JP2006170073A - Evaporated fuel treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent fuel vapor from being emitted into the atmosphere when an evaporated fuel path is checked for leakage. <P>SOLUTION: An evaporated fuel treatment device is provided with; a fuel tank 10; a canister 12 connected to the fuel tank 10 so as to adsorb the evaporated fuel generated in the fuel tank 10; a negative pressure pump 38 connected to the canister 12 so as to introduce negative pressure into a closed space including the fuel tank 10 via the canister 12; a pressure sensor 40 which detects the pressure in the closed space under such a condition that the negative pressure is introduced in the closed space by the negative pressure pump 38; a judgement means for judging the state of leakage of the closed space including the fuel tank 10 based on the pressure detected by the pressure sensor 40; and a positive pressure introducing means which introduces positive pressure into the closed space by reversing the negative pressure pump 38 before introducing the negative pressure into the closed space. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an evaporated fuel processing apparatus, and is particularly suitable for application to an apparatus for processing evaporated fuel generated in a fuel tank.

  2. Description of the Related Art Conventionally, there is known an evaporative fuel processing apparatus that prevents vaporized fuel (fuel vapor) generated in a fuel tank from being released into the atmosphere by adsorbing it to a canister.

  In such an evaporative fuel processing apparatus, a method of applying pressure to the evaporative fuel path in order to determine leakage in a closed space is known. For example, Japanese Patent Laid-Open No. 2003-42014 describes a method of introducing a negative pressure using a pump into an evaporative fuel path including a fuel tank and determining leakage in a closed space based on pressure information at that time. Yes.

Japanese Patent Laid-Open No. 2003-42014 JP 2003-155958 A JP 2004-156492 A JP-A-9-184454

  However, in the above conventional technique, when a negative pressure is introduced by a pump when performing leakage determination, a flow from the closed space toward the pump is generated. For this reason, when the fuel vapor is floating in the vicinity of the pump in the closed circuit space, there arises a problem that the fuel vapor is discharged from the pump into the atmosphere.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to surely prevent the fuel vapor from being released into the atmosphere when performing the leakage determination of the evaporated fuel path. .

  In order to achieve the above object, a first invention is connected to a fuel tank, a canister that is connected to the fuel tank and absorbs evaporated fuel generated in the fuel tank, and is connected to the canister, via the canister. A pump for introducing a negative pressure into the closed space including the fuel tank, and a positive pressure is introduced into the closed space via the canister by reversing the pump before introducing the negative pressure into the closed space. And a positive pressure introducing means.

  According to a second invention, in the first invention, a pressure detecting means for detecting a pressure in the closed space in a state where a negative pressure is introduced into the closed space by the pump, and a pressure detected by the pressure detecting means And determining means for determining a leakage state in a closed space including the fuel tank.

  In order to achieve the above object, a third aspect of the invention is a fuel tank, a canister connected to the fuel tank, and adsorbing evaporated fuel generated in the fuel tank, and connected to the canister, via the canister A pump for introducing a negative pressure into a closed space including the fuel tank, and a collecting means for collecting the evaporated fuel discharged from the pump when the negative pressure is introduced by the pump. And

  According to a fourth invention, in the third invention, in the state where a negative pressure is introduced into the closed space by the pump, a pressure detecting means for detecting a pressure in the closed space, and a pressure detected by the pressure detecting means And determining means for determining a leakage state in a closed space including the fuel tank.

  According to a fifth invention, in the third or fourth invention, after introducing negative pressure into the closed space, the pump is reversed to introduce positive pressure into the closed space via the canister, and the trapping is performed. And a positive pressure introducing means for returning the evaporated fuel in the collecting means to the closed space.

  According to the first invention, before the negative pressure is introduced into the closed space, the pump is inverted to introduce the positive pressure into the closed space, so that the fuel vapor floating in the vicinity of the pump is sent to the canister. be able to. Therefore, when a negative pressure is introduced into the closed space, it is possible to reliably prevent the fuel vapor from being released into the atmosphere.

  According to the second invention, it is possible to determine the state of leakage in the closed space including the fuel tank based on the pressure detected by the pressure detecting means.

  According to the third aspect of the invention, since the collecting means for collecting the evaporated fuel discharged from the closed space is provided, the fuel vapor is reliably prevented from being released into the atmosphere when the negative pressure is introduced into the closed space. can do.

  According to the fourth aspect, it is possible to determine the state of leakage in the closed space including the fuel tank based on the pressure detected by the pressure detecting means.

  According to the fifth aspect of the present invention, after introducing negative pressure into the closed space, the positive pressure is introduced into the closed space by reversing the pump, and the evaporated fuel in the collecting means is returned to the closed space. It is possible to reliably prevent the evaporated fuel in the space from being released into the atmosphere.

  Several 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. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram for explaining an outline of the fuel vapor 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, a canister 12, a pump module 14, and an air filter 16.

  A canister 12 communicates with the fuel tank 10 through a vapor passage 18. A pump module 14 communicates with the canister 12 through a pump passage 20. The canister 12 is filled with activated carbon 22 for adsorbing fuel vapor flowing from the fuel tank 10. The canister 12 is provided with a vapor port 24 connected to the vapor passage 18, a pump side port 26 connected to the pump passage 20, and a purge port 32 communicating with a purge passage 30 described later. As shown in FIG. 1, the vapor port 24, the pump side port 26, and the purge port 32 are provided on the same side with respect to the activated carbon 22. Further, barriers 34 and 35 for restricting the flow of gas and fuel vapor in the activated carbon 22 are provided inside the canister 12.

  The purge passage 30 is a passage communicating with an intake passage (not shown) of the internal combustion engine. In the middle of the purge passage 30, a purge VSV 36 for controlling the conduction state is provided. During operation of the internal combustion engine, the intake negative pressure of the internal combustion engine is guided into the purge passage 30. Further, as will be described later, during operation of the internal combustion engine, the state of the pump module 14 is set so that the pump-side port 26 is opened to the atmosphere (air filter 16 side). When the purge VSV 36 is opened in this state, the intake negative pressure reaches the purge port 32 of the canister 12, and as a result, an air flow from the pump side port 26 toward the purge port 32 is generated. When such an air flow occurs, desorption occurs in the fuel adsorbed on the activated carbon 22. Therefore, by appropriately opening the purge VSV 36 during operation of the internal combustion engine, the fuel adsorbed by the canister 12 can be appropriately purged by the internal combustion engine.

FIG. 2 is a schematic diagram showing the configuration of the pump module 14. The pump module 14 includes a negative pressure pump 38, a pressure sensor 40, a switching valve (VSV) 42, a switching actuator 44, a reference orifice 46, a check valve 48, and a positive pressure introduction valve 49. The switching valve 42 has a passage 42a and a passage 42b. The reference orifice 46 is a reference hole (for example, φ0.5 mm) provided for measuring a reference pressure P _REF used for leak determination. The check valve 48 has a function of blocking the gas flow from the negative pressure pump 38 toward the pressure sensor 40.

  The switching valve 42 is driven by energizing the switching actuator 44, and is set to one of the states shown in FIG. 2 (A) and FIG. 2 (B). Here, in the state (VSV-ON) shown in FIG. 2A, the negative pressure pump 38 and the pump-side port 26 of the canister 12 are connected by the passage 42a. In the state shown in FIG. 2B, a path from the air filter 16 through the reference orifice 46 to the negative pressure pump 38 is connected by the passage 42b.

  As shown in FIG. 1, the evaporated fuel processing apparatus of this embodiment includes an ECU (Electronic Control Unit) 50. The ECU 50 is connected to a negative pressure pump 38, a pressure sensor 40, a switching actuator 44, a positive pressure introduction valve 49, and the like in the pump module 14.

  In the evaporative fuel processing apparatus of the present embodiment configured as described above, a method for determining evaporative fuel path leakage will be described below. In the present embodiment, a negative pressure is applied to the fuel vapor path including the fuel tank 10 and the canister 12 by the pump module 14, and leakage determination is performed based on the pressure detected by the pressure sensor 40.

When performing leak determination, first, the reference pressure P _REF is measured. When measuring the reference pressure _PREF , the switching valve 42 is set to the position shown in FIG. 2B (VSV-OFF). Further, the positive pressure introduction valve 49 is closed. When the negative pressure pump 38 is driven in the state shown in FIG. 2B, the air on the check valve 48 side is sucked by the negative pressure pump 38, and the flow of air in the direction indicated by the arrow in FIG. Arise. As a result, the upstream side of the reference orifice 46 provided with the pressure sensor 40 has a negative pressure. In this state, the pressure is measured by the pressure sensor 40 to detect the reference pressure P _REF corresponding to the φ 0.5 mm reference orifice 46. can do.

Next, in order to introduce a negative pressure into the evaporated fuel path including the fuel tank 10 and the canister 12, the purge VSV 36 is closed, and the switching valve 42 is set to the position shown in FIG. 2A (VSV-ON). The positive pressure introduction valve 49 is kept closed. When the negative pressure pump 38 is driven in this state, the air in the canister 12 is sucked by the negative pressure pump 38, and an air flow in the direction indicated by the arrow in FIG. As a result, a negative pressure is introduced into the evaporated fuel path including the fuel tank 10 and the canister 12. And the pressure P _{actual value} at this time is _measured with the pressure sensor 40.

FIG. 3 is a schematic diagram showing the relationship between the transition of the _{actual measurement value} of the pressure P detected by the pressure sensor 40 and the reference pressure P _REF when a negative pressure is introduced into the fuel vapor path including the fuel tank 10 and the canister 12. It is. As shown in FIG. 3, when the negative pressure pump 38 is operated to apply a negative pressure to the fuel vapor path including the fuel tank 10 and the canister 12, the _{actual measurement value} of the pressure P decreases and a certain time has passed. Then settle down to a steady state. The _{actual value} of the pressure P is compared with the reference pressure _PREF after having settled to a steady state. In FIG. 3, P _REF and P _{actually measured values} are both negative values.

As shown by a solid line in FIG. 3, when the _{actual measurement value} of the pressure P is higher than the reference pressure P _REF, a leak hole whose pressure in the evaporated fuel path is equivalent to φ0.5 mm even though a negative pressure is applied. It can be determined that the pressure is higher than the pressure in the case of occurrence of Therefore, in this case, it can be determined that a leak hole larger than φ0.5 is formed in the evaporated fuel path.

On the other hand, as shown by the dashed line in FIG. 3, when the pressure P _{measured value} is lower than the reference pressure P _REF is lower than the pressure when the pressure in the fuel vapor passage occurs leaking hole of the corresponding φ0.5mm It can be judged that it is in a state. Therefore, in this case, it can be determined that the leak hole in the evaporated fuel path is smaller than φ0.5.

As described above, according to the evaporated fuel processing apparatus of the present embodiment, it is determined whether or not there is a leak hole in the evaporated fuel path based on the result of comparing the pressure P _{actual measurement value} with the reference pressure _PREF. Can do.

  When a negative pressure is introduced into the evaporated fuel path, gas in the evaporated fuel path including the fuel tank 10 is released from the air filter 16 to the atmosphere. At this time, if the fuel vapor is floating in the evaporated fuel path, the fuel vapor may be released into the atmosphere. In particular, when the fuel vapor is floating in the pump module 14 and the pump passage 20, when a negative pressure is introduced, the fuel vapor is easily released into the atmosphere. Further, when the adsorption state of the fuel vapor in the canister 12 is saturated, a part of the fuel vapor adsorbed by the introduction of the negative pressure is deviated, and the fuel vapor is also easily released into the atmosphere.

  For this reason, in this embodiment, before the negative pressure is introduced into the evaporated fuel path, the negative pressure pump 38 is reversed and air is sent from the air filter 16 side toward the canister 12 side. Thereby, the fuel vapor floating near the pump module 14 or the pump passage 20 can be sent to the canister 12, and the fuel vapor floating can be attached to the activated carbon 22 of the canister 12. Therefore, it is possible to prevent the floating fuel vapor from being released into the atmosphere when a negative pressure is introduced into the evaporated fuel path at the time of leak detection.

  FIG. 4 is a schematic diagram showing a state of the pump module 14 when the negative pressure pump 38 is reversed and air is sent into the evaporated fuel path. When air is sent into the fuel vapor path, the switching valve 42 is set to the position shown in FIG. 4 (VSV-ON), and the positive pressure introduction valve 49 is opened. In this state, the negative pressure pump 38 is reversed. Thereby, the air by the side of the air filter 16 is attracted | sucked by the negative pressure pump 38, and the flow of the air which goes to the direction shown by the arrow in FIG. 4 arises. As a result, positive pressure is introduced into the evaporated fuel path including the fuel tank 10 and the canister 12, and air is sent into the evaporated fuel path.

  FIG. 5 is a schematic view showing the floating state and adsorption state of the fuel vapor in the vicinity of the canister 12. Here, FIG. 5 (A) shows a state before the negative pressure is introduced into the evaporated fuel path. As shown in FIG. 5A, the fuel vapor generated in the fuel tank 10 is adsorbed by the activated carbon 22 of the canister 12. A part of the fuel vapor flows from the canister 12 toward the pump module 14 and floats in the pump module 14 or in the vicinity of the pump passage 20.

  FIG. 5B shows a state where the negative pressure pump 38 is reversed from the state shown in FIG. As shown in FIG. 5B, when the negative pressure pump 38 is operated in reverse, an air flow from the pump module 14 side toward the canister 12 is generated and floated in the vicinity of the pump module 14 or the pump passage 20. The fuel vapor is adsorbed on the activated carbon 22 of the canister 12.

  In the state of FIG. 5 (B), the fuel vapor hardly floats in the vicinity of the pump module 14 or the pump passage 20, so that the negative pressure pump 38 is rotated forward so that a negative pressure is applied to the evaporated fuel path including the canister 12. Even if it is a case where it introduce | transduces, it can suppress that fuel vapor is discharged | emitted from the air filter 16 in air | atmosphere.

  FIG. 5C shows a case where negative pressure is introduced into the evaporated fuel path from the state shown in FIG. 5A without causing the negative pressure pump 38 to reverse. Thus, when the negative pressure pump 38 is not reversed, the fuel vapor floating near the pump module 14 or the pump passage 20 passes through the air filter 16 and is released into the atmosphere.

  Therefore, according to the present embodiment, the fuel vapor that has floated in the pump module 14 is sent to the canister 12 by reversing the negative pressure pump 38 before detecting the leak, so that the fuel vapor is detected when the leak is detected. Release to the atmosphere can be reliably suppressed.

  Next, a processing procedure in the system of the evaporated fuel processing apparatus of the present embodiment will be described based on the flowchart of FIG. The process of FIG. 6 is performed every predetermined time. First, in step S1, it is determined whether or not the current condition corresponds to a condition for detecting leakage of the evaporated fuel path. Specifically, it is determined whether a predetermined time has elapsed after the engine is stopped. If the condition for leak detection is met, the process proceeds to step S2, and if the condition is not met, the process is terminated (RETURN).

  In the next step S2, it is determined whether or not the operating condition of the negative pressure pump 38 is satisfied. If the operating condition is satisfied, the process proceeds to step S3. If the operating condition is not satisfied, the process is terminated (RETURN).

  In the next step S3, it is determined whether or not the state of the X pump inversion flag is 1. Here, the X pump inversion flag is a flag for identifying whether or not the operation of inverting the negative pressure pump 38 is completed. The X reference flag is set to 1 when the inversion operation is completed, and the X reference flag is set to 0 when the inversion operation is not completed.

  If the X pump inversion flag = 1 in step S3, the process proceeds to step S4. In step S4, it is determined whether or not a predetermined time A has elapsed after the operation for reversing the negative pressure pump 38 is completed. If the A time has elapsed, the process proceeds to step S5. If the A time has not elapsed, the process is terminated (RETURN).

  On the other hand, if the X pump inversion flag = 0 in step S3, the process proceeds to step S23. In step S23, the inversion time of the negative pressure pump 38 is compared with a predetermined B time, and it is determined whether or not the inversion time <B time. If the inversion time is less than B time, the process proceeds to step S24. In this case, since the reversing operation of the negative pressure pump 38 is not performed at all, or the reversing operation of the negative pressure pump 38 is insufficient, in step S24, the state of the switching valve 42 is shown in FIG. The state is set (VSV-ON), the positive pressure introduction valve 49 is opened, and the negative pressure pump 38 is reversed. As a result, as described with reference to FIG. 5B, the fuel vapor floating in or near the pump module 14 is sent into the canister 12.

  If inversion time ≧ B time in step S23, the process proceeds to step S25. In this case, since the inversion operation of the negative pressure pump 38 is sufficiently performed, the X pump inversion flag is set to 1 in step S25. After step S25, the process proceeds to step S26. In step S26, the state of the switching valve 42 is set to the state shown in FIG. 2B (VSV-OFF), the positive pressure introduction valve 49 is closed, and the negative pressure pump 38 is stopped. After step S26, the process is terminated (RETURN).

When the process proceeds from step S4 to step S5, it is determined in step S5 whether or not the state of the X reference flag is zero. Here, the X reference flag is a flag for identifying whether or not the measurement of the reference pressure P _REF is completed. X Reference flag if the measured reference pressure P _REF is completed is set to 1, when the measurement of the reference pressure P _REF is not completed X reference flag is set to 0.

If the X reference flag = 0 in step S5, the process proceeds to step S6. In this case, since the measurement of the reference pressure P _REF is not completed, the reference pressure P _REF is measured in the subsequent processing. That is, in step S6, the state of the switching valve 42 is set to the state shown in FIG. 2B (VSV-OFF), and the positive pressure introduction valve 49 is closed. In the next step S7, the negative pressure pump 38 is rotated forward, and in the next step S8, it is determined whether or not the operating time of the negative pressure pump 38 has passed a predetermined time (T time). Here, the time T is a threshold value for determining whether or not the reference pressure P _REF has reached a steady state.

If the operating time of the negative pressure pump 38 has elapsed T time in step S8, the process proceeds to step S9. In this case, since the reference pressure _{P REF} is considered to have reached a steady state, in step S9, determine the reference pressure _{P REF} from the detection value of the pressure sensor 40. On the other hand, if the operating time of the negative pressure pump 38 has not reached T time in step S8, the process is terminated (RETURN).

After step S9, the process proceeds to step S10. In step S10, the absolute value of the reference pressure P _REF is compared with a predetermined threshold value (target PM1 (> 0)) to determine whether or not target PM1 <| P _REF |. Here, the threshold value PM1 is a threshold value for determining an abnormality of the system based on the reference pressure _PREF .

If PM1 <| P _REF | in step S10, the reference pressure P _REF is sufficiently reduced, so that the measured P _REF is determined to be a normal value, and the process proceeds to step S11. At step S11, it is set as the target pressure (= PM2) during determining leakage absolute value of the measured _{P REF.} On the other hand, if PM1 ≧ | P _REF | in step S10, it can be determined that an abnormality has occurred in the negative pressure pump 38, the pressure sensor 40, or the like because the reference pressure P _REF has not sufficiently decreased. Therefore, in this case, the process proceeds to step S14, where it is determined that an abnormality has occurred in the negative pressure pump 38 and the like, the state of the switching valve 42 is set to the state shown in FIG. 2A (VSV-OFF), and pressure suppression is introduced. The valve 49 is closed and the operation of the negative pressure pump 38 is stopped. After step S14, the process ends (END).

On the other hand, when the process proceeds from step S10 to step S11, the process proceeds to the next step S12, and since the acquisition of the reference pressure P _REF (target pressure PM2) is completed, the state of the X reference flag is set to 1. In the next step S13, the state of the switching valve 42 is set to the state shown in FIG. 2A (VSV-ON), and the operation of the negative pressure pump 38 is stopped. After step S13, the process ends (RETURN).

If the reference pressure P _REF (target pressure PM2) has already been acquired, that is, if the X reference flag = 1 in step S5, the process proceeds to step S15. In this case, leak determination is performed based on the reference pressure P _REF in the subsequent processing.

  In step S15, the state of the switching valve 42 is set to the state shown in FIG. 2A (VSV-ON), and the negative pressure pump 38 is rotated forward. As a result, a negative pressure is introduced into the evaporated fuel path including the fuel tank 10 and the canister 12.

In the next step S16, the pressure P _{actual measurement value} is obtained from the detection value of the pressure sensor 40 with the negative pressure introduced into the fuel vapor path. In the next step S17, the target pressure PM2 set in step S11 is compared with the absolute value of the pressure P _{actual value} detected in step S16, and it is determined whether or not the target pressure PM2> | P _{actual value} |. .

When the target pressure PM2> | P _{actual measurement value} | is satisfied in step S17, the process proceeds to the next step S18. In this case, since the absolute value of the P _{actual measurement value} does not reach the target pressure PM2, there is a possibility that a leak hole having a size of φ0.5 mm or more is generated in the evaporated fuel path. It is also conceivable that the absolute value of the P _{actual measurement value} has not reached the target pressure PM2 because the time is short. Therefore, in step S18, it is determined whether or not the operating time of the negative pressure pump 38 is within the upper limit C time.

If the operation time of the negative pressure pump 38 is within B hours in step S18, it is assumed that the P _{actual measurement value} has not reached the target pressure PM2 because the operation time of the negative pressure pump 38 is short. The operation of the negative pressure pump 38 is continued.

On the other hand, if the operating time of the negative pressure pump 38 exceeds the B time in step S18, the process proceeds to step S21. In this case, since the negative pressure pump 38 is operating sufficiently, it can be determined that the value of the _actual pressure P detected in step S16 is a value that can be compared with the reference pressure _PREF . Therefore, it is possible to make a leak determination based on the pressure P _{actual measurement value} . In this case, since it has already been determined in step S17 that the _{actually measured} pressure P has not reached the target pressure PM2, it can be determined that a leak hole having a size of φ0.5 mm or more has occurred in the evaporated fuel path. Accordingly, in step S21, it is determined (abnormality determination) that there is a leak in the evaporated fuel path.

If PM1 ≦ | P _{actual value} | in step S17, since the _actual pressure P has reached the target pressure PM2, there is no leakage hole having a size of φ0.5 mm or more in the evaporated fuel path. I can judge. Accordingly, in this case, the process proceeds to step S20, and it is determined that there is no leakage in the evaporated fuel path (normal determination).

  After the determination in step S20 or step S21, the process proceeds to step S22, the state of the switching valve 42 is set to the state shown in FIG. 2B (VSV-OFF), the positive pressure introduction valve 49 is closed, and the negative pressure is set. The pressure pump 38 is stopped. After step S22, the process ends (END).

  As described above, according to the first embodiment, since the negative pressure pump 38 is reversed before the leak detection is performed and the fuel vapor floating in the pump module 14 is sent to the canister 12, the leak detection is performed. In this case, it is possible to reliably prevent the fuel vapor from being released into the atmosphere.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described. FIG. 7 is a diagram for explaining the outline of the evaporated fuel processing apparatus according to the second embodiment. As shown in FIG. 7, in the second embodiment, a trap container 52 is provided between the air filter 16 and the pump module 14.

  As described in the first embodiment, when a negative pressure is introduced into the evaporated fuel path while the fuel vapor is floating in the vicinity of the pump module 14 or the pump passage 20, the floating fuel vapor is brought into the atmosphere. May be released.

  In the second embodiment, when negative pressure is introduced into the evaporated fuel path, if fuel vapor floating near the pump module 14 or the pump passage 20 flows to the air filter 16 side, the fuel vapor is removed from the trap container. It is made to capture in 52. In other words, in the present embodiment, the trap container 52 functions as a collecting means (adsorbent, buffer) for collecting fuel vapor and gas from the pump module 14 toward the air filter 16 side.

  The volume of the trap container 52 is desirably equal to or larger than the volume of air discharged from the evaporated fuel path when a negative pressure is introduced into the evaporated fuel path at the time of leakage determination. As a result, even when the fuel vapor floating near the pump module 14 or the pump passage 20 flows to the trap container 52 side when the negative pressure is introduced into the evaporated fuel path, the fuel vapor is trapped in the trap container 52. It can suppress that it is discharged | emitted outside. Therefore, if a trap volume equal to or greater than the volume of the discharged air is provided, it is possible to reliably prevent the fuel vapor from being released into the atmosphere.

Specifically, assuming that the fuel tank 10 is empty, the space volume of the fuel vapor path including the fuel tank 10 and the canister 12 is 100 liters, the atmospheric pressure is 760 mmHg, and the reference pressure P _REF is −30 mmHg. If there is no leakage in the evaporated fuel path, the amount of air V1 discharged from the evaporated fuel path until the _measured pressure P reaches −30 mmHg can be obtained from the following equation.
V1 = 100 (liter) × (1− (760−30) / 760) ≈4 (liter) (1)
Therefore, when the atmospheric pressure is 760 mmHg, about 4 liters of air is discharged from the evaporated fuel path when determining the leak. Therefore, the volume of the trap container 52 is preferably set to 4 liters or more.

  FIG. 8 is a schematic view showing the floating state and adsorption state of the fuel vapor around the canister 12 and the trap container 52. Here, FIG. 8 (A) shows a state before the negative pressure is introduced into the evaporated fuel path. As shown in FIG. 8A, the fuel vapor generated in the fuel tank 10 is adsorbed by the activated carbon 22 of the canister 12. A part of the fuel vapor flows from the canister 12 toward the pump module 14 and floats in the vicinity of the pump module 14 or the pump passage 20.

  FIG. 8B shows a state in which negative pressure is introduced into the evaporated fuel path by operating the negative pressure pump 38 from the state shown in FIG. When negative pressure is introduced into the evaporated fuel path, an air flow from the canister 12 toward the trap container 52 is generated.

  At this time, the volume of the trap container 52 is equal to or larger than the volume of the air discharged from the evaporated fuel path when the negative pressure is introduced as described above, and as shown in FIG. In addition, the fuel vapor floating in the vicinity of the pump module 14 or the pump passage 20 is captured in the trap container 52 and does not flow to the air filter 16 side.

  As shown in FIGS. 7 and 8, since the partition plate 52a is provided in the trap container 52, the gas and fuel vapor flowing from the pump module 14 to the trap container 52 are trapped in the trap container 52 by the partition plate 52a. Sent to the bottom. Therefore, it is possible to reliably prevent the fuel vapor that has flowed into the trap container 52 from flowing toward the air filter 16.

  After the operation of the negative pressure pump 38 is stopped, the fuel vapor is heavier than air, so that it accumulates toward the bottom of the trap container 52. At this time, as shown in FIG. 8B, since the air filter 16 is connected to the upper portion of the trap container 52, the fuel vapor accumulated at the bottom of the trap container 52 is prevented from flowing to the air filter 16 side. The Therefore, even after the operation of the negative pressure pump 38 is stopped, the fuel vapor can be prevented from being released into the atmosphere.

  When the internal combustion engine is operated after performing the leak determination, the purge VSV 36 is opened, and the negative pressure of the intake pipe is introduced to the canister 12 side. As a result, the fuel vapor adsorbed on the canister 12 is purged into the intake pipe. At this time, by setting the switching valve 42 of the pump module 14 to the state (VSV-OFF) shown in FIG. 2B, a flow from the trap container 52 toward the canister 12 is generated by the intake pipe negative pressure. Can do. As a result, the fuel captured in the trap container 52 can be sent to the canister 12 side, and the fuel vapor can be discharged from the trap container 52.

  Further, in order to discharge the fuel vapor in the trap container 52, the negative pressure pump 38 may be operated in reverse. FIG. 9 shows a state in which the negative pressure pump 38 is reversely operated after the state shown in FIG.

  At this time, the state of the switching valve 42 of the pump module 14 is set to the state described with reference to FIG. When the negative pressure pump 38 is reversely operated in this state, a flow from the trap container 52 toward the canister 12 is generated, and the fuel vapor in the trap container 52 is sent to the canister 12 side. Thereby, the fuel vapor can be discharged from the trap container 52. Then, by opening the purge VSV 36 during operation of the internal combustion engine, the fuel vapor sent to the canister 12 can be purged to the intake pipe.

  As described above, according to the second embodiment, since the trap container 52 is provided between the pump module 14 and the air filter 16, the pump module 14 moves toward the air filter 16 when negative pressure is introduced at the time of leakage determination. The fuel vapor that has flowed can be captured in the trap container 52. Therefore, it is possible to reliably prevent the fuel vapor from being released into the atmosphere.

  In each of the above-described embodiments, in the system for determining the leak of the evaporated fuel path, negative pressure is introduced into the closed space of the evaporated fuel path including the fuel tank 10, but the present invention is a system for determining the leak. It is also possible to apply to other systems. For example, the negative pressure pump 38 is operated to prevent the fuel vapor from filling the closed space of the evaporated fuel path including the fuel tank 10 when the vehicle equipped with the evaporated fuel processing apparatus of the present embodiment stops. Thus, by introducing a negative pressure into the closed space, it can be applied to various systems such as a system for adsorbing fuel vapor in the closed space to the canister 12. Even in this case, it is possible to reliably prevent the fuel vapor from being released into the atmosphere.

It is a figure for demonstrating the outline | summary of the evaporative fuel processing apparatus which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the structure of a pump module. FIG. 6 is a schematic diagram showing a relationship between a transition of an _{actual measurement value} of pressure P detected by a pressure sensor and a reference pressure _PREF when a negative pressure is introduced into an evaporative fuel path including a fuel tank and a canister. It is a schematic diagram which shows the state of the pump module at the time of reversing a negative pressure pump and sending air into an evaporative fuel path | route. 3 is a schematic diagram showing a floating state and an adsorbing state of fuel vapor in the vicinity of the canister 12. FIG. 3 is a flowchart illustrating a processing procedure in the system according to the first embodiment. It is a figure for demonstrating the outline | summary of the evaporative fuel processing apparatus which concerns on Embodiment 2. FIG. In Embodiment 2, it is a schematic diagram which shows the floating state and adsorption state of the fuel vapor in the periphery of a canister and a trap container. It is a schematic diagram which shows the state which made the negative pressure pump reversely operate | move after the state shown to FIG. 8 (B).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel tank 12 Canister 38 Negative pressure pump 40 Pressure sensor 52 Trap container

Claims (5)

A fuel tank,
A canister connected to the fuel tank and adsorbing the evaporated fuel generated in the fuel tank;
A pump connected to the canister and for introducing a negative pressure into a closed space including the fuel tank via the canister;
A positive pressure introduction means for introducing a positive pressure into the closed space via the canister by reversing the pump before introducing a negative pressure into the closed space;
An evaporative fuel processing apparatus comprising: Pressure detecting means for detecting a pressure in the closed space in a state where negative pressure is introduced into the closed space by the pump;
Determining means for determining a state of leakage in a closed space including the fuel tank based on the pressure detected by the pressure detecting means;
The evaporative fuel processing apparatus according to claim 1, further comprising: A fuel tank,
A canister connected to the fuel tank and adsorbing the evaporated fuel generated in the fuel tank;
A pump connected to the canister and for introducing a negative pressure into a closed space including the fuel tank via the canister;
A collecting means for collecting the evaporated fuel discharged from the pump when a negative pressure is introduced by the pump;
An evaporative fuel processing apparatus comprising: Pressure detecting means for detecting a pressure in the closed space in a state where negative pressure is introduced into the closed space by the pump;
Determining means for determining a state of leakage in a closed space including the fuel tank based on the pressure detected by the pressure detecting means;
The evaporated fuel processing apparatus according to claim 3, further comprising: After introducing a negative pressure into the closed space, a positive pressure is introduced by introducing the positive pressure into the closed space via the canister by reversing the pump and returning the evaporated fuel in the collecting means to the closed space. Means,
The evaporative fuel processing apparatus of Claim 3 or 4 characterized by the above-mentioned.

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