Information
-
Patent Grant
-
6761154
-
Patent Number
6,761,154
-
Date Filed
Thursday, May 29, 200321 years ago
-
Date Issued
Tuesday, July 13, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 123 520
- 123 519
- 123 518
- 123 198 D
- 073 1181
-
International Classifications
-
Abstract
In an evaporative fuel processing apparatus, a fuel tank and a canister communicate with each other through a vapor passage, and an intake passage of an internal combustion engine and the canister communicates with each other through a purge passage. The evaporative fuel processing apparatus includes an open/close valve which opens or closes the vapor passage, a switching valve which makes the canister open to the atmosphere or isolates the canister from the atmosphere, a booster pump capable of applying pressure to the canister while the switching valve isolates the canister from the atmosphere, a purge control valve which opens or closes the purge passage, and an ECU which controls the open/close valve, the switching valve, the booster pump and the purge control valve.
Description
INCORPORATION BY REFERENCE
The disclosure of Japanese patent application no.2002-167749 filed on Jun. 7, 2002 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an evaporative fuel processing apparatus. More particularly, the invention relates to an evaporative fuel processing apparatus suitable for processing evaporative fuel generated in an internal combustion engine without releasing the evaporative fuel into the atmosphere, and a control method of the same.
2. Description of the Related Art
As art related to the invention, for example, as disclosed in Japanese Patent Laid-Open Publication No. 7-91330, an evaporative fuel processing apparatus is known in which evaporative fuel generated in a fuel tank is stored in a canister so as to be processed. The evaporative fuel processing apparatus is for preventing the evaporative fuel from being released into the atmosphere. Accordingly, the evaporative fuel processing apparatus needs to have a function of promptly detecting leakage which has occurred therein.
The apparatus according to the related art has a function of applying pressure to a system including the fuel tank and the canister using a booster pump after closing the system. There is a difference in changes in pressure in the system after the application of pressure between when leakage has occurred in the system, and when leakage has not occurred in the system. Accordingly, the apparatus determines the presence or absence of leakage based on a change in the pressure in the system after the application of pressure.
When leakage has occurred in the evaporative fuel processing apparatus, it is preferable that the location of leakage can be determined. However, the apparatus cannot determine the location of leakage in the system including the fuel tank and the canister.
Also, in the evaporative fuel processing apparatus, it is necessary to isolate the fuel tank from the atmosphere in order to prevent the evaporative fuel that is generated while an internal combustion engine is stopped from being released into the atmosphere. According to the apparatus, it is possible to satisfy this requirement by maintaining the entire system including the fuel tank and the canister in a closed state.
However, an internal pressure in the system may become high due to generation of the evaporative fuel. Accordingly, it is necessary to make the structure of the entire system including the fuel tank and the canister pressure-resistant in order to close the system so as to prevent the evaporative fuel from being released into the atmosphere. Therefore, it is difficult to realize the apparatus at a low cost and in a light weight.
SUMMARY OF THE INVENTION
The invention is made in order to solve the above-mentioned problem. Accordingly, it is an object of the invention to provide an evaporative fuel processing apparatus and control method of the same, in which a state where a fuel tank and a canister are isolated from each other can be realized.
An evaporative fuel processing apparatus according to a first aspect of the invention includes a fuel tank; a canister which communicates with the fuel tank through a vapor passage; a purge passage which permits communication between an intake passage of an internal combustion engine and the canister; an open/close valve which opens or closes the vapor passage; an isolated state switching mechanism which makes the canister open to the atmosphere or which isolates the canister from the atmosphere; a pressure adjusting mechanism which increases or reduces the pressure in the canister; a purge control valve which opens or closes the purge passage; and a control system which controls the open/close valve, the isolated state switching mechanism, the pressure adjusting mechanism and the purge control valve.
According to the first aspect of the invention, in addition to the fact that it is possible to realize the basic functions (storage/purge of the evaporative fuel, and a leakage diagnosis) as the evaporative fuel processing apparatus, it is possible to allow the canister and the fuel tank to form a single space or separate spaces by opening or closing the open/close valve.
In a second aspect of the invention, the control system according to the first aspect may further closes a canister space which includes the canister and which does not include the fuel tank by closing the open/close valve, isolating the canister from the atmosphere using the isolated state switching mechanism, and closing the purge control valve, adjusts an internal pressure in the closed canister space using the pressure adjusting mechanism, and performs a diagnosis on leakage (hereinafter, referred to as a “leakage diagnosis”) in the canister space based on the adjusted internal pressure in the canister space.
According to the second aspect of the invention, it is possible to perform a leakage diagnosis for the canister space while the fuel tank is isolated from the canister. Therefore, it is possible to detect leakage only for the canister space.
In a third aspect of the invention, the control system according to the second aspect may further prohibits the opening of the open/close valve when it is determined that leakage has occurred in the canister space.
According to the third aspect of the invention, when there is leakage in the canister space, it is possible to prohibit the opening of the open/close valve and prevent leakage of the evaporative fuel from the leakage portion.
In a fourth aspect, the control system according to either the second or third aspect may further closes an entire space including the canister and the fuel tank as a single space by opening the open/close valve, isolating the canister from the atmosphere using the isolated state switching mechanism, and closing the purge control valve when it is determined that leakage has not occurred in the canister space, adjusts the internal pressure in the closed entire space using the pressure adjusting mechanism, and performs a leakage diagnosis for the entire space based on the adjusted internal pressure in the entire space.
According to the fourth aspect of the invention, when it is determined that there is no leakage in the canister space, it is possible to determine whether there is leakage in the entire space including the fuel tank. In this case, when there is leakage on the fuel tank side, it is possible to detect leakage as an abnormality on the fuel tank side.
In a fifth aspect of the invention, the control system according to the second aspect may further close an entire space including the canister and the fuel tank as a single space by opening the open/close valve, isolating the canister from the atmosphere using the isolated state switching mechanism, and closing the purge control valve after the completion of the leakage diagnosis for the canister space, adjusts the internal pressure in the closed entire space using the pressure adjusting mechanism, performs a leakage diagnosis for the entire space based on the adjusted internal pressure in the entire space.
According to the fifth aspect of the invention, it is possible to determine whether leakage has occurred in the entire space including the fuel tank regardless of whether leakage has occurred in the canister space. According to the results of the two diagnoses performed in the fifth aspect of the invention, it is possible to detect leakage in the apparatus and specify the location of the leakage.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a diagram describing a configuration of an evaporative fuel processing apparatus according to a first embodiment;
FIG. 2
is a diagram for describing operation of an open/close valve included in the apparatus according to the first embodiment;
FIGS. 3A
to
3
D are a timing chart for describing details on a leakage diagnosis performed by the apparatus according to the first embodiment,
FIG. 3A
shows a state of an open/close valve
20
,
FIG. 3B
shows a state of a switching valve
36
,
FIG. 3C
shows a state of a booster pump
40
, and
FIG. 3D
shows a change (a dashed line) in a tank side pressure Pt detected by a tank side pressure sensor
12
, and a change (a solid line) in a pump side pressure Pp detected by a pump side pressure sensor
48
;
FIG. 4
is a flowchart of a leakage diagnosis routine performed by the apparatus according to the first embodiment;
FIG. 5
is a flowchart of a sensor output correction routine performed by the apparatus according to the first embodiment;
FIG. 6
is a diagram for describing a configuration of a first modified example of the apparatus according to the first embodiment;
FIG. 7
is a diagram for describing a configuration of a second modified example of the apparatus according to the first embodiment;
FIG. 8
is a diagram for describing a configuration of a third modified example of the apparatus according to the first embodiment;
FIG. 9
is a flowchart of a first example of a leakage diagnosis routine performed by an apparatus according to a second embodiment;
FIG. 10
is a flowchart of a second example of the leakage diagnosis routine performed by the apparatus according to the second embodiment;
FIG. 11
is a flowchart of the leakage diagnosis routine performed by an apparatus according to a third embodiment;
FIG. 12
is a flowchart of a purge control routine performed by an apparatus according to a fourth embodiment;
FIG. 13
is a diagram for describing a configuration of an evaporative fuel processing apparatus according to a fifth embodiment;
FIG. 14
is a flowchart of a CCV control routine performed by the apparatus according to the fifth embodiment;
FIG. 15
is a diagram for describing a configuration of an evaporative fuel processing apparatus according to a sixth embodiment;
FIG. 16
is a flowchart of a pressure sensor control routine performed by the apparatus according to the sixth embodiment; and
FIG. 17
is a flowchart of a sensor abnormality determination routine performed by the apparatus according to the sixth embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereafter, embodiments according to the invention will be described with reference to accompanying drawings. Note that the same reference numerals will be assigned to elements common to each of the drawings and overlapping description will be omitted.
FIG. 1
is a diagram for describing a configuration of an evaporative fuel processing apparatus according to a first embodiment of the invention. A system shown in
FIG. 1
includes a fuel tank
10
. A tank side pressure sensor
12
for measuring an internal pressure in the fuel tank
10
is attached to the fuel tank
10
. Hereinafter, a pressure detected by the tank side pressure sensor
12
will be referred to as a “tank side pressure Pt”.
The fuel tank
10
communicates with a canister
16
through a vapor passage
14
. A mechanical positive/negative pressure valve
18
and an electromagnetic open/close valve
20
are provided in parallel in the vapor passage
14
. The positive/negative pressure valve
18
is a bidirectional relief valve which opens when a differential pressure equal to or higher than an opening pressure is generated between both sides thereof. The open/close valve
20
is an electromagnetic valve which opens or closes according to a driving signal supplied from the outside.
A purge passage
22
communicates with the canister
16
as well as the vapor passage
14
. The purge passage
22
communicates with an intake passage
24
of an internal combustion engine. More particularly, the purge passage
22
communicates with the intake passage
24
on a downstream side of a throttle valve
26
, where an intake negative pressure is generated. A buffer layer
28
and a purge control valve
30
are embedded in the purge passage
22
. The buffer layer
28
is a unit in which activated carbon is filled, and is provided so as to prevent a drastic change of the fuel concentration in the purge gas flowing through the purge passage
22
. The purge control valve
30
is a control valve for realizing an opening according to a driving signal which is actually supplied from the outside, and is provided so as to control a flow amount of the purge gas purged to the intake passage
24
.
The canister
16
includes an atmosphere introducing hole
32
. A new atmosphere introducing hole
34
communicates with the atmosphere introducing hole
32
. The new atmosphere introducing passage
34
is a passage whose end portion is open to the atmosphere, and includes a switching valve
36
, a bypass passage
38
, a booster pump
40
and a filter
42
.
The booster pump
40
takes in the air which has passed through the filter
42
and discharges the air from a discharging opening. A check valve
44
which permits only the discharge of the air by the booster pump
40
is provided in the discharging opening of the booster pump
40
. The bypass passage
38
bypasses the switching valve
36
, and allows the atmosphere introducing hole
32
of the canister
16
and the discharging opening of the booster pump
40
to communicate with each other at all times. A reference orifice
46
of 0.5 mm in diameter and a pump side pressure sensor
48
are provided in the bypass
38
. Hereinafter, a pressure detected by the pump side pressure sensor
48
will be referred to as a “pump side pressure Pp”.
The switching valve
36
selectively realizes a state (atmospheric state) in which the canister
16
directly communicates with the filter
42
, and a state (pressurized state) in which the canister
16
communicates with the discharging opening of the booster pump
40
without passing through the bypass passage
38
. According to a system in the embodiment, it is possible to make the canister
16
open to the atmosphere and to introduce the atmospheric pressure to the space whose pressure is detected by the pump side pressure sensor
48
, by controlling the switching valve
36
to be at the atmospheric state realizing position. Meanwhile, it is possible to isolate the canister from the atmosphere and to introduce the discharge pressure of the booster pump
40
to the canister
16
and the space whose pressure is detected by the pump side pressure sensor
48
, by controlling the switching valve
36
to be at the pressurized state realizing position.
As shown in
FIG. 1
, the evaporative fuel processing apparatus according to the embodiment includes an ECU (Electronic Control Unit)
50
. The ECU
50
is a control unit of the evaporative fuel processing apparatus. The outputs from the tank side pressure sensor
12
and the pump side pressure sensor
48
are supplied to the ECU
50
. Also, the open/close valve
20
, the purge control valve
30
, the switching valve
36
and the booster pump
40
are controlled by the ECU
50
.
Next, operation of the evaporative fuel processing apparatus according to the embodiment will be described.
FIG. 2
is a diagram describing states of the open/close valve
20
included in the evaporative fuel processing apparatus depending on the states of a vehicle. As shown in
FIG. 2
, the open/close valve
20
is kept open while the vehicle is running (during the operation of the internal combustion engine). When the open/close valve
20
is kept open, the fuel tank
10
and the canister
16
communicates with each other. In this case, the evaporative fuel generated in the fuel tank
10
can flow into the canister
16
and the purge passage
22
.
The ECU
50
controls the switching valve
36
to be at the atmospheric state (the state shown in
FIG. 1
) realizing position in principle while the vehicle is running. In this case, the canister
16
is open to the atmosphere. While the vehicle is running (during the operation of the internal combustion engine), an intake negative pressure is generated in the intake passage
24
. Accordingly, the purge control valve
30
is opened while the vehicle is running, and the intake passage
24
communicates with the canister
16
through the purge passage
22
. Consequently, the intake negative pressure is introduced to the canister
16
. As a result, air flows into the canister
16
from the atmosphere introducing hole
32
, and the fuel stored in the canister
16
is removed due to the flow of air. Then, the purge gas containing fuel is purged to the intake passage
24
through the purge passage
22
.
In this case, when the evaporative fuel has been generated in the fuel tank
10
, the evaporative fuel in the fuel tank
10
is mixed with the purge gas and is taken in the intake passage
24
to a degree at which the tank side pressure Pt is balanced with the internal pressure in the canister. Therefore, according to the evaporative fuel processing apparatus in the embodiment, it is possible to purge the fuel stored in the canister
16
, and the evaporative fuel generated in the fuel tank
10
to the intake passage
24
by opening the purge control valve
30
while the vehicle is running.
As shown in
FIG. 2
, the open/close valve
20
is kept open even during fueling. Namely, according to the apparatus in the invention, the open/close valve
20
is kept open during fueling even while the internal combustion engine is stopped. During fueling, it is necessary to permit discharge of a large amount of the evaporative fuel from the fuel tank
10
such that a large empty capacity in the fuel tank
10
is smoothly replaced by the fuel. According to the apparatus in the embodiment, it is possible to efficiently capture the evaporative fuel which is discharged during fueling using the canister
16
.
As shown in
FIG. 2
, the open/close valve
20
is kept closed while the vehicle is parked (while the internal combustion engine is stopped) except for the leakage detection time, to be described later. The evaporative fuel is generated in the fuel tank
10
due to remaining heat of the internal combustion engine and the like even while the vehicle is parked. Accordingly, when the fuel tank
10
is open to the atmosphere while the vehicle is parked, the evaporative fuel may be released into the atmosphere.
It is possible to prevent such release of the fuel into the atmosphere by isolating the canister
16
from the atmosphere while keeping the open/close valve
20
open. However, in this case, an increase in the internal pressure due to the generation of the evaporative fuel occurs in the canister
16
as well. Accordingly, in this case, it is necessary to make the structure of the canister
16
and the purge passage
22
pressure-resistant as well as the fuel tank
16
.
Meanwhile, in the apparatus according to the embodiment, since the open/close valve
20
is kept closed in principle while the vehicle is parked, it is possible to allow an increase in the pressure due to the generation of the evaporative fuel to occur only in the fuel tank
20
. In this case, since it is not necessary to make the structure of the canister
16
and the purge passage
22
pressure-resistant, it is possible to realize the apparatus according to the embodiment at low cost and in a light weight. Thus, according to the embodiment, the evaporative fuel generated while the internal combustion engine is stopped can be prevented from leaking into the atmosphere, by making only the purge gas concentration which accurately indicates the fuel storage state of the canister.
The evaporative fuel processing apparatus according to the embodiment performs a leakage diagnosis for detecting leakage in the system at predetermined timing while the vehicle is parked. It is possible to perform a leakage diagnosis not only while the vehicle is parked but also while the vehicle is running. However, while the vehicle is running, an external cause such as swinging of a fluid level in the fuel tank
10
due to running vibration and a change in the temperature of the fuel tank
10
is generated, which has a negative effect on the accuracy of the leakage diagnosis. According to the apparatus in the embodiment, since a leakage diagnosis is performed while the vehicle is parked, it is possible to avoid the negative effect of such an external cause, and consequently, it is possible to enhance the accuracy of the leakage diagnosis.
As shown in
FIG. 2
, the open/close valve
20
which has been closed is opened during the leakage diagnosis. Since a leakage diagnosis is performed while the vehicle is parked, after the completion of the diagnosis process, the open/close valve
20
is closed again according to the basic control. Hereafter, the details on the process of the leakage diagnosis will be explained in detail with reference to FIG.
3
and FIG.
4
.
FIGS. 3A
to
3
D are a timing chart describing the operation of the apparatus during the leakage diagnosis. More particularly,
FIG. 3A
shows the state of the open/close valve
20
,
FIG. 3B
shows the state of the switching valve
36
, and
FIG. 3C
shows the state of the booster pump
40
.
FIG. 3D
shows a change (a dashed line) in the tank side pressure Pt detected by the tank side pressure sensor
12
, and a change (a solid line) in the pump side pressure Pp detected by the pump side pressure sensor
48
. The purge control valve
30
is kept closed at all times while the vehicle is parked and a leakage diagnosis is performed. Accordingly, the state of the purge control valve
30
is not shown in the diagram.
In the examples shown in
FIGS. 3A
to
3
D, pre-detection process is started at time t0. As shown in
FIG. 3A
, the open/close valve
20
is closed before time t0 (the fuel tank
10
is closed). Accordingly, as shown by the dashed line in
FIG. 3D
, the tank side pressure Pt becomes a positive pressure at time t0. Before time t0, the switching valve
36
is at the atmospheric state realizing position, as shown in FIG.
3
B. Accordingly, the pump side pressure Pp is kept at the atmospheric pressure at time t0, as shown by the solid line in FIG.
3
D.
At time t0, which is a start time of the pre-detection process, the booster pump
40
is turned ON, as shown in FIG.
3
C. Since the switching valve
36
is kept at the atmospheric state realizing position at this time, the air discharged from the booster pump
40
is released into the atmosphere through the reference orifice
46
of 0.5 mm in diameter. In this case, the pump side pressure Pp is the same pressure as in the case where there is a hole of 0.5 mm in diameter in the apparatus (refer to FIG.
3
D). In the embodiment, the ECU
50
stores this final pressure as a reference value Pth for the leakage diagnosis. According to such a method, it is possible to accurately set the reference value Pth for determining the presence or absence of leakage portion of substantially 0.5 mm in diameter.
The pre-detection process is performed only for a length of time which is necessary for the pump side pressure Pp to reach the above-mentioned pressure. In the example shown in
FIGS. 3A
to
3
D, the pre-detection process is performed until time t1, and then a leakage diagnosis for the canister space is started. The “canister space” in this case corresponds to a space which is partitioned by the open/close valve
20
, the purge control valve
30
, the booster pump
40
(the check valve
44
), that is, a space which includes the canister
16
and does not include the fuel tank
10
.
At time t1, which is the start time of the leakage diagnosis for the canister space, the switching valve
36
is controlled to be at the pressurized state realizing position, as shown in FIG.
3
B. As a result, the passage through which the air discharged from the booster pump
40
is released into the atmosphere is interrupted, and the canister space starts being pressurized by the discharge pressure. Consequently, the output from the pump side pressure sensor
48
, that is, the pump sire pressure Pp temporarily decreases, and becomes the pressure corresponding to the state of the leakage in the canister space (refer to FIG.
3
D).
The final value of the pump side pressure Pp during the leakage diagnosis for the canister space is equal to or lower than the reference value Pth which is set in the pre-detection process, when leakage portion of equal to or larger than substantially 0.5 mm in diameter has been formed in the canister space. Meanwhile, when such leakage has not occurred, the final value is larger than the reference value Pth. Accordingly, the ECU
50
waits until the pump side pressure Pp reaches the final value and determines whether leakage has occurred in the canister space by comparing the final value with the reference value Pth.
In the example shown in
FIGS. 3A
to
3
D, a leakage diagnosis for the canister space is performed until time t2, and then a leakage diagnosis for the entire space is started. In this case, the “entire space” is referred to as a space formed by adding the fuel tank
10
to the above-mentioned canister space. In the embodiment, a leakage diagnosis for the entire space is performed only when leakage has not been detected in the canister space. Accordingly, a leakage diagnosis for the entire space substantially corresponds to a leakage diagnosis for the fuel tank
10
.
At time t2, which is the start time of the leakage diagnosis for the entire space, the open/close valve
20
is opened, as shown in FIG.
3
A. When the open/close valve
20
is opened, since the fuel tank
10
and the canister
16
form a single space, the tank side pressure Pt becomes equal to the pump side pressure Pp. Then, the tank side pressure Pt temporarily decreases, and becomes the pressure corresponding to the state of the leakage in the entire space by being supplied with the air discharged from the booster pump
40
, (refer to FIG.
3
D).
The tank side pressure Pt during the leakage diagnosis for the entire space becomes a value equal to or lower than the reference value set in the pre-detection process when the leakage portion of equal to or larger than substantially 0.5 mm in diameter has been formed in the entire space. Meanwhile, when such leakage has not occurred in the entire space, the tank side pressure Pt becomes a value larger than the reference value Pth. Accordingly, the ECU
50
waits until the tank side pressure Pt reaches the final value, and determines whether leakage has occurred in the entire space by comparing the final value with the reference value Pth.
In the apparatus according to the embodiment, when a leakage diagnosis for the entire space is completed, a series of processes necessary for a leakage diagnosis is completed. In the example shown in
FIGS. 3A
to
3
D, a leakage diagnosis for the entire space is completed at time t3. When a leakage diagnosis is completed, the open/close valve is closed, and the fuel tank
10
becomes a closed space again, as mentioned above. Accordingly, as shown in
FIG. 3D
, after time t3, the tank side pressure Pt is kept at a value close to the final value which the tank side pressure Pt reached during the leakage diagnosis.
When a leakage diagnosis is completed, the switching valve
36
is further controlled to be at the atmospheric state realizing position. Also, as shown in
FIG. 3C
, the booster pump
40
is turned OFF. As a result, after time t3, the canister space becomes open to the atmosphere and the pump side pressure Pp decreases to the atmospheric pressure as shown in FIG.
3
D.
FIG. 4
shows a flowchart of the control routine which the ECU
50
performs when the above-mentioned leakage diagnosis is performed. The routine shown in
FIG. 4
is performed when a predetermined condition is satisfied in a state where the vehicle is parked and therefore each component of the apparatus is in the following state. The open/close valve
20
: closed; the purge control valve
30
: closed; the switching valve
36
: atmospheric state realizing position; the booster pump
40
: OFF state.
In the routine shown in
FIG. 4
, the booster pump
40
is initially turned ON, and the pre-detection process is performed. When the reference value Pth is set in the pre-detection process, the switching valve
36
is controlled to be at the pressurized state realizing position, and a leakage diagnosis for the canister space is performed (step S
1100
).
When time for converging the pump side pressure Pt has elapsed, it is determined whether there is leakage in the canister space based on the comparison of the pump side pressure Pp with the reference value Pth at this time (step
102
).
As a result of the comparison, when it is determined that the pump side pressure Pp is equal to or lower than the reference value Pth (in the case of Pp=Pth), it can be determined that there is leakage in the canister space. In this case, it is determined that there is an abnormality due to leakage in the canister space (step
104
), afterwhich the present process cycle is completed.
Meanwhile, when it is determined in step
102
that the pump side pressure Pp is higher than the reference value Pth (in the case of Pp>Pth), it can be determined that there is no leakage in the canister space. In this case, the open/close valve
20
is opened, and a leakage diagnosis for the entire space is performed (step
106
).
When time for converging the tank side pressure Pt has elapsed, it is determined whether there is leakage in the entire space, that is, whether there is leakage in the fuel tank
10
based on the comparison of the tank side pressure Pt with the reference value Pth at this time (step
108
).
As a result, when it is determined that the tank side pressure Pt is lower than the reference value Pth (in the case of Pt=Pth), it can be determined that there is leakage in the entire space, that is, there is leakage in the fuel tank
10
. In this case, it is determined that there is an abnormality due to leakage in the fuel tank
10
(step
110
), afterwhich the present process cycle is completed.
Meanwhile, when it is determined in step
108
that the tank side pressure Pt is higher than the reference value Pth (in the case of Pt>Pth), it can be determined that there is no leakage in the entire space. In this case, it is determined that the apparatus is in the normal state (step
112
), afterwhich the present process cycle is completed.
As described so far, according to the routine shown in
FIG. 4
, it is possible to perform diagnosis while the canister space is isolated from the fuel tank
10
. Therefore, according to the apparatus in the embodiment, when there is leakage in the canister space, it is possible to detect leakage while identifying the leakage as an abnormality in the canister space.
Also, according to the routine shown in
FIG. 4
, it is possible to substantially perform a leakage diagnosis for the fuel tanks
10
by performing diagnosis for the entire space after a diagnosis for the canister space. Therefore, according to the apparatus in the embodiment, when there is leakage in the fuel tank
10
, it is possible to detect leakage while identifying the leakage as an abnormality in the fuel tank
10
.
Further, according to the routine shown in
FIG. 4
, when leakage is detected in the canister space, it is possible to complete a leakage diagnosis without opening the open/close valve
20
. Therefore, according to the apparatus in the embodiment, when leakage has occurred in the canister space, it is possible to minimize the amount of the evaporative fuel leaking from the leakage portion.
The pump side pressure sensor
48
employed in the embodiment is a relative pressure sensor which detects a pressure in the space subject to detection as a relative pressure to the atmospheric pressure. Therefore, in order to accurately detect the pressure in the space subject to detection based on the output from the pump side pressure sensor
48
, it is preferable to make a correction to the output from the sensor.
In order to correct the output from the pump side pressure sensor
48
, it is necessary to detect the output (hereinafter, referred to as a “reference output”) from the pump side pressure sensor
48
when the reference pressure (the atmospheric pressure) is introduced to the space subject to detection. In the embodiment, it is possible to introduce the atmospheric pressure to the space whose pressure is detected by the pressure sensor
48
by controlling the switching valve
36
to be at the atmospheric state realizing position. Accordingly, the ECU
50
can correct the output from the pump side pressure sensor
48
using the output from the sensor, which can be obtained in this state, as the reference output.
FIG. 5
shows a flowchart of a routine performed such that the ECU
50
corrects the output from the pump side pressure sensor
48
. In the routine shown in
FIG. 5
, it is determined whether correction of the output from the sensor is required (step
120
).
Correction of the output from the sensor is required each time the internal combustion engine is started, or at predetermined intervals. When it is determined in step
120
that correction is not required, the present process cycle is promptly completed. Meanwhile, when it is determined that correction is required, the open/close valve
36
is controlled to be at the atmospheric state realizing position (step
122
).
Next, the output from the pump side pressure sensor
48
is detected. At this time, the atmospheric pressure is introduced to the space whose pressure is detected by the pump side pressure sensor
48
. Therefore, according to the process in step
124
, it is possible to detect the reference output for the atmospheric pressure, which the pump side pressure sensor
48
(step
124
) produces.
Next, an output correction value is computed based on the reference output detected in the process in step
124
(step
126
). Then, the output correction value stored in the ECU
50
is updated to the latest output correction value which is computed in step
126
(step
128
). After this, the ECU
50
recognizes the pressure introduced to the space whose pressure is detected by the pump side pressure sensor
48
after correcting the output from the pump side pressure sensor
48
using the latest output correction value.
As described so far, according to the routine shown in
FIG. 5
, it is possible to appropriately correct the output from the pump side pressure sensor
48
at appropriate timing. Therefore, according to the apparatus in the embodiment, it is possible to accurately detect the pressure in the canister space regardless of an individual difference of the pump side pressure sensor
48
or a change with time in the pump side pressure sensor
48
.
Modified example of first embodiment will be described below. In the apparatus according to the first embodiment, it is necessary that a state can be realized in which the atmosphere introducing hole
32
of the canister
16
is open to the atmosphere, in order to make it possible to purge the evaporative fuel in the canister
16
(first function). Also, it is necessary that the canister space can be pressurized after the atmosphere introducing hole
32
is isolated from the atmosphere in order to make it possible to perform a leakage diagnosis for this apparatus (second function). The apparatus according to the first embodiment employs the switching valve
36
, the booster pump
40
and the check valve
44
so as to realize these two functions.
However, the configuration for realizing the two functions is not limited to the configuration of the first embodiment.
FIG. 6
is a block diagram of a first modified example in which these functions can be realized. In the first modified example, the switching valve
36
and the check valve
44
, shown in
FIG. 1
, are omitted, and only the booster pump
40
is provided in the new atmosphere introducing passage
34
. In this configuration, the booster pump
40
has a structure for permitting the countercurrent of the fluid flowing from the discharging opening to the intake opening during non-operation time.
According to this configuration, the first function can be realized by controlling the booster pump
40
to be in the non-operation state. Also, since the atmosphere introducing hole
32
is substantially isolated from the atmosphere during the operation of the booster pump
40
, the second function can be realized by operating the booster pump
40
. Therefore, according to the first modified example shown in
FIG. 6
as well as according to the first embodiment, it is possible to appropriately perform a purge of the evaporative fuel in the canister
16
and the leakage diagnosis for the apparatus.
FIG. 7
is a block diagram of a second modified example in which the two functions can be realized. In the second modified example, the switching valve
36
is omitted from the configuration shown in
FIG. 1
, and a CCV (Canister Closed valve)
52
is added to the new atmosphere introducing passage
34
so as to be provided in parallel to the booster pump
40
. The CCV
52
is an electromagnetic valve which is kept open when a driving signal is not supplied from the outside, and which closes when the driving signal is supplied.
According to this configuration, it is possible to realize the first function by opening the CCV
52
. Also, it is possible to realize the second function by closing the CCV
52
and operating the booster pump
40
. Therefore, according to the second modified example shown in
FIG. 7
as well as according to the first embodiment, it is possible to appropriately perform a purge of the evaporative fuel in the canister
16
and the leakage diagnosis for the apparatus.
According to the first embodiment, the first modified example, or the second modified example, the canister space or the entire space is pressurized using the booster pump
40
when a leakage diagnosis is performed (hereinafter, such a diagnosis method will be referred to as a “pressurization diagnosis”). However, the method for a leakage diagnosis is not limited to this. For example, a leakage diagnosis may be performed based on the pressure at the pressure reduction time when the booster pump
40
shown in
FIGS. 1
,
6
and
7
is provided in a reverse direction in the apparatus and make it possible to reduce the pressure in the canister space and the entire space (hereinafter, such a diagnosis method will be referred to as a “pressure reduction diagnosis”).
In the case where the pressure reduction diagnosis is employed as a method for a leakage diagnosis, gas containing evaporative fuel may flow from the canister
16
to the new atmosphere introducing passage
34
when a leakage diagnosis is performed. It is possible to capture this flowing evaporative fuel by providing the activated carbon in the filter
42
. Also, it is possible to purge the fuel captured by the filter
42
when the fuel in the canister
16
is purged. Accordingly, when the pressure reduction diagnosis is employed as a method for a leakage diagnosis, it is possible to maintain a good emission characteristic.
Further, according to the first embodiment, the first modified example, or the second modified example, pressure adjustment necessary for a leakage diagnosis is performed using the booster pump
40
. However, the invention is not limited to this. Namely, the pressure reduction necessary for a leakage diagnosis may be performed using the intake negative pressure and a leakage diagnosis may be performed during the operation of the internal combustion engine.
FIG. 8
is a block diagram of an apparatus (a third modified example) for performing a leakage diagnosis using the intake negative pressure. In the third modified example, the switching valve
36
, the booster pump
40
and the check valve
44
are omitted from the configuration shown in
FIG. 1
, and the CCV (Canister Closed valve)
52
is added to the new atmosphere introducing passage
34
.
According to this configuration, the first function can be realized by opening the CCV
52
. It is possible to control the pressure in the closed canister space or the closed entire space to be negative by closing the CCV
52
and opening the purge control valve
30
during the operation of the internal combustion engine (corresponding to the second function). Therefore, according to the third modified example shown in
FIG. 8
as well as according to the first embodiment, it is possible to appropriately perform a purge of the evaporative fuel in the canister
16
and a leakage diagnosis for the apparatus.
In the first embodiment, the switching valve
36
serves as one example of an “isolated state switching mechanism” in claims, and the booster pump
40
serves as one example of a “pressure adjusting mechanism” in claims. Also, the ECU
50
, the tank side pressure sensor
12
and the pump side pressure sensor
48
serve as one example of a “control system” in claim
1
.
In the first embodiment, the pump side pressure sensor
48
serves as one example of a “pressure sensor” in claim
13
.
In the first modified example, the booster pump
40
scarves as one example of both an “isolated state switching mechanism” and a “pressure adjusting mechanism” in claims. In the second modified example, the CCV
52
serves as one example of an “isolated state switching mechanism” in claims, and the booster pump
40
serves as one example of a “pressure adjusting mechanism” in claims. Further, in the third modified example, the CCV
52
serves as one of an “isolated state switching mechanism” in claims, and the purge control valve
30
serves as one example of a “ purge control valve” in claims and part of the “pressure adjusting mechanism”. Namely, in the third modified example, a “pressure adjusting mechanism” may be realized by the internal combustion engine which generates the intake negative pressure, and the purge control valve
30
which introduces the intake negative pressure to the canister
16
.
Next, a second embodiment according to the invention will be described with reference to
FIGS. 9 and 10
. It is possible to realize an evaporative fuel processing apparatus according to the embodiment when the ECU
50
performs the routine shown in
FIG. 9
or
FIG. 10
instead of the routine shown in
FIG. 4
in the configuration (the configuration shown in
FIG. 1
) of the first embodiment.
FIG. 9
show a flowchart of a first example of the control routine which the ECU
50
performs so as to perform a leakage diagnosis in the embodiment. In
FIG. 9
, the same reference numerals are assigned to steps in which the same processes are performed as those in steps shown in
FIG. 4
, and description thereof is omitted or simplified.
The routine shown in
FIG. 9
is the same routine as that shown in
FIG. 4
, except that the processes in step
106
and the following steps are performed subsequent to the process in step
104
. Namely, the routine shown in
FIG. 9
is different from that shown in
FIG. 4
in that even when leakage is detected by performing a leakage diagnosis for the canister space (steps
100
to
104
), a leakage diagnosis for the entire space is performed (steps
106
to
112
).
According to the routine shown in
FIG. 9
, even when there is leakage in the canister space, it is possible to perform a leakage diagnosis for the entire space. Therefore, according to the apparatus in the embodiment, for example, when there are leakages in both the canister space and the fuel tank
10
, it is possible to detect these leakages simultaneously. Therefore, according to the apparatus in the embodiment, when a plurality of leakages has occurred, the driver is not required to have the vehicle repaired plural times.
FIG. 10
shows a flowchart of a second example of the control routine which the ECU
50
performs so as to perform a leakage diagnosis in the embodiment. In
FIG. 10
, the same reference numerals are assigned to steps in which the same processes are performed as steps in
FIG. 4
(FIG.
9
), and description thereof is omitted or simplified.
The routine shown in
FIG. 10
is the same routine as that shown in
FIG. 9
, except that the processes in step
130
and step
132
are performed subsequent to the process in step
104
. Namely, in the routine shown in
FIG. 10
, when leakage is detected by a leakage diagnosis for the canister space (steps
100
to
104
), the final value of the pump side pressure Pp, which the pump side pressure has reached in the process of the diagnosis, is detected (step
130
).
The detected final value is a value reflecting the effect of the leakage in the canister space. When leakage has not occurred in the fuel tank
10
, the pressure in the entire space becomes the value reflecting only the effect of leakage in the canister space, even when a leakage diagnosis for the entire space is performed. Accordingly, in this case, the tank side pressure Pt is supposed to become the final value detected in step
130
.
Meanwhile, when leakage has occurred in the fuel tank
10
, the pressure in the entire space becomes the value reflecting effects of both leakage in the canister space and leakage in the fuel tank
10
when a leakage diagnosis for the entire space is performed. Accordingly, in this case, the tank side pressure Pt is supposed to become the value which is lower than the final value detected in step
130
(in the case of the pressurized diagnosis).
Accordingly, in the case where there is leakage in the canister space, when a leakage diagnosis for the entire space is performed, it is preferable to use the final value detected in step
102
as the reference value Pth to using the reference value Pth set in the pre-detection process, in order to enhance the accuracy in the diagnosis. Therefore, in the routine shown in
FIG. 10
, when leakage in the canister space is detected, the reference value Pth used in the leakage diagnosis for the entire space is modified from the value set in the pr-detection process to the final value detected in step
132
(step
132
).
When leakage in the canister space has not been detected, the presence or absence of leakage in the entire space, that is, the presence or absence of leakage in the fuel tank
10
is determined based on the reference value Pth set in the pre-detection process in step
108
in the routine shown in
FIG. 10
, as well as in the case of the routine shown in
FIG. 4
or FIG.
9
.
Meanwhile, when leakage in the canister space has been detected, it is determined in step
132
whether there is another leakage in the entire space, that is, whether there is leakage in the fuel tank
10
based on the reference value modified in step
132
.
According to the above-mentioned process, even when there is leakage in the canister space, it is possible to perform a leakage diagnosis for the entire space, and it is possible to accurately determine the presence or absence of leakage in the entire space, that is, the presence or absence of leakage in the fuel tank
10
. Accordingly, when a leakage diagnosis is performed according to the routine shown in
FIG. 10
, it is possible to realize a more accurate leakage diagnosis as compared with the case in which a leakage diagnosis is performed according to the routine shown in FIG.
9
.
The above-mentioned description is made on the assumption that the apparatus according to the second embodiment determines the presence or absence of leakage by performing pressurized diagnosis. However, the invention is not limited to this. Namely, in the apparatus according to the second embodiment as well as in the apparatus according to the first embodiment, the presence or absence of leakage may be determined by performing pressure reduction diagnosis. In the apparatus according to the second embodiment, a leakage diagnosis for the entire space is performed even when there is leakage in the canister space. Accordingly, when diagnosis is performed by the pressurized diagnosis, the gas containing fuel may leak from the leakage portion in the canister space while a leakage diagnosis for the entire space is performed. When the pressure reduction diagnosis is employed as the method for a leakage diagnosis, fuel does not leak from the leakage portion when a leakage diagnosis for the entire space is performed even in the case where leakage has occurred in the canister space. In terms of this, it is preferable to use the apparatus according to the embodiment in combination with the pressurized diagnosis to using it in the combination with the pressure reduction diagnosis.
Also, the above-mentioned description is made on the assumption that the apparatus according to the second embodiment has the same configuration as the apparatus according to the first embodiment, that is the configuration shown in FIG.
1
. However, the configuration is not limited to the configuration shown in FIG.
1
. Namely, the configuration of the apparatus according to the second embodiment may be any one of the configurations shown in
FIGS. 6
to
8
.
Next, a third embodiment according to the invention will be described with reference to FIG.
1
. An evaporative fuel processing apparatus according to the embodiment can be realized when the ECU
50
performs the routine shown in
FIG. 11
instead of the routine shown in
FIG. 4
in the configuration (the configuration shown in
FIG. 1
) of the first embodiment.
FIG. 11
shows a flowchart of the control routine which the ECU
50
performs so as to perform a leakage diagnosis in the embodiment. Note that, in
FIG. 11
, the same reference numerals are assigned to steps in which the same processes are performed as in steps shown in
FIG. 4
, and description thereof is omitted or simplified.
The routine shown in
FIG. 11
is the same as that shown in
FIG. 4
except that step
140
and step
142
are inserted between step
102
and step
106
. Namely, in the routine shown in
FIG. 11
, when it is determined in step
102
that there is no leakage in the canister space, the tank side pressure Pt at this time is detected (step
140
).
A leakage diagnosis for the canister space is performed while the open/close valve
20
is kept closed. Before the open/close valve
20
is opened, the fuel tank
10
is kept closed. In this case, when leakage has not occurred in the fuel tank
10
, the internal pressure in the fuel tank
10
may be a value which greatly deviates from the atmospheric pressure. Meanwhile, when leakage has occurred in the fuel tank
10
, the internal pressure in the fuel tank
10
becomes a value close to the atmospheric pressure since pressure is adjusted through the leakage portion. Accordingly, in the apparatus according to the embodiment, when the tank side pressure Pt which greatly deviates from the atmospheric pressure has been generated at the completion of the leakage diagnosis for the canister space, it can be determined at this time that there is no leakage in the fuel tank
10
.
In the routine shown in
FIG. 11
, it is determined subsequent to the process in step
140
whether the tank side pressure Pt is equal to or higher than the positive side reference value α, or is equal to or lower than the negative side reference value β, (step
142
). As a result, when it is determined that the condition, Pt=α or Pt=β is satisfied, the process in step
112
is performed, that is, it is determined that the apparatus is in a normal state, without performing a leakage diagnosis for the entire space. Meanwhile, when it is determined that neither of the above-mentioned conditions are satisfied, the processes in step
108
and the following steps are performed, that is, a leakage diagnosis for the entire space is performed, as well as in the routine shown in FIG.
4
.
As described so far, according to the routine shown in
FIG. 11
, when the tank side pressure Pt which greatly deviates from the atmospheric pressure has been generated, it can be determined that the fuel tank
10
is in the normal state without performing a leakage diagnosis for the entire space. Therefore, according to the evaporative fuel processing apparatus in the embodiment, it is possible to complete a leakage diagnosis for the entire space more efficiently than in the first embodiment.
The above description is made on the assumption that the apparatus according to the third embodiment has the configuration shown in FIG.
1
. However, the configuration is not limited to this. Namely, the configuration of the apparatus according to the third embodiment as well as the configuration of the apparatus according to the first embodiment may be any one of the configurations shown in
FIGS. 6
to
8
.
In the third embodiment, the processes (the processes in step
140
and step
142
) for determining whether the tank side pressure Pt which greatly deviates from the atmospheric pressure has been generated are combined with the routine (the routine shown in
FIG. 4
) employed in the first embodiment. However, the invention is not limited to this. Namely, these processes may be combined with the routine (the routine shown in
FIG. 9
or
FIG. 10
) employed in the second embodiment.
Next, a fourth embodiment according to the invention will be described with reference to FIG.
12
. An evaporative fuel processing apparatus according to the embodiment can be realized when the ECU
50
performs the routine shown in
FIG. 12
in the configuration in FIG.
1
.
FIG. 12
shows a flowchart of a control routine which the ECU
50
performs so as to purge the fuel stored in the canister
16
to the intake passage
24
of the internal combustion engine. In the routine shown in
FIG. 12
, it is initially determined whether the condition for performing a purge has been satisfied in the present process cycle, which was not satisfied in the previous process cycle (step
150
).
As a result, when it is determined that the condition for performing a purge has been satisfied in the present process cycle, which was not satisfied in the previous process cycle, the open/close valve
20
is closed (step
152
). The routine shown
FIG. 12
is the routine which is performed during the operation of the internal combustion engine (while the vehicle is running). The open/close valve
20
is kept open in principle while the vehicle is running in the embodiment as well as in the first embodiment. Therefore, according to the process in step
152
, it is possible to open the open/close valve which has been closed.
In the routine shown in
FIG. 12
, purge of the evaporative fuel is started (step
154
). When the process in step
154
is performed, the switching valve
36
is kept at the atmospheric state realizing position such that an appropriate amount of the purge gas flows from the canister
16
to the intake passage
24
, and the purge control valve
30
is driven at an appropriate duty ratio.
Next, the vapor concentration in the purge gas purged to the intake passage
24
is learned (step
156
). It is possible to learn the vapor concentration by a known method based on the deviation in the exhaust air-fuel ratio which is generated due to the purge gas flowing into the intake passage
24
, or based on the amount of correction made to the fuel injection amount in order to correct the deviation.
In the routine shown in
FIG. 12
, it is determined whether the learned vapor concentration is lower than the predetermined reference value (step
158
).
As a result, when it is determined that the vapor concentration is not lower than the reference value, it can be determined that a large amount of fuel has been stored in the canister
16
. Namely, it can be determined that the fuel in the canister
16
needs to be purged promptly. In this case, in the routine shown in
FIG. 12
, the present process cycle is completed while the open/close valve is kept closed.
Meanwhile, when it is determined in step
158
that the vapor concentration is lower than the reference value, it can be determined that the amount of the fuel stored in the canister
16
is small. Namely, in this case, it can be determined that purge of the fuel in the canister
16
has been almost completed. In this case, in the routine shown in
FIG. 12
, the open/close valve
20
is opened (step
160
), afterwhich the present process cycle is completed.
When it is determined in the routine shown in
FIG. 12
that the condition in step
150
is not satisfied, it is determined whether the purge condition has been satisfied (step
162
).
As a result, when it is determined that the purge condition itself has been satisfied, the processes in step
156
and the following steps are performed. Meanwhile, when it is determined that the purge condition itself has not been satisfied, the process for completing purge of the evaporative fuel is performed, such as closing the purge control valve
30
, afterwhich the present process cycle is completed.
According to a series of the above-mentioned processes, it is possible to learn the vapor concentration in the purge gas while the open/close valve
20
is kept closed after purge of the evaporative fuel is started. In this case, it is possible to allow only the gas flowing out of the canister
16
to flow into the intake passage
24
as the purge gas. Namely, it is possible to allow the purge gas which does not contain evaporative fuel generated in the fuel tank to flow into the intake passage
24
.
In this case, the vapor concentration learned in the process in step
156
becomes a value that accurately reflects the storage state of the fuel in the canister
16
. Therefore, according to the apparatus in the embodiment, it is possible to detect the vapor concentration in the purge gas as a value which accurately indicates the storage state of the fuel in the canister
16
.
Also, according to the above-mentioned series of the processes, it is possible to purge the fuel in the canister
16
at the highest priority while the open/close valve is kept closed, during a period in which the vapor concentration is high after purge of the evaporative fuel is started. Therefore, according to the apparatus in the embodiment, when it is necessary to promptly purge the fuel in the canister
16
, for example when a large amount of fuel has been stored in the canister, it is possible to promptly purge the fuel. Then, after the fuel stored in the canister
16
has appropriately decreased, it is possible to appropriately purge the evaporative fuel generated in the fuel tank into the intake passage
24
by performing a purge while the open/close valve
20
is kept open.
The above-mentioned description is made on the assumption that the apparatus according to the fourth embodiment has the configuration shown in FIG.
1
. However, the configuration is not limited to this. Namely, the configuration of the apparatus according to the fourth embodiment as well as the configuration of the apparatus according to the first embodiment may be any one of the configurations shown in
FIGS. 6
to
8
.
Next, a fifth embodiment according to the invention will be described with reference to FIG.
13
and FIG.
14
.
FIG. 13
is a diagram for describing a configuration of an evaporative fuel processing apparatus according to the embodiment. The evaporative fuel processing apparatus shown in
FIG. 13
has the same configuration in the first embodiment, except that a CCV
54
is provided in the atmosphere introducing hole
32
of the canister
16
. The CCV
54
is an electromagnetic valve which is kept open while a driving signal is not supplied from the outside, and which closes when a driving signal is supplied.
The evaporative fuel processing apparatus according to the embodiment as well as the apparatus according to the first embodiment performs a leakage diagnosis for the apparatus by the method of the pressurized diagnosis, and closes the open/close valve
20
and controls the switching valve
36
to be at the atmospheric state realizing position at the completion of the leakage diagnosis, (refer to time t3 in
FIG. 3A
, and FIG.
3
B). When a leakage diagnosis is performed by the pressurized diagnosis, a pressure higher than the atmospheric pressure remains in the canister
16
and the fuel tank
10
at the completion of the leakage diagnosis (refer to time t3 in FIG.
3
D).
When the canister
16
is controlled to be open to the atmosphere while such a high pressure remains in the canister
16
, the gas containing fuel may flow from the inside of canister
16
to the atmosphere. Therefore, the apparatus according to the embodiment closes the CCV
54
during the period in which a high pressure remains in the canister
16
after the completion of the leakage diagnosis by the pressurized diagnosis so as to isolate the canister
16
from the atmosphere.
FIG. 14
shows a flowchart of the control routine which the ECU
50
performs in the embodiment so as to realize the above-mentioned function. In the routine shown in
FIG. 14
, it is initially determined whether the start time of the present process cycle is the completion time of the leakage diagnosis (step
170
).
As a result, when it is determined that the start time of the present process cycle is not the completion time of the leakage diagnosis, it is determined whether the leakage diagnosis has been completed (step
172
).
When it is determined in step
172
that the leakage diagnosis has not been completed, it can be determined that the leakage diagnosis has not been started, or the leakage diagnosis is being performed. When the leakage diagnosis has not been started, it is preferable that the CCV
54
should be kept open since it is not necessary to isolate the canister
16
from the atmosphere. During the leakage diagnosis, it is necessary that the CCV
54
is kept open. Accordingly, when the condition in step
172
is not satisfied, the CCV
54
is opened (step
174
).
When a leakage diagnosis is started and then completed, the condition in step
170
is satisfied at this time. As mentioned above, at the completion of the leakage diagnosis, the switching valve
36
is controlled to be at the atmospheric state realizing position again while a high pressure remains in the canister
16
. Accordingly, in the routine shown in
FIG. 14
, when the condition in step
170
is satisfied, the CCV
54
is opened so as to prevent the fuel from leaking from the canister
16
to the atmosphere (step
176
).
When the routine shown in
FIG. 14
is restarted after a leakage diagnosis is completed, it is determined that the leakage diagnosis has been completed in step
172
. In this case, the internal pressure in the canister
16
is estimated (step
178
).
In the apparatus according to the embodiment, the open/close valve
20
and the CCV
54
are closed simultaneously with the completion of the leakage diagnosis. Accordingly, when step
178
is performed, it is impossible to measure the internal pressure in the canister
16
neither by the tank side pressure sensor
12
nor by the pump side pressure sensor
48
. Therefore, in the routine shown in
FIG. 14
, the internal pressure in the canister
16
is estimated in step
178
according to the rule predetermined.
It is possible to estimate the internal pressure in the canister
16
as a function of the time which has elapsed since the completion of the leakage diagnosis using the pressure (the pump side pressure Pp or the tank side pressure Pt) at the completion of the leakage diagnosis as an initial value. The internal pressure in the canister
16
may be estimated on the assumption that a substantially constant pressure is maintained until the purge control valve
30
is opened after the completion of the leakage diagnosis, and the pressure decreases to a value close to the atmospheric pressure when the purge control valve
30
is opened.
In the routine shown in
FIG. 14
, it is determined subsequent to the process in step
178
whether the internal pressure in the canister
16
is higher than the predetermined reference pressure (step
180
).
The predetermined reference pressure is a pressure higher than the atmospheric pressure, and is a value for determining whether the gas containing fuel flows from the canister
16
to the atmosphere when the CCV
54
is opened. Accordingly, when it is determined in step
180
that the internal pressure in the canister
16
is higher than the reference value, it can be determined that the CCV
54
should not be opened. In this case, in order to keep the CCV
54
closed, the process in step
176
is performed, afterwhich the present process cycle is completed.
Meanwhile, when it is determined in step
180
that the internal pressure in the canister
16
is not higher than the reference pressure, it can be determined that the fuel leakage does not occur even when the CCV
54
is opened. Accordingly, when such determination is made, the process in step
174
is performed so as to open the CCV
54
, afterwhich the present process cycle is completed.
As described so far, according to the routine shown in
FIG. 14
, the canister
16
is prevented from being opened to the atmosphere while the internal pressure in the canister
16
is being increased by performing a leakage diagnosis by the pressurized diagnosis. Therefore, according to the evaporative fuel processing apparatus in the embodiment, the gas containing fuel can be prevented from leaking from the canister into the atmosphere, therefor it is possible to realize an emission characteristic superior to that of the apparatus according to the first embodiment.
In the fifth embodiment, since priority is given to isolating the fuel tank
10
and the canister
16
from each other while the vehicle is parked, the open/close valve
20
is closed at the completion of the leakage diagnosis. However, the open/close valve
20
may be kept open even while the vehicle is parked until the internal pressure in the canister
16
becomes equal to or lower than the reference pressure after the completion of the leakage diagnosis, and the internal pressure may be measured by the tank side pressure sensor
12
.
In the fifth embodiment, the internal pressure in the canister
16
is estimated after the completion of the leakage diagnosis, and when the internal pressure decreases to the reference pressure, the CCV is opened. However, the invention is not limited to this. Namely, the processes such as the estimation of the internal pressure in the canister and the like may be omitted, and the CCV
54
may be kept closed until purge of the evaporative fuel is required, after the completion of the leakage diagnosis.
In the fifth embodiment, the CCV
54
is closed only after the completion of the leakage diagnosis. However, the invention is not limited to this. Namely, the CCV
54
may be closed at all times when the internal pressure in the canister
16
increases in the case in which there is not any positive reason for opening the CCV
54
, for example, in the case in which purge of the evaporative fuel is required.
The above description is made on the assumption that the apparatus according to the fifth embodiment has a configuration shown in
FIG. 13
, that is, the configuration formed by adding the CCV
54
to the configuration shown in FIG.
1
. However, the configuration is not limited to the configuration shown in FIG.
13
. Namely, it is possible to realize the apparatus according to the fifth embodiment by employing the configuration formed by adding the CCV
54
to the configuration shown in FIG.
6
.
It is possible to realize the apparatus according to the fifth embodiment by controlling the CCV
52
in
FIG. 7
in the same manner as in the case of the CCV
54
in
FIG. 13
using the configuration shown in FIG.
7
. In this case, it is possible to measure the internal pressure in the canister
16
even when the CCV
52
is closed. Accordingly, when the configuration shown in
FIG. 7
is employed, it is possible to control the opening time of the CCV
52
based on the measured value of the internal pressure in the canister
16
.
The apparatus (the configuration shown in
FIG. 13
) according to the fifth embodiment employs the CCV
54
which is kept open during non-driving time, as a mechanism for isolating the canister
16
from the atmosphere. However, the invention is not limited to this. Namely, the mechanism may be realized by an open/close valve which is kept closed during non-driving time.
In the above description, the CCV
54
shown in
FIG. 13
or the open/close valve which is a substitute for the CCV
54
is provided alone in the atmosphere introducing hole
32
of the canister
16
. However, the invention is not limited to this. Namely, a mechanical positive/negative pressure valve may be provided in the atmosphere introducing hole
32
in parallel with the CCV
54
or the open/close valve.
In the above description, the CCV
54
shown in
FIG. 13
, the open/close valve which is a substitute for the CCV
54
, or the combination of at least one of them and the positive/negative pressure valve is provided in the atmosphere introducing hole
32
of the canister
16
. However, the invention is not limited to this. Namely, any one of these mechanisms may be provided between the switching valve
36
and the booster pump
40
, and the filter
42
. According to such an arrangement, it is possible to measure the internal pressure in the canister
16
using the pump side sensor
48
even when the CCV
54
or the open/close valve is kept closed. Accordingly, when the above-mentioned arrangement is employed, it is possible to control the opening time of the CCV
54
or the open/close valve based on the measured value of the internal pressure in the canister
16
.
In the above description, the CCV
54
, the open/close valve, or the combination of at least one of them and the positive/negative pressure valve is provided only either in the atmosphere introducing hole
32
or immediately behind the filter
42
. However, the invention is not limited to this. Namely, one of these mechanisms may be provided both in the atmosphere introducing hole
32
and immediately behind the filter
42
. Further, when the above-mentioned mechanism is provided at both of the above-mentioned positions, the CCVs
54
may be provided at both of these positions, the open/close valves may be provided at both of these positions, or the CCV
54
may be provided at one of these positions, and the open/close valve may be provided at the other position.
In the eleventh embodiment, the CCV
54
serves as one example of part of “the isolated state switching mechanism” in the first aspect of the invention.
Next, a sixth embodiment according to the invention will be described with reference to
FIGS. 15
to
17
.
FIG. 15
is a diagram for describing a configuration of an evaporative fuel processing apparatus according to the embodiment. The configuration shown in
FIG. 15
is the same as that shown in
FIG. 1
, except for the following points. (1) The tank side pressure sensor
12
and the pump side pressure sensor
48
are removed, and a pressure sensor
56
is included instead of them. (2) A communicating passage
58
is provided which allows the bypass passage
38
and the fuel tank
10
to communicate with each other. (3) A three-way valve
60
is provided which connects the pressure sensor
56
to the communicating passage
58
.
The three-way valve
60
is an electromagnetic valve controlled by the ECU
50
(not shown in FIG.
15
). According to the three-way valve
60
, it is possible to selectively realize the following states (a pump side state and a tank side state). In the pump side state, the pressure in the bypass passage
38
is introduced to the space whose pressure is detected by the pressure sensor
56
. In the tank side state, the internal pressure in the fuel tank
10
is introduced to the space whose pressure is detected by the pressure sensor
56
. Hereafter, the pressure, which is detected by the pressure sensor
56
when the three-way valve
60
realizes the pump side state, will be referred to as a “pump side pressure Pp” and the pressure, which is detected by the pressure sensor
56
when the three-way valve
60
realizes the tank side state, will be referred to as a “tank side pressure Pt”.
According to the evaporative fuel processing apparatus in the embodiment, it is possible to allow the pressure sensor
56
to function in the same manner as the pump side pressure sensor
48
shown in
FIG. 1
by controlling the three-way valve
60
to be at the pump side state realizing position. Also, it is possible to allow the pressure sensor
56
to function in the same manner as the tank side pressure sensor
12
shown in
FIG. 1
by controlling the three-way valve
60
to be at the tank side state realizing position. Therefore, according to the apparatus in the embodiment, it is possible to realize the same function as in the first embodiment using the single pressure sensor
56
.
FIG. 16
is a flowchart of a routine which the ECU
50
performs so as to switch a state in which the pressure sensor
56
functions as the pump side pressure sensor
48
and a state in which the pressure sensor
56
functions as the tank side pressure sensor
12
. In the routine shown in
FIG. 16
, it is initially determined whether the tank side pressure Pt is required by the ECU
50
(step
190
).
As a result, when it is determined that the tank side pressure Pt is required, the three-way valve
60
is controlled so as to realize the tank side state (step
92
). Meanwhile, when it is determined that the tank side pressure Pt is not required, the three-way valve
60
is controlled so as to realize the pump side state (step
194
).
In the routine shown in
FIG. 16
, the pressure detection is performed using the pressure sensor
56
subsequent to the process in step
192
or step
194
(step
196
).
The ECU
50
recognizes the detected pressure as the tank side pressure Pt when the process in step
196
is performed via step
192
. Meanwhile, when the process in step
196
is performed via step
194
, the ECU recognizes the detected pressure as the pump side pressure Pp. Accordingly, the ECU
50
can detect both the pump side pressure Pp and the tank side pressure Pt as necessary, as well as in the first embodiment.
As mentioned above, the apparatus according to the first embodiment can correct the output from the pump side pressure sensor
48
by performing the routine shown in FIG.
5
. Likewise, the apparatus according to the embodiment can correct the output from the pressure sensor
56
by controlling the three-way valve
60
to be at the pump side state realizing position and the performing the routine shown in FIG.
5
. Therefore, according to the evaporative fuel processing apparatus in the embodiment, it is possible to detect both the pump side pressure Pp and the tank side pressure Pt using the pressure sensor
56
whose output is appropriately corrected using the atmospheric pressure as a reference pressure.
Next, details on the processes which the apparatus according to the embodiment performs so as to detect an abnormality in the pressure sensor
56
will be described.
FIG. 17
shows a flowchart of the control routine which the ECU
50
performs so as to detect an abnormality in the pressure sensor
56
. It is initially determined in this routine whether purge of the evaporative fuel is performed while the open/close valve
20
is kept open (step
200
).
As a result, when it is determined that the above-mentioned condition is not satisfied, the present process cycle is promptly completed. Meanwhile, when it is determined that purge is performed while the open/close valve
20
is kept open, the tank side pressure Pt is detected (step
202
). When detection of the tank side pressure Pt is required, the three-way valve
60
is controlled to be on the fuel tank
10
side in the process (
FIG. 16
) in step
192
. As a result, the ECU
50
can detect the output from the pressure sensor
56
as the tank side pressure Pt.
Detection of the tank side pressure Pt is performed for a predetermined time (step
204
). When the predetermined time has elapsed, it is determined whether a change has occurred in the output from the pressure sensor
56
(step
206
).
In the case where purge is performed while the open/close valve
20
is kept open, the internal pressure in the fuel tank
10
changes when the intake negative pressure is introduced to the tank
10
. Accordingly, when the pressure sensor
56
functions properly, a change is to occur in the output from the pressure sensor
56
in step
204
. Therefore, when it is determined in step
206
that there is no change in the output from the sensor, it is determined that there is an abnormality in the pressure sensor
56
(step
208
), afterwhich the present process cycle is completed.
Meanwhile, when it is determined in step
206
that there is a change in the output from the pressure sensor
56
, the atmospheric pressure is detected (step
210
). When detection of the atmospheric pressure is required, the three-way valve
60
is controlled to be on the booster pump
40
side in the process (
FIG. 16
) in step
194
. Also, step
210
is performed during execution of purge, that is, while the switching valve
36
is at the atmospheric state realizing position. In this case, since the atmospheric pressure is introduced to the space whose pressure is detected by the pressure sensor
56
, the ECU
50
can detect the atmospheric pressure based on the output from the sensor.
Detection of the atmospheric pressure is performed for a predetermined time (step
212
). When the predetermined time has elapsed, it is determined whether a change has occurred in the output from the output sensor
56
(step
214
).
When the pressure sensor
56
functions properly, the output from the sensor does not greatly change during detection of the atmospheric pressure. Accordingly, when it is determined in step
214
that there is a change in the output from the sensor, it can be determined that there is an abnormality in the pressure sensor
56
. In this case, it is determined in step
208
that there is an abnormality in the sensor, afterwhich the present process cycle is completed.
Meanwhile, when it is determined in step
214
that there is no change in the output from the sensor, it can be determined that the pressure sensor
56
functions properly. In this case, it is determined that the pressure sensor
56
is in the normal state, afterwhich the present process cycle is completed.
As described so far, according to the routine shown in
FIG. 17
, a fluctuating pressure and a non-fluctuating pressure are supplied to the pressure sensor
56
alternately, whereby it can be determined whether an appropriate output can be obtained in each of the states. Then, the apparatus according to the embodiment can accurately perform diagnosis of the state of the pressure sensor
56
based on the result of the determination.
In the routine shown in
FIG. 17
, the internal pressure in the fuel tank
10
during purge is supplied to the pressure sensor
56
as a fluctuating pressure. However, the pressure is not limited to this. Namely, the fluctuating pressure supplied to the pressure sensor
56
may be a discharge pressure of the booster pump
40
.
In the sixth embodiment, a configuration formed by making modifications (1) to (3) to the configuration shown in
FIG. 1
is employed. However, the configuration of the apparatus is not limited to this. Namely, the configuration of the evaporative fuel processing apparatus according to the embodiment may be a configuration formed by making modifications (1) to (3) to the configuration shown in
FIG. 13
or to the configuration described as a modified example thereof (the configuration in which the CCV
54
, the open/close valve or the combination of at least one of them and the positive/negative pressure valve is provided al least one of a position immediately behind the filter
42
and a position in the atmosphere introducing hole
32
). Also, the configuration may be a configuration formed by making the modifications (1) to (3) to any one of the configurations shown in the
FIGS. 6
to
8
.
In the sixth embodiment, “detection pressure switching mechanism” in claim
14
is realized when the ECU
50
performs the processes in steps
190
to
194
.
The control system (e.g., the electronic control units
50
) of the illustrated exemplary embodiments are implemented as one or more programmed general purpose computers. It will be appreciated by those skilled in the art that the controllers can be implemented using a single special purpose integrated circuit (e.g., ASIC) having a main or central processor section for overall, system-level control, and separate sections dedicated to performing various different specific computations, functions and other processes under control of the central processor section. The controller can be a plurality of separate dedicated or programmable integrated or other electronic circuits or devices (e.g., hardwired electronic or logic circuits such as discrete element circuits, or programmable logic devices such as PLDs, PLAs, PALs or the like). The controller can be implemented using a suitably programmed general purpose computer, e.g., a microprocessor, microcontroller or other processor device (CPU or MPU), either alone or in conjunction with one or more peripheral (e.g., integrated circuit) data and signal processing devices. In general, any device or assembly of devices on which a finite state machine capable of implementing the procedures described herein can be used as the control system. A distributed processing architecture can be used for maximum data/signal processing capability and speed.
While the invention has been described with reference to preferred exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments or constructions. On the contrary, the invention is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the invention are shown in various combinations and configurations, which are exemplary, other combinations and configurations, including more less or only a single element, are also within the spirit and scope of the invention.
Claims
- 1. An evaporative fuel processing apparatus comprising:a fuel tank; a canister which communicates with the fuel tank through a vapor passage; a purge passage which allows an intake passage of an internal combustion engine and the canister to communicate with each other; an open/close valve which opens or closes the vapor passage; an isolated state switching mechanism which makes the canister open to an atmosphere or isolates the canister from the atmosphere; a pressure adjusting mechanism which increases or decreases a pressure in the canister; a purge control valve which opens or closes the purge passage; and a control system which controls the open/close valve, the isolated state switching mechanism, the pressure adjusting mechanism and the purge control valve.
- 2. The evaporative fuel processing apparatus according to claim 1, wherein the control systemcloses a canister space which includes the canister and does not include the fuel tank by closing the open/close valve, isolating the canister from the atmosphere using the isolated state switching mechanism, and closing the purge control valve; adjusts an internal pressure in the closed canister space using the pressure adjusting mechanism; and performs a diagnosis on leakage in the canister space based on the adjusted internal pressure in the canister space.
- 3. The evaporative fuel processing apparatus according to claim 2, wherein, the control system prohibits opening of the open/close valve when it is determined that there is leakage in the canister space.
- 4. The evaporative fuel processing apparatus according to claim 2, wherein the control systemcloses an entire space including both of the canister and the fuel tank as a single space by opening the open/close valve, isolating the canister from the atmosphere using the isolated state switching mechanism, and closing the purge control valve, when it is determined that there is no leakage in the canister space; adjusts an internal pressure in the closed entire space using the pressure adjusting mechanism; and performs a diagnosis on leakage in the entire space based on the adjusted internal pressure in the entire space.
- 5. The evaporative fuel processing apparatus according to claim 2, wherein the control systemcloses an entire space including both of the canister and the fuel tank as a single space by opening the open/close valve, isolating the canister from the atmosphere using the isolated state switching mechanism, and closing the purge control valve after a completion of a leakage diagnosis for the canister space; adjusts an internal pressure in the closed entire space using the pressure adjusting mechanism; and performs a diagnosis on leakage in the entire space based on the adjusted internal pressure in the entire space.
- 6. The evaporative fuel processing apparatus according to claim 5, wherein the control systemstores a pressure which the internal pressure in the canister space has reached in a process of a leakage diagnosis as an abnormal time pressure when it is determined that there is leakage in the canister space; and sets a reference value used in a leakage diagnosis for the entire space based on the abnormal time pressure, and performs a leakage diagnosis for the entire space based on the set reference value when it is determined that there is leakage in the canister space.
- 7. The evaporative fuel processing apparatus according to claim 1, wherein the control systemdetects an internal pressure in the fuel tank when the open/close valve is kept closed; and performs a leakage diagnosis for the fuel tank based on the closed time tank internal pressure.
- 8. The evaporative fuel processing apparatus according to claim 1, wherein the control systemcloses the open/close valve when an internal combustion engine is stopped; openes the open/close valve when it becomes necessary to allow the fuel tank and the canister to communicate with each other while the internal combustion engine is stopped; and closes the open/close valve when it becomes unnecessary to allow the fuel tank and the canister to communicate with each other while the internal combustion engine is stopped, after the open/close valve is opened.
- 9. The evaporative fuel processing apparatus according to claim 8, wherein when it becomes necessary to allow the fuel tank and the canister to communicate with each other is when the leakage diagnosis is performed.
- 10. The evaporative fuel processing apparatus according to claim 1, wherein the control systemallows purge gas to flow from the canister to the intake passage by making the canister open to the atmosphere using the isolated state switching mechanism, and opening the purge control valve during operation of an internal combustion engine; detects concentration of the purge gas while the purge gas flows; and allows the purge gas to flow while the open/close valve is kept closed, and detects concentration of purge gas generated at this time as closed time concentration.
- 11. The evaporative fuel processing apparatus according to claim 1, wherein, the control systemallows purge gas to flow from the canister to the intake passage by making the canister open to the atmosphere using the isolated state switching mechanism, and opening the purge control valve during operation of an internal combustion engine; detects concentration of the purge gas while the purge gas flows; and maintains the open/close valve in a closed state while the concentration of the purge gas is equal to or higher than predetermined concentration.
- 12. The evaporative fuel processing means according to claim 1, wherein the control systemcontrols the isolated state switching mechanism such that the canister is isolated from the atmosphere when an internal pressure in the canister exceeds a predetermined reference value which is higher than the atmospheric pressure.
- 13. The evaporative fuel processing apparatus according to claim 12, wherein the control system controls the isolated state switching mechanism such the canister is isolated from the atmosphere after the internal pressure in the canister is increased by the pressure adjusting mechanism at least until the internal pressure decreases to a value equal to or lower than the predetermined reference value.
- 14. The evaporative fuel processing apparatus according to claim 1, wherein the control system includes a pressure sensor capable of selectively measuring an internal pressure in the canister which is made to be open to the atmosphere by the isolated state switching mechanism and an internal pressure in the canister which is isolated from the atmosphere by the isolated state switching mechanism.
- 15. The evaporative fuel processing apparatus according to claim 14, wherein the control system includes detection pressure switching mechanism for selectively introducing the internal pressure in the canister and an internal pressure in the fuel tank to a space whose pressure is detected by the pressure sensor.
- 16. The evaporative fuel processing apparatus according to claim 14, wherein the control systemforms a first state in which an atmospheric pressure is introduced to a space whose pressure is detected by the pressure sensor; forms a second state in which a fluctuating pressure is introduced to the space whose pressure is detected by the pressure sensor; and determines that the pressure sensor is in a normal state when a change in an output from the pressure sensor in the first state is smaller than a first reference value and a change in an output from the pressure sensor in the second state is larger than a second reference value.
- 17. A control method of an evaporative fuel processing apparatus comprising a fuel tank, a canister which communicates with the fuel tank through a vapor passage, a purge passage which allows an intake passage of an internal combustion engine and the canister to communicate with each other, an isolated state switching mechanism which makes the canister open to an atmosphere or which isolates the canister from the atmosphere, and a purge control valve which opens or closes the purge passage, comprising the steps of:closing the canister space which includes the canister and which does not include the fuel tank by closing an open/close valve provided in the vapor passage, isolating the canister from the atmosphere using the isolated state switching mechanism, and closing the purge control valve; adjusting an internal pressure in the closed canister space to increase or decrease; and performing a leakage diagnosis based on the internal pressure in the canister space adjusted by the canister space internal pressure adjusting mechanism.
- 18. The evaporative fuel processing method according to claim 17, further comprising by further comprising the step of:prohibiting opening of the open/close valve when it is determined that there is leakage in the canister space.
- 19. The evaporative fuel processing method according to claim 17, characterized by further comprising the steps ofclosing an entire space including both of the canister and the fuel tank as a single space by opening the open/close valve, isolating the canister from the atmosphere using the isolated state switching mechanism, and closing the purge control valve, when it is determined that there is no leakage in the canister space; adjusting an internal pressure in the closed entire space to increase or decrease; and performing a diagnosis on leakage in the entire space based on the adjusted internal pressure in the entire space.
- 20. The evaporative fuel processing method according to claim 17, characterized by further comprising the steps of:closing an entire space including both of the canister and the fuel tank as a single space by opening the open/close valve, isolating the canister from the atmosphere using the isolated state switching mechanism, and closing the purge control valve after a completion of a leakage diagnosis for the canister space; adjusting an internal pressure in the closed entire space to increase or decrease; and performing a diagnosis on leakage in the entire space based on the adjusted internal pressure in the entire space.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2002-167749 |
Jun 2002 |
JP |
|
US Referenced Citations (4)
Number |
Name |
Date |
Kind |
5592923 |
Machida |
Jan 1997 |
A |
5794599 |
Blumenstock |
Aug 1998 |
A |
5845625 |
Kidokoro et al. |
Dec 1998 |
A |
6223732 |
Isobe et al. |
May 2001 |
B1 |
Foreign Referenced Citations (1)
Number |
Date |
Country |
A 7-91330 |
Apr 1995 |
JP |