EP1788230A1

EP1788230A1 - Canister for evaporated fuel processing system with a monolithically formed block of activated carbon and a method of manufacturing thereof

Info

Publication number: EP1788230A1
Application number: EP05025302A
Authority: EP
Inventors: Pawel Zuchara
Original assignee: Delphi Technologies Inc
Current assignee: Delphi Technologies Inc
Priority date: 2005-11-19
Filing date: 2005-11-19
Publication date: 2007-05-23

Abstract

The invention relates to a canister for evaporated fuel processing system, having a number of adsorbing chambers, wherein the last chamber 10 is connected with an atmospheric port 7 and comprises a monolithically formed block 12 of activated carbon. The block 12 is surrounded, at least from its atmospheric port 7 side by plastic, advantageously polyurethane, covering 13. Preferably, the block 12 is distanced from the atmospheric port 7 side of the last adsorbing chamber 10, defining an improved purge zone 15. The invention also relates to a method of manufacturing such a canister, where, after positioning the block of activated carbon inside the last adsorbing chamber, a covering surrounding the block is formed by injecting plastic, preferably polyurethane foam, into a space between the outer casing of the block and the inner casing of the chamber.

Description

The invention relates to a canister for evaporated fuel processing system, having a number of adsorbing chambers, wherein the last chamber is connected with an atmospheric port and comprises a monolithically formed block of activated carbon. The invention relates also to a method for manufacturing such a canister.
A typical canister of the above kind is disclosed e.g. in the U.S. patent application 2002/0078931 or European patent application 04460022.9 co-owned by the present applicant.
As the emission of evaporated fuel into the atmosphere must meet appropriate governmental emission standards, many canisters contain an additional adsorbing chamber (a so called scrubber), where a monolithically formed block of activated carbon is placed. The scrubber may be either a separate chamber connected with the canister housing through a pipe (cf. Fig. 2) or form a part of appropriately moulded canister housing (cf. Fig. 1).
The monolithically formed block of activated carbon usually has a honey-comb or similar structure, enabling a unidirectional flow of vapors, and is typically sealed with the housing of the scrubber by two sealings usually made of fluorosilicone rubber, surrounding its top and bottom sides. The sealings greatly impair the costs of a canister.
The object of the present invention is to provide a canister having an improved and uncomplicated construction, which increases its tightness, enables its manufacturing in a more efficient and economic manner and protects the block against vibrations of the car chassis.
According to the present invention, there is provided a canister, where the monolithically formed block of activated carbon is surrounded, at least from its atmospheric port side, by plastic covering.
Such a construction enables to achieve a perfect tight sealing of the block, protects the block against vibrations of the canister in the car and, as only one inexpensive additional element is required, is much more efficient when compared to known solutions.
The covering is preferably made of polyurethane. Closed cells of the polyurethane foam generate a high restriction level, so that it is virtually impossible for the flow of vapors to by-pass the block.
The covering has advantageously a form of a separate tubular element, e.g. a segment of a plastic pipe. The block may also be coated with covering prior placing in the last adsorbing chamber.
Alternatively, the covering may have a form of a filler between the outer casing of the block and the inner casing of the last adsorbing chamber. In this case the covering shall be formed e.g. by supplying polyurethane foam into a space between the block and the housing of the last adsorbing chamber.
Preferably the last adsorbing chamber comprises a filter placed at the atmospheric port, which is glued to the covering. The filter, among others, protects the detection module tank leak (Onboard Diagnostic System OBD II) pump used to check the tightness of the installation from damage by big carbon particles.
The block is advantageously distanced from the atmospheric port side of the last adsorbing chamber.
If the block adjoins the opening of the chamber or the filter placed on the opening, the fragment of the block is normally unavailable for the flow of vapors, as during purging of the system, the vapors flow mainly through the central area of the block. Providing a distance between the block and the atmospheric port opening of the chamber substantially increases an effective purge zone, and lowers the restrictions for the vapors flowing through the block.
According to the present invention, there is also provided a method of manufacturing a canister for evaporated fuel processing system, as described above, said method comprising the steps of:

(i) positioning monolithically formed block of activated carbon inside a form, providing a space between the outer casing of the block and the inner casing of the form, and
(ii) forming a covering surrounding the block, at least from one of its sides, by injecting plastic, preferably polyurethane foam, into the space between the outer casing of the block and the inner casing of the form.

Preferably, prior positioning the block inside the form, said method comprises the step of placing a filter at the bottom of the form. The filter is consequently automatically glued to the covering with no need of additional technological operation, e.g. ultrasonic welding.
To create a predefined purge zone, prior positioning the block inside the form, said method comprises the step of placing a separator between the filter and the block.
Advantageously the form is the last adsorbing chamber of the canister, which substantially increases the vapor-tightness of the chamber.
The method of the invention substantially reduces the number of steps required to manufacture the scrubber and is preferably implemented as a separate technological step on a canister assembly line.
The invention is presented below in exemplary embodiments with reference to the drawings, of which:

Fig. 1 shows an axonometric view of a canister embodiment, where the scrubber is integrated with the canister housing,
Fig. 2 shows an axonometric view of a canister embodiment, where the scrubber is a separate element of the housing,
Fig. 3 shows an axonometric, exploded view of a scrubber of the type shown in Fig. 2,
Fig. 4 shows a cross section of the lower part of a scrubber provided with the purge zone,and
Fig. 5 schematically illustrates the method of manufacturing a scrubber according to the invention.

Exemplary embodiments of typical canisters are shown in Figs. 1 and 2. Each canister 1 contains two serially connected adsorbing chambers 2 and 3 and a scrubber 4 containing the last adsorbing chamber, where the first chamber 2 is connected with the fuel tank (not shown) through the inlet port 5 and with the intake pipe of an engine through the outlet port 6. After passing through the adsorbent layers of the first chamber 2 and subsequently of the second chamber 3, fuel vapors enter the last adsorbing chamber of the scrubber 4, from which they are eventually discharged into the surrounding atmosphere through the atmospheric port 7. Usually the atmospheric port 7 of the canister 1 is additionally connected with the OBD II pump (not shown) used to check the tightness of the fuel installation. The last adsorbing chamber of the canister 1 shown in Fig. 1 is integrated with the canister housing, while in Fig. 2 it forms a separate element connected with the canister via pipe 8. In any case, however, its operating principles are the same.
The scrubber 4, according to an embodiment of the present invention, is shown exploded in Figs. 3a and 3b with all its characteristic elements. The scrubber 4 comprises a cylindrical hollow housing 9 with an atmospheric port 7, which after assembling the scrubber is tightly closed by a cylindrical cap 11.
The housing 9 forms an adsorbing chamber 10 containing a block 12 of activated carbon surrounded by a covering 13 made of polyurethane foam. After assembling the scrubber 4, the inner surface of the covering 13 tightly adjoins to the outer casing of the block 12 and the outer surface of the covering 13 tightly adjoins the inner casing of the adsorbing chamber 10. Such a construction efficiently protects the block 12 against failure during vibrations. Furthermore, the closed cells of polyurethane foam generate a very high resistance for vapors flow. Consequently, the total flow of vapors is routed through the block 12.
Additionally, the scrubber 4 comprises a flat filter 14, glued below the polyurethane covering 13 at the bottom of adsorbing chamber 10. The filter 14 protects the outlet 7 from possible clogging by the block particles that may crumb.
As shown in Fig. 3b the height of the polyurethane covering 13 is greater than the height of the block 12, therefore, when the block 12 is surrounded by the covering 13 in the interior of the covering 13, below the block 12 a hollow space is formed. The space defines a purge zone 15, which decreases restrictions for air flow through the block 12 and increases effective purge area in the block 12. Purging of the block 12 normally takes place after starting the engine, when the vapours are inducted by negative pressure of the intake pipe and then burnt inside the combustion chamber.
Fig. 4 shows schematically a cross-section of the scrubber 4 after its assembling. The optimal height H of the purge zone 15 should be theoretically equal to three block diameters D. Obviously in practical embodiments, due to constructional limitations it shall be lower.
Fig. 5 shows schematically a process of manufacturing an integrated scrubber module 4 according to the invention. The process begins with placing a filter 14 at the bottom of the scrubber housing 9 defining the last adsorbing chamber 10. Afterwards, on the filter 14 there is placed a separator in a form of a cylinder sleeve 16 and a honeycombed activated carbon monolith block 12, where diameters of the sleeve 16 and the block 12 are equal. By distancing the block 12 from the filter 14, the spacing sleeve 16 defines a purge zone 15 below the block 12.
Finally, a moulding head 17 connected to a polyurethane feeding aggregate (not shown) is inserted into the space between block 12 and the housing 9. After starting the aggregate, the head 17 injects polyurethane foam into the space between the block 12 and the housing 9 stowing this space with polyurethane and forming a covering 13. Other forms of plastic, such as polyethylene, are also allowed.
Obviously, the process may also be realized in a separate tubular form, what, after removing the form, shall result in an integrated covering-filter-block unit. Nevertheless forming the covering directly in the housing 9 substantially improves the vapor-tightness of the scrubber.

Claims

A canister for evaporated fuel processing system, having a number of adsorbing chambers, wherein the last chamber is connected with an atmospheric port and comprises a monolithically formed block of activated carbon, characterized in that , the block 12 is surrounded, at least from its atmospheric port 7 side, by plastic covering 13.
The canister according to claim 1, characterized in that , the covering 13 is made of polyurethane.
The canister according to claim 1 or 2, characterized in that , the covering 13 has a form of a separate tubular element.
The canister according to claim 1 or 2, characterized in that , the covering 13 has a form of a filler between the outer casing of the block 12 and the inner casing of the last adsorbing chamber 10.
The canister according to any of the preceding claims, characterized in that , the last adsorbing chamber 4 comprises a filter 14 placed at the atmospheric port 7, which is glued to the covering 13.
The canister according to any of the preceding claims, characterized in that , the block 12 is distanced from the atmospheric port 7 side of the last adsorbing chamber 10.
A method of manufacturing a canister for evaporated fuel processing system, having a number of adsorbing chambers, wherein the last chamber is connected with an atmospheric port and comprises a monolithically formed block of activated carbon, characterized in that , it comprises the steps of:
(i) positioning the block inside a form, providing a space between the outer casing of the block and the inner casing of the form,

(ii) forming a covering surrounding the block, at least from one of its sides, by injecting plastic, preferably polyurethane foam into the space between the outer casing of the block and the inner casing of the form.
The method according to claim 7, characterized in that , prior positioning the block inside the form, said method comprises the step of placing a filter at the bottom of the form.
The method according to claim 8, characterized in that , prior positioning the block inside the form, said method comprises the step of placing a separator between the filter and the block.
The method according to claim 7 to 9, characterized in that , the form is the last adsorbing chamber of the canister.