Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2002-02-07
2004-08-03
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S189000, C310S200000, C310S184000
Reexamination Certificate
active
06770998
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technique suitable for use in a thin-type inner-rotor motor for driving to rotate a media used in, for example, a floppy disk drive and so forth.
2. Description of the Related Art
The floppy disk drive and other disk drives are widely employed in the field from the personal computer to the office computer and the word processor, and so forth, which shows remarkable popularization. This type of disk drive is made up as shown in
FIG. 10
, for example.
This will be outlined on the basis of the drawing. In
FIG. 10
, the symbol
101
signifies a chassis, which possesses a spindle center
102
as the rotational center of a disk, which is housed in, for example, an equipment enclosure (not illustrated) of the personal computer. On the whole, the chassis opens to the front and to the upper, and is formed into a box with the bottom having a space to house a disk cartridge
103
.
The chassis
101
has a stepping motor
124
for feeding a head carriage on the rear thereof, and the stepping motor
124
freely travels the head carriage forward backward. The head carriage holds a first head
130
on the front thereof, which reads information recorded on a disk. On the rear upper of the head carriage is attached a head arm
132
that freely swings through an elastic body, which has a second head
131
corresponding to the first head
130
. The head arm
132
is energized in the direction that the second head
131
approaches to the first head
130
. This type of disk drive is furnished with a cartridge holder
136
that holds the disk cartridge
103
to be freely pulled out, and a mechanism that opens and shuts the shutter of the disk cartridge
103
.
Now, in order to satisfy the demand for a thinner type in recent years, this type of disk drive has been adopting one provided with an inner-rotor motor as illustrated in FIG.
11
A and
FIG. 11B
as the motor for rotating a disk.
The inner-rotor motor is composed of a stator
164
and a rotor
166
. The stator
164
has an annular yoke
161
extending circumferentially, and multiple cores
163
having coils
162
wound, which are provided radially on the inner periphery of the yoke
161
. The rotor
166
has an annular magnet
165
installed to freely rotate on the inside of the stator
164
, which faces to the cores
163
. And, the symbol
168
denotes a circuit board on which is mounted a holder
170
incorporating bearings
169
. The symbol
171
denotes a spindle for fixing the rotor that is pivoted to freely rotate through the bearings
169
on the holder
170
on the circuit board
168
, which has the vertically extending axis. Further, the rotor
166
of this inner-rotor motor functions as a turntable having a disk chucking magnet (not illustrated) and a disk chucking swing lever (not illustrated).
In the stator for this type of inner-rotor motor, the yoke
161
and the cores
163
are placed to surround almost all the circumferences of the round rotor
166
except for the moving range of the heads
130
and
131
. From the requirements of the magnetic characteristics of these, the yoke
161
and the cores
163
are formed of, for example, a silicon steel plate that is expensive in comparison to a galvanized sheet iron to form the chassis
101
and so forth.
However, in this type of disk drive, there has been an unremitting demand for reducing the production cost thereof, and still a strong demand for a smaller size and lighter weight of the drive.
Therefore, the inventor considers that there has been a demand for reducing the area of the yoke
161
and the cores
163
made of the expensive silicon steel plate, in the stator for the inner-rotor motor.
However, when the area of the yoke
161
and the cores
163
is reduced according to the foregoing demand, there has been found a possibility that the magnetic mutual effect to the rotor
166
becomes circumferentially nonuniform and the operational stability of the disk cannot be maintained accordingly.
Further, it is conceivable to divide the cores so as to have three yokes, in order to reduce the area of the cores
163
. In this case, since the yokes each are placed in parallel, the spacings of the fronts each of the yokes become too narrow, and the coil winding cannot be performed, which is a problem.
SUMMARY OF THE INVENTION
The present invention has been made in view of the aforementioned circumstances, and the object of the invention is to achieve the following:
(a) reducing the production cost,
(b) making the drive smaller and lighter,
(c) maintaining the rotational stability of the motor,
(d) enhancing the operational stability of the disk drive,
(e) stepping up miniaturization of the stator.
According to one aspect of the invention, to accomplish the above object, the inner-rotor motor includes a rotor having plural magnetic poles disposed circumferentially, and a stator having a stator core with plural magnetic pole teeth facing to the rotor, located outside a circumference of the rotor, which have coils each wound around thereof.
In this construction, the coils are set such that the numbers of turns of adjacent coils are unequal, and respective sums of the numbers of turns of the coils in respective phases are equal.
In the invention, the windings of the coils may be set such that lengths of adjacent windings of the coils are unequal, and respective sums of the lengths of the windings corresponding to respective phases of the coils are equal.
In the invention, the coils may be placed such that at least one of points at which the extensions of lines connecting base end centers and front end centers of the adjacent coils intersect is positioned on an opposite side to the coils with regard to a rotational center of the rotor.
Further, in the invention, preferably the coils are arranged such that the base end centers of the adjacent coils are each placed with an equal spacing.
Further, in the invention, preferably the stator is placed within a central angel 180° with regard to a rotational center of the rotor.
Further, in the invention, preferably the stator is provided with six of the coils.
The disk drive of the invention may be configured with the aforementioned inner-rotor motor.
According to this invention, the coils of the stator is configured by setting the numbers of turns of adjacent coils to be unequal, and respective sums of the numbers of turns of the coils in respective phases to be equal. Thereby, even when the lengths of the magnetic pole teeth are made unequally because the spacings of the adjacent coils are reduced for miniaturization, the uniformity of drive in respective phases of the coils can be achieved, the decrease of torque can be prevented, and the effective drive and rotational stability of the rotor can be accomplished.
According to this invention, the windings of the coils are made up by setting the lengths of adjacent windings to be unequal, and respective sums of the lengths of the windings corresponding to respective phases of the coils to be equal. Thereby, it is possible to avoid a situation where the coil winding becomes impossible even when the spacings of the adjacent magnetic pole teeth become extremely small, and to achieve miniaturization of the coil portion with a constant thickness of the coils in the coil windings.
Here, the base end center represents the center position of a part where the magnetic pole teeth with the coil formed thereon is connected to the yoke in the circumferential direction of the rotor, and the front end center represents the center position of the rotor facing side of the magnetic pole teeth of the front of the coil in the circumferential direction of the rotor.
The coils according to the invention can be placed such that at least one of the points at which the extensions of the lines connecting the base end centers and front end centers of the adjacent coils intersect is positioned on the opposite side to the coils with regard to the rotational center of the rotor. Thereby, in correspondence with the front end centers of the
Brinks Hofer Gilson & Lione
Mullins Burton S.
Pham Leda
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