JP2004156468A - Failure diagnosis device and method for fuel vapor purge system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a failure diagnosis device for fuel vapor purge system which can precisely perform diagnosis of leakage failure of an evaporation passage including a canister and a fuel tank, and suppress cost increase without providing exclusive passage for failure diagnosis in the fuel tank. <P>SOLUTION: The evaporation passage is formed by disposing the canister 22 in the fuel tank 21. In diagnosis of leakage failure of the evaporation passage, a differential pressure is formed between an internal pressure of the canister 22 and an internal pressure of the fuel tank 21 by feeding fuel vapor in the fuel tank 21 to the canister 22 with a motor-driven air pump 50 through a vapor passage 23. An ECU 60 determines the leakage failure of the evaporation passage based on the differential pressure to be formed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a failure diagnosis device for a fuel vapor purge system that collects fuel vapor generated in a fuel tank in a canister, and purges the fuel vapor collected in the canister to an intake passage of an internal combustion engine through a purge passage. The present invention relates to a failure diagnosis method for a fuel vapor purge system.
[0002]
[Prior 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 introduced into a canister through a vapor passage and collected, and the collected fuel vapor is purged to an intake passage of an internal combustion engine via a purge passage. Release).
[0003]
In order to ensure the reliability of such a fuel vapor purge system, many purge systems include holes and tears in an evaporative passage (including a fuel tank, a vapor passage, a canister, and a purge passage). A failure diagnosis device for finding a leak caused by the failure is incorporated. In order to diagnose such a leak, after a differential pressure is provided between the inside and the outside of the evaporation path, the behavior of the internal pressure is detected. Then, by comparing the internal pressure determination level in a state where there is no leakage in the evaporative path and the behavior of the detected internal pressure, it is possible to diagnose a leakage failure in the evaporative path.
[0004]
On the other hand, in recent years, an in-tank canister type fuel vapor purge system in which a canister is arranged in a fuel tank (hereinafter, referred to as an in-tank canister system) has been proposed as a fuel vapor purge system. This can reduce costs by reducing the distance between the fuel tank and the canister, thereby reducing costs.Furthermore, many of the pipes are arranged in the fuel tank, and the fuel from rubber hoses and joints, etc. There are advantages such as the ability to solve the problem of vapor transmission.
[0005]
In such an in-tank canister system as well, it is necessary to diagnose a leak failure in the evaporative path, and a failure diagnosis device disclosed in Patent Documents 1 and 2 has been proposed. These failure diagnosis devices include a vapor passage for introducing fuel vapor to a canister in a fuel tank via a check valve, a fresh air introduction passage for introducing fresh air from outside the fuel tank into the canister, and a fuel vapor passage in the canister. And a purge passage for purging the fresh air together with fresh air to an intake passage of the internal combustion engine via a purge control valve. Further, between the canister and the purge control valve in the purge passage, a three-way switching valve and a pipe branched from the three-way switching valve and communicating with a space in the fuel tank are provided. At the time of failure diagnosis, by switching the three-way switching valve to the fuel tank side, the intake passage communicates with the space in the fuel tank without passing through the canister. Negative pressure can be introduced into the space inside. Therefore, when there is a hole in the fuel tank side, the negative pressure of the fuel tank leaks, and when there is a hole in the canister side, the negative pressure of the fuel tank leaks to the canister side. Also in this case, it is possible to diagnose a leak failure from the pressure in the fuel tank. The inside of the canister can be maintained at substantially atmospheric pressure because the inside of the canister is opened to the atmosphere by a fresh air introduction passage, and the negative pressure from the fuel tank side into the canister is operated by the check valve in the vapor passage. Is prevented from being introduced.
[0006]
[Patent Document 1]
JP 2001-115915 A
[Patent Document 2]
JP 2001-317417 A
[0007]
[Problems to be solved by the invention]
However, the failure diagnosis devices described in Patent Document 1 and Patent Document 2 are designed to reduce the cost by reducing the piping between the fuel tank and the canister or the like. It is necessary to provide a dedicated path for failure diagnosis for introducing the apparatus, which causes a problem that the cost is increased.
[0008]
The present invention has been made in view of the above circumstances, and an object of the present invention is to accurately diagnose a leakage failure in an evaporative path including a canister and a fuel tank without providing a dedicated passage for failure diagnosis in the fuel tank. Another object of the present invention is to provide a failure diagnosis device and a failure diagnosis method for a fuel vapor purge system that can suppress an increase in cost.
[0009]
[Means for Solving the Problems]
Hereinafter, the means for achieving the above object and the effects thereof will be described.
According to the first aspect of the present invention, a canister is arranged in a fuel tank, an evaporative path including the fuel tank and the canister is formed, and fuel vapor generated in the fuel tank is collected by the canister. A fuel vapor purge system for purging fuel vapor collected in the engine to an intake passage of an internal combustion engine via a purge passage, wherein a failure diagnosis of a fuel vapor purge system for diagnosing a leakage failure of fuel vapor from the evaporative passage is provided. When diagnosing a leakage failure in the evaporative path, an air supply means for supplying gas present in one of the fuel tank and the canister to the other, an internal pressure of the canister based on the operation of the air supply means and a fuel tank Determination means for determining a leak failure in the evaporative path based on a pressure difference between the internal pressure and the internal pressure.
[0010]
The leak failure of the evaporative path forms a differential pressure between the internal pressure and the external pressure of the evaporative path, and is based on a change state of the differential pressure when the differential pressure is formed and a change in the differential pressure after the differential pressure is formed. Can be diagnosed. In the evaporative path formed by disposing the canister in the fuel tank, if the canister internal pressure and the fuel tank internal pressure are the same and a differential pressure is formed between the fuel tank and the outside air, if there is a hole on the fuel tank side, It changes so that the differential pressure decreases, and it can be diagnosed that there is a leak failure in the evaporation path. However, even if there is a hole only on the canister side, since the canister internal pressure and the fuel tank internal pressure are the same pressure, the differential pressure does not change, and it is determined that there is no leak failure in the evaporation path. Therefore, when diagnosing a leak failure of the evaporative path formed by disposing the canister in the fuel tank, a differential pressure is formed between the canister internal pressure and the fuel tank internal pressure, and the fuel tank internal pressure and the external pressure are compared. It is necessary to form a pressure difference between them.
[0011]
In this regard, according to the above configuration, the gas supply means is operated to supply gas present in one of the fuel tank and the canister to the other, so that the internal pressure of the fuel tank and the internal pressure of the canister are reduced. A differential pressure can be easily formed, and at the same time, a differential pressure is formed between the internal pressure of the fuel tank and the external pressure. If there is a hole in the fuel tank, leakage occurs inside and outside the fuel tank, and the differential pressure between the internal pressure of the fuel tank and the external pressure changes, and the differential pressure between the internal pressure of the fuel tank and the internal pressure of the canister also changes. If the canister has a hole, leakage occurs inside and outside the canister, and the pressure difference between the internal pressure of the fuel tank and the internal pressure of the canister changes. Therefore, it is possible to accurately determine a leakage failure in the evaporation path based on the pressure difference between the internal pressure of the canister and the internal pressure of the fuel tank.
[0012]
Incidentally, the pressure difference between the internal pressure of the fuel tank and the internal pressure of the canister by the operation of the air supply means may be performed by sucking the gas in the fuel tank and sending it into the canister, or It may be performed by sucking gas inside and sending it into the fuel tank.
[0013]
Further, in the above-described configuration, it is not necessary to provide a dedicated path for failure diagnosis for forming a differential pressure between the internal pressure of the canister and the internal pressure of the fuel tank in the fuel tank, thereby suppressing an increase in cost.
[0014]
According to a second aspect of the present invention, in the failure diagnosis apparatus for a fuel vapor purge system according to the first aspect, the determination unit determines a differential pressure when the air supply unit is operated for a predetermined time to supply air. And determining whether there is a leak failure in the evaporative path based on whether the value is equal to or greater than a predetermined value.
[0015]
By operating the air supply means for a predetermined time as in the above configuration, if there is no leakage in the evaporative passage, a predetermined pressure difference between the internal pressure of the canister and the internal pressure of the fuel tank can be obtained. it can. Therefore, it is possible to determine the leak failure of the evaporative path based on whether or not the differential pressure after the air supply means is operated for a predetermined time and air is supplied is equal to or greater than a predetermined value.
[0016]
According to a third aspect of the present invention, in the failure diagnosis device for a fuel vapor purge system according to the first or second aspect, the determination unit determines that the differential pressure has changed after the differential pressure has reached a predetermined value. A leakage failure in the evaporative path is determined on the basis of this.
[0017]
Even if there is a hole in the evaporation path, the differential pressure between the internal pressure of the canister and the internal pressure of the fuel tank can be reduced to a predetermined value by operating the air supply means for a predetermined time, depending on the method of setting the leak failure determination value. In this case, the presence or absence of a leak failure cannot be reliably diagnosed.
[0018]
In this regard, according to the above-described configuration, the state of change of the differential pressure after the differential pressure between the internal pressure of the canister and the internal pressure of the fuel tank reaches a predetermined value is monitored. It is determined that there is a leak failure, and if there is little change in the differential pressure, it can be determined that there is no leak failure in the evaporative path.
[0019]
According to a fourth aspect of the present invention, in the failure diagnosis apparatus for a fuel vapor purge system according to any one of the first to third aspects, the air supply means supplies fuel vapor generated in the fuel tank to the canister. It is an electric air pump provided in a vapor passage to be introduced.
[0020]
According to this configuration, when the electric air pump is operated, a differential pressure can be formed between the internal pressure of the canister and the internal pressure of the fuel tank in the evaporative path. Diagnosis of failure can be performed.
[0021]
According to a fifth aspect of the present invention, in the failure diagnosis apparatus for a fuel vapor purge system according to any one of the first to fourth aspects, further, when diagnosing a leakage failure in the evaporative path, the evaporative path is shut off from outside air. It is characterized by having a shut-off means for sealing.
[0022]
In particular, as in the invention according to claim 6, the shutoff means may include a purge control valve for opening and closing the purge passage, and an air shutoff valve for opening and closing an air introduction passage for introducing air into the canister. it can.
[0023]
According to this configuration, when forming a differential pressure between the internal pressure of the canister and the internal pressure of the fuel tank, the evaporative path can be reliably shut off from the outside air, and one of them is pressurized by being supplied with air, The other is depressurized by suction of the gas, and the differential pressure is efficiently formed. In addition, since the evaporative passage is closed, the release of fuel vapor into the atmosphere is prevented when the pressure difference is formed.
[0024]
The invention according to claim 7, wherein a canister is arranged in a fuel tank, an evaporative path is formed including the fuel tank and the canister, and fuel vapor generated in the fuel tank is collected in the canister. In a fuel vapor purge system for purging fuel vapor collected in a fuel tank into an intake passage of an internal combustion engine via a purge passage, a failure diagnosis method of the fuel vapor purge system for diagnosing a leakage failure of fuel vapor from the evaporative passage. Sending a gas present in one of the fuel tank and the canister to the other at the time of diagnosing a leak failure in the evaporative path, and the internal pressure of the canister and the internal pressure of the fuel tank in the sealed evaporative path. Determining a leakage failure of the evaporation path based on the differential pressure of the evaporative path.
[0025]
According to this configuration, similarly to the operation and effect of the first aspect, the gas existing in one of the fuel tank and the canister is supplied to the other, so that the internal pressure of the fuel tank and the internal pressure of the canister can be easily changed. A pressure difference can be formed between the internal pressure of the fuel tank and the external pressure at the same time. Therefore, it is possible to accurately determine a leakage failure in the evaporation path based on the pressure difference between the internal pressure of the canister and the internal pressure of the fuel tank. In the case where this method is adopted, the pressure difference between the internal pressure of the fuel tank and the internal pressure of the canister may be formed by sucking the gas in the fuel tank and sending it into the canister. May be performed by sucking the gas in the canister and sending it into the fuel tank.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
A first embodiment of a failure diagnosis apparatus for a fuel vapor purge system mounted on a vehicle or the like embodying the present invention will be described below with reference to FIGS.
[0027]
FIG. 1 is a schematic configuration diagram showing a fuel vapor purge system and a failure diagnosis device according to the present embodiment.
As shown in FIG. 1, a throttle valve 13 is provided upstream of a surge tank 12 in an intake passage 11 that guides intake air to an engine 10 as an internal combustion engine. An air cleaner 14 is provided in the intake passage 11 upstream of the throttle valve 13.
[0028]
The fuel vapor purge system 20 shown in FIG. 1 constitutes a part of the engine 10, and a canister 22 for adsorbing fuel vapor generated therein is accommodated in a fuel tank 21. The canister 22 has a vapor passage 23 for introducing fuel vapor generated in the fuel tank 21, and is connected to the surge tank 12 via a purge passage 24. Further, a purge passage 24 is provided for communicating the canister 22 with the intake passage 11 communicating with the intake passage 11. The canister 22 is connected to an air introduction passage 25 for introducing fresh air into the canister 22.
[0029]
A fuel supply pipe 26 for refueling is attached to the fuel tank 21. A cap 27 is attached to an oil supply port of the oil supply pipe 26, and a check valve 28 is provided at an outlet thereof. Further, a circulation path 29 is provided in the fuel supply pipe 26 in a branched manner, and an open end of the circulation path 29 is open to the upper space S in the fuel tank 21.
[0030]
At one end of the vapor passage 23 of the canister 22, a float valve 31, a liquid reservoir 32, and a throttle 33 are provided in this order from the opening end of the passage. Fuel vapor generated in the fuel tank 21 is sent to the canister 22 via the liquid reservoir 32 and the throttle 33.
[0031]
The canister 22 has an adsorbent therein, and after the fuel vapor from the fuel tank 21 is adsorbed by the adsorbent and temporarily stored therein, when the inside is placed under a negative pressure, the canister is adsorbed by the adsorbent. It is configured so that the fuel vapor can be released again.
[0032]
The interior of the canister 22 is partitioned into two adsorbent chambers 41 and 42 by a partition plate 40. The two adsorbent chambers 41 and 42 are filled with an adsorbent, and communicate with each other via a permeable filter 43. The adsorbent chamber 41 communicates with the upper space S inside the fuel tank 21 via the vapor passage 23 and communicates with the surge tank 12 of the intake passage 11 via the purge passage 24. On the other hand, the adsorbent chamber 42 communicates with the air introduction passage 25. Further, the canister 22 is provided with a guide member 44 so that the fuel vapor flowing from the fuel tank 21 once passes through the adsorbent and is then introduced into the purge passage 24.
[0033]
Further, a pressure sensor 45 composed of a relative pressure sensor is provided on the wall of the canister 22 on the side of the air permeable filter 43. The pressure sensor 45 has both ends facing the canister 22 and the fuel tank 21, respectively. The pressure sensor 45 detects a differential pressure between the internal pressure of the canister 22 and the internal pressure of the fuel tank 21, and detects an electric pressure corresponding to the detected differential pressure. An absolute pressure sensor is used as the pressure sensor 45 so as to output a signal.
[0034]
A purge control valve 46 composed of an electromagnetic valve is provided in the middle of the purge passage 24. The purge control valve 46 is always closed, and when the control valve 46 is opened, the intake negative pressure generated in the surge tank 12 during the operation of the engine 10 causes the intake negative pressure in the canister 22 to flow through the purge passage 24 into the canister 22. Will be introduced.
[0035]
On the other hand, the air introduction passage 25 communicates with an inlet port 47 provided in an oil supply opening which is opened and closed by a fuel lid (not shown). An air cutoff valve 48 composed of an electromagnetic valve as a shutoff means is provided in the middle of the air introduction passage 25. The atmosphere shutoff valve 48 is always open, and fresh air entering from the inlet port 47 is introduced into the canister 22 through the atmosphere introduction passage 25. When the atmosphere shutoff valve 48 is closed, the introduction of fresh air through the atmosphere introduction passage 25 is shut off, and the canister 22 is closed. Note that an air dust filter 49 is provided in the middle of the air introduction passage 25 on the upstream side of the air shutoff valve 48.
[0036]
In the present embodiment, an electric air pump 50 is provided at the connection between the vapor passage 23 and the canister 22 as air supply means. When not operating, the electric air pump 50 communicates between the vapor passage 23 and the fresh air inlet of the canister 22. When the electric air pump 50 operates, the electric air pump 50 sucks the fuel vapor in the fuel tank 21 and sends it to the canister 22 to form a differential pressure between the internal pressure of the fuel tank 21 and the internal pressure of the canister 22. It has become.
[0037]
In the fuel vapor purge system 20 configured as described above, the fuel vapor generated in the fuel tank 21 is sent to the canister 22 through the vapor passage 23 and is absorbed by the canister 22. When the purge control valve 46 opens, the negative pressure in the surge tank 12 is supplied to the canister 22 via the purge passage 24. At this time, the atmosphere is introduced into the canister 22 via the atmosphere introduction passage 25, the atmosphere dust filter 49, and the atmosphere shutoff valve 48. By introducing the atmosphere in this manner, the adsorbed fuel vapor is purged (released) from the canister 22 to the surge tank 12.
[0038]
Further, when the atmosphere shutoff valve 48 is also closed in a state where the purge control valve 46 is closed, the inside of the fuel vapor purge system 20, that is, the inside of the evaporation path becomes a closed space. Here, the “evaporation path” of the fuel vapor purge system 20 is a path including a passage between the canister 22 and the purge control valve 46 among the fuel tank 21, the vapor passage 23, the canister 22, and the purge passage 24. It is. In the state where the inside of the “evaporation path” of the fuel vapor purge system 20 is a closed space, a failure diagnosis process described later is performed.
[0039]
In the engine, the fuel vapor purge system 20 and the failure diagnosis device configured as described above, the outputs of various sensors such as the pressure sensor 45 function as an engine control system and an electronic control device (function as a failure diagnosis device). (Hereinafter referred to as ECU). The ECU 60 includes a microcomputer including a CPU, a ROM, a RAM, an A / D converter, an input / output interface, and the like, and receives signals from various sensors. As the various sensors, in addition to the pressure sensor 45, a crank angle sensor that outputs a crank angle signal in synchronization with the rotation of the engine 10 to detect the engine rotation speed, an air flow meter that measures an intake air amount, an engine exhaust The system is provided with an air-fuel ratio sensor (oxygen sensor) for detecting the air-fuel ratio, a vehicle speed sensor for detecting the vehicle speed, and the like.
[0040]
The ECU 60 executes various controls related to the operation of the engine 10, such as fuel injection control, based on the output of the various sensors taken in, and also drives and controls the purge control valve 46, the atmosphere cutoff valve 48, the electric air pump 50, and the like. Thus, the purge control of the fuel vapor purge system 20 and the processing of the failure diagnosis are executed.
[0041]
Next, a processing procedure of the failure diagnosis of the fuel vapor purge system 20 executed by the ECU 60 will be described with reference to FIG.
First, at step 100, it is determined whether or not the diagnostic condition is satisfied. When it is determined that the diagnosis condition is not satisfied (step 100; "NO"), the present process is temporarily terminated. On the other hand, when it is determined that the diagnosis condition is satisfied (Step 100; “YES”), in Step 105, the purge control valve 46 is closed and the air cutoff valve 48 is closed. Thus, the evaporative path including the canister 22 and the fuel tank 21 is cut off from the atmosphere.
[0042]
When the evaporative path including the canister 22 and the fuel tank 21 is cut off from the atmosphere, the driving of the electric air pump 50 is started in the next step 110, and the fuel vapor in the fuel tank 21 is sucked to supply air to the canister 22. Is done. By the operation of the electric air pump 50, the internal pressure of the canister 22 increases, and the internal pressure of the fuel tank 21 decreases, so that a pressure difference is formed between the two.
[0043]
Next, in step 115, it is determined whether or not a predetermined time T1 has elapsed from the start of driving the electric air pump 50. If it is determined that the operation time of the electric air pump 50 has not elapsed the predetermined time T1 (“NO” in step 115), the process returns to step 110, and the electric air pump 50 is continuously driven.
[0044]
Then, when it is determined in step 115 that the operation time of the electric air pump 50 has passed the predetermined time T1 (“YES” in step 115), the drive of the electric air pump 50 is stopped in step 120.
[0045]
Next, at step 125, it is determined whether or not the differential pressure Pct between the internal pressure of the canister 22 and the internal pressure of the fuel tank 21 is equal to or greater than a predetermined value P1. If there is no leak in the evaporation path, the differential pressure of the predetermined value P1 or more can be formed between the internal pressure of the canister 22 and the internal pressure of the fuel tank 21 by operating the electric air pump 50 for a predetermined time. Here, if it is determined that the differential pressure Pct is less than the predetermined value P1 (“NO” in step 125), it is determined in step 135 that there is a leak failure.
[0046]
If it is determined that the differential pressure Pct is equal to or greater than the predetermined value P1 (“YES” in step 125), it is determined in step 130 that there is no leakage failure.
FIG. 3 shows a transition of the differential pressure at the time of forming the differential pressure in the failure diagnosis processing of the fuel vapor purge system 20 in the present embodiment. CASE1 indicates a change in the differential pressure Pct when neither the fuel tank 21 nor the canister 22 has a hole. At a time t1 when the electric air pump 50 is operated for a predetermined time T1, the differential pressure Pct is equal to or more than the predetermined value P1. It becomes. Therefore, in the case of CASE1, it is determined that there is no leak failure in the evaporative path.
[0047]
CASE 2 indicates a change in the differential pressure Pct when a hole of Φ0.5 mm exists in the fuel tank 21 and no hole exists in the canister 22. At the time t1 when the electric air pump 50 is operated for the predetermined time T1, the hole between the fuel tank 21 and the outside air occurs due to the presence of the hole of 0.5 mm in the fuel tank 21, and the pressure reduction amount of the fuel tank 21 is small. And the differential pressure Pct becomes less than the predetermined value P1. Therefore, in the case of CASE2, it is determined that there is a leak failure in the evaporative path.
[0048]
CASE 3 indicates a change in the differential pressure Pct when the fuel tank 21 has no hole and the canister 22 has a Φ0.5 mm hole. At time t1 when the electric air pump 50 is operated for a predetermined time T1, a leak occurs between the canister 22 and the fuel tank 21 due to the presence of a hole of Φ0.5 mm in the canister 22, and the differential pressure Pct becomes equal to the predetermined value P1. It becomes a small value in comparison. Therefore, even in the case of CASE3, it is determined that there is a leak failure in the evaporative path. In the case of CASE3, since the differential pressure Pct is a leak between the canister 22 and the fuel tank 21 where the differential pressure Pct is formed, the differential pressure Pct formed is smaller than in the case of CASE2.
[0049]
CASE 4 indicates a change in the differential pressure Pct when a hole of φ0.4 mm exists in the fuel tank 21 and a hole of φ0.3 mm exists in the canister 22. The sum of the area of the hole of Φ0.4 mm and the area of the hole of Φ0.3 mm is equal to the area of the hole of Φ0.5 mm, and the existence of the hole of Φ0.4 mm and the hole of Φ0.3 mm is Φ0. This is equivalent to the presence of a 5 mm hole. At a time t1 when the electric air pump 50 is operated for a predetermined time T1, a leak occurs between the fuel tank 21 and the outside air, and a leak also occurs between the canister 22 and the fuel tank 21, and the differential pressure Pct becomes a predetermined value. This is an extremely small value compared to P1. Therefore, even in the case of CASE4, an abnormality determination is made that there is a leak failure in the evaporative path. In the case of CASE4, there is a leak between the canister 22 and the fuel tank 21 where the differential pressure Pct is formed, and the amount of pressure reduction in the fuel tank 21 is reduced. It becomes smaller than the case.
[0050]
Further, CASE 5 indicates a change in the differential pressure Pct when a hole of φ0.3 mm exists in the fuel tank 21 and a hole of φ0.4 mm exists in the canister 22. Also in this case, the existence of the hole of φ0.4 mm and the hole of φ0.3 mm is equivalent to the existence of the hole of φ0.5 mm. At a time t1 when the electric air pump 50 is operated for a predetermined time T1, a leak occurs between the fuel tank 21 and the outside air, and a leak also occurs between the canister 22 and the fuel tank 21, and the differential pressure Pct becomes a predetermined value. This is an extremely small value compared to P1. Therefore, even in the case of CASE5, it is determined that there is a leak failure in the evaporative path. In addition, in the case of CASE5, since the hole of the canister 22 is larger than that of CASE4, leakage between the canister 22 and the fuel tank 21 increases, and the pressure reduction amount of the fuel tank 21 decreases. The differential pressure Pct becomes smaller than in the case of CASE4.
[0051]
According to the present embodiment described in detail above, the following effects can be obtained.
(1) At the time of failure diagnosis of the fuel vapor purge system 20, the electric air pump 50 is operated to supply the fuel vapor in the fuel tank 21 to the canister 22, thereby easily causing the differential pressure Pct between the fuel tank 21 and the canister 22. , And at the same time, a differential pressure can be formed between the internal pressure of the fuel tank 21 and the external pressure. At this time, if there is a hole in the fuel tank 21, leakage occurs inside and outside the fuel tank 21, and the differential pressure between the internal pressure of the fuel tank 21 and the external pressure changes, and the internal pressure of the fuel tank 21 and the internal pressure of the canister 22 change. , Also changes. If the canister 22 is perforated, leakage occurs inside and outside the canister 22 and the differential pressure Pct between the internal pressure of the fuel tank 21 and the internal pressure of the canister 22 changes. Therefore, it is possible to accurately determine a leak failure in the evaporation path based on the pressure difference between the internal pressure of the canister 22 and the internal pressure of the fuel tank 21.
[0052]
(2) According to the present embodiment, the differential pressure Pct between the internal pressure of the canister 22 and the internal pressure of the fuel tank 21 can be formed by operating the electric air pump 50, for example, to introduce a negative pressure. It is not necessary to provide a passage dedicated to the failure diagnosis in the fuel tank 21, and it is possible to suppress an increase in cost.
[0053]
(3) In the failure diagnosis device of the present embodiment, if the electric air pump 50 is operated for a predetermined time T1, if there is no leak in the evaporation path, a predetermined value is set between the internal pressure of the canister 22 and the internal pressure of the fuel tank 21. A differential pressure Pct equal to or larger than P1 can be obtained. Therefore, it is possible to determine the leak failure of the evaporative path based on whether or not the differential pressure Pct after the electric air pump 50 is operated for a predetermined time T1 to supply air is equal to or more than a predetermined value P1.
[0054]
(4) In the failure diagnosis device according to the present embodiment, when the differential pressure between the internal pressure of the canister 22 and the internal pressure of the fuel tank 21 is formed, the purge control valve 46 of the purge passage 24 is closed, and the air introduction passage is closed. By closing the 25 air shutoff valve 48, the evaporation path can be reliably shut off from the outside air. Therefore, based on the operation of the electric air pump 50, the fuel tank 21 is depressurized by suctioning the fuel vapor, and the canister 22 is pressurized by air supply, thereby efficiently forming a differential pressure Pct between the two. can do. Further, at the time of failure diagnosis, the evaporation path is closed by closing the purge control valve 46 and the atmosphere shutoff valve 48, so that the release of fuel vapor into the atmosphere can be prevented when this pressure difference is formed.
[0055]
(2nd Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS.
In the first embodiment, the leakage failure of the evaporative path is determined based on whether the differential pressure Pct formed by performing the operation of the electric air pump 50 for the predetermined time T1 is equal to or more than the predetermined value P1. I did it. For this purpose, the predetermined value P1 for determination is set to a value near the saturation differential pressure based on the operation of the electric air pump 50, and the operation time of the electric air pump 50 is set to a predetermined value at which a differential pressure equal to or more than the predetermined value P1 is obtained. It is set to time T1.
[0056]
In contrast, in the present embodiment, the electric air pump 50 is operated for a predetermined time T2 shorter than the predetermined time T1, and the differential pressure Pct after the differential pressure Pct reaches the predetermined value P2 smaller than the predetermined value P1. Is determined based on the change state of the evaporative path.
[0057]
In order to perform the above-described failure diagnosis, in the failure diagnosis apparatus of the present embodiment, a check valve (not shown) is provided, for example, on the upstream side of the electric air pump 50 with respect to the vapor passage 23 shown in FIG. When the internal pressure of the fuel tank 21 is higher than the internal pressure of the canister 22, the check valve communicates with the vapor passage 23. When the internal pressure of the fuel tank 21 is lower than the internal pressure of the canister 22, this check valve is used. The valve blocks the vapor passage 23.
[0058]
Next, a procedure of a failure diagnosis performed by the ECU 60 in the failure diagnosis device configured as described above will be described with reference to FIG.
When the processing shifts to this processing, the processing of steps 200, 205 and 210 similar to the steps 100, 105 and 110 is executed. That is, when it is determined in step 200 that the diagnosis condition is satisfied (step 200; “YES”), in step 205, the purge control valve 46 is closed and the air cutoff valve 48 is closed. . Thus, the evaporative path including the canister 22 and the fuel tank 21 is cut off from the atmosphere.
[0059]
When the evaporative path including the canister 22 and the fuel tank 21 is cut off from the atmosphere, the driving of the electric air pump 50 is started in the next step 210, and the fuel vapor in the fuel tank 21 is sucked from the vapor passage 23 and checked. The valve is opened and air is supplied to the canister 22. By the operation of the electric air pump 50, the internal pressure of the canister 22 increases, and the internal pressure of the fuel tank 21 decreases, and a differential pressure is formed between the two.
[0060]
Next, in step 215, it is determined whether or not a predetermined time T2 (<T1) has elapsed from the start of driving the electric air pump 50. If there is no leak in the evaporative passage, the electric air pump 50 is operated for a predetermined time T2 to form a differential pressure equal to or more than a predetermined value P2 (<P1) between the internal pressure of the canister 22 and the internal pressure of the fuel tank 21. Can be. If it is determined that the operation time of the electric air pump 50 has not elapsed the predetermined time T2 ("NO" in step 215), the process returns to step 210, and the electric air pump 50 is continuously driven.
[0061]
If it is determined in step 215 that the operation time of the electric air pump 50 has passed the predetermined time T2 (“YES” in step 215), the drive of the electric air pump 50 is stopped in step 220.
[0062]
Next, at step 225, it is determined whether or not the differential pressure Pct between the internal pressure of the canister 22 and the internal pressure of the fuel tank 21 is equal to or greater than a predetermined value P2 (<P1). Here, when it is determined that the differential pressure Pct is less than the predetermined value P2 (“NO” in step 225), it is determined in step 245 that there is a leak failure.
[0063]
If it is determined that differential pressure Pct is equal to or greater than predetermined value P2 (“YES” in step 225), the process proceeds to step 230. In step 230, it is determined whether or not a predetermined time T3 has elapsed after the driving of the electric air pump 50 was stopped.
[0064]
If it is determined in step 230 that the predetermined time T3 has elapsed after the operation of the electric air pump 50 has stopped (“YES” in step 230), the process proceeds to step 235.
[0065]
In step 235, it is determined whether or not the change amount ΔPct of the differential pressure Pct after the stoppage of the electric air pump 50 is less than a predetermined value ΔP0. If there is no leakage in the evaporative path, the change amount ΔPct of the differential pressure Pct after the lapse of the predetermined time T3 after the stop of the electric air pump 50 becomes less than the predetermined value ΔP0. If it is determined that the amount of change ΔPct is equal to or greater than the predetermined value ΔP0 (“NO” in step 235), it is determined in step 245 that there is a leak failure.
[0066]
On the other hand, if it is determined that the amount of change ΔPct of differential pressure Pct is smaller than predetermined value ΔP0 (“YES” in step 235), it is determined in step 240 that there is no leakage failure.
[0067]
FIG. 5 shows the transition of the differential pressure at the time of forming the differential pressure in the failure diagnosis processing of the fuel vapor purge system 20 in the present embodiment. In FIG. 5, CASE1 to CASE5 are transitions of the differential pressure Pct when the fuel tank 21 and the canister 22 have the same holes as in the first embodiment.
[0068]
In the cases CASE3, CASE4, and CASE5, the differential pressure Pct becomes smaller than the predetermined value P2 at time t2 when the electric air pump 50 is operated for the predetermined time T2. Therefore, in the case of CASE3, CASE4, and CASE5, it is not necessary to detect the change amount ΔPct of the differential pressure Pct, and it is determined at time t2 that there is a leak failure in the evaporative path.
[0069]
In the case of CASE1 and CASE2, at time t2 when the electric air pump 50 is operated for the predetermined time T2, the differential pressure Pct becomes equal to or more than the predetermined value P2. Therefore, a comparison is made between the variation ΔPct of the differential pressure Pct and the predetermined value ΔP0 at the time t3 when the predetermined time T3 has elapsed after the operation of the electric air pump 50 has stopped.
[0070]
At this time, in the case of CASE1, since there is no hole in both the fuel tank 21 and the canister 22, there is almost no change amount ΔPct of the differential pressure Pct, so that ΔPct <ΔP0, and it is determined that there is no leak failure in the evaporative path. Is made.
[0071]
In the case of CASE2, although the canister 22 has no hole, the fuel tank 21 has a hole of Φ0.5 mm. For this reason, a leak occurs between the fuel tank 21 and the outside air, and the change amount ΔPct ≧ ΔP0 of the differential pressure Pct is established, so that it is determined that there is a leak failure in the evaporative path.
[0072]
According to the present embodiment configured as described above, the following effects can be obtained in addition to the operations and effects (1) to (4) of the first embodiment.
(5) The change amount ΔPct of the differential pressure Pct after the differential pressure Pct between the internal pressure of the canister 22 and the internal pressure of the fuel tank 21 reaches the predetermined value P2 is monitored, and if the change amount ΔPct is equal to or more than the predetermined value ΔP0, the evaporator It is determined that there is a leak failure in the route, and if the amount of change ΔPct is less than the predetermined value ΔP0, it is determined that there is no leak failure in the evaporative route. Therefore, even if the predetermined value P2 for determining the leak failure is set to a value smaller than the predetermined value P1, and the predetermined time T2 for operating the electric air pump 50 is set shorter than the predetermined time T1, It is possible to reliably diagnose the presence or absence of a failure. Further, since the predetermined time T2 for operating the electric air pump 50 can be set short, energy consumption can be reduced, and a long life can be achieved by eliminating unnecessary operation of the electric air pump 50. .
[0073]
It should be noted that the embodiment is not limited to the above, and may be changed as follows. Even in such a case, the same operation and effect as those of the above embodiments can be obtained.
In the above embodiment, the electric air pump 50 is provided inside the fuel tank 21, but the electric air pump 50 may be provided outside the fuel tank 21 and the vapor passage 23 may be provided inside the fuel tank 21. Good.
[0074]
In the above embodiments, the differential pressure Pct is formed by sucking the fuel vapor in the fuel tank 21 by the electric air pump 50 and sending it to the canister 22, but the gas in the canister 22 is sucked. Then, the differential pressure Pct may be formed by feeding air into the fuel tank 21.
[0075]
In the above embodiments, when the differential pressure Pct is formed between the internal pressure of the fuel tank 21 and the internal pressure of the canister 22, the purge control valve 46 and the air shutoff valve 48 are closed to seal the evaporation passage. did. However, the differential pressure Pct can be formed by operating the electric air pump 50 without completely closing at least one of the purge control valve 46 and the atmosphere cutoff valve 48.
[0076]
In the above embodiments, the air introduction passage 25 communicates with the inlet 47 provided in the fuel supply opening which is opened and closed by the fuel lid and the fresh air introduction of the canister 22, and enters from the same 47. Although the atmosphere is introduced into the canister 22, the present invention is not limited to such a configuration. The atmosphere introduced into the canister 22 may be introduced from a location other than the refueling opening.
[0077]
In the failure diagnosis of the fuel vapor purge system in each of the above embodiments, the ECU 60 is automatically activated and the operation of the atmosphere cutoff valve 48 is controlled during the vehicle soak with the engine 10 stopped based on the turning off of the ignition key. Alternatively, it may be performed. In this case, since the electric air pump 50 is employed as the air supply means, if the electric air pump 50 is operated, a differential pressure is formed between the fuel tank 21 and the canister 22 constituting the evaporation path. Thus, even when the engine 10 is stopped, it is possible to determine a leakage failure in the evaporation path.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a failure diagnosis device for a fuel vapor purge system according to a first embodiment.
FIG. 2 is a flowchart showing the operation of the failure diagnosis device according to the first embodiment.
FIG. 3 is a time chart showing a transition of a differential pressure when a differential pressure is formed in the first embodiment.
FIG. 4 is a flowchart showing the operation of the failure diagnosis device according to the second embodiment.
FIG. 5 is a time chart showing a transition of a differential pressure when a differential pressure is formed in a second embodiment.
[Explanation of symbols]
P1, P2: predetermined value, Pct: differential pressure, ΔPct: change amount, ΔP0: predetermined value, T1, T2: predetermined time, 10: engine (internal combustion engine), 11: intake passage, 20: fuel vapor purge system, 21 ... Fuel tank, 22 ... Canister, 23 ... Vapor passage, 24 ... Purge passage, 25 ... Atmosphere introduction passage, 45 ... Pressure sensor, 46 ... Purge control valve as shutoff means, 48 ... Atmosphere shutoff valve as shutoff means, 50 ... an electric air pump as air supply means, 60 ... an electronic control unit (ECU) as determination means.

Claims (7)

A canister is arranged in the fuel tank, an evaporative path including the fuel tank and the canister is formed, the fuel vapor generated in the fuel tank is collected in the canister, and the fuel vapor collected in the canister is purged. In a fuel vapor purge system for purging an intake passage of an internal combustion engine through a passage, a failure diagnosis device of the fuel vapor purge system for diagnosing a leakage failure of fuel vapor from the evaporation path,
When diagnosing a leakage failure of the evaporative path, an air supply unit that supplies gas present in one of the fuel tank and the canister to the other,
Determining means for determining a leak failure of the evaporative path based on a differential pressure between the internal pressure of the canister and the internal pressure of the fuel tank based on the operation of the air supply means;
A failure diagnosis device for a fuel vapor purge system, comprising: The failure diagnosis device for a fuel vapor purge system according to claim 1,
The determining means determines the leak failure of the evaporative path based on whether or not a differential pressure when air is supplied by operating the air supplying means for a predetermined time is equal to or greater than a predetermined value. Diagnosis device for fuel vapor purge system. The failure diagnosis device for a fuel vapor purge system according to claim 1 or 2,
A failure diagnosis device for a fuel vapor purge system, wherein the determination means determines a leakage failure of the evaporation path based on a change state of the differential pressure after the differential pressure reaches a predetermined value. The failure diagnosis device for a fuel vapor purge system according to any one of claims 1 to 3,
The failure diagnosis device for a fuel vapor purge system, wherein the air supply means is an electric air pump provided in a vapor passage for introducing fuel vapor generated in the fuel tank into the canister. The failure diagnosis device for a fuel vapor purge system according to any one of claims 1 to 4,
Further, a failure diagnosis device for a fuel vapor purge system, further comprising a shut-off means for shutting off the evaporative passage from outside air when diagnosing a leak failure of the evaporative passage. The fault diagnosis device for a fuel vapor purge system according to claim 5,
The failure diagnosis device for a fuel vapor purge system, wherein the shutoff means includes a purge control valve for opening and closing the purge passage, and an air shutoff valve for opening and closing an air introduction passage for introducing air into the canister. A canister is arranged in the fuel tank, an evaporative path including the fuel tank and the canister is formed, the fuel vapor generated in the fuel tank is collected in the canister, and the fuel vapor collected in the canister is purged. In a fuel vapor purge system for purging an intake passage of an internal combustion engine through a passage, a failure diagnosis method for a fuel vapor purge system for diagnosing a leakage failure of fuel vapor from the evaporation path,
Sending a gas present in one of the fuel tank and the canister to the other at the time of diagnosing a leak failure of the evaporation path;
Determining a leak failure of the evaporative path based on a differential pressure between the internal pressure of the canister and the internal pressure of the fuel tank based on the air supply;
A failure diagnosis method for a fuel vapor purge system, comprising:

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