US2440566A - Fuel supply system for internalcombustion engines - Google Patents

Description

P 7, 1948. ca. J. ARMSTRONG 4 FUEL SUPPLY SYSTEM FOR INTERNAL-COMBUSTION ENGINES Filed Feb. 27, 1945 4 Sheets-Sheet 1 I9 FIGZI.

32 33 D Z l8 3/ 3O a as L za II I In venlor A ttorney April 27, 1948. G. J. ARMSTRONG 2,

FUEL SUPPLY SYSTEM FOR INTERNAL-COMBUSTiON ENGINES Filed Feb. 27, 1945 4 Sheets-Sheet 2 Pas/r1 v p/sPLA CEMENT PUMP In uenlor p i 1948.- G. J. ARMSTRONG 2, 40,

FUEL SUPPLY SYSTEM FOR INTERNAL-COMBUSTION ENGINES Filed Feb. 27, 1945 4 Sheets-Sheet 3 16 F IG .3.

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D/Sfll. n cane/v 7' pump Inventor By 2 Attorney Patented Apr. 27, 1948 UNITED STATES PATENT OFFICE FUEL SUPi'LY SYSTEM FOR INTERNAL- GOMBUSTION ENGINES George Jefl'rey Armstrong, Farnborougli, England Application February 27, 1945, Serial No. 580,029 In Great Britain June 26, 1943 6 Claims. (Cl. 123-119) The invention relates to fuel supply systems for reciprocating internal combustion engines in which fuel is injected into an intake manifold along which air is passing to the engine. It is known that in such systems the mass air consumntion, i. e, the air consumption measured in units of mass per unit time, and hence the 1 mospheric pressure, and hence atmospheric.

pressure may be measured instead of exhaust back pressure to .control the fuel flow. More particularly the invention relates to such a system in which the flow of fuel is controlled by an adjustable metering valve or valves whose effective flow area is adjusted in accordance with the intake manifold pressure, atmospheric or exhaust back pressure, and it is an object of the invention to provide a means for controlling the pressure difference across-the metering valve or valves by an adjustable pressure-reducing valve which regulates said pressure difference in accordance with the square of the engine speed whereby for a given adjustment of the meterin valve or valves the flow through said metering valveor valves is' made dependent on the engine speed.

In accordance with the invention in a system of the kind hereinbefore specified, the output of a positive displacement pump driven at a speed proportional to engine speed is passed through a passage having a pressure-reducing constriction, e. g. a sharp edged orifice, and the pressure difference across said constriction is applied to a pressure responsive element which actuates the pressure reducing valve; It will be appreciated that since the flow from a positive displacement pump is proportional to the speed at which the pump is driven, the pressure difference at the two sides of the constriction will be proportional to the square of the engine speed and hence the pressure-reducingvalve will be adjusted in accordance with the square of the engine speed so that for a given adjustment of the metering valve or valves the desired proportionality between flow through the metering valve and engine speed will be maintained.

ments, one of said elements being exposed to the i 2 pressure difference across the constriction and the other to the pressure difference across the metering valve or valves, so that the pressure reducing valve is continuously adjusted to provide a relationship between the two pressure differences, which relationship is determined by the I relative areas of the two diaphragms or the like.

The invention is illustrated in the accompanying schematic drawings, in which:

Fig. 1 is a sectional view of a system embodying the invention and also incorporating the invention of co-pending British application No. 9250/43 (U. S. Serial No. 580,028).

. Fig. 2 is a fragmentary sectional view showing an alternative means of introducing temperature correction,

Fig. 3 is a fragmentary sectional view showing an alternative diaphragm assembly,

Figs. 4 and 5 are views showing alternative arrangements each having two positive displace- Conveniently, the positive displacement pump ment pumps connected in series.

Referring to Fig. 1 fuel passes through pipe Ill to a positive displacement pump ll driven by a shaft ill from the engine 21a to which fuel is to be supplied, said shaft i ll being the engine accessory driving shaft. From the pump II the fuel is supplied to the engine through a sharpedged orifice l2, passage 13, chamber ll, pressure reducing valve l5, chamber l6, metering valve l'l, passage l8, chamber l9 and discharge nozzle 20. whose effective area is adjusted by a tapering needle 2| connected to a link 22 pivoted at 23 to the wall of a chamber 24 and connected to a link to which are attached resilient bellows 25, 26, bellows 25 being subject internally to the pressure in the intake manifold 21 of the engine 21a, 9. connecting pipe 28 being provided for this purpose, and bellows 26 being evacuated internally. The inside of chamber 24 communicates with the passage l8 through a port 29 and is filled with fuel in which both bellows are immersed. The fuel in the passage l8 and consequently in the chamber 24 is maintained at a pressure exceeding atmospheric by a predetermined amount by a tapering needle 30 which co-operates with the discharge nozzle 20 and which is anchored to a The valve ll comprises an orifice I'I forms no part of the present invention and that the present invention may be embodied in systems employing other means for producing such adjustment. The present invention is concerned .with the regulation of the pressure difference across the metering orifice I1, and this means will now be described.

The engine driven pump H is arranged to have an output exceeding the maximum fuel requirements of the engine at any engine speed. and to,

provide for conditions in which the fuel requirements are less than the output of the pump H a spring-loaded relief valve 34 is provided preferably of balanced type. The whole of the output of the pump II is passed through the orifice I2 and the relief valve 34 is accordingly located on the output side downstream of the orifice l2. Since the output of the pump II is proportional to the engine speed, the pressure difference across the orifice I2 is proportional to the square of said speed. A tapping 35 is led from the high pressure side of the orifice I 2 to chamber 36 sealed by a flexible diaphragm 31 the righthand side of which is acted upon by the pressure existing in the chamber 4, i. e. the pressure at the low pressure side of the orifice l2. The diaphragm 31 is consequently blessed by the pressure difference across the orifice I2. Connected to the diaphragm 31 is one end of a link 38 carrying a tapering plug 39 which forms the adjustable member of the pressure reducing valve I5. The link 38 is also connected through a pivoted lever 40 to a further link 4| carried by a second diaphragm 42. The pressure at the left hand side of the diaphragm 42 is that existing in the chamber l6, 1. e. the pressure immediately upstream of the metering valve I! while at the right hand side of the diaphragm 42 the pressure existing is that immediately downstream of the metering valve, a port 43 being provided to admit such pressure to the right hand side of diaphragm 42. Accordingly, when the system is operating, the pressure difference across the orifice i2 applies to the diaphragm 31 a force proportional to the square of the engine speed, and this force is transmitted through the link 33, lever 40 and link 4| to the diaphragm 42 and the pressure reducing valve I5 is thus so adjusted that the flow through the valves causes the forces applied by the diaphragms 31 and 42 to be in equilibrium. Such equilibrium will exist when the pressure differences across the two diaphragms achieve a relationship which is determined by the relative areas of the diaphragms and the relative effective lengths of the arms of the lever". The Dressure difference across the metering orifice I! will therefore be maintained proportional to the square of the engine speed. Temperature control may be introduced in a variety of ways, thus in the form illustrated, a bulb 44 filled with liquid is located in the intake manifold 21 and is connected by a capillary tube 45 to a. capsule 46 one end of which is fixed and the other end of which is connected to a pivoted arm 41 on which the lever 40 is mounted. Movement of the capsule in response to changes in temperature in the intake manifold will displace the pivot of the lever 4|! in relation to the links 38, 4| to which it is connected and will accordingly vary the relationship between the effective lengths of the arms of the lever 40 and hence the ratio between the square of the engine speed and the pressure difference across the metering orifice.

The system also embodies a slow running device in which fuel from the chamber I4 is fed to passage l8 past a tapered plug 48 anchored to a diaphragm 49, the two sides of which are exposed to the pressures of fuel in the chambers 36 and I4 and on which a tension spring 30 acts to hold the plug 48 away from its seating. As

the engine speed increases the pressure difference across the diaphragm 49 rises overcoming the resistance of the tension spring 50 and diminishing the flow of fuel through the slow running device.

Referring to Fig. 2. temperature correction is produced by varying the effective area of the oriicel2 instead of by varying the effective lengths of the arms of the lever 40. For this purpose a tapered needle 63 is pivoted to one end of a pivoted arm 6|, the other end of which is moved by a Bourdon tube 62 or like element which responds to changes of temperature in the intake manifold. 1

Other alternative means of introducing temperature correction are possible, e. g. any of the means described in co-pending British application No. 9250/43. If the temperature correction is eflected as shown in Fig. 2 or as in British application No. 9250/43, the capsule 46 shown in Fig. 1 may be retained and made responsive to some other variation for which it is desired to correct or vary the fuel-air ratio. Thus if the capsule 46 were evacuated the pressure difference across the metering valvell would become pro portional not to the square of the engine speed but to apower of the engine speed differing from the square thereof.

Referring now to Fig. 3, fuel from pump I after passing through the orifice I2 is supplied to the engine through passage I3, pressure reducing valve l5, metering valve II and passage IS. The effective flow passage of the metering valve I1 is varied by a tapered needle 2| which may be operated by means not shown but which may be analogous to those shown in Fig. 1. The means for adjusting the pressure reducing valve however diifers from that shown in Fig. 1. As illustrated in Fig. 3 the pressure reducing valve comprises a tapered plug 39 attached to a link 38 secured to four diaphragms, 3H, 31, I31 and 3'. Between diaphragms 3|! and 31 is a chamber 36 communicating with the upstream side oforifice l2 through a passage 35, while the space I40 between diaphragms 3|! and I3! communicates with the downstream side of the orifice |2 through passage I311. The pressure at the right hand side of diaphragm 3H is the same as that at the upstream side of the metering valve I1, while the space between the diaphragms l3'l'and 3' is filled with fuel at the pressure existing at the downstream side of valve l1, said pressure being transmitted through port 29, chamber 24 and balance tube I24. Diaphragms 3|1 and I3! are in the nature of flexible walls the fluid forces on which are balanced one against the other by design and in particular by the inclusion of a duct H3. The system will consequently be in equilibrium when the pressure difference across the diaphragm 31, which is proportional to the square of the engine speed, is equal to the pressure difference across the diaphragm 3, which is equal to the pressure difference across the metering valve l1, so that said latter pressure difference is continuously maintained proportional to the square of the engine speed.

tained constant and substantially zero by feeding the inlet of the positive displacement pump from a second positive displacement pump of higher output. Figs. 4 and 5 show two arrangements embodying twin pumps,

In Fig. 4 the pump II is fed from a positive displacement pump of higher capacity than pump II. The output of pump H is fed through an orifice l2 into a passage l3 as in Fig. 1 a tapping 35 being taken from the upstream side of orifice I2. The passage 13 also receives fuel direct from pump 10 through orifice H. A deaerator I2 of conventional design is provided for de-aeration of the fuel before it enters the pump ll and passage IS, A spring loaded and balanced relief valve 13 isprovided between the passage I3 and the inlet of pump 10, so that if the pressure in passage l3 exceeds atmospheric by more than an amount determined by the, spring bias on valve 13 the valve opens and fuel passes from passage l3 to the inlet of pump 10.

In Fig. 5 in addition to the relief valve 13 a second relief valve 14 is provided. This valve has a movable member whose head is acted on by the pressure at the outlet from pump Ill and which is secured to a diaphragm, against which a spring abuts and which as shown is also acted upon by the pressure difference between the outlet of pump l I (through passage 35 and pipe 15) and the inlet of pump 10. The valve M will therefore open when the pressure existing in the outlet from pump 10 exceeds a predetermined relationship with the pressure in the passage 35.

- Although no supercharger is shown in the drawings it will be appreciated that the invention may be embodied in a fuel supply system for a supercharged engine.

I claim:

1. A fuel supply system for an internal combustion engine comprising an adjustable metering value, an adjustable pressure regulating valve in series with said metering valve, an enginedriven positive displacement pump having an outlet duct with a constriction therein located to pass the whole output of said pump, a pressureresponsive element located to respond to changes in pressure difference across said constriction,

series with said metering valve, a constriction" located in said duct between said pump and adjustable valves to pass the whole output of said pump,.a pair of diaphragms one of which is located to be acted upon by thepressure difference across said constriction and the other of which is located to be acted upon by the pressure difference across said metering valve. and a connection between said diaphragms whereby the pressure difference across said metering orifice is maintained proportional'to the. pressure diiler ence across said constriction.

3. A fuel supply system for an internal com bustion engine, comprising an engine-driven positive displacement pump for supplying fuel through a duct to said engine, an adjustable metering valve in said duct, an adjustable pressure regulating valve also in said duct, and in series with said metering valve, a constriction located in said duct between said pump and adjustable valve to pass the whole output of said pump, a pair of diaphragms one of which is located to be acted upon by the pressure difference across said constriction and the other of which is'located to be acted upon by the pressure difference across said metering valve, and a pivoted lever connecting said diaphragms and also actuating said pressure regulating valve.

4. A fuel supply system for an internal combustion engine, comprising an engine-driven positive displacement pump for supplying fuel through a duct to said engine, an adjustable metering valve in said duct, an adjustable pressure regulating valve also in said duct, and in series with said metering valve, 2. constriction located in said duct between said pump and adjustable valves to pass the whole output of said pump, a

pair of diaphragms one of which is located to be acted upon by the pressure difierence across said constriction and the other of which is located to be acted upon by the pressure difference across said metering valve, a pivoted lever connecting said diaphragms and also actuating said pressure regulating valves, and a temperature-responsive member carrying the pivot for said lever.

5. A fuel supply system for an internal combustion engine, comprising an engine-driven positive displacement pump for supplying fuel I through a duct to said engine, an adjustable metering valve in said duct, an adjustable pressure-regulating valve also in said duct, and in series with said metering valve, a constriction located in said duct between said pump and adjustable valves to pass the whole output of said pump, a pair of diaphragms one of which is located to be acted upon by the pressure diflerence across said constriction. and the other of which is located to be acted upon by the pressure difference across said metering valve, a temperature sensitive member for varying the flow area of said constriction, and a connection between said diaphragms, whereby the pressure difference across said metering valve is maintained proportional to the pressure difference across said constriction.

6. A fuel supply system as claimed in claim 2. in which the positive displacement pump is in series with a second positive displacement-pump whereby the pressure difference across the first of said pumps is maintained substantially zero.

GEORGE JEFFREY ARMSTRONG.

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

UNITED STATES PATENTS

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