JP2007177653A - Evaporated fuel processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To positively prevent emission of fuel vapor into the atmosphere even when the outside temperature changes when checking an evaporated fuel path for leakage. <P>SOLUTION: The evaporated fuel processing device includes: a fuel tank 10 for storing fuel for combustion of an internal combustion engine; a canister 12 connected to the fuel tank 10 to adsorb the evaporated fuel generated in the fuel tank 10; a negative pressure pump 38 connected to the canister 12; a pump drive means for driving the negative pressure pump 38 when a predetermined precondition is satisfied after operation of the internal combustion engine is stopped, and introducing negative pressure into a closed space including the fuel tank 10 via the canister 12; a pressure sensor 40 for detecting the pressure in the closed space under such a condition that the negative pressure is introduced into the closed space by the negative pressure pump 38; a determination means for determining the state of leakage of the closed space including the fuel tank 10 based on the pressure detected by the pressure sensor 40; a temperature sensor 52 for obtaining the outside temperature; and a correction means for correcting the precondition based on a difference obtained by subtracting the outside temperature during an operation of the internal combustion engine from the outside temperature when determining the leakage state. <P>COPYRIGHT: (C)2007,JPO&INPIT

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, Japanese Patent Application Laid-Open No. 2003-74420 describes a method of applying a negative pressure to the evaporative fuel path in order to determine leakage in a closed space. Japanese Patent Laid-Open No. 2002-357163 discloses that when determining whether to perform a leak determination based on a comparison between the fuel gas concentration and a predetermined condition, the predetermined condition is set to atmospheric pressure, fuel temperature, outside air temperature, intake air temperature, and the like. A technique for correcting based on this is disclosed.

JP 2002-357163 A JP 2003-74420 A

  However, even when the conditions are corrected based on parameters such as atmospheric pressure, fuel temperature, outside air temperature, intake air temperature, etc. by the method described in Japanese Patent Application Laid-Open No. 2002-357163, these parameters are introduced with negative pressure. Since it does not necessarily correlate with the amount of fuel vapor released at the time, fuel vapor floating in the system may be released to the atmosphere when negative pressure is introduced.

  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 a fuel tank that stores combustion fuel for an internal combustion engine, a canister that is connected to the fuel tank and adsorbs evaporative fuel generated in the fuel tank, A pump connected to the canister and after the operation of the internal combustion engine is stopped, when a predetermined precondition is satisfied, the pump is driven to introduce a negative pressure into the closed space including the fuel tank through the canister A pump driving means; 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 the fuel tank based on the pressure detected by the pressure detecting means. Determining means for determining the state of leakage in a closed space including the outside air temperature acquiring means for acquiring the outside air temperature, and the operation of the internal combustion engine from the outside air temperature when determining the state of leakage Based on the difference obtained by subtracting the air temperature, characterized by comprising a correction means for correcting the assumptions.

  According to a second invention, in the first invention, a purge valve provided in a flow path connecting the intake passage of the internal combustion engine and the canister, and the purge valve is opened during operation of the internal combustion engine and adsorbed to the canister Purge means for purging the evaporated fuel to the intake passage, and the precondition is an integrated value of the purge amount of the evaporated fuel to the intake passage, and the pump drive means The pump is driven when the value is equal to or greater than a predetermined determination value, and the correction means increases the determination value as the difference increases.

  In a third aspect based on the first aspect, the precondition is a concentration of the evaporated fuel in the closed space, and the pump driving means is configured so that the concentration of the evaporated fuel is within a predetermined determination value range. The pump is driven, and the correction means corrects the determination value in a direction in which the concentration of the evaporated fuel decreases as the difference increases.

  According to the first aspect of the present invention, the larger the difference obtained by subtracting the outside air temperature during operation of the internal combustion engine from the outside air temperature at the time of determining the leakage state, the greater the amount of evaporated fuel generated. Since the fuel vapor adsorption amount increases, it is possible to stop the driving of the pump under conditions in which evaporated fuel is likely to be generated by correcting the precondition based on the difference. Therefore, it is possible to reliably prevent the evaporated fuel from being released into the atmosphere by driving the pump.

  According to the second aspect of the invention, the larger the difference obtained by subtracting the outside air temperature during operation of the internal combustion engine from the outside air temperature at the time of determining the leakage state, the greater the determination value of the purge amount integrated value. Therefore, the leak determination can be stopped under the condition that the difference is large and the evaporated fuel is easily released into the atmosphere.

  According to the third aspect of the invention, the larger the difference obtained by subtracting the outside air temperature during operation of the internal combustion engine from the outside air temperature at the time of determining the leakage state, the lower the concentration value of the evaporated fuel is. Therefore, the leak determination can be stopped under the condition that the difference is large and the evaporated fuel is easily released to 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 the outline of the fuel vapor processing apparatus according to each embodiment of the present invention. The apparatus shown in FIG. 1 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 in the pump module 14, a pressure sensor 40, a switching actuator 44, a positive pressure introduction valve 49, a temperature sensor 52 for detecting the outside air temperature, and the like.

  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 where the pressure is generated. 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.

  The leak determination is performed when a predetermined precondition is satisfied after the operation of the internal combustion engine is stopped. At this time, it is determined whether or not the precondition is satisfied by comparing the characteristic value such as the integrated value of the fuel vapor purge amount and the fuel vapor concentration during the previous operation with a predetermined determination value. Here, the purge amount integrated value is a value obtained by integrating the amount of purge of the fuel vapor by opening the purge VSV 36 from the start of the previous operation until the stop of the operation. Further, the fuel vapor concentration is the concentration of fuel vapor on the canister 12 side of the purge passage 30 with respect to the purge VSV 36, and the difference between the A / F detected by the air-fuel ratio sensor of the internal combustion engine and the stoichiometry (14.6). Converted from the quantity.

  In this embodiment, when determining whether or not the precondition for the purge amount integrated value is satisfied, the condition is determined based on the difference between the outside air temperature during traveling and the outside air temperature at the time of leak detection (soak). Control is performed to correct a determination value for determining whether or not it is established. Hereinafter, a method for determining whether or not a condition for performing leakage determination based on the purge amount integrated value is satisfied will be described.

  When the fuel vapor purge amount integrated value is small, since the amount of fuel vapor desorbed from the canister 12 is small, it is assumed that a large amount of fuel vapor is adsorbed to the canister 12. Therefore, when a negative pressure is introduced for leak determination, it is assumed that the fuel vapor adsorbed on the canister 12 is desorbed and released from the air filter 16 to the atmosphere. Accordingly, when the purge amount integrated value is less than the predetermined determination value, processing for stopping the leakage determination after the operation stop is performed. Thereby, it can suppress that fuel vapor is discharge | released to air | atmosphere.

  On the other hand, the amount of fuel vapor generated in the fuel tank 10 and the amount of fuel vapor adsorbed in the canister 12 fluctuate depending on the outside air temperature. Therefore, if the above judgment value is set to a constant value, the purge amount integrated value exceeds the judgment value. Even in this case, the fuel vapor may be released to the atmosphere.

  FIG. 4 is a schematic diagram showing how the amount of fuel vapor desorption in the canister 12 changes according to the outside air temperature during travel. Here, FIG. 4A shows a case where the outside air temperature during traveling is relatively low. FIG. 4B shows a case where the outside air temperature during traveling is higher than in the case of FIG. In the state shown in FIG. 4B, more fuel vapor is detached from the canister 12 than in the state shown in FIG. That is, as shown in FIG. 5, fuel vapor desorption from the canister 12 is promoted as the outside air temperature during traveling increases. For this reason, when the outside air temperature during traveling is high, the amount of fuel vapor desorbed from the canister 12 becomes larger than the amount of purge from the purge VSV 36. Therefore, the lower the outside air temperature during traveling, the greater the amount of fuel vapor adsorbed in the canister 12 and the greater the amount of fuel vapor desorbed from the canister 12 when negative pressure is introduced.

  FIG. 6 is a characteristic diagram showing how the amount of fuel vapor generated changes according to the outside air temperature at the time of leak determination. Here, FIG. 6A shows a case where the outside air temperature at the time of leak determination is relatively low. FIG. 6B shows a case where the outside air temperature at the time of leak determination is higher than in the case of FIG. Since fuel vapor is more likely to be generated when the outside air temperature is higher, the amount of fuel vapor generated in the fuel tank 10 is larger in the state shown in FIG. 6B than in the case of FIG. 6A. That is, as shown in FIG. 7, the amount of fuel vapor generated increases as the outside air temperature at the time of leak determination increases. Accordingly, the higher the outside air temperature at the time of leak judgment, the more fuel vapor is adsorbed to the canister 12 and the more fuel vapor is floated to the atmosphere side than the canister 12, and the fuel vapor from the canister 12 when negative pressure is introduced. The amount of desorption increases.

  In this way, the amount of fuel vapor adsorbed in the canister 12 increases as the outside air temperature during traveling decreases, and the amount of fuel vapor generated from the canister 12 increases as the outside air temperature during soaking increases. Therefore, the amount of fuel vapor generated in the fuel tank 10 and the amount of fuel vapor adsorbed to the canister 12 increase as the outside air temperature during soaking is higher than the outside air temperature during traveling and the difference between the two outside air temperatures increases. The fuel vapor floating in the space on the atmosphere side (air filter 16 side) than the canister 12 increases.

  Therefore, based on the difference obtained by subtracting the outside air temperature during traveling from the outside air temperature during soaking (hereinafter referred to as the difference between the outside air temperatures), whether or not fuel vapor is released to the atmosphere when negative pressure is introduced Can be evaluated. When the difference between the outside air temperatures is large, if a negative pressure is introduced into the canister 12 for leak determination, the fuel vapor may be desorbed from the canister 12 and released to the atmosphere.

  For this reason, in this embodiment, as the difference in the outside air temperature is larger, the determination value of the purge amount integrated value is increased, and the condition for performing the leakage determination is made stricter. Thereby, the leak determination can be stopped under the condition that the difference in the outside air temperature is large and the fuel vapor is easily released to the atmosphere.

  FIG. 8 is a schematic diagram showing a map that defines the relationship between the difference between the outside air temperatures and the determination value of the purge amount integrated value. In the present embodiment, it is determined whether or not the leakage determination is performed based on the purge amount integrated value using the two determination values (A) and (B) shown in FIG. As shown in FIG. 8, the determination value (A) is a constant value, and the determination value (B) is a value that increases as the difference in the outside air temperature increases. When the purge amount integrated value is not less than the determination value (A) and not less than the determination value (B), the leakage determination is executed. Accordingly, it is possible to tighten the conditions for performing the leak determination particularly in a region where the difference in the outside air temperature is large, and the leak determination is performed only when the purge amount integrated value is larger. Thereby, it can suppress that fuel vapor will be discharge | released to air | atmosphere.

  Next, a processing procedure in the evaporated fuel processing apparatus of this embodiment will be described with reference to FIG. First, in step S1, it is determined whether or not there is a travel history. If there is a travel history, the process proceeds to step S2. Here, the travel history is a history of characteristic values such as purge amount integrated value and fuel vapor concentration acquired during operation. On the other hand, if there is no travel history, the process proceeds to step S14 to stop leak detection.

  In step S2, it is determined whether or not the soak timer determination is permitted, that is, whether or not a predetermined time has elapsed since the engine stop. If the determination is permitted, the process proceeds to step S3. On the other hand, if the determination is not permitted, the process proceeds to step S14 to stop leak detection.

  In step S3, it is determined whether or not the ignition switch (IG SW) is turned off (OFF). If the ignition switch is turned off, the process proceeds to step S4. On the other hand, if the ignition switch is on, the process proceeds to step S14 to stop leak detection.

  In step S4, it is determined whether or not the cooling water temperature is lower than a predetermined temperature. If the cooling water temperature is lower than the predetermined temperature, the process proceeds to step S5. On the other hand, when the cooling water temperature is equal to or higher than the predetermined temperature, the process proceeds to step S14 and the leak detection is stopped.

  In step S5, it is determined whether or not the temperature in the intake pipe is lower than a predetermined temperature. If the temperature in the intake pipe is lower than the predetermined temperature, the process proceeds to step S6. On the other hand, when the temperature in the intake pipe is equal to or higher than the predetermined temperature, the process proceeds to step S14, and the leak detection is stopped.

  In step S6, it is determined whether or not the fuel vapor concentration during traveling (previous operation) is within a predetermined range. Here, the predetermined determination values a and b (a <b) are compared with the fuel vapor concentration acquired during traveling, and it is determined whether b <fuel vapor concentration <a. If b <fuel vapor concentration <a, the process proceeds to step S7. On the other hand, if b <fuel vapor concentration <a is not satisfied, the process proceeds to step S14 to stop leak detection.

  In step S7, a determination value (A) of the purge amount integrated value is acquired. Here, the determination value (A) shown in FIG. 8 is acquired. In the next step S8, the outside air temperature during travel acquired during the previous travel is captured. The outside air temperature during traveling is detected during the previous traveling and is stored in a memory or the like in the ECU 50.

  In the next step S9, the outside temperature at the time of leak determination, that is, the current outside temperature is acquired. In the next step S10, a process of subtracting the outside air temperature during traveling from the outside air temperature during leak determination is performed. Thereby, the difference of outside temperature is calculated | required.

  In the next step S11, the determination value (B) of the purge amount integrated value is acquired from the map of FIG. 8 based on the value calculated in step S10. In the next step S12, the purge amount integrated value at the previous operation is acquired and compared with each of the determination value (A) and the determination value (B). The purge amount integrated value at the time of the previous operation is an integrated value of the purge amount performed from the start to the end of the previous operation, and is stored in a memory or the like in the ECU 50.

  In step S12, if the purge amount integrated value during the previous operation is not less than the determination value (A) and not less than the determination value (B), the process proceeds to step S13. In this case, since a sufficient amount of purging has been performed during the previous operation, it is considered that the fuel vapor is not released to the atmosphere when the leak is detected. Accordingly, leak detection is executed in step S13. On the other hand, when the purge amount integrated value during the previous operation is smaller than either the determination value (A) or the determination value (B), the purge amount integrated value is small, and the fuel vapor is released to the atmosphere when a leak is detected. Therefore, the process proceeds to step S14, and the leakage detection is stopped. After steps S13 and S14, the process is terminated (RETURN).

  As described above, according to the first embodiment, the determination value of the purge amount integrated value at the time of leak determination is varied according to the difference obtained by subtracting the outside air temperature during traveling from the outside air temperature during soaking. Therefore, the leak determination can be stopped under the condition that the difference is large and the fuel vapor is easily released to the atmosphere at the time of the leak determination.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described. In the second embodiment, the determination value of the fuel vapor concentration is varied based on the difference between the outside air temperature during soaking and the outside air temperature during traveling.

  As described in the first embodiment, the leak determination is performed when the fuel vapor concentration acquired during traveling satisfies the preconditions, and b <fuel vapor concentration <a (a and b are predetermined determination values). In this case, a leak determination is performed. However, if the difference between the outside air temperature at the time of leak judgment and the outside air temperature at the time of travel is large, a lot of fuel vapor is generated at the time of leak judgment, so the fuel vapor concentration at the time of leak judgment is the fuel vapor concentration at the time of travel. May be higher.

  When the fuel vapor concentration at the time of leak determination increases, the amount of fuel vapor adsorbed in the canister 12 increases, and the amount of fuel vapor floating in the space on the atmosphere side of the canister 12 increases. Therefore, even when the fuel vapor concentration during traveling satisfies the above preconditions, it is assumed that the fuel vapor is released to the atmosphere if a negative pressure is introduced during the leak determination.

  For this reason, in this embodiment, the determination value of the fuel vapor concentration is corrected based on the difference between the outside air temperature during soaking and the outside air temperature during traveling. FIG. 10 is a schematic diagram illustrating a state in which the fuel vapor concentration determination value is corrected based on the difference in the outside air temperature. In FIG. 10, the characteristics of the broken line indicate the determination values a and b before correction. The solid line characteristic indicates a state in which the determination value of the fuel vapor concentration is corrected according to the difference in the outside air temperature. According to the corrected characteristic, the leak determination is performed when the fuel vapor concentration falls within the range between the two solid lines shown in FIG.

  As indicated by the solid line characteristics in FIG. 13, in the method of this embodiment, the determination value of the fuel vapor concentration is corrected to a lower concentration side as the difference in the outside air temperature is larger.

  As a result, when the difference in the outside air temperature is large, the fuel vapor concentration at which the leak determination is permitted is set to a thinner side, so the fuel vapor concentration at the time of the leak determination is higher than the fuel vapor concentration at the time of traveling. If it is, the leak determination can be stopped. Therefore, even when the fuel vapor concentration is increased at the time of the leak determination, the leak detection can be stopped based on the fuel vapor concentration acquired during traveling, and the fuel vapor is released to the atmosphere. Can be suppressed.

  Next, a processing procedure in the present embodiment will be described based on the flowchart of FIG. First, in step S21, it is determined whether or not there is a travel history. If there is a travel history, the process proceeds to step S22. On the other hand, if there is no travel history, the process proceeds to step S33 to stop leak detection.

  In step S22, it is determined whether or not the soak timer determination is permitted. If the determination is permitted, the process proceeds to step S23. On the other hand, if the determination is not permitted, the process proceeds to step S33 to stop leak detection.

  In step S23, it is determined whether or not the ignition switch (IG SW) is turned off (OFF). If the ignition switch is turned off, the process proceeds to step S24. On the other hand, if the ignition switch is on (ON), the process proceeds to step S33 to stop leak detection.

  In step S24, it is determined whether or not the cooling water temperature is lower than a predetermined temperature. If the cooling water temperature is lower than the predetermined temperature, the process proceeds to step S25. On the other hand, when the cooling water temperature is equal to or higher than the predetermined temperature, the process proceeds to step S33, and leakage detection is stopped.

  In step S25, it is determined whether or not the temperature in the intake pipe is lower than a predetermined temperature. If the temperature in the intake pipe is lower than the predetermined temperature, the process proceeds to step S26. On the other hand, when the temperature in the intake pipe is equal to or higher than the predetermined temperature, the process proceeds to step S33, and the leak detection is stopped.

  In step S26, it is determined whether or not the purge amount integrated value during the previous operation is greater than or equal to a predetermined value. If the purge amount integrated value is greater than or equal to the predetermined value, the process proceeds to step S27. On the other hand, if the integrated purge amount is less than the predetermined value, the process proceeds to step S33, and the leak detection is stopped.

  In step S27, the outside air temperature during travel acquired during the previous travel is captured. In the next step S28, the outside temperature at the time of leak determination, that is, the current outside temperature is acquired. In the next step S29, a process of subtracting the outside air temperature during traveling from the outside air temperature during leakage determination is performed. Thereby, the difference of outside temperature is calculated | required.

  In the next step S30, the determination value of the fuel vapor concentration is acquired from the map of FIG. 10 based on the value calculated in step S29. In the next step S31, it is determined whether or not the fuel vapor concentration during traveling is within the range of the determination value calculated in step S30.

  If the fuel vapor concentration is within the determination value range in step S31, the process proceeds to step S32. In this case, since the fuel vapor concentration is sufficiently low, the fuel vapor is not released to the atmosphere when the leak is detected. Accordingly, leak detection is executed in step S32.

  On the other hand, if it is determined in step S31 that the fuel vapor concentration is not within the range of the determination value, the process proceeds to step S33, and the leak detection is stopped. After steps S32 and S33, the process is terminated (RETURN).

  As described above, according to the second embodiment, the determination value of the fuel vapor concentration at the time of leak determination is varied according to the difference obtained by subtracting the outside air temperature at the time of traveling from the outside air temperature at the time of leak determination. Therefore, the leak determination can be stopped under the condition that the difference is large and the fuel vapor is easily released to the atmosphere at the time of the leak determination.

It is a figure for demonstrating the outline | summary of the evaporative fuel processing apparatus which concerns on each embodiment of this invention. It is a schematic diagram which shows the structure of a pump module. Fuel tank, when the introduction of negative pressure to the fuel vapor passage comprising a canister, which is a schematic diagram showing the transition of the pressure P _{measured value} detected by the pressure sensor, the relationship between the reference pressure P _REF. It is a schematic diagram which shows a mode that the desorption amount of the fuel vapor in a canister changes according to the external temperature at the time of driving | running | working. FIG. 6 is a characteristic diagram showing the relationship between the outside air temperature during travel and the amount of fuel vapor desorbed from the canister. It is a characteristic view which shows a mode that the generation amount of a fuel vapor changes according to the external temperature at the time of leak determination (during soak). It is a characteristic view which shows the relationship between the external temperature at the time of a soak, and the generation amount of fuel vapor. It is a schematic diagram which shows the map which prescribed | regulated the relationship between the difference of outside temperature, and the determination value of purge amount integrated value. 3 is a flowchart illustrating a processing procedure in the system according to the first embodiment. It is a schematic diagram which shows the state which varied the determination value of the fuel vapor density | concentration based on the difference of external temperature. 10 is a flowchart illustrating a processing procedure in the system according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel tank 12 Canister 14 Pump module 38 Negative pressure pump 40 Pressure sensor 50 ECU
52 Temperature sensor

Claims (3)

A fuel tank for storing combustion fuel for the internal combustion engine;
A canister connected to the fuel tank and adsorbing the evaporated fuel generated in the fuel tank;
A pump connected to the canister;
A pump driving means for driving the pump when a predetermined precondition is satisfied after the operation of the internal combustion engine is stopped, and for introducing a negative pressure into a closed space including the fuel tank via the canister;
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;
Outside temperature acquisition means for acquiring outside temperature;
Correction means for correcting the precondition based on the difference obtained by subtracting the outside air temperature during operation of the internal combustion engine from the outside air temperature at the time of determining the state of leakage;
An evaporative fuel processing apparatus comprising: A purge valve provided in a flow path connecting the intake passage of the internal combustion engine and the canister;
A purge unit that opens the purge valve during operation of the internal combustion engine and purges the evaporated fuel adsorbed by the canister into the intake passage;
The precondition is an integrated value of the purge amount of the evaporated fuel to the intake passage,
The pump driving means drives the pump when the integrated value is a predetermined determination value or more,
The evaporated fuel processing apparatus according to claim 1, wherein the correction unit increases the determination value as the difference increases. The precondition is the concentration of the evaporated fuel in the closed space,
The pump driving means drives the pump when the concentration of the evaporated fuel is within a predetermined determination value range,
The evaporated fuel processing apparatus according to claim 1, wherein the correction unit corrects the determination value in a direction in which the concentration of the evaporated fuel decreases as the difference increases.

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