Internal-combustion engines – Charge forming device – Auxiliary air or gas used to inject fuel
Reexamination Certificate
2000-12-06
2002-10-15
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Charge forming device
Auxiliary air or gas used to inject fuel
C123S456000
Reexamination Certificate
active
06463916
ABSTRACT:
The present invention is directed to a fuel injection system for an internal combustion engine. In particular, the present invention is applicable for direct fuel injection into a combustion chamber of an engine and will be described in this application. It is however to be appreciated that the present invention is equally applicable for manifold and other fuel injection applications.
The Applicant is involved in the development of air-assisted fuel injection systems for use in internal combustion engines. As a primary feature, these systems utilise air to entrain and inject a quantity of fuel directly into a combustion chamber of the engine. In one particular system, such as that described in the Applicants' U.S. Pat. No. 4,934,329 , the contents of which are hereby incorporated by reference, a separate fuel injector and delivery valve are provided for each combustion chamber, the fuel injector supplying a metered quantity of fuel to a delivery chamber of the delivery valve. The fuel is then delivered to the combustion chamber by opening the delivery valve so that fuel is entrained and delivered by pressurised gas. Typically, an air compressor supplies the pressurised gas to the delivery chamber.
In a variation of the above system, such as that described in the Applicants' U.S. Pat. No. 5,622,155 , the contents of which are hereby incorporated by reference the pressurised gas is supplied from an air chamber in communication with the delivery chamber. Combustion gases from the combustion chamber are allowed to enter this air chamber by delaying the closing of the delivery valve, the trapped combustion gases being subsequently used for the next fuel injection event. The latter system is particularly applicable in lower cost and small engine applications where reduced complexity is often desirable.
However, the latter system presents a number of challenges in regard to certain applications in that functionality of the fuel system may often be reduced and less accurate fuel metering may be evidenced. Accordingly, an air-assisted fuel injection system which avoids the need for separate fuel injectors and delivery valves for each combustion chamber but which maintains functionality and fuel metering accuracy would be advantageous.
To this end, the Applicant has developed a fuel injection system which eliminates the need for a separate fuel injector for each combustion chamber. This system, which is described in the Applicant's U.S. Pat. Nos. 4,794,902, 4,841,942 and 5,024,202, uses an injection apparatus having a delivery chamber and a delivery valve. Pressurised fuel and pressurised gas are separately supplied to the delivery chamber of the injection apparatus. The pressure differential between the fuel and gas supplied to the chamber is regulated such that the gas pressure is less than the fuel pressure. During the opening of the delivery valve, an associated valve allows the pressurised gas to flow into the delivery chamber, said pressure differential controlling the quantity of fuel delivered during the period of opening of the delivery valve. Nevertheless, whilst this fuel injection system does not require a fuel injector for each combustion chamber, the injection apparatus utilises numerous components to enable the gas flow to be controlled such that the gas only flows when the delivery valve is opened. It is necessary to separate the air and fuel flows until the actual injection event because of the difference in the gas and fuel pressures.
Another air-assisted fuel injection system is described in SAE Paper No. 9,703,62 M Nuti et al, “FAST Injection System: PIAGGIO Solution for VLEV 2T SI Engines”. This system incorporates a piston pump driven by a crankshaft. An air/fuel mixture is provided by a carburettor to the crankcase of the pump. This mixture is then pressurised and transferred to a working chamber. A poppet valve delivers this mixture to the combustion chamber of the engine, the opening pressure of the poppet valve being regulated by a calibrated preloaded spring. Apart from the complexity of this arrangement, another disadvantage of this purely mechanical system is that it is not possible to control the opening and closing times and the period of opening of the poppet valve thus limiting the overall functionality of the system. This limits the applicability of such a system to small engines which can tolerate relatively inaccurate control of the fuelling rate.
It is therefore an object of the present invention to provide a fuel injector assembly, which avoids one or more of the disadvantages referred to above.
With this in mind, according to one aspect of the present invention, there is provided a fuel injector assembly for an internal combustion engine, including:
a delivery chamber located within the injector assembly;
a mass flow rate control means for controlling the mass flow rate of fuel and compressed gas supplied to the delivery chamber, the mass flow rate being a function of a differential pressure across the mass flow rate control means; and
valve means for selectively communicating the delivery chamber to the engine to deliver fuel to the engine;
wherein the assembly is adapted such that in use, when the valve means is opened, at least compressed gas is caused to flow thereby generating a differential pressure across the mass flow rate control means such that a controlled fuel flow is provided to the engine.
According to another aspect of the present invention, there is provided a fuel injector system for an internal combustion engine, including;
at least one fuel injector assembly having a delivery chamber located therein;
a fuel supply means for supplying fuel to the delivery chamber;
a compressed gas supply means for supplying compressed gas to the delivery chamber;
a mass flow rate control means for controlling the mass flow rate of the fuel and the compressed gas supplied to the delivery chamber, the mass flow rate being a function of the differential pressure across the mass flow rate control means; and
valve means for selectively communicating the delivery chamber of the fuel injector assembly to the engine to deliver fuel to the engine,
wherein said system is adapted such that in use, when the valve means is opened, at least compressed gas is caused to flow thereby generating a differential pressure across the mass flow rate control means such that a controlled fuel flow rate is provided to the engine.
The fuel and gas flow rates are a function of the differential pressure across the mass flow rate control means. Furthermore, the amount of fuel delivered to the engine is a function of the differential pressure, the timing of the opening of the valve means and the characteristics of the mass flow rate control means.
A pressure-time fuel metering system is therefore provided. The amount of fuel may be varied by controlling the fuel and gas supply pressures to thereby control the differential pressure. Furthermore, the amount of fuel delivered to the engine may be controlled by varying the period of opening of the valve means, and/or the start and end times of the valve period opening for a given gas and fuel flow rate control means and differential pressure.
The differential pressure is generated by the pressure loss due to the flow of the gas through the mass flow rate control means. This differential pressure then promotes fuel flow through the mass flow rate control means. The differential pressure across the mass flow rate control means may be the difference between the supply pressure of the supplied fuel and the supplied compressed gas and the pressure immediately downstream of the mass flow rate control means. In applications where the fuel injection system is used in direct injection applications, the delivery chamber pressure is affected by cylinder pressure but controlled by losses across the valve means.
The fuel injection system may further include pressure equalising means for at least substantially equalising the supply pressure of the fuel supplied by the fuel supply means and the compressed gas supplied by the compr
Coplin Nicholas
Hill Raymond John
McKay Michael Leonard
Arent Fox Kintner Plotkin & Kahn
Gimie Mahmoud
Orbital Engine Company (Australia) Pty Limited
Wolfe Willis R.
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