Information
-
Patent Grant
-
6829921
-
Patent Number
6,829,921
-
Date Filed
Tuesday, June 11, 200222 years ago
-
Date Issued
Tuesday, December 14, 200419 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 073 497
- 073 1181
- 073 498
- 073 40
- 073 168
-
International Classifications
-
Abstract
An abnormality detecting device for an evaporative fuel processing system is disclosed. The evaporative fuel processing system includes a fuel tank, a canister for trapping evaporative fuel generated in the fuel tank, a charging passage for connecting the fuel tank and the canister, a tank pressure regulating valve provided in the charging passage, a bypass passage bypassing the tank pressure regulating valve, a bypass valve provided in the bypass passage, and a pressure sensor provided in the fuel tank or in the charging passage at a position between the tank pressure regulating valve and the fuel tank. The pressure in the canister is reduced to a pressure which is lower than the atmospheric pressure in the condition where a valve closing command signal for the bypass valve is output. It is determined that the tank pressure regulating valve or the bypass valve is abnormal, when the pressure detected by the pressure sensor becomes equal to or less than a predetermined threshold during execution of the pressure reduction in the canister.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an abnormality detecting device for an evaporative fuel processing system for processing evaporative fuel generated in a fuel tank containing fuel to be supplied to an internal combustion engine.
An abnormality detecting device for determining an abnormality in an evaporative fuel processing system is known from Japanese Patent No. 2857656, for example. In this conventional abnormality detecting device, a negative pressure (a pressure lower than the atmospheric pressure) generated in an intake pipe of an internal combustion engine is introduced into the evaporative fuel processing system to reduce the pressure in the evaporative fuel processing system, and the abnormality in the evaporative fuel processing system is determined according to the pressure in this system after the above pressure reduction. The evaporative fuel processing system includes a fuel tank, a canister for temporarily storing evaporative fuel generated in the fuel tank, and a charging passage for connecting the fuel tank and the canister.
According to the above abnormality detecting device, a leak in the fuel tank or the canister can be detected. However, the failure of an on-off valve provided in the charging passage cannot be detected.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide an abnormality detecting device for an evaporative fuel processing system, which can detect the failure of the on-off valve provided in the charging passage for connecting the fuel tank and the canister.
In order to attain the above object, the present invention provides an abnormality detecting device for an evaporative fuel processing system. The evaporative fuel processing system includes a fuel tank (
9
), a canister (
33
) for trapping evaporative fuel generated in the fuel tank (
9
), a charging passage (
31
) for connecting the fuel tank (
9
) and the canister (
33
), a tank pressure regulating valve (
35
) provided in the charging passage (
31
), a bypass passage (
31
a
) bypassing the tank pressure regulating valve (
35
), a bypass valve (
36
) provided in the bypass passage (
31
a
), and a pressure sensor (
15
) provided in the fuel tank (
9
) or in the charging passage (
31
) at a position between the tank pressure regulating valve (
35
) and the fuel tank (
9
). The abnormality detecting device includes pressure reducing means and diagnosing means. The pressure reducing means reduces a pressure in the canister (
33
) to a pressure which is lower than the atmospheric pressure in the condition where a valve closing command signal for the bypass valve (
36
) is output. The diagnosing means determines that the tank pressure regulating valve (
35
) or the bypass valve (
36
) is abnormal when the pressure detected by the pressure sensor (
15
) becomes equal to or less than a predetermined threshold (the atmospheric pressure PA—DBPSOPN) during execution of the pressure reduction by the pressure reducing means.
With this configuration, the pressure in the canister is reduced in the condition where the valve closing command signal for the bypass valve is output, and when the pressure detected by the pressure sensor becomes equal to or less than the predetermined threshold during this pressure reduction, it is determined that the tank pressure regulating valve or the bypass valve is abnormal. If the bypass valve is normally closed in the condition where the valve closing command signal for the bypass valve is output, and the tank pressure regulating valve is normal, the pressure reduction in the canister has no influence on the pressure sensor output. In other words, if the pressure detected by the pressure sensor becomes equal to or less than the predetermined threshold during the pressure reduction in the canister, the tank pressure regulating valve or the bypass valve remains open. Accordingly, when the pressure detected by the pressure sensor becomes equal to or less than the predetermined threshold during the pressure reduction in the canister, it can be determined that the tank pressure regulating valve or the bypass valve is abnormal.
Preferably, the tank pressure regulating valve (
35
) includes a positive-pressure valve opened when the pressure in the fuel tank (
9
) is higher than the atmospheric pressure by a first predetermined pressure or more, and a negative-pressure valve opened when the pressure in the fuel tank (
9
) is lower than the pressure in the canister (
33
) by a second predetermined pressure or more. The diagnosing means preferably determines that the bypass valve (
36
) has failed or that the tank pressure regulating valve (
35
) has been improperly mounted, when the pressure (PTANK) detected by the pressure sensor (
15
) becomes equal to or less than the predetermined threshold (PA—DPBSOPN) during execution of the pressure reduction by the pressure reducing means.
With this configuration, in the case where the tank pressure regulating valve is a two-way valve including a positive-pressure valve and a negative-pressure valve, it is determined that the bypass valve has failed or that the tank pressure regulating valve has been improperly mounted, when the pressure detected by the pressure sensor becomes equal to or less than the predetermined threshold during the pressure reduction in the canister. That is, if a first port of the tank pressure regulating valve to be connected to the fuel tank is improperly connected to the canister, and a second port of the tank pressure regulating valve to be connected to the canister is improperly connected to the fuel tank, the negative-pressure valve opens due to the pressure reduction in the canister, resulting in a reduction in the pressure sensor output. Accordingly, when the pressure sensor output becomes equal to or less than the predetermined threshold during the pressure reduction in the canister, it can be determined that the tank pressure regulating valve has been improperly mounted or that the bypass valve has failed.
Preferably, the diagnosing means executes the determination when a predetermined waiting period (TSDEC
1
) has elapsed from the time of starting the pressure reduction by the pressure reducing means.
Preferably, the predetermined threshold is set to a value which is lower than the atmospheric pressure by a predetermined determination pressure.
Preferably, the diagnosing means determines that the tank pressure regulating valve (
35
) or the bypass valve (
36
) is abnormal, when the condition where the pressure (PTANK) detected by the pressure sensor (
15
) is less than or equal to the predetermined threshold (PA—DPBSOPN) continues for a predetermined determination period (CBPSCHK).
The present invention further provides an abnormality detecting device for an evaporative fuel processing system. The evaporative fuel processing system includes a fuel tank (
9
), a canister (
33
) for trapping evaporative fuel generated in the fuel tank (
9
), a charging passage (
31
) for connecting the fuel tank (
9
) and the canister (
33
), an on-off valve (
36
) provided in the charging passage (
31
) for opening and closing the charging passage (
31
), and a pressure sensor (
15
) provided in the fuel tank (
9
) or in the charging passage (
31
) at a position between the on-off valve (
36
) and the fuel tank (
9
). The abnormality detecting device includes pressure reducing means and diagnosing means. The pressure reducing means reduces a pressure in the canister (
33
) to a pressure which is lower than the atmospheric pressure in the condition where a valve closing command signal for the on-off valve (
36
) is output. The diagnosing means determines that the on-off valve (
36
) has failed, when the pressure (PTANK) detected by the pressure sensor (
15
) becomes equal to or less than a predetermined threshold (PA—DPBSOPN) during execution of the pressure reduction by the pressure reducing means.
With this configuration, the pressure in the canister is reduced in the condition where the valve closing command signal for the on-off valve is output, and when the pressure detected by the pressure sensor becomes equal to or less than the predetermined threshold during this pressure reduction, it is determined that the on-off valve has failed. If the on-off valve is normally closed in the condition where the valve closing command signal for the on-off valve is output, the pressure reduction in the canister has no influence on the pressure sensor output. In other words, if the pressure detected by the pressure sensor becomes equal to or less than the predetermined threshold during the pressure reduction in the canister, it is determined that a valve opening failure of the on-off valve has occurred such that the on-off valve is not closed in spite of supplying the valve closing command signal to the on-off valve. Accordingly, such a valve opening failure of the on-off valve can be detected.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a schematic diagram showing the configuration of an evaporative fuel processing system and a control system for an internal combustion engine according to a preferred embodiment of the present invention.
FIG. 2
is a schematic diagram showing the configuration of an external abnormality diagnosis apparatus and illustrating the connection of the external abnormality diagnosis apparatus and the control system for the internal combustion engine shown in FIG.
1
.
FIG. 3
is a flowchart of an abnormality diagnosis process.
FIG. 4
is a flowchart showing a process for determining an execution condition of the abnormality diagnosis.
FIG. 5
is a flowchart of an open-to-atmosphere process.
FIG. 6
is a flowchart of a short pressure reduction process.
FIGS. 7A
to
7
D are time charts for illustrating an abnormality diagnosis method by the process of FIG.
6
.
FIG. 8
is a flowchart of a pressure recovery process.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A preferred embodiment of the present invention will now be described with reference to the drawings.
FIG. 1
is a schematic diagram showing the configuration of an evaporative fuel processing system and a control system for an internal combustion engine according to a preferred embodiment of the present invention. Referring to
FIG. 1
, reference numeral
1
denotes an internal combustion engine (which will be hereinafter referred to simply as “engine”) having a plurality of (e.g., four) cylinders. The engine
1
is provided with an intake pipe
2
, in which a throttle valve
3
is mounted. A throttle valve opening (THA) sensor
4
is connected to the throttle valve
3
. The throttle valve opening sensor
4
outputs an electrical signal corresponding to the opening angle of the throttle valve
3
and supplies the electrical signal to an electronic control unit (which will be hereinafter referred to as “ECU”)
5
for controlling the engine
1
.
Fuel injection valves
6
, only one of which is shown, are inserted into the intake pipe
2
at locations intermediate between the cylinder block of the engine
1
and the throttle valve
3
and slightly upstream of the respective intake valves (not shown). The fuel injection valves
6
are connected via a fuel supply pipe
7
to a fuel tank
9
. The fuel supply pipe
7
is provided with a fuel pump
8
. The fuel tank
9
has a fuel inlet
10
for use in refueling, and a filler cap
11
is mounted on the fuel inlet
10
.
Each fuel injection valve
6
is electrically connected to the ECU
5
, and its valve opening period is controlled by a signal from the ECU
5
. The intake pipe
2
is provided with an intake pipe absolute pressure (PBA) sensor
13
for detecting an absolute pressure PBA in the intake pipe
2
and an intake air temperature (TA) sensor
14
for detecting an air temperature TA (ambient temperature) in the intake pipe
2
at positions downstream of the throttle valve
3
.
An engine rotational speed (NE) sensor
17
for detecting an engine rotational speed is disposed near the outer periphery of a camshaft or a crankshaft (both not shown) of the engine
1
. The engine rotational speed sensor
17
outputs a pulse (TDC signal pulse) at a given crank angle per 180° rotation of the crankshaft of the engine
1
. There are also provided an engine coolant temperature sensor
18
for detecting a coolant temperature TW of the engine
1
and an oxygen concentration sensor (which will be hereinafter referred to as “LAF sensor”)
19
for detecting an oxygen concentration in exhaust gases from the engine
1
. Detection signals from these sensors
13
to
19
are supplied to the ECU
5
. The LAF sensor
19
functions as a wide-region air-fuel ratio sensor which outputs a signal substantially proportional to an oxygen concentration in exhaust gases (proportional to an air-fuel ratio of air-fuel mixture supplied to the engine
1
).
An atmospheric pressure sensor
41
for detecting an atmospheric pressure PA and a vehicle speed sensor
42
for detecting a running speed (vehicle speed) VP of a vehicle on which the engine
1
is mounted are also connected to the ECU
5
, and detection signals from these sensors
41
and
42
are supplied to the ECU
5
.
The fuel tank
9
is connected through a charging passage
31
to a canister
33
. The canister
33
is connected through a purging passage
32
to the intake pipe
2
at a position downstream of the throttle valve
3
.
The charging passage
31
is provided with a two-way valve
35
. The two-way valve
35
consists of a positive-pressure valve and a negative pressure valve. The positive pressure valve opens when the pressure in the fuel tank
9
is higher than the atmospheric pressure by a first predetermined pressure (e.g., 2.7 kPa (20 mmHg)) or more. The negative-pressure valve opens when the pressure in the fuel tank
9
is lower than the pressure in the canister
33
by a second predetermined pressure or more.
The charging passage
31
is branched to form a bypass passage
31
a bypassing the two-way valve
35
. The bypass passage
31
a is provided with a bypass valve (on-off valve)
36
. The bypass valve
36
is a normally closed solenoid valve, which is opened and closed during execution of abnormality diagnosis to be hereinafter described. The operation of the bypass valve
36
is controlled by the ECU
5
.
The charging passage
31
is further provided with a pressure sensor
15
at a position between the two-way valve
35
and the fuel tank
9
. A detection signal output from the pressure sensor
15
is supplied to the ECU
5
. The output PTANK from the pressure sensor
15
takes a value equal to the pressure in the fuel tank
9
(the pressure detected by the pressure sensor
15
will be hereinafter referred to as “tank pressure”) in a steady state where the pressures in the canister
33
and in the fuel tank
9
are stable. On the other hand, the tank pressure PTANK takes a value which is different from the actual tank pressure in a transient state where the pressure in the fuel tank
9
is being reduced, for example.
The canister
33
contains active carbon for adsorbing the evaporative fuel in the fuel tank
9
. The canister
33
communicates with the atmosphere through a vent passage
37
.
The vent passage
37
is provided with a vent shut valve (on-off valve)
38
. The vent shut valve
38
is a solenoid valve, and its operation is controlled by the ECU
5
. The vent shut valve
38
is opened in refueling or during purging of evaporative fuel from the canister
33
to the intake pipe
2
. Further, the vent shut valve
38
is opened and closed during execution of the abnormality diagnosis to be hereinafter described.
The purging passage
32
connected between the canister
33
and the intake pipe
2
is provided with a purge control valve
34
. The purge control valve
34
is a solenoid valve whose opening degree can be continuously controlled by changing the on-off duty ratio of a control signal. The control signal of the purge control valve
34
is supplied from the ECU
5
, and the operation of the purge control valve
34
is controlled by the ECU
5
.
The fuel tank
9
, the charging passage
31
, the bypass passage
31
a
, the canister
33
, the purging passage
32
, the two-way valve
35
, the bypass valve
36
, the purge control valve
34
, the vent passage
37
, and the vent shut valve
38
constitutes an evaporative fuel processing system
40
.
When a large amount of evaporative fuel is generated in refueling into the fuel tank
9
, the two-way valve
35
opens to make the canister
33
store (trap) the evaporative fuel. In a predetermined operating condition of the engine
1
, the duty control of the purge control valve
34
is performed to supply a suitable amount of evaporative fuel from the canister
33
to the intake pipe
2
.
The ECU
5
includes an input circuit having various functions including a function of shaping the waveforms of input signals from the various sensors, a function of correcting the voltage levels of the input signals to a predetermined level, and a function of converting analog signal values into digital signal values, a central processing unit (which will be hereinafter referred to as “CPU”), a memory circuit preliminarily storing various operational programs to be executed by the CPU and for storing the results of computation or the like by the CPU, and an output circuit for supplying drive signals to the fuel injection valves
6
, the purge control valve
34
, the bypass valve
36
, and the vent shut valve
38
.
For example, the CPU of the ECU
5
controls the amount of fuel to be supplied to the engine
1
and the duty control of the purge control valve
34
according to output signals from the various sensors including the engine rotational speed sensor
17
, the intake pipe absolute pressure sensor
13
, and the engine coolant temperature sensor
18
.
The ECU
5
is connected to a connector
51
. As shown in
FIG. 2
, the ECU
5
is connectable through the connector
51
to an external abnormality diagnosis apparatus
70
. The abnormality diagnosis apparatus
70
includes an electronic control unit
61
for executing abnormality diagnosis (this control unit will be hereinafter referred to as “abnormality diagnosis ECU”), an input section
62
for inputting necessary information from an operator and instructing the ECU
5
to execute the abnormality diagnosis, and a display section
63
for displaying the result of the abnormality diagnosis. The abnormality diagnosis ECU
61
includes a central processing unit (CPU), a memory circuit preliminarily storing various operational programs to be executed by the CPU and for storing the results of computation or the like by the CPU, and an interface circuit for exchanging information between the abnormality diagnosis ECU
61
and the engine control ECU
5
.
In executing the abnormality diagnosis, the abnormality diagnosis ECU
61
is connected through the connector
51
to the engine control ECU
5
to supply drive command signals for the bypass valve
36
, the purge control valve
34
, and the vent shut valve
38
to the engine control ECU
5
. The engine control ECU
5
supplies detection signals from the various sensors to the abnormality diagnosis ECU
61
. Accordingly, the abnormality diagnosis for the evaporative fuel processing system
40
can be executed by the external abnormality diagnosis apparatus
70
through the ECU
5
.
FIG. 3
is a flowchart showing a program for executing the abnormality diagnosis by the external abnormality diagnosis apparatus
70
. This program is executed by the CPU of the abnormality diagnosis ECU
61
at predetermined time periods (e.g., 80 msec).
In step S
11
, the execution condition determination process shown in
FIG. 4
is executed. When the execution condition of the abnormality diagnosis is satisfied, a monitor execution flag FEVPLKM and an execution condition flag FMCND
90
F are both set to “1”. When the execution condition becomes dissatisfied after the execution condition is once satisfied, the execution condition flag FMCND
90
F is returned to “0”, but the monitor execution flag FEVPLKM is maintained at “1” until the pressure recovery process shown in
FIG. 8
is completed.
In step S
12
, it is determined whether or not the monitor execution flag FEVPLKM is “1”. If FEVPLKM is “0”, normal control is executed (step S
13
). That is, a valve closing command signal for the bypass valve (BPV)
36
, a valve opening command signal for the vent shut valve (VSV)
38
, and a duty control signal for the purge control valve (PCV)
34
are output. Thereafter, a downcount timer TPATMDEC, which is referred to in the open-to-atmosphere process (step S
21
and
FIG. 5
) described below, is set to a predetermined time period TPATMOFD (e.g., 30 sec) and then started (step S
14
). Further in step S
14
, a open-to-atmosphere flag FPATMDEC is set to “1”. When the open-to-atmosphere flag FPATMDEC is set to “1”, the open-to-atmosphere process is executed.
In step S
15
, a short pressure reduction flag FSTKDEC and a pressure recovery flag FPCNCL are both set to “0”, and this program ends. When the short pressure reduction flag FSTKDEC is set to “1”, the short pressure reduction process shown in
FIG. 6
is executed. When the pressure recovery flag FPCNCL is set to “1”, the pressure recovery process shown in
FIG. 8
is executed.
When the monitor execution flag FEVPLKM is set to “1”, the program proceeds from step S
12
to step S
16
, in which it is determined whether or not the execution condition flag FMCND
90
F is “1”. Since the answer to step S
16
is normally affirmative (YES), the program proceeds to step S
21
, in which the open-to-atmosphere process is executed. Thereafter, the short pressure reduction process shown in
FIG. 6
is executed (step S
22
), and it is determined whether or not the pressure recovery flag FPCNCL is “1” (step S
23
). The pressure recovery flag FPCNCL is set to “1” at the time the short pressure reduction process is completed in step S
22
. If the answer to step S
23
is negative (NO), a downcount timer TPTCNCL, which is referred to in the pressure recovery process of step S
25
, is set to a predetermined time period TCNCLOF (e.g., 10 sec) and then started (step S
24
), and the program proceeds to step S
25
. When the pressure recovery flag FPCNCL is set to “1”, the program proceeds from step S
23
directly to step S
25
.
In step S
25
, the pressure recovery process shown in
FIG. 8
is executed. Thereafter, this program ends.
When the execution condition of the abnormality diagnosis becomes dissatisfied, the execution condition flag FMCND
90
F is returned to “0”, but the monitor execution flag FEVPLKM is maintained at “1”. Accordingly, the program proceeds from step S
12
through step S
16
to step S
25
to execute the pressure recovery process. After completing the pressure recovery process, the monitor execution flag FEVPLKM is returned to “0” to restore the normal control.
FIG. 4
is a flowchart showing the execution condition determination process executed in step S
11
shown in FIG.
3
.
In step S
41
, it is determined whether or not the engine
1
is stopped. If the engine
1
is stopped, it is determined that the execution condition is not satisfied, and a downcount timer TDLYOFF, which is referred to in step S
50
, is set to a predetermined time period TMDLYOFF (e.g., 5 sec) and then started (step S
49
). Thereafter, the execution condition flag FMCND
90
F is set to “0” (step S
51
), and this process ends.
If the engine
1
is in operation, it is determined whether or not a diagnosis permission flag FOFFBORD is “1” (step S
42
). The flag FOFFBORD is set to “1” when the abnormality diagnosis by the external abnormality diagnosis apparatus
70
is permitted by other process (not shown).
If FOFFBORD is “1”, it is determined whether or not a diagnosis execution command flag FGO
90
F is “1” (step S
43
). The flag FGO
90
F is set to “1” when the execution of the abnormality diagnosis is commanded by another process not shown.
If FGO
90
F is “1”, it is determined whether or not the value of an upcount timer TO
1
ACR for measuring the time after completion of starting of the engine
1
is greater than or equal to a predetermined time period TMOFACR (e.g., 10 sec) (step S
44
).
If TO
1
ACR is greater than or equal to TMOFACR, it is determined whether or not a purge permission flag FPGACT is “1” (step S
45
). The flag FPGACT is set to “1” when it is permitted to purge the evaporative fuel stored in the canister
33
to the intake pipe
2
.
If FPGACT is “1”, it is determined whether or not a battery voltage VB is higher than a predetermined voltage VBEVCKLO (e.g., 8 V) (step S
46
). If VB is greater than VBEVCKLO, it is determined whether or not the intake air temperature TA is in a range between a predetermined upper limit TAOFCNDH (e.g., 100° C.) and a predetermined lower limit TAOFCNDL (e.g., 0° C.), and it is also determined whether or not the engine coolant temperature TW is in a range between a predetermined upper limit TWOFCNDH (e.g., 100° C.) and a predetermined lower limit TWOFCNDL (e.g., 0° C.) (step S
47
).
If the intake air temperature TA is in the range between TAOFCNDL and TAOFCNDH, and the engine coolant temperature TW is in the range between TWOFCNDL and TWOFCNDH, it is determined whether or not the vehicle speed VP is “0” (step S
48
).
If the answer to any one of steps S
42
to S
48
is negative (NO), it is determined that the execution condition is not satisfied, and the program proceeds to step S
49
. If the answers to all of steps S
42
to S
48
are affirmative (YES), it is determined whether or not the value of the timer TDLYOFF started in step S
49
is “0” (step S
50
). If TDLYOFF is greater than “0”, the program proceeds to step S
51
. If TDLYOFF is “0”, it is determined that the execution condition is satisfied, so that the execution condition flag FMCND
90
F is set to “1” (step S
52
) and the monitor execution flag FEVPLKM is set to “1” (step S
53
). Then, this process ends.
FIG. 5
is a flowchart showing the open-to-atmosphere process executed in step S
21
shown in FIG.
3
.
In step S
60
, it is determined whether or not the open-to-atmosphere flag FPATMDEC is “1”. Initially, the flag FPATMDEC is “1”. Accordingly, the program proceeds to step S
61
to output a valve opening command signal for the bypass valve
36
, a valve opening command signal for the vent shut valve
38
, and a valve closing command signal for the purge control valve
34
. In step S
62
, it is determined whether or not the value of the timer TPATMDEC started in step S
14
shown in
FIG. 3
is “0”. Initially, TPATMDEC is greater than “0”, so that this process ends immediately.
If TPATMDEC is “0” in step S
62
, the open-to-atmosphere flag FPATMDEC is set to “0” and the short pressure reduction flag FSTKDEC is set to “1” (step S
63
). By setting the open-to-atmosphere flag FPATMDEC to “0”, the answer to step S
60
in the subsequent executions becomes negative (NO), so that the open-to-atmosphere process is not substantially executed.
In step S
64
, a predetermined limit pressure PTLMT, which is referred to in the short pressure reduction process, is set to a predetermined value PTLMTS
1
(e.g., a pressure value which is lower than the atmospheric pressure by about 6 kPa (45 mmHg)). Further, a downcount timer TSEVPDEC, which is referred to in the short pressure reduction process, is set to a predetermined time period TSDEC
1
(e.g., about 3 to 5 sec) and then started. Thereafter, a present output PTANK from the pressure sensor
15
is stored as a memory value PATMTKM (step S
65
), and this process ends.
FIG. 6
is a flowchart showing the short pressure reduction process executed in step S
22
shown in FIG.
3
.
In step S
151
, it is determined whether or not the short pressure reduction flag FSTKDEC is “1”. If FSTKDEC is “0”, this process ends immediately. That is, the short pressure reduction process is substantially executed when the short pressure reduction flag FSTKDEC is set to “1”.
When the short pressure reduction flag FSTKDEC is set to “1” in step S
63
shown in
FIG. 5
, the program proceeds from step S
151
to step S
153
to output a valve closing command signal for the bypass valve
36
, a valve closing command signal for the vent shut valve
38
, and a duty control signal (constant duty ratio) for the purge control valve
34
. Accordingly, the negative pressure in the intake pipe
2
is introduced into the evaporative fuel processing system
40
. Since the valve closing command signals for the bypass valve
36
and the vent shut valve
38
are output, the pressure in the canister
33
is reduced as far as these valves
36
and
38
are normally (properly) operated.
In step S
155
, it is determined whether or not the pressure sensor output PTANK is lower than the predetermined limit pressure PTLMT. Normally, the answer to step S
155
is negative (NO), so that the program proceeds to step S
156
to determine whether or not the value of the downcount timer TSEVPDEC is “0”. Initially, TSEVPDEC is greater than “0”, so that a downcounter CBPSOPN is set to a predetermined value CBPSCHK (e.g., 2) (step S
157
), and this process ends.
If PTANK is less than PTLMT or TSEVPDEC is “0”, the program proceeds to step S
162
to determine whether or not the difference (PATMTKM—PTANK) between the memory value PATMTKM stored in step S
65
shown in FIG.
5
and the pressure sensor output PTANK, is greater than or equal to a predetermined pressure difference DBPSOPN (e.g., 0.67 kPa (5 mmHg)). If the answer to step S
162
is negative (NO), this indicates that the pressure PTANK detected by the pressure sensor
15
has not decreased. Accordingly, it is determined that the bypass valve
36
is normally (properly) closed and no valve opening failure has occurred in the two-way valve
35
. Then, the program proceeds to step S
168
.
In step S
168
, the short pressure reduction flag FSTKDEC is returned to “0” and the pressure recovery flag FPCNCL is set to “1”. Then, this process ends.
If the answer to step S
162
is affirmative (YES), that is, if the pressure sensor output PTANK has decreased by a value which is equal to or greater than the predetermined pressure difference DBPSOPN in the short pressure reduction process, it is determined whether or not the value of the counter CBPSOPN is “0” (step S
163
). Initially, CBPSOPN is greater than “0”, so that the value of the counter CBPSOPN is decremented by “1” (step S
164
), and this process ends.
If the condition where the pressure difference (PATMTKM—PTANK) is greater than or equal to DBPSOPN continues and the value of the counter CBPSOPN becomes “0”, it is determined that a valve opening failure has occurred in the bypass valve
36
or the two-way valve
35
(i.e., the bypass valve
36
or the two-way valve
35
is in an abnormal condition where it remains open and does not close) or that the two-way valve
35
is improperly mounted. In this case, a valve opening abnormality flag FFSD
90
F
2
is set to “1” (step S
165
), and the program proceeds to step S
168
.
In the case that the two-way valve
35
is properly mounted, the positive-pressure valve in the two-way valve
35
opens when the pressure in the fuel tank
9
is higher than the atmospheric pressure by the first predetermined pressure or more, and the negative-pressure valve in the two-way valve
35
opens when the pressure in the fuel tank
9
is lower than the pressure in the canister
33
by the second predetermined pressure or more. Accordingly, the two-way valve
35
in its properly mounted condition does not open during the short pressure reduction process. However, if the two-way valve
35
is reversely mounted by mistake, that is, if a port of the two-way valve
35
to be connected to the fuel tank
9
is improperly connected to the canister
33
and the other port of the two-way valve
35
to be connected to the canister
33
is improperly connected to the fuel tank
9
, the negative-pressure valve opens in the short pressure reduction process. Accordingly, such a possibility of improper mounting of the two-way valve
35
is considered.
FIGS. 7A
to
7
D are time charts for illustrating the abnormality determination in the short pressure reduction process. When both the bypass valve
36
and the two-way valve
35
are normal, the pressure sensor output PTANK is kept near the memory value PATMTKM and does not decrease as shown by the solid line in FIG.
7
D. In the case of the valve opening failure of the bypass valve
36
or the two-way valve
35
, or the improper mounting of the two-way valve
35
, the pressure sensor output PTANK decreases as shown by the broken line in
FIG. 7D
, thereby detecting the abnormality of the valve
35
or
36
.
FIG. 8
is a flowchart showing the pressure recovery process executed in step S
25
shown in FIG.
3
.
In step S
421
, it is determined whether or not the pressure recovery flag FPCNCL is “1”. If FPCNCL is “0”, it is determined whether or not the execution condition flag FMCND
90
F is “1”. If FMCND
90
F is “1”, which indicates that the execution condition of the abnormality diagnosis is satisfied, this process ends immediately. On the other hand, if the pressure recovery flag FPCNCL is “1” or the execution condition is not satisfied (FMCND
90
F=0), the program proceeds to step S
423
to output a valve opening command signal for the bypass valve
36
, a valve opening command signal for the vent shut valve
38
, and a valve closing command signal for the purge control valve
34
.
Thereafter, it is determined whether or not the value of the timer TPTCNCL started in step S
24
shown in
FIG. 3
is “0” (step S
424
). Initially, TPTCNCL is greater than “0”, so that this process ends immediately. If TPTCNCL is “0”, both the pressure recovery flag FPCNCL and the monitor execution flag FEVPLKM are returned to “0” (step S
425
). As a result, the program of
FIG. 3
proceeds from step S
12
to step S
13
to restore the normal control.
According to this preferred embodiment as mentioned above, the short pressure reduction process for reducing the pressure in the canister
33
to a pressure lower than the atmospheric pressure is executed in the condition where a valve closing command signal for the bypass valve
36
is output, and when the pressure difference (PATMTKM—PTANK) between the pressure PTANK detected by the pressure sensor
15
and the memory value PATMTKM becomes greater than or equal to the predetermined pressure difference DBPSOPN, it is determined that the valve opening failure of the two-way valve
35
or the bypass valve
36
has occurred, or the two-way valve
35
has been improperly mounted. Accordingly, the abnormality of the bypass valve
36
or the two-way valve
35
can be quickly detected.
The memory value PATMTKM is a pressure sensor output value after the open-to-atmosphere process, and this value is therefore substantially equal to the atmospheric pressure. Accordingly, the determination in step S
162
shown in
FIG. 6
is equivalent to the determination whether or not the pressure sensor output PTANK is less than or equal to a predetermined threshold that is defined as a pressure obtained by subtracting the predetermined pressure difference DBPSOPN from the atmospheric pressure PA.
In this preferred embodiment, the engine
1
, the intake pipe
2
, the purging passage
32
, the purge control valve
34
, the ECU
5
, and the ECU
61
constitute the pressure reducing means, and the ECU
61
constitutes the diagnosing means. More specifically, step S
63
in FIG.
5
and steps S
153
and S
156
in
FIG. 6
correspond to a part of the pressure reducing means, and steps S
162
to S
165
in
FIG. 6
correspond to the diagnosing means.
It should be noted that the present invention is not limited to the above preferred embodiment, but various modifications may be made. For example, in the above preferred embodiment, the two-way valve
35
is provided in the charging passage
31
and the bypass valve
36
is provided in the bypass passage
31
a bypassing the two-way valve
35
. Alternatively, only an electromagnetic on-off valve similar to the bypass valve
36
may be provided in the charging passage
31
in place of the two-way valve
35
. With this configuration, the duty control of the purge control valve
34
is performed in the condition where the electromagnetic on-off valve provided in the charging passage
31
and the vent shut valve
38
are closed, thereby introducing the negative pressure into the canister
33
. During the pressure reduction, the abnormality diagnosis according to the pressure sensor output PTANK is executed like by a method similar to that of the above preferred embodiment.
Further, the above-mentioned abnormality diagnosis method is applicable also to an evaporative fuel processing system having two bypass passages bypassing a two-way valve, wherein each bypass passage is provided with an electromagnetic on-off valve, as described in Japanese Patent No. 2857656. With this configuration, the pressure in the canister is reduced in the condition where valve closing command signals for the two electromagnetic on-off valves (bypass valve and puff-loss valve) are output, and when the pressure detected by the pressure sensor becomes less than or equal to a predetermined threshold during this pressure reduction, it is determined that the two-way valve (tank pressure regulating valve) or at least one of the two on-off valves is abnormal.
Further, the abnormality diagnosis process (
FIG. 3
) may be executed by the CPU of the ECU
5
without using the external abnormality diagnosis apparatus
70
.
Further, the pressure sensor
15
may be mounted in the fuel tank
9
.
The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are, therefore, to be embraced therein.
Claims
- 1. An abnormality detecting device for an evaporative fuel processing system including:a fuel tank; a canister for trapping evaporative fuel generated in said fuel tank; a charging passage for connecting said fuel tank and said canister; a tank pressure regulating valve provided in said charging passage; a bypass passage bypassing said tank pressure regulating valve; a bypass valve provided in said bypass passage; and a pressure sensor provided in said fuel tank or in said charging passage at a position between said tank pressure regulating valve and said fuel tank, said abnormality detecting device comprising: pressure reducing means for reducing a pressure in said canister to a pressure which is lower than an atmospheric pressure in the condition where a valve closing command signal for said bypass valve is output; and diagnosing means for determining that said tank pressure regulating valve or said bypass valve is abnormal when the pressure detected by said pressure sensor becomes equal to or less than a predetermined threshold during execution of the pressure reduction by said pressure reducing means.
- 2. An abnormality detecting device according to claim 1, whereinsaid tank pressure regulating valve comprises a positive-pressure valve which opens when the pressure in said fuel tank is higher than the atmospheric pressure by a first predetermined pressure or more, and a negative-pressure valve which opens when the pressure in said fuel tank is lower than the pressure in said canister by a second predetermined pressure or more; and said diagnosing means determines that said bypass valve has failed or that said tank pressure regulating valve has been improperly mounted, when the pressure detected by said pressure sensor becomes equal to or less than the predetermined threshold during execution of the pressure reduction by said pressure reducing means.
- 3. An abnormality detecting device according to claim 1, wherein said diagnosing means executes the determination when a predetermined waiting period has elapsed from the time of starting the pressure reduction by said pressure reducing means.
- 4. An abnormality detecting device according to claim 1, wherein the predetermined threshold is set to a value which is lower than the atmospheric pressure by a predetermined determination pressure.
- 5. An abnormality detecting device according to claim 1, wherein said diagnosing means determines that said tank pressure regulating valve or said bypass valve is abnormal, when the condition where the pressure detected by said pressure sensor is less than or equal to the predetermined threshold continues for a predetermined determination period.
- 6. An abnormality detecting device for an evaporative fuel processing system including:a fuel tank; a canister for trapping evaporative fuel generated in said fuel tank; a charging passage for connecting said fuel tank and said canister; an on-off valve provided in said charging passage for opening and closing said charging passage; and a pressure sensor provided in said fuel tank or in said charging passage at a position between said on-off valve and said fuel tank, said abnormality detecting device comprising: pressure reducing means for reducing a pressure in said canister to a pressure which is lower than an atmospheric pressure in the condition where a valve closing command signal for said on-off valve is output; and diagnosing means for determining that said on-off valve has failed, when the pressure detected by said pressure sensor becomes equal to or less than a predetermined threshold during execution of the pressure reduction by said pressure reducing means.
- 7. An abnormality detecting device for an evaporative fuel processing system including:a fuel tank; a canister for trapping evaporative fuel generated in said fuel tank; a charging passage for connecting said fuel tank and said canister; a tank pressure regulating valve provided in said charging passage; a bypass passage bypassing said tank pressure regulating valve; a bypass valve provided in said bypass passage; and a pressure sensor provided in said fuel tank or in said charging passage at a position between said tank pressure regulating valve and said fuel tank, said abnormality detecting device comprising: a pressure reducing module for reducing a pressure in said canister to a pressure which is lower than the atmospheric pressure in the condition where a valve closing command signal for said bypass valve is output; and a diagnosing module for determining that said tank pressure regulating valve or said bypass valve is abnormal when the pressure detected by said pressure sensor becomes equal to or less than a predetermined threshold during execution of the pressure reduction by said pressure reducing module.
- 8. An abnormality detecting device according to claim 7, whereinsaid tank pressure regulating valve comprises a positive-pressure valve which opens when the pressure in said fuel tank is higher than the atmospheric pressure by a first predetermined pressure or more, and a negative-pressure valve which opens when the pressure in said fuel tank is lower than the pressure in said canister by a second predetermined pressure or more; and said diagnosing module determines that said bypass valve has failed or that said tank pressure regulating valve has been improperly mounted, when the pressure detected by said pressure sensor becomes equal to or less than the predetermined threshold during execution of the pressure reduction by said pressure reducing module.
- 9. An abnormality detecting device according to claim 7, wherein said diagnosing module executes the determination when a predetermined waiting period has elapsed from the time of starting the pressure reduction by said pressure reducing module.
- 10. An abnormality detecting device according to claim 7, wherein the predetermined threshold is set to a value which is lower than the atmospheric pressure by a predetermined determination pressure.
- 11. An abnormality detecting device according to claim 7, wherein said diagnosing module determines that said tank pressure regulating valve or said bypass valve is abnormal, when the condition where the pressure detected by said pressure sensor is less than or equal to the predetermined threshold continues for a predetermined determination period.
- 12. An abnormality detecting device for an evaporative fuel processing system including:a fuel tank; a canister for trapping evaporative fuel generated in said fuel tank; a charging passage for connecting said fuel tank and said canister; an on-off valve provided in said charging passage for opening and closing said charging passage; and a pressure sensor provided in said fuel tank or in said charging passage at a position between said on-off valve and said fuel tank, said abnormality detecting device comprising: a pressure reducing module for reducing a pressure in said canister to a pressure lower than an atmospheric pressure in the condition where a valve closing command signal for said on-off valve is output; and a diagnosing module for determining that said on-off valve has failed, when the pressure detected by said pressure sensor becomes equal to or less than a predetermined threshold during execution of the pressure reduction by said pressure reducing module.
- 13. A computer program for causing a computer to carry out an abnormality detecting method for an evaporative fuel processing system including:a fuel tank; a canister for trapping evaporative fuel generated in said fuel tank; a charging passage for connecting said fuel tank and said canister; a tank pressure regulating valve provided in said charging passage; a bypass passage bypassing said tank pressure regulating valve; a bypass valve provided in said bypass passage; and a pressure sensor provided in said fuel tank or in said charging passage at a position between said tank pressure regulating valve and said fuel tank, said abnormality detecting method comprising the steps of: a) reducing a pressure in said canister to a pressure which is lower than the atmospheric pressure in the condition where a valve closing command signal for said bypass valve is output; b) detecting a pressure by said pressure sensor; and c) determining that said tank pressure regulating valve or said bypass valve is abnormal, when the detected pressure becomes equal to or less than a predetermined threshold during execution of the pressure reduction in said canister.
- 14. A computer program according to claim 13, whereinsaid tank pressure regulating valve comprises a positive-pressure valve which opens when the pressure in said fuel tank is higher than the atmospheric pressure by a first predetermined pressure or more, and a negative-pressure valve which opens when the pressure in said fuel tank is lower than the pressure in said canister by a second predetermined pressure or more; and it is determined that said bypass valve has failed or that said tank pressure regulating valve has been improperly mounted, when the pressure detected by said pressure sensor becomes equal to or less than the predetermined threshold during execution of the pressure reduction.
- 15. A computer program according to claim 13, wherein the determination is executed when a predetermined waiting period has elapsed from the time of starting the pressure reduction by said pressure reducing means.
- 16. A computer program according to claim 13, wherein the predetermined threshold is set to a value which is lower than the atmospheric pressure by a predetermined determination pressure.
- 17. A computer program according to claim 13, wherein it is determined that said tank pressure regulating valve or said bypass valve is abnormal, when the condition where the pressure detected by said pressure sensor is less than or equal to the predetermined threshold continues for a predetermined determination period.
- 18. A computer program for causing a computer to carry out an abnormality detecting method for an evaporative fuel processing system including:a fuel tank; a canister for trapping evaporative fuel generated in said fuel tank; a charging passage for connecting said fuel tank and said canister; an on-off valve provided in said charging passage for opening and closing said charging passage; and a pressure sensor provided in said fuel tank or in said charging passage at a position between said on-off valve and said fuel tank, said abnormality detecting method comprising the steps of: a) reducing a pressure in said canister to a pressure lower than an atmospheric pressure in the condition where a valve closing command signal for said on-off valve is output; b) detecting a pressure by said pressure sensor; and c) determining that said on-off valve has failed, when the detected pressure becomes equal to or less than a predetermined threshold during execution of the pressure reduction in said canister.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2001-176732 |
Jun 2001 |
JP |
|
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
5739421 |
Iochi et al. |
Apr 1998 |
A |
6227037 |
Kawamura et al. |
May 2001 |
B1 |
6487892 |
Ito et al. |
Dec 2002 |
B1 |
Foreign Referenced Citations (1)
Number |
Date |
Country |
2857656 |
Dec 1998 |
JP |