AU594357B2 - Direct fuel injection by compressed gas - Google Patents

Description

PWT WORLD ITEL L I )Y AM 0P7 INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (51) International Patent Classification 4 (11) International Publication Number: WO 87/ 00578 F02D 3/00, 7/02, F02B 13/00 F02B 17/00, F02M 67/02 Alionl ubli n D 29 January 1987 (9.01 (43) International Publication Date: 29 January 1987 (29.01 8") (21) International Application Number: PCT/AU86/00203 (81) Designated States: AU, BR, DE, GB, JP, KR, NL, SE.

US.

(22) International Filing Date: (31) Priority Application Number: (32) Priority Dave: (33) Priority Country: 18 July 1986 (18.07.86) PH 1560 19 July 1985 (19.07.85)

AU

Published With international search report.

econta""s t1he This document co ,ner anendllets made Sction 4 ad is corrc f pr inti2 MAR A.O.J.P. 1 2 MAR i987 (71) Applicant (for ai' designated States except US): ORBI- TAL ENGINL COMPANY PROPRIETARY LI- MITED [AU/AU]; 4 Whipple Street, Balcatta, W.A.

6021 (AU).

(72) Inventors; and Inventors/Applicants (for US only) McKAY, Michael, Leonard [AU/AU]; 3 Meidreth Court, Willetton, W.A.

6155 AHERN, Steven, Ross [AU/AU]; 7 Corry Lynn Road, Claremont, W.A. 6010 (AU).

(74) Agent: EDWD. WATERS SONS: 50 Queen Street, Melbourne, VIC 3000 (AU).

(54) Title: DIRECT FUEL INJECTION BY COMPRESSED GAS (57) Abstract In a spark ignition engine, fuel is injected directly into the cylinder volume. In order to obtain improved levels of combustion efficiency and reduced emissions the position of the fuel cloud within the cylinder volume is varied with en gine loud by controlled variation of fuel injection pressure. In particular, there is disclosed a method and apparatus for injection of fuel by compressed air where the position of the fuel cloud within the ,fli hder volume is controlled by conjoint control of fuel and air injection pressure. The invention has particular application to two-stroke cycle engines.

r L ?i 11 -1- IMPROVEMENTS RELATING TO FUEL INJECTION TO INTERNAL COMBUSTION ENGINES 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 emissior control it is desirable to control the position of the fuel cloud in the combustion chamber. It has been observed that the preferred cloud nosition is not constant, and particularly varies with engine load, which itself is engine speed related. 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 cylilnder should be restricted to reduce the degree S" of dilution of the fuel by mixing 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.

o With this object in view, there is provided a method of controlling the fuel distributiun in the combustion chamber of a spark ignited internal combustion engine comprising entraining a metered quantity of fuel in a gas under pressure to form a fuel-gas charge, the quantity Disk 0063/1.45 I;rW1~ lll*C--rB~- -2of fuel being metered in response to the engine load as the fuel is delivered for entrainment into the gas, directly injecting the fuel-gas charge into the combustion chamber through a nozzle under an injection pressure determined by the pressure of the gas so the fuel penetrates into the combustion chamber a distance dependent upon said injection pressure, the fuel-gas charge being injected at one injection pressure when the engine is operating at a load or speed below a preselected value, and increasing the fuel-gas charge injection pressure in response to the engine load and/or speed exceeding said preselected value so that the fuel penetrates into the combustion chamber a greater distance at engine loads or speeds above said preselected value, the fuel being maintained at a predetermined pressure differential above the gas over substantially the whole engine load and/or speed range.

The p:essure effecting delivery of the fuel through the nozzle may be increased in a stepwise manner at one or 06more selected levels of engine load and/or speed.

Alternatively, the pressure increase may be progressive over one or more ranges of engine load and/or speed to vary the degree of penetration of the fuel.

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 achieved by varying the fuel pressure with engine load and/oi speed and consequently varying the gas pressure to maintaiLn 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 nozzle to the combustion chamber.

Disk 0063/1.45 c 3 -3- An increase in pressure can be effected at more than one selected engine speed within the normal operating speed range, but 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 in the 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 the 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 ou and gas are engine driven and have outputs that are S significantly speed related.

Also in accordance with the invention there is provided a fuel injection system for a spark ignited internal combustion engine, wherein a quantity of fuel is metered under pressure into a gas to form a fuel-gas charge, the gas-fuel charge is delivered through a nozzle into a combustion chamber of the engine at an injection pressure determined by the pressure of the gas so the fuel penetrates into the combustion chamber distance dependent upon said injection pressure, characterised by means to regulate the fuel and gas pressures to maintain a predetermined pressure differential between the fuel. and gas pressures, and means to increase the regulated pressures in response to the engine load and/or speed increasing above a predetermined value whereby, while maintaining said predetermined pressure differential, the fuel/gas mixture is injected at one injection pressure when the engine is operating at a load or Disk 0063/1.45 c -4speed below said predetermined value and at a higher pressure when operating at a load or speed above said predetermined value to increase the distance of penetration of the fuel into the combustion chamber.

Conveniently the means to regulate the fuel and gas pressures is arranged to change fuel pressure in response to the change in engine load and/or speed, and to regulate the gas pressure relative to the fuel pressure to maintain the predetermined differential.

The fuel injection system preferably includes a combined fuel and gas pressure regulator comprising first means to regulate the fuel pressure to a first predetermined pressure above atmospheric pressure, and second means to regulate the gas pressure to a predetermined value below the fuel pressure.

Conveniently the first predetermined pressure is of l set by a resilient means prestressed to a set deaLee.

Preferably the resilient means is spring tensioned or r r compressed to a degree to provide a load necessary to set the required fuel pressure. The degree of compression or tension of the spring can be increased to increase the first predetermined pressure upon the engine reaching a predetermined load. In this specification reference is made to varying the penetration of the fuel spray by adjusting the delivery pressure of the fuel into the combustion chamber, in relation to a particular change or changes in engine load and/or speed. Engine load may be detected in a number of ways. In many engine applications, the speed of B the engine under most operating conditions is indicative of the engine load, particularly where the engine is normally S.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.

Disk 0063/1.45 i i i WO 87/00578 5PCT/AU86/00203 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 system.

In the drawings:- Figure 1 is an axial section view of ai two stro-e cycle engine having a dirazt 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 shc7.ai in Figure 1.

Figure 3 is a sectional view of a combined fuel and air pressure regulatoCr suitable for use with the metering and inj ection unit shown in Figure 2, shown in conjunction diagrammatically with other components of a fuel injection system.

Referring now to Figure 1 the engine 109 is a single cylinder two stroke cycle engine, of generally conventional construiction, having a cylinder 110, crankcase 11.1 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 induc,:ion ports 115, incorporating conventional reed valves 119 and three transfer passages 116 (only oi-' s hown) communicate the crankcase with respective transfer ports, two of which are shown at 117 and 118, the third being the equivalent to 117 on the opposite side of port 118.

The tran~fer ports are each formed in the wall of the cylinder 110 with their respective upper edge located in the same 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 oombustion cavity 122 into which the spark plug 123 proje~cts. the cavity 122 ivx located substantially symmetrica'aly with WO 87/00578 PCT/AU86/00203 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 configiration 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 nf 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 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 present 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 WO 87/00578 PCT/AU86/00203 stem 144, which passes through the holding chamber 132, to the armature 141 of 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. Energising of the solenoid 147 is controlled in time relation to the engine cycle to effect delivery of the fuel from the holding chamber 132 to the engine combustion chamber.

Further details of the operation of the fuel metering and injection systems incorporating a holding chamber such as that described with reference to Figure 2 is disclosed in Australian Patent Application No. 32132/84 and corresponding United States Patent Application No. 740067 filed 2nd April 1985, the disclosures of which are each incorporated herein by reference.

It will be appreciated that the fuel is delivered into the holding chamber 132 by the metering device 130 against the pressure of the air existing in the chamber.

Accordingly, the difference in pressure between the fuXe supply at the metering device and the air in the holding chamber is relevant to the quantity of fuel that will be delivered into the holding chamber. In view of the need for accuracy in the fuel metering, both from the aspect of fuel economy and exhaust emission control, it is important to effectively control this presure differenc'.

Figure 3 illustrates a fuel injection system incorporating a combined fuel and air regulator which is suitable for use with the fuel metering and injection unit as described above with reference to Figure 2. However, it is to be understood that the regulator hereinafter described with reference to Figure 3 may be used in other fuel metering and injection 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 unit 5 to which air and fuel are provided from the compressor 2 and WO 87/00578 8 PCT/AU86/00 2 03 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 The regulator 10 comprises a fuel pressure regulation portion 9 and an air pressure regulation portion 11 incorporated in an integral construction. The fuel regulation 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-'perates 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 of the low pressure pump 3 and the suction side of the >igh pressure pump 7.

The high pressure fuel inlet passage 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 whilst 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 WO 87/00578 PCT/AU86/00203 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 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 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 required 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 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 activate 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 is admitted to the portion 30 of the control cavity 28.

S* 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 device may be used to effect the adjustment. The cvrrent supplied to the device may be varied to effect the adjustment of the movement of the diaphragm.

An appropriate hysteresis function is preferably incorporated in the actuation of the solenoid valve 49 to prevent 'hunting' between the alternative fuel pressur e.

The fuel pressure regulation portion 9, of the composite fuel and air pressure regulator 10 so far described with reference to Figure 3, may be constructed as an individual fuel pressure regulator wherein the regulated pressure is variable during operation. The desirability of an adjustable injection pressure has previously been discussed as a means of varying the penetration of the fuel into the combustion chamber, and this is equally applicable to injection system where liquid fuel alone is injected as to systems wherein liquid fuel is entrained in air or other suitable gas. Accordingly the fuel pressure regulator portion 9 may be used as a variable pressure regulator in injection systems injecting liquid alone.

Continuing with the description of the combined 25 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 is in communication.with the air from the 30 compressor 2 via the passage 39, and air outlet passage leads from chamber 37 to the injector unit 5. The diaphragm 38 carries the valve 41 which co-operates with the port 42 Swhich 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 1 'T~iii~aiSM~uffliiiirriai~ v- 1 1 -11chamber 37 and the action of the spring 45 together is sufficient 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 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, regulate relative to the fuel pressure, the pressure of 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 15 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 and injection unit. The fuel spray penetration m y us be altered without other adjustments or corrections to the metering of the fuel.

The degree of change in the pressure of the atir provided to effect delivery of the fuel-air mixture to the 25combustion chamber is selected by experiment for each engine S 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 9.

stroke cycle engine with a displacement of 0.4 litres per combustion chamber the air pressure is increased from 250 to 1 .500 KPA at an engine speed of 2500 RPM which is in the mid-speed range of the engine.

The above describd fuiel S prtsze Iti'gul the integrated fuel and air press~r'e 44'fe-iential regulator may be used in combination wit,' 'ering and delivery system described Figura 2 and as o h.

I _Ill IXI1_wn R7mn/f7R PCT/AI Ii6/00203 T V

V

f2 disclosed in our co-pending Australian Patent Application No. 32132/84 and, may be used in the fuelling of a two stroke cycle engine as described in our co-pending Australian Patent Application Nos. PH01559, PH1991 and PH3344 entitled "Improvements Relating to Direct Fuel Injected Engines" and in applications lodged in Australia and elsewhere claiming priority from said Australian applications. By this reference the disclosure in the specifications of said applications is incorporated within this speci.ication by reference.

In the preceeding description with reference to the drawing specific reference has been made to the use of the present invention in conjunction with an engine operating on the two stroke cycle and with spark ignition and reciprocating piston, however it is to be understood that the invention is also applicable to spark ignited engines operating on the four stroke cycle and/or other configurations such as rotary piston. This invention is applicable to internal combustion engines for all uses and is particularly useful in contributing to fuel economy and exhaust emissions control in engines for or in vehicles including automobiles, motor cycles and boats and including outboard marine engines.

Claims (4)

1. A method of controlling the fuel distribution in the combustion chamber of a spark ignited internal combustion engine comprising entraining a metered quantity of fuel in a gas under pressure to form a fuel-gas charge, the quantity of fuel being metered in response to the engine load as the fuel is delivered for entrainment into the gas, directly injecting the fuel-gas charge into the combustion chamber through a nozzle under an injection pressure determined by the pressure of the gas so the fuel penetrates into the combustion chamber a distance dependent upon said injection pressure, the fuel-gas charge being injected at one injection pressure whko :he engine is operating at a load or speed below a pr -selected value, and increasing the fuel-gas charge injection pressure in response to the engine load and/or speed exceeding said preselected value so that the fuel penetrates into the combustion chamber a greater distance at engine loads or speeds above said preselected value, the fuel being maintained at a predetermined pressure differential above the gas over substantially the whole engine load and/or speed range.

2. A method as claimed in claim 1, wherein the change in injection pressure is effected by changing fuel pressure in response to said change in engine load and/or speed and regulating the gas pressure relative to the fuel pressure to maintain the predetermined pressure differential over the engine load and/or speed range.

3. A fuel injection system for a spark ignited internal combustion engine, wherein a quantity of fuel is metered under pressure into a gas to form a fuel-gas charge, the gas-fuel charge is delivered through a nozzle into a 9 990 .9.

9. 9 9 9999 9 9 9 9* 9 9. 9 9 9 Disk 0063/1.45 -~.~,rflrt -14 combustion chamber of the enjine at an injection press-ure determined by the pressure of the gas so the fuel penetrates into the combustion chamber a distance dependent u~pon said injection pressure, characterised by means to regulate the fuel and gas pressures to maintain a predetermined pressure differential between the fuel and gas pressures, and means tincrease the regulated pressures in response to the engine load and/or speed increasing above a predetermined value whereby, while maintaining said predetermined prnssure differential, the fuel/gas mixture is injected at one injection pressure when the engine is operating at a load or speed below said predetermined value and at a higher pressure when operating at a load or speed above said predetermined value to increase the distance of penetration of the fuel into the combustion chamber. 4. A fuel injection system, as claimed in claim 3, wherein said means to regulate the fuel and gas pressures is arranged to change the fuel pressure in re-sponse to the change in engine load and/or speed, and to regulate the gas pressure relative to the fuel presrure to maintain the 0 predetermined differential. A fuel injection system as claimed in rlaim 4, including a combined fuel and gas pressure regulator comprising first means to regulate the fuel pressure to a first predetermined pressure above atmospheric pressure, and second means to regulate the gas pressure to a second predetermined value below the first predetermined pressure 0 of the fuel. 06. A fuel injection system as claimed in claim wherein the first means comprise a fuel chamber and an air chamber separated by a movable wall, a fuel inlet port and a Disk 0063/1.45 fuel return port in said fuel chamber, means to selectively open said fuel return port in response to movement of said wall in one direction, biasing means resisting movement; of the wall in said direction, a vent port in said air chamber to admit atmn -3heric air thereto, said biasing means and atmospheric air in the air chamber together permitting movement of the wall to open the return port when the pressure of the fuel in the fuel chamber is above said first predetermined pressure. 7. A fuel injection system as claimed in claim 6, wherein said second means comprises a gas chamber and a further fuel chamber separated by a further movable wall therebetween, said further fuel chamber communicating with the fuel chamber of the first means, and a gas inlet port and a gas by-pass port in said gas chamber, means to selectively open said gas by-pass port in response to movement of said further wall in one direction, further biasing means urging said wall to move in said one direction, said further biasing means and the pressure in said gas chamber effecting movement of said further wall to open said gas by-pass port when the pressure in the gas chamber is above said second predetermined value. 8. A fuel insection system as claimed in any one of claims 6 or 7, wherein means are provided to selectively increase the force applied by the biasing means to raise Said first predetermined pressure of the fuiel. 9. An internal combustion engine including a fuel injection system, arranged to operate in accordance with the method claims in claim 1 or 2. Disk 0063/1.45 L i- p~ F- U -16- An internal combustion engine including a fuel injection system as claimed in any one of claims 4 to 8. DATED this 16th day of November, 1989. ORBITAL ENGINE COMPANY PTY. LIMITED WATERMARK PATENT ATTORNEYS SUITE 18, 159 ADELAIDE TERRACE, EAST PERTH, W.A. 6004. C. t C CI C Ce C S 0 C I C Ce S S be .5 C C. C 6 C se... C C. 4. eec C. C Sb C4 Disk 0063/1.45