US2633187A

US2633187A - Fuel system

Info

Publication number: US2633187A
Application number: US49967A
Authority: US
Inventors: Jr Stanley B Smith
Original assignee: Bendix Aviation Corp
Current assignee: Bendix Aviation Corp
Priority date: 1948-09-18
Filing date: 1948-09-18
Publication date: 1953-03-31
Anticipated expiration: 1970-03-31

Description

March 31, 1953 s. B. SMITH, JR 2,633,137

FUEL SYSTEM Filed Sept. 18, 1948 s Sheets-Sheet 1 IN V EN TOR {Wm B. JMITH JR.

AT TOENE Y Margh 31, 1953 s. B. SMITH, JR

FUEL SYSTEM 5 Sheets-Sheet 2 Filed Sept. 18, 1948 INVENTOR. Q ANLEY B. 5mm Ja ATTORNEY Patented Mar. 31, 1953 FUEL SYSTEM.

Stanley B. Smith, Jr., South Bend, Ind., assignor to Bendix Aviation Corporation, South Bend, Ind.-, a corporation of Delaware Application September 18, 1948, Serial No. 49,967

Claims. (Cl. NS -36.3)

The present invention relates to a charge forming device for an engine, and more particularly to a fuel system for an engine wherein the fuel is delivered under positive pressure to a p1urality of discharge jets or nozzles.

In fuel supply systems for internal combustion engines and the like, it is usually desirable to meter the fuel at relatively low pressures in order to minimize line or joint failures and fuel leakage and to permit the use of comparatively light sections in the several elements comprising the system.- However, in fuel systems in which the fuel is distributed to a plurality of discharge jets,

. the low pressure of the fuel coming from the metering device may permit substantial variations from one jet to another in the quantity of fuel delivered to the engine when the jets become impaired and restricted by foreign materials. It is, therefore, one of the principal objects of the present invention to provide a fuel system for an engine having aplurality of discharge jets or nozzles wherein equality of fuel distribution is maintained under all operating conditions regardless of minor impairments in the fuel jets or nozzles. Another object of the invention is to provide a fuel supply system of the aforesaid type, wherein the fuel is metered at relatively low pressures and thereafter positively distributed equally to the several jets at relativelyhigh pressures.

Another object of the invention is to provide a fuel metering system for an enginein which the metered fuel ismaintained at a relatively low sub stantially constant pressure adjacent the downstream side of the metering orifice and is thereafter delivered at a substantially increased pressure.

Still another object of the invention is to provide a compact relatively lightweight fuel pump andv distributor which can readilybe adapted for use on most conventional fuel metering devices without substantially modifying the metering device or without materially affecting the metering characteristics of the device.

A further object of the invention is to provide a comparatively simple, compact and easily assembled fuel distributor which canreadily be regulated to control the pressure of fuel therein in accordance with engine operating conditions.

In order to obtain the foregoing objects and other objects which will become apparent from the following description, the present fuel supply system for a multiple cylinder engine includes a full metering device in which the fuel is maintained under positive pressure, a pump for delivering the metered. fuel at a substantially increased pressure, a by-pass unit for maintaining a constant pressure or a predetermined variable pressure at the inlet of the pump and thus at the outlet of the metering device, and a distributor for delivering the fuel to a plurality of discharge jets or nozzles in the intake manifold of the engine adjacent the inlet ports of the cylinders or in the cylinder head adjacent the combustion chambers of the cylinders. My invention may be more fully understood by reference to the accompanying drawings, wherein:

Figure l is a schematic view of a fuel supply system for an internal combustion engine, showmg diagrammatically the several elements comprisingthe system;

Figure 2. is a cross-sectional view through a fuel metering device in which some of the elements thereof have been rearranged to more clearly show their operative relationship to one another;

Figure 3 is a cross-sectional View throu h a pressure control mechanism and fluid distributor taken on line 33 of Figure 1;

Figure 4 is a cross-sectional View through the pressure control mechanism taken on line 4-4 of Figure 1;

Figure 5 is a cross-sectional view through the pump by-pass taken on line 5-5 of Figure 4;

Figures 6, 7 and 8 are plan views of the plates of the distributor unit;

FiguresQ and 10 are plan views of the distributor plates showing them assembled in operative position; and

Figure 11 is a sectional view of the fuel discharge nozzle.

Referring more specifically to the drawings, wherein like numerals are used to designate like parts throughout the various figures, in Figure 1,-

numeral iii designates a fuel metering-device mounted on an intakemanifold [2 of an aircraftinternal combustion engine, numeral M a pump for supplying fuel to the fuel metering device, preferably at a substantially contant pressure, it a fuel pump for increasing the pressure of the metered. fuel received from the fuel metering device l6, It a fuel by-pass unit for maintaining the pressure of the metered fuel on the inlet side of the pump at a substantially constant or an otherwise predetermined value, and 20 a fuel distributor for delivering fuel to a plurality of fuel discharge-nozzles 22, only one of said nozzles being shown in the drawings, mounted in the intake manifold adjacent the inlet valves of the cylinders. Pump it is. adapted to be driven by the engine through a suitable drive means connected to shaft' 2 i of the pump.

The fuel meteringdevice Ill which is shown in detail in Figure 2 is one of several types suitable for use in the present fuel supply systems. The metering device shown is covered by U. S. Patent No. 2,445,846 to Barfod et al., dated July 27, 1948, and contains a main body member 38 having an induction passage 32 with a venturi 34 positioned adjacent the air inlet end thereof and a manually actuated throttle valve 36 pivotally mounted on shaft 38 posterior to the venturi. The fuel flow is regulated or controlled by the combined operation of a control unit 48 on the upstream side of the fuel metering orifices 42 and 43 and the pump I6 and by-pass I8 on the downstream side of the metering orifices. The metering orifices may be either of a fixed or variable size type, the two shown illustrating both types.

The interior of the regulator unit 48 is divided into three

chambers

58, 52 and 54 by

diaphragms

56 and 58. Chamber 58 receives fuel from a source under pressure, such as pump I4, through a conduit 68 and an inlet port 62 controlled by a valve 64 operatively connected to

diaphragms

56 and 58 by a linkage 66. A spring 68 urges the valve to the left, as shown in Figure 2, to its closed position and a spring 18 in chamber 54 urges the diaphragms in a direction to open the valve 64. The chamber 52 is connected to the venturi by means of a passage 12 and an annular chamber 14 and is thus subjected t a pressure primarily derived from the throat of the venturi 34, though this pressure may be modified by air inlet pressure transmitted through passages 16 and 18 and a manual mixture control valve 88. The chamber 54 is connected to the air inlet by passage 16 and is, therefore, subjected to a pressure primarily derived from the induction passage entrance or source of air pressure. Fuel entering the chamber 58 from the fuel inlet 62 flows through metering orifice 43 and a passage 82 to a chamber 84 f the fuel metering unit 86, and thence through orifice 42 to conduits-88 and 98 leading to pump I6. The effective area of orifice 42 is controlled in accordance with throttle position by a stepped valve 92 and a linkage 94, the valve being adapted to limit the fuel fiow for idling and to provide a rich fuel-air mixture for high power output.

An acceleration pump, indicated generally at 98, an altitude mixture control, and an automatic power enrichment means (not shown) are preferably included in the metering device.

' Referring to Figures 3 and 4, the pump I6 and bypass unit I8 are shown in combination with the fuel distributor 28, said units being claimed in applications Serial Nos. 48,613, filed September 10, 1948, and 244,050, filed August 28, 1951. The pump, which is of the vane type, though any other suitable pump such as a centrifugal, gear or reciprocating piston type may be used, consists of a sleeve I48, and a rotor I42 having, as shown in the drawings, four vanes I46, abutting against a floating pin I48 and contacting the internal surface of the sleeve, said rotor being adapted to revolve in a clockwise direction in said sleeve.

The fuel is discharged from the pump through conduit I52 connecting the pump with the fuel distributor 28 and is divided into two portions, one portion of the fuel continuing through conduit I52 to distributor 28 and the other portion flowing through passage I54 to by-pass unit I8 and thence through chambers I56 and I58 and a passage I68 to the pump inlet. Chamber I56 is connected to chamber I58 by an orifice I62 controlled by a valve I64. Communication between the two chambers is also established by a passage I66, chamber I68 and an orifice I18 controlled by a valve I12, said orifice and valve being provided primarily for the purpose of balancing valve I64. Valves I64 and I12 are mounted on an axially movable stem I14 which in turn is connected t a flexible diaphragm I16 subjected on one side to the pressure of the metered fuel transmitted from the metering device I8 through conduit 96 to the inlet of the pump, thence through passage I68, chamber I58, passage I66 to chamber I68 adjacent the underside of said diaphragm. The diaphragm is subjected on the other side to some preselected pressure, such as for example atmospheric pressure, and to the force of a calibrated spring I18 preferably provided with some adjustment means, such as an adjustment screw (not shown), for regulating the tension of the spring. While the chamber I 88 in which spring I 18 is located is shown vented to the atmosphere through a port I82, it may be desirable to subject the diaphragm to a variable pressure to obtain certain fuel flow characteristics, particularly when the type of metering device shown in Figure 2 is included in the fuel system, as will be more fully explained hereinafter. Since valves I64 and I12 are the same size and are subjected to the same pressures, the operation of the valves is entirely controlled by diaphragm I16, and is otherwise unaffected by changes in pump inlet and outlet pressures transmitted to said valves.

The fuel in conduit I52 which is not diverted through the by-pass unit is delivered to the distributor unit 28, entering said unit at chamber I 98 and thence flowing through the several ports of the distributor plates I92, I94 and I96, wherein separate charges are formed for each cylinder of a multiple cylinder engine. Plate I92 is a stationary element and, as shown in Figure 6, contains six ports I98, one for each cylinder of a six-cylinder engine. This plate is held in substantially fixed position in the distributor by a pin 288 extending through the plate into the distributor housing, the fit between the pin and hole for the pin in the plate preferably being such that slight axial movement of the plate is possible. While the ports in this distributor plate and also those in plate I96 are approximately frustoconical in shape, other shapes may be used satisfactorily or a combination of different shapes may be desirable under certain conditions to obtain special fuel delivery characteristics.

The rotatable distributor plate I94 is mounted on the end of shaft 284 for rotation therewith and, as shown in Figure '7, contains two arcuate ports 285 and 286 for registering with ports I98 of plate I92 for a fixed portion of each revolution, this being, in the plate shown, one-fifth of the time that the distributor is in operation. Shaft 284 is operatively connected to one end of pump rotor I42 and is journaled in bearing 281 and held against axial movement by a fixed collar 288 inserted in an annular space in the end of the pump housing. A spring 2I8 reacting between bearing 281 and a retainer ring 2I2 urges plate I92 into rather tight face-to-face contact with plate I94 and plate I94 into contact with plate i96. While, in the present embodiment, the pump rotor and distributor are driven in unison, the pump may be driven at any other speed so long as the capacity of the pump at the selected speed is at all times greater than the supply of metered fuel delivered to the pump inlet.

Plate I96, as "shown Figure 8, is substantially the same as plate 'I92, i. c. it contains two circumferentially arranged rows of frustoconicallyshaped fuel ports 216 which are adapted to register with the corresponding ports of plate I92 and with the two arcuate ports of rotatable plate I94, for a portion of each revolution of said latter plate. Plate I96, which is rigidly mounted on one end of shaft 229 axially aligned with shaft 204, though not operatively connected therewith, is adapted to be oscillated fora part revolution with each opening and closing movement of the throttle valve by a linkage consisting of a lever 222 mounted on the throttle valve shaft, a lever 224 mounted on the end of shaft 220 and a rod 226 pivotally connected to the free end of each lever. When the throttle valve is in closed position, the three plates occupy approximately the position in relation to one another shown in Figure 9, i. -'e. the ports of, plate I92 and the corresponding ports of plate I96 are as far apart as possible and still in direct communication with one another through arcuate ports 295 and 206 during some portion of each revolution of plate I94. When the throttle valve has been moved to its fully opened position, the three plates occupy the position in relation to one another shown in Figure 10, i. e. the ports in plate I92 are in direct alignment with the ports of plate I96. It is thus seen that by oscillating plate I96 in relation to plate I92 'itis possible to vary over a wide range the duration of direct communication between ports I98 ofplate I92 and .ports .2 I601? plate I93 and thus to vary the 'quantity'of fuel discharged per each revolution of plate I94 .for any given fuel pressure in chamber I99, or to vary the pressure required in "chamber I90 to deliver a given amount of fuel in a given period of time. While in the embodiment shown the duration plate I93 is mechanically linked to the throttle valve actuating mechanism, it is contemplated that other arrangements for controlling plate I96 may be made. For example, lever 224 can be connected to a means actuated in response to variations in intake manifold pressure so that, for high manifold vacuum such as exists during idling, the duration of direct communication between ports I99 and 2 It is relatively short and for flow manifold vacuum such as "exists during wide open throttle, the duration of communication between said ports is relatively long.

The fuel, on leaving the distributor, passes through conduits 228, restrictions 230 and conduits 232 to a plurality of discharge nozzles 22 located-in the intake manifold in the proximity of the intake valves-of the-cylinders. The nozzle, shown in detail in Figure 11, includes a sleeve 234 havinga central passage 236 through which the fuel is discharged into the manifold and in which a valve element 231 is adapted to move axially and seat over the discharge end of said passage, the central passage of said sleeve being connected with conduit 232 by a plurality of "ports 239 and "a chamber 239. The valve element is "urged to its closed position "by a spring 240 reacting between a shoulder 242 on sleeve 234 and a spring retainer 246 secured to the end of said element, said spring being calibrated-to maintain a substantially constant, pressure in conduit 232 immediately downstream from restriction 23D.

In theop'eration of the present fuel supply systern, fuel is delivered by pump It at a substant'ialiy constant *superatmospheric pressure through conduit 60 to the fuel metering device In wherein the fuel is metered in accordance with air flow through the induction passage .32 to the engine. As the throttle valve is opened and the air :flow increases, the decrease in pressure which occurs at the throat of the venturi is transmitted to chamber 52, causing diaphragms :56 and 58 to move to the 'right -and urge valve .64 in the opening direction to admit a greater quantity of fuel :into chamber 50. The increased .fuel flow causes the "pressure to (rise in chamber 50, conduit 82 and chamber 84 and provides a greater differential in pressure across the metering orifices 42 and 43 and thus an increase in the flow of metered ffuel through

conduits

88 and 90 to pump Hi. In the fuel metering device shown in .Figure '2, the iunmetere'd fuel in chamber 50 .is controlled independently of the metered fuel in conduits 8B and 90; consequently, it is necessary to maintain accurately predetermined pressures in the fuel conduits -rboth upstream and downstream "from the metering orifices. The pressure of the metered fuel is controlled by pump I6 and by-pass unit I8, the spring I18 and fluid pressure in chamber I determining the pressure maintained by the metered :fuel in conduit 90. .If the pressure in chamber 189 is maintained substantially constant, for example at atmospheric pressure, the pressure of the metered .fuel in conduit will remain substantially constant. The pressure .in chamber I89, however, may be varied according to some engine operating condition, such as Venturi suction, as will be more fully explained later.

Pump It, which may be of any type having a capacity sufficiently large to pump, at all times, the entire quantity of metered fuel :delivered by the metering device under all operating conditions, discharges the fuel through conduit I52 at a greatly increased pressure, .a portion of said fuel, which is equal in quantity to the fuel delivered to the pump, passing through the distributor, and the other portion, which is in excess of that delivered to the pump, passing through conduit I54 and the -by-'pass unit back to the pump inlet. The quantity of fuel returned to the pump inlet is controlled by valves I34 and =-I12 actuated by diaphragm I16 in response to variations in pump inlet pressure. For example, if the pump inlet pressure increases in response to an increase in fuel delivery by the metering device, valves I64 and I12 are moved by the higher pressure on diaphragm I16 to a more nearly closed position so that the entire quantity of metered fuel will be delivered to the engine and the original inlet pressure re-established.

In the "distributor, "plate I93 rotated at onehalf engine speed and arcuateports 2il5 and 206 permit one charge 'of fuel to be delivered'through each distributor port for each revolution of plate I94 and thus provide one charge of fuel per cylinder for each intake stroke of a "four-cycle engine. The oscillating or duration plate 196 has beenin'luded to limit the pressure range re quired to deliver the metered fuel to the engine and at'the same time'to maintain under an operating conditions ti-substantial differential across restrictions 230. 'A large differential across said restrictions is desirable to minimize the effect of unavoidable pressure changes in conduits 232 be tween said'restrictions and the discharge nozzles. When the engine is operating with the throttle valve fully opened, duration plate 'I 96'is so positioned in relation to plate I92 that the respective ports of each plate are in alignment to provide the greatest period of time of direct communication between said ports for each revolution of plate I94. When the throttle valve is returned to closed position, the quantity of metered fuel delivered to pump I6 is substantially decreased and a larger quantity of fuel is by-passed from the pump outlet to the inlet to maintain the predetermined pressure in

conduits

88 and 90. This normally would cause a substantial decrease in the pressure between the pump and the distributor so that the differential of pressure across restrictions 230 would become relatively small and would be materially affected by the unavoidable changes in pressure in conduits 232. The duration plate prevents this by limiting the time during which the fuel is discharging through each restriction 239. As previously explained, the pump, together with the by-pass unit, operates to discharge all the metered fuel delivered to it. Consequently, when the period of time during which the fuel is discharged through each distributor port is substantially shortened by the duration plate, the pressure between the pump and the distributor immediately rises to the point required to discharge the entire quantity of fuel through said ports in the shortened period. When the throttle valve is again moved toward wide open position, the duration plate moves toward its non-limiting position to permit the larger quantity of fuel to be delivered through the distributor at relatively lower pressures. It is thus seen that the duration plate functions to limit the pressure range maintained between the pump and distributor and to maintain a relatively high minimum pressure for said range. The ports in the distributor plates are preferablyof such size that, when there is direct communication between corresponding ports of plates I92 and I96, the pressure in the corresponding conduit 228 anterior to restriction 230 immediately becomes substantially equal to the pressure in chamber I99 anterior to the distributor plates, thus immediately establishing the desired high differential in pressure across restriction 230 for the delivery of a fuel charge to the engine.

As previously pointed out, chamber I80 above diaphragm I'I6 may be vented to some pressure other than atmospheric pressure. For example, in the present fuel system, said chamber may be connected by a conduit 250 as shown in Figures 1 and 2 with the Venturi in the fuel meterin device so that with a decrease in Venturi pres-. sure on an increase in air flow to the engine, the pressure in chamber I86 causes diaphragm I76 to move in the direction to close valves I64 and I12. With these valves in a more nearly closed position, less fuel is by-passed back to the pump inlet, thus resulting in a greater delivery of fuel to the engine and in a slightly lower metered fuel pressure in conduits 88 and 96. With this condition prevailing, a greater differential across the metering orifice and thus a greater flow through the system are established for high power output.

Various modifications and arrangements may be made in the present fuel supply system and elements thereof. For example, the fuel metering device shown in the drawings may be replaced by a speed density fuel metering device such as the one shown in U. S. patent application Serial No. 600,756 filed on June 21, 1945, by Frederik Barfod, now Patent No. 2,489,214, issued November 22, 1949. a

Further, the plates of the fuel distributor may be replaced by cylinders, i. e. a stationary cylinder, a rotatable cylinder around said stationary cylinder, and an oscillating cylinder around said rotatable cylinder, each of said cylinders containin ports operative y arranged in the same relationship as those of the corresponding plates of the distributor shown in the drawings. Many other modifications may be made in the present fuel supply system to suit requirements.

I claim:

1. A fuel supply system for an engine, comprising a conduit adapted to connect a source of fuel supply to the engine, a metering restriction in said conduit, a means for varying the fuel pressure in said conduit anterior to said metering restriction in response to variations in engine fuel requirements, a pressure creating means in said conduit posterior to said metering restriction, and a pressure regulating means communicating with the inlet and outlet passages of said pressure creating means for maintaining a substantially constant pressure in the conduit between said metering restriction and said pressure creating means.

2. A fuel supply system for an engine, comprising a conduit adapted to connect a source of fuel supply to the engine, a metering restriction in said conduit, a means for varying the fuel pressure in said conduit anterior to said metering restriction in response to variations in engine fuel requirements, a pressure creating means in said conduit posterior to said metering restriction, and a pressure regulating means for maintaining a substantially constant pressure in the conduit be-- tween said metering restriction and said pressure creating means.

3. A fuel supply system for an engine, comprising a conduit adapted to connect a source of fuel supply to the engine, a metering means in said conduit, a means for varying the fuel pressure in said conduit anterior to said metering means in response to variations in engine fuel requirements, a pressure creating means in said conduit posterior to said metering means, a pressure regulating means communicating with the inlet and outlet passages of said pressure creating means for maintaining a substantially constant pressure in the conduit between said metering means and said pressure creating means, and a fuel distributor in said conduit posterior to said pressure creating means.

4. A fuel supply system for an engine, comprising a conduit adapted to connect a source of fuel supply to the engine, a metering means in said conduit, a means for varying the fuel pressure in said conduit anterior to said metering means in response to variations in engine fuel requirements, a pressure creating means in said conduit posterior to said metering means, and a pressure regulating means communicating with the inlet and outlet passages of said pressure creating means for maintaining a predetermined pressure in the conduit between said metering means and said pressure creating means.

5. A fuel supply system for an engine, comprising a conduit adapted to connect a source of fuel supply to the engine, a metering means in said conduit, a means for varying the fuel pressure in said conduit anterior to said metering means in response to variations in engine fuel requirements, a pressure creating means in said conduit posterior to said metering means, and a pressure regulating means for maintaining a predetermined pressure in the conduit between said metering means and said pressure creating means.

STANLEY B. SMITH, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Weiss Jan. 28, 1919 Hamilton July 31, 1934 Number