the canister. Although the valve is normally closed, the bypass control valve may be erroneously determined to be an abnormal opening.

According to the study of the present inventors, it has been confirmed that when certain conditions are overlapped during turning of a vehicle, the differential pressure valve opens unexpectedly. This is because the centrifugal action during the turning of the vehicle causes the liquid level to be tilted in the fuel tank, which causes a change in the differential pressure that the differential pressure valve mechanically detects (or monitors). (The details will be described in the embodiments of the invention). Therefore,
Even if a valve abnormality diagnosis is performed in such a situation, a reliable diagnosis result cannot be obtained.

SUMMARY OF THE INVENTION It is an object of the present invention to make it possible to suspend the abnormality diagnosis of a bypass control valve during the turning operation of the vehicle, which may cause an erroneous determination in the abnormality diagnosis of the bypass control valve, or to reject the diagnosis result. It is another object of the present invention to provide an abnormality diagnosis apparatus for a fuel vapor purge system for a vehicle which has excellent diagnostic accuracy.

[0008]

According to a first aspect of the present invention, there is provided a fuel tank, a canister, a purge control valve provided in a passage for purging fuel vapor from the canister to an engine intake passage, the canister and the fuel tank. A fuel vapor purge system for a vehicle, comprising: a bypass control valve provided in a bypass passage connecting the canister; and a differential pressure valve provided in a passage parallel to the bypass passage between the canister and the fuel tank. An abnormality diagnosis device for diagnosing the presence or absence of an abnormality in a control valve, comprising: a tank internal pressure detection means for directly or indirectly detecting an internal pressure of a fuel tank; and a canister internal pressure detection for directly or indirectly detecting an internal pressure of a canister. Means for controlling the drive of the purge control valve and the bypass control valve, and information from the two detection means. A hand can diagnostic control means,
Opening the purge control valve to create a reduced pressure suction state of the canister and monitoring a change in the canister internal pressure and the fuel tank internal pressure under a situation in which a valve closing command is issued to the bypass control valve, the relationship between the two internal pressures is monitored. Diagnostic control means for judging the presence or absence of an abnormality in the bypass control valve based on the vehicle, and monitoring the running state of the vehicle, and the differential pressure valve may be autonomously opened due to turning of the vehicle. in case of,
The gist of the invention is an abnormality diagnosis device for a fuel vapor purge system for a vehicle, comprising: an erroneous determination avoiding unit that suspends a determination regarding the presence or absence of an abnormality of a bypass control valve by the diagnosis control unit or that does not adopt the determination result. .

According to this configuration, as long as the erroneous determination avoiding means does not operate, the diagnosis control means determines whether or not the bypass control valve is abnormal. That is, first, the pressure reduction suction state of the canister is created by utilizing the suction action from the engine intake passage when the purge control valve is opened. Then, under the condition that a valve closing command is issued to the bypass control valve, the changes in the canister internal pressure and the fuel tank internal pressure are monitored, and the relationship between the two internal pressures (that is, the tendency of the fuel tank internal pressure to follow the change trend of the canister internal pressure). The presence or absence of an abnormality in the bypass control valve is determined based on the presence / absence of the bypass control valve. On the other hand, in parallel with or prior to the diagnostic operation of the diagnostic control means, the erroneous determination avoidance means monitors the traveling state of the vehicle, and the possibility that the differential pressure valve is autonomously opened due to the turning traveling of the vehicle. To explore. And
When the turning of the vehicle is sensed and there is a possibility that the differential pressure valve is opening autonomously, the determination regarding the presence or absence of abnormality of the bypass control valve by the diagnostic control unit is suspended or the determination result is not adopted. I do. Thus, despite the fact that the bypass control valve to be inspected is closed as instructed by the diagnostic control means, the autonomous opening of the differential pressure valve causes the fuel tank internal pressure to follow the canister internal pressure change. As a result, an erroneous diagnosis that the bypass control valve is in the abnormal opening state is avoided.

According to a second aspect of the present invention, in the abnormality diagnosis apparatus for a fuel vapor purge system for a vehicle according to the first aspect, the erroneous determination avoiding means outputs a steering signal for notifying an operation state of a steering wheel of the vehicle. With an operation detection sensor, while the steering signal from the sensor is at an active level and for a predetermined time after the steering signal is at an inactive level, assuming that the differential pressure valve may have autonomously opened, The determination by the diagnosis control unit may be suspended or the result of the determination may be rejected.

A second aspect is directed to a first embodiment described later. The situation in which the differential pressure valve autonomously opens due to the turning of the vehicle is regarded as a period during which the steering signal from the steering operation detection sensor is at the active level and a period of time after the steering signal is at the inactive level. The period is set as the determination suspension period (see FIG. 10). The active level (or inactive level) of the steering signal may be either the ON level or the OFF level in the case of a binary signal.

According to a third aspect of the present invention, in the abnormality diagnosis apparatus for a fuel vapor purge system for a vehicle according to the first aspect, the fuel tank has a float valve type cut at an end of a passage through which the differential pressure valve is interposed. An off-valve is provided, and the erroneous determination avoiding means is provided in addition to a case where the differential pressure valve may be autonomously opened due to the turning of the vehicle, and may be caused by a turning of the vehicle. In a case where the cutoff valve may be closed, the determination by the diagnostic control unit is suspended or the result of the determination is not adopted.

Claims 3, 4 and 5 are directed to a second embodiment described later. When the centrifugal force acting on the vehicle is so large that the cutoff valve closes due to the turning movement of the vehicle and the liquid surface inclination of the fuel tank is large, the time for the autonomous opening of the differential pressure valve is also near. Therefore, this period is also referred to as a determination suspension period (see FIG. 14). In order to eliminate the possibility of erroneous determination as much as possible, the diagnosis is performed even when the cutoff valve may be closed due to turning of the vehicle. The judgment by the control means is suspended or the judgment result is rejected.

According to a fourth aspect of the present invention, in the abnormality diagnosis apparatus for a fuel vapor purge system for a vehicle according to the third aspect, the erroneous determination avoiding means detects a lateral acceleration (lateral G) acting on the vehicle. A lateral G detecting means is provided, and the possibility of opening the differential pressure valve and the possibility of closing the cutoff valve are estimated with reference to the lateral G detected by the lateral G detecting means.

According to this configuration, the lateral acceleration (lateral G) detected by the lateral G detecting means is compared with a predetermined lateral G determination value internally held by the erroneous determination avoiding means, thereby obtaining the value at that time. It can be reasonably estimated that the lateral G is sufficient to cause the differential pressure valve to open autonomously or to cause the cutoff valve to close. The technical significance of claim 4 will be apparent in the description of the second embodiment described later.

According to a fifth aspect of the present invention, in the abnormality diagnosis apparatus for a fuel vapor purge system for a vehicle according to the fourth aspect, the lateral G detecting means includes information on a vehicle speed, a speed difference between the left and right wheels, and an interval between the left and right wheels. The lateral G is detected on the basis of the lateral G.

This limits the lateral G detection method to a preferred embodiment, and its technical significance will be clear in the description of a second embodiment described later. According to a sixth aspect of the present invention, in the abnormality diagnosis device for a fuel vapor purge system for a vehicle according to any one of the first to fifth aspects, the fuel remaining amount detecting means for detecting a remaining amount of fuel in the fuel tank is further provided. If the remaining fuel amount is less than a predetermined amount, the erroneous determination avoiding means is invalidated.

This is because when the remaining fuel amount in the fuel tank is less than a predetermined amount, even if the liquid level is tilted in the fuel tank due to turning of the vehicle, the differential pressure valve autonomously operates. This is in consideration of the fact that the opening of the valve or the unexpected closing of the cutoff valve does not occur. According to this configuration,
If there is no possibility that the turning of the vehicle will erroneously determine the abnormality of the valve by the diagnostic control means, the function of the erroneous determination avoiding means is invalidated, and as a result, the frequency of valve diagnosis is secured.

According to a seventh aspect of the present invention, in the abnormality diagnosing apparatus for a fuel vapor purge system for a vehicle according to any one of the first to sixth aspects, the diagnostic control means includes a first predetermined amount or more of a canister internal pressure. And a change in the fuel tank internal pressure equal to or greater than a second predetermined amount, and a correlation rate that is the frequency of occurrence of the latter with respect to the former, and when the correlation rate is equal to or greater than a predetermined threshold, the bypass control valve is abnormal. Is determined to have occurred.

That is, according to this configuration, the diagnostic control means:
A second synchronous with a canister internal pressure change of a first predetermined amount or more;
The presence or absence of an abnormality in the bypass control valve is determined on condition that the occurrence frequency (or occurrence ratio) of the fuel tank internal pressure change equal to or more than the predetermined amount becomes equal to or more than the predetermined threshold value. That is, the final determination that the valve opening is abnormal is made only when it is statistically certain that the internal pressure of the fuel tank follows the change in the internal pressure of the canister, so that the reliability of the diagnosis result is improved.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Hereinafter, a fuel vapor purging system and an abnormality diagnosis apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows an outline of a fuel vapor purge system for a vehicle engine (not shown). During operation of the engine, fuel (gasoline in this example) stored in the fuel tank 1 is pumped out by the fuel pump 38, sent to the fuel injection valve 39 through the fuel supply passage, and supplied to the intake passage 9 from there. Is done. In the intake passage 9, a surge tank 9a, a throttle valve 9b,
An air flow meter 9c and an air cleaner 9d are provided.

The fuel vapor purge system mainly comprises a fuel tank 1, a canister 2, and other piping and valves. The fuel tank 1 has a fuel vapor introduction passage 3
Is connected via a float valve 3a, and the other end of the fuel vapor introduction passage 3 is connected to the canister 2 via a tank internal pressure control valve 4 provided above the canister 2. The fuel vapor generated in the fuel tank 1 is guided to the canister 2 through the fuel vapor introduction passage 3. The tank internal pressure control valve 4 is configured to open when the internal pressure of the fuel tank 1 exceeds a specified value.

Above the fuel tank 1, there is provided a differential pressure valve 5 which can be opened autonomously when refueling the tank. The differential pressure valve 5 is connected to the canister 2 via a breather passage 7. When the differential pressure valve 5 is opened at the time of refueling or the like, fuel vapor in the fuel tank 1 is guided to the canister 2 through the breather passage 7. The canister 2 can communicate with the surge tank 9a via the purge passage 8. The purge passage 8 is provided with a purge control valve 11 composed of, for example, a vacuum switching valve (VSV).
This purge control valve 11 is connected to an ECU (electronic control unit) 1
Open / close operation is performed based on a control signal from 0. The purge control valve 11 adjusts the amount of fuel supplied from the canister 2 to the intake passage 9 during purge control, and shuts off or opens the purge passage 8 during abnormality diagnosis.

The interior of the canister 2 is divided into two chambers by a partition plate 15 extending vertically. That is, a main chamber 16 located below the tank internal pressure control valve 4 and a sub chamber 17 located below the atmosphere control valve 14 and having an inner volume smaller than the main chamber 16 are formed in the canister 2. I have. Air layers 18a and 18b are secured above the main chamber 16 and the sub chamber 17, respectively. Each air layer 18a,
Below the 18b, adsorbent layers 20a and 20b composed of activated carbon adsorbents 19a and 19b are formed, respectively. The main room 16 has an activated carbon adsorbent 19a from its ceiling.
A steam guide 40 extending so as to be immersed therein is provided. The steam guide 40 prevents the fuel vapor introduced from the fuel tank 1 into the canister 2 from being directly guided to the purge passage 8 without passing through the adsorbent layer. Activated carbon adsorbent 1
9a and 19b are held or filled between a pair of filters 20c and 20d provided above and below the adsorbent layers 20a and 20b. A space below the filter 20 d is a diffusion chamber 21, and the main chamber 16 and the sub-chamber 17 communicate with each other via the diffusion chamber 21.

A vapor introduction port 22 for guiding the fuel vapor generated in the fuel tank 1 into the canister 2 is provided on the upper wall of the canister 2 that partitions the main chamber 16. In the vicinity of the vapor introduction port 22, a check ball type vapor relief valve 23 for ventilating when the inside of the fuel tank 1 becomes a negative pressure is provided.

The tank internal pressure control valve 4 is provided so as to surround the vapor introduction port 22. The tank internal pressure control valve 4 includes a diaphragm 4a.
Thereby, the front end opening of the vapor introduction port 22 can be closed. As a result of the inside of the tank internal pressure control valve 4 being partitioned by the diaphragm 4a, a back pressure chamber 4b is formed on one side of the diaphragm 4a, and a positive pressure chamber 4b is formed on the other side.
c is formed. The positive pressure chamber 4c communicates with the fuel tank 1 via the fuel vapor introduction passage 3. At the side of the back pressure chamber 4b, an atmosphere opening port 24 for maintaining the inside of the chamber at atmospheric pressure is provided. A spring 4d provided in the back pressure chamber 4b connects the diaphragm 4a to the vapor introduction port 2
2, and the closed state of the tank internal pressure control valve 4 is maintained until the internal pressure of the fuel tank 1 becomes equal to or higher than a specified pressure.

One end of the breather passage 7 is connected to the upper wall of the canister 2 above the main chamber 16. On the left side of the opening position of the breather passage 7 in the figure, a steam guide 40 is provided.
Is connected to the purge passage 8. In particular, when the purge control valve 11 is open and a pressure (negative pressure) lower than the atmospheric pressure is introduced into the canister 2, the space in the purge passage 8 is changed from the main chamber 16 to the tank internal pressure. The control valve 4 is connected to the fuel tank 1 via the fuel vapor introduction passage 3. Further, since the space in the breather passage 7 is also in communication with the main chamber 16, the same space as the purge passage 8 is shared. As described above, the shared space in the fuel vapor purge system that communicates with each other while the negative pressure is being introduced into the canister 2 serves as a “purge path”. The abnormality diagnosis device for the fuel vapor purge system according to the present embodiment diagnoses whether there is an abnormality by determining whether there is a leak in the purge path. In this specification, a pressure lower than the atmospheric pressure is referred to as a negative pressure, and a pressure higher than the atmospheric pressure is referred to as a positive pressure.

Further, a ventilation port 25 is formed in the upper wall of the canister 2 above the sub chamber 17. Atmospheric control valve 1
Reference numeral 4 denotes an air release valve 12 and an air introduction valve 13 which are arranged to face left and right in the figure. Atmospheric release valve 12
An atmospheric pressure chamber 12b is formed on the left side in the figure of the diaphragm 12a provided in the air conditioner, and a negative pressure chamber 13b is formed on the right side in the figure of the diaphragm 13a provided in the air introduction valve 13. The space sandwiched between these two diaphragms 12a and 13a is partitioned by a partition wall 28 into two pressure chambers. One of the two pressure chambers is a positive pressure chamber 12d of the atmosphere release valve 12, and the other is an atmospheric pressure chamber 13d of the atmosphere introduction valve 13.

A pressure port 28a is provided in a part of the partition wall 28.
Is formed, and the opening at the tip can be closed by the diaphragm 13a. Atmospheric pressure chamber 13d
Is connected to an air introduction passage 27. The diaphragm 13a is connected to a spring 13 provided in the negative pressure chamber 13b.
The air introduction valve 13 is normally closed by being pressed against the opening at the distal end of the pressure port 28a by the urging force of c. In the middle of the air introduction passage 27 connecting the air cleaner 9d and the air introduction valve 13, a pressure shutoff valve 27a composed of, for example, VSV is provided. Pressure shutoff valve 27
Although a is normally open, at the time of abnormality diagnosis, opening and closing control is performed by the ECU 10 as described later.

The negative pressure chamber 13b of the atmosphere introduction valve 13 is connected to the communication passage 3
The pressure generated in the surge tank 9a of the intake passage 9 is guided into the negative pressure chamber 13b. That is, during the execution of the purge, the negative pressure generated in the surge tank 9a due to the intake of the engine into the negative pressure chamber 13
b, the diaphragm 13a is separated from the opening of the pressure port 28a and the air introduction valve 13 is opened despite the bias by the spring 13c under the influence of the negative pressure. On the other hand, during purge cut, the diaphragm 13a
Is brought into contact with the opening of the pressure port 28a and the air introduction valve 13
Closes the valve. Therefore, when the adsorbed fuel in the canister 2 is purged (discharged) into the intake passage 9 based on the negative pressure generated in the surge tank 9a during operation of the engine, the atmosphere introduction passage 27, the pressure port 28a, and the ventilation port 25 are connected. External air can be introduced into the canister 2 from the side of the sub chamber 17 via the sub chamber 17. Due to the introduction of the outside air, the fuel vapor adsorbed by the activated carbon adsorbents 19 a and 19 b in the main chamber 16 and the sub chamber 17 is pushed out to the purge passage 8 and is purged to the intake passage 9.

The atmospheric pressure chamber 12 of the atmosphere release valve 12 is connected to the atmosphere control valve 14 through an atmosphere release port 29 formed above the atmosphere control valve 14.
The inside of b is always at atmospheric pressure. Further, the atmosphere control valve 14 is provided with an atmosphere discharge port 26 for leading out the gas after the fuel component is collected in the canister 2 to the outside. The inner end opening of the air discharge port 26 can be closed by the diaphragm 12a. The diaphragm 12a is pressed against the opening of the air discharge port 26 by the urging force of a spring 12c disposed in the atmospheric pressure chamber 12b. For this reason, the atmosphere release valve 12 is kept closed until the internal pressure of the canister 2 becomes equal to or higher than the specified pressure. For example, when pressure is applied to the canister 2 via the breather passage 7 during refueling, the positive pressure chamber 12 of the atmosphere release valve 12
The pressure of d increases. When the pressure difference between the internal pressure of the positive pressure chamber 12d and the atmospheric pressure guided from the atmosphere release port 29 to the atmospheric pressure chamber 12b reaches a specified pressure difference, the atmosphere release valve 12 opens. Thus, the gas from which the fuel vapor has been removed through the main chamber 16 and the sub chamber 17 is discharged to the outside through the ventilation port 25 and the air discharge port 26.

As shown in FIG. 1, a fitting hole 31 is formed in the upper part of the fuel tank 1, and a cylindrical breather tube 32 forming a part of the breather passage 7 is inserted and fixed in the fitting hole 31. ing. At the lower end of the breather pipe 32, a float valve type cutoff valve 33 is provided. The cutoff valve 33 is a check valve for detecting a full tank and supporting a rollover. A differential pressure valve 5 is provided at the upper end of the breather pipe 32 above the fuel tank.

As shown in FIGS. 2 and 3, the inside of the differential pressure valve 5 is vertically divided by a diaphragm 5a, a first pressure chamber 5b is provided above the diaphragm 5a, and a second pressure chamber 5b is provided below the diaphragm 5a.
Each of the pressure chambers 5c is formed. First pressure chamber 5b
Communicates with an upper region of a fuel injection pipe 36 provided in the fuel tank 1 via a pressure passage 34 (see FIG. 1).
The upper region of the fuel injection pipe 36 communicates with the upper internal space of the fuel tank 1 via the circulation line pipe 37, and the upper internal space can also communicate with the second pressure chamber 5c. As long as the tank is not full, the internal pressure of the fuel tank 1 is guided to both the first and second pressure chambers 5b and 5c.
As shown in FIG. 2, the diaphragm 5a is
The upper end opening 7a of the breather passage 7 in the second pressure chamber 5c is pressed by the urging force of the spring 5d disposed in the second pressure chamber 5b. That is, the breather passage 7 is formed by the diaphragm 5a.
Can be closed.

Here, the internal pressure of the first pressure chamber 5b is Pα, the internal pressure of the second pressure chamber 5c is Pβ, and the internal pressure of the breather passage 7 is Pα.
γ, the pressure of the diaphragm 5a due to the action of the spring 5d is Pδ. The area of the diaphragm 5a on the first pressure chamber 5b side is S1, and the area of the diaphragm 5 on the second pressure chamber 5c side is S1.
The area of a is S2, and the diaphragm 5a on the breather passage 7 side
Is defined as S3. Then, the force f in the direction of closing the passage by the diaphragm 5a is expressed as f = Pα * S1 + Pδ * S1-Pβ * S2-Pγ * S3. When the force f is a positive value, the differential pressure valve 5 is closed, and when the force f is a negative value, the differential pressure valve 5 is opened.

In this embodiment, the ratio of the three areas is S1:
S2: S3 = 7: 6: 1, and the pressure Pδ per unit area by the spring 5d is 0.27 kPa (= 2 mmH
g). Pα = Pβ except when fuel is supplied to the fuel tank 1. Summarizing the force f based on these conditions, f = Pα * 7 * S3 + Pδ * 7 * S3-Pβ * 6 * S3-Pγ * S3 = S3 (1.89 + Pα−Pγ). That is, the internal pressure Pα of the fuel tank 1 is
Predetermined pressure P0 = 1.89 kPa (= 1
When the pressure becomes lower than 4 mmHg), the differential pressure valve 5 is opened, and the back purge from the canister 2 to the fuel tank 1 is performed. For example, during engine operation, the tank internal pressure is -1.89.
If the value is smaller than kPa (= -14 mmHg),
By closing the purge control valve 11 and introducing atmospheric pressure into the canister 2, the differential pressure valve 5 is opened.

A throttle 36a is provided at the lower end of the fuel injection pipe 36.
Are formed. The throttle 36a regulates the flow direction of the fuel vapor in the fuel injection pipe 36 to the direction flowing from the fuel supply port 36b to the fuel tank 1 side when the supplied fuel passes therethrough. To prevent leakage from outside. A circulation line pipe 37 connecting the upper region of the fuel injection pipe 36 and the upper part of the fuel tank 1 enables the fuel vapor in the fuel tank 1 to be circulated between the fuel injection pipe 36 and the fuel tank 1 at the time of refueling, thereby enabling smooth lubrication. I do.

Above the fuel tank 1, there is provided a pressure sensor 1a as tank internal pressure detecting means for detecting the internal pressure of the fuel tank 1. The pressure sensor 1a is of a type that detects a relative pressure based on the atmospheric pressure, and a detection signal is output to the ECU 10.

The fuel vapor purge system further includes a positive pressure chamber 4c of the tank internal pressure control valve 4 and a sub chamber 17 of the canister 2.
Is provided. That is, the bypass passage 41 connects the fuel tank 1 and the canister 2 via the positive pressure chamber 4 c of the tank internal pressure control valve 4 and the fuel vapor introduction passage 3. In the middle of the bypass passage 41, a bypass control valve 42 composed of, for example, VSV is provided. The bypass control valve 42 is normally closed, but controls the open / close state of the bypass passage 41 based on a command from the ECU 10 at the time of abnormality diagnosis. The bypass control valve 42 and the breather passage 7 are in a parallel relationship between the fuel tank 1 and the canister 2.

(Electronic Control Configuration) The electronic control unit (ECU) 10 functions as a control system and a diagnostic system of the engine, and further includes a canister internal pressure detecting means, a diagnostic control means, an erroneous determination avoiding means, and Functions as fuel remaining amount detection means. As shown in FIG. 4, the ECU 10 is mainly configured by a microcomputer 51. The microcomputer 51 includes a CPU 51a that executes various processes related to engine control and system diagnosis, a ROM 51b that is a read-only memory storing various programs related to the control and diagnosis, a RAM 51c that is a volatile memory that can be freely read and written, and A backup RAM 51d, which is a non-volatile memory in which writing is free and stored contents are maintained even after the engine is stopped by being backed up by a battery, is provided. Further, the microcomputer 51 includes a first counter 52, a second counter 53, a first timer 54, and a second timer 55. However, when the internal register of the CPU 51a is to serve as a counter, the first and second counters 5 are used.
There is no need to dare provide 2,53.

On the input side of the microcomputer 51,
In addition to the pressure sensor 1a and the air flow meter 9c, various sensors necessary for engine operation control such as a steering operation detection sensor 61, a fuel remaining amount sensor (for example, a fuel meter), a vehicle speed sensor, a rotation speed sensor, and a cylinder discrimination sensor are directly provided. Connected indirectly or indirectly. The steering operation detection sensor 61 is turned ON when the steering wheel (so-called steering wheel) of the vehicle is turned to the left or right, outputs an ON-level steering signal, and is turned OFF when the steering wheel is turned and held. This is a kind of steering amount monitoring sensor that outputs a steering signal at an OFF level. On the other hand, the output side of the microcomputer 51 is connected to the fuel injection valve 39, the fuel pump 38, the purge control valve 11, the pressure shut-off valve 27a, and the bypass control valve 42 via respective drive circuits.

The ECU 10 executes engine control such as fuel injection control and air-fuel ratio control based on various information provided from each sensor. Further, the ECU 10 performs abnormality diagnosis of the purge system by appropriately opening and closing the purge control valve 11, the pressure closing valve 27a, and the bypass control valve 42 while recognizing an output signal from the pressure sensor 1a and the like. In particular, in order to ensure the accuracy or reliability of the abnormality diagnosis, the abnormality diagnosis is performed. In this sense, the ECU 10 is positioned as a diagnostic control unit of the bypass control valve 42.

(Outline of Fuel Purge Operation) When fuel evaporates in the fuel tank 1 and the internal pressure of the fuel tank 1 increases to a specified pressure value or more, the tank internal pressure control valve 4 opens. Then, the fuel vapor in the fuel tank 1 is introduced into the canister 2 via the tank internal pressure control valve 4. In the canister 2, first, the fuel component is collected by the activated carbon adsorbent 19 a filled in the adsorbent layer 20 a of the main chamber 16. Subsequently, the fuel vapor passes through the diffusion chamber 21 from the adsorbent layer 20a and enters the sub chamber 17, and in the adsorbent layer 20b of the sub chamber 17, fuel components that could not be collected in the main chamber 16 are collected. You. As described above, since the fuel vapor flows along the U-shaped movement path in the canister, the time for contact with the activated carbon adsorbents 19a and 19b of the adsorbent layers 20a and 20b becomes longer, and the fuel components are effectively collected. You. Most of the fuel component is adsorbent layer 2
The gas collected by the activated carbon adsorbents 19a and 19b of 0a and 20b opens the air release valve 12 and is discharged outside through the air discharge port 26. At this time, the internal pressure of the negative pressure chamber 13b of the atmosphere introduction valve 13 is set to the atmospheric pressure chamber 1
Since the pressure is higher than the internal pressure of 3d, the air introduction valve 13 does not open. Therefore, the fuel vapor does not leak outside through the atmosphere introduction valve 13 and the atmosphere introduction passage 27.

The fuel component collected in the canister 2 is supplied to the intake passage 9 as follows. During operation of the engine, the pressure near the opening of the purge passage 8 on the side of the surge tank 9a is turned to a negative pressure. Therefore, each time the purge control valve 11 is opened by the control signal of the ECU 10, the air introduction valve 13 is opened and the purge passage 8 is opened. Inside the canister 2 from the side of the surge tank 9
The flow of the fuel vapor toward the a side is formed. as a result,
The inside of the canister 2 is in a negative pressure state, and the atmosphere introduction passage 27
Air is introduced into the canister 2 from the outlet. Then, the fuel component adsorbed by the activated carbon adsorbents 19a and 19b is separated and absorbed in the air. The fuel vapor together with the air thus introduced is supplied to the purge passage 8 and the purge control valve 1.
1 to the surge tank 9a.

Note that the fuel tank 1 may be
Is cooled, the generation of fuel vapor stops, and when the internal pressure of the fuel tank 1 becomes relatively lower than the internal pressure of the canister 2, the pressure of the positive pressure chamber 4c of the tank internal pressure control valve 4 becomes negative, The vapor relief valve 23 is opened. Then
Fuel vapor in the canister 2 is returned to the fuel tank 1 through the fuel vapor introduction passage 3.

(Outline of Leak Diagnosis) In this abnormality diagnosis apparatus, a path (hereinafter referred to as a path) constituted by a portion where fuel vapor is introduced, such as a fuel tank 1, a fuel vapor introduction passage 3, a breather passage 7, a canister 2, and a purge passage 8 These are collectively referred to as a “purge path”), and it is diagnosed whether or not there is a leak abnormality due to a hole in the pipe or disconnection of the pipe. The diagnosis method is to seal the inside of the fuel vapor introduction passage 3 under a predetermined negative pressure, and to determine the presence or absence of leakage based on the subsequent pressure behavior in the passage. Hereinafter, a specific procedure of the leak diagnosis will be described with reference to a timing chart of FIG.

In the leak diagnosis, purge processing is performed in addition to various conditions such as that the tank internal pressure is stable, that a predetermined time has not elapsed since the start of the engine, and that there is no abnormality in the pressure sensor 1a. (That is, the purge control valve 11 is opened at a predetermined opening degree based on the operating state). If such diagnostic prerequisites are met, the EC
U10 closes the pressure closing valve 27a (time t10), and introduces the negative pressure of the intake passage 9 into the purge passage. Then, the pressure in the purge passage (= tank internal pressure) gradually decreases (time t10 to t20). When the tank internal pressure reaches the target negative pressure TP (time t20), the ECU 10 sets the purge control valve 1
1 is forcibly closed, and the inside of the purge path is closed. still,
If the tank internal pressure does not decrease to the target negative pressure TP even if a predetermined time has elapsed after the introduction of the negative pressure, it is diagnosed that a relatively large leak has occurred in the purge path.

As described above, when the purge path is closed under a low pressure (negative pressure), the tank internal pressure once becomes T.
Although the pressure further decreases from P, as the fuel in the same path (for example, the fuel in the fuel tank 1 or the fuel adsorbed in the canister 2) evaporates, the tank internal pressure starts to increase (after time t21). Then, based on the rising speed of the tank internal pressure at this time, the presence or absence of leakage in the purge path is determined. That is, when the increasing speed of the tank internal pressure is less than a predetermined value (normal determination value), the tank internal pressure is increased only by the evaporation of the fuel in the purge path, and it is determined that there is no leakage in the purge path. (Normal judgment). On the other hand, when the rising speed of the tank internal pressure is equal to or higher than a predetermined value (abnormality determination value), the tank internal pressure is increased due to the inflow of air into the same path in addition to the fuel evaporation in the same path, It is determined that there is a leak in the same route (abnormality determination). On the other hand, when the increasing speed of the tank internal pressure is equal to or higher than the normal determination value and lower than the abnormality determination value, it is difficult to accurately determine whether or not there is a leak, and the determination is temporarily suspended.

(Abnormality Diagnosis of Valves Constituting Fuel Vapor Purge System) In order for the leakage diagnosis of the purge path to be reliable, the sensors and valves composing the system must be operating normally. You need to always check. Hereinafter, a method of diagnosing a malfunction of the bypass control valve 42 provided in the bypass passage 41 will be particularly described. In an actual system, abnormality diagnosis is performed for other valves and the pressure sensor 1a, but the description thereof is omitted.

The flowcharts of FIGS. 7 to 9 show a procedure for diagnosing the presence or absence of a malfunction (abnormal) of the bypass control valve 42. The core analysis procedure of the valve abnormality determination is step 200 in FIG. 7, and details thereof are shown in FIGS. The analysis procedure of FIG. 8 and FIG.
Despite issuing a valve closing command to the bypass control valve 42 under the condition that the valve 1 is opened and the negative pressure is being guided to the canister 2, the fuel tank internal pressure shows a suitable follow-up property with respect to the temporal change of the canister internal pressure. In this case (that is, when there is a correlation between the two), the idea of acknowledging that the bypass control valve 42 is stuck open is specified. Therefore, for this diagnostic principle to work effectively, it is necessary that the differential pressure valve 5 of the breather passage 7 be kept closed at least during the abnormality diagnosis of the valve. Otherwise, the bypass control valve 42
Although the valve is closed as instructed by the ECU 10, the opening of the differential pressure valve 5 causes a correlation between the canister internal pressure and the fuel tank internal pressure, and erroneously opens the bypass control valve 42. This is because a fixation abnormality may be recognized.

In this regard, step 110 of FIG.
160 and steps 310 to 342 are to adopt the analysis result in the step 200 as the final judgment,
Alternatively, it is a pre- and post-procedure for determining whether to suspend the determination itself. In other words, in these processes, when there is a risk that the differential pressure valve 5 is inadvertently opened, the abnormality determination of the valve is temporarily suspended, and the situation where the differential pressure valve 5 is securely closed is determined in step 200. Is to respect the results of the analysis. Whether or not the valve abnormality determination is suspended is mainly determined by whether or not the vehicle is in a turning traveling state (more specifically, the ON / OFF state of the steering signal output by the steering operation detection sensor 61 and the steering signal OF
It is determined based on the elapsed time after returning to the F level). This is due to the following circumstances.

As described with reference to the system configuration of FIG. 1, the first pressure chamber 5b and the second pressure chamber 5c of the differential pressure valve 5 are normally under the same pressure by communicating with the gas phase, and the differential pressure valve 5 is in the closed state. Always. However, when a vehicle with the fuel tank 1 almost full is turning and a certain kind of centrifugal force acts on the vehicle body,
The liquid level in the tank may be inclined, for example, as shown in FIG. Note that the horizontal broken line in FIG. 6 indicates the position of the horizontal liquid surface before the centrifugal force acts. In the state where the liquid surface is inclined as shown in FIG. 6, the lower end of the circulation line pipe 37 is closed by the fuel liquid, and the float valve body of the cutoff valve 33 floats to be in a closed state. That is, the first pressure chamber 5b and the second pressure chamber 5
The gas phase communication with c is cut off. In addition, the fuel injection pipe 36
Inside, the liquid level drops from the broken line position to the solid line position. This liquid level drop causes a decrease in the internal pressure of the first pressure chamber 5b. In such a case, the internal pressure of the first pressure chamber 5b is significantly lower than the internal pressure of the second pressure chamber 5c, and the condition for opening the differential pressure valve 5 may be satisfied. That is, if the abnormality diagnosis of the bypass control valve 42 is performed while the vehicle that has stored the fuel in the fuel tank 1 to some extent or more is turning, the bypass control valve 42 is normally closed, Due to the autonomous opening of the differential pressure valve 5 (see FIG. 3), the interior of the canister 2 communicates with the second pressure chamber 5c of the differential pressure valve 5 to equalize the pressure (that is, the second pressure chamber 5c is reduced in pressure). . Thereafter, when the liquid level in the tank returns to horizontal after the turning traveling, the second pressure chamber 5c communicates with the gas phase portion of the fuel tank 1 (that is, the region connected to the pressure sensor 1a), and temporarily. A decrease in the tank internal pressure is detected by the pressure sensor 1a. This is erroneously recognized as a decrease in the internal pressure of the fuel tank following the decrease in the internal pressure of the canister, and induces an erroneous determination that the bypass control valve 42 is stuck open. In order to prevent such an erroneous determination beforehand, the valve abnormality diagnosis is reserved when the vehicle is turning.

Next, the details of the valve abnormality diagnosis processing will be described with reference to the flowcharts of FIGS. 7, 8 and 9.
Note that the main routine of FIG. 7 is executed by the ECU 10 as a periodic interrupt process every predetermined time (for example, several tens to several hundreds of milliseconds).

When there is an interrupt request, the ECU 10 first determines in step 110 whether or not the remaining amount of fuel in the fuel tank 1 is equal to or more than a predetermined remaining amount x (for example, 85% of full state). The remaining amount of fuel can be known, for example, based on the output (electric signal) of a fuel meter provided in the instrument panel of the vehicle. If the determination at step 110 is NO, the process proceeds to step 200. In other words, when the remaining fuel amount is less than x, even if the vehicle is in a turning traveling state, the situation shown in FIG. 6 cannot occur due to that, and the differential pressure valve 5 does not open, and This is because such an erroneous determination can hardly occur.

If the determination in step 110 is YES,
In step 120, the ECU 10 determines whether or not the vehicle speed is lower than a predetermined speed y (for example, 80 km / h). If the determination in step 120 is NO, step 2
The process moves to 00. In other words, when the vehicle speed is equal to or higher than y, a large amount of steering is not provided so as to turn the vehicle.

If both the judgments of step 110 and step 120 are YES, then at step 130 the ECU
10 determines whether or not the steering signal from the steering operation detection sensor 61 is ON. If the determination in step 130 is YES (the steering signal is ON level), the ECU 10
Sets the abnormality determination suspension flag F to ON (step 140). The abnormality determination suspension flag F is set in step 200
Registration information for temporarily storing or suspending the abnormality determination of the bypass control valve 42 according to the method described above, and for suspending the determination when the flag is ON and validating the determination when the flag is OFF. It is.

Step 130: NO (steering signal is O
FF level), in step 150, the ECU 1
0 indicates that the abnormality determination suspension flag F that has been
It is determined whether or not N has been reached. If the determination in step 150 is NO (the flag F is OFF), the process proceeds to step 200 as it is. On the other hand, if the determination in step 150 is YES (the flag F is ON), in step 160, the ECU 10 activates the stopped first timer 54. If the first timer 54 is already operating, the time measurement is continued without clearing the timer to zero.

Subsequently, in step 200, the ECU 10 checks whether there is a correlation between the canister internal pressure Pc and the tank internal pressure Pt of the fuel tank 1. The analysis procedure in step 200 will be described later in detail. As a result of the processing in step 200, one of three conclusions is obtained. That is, the determination that the correlation of the Pt change to the Pc change is high, the determination that the correlation of the Pt change to the Pc change is low, and the determination that the correlation between the two cannot be determined are suspended. If the determination is suspended in step 200, the processing in FIG. 7 is temporarily terminated, and the next interrupt processing is awaited.

If it is determined in step 200 that the correlation is low, it is determined that the bypass control valve 42 has no open fixation abnormality (step 310). On the other hand,
If it is determined in step 200 that the correlation is high, the state of the abnormality determination suspension flag F is checked in step 320. That is, it is determined whether the flag F is in the ON state. Here, step 320
If the determination is NO (flag F is OFF), the analysis result (high correlation) in step 200 is respected as it is,
It is determined that the bypass control valve 42 has an open sticking abnormality (step 330). Step 320 is YES
If (flag F is ON), there is a possibility that the differential pressure valve 5 is opening autonomously, and the analysis result in step 200 is not respected, and the determination is suspended. However, in that case, the routine of FIG. 7 is terminated after performing predetermined post-processing.

That is, if the determination in step 320 is YES,
In step 341, the ECU 10 sets the first timer 54
It is determined whether or not the measured time is equal to or longer than the predetermined time TM1. If the determination in step 341 is NO, step 342 is skipped and the routine in FIG. 7 ends. On the other hand, if the determination in step 341 is YES, in step 342, the abnormality determination suspension flag F is set to OFF and the first timer 54 is cleared to zero.
Ends the routine.

By adopting the processing procedure as shown in FIG. 7, the abnormality determination of the valve is suspended according to the time series as shown in each timing chart of FIG. 10, for example. FIG.
In case 1, the rising of the steering signal (OFF → O
In synchronization with N), the abnormality determination suspension flag F is turned ON, and the determination suspension period starts. Thereafter, the determination suspension period ends when a predetermined time TM1 elapses from the fall of the steering signal (ON → OFF). Before the suspension period ends, it is determined that the correlation between the canister internal pressure Pc and the tank internal pressure Pt is high. Even if the analysis result is obtained, the final determination that the bypass control valve 42 is stuck open is delayed until the end of the determination suspension period. Further, in case 2 of FIG. 10, at the end of the determination suspension period (the predetermined time TM1 from the fall of the steering signal)
After that, the analysis that the correlation between the canister internal pressure Pc and the tank internal pressure Pt is high has occurred.
At the same time that the correlation analysis is switched from low correlation to high correlation, the final determination that the bypass control valve 42 is stuck open is determined. As described above, the determination suspension period is the sum of the time during which the steering signal is ON and the predetermined time TM1. The predetermined time TM1 at this time takes into account the time required for the liquid level in the fuel tank 1 to return from the inclined state in FIG. 6 to the horizontal state after the vehicle shifts to the turning traveling state.

Next, details of the analysis procedure in step 200 of FIG. 7 will be described with reference to FIGS. 8, 9 and 11. The processing here is based on the possibility that the bypass control valve 42 is stuck in the open state and the relationship between the canister internal pressure Pc and the tank internal pressure Pt after issuing a valve closing command to the bypass control valve 42. This is to check based on. Therefore,
At least under the condition that the purge control valve 11 is open,
The premise of the analysis is that a valve closing command is issued from the ECU 10 to the bypass control valve 42.

Under these prerequisite conditions, the ECU 10 first calculates the purge flow rate Qp in step 201. “Purge flow rate” means the flow rate of gas discharged into the intake passage 9 of the engine via the purge passage 8. When the opening degree of the purge control valve 11 and the degree of the negative pressure in the purge passage 8 are known, the purge flow rate Qp is calculated based on these or by referring to a characteristic map obtained by calculation or by experiment or computer simulation. can do. Here, the purge control valve 11 is connected to the ECU 10
The ECU 10 holds information on the valve opening of the purge control valve 11 as internal data. On the other hand, the degree of the negative pressure in the purge passage 8 has a correlation with the engine load, and the relationship between the two is formed into a characteristic map through experiments and computer simulations for each vehicle. The engine load can be calculated based on the rotation speed data from the engine speed sensor and the intake air amount data from the air flow meter 9c. That is, the purge passage 8
Can be grasped on the basis of data from various sensors, and the purge flow rate Qp can be calculated based on external data and internal data. In this sense, various sensors including the engine speed sensor and the air flow meter 9c, and the ECU 10 are referred to as “purge flow rate calculating means”.
Is configured.

In step 202, the ECU 10 calculates the simulated canister internal pressure Pc. In this step, since the pressure sensor for directly detecting the internal pressure is not attached to the canister 2, the internal pressure of the canister is estimated based on other information that can be obtained. The estimated value is the simulated canister internal pressure Pc. There is a close correlation between the internal pressure of the canister and the purge flow rate Qp according to the characteristics of the atmospheric control valve 14 of the canister. The relationship between the two is mapped into a characteristic through experiments and computer simulations for each vehicle. I have. Its characteristic map is ECU
The internal pressure Pc is stored as internal data, and by referring to the internal data, the simulated canister internal pressure Pc can be calculated from the purge flow rate Qp obtained in the previous step. In this sense, the ECU 10 constitutes “canister internal pressure calculation means”. The purge flow rate calculating means and the canister internal pressure calculating means constitute a canister internal pressure detecting means for indirectly detecting the internal pressure of the canister.

In step 203, it is determined whether or not the elapsed time from the previous zero clear of the second timer 55 has reached a predetermined time TM2 (for example, 15 seconds). If the predetermined time TM2 has elapsed at that time, the processing of step 204 is executed, but if the predetermined time TM2 has not been reached, the processing of step 204 is skipped. That is,
The processing of step 204 is performed for a predetermined time TM2 (for example, 15
Every second).

Step 204 is a reset operation every predetermined time TM2. Here, first, the second timer 55 is cleared to zero. Further, the simulated canister internal pressure Pc obtained in step 202 is set as the provisional canister reference internal pressure Pcs, and the detected pressure of the pressure sensor 1a (tank internal pressure Pt) at that time is set as the provisional tank reference internal pressure Pts. That is, the simulated canister internal pressure Pc after the lapse of the predetermined time TM2 is stored as a provisional comparison reference value (or reference point) Pcs, and the tank internal pressure Pt after the lapse of the predetermined time TM2 is provisionally compared to the reference value (or The reference point is stored as Pts (see FIG. 11). That is, in step 204, the provisional canister reference internal pressure P
cs and the provisional tank reference internal pressure Pts are updated every predetermined time TM2.

Steps 205 to 207 are a series of processes for counting the number of times the simulated canister internal pressure Pc has changed from the provisional canister reference internal pressure Pcs by a predetermined pressure value α or more. Specifically, in step 205, the absolute value of the difference ΔPc between the simulated canister internal pressure Pc and the provisional canister reference internal pressure Pcs at that time, that is, the absolute value of the amount of change in the canister internal pressure from the reference point is equal to the first predetermined amount. Pressure value α (for example, 0.67 kPa = 5.0 mmH)
g) It is determined whether or not it is greater than or equal to. If the determination in step 205 is YES, in step 206, the first counter 5 assigned for counting the number of canister internal pressure changes is determined.
The value C1 of 2 is incremented (addition of 1), and in step 207, similarly to step 204, zero clear of the second timer 55 and resetting of the provisional canister reference internal pressure Pcs are performed (see FIG. 11). The predetermined pressure value α is set to such a value that a change in the simulated canister internal pressure Pc, which is only a slight fluctuation, can be excluded from the count target.

If the determination in step 205 is NO, the amount of change in the simulated canister internal pressure Pc and the tank internal pressure Pt is not checked at all (that is, without adding or subtracting the first and second counters 52 and 53 at all). ), Skip to step 213. This is the simulated canister internal pressure P
This is because if the change in c is too small, it is not appropriate to rely on the method of determining a valve operation failure according to the present invention.

After step 207, the process proceeds to step 208 in FIG. In step 208, the absolute value of the difference ΔPt between the current tank internal pressure Pt and the provisional tank reference internal pressure Pts, that is, the absolute value of the amount of change in the tank internal pressure from the reference point, is determined by a predetermined pressure value β as a second predetermined amount. (For example, 0.4
7 kPa = 3.5 mmHg) or more is determined. If the determination in step 208 is YES, in step 209, the value C2 of the second counter 53 allocated for counting the number of changes in the tank internal pressure is incremented (addition of 1). In other words, if the determination at step 205 is YES and the determination at step 208 is YES, it is determined that the change in Pt with respect to the change in Pc has a proper followability (positive affirmation of the followability), and the counter values C1, C2 Is the result of adding 1 to both. Note that the predetermined pressure value β is
The value is set to a value smaller than the value α (β <α).

On the other hand, if the determination in step 208 is NO, in step 210, the absolute value of the difference ΔPt between the tank internal pressure Pt and the provisional tank reference internal pressure Pts, that is, the absolute value of the amount of change in the tank internal pressure from the reference point is determined. , Predetermined pressure value γ
(For example, 0.11 kPa = 0.8 mmHg). If the determination in step 210 is YES, in step 211, the value C of the second counter 53 is set.
Decrement 2 (subtract 1). That is, step 2
If the determination at Step 05 is YES and the determination at Step 210 is YES, it is determined that a clear change in Pt is not recognized despite a sufficient change in Pc (aggressive negation of the change), and the counter value C1 is determined. The result is that the counter value C2 is minus one despite the increase of The predetermined pressure value γ is set to a value smaller than the value β (γ <
β).

When the determination in step 210 is NO, that is, when γ ≦ ΔPt <β, the addition / subtraction of the second counter 53 is not performed at all. In other words, in this case, the change of Pt is halfway despite the sufficient change of Pc, and the followability of Pt to the change of Pc cannot be positively affirmed or denied. Therefore, the counter value C2 is maintained as it is despite the increase in the counter value C1.

After the processing of step 209, 210 or 211, in step 212, the ECU 10 resets the provisional tank reference internal pressure Pts, as in step 204, in preparation for the determination in the next cycle. Step 21
After 2 or after the determination in step 205 is NO, the process proceeds to the final analysis procedure of step 213 and subsequent steps.

At step 213, the value C of the first counter
It is determined whether 1 is equal to a predetermined determination value DA (for example, 10 times). If the first counter value C1 is less than the determination value DA, it is considered that the number of changes of the simulated canister internal pressure Pc has not reached the specified number and it is not in a state where proper abnormality diagnosis can be performed, and the determination is suspended (step 217). 8 and 9 are ended. That is, the determination value DA is equal to Pc
Is the minimum specified number of times for ensuring statistical reliability in determining the follow-up of the change in Pt with respect to the change in Pt.
Naturally, if the determination value DA is increased, the reliability of the analysis is statistically increased, but on the other hand, it takes a long time to reach a conclusion.

If the determination in step 213 is YES,
It is determined that the number of changes of the simulated canister internal pressure Pc has reached the specified number of times for performing an appropriate failure diagnosis, and the determination in step 214 is performed. That is, in step 214, it is determined whether or not the value C2 of the second counter is equal to or greater than a predetermined determination value DB (for example, seven times). This judgment value DB is equal to the judgment value DA (DB = DA) or a value close thereto (however, D
B <DA).

If the determination in step 214 is YES, there is a high correlation between the change trend of the simulated canister internal pressure Pc and the change trend of the tank internal pressure Pt, that is, the followability of Pt to the Pc change is reasonably recognized. It is concluded that it can be done (step 215). Satisfaction of the determination condition of step 214 is because the number of times of change C2 of the tank internal pressure is equal to or very close to the number of times of change C1 of the canister internal pressure. The determination of “high correlation” indicates that there is a high possibility that the bypass control valve 42 is stuck open. That is, the fuel tank 1 and the canister 2
Despite the fact that a valve closing command has been issued to the bypass control valve 42 provided in the passage connecting the two internal pressures Pc,
If there is a close correlation with the change trend of Pt, it means that the two regions are clearly in communication with each other, and there is a high possibility that the bypass control valve 42 is open and fails. Note that the processing in steps 213 and 214 is
The correlation rate or the follow-up rate R calculated by B / DA is obtained, and the correlation rate R is equal to or more than a predetermined threshold (7/10 = 7 in this example).
0% or more).

On the other hand, if the determination in step 214 is NO,
It is concluded that there is no significant correlation between the changing trend of the simulated canister internal pressure Pc and the changing trend of the tank internal pressure Pt, that is, it cannot be asserted that the followability of Pt to the Pc change is reasonably recognized. (Step 21
6). This is because the correlation rate R has not reached a predetermined threshold value (70% in this example). The determination of “low correlation” indicates that the possibility of the opening control abnormality of the bypass control valve 42 is low. In other words, passively "normal valve"
Can be estimated. By the way, bypass control valve 4
When the fuel tank 2 is normally closed, the fuel tank 1 should be in an isolated space. In this case, the tank internal pressure Pt should maintain a substantially constant value as shown by a dashed line in FIG. It is.

As described above, the “high correlation” in step 215, the “low correlation” in step 216, or the step 217
After obtaining one of the analysis results of “determination pending” in FIG.
Is executed as described above.

(Effects) According to the first embodiment, the following effects can be obtained. In the present embodiment, a method is employed in which the open / closed abnormality of the bypass control valve 42 is detected based on whether or not the tank internal pressure Pt follows the change in the simulated canister internal pressure Pc or whether or not there is a correlation between the two. are doing. As described above, the differential pressure valve 5 may open autonomously during turning of the vehicle, and if this overlaps with the abnormality diagnosis of the bypass control valve 42, the diagnosis result of the bypass control valve 42 may be erroneous. . In this regard, in the present embodiment, whether or not the vehicle is in a turning traveling state is determined by referring to the ON / OFF level of the steering signal output from the steering operation detection sensor 61, and at the time of turning of the vehicle (and Predetermined time TM1
In (2), the determination of a valve abnormality in the abnormality diagnosis is temporarily suspended or avoided. For this reason, the erroneous diagnosis is prevented beforehand by not using the diagnosis result regarding the bypass control valve 42 during turning (and within the predetermined time TM1) of the vehicle in which the differential pressure valve 5 may be opened. Therefore, the reliability of the valve abnormality diagnosis method based on the relationship between the canister internal pressure and the tank internal pressure is greatly improved.

In the analysis and diagnosis procedure of step 200 and subsequent steps, the diagnosis is made based on the presence or absence of a correlation between the simulated canister internal pressure Pc and the tank internal pressure Pt, or the presence or absence of Pt following the Pc change. A diagnosis is made as to whether or not the valve (bypass control valve 42) is stuck open. That is, regardless of the absolute value of Pt, it is possible to diagnose whether there is a valve opening abnormality by focusing only on the relative relationship between Pc and Pt. For this reason, it is not required that the vehicle, engine or tank internal pressure Pt is in a predetermined stable state as a precondition for entering the diagnosis process. For example, even if the vehicle is traveling on a rough road, it is possible to diagnose the abnormality of the valve,
At this point, it is possible to frequently perform the abnormality diagnosis without being restricted by the strict prerequisites.

Even when it is determined that the valve to be diagnosed is abnormally open, the correlation between the change in the simulated canister internal pressure Pc and the change in the tank internal pressure Pt is statistically reasonable. Is a condition for judgment. That is, the valve open abnormality is determined only when the correlation rate R is large enough to be statistically certain. Therefore, the accuracy and reliability of valve abnormality diagnosis are excellent.

(Second Embodiment) Next, a second embodiment of the present invention will be described. The second embodiment is different from the first embodiment in mechanical and electrical configuration of the fuel vapor purge system.
The second embodiment is the same as the first embodiment, but differs from the first embodiment in the method of diagnosing an abnormality of the bypass control valve 42. Hereinafter, the difference will be mainly described.

The flowchart of FIG. 12 shows a main procedure for diagnosing the presence or absence of a malfunction (abnormal) of the bypass control valve 42. Figure 1 shows the core analysis procedure for determining valve abnormalities.
The second step 200 is as described above (see FIGS. 8 and 9). Step 410 in FIG.
Steps 470 are pre-procedures for deciding whether to permit the entry into the analysis process in step 200 or to suspend the entry. That is, in these processes, when there is a possibility that the cutoff valve 33 is closed or the differential pressure valve 5 is opened, the abnormality determination of the bypass control valve 42 is temporarily suspended, and the cutoff valve 33 is opened and the differential pressure valve 5 is closed. That is, the result of the analysis in step 200 is respected in anticipation of a situation where it is certain that the operation is performed. Step 200
Is mainly determined by whether the vehicle is in a turning traveling state (in the second embodiment, the magnitude of the lateral acceleration (hereinafter referred to as “lateral G”) acting on the vehicle) The determination is made based on the elapsed time after the lateral G has decreased to the predetermined level. The meaning of temporarily suspending the abnormality determination of the valve is the same as that of the first embodiment.

Next, the details of the valve abnormality diagnosis processing will be described with reference to FIG. Note that the main routine of FIG. 12 is executed by the ECU 10 as a periodic interruption process every predetermined time (for example, several tens to several hundreds of milliseconds).

When there is an interrupt request, the ECU 10 first determines in step 410 whether or not the remaining amount of fuel in the fuel tank 1 is equal to or larger than a predetermined remaining amount x (for example, 85% of the full state). If the determination at step 110 is NO, the process proceeds to step 200. Step 410: Y
In the case of ES, in step 420, the ECU 10 determines whether or not the vehicle speed is lower than a predetermined speed y (for example, 80 km / h). If the determination in step 420 is NO,
The process moves to step 200. Step 41
0 and 420 correspond to steps 110 and 120 in FIG. 7, respectively, and the technical significance of each is the same as in the first embodiment.

If the determinations at step 410 and step 420 are both YES, at step 430 the ECU
10 calculates the size of the lateral G acting on the vehicle. FIG.
As shown in FIG. 3, for example, if the front (or rear) left and right wheels of a four-wheeled vehicle running at a vehicle speed V turn at an angular speed ω, the lateral G acting on the vehicle at that time is V · ω
Becomes Since the angular velocity ω is equal to the value obtained by dividing the speed difference ΔVLR between the left and right wheels by the vehicle width (the interval between the left and right wheels) W, the lateral G is
It is expressed by (V · ΔVLR) / W. In the second embodiment, the inclination of the liquid level in the fuel tank 1, the possibility of the cutoff valve 33 being closed, and the differential pressure
Estimate the possibility of opening the valve. In this case, a speed sensor (for example, a rotating wheel speed sensor for ABS) provided on each of the left and right wheels and the ECU 10 constitute a lateral G detecting unit.

Subsequently, in step 440, the ECU 10 determines whether or not the lateral G is equal to or greater than the first lateral G determination value A (G1). The lateral G determination value A (G1) corresponds to the lateral G that causes the fuel tank liquid surface to be inclined such that the cutoff valve 33 is closed.
If the lateral G obtained in step (1) is equal to or greater than the lateral G determination value A (G1), there is a high probability that the cutoff valve 33 is closed (see FIG. 14). Therefore, the determination in step 440 is YES.
In this case, the routine of FIG. 12 is terminated without performing the procedure of steps 200, 310 and 330 (that is, the determination is suspended).

If the determination in step 440 is NO, in step 450, the ECU 10 determines whether or not the lateral G is greater than or equal to a second lateral G determination value A (G2). The lateral G determination value A (G2) corresponds to the lateral G that causes the fuel tank liquid surface to incline enough to cause the autonomous opening of the differential pressure valve 5, and the lateral G obtained in step 430 is the lateral G. If it is equal to or greater than the determination value A (G2), the differential pressure valve 5 may be open (see FIG. 14). Therefore, step 45
If the 0 determination is YES, after the processing of step 460, the routine of FIG. 12 ends without performing the procedure of steps 200, 310 and 330 (that is, the determination is suspended).

The process of step 460 is a process of clearing the first timer 54 to zero and starting the measuring operation. In other words, the determination condition of step 450 is satisfied when the level of the determination value A (G2) reaches the level of the determination value A (G2) for the first time after the lateral G falls in the timing chart of FIG. The start of measurement at 54 corresponds to advance preparation for measuring the elapsed time from the time point t4.

If both the judgments at step 440 and step 450 are NO, at step 470 EC
U10 determines whether the time measured by the first timer 54 is less than a predetermined time TM3. If the timer measurement time is within the predetermined time TM3, there is a high possibility that the differential pressure valve 5 is open (see FIG. 14), so the routine of FIG. 12 ends (ie, the determination is suspended). That is, step 440
As shown in FIG. 14, the series of processes from the time t3 to the time t3 after the lapse of the predetermined time TM3 from the time t3 when the horizontal G occurs and the value reaches A (G2), as shown in FIG.
5) is a judgment suspension period, and if it is within this period, this is a process for avoiding the processing of step 200 and subsequent steps.

If the determination in step 470 is NO, it means that the interrupt processing time is not within the determination suspension period, and at least the cutoff valve 33 is closed due to the lateral G or the differential pressure valve 5 is opened. There is no possibility of doing it. That is, a bad condition that causes the analysis result in step 200 to be erroneous is eliminated. Therefore, the ECU 10 determines in step 200 that the canister internal pressure Pc and the tank internal pressure Pc
Check for a correlation with t. This correlation check is exactly the same as the procedure shown in FIGS. 8 and 9, and will not be described again.

If it is determined in step 200 that the correlation between the Pt change and the Pt change is low (step 2).
16), it is determined that the bypass control valve 42 has no open fixation abnormality, that is, normal.
0). If it is determined in step 200 that the correlation between the Pt change and the Pt change is high (see step 215), it is determined that the bypass control valve 42 has an open fixation abnormality, that is, an open abnormality (step 330). . If the determination is suspended in the processing of step 200 (see step 216), the processing of FIG. 12 is terminated without making a definitive determination on whether the bypass control valve 42 is normal or abnormal.

According to the second embodiment, the same effects as those of the first embodiment can be obtained. In particular, by calculating the lateral G acting on the vehicle and comparing the obtained lateral G with a predetermined determination value, not only the opening / closing state of the differential pressure valve 5 but also the opening / closing state of the cutoff valve 33 can be rationalized. It can be presumed that the abnormality diagnosis result of the bypass control valve 42 is erroneously determined.

(Another Example) The embodiment of the present invention may be modified as follows.・ Simulated canister internal pressure P, which is an estimated value of canister internal pressure
Instead of relying on c, a pressure sensor for directly detecting the internal pressure of the canister 2 may be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a fuel vapor purge system and an abnormality diagnosis device thereof.

FIG. 2 is a sectional view showing a closed state of a differential pressure valve.

FIG. 3 is a sectional view showing an open state of a differential pressure valve.

FIG. 4 is a block diagram showing an outline of an electrical configuration related to valve abnormality diagnosis.

FIG. 5 is a timing chart showing an outline of leakage diagnosis of the purge system.

FIG. 6 is a sectional view showing a liquid level state in the fuel tank.

FIG. 7 is a flowchart of a valve abnormality diagnosis procedure according to the first embodiment.

FIG. 8 is a flowchart showing details of a pressure correlation check procedure.

FIG. 9 is a flowchart showing details of a pressure correlation check procedure. No.

FIG. 10 is a timing chart showing various patterns of a determination suspension period in the first embodiment.

FIG. 11 is a timing chart showing various patterns relating to pressure correlation.

FIG. 12 is a flowchart of a valve abnormality diagnosis procedure according to the second embodiment.

FIG. 13 is a view for explaining various parameters required for calculation of a horizontal G;

FIG. 14 is a timing chart showing a pattern of a determination suspension period in the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel tank, 1a ... Pressure sensor (tank pressure detection means), 2 ... Canister, 5 ... Differential pressure valve, 7 ... Breather passage, 8 ... Purge passage, 9 ... Engine intake passage, 10 ... E
CU (canister internal pressure detecting means, diagnostic control means, misjudgment avoiding means, lateral G detecting means, fuel remaining amount detecting means) 11: purge control valve, 33: float valve cut-off valve,
41: bypass passage, 42: bypass control valve, 61: steering operation detection sensor.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor ▲ Mr. Mamoru Oka 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Kenichiro Kawase 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation Inside the company (72) Inventor Masahiro Tominaga 2-1-1 Toyota-cho, Kariya-shi, Aichi Prefecture Inside Toyota Industries Corporation (72) Inventor Hitoshi Tanaka 2-1-1 Toyota-cho, Kariya-shi, Aichi Prefecture Toyota Auto Corporation F term in the loom mill (reference) 3G044 BA23 CA15 CA17 DA03 EA03 EA30 EA32 EA53 EA55 EA57 EA69 FA03 FA04 FA20 FA23 FA31 FA32 FA39 GA01 GA02 GA03 GA04 GA05 GA06 GA07 GA10 GA13 GA14 GA15 GA16 GA20 GA22 GA23 GA24 GA27 GA28

Claims (7)

[Claims] 1. A purge control valve provided in a passage for purging fuel vapor from a fuel tank, a canister, the canister to an engine intake passage, and a bypass control valve provided in a bypass passage connecting the canister and a fuel tank. And a fuel vapor purge system for a vehicle comprising a differential pressure valve provided in a passage in parallel with the bypass passage between the canister and a fuel tank,
An abnormality diagnostic device for diagnosing the presence or absence of an abnormality in said bypass control valve, comprising: a tank internal pressure detecting means for directly or indirectly detecting an internal pressure of a fuel tank; and a canister for directly or indirectly detecting an internal pressure of a canister. An internal pressure detecting means, a diagnostic control means for controlling the driving of the purge control valve and the bypass control valve and obtaining information from the two detecting means, wherein the purge control valve is opened to reduce the pressure of the canister. Under the condition that a condition is created and a valve closing command is issued to the bypass control valve, changes in the canister internal pressure and the fuel tank internal pressure are monitored, and the presence or absence of abnormality of the bypass control valve is determined based on a relationship between the two internal pressures. Diagnostic control means to monitor the running state of the vehicle, and if there is a possibility that the differential pressure valve has autonomously opened due to the turning of the vehicle, An abnormality diagnosis device for a fuel vapor purge system for a vehicle, comprising: an erroneous determination avoiding unit that suspends a determination regarding the presence or absence of an abnormality of a bypass control valve by the diagnostic control unit or that rejects the determination result. 2. The erroneous determination avoiding means includes a steering operation detection sensor for outputting a steering signal for notifying an operation state of a steering wheel of a vehicle, wherein the steering signal from the sensor is at an active level and the steering signal is inactive. For a predetermined time after the level has been reached, it is determined that the differential pressure valve may be autonomously opened, and the determination by the diagnostic control unit is suspended or the determination result is not adopted. An abnormality diagnosis device for the fuel vapor purge system for a vehicle according to claim 1. 3. The fuel tank is provided with a float valve type cut-off valve at an end of a passage in which the differential pressure valve is interposed. In addition to the case where the differential pressure valve may have opened autonomously, the determination by the diagnosis control unit may also be performed when the cutoff valve may be closed due to turning of the vehicle. 2. The abnormality diagnosis device according to claim 1, wherein the determination is suspended or the determination result is not adopted. 4. The erroneous determination avoiding means includes lateral G detecting means for detecting a lateral acceleration (lateral G) acting on the vehicle,
4. The fuel vapor for a vehicle according to claim 3, wherein the possibility of opening the differential pressure valve and the possibility of closing the cutoff valve are estimated with reference to the lateral G detected by the lateral G detecting means. Abnormality diagnosis device in the purge system. 5. The fuel vapor purge for a vehicle according to claim 4, wherein said lateral G detecting means detects lateral G based on information on a vehicle speed, a speed difference between left and right wheels, and an interval between left and right wheels. Abnormality diagnostic device in the system. 6. The apparatus according to claim 6, further comprising a fuel remaining amount detecting means for detecting a fuel remaining amount in said fuel tank, wherein said erroneous determination avoiding means is invalidated when said fuel remaining amount is less than a predetermined amount. The abnormality diagnosis device for a fuel vapor purge system for a vehicle according to any one of claims 1 to 5, wherein: 7. The diagnostic control means monitors a change in the internal pressure of the canister by a first predetermined amount or more, a change in the internal pressure of the fuel tank by a second predetermined amount or more, and a correlation rate indicating a frequency of occurrence of the latter with respect to the former. The fuel vapor for a vehicle according to any one of claims 1 to 6, wherein it is determined that an abnormality has occurred in the bypass control valve when the correlation ratio is equal to or greater than a predetermined threshold. Abnormality diagnosis device in the purge system.