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Claims  |
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I claim:
1. A carburetor for a combustion engine, comprising induction passage means
for supplying motive fluid to said engine, a source of fuel, main fuel
metering system means communicating generally between said source of fuel
and said induction passage means, idle fuel metering system means
communicating generally between said source of fuel and said induction
passage means, and a closed-loop feedback fuel control system, said system
comprising selectively controlled modulating valving means effective to
controllably alter the rate of metered fuel flow through each of said main
fuel metering system means and said idle fuel metering system means, first
electrical circuit means effective for sensing the oxygen content within
the exhaust gases of said engine and in response thereto controlling said
valving means, said first electrical circuit means comprising oxygen
sensor means effective for sensing the relative amount of said oxygen in
said exhaust gases and producing in response thereto an electrical output
signal, said system being free of any means to monitor any exhaust gas
component other than oxygen, means for comparing said output signal to a
preselected reference value, amplifier means for amplifying any difference
as between said preselected value and said output signal and for producing
an electrical control signal effective for controlling said modulating
valving means, and additional circuit means effective during selected
engine operating parameters for rendering said first electrical circuit
means ineffective for controlling said modulating valving means in
response to said relative amount of said oxygen sensed in said exhaust
gases.
2. A carburetor according to claim 1 wherein said modulating valving means
comprises solenoid means.
3. A carburetor according to claim 1 wherein said modulating valving means
comprises pressure responsive motor means.
4. A carburetor according to claim 1 wherein said modulating valving means
comprises first and second valve means, wherein said idle fuel metering
system means comprises idle air bleed means, wherein said first valve
means is effective to vary the effective flow area of said idle air bleed
means in order to thereby alter said rate of metered fuel flow through
said idle fuel metering system means, wherein said main fuel metering
means comprises metering restriction means, and wherein said second valve
means is effective to vary the effective flow area of said metering
restriction means to thereby alter said rate of metered fuel flow through
said main fuel metering system means.
5. A carburetor according to claim 4 wherein said main fuel metering system
means comprises first and second passage means communicating with said
source of fuel, wherein said metering restriction means comprises first
and second flow restrictor means, wherein said first and second flow
restrictor means are respectively situated in said first and second
passage means, wherein said second valve means is effective to vary the
effective flow area of said second flow restrictor means, and wherein said
second passage means communicates generally with first passage means at a
point downstream of said first restrictor means.
6. A carburetor according to claim 4 wherein said idle air bleed means
comprises first and second air bleed orifices, and wherein said first
valve means is effective for varying the effective flow area of said first
air bleed orifice.
7. A carburetor according to claim 4 wherein at least one of said first and
second valve means is pressure responsive.
8. A carburetor according to claim 4 wherein said first and second valve
means are each pressure responsive.
9. A carburetor according to claim 4 wherein said idle air bleed means
comprises first and second air bleed orifices, wherein said first valve
means is effective for varying the effective flow area of said first air
bleed orifice, wherein said main fuel metering system means comprises
first and second passage means communicating with said source of fuel,
wherein said metering restriction means comprises first and second flow
restrictor means, wherein said first and second flow restrictor means are
respectively situated in said first and second passage means, wherein said
second valve means is effective to vary the effective flow area of said
second flow restrictor means, and wherein said second passage means
communicates generally with said first passage means at a point downstream
of said first restrictor means.
10. A carburetor according to claim 9 wherein said first and second valve
means are pressure responsive.
11. A carburetor according to claim 1 and further comprising venturi means
carried in said induction passage means, wherein said main fuel metering
system means comprises main fuel discharge nozzle means situated generally
in the throat of said venturi means, and further comprising variably
positionable throttle valve means situated in said induction passage
means, idle fuel discharge aperture means formed in a wall of said
induction passage means and situated as to be generally juxtaposed to a
portion of said throttle valve means.
12. A carburetor according to claim 11 wherein said main fuel metering
system means further comprises a main fuel well, a first flow restrictor
communicating between said source of fuel and said main fuel well, a
second flow restrictor communicating between said main fuel well and said
source of fuel, said first and second flow restrictors being in generally
parallel flow relationship to each other, and wherein said modulating
valving means is effective for varying the effective flow area of one of
said first and second flow restrictors.
13. A carburetor according to claim 12 wherein said idle fuel metering
system means comprises first air bleed orifice means effective for
bleeding generally ambient atmospheric air into the fuel flowing through
said idle fuel metering system means, and further comprising second air
bleed orifice means effective for bleeding generally ambient atmospheric
air into said fuel flowing through said idle fuel metering system means,
and wherein said modulating valving means is effective for barying the
effective flow area of said second air bleed orifice means.
14. A carburetor according to claim 13 wherein said modulating valving
means comprises a first variably positionable valve member, a second
variably positionable valve member, a first pressure responsive wall
member operatively connected to said first valve member, a second pressure
responsive wall member operatively connected to said second valve member,
said first and second wall members each being adapted to be exposed to a
controlled pressure differential as to be thereby urged in respective
first directions, and resilient means operatively connected to said first
and second valve members to yieldingly resist movement of said first and
second valve members in said first direction.
15. A carburetor according to claim 14 wherein said pressure differential
is at least in said determined by the magnitude of venturi vacuum
generated by air flow through said venturi throat.
16. A carburetor according to claim 14 wherein said pressure differential
is at least in part determined by engine vacuum communicated from said
engine to said first and second pressure responsive wall members.
17. Electrical closed-loop circuit means for a fuel metering device having
valving means for controlling the rate of flow of fuel into an associated
engine, comprising composition of exhaust gas sensor means for sensing the
relative the exhaust gases of said engine and effective for producing a
first electrical output signal of a magnitude reflective of said relative
amount, first electrical buffer means effective for receiving said first
output signal and in response thereto creating a second output signal of
related magnitude, means for establishing a preselected reference
magnitude, electrical amplifier means effective to receive said second
output signal and compare said related magnitude to said reference
magnitude and produce an amplified third output signal of a magnitude
related to the difference therebetween, solenoid winding means associated
with said valving means for varying the operation of said valving means,
electrical switching means responsive to the occurrence of said third
output signal for energizing said solenoid winding means in relation to
the magnitude of said third output signal, and additional override circuit
means effective to at times prevent the application of said third output
signal to said electrical switching means.
18. Electrical circuit means according to claim 17 wherein said additional
override circuit means comprises additional switching means closable
during certain conditions of engine operation for effectively electrically
connecting the output of said amplifier means to electrical ground
potential.
19. Electrical circuit means according to claim 18 wherein said additional
switching means comprises at least first and second additional electrical
switch means, wherein one of said additional electrical switch means is
closed during periods of engine operation when said engine is at an
operating temperature less than a predetermined normal operating
temperature, and wherein the other of said additional electrical switch
means is closed during periods of engine operation when said engine is
operating under maximum engine loads.
20. Electrical circuit means according to claim 19 and further comprising
attenuating circuit means associated with said amplifier means effective
to cause said third output signal to be attenuated with respect to the
rate of change of said difference.
21. Electrical circuit means according to claim 17 wherein said first
mentioned switching means comprises transistor means situated generally
between a source of electrical potential and said solenoid winding means.
22. Electrical circuit means according to claim 21 wherein said transistor
means comprises a Darlington circuit. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
Even though the automotive industry has over the years, if for no other
reason than seeking competitive advantages, continually exerted
substantial efforts to increase the fuel economy of automotive engines,
the gains continually realized thereby have been deemed by various levels
of governments as being insufficient. Further, such levels of government
have also imposed regulations specifying the maximum permissible amounts
of carbon monoxide (CO), hydrocarbons (HC) and oxides of nitrogen
(NO.sub.x) which may be emitted by the engine exhaust gases into the
atmosphere.
Unfortunately, the available technology employable in attempting to attain
increases in engine fuel economy is, generally, contrary to that
technology employable in attempting to meet the governmentally imposed
standards on exhaust emissions.
For example, the prior art, in trying to meet the standards for NO.sub.x
emissions, has employed a system of exhaust gas recirculation whereby at
least a portion of the exhaust gas is re-introduced into the cylinder
combustion chamber to thereby lower the combustion temperature therein and
consequently reduce the formation of NO.sub.x.
The prior art has also proposed the use of engine crankcase recirculation
means whereby the vapors which might otherwise become vented to the
atmosphere are introduced into the engine combustion chambers for burning.
The prior art has also proposed the use of fuel metering means which are
effective for metering a relatively overlyrich (in terms of fuel) fuel-air
mixture to the engine combustion chamber means as to thereby reduce the
creation of NO.sub.x within the combustion chamber. The use of such
overly-rich fuel-air mixtures results in a substantial increase in CO and
HC in the engine exhaust, which, in turn, requires the supplying of
additional oxygen, as by an associated air pump, to such engine exhaust in
order to complete the oxidation of the CO and HC prior to its delivery
into the atmosphere.
The prior art has also heretofore proposed retarding of the engine ignition
timing as a further means for reducing the creation of NO.sub.x. Also,
lower engine compression ratios have been employed in order to lower the
resulting combustion temperature within the engine combustion chamber and
thereby reduce the creation of NO.sub.x.
The prior art has also proposed the use of fuel metering injection means
instead of the usually-employed carbureting apparatus and, under
superatmospheric pressure, injecting the fuel into either the engine
intake manifold or directly into the cylinders of a piston type internal
combustion engine. Such fuel injection systems, besides being costly, have
not proven to be generally successful in that the system is required to
provide metered fuel flow over a very wide range of metered fuel flows.
Generally, those injection systems which are very accurate at one end of
the required range of metered fuel flows, are relatively inaccurate at the
opposite end of that same range of metered fuel flows. Also, those
injection systems which are made to be accurate in the mid-portion of the
required range of metered fuel flows are usually relatively inaccurate at
both ends of that same range. The use of feedback means for altering the
metering characteristics of a particular fuel injection system have not
solved the problem because the problem usually is intertwined with such
factors as: (a) effective aperture area of the injector nozzle; (b)
comparative movement required by the associated nozzle pintle or valving
member; (c) inertia of the nozzle valving member; and (d) nozzle
"cracking" pressure (that being the pressure at which the nozzle opens).
As should be apparent, the smaller the rate of metered fuel flow desired,
the greater becomes the influence of such factors thereon.
It is now anticipated that the said various levels of government will be
establishing even more stringent exhaust emission limits of for example,
1.0/gram/ mile of NO.sub.x (or even less).
The prior art, in view of such anticipated requirements with respect to
NO.sub.x, has suggested the employment of a "three-way" catalyst, in a
single bed, within the stream of exhaust gases as a means of attaining
such anticipated exhaust emission limits. Generally, a "three-way"
catalyst (as opposed to the "two way" catalyst system well known in the
prior art) is a single catalyst, or catalyst mixture, which catalyzes the
oxidation of hydrocarbons and carbon monoxide and also the reduction of
oxides of nitrogen. It has been discovered that a difficulty with such a
"three-way 38 catalyst system is that if the fuel metering is too rich
(in terms of fuel), the NO.sub.x will be reduced effectively, but the
oxidation of CO will be imcomplete. On the other hand, if the fuel
metering is too lean, the CO will be effectively oxidized but the
reduction of NO.sub.x will be incomplete. Obviously, in order to make such
a "three-way" catalyst system operative, it is necessary to have very
accurate control over the fuel metering function of associated fuel
metering supply means feeding the engine. As hereinbefore described, the
prior art has suggested the use of fuel injection means with associated
feedback means (responsive to selected indicia of engine operating
conditions and parameters) intended to continuously alter or modify the
metering characteristics of the fuel injectio means. However, at least to
the extent hereinbefore indicated, such fuel injection systems have not
proven to be successful.
It has also heretofore been proposed to employ fuel metering means, of a
carbureting type, with feedback means responsive to the presence of
selected constituents comprising the engine exhaust gases. Such feedback
means were employed to modify the action of a main metering rod of a main
fuel metering system of a carburetor. However, tests and experience have
indicated that such a prior art carburetor and such a related feedback
means cannot, at least as presently conceived, provide the degree of
accuracy required in the metering of fuel to an associated engine as to
assure meeting, for example, the said anticipated exhaust emission
standards.
Accordingly, the invention as disclosed, described and claimed is directed
generally to the solution of the above and related problems and more
specifically to circuit means, structure, apparatus and systems enabling a
carbureting type fuel metering device to meter fuel with an accuracy at
least sufficient to meet the said anticipated standards regarding engine
exhaust gas emissions.
SUMMARY OF THE INVENTION
According to the invention, a carburetor having an induction passage
therethrough with a venturi therein has a main fuel discharge nozzle
situated generally within the venturi and a main fuel metering system
communicating generally between a fuel reservoir and the main fuel
discharge nozzle. An idle fuel metering system communicates generally
between a fuel reservoir and said induction passage at a location
generally in close proximity to variably openable throttle valve situated
in said induction passage downstream of the main fuel discharge nozzle.
Electrical circuit means are provided for sensing the oxygen content of
the exhaust gases and in turn controlling valving means which are provided
to controllably alter the rate of metered fuel flow through each of said
main and idle fuel metering systems in response to control signals
generated in said circuit means.
Various general and specific objects and advantages of the invention will
become apparent when reference is made to the following detailed
description of the invention considered in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings wherein for purposes of clarity certain details and/or
elements may be omitted from one or more views:
FIG. 1 illustrates, in side elevational view, a vehicular combustion engine
employing a carbureting apparatus and an el-ctrical control system
embodying teachings of the invention;
FIG. 2 is an enlarged view, in cross-section, of the carburetor of FIG. 1;
FIG. 3 is a graph illustrating, generally, fuel-air ratio curves obtainable
with structures employing teachings of the invention;
FIG. 4 is a graph depicting fuel-air ratio curves obtained from one
particular tested embodiment employing teachings of the invention;
FIG. 5 is a generally cross-sectional view of another form of carbureting
apparatus controlled in accordance with the teachings of the invention;
FIGS. 6 and 7 are each generally fragmentary and schematic illustrations of
different arrangements for variably and controllably determining the
magnitude of the actuating pressure differential employed as by structures
generally typically depicted as by FIG. 2 and 5;
FIG. 8 is a generally cross-sectional view illustrating yet another aspect
of the invention;
FIG. 9 is a schematic wiring diagram of one embodiment of logic and control
circuit means embodying teachings of the invention; and
FIG. 10 is a cross-sectional view of one embodiment of valving means
employable in the practice of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now in greater detail to the drawings, FIG. 1 illustrates a
combustion engine 10 used, for example, to propell an associated vehicle
as through power transmission means fragmentarily illustrated at 12. The
engine 10, for example, may be of the internal combustion type employing,
as is generally well known in the art, a plurality of power piston means
therein. As generally depicted, the engine assembly 10 is shown as being
comprised of an engine block 14 containing, among other things, a
plurality of cylinders respectively reciprocatingly receiving said power
pistons therein. A plurality of spark or ignition plugs 16, usually one
for each cylinder, are carried by the engine block and respectively
electrically connected to an ignition distributor assembly or system 18
operated in timed relationship to engine operation.
As is generally well known in the art, each cylinder containing a power
piston has exhaust aperture or port means and such exhaust port means
communicate as with an associated exhaust manifold which is fragmentarily
illustrated in hidden line at 20. Exhaust conduit means 22 is shown
operatively connected to the discharge end 24 of exhaust manifold 20 and
leading as to the rear of the associated vehicle for the discharging of
exhaust gases to the atmosphere.
Further, as is also generally well known in the art, each cylinder which
contains a power piston also has inlet aperture means or port means and
such inlet aperture means communicate as with an associated inlet manifold
which is fragmentarily illustrated in hidden line at 26.
As generally depicted, a carbureting type fuel metering apparatus 28 is
situated atop a cooperating portion of the inlet or intake manifold means
26. A suitable inlet air cleaner assembly 30 may be situated atop the
carburetor assembly 28 to filter the air prior to its extrance into the
inlet of the carburetor 28.
As generally shown in FIG. 2, the carburetor 28, employing teachings of the
invention, comprises a main carburetor body 32 having induction passage
means 34 formed therethrough with an upper inlet end 36, in which
generally is situated a variably openable choke valve 38 carried as by a
pivotal choke shaft 40, and a discharge end 42 communicating as with the
inlet 44 of intake manifold 26. A venturi section 46, having a venturi
throat 48, is provided within the induction passage means 34 generally
between the inlet 36 and outlet or discharge end 42. A main metering fuel
discharge nozzle 50, situated generally within the throat 48 of venturi
section 46, serves to discharge fuel, as is metered by the main metering
system, into the induction passage means 34.
A variably openable throttle valve 52, carried as by a rotatable throttle
shaft 54, serves to variably control the discharge fuel, as is metered by
the main metering system, into the induction passage means 34.
A variably openable throttle valve 52, carried as by a rotatable throttle
shaft 54, serves to variably control the discharge and flow of combustible
(fuel-air) mixtures into the inlet 44 of intake manifold 26. Suitable
throttle control linkage means, as generally depicted at 56, is provided
and operatively connected to throttle shaft 54 in order to affect throttle
positioning in response to vehicle operator demand. The throttle valve, as
will become more evident, also serves to vary the rate of fuel flow
metered by the associated idle fuel metering system and discharged into
the induction passage means.
Carburetor body means 32 may be formed as to also define a fuel reservoir
chamber 58 adapted to contain fuel 60 therein the level of which may be
determined as by, for example, a float operated fuel inlet valve assembly,
as is generally well known in the art.
The main fuel metering system comprises passage or conduit means 62
communicating generally between fuel chamber 58 and a generally upwardly
extending main fuel well 64 which, as shown, may contain a main well tube
66 which, in turn, is provided with a plurality of generally radially
directed operatures 68 formed through the wall thereof as to thereby
provide for communication as between the interior of the tube 66 and the
portion of the well 64 generally radially surrounding the tube 66. Conduit
means 70 serves to communicate between the upper part of well 64 and the
interior of discharge nozzle 50. Air bleed type passage means 72,
comprising conduit means 74 and calibrated restriction or metering means
76, communicates as between a source of filtered air and the upper part of
the interior of well tube 66. A main calibrated fuel metering restriction
78 is situated generally upstream of well 64, as for example in conduit
means 62, in order to meter the rate of fuel flow from chamber 58 to main
well 64. As is generally well known in the art, the interior of fuel
reservoir chamber 58 is preferably pressure vented to a source of
generally ambient air as by means of, for example, vent-like passage means
80 leading from chamber 58 to the inlet end 36 of induction passage 34.
Generally, when the engine is running, the intake stroke of each power
piston causes air flow through the induction passage 34 and venturi throat
48. The air thusly flowing through the venturi throat 48 creates a low
pressure commonly referred to as a venturi vacuum. The magnitude of such
venturi vacuum is determined primarily by the velocity of the air flowing
through the venturi and, of course, such velocity is determined by the
speed and power output of the engine. The difference between the pressure
in the venturi and the air pressure within fuel reservoir chamber 58
causes fuel to flow from fuel chamber 58 through the main metering system.
That is, the fuel flows through metering restriction 78, conduit means 62,
up through well 64 and, after mixing with the air supplied by the
discharges from nozzle 50 into induction passage means 34. Generally, the
calibration of the various controlling elements are such as to cause such
main metered fuel flow to start to occur at some pre-determined
differential between fuel reservoir and venturi pressure. Such a
differential may exist, for example, at a vehicular speed of 30 m.p.h. at
normal road load.
Engine and vehicle operation at conditions less than that required to
initiate operation of the main metering system are achieved by operation
of the idle fuel metering system, which may not only supply metered fuel
flow during curb idle engine operation but also at off idle operation.
At curb idle and other relatively low speeds of engine operation, the
engine does not cause a sufficient air flow through the venturi section 48
as to result in a venturi vacuum therein of sufficient magnitude to
operate the main metering system. Because of the relatively almost closed
throttle valve means 52, which greatly restricts air flow into the intake
manifold 26 at idle and low engine speeds, engine or intake manifold
vacuum is of a relatively high magnitude. This high manifold vacuum serves
to provide a pressure differential which operates the idle fuel metering
system.
Generally, the idle fuel system is illustrated as comprising calibrated
idle fuel restriction metering means 82 communicating as between the fuel
60, within fuel reservoir or chamber 58, and a generally upwardly
extending passage or conduit 84 which, at its upper end, is in
communication with a second generally vertically extending conduit 86 the
lower end of which communicates with a generally laterally extending
conduit 88. A downwardly depending conduit 90 communicates at its upper
end with conduit 88 while, at its lower end, it communicates with
induction passage means 34 as through aperture means 92. The effective
size of discharge aperture 92 is variably established as by an axially
adjustable needle valve member 94 threadably carried by body 32. As
generally shown and as generally known in the art, passage 88 may
terminate in a relatively vertically elongated discharge opening or
aperture 96 located as to be generally juxtaposed to an edge of throttle
valve 52 when such throttle valve 52 is in its curb-like or nominally
closed position. Often, apertures 96 is referred to in the art as being a
transfer slot effectively increasing the area for flow of fuel to the
underside of throttle valve 52 as the throttle valve is moved toward a
more fully opened position.
Conduit means 98, provided with calibrated air metering or restriction
means 100, serves to communicate as between an upper portion of conduit 86
and a source of atmospheric air as at the inlet end 36 of induction
passage 34.
At idle engine operation, the greatly reduced pressure area below the
throttle valve means causes fuel to flow from the fuel reservoir 58
through restriction means 82 and upwardly through conduit means 84 where,
generally at the upper portion thereof, the fuel intermixes with the bleed
air provided by conduit 98 and air bleed restriction means 100. The
fuel-air emulsion then is drawn downwardly through conduit 86 and through
conduits 88 and 90 ultimately discharged, posterior to throttle valve 52,
through the effective opening of aperture 92.
During off-idle operation, the throttle valve means 52 is moved in the
opening direction causing the juxtaposed edge of the throttle valve to
further effectively open and expose a greater portion of the transfer slot
or port means 96 to the manifold vacuum existing posterior to the throttle
valve. This, of course, causes additional metered idle fuel flow through
the transfer port means 96. As the throttle valve means 52 is opened still
wider and the engine speed increases, the velocity of air flow through the
induction passage 34 increases to the point where the resulting developed
venturi vacuum is sufficient to cause the hereinbefore described main
metering system to be brought into operation.
The structure as herein disclosed and described provides means, in addition
to those hereinbefore described, for controlling and/or modifying the
metering characteristics otherwise established by the fluid circuit
constants previously described. In the embodiment thus far disclosed,
among other cooperating elements, valving assemblies 102 and 104 are
provided to enable the performance of such modifying and/or control
functions.
Valve assembly 102 is illustrated as comprising variable but distinct
chambers 106 and 108 effectively separated as by a pressure responsive
wall or diaphragm member 110, which, in turn, has a valving member 112
operatively secured thereto for movement therewith. The valving surface
114 of valving member 112 cooperates with a calibrated aperture 116 of a
member 118 as to thereby variably determine the effective cross-sectional
flow area of said aperture 116 and therefore the degree to which
communication between the upper portion of conduit 86 and chamber 108 is
permitted. Resiliant means, as in the form of a compression spring 120
situated generally in chamber 106, serves to continually bias and urge
diaphragm member 110 and valving member 112 toward a fully closed position
against coacting aperture 116. As shown, chamber 108 is placed in
communication with ambient atmosphere preferably through associated
calibrated restriction or passage means 122 and via conduit means 98.
Without at this time considering the overall operation, it should be
apparent that for any selected differential between the manifold vacuum,
P.sub.m, and the pressure, P.sub.a, within reservoir 58, the "richness" of
the fuel delivered by the idle fuel metering system can be modulated
merely by the moving of valving member 112 toward and/or away from
coacting aperture means 116. That is, for any such given pressure
differential, the greater the effective opening of aperture means 116
becomes the more air is bled into the idle fuel passing from conduit 84
into conduit 86. Therefore, because of such proportionately greater rate
of idle bleed air, the less, proportionately, is the rate of metered idle
fuel flow, thereby causing a reduction in the richness (in terms of fuel)
in the fuel-air mixture supplied through the induction passage 34 and into
the intake manifold 26. The converse is also true; that is, as aperture
means 116 is more nearly totally closed, the total rate of flow of idle
bleed air becomes increasingly more dependent upon the comparatively
reduced effective flow area of restriction means 100 thereby
proportionately reducing the rate of idle bleed air and increasing,
proportionately, the rate of metered idle fuel flow. Accordingly, there is
an accompanying increase in the richness (in terms of fuel) in the
fuel-air mixture supplied through induction passage 34 and into the intake
manifold 26.
Valving assembly 104 is illustrated as comprising upper and lower variable
and distinct chambers 124 and 126 separated as by a pressure responsive
wall or diaphragm member 128 to which is secured one end of a valve stem
130 as to thereby move in response to and in accordance with the movement
of wall or diaphragm means 128. The structure 129 defining the lower
portion of chamber 126 serves to provide guide surface means for guiding
the vertical movement of valve stem 130; chamber 126 is vented to
atmospheric pressure, P.sub.a, as by vent or aperture means 132 formed as
through structure 129.
A first compression spring 134 situated generally within chamber 124
continually urges valve stem 130 in a downward direction as does a second
spring 136 which is carried generally about stem 130 and axially contained
as between structure 129 and a movable spring abutment 138 carried by stem
130.
An extension of stem 130 carries a valve member 140 with a valve surface
142, formed thereon, adapted to cooperate with a valving orifice 144
communicating generally between chamber 58 and a chamber-like area 146
which, in turn, communicates as via calibrated metering or restriction
means 148 and conduit means 150 with a portion of the main metering system
downstream of the main metering restriction means 78. As illustrated, such
communication may be at a suitable point within the main well 64.
Additional spring means 147 which may be situated generally in the
chamber-like area 146, serve to continually urge valve member 142 and stem
130 upwardly.
Without at this time considering the overall operation of the structure of
FIG. 2, it should be apparent that for any selected metering pressure
differential between the venturi vacuum, P.sub.v, and the pressure,
P.sub.a, within reservoir 58, the "richness" of the fuel delivered by the
main fuel metering system can be modulated merely by the moving of valving
member 140 toward and/or away from coacting aperture means 144. That is,
for any such given metering pressure differential, the greater the
effective opening of aperture means 144 becomes, the greater also becomes
the rate of metered fuel flow since one of the factors controlling such
rate is the effective area of the metering orifice means. With the opening
of orifice means 144 it can be seen that the then effective metering area
of orifice means 144 is, generally, additive to the effective metering
area of orifice means 78. Therefore, a comparatively increased rate of
metered fuel flow is consequently discharged, through nozzle 50, into the
induction passage means 34. The converse is also true; that is, as
aperture means 144 is more nearly or totally closed, the total effective
main fuel metering area decreases and approaches the effective metering
area determined by metering means 78. Consequently, the total rate of
metered main fuel flow decreases and a comparatively decreased rate of
metered fuel flow is discharged through nozzle 50, into the induction
passage 34.
As shown, chamber 106 and 124 are each in communication with conduit means
152, as via conduit means 154 and 156, respectively.
As illustrated in FIG. 1, conduit means 152 is placed in communication with
associated conduit means 158 effective for conveying a fluid control
pressure to said conduit 152 and chambers 106 and 124. For purposes of
illustration, such control pressure will be considered as being
sub-atmospheric and to that extent a control vacuum, V.sub.c, the
magnitude of which, of course, increases as the absolute value of the
control pressure decreases.
FIG. 1 also illustrates suitable logic control means 160 which, as
contemplated in the preferred mode of operation of the invention and as
hereinafter more fully described, comprises may be electrical logic
control means which may have suitable electrical signal conveying
conductor means 162, 164, 166 and 168 leading thereto for applying
electrical input signals, reflective of selected operating parameters, to
the circuitry of logic means 160. It should, of course, be apparent that
such input signals may convey the required information in terms of the
magnitude of the signal as well as conveying information by the absence of
the signal itself. Output electrical conductor means, as at 170, serves to
convey the output electrical control signal from the logic means 160 to
associated electrically operated control valve means 172. A suitable
source of electrical potential 174 is shown as being electrically
connected to logic means 160, while control valve means 172 may be
electrically grounded, as at 176.
In the preferred embodiment, the various electrical conductor means 162,
164, 166 and 168 are respectively connected to parameter sensing and
transducer signal producing means 178, 180 and 182. In the embodiment
depicted, the means 178 comprises oxygen sensor means communicating with
exhaust conduit means 22 at a point generally upstream of a catalytic
converter 184. The transducer means 180 may comprise electrical switch
means situated as to be actuated by cooperating lever means 186 fixedly
carried, as by the throttle shaft 54 and swingably rotatable therewith
into and out of operating engagement with switch means 181, in order to
thereby provide a signal indicative of the throttle 52 having attained a
preselected position.
The transducer 182 may comprise suitable temperature responsive means, such
as, for example, thermocouple means, effective for engine temperature and
creating an electrical signal in accordance therewith. For sake of clarity
certain of said transducer means are further illustrated in Figures
hereinafter more fully described.
A vacuum reservoir or tank 188 is shown being operatively connecte | | |
