JP4153354B2 - Evaporative fuel processing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an evaporative fuel processing apparatus, and more particularly, to an evaporative fuel processing apparatus that processes evaporative fuel generated in a fuel tank without being adsorbed by a canister and released to the atmosphere.
[0002]
[Prior art]
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 by the canister by the flow of air, and a separation unit 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 unit, and a reflux path for returning the condensed fuel to the fuel tank. According to such an evaporative fuel processing apparatus, the evaporative fuel generated in the fuel tank can be processed without being released to the atmosphere.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-274106 [Patent Document 2]
JP-A-6-147037 [Patent Document 3]
Japanese Patent Laid-Open No. Sho 62-279825 [Patent Document 4]
Japanese Patent Laid-Open No. 63-270524
[Problems to be solved by the invention]
In the above-described conventional apparatus, the path for leading the evaporated fuel from the fuel tank is directly connected to the canister. In this case, all the evaporated fuel generated in the fuel tank is necessarily adsorbed by the canister before reaching the separation unit. If all the evaporated fuel generated is adsorbed by the canister, it is necessary to give a large capacity to the canister. For this reason, the above-described conventional apparatus has a characteristic that an increase in size of the canister cannot be avoided.
[0005]
The separation unit can process the evaporated fuel more efficiently as the fuel concentration in the gas flowing into the separation unit is higher. Contrary to this requirement, the fuel concentration in the gas purged from the canister is usually not so high. For this reason, the above-mentioned conventional apparatus also has a characteristic that the evaporated fuel cannot always be processed with high efficiency.
[0006]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an evaporative fuel processing apparatus that can reduce the size of a canister and efficiently process evaporative fuel.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a first invention is a fuel vapor processing apparatus,
A canister capable of adsorbing evaporated fuel,
A purge passage communicating with the canister;
A separation unit having a separation chamber communicating with the purge passage, and separating a processing gas containing evaporated fuel at a high concentration from the gas guided to the separation chamber;
A processing gas passage for guiding the processing gas to a fuel tank;
The fuel tank, through the purge passage, the vapor passage for communicating simultaneously with both the canister and the separation chamber,
It is characterized by providing.
[0008]
The second invention is the first invention, wherein
A purge gas circulation pump that is disposed in the middle of the purge passage and that pumps gas from the canister side toward the separation unit;
The vapor passage is communicated between the canister and the purge gas circulation pump.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.
[0010]
Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining the configuration of the evaporated fuel processing apparatus according to Embodiment 1 of the present invention. As shown in FIG. 1, the apparatus of this embodiment includes a fuel tank 10. The fuel tank 10 communicates with a vapor passage 12 for leading the evaporated fuel generated inside to the outside. The vapor passage 12 is connected to a purge passage 18 that connects the canister 14 and the purge gas circulation pump 16.
[0011]
The canister 14 has activated carbon inside thereof, and when a gas containing evaporated fuel flows in through the vapor passage 12 and the purge passage 18, the canister 14 can adsorb the evaporated fuel in the gas. A heater 20 for heating the activated carbon is disposed inside the canister 14. The activated carbon is heated by the heater 20 so that the adsorbed fuel is easily released as compared with a case where the activated carbon is not heated.
[0012]
The purge gas circulation pump 16 can suck the gas guided through the purge passage 18 and pump it out from the discharge port. A high concentration separation unit 22 communicates with the discharge port of the purge gas circulation pump 16. The high concentration separation unit 22 includes a first separation membrane 24 and a low concentration chamber 26 and a high concentration chamber 28 that are isolated by the first separation membrane 24. More specifically, the discharge port of the purge gas circulation pump 16 described above communicates with the low concentration chamber 26. On the other hand, the processing gas passage 30 communicates with the high concentration chamber 28.
[0013]
A fuel feed pump 32 and a jet pump 34 are arranged inside the fuel tank 10. The fuel feed pump 32 is a pump for feeding fuel toward an internal combustion engine (not shown). The fuel feed pump 32 discharges a larger amount of fuel than the amount actually consumed in the internal combustion engine. The excess fuel discharged in this manner passes through the jet pump 34 and is returned to the inside of the fuel tank 10.
[0014]
The jet pump 34 generates a negative pressure at the suction port in the process in which the excess fuel discharged by the fuel feed pump 32 circulates therein, and sucks the fluid supplied to the suction port to pump the fluid. It is a pump. In the system shown in FIG. 1, the processing gas passage 30 described above communicates with the suction port of the jet pump 34. Therefore, according to the jet pump 34, the gas in the high concentration chamber 28 of the high concentration separation unit 22 can be sucked and discharged through the processing gas passage 30.
[0015]
Above the high concentration separation unit 22, a medium concentration separation unit 36 is arranged. The medium concentration separation unit 36 includes a second separation membrane 38 and also includes a low concentration chamber 40 and a high concentration chamber 42 that are isolated by the second separation membrane 38. The low concentration chamber 40 of the medium concentration separation unit 36 communicates with the low concentration chamber 26 of the high concentration separation unit 22 described above via a communication path 44.
[0016]
The low concentration chamber 40 of the intermediate concentration separation unit 36 is also connected to a canister inlet gas passage 46. The canister inlet gas passage 46 communicates with the canister 14 described above, and the gas flowing out from the intermediate concentration separation unit 36 can be recirculated to the canister 14. The canister inlet gas passage 46 includes a pressure regulating valve 48 in the vicinity of the end portion on the intermediate concentration separation unit 36 side, and a check valve pair 50 in the vicinity of the end portion on the canister 14 side.
[0017]
The pressure regulating valve 48 is a one-way valve that allows only the flow of fluid from the medium concentration separation unit 36 toward the canister 14. The pressure regulating valve 48 is in the upstream path, that is, the path from the purge gas circulation pump 16 to the pressure regulating valve 48. It is provided in order to generate a predetermined positive pressure. On the other hand, the check valve pair 50 is provided to prevent the pressure in the system including the canister 14 from being unduly high or low.
[0018]
A circulating gas passage 52 communicates with the high concentration chamber 42 of the intermediate concentration separation unit 36. The circulation gas passage 52 communicates with the purge passage 18. Therefore, according to the circulation gas passage 52, the high concentration chamber 42 of the intermediate concentration separation unit 36 and the suction port of the purge gas circulation pump 16 can be brought into conduction.
[0019]
[Description of basic operation]
In the apparatus shown in FIG. 1, when the purge gas circulation pump 16 is stopped, gas containing evaporated fuel may flow from the fuel tank 10 to the canister 14. For example, when a large amount of evaporated fuel is generated in the fuel tank 10 after the vehicle stops due to residual heat, or when a large amount of gas is pushed out during the refueling, the evaporated fuel is reduced. A large amount of the contained gas flows into the canister 14. At this time, the canister 14 adsorbs the evaporated fuel in the gas and allows only air to flow toward the check valve pair 50.
[0020]
When the purge gas circulation pump 16 is operated, the negative pressure generated therein is guided to the canister 14. When such a negative pressure is introduced to the canister 14 that adsorbs the fuel, the canister outgas including the evaporated fuel flows out to the purge passage 18. The negative pressure generated by the purge gas circulation pump 16 is also led to the high concentration chamber 42 of the intermediate concentration separation unit 36 via the circulation gas passage 52. Therefore, in the steady state, the purge gas circulation pump 16 sucks the canister outlet gas supplied from the purge passage 18 and the circulation gas supplied from the circulation gas passage 52. In this case, the purge gas circulation pump 16 supplies the mixed gas as a purge gas to the low concentration chamber 26 of the high concentration separation unit 22.
[0021]
When the purge gas circulation pump 16 operates as described above, the system from the discharge port of the pump 16 to the pressure regulating valve 48 (the low concentration chamber 26 of the high concentration separation unit 22 and the low concentration chamber of the medium concentration separation unit 36). 40) includes the discharge pressure of the pump. On the other hand, a negative pressure accompanying the operation of the jet pump 34 is introduced into the high concentration chamber 28 of the high concentration separation unit 22. Further, the negative pressure generated by the purge gas circulation pump 16 is introduced into the high concentration chamber 42 of the intermediate concentration separation unit 36. Therefore, in this case, on both sides of the first separation membrane 24 of the high-concentration separation unit 22 and on both sides of the second separation membrane 38 of the medium-concentration separation unit 36, the low concentration chambers 26 and 40 side are on the high concentration side. A differential pressure is generated that is higher than the chambers 28 and 42 side.
[0022]
The first separation membrane 24 and the second separation membrane 38 are thin films made of a polymer material such as polyimide. When exposed to a gas containing air and fuel, the solubility of air and the solubility of fuel in the membrane are as follows. Due to the difference between the two, the characteristic of separating the two is shown. More specifically, the first separation membrane 24 and the second separation membrane 38 have a differential pressure on both sides of the membrane so that the gas containing the evaporated fuel is guided to one surface and the side of the surface becomes high pressure. When given, it has the characteristic of allowing the condensed gas having an increased fuel vapor concentration to pass through the low pressure side of the membrane.
[0023]
Therefore, with the operation of the purge gas circulation pump 16, the mixed gas flows into the low concentration chamber 26 of the high concentration separation unit 22 and the low concentration chamber 26 becomes high pressure on both sides of the first separation membrane 24. When such a differential pressure is generated, the evaporated fuel in the mixed gas is condensed on the high concentration chamber 28 side. As a result, the mixed gas in the low-concentration chamber 26 becomes a gas having a lower fuel concentration (hereinafter referred to as “medium concentration gas”) than when it flows, and the high-concentration chamber 28 contains a high-concentration processing gas. Is generated.
[0024]
The medium concentration gas flowing out from the low concentration chamber 26 of the high concentration separation unit 22 flows into the low concentration chamber 40 of the medium concentration separation unit 36. When the intermediate concentration gas flows into the low concentration chamber 40, the intermediate concentration separation unit 36 condenses the evaporated fuel in the intermediate concentration gas by the second separation membrane 38, and the circulating gas having a higher concentration than the intermediate concentration gas. In the high concentration chamber 42. The generated circulation gas is supplied to the suction port of the purge gas circulation pump 16 through the circulation gas passage 52.
[0025]
In the apparatus of the present embodiment, when the fuel concentration of the canister gas is 15%, the fuel concentration of the circulating gas is about 65% in the steady state. As a result, the mixed gas discharged from the purge gas circulation pump 16 ( The fuel concentration of the purge gas is about 60%. When the purge gas of about 60% is supplied, the high concentration separation unit 22 separates the purge gas into a processing gas having a fuel concentration of 95% or more and a medium concentration gas having a fuel concentration of about 40%. When the medium concentration separation unit 36 is supplied with a medium concentration gas having a fuel concentration of about 40%, the medium concentration gas is supplied to a circulating gas having a fuel concentration of about 65% and a canister having a fuel concentration of less than 5%. Separate into gas. That is, when the fuel concentration of the canister outgas is about 15%, the apparatus according to the present embodiment is a steady state, a processing gas having a fuel concentration of 95% or more, and a canister input gas having a fuel concentration of less than 5%. And can be generated.
[0026]
The processing gas generated in the high concentration separation unit 22 is sucked into the jet pump 34. If the air concentration is about 5%, the jet pump 34 can compress the processing gas to such an extent that the air dissolves in the fuel. For this reason, according to the configuration of the present embodiment, the processing gas generated by the high concentration separation unit 22 can be returned to the inside of the fuel tank 10 in a liquefied state.
[0027]
[Description of Features of this Embodiment]
Inside the fuel tank 10, vaporized fuel may be generated even during the purge. If the vapor passage 12 is connected not to the purge passage 18 but to the canister 14, the evaporated fuel generated during the execution of the purge once flows into the canister 14. If the evaporated fuel generated during the purge is necessarily adsorbed by the canister 14, the capacity of the canister 14 needs to be set to a large value in consideration of the adsorption of the evaporated fuel. . For this reason, in the configuration in which the vapor passage 12 is connected to the canister 14, it is necessary to give a large capacity to the canister 14.
[0028]
On the other hand, in the apparatus of the present embodiment, the vapor passage 12 is connected to the purge passage 18 instead of the canister 14 as described above. According to this configuration, the evaporated fuel generated during the execution of the purge is guided directly from the inside of the fuel tank 10 to the high concentration separation unit 22 without being adsorbed by the canister 14. For this reason, in the system according to the present embodiment, it is possible to reduce the capacity of the fuel vapor generated during the purge, assuming that the fuel is not adsorbed by the canister 14.
[0029]
The configuration of the present embodiment is superior to that in which the vapor passage 12 is connected to the canister 14 in terms of the processing efficiency of the evaporated fuel. That is, the high concentration separation unit 22 and the medium concentration separation unit 36 can process the evaporated fuel more efficiently as the fuel concentration in the gas discharged from the purge gas circulation pump 16 is higher. The fuel concentration in the gas discharged from the purge gas circulation pump 16 is the same as when the evaporated fuel generated in the fuel tank 10 flows directly into the purge gas circulation pump 16 from the vapor passage 12 and after being adsorbed by the canister 14. In the case of purging toward the pump 16, it is usually darker in the former case. The apparatus of the present embodiment can cause the evaporated fuel generated during the purge to flow into the purge gas circulation pump 16 through the former path. For this reason, according to this apparatus, the evaporated fuel can be processed more efficiently than the case where the vapor passage 12 is connected to the canister 14.
[0030]
Embodiment 2. FIG.
Next, Embodiment 2 of the present invention will be described with reference to FIG.
FIG. 2 is a diagram for explaining the configuration of the fuel vapor processing apparatus according to Embodiment 2 of the present invention. In FIG. 2, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted or simplified.
[0031]
In the apparatus of the second embodiment, the canister 14 is directly connected to the low concentration chamber 26 of the high concentration separation unit 22 via the purge passage 18. The low concentration chamber 26 of the high concentration separation unit 22 is connected to the intake passage of the internal combustion engine via the purge passage 60. The purge passage 60 includes a purge control valve (not shown), and can connect the intake passage of the internal combustion engine and the low concentration chamber 26 as necessary.
[0032]
Like the device of the first embodiment, the device of the second embodiment can adsorb the evaporated fuel generated after the vehicle stops or the evaporated fuel pushed out during refueling and flowing out of the fuel tank 10 by the canister 14. it can. The apparatus can process the evaporated fuel adsorbed on the canister 14 by returning a part thereof to the fuel tank 10 and sucking the remaining part into the intake passage of the internal combustion engine 10. Hereinafter, the operation when the apparatus of the present embodiment processes the evaporated fuel will be described.
[0033]
As in the case of the first embodiment, the high concentration separation unit 22 treats the high concentration chamber 28 with a high fuel concentration when the internal pressure of the low concentration chamber 26 is higher than the internal pressure of the high concentration chamber 28. Generate gas. In the configuration shown in FIG. 2, the internal pressure of the low concentration chamber 26 is opened to the internal pressure of the canister 14 and the fuel tank 10, that is, close to the atmospheric pressure. On the other hand, a negative pressure accompanying the operation of the jet pump 34 is introduced into the high concentration chamber 28. For this reason, a differential pressure capable of generating a processing gas having a high fuel concentration in the high concentration chamber 28 is secured on both sides of the separation membrane 24.
[0034]
In the apparatus according to the present embodiment, when a request to positively purge the evaporated fuel in the canister 14 occurs, the pressure in the low concentration chamber 26 is within a range in which the differential pressure is ensured, that is, the high concentration chamber 28. In the range where the internal pressure is maintained higher than the internal pressure (negative pressure by the jet pump 34), the purge control valve is opened to introduce the intake negative pressure of the internal combustion engine into the low concentration chamber 28. In this case, the high-concentration chamber 28 generated in the high-concentration chamber 28 is returned to the fuel tank 10 by the jet pump 34, and in the low-concentration chamber 26, the fuel concentration is lowered by the action of the separation membrane 24. Concentrated gas is generated, and this medium-concentrated gas is purged into the intake passage of the internal combustion engine.
[0035]
In the apparatus of the present embodiment, the vapor passage 12 is connected to the purge passage 18 as in the case of the first embodiment. For this reason, also in this embodiment, the capacity of the canister 14 can be suppressed to be small, and the evaporated fuel generated in the fuel tank 10 is directly guided to the high concentration separation unit 22 to achieve high processing efficiency. Can be realized. If the evaporated fuel generated in the fuel tank 10 is purged by the internal combustion engine without being diluted at all, a large air-fuel ratio roughening is likely to occur due to the purge. On the other hand, if the medium concentration gas diluted by the high concentration separation unit 22 is supplied to the internal combustion engine as in the present embodiment, such a rough air-fuel ratio can be sufficiently suppressed. For this reason, according to the apparatus of the present embodiment, the configuration in which the evaporated fuel is allowed to flow into the intake passage without using the purge gas circulation pump 16 can be carried out without deteriorating the drivability and emission characteristics of the internal combustion engine. The effect similar to the case of the form 1 of this can be implement | achieved.
[0036]
In the first or second embodiment, the low concentration chamber 26 of the high concentration separation unit 22 is the “separation chamber” in the first invention, and the high concentration separation unit 22 is the first invention. Each corresponds to a “separation unit”.
[0037]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
According to the first aspect, the evaporated fuel generated inside the fuel tank can be led out between the canister and the separation unit via the vapor passage. Therefore, according to the present invention, the evaporated fuel derived from the fuel tank can be directly supplied to the separation unit, the canister can be downsized, and the evaporated fuel can be efficiently processed. It can be.
[0038]
According to the second invention, the gas derived from the fuel tank can be pumped to the separation unit by the purge gas circulation pump. Therefore, according to the present invention, the amount of evaporated fuel flowing into the canister can be sufficiently reduced, and the processing efficiency of the evaporated fuel in the separation unit can be sufficiently increased.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a configuration of a fuel vapor processing apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a diagram for explaining a configuration of a fuel vapor processing apparatus according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Fuel tank 12 Vapor passage 14 Canister 16 Purge gas circulation pump 18, 60 Purge passage 22 High concentration separation unit 24, 38 Separation membrane 26, 40 Low concentration chamber 28, 42 High concentration chamber 36 Medium concentration separation unit 34 Jet pump

Claims (2)

A canister capable of adsorbing evaporated fuel,
A purge passage communicating with the canister;
A separation unit having a separation chamber communicating with the purge passage, and separating a processing gas containing evaporated fuel at a high concentration from the gas guided to the separation chamber;
A processing gas passage for guiding the processing gas to a fuel tank;
The fuel tank, through the purge passage, the vapor passage for communicating simultaneously with both the canister and the separation chamber,
An evaporative fuel processing apparatus comprising: A purge gas circulation pump that is disposed in the middle of the purge passage and that pumps gas from the canister side toward the separation unit;
The evaporated fuel processing apparatus according to claim 1, wherein the vapor passage is communicated between the canister and the purge gas circulation pump.

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