Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-12-05
2002-11-26
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S085000, C310S091000
Reexamination Certificate
active
06486578
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a motor and a disk unit, more particularly to an inner rotor spindle motor preferred for a super-compact hard disk unit and a disk unit that employs this spindle motor.
2. Description of the Related Art
As hard disk units are getting smaller and smaller in size, it has also been required that their driving systems are reduced in size while their driving powers, as well as their strength and safety, and other properties are improved more and more.
FIG. 11
is a cross sectional view of a configuration of a spindle motor
1
of a conventional 2.5-inch hard disk unit realized to meet such the requirements. A base
2
covering the bottom portion of the spindle motor
1
entirely is formed so that its bottom portion
15
formed under a recording surface of a disk
3
and in parallel to the recording surface and a cylindrical strut portion
4
for holding a hub
5
are unitarily formed.
In a center recessed portion
4
a
formed so as to be surrounded by the strut portion
4
is press-fit a center shaft
6
of the hub
5
with a bearing
7
therebetween, thereby the hub
5
is rotationally held there. The hub
5
, while its outer peripheral wall portion
8
is fit in a center hole
3
a
of each disk
3
, holds three disks
3
via a supporting member
16
respectively.
On the outer peripheral surface of the strut portion
4
are disposed at equal pitches cores
17
and the predetermined number of stator coils
9
wound on the cores
17
. In the inner peripheral surface of the peripheral wall
8
of the hub
5
are disposed fixedly the predetermined number of rotor magnets
10
at equal pitches. The rotor magnets
10
, located closely to the stator coils
9
, face the stator coils
9
respectively.
Numeral
11
denotes a disk holding spring. The spring
11
is fixed to the hub
5
by a flange
12
a
of a stopper screw
12
engaged with a female screw
6
a
formed in the center shaft
6
of the hub
5
. The outer peripheral portion
13
of the disk holding spring
11
is bent towards the disk surface so as to press the extreme inner peripheral portion of each disk
3
. The three disks
3
are thus held between the flange
14
formed at the lower end of the outer peripheral wall portion
8
of the hub
5
and the disk holding spring
11
, so that those disks
3
are rotated unitarily with the hub
5
.
According to the above mentioned configuration, all the magnetic circuits (bearings
7
, cores
17
, stator coils
9
, and rotor magnets
10
) of the spindle motor
1
are all disposed in a space generated by the outer diameter of the hub
5
substantially equal to the diameter of the center hole
3
a
of the disk
3
and the height of the hub
5
, which is decided appropriately to hold the three disks.
Furthermore, according to the above described configuration, an outer rotor spindle motor is formed so that a stator is composed of stator coils
9
and cores
17
and a rotor is composed of the hub
5
and the rotor magnets
10
, and rotor magnets are disposed outside the stator coils. And, the outer peripheral wall portion of the rotor is located inside the inner peripheral portion of the disk and the inner peripheral portion of the disk is in contact with the outer surface of the outer peripheral wall portion of the rotor.
However, if such a hard disk unit is further reduced in size so that, for example, the outer diameter is decided approximately to be 42.08 mm in height, 36.4 mm in width, and 5 mm in thickness while the configuration shown in
FIG. 11
remains the same, there will arise various problems.
Concretely, when the outer diameter of the hard disk unit is reduced, the outer diameter of each disk must also be reduced. And, in order to assure a required storage capacity, that is, a certain area of the storage portion of the disk, the inner diameter of the disk must further be reduced. On the other hand, the outer diameter of the rotor cannot be reduced so much. If the outer diameter of the rotor is reduced, it is impossible to house the stator coils and the bearings in a space inside the rotor. Consequently, if the outer peripheral wall portion of the rotor is positioned inside the inner peripheral portion of the disk, the hard disk unit cannot be reduced in size satisfactorily as described above. Under such circumstances, a spindle motor constructed in accordance with the present, invention, as shown in
FIG. 10
, is not publicly known, and therefore is not the prior art. In this configuration, the inner peripheral portion of each disk is positioned inside the outer peripheral wall portion of the rotor. In addition, both rotor and stator are extended to a portion under the disk.
Concretely, the strut portion
51
for holding the hub
52
is formed unitarily with the base
70
in FIG.
10
. The center shaft
53
of the hub
52
is press-fit in the center hole
71
formed by this strut portion
51
with a bearing
54
therebetween. Consequently, the base
70
comes to hold the hub
52
rotationally.
Furthermore, the hub
52
is provided with a center portion
56
formed so as to cover the tip of the strut portion
51
and used to place a disk
26
thereon; a planar portion
57
extended outwards in the radial direction of the disk from this center portion
56
; and an outer peripheral wall portion
58
extended into the lower portion of this planar portion
57
from the outer peripheral portion. On the outer peripheral surface of the strut portion
51
are disposed the predetermined number of stator coils
60
at equal pitches. Each stator coil is wound on a core
68
. On the inner peripheral coil is wound on a core
68
. On the-inner peripheral surface of the outer peripheral wall portion
58
of the hub
52
are disposed the predetermined number of rotor magnets
61
at equal pitches so as to face the inner peripheral surface closely thereto.
The holding spring
62
of the disk
26
is fixed to the hub
52
by a stopper screw
64
engaged with a female screw formed in the center shaft
53
of the hub
52
. At this time, the extreme outer peripheral portion
63
of the holding spring
62
is bent towards the disk surface so as to press the extreme inner peripheral portion of the disk
26
. The disk
26
is thus held between the center portion
56
of the hub
52
and the holding spring
62
and rotated unitarily with the hub
52
.
At the bottom of the base
70
are formed a through-hole
65
used to pull out a lead wire.
66
and a groove used to guide the lead wire
66
to external, so as to prevent the lead wire
66
from protruding from the bottom. The lead wire
66
is connected electrically to a stator coil.
The outer rotor super-compact spindle motor composed as shown in
FIG. 10
, however, has been confronted with various problems to be described below.
1. The thickness of the planar portion
57
of the hub
52
is limited within about 0.3 mm, so that it is difficult to form the planar portion
57
.
2. The thin planar portion
57
has a large area, so that large surface vibration occurs when the hub
52
rotates.
3. Because rotor magnets are disposed outside the thin planar portion
57
, the hub
52
is weak in shock.
4. It is impossible to increase the thickness of the wall of the strut portion
51
of the base for holding the bearings, the rotor section (the hub
52
and the rotor magnets
61
), the disk
26
, etc., so that the rigidity of the strut portion is not enough.
5. An arm for holding a head moves between the hub and the disk that rotate together. And, a clearance cannot be secured substantially enough between the hub and the disk due to the surface vibration of the hub.
6. Because the lead wire
66
is pulled out from under the base, a groove as described above must be formed unavoidably, so that the strength of the base is lowered.
7. Because the magnetic circuit extends closely under the recording surface of the disk, the planar portion
57
of the hub
52
is also used as a shielding member, thereby the shielding member cannot be formed enough in thickness and its employable mate
Albrecht David W.
Kitahori Hiroki
Bracewell & Patterson L.L.P.
International Business Machines - Corporation
Martin Robert B.
Nguyen Tran
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