Motor vehicles – Including one or more ski-like or runner members – With at least one surface-engaging propulsion element
Reexamination Certificate
1998-02-23
2001-05-08
Boehler, Anne Marie (Department: 3618)
Motor vehicles
Including one or more ski-like or runner members
With at least one surface-engaging propulsion element
C180S186000, C180S309000, C123S0650PE, C123S323000
Reexamination Certificate
active
06227323
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an engine powering a snow vehicle such as a snowmobile and more particularly to an exhaust control system for such an engine.
BACKGROUND OF THE INVENTION
Snow vehicles such as snowmobiles generally ride upon one or more skis and a driven track. The track is driven by one or more drive wheels which are turned by an output shaft of an internal combustion engine.
Two-cycle internal combustion engines are the most common type of engine used to power snowmobiles. These engines have a large power output relative to their size.
As is well known in the art of two-cycle engines, an exhaust timing control valve is provided corresponding to the exhaust port of each combustion chamber or cylinder of the engine. The exhaust timing control valve is of the type which does not ever completely close the exhaust port, but moves between positions in which it partially obscures the port to varying degrees.
Generally, the timing valve is moved to a retracted position in which the valve does not obscure or obscures very little of the port when the engine speed is relatively high. In this manner, the exhaust time is lengthened. On the other hand, when the engine speed is relatively low, the valve is moved to a position in which it obscures a larger portion of the port. This delays the opening of the exhaust port and thus increases the duration of combustion. This permits higher power output with lower emissions.
A problem arises with the use of this type of exhaust timing system when the engine is mounted in a snowmobile or similar snow vehicle. Snowmobiles are often operated on very rough terrain and the intense vibrations which are transmitted through the frame may damage the exhaust timing valve system. In addition, the engine is normally mounted in an enclosed space defined by a shroud of the snowmobile in order to maintain the operating temperature of the engine. The higher temperatures within the shroud may also damage the exhaust timing valve system.
It is, therefore, a principal object of this invention to provide an improved exhaust control system for an engine powering a snowmobile or similar snow vehicle.
SUMMARY OF THE INVENTION
The present invention relates to a snowmobile including a frame having a centerline in a front to rear direction. An engine is supported by the frame, the engine having a body defining at least one combustion chamber and having a crankshaft extending generally perpendicular to the centerline. The crankshaft is arranged to drive a snow-engaging drive member, such as a drive track.
The engine of the snowmobile has an exhaust system including an exhaust passage extending through the body from the combustion chamber and an exhaust pipe leading from the exhaust passage along a first side of the engine and on one side of the centerline. A valve member is movably mounted with respect to the body for controlling the timing of the flow of exhaust through the passage.
A drive mechanism is provided for moving the valve. In accordance with the present invention, this drive includes a motor positioned on an opposite side of the centerline of the snowmobile from the exhaust pipe.
Further objects, features, and advantages of the present invention over the prior art will become apparent from the detailed description of the drawings which follows, when considered with the attached figures.
REFERENCES:
patent: 3795287 (1974-03-01), Rose
patent: 4785626 (1988-11-01), Shiraishi
patent: 4795420 (1989-01-01), Sakurai et al.
patent: 4892164 (1990-01-01), Yasui et al.
patent: 5117932 (1992-06-01), Kurosu
patent: 5152255 (1992-10-01), Fukuda
patent: 5152365 (1992-10-01), Aoshima
patent: 5279381 (1994-01-01), Fukuda
patent: 5934958 (1999-08-01), Ochiai
patent: 5992552 (1999-11-01), Eto
patent: 403281492 (1991-12-01), None
Boehler Anne Marie
Knobbe Martens Olson & Bear LLP
Yamaha Hatsudoki Kabushiki Kaisha
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