Motor vehicles – Special wheel base – Having only two wheels
Reexamination Certificate
1999-10-05
2001-02-20
Boehler, Anne Marie (Department: 3618)
Motor vehicles
Special wheel base
Having only two wheels
C180S309000, C060S323000
Reexamination Certificate
active
06189637
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a horizontally-opposed type engine for a motorcycle, in which a pair of left and right cylinder heads are connected to a pair of left and right cylinder blocks in such a manner that combustion chambers are formed between each of the cylinder blocks containing a plurality of cylinder bores disposed in parallel with the axial lines thereof extending substantially in the horizontal direction and pistons slidably fitted in the cylinder bores; a crank shaft is disposed in such a manner as to be perpendicular to the axial lines of the cylinder bores; and the engine is mounted on the motorcycle with the axial line of the crank shaft extending in the longitudinal direction.
2. Description of Background Prior Art
The horizontally-opposed type engine of this type has been generally configured such that exhaust passages are provided in cylinder heads protruded on the left and right sides of a motorcycle in such a manner as to be simply opened downwardly.
It may be desirable to make a bank angle of a motorcycle at a relatively large value; however, in the horizontally-opposed type engine, since exhaust pipes are connected to the bottom surfaces of cylinder heads protruded on both sides of the motorcycle, the bank angle of the motorcycle is restricted by the presence of the exhaust pipes.
SUMMARY AND OBJECTS OF THE INVENTION
In view of the foregoing, the present invention has been made, and an object of the present invention is to provide a horizontally-opposed type engine, which is capable of reducing the restriction to the bank angle given by the exhaust pipes, thereby easily ensuring the bank angle of the motorcycle.
To achieve the above object, according to the present invention, there is provided a horizontally-opposed type engine for a motorcycle, in which a pair of left and right cylinder heads are connected to a pair of left and right cylinder blocks in such a manner that combustion chambers are formed between each of the cylinder blocks containing a plurality of cylinder bores disposed in parallel with the axial lines thereof extending substantially in the horizontal direction and pistons slidably fitted in the cylinder bores; a crank shaft is disposed in such a manner as to be perpendicular to the axial lines of the cylinder bores; and the engine is mounted on the motorcycle with the axial line of the crank shaft extending in the longitudinal direction, the engine being characterized in that a plurality of exhaust passages for introducing exhaust gas from the combustion chambers are provided in each of the cylinder heads in such a manner as to be tilted toward the central side of the motorcycle in the width direction and to be opened downwardly.
With this configuration, since the exhaust pipes connected to the exhaust passages can be disposed near the center of the motorcycle in the width direction, it is possible to moderate the restriction to the bank angle of the motorcycle given by the exhaust pipes, and to easily ensure the bank angle of the motorcycle.
According to the present invention, in addition to the configuration of the invention described above, exhaust pipes connected to the exhaust passages are disposed in such a manner as to be tilted toward the central side of the motorcycle in the width direction as extending downwardly from each of the cylinder heads. With this configuration, it is possible to further moderate the restriction to the bank angle of the motorcycle given by the exhaust pipes, and to more easily ensure the bank angle of the motorcycle.
According to the present invention, in addition to the configuration of the invention described above, exhaust valves for communicating or cutting-off the exhaust passages to or from the combustion chambers corresponding to the exhaust passages are disposed in each of the cylinder heads over a plane passing through the axial lines of the cylinder bores. With this configuration, it is possible to make relatively large a distance between each of the combustion chambers and the opening end of the associated one of the exhaust passages opened to the bottom surface of the cylinder head, and to make relatively gentle the curving of the exhaust passages within the plane perpendicular to the axial line of the crank shaft although the exhaust passages are opened while being tilted to the central side of the motorcycle in the width direction and hence to suppress the increase in exhaust resistance.
According to the present invention, in addition the configuration of the invention described above, cover portions for covering connection portions of the exhaust passages to the exhaust pipes from outside are integrally formed on head covers connected to the cylinder heads, respectively. With this configuration, it is possible to improve the appearance characteristics of the connecting portions of the exhaust passages to the exhaust pipes. Further, since the exhaust pipes are separated apart from the cover portion as being directed downwardly, even if the head cover is made from a synthetic resin, it is possible to avoid occurrence of thermal degradation of the cover portion.
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: 1131781 (1915-03-01), Hill
patent: 3453824 (1969-07-01), Biesecker
patent: 4545200 (1985-10-01), Oike et al.
patent: 4699232 (1987-10-01), Nebu et al.
patent: 5568726 (1996-10-01), Yamada et al.
patent: 5653303 (1997-08-01), Kawamoto
patent: 5966933 (1999-10-01), Ishihara et al.
Kanbe Takashi
Nakashima Masahiro
Tosaka Tetsuya
Birch & Stewart Kolasch & Birch, LLP
Boehler Anne Marie
Honda Giken Kogyo Kabushiki Kaisha
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