U.S. patent number 3,885,545 [Application Number 05/375,973] was granted by the patent office on 1975-05-27 for carburetor cold enrichment device.
This patent grant is currently assigned to Ford Motor Company. Invention is credited to William W. Charron, William E. Dickensheets, Robert S. Harrison, Alvin P. Nowroski.
United States Patent |
3,885,545 |
Charron , et al. |
May 27, 1975 |
Carburetor cold enrichment device
Abstract
A carburetor without a choke valve has a cold enrichment system
that adds additional fuel and air to the system for cold weather
operation. The added mixture is controlled by a valve that is
responsive to engine and ambient temperatures as well as manifold
vacuum changes to properly proportion the added mixture.
Inventors: |
Charron; William W. (Orchard
Lake, MI), Dickensheets; William E. (Southfield, MI),
Harrison; Robert S. (Grosse Ile, MI), Nowroski; Alvin P.
(Livonia, MI) |
Assignee: |
Ford Motor Company (Dearborn,
MI)
|
Family
ID: |
23483148 |
Appl.
No.: |
05/375,973 |
Filed: |
July 2, 1973 |
Current U.S.
Class: |
123/179.15;
261/39.5; 123/179.16 |
Current CPC
Class: |
F02M
1/046 (20130101) |
Current International
Class: |
F02M
1/00 (20060101); F02M 1/04 (20060101); F02m
001/06 (); F02m 001/10 () |
Field of
Search: |
;123/18R,18T,179G,187.5R
;261/39B,39D,DIG.8 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Myhre; Charles J.
Assistant Examiner: Rutledge, Jr.; W.
Attorney, Agent or Firm: McCollum; Robert E. Zerschling;
Keith L.
Claims
We claim:
1. An air/fuel mixture enrichment device for use with a carburetor
having an induction passage open to air essentially at atmospheric
pressure at one end and adapted to be connected to an internal
combustion engine intake manifold at the opposite end, a throttle
valve mounted for a rotative movement across the passage between
closed and fully open positions to control flow through the
passage, and a fuel reservoir, the device including control means
to supply an air/fuel mixture to the carburetor during cold weather
engine cranking and running operations that is supplemental to the
carburetor normal air/fuel mixture supply, the control means
comprising;
first conduit means connecting fuel from the reservoir and air to a
port in the induction passage located at a point below the closed
position of the throttle valve and subject to engine vacuum,
first temperature responsive valve means variably movable from a
first position closing the conduit means when the temperature is at
a predetermined level to subsequent positions progressively opening
wider the conduit means when the temperature progressively
decreases below the predetermined level, and
vacuum servo means responsive to the engine vacuum attaining an
engine running level and acting thereon for moving the valve means
at times in a closing direction to decrease the supplemental fuel
and airflow,
second temperature responsive means operably connected to the servo
means for controlling the movement of the servo means as a function
of temperature changes,
the second temperature responsive means being responsive to ambient
temperature changes from a predetermined level.
2. An enrichment device as in claim 1, wherein the valve means
includes means responsive to changes in engine operating
temperatures from a predetermined level for moving the valve
means.
3. An air/fuel mixture enrichment device for use with a carburetor
having an induction passage open to air essentially at atmospheric
pressure at one end and adapted to be connected to an internal
combustion engine intake manifold at the opposite end, a throttle
valve mounted for a rotative movement across the passage between
closed and fully open positions to control flow through the
passage, and a fuel reservoir, the device including control means
to supply an air/fuel mixture to the carburetor during cold weather
engine cranking and running operations that is supplemental to the
carburetor normal air/fuel mixture supply, the control means
comprising;
first conduit means connecting fuel from the reservoir and air to a
port in the induction passage located at a point below the closed
position of the throttle valve and subject to engine vacuum,
first temperature responsive valve means variably movable from a
first position closing the conduit means when the temperature is at
a predetermined level to subsequent positions progressively opening
wider the conduit means when the temperature progressively
decreases below the predetermined level, and
vacuum servo means responsive to the engine vacuum attaining an
engine running level and acting thereon for moving the valve means
at times in a closing direction to decrease the supplemental fuel
and airflow,
the temperature responsive valve means including means responsive
to changes in engine operating temperature levels from a
predetermined level for moving the valve means,
the last mentioned means comprising a bimetallic coil spring, the
valve means comprising a spool valve having first and second spaced
lands interconnected by a neck portion of reduced diameter, means
connecting one end of the coil spring to the spool valve, second
conduit means supplying engine exhaust manifold heated air to the
first conduit means past the coil spring and spool valve lands, the
first land blocking the flow of the heated air during engine
vacuums lower than engine running levels and unblocking the flow
upon movement of the valve in one direction, the movement of the
valve in the one direction from the first land closed position
moving the neck portion to restrict fuel flow from the reservoir,
the second land variably controlling the flow of the heated air and
fuel as well as additional airflow to the first conduit means,
movement of the second land to one position completely blocking all
flow to the first conduit means.
4. An enrichment device as in claim 3, wherein the servo means and
spool valve are interconnected by a lost motion connection
permitting a limited independent operation of each of the servo
means and spool valve.
5. An air/fuel mixture enrichment device for use with a carburetor
having an induction passage open to air essentially at atmospheric
pressure at one end and adapted to be connected to an internal
combustion engine intake manifold at the opposite end, a throttle
valve mounted for a rotative movement across the passage between
closed and fully open positions to control flow through the
passage, and a fuel reservoir, the device including control means
to supply an air/fuel mixture to the carburetor during cold weather
engine cranking and running operations that is supplemental to the
carburetor normal air/fuel mixture supply, the control means
comprising;
first conduit means connecting fuel from the reservoir and air to a
port in the induction passage located at a point below the closed
position of the throttle valve and subject to engine vacuum,
first temperature responsive valve means variably movable from a
first position closing the conduit means when the temperature is at
a predetermined level to subsequent positions progressively opening
wider the conduit means when the temperature progressively
decreases below the predetermined level, and
vacuum servo means responsive to the engine vacuum attaining an
engine running level and acting thereon for moving the valve means
at times in a closing direction to decrease the supplemental fuel
and airflow,
second temperature responsive means operably connected to the servo
means for controlling the movement of the servo means as a function
of temperature changes,
the second temperature responsive means comprises a bimetallic
spring coil responsive to changes in ambient temperature conditions
from a predetermined level, and further means connected to the coil
for movement therewith variably into the path of movement of the
servo means to variably restrict the movement of the servo means
and valve means as a function of the temperature.
6. An enrichment device as in claim 5, wherein the further means
comprises a member having a stepped face, the servo means having a
plunger connected to the valve means by a lost motion connection
and projecting towards the steps of the stepped face for individual
engagement therewith, spring means biasing the plunger towards the
valve means, the steps being of progressively greater axial depth
relative to the axis of the plunger, the movement of the coil in
response to temperature changes progressively presenting the steps
for engagement by the plunger to vary and limit its movement and
thereby vary the position of the valve means.
Description
This invention relates, in general, to an internal combustion
engine carburetor. More particularly, it relates to a device for
use during cold weather engine cranking and running operations to
supply a mixture of air and fuel to the carburetor that supplements
the normal running air/fuel mixture carburetor requirements.
The advent of lower vehicle hoodlines necessitates a change in
engine carburetion design. The prior art carburetor designs of the
downdraft type generally include in the induction passage a choke
valve located above the fuel metering venturi. This adds height to
the carburetor and necessitates either providing a hump in the hood
or higher hood profiles.
This invention relates to a carburetor design that eliminates the
need for a choke valve and thereby permits decreasing the overall
height of the carburetor. The invention compensates for the lack of
a choke system by providing a cold enrichment device that adds fuel
and air to the carburetor during cold weather operation to
supplement that fuel and air normally supplied to the carburetor
under warm operating conditions. The conventional choke valve
effects an overrich mixture during engine cranking operations,
followed by a cracking open of the choke valve to lean the mixture
to a less rich but still richer than normal level. The conventional
choke valve, therefore, controls the flow of both air and fuel and
causes additional fuel to be added to the system during cold
weather operation.
The present invention accomplishes the same objectives as a
conventional choke valve without requiring the use of one.
More particularly, the invention connects an additional conduit
from the carburetor fuel reservoir with additional air to a point
in the carburetor induction passage downstream of the throttle
valve. The flow of extra fuel and air is controlled by a valve
movable in response to temperature changes as well as manifold
vacuum changes to schedule a desired air/fuel mixture richness
corresponding to that normally provided by a conventional choke
valve. During cranking of the engine, therefore, an overrich
mixture is supplied to the engine. When the manifold vacuum
increases above the engine cranking level, the rich mixture is
immediately leaned by the valve closing down the added fuel supply
somewhat and allowing other means to introduce further heated air
to the system. Various temperature and vacuum controls
automatically schedule the correct proportion of additional fuel
and air to the engine until the normal engine operating
temperatures are reached, at which point the enrichment device is
completely shut off so that the carburetor fuel system then
operates in a conventional manner.
It is a primary object of the invention, therefore, to provide a
cold enrichment system for an internal combustion engine carburetor
to supplement the normal carburetor air/fuel mixture requirements
during cold weather engine cranking and running operations.
It is a further object of the invention to provide a cold
enrichment device of the type described in which a valve movable by
temperature and manifold vacuum controls automatically schedules
additional amounts of fuel and airflow to the carburetor in
accordance with engine and ambient temperatures.
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 the preferred embodiment
thereof; wherein,
FIG. 1 is a top or plan view of a carburetor embodying the
invention;
FIGS. 1a and 2 are enlarged cross-sectional views taken on planes
indicated by and viewed in the direction of the arrows 1a --1a and
2--2, respectively, of FIG. 1; and,
FIGS. 3 and 4 are cross-sectional views taken on planes indicated
by and viewed in the direction of the arrows 3--3 and 4--4,
respectively, of FIG. 1.
FIGS. 1 and 1a show in general a carburetor of the downdraft type
on which the cold enrichment device to be described is installed.
This particular carburetor is of the variable venturi type. It has
a rectangular induction passage 10, one wall 12 of which is
pivotally movable and has the profile of one-half of a venturi.
FIG. 1a also shows that the opposite cooperating wall 14 is also
formed with a mating profile of a portion of a venturi. The opening
10 thereby comprises a variable area, rectangular venturi in which
the airflow varies in proportion to the opening movement of the one
wall 12 of the induction passage.
The movable wall 12 is pivotally mounted at 15 on the carburetor
body and has a fuel metering rod 16 that is tapered for cooperation
with a main fuel metering jet 18. The jet is located in an aperture
in sidewall 14 at approximately the throat or constricted section
of the venturi. The carburetor body includes a fuel reservoir 20
with a passage 22 conducting fuel to the main metering jet 18; a
conventional throttle valve 24 in the induction passage below the
venturi to control the flow of air and fuel through the passage;
and a spring returned, vacuum actuated diaphragm 26 connected to
the space between the throttle valve and venturi for moving the
venturi wall 12 as a function of changes in venturi vacuum upon
movement of the vehicle accelerator pedal between idle and wide
open throttle speed positions. It will be seen, therefore, that the
air and fuel flow change proportionally with movements of the
venturi wall. Further details of construction and operation of this
particular carburetor are not given since they are believed to be
unnecessary for an understanding of the invention.
Returning to FIG. 1, the cold enrichment device 28 of the invention
in this case is attached to one end of the carburetor, and is shown
more clearly in cross section in FIG. 2. FIG. 2 also illustrates
schematically the carburetor induction passage 10 and the float
bowl or fuel reservoir 20.
The cold enrichment device shown in FIG. 2 consists of a
multi-piece, hollow casting 50 that is open at opposite ends 52 and
54. The casting defines hollow chambers 56 and 58 sealingly
separated by a narrow portion 60 of the casting. The chamber 56 has
three ports 62, 64 and 66 that project through the sidewall. The
port 62 connects by a passage 68 to a port 70 in the carburetor
induction passage 10 located just below the closed position of the
throttle valve 24 so as always to be subject to engine intake
manifold vacuum. The port 64 is connected by a passage 72 to a port
74 in the induction passage at a point located above the closed
position of the throttle valve 24 so as to be subject to
atmospheric pressure and to be a source of additional clean air for
the cold enrichment device. Port 66 connects by a passage 76 to a
tube 78 opening into the carburetor fuel reservoir. The additional
fuel required by the cold enrichment device thus is inducted
separately from the main source of fuel supply that supplies the
carburetor requirements during normal engine running operation. A
further passage 80 is formed in casting 50 for conducting this fuel
to the port 62, in a manner to be described.
The wall portion 82 defining a portion of passage 80 also serves as
a guide for an annular rib cage and valve body 84. The latter is
mounted within the open end of chamber 56 against a shoulder 87 on
the casting. More specifically, the cage 84 has a reduced diameter
front portion 86 consisting of circumferentially spaced ribs 88
that slidably house a conically shaped spool type valve land 90.
The rear portion of cage 84 includes a second valve body 92 that
has a valve seat 94 formed at one end and openings 96 at the
opposite end. The openings communicate with a passage 98 connected
by a passage 100 to the fuel passage 80.
Slidably received within valve body 92 is a second conically faced
valve land 102. The land is connected by first and second reduced
diameter stem portions 104 and 106 to the first valve land 90.
The annular rib cage 84 has a central partition 108 that defines an
orifice type valve opening area 110 for cooperation with the
slightly lesser diameter stem portion 104 and the more reduced neck
portion 106. These two diameters provide varying areas for the flow
of fuel from the passage 98 to the ports 64 and 62 in chamber 56.
The end portion 112 of rib cage 84 also constitutes a valve opening
cooperating with the conical face of valve land 90 either to
completely block communication of flow to port 62 or at other times
to vary the flow as a degree of axial movement of the valve.
At the left hand end of the enrichment device, as seen in FIG. 2, a
thermostatically responsive bimetallic coil spring 114 is housed in
an annular hollow casting 116 secured to the end 54 of casting 50.
More particularly, the inner end (not shown) of the spring coil is
anchored to a stationary stub shaft 120 fixed to casting 116, as
best seen in FIG. 3. The opposite end of coil spring 114 is engaged
in a slot in the upturned end 124 of a lever 126 that is pivotally
mounted on the casting 116 at 127. The lower end 128 of lever 126
is loosely mounted within a box-like bracket 130 fixed to the end
of a plunger or shaft 132 integral with the valve lands 102 and
90.
An air passage 134 is adapted to be connected to a tube leading
from a conventional engine exhaust manifold heat stove to supply
heated air at times to the spring coil as the engine warms. This
will cause an expansion of the coil and counterclockwise rotation
of lever 126 to move the spool valve lands to the right for
purposes to be described. Likewise, cooling of the engine operating
temperatures will cause a contraction of the spring coil 114 and a
resultant clockwise rotation as seen in FIG. 2 for movement of
plunger 132 towards the left.
The right-hand casting portion is closed at its end 52 by the
annular flexible diaphragm member 140 of a vacuum servo 141.
Secured to the diaphragm at its central portion is a plunger 144
that extends sealingly through the stationary servo housing 146 and
the connecting casting portion 60 into an annular recess 148 in the
conical valve land 90. An enlarged guide and retaining end portion
150 is slidably received within the recess to constitute a lost
motion connection between the plunger 144 and the valve land 90.
The housing 146 serves as a stop for the leftward movement of
diaphragm 140, which is biased to that position by a compression
spring 152. The spring is seated at its opposite end against a
suitable retainer indicated schematically at 154.
A second thermostatically responsive bimetallic coil spring element
156 is enclosed within a hollow housing or shell 158 secured to the
open end 52 of casting 50. This element in this case is responsive
to ambient temperature conditions. More particularly, the coil
spring 156 has the inner end (not shown) mounted on a stub shaft
160 projecting from the shell wall (FIG. 4). The opposite end of
the coil is received in a slot in the upturned end 164 of a lever
166 mounted on a pivot 168 also mounted in the shell wall. In this
case, loosely mounted on the pin 168 between a pair of washers 170
is a fast idle speed cam plate 172. The plate has a first elongated
slot 174 that engages the shank portion of pin 168 and a second
shorter elongated slot 176 that is engaged by the shank of a pin
178 mounted on the lever 166. The lower portion of plate 172 is
provided with a number of receding steps 178 on one edge that are
each adapted to cooperate individually with the end of the plunger
144 to limit its rightward movement as a function of ambient
temperature conditions. A manifold vacuum passage 180 connects
manifold vacuum to the chamber 58 defined within casting 158 to
move diaphragm 140 and plunger 144 rightwardly against whichever
step 178 is in the path of the plunger at that particular time. As
ambient temperature increases, the rotation of lever 166 in a
clockwise direction will raise the cam plate 172 to permit the
plunger 144 to then engage the next succeeding step and move
further to the right.
In operation, the parts shown in FIG. 2 are in the engine off,
cranking position. The thermostatic coil spring 114 is shown in the
coldest position in which it exerts the greatest leftward closing
force on the valve land 102. The spool valve 179, therefore, is
pulled to the left the maximum amount shutting the heated air
orifice 182. The ambient temperature responsive coil spring 156
also is shown in its coldest position positioning the plate 172
downwardly to the lowest position so that the high cam step 184 is
located opposite the end of plunger 144.
Spool valve land 90 is positioned so that the passage opening 112
interconnects air port 64 to manifold port 62. The valve reduced
neck portion 106 provides the larger area orifice opening 110
through which cranking fuel admitted to passage 98 will flow.
When the engine is cranked for starting purposes the manifold
vacuum at this time acting on diaphragm 140 is not great enough to
overcome the force of spring 152. Accordingly, plunger 144 is not
moved in this case by diaphragm 140. This initial manifold vacuum
or cranking vacuum, however, in port 70 is sufficient to create a
pressure differential across the opening 112 to draw clean air from
port 64 into manifold vacuum port 62. Simultaneously, a pressure
differential is caused across fuel orifice 110 causing the flow of
additional fuel from the fuel conduit 78 through orifice 110 into
the manifold vacuum port 62 where it flows to the induction passage
through port 70. This results in a cranking air/fuel mixture that
is overrich to provide the necessary fuel vapor for starting the
engine.
As soon as the engine is started, the increased engine running
vacuum acting on diaphragm 140 now pulls the plunger 144 to the
right against the high cam stop 184. This immediately moves spool
valve 179 to the right to open orifice 182. A pressure differential
then is created across the orifice permitting the flow of hot
exhaust manifold heated air at near atmospheric pressure from
conduit 134 into the coil spring chamber 116 and out through the
orifice 182 to mix with the air from port 64 and fuel flow from
passage 98 flowing into the manifold. Also in this case, the
rightward movement of plunger 144 will move the larger diameter
stem portion 104 of the spool valve 179 into the fuel orifice
opening 110 to decrease the orifice size. This will immediately
decrease the quantity of additional fuel flowing from the reservoir
20 and thereby lean out the cranking mixture to a less fast but
faster than normal cold running idle speed mixture, assuming cold
operation continues.
The spool valve 179 will continue to move to the right either as a
function of the heating of the engine temperature responsive spring
coil 114 or responsive to increases in ambient temperature as
reflected by the coil spring 156 raising the fast idle cam plate
172 to thereby permit further rightward movement of plunger 144. It
will be seen, therefore, that when the engine temperature reaches
its normal operating level, the spool valve lands 102 and 90 will
have moved to the right sufficient to completely close outlets 110
and 112 by the conical backside 186 of valve land 102 and the
conical face of land 90 to thereby block off all flow of additional
fuel and air into the manifold passage 68 and port 70. The cold
enrichment device is thereby shut off. It will also be seen that
this will be accomplished regardless of the ambient temperature
since there is a lost motion connection between the plunger 144 and
the spool valve land 90.
It will be seen, therefore, that the invention provides a cold
enrichment device to provide a supplemental mixture of air and fuel
to the engine during engine cranking conditions where an overrich
mixture is demanded; and during engine running conditions when it
is desired to immediately lean the cranking mixture to a less rich
mixture but richer than normal because of cold operating conditions
to overcome the effects of cold engine friction and poor fuel
vaporization. It will be seen that the above is all accomplished
proportional to engine and ambient temperatures.
It will further be seen that the engine provides good cold weather
accelerations because when the manifold vacuum decays to a low
level in the ambient temperature chamber 182, the spring 152 will
force the spool valve 179 to the left to thereby open the valve in
proportion to the vacuum decay below the spring preload force and
provide additional fuel by presenting the smaller neck portion 106
of the valve in the fuel orifice 110. The system, therefore,
responds to carburetor airflow and manifold vacuums to meter the
added fuel flow accurately during these times.
While the invention has been described and illustrated in its
preferred embodiment, it will be clear to 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. For
example, it will be clear that a symmetrical spool land could be
substituted for the conically faced land 90 of the spool valve; in
this case, no pressure differential would act on the valve as it
does in the preferred embodiment, where there is a tendency for the
valve to quickly shut when it approaches the closing position.
* * * * *