Note: Descriptions are shown in the official language in which they were submitted.
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ENGINE WIT~ EVAPORATION CONTROL SYSTEM
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Technical Field -
This invention relates to an engine with an
evaporation control system that captures substantially
all the fuel vapor displaced from the engine fuel system.
Background
Automotive engines~generally have the vent
lines from the fuel tank and carburetor fuel bowl con-
nected to a fuel vapor storage canister. As air and
fuel vapor are displaced through the vent lines by
increasing temperatures when~the engine is not operating~,
the canister captures the fuel vapor to prevent its
loss to the atmosphere.
~ If the canister in such a system should become
saturated with fuel vapor~, any additional vapor displaced
from the fuel tank or carburetor fuel bowl will travel
through the canister and out its vent to the atmosphere.
Moreov~r, even when the canister is not saturated, the
flow of air and fuel vapor khrough the canister causes
some of the fuel vapor previously stored ln the canister
to be purged out the canister vent to the atmosphere.
Earlier proposals to prevent loss of fuel
vapor through the canister involved either incr~asing the
size of the canister or venting the canister through a
supplementary canister.
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Su~nar~ of the Invention
We have discovered that while such proposals
may prevent saturation of the canister or canisters with
fuel vapor, they lead to increased loss of fuel vapor from
the canister or canisters due to the flow of air and fuel
vapor therethrough. On the other hand, we have found that
such loss is prevented when a fuel vapor storage canister
is vented to the engine air cleaner and a supplementary
fuel vapor storage bed is disposed in the air cleaner to
capture fuel vapor lost from the canister. The supplemen-
tary storage bed then .is thoroughly purged by engine air
flow when the engine is operating and the substantialIy
completely purged supplementary storage bed is able to
capture substantially all fuel vapor which ma~.be lost
from the canister.
The details as well as other features and ad-
vantages of this invention are set forth in the remainder
of the specification and are shown in the accompanying
drawings.
Summary of the Drawings
In the drawings:
: Figure 1 is a schematic view of an engine with
an evaporation control system employing this invention,
and
Figure 2 is a sectional view of the engine air
cleaner showing the supplementary fuel vapor storage~bed
and the vent connection for the canister.
Best Mode for Carrying Out the Invention
Referring first to Figure 1, an engine 10 has
a carburetor 12 and an air cleaner 1~ which define an
air induction passage 16.
Carburetor 12 has a fuel bowl 18 which receives
liquid fuel from a fuel tank 20 through a fuel line (not
shown). Fuel bowl 18 delivers fuel to the induction
passage 16 in a conventional manner and has an internal
vent 22 to maintain the fuel bowl pressure equal to that
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in the inlet portion of induction passage 16.
A fuel tank vent line 24 extends from fuel ~:
tank 20 to a fuel vapor storage canister 26, and a fuel
bowl vent line 28 extends from carburetor fuel bowl 18
to canister 26.
Canister 26 is formed of a cupped housing 30
closed at the bottom by a grid 32 and a cover 34. An
annular partition 36 divides the interior of canister
26 into an inner section 38 and an outer section 40
each of which is filled with activated charcoal to ~orm
a main fuel vapor storage bed. Tank vent line 24 opens
through a fitting 42 into the upper portion of outer
section 40 while bowl vent line 28 is connected through
a fitting 44 to the upper portion of inner section 38.
A bowl vent valve 46 disposed in fi-tting 44 is biased
by a spring 48 to permit vapor flow from fuel bowl 18
through bowl vent line 28 to canister 26 when the
engine is not operating. When the engine i.s operating,
a diaphragm 50 responds to the subatmospheric pressure
in induction passage 16 downstream of the thro-ttle 52
and lifts vent valve 46 against the bias of spring 48
to close fitting 44.
Upon an increase in temperature when the
engine is not operating, air and fuel vapor are dis-
placed from fuel bowl 18 and fuel tank 20 and flowthrough vent lines 28 and 24 to canister 26. The
flow travels downwardly through the lnner and outer
sections 38 and 40 of the main fuel vapor s-torage
bed, into the plenum 54 between ~rid 32 and cover 34,
and then upwardly through a standpipe 56 and a canister
vent line 58 to air cleaner 14; The activated
charcoal in the fuel vapor storage bed captures -the
fuel vapor to prevent its loss to the
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atmosphere~
During engine operation, the subatmospheric
pressure in induction passage 16 downstream of throttle
52 draws air cleaned by the filter element 60 ~rom air
5 cleaner 14 through the canister vent line 58 and stand- , `
pipe 56 into plenum 54 and then upwardly through the
inner and outer sections 38 and 40 of the fuel vapor
storage bed to a purge fitting 62. Such air flow purges
the fuel vapor from the charcoal so that the charcoal may
again adsorb fuel vapor when the engine is not operating.
The purge air flow rate is determined by a pair of purge '
orifices_63a and 63b.
If desired, a diaphragm purge valve 64 may
close across purge fittiny 62 under the bias of a spring
66 during closed throttle engine operation. When throttle
52 is opened, the subatmospheric induction passage pres-
sure therebelow lifts diaphragm valve 64 against t'he bias
of spring 66 to open purge fitting 62. An additional
purge orifice 63c may bypass purge valve 64 to allow a
limited purge flow during closed throttl~ engine operation.
Canister 26 is highly effective in capturing
the fuel vàpor displaced from the fuel bowl 18 and fuel
tank 20. However, the flow of air and fuel vapor through
the fuel vapor storage bed may cause some fuel vapor to
be purged from the bed and be carried ~hrough plenum 54,
standpipe 56, canister vent line 58, and air cleaner 14
to the atmosphere. To capture such fuel vapor, we have
provided a supplementary fuel va~Qr storage~",bed ~,8,; in
air cleaner 14. As shown particularly in Figure 2, bed
68 is located inwardly of filter element 60 and has an
annular configuration; it is formed of activated charcoal
which is retained by inner and outer screens 70 and 72
mounted in upper and lower caps 74 and 76. Bed 68 is
secured to a lower air cleaner plate 78 and extends
upwardly part way to an upper air cleaner plate 80.
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Accordingly, it will be observed that a portion of the
engine induction air flow passes through bed 68 to purge
fueI vapor therefrom while some of the engine induction
air flow passes through -the space 82 between bed 68 and
upper air cleaner plate 80. Fùel vapor stored in bed
68 thus may be substantially completely purged by air
flow through induction passage 16, yet bed ~8 does not
overly restrict the induction air flowO
Canister vent line 58 is connected to air ~
cleaner 14 through a fit-ting 84 disposed inwardly of \
bed 68. If desired, a diffuser (not shown) may be dis
posed over fitting 84 to assure dispersion of any fuel
vapor passing through'canister vent line 58 into bed 68.
Air cleaner 14 includes a,thermal sensor 86
and a vacuum operated snorkel damper mechanism 88
(Figure 1), such as that shown in U.S. patent 3,459,163
issued August 5, 1969 in the name of D. B. Lewis, to
maintain the induction air flow at a substantially
constant temperature.'
With this cons~ruction, any fuel vapor stored
in supplementary bed 68 will be substantially completely
purged by engine'induction air flow through air cleaner
14 when the engine is operating to thereby permit sub-
stantially ail fuel vapor lost from canister 26 to be
stored in bed 68 when the engine is not operating.
It will be appreciated of course, that bed 68
also may capture fuel vapor displaced from carburetor
fuel bowl 18 through internal vent 22 and that similar
air cleaner mounted fuel vapor storage beds have been
proposed in the past. ~lowever, until our invention it
was not recognized that -the thorough purge experienced
by such an ai.r cleaner mounted storage bed ls necessary
if a supplementary fuel vapor storage bed is to be used
to capture fuel vapor lost from a main storage bed.
