U.S. patent application number 10/445917 was filed with the patent office on 2004-10-07 for brushless dc motor with a reduced thickness.
This patent application is currently assigned to Sunonwealth Electric Machine Industry Co., Ltd.. Invention is credited to Hong, Ching-Sheng, Horng, Alex, Horng, Yin-Rong.
Application Number | 20040196832 10/445917 |
Document ID | / |
Family ID | 34066598 |
Filed Date | 2004-10-07 |
United States Patent
Application |
20040196832 |
Kind Code |
A1 |
Horng, Alex ; et
al. |
October 7, 2004 |
BRUSHLESS DC MOTOR WITH A REDUCED THICKNESS
Abstract
A brushless DC motor includes a pole plate, a magnetic pole
base, a coil assembly, a circuit board, and a rotor. Each of the
pole plate and the magnetic pole base is formed by punching a
magnetically conductive plate and includes several pole faces and a
magnetically conductive tube, with the respective pole faces being
annularly located around the respective magnetically conductive
tube. The magnetically conductive tube of the magnetic pole plate
and the magnetically conductive tube of the pole base are securely
mounted one around the other to form an axle tube. At least one
bearing is received in the axle tube for rotatably holding a shaft
of the rotor. The pole faces of the magnetic pole base and the pole
faces of the pole plate are alternately disposed and located around
the axle tube.
Inventors: |
Horng, Alex; (Kaohsiung,
TW) ; Horng, Yin-Rong; (Kaohsiung, TW) ; Hong,
Ching-Sheng; (Kaohsiung, TW) |
Correspondence
Address: |
BACON & THOMAS, PLLC
625 SLATERS LANE
FOURTH FLOOR
ALEXANDRIA
VA
22314
|
Assignee: |
Sunonwealth Electric Machine
Industry Co., Ltd.
Kaohsiung
TW
|
Family ID: |
34066598 |
Appl. No.: |
10/445917 |
Filed: |
May 28, 2003 |
Current U.S.
Class: |
370/352 |
Current CPC
Class: |
H02K 1/145 20130101;
H02K 21/227 20130101 |
Class at
Publication: |
370/352 |
International
Class: |
H02K 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 4, 2003 |
TW |
92107959 |
Claims
1. A brushless DC motor comprising: a pole plate formed by means of
punching a magnetically conductive plate made of a single metal
sheet, the pole plate including a plurality of pole faces and a
magnetically conductive tube, the pole faces of the pole plate
being annularly located around the magnetically conductive tube of
the pole plate; a magnetic pole base formed by means of punching
another magnetically conductive plate made of a single metal sheet,
the magnetic pole base including a plurality of pole faces and a
magnetically conductive tube, the pole faces of the magnetic pole
base being annularly located around the magnetically conductive
tube of the magnetic pole base; a coil assembly directly mounted on
the magnetic pole base and situated in a space between the pole
plate and the magnetic pole base; a circuit board also mounted on
the magnetic pole base; a rotor including a shaft and a permanent
magnet; a holder ring mounted around the shaft of the rotor; the
magnetically conductive tube of the magnetic pole plate being
received in the magnetically conductive tube of the pole base to
form an axle tube, at least one bearing being received in the axle
tube for rotatably holding the shaft of the rotor such that said
holder ring is sandwiched between an end face of the magnetically
conductive tube of the magnetic pole base and an end face of the
bearing; and the pole faces of the magnetic pole base and the pole
faces of the pole plate being alternately disposed and located
around the axle tube.
2. The brushless DC motor as claimed in claim 1, wherein the pole
faces of the magnetic pole base are located around the magnetically
conductive tube of the magnetic pole base and spaced at intervals,
and wherein the pole faces of the pole plate are located around the
magnetically conductive tube of the pole plate and spaced at
intervals.
3. The brushless DC motor as claimed in claim 1, wherein each said
pole face has a cut-out on a top end thereof.
4. (Canceled)
5. The brushless DC motor as claimed in claims 1, further including
a support mounted to an inner periphery of the magnetically
conductive tube of the magnetic pole base for rotatably supporting
a distal end of the shaft of the motor.
6. The brushless DC motor as claimed in claim 5, wherein the
support includes an annular wall for restraining a position of the
distal end of the shaft the rotor.
7. The brushless DC motor as claimed in claim 1, wherein the
magnetically conductive tube of the pole plate extends toward the
rotor, the magnetically conductive tube of the pole plate being
mounted around the magnetically conductive tube of the magnetic
pole base, thereby reducing a gap between an upper end of the axle
tube and an inner periphery of the rotor.
8. The brushless DC motor as claimed in claim 1, wherein the
circuit board further includes an extension on which a sensor is
mounted, the sensor being located below the permanent magnet of the
rotor.
9. The brushless DC motor as claimed in claim 8, wherein the
magnetic pole base includes an opening for receiving the
sensor.
10. The brushless DC motor as claimed in claim 1, wherein the
magnetic pole base includes a slot, the circuit board including a
wire and a sensor attached to the wire, the wire extending along
the slot, the sensor being located below the permanent magnet of
the rotor.
11. The brushless DC motor as claimed in claim 10, wherein the
magnetic pole base includes a plurality of openings that are formed
as a result of punching the magnetic pole base for forming the pole
faces of the magnetic pole base, and wherein the sensor is located
in one of the openings.
12. The brushless DC motor as claimed in claim 1, wherein the
circuit board is mounted to an underside of the magnetic pole
base.
13. The brushless DC motor as claimed in claim 1, wherein the
magnetic pole base includes a plurality of fixing portions for
mounting the magnetic pole base.
14. The brushless DC motor as claimed in claim 13, wherein each of
the fixing portions is a lug projecting radially outward from a
periphery of the magnetic pole base and a hole in the lug.
15. The brushless DC motor as claimed in claim 13, wherein each of
the fixing portions is a hole defined in the magnetic pole
base.
16. The brushless DC motor as claimed in claim 1, wherein the
magnetically conductive tube of the pole plate is located in a
center of the pole plate.
17. The brushless DC motor as claimed in claim 1, wherein the
magnetically conductive tube of the magnetic pole base is located
in a center of the magnetic pole base.
18. The brushless DC motor as claimed in claim 1, wherein said
circuit board is situated in the space between the magnetic pole
base and the pole plate.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a brushless DC motor with a
reduced thickness.
[0003] 2. Description of Related Art
[0004] FIG. 9 of the drawings illustrates a conventional brushless
DC motor with an axial winding. The brushless DC motor includes an
upper pole plate 10a, a lower pole plate 10a, a coil assembly 20, a
rotor 30, a circuit board 40, a metal axle tube 50, and a base 60.
The upper and lower pole plates 10a are mounted to two sides of a
bobbin 21 of the coil assembly 20 to form a stator. The stator and
the circuit board 40 are mounted around the metal axle tube 50 and
thus stacked on the base 60. The rotor 30 includes a shaft 31
extended through the metal axle tube 50. A change in the polarities
of a plurality of magnetic pole faces 101 on the pole plates 10a
drives the rotor 30 to turn. Although such a brushless DC motor is
widely used in various kinds of electronic devices, there are too
many parts for the stator (including the coil assembly 20, the
bobbin 21, the circuit board 40, the metal axle tube 50, and the
upper and lower pole plates 10a). The parts of the stator are
stacked on the base 60 and thus increase an overall thickness and
overall volume of the brushless DC motor. As a result, it is
difficult to further reduce the overall thickness and volume of the
brushless DC motor.
OBJECTS OF THE INVENTION
[0005] The object of the present invention is to provide a
brushless DC motor including a magnetic pole base and a pole plate
that are respectively formed by means of punching a magnetically
conductive plate. Each of the magnetic pole base and the pole plate
includes a plurality of pole faces and a magnetically conductive
tube. The magnetic pole base can be used as a base on which the
parts of the stator are mounted, thereby reducing the number of
parts of the brushless DC motor, simplifying the structure of the
brushless DC motor, and reducing the manufacture cost of the
brushless DC motor.
[0006] Another object of the present invention is to provide a
brushless DC motor in which the magnetic pole base can be used as a
base for mounting a coil assembly and a circuit board of a stator,
thereby reducing the thickness of the stator in the axial
direction. The overall thickness of the motor is reduced
accordingly.
[0007] A further object of the present invention is to provide a
brushless DC motor, wherein no positioning means of fixing means is
required for the pole plate and the magnetic pole base. The pole
plate and the magnetic pole base can be assembled together by two
magnetically conductive tubes respectively formed on the pole plate
and the magnetic pole base. The convenience and stability of
assembly are increased.
SUMMARY OF THE INVENTION
[0008] To achieve the aforementioned objects, the present invention
provides a brushless DC motor including a pole plate formed by
means of punching a magnetically conductive plate, a magnetic pole
base formed by means of punching another magnetically conductive
plate, a coil assembly mounted on the magnetic pole base, a circuit
board mounted on the magnetic pole base, and a rotor.
[0009] The pole plate includes a plurality of pole faces and a
magnetically conductive tube. The pole faces of the pole plate are
annularly located around the magnetically conductive tube of the
pole plate. The magnetic pole base includes a plurality of pole
faces and a magnetically conductive tube. The pole faces of the
magnetic pole base are annularly located around the magnetically
conductive tube of the magnetic pole base.
[0010] The magnetically conductive tube of the magnetic pole plate
and the magnetically conductive tube of the pole base are securely
mounted one around the other to form an axle tube. At least one
bearing is received in the axle tube for rotatably holding the
shaft of the rotor. The pole faces of the magnetic pole base and
the pole faces of the pole plate are alternately disposed and
located around the axle tube.
[0011] Other objects, advantages and novel features of this
invention will become more apparent from the following detailed
description when taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is an exploded perspective view of a first embodiment
of a brushless DC motor in accordance with the present
invention;
[0013] FIG. 2 is a sectional view of the brushless DC motor in FIG.
1;
[0014] FIG. 3 is an exploded perspective view of a second
embodiment of a brushless DC motor in accordance with the present
invention;
[0015] FIG. 4 is a sectional view of the brushless DC motor in FIG.
3;
[0016] FIG. 5 is an exploded perspective view of a third embodiment
of a brushless DC motor in accordance with the present
invention;
[0017] FIG. 6 is a sectional view of the brushless DC motor in FIG.
5;
[0018] FIG. 7 is an exploded perspective view of a fourth
embodiment of a brushless DC motor in accordance with the present
invention;
[0019] FIG. 8 is a sectional view of the brushless DC motor in FIG.
7; and
[0020] FIG. 9 is an exploded perspective view of a conventional
brushless DC motor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Preferred embodiments of the present invention are now to be
described hereinafter in detail, in which the same reference
numerals are used in the preferred embodiments for the same parts
as those in the prior art to avoid redundant description.
[0022] Referring to FIGS. 1 and 2, a first embodiment of a
brushless DC motor in accordance with the present invention
comprises a magnetic pole base 10 and a pole plate 10' that are
respectively preferably formed by means of punching a magnetically
conductive plate. The magnetic pole base 10 can be used as a base
for mounting a coil assembly 20 and a circuit board 40 of a stator.
Preferably, the magnetic pole base 10 is punched to form a
plurality of pole faces 11, a magnetically conductive tube 12, a
plurality of fixing portions 13, and an opening 14. The pole plate
11' is punched to form a plurality of pole faces 11' and a
magnetically conductive plate 12'. Preferably, the pole faces 11
are located around the magnetically conductive tube 12 of the
magnetic base 10 and spaced at intervals. Similarly, the pole faces
11' are located around the magnetically conductive tube 12' of the
pole plate 10' and spaced at intervals. Further, the pole faces 11
and 11' are alternately disposed and adjacent to the coil assembly
20.
[0023] The magnetically conductive tube 12 is formed by means of
punching a central area of the magnetic pole base 10, and the
magnetically conductive tube 12' is formed by means of punching a
central area of the pole plate 10', with the magnetically
conductive tube 12 of the magnetic pole base 10 and the
magnetically conductive tube 12' of the pole plate 10' being
securely mounted one around the other, thereby securing the
magnetic pole base 10 and the pole plate 10' together. Thus, the
magnetically conductive tube 12 of the magnetic pole base 10 and
the magnetically conductive tube 12' of the pole plate 10' together
form an axle tube for receiving at least one bearing 121 (a
self-lubricating bearing or ball bearing) and a support 122. The
bearing 121 not only rotatably holds a shaft 31 of a rotor 30 but
also increases the strength of the magnetically conductive tube 12
of the magnetic pole base 10 and the magnetically conductive tube
12' of the pole plate 10' after assembly. A distal end of the shaft
31 of the rotor 30 is supported by the support 122, best shown in
FIG. 2.
[0024] In this embodiment, each fixing portion 13 is a lug
projecting radially outward from a periphery of the magnetic pole
base 10 and has a hole 130 through which a fastener 131 is
extended, thereby fixing the magnetic pole base to a casing of a
heat-dissipating fan or an inner side of an electronic device such
as a notebook type computer. The circuit board 40 includes an
extension 41 on which a sensor 42 is mounted. The sensor 42 is
located in the opening 14 and adjacent to a permanent magnet 32 on
the rotor 30 to thereby detect a change in the polarity of the
permanent magnet 32.
[0025] Further, a top end of each pole face 11, 11' may include a
notch 111, 111' of an appropriate shape for creating non-uniform
alternating magnetic fields when the power is turned on, thereby
allowing easy starting of the rotor 30.
[0026] FIGS. 3 and 4 illustrate a second embodiment of the
brushless DC motor that is modified from the first embodiment. In
this embodiment, the circuit board 40 is mounted to an underside of
the magnetic pole base 10 (the base), providing a better
heat-dissipating effect for the circuit board 40. No central hole
is required for the circuit board 40 (c.f. FIG. 1). allowing more
electronic elements to be mounted on the circuit board 40. Further,
the length of the magnetically conductive tube 12 of the magnetic
pole base 10 is reduced, and the magnetically conductive tube 12 of
the magnetic pole base 10 is securely engaged to an inner periphery
of the magnetically conductive tube 12' of the pole plate 10'. A
holder ring 311 is sandwiched between an end face of the
magnetically conductive tube 12 of the magnetic pole base 10 and an
end face of the bearing 121. The holder ring 311 is mounted around
a reduced section 33 of the distal end of the shaft 31 of the rotor
30, thereby restraining the position the distal end of the shaft 31
of the rotor 30. A support 122 is mounted in the magnetically
conductive tube 12 of the magnetic pole base 10 for supporting the
distal end of the shaft 31 of the rotor 30. The support 122 is
engaged to the inner periphery of the magnetically conductive tube
12 of the magnetic pole base 10 for increasing the strength of the
magnetically conductive tube 12 of the magnetic pole base 10 and
the magnetically conductive tube 12' of the pole plate 10' after
assembly. The assembling stability of the magnetically conductive
tube 12 of the magnetic pole base 10 and the magnetically
conductive tube 12' of the pole plate 10' is thus improved.
Further, the fixing portions (now designated by 13') in this
embodiment are a plurality of holes defined in the magnetic pole
base 10 (the base), allowing the brushless DC motor to be mounted
to an appropriate position.
[0027] FIGS. 5 and 6 illustrate a third embodiment of the brushless
DC motor in accordance with the present invention. In this
embodiment, the magnetically conductive tube (now designated by
12') of the pole plate 10' extends upward toward the rotor 30 and
has a length smaller than that of the first embodiment and that of
the second embodiment. The magnetically conductive tube 12' of the
pole plate 10' is mounted to an outer periphery of the magnetically
conductive tube 12 of the magnetic pole base 10, thereby reducing
the gap between an upper end of the magnetically conductive tube 12
of the magnetic pole base 10 and an inner periphery of the rotor 30
and reducing the gap between an upper end of the magnetically
conductive tube 12' of the pole plate 10' and the inner periphery
of the rotor 30. This prevents the shaft 31 of the rotor 30 from
being stuck as a result of entrance of dust into the bearing 121.
The life of the brushless DC motor is prolonged accordingly.
Further, a support 122' is securely mounted to an inner periphery
of the magnetically conductive tube 12. A holder ring 311 that
rotatably holds a reduced section 33 of the distal end of the shaft
31 of the rotor 30 is sandwiched between an end face of the support
122' and an end face of the bearing 121, thereby restraining the
position the shaft 31 of the rotor 30. Preferably, the support 122'
includes an annular wall 123' for further restraining the position
of the distal end of the shaft 31 of the rotor 30.
[0028] FIGS. 7 and 8 illustrate a fourth embodiment of the
brushless DC motor in accordance with the present invention,
wherein a slot 15 is formed in the magnetic pole base 10 by means
of punching for receiving a wire 43 that connects a sensor 42 to
the circuit board 40. The sensor 42 is directly mounted in one of a
plurality of openings 120 that are formed as a result of punching
the magnetic pole base 10 for forming the pole faces 11. The
circuit board 40 of this embodiment has no extension (c.f. FIGS. 1,
3, and 5) and thus has a relatively smaller area. This also reduces
the risk of increasing the overall thickness of the brushless DC
motor as a result of stacking the circuit board 40 and the coil
assembly 20 in the axial direction. Further, the turns of the coil
assembly 20 can be increased to thereby increase the intensity of
the alternating energizing of the stator.
[0029] In conclusion, the present invention provides a brushless DC
motor including a magnetic pole base 10 and a pole plate 10' that
are respectively formed by means of punching a magnetically
conductive plate. Each of the magnetic pole base 10 and the pole
plate 10' includes a plurality of pole faces 11, 11' and a
magnetically conductive tube 12, 12'. The magnetic pole base 10 can
be used as a base on which the parts of the stator are mounted,
thereby reducing the number of parts of the brushless DC motor,
simplifying the structure of the brushless DC motor, and reducing
the manufacture cost of the brushless DC motor.
[0030] While the principles of this invention have been disclosed
in connection with specific embodiments, it should be understood by
those skilled in the art that these descriptions are not intended
to limit the scope of the invention, and that any modification and
variation without departing the spirit of the invention is intended
to be covered by the scope of this invention defined only by the
appended claims.
* * * * *