U.S. patent application number 10/980871 was filed with the patent office on 2006-05-04 for magnetic suspension bearing with damping system.
Invention is credited to Yu-hsiu Chang, Wei-cheng Chen, Der-ray Huang, Chien-sheng Liu, Pi-cheng Tung, Chien-chang Wang, Ren-bin Xiao.
Application Number | 20060091750 10/980871 |
Document ID | / |
Family ID | 36216041 |
Filed Date | 2006-05-04 |
United States Patent
Application |
20060091750 |
Kind Code |
A1 |
Wang; Chien-chang ; et
al. |
May 4, 2006 |
MAGNETIC SUSPENSION BEARING WITH DAMPING SYSTEM
Abstract
A magnetic suspension bearing with damping system includes a
stator having a stator magnetic unit mounted on the internal
portion of the stator, and a rotor rotatably located at the stator.
A rotor magnetic unit installed on the rotor corresponding to the
stator magnetic. The rotor further has a yoke having a magnetic
driving unit corresponding to the external portion of the stator. A
magnetic damping device located has a magnetic unit and an elastic
unit, wherein the magnetic unit corresponding to the magnetic
driving unit generates magnetic force between them, and the elastic
unit coupled below the magnetic unit uses to reduce the vibration
of the magnetic unit for maintaining the rotation of the rotor
smooth and steady.
Inventors: |
Wang; Chien-chang; (Hsinchu,
TW) ; Tung; Pi-cheng; (Hsinchu, TW) ; Xiao;
Ren-bin; (Hsinchu, TW) ; Chen; Wei-cheng;
(Hsinchu, TW) ; Liu; Chien-sheng; (Hsinchu,
TW) ; Chang; Yu-hsiu; (Hsinchu, TW) ; Huang;
Der-ray; (Hsinchu, TW) |
Correspondence
Address: |
RABIN & BERDO, P.C.
Suite 500
1101 14 Street, N.W.
Washington
DC
20005
US
|
Family ID: |
36216041 |
Appl. No.: |
10/980871 |
Filed: |
November 4, 2004 |
Current U.S.
Class: |
310/90.5 |
Current CPC
Class: |
F16C 39/063 20130101;
F16C 32/0406 20130101; H02K 7/09 20130101 |
Class at
Publication: |
310/090.5 |
International
Class: |
H02K 7/09 20060101
H02K007/09 |
Claims
1. A magnetic suspension bearing with damping system, comprising: a
stator having an internal portion and an external portion, and a
stator magnetic unit mounted on the internal portion of the stator,
the stator magnetic unit being provided at the top side of the
stator, and the stator further including a sub stator magnetic unit
located on the bottom side of the stator; a rotor rotatably located
at the internal portion of the stator, including a rotor magnetic
unit corresponding to the stator magnetic unit and a yoke coupling
with one end of the rotor, and the yoke having a magnetic driving
unit corresponding to the external portion of the stator, the rotor
further having a sub rotor magnetic unit, corresponding to the sub
stator magnetic unit, located on the bottom side of the rotor; and
a magnetic damping device located below the magnetic driving unit
having a magnetic unit and an elastic unit; wherein the magnetic
unit corresponding to the magnetic driving unit to generate
magnetic force between them, and the elastic unit coupled below the
magnetic unit to reduce the vibration of the magnetic unit, wherein
the sub stator magnetic unit and the sub rotor magnetic unit
separately have a magnetic center line, and the magnetic center
line of the sub rotor magnetic unit is lower than the magnetic
center line of the sub stator magnetic unit for generating an axial
prestressing force to the rotor.
2. The magnetic suspension bearing with damping system of claim 1,
wherein the elastic unit is made of rubber material.
3. The magnetic suspension bearing with damping system of claim 1,
further having a loading section located on another end of the
rotor to hold the rotor.
4. The magnetic suspension bearing with damping system of claim 3,
wherein the loading section is a friction pad.
5. The magnetic suspension bearing with damping system of claim 3,
wherein the rotor is in contact with the loading section on a
single point.
6-8. (canceled)
9. The magnetic suspension bearing with damping system of claim 1,
wherein the stator magnetic unit and rotor magnetic unit separately
having a magnetic center line, and the magnetic center line of the
rotor magnetic unit is lower than the magnetic center line of the
stator magnetic unit for generating an axial prestressing force to
the rotor.
10. The magnetic suspension bearing with damping system of claim 1,
further comprising a base dock for holding the magnetic damping
device.
11. A magnetic suspension bearing with damping system, comprising:
a stator, having an internal portion, an external portion, a stator
magnetic unit mounted on the internal portion and being provided at
a top side of the stator, and a sub stator magnetic unit located on
a bottom side of the stator, being coaxial with said stator
magnetic unit, and being separated from said stator magnetic unit
by a distance; a rotatable rotor, having a rotor magnetic unit
corresponding to the stator magnetic unit and being disposed inside
said stator magnetic unit, a sub rotor magnetic unit, corresponding
to the sub stator magnetic unit, located on the bottom side of the
rotor and being disposed inside said sub stator magnetic unit,
being coaxial with said rotor magnetic unit, and being separated
from said rotor magnetic unit by a distance, and a yoke coupling
with one end of the rotor, the yoke having a magnetic driving unit
corresponding to the external portion of the stator; and a magnetic
damping device located below the magnetic driving unit, and having
a magnetic unit and an elastic unit, the magnetic unit
corresponding to the magnetic driving unit to generate a magnetic
force therebetween, the elastic unit being coupled below the
magnetic unit to reduce a vibration of the magnetic unit, wherein
the sub stator magnetic unit and the sub rotor magnetic unit each
separately have a magnetic center line, the magnetic center line of
the sub rotor magnetic unit being lower than the magnetic center
line of the sub stator magnetic unit for generating an axial
prestressing force to the rotor; and wherein the stator magnetic
unit and rotor magnetic unit each separately have a magnetic center
line, the magnetic center line of the rotor magnetic unit being
lower than the magnetic center line of the stator magnetic unit for
generating an axial prestressing force to the rotor.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a magnetic suspension bearing, and
more particularly to a magnetic suspension bearing with damping
system that can greatly reduce the vibration of the rotor, and is
simple and low in cost.
BACKGROUND OF THE INVENTION
[0002] In recent years rapid innovations and developments have
occurred with electronic products. With the continuous advance of
semiconductor manufacturing technologies, electronic products have
become more powerful and their prices have dropped. They are now
widely accepted by the general public. Nowadays there are a wide
variety of electronic products on the market. For the driving motor
bearings used in information storage devices, there are oil
impregnated bearings, ball bearings, and the like. The oil
impregnated bearing has a lower price and thus cost advantage.
However, its service life is shorter. The ball bearing has a longer
service life, but it is more expensive and has a lower capability
to withstand impact. These two types of bearings have their
spindles in contact with the inner walls of the bearings. As a
result, the motor tends to generate vibration and noise, and its
service life becomes lower. On the other hand, dynamic bearings
also are frequently used in the industry. The dynamic bearing is
more precise and has a longer service life. It has become the
mainstream in the market. However, it has starting friction and
wearing problem that has yet to be overcome. Moreover, its
production cost is higher, and production yield still does not
reach the level desired. These issues remain to be resolved. It is
well known that the magnets of the same polarity repel each other.
This property can be used to reduce the wearing when the spindle
rotates. Thus it gradually becomes an important research and
development direction in the industry. Some techniques are known in
the art. For instance, U.S. Pat. Nos. 5,521,448 and 6,448,679 and
so on disclose a technique regarding spindle motor having magnetic
bearing. U.S. Pat. No. 5,521,448 discloses a technique regarding
damping for passive magnetic bearings. It includes a passive
magnetic bearing where the magnets are arranged radially in
concentric rings. The rotating portion of the bearing is fixed to
the shaft while the non-rotating stack is mounted to a fixed
structure through a resilient material so that vibratory loads are
carried in shear. Two sheets may be used, one on each side of the
stationary bearing mount, so that the resilient material can be
preloaded axially. The shear stiffness of the resilient material is
adjusted so that it is low enough to permit the mount material to
be strained enough to absorb a significant amount of energy and
thereby produce system damping.
[0003] U.S. Pat. No. 6,448,679 discloses a type of passive magnetic
support and damping system. It is comprised of a series of disks or
annular rings of permanently magnetized material fixedly attached
to the rotor of the machine. The stator portion is also comprised
of a series of annular rings of permanently magnetized material,
which are positioned concentrically with the rotor magnets. The
stator and rotor magnets are formed and positioned such that a
radial gap is present between said stator magnets and said rotor
magnets. At least one, and preferably an even number, of the stator
magnets are mounted in a damping material, which, in turn, is
fixedly attached to the machine stator. This damping material may
be an elastomeric material in response to shear or compressive
strains. The soft mounted stator magnets provide damping to the
system. The remaining stator magnets are fixedly attached to the
machine stator and provide stiffness. By varying the number, size,
and magnetic strength of the stator magnets mounted in these two
ways, the stiffness and damping of the bearing assembly can be
varied substantially independently.
[0004] However, the foregoing conventional techniques suit to large
scale mechanism. In other words, it is so complex so that difficult
to assemble, and unable apply to the small scale motor which are
widely used in various types of electronic products, especially on
data storage devices.
[0005] Besides, U.S. Pat. Nos. 6,050,785 and 6,097,120 disclose
another type of damping system applied to a ball bearing or a
sleeve bearing. They have a balance plate mounted above the circuit
board corresponding to the magnet of the rotor, for providing a
balancing force to ensure the rotor keeping at the center position
corresponding to the stator. However, above-mentioned conventional
techniques remain unstable. That is to say, the motors such as the
ball bearing or the sleeve bearing are difficult to prevent from
the rotor touching with the stator even with the balancing force
between the balance plate and the magnet of the rotor. Moreover,
the efficiency of the dissipation the vibration energy is limited
because of lack of damper. In short, there are still a lot of
problems in the conventional techniques remained to be
overcome.
SUMMARY OF THE INVENTION
[0006] In view of the aforesaid disadvantages, the primary object
of the invention is to provide a magnetic suspension bearing with
damping system that has capability to reduce the vibration of the
rotor and may be fabricated at a lower cost.
[0007] The magnetic suspension bearing with damping system of the
invention is adopted for use on rotational devices such as
precision motor bearings, precision air fan bearings and the like,
which are widely used in various types of electronic products,
especially on data storage applications.
[0008] The magnetic suspension bearing with damping system
generally consists of a stator, a rotor and a magnetic damping
device. The stator has a stator magnetic unit mounted on the
internal portion of the stator. The rotor located at the internal
portion of the stator includes a rotor magnetic unit corresponding
to the stator magnetic unit. There is a yoke coupled with an one
end of the rotor, and a magnetic driving unit corresponding to the
external portion of the stator mounts on the yoke.
[0009] The magnetic damping device located below the magnetic
driving unit. The magnetic damping device has a magnetic unit and a
elastic unit. The magnetic unit corresponding to the magnetic
driving unit uses to generate magnetic force between them. The
elastic unit coupled below the magnetic unit so reduces greatly the
vibration of the magnetic unit.
[0010] The foregoing, as well as additional objects, features and
advantages of the invention will be more readily apparent from the
following detailed description, which proceeds with reference to
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a sectional view of a first embodiment of the
magnetic suspension bearing with damping system of the
invention.
[0012] FIG. 2 is a schematic view of the invention showing the
magnetic damping device and the magnetic driving unit of the
yoke.
[0013] FIG. 3A through 3C are schematic views of the invention
showing the shape of the magnetic unit of the magnetic damping
device FIG. 4 is a sectional view of the invention showing the
swing phenomenon of the rotor.
[0014] FIG. 5A is a chart showing an experiment result of time
response of a conventional magnetic bearing.
[0015] FIG. 5B is a chart showing an experiment result of time
response of the magnetic suspension bearing with damping system of
the invention.
[0016] FIG. 6A is a chart showing an experiment result of the
frequency response in radial direction of a conventional magnetic
suspension bearing.
[0017] FIG. 6B is a chart showing an experiment result of frequency
response in radial direction of the magnetic suspension bearing
with damping system of the invention.
[0018] FIG. 7 is a sectional view of a second embodiment of the
magnetic suspension bearing with damping system of the
invention.
[0019] FIG. 8 is schematic view of the stator magnetic unit and the
rotor magnetic unit of the second embodiment of the magnetic
suspension bearing with damping system of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] The magnetic suspension bearing of the invention aims at
reducing the vibration of rotor and increase the service life of
the product, and to provide a simple magnetic bearing at a low
coast. Refer to FIG. 1 for a first embodiment of the invention. The
invention includes a stator 10, a rotor 20 and a magnetic damping
device 40. The stator 10 such as the iron core has an internal
portion 12 and an external portion 13, and the rotor 20 may
rotatably locate at the internal portion 12. A loading section 60
such as a friction pad installed on base dock 50 locates at the
bottom end of the rotor 20 to hold the rotor 20, and the rotor 20
is in contact with the loading section 60 on a single point. A yoke
30 couples with a top end of the rotor 20, and the yoke 30 includes
a magnetic driving unit corresponding to the external portion 13 of
the stator 10.
[0021] The stator 10 has a stator magnetic unit 11 mounted on the
internal portion 12. The rotor 20 includes a rotor magnetic unit 21
corresponding to the stator magnetic unit 11. The stator magnetic
unit 11 and the rotor magnetic unit 21 generate repulsive magnetic
force between them to enable the stator 10 and the rotor 20 to
maintain a radial suspension state and space them from one another
at a selected distance in normal conditions. Refer to FIG. 2, the
magnetic damping device 40 installed on the base dock 50 includes a
magnetic unit 41 and an elastic unit 42, wherein the former is made
of permeance material and the latter is made of rubber material.
The magnetic damping device 40 locates below the magnetic driving
unit 31, and further, the magnetic unit 41 corresponds to the
magnetic driving unit 31. The elastic unit 42 is located below the
magnetic 41, in other words, the elastic unit 42 is mounted between
the base dock 50 and the magnetic 41. In addition, refer to FIG. 3A
through 3C, these are shapes of the magnetic damping device 40, the
magnetic damping device 40 can be fabricated at circle type, or
separated into semicircle and quadrant. Refer to FIG. 3B and FIG.
3C, a sensor 80 installs on the space 43 of the magnetic damping
device 40 for detecting the magnetic flux of the magnetic driving
unit 31.
[0022] Please Refer to FIG. 4, the yoke 30 of the rotor 20 receives
the external force and then causes swing. In the meanwhile, the
magnetic unit 41 results in vibration via the magnetic force
between the magnetic driving unit 31 and the magnetic unit 41. The
vibration of the magnetic unit 41 absorbs by the elastic unit 42,
and then moderates the unstable equilibrium of the yoke 31 of the
rotor 20. By using Fast Fourier Transform (FFT) and impulse method,
we obtain experiment results of the time response of the
conventional techniques as FIG. 5A, and experiment results of the
frequency response of the conventional techniques as FIG. 6A. They
indicate that the rotor 20 generates the vibration and related
frequency response when the rotor 20 received the external
force.
[0023] A further research and study indicates that a vibration
damper installed on the product may reduce the vibration of the
rotor 20. Hence the invention has the magnetic unit 41 installed
corresponding to the magnetic driving unit 31 to response the
magnetic force between them, and then utilizes the elastic unit 42
for absorbing the vibration of the magnetic unit 41.
[0024] By using Fast Fourier Transform (FFT) and impulse method, we
obtain experiment results of the time response of the invention as
FIG. 5B, and experiment results of the frequency response of the
invention as FIG. 6B.
[0025] Refer to FIGS. 5B and 6B, the experiment results indicate
that the time response and related frequency response of the
conventional techniques shown in FIGS. 5A and 6A are decreased in
the invention. Namely, the magnetic damping device 40 greatly
reduces the vibration of the rotor 20.
[0026] For further reduce the vibration of the rotor 20, please
refer to FIG. 7 for yet another embodiment of the invention. The
second embodiment of the invention includes a sub stator magnetic
unit 14 located on the bottom side of the stator 10, and the stator
magnetic unit 11 installed on the top side of the stator 10.
Similarly, a sub rotor magnetic unit 22 corresponding to the sub
stator magnetic unit mounts on the bottom side of the rotor 20, and
the rotor magnetic unit 21 installs on the top side of the rotor 20
corresponding to the stator magnetic unit 11. In addition, refer to
FIG. 8, the stator magnetic unit 11 has a magnetic center line B-B'
and the rotor magnetic unit 21 also has a magnetic center line
A-A'. The magnetic center line A-A' is lower than the magnetic
center line B-B' for generating an axial prestressing force to the
rotor 20. Likewise, the sub stator magnetic unit 14 has a magnetic
center line C-C' and the sub rotor magnetic unit 22 also has a
magnetic center line D-D'. The magnetic center line D-D' is lower
than the magnetic center line C-C' for generating an axial
prestressing force to the rotor 20.
[0027] Therefore, the axial prestressing force raises the friction
properly between the rotor 20 and the loading section 60.
Therefore, the axial prestressing force cooperates with the
magnetic force between the magnetic damping device 40 and the
magnetic driving unit 31 to apply the rotor 20 rotate smooth and
steady, and substantially reduces the vibration of the rotor
20.
[0028] By means of the aforesaid constructions, it is clear that
the magnetic suspension bearing with damping system of the
invention can provide the following advantages:
[0029] 1. Preventing generation of vibration and noise: compared
with the conventional techniques that have swing appearance caused
by the external force and then generated vibration and noise, the
invention stabilizes the rotor through the magnetic damping system
and decrease the amplitude of the vibration
[0030] 2. Increasing service life of products: in general the swing
of the rotor caused by the rotor frequently touch with the stator
is the main reason for product damage and shorter service life. The
invention can greatly reduce the vibration and noise, and product
service life extends.
[0031] 3. Effectively reducing cost: conventional techniques often
have complex structures and are difficult to assemble, and result
in increasing production cost. The invention provides a simple
structure to reduce the vibration. Assembly is easy and product
cost can be greatly reduced.
[0032] While the preferred embodiments of the invention have been
set forth for the purpose of disclosure, modifications of the
disclosed embodiments of the invention as well as other embodiments
thereof may occur to those skilled in the art. Accordingly, the
appended claims are intended to cover all embodiments which do not
depart from the spirit and scope of the invention.
* * * * *