Note: Descriptions are shown in the official language in which they were submitted.
CA 02327492 2010-02-01
Description
Title
= Magnetically Suspended Flywheel System
Technical Field
= This invention relates to flywheel systems, more particularly to a
magnetic flywheel system.
Background Art
= There are many instances where it would be desirable to be able to use a
magnetic force in order to suspend a flywheel for a low-friction
operation.
= A number of patents disclose flywheel systems having active magnetic
suspension systems, or superconducting magnetic bearings comprising
low-temperature superconductors or high-temperature superconductors using
Meissner effect, in order to circumvent Earnshaw's Theorem and to
levitate a flywheel with static stability.
= Canadian Patent 2 190 298 discloses "Magnetically Levitated Axleless
Wheel System". This prior art has a magnetically levitated wheel made of
permanent magnets, but it does not have a flywheel for kinetic energy
storage.
= U.S. Patent 4 382 245 discloses "Levitation device", or Levitron (Trade
Mark). This prior art has a dish-shaped permanent magnet in one form with
an upper surface of a first polarity and a lower surface of a second
polarity disposed in co-axial relationship to a second magnet having the
opposite polar relationships.
= U.S. Patent 5 495 221 discloses "Dynamically stable magnetic
suspension/bearing system". This prior art contains magnetic subsystems
which act together to support a rotating element in a state of dynamic
equilibrium.
= U.S. Patent 5 760 506 discloses "Flywheels for energy storage". This
prior art has a bearing assembly including a bulk high temperature
superconductive magnet that provides lateral stability to the flywheel.
= These prior art arrangements do not have a passive magnetic suspension
system which operates at room temperature, and uses permanent magnets to
form a cone-shaped well in a toroidal magnetic field.
Description of the Invention
= It is a primary object of the invention to provide a flywheel system
which has a passive magnetic suspension system.
= It is another object of the invention to provide a flywheel system which
operates at room temperature.
= It is another object of the invention to provide a flywheel system which
uses permanent magnets in order to form a cone-shaped well in a toroidal
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CA 02327492 2010-02-01
magnetic field.
= A magnetically suspended flywheel system comprises a housing, a stator
assembly, and a rotor assembly. The stator assembly comprises a
ring-shaped stator magnet having a substantially triangular cross
section. The rotor assembly comprises a vertical shaft, a cone-shaped
rotor magnet having a substantially triangular cross section, and a
flywheel. The ring-shaped stator magnet has the same sense of
magnetisation as the cone-shaped rotor magnet. The ring-shaped stator
magnet forms inverse heart-shaped magnetic flux lines, and the
cone-shaped rotor magnet forms heart-shaped magnetic flux lines. An
upward magnetic repulsion force between the inverse heart-shaped magnetic
flux lines of the ring-shaped stator magnet and the heart-shaped magnetic
flux lines of the cone-shaped rotor magnet equals a downward
gravitational force by the rotor assembly in order to passively suspend
the rotor assembly so that the rotor assembly is capable of rotating
around the central axis of rotation.
Brief Description of the Figures in the Drawings
= In drawings which illustrate embodiments of the invention:
o Figure 1 marked "Prior Art" is a sectional side view of a
conventional magnetically suspended flywheel system;
o Figure 2 marked "Prior Art" is a sectional top view of a
conventional magnetically suspended flywheel system;
o Figure 3 marked "Prior Art" is a schematic diagram of a conventional
magnetically suspended flywheel system;
o Figure 4 is a sectional side view of one embodiment of a
magnetically suspended flywheel system according to the invention;
o Figure 5 is a sectional top view of one embodiment of a magnetically
suspended flywheel system according to the invention;
o Figure 6 is a schematic diagram of one embodiment of a magnetically
suspended flywheel system according to the invention;
o Figure 7 is a sectional side view of another embodiment of a
magnetically suspended flywheel system according to the invention;
o Figure 8 is a sectional top view of another embodiment of a
magnetically suspended flywheel system according to the invention;
and
o Figure 9 is a schematic diagram of another embodiment of a
magnetically suspended flywheel system according to the invention.
Modes for Carrying Out the Invention
= One conventional flywheel system shown in Figure 1 in sectional side view
marked "Prior Art" and Figure 2 in sectional top view marked "Prior Art"
comprises a housing 1-0, a stator assembly, and a rotor assembly.
= The stator assembly comprises a ring-shaped stator magnet 1-1, securely
attached to the housing 1-0.
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= The rotor assembly has a central axis of rotation, and is co-axially
placed relative to the stator assembly. The rotor assembly comprises a
vertical shaft 1-2 made of a non-magnetic material, a disc-shaped rotor
magnet 1-3, and a flywheel 1-4 made of a ferromagnetic material such as
iron (Fe), cobalt (Co) or nickel (Ni) so that the rotor assembly can be
set in motion by an external prime mover magnetically coupled to the
flywheel. The vertical shaft 1-2 has a top portion and a bottom portion.
The disc-shaped rotor magnet 1-3 is securely attached to the top portion
of the vertical shaft 1-2. The flywheel 1-4 is securely attached to the
bottom portion of the vertical shaft 1-2.
= The ring-shaped stator magnet 1-1 has the opposite sense of magnetisation
to the disc-shaped rotor magnet 1-3. The ring-shaped stator magnet 1-1
forms magnetic flux lines, and the disc-shaped rotor magnet 1-3 forms
magnetic flux lines. An upward magnetic repulsion force (Fm) between the
magnetic flux lines of the ring-shaped stator magnet 1-1 and the magnetic
flux lines of the disc-shaped rotor magnet 1-3 equal a downward
gravitational force (Fg) by the rotor assembly in order to passively
suspend the rotor assembly so that the rotor assembly is capable of
rotating around the central axis of rotation, as shown in the schematic
diagram of Figure 3 marked "Prior Art".
= Magnetic flux lines flowing in a same direction indicate a stable
pattern, while magnetic flux lines flowing in opposite directions
indicate an unstable pattern. The unstable magnetic flux line patterns at
the air gap between the ring-shaped stator magnet 1-1 and the disc-shaped
rotor magnet 1-3 in Figure 3 provide axial stability and radial
instability. Although the diameter of the ring-shaped stator magnet 1-1
is different from the diameter of the disc-shaped rotor magnet 1-3, an
eddy-current stabiliser 1-5 is required in order to overcome the radial
instability. The gravitational force is used to suppress "tilt" and
"whirl" instabilities.
= In one embodiment of the invention shown in Figure 4 in sectional side
view and Figure 5 in sectional top view, a flywheel system comprises a
housing 2-0, a stator assembly, and a rotor assembly.
= The stator assembly comprises a ring-shaped stator magnet 2-1 having a
substantially triangular cross section, securely attached to the housing
2-0.
= The rotor assembly has a central axis of rotation, and is co-axially
placed relative to the stator assembly. The rotor assembly comprises a
vertical shaft 2-2 made of a non-magnetic material, a cone-shaped rotor
magnet 2-3 having a substantially triangular cross section, and a
flywheel 2-4 made of a non-magnetic material. The vertical shaft 2-2 has
a top portion and a bottom portion. The cone-shaped rotor magnet 2-3 is
securely attached to the top portion of the vertical shaft 2-2. The
flywheel 2-4 is securely attached to the bottom portion of the vertical
shaft 2-2.
= Unlike the conventional flywheel system, the ring-shaped stator magnet
2-1 has the same sense of magnetisation as the cone-shaped rotor magnet
2-3. The ring-shaped stator magnet 2-1 forms inverse heart-shaped
magnetic flux lines, and the cone-shaped rotor magnet 2-3 forms heart-
shaped magnetic flux lines. An upward magnetic repulsion force (Fm)
between the inverse heart-shaped magnetic flux lines of the ring-shaped
stator magnet 2-1 and the heart-shaped magnetic flux lines of the
cone-shaped rotor magnet 2-3 equals a downward gravitational force (Fg)
by the rotor assembly in order to passively suspend the rotor assembly so
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that the rotor assembly is capable of rotating around the central axis of
rotation, as shown in the schematic diagram of Figure 6.
= Magnetic flux lines flowing in a same direction indicate a stable
pattern, while magnetic flux lines flowing in opposite directions
indicate an unstable pattern. The stable magnetic flux line patterns at
the air gap between the ring-shaped stator magnet 2-1 and the cone-shaped
rotor magnet 2-3 in Figure 6 provide axial stability and radial
stability. These stabilities are due to a cone-shaped well in a toroidal
magnetic field, which is formed by a concentrated first magnetic pole and
a distributed second magnetic pole. The stable force field counters any
overturning tendencies of the magnets. The gravitational force is used to
suppress "tilt" and "whirl" instabilities.
= The equilibrium in this configuration is analogous to the Lagrange Points
between gravitational bodies in space.
= Preferably, the ring-shaped stator magnet 2-1 of the stator assembly and
the cone-shaped rotor magnet 2-3 of the rotor assembly are made of
rare-earth permanent magnet, which is an electrical insulator so that
eddy current is not induced during operation.
= The ring-shaped stator magnet 2-1 of the stator assembly may consist of a
plurality of ring-shaped magnets having different diameters,
concentrically stacked together.
= The cone-shaped rotor magnet 2-3 of the rotor assembly may consist of a
plurality of disc-shaped magnets having different diameters,
concentrically stacked together.
= In another embodiment of the invention shown in Figure 7 in sectional
side view and Figure 8 in sectional top view, a flywheel system comprises
a housing 3-0, a stator assembly, and a rotor assembly.
= The stator assembly comprises a cone-shaped stator magnet 3-1 having a
substantially triangular cross section, securely attached to the housing
3-0.
= The rotor assembly has a central axis of rotation, and is co-axially
placed relative to the stator assembly. The rotor assembly comprises a
vertical shaft 3-2 made of a non-magnetic material, a ring-shaped rotor
magnet 3-3 having a substantially triangular cross section, and a
flywheel 3-4 made of a ferromagnetic material such as iron (Fe), cobalt
(Co) or nickel (Ni) so that the rotor assembly can be set in motion by an
external prime mover magnetically coupled to the flywheel. The vertical
shaft 3-2 has a top portion and a bottom portion. The ring-shaped rotor
magnet 3-3 is securely attached to the top portion of the vertical shaft
3-2. The flywheel 3-4 is securely attached to the bottom portion of the
vertical shaft 3-2.
= Unlike the conventional flywheel system, the cone-shaped stator magnet
3-1 has the same sense of magnetisation as the ring-shaped rotor magnet
3-3. The cone-shaped stator magnet 3-1 forms inverse heart-shaped
magnetic flux lines, and the ring-shaped rotor magnet 3-3 forms heart-
shaped magnetic flux lines. An upward magnetic repulsion force (Fm)
between the inverse heart-shaped magnetic flux lines of the cone-shaped
stator magnet 3-1 and the heart-shaped magnetic flux lines of the
ring-shaped rotor magnet 3-3 equals a downward gravitational force (Fg)
by the rotor assembly in order to passively suspend the rotor assembly so
that the rotor assembly is capable of rotating around the central axis of
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rotation, as shown in the schematic diagram of Figure 9.
= Magnetic flux lines flowing in a same direction indicate a stable
pattern, while magnetic flux lines flowing in opposite directions
indicate an unstable pattern. The stable magnetic flux line patterns at
the air gap between the cone-shaped stator magnet 3-1 and the ring-shaped
rotor magnet 3-3 in Figure 9 provide axial stability and radial
stability. These stabilities are due to a cone-shaped well in a toroidal
magnetic field, which is formed by a concentrated first magnetic pole and
a distributed second magnetic pole. The stable force field counters any
overturning tendencies of the magnets. The gravitational force is used to
suppress "tilt" and "whirl" instabilities.
= The equilibrium in this configuration is analogous to the Lagrange Points
between gravitational bodies in space.
= Preferably, the cone-shaped stator magnet 3-1 of the stator assembly and
the ring-shaped rotor magnet 3-3 of the rotor assembly are made of
rare-earth permanent magnet, which is an electrical insulator so that
eddy current is not induced during operation.
= The cone-shaped stator magnet 3-1 of the stator assembly may consist of a
plurality of disc-shaped magnets having different diameters,
concentrically stacked together.
= The ring-shaped rotor magnet 3-3 of the rotor assembly may consist of a
plurality of ring-shaped magnets having different diameters,
concentrically stacked together.
= The housing 2-0 in Figure 4 and the housing 3-0 in Figure 7 may be
hermetically sealed in a partial vacuum in order to reduce air resistance
by rotational movement of the rotor assembly.
= The flywheel system may further comprise a bearing assembly securely
attached to the housing and to the vertical shaft in order to provide
additional stability. The bearing assembly may be placed above the
flywheel or below the flywheel. The bearing assembly may be a magnetic
bearing or a mechanical bearing.
