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Claims  |
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The claims defining the invention are as follows:
1. A method of metering fuel to an engine having a fuel delivery port and a
selectively openable valve element to provide communication to the engine
through the port when open, and to provide when the port is closed,
sealable engagement at two locations spaced in the direction of flow
through the port and defining between said locations a cavity, the method
comprising supplying fuel and gas independently to the port at respective
pressures, one of the fuel and gas being supplied to said cavity and the
other being supplied upstream of both sealable engagement locations,
cyclicly opening the valve element to communicate said port with the
engine to permit delivery of fuel entrained in gas to the engine, and
regulating the pressure differential between the fuel and the gas at the
cavity to control the rate of fuel flow into the gas at the cavity.
2. A method as claimed in claim 1 wherein the pressure differential is
regulated in accordance to the engine load.
3. A method as claimed in claim 1 or 2 wherein the period of communication
between the port and the engine is regulated in accordance with engine
load.
4. A method as claimed in claim 1 or 2 wherein the fuel is supplied to the
cavity.
5. A method as claimed in claim 1 or 2 wherein the fuel is supplied to the
cavity at a plurality of locations spaced along the cavity length.
6. A method as claimed in claim 5 wherein, during operation of the engine,
the number of said locations at which fuel is supplied is varied to
control the distribution of the fuel as delivered to the engine.
7. A method as claimed in claim 5 where the rate of fuel supplied to the
cavity at at least some of the location is varied to control the
distribution of the fuel as delivered to the engine.
8. Apparatus for metering fuel to an engine comprising fuel supply means
and gas supply means each adapted to deliver to the same delivery port, a
valve element operable to selectively open said port to communicate the
port in use with an engine, said port and valve element when closed
sealably engaging at two locations spaced in the direction of flow through
the port and defining between said locations a cavity, one of the fuel
supply means and gas supply means communicating with said cavity and the
other of the fuel supply means and gas supply means communicating with the
port upstream of said two sealably engaging locations, means to cyclically
operate the valve element to open said port to permit delivery of fuel
entrained in gas to the engine through said port, and means to regulate
the pressure differential between the fuel supply and gas supply at the
cavity to control the rate of fuel flow into the gas.
9. Apparatus as claimed in claim 8 wherein the fuel supply means
communicates with the cavity.
10. Apparatus as claimed in claim 8 wherein the fuel supply means
communicates with the cavity through a plurality of apertures spaced along
the periphery of the cavity.
11. Apparatus as claimed in claim 10 wherein means are provided to vary the
number of said apertures providing communication between the fuel supply
means and the cavity
12. Apparatus as claimed in claim 10 or 11 wherein means are provided to
vary the fuel flow rate through at least some of said apertures.
13. Apparatus as claimed in claim 11 wherein said means to vary the number
of apertures in communication with the fuel supply means is operable in
response to engine operating conditions.
14. Apparatus as claimed in claims 8 to 10 or 13 wherein the means to
regulate the pressure differential between the fuel supply and gas supply
at the cavity are operable in response to engine fuel demand.
15. Apparatus as claimed in claim 8 to 10 or 13 wherein the means to
regulate the pressure differential is adapted to regulate the fuel
pressure in response to the engine fuel demand.
16. Apparatus as claimed in claims 8 to 10 or 13 wherein the port has two
coaxial annular sealing faces spaced in the direction of opening movement
of the valve element, said valve element being adapted to sealably engage
said faces when in the closed position, said cavity being an annular
groove in the port coaxial with and located between the annular sealing
faces.
17. Apparatus as claimed in any one of claims 8 to 10 or 13, wherein the
port has two co-axial annular sealing faces spaced in the direction of
opening movement of the valve element, said valve element being adapted to
sealably engage said faces when in the closed position, said cavity being
an annular groove in the port co-axial with and located between the
annular sealing faces, and the port has a truncated conical or spherical
internal surface on which sealing faces are provided.
18. Apparatus as claimed in any one of claims 8 to 10 or 13, wherein the
port has two co-axial annular sealing faces spaced in the direction of
opening movement of the valve element, said valve element being adapted to
sealably engage said faces when in the closed position, said cavity being
an annular groove in the port co-axial with and located between the
annular sealing faces, and an annular orifice is provided co-axial with
and upstream of the annular sealing faces.
19. Apparatus as claimed in any one of claims 8 to 10 or 13, wherein the
port has two co-axial annular sealing faces spaced in the direction of
opening movement of the valve element, said valve element being adapted to
sealably engage said faces when in the closed position, said cavity being
an annular groove in the port co-axial with and located between the
annular sealing faces, and an orifice is provided downstream of the
annular sealing faces.
20. A method of delivering fuel to an engine comprising supplying fuel and
gas at respective pressures independently to a port selectively
communicable with the engine combustion charge, cyclically communicating
said port with the engine combustion charge to permit a flow of fuel and
gas from the port into said combustion charge with the fuel entrained in
the gas and while the port is in communication with the combustion charge
controlling the location of admission of the fuel into the gas to regulate
the fuel distribution pattern in the combustion charge, and regulating the
pressure difference between the fuel and gas supplies in accordance with
engine load to control the quantity of the fuel delivered to the engine
per cycle.
21. A method as claimed in claim 20 wherein the fuel is deliverable to the
port at a plurality of spaced locations, and the number of locations at
which fuel is delivered is varied in accordance with the required fuel
distribution pattern.
22. A method as claimed in claim 20 wherein the rate of delivery of fuel at
at least some of the locations is varied in accordance with the required
fuel distribution pattern.
23. A method as claimed in any one of claims 20 to 22 where the period that
communication exists between the port and combustion charge is controlled
to control the quantity of fuel delivered to the engine per cycle.
24. Apparatus for delivering fuel to an engine comprising fuel supply means
and gas supply means each adapted to deliver to a selectively openable
delivery port, means to cyclically open said port to communicate with an
engine combustion charge to permit a flow of fuel and gas into the
combustion charge, means to control the location of admission of fuel into
the gas while the port is open to regulate the fuel distribution pattern
in the combustion charge, and means to regulate the pressure difference
between the fuel and gas supplies at the port in accordance to engine fuel
demand to control the quantity of fuel delivered to the engine.
25. Apparatus as claimed in claim 24 wherein the fuel supply means is
adapted to supply fuel to a plurality of locations for admission to the
port, and the means to control the location of fuel admission is adapted
to vary the locations at which fuel is admitted in accordance with the
required fuel distribution pattern.
26. Apparatus as claimed in claim 24 wherein means are provided to vary the
rate of fuel delivery at at least some of said locations in accordance
with the required fuel distribution pattern.
27. Apparatus as claimed in any one of claims 24 or 25 wherein means are
provided to vary the period per engine cycle that the port is in
communication with the combustion charge.
28. A method as claimed in any one of claims 1, 2, 20 21 or 22 wherein the
port delivers the fuel-gas mixture directly into a combustion chamber of
the engine.
29. Apparatus as claimed in any one of claims 8 to 10, 13, 22 or 24 wherein
the port is adapted to deliver the fuel-gas mixture directly into an
engine combustion chamber.
30. An internal combustion engine including means to deliver fuel thereto,
said means being adapted to operate in accordance with the method as
claimed in any one of claims 1, 2, 20, 21 or 22.
31. In an automotive vehicle an internal combustion engine including means
to deliver fuel thereto, said means being adapted to operate in accordance
with the method as claimed in any one of claims 1, 2, 20, 21 or 22.
32. An outboard marine engine including means to deliver fuel thereto said
means being adapted to operate in accordance with the method as claimed in
any one of claims 1, 2, 20, 21 or 22.
33. An internal combustion engine including apparatus to deliver fuel
thereto as claimed in any one of claims 8 to 10, 13, 22, 24, 25 or 26.
34. In an automotive vehicle and internal combustion engine including
apparatus to deliver fuel thereto as claimed in any one of claims 8, to
10, 13, 22, 24, 25 or 26.
35. An outboard marine engine including apparatus to deliver fuel thereto
as claimed- in any one of claims 8 to 10, 13, 22, 24, 25 or 26.
36. A method of metering fuel to an engine having a fuel delivery port and
a selectively openable valve element associated with the port and when
open providing communication to the engine through the port and when
closed providing sealable engagement at two locations spaced in the
direction of flow through the port, said two locations defining a cavity
therebetween, said method comprising supplying fuel and gas at respective
pressures independently to the port with one of the fuel and gas being
supplied to said cavity and the other being supplied upstream of the two
sealable engagement locations, cyclically opening the valve element to
communicate the port with the engine to deliver fuel entrained in gas to
the engine, and controlling the rate of fuel flow into the gas at the
cavity by regulating the pressure differential between the fuel and the
gas at the cavity.
37. A method of delivering fuel to an engine comprising supplying fuel and
gas at respective pressures to a port selectively communicable with the
engine, cyclically communicating the port with the engine to deliver a
flow of fuel entrained in gas from the port to the engine, regulating the
fuel distribution pattern in an engine combustion charge by controlling
the location of admission of the fuel into the gas, and controlling the
quantity of fuel delivered to the engine per cycle by regulating the
pressure differential between the fuel and gas supplied to the port.
38. Apparatus for metering fuel to an engine comprising fuel supply means
for delivery fuel at a first pressure to a delivery port, gas supply means
for delivering gas at a second pressure to the delivery port, valve means
for selectively opening the port to in use communicate in a direction of
flow the port with the engine, said port and said valve means when closed
sealably engaging at two locations spaced in the direction of flow and
defining a cavity therebetween, one of the fuel supply means and the gas
supply means communicating with the cavity and the other of the fuel
supply means and the gas supply means communicating with the port upstream
of the two sealable engaging locations, operating means for cyclically
operating the valve means to open the port to deliver fuel entrained in
gas to the engine through the port, and control means for controlling the
quantity of fuel delivered to the engine per cycle by regulating the
pressure differential between the fuel supply means and the gas supply
means at the cavity.
39. Apparatus for delivering fuel to an engine fuel supply means for
delivering fuel at a first pressure to a selectively openable delivery
port, gas supply means for delivering gas at a second pressure to the
port, opening means for cyclically opening the port to communicate the
port with an engine combustion charge to deliver a flow of fuel and gas to
the combustion charge, pattern means for regulating the fuel distribution
pattern in the combustion charge by controlling the location of admission
of fuel into the gas while the port is open, and control means for
controlling the quantity of fuel delivered to the engine by regulating the
pressure difference between the fuel and gas supplies at the port in
accordance to engine fuel demand. |
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Claims |
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Description |
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This invention relates to the metering of fuel to an engine particularly in
applications where the fuel is injected directly into the combustion
chamber of an engine.
There has previously been proposed methods of metering fuel wherein the
metered quantity of fuel is displaced from a variable capacity chamber by
a charge of gas, such as air, at an appropriate pressure. It is considered
that the charge of gas contributes significantly to the efficient
combustion of the fuel, at least in part because of improved atomisation
of the fuel.
There has been proposed in our International patent application No.
PCT/AU85/00176 and U.S. patent application No. 849501 derived therefrom,
still pending an improved method of metering fuel to an engine wherein a
continuous supply of fuel under pressure is provided to a closed fixed
capacity chamber having a selectively openable delivery port. Gas is
periodically admitted to the chamber to maintain in the chamber a pressure
not greater than the fuel pressure and the delivery port is opened during
the period of admission of gas to the chamber, whereby the fuel in the
chamber at the time of opening the delivery port, and fuel that enters the
chamber during that period is delivered from the delivery port to the
engine. This method of metering and delivering fuel is effective, but
presents some difficulties in manufacture, particularly high volume
commercial manufacture, partly due to the need for substantially
simultaneous operation of the valves controlling the discharge port and
the supply of gas to the chamber.
It is the object of the present invention to provide an improved method and
apparatus for delivering a metered quantity of fuel to an engine that is
effective and accurate in operation, convenient to manufacture and
maintain, and assists in promoting a high degree of atomisation of the
fuel.
With this object in view there is provided a method of metering fuel to an
engine having a fuel delivery port and a selectively openable valve
element to provide communication to the engine through the port when open,
and to provide when the port is closed sealable engagement at two
locations spaced in the direction of flow through the port and defining
between said locations a cavity, the method comprising supplying fuel and
gas independently to the port at respective pressures, one of the fuel and
gas being supplied to said cavity and the other being supplied upstream of
both sealable engagement locations, cyclically opening the valve element
to communicate said port with the engine to permit delivery of fuel
entrained in gas to the engine, and regulating the pressure differential
between the fuel and the gas at the cavity to control the rate of fuel
flow into the gas at the cavity.
When the port is in communication with the engine, the gas establishes a
pressure in the port that is less than the fuel pressure so that fuel will
flow into the gas as it passes through the port. Accordingly control of
the quantity of fuel delivered into the gas may be effected by varying the
pressure difference between the gas pressure in the port and the fuel
supply pressure. Alternatively the control of the quantity of fuel
delivered may be effected by maintaining the above pressure difference
steady and varying the duration of the period that the port is open.
Rapidly occuring variations of fuel demand may be accommodated by varying
the period that the port is open, while more gradual variations in fuel
demand are accommodated by varying the pressure difference between the
fuel and gas. The varying of the pressure difference may be achieved by
varying the pressure of the fuel supply and/or the pressure of the gas
supply. When the fuel is liquid, it is more convenient to regulate the
fuel pressure and to maintain the gas pressure substantially constant.
Conveniently the fuel supply pressure may be controlled by a regulator that
is responsive to the fuel demand of the engine. The regulator may be
electrically actuated under the control of a current determined
electronically from sensings of a number of engine load condition
parameters.
In many engines and engine applications it is desirable to vary the pattern
of fuel distribution within a combustion chamber as engine operating
conditions change. This is particularly so in endeavouring to achieve
required fuel economy and/or exhaust emission control.
As the fuel is delivered into the gas within the port, through which the
delivery to the engine is effected, it is possible to achieve control of
the distribution of the fuel within the combustion area of the engine
through control of the location or timing of delivery of the fuel into the
gas.
The fuel may be introduced into the gas flow at the port at two or more
locations. The locations may be selected so as to influence the spray
pattern of the fuel as it issues from the port. Alternatively, or in
addition, the timing of fuel delivery to, and/or the fuel flow rates at,
each location may be controlled to different rates to also influence the
spray pattern. Further the fuel flow rates at one or more locations may be
variable in response to selected engine operating conditions.
In accordance with one preferred embodiment of the invention, there is
provided a method of delivering fuel to an engine comprising supplying
fuel and gas at respective pressures independently to a port selectively
communicable with the engine combustion charge, cyclically communicating
said port with the engine combustion charge to permit a flow of fuel and
gas from the port into said combustion charge with the fuel entrained in
the gas, and while the port is in communication with the combustion charge
controlling the location and/or rate of admission of the fuel into the gas
to regulate the fuel distribution pattern in the combustion charge, and
regulating the pressure difference between the fuel and gas supplies
and/or the period of communication between the port and combustion change
in accordance with engine load to control the quantity of the fuel
delivered to the engine per cycle.
It will be appreciated that fuel will only flow into the gas in the port if
the fuel pressure at the port is above the gas pressure at the point of
entry of fuel to the port. This differential in pressure is initially
derived from regulating the respective pressures of the fuel and gas to
establish a base differential in pressure, and varying the pressure of the
fuel or the gas in accordance with the variations in the fuel demand of
the engine to obtain the necessary variation in fuel supply. The physical
arrangement of the port and the associated valve will influence the actual
pressure condition in the gas stream where the fuel is introduced to the
gas stream, and these will be accounted for in the calibration of the
pressure regulators controlling the fuel and gas pressure.
In the regulation of the pressure of the gas and fuel, respectively, to
effect the metering of the fuel, it will be appreciated that the actual
pressure differential at the point where the fuel enters the gas stream is
the controlling factor in the metering of the fuel. However a number of
factors, particularly space constraints prevent controlled regulator
devices being located in close proximity to the point of entry of the fuel
into the gas in the cavity formed in the port. The distancing of the
regulator devices from the point of entry of the fuel into the gas
requires the flow areas of the passages carrying the fuel and gas
respectively to the cavity to be adequate to ensure changes in pressure at
the regulator devices are accurately reflected at the cavity. It is
therefore preferable for a relatively small fixed size orifice to be
provided in the fuel and gas passages in close proximity to the cavity,
and the passages upstream of the orifices to be of sufficient area to
minimise the pressure drop therealong. Such orifices close to the cavity
in the port allow the sensitivity of the pressure changes of the gas and
fuel at the regulators to achieve the required accuracy in the metering of
the fuel.
Conveniently a plurality of fuel orifices may be provided to deliver fuel
into the cavity at selected areas of the port to obtain a desired fuel
distribution in the combustion charge. Preferably the fuel issues from a
plurality of fuel orifices arranged in a circular formation about the axis
of an annular gas orifice. The number and location of the fuel orifices
from which fuel issues may be varied in accordance with predetermined
engine operating conditions and so influence the shape of the fuel spray
issuing from the port and hence control the distribution of the fuel in
the engine combustion charge.
In order to achieve efficient combustion and emission control it is
desirable to ensure a readily ignitable fuel-air mixture is established at
the ignition point, particularly under low load engine operating
conditions. The variation in the number of fuel orifices in operation may
be controlled, to achieve the required fuel-air ratio at the ignition
point, by directing a greater proportion of the fuel per delivery into the
combustion charge adjacent the ignition point. Conveniently, under low
engine load conditions all of the fuel is delivered into the combustion
charge to be adjacent the ignition point at ignition.
There is also provided by the present invention an apparatus for metering
fuel to an engine comprising fuel supply means and gas supply means each
adapted to deliver to the same delivery port, a valve element operable to
selectively open said port to communicate the port in use with an engine,
said port and valve element when closed sealably engaging at two locations
spaced in the direction of flow through the port and defining between said
locations a cavity, at least one of the fuel supply means and gas supply
means communicating with said cavity and the gas supply means
communicating with the port upstream of said two sealably engaging
locations, means to cyclically operate the valve element to open said port
to permit delivery of fuel entrained in gas to the engine through said
port, and means to regulate the pressure differential between the fuel
supply and gas supply at the cavity to control the rate of fuel flow into
the gas.
A number of fuel ports may be provided, each feeding fuel into the cavity.
The location of the fuel ports is selected to provide the desired fuel
distribution in the spray pattern of the fuel-gas mixture issuing from the
delivery port. Means may be provided to selectively control the timing
and/or the fuel flow rate from one or more of the fuel ports so the spray
pattern may be varied in response to engine operating conditions.
Conveniently the rate of fuel supplied to the port when the port is open is
controlled by means operable in response to engine load to regulate the
differential between the pressure of the gas and the fuel supplied to the
cavity.
A plurality of fuel orifices may be provided communicating with the cavity.
The fuel orifices may be distributed along the length of the cavity to
achieve the desired fuel distribution into the combustion charge as the
fuel-gas mixture is delivered. The fuel orifices may be generally
uniformly distributed with means provided to selectively terminate the
flow through at least some of them to control the fuel distribution.
The provision of the two spaced locations of sealing engagement between the
port and valve element, and the communication of the fuel and gas supplies
with the port at locations separated by one of the locations of sealing
engagement, enables the single valve element to control the introduction
of the fuel into the gas and the delivery of the resultant fuel-gas
mixture to the engine. The construction of the fuel metering apparatus is
thereby simplified and control of the fuel supply rate is achieved with
accuracy.
The cavity may be in an annular form provided by a peripheral groove in the
sealing face of the port to form a annular seal surface on either side of
the groove with the orifices entering the base of the groove. This
construction results in the sealing surface of the valve element not
contacting the edges of the orifices when the valve element is in the
closed position. This improves sealing efficiency and the effective life
of the seal between the valve element and the port.
The invention will be more readily understood from the following
description of one practical arrangement of the fuel metering apparatus
and method of operation thereof with reference to the accompanying
drawings.
FIG. 1 is a schematic diagram of the fuel supply system embodying the
present invention.
FIG. 2 is a sectional, partly exploded, view of the metering unit.
FIG. 3 is an enlarged sectional view of the delivery port and valve portion
of the metering unit shown in FIG. 2.
FIG. 4 is a view similar to FIG. 3 of a modified port and valve.
Referring now to FIG. 1 the metering apparatus 10 comprises a stem 11 with
a central air passage 13 and two fuel passages 8 and 9. Communicating with
the fuel passages 8 and 9 is a fuel supply conduit 12 that receives fuel
from the fuel pump 14 which draws fuel from the fuel reservoir 15. The
pressure of the fuel in the conduit 12 on the delivery side of the pump 14
is controlled by the fuel pressure regulator 16 and pressure regulator 34
which will be described in further detail hereinafter.
The air passage 13 has at the lower end a delivery port 20 and an
operatively associated valve element 22 rigidly connected to the actuator
rod 24.
The fuel passages 8 and 9 terminate in the seat surface of the port 20, as
later described in detail, and are located so that when the valve element
22 is in closed relation with the port 20 the end of the fuel passages 8
and 9 are also closed by the valve element.
The solenoid type valve actuator 25 has an electro-magnet coil 26, and an
armature 27 which is coupled to the rod 24. The armature 27 is loaded by
springs 28 in the upward direction, as seen in the drawing, so as to
normally hold the valve element 22 so the port 20 is closed. Energising of
the coil 26 by an electric current causes the armature 27 to move
downwardly as viewed in the drawing, and hence displace the valve element
22 and open the port 20.
The air compressor 30 is connected by the conduit 31 to the air passage 13.
The conduit 31 and hence the air on the delivery side of the compressor 30
is in communication with the referencing regulator 34.
The compressor 30 may have its own air pressure regulator to control the
basic supply pressure relative to atmospheric conditions, but this is not
essential to the function of the metering system of the present invention,
and is therefore not further discussed here. Additionally the air
compressor could be replaced by an alternative compressed gas source, and
this may be practical where that alternative gas source is more convenient
for other purposes.
The referencing pressure regulator 34 acts in a manner whereby the pressure
difference between conduits 35 and 37 is maintained essentially constant.
This characteristic allows the fuel pressure in conduit 37 to rise or fall
to compensate for variations in the air supply pressure. This
characteristic may be explained as follows. Fuel supplied by the pump 14
passes into both conduit 38 and conduit 37. In the latter case fuel passes
through port 40 and past the member 41, incurring a pressure drop or not,
depending on the control of fuel pressure regulator 16. The operation of
this device does not impact the present explanation and will be described
further in due course.
Fuel passing through conduit 37 enters chamber 48 where the pressure of the
fuel on diaphragm 49 supplements the force applied thereto by a spring 47
to oppose the force created by the air pressure in chamber 50 acting on
the opposite side of the diaphragm 49. When the total force on the fuel
side of the diaphragm increases above that on the air side, the port 51
will open to permit fuel to flow from the chamber 48 through the return
conduit 36 to the fuel reservoir 15. Any tendency for the pressure to rise
in chamber 48 relative to that in chamber 50 results in further
displacement of the diaphragm 49 to increase the flow path at the port 51,
to prevent that increase in fuel pressure in the chamber 48.
It will be appreciated that the pressure each side of the diaphragm would
become essentially equal if the spring 47 were not present. The spring
loading allows an essentially fixed pressure difference to be maintained.
In this case the fuel pressure is regulated to be lower than the air
pressure, which determines a basic reference of the fuel supply pressure
to the air supply pressure for the metering apparatus 10. This pressure
relationship would be reflected at conduits 12 and 31 if no pressure drop
exists across the regulator 16.
The function of the controlled regulator 16 is to modify the relative fuel
and air pressure at the metering apparatus 10 by forcing a pressure
difference to exist between port 40 and conduit 37. This pressure
difference is reflected as an increased fuel pressure upstream of port 40
relative to the air supply pressure, given that a fixed relationship
exists between conduits 37 and 35. It will be appreciated that a
sufficiently high pressure difference across the controlled regulator 16
will result in the fuel pressure in conduit 12 being above the air
pressure in conduit 31 and air passage 13.
The controlled regulator 16 may be configured to operate in a variety of
ways. Conveniently the device is electronically controlled. In the example
shown, fuel from the fuel pump 14 passes through the check valve 9 and
restriction 39, which acts only to conveniently limit flow, but is not
essential to the operation of the regulator 16. The fuel passes through
port 40 via the spill member 41, which is controlled to vary the flow path
area through port 40. Depending on the variation, a corresponding change
in pressure difference between port 40 and conduit 37 is established.
Although the magnitude of this change may be affected to some degree by
pressure flow characteristics of the pump 14, conveniently, the pump
characteristics may be made to have little effect on the control
characteristics of the regulator 16, as in the particular configuration
shown.
This arises from the fact that the change in the flow path area through
port 40 may be accomplished by a force equilibrium in the member 41. This
equilibrium is between firstly the fluid pressure at port 40, acting over
the projected area of the port, perpendicular to the member and secondly,
an electro-magnetic force being created on the coil 42, again
perpendicular to the member 41 about a pivot 45. This pivot is not
essential to the operation of the device insofar as direct application of
the electro-magnetic force may be made to a valve element associated with
the port 40.
Conveniently, the electro-magnetic force is created by a permanent magnet
44, through magnetic paths 43, interacting with a current in the coil 42.
A force proportional to the current in the coil is thus created which, in
turn, creates a proportional pressure drop between port 40 and conduit 37.
Thus, an input of electrical current in coil 42 may produce a
corresponding pressure drop in proportion to the current, and essentially
independent of the characteristics of the pump 14.
It will be appreciated that there are alternative ways to control the
pressure differences between conduit 12 and air passage 13 communicating
with conduit 31.
Further information in regard to details of construction of devices
suitable for performing the function of the referencing regulator 34 and
the control regulator 16 are disclosed in our International Patent
Application No. PCT/AU85/00176 and corresponding U.S. patent application
No. 849501, and the disclosures in the specifications of these
applications are incorporated herein by reference.
With the above discussed relationship between the pressure of the fuel in
the fuel passages 8 and 9 and the pressure of the air supply available in
the air passage 13, the metering of the fuel is carried out in the
following manner. Upon energising the coil 26 of the solenoid 25, the
armature 27 moves downwardly so that the valve element 22 opens the port
20. At this stage, air flows from the air passage 13 through the delivery
port 20, whilst at the same time fuel flows from the fuel passages 8 and 9
into the port 20 and is immediately entrained in the air passing through
the fuel delivery port 20. There is therefore a continuing flow of fuel
and air from the delivery port 20 so long as the solenoid coil 26 remains
energised.
Upon the de-energising of the coil 26 the valve element 22 is immediately
returned by spring loading to the closed position, seated in the port 20,
terminating the supply of air and fuel from the fuel delivery port 20.
The operation of the solenoid 25 is controlled by a suitable mechanism
which energises the solenoid in timed relation to the engine cycle, this
timing being capable of variation in response to engine operating
conditions. The period that the solenoid is energised is sufficient for
the fuel delivered from the delivery port 20 to meet the engine demand at
that time.
The regulation of the amount of fuel supplied may be achieved by either
varying the time for which the solenoid is energised, or by energising the
solenoid for a fixed period each time but varying the number of periods
that the solenoid is energised for each cycle of the engine In addition to
the control that may be obtained by the varying of the period or number of
cycles of the solenoid it is also possible, as previously discussed, to
vary quantities of fuel delivered to the engine by controlling the
pressure of the fuel relative to the pressure of the air. Also it is
possible for both these controls to be operated so that the combined
effect produces the required quantities of fuel to be delivered to the
engine.
Suitably controlling processes may be set up to regulate the energising of
the solenoid 25 and the operation of the regulator 16 in accordance with
the various known programmes of sensing a range of engine conditions and
processing these to produce electric signals appropriate to operate a
solenoid or like device for regulation of the amount of fuel delivered to
an engine.
Referring now to FIG. 2 of the drawings, which illustrates in more detail a
metering unit 10 comprising a body 60 and a solenoid unit 65. The body 60
has a fuel inlet port 61 to which the fuel supply line 12 is connected and
an air inlet port 62 to which the air supply line 31 is connected.
The body 60 has a stem portion 63 with a central axial chamber 66 extending
axially therethrough. The axial chamber 66 communicates, as later
described, at the upper end with the air inlet port 62, and at the lower
end has a delivery port 71 with which the delivery valve 72 co-operates.
The delivery valve 72 is rigidly attached to the actuator rod 76 which
extends from the solenoid unit 65 through the axial chamber 66.
The fuel inlet port 61 communicates with the two fuel passages 68 provided
in the stem portion 63 on either side of the axial chamber 66. The fuel
passages 68 terminate in ports 69 provided in the sealing face 67 of the
delivery port 71. As seen in more detail in FIG. 3, the fuel passages 68
each incorporate a restricting orifice 90 at the port 69. The bore of the
orifices 90, relative to passages 68 and the other fuel passages leading
from the fuel pressure regulator, are such that the regulator and the
orifices determine the pressure of the fuel issuing from the orifices. The
downstream end of each orifice 90 opens into an annular cavity 91 formed
in the sealing face 67 of the delivery port 71. The sealing face 67 is
thus divided into two annular seal surfaces 67a and 67b.
In the preferred embodiment, as shown in FIG. 3, the minimum flow path
areas presented to a gas flow from central chamber 66 are formed in the
respective annular restrictions created between the sealing surfaces 87a
and 87b in relation to the valve member 72, with its particular open
position. The ratio of the annular areas, as well as the ratio of the air
pressure supply provided to the annular cavity 66 relative to the pressure
existing downstream of the port 71, determines an air pressure in the
annular cavity 91. The air pressure is regulated to establish in the
cavity 91, when the valve 72 is open, a pressure below the fuel pressure,
as previously described, and so the fuel flow rate through port 71 when
the valve 72 is open is determined by the difference in these pressures at
the cavity 91.
The provision of accurately specified restrictions in the fuel and air
passages adjacent to the port 71 provides improved accuracy in the control
of the pressure differential and hence the fuel delivery rate. Further,
the provision of restrictions between sealing faces 87a and 87b and the
valve member 72, created by the limited extent of movement of the valve
member 72, has the further advantage that the pressure developed in cavity
91 as the gas flows through is not strongly affected by variations in the
degree of opening of the valve which may arise due to undesirable
variations in the degree of movement, or stroke, provided by the solenoid
actuation assembly connected to the valve member 72.
It will be appreciated that the above-described construction provides that
downward movement of the actuator rod 76 will displace the delivery valve
72 relative to port 71 and thereby open the valve so that sealing face 70
of the valve element 72 is displaced from both seal surfaces 67a and 67b.
The port 71 is thereby opened so that the air enters past sealing surface
67a and leaves past sealing surface 67b establishing a pressure in the
cavity 91 a pressure which depends on the ratio of the areas of
restrictions produced by the sealing surfaces 67a and 67b in spaced
relationship to valve 72. Fuel enters the cavity to be entrained with the
air and is hence delivered to the engine as a fuel-air mixture. The
pressure differential between the air in the cavity 91 and the fuel
entering the cavity through the orifices 90 determines the rate of fuel
entry into the air stream and hence the rate of fuel supply to the engine.
Accordingly, variation of this pressure difference is one factor in
controlling the fuel demand. The orifices 90 and the restriction provided
by sealing surfaces 67a, 67b and valve 72 have respective fixed
calibrations and, in combination with the regulation of the pressure
difference between the fuel in the passages 68 and the air in the axial
passage 66 as previously described, provide an effective manner of
metering the fuel to an engine to meet the fuel demand thereof.
The preferred embodiment, as stated above, incorporates two restrictions
defined by surfaces 67a and 67b in spatial relationship to valve 72. This
has the advantage that variations in the degree of opening of the valve do
not strongly affect the pressure in cavity 91, due to the fact that the
pressure is more strongly related to the ratio of the respective areas of
restriction rather than the magnitude of each area of restriction. It may
be appreciated that the area of restriction of each varies in direct
proportion to the degree of opening of the valve 72 and thus the ratio of
areas remains essentially constant, in turn, resulting in a relatively
constant pressure in cavity 91.
Notwithstanding this, it has been found useful in some applications of the
injection system to provide a flow directive nozzle beyond the port 71 in
a downstream direction to allow more directive flow trajectories for the
issuing fuel spray. With this modification, as shown in FIG. 4, it is
convenient to provide a fixed restrictive orifice 102 upstream of the port
71, which is a complement to the fixed restriction of the directive nozzle
105. The ratio of the fixed restrictions 102 and 105 largely determines
the pressure in the cavity 91 for a given air supply pressure in the
annular space 66, of FIG. 4. In this case, the restrictions formed by the
sealing surfaces 67a and 67b as referred to above, each side of cavity 91
also affect the pressure to a much smaller degree than previously.
As previously discussed where two or more fuel ports 69 are provided, the
fuel spray pattern and hence the fuel distribution in the engine
combustion chamber may be varied by regulati | | |
