US2989043A - Fuel control system - Google Patents

Description

June 20, 1961 F. c. REGGIO FUEL CONTROL SYSTEM Original Filed Feb. 3, 1939 3 Sheets-Sheet 1 lNvl-:NToR

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June 20, 1961 Original Filed Feb. 3, 1959 F. c. REGGIO FUEL CONTROL SYSTEM Il 3 l 74 u2 |06 AIHIM 3 Sheets-Sheet 2 IN VEN TDR new June 20, 1961 F. c. REGGIO 2,989,043

FUEL CONTROL SYSTEM Original Filed Feb. 3, 1939 3 Sheets-Sheet 3 'ff- W 2,989,043 'FUEL CONTROL SYSTEM Ferdinando Carlo Reggio, Tampa, Fla. (R0. Box 692, Norwalk, Conn.)

Application July 27, 1943, Ser. No. 496,296, now abandoned, which is 'a division of application Ser. No. 254,355, Feb. 3, 1939, now abandoned. Divided and this application .lune 7, 1956, Ser. No. 591,511

20 Claims. (Cl. 123--119) The present application is a division of my application Serial No. 496,296, filed luly 27, 1943, now abandoned, which is a division of my application Serial No. 254,355, filed lFebruary 3, 1939 now also abandoned.

'I'his invention relates to fuel supply systems for internal combustion engines and in particular to mechanisms for the control of the relative proportion of fuel and air composing the combustible mixture of internal combustion engines.

It is chiefly although not exclusively, applicable to spark-ignition aircraft engines including a fuel injection system discharging liquid fuel into the engine cylinders or the engine induction manifold.

Spark-ignition engines having a -fuel injection system are usually provided with means for controlling the fuel supply and means for controlling the air supply of the engine. It is important that the adjustment of the fuel and air control means be interrelated so that the engine cylinders may be charged with a combustible mixture having a suitable fuel-air ratio. Extensive experimental work connected in particular with the development of aircraft engines has shown that the most suitable value of fuel-air ratio varies with the engine operating conditions such as, for example, the air pressure or density in the induction manifold, the speed of the engine, the properties of the fuel. The fuel-air ratio corresponding to best economy operation required, for instance, in a cruising airplane, is dierent from that corresponding to maximum power operation which is necessary for take-off. Furthermore, enrichment of the combustible mixture may be desirable when the temperature of the engine cylinders attains or exceeds a safe limit. It is therefore advantageous that, while the means for controlling the engine supply of one of the components of the combustible mixture (eitherithe air or the fuel). may be directly actuated by the operator, the supply of the other component may be controlled by automatic means so as to vary the fuel-air ratio as a predetermined function of certain engine operative conditions. l

One of the objects of the present invention is to provide, in combination with an internal combustion engine including fuel metering means, means whereby the fuelair ratio of the combustible mixture may be automatically `controlled and caused to vary as a predetermined function of certain engine operative conditions such las, for instance, induction air density or cylinder air charge, engine speed, engine cylinder temperature.

Another object is to provide, in combination with a spark-ignition engine having a fuel injection system and in which the pilot controls the engine supply of one of the components of the combustible mixture, automatic devices for controlling the engine supply of the other component, including mixture control means whereby the fuel-air ratio of the combustible mixture is determined by the adjustment of said mixture control means and for a given adjustment thereof is substantially independent of the engine operative conditions.

Such mixture control member may be adjusted by the pilot or, according to `further objects of the "invention, by automatic devices.

The above and otherobjects of the invention be ap- Patented .lune 2), 1961 parent as the description proceeds; and while I have illustrated and described the preferred embodiments of the invention as they now appear to me, it will be understood that such changes may be made as fall within the scope of theappended claims. In the following description and in the claims various details will be identiiied by specific names for convenience, but they are intended to be as generic in the application as the art will permit.

In the drawings: FIG. l is a sectional elevation of a fuel metering pump; FIG. 2, in part a section on line 2--2 of FIG. l, shows two fuel metering pump units together with means for feeding fuel at variable pressure thereto; FIG. 3 diagrammatically indicates a fuel metering pump applied to a radial aircraft engine and control means therefor; FIG. 4 shows a modification of the fuel pressure regulating means of FIG. 2; FIG. 5 diagrammatical'ly illustrates means responsive to the induction system pressure for adjusting the fuel delivering; FIG. 6 indicates means similar to those of FIG. 5 but simultaneously responsive to pressure and temperature in the induction system; FIG. 7 is a partial modication of FIG. 6 showing a resilient means having a nonlinear characteristic; FIG. `8 is a partial modification of the pressure responsive means of FIG. 6; FIG. 9 is a further modification of the same means; FIG. 10 is a partial modification indicating the application of the device of FIG. 6 to control a conventional fuel pump; FIG. l1 partially shows an airthrottle regulating device; FIG. 12 indicates a modification of IFIG. ll; FIG. 13 illustrates the application of the control means of FIG. 1l to a conventional fuel pump; FIG. 14 is a diagrammatic View of means responsive to an engine operating temperature for controlling the fuel-air ratio; FIG. l5 shows means responsive to the induction pressure for controlling the fuel-air ratio; and FIG. 16 illustrates speed-responsive means for varying the fuel-air ratio.

As shown in FIG. 1, a fuel pump 1 has a plunger 2 reciprocating ain a barrel 3 having a port 5. At its upper end, beyond an annular groove 6, the plunger 2 has edges 7, 8 which limit the plunger surface in contact With the bore of barrel 3. Below groove 6 and at suitable distance therefrom plunger 1 has a splined portion 10 formed as a pinion and meshing with a rack 11 formed in a piston 12 slidable in a cylindric cavity 15 of barrel 3. The lower 'end of plunger 2 is urged by a spring 1.6 against a lifter 18 operated by a cam 19 driven by the engine. A cupshaped cap 20 screwed on the upper end of barrel 3 closes the pumping chamber 22 and provides, between barrel and cap, an annular chamber or reservoir 24 communicating through port 5 with pumping chamber 22 and through annular apertures of very small area provided between barrel 3 and cap 20 with annular chambers 26 and 27. A gasket 21 prevents fuel leakage between barrel 3 and cap 26.

Annular chambers 26 and 127 communicate with chamber 2S at one end of cylindric cavity 1S by means of ducts 30, 31, 32 and 33. Chamber 29 at the opposite end of cavity 15 communicates with reservoir 24 through duct 35. At the upper end of pumping chamber 22 a spring loaded check valve 36 admits fuel, through duct 38, annular groove 39, duct 40 and hollow fastening bolt 41, to conduit 42 leading to the nozzle. A spring 44 acting on piston 12 is provided in chamber 28. In the preferred embodiment, a multicylinder engine has number of pumps 1 each arranged near the corresponding cylinder. As indicated in FIG. 2, a fuel transfer pump 48, connected through pipe 51 with a fuel tank, not shown, delivers fuel to a conduit `45 which communicates, through a hollow bolt similar to bolt 41 and a duct 47, with chamber 29 and reservoir 24 of each pump 1, which chamber 28 of each pump communicates, through a duct 33 and another hollow bolt, with a fuel return line 49 and a pipe 50 leading fuel back to the tank. Between outlet and inlet ports of transfer pump 48 a bypassis provided, controlled by ya pressure regulating valve 1ncluding a piston 52 urged by a spring 53 Whose load may be varied by screwing or unscrewing the threaded cap 54 provided with a lever arm 55. A groove 56 and a duct 57 lead fuel leakage back to return line 49.

As the delivery of transfer pump 48 is substantially larger than the total requirement of pumps llunder all operating conditions, excess fuel flows past regulating valve 52, and the fuel pressure in feed line 45 and in chambers 29 of pumps 1 will therefore be controlled by the load of spring 53 and the adjustment of lever 55. Changes of pressure in chamber 29 axially displace piston 12 and vary the angular adjustment of plunger 2. In FIG. 3 -a pump 1 is shown equipping an aircraft engine of the radial type having a cylinder 60 to which air supplied by a supercharger 61 is fed through induction pipe 62. A throttle valve 63 controlled by a lever 64 and control lever 65 is provided to regulate the air charge. A second control lever 66 adjusts the angular position of lever 55 shown in detail in FIG. 2. Fuel conduit 42 communicates with nozzle 70 through which fuel is injected into pipe 62 during part of the suction stroke of cylinder 60. Nozzle 70 may obviously be mounted in any other suitable position, such as near the intake cylinder port or valve, or inside the cylinder.

In the position shown in FIG. 1, the plunger 2 is at the end of its suction stroke and has uncovered the port 5 allowing fuel to flow into the pumping space 22. As the plunger rises, operated by cam 19, the surface comprised between edges 7 and 8 covers the port 5. The pressure rises rapidly in space 22 and lifts the check valve 36 and through nozzle 70 fuel is injected in the i11- duction pipe 62 and carried by the incoming air into the cylinder 60. The injection continues until edge 8 uncovers port 5 which now functions as a pressure relief port through which the remaining fuel displaced by the plunger is bypassed into the reservoir 24.

While the engine is in operation, the fuel pressure in grooves 26 and 27, substantially the same as in chamber 28 and fuel return line 49, is lower than in reservoir 24, and a continuous flow of fuel is vented through the annular `apertures of very small area provided between reservoir 24 and grooves 26 and 27. T he volume flow- 1ng through an orifice under a given difference of pressure being for a gas or a vapor several times greater than for a liquid, the area of said apertures may be made such that under the existing difference of pressure vapor or gas separating from the fuel in reservoir 24 can be eliminated therefrom, while only a relatively small volume of liquid fuel escapes through said apertures. As said annular apertures surround port 5, whatever the orientation of pump l may be relative to the vertical line, gas or vapor bubbles can be vented from reservoir 24 at a point higher than port 5, thereby reducing the risk of such bubbles being drawn into pumping space 22 where they might interfere with the correct operation of the pump.

The plunger 2 being provided with at least one substantially helical control edge, the duration of its effective delivery stroke and thereby the weight of fuel delivered per stroke may be varied by a turning adjustment of the plunger obtained by adjusting the fuel pressure regulating valve 55. In the preferred embodiment of the invention the fuel supply system is so arranged that changes in fuel pressure in conduit 45 and the corresponding variations in delivery per cycle of pumps 1 are proportional. Owing to the fact that axial displacement of valve piston 52 corresponding to changes in the fuel flow through the valve is very small, and the spring 53 is very flexible, changes in the load of the latter due to said axial displacement of piston 5'2 are practically negligible, variations of angular adjustment of lever 55 and corresponding changes of fuel `delivery per cycle of pumps 1 may also be considered proportional. To secure proper venting and cooling of pumps 1 under all conditions, it is convenient that the zero delivery angular adjustment of plunger 2 correspond to a predetermined pressure in feed line 45 higher than in fuel return line 49. FIG. 4 indicates an alternative form of pressure regulating valve wherein a highly resilient spring 73 is adjusted to exert on valve piston 72 a load which balances said predetermined fuel pressure that corresponds to said zero delivery angular adjustment of plungers 2. Since, as previously stated, the maximum axial displacement of valve piston 72, under extreme operating values of fuel ow through the port controlled by piston 72, is very small and the spring 73 is very flexible, if no load is applied to the outer end of piston 72, the fuel pressure in conduit 45 is maintained by springs 73 substantially constant at said predetermined value independently of changes of delivery of fuel transfer pump 48, and the plungers 2 are maintained angularly adjusted for zero delivery. If a further load is applied to valve piston 72, for instance by means of lever 74, the fuel pressure in conduit 45 is increased beyond said predetermined value and the plungers 2 are turned to deliver the corresponding quantity of fuel. Therefore in the preferred embodiment of the invention, as already pointed out, the fuel delivery per cycle of pumps 1 is proportional to the load transmitted to piston 72 by lever 74.

One of the advantages of this fuel supply system is that control of fuel delivery is obtained by adjusting the pressure regulating Valve, which may be performed by automatic devices of very little energy, especially if compared With fuel pumps of the same general character in which turning adjustment of the pump plunger is obtained fb-y means of links positively inter-connecting all plungers with the control means, whereby, if a plunger is scored and cannot be turned in its barrel, it may prevent the adjustment of all other pump plungers and put the engine out of control. In the fuel supply system which is herein described, a failure occurring to one pump does not interfere with the operation of the other pumps.

The arrangement of FIG. 3 in which air and fuel supplies are controlled by distinct levers 65, 66 is not suitable for spark-ignition engines, which require a combustible mixture having definite fuel-air ratio. A more convenient arrangement, shown in FIG. 5 includes pressure responsive means, such as a resilient and evacuated bellows 75 surrounded by fluid having the same pressure as in the induction pipe 62, transmitting to a fuel pressure regulating valve 72, through a link 76 and a lever 74, a load proportional to the induction pressure. The operating distance of link 76 from the fulcrum of lever 74 may be varied by lever 79 connected with control lever 78 whereby the ratio of fuel delivered per cycle to induction pressure depends on the adjustment of control lever 78 and is independent of engine operating conditions or altitude. This simple device, applied to an internal combustion engine in which the induction temperature, or temperature of the air in engine manfold 62, is substantially constant, as it may be the case when an intercooler is used, and in which the cylinder air charge is proportional to the induction pressure, automatically controls the fuel delivery so as to maintain, for each adjustment of lever 78, a corresponding constant value of fuel-air ratio in the combustible mixture. This device is intended to be used in combination with means for controlling the air supply of the engine, such as, for instance, that indicated by numerals 63 to 65 in FIG. 3, by which the induction pressure in manifold 62 may be regulated. The main control of the engine throttle lever 65, and the fuel-air ratio may be adjusted by mixture lever 78, either by the operator or by automatic devices. In combination with engines in which the variations in induction temperature are small but not negligible, it may be convenient in order to compensate for variations in air density and engine air supply due to small changes of temperature in manifold 62, to provide in bellows75 a certain weight of fluid, the pressure of which increases with the temperature, the arrangement being such that the temperature of bellows 75 be the same as in pipe 62 whereby, fora given pressure in said pipe, the fuel delivery is reduced ywhen the induction temperature increases and the density of the air in manifold 62 correspondingly decreases.

As shown in FIG. 5, bellows 75 is enclosed ina housing, whose walls are preferably heat-insulated, connected with induction pipe 62 by means of a large and short conduit. Eddy currents or turbulence in said conduit and housing caused by the high velocity of `the air ilow in pipfe 62 aswell as the pulsations of pressure therein, produce an active thermic exchange, by conduction and convection, between the air flowing in pipe 62 and bellows 75. The thermal capacity yof such bellows usually is, or may be made, extremely small. Therefore, as previously pointed out, the'air ilowingthrough pipe 6 2 and the expansible fluid contained in bellows 75 will have substantially the same temperature.

While the lfuel metering pump describedk above and shown in FIGS. l `and 2 offers various advantages, it is no part of the invention covered in the present application; and it will be understood that, in lieu of said pump, any other suitable type of injection unit or spray nozzle may be used, such for example as the usual type of nozzle consisting essentially of a calibrated orifice, through which fuel from the fuel manifold 45 can be injected into the engine induction manifold or other place of utilization of the engine. It will be appreciated, of course, that the by-pass or fuel pressure regulating valve 52 or 72 which controls the fuel pressurev in the 'fuel manifold 45 will also control the rate of fuel discharge through such nozzles. Where important variations in engine induction vtemperature may occur, such as in aircraft engines supercharged for high altitude, according to the present invention an arrangement such as that shown in FIG. 6 may be provided, in which a casing 80, communicating through a large duct 81 with induction pipe 62, contains air at induction pressure and, as already stated in connection with FIG. 5, at induction temperature. An evacuated resilient bellows 82 in said casing acts on lever 83 to operate rod 94 and pistons 84, 85 which control admission of oil under pressure, usually `led from the engine lubricating system through pipes 87, 88 as indicated by the arrows, to opposite lsides of piston 86. Pipes S9 drains oil back to the engine sump. A floating lever 90 is connected at its ends with rod 94 and piston 86, and at an intermediate point with rod 91 connected through lever 92, rod 93 and lever 74 with fuel pressure regulating valve 72. Also in casing 80 there is a bellows 95 which contains a definite weight of gas or other suitable iiud at constant volume and induction temperature. The absolute pressure in said bellows is therefore proportional to the absolute induction temperature. Bellows 95 and a similar and evacuated bellows 96 act against each other and on a lever 97 to operate rod 100 of a servo mechanism similar to that already described in detail. Engine lubricating oil is led thereto and evacuated therefrom as indicated by the arrows. The pressure of the air in housing 80 acts in opposite directions on bellows 95 and 96 thereby b-alancing out the effect of any change of pressure in housing 80 so that the load transmitted to lever 97 is only dependent on the induction temperature. The servo mechanism acts on lever 98 to vary the operating distance of rod 93y from the fulcrum of lever 92. Spring 99 balances the load transmitted by the bellows to rod 100 and is designed so that the operating distance o-f rod 93 from the fulcrum of lever 92 is proportional to the actual absolute induction temperature. Any chan-ge in said temperature operates bellows 95 and in turn the servo mechanism to rotate lever 98 and Vvary the load of spring 99 until the4 balance of rod 4100 in its neutral position is re-established. Mixture control 78, as already shown in FIG. S, is adapted to modify the distance of rod 93 from the fulcrum of lever 74. The device works as follows: The evacuated resilient bellows 82 exerts on rod 94 an upward load proportional to the induction pressure. In normal operation rod 94 and control pistons 84 and 85 are maintained in equilibrium in neutral position by a downward load of equal magnitude transmitted from fuel pressure regulating valve 72 to rod 94. Thus, for a given adjustment of lever 98 and mixture control 78, the induction pressure and the load of valve 72 (and in turn the engine fuel supply) are proportional. If now the pilot operates the engine throttle indicated 4by numeral 65 in FIGURE 3 to reduce the engine air supply, or if the altitude at which the engine operates increases, the induction pressure surrounding bellows 82 decreases, and with it decreases the upward load transmitted by Vthe bellows to rod 94, while the downward load transmitted thereto from valve 72. remains unchanged.

Bellows 82 thus expands and determines downward motion of the rod 94 and oil control pistons at valves 84 and 85. Oil under pressure, admitted over piston 86, displaces the latter downwardly, causing anti-clockwise rotation of lever 74 and displacement toward the left of valve 72, thereby increasing the open area of the bypass controlled by said valve. The result is that the fuel pressure in conduit 45, and the engine fuel supply decrease. But also the hydraulic load on valve 72 and in turn the downward load transmitted from valve to rod 94 decrease, causing rod 94 to move upwardly toward its neutral position. Downward movement of piston 86 continues until the loads transmitted to rod 94 by valve 72 and, through bellows 82, by the induction pressure have once more attained equal magnitudes and rod 94 resumes its neutral position. Obviously, an increase of induction pressure, due either to a change of adjustment of the ,throttle control 65 or to a decreased altitude causes the device of FIGURE 6 to correspondingly increase the engine lfuel supply. Induction pressure and fuel delivery per cycle thus vary proportionally.

As has already been stated, lever 97 actuated by bellows and 96 transmits an upward load to rod 180 which is proportional to the induction temperature. In normal operation, that is when said temperature is constant, said load is balanced by spring 99 and rod 100 is in its neutral position. An increase of induction ternperature causes a proportional increase of presure within bellows 95 and of the upward load transmitted to rod 100. Bellows 95 resiliently expands, bellows 96 contracts, and rod 100 `is lifted to a position in which the elastic reaction due to the resilient deformation of the bellows balances the difference between the upward load transmitted to rod 100 due to the fluid pressure within bellows 95 andthe load of spring 99. Oil under pressure is led above the piston of the servo motor, thus causing lever 98 to rotate anti-clockwise and gradually increasing the load of spring 99. As the latter load increases, rod 100 moves downwardly. Operation of the servo-motor and krotation of lever 98 continues until rod 100 reaches its neutral position, the load of spring 99 having ,in the -meantime assumed a value equal in magitude to the new upward load transmitted to rod 100 by the bellows and due to the new value of the induction temperature, the result being that lever 98 assumes a new position of equilibrium in which `the distance of rod 93 from the fulcrum of lever 92 has increased in proportion to the increase of absolute induction temperature.

Thus, the upward load on rod 93 is proportional to the absolute .pressure and inversely proportional to the absolute temperature in induction pipe 62, and is therefore proportional to the air density therein.

If the air charge per cycle, or weight of air present in the engine cylinder during the compression and power 7 Y Y l n strokes, is proportional to the induction density, the mechanism shown in FIGURE 6 gives for each adjustment of mixture control lever 78 a corresponding constant fuel-air ratio.

In certain engines it has been found that the air charge is inversely proportional not to the absolute induction temperature, but to the square root thereof. To automatically maintain in such engines a constant value of the fuel-air ratio for each position of the mixture control lever 78, the mechanism of FIG. 6 may be modified by the adoption of a spring 101, shown in FIG. 7, whose dellection is, within the designed limits, proportional to the square root of the load, such as a coil spring having a uniform diameter and a non-uniform pitch so designed that, within the operating range, the number of free coils is inversely proportional to the spring deflection, whereby the distance between rod 93 and the fulcrurn of lever 92 is proportional, and thereby the load on rod 93 inversely proportional, to the square root of the absolute temperature in induction pipe 62.

In engines in which the air charge is found to be a still different function of the induction temperature, an automatically constant value of fuel-air ratio may be obtained either by providing resilient means 101 of suitable characteristic, or by establishing the suitable relation between rotation of lever 98 and distance of rod 93 from the fulcrum of lever 92 by means of a cam substantially as shown in FIGS. 14 or l5.

Furthermore it has been observed that in certain engines, in particular those highly supercharged and having a large valve overlap, such as applied conveniently to injection engines wherein it is possible to secure scavenging of the combustion chamber without loss of fuel, the air charge, or weight of air remaining in the engine cylinder during compression and power strokes, is affected, for a given induction pressure, by the surrounding atmospheric, or exhaust pressure. To correct such influences so that the load on rod 93 be proportional to the effective cylinder yair charge, a comparatively small bellows, whose interior is maintained by means of a suitable conduit at the surrounding atmospheric pressure or substantially at the engine exhaust pressure, may be added to the pressure responsive bellows 82 of FIG. 6, either within the evacuated bellows 82, as indicated by numeral 102 in FIG. 8, or on opposite side of lever 83, as indicated by numeral 103 in FIG. 9, its size and position being determined in accordance with engine tests.- Passages 102 and 103 provided in the wall of housing 80 maintain the pressure within bellows 102 and 103, respectively, equal to the surrounding atmospheric pressure.

It is to be clearly understood that, while the fuel metering pump described above and illustrated in some of the drawings, and the hydraulic control thereof are believed to be particularly suitable for automatic control, the means for automatically adjusting the fuel delivery or the fuel-air ratio according to the present invention may be applied to any suitable fuel supply system.` FIG. l diagrammatically shows a conventional injection or metering pump of the plunger type 104 driven by the engine and comprising a plurality of pump elements connected by pipes 105 with the various engine cylinders and whose delivery is adjusted by axial displacement of control rod 106 connected with a spring 107 designed and mounted so that its load is proportional to the fuel delivery per cycle. Such pump may therefore be operated by lever 74 shown in FIG. 6 in the manner described above.

The device shown in FIG. 6 is used in combination with means operable by the pilot for controlling the engine air supply, such as means for adjusting the speed of an exhaust-driven turbo-supercharger, or other suitable means for varying the peripheral velocity of the supercharger impeller, or, as shown in FIG. 3, a controlI lever 65 operating the air throttle valve 63.

FIG. 1l diagrammatically indicates an alternative control system wherein control lever 108 operable by the pilot adjusts the fuel delivery and a device having the same character as that shown in FIG. 6 in that it exerts on a rod 93 a load proportional to the air density in induction pipe `62, or substantially proportional to the air charge per cycle of the engine cylinders, operates the means for controlling the engine air supply, such as the air throttle valve 63, to maintain the fuel-air ratio constant or substantially constant at a value determined by the adjustment of the mixture control lever 78. Fuel control lever 108 is connected through a rod having a lost motion device such as an elongated slot 109 with lever 111, similar to the lever 55 of FIG. 2, for adjusting the spring load of the fuel pressure regulating valve. Clockwise rotation of lever 111 causes an increase of fuel delivery and a proportional increase of the load transmitted by spring 112 to the rod 113 carrying pistons 114 and 115 controlling the admission of oil to opposite sides of piston 116. A tension spring is provided, tending to resiliently maintain, against the action of spring 112, lever 111 applied against the left side of slot 109. Oil under pressure from the engine lubricating system is led to pistons 114, 115 and is conducted back to the engine sump as indicated by the arrow. A floating lever 117 is connected with piston 116, with lever 64 operating the air throttle valve 63 and, through a lost motion device such as an elongated slot 121, with lever 111. A tension spring 118 tends to rotate the lever 117 clockwise, and stops 119, 120 limit its motion. Lever 74', cooperating with the rod 93, is connected with rod 113 and transmits to the latter a load proportional or substantially proportional to the air charge per cycle. In normal operation the rod 113 is in balance, in its neutral position, under the action of lever 74 and spring 112 whose load is proportional to the fuel delivery per cycle. 'If the pilot rotates clockwise either lever 108 to increase the fuel delivery, which increases proportionally the load of spring 112, or lever 78 to decrease the fuel-air ratio, which decreases the torque transmitted by rod 93 to lever 7'4, or if the air charge per cycle decreases owing either to increased altitude or increased engine speed, in which latter case the automatic device of FIG. 6 proportionally decreases the load transmitted to lever 74 by rod 93, the rod 113 is displaced to the right to admit oil under pressure to the left side of the piston 116 and thereby rotate the lever 117 clockwise to open the air throttle valve 63 and increase the flow of air, which in turn increases the induction air density, and the cylinder air charge. The device shown in the upper part of FIG. 6 causes the load transmitted by rod 93 to the lever 74 to increase proportionally, thus bringing rod 113 back toward its neutral position. Displacement of piston 116 of the servo-motor goes on until the balance of the rod 113 in said neutral position is again attained. This means that in the lirst case, in which the pilot rotates clockwise the control lever 108 to increase the engine fuel supply, the combined servo-motors shown in the upper part of FIGURE 6 and in FIGURE ll automatically open the air throttle to proportionally increase the engine air supply, thereby maintaining the fuel-air ratio constant. In the second case, in which the pilot rotates the mixture control lever 78 clockwise, the air charge is automatically increased so as to bring the fuel-air ratio to a lower value corresponding to the new adjustment of the lever 78. In the third case, in which the air charge decreases owing to increase in altitude, or increase in engine speed and corresponding reduction in engine volumetric eciency, said device automatically increases the opening of the throttle to maintain the fuel-air ratio constant at the value corresponding to the setting of the mixture control lever 78. The device will obviously operate in the opposite Way when the pilot rotates the lever 108 or .the lever 78 anti-clockwise, when the altitude decreases, or when the engine speed decreases.

It is therefore clear that, while the device shown in FIGURE 6, intended to be used in connection with an engine in which the pilot directly controls the engine air supply, automatically adjusts the engine fuel supply so as to maintain the fuel-air ratio constant at a value corresponding to the setting of the mixture control lever 78, the arrangement combining the upper part of FIG- URE 6 with the device shown in FIGURE ll, intended tov be used in connection with an engine in which the pilot directly controls the fuel supply, automatically adjusts the air supply thereof to keep the fuel-air ratio at a value corresponding to the adjustment of the lever '78. In both cases the pilot controls the supply of one of the components of the combustible mixture, while the auto matic device adjusts the supply of the other component in such a way that the fuel-air ratio is determined by the setting of a mixture control member 78.

However, in the operation of the device shown in FIGURE 1l, especially at high altitude, the lever 117 may reach the stop l119, in which position the air throttle valve `63 Vis wide open, before the rod 113 is led back to its neutral position, and the piston 116 will be further displaced to the right to rotate the levers 117 and 111 anticlockwise and decrease the fuel delivery until the fuel-air ratio assumes the value corresponding to the adjustment of lever 78 and the balance `of rod 113 is attained. Inverse operation of the devicewill occur when either lever 108 or lever 78 are rotated anticlockwise or the air charge per cycle tends to increase` FIG. 12, a partial Vmodification of FIG. 11, shows a lever 123 which, like lever :111 of FIG. ll or lever 55 of FIG. 2 controls the spring load of the fuel pressure regulating valve. `A load `proportional to the fuel delivery per cycle is transmitted `to rod 113 by a plunger 124 whose inner end is exposed to the fuel pressure of conduit 45, and on which a highly resilient lspring 125, similar to spring 73 of FIG. 4, exerts a substantially constant pressure balancing the fuel pressure on the plunger 124 corresponding to `zero fuel delivery.

Obviously, the same device of FIG. 11 may be applied to a conventional injection or metering Vpurnp -4 shown in FIG. 13 in which the lever 127, controlled by way of likages including elongated slots 109 and 121 and connected with spring y112 controls by means of a -rod 1196 the fuel delivery per cycle of pump 1104, the arrangement being such that when rod 1.13 yis 'in neutral position, the load `of spring 112 is proportional to the fuel delivery per cycle.

The above arrangements, yin which the adjustment of fuel-air ratio of the Vcombustible mixture is left to the arbitrary choise of the pilot or operator, is not the most suitable in connection .with aircraft engines. As it has already been stated, `engine tests show that the most suitable value of fuel-air ratio varies with the engine operative conditions, ramong which are the air `pressure or density in the induction manifold, the engine speed, the engine cylinder temperature. Accordingly, one of the objects of the invention is to provide, in combination with the previously disclosed arrangements, means responsive to one or more engine operative conditions whereby the adjustment of the mixture control member, and in turn the fuel-air ratio, may be automatically controlled and vary as a predetermined function of said operative condition or conditions.

Operation of the engine with best economy ymixture is possible overa certain range of power, beyond which the engine cannot Vsafely be operated without resorting to someadditional enrichment of the Amixture yto suppress over-heating and Adetonation. A temperature responsive element 131i, FIG. `14, mounted in suitable location such as on a cylinder 'head or near an exhaust port, is connected with a bellows 131 placed to act against an evacuated bellows v132 so that changes in the pressure surrounding the bellows act in opposite directions on said bellows and therefore have no effect on their operation. Temperature changes about element operate the bellows 131 and in turn the rod 133 of a servomechanism, similar to those already described in detail, to control the angular adjustment of lever l134, of cam 135 and to vary the load of spring 136 acting on the rod 133. An increase in temperature of the element 130 lowers the rod 133 and in turn rotates the lever 4134 clockwise thereby increasing the load of spring 136 until the balance of rod 133 in its neutral position is rees tablished. The cam 135 is adapted to operate lever 137, having the same function as lever 79 previously illustrated, so that, for each temperature of element 130, it determines a corresponding predetermined minimum possible value of the fuel-air ratio. Mixture control lever i3 and lever 137 are connected through a lost motion device such as an elongated slot 138 and a tension spring 139 whereby the lever 78, whatever its adjustment may be, does not oppose anticlockwise rotation of lever 137 when the latter is operated by the cam 135.

It has been pointed out in the foregoing that the device illustrated in FIG. 6 may automatically vary the engine fuel supply per cycle in direct proportion to the air induction pressure and in inverse proportion to the absolute temperature thereof, the proportionality ratio, and in turn the fuel-air mixture ratio being determined by the elfective length of the horizontal arm -of the bell crank lever 74, or in other words by the distance between rod 93 and the pivot of lever 74. lt has also been set forth that such a device will operate correctly as stated with an engine in which the cylinder air charge varies proportionally to the air induction density, but that in certain types of engines, for instance highly supercharged and air scavenged aircraft engines, the effective cylinder air charge is appreciably affected by changes of exhaust or surrounding atmospheric pressure, and may vary with the induction air absolute temperature according to a function of the latter substantially different from inverse proportionality, land that in combination `with ysaid engines devices partially modiied according to FIGS. 7, 8 or 9 will therefore be more suitable. However, whether or not it includes any of said modifications, the device of FIG. 6i is provided with manually actuatable control means 78 for adjusting the effective length of the lever 74 to control the fuelair ratio. In order to obtain, as stated among the ob- 'ects of the invention, a fuel-air ratio that varies automatically as a predetermined function of engine operative conditions, the lever 79 of the device represented in FIG. 6 may be eliminated, and in substitution therefor there may be provided a .lever `137 actuated by a cam having two distinct ways of adjustment, for example a slidable and rotatable cam 146 as shown in FIGS. l5 and 16, there being provided means responsive to engine operative conditions for adjusting said cam in said two `distinct ways, whereby the mixture ratio may automatically be caused to vary as a predetermined function of two independent variables, said function being dependent on the configuration of the cam.

The upper arm of lever 137 is connected with the lower end of rod 93, shown `in FIG. 6, for adjusting the effective length of lever 74, and has therefore the same function as the upper arm of lever 79. The lower arm of lever 137 has a lost motion connection with a rod 138 which may be actuated by Way of the manual control member 78 of FIG. 6. A third, horizontally extending arm of the lever 137 shown in FIGS. l5 and 16 is actuated by the cam 146 which may be axially and angularly adjusted by engine condition responsive devices, shown in FIGS. `l5 and 16 as mechanisms responsive to the engine speed and to the manifold air pressure respectively.

The automatic mixture ratio control device may thus include the mechanism of FIG. 6 minus lever 79 in combination with the structure represented in FIGS. 15 and `l6. FIG. 15 shows means for regulating the fuel-air ratio as a function of the induction pressure, assuming the mixture control lever 78 to be in lean adjustment, with rod 138 in the position shown in the drawing, thus permitting contact between the horizontal arm of lever 137 and cam 146. A bellows 141, evacuated totally or in part, and enclosed in a housing communicating with engine induction pipe 62, operates rod 142 of a servo mechanism similar to those already described, whereby an increase in induction pressure raises rod 142 and causes lever 143 to be rotated anticlockwise until the increased load of tension spring 144 re-establishes the balance of rod 142 in its neutral position. Lever 143 is secured to an externally splined sleeve 147 rotatably mounted on an engine driven shaft 145. The warped cam 146 is slidably but non-rotatably mounted on sleeve 147, so that the angular adjustment of the cam is dependent on the induction pressure, while the axial adjustment of said cam is determined by speed responsive means such as a governor 148 dliven from the engine through shaft 145. The governor 148 controls rod 149 of a servo mechanism whereby an increase in engine speed displaces rod 149 to the left and causes lever 150 to be rotated clockwise until the increased load of tension spring 151 returns the rod 149 to its neutral position. The cam 146 therefore determines for each value of induction pressure and engine speed a corresponding minimum possible value of fuel-air ratio. In the preferred embodiment the form of the cam is such that in the cruising range of induction pressure and engine speed combinations such minimum value corresponds substantially to the best economy mixture, while for combinations of engine speed and induction pressure corresponding to higher power output the minimum fuel-air ratio will be higher than that corresponding to best economy mixture. Automatic van'- ation of the mixture ratio is obtained by means of the cam 146 whenever the mixture control lever 78 is set for lean mixture, owing to the elongated slot 138 and spring 139, while further enrichment may be obtained by moving the lever 78 anticlockwise.

It is to be expressly understood that the invention is not limited to the specific embodiments shown, but may be used in various other ways, and changes, modifications, substitutions, additions and omissions may be made in the construction, arrangement and manner of operation of the parts without departing from the limits or scope of the invention as defined in the following claims. Where the claims are directed to less than all of the elements of the complete systems disclosed, they are intended to cover possible uses of the recited elements in installations which may lack the non-recited elements.

I claim:

l. In a control device for an engine having an air induction system and a fuel supply system with fuel conduit means and valve means therein for regulating the rate of engine fuel supply, the combination with said valve means of air induction pressure responsive means, air induction temperature responsive means and engine speed responsive means operatively connected to said valve means for actuating the same to control the rate or' engine fuel supply as a predetermined function of said pressure, temperature and speed.

2. In a fuel supply system for an engine having an air induction system, the combination with valve means for regulating the rate of engine fuel supply, of engine speed responsive means, induction air pressure responsive means, induction air temperature responsive means and manually operable control means for actuating said valve means to control the rate of engine fuel supply as a preselected function of said speed, pressure, temperature and the setting of said manual control means.

3. For an engine having an air intake system and a fuel supply system including a variable-pressure fuel conduit through which liquid fuel is delivered to the engine at a rate dependent on the fuel pressure in said conduit, the combination with valve means associated with said conduit for variably regulating the fuel pressure therein, of intake air pressure responsive means, intake air temperature responsive means and engine speed responsive means operatively connected to actuate said valve means for regulating the fuel pressure in said conduit as a preselected function of said speed, pressure and temperature.

4. For an engine having an air intake system and a fuel supply system including variable-pressure fuel conduit means through which liquid fuel is supplied to the engine at a rate dependent upon the fuel pressure in said conduit means, the combination with pressure-regulating valve means for controlling the fuel pressure in said fuel conduit means, of intake air pressure responsive means, intake air temperature responsive means and engine speed responsive means and manually settable control means operatively interconnected to actuate said valve means for regulating the fuel pressure in said conduit means as a preselected function of said speed, pressure, temperature and the setting of the manual means.

5. In control apparatus for an engine having an air induction system with air flow control means therein, a fuel supply system including variable-pressure fuel conduit means through which fuel flows to the engine at a rate dependent on the fuel pressure therein, the combination with pressure-regulating valve means under the control of the operator for controlling the fuel pressure in said fuel conduit means, of fuel pressure responsive means connected with said fuel conduit means for sensing pressure variations therein, engine induction air pressure responsive means, engine induction air temperature responsive means, and an operative connection for actuating said air ow control means from said fuel pressure responsive means and said air pressure and air temperature responsive means.

6. Engine control mechanism including a fuel injection system, means connected with said system for controlling the engine fuel supply, engine air supply control means, and means for actuating said air supply control means in dependence upon the engine fuel supply and the engine induction air pressure and temperature.

7. Engine control system including manually operable means for controlling the engine fuel supply, engine air supply control means, and means for actuating said air supply control means in response to variations of engine fuel supply and induction air pressure and temperature.

8. In a fuel supply system including variable-pressure fuel conduit means through which liquid fuel is supplied to the engine at a rate dependent on the fuel pressure in said conduit means, the combination with a fuel pump for supplying fuel to said conduit means, of valve means for regulating the fuel pressure in said conduit means, and means responsive to speed, pressure and temperature conditions of said engine for acting on said valve means to control the rate of engine fuel supply.

9. In a fuel supply system for an engine having an air intake system, said fuel system including variable-pressure fuel conduit means through which liquid fuel is supplied to the engine at a rate dependent upon the fuel pressure in said conduit means, the combination with a fuel pump for supplying fuel to said conduit means, of valve means for regulating the fuel pressure in said conduit means, air intake pressure responsive means for acting on said valve means to vary said fuel pressure substantially in proportion to said air pressure, and means responsive to temperature and speed conditions of the engine for acting on said valve means to vary said fuel pressure in predetermined relation to said temperature and speed conditions.

10. In control apparatus for an engine having an air induction system for supplying air flow to the engine, and a liquid fuel supply system with a variable-pressure fuel manifold and spray nozzles connected with said fuel manifold for supplying the engine with liquid fuel at a rate dependent upon the pressure in said fuel manifold, the combination with a fuel pump for delivering fuel to said fuel mani-fold, of valve means for controlling the fuel pressure in s'aid fuel manifold, and means responsive to variations of air induction pressure and atmospheric pressure and means responsive to speed and temperature conditions of the engine for acting on said valve means to control the pressure in said fuel manifold.

11. An engine fuel metering system comprising: a fuel pump adapted to be driven fromy the engine; fuel pressure actuated fuel ilow controlling valve means responsive to changes of fuel pressure on the discharge side of said pump for regulating the rate of fuel delivered by the pump to the engine; and means operatively connected with said valve means for actuating the same, including: a closed housing adapted to be connected with the engine air induction system, a pressure responsive bellows assembly in said housing including a larger bellows which is evacuated and a smaller bellows which is internally vented to atmospheric pressure, means responsive to changes of temperature in said air induction system, and speed responsive means adapted to be driven from the engine.

l2. An engine fuel supply system including an engine driven fuel pump; fuel delivery control means for regulating the engine fuel supply; engine air induction pressure and atmospheric pressure responsive means, engine air induction temperature responsive means, and engine speed responsive means' for actuating said fuel delivery control means; said fuel delivery control means including a resiliently loaded slidable valve actuated by fuel pressure variations on the discharge side of said fuel pump and operatively connected with said speed responsive means.

13. Engine fuel supply system including an engine driven fuel pump; control means responsive to fuel pressure on the discharge side of said pump for regulating the rate of delivery of fuel from said pump to the engine; and means including engine speed responsive means, engine operative temperature responsive means and means responsive to changes of atmospheric pressure and acting on said control means in opposition to the fuel pressure applied thereon for positioning said control means.

14. Engine fuel supply system including an engine driven fuel pump; delivery control means for varying the quantity of fuel supplied by the pump to the engine, including valve means responsive to fuel pressure on the discharge side of said pump; and means, including operatively interconnected engine speed responsive means, engine operating temperature responsive means and a manually operable control lever for applying a variable load to said valve means in opposition to said fue] pressure, to position said valve means.

15. Engine fuel supply system including a fuel pump; control means for regulating the rate of fuel supply from the pump to the engine; said control means including valve means responsive to fuel pressure on the discharge side of the fuel pump; engine induction air pressure responsive means acting on said valve means in opposition to said fuel pressure for positioning said valve means; and means including engine speed responsive means for varying the effect of said induction air pressure responsive means on said valve means.

16. An engine having `an air induction system; a variable-pressure fuel supply system whose delivery increases or decreases with the fuel pressure; a valve in the fuel system; air pressure responsive means connected with the induction system to actuate the valve; air density responysive means connected with the induction system to actuate said valve; and means for actuating said valve in response to variations of said fuel pressure.

17. For use with -an air-consuming combustion engine having an air intake system, a fuel system including: a fuel supply pump; means movable in response to variations of fuel pressure on the discharge side of said pump for varying the delivery of fuel by said pump tothe engine; a pressure sensitive device adjusting by its movements the means for varying the delivery of fuel to the engine, said device including intake air pressure responsive means, intake air temperature responsive means, and engine speed responsive means.

18. In a fuel control for a thermal powerplant, a hydraulic cylinder with a slidable piston defining a pressure chamber, means for supplying -a control iluid under pressure to said chamber, means for varying the fuel supply rate in accordance with changes in the quantity of control fluid in said chamber, a spring adapted to bias said piston `against the pressure of the control fluid, rst means including a pilot valve connected to the piston by a follow-up lever for controlling the quantity of control fluid admitted to and released from said chamber, a variable ratio lever mechanism connecting the spring to the piston, and means including a servo-motor connected to said mechanism and operable to vary the effective lever ratio in response to changes in a control pressure which is a function of ambient atmospheric pressure.

19. A fuel and speed con-trol apparatus for a combustion engine having an air compressor, and a pump for supplying fuel to said engine; comprising a manual control lever and a fuel regulating system for controlling the delivery of fuel from said pump to said engine; said system comprising a fuel metering orifice having a variable flow area and first fuel control means responsive to the discharge pressure of said compressor, second fuel control means responsive to the position of said manual control lever, and a third fuel control means responsive to the engine speed for varying the ilow area of the same fuel metering orifice to control the rate of supply of liquid fuel to the engine.

20. A fuel and speed contro-l apparatus for a combustion engine having `an air compressor, and a pump for supplying fuel to said engine; comprising a manual control lever and a fuel regulating system for controlling the delivery of fuel from said pump to said engine; said system comprising a fuel metering orifice having a variable flow area, first fuel control means responsive to the discharge pressure of said compressor for varying said variable flow area in accordance with said pressure, second fuel control means responsive to said manual control lever for varying said variable ow area in response to changes in the position of said lever, and third fuel control means responsive to engine speed for varying said variable iloW area in accordance with said speed.

References Cited in the le of this patent UNITED STATES PATENTS 2,004,869 Hogg June 11, 1935 2,088,954 Gregg Aug. 3, 1937 2,177,120 Schaeren Oct. 24, 1939 2,214,766 Hurst Sept. 17, 1940 2,217,364 Halford et al. Oct. 8, 1940 2,245,562 Becker June 17, 1941 2,274,693 Heinrich et al Mar. 3, 1942 2,290,921 Udale July 28, 1942 2,341,257 Wnsch Feb. 8, 1944-

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