Internal-combustion engines – Two-cycle – Rear compression
Patent
1997-10-28
1999-07-13
Kamen, Noah P.
Internal-combustion engines
Two-cycle
Rear compression
123 73A, 123438, F02B 3304
Patent
active
059212080
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a thermodynamic aspirating valve.
More specifically, this invention relates to a thermodynamic aspirating valve for controlling and regulating the flow of fuel to the carburettor and to the crankcase of a two-stroke engine.
This invention can be applied specifically in the mechanical and automotive industry.
BACKGROUND ART
In the two-stroke engines known at present, the piston opens and shuts the aspiration inlet; therefore, the control of the mixture flow is symmetric relative to the two return positions.
The angle between the beginning of the opening of the aspiration inlet and the return position of the piston is equal to the angle between the return position and the end of the closure of the aspiration inlet.
In typical two-stroke engines the full angle of the opening of the aspiration inlet is contained within 100.degree. and 110.degree. of the cam shaft rotation; the half of the angle corresponds to the rotation of the piston in the external direction and the other half corresponds to the return of the piston.
It has been observed that the symmetrical control of the flow of fuel to the crankcase is not a good solution as the aspiration inlet should open much earlier and close later and this is not possible with the traditional piston position.
To avoid this inconvenience a solution has been adopted, according to which circulation of gas is made independent from the piston movements with a rotary throttling valve mounted on the cam shaft.
This valve allows a symmetrical inflow of fuel to the crankcase while it is opened and shut by a rotary plate.
This plate is cut accordingly to the angle corresponding to the angle of the opening of the aspiration inlet and the inflow of fuel to the crankcase is dependent on the size of the aspiration inlet.
Other known solutions allow automatic control of the inflow of fuel by the alteration of pressure in the crankcase.
For this purpose plate valves are applied that consist of springing plates interconnected in parallel.
Due to the pressure within the crankcase, these plates move away proportionally to the depression value which allows the fuel inflow.
When the balance of pressures is achieved the plates shut the aspiration inlet without allowing the fuel to return.
A system of this kind is based on a mode of mechanical control of the inflow of fuel to the crankcase and, in the case where rotary plates are used, the construction of the engine is complicated, which increases costs of production.
Another disadvantage of these systems arises from the fact that their accurate functioning takes place only if the r.p.m. value of the cam shaft rotation is strictly specified, which renders them virtually inapplicable; therefore, such systems practically are not employed in circuit racing engines and rally engines.
In the case where the plate valves are used, proper functioning and capacity of those depend on the materials from which they are manufactured.
Nevertheless, considering the fact that the plates are mounted rigidly, they do not sustain prolonged strain and are deformed and worn out, which causes breakdown that, in turn requires frequent replacements.
Additionally, operation of the plates prohibits, due to internal reactions, the slow inflow of fuel to the degree in which the increasing resistance of the plates does not allow the fuel to inflow when it is most demanded.
The above solutions have other disadvantages, such as unsolved problem of uneconomical fuel consumption and high degree of environmental pollution which are caused by the two-stroke engines.
However, the pollution produced by two-stroke engines is generally caused by faulty fuel supply during the work cycle.
Actually, the combustion chamber is flooded with fuel that cannot be fully consumed, i.e. burnt up, during the only two strokes of the cycle.
Due to the above, the application of two-stroke engines has been significantly reduced lately in spite of their cost-effective construction and economical operation.
U.S. Pat. No. 4,356,798 discloses an aspira
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Benton Jason
Kamen Noah P.
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