JP2012082753A - Fuel vapor treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel vapor treatment apparatus which has high separation and recovery efficiency of fuel vapor despite using a separating means separating fuel vapor-containing gas into an air component and a fuel component.SOLUTION: The fuel vapor treatment apparatus has a fuel tank 1, a canister 3, an aspirator 4 separating the fuel vapor from inside the canister 3, and a separation membrane module 5. When the fuel vapor is separated from inside the canister 3 by the aspirator 4, a purge gas Gfrom the canister 3 is introduced to a permeation chamber 5c while a fuel component Gseparated by a separation membrane 5d is recovered to the fuel tank 1. A plurality of scavenging ports 5p to be introduction ports of the purge gas Gare formed in the permeation chamber 5c so as to be in parallel with a gas flowing direction. A selector valve 27 for switching the purge gas Gso as to be introduced from any one of the scavenging ports 5p is provided.

Description

  The present invention relates to a fuel tank, a canister for adsorbing evaporated fuel generated in the fuel tank, negative pressure applying means for applying a negative pressure to the canister and detaching the evaporated fuel from the canister, and an evaporated fuel-containing gas The present invention relates to an evaporative fuel processing apparatus that includes a separation means including a separation membrane that separates the fuel into an air component and a fuel component, and separates and recovers the evaporated fuel from the evaporated fuel-containing gas into a fuel tank via the separation membrane.

  As this type of evaporative fuel processing apparatus, for example, there is Patent Document 1 below. In the evaporated fuel processing apparatus of Patent Document 1, a vacuum pump is used as a negative pressure applying unit, and an evaporated fuel containing gas (purge gas) containing evaporated fuel desorbed from a canister by the vacuum pump is used as a separating unit. The fuel component is introduced into the separation membrane module, and the fuel component is separated and recovered into the fuel tank through the separation membrane. Specifically, the vacuum pump is provided between the canister and the separation membrane module, and the purge gas from the canister is supplied to the introduction chamber of the separation membrane module. On the other hand, the air that has not passed through the separation membrane is finally supplied to the canister as a desorption promoting gas. During the desorption recovery of the evaporated fuel from the canister, the evaporated fuel-containing gas from the fuel tank is not processed.

JP 2010-116872 A

  In a separation membrane module equipped with this type of separation membrane, it is known that the separation efficiency (permeation separation amount per unit time) increases as the partial pressure difference of the evaporated fuel between the introduction chamber and the permeation chamber across the separation membrane increases. ing. Therefore, in the state where the evaporated fuel is present in the introduction chamber, the lower the fuel component concentration in the permeation chamber, the higher the separation efficiency. However, in Patent Document 1, only a positive pressure is applied to the introduction chamber of the separation membrane module by a vacuum pump, and positive gas flow is not achieved in the permeation chamber. In this case, the fuel component concentration (evaporated fuel partial pressure) is constantly high in the permeation chamber, and the evaporative fuel separation and recovery efficiency is limited.

  Accordingly, the present invention provides an evaporative fuel processing apparatus that solves the above-described problems and that has high evaporative fuel separation and recovery efficiency while using a separation unit that separates an evaporative fuel-containing gas into an air component and a fuel component. For the purpose.

  To that end, the first invention comprises a fuel tank, a canister for adsorbing the evaporated fuel generated in the fuel tank, a negative pressure applying means for applying a negative pressure to the canister and detaching the evaporated fuel from the canister, A separation means for separating the evaporated fuel-containing gas into an air component and a fuel component, and the separation means is divided by the separation membrane that preferentially permeates and separates the fuel component from the evaporated fuel-containing gas. An evaporative fuel processing apparatus for introducing evaporative fuel-containing gas into the separation means and recovering the evaporative fuel to the fuel tank via the separation membrane, the negative pressure applying means When the evaporated fuel is desorbed (purged) from the inside of the canister, the evaporated fuel-containing gas (introduced gas) from the fuel tank is introduced into the introduction chamber of the separation means, and the permeation is performed through the separation membrane. Separated fuel components (permeate gas) while recovering to the fuel tank to supply the purge gas from the canister to the permeate chamber of the separation means.

  If the vaporized fuel-containing gas from the fuel tank is introduced into the separation means while evacuating the vaporized fuel from the canister, the vaporized fuel regenerated in the fuel tank is simultaneously produced together with the vaporized fuel adsorbed in the canister. It can be recovered. As a result, it is possible to reduce a rapid internal pressure increase of the fuel tank during the process of the evaporated fuel, a load (evaporated fuel adsorption amount) on the canister while the system is stopped, and the like. Note that the purge gas from the canister can also be said to be an evaporated fuel-containing gas containing the desorbed evaporated fuel, but the fuel component concentration (purge gas concentration) in the purge gas is usually in the evaporated fuel-containing gas introduced from the fuel tank. The fuel component concentration (introduced gas concentration) is lower. In addition, purge gas from the canister is supplied to the permeation chamber of the separation means. Therefore, if the purge gas from the canister is supplied to the permeation chamber of the separating means, the permeation chamber is scavenged by the purge gas, so that the fuel component concentration in the permeation chamber can be actively reduced. Thus, the permeation and separation of the evaporated fuel by the separation membrane is promoted, and the efficiency of separating and recovering the evaporated fuel is improved. By improving the evaporative fuel separation efficiency, the separation means and the negative pressure application means can be downsized. The purge gas is recovered into the fuel tank together with the permeated and separated fuel component.

  Furthermore, in the present invention, gas such as introduced gas (evaporated fuel-containing gas) introduced from the fuel tank or fuel component (permeated gas) permeated through the separation membrane flows along the separation membrane in the separation means. It has a configuration. According to this, since the accumulated contact area and contact time between the evaporated fuel-containing gas and the separation membrane increase, the evaporated fuel can be permeated and separated with high accuracy. That is, it is possible to reduce the remaining separation of the evaporated fuel.

  In addition, a plurality of inlets for the purge gas are formed in the permeation chamber in parallel with the gas flow direction, and switching means for switching the purge gas to be introduced from any one of the plurality of inlets. It is characterized by having. When the introduced gas flows in the separation means along the separation membrane, the concentration of the evaporated fuel in the introduced gas gradually decreases from the upstream to the downstream in the introduction chamber. In proportion to this, the distribution of the evaporated fuel concentration gradually decreases in the permeation chamber with respect to the flow direction of the introduced gas. In the downstream region in the flow direction of the introduced gas, the evaporated fuel concentration is extremely low. Therefore, if purge gas is supplied to the downstream area, the separation efficiency in the downstream area may be reduced. However, the distribution of the fuel component concentration in the permeation chamber varies depending on the introduced gas concentration, the degree of negative pressure applied to the permeation chamber, and the like, and the purge gas concentration is not constant. Therefore, if it is possible to switch the purge gas to be introduced from any one of the plurality of inlets, the purge gas can be introduced from an appropriate inlet according to various situations, so that the separation efficiency is lowered. It is possible to improve the separation efficiency by efficiently scavenging the permeation chamber without causing the separation.

  According to a second invention, in the first invention, there is provided a purge gas concentration detecting means for detecting a fuel component concentration in the purge gas. Then, the introduction port is switched according to the purge gas concentration. According to this, since the inlet for purge gas can be changed according to the fluctuation of the purge gas concentration, the permeation chamber can be scavenged more efficiently and the separation efficiency can be improved without lowering the separation efficiency.

  According to a third invention, in the second invention, there is provided an introduction gas concentration detection means for detecting a fuel component concentration in the evaporated fuel-containing gas introduced from the fuel tank into the introduction chamber. Then, an introduction port is opened at a position where the fuel component concentration in the permeation chamber identified from the introduction gas concentration and the purge gas concentration are approximately the same. As described above, the fuel component concentration distribution in the permeation chamber varies depending on the introduced gas concentration. Therefore, by detecting the introduction gas concentration and the supply gas concentration, it is possible to grasp (identify) a position where the fuel component concentration and the purge gas concentration in the permeation chamber are approximately the same. Then, by introducing the purge gas from the position, the permeation chamber can be accurately scavenged without lowering the separation efficiency, and the separation efficiency can be improved. In the present invention, “same level” means “almost equal” even if there is a slight error.

  According to a fourth invention, in the third invention, a negative pressure detecting means for detecting a negative pressure applied to the permeation chamber by the negative pressure applying means is provided between the permeation chamber and the negative pressure applying means. It has been. The position where the fuel component concentration and the purge gas concentration in the permeation chamber are approximately the same is based on a map obtained experimentally in advance from the negative pressure in the permeation chamber, the introduced gas concentration, and the purge gas concentration. It is detected. The distribution of the fuel component concentration in the permeation chamber depends on the concentration of the introduced gas and the negative pressure in the permeation chamber, but the fluctuation characteristics are constant depending on the separation membrane module. Therefore, using a separation membrane module of the same type as the separation membrane module to be used, the correlation between the negative pressure in the permeation chamber, the introduced gas concentration, and the purge gas concentration is experimentally measured in advance, and the characteristics are measured in three dimensions. Can be mapped. According to this, accurate positioning can be performed corresponding to various variable elements. Moreover, since it is not necessary to calculate from the various density | concentrations and negative pressure which were detected at any time, an introduction port can be switched smoothly and a control program can also be simplified.

  According to a fifth invention, in the fourth invention, the fuel tank is provided with an internal pressure detecting means for detecting an internal pressure of the fuel tank, and the negative pressure applying means is a fuel that is discharged from a fuel pump. An aspirator that introduces a portion to generate a negative pressure is used. The introduced gas concentration is obtained by an expression represented by (fuel vapor pressure identified from the detection result of the negative pressure detecting means / absolute value of the fuel tank internal pressure) × 100.

  Although details will be described later, the aspirator introduces a part of the fuel discharged from the fuel pump and generates a negative pressure by the venturi effect in the decompression chamber. At this time, the fuel introduced into the aspirator is vaporized under reduced pressure in the decompression chamber, thereby generating a vapor pressure. Therefore, the internal pressure of the decompression chamber, that is, the negative pressure generated by the aspirator is in an equilibrium state based on the vapor pressure of the introduced fuel. Therefore, if the negative pressure of the aspirator in this equilibrium state is detected by the negative pressure detection means, the fuel vapor pressure can be calculated automatically based on the detection result. That is, the fuel vapor pressure can be identified from the negative pressure generated by the aspirator. According to this, the introduction gas concentration can be accurately detected without providing a detection means for directly detecting the introduction gas concentration.

  In a sixth aspect based on the first aspect, the introduction port is sequentially switched from the downstream side to the upstream side on the basis of the gas flow direction in the permeation chamber based on the elapsed time from the start of desorption of the evaporated fuel from the canister. It is characterized by that. According to this, since the purge gas inlet can be sequentially moved according to the purge gas concentration that decreases with time, it is possible to efficiently scavenge the permeation chamber and improve the separation efficiency while avoiding a decrease in the separation efficiency. it can. Moreover, since it is not necessary to provide various detection means, the apparatus can be simplified. Complex programming is also unnecessary.

  According to the present invention, the purge gas can be actively scavenged by introducing the purge gas into the permeation chamber from an appropriate position while using the separation means that separates the evaporated fuel-containing gas into the air component and the fuel component. Efficiency can be improved accurately.

It is a schematic diagram of an evaporative fuel processing apparatus. It is a longitudinal cross-sectional view of an aspirator. It is a schematic diagram which shows the gas flow in a separation membrane module. It is a schematic diagram which shows the modification of a switching means.

  Hereinafter, representative embodiments of the present invention will be described, but the present invention is not limited thereto, and various modifications can be made without departing from the gist of the present invention. In particular, as long as it has a basic configuration including a fuel tank, a canister, a negative pressure application unit, and a separation unit, which are essential components for the evaporated fuel processing apparatus of the present invention, various other components can be added. The evaporative fuel processing apparatus can be suitably applied to a vehicle such as an automobile that uses highly volatile fuel (for example, gasoline) as fuel.

(Example)
As shown in FIG. 1, the evaporative fuel processing apparatus includes a fuel tank 1 that stores fuel F, a fuel pump 2 that supplies fuel F in the fuel tank 1 to an internal combustion engine (engine) that is not shown, and a fuel tank 1 The canister 3 for adsorbing the evaporated fuel (vapor) generated in the above, the aspirator 4 for applying a negative pressure to the canister 3 to suck and desorb the evaporated fuel from the canister 3, and the evaporated fuel-containing gas into an air component and a fuel component Separation membrane module 5 to be separated, capture vapor passage 10 for introducing and capturing the evaporated fuel in the fuel tank 1 to the canister 3, and processing vapor for introducing and processing the evaporated fuel in the fuel tank 1 to the separation membrane module 5 It has a passage 11 and the like. The aspirator 4 corresponds to the negative pressure applying means of the present invention, and the separation membrane module 5 corresponds to the separating means of the present invention.

  The fuel tank 1 is a closed tank. The fuel tank 1 is provided with an internal pressure sensor 36 that detects the internal pressure of the fuel tank 1. A detection signal from the internal pressure sensor 36 is input to an engine control unit (ECU) 35. The internal pressure sensor 36 corresponds to the internal pressure detection means of the present invention.

  The fuel pump 2 is disposed in the fuel tank 1 and pumps the fuel F through the fuel supply passage 12 to the engine. The canister 3 is filled with an adsorbent C. As the adsorbent C, a porous body that allows air to pass through but adsorbs and desorbs the evaporated fuel can be used. In this embodiment, activated carbon is used. Reference numeral 33 denotes a heater for heating the inside of the canister 3 (adsorbent C). The adsorbent C has a characteristic that the higher the temperature, the smaller the amount of adsorption of the specific component (evaporated fuel in the present invention), and the lower the temperature, the larger the amount of adsorption of the specific component. Therefore, when the vaporized fuel adsorbed and captured by the adsorbent C is desorbed, the temperature of the adsorbent C is preferably as high as possible. However, when the evaporated fuel is desorbed from the adsorbent C, the temperature of the adsorbent C decreases due to the heat of vaporization. Therefore, the desorption efficiency can be improved by heating the adsorbent C with the heater 33 at the time of evaporative fuel desorption.

  The separation membrane module 5 includes a sealed container 5a, and a separation membrane 5d arranged so as to divide the sealed container 5a into an introduction chamber 5b and a permeation chamber 5c. As the separation membrane 5d here, a well-known separation membrane having a high dissolution diffusion coefficient with respect to the fuel component and preferentially permeating and separating the fuel component but hardly permeating the air component is used. Specifically, the separation membrane 5d includes a non-porous thin film layer (functional layer) that performs a main function of gas separation, and a porous support layer that supports the thin film layer. For the thin film layer, for example, a silicone rubber or the like that is cross-linked and three-dimensionally insolubilized is used. For the porous support layer, for example, a synthetic resin such as polyimide (PI), polyetherimide (PEI), or polyvinylidene fluoride (PVDE), or ceramic is used. Examples of the separation membrane 5d include a hollow fiber shape, a flat plate shape, a honeycomb shape, and a spiral shape.

  The fuel tank 1 and the canister 3 are communicated with each other via a capture vapor passage 10. A trapping vapor passage valve 20 is provided on the trapping vapor passage 10 as an opening / closing means for switching between a communication state and a blocking state of the trapping vapor passage 10. The canister 3 is connected to an atmospheric passage 13 whose tip is open to the atmosphere. An atmospheric passage valve 23 is also provided on the atmospheric passage 13 as an opening / closing means for switching between a communication state and a cutoff state of the atmospheric passage 13. The fuel tank 1 and the introduction chamber 5 b of the separation membrane module 5 are communicated with each other via a processing vapor passage 11. A processing vapor passage valve 21 is provided on the processing vapor passage 11 as an opening / closing means for switching between a communication state and a blocking state of the processing vapor passage 11.

  The canister 3 and the introduction chamber 5 b of the separation membrane module 5 are communicated with each other through an impermeable gas passage 16. The impervious gas passage 16 branches in the middle and is also connected to the intake passage 30. The intake passage 30 is a passage through which air (atmosphere) is sucked into the engine while the engine is being driven. Reference numeral 31 denotes a throttle valve that controls the amount of intake air in accordance with the amount of depression of an accelerator pedal (not shown). Reference numeral 32 denotes an air filter. Between the branch point on the impervious gas passage 16 and the intake passage 30, a pressure relief valve 26 that switches between the communication state and the shut-off state of the impermeable gas passage 16 is provided. The impervious gas passage 16 is connected to the intake passage 30 upstream of the throttle valve 31 (on the air filter 32 side).

  The canister 3 and the permeation chamber 5 c of the separation membrane module 5 are communicated with each other via a purge passage 17. A concentration sensor 37 for detecting the fuel component concentration (purge gas concentration) in the purge gas is provided on the purge passage 17. A detection signal from the concentration sensor 37 is input to the ECU 35. The concentration sensor 37 corresponds to the purge gas concentration detection means of the present invention.

  A branch passage 14 is connected to the fuel supply passage 12 in a branched manner, and the aspirator 4 is connected to the other end. A recovery passage 15 leading to the permeation chamber 5 c of the separation membrane module 5 is also connected to the aspirator 4. The aspirator 4 is a negative pressure generating unit that introduces a part of the fuel F discharged from the fuel pump 2 to generate a negative pressure. Specifically, as shown in FIG. 2, the aspirator 4 includes a venturi portion 41 and a nozzle portion 45. The venturi section 41 includes a throttle 42, a tapered decompression chamber 43 provided on the upstream side of the throttle 42 in the fuel flow direction, and a diverging diffuser section 44 provided on the downstream side of the throttle 42 in the fuel flow direction. And a suction port 41p. The decompression chamber 43, the throttle 42, and the diffuser portion 44 are each formed coaxially. The suction port 41 p is formed in communication with the decompression chamber 43. The collection passage 15 is connected to the suction port 41p. The nozzle part 45 is joined to the upstream side of the venturi part 41. The nozzle portion 45 includes an introduction port 45p for introducing the fuel F into the aspirator 4 and a nozzle body 46 for injecting the introduced fuel F. The branch passage 14 is connected to the introduction port 45p. The nozzle body 46 is coaxially accommodated in the decompression chamber 43, and the injection port 46 p of the nozzle body 46 faces the aperture 42.

  Part of the fuel F discharged from the fuel pump 2 is introduced into the aspirator 4 from the fuel supply passage 12 through the branch passage 14. Then, the introduced fuel F is injected from the nozzle body 46 and flows in the central portion of the throttle 42 and the diffuser portion 44 at high speed in the axial direction. At this time, a negative pressure is generated in the decompression chamber 43 due to the venturi effect. Thereby, a negative pressure (suction force) is generated in the recovery passage 15 via the suction port 41p. The gas sucked from the suction port 41p through the recovery passage 15 is mixed and discharged from the diffuser portion 44 together with the fuel F injected from the nozzle body 46.

  A negative pressure sensor 38 that detects a negative pressure between the permeation chamber 5 c and the aspirator 4 is provided on the recovery passageway 15, that is, between the permeation chamber 5 c and the aspirator 4. A detection signal from the negative pressure sensor 38 is input to the EUC 35. The negative pressure sensor 38 is the same type as the internal pressure sensor 36. The negative pressure sensor 38 corresponds to the negative pressure detection means of the present invention.

As shown in FIG. 3, the sealed container 5a of the separation membrane module 5 has an introduction port 5m for introducing an introduction gas (evaporated fuel-containing gas) G ₁ from the fuel tank 1 and air that has not permeated through the separation membrane 5d. introducing a non-permeate gas port 5n for exhausting the component (impermeable gas) G _2, it permeated fuel component separation membrane 5d (the permeate gas) G ₃ and collecting port 5f for exhausting recovering the purge gas G ₄ from the canister 3 The scavenging port 5p is formed so as to penetrate inside and outside. The introduction port 5m and the impermeable gas port 5n are formed in the introduction chamber 5b. The processing vapor passage 11 is connected to the introduction port 5m. An impermeable gas passage 16 is connected to the impermeable gas port 5n. The introduction port 5m and the impervious gas port 5n are formed to face each other in the introduction chamber 5b. Therefore, the introduction gas G ₁ introduced into the introduction chamber 5b flows along the separation membrane 5d from the upstream introduction port 5m side to the downstream impermeable gas port 5n side.

The recovery port 5f and the scavenging port 5p are formed in the transmission chamber 5c. A recovery passage 15 is connected to the recovery port 5f. Recovery port 5f is formed at the upstream end (inlet port 5m side) with respect to the flow direction of the fuel vapor containing gas G _1. Therefore, even permeate gas G ₃ having passed through the separation membrane 5d, including the downstream region of the supply chamber 5b flows along the separation membrane 5d, is exhausted from the recovery port 5f. Thus, the gas flow direction in the permeation chamber 5c is opposite to the gas flow direction in the introduction chamber 5b.

Meanwhile, the scavenging port 5p is permeated gas are formed in plural in parallel with the flow direction of G _3, respectively purge passage 17 is connected to branched to each scavenging port 5p. Scavenging port 5p may be formed of at least two or more positions, it is preferable to only a number form as possible over the entire flow field of the permeate gas G _3. Moreover, it is preferable to arrange the scavenging ports 5p in parallel at equal intervals. In this embodiment, four scavenging ports 5p _{1 to} 5p ₄ are formed from the downstream. Sonouede, recovery passage 15 On each connection portion which is branched, the switching valve 27 for switching to introduce a purge gas G ₄ from any one of the plurality of scavenging ports 5p, respectively. In this embodiment, four switching valves 27a to 27d are provided from the downstream in accordance with the scavenging port 5p. The scavenging port 5p corresponds to the purge gas inlet in the present invention, and the switching valve 27 corresponds to the switching means of the present invention.

  The capture vapor passage valve 20, the processing vapor passage valve 21, the atmospheric passage valve 23, the pressure relief valve 26, and each switching valve 27 are electromagnetic valves whose opening / closing timing is controlled by the ECU 35. The ECU 35 includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and the like. A predetermined control program and a later-described three-dimensional map are stored in advance in the ROM, and the CPU controls each component of the evaporated fuel processing apparatus at a predetermined timing based on the control program and the three-dimensional map. .

Basically, with respect to the flow direction of permeate gas G ₃ in a transmission chamber 5c, it is preferable to introduce a purge gas G ₄ as possible from the upstream. This is because the entire interior of the transmission chamber 5c can be scavenged. However, the introduction of purge gas G ₄ into a region of low fuel component concentration than the purge gas concentration, the fuel component concentration permeation chamber 5c enhanced by the purge gas G _4, the risk that the separation efficiency by the separation membrane 5d warped decreases is there. Therefore, it is desirable to introduce the purge gas G ₄ from a position where the purge gas concentration and the fuel component concentration in the permeation chamber 5c are approximately the same. However, during operation of the system (evaporative fuel processing apparatus), the purge gas concentration decreases with time as the evaporated fuel is desorbed from the canister 3. In addition, the concentration of the introduced gas is not always constant, and the fuel component concentration distribution in the permeation chamber 5c varies depending on the introduced gas concentration. Therefore, the position where the purge gas concentration and the fuel component concentration in the permeation chamber 5c are approximately the same also inevitably varies. Therefore, it switched each switching valve 27a~27d by ECU 35, as a fuel component concentration and the purge gas concentration in permeation chamber 5c purge gas G ₄ from one scavenging port 5p corresponding to the position where the same level is introduced It is configured.

  The detection means for the position where the fuel component concentration and the purge gas concentration in the permeation chamber 5c are approximately the same will be described. First, the distribution of the fuel component concentration in the permeation chamber 5 c depends on the introduced gas concentration and the degree of the negative pressure in the permeation chamber 5 c, but its fluctuation characteristics are constant by the separation membrane module 5. Therefore, by using a separation membrane module of the same type as the separation membrane module 5 to be used, various changes are made to the negative pressure, the introduced gas concentration, and the purge gas concentration in the permeation chamber 5c, and these correlations are experimentally measured in advance. The characteristics can be converted into a three-dimensional map. Then, the three-dimensional mapping is stored in the EUC 35. Thereby, during the evaporative fuel treatment, the negative pressure, the introduced gas concentration, and the purge gas concentration in the permeation chamber 5c are detected in real time, and these detection results are compared with the three-dimensional map of the ECU 35, so that the concentrations are approximately the same. Thus, the scavenging port 5p to be opened can be easily detected.

In this embodiment, no detection means for directly detecting the introduced gas concentration is provided. Instead, the introduced gas concentration is
Introduced gas concentration = (fuel vapor pressure / absolute value of internal pressure of fuel tank 1) × 100
It can obtain | require by the formula represented by. The calculation formula is also stored in the ECU 35.

  Here, the fuel vapor pressure can be calculated from the degree of negative pressure generated by the aspirator 4. The aspirator 4 introduces a part of the fuel F discharged from the fuel pump 2 to generate a negative pressure, but the fuel F introduced into the aspirator 4 is vaporized under reduced pressure in the decompression chamber 43. Fuel vapor pressure is generated. Therefore, the internal pressure of the decompression chamber 43, that is, the negative pressure generated by the aspirator 4 is in an equilibrium state based on the vapor pressure of the introduced fuel F. In addition, the negative pressure generated by the aspirator 4 is detected by the negative pressure sensor 38. As described above, the negative pressure detected by the negative pressure sensor 38 is a balance between the fuel vapor pressure obtained by vaporizing the fuel F introduced into the aspirator 4 in the decompression chamber 43 and the negative pressure actually generated by the venturi effect. This is the equilibrium pressure that has been reached. The ECU 35 stores the relationship (map) of the fuel vapor pressure with respect to the detection result by the negative pressure sensor 38, and the fuel vapor pressure can be calculated (identified) by detecting the negative pressure by the aspirator 4. Therefore, to accurately describe the above calculation formula, the introduced gas concentration = (the fuel vapor pressure identified from the detection result of the negative pressure sensor 38 / the absolute value of the internal pressure of the fuel tank 1) × 100.

  Next, an evaporative fuel processing mechanism by the evaporative fuel processing apparatus will be described. In the following description, the opening / closing timing of each valve, the driving timing of the fuel pump 2, calculation and detection based on various detection results are all controlled by the ECU 35. During parking (when the vehicle is off), the atmospheric passage valve 23 is open, but the capture vapor passage valve 20, the processing vapor passage valve 21, the pressure relief valve 26, and the switching valves 27 are closed. At the time of refueling, the capture vapor passage valve 20 is opened. Then, when the internal pressure of the fuel tank 1 increases with refueling, the evaporated fuel-containing gas in the fuel tank 1 flows into the canister 3 through the trapping vapor passage 10. Then, the evaporated fuel is selectively adsorbed and captured by the adsorbent C in the canister 3. The remaining air passes through the adsorbent C and is dissipated from the canister 3 through the atmospheric passage 13 into the atmosphere. Thereby, the pressure of the fuel tank 1 is released while avoiding air pollution, and damage to the fuel tank 1 is prevented. After refueling is completed, the capture vapor passage valve 20 is opened again.

While the vehicle is running (when the engine is running), the atmospheric passage valve 23 is closed, while any one of the processing vapor passage valve 21 and the plurality of switching valves 27 is opened. The capture vapor passage valve 20 is normally closed, and the pressure relief valve 26 is basically closed. Further, the heater 33 is energized and the inside of the canister 3 is heated. When the process vapor passage valve 21 is opened, fuel vapor containing gas in the fuel tank 1 is introduced as the introduced gas G ₁ into the introduction chamber 5b of the separation membrane module 5 through the process vapor pipe 11. Then, as shown in FIG. 3, the introduction gas G ₁ flows in the introduction chamber 5b along the separation membrane 5d from the introduction port 5m toward the non-permeable gas port 5n. In the meantime, the fuel component in the introduced gas G ₁ permeates through the separation membrane 5d preferentially, so that the permeated gas G ₃ mainly composed of evaporated fuel is separated and purified in the permeation chamber 5c. On the other hand, the impermeable gas G ₂ remaining in the introduction chamber 5 b without passing through the separation membrane 5 d is introduced into the canister 3 through the impermeable gas passage 16. Thereby, desorption of the evaporated fuel adsorbed in the canister 3 is promoted.

At the same time, when the fuel pump 2 is driven, a part of the fuel F discharged from the fuel pump 2 is introduced from the fuel supply passage 12 into the aspirator 4 through the branch passage 14. Then, a negative pressure is generated by the aspirator 4, and the inside of the collection passage 15 and the permeation chamber 5 c of the separation membrane module 5 is decompressed. As a result, the permeated gas G _{3 that} has permeated through the separation membrane 5d flows along the separation membrane 5d in the permeation chamber 5c, is sucked into the aspirator 4 from the recovery port 5f through the recovery passage 15, and into the fuel tank 1 At the same time, it is discharged and collected.

  The negative pressure generated by the aspirator 4 is also applied from the purge passage 17 into the canister 3 through the permeation chamber 5 c of the separation membrane module 5. Thereby, the evaporated fuel adsorbed in the canister 3 is sucked and desorbed (purged). At this time, the real-time negative pressure applied from the aspirator 4 to the permeation chamber 5c is determined by the negative pressure sensor 38, and the real-time internal pressure of the fuel tank 1 is determined by the internal pressure sensor 36. ) Are detected and monitored by the concentration sensor 37, and each detection result is input to the ECU 35. Then, the real-time fuel vapor pressure is identified in the EUC 35 from the detection result by the negative pressure sensor 38. Then, from the identified fuel vapor pressure and the detection result of the internal pressure sensor 36, the introduced gas concentration is identified in the EUC 35 based on the calculation formula of (fuel vapor pressure / absolute value of the internal pressure of the fuel tank 1) × 100. . After that, the negative pressure in the permeation chamber 5c, the introduced gas concentration, and the purge gas concentration are compared with the three-dimensional map stored in advance in the ECU 35, so that the fuel component concentration and the purge gas concentration in the permeation chamber 5c are the same. An approximate position is detected. Only the switching valve 27 of the scavenging port 5p corresponding to the calculated position is opened.

When the predetermined switching valve 27 is opened, the purge gas from the canister 3 is supplied from the predetermined scavenging port 5p to the permeation chamber 5c of the separation membrane module 5 through the purge passage 17. Then, since the purge gas concentration at a downstream region from the scavenging port 5p less than the fuel component concentration transparent chamber 5c, as shown in FIG. 3, transmission chamber 5c with a purge gas G ₄ are actively scavenging transmission chamber 5c The fuel component concentration, that is, the partial pressure of the fuel component is actively reduced. Thereby, the separation efficiency by the separation membrane 5d is improved. On the other hand, in the upstream area from the scavenging port 5p, the fuel component concentration is lower than in the downstream area. However, since the purge gas G ₄ is not introduced into the upstream region, the fuel component concentration in the upstream region is not increased by the purge gas G ₄ .

The purge gas concentration decreases with time, and the introduced gas concentration and the negative pressure by the aspirator 4 can also vary depending on the fuel temperature and the like. Therefore, the position where the fuel component concentration and the purge gas concentration in the permeation chamber 5c are approximately the same is not constant. Therefore, the position is constantly detected by the ECU 35, and switching control is performed so that only one of the switching valves 27 corresponding to the position is opened as the position changes. Thereby, even if the position where the fuel component concentration and the purge gas concentration in the permeation chamber 5c are approximately the same, the high separation efficiency in the separation membrane 5d can always be maintained. The purge gas G ₄ is exhausted from the recovery port 5 f together with the permeate gas G ₃ and finally recovered to the fuel tank 1.

  Further, when the internal pressure sensor 36 detects that the internal pressure of the fuel tank 1 has become a predetermined value (for example, 5 kPa) or more during engine driving, the pressure relief valve 26 is opened. Then, the impermeable gas is introduced into the intake passage 30 through the impermeable gas passage 16 and the fuel tank 1 is depressurized. When the internal pressure sensor 36 detects that the internal pressure of the fuel tank 1 has decreased sufficiently (for example, about atmospheric pressure), the pressure relief valve 26 is closed again.

(Modification)
In the above embodiment, a plurality of switching valves 27 corresponding to each scavenging port 5p are provided, but one multi-way switching valve 47 may be provided at the branch point of the purge passage 17 as shown in FIG.

In the above-described embodiment, the negative pressure in the permeation chamber 5c, the introduced gas concentration, and the purge gas concentration are detected or identified, and an accurate position is detected based on the three-dimensional map to switch and control the switching valve 27. The switching control of the switching valve 27 is not limited to this. For example, the switching valve 27 can be switched based on only the detection result of the concentration sensor 37. This is because the purge gas concentration surely decreases with time, but the introduced gas concentration and the degree of negative pressure may not vary greatly. In this case, on the basis of the flow direction of the permeated gas G ₃ , the switching valve 27 on the upstream side is switched from the switching valve 27 on the most downstream side to sequentially open.

Or based from the canister 3 to the fuel vapor to the elapsed time from the start desorbed sequentially as inlet to the upstream side from the downstream side in the flow direction criteria permeate gas G ₃ in the transmission chamber 5c (scavenging ports 5p) is opened The switching valve 27 can also be switched.

  In the above embodiment, the introduced gas concentration is calculated by a predetermined calculation formula. However, it is also possible to directly detect the introduced gas concentration by providing a concentration sensor as the introduced gas concentration detecting means on the processing vapor passage 11 or in the fuel tank 1. it can. In this case, the negative pressure applying means is not limited to the aspirator 4 but may be a vacuum pump provided on the recovery passage 15. Further, the switching valve 27 can be switched only by the correlation between the purge gas concentration and the introduced gas concentration.

  Instead of the pressure relief valve 26, a three-way valve can be provided at the branch point of the impermeable gas passage 16. Further, when the internal pressure of the fuel tank 1 becomes a predetermined value or more during the process of the evaporated fuel, the pressure can be released through the canister 3. In this case, an electromagnetic valve is provided on the branch passage 14. In addition, when the internal pressure sensor 36 detects that the internal pressure of the fuel tank 1 has exceeded a predetermined value during the process of the evaporated fuel, the processing vapor passage valve 21 and the electromagnetic valve on the branch passage are closed while being captured. The vapor passage valve 20 is opened. Then, the pressure in the fuel tank 1 is released in the same manner as when refueling. When the internal pressure sensor 36 detects that the internal pressure of the fuel tank 1 has sufficiently decreased, the trapped vapor passage valve 20 is closed again, while the processing vapor passage valve 21 and the electromagnetic valve on the branch passage are closed. And evaporative fuel processing is resumed. Therefore, in such a modification, the impermeable gas passage 16 does not necessarily need to be branched to the intake passage 30. Of course, the pressure relief valve 26 is also unnecessary.

  In the first and second embodiments, the impervious gas is supplied to the canister 3. However, the impervious gas may be exhausted to the intake passage 30 or the atmosphere together with the canister 3 or without being supplied to the canister 3. it can. When exhausting the impervious gas to the intake passage 30, even when the internal pressure of the fuel tank 1 is less than a predetermined value during the processing of the evaporated fuel, the pressure relief valve 26 is opened at an appropriate timing. Alternatively, the pressure relief valve 26 may not be provided. When the impervious gas is exhausted to the atmosphere, the tip of the impervious gas passage 16 may be opened to the atmosphere. When the impermeable gas is not supplied to the canister 3, the impermeable gas passage 16 may not be connected to the canister 3. In this case, it is preferable to open the atmospheric passage valve 23 even during the process of evaporative fuel and introduce the atmosphere from the atmospheric passage 13 into the canister 3 as a desorption promoting gas.

DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Fuel pump 3 Canister 4 Aspirator 5 Separation membrane module 5b Introduction chamber 5c Permeation chamber 5d Separation membrane 5m Introduction port 5n Impervious gas port 5p Scavenging port 5f Recovery port 10 Capture vapor passage 11 Process vapor passage 12 Fuel supply passage 13 Atmospheric passage 14 Branch passage 15 Recovery passage 16 Impervious gas passage 17 Purge passage 27 Switching valve 36 Internal pressure sensor 37 Concentration sensor 38 Negative pressure sensor C Adsorbent F Fuel G ₁ Gas containing evaporated fuel (introduced gas)
G ₂ impervious gas G ₃ permeate gas G ₄ purge gas

Claims (6)

A fuel tank, a canister for adsorbing the evaporated fuel generated in the fuel tank, a negative pressure applying means for applying a negative pressure to the canister to desorb the evaporated fuel from the inside of the canister, and an evaporated fuel-containing gas as an air component Separating means for separating the fuel component from the vaporized fuel-containing gas, the separation means comprising: a separation membrane that preferentially permeates and separates the fuel component; and an introduction chamber and a permeation chamber separated by the separation membrane. An evaporative fuel processing apparatus that introduces an evaporative fuel-containing gas into the separation means and recovers the evaporative fuel to the fuel tank via the separation membrane,
When the evaporated fuel is desorbed from the canister by the negative pressure applying means, the evaporated fuel-containing gas from the fuel tank is introduced into the introduction chamber of the separation means and separated into the permeation chamber via the separation membrane. The purge gas from the canister is introduced into the permeation chamber of the separation means, while the recovered fuel component is recovered in the fuel tank,
In the separation means, an introduced gas introduced from the fuel tank or a gas such as a fuel component that has permeated the separation membrane flows along the separation membrane,
In the permeation chamber, a plurality of inlets for the purge gas are formed in parallel with the gas flow direction,
An evaporative fuel processing apparatus comprising switching means for switching the purge gas to be introduced from any one of the plurality of inlets. It is an evaporative fuel processing apparatus of Claim 1, Comprising:
A purge gas concentration detecting means for detecting the fuel component concentration in the purge gas;
An evaporative fuel processing apparatus, wherein the inlet is switched according to a purge gas concentration. The evaporative fuel processing apparatus according to claim 2,
An introduction gas concentration detection means for detecting a fuel component concentration in the evaporated fuel-containing gas introduced from the fuel tank into the introduction chamber;
An evaporative fuel processing apparatus, wherein an inlet is opened at a position where the concentration of the fuel component in the permeation chamber identified from the concentration of the introduced gas is approximately equal to the purge gas concentration. The evaporative fuel processing apparatus according to claim 3,
Between the permeation chamber and the negative pressure application means, a negative pressure detection means for detecting a negative pressure applied to the permeation chamber by the negative pressure application means is provided,
The position where the fuel component concentration and the purge gas concentration in the permeation chamber are approximately the same is based on a three-dimensional map obtained experimentally in advance from the negative pressure in the permeation chamber, the introduced gas concentration, and the purge gas concentration. The evaporative fuel processing apparatus is characterized by being detected. It is an evaporative fuel processing apparatus of Claim 4, Comprising:
The fuel tank is provided with an internal pressure detecting means for detecting the internal pressure of the fuel tank,
The negative pressure applying means is an aspirator that introduces a part of the fuel discharged from the fuel pump to generate a negative pressure,
The concentration of the introduced gas is (fuel vapor pressure identified from the detection result of the negative pressure detecting means / absolute value of the fuel tank internal pressure) × 100.
An evaporative fuel processing apparatus characterized by being obtained by an expression represented by: It is an evaporative fuel processing apparatus of Claim 1, Comprising:
An evaporative fuel processing apparatus, wherein the introduction port is sequentially switched from a downstream side to an upstream side based on a gas flow direction reference in the permeation chamber based on an elapsed time since the evaporative fuel starts to be desorbed from the canister.

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