Internal-combustion engines – Two-cycle – Pump and cylinder adjacent
Patent
1996-09-20
1998-07-28
Okonsky, David A.
Internal-combustion engines
Two-cycle
Pump and cylinder adjacent
123560, F02B 3306
Patent
active
057850151
DESCRIPTION:
BRIEF SUMMARY
The present invention is related to a special system of direct fuel-injection with pneumatic assistance, suitable for internal combustion engines, mainly those provided with spark ignition.
Direct fuel-injection into the combustion chamber of spark ignition engine provides improvements which hardly can be obtained with an external carburetted mixture: lets state some examples:
The suppression of the short-circuiting of the air/fuel mixture during scavenging in two stroke engines.
The suppression of the fuel short-circuiting, distinctive for four stroke engines with high valve overlap.
The stratification of the air/fuel mixture within the combustion chamber in order to improve combustion, specially with lean mixture.
The regulation of the engine load only by altering the injected fuel flow rate, which permits to eliminate the throttling of the inlet and therefore pumping losses, distinctive for four stroke engines.
The conjunction of the above mentioned points provides an increase of the engine efficiency and the reduction of exhaust emissions mainly at part load.
In this context the direct fuel injection requires an accurate injection timing and a high fuel atomization, which makes this system more complex than the one of external vaporization of fuel.
One knows several types of direct fuel-injection suitable for two stroke engines, in particular:
In case of a pneumatic assistance, the compressed air needed can be delivered by an auxiliary compressor supplying injectors which are placed directly on the cylinder head, on top of each combustion chamber and which inject the fuel with a certain quantity of compressed air in order to promote the mixing and the atomization of said fuel.
An example of this system is described in "K. Schlunke--The Orbital Combustion Process Engine--10th Vienna Motor Symposium--VDI n 122, p. 63-78".
According to the publication SAE - 941 687, a mechanism allows to capture a small quantity of air from the compression stroke in the combustion chamber and restitues it for the pneumatic assistance during fuel injection. opening and the closing of the injectors which are under electronic control.
According to the documents EP 296969 and U.S. Pat. No. 4,244,255, a tapping of the crankcase-pump of a two stroke engine allows to send one part of the intake air towards the cylinder head via a controlled popped valve; the fuel is provided by an external injector placed before the valve. In this case, the injection timing is determined by the timing of the valve.
The purpose of the invention is to provide a system of air-assisted direct fuel-injection, which by means of a conventional carburettor forms an air-fuel mixture with the air of pneumatic assistance, requiring neither a controled valve, nor an electronic control for injection into the combustion chamber.
According to the invention, this objective is achieved in an engine including a single-piston compressor which is associated to each combustion chamber and sucks an air-fuel mixture and, by its discharge stroke, injects the mixture directly into said chamber at a precise moment determined by the timing of said compressor. This mixture is added to the air sucked by the chamber. The peculiarity of this invention is that the discharge valve of the compressor is placed inside the combustion chamber. The invention offers the following improvements:
Simplicity of setting or implementation, at a low cost thanks to the possibility to adapt directly the commonly used fuel management devices for external vaporization (i.e. carburettor, mechanical or electronic injection): those will be placed at the inlet of the auxiliary compressors, while the engine inlet will remain independent and only air-feeded.
Wide range of injection timing, allowing to achieve a better charge-stratification for any working condition.
High speed potential of the engine (for example 12,000 t/min), as to the fact that the mixing of the fuel is independent of the injection time and that the compressor valves are valves which autorize high opening and closing frequences.
Hi
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Philippe Benoit
Philippe Luc
Miller James W.
Okonsky David A.
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