US2999488A - Fuel control with feedback and force multiplication - Google Patents

Description

Sept. 12, 1961 F. c. REGGIO 2,999,488

FUEL CONTROL WITH FEEDBACK AND FORCE MULTIPLICATION Original Filed Feb. 5, 19:59

United States The present application is a division of my application Serial No. 591,511 filed June 7, 1956, which is a continuation of Serial No. 496,296 filed July 27, 1943, now abandoned, which in turn is a division of Serial No. 254,355 filed February 3, 1939, now also abandoned.

The invention relates to fuel control devices for combustion engines, and more particularly to devices for automatically controlling the engine supply of liquid fuel, or the relative proportions of the fuel and air composing the engine combustible mixture.

An object of the invention is to provide improved devices of the type indicated utilizing feedback and force multiplication.

Further objects of the invention will be apparent from the following description, taken in connection with the appended drawing which is a diagrammatic sectional View of a device embodying the invention.

The invention is in no way limited to use with reciprocating engines, but may be practiced in connection with any suitable thermal or combustion engine.

Referring more specifically to the drawing, the arrangement shown therein comprises an engine 60 having an induction passage 59 communicating with the inlet side of a supercharger or compressor 61 of any suitable type, which in turn leads to an induction pipe 62 and thence to the inlet port, not shown, of the engine. The passage 59 is controlled by a throttle valved? actuated through a lever 64.

A casing 80, communicating through a large duct 81 with the induction pipe 62, contains air at induction pressure and temperature. An evacuated bellows 82 in said casing acts on lever 83 to operate rod 94 and pilot valve 84, 85 which controls admission of oil under pressure, usually led from the engine lubricating system through pipes 87 and 8% as indicated by thejarrows, to opposite sides of piston as. Low pressure oil is returned to the engine sump through line 89. A floating lever 90 is connected at its ends with rod 94 and piston 86, and at an intermediate point with rod 91 which is connected, through lever 92 and rod 93, with the horizontal arm of a bell-crank lever 74.

Also enclosed within casing 80 there is a bellows 95 which containing a definite weight of gas or other suitable iluid at constant volume. The high velocity of the air flow in the induction manifold 62 as well as the pulsations of pressure therein determine eddy currents and turbulence within the large and short conduit 81 and casing 80, thus causing an active thermic exchange, by conduction and convection, between the air flowing in the manifold 62 and the bellows 95. Furthermore the thermal capacity of the latter is extremely small, and it follows that the fluid within bellows 95 is at all times maintained at the same temperature as the air in the pipe 62.

The absolute pressure within bellows 95 is therefore proportional to the absolute manifold or 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 the servo motor 86. Engine lubricating oil is led thereto and atent Patented Sept. 12, 1961 evacuated therefrom as indicated by the arrows. The pressure of the air in casing acts in opposite directions on bellows and 96, thereby balancing out the eifect of any pressure change therein, so that the load transmitted to lever 97 by the two bellows is only dependent on the induction or manifold temperature. The servo mechanism controlled by rod acts on lever 98 to vary the operating distance of rod 93 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 of rod 93 from the fulcrum of lever 92 is proportional to the actual absolute manifold temperature. Any temperature change in the induction manifold operates bellows 95 and in turn the servo mechanism to rotate lever 98 and vary the load of spring 99 until the balance of the rod 100 in its neutral position is restored. Thus the load on rod 93 is proportional to the absolute pressure and inversely proportional to the absolute temperature in the induction pipe 62, and therefore is directly proportional to the air density therein.

A control lever 78 is adapted to modify the angular setting of lever 79 and in turn to alter the distance of the lower end of rod 93 from the fulcrum of lever 74.

The engine 60 is provided with a fuel feed, such for example as a conventional injection or metering pump 104 driven by the engine and comprising one or more pump elements connected. by ducts or pipes and nozzles 70 with the various engine cylinders. These nozzles 79 may be mounted in any suitable position, such as near the intake cylinder port or valve or inside the cylinder, or they may be mounted to inject fuel into the induction pipe 62, as shown in detail in the parent application.

The delivery of the engine fuel feed or metering pump is adjusted by axially displacing the control rod 106. This rod is biased by a spring 107 and is actuated by the upper arm of the bellcrank lever 74. The spring 107 is so designed as to exert on the control rod 106 a load which is proportional to the quantity of fuel delivered per cycle by the metering pump 104.

The device works as follows: the evacuated resilient bellows 82 exerts on the rod 94 an upward load. or force proportional to the induction pressure. in normal operation the rod 94 with the control valves 84 and 85 is maintained in equilibrium in neutral position by a down ward load of equal magnitude transmitted thereto from the calibrated spring 107 of the fuel metering pump 104. Thus, for a given adjustment of the temperature compensating lever 98 and manual control lever 78 the induction pressure and the load of the spring 107 (and in turn the engine fuel supply) are proportional. If now the pilot operates the engine throttle control lever 65 in a direction to decrease the engine air supply, or if the aircraft climbs to higher altitude, the induction pressure surrounding bellows 82 decreases, and with it decreases the upward load transmitted by the bellows to the rod 94, while the downward load transmitted thereto from the spring 107 remains unchanged.

Thus the bellows 82 expands, the rod 94 moves downward, and oil under pressure admitted over piston 86 displaces the same downward, causing counter-clockwise rotation of lever '74 and movement of the control rod 106 to the left, thereby decreasing the engine fuel supply. As the spring 107 expands, its load decreases and determines a corresponding decrease of the downward load applied to the rod 94. As a result the downward motion of the latter is stopped, and thereafter the rod 94 moves upward toward its neutral position. The downward movement of the piston 86 continues until the loads transmitted to the rod 94 by the spring 107 and by the induction pressure have once more 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 lever 65 or to a decrease of altitude, causes a corresponding increase of the engine fuel supply. Induction pressure and fuel delivery per cycle thus vary proportionally.

As already stated, lever 97 actuated by bellows 95 and 96 exerts on rod 100 an upward load which is proportional to the induction temperature. In normal operation, that is to say when said temperaure is constant, said. load is balanced by the spring 99, and the rod 100 is in its neutral position. An increase in induction temperature causes a proportional increase of pressure within bellows 95 and upward load applied to the rod 100. Bellows 95 expands, the rod 100 is lifted, and oil under pressure is led above the piston of the servomotor, thus causing lever 98 to rotate counter-clockwise, and gradually increasing the load ofspring 99. This increase in the spring load causes the rod 100 to move downward toward its neutral position. Operation of the servomotor and rotation of lever 98 continue until rod 160 resumes its neutral position, the load of spring 99 having in the meantime assumed a value equal to the new upward load exerted on the rod 190 by the bellows and corresponding to the new value of the induction temperature; the result being that lever 93 assumes a new position of equilibrium in which the distance of rod 3 from the fulcrum of lever 92 has increased in proportion to the increase of absolute induction temperature.

Thus the load exerted by the rod 93 to the bell-crank lever 74 is proportional to the absolute pressure and inversely proportional to the absolute temperature in the induction pipe 62, and is therefore proportional to th air density therein.

The mixture control lever 78 is adapted to modify the distance of rod 93 from the fulcrum of lever 74 so as to vary the proportionality ratio between the air density in theinduction pipe 62 and the fuel delivery per cycle.

If the air charge per cycle, or weight of air present in the engine cylinder during the compression and power strokes, is proportional to the induction density, then the mechanism shown in the drawing gives for each adjustment of the 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, or a still different function of said temperature; and it has further been observed that the said air charge may be affected by the surrounding pressure. In this connection various compensating devices are disclosed in the parent cases.

It is to be clearly understood that while the fuel metering pump 104 described above and illustrated in the drawing is a conventional multi-plunger variable-delivery fuel injection pump, and means for automatically controlling the fuel delivery or the fuel-air ratio according to the present invention may be applied to any suitable fuel supply system.

, The arrangement described above, in which the engine fuel flow or the fuel-air ratio can be adjusted only man ually by the pilot or operator through the control lever 78 is not the most suitable in connection with aircraft engines. Accordingly, means responsive to one or more engine operative conditions, such for example as the induction manifold pressure or density, engine speed, atmospheric pressure, engine temperature may be provided for controlling said fuel supply or fuel-air ratio automatically, as described in detail in the parent cases.

1 Where the claims are directed to less than all of the elements of the complete system disclosed, they are inservo motor control valve, a valve actuating mechanism, pressure responsive means connected with said air intake system downstreamfrom the compressor for transmitting to the said valve actuatingmechanism a first force substantially proportional to the compressor discharge pressure in the direction to increase the rate of engine fuel supply, and a feed-back spring connected with the fuel control member and adjusted thereby for applying to the same valve actuating mechanism a second force opposing said first force and varying in predetermined relation to the position of the fuel control member, the arrangement being such that during steady operation the said actuating mechanism is in equilibrium under said two forces acting against each other, but as soon as such equilibrium is disturbed the said actuating mechanism will move the servo motor control valve and set in motion the servo motor to vary the adjustment of the fuel control member and thereby alter the said second force set up by the feed-back spring until the equilibrium of the valve actuating mechanism is restored.

2. In a fuel control for an engine having an air intake system with a compressor therein, a fuel control member controlling the rate of fuel supply to the engine, a servo motor for positioning said control member, a servo motor control valve, a valve actuating mechanism, compressor discharge pressure responsive means connected tothe valve actuating mechanism for transmitting thereto a first force tending to increase the rate of engine fuel supply, and a feed-back spring connected with the fuel control member for transmitting to the valve actuating mechanism a second force opposing said first force and varying substantially in direct proportion to the rate of engine fuel supply.

3. In a fuel control for an aircraft engine having an air intake system with a compressor therein, a fuel control member for controlling the rate of fuel supply to the engine, a hydraulic servo motor for positioning said control member, a servo motor control valve, a valve actuating mechanism, compressor discharge pressure responsive means connected to the valve actuating mechanism for transmitting thereto a first force indicative of the rate of engine air flow and tending to move the fuel con-' trol member in the direction to increase the rate of engine fuel supply, and a feed-back spring connected with the fuel control member for transmitting to the valve actuating mechanism a second force for opposing and balancing the said first force and indicative of the rate of engine fuel supply to maintain the desired fuel-air ratio irrespective of changes in altitude. v

4-. In a fuel control for an aircraft engine having an air intake system with a compressor therein, a fuel control member controlling the rate of fuel supply to the engine, a servo motor for positioning said control member, a servo motor control valve, a valve actuating mechanism, compressor discharge pressure responsive means connected to the valve actuating mechanism for transmitting thereto a first signal tending to increase the rate of engine fuel supply, a feed-back spring connected with the fuel control member for transmitting to the valve actuating mechanism a second signal opposed to the first signal and indicative of the rate of engine fuel supply to maintain the desired fuel-air ratio irrespective of changes in altitude, and a variable-ratio device in said valve actuating mechanism for changing the magnitude of one of said two signals to vary the engine fuel-air mixture ratio.

5. In a fuel control for an engine having an air intake system with a compressor therein, a fuel control member for controlling the rate of fuel supply to the engine, a servo motor for positioning said control member, a control element for controlling the servo motor, an actuating mechanism for said control element, compressor discharge pressure responsive means'for transmitting to said actuating mechanism a first signal in the direction to increase the engine fuel-supply, a feed-back spring connected with said fuel control member for transmitting to said actuating mechanism a second signal opposed to the first signal and varying substantially in proportion to the engine fuel supply, a variable-ratio lever device for changing the magnitude of one of said two signals, and a regulating system subject to manual supervision for adjusting the variable-ratio device.

6. In a fuel control for an engine having an air intake system with a compressor therein, a fuel control member for controlling the rate of engine fuel supply, a servo motor for positioning said control member, a control element for controlling the servo motor, an actuating mechanism for said control element, air pressure responsive means connected with said air intake system for trans mitting to said actuating mechanism a first signal in the direction to increase the rate of engine fuel supply, a feedback spring connected with said fuel control member for transmitting to said actuating mechanism a second signal opposed to the first signal and indicative of the rate of engine fuel supply, a variable-ratio lever device for changing the magnitude of one of said two signals, and means responsive to parameters of engine operation for adjusting the variable-ratio lever device.

7. In a fuel control for a power plant having an air induction system leading to a combustion chamber, a compressor in said induction system, a fuel supply system for feeding fuel to the combustion chamber, a fuel control member in said fuel supply system for regulating the rate of fuel flow to the combusion chamber, a servo device for positioning said fuel control member, a servo control element for controlling said servo device, means responsive to compressor discharge pressure for producing a first control force varying in direct proportion to absolute compressor discharge pressure, a feed-back spring connected to said fuel control member for producing a second control force which various with changes in the position of said fuel control member, power plant control means subject to manual supervision for producing a variable control signal, multiplying means for multiplying said variable control signal and one of said control forces to provide a resultant force, a first operating connection for transmitting said resultant force to said servo control element in one direction, and a second operative connection for transmitting the other, non-multiplied control force to the same servo control element in the opposite direction.

8. In a fuel control for a power plant having an air induction system with a compressor therein, a combustion chamber and a manually operable control lever, a fuel supply system with a control member for regulating the rate of fuel flow to the combustion chamber, means responsive to the position of said lever for providing a first signal, means responsive to compressor discharge pressure for providing a second signal, means responsive to tempera ture in the air induction system for providing a third signal, means for receiving said signals to provide a resultant signal, a spring responsive to the position of the control member for providing a feedback signal, and a servo device controlled by said resultant signal and feedback signal for positioning the control member.

9. In a fuel control for a power plant having an air induction system with a compressor therein and a combustion chamber, a fuel supply system with :a control member for regulating the rate of fuel flow to the combustion chamber, means responsive to compressor discharge pressure for providing a first signal, means responsive to temperature in the air induction system for providing a second signal, means for receiving said signals to provide a resultant signal, means responsive to the position of the control member for providing a feedback signal, and a servo device controlled by said resultant signal and feedback signal for positioning the control member.

10. In a fuel control for a power plant having an air induction system and a combustion chamber, a fuel supply system with a control member for regulating the rate of fuel flow to the combustion chamber, means responsive to pressure in said air induction system for providing a first signal, means responsive to temperature in said air induction system for providing a second signal, means for receiving said signals and providing a resultant signal, means for receiving said signals and providing a. resultant signal, means responsive to the adjustment of the control member for providing a feedback signal, and a servo device controlled by said resultant signal and feedback signal for adjusting the control member.

11. In a fuel control for a power plant having a combustion chamber, a fuel supply system with a control member for regulating the rate of fuel flow to the combustion chamber, a plurality of means responsive to various parameters of power plant operation for providing corresponding signals, means for receiving said signals to provide a resultant force, means responsive to the adjustment of the control member to provide a feedback force, a servo device for adjusting the control member, servo control means for controlling the operation of said servo device, means for applying said resultant force to said servo control means in one direction, and means for applying said feedback force to the same servo control means in the opposite direction.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,999,488 September 12, 1961 Ferdinando Carlo Reggio I It is hereby certified that error appears in ,the above numbered patentrequiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 53, for "and" read the column 6, lines 28 and 29, strike out "means for receiving said signals and providing a resultant signal,".

Signed and sealed this 6th day of February 1962 (SEAL) Attest:

ERNEST W. 'SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents

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