US2400415A

US2400415A - Automatic fuel control

Info

Publication number: US2400415A
Application number: US416068A
Authority: US
Inventors: Donald S Hersey
Original assignee: United Aircraft Corp
Current assignee: Raytheon Technologies Corp
Priority date: 1941-10-22
Filing date: 1941-10-22
Publication date: 1946-05-14
Anticipated expiration: 1963-05-14

Description

May 14, 1946.

D. S. HERSEY AUTOMATIC FUEL ICONTROL Filed Oct. 22, 1941 Patented May 14,1946

AUTOMATIC FUEL CONTROL Donald S. Hersey, West Hartford, Conn., assignorto United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application October 22, 1941, Serial No. 416,068

16 claims. (o1. 12s-1840 This invention relates to improvements in fuel supplying andfuel regulating apparatus for anv internal-combustion engine and has particular reference to such an apparatus for suplying to such an engine a quantity Of fuel metered in proportion to the mass quantity of air flowing through the engine air intake per unit of time. An object of the invention resides in the provision of improved and simplified mechanism for determining the mass rate iiow of engine intake air and adjusting the engine fuel-supply means in accordance with variations in the mass rate ilow of intake air as determined.

A still further object resides in the provision Of an improved apparatus for continuously sam# pling the air in the engine intake system between the engine throttle and the engine cylinders and determining the density of such intake air and applying to such density determination a correction factor to compensate for variation in the volumetric efficiency of the engine at different engine speeds, and in the provision of engine fuel supply means responsive to the speed of thev engine and the compensated density determinations of said density determining device for supplyingv to said engine a quantity of fuel metered in proportion to the mass rate flow of engine intake air.

Other objects and advantages lwill be more particularly pointed out hereinafter or will become apparent as the description proceeds.

In the accompanying drawing, in which like referencenumerals are used to designate similar parts throughout, there is illustrated a suitable mechanical embodiment for the purpose of disclosing the invention. The drawing, however. is for the purpose oi' illustration only and is not to be takenas limiting or restricting the invention, since it will be apparent to those lskilled in the art that various changes in the illustrated embodimentmay lbe resorted to without in any way exceeding the scope of the invention.

In the drawing, the single figure is a diagrammatic illustration of an engine fuel supplying and metering apparatus constructed according vto the invention. certain parts being shown in f section to better illustrate the construction thereoi'.

parts have been illustrated for the purpose of disclosing the invention, it is to be understoolti that the invention is in no way limited to the particular type of engine so illustrated and hereinabove described but that the improved fuel metering apparatus may be applied to various forms of internal-combustion engines.

Adjacent to the engine air intake there is provided a casing 26 enclosing two,

chambers

28 and 30 separated by a partition 32 through which extend two apertures o r orices 34 and 36. The chamber 28 is connected to some portion of the engine intake system between the throttle and the engine cylinders, such as the diffuser chamber I8, by a Iconduit 38 and the chamber 30 is coneoted to the engine air intake system through the conduit 40.

While the

conduits

38 and 40 are shown connected with the diffuser chamber I8 they may,

if desired, be connected with 'some other part of the intake system, such as the air intake duct 22 as indicated by the blanked Off

connections

42 and 44. y v

Intake air is forced through the casing 26 from one of the

ducts

38 or 40, 'to the other, by

suitable means such as the positive displacement fluid pump 46 driven by the constant-speed electric motor 48.

With this arrangement, the pump 46 will force 30 a constant volumetric quantity of air through` the casing 26 and through the orifice apertures 34 and 36. With aperture 36 closed the pressure drop across aperture 34 from one of the

chambers

28 or 30 to the other chamber will con- 35 stitute at all times a direct measurement of the density of the air in the engine intake system at the point where

ducts

38 and 40 connect to the system.

'I'he pressure drop between the chambers 28 40 and 30 is applied to a pneumatic device, generally indicated at 5I), through the

conduits

52 and 54 and this pneumatic device operates a valve 68 which controls a servo-motor, generally indir cated at 58, which in turn regulates the stroke or. 4" capacity of a fuel pump,^generally indicated at 80, which supplies fuell to an engine fuel injection device such as the injection nozzle, generally indicated at 62, of some form well known to Referring to the drawing in detail, the nu- 50 the art, which nozzle may -be'inserted in chammeral I0 generally indicates an internal-com bustion engine having one or more cylinders as indicated at I2 mounted upon a orankcase I4 and supplied with combustible mixture through ber 22.

The pump is driven in some definite proportion to engine speed by suitable means such as the

drive shafts

84 and 86 and the gear connecan individual intake pipe I8 leading from a 55 tion 68.

supercharger diffuser lchamber I8 into which intake air or combustible mixture is forced by a supercharger impeller 28 from an air intake conduit 22 provided with a throttle 24.

While a particular arrangement of` engine 6 If'engine volumetric eiiiciency remained a iixed y,

found to .be necessary for the reason that, volumetric efficiency of the engine changes due to variations in engine speed, therefore, the product of intake air density, engine displacement and engine speed is not necessarily an adequate measurement; of the mass ow rate of engine intake air, as engine volumetric efficiency is an added factor variably affecting the mass flow rate. Also it is found desirable to change the fuel mixture ratio at both ends of the engine speed range to provide a somewhat richer mixture for cooling the engine to some extent and preventing detonation at the highe speed end of the range, and for insuring proper ignition of the fuel mixture at the low speed end of the engine speed range,

Compensation for the change in volumetric efficiency and in the fuel mixture at the upper end of the engine speed range is accomplished by the provision of the second orifice 36, the area of which is controlled by a tapered plug 'I0 actuated by a governor 12 driven from the engine by suitable means, such as the shaft 64 and the gear connections 14 and 1G. The governor` 12 may be a conventional type of centrifugal governor having centrifugal weights 'I8 acting against the force of a compression spring 80.

The operation of this compensating mechanism is to increase the areay of the orce 36 at the upper end of the engine speed range. This permits a freer flow of air between the

chambers

28 and 30 with a consequent drop in the .pressure differential between these chambers. This drop in pressure differential has the same effect on the fuel regulating mechanism as would be accomplished by a decrease in specific density of the engine intake air and will result in a decrease in the amount of fuel supplied to the engine to compensate for the somewhat smaller weight OW f intake air to the engine. occasioned by the above mentioned decrease in volumetric efliciency at the upper end of the engine speed range. The shape of the plug 'lll also may be so designed, that the deci-casein amount of fuel supplied will not be as much as would be necessary to completely compensate for the decrease in volumetric emciency so that a somewhat richer fuel mixture will .be supplied to the engine at the upper end of the speed range thus providing an economizer action which will protect the engine at high speeds but will not result in excessive use of fuel ,in the intermediate portion of the engine speed range. The shape of plug lllv may also be such as to provide a richer mixture at low engine speeds for insuring proper ignition, as stated above.

A manually operated mixture controll may be supplied by providing a bleed line 82 connected between the

conduits

52 and 54 and a valve 84 in the bleed line controlled tby suitable means such as the link 86 which may be connected to an independent manual control.

The pneumatic device 58 and the servo-motor 58 may be of some form already known to the art or may be specially designed for this particular application and are not necessarily restricted to the particular arrangement illustrated in the accompanying drawing. In theA illustrated arrangement, however, the pneumatic device comprises a hollow casing 83 divided into two sub stantially equal chambers by a flexible transverse partition or diaphragm 90 secured at ,its center to the intermediate portion of a valve shaft 82. At each end of the casing the valve shaft 92 is sealed to the casing by respective flexible diaphragms 94 and SS and at one end this shaft carries the valve member 56 which cooperates y with a valve seat provided at the end of a pressure fluid conduit 98. The valve is contained in a casing |00 from which a drain line |02 leads to a suitable sump or reservoir from which the fluid may be drawn by a pressure creating device, such as the engine lubricating oil pump, and returned through a pressure conduit |04 to the tube 98. At its end opposite the valve 5B the shaft 92 may be connected with a dash-pot comprising a piston |06 reciprocable in a closed cylinder |08 provided with restricted openings, as indicated at ||0 and ||2 respectively at opposite sides of the piston. 'Ihe purpose of this dash-pot is to control the rate of change of the capacity of the -pump 60 under conditions of rapid opening and closing of the engine throttle.

The servo-motor 58 is connected to the end of the tube 98 opposite the valve 56 and comprises a cylinder ||4 connected at one end with the tube 98 and containing a piston ||6 connected through a piston rod ||8 with the displacement adjusting element |20 of the variable displacement fuel pump 60. A coiled compression spring |22 urges the piston l I6 in a pump capacity decreasing direction opposed by the pressure fluid in the tube 98. A flxed restriction |24` is provided in the pressure line |04 so that the valve 56 may accurately control the fluid pressure in the tube 98 by adjusting the opening at the valve end of the tube.

When the bleed valve 84 is opened the bleed between the

conduits

52 and 54 has the effect of reducing the pressure differential between -theV chambers 28 and A3|) as determined byithe fluid now created by the pump and on the opposite sides of the diaphragm 90. This decrease in the effective pressure differential will permit the action of the spring |22 to decrease the output capacity of the pump 60 and will result in a decreased quantity of fuel being supplied to the engine intake air to somewhatl lean the fuel mixture.

With the above described apparatus the fuel supplied to the engine will be accurately metered in proportion to the mass flow rate of the engine intake air and in addition compensation will be made at the opposite ends of the engine speed l range to somewhat richen the mixture for improved operation' and protection of the engine without permitting the mixture to become excessively rich at the upper end of the Speed range because of the change in volumetric eiciency of the4 engine at this end of the range.

While a suitable mechanical embodiment has been hereinabove described and illustrated in the accompanying drawing for the vpurpose of dis.

closing the invention, it is to be understood that the invention is not limited to the particular embodiment so illustrated and described, but that such changes in the size, shape and arrangements of the Ivarious parts may be resorted to as come within the scope .of the sub-joined claims.

Reference is made-to my copending applications Serial Nos'. 311,153 (led December 27, 1939), 370,160 (filed December 14,- 1940), 334,393 (led May 10, 1940), and 417,266- (flled October 3l, 1941), which show and claim subject matter shown but not claimed in the application. Having now described the invention so that others skilled in the art may clearly understand the same, what it is desired to secure by Letters Patent is as follows:

` 1. A charge forming device for an internalcombustion engine having an air intake system and a fuel supply means driven at a fixed ratio to engine speed and having a controllable displacement per operating cycle comprising; a fluid conduit connected at both ends with said air intake system, a pump in said conduit having a `constant volumetric displacement per operating cycle, constant speed means for driving said pump, a restriction in said conduit, and means pneumatically connected with said conduitat opposite sides of .said restriction and operated fby variations in the pressure diil'erentialv across said restriction to vary the displacement of said fuel supply' means. f

2.. A charge forming device for an internalcombustion engine having an air intake system and a fuel supply means driven at a ilxedl ratio to engine speed and having a controllable displacement per operating cycle comprising, a fluid conduit connected at both ends with said air l intake system, a pump in said conduit having a vconstant volumetric displacement per operating cycle, constant'speed means i'or driving said pump, a restriction in said conduit, and means pneumatically connected with said conduit at opposite sides of said restriction and operated by l variations in the pressure diiferentia1 across said restriction to'vary the displacement of said fuel supply means `and speed responsive means i'or varying said restriction to compensate the variations in the pressure differential across said restriction for variations in the relation of the volumetric elcien'cy of said engine `to engine speed.

3. A charge-forming device for an internalcombustion engine having an air intake system variable displacement pump arranged .to discharge into said stream for adding said liquid to al .gas and driven at said speed proportional to the volumetric flow rate of said gas, means for continuously sampling said gas and establishing' across a restriction a pressure differential proportional to the density of said gas, and means actuated by variations in said gas pressure differential for varying the displacement of said liquid pump in accordance with variations in said gas pressure differential, said gas sampling device comprising a casing, ka partition dividing said casing into two chambers, means connecting each of said chambers with said stream of gas, a pump having a constant displacement for each operating cycle disposed in one of said connecting means, constant speed means driving said pump;

and a constant area orifice in the partition between said chambers. l

6. Apparatus for adding toa stream of gas a quantity of liquid suilicient to create a mixture in which the weight of liquid in a unit volume of gas and a `fuel supply means driven at a ixed ratio to engine speed and having a controllable displacement per operating cycle comprising, a fluid conduit connected at both ends with said intakel system, a pump having a constant displacement per operating cycle in said conduit for forcing a stream of sample intake air therethrough, constant speed means for driving said pump, a res triction, in said conduit comprising a constant area orifice and a variable area orifice, means responsive to engine speed regulating the area of said variable area orifice to compensate the air pressure drop kacross said restriction for change in engine volumetric'efiiciency with a change in engine speed, and means connected with said conduit at opposite sides of said restriction and ac- .uatedby'variationsin the air pressure drop across said restriction to vary the displacement of said fuel supply means.

4. Apparatusfor adding to a stream lof gas a quantity of liquid sufficient to create a mixture in which the weight of liquid in a unit volume of gas bears a definite predetermined ratio to the weight of gas in said unit volume comprising, a variable displacement pump arranged to discharge into said stream for adding said liquid to said gas and operated at a speed proportional to the volul metric iiow rate of said gas, means for continuously sampling said gas, said gas sampling device comprising a conduit having its inlet .end in contact with said stream of gas, a pump in -said conduit having a constant displacement pe operating cycle, constant speed means for driving said pump, and a restriction in said conduit, said pump establishing acrossvsaid restriction a pressure diilerential proportional lto the density of said gas, and means actuated by variations in .said gas pressure differential for varying' the displacement of said liquid pump. y

5. Apparatus `for adding to a. streamof gas a quantity of liquid sufficient to create a mixture bears a denite predetermined ratio to the weight of gas in said unit volume comprising, a variable displacement pump driven at a speed proportional to the volumetric flow rate of said gas arranged to discharge into said stream for adding said liquid to said gas. means for continuously sampling said gas and establishing across a re' striction a pressure differential proportional to the density of said gas, and means actuated by variations in said gas pressurediiferential for varying the displacement of said liquid pump in accordance with variations in said gas pressure differential, said gas sampling device comprising a casing, a partition dividing said casing into two chambers, means connecting each of said chambers with said stream of gas, a Pump having a constant displacement for each operating vcycle disposed in one of said connecting means, constant speed means driving said pump, and a constant area orice and a variable' area orifice in the partition between said chambers.

7. Apparatus for adding to a stream of gas i a quantity of liquid sufficient to create a mixture in which the weight of liquid in a unit volume of gas bears definite predetermined ratio to the weight of gas in said unit volume comprising, a

- comprising a conduit, a restriction in said conduit, a pump having a constant displacement for each operating cycle disposed in said conduit producing said pressure differential across said restriction, constant speed meansv driving said pump, and a constant area orifice and a variable varea orifice constituting said restriction, and speed in which the weight of liquid in' a unit volume of gas bears a denite predetermined ratio to the responsive `means for varying the area of said variable area orifice.

8. Apparatus-for adding to a stream of .gas a quantity o! liquid suiiicient to create a mixture in which the'weight of liquid in a unit volume of gas bears a, deiinlte predetermined ratio to the weight or gas in. said unit volume comprising, a variable displacement liquid pump driven at a weight of gas in said unit volume comprising, a l

v liquid pump in accordance gas pressure drop across said restriction through.

vflow rate' of said gas and arranged to discharge into said gas, means for continuously sampling s aid gas and establishing across a restriction a pressure differential proportional to the density of said gas, and means actuated by variations in said gas pressure differential for varying the displacement of said liquid pump in accordance with variations in said gas pressure diiferential, said liquid pump displacement varying means comprising, a hydraulic motor operatively connected with the displacement varying element of said pump. a valve for controlling said hydraulic motor and a pneumatic motor operativelylconnected with said valve and pneumatically connected with said gas sampling device at opposite sides of said restriction.

9. Apparatus for adding to a stream of gas a quantity of 'liquid sufficient to create a mixture in which the weight of liquid in a unit volume of gas bears a denite predetermined ratio to the weight of gas infsaid unit volume comprising, a duct for said gas, a constant speed constant displacement pump pneumatically connected with said duct for.

continuouslywithdrawing a sample quantity of gas therefrom, a restriction in the connection between said pump and said duct for establishing in said connection a pressure differential proportional to the density of the gas, a variable speed adjustable ldisplacement liquid pump connected at its intake side with a supply of liquid and at its outlet side with an injecting device adjacent said gas stream, a. hydraulically actuated variable volume mechanism operatively connected with said liquid pump for adjusting the displacement l thereof, and a pneumatically actuated. mechanism connected to s'aid'pump connection across said restriction and operatively connected with said hydraulically actuated mechanism to adjust the displacement of said liquid pump in accordance with variations in the gas pressure drop across said restriction through the intermediacy of said hydraulically actuated mechanism.

10. lApparatus for adding to a stream ofV gas a quantity of liquid sufficient to create a mixture in which the weight of liquid in a unit volume of the capacity varying element of said liquid pump, a'spring urging said .piston in a direction to decrease the capacity of said pump, a fluid pressure line having a restriction therein connected .to said cylinder in a manner to apply fluid pressure to said piston to increase the capacity of said fluid pump, and a bleed valve in said fluid line operatively'connected with said pneumatically actuated mechanism to control the fluid pressure applied to said piston.

11. Apparatus for adding to a stream of -gas a quantity of liquid sufficient to create a mixture in which the Weight of liquid in a unit volume of gas bears a definite predetermined ratio to the weight of gas in said unit volume comprising, a variable displacement pump driven at a speed substantially proportional to the volumetric flow rate of said gas and arranged to discharge into saidv stream for adding said liquid to said gas, means for continuously sampling said gas and establishing across a restriction a pressure differential proportional to the density of said gas, andv meansactuated by variations ,in said gas pressure differential for varying theI displacement gas y,bears a denite predetermined ratio tc the weight of gas in said unit volume comprising, a duct for said gas, a constant speed constant displacement pump pneumatically connected with said duct'for continuously withdrawing a samplev quantity-of gas therefrom, a restriction in the connection between said pump and said duct for establishing in said connection a pressure .diierential proportional to the density of the gas, a variable speed adjustable displacement liquid pump connectedv at its intake side with a supply v of liquid and at itsoutlet side with an injecting device adjacent said gas stream, a hydraulically actuated variable lvolume mechanism operatively connected with said liquid pump for adjusting .the 'displacement thereof, and apneumatically actuated mechanism' connected to said pump connection across said restriction and' operatively connectedy with said hydraulically actuated mechanism toadjust the displacement of said with variations in the the intermediacy of said hydraulically actuated mechanism, said hydraulically actuated mechanism comprising, a cylinder, a piston reciprocable in said cylinder and operatively connected with of said liquid pump in accordance with variations in saidV gas pressure differential said liquid pump displacement varying` means comprising, a hydraulic motor device including a cylinder, a piston reciprocable in said cylinder and operatively connected with the capacity varying elcment of said liquid pump, a spring urging said piston in a direction to decrease the capacity oi said pump, a fluid pressure line having a restriction therein connected to said cylinder in a manner to apply fluid pressure to said piston in a direction to increase the capacity of said pump, a bleed valve in said fluid line for controlling the fluid pressure applied to said piston, and a pneumatic motor pneumatically connected to said gas `sampling device at opposite sides of said restriction and operatively connected with said valve for controlling the same and a dash-pot associated with s ald pneumatic lmotor for stabilizing the operation thereof.

12. The device of claim 1, including manually operated means for varying said pressure differ'- ential.

l13. The apparatus of claim 1, wherein the variable displacement pump discharges into said intake system at a point upstream of said gas sampling means.

14. In the combination of claim 1, a supercharger having a diiluser section in said air intake system, said conduit being connected with said diffuser section.

15. The device of claim 2, including means to automatically increase thefuel-air weight ratio of said charge at atleast one end of the engine speed range. A

16. In a charge forming device for an internal combustion engine having an air intake system and a vvariable delivery fuel pump discharging into said intake air, a conduit connected with said air intake system, a pump having a constant volumetric displacement per operating cycle in said conduit, constant speed means for driving said pump, means connected with said conduit at opposite sides of said restriction and operated by varia-l tions inthe pressure striction to vary the delivery of said fuel pump.

DONALD S. HERSEY.

a restriction in said conduit, andv differential across said re