IL26393A - Fuel injection systems - Google Patents

Description

PATENTS AND DESIGNS ORDINANCE SPECIFICATION injection systems " V-9*v2-i Ρ¾ΊΠ¾-"ΗΚ many oa- e-*-VvVa©- PETROL INJECTION LIMITED, a British company, of Valley Road, Plympton, Plymouth, Devon, England and HAROLD BRETE3T JIGKSGN, a British subject, of "Panorama", Vicarage Road, Plympton St. Mary, Devon, England do hereby declare the nature of this invention and in what manner the same is to be performed, to particularly described and ascertained in and by t following statement :- This invention relates to continuous low-pressure fuel-injection systems for internal combustion engines and also to components for use in such systems. p , British Patent Fo . 1140901 The/Specification o^-e<-pei^ii¾^-A^3rie^ Z1 8528/65 describes a fuel injection system for an internal combustion engine which includes a fuel circulation conduit system having supply and return branches, and vented open fuel injector devices connected to the supply branch to receive fuel from it and each adapted to discharge such fuel into branch pipes leading from the engine intake manifold to the respective engine cylinders. That Specification also describes how fuel is metered by pressurisation at relatively low pressures dependent on engine speed and by a fuel metering valve device to vary the fuel supply to the injector devices in dependence upon at least one other engine operating parameter, for example, engine intake air density represented by engine inlet manifold vacuum by pressure drop across a venturi in the manifold or by the engine throttle opening.

The temperature conditions under which such a system has to operate are sometimes such that vaporization of the fuel in the supply and return branches takes place and this prejudices the satisfactory operation of the system. t By the present invention there is provided a low pressure fuel -iajeotion system for an internal combustion engine, including a valve having firs and second compartment and a closure membery the closure member having a closed positio in which it closes communication between the first and second compartmentsrand feeing movable through a range of open positions to vary the flow path cross-section between the first and second compartments, a plurality of fuel injector nozzles connected to the second compartment, and a fuel supply line connected to the first compartmen and including Tan engine driven fuel pressuriaing device operable to supply fuel to the supply line at a pressure which increases with increasin engine 'speed, the valve closure member being,resiliently biased to the closed position to maintai a^ predetermined minimum fuel pressure in the supply line and being movable, by fuel pressure in the supply line exceeding the said predetermined minimum value, to an open position which varies withi fuel flow, the said predetermined minimum value being sufficient educe substantiall or to prevent fuel vaporisatio during operation of the engine. : 7 The valve"closure member ma be a resilient diaphragm. r teraatively, the present invention provides, low pressure fuel injection sys em for an internal combustion engine, including a fuel circulation conduit system having supply and return branches and i jectdr devices connected to reoeive fuel from the suppl branch, the suppl branch including an engine driven fuel pressurising device operable to supply fuel to the supply branch at a preseure whioh increases with increasing engine speed, a first; alve having a first compartment connecting the supply and return branches, a second compartment connected to the the pump mechanism whilst fuel flow is adjusted by the metering valve in dependence on engine loading. p«nd ng--&p¾4^a^ By way of example only, an embodiment of the invention will now be described in greater detail with reference to the accompanying drawings of which Pig. 1 shows the embodiment in diagrammatic form only, Pigs* 2 and 3 are cross sections on the lines II-II and III-III respectively of Pigs. 3 and 2 of a component of the system of Pig. 1 , Pig. 4 is a section through another component of the system of Pig. 1 , and Pig. 5 is a section on the line V-V in Pig. 1 .

The system shown in Pig. 1 includes a fuel circulation conduit system comprising a fuel supply branch 1 and a fuel return branch 2. The supply branch 1 contains a distribution chamber 3 with exit orifices 4 joined by conduits 50 to fuel injection devices 51 located in branch pipes leading from the engine intake manifold to the respective engine cylinders^. The injector devices each has a fuel tube 52 extending along an outer tube 53 terminating in an outlet orifice 54. The fuel tube terminates in a capilliary tube 55 (acting as a flow equalising restrictor) short of and aligned with the outlet orifice 54. The outer tube 53 has a vent 56 to atmosphere.

The capilliary tube 55 has a bore size relative to that of the orifice 54 such that fuel emergent from the capilliary tube is discharged through the outlet orifice without contacting the walls of the orifice. The injection devices shown are described in greater detail in British Patent 1140901 the Specification No. 620/65 but could be constructed as British patent Ν*· }S l3. * shown in the/Specification -ef-co-pondi-Kg--Α^^Ι-ι βτΦίο»-$o-_-j£' 5Θ3-95 65. The return branch 2 extends from an exit orifice in the chamber 3 containing a flow restrictor 6 via a pressure loading valve 7 and a vapour separator 8 to the fuel tank of the engine (not shown).

Connected to the vapour separator 8 is an inlet pipe 9 leading from the usual engine-powered fuel lift pump (not shown) and also an outlet pipe 10 leading to the inlet of an engine driven fuel pump mechanism 11 which supplies fuel to supply branch 1 at a minimum pressure of the order of 10 p.s.i. This pressure increases with increasing engine speed. The pump mechanism 11 comprises a priming pump 12 which supplies fuel to a main pump 13 at a pressure determined by a pressure relief valve 14 connected between the outlet of the priming pump 12 and the return branch 2. The construction of the main pump 13 is shown in more detail in Fig. 5 which is a section on line V-V in Pig. 1. The pump has a rotor 80 keyed to a shaft 81 connected to a gear 82 (Fig. 1 ) adapted to be driven by the engine. The rotor 80 has circumferential vanes or teeth 83 and is mounted for rotation in a closely fitting shallow cylindrical chamber one end face 84 of which has an arcuate groove 85, registering with the teeth 83, describing an arc of about 305° around the end face 84.

One end of the groove 85 communicates with an inlet port 86, fed from the priming pump 12, and the other end communicates with an outlet port 87 leading to the supply-branch 1. In operation of the pump 13 * the rotor 80 is rotated at a speed determined by the engine speed and fuel entering the inlet port 86 is swept around the groove 85 by the teeth 83 at a speed dependent on engine speed. At the opposite end of the groove, the velocity energy of the fuel is converted to pressure energy, the fuel thereby being forced through the outlet port 87. Thus, the is pressure of fuel flowing through the outlet port/ directly controlled by engine speed.

The output from the main pump 13 passes to the supply branch 1 which contains a fuel metering valve which is controlled by the engine inlet manifold vacuum or by the opening of the engine throttle to vary the area of a metering orifice in the supply branch 1 and thereby to ad ust fuel flow to chamber 3 in dependence upon the inlet manifold vacuum or the throttle opening.

One version of a suitable metering valve 15 is functionally illustrated and has upper and lower chambers 60, 61. The former chamber has an inlet 62 for connection to the engine air intake manifold to communicate manifold vacuum changes to the interior of chamber 60, thereby causing movement of a piston 63 therein against a spring 64 in response to such changes. The piston 63 is coupled by a linkage 65 to a pivoted cam 66 in the chamber 61 so that movement of the piston £c¾^% the cam to pivot and to rotate a cam follower 67. Rotation of the cam follower rotates a valve stem 68 in a sleeve 69. The valve stem 68 is open at one end and closed at the other, the open end communicating with the supply branch 1 downstream of the valve 15. Upstream of the valve 15, the branch 1 communicates via a rectangular aperture 70 in the sleeve 69 with the interior of the valve stem 68 under control of a transverse slot 71 in the wall of the stem. The width of the slot 71 changes along its length so that rotation of the valve stem 68 in the sleeve 69 varies the area of the slot in registration with the rectangular aperture 70 and hence controls the flow of fuel through the metering valve 5. This metering valve is described British Patent Specification No. 1140901 j^f in greater detail ± /e9^pe^1T^-kppliea.^ en- e-e-B^£&/ ^ Pigs. 2 and 3 show in more detail the chamber 3 and the pressure removing valve contained therein. The chamber 3 has an inlet 16 leading to an annular inlet chamber 17 separated from an outlet chamber 18 by a resilient diaphragm 19 carrying a diaphragm disc 20. The diaphragm 19 acts as a closure valve and controls flow of fuel from chamber 17 to chamber 18 via a central chamber 21 and a central opening 22 in both diaphragm 19 and disc . The wall of the central chamber 21 forms a seating for the diaphragm which is loaded by a spring 23 located by the disc 20 and a spring plate 24. The loading of the diaphragm 19 hy the spring 23 is adjustable by an adjusting screw 25. Also located in the chamber 17 is an annular shaped fuel filter 26.

The chamber 17 has an outlet passage 27 leading to a chamber 28 containing an orifice disc 29 and an axially adjustable rod 30 which passes through the disc 29 and has a portion 31 the cross sectional area of which transverse to the axis of the rod 30 changes along that axis and the position of which relative to the orifice diso 29 determines the rate of fuel flow through the latter. Thus, the rod 30 and the orifice disc 29 perform the function of the restrictor 6 in Pig. 1. The chamber 28 is connected to the outlet 5 leading to the return branch and which is located on that side of disc 29 remote from passage 27. The position of rod 30, and hence the effective area of the orifice 29, is determined by the setting of an adjusting sorew 32 against which the restrictor is held by a spring 33.

Conveniently, the pressure loading valve 7 and the relief valve 14 are contained in a common housing which is shown in more detail in Pig. 4.

The housing has fuel inlets 34, 35 separated from a common outlet chamber 36 by spring-loaded resilient diaphragms 37 and 38 respectively. The inlet 34 communicates with an annular inlet chamber 39 the access of which to the outlet chamber 36 is controlled by the diaphragm 37 which coacts with a seating provided by the upper (as seen in Pig. 4) end of chamber 36. Similarly, the inlet 35 communicates with an annular inlet chamber 40 the access of which to the outlet chamber 36 is controlled by the diaphragm 38 which coacts with a seating provided by the lower (as seen in Pig. 4) end of chamber 36. The diaphragms 37, 38 both have diaphragm discs 41 which each support loading springs 42, 43 adjustable by adjusting nuts 44 and adjusting screws 45 respectively. The springs 42, 43 are relatively heavy and relatively light springs respectively, allowing very accurate adjustment of the The inlets 34, 35 are joined respectively to the return branch 2 (Fig. 2) leading from the outlet 5 and to the output of the priming pump 12, whilst the outlet chamber 36 is joined by the return branch 2 to the vapour separator 8.

The vapour separator Θ (Fig. 1 ) is of known form and comprises an inverted cone 46 connected at its apex to the return branch 2 and to the fuel inlet 9. A restricted vapour venting connection 47 at the top of the separator permits the return of vapour from the separator to the fuel tank (not shown).

Before operation of the system, the pressure relief valve in the chamber 3 (as shown in Figs. 2 and 3) is set so that the loading on diaphragm 19 is equal to the predetermined additional pressure to be applied to the fuel to prevent or substantially reduce fuel vaporization in the components of the system shown in Fig. 1 due to engine temperature. Thus, the fuel pressure in chamber 18 is equal to the low pressure necessary for effective atomisation of the fuel in the injector devices.

The pressure loading valve 7 ensures that the fuel pressure in the return branch 2 is sufficient to stop or substantially prevent vaporization in that branch. A pressure of the order of 10 lbs. per square inch is satisfactory for most conditions. If, due to overheating, vapour does form, it is separated out in the separator 8.

In operation of the system described above, the diaphragm 19 determines the minimum fuel pressure in the supply branch 1 and the valve 7 ensures that a similar pressure exists in the return branch 2. Fuel is metered to the injector devices 51 by the engine driven pump mechanism 11 acting in conjunction with the metering valve 5. The pump mechanism adjusts fuel pressure in the supply branch with changes in engine speed and the metering valve 15 is controlled by engine air intake manifold vacuum to adjust fuel flow to the chamber 3 in dependence on engine loading. Prom the distribution chamber 3, the fuel flow divides between the injector devices 51 and the return branch 2 in dependence upon the setting of the restrictor rod 30, the restriction offered by the flow equalising restrictors 55 in the actual injector devices and the spring loading on diaphragm 37. Pressure in the return branch is maintained by the valve 7 at the value necessary to stop or substantially prevent vaporization of fuel in the return branch under normal conditions of engine temperature.

Claims (1)

1. A low pressure fuel Injection for an combustion including a valve fi and second compartments and a closure the closure member a closed position in which it closes cation between the first and second compartments and being movable through a range of open positions to vary the path between the first and second a plurality of fuel injector nozzles connected to the second and a fuel supply line connected to first compartment and including driven fuel pressurizing device operable to supply fuel to line at a sure which increases with increasing engine the valve closure being resiliently to the closed position to maintain predetermined minimum fuel pressure in the supply lino and by fuel pressure in the supply line exceeding the to an open position which varies fuel the said ined minimum value sufficient to reduce substantially or to prevent fuel vaporization during operation of t A system to claim in which the valve is a resilient pressure fuel injection for an internal combustion a fuel circulation conduit system having supply and return branches and injector devices connected to receive fuel from the supply the supply branch including a engine driven fuel pressurising device operable to supply fuel to the supply branch at a pressure which increases with increasing a first valve a first compartment connecting the supply and return a second compartment connected to the injector devices and a valve closure member which has a position in which it closes communication between the first and second compartments and which is movable through a range of open positions to vary the flowpath section between the and second the first valve closure member being resiliently biased to the closed position to maintain predetermined minimum fuel pressure in the supply branch and being by fuel pressure in the supply branch exceeding the said predetermined minimum to an open position which varies with fuel flow through the supply the said minimum value being sufficient to reduce substantially or to prevent fuel vaporisation during operation of the the system further including a second valve connected in the return the second valve having a closure member movable between an open and closed position and resiliently biased to the closed the second valve closure member being movable to the open position by to opon poaition fuel pressure in the return branch a predetermined A system according to claim in which the valve closure members are resilient and in which in the closed position the diaphragm the first valve is against an upstanding seating in the first the annular seating surrounding an aperture in diaphragm whe that diaphragm is cates the first compartment with the second A system according to claim 3 or claim i which the fuel circulation conduit system includes a fuel flow control valve controlled in response to engine A system according to claim which the flow to the open position by fuel pressure than the said predetermined system according to claim in which the fuel flow control valve includes a valve member adjustable to control the area of a flow control the valve member being adjustable in response to changes in engine air intake manifold A system according to an one of the preceding in which the engine driven fuel pressurising device comprises a priming pump connected supply fuel to a pressurising device a constant pressure determined by relief valve connected to the priming A system according to any one of claims to in which the return branch includes a fuel vapour separator located downstream of the second A low pressure fuel injection system substantially as described with reference to and as illuatrated by the accompanying For the ARTNERS insufficientOCRQuality