Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVEMENTS RELATING TO FUEL INJECTION TO
INTERNAL COMBUSTION ENGIN~S
This invention relates to the injection of metered
quantities of fuel into the combustion chamber of an
internal combustion engine.
In order to obtain the more desirable levels of
fuel efficiency and exhaust emission control it is desirable
to control the position of the fuel cloud in the combustion
chamber. It has been observed that the preferred cloud
position is not constant, and particularly varies with
engine load, which itself is engine speed relatsd. In two
stroke cycle engines the control of the fuel cloud is of
particular importance to limit the loss of fuel through the
exhaust port which may not be fully closed during at least
part of the period of injection of the fuel.
It is understood that under light loads, and hence
low fuelling rates, the degree of penetration of the fuel
into the cylinder should be restricted to reduce the degree
of dilution of the fuel by mi~ing with the air in the
combustion chamber. The dilution of the fuel gives a lean
mixture that is more difficult to ignite, and to maintain
combustion until the full fuel charge is burnt. However at
high load and high fuelling rates the degree of penetration
should be increased to ensure the greater quantity of fuel
has access to sufficient air (oxidant) to achieve combustion
of all of the fuel.
The principal object of the present invention is
to provide a method of control of the fuelling of an engine
so that the position of the fuel cloud may be varied to
assist in the more efficient combustion of the fuel.
With this object in view there is provided a
method of controlling fuel distribution in an internal
combustion engine comprising directly injecting fuel into
the combustion chamber through a nozzle under conditions so
the fuel penetrates a first distance into the combustion
chamber, and varying said conditions in response to the
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engine load demand being above a predetermined value to
increase the distance of penetration of the fuel into the
combustion chamber.
Conveniently the pressure effecting delivery of
the fuel through the nozzle may be increased in a stepwise
manner at one or more selected levels of engine load demand
or the pressure increases may be progressive over one or
more ranges of engine speed or load to vary the degree of
penetration of the fuel.
More specifically there is provided a method of
controlling fuel distribution in the combustion chamber of
an internal combustion engine comprising combining a metered
quantity of fuel delivered at delivery pressure and a gas
mass, delivering the fuel-gas mixture so formed at a mixture
delivery pressure through a nozzle into the combustion
chamber, regulating the pressure differential between the
fuel and gas mass to maintain a substantially uniform
pressure differential over the engine load demand, and
controlling the pressure of the fuel-gas mixture during
delivery to the combustion chamber so said pressure is
increased in response to the engine load demand above a
predetermined value, whereby the extent of penetration of
the fuel into the chamber is increased.
The maintenance of the steady pressure
differential between the fuel and the gas mass simplifies
the controlling of the metered quantity of fuel as in that
control procedure it is not necessary to provide
compensation for variation in that pressure differential.
Preferably the control of the fuel penetration is
3a achieved by varying the fuel pressure with engine speed and
consequently varying the gas pressure to maintain a steady
pressure differential. Accordingly the variation of the
fuel pressure will have the end result of varying the
pressure available to deliver the fuel-gas mixture through
the noz~le to the combustion chamber.
The increases in pressure are preferably effected
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at one or more selected engine speeds within the normal
operating speed range, and it has been found that one
increase in the mid-speed range is sufficient in many engine
applications.
In the regulation of the pressure differential
between the gas and the fuel delivered thereinto, specific
advantages arise from the regulations being based on varying
the pressure of the fuel as the control function, and
effecting a consequential variation int he gas pressure to
maintain the selected pressure differential.
one of the advantages is the gas is less viscous
than a liquid fuel and so, in a regulation situation, the
controlled gas pressure will not be as affected by flow rate
variations through the pressure regulator. This results in
tne pressure differential being less sensitive to flow rate
variation of either the fuel or gas. This feature is of
particular significance where the pumps providing the fuel
and gas are engine driven and have outputs that are
significantly speed related.
Accordingly it is another object of the present
invention to provide a fuel-gas regulation system that is
particularly suitable for incorporation in a fuel injection
system employing pressurised fuel and gas supplies.
With this other object in view there is provided a
fuel injection system for internal combustion engines
wherein a metered quantity of fuel under pressure is
delivered into a gas to form a fuel gas charge,
characterised in that the fuel pressure is regulated to a
reselected value and the gas pressure is regulated relative
to the fuel pressure to maintain a predetermined pressure
differential between the fuel and gas during metering of the
fuel.
Conveniently the regulated pressure of the fuel is
selectable between at least two predetermined values.
Preferably the variation in the regulated fuel pressure is
effected at a selected speed, within the normal operating
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speed range of the engine, and the variation is preferably
an increase as the engine speed exceeds the selected value.
A corresponding decrease is ef~ected as the engine speed
falls below that selected value. Preferably the fuel
pressure is regulated to a preselected value relative to
atmospheric pressure.
In accordance with a further aspect of the present
invention there is provided for an engine fuel system, a
fuel pressure regulator set to provide a predetermined fuel
output pressure, and means adapted to vary said pressure a
predetermined amount in response to a selected engine
condition.
Conveniently the predetermined fuel output
pressure is set by a resilient means prestressed to a set
degree, and the means to vary the output pressure adjust the
degree of stress on the resilient means. Preferably the
resilient means is a spring tensioned or compressed to a
degree to provide a load necessary to set the required base
fuel pressure. The degree of compression or tension of the
spring is increased to increase the fuel output pressure
upon the engine reaching a predetermined load and is
subse~uently reduced upon the engine speed falling below the
selected load.
In this specification reference is made to varying
the penetration of the fuel spray by adjusting the delivery
presure of the fuel into the combustion chamber, in relation
to a particular change or changes in engine load demand, and
this demand may be detected in a number of ways. In many
engine applications, the speed of the engine under most
operating conditions is indicative of the engine load,
particularly where the engine is normally operated within
specific speed ranges, such as in outboard marine engines.
Accordingly as engine speed is conveniently sensed, and
requires comparatively simple sensors, the engine speed is
monitored to detect the occurrence of the load change at
which the change in fuel penetration is to be effected.
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The invention will be more readily understood from
the following description, with reference to the
accompanying drawings, of one practical arrangement of the
fuel and air pressure regulating device incorporated in a
fuel injection sys~em.
In the drawings:-
Figure l is an axial section view of a two stroke
cycle engine having a direct` in-cylinder fuel injection
system.
Figure 2 is an elevational view, partly in section
of a fuel metering and injection unit suitable for use with
the engine shown in Figure 1.
Fi~ure 3 is a sectional view of a combined fuel
and air pressure regulator suitable for use with the
metering and injection unit shown in Figure 2, shown in
conjunction diagrammatically with other components of a fuel
injection system.
Referring now to Figure l the engine lO9 is a
single cylinder two stroke cycle engine, of generally
conventional construction, having a cylinder 110, crankcase
lll and piston 112 that reciprocates in the cylinder 110.
The piston 112 is coupled by the connecting rod 113 to the
crankshaft 114. The crankcase is provided with air
induction ports 115, incorporating conventional reed valves
119 and three transfer passages 116 (only one shown)
communicate the crankcase with respective transfer ports,
two of which are shown at 117 and 118, the third being the
e~uivalent to 117 on the opposite side of port 118.
The transfer ports are each formed in the wall of
the cylinder 110 with their respective upper edge located in
the sa~e diametral plane of the cylinder. An exhaust port
120 is formed in the wall of the cylinder generally opposite
the central transfer port 118.
The detachable cylinder head 121 has a combustion
cavity 122 into which the spark plug 123 projects. the
cavity 122 is located substantially symmetrically with
respect to the axis of the cylinder, and the spark plug is
located on that axis. The fuel injector 124 is located in
the wall of the cylinder 110 between the transfer ports and
the cylinder head. In the configuration shown the injection
nozzle 124 is directly above the central transfer port 118.
The injector 124 is an integral part of a fuel
metering and injection system whereby fuel entrained in air
is injected directly into the combustion chamber of the
engine by the pressure of the air supply. One particular
form of fuel metering and injection unit is illustrated in
Figure 2 of the drawings which is representative of a type
of metering and injection unit that the fuel and air
pressure regulating system of the present invention is
applicable to.
The fuel metering and injection unit in Figure 2
incorporates a suitable metering device 130, such as an
automotive type throttle body injector, coupled to an
injector body 131 having a holding chamber 132 therein.
Fuel is delivered from a fuel pump (not shown) through fuel
inlet port 133 to the metering device 130 which meters an
amount of fuel into the holding chamber 132 in accordance
with the engine fuel demand. Excess fuel supplied to the
metering device is returned to a fuel reservoir via fuel
return port 134. The particular construction of the fuel
metering device 130 is not critical to the presen~ invention
and any suitable device may be used.
In operation, the holding chamber 132 is
pressurised by air supplied supplied through an air inlet
port 145 in the body 131. An injection valve 143 is
actuated to permit the pressurised air to discharge the
metered amount of fuel from the chamber 132 through injector
nozzle 142 into a combustion chamber of the engine.
Injection valve 143 of the injector nozzle is of the poppet
valve construction opening inwardly to the combustion
chamber, that is, outwardly from the holding chamber.
The injection valve 143 is coupled, via a valve
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stem 144, whlch passes through the holding chamber 132, to
the armature 141 of solenoid 147 located w~thin the
lnjector body 131. T~,e valve 143 is biased into the closed
po~itlon by the di6c ~pring 140 and i~ opened by energising
the solenoid 147. Energising o~ tha ~olenoid 147 i~
controlled ln tim~ relation to the engine cycle to efect
delivery o~ the ~uel fro~ the holding chamber 132 to the
englne combustion chamber.
Further detalls of the operation of the fuel
metering and in~ection syBtems incorporating a holding
chamber ~uch a~ that described with reference to Fiqure 2 $s
di~closed in Canadian Patent Application No. 460,403
It will be appreclated that the fuel ~ delivered
lnto the holdlng chamber 132 by the metering device 130
against the pr~s~ure of the air existing ~n the chamber.
Accordingly, the difference in pressure between the fuel
supply ak the ~etering device and the a$r in the holding
chamber ls relev~nt to the quantlty o~ fuel that w~ll be
delivered lnto the holding chamber. ~n view of the need for
accuracy in the ~uel metering, both from the aspect of fuel
economy and exhau~t emi~sion control, it is important to
ef~ectively control this presure difference.
Flgur~ 3 illustrates a fuel in~ection system
incorporatlng ~ combined fuel and ~lr regulator which i8
2s suitable for use with the ~uel metering and injection unit
as described above with re~erence to Figure 2. Howsver, it
i8 to be understood that the regulator hereinafter described
with raferencc to Fiqure 3 may be used in other ~uel
meter~ng and in~ect~on systems and is not limited to use in
the system described with reference to Figure 2.
Referring now to Figure 3 the fuel injection
system comprises a fuel metering and injecting unlt 5 to
wh~ch air and fuel are provided from the compressor 2 and
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fuel reservoir 6 respectively via the regulator 10. The
fuel is delivered from the reservoir 6 by the low pressure
lift pump 3 to the high pressure pump 7 via the through
passage 18 in the regulator 10.
The regulator 10 comprises a fuel pressure
regulation portion 9 and an air pressure regulation portion
11 incorporated in an integral construction. The fuel
reyulation chamber 12 has one wall thereof formed by the
flexible diaphragm 13 which is secured around its marginal
perimeter. The diaphragm 13 has secured thereto a valve
element 14 which co-operates with the port 15 provided in
the wall 17 of the fuel regulation chamber opposite the
diaphragm 13. The port 15 communicates with the low
pressure fuel passage 18 which in turn communicates with the
delivery side o~ the low pressure pump 3 and the suction
side of the high pressure pump 7.
The high pressure fuel inlet passage 20
communicates the fuel regulation chamber 12 with the
delivery side of the high pressure fuel pump 7. The one way
valve 21 between the passage 18 and the chamber 12 is only
lightly pre-loaded, so that during start up the lower
pressure fuel may flow from the passage 18 through the fuel
chamber 12 to purge the high pressure fuel circuit and
injector 5 of air.
The diaphragm 13 is located by the spring 25 so as
to normally position the valve 14 to close the port 15. The
spring backing plate 24 normally abuts the stop 19 provided
on the end wall 26 of the regulator body. The spring
backing plate 24 is attached to the diaphragm 27 which
divides the control cavity 28. The portion 29 of the
control cavity on the spring side of the diaphragm 27 is
subject to atmospheric air via the port 22 whil~t the
portion 30 on the opposite side of the diaphragm 27 may be
selectively communicated with the regulated air source via
the port 31 and solenoid valve 49. When air pressure is
applied through port 31 to the portion 30 of the control
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cavity 28, the diaphragm 27 and the spring backing plate 24
will be moved to the right as seen in the drawing, to apply
further compression to the spring 25. The extent of
movement of the backing plate 24 to the right is limited by
the edge band 32 of the backing plate 24 contacting the
S annular should 33 on the regulator body.
Upon the pressure of the fuel in regulation
chamber 12 exceeding the regulated presure, the diaphragm 13
is displaced against the action of the spring 25, and valve
element 14 is moved away from engagement with port 15,
allowing fuel to flow through port 15 to passage 18 and thus
lower the pressure in regulation chamber 12 to that
required.
It will thus be seen that the application of the
control air to the portion 30 of the control air cavity 28
will increase the spring pressure on the diaphragm 13 by a
predetermined amount, which in turn will increase the
release pressure of valve element 14 and so the pressure of
the fuel delivered to the injector unit 5 by the high
pressure pump 7 will be correspondingly increased.
In order to reduce the re~uired pressure of the
air admitted to the portion 30 of the control cavity a
spring (not shown) may be provided between the backing plate
24 and the end wall 26 to partially counteract the spring
25.
The actuation of the solenoid valve 49, to
increase in fuel delivery pressure, may be effected by a
suitable engine speed sensor being provided to activat- a
switch when the engine speed reaches a selected value. The
switch when activated energises the solenoid valve 49 so
that air from the regulated air supply to the injector unit
5 is admitted to the portion 30 of the control cavity 28.
The application of pressure by this air to the diaphragm 27
will move the backing plate 24 so that the edge band 32 will
abut the shoulder 33, thus increasing the load applied by
the spring 25 to the diaphragm 13 by a set amount.
The operation of the solenoid valve 49 and control
cavity 28 to increase the fuel pressure, may be adapted to
provide more than one increase in the regulated fuel
pressure. Alternatively an electrically operated deYice may
be used to ef~ect the adjustment. The current supplied to
the device may be varied to effect the ad~ustment o~ the
movement of the d~aphrag~.
An appropriate hysteresis function i~ preferably
incorporated in the actuation of the solenoid valve 49 to
prevent 'hunting' between the alternative fuel p~essures .
The fuel pressure regulation portion 9, of the
composite fuel and air pressure regulator 10 so far
described with reference to Figure 3, may he constructed as
an individual fuel pressure regulator wherein the regulated
pressure i6 variable during operation. The desirability of
an ad~ustablQ in~ection pressure has previously been
di~cusæed as a means o varying the penetration of the fuel
into the combu~tion chamber, and this is equally applicable
to in~ection ~ystem where liquid fuel alone is in~ect~d as
to systems wherein l~quid fuel is entrained in air or other
suitable gas. ~ccordingly the fuel pressure regulator
portion 9 may be used as a variable pressure regulator in
in~ection systems in~ecting liquid alone.
Continuing with the description of the com~ined
regulated illustrated in Figure 3 the fuel chamber 12 is in
communication, via the passage 35, with the chamber 36 in
the air regulation portion 11 and is separated from the air
pressure chamber 37 by the diaphragm 38. The air pressure
chamber 37 i8 in com~unication with the air from the
compressor 2 via the passage 3g, and air outlet passage 40
lead~ from chamber 37 to the injector unit 5. The diaphragm
38 carries the valve 41 which co-operates with the port 42
which communicates with the air bypass passage 43.
The spring 45 applies presure to the diaphragm 38
to normally hold the valve 41 open. Accordingly the valve
41 will open the port 42 when the air pressure in the
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chamber 37 and the action of the spring 45 together issufficient to overcome the force created by the fuel presure
in the chamber 36 on the diaphragm 38. Accordingly it will
be appreciated that the air pressure will always be less
than the fuel pressure by the amount represented by the
force applied to the diaphragm 38 by the spring 45.
The regulator as above described will in use
regulate, relative to atmospheric pressure, the pressure of
the fuel supplied to a fuel injection unit 5 by the pump 7,
and regulate relative to the fuel pressure, the pressure of
the air the air supply to the fuel injector unit, so that
during operation of the fuel injection unit there is a
predetermined pressure differential between the fuel and air
supplies. In addition, by the application of air pressure
to the portion 30 of the control cavity 28, the regulated
fuel pressure can be increased by a preset amount, and the
air pressure will consequently be correspondingly increased
by the same amount so that the same pressure differential is
maintained between the fuel and the air supplies to the fuel
metering and injection unit. The fuel spray penetration may
thus be altered without other adjustments or corrections to
the metering of the fuel.
The degree of change in the pressure of the air
provided to effect delivery of the fuel-air mixture to the
combustion chamber is selected by experiment for each engine
depending on the geometry of the engine, and the required
degree of fuel penetration with varying load or speed
conditions. In one particular example applicable to a two
stroke cycle engine with a displacement of 0.4 litres per
combustion chamber the air pressure is increased from 250 to
500 KPA at an engine speed of 2500 RPM which is in the
mid-speed range of the engine.
The above described fuel pressure regulator, and
the integrated fuel and air pressure differential regulator
may be used in combination with the fuel metering and
delivery system described with rsference to Figure 2 and as
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disclosed in Canadian Patent Application No. 460,403 and,
may be used in the fuelling of a two stroke cycle engine as
described in Canadian Patent Application No. 514,180
entitled WImprovements Relating to Direct Fuel Injected
Engines" and in applications lodge~ in Australia and
elsewhere claiming priori~y from said Australian
applications.
In the preceeding description with reference to
the drawing specific reference has been made to the use of
the present invention in con~unction with an engine
operating on the two stroke cycle and with spark ignition
and reciprocating piston, however lt is to be understood
th~t the invention is also applicable to spark lgnited
engines operating on the four stroke cycle and/or other
; 15 configurations such as rotary piston. This invention i8
~pplicable to internal combustion engines for all use~ and
iB particularly useful in contributing to fuel economy and
exhaust emissions control in engines for or in vehicle~
including automobiles, motor cycles and boats and including
outboard marlne engines.
