Apparatus and system for controlling the air-fuel ratio supplied to a combustion engine

A carbureting type fuel metering apparatus has an induction passage into which fuel is fed by several fuel metering systems among which are a main fuel metering system and an idle fuel metering system, as generally known in the art; engine exhaust gas analyzing means sensitive to selected constituents of such exhaust gas creates feedback signal means which through associated solenoid transducer means become effective for controllably modulating the metering characteristics of the main fuel metering system, and, if desired, the idle fuel metering system as to thereby achieve the then desired optimum metering functions.

BACKGROUND OF THE INVENTION 
Even though the automotive industry has over the years, if for no other 
reason than seeking competitive advantages, continually exerted efforts to 
increase the fuel economy of automotive engines, the gains continually 
realized thereby have been deemed by various levels of governments to be 
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 the 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 overly-rich (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 system, 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 system 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: effective aperture area of the injector nozzle; comparative 
movement required by the associated nozzle pintle or valving member; 
inertia of the nozzle valving member and 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 also 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" 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 incomplete. 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 hereinafter 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 injection means. However, at least to 
the extent hereinafter 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 structure, apparatus and system 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 one aspect of the invention, a carburetor having an induction 
passage therethrough with a venturi therein having a main 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, and having an idle fuel metering system communicating 
generally between a fuel reservoir and said induction passage at a 
location generally in close proximity to an edge of a variably openable 
throttle valve situated in said induction passage downstream of the main 
fuel discharge nozzle, is provided with solenoid valving means effective 
to controllably alter the rate of metered fuel flow through the main fuel 
metering system and/or the idle fuel metering system as to thereby 
precisely control the rate of total metered fuel flow through such 
metering system to the associated engine. 
Various general and specific objects, advantages and aspects of the 
invention will become apparent when reference is made to the following 
detailed description of the invention considered in conjuction with the 
related accompanying drawings.

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 may, for example, 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, as for example 
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 entrance into the 
inlet of the carburetor 28. 
FIG. 2 illustrates the carburetor 28, employing teachings of the invention, 
as comprising 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 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 apertures 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 main 
well air bleed means 72, passes through conduit means 70 and 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 sufficient 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 and passage means 83 communicating 
as between a source of fuel, as within, for example, the fuel well 64, and 
a generally upwardly extending passage or 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-idle or nominally closed position. Often, aperture 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 as from the fuel reservoir 58 and 
well 64 through conduit means 83 and restriction means 82 and generally 
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 invention 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 disclosed, among other 
cooperating elements, solenoid valving means 102 is provided to enable the 
performance of such modifying and/or control functions. 
The solenoid valving means 102 is illustrated in greater detail in FIG. 3 
and the detail description thereof will hereinafter be presented in regard 
to the consideration of said FIG. 3. However, at this point, and still 
with reference to FIG. 2, it will be sufficient to point out that, in the 
embodiment disclosed, the solenoid means or assembly 102 has an operative 
upper end and an operative lower end and that such means or assembly 102 
is carried by the carbureting body means as, for example, to be partly 
received by the fuel reservoir 58. As generally depicted in FIG. 2, the 
lower operative end of solenoid valving means or assembly 102 is 
operatively received as by an opening 104 formed as in the interior of 
fuel reservoir 58 with such opening 104 generally, in turn, communicating 
with passage means 106 leading to the main fuel well 64. In fact, as also 
depicted, the idle fuel passage 83 may communicate with main well 64 
through a portion of such passage means 106 which is preferably provided 
with calibrated restriction means 108. 
The carbureting means 28 may be comprised of an upper disposed body or 
housing section 110 provided as with a cover-like portion 112 which serves 
to in effect cover the fuel reservoir 58. As also depicted in FIG. 2, the 
upper end of solenoid assembly 102 may be generally received through cover 
section 112 as to have the upper end of assembly 102 received as by an 
opening 114 formed as within a cap-like housing or body portion 116 which 
has a relatively enlarged passage or chamber 118 formed therein and 
communicating with laterally extending passages or conduits 120 and 122 
which, in turn, respectively communicate with illustrated downwardly 
extending passage or conduits 124 and 126. A conduit 128, formed in 
housing section 110, serves to interconnect and complete communication as 
between the lower end of conduit 124 and the upper end of conduit 86, 
while a second conduit 130, also formed in housing section 110, serves to 
interconnect and complete communication as between the lower end of 
conduit 126 and a source of ambient atmosphere as, preferably, at a point 
in the air inlet end of induction passage means 34. Such may take the form 
of an opening 132, communicating with passage means 34, situated generally 
downstream of choke ir air valve means 38. 
Referring in greater detail to both FIGS. 2 and 3, and in particular to 
FIG. 3, chamber 118 of housing portion 116 is shown as having a 
cylindrical passage portion 133 with an axially extending section thereof 
being internally threaded as at 135 in order to threadably engage a 
generally tubular valve seat member 137 which has its inner-most end 
provided with an annular seal, such as an O-ring, 139 thereby sealing such 
inner-most end of member 137 against the surface of cylindrical passage 
portion 133. As depicted, valve seat member 137 is generally necked-down 
at its mid-section thereby providing for an annular chamber 141 thereabout 
with such annular chamber 141 being, of course, partly defined by a 
cooperating portion of chamber or passage means 118. A plurality of 
generally radially directed apertures or passages 143 serve to complete 
communication as between annular chambe 141 and an axially extending 
conduit 145, formed in the body of valve seat member 137, which, in turn, 
communicates with a valve seat calibrated orifice or passage 147. After 
the valve seat member 137 is threadably axially positioned in the selected 
relationship, a suitable chamber closure member 149 may be placed in the 
otherwise open end of chamber 118. 
The solenoid assembly 102 is illustrated as comprising a generally tubular 
outer case 151 the upper end of which is slotted, as depicted at 153, and 
receives an upper end sleeve member 155 which may be secured to the outer 
case or housing 151 as by, for example, having the end member 155 pressed 
into the housing 151 and then further crimping housing 151 against member 
155. The outer surface 157 of the upper end of sleeve member 155 is 
closely received within cooperating receiving opening 114. 
A generally lower disposed end sleeve member 159 may be similarly received 
by the lower open end of case or housing 151 and suitably secured thereto 
as by, for example, crimping. Preferably, sleeve member 159 is provided 
with a flange portion 161 against which the end of case 151 may axially 
abut. The lower-most end of sleeve member 159 is closely received within 
cooperating opening or passage 104 and is provided with an annular groove 
or recess which, in turn, receives and retains a seal, such as, for 
example, an "O"-ring, 163 which serves to assure such lower-most portion 
of sleeve 159 being peripherally sealed against the surface of opening 
104. A generally medially situated chamber 165, formed in sleeve member 
159, is preferably provided with an internally threaded portion 167 which 
threadably engages a threadably axially adjustable valve seat member 169 
which, in turn, is provided with a calibrated valve orifice or passageway 
171 effective for communicating as between chamber 165 and passage or 
conduit means 106. A plurality of generally radially directed apertures or 
passages 173 serve to complete communication as between chamber 165 and 
the interior of the fuel reservoir 58. 
A spool-like member 175 has an axially extending cylindrical tubular 
portion 177 the upper end 179 of which is closely received within a 
cooperating recess-like aperture 181 provided by upper sleeve member 155. 
Near the upper end of spool member 175, such member is provided with a 
generally cylindrical cup-like portion 183 which, in turn, defines an 
upper disposed abutment or axial end mounting surface 185 which abuts as 
against a flat insulating member 187 situated against the lower end 
surface 189 of upper sleeve member 155 and about the upper portion 179 of 
tubular portion 177. An electrical coil or winding 191, carried generally 
about tubular portion 177 and between axial end walls 193 and 195 of spool 
175, may have its leads 197 and 199 pass as through wall portion 193 for 
connection to related circuitry, to be described. An annular bowed spring 
203 is axially contained between end wall 195 of spool 175 and the upper 
face 205 of lower sleeve member 159 and serves to resiliently hold the 
spool and coil assembly (175 and 191) in its depicted assembled condition 
within case or housing 151. 
A cylindrical armature 207, slidably reciprocatingly received within 
tubular portion 177 and aligned passageway 209, formed as in a bushing 
member 201 situated in sleeve member 155, has an upper disposed axial 
extension 211 and an integrally formed annular flange-like portion 217 
which internally engage and both laterally and axially retain a related, 
at least somewhat resilient, generally cup-like valve member 213. 
Somewhat similarly, the lower end of armature 207 is in operative abutting 
engagement with an axial extension, such as a pin or rod 221 which passes 
through a clearance passageway 223, formed in lower sleeve member 159, 
(including its tubular extension 215 received with tubular portion 177 of 
spool 175) and abutably engages a lower disposed valving member 225 which 
is provided with an axial extension 219 and integrally formed annular 
flange 251 which internally engage and laterally and axially retain, at 
least a somewhat resilient, generally cup-like valve member 227. A 
compression spring 229 has one end seated as against valve seat member 169 
and its other end seated against a suitable flange portion 231 of valving 
member 225 as to thereby normally yieldingly urge the valve member 227 and 
armature 207 axially away from the valve seat member 169 (that being the 
opening direction for valve passageway 171). 
As should be apparent, upon energization and de-energization of the coil 
191, armature 207 will experience reciprocating motion with the result 
that, in alternating fashion, valve member 213 will close and open 
calibrated passageway 147 while valve member 227 will open and close 
calibrated passageway 171. 
Without, at this point, considering the overall operation, it should now be 
apparent that when, for example, armature 207 is in its upper-most 
position and valve member 227 has fully closed passageway or orifice 147, 
all communication between conduits 120 and 122 is terminated. Therefore, 
the only source for any bleed air, to be mixed with raw or solid fuel 
being drawn through conduit means 83 (to thereby create the fuel-air 
emulsion previously referred to herein), is through bleed air passage 98 
and calibrated bleed air restriction means 100 (FIG. 2). The ratio of 
fuel-to-air in such an emulsion (under such an assumed condition) will be 
determined by the restrictive quality of air bleed restriction means 100, 
alone. 
However, let it be assumed that armature 207 has moved to its lowest-most 
position, as depicted, and that valve member 213 has, thereby, fully 
opened calibrated passageway 147. Under such an assumed condition, it can 
be seen that communication, via passage or orifice 147, is completed as 
between conduits 120 and 122 with the result that now, the top of conduit 
86 (FIG. 2) is in controlled (by virtue of the restrictive qualities or 
characteristics occurring at passageway 147) communication with a source 
of ambient atmosphere via conduits 128, 124, 120, 143, 145, 147, 122, 126 
and 130 and opening 132 (FIG. 2). Accordingly, it can be seen that under 
such an assumed condition the source for bleed air, to be mixed with raw 
or solid fuel being drawn through conduit means 83 (to thereby create the 
fuel-air emulsion hereinbefore referred to), is through both bleed air 
passage 98 and restriction means 100 as well as conduit means 130 as set 
forth above. Therefore, it can be readily seen that under such an assumed 
condition significantly more bleed-air will be available and the resulting 
ratio of fuel-to-air in such an emulsion will be accordingly significantly 
leaner (in terms of fuel) than the fuel-to-air ratio obtained when only 
conduit 98 and restriction 100 were the sole source for bleed air. 
Obviously, the two assumed conditions discussed above are extremes and an 
entire range of conditions exist between such extremes. Further, since the 
armature 207 and valve member 213 will, during operation, intermittently 
reciprocatingly open and close passageway or orifice 147, the percentage 
of time, within any selected unit or span of time used as a reference, 
that the orifice 147 is opened will determine the degree to which such 
variably determined additional bleed air becomes available for intermixing 
with the said raw or solid fuel. 
Generally, and by way of summary, with proportionately greater rate of flow 
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 or 
orifice means 147 is more nearly totally, in terms of time, closed, the 
total rate 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 and, thereby, 
resulting in an increase in the richness (in terms of fuel) in the 
fuel-air mixture supplied through induction passage 34 and into the intake 
manifold 26. 
Further, and still without considering the overall operation of the 
invention, 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 valve 
member 227 toward and/or away from coacting aperture means 171. That is, 
for any such given metering pressure differential, the greater the 
effective opening of aperture 171 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. Obviously, in the 
embodiment disclosed, the effective flow area of orifice means 171 is 
fixed; however, the effectiveness of flow permitted therethrough is 
related to the percentage of time, within any selected unit or span of 
time used as a reference, that the orifice means 171 is opened (valving 
means 225 and valve member 227 being moved away from passage means 171) 
thereby permitting an increase in the rate of fuel flow through passages 
173, 165, 171 and 106 to main fuel well 64 (FIG. 2). With such opening of 
orifice means 171 it can be seen that the metering area of orifice means 
171 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, the less that orifice means 
171 is effectively open or opened, the total effective main fuel metering 
area effectively decreases and approaches that effective 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. 
FIG. 1 further illustrates suitable logic control means 160 which may be 
electrical logic control means having 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 presence 
of 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 embodiment disclosed, 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 
shown, 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 180, 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 sensing engine 
temperature and creating an electrical signal in accordance therewith. 
FIG. 7 illustrates, by way of example, a form of circuitry employable as 
the logic circuitry 160 of FIG. 1. Referring now in greater detail to FIG. 
7, such a one embodiment of the control and logic circuit means 160 is 
illustrated as comprising a first operational amplifier 301 having input 
terminals 303 and 305 along with output terminal means 306. Input terminal 
303 is electrically connected as by conductor means 308 and a connecting 
terminal 310 as to output electrical conductor means 162 leading from the 
oxygen sensor 178. Although the invention is not so limited, it has, 
nevertheless, been discovered that excellent results are obtainable by 
employing an oxygen sensor assembly produced commercially by the 
Electronics Division of Robert Bosch GmbH of Schwieberdingen, Germany and 
as generally illustrated and described on pages 137-144 of the book 
entitled "Automotive Electronics II" published February 1975, by the 
Society of Automotive Engineers, Inc., 400 Commonwealth Drive, Warrendale, 
Pa., bearing U.S.A. copyright notice of 1975, and further identified as 
SAE (Society of Automotive Engineers, Inc.) Publication No. SP-393. 
Generally, such an oxygen sensor comprises a ceramic tube or cone of 
zirconium dioxide doped with selected metal oxides with the inner and 
outer surfaces of the tube or cone being coated with a layer of platinum. 
Suitable electrode means are carried by the ceramic tube or cone as to 
thereby result in a voltage thereacross in response to the degree of 
oxygen present in the exhaust gases flowing by the ceramic tube. 
Generally, as the presence of oxygen in the exhaust gases decreases, the 
voltage developed by the oxygen sensor decreases. 
A second operational amplifier 312 has input terminals 314 and 136 along 
with output terminal means 318. Inverting input terminal 314 is 
electrically connected as by conductor means 320 and resistor means 322 to 
the output 306 of amplifier 301. Amplifier 301 has its inverting input 305 
electrically connected via feedback circuit means, comprising resistor 
324, electrically connected to the output 306 as by conductor means 320. 
The input terminal 316 of amplifier 312 is connected as by conductor means 
326 to potentiometer means 328. 
A third operational amplifier 330, provided with input terminals 332 and 
334 along with output terminal means 336, has its inverting input terminal 
332 electrically connected to the output 318 of amplifier 312 as by 
conductor means 338 and diode means 340 and resistance means 342 serially 
situated therein. 
First and second transistor means 344 and 346 each have their respective 
emitter terminals 348 and 350 electrically connected, as at 354 and 356, 
to conductor means 352 leading to the conductor means 455 as at 447. A 
resistor 358, has one end connected to conductor 455 and its other 
resistor end connected to conductor 359 leading from input terminal 334 to 
ground 361 as through a resistor 363. Further a resistor 360 has its 
opposite ends electrically connected as at points 365 and 367 to 
conductors 359 and 416. A feedback circuit comprising resistance means 362 
is placed as to be electrically connected to the output and input 
terminals 336 and 332 of amplifier 330. 
A voltage divider network comprising resistor means 364 and 366 has one 
electrical end connected to conductor means 352 as at a point between 354 
and resistor 358. The other electrical end of the voltage divider is 
connected as to switch means 368 which, when closed, completes a circuit 
as to ground at 370. The base terminal 372 of transistor 344 is connected 
to the voltage divider as at a point between resistors 364 and 366. 
A second voltage divider network comprising resistor means 374 and 376 has 
one electrical end connected to conductor means 352 as at a point between 
354 and 356. The other electrical end of the voltage divider is connected 
as to second switch means 378 which, when closed, completes a circuit as 
to ground at 380. The base terminal 390 of transistor 346 is connected to 
the voltage divider as at a point between resistors 374 and 376. Collector 
electrode 382 of transistor 346 is electrically connected, as by conductor 
means 384 and serially situated resistor means 386 (which, as shown, may 
be variable resistance means), to conductor means 338 as at a point 388 
generally between diode 340 and resistor 342. Somewhat similarly, the 
collector electrode 392 of transistor 344 is electrically connected, as by 
conductor means 394 and serially situated resistor means 396 (which, as 
shown, may also be a variable resistance means), to conductor means 384 as 
at a point 398 generally between collector 382 and resistor 386. 
As also shown, resistor and capacitor means 400 and 402 have their 
respective one electrical ends or sides connected to conductor means as at 
points 388 and 404 while their respective other electrical ends are 
connected to ground as at 406 and 408. Point 404 is, as shown, generally 
between input terminal 332 and resistor 342. 
A Darlington circuit 410, comprising transistors 412 and 414, is 
electrically connected to the output 336 of operational amplifier 330 as 
by conductor means 416 and serially situated resistor means 418 being 
electrically connected to the base terminal 420 of transistor 412. The 
emitter electrode 422 of transistor 414 is connected to ground 424 while 
the collector 425 thereof is electrically connected as by conductor means 
426 connectable, as at 428 and 430, to related solenoid means 102, and 
leading to the related source of electrical potential 174 grounded as at 
432. 
The collector 434 of transistor 412 is electrically connected to conductor 
means 426, as at point 436, while the emitter 438 thereof is electrically 
connected to the base terminal 440 of transistor 414. 
Preferably, a diode 442 is placed in parallel with solenoid means 102 and a 
light-emitting-diode 444 is provided to visually indicate the condition of 
operation. Diodes 442 and 444 are electrically connected to conductor 
means 426 as by conductors 446 and 448. 
Conductor means 450, connected to source 174 as by means of conductor 446 
and comprising serially situated diode means 452 and resistance means 454, 
is connected to conductor means 455, as at 457, leading generally between 
amplifier 312 and one side of a zener diode 456 the other side of which is 
connected to ground as at 458. Additional resistance means 460 is situated 
in series as between potentiometer 328 and point 457 of conductor 455. 
Conductor 455 also serves as a power supply conductor to amplifier 312; 
similarly, conductor 426 and 464, each connected as to conductor means 
455, serve as power supply conductor to operational amplifier 301 and 330, 
respectively. 
OPERATION OF THE INVENTION 
Generally, the oxygen sensor 178 senses the oxygen content of the exhaust 
gases and, in response thereto, produces an output voltage signal which is 
proportional or otherwise related thereto. The voltage signal is then 
applied, as via conductor means 162, to the electronic logic and control 
means 160 which, in turn, compares the sensor voltage signal to a bias or 
reference voltage which is indicative of the desired oxygen concentration. 
The resulting difference between the sensor voltage signal and the bias 
voltage is indicative of the actual error and an electrical error signal, 
reflective thereof, is employed to produce a related operating voltage 
which is ultimately applied to the solenoid valving means 102 as by 
conductor means schematically shown at 197 and 199. 
The graph of FIG. 5 generally depicts fuel-air ratio curves obtainable by 
the inventon. For purposes of illustration, let it be assumed that curve 
200 represents a combustible mixture, metered as to have a ratio of 0.068 
lbs. of fuel per pound of air. Then, as generally shown, the carbureting 
device 28 could provide a flow of combustible mixtures in the range 
anywhere from a selected lower-most fuel-air ratio as depicted by curve 
202 to an uppermost fuel-air ratio as depicted by curve 204. As should be 
apparent, the invention is capable of providing an infinite family of such 
fuel-air ratio curves between and including curves 202 and 204. This 
becomes especially evident when one considers that the portion of curve 
202 generally between points 206 and 208 is achieved when valving member 
213 of FIG. 3 is moved as to more fully effectively open orifice 147, to 
its maximum intended effective opening, and cause the introduction of a 
maximum amount of bleed air therethrough. Similarly, that portion of curve 
202 generally between points 208 and 210 is achieved when valve member 227 
of FIG. 3 is moved downwardly as to thereby close orifice 171 to its 
intended minimum effective opening (or totally effectively closed) and 
cause the flow of fuel therethrough to be terminated or reduced 
accordingly. 
In comparison, that portion of curve 204 generally between points 212 and 
214 is achieved when valving member 213 of FIG. 3 is moved as to more 
fully effectively close orifice 147 to its intended minimum effective 
opening (or totally effectively closed) and cause the flow of bleed air 
therethrough to be terminated or reduced accordingly. Similarly, that 
portion of curve 204 generally between points 214 and 216 is achieved when 
valve member 227 is moved upwardly as to thereby open orifice 171 to its 
maximum intended opening and cause a corresponding maximum flow of fuel 
therethrough. 
It should be apparent that the degree to which orifices 147 and 171 are 
respectively effectively opened, during actual operation, depends on the 
control signal produced by the logic control means 160 and, of course, the 
control signal thusly produced by means 160 depends, basically, on the 
input signal obtained from the oxygen sensor 178, as compared to the 
previously referred-to bias or reference signal. Accordingly, knowing what 
the desired composition of the exhaust gas from the engine should be, it 
then becomes possible to program the logic of means 160 as to create 
signals indicating deviations from such desired composition as to in 
accordance therewith modify the effective opening of orifices 147 and 171 
to increase and/or decrease the richness (in terms of fuel) of the 
fuel-air mixture being metered to the engine. Such changes or 
modifications in fuel richness, of course, are, in turn, sensed by the 
oxygen sensor 178 which continues to further modify the fuel-air ratio of 
such metered mixture until the desired exhaust composition is attained. 
Accordingly, it is apparent that the system disclosed defines a 
closed-loop feedback system which continually operates to modify the 
fuel-air ratio of a metered combustible mixture assuring such mixture to 
be of a desired fuel-air ratio for the then existing operating parameters. 
It is also contemplated, at least in certain circumstances, that the 
upper-most curve 204 may actually be, for the most part, effectively below 
a curve 218 which, in this instance, is employed to represent a 
hypothetical curve depicting the best fuel-air ratio of a combustible 
mixture for obtaining maximum power from engine 10, as during wide open 
throttle (WOT) operation. In such a contemplated contingency, transducer 
means 180 (FIG. 1) may be adapted to be operatively engaged, as by lever 
means 186, when throttle valve 52 has been moved to WOT condition. At that 
time, the resulting signal from transducer means 180, as applied to means 
160, causes logic means 160 to appropriately respond by further altering 
the effective opening of orifices 147 and 171. That is, if it is assumed 
that curve portion 214-216 is obtained when orifice means 171 is 
effectively opened to a degree less than its maximum effective opening, 
then further effective opening thereof may be accomplished by causing a 
proportionately longest (in terms of time) opening movement of valve 
member 227. During such phase of operation, the metering becomes an open 
loop function and the input signal to logic means 160 provided by oxygen 
sensor 178 is, in effect, ignored for so long as the WOT signal from 
transducer 180 exists. 
Similarly, in certain engines, because of any of a number of factors, it 
may be desirable to assure a lean (in terms of fuel richness) base 
fuel-air ratio enriched (by the well known choke mechanism) immediately 
upon starting of a cold engine. Accordingly, engine temperature transducer 
means 182 may be employed for producing a signal, over a predetermined 
range of low engine temperatures, and applying such signal to logic 
control means 160 as to thereby cause such logic means 160 to, in turn 
produce and apply a control signal, via 197 and 199 to solenoid fuel 
valving means 102 as to cause the resulting fuel-air ratio of the metered 
combustible mixture to be, for example, in accordance with curve 202 of 
FIG. 5 or some other selected relatively "lean" fuel-air ratio. 
Further, it is contemplated that at certain operating conditions and with 
certain oxygen sensors it may be desirable or even necessary to measure 
the temperature of the oxygen sensor itself. Accordingly, suitable 
temperature transducer means, as for example thermocouple means well known 
in the art, may be employed to sense the temperature of the operating 
portion of the oxygen sensor means 178 and to provide a signal in 
accordance or in response thereto as via conductor means 164 to the 
electronic control means 160. That is, it is anticipated that it may be 
necessary to measure the temperature of the sensory portion of the oxygen 
sensor 178 to determine that such sensor 178 is sufficiently hot to 
provide a meaningful signal with respect to the composition of the exhaust 
gas. For example, upon re-staring a generally hot engine, the engine 
temperature and engine coolant temperatures could be normal (as sensed by 
transducer means 182) and yet the oxygen sensor 178 is still too cold and 
therefore not capable of providing a meaningful signal, of the exhaust gas 
composition, for several seconds after such re-start. Because a cold 
catalyst cannot clean-up from a rich mixture, it is advantageous, during 
the time that sensor means 178 is thusly too cold, to provide a relatively 
"lean" fuel-air ratio mixture. The sensor means 178 temperature signal 
thusly provided along conductor means 164 may serve to cause such logic 
means 160 to, in turn, produce and apply a control signal, as via 197 and 
199 to solenoid valving means 102, the magnitude of which is such as to 
cause the resulting fuel-air ratio of the metered combustible mixture to 
be, for example, in accordance with curve 202 of FIG. 5 or some other 
selected relatively "lean" fuel-air ratio. 
FIG. 6 illustrates fuel-air mixture curves obtainable with embodiments 
employing teachings of the invention with such curves being obtained at 
various conditions of engine operation. That is, flow curve 220 
corresponds generally to a typical part throttle fuel delivery curve while 
the flow curve 226 corresponds generally to a typical best engine power or 
wide open throttle delivery curve. Curves 222 and 224 are, of course, 
illustrative of a family of mid-range flow curves. In the embodiment of 
the invention disclosed the weight of armature means 207, and associated 
movable structure, is overcome by the force and preload of spring 229, 
whenever the coil 191 is in a de-energized state, thereby causing valve 
member 213 to become fully seated against and closing passage 147 while 
valve member 227 becomes fully unseated from passage 171. 
Accordingly, it can be seen that in the event of a total electronic failure 
in the system disclosed, the associated vehicle remains drivable. 
Referring in greater detail to FIG. 7 and the logic circuitry illustrated 
therein, the oxygen sensor 178 produces a voltage input signal along 
conductor means 162, terminal 310 and conductor means 162, terminal 310 
and conductor means 308 to the input terminal 303 of operational amplifier 
301. Such input signal is a voltage signal indicative of the degree of 
oxygen present in the exhaust gases and sensed by the sensor 178. 
Amplifier 301 is employed as a buffer and preferably has a very high input 
impedence. The output voltage at output 306 of amplifier 301 is the same 
magnitude, relative to ground, as the output voltage of the oxygen sensor 
178. Accordingly, the output at terminal 306 follows the output of the 
oxygen sensor 178. 
The output of amplifier 301 is applied via conductor means 320 and 
resistance 322 to the inverting input terminal 314 of amplifier 312. 
Feedback resistor 313 causes amplifier 312 to have a preselected gain so 
that the resulting amplified output at terminal 318 is applied via 
conductor means 338 to the inverting input 332 of amplifier 330. 
Generally, at this time it can be seen that if the signal on input 314 
goes positive (+) then the output at terminal 318 will go negative (-) 
then the output at 336 of amplifier 330 will go positive (+). 
The input 316 of amplifier 312 is connected as to the wiper of 
potentiometer 328 in order to selectively establish a set-point or a 
reference point bias for the system which will then represent the desired 
or reference value of fuel-air mixture and to then be able to sense 
deviations therefrom by the value of the signal generated by sensor 178. 
Switch means 368, which may comprise the transducer switching (or 
equivalent structure) means 182, when closed, as when the engine is below 
some preselected temperature, causes transistor 344 to go into conduction 
thereby establishing a current flow through the emitter 348 and collector 
392 thereof and through resistor means 396, point 388 and through resistor 
400 to ground 406. The same happens when, for example, switch means 378, 
which may comprise the throttle operated switch 181, is closed during WOT 
operation. During such WOT conditions (or ranges of throttle opening 
movement) it is transistor 346 which becomes conductive. In any event, 
both transistors 344 and 346, when conductive, cause current flow into 
resistor 400. 
An oscillator circuit comprises resistor 342, amplifier 330 and capacitor 
402. When voltage is applied as to the left end of resistor 342, current 
will flow through such resistor 342 and tend to charge up capacitor 402. 
If it is assumed, for purposes of discussion, that the potential of the 
inverting input 332 is for some reason lower than that of the 
non-inverting input 334, the output of the operational amplifier at 336 
will be relatively high and near or equal to the supply voltage of all of 
the operational amplifiers as derived from the zener diode 456. 
Consequently, current will flow as from point 367 through resistor 360 to 
point 365 and conductor 359, leading to the non-inverting input 334 of 
amplifier 330, and through resistor 363 to ground at 361. Therefore, it 
can be seen that when amplifier 330 is in conduction, there is a current 
component through resistor 360 tending to increase the voltage drop across 
resistor 363. 
As current flows from resistor 342, capacitor 402 undergoes charging and 
such charging continues until its potential is the same as that of the 
non-inverting input 334 of amplifier 330. When such potential is attained, 
the magnitude of the output at 336 of operational amplifier is placed at a 
substantially ground potential and effectively places resistor 360 to 
ground. Therefore, the magnitude of the voltage at the non-inverting input 
terminal 334 suddenly drops and the inverting input 332 suddenly becomes 
at a higher potential than the non-inverting input 334. At the same time, 
resistor 362 is also effectively to ground thereby tending to discharge 
the capacitor 402. 
The capacitor 402 will then discharge thereby decreasing in potential and 
approaching the now reduced potential of the non-inverting input 334. When 
the potential of capacitor 402 equals the potential of the non-inverting 
input 334, then the output 336 of amplifier 330 will suddenly go to its 
relatively high state again and the potential of the non-inverting input 
334 suddenly becomes at a much higher potential than the discharged 
capacitor 402. 
The preceding oscillating process keeps repeating. 
The ratio of "on" time to "off" time of amplifier 330 depends on the 
voltage at 388. When that voltage is high, capacitor 402 will charge very 
quickly and discharge slowly, and amplifier 330 output will stay low for a 
long period. Conversely, when voltage at 388 is low, output of amplifier 
330 will stay high for a long period. 
The consequent signal generated by the turning "on" and turning "off" of 
amplifier 330 is applied to the base circuit of the Darlington circuit 
410. When the output of amplifier 330 is "on" or as previously stated 
relatively high, the Darlington 410 is made conductive thereby energizing 
winding 191 of the solenoid valving assembly 102. Diode 442 is provided to 
suppress high voltage transients as may be generated by winding 191 while 
the LED may be employed, if desired, to provide visual indication of the 
operation of the winding 191. 
As should be evident, the ratio of the "on" or high output time of 
amplifier 330 to the "off" or low output time of amplifier 330 determines 
the relative percentage or portion of the cycle time, or duty cycle, at 
which coil 191 is energized thereby directly determining the effective 
orifice opening of orifice 147. 
Let it be assumed, for purposes of description, that the output of oxygen 
sensor 178 has gone positive (+) or increased meaning that the fuel-air 
mixture has become enriched (in terms of fuel). Such increased voltage 
signal is applied to input 314 of amplifier 312 and the output 318 of 
amplifier 312 drops in voltage because of the inverting of input 314. 
Because of this less voltage is applied to the resistor 342 and therefore 
it takes longer to charge up capacitor 402. Consequently, the ratio of the 
"on" or high output time to the "off" or low output time of amplifier 330 
increases. This ultimately results in applying more average current to the 
coil 191 which, in turn, means that, in terms of percentage of time, 
valving orifice 147 is opened longer while valving orifice 171 is closed 
longer thereby reducing the rate of metered fuel flow through both the 
main and idle fuel system. 
It should now also become apparent that with either or both switch means 
368 and 378 being closed a greater voltage is applied to resistor 342 
thereby reducing the charging time of the capacitor 402 with the result, 
as previously described, of altering the ratio of the "on" time to "off" 
time of amplifier 330. 
When current, as through Darlington 440, is applied to coil or winding 191 
of FIG. 3, the resulting magnetic field moves armature 207 and valving 
members 213 and 227 downwardly (for a proportionately longer period of 
time), as viewed in FIG. 3, causing valve member 227 to sealingly seat 
against valve seat member 169 and thereby terminate any communication as 
between passage 106 and chamber 165. At the same time, the downward 
movement of valve 213 permits communication to be established, through 
orifice means 147, between passage means 120 and 122. When the current 
through Darlington 440 is terminated, as during periods when the output of 
amplifier 330 is low or "off", the magnetic field created by the winding 
191 ceases to exist and spring 229 moves armature 207 and valve members 
213 and 227 upwardly causing valve member 213 to effectively sealingly 
seat against valve seat 137 to terminate communication as between passages 
120 and 122. At the same time, the upward movement of valve member 227 
permits communication to be established, through orifice means 171, 
between passage means 106 and chamber 165. Accordingly, it can be seen 
that, generally, when excess fuel richness is sensed (or amplifier 330 is 
"on"), communication as between passage 106 and chamber 165 is terminated 
while communication between passages 120 and 122 is completed. Likewise, 
generally, when an insufficient rate of fuel is being supplied and sensed 
(or amplifier 330 is "off") communication as between passage 106 and 
chamber 165 is completed while communication between passages 120 and 122 
is terminated. 
As should be apparent, even though in the preferred embodiment of the 
invention, when amplifier 330 is "off" the selection of spring 229 is such 
as to result in armature 207 and valve members 213 and 227 assuming a 
position opposite to that depicted in FIG. 3, such could be changed, if 
desired, as to have, during such "off" state of amplifier 330, the 
armature 207 and valve members 213 and 225 in a downmost position as 
depicted. In the embodiment disclosed, upon total failure of the related 
electrical system, the fuel-air ratio of the fuel metered to the engine 
would become "rich", in terms of fuel, while, if the armature 207 and 
members 213 and 227, during such "off" state of amplifier 330, are in a 
downmost position, upon total failure of the related electrical system, 
the fuel-air ratio of the fuel metered to the engine would become "lean", 
in terms of fuel. 
In the event it is not yet totally apparent, threaded end members or 
adjustment members 169 and 137 are also employed for selectively adjusting 
or establishing the solenoid armature gap and stroke, respectively. That 
is, during assembly and calibration of the solenoid valving assembly 102 
end members 169 and 137 are employed for positioning the armature 207 in a 
relatively advantageous position, force-wise, relative to the pole piece 
215 and for establishing the maximum stroke or travel of the armature 207. 
For example, referring to FIG. 3, let it be assumed that the entire 
solenoid valving assembly 102 is placed as within suitable fixture means 
and that, at such time, member 137 is not yet assembled thereto. Further, 
let it be assumed that gauge means such as, for example, a dial indicator 
gauge is placed as to be operatively against the axial end surface or 
valve face of valve member 213. Now with such assumed conditions, the 
adjustable member 169 is threadably rotated as to cause such member 169 to 
move downwardly (as viewed in FIG. 3). Such downward movement by member 
169 is accompanied by a downward movement of push rod 221 and armature 207 
and when member 169 is thusly moved downwardly a sufficient distance, the 
lower generally conical end of armature 207 finally abuts against the 
juxtaposed generally conical concave upper surface of pole piece 215. At 
this point member 169 is threadably rotated as to move upwardly (as viewed 
in FIG. 3) with such movement being continued until (in at least one 
successful embodiment of the invention) the dial indicator gauge indicates 
that the armature 207 (through the action of the push rod 221) has moved 
upwardly 0.015 inch. (The practice of the invention is not limited to any 
particular dimensional relationships; such being herein stated, by way of 
example, in order to clearly teach the many important benefits obtainable 
with the invention.) The ability of being able to so selectively position 
the armature 207 with respect to the pole piece 215 enables assuring the 
existance of a gap therebetween thereby, in turn, assuring that the 
armature 207 will be able, during actual operation, to move downwardly a 
distance sufficient to cause valving member 227 to close-off port or 
passage 171. Further, it has been discovered that the degree or magnitude 
of generated magnetic force varies somewhat in relationship to the mutual 
proximity of armature 207 and pole piece 215. It has also been discovered 
in one successful embodiment of the invention that, for example, 
positioning of the armature 0.015 to 0.030 inch axially away from the pole 
piece 215 apparently physically places the armature 207 in a position 
where it is acted upon by the most effective part of the generated 
magnetic force. 
With the lower adjustable member 169 being thusly adjusted, let it be 
assumed that the dial indicator gauge is removed and that the member 137 
is threadably engaged and threadably rotated as to move downwardly (as 
viewed in FIG. 3) with such downward motion continuing until orifice 147 
is closed by the valve face of valve member 213 (such can be determined, 
for example, as by related flow gauges). At that time member 137 is then 
threadably rotated in the opposite direction as to move generally upwardly 
to where the lower end thereof is approximately 0.015 inch away from the 
valve face of valve member 213. The result of this is that a desirable 
armature-pole piece air gap is first attained and then the overall stroke 
or travel of the armature 207 is determined with such stroke, in the 
example disclosed, being 0.030 inch which is within the preferred 
distance, from the pole piece 215, for maximum magnetic field effect. 
The adjustments described with regard to members 169 and 137 have been 
described in connection with the use of a dial indicator. However, it 
should be apparent that no such gauge is necessary and that reference 
thereto has been made primarily for ease of disclosure and related ease of 
mental visualization. It is equally possible to employ the actual axial 
lead of the threads of the members 137 and 169 in order to determine axial 
motion. For example, if the lead on the threads was 0.030 then a half-turn 
of such respective members 137 and 169 would equal an axial travel of 
0.015 inch. Also, it would be possible to determine when the valve 
orifices 147 and 171 become closed as by related flow gauges as generally 
well known in the art. 
Of course, while the solenoid valving assembly is in such a test or 
calibrating fixture means, the actual flows through the orifices 147 and 
171, for various operating conditions and specifications, can be easily 
determined through associated test flow gauges. Slight deviations from 
prescribed limits can be overcome by the further adjustment of member 137 
and/or 169. 
Important advantages are gained because of being able to totally calibrate 
the solenoid valving assembly of the invention in test stand means or the 
like and not requiring that calibration thereof be conducted only after 
its assembly into a related cooperating carbureting structure. That is, 
the solenoid valving assembly 102 is a totally integrated self-contained 
valving assembly and as such can easily be calibrated to provide the 
desired flow rates through orifices 147 and 171 for specified conditions 
without having to first assemble such solenoid assembly into the 
carbureting structure where only then, in conjunction with components 
separately carried by the carbureting structure, a total or calibratable 
flow system is established. Consequently, it becomes possible, with the 
invention, to, if the need should ever arise, remove from a carbureting 
structure and replace a failed solenoid valving assembly (of the 
invention) with another (already calibrated) solenoid valving assembly (of 
the invention) without in any way having to make any further adjustments 
to such carbureting structure. This feature, of course: (a) minimizes any 
vehicular down-time as might be caused by a failure in the solenoid 
valving assembly; (b) reduces attendant labor costs and (c) maintains the 
integrity of the overall metering system and related structure thereby 
assuring, for example, that engine exhaust emissions will continue within 
prescribed limits. 
Although various arrangements are, of course, possible, in the preferred 
embodiment the coil leads 197 and 199 (FIG. 3) may pass through suitable 
clearance or passage means 500 and 502 (FIG. 4) and pass through relieved 
portions 504, 506 (formed in integrally formed arm portion 512) and then 
be respectively received as within eyelets 508, 510 which also 
respectively receive enlarged conductor extensions of such leads 197 and 
199 (one of such being partly depicted at 514 in FIG. 3). Such extensions 
may, of course, be brought out of the carburetor housing means in any 
suitable manner as to thereby, in effect, comprise the conductor means 197 
and 199 as depicted in FIGS. 1 and 7. 
Although only one preferred embodiment of the invention has been disclosed 
and described, it is apparent that other embodiments and modifications of 
the invention are possible within the scope of the appended claims.