Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reexamination Certificate
1999-04-20
2001-05-29
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
C123S518000, C123S1980DA
Reexamination Certificate
active
06237574
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to evaporative emission systems for automotive vehicles, and more particularly to evaporative emissions canisters.
BACKGROUND OF THE INVENTION
Conventional automotive evaporative systems include a carbon canister communicating with a fuel tank to adsorb fuel vapors from the fuel tank. The carbon canister adsorbs the fuel vapor until it is saturated, at which time, the fuel vapor is desorbed from the carbon canister by drawing fresh air therethrough. Such a system is shown in FIG.
1
. System
10
includes fuel tank
12
coupled to carbon canister
14
and engine
16
via vapor purge lines
17
and
24
, respectively. Fuel vapor from tank
12
flows through line
17
into canister
14
, where the fuel is adsorbed onto the carbon. Fresh air is then emitted through vent port
18
to atmosphere. When the canister becomes saturated with fuel, engine controller
19
commands valve
20
to open so that the fuel may be desorbed from the carbon and flow to engine
16
via purge line
24
.
Occasionally, it may be necessary to purge the canister when both the canister is full and a large vapor volume exists in the fuel tank. Thus, upon purging, in the system described with reference to
FIG. 1
, vapor is drawn from both the canister and the engine. As a result, the large vapor volume flowing directly from the tank to the engine may cause the engine to temporary run in an undesirably rich condition. To prevent this, a relatively small carbon canister
26
, typically termed a buffer canister, is disposed between the fuel tank and the engine. This buffer canister
26
, due to its relatively small size, quickly saturates such that the vapors flowing to the engine may break through the carbon bed to be consumed by the engine. The effect of the buffer canister is to reduce any large hydrocarbon or fuel vapor spikes going to the engine to prevent the over rich condition. In other words, the buffer canister acts to dampen any fuel vapor spikes typically flowing directly from the fuel tank to the engine.
The disadvantage with this approach is primarily due to the fact that a secondary canister must be utilized in the system. This creates added expense due to couplings, vapor lines, associated hardware and general system complexity. To overcome these disadvantages, some systems utilize a vapor purge line flowing directly from the tank to the primary carbon canister, with the purge line being embedded deep into the carbon bed. Such a system is depicted in FIG.
2
. In this system, when fuel vapor from the fuel tank
12
is to be purged directly into engine
16
, the fuel vapor must at least go through a portion of the primary carbon canister, shown at bracket
28
. Thus, a portion of the canister acts to buffer any hydrocarbon spikes from the fuel tank.
The inventors of the present invention have found certain disadvantages with the system described in FIG.
2
. For example, in order to utilize a portion of the primary canister as a buffer, fuel vapor line
17
must necessarily penetrate into the carbon bed. Because of this, manufacturing issues arise in that the vapor purge line must be sealed in a manner so as to prevent leakage between the line and the atmosphere at the intersection with the primary canister. In addition, the purge line must contain a screen or filter to prevent the carbon from dislodging from the canister. Furthermore, the amount of penetration is determined on a vehicle line basis. Thus, a relatively small engine may require a certain volume for the buffer whereas a relatively large engine may require a different volume. This fact requires unique manufacturing tooling to precisely locate the depth of the fuel tank purge line within the carbon canister.
The inventors of the present invention have found further disadvantages with both prior art systems. For example, because the relatively constant cross-sectional area of the canister, vapor may inadvertently break through the vent port. In addition, these canisters are generally laid out such that the vapor flows through the canister in a serpentine manner. This may cause an increase in the flow restriction, which may have the effect of premature shutting off of the fuel fill nozzle, for example. Also, to accommodate various vehicle line applications, each system may require a plurality of different size canisters located in a variety of positions throughout the system, making packaging on a vehicle a concern.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an easily manufacturable, multiple application carbon canister which overcomes the disadvantages of prior art canisters. This object is achieved, and disadvantages of prior art are overcome, by providing a novel evaporative emission canister for an evaporative emission system.
Accordingly, an evaporative emissions canister is provided for an evaporative emission system. The system includes a fuel tank coupled to an engine via a vapor purge line. The canister, in turn, is coupled to the fuel tank and the engine. The canister is a generally cylindrical housing defining a circumference and has a first, relatively smaller cross-sectional area portion and a second, relatively larger cross-sectional area portion, with a tapered section therebetween. At the end of the canister opposite the first portion, a third relatively smaller cross-sectional area portion is provided, with a second tapered section between the second and third portions.
The housing contains hydrocarbon adsorbing material for adsorbing hydrocarbons from fuel vapor flowing therethrough. A vent port is formed on the third portion to vent air to atmosphere upon adsorption of hydrocarbons and for admits air upon desorption of hydrocarbons during a purging operation of said canister. A purge port is formed on the first portion and is adapted for connection to the engine to allow desorbed hydrocarbon to flow thereto. An intermediate port is formed on the second portion and disposed between the vent port and the purge port, with the intermediate port being selectively coupled to the fuel tank.
The second plenum is preferably adapted to receive at least one standoff. The standoff separates the first and second hydrocarbon adsorbing zones. The standoff is sufficiently sized so as to accommodate a plurality of sizes of the first hydrocarbon adsorbing zone, respectively. The canister may also include a biasing means to bias the first and the second hydrocarbon adsorbing zones in a compressed manner.
Accordingly, an advantage of the present invention is ease of manufacturability and reduced manufacturing costs.
Another advantage of the present invention is that a multiple application canister may be produced and slightly adapted for a particular vehicle line.
Another, more specific advantage is the reduced cross sectional area of the first zone creates a high concentration of fuel vapor therein during adsorption, thereby increasing the mass ransfer rate thereacross during purge.
Another, more specific, advantage of the present invention is that the canister may be quickly configured to provide maximum vapor storage capacity.
Another, more specific, advantage of the present invention is that the canister may be quickly configured with different buffering zone volumes.
Yet another advantage of the present invention is that a single unit may be easily packaged on a particular vehicle line.
Still another advantage of the present invention is reduced flow restriction through the canister.
Yet another advantage of the present invention is reduced potential for hydrocarbon breakthrough.
Other objects, features and advantages of the present invention will be readily appreciated by the reader of this specification.
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Jamrog James Richard
Johnson Philip Jeffrey
Pierce Michael Anthony
Drouillard Jerome R.
Ford Motor Company
Gimie Mahmoud
Yuen Henry C.
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