Internal-combustion engines – Two-cycle – Whirl through piston-controlled ports
Reexamination Certificate
2000-03-31
2001-08-14
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Two-cycle
Whirl through piston-controlled ports
Reexamination Certificate
active
06273036
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exhaust control valve assembly for an engine, such as a two-cycle engine.
2. Description of the Relevant Art
In accordance with the background art, an exhaust control valve assembly includes an exhaust control valve. The exhaust control valve is opened or closed in order to advance or retard the opening of an exhaust port. A drive system causes opening and closing of the exhaust control valve. Such an arrangement in disclosed, for example, in Japanese Patent Laid-Open Publication No. Sho. 63-306227.
The background art's exhaust control valve assembly suffers drawbacks. When the engine is running at high speed, the actual timing or degree of opening of the exhaust control valve gets ahead of the desired timing or degree of opening. When the actual timing or degree of opening is ahead of the desired timing or degree of opening, the engine's output performance is reduced.
SUMMARY OF THE INVENTION
The present inventors have discovered the source of the drawbacks, and invented a solution to the drawbacks. The present inventors observed that pressure within the exhaust port increases with increases in engine speed. The increased pressure, within the exhaust port, acts on the exhaust control valve, in the opening direction of the exhaust control valve, causing the exhaust control valve to open sooner or more than required.
It is therefore the object of the present invention to provide an exhaust control valve assembly, which increases the output performance of an engine.
It is another object of the present invention to provide an exhaust control valve assembly, which opens the exhaust control valve to a desired timing and degree.
These and other objects of the invention are accomplished by an engine comprising: a cylinder block having a cylinder bore; an exhaust opening at an inner wall of said cylinder bore; an exhaust control valve moveable in an opening direction and a closing direction to at least partially block said exhaust opening, and a governor attached to said exhaust control valve for moving said exhaust control valve in the opening direction in response to an increased engine speed, said governor including a governor spring urging said exhaust control valve in the closing direction, wherein said governor spring has a spring force which changes as said exhaust control valve moves.
Further, these and other objects of the invention are accomplished by an engine comprising: a cylinder block having a cylinder bore; an exhaust opening at an inner wall of said cylinder bore; an exhaust control valve moveable in an opening direction and a closing direction to at least partially block said exhaust opening; and a governor attached to said exhaust control valve for moving said exhaust control valve in the opening direction in response to an increased engine speed, said governor including a first spring and a second spring urging said exhaust control valve in the closing direction, wherein said first and second springs present an overall spring force which changes as said exhaust control valve moves.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 4368703 (1983-01-01), Shibata
patent: 4621596 (1986-11-01), Uchinishi
patent: 4829946 (1989-05-01), Boyesen
patent: 63-306227 (1988-12-01), None
Hara Shigeyuki
Uchida Hiroyuki
Birch & Stewart Kolasch & Birch, LLP
Honda Giken Kogyo Kabushiki Kaisha
Kamen Noah P.
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