Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2002-02-07
2004-08-10
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S216006, C310S254100, C310S06700R, C310S156460, C310S0400MM, C360S098070
Reexamination Certificate
active
06774520
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technique which can be preferably used for a thin inner rotor motor for rotatably driving a medium which is used in a floppy disk driving device or the like, for example.
2. Description of the Prior Art
A disk device such as a floppy disk device has been popularly used in an office computer, a word processor and the like in addition to a personal computer and the application of the disk device has been spreading. This type of disk device is constituted as shown in
FIG. 10
, for example.
To explain the general construction of the disk device based on the drawing, in the drawing, numeral
101
indicates a chassis having a spindle center
102
as the center of rotation of a disk. The chassis
101
is housed in the inside of an equipment housing (not shown in the drawing) of a personal computer or the like, for example, and is formed in a bottomed box having a housing space which opens at a front side and an upper side as the entire configuration. A disk cartridge
103
faces the housing space.
A stepping motor
124
for feeding a head carriage and a head carriage which is arranged to be reciprocated in the back and forth direction by the stepping motor
124
are mounted on a rear end of the chassis
101
. A first head
130
for reading recorded information on a disk is held at a distal end of the head carriage, while a head arm
132
having a second head
131
which corresponds to the first head
130
is tiltably mounted on a rear upper end of the head carriage by way of a resilient body. The head arm
132
is biased in the direction that the second head
131
approaches the first head
130
. This type of disk device is further provided with a cartridge holder
136
for holding the disk cartridge
103
such that the disk cartridge
103
can be inserted and removed and a mechanism for opening and closing a shutter of the disk cartridge
103
.
Here, as this type of disk device, to cope with the recent requirement for thin configuration of the disk drive, a disk device which is provided with an inner rotor motor shown in FIG.
11
A and
FIG. 11B
as a motor for rotating a disk has been adopted.
This inner rotor motor is constituted of a stator
164
which includes an annular yoke
161
extending in the circumferential direction and a large number of cores
163
which are radially mounted on an inner peripheral surface of the yoke
161
and around which coils
162
are wound, and a rotor
166
which is rotatably arranged in an inner periphery of the stator
164
and having an annular magnet
165
which faces the cores
163
in an opposed manner. Further, in the drawing, numeral
168
indicates a circuit board on which a holding portion
170
which incorporates a bearing
169
therein is mounted, and numeral
171
indicates a rotary shaft for fixing rotor which is rotatably supported on the holding portion
170
on the circuit board
168
by way of the bearing
169
and has an axis extending in the vertical direction. Here, the rotor
166
of the inner rotor motor functions as a turn table which has a magnet for chucking disk (not shown in the drawing) and a rotary lever for chucking disk (not shown in the drawing).
With respect to the stator
164
for this type of inner rotor motor, the yoke
161
and the cores
163
are arranged to surround substantially the entire periphery of the rotor
166
except for a position where the heads
130
,
131
move. To satisfy the required magnetic characteristics to these elements, they are formed of silicon steel which is costly compared to galvanized steel plate which constitutes the chassis
101
and the like.
However, with respect to this type of disk device, there has been a continuing demand for the reduction of the manufacturing cost. Further, the demand for making the device small-sized and light-weighted has been still strong.
Accordingly, the inventors of the present invention consider that there has been a demand for the reduction of areas of the yoke
161
and the cores
163
made of the expensive silicon steel with respect to the stator
164
for the inner rotor motor.
However, when the areas of the yoke
161
and the cores
163
are reduced to meet the abovementioned requirement, the magnetic interaction with respect to the rotor
166
becomes non-uniform in the circumferential direction so that there exists a possibility that the operational stability of the disk cannot be ensured.
Further, with respect to the inner rotor motor which is driven with three phases, for example, it is demanded to establish a state in which the coils which correspond to respective phases uniformly act on the rotor.
SUMMARY OF THE INVENTION
The present invention has been made in view of the abovementioned circumstances and has been provided to achieve following objects.
(a) Reduction of manufacturing cost
(b) Making device small-sized and light-weighted
(c) Maintenance of stability of rotation of motor
(d) Enhancement of operational stability of disk device
To achieve the abovementioned objects, the present invention provides an inner rotor motor comprising a rotor which includes a plurality of magnetic poles arranged circumferentially and a stator which is positioned outside a circumference of the rotor, has a stator core which includes a plurality of magnetic pole teeth which face the rotor in an opposed manner and arranges coils on respective magnetic pole teeth, wherein pitches of the magnetic pole teeth in the rotor circumferential direction along which respective rotor facing surfaces of the magnetic pole teeth are arranged are set smaller than pitches of the rotor in the rotor circumferential direction along which the magnetic poles of the rotor are arranged.
In the present invention, it is desirable that the pitches of the rotor in the rotor circumferential direction along which the magnetic poles of the rotor are arranged are preferably set 1.5 times greater than the pitches of the magnetic pole teeth in the rotor circumferential direction along which respective rotor facing surfaces are arranged.
The stator of the present invention is preferably arranged within 180° with respect to a center angle of the rotor.
In the present invention, six magnetic pole teeth are preferably provided.
A disk device according to the present invention is provided with the abovementioned inner rotor motor.
According to the present invention, the pitches of the magnetic pole teeth in the rotor circumferential direction along which respective rotor facing surfaces of the magnetic pole teeth are arranged are set smaller than the pitches of the rotor in the rotor circumferential direction along which the magnetic poles of the rotor are arranged. Accordingly, compared to a case in which the magnetic pole teeth are provided with the pitches which are equal to or greater than the pitches of the magnetic poles of the rotor, the area of the magnetic pole teeth can be reduced and, at the same time, the area of portions which connect the magnetic pole teeth, that is, a yoke, can be reduced whereby the stator can be miniaturized and, at the same time, winding portions of the coils can be miniaturized thus leading to the reduction of the manufacturing cost. In other words, since the angular density of the arrangement of magnetic pole teeth with respect to the center angle of the center of rotation of the rotor can be set larger than the angular density of the arrangement of magnetic poles of the rotor, the size of the whole stator can be reduced while ensuring a fixed number of magnetic pole teeth of the stator.
Further, the coils of the present invention include U phase coils to which a first driving current is supplied, V phase coils to which a second driving current having a phase advanced by 120° compared to the first driving current is supplied and W phase coils to which a third driving current which has a phase advanced by 120° compared to the second driving current is supplied, and respective coils are arranged in the order of the U phase, the W phase and the V phase. Accordingly, th
Alps Electric Co. ,Ltd.
Comas Yahveh
Mullins Burton S.
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