Note: Descriptions are shown in the official language in which they were submitted.
N'(> 9tf/~295:5 .,-J"~~y, ~ ~,~7,;~.a PC'T/~1LJ90/00158 '
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A METHOD FOR REMOVING INJECTOR NOZZLE DEPOSITS
This invention relates to a fuel injection system
i:or direct injection into the combustion chamber of an
;internal combustion engine through a valve controlled port.
The characteristics of the spray of the fuel
droplets issuing ~rom a nozzle into a combustion chamber
have major effects on the efficiency of the burning of the
fuel, which in turn affects the stability of the operation
of the engine, the engine fuel efficiency and the compostion
of the engine exhaust gases. To optimise these effects,
particularly in a spark ignited engine, the desirable
characterisics of the spray pattern of the fuel issuing from
the nozzle include small fuel droplet size, controlled
penetration of the fuel spray into the chamber, and at least
at low engine loads, a relatively contained ignitable cloud
of. fuel vapour in the vicinity of the spark plug.
Some known injection nozzles, used for the delivery
of fuel directly into the combustion~chamber of an engine,
are of the poppet valve type, from which the fuel usually
issues in the ~orm of a conical spray, with the fuel
droplets forming a generally continuous conical wall
extending from the peripheral edge of the poppet valve.
The nature of the shape of the fuel spray is
dependent on a number of factors including the geometry of
the port and valve constituting the nozzle, especially the
surfaces of the port and valve immediately downstream of the
seat where the port and valve engage to seal when the nozzle
is closed. Once a nozzle geometry has been selected to give
the reciuired spray pattern, relatively minor departures from
that geometry can impair the engine performance. In
particular the build-up of solid combustion products on
surfaces over which the fuel flows is detrimental to the
desired spray pattern and correct performance of the nozzle.
When build-up does occur it is normally not of a
uniform nature around the peripheral extent of the surface
SUBSTITUTE SHgET
WO 90/129;4 r, , e. h. PCT/AL~90/OOISR
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of the nozzle over which the fuel flows, thus severely
disturbing the symmetry of the fuel spray.
It is known that build-up on the surface of the
injection nozzle, such as carbon deposits, can be removed or
the formatian thereof controlled, if the relevant surface of
the nozzle is exposed to temperature conditions sufficient
to burn off the build up of contaminants such as carbon.
However, the cooling effects of the adjacent walls of the
combustion chamber, which are frequently water or air
ZO cooled, and the cooling effect of the fuel being delivered
through the nozzle, are such that under normal operating
conditions, the relevant surfaces of the nozzle do not reach
a sufficiently high temperature to effect removal of the
contaminants that may build up on the surfaces of the
nozzle.
There have previously been proposals to construct
the delivery area of the nozzle so as to restrict the heat
flow path therefrom in the endeavour to raise the
temperature of the relevant surfaces where contaminants may
build up. A typical example of such nozzle constructions is
to be found in United States Patent No. 4,817,873. These
proposals have met with varying degrees of success, but have
the major problem that the useful life of the nozzle is
seriously reduced as a result of the relevant areas being
maintained for long periods at the higher temperature
necessary to effect removal of the contaminants.
There i$ disclosed in U.S. Patent No. 4,395,025 a
direct injected internal combustion engine wherein a
mechanically operated injector nozzle is cyclically opened
and closed to permit delivery of fuel to the combustion
chamber. The delivery of the fuel is effected by a high
pressure charge of combustion gases from the combustion
chamber which is delivered into a fuel chamber in the
injector body by maintaining the injector nozzle open for an
extended period after completion of the injection of the
fuel into the combustion chamber. Upon the initial opening
SU~STiTUTE SHEET
WO 90/12954 Pt~T/AU90f00158
of the injector nozzle, the pressure of the gas in the fuel
chamber is sufficiently above the compression pressure in
t:he combustion chamber to discharge the vapourised fuel from
t:he fuel chamber into the combustion chamber. Ignition and
combustion of the fuel subsequently commences and the
~'.njector nozzle is maintained in the open position well into
t:he combustion period so that the hot high pressure gases
generated by combustion will flow into the fuel chamber and
be subsequently trapped therein on closing of the injector
nozzle. The trapped hot gases are at a pressure sufficient
to effect injection of the fuel during the next engine
cycle, where such injection is timed to occur at a point in
the compression stroke when the pressure in the combustion
chamber is below the pressure of the gas trapped in the fuel
chamber.
In this proposal, a charge of high temperature,
high pressure combustion gas is delivered to the fuel
chamber each cycle o the engine and fuel is constantly
delivered into the injector chamber through a permanently
°Pen metering orifice. The metering of the fuel is effected
by the fixed size orifice and a variable pressure pump
supplying fuel to that orifice.
It is to be noted that the proposal in U.S. patent
No. 4,359,025 does not deal with the problem of the build up
of deposits in the injector nozzle, which adversely
influence the spray pattern of fhe fuel delivered to the
nozzle, and is primarily directed to mixing the fuel with
high temperature gas to effect vapourisation thereof prior
to delivery through the nozzle to the combustion chamber.
There is no discussion in this disclosure of the problem
arising from the build up of solid contaminants in the
nozzle or a solution to this problem. It is considered that
in the light of experience, the high temperature conditions
in the fuel chamber, generated by the presence of combustion
pr°ducts therein together with unburnt fuel would lead to
the generation of solid and/or gum deposits which would
seriously impair the operation of the injector. In
SUBSTITUTE SHECT
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par;.icular, it is considered that gum deposits would be
generated in the upper pressure chamber wherein a piston
operates to effect closure of the injector nozzle. This
could lead to sticking of the piston and hence potential
ineffective closing of the injector nozzle. Further it is
Ibel.ieved that there would he a build up of deposits in fuel
metering orifice and the passage leading therefrom, which
would adversely effect the accuracy of the fuel metering
system.
It is therefore the object of the present invention
to provide a method of operating an internal combustion
engine direct fuel injection system so as to control the
build-up of contaminants in those areas which would
influence the spray pattern of the fuel being delivered
through the injection nozzle to the engine.
With this object in view there is provided a method
of operating an internal combustion engine fuel injection
system wherein fuel is cyclically injected directly into an
engine combustion chamber through a selectively openable
nozzle means, the method including controlling the operation
of the nozzle means to periodically maintain the ,nozzle
means open while fuel is not delivered to or through the
nozzle means and during a portion of at least one cycle when
the gas in the combustion chamber is at a temperature and
pressure so that gas from the combustion chamber will pass
into the open nozzle means to raise the temperature thereof
sufficient to combust contaminate deposits thereon.
Normally it is considered that carbon and other
contaminant deposits on the surface of injection nozzles
will be burned off at a temperature of above about 400°C,
however, the actual temperature required to remove the
contaminants will be dependent upon the nature of the
contaminants including the composition and physical form
thereof. Gum deposits and finely divided particles will
ignite at a lower temperature than hard compacted particles.
The nature of the contaminant is in part related to the
SUBSTITUTE Si~E~T
WO tl()/1295:~ PC_'T/AL!9010(?158
v"~'.. ~~ C~'~J .~r.~n ~~
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length of the period of operation of the engine between
successive nozzle cleaning operations.
Also, care must be taken to ensure that the
rE:levant surfaces of the nozzle are not heated to a
ta~mperature which would adversely affect the physical
properties of the material from which the components of the
nozzle are manufactured. Usually such nozzle components are
manufactured from heat treated stainless steel, and care
must be taken to ensure that such components are riot heated
to a temperature which will temper or soften the stainless
steel, particularly on the surfaces constituting the valve
and valve seat of the nozzle.
It has been found that effective cleaning of the
nozzle means can normally be achieved with combustion gas
temperatures in the range of about 450° to 700°C, preferably
in the range of about 500° to 600°C.
Conveniently the nozzle means is maintained open
for a period in each o.f a plurality of engine cycles,
preferably successive engine cycles. Preferably the nozzle
means is maintained open while the engine is operating in a
selected area of normal operation, preferred a steady state
operating area that is with no substantial change in engine
load or speed, particularly no increase in load. the
cleaning may be carried out while the engine is operating in
an over-run condition.
The temperature of the gas in the combustion
chamber resulting from the maximum compression pressure of
the gas, even without combustion of fuel, can be
sufficiently high to raise the temperature of contaminants
on those surfaces of the nozzle exposed directly to the gas,
while the nozzle is open, to remove these contaminates by
combustion thereof. However this is dependent on the
compression ratio of the engine being high enough to raise
the combustion chamber gas to a temperature above about
450°C.
SUBSTITUTE Shll~L'~'
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preferably, the timing of the commencement of the
normal injection period remains unaltered and fuel is
injected in the normal manner. However, the period of
opening of the injector nozzle is extended to include an
appropriate time in the compression cycle to deliver high
temperature gas into the nozzle.
In one form of control of the fuel injection
system, the timing of the period of opening of the injector
nozzle is adjusted to late in the compression stroke where
the temperature of the compressed gases will be sufficiently
high to burn off the contaminant deposits.
In a multi cylinder engine the injector nozzle of
the respective cylinders may undergo the cleaning treatment
at different times, particularly when the cleaning treatment
is carried out while the engine is operating under load.
The frequency at which the cleaning operation is
implemented can be programmed into the ECU, which normally
controls the operation of the fuel injection system, so that
the nozzle cleaning procedure is implemented on a regular
time interval basis, or o,n the basis of the completion of a
selected number of engine cycles. The ECL~ may also be
programmed so that the cleaning procedure is not initiated
immediately on the expiry of the set time or number of
cycles, but will 'occur when next the engine is in a
particular operating condition after the expiry of such time
interval or number of cycles. The time interval or number
of cycles may each be determined on an approximate basis on
the number of revolutions of the engine.
In one embodiment of the invention as applied to an
internal combustion engine of a vehicle, it is proposed that
the cleaning procedure be implemented approximately each
1,500 kilometres of travel of the vehicle, and the passage
of this distance can be approximated by counting the number
of cold engine start-ups. Statistically it is considered
that normally a motor passenger vehicle travels about 10
kilometres for each cold start-up and thus in 150 cold
SUt~STiTUTE St-SEE i
wo ~~0 n29~:~ y y.~~~n3
PC.'I~/A 090/00158
starts of the engine, the vehicle will have travelled
approximately 1,500 kilometres. The ECU controlling the
fuel injection system can readily be programmed to count the
number of cold starts of the engine and to initiate the
nozzle cleaning procedure each 150 starts.
Further, in the motor vehicle application, the
cleaning cycle may be carried out whilst the engine is
operating in a steady state, such as cruising at a selected
road speed, say 90 to 95 kph. Thus upon the ECU determining
that the 150 cold starts have been effected, it will then
implement the injector nozzle procedure when the engine is
operating in a load range indicating the vehicle is cruising
and in the 90 to 95 kph speed range, which can be determined
from the normal inputs to the ECU. Also it is preferable
that the nozzle cleaning procedure is not initiated whilst
the engine is cold, that is within the short period after
start up, thus the ECU is also programmed to only implement
the nozzle cleaning procedure when the engine is operating
above a preselected temperature.
It has been found that when the cleaning procedure
is carried out on the basis of the above conditions the
injection nozzle is effectively cleaned if the cleaning
procedure is allowed to operate for 300 to 500 consecutive
cycles of the engine, each open period of the injector
nozzle in the cleaning procedure in the order of 10 to 15
milliseconds, with the engine operating at about 2,000 RPM.
The invention will be more readily understood from
the following description of one practical arrangement of a
fuel metering system for an internal combustion engine as
illustrated in the accompanying drawings.
In the drawings,
Figure 1 is a diagramatic representation of a
direct fuel injected engine.
Figure 2 is a sectional view through a typical form
of metering and injector unit as used in the system shown in
Figure 1.
S~JFSTiTUTE SHcd T
1 ~~
WO 90/12954 °''~~-:~W.l.~ fCT/AL!90/00178
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Referring now to Figure 1, the engine 70 may be of
any conventional type, having an air intake system 71) an
ignition system 72, a fuel pump 73, and a fuel reservoir 74.
",ehe engine further includes an electric starter motor 75,
which is energised by the battery 76 upon operation of the
:starter switch 78. The air compressor 77 is driven by the
belt 79 from the engine crankshaft pulley 80.
Mounted in the rylinder head 90 of the engine 70 is
a fuel metering and injection unit 81, (one foc each cylinder
in a multi-cylinder engine). The metering and injection
unit 81 receives fuel via the conduit 82 from the fuel pump
73 and receives air from the compressor 77 via the conduit
83. An air pressure regulator 84 is provided in the conduit
83 and the latter delivers air to the air manifold 85 to
which each metering and injection unit 81 of each of the
cylinders of the engine is connected to receive air.
The electronic control unit (ECU) 86 receives
signals from a crankshaft speed and position sensor 87 via
the lead 93 and an air flow sensor 88 located in the air
intake system 71 via the lead 96 and the engine temperature
sensor 84 via the lead 94 and ambient temperature (not
shown). The ECU B6 is programmed to determines from all
input signals the quantity of fuel required to be delivered
to each of the cylinders of the engine, each cycle of the
respective cylinder. This general type of ECU and the
programming thereof is well=known in the art of
- electronically controlled fuel injection systems and will
not be described here in further detail.
The fuel metering and injection unit 81 as shown in
Figure 2 incorporates a suitable fuel metering device 130)
such an an automotive type throttle body injector, coupled
to an injector body 131 having a fuel chamber 132 therein.
Fuel is delivered from the fuel pump 73 through fuel inlet
part 133 to the metering device 130 which meters the amount
of fuel supplied to the fuel chamber 132 per engine cycle in
accordance With the engine fuel demand. Excess fuel
5i,ic~S's ITU i E SME'"T'
CA 02049923 1999-03-29
_9_
supplied to the metering device is returned to a fuel
reservoir 75 via fuel return port 134. The particular
construction of the fuel metering device 130 is not critical
to the present invention and any suitable device may be
used.
The valve 143 of the injector nozzle 142 is
coupled, via a valve stem 144, which passes through the fuel
chamber 132, to the armature 141 of the solenoid 147 located
within the injector body 131. The valve 143 is biased into
the closed position by the disc spring 140 and is opened by
energising the solenoid 147. The valve _143 is shown in the
open position in Figure 2. Energising of the solenoid 147
is controlled by the ECU 86 via the lead 95 in time
relation to the engine cycle to effect delivery of the fuel
from the fuel chamber 132 to a cylinder of the engine 70.
The fuel chamber 132 is in constant communication
with the air manifold 85 via the air inlet port 145 and thus
under normal operation is maintained charged with air at a
substantially steady pressure. Upon energising of the
Solenoid 147 the valve 143 is displaced downwardly to open
the nozzle 142 so that the metered quantity of fuel held in
the fuel chamber 132 is carried by the high pressure air out
of the fuel chamber 132 through the nozzle 142 into the
combustion chamber 91 of a cylinder of the engine.
Further details of the operation of the fuel
metering and injection systems incorporating a fuel chamber
such as indicated at 132 in Figure 2 is disclosed in
United States Patent No. 4693224
It will be appreciated from the above
description that the nozzle 142 is located within the
cylinder head 90 of the engine, and in communication with
the combustion chamber 91 defined within the engine
cylinder. As above described, when the nozzle 142 is opened
and the air supply available via the air inlet port 145 is
above the pressure in the combustion chamber 91, air, with
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fuel from the fuel chamber 132 entrained therein, will flow
through the nozzle 142 into the engine combustion chamber
9 .1 .
It will be appreciated that under normal operating
conditions, the injection of the fuel into the combustion
clhamber is normally carried out before or shortly after the
closing of the inlet port of the engine through which the
a;ir required to support the combustion of the fuel is
provided. Normally the injection of the fuel into the
combustion chamber is completed before the piston has
reached the 45° before top dead centre position in the
compression stroke. At that point in the compression
stroke, the compression pressure is relatively low so that
the pressure of the air supplied via the air port 145 is
sufficiently above the compression pressure in the
combustion chamber 91 to effect delivery of the fuel
thereinto. Normally the pressure of the air supply to the
air port is of the order of 400 to 500 kPa, and the
compression pressure in the combustion chamber at. opening of
the nozzle 142 to inject the fuel is normally of the order
of 100 kPa. The maximum compression pressure in the
combustion chamber, without combustion, is of the order of
800 kPa.
The ECU 86 is programmed to receive a signal from
the engine starter switch 78 when the switch is operated to
energise the starter motor 75, so that the ECU may store a
progressive total of the number of engine start-ups. The
ECU 86 also receives information from an engine temperature
sensor 72 and is programmed to keep a progressive total of
the number of engine start-ups effected while the engine
temperature is below a pre-selected value, that value, for
example) being selected as indicative that the engine is
starting from a cold condition. On the basis of these
inputs, the ECU can keep a running total of the number of
cold start-ups of the engine.
~~aS3l~'UTE SIiEET~
WO 90/129.54 PCT/AU90f001~8
-11-
The ECU 86 is also programmed to determine when the
number of cold start-ups reaches 150, or some other
appropriately selected figure, indicating the vehicle has,
an a statistical average, been operating for a particular
p~sriod of time or in a motor vehicle, the vehicle has
travelled a particular distance. This time or distance
h<~ving been previously selected as an appropriate interval
between successive cleaning operations of the injector
nozzle.
The ECU has thus determined that the point has been
reached in the engines operation life when the injector
nozzle should be cleaned. The ECU must now determine when
the operating conditions of the engine are suitable for
carrying out the nozzle cleaning operation. That is, is the
engine sufficiently warmed up and is the engine operating at
a suitable speed and/or load where the nozzle cleaning
operation will not significantly adversely affect the engine
operation. To this end, the ECU is programmed to only
commence the nozzle cleaning operation if the engine
temperature is above a preselected value, and the engine
speed is steady within a preselected speed range.
The ECU having determined that an injector nozzle
cleaning operation is required, and the operation conditions
are suitable, sets the timing of the commencement and
termination of the open period of the injector nozzle 142 to
extend into the high compression' pressure and temperature
area of the engine cycle and terminates the supply of fuel
to the injector for the period of opening of the injector
nozzle 142.
The flow of air from the combustion chamber 91 into
the nozzle 142 during the portion of the compression stroke
where the temperature of the compressed air is such that it
will, and over a number of engine cycles, raise the
temperature of the seat of the injector nozzle valve 143 and
adjacent areas of the nozzle 142 to a temperature that will
effect removal of the contaminants, such as carbon, from the
surfaces, by the ignition and combustion of that carbon)
~U~STITUTE SHfET
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Typically the open period of the injector nozzle
for the delivery of fuel when the engine is operating
normally is 4 milliseconds at 2000 RPM and during the nozzle
cleaning cycle is extended to typically 10 milliseconds.
With a 60° BTDC commencement of injector opening this would
result in the injector closing approximately 30° ATDC when
the engine is operating at 2000 RPM. It will be appreciated
that the actual time interval that the injector is open each
cycle is not critical, but the injector must be open during
a Period when the pressure,and temperature of the gas in the
combustion chamber is sufficient to enter the injector
nozzle and ignite the contaminant deposits therein. The
pressure of the gas and the duration of opening of the
injector nozzle can influence the extent of penetration of
the hot gas into the nozzle, therefore it is desirable to
select an open period that will prevent sensitive components
of the nozzle being exposed to excessive neat. A similar
process is continued over a number of successive engine
cycles, sufficient to remove substantially all contaminate
build up in the nozzle. It has been found that 300 to 500
cycles are normally adequate. In a multi-cylinder engine,
the ECU is programmed to only carry out the nozzle cleaning
operation on one cylinder at any one time. A set sequence
of cleaning the nozzles of the respective cylinders is
programmed into the ECU.
The nozzle cleaning procedure disclosed herein may
be applied to all forms of direct injected internal
combustion engines, including spark ignited and compression
ignited engines, and both two stroke and four stroke cycle
engines. Also the cleaning.procedure may be applied to
injectors that deliver liquid or gaseous fuels either alone
or entrained in a carrier gas.
SU~S~'i i 1.lTE $Ei~~ i
