JP2004308493A - Evaporated fuel treatment device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaporated fuel treatment device for an internal combustion engine capable of determining whether a leakage occurs in a system or not simply. <P>SOLUTION: A vapor passage 20 communicating with a fuel tank 10 is provided. A sealing valve 28 controlling opening of the vapor passage 20 for the atmosphere is provided. A tank internal pressure sensor 12 detecting tank internal pressure Ptnk is provided. After the sealing valve 28 is closed and a condition for sealing the fuel tank 10 is maintained, whether tank internal pressure Ptnk is a value close to the atmospheric pressure or not is determined. If frequency by which tank internal pressure Ptnk is the value close to the atmospheric pressure when the tank is sealed exceeds a predetermined determination value, it is determined that leakage failure occurs in the system. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel vapor processing apparatus for an internal combustion engine, and more particularly to a fuel vapor processing apparatus for preventing fuel vapor generated inside a fuel tank from being released to the atmosphere.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-294052, an evaporative fuel processing apparatus including a canister communicating with a fuel tank has been disclosed. This device includes an on-off valve for sealing the fuel tank in a path communicating the fuel tank and the canister. The on-off valve is kept closed to shut off the fuel tank while the internal combustion engine is stopped. After the internal combustion engine is stopped inside the fuel tank, phenomena such as generation of further evaporated fuel due to residual heat and liquefaction of the evaporated fuel due to cooling occur. Therefore, if there is no leak in the fuel tank, the tank internal pressure may deviate from a value near the atmospheric pressure while the internal combustion engine is stopped.
[0003]
The above-described conventional device has a function of determining whether or not the fuel tank has leaked by utilizing the fact that the tank internal pressure at the time of sealing indicates the above change. That is, this device measures the internal pressure of the tank before the on-off valve is opened when the internal combustion engine is started, and when the internal pressure of the tank deviates from a value near the atmospheric pressure, no leakage occurs in the fuel tank. Judge. According to such a method, when starting the internal combustion engine, it is possible to accurately determine that no leak has occurred in the fuel tank without performing any special processing.
[0004]
[Patent Document 1]
JP 2001-294052 A [Patent Document 2]
Japanese Patent Laid-Open Publication No. Hei 8-261703
[Problems to be solved by the invention]
When the fuel tank is closed, the tank internal pressure converges to a value near the atmospheric pressure if there is a leak in the fuel tank. On the other hand, even if there is no leak in the fuel tank, the internal pressure of the sealed fuel tank may be close to the atmospheric pressure. Therefore, in the above-described conventional apparatus, when the internal pressure of the tank is near the atmospheric pressure when the internal combustion engine is started, it cannot be determined that the fuel tank is normal or that the fuel tank is leaking.
[0006]
Therefore, when the internal pressure of the tank at the time of startup is near the atmospheric pressure, this device suspends the determination of a leak failure, and then introduces a negative pressure into the fuel tank by a so-called negative pressure method. It is decided to determine the presence or absence of a leak failure by a method of checking the change in the tank internal pressure. For this reason, in the above-described conventional apparatus, when the internal pressure of the tank is close to the atmospheric pressure when the internal combustion engine is started, it is necessary to perform complicated processing to detect a leakage failure of the system.
[0007]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and provides an evaporative fuel processing apparatus for an internal combustion engine that can always determine whether or not a leakage failure has occurred in a system by a simple process. The purpose is to:
[0008]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided an evaporative fuel processing apparatus for an internal combustion engine,
A fuel tank,
A vapor passage communicating with the fuel tank;
A valve mechanism for controlling the atmosphere passage of the vapor passage;
Tank internal pressure detecting means for detecting tank internal pressure,
Tank sealing means for closing the valve mechanism to seal the fuel tank,
Internal pressure determining means for determining whether or not the tank internal pressure when the fuel tank is closed is near atmospheric pressure;
Leakage occurrence determination means that determines the occurrence of leakage when the frequency of the tank internal pressure at the time of sealing is near the atmospheric pressure exceeds the determination value,
It is characterized by having.
[0009]
A second invention is a fuel vapor treatment device for an internal combustion engine,
A fuel tank,
A vapor passage communicating with the fuel tank;
A valve mechanism for controlling the atmosphere passage of the vapor passage;
Tank internal pressure detecting means for detecting tank internal pressure,
Tank sealing means for closing the valve mechanism to seal the fuel tank,
Internal pressure determining means for determining whether or not the tank internal pressure when the fuel tank is closed is near atmospheric pressure;
Leakage occurrence determination means for determining the occurrence of leakage when the number of consecutive times that the tank internal pressure at the time of sealing is determined to be a value near the atmospheric pressure exceeds the determination value,
It is characterized by having.
[0010]
Further, a third invention is the first or the second invention, wherein
The tank sealing unit includes a stop-time sealing unit that maintains the valve mechanism in a closed state while the internal combustion engine is stopped,
The internal pressure determining means measures the tank internal pressure at the time of the closing while the valve mechanism is closed by the stop-time closing means.
[0011]
In a fourth aspect based on the third aspect, the internal pressure determination means measures the internal pressure of the tank at the time of the hermetic period after the start of the internal combustion engine is requested and before the valve mechanism opens. Features.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Elements common to the drawings are denoted by the same reference numerals, and redundant description will be omitted.
[0013]
Embodiment 1 FIG.
[Explanation of device configuration]
FIG. 1 is a diagram for explaining the configuration of the evaporated fuel processing apparatus according to Embodiment 1 of the present invention. As shown in FIG. 1, the device of the present embodiment includes a fuel tank 10. The fuel tank 10 is provided with a tank internal pressure sensor 12 for measuring the tank internal pressure Ptnk. The tank internal pressure sensor 12 is a sensor that detects the tank internal pressure Ptnk as a relative pressure with respect to the atmospheric pressure and generates an output according to the detected value. A liquid level sensor 14 for detecting the liquid level of the fuel is disposed inside the fuel tank 10.
[0014]
A vapor passage 20 is connected to the fuel tank 10 via ROVs (Roll Over Valves) 16 and 18. The vapor passage 20 has a closing valve unit 24 in the middle thereof, and communicates with a canister 26 at an end thereof. The closing valve unit 24 includes a closing valve 28 and a relief valve 30. The closing valve 28 is a normally-closed type solenoid valve that closes in a non-energized state and is opened when a drive signal is supplied from the outside. The relief valve 30 opens when the pressure on the fuel tank 10 side is sufficiently higher than the pressure on the canister 26 side, and the reverse direction relief valve that opens when the pressure on the fuel tank 10 side is sufficiently higher than the pressure on the canister 26 side. And a mechanical two-way check valve. The valve opening pressure of the relief valve 30 is set to, for example, about 20 kPa in the forward direction and about 15 kPa in the reverse direction.
[0015]
The canister 26 has a purge hole 32. A purge passage 34 communicates with the purge hole 32. The purge passage 34 is provided with a purge VSV (Vacuum Switching Valve) 36 in the middle thereof, and communicates at its end with an intake passage 38 of the internal combustion engine. The intake passage 38 of the internal combustion engine is provided with an air filter 40, an air flow meter 42, a throttle valve 44, and the like. The purge passage 34 communicates with the intake passage 38 downstream of the throttle valve 44.
[0016]
Inside the canister 26, a vapor suction section 46 and a buffer section 48 are provided. The canister 26 is provided with an atmospheric hole 50. Both the vapor adsorption section 46 and the buffer section 48 are filled with activated carbon. The activated carbon of the vapor adsorbing section 46 can adsorb the vaporized fuel contained therein when the gas flowing through the vapor passage 20 blows through the atmospheric holes 50. On the other hand, the activated carbon in the buffer section 48 can prevent a sudden change in the vapor concentration in the purge gas flowing out of the purge hole 32.
[0017]
An atmosphere passage 54 communicates with the atmosphere hole 50 of the canister 26 via a negative pressure pump module 52. The air passage 54 has an air filter 56 in the middle thereof. The end of the atmosphere passage 54 is open to the atmosphere in the vicinity of a fuel supply port 58 of the fuel tank 10.
[0018]
The negative pressure pump module 52 includes a negative pressure pump and a switching valve (neither is shown). The switching valve can selectively realize an open-to-atmosphere state in which the air hole 50 of the canister 26 is communicated with the air passage 54 and a negative pressure introduction state in which the air hole 50 communicates with the suction hole of the negative pressure pump. It is a valve mechanism. According to the negative pressure pump module 52, the inside of the canister 26 can be opened to the atmosphere by setting the switching valve to the atmosphere opening state. Further, by operating the negative pressure pump with the switching valve in a negative pressure introducing state, a negative pressure can be introduced into the canister 26. In this state, the negative pressure pump is stopped, so that the air hole 50 in the canister 26 can be reduced. Can be closed.
[0019]
As shown in FIG. 1, the fuel vapor processing apparatus according to the present embodiment includes an ECU 60. The ECU 60 has a built-in soak timer for counting the elapsed time while the vehicle is parked. The ECU 60 is connected with a lid switch 62 and a lid opener open / close switch 64 together with the tank internal pressure sensor 12, the closing valve 28, or the negative pressure pump module 52 described above. In addition, a lid manual opening / closing device 66 is connected to the lid opener opening / closing switch 64 by a wire.
[0020]
The lid switch 62 is a switch for transmitting to the ECU 60 a request to open a lid (cover of the vehicle body) 68 that covers the fuel filler 58. When the lid switch 62 is operated, the ECU 60 supplies a signal to the lid opener open / close switch 64 to request the lid 68 to open. The lid opener opening / closing switch 64 is a mechanism for maintaining the lid 68 in a closed state, and releases the closed state of the lid 68 when the above signal is received from the ECU 60 or when an opening operation is performed on the lid manual opening / closing device 66. I do.
[0021]
[Description of device operation]
Next, the operation of the evaporated fuel processing apparatus according to the present embodiment will be described.
The evaporated fuel processing apparatus of the present embodiment maintains the closing valve 28 in a closed state while the vehicle is parked. When the closing valve 28 is closed, the fuel tank 10 is disconnected from the canister 26 as long as the relief valve 30 is closed. Therefore, as long as the tank internal pressure Ptnk does not exceed the positive opening pressure (20 kPa) of the relief valve 30, the fuel vapor is not newly adsorbed to the canister 26 while the vehicle is parked. Further, as long as the tank internal pressure Ptnk does not fall below the reverse valve opening pressure (−15 kPa) of the relief valve 30, no air is sucked into the fuel tank 10 while the vehicle is parked.
[0022]
Immediately after the stop of the internal combustion engine, the fuel in the fuel tank 10 evaporates due to the effect of residual heat or the like, and as a result, the tank internal pressure Ptnk may increase. If the closing valve 28 is open at this time, the fuel vapor flows out of the fuel tank 10 into the atmosphere. After a certain period of time has elapsed since the internal combustion engine was stopped, the temperature in the fuel tank 10 is reduced by natural cooling. If the closing valve 28 is open at this time, air is sucked into the fuel tank 10 as the tank internal pressure Ptnk decreases. When the air is sucked into the fuel tank 10, when the temperature rises again, the tank internal pressure Ptnk is likely to be increased, and the fuel vapor in the fuel tank 10 is likely to flow out to the atmosphere.
[0023]
On the other hand, as described above, if the shut-off valve 28 is closed while the internal combustion engine 10 is stopped, the evaporated fuel does not flow out of the fuel tank 10 into the atmosphere immediately after the stop, and After a while, no air is sucked into the fuel tank 10. Therefore, according to the system of the present embodiment, even if the temperature of the fuel tank 10 changes while the internal combustion engine 10 is stopped, it is possible to reliably prevent the emission characteristics from being deteriorated as a result.
[0024]
If the closing valve 28 is maintained in the closed state while the internal combustion engine 10 is stopped, the tank internal pressure Ptnk increases while the fuel vapor is further generated, unless the fuel tank 10 leaks, and As the temperature of the fuel tank 10 decreases, the tank internal pressure Ptnk decreases. On the other hand, when the fuel tank 10 is leaking, the tank internal pressure Ptnk eventually converges to a value near the atmospheric pressure even if the closing valve 28 is closed. Therefore, if the tank internal pressure Ptnk converges to a value sufficiently distant from the atmospheric pressure after the internal combustion engine is stopped, it can be determined that the fuel tank 10 has not leaked.
[0025]
However, the tank internal pressure Ptnk in a state where the shut-off valve 28 is closed may become a value near the atmospheric pressure even if the fuel tank 10 does not leak. For this reason, even if the tank internal pressure Ptnk converges to a value near the atmospheric pressure while the internal combustion engine 10 is stopped, it cannot be concluded immediately from the fact that the fuel tank 10 is leaking.
[0026]
However, when the shut-off valve 28 is closed and there is no leak in the fuel tank 10, the tank internal pressure Ptnk usually converges to a value different from the atmospheric pressure, and the internal pressure Ptnk becomes a value close to the atmospheric pressure. It is rare to converge to. Therefore, when the tank internal pressure Ptnk after the stop of the internal combustion engine 10 frequently converges to a value near the atmospheric pressure, it is possible to estimate the occurrence of leakage of the fuel tank 10 from the phenomenon. Therefore, in the device according to the present embodiment, when the situation in which the tank internal pressure Ptnk converges to a value near the atmospheric pressure after the stop of the internal combustion engine 10 occurs repeatedly and continuously, leakage occurs in the system including the fuel tank 10. It is decided to judge.
[0027]
FIG. 2 shows a flowchart of a control routine executed by the ECU 60 to realize the above functions.
In the routine shown in FIG. 2, first, it is determined whether a precondition for executing this routine is satisfied (step 100).
Here, for example, after the start of the internal combustion engine, the closing valve 28 has not been opened yet, and the determination process of the leak detection has not been executed yet, and further, the driving state of the vehicle is stable. , Etc. are determined as the above preconditions.
[0028]
If it is determined in step 100 that the precondition is not satisfied, the current processing cycle ends. On the other hand, when it is determined that the precondition is satisfied, the tank internal pressure Ptnk is measured (step 102).
[0029]
Next, it is determined whether the tank internal pressure Ptnk measured in step 102 is a value near the atmospheric pressure, specifically, whether −α ≦ Ptnk ≦ β is satisfied (step 104).
-Α and β are a negative pressure side limit value and a positive pressure side limit value, respectively, at which the tank internal pressure Ptnk may reach even under a situation where the system is leaking. Therefore, when the tank internal pressure Ptnk does not satisfy the above condition, it can be determined that no leak failure has occurred. On the other hand, if the condition is not satisfied, it can be determined that the possibility that a leak failure has occurred cannot be denied.
[0030]
In the routine shown in FIG. 2, when it is determined in step 104 that -α ≦ Ptnk ≦ β is not established, that is, it is determined that the tank internal pressure Ptnk is greatly deviated from the atmospheric pressure when the internal combustion engine is started. In this case, after that, a normality determination is made for the leak check (step 106), and then a counter clearing process is performed (step 108), and then the current processing cycle is ended. The counter cleared here is a counter for counting the number of consecutive times that the condition of step 104 is satisfied.
[0031]
On the other hand, if it is determined in step 104 that −α ≦ Ptnk ≦ β is satisfied, that is, if it is determined that the tank internal pressure Ptnk is a value near the atmospheric pressure when the internal combustion engine is started, first, this condition is satisfied. A counter for counting the number of consecutive establishments is counted up (step 110).
[0032]
Next, it is determined whether or not the count value of the counter exceeds a predetermined determination value (step 112).
According to the processing of steps 100 to 110 described above, each time the internal combustion engine is started, it is determined whether or not the tank internal pressure Ptnk is near atmospheric pressure, and it is determined whether Ptnk is near atmospheric pressure. The number is counted in a counter. In the system of the present embodiment, the tank internal pressure Ptnk immediately after the start of the internal combustion engine 10 is usually a value deviating from the atmospheric pressure. Therefore, when the phenomenon that Ptnk becomes a value near the atmospheric pressure is repeatedly and continuously established, it is reasonable to judge that the system is leaking.
[0033]
The predetermined determination value used in step 112 is a value experimentally determined as a determination value for accurately determining the presence or absence of a leakage failure. Therefore, when it is determined that the count value of the counter does not exceed the determination value, it can be determined that the state is not yet in a state where it is possible to determine the occurrence of leakage. In this case, after the result of the current leak detection is put on hold (step 114), the processing cycle ends.
[0034]
On the other hand, when it is determined in step 112 that the count value of the counter exceeds the predetermined determination value, it can be determined that it is reasonable to recognize the occurrence of leakage. In this case, thereafter, after the abnormality is determined with respect to the leak detection (step 116), the current processing cycle is ended.
[0035]
As described above, according to the device of the present embodiment, when the phenomenon that the tank internal pressure Ptnk becomes a value close to the atmospheric pressure appears continuously at the time of starting the internal combustion engine, the occurrence of the leak failure is directly determined from the phenomenon. You can judge. For this reason, according to the device of the present embodiment, it is not only possible to determine the absence of a leak failure, but also to accurately determine the occurrence of a leak failure by merely looking at the tank internal pressure Ptnk when the internal combustion engine is started. it can.
[0036]
In the first embodiment, the closing valve 28 corresponds to the “valve mechanism” in the second invention, and the tank internal pressure sensor 12 corresponds to “tank pressure detecting means” in the second invention. At the same time, the ECU 60 closes the closing valve 28 while the internal combustion engine is stopped, so that the “tank sealing means” in the second invention executes the processing of step 104 described above. The “internal pressure judging means” of the second invention executes the processing of steps 112 and 116 to realize the “leakage judging means” of the second invention.
[0037]
Embodiment 2 FIG.
Next, a second embodiment of the present invention will be described with reference to FIG.
The device of the present embodiment can be realized by causing the ECU 60 to execute a routine shown in FIG. 3 to be described later instead of the routine shown in FIG. 2 in the device of the above-described first embodiment.
[0038]
The device of the first embodiment described above determines the occurrence of leakage when the number of consecutive times that the tank internal pressure Ptnk becomes a value near the atmospheric pressure at the time of starting the internal combustion engine exceeds a predetermined determination value. Therefore, according to this device, if the tank internal pressure Ptnk at the time of starting the internal combustion engine may deviate from the vicinity of the atmospheric pressure due to some influence before the continuous number of times reaches the determination value, it is determined that a leakage failure has occurred. May be delayed.
[0039]
The internal combustion engine is usually started after a certain period of time has elapsed after its operation has been stopped, but it is not uncommon for the internal combustion engine to be restarted immediately after the stop. If the internal combustion engine is restarted immediately after the stop in a situation where a large amount of evaporative fuel is generated inside the fuel tank 10, even if the system has a leak, the restart of the restart may be performed. Immediately thereafter, a situation may occur in which the tank internal pressure Ptnk deviating from the value close to the atmospheric pressure is detected. In the device of the first embodiment described above, when such a restart is performed, a situation may occur in which the detection time of the leak failure is delayed.
[0040]
As will be described later, the device of the present embodiment determines the occurrence of a leak failure based on the “frequency” at which the tank internal pressure Ptnk at the time of starting the internal combustion engine becomes a value near the atmospheric pressure. Since it is based on the “frequency”, even if a situation occurs in which the tank internal pressure Ptnk at the start of the internal combustion engine is detected as a value near the atmospheric pressure in the process up to the determination of the occurrence of the leak failure, as a result, The time at which occurrence is determined is not greatly delayed. Therefore, according to the device of the present embodiment, it is possible to detect the occurrence of a leak failure more quickly than in the device of the first embodiment.
[0041]
FIG. 3 shows a flowchart of a control routine executed by the ECU 60 in the present embodiment to realize the above functions. In FIG. 3, steps that are the same as the steps shown in FIG. 2 are given the same reference numerals, and descriptions thereof are omitted or simplified.
[0042]
In the routine shown in FIG. 3, the total number of leak detections performed is counted as a denominator, while the number of times that the tank internal pressure Ptnk is determined to be near atmospheric pressure is counted as a numerator, and the ratio between the two is taken. , The frequency at which the tank internal pressure Ptnk becomes a value near the atmospheric pressure is calculated.
In this routine, when it is determined that the condition of step 100 is satisfied, first, a process of counting up a denominator counter is performed to count the total number of leak detections executed (step 120).
[0043]
In the routine shown in FIG. 3, when it is determined in step 104 that the tank internal pressure Ptnk satisfies -α ≦ Ptnk ≦ β, that is, it is determined that the tank internal pressure Ptnk at the time of starting is a value near the atmospheric pressure. In this case, the molecular counter is counted up (step 122).
[0044]
Next, it is determined whether or not the value of the denominator counted up in step 120 has reached a predetermined lower limit (for example, 10) (step 123).
If it is determined in step 123 that the count value of the denominator has not yet reached the lower limit value, the process of step 114 is performed to reserve the determination of leak detection.
[0045]
On the other hand, if it is determined in step 123 that the count value of the denominator has already reached the lower limit, then the ratio of the count values counted up in steps 120 and 122, that is, the tank internal pressure Ptnk Is calculated as a value near the atmospheric pressure (numerator / denominator), and it is determined whether or not the calculated value exceeds a predetermined determination value (step 124).
[0046]
If it is determined in step 124 that (numerator / denominator)> determination value does not hold, the process of step 114 is executed to reserve the determination of leak detection. On the other hand, if it is determined that the above condition is satisfied, the process of step 116 is performed to determine whether an abnormality has occurred.
[0047]
In the routine shown in FIG. 3, following the processing in step 100, 106, 114 or 116, it is determined whether or not the count value of the denominator counter has reached a predetermined upper limit (step 126).
If it is determined that the denominator has reached the upper limit, both the count value of the denominator counter and the count value of the numerator counter are cleared (step 128).
On the other hand, if it is determined that the denominator has not yet reached the upper limit, the current processing cycle ends without clearing those count values.
[0048]
As described above, according to the routine shown in FIG. 3, it is possible to calculate the frequency at which the tank internal pressure Ptnk becomes a value near the atmospheric pressure when the internal combustion engine 10 is started, and determine the occurrence of a leak when the frequency is high. it can. According to such processing, even if the tank internal pressure Ptnk immediately after the start deviates from the value close to the atmospheric pressure for some reason under the situation where the system is leaking, the occurrence of the leak is determined. Can be prevented from being greatly delayed. Therefore, according to the device of the present embodiment, it is possible to more quickly determine the occurrence of a leak failure as compared with the device of the first embodiment.
[0049]
In the first embodiment, the closing valve 28 corresponds to the “valve mechanism” in the first invention, and the tank internal pressure sensor 12 corresponds to “tank pressure detecting means” in the first invention. At the same time, the ECU 60 closes the closing valve 28 while the internal combustion engine is stopped, so that the “tank sealing means” in the first invention executes the processing of step 104 described above. The “internal pressure judging means” in the first embodiment executes the processing of steps 124 and 116, thereby realizing the “leakage judging means” in the first invention.
[0050]
By the way, in the above-described first or second embodiment, it is determined whether or not the tank internal pressure Ptnk is a value close to the atmospheric pressure at the time of starting the internal combustion engine in order to increase the detection accuracy of the leakage failure. The invention is not limited to this. That is, whether or not the tank internal pressure Ptnk is close to the atmospheric pressure is determined by determining whether the shut-off valve 28 is closed, some time has passed since the closing, and the state inside the fuel tank 10 is stable. In such a situation, the determination may be made at a time other than when the internal combustion engine is started.
[0051]
Further, in the first or second embodiment described above, the fuel tank 10 is hermetically sealed using the closing valve 28, but the present invention is not limited to this. That is, the present invention is also applicable to, for example, an on-off valve (CCV) provided in an atmospheric hole of a canister, or a system capable of closing the fuel tank 10 by closing a purge VSV.
[0052]
【The invention's effect】
Since the present invention is configured as described above, it has the following effects.
According to the first aspect, when the internal pressure of the sealed fuel tank is detected as a value near the atmospheric pressure with high frequency, it is possible to detect the occurrence of leakage. According to such a method, even when the tank internal pressure becomes a value near the atmospheric pressure, the occurrence of a leakage failure can be accurately detected without performing complicated processing.
[0053]
According to the second aspect, when the internal pressure of the sealed fuel tank is continuously detected as a value near the atmospheric pressure for a long period of time, it is possible to detect the occurrence of leakage. According to such a method, even when the tank internal pressure becomes a value near the atmospheric pressure, the occurrence of a leakage failure can be accurately detected without performing complicated processing.
[0054]
According to the third aspect, the tank internal pressure can be measured in a situation where the internal combustion engine is stopped and the thermal environment surrounding the fuel tank is stable. For this reason, according to the present invention, it is possible to prevent the tank internal pressure from being measured in a situation where a large amount of fuel vapor is generated. When the leakage is very small, the tank internal pressure may not be close to the atmospheric pressure under a situation where a large amount of fuel vapor is generated. According to the present invention, it is possible to avoid measuring the tank internal pressure in such a situation, so that a minute leak can be detected with high accuracy.
[0055]
According to the fourth aspect, the tank internal pressure can be measured when the internal combustion engine is started. The internal combustion engine is often started after a sufficiently long time has elapsed since the last stop. The difference between the tank internal pressure when a leak occurs and the normal tank internal pressure tends to be evident as the time during which the fuel tank is kept in a sealed state is increased. Therefore, according to the present invention, it is possible to accurately detect the occurrence of a system leak.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a configuration of a first embodiment of the present invention.
FIG. 2 is a flowchart of a control routine executed in the device according to the first embodiment of the present invention.
FIG. 3 is a flowchart of a control routine executed in a second embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 10 Fuel tank 12 Tank internal pressure sensor 20 Vapor passage 26 Canister 28 Sealing valve 60 ECU (Electronic Control Unit)
Ptnk tank internal pressure

Claims (4)

A fuel tank,
A vapor passage communicating with the fuel tank;
A valve mechanism for controlling the atmosphere passage of the vapor passage;
Tank internal pressure detecting means for detecting tank internal pressure,
Tank sealing means for closing the valve mechanism to seal the fuel tank,
Internal pressure determining means for determining whether or not the tank internal pressure when the fuel tank is closed is near atmospheric pressure;
Leakage occurrence determining means for determining the occurrence of leakage when the frequency of the tank internal pressure at the time of the hermetic seal is near the atmospheric pressure exceeds the determination value,
An evaporative fuel processing apparatus for an internal combustion engine, comprising: A fuel tank,
A vapor passage communicating with the fuel tank;
A valve mechanism for controlling the atmosphere passage of the vapor passage;
Tank internal pressure detecting means for detecting tank internal pressure,
Tank sealing means for closing the valve mechanism to seal the fuel tank,
Internal pressure determining means for determining whether or not the tank internal pressure when the fuel tank is closed is near atmospheric pressure;
Leakage occurrence determination means for determining the occurrence of leakage when the number of consecutive times that the tank internal pressure at the time of sealing is determined to be a value near the atmospheric pressure exceeds the determination value,
An evaporative fuel processing apparatus for an internal combustion engine, comprising: The tank sealing means includes a stop-time sealing means for maintaining the valve mechanism in a closed state while the internal combustion engine is stopped,
3. The evaporative fuel processing apparatus for an internal combustion engine according to claim 1, wherein the internal pressure determination unit measures the tank internal pressure at the time of the closing while the valve mechanism is closed by the stop time closing unit. . 4. The evaporative fuel processing of an internal combustion engine according to claim 3, wherein the internal pressure determination means measures the internal pressure of the tank at the time of the closed state after the start of the internal combustion engine is requested and before the valve mechanism is opened. apparatus.

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