United States Patent [19]
`Ahem et al.
`
`[11] Patent Number:
`[45] Date of Patent:
`
`4,926,806
`May 22, 1990
`
`[54] TWO-FLUID FUEL INJECI'ED ENGINES
`[75]
`Inventors: Steven R. Ahem, Claremont; Roy S.
`Brooks; Martin J.P. Cebis, both of
`South Perth, all of Australia
`
`[73] Assignee:
`
`Orbital Engine Co., Proprietary
`Limited, Balcatta, Australia
`313,831
`Feb. 23, 1989
`Foreign Application Priority Data
`[30]
`Feb. 25, 1988 [AU] Australia ................................ PI6956
`Int. CI.s .......•.............. F02M 67/02; F02D 41/06
`[51]
`[52] u.s. Cl ................................. 123/179 L; 123/305;
`123/491; 123/531
`[58] Field of Search ................... 123/179 L, 491, 531,
`123/532, 533, 534, 305
`References Cited
`U.S. PATENT DOCUMENTS
`4,262,645 4/1981 Kobayashi et al .............. 123/179 L
`
`[21] Appl. No.:
`
`[22] Filed:
`
`[56]
`
`4,771,754 9/1988 Reinke ................................. 123/533
`4,800,862 1/1989 McKay et al ....................... 123/531
`
`Primary Examiner-Andrew M. Dolinar
`Attorney, Agent, or Firm-Armstrong, Nikaido,
`Marmelstein, Kubovcik & Murray
`
`[57]
`ABSTRAcr
`A method and apparatus of controlling the direct injec(cid:173)
`tion of fuel directly into the combustion chamber of an
`engine by a charge of gas, wherein the control of the
`timing of injection of the fuel includes at the commence(cid:173)
`ment of start up of the engine, adjusting the timing of
`injection so injection occurs at a timing earlier in the
`combustion chamber cycle than the normal timing of
`injection for idle running; and in response to the engine
`reaching a predetermined speed or rotation during start
`up, the timing of injection is progressively adjusted
`each engine cycle towards the normal timing of injec(cid:173)
`tion at idle running.
`
`21 Claims, 3 Drawing Sheets
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`BOSCH-DAIMLER EXHIBIT 1011
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`Page 1 of 9
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`U.S. Patent May 22, 1990
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`Sheet 1 of3
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`4,926,806
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`23
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`12
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`26
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`F/GUR£5.1
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`Page 2 of 9
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`U.S. Patent May 22, 1990
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`Sheet 2 of3
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`4,926,806
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`F/GUR5.2
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`52
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`r:JJ
`/-
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`51
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`45
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`25
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`Page 3 of 9
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`U.S. Patent May 22, 1990
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`Sheet 3 of3
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`4,926,806
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`AIR PRE-SSURB (kPa..)
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`/
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`/
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`Page 4 of 9
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`
`1
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`4,926,806
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`TWO-FLUID FUEL INJECI'ED ENGINES
`
`2
`(1) the timing of injection when the engine is idling is
`preset,
`(2) at the commencement of start up of the engine, the
`timing of injection is adjusted to occur at a preselected
`This invention relates to fuel injected internal com-
`bustion engines wherein the fuel is injected directly into 5 timing earlier in the combustion chamber cycle than
`said preset timing of injection at idle,
`the combustion chamber in timed relation to the engine
`cycle, the fuel being delivered entrained in a gas with
`(3) in response to the engine reaching a predeter-
`the pressure of the gas sufficient to effect the delivery of mined speed of rotation during start up, the timing of
`the fuel.
`injection is progressively adjusted each engine cycle
`Fuel injection systems of the two-fluid type, that is, 10 towards said preset injection timing at idle during a time
`where a metered quantity of liquid fuel is delivered to
`interval of between 0.2 to 0.5 seconds commencing
`the engine by a pulse of gas, such as air, the pressure of
`from the engine attaining said predetermined speed; and
`the gas available must be such that there is an adequate
`( 4) thereafter adjusts the timing of injection in accor-
`pressure difference between the gas delivering the fuel
`dance with the engine speed and/or load.
`and the gas in the environment where the fuel is to be 15
`There is also provided a fuel injection system for an
`delivered. In manifold injected engines the fuel is deliv-
`internal combustion engine, wherein a metered quantity
`ered by the gas into the manifold where normally a
`of fuel is injected directly into the combustion chamber
`by a charge of gas at an above atmospheric pressure,
`sub-atmospheric pressure exists, whilst in direct in-
`jected engines, the fuel must be delivered into the com-
`said system including means to control the timing of
`bustion chambers of the engine, normally during the 20 injection of the fuel in relation to the combustion cham-
`ber cycle, said timing of injection control means being
`compression stroke when an above atmospheric pres-
`sure will exist of the order of 200 to 500 kPa. The com-
`arranged to:
`pressed gas supply, such as air, is usually provided by a
`(1) effect injection of the fuel at a preset time in the
`combustion chamber cycle when the engine is idling;
`compressor driven by the engine, and for economic
`reasons, there is a minimum storage capacity for the 25
`(2) to adjust the timing of injection for commence-
`compressed gas, and the compressor output is closely
`ment of start up of the engine to occur at a preselected
`matched to the requirements of the fuel injection sys-
`timing earlier in the combustion chamber cycle than
`said preset idle timing of injection,
`tern, with only a limited excess.
`It will therefore be appreciated that during start up of
`(3) in response to the engine reaching a predeter-
`the engine, the gas pressure available may frequently be 30 mined speed of revolution during start up, for each
`engine cycle progressively adjust the timing of injection
`below the normal operating pressure and this may result
`in a lag in start up of the engine. In this regard, it should
`towards said preset injection timing for idle during a
`be noted that in order to have customer acceptability an
`time interval of between bout 0.2 and 1.0 seconds, pref-
`auto or marine engine is required to start up with a
`erably between about 0.2 and 0.5 seconds commencing
`minimum of cranking time. This requirement may be 35 from the engine attaining said predetermined speed; and
`(4) thereafter adjust the timing of injection in accor-
`difficult to achieve with a two fluid fuel injection sys-
`dance with the engine load and/or speed.
`tem when the engine has been not operating for a signif-
`icant period, that is a period sufficient to allow the
`Normally the preselected injection timing is up to 60°
`pressure of the gas available to effect injection of the
`earlier in the combustion chamber cycle than the nor-
`fuel to have fallen substantially, due to inherent leak- 40 mal injection ti.miilg at idle preferably in the range of
`ages in the gas supply system which cannot be effec-
`40° to 60° prior to injection timing at idle.
`tively avoided.
`Conveniently, the rate of progressive adjustment of
`It is also to be understood that the degree of the
`the timing of injection after the engine has reached the
`pressure drop experienced by the fuel/gas mixture dur-
`predetermined speed of rotation towards the preset
`ing delivery to the engine contributes significantly to 45 injection timing at idle is at a rate of between 1 o and 3 o
`the atomisation of the fuel, particularly liquid fuel, and
`of crank angle per cycle" of the engine, preferably 2".
`hence to the ignitability of the charge in the engine
`The engine normally would be cranked by the starter
`combustion chamber. Thus, under conditions where the
`motor during start up at a speed of the order of 200 to
`pressure of the gas is below the desired working pres-
`400 rpm, depending on starter battery condition, while
`sure at the commencement of start-up, the atomisation 50 normal idle speed of the engine will be of the order to
`of the fuel will be adversely affected, and consequently
`700 to 1200 rpm, depending on engine characteristics.
`the ignitability of the fuel/air charge will be reduced. It
`The means to control the timing of the injection of
`will be appreciated that such reduction in ignitability of
`the fuel during start up may be arranged so that once
`the fuel/air mixture may further contribute to lengthen-
`the engine has been brought up to predetermined speed
`ing of the start up time of the engine.
`55 related to normal idling speed, such as of the order to
`It is therefore the object of the present invention to
`700 to 1200 rpm, the injection timing will commence to
`provide a method of injecting fuel and a fuel injection
`return to the preset timing for normal idle, as the engine
`system for an internal combustion engine wherein pro-
`will have now driven the compressor through sufficient
`vision is made to contribute to rapid start up of the
`cycles to have the gas up to normal operating pressure.
`engine under adverse fuel supply conditions.
`The timing of injection may be controlled by an ap-
`With this object in view, there is provided according
`propriate electronic control unit (ECU), as is customar-
`to the present invention a method of controlling the
`ily used in fuel injection systems to control injection
`injection of fuel directly into the combustion chamber
`timing throughout the full operating load and speed
`of an engine comprising injecting a metered quantity of
`range of the engine. The present invention may be in-
`fuel into the combustion chamber by a charge of gas at 65 corporated into the program of that ECU so that the
`an above atmospheric pressure, and controlling the
`adjustment of the injection timing will occur in re-
`timing of said injection of the fuel in relation to the
`sponse to the initiation of revolution of the engine,
`combustion chamber cycle whereby:
`which indicates that cranking for engine start up has
`
`60
`
`Page 5 of 9
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`

`
`4,926,806
`
`4
`3
`(cylinder) of an engine. The combustion chamber cycle
`commenced. Alternatively the ECU may be pro-
`is individual to a particular combustion chamber and in
`grammed to respond to zero rotation of the engine and
`a multi-combustion chamber engine, the combustion
`effect adjustment of the injection timing to ready the
`chamber cycle of respective combustion chambers
`engine for the next start up operation.
`As is standard practice in ECU controlled fuel injec- S overlap in time.
`The term "engine cycle" is the total of single sequen-
`tion systems, the engine is fitted with an appropriate
`sensor to detect each revolution or equal parts of a
`ces of combustion chamber cycles of all combustion
`revolution of the engine. This sensor provides the ap-
`chambers of an engine. In a single cylinder engine the
`propriate indication that the cranking of the engine has
`combustion chamber cycle and the engine cycle are the
`commenced and that the injection timing should be 10 same. In a two stroke cycle engine each combustion
`adjusted to or held in the adjusted preselected start up
`chamber cycle and the engine cycle occupy one revolu-
`timing. It also indicates when the engine has reached
`tion of the engine, while in a four stroke cycle engine,
`the predetermined speed at which the injection timing
`they each occupy two revolutions.
`should commence to return to the normal idle setting,
`The invention will be more readily understood from
`and also provides the required revolution countdown to 15 the following description of one practical arrangement
`of the method and system of fuel injection for an inter-
`effect the progressive adjustment of the injection tim-
`ing, at the set rate per engine cycle.
`nal combustion engine with reference to the accompa-
`In a typical two fluid fuel injection system, for a spark
`nying drawings.
`In the drawings:
`ignition the engine running at conventional compres-
`sion ratios, the gas supply for the injection of the fuel is 20
`FIG. 1 is a sectional elevation of one cylinder of a
`normally maintained at a pressure between 450 to 650
`two stroke cycle internal combustion engine;
`k.Pa. If the gas pressure is below about 450 k.Pa there
`FIG. 2 is an elevation, partly in section, of a fuel
`will be insufficient pressure to effect delivery and ato-
`metering and injector unit for use in the engine shown
`mise the fuel against the compression pressure in the
`in FIG. 1;
`combustion chamber when the injection timing is at the 25
`FIG. 3 is a composite graph illustrating the variations
`normal preset idle timing. In the present invention the
`in injection timing and air pressure in relation to time
`injection of the fuel is timed to occur earlier in the
`from commencement of engine start up.
`compression stroke of the combustion chamber, when
`Referring now to FIG. 1, the engine 9 is a single
`the compression pressure is lower, and the fuel can be
`cylinder two stroke cycle engine, of generally conven-
`effectively injected and atomised.
`30 tional construction, having a cylinder 10, crankcase 11
`If the engine injection timing is returned to the preset
`and piston 12 that reciprocates in the cylinder 10. The
`piston 12 is coupled by the connecting rod 13 to the
`idle timing in a single step, during initial start up condi-
`tions, when the pressure of the gas supply may still be
`crankshaft 14. The crankcase is provided with air indue-
`low, stalling of the engine is likely to occur. Also the
`tion ports 15, incorporating conventional reed values
`engine has difficulty in continuing to run when a change 35 19, and three transfer passages 16 (only one shown)
`in injection timing of the order to 40" to 60" is made in
`communicate the crankcase with respective transfer
`ports, two of which are shown at 17 and 18, the third
`a single step, particularly during start up, and conse-
`quently may stall. Accordingly, as proposed by the
`being the equivalent to 17 on the opposite side of port
`present invention, there is a progressive controlled rate
`18. The engine 9 drives an air compressor 25 such as by
`of return of the injection timing from the preselected 40 the belt 26 from the engine crankshaft 14.
`start up timing to the normal preset idle timing, so as to
`The injector 24 is located at the deepest part of the
`ensure there is not a sudden change in injection timing
`cavity 22, in the cylinder head 21, while the spark plug
`before the engine bas settled into an operating condi-
`23 projects into the cavity 22 at the face of the cavity
`remote from the transfer port 18. Accordingly, the air
`tion.
`However, it must also be taken into account that if 45 charge entering the cylinder will pass along the cavity
`the preselected early start up injection timing were to
`past the injector 24 toward the spark plug 23, and so
`be maintained for too long a period after the engine has
`carry the fuel from the nozzle to the spark plug.
`The injector 24 is an integral part of a fuel metering
`started, and the gas system has reached normal pressure,
`the engine speed would rapidly rise above normal idle
`and injection system whereby fuel entrained in air is
`speed, potentially of undesirable operating speed so SO delivered to the combustion chamber 27 of the engine
`by a pressurized air supply. One particular form of such
`soon after start up. This possibility is prevented by limit-
`ing the time interval from the reaching of the preset
`a fuel metering and injection unit is illustrated in FIG. 2
`speed to the return to idle injection timing.
`of the drawings.
`The fuel metering and injection unit incorporates a
`Accordingly, the present invention provides an effec-
`tive control over the injection timing to achieve rapid 55 suitable commercially available metering device 30,
`start up of the engine and then a progressive adjustment
`such as an automotive type throttle body injector, cou-
`of the injection timing so that the engine will remain
`pled to an injector body 31 having a holding chamber
`32 therein. Fuel is drawn from the fuel reservoir 35 by
`running once started and will progress smoothly and
`without over-revving to the normal idle running condi-
`the fuel pump 36, preferably driven by the engine 9, via
`tion. The invention above described is applicable to 60 the pressure regulator 37 and delivered through fuel
`engines operating on either the two stroke or four
`inlet port 33 to the metering device 30. The metering
`stroke cycle, and to engines for any use including auto-
`device, operating in a known manner, meters an amount
`motive and marine engines.
`of fuel into the holding chamber 32 in accordance with
`In this specification, reference is made to an engine
`the engine fuel demand. Excess fuel supplied to the
`cycle and a combustion chamber cycle. The term "com- 65 metering device is returned to the fuel reservoir 35 via
`bustion chamber cycle" is the sequence of intake of
`the fuel return port 34. The particular construction of
`charge, compression of charge, expansion of charge and
`the fuel metering device 30 is not critical to the present
`exhaust of charge for a particular combustion chamber
`invention and any suitable device may be used.
`
`Page 6 of 9
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`

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`4,926,806
`
`55
`
`5
`In operation, the holding chamber 32 is pressurised
`by air supplied from the air compressor 25 via pressure
`regulator 39 and .air inlet port 45 in the body 31. Injec(cid:173)
`tion valve 43 is actuated to permit the pressurised air to ·
`discharge the metered amount of fuel through injector 5
`nozzle 42 into a combustion chamber 27 of the engine.
`Injection valve 43 is of the poppet valve construction
`opening inwardly to the combustion chamber, that is,
`outwardly from the holding chamber.
`The injection valve 43 is coupled, via a valve stem 44, 10
`which passes through the holding chamber 32, to the
`armature 41 of solenoid 47 located within the injector
`body 31. The valve 43 is biased to the closed position by
`the disc spring 40, and is opened by energising the sole(cid:173)
`noid 47.
`Further details of the operation of this fuel injection
`system is disclosed in U.S. Pat. No. 4693224, the disclo(cid:173)
`sures of which are incorporated herein by reference.
`The energising of the solenoid 47 is timed in relation
`to the combustion chamber cycle by a suitable elec- 20
`tronic processor 50. The processor receives an input
`signal from the engine speed sensor 51, which signal is
`indicative of the engine speed of rotation and also iden(cid:173)
`tifies a reference point in the combustion chamber cycle
`in respect of which operations may be timed in relation 25
`to the engine and/or combustion chamber cycle. The
`processor 50 also receives a signal from the load sensor
`52 which signal is indicative of the air flow rate in the
`engine air induction system. The processor is pro(cid:173)
`grammed to determine, from the air flow rate signal, the 30
`fuel requirement of the engine, and control the fuel
`metering device 30 accordingly to deliver the required
`amount of fuel to the holding chamber 32.
`The processor SO is further programmed to determine
`from the speed and load conditions of the engine the 35
`required timing of the injection of the fuel into the
`combustion chamber, and of the ignition thereofby the
`spark plug 23.
`Conveniently the processor 50 incorporates a multi(cid:173)
`point map designating the required injection timing for 40
`a range of engine loads and speeds, these having been
`determined from tests carried out to obtain required
`engine power and exhaust emission levels. The proces(cid:173)
`sor 50 is similarly programmed to determine and con(cid:173)
`trol the ignition timing of the engine in relation to en- 45
`gine load and speed.
`The processor provides appropriate signals to the
`injector actuator 53 and ignition actuator 54, in accor(cid:173)
`dance with the determinations, to energise the solenoid
`47 at the required time for fuel injection, and to activate 50
`the spark plug 23 at the required time for ignition. The
`general construction of the load and speed sensors suit(cid:173)
`able for use as above indicated are well known in the
`industry, as are processors for performing the functions
`required by the processor SO.
`Incorporated in the program of the processor is an
`instruction to set the timing of the injection of the fuel
`and the activation of the spark plug at preset timings in
`the combustion chamber cycle when the engine is in an
`idle condition, with no external load applied to the 60
`engine. A typical timing for the injection of fuel to a
`two stroke cycle when idling is 30" to 35" before top
`dead centre (BTDC) position of the piston 12 in the
`combustion chamber 27. The processor may typically
`detect the existence of the idle condition in the conven- 65
`tional manner by a signal indicating that the throttle
`valve in the conventional air intake passage of the en(cid:173)
`gine is in the closed position.
`
`6
`In order to practice the present invention, the proces(cid:173)
`sor must also be able to determine when the engine is
`commencing a start up procedure and this may conve(cid:173)
`niently be achieved by the processor being programmed
`to detect when the engine crankshaft is stationary, that
`is, when it is rotating at zero rpm. This can readily be
`achieved by the processor detecting that it has not re(cid:173)
`ceived a signal from the engine speed sensor for a se(cid:173)
`lected period of time, such as for half a second. The
`processor having detected a zero rpm condition is pro(cid:173)
`grammed to then set the injection timing so as to occur
`at a predetermined timing in the combustion chamber
`cycle, that is earlier than the idle injection timing, by up
`to as much as so· to 60" in readiness for whenever the
`15 engine is next started up. Although this adjustment to
`the fuel injection timing is effected after the engine has
`stopped, it will be appreciated that it is common prac(cid:173)
`tice to maintain the processor activated for a short per-
`iod after stopping of the engine, by the provision of a
`suitable delayed switch in the power supply to the pro(cid:173)
`cessor.
`Upon initiation of the next start up procedure for the
`engine, the timing of injection will be at this earlier
`point in the combustion chamber cycle, e.g., 85" BTDC
`and thus during start up the fuel will be injected into the
`combustion chamber when there is a relatively low
`pressure therein. The processor is further programmed
`so that this injection timing will be retained until the
`engine has reached a predetermined rotational speed,
`such as for example, 1200 rpm.
`Upon the processor detecting that the predetermined
`speed has been attained, it commences to retard the
`timing of injection towards the normal injection timing
`at idle. This retarding of the injection timing is at a set
`rate, such as 2" of crank angle each cycle of the engine,
`and continues over a fixed interval of time programmed
`into the processor, commencing from when the engine
`attained the predetermined speed. In the above exam-
`ple, where the predetermined speed is 1200 RPM, the
`fixed period of time, may be half a second, which would
`mean a retardation in the timing of the injection by
`approximately 20".
`At the elapse of this half second, the injection timing
`will be returned in a single step to the normal injection
`timing for the engine when running at idle speed. After
`the engine has returned to this condition, the injection
`timing will be varied in the normal manner in accor(cid:173)
`dance with the load and speed conditions of the engine,
`as is conventional practice.
`In the above programming of the processor, the pre(cid:173)
`determined speed at which the processor commences to
`return the injection timing to the idle injection timing is
`a speed considerably in excess of the maximum cranking
`speed of the engine, so that detecting the attainment of
`this predetermined speed is verification that the engine
`has fired and commenced to run independently of the
`cranking mechanism.
`FIG. 3 of the accompanying drawings is a graphical
`representation of the injection timing and of the build(cid:173)
`up in the pressure of the air supply from the compressor
`plotted against time measured from the commencement
`of cranking until full pressure is attained, and the injec(cid:173)
`tion timing has been returned to the normal idle timing.
`The air pressure is shown as the full line plot, and the
`injection timing as the broken line plot. It is to be noted
`that for the purpose of clarity, the injection timing and
`time axes, are not to scale.
`
`Page 7 of 9
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`

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`4,926,806
`
`25
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`40
`
`7
`It will be noted that as cranking of the engine com(cid:173)
`mences, the air pressure increases, however, once the
`engine fires and commences running, the pressure in(cid:173)
`creases rapidly until the normal operating pressure of
`550 kPa is attained. At this pressure a conventional S
`regulator operates to maintain the pressure at substan(cid:173)
`tially 550 kPa. It is further noted that at the commence(cid:173)
`ment of cranking, the timing of injection is early in the
`compression stroke, and remains at this timing until the
`engine fires and the rotational speed of the engine rap- 10
`idly increases. From this point, as represented at "A" on
`FIG. 3, the timing of injection is progressively retarded
`at a fixed rate over an interval of time, and at the expiry
`of that time, as indicated by "B" in FIG. 3, the injection
`timing is changed in a single step to the normal injection 15
`timing for the engine when operating at idle speed.
`Throughout this specification, reference has been
`made to determinations of engine speed, and it is to be
`realised that modem engine management systems pro(cid:173)
`vide for determining the speed of rotation of the engine 20
`by the time interval between selected points defining
`part of a revolution of the engine. Thus references in the
`specification to speed determination are on the basis of
`such determinations being made at predetermined frac-
`tions of a revolution of the engine.
`The timing of injection of the fuel may be specified on
`several bases, such as the commencement of the open(cid:173)
`ing of the port through which the fuel is delivered to the
`engine, or the commencement of the energising of the 30
`device that effects opening of the port, such as a sole(cid:173)
`noid. Also timing of injection may be specified in rela(cid:173)
`tion to closing of the port or de-energising of the sole(cid:173)
`noid or like device. In this specification timing of injec(cid:173)
`tion is specified as the commencement of the opening of 35
`the port through which fuel is delivered to the engine.
`The practical application of the invention has been
`described with reference to a two stroke cycle engine,
`however, the invention is also applicable to a four
`stroke cycle engine.
`The claims defining the invention are as follows:
`1. A method of controlling the injection of fuel di(cid:173)
`rectly into the combustion chamber of an engine com(cid:173)
`prising injecting a metered quantity of fuel into the
`combustion chamber by a charge of gas at an above 45
`atmospheric pressure, and controlling the timing of said
`injection of the fuel in relation to the combustion cham(cid:173)
`ber cycle whereby:
`(1) the timing of injection fuel when the engine is
`idling is preset,
`(2) at the commencement of start up of the engine, the
`timing of injection is adjusted so injection occurs at
`a preselected timing earlier in the combustion
`chamber cycle than said preset timing of injection
`for idle,
`(3) in response to the engine reaching a predeter(cid:173)
`mined speed of rotation during start up, the timing
`of injection is progressively adjusted each engine
`cycle towards said preset injection timing at idle
`during a time interval of between about 0.2 to 1.0 60
`seconds commencing from the engine attaining
`said predetermined speed, and
`(4) thereafter adjusts the timing of injection in accor(cid:173)
`dance with the engine speed and/or load.
`2. A method as claimed in claim 1 wherein said time 65
`interval is about 0.2 to 0.5 seconds.
`3. A method as claimed in claim 1 or 2, wherein said
`preselected timing of injection is up to about 60° earlier
`
`so
`
`55
`
`8
`in the combustion chamber cycle than said preset timing
`of injection at engine idle.
`4. A method as claimed in claim 3, wherein said pro(cid:173)
`gressive adjustment of the timing of injection toward
`the idle injection timing is initially at the rate of about 1 o
`to 3" of crank angle per revolution of the engine during
`said time interval, and at the expiry of said time interval
`returns directly to said preset timing of injection at
`engiDe idle.
`5. A method as claimed in claim 3, wherein said pro(cid:173)
`gressive adjustment of the timing of injection toward
`the idle injection timing is initially at the rate of about 2o
`of crank angle per revolution of the engine during said
`time interval, and at the expiry of said time interval
`returns directly to said preset timing of injection engine
`idle.
`6. A method as claimed in claim 1 or 2, wherein said
`preselected timing of injection is between about 40° and
`60" earlier in the combustion chamber cycle than said
`preset timing of injection at engine idle.
`7. A method as claimed in claim 6, wherein said pro(cid:173)
`gressive adjustment of the timing of injection toward
`the idle injection timing is initially at the rate of about l o
`to 3" of crank angle per revolution of the engine during
`said time interval, and at the expiry of said time interval
`returns directly to said preset timing of injection at
`engine idle.
`8. A method as claimed in claim 6, wherein said pro(cid:173)
`gressive adjustment of the timing of injection toward
`the idle injection timing is initially at the rate of about 2 o
`of crank angle per revolution of the engine during said
`time interval, and at the expiry of said time interval
`returns directly to said preset timing of injection at
`engine idle.
`9. A method as claimed in claim 1 or 2, wherein said
`progressive adjustment of the timing of injection
`toward the idle injection timing is initially at the rate of
`about t• to 3• of crank angle per revolution of the en(cid:173)
`gine during said time interval, and at the expiry of said
`time interval returns directly to said preset timing of
`injection at engine idle.
`10. A method as claimed in claim 1 or 2, wherein said
`progressive adjustment of the timing of injection
`toward the idle injection timing is initially at the rate of
`about 2• of crank angle per revolution of the engine
`during said time interval, and at the expiry of said time
`interval returns directly to said preset timing of injec(cid:173)
`tion at engine idle.
`11. A method as claimed in claim 1 or 2, wherein the
`predetermined engine speed is about 800 to 1400 revolu(cid:173)
`tions per minute.
`12. A fuel injection system for an internal combustion
`engine, wherein a metered quantity of fuel is injected
`directly into the combustion chamber by a charge of gas
`at an above atmospheric pressure, said system including
`means to control the timing of injection of the fuel in
`relation to the combustion chamber cycle, said timing of
`injection control means being arranged to:
`(1) effect injection of the fuel at a preset time in the
`combustion chamber cycle when the engine is
`idling;
`(2) to adjust the timing of injection for commence(cid:173)
`ment of start up of the engine, to occur at a prese(cid:173)
`lected timing earlier in the combustion chamber
`cycle than said preset idle timing of injection,
`(3) in response to the engine reaching a predeter(cid:173)
`mined speed of revolution during start up, for each
`engine cycle progressively adjust the timing of
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`injection towards said preset injection timing for
`idle during a time interval of between about 0.2 and
`1.0 seconds commencing from the engine attaining
`said predetermined speed; and
`(4) thereafter adjust the timing of injection in accor- 5
`dance with the engine load and/or speed.
`13. A fuel injection system as claimed in claim 12,
`wherein the time interval is about 0.2 to 0.5 seconds.
`14. A fuel injection system as claimed in claim 12 or 10
`13, wherein said control means to timing of injection is
`arranged so said preselected timing for injection is up to
`about 60° earlier in the combustion chamber cycle than
`said preset timing of injection at engine idle.
`15. A fuel injection system as claimed in claim 14, 15
`wherein said control means for timing of injection is
`arranged so said progressive adjustment of the timing of
`injection toward the idle timing of injection is initially
`at the rate of about 1• to 3 • of crank angle per revolution
`of the engine during said time interval, and at the expiry 20
`of said time returns directly to said timing of injection at
`engine idle.
`16. A fuel injection system as claimed in claim 14,
`wherein said control means for timing