FR2585079A1 - FUEL INJECTION METHOD FOR INTERNAL COMBUSTION ENGINES FOR INJECTING DOSE QUANTITIES IN THE COMBUSTION CHAMBER - Google Patents

Abstract

THE INVENTION RELATES TO A FUEL INJECTION PROCESS FOR INTERNAL COMBUSTION ENGINES ALLOWING THE INJECTION OF DOSE QUANTITIES OF FUEL INTO THE COMBUSTION CHAMBER. THIS PROCESS IMPLETS A FUEL INJECTION SYSTEM INCLUDING A FUEL DOSING AND INJECTION UNIT 5 TO WHICH THE AIR AND THE FUEL ARE SUPPLIED FROM A COMPRESSOR 2 AND FROM A FUEL TANK 6 TO THE REGULATOR 10. THE FUEL IS SUPPLIED FROM TANK 6 BY THE LOW PRESSURE SUCTION PUMP 3 TO THE HIGH PRESSURE PUMP 7 THROUGH PASS 18 IN THE REGULATOR 10 INCLUDING A PART FOR ADJUSTING THE FUEL PRESSURE 9 AND A AIR PRESSURE ADJUSTMENT PART 11. A FUEL ADJUSTMENT CHAMBER 12 INCLUDES A DIAPHRAGM 13. WHEN THE FUEL PRESSURE IN CHAMBER 12 EXCEEDS THE SET PRESSURE, DIAPHRAGM 13 MOVES AGAINST A SPRING 25 AND A VALVE 14 GOING AWAY FROM PORT 15 ALLOWS THE FUEL TO GO ON PASSAGE 18 AND LOWER THE PRESSURE IN CHAMBER 12.

Description

 The present invention relates to the injection of metered quantities of fuel into the combustion chamber of an internal combustion engine.

 In order to achieve the most 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 position of the preferred cloud is not constant and varies in particular with the engine load which is itself a function of the engine speed. In two-stroke engines, control of the fuel cloud is of particular importance in limiting the loss of fuel through the exhaust port which may not be fully closed during at least a portion of the fuel injection period.

 It is understood that under low loads, and from low feed rates, the degree of fuel penetration into the cylinder should be decreased to reduce the degree of fuel dilution by mixing with air in a combustion chamber. . Diluting the fuel gives a lean mixture that is more difficult to ignite and keep burning until the total fuel load is burned.

However, under heavy load and at high feed rates, the degree of penetration should be increased to ensure that more fuel accesses sufficient air (oxidant) to burn all the fuel. .

 The main object of the present invention is to provide a method of controlling the power supply of an engine so that the position of the fuel cloud can vary to most effectively assist fuel combustion.

 For this purpose, there is provided a method of controlling the fuel distribution in an internal combustion engine of directly injecting the fuel into the combustion chamber through a nozzle under conditions such that the fuel enters a fuel chamber. first distance in the combustion chamber and varying said conditions in response to the demand of the engine load remaining above a predetermined value to increase the fuel penetration distance into the combustion chamber.

 Conveniently, the fuel supplying pressure through the nozzle may be stepwise controlled at one or more selected levels of engine load demand or the increasing pressure may be incremental along one or more ranges of engine speed or load to vary the degree of fuel penetration.

 More particularly, there is provided a method for controlling the distribution of fuel in the combustion chamber of an internal combustion engine by combining a metered quantity of fuel fed to the feed pressure and a mass of gas, by feeding the mixture. fuel-gas thus formed at a mixing feed pressure through a nozzle in the combustion chamber, adjusting the differential pressure between the mass of fuel and gas to maintain a substantially uniform differential pressure according to the load demand of the engine and controlling the pressure of the fuel-gas mixture during supply to the combustion chamber so that said pressure increases in response to the load demand of the engine, above a predetermined value, so that the distance of fuel penetration inside the chamber be increased.

 Maintaining a stable differential pressure between the fuel mass and the gas simplifies the control of the metered quantity of fuel since in this control method it is not necessary to provide a differential compensation in this differential pressure. .

 Preferably, control of fuel penetration is achieved by varying the fuel pressure with the engine speed and thereby varying the gas pressure to maintain a stable differential pressure. Accordingly, the change in fuel pressure will have the ultimate result of varying the available pressure to feed the fuel-gas mixture through the nozzle within the combustion chamber.

 The pressure increases are preferably achieved at one or more selected engine speeds in the normal operating speed range and it has been found that an increase in the median velocity range is sufficient in many engine applications.

 When adjusting the differential pressure between the gas and the fuel supplied for this purpose, particular advantages arise from the fact that the settings are based on the fuel pressure variation as a control function and making a corresponding variation in the fuel pressure. gas pressure to maintain the chosen differential pressure.

 One of the advantages is that the gas is less viscous than a liquid fuel and thus, in a setting situation, the controlled gas pressure will not be affected by changes in flow rate through the pressure control device. This has the effect of making the differential pressure less sensitive to changes in flow flow, either fuel or gas. This characteristic is particularly significant in the case where the pumps delivering the fuel and the gas are driven by engines and have efficiencies that are significantly a function of the speeds.

 It is another object of the present invention to provide a fuel gas control system which is particularly suitable for mounting in a fuel injection system utilizing fuel and pressurized gas supplies.

 In view of this other object, there is provided a fuel injection system for internal combustion engines in which a metered quantity of pressurized fuel is fed into a gas to form a fuel-gas charge, characterized in that that the fuel pressure is set to a preselected value and the gas pressure is adjusted with respect to the fuel pressure to maintain a predetermined differential pressure between the fuel and the gas during fuel metering.

 Suitably, the fuel control pressure is selected from at least two predetermined values. Preferably, the variation in the set fuel pressure is made at a speed selected from the normal operating speed range of the engine and the variation is preferably an increase as the engine speed exceeds the chosen value. A corresponding decrease is obtained when the engine speed falls below the chosen value. Preferably, the fuel pressure is set to a preselected value with respect to the atmospheric pressure.

 In accordance with another aspect of the present invention, there is provided for a motor fuel system, a fuel pressure regulator set to provide a predetermined fuel output pressure and means adapted to vary said pressure by a predetermined value. in response to a selected engine condition.

 Suitably, the predetermined fuel outlet pressure is adjusted by means of resilient means prestressed to a degree of adjustment, and the means for varying the outlet pressure adjusts 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 adjust the required base fuel pressure. The degree of compression or tension of the spring is increased to increase the fuel outlet pressure until the engine reaches a predetermined load and is subsequently reduced until the engine speed falls below the pressure. chosen.

 In this application reference is made to fuel spray penetration variations by adjusting the fuel supply pressure in the combustion chamber as a function of the particular engine load demand change (s) and this demand may be detected in many ways. In many engine embodiments, the engine speed under most operating conditions is a function of the engine load, particularly when the engine is operating normally in specific speed ranges such as outboard boat engines.

Accordingly, when the engine speed is suitably detected, and requires relatively simple detectors, the engine speed is monitored to detect the moment of change of load at which the change in fuel penetration must be made.

 The invention will be more readily understood from the following description, made with reference to the accompanying drawings, of a practical embodiment of a fuel control and air pressure device incorporated in a control system. fuel injection.

In the drawings:
- Figure 1 is an axial sectional view of a two-stroke engine having a fuel injection system directly into the cylinder;
- Figure 2 is an elevational view, partly in section of a fuel injection and dosing unit suitable for use with the motor shown in Figure 1.

 FIG. 3 is a sectional view of a combined fuel and air pressure adjusting device suitable for use with the dosing and injection unit shown in FIG. 2, together with other elements in schematic form; fuel injection system.

 Referring now to Figure 1, the engine 109 is a conventional two-stroke general-purpose single-cylinder engine comprising a cylinder 110, a crankcase 111 and a reciprocating piston 112 in the cylinder 110. The piston 112 is coupled by the connecting rod 113 to the crankshaft 114. The crankcase is provided with air intake ports 115 provided with conventional diaphragm valves 119 and three transfer passages 116 (one of which is only shown) and which cause the crankcase to communicate with the corresponding transfer ports, two of which are shown at 117 and 118, the third being similar to the orifice 117 on the opposite side of the orifice 118.

 Each of the transfer orifices is formed in the wall of the cylinder 110 with their respective upper side housed in the same diametral plane as the cylinder. An exhaust port 120 is provided in the cylinder wall generally opposite the central transfer port 118.

 The removable yoke 121 comprises a combustion cavity 122 in which the spark plug 123 projects. The cavity 122 is disposed substantially symmetrically with respect to the axis of the cylinder and is housed on this axis. The fuel injector 124 is housed in the wall of the cylinder 110 between the transfer ports and the cylinder head. In the form shown, the injection nozzle or injector 124 is directly mounted above the central transfer port 118.

 The injector 124 came in one piece with the fuel injection and metering system so that the fuel entrained in the air is directly injected into the combustion chamber of the engine by the supply pressure. 'air. A particular embodiment of the metering and fuel injection unit is shown in FIG. 2 of the accompanying drawings which shows a type of injection and metering unit which is applicable to the pressure control system of fuel and air of the present invention.

 The metering and fuel injection unit shown in FIG. 2 comprises a suitable metering device 130, such as a car-type throttle body injector, and coupled to an injector body 131 provided with the The fuel is supplied from a fuel pump (not shown) through the fuel inlet port 133 to the metering device 110 which measures a quantity of fuel. in the holding chamber 132 depending on the demand of the engine fuel. The excess fuel fed to the metering device is returned to the fuel tank via the fuel return port 134. The particular construction of the metering device 130 is not essential to the present invention and it is possible to use any suitable device.

 In operation, the holding chamber 132 is pressurized by air supplied from the air inlet 145 into the body 131. The injection valve 143 is actuated to allow the discharge of pressurized air with the metered amount of fuel from the chamber 132 through the injector 142 into the combustion chamber of the engine. Injection valve 143 of the injector is a poppet valve opening inward towards the combustion chamber, i.e. outwardly of the holding chamber.

 The injection valve 143 is coupled by the tail of the valve 144 passing through the holding chamber 132 to the armature 141 of the solenoid 147 housed in the injector body 131. The valve 143 is pushed into its closed position by the intermediate disc springs 140 and is opened by the excitation of the solenoid 147. The excitation of the solenoid 147 is controlled rhythmically following the engine cycle to send the fuel from the holding chamber 132 towards the combustion chamber of the motor.

Other operating details of the fuel injection and metering systems comprising a holding chamber are described with reference to FIG.
Figure 2 and Australian Application No. 32132/84 corresponding to US Application No. 740067 filed April 2, 1985, the descriptions of these applications being incorporated herein by reference.

 It will be understood that the fuel is fed into the holding chamber 132 by the metering device 130 against the pressure of the air prevailing in the chamber. As a result, the pressure difference between the fuel supply to the metering device and the air in the holding chamber is a function of the amount of fuel that will be delivered to the holding chamber. Given the need for precision in fuel metering, both from the point of view of fuel economy and exhaust emission control, it is important to effectively control this pressure difference.

 Fig. 3 shows a fuel injection system comprising a combined fuel and air regulator which is suitable for use with the metering and fuel injection unit as described above with reference to Fig. 3. 2. However, it will be understood that the regulator described hereinafter with reference to FIG. 3 may be used in other metering and fuel injection systems and is not limited to use in the system described by reference. in Figure 2.

 Referring now to Figure 3, the fuel injection system includes a fuel injection and metering unit to which air and fuel are supplied from a compressor 2 and a fuel tank. The fuel is fed from the tank 6 by the low pressure suction pump 3 to the high pressure pump 7 through the passage 18 in the regulator 10.

 The regulator 10 includes a fuel pressure adjusting portion 9 and an air pressure adjusting portion 11 incorporated in a one-piece construction. The fuel control chamber 12 has a wall formed by the flexible diaphragm 13 which is fixed around its periphery. A valve element 14 is fixed to the diaphragm 13 and cooperates with the orifice 15 formed in the wall 17 of the fuel control chamber located opposite the diaphragm 13.

The orifice 15 communicates with the low-pressure fuel passage 18 which in turn communicates with the supply side of the low-pressure pump 3 and the suction side of the high-pressure pump 7.

 The intake passage d; high pressure fuel 20 communicates the fuel control chamber 12 with the supply side of the high pressure fuel pump 7. A one-way valve 21 is provided between the passage 18 and the chamber 12 and is only slightly preloaded such that during starting the low pressure fuel can flow from the passage 18 through the fuel chamber 12 to purge the high pressure fuel system and the air injector 5.

 The diaphragm 13 is centered by the spring 25 so as to set up the valve 14 normally to close the orifice 15. The spring support plate 24 normally abuts against the stop 19 formed on the end wall 26 of the body of the regulator. The spring support plate 24 is connected 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 subjected to atmospheric pressure through the orifice 22 while the portion 30 on the opposite side of the diaphragm 27 can selectively communicate with the controlled air source via the orifice 31 and the solenoid valve 49. When pressurized air is applied through the orifice 31 at the portion 30 of the control cavity 28, the diaphragm 27 and the spring support plate 24 will be displaced to the right as shown in the drawings to apply additional pressure to the spring 25. The extent of the plate displacement support 24 to the right is limited by the marginal band 32 of the support plate 24 coming into contact with the annular shoulder 33 formed on the body of the regulator.

 When the fuel pressure in the regulating chamber 12 exceeds the set pressure, the diaphragm 13 is displaced against the action of the spring 25 and the valve member 14 is disengaged from the orifice 15 allowing the fuel to flow. flow through the orifice 15 to the passage 18 and thus lower the pressure in the adjustment chamber 12 to the necessary pressure.

 It will be seen that the application of the control air to the portion 30 of the control air cavity 28 will increase the pressure of the spring on the diaphragm 13 by a predetermined amount which will in turn increase the release pressure. of the valve member 14 and thus the fuel pressure supplied to the injection unit 5 by the high pressure pump 7 will be increased accordingly.

 In order to reduce the required pressure of the intake air to the portion 30 of the control cavity, a bearing (not shown) may be provided between the support plate 24 and the end wall 26 to partially offset the spring 25.

 Actuation of the solenoid 49 to increase the fuel supply pressure may be effected by a suitable engine speed sensor for operating a switch when the engine speed reaches a chosen value. When actuated, the switch energizes solenoid 49 such that air from the air supply to injection unit 5 is admitted to portion 30 of control cavity 28. The application of pressure by this air to the diaphragm 27 will move the support plate 24 so that the marginal strip 32 will abut against the shoulder 33, thus increasing the load applied by the spring 25 to the diaphragm 13 by a pre-determined amount. adjustments as set.

 The operation of the solenoid 49 and the control cavity 28 to increase the fuel pressure can be adapted to provide more than one increase in the pre-set fuel pressure. Alternatively, an electrically powered device may be used to effect adjustment. The current applied to the device may vary to adjust the displacement of the diaphragm.

 An appropriate hysteresis function is preferably incorporated in the actuation of the solenoid 49 to prevent "pumping action" between the alternating fuel pressures.

 The fuel pressure adjusting portion 9 of the fuel and air pressure adjusting portion 11, as described with reference to FIG. 3, may be embodied as a fuel pressure regulator in which the set pressure is variable during operation. The advantage of an adjustable injection pressure has previously been discussed as a means for varying the fuel penetration into the combustion chamber, and this is also applicable to the injection system where the liquid fuel alone is injected as in systems in which the liquid fuel is entrained in the air or other suitable gases. As a result, the fuel pressure regulating portion 9 can be used as a variable pressure regulator in the injection systems, injecting the liquid alone.

 Continuing with the description of the combined setting shown in FIG. 3, the fuel combustion chamber 12 is in communication with the passage 35 with the chamber 36 in the air adjusting portion 11 and is separated from the pressure chamber air 37 through the diaphragm 38. The air pressure chamber 37 is in communication with the air from the compressor 2 through the passage 39 and an air outlet passage 40 leads from the chamber 37 to the unit 5. The diaphragm 38 carries the valve 41 which cooperates with the orifice 42 which communicates with the two-way air passage 43.

 The spring 45 applies pressure to the diaphragm 38 to keep the valve 41 normally open. Accordingly, the valve 41 will open the port 42 when the air pressure in the chamber 37 and the action of the spring 45 are together sufficient to overcoming the force created by the fuel pressure prevailing in the chamber 36 on the diaphragm 38. Accordingly, it will be understood that the air pressure will always be lower than the fuel pressure by an amount represented at the force applied to the diaphragm 38 by the spring 45.

The regulator as described above will be used to regulate, with respect to the atmospheric pressure, the fuel pressure supplied to the fuel injection unit 5 by the pump 7 and to adjust with respect to the fuel pressure, the pressure from the supply air to the fuel injection unit such that during operation of the fuel injection unit there is always a predetermined differential pressure between the feeds. In addition, by applying air pressure to the portion 30 of the control cavity 28, the adjusted fuel pressure can be increased by a pre-set amount and the air pressure will be increased. accordingly increased by the same amount so that the same differential pressure is maintained between the fuel and air supplies to the dosing and injection unit. The penetration of fuel vaporization can thus be modified without any other adjustment or
fuel metering pressure.

 The degree of change in the air pressure supplied to supply the air-to-air mixture to the combustion chamber is selected by testing for each engine according to the engine configuration and the required degree of fuel penetration. with variable conditions of load or speed. In a particular example applicable to a two-cycle engine, with a displacement of 0.4 liter per combustion chamber, the air pressure is increased from 250 to 500 kPa at an engine speed of 2500 rpm which is in the median speed range of the engine.

 The fuel pressure regulator described above and the integrated fuel and air differential pressure regulator can be used in combination with the fuel delivery and metering system described with reference to Figure 2 as described. in Australian Patent Application No. 32132/84 filed July 19, 1985 in the name of the Applicant and may be used in the fuel supply of a two-stroke engine as described in Australian Patent Application No. PH 01559, PH 1991 and PH 3344 filed on July 19, 1985 in the name of the Applicant. The description of these applications in this application is incorporated herein by reference.

 In the foregoing description, with reference to the accompanying drawings, the present invention has been implemented with a motor operating in a two-cycle cycle and with a spark ignition and a reciprocating piston; however, it should be understood that the present invention is equally applicable to spark ignition engines operating in a four-stroke cycle and / or to other forms such as rotary piston engines. The invention is applicable to internal combustion engines intended for all uses and in particular, used to contribute to fuel savings and the control of exhaust emissions from engines on vehicles including automobiles, motorcycles and boats, including outboard marine engines.

Claims (25)

 1. A method of controlling the fuel distribution in an internal combustion engine combustion chamber of directly injecting the fuel into the combustion chamber by means of an injection nozzle under conditions such that the fuel enters the combustion chamber. a first distance within the combustion chamber and varying said conditions in response to the engine load demand above a predetermined value to increase the fuel penetration distance inside the combustion chamber. combustion chamber.  2. A method of controlling the dispensing of fuel into a combustion chamber of an internal combustion engine by driving a metered quantity of fuel into a gas to form a fuel-gas charge, controlling the amount of fuel entrained in response at the engine load demand, and by directly injecting said fuel-gas charge into the combustion chamber via an injection nozzle under conditions such that the fuel enters a first distance to the interior of the combustion chamber and varying said conditions in response to the engine load demand above a predetermined value to increase the fuel penetration distance within the combustion chamber.  A fuel distribution control method according to claim 1 or 2, characterized in that the injection conditions through the injection nozzle which vary are the differential pressure ensuring the fuel supply to the fuel. through the injection nozzle.  4. A fuel dispensing method according to any of the claims. 1 to 3, characterized in that said injection conditions vary in response to the operation of the engine at a speed above a predetermined value.  - 5. A method according to claim 2 or the combination of claims 2 and 3, characterized in that the fuel is metered during the feed to be driven into the gas, and the fuel is maintained at a predetermined differential pressure above that of the gas, virtually over the full range of engine load demand.  6. A method according to claim 5, characterized in that the pressure of the gas ensures the supply of fuel through the injection nozzle.  7. A method according to claim 5 or 6, characterized in that the fuel pressure is increased in response to the engine load demand above said predetermined value, so that the gas pressure is increased accordingly.  8. A method of controlling fuel dispensing in the combustion chamber of an internal combustion engine by providing a metered quantity of fuel supplied to a fuel supply pressure and a mass of gas by directly injecting the fuel mixture. thus formed at a mixing feed pressure through an injection nozzle within the combustion chamber, adjusting the differential pressure between the fuel and the gas mass to maintain a substantially uniform differential pressure at the load demand of the engine and controlling the pressure of the fuel-gas mixture during fueling of the combustion chamber, such that said pressure has increased in response to the load demand of the engine above a value predetermined so as to increase the penetration of fuel within the chamber.  9. A fuel dispensing method according to claim 8, characterized in that the fuel pressure is set to increase in response to said engine load demand above said predetermined value.  A fuel dispensing method according to any one of the preceding claims, characterized in that said predetermined value of the engine load demand is determined by determining when the engine reaches a predetermined value.  A fuel injection system for an internal combustion engine in which a quantity of fuel is metered under pressure in a gas to form a fuel-gas charge characterized in that the fuel pressure is set to a preselected value and the gas pressure is adjusted with respect to the fuel pressure to maintain a predetermined differential pressure between the fuel and the gas during fuel metering.  12. A fuel injection system according to claim 11, characterized in that the set fuel pressure is selected from at least two predetermined values.  A fuel injection system according to claim 11, characterized in that the adjusted fuel pressure is increased as a function of the engine load demand exceeding a predetermined value.  14. A fuel injection system according to claim 11, characterized in that the adjusted fuel pressure is increased in response to the engine speed above a predetermined value.  15. A method of controlling fuel dispensing in a combustion chamber of an internal combustion engine essentially consisting in preparing a metered quantity of fuel outside the combustion chamber, injecting said metered quantity of fuel into the combustion chamber. combustion chamber through an injection nozzle by applying pressurized gas to the fuel, controlling said gas pressure in response to said engine load demand so that for load demands located below a predetermined value, the gas pressure is at a first level to provide a first fuel penetration distance into the combustion chamber and load demands located above said predetermined value, the gas pressure at a second level above said first level to increase fuel penetration within the combustion chamber.  16. A fuel dispensing control method according to claim 15, characterized in that the fuel is metered during the supply into the gas to form a fuel-gas charge.  A fuel injection system for an internal combustion engine, characterized in that the fuel is metered into the gas and propelled by the pressure of the gas inside the engine, a combined fuel-gas pressure regulator comprising first means for adjusting the fuel pressure at a first predetermined pressure above atmospheric pressure and second means for adjusting the pressure of the gas to a predetermined value above the fuel pressure.  The combination of claim 17, wherein a first means comprises a fuel chamber and an air chamber separated by a movable partition, a fuel inlet and a fuel return port in said fuel chamber. means for selectively opening said fuel return port in response to movement of said wall in one direction, means for urging movement of movement of the wall in said direction, vent in said air chamber; for receiving atmospheric air therein, said thrust means and atmospheric air in the air chamber together ensuring movement of the wall to open the return port when the fuel pressure in the fuel chamber is above said predetermined pressure.  19. The combination according to claim 18, wherein said second means comprises a gas chamber and another fuel chamber separated by another movable wall, arranged between them, said other fuel chamber communicating with said fuel chamber of said first means. and a gas inlet port and a two-way gas port in said gas chamber, means for selectively opening said two-way air port in response to displacement of said other wall in a direction of other biasing means biasing said wall to move in said first direction, said other biasing means, and pressure in said air chamber moving said other wall to open said two-way port when the pressure in the air chamber is above the pressure in the other fuel chamber by said predetermined value.  20. The combination according to any one of claims 17 to 19, characterized in that means are provided for selectively increasing the force applied by the biasing means to raise said predetermined first fuel pressure.  An internal combustion engine comprising a fuel injection system operable in accordance with the method claimed in any one of claims 1 to 10, 15 or 16.  22. An internal combustion engine having a fuel injection system according to any one of claims 11 to 14 and 17 to 20.  23. An internal combustion engine according to claims 21 or 22, characterized in that the engine operates in a two-stroke cycle.  24. An automobile having an internal combustion engine as claimed in any one of claims 21 to 23.  25. An internal combustion engine according to any one of claims 21 to 23 constituted by an outboard marine engine.