Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-11-21
2004-03-09
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S254100
Reexamination Certificate
active
06703738
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to an outer rotor type brushless motor having a rotor rotating outside of a stator.
BACKGROUND OF THE INVENTION
As shown in
FIGS. 12
,
13
A, and
13
B, an outer rotor type brushless motor of the prior art comprises an outer rotor
3
having a plural of permanent magnets
2
fixed onto an inner periphery of a cup-like metal rotor yoke
1
, a stator
7
including a stator core
4
having a plural of magnetic pole portions
4
a
protruded on an outer periphery of an annular portion
4
b
and coils
6
wound on the magnetic pole portions
4
a
of the stator core
4
and faced to the permanent magnets
2
of the outer rotor
3
, respectively, with coil insulation layers
5
provided between the magnetic pole portions
4
a
and the coils
6
, respectively, a cylindrical metal boss
8
′ disposed on an inner periphery of the annular portion
4
b
of the stator core
4
, a rotational shaft
10
extending along an axis of the boss
8
′ and rotationally supported on the boss
8
by a bearing
9
with a leading end of the shaft
10
having a center portion of the rotor yoke
1
fixed thereto, a metal mounting plate
11
fixed onto an outer periphery of the boss
8
′ for attaching the stator
7
on a support body not shown and a circuit board
13
fixed to the mounting plate
11
by screws
12
and having a drive circuit mounted thereon. The annular portions
4
b
of the stator core
4
are fixed to the outer periphery of the boss
8
′ by screws
14
. The mounting plate
11
is fixed to the boss
8
′ by a pressurization enlarged portion
8
′
ak
formed by deforming an annular base
8
′
a
of the boss
8
′ so as to enlarge the diameter thereof after the mounting plate
11
engages the annular base
8
′
a
extending through a hole
15
in the mounting plate
11
.
However, since this prior outer rotor type brushless motor has the stator
7
fixed to the boss
8
′, which is in turn fixed to the mounting plate
11
, the heat of the stator
7
radiates through the metal boss
8
′ from the mounting plate
11
. Thus, there is a problem that the heat radiation efficiency is poor because of the boss
8
′ provided between the stator
7
and the mounting plate
11
.
Furthermore, since the outer rotor type brushless motor has the stator core
4
fixed to the boss
8
′ by the screws
14
which extend through the annular portion
4
b
of the stator core
4
, there tends to be a gap formed between the annular portion
4
b
of the stator core
4
and the boss
8
′. Thus, there is another problem that it is hard to get the accuracy of assembly after the stator core
4
is fixed to the boss
8
′.
Since the step of forming the boss
8
′ is performed separately from the step of forming the coil insulation layers
5
on the magnetic pole portions
4
a
of the stator core
4
, much trouble is taken for manufacturing the motor, which disadvantageously causes the cost for manufacture to be higher.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide an outer rotor type brushless motor adapted to improve the heat radiation characteristic of a stator.
It is another object of the invention to provide an outer rotor brushless motor adapted to be easily assembled while the heat radiation characteristic is improved.
It is further object of the invention to provide an outer rotor type brushless motor adapted to improve the accuracy with which a stator is assembled to a boss while the heat radiation characteristic of the stator is improved.
It is further object of the invention to provide an outer rotor type brushless motor adapted to reduce the cost of manufacture while the accuracy with which a stator is assembled to a boss as well as the heat radiation characteristic of a stator are improved.
The invention is applied to an outer rotor type brushless motor comprising an outer rotor having permanent magnets fixed onto an inner periphery of a cup-like rotor yoke, a stator including a stator core having a plural of magnetic pole portions protruded on an outer periphery of an annular portion of the stator core and faced to the permanent magnets and coils wound on the magnetic pole portions, respectively, a cylindrical boss disposed on an inner periphery of the annular portion of the stator core, a rotational shaft extending along an axis of the boss and rotationally supported on the boss by a bearing with a leading end of the shaft having a center portion of the rotor yoke fixed thereto and a mounting plate fixed onto an outer periphery of the boss.
In the invention, the boss is formed of resin mold and extends through a hole in the mounting plate and fixed thereto. The annular portion of the stator core is fixed to a rising portion of the inner periphery of the mounting plate.
As the annular portion of the stator core is fixed directly to the mounting plate, the heat radiation characteristic of the stator can be improved. As the annular portion of the stator is fixed to the rising portion of the mounting plate, the stator can be fixed without any obstacle such as the coils because of the presence of the rising portion even though the stator is fixed directly to the mounting plate.
In a preferred mode of the invention, the boss may be formed of resin mold, the annular portion of the stator core is molded in and fixed to the outer periphery of the boss and also fixed to the rising portion of the inner periphery of the mounting plate.
As the annular portion of the stator core is fixed directly to the mounting plate, the heat radiation characteristic of the stator can be improved. Also, as the stator core is fixed to the rising portion of the mounting plate, the stator can be fixed without any obstacle such as the coils because of the presence of the rising portion even though the stator is fixed directly to the mounting plate. Furthermore, as the annular portion of the stator core is molded in and fixed to the outer periphery of the boss, there is no gap between the annular portion of the stator core and the boss while the relative position of them is fixed, which improves the accuracy with which the stator is assembled with the boss.
REFERENCES:
patent: 5363003 (1994-11-01), Harada et al.
patent: 5508578 (1996-04-01), Suzuki et al.
patent: 5910693 (1999-06-01), Park
patent: 03-112334 (1991-05-01), None
patent: 08-322222 (1996-12-01), None
patent: 2000-324748 (2000-11-01), None
Mochizuki Katsuhiro
Yoshikawa Rikio
Hanh Nguyen N
Kokusan Denki Co. Ltd.
Pearne & Gordon LLP
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