Internal-combustion engines – Combustion chamber means having fuel injection only – Using multiple injectors or injections
Patent
1993-12-23
1995-08-22
Nelli, Raymond A.
Internal-combustion engines
Combustion chamber means having fuel injection only
Using multiple injectors or injections
F02B 300
Patent
active
054430453
DESCRIPTION:
BRIEF SUMMARY
ART FIELD
The present invention relates to a two-stroke internal combustion engine with direct low pressure electronic fuel injection.
Traditionally, two-stroke internal combustion engines afford highly advantageous characteristics in terms of their simplicity in construction and high power-to-weight ratio. By virtue of the latter feature, two-stroke motor cycle engines are well suited for mounting to lightweight and therefore easily handled frames.
Conversely, one has the very prominent drawback that engines of the type in question constitute a source of considerable pollution, and do not comply with the legal requirements encountered in many countries of the world. Moreover, the directives on environmental pollution destined gradually to be enacted in Europe during the course of the 1990s will be so stringent as effectively to outlaw the two-stroke internal combustion engines currently manufactured as motor cycle propulsion units.
The marked level of environmental pollution produced by conventional two-stroke engines having a carburettor type fuel system is due essentially to the fact that in the typical embodiment of the design, with induction taking place on the down stroke of the piston as fuel-air mixture is forced into the combustion chamber by way of the transfer ports, a not inconsiderable portion of the mixture escapes to the exhaust passage while the relative port is still open, without undergoing combustion.
BACKGROUND ART
One attempt aimed at overcoming this drawback, which envisages the utilization of mechanical fuel injection, is successful in reducing though not in wholly eliminating the escape of fuel-air mixture. The limited success of such a solution is explained principally by the fact that the injection time lapse is relatively long with a mechanical system, so that it will often be necessary to ensure that the injection of the fuel is completed well before the exhaust passage closes. Such a situation can be avoided in some measure though only in engines of small displacement, given that the amount of fuel injected is markedly small and the time required to effect the injection can be made relatively short, albeit using particularly sophisticated and costly injectors. With engines of large displacement, by contrast, or at least larger than the very smallest capacities, the quantities of fuel injected become considerably greater and the injection time lapses especially long.
A further drawback betrayed by conventional two-stroke internal combustion engines is reflected in their particular sensitivity to variations in temperature, pressure and humidity of the ambient air; in situations where these parameters may drift from the operating values under which the engine is rated, the effects are a marked loss of performance (power and torque) and a discernible rise in fuel consumption, resulting in an increased capacity of the engine to pollute the environment.
Accordingly, the object of the invention is to overcome the drawbacks mentioned above through the adoption of a two-stroke internal combustion engine such as can deliver highly respectable performance characteristics, while generating emissions broadly comparable to those from a four-stroke engine and remaining substantially free of the problems which occur in varying ambient conditions, as described above.
A further object of the invention is to provide a two-stroke internal combustion engine capable of achieving fuel consumption up to 60% lower than in a conventional engine of similar rated output.
DISCLOSURE OF THE INVENTION
The stated objects are realized, according to the invention, in a two-stroke internal combustion engine of the type comprising a cylinder exhibiting an internal cavity of substantially cylindrical shape, a reciprocating piston accommodated slidably and coaxially within the cavity, a cylinder head connected to one end of the cylinder, of which the inwardly directed face affords a combustion chamber in communication with the cavity, and at least one spark plug supported by the cylinder head, of which the i
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patent: 4924828 (1990-05-01), Oppenheim
patent: 5140959 (1992-08-01), Durbin
patent: 5271362 (1993-12-01), Kobayashi et al.
Bimota, S.P.A.
Nelli Raymond A.
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