JP2006144601A - Evaporated fuel processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaporated fuel processing device mounted on a vehicle which sufficiently suppresses emission of evaporated fuel generated inside an intake passage into the atmosphere after stopping an internal combustion engine. <P>SOLUTION: The device is provided with a canister 14 for adsorbing evaporated fuel generated in a fuel tank 10. The canister 14 communicates to an intake passage 26 through the medium of a purge passage 22. The purge passage 22 is provided with a purge VSV 24. A throttle valve 30 is arranged in the intake passage 26. While closing a throttle valve 30 for a set period after stopping an internal combustion engine, a purge control valve 24 is opened so as to make the canister 14 absorb evaporated fuel in the intake passage 26. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an evaporative fuel processing apparatus, and more particularly to an evaporative fuel processing apparatus for processing evaporative fuel generated in the vicinity of an internal combustion engine mounted on a vehicle without releasing it into the atmosphere.

  Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 11-182359, an evaporative fuel processing apparatus for processing evaporative fuel generated in a vehicle is known. The conventional apparatus includes a canister for adsorbing evaporated fuel generated inside the fuel tank. The canister is connected to the intake passage of the internal combustion engine via a purge passage. Further, the purge passage incorporates a control valve for controlling the conduction state of the passage.

  The gas in the fuel tank is pushed out when refueling, for example, and flows into the canister. At this time, the canister adsorbs the evaporated fuel in the gas and causes only air to flow out from the atmosphere hole to the atmosphere. For this reason, according to the conventional apparatus, it is possible to effectively prevent the evaporated fuel in the fuel tank from being released to the atmosphere.

  Further, the above-described conventional apparatus appropriately opens the control valve during operation of the internal combustion engine. When the control valve opens, intake negative pressure is introduced to the canister. As a result, the purge gas containing the evaporated fuel flows from the canister toward the intake passage. The evaporated fuel that has flowed into the intake passage burns inside the internal combustion engine together with the injected fuel. For this reason, according to the conventional apparatus, the fuel adsorbed by the canister can be appropriately processed without being released to the atmosphere.

JP 11-182359 A JP 2001-227421 A

  During operation of the internal combustion engine, liquid fuel (port wet) adheres to the wall surface of the intake passage. For this reason, evaporative fuel is produced | generated by vaporizing port wet in the inside of an intake passage. During the operation of the internal combustion engine, the evaporated fuel generated in this manner is eventually sucked into the internal combustion engine, so that no emission problem occurs.

  However, after the internal combustion engine is stopped, the flow of the intake air is interrupted, so that the evaporated fuel generated with the vaporization of the port wet is not sucked into the internal combustion engine. In order to sufficiently suppress the total amount of emissions released from the internal combustion engine, it is necessary to sufficiently suppress the atmospheric release of evaporated fuel generated inside the intake passage after the internal combustion engine is stopped in this way. .

  However, in the above-described conventional apparatus, no consideration is given to how to handle the evaporated fuel generated inside the intake passage after the internal combustion engine is stopped. For this reason, it is difficult to reliably prevent such evaporated fuel from being released into the atmosphere depending on the conventional apparatus.

  The present invention has been made to solve the above-described problems, and can sufficiently suppress the evaporative fuel generated inside the intake passage after the internal combustion engine is stopped from being released into the atmosphere. An object of the present invention is to provide a fuel vapor processing apparatus.

In order to achieve the above object, a first invention is a fuel vapor processing apparatus,
A canister that adsorbs the evaporated fuel generated in the fuel tank;
A purge passage communicating the canister with an intake passage of an internal combustion engine;
A purge control valve for controlling a conduction state of the purge passage;
A throttle valve disposed in the intake passage of the internal combustion engine;
Intake system scavenging means for closing the throttle valve and opening the purge control valve for a certain period after the internal combustion engine is stopped;
It is characterized by providing.

The second invention is the first invention, wherein
A pressure determining means for determining whether the intake pipe pressure is equal to or higher than the tank internal pressure;
The intake system scavenging means includes valve opening prohibiting means for prohibiting the opening of the purge control valve when the intake pipe pressure is not equal to or higher than the tank internal pressure.

The third invention is the first or second invention, wherein
A generation condition determining means for determining establishment of an evaporated fuel generation condition in which evaporated fuel is generated inside the intake passage after the internal combustion engine is stopped;
The certain period includes all of the period in which the fuel vapor generation situation is established.

Moreover, 4th invention is set in 3rd invention,
A cooling water temperature detecting means for detecting the cooling water temperature of the internal combustion engine;
The generation state determining means determines that the evaporated fuel generation state is established when the cooling water temperature is equal to or higher than a predetermined determination temperature.

The fifth invention is the third or fourth invention, wherein
A canister closing valve for opening and closing the atmospheric hole of the canister;
While the evaporated fuel generation situation is established, a closing valve control means for opening the canister closing valve,
It is characterized by providing.

According to a sixth invention, in any one of the first to fourth inventions,
A canister closing valve for opening and closing the atmospheric hole of the canister;
A condensing state determination means for determining the establishment of an evaporating fuel condensing state in which evaporative fuel condenses inside the fuel tank after the internal combustion engine is stopped,
The predetermined period includes all of the period in which the evaporated fuel condensation situation is established,
While the evaporated fuel condensing state is established, it further comprises a closing valve control means for closing the canister closing valve.

The seventh invention is the first invention, wherein
A pump that generates a gas flow from the intake passage to the canister is provided.
The certain period includes an on period of the pump.

The eighth invention is the seventh invention, wherein
A canister closing valve for opening and closing the atmospheric hole of the canister;
A condensing state determination means for determining the establishment of an evaporating fuel condensing state in which evaporative fuel condenses inside the fuel tank after the internal combustion engine is stopped,
The predetermined period includes all of the period in which the evaporated fuel condensation situation is established,
After the internal combustion engine is stopped, the canister closing valve is opened and the pump is operated until the evaporative fuel condensation state is established, and after the evaporative fuel condensation state is established, the pump is stopped. And scavenging path switching means for closing the canister closing valve.

The ninth invention is the sixth or eighth invention, wherein
Fuel temperature detecting means for detecting the fuel temperature in the fuel tank;
Fuel temperature storage means for storing the fuel temperature when the internal combustion engine is stopped,
The condensing state determination means determines the establishment of the evaporated fuel condensing state when the fuel temperature becomes lower than the fuel temperature when the internal combustion engine is stopped after the internal combustion engine is stopped.

The tenth invention is the sixth or eighth invention, wherein
A stop time timer for counting the elapsed time after the internal combustion engine stops,
The condensing state determination means determines that the evaporated fuel condensing state is established when the stop time reaches a predetermined time.

  According to the first invention, after the internal combustion engine is stopped, the throttle valve is closed and the purge control valve is opened for a certain period. For a while after the internal combustion engine is stopped, the fuel adhering to the wall surface of the intake passage or the fuel leaking from the fuel injection valve is vaporized to generate evaporated fuel inside the intake passage. According to the above state, the evaporated fuel can be guided to the canister and adsorbed. For this reason, according to the present invention, the emission characteristics after the internal combustion engine is stopped can be made extremely good.

  According to the second aspect of the invention, even after the stop of the internal combustion engine is instructed, the purge control valve is kept closed while the intake pipe pressure is lower than the tank internal pressure. When the purge control valve is opened under a situation where the intake pipe pressure is lower than the tank internal pressure, a gas flow from the fuel tank toward the intake passage occurs, and a situation occurs in which evaporated fuel flows into the intake passage. According to the present invention, it is possible to reliably prevent the above situation from occurring after the internal combustion engine is stopped.

  According to the third aspect of the present invention, the purge control valve can always be opened while the evaporated fuel generation situation is established, that is, during the period in which the evaporated fuel is generated inside the intake passage. While evaporative fuel is generated inside the intake passage, a gas flow from the intake passage toward the canister naturally occurs due to an increase in the amount of gas in the intake passage. According to the present invention, the fuel remaining in the intake passage can be efficiently guided to the canister by effectively utilizing this natural flow.

  According to the fourth aspect of the invention, it is possible to easily and accurately determine whether or not the evaporated fuel generation situation is established by checking whether or not the cooling water temperature of the internal combustion engine is equal to or higher than the determination temperature. it can.

  According to the fifth aspect of the present invention, the canister closing valve can be opened and the internal pressure of the canister can be maintained at atmospheric pressure while the fuel vapor generation situation is established. If the internal pressure of the canister is maintained at atmospheric pressure, the evaporated fuel generated inside the intake passage smoothly flows into the canister. Therefore, according to the present invention, it is possible to efficiently scavenge the inside of the intake passage while the evaporated fuel generation situation is established.

  According to the sixth aspect of the present invention, the purge control valve can be opened and the canister closing valve can be closed while the evaporated fuel condensation state is established. During the evaporative fuel condensation state, gas condenses in the fuel tank, and a gas flow from the canister toward the fuel tank is generated. At this time, if the canister closing valve is closed, the gas in the intake passage is sucked toward the canister. For this reason, according to the present invention, the inside of the intake passage can be effectively scavenged by utilizing the condensation of gas generated in the fuel tank.

  According to the seventh aspect, after the internal combustion engine is stopped, the purge control valve is opened and the pump is operated, so that the gas in the intake passage can be forced to flow out toward the canister. For this reason, according to this invention, the inside of an intake passage can be scavenged effectively.

  According to the eighth aspect of the present invention, the gas in the intake passage passes through the canister by opening the canister closing valve and operating the purge pump until the evaporated fuel condensation state is established after the internal combustion engine is stopped. It can create a condition that flows into the atmosphere. In addition, after the evaporative fuel condensing state is established, a state in which the gas in the intake passage is sucked into the fuel tank through the canister can be created by closing the canister closing valve. For this reason, according to the present invention, the evaporated fuel in the intake passage can be appropriately captured by the canister after the internal combustion engine is stopped.

  According to the ninth aspect, based on whether or not the fuel temperature in the fuel tank has become lower than the temperature at the time of stop of the internal combustion engine, whether or not the evaporated fuel condensation state is established, that is, the inside of the fuel tank Thus, it is possible to easily and accurately determine whether or not condensation of the evaporated fuel has started.

  According to the tenth aspect of the present invention, it is easy and accurate to determine whether or not the evaporative fuel condensing state is established based on the stop time of the internal combustion engine, that is, whether or not evaporative fuel condensation has started inside the fuel tank. Can be judged.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining the configuration of the first embodiment of the present invention. The system of the present invention is assumed to be mounted on a vehicle, and includes a fuel tank 10. A canister 14 communicates with the fuel tank 10 through a vapor passage 12. The canister 14 includes activated carbon therein, and can adsorb evaporated fuel flowing in from the fuel tank 10.

  An atmospheric passage 16 communicates with the canister 14. A canister block valve (CCV) 18 is provided in the atmospheric passage 16. The CCV 18 is an electromagnetic valve for blocking the atmospheric passage 16. Further, a purge passage 22 communicates with the canister 14. The purge passage 22 includes a purge VSV 24 and communicates with an intake passage 26 of the internal combustion engine at an end portion thereof. The intake passage 26 includes a throttle valve 30 downstream of the air filter 28. The throttle valve 30 is an electronically controlled valve mechanism and can change the throttle opening degree TA in response to a drive signal supplied from the outside.

  The purge passage 22 described above communicates with the intake passage 26 downstream of the throttle valve 30. The intake passage 26 communicates with an intake port 32 of the internal combustion engine. The intake port 32 is assembled with a fuel injection valve 33 for injecting fuel therein. An exhaust passage 34 communicates with the internal combustion engine. A catalyst 36 for purifying exhaust gas is incorporated in the exhaust passage 34.

  The internal combustion engine further includes an intake valve 38 and an exhaust valve 40. Variable valve mechanisms 42 and 44 are connected to the intake valve 38 and the exhaust valve 40, respectively. According to the variable valve mechanisms 42 and 44, the valve opening timing of the intake valve 38 and the valve opening timing of the exhaust valve 40 can be appropriately changed.

  The system of this embodiment includes an ECU (Electronic Control Unit) 50. The ECU 50 is supplied with outputs from various sensors mounted on the internal combustion engine. The ECU 50 is connected to various actuators mounted on the internal combustion engine, such as the fuel injection valve 33 and the throttle valve 30. The ECU 50 can appropriately drive the actuators based on the sensor outputs.

[Basic operation of the first embodiment]
In the system of this embodiment, for example, when refueling, the CCV 18 is opened to open the canister 14 to the atmosphere. When refueling is performed in this state, the gas present in the fuel tank 10, that is, the gas containing the evaporated fuel flows into the canister 14 through the vapor passage 12. At this time, the canister 14 adsorbs the evaporated fuel in the gas and releases only the air component not containing the fuel component from the atmospheric passage 16 to the atmosphere.

  The system according to the present embodiment adsorbs the evaporated fuel to the canister 14 by the same operation under a situation where a large amount of evaporated fuel is generated in the fuel tank 10 in addition to refueling. According to such a function, it is possible to effectively prevent the fuel vapor from flowing out to the atmosphere.

  The system according to the present embodiment executes normal purge control for purging the canister 14 during operation of the internal combustion engine. During execution of the normal purge control, the CCV 18 is opened, and the purge VSV 24 is driven to open and close at an appropriate duty ratio. When the purge VSV 24 opens during operation of the internal combustion engine, intake negative pressure is introduced to the canister 14. As a result, air is sucked from the atmospheric passage 16, the canister 14 is purged by the air, and purge gas containing evaporated fuel flows into the intake passage 26.

  The evaporated fuel flowing into the intake passage 26 is combusted in the cylinder together with the fuel injected from the fuel injection valve 33. For this reason, according to the system of the present embodiment, the fuel adsorbed by the canister 14 can be processed without being released to the atmosphere.

[Characteristic Operation in Embodiment 1]
A part of the fuel injected into the intake port 32 during operation of the internal combustion engine adheres to the port wall surface and the intake valve 38 as liquid fuel and becomes so-called port wet. Since this port wet remains even when the internal combustion engine is stopped, fuel exists in the intake passage 26 even after the internal combustion engine is stopped. Since the fuel is vaporized over time, evaporated fuel is generated inside the intake passage after the internal combustion engine is stopped.

  If the throttle valve 30 is opened after the internal combustion engine is stopped, the evaporated fuel generated in the intake passage 26 flows backward through the intake passage 26 and is discharged from the air filter into the atmosphere. If the throttle valve 30 is closed, the evaporated fuel can be confined in the intake passage 26. In this case, the evaporated fuel is discharged from the intake passage 26 to the exhaust passage 34 when the internal combustion engine is restarted. Is done. For this reason, as long as the evaporated fuel is left in the intake passage 26, a situation occurs in which the evaporated fuel is eventually discharged into the atmosphere.

  Therefore, in this embodiment, the vaporized fuel generated inside the intake passage 26 after the internal combustion engine is stopped is prevented from being captured by the canister 14 and released to the atmosphere. Hereinafter, with reference to FIG. 2 (A) and FIG. 2 (B), a method for guiding the evaporated fuel generated in the intake passage 26 to the canister 14 after the internal combustion engine is stopped will be described.

  FIG. 2A is a diagram for explaining a first method for guiding the evaporated fuel in the intake passage 26 to the canister 14. In FIG. 2A, the internal combustion engine is stopped and the throttle valve 30 is closed. Further, both the VSV 24 and the CCV 18 are opened.

  Immediately after the internal combustion engine is stopped, the vicinity of the intake passage 26 is also usually hot. While the temperature of the intake passage 26 is high, the fuel is actively vaporized therein. And under the situation where fuel is actively vaporized inside the intake passage 26, the inside tends to be positive pressure. On the other hand, in the system of the present embodiment, when the CCV 18 is open, the inside of the fuel tank 10 and the canister 14 is opened to the atmospheric pressure. Therefore, according to the state shown in FIG. 2, the flow of gas from the intake passage 26 toward the canister inevitably occurs as the fuel is vaporized inside the intake passage 26. For this reason, according to the system of the present embodiment, after the internal combustion engine is stopped, while the temperature of the intake passage 26 is sufficiently high, it is generated inside the intake passage 26 by creating the state shown in FIG. The evaporated fuel to be captured can be efficiently captured inside the canister 14.

  FIG. 2B is a view for explaining a second method for guiding the evaporated fuel in the intake passage 26 to the canister 14. The state shown in FIG. 2 (B) is the same as the state shown in FIG. 2 (A) except that the CCV 18 is closed. That is, also in FIG. 2B, the internal combustion engine is stopped, the throttle valve 30 is closed, and the VSV 24 is opened.

  When the ambient temperature of the intake passage 26 decreases, the amount of fuel evaporation inside the intake passage 26 decreases. As the amount of evaporation decreases, a difference in pressure between the intake passage 26 and the atmospheric pressure hardly occurs. Depending on the state shown in FIG. 2A, the flow of gas from the intake passage 26 toward the canister 14 may be reduced. It becomes difficult to maintain.

  The fuel stored in the fuel tank 10 rises during operation of the internal combustion engine, and falls with a decrease in engine temperature after the internal combustion engine is stopped. In the process in which the fuel temperature in the fuel tank 10 decreases, the fuel vapor condenses inside the fuel tank 10 as the saturated vapor pressure decreases. In the process of condensing the fuel, the internal pressure of the fuel tank 10 decreases, and a gas flow from the canister 14 toward the fuel tank 10 is generated.

  According to the state shown in FIG. 2B, since the CCV 18 is closed, when gas is sucked into the fuel tank 10, a gas flow from the intake passage 26 toward the canister 14 is inevitably generated. . For this reason, according to the system of this embodiment, after the internal combustion engine is stopped, under the situation where the evaporated fuel is condensed inside the fuel tank 10, the state shown in FIG. The evaporated fuel generated inside can be efficiently captured inside the canister 14.

[Specific Processing in Embodiment 1]
The system of the present embodiment is appropriately shown in the state shown in FIG. 2A or FIG. 2B in accordance with changes in the ambient temperature of the intake passage 26 and the fuel temperature in the fuel tank 10 after the internal combustion engine is stopped. Create a state. Hereinafter, the contents of the processing executed by the ECU 50 in order to appropriately create those states will be specifically described.

  FIG. 3 is a flowchart of a routine executed by the ECU 50 in order to realize the above function. In the routine shown in FIG. 3, it is first determined whether or not the ignition (IG) of the vehicle is turned off (step 100).

  If it is determined that the IG is not turned off, it is determined that there is no need to consider scavenging of the intake passage 26. In this case, first, the post-stop elapsed time TOFF is set to 0 (step 102), and then the current tank fuel temperature TTNK is stored as the storage temperature TTNKO (step 104).

  When the above processing is completed, normal purge control is then executed (step 106). According to the normal purge control, as described above, the canister 14 can be purged during the normal operation of the internal combustion engine without deteriorating the emission characteristics.

  When the vehicle IG is turned off, the determination in step 100 is affirmed. In this case, first, the increment processing of the elapsed time TOFF after the stop is executed (step 108).

  Next, it is determined whether the post-stop elapsed time TOFF is equal to or longer than a determination time K60 (for example, 60 minutes) (step 110). When it is determined that TOFF has reached K60, it is determined that the period for performing the scavenging process of the intake passage 26 has elapsed. In this case, the purge VSV 24 is turned off (closed) (step 112), and after the CCV 18 is opened (step 114), the current routine is terminated.

  According to the above processing, it is possible to create a state in which the intake passage 26 is disconnected from the canister 14 and the canister 14 is opened to the atmosphere when the determination time K60 has elapsed after the internal combustion engine is stopped.

  Until the time K60 elapses after the internal combustion engine is stopped, it is determined in step 110 that TOFF ≧ K60 is not satisfied. In this case, the scavenging process for the intake passage 26 is thereafter performed. Here, specifically, first, throttle closing control is performed (step 116).

  As shown in the frame of step 116, the ECU 50 stores a map that defines the throttle opening degree TA in relation to the engine speed NE. In step 116, specifically, the throttle opening degree TA corresponding to the current engine speed NE is read according to this map, and the throttle valve 30 is controlled so that the TA is realized.

  After the vehicle IG is turned off, a certain period of time is required until the internal combustion engine stops completely. If the throttle valve 30 is completely closed during this time, excessive intake negative pressure is generated, so-called oil rise (a phenomenon in which oil flows into the combustion chamber from the periphery of the piston) and oil fall (from the circumference of the valve stem to the combustion chamber). The phenomenon of oil inflow) occurs.

  The throttle closing control described above is a control for setting the throttle opening degree TA to zero without causing excessive intake negative pressure in the process of the internal combustion engine reaching a complete stop. If such control is executed, after the IG is turned off, the throttle valve 30 can be properly shifted to the fully closed state without causing an oil increase or an oil decrease.

  When the throttle closing control is finished, it is next determined whether or not the coolant temperature THW of the internal combustion engine is equal to or higher than a determination temperature KTH70 (for example, 70 ° C.) (step 118). The determination temperature KTH70 is a lower limit value of the temperature at which the liquid fuel adhering to the wall surface or the like is actively vaporized inside the intake passage 26. More specifically, the determination temperature KTH70 is determined as the internal pressure of the intake passage 26 increases as the fuel vaporizes. This temperature is defined as the lower limit temperature that can be predicted to be positive.

  Therefore, if it is recognized that THW ≧ KTH70 is established, it can be determined that the temperature condition for guiding the evaporated fuel in the intake passage 26 to the canister 14 is established through the route shown in FIG. In this case, it is next determined whether the pressure MV in the intake passage 26 is equal to or higher than the tank internal pressure PTNK (step 120).

  In the system of the present embodiment, the CCV 18 is opened when IG is turned off. Therefore, at that time, the tank internal pressure PTNK is set to the atmospheric pressure similarly to the internal pressure of the canister 14. On the other hand, after IG is turned off, the pressure MV in the intake passage 26 is maintained at a negative pressure at least while the internal combustion engine is moving. If the purge VSV 24 is opened under the condition where the MV is negative pressure, a gas flow from the fuel tank 10 toward the intake passage 26 occurs.

  Such a gas flow unnecessarily increases the amount of fuel adsorbed in the canister 14, and further causes the evaporated fuel to flow into the intake passage 26. Therefore, it is desirable not to open the purge VSV 24 while MV is lower than PTNK, that is, while MV ≧ PTNK is not established. For the reasons described above, in the routine shown in FIG. 3, when MV ≧ PTNK is not established in step 120, the processes of steps 112 and 114 are subsequently executed to prohibit the opening of the purge VSV 24. Is done.

  On the other hand, when the establishment of MV ≧ PTNK is recognized in step 120, it can be determined that there is no possibility that the purge gas is sucked into the intake passage 26. In this case, the purge VSV 24 is then turned on (opened state), and the state shown in FIG.

  The state shown in FIG. 2A is subsequently maintained until the cooling water temperature THW falls below the determination temperature KTH70. During this time, the evaporated fuel generated in the intake passage 26 flows into the canister 14 by its own expansion force and is captured therein.

  When the cooling water temperature THW falls to a temperature lower than the determination temperature KTH70, in the above step 118, it is recognized that THW ≧ KTH70 is not satisfied. In this case, the stored value TTNKO of the in-tank fuel temperature is compared with the current in-tank fuel temperature TTNK (step 124). That is, according to the routine shown in FIG. 3, when reaching a stage where the positive pressure MV due to fuel vaporization cannot be sufficiently expected, the success or failure of TTNKO> TTNK is determined.

  At the time when the processing of step 124 is executed, the stored fuel value TTNKO stores the in-tank fuel temperature TTNK immediately before IG is turned off. Therefore, in the above step 124, it is substantially determined whether or not the current in-tank fuel temperature TTNK is lower than the in-tank fuel temperature TTNK at the time of stop.

  If the current in-tank fuel temperature TTNK is not lower than that at the time of stopping, it can be determined that no fuel condensation has occurred inside the fuel tank 10. That is, if it is determined in step 124 that TTNKO> TTNK is not established, it can be determined that the gas amount is increased or maintained inside the fuel tank 10. In this case, even if the CCV 18 is closed, the gas flow as shown in FIG. 2B, that is, the gas flow flowing into the fuel tank 10 does not occur. Rather, when the CCV 18 is closed, the tank internal pressure PTNK increases and a gas flow toward the intake passage 26 may occur. For this reason, when it is recognized that TTNKO> TTNK is not established, the processing of steps 112 and 114 is executed to prohibit the flat valve of the CCV 18.

  On the other hand, if TTNKO> TTNK is established in step 124, gas condensation occurs in the fuel tank 10, and as a result, a gas flow from the canister 14 toward the fuel tank 10 occurs. Can be estimated. In this case, after the CCV 126 is closed (step 126), the processing after step 120 is executed.

  At the stage where step 126 is executed, the pressure MV in the intake passage 26 has reached the atmospheric pressure, so it is usually considered that the condition of step 120 (MV ≧ PTNK) is satisfied. If this condition is satisfied, the process of step 122 is executed to form the state shown in FIG.

  The state shown in FIG. 2B is maintained until the post-stop elapsed time TOFF reaches the determination time K60. During this time, the evaporated fuel generated in the intake passage 26 is guided to the canister 14 by the suction force of the fuel tank 10 and captured therein.

  As described above, according to the routine shown in FIG. 3, the evaporated fuel generated in the intake passage 26 after the internal combustion engine is stopped can be efficiently guided to the canister 14. For this reason, according to the system of the present embodiment, it is possible to prevent the fuel remaining in the intake passage 26 from being released into the atmosphere and to realize extremely excellent emission characteristics.

  By the way, in the first embodiment described above, the cooling water temperature THW determines whether or not the state shown in FIG. 2A is formed, that is, whether or not the purge using the expansion force of the evaporated fuel is performed. Although the determination is based on whether or not KTH70 or higher, the determination method is not limited to this. That is, here, it is sufficient to determine whether or not fuel vaporization occurs to such an extent that the expansion force of the evaporated fuel can be used. For example, it is assumed that the expansion force can be used for a certain period after the internal combustion engine is stopped. ) State may be formed.

  In the first embodiment described above, it is determined whether or not the state shown in FIG. 2B is formed, that is, whether or not purging using the suction force of the fuel tank 10 is performed. However, the determination method is not limited to this. In other words, here, it is sufficient to determine whether or not fuel condensation has occurred within the fuel tank 10 to such an extent that the suction force can be used. For example, after a certain period of time has elapsed after the internal combustion engine is stopped, the suction force is reduced. It is good also as forming the state of FIG. 2 (B) as what can be utilized.

  In the first embodiment described above, the state shown in FIG. 2A and the state shown in FIG. 2B are switched according to the situation, but these need not necessarily be used in combination. Absent. That is, only one of the states may be realized and the intake passage 26 may be scavenged after the internal combustion engine is stopped.

  In the first embodiment described above, the determination time K60 corresponds to the “predetermined period” in the first invention, and the ECU 50 executes the processing of steps 116 and 122, whereby the first The “intake system scavenging means” in the present invention is realized.

  Further, in the first embodiment described above, the ECU 50 executes the process of step 120 so that the “pressure determination means” in the second aspect of the present invention does not satisfy the condition of step 112 when the condition of step 120 is not satisfied. By executing the processing, the “valve opening prohibiting means” in the second aspect of the present invention is realized.

  In the first embodiment described above, the ECU 50 detects the cooling water temperature THW to realize the “cooling water temperature detecting means” in the fourth aspect of the invention, and the ECU 50 executes the processing of step 118. As a result, the “occurrence state determination means” in the third or fourth aspect of the present invention is realized.

  In the first embodiment, the ECU 50 always maintains the CCV 18 in the valve open state when the condition of step 118 is satisfied, thereby realizing the “blocking valve control means” in the fifth aspect of the invention. ing.

  In the first embodiment described above, the ECU 50 executes the process of step 124, so that the “condensation state determination means” in the sixth aspect of the invention executes the process of step 126. The “blocking valve control means” in the sixth invention is realized.

  Further, in the first embodiment described above, the ECU 50 detects the in-tank fuel temperature TTNK in steps 104 and 124, so that the “fuel temperature detection means” in the ninth aspect of the invention is the step 104. By storing the stored value TTNKO, the “fuel temperature storage means” according to the ninth aspect of the present invention performs execution determination after step 126 when the condition of step 124 is satisfied, thereby “condensation state determination means” according to the ninth aspect of the present invention. "Is realized.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIG. 4 and FIG.
FIG. 4 is a diagram for explaining the configuration of the present embodiment. The configuration shown in FIG. 4 is the same as the system shown in FIG. 1 except that the purge pump 20 is disposed in the atmospheric passage 16. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 5 described later in the configuration shown in FIG.

  The system of the first embodiment described above realizes scavenging of the intake passage 26 by utilizing the fact that the evaporated fuel naturally flows out from the intake passage 26 toward the canister 14 after the internal combustion engine is stopped. Yes. On the other hand, the system of this embodiment is characterized in that scavenging of the intake passage 26 is forcibly performed using the purge pump 20 after the internal combustion engine is stopped.

[Specific Processing in Second Embodiment]
FIG. 5 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. In FIG. 5, the same steps as those shown in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  According to the routine shown in FIG. 5, while the IG is on, the process of setting the elapsed time TOFF after the stop to 0 and the process for realizing the normal purge control are repeatedly executed (steps 100, 102, 106).

  When IG is turned off, the post-stop elapsed time TOFF is incremented (step 108), and then it is determined whether TOFF has reached the determination time K60 (step 110). Immediately after IG is turned off, it is determined that TOFF ≧ K60 is not satisfied. In this case, after the throttle closing control is executed (step 116), it is determined whether the post-stop elapsed time TOFF has reached a second determination time K30 (for example, 30 minutes) (step 130).

  In the system of the present embodiment, by operating the purge pump 20 with the CCV 18 open and the purge VSV 24 open, a gas flow that follows the path of the intake passage 26 → canister 14 → purge pump 20 is generated. Can be made. Therefore, if the above-mentioned state is formed after the internal combustion engine is stopped, the inside of the intake passage 26 can be forcibly scavenged, and the evaporated fuel generated in the inside can be captured in the canister 14.

  The second determination time K30 described above is set to a time during which the inside of the intake passage 26 can be purified to some extent by such forced scavenging. According to the routine shown in FIG. 5, while it is determined that the post-stop elapsed time TOFF has not reached the second determination time K30, the CCV 18 is opened (step 132) and the purge pump 20 is turned on. (Step 134). In this case, the purge VSV 24 is turned on (opened) after the above processing.

  According to the above processing, after the IG is turned off, the forced scavenging of the intake passage 26 by the purge pump 20 is continued until the post-stop elapsed time TOFF reaches the second determination time K30. . For this reason, according to the system of the present embodiment, the interior of the intake passage 26 can be quickly cleaned after the internal combustion engine is stopped.

  After the post-stop elapsed time TOFF reaches the second determination time K30, the establishment of TOFF ≧ K30 is recognized in step 130. In this case, after that, the purge pump 20 is turned off (step 136), the CCV 18 is closed (step 138), and then the process of step 122 is executed. As a result, the state substantially shown in FIG. 2B, that is, the state in which the intake passage 26, the canister 14, and the fuel tank 10 form a closed space is formed.

  The second determination time K30 is set to a time during which the intake passage 26 can be purified to some extent by forced scavenging. More specifically, the second determination time K30 is set to a time required until gas condensation is reliably started inside the fuel tank 10 after the internal combustion engine is stopped. For this reason, if the state shown in FIG. 2B is formed under a situation where TOFF ≧ K30, the intake passage 26 is utilized using the suction force of the fuel tank 10 as in the first embodiment. The scavenging can be continued.

  According to the routine shown in FIG. 5, thereafter, in step 110, it is determined that it is no longer necessary to continue scavenging of the intake passage 26 until it is determined that the post-stop elapsed time TOFF has reached the determination time K60. Until then, substantially the same state as shown in FIG. 2B is maintained. For this reason, also in the system of the present embodiment, the intake passage 26 can be efficiently scavenged using the suction force of the fuel tank 10 as in the case of the first embodiment.

  In the second embodiment described above, the purge pump 20 corresponds to the “pump” in the seventh aspect of the invention, and the second determination time K30 is the “pump on period” in the seventh aspect of the invention. It corresponds.

  In the second embodiment described above, the ECU 50 executes the process of step 130, so that the “condensation state determining means” in the eighth invention executes the processes of steps 132 to 138 and 122. Thus, the “scavenging path switching means” according to the eighth aspect of the present invention is realized.

  In the second embodiment described above, the timer for counting the elapsed time TOFF after stop corresponds to the “stop time timer” in the tenth aspect of the invention, and the ECU 50 performs step 136 after the condition of step 130 is satisfied. By determining the execution of the subsequent processing, the “condensation state determination means” in the tenth aspect of the present invention is realized.

It is a figure for demonstrating the structure of Embodiment 1 of this invention. It is a figure for demonstrating the method at the time of scavenging an intake passage in Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the structure of Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention.

Explanation of symbols

10 Fuel tank 14 Canister 18 Canister shut-off valve (CCV)
22 Purge passage 24 Purge VSV
26 Intake passage 30 Throttle valve 34 Exhaust passage 50 ECU (Electronic Control Unit)

Claims (10)

A canister that adsorbs the evaporated fuel generated in the fuel tank;
A purge passage communicating the canister with an intake passage of an internal combustion engine;
A purge control valve for controlling a conduction state of the purge passage;
A throttle valve disposed in the intake passage of the internal combustion engine;
Intake system scavenging means for closing the throttle valve and opening the purge control valve for a certain period after the internal combustion engine is stopped;
An evaporative fuel processing apparatus comprising: A pressure determining means for determining whether the intake pipe pressure is equal to or higher than the tank internal pressure;
2. The evaporative fuel processing apparatus according to claim 1, wherein the intake system scavenging means includes valve opening prohibiting means for prohibiting the opening of the purge control valve when the intake pipe pressure is not equal to or higher than the tank internal pressure. A generation condition determining means for determining establishment of an evaporated fuel generation condition in which evaporated fuel is generated inside the intake passage after the internal combustion engine is stopped;
3. The evaporative fuel processing apparatus according to claim 1, wherein the predetermined period includes all of the period in which the evaporative fuel generation situation is established. A cooling water temperature detecting means for detecting the cooling water temperature of the internal combustion engine;
4. The evaporative fuel processing apparatus according to claim 3, wherein the generation status determination unit determines that the evaporative fuel generation status is established when the cooling water temperature is equal to or higher than a predetermined determination temperature. A canister closing valve for opening and closing the atmospheric hole of the canister;
While the evaporated fuel generation situation is established, a closing valve control means for opening the canister closing valve,
The evaporative fuel processing apparatus according to claim 3, further comprising: A canister closing valve for opening and closing the atmospheric hole of the canister;
A condensing state determination means for determining the establishment of an evaporating fuel condensing state in which evaporative fuel condenses inside the fuel tank after the internal combustion engine is stopped,
The predetermined period includes all of the period in which the evaporated fuel condensation situation is established,
5. The evaporated fuel processing according to claim 1, further comprising: a closing valve control unit that closes the canister closing valve while the evaporated fuel condensation state is established. apparatus. A pump that generates a gas flow from the intake passage to the canister is provided.
The evaporated fuel processing apparatus according to claim 1, wherein the predetermined period includes an on period of the pump. A canister closing valve for opening and closing the atmospheric hole of the canister;
A condensing state determination means for determining the establishment of an evaporating fuel condensing state in which evaporative fuel condenses inside the fuel tank after the internal combustion engine is stopped,
The predetermined period includes all of the period in which the evaporated fuel condensation situation is established,
After the internal combustion engine is stopped, the canister closing valve is opened and the pump is operated until the evaporative fuel condensation state is established, and after the evaporative fuel condensation state is established, the pump is stopped. 8. The evaporated fuel processing apparatus according to claim 7, further comprising a scavenging path switching means for closing the canister closing valve. Fuel temperature detecting means for detecting the fuel temperature in the fuel tank;
Fuel temperature storage means for storing the fuel temperature when the internal combustion engine is stopped,
The condensing state determining means determines that the evaporated fuel condensing state is established when the fuel temperature becomes lower than the fuel temperature when the internal combustion engine is stopped after the internal combustion engine is stopped. The evaporative fuel processing apparatus according to 6 or 8. A stop time timer for counting the elapsed time after the internal combustion engine stops,
9. The evaporative fuel processing apparatus according to claim 6, wherein the condensing state determination means determines that the evaporative fuel condensing state is established when the stop time reaches a predetermined time.

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