Internal-combustion engines – Charge forming device – Auxiliary air or gas used to inject fuel
Reexamination Certificate
2000-06-09
2002-05-14
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Charge forming device
Auxiliary air or gas used to inject fuel
C123S533000, C123S521000
Reexamination Certificate
active
06386186
ABSTRACT:
The present invention generally relates to fuelling control systems for internal combustion engines, and in particular to fuel vapour handling systems for fuel injection systems. The invention is applicable for use in marine outboard engines, and will in the main, be described in respect of such engines in this application. It should however be appreciated that the present invention is also applicable for engines used in other applications.
Marine outboard engines that are designed to comply with, for example, U.S. Coast Guard regulations, conventionally utilise fuel recirculation under the cowl of the engine. This is primarily because safety regulations prohibit the recirculation of fuel to a fuel tank located outside the engine. It is therefore normally necessary to include under the cowl of the engine a fuel reservoir from which a fuel pump draws fuel and to which excess fuel can be returned. Further, because the fuel being recirculated under the cowl typically becomes heated, in part by the pumping action of the fuel pump, a water cooled heat exchanger is typically required to keep the fuel temperature relatively low thereby minimising the generation of fuel vapour.
Nevertheless, and will be expanded upon, hereinafter, the fuel recirculation process still typically generates some fuel vapour which generally accumulates within the fuel reservoir. This fuel vapour can be handled in numerous different ways and can for example be vented to the inlet manifold of the outboard engine or simply exhausted into the atmosphere. The pumping and subsequent recirculation of fuel also results in a significant waste of power from running the fuel pump. It would therefore be advantageous to avoid the need to recirculate fuel under the cowl of a marine outboard engine and hence avoid certain undesirable requirements that this imposes, namely, the need for a water cooled heat exchanger, vapour separator and other such fuel vapour handing/minimising devices, which may be bulky, heavy and costly items. The resultant waste of power associated with running a fuel pump while fuel is being recirculated would also be advantageously avoided. However, whilst it is desirable to avoid the above aspects, such engines are still required to comprise some form of vapour handling capability, such that any vapour that is generated and present in the fuel system can be satisfactorily handled.
The Applicant has developed various air-assisted fuel injection systems, also known as “dual fluid fuel injection systems”, for use in internal combustion engines. These systems utilise air to entrain and inject a metered quantity of fuel directly into a combustion chamber of an engine. In the Applicant's U.S. Pat. No. 4,934,329, the details of which are incorporated herein by reference, a separate fuel metering injector and delivery injector are provided for each combustion chamber, the fuel injector supplying a metered quantity of fuel to a delivery chamber of the delivery injector. This will be referred to as the Applicant's “electronic fuel injection system” in the present application.
In the Applicant's co-pending International Patent Application No. PCT/AU99/00354, there is also disclosed a dual fluid fuel injection system, the details of which are incorporated herein by reference, in which the need for a separate fuel metering injector is eliminated. This system will be referred to as a “passive fuel injection system” in the present application. In such a system, the opening of the delivery injector generates a differential pressure across a mass flow rate control means which controls the mass flow rate of fuel to the engine.
In regard to these and other fuel systems in general, and as alluded to hereinbefore, it is common for an amount of fuel vapour to be generated during operation of the engine and there are typically a number of particular areas where fuel vapour is commonly generated within such fuel systems. Conventionally, fuel vapour is generated by the increase in the temperature of the fuel and this commonly occurs through heat input from the engine (conduction and convection), heat input from the fuel pump (from electrical and mechanical losses) and the throttling process associated with the conventional process of fuel pressure regulation. There are also a number of other areas where fuel vapour may be generated which would be understood by those skilled in the art. It has however been found in practice that the substantial portion of the fuel vapour is generated downstream of the fuel pump for the above stated reasons. In any event, the generation and accumulation of fuel vapour in most fuel systems is a common phenomenon.
Current exhaust emission standards for certain engine applications necessitate that this fuel vapour be collected and prevented from being emitted into the atmosphere. This has been conventionally achieved by use of air/fuel separators for absorbing and/or dealing with the generated fuel vapour.
It is therefore an object of the present invention to provide an improved means for satisfactorily handling fuel vapour generated within dual fluid fuel injection systems for internal combustion engines.
It is also a preferred object of the present invention to provide a fuelling control system for an internal combustion engine which does not require recirculation of fuel.
With this object in mind, according to one aspect of the present invention, there is provided a fuel vapour handling system for a dual fluid fuel injection system, including:
a fuel supply means, and a gas supply means for respectively supplying fuel and gas to at least one delivery injector of the dual fluid fuel injection system for subsequent delivery thereby, the fuel supply means including a fuel pump;
and a fuel vapour control means providing a fluid communication between the fuel supply means downstream of the fuel pump and the gas supply means to allow fuel vapour present within the fuel supply means to pass to the gas supply means for subsequent delivery by the delivery injector.
Because a substantial portion of the fuel vapour is generated downstream of the fuel pump, it is advantageous for the fuel vapour control means to be located downstream of the fuel pump. Such an arrangement, also allows for fuel vapour control in “dead headed” fuel systems.
The fuel vapour control means preferably allows the pressure of the fuel supplied to the delivery injector to be substantially equalised with the pressure of the gas supplied to delivery injector. This renders the fuel vapour handling system particularly applicable to the Applicants' passive fuel injection system where the pressure of the gas supplied to the injection system is preferably at least substantially balanced with the pressure of the fuel supplied to the injection system. However by throttling or regulating the air pressure downstream of the fuel vapour control means to generate a pressure differential between the fuel pressure and the gas pressure, this particular system can also be applicable to the Applicants' electronic fuel system.
The fuel vapour control means may provide a fuel/gas interface which allows vapour from the fuel supply means to freely migrate into the gas supply means where it can subsequently be injected into an engine to which the fuel injection system is operatively connected. That is, the fuel/gas interface allows the fuel vapour generated within the fuel supply means to be supplied to the delivery injector(s) through the gas supply means. It should be noted that the gas supply means is typically independent of the air induction means for supplying bulk air to the engine for subsequent combustion.
Preferably, the gas supply means is arranged to deliver compressed gas, typically air, to the dual fluid fuel injection system. Because the gas supply means is in fluid communication with the fuel within the vapour control means, the compressed gas pressure may be at least substantially balanced with the fuel pressure in the vapour control means, the fuel pressure thereby being maintained regardless of the fuel leve
Coplin Nicholas
Hill Raymond John
Arent Fox Kintner & Plotkin & Kahn, PLLC
Gimie Mahmoud
Orbital Engine Company (Australia) Pty Limited
Wolfe Willis R.
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