Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-01-07
2002-05-28
Tamai, Karl (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S06700R, C310S156210, C310S156260, C068S023700
Reexamination Certificate
active
06396177
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a structure of a rotor for an outer rotor type brushless motor (BLDC), and in particular to a structure of a rotor for an outer rotor type brushless motor (BLDC) which can improve structural stiffness, restrict noise generation by reducing vibration during the rotation, efficiently cool a heat generated in the motor, decrease a fabrication cost and improve durability.
2. Description of the Background Art
As illustrated in
FIG. 1
, a general outer rotor type brushless motor (BLDC) includes: a stator
100
where a coil is wound round a magnetic core
10
; a resin frame
220
in a predetermined shape fabricated with a resin by using a die; a rotor
200
positioned outside the stator
100
in order to be alternately rotated in the right and left directions; and a sensor unit
300
connected to the stator
100
, detecting a position of a permanent magnet
210
of the rotated rotor
200
. and sequentially transmitting a current to the stator
100
.
A driving shaft
400
is inserted into a center portion of the rotor
200
.
The structure of the rotor
200
will now be described in more detail.
As depicted in
FIGS. 2
a
and
2
b
, in the conventional outer rotor type brushless motor, the resin frame
220
forming an outer shape of the rotor
200
is formed having a predetermined height, a permanent magnet supporting unit
222
connected with the permanent magnet
210
being vertically curved and extended in an upward direction, and curved toward the center portion, at the outer circumferential portion to a disc-shaped base unit
221
.
A ring-shaped deposition groove
223
having a predetermined height and width is formed at the inner wail of the permanent magnet supporting unit
222
. A ring-shaped back yoke
230
having a predetermined width is inserted into the deposition groove
223
. The plurality of permanent magnets
210
are stacked and adhered to the inner side portion of the back yoke
230
at predetermined intervals in a circumference direction.
The back yoke
230
is fabricated by rolling a thin steel plate. and serves to form a magnetic circuit of the permanent magnet
210
. The back yoke
230
and the permanent magnet
210
are formed in a single body by a thermoplastic resin.
On the other hand, a boss unit
224
having a predetermined height is formed at the center portion of the base unit
221
. A through hole
224
a
is formed at the center portion of the boss unit
224
. A serration unit
225
having a plurality of triangle-shaped teeth is formed at the inner circumferential surface of the through hole
224
a.
A shaft serration unit
401
formed at the outer circumferential surface of the driving shaft
400
is inserted into the serration unit
225
of the resin frame
220
, and thus the resin frame
220
and the driving shaft
400
are combined. A spacer
410
is inserted into the lower portion of the shaft serration unit
401
inserted into the serration unit
225
of the resin frame
220
. A nut
420
is fastened to a lower portion of the spacer
410
, namely an end portion of the driving shaft
400
.
On the other hand, a radiation fan blade
226
and a radiation hole
227
are provided on the bottom surface of the base unit
221
in order to cool a heat which is always generated during the rotation of the rotor
200
by means of an external air inflow.
As shown in
FIG. 2
b
, a plurality of radiation blades
226
are formed in the base unit
221
in a radial shape centering around the boss unit
224
. The plurality of radiation blades
226
have a predetermined thickness and width, and are formed in a vertical direction from the boss unit
224
to the permanent magnetic supporting unit
222
.
In addition, a plurality of radiation holes
227
are formed in the base unit
221
at predetermined intervals in a circumferential direction. The plurality of radiation holes
227
are positioned to form a concentric circle, and cross the radiation blades
226
.
In the above-described rotor
200
, the permanent magnets
210
are positioned having a predetermined space from the stator
100
. The driving shaft
400
connected to the resin frame
220
is fixedly connected to other constitutional elements.
In the conventional outer rotor type brushless motor, when a current sequentially flows to the coil
20
wound round the stator
100
, the rotor
200
is rotated according to interaction between the current flowing in the coil
20
and the permanent magnet
210
. The rotation force of the rotor
200
is transmitted to other constitutional elements through the driving shaft
400
.
For example, in case the outer rotor type brushless motor adapts to a washing machine, the stator
100
is deposited in an outer casing including an inner casing, the driving shaft
400
is connected to the inner casing of the washing machine, and thus the driving force of the rotor can be transmitted to the devices such as the washing machine through the driving shaft
400
.
During the rotation of the rotor
200
, the air flows into the motor by the radiation fan blades
226
and the radiation holes
227
, thereby cooling the heat generated in the motor.
However, while rotated by the interaction force with the current applied to the winding coil of the stator, as depicted in
FIGS. 3
a
and
3
b
, the rotor for the conventional outer rotor type brushless motor is vibrated in a shaft direction and a radius direction.
The vibration is generated because the resin frame connected with the permanent magnet consists of the resin, and thus stiffness of the material is weak (approximately 15% of the steel plate). Especially, the vibration of the resin frame resulting from the vibration in the radius direction increases noise.
Moreover, since the frame consists of the resin, the serration unit of the frame connected to the driving shaft transmitting the driving force generated from the rotor is easily abraded under the operational conditions of high temperature, high torque and impact load, and thus a life span thereof is reduced.
In addition, the radiation fan blades for cooling the inside of the motor with the external air are formed in a vertical direction. Therefore, when the rotor is rotated in one direction, an amount of the air which flows into the motor and is discharged therefrom is increased. As the thermal conductivity of the resin is low, radiation is not efficient.
Furthermore, the frame consisting of the resin is very weak to a fatigue destruction resulting from a repeated stress generated by alternation of the washing machine. Accordingly, the radiation holes must be formed small. However, the small radiation holes cannot sufficiently perform a cooling operation. As a result, when the cooling operation is ill-performed, a resistance of the coil is increased, motor efficiency is reduced, a temperature of the coil is more increased, and thus the coil may be easily damaged. Consequently, an expensive coil of high quality must be used.
The resin frame consists of the resin, and thus a price thereof is relatively high. Also, it is necessary to separately fabricate and connect the back yoke in order to form the magnetic circuit, which results in increased production and assembly costs.
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention to provide a structure of a rotor for a brushless motor (BLDC) which can improve structural stiffness, reduce noise by restricting generation of vibration, use cheap materials, reduce a fabrication cost by forming a back yoke and a base plate unit in a single body, and improve durability.
It is another object of the present invention to provide a structure of a rotor for a brushless motor (BLDC) which can efficiently cool a heat generated in a motor during the operation by promoting inflow of an external air.
In order to achieve the above-described objects of the present invention, there is provided a structure of a rotor for an outer rotor type brushless motor (BLDC), including: a steel plate frame provided with a base plate unit in a disc shap
Hong Sang Wook
Park Jin Soo
Rew Ho Seon
Shin Hyoun Jeong
LG Electronics Inc.
Ostrolenk, Faber, Gerg & Soffen, LLP
Tamai Karl
LandOfFree
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