JPH0830452B2 - Fuel evaporation prevention device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel evaporation preventing device such as a canister attached to a fuel tank of an automobile, and more specifically, a two-stage absorption is performed by using a special absorbent. The present invention relates to a fuel evaporation prevention device.

[Prior art]

When fuel is supplied to the fuel tank of an automobile by a refueling gun, a relatively large amount of fuel evaporates. In addition, the fuel inside the fuel tank and the vaporizer float chamber is partially vaporized both when the vehicle is running and when the vehicle is stopped. Therefore, in order to prevent these evaporated fuels from leaking to the atmosphere, a canister filled with an absorbent is connected between these tanks and the space. This absorbent is for capturing evaporated fuel. Further, in order to capture the evaporated fuel from the fuel storage tank or the like as well as the leaked fuel liquid not only in the automobile, a fuel evaporation preventing device similarly filled with an absorbent is used.

Activated carbon has been conventionally used as the absorbent used in the fuel evaporation preventing devices such as canisters.

[Problems to be solved]

However, in a canister using the above activated carbon,
Often, the vaporized fuel cannot be captured and the vaporized fuel is released to the atmosphere.

When the cause of this was investigated, it became clear that when activated carbon comes into contact with liquid gasoline, the ability of activated carbon to capture gasoline vapor decreases significantly. Furthermore, it was found that the reason why activated carbon comes into contact with liquid gasoline is that the liquid gazoline condensed on the inner surface of the pipe connected to the canister and the space above the canister where the activated carbon does not exist contacts the activated carbon.

Another cause of the decrease in the vapor-capturing ability (working capacity) of activated carbon is the canister purging (desorption) process for small molecules with 4 or 5 carbon atoms among the vaporized fuel molecules adsorbed on activated carbon. In contrast to easy desorption inside, molecules larger than that are difficult to desorb, and the vapor trapping capacity decreases as the canister usage time increases.

It should be noted that the condensation of gasoline vapor as described above occurs in the surrounding pipe and the space above the canister when the ambient temperature is high and the vapor pressure of gasoline is extremely high in the fuel tank or the carburetor.

The present invention has been made as a result of extensive studies on measures for preventing activated carbon from coming into contact with liquid fuel. Various investigations have been made on the absorbent for trapping the vaporized fuel, and a fuel vaporization prevention device having an excellent vaporized fuel trapping ability. Is to provide.

[Means for solving problems]

The present invention relates to a fuel vaporization preventing device comprising an absorbent for capturing evaporative fuel and an absorbent container for accommodating the absorbent and introducing the evaporated fuel, wherein the absorbent container is dissolved in the fuel or It is composed of a first absorption chamber filled with an organic polymer having a swelling property and a second absorption chamber filled with activated carbon, and the vaporized fuel is introduced into the second absorption chamber after passing through the first absorption chamber. The fuel vaporization preventing device is characterized by doing so.

In the present invention, the absorbent means a substance that captures evaporated fuel (including leaked fuel liquid). As the absorbent, two kinds of organic polymer compounds having a property of being dissolved in a fuel or swollen by a fuel and activated carbon are used. The organic polymer of the absorbent is filled in the first absorption chamber and the activated carbon is filled in the second absorption chamber, and the evaporated fuel is introduced into the second absorption chamber after passing through the first absorption chamber. To do.

Specific examples of the organic polymer compound include polypropylene, polyisoprene, polybutadiene, polyisobutylene, polystyrene, polynorbornene, ethylene-propylenediene copolymer, styrene-butadiene copolymer, ethylene-propylene copolymer, One or more of isobutylene-isoprene copolymer and butadiene-acrylonitrile copolymer are used.

Thus, the above-mentioned polymer compound includes the present cross-linked polymer and the cross-linked polymer (polymer gel), and both can be used. The former uncrosslinked polymer is of a type that dissolves or swells in fuel, and is generally called a hydrophobic polymer. It is a homopolymer such as polyisoprene or a co-polymer such as styrene-butadiene copolymer. and so on.
The latter polymer gel is a cross-link of the above-mentioned hydrophobic polymer, and this cross-link makes the polymer gel insoluble in fuel but swellable. Here, the term "crosslinking" includes not only chemical crosslinking introduced using a crosslinking agent but also chemical self-crosslinking and physical crosslinking.

The shape of the above absorbent is not particularly limited to powder, particles, film, thread, honeycomb, plate, etc., but if a too large lump is used, only the surface swells and the absorption does not proceed to the inside, There is a risk of reduced ability. Therefore,
The absorbent preferably has a diameter or thickness of 5 mm or less.

In addition, the absorbent according to the present invention dissolves or swells the uncrosslinked polymer and swells the crosslinked polymer but is insoluble when absorbing the evaporated fuel as described above. Therefore, the former polymer may not be returned to the original aggregation state even if it is regenerated, and may be disposable. In the case of the latter crosslinked polymer, regeneration can be repeated.

Next, as the activated carbon, activated carbon such as steam activated / granular activated carbon, which has been used in the conventional fuel evaporation preventing device, is used.

Further, the first and second absorption chambers may be partitioned by a wall and connected to each other by a pipe. However, as shown in the embodiment, it is preferable that the first and second absorption chambers are partitioned by a perforated plate, a wire mesh or the like through which vaporized fuel can easily pass. The fuel evaporation prevention device of the present invention is not limited to the canister for automobiles, but can be used for various fuel evaporation prevention devices such as a fuel tank for a boiler.

[Action and effect]

In the present invention, as the absorbent, the first absorption chamber is filled with the organic polymer compound having the above properties, the second absorption chamber is filled with activated carbon, and the evaporated fuel is sequentially passed through the first absorption chamber to the second absorption chamber.
It is configured to be introduced into the absorption chamber. And, as will be apparent from the description below, this polymer has a high absorption capacity for evaporated fuel. This high absorption capacity is based on the tendency of the polymer to dissolve or swell in fuel such as gasoline. This is because the organic polymer and the evaporated fuel have a high affinity.

Therefore, in the present invention, since the evaporated fuel passes through the absorbent in the above order, the evaporated fuel is first absorbed by the organic polymer and the rest is absorbed by the activated carbon. The organic polymer has a large absorptivity for a large molecule having 6 or more carbon atoms, as shown in Examples described later. Therefore,
By contacting the evaporative fuel with the absorbent composed of organic polymer before contacting with the activated carbon, large molecules that reduce the ability of activated carbon to capture vapor are adsorbed on the organic polymer. Therefore, it is possible to prevent a decrease in the vapor capturing ability of the activated carbon.

Therefore, according to the present invention, the liquid evaporated fuel does not come into direct contact with the activated carbon, and the vapor capturing ability of the activated carbon is not deteriorated.

Further, since the vapor capturing ability of the activated carbon can be used 100%, it is not necessary to unnecessarily increase the amount of the activated carbon, and the fuel evaporation prevention device can be downsized.

In addition, the organic polymer compound swollen by absorbing the evaporated fuel is de-swelled in the normal process of purging the inside of the fuel evaporation prevention device, and the evaporated fuel absorbing capacity is restored,
It can be used continuously.

As described above, according to the present invention, it is possible to provide a fuel evaporation preventing device having an excellent evaporated fuel capturing ability. Therefore,
The on-board canister for automobiles does not require a large capacity as in the case of using only activated carbon,
It is possible to provide a small canister having a large absorption capacity.

〔Example〕

First Embodiment A fuel evaporation preventing device according to an embodiment of the present invention will be described with reference to FIG.

The device of this example relates to an automobile canister. As shown in FIG. 1, the canister 1 includes a main body 10 which is a container for containing an absorbent, an organic polymer 20 filled in an upper first absorption chamber 2 in the main body 10, and a lower second
It consists of activated carbon 30 filled in the absorption chamber 3.

The main body 10 has a cylindrical shape, and has a lid 11 provided on the upper end and a bottom plate 12 provided on the bottom. In addition, the lid 11 has a second introduction pipe 14 in which the tip portion 141 is inserted up to the vicinity of the center of the first absorption chamber 2 of the main body 10, a first introduction pipe 13 similarly inserted,
Also, the purging pipe 16 is fixed. The first introduction pipe
13 communicates with the space above the vaporizer float chamber 81, and the second introduction pipe 14 communicates with the fuel tank 82. Further, the purge pipe 16 communicates with a purge port 85. Further, a purge air pipe 15 is opened in the bottom plate 12. Each of the above pipes has valves 131, 142, 151, 161, respectively. Further, in the main body 10, a perforated plate 17 is provided below it, a perforated plate 18 is provided above it, and the first absorption chamber 2 is provided approximately in the middle thereof.
A porous plate 19 for partitioning the second absorption chamber 3 is provided. And
Particles of activated carbon 30 are filled between the porous plates 17 and 19, and particles of the organic polymer 20 according to the present invention are filled between the porous plates 19 and 18. The perforated plate 17 is pressed upward by the spring 101, and the perforated plate 18 is pressed downward by the spring 102. In the figure, reference numeral 8 denotes gasoline.

As described above, the canister 1 captures the evaporated fuel by the vaporizer float chamber 81 or the fuel tank.
The gasoline vapor evaporated in 82 enters the first absorption chamber 2 in the canister 1 through the first or second introduction pipes 13 and 14, comes into contact with the organic polymer 20 which is the absorbent, and is absorbed by this. It Further, the gasoline vapor not absorbed by the organic polymer 20 is introduced into the second absorption chamber 3 and absorbed by the activated carbon 30. At this time, the valves 131,1 of the above-mentioned introduction pipes 13,14
The valve 42 of the purge pipe 16 and the valve 151 of the purge air pipe 15 are closed.

The above absorption occurs when the organic polymer 20 is dissolved or swollen, and the activated carbon 30 is further absorbed.

Then, when these absorbents have absorbed a large amount of gasoline vapor, the lid 11 is removed and replaced with a new absorbent, or the absorbent is left as it is for regeneration. In this regeneration, opening and closing of the valves 131, 142, 151, 161 are reversed, and air is sent through the purge air pipe 15. Then, the exhaust gas is discharged from the upper purge pipe 16 to the purge port 85. At this time, the introduced air serves to release the gasoline absorbed by the organic polymer and the activated carbon and discharge it as described above.

As described above, according to the device of the present example, it is possible to prevent deterioration of the vaporized fuel vapor capturing ability of the activated carbon and capture the gasoline vapor as the vaporized fuel with high efficiency.

Second Example Gel beads of polybutadiene as an organic polymer and activated carbon were prepared, and liquid or vapor of gasoline was introduced into them, and the vapor capturing ability thereof was measured.

That is, first, the gel beads of the polybutadiene were produced as follows. 200 g of shredded polybutadiene
It was put in ml of toluene, melted at 60 ° C, cooled and then mixed with 6 g of benzoyl peroxide and mixed, and bubbling with nitrogen (N ₂ ) gas was carried out to expel oxygen in the liquid. Then 80
The reaction was carried out at ℃ for 4 hours, and after the gelation was completed, it was allowed to cool. Next, the solidified gel was crushed, the same volume of cyclohexane was added, and the mixture was crushed with a mixer to remove cyclohexane at 60 ° C, and dried at 45 ° C for 10 hours in a vacuum dryer.

10 g of the gel beads obtained above was immersed in liquid gasoline, and the absorption amount of gasoline was measured. The gasoline used was commercially available. Similarly, 10 g of activated carbon was also measured. As this activated carbon, Kuraray Chemical KGD (8-28 mesh) manufactured by Kuraray Chemical Co., Ltd. was used.

The measurement results are shown in FIG. 2 with the horizontal axis representing elapsed time and the vertical axis representing absorbent weight. Here, the absorbent weight is the total amount of the absorbent and the gasoline absorbed by the absorbent.

As is known from FIG. 2, the gel beads as an organic polymer have a fast absorption rate and absorb a large amount of gasoline liquid. On the other hand, activated carbon can absorb only about the same amount (10 g) of gasoline liquid.

Next, put commercially available gasoline at the bottom of the container that can be sealed, and do not directly touch the gel beads with the gasoline solution.
The amount of gasoline vapor absorbed per unit weight of gel beads when it was held in the container and brought into contact with saturated gasoline vapor was measured. The same measurement was performed for activated carbon. The results are shown in FIG. 3 with the horizontal axis representing time (day) and the vertical axis representing absorption. As can be seen from the figure, the gel beads absorb a larger amount of gasoline vapor than activated carbon.

Next, the gel beads and activated carbon that absorbed gasoline vapor for 4 days were set in a gas chromatography device, and when the sample was heated at 150 ° C. for 5 minutes, the components of the gas generated from the sample were analyzed. The results are shown in Table 1.

The gasoline vapor phase and liquid phase component% in the above table were obtained by collecting the gasoline liquid and gasoline vapor used in this test with a syringe and analyzing them by gas chromatography.

As is known from Table 1, the proportion of low boiling point components such as pentane (C ₅ ) and butane (C ₄ ) absorbed in gel beads was higher than that in the original gasoline liquid phase and the activated carbon absorption gas. ， Slightly smaller. Also, as can be seen from the table comparing the components in the gasoline vapor phase with the absorption components in the activated carbon or gel beads, it is found that the low boiling point component absorption capacity from the gasoline vapor phase in gel beads is slightly inferior to that of activated carbon. .

Third Embodiment The gel beads and the activated carbon shown in the second embodiment are filled in a model canister shown in FIG. 4, and butane gas, which is the main component of gasoline, is introduced into the model canister, and the vapor trapping ability of the canister, that is, the working capacity. Changes in city (WC) were measured.

That is, the model canister 5 is as shown in FIG.
This is the same as the fuel evaporation preventing device (FIG. 1) shown in the first embodiment, and the inside of the container 50 is filled with gel beads 25 and the lower part is filled with activated carbon 35, and a porous plate 54 is provided between the two. It is divided by. Further, a butane gas introduction nozzle 51 is provided above the container 50, and an unabsorbed gas discharge nozzle 52 is provided below the container 50. Reference numerals 53, 54 and 55 are perforated plates. Further, the introduction nozzle 51 is connected to the butane gas cylinder 61 by a pipe 63 by interposing a flow meter 62. Further, the discharge nozzle 52 is connected to a hydrocarbon (HC) analyzer 65 by a pipe 64. Further, a pipe 69 is connected to the HC analyzer 65 at the introduction nozzle 51 in order to send absorbed gasoline at the time of purging.
In addition, the nozzle 52 has a nitrogen gas cylinder 66 for purging.
To a pipe 68 via a flow meter 67.

Then, in the measurement, butane gas was introduced into the canister 5 at a rate of 1 / minute, and the nozzle was measured by the analyzer 65.
When the butane gas discharged from 52 is detected, the above introduction is stopped. Then, obtain the weight of the entire canister after absorbing butane.

Then, for purging (desorption), the canister 5 is passed through the nozzle 52 from the nitrogen gas cylinder 66 as shown by the dotted line.
Send nitrogen gas at a rate of 15 / min, check that the butane gas is no longer detected by the analyzer 65, and obtain the weight of the entire canister. In this way, butane gas introduction and desorption are repeated. As a result, as shown in Fig. 5, the absorption weight W ₁ ~
Find the change in W ₆ .

Next, the above working capacity WC was calculated by the following formula.

WC = _{[(W 3 -W 2) + (} W 3 -W 4) + (W 5 -W 4) + (W 5 -W 6) ] / 4 In other words, the WC is the weight after the purge after the absorption Obtained as the average value of the weight difference, the larger this value, the greater the capacity of the canister.

Therefore, using the above model canister and WC measurement method, for three types of canister Nos. 1 to 3 with different loadings of gel beads and activated carbon, three types of gases A to C shown in Table 2 were used. We introduced gasoline. Table 2 shows the results.

As can be seen from Table 2, the Nos. 2 and 3 canisters containing gel beads had an increase in RC even if gasoline liquid was injected. On the other hand, the No. 1 canister containing only activated carbon showed a decrease in WC when injected with 3 ml of gasoline (condition B), and when 6 ml was injected, the gasoline leaked out of the canister and had an extremely high ability to absorb gasoline. It turns out to be low.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a fuel evaporation prevention device in the first embodiment, FIGS. 2 and 3 are evaporative fuel absorption characteristic diagrams in the second embodiment, and FIGS. 4 and 5 show a third embodiment. , 4th
FIG. 5 is a conceptual diagram of the model canister at the time of measurement, and FIG. 5 is an explanatory diagram of the working capacity measurement. 1 ... Canister, 13 ... First introduction pipe, 14 ... Second introduction pipe, 17,18,19 ... Perforated plate, 2 ... First absorption chamber, 20 ... Organic polymer, 3 ... Third 2 absorption chambers, 30 ... activated carbon, 8 ... gasoline,

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Miji Hirose, Aichi Prefecture, Nagakute Town, Aichi Prefecture, Nagachote 1 41 of Yokomichi Yokoido Central Research Institute Co., Ltd. (72) Inventor, Toga Shiga, Aichi County, Nagachite Town, Aichi Prefecture 1 in 41, Yokochi Central Road, Toyota Central Research Institute Co., Ltd. (72) Inventor, Minka Ohashi Nishikasugai-gun Kasuga-mura, Aichi Ochiai, Nagahata No. 1 Toyoda Gosei Co., Ltd. (72) Inventor Masami Mizuno Nishi-Kasugai-gun, Aichi Kasugamura Ochiai, Nagahata No. 1 in Toyoda Gosei Co., Ltd. (72) Inventor Tomohide Aoki Kasuga, Aichi Prefecture Kasugamura, Ochiai, Nagahata No. 1 in Toyoda Gosei Co., Ltd. (56) References Japanese Patent Publication 6-26646 (JP) , B2)

Claims (2)

[Claims] 1. A fuel evaporation preventing device comprising an absorbent for capturing evaporated fuel and an absorbent container for accommodating the absorbent and introducing the evaporated fuel, wherein the absorbent container is dissolved in the fuel. Alternatively, it comprises a first absorption chamber filled with an organic polymer having a swelling property and a second absorption chamber filled with activated carbon, and the vaporized fuel is introduced into the second absorption chamber after passing through the first absorption chamber. A fuel evaporation preventing device characterized by the above. 2. The fuel evaporation preventing device according to claim 1, wherein the organic polymer is polypropylene, polyisoprene, polybutadiene, polyisobutylene, polystyrene, polynorbornene, ethylene-proprenediene copolymer, styrene-butadiene. 1. A fuel evaporation preventive device comprising one or more of a copolymer, an ethylene-propylene copolymer, an isobutylene-isoprene copolymer, and a butadiene-acrylonitrile copolymer.