AU469585B2

AU469585B2 - Improvements relating to fuel injection apparatus for internal combustion engines

Info

Publication number: AU469585B2
Application number: AU52548/73A
Authority: AU
Inventors: Colin Paguin Brian
Original assignee: GKN Transmissions Ltd
Current assignee: GKN Automotive Ltd
Priority date: 1972-03-03
Filing date: 1973-02-23
Publication date: 1976-02-19
Also published as: DE2310289C3; DE2310289B2; FR2174990A1; FR2174990B1; GB1417703A; US3839998A; AU5254873A; JPS48103921A; SE402327B; JPS5815622B2; CA967443A; DE2310289A1; ZA731186B; IT977958B

Description

52, 54 8 n3 This invention relates to fuel injection apparatus for (hereinafter referred to as being of the kind specified)

an internal combustion engine, the apparatus comprising a

body affording an air inlet duct, a fuel pump means for means establishing flow of fuel from inlet means to outlet for on the pump body, the latter being connected or adapted in connection to one or more fuel injectors, metering means means the pump body operative between the inlet and outlet

and adapted to be driven in timed relation with the crank-

shaft or other rQtary output member of the engine for

delivering a measured quantity of fuel to the outlet means

in each cycle of operation of the engine, and sensing means

controlling-operation of the metering means and sensing to parameters which are selected to provide a proper air

fuel ratio for a range of engine loads and a range of

external conditions of operation.

The invention has been developed in relation to for fuel injection apparatus of the kind specified intended

use in conjunction with an engine having one or more air- cylinders and having ignition means for igniting the

fuel mixture in the cylinders by means of spark discharge.

The fuel is a volatile hydro-carbon such as petrol.

Again, the invention has been developed primarily

in relation to a fuel injection apparatus of the kind

specified wherein the metering means comprises a metering

cylinder containing a free or shuttle piston element

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52, 54 8 n3 movable between stops, the distance between which is

determined by an adjustment means to determinethe quantity

of fuel delivered each stroke of the free piston, and

cylinder spaces on opposite sides of the piston are connected

in successive cycles of operation through commutating valve

means respectively to the pump means and to the outlet means,

the other valve space in each case being connected respectively

to the outlet means and the pump means. When the fuel

injection apparatus is intended to be utilised in conjunction

with a multi-cylinder engine the outlet means would comprise

a plurality of outlets, and the commutating valve means would

be associated with, or would be constructed to act as, a

distributing valve means to effect delivery of fuel from

respective outlets in the proper succession.

In operation of fuel injection apparatus of the kind

specified, and more especially the form referred to in the

preceding paragraph, delivery of fuel into the inlet manifold

of the associated engine is by way of a succession of discrete

volumes or pulses. The quantity of fuel in each pulse is

varied by operation of the metering means and for proper

operation at the highest speed of the engine it is necessary

that the pulses injected shall still be discrete or individual,

as distinct from merging with each other. Further, the air

inlet valve of the cylinder which is to receive the pulse

of fuel is open only for a relatively short time, and it is

important that the fuel be injected into a moving air stream

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52,54 8 /73 so as to be converted into the form of a spray. These

considerations require the provision of a pump means for

establishing a relatively high pressure of fuel at its

outlet, for example upwards of 100 lbs. per square inch.

One of the problems, however, which arises when

utilising pump means of relatively high output pressure is

that the engine can be rotated during cranking or starting

purposes only at a relatively low speed 100 to 200 r.p.m. At this spoed of operation the pump means of relatively

simple design capable of being manufactured economically

will not develop requisite output pressure to enable fuel

to be delivered through the injector or injectors.

It has been proposed to overcome this problem by

providing a carburettor device in the fuel injection

apparatus but the arrangement proposed involved certain

disadvantages. Firstly, the carburettor was not entirely

disabled during subsequent operation of the associated engine,

e.g. when cold, and consequently during this phase precise

-control over air to fuel ratio would not be established,

thereby leading to a degree of atmospheric pollution not

acceptable by present and future standards. Secondly, the

bringing into operation and the eventual disablement of

the carburettor device entailed the provision of complex

electrical circuitry which not only would give rise to

complication and high manufacturing cost but also would be

a potential source of maintainance problems and unreliability.

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52, 548 3 The object of the invention is to overcome or reduce

these disadvantages.

According to the present invention a fuel injection

apparatus of the kind specified is provided in which a

carburettor device is provided including a carburettor air

inlet passageway of smaller cross-sectional area than that

of the inlet duct communicating with the latter at a

position downstream of an adjustable throttle valve provided

in or in association with the air inlet duct, a fuel jet

element communicating at its inlet end with said fuel

inlet means and having its delivery end arranged in relation

to the carburettor air inle-t passageway to deliver fuel

thereinto in response to depression of pressure in the air

inlet duct below atmospheric pressure, and air cut-off and

fuel cut-off valves movable from open positions to closed

positions by fluid pressure developed by the fuel pump means.

By the expression "carburettor device" is meant a

device which delivers a jet of fuel into a moving air stream

in a manner such that the fuel is broken up into small

particles (frequently referred to as emulsification) in the

air stream and is carried by the air stream and evaporates

therein before reaching the cylinder or cylinders of the

engine.

In one simple and advantageous arrangement according

to the invention the body of the apparatus is formed with

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52, 54 8 n3 a carburettor bore containing said jet element, said air

cut-off valve, and said fuel cut-off valve, both of these

valves being closed by operation of a piston element in

said bore under pressure of fuel from said pump means, the

carburettor air inlet passageway communicating with said

bore at a position adjacent to the delivery end of said

jet element.

Conveniently the air and fuel cut-off valves may

comprise a plunger movable longitudinally of said carburettor

bore and incorporating or operated by said piston element.

The pump means may, and preferably does, include two

pumps of which one is a high pressure pump contained in

or mounted on the body of the apparatus, and the other is

a low pressure pump (for supplying fuel to the inlet means

and having an outlet pressure which is lower than that of

the high pressure pump), a supply of fuel to the carburettor

device being derived from the low pressure pump. The low

pressure pump may be mounted remotely from the body of the

fuel injection apparatus, for example in the locality of

or within a tank containing a bulk supply of fuel.

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52, 54 8 The invention will now be described, by way of

example, with reference to the accompanying drawings

wherein:-

FIGURE 1 is a schematic diagram illustrating the main

components of a fuel supply system incorporating a fuel

injection apparatus in accordance with the invention;

FIGURE 2 is a view in side elevation and partly in

cross-section illustrating a constructional embodiment of

the fuel injection apparatus in accordance with the

invention;

FIGURE 3 is a plan view in cross-section on the line

3-3 of Figure 2 illustrating the carburettor device incorporated in the fuel injection apparatus;

FIGURE 4 is a cross-sectional view on the line 4-4

of Figure 2 of the body of the apparatus;

FIGURE 5 is a diagrammatic view illustrating the

general arrangement and.manner of operation of the metering

means comprising the metering piston and cylinder unit

and a commutating and distributing valve means of the

fuel injection apparatus.

The complete system for the supply of fuel and the

constructional embodiment of apparatus are more fully

described in our copending application No. t- P5' /73 to which reference may be made. For convenience the main

7 469.585

52, 54 8 n3 features of the fuel supply system and fuel injection

apparatus will be referred to before describing in more

detail those parts of the embodiment of fuel injection

apparatus with which the present invention is concerned.

The fuel supply system shown in Figure 1 comprises a

fuel tank 10 feeding the inlet of a fuel injection apparatus

through a filter 12 and low pressure pump 13 by way of

pipes 11 and 14, excess fuel being returned to the tank

by pipe 32.

The fuel injection apparatus is shown mounted on the

inlet manifold 16 of a V-six cylinder internal combustion

engine 17 having injectors 26 fed by pipes 27 from outlets

of the fuel injection apparatus. The injectors include

spring loaded injector valves which are normally closed

but open at a predetermined injecting pressure of fuel

delivered to the injectors.

The fuel injection apparatus includes main units or

assemblies which are identified by blocks in the schematic

circuit diagram and by corresponding references in Figure 2

as follows.

A high pressure pump 18 of the rotary vane type

develops the requisite injecting pressure and supplies

fuel such as petrol from an inlet 14a to a metering means

through the intermediary of a commutating and distributing

valve means 19 which serves to operate a free or shuttle,

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52,54 8 3 piston 20a of the metering means and also distribute the

fuel successively to six outlets connected by pipes such as

27 to the injectors 26.

Excess fuel is returned through blow-off valve 31 to

pipe 32.

The stroke of the piston 20a of the metering means

between stops 20b, 20c is determined by sensing or control

means 29 which includes an evacuated bellows 29a for

sensing absolute pressure in a chamber 34 forming part of

the air inlet duct to which admission of air is controlled

by a throttle valve fitting 35 incorporating a manually

operable butterfly valve plate 36.

Temperature of the air in the chamber 34 is sensed

by a temperature sensing element 37 of the wax capsule

type, while a further temperature parameter, for example

engine cooling fluid temperature, is sensed by a temperature

sensing element 38. Mechanical outputs in the form of

axial displacements of the elements 37 and 38 are added in

an addition mechanism 39, the output element of which is

a rotary sleeve 40 on which one end plate of the bellows

29. is fixed.

The other end plate of the bellows carries a cam

element 41 having a frusto-conical cam surface eccentric

to axis 41a so that axial displacement of the cam in con-

.sequence of pressure sensing by the bellows 29a and

rotation of the cam in consequence.-of sensing of temperature

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2 ,54 83 multiplied and applied parameters by elements 36 and 37 are position of the lower to tappet 42 serving to adjust the

stop of the metering piston.

of operation of The general arrangement and manner and distributing the metering means 20 and the commutating

valve means 19 is illustrated in Figure

are secured Rotary valve plates 48 and 49 which by carrier 47 and valve together are supported and rotated formed in its left-hand plate 48 has the T-shaped cavity limb b6 being longer face, as seen in Figure 5, with the to overlap distributing than the other limbs b2 and b4 so as each port d in plate 49. The valve plates have ports

designated by letters b, and f with a suffix 1 to 6 6 outlet gl to g and hence pertaining to the particular 6 of the engine. cylinder No.1 to cylinder No.

the flow of fuel from Full line arrows 43 illustrate cycle to the upper cylinder the high pressure pump 18 in one 44, while broken line space s1 of the metering cylinder fuel from the lower arrows 45 illustrate the flow of 6 outlets g In this cycle cylinder space s2 to one of the pressure pump traverses of operation fuel from the high s1. Fuel from ports ia,bl, cl, el to reach cylinder space ports e2, c4, limb b4 of a cylinder space s2 traverses 6 T-shaped cavity, b6 thereof, port £6 and g

46 95 8

52,54 8 n3 A supplementary pressure sensing means in the form

of an accelerator piston 50 is rotatably mounted on the

output sleeve 40 through the intermediary of a substantially

sealed bearing 51 and undergoes displacement to the right

in response to sudden opening of the throttle valve producing

a sudden increase of'absolute pressure in the chamber 34.

This displaces the bellows and the cam element to the right

and lowers the stop 20c to produce a short term enrichment.

of the mixture. The bearing 51 allows leakage of air from

one side of the piston to the other at a slow rate and the

piston thus returns to its initial position by virtue of

a spring 52 incorporated in the adding mechanism 39.

The pressure of fuel delivered from the high pressure

pump 18 may be of the order of 120 Ibs. per square inch

but this is not developed at cranking speeds which are

capable of being attained by operation of a normal starter

motor on the associated engine.

Accordingly the fuel injection apparatus includes a

carburettor device 30 which comes into operation only during

starting operations at cranking speeds.

It is necessary to prevent duplicate delivery of fuel

by way of both the carburettor device and the injectors of

the fuel injection apparatus, and accordingly a controlling

signal is applied to the carburettor to disable this in

a manner such as to prevent the delivery of fuel from the

carburettor device when conditions of operation in the

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52,548/73

fuel injection apparatus are such that delivery of fuel

from the outlets thereof to the injectors is established.

One convenient signal which may be employed for this purpose

is a fluid pressure signal derived from the output side of

the high pressure pump.

The carburettor device is illustrated more particularly

in Figure 3 and Figure 4 and comprises a carburettor bore

100 formed in the body 33 of the fuel injection apparatus

along an axis parallel to that of the driving shaft and

the bellows and situated about midway between these components

in that wall of the body 33 which forms the boundary between

the chamber 34 on the one hand and the chamber in which

the metering cylinder block, commutating and distributing

valve means, and high pressure pump on the other hand are

accommodated.

The carburettor bore 100 includes portions 101 and

102 respectively of larger and smaller diameters. Slidably

mounted in the smaller diameter portion 102 is one element

103 of a jet assembly. Such element comprises an inner

tube 104 having a fuel passageway 105 extending axially

through it and terminating in an end portion 106 of

enlarged diameter containing a threshold valve which

includes a valve seat element 107, a ball 108 and a biasing

coiled compression spring 109 urging the ball onto the

seat element.

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52, 54 8 n3

The seat element 107 has an opening 110 in its end

face through which liquid fuel in the annular space 111

can pass, the annular space 111 in turn being fed with

fuel through passageway 136 connected internally with inlet 14a on the body of the apparatus.

The strength of the spring 109 is selected to provide opening of the threshold valve at a predetermined low

pressure is greater than any gravitational pressure of

fuel at the valve but less than fuel injection pressure,

for example about 2 Ibs. per square inch, This can be developed by the low pressure fuel pump 13. The valve is thus effective to prevent draining of fuel through the carburettor device gravitationally when the engine and

fuel injection apparatus is at rest.

The valve element 103 also includes a head 113 which is a close fit in the smaller diameter portion 102 of the carburettor bore and is equipped with a sealing ring 114

seated in a groove to seal the annular space 111 from the

remaining portion of the carburettor bore.

The jet assembly includes a further jet element 115

in the form of an outer tube fitting telescopically with

the inner tube 104 and formed with holes 116 constituting

a jet orifice extending through its wall at diametrically

opposed positions adjacent to the free or delivery end of

the inner tube 104.

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52, 54 8 n3 two valves, The carburettor device further comprises air cut-off valve. namely a fuel cut-off valve and an

incorporating or The valves comprise a plunger 117 movable axially in operable by a piston portion 117a and the carburettor bore the largerdiameter section 101 of in Figure 3, and a closed between an open position, as seen the mouth or position in which its inner end overlaps the larger opening of an air passageway 101b traversing bore situated in diameter portion 101 of the carburettor end of the inner tube the vicinity of the free or delivery by pipe 101a 104. Air is admitted to this passageway an air cleaner (not (Figure 4) which may be connected to by way of a portion 101b shown), the passageway continuing bore and the chamber 34. (Figure 4) connecting the carburettor

a valve The fuel shut-off valve further comprises the bottom of element 118 of resilient material seated in constitutes a a bore 119 in the plunger 117, which bore of the outer tube 115 continuation of the interior surface

of the jet assembly.

a coiled The plunger 117 is biased by means of the head 113 and the compression spring 120 acting between in a position in which plunger 117 to maintain the latter valves are open. both the fuel cut-off and air cut-off

14 469.585

52, 54 8 n3 Movement of the plunger 117 to close both of these valves takes place in response to the admission of fuel under pressure from the outlet of the high pressure pump 18 to the space 121 through bores 123 and 122 and space

131 which communicates with the outlet side of the high pressure pump through bore 131 (Figure 4) formed in an inlet plug fitting 124 screwing into an internally threaded end portion of the carburettor bore, such fitting being equipped with a sealing ring 125 seated in a circumferential

recess therein.

The bore 123 may contain a restrictor bush 126 formed with a constrictor passageway 127 to control the rate of admission of fuel under pressure to the space 121 and hence to determine the duration of the starting period for which the carburettor device remains operative, such period terminating with closure of the fuel and air cut-off valves under injecting pressure of fuel in the space 121.

When the throttle valve of the fuel injection device is closed, or only slightly open, pressure in the air inlet duct downstream of this valve is low and air will be drawn through the air inlet pipe 101 of the carburettor device because the cross-sectional areas of pipe 101a and passageway 101b are small compared with the main air inlet duct of the throttle valve fitting 35 and chamber 34. The air velocity will be higher than that which would be produced by opening the throttle valve plate 36. Fuel

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52,548 3

delivered from the free or delivery end of the inner tube

104 and emerging from the holes 116 in the outer tube 115

will thus readily be broken up. into particles in the manner

of a slow running jet assembly of the conventional carburet-

tor, and will be conveyed along the passageway-101b connect-

ing the carburettor device to the chamber 34 of air.inlet

duct of the fuel injection apparatus.

The carburettor device is also able to supply fuel

to the engine in the event of a fault developing in the

high pressure fuel pump such as to prevent the pressure at

the outlet thereof reaching a value at which it will effect

delivery of fuel from the outlets of the fuel pump to the

injectors, and such that the plunger 117 remains in the

position shown in Figure 3. For operation under these

conditions the throttle valve 36 would be opened only to

a slight extent.

Pressure control and relief of fuel delivered from

the outlet of the high pressure fuel pump is regulated by

a blow-off valve 31. This comprises a valve head 128

(Figure 3) of conical form cooperating with a valve seat

in a body 129 against which it is spring loaded by a

coiled compression spring 130. High pressure fuel is fed

through a bore 131a to a chamber 131 from which it passes

through a filter 133 to the interior bore 134 of the body

129 of the blow-off valve. The latter opens at a pressure

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52,54 8 73

determined by the spring 130 to discharge excess fuel to

the portion 135 of the blow-off valve bore and thence to

a passageway 136. The passageway 136 communicates with

the annular space 111 from which excess fuel is fed back

to the fuel tank via an outlet fitting 112.

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Claims

52, 54 8 n3

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- 1. A fuel injection apparatus of the kind specified

in which a carburettor ddvice is provided including a carburettor air inlet passageway of smaller cross-sectional

area than that of the inlet duct communicating with the latter at a position downstream of an adjustable throttle

valve provided in or in association with the air inlet duct, a fuel jet element communicating at its inlet end

with said fuel inlet means and having its delivery end arranged in relation to the. carburettor air inlet passageway

to deliver fuel thereinto in response to depression of pressure in the air inlet duct below atmospheric pressure,

and air cut-off and fuel cut-off valves movable from open positions to closed positions by fluid pressure developed

by the fuel pump means.

2. A fuel injection apparatus according to claim 1

wherein the carburettor device comprises a carburettor

bore containing said jet element, said air cut-off valve and said fuel cut-off valve, both of these valves being closed by operation of a piston element in said bore under pressure of fuel from said pump means, the carburettor air inlet passageway communicating with said bore at a position adjacent to the delivery end of said jet element.

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52,54 8 3

3. A fuel injection apparatus according to claim 2 wherein the air and fuel cut-off valves comprise a plunger movable longitudinally of said carburettor bore and incorporating or operated by said piston element.

4. A fuel injection apparatus according to any one of the preceding claims wherein the pump means includes two pumps, one of which is a high pressure pump contained in, or mounted on, the body of the apparatus, and the other of which is a low pressure pump for supplying fuel to the inlet means of the apparatus, and having an outlet pressure which is lower than that of the high pressure pump, the supply of fuel to the carburettor device being derived from the low pressure pump.

A fuel injection apparatus according to any one of the preceding claims wherein a threshold valve is provided controlling the supply of fuel to the carburettor device, such threshold valve being normally closed when the apparatus is out of use and opened in response to attainment of a threshold pressure of fuel when the fuel injection apparatus is brought into operation.

6. A fuel injection apparatus having a carburettor

device substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

D A T E D this 22nd day of February, 1973.

GKN TRANSMISSIONS LIMITED SBy its Patent Attorneys: CALLINAN AND NEWTON.

19 469.585

2,5 4 Sn FIG .1

P,6 9.585

2,54 8 n3. FIG. 2.

9e

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52, 54 8 n3

FIG. 3.

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52, 548 /3

FIG. 4.

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52, 54 8 M.

-2..9 29469.58