Carburetor with feedback means and system

Abstract

A carburetor having a fuel metering restriction is provided with air bleed valving means for varying the pressure at one side of the metering restriction to thereby change the metering pressure differential across the metering restriction and consequently vary the fuel-air ratio of the combustible mixture discharged by the carburetor to reflect changes in engine operating parameters.

Description

BACKGROUND OF THE INVENTION

Because of recent governmental regulations relating to engine exhaust emissions, the automotive industry generally has been considering, to an ever increasing degree, the use of very expensive and complicated fuel metering systems, including various forms of fuel injection systems. This has been done with the belief that such injection systems are the only means which can be made responsive to various engine operating parameters for, in turn, varying the fuel-air ratio of the mixture supplied to the engine in response to such operating parameters.

The invention as herein disclosed and described is primarily concerned with the general problem of being able to very closely and accurately meter the rate of flow of fuel and to vary such rate in response to atmospheric variations as well as engine operating parameters and more specifically to providing, by comparison, such means within a carbureting structure.

SUMMARY OF THE INVENTION

According to the invention, a carburetor for an internal combustion engine has induction passage means with air inlet means at one end thereof and outlet means at another end thereof, fuel supply and metering means communicating between a source of fuel and said induction passage means, and air bleed means (referred to as the dry system) effective for varying the pressure differential across said metering means to alter the rate of flow of fuel therethrough.

Various general and specific objects and advantages of the invention will become apparent when reference is made to the following detailed description, considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein for purposes of clarity certain details and elements may be omitted:

FIG. 1 is somewhat a diagrammatic representation of an internal combustion engine equipped with a carburetor embodying the teachings of the invention;

FIG. 2 is an elevational cross-sectional view of a variable venturi type carburetor constructed in accordance with the teachings of the invention;

FIG. 3 is a graph depicting venturi vacuum compared to the rate of air flow;

FIG. 4 is a graph depicting the fuel-air ratio (with fuel in terms of pounds and air in terms of cubic feet) compared to the rate of air flow in cubic feet;

FIG. 5 is a graph depicting the fuel-air ratio (with fuel in terms of pounds and air in terms of pounds) compared to the rate of air flow;

FIG. 6 is an elevational cross-sectional view of a fixed venturi type carburetor constructed in accordance with the invention; and

FIG. 7 is a schematic representation of the metering concept of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now in greater detail to the drawings, FIG. 1, partly in schematic and partly in simplified pictorial, illustrates an internal combustion engine 10 having an intake manifold 12, with a carbureting structure 14 mounted thereatop, a multi-speed power output transmission assembly 16, and an exhaust system 18 comprising an exhaust manifold 20, exhaust conduit means 22, 24 and 26 with a reduction-type reactor 28 and an oxidizing reactor 30 serially situated therein. An oxygen sensor and transducer 32 may be placed in communication with exhaust conduit means 22, while engine speed sensing and transducer means 34 may be driven as by any suitable transmission means 36.

The carburetor structure 14 as shown in FIG. 2, is illustrated as comprising a body or housing means 38 with an induction passage 40 formed therethrough with such induction passage 40 having an air inlet end 42 and an outlet or discharge end 44 leading to an inlet 46 of the interior 48 of the intake manifold 12 of the associated internal combustion engine 10. A variably positionable throttle valve 50, mounted as on a throttle shaft 52 for pivotal rotation therewith, is situated within the induction passage and effective for controlling the flow of motive fluid or combustible mixture from said induction passage 40 into the intake passage 48 of manifold 12. Generally, such combustible mixture will, of course, be comprised of atmospheric air admitted into inlet end 42 and fuel supplied to the induction passage 40 from an associated fuel reservoir or fuel bowl assembly 54.

The fuel bowl assembly 54 is illustrated as comprising a suitable bowl or housing structure 56 which may contain a float member 58 controlling an associated fuel inlet needle valve assembly (not shown but well known in the prior art) so as to maintain the level of the fuel 60 within the bowl 56 at a preselected level as at 62.

As illustrated, a variable venturi may be comprised of a variably positionable venturi plate 64 which may be fixedly secured as by fastener means 66 and 68 to an internally disposed arm 70 which, in turn, is fixedly secured to a rotatable shaft 72 journalled in the housing means 38. The venturi arrangement may be such as to define a generally rectangular opening at the throat of the variable venturi when viewed, for example, in the direction of arrow 74. In fact, opposite walls, one of which is shown at 76, may define flat planar surfaces permitting the variable or movable venturi plate 64 to be closely received therebetween for swingable motion about the centerline of rod or shaft 72. Such flat or planar surfaces would preferably terminate as at a boundary line 78 from which the portion of the induction passage means 40 downstream may transitionally change configuration until it became circular to accommodate a generally circular throttle valve 50 if such configuration thereof is employed.

A second lever 80, which may be situated generally outboard of the housing means 38, is fixedly secured as at one end to shaft 72 for rotation therewith and has its swingable arm portion connected as to linkage means or rods 82 and 84. Rod 84 comprises a portion of a dashpot assembly 86 which is illustrated as having an internal cylindrical chamber 88 containing therein a suitable fluid and a slidable piston member 90 through which the rod 84 freely extends as to be abutingly engageable therewith at its lower portion 92. A compression spring 94 also contained within chamber 88 continually resiliently urges piston 90 downwardly. Suitable sealing means such as at 96 may be provided for preventing the escape of damping fluid from chamber 88. Generally, as piston 90 is moved upwardly by rod 84, the fluid in chamber 88 above the piston 90 is forced to a position below the piston 90. This may be done as by calibrated bleed means 98 formed through piston 90 or any other such equivalent means well known in the art.

A lever 100 suitably fixedly secured to throttle shaft 52, for rotation therewith, is operatively connected to motion transmitting linkage means 102 leading to, for example, the vehicle operator's foot-controlled throttle pedal 103 so that when moved in the direction of arrow 104 the throttle valve 50 is moved counter-clockwise in the opening direction about the centerline of throttle shaft 52.

A second lever 106 mounted on throttle shaft 52 in a manner permitting free relative angular motion with respect to and about shaft 52, has an arm portion 108 pivotally connected to linkage 82. Levers 100 and 106, in turn, respectively have arm portions 110 and 112 which carry generally transversely extending abutment portions 114 and 116. A torsion spring 118, having its main coil generally about shaft 52, has its arms 120 and 122 respectively operatively engaged with lever arm portions 110 and 112 as to thereby normally resiliently maintain abutments 114 and 116 engaged with each other resulting in unitary motion of levers 100 and 106.

Suitable vent passage means 124 has a first end 126 communicating with a suitable source of atmospheric pressure (or some source indicative of such atmospheric pressure), and has its other end 128 communicating with the interior 140 of the fuel bowl 56.

Fuel delivery and metering means is illustrated as preferably comprising passage or conduit means 130 communicating with the fuel bowl 56 as at 132 and with a second generally transversely disposed fuel delivery conduit means 134 which has an end 138 communicating with induction passage 40 preferably at a point immediately downstream of venturi throat portion 136 of a fixed venturi section 137.

Calibrated passage or orifice means 142, provided in conduit means 134, may be suitably contoured so as to cooperate with a contoured metering portion 144 of a needle-like valve member 146 which may be pivotally secured as by a pivot member 148 to the movable venturi plate or section 64 as within a recess 150 formed therein.

General Operation of Carburetor Thus Far Described

The operation of the carburetor 14 is generally as follows. That is, if it is assumed that the associated engine is operating, as foot throttle pedal 103 is moved counter-clockwise about pivot 105 linkage 102 is moved to the right causing levers 100 and 106, shaft 52 and throttle valve 50 to rotate generally counter-clockwise about the centerline of shaft 50 in the throttle valve opening direction. Such opening movement or motion is transmitted via cooperating linkage means 82 to lever 80 which rotates generally counter-clockwise about the centerline of shaft 72 causing corresponding motion of lever 70 and movable venturi means 64.

As lever 80 is thusly rotated counter-clockwise, stem or linkage 84 moves dashpot piston 90 upwardly through the fluid medium in chamber 88 forcing such fluid medium to pass through the calibrated passage means 98. If the rate of rotation of lever 100 is in excess of a predetermined rate, the resistance to flow of fluid medium through passage means 98 will be sufficient to retard the rate of upward movement of piston 90 to the degree resulting in the actual rate of rotation of lever 80 and variable venturi plate 64 being less than the rate of rotation of throttle lever 100. If this condition is achieved as, for example, during requests for rapid engine acceleration or increased output power of the engine, abutment portions 114 and 116 of levers 100 and 106 will momentarily separate from each other against the resistance of spring 118 and will subsequently return to their abutting condition once sufficient travel of linkage 82 and lever 80 is permitted by the time delay or dashpot means 86.

Such time delay means 86 is preferably provided to overcome a condition which may be referred to as fuel lag. That is, between the fuel and air, fuel has a greater density and therefore greater inertia. Consequently, if the venturi plate 64 were to be rapidly opened, the volume rate of air flow would respond to the newly indicated desired rate of air flow much more rapidly than would the fuel. If this were to occur, the ratio of the fuel-air mixture might well become too lean (in terms of fuel) causing improper engine operation. Accordingly, by providing such time-delay means 76, a maximum rate of opening movement of variable venturi plate 64 is established as to make sure that the fuel flow will have sufficient time to correspondingly respond to the indicated change in demand for rate of fuel flow.

Obviously, as throttle valve 50 is rotated clockwise toward the more nearly closed throttle position, lever 80 will positively follow such movement because stem 84 may slide relatively to piston 90, regardless of the resistance experienced by piston 90; this, in turn, causes corresponding positive movement of variable venturi plate 64. Accordingly, it can be seen that under rapid throttle opening conditions the venturi opening lags the throttle opening which eliminates the need for an acceleration pump.

As should be evident, generally, the rate of fuel flow from fuel bowl 56 to the induction passage 40 (as from the discharge orifice or nozzle means 138) is primarily dependent upon the metering pressure differential .DELTA.P (often referred to as metering depression) determined by the difference of P.sub.b - P.sub.v where P.sub.b is the pressure above the fuel 60 within fuel bowl 56 and P.sub.v is the effective pressure (often referred to as venturi vacuum) in the induction passage 40 at or slightly downstream of the venturi throat as generally depicted by the variable dimension, D. (For purposes of discussion, although in some applications this may not be the case, P.sub.b will be assumed to be completely equivalent to atmospheric pressure P.sub.o.)

Unlike a carburetor having a fixed venturi throat dimension whereby, generally, a change in the volume rate of air flow therethrough produces a correlated change in the value of the venturi vacuum, a carburetor having a variable venturi does not exhibit such characteristics.

For example, in fixed venturi carburetors, the venturi vacuum or reduced pressure generated at the venturi throat is actually dependent on the velocity of flow of air through such venturi throat. However, in reality, because of the fact that the venturi throat is of a permanently fixed dimension (and therefore of a fixed flow area), such rate of flow of air is usually referred to in terms of a volume rate of flow because the rate of flow of air described in either terms of volume rate of flow or velocity rate of flow is the same since velocity and volume are directly related.

However, in a carburetor employing a variable venturi, the venturi throat area is variable in accordance with the variable dimension, D. Therefore, the velocity rate of flow of air through the variable venturi throat is not directly related to the volume rate of flow of air at all positions of the movable venturi plate 64.

Accordingly, it can be seen that where in a carburetor of a fixed venturi the generated venturi vacuum is proportional to the square of the volume rate of air flow through the induction passage, in a carburetor having a variable venturi no such relationship exists because the size of the variable venturi throat is variably openable.

In carburetor assembly 14, the movable venturi plate 64 is placed at a relatively close distance with respect to the fixed venturi section 137 during idle engine operation (as for purposes of illustration might be considered to be depicted by the positions of the various elements hereinbefore referred to and shown in FIG. 2) to thereby create a metering vacuum or pressure P.sub.v sufficient to cause metered fuel flow through passage means 130 and 134 into the induction passage 40 even though the volume rate of air flow at this condition of engine operation is, relatively, very small. By thusly closely spacing the movable venturi plate 64, the small volume rate of air flow, during idle engine operation, is caused to sufficiently accelerate through the venturi throat resulting in the necessary venturi vacuum being generated.

FIG. 3 graphically depicts characteristic curves, of a fixed venturi carburetor and a variable venturi carburetor, attained by plotting the generated venturi vacuum against the volume rate of air flow in each of said carburetors. Curve A represents the curve characteristically developed by a fixed venturi carburetor while curve B characteristically represents a curve developed by a variable venturi carburetor.

From an inspection of the graph of FIG. 3, it can be seen that curves A and B, which of course must each originate at the zero point, intersect at a point 150. Further, if vertical dash-line 152 is assumed to represent a typical air flow for a particular engine at curb-idle operation, it can be seen that line 152 intersects curves B and A respectively at points 154 and 156 and that point 154 represents a substantially greater magnitude of generated venturi vacuum than that represented by point 156. It is also apparent that for all values of air flow between line 152 and point 150, curve B represents venturi vacuum values greater than those vacuum values represented by corresponding portion of curve A. Consequently, since such high vacuum values are not necessary during that range of engine operation, the effect thereof is reduced by varying (in fact reducing) the effective metering orifice area by cooperating valving means 142 and 144 with valving member 146 being positioned by the venturi plate 64 so as to, generally, more nearly reduce the effective flow area through orifice 152 as the venturi plate 64 more nearly approaches fixed venturi section 137.

This, of course, means that the effect of the actual vacuum generated at the venturi throat is to that degree diminished as a factor in the rate of metered fuel flow discharged at the nozzle means or discharge orifice 138. Further, as the venturi plate 64 is opened, the actual volume rate of air flow through the venturi throat may actually increase by a factor substantially greater than the resulting venturi vacuum. Therefore, in order to compensate for such a diverse relationship, metering surface 144 is moved further to the right as to provide for a greater effective fluid flow area as between orifice 142 and metering rod surface 144 thereby properly increasing the rate of metered fuel flow therethrough even though the magnitude of the actually generated venturi vacuum may not have greatly increased.

The preceding discloses the general nature of operation of the carburetor assembly 14 without regard to the control or modifying means generally depicted at 160 and as if the conduit or passage means 162 were non-existant.

Description of Modifying Means 160

With reference to FIG. 2, it can be seen that the control means 160 may be comprised of a housing portion 164 containing various control means such as solenoid operated valve assemblies 166, 168 and 170 along with manually positionable adjusting means 172 and ambient pressure responsive means 174.

Solenoid valving assembly 166 may be of the two-position type comprising housing means 176, containing solenoid means having electrical terminals 178 and 180. The housing means 176 may be threadably engaged as at 182 with housing portion 164 in a manner placing stem and valve portion 184 in closed position against conduit means 186 so as to thereby prevent communication between conduit means 186 and chamber 188 which generally contains valve 184.

Solenoid valving assembly 168 may be of the proportional type, wherein movement of the associated valving member is generally proportional to the strength of the signal applied to the solenoid portion thereof, comprising housing means 190, containing solenoid means having electrical terminals 192 and 194. The housing means 190 may be threadably engaged as at 196 with housing portion 164 in a manner placing valving portion 198 in closed position against conduit means 200 so as to thereby prevent communication between conduit means 200 and chamber 202 which generally contains valving means 198.

Solenoid valving assembly 170 may be of the two-position type comprising housing means 204 containing solenoid means having electrical terminals 206 and 208. The housing means 204 may be threadably engaged as at 210 with housing portion 164 in a manner placing stem and valve portion 212 in closed position against conduit means 214 so as to thereby prevent communication between conduit means 214 and chamber 216 which generally contains valving means 212.

As can be seen the various chambers 216, 202 and 188 may be interconnected as by conduit means 218 and 220 ultimately leading to conduit means 222 which, as at 224, is in communication with the ambient atmosphere or a suitable source related thereto.

While the power source for the solenoids is not shown, this is well known in the art and may comprise the vehicle battery.

The manually adjustable means 172 is illustrated as comprising a threadably axially adjustable body 226 carrying therewith a valving portion 228 adapted to cooperate as with a seat portion 230 to vary the effective flow area as between a chamber portion 232 and conduit means 234. As shown, chamber 232 is in communication with ambient atmosphere as by means of conduit portion 236 while conduit means 234 is in communication with conduit means 162, 186, 200 annd 214 as well as with conduit means 238 leading generally to the altitude responsive means 174.

The ambient pressure and altitude responsive means 174 may be comprised of a threadably axially adjustable evacuated bellows assembly 240, situated as within a chamber 242, having one end 244 threadably secured to housing portion 164 and another end 246 operatively connected to a lever means 248 having one end pivotally secured as at 250 and another end 252 swingable and operatively connected to a valving member 254 slidable within guide passage 256.

Valving member 254 may include a body 258 of generally diamond shape, in transverse cross-section, thereby permitting unrestricted flow therepast. A valving portion 260 is adapted to cooperate with a suitable seat 262 to control the flow therebetween and through conduit means 238. Chamber 242 may be suitably vented to the ambient atmosphere as by vent means 264.

As will be noted, conduit means 162 at one end communicates with conduit means 234 while at its other end it communicates with an area generally forwardly of the calibrated orifice means 142. Such area may be determined as by a chamber-like portion 266 generally between calibrated orifice means 142 and discharge orifice means 138.

General Operation of Invention as Shown in FIG. 2

If it is first assumed that valves 260, 228, 184, 198 and 212 are all closed, it can be seen that during operation of the engine the value of the variable pressure P.sub.c within chamber 266 will be substantially equal to the value of the variable pressure P.sub.v generated in the venturi throat and would follow curve B of FIG. 3. Further, this particular assumed condition would result in a first fuel-air ratio generally depicted as by curve 270 of FIG. 4 wherein vertical line 272 corresponds to line 152 of FIG. 3.

Now, let it be assumed that manually adjustable valve means 172 is opened to some degree. Because of this the relatively high pressure P.sub.o will cause air to flow from 224, through 236, 232, conduit means 234 and 162 into chamber 266 thereby effectively increasing the value of pressure P.sub.c and effectively reducing the effect of the generated venturi vacuum. This, of course, causes a reduction in the metering depression (now determined by the difference of P.sub.b - P.sub.c) and consequently a reduction in the rate of metered fuel flow through orifice means 142 even though the rate of air flow has remained the same. Under this second assumed condition of operation the resulting fuel-air ratio would be reduced or made leaner (in terms of fuel) and might be represented or depicted as by curve or line 274 of FIG. 4. Further, for sake of general illustration, the value of P.sub.c may be depicted generally by the dash-line curve 276 of FIG. 3 because, as far as the actual effective flow area of orifice means 142 is concerned, it is lead to believe that the actual sensed value of P.sub.c is actually the generated venturi pressure.

Accordingly, in view of the above, it can be seen that as more air is bled into chamber 266, the leaner the fuel-air ratio of the resulting mixture. One immediate benefit of such an arrangement is that it makes it possible (and cost-wise very practical) for a manufacturer of carburetors to produce what might be referred to as carburetors having a standard fuel-air ratio mixture delivery as depicted by curve or line 270 and then having the engine manufacturer (or some such customer) manually adjust the degree of air bleed permitted through means 172 as to reduce the fuel-air ratio of the mixture to suit the requirements of any and all associated engines. (Of course, this could also be done by the carburetor manufacturer to meet customer specifications. However, the point is that the carburetor, basically, could be a standard type structure.)

Now, if the fuel-air ratio is determined in terms of weight-rate of flow of fuel and volume-rate of flow of air, as in the graph of FIG. 4, it becomes apparent that with diminished atmospheric pressure as by an increase in altitude the density of the air flowing through the induction passage 40 is decreased therefor requiring a reduction in the rate of metered fuel flow even though the generated venturi vacuum may ordinarily indicate otherwise. That is, as compared to, for example, a sea-level fuel-air ratio curve 274, the required or proper fuel-air ratio curve at some increased elevation may be as indicated by the dash-line curve 278.

This is achieved by bellows 240 axially elongating, in response to the decrease in value of pressure P.sub.o, and consequently moving valve member 254 downwardly opening, to some degree, the effective flow or bleed area through orifice means 262. As this happens atmospheric air is bled through conduit means 264, chamber 242, past valve 254, through orifice means 262, and conduit means 238, 234, 162 into chamber 266 causing an increase in the value of pressure P.sub.c as compared to the actual value of the generated venturi pressure P.sub.v. Again, as a consequence of the above, a reduction in the rate of metered fuel flow through orifice means 142 occurs as compared to the rate of metered fuel flow which would occur if the actual value of P.sub.v were applied to the low pressure side of orifice means 142. Such a controlled or modified value of pressure P.sub.c could be considered for example as being a "false" type of venturi vacuum and depending on the degree of opening or air bleed could be depicted, for example, as being a surce such as at 276 or 280 or even any of the other proportional-type curves of FIG. 3 which are less than curve B.

In the embodiment illustrated, valving means 168 is like 174 in the respect that each are proportional type means capable of progressively varying the degree of air bleed in accordance with a predetermined schedule or input parameters. However, as also shown, in the preferred embodiment valving means 166 and 170 are of the on-off type providing only for either a closed or opened air bleed condition. The effect of such air bleed through any or all of such valving or control means is as described in detail with reference to means 172 and 174.

Operation of Invention Within a Typical Environment

For ease of reference, FIG. 1 includes fragmentarily illustrated valving means 166, 168 and 170. Speed sensing and responsive means 34 is effective for producing a signal, N, along suitable signal-conveying transmission means 282 leading to suitable related transducer means 284. Upon the proper value or magnitude of signal N being generated, transducer means 284 becomes effective, as via conductor means 286, for energizing valving means 166 so as to thereby move valving member 184 (FIG. 2) to the left opening air-bleed passage 186.

Similarly, the oxygen sensor means 32 may continually provide a signal, O, along suitable signal-conveying transmission means 288 leading to suitable related transducer means 290. Whenever the value or magnitude of the signal, O, (which may be considered as being the relative amount of carbon monoxide) exceeds a predetermined amount, transducer means 290 becomes effective to, via conductor means 292, energize valving means 168 so as to thereby move valving member 198 some degree to the left generally in accordance with the magnitude of signal O (to the left for leaner mixtures and to the right for richer mixtures) thereby variably opening the air-bleed passage means 200.

Valving means 170 is illustrated as being actuable or controlled by either of two transducer means 298 and 296 via conductor means 294 and 300. Transducer 296 is responsive to a signal, M, indicative of engine intake manifold pressure (or vacuum) which may be transmitted via signal transmission means 302. Whenever the engine undergoes deceleration, the throttle valve 50 will be closed and the manifold vacuum then exceeds the value of manifold vacuum generated at idle engine operation. Accordingly, when such signal, M, indicates that the engine is experiencing deceleration, transducer means 296 becomes effective to cause valve member 212 of valving means 170 to move to the left thereby opening air-bleed passage means 214. Further, transducer means 298 is responsive to the closure and/or opening of, for example, the vehicle ignition switch 304 (a portion of a related ignition circuit is illustrated at 306 while a related source of electrical potential is shown at 308). The general operation is that when the ignition switch 304 is opened, transducer means 298 becomes effective to also cause valve member 212 of valving means 170 to move to the left thereby opening air-bleed passage means 214.

Because of various governmental regulations relating to vehicular engine exhaust emissions, the automotive industry, generally, has found that in order to meet governmentally imposed emission standards, especially the removal from the engine exhaust of oxides of nitrogen, catalytic converters will in all probability have to be employed within the engine exhaust system. Generally, even though such converters may take different forms, the anticipated converter will have two stages the first of which is a reduction chamber or stage with the second being an oxidizing chamber or stage. These are respectively schematically illustrated at 28 and 30 of FIG. 1.

In the first reduction chamber or stage 28, the oxides of nitrogen will react with some of the carbon monoxide to produce free molecular nitrogen and carbon dioxide with some additional quantities of carbon monoxide and, for example, methane remaining. The free nitrogen and carbon dioxide is passed to atmosphere without further reaction while the methane (and other such exhaust gases) and remaining carbon monoxide are then oxidized in the second stage as for example reacting and producing carbon dioxide and free water.

In order to achieve such chemical conversion, it is necessary to provide an overly righ (in terms of fuel) fuel-air ratio mixture to the engine so that the exhaust gases, as, for example, in the area sensed by means 32 upstream of the reactor 28, contain about 1.5 percent of carbon monoxide (CO). This then provides an adequate quantity of CO for reaction in the reduction stage 28 and a sufficient amount of excess CO to complete the oxidation in stage 30. The carburetor, of course, can be initially set to provide such 1.5% CO and such a fuel-air ratio curve is typically depicted as at 310 of FIG. 5.

However, a problem does occur at relatively fast road speeds at normal or greater than normal road loads. That is, at speeds in excess of, for example, 55.0 m.p.h. the converter will often become overheated because of the quantity of such over-rich mixture being passed therethrough per unit of time. Therefore, at speeds above the assumed speed of 55.0 m.p.h., the signal, N, becomes sufficient to actuate transducer means 284 which, in turn, causes valve member 184 of valving means 166 to open air-bleed passage means 186 with the result that pressure P.sub.c is increased, as previously explained, and the rate of metered fuel flow is decreased. Consequently, the fuel-air ratio is made leaner (in terms of fuel) and such is generally depicted by line or curve 312 of FIG. 5. The degree of air-bleed would be such as to result in the fuel-air ratio of curve 312 being sufficiently lean as to prevent the overheating of the exhaust converter means at speeds in excess of the assumed 55.0 m.p.h.

Valving means 170, as depicted is normally closed with the term "normally" designating engine operating conditions other than engine operating conditions other than engine shut-down or engine deceleration. That is, during conditions of engine deceleration when the magnitude of the manifold pressure signal M is sufficiently low, in terms of pressure, or high in terms of vacuum, transducer means 296 causes valve member 212 of valving means 170 to open air-bleed passage means 214 thereby, as previously described, increasing the value of pressure P.sub.c and reducing the rate of metered fuel flow to such a low rate that the resulting fuel-air ratio as depicted, for example, by curve 314 of FIG. 4, is too lean to support combustion. The value of pressure P.sub.c at this time, if considered as being a "false venturi vacuum," value might be graphically represented as by the point 316 in FIG. 3. Therefore, it can be seen that during such conditions of engine deceleration the rate of metered fuel flow is drastically reduced resulting in a corresponding reduction in exhaust emissions.

Because the richness of fuel-air ratio can be decreased to such an extremely lean condition as to be insufficient to support combustion, valving means 170 may also be employed to thereby lean-out the fuel-air mixture which might flow at the instant of engine shut-down to thereby prevent the occurrence of the condition often referred to as "engine dieseling." That is, when ignition switch 304 is opened transducer means 298 becomes effective for causing valve member 212 of valving means 170 to again move and open the air-bleed passage means 214 with the result that point 316 of FIG. 3 and point 318 of FIG. 4 are again achieved. Since at this time the fuel-air ratio is such as to be incapable of supporting combustion, the engine is prevented from "dieseling" after the ignition is turned off.

The various parameters and means for sensing thereof as well as generating signals in response thereto are merely exemplory. It should be apparent that the invention, among other things, provides for a carburetor type fuel delivery system includes closed loop type feedback means effective for varying the fuel-air ratio of the fuel-air mixture supplied by such carburetor in accordance with operating parameters indicative of any produced by the engine itself.

Further, as generally illustrated by FIG. 6, the invention can be practiced equally well with a carbureting structure of the fixed venturi type.

For example, referring in greater detail to FIG. 6, the carburetor assembly 320 is illustrated as comprising body or housing means 322 with an induction passage 324 formed therethrough and having an air inlet end 326, which may be controlled as by a variably positionable choke valve 328, and an outlet end 330 with a variably positionable throttle valve 332 therein for controlling the flow of combustible mixtures into the inlet 334 of the intake manifold chamber 336 of the engine intake manifold 338 (which may in fact be as manifold 12 of FIGS. 1 and 2).

The carburetor assembly may be provided with an idle fuel system 340 and a main fuel system 342, as are generally well known in the art, wherein the fragmentarily illustrated idle fuel system 340 is comprised of fuel delivery conduit means 344, leading to the fuel 346 within an associated fuel reservoir or supply means 348, and communicating with the induction passage 324 as via passage means 350 and 352 with passage means 250 providing for idle fuel flow to the induction passage posterior (downstream) of the throttle valve 332 when such is in the closed idle position as shown. Passage means 352 is effective for providing increasing amounts of fuel flow as the throttle valve 332 is rotated clockwise in the throttle opening direction as during periods of off-idle engine operation.

The main fuel metering system 342, shown in somewhat simplified form, may be comprised of a fuel discharge nozzle 354, situated generally in the throat 356 of the fixed venturi section 358, having orifice means 260 leading to fuel delivery conduit means 362 communicating with the fuel 346 as through calibrated orifice or restriction means 364. When the velocity rate of air flow through the venturi throat attains a sufficient magnitude, the resulting venturi pressure, P.sub.v, becomes sufficiently reduced as to have the differential of pressures P.sub.b - P.sub.v cause fuel flow through passage means 362, orifice means 360 and into the induction passage 324.

As is generally depicted, the carburetor assembly 320 is provided with the control means 160, described in detail with reference to the preceding Figures, so as to have the bleed-air conduit 162 communicating with fuel supply passage means 362. The operation would, of course, be as that described with reference to FIGS. 1 and 2 with the result that a closed loop feedback carbureting system would again be achieved.

Further, if desired, the structure of FIG. 6 and the control means 160 (shown in detail in FIG. 2) may be modified as by providing passage means 366 in housing means 322 communicating with idle fuel supply passage means 344 and to in effect isolate air bleed passage 214 (FIG. 2) from conduits 200 and 162 as by placing suitable blockage in conduit 234 between conduit 214 and conduits 200 and 162. With such a modification a second air-bleed conduit 162a, functioning generally as does conduit 162, would be connected as to then communicate between conduit 214 and conduit 366. By so doing, the pressure resulting from the air bled through conduit means 214 during either engine shut-down or deceleration would be applied in the area upstream of the passage means 350, 352 and downstream of the related idle fuel metering means or generally schematically depicted at 368.

Referring to FIG. 7, it can be seen that the invention in its utmost simplicity (where: a pressure P.sub.v is developed by the velocity rate of air flow to an engine; pressure P.sub.o is atmospheric pressure; pressure P.sub.b is the pressure applied to the fuel, in this case P.sub.b and P.sub.o are assumed to be equal) is the provision of means such as at 160 sensitive to engine and/or vehicle operating parameters to vary the actual available metering pressure differential of P.sub.b - P.sub.v to more accurately satisfy the needs of the engine at such sensed parameters as by variably restricting (by means depicted at 370 and equivalent to the valving means of control 160) the flow of ambient air to create a control pressure P.sub.c and thereby develop an actual and variable metering pressure differential of P.sub.b - P.sub.c which when applied across the related calibrated metering orifice means, as depicted at 372, will provide for precisely the proper rate of metered fuel flow to the discharge area generally designated at 374 in which the relatively lower pressure P.sub.v exists.

It should be apparent that various modifications and embodiments of the invention are possible. For example, various indicia of engine operation as well as various parameters may be employed to create feed-back type signals to which response may be made as by the control means shown or any other suitable means. By way of partial illustration, if desired air bleed valving means in addition to those shown in FIG. 2 could be employed as to be responsive to additional parameters of operation; also, other specific forms of valving means may be employed as, for example, pressure responsive diaphragm means or the like. Other means employable in carrying out the inventive concepts herein disclosed will become apparent to those skilled in the art.

Although only one preferred embodiment and a select number of modifications of the invention have been disclosed and described, it is apparent that other embodiments and modifications of the invention are possible within the scope of the appended claims.

Claims

I claim:

1. In a carburetor type fuel metering device, for an internal combustion engine, of the type having induction passage means with venturi means carried therein for creating a reduced first pressure proportional to the square of the flow of air therethrough, a fuel bowl, a fuel passage between the fuel bowl and an orifice for discharging fuel adjacent the venturi and a throttle valve disposed in the inducation passage downstream from the venturi means for controlling the flow of a fuel-air mixture to the engine and wherein said first pressure is employed in combination with a relatively high, substantially atmospheric second pressure in the fuel bowl as the only means for causing metered main fuel to flow to said induction passage means, said device being free of main fuel flow pressurizing means for pressurizing main fuel at pressures appreciably above atmospheric pressure, the improvement of providing additional means responsive to indicia of engine operation, said additional means being effective for at times modifying the effective magnitude of said first pressure in response to said indicia of engine operation in order to thereby correspondingly modify the effect of said first pressure on the rate of metered fuel flow and thereby cause said rate of metered fuel flow, at any air flow during such modification of the effect of said first pressure, to be reflective of said indicia of engine operation.

2. A fuel metering device according to claim 1 wherein said indicia comprises means responsive to conditions of engine deceleration.

3. A fuel metering device according to claim 1 wherein said indicia comprises means responsive to conditions of engine speed.

4. A fuel metering device according to claim 1 wherein said indicia comprises means responsive to conditions indicative of engine shut-down.

5. A fuel metering device according to claim 1 wherein said indicia comprises means responsive to conditions of engine intake manifold pressure.

6. A fuel metering device according to claim 1 wherein said indicia comprises means responsive to the presence of oxygen within the exhaust gases of said engine.

7. A fuel metering device according to claim 1 wherein said indicia comprises means responsive to conditions of engine deceleration and engine speed.

8. A fuel metering device according to claim 1 wherein said indicia comprises means responsive to conditions of engine deceleration, engine speed and engine shut-down.

9. A fuel metering device according to claim 1 wherein said indicia comprises means responsive to conditions of engine deceleration, engine speed, engine shut-down and the presence of oxygen within the exhaust gases of said engine.

10. A fuel metering device according to claim 1 wherein said indicia comprises means responsive to atmospheric pressure.

11. A fuel metering device according to claim 1 and further comprising further manually adjustable means for manually modifying the effective magnitude of said first pressure.

12. A fuel metering device according to claim 1 wherein said additional means comprises air-bleed means communicating generally between a source of relatively high pressure air and the vicinity in which said first pressure exists.

13. A fuel metering device according to claim 1 wherein said additional means comprises air-bleed means communicating generally between a source of relatively high pressure air and the vicinity in which said first pressure exists, and valving means responsive to said indicia of engine operation for variably opening and closing said air-bleed means generally in accordance with said indicia of engine operation.

14. A fuel metering device according to claim 1 wherein said venturi means comprises variable venturi means.

15. A carburetor for an internal combustion engine, comprising body means, induction passage means with a venturi restriction formed through said body means and having air inlet means formed at one end thereof and outlet means formed at another end thereof, a throttle valve disposed in said inducation passage downstream from said venturi restriction, first means for creating a fuel metering pressure by creating a first relatively low metering pressure of variable magnitude proportional to the square of the velocity of flow of air through said induction passage venturi restriction means, fuel metering means communicating between a source of fuel and said induction passage means, said fuel metering means being so positioned as to have one end thereof generally exposed to said fuel metering pressure in order to in response to the magnitude thereof cause a metered rate of fuel flow to said inducation passage means, said carburetor being free of fuel pressurizing means for pressuring said main fuel at pressures appreciably above atmospheric pressure, and air bleed means communicating generally between a source of relatively high, substantially atmospheric pressure air and said one end of said fuel metering means, said air bleed means being effective to bleed said high pressure air in order to effectively increase the magnitude of said fuel metering pressure, thereby decreasing the metering depression, without modifying the magnitude of said first relatively low pressure and thereby reduce the rate of metered fuel flow to said induction passage.

16. A carburetor according to claim 15, wherein said first means comprises variably openable venturi means.

17. A carburetor according to claim 15, wherein said first means comprises variably openable venturi means operatively connected to throttle valve means situated in said induction passage means downstream thereof.

18. A carburetor according to claim 15, wherein said first means comprises fixed venturi means.

19. A carburetor according to claim 15, wherein said air bleed means comprises variably openable air bleed passage means the effective opening of which is controlled generally in response to atmospheric pressure.

20. A carburetor according to claim 15, wherein said air bleed means comprises variably openable air bleed means the effective opening of which is controlled generally in response to the degree of presence of oxygen in exhaust gases of said engine.

21. A carburetor according to claim 15, wherein said air bleed means comprises openable air bleed means the opening of which is controlled in response to conditions of engine deceleration.

22. A carburetor according to claim 15, wherein said air bleed means comprises openable air bleed means the opening of which is controlled in response to engine speed.

23. In a carburetor type fuel metering system, for an internal combustion engine, wherein fuel is metered through calibrated restriction means from a source of fuel to induction passage means communicating with said engine, wherein a first relatively high, substantially atmospheric pressure is applied to said source of fuel, wherein a second relatively low, subatmospheric pressure of variable magnitude is created to be indicative of the air flowing to said engine, and wherein the difference in magnitudes between said first and second pressures is employed for creating a fuel metering pressure differential generally across said source of fuel and said calibrated restriction means causing metered fuel flow, the improvement of forming chamber-like means generally downstream of said calibrated restriction means and at least at times variably bleeding air thereto so as to thereby create a third pressure within said chamber-like means with said third pressure being greater in magnitude than said second pressure, and means responsive to conditions of engine operation for controlling the degree of such air bled to said chamber-like means.

24. A fuel metering system according to claim 23 wherein said calibrated restriction means comprises a portion of the idle fuel delivery system of a carburetor structure.

25. In an internal combustion engine carburetor of the type having induction passage means, associated fuel reservoir means containing fuel to be metered into said induction passage means, venturi means defined within said induction passage means for creating a first pressure of relatively reduced magnitude in response to the flow of air therethrough and a throttle valve disposed downstream of the venturi means, and wherein said first pressure is employed for creating a fuel-metering pressure differential generally across said fuel within said fuel reservoir means to thereby cause a corresponding rate of metered flow of said fuel into said induction passage means, the improvement of providing additional means responsive to indicia of engine operation, said additional means being effective for at times effectively modifying the magnitude of said first pressure in response to said indicia of engine operation in order to thereby correspondingly modify the magnitude of said fuel-metering pressure differential and thereby correspondingly alter said rate of metered flow of said fuel into said induction passage means even during conditions of engine operation wherein the rate of flow of air through said induction passage means has remained substantially constant.