JP2019031980A - Canister - Google Patents

Abstract

To improve DBL performance of a canister to be used for an evaporation fuel treatment device.SOLUTION: A canister consists of: a main canister to be a non-heating area; and a buffer canister 3 to be a heating area equipped with an electrothermal heater 48. A purge port and a charge port are provided in the main canister, and a drain port 25 is provided in the buffer canister 3. First activated carbon 46 whose BWC is 6 g/dL-10 g/dL is filled with a first area 44 on a side of the drain port 25 of the buffer canister 3, and second activated carbon 47 whose BWC is 13 g/dL or more is filled with a second area 45 on a side of the main canister. Since purge is promoted by heating, and the first activated carbon 46 is excellent in adsorption characteristics of thin paper, DB performance improves.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a canister used for an evaporative fuel processing apparatus of an automobile, and more particularly, to a canister that improves DBL (Diurnal Breathing Loss) performance.

  As is well known, an automobile using an internal combustion engine is provided with an evaporative fuel treatment device mainly composed of a canister in order to suppress the evaporative fuel in the fuel tank from being released into the atmosphere.

  The canister is a casing filled with an adsorbent such as activated carbon. The canister adsorbs the evaporated fuel generated from the fuel tank when the vehicle is stopped, etc. to the adsorbent, while the internal combustion engine is operated by the air introduced from the drain port. The fuel component is desorbed (purged) from the adsorbent and sucked into the intake system of the internal combustion engine.

  Patent Documents 1 and 2 disclose a configuration in which a heater for heating the adsorbent is provided in a canister using such an adsorbent in order to promote desorption of the adsorbed fuel component. In particular, in Patent Document 1, in order to reduce the amount of fuel component adsorbed on the adsorbent near the drain port, the temperature near the drain port is higher than the temperature near the purge port when heated by a heater. Thus, a gradient is given to the amount of heat generated by the heater. Patent Document 2 discloses heating activated carbon to 40 ° C to 100 ° C.

JP 2013-249797 A Japanese Utility Model Publication No. 61-118956

  Emission regulations related to automobile internal combustion engines tend to be stricter year by year, and higher DBL performance is required for canisters in evaporative fuel processing apparatuses. The DBL test is intended to measure the amount of fuel component discharged from the canister in association with a change in the outside air temperature during a long day such as one day and night.

  On the other hand, in a hybrid vehicle in which the internal combustion engine is temporarily operated, both the opportunity to purge the canister and the amount of gas that can be used for purging (the amount of air introduced from the drain port) tend to decrease. The requirements are becoming increasingly demanding.

  In response to such various requirements, canisters having conventional heaters such as Patent Documents 1 and 2 cannot always obtain sufficient performance, and there is still room for improvement. For example, as disclosed in Patent Document 1, when the temperature of the drain port side is high as in Patent Document 1, the adsorption capacity near the drain port is decreased due to excessively high temperature of the activated carbon as disclosed in Patent Document 2. For example, in the DBL test, relatively lean fuel vapor is likely to be discharged from the drain port. Patent Document 2 discloses that it is desirable to heat to less than 100 ° C. However, it is impossible to heat activated carbon having a predetermined capacity to a uniform temperature with a heater, for example, adjacent to the heater. Since the portion to be heated locally becomes high temperature, it is inevitable that the adsorption capacity is partially lowered.

The canister according to the present invention is
A main canister having a relatively large capacity, comprising a charge port and a purge port at one end in the flow direction of the internal volume filled with activated carbon, and a connection port at the other end in the flow direction;
A buffer canister having a relatively small capacity, having an independent cylindrical housing, having a connection port connected to the connection port of the main canister at one end, and a drain port at the other end.
With
An internal volume of the buffer canister is divided into a first region on the drain port side and a second region on the connection port side;
The first region is filled with first activated carbon having a butane working capacity of 6 g / dL or more and less than 10 g / dL,
The second region is filled with a second activated carbon having a butane working capacity of 13 g / dL or more,
An electric heater is disposed in the housing of the buffer canister over both the first region and the second region. The electric heater includes the first activated carbon and the second activated carbon. Embedded in activated carbon,
It is characterized by that.

  In the above configuration, since the buffer canister having a relatively small capacity provided with the electric heater is disposed on the downstream side of the main canister, that is, on the drain port side, the activated carbon (the first The fuel components adsorbed on the activated carbon and the second activated carbon) are actively desorbed. For example, in the DBL test, the fuel component remaining in the main canister diffuses and moves toward the drain port while the vehicle is left, but most of the fuel component is adsorbed by the buffer canister. By locally heating the buffer canister on the drain port side in this way, leakage of fuel components from the drain port while the vehicle is left standing, that is, small breakthrough, with a relatively small amount of heat (in other words, low power). It can be effectively suppressed. In particular, since the buffer canister is provided with an independent housing, the inside thereof can be effectively heated with an electric heater over both the first region and the second region.

  Since the fuel component (mainly butane) that diffuses and moves while the vehicle is left is gradually adsorbed toward the drain port inside the main canister and the buffer canister, the concentration of the fuel vapor gradually increases toward the drain port. To become sparse. In particular, since the second activated carbon in the second region, which is relatively upstream with respect to diffusion movement in the buffer canister, has a high butane working capacity (BWC), sufficient adsorption before reaching the first region Is done. Further, when comparing the first activated carbon having a BWC filled in the first region of 6 g / dL to 10 g / dL and the second activated carbon having a BWC filled in the second region of 13 g / dL or more, The activated carbon of No. 1 has better adsorption characteristics with respect to diluted vapor. Therefore, in the first region near the drain port, the lean fuel vapor can be adsorbed more effectively, and minute breakthrough due to the lean vapor can be suppressed.

  In addition, since the first activated carbon has lower moisture adsorption than the second activated carbon, even when the hydrocarbon components that have been excessively heated by the electric heater and stabilized on the activated carbon are desorbed, No decrease in adsorption performance for fuel vapor. In other words, even if there is an excessive local high temperature inevitably generated when heating the activated carbon with an electric heater, stable adsorption characteristics to the diluted vapor can be obtained, and the diluted vapor near the drain port when the vehicle is left standing. Can be reliably adsorbed.

  In the present invention, the activated carbon in the buffer canister is preferably heated to a temperature of less than 100 ° C. by the electric heater. Furthermore, it is preferable to heat to a temperature of 50 ° C to 90 ° C.

  By heating to such a temperature, desorption of adsorbed fuel components can be promoted, while moisture adsorption to activated carbon due to excessive heating can be prevented, and the adsorption capacity of fuel components accompanying moisture adsorption decreases. Can be avoided.

  In a preferred aspect of the present invention, the volume of the first region is smaller than the volume of the second region.

  Preferably, the first region and the second region are partitioned by a screen member, and the electric heater penetrates the screen member.

Also preferably, the butane working capacity of the activated carbon filled in the internal volume of the main canister is higher than the butane working capacity of the first activated carbon and lower than the butane working capacity of the second activated carbon. ,
The BWC of the activated carbon in the present invention is a value based on ASTM D5228.

  According to the present invention, a buffer canister having an electric heater is connected to an independent housing on the drain port side of the main canister, and activated carbon having a BWC of 6 g / dL to 10 g / dL on the drain port side of the buffer canister. And a high DBL performance can be obtained by arranging activated carbon of 13 g / dL or more on the main canister side.

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing which shows the whole structure of one Example of the canister which concerns on this invention. Sectional drawing of one Example of a buffer canister. The characteristic view which showed the relationship between the canister adsorption amount and breakthrough amount in a DBL test regarding the presence or absence of 60 degreeC heating. The characteristic view which showed the relationship between the canister adsorption amount and breakthrough amount in a DBL test regarding the combination of activated carbon. The characteristic view which showed the relationship between the adsorption amount at the time of breakthrough, and heating temperature.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a canister 1 according to the present invention together with a schematic configuration of a fuel vapor processing apparatus. A canister 1 for temporarily storing a fuel component is composed of a main canister 2 having a relatively large capacity serving as a non-heating region and a buffer canister 3 having a relatively small capacity serving as a heating region. It is connected via a tube 4 having flexibility.

  The main canister 2 has a housing 5 made of synthetic resin. The housing 5 has an elongated rectangular tube-shaped first tubular portion 8 provided with a purge port 6 and a charge port 7 adjacent to each other at an end portion, and an elongated rectangular tube shape provided with a connecting port 9 at an end portion. The two cylindrical portions 10 are arranged adjacent to each other with a slight gap and are integrally connected to each other. The other end portions of the first cylindrical portion 8 and the second cylindrical portion 10 communicate with each other via a connection path 11, whereby an internal volume, that is, a flow path that is continuous in a U shape inside the housing 5. It is configured.

  The inside of the 1st cylindrical part 8 and the inside of the 2nd cylindrical part 10 are filled with the granular activated carbon 12 as an adsorbent which can adsorb | suck and desorb | suck a fuel component (for example, gasoline vapor). Specifically, screen members 14 and 15 having air permeability for partitioning between the purge port 6 and the charge port 7 are provided at one end portion of the first cylindrical portion 8, and a connection path is provided at the other end portion. A screen member 16 having air permeability for partitioning between the screen members 11 and 11 is provided, and activated carbon 12 is filled in a volume between the screen members 14 and 15 and the screen member 16. Similarly, in the second cylindrical portion 10, screen members 17 and 18 having air permeability are respectively provided at both ends, and activated carbon 12 is filled in a volume between the screen members 17 and 18. . The screen members 16 and 18 on the connection path 11 side of the first tubular portion 8 and the second tubular portion 10 are respectively supported by perforated plates (not shown), and springs 19 and 18 disposed in a compressed state are provided. By being energized with 20, the activated carbon 12 is appropriately compressed.

  In the present invention, the adsorbent used for the main canister 2 is not particularly limited, and any type of adsorbent may be used. As an example, a general BWC of 11.0 g / dL is used. A typical activated carbon 12 is used. In addition, you may make it use the activated carbon of a different characteristic in the 1st cylindrical part 8 and the 2nd cylindrical part 10. FIG. The volume of the space in which the activated carbon 12 of the main canister 2 is accommodated is 2300 cc, for example.

  On the other hand, the buffer canister 3 has an independent housing 21 made of synthetic resin. The housing 21 has a substantially cylindrical shape in which a large-diameter portion 22 having a relatively large diameter and a small-diameter portion 23 having a relatively small diameter are connected in series, and a connecting port is provided on an end side surface on the large-diameter portion 22 side. 24 is provided, and a drain port 25 is provided on an end side surface on the small diameter portion 23 side. The connection port 24 of the buffer canister 3 is connected to the connection port 9 of the main canister 2 via the tube 4 described above.

  Therefore, the canister 1 as a whole has a first cylindrical portion 8 and a second cylindrical portion 8 so as to form a series of flow paths from the purge port 6 at one end of the flow path and the drain port 25 at the other end of the flow path. The three internal volumes of the cylindrical portion 10 and the buffer canister 3 are configured to be substantially continuous in series.

  The charge port 7 is connected to an upper space of a fuel tank 32 of the vehicle via a charge passage 31, and the purge port 6 is connected to an intake passage 35 (specifically, downstream of the throttle valve 36) of the internal combustion engine 34 via a purge passage 33. Side). A purge control valve 37 is interposed in the purge passage 33, and the opening degree of the purge control valve 37 is controlled by the engine control unit 38. The drain port 25 is opened to the atmosphere, but an electromagnetic valve 39 is added to the end of the buffer canister 3 so as to block the opening of the drain port 25 to the atmosphere as necessary. .

  FIG. 2 shows an internal configuration of the buffer canister 3 serving as a heating region. The internal volume of the buffer canister 3 includes an air-permeable screen member 41 provided at the end on the small diameter portion 23 side, a similar screen member 42 provided on the end on the large diameter portion 22 side, and an intermediate portion. Are divided into two regions 44 and 45 by a similar screen member 43 provided in Of the two regions 44 and 45, the first region 44 on the drain port 25 side is filled with the first activated carbon 46 having a granular shape, and the second region 45 on the connection port 24 side is filled with the first region 44. The second activated carbon 47, which is also granular, is filled. In addition, an electric heater 48 serving as a heating means is disposed over both the first region 44 and the second region 45. The electric heater 48 passes through the intermediate screen member 43 and is embedded in the filled activated carbons 46 and 47.

  Here, as the first activated carbon 46 filled in the first region 44 on the drain port 25 side, activated carbon having a BWC of 6 g / dL or more and less than 10 g / dL is used. For example, activated carbon having a BWC of 8.0 g / dL is used. This activated carbon is, for example, activated carbon whose pore distribution is controlled so that the proportion of pores having relatively large pore diameters (macroporous) is increased. Further, as the second activated carbon 47 filled in the connection port 24 side, that is, in the second region 45 near the main canister 2, activated carbon having a BWC of 13 g / dL or more is used. For example, activated carbon having a BWC of 15.3 g / dL is used. This activated carbon is, for example, a general activated carbon in which the macroporous ratio is not particularly controlled. As an example, the volume of the first region 44 is 40 cc, and the volume of the second region 45 is 160 cc.

  In the canister 1 configured as described above, the first cylindrical portion 8, the second cylindrical portion 10, and the buffer canister 3 are substantially continuous as one flow path, The purge port 6 and the charge port 7 are located at one end in the flow direction of the flow path, and the drain port 25 is located at the other end. As is obvious to those skilled in the art, fuel vapor generated in the fuel tank 32 while the vehicle is stopped or refueled is introduced into the canister 1 from the charge port 7, and from the first cylindrical portion 8 to the buffer canister 3. During the flow to the first region 44, the activated carbon 12, 46, 47 of each part is adsorbed. The fuel component adsorbed in this way is desorbed from the activated carbon 12, 46, 47 by the atmospheric air being taken in through the drain port 25 due to the negative pressure generated in the intake system during operation of the internal combustion engine, and becomes the purge gas to become the purge port 6 flows into the intake passage 35 of the internal combustion engine 34 and is finally burned in the internal combustion engine 34.

  In this way, the canister 1 repeatedly adsorbs and desorbs the evaporated fuel. In the canister 1, in order to promote the desorption of the fuel component during the operation of the internal combustion engine 34, a buffer canister is used by the electric heater 48. The internal volume of 3 is heated. This heating is preferably performed so that the first activated carbon 46 and the second activated carbon 47 have an average temperature of 50 ° C. to 90 ° C. When the activated carbon is heated to 100 ° C. or higher, the hydrocarbon components that have been stabilized on the pore surface of the activated carbon are desorbed, and moisture is adsorbed instead of this, resulting in adsorption characteristics for fuel components. It will decline. By heating within the range of 50 ° C. to 90 ° C., desorption can be promoted while avoiding such a phenomenon. It should be noted that energization of the electric heater 48 is preferably started immediately after the vehicle ignition key is turned on, but the electric heater is operated when the operation of the internal combustion engine 34 (in other words, purge of the adsorbed fuel component) is performed for a certain period of time. 48 may be stopped, or heating may be continued during operation of the vehicle.

  In the DBL test, after a certain amount of purging was performed by running of the vehicle, the vehicle was stopped for a long time, for example, 1 day to 3 days, and the air flowed out of the drain port 25 as the outside air temperature changed during that time. Although the amount of the fuel component (so-called micro breakthrough) is evaluated, in the canister 1 described above, only the buffer canister 3 having a relatively small capacity added to the rear stage (that is, the drain port 25 side) of the main canister 2 is electrically heated. Since it is heated by the heater 48, the DBL performance is effectively improved with a small amount of electric power. In particular, in the above embodiment, since the heating region is surrounded by the independent housing 21 as the buffer canister 3, only the activated carbons 46 and 47 inside thereof can be efficiently heated.

  FIG. 3 is a graph showing the difference in DBL performance with and without heating. After the fuel vapor was adsorbed to the canister 1 to the breakthrough state according to a general DBL test, 50 times the total activated carbon capacity of the canister 1 was obtained. An amount (so-called 50 bed volume) of air is passed through the drain port 25 for purging, and then the minute breakthrough amount flowing out of the drain port 25 is measured by the 3 days and nights DBL test. It shows the relationship with the adsorption amount when the purge end time is 0. Note that the amount of adsorption of the canister 1 gradually increases from day to day due to repeated temperature changes during three days and nights. Line L1 is the target breakthrough amount. In FIG. 3, the solid line indicates the characteristics when heating to 60 ° C. is performed by the electric heater 48 during the purge in the configuration of the above-described embodiment, and the broken line indicates the characteristics when heating is not performed as a comparative example. ing.

  As indicated by the broken line, when heating is not performed, the minute breakthrough amount is large even in the state immediately after the purge, and the target value L1 cannot be satisfied. This indicates that when heating is not performed, a small amount of air such as 50 bed volumes cannot be sufficiently purged. On the other hand, in the embodiment shown by the solid line, the heating using the electric heater 48 promotes the detachment in the second region 45 and the first region 44 in the buffer canister 3 near the drain port 25. Even a purge with a small amount of air such as a 50 bed volume suppresses micro breakthrough in the DBL test. Although not shown, even if the entire canister 1 including the main canister 2 is heated, the reduction of the breakthrough amount is not so great as compared with the increase in power consumption. That is, as the DBL performance, the fuel component remaining in the main canister 2 gradually diffuses and moves to the drain port 25 side, and when it finally reaches the drain port 25, a minute breakthrough occurs. The fuel component to be absorbed is gradually adsorbed by the activated carbon 47 and 46 inside the main canister 2 and further inside the buffer canister 3, so that a high effect can be obtained by heating the small-capacity buffer canister 3. In particular, since the second activated carbon 47 in the second region 45 relatively upstream with respect to the diffusion movement in the buffer canister 3 has a high BWC, sufficient adsorption is performed before reaching the first region 44. The

  Further, as described above, the fuel vapor in the region close to the drain port 25 is very lean as a result of the gradual adsorption inside the main canister 2 and the buffer canister 3. Compared to the second activated carbon 47 in the second region 45, the first activated carbon 46 filled in the first region 44 on the drain port 25 side with respect to such a diluted vapor has an adsorption characteristic of the diluted vapor. Is excellent. Accordingly, by arranging the first activated carbon 46 having a relatively small volume downstream of the second region 45 with respect to the flow toward the drain port 25, the lean vapor that has passed through the second region 45 can be effectively used. Can be adsorbed on.

  Furthermore, in the heating using the electric heater 48, even if it is intended to heat in the range of 50 ° C. to 90 ° C. as described above, it is locally heated to 100 ° C. or more at a location adjacent to the electric heater 48. Activated carbon is inevitably generated. When heated excessively in this way, the first activated carbon 46 has lower moisture adsorption than the second activated carbon 47. Therefore, even when the hydrocarbon component that has been excessively heated and stabilized on the activated carbon is desorbed, the adsorption performance for the fuel vapor does not deteriorate. That is, even if the first activated carbon 46 inevitably causes local excessively high temperature, the adsorption characteristic to the diluted vapor can be stably obtained, and the diluted vapor in the vicinity of the drain port 25 while the vehicle is left is left. Reliable adsorption is possible.

  Therefore, high DBL performance can be obtained by combining the first activated carbon 46 and the second activated carbon 47 as in the above embodiment.

  FIG. 4 is a characteristic diagram showing the relationship between the minute breakthrough amount flowing out from the drain port 25 and the adsorption amount after purging in the three day and night DBL test, as in FIG. 3 described above, and the solid line indicates the embodiment described above. That is, the characteristic when the first activated carbon 46 and the second activated carbon 47 are combined is shown. On the other hand, the broken line shows the characteristic when the second activated carbon 47 is filled in both the second region 45 and the first region 44 of the buffer canister 3 as a comparative example. All the characteristics are obtained when heating to 60 ° C. by the electric heater 48, and purging at the time of the DBL test is performed by air of 50 bed volumes as in FIG. As shown in FIG. 4, by combining the first activated carbon 46 and the second activated carbon 47, high DBL performance can be obtained.

  Next, FIG. 5 shows the amount of adsorption after purging (corresponding to the horizontal axis in FIGS. 3 and 4) and electric heating when the minute breakthrough amount exceeds the target value (corresponding to L1 in FIGS. 3 and 4) in the DBL test. The correlation with the heating temperature by the heater 48 is shown. This also shows the characteristics when purging with 50 bed volumes of air. As shown in FIG. 5, when the activated carbons 46 and 47 in the buffer canister 3 are heated to around 60 ° C., the most adsorption amount can be obtained. That is, it means that the purge is most effectively performed and the micro breakthrough in the DBL test can be suppressed. A line L2 in the figure indicates a target value of the adsorption amount after purging, and the target value L2 may be heated to a temperature of 50 ° C. to 90 ° C. In the low temperature region indicated by the broken line, the minute breakthrough amount exceeds the target value L1 immediately after the purge, as described with reference to FIG. Therefore, in the present invention, it is desirable to heat to a temperature of 50 ° C. to 90 ° C. by the electric heater 48, and most preferable to heat to 60 ° C.

  As mentioned above, although one Example of this invention was described in detail, this invention is not limited to the said Example, A various change is possible.

DESCRIPTION OF SYMBOLS 1 ... Canister 2 ... Main canister 3 ... Buffer canister 5 ... Housing 6 ... Purge port 7 ... Charge port 21 ... Housing 25 ... Drain port 44 ... 1st area | region 45 ... 2nd area | region 46 ... 1st activated carbon 47 ... 1st 2 activated carbon 48 ... electric heater

Claims (4)

A main canister having a relatively large capacity, comprising a charge port and a purge port at one end in the flow direction of the internal volume filled with activated carbon, and a connection port at the other end in the flow direction;
A buffer canister having a relatively small capacity, having an independent cylindrical housing, having a connection port connected to the connection port of the main canister at one end, and a drain port at the other end.
With
An internal volume of the buffer canister is divided into a first region on the drain port side and a second region on the connection port side;
The first region is filled with first activated carbon having a butane working capacity of 6 g / dL or more and less than 10 g / dL,
The second region is filled with a second activated carbon having a butane working capacity of 13 g / dL or more,
An electric heater is disposed in the housing of the buffer canister over both the first region and the second region. The electric heater includes the first activated carbon and the second activated carbon. Embedded in activated carbon,
Canister characterized by that.   The canister according to claim 1, wherein the volume of the first region is smaller than the volume of the second region.   The canister according to claim 1 or 2, wherein the first region and the second region are partitioned by a screen member, and the electric heater penetrates the screen member.   The butane working capacity of the activated carbon filled in the internal volume of the main canister is higher than the butane working capacity of the first activated carbon and lower than the butane working capacity of the second activated carbon. The canister according to any one of claims 1 to 3.

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