Machine element or mechanism – Elements – Flywheel – motion smoothing-type
Reexamination Certificate
1999-08-05
2001-06-19
Bucci, David A. (Department: 3682)
Machine element or mechanism
Elements
Flywheel, motion smoothing-type
C428S299100, C403S370000, C403S372000
Reexamination Certificate
active
06247382
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to a composite material flywheel device used for temporarily storing energy.
2. Description of the Related Art
The use of flywheel devices as apparatus for temporarily storing energy that is dissipated when transportation facilities, such as motor vehicles or railroad cars, are braked as well as nighttime surplus electric power that occurs in electric power systems is currently a subject under study.
While a large majority of flywheels of the flywheel devices are metallic ones, composite material flywheels made by molding a glass-fiber reinforced plastic, aramid fiber reinforced plastic or carbon-fiber reinforced plastic are also used to cater to the need for high-speed rotation.
A composite material flywheel is described in Japanese Unexamined Patent Publication No. 58-30545, for example, in which the flywheel is of such a construction that an outer part of a rotary shaft mounting portion
2
of a circular disk
1
made of an aluminum alloy thickens toward the outer periphery, a plurality of surfaces that are nearly vertical surfaces of the rotary shaft mounting portion
2
are made to have different inclinations from one another, a ring
4
molded of a high-strength carbon-fiber reinforced plastic is firmly fitted on a cylindrical portion
3
which is formed by the outermost part of the circular disk
1
, and a plurality of radially directed slits
5
are provided in the circular disk
1
and ring
4
, as shown in
FIGS. 6 and 7
.
Also, a flywheel intended for storing energy is described in U.S. Pat. No. 4,569,114, for example, in which the flywheel is of a construction comprising a metallic hub
8
having a plurality of spokes
6
and a ring
7
which are one-piece molded, a glass-fiber reinforced plastic inner ring
9
provided on an outer surface of the metallic hub
8
and a carbon-fiber reinforced plastic outer ring
10
provided on an outer surface of the glass-fiber reinforced plastic inner ring
9
, as shown in FIG.
8
.
With the composite material flywheel in which a high-strength carbon-fiber reinforced plastic ring is firmly fitted on a cylindrical portion of a circular disk and a plurality of radially directed slits are provided in the circular disk and a ring, the ring could oscillate in its axial direction due to bending of the circular disk during high-speed rotation, making it difficult to maintain delicate geometric relationship with surrounding equipment.
Although the composite material flywheel molded of a high-strength carbon-fiber reinforced plastic allows operation at such a high rotating speed that is not achieved with glass-fiber reinforced flywheels or aramid fiber reinforced flywheels, high degrees of stress and strain occur in the interior of the flywheel and the inside diameters of the metallic circular disk and hub increase due to expansion caused by a centrifugal effect, thus creating a gap between the flywheel and its shaft. This could cause such problems as whirling or other instability-related phenomena.
Furthermore, because the ring of the metallic hub is formed of the same metal as the spokes in the aforementioned energy storage flywheel, there arises a problem related to the strength of the ring and there exist limitations in increasing the rotating speed.
SUMMARY OF THE INVENTION
This invention has been made in the light of the aforementioned problems. Accordingly, it is an object of the invention to provide a composite material flywheel which is applicable to high-speed rotation at 1,300 m/sec or above in terms of tangential speed and can alleviate strain due to residual stress and suppress whirling vibrations.
A composite material flywheel according to the invention is constructed by joining a plastic spoke member reinforced with fiber having a modulus of elasticity lower than high-strength carbon fiber to the inside of a high-strength carbon-fiber reinforced plastic ring by press-fitting means. This flywheel is applicable to high-speed rotation at 1300 m/sec or above in terms of tangential speed and can alleviate stress due to initial residual strain.
A composite material flywheel device according to the invention has a composite material flywheel in which a plastic spoke member reinforced with fiber having a modulus of elasticity lower than high-strength carbon fiber is joined to the inside of a high-strength carbon-fiber reinforced plastic ring by press-fitting means, a taper bush fitted into a truncated conical shaft hole formed in a central part of the spoke member of the composite material flywheel, and spring means which forces the taper bush toward the spoke member. As the taper bush is forced into the composite material flywheel by way of the spring means, it becomes possible to absorb looseness which occurs when the rotating speed increases and prevent whirling vibrations, and the service life of the flywheel device is increased.
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“Fiber Composite Materials”, Marks' Standard Handbook for Mechanical Engineers, Tenth Edition, McGraw Hill, pp 6-202-6-203, 1996.*
“Batteries for the 21st Century: Composite Flywheels”, by Charles, E. Bakis, Engieered Materials and Systems, Penn State University, 1998.
Sugahara Noriaki
Umeki Kazunobu
Bucci David A.
Fuji Jukogyo Kabushiki Kaisha
Kim Chong H.
Smith , Gambrell & Russell, LLP
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