JP2006300074A - Evaporative fuel processing equipment - Google Patents

Abstract

The present invention relates to an evaporative fuel processing apparatus for condensing and processing evaporative fuel generated in a fuel tank with a separation membrane, and aims to prevent a large amount of air from flowing into the fuel tank immediately after the start of purging. To do.
A canister for adsorbing evaporated fuel generated in a fuel tank is provided. A purge gas circulation pump 32 for allowing the canister out gas to flow out of the canister 20 is provided. A high concentration separation unit 34 is provided for concentrating the canister outgas to a high concentration process gas. A processing gas passage 42 for introducing the processing gas to the fuel tank 10 is provided. A heater 22 for heating the canister 20 is provided. By heating the canister 20 with the heater 22, the purge efficiency of the evaporated fuel from the canister 20 is increased.
[Selection] Figure 1

Description

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

  Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 10-274106, an evaporative fuel processing apparatus including a canister for adsorbing evaporative fuel generated in a fuel tank is known. This apparatus includes a mechanism for purging the evaporated fuel adsorbed on the canister by the flow of air, and a separation membrane for separating the evaporated fuel from the purge gas. The apparatus further includes a condensing unit for liquefying the evaporated fuel separated by the separation membrane, and a reflux path for returning the condensed fuel to the fuel tank. According to such a fuel vapor processing apparatus, the fuel vapor generated in the fuel tank can be processed in a closed system including the canister. For this reason, according to the above-described conventional apparatus, it is possible to effectively prevent the evaporated fuel from being released into the atmosphere without requiring complicated control such as correction of the fuel injection amount.

JP-A-10-274106

  The conventional apparatus cannot sufficiently condense evaporated fuel with a separation membrane alone. For this reason, as described above, the conventional apparatus includes a condensing unit for further condensing and liquefying the evaporated fuel gas condensed by the separation membrane. On the other hand, when a sufficiently high condensing capacity can be obtained only by the separation membrane, a configuration in which the evaporated fuel gas condensed by the separation membrane is allowed to flow into the fuel tank as it is. According to such a configuration, since the condensing unit is unnecessary, simplification and cost reduction of the system can be promoted.

  However, when the evaporated fuel is not purged from the canister, that is, when the purge gas is not circulated, an air-based gas containing almost no evaporated fuel may stay on the upstream side of the separation membrane. For this reason, even if the separation membrane has an excellent condensing capacity, immediately after the start of the flow of the purge gas, a processing gas whose concentration is not sufficiently increased may be generated on the downstream side of the separation membrane.

  If the processing gas having such a low concentration flows directly into the fuel tank, the air contained in the gas cannot be completely dissolved in the fuel. This air causes inconveniences such as vapor lock of the fuel feed pump and mixing of bubbles into the injected fuel.

  The present invention has been made to solve the above-described problems, and has a function of condensing evaporated fuel using a separation membrane, and a large amount of air flows into the fuel tank immediately after the start of circulation of the purge gas. It is an object of the present invention to provide an evaporative fuel processing apparatus capable of preventing the above.

In order to achieve the above object, a first invention is an evaporated fuel processing apparatus for an internal combustion engine,
A canister that adsorbs the evaporated fuel generated in the fuel tank;
Canister outgas generating means for flowing out canister outgas from the canister;
Vapor condensing means for concentrating the canister output gas to a processing gas containing a high concentration of evaporated fuel;
A processing gas passage for guiding the processing gas to the fuel tank;
Canister heating means for heating the canister;
It is characterized by providing.

  According to a second aspect of the present invention, in the first aspect of the invention, prior to the start of the canister outgas generating means, a heating operation preceding means for starting the operation of the canister heating means is provided.

  The third invention is characterized in that, in the first or second invention, a heating stop preceding means for stopping the operation of the canister heating means is provided before the canister outgas generating means is stopped.

Since the present invention is configured as described above, the following effects can be obtained.
According to the first aspect of the invention, the canister is heated by the canister heating means, whereby the purge efficiency of the evaporated fuel from the canister can be increased.

  According to the second aspect of the invention, when the canister outgas generating means is started, the canister heating means starts operating prior to the start, so that the evaporated fuel in the canister is discharged immediately after the canister outgas generating means is started. Purge can be performed with high efficiency.

  According to the third aspect of the present invention, the canister is heated by the canister heating means, so that the evaporative fuel purge efficiency from the canister can be increased. Further, when the canister outgas generating means is stopped, the canister can be sufficiently cooled by stopping the operation of the canister heating means prior to the stop. For this reason, according to the present invention, the canister can exhibit a high evaporative fuel adsorption capability while the canister outgas generating means is stopped.

  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.

Embodiment 1 FIG.
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. A low-pressure feed pump 12 (hereinafter simply referred to as “feed pump 12”) is disposed inside the fuel tank 10. The feed pump 12 communicates with a suction pipe 14 for sucking fuel in the fuel tank 10 and a fuel pipe 16 for feeding fuel to an internal combustion engine (not shown).

  A canister 20 communicates with the fuel tank 10 through a vapor passage 18. The canister 20 has activated carbon inside. The evaporated fuel generated inside the fuel tank 10 flows into the canister 20 through the vapor passage 18 and is adsorbed by the activated carbon.

  Inside the canister 20, a heater 22 is disposed together with the activated carbon. According to the heater 22, activated carbon can be heated appropriately. The canister 20 is also provided with an air outlet 24. The atmosphere port 24 is provided with an overpressure prevention valve 26 for preventing an excessive pressure from being generated inside the canister 20. The overpressure prevention valve 26 is a one-way valve that allows only the flow of fluid flowing out of the canister 20 and is opened to the atmosphere via an air cleaner (not shown).

  A purge passage 28 communicates with the canister 20. The purge passage 28 includes a negative pressure adjustment valve 30, and communicates with the suction port of the purge gas circulation pump 32 downstream of the adjustment valve 30. The negative pressure adjusting valve 30 is a one-way valve that allows only the flow of fluid from the canister 20 toward the purge gas circulation pump 32, and generates a predetermined negative pressure near the suction port when the purge gas circulation pump 32 is operated. Is provided.

  A high concentration separation unit 34 communicates with the discharge port of the purge gas circulation pump 32. The high concentration separation unit 34 includes a first separation membrane 36 and an upper chamber 38 and a lower chamber 40 that are separated by the first separation membrane 36. More specifically, the purge gas circulation pump 32 described above communicates with the upper chamber 38 of the high concentration separation unit 34. On the other hand, a processing gas passage 42 and a processing gas circulation passage 43 communicate with the lower chamber 40 of the high concentration separation unit 34 via a switching valve 41.

  The switching valve 41 is a switching valve that selectively connects the lower chamber 40 of the high concentration separation unit 34 to the processing gas passage 42 or the processing gas circulation passage 43. The processing gas passage 42 communicates with the suction pipe 14, that is, the suction port of the feed pump 12 inside the fuel tank 10. On the other hand, the processing gas circulation passage 43 communicates with the purge passage 28 downstream of the negative pressure adjustment valve 30. That is, the processing gas circulation passage 43 communicates with the suction port of the purge gas circulation pump 32.

  A medium concentration separation unit 44 is disposed above the high concentration separation unit 34. The intermediate concentration separation unit 44 includes a second separation membrane 46 and an upper chamber 48 and a lower chamber 50 that are isolated by the second separation membrane 46. The upper chamber 48 of the medium concentration separation unit 44 communicates with the upper chamber 38 of the high concentration separation unit 34 through the communication passage 52.

  A canister inlet gas passage 54 communicates with the upper chamber 48 of the intermediate concentration separation unit 44. The canister inlet gas passage 54 communicates with the canister 20 described above, and the gas flowing out from the intermediate concentration separation unit 44 can be recirculated to the canister 20. The canister inlet gas passage 54 includes a pressure regulating valve 56 in the vicinity of the end portion on the intermediate concentration separation unit 44 side, and a negative pressure prevention valve 58 in the vicinity of the end portion on the canister 20 side.

  The pressure regulating valve 56 is a one-way valve that allows only the flow of fluid from the intermediate pressure separation unit 44 toward the canister 20, and more specifically, a path from the purge gas circulation pump 32 to the pressure regulating valve 56. It is provided in order to generate a predetermined positive pressure. On the other hand, the negative pressure prevention valve 58 communicates with the atmosphere via an air cleaner (not shown), and is a one-way valve that allows only the inflow of the atmosphere into the canister inlet gas passage 54. The negative pressure prevention valve 58 is provided to prevent an unreasonably large negative pressure from being generated in the canister inlet gas passage 54 or in the canister 20.

  A circulating gas passage 60 communicates with the lower chamber 50 of the intermediate concentration separation unit 44. The circulation gas passage 60 communicates with the purge passage 28 downstream of the negative pressure adjustment valve 30. Therefore, according to the circulation gas passage 60, the lower chamber 50 of the intermediate concentration separation unit 44 and the suction port of the purge gas circulation pump 32 can be brought into conduction.

  As shown in FIG. 1, the apparatus of this embodiment includes a concentration sensor 61 for measuring the concentration of the processing gas generated in the lower chamber 40 of the high concentration separation unit 34. In addition, the apparatus according to the present embodiment includes an evaporation process control computer 62 (hereinafter referred to as ECU: Electronic Control Unit). The ECU 62 can detect the concentration of the processing gas based on the output of the concentration sensor 61. The heater 22 and the purge gas circulation pump 32 described above are controlled by the ECU 62.

  The apparatus according to the present embodiment further includes an oil supply detection unit 63. Specifically, the fuel supply detection unit 63 is realized by a fuel remaining amount sensor that detects the remaining amount of fuel in the fuel tank 10 or an open / close detection sensor that detects an open / closed state of the lid opener. The ECU 62 can determine whether or not refueling is performed based on the output of the refueling detection unit 63.

Next, the characteristics of the first separation membrane 36 and the second separation membrane 46 will be described with reference to FIG.
The first separation membrane 36 and the second separation membrane 46 are thin films made of a polymer material such as polyimide, and when exposed to a gas containing air and fuel, the solubility of air in the membrane and the fuel Due to the difference in solubility, it shows the property of separating the two.

  FIG. 2 is a diagram schematically showing the principle that the separation membrane 64 having the above structure condenses evaporated fuel. Specifically, FIG. 2 shows that gas containing evaporated fuel at a concentration of 15% is introduced into the upstream space 66 (upper left space) of the separation membrane 64 at a pressure of 30 kPa, and the downstream space 68 (lower right space) A state in which a pressure of 100 kPa is acting on the space.

  The separation membrane 64 ideally allows the vaporized fuel to pass freely while preventing the passage of air. In this case, the vapor partial pressure of the evaporated fuel becomes equal on both sides of the separation membrane 64. In the state shown in FIG. 2, an air partial pressure of 170 kPa and a fuel partial pressure of 30 kPa are generated in the upstream space 66 (200 kPa, 15%) of the separation membrane 64. If the fuel partial pressure is the same on both sides of the separation membrane 64, an air partial pressure of 70 kPa and a fuel partial pressure of 30 kPa are generated in the downstream space 68. That is, in this case, the concentration of the evaporated fuel is increased from 15% to 30% by the function of the separation membrane 64.

  As described above, according to the separation membrane 64 used in the present embodiment, the concentration of evaporated fuel in the gas is reduced by introducing a high-pressure gas upstream of the separation membrane 64 and maintaining the pressure on the downstream side low. Can be increased. At this time, the ability to concentrate the evaporated fuel increases as the differential pressure generated on both sides of the separation membrane increases and as the pressure downstream of the separation membrane decreases. Therefore, according to the first separation membrane 36 and the second separation membrane 46, a high pressure is introduced to the upstream side (upper chambers 38, 48) thereof, and to the downstream side (lower chambers 40, 50) thereof. The lower the pressure, the higher the evaporative fuel concentration capability.

Next, the operation of the apparatus of the present embodiment will be described with reference to FIG. 1 again.
In the present embodiment, the ECU 62 operates the purge gas circulation pump 32 when a predetermined purge condition is satisfied. In the present embodiment, the purge condition is determined to be satisfied only when the fuel concentration of the canister output gas is equal to or higher than a predetermined value, specifically, 15% or higher. Therefore, the purge gas circulation pump 32 operates only when the fuel concentration of the canister output gas is 15% or more.

  When the purge gas circulation pump 32 is operated, the negative pressure generated on the suction port side is guided to the canister 20, and the canister outflow gas flows out into the purge passage 28. The negative pressure generated by the purge gas circulation pump 32 is also led to the lower chamber 50 of the intermediate concentration separation unit 44 via the circulation gas passage 60. Therefore, the purge gas circulation pump 32 compresses the mixed gas of the canister outlet gas supplied from the purge passage 28 and the circulation gas supplied from the circulation gas passage 60 in a steady state to Supply to the upper chamber 38. In the present embodiment, the negative pressure generated by the purge gas circulation pump 32 is also introduced into the processing gas circulation passage 43.

  When the purge gas circulation pump 32 operates as described above, the discharge pressure of the pump acts on the system from the discharge port of the pump 32 to the pressure regulating valve 56. On the other hand, the internal pressure of the fuel tank or the negative pressure generated by the pump 32 is introduced into the lower chamber 40 of the high concentration separation unit 34 according to the state of the switching valve. Further, the negative pressure generated by the pump 32 is guided to the lower chamber 50 of the intermediate concentration separation unit 44. That is, in this case, a differential pressure suitable for condensing evaporated fuel gas is generated on both sides of the first separation membrane 36 and the second separation membrane 46. For this reason, during the operation of the purge gas circulation pump 32, the high concentration separation unit 34 and the medium concentration separation unit 44 each exhibit a condensing function of the evaporated fuel gas.

  Specifically, when the mixed gas flows into the upper chamber 38 with the operation of the pump 32, the high concentration separation unit 34 condenses the evaporated fuel in the mixed gas by the first separation membrane 36, A high-concentration processing gas is generated in the chamber 40. The generated processing gas passes through the switching valve 41 and is supplied to the processing gas passage 42 or the processing gas circulation passage 43.

  The mixed gas flowing into the upper chamber 38 of the high-concentration separation unit 34 decreases its concentration as a result of the condensation process by the first separation membrane 36. Hereinafter, the mixed gas after concentration reduction is referred to as “medium concentration gas”. The medium concentration gas flows out from the upper chamber 38 of the high concentration separation unit 34 and then flows into the upper chamber 48 of the medium concentration separation unit 44. When the intermediate concentration gas flows into the upper chamber 48, the intermediate concentration separation unit 44 condenses the evaporated fuel in the intermediate concentration gas by the second separation membrane 46, and circulates at a higher concentration than the intermediate concentration gas. Gas is generated in the lower chamber 50. The generated circulation gas is supplied to the suction port of the purge gas circulation pump 32 through the circulation gas passage 60.

  The apparatus of the present embodiment is provided such that the concentration of the circulating gas is about 65% in a steady state when the concentration of the canister outgas is 15%. In this case, the concentration of the mixed gas is about 60%. The high-concentration separation unit 34 is designed to separate the mixed gas into a processing gas of 95% or more and a medium-concentration gas of about 40% when about 60% of the mixed gas is supplied. ing. Further, the intermediate concentration separation unit 44 is designed to separate the intermediate concentration gas into about 65% circulating gas and less than 5% canister gas when about 40% intermediate concentration gas is supplied. Has been. For this reason, according to the apparatus of this embodiment, 95% or more of processing gas and less than 5% of canister gas can be generated in a steady state.

  The feed pump 12 has the ability to overpressure the fuel to about 300 kPa. When the processing gas sucked into the feed pump 12 is pressurized at such a pressure, it becomes liquid fuel. At this time, if the processing gas contains a large amount of air, problems such as vapor lock of the feed pump 12 and generation of abnormal noise occur. On the other hand, if the amount of air contained in the processing gas is small, those problems do not occur because the air dissolves in the fuel as the processing gas is pressurized.

  The ratio of air that does not cause vapor lock or abnormal noise is determined according to the capability of the feed pump 12, that is, the fuel flow rate and fuel pressure generated by the feed pump 12. In general, in a feed pump mounted on a vehicle, if the concentration of air in the processing gas is less than 5%, that is, if the fuel concentration of the processing gas is 95% or more, vapor lock and abnormal noise may occur. There is no. For this reason, according to the system of the present embodiment, the processing gas is recirculated to the fuel tank 10 without causing a vapor lock or abnormal noise problem in combination with a general feed pump 12 mounted on the vehicle. be able to.

  In the apparatus of the present embodiment, the canister input gas is reused as a gas for purging the evaporated fuel adsorbed by the canister 20. The evaporated fuel adsorbed by the canister 20 is purged by the gas having a sufficiently low concentration flowing inside the canister 20. In the apparatus of the present embodiment, as described above, the fuel concentration of the canister input gas is suppressed to 5% or less. Further, in the apparatus of the present embodiment, the canister 20 is heated by the heater 22 during the purge of the evaporated fuel. The evaporated fuel adsorbed on the canister 20 is in a state where it can be easily detached as the temperature of the canister 20 rises. For this reason, according to the apparatus of the present embodiment, the evaporated fuel can be efficiently purged by the canister input gas.

  As described above, the apparatus of this embodiment can make the concentration of the processing gas 95% or more in the steady state where the concentration of the mixed gas is about 60%. However, immediately after the start of the operation of the purge gas circulation pump 32, a low-concentration mixed gas significantly lower than 60% may flow into the high-concentration separation unit 34. In this case, a processing gas having a concentration lower than 95% is generated in the lower chamber 40 of the high concentration separation unit 34.

  When the processing gas having a concentration lower than 95% is supplied to the feed pump 12 through the processing gas passage 42, the vapor generation of the feed pump 12 and the generation of abnormal noise, and the injection accompanying the mixing of bubbles into the injected fuel Inconvenience such as an increase in quantity error occurs. Therefore, the apparatus of the present embodiment detects the concentration of the processing gas based on the output of the concentration sensor 61, and the processing gas flows into the processing gas circulation passage 43 when the concentration is lower than the target concentration (95%). Thus, the switching valve 41 is switched as described above.

  FIG. 3 is a flowchart of a control routine executed by the ECU 62 in the present embodiment in order to realize the above function. Note that the routine shown in FIG. 3 is started in synchronization with the start of the internal combustion engine and is repeatedly executed until the internal combustion engine stops.

In the routine shown in FIG. 3, first, the switching valve 41 is switched to the circulation side so that the lower chamber 40 of the high concentration separation unit 34 is connected to the processing gas circulation passage 43, and the purge gas circulation pump 32 and the heater 22 are turned on. Processing to turn ON is executed (step 80).
When this process is executed, the evaporated fuel gas starts to flow through the inside of the apparatus as the purge gas circulation pump 32 starts to operate. As a result, the processing gas obtained by condensing the mixed gas is generated in the lower chamber 40 of the high concentration separation unit 34. The processing gas generated in this way is supplied not to the processing gas passage 42 but to the processing gas circulation passage 43. For this reason, according to the apparatus of this embodiment, even if a processing gas having a low concentration is generated immediately after the purge gas circulation pump 32 is started, the processing gas is reliably prevented from being supplied to the feed pump 12. be able to.

  In the routine shown in FIG. 3, next, based on the output of the concentration sensor 61, it is determined whether or not the concentration of the processing gas is higher than a target value, that is, 95% (step 82).

As a result, when it is determined that the concentration of the processing gas is not higher than the target value, the switching valve 41 is controlled to the circulation side (step 84).
Therefore, according to the routine shown in FIG. 3, it is possible to reliably prevent the low-concentration processing gas from being sucked into the feed pump 12.

On the other hand, if it is determined in step 82 that the concentration of the processing gas is higher than the target value, the switching valve 41 is switched to the fuel tank 10 side, and the lower chamber 40 of the high concentration separation unit 34 is connected to the feed pump 12. Conduction is made to the suction port (step 86).
According to the above processing, when the concentration of the processing gas rises to a recoverable concentration, the processing gas can be quickly recovered as fuel.

  As described above, according to the routine shown in FIG. 3, the processing gas having a concentration lower than the target value is surely prevented from being sucked into the feed pump 12, and the concentration reaches the target value promptly. Then, the recovery of the evaporated fuel can be started. For this reason, according to the apparatus of this embodiment, it is possible to achieve a high fuel recovery capability while avoiding inconveniences such as vapor lock and abnormal noise.

  In the first embodiment described above, the concentration sensor 61 directly detects the concentration of the processing gas and controls the state of the switching valve 41 based on the concentration, but the switching valve 41 is connected to the circulation side. The basic data for determining whether to use the fuel tank 10 is not limited to the concentration of the processing gas itself, and may be any characteristic value correlated with the concentration of the processing gas.

  More specifically, the basic data may be a flow rate of canister output gas or canister input gas. The flow rate of the canister output gas and the canister input gas is small when the concentration of the mixed gas flowing into the high concentration separation unit 34 is high and a large amount of circulating gas is generated, while it flows into the high concentration separation unit 34. When the concentration of the mixed gas is low and the circulating gas is small, the amount becomes large. That is, the flow rate of the canister output gas and the canister input gas is small when the concentration of the mixed gas is high and the processing gas is high, and is large when the concentration of the mixed gas is low and the circulating gas is low. Therefore, these flow rates can be used as a basis for controlling the switching valve 41 as a characteristic value of the concentration of the processing gas.

  In the first embodiment described above, the switching valve 41 is controlled after actually determining whether or not the concentration of the processing gas has reached the target value. It is not limited to this. That is, after the operation of the purge gas circulation pump 32 is started, the process gas concentration is estimated to be lower than the target value for a predetermined period (a fixed time or a time until the integrated purge flow rate reaches a predetermined amount). The switching valve 41 may be controlled to the circulation side, and the switching valve 41 may be switched to the fuel tank 10 side after the period has elapsed.

  In Embodiment 1 described above, when the concentration of the processing gas is low, the processing gas is returned to the upstream side of the purge gas circulation pump 32. However, the low concentration processing gas is recovered in the fuel tank 10. The processing method is not limited to the above method. That is, the low-concentration processing gas may be simply confined in the lower chamber 40 of the high-concentration separation unit 34 without being refluxed upstream of the pump 32.

  Further, in the first embodiment described above, when the concentration of the processing gas is low, the inflow of the processing gas into the fuel tank 10 is completely prohibited, but the present invention is not limited to this. . That is, in the present invention, any process may be used as long as the low concentration process gas is prevented from flowing into the fuel tank 10.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. 4 and 5 together with FIG.
The evaporative fuel processing apparatus of the present embodiment can be realized by causing the ECU 62 to execute the routine shown in FIG. 4 in the system configuration shown in FIG.

  The apparatus of the first embodiment described above continuously operates the purge gas circulation pump 32 and the heater 22 even when the processing gas concentration is low. For this reason, in the apparatus according to the first embodiment, the purge gas circulation pump 32 and the heater 22 are continuously operated even when the concentration of the processing gas is reduced by completing the purge of the evaporated fuel in the canister 20. However, after the purge is completed, it is desirable to stop the pump 32 and the heater 22 in order to avoid unnecessary energy consumption. Therefore, the apparatus of the present embodiment stops the pump 32 and the heater 22 when the concentration of the processing gas is reduced due to the completion of the purge.

  FIG. 4 is a flowchart of a control routine executed by the ECU 62 in the present embodiment in order to realize the above function. In FIG. 4, the same steps as those shown in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

The routine shown in FIG. 4 is a routine that is started when the internal combustion engine is started, and then repeatedly executed until the internal combustion engine is stopped, similarly to the routine shown in FIG. 3 described above. In the routine shown in FIG. 4, after the process of step 80, that is, the process of starting purge with the switching valve 41 as the circulation side, is executed, the period counting timer is reset to 0 (step 90).
The period counting timer is used here to count a period during which the concentration of the processing gas does not reach the target value, that is, a low concentration period. Note that the value of the period counting timer is counted up by another routine.

In the routine shown in FIG. 4, the process of step 82 for determining whether or not the concentration of the processing gas is higher than the target value is executed after the process of step 90.
In the apparatus of the present embodiment, it may be determined that the concentration of the processing gas is not higher than the target value immediately after the purge of the evaporated fuel is started and after the purge of the evaporated fuel is completed. Therefore, if the current processing cycle is executed immediately after the start of purging, it may be determined in step 82 that the processing gas concentration is not higher than the target value.

  In the routine shown in FIG. 4, when such a determination is made in step 82, after the process of step 84 is executed to control the switching valve 41 to the circulation side, the value of the period counting timer is set to a predetermined value. It is determined whether or not the stop determination period T1 has been reached (step 92).

  The stop determination period T1 is a time determined as a time required for the concentration of the processing gas to rise to the target value when the purge is started in an environment where the evaporated fuel to be purged exists in the canister 20. . Therefore, if the current processing cycle is a cycle immediately after the start of purge, it is determined in step 92 that the value of the period counting timer has not yet reached the stop determination period T1.

  In this case, in the routine shown in FIG. 4, it is next determined whether or not the processing gas concentration is decreasing or maintaining (step 94).

  When evaporated fuel to be purged is present in the canister 20, the concentration of the processing gas may temporarily fall below the target value immediately after the purge is started, as described above. However, in this case, the concentration of the processing gas always shows an upward trend as the canister gas starts to flow along with the start of the purge. Therefore, if the current processing cycle is performed under the condition that the evaporated fuel to be purged exists in the canister 20, the above-mentioned step 94 shows that the processing gas concentration tends to decrease and maintain. It is judged that it is not. In this case, thereafter, the processing after step 82 is repeated again.

  When purging is started under the condition that the evaporated fuel to be purged exists in the canister 20, the above-described series of processing is performed until it is determined in step 82 that the processing gas concentration exceeds the target value. Is repeatedly executed. If it is determined that the processing gas concentration has exceeded the target value, then the processing of step 86 is executed to switch the switching valve 41 to the fuel tank side. As a result, the high-concentration processing gas exceeding the target value starts to be collected in the fuel tank 10.

  In the routine shown in FIG. 4, as long as the processing gas concentration exceeds the target value, the processing of steps 90, 82 and 86 is repeated. When these processes are repeated, the evaporated fuel in the canister 20 is continuously purged. As a result, the evaporative fuel purge eventually progresses, and a situation is formed in which there is no evaporative fuel to be purged in the canister 20.

  When there is no evaporated fuel to be purged in the canister 20, the concentration of the processing gas becomes smaller than the target value, and the condition of step 82 is not satisfied again. As a result, in step 84, the switching valve 41 is switched to the circulation side, and the processing gas generated by the high concentration separation unit 34 starts to be recirculated to the upstream side of the purge gas circulation pump 32.

  In the routine shown in FIG. 4, after step 84, it is determined again whether or not the value of the period counting timer has reached a predetermined stop determination period T1 (step 92).

  The stop determination period T1 is a time required for the processing gas concentration to rise to the target value when there is evaporated fuel to be purged in the canister 20 as described above. Accordingly, in step 92, it is determined that the value of the period counting timer has reached the stop determination time T1 only when there is no evaporated fuel to be purged in the canister 20. Therefore, in the routine shown in FIG. 4, when the condition of step 92 is satisfied, it can be determined that the purge of the evaporated fuel is completed.

  On the other hand, if it is determined in step 92 that the value of the period counting timer has not reached the stop determination period T1, it is not possible to determine the completion of the purge from that fact. In this case, it is again determined whether or not the processing gas concentration shows a decreasing or maintaining tendency (step 94).

  When evaporated fuel to be purged is present in the canister 20, the processing gas concentration tends to increase as described above. Therefore, if it is determined in step 94 that the processing gas concentration shows a tendency to decrease or maintain, there is no evaporated fuel to be purged in the canister 20 even before the stop determination period T1 has elapsed. It can be confirmed.

  On the other hand, if it is determined in step 94 that the above condition is not satisfied, the process of step 82 is executed again. When the evaporated fuel to be purged does not exist in the canister 20, the process gas concentration does not exceed the target value. Therefore, the above-described steps 82, 84, 92, and 94 are performed until the condition of step 92 or 94 is satisfied. The process is repeated. Accordingly, when there is no evaporated fuel to be purged in the canister 20, the condition of step 92 or 94 is satisfied.

In the routine shown in FIG. 4, when the condition of step 92 or 94 is satisfied, both the purge gas circulation pump 32 and the heater 22 are turned off, and the fuel vapor processing apparatus is stopped (step 96).
As described above, according to the routine shown in FIG. 4, the pump 32 and the heater 22 can be stopped when there is no evaporated fuel to be purged in the canister 20.

Next, in the routine shown in FIG. 4, the period counting timer is reset to 0 (step 98).
Thereafter, the period counting timer is used as a timer for counting the stop period of the evaporated fuel processing apparatus.

Next, it is determined whether or not the value of the period counting timer has reached the reactivation determination period T2 (step 100).
While the fuel vapor processing apparatus is stopped, the fuel vapor newly generated in the fuel tank 10 is adsorbed by the canister 20. For this reason, if the apparatus maintains the stop state for an unreasonably long period, a situation may occur in which the evaporated fuel overflows from the canister 20 and leaks to the atmosphere. The reactivation determination period is a standard time during which the fuel vapor processing apparatus can be maintained in a stopped state without causing such leakage. The method for setting the reactivation determination time will be described in detail later with reference to FIG.

  If it is determined in step 100 that the value of the period counting timer has reached the restart determination period, it can be determined that it is time to restart the fuel vapor processing apparatus. In this case, the process from step 80 onward is executed promptly and the purge of the evaporated fuel is resumed.

  On the other hand, if it is determined in step 100 that the value of the period counting timer has not reached the reactivation determination period T2, it can be determined that the apparatus can still be maintained in a stopped state as a standard. In the routine shown in FIG. 4, in this case, it is next determined whether or not refueling is being executed based on the output of the refueling detection unit 63 (step 102).

  At the time of refueling, a large amount of evaporated fuel existing in the space of the fuel tank 10 flows out toward the canister 20 at once. For this reason, when refueling is executed, it is desirable to restart the purge of the evaporated fuel even if the stop period of the apparatus has not reached the reactivation determination period T2.

  In the routine shown in FIG. 4, when refueling is not detected in step 102, the process of step 100 is executed again. In this case, thereafter, the evaporated fuel processing apparatus is maintained in a stopped state until the re-operation determination period T2 elapses or refueling is detected.

  On the other hand, when the execution of refueling is detected in step 102, the processing after step 80 is resumed immediately thereafter. As a result, the purge gas circulation pump 32 and the heater 22 are activated, and the vaporized fuel purge is resumed.

As described above, according to the routine shown in FIG. 4, when the processing gas concentration does not reach the target value, the processing gas is circulated to the suction port side of the purge gas circulation pump 32 and the low concentration gas is supplied to the fuel tank 10. Inflow can be prevented.
Further, when the state where the processing gas concentration does not reach the target value continues for the stop determination period T1, it is possible to determine the completion of the purge at that time and stop the purge gas circulation pump 32 and the heater 22.
Furthermore, even if the stop determination time T1 has elapsed, if the concentration of the processing gas shows a tendency to decrease or maintain, the purge is determined to be completed at that time, and the purge gas circulation pump 32 and the heater 22 are stopped. Can be made.
When the reactivation determination time T2 elapses after the evaporative fuel processing device stops, purging can be restarted to prevent the evaporative fuel from leaking to the atmosphere.
In addition, even if the reactivation determination time T2 has not elapsed after the apparatus has been stopped, when refueling is performed, purging can be restarted promptly in order to prevent leakage of evaporated fuel to the atmosphere.
For this reason, according to the evaporative fuel processing apparatus of this embodiment, it is possible to effectively prevent the evaporative fuel from leaking to the atmosphere while sufficiently suppressing wasteful energy consumption.

FIG. 5 is a flowchart of a control routine executed by the ECU 62 in order to determine the reactivation determination period T2 used in step 100 in the routine shown in FIG. 4 described above.
In the routine shown in FIG. 5, first, the intake air temperature is detected based on the output of an intake air temperature sensor (not shown) provided in the internal combustion engine (step 110).

Next, the operating state of the internal combustion engine is detected (step 112).
As the operating state of the internal combustion engine, for example, the engine speed, the intake air amount, the fuel injection amount, or the like is detected. The engine speed and the intake air amount can be detected based on the output of a speed sensor and an air flow meter (both not shown) incorporated in the internal combustion engine. The fuel injection amount can be detected by reading a value calculated by a control unit (not shown) for engine control.

Next, the fuel temperature in the fuel tank 10 is estimated based on the intake air temperature detected in steps 110 and 112 and the operating state of the internal combustion engine (step 114).
The higher the atmospheric temperature (intake air temperature), the higher the fuel temperature. Further, the higher the internal combustion engine is operated, that is, the higher the exhaust heat is generated, the higher the temperature becomes. Therefore, a correlation is recognized between the fuel temperature and the intake air temperature, and between the fuel temperature and the operating state of the internal combustion engine. In the present embodiment, the ECU 62 stores a map determined based on their correlation. In this step 114, referring to the map, the fuel temperature corresponding to the intake air temperature and the operating state of the internal combustion engine is estimated.

In the routine shown in FIG. 5, next, the reactivation determination time T2 is calculated based on the estimated fuel temperature (step 116).
The reactivation determination time T2 is a time during which the evaporated fuel can be maintained in a stopped state while preventing the evaporated fuel from leaking. Therefore, it is desirable that the time be short when a large amount of evaporated fuel is generated in the fuel tank 10 and long when the amount of evaporated fuel is small.
The amount of evaporated fuel generated increases as the fuel temperature increases, and decreases as the temperature decreases. Therefore, the reactivation determination time T2 should be shorter as the fuel temperature is higher and longer as the temperature is lower. In the present embodiment, the ECU 62 stores a map in which the relationship between the fuel temperature and the reactivation determination time T2 is determined so that the above requirement is satisfied. In step 116, the reactivation determination time T2 is calculated with reference to the map.

  As described above, according to the routine shown in FIG. 5, it is possible to set an appropriate reactivation determination time T2 according to the state of generation of evaporated fuel. For this reason, according to the apparatus of the present embodiment, it is possible to set a stop period without excess or deficiency according to the generation state of the evaporated fuel, and it is possible to minimize wasteful energy consumption while reliably preventing the leakage of the evaporated fuel. Can be suppressed.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG.
In addition to the configuration shown in FIG. 1, the apparatus of the present embodiment controls a negative pressure introduction passage 120 that connects any part of the system to the intake passage of the internal combustion engine, and the conduction state of the negative pressure introduction passage 120. A control valve 122 and a pressure sensor 124 for detecting the pressure in the system are provided.

  In FIG. 6, the negative pressure introduction passage 120 is connected to the communication passage 52 that connects the high concentration separation unit 34 and the medium concentration separation unit 44, and the pressure sensor 124 is connected to the purge gas circulation pump 32 and the high concentration separation. The structure arrange | positioned between the units 34 is illustrated.

  In the present embodiment, the ECU 62 normally performs the same control as in the first or second embodiment. At this time, the control valve 122 is always kept closed. In this case, the evaporated fuel processing apparatus of the present embodiment operates in the same manner as the apparatus of the first or second embodiment.

  The ECU 62 executes an abnormality detection process at a predetermined timing during operation of the internal combustion engine. In the abnormality detection process, first, the switching valve 41 is switched to the circulation side, and the control valve 122 is opened. When the control valve 122 is opened, the intake negative pressure of the internal combustion engine is guided to the communication passage 52 through the negative pressure introduction passage 120. The negative pressure is introduced into the upper chamber 38 of the high concentration separation unit 34 and the upper chamber 48 of the intermediate concentration separation unit 44 via the communication passage 52.

  The negative pressure introduced to the upper chamber 38 of the high concentration separation unit 34 passes through the purge gas circulation pump 32 that is stopped (the pump 32 is allowed to pass through) and reaches the purge passage 28. The negative pressure guided to the purge passage 28 is guided to the lower chamber 50 of the intermediate concentration separation unit 44 via the circulation gas passage 60 and also to the high concentration separation unit via the processing gas circulation passage 43 and the switching valve 41. 34 is led to the lower chamber 40. Further, the negative pressure guided to the purge passage 28 is guided to the canister 20 via the negative pressure regulating valve 30. The negative pressure guided to the canister 20 is guided to the canister inlet gas passage 54 and to the fuel tank 10 via the vapor passage 18.

  Thus, when the abnormality detection process is started, the intake negative pressure is introduced to the entire area of the fuel vapor processing apparatus. Thereafter, when the pressure in the system decreases to a predetermined initial pressure, the ECU 62 closes the control valve 122 and stops introducing the negative pressure. Then, based on the subsequent change in the system pressure, it is determined whether or not a leakage abnormality has occurred in the system.

  As described above, according to the evaporated fuel processing apparatus of the present embodiment, a negative pressure is introduced into the system, and a change in the system pressure accompanying the introduction is monitored, thereby leaking to any part of the system. Whether or not an abnormality has occurred can be determined easily and accurately. Therefore, according to the apparatus of the present embodiment, it is possible to quickly detect the occurrence of a leakage abnormality that accompanies the leakage of evaporated fuel.

  By the way, in Embodiment 3 mentioned above, it is supposed that the presence or absence of leakage abnormality will be judged based on the pressure change after introducing a negative pressure in the system, but the judgment method is not limited to this. Absent. That is, the presence or absence of leakage abnormality may be determined from the speed of pressure change in the process of introducing negative pressure into the system.

  In the above-described third embodiment, the connection destination of the negative pressure introduction passage 120 is the communication passage 52, but the connection destination is not limited to the communication passage. That is, the negative pressure introduction passage 120 may be connected to any location as long as the negative pressure can be guided to the entire area in the system.

  In Embodiment 3 described above, the pressure sensor 124 is arranged between the purge gas circulation pump 32 and the high concentration separation unit 34, but the arrangement position is not limited to this. . That is, as long as the pressure in the system can be detected, the pressure sensor 124 may be disposed at any location.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIG.
In addition to the configuration shown in FIG. 1, the apparatus of the present embodiment includes a bypass passage that bypasses the intake pressure switching valve 130 and the negative pressure adjustment valve 30 that selectively connect the suction port of the purge gas circulation pump 32 to the purge passage 28 or the atmosphere. 132, a bypass control valve 134 for controlling the conduction state of the bypass passage 132, and a pressure sensor 136 for detecting the pressure in the system.

  In the present embodiment, the ECU 62 normally performs the same control as in the first or second embodiment. At this time, the intake air switching valve 130 causes the suction port of the purge gas circulation pump 32 to conduct to the purge passage 28. Further, the bypass control valve 134 is kept closed. As a result, the evaporated fuel processing apparatus of the present embodiment operates in the same manner as the apparatus of the first or second embodiment.

  The ECU 62 executes an abnormality detection process at a predetermined timing. In the abnormality detection process, first, the switching valve 41 is switched to the circulation side, the intake switching valve 130 is switched so that the suction port of the purge gas circulation pump 32 is opened to the atmosphere, and the bypass passage 132 is further conducted. The bypass control valve 134 is opened. Next, the operation of the purge gas circulation pump 32 is started in this state.

  In the course of the abnormality detection process, the purge gas circulation pump 32 pumps the air sucked from the atmosphere to the upper chamber 38 of the high concentration separation unit 34. This air reaches the pressure regulating valve 56 through the upper chamber 48 of the intermediate concentration separation unit 44, and further flows into the canister 20 through the pressure regulating valve 56 and the canister inlet gas passage 54. The air that has flowed into the canister 20 is guided from the purge passage 28 to the bypass passage 132 and also to the fuel tank 10 through the vapor passage 18. Further, the air that has passed through the bypass passage 132 is further led to the lower chamber 50 of the separation unit for medium concentration 44 through the circulation gas passage 60, and at the high concentration separation unit 34 through the processing gas circulation passage 43. Guided to lower chamber 40.

  In this manner, when the abnormality detection process is started, the air discharged from the purge gas circulation pump 32 is guided to the entire area of the evaporated fuel processing apparatus. As a result, the inside of the system is pressurized throughout the entire area. When the pressure in the system rises to a predetermined initial pressure, the ECU 62 switches the intake air switching valve 130 so that the suction port of the pump 32 is connected to the purge passage 28 and stops the operation of the pump 32. Then, based on the subsequent change in the system pressure, it is determined whether or not a leakage abnormality has occurred in the system.

  As described above, according to the fuel vapor processing apparatus of the present embodiment, the system interior is pressurized to a predetermined pressure, and a change in the system pressure accompanying the pressurization is monitored, so that any location in the system It is possible to easily and accurately determine whether or not a leakage abnormality has occurred. Therefore, according to the apparatus of the present embodiment, it is possible to quickly detect the occurrence of a leakage abnormality that accompanies the leakage of evaporated fuel.

  By the way, in Embodiment 4 mentioned above, after pressurizing the inside of the system to a predetermined pressure, it is determined whether there is a leakage abnormality based on the pressure change in the system. It is not limited. In other words, the presence or absence of leakage abnormality may be determined from the speed of pressure change in the process of pressurizing the system.

  In Embodiment 4 described above, the pressure sensor 136 is arranged between the purge gas circulation pump 32 and the high concentration separation unit 34, but the arrangement position is not limited to this. . That is, as long as the pressure in the system can be detected, the pressure sensor 124 may be disposed at any location.

Embodiment 5. FIG.
Next, a fifth embodiment of the present invention will be described with reference to FIGS.
FIG. 8 is a view for explaining the configuration of the evaporated fuel processing apparatus of the present embodiment. In FIG. 8, parts that are the same as the parts shown in FIG. 1 are given the same reference numerals, and descriptions thereof will be omitted or simplified.

  As shown in FIG. 8, the evaporated fuel processing apparatus of this embodiment includes a bypass passage 140 and a conduction state switching valve 142. The bypass passage 140 is a passage that bypasses the high-concentration separation unit 34 and communicates with the internal space of the fuel tank 10 in the downstream space of the purge gas circulation pump 32. The conduction state switching valve 142 is a valve mechanism for selectively setting the bypass passage 140 to a conduction state or a cutoff state.

The fuel vapor processing apparatus of the present embodiment can be realized by causing the ECU 62 to execute the control routine shown in FIG. 9 in the configuration shown in FIG.
FIG. 9 is a flowchart of a routine executed by the ECU 62 for controlling the state of the conduction state switching valve 142 in the present embodiment.
In the routine shown in FIG. 9, first, it is determined whether or not the purge of evaporated fuel is stopped, more specifically, whether or not the purge gas circulation pump 32 is stopped (step 150).

As a result, when it is determined that the purge of the evaporated fuel is stopped, the conduction state switching valve 142 is opened (step 152).
When the conduction state switching valve 142 is opened, the downstream space of the pump 32 is brought into conduction with the internal space of the fuel tank 10. In this case, the evaporated fuel generated in the fuel tank 10 is guided to the downstream space. For this reason, according to the apparatus of the present embodiment, the fuel concentration in the downstream space of the pump 32 can be maintained high even when the purge is stopped when the canister output gas does not flow inside the system.

In the routine shown in FIG. 9, when it is determined in step 150 that the purge of the evaporated fuel is not stopped, that is, the purge gas circulation pump 32 is operating, the conduction state switching valve 142 is in the closed state. (Step 154).
If the conduction state switching valve 142 is closed, the mixed gas discharged from the pump 32 reaches the high concentration separation unit 34 without flowing into the bypass passage 140. Therefore, in this case, it is possible to cause the high concentration separation unit 34 and the medium concentration separation unit 44 to perform the same condensation process as in the first embodiment.

  As described above, according to the evaporated fuel processing apparatus of this embodiment, when the evaporated fuel is purged, the same fuel condensing function as in the first or second embodiment can be realized. At the same time, when the purge is stopped, the downstream space of the pump 32 can be filled with the high-concentration evaporated fuel gas. If the downstream space of the pump 32 is filled with high-concentration evaporated fuel gas when the purge is stopped, the high-concentration separation unit 34 can generate a high-concentration process gas immediately after the purge is started. For this reason, according to the fuel vapor processing apparatus of this embodiment, the processing gas having a low concentration is supplied to the fuel tank 10 without taking measures such as refluxing the processing gas generated immediately after the start of the purge to the upstream of the pump 32. It is possible to surely prevent the liquid from flowing into.

Embodiment 6 FIG.
Next, a sixth embodiment of the present invention will be described with reference to FIG. 1, FIG. 6 to FIG. 8 and FIG.
The evaporative fuel processing apparatus of the present embodiment executes the routine shown in FIG. 10 on the ECU 62 in any one of the configurations shown in FIGS. 1 and 6 to 8, that is, in any configuration of the first to fifth embodiments. This can be realized.

In the present embodiment, the routine shown in FIG. 10 is a control routine executed by the ECU 62 to cause a desired time difference between the ON / OFF timing of the purge gas circulation pump 32 and the ON / OFF timing of the heater 22. is there.
In the routine shown in FIG. 10, first, it is determined whether or not the start of the purge of evaporated fuel is requested (step 160).

  As a result, when it is determined that the start of purging has been requested, first, the heater 22 is turned on to start heating the canister 20 (step 162).

  Next, the standby state is maintained for a predetermined time until the canister 20 is in a desired heating state (step 164).

  When it is determined that the predetermined time has elapsed, the purge gas circulation pump 32 is turned on at that time (step 166).

  According to the processing described above, before the purge gas circulation pump 32 starts to operate, it is possible to prepare a state in which the evaporated fuel is easily purged by setting the canister 20 in a desired heating state. For this reason, according to the apparatus of the present embodiment, the high concentration mixed gas is supplied to the high concentration separation unit 34 to generate the high concentration processing gas immediately after the evaporated fuel actually starts to be purged. it can. Therefore, according to the apparatus of the present embodiment, it is possible to effectively prevent the processing gas having a low concentration from flowing into the fuel tank 10 immediately after the purge is started.

  In the routine shown in FIG. 10, if it is determined in step 160 that the start of purge of the evaporated fuel is not requested, it is next determined whether or not the purge stop is requested (step 168). .

  As a result, if it is determined that the purge stop is not requested, the current processing cycle is immediately terminated. On the other hand, if it is determined that the purge stop is requested, first, the heater 22 is turned off to stop the heating of the canister 20 (step 170).

  Next, the purge is continued with the heater 22 turned off for a predetermined time until the canister 20 is cooled to a desired state (step 172).

  When it is determined that the predetermined time has elapsed, the purge gas circulation pump 32 is turned OFF at that time (step 174).

  According to the process described above, the canister 20 can be cooled to some extent before the purge gas circulation pump 32 stops. The canister 20 exhibits superior adsorption capacity as its temperature is lower. For this reason, according to the apparatus of this embodiment, the canister can exhibit the evaporative fuel adsorption capability excellent during the stoppage of the purge.

  As described above, according to the routine shown in FIG. 10, the heater 22 can be turned on / off prior to turning on / off the purge gas circulation pump 32 at the start and stop of the purge. As a result, according to the apparatus of the present embodiment, the processing gas having a high concentration can be collected in the fuel tank 10 immediately after the purge is started, and a large amount of evaporated fuel is captured by the canister 20 when the purge is stopped. can do.

  In the above-described sixth embodiment, the purge 22 is limited to a configuration in which energization of the heater 22 is started prior to the start of the operation of the purge gas circulation pump 32 at the start of the purge. It is not limited. That is, at the start of the purge, the purge gas circulation pump 32 and the heater 22 may be operated simultaneously. Even with such a configuration, the desorbability of the evaporated fuel is improved by the heating action of the heater 22, so that a high-concentrated canister gas can be generated immediately after the start of the purge.

  In the sixth embodiment described above, the purge gas circulation pump 32 is the “canister outgas generating means” in the first invention, and the high concentration separation unit 34 is the “vapor concentrating means” in the first invention. The heaters 22 correspond to the “canister heating means” in the first invention.

  Further, in the above-described sixth embodiment, by causing the ECU 62 to execute the processing of steps 160 to 166, the “heating operation preceding means” in the second invention causes the processing of steps 168 to 174 to be executed. Thus, the “heating stop preceding means” in the third aspect of the present invention is realized.

It is a figure for demonstrating the structure of the evaporative fuel processing apparatus of Embodiment 1 of this invention. It is a figure for demonstrating the principle of the separation membrane with which the apparatus of Embodiment 1 is provided. 3 is a flowchart of a control routine executed in the apparatus according to the first embodiment. 6 is a flowchart of a first control routine executed in the apparatus according to the second embodiment. 6 is a flowchart of a second control routine executed in the apparatus according to the second embodiment. It is a figure for demonstrating the structure of the evaporative fuel processing apparatus of Embodiment 3 of this invention. It is a figure for demonstrating the structure of the evaporative fuel processing apparatus of Embodiment 4 of this invention. It is a figure for demonstrating the structure of the evaporative fuel processing apparatus of Embodiment 5 of this invention. It is a flowchart of the control routine performed in the apparatus of Embodiment 5 of this invention. It is a flowchart of the control routine performed in the apparatus of Embodiment 6 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel tank 12 Low pressure feed pump 20 Canister 22 Heater 28 Purge passage 30 Negative pressure adjustment valve 32 Purge gas circulation pump 34 High concentration separation unit 36 First separation membrane 38, 48 Upper chamber 40, 50 Lower chamber 41 Switching valve 42 Processing Gas passage 43 Processing gas circulation passage 44 Middle concentration separation unit 46 Second separation membrane 54 Canister inlet gas passage 60 Processing gas passage 61 Concentration sensor 62 ECU (Electronic Control Unit)
63 Oil supply detection unit 64 Separation membrane 66 Upstream space 68 Downstream space

Claims (3)

An evaporative fuel processing apparatus for an internal combustion engine,
A canister that adsorbs the evaporated fuel generated in the fuel tank;
Canister outgas generating means for flowing out canister outgas from the canister;
Vapor condensing means for concentrating the canister output gas to a processing gas containing a high concentration of evaporated fuel;
A processing gas passage for guiding the processing gas to the fuel tank;
Canister heating means for heating the canister;
An evaporative fuel processing apparatus comprising:   2. The evaporative fuel processing apparatus according to claim 1, further comprising a heating operation preceding means for starting the operation of the canister heating means prior to starting of the canister outgas generating means.   3. The evaporative fuel processing apparatus according to claim 1, further comprising a heating stop preceding means for stopping the operation of the canister heating means prior to stopping the canister outgas generating means.

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