Internal-combustion engines – Charge forming device – Auxiliary air or gas used to inject fuel
Reexamination Certificate
2000-07-21
2004-01-20
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Charge forming device
Auxiliary air or gas used to inject fuel
C123S534000
Reexamination Certificate
active
06679233
ABSTRACT:
This invention relates to fuel injected internal combustion engines where delivery or air injectors respectively deliver metered quantities of fuel directly into the or each cylinder of the engine by means of compressed gas. In engines comprising such two fluid injection systems, the metered quantities of fuel are delivered into the or each combustion chamber of the engine entrained in the gas, typically air, which is supplied from a pressurized gas source, typically a gas duct or rail.
In most engines, a delay is normally experienced between the initial rotation of the engine and the subsequent firing of the engine. Due to commercial and user considerations, this delay or start-up period is typically desired to be as short as possible under a wide range of conditions. For example, an engine may be employed for operation under ambient and extreme ambient conditions. Efficient engine operation is important no matter the conditions.
In engines having a fuel injection system of the type above described, an important part of achieving a rapid start-up period is the ready availability of compressed gas at an adequate pressure to assure effective fuel delivery as close to start of cranking as possible. However, for cost and other considerations, it is not convenient to provide a relatively large compressed air storage capacity or generation means and, in any event, there is also the risk of loss of pressure due to leakage, particularly when the engine has been inoperative for a period.
Typically, a compressor driven by the engine is provided as the means for supplying compressed gas to a two-fluid fuel injection system as above described. For both reasons of economy and energy efficiency, it is customary to select the compressor capacity to closely match the air consumption rate of the engine during running conditions. Thus, the compressor would typically require a certain period of time to increase the air pressure to a suitable level as required during start-up. That is, the compressor, and thus the engine, must complete a number of cycles before air is available for satisfactory injection of fuel at the required pressure.
The above factors contribute to the lengthening of the period between commencement of the start-up sequence of the engine and the availability of air at the required pressure for injection of fuel. In this regard, the Applicant has developed several methods for minimizing the start-up period in certain engines.
In the Applicant's U.S. Pat. No. 4,936,279, there is described a method of operating an engine during an engine start-up period. The engine includes a gas supply system for supplying gas to the delivery or air injectors. The gas supply system normally includes a gas supply volume, commonly known as an “air rail”, from which pressurized gas is supplied to each of the delivery injectors. Compressed gas for the air rail is normally supplied by a compressor driven by the engine. As alluded to hereinbefore, the compressor must however complete a number of cycles after engine start-up before the compressor can provide sufficient compressed gas to pressurize the air rail to within a working pressure range. The gas within the air rail and as supplied to the delivery injectors needs to be at a high enough pressure to enable the delivery injectors to inject a metered quantity of fuel into cylinders supporting a piston typically undergoing a compression stroke and therefore containing gas under a relatively high pressure. The pressure of the gas must also be sufficient to enable satisfactory atomisation and entrainment of the fuel being injected. The method described in this patent involves effecting one or more “pump-up” events by delivering pressurized gas from respective cylinders of the engine into the gas supply system during the engine start-up period by opening the delivery injector nozzle for each cylinder undergoing a compression stroke of the piston located therein. This results in a progressive increase in the pressure within the gas supply system until the pressure is within the required working pressure range at which time the delivery injectors can begin delivering fuel.
It is further known from the Applicant's subsequent PCT Patent Application No. PCT/AU97/00438 filed on Jul. 10, 1997 that the delivery injector nozzle
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may be opened and closed at successively closer timings to the top dead centre (TDC) position of a piston reciprocating in a cylinder of the engine over a sequence of pump-up events to shorten the start-up period of the engine. This patent application also discusses holding the delivery injector nozzle open for a certain period after the engine has commenced firing to continue pressurising the gas supply system prior to the main source of compressed gas being able to adequately pressurize the gas supply system.
It has however been found that the period required to pressurize the air rail to within the working pressure range during start-up of the engine can still be too long for certain engine applications. For example, in cord or pull start engines as typically used in snowmobiles, small outboard engines and lawn-mowers, the start-up period needs to be relatively short, such that start-up can be achieved within the period prior to full extension of the cord. Because the above methods require a sufficient period of time for the engine to determine its angular position and to subsequently pressurize the air rail by suitable means, these methods may therefore not be applicable for certain cord or pull start engines. More generally, the ever increasing requirement for shorter start-up periods may result in these methods not being able to provide for start-up periods below a certain point.
It is therefore an object of the present invention to provide a method of fuel delivery for a two-fluid fuel injection system wherein the gas provided to enable delivery of a metered quantity of fuel into a cylinder of the engine is derived directly from a different cylinder of the engine.
It is a further preferred object of the present invention to provide a method for enabling the reduction of the duration of the start-up period for an engine incorporating a two-fluid fuel injection system.
With this in mind, the present invention provides in one aspect a method of operating an internal combustion engine, the engine having a plurality of cylinders each respectively supporting a piston therein, a fuel injection system including a plurality of selectively operable delivery injector nozzles, and a gas supply system for supplying gas to the delivery injector nozzles, each delivery injector nozzle arranged to respectively deliver fuel by way of said gas directly into a said engine cylinder, the method including opening the delivery injector nozzles of a first said cylinder and a second said cylinder such that gas within the first said cylinder is transferred through the delivery injector nozzle thereof and into the gas supply system resulting in gas being supplied to the delivery injector nozzle of the second said cylinder to thereby effect the delivery of fuel by way of the gas to the second said cylinder, wherein each second said cylinder into which fuel is delivered is operated to effect combustion of said delivered fuel for each cylinder cycle.
The method according to the present invention may be used during start-up of the engine to facilitate the reduction of the start-up time for the engine. It is however also possible for this method to be used when the engine is operating under alternative conditions. For example, the method could be used to operate the engine under a “limp-home” mode if an air compressor supplying compressed gas to the fuel injection system fails resulting in a loss of pressure within an air rail of the fuel injection system.
The method may be implemented so as to not effect the normal start-up firing sequence of the cylinders, and each delivery injector nozzle and associated cylinder may be operated to effect combustion of a said delivered fuel in the normal manner. That is, the method may be implemented such that e
Dolinar Andrew M.
Orbital Engine Company (Australia) Pty Limited
Rothwell Figg Ernst & Manbeck
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