SE466864B - Fuel injection method for two=stroke engine - Google Patents

Abstract

The procedure for control of fuel injection into a two stroke engine cylinder includes variation of the differential pressure across the injection according to the operating conditions. This then controls the distance which the fuel penetrates into the combustion chamber. The fuel may be formed into a gas, with the quantity of fuel being controlled according to the load demand on the engine. The differential pressure between the fuel and the gas which is to be injected into the engine may be maintained practically uniform, while the pressure at which the gas is injected into the engine varies according to the conditions.

Description

15 20 25 30 35 466 864 2 on the engine load when the fuel is supplied for containment in the gas, to directly inject the fuel gas set into the combustion chamber through a nozzle with an injection pressure determined by the gas pressure so that the fuel penetrates into the combustion chamber a distance depending on the injection pressure, the fuel gas batch being injected with an injection pressure when the engine is operating at at least one engine speed and an engine load which is either below a selected value, and increasing the fuel gas batch injection pressure in response to that at least one of the engine speeds and the engine load exceeds the selected value so that the fuel enters the combustion chamber a greater distance at engine loads or speeds exceeding the selected value, the fuel being maintained at the determined pressure difference across the gas pressure over substantially the entire of at least either of the engine speed range and engine load range.

Suitably, the pressure that provides the fuel supply through the nozzle may be increased stepwise at one or more selected levels of engine load requirements, or the pressure increases may be progressive over one or more ranges of engine speeds or loads to vary the degree of penetration of the fuel.

More particularly, a method is provided for controlling the fuel distribution in the combustion chamber of an internal combustion engine, comprising combining a metered quantity of fuel delivered at supply pressure and an amount of gas, to deliver the fuel-gas mixture thus formed at a mixture supply pressure. through a nozzle into the combustion chamber, to regulate the pressure difference between the amount of fuel and gas to maintain a substantially even pressure difference over the engine load requirements, and to regulate the pressure of the fuel-gas mixture during supply to the combustion chamber so that the pressure increases load requirements exceed a predetermined value, thereby increasing the penetration depth of the fuel into the room. von 10 15 20 25 30 35 466 864 3 Maintaining the even pressure difference between the amount of fuel and gas simplifies the control of the quantity of fuel dosed, since in this control method it is not necessary to compensate for variations in the pressure difference.

Preferably, the control of the penetration of the fuel is achieved by varying the fuel pressure with the engine speed and consequently varying the gas pressure in order to maintain an even pressure difference. The variation of the fuel pressure consequently has the end result of varying the available pressure to supply the fuel-gas mixture through the nozzle to the combustion chamber.

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

When regulating the pressure difference between the gas and the supplied fuel in it, special advantages arise, in that the regulation is based on varying the fuel pressure as the control function and as a result achieving a variation in the gas pressure to maintain the selected pressure difference. One of the advantages is that the gas is less viscous than a liquid fuel and therefore, in a control situation, the regulated gas pressure will not be affected as much by variations in flow rate through the pressure control device. This results in the pressure difference being less sensitive to variations in flow rate of either the fuel or the gas. This feature is of particular importance where the pumps which supply the fuel and the gas are driven by the engine and have outputs which are highly speed-related. Accordingly, another object of the present invention is to provide a fuel-gas control system which is particularly suitable for incorporation into a fuel injection system utilizing pressurized fuel and gas sources. With this second object in mind, a fuel injection system has been provided for regulating the fuel distribution in the combustion chamber of a spark-ignited internal combustion engine, according to which a quantity of fuel is dosed under pressure in a gas to form a fuel gas batch, the fuel gas batch being discharged through a nozzle into a combustion chamber in the engine with an injection pressure determined by the gas pressure so that the fuel enters the combustion chamber a distance depending on the injection pressure, comprising means for regulating the fuel and gas pressures to maintain a certain pressure difference between the fuel and gas pressures, and means for increasing the regulated pressures in response to the engine load and / or speed increasing above a certain value, while maintaining the determined pressure difference, the fuel / gas mixture is injected at an injection pressure when the engine is operating at a load or speed exceeding the specified to increase the penetration distance of the fuel into the combustion chamber.

Conveniently, the controlled pressure of the fuel can be selected between at least two predetermined values. Preferably, the variation in the controlled fuel pressure is achieved at a selected speed, within the normal operating speed range of the engine, and the variation is preferably an increase when the engine speed exceeds the selected value. A corresponding reduction is achieved when the engine speed falls below the selected value. Preferably, the fuel pressure is regulated to a predetermined value relative to the atmospheric pressure. In accordance with a further aspect of the present invention, there is provided an engine fuel system, a fuel pressure control device set to provide a predetermined fuel outlet pressure, and means adapted to vary the pressure a predetermined value in response to a selected condition of the engine. . suitably, the predetermined fuel outlet pressure is set by means of a resilient member biased to a set value, and the means for varying the outlet pressure adjusts the degree of tension on the resilient member.

Preferably, the resilient member is a spring which is extended or compressed to some degree to provide a load necessary to adjust the required fuel back pressure. The degree of compression or extension of the spring is increased to increase the fuel-A output pressure when the engine reaches a predetermined load and consequently decreases when the engine speed falls below the selected load.

In this description, reference is made to varying the penetration of the fuel jet by adjusting the fuel supply pressure in the combustion chamber, in relation to a specific change or changes in the engine load requirements, and this requirement can be sensed in a number of ways. In many engine applications, engine speed indicates engine load under most operating conditions, especially where the engine normally operates within specified speed ranges, such as outboard engines.

Accordingly, since the engine speed can be sensed without inconvenience, and requires comparatively simple sensors, the engine speed is read to sense the occurrence of the load change at which the change in fuel penetration is to be effected.

The invention will be more readily understood from the following description, with reference to the accompanying drawings, of a practical arrangement of the fuel and air pressure regulating device built into a fuel injection system.

Fig. 1 is a section through a two-stroke engine, which shows a fuel injection system with injection directly into the cylinder.

Fig. 2 is a side view, partly in section, of a fuel metering and injection unit suitable for use with the engine shown in Fig. 1.

Fig. 3 is a section through a combined fuel and air pressure regulating device suitable for use at a set value, and the means for varying the output pressure adjust the degree of tension on the resilient means.

Preferably, the resilient member is a spring which is extended or compressed to some degree to provide a load necessary to adjust the required fuel back pressure. The degree of compression or extension of the spring is increased to increase the fuel-A output pressure when the engine reaches a predetermined load and consequently decreases when the engine speed falls below the selected load.

In this description, reference is made to varying the penetration of the fuel jet by adjusting the fuel supply pressure in the combustion chamber, in relation to a specific change or changes in the engine load requirements, and this requirement can be sensed in a number of ways. In many engine applications, engine speed indicates engine load under most operating conditions, especially where the engine normally operates within specified speed ranges, such as outboard engines.

Accordingly, since the engine speed can be sensed without inconvenience, and requires comparatively simple sensors, the engine speed is read to sense the occurrence of the load change at which the change in fuel penetration is to be effected.

The invention will be more readily understood from the following description, with reference to the accompanying drawings, of a practical arrangement of the fuel and air pressure regulating device built into a fuel injection system.

Fig. 1 is a section through a two-stroke engine, which shows a fuel injection system with injection directly into the cylinder.

Fig. 2 is a side view, partly in section, of a fuel metering and injection unit suitable for use with the engine shown in Fig. 1.

Fig. 3 is a sectional view of a combined fuel and air pressure regulating device suitable for use. The fuel metering and injection unit of Fig. 2 includes a suitable metering device 130, such as an injection device with a choke body of a self. driving stroke, which is connected to an injection housing 131 with a retaining chamber 132 therein. Fuel is dispensed by a fuel pump (not shown) through the fuel inlet port 133 to the metering device 130, which dispenses a quantity of fuel into the retaining space 132 in accordance with the fuel needs of the engine. Excess fuel fed to the metering device is returned to the fuel tank via the fuel return port 134. The special design of the fuel metering device 130 is not critical to the present invention and any suitable device may be used.

In operation, the retaining chamber 132 is pressurized with air fed through an air inlet port 145 into the housing 131. An injection valve 143 is actuated to allow the pressurized air to discharge the metered quantity of fuel from the chamber 132 through the injection nozzle 142 into the engine combustion chamber. The injection nozzle 143 of the injection nozzle is of the disc structure which opens inwards towards the combustion chamber, i.e. out of the retaining chamber.

The injection valve 143 is, via a valve stem 144 extending through the retaining space 132, connected to the armature 141 of the solenoid 147 which is arranged inside the injection housing 131. The valve 143 is biased towards the closed position of the disc spring 140 and is opened by closing the solenoid 147 The switching on of the solenoid 147 is controlled in relation to the time of the engine cycle in order to supply the fuel from the retaining chamber 132 to the combustion chamber of the engine.

Further details of the operation of the fuel metering and injection system, which includes a retaining chamber such as that described with reference to Fig. 2, are set forth in Australian Patent Application 32132/84 and the corresponding U.S. Patent Application 740067, which are hereby incorporated by reference. It is to be understood that the fuel is supplied to the retaining space 132 by the metering device 130 against the pressure of the air present in the space. The difference in pressure between the fuel source at the dosing device and the air in the retaining chamber is consequently relevant to the quantity of fuel that will be supplied to the retaining chamber. Due to the need for accuracy in fuel dosing, both from the point of view of fuel economy and exhaust emission control, it is important to effectively regulate this pressure difference.

Fig. 3 shows a fuel injection system comprising a combined fuel and air control device suitable for use with the fuel metering and injection unit described above with reference to Fig. 2. However, it is to be understood that the control device described below with reference to to Fig. 3, can be used in other fuel dosing and injection systems and is not limited to use in the system described with reference to Fig. 2.

Reference is now made to Fig. 3, where the fuel injection system comprises a fuel metering and injection unit 5, to which air and fuel are supplied from the compressor 2 and the fuel tank 6 via the control device 10. The fuel is discharged from the tank 6 through the low pressure pump 3 to the high pressure pump 7 via the through passage 18 in the control device 10.

The control device 10 comprises a fuel pressure control portion 9 and an air pressure control portion 11, which are built into an integrated construction. The fuel control chamber 12 has a wall formed of a flexible membrane 13, which is fixed around its outer edge. A valve element 14 is attached to the diaphragm 13, which cooperates with the port 15 which is arranged in the wall 17 of the fuel control space opposite the diaphragm 13.

The port 15 communicates with the low pressure fuel passage 18, which in turn communicates with the outlet side of the low pressure pump 3 and the suction side of the high pressure pump 7. 10 15 20 25 30 35 466 864 9 The high-pressure fuel inlet passage 20 connects the fuel control chamber 12 to the outlet side of the high-pressure fuel pump 7. The non-return valve 21 between the passage 18 and the space 12 is only slightly biased, so that during start-up the low-pressure fuel can flow from the passage 18 through the fuel space 12 to clean the high-pressure fuel circuit and the injector 5 from air.

The diaphragm 13 is positioned by the spring 25 to normally position the valve 14 to close the port 15. The spring support plate 24 normally abuts the stop 19, which is arranged on the end wall 26 of the control housing. The spring support 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 exposed to atmospheric air via the port 22, while the portion 30 on the opposite side of the diaphragm 27 may optionally be connected to the regulated air source via the port 31 and the solenoid valve 49. When air pressure is applied through the port 31 in the control cavity 28 portion 30, the diaphragm 27 and the spring support plate 24 will be moved to the right, as seen in the drawing, to apply further compression of the spring 25. The extent of the movement of the support plate 24 to the right is limited by the fact that the edge band 32 of the support plate 24 comes to intervention with the annular shoulder 33 on the control housing.

When the fuel pressure in the control space 12 exceeds the regulated pressure, the diaphragm 13 is displaced against the action of the spring 25, and the valve element 14 is moved away from the engagement with the port 15, to allow fuel to flow through the port 15 to the passage 18 and thus lower the pressure in the control space 12 to what is required.

It thus appears that the application of control air in the portion 30 of the control air cavity 28 will increase the spring pressure on the diaphragm 13 by a predetermined value, which in turn will increase the relief pressure of the valve element 14 and therefore the fuel pressure supplied to the injection unit 5 the high pressure pump 7 correspondingly to be increased. To reduce the required air pressure applied to the portion 30 of the control cavity, a spring (not shown) may be provided between the support plate 24 and the end wall 26 to partially counteract the spring 25.

The actuation of the solenoid valve 49, in order to increase the fuel supply pressure, can be effected by a suitable engine speed sensor which is arranged to operate a switch when the engine speed reaches a selected value. When the switch is actuated, it actuates the solenoid valve 49 so that air from the regulated air source to the injection unit 5 is supplied to the portion 30 of the control cavity 28. The application of pressure through this air to the diaphragm 27 will move the support plate 24 so that the edge band 32 abuts against the shoulder 33 and thus increase the load, which is applied through the spring 25, on the diaphragm 13 a set value.

The operation of the solenoid valve 49 and the control cavity 28 to increase the fuel pressure may be adapted to effect more than an increase in the controlled fuel pressure. Alternatively, an electrically driven device may be used to effect the adjustment. The current supplied to the device can be varied to effect the adjustment of the movement of the diaphragm.

A suitable hysteresis function is preferably included in the operation of the solenoid valve 49 to prevent "oscillations" between the alternative fuel pressures. The fuel pressure control portion 9, of the hitherto described composite fuel and air pressure control portion 11 with reference to Fig. 3, can be constructed as an individual fuel pressure control device, in which the controlled pressure is variable during operation. The desirability of an adjustable injection pressure has previously been discussed as a way of varying the penetration of the fuel into the combustion chamber and this is equally applicable to injection systems where only liquid fuel is injected as to systems in which liquid fuel is trapped in air or other suitable gas. The fuel pressure regulating portion 9 10 15 20 25 30 35 466 864 ll can consequently be used as a variable pressure regulating device in injection systems, which only inject liquid.

Continuing with the description of the combined control device shown in Fig. 3, the fuel chamber 12 communicates, via the passage 35, with the space 36 in the air control portion 11 and is separated from the air pressure chamber 37 by the diaphragm 38. The air pressure chamber 37 communicates with the air from the compressor 2. via the passage 39 and the air outlet passage 40 leads from the space 37 to the injection unit 5. The diaphragm 38 carries the valve 41, which cooperates with the port 42 which communicates with the air bypass passage 43.

The spring 45 applies pressure to the diaphragm 38 to normally keep the valve 41 open. Consequently, the valve 41 will open the port 42 when the air pressure in the chamber 37 and the action of the spring 45 together are sufficient to overcome the force generated by the fuel pressure in the space 36 on the diaphragm 38. Accordingly, it will be understood that the air pressure will always be less than fuel. the pressure to the extent represented by the force applied to the diaphragm 38 by the spring 45.

The control device described above will, in use, regulate, relative to the atmospheric pressure, the pressure of the fuel supplied to a fuel injection unit 5 through the pump 7, and regulate, relative to the fuel pressure, the pressure of the air supply to the fuel injection unit, so that during the operation of the fuel injection unit is a predetermined pressure difference between the fuel and air supply. In addition, by applying air pressure to the portion 30 of the control cavity 28, the regulated fuel pressure can be increased by a preset value and the air pressure will consequently be increased correspondingly by the same value, so that the same pressure difference is maintained between the fuel and air supply to the fuel metering and injection unit. The penetration of the fuel jet can thus be changed without other adjustments or adjustments of the fuel dosage. The degree of change in the air pressure provided to effect the supply of the fuel-air mixture to the combustion chamber is selected by experiment for each engine depending on the engine geometry and the degree of fuel penetration required at varying load or speed ratio. In a special example applicable to a two-stroke engine with a displacement of 0.4 liters per combustion chamber, the air pressure is increased from 250 to 500 kPa at an engine speed of 2500 rpm, which is in the intermediate speed range of the engine.

The fuel pressure control device described above and the integrated fuel and air pressure differential control device can be used in combination with the fuel metering and supply system described with reference to Fig. 2 and as set forth in our Australian Patent Application No. 32132/84 and can be used in fuel feeding a two-stroke engine as described in our Australian patent applications Nos. PHOl559, PH1991 and PH3344, to which reference is hereby made.

In the foregoing description with reference to the drawing, particular reference has been made to the use of the present invention in connection with an engine operating in two strokes and with spark plug ignition and reciprocating piston. It is to be understood, however, that the invention may also be applied to spark plug ignition engines operating in four stroke and / or other structures, such as rotating pistons. The present invention is applicable to internal combustion engines for all uses and is particularly useful in contributing to fuel economy and exhaust emission control in engines for or in vehicles, including cars, motorcycles and boats, and including outboard engines.

Claims (4)

1. 0 15 20 25 30 35 466 864 / s PATENT CLAIM 1. A method for regulating the fuel distribution in a - characterized in that it comprises the steps of inside the combustion chamber of a spark-ignited internal combustion engine, closing a metered quantity of fuel in a gas under pressure to form a fuel gas batch, the quantity of fuel being metered in response to the engine load when the fuel is supplied for entrapment in the gas, to directly inject the fuel gas batch into the combustion chamber (110) through a nozzle (124) with an injection pressure determined by the gas pressure so that the fuel penetrates in the combustion chamber (110) a distance depending on the injection pressure, the fuel gas batch being injected with an injection pressure when the engine operates at at least one engine speed and an engine load which is either below a selected value, and increasing the fuel gas batch injection pressure in response that at least either of the engine speed and engine load exceeds the selected value so that the fuel penetrates into the combustion chamber (110) a greater distance at engine loads or speeds in excess of the selected value, the fuel being maintained at the determined pressure difference across the gas pressure over substantially the whole of at least either of the engine speed range and the engine load range. 2. A method according to claim 1, characterized in that the injection pressure is varied in response to the engine operating at a speed exceeding a certain value. 3. A method according to claim 1, characterized in that the gas pressure provides supply of the fuel through the nozzle (124). 4. A method according to claim 1, 2 or 3, characterized in that the fuel pressure is increased in response to at least one of the engine speed and the engine load exceeding the determined value, thereby increasing the gas pressure correspondingly. characterized by the steps of combining a metered quantity of fuel, supplied at a fuel supply pressure, with an amount of gas, to directly inject the fuel-gas mixture thus formed at a mixture supply pressure through a nozzle (124) into the combustion chamber (110), to regulate the pressure difference between the amount of fuel and the gas to maintain a substantially even pressure difference across the engine load range, and to regulate the pressure of the fuel-gas mixture during supply to the combustion chamber (110) so that the pressure increases in response to an engine load exceeding one determined value, thereby increasing the distance that the fuel penetrates into the combustion chamber (110). A method according to claim 5, 5. A method according to claim 1, characterized in that the fuel pressure is regulated to increase in response to the engine load exceeding the determined value. Method according to one of the preceding claims, characterized in that the determined value for the motor load is determined by determining when the motor reaches a certain speed. Method according to one of the preceding claims, characterized in that the fuel pressure is regulated to a certain value, wherein the fuel pressure can be chosen between at least two determined values and that the gas pressure is regulated relative to the fuel pressure in order to maintain a certain pressure difference between the fuel and the gas. dosage. A fuel injection system for controlling the fuel distribution in the combustion chamber of a spark-ignited internal combustion engine, according to which a quantity of fuel is metered under pressure into a gas to form a fuel gas batch, the fuel gas batch being discharged through a nozzle (124) to a combustion chamber (110) in the engine with an injection pressure determined by the pressure of the gas so that the fuel enters the combustion chamber (110) a distance which depends on the injection pressure, characterized by means ( 13, 14, 25 and 38, 41, 42, respectively, to regulate the fuel and gas pressures to maintain a definite pressure difference between the fuel and gas pressures, and means (9, 11) to increase the regulated pressures in response to the engine load and / or speed increases above a certain value, while maintaining the determined pressure difference, the fuel / gas mixture is injected at an injection pressure when the engine operates at a load or speed exceeding e the determined value to increase the penetration distance of the fuel in the combustion chamber. Fuel injection system according to claim 9, characterized in that the means (13, 14, 25 and 38, 41, 42) for regulating the fuel and gas pressures are arranged to change the fuel pressure in response to the change in engine load and / or speed and to regulate the gas pressure in relation to the fuel pressure in order to maintain the determined pressure difference. Fuel injection system according to claim 10, characterized in that it comprises a combined fuel and gas pressure regulator (10), which comprises a first means (13, 14, 25) for regulating the fuel pressure to a first determined pressure above atmospheric pressure and a second means (38, 41, 42) for regulating the gas pressure to a second determined value below the first determined pressure of the fuel. Fuel injection system according to claim 11, characterized in that the first regulating means (13, 14, 25) comprises a fuel compartment (12) and an air space (29) separated by a movable wall (13), a fuel inlet port ( 20) and a fuel return port (21) in the fuel compartment, control means (13, 14) for selectively opening the fuel inlet port (21) in response to the movement of the wall (13) in one direction, biasing means (25) which resist movement of the wall (13) in said direction, an air port (22) in the air space (29) for admitting atmospheric air therein, the biasing means (25) and the atmospheric air in the air space (29) together allowing the wall (13) moving to open the fuel return port in (21), when the fuel pressure in the fuel chamber (12) exceeds the first determined pressure. Fuel injection system according to claim 11, characterized in that the second regulating means (38, 41, 42) comprises a gas space (37) and a further fuel space (36) separated by a further, movable wall (38). between them, the further fuel space (36) communicating with the fuel space (12) of the first regulating member (13, 14, 15), and a gas inlet port (39) and a gas bypass port (42) in the gas space ( 37), means (41) for selectively opening the gas bypass port (42) in response to the movement of the further wall (38) in one direction, further biasing means (45) forcing the wall (38) to move in said one direction, the additional biasing means (45) and the pressure in the gas space (37) causing movement of the additional wall (38) to open the bypass port (42) when the pressure in the gas space (37) exceeds the determined value. Fuel injection system according to any one of claims 12 or 13, characterized in that control means (27, 31, 49) are arranged to selectively increase the force applied to the biasing means (25) to increase the first determined pressure of the fuel.