JP2001304053A - Valve abnormality diagnostic device for fuel vapor purge system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abnormality diagnosing device capable of numerously having diagnostic chances and finally judgeable on the existence of valve abnormality in its early stages while securing diagnostic reliability. SOLUTION: A valve closing command is issued to a bypass control valve 80a being a diagnostic object in a sucking situation of a canister 40 for opening a purge control valve 71a. When recognizing follow-up of a fuel tank internal pressure to a change in canister internal pressure, a process transfers to the next diagnostic process by doubting abnormality of a valve opening state of the bypass control valve 80a. An atmospheric introducing valve 72a is forcedly closed in the first place in the next process to enhance a pressure reducing level of the canister 40. A changing tendency of the fuel tank internal pressure after forced valve closing is investigated to finally judge the existence of abnormality of the bypass control valve 80a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve abnormality diagnostic apparatus for diagnosing the abnormality or malfunction of a valve used in a fuel vapor purge system.

[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 purge system, fuel vapor generated in a fuel tank is once collected in a canister, and the collected fuel vapor is appropriately purged (discharged) into an intake passage of an 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. The abnormality diagnosis device includes, for example, a pressure sensor for detecting an internal pressure in a fuel tank and a region communicating with the fuel tank, and an electromagnetic valve provided in a passage connecting the fuel tank and the canister. Further, a diagnostic program for detecting an abnormality of each device component such as the pressure sensor and the valve is incorporated in such an abnormality diagnostic device, thereby further ensuring the reliability of the purge system.

[0003] For example, Japanese Patent No. 274169 discloses a device and a judgment method for diagnosing whether or not the above-described pressure sensor and electromagnetic valve are operating normally.
No. 9 is cited. This patent publication discloses an example of a method of detecting an abnormality of an electromagnetic valve (first control valve 24) provided in a passage connecting a fuel tank and a canister. According to this method, a valve closing signal (valve closing command) is given to the electromagnetic valve in a situation where the suction negative pressure from the engine intake passage is applied to the canister. If the tank internal pressure continues to decrease for more than the predetermined allowable time even though the electromagnetic valve should have been closed, the electromagnetic valve is stuck in the open state for some reason. It is presumed that the valve has become abnormal, and it is determined that the valve is abnormal (open abnormality).

[0004]

However, there are prerequisites to be satisfied in order to use the above-mentioned determination method. In other words, the engine or the vehicle is confirmed to be in a stable state before starting the valve abnormality diagnosis, and the reliability of the abnormality diagnosis is ensured only when the precondition (abnormality diagnosis permission condition) is satisfied. Is done. This is because, for example, when the vehicle is traveling on a rough road (uneven road, etc.) and the liquid level and liquid area in the fuel tank fluctuate drastically, the tank internal pressure (fuel (Evaporation amount) also fluctuates greatly. Under such a turbulent situation, there is a high possibility of erroneous determination even if it is attempted to determine the presence or absence of a malfunction of the valve simply by monitoring the temporal change of the tank internal pressure. Under such circumstances, in the above-described conventional technology, valve diagnosis is not performed unless the state of the engine or the vehicle satisfies the abnormality diagnosis permission condition based on information from various sensors. .

[0005] However, as long as such a determination method is used, valve abnormality diagnosis cannot be performed unless the engine or vehicle strictly meets the abnormality diagnosis permission condition.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a diagnostic method which does not require strict prerequisites to enter a diagnostic process and is relatively unrestricted by the establishment of prerequisites. This provides a valve abnormality diagnosis device in a fuel vapor purge system that can provide a large number of opportunities for abnormality diagnosis, and can make a final decision on the presence or absence of a valve abnormality early while maintaining the reliability of diagnosis. Is to do.

[0007]

According to a first aspect of the present invention, there is provided a fuel tank, a canister, an atmosphere introduction valve provided in a passage for introducing air to the canister, and a purge of fuel vapor from the canister to an engine intake passage. To determine whether the bypass control valve is abnormal in a fuel vapor purge system including a purge control valve provided in a passage for connecting the canister and the fuel tank, and a bypass control valve provided in a bypass passage connecting the canister and the fuel tank. An abnormality diagnosis device for a valve, a tank internal pressure detecting means for directly or indirectly detecting the internal pressure of the fuel tank, a canister internal pressure detecting means for directly or indirectly detecting the internal pressure of the canister, the atmosphere introduction valve, In addition to controlling the drive control for each of the purge control valve and the bypass control valve, the fuel tank Diagnostic control means capable of obtaining information on pressure and canister internal pressure, wherein the diagnostic control means issues a valve closing command to the bypass control valve to be diagnosed under the canister suction condition in which the purge control valve is opened. Then, the changes in the internal pressure of the canister and the internal pressure of the fuel tank are monitored, and when the internal pressure of the fuel tank follows the change in the internal pressure of the canister. The trend is further examined to determine whether the bypass control valve is abnormal.

[0008] According to this configuration, the diagnosis control means performs the diagnosis in the first stage of the abnormality diagnosis under the canister suction condition in which the purge control valve is opened to apply a suction negative pressure from the engine intake passage to the canister. A valve closing command is issued to the bypass control valve. Then, changes in the internal pressure of the canister and the internal pressure of the fuel tank are monitored to check whether the internal pressure of the fuel tank follows the internal pressure of the canister. If a change such as the internal pressure of the fuel tank follows the change in the internal pressure of the canister is recognized, the bypass control valve is in the open state despite the valve closing command from the diagnostic control means (ie, Abnormal when the valve is open) is suspected. However, in order to make a highly reliable abnormality judgment based only on such followability monitoring, the change trends of the canister internal pressure and the fuel tank internal pressure are tracked for as long as possible, and the correlation ratio of the pressure follow-up is statistically high. You need to make sure. That is, in the first-stage diagnosis method, it is impossible to make a highly reliable abnormality determination by monitoring for a short time. Therefore, in the present invention, the first
The steps should only be preliminary to detect possible anomalies. That is, when the internal pressure of the fuel tank follows the change in the internal pressure of the canister to some extent during monitoring for a relatively short time, it is determined that there is a possibility that the bypass control valve may be abnormal in the open state, and the precise diagnosis process of the second stage is performed. Transition.

In the second stage, the pressure reduction level of the canister is increased by forcibly closing the air introduction valve to prevent the air from being introduced into the canister. In such a situation, if the change trend of the fuel tank internal pressure after the forcible valve closing is closely examined, the bypass control valve interposed in the bypass path connecting the canister and the fuel tank exhibits an abnormality in a truly open state. Can be determined in a relatively short time with high reliability. As described above, according to the present invention, the method of detecting the possibility of the abnormality of the bypass control valve in the first stage is based on the relative relationship between the internal pressure of the canister and the internal pressure of the fuel tank. Satisfaction of strict preconditions such as that the internal pressure is in an absolutely stable state is not required as a condition for entering the diagnostic process. Therefore, a relatively large number of opportunities for valve abnormality diagnosis can be secured. In addition, the procedure of the second step is started only when the possibility of abnormality of the bypass control valve is suspected. In the second step, the change in the fuel tank internal pressure alone under the condition that the canister pressure is further increased is considered. Since the presence or absence of an abnormality in the opening state of the bypass control valve is closely examined based on the trend, highly reliable diagnosis can be made at an early stage.

According to a second aspect of the present invention, in the fuel vapor purge system according to the first aspect of the present invention, the fuel vapor purge system includes a canister and a fuel tank in addition to the bypass control valve in the bypass passage. An autonomous operation type differential pressure valve which is in parallel with the bypass control valve in a path connecting the fuel tank and the air introduction when the internal pressure of the fuel tank follows the change in the internal pressure of the canister. After a lapse of a predetermined time from the forced closing of the valve, the air introduction valve is opened.

In many cases, the fuel vapor purge system requires an autonomous operation type differential pressure valve in parallel with the bypass control valve in a path connecting the canister and the fuel tank. If the air introduction valve continues to be closed indefinitely even after the forced closing, if the bypass control valve is normally closed as instructed by the diagnostic control means, the air introduction valve will be closed continuously. The internal pressure of the canister is excessively reduced, and as a result, the difference between the internal pressure of the tank and the internal pressure of the canister is increased, and the differential pressure valve may open autonomously. If the differential pressure valve opens on its own during the diagnosis process, the internal pressure of the fuel tank drops at once, and in this case, the diagnosis control means opens the valve even though the bypass control valve is normally closed. An erroneous determination is made that the state is abnormal. In order to avoid such an erroneous determination, it is desirable to set the predetermined time until the restart valve is short enough to prevent unexpected autonomous opening of the differential pressure valve during diagnosis.
That is, the predetermined time has a meaning as a kind of time limit for preventing occurrence of the erroneous determination as described above.

According to a third aspect of the present invention, in the fuel vapor purge system according to the second aspect of the present invention, the diagnostic control means is configured to execute the predetermined time from the forced closing of the air introduction valve. The change amount of the internal pressure of the fuel tank is grasped, and when the absolute value of the change amount of the internal pressure of the fuel tank does not become less than a predetermined determination value, it is determined that the bypass control valve is abnormal, and the predetermined determination value is determined by the fuel. It is characterized by being variably set according to the remaining fuel amount of the tank.

If the canister is guided to increase the pressure reduction level for a predetermined time after the forced closing of the air introduction valve, the pressure in the area communicating with the canister should follow the tendency to decrease. If the absolute value of the fuel tank internal pressure change during that time is less than the predetermined determination value, it is not possible to recognize the change in the fuel tank internal pressure that follows the improvement of the degree of depressurization of the canister, and it is convinced that the bypass control valve is abnormal. Cannot be performed (ie, passive normality determination due to the fact that the possibility of valve abnormality in the first stage cannot be positively affirmed). On the other hand, when the absolute value of the fuel tank internal pressure change amount during that period does not become less than the predetermined determination value (that is, when the absolute value is equal to or more than the predetermined determination value), the possibility of the valve abnormality in the first stage is determined more precisely. It is confirmed under diagnosis, and in that case, a final determination is made that the bypass control valve is abnormal. By setting the determination value variably according to the remaining amount of fuel in the fuel tank, it is possible to reduce the probability of erroneous determination and improve the reliability of diagnosis determination. The validity of such variable setting will be described in detail in “Embodiments of the invention”.

According to a fourth aspect of the present invention, in the fuel vapor purge system according to any one of the first to third aspects of the present invention, the diagnostic control means includes: As a precondition for judging the presence or absence of an abnormality of the bypass control valve by closely examining the change trend of the fuel tank internal pressure, in addition to following the fuel tank internal pressure with respect to the canister internal pressure change, it is purged through the purge passage. The concentration of the fuel vapor is less than a predetermined threshold concentration.

This is because if the air introduction valve is forcibly closed in a situation where the concentration of the fuel vapor purged from the canister into the engine intake passage via the purge passage (purge concentration) is high, the air-fuel ratio tends to be over-rich. This is because there is a possibility that engine stall or drivability may be deteriorated. Therefore, the diagnosis control means validates the diagnosis method of the present invention only when the concentration of the fuel vapor is lower than the predetermined threshold concentration.

According to a fifth aspect of the present invention, there is provided a fuel tank, a canister, an atmosphere introduction valve provided in a passage for introducing air to the canister, and a passage for purging fuel vapor from the canister to an engine intake passage. Abnormality diagnostic device for determining whether there is an abnormality in the bypass control valve in a fuel vapor purge system including a purge control valve provided and a bypass control valve provided in a bypass passage connecting the canister and the fuel tank Wherein tank internal pressure detecting means for directly or indirectly detecting the internal pressure of the fuel tank, canister internal pressure detecting means for directly or indirectly detecting the internal pressure of the canister, and the atmosphere introduction valve, purge control valve, and bypass control In addition to controlling the driving of each of the valves, the internal pressure detecting means and the canister are controlled by the internal pressure detecting means. Diagnostic control means capable of obtaining information on the internal pressure, wherein the diagnostic control means issues a valve closing command to the bypass control valve to be diagnosed under a canister suction condition in which the purge control valve is opened, and thereafter, The changes in the canister internal pressure and the fuel tank internal pressure are monitored, and when it is recognized that the fuel tank internal pressure follows the change in the canister internal pressure, the bypass control valve is forcibly opened, and the change in the fuel tank internal pressure after the forcible opening is further monitored. It is characterized in that the presence or absence of an abnormality of the bypass control valve is determined by scrutinizing.

According to this configuration, as the first stage of the abnormality diagnosis, the diagnosis control unit opens the purge control valve to perform a diagnosis under a canister suction condition in which a suction negative pressure is applied from the engine intake passage to the canister. A valve closing command is issued to the bypass control valve. Then, changes in the internal pressure of the canister and the internal pressure of the fuel tank are monitored to check whether the internal pressure of the fuel tank follows the internal pressure of the canister. If a change such as the internal pressure of the fuel tank follows the change in the internal pressure of the canister is recognized, the bypass control valve is in the open state despite the valve closing command from the diagnostic control means (ie, Abnormal when the valve is open) is suspected. However, in order to make a highly reliable abnormality judgment based only on such followability monitoring, the change trends of the canister internal pressure and the fuel tank internal pressure are tracked for as long as possible, and the correlation ratio of the pressure follow-up is statistically high. You need to make sure. That is, in the first-stage diagnosis method, it is impossible to make a highly reliable abnormality determination by monitoring for a short time. Therefore, in the present invention, the first
The steps should only be preliminary to detect possible anomalies. That is, when the internal pressure of the fuel tank follows the change in the internal pressure of the canister to some extent during monitoring for a relatively short period of time, it is determined that there is some possibility of an abnormality in the bypass control valve, and the process proceeds to the second stage precise diagnosis process.

In the second stage, the bypass control valve is forcibly opened to achieve intentional communication between the canister and the fuel tank (that is, the two are in the same pressure region). Under these circumstances, if the change trend of the fuel tank internal pressure after the forced valve opening is closely examined, it is determined whether or not the bypass control valve interposed in the bypass path connecting the canister and the fuel tank is opened as intended. Can be determined in a relatively short time with high reliability. As described above, according to the present invention, the method of detecting the possibility of the abnormality of the bypass control valve in the first stage is based on the relative relationship between the internal pressure of the canister and the internal pressure of the fuel tank. Satisfaction of strict preconditions such as that the internal pressure is in an absolutely stable state is not required as a condition for entering the diagnostic process. Therefore, a relatively large number of opportunities for valve abnormality diagnosis can be secured. In addition, the procedure of the second step is started only when it is suspected that the bypass control valve may be abnormal. In the second step, the fuel is supplied to the canister and the fuel tank under the same pressure range. Since the presence or absence of an abnormality in the bypass control valve is closely examined based on the change trend of the tank internal pressure alone, highly reliable diagnosis can be made at an early stage.

According to a sixth aspect of the present invention, in the valve abnormality diagnostic apparatus of the fuel vapor purge system according to the fifth aspect, the diagnostic control means is configured to perform a predetermined period of time after the forced opening of the bypass control valve. The amount of change in the fuel tank internal pressure is grasped, and when the absolute value of the amount of change in the fuel tank internal pressure is less than a predetermined determination value, it is determined that the bypass control valve is abnormal, and the predetermined determination value is determined by the fuel tank. Variably set in accordance with the remaining fuel amount.

When a predetermined period of time has passed since the forcible valve opening command of the bypass control valve, the pressure range of the fuel tank and the canister should be the same, and the internal pressure of the fuel tank should follow the internal pressure of the canister. Therefore, when the absolute value of the fuel tank internal pressure change amount during that time is equal to or greater than a predetermined determination value, it is possible to recognize the change in the fuel tank internal pressure that follows the progress of depressurization of the canister, and it is possible to make the bypass control valve abnormal. No (passive normal judgment). On the other hand, if the absolute value of the fuel tank internal pressure change amount during that time is less than the predetermined determination value, it is not possible to recognize the fuel tank internal pressure change that follows the depressurization progress of the canister, and the forced opening of the bypass control valve is performed. The state of the bypass control valve does not change before and after the command is output, and it is highly probable that the bypass control valve is maintained in the open state or the closed state regardless of the presence or absence of the forced valve opening command. That is, the possibility of the valve abnormality in the first stage is also confirmed by a diagnosis based on a valve operation different from that in the first stage (forcibly opening the bypass control valve). The final determination that there is an abnormality is made.
By setting the determination value variably according to the remaining amount of fuel in the fuel tank, it is possible to reduce the probability of erroneous determination and improve the reliability of diagnosis determination. The validity of such variable setting will be described in detail in “Embodiments of the invention”.

According to a seventh aspect of the present invention, in the valve abnormality diagnostic apparatus for a fuel vapor purge system according to any one of the first to sixth aspects, the diagnostic control means includes a canister internal pressure equal to or greater than a first predetermined amount. When there is a predetermined number of changes in the fuel tank internal pressure greater than or equal to a second predetermined amount synchronized with the change,
It is characterized in that it is determined that the fuel tank internal pressure follows the canister internal pressure change.

This is a more specific limitation of the contents of the diagnosis at the first stage, and the technical significance thereof will be clear in the description of “Embodiments of the invention” described later. In order to move from the first stage to the diagnostic process of the second stage at an early stage and to make the final determination regarding the presence or absence of the abnormality of the valve earlier,
Preferably, the predetermined number of times is “once”.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Several embodiments of a fuel vapor purge system for a vehicle and an abnormality diagnosis device therefor will be described below with reference to the drawings.

(First Embodiment) As shown in FIG. 1, an engine 10 includes a combustion chamber 11, an intake passage 12, and an exhaust passage 13.
It has. When the engine 10 is operated, fuel (for example, gasoline) stored in the fuel tank 30 is pumped out by the fuel pump 31 and sent to the delivery pipe 12a through the fuel supply passage.
Thus, the fuel is injected and supplied into the intake passage 12. A throttle valve 12c is provided upstream of the intake passage 12 to change the flow passage area of the intake passage 12 based on a depression operation of an accelerator pedal (not shown). Further upstream, an air cleaner 12d for purifying intake air is provided.
Further, an air flow meter 12e for detecting the amount of intake air to the engine 10 is provided.

The fuel vapor purge system 20 includes a canister 40 for collecting fuel vapor generated from the fuel tank 30.
Also, a purge passage 71 for purging the collected fuel vapor into the intake passage 12 of the engine 10 is provided. In the purge system 20, a pressure sensor 32 and a breather control valve 33 are provided in a ceiling portion of the fuel tank 30. Pressure sensor 3 as tank internal pressure detecting means
2 detects a pressure in the fuel tank 30 and a region communicating with the fuel tank 30 as a relative pressure based on the atmospheric pressure. The breather control valve 33 is a diaphragm type differential pressure valve, and opens automatically when the internal pressure Pt of the fuel tank becomes higher than a predetermined pressure Pc in the breather passage 34 and the canister 40 by, for example, refueling. The steam escapes to the canister 40 via the breather passage 34.

Further, the space inside the fuel tank 30 can communicate with the canister 40 via a vapor passage 35 having a smaller passage inner diameter than the breather passage 34. The tank internal pressure control valve 60 provided between the vapor passage 35 and the canister 40 is a diaphragm type differential pressure valve having substantially the same function as the breather control valve 33 described above. The diaphragm 61 in the tank internal pressure control valve 60 is provided with a fuel tank internal pressure Pt.
When the pressure becomes higher than the internal pressure Pc of the canister 40 by a predetermined pressure or more, the tank internal pressure control valve 60 is opened autonomously. However, the valve opening set differential pressure of the breather control valve 33 and the valve opening set differential pressure of the tank internal pressure control valve 60 are different.

The canister 40 is provided with an adsorbent (eg, activated carbon) therein, and temporarily stores fuel vapor by adsorbing the adsorbent on the adsorbent and then placing the fuel vapor under a pressure lower than the atmospheric pressure. The fuel vapor adsorbed on the material can be released again. Hereinafter, 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. The canister 40 communicates with the fuel tank 30 via a breather passage 34 and a vapor passage 35, can communicate with the intake passage 12 via a purge passage 71, and further has an atmosphere introduction passage 72 via an atmosphere valve 70. And the atmosphere discharge passage 73. Note that a purge control valve 71a formed of a solenoid valve or a VSV (vacuum switching valve) is provided in the middle of the purge passage 71. In the middle of the air introduction passage 72 communicating with the air cleaner 12d, an air introduction valve 72a made of a solenoid valve or a VSV is provided.
Is provided. The atmosphere introduction valve 72a is also called a canister closed valve (CCV).

In the atmosphere valve 70, two diaphragm valve bodies 74 and 75, each having a different valve function, are provided. The first diaphragm valve element 74 has a space 74 a on the back side thereof communicating with the purge passage 71, and
When 1 becomes a negative pressure lower than a predetermined pressure, the valve is opened to allow the outside air to flow into the canister 40 from the atmosphere introduction passage 72. On the other hand, the second diaphragm valve body 75 opens when the pressure inside the canister 40 reaches a positive pressure equal to or higher than a predetermined pressure, and discharges excess air from the canister 40 to the atmosphere discharge passage 73.

The interior of the canister 40 is divided by a partition plate 41 into a first adsorbent chamber 42 and a second adsorbent chamber 43. Although both the adsorbent chambers 42 and 43 are filled with an adsorbent (activated carbon), both chambers communicate with each other via a gas permeable filter 44 at the bottom of the canister. The fuel tank 30 is connected via a vapor passage 35 and a tank internal pressure control valve 60 on the one hand, and a breather control valve 33 and a breather passage 34 on the other hand.
Can be connected to the first adsorbent chamber 42 via the The atmosphere introduction passage 72 and the atmosphere discharge passage 73 are provided with the atmosphere valve 7.
0 can communicate with the second adsorbent chamber 43.
A purge passage 71 having a purge control valve 71a
Corresponds to the first adsorbent chamber 42 of the canister 40 and the intake passage 12
And the downstream position of the throttle valve 12c.
The first adsorbent chamber 4 is opened or closed according to the opening / closing operation of the purge control valve 71a.
2 and the downstream of the throttle valve 12c. That is, after the fuel vapor introduced from the vapor passage 35 or the breather passage 34 is temporarily adsorbed by the first adsorbent chamber 42,
It is carried to the purge passage 71. Further, even when the second diaphragm valve element 75 provided in the atmosphere valve 70 is opened and excess air in the canister 40 is discharged from the atmosphere discharge passage 73, the residual air remains in the gas in the canister 40. When passing through the first adsorbent chamber 42 and the second adsorbent chamber 43, the fuel vapor is adsorbed by the adsorbent inside the adsorbent chamber 42 and does not leak out.

In addition, the fuel vapor purge system 20 includes
A bypass passage 8 for introducing a negative pressure so as to connect the tank internal pressure control valve 60 to the second adsorbent chamber 43 side of the canister 40.
0 is provided. In the middle of the bypass passage 80, a bypass control valve 80a composed of a solenoid valve or a VSV is provided.
(Valve to be diagnosed) is provided. Note that the bypass control valve 80a, the tank internal pressure control valve 60, and the breather control valve 33 are all disposed in the middle of a path connecting the fuel tank 30 and the canister 40, and are in a parallel relationship with each other. When the bypass control valve 80a is opened, the inside of the tank internal pressure control valve 60 and the second adsorbent chamber 43 are directly communicated via the bypass passage 80. And
In particular, when the purge control valve 71a is open and a negative pressure is being introduced into the canister 40, the bypass control valve 80
When the valve a is opened, the space in the purge passage 71 is changed from the first adsorbent chamber 42 to the air-permeable filter 44 to the second adsorbent chamber 43.
It communicates with the fuel tank 30 via the bypass passage 80 → the tank internal pressure control valve 60 → the vapor passage 35. Further, since the space in the breather passage 34 is also in communication with the first adsorbent chamber 42, the same space as the purge passage 71 is shared.

As described above, by opening the bypass control valve 80a in a state where the negative pressure is introduced into the canister 40, the shared space in the fuel vapor purge system 20 communicating with each other is connected to the evaporative path in the system 20. Becomes
The abnormality diagnosis device for the fuel vapor purge system according to the present embodiment determines whether or not there is a failure by determining whether or not there is a leak in the evaporation path. At the same time, a diagnosis is made also about an abnormality or malfunction of the bypass control valve 80a.

Further, the engine 10 and the fuel vapor purge system 20 include an electronic control unit (ECU) 50 which plays a role as an engine control system and a purge system diagnostic system. As shown in FIGS. 1 and 2, outputs from various sensors including the pressure sensor 32 and the air flow meter 12e are input to the ECU 50. ECU
50 denotes a fuel injection valve 12b, a fuel pump 31, a purge control valve 71a, an atmosphere introduction valve 72a, and a bypass control valve 80.
In addition to controlling the driving of the e.g. a, a diagnosis regarding the presence or absence of leakage in the evaporation path and an abnormality diagnosis of the bypass control valve 80a are executed.

As shown in FIG. 2, the ECU 50 is mainly composed of a microcomputer 51. The microcomputer 51 includes a CPU 51a that executes various processes related to the control and diagnosis, and a ROM 51 that is a read-only memory that stores various programs related to the control and diagnosis.
b, RAM that is a volatile memory that can be freely read and written
51c, a backup RAM 51 which is a non-volatile memory in which reading and writing are free and a battery is backed up, so that the stored contents are retained even after the engine 10 is stopped.
d, a first counter 52, a second counter 53, a first internal timer 54, and a second internal timer 55 are incorporated. However, when the internal register of the CPU 51a is to serve as a counter, the first and second counters 52, 5
There is no need to dare to set 3.

On the output side of the microcomputer 51,
Fuel injection valve 12b, fuel pump 31, purge control valve 71
a, the air introduction valve 72a and the bypass control valve 80a are connected via respective drive circuits. On the input side of the microcomputer 51, in addition to the pressure sensor 32 and the air flow meter 12e, various sensors necessary for operation control of the engine 10, such as a rotation speed sensor and a cylinder discrimination sensor, are directly or indirectly connected. . The ECU 50 executes engine control such as fuel injection control and air-fuel ratio control based on various information provided from each sensor. The ECU 5
0 performs an abnormality diagnosis of the purge system by appropriately opening and closing the purge control valve 71a, the air introduction valve 72a, and the bypass control valve 80a while recognizing the output signal from the pressure sensor 32, and performing an abnormality diagnosis of the purge system. In order to make an accurate diagnosis, in particular, the bypass control valve 80a
Execute the abnormality diagnosis of. In this sense, the ECU 50 is positioned as “diagnosis control means”.

(Outline of Fuel Purge by Fuel Vapor Purge System) When the fuel in the fuel tank 30 is vaporized and its vapor pressure reaches a predetermined pressure or more, the tank internal pressure control valve 60 is opened and the fuel tank 30 is removed from the canister 40. The fuel vapor is allowed to flow into the inside. Further, when the vapor pressure of the fuel vapor suddenly increases in the fuel tank 30, for example, during fueling, the breather control valve 33 is opened, and the pressure from the fuel tank 30 into the canister 40 is reduced. Large inflows of fuel vapor are allowed. The fuel vapor flowing into the canister 40 is temporarily adsorbed by the adsorbent in the canister 40. Thereafter, for example, as shown in FIG. 3, the cooling water temperature of the engine 10 is reduced to a predetermined purge start water temperature (80 in the present embodiment).
° C), the purge control valve 71a and the atmosphere introduction valve 72a are set to open by the control of the ECU 50. Then, the suction negative pressure is guided from the intake passage 12 into the canister 40 through the purge passage 71, and the air introduction passage 7
Fresh air is introduced into the canister 40 from the air cleaner 12d through 2. The fuel vapor is released from the adsorbent by the introduction of the negative pressure and the fresh air, and is purged to the intake passage 12 through the purge passage 71.

(Outline of Evaporation Path Leak Diagnosis in Purge System) In performing the evaporative path leakage diagnosis, it is necessary that the cooling water temperature of the engine 10 reaches the purge start water temperature and the purge is started (ie, the purge control valve 71a).
And that the air introduction valve 72a is both open) and that the tank internal pressure Pt of the fuel tank 30 is stable. Regarding the latter, as shown in FIG. 3, for example, the change amount Δ in the tank internal pressure every predetermined time (for example, 15 seconds) based on detection information of the pressure sensor 32
P1 is calculated, and when it is confirmed three consecutive times that the pressure change amount ΔP1 is equal to or less than the predetermined value, the tank internal pressure Pt
Is determined to be stable. At the time when these preconditions are satisfied (time t0), the atmosphere introduction valve 72a is closed and the bypass control valve 8
0a is opened. As a result, the canister 40 is shut off from the atmosphere, and the canister 40 is connected to the intake passage 12.
, A negative pressure is led through a purge passage 71. in addition,
By opening the bypass control valve 80a, the fuel tank 30,
The canister 40, the breather passage 34, the vapor passage 35, and the purge passage 71 (that is, the entire inside of the evaporation passage) are in a negative pressure state. The internal pressure of this evaporation path is
Is detected by a pressure sensor 32 on the ceiling of the vehicle.

When the purge control valve 71a is once closed at time t1 under a condition where the pressure in the entire evaporation path is reduced to some extent, the inside of the evaporation path is closed under a negative pressure. At this time, if there is no abnormality such as a hole in the evaporation path, the fuel tank 3
As the fuel in the evaporator evaporates, the internal pressure of the evaporative passage should gradually approach (slowly increase) the equilibrium pressure of the air and fuel vapor remaining in the evaporative passage. On the other hand, if there is a leak in the evaporative path, the internal pressure in the evaporative path rapidly approaches the external pressure (atmospheric pressure). In any case, the evaporative path internal pressure increases after time t1,
The degree of internal pressure rise differs depending on the presence or absence of leakage. In the present embodiment, the internal pressure of the evaporation path is again reduced to the predetermined negative pressure (−2.00
At time t2 when the pressure reaches kPa = −15 mmHg), the pressure change rate ΔP (−15) (kPa
/ S or mmHg / s). Then, based on the pressure change rate ΔP (−15), it is determined whether or not there is an abnormality such as a hole in the evaporation path.

(Abnormal Diagnosis of Valves Constructing Purge System) In order for the leak diagnosis of the evaporative path to be reliable, it is always necessary to make sure that the sensors and valves composing the system are operating normally. You need to confirm. Hereinafter, a method of diagnosing a malfunction of the bypass control valve 80a provided in the bypass passage 80 will be particularly described. In an actual system, abnormality diagnosis is performed for other valves and the pressure sensor 32, but the description thereof is omitted.

FIGS. 4 to 7 are flowcharts showing the outline of an abnormality diagnosis routine for diagnosing the presence or absence of a malfunction of the bypass control valve 80a. This routine is executed by the ECU 5
When the value is 0, it is executed as a periodic interrupt process every predetermined time (for example, several tens to several hundreds of milliseconds). Note that this diagnostic processing is particularly for detecting a defect (open fixation) in which the bypass control valve 80a is fixed in the open state. For this reason, before entering this diagnostic routine, a valve closing drive signal (valve closing command) is issued from the ECU 50 to the bypass control valve 80a under the condition that the purge control valve 71a is opened.

When the interrupt processing request is issued, the ECU 50
First, in step 101, the purge flow rate Qp is calculated. “Purge flow rate” means the flow rate of gas discharged into the intake passage 12 through the purge passage 71. The purge flow rate Qp depends on the valve opening of the purge control valve 71a and the purge passage 7.
If the degree of the negative pressure of 1 is known, it can be calculated based on these or by referring to a characteristic map obtained by experiment or computer simulation. Here, since the opening of the purge control valve 71a is controlled by the ECU 50, the ECU 50 holds information on the valve opening of the purge control valve 71a as internal data. On the other hand, the degree of the negative pressure in the purge passage 71 is correlated 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 12e. That is, the degree of the negative pressure in the purge passage 71 can be grasped based on data from various sensors, and the purge flow rate Qp can be calculated based on the external data and the internal data. In this sense, the ECU 50 and various sensors including the engine speed sensor and the air flow meter 12e constitute "purge flow rate calculating means".

In step 102, the ECU 50 calculates the simulated canister internal pressure Pc. In this step, since the canister 40 is not provided with a pressure sensor for directly detecting its internal pressure, the canister internal pressure is estimated based on other obtainable information, and the estimated value is used as the simulated canister internal pressure Pc It is. 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 valve 70 of the canister, and the relationship between the two is formed into a characteristic map through experiments and computer simulations for each vehicle. . The characteristic map is ECU5
0 is held as internal data, and by referring to it, 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 50 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 40.

In step 103, the first internal timer 54
Is the predetermined time TM1
(For example, 15 seconds). If the predetermined time TM1 has elapsed at that time, step 10
The processing of step 4 is executed, but if the predetermined time TM1 has not been reached, the processing of step 104 is skipped. That is, the process of step 104 is performed every predetermined time TM1 (for example, 15 seconds).

Step 104 is a reset operation every predetermined time TM1. Here, first, the first internal timer 54
Is cleared to zero. Further, the simulated canister internal pressure Pc obtained in step 102 is the provisional canister reference internal pressure Pcs.
And the detected pressure of the pressure sensor 32 (tank internal pressure Pt) at that time is set to the provisional tank reference internal pressure Pt.
s. That is, the simulated canister internal pressure Pc when the predetermined time TM1 has elapsed is stored as a provisional comparison reference value (or reference point) Pcs, and the predetermined time TM1
The tank internal pressure Pt at the time of lapse is stored as a provisional comparison reference value (or reference point) Pts (see FIG. 9).
That is, in step 104, the provisional canister reference internal pressure Pcs and the provisional tank reference internal pressure Pts are set to the predetermined time TM1.
Updated every time.

Steps 105 to 107 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 105, 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 at step 105 is YES (Yes), at step 106, the value C1 of the first counter 52 assigned for counting the number of canister internal pressure changes is incremented (addition of 1). Similarly to the above, zero clear of the first internal timer 54 and resetting of the provisional canister reference internal pressure Pcs are performed (see FIG. 9). still,
The predetermined pressure value α is set to such an extent 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 105 is NO (No), the change in the simulated canister internal pressure Pc and the tank internal pressure Pt is not checked at all (that is, the addition and subtraction of the first and second counters 52 and 53 are performed at all). No), and skip to step 113 in FIG. This is because if the change in the simulated canister internal pressure Pc is too small, it is not appropriate to rely on the method of determining a malfunction of the valve of the present invention.

After step 107, the process proceeds to step 108 in FIG. In step 108, the absolute value of the difference ΔPt between the tank internal pressure Pt and the provisional tank reference internal pressure Pts at that time, 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 ( For example, 0.
It is determined whether or not the pressure is 47 kPa = 3.5 mmHg) or more. If the determination in step 108 is YES, in step 109, the value C2 of the second counter 53 allocated for counting the number of times of change in the tank internal pressure is incremented (1
to add. In other words, if the determination in step 105 is YES and the determination in step 108 is YES, it is determined that the followability corresponding to the change in Pt with respect to the change in Pc is recognized (positive affirmation of the followability), and the counter values C1, C2 Is the result of adding 1 to both. The predetermined pressure value β
Is set to a value smaller than the value α (β <α).

On the other hand, if the determination in step 108 is NO, in step 110, 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 110 is YES, in step 111, the value C of the second counter 53 is set.
Decrement 2 (subtract 1). That is, step 1
If the determination at step 05 is YES and the determination at step 110 is YES, it is determined that a clear change in Pt is not recognized despite a sufficient change in Pc (aggressive denial of change in tracking), 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).

If the determination in step 110 is NO, that is, if γ ≦ ΔPt <β, the addition / subtraction of the second counter 53 is not performed at all. In other words, in this case, the change in Pt is halfway despite a sufficient change in Pc, and it is not possible to positively affirm or deny the followability of the change in Pt to the change in Pc. Therefore, the counter value C1
The result is that the counter value C2 is maintained as it is despite the increase of the counter value.

After the processing in step 109, 110 or 111, in step 112, the ECU 50 resets the provisional tank reference internal pressure Pts similarly to step 104, and prepares for the determination in the next cycle. Step 11
After 2 or after the determination in step 105 is NO, the process proceeds to the determination procedure of step 113 and subsequent steps.

By the way, the predetermined time TM of step 103
1 can be understood as a time limit until zero clearing of the timer and resetting of the provisional reference internal pressures Pcs and Pts are forced in step 104 when the determination in step 105 does not easily become YES. That is, in the diagnosis procedure of FIGS. 4 and 5, if the variation ΔPc of the simulated canister internal pressure is not greater than or equal to the predetermined pressure value α within this time limit, a meaningful (or suitable for diagnosis) change in the simulated canister internal pressure can be obtained. It is assumed that there was no diagnosis, and the diagnosis is repeated without changing the count value. It does not make sense to take a long time to make the determination in step 105 YES. A preferable range of the predetermined time TM1 as the time limit is empirically in a range of 10 to 20 seconds (preferably around 15 seconds).

Steps 113 to 117 are a series of pre-procedures for checking in advance whether or not the prerequisites for diagnosing the abnormality of the valve are satisfied, and selecting an optimum diagnosis method.

First, at step 113, the ECU 50
Means that the tank internal pressure Pt detected by the pressure sensor 32 is equal to a predetermined lower limit PL (for example, −4.0 kPa = −30 mmHg).
It is determined whether or not this is the case. If the tank internal pressure Pt is less than the lower limit PL, the tank 30 is in an excessively negative pressure state, and in such a case, accurate abnormality diagnosis cannot be expected by any of the diagnostic methods described later.

When the determination in step 113 is YES, in step 114, the ECU 50 determines the value C of the second counter.
It is determined whether or not 2 is equal to or greater than a predetermined determination value DA. In the first embodiment, the determination value DA is set to 1, and if the determination in step 114 is YES, the process proceeds to the next condition check. That is, in step 114, step 105
If the determination is YES and the determination of step 108 is YES at least once, that is, if the Pt change is sufficiently followed to the Pc change even once, the main preconditions for the abnormality diagnosis are satisfied. It must have been done. Conversely, while the second counter value C2 remains zero, the necessity of performing the valve abnormality diagnosis is not recognized.

Subsequently, at step 115, the ECU 50
Determines whether the cylinder intake air amount Ga per cylinder in each cylinder of the engine is equal to or greater than a predetermined lower limit value EL. The cylinder intake air amount Ga corresponds to a value (Q / NE) obtained by dividing the intake air amount Q detected by the air flow meter 12e by the engine rotation speed NE, and is a parameter indicating the magnitude of the suction negative pressure with respect to the evaporative passage. The reason for setting such a lower limit condition is that if the suction negative pressure with respect to the evaporative passage is too weak, the vapor concentration (fuel vapor concentration) becomes high immediately after forcibly closing the air introduction valve 72a. There is a possibility that inconvenience such as deterioration of the image may occur, and this is to be avoided in advance.

When the determination in step 115 is YES, in step 116, the ECU 50 confirms whether or not purging is being performed. Whether or not purging is being performed is determined by referring to internal data of the ECU (status information of each valve) and confirming whether or not the purge control valve 71a is in an open state. At least in the diagnosis method of the routine A described later, the fact that the purge is being performed is a prerequisite for the abnormality diagnosis of the valve.

If the determination in step 116 is YES, in step 117, the ECU 50 determines whether the purge concentration Cp is less than a predetermined threshold concentration Ct, and selects a valve abnormality diagnosis method according to the determination result. Select uniformly. The purge concentration Cp can be calculated by a known method based on internal data such as the air-fuel ratio (A / F) that the ECU 50 has learned and updated appropriately for engine control. That is, the ECU 50 involved in engine control can calculate the purge concentration Cp based on the internal data. Switching the valve abnormality diagnosis method depending on the level of the purge concentration Cp may cause inconveniences such as engine stall and deterioration of drivability especially when the diagnosis method of the routine A is employed at a high purge concentration. In order to avoid this. The diagnostic method of the routine B can be employed regardless of the level of the purge concentration Cp.
In the case where the diagnosis method is low, the diagnosis method of the routine A is more efficient in diagnosis than the diagnosis method of the routine B, so that the purge concentration determination in step 117 is added, and the diagnosis method can be selected.

If the determination in step 117 is YES (that is, the purge concentration Cp is relatively low), valve abnormality diagnosis is performed according to a series of procedures shown in the routine A of FIG. On the other hand, if the determination in step 117 is NO (that is, the purge concentration Cp is relatively high), the routine B of FIG.
The abnormality diagnosis of the valve is performed according to a series of procedures shown in FIG. Steps 113, 114, 115 or 116
If the determination of NO is made in any of the above cases, the interrupt processing for the abnormality diagnosis of FIGS. 4 and 5 is temporarily ended without performing the abnormality diagnosis of the valve.

(Routine A) Step 117: YE
In the case of S (at the time of low purge concentration), abnormality diagnosis of the valve is performed according to a series of procedures shown in FIG. First, in step 121, the ECU 50 operates the atmosphere introduction valve (CCV).
The valve 72a is forcibly closed, and the pressure sensor 32 detects and stores the internal tank pressure Pt (S121) at that time.
If the air introduction valve 72a is already closed before the processing of step 121 is reached, the second internal timer 5
Although zero clear of 5 is not performed, if the air introduction valve 72a in the open state is closed for the first time in step 121, zero clear of the second internal timer 55 is also performed.

Thereafter, at step 122, the ECU 5
0 determines whether the elapsed time from the first CCV forced valve closing (that is, the previous zero clear of the timer 55) has reached a predetermined time TM2 (for example, several seconds to ten and several seconds). Step 12
If the determination of step 2 is YES, the processing of step 123 and subsequent steps is performed. If the determination of step 122 is NO (unless the predetermined time TM2 has not arrived), the processing of step 123 and subsequent steps is skipped and a series of interrupt processing is performed once. finish. In this case, the diagnosis determination of the valve abnormality is suspended.

After several interrupt processes, the first CC
When the elapsed time from the V forced valve closing has reached the predetermined time TM2 (when the determination in step 122 is YES), in step 123, the ECU 50 detects the tank pressure Pt (S123) at that time by the pressure sensor 32. At the same time, the air introduction valve 72a is returned to the open state again. That is, for at least the time TM2 from when the atmosphere introduction valve 72a is forcibly closed to when it is opened again, the introduction of outside air to the canister 40 is temporarily stopped, and the canister 40 and the space communicating therewith are subjected to a pressure reducing operation. Will be.

Then, at step 124, the ECU 5
0 is the difference ΔPt between the tank internal pressure Pt (S123) and the tank internal pressure Pt (S121).
The absolute value of 1) is calculated, and it is determined whether or not the absolute value of the difference is less than a predetermined determination value F (a relatively small value). The absolute value of the difference ΔPt (S123-S121) is
It represents the amount of change in the tank internal pressure during the period from the forced closing of the air introduction valve 72a to the restart valve. If the tank internal pressure change amount is less than the predetermined determination value F (the determination in step 124 is Y
In the case of ES, the ECU 50 determines that the bypass control valve 80a to be diagnosed is normal (step 12).
5). That is, as described above, when the canister 40 and the space communicating therewith continue to be subjected to the depressurizing operation for the time TM2, but the change in the tank internal pressure is hardly recognized or is very small, the tank 30 and the canister This is because no communication state exists between the bypass control valve 80 and the bypass control valve 80a, and it is appropriate to determine that the bypass control valve 80a has maintained the valve closed state in accordance with the original command from the ECU 50.

On the other hand, when the change in the tank internal pressure is equal to or greater than the predetermined determination value F (when the determination in step 124 is NO), the ECU 50 sets the bypass control valve 80 to be diagnosed.
It is determined that a has failed in the open state (open abnormality) (step 126). That is, as described above, when a change in the tank internal pressure is clearly recognized in response to the canister 40 and the space communicating therewith being continuously subjected to the pressure reducing operation for the time TM2, the tank 30 and the canister 40 are connected to each other. Is that there is communication between
This is because it can be determined that the bypass control valve 80a has not been closed according to the initial command from the ECU 50. When it is determined that the opening is abnormal, a warning display (for example, installed in the instrument panel of the vehicle) for notifying the crew of the abnormality of the fuel vapor purge system is lit.

As described above, according to the routine A, by setting the predetermined time TM2 to an appropriate time width (interval), it is possible to diagnose whether or not the bypass control valve 80a is abnormal relatively early. The predetermined time TM2 in step 122 has another meaning as a time limit. If the time TM2 as the time limit is not set, if the bypass control valve 80a normally operates and is closed as expected, the atmosphere introduction valve (CCV) 72
Due to the forced closing of a, the inside of the canister 40 falls into an excessively negative pressure state, and at that time, the autonomous operation type differential pressure valve (that is, the breather control valve 33 or the tank internal pressure control valve 60) may open without permission. is there. If any one of these differential pressure valves autonomously opens, the tank internal pressure Pt drops at once due to the suction negative pressure in the purge passage 71. Then Pt
It is inevitable that the difference between (S121) and Pt (S123) expands, and the result of determination in step 124 is NO even though the bypass control valve 80a is normal, resulting in erroneous determination that the valve is abnormally opened. Becomes On the other hand, by setting the predetermined time TM2 to be appropriately short, it is possible to prevent the differential pressure valve from unexpectedly opening autonomously, thereby preventing the erroneous determination. From this viewpoint, the predetermined time TM2
Has a meaning as a time limit for preventing erroneous determination in the valve abnormality diagnosis by the method of the routine A.

The determination value F used in step 124 is not a fixed value, but a variable value that is appropriately changed according to the amount of remaining fuel in the tank 30. The reason why the determination value F is a variable value will be described with reference to FIG. FIG. 8 shows the correlation between the amount of change in the tank internal pressure during a predetermined time when the bypass control valve 80a is open and the atmosphere introduction valve 72a is closed during the purging operation, and the amount of fuel remaining in the tank 30. 7 is a graph (general tendency model) showing. Even if the suction negative pressure to the canister 40 is constant,
As shown in FIG. 8, the amount of change in the tank internal pressure tends to increase as the fuel approaches the full state.
As 0 approaches an empty state, the amount of change in tank internal pressure tends to decrease. This tendency is caused by a change in the equilibrium behavior based on the quantitative relationship between the liquid phase and the gas phase in the fuel tank 30, and is a kind of natural phenomenon that cannot be avoided. Therefore, in order to ensure the accuracy of the determination in step 125 or 126, it is preferable that the determination value F in step 124 is also changed according to the remaining amount of fuel in the fuel tank 30.

In the first embodiment, the ECU 50 determines the remaining fuel amount by referring to the electric output from the fuel meter incorporated in the instrument panel in the driver's seat of the vehicle.
Based on this, the judgment value F is determined in multiple stages (for example, two stages).
Is switching. Specifically, a relatively small value F1 is usually adopted as the determination value F. However, when the remaining fuel amount is equal to or more than a predetermined threshold value Ft (when the remaining fuel amount is close to being full), the above-mentioned F1 is used. Instead, a relatively large value F2 (F1 <
F2) is adopted as the determination value F. By appropriately switching the determination value F according to the remaining amount of fuel in the fuel tank 30 as described above, erroneous determination of abnormality diagnosis is prevented as much as possible. The method of changing the determination value F does not need to be stepwise, and may be changed continuously in response to a change in the remaining fuel amount.

(Routine B) The determination in step 117 is NO.
In the case of (1) (at the time of high purge concentration), valve abnormality diagnosis is performed according to a series of procedures shown in FIG. First, in step 131, the ECU 50 determines whether or not the value C1 of the first counter has reached a predetermined determination value DB (for example, 10 times). If the first counter value C1 is less than the determination value DB, it is considered that the number of changes of the simulated canister internal pressure Pc has not reached the specified number and that it is not in a state where proper failure diagnosis can be performed, and a malfunction occurs in the valve. The series of interrupt processing in FIGS. 4 and 5 is once ended without diagnosing whether or not there is. In other words, the determination value DB is a value that can be called the minimum specified number of times for ensuring statistical reliability in determining the followability of the change of Pt to the change of Pc. Naturally, if the determination value DB is increased, the reliability of the determination is statistically increased, but it takes a long time to reach a conclusion.

If the determination in step 131 is YES (C1
= DB), it is determined that the number of changes of the simulated canister internal pressure Pc has reached the specified number of times for performing appropriate failure diagnosis, and the determination in step 132 is performed. That is, in step 132,
The value C2 of the second counter is equal to a predetermined determination value DC (for example, 7
Times) or not. The determination value DC is set to a value equal to or close to the determination value DB (where DC <DB).

If the determination in step 132 is YES, it is determined that the bypass control valve 80a is in the open state and malfunctions (open abnormality) (step 133). This is because satisfying the determination condition of step 132 means that the number of changes C2 in the tank internal pressure is equal to or very close to the number of changes C1 in the canister internal pressure, and the change in the simulated canister internal pressure Pc and the tank internal pressure Pt This is because there is a high correlation with the change trend, that is, it is possible to rationally determine the ability of the Pt change to follow the Pc change. If there is a close correlation between the changes in the two internal pressures Pc and Pt, it means that the two regions are clearly in communication with each other, and is provided in the bypass passage 80 connecting the fuel tank 30 and the canister 40. Although the valve close command is issued to the bypass control valve 80a, the bypass control valve 80a is open and is likely to have a failure. In this case, the processing of steps 131 and 132 is implicitly performed by DC.
/ DB calculates a correlation rate R (or a follow-up rate R) calculated by:
The correlation rate R is equal to or greater than a predetermined threshold (in this example, 7/10
= 70% or more), it can be understood that the process determines that the bypass control valve 80a is in the abnormal opening state.

On the other hand, if the determination in step 132 is NO,
It is determined that the bypass control valve 80a has no failure in the open state (normal) (step 134). This is so regarded as a flip in the case of an opening error. That is, the fact that the determination condition of step 132 is not satisfied means that there is not so much 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 Pt change follows the Pc change. This is because it indicates that sex cannot be asserted until it is reasonably recognized.
In terms of the scale of the correlation rate R, the ratio R has not reached a predetermined threshold value (70% in this example). Therefore,
The bypass control valve 80a is in the abnormal opening state and the fuel tank 30 and the canister 40 are not in communication with each other.
It is passively determined that the valve is normally closed according to the valve closing command from. Incidentally, when the bypass control valve 80a is normally closed, the fuel tank 30 should be in an isolated space, and in that case, the tank internal pressure Pt becomes
It should maintain a substantially constant value as shown by the dashed line in FIG.

(Effects) According to the first embodiment, the following effects can be obtained. First, in the diagnostic method from the main routine to the routine B, based on whether or not the tank internal pressure Pt can follow a change in the simulated canister internal pressure Pc (or whether or not there is a close correlation between the Pc change and the Pt change). It diagnoses whether there is an abnormal opening of the bypass control valve 80a to be diagnosed. That is, it is possible to diagnose the presence / absence of an abnormal valve opening not by focusing on the absolute value of Pt but by focusing only on the relative relationship between Pc and Pt. Therefore, maintaining the vehicle or tank internal pressure Pt in a predetermined stable state for a certain period of time is not required as a precondition for entering the diagnostic process. In extreme terms, even if the absolute value of the tank internal pressure (that is, the fuel evaporation pressure) becomes unstable irrespective of whether the valve is normal or abnormal because the vehicle is traveling on a rough road, the above-mentioned preconditions must be satisfied. The diagnosis of the valve can be performed without seeking the pre-establishment of.

Further, according to the diagnostic method of routine B,
Even when it is determined that the valve to be diagnosed is abnormally open, the determination condition is that there is a statistically reasonable correlation between the change trend of the simulated canister internal pressure Pc and the change trend of the tank internal pressure Pt. I have. That is, only when the correlation ratio R = DC / DB is large enough to be statistically certain (when the correlation ratio is equal to or more than a predetermined threshold), the valve open abnormality is determined. Therefore, the diagnostic accuracy and reliability are excellent.

However, even in the diagnostic method of the routine B having the above-described superior points, the accuracy and reliability of the diagnosis are ensured so as not to be affected by a small or temporary change in the vehicle environment. In this case, the pressure value β for determination in the determination at step 108 in FIG. 5 cannot be set too small. Also, in order to secure statistical certainty, the determination value D in steps 131 and 132 of the routine B is used.
B and DC cannot be reduced too much. Further, when the remaining amount of fuel in the tank 30 is small, the change amount ΔPt of the tank internal pressure tends to be small (see FIG. 8), and there is little chance that the determination in step 108 becomes YES, and the detection frequency of the valve opening abnormality is low. descend. Under such circumstances, it takes a slightly longer time to determine that the valve is abnormally opened by the diagnosis method of the routine B.

The diagnosis method of the routine A compensates for such a disadvantage. That is, in the diagnosis method from the main routine to the routine A, the second counter value C2 has reached the predetermined determination value DA (once in this example), that is, the tank internal pressure Pt with respect to a sufficient change in the simulated canister internal pressure Pc. Is found a predetermined number of times DA (once in this example), the possibility of an abnormality in the bypass control valve 80a is suspected for the time being, and step 1 of the routine A is performed to further investigate the point.
Perform the following processes. Then, the pressure reduction level of the canister 40 is increased by forcibly closing the air introduction valve 72a, and it is determined whether there is a valve opening abnormality based on the tank internal pressure behavior or the tank internal pressure change amount ΔPt (S123-S121) within the predetermined time TM2. ing. Therefore, by setting the time TM2 short enough not to impair the diagnostic accuracy, it is possible to make a final determination that the valve is abnormal in a short time. At least the diagnostic method of the routine A includes step 12
After a lapse of a predetermined time TM2 from the CCV forced valve closing of No. 1, the time required until a highly reliable judgment can be made because a conclusion can be made as to whether or not there is an abnormality in the valve to be diagnosed (bypass control valve 80a). Unclear routine B
It is clearer than the diagnostic method.

According to the diagnostic method of the routine A, as described above, by setting the time TM2 as the time limit, erroneous detection or erroneous determination caused by an unexpected opening of the autonomous operation type differential pressure valve is determined. Can be prevented, and the accuracy and reliability of diagnosis are excellent.

When the diagnostic method of the routine A or the diagnostic method of the routine B is selected, the selection is made based on the purge concentration Cp. Therefore, even if the purge concentration Cp is high, Regardless, the diagnostic method of routine A is not adopted. Therefore, as a result of executing the procedure of the routine A, the above-mentioned problems such as engine stall and deterioration of drivability do not occur. As described above, according to the first embodiment, an appropriate valve abnormality diagnosis method can be appropriately selected according to the conditions of the engine and the fuel vapor purge system.

In the present embodiment, since the simulated canister internal pressure Pc is calculated based on the purge flow rate, a second pressure sensor for measuring the pressure in the canister 40 is not required, and cost is reduced. It is advantageous.

(Second Embodiment) The diagnostic method of the routine A in the first embodiment is the same as that of the atmosphere introduction valve (CCV) 72.
a forcibly closing the valve a, grasping the behavior of the tank internal pressure within a predetermined time TM2, and judging the presence / absence of abnormal opening of the valve to be diagnosed (bypass control valve 80a) based on the amount of change in the tank internal pressure at that time. Was. In the second embodiment, an abnormality (opening abnormality or closing abnormality) of the valve to be diagnosed (bypass control valve 80a) is performed using a diagnostic method of routine C (see FIG. 10) slightly different from the diagnostic method of routine A.
Is determined. That is, the fuel vapor purge system and the abnormality diagnosis device thereof according to the second embodiment
The hardware configuration of the embodiment (FIGS. 1 and 2) and the leak diagnosis method of the purge system (FIG. 3) are directly followed, and a main part of the valve abnormality diagnosis routine (FIGS. 4, 5, 7, and 7). 9) is common, but the part corresponding to the routine A is replaced with the routine C in FIG. Therefore, the following description focuses on the differences (routine C) from the first embodiment, and avoids redundant description of common procedures.

In the second embodiment, step 117 in FIG.
When the determination is NO (at the time of high purge concentration), the abnormality of the valve is diagnosed by the diagnostic method of the routine B (FIG. 7) described above. On the other hand, if the determination in step 117 of FIG. 5 is YES (at the time of low purge concentration), the diagnostic method of routine C shown in FIG. 10 is employed.

(Routine C) First, in step 141, the ECU 50 forcibly opens the bypass control valve 80a, and the pressure sensor 32 detects the tank internal pressure Pt at that time.
(S141) is detected and stored. Step 14
If the bypass control valve 80a has already been opened before the processing of step 1, the second internal timer 55 is not zero-cleared, but the closed bypass control valve 80a is opened for the first time in step 141. In such a case, the second internal timer 55 is also cleared to zero.

Thereafter, at step 142, the ECU 5
0 indicates the first forced opening of the bypass control valve (that is, the timer 55
The predetermined time TM3
(For example, several seconds to ten and several seconds) is determined. If the determination in step 142 is YES, step 143
The following processing is performed. If the determination in step 142 is NO (unless the predetermined time TM3 has not come), step 143 is executed.
The following processing is skipped, and a series of interrupt processing is temporarily ended. In this case, the diagnosis determination of the valve abnormality is suspended.

If the elapsed time from the first forcible opening of the bypass control valve has reached the predetermined time TM3 after several interrupt processes (when the determination in step 142 is YES), the ECU 50 proceeds to step 143. The tank pressure Pt (S143) at that time is detected and stored by the pressure sensor 32, and the bypass control valve 80a is returned to the closed state again. That is, at least the time TM3 from when the bypass control valve 80a is forcibly opened to when it is closed again.
During this period, the canister 40 and the fuel tank 30 communicating therewith have been subjected to a pressure reducing operation.

Then, at step 144, the ECU 5
0 is the difference ΔPt (S143-S14) between the tank internal pressure Pt (S143) and the tank internal pressure Pt (S141).
The absolute value of 1) is calculated, and it is determined whether or not the absolute value of the difference is less than a predetermined determination value F (a relatively small value). The absolute value of the difference ΔPt (S143-S141) is
It indicates the amount of change in the tank internal pressure during the period from the forced opening of the bypass control valve 80a to the re-closing. If the amount of change in the tank internal pressure is less than the predetermined determination value F (YES in step 144), the ECU 50 determines that the bypass control valve 80a to be diagnosed is abnormal (step 145). This is because even though the canister 40 and the tank 30 should have been subjected to the pressure reducing operation for the time TM3 as described above, the change in the tank internal pressure is hardly recognized or very small.
50, the state of the bypass control valve 80a does not change before and after the forced valve opening command of the bypass control valve 80a is output, the bypass control valve 80a continues to maintain the open state or the closed state, and the tank 30 and the canister This means that the communication between the bypass control valve 80a and the canister 40 is continued, or that the communication between the tank 30 and the canister 40 is continuously interrupted.

On the other hand, when the amount of change in the tank internal pressure is equal to or greater than the predetermined determination value F (when the determination in step 144 is NO), the ECU 50 sets the bypass control valve 80 to be diagnosed.
"a" is determined to be normal (step 146). This is because, as described above, when a change in the tank internal pressure is apparently recognized in response to the canister 40 and the tank 30 being continuously subjected to the pressure reducing operation for the time TM3, the gap between the tank 30 and the canister 40 is determined. This is because it can be determined that the bypass control valve 80a has been opened according to the forced valve opening command from the ECU 50.

The determination value F used in step 144 is not a fixed value but a variable value which is appropriately changed depending on the remaining amount of fuel in the tank 30. The method of changing the determination value F is the same as that of the determination value F in step 124 in FIG. 6 of the first embodiment.

As described above, according to the routine C, by setting the predetermined time TM3 to an appropriate time width (interval), it is possible to diagnose whether or not the bypass control valve 80a is abnormal relatively early. Even when the procedure of the second embodiment is adopted, the same effect as that of the first embodiment can be obtained.

(Alternative Example) The above embodiments may be modified as follows. In the routine B (FIG. 7) in the first and second embodiments, the abnormality diagnosis of the valve is performed based on the correlation rate R obtained from the first counter value C1 and the second counter value C2. The program of the routine B may be modified or simplified so that the abnormality diagnosis is performed based only on the two counter values C2. For example, if the second counter value C2 reaches the determination value DC (for example, seven times) within a certain predetermined time, the valve to be diagnosed (bypass control valve 80a) is determined to be abnormally open. It may be determined that it is normal. By doing so, the first counter 5 is provided to the ECU 50.
2 can be omitted, and not only the routine B but also the procedure shown in FIG. 4 can be simplified. However,
It is necessary to separately prepare a third internal timer.

A second pressure sensor (canister internal pressure detecting means) is provided in the canister 40 without directly relying on the simulated canister internal pressure Pc which is an estimated value of the internal pressure based on indirect data, and the canister internal pressure is directly detected. You may make it.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing an outline of an electrical configuration relating to abnormality diagnosis.

FIG. 3 is a timing chart showing an outline of a leak diagnosis of the purge system.

FIG. 4 is a flowchart of a valve abnormality diagnosis routine according to the first embodiment;

FIG. 5 is a flowchart showing a continuation of the abnormality diagnosis routine of FIG. 4;

FIG. 6 is a flowchart showing a routine A that is a continuation of the routine of FIG. 5;

FIG. 7 is a flowchart showing a routine B that is a continuation of the routine of FIG. 5;

FIG. 8 is a graph showing a correlation between the remaining amount of fuel and the amount of change in tank internal pressure.

FIG. 9 is a timing chart showing several patterns relating to the correlation between the canister internal pressure and the tank internal pressure when the valve is abnormal.

FIG. 10 is a flowchart showing a routine C as a procedure of the second embodiment.

[Explanation of symbols]

12: engine intake passage, 12e: air flow meter (canister internal pressure detecting means), 20: fuel vapor purge system, 30: fuel tank, 32: pressure sensor (tank internal pressure detecting means), 33: breather control valve (differential pressure valve), 4
0: canister, 50: ECU (canister internal pressure detecting means and diagnostic control means), 60: tank internal pressure control valve (differential pressure valve), 71: purge passage, 71a: purge control valve, 72
... atmosphere introduction passage, 72a ... atmosphere introduction valve, 80 ... bypass passage for negative pressure introduction, 80a ... bypass control valve, α ... predetermined pressure value (first predetermined amount), β ... predetermined pressure value (second place) Quantitative).

Continuing on the front page (72) Inventor ▲ Mr. Oka Mamoru 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Kenichiro Kawase 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation ( 72) Inventor Takataka Taga 1-1-1, Kyowa-cho, Obu City, Aichi Prefecture F-term (reference) 3G044 BA23 EA33 EA53 EA55 FA03 FA04 FA10 FA23 FA39 GA01 GA02 GA04 GA05

Claims (7)

[Claims] An air introduction valve provided in a fuel tank, a canister, and a passage for introducing air into the canister;
The fuel vapor purge system includes a purge control valve provided in a passage for purging fuel vapor from the canister to an engine intake passage, and a bypass control valve provided in a bypass passage connecting the canister and the fuel tank. An abnormality diagnostic device for a valve for determining the presence or absence of an abnormality in a bypass control valve, wherein a tank internal pressure detecting means for directly or indirectly detecting an internal pressure of a fuel tank, and a direct or indirect detection of an internal pressure of a canister A canister internal pressure detecting means, and a diagnostic control means for controlling the driving of each of the atmosphere introduction valve, the purge control valve and the bypass control valve, and capable of obtaining information on the fuel tank internal pressure and the canister internal pressure from the both internal pressure detecting means. Wherein the diagnosis control means is configured to open the purge control valve, and the suction state of the canister being opened. A valve closing command is issued to the bypass control valve to be diagnosed below, and changes in the canister internal pressure and the fuel tank internal pressure are monitored thereafter.When it is recognized that the fuel tank internal pressure follows the canister internal pressure change, the air introduction valve is closed. A valve abnormality diagnosis apparatus for a fuel vapor purge system, comprising: forcibly closing a valve; and further examining a change in the internal pressure of the fuel tank after the forcibly closing the valve to determine whether the bypass control valve is abnormal. 2. The fuel vapor purge system according to claim 1, further comprising, in addition to a bypass control valve in the bypass passage, an autonomous operation type differential pressure valve in parallel with the bypass control valve in a path connecting a canister and a fuel tank. The diagnostic control means opens the air introduction valve after a lapse of a predetermined time from the forced closing of the air introduction valve when it is recognized that the fuel tank internal pressure follows the canister internal pressure change. The abnormality diagnosis device for a valve in the fuel vapor purge system according to claim 1, wherein: 3. The diagnostic control means ascertains the amount of change in the fuel tank internal pressure from the forced closing of the air introduction valve to the lapse of the predetermined time, and determines the absolute value of the change in the fuel tank internal pressure to a predetermined value. 3. The fuel according to claim 2, wherein when the predetermined value is not less than the determination value, the bypass control valve is determined to be abnormal, and the predetermined determination value is variably set according to a remaining amount of fuel in the fuel tank. 4. Abnormal diagnostic device for valve in steam purge system. 4. The canister as a prerequisite for judging the presence or absence of an abnormality in a bypass control valve by closely examining a change in the internal pressure of a fuel tank after forcibly closing the air introduction valve. The method according to any one of claims 1 to 3, wherein in addition to following the internal pressure of the fuel tank with respect to the internal pressure change, it is confirmed that the concentration of the fuel vapor purged through the purge passage is lower than a predetermined threshold concentration. An abnormality diagnosis device for a valve in the fuel vapor purge system according to claim 1. 5. An air introduction valve provided in a fuel tank, a canister, and a passage for introducing air to the canister,
The fuel vapor purge system includes a purge control valve provided in a passage for purging fuel vapor from the canister to an engine intake passage, and a bypass control valve provided in a bypass passage connecting the canister and the fuel tank. An abnormality diagnostic device for a valve for determining the presence or absence of an abnormality in a bypass control valve, wherein a tank internal pressure detecting means for directly or indirectly detecting an internal pressure of a fuel tank, and a direct or indirect detection of an internal pressure of a canister A canister internal pressure detecting means, and a diagnostic control means for controlling the driving of each of the atmosphere introduction valve, the purge control valve and the bypass control valve, and capable of obtaining information on the fuel tank internal pressure and the canister internal pressure from the both internal pressure detecting means. Wherein the diagnosis control means is configured to open the purge control valve, and the suction state of the canister being opened. A valve closing command is issued to the bypass control valve to be diagnosed below, and the subsequent changes in the canister internal pressure and the fuel tank internal pressure are monitored.When it is recognized that the fuel tank internal pressure follows the canister internal pressure change, the bypass control valve is closed. A valve abnormality diagnostic device in a fuel vapor purge system, wherein the valve is forcibly opened, and the presence or absence of an abnormality in the bypass control valve is determined by further examining the change in the internal pressure of the fuel tank after the forcible opening. 6. The diagnostic control means ascertains the amount of change in the fuel tank internal pressure from the forced opening of the bypass control valve until a predetermined time has elapsed, and determines the absolute value of the amount of change in the fuel tank internal pressure to a predetermined value. The fuel vapor according to claim 5, wherein when the value is less than the predetermined value, the bypass control valve is determined to be abnormal, and the predetermined determination value is variably set according to the remaining amount of fuel in the fuel tank. Abnormality diagnosis device for valve in purge system. 7. A valve abnormality diagnostic device in a fuel vapor purge system according to claim 1, wherein said diagnostic control means is configured to synchronize with a canister internal pressure change of a first predetermined amount or more. 2. An abnormality diagnosis apparatus for a valve in a fuel vapor purge system, wherein it is determined that the fuel tank internal pressure follows a change in the canister internal pressure when a change in the internal pressure of the fuel tank by a predetermined amount or more occurs a predetermined number of times.