Internal-combustion engines – Charge forming device – Auxiliary air or gas used to inject fuel
Reexamination Certificate
2001-02-16
2001-11-13
Solis, Erick (Department: 3747)
Internal-combustion engines
Charge forming device
Auxiliary air or gas used to inject fuel
C123S479000
Reexamination Certificate
active
06314948
ABSTRACT:
The present invention is generally directed to dual fluid fuel injection systems for internal combustion engines, and in particular to a method of controlling such dual fluid fuel injection systems.
The Applicant has developed dual fluid fuel injection systems for use in internal combustion engines wherein metered quantities of fuel are injected into the combustion chamber(s) of an engine, entrained in a compressed gas. An example of such a system is described in the Applicant's U.S. Pat. No. 4,934,329, the details of which are incorporated herein by reference. Such systems require a source of compressed gas such as an air compressor to operate properly. The compressed gas is supplied to the delivery or air injectors of the fuel injection system which deliver fuel into the engine. Typically, separate fuel supply means supply metered quantities of fuel to each delivery injector and the compressed gas entrains and delivers the fuel to the engine when the delivery injector is opened. Such air-assisted fuel injection has been shown to promote improved fuel spray formation and distribution within the combustion chambers of the engine, leading to benefits such as improved emissions, fuel economy and engine operating stability.
However, the gas supply upon which the dual fluid fuel injection system is reliant can be lost if for example there is a mechanical failure of the air compressor or a break or significant leak in the air supply system between the air compressor and the delivery injectors of the dual fluid fuel injection system. Such a loss of the compressed gas supply to the delivery injectors will prevent the dual fluid fuel injection system from operating properly resulting in unsatisfactory engine operation or in fact thereby disabling the engine. That is, no, or an unsatisfactory quantity of compressed gas will be available at each delivery injector to entrain and deliver fuel into the combustion chambers of the engine.
It is therefore an object of the present invention to provide a method of operating a dual fluid fuel injection system if there is such a disruption of the compressed gas supply to the delivery injector.
With this in mind, there is provided a method of controlling a dual fluid fuel injection system of an internal combustion engine having at least one cylinder, the fuel injection system having at least one delivery injector and a compressed gas supply means for supplying gas to the at least one delivery injector, the method including:
determining if there has been a reduction in the compressed gas supplied to the at least one delivery injector below a required supply level;
opening the at least one delivery injector when there is a depression in a respective said cylinder such that the pressure within said cylinder is lower than the pressure upstream of the delivery injector if the compressed gas supply is below said required supply level; and
delivering fuel to the delivery injector such that the fuel is drawn into the cylinder by virtue of the pressure differential existing across the delivery injector.
The term “cylinder depression” refers to the condition where the pressure within the cylinder is lower than a reference pressure, in this case, the pressure upstream of the delivery injector.
The delivery injector(s) may inject fuel directly into a respective said cylinder. In the case of a multi-cylinder engine, each cylinder may be provided with a respective said delivery injector.
Conveniently, the compressed gas supply means comprises an air compressor and air supply means for communicating the output of the air compressor with the delivery injector(s) of the fuel injection system. The reduction in the compressed gas supplied to the at least one delivery injector may typically be constituted by an interruption of the compressed gas supply from the air compressor. Alternatively, the reduction may arise due to a failure, break or leak within the air supply means communicating the compressor with the delivery injector(s).
The method according to the present invention may control the duration of opening of the delivery injector. Alternatively or in addition, the start of opening of the delivery injector may be controlled.
Preferably, the start of opening and duration of opening of a said delivery injector of a said cylinder of the engine occurs when the cylinder is undergoing an intake stroke therein. Preferably, fuel is delivered to the delivery injector at least in the period when the delivery injector is opened.
Conveniently, the delivery injector is actuated by way of an electromagnetic solenoid such that, even though the source of compressed gas may have been interrupted or reduced, the delivery injector may still be operated to provide communication with a cylinder of the engine. Such electromagnetic control is well known in the field of fuel injection systems. It should however be noted that other suitable forms of delivery injector may also be used in accordance with the present invention.
The present invention relies on there being a lower pressure within the cylinder when the delivery injector is opened. As is well understood, when a piston within the cylinder is moving towards bottom dead centre on the intake stroke thereof, a vacuum is created within the cylinder. The vacuum induced in the cylinder during the intake stroke helps to draw the fuel held within or being supplied to the delivery injector into the cylinder whilst the delivery injector is held opened. This is because a pressure differential is created across the open delivery injector which enables a net mass flow of fluid from the delivery injector into the cylinder. This ensures that sufficient fuel is drawn into the cylinder to sustain the subsequent combustion event in the cylinder.
Depending on the timing of the opening of the delivery injector and hence the level of the pressure differential across the open delivery injector, sufficient air may be drawn from upstream of the delivery injector to still provide a desirable level of atomisation and entrainment of the fuel. That is, air may be drawn through the failed air compressor or the air supply means, and through the delivery injector to assist with the delivery of the metered quantity of fuel into the cylinder in the normal manner. This may of course depend on the type of failure or leak upstream of the delivery injector, however, measures may be adapted to ensure that air is able to be drawn through the delivery injector under such situations. For example, air may be drawn from another cylinder of the engine whose delivery injector is also controlled to be open.
Conveniently, the fuel may be delivered to the delivery injector during the period when the injector is opened. This may, for example, be the preferred timing at relatively low loads of the engine. However, as the load increases, and the fuel delivery requirements increase, the fuel delivery to the delivery injector may commence before the injector opens and continue while the injector is opened. In certain circumstances, all of the fuel may of course be metered into the delivery injector prior to the opening thereof. These alternatives ensure that a sufficient amount of fuel is delivered to the engine cylinder for different operating conditions. A fuel injector or other fuel metering means such as a positive displacement pump means may be used to supply fuel to the delivery injector.
The fuel metering means may deliver the fuel at a pressure sufficient to deliver the fuel through the delivering injector when open directly to the cylinder.
The operation of the delivery injector(s) and/or fuel injector or fuel metering means may be controlled by an Electronic Control Unit (ECU). Engine control systems utilising such ECUs are described in standard texts such as “The Motor Vehicle, twelfth edition (1996)” by K. Newton, W. Steeds and T. K. Garret and published by the Society of Automotive Engineers. Therefore, as the use of ECUs in engine control systems is well known to persons skilled in this art, the ECU will not be described herein in any detail.
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Arent Fox Kintner & Plotkin & Kahn, PLLC
Obital Engine Company (Australia) Pty Limited
Solis Erick
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