US 3628774 A
Description (OCR text may contain errors)
United States Patent 69 R, DIG. 69; l37/81.5
 Relerenees Cited UNITED STATES PATENTS 3,386,710 6/1968 York, Jr. 26l/DIG. 69 3,428,065 2/1969 Cawley.... l37/8 l .5 3,469,593 9/1969 O'Keffe 137/8 l .5 3,565,091 2/l97l Auger 137/815 3,567,191 3/l97l Morgan 26l/DIG. 69
1 Primary Examiner-Tim R. Miles- Anomeys-Robert A. Benziger and Flame, Hartz, Smith &
Thompson ABSTRACT: In a fluidic fluid-metering system having a return line, a means is provided of reducing or completely-eliminating the back pressure effects of the fluid in the return line of the fluidic portion of the system. The means comprise a jet pump operative to draw excess or unmetered fluid away from the fluidic portion of the system and to provide the fluidic portion of the system with a stable back pressure.
PATENTEUHEEZI an 3628.774
I6 I T T l |8- 1 I I I 36 IL A l 424/ 34 40 30 l 3a R .4 I as 1 \SI Yd l T -20 10 W W J A V FIGURE SUPPLY LIN E FROM PRESSURE SOURCE RETURN LINE FIGURE 2 dANUSZ S SULI H INVENTOR.
BY Wx ATTORNEY FLUIDIC FLUID-METERING SYSTEM CROSS-REFERENCE TO RELATED APPLICATION The present case is a division of my copending US. Pat. application Ser. No. 858,021, tiled on Sept. 15, 1969, and titled Fluidic Fluid-Metering System."
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the art of fluid-handling and metering systems and particularly those systems which control the flow of fuel for mixture with air prior to combustion in an engine. More specifically, thepresent invention relates to fuel systems which incorporate one or more fluid amplifier elements to control the fuel delivery.
2. Description of the Prior Art A wide variety of fluid-flow-controlling systems are known in the art. Such systems as utilize one or more fluidic elements are also known and are of recent advent in the art of fuel control and metering for combustion engines. Examples of these systems may be found in U.S. Pat. Nos. 3,386,710 issued to .l. B. York, .Ir., 3,389,894 issued to A. M. Binder and 3,406,951 issued to C. Marks, to name a few. While the systems disclosed in the referenced patents utilize fluidic elements, they should not be thought of as complete fuel systems since these systems utilize an essentially constant fuel/air ratio whereas, in an engine-operating cycle, the fuel/air ratio must be varied to provide various enriched ratios such as cold start, full load, acceleration, and wide-open throttle enrichment. All of these variously ratioed enriched mixtures may be provided by controllably altering the control signals to the primary control element through additional fluidic control circuitry. However, systems that provide accurate fuel/air ratios in tests simulating all engine-operating requirements suddenly become highly inaccurate misapproximations when these identical systems are installed in vehicles wherein the system is subjected to varying return fuel pressure due to attitudes or dynamic motions of the vehicle.
It is characteristic of the known fluidic fuel systems that the main, or primary fluidic stage comprises a nozzle for discharging pressurized fluid into a fluid interaction region where control signals, disposed laterally of the fluid stream, deflect the stream towards one of a pair of outlets. In systems where the fluid is fuel, one outlet port is in communication with a fuel discharge nozzle while the other outlet permits fuel entering thereinto to return to the fuel tank. In such systems, when installed in vehicles, it has been found that vehicle attitude, accelerations and decelerations to which the vehicle is subjected and combinations thereof, produce forces which are not instantly transmitted to the fuel in the wehicles fuel system thereby causing undesired variations in the fuel pressure within the fuel system. This effect is not particularly noticeable on the fluid which is upstream from the fluidic amplifier means power nozzle. However, the effect is quite noticeable on the fuel in the return line which, in most instances must run the length of the automobile in the direction of greatest variations in acceleration. For instance, the vehicles descending a grade or a deceleration of the vehicle caused by braking will cause the fuel in the return line to tend to travel toward the front of the vehicle. In most cases, this would mean that return-line fuel is traveling toward the return-line inlet. Since this would also be at the fluid interaction region of the fluidic computation means, the result would be a relatively sudden increase in the pressure at the outlet ports and interaction region of the fluidic amplifier means resulting in an undesirably high quantity of fuel being directed to the outlet port associated with the air intake of the internal combustion engine causing the fuel/air ratio to be higher than required for air source and emissions control performance.
On the other hand, vehicle accelerations could cause fuel in the return-line to flow away from the fluid-logic-computing means at a higher flow rate than normal thereby causing a lowpressure zone to form adjacent the power stream which would be operative to divert a larger portion of the power stream into the return-line port. The fuel/air ratio would then become leaner than desired. As a result, it has become evident that fluid logic fuel systems, at least as applied in vehicular installations, require some means for maintaining the pressure in the return passage system, and particularly at the return-line system inlet port, at a level which is not readily affected by acceleration (and deceleration) of the vehicle or by changes in the attitude of the vehicle. It is a primary objective of this invention to provide a means for maintaining the pressure within a fuel system return-line system at a value which is unaffected by, and is capable of substantially ignoring, inertial effects on the fuel caused by changes in the attitude or speed of the associated vehicle. It is a further object of the present invention to provide such a means which is low in cost, reliable in operation and which is fully compatible with fluidic systems. It is a still further object of the present invention to provide a device for a fluidic fuel system which is capable of isolating the fluidic control circuitry from the back pressure effects of inertial forces and attitude changes on the fluid in the return-line portion of the systems. It is a still further object of the present invention to provide a means for isolating the fluidic control circuitry from back pressure effects while preserving the general advantages of fluidics, namely few or no moving parts.
SUMMARY OF THE INVENTION The present invention comprises the addition to the fluid return system of a jet pump operative to cause the fluid return passages and fluid vents or dumps of the associated fluidic amplifier computing system to be exposed to a low or suction pressure and further operative to cause the fluid in the returnline system downstream of the jet pump to be energized sufficiently to overcome the inertial force and attitude changes referred to hereinabove. The jet pump is energized by a bypass fluid flow from the pressurized side of the fluid system pump and, by entrainment, is operative to aspirate excess fluid from the fluidic computing means and to cause it to enter the fluid return at a somewhat elevated pressure level thereby isolating the fluidic control portion of the system.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows a schematic drawing of a representative fuel supply system incorporating the preferred embodiment of the present invention.
FIG. 2 shows a sectional view of a jet pump suitable for use in a system as shown in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. 1, my invention is illustrated as being applied to a fuel system utilizing a fluidic amplifier l0 as the fuel flow controlling stage. Fuel is drawn by pumping means 12 from the fuel source or tank 14 and is provided an elevated pressure to the computing and metering means indicated generally as 16. A bypass fuel flow is provided to energize the isolating means 18 through conduit 20 and restriction 22. A conduit 24 is provided to communicate the outlet of the isolating means 18 with fuel tank 14.
The computing and metering means 16 are illustrated as being comprised of a computation means illustrated as fluiclic amplifier 10, a fuel nozzle 26, and an air intake 28 having airflow sensing means in the form of venturi 30. The airflowsensing means 30 are connected to a control port 32 of the fluidic element 10 and are operative to proportion the fuel flow through outlet passages 34 and 36 of the amplifier 10 in accord with the engine fuel requirements. To balance the signal to the fluidic element, passage 31 communicates control port 33 to the intake mainfold 28 upstream of the venturi 30. This is merely illustrative of a system having a single control input. However, more complete and complex systems are known and in such systems, the inertial effects upon the fuel in the return system become more critical. Outlet passage 36 is connected to nozzle 26 to provide metered fuel to the air intake 28 for ultimate supply to an engine, not shown. The fluidic amplifier is also illustrated as having a pair of vents 38 and 40 which are connected via passage system 42 to the outlet passage 34. The particular computation means shown is intended to be merely illustrative of fluidic computation means utilizing at least one fluidic amplifier and having at least one control input signal. Furthermore, the type of fluidic element shown is intended to be illustrative rather than definitive of a fluidic amplifier having utility for controlling fluid flow in the illustrated embodiment.
Referring now to FIG. 1 and 2, and particularly to FIG. 2, the jet pump used in the present invention as the isolating means 18 is illustrated. The jet pump is comprised of a body 50 having a fluid-receiving chamber 52 located therein. The chamber 52 communicates via ports 54 with the excess fluid passage system 42. A nozzle 56 is centrally located to expel a jet of pressurized fluid into the chamber 52 while aperture or port 58 is arranged to receive the jet of fluid and to exhaust it from the chamber. Nozzle 56 is in communication via passage 20 with a source of pressurized fluid which, in this instance, is the output or high-pressure side of fuel pump 12 and aperture 58 is in communication via conduit or passage 24 with a fluid dump or reservoir. in the embodiment described, the fluid reservoir is the fuel tank 14 but the man skilled in the art will recognize that other operating fluids and hence other reservoirs and sources may be utilized in the practice and application of my invention. For instance, a system which used air as the operation fluid would be supplied from a compresses return-line or air motor while using the atmosphere as a fluid dump and systems using water would look to the water pump for a source and could then use the fluid supply as the fluid dump.
OPERATION OF THE PREFERRED EMBODlMENT Upon energization of the fluid-pumping means 12, fluid is drawn from the tank 14 and supplied under pressure to the computing and metering means 16 and the supply conduit 20 of the isolating means 18. The fluid utilized in the computing and metering means 16 may be acted upon by various command signals, here represented by signals indicative of airflow through the intake manifold 28 of an internal combustion engine, not shown. In the operation of the system, fluid in excess of that required for flow through outlet passage 36 will be directed into the excess fluid return passage system 42 from the various fluidic element vents as at 38 and 410 and from the outlet passage 34. The fluid directed into the conduit 20 will be ejected by nozzle 56 into chamber 52 and will be received by aperture 58. By fluid entrainment principles, the pressure within chamber 52 will be reduced whereby fluid in the excess fluid conduit system 42 will be drawn into chamber 52 through the various ports 54 provided for that purpose. As this excess fluid enters the chamber 52 it also is entrained and flows with the supply fluid into the aperture 58 to be returned to the fluid dump. in this manner, the isolating means 18 in the form of the jet pump will effectively aspirate the excess fluid passages and the fluid vents of the fluidic flow control portion of the system. Any fluid entering the aspirated regions will be immediately drawn into the jet pump and forced into the retum-line 24 at an elevated pressure.
The efiects of this are twofold. Firstly, the fluidic devices will be exposed to a substantially uniform suction in the excess fluid portions of the system permitting the system designer to ignore the consequences of vehicular motion in designing a system for an automobile. Secondly, the fluid within the return system downstream of the isolating means 18 will be at an elevated pressure or energy level such that the inertial forces on the return-line fluid will be effectively masked and will not be apparent upstream of the isolating means 18.
1. A fuel system for internal combustion engines comprising in combination:
asource of fuel; I nozzle means communicating with said source operative to discharge fuel for mixture with air;
fluidic computing means operative to control fuel flow through said nozzle to meet engine-operating requirements;
first pumping means operative to pressurize fuel from said source to said nozzle means;
return passage means intercommunicating said fluidic computing means and said source operative to return fuel in excess of engine requirements to said source; and
isolating means comprising second pumping means within said return passage means operative to prevent inertial effects on the fuel downstream of the isolating means from appearing upstream of the isolating means.
2. The system of claim 1 wherein said second pumping means comprises a jet pump.