Brushless DC motor with a reduced thickness

Details Brushless DC motor with a reduced thickness Brushless DC motor with a reduced thickness

2003-05-28

2004-10-26

Mullins, Burton S. (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S261100, C310S049030, C310S06800R

Reexamination Certificate

active

06809457

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a brushless DC motor with a reduced thickness.
2. Description of Related Art
FIG. 9
of the drawings illustrates a conventional brushless DC motor with an axial winding. The brushless DC motor includes an upper pole plate
10
a
, a lower pole plate
10
a
, 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
10
a
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
10
a
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
10
a
). 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
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.
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.
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
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.
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.
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.
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.


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The American Heritage Dictionary of the English Language, 1992, Houghton Mifflin Company, 3rd edition.

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