JPS6318024B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel evaporation prevention device used in automobiles, motorcycles, etc., and specifically relates to an adsorbent used therein.

For example, granular activated carbon has conventionally been generally used as an adsorbent for fuel evaporation prevention devices for automobiles. However, in the case of granular activated carbon, each particle is a particle, and when the particles are filled into a container, they come into partial contact with each other. However, since the automobile fuel evaporation prevention device is directly attached to the vehicle body, vibrations of the vehicle body during vehicle operation are directly transmitted to the container. As a result, the granular activated carbon in the container rubs against each other and becomes powder, which can lead to a number of problems such as functional deterioration.

For the above reasons, the present inventor considered using activated carbon having a monolithic structure, which is an integrally molded product, as an adsorbent.

As shown in FIG. 1, the monolith-structured activated carbon has a structure in which each ventilation passage communicates from the upper end surface to the lower end surface while being spaced apart from each other via a partition wall. For this reason, when this is used as an adsorbent, the "blow-through" phenomenon tends to occur because each ventilation passage is short, and even though the monolithic activated carbon itself has sufficient adsorption capacity, it is difficult to absorb water from vehicle fuel tanks, etc. There is a high risk that the generated fuel vapor will not be fully recovered and will be released into the atmosphere.

In the present invention, a plurality of monolithic activated carbons are stacked as adsorbents, and this stack is structured so that turbulence occurs in the fuel vapor flowing inside the stack, thereby promoting adsorption and desorption of fuel vapor, thereby reducing weight. The purpose is to provide a high-performance fuel evaporation prevention device.

Examples of the present invention are shown below. In Figures 2 and 3, 1 is a fuel vapor introduction pipe leading to the fuel tank, 2 is a mixture outlet pipe leading upstream of the throttle valve of the intake pipe of the internal combustion engine, 3a, 4a, 5a are check valves, 3b, 4b , 5b is a check valve spring; 6a, 6b are breathable filters made of a material having fuel deterioration resistance such as nonwoven fabric; 7a, 7;
b and 7c are air permeable filters, which are similar to the filters 6a and 7c.
Made of the same material as 6b. 8 is a container, 9a, 9b,
9c and 9d are activated carbon having a monolithic structure in which a large number of passages are separated by partition walls, 10 is a lid, 11 is an air opening, and 12 is a space.

The activated carbons 9a to 9d have the same shape, the same size, and the same number of passages, and are stacked so that these passages communicate with each other. ) are made to be different from each other. The filters 6a and 6b are attached to both end faces of the laminate A constructed as described above, and the laminated body A is placed in a resin container 8. In addition, fuel vapor introduction pipe 1, base 1
A lid 10 made of resin and having parts 3, 14, etc. is welded to the container 8. The filters 6a and 6b function to prevent foreign matter mixed in the desorbing air from entering the stack A and, furthermore, the engine combustion chamber. Also, lid 1
The spacer 10a combined with the spacer 12
It also serves to firmly fix the laminate A together with the container 8. Filters 7a to 7c
serves to temporarily disturb the flow passing through the activated carbons 9a to 9d, and also serves as the filters 6a, b described above. Furthermore, differentiating the arrangement direction of the passages of the activated carbons 9a to 9d serves to further disrupt the flow within the stacked body A.

The method for manufacturing the activated carbons 9a to 9d is as follows.

Add 100 g of methyl cellulose to 1 kg of 200 mesh coal-based activated carbon powder, mix well, and use this as the first raw material. Water-soluble varnish containing 40% water-soluble imide resin (the remaining 60% is water) and 950 c.c. of water.
Add and mix. This is used as the first solution. The first solution is gradually added to the first raw material in a kneader, and the mixture is thoroughly mixed.Then, the kneaded material is put into an extruder equipped with a mold for forming a monolith structure, and the material is Monolith-shaped activated carbon is molded by extruding it from a monolith mold. Next, the obtained monolithic activated carbon is dried at 60°C for 8 hours, further heated to 120°C at a rate of 12°C/Hr, and kept at 120°C for 5 hours to be thoroughly dried. Finally, this monolithic activated carbon was heated at 270° C. for 2 hours in a nitrogen atmosphere to obtain activated carbon with a monolithic structure that was sufficiently thermoset.

In the above configuration, the fuel vapor generated in the fuel tank passes through the fuel vapor introduction pipe 1, and passes through the check valve 4a.
It flows into the space 12 through the. Here filter 6
Because of the presence of carbon a, it spreads uniformly in the space 12, and eventually flows into the activated carbons 9a to 9d through the filter 6a, where it is adsorbed and held.

On the other hand, when the engine is operated under certain conditions, i.e., conditions in which the desorbed fuel vapor can enter the engine suction section together with the desorbing air as a mixture, the desorbing air becomes the desorbing air. It is led from the intake port 11 by the negative pressure of the engine and flows into the activated carbons 9a to 9d through the filter 6b. At this time, the adsorbed and retained fuel vapor is desorbed and activated carbon 9a to 9
After the adsorption capacity of d is regenerated, the air-fuel mixture passes through the filter 6a, passes through the check valve 5a, is guided from the air-fuel mixture outlet pipe 2 into the combustion chamber via the engine suction section, and is combusted.

By the way, the spread of fuel vapor in the activated carbons 9a to 9d can be thought of as "diffusion" or "flow".
What controls this way of spreading is "flow." Therefore, when the monolithic activated carbon is used alone, the "flow" tends to shift to the laminar region due to the structure of the activated carbon. Furthermore, since the flow velocity of the fuel vapor and desorption air is slow, the "flow" is further promoted to the laminar region. In addition, even according to the calculation, the Re number is in the laminar region of several tens to hundreds of levels. Although this value varies depending on the diameter of the activated carbon passage, it was found that the Re number was approximately within this range.

For the reasons mentioned above, as shown in Figure 4, when the flow is viewed microscopically in activated carbon with a monolithic structure, the direction of the "flow" is mainly in the y direction along the wall, and adsorption and desorption effects occur. It was found that there was not much flow in the X direction toward the wall α, which is effective for the flow, and that the "blow-through" phenomenon as described above appeared prominently.

The present invention aims to improve the adsorption and desorption effects by temporarily disrupting the above-mentioned "flow" so that it does not flow through the monolithic activated carbon in a laminar region. To explain this with reference to FIG. 5, which shows an enlarged cross section of a part of the stacked body A in FIG. 2, taking fuel vapor as an example, the fuel vapor that has passed through the filter 6a flows into the passage of the activated carbon 9a. Then, it gradually shifts to "laminar flow", but there is a filter 7a,
Moreover, since the passages of the activated carbons 9a and 9b are not aligned, the "flow" is disturbed in this region, and the flow in the X direction, which is effective for adsorption, increases, resulting in an improved adsorption effect. As the above steps are repeated, fuel vapor is adsorbed and retained. The same applies when the desorption air flows, and the adsorbed and retained fuel vapor is desorbed.

As described above, the present invention prevents the above-described "blow-through" phenomenon of monolithic activated carbon, and also makes it possible to effectively utilize monolithic activated carbon as an adsorbent.
A lightweight, high-performance fuel evaporation prevention device can be provided.

As a result of the experiment, FIG. 8 shows a comparison of the adsorption rates between the monolithic activated carbon and the present invention using the same amount of monolithic activated carbon.

Figure 6 shows a plurality of activated carbons 9a, 9b, etc. whose passages have the same shape, size, and number, are stacked so that the passages are arranged in the same direction, and ventilation is provided between the stacked layers. gender filters 7a, 7
Fig. 3 shows another embodiment of the present invention in which b... is interposed. According to this embodiment, the filters 7a,
7b causes turbulence in the flow of activated carbon in the passage.

FIG. 7 shows another embodiment of the present invention in which the sizes of the passages of a plurality of activated carbons 9a, 9b, . . . are mutually different, and the directions in which the passages are arranged are mutually different. According to this embodiment, the flow of activated carbon within the passages is disturbed due to the difference in the size of the passages and the difference in the arrangement direction of the passages.

The present invention is not limited to the above embodiments, but can be modified in various ways as described below.

(1) In Fig. 5, the passages of the plurality of activated carbons 9a and 9b are slightly staggered, but with such a configuration, even without the filters 6a and 7a, there is no disturbance in the flow of fuel vapor and desorbed air. can be caused.

(2) The activated carbons are stacked so that the passage sizes of the plurality of activated carbons are different from each other, and the sizes of the passages are alternately large, small, large, and small in the stacking direction of the activated carbon. , and even if the centers of the respective passages are concentric, turbulence can be caused in the flow.

(3) In addition to the fuel tank, sources of fuel evaporation include the float chamber of the carburetor.

(4) Of course, the individual height dimensions of the plurality of activated carbons may be different from each other.

As detailed above, in the present invention, a plurality of monolithic activated carbons are stacked, and this stacked body is configured to cause turbulence in the flow in the passages. (1) A plurality of monolithic activated carbon passages. This prevents the flow from becoming laminar and improves the adsorption and desorption effects of fuel vapor.

(2) The "blow-through" phenomenon can be prevented, and activated carbon with a monolithic structure can be used effectively as an adsorbent.

(3) Since it has an integrated monolith structure, it will not turn into powder even if vibrations occur.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional perspective view showing a monolith-structured activated carbon used to explain the present invention, FIG. 2 is a partially sectional view showing an embodiment of the present invention, and FIG. 3 is a laminate shown in FIG. 2. A partially sectional perspective view, FIGS. 4 and 5 are cross-sectional views showing the flow state of fuel vapor in a channel of activated carbon having a monolith structure, and FIGS. FIG. 8, a partially cross-sectional perspective view showing a laminate in another embodiment, is a characteristic diagram for explaining the effects of the present invention. 6a, 7a, 7b, 7c, 7d...filter,
9a, 9b, 9c, 9d... activated carbon.

Claims (1)

[Claims] 1. A fuel evaporation prevention device that adsorbs fuel vapor from a fuel vapor source and guides the adsorbed fuel to an internal combustion engine, which has a monolithic structure in which a number of passages are separated by partition walls. The activated carbon is provided with a plurality of activated carbons, the plurality of activated carbons are stacked in series so that their passages communicate with each other, and the stack is configured such that turbulence occurs in the fuel vapor passing through the passages inside the stack. A fuel evaporation prevention device characterized by: 2. Claims characterized in that in the laminate, a ventilation filter is interposed between the plurality of layers of activated carbon, so that turbulence occurs in the flow of fuel vapor passing through the laminate. 1. The fuel evaporation prevention device according to 1. 3. The fuel according to claim 1 or 2, characterized in that the pitches of the plurality of activated carbon passage groups are different from each other, so that turbulence occurs in the flow of fuel vapor passing through the stacked body. Evaporation prevention device. 4. The fuel evaporator according to claim 1, wherein the arrangement directions of the plurality of activated carbon passage groups are different from each other, so that turbulence occurs in the flow of fuel vapor passing through the stacked body. Prevention device.