U.S. patent number 3,554,175 [Application Number 04/883,054] was granted by the patent office on 1971-01-12 for evaporative emission control system.
This patent grant is currently assigned to Chrysler Corporation. Invention is credited to Jorma O. Sarto.
United States Patent |
3,554,175 |
Sarto |
January 12, 1971 |
EVAPORATIVE EMISSION CONTROL SYSTEM
Abstract
A system for controlling evaporative emissions from the fuel
system of a motor vehicle wherein the fuel tank and carburetor bowl
are vented to the crankcase of the engine so that the crankcase
serves as an accumulator to collect fuel vapors from the fuel tank
and fuel bowl while the engine is turned off; the crankcase is in
turn vented to the engine intake so that the collected vapors are
subsequently burned in the engine during subsequent operation of
the engine. The venting of the carburetor bowl to the crankcase is
selectively controlled by a valve.
Inventors: |
Sarto; Jorma O. (Orchard Lake,
MI) |
Assignee: |
Chrysler Corporation (Highland
Park, MI)
|
Family
ID: |
25381875 |
Appl.
No.: |
04/883,054 |
Filed: |
December 8, 1969 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
711680 |
Mar 8, 1968 |
3517654 |
|
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Current U.S.
Class: |
123/519; 123/572;
96/134; 96/109 |
Current CPC
Class: |
F02M
25/08 (20130101); F02M 25/06 (20130101); Y02T
10/12 (20130101); Y02T 10/121 (20130101); F02M
2025/0863 (20130101) |
Current International
Class: |
F02M
25/06 (20060101); F02M 25/08 (20060101); F02m
025/08 () |
Field of
Search: |
;123/119,120,121,136 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Goodridge; Laurence M.
Parent Case Text
BACKGROUND OF THE INVENTION
This invention is a division of application Ser. No. 711,680, filed
Mar. 8, 1968 and it relates to an evaporative control system for a
motor vehicle fuel system.
Claims
I claim:
1. In a power system for a motor vehicle including an internal
combustion engine having at least one combustion chamber and a
crankcase, a fuel tank for storing a volatile fuel, and a charge
delivery system including a carburetor having a throttle valve and
a fuel bowl and an air intake conduit defined in part by said
carburetor and communicating with the combustion chamber; an
evaporative emission control system comprising:
A. first conduit means extending between said fuel tank and said
crankcase, whereby to allow said crankcase to function as an
accumulator to collect vapor evaporating from said fuel tank;
B. second conduit means extending between said fuel bowl and said
crankcase;
C. a control valve in said second conduit means;
D. means operative in response to movement of said throttle valve
to selectively open and close said control valve, whereby to allow
said crankcase to function under selected throttle conditions as an
accumulator to collect vapor evaporating from said fuel bowl;
E. third conduit means extending between said crankcase and said
air intake conduit at a location therein downstream of said
throttle valve, whereby to allow the vapor accumulated in said
crankcase to be supplied to said intake conduit for delivery to
said combustion chamber;
F. said third conduit means is closed during shutdown of said
engine so that the evaporative emissions entering said crankcase
during such shutdown are accumulated therein;
G. said emission control system further includes an absorption type
filter capable of absorbing evaporative emissions; and
H. fourth conduit means are provided to route any evaporative
emissions in excess of crankcase storage capacity to said filter,
whereby the filter supplements the operation of said crankcase in
recovering the evaporative emissions.
2. An evaporative emission control system according to claim 1
wherein:
I. said fourth conduit means comprises the only source of fresh air
for said crankcase so that fresh purging air enters said crankcase
through said fourth conduit means as said accumulated vapors leave
the crankcase through said third conduit means; and
J. said filter is also capable of desorption of the evaporative
emissions so that the fresh air passing through said fourth conduit
means en route to said crankcase purges said filter and delivers
the previously absorbed evaporative emissions to said crankcase and
thence to said intake conduit for combustion in said engine.
3. An evaporative emission control system according to claim 2
wherein:
K. said charge delivery system includes an air cleaner;
L. said fourth conduit means comprises a conduit extending from
said air cleaner to said crankcase; and
M. said filter comprises a charcoal canister interposed in said
fourth conduit.
4. An evaporative emission control system for a motor vehicle of
the type having an internal combustion engine including a
carburetor with a fuel bowl; said system comprising:
A. a first conduit extending from said fuel bowl to the crankcase
of said engine;
B. a valve in said first conduit;
C. means operative in response to operation of the throttle of said
vehicle to selectively open and close said valve, whereby to
selectively provide vapor communication between said fuel bowl and
said crankcase;
D. a second conduit having vapor communication at one end with the
fuel tank of the vehicle and extending therefrom to said crankcase,
whereby to provide vapor communication between said fuel bowl and
said crankcase;
E. a third conduit extending from said crankcase to the intake
manifold of said engine, whereby to provide a path to deliver
evaporative emissions from said crankcase to the combustion
chambers of said engine;
F. said first and second conduits connect to a common cap member
which is removably positioned on said engine over an opening in
said engine communicating with said crankcase; and
G. a fourth conduit extending from the air cleaner of said engine
to said cap member, whereby to provide a supply of clean purging
air to said crankcase.
5. An evaporative emission control system according to claim 4 and
further including:
H. an absorption type filter element interposed in said fourth
conduit operative to absorb evaporative emissions from said fuel
bowl and fuel tank in excess of crankcase capacity.
Description
The atmospheric condition commonly referred to as "smog" has
generated considerable interest in the problem of polluting
emissions from automobiles. Many corrective devices and systems
have been proposed and/or utilized to control and at least
partially eliminate the fumes from the engine exhaust. Another, and
quite distinct, source of hydrocarbon emissions from the automobile
is the fuel vapor escaping from the fuel system. Specifically,
significant quantities of gasoline vapor escape from the external
vents of both the fuel tank and the carburetor fuel bowl. Various
proposals have been advanced to control these evaporative
emissions. While some of the proposed systems have successfully
controlled the evaporative emissions they have been prohibitively
expensive and complicated, either from an initial cost standpoint
or from a maintenance standpoint.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide improved
evaporative emission control for motor vehicles.
In the evaporative emission control system of the invention, the
fuel tank and carburetor fuel bowl are both vented to the crankcase
of the engine, the carburetor vent line including a vent valve.
When the engine is turned off, the vapors emitting from the fuel
tank and fuel bowl are routed to the crankcase which serves as an
accumulator to collect these vapors. The emissions entering the
crankcase, being heavier than the air in the crankcase, gradually
and progressively displace the air in the crankcase. Provision is
made to route the collected vapors from the crankcase to the engine
intake manifold when the engine is again started so that the
collected vapors may be internally combusted in the engine.
In a specific form of the invention disclosed, two vent tubes are
connected to the crankcase breather cap of the engine. One vent
tube communicates with the vent of the carburetor fuel bowl, which
includes a throttle-controlled vent valve, and the other tube
communicates with a vent in the fuel tank. Both vent tubes
communicate through the breather cap with the engine crankcase so
that the breather cap provides storage communication between the
crankcase and both the fuel bowl and the fuel tank.
Other objects, features and advantages of the invention will be
apparent from the detailed description to follow.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the invention is illustrated in the
accompanying drawings. In the drawings:
FIG. 1 is a fragmentary, partially schematic view of an evaporative
emission control system according to the invention;
FIG. 2 is a sectional view on an enlarged scale of the carburetor
assembly of the system of FIG. 1;
FIG. 3 is a sectional view taken on line 3-3 of FIG. 1;
FIG. 4 is a schematic fragmentary view of the luggage compartment
of a motor vehicle; and
FIG. 5 is a fragmentary sectional view taken on line 5-5 of FIG.
1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The emission control system of the invention is seen in FIG. 1 in
conjunction with a gasoline internal combustion engine 10 and a
fuel tank 12.
Engine 10 is of the so-called V-eight type and includes a block 14,
oil pan 15, heads 16, 17 and valve covers 18, 19. Pistons 22
slidably received in cylinders 24 are drivingly connected to
crankshaft 26 through connecting rods 28. Valves 30 selectively
control the intake to and exhaust from cylinders 24 with the
selective opening and closing movement of the valves controlled in
known manner by a cam shaft 31 engaging lifters 32 for actuation of
rocker arms 33. Lifters 32 (see also FIG. 3) move within aligned
passages 34 and 35 in block 14 and heads 13, 16, aligned passages
34 and 35 thereby providing vapor communication between crankcase
36 and valve covers 18, 19. Spark plugs 38 function in known manner
to ignite the combustible mixtures introduced into combustion
chambers 40 through intake manifold 42.
A carburetor 44 (see also FIG. 2) is carried by manifold 42 and
functions to deliver combustible charge material to the cylinders.
Carburetor 44 is generally of known form and includes a venturi
section 46, a throttle 48 controlled from accelerator pedal 50 by a
throttle linkage 52, 54, 56, a fuel bowl 58, a bowl balance tube
60, a main fuel discharge tube 61 and a vent valve 62. The usual
accelerator pump assembly 63 is provided within the fuel bowl; pump
assembly 63 functions in known manner in response to a downward
stroke of piston rod 64 to squirt a measured quantity of fuel into
carburetor venturi section 46 through aperture or "window" 47. The
working stroke of piston rod 64 is effected by a coil spring 66
compressed between piston 68 and the lower face of the body 70 of
carburetor vent valve 62. The return stroke of piston rod 64 is
effected by a linkage 72, 74, 76 operatively connected to the
throttle linkage. A valve disc 78 on piston rod 64 coacts with a
valve seat 80 defined by valve body 70 to selectively communicate
the interior of the fuel bowl to vent fitting 82 in response to
reciprocal movement of rod 64.
An air cleaner 84 of known form is carried on top of carburetor 44
and includes an intake horn 86 and a filter element 88.
Engine 10 also includes a positive crankcase ventilation system.
The positive crankcase ventilation system includes a hose 90
extending between a fitting 92 on horn 86 and a fitting 94 on the
annular periphery of a breather cap 95, a crankcase ventilation
valve 96 on valve cover 18, and a hose 98 extending between a
fitting 99 on valve 96 and a fitting 100 on the base of carburetor
44. Fitting 94 communicates with an annular chamber 101 defined
between the sidewall of the cap and an annular filter element 102
positioned within the cap. Hose 90 thus provides vapor
communication between the air inlet of horn 86 and the crankcase 36
of the engine. Valve 96 includes a spool 104 having a base portion
106 for seating coaction with an aperture 107 in the valve housing
and a conical portion 108 for throttling coaction with a port 110
defined at the base of fitting 100. A coil spring 112 acts to
normally maintain spool base portion 106 in seating engagement with
the valve housing to preclude communication between crankcase 36
and carburetor 44.
Fuel tank 12 includes a filler pipe 114 and a sending unit 116.
Pipe 114 is of known form and includes a cap 118. Sending unit 116
may be any of several known constructions; it includes a plug
member 120 carrying a fitting 122 for connection to an electrical
wire 128. Fuel line 124 extends to a fuel pump (not shown) which is
in turn communicated with carburetor 44. Fitting 122 communicates
with a syphon hose positioned inside tank 12 and terminal 126 is
electrically connected to a rheostat assembly positioned inside the
tank.
As previously stated, both the fuel tank and the carburetor fuel
bowl are vented to the engine crankcase. Specifically, a carburetor
vent hose 128 extends from carburetor vent fitting 82 to a fitting
130 press fitted into the sidewall of breather cap 95, and a fuel
tank vent hose 132 extends generally from the fuel tank to a
fitting 134 centrally press fitted into the top wall of the
breather cap and extending downwardly therein within annular filter
element 102. It will be noted that hoses 90, 128, and 132 all
connect with a common cap member 95. It is contemplated that this
breather cap member would be mounted on the adjacent mouth or spout
on the valve cover with a tight, resiliently sealing, but removable
fit and that a separate oil filler cap (not shown) would be
provided to allow addition of lubricating oil to the crankcase. Cap
95 serves only as a connector for the various vent and breather
hoses and therefore need not be removed during the normal operation
and servicing of the vehicle.
When engine 10 is operating under a steady state or cruise
condition, carburetor vent valve 62 is closed by valve disc 78,
fuel tank 12 is vented to the crankcase through vent hose 132, and
blowby is entering the crankcase around pistons 22; crankcase
ventilation valve 96 is maintained at this time in a throttling
condition by the interaction of intake manifold vacuum and valve
spring 142. Specifically, base portion 106 of valve spool 104 is
lifted clear of aperture 107 and conical portion 108 defines an
annular throttling orifice with port 110 with the size of the
orifice increasing with increasing engine speed because of the
diminishing magnitude of the manifold vacuum with increasing engine
speed. Under these conditions, the evaporative emissions entering
the crankcase from the fuel tank through vent hose 132 and the
blowby products entering the crankcase around the pistons are
constantly vented from the crankcase through ventilation valve 96
and enter the intake manifold from where they are routed to the
engine cylinders for combustion. Purging air continuously enters
the crankcase at this time through air cleaner horn 86, hose 90,
and breather cap 95; this air flows through the crankcase where it
picks up contaminants and thereafter leaves the crankcase through
ventilation valve 96 along with the evaporative emissions and the
blowby products.
When the engine is thereafter turned off, the invention evaporative
emission control system functions to allow the crankcase to serve
as a collector for the evaporative emissions from the fuel tank and
the carburetor fuel bowl. Specifically, when the engine is shut
off, vent hose 132 continues to vent the fuel tank to the
crankcase, and carburetor vent valve 62 is opened by the return
spring of the throttle linkage to vent the carburetor fuel bowl to
the crankcase through hose 128. The evaporative emissions from the
fuel tank and the carburetor fuel bowl during shut down or "hot
soak" conditions are thus routed to the crankcase where they are
stored. The emissions are precluded from leaving the crankcase by
the ventilation valve 96 which is now closed by the action of
spring 112. As the emissions, which are heavier than air, enter the
crankcase, they gradually and progressively displace the air in the
crankcase; the displaced air leaves the crankcase through the
breather cap, air hose 90, and air cleaner horn 86. The capacity of
the crankcase, valve covers, and connecting passages is quite large
relative to the volume of emissions generated by the fuel tank and
fuel bowl during typical shutdown conditions so that the storage
volume provided is normally more than adequate to handle the
emissions. If the storage capacity is exceeded, as for example due
to a long shutdown under rising temperature conditions, the
emissions in excess of the storage capacity leave the crankcase
through the breather cap 95 and air hose 90, and are trapped in a
charcoal canister 135 interposed in hose 90. Canister 135 includes
a cylindrical casing 200 receiving hose 90 at its opposite ends, a
lower screen 202 secured to the sidewall of the casing and defining
with the casing a lower plenum chamber 204, an upper screen 206
slidably mounted in the casing and defining with the casing on
upper plenum chamber 208, and a coil spring 210 urging screen 206
downwardly to compress a quantity of granulated activated charcoal
212 between screens 202 and 206. The activated charcoal in canister
135 functions in known manner to absorb the evaporative emissions
and preclude their discharge into the atmosphere through horn 86.
When the engine is started up following a shut down, the
ventilation valve 96 open immediately to vent the accumulated
evaporative emissions in the crankcase through hose 98 to the
intake manifold for combustion in the engine. As the evaporative
emissions leave the crankcase, fresh air is drawn into the
crankcase through air line 90 to purge the crankcase; if the
crankcase capacity has been exceeded during the preceding hot soak
cycle so that charcoal canister 135 has been required to absorb
evaporative emissions in excess of crankcase capacity, the fresh
air being drawn in through horn 86 and hose 90 will purge the
canister which yields all or at least a major portion of its
absorbed emissions to the fresh air in a desorption process. The
fresh air passing through hose 90 carries the desorption product
through the crankcase and through the ventilation valve for
combustion in the engine.
Provision for ensuring that vapor communication will always be
maintained between fuel tank vent line 132 and the vapor in the
fuel tank irrespective of the attitude of the tank and/or the
existent climatic conditions, thereby preventing liquid fuel
carryover into the crankcase may be included if desired. As best
seen in FIG. 1, vent line 132 does not communicate directly with
the fuel tank but rather is fitted onto the lower end of a vent
tube 136 positioned within a standpipe 138. Standpipe 138 includes
an upstanding pipe portion 140 having a closed upper end, and a
base portion 141 in which vent tube 136 is press fitted. Standpipe
138 is positioned on the floor 142 of the luggage compartment of
the vehicle with base portion 141 overlying and closing an opening
144 in floor 142 to allow tube 136 to extend downwardly through
opening 144 for connection to vent line 132. Standpipe 138 is
preferably positioned in the luggage compartment immediately
rearwardly of a wheel housing 146 as best seen in FIG. 4. In
addition to vent tube 136, standpipe 138 also houses vent tubes
148, 150, 152 and 154, each passing at its lower end with a press
fit through the base portion 141 as shown in FIG. 1.
Hoses 156 connect vent tubes 148, 150, 152 and 154 with a plurality
of horizontal vent tubes suitably positioned within the fuel tank.
Specifically, standpipe vent tube 148 is connected to fuel tank
vent tube 158 opening in the right front corner of the fuel tank,
standpipe vent tube 150 is connected to fuel tank vent tube 160
opening in the left front corner of the fuel tank, standpipe vent
tube 152 is connected to fuel tank vent tube 162 opening in the
left rear corner of the fuel tank, and standpipe vent tube 154 is
connected to fuel tank vent tube 164 opening in the right rear
corner of the fuel tank. It will be noted that vent tube 136
extends almost the full height of the standpipe, vent tubes 148 and
150 are of equal height and extend to a level just below that of
tube 136, vent tube 152 is cut off substantially flush with the
upper face of standpipe base portion 141, and vent tube 154 extends
to about half the height of tubes 148 and 150. The standpipe is
preferably positioned substantially over the fuel tank vent tubes
where the latter emerge from the fuel tank. Thus, in the disclosed
embodiment where the fuel tank vent tubes emerge from the fuel tank
adjacent the right front corner of the tank, the standpipe is
positioned at the right-hand side of the luggage compartment behind
the right-hand wheel housing as can be seen in FIG. 4.
The vent tube and standpipe arrangement preclude liquid carryover
from the fuel tank to the crankcase. Specifically, since a vent
tube is provided in each corner of the tank, at least one vent tube
will always be in communication with the vapor in the tank above
the liquid fuel irrespective of the attitude of the vehicle and/or
inertia forces generated by maneuvering of the vehicle. For
example, if the vehicle is parked on a downhill attitude, rear
vents 162, 164 communicate with the vapor in the tank to establish
the vapor communication with the crankcase. However, liquid fuel is
often trapped in the rear vent tubes due to sloshing, maneuvering
etc., so that, with the vehicle parked in a downhill attitude, the
rear vent tubes must be purged of liquid before the vapor can
escape to the crankcase. As the fuel in the tank vaporizes due to
heating of the fuel in response to increasing ambient temperatures,
a vapor pressure is created in the tank. Since the crankcase and
thus the standpipe are at atmospheric pressure, any increase in the
tank pressure creates a pressure differential as between the tank
and the standpipe corresponding to a head of fuel h. A head of fuel
h is thus created in the standpipe vent tubes. In the front
standpipe vent tubes 148, 150, this head h appears as a full head
above the level of the fuel in the tank since the associated fuel
tank vent tubes 158, 160 have their openings submerged due to the
downward slope of the tank. In the rear standpipe vent tubes, this
head appears as a head above the level of the fuel in the tank
since the combined vent tubes 164-154, for example, act in the
downhill attitude of the vehicle as a manometer with the vapor in
fuel tank vent tube 164 pushing against and counterbalancing the
column of trapped fuel in standpipe vent tube 154. It will be
apparent that the vapor cannot escape through tubes 154-164 until
the trapped fuel is completely purged from fuel tank vent tube 164
into standpipe vent tube 154. Since the head of fuel rises twice as
fast in the front standpipe vent tubes as in the rear standpipe
vent tubes, it is imperative that the distance from the lowest
point of the rear fuel tank vent tube to the level of the fuel in
the tank be less than half the distance from the level of the fuel
in the tank to the top of standpipe vent tubes 148 and 150 in order
to avoid having liquid spill over from standpipe vent tubes 148 and
150 before the vapor can escape to the crankcase through the rear
standpipe vent tubes. Accordingly, standpipe vent tubes 148, 150
are arranged to have a height greater than twice the height of
standpipe tube 154. A similar manometer effect occurs in combined
vent tubes 162--152 when the vehicle is parked on the right hand
side of a crowned road since fuel tank vent tube 162 is now vented
to the vapor in the tank while fuel tank vent tube 164 is submerged
in the liquid with the result that the vapor pressure head rises
twice as fast in the standpipe vent tube 154 as in standpipe vent
tube 152. Standpipe vent tube 154 is accordingly designed to have
an effective height of more than twice that of standpipe vent tube
152 to allow vapor to purge out of tube 152 before liquid fuel
spills over into the standpipe through tube 154. Any liquid that
does spill over into standpipe 138 as a result of the above
described purging actions will subsequently drain back into the
fuel tank through standpipe vent tube 152.
In order to ensure that some thermal expansion space will always
remain above the liquid fuel in the tank and thereby ensure that at
least one fuel tank vent tube will have vapor communication, an
auxiliary chamber 170 may be provided in the fuel tank. As best
seen in FIG. 5, chamber 170 is defined by a partition 172 formed
integrally within the fuel tank. Chamber 170 is sealed from the
remainder of the fuel tank except for a tiny bleed aperture 174 in
its lower wall and a larger bleed aperture 176 in its upper wall;
aperture 176 communicates with a passageway 178 which is defined
beneath an external bulge 180 in the top wall of the tank.
Passageway 178 is open at both ends for communication with the main
portion of the fuel tank. Even if the tank is filled by an
attendant to the very top, gasoline will thereafter bleed through
aperture 174 into chamber 170 to lower the level of the fuel in the
tank and provide a vapor space above the fuel. The air in chamber
170 displaced by the entering gasoline leaves through aperture
176.
It will be seen that the disclosed system provides an inexpensive
and effective means for recovering and eliminating evaporative
emissions. The disclosed system is inexpensive not only in terms of
initial cost but also in terms of upkeep since it utilizes existing
storage capacity rather than artificially, and expensively, created
capacity.
Although a preferred embodiment of the invention has been
illustrated and described in detail, it will be apparent that
various changes and modifications may be made in the disclosed
embodiment without departing from the scope or spirit of the
invention as defined by the appended claims:
* * * * *