JPH0448937B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an evaporative fuel adsorption device for an automobile or the like, and particularly to a structure of a canister that efficiently collects hydrocarbons (HC) generated from a fuel tank or a vaporizer when the engine is stopped. HC evaporated from automobile fuel tanks and vaporizers
Since the HCs vary from those with low boiling points to those with high boiling points, it is difficult to collect these HCs with a single type of adsorbent as in conventional canisters. Meanwhile, fuel mixed with alcohol is beginning to become popular in order to protect oil resources. Since alcohol has a high vapor pressure and also contains polar groups, it is difficult to collect the alcohol content with the activated carbon filled in the canister as an adsorbent due to its characteristics. The use of multiple types of adsorbents depending on the fuel to be adsorbed has been proposed in Japanese Patent Laid-Open No. 151725/1983. Here, in order to adsorb HC generated from the vaporizer and fuel tank, a high-boiling point adsorbent is used on the vaporizer side, and a low-boiling point adsorbent is used on the fuel tank side. However, this does not mean that only high-boiling point components are evaporated on the vaporizer side, and only low-boiling point components are generated on the fuel tank side, but only whether the proportion of these components is high or low, so in this proposal, from the fuel tank side. There is a risk of HC leaking and early deterioration of the adsorbent on the fuel tank side. Furthermore, in the proposed configuration, activated carbon is used for both the high-boiling point adsorbent and the low-boiling point adsorbent, and the structure is such that only the adsorption power thereof is changed. For this reason, it has been difficult to reliably adsorb alcohol containing polar groups. The present invention has been made in view of the above points, and the second adsorbent layer of the two-layer structure adsorbent is replaced with the first adsorbent layer.
By using a material that adsorbs polar substances more easily than other adsorbents, the present invention provides an adsorption device that can effectively collect various HC or alcohol components from sources. Therefore, in the evaporated fuel adsorption device according to the present invention,
At least two layers of at least two
The second adsorbent layer near the atmosphere opening is made of a material that easily adsorbs polar substances compared to the first adsorbent layer near the adsorbed fuel inlet. It is characterized by this. Alternatively, the first adsorbent layer and the second adsorbent layer may be separated by a filter plate. Further, the volume of the second adsorbent layer may be 20 to 80% of the volume of the first adsorbent layer. Furthermore, the second adsorbent layer may be made of silica gel, zeolite, or alumina, which can more easily adsorb polar substances than the activated carbon of the first adsorbent layer. To explain an embodiment of the present invention with reference to the drawings, a canister 1 for adsorbing evaporated fuel includes a bottomed cylindrical container 4 having a lid 2 as one end surface and a bottom 3 as the other end surface. An atmosphere opening port 5 is formed. An annular stepped portion 6 is provided in an area close to the bottom 3 of the container 4.
is formed, and a perforated plate 7 and a filter plate 8 are placed on this stepped portion 6. This filter plate 8
Above is a layer 9 of granular adsorbent that mainly adsorbs low-boiling components of the vapor fuel, and a filter plate 10
Above this layer 9 is a layer 11 of granular adsorbent which primarily adsorbs high boiling components of the fuel. When selecting the materials for each of the layers 9 and 11, the material for the granular adsorbent layer 9 that adsorbs low boiling point components is selected to be a material that can more easily adsorb polar substances than the granular adsorbent layer 11 that adsorbs high boiling point components. ing. Further, the volume of the lower layer 9 is 20 to 80% of the volume of the upper layer 11. The type and specifications of the adsorbent for both layers are shown in the table below.

[Table] A filter plate 12 and a perforated plate 13 are placed on the surface of the upper layer 11 and are pressed against the upper layer 11 by a spring 14 supported by the lid 2 of the container 4. The lid 2 has an adsorbent fuel inlet 17 connected to an adsorption line 16 leading to the fuel evaporation space of the fuel tank 15, and a large diameter conduit 18 leading to the inlet 17.
penetrates into the upper layer 11 to a predetermined depth.
The lid 2 further includes an adsorption fuel inlet 21 connected to an adsorption pipe, so-called outer vent 20, which exits from the fuel evaporation space of the float chamber 19 of the carburetor 18, and a separation pipe 23, which opens to the intake passage 22 of the carburetor 18. There is a breakaway fuel outlet 24 connected thereto. Now, fuel tank 15 and carburetor float chamber 1
The evaporated fuel generated in the canister 9 is adsorbed by the adsorbent in the canister 1 through the inlets 17 and 21 via the adsorption lines 16 and 20, respectively. In this case, the fuel
Most of the HC components are first adsorbed onto the adsorbent particles in the upper layer 11. However, in the upper layer 11, which has a weak ability to adsorb polar substances, components with polar groups such as alcohol mixed in the fuel, low boiling point components with high vapor pressure, and unsaturated HC are mostly absorbed in the upper layer 11. I passed 11. Components with polar groups, low boiling point components with high vapor pressure, and unsaturated HCs that have passed through the upper layer 11 flow into the lower layer 9 through the filter plate 10. As described above, since the lower layer 9 is made of a material (silica gel, zeolite, alumina) that adsorbs polar substances more easily than the upper layer 11, alcohols and the like having polar groups can be adsorbed to the fruit. Further, since the lower layer 9 has a higher ability to adsorb low-boiling components having a higher vapor pressure and unsaturated HC than the upper layer 11, it can also effectively adsorb these substances. Therefore, various substances that have passed through the upper layer 11 are also reliably adsorbed by the lower layer 9, and do not leak into the atmosphere from the atmosphere opening 5. In this way, according to the present invention, the adsorbent of the canister is made into multiple layers, and adsorbents suitable for fuel components with different boiling points or fuel components with polar groups are used. It is also possible to sufficiently capture HC that would otherwise have been released into the atmosphere. Furthermore, even if fuel is mixed with alcohol, the evaporated alcohol can be sufficiently collected by this canister and prevented from being released into the atmosphere. Note that the present invention is not limited to the illustrated embodiment. For example, if three or more different adsorbents are
More than one layer can be stacked, and the canister can also have a different structure than shown.

[Brief explanation of the drawing]

The figure is a configuration diagram of a vaporized fuel adsorption device according to the present invention. 1... Canister, 2... One end surface (lid),
3...other end surface (bottom), 4... cylindrical container, 5...
...Atmospheric opening, 9...Second adsorbent layer (lower layer),
11...first adsorbent layer (upper layer), 17, 21
... Adsorption fuel inlet, 24 ... Detachment fuel outlet.

Claims (1)

[Claims] 1. At least two types of adsorbents are contained in at least two layers in a cylindrical container having an adsorbed fuel inlet and a separated fuel outlet on one end face and an atmosphere opening on the other end face. The second adsorbent layer that is housed in the adsorbent and is located closer to the atmosphere opening is made of a material that easily adsorbs polar substances to the first adsorbent layer that is located closer to the adsorbed fuel inlet. , evaporative fuel adsorption device. 2. The device according to claim 1, characterized in that the first adsorbent layer and the second adsorbent layer are separated by a filter plate. 3. The device according to claim 1 or 2, characterized in that the volume of the second adsorbent layer is 20 to 80% of the volume of the first adsorbent layer. 4. Any one of claims 1 to 3, wherein the second adsorbent layer is made of silica gel, zeolite, or alumina, which adsorbs polar substances more easily than the activated carbon of the first adsorbent layer. The device described in.