JP4144407B2 - Evaporative fuel processing device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an evaporated fuel processing apparatus for an internal combustion engine, and more particularly to an evaporated fuel processing apparatus for preventing the evaporated fuel generated inside a fuel tank from being released into the atmosphere.
[0002]
[Prior art]
Conventionally, as disclosed in, for example, Japanese Patent Laid-Open No. 6-33838, an evaporative fuel processing apparatus including a canister communicating with a fuel tank has been disclosed. This device is provided with a tank internal pressure control valve capable of sealing the fuel tank in a path communicating with the fuel tank and the canister. The tank internal pressure control valve is controlled so that the fuel tank is sealed while the internal combustion engine is stopped, and the tank internal pressure becomes an appropriate value near atmospheric pressure while the internal combustion engine is operating. According to such control, the vapor in the fuel tank is prevented from being released into the atmosphere while the internal combustion engine is stopped, and the tank internal pressure is set to an appropriate pressure in preparation for refueling during operation of the internal combustion engine. Can be maintained.
[0003]
In the conventional apparatus described above, the valve opening pressure of the tank internal pressure control valve is set to a high pressure while the internal combustion engine is stopped, while the valve opening pressure is changed to a low pressure while the internal combustion engine is operating. is necessary. By the way, immediately after the valve opening pressure is switched from the high pressure to the low pressure, a situation occurs in which the vapor in the fuel tank is discharged until the tank internal pressure becomes equal to or lower than the low valve opening pressure after the switching. When a large amount of vapor is discharged from the fuel tank in this way, the vapor can not be captured by the canister, and a situation may occur where the vapor blows through the atmospheric hole of the canister.
[0004]
In the conventional apparatus, in order to prevent the occurrence of such blow-through, the opening pressure of the tank internal pressure control valve is switched in synchronization with the time when the vapor is purged into the intake passage. In this case, the vapor discharged from the fuel tank in accordance with the switching of the valve opening pressure can be directly sucked into the intake passage side, so that it is possible to create a situation in which the vapor is difficult to blow through the atmospheric hole of the canister.
[0005]
[Patent Document 1]
JP-A-6-33838
[Patent Document 2]
Japanese Utility Model Publication No. 4-17156
[Patent Document 3]
Japanese Patent Laid-Open No. 5-223025
[Patent Document 4]
Japanese Utility Model Publication No. 5-96457
[0006]
[Problems to be solved by the invention]
However, when the tank internal pressure is sufficiently high, an amount of vapor that cannot be processed by the purge may be discharged from the fuel tank as the valve opening pressure is switched. Under such circumstances, even if the switching of the valve opening pressure is performed in synchronism with the purge, there is an undeniable possibility that part of the vapor discharged from the fuel tank will blow through the canister. In this regard, the above-described conventional apparatus leaves room for further improvement with respect to the function of preventing the vapor blow-through accompanying the switching of the valve opening pressure.
[0007]
The present invention has been made to solve the above-described problems, and can effectively prevent the vapor discharged in synchronism with the release of the sealing of the fuel tank from being blown from the atmospheric hole of the canister. An object of the present invention is to provide a fuel vapor processing apparatus for an internal combustion engine.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a first invention is an evaporative fuel treatment apparatus for an internal combustion engine having a function of sealing a fuel tank and prohibiting evaporative fuel from flowing out,
A canister communicating with the fuel tank;
A sealing valve interposed between the fuel tank and the canister;
An on-off valve for opening and closing the atmospheric hole of the canister;
A purge mechanism for conducting the canister to an intake passage of an internal combustion engine;
When the fuel tank is connected to both the intake passage and the canister, if the tank internal pressure exceeds the determination pressure, the on-off valve is closed, while the tank internal pressure is equal to or lower than the determination pressure. Is an on-off valve control means for opening the on-off valve; and
It is characterized by providing.
[0013]
Also, Second invention Is In the first invention The closed valve is closed when the internal combustion engine is stopped, and the closed valve is opened when the evaporated fuel is purged from the canister to the intake passage during operation of the internal combustion engine. Control means is provided.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.
[0015]
Embodiment 1 FIG.
[Description 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 apparatus of this 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 a tank internal pressure Ptnk as a relative pressure with respect to the atmospheric pressure and generates an output corresponding to the detected value. A liquid level sensor 14 for detecting the liquid level of the fuel is disposed inside the fuel tank 10.
[0016]
A vapor passage 20 is connected to the fuel tank 10 via ROV (Roll Over Valve) 16 and 18. The vapor passage 20 includes a block valve unit 24 in the middle thereof, and communicates with the canister 26 at the end thereof. The block valve unit 24 includes a block valve 28 and a relief valve 30. The block valve 28 is a normally closed electromagnetic valve that closes in a non-energized state and opens when a drive signal is supplied from the outside. The relief valve 30 includes a forward 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 reverse relief valve that opens in the opposite case. This is a mechanical two-way check valve. The valve opening pressure of the relief valve 30 is set, for example, to about 20 kPa in the forward direction and about 15 kPa in the reverse direction.
[0017]
The canister 26 includes a purge hole 32. A purge passage 34 communicates with the purge hole 32. The purge passage 34 includes a purge VSV (Vacuum Switching Valve) 36 in the middle of the purge passage 34 and communicates with an intake passage 38 of the internal combustion engine at the end thereof. An air filter 40, an air flow meter 42, a throttle valve 44, and the like are provided in the intake passage 38 of the internal combustion engine. The purge passage 34 communicates with the intake passage 38 downstream of the throttle valve 44.
[0018]
A vapor adsorption unit 46 and a buffer unit 48 are provided inside the canister 26. The canister 26 is provided with an air hole 50. Both the vapor adsorption part 46 and the buffer part 48 are filled with activated carbon. The activated carbon of the vapor adsorbing section 46 can adsorb the evaporated fuel contained therein when the gas flowing in through the vapor passage 20 blows through the air holes 50. On the other hand, the activated carbon in the buffer unit 48 can prevent a sudden change in the vapor concentration in the purge gas flowing out from the purge hole 32.
[0019]
An atmospheric passage 54 communicates with the atmospheric hole 50 of the canister 26 via a negative pressure pump module 52. The air passage 54 includes an air filter 56 in the middle thereof. The end of the atmospheric passage 54 is open to the atmosphere in the vicinity of the fuel filler port 58 of the fuel tank 10.
[0020]
The negative pressure pump module 52 includes a negative pressure pump and a switching valve (both not shown). The switching valve can selectively realize an atmospheric open state in which the atmospheric hole 50 of the canister 26 is conducted to the atmospheric passage 54 and a negative pressure introduction state in which the atmospheric hole 50 is communicated 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 opening the switching valve to the atmosphere. Further, the negative pressure can be introduced into the canister 26 by operating the negative pressure pump while the switching valve is in the negative pressure introduction state, and the atmospheric hole 50 of the canister 26 is stopped by stopping the negative pressure pump in this state. Can be occluded.
[0021]
As shown in FIG. 1, the evaporated fuel processing apparatus of this embodiment includes an ECU 60. The ECU 60 incorporates a soak timer for counting the elapsed time while the vehicle is parked. A lid switch 62 and a lid opener opening / closing switch 64 are connected to the ECU 60 together with the tank internal pressure sensor 12, the sealing valve 28, or the negative pressure pump module 52 described above. The lid opener opening / closing switch 64 is connected to a lid manual opening / closing device 66 by a wire.
[0022]
The lid switch 62 is a switch for notifying the ECU 60 of a request for opening a lid (vehicle body lid) 68 that covers the fuel filler port 58. When the lid switch 62 is operated, the ECU 60 supplies a signal for requesting an opening operation of the lid 68 to the lid opener opening / closing switch 64. The lid opener opening / closing switch 64 is a mechanism for maintaining the lid 68 in a closed state. When the above signal is received from the ECU 60 or when the lid manual opening / closing device 66 is opened, the lid 68 is released from the closed state. To do.
[0023]
[Description of basic operation of the device]
Next, the operation of the evaporated fuel processing apparatus of this embodiment will be described.
(1) Parking
In principle, the fuel vapor processing apparatus of the present embodiment maintains the closing valve 28 in a closed state while the vehicle is parked. When the blocking valve 28 is closed, the fuel tank 10 is cut off from the canister 26 as long as the relief valve 30 is closed. Therefore, in the evaporated fuel processing apparatus of the present embodiment, the evaporated fuel is newly adsorbed to the canister 26 while the vehicle is parked unless the tank internal pressure Ptnk exceeds the positive valve opening pressure (20 kPa) of the relief valve 30. There is nothing. 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, air is not sucked into the fuel tank 10 while the vehicle is parked.
[0024]
(2) Refueling
In the apparatus of the present embodiment, the tank internal pressure Ptnk may be higher than the atmospheric pressure while the vehicle is stopped. When the tank cap is opened under such circumstances, the evaporated fuel existing in the fuel tank 10 is easily released to the atmosphere. Therefore, in the case where the execution of refueling is requested while the vehicle is stopped, that is, when the lid switch 62 is operated, first, the tank internal pressure Ptnk is reduced, and the tank internal pressure Ptnk is sufficiently reduced. After that, the opening of the fuel filler port 58 is permitted.
[0025]
More specifically, when the ECU 60 detects the operation of the lid switch 62 while the vehicle is stopped, the ECU 60 first opens the block valve 28. At this time, since the switching valve in the negative pressure pump module 52 opens the air hole 50, when the air blocking valve 28 is opened, the gas in the fuel tank 10 circulates inside the canister 26, and evaporates fuel. It flows out of the air hole 50 in a state where it is not included. As a result, the tank internal pressure Ptnk decreases, and when the value Ptnk falls below the determination pressure Ptnkh, the closed state of the lid 68 is released.
[0026]
When the lock of the lid 68 is released, it is possible to open the lid 68, remove the tank cap, and start refueling. In other words, in the apparatus of the present embodiment, the act of removing the tank cap, that is, the act of opening the fuel filler port 58 is prohibited until the tank internal pressure Ptnk drops below the determination pressure Ptnkh. For this reason, according to this device, it is possible to effectively prevent the evaporated fuel from being discharged from the fuel filler port 58 to the atmosphere during fueling.
[0027]
Thereafter, the ECU 60 detects the end of refueling based on the output of the liquid level sensor 14, the elapsed time, the closing operation of the lid 68, or the like. Then, the closing valve 28 is kept open until the end of refueling is detected, and when the end is detected, the closing valve 28 is closed again at that time. According to the above processing, gas is allowed to flow out from the fuel tank 10 to the canister 26 during refueling, and as a result, good refueling characteristics can be obtained. And after completion | finish of refueling, since the fuel tank 10 can be again made into a sealing state, the atmospheric | air discharge of evaporative fuel can fully be suppressed.
[0028]
(3) Running
As described above, the apparatus of the present embodiment releases the lock of the lid 68 after the pressure of the fuel tank 10 is released after the lid switch 62 is operated. That is, in the apparatus of the present embodiment, a waiting time required for depressurization occurs after the lid switch 62 is operated and before refueling is actually permitted. The waiting time becomes longer as the tank internal pressure Ptnk at the time of operating the lid switch 62 is higher.
[0029]
If a large amount of fuel is adsorbed to the canister 26 before refueling is started, the evaporated fuel flowing from the fuel tank 10 into the canister 26 during refueling blows through the canister 26 and is released to the atmosphere. Things happen. For this reason, it is desirable that the amount of fuel adsorbed by the canister 26 is always kept small in preparation for refueling.
[0030]
In order to reduce the amount of fuel adsorbed in the canister 26, the block valve 28 is always closed while the vehicle is running (when the internal combustion engine is operating), and the flow of evaporated fuel from the fuel tank 10 toward the canister 26 is completely avoided. It is desirable to ban. However, if the closing valve 28 is always closed while the vehicle is running, the tank internal pressure Ptnk becomes extremely high, and an unreasonably long waiting time occurs during refueling. In view of this, the apparatus of this embodiment is configured to maintain the tank internal pressure Ptnk at a value close to the atmospheric pressure by appropriately opening the closing valve 28 within a range in which the evaporated fuel is not adsorbed by the canister 26 while the vehicle is traveling.
[0031]
Specifically, the ECU 60 opens the block valve 28 when the tank internal pressure Ptnk exceeds the target upper limit value (> atmospheric pressure) on the condition that the intake passage 38 is purged, and the tank internal pressure Ptnk is This state is maintained until the target lower limit value (> atmospheric pressure) is reached. According to this control, unless the purge is cut for a long time, the tank internal pressure Ptnk is maintained between the target upper limit value and the target lower limit value. That is, it is possible to prevent the tank internal pressure Ptnk from excessively exceeding the target upper limit value. Since the blocking valve 28 is opened only during the execution of the purge, the evaporated fuel discharged from the fuel tank 10 can be guided to the intake passage 38. As a result, the amount of fuel adsorbed in the canister 26 is increased. Can be sufficiently suppressed.
[0032]
[Explanation of problems and solutions for basic operations]
As already described, the device of the present embodiment maintains the closing valve 28 in a closed state in principle while the vehicle is stopped. In this case, the tank internal pressure Ptnk can rise to 20 kPa, which is the valve opening pressure of the relief valve 30. The target upper limit value that becomes the valve opening pressure of the blocking valve 28 while the vehicle is traveling is sufficiently lower than the valve opening pressure of the relief valve 30. Therefore, when the tank internal pressure Ptnk has increased to around 20 kPa when the internal combustion engine is started, according to the above basic operation, the shutoff valve 28 is opened simultaneously with the start of the purge, and a large amount of gas containing evaporated fuel is fueled. It is discharged from the tank 10.
[0033]
During the purge, in order to take in air from the atmospheric hole 50, the switching valve in the negative pressure pump module 52 is maintained in a state in which the atmospheric hole 50 is opened in principle. If a large amount of gas flows from the fuel tank 10 into the canister 26 under such circumstances, a part of the gas is led to the intake passage 38, but the remainder flows through the vapor adsorbing portion 46 to the outside of the air hole 50. To do. When the amount of evaporated fuel in the gas flowing toward the atmospheric hole 50 exceeds the amount that can be captured by the vapor adsorbing unit 46, the evaporated fuel is blown into the atmosphere.
[0034]
A similar phenomenon can occur when the purge is cut for a long time while the vehicle is running. That is, the apparatus of this embodiment prohibits the opening of the closing valve 28 during the purge cut. Therefore, if the cutting is continued for a long period of time, the tank internal pressure Ptnk may be significantly higher than the target upper limit value. Under such circumstances, if the sealing valve 28 is opened as the purge is resumed, a large amount of gas is discharged from the fuel tank 10 toward the canister 26, and as a result, evaporated fuel is discharged from the atmospheric hole 50 of the canister 26. A situation can occur where it blows into the atmosphere.
[0035]
Therefore, in the present embodiment, the ECU 60 determines whether or not the tank internal pressure Ptnk is high enough to cause the vaporized fuel to blow through to the atmosphere when a valve opening request for the blockade valve 28 occurs. If the result is affirmative, the air hole 50 is closed by the negative pressure pump module 52 and the opening of the block valve 28 is permitted. Hereinafter, specific processing contents for realizing this function will be described.
[0036]
FIG. 2 shows a flowchart of a control routine executed by the ECU 60 in order to realize the above function.
In the routine shown in FIG. 2, it is first determined whether or not the internal combustion engine is in operation (step 100).
As a result, when it is determined that the internal combustion engine is not in operation, it is assumed that the vehicle is parked, and the blocking valve 28 is closed (step 102).
[0037]
On the other hand, if it is determined in step 100 that the internal combustion engine is in operation, the current tank internal pressure Ptnk is measured assuming that the vehicle is running (step 104).
[0038]
Next, it is determined whether the blocking valve 28 is currently open or closed (step 106).
[0039]
As a result, if it is determined that the blocking valve 28 is closed, it is next determined whether or not the tank internal pressure Ptnk is higher than a predetermined pressure (1) (> atmospheric pressure) (step 108). .
The predetermined pressure {circle around (1)} corresponds to the target upper limit value described above, and is a value set experimentally from the viewpoint of preventing an unreasonably long time required for pressure release during refueling.
[0040]
If it is determined that the tank internal pressure Ptnk is not higher than the predetermined pressure (1), it can be determined that it is not necessary to open the block valve 28. In this case, the current processing cycle is immediately terminated thereafter. On the other hand, if it is determined that the tank internal pressure Ptnk is higher than the predetermined pressure (1), it is determined whether or not the purge is being performed at a purge rate PGR exceeding α% (step 110).
[0041]
Here, the purge rate PGR is a ratio QPG / Ga between the flow rate of gas flowing into the intake passage 38 through the purge VSV 36 (purge flow rate QPG) and the amount of air flowing into the intake passage 38 (intake air amount Ga). is there. The purge flow rate QPG is a value uniquely determined by the opening degree of the purge VSV 36 and the intake pipe pressure Pm. The apparatus of this embodiment sets a target purge rate PGR according to the operating state of the internal combustion engine and the like, and opens the purge VSV 36 based on the intake air amount Ga and the intake pipe pressure Pm so that the target is realized. Control the degree.
[0042]
A larger intake negative pressure is introduced into the canister 26 as the purge rate PGR is larger. Therefore, the larger the purge rate PGR, the more gas discharged from the fuel tank 10 can be guided to the intake passage 38. The determination value α used in step 110 is a value set as a minimum purge rate PGR necessary for opening the sealing valve 28 and discharging the evaporated fuel from the fuel tank 10. Therefore, if it is determined that PGR> α is not established, the process of step 102 is performed to close the block valve 28, and then the current process cycle is terminated. On the other hand, if it is determined in step 110 that the purge rate PGR is greater than α%, the following processing is executed to open the block valve 28.
[0043]
That is, if it is determined in step 110 that the purge rate PGR is greater than α%, it is first determined whether or not the tank internal pressure Ptnk is greater than a predetermined pressure (3) (step 112).
The predetermined pressure {circle over (3)} is a target upper limit value of the tank internal pressure Ptnk during operation of the internal combustion engine, that is, a pressure higher than the predetermined pressure {circle around (1)}. When the valve 28 is opened, it is a boundary value (lower limit value) of the pressure at which the evaporated fuel may blow through the atmospheric hole 50 even if the purge is executed. Therefore, when the tank internal pressure Ptnk exceeds the predetermined pressure (3), it can be determined that if the block valve 28 is opened while the air hole 50 is open, there is a possibility that the evaporated fuel will blow through.
[0044]
In the routine shown in FIG. 2, if it is determined in step 112 that Ptnk> predetermined pressure (3) is established, the switching valve (CCV) of the negative pressure pump module 52 is controlled to close the air hole 50. (Step 114).
On the other hand, when it is determined that Ptnk> predetermined pressure (3) is not established, the switching valve (CCV) is controlled to open the air hole 50 (step 116).
Then, after any of the processes of steps 114 and 116 is executed, a valve opening process of the blocking valve 28 is performed (step 118).
[0045]
According to the above processing, when there is a possibility that the evaporated fuel will blow through when the blocking valve 28 is opened, the blow-through can be reliably prevented by closing the air hole 50. In this case, all of the gas discharged from the fuel tank 10 passes through the buffer portion 48 and is purged to the intake passage 38. On the other hand, in a situation where there is no possibility that the evaporated fuel will blow through, the atmosphere hole 50 is opened, so that a state in which purging can proceed while taking air into the canister 26 can be maintained. For this reason, according to the apparatus of this embodiment, it is possible to maintain good emission characteristics even immediately after the closing valve 28 is opened, and to efficiently purge the canister 26.
[0046]
In the routine shown in FIG. 2, if it is determined in step 106 that the blocking valve 28 is open, it is determined whether or not the tank internal pressure Ptnk has dropped below a predetermined pressure (2) (step 120). ).
The predetermined pressure (2) is a value corresponding to the target lower limit value described above, and is experimentally set to an appropriate value equal to or higher than the atmospheric pressure.
[0047]
When it is determined that the tank internal pressure Ptnk has not decreased below the predetermined pressure (2), the processing after step 110 is executed. Therefore, in this case, as long as the purge rate PGR is not less than α%, the blocking valve 28 is kept open. On the other hand, if it is determined that the tank internal pressure Ptnk has decreased below the predetermined pressure {circle around (2)}, the process of step 102, that is, the blocking valve is performed in order to avoid excessive evaporative fuel flowing out of the fuel tank 10. A process of closing 28 is executed.
[0048]
According to the above processing, during the operation of the internal combustion engine, as long as the purge is performed at the purge rate PGR exceeding α%, the tank internal pressure Ptnk is controlled between the predetermined pressures (1) and (2). Can do. Further, since the opening of the blocking valve 28 is permitted only during the execution of the purge, it is possible to prevent the amount of adsorbed fuel in the canister 26 from increasing in the process of controlling the tank internal pressure Ptnk to the above range. Therefore, according to the apparatus of the present embodiment, the tank internal pressure Ptnk can be controlled to a value close to the atmospheric pressure while the canister 26 is kept sufficiently clean while the vehicle is traveling.
[0049]
As described above, according to the routine shown in FIG. 6, the shutoff valve 28 is closed while the internal combustion engine is stopped, and the tank internal pressure Ptnk is controlled to be close to the atmospheric pressure by opening the shutoff valve 28 during the operation. can do. And according to this routine, under the situation where the tank internal pressure Ptnk is high, the block valve 28 after the atmospheric hole 50 of the canister 26 is closed can be opened. For this reason, according to the apparatus of the present embodiment, the emission characteristics when the internal combustion engine is stopped are well maintained, and the emission characteristics are excellent even during operation of the internal combustion engine while shortening the waiting time during refueling. Can be realized.
[0050]
In the first embodiment described above, the switching valve of the negative pressure pump module 52 is the “open / close valve” in the first invention, and the purge passage 34 and the purge VSV are the “purge mechanism” in the first invention. The ECU 60 executes the processing of steps 112 to 116, thereby realizing the “open / close valve control means” in the first aspect of the invention.
Further, in the above-described first embodiment, the ECU 60 executes the processing of steps 100, 102, 110 and 118 described above, thereby Second The “blocking valve control means” in the present invention is realized.
[0051]
Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS.
In the apparatus of the first embodiment described above, when it is necessary to open the blocking valve 28 under a situation where the evaporated fuel may blow through the atmospheric hole 50 of the canister 26, the blocking valve with the atmospheric hole 50 closed is used. Opening 28 prevents the fuel vapor from blowing through. On the other hand, the apparatus of this embodiment adjusts the opening degree of the blocking valve 28 with the atmosphere hole 50 opened under such circumstances, that is, the amount of gas discharged from the fuel tank 10. Is adjusted to prevent the fuel vapor from blowing through.
[0052]
FIG. 3 is a flowchart of a control routine executed by the ECU 60 in order to realize the above functions in the present embodiment. The apparatus of the present embodiment can be realized by causing the ECU 60 to execute the routine shown in FIG. 3 instead of the routine shown in FIG. 2 described above in the apparatus of the first embodiment. In FIG. 3, the same steps as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted or simplified.
[0053]
That is, in the routine shown in FIG. 3, if it is determined in step 110 that the purge rate PGR exceeds α%, that is, if it is determined that the block valve 28 should be opened by the processing in steps 100 to 110. First, the valve opening time T1 and the valve closing time T2 of the block valve 28 are determined based on the tank internal pressure Ptnk and the purge amount at that time (step 130).
[0054]
4 (A) and 4 (B) show examples of maps that the ECU 60 refers to when determining the valve opening time T1 and the valve closing time T2, respectively. As shown in FIG. 4A, the valve opening time T1 is set to a larger value as the tank internal pressure is higher and the purge amount is smaller. On the other hand, as shown in FIG. 4B, the valve closing time T2 is set to a smaller value as the tank internal pressure is higher and the purge amount is smaller. That is, the valve opening time T1 is determined to be a small value so that the evaporated fuel is easily blown out from the air hole 50, while the valve closing time T2 is determined to be a large value so that the vaporized fuel is easily blown through.
[0055]
In the routine shown in FIG. 3, when T1 and T2 are determined, thereafter, the process for opening the block valve 28 for the valve opening time T1 (step 132) and the process for closing the block valve 28 for the valve closing time T2 are performed. (Step 134) is subsequently performed.
[0056]
FIG. 5 is a timing chart for explaining the operation of the apparatus of the present embodiment realized by the above processing. More specifically, FIG. 5A is a timing chart showing the operation of the blocking valve 28, and FIG. 5B is a timing chart showing a change in the tank internal pressure Ptnk.
[0057]
As shown in these drawings, in the apparatus of the present embodiment, the blocking valve 28 is driven with a duty cycle of (T1 + T2) and a duty ratio of {T1 / (T1 + T2)} × 100, so that the tank internal pressure Ptnk is stepped. The pressure is reduced. T1 and T2 are determined such that the duty ratio becomes smaller as the evaporated fuel is more likely to blow through. And as the duty ratio is smaller, the gas in the fuel tank 10 becomes harder to be discharged. For this reason, according to the apparatus of the present embodiment, the amount of gas discharged from the fuel tank 10 when the closing valve 28 is opened is not unnecessarily suppressed, and is suppressed to an amount that does not allow the evaporated fuel to blow through. it can.
[0058]
The closing valve 28 is opened for the purpose of reducing the tank internal pressure Ptnk. In order to satisfy this requirement early, it is desirable that the amount of gas discharged from the fuel tank 10 is not unnecessarily limited. On the other hand, in order to maintain good emission characteristics, the amount of gas discharged from the fuel tank 10 needs to be suppressed to an amount that does not cause the fuel vapor to blow through. Further, if attention is focused on the durability of the blocking valve 28, it is desirable that the number of opening and closing of the blocking valve 28 be minimized.
[0059]
According to the routine shown in FIG. 3, the closing valve 28 can be opened and closed so that all three requirements are satisfied. For this reason, according to the apparatus of the present embodiment, the internal pressure Ptnk is quickly reduced during the operation of the internal combustion engine without significantly deteriorating the durability of the blocking valve 28 and without deteriorating the emission characteristics. can do.
[0060]
In the second embodiment described above, both the valve opening time T1 and the valve closing time T2 of the blocking valve 28 are set as appropriate. However, the setting target is not limited to this. That is, one of the valve opening time T1 and the valve closing time T2 may be a fixed value, and only the other may be set as appropriate.
[0061]
In the second embodiment described above, the valve opening time T1 and the valve closing time T2 are determined based on both the tank internal pressure Ptnk and the purge amount. However, the determination method is limited to this. It is not a thing. That is, the valve opening time T1 and the valve closing time T2 may be simply determined based only on the tank internal pressure Ptnk or based only on the purge amount.
[0062]
In the second embodiment described above, the operation pattern of the blocking valve 28 is determined by determining the valve opening time T1 and the valve closing time T2, but the method of determining the pattern is limited to this. is not. That is, the operation pattern of the blocking valve 28 may be determined by, for example, the driving duty ratio, the driving duty cycle, or a combination of both.
[0063]
In the second embodiment described above, when the opening of the blocking valve 28 is required, the operation pattern of the blocking valve 28 is always determined. However, the present invention is not limited to this. . That is, when opening of the blocking valve 28 is requested, the operation pattern determination process is performed only when the tank internal pressure Ptnk is high (for example, the pressure exceeding the predetermined pressure (3) in the first embodiment). When the tank internal pressure Ptnk is low, the operation pattern determination process may be omitted and the block valve 28 may be fully opened.
[0064]
still , In the second embodiment described above, the ECU 60 executes the processing of steps 100, 102, 110 and 132 described above, thereby Second The “blocking valve control means” in the present invention is realized.
[0065]
Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG.
The blow-through of the evaporated fuel accompanying the opening of the blocking valve 28 occurs when the amount of gas discharged from the fuel tank 10 exceeds a certain limit value. Therefore, it is possible to prevent the vaporized fuel from blowing through if the amount of exhaust gas per unit time can be limited to the above limit value or less.
[0066]
The apparatus of the second embodiment described above determines the valve opening pattern (valve opening time T1, valve closing time T2, duty ratio, duty cycle, etc.) of the block valve 28 so that the above requirements are satisfied. By driving the block valve 28, the fuel vapor is prevented from being blown through. On the other hand, the apparatus of the present embodiment prevents the vaporized fuel from being blown out by regulating the pressure reduction amount ΔP of the tank internal pressure Ptnk generated by opening the block valve 28 once in accordance with the above-described requirements.
[0067]
FIG. 6 is a flowchart of a control routine executed by the ECU 60 in order to realize the above function. The apparatus of the present embodiment can be realized by causing the ECU 60 to execute the routine shown in FIG. 6 instead of the routine shown in FIG. 2 described above in the apparatus of the first embodiment. In FIG. 6, the same steps as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted or simplified.
[0068]
That is, in the routine shown in FIG. 6, when it is determined in step 110 that the purge rate PGR exceeds α%, first, the vaporized fuel is blown out based on the tank internal pressure Ptnk and the purge amount at that time. The maximum pressure reduction amount ΔP that can be applied to the tank internal pressure Ptnk without being generated is determined as the pressure reduction target value ΔPtnkgt (step 140).
The ECU 60 has a map related to the pressure reduction target value ΔPtnkgt. In this step 140, ΔPtnkgt is determined according to the map. Similar to the map of the valve opening time T1 shown in FIG. 4A, this map is set so that ΔPtnkgt becomes smaller as the tank internal pressure Ptnk is higher and the purge amount is smaller. Therefore, the pressure reduction target value ΔPtnkgt is set to a smaller value in an environment where the evaporated fuel is likely to blow through.
[0069]
In the routine shown in FIG. 6, it is next determined whether or not the pressure reduction amount ΔP generated in the tank internal pressure Ptnk is smaller than the pressure reduction target value ΔPtnkgt (step 142).
As a result, when it is determined that ΔP <ΔPtnkgt is established, it can be determined that the pressure reduction amount ΔP of the tank internal pressure Ptnk has not yet reached the target pressure reduction value ΔPtnkgt. In this case, after the blocking valve 28 is controlled to be in an open state (step 144), the current processing cycle is terminated.
On the other hand, if it is determined in step 142 that ΔP <ΔPtnkgt does not hold, it can be determined that the tank internal pressure Ptnk has already been depressurized more than the target depressurization value ΔPtnkgt. In this case, after the closing valve 28 is closed (step 102), the current processing cycle is terminated.
[0070]
According to the above processing, the blocking valve 28 is always closed every time the tank internal pressure Ptnk is reduced by a value ΔPtnkgt that does not cause the fuel vapor to blow through. For this reason, according to the routine shown in FIG. 6, the amount of gas discharged from the fuel tank 10 per unit time can be suppressed, and the vaporized fuel can be prevented from being blown through. Further, according to this routine, since the pressure reduction target value ΔPtnkgt is not set to an unnecessarily small value, the tank internal pressure Ptnk can be quickly reduced and the number of times of operation of the block valve 28 can be reduced. Can do. Therefore, according to the apparatus of this embodiment, the same effect as that of the apparatus of Embodiment 2 can be achieved.
[0071]
By the way, in the above-described third embodiment, the pressure reduction target value ΔPtnkgt to be generated in the tank internal pressure Ptnk with the opening of the blocking valve 28 is determined based on the tank internal pressure Ptnk and the purge amount. The determination method is not limited to this. That is, the depressurization target value ΔPtnkgt may be simply determined based only on the tank internal pressure Ptnk or based only on the purge amount. More precisely, the pressure reduction target value ΔPtnkgt is determined in consideration of the amount of fuel remaining in the fuel tank 10 when the blocking valve 28 is opened (that is, the space volume in the fuel tank 10). It is also good. Since the amount of gas flowing out of the fuel tank 10 per unit time changes in accordance with the space volume in the fuel tank 10, the tank can be maximized without causing the vaporized fuel to blow through by taking that factor into consideration. In reducing the internal pressure Ptnk, the valve opening operation of the block valve 28 can be controlled more accurately.
[0072]
still , In the above-described third embodiment, the ECU 60 executes the processing of steps 100, 102, 110 and 144 described above, thereby Second The “blocking valve control means” in the present invention is realized.
[0073]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
According to the first invention, when the fuel tank is connected to both the intake passage and the canister, the air hole of the canister is closed when the tank internal pressure is high, and the air hole when the tank internal pressure is low. Can be released. Therefore, according to the present invention, when the tank internal pressure is high, the vaporized fuel is prevented from being blown from the atmospheric hole. On the other hand, when the tank internal pressure is low, the air is taken in from the atmospheric hole and the purge is efficiently advanced. be able to.
[0078]
Second According to the invention, when the internal combustion engine is stopped, the shutoff valve is closed to prevent vapor blow-through, and during the operation of the internal combustion engine, the internal pressure of the tank is brought close to the atmospheric pressure by opening the shutoff valve in synchronization with the purge. The value can be kept. According to the present invention, when the internal pressure of the tank is high, such as when the internal combustion engine is started or immediately after a long-term purge cut, the fuel tank is connected to both the intake passage and the canister with the start of the purge. Since the on-off valve is closed simultaneously with the conduction, it is possible to reliably prevent vapor blow-through from the canister under such a situation.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining the configuration of a first embodiment of the present invention.
FIG. 2 is a flowchart of a control routine executed in the apparatus according to the first embodiment of the present invention.
FIG. 3 is a flowchart of a control routine executed in the apparatus according to the second embodiment of the present invention.
FIG. 4A is an example of a map of the valve opening time T1 referred to in the execution process of the routine shown in FIG. FIG. 4B is an example of a map of the valve closing time T2 referred to in the execution process of the routine.
FIG. 5 is a timing chart for explaining the operation of the apparatus of the second embodiment realized by executing the routine shown in FIG. 3;
FIG. 6 is a flowchart of a control routine executed in the apparatus according to the third embodiment of the present invention.
[Explanation of symbols]
10 Fuel tank
12 Tank pressure sensor
20 Vapor passage
26 Canister
28 Blockade valve
38 Air intake passage
50 Air holes
52 Negative pressure pump module
60 ECU (Electronic Control Unit)

Claims (2)

An evaporative fuel processing apparatus for an internal combustion engine having a function of sealing a fuel tank and prohibiting the evaporative fuel from flowing out,
A canister communicating with the fuel tank;
A sealing valve interposed between the fuel tank and the canister;
An on-off valve for opening and closing the atmospheric hole of the canister;
A purge mechanism for conducting the canister to an intake passage of an internal combustion engine;
When the fuel tank is connected to both the intake passage and the canister, if the tank internal pressure exceeds the determination pressure, the on-off valve is closed, while the tank internal pressure is equal to or lower than the determination pressure. Is an on-off valve control means for opening the on-off valve; and
An evaporative fuel processing apparatus for an internal combustion engine, comprising: A shut-off valve control for closing the shut-off valve when the internal combustion engine is stopped, and for opening the shut-off valve when the evaporated fuel is purged from the canister to the intake passage during the operation of the internal combustion engine. The evaporative fuel processing apparatus for an internal combustion engine according to claim 1, further comprising means.

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