Internal-combustion engines – Charge forming device – Auxiliary air or gas used to inject fuel
Reexamination Certificate
2001-04-30
2002-08-20
Solis, Erick (Department: 3747)
Internal-combustion engines
Charge forming device
Auxiliary air or gas used to inject fuel
C123S533000, C123S479000
Reexamination Certificate
active
06435165
ABSTRACT:
The present invention is generally directed to dual fluid fuel injection systems for internal combustion engines, and in particular to a method of regulating air pressure for such dual fluid fuel injection systems. The present invention is applicable for both two and four stroke engines and may be adapted for use on both single and multicylinder engines.
Dual fluid fuel injection systems typically utilise compressed air during the injection event to entrain metered quantities of fuel for delivery into the combustion chambers of an internal combustion engine. The Applicant has developed such fuel injection systems and one version thereof is described in U.S. Pat. No. 4,934,329, the details of which are incorporated herein by reference. Generally, a source of compressed gas, for example an air compressor, is required for these fuel injection systems to operate. The term “air”is used herein to refer not only to atmospheric air, but also to other gases including air and exhaust gas or fuel vapour mixtures.
Such systems typically require the pressure of the compressed air to be regulated to thereby help to maintain accurate control of the fuel delivery to the engine. Various means may be used to regulate the air pressure from the compressed air source. One common method of regulating the air pressure of the compressed air supplied to the fuel injection system relies on the use of suitably located mechanical air regulators within the air delivery circuit. In such systems, regulation of the air pressure can however be lost if there is a mechanical failure of the air regulator(s).
Another possible method of regulating the air pressure supplied to the fuel injection system is by use of a demand compressor which is able to control the pressure of the output air delivered therefrom. Typically, such a demand compressors seek to closely match the air delivered therefrom to the actual requirements of the apparatus or system to which air under pressure is being supplied. Accordingly, in certain applications, such a compressor may eliminate the need for any further means to regulate the air pressure. However, under certain operating conditions or as a result of a particular failure mode which may occur, the demand compressor may deliver more air than is required to, for example, a dual fluid fuel injection system. For example, under cold ambient conditions, the battery voltage for the system may be significantly lower than normal, typically 12V. Depending upon the actual configuration of the demand compressor, it is possible in these conditions for there to be an insufficient voltage to satisfactorily operate a pressure control arrangement of the demand compressor. This could lead to the supply of excess compressed air resulting in an undesirable or excessive pressure condition within the fuel injection system if no other air regulation means is provided. It would therefore be advantageous to be able to maintain regulation of the air pressure in such systems when such a pressure control arrangement of the demand compressor fails or is not operating properly.
It is therefore an object of the present invention to provide a method of regulating the gas pressure in a dual fluid fuel injection system that avoids at least one of the abovenoted disadvantages.
With this in mind, there is provided a method of regulating gas pressure in a dual fluid fuel injection system for an internal combustion engine having at least one delivery injector during running of the engine, including;
determining when the gas pressure supplied to the fuel injection system is above a desired level; and
opening the at least one delivery injector of the dual fluid fuel injection system for a determined duration when the gas pressure is above the desired level to allow gas to be passed through the delivery injector and thereby regulate the gas pressure of the supplied gas.
The running of the engine includes engine operation during engine cranking, start up, over-run cut operating states as well as other running states such as idle or various states of engine load where the engine is driving a vehicle or other apparatus.
The opening of the delivery injector results in a reduction in the gas pressure within the fuel injection system, the degree of reduction being a function of the duration and/or timing of opening of the injector. Conveniently, gas is supplied to the fuel injection system by way of an air compressor which in certain applications may be driven off the engine.
The dual fluid fuel injection system may include one or more delivery injectors. The or each injector may be arranged to inject directly into a cylinder of the engine, and one or more injectors may be opened at the same time to relieve gas pressure within the fuel injection system. The present invention is therefore equally applicable for engines having one or more cylinders.
The duration of opening of the or each injector may be sufficient to allow the gas pressure to return to or at least approach the desired level. Conveniently, the or each injector is controlled over successive cycles to gradually or incrementally reduce the gas pressure in the fuel injection system down to the desired level. In the case of a multicylinder engine, one or a number of the injectors may be selected to perform the gas pressure regulation function. Further, in relation to the operation of one, some or all of the injectors to perform the gas pressure regulation function, it is to be understood that successive cycles doesn't necessarily constitute consecutive cycles.
The timing of the opening of the, some, or each of the injectors for regulation of the gas pressure may conveniently be between the normal fuel injection events of the injector. Hence, the opening of the injector(s) to effect gas pressure reduction in the fuel injection system may occur(s) at timings at which the air injectors would not normally be open for fuel delivery. Nonetheless, in certain applications, the control of the injector(s) for gas pressure regulation may be immediately before, after, or in some cases may overlap slightly with a fuel delivery event.
Preferably, the opening of the injector(s) for gas pressure regulation will be effected at a point in time at which the pressure in the corresponding cylinder is lower than the gas pressure within the fuel injection system. Accordingly, the timing of opening of the injector(s) as well as the duration of opening may be used to affect gas pressure regulation. That is, opening an injector for the same period of time, but, for example, at a point in the cylinder cycle when the cylinder pressure is lower will typically result in a greater decrease of the gas pressure within the fuel injection system.
Conveniently, in the case of engines operating on the four stroke cycle, the injector(s) may be controlled to relieve gas pressure during the latter part of the power/expansion stroke and certain parts of the intake and/or exhaust stroke. Conveniently, in the case of engines operating on the two stroke cycle, the injector(s) may be controlled to relieve gas pressure during certain parts of the exhaust/intake event (ie. during latter parts of the power stroke) and/or an initial portion of the compression stroke. The present invention is therefore equally applicable to engines operating on both the two and four stroke cycles.
The opening of the injector(s) may be controlled by an Electronic Control Unit (ECU) controlling the operation of the engine. Conveniently, the ECU may determine the gas pressure of the compressed gas supplied to the fuel injection system by means of a suitably located pressure sensor. The fuel injection system may include an air rail for supplying gas to the injector(s) and to which the compressed gas is supplied. The pressure sensor may, for example, be located to measure the air pressure within the air rail. Hence, the air pressure sensor is one means by which the gas pressure in the fuel injection system may be assessed to see if it is above the desired level.
The ECU may determine a desired level for the air pressure within the fue
Andersen Luke Newman Henry
Hill Raymond John
Melbourne Keith
Arent Fox Kintner & Kahn
Orbital Engine Company (Australia) Pty Limited
Solis Erick
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