Constant pressure-differential fuel injection system

COMPLETE SPECIFICATION (ORIGINAL)

FOR OFFICE USE

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Short Title:

<td> (</td><td> Int. Cl:</td>

<td> i</td><td> Application Number:</td>

<td> • 4 ί » &lt; Ο ί ' • ο &lt; a «</td><td> Lodged:</td>

<td> j K « 0 ' u 0 0 r·</td><td> Complete Specification-Lodged:</td>

<td> Ί ο δ o s</td><td> Accepted:</td>

<td> G 0 0 ft · 0 3 &lt;</td><td> Lapsed:</td>

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<td> ’ ¢000</td><td></td>

<td></td><td> Related Art:</td>

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TO BE COMPLETED BY APPLICANT

ί) ⁵₀%“’t Name of Applicant:

’ WALBRO CORPORATION

Address of Applicant: 6242 GARFIELD AVENUE c CASS CITY ”⁴· MICHIGAN 48726

USA ί '

Actual Inventor:

: © - ’ _: [ * Address for Service: GRIFFITH HACK &amp; CO., ί 601 St. Kilda Road, } Melbourne, Victoria 3004, &lt; Australia.

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ί Complete Specification for the invention entitled:

i CONSTANT PRESSURE-DIFFERENTIAL FUEL INJECTION SYSTEM.

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The following statement is a full description of this invention including the best method of performing it known to me:-

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RAC/RCC/pla

W-160R

CONSTANT PRESSURE-DIFFERENTIAL FUEL INJECTION SYSTEM

The present invention is directed to fuel delivery

Xfa 'out, odt, &amp;xclu.e,iv’-e, fcatwn systems for internal combustion engines.k«=ad==mo^e===pa=^te4®u4=a=¥4^«· to a fuel, injection system comprising at least one fuel injector positioned between a pressurized fuel supply and an engine air intake manifold.

Background and Objects of the Invention

In engine fuel delivery systems of current design, fuel is fed by a constant-delivery pump from a fuel tank to the engine, and excess fuel is returned from the engine to the fuel tank. Such return fuel carries engine heat to the fuel supply, and consequently increases temperature and vapor pressure at the fuel supply. Venting of excess vapor pressure to the atmosphere not only causes pollution problems, but also i deleteriously affects fuel mileage . Excess fuel tank temperature ; can also cause vapor lock at the pump, particularly where fuel j level is relatively low. Constant pump operation also increases j energy consumption while decreasing both pump life and fuel ’ filter life.

J U.S. Patent No. 4,649,884 discloses a fuel injection

Π ' j system for an internal combustion engine in which an electricJ motor constant-delivery fuel pump supplies fuel under pressure j from a tank to a fuel rail positioned on the engine. Excess fuel is returned to the supply tank as a function of pressure .&lt; differential between the fuel rail and the engine air intake manifold. A plurality of fuel injectors are mounted between the fuel rail and the engine air manifold, with the injector nozzles being positioned adjacent to the fuel/air intake ports of the individual engine cylinders. United States Patent No.

A.U.

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308 issued December 6, 1988 and assigned to the assignee

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hereof, discloses a fuel delivery system for an internal combustion engine in which outlet pressure of an electric-motor fuel pump is monitored, and pump motor current is controlled as a function of such outlet pressure. Although the fuel delivery systems disclosed in the noted patent and application address the aforementioned problems in current fuel delivery system designs, further improvements remain desirable.

SUMMARY OF THE INVENTION • « ’ t ft ? f ’ &lt; t : « « ϊ t c c β

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According to the present invention there is provided a fuel delivery system for an internal combustion engine that includes a fuel supply with a fuel pump responsive to application of electrical power for delivering fuel under pressure, an engine air intake manifold including means for supplying combustion air to said manifold, fuel delivery means coupled to said fuel supply for controlled delivery of fuel from said supply to said manifold, and means for applying electrical power to said pump, characterized in that said power-applying means comprises:

differential pressure sensor means having a first input coupled to said fuel supply and responsive to fuel pressure delivered to said fuel delivery means, a second input coupled to said engine manifold ana responsive to air pressure in said manifold, and an output for supplying an electrical sensor signal that varies as a direct continuous function of a pressure difference between said first and second inputs, and sensor responsive means responsive to said signal for applying electrical power to said pump as a continuous inverse function of said pressure difference so as to maintain a substantially constant pressure differential across said fuel delivery means through controlled variation of pump speed.

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BRIEF DESCRIPTION OF THE DRAWINGS

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In order that the present invention might be more fully understood, embodiments of the invention will be described by way of example only with reference to the accompanying drawings in which:

Fig. 1 is a schematic diagram of a fuel delivery system in accordance with a preferred embodiment of the invention;

Fig. 2 is a sectional elevational view of an enclosure for mounting the pump control electronics in the embodiment of Fig. 1;

Fig. 3 is a sectioned elevational view of the pump control electronics enclosure in accordance with a further embodiment of the invention;

Fig. 4 is an electrical schematic diagram of digital pump control electronics in accordance with another embodiment of the invention; and

Fig. 5 is a schematic diagram of a modified fuel delivery system in accordance with yet another preferred embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An embodiment of the present invention consists of a fuel delivery system that maintains constant pressure differential across the fuel delivery mechanism, specifically the fuel injectors, so that quantity of fuel supplied for a given injector activation time remains substantially constant and independent of fluctuations in air manifold pressure. A pressure differential control system is provided that is economical to implement in mass production of automotive fuel delivery systems, for ey'mple, and is reliable over an extended vehicle lifetime, fhe fuel delivery system achieves on-demand fuel delivery, and thus reduces energy consumption while increasing pump

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0 0 0 c Q o oooo oooo cc o oc c oc roO and fuel filter operating lifetimes. The fuel delivery system reduces delivery of engine heat to the fuel tank, and thus reduces problems associated with fuel vaporization as hereinabove discussed. The fuel delivery system also implements electronic control of the fuel pump as a function of fuel requirements, and in which the control electronics is cooled by fuel circulating in the delivery system.

A fuel delivery system for an internal combustion engine is provided that includes a fuel supply having an electric-motor fuel pump responsive to application of electrical power for delivering fuel under pressure. An engine air intake manifold supplies combustion air to the various engine cylinders, and at least one fuel injector is connected between the fuel supply and the air manifold. Pressure sensor mechanisms, preferably in the form of an integral differential pressure sensor, are responsive to pressure at the fuel injector and at the engine air manifold for supplying an electrical signal that varies as a function of pressure differential therebetween. The electric-motor fuel pump is driven as a function of such pressure differential, preferably by a pulse-width modulation amplifier for applying pulsed d.c. power to the motor at constant frequency, and at a duty cycle that varies as a function of the pressure differential signal. In this way, fuel pressure at the injector is automatically controlled so as to maintain a constant pressure differential across the injector between the fuel rail and the engine air manifold, to reduce volume of circulating fuel and thus engine heat delivered to the fuel tank, and to energize the fuel delivery pump as a function of fuel demand.

In a preferred embodiment of the invention, the pump control electronics, which may be either digital or analog in nature, is mounted on a printed circuitboard. The circuitboard is mounted on a body of heat conductive v

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material having a passage through which circulating fuel is fed, so that the circulating fuel draws heat from and effectively cools the pump drive electronics. A check valve is positioned in the fuel return line to maintain fuel at the injector when the pump is not operating. In one embodiment of the invention, this check valve is mounted within the passage that extends through the electronics heat-sink body. This body may also contain a fuel pressure-pulse dampener in the form of a diaphragmed cavity open on one side to the fuel passage.

Referring to the drawings, Fig. 1 illustrates a ο o^ooa fuel delivery system 10 in accordance with a preferred

GOO O _o°'”_o embodiment of the invention as comprising an electric-motor

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a fuel line 16 to a fuel rail 18 carried on the engine (not shown). Excess fuel at rail 18 is returned to tank 14 through return lines 20, 22 and a fuel rail check valve 24. Check valve 24 maintains fuel in rail 18 when motor 12 is idle - i.e., when the engine is stopped. A plurality of fuel injectors 26, 28, 30 and 32 are mounted between rail 18 and an engine air intake manifold 34 carried by the engine, with the nozzles of the individual fuel injectors 26-32 being positioned adjacent to the fuel/air intake ports 36-42 of associated cylinders of the e «« engine. To the extent thus far described, fuel delivery system β e β 5 is disclosed in U.S. Patent No. 4,649,884 noted above. 5 &lt;5 fi ?

Combustion air may be supplied to manifold 34 through an air »’*’*· filter or the like at atmospheric pressure, or by a turbocharger H » I or the like driven by the engine and supplying air at pressure that varies with engine operation and/or throttle demand, etc.

Injector 26-32 may be solenoid-activated, for example, by an on-board engine control computer, not shown.

4,·η·ν.®.η4ίί-€&gt;·ΕΗ· differential pressure sensor 46 receives a first input as a function of pressure within fuel rail 18, and a second input as a function of pressure within air manifold 34. Such inputs may be supplied by any suitable pressure delivery mechanisms. Sensor

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supplies an electric signal as a function of the pressure differential between rail 18 and manifold 34. Such electrical pressure differential signal, which takes the form of an analog signal in the embodiment of FIG. 1, is fed to a pulse-width modulation amplifier 48. Amplifier 48 also receives d.c. electrical power from the vehicle electrical system, and supplies a pulse width modulated output signal 50 to energize the electric motor of pump 12. The pulse-width modulated output of amplifier 48 is preferably supplied at constant frequency and at a duty

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-5cycle that varies as a function, preferably an inverse linear function, of the pressure differential signal from sensor 46.

When pressure differential between rail 18 and manifold 34 is low, such as during periods of accelerated engine operation when fuel demand is high, the duty cycle of signal 50 is high. Thus, average d.c. power applied to pump 12 is high and the pump is energized accordingly.

On the other hand, when pressure differential between rail 18 and manifold 34 is high, such as when the engine is idling and therefore has lower fuel demand, the duty cycle of the amplifier output is correspondingly low, and the fuel pump is energized at a lower level.

FIG. 2 illustrates the pump control electronics, including pressure sensor 46 and amplifier 48, mounted as a printed circuitboard assembly on a body 54 of heat conductive material construction, such as stainless steel.

Body 54 has a

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0 i fl ft 4 passage 56 that extends therethrough, having an for receiving fuel from connection to fuel rail 18 in line through control inlet opening with fuel line 16 line 16 draws heat pump 12 and an outlet opening 60 for (FIG. 1). Thus, body 54 is connected in FIG. 1, sc that fuel circulating from and effectively cools the pump electronics. Differential pressure sensor 46 has one pressure input connected by a lateral communicate with the main fuel passage input connected by a nipple 64 and a passage 62 in body 54 to

56, and a second pressure hose 66 to air manifold (FIG. 1). Assembly 52, including sensor 46, is enclosed by a cover 67 to form an integral package 68.

FIG. 3 illustrates a modified embodiment 70 of the control package suitable for connection in return line 20, 22 (FIG. 1) between fuel rail 18 (FIG. 1)

56, as is a flow dampening orifice 72.

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A cover 74 cooperates control package 70, check valve 24 is mounted within passage

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with body 54 to form a chamber 7 6 that is divided by a diaphragm 78 of stainless steel construction or the like. The upper portion of chamber 76 is connected by a port 80 to fuel passage 56. The lower portion of chamber 76 is vented to atmosphere by an orifice 82 in cover 74. Thus, diaphragm 78 functions to dampen pressure fluctuations in the fuel delivery . system.

FIG. 4 illustrates a digital embodiment 84 of the pump control electronics. Pressure sensor 46 is connected through a differential stage 86 to a microprocessor 88 that is suitably programmed to provide pulse-width modulated signal 50 (FIG. 1) to a power amplifier stage 90. Pump motor 92 is connected to power amplifier stage 90 for delivering fuel on demand as previously described.

FIG. 5 illustrates a modified fuel delivery system 94 in accordance with yet another preferred embodiment of the invention in which a single fuel injector 26 is positioned within the central passage 96 of a throttle body 98 for delivering fuel past the throttle valve 100 to engine air intake manifold 34. Fuel delivery system 94 in FIG. 5 is otherwise identical to system 10 of FIG. 1.

There have thus been disclosed several embodiments of a fuel delivery system that fully satisfies all of the objects and aims previously set forth. The fuel pump is energized on demand, as distinguished from constant-delivery fuel pumps characteristic of the prior art, thus reducing energy consumption and increasing both pump life and the operating life of the fuel filter (not shown). Because the fuel pump is energized only on demand, volume of circulating fuel returned to the fuel tank is greatly reduced, thus decreasing delivery of heat to the fuel tank. Consequently, problems associated with fuel vaporization are likewise reduced. Although the invention has

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been described in conjunction with presently preferred embodiments thereof illustrated in the drawings, it will be appreciated that many alternatives and modifications may be implemented without departing from the general principles of the invention. For example, differential pressure sensor 46, which preferably is provided in the form of an integral sensor unit of silicon or other solid state construction, could take the form of separate electrical or mechanical sensors whose &amp; M os a ode © ooso

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current or voltage control could also be employed.

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