US3831353A

US3831353A - Fuel vapor control device

Info

Publication number: US3831353A
Application number: US00295047A
Authority: US
Inventors: R Toth
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1972-10-04
Filing date: 1972-10-04
Publication date: 1974-08-27
Anticipated expiration: 1991-08-27
Also published as: GB1391890A; DE2346623A1; JPS49100413A; CA985106A; IT990401B; JPS5144252B2

Abstract

A canister containing a fuel vapor adsorbent has a fuel vapor inlet, a fresh air inlet and a purge vapor outlet. It additionally contains a baffle between the vapor inlet and purge outlet to prevent direct communication of fuel vapors to the purge outlet while forcing the flow of fuel vapors through the adsorbent.

Description

[451 Aug. 27, 1974 FUEL VAPOR CONTROL DEVICE 8/1972' Jones, 55/387 [75] Inventor: Robert L. Toth, Allen Park, Mich.

Primary ExaminerFrank A. Spear, Jr. Assistant Examiner-Ferris H. Lander 0r FirmKeith L. Zerschling; Robert m am Am m V1. Ma r mM AE FM &

[21] App]. No.: 295,047

[57] ABSTRACT A canister containing a fuel vapor adsorbent has a fuel vapor inlet, a fresh air inlet and a purge vapor outlet.

[52] US. 55/387, 55/DIG. 28, 55/DlG. 30 [51] Int. B0ld 53/00 [58] Field of Searchmm' 55/74 lt additionally contains a baffle between the vapor 55/DlG. 30, DIG. 28

inlet and purge outlet to prevent direct communica- ,tion of fuel vapors to the purge outlet while forcing References Cited UNITED STATES PATENTS the flow of fuel vapors through the adsorbent.

3,464,186 Hankison et 55/387 6 Claims, 3 Drawing Figures FUEL VAPOR CONTROL DEVICE This invention relates, in general, to a fuel vapor emission control device. More particularly, it relates to a fuel system of the automotive type, and to a device to prevent the emission of fuel vapors into the atmosphere.

Systems are known today to prevent the unwanted escape of fuel vapors into the atmosphere from fuel tanks and carburetor float bowls of a motor vehicle, for

' example, during hot soak cycles of the engine when the vehicle may be subjected to extreme temperature gradients. These systems in the past generally have consisted of fuel vapor vent lines from the fuel tank and the carburetor float bowl that lead to a canister containing in most instances activated carbon so that the fuel vapors can be adsorbed. Subsequent operation of the engine purges these adsorbed fuel vapors back into the engine.

In the past, the canister generally was constructed with air/fuel vapor chambers at opposite ends, with the adsorbent material sandwiched between. The end chambers constituted air distribution manifolds for better presentation of the fuel vapors to the surfaces of the adsorbent. However, with such a construction it may be possible at times for the fuel vapor flow to short circuit the adsorbent and flow directly from the fuel vapor inlet to the purge outlet and therefrom out to the atmosphere under the pressure of the hot soak cycle.

The invention relates to a canister construction containing a baffle that prevents the direct communication of the fuel vapors in the inlet to the purge outlet and forces them to pass through the vapor adsorbent; while, however, at the same time effecting a purge of fuel vapors in any dead spots behind the baffle to the adsorbent.

The invention consists of an open celled foam material that is compressible, the open cells being of such small porosity such that a high restriction to flow therethrough is provided. The majority of the fuel vapors are thereby forced to flow past the baffle into the adsorbent during the hot soak cycle. However, the small amount of fuel vapor that may become trapped in dead air spaces behind the baffle can flow through the open cells of the baffle to the adsorbent during the high pressure differential purge cycle.

It is a primary object of the invention, therefore, to provide a fuelvapor emission control device that effectively prevents the emission of undesirable fuel vapors into the atmosphere.

It is another object of the invention to provide a fuel vapor storage canister with a baffled construction preventing the escape of fuel vapors'into the atmosphere and forcing them through the adsorbent therein.

It is another object of the invention toprovide a baffle as described above of an open cell foam construction of small porosity providing a high restriction to flow therethrough but pennitting a small amount of flow during the purge cycle so that purge air can remove fuel vapors in dead air spaces that may be created behind the baffle member.

A still further object of the invention is to provide a Other objects, features and advantages of the invention will become more apparent upon reference to the succeeding detailed description thereof, and to the drawings illustrating a preferred embodiment thereof; wherein,

FIG. 1 is a schematic illustration of a fuel vapor loss control system embodying the invention;

FIG. 2 is an enlarged top plan view of the carbon canister shown in FIG. 1; and,

FIG. 3 is a cross-sectional view taken on a plane indicated by and viewed in the direction of the arrows 33 of FIG. 2.

FIG. 1 illustrates schematically a typical fuel vapor loss control system for use with a motor vehicle power plant. It shows a conventional engine 10 having mounted thereon a carburetor 12 with a fuel or float bowl 14. The air taken into the carburetor and engine is filtered by a conventional air cleaner 16 having a suitable dry filter element such as, for example, of the pleated paper type.

The fuel loss control system includes a vent line 18 connected at one end to the vehicle fuel tank 20 and to a vapor storage canister 22 at the other end. As will be explained more fully later, the canister contains a quantity of activated charcoal that will adsorb and store excess fuel vapors. The vapors enter therein under slight pressure from the fuel tank when hot soak conditions occur. The canister has a fresh air inlet 24 and a purge outlet tube or line 26 to the air cleaner.

In general operation, when the vehicle is stationary with the engine off, and is subjected to a heat buildup such as on a warm day, the conversion of liquid fuel into vapor creates a pressure in line 18 driving the fuel vapors into the canister where they are adsorbed by the charcoal elements. Upon start of the engine, the suction in the engine cylinders creates a purge flow of vapors from the canister by the flow of fresh air through inlet 24 through the carbon elements to desorb them of vapors and conduct them through the outlet line 26 back into the engine where they are burned.

As stated previously, the invention is concerned primarily with the construction of the carbon canister to prevent the escape of fuel vapors into the atmosphere at any time. Referring to FIGS. 2 and 3, it will be seen that the canister has a hollow outer shell 30 closed at its upper end by a beaded cover member 32. The cover has an opening 34 in which tube 26 is fixed, a fresh air inlet tube 36 connected to inlet 24, and a fuel vapor opening 38 connected to line 18.

The interior of the shell 30 is partitioned into two

end chambers

40 and 42 by a pair of annular steel perforated

screen plates

44 and 46, the space between the screens being filled with activated charcoal or some other suitable vapor adsorbent 47. The two

end chambers

40 and 42 constitute fluid distribution manifolds so that the fuel vapors and air will be evenly distributed over the entire end surfaces of the activated charcoal. If

chambers

40 and 42 were not provided, then any flow of air down the fresh air tube 36 would tend to return along its outer diameter to soon saturate the adsorbent to a point where further flow of fuel vapors would cause a breakthrough without adsorption. That is,

rather than spread laterally to pass through unsaturated adsorbent, the fuel vapors would pass in a shorter, easier path over the saturated elements and, therefore, fuel vapor would pass out into the atmosphere through the purge tube prior to the capacity of the adsorbent being utilized.

The fresh air tube 36 extends through cover 32, manifold 40, and both

screens

44 and 46 into the opposite end chamber 42, with a suitable spacer element 48 on the end of the tube. A dust cap 49 covers the fresh air inlet end 24 of the tube, and a spring 50 located between screen 44 and the cover 32 biases the upper screen against the activated adsorbent to maintain it in place.

The canister is constructed as described above so that the fuel vapors forced into manifold 40 will pass through the activated charcoal and be adsorbed thereon. The connection of the fresh air to the end chamber 42 through tube 36, with the purge outlet 34 being at the opposite end chamber 40, forces a flow of air through the charcoal from one end to the other during the purge operation when the engine is running, thereby desorbing the fuel vapors.

The above construction is known and further details of construction and operation are not given since they are believed to be unnecessary for an understanding of the invention.

With the above construction, it will be seen that it is possible at times for the fuel vapors under pressure entering manifold 40 to bypass the adsorbent and pass directly out to the air cleaner through the purge outlet 34. This naturally is undesirable since the vapors could then pass out into the atmosphere through the air cleaner main air inlet, in the absence of suction from the engine. Accordingly, a baffle member 52 is interposed in the upper manifold 40 between the vapor inlet 38 and the purge outlet 34 to positively prevent the escape of fuel vapors into the atmosphere without having first passed through and being adsorbed and stored by the activated charcoal elements.

The baffle 52 in this case consists of a compressible open cell, foam material of an essentially rectangular shape and has a central arcuate portion merely to avoid interference with spring 50. It will be clear of course that other suitable shapes may be used as desired. The open cell foam baffle in this case has a very small porosity, which causes a high restriction to flow through it so that fuel vapor cannot freely flow through the baffle member and thereby bypass the charcoal elements during the purge or storage operations.

The open cell construction serves many functions. In most instances, the canister would be filled with activated carbon by weight, in contrast to volume. Accordingly, its depth will vary for the same size canister, and it is, therefore, desirable to have a varying thickness baffle member so as to be adaptable to positively prevent leakage of vapor into the purge outlet 34. The open cell compressible foam construction accomodates a varying depth manifold 40 since it is a soft spongy material.

The baffle 52 furthermore because of its open cell construction permits a purging through it of any fuel vapor that may collect in the dead air space between the baffle and the canister wall in manifold 40.

In operation, therefore, when the engine in FIG. 1 is shut down and the fuel tank experiences a temperature gradient large enough to cause the evaporation of considerable fuel vapor from the tank, the fuel vapor under slight pressure will pass up into line 18 and into the canister inlet 38. At this time, as best seen in FIG. 2, the fuel vapors will flow into the space 54 between the baffie 52 and the end of chamber 40 and therefrom be forced into the activated charcoal bed 47 to be adsorbed thereon.

When the engine is again restarted, the large intake manifold depression will cause a flow of air through the fresh air inlet opening 49 and through the tube 36 to the bottom manifold 42. It will then flow upwardly towards the purge outlet 34 through the activated charcoal, and thus desorb the charcoal of fuel vapors.

It can be seen, however, that while it might be possible for fuel vapors to be trapped in the space 54 between baffle 52 and the end of manifold 40, the open cell construction of the baffle 52 permits a purging of the fuel vapor through the baffle into the charcoal and around the air tube 36 and finally out through the purge outlet 34.

From the foregoing, it will be seen that the invention provides a device for use with a fuel vapor storage system to prevent undesirable escape of fuel vapors to the atmosphere, and that it is accomplished in a simple and inexpensive manner.

While the invention has been described and illus- 'trated in the drawings in its preferred embodiment, it

will be clear of those skilled in the arts to which it pertains that many changes and modifications may be made thereto without departing from the scope of the invention.

1 claim:

1. A fuel vapor loss control device for use with a motor vehicle fuel system to control the emission of fuel vapors, comprising, a hollow closed canister containing vapor adsorbent material centrally located to provide chambers at opposite ends, first tube means having an air inlet at one end of the canister and projecting through the canister to the other end for connecting purge air from outside the canister to the other end chamber, second tube means at the one end of the canister connected to the adjacent one end chamber for the purge flow of desorbed vapors therefrom, additional inlet means to the one chamber containing fuel vapors to be adsorbed at a higher pressure than the pressure level in the second tube means thereby effecting flow therebetween, and vapor barrier means comprising a baffle in the one end chamber between the second and additional inlets preventing direct communication between the two and forcing flow of fuel vapors through the adsorbent.

2. A fuel vapor control device as in claim 1, the baffle comprising an open cell material of predetermined porosity providing restricted purge of fuel vapors through it from the opposite end chamber space on the side of the baffle adjacent the additional inlet to the opposite end chamber space on the other side of the baffle.

3. A fuel vapor control device as in claim 1, the baffle comprising a compressible material rendering it universally adaptable to variable density loads of adsorbent.

4. A fuel vapor control device as in claim 1, the baffle comprising a soft spongy material with small porosity providing sufficiently high restriction to flow of air and fuel vapors therethrough to prevent the free flow therethrough, the porosity permitting the purge of air and fuel vapors from the area in the opposite end chamber behind the baffle to the other side of the baffle.

5. A fuel vapor control device as in claim 4, the baffle comprising an open cell foam material dividing the opposite end chamber into two parts each associated with a separate inlet.

6. A fuel vapor control device as in claim 1, the end chambers comprising vapor manifolds for evenly distributing the flow of fuel vapors to the adsorbent.