Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-03-08
2001-11-13
Waks, Joseph (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S06700R, C384S100000
Reexamination Certificate
active
06316856
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of the Invention
The present invention relates to a motor for rotating a disc-shaped information recording medium in a disk drive apparatus. The present invention further relates to a motor for rotating a magnetic recording medium, such as a floppy disk, in a disk drive apparatus.
B. Related Art
Floppy disk drives (hereinafter abbreviated as FDDs) that are commonly used as computer peripheral equipment use a disk having an unformatted capacity of about 2 MB per disk. In recent years, disk drives are known which are capable of driving a high-capacity floppy disk having a capacity of more than 100 MB per disk which enable a high data transfer rate.
In general, the bearing of a spindle motor for an ordinary FDD that uses only a disk of about 2 MB is a sintered metal oil-retaining bearing (also called simply a metal bearing or an oil-retaining bearing) which is inexpensive. This bearing is formed by compression-molding and then sintering a copper-type or iron-type metal powder, and is a type of sliding bearing that is impregnated with oil as a lubricant.
FIG. 4
is a conceptual diagram of a conventional spindle motor using a ball bearing. The rotor of this motor is arranged as follows.
As shown in
FIG. 4
, a rotor magnet
106
, which is magnetized in such a manner that N poles and S poles are arranged alternately in the circumferential direction, is bonded to a rotor case
105
that is made of a magnetic material, such as galvanized sheet iron SECC. The rotor case
105
is fixed to a boss
103
by caulking, which is made of brass or a brass-like material. The boss
103
is press fit to a shaft
101
, and the shaft
101
is rotatably supported by bearings
107
and
108
. To reliably support and chuck a disk, a disk chucking magnet
104
and a disk chucking pin
115
in the rotor are attached to the rotor case
105
. To improve slidability at the time of disk chucking, a disk hub seating sheet
102
, typically made of ethylene tetrafluoride film, is bonded to the boss
103
with an adhesive.
On the other hand, in the stator of the motor, each iron core
111
formed by laminating magnetic steel sheets, such as silicon steel sheets, is provided with a winding
112
. Stator assemblies formed of a laminated iron core
111
and a winding
112
are fixed to a bearing housing
110
so as to be opposed to the magnet
106
in radial directions. The bearing housing
110
is caulked to a motor base
113
that is made of galvanized sheet iron or similar metal.
In this conventional motor, the motor base
113
is a metal circuit board. In addition, the rotor is driven by supplying electricity to the windings
112
via the wiring on the motor base
113
, a harness and a drive circuit (both the harness and the drive circuit not shown in FIG.
4
).
FIG. 4
illustrates that in this conventional motor, a spacer
109
for determining the bearing position and the bearings
107
and
108
are bonded to the bearing housing
110
. A prop
114
for attaching the motor to a high-capacity FDD is caulked to the motor base
113
. Although this motor has higher axial deviation accuracy than a conventional motor using the sintered metal oil-retaining bearing, this motor is disadvantageous in cost because of the use of the ball bearing (i.e., bearing
108
) which is expensive.
However, the sintered metal oil-retaining bearing cannot be used, in itself, in a high-capacity FDD that is required to have high axial deviation accuracy to cope with a small track pitch. Therefore, a ball bearing (i.e., a rolling bearing) is employed in spindle motors for a high-capacity FDD. Further, it has been found desirable to drive both a lower-capacity FD and a higher-capacity FD with a single drive motor.
OBJECTS AND SUMMARY OF THE INVENTION
Therefore, it is an object of the invention to provide an improved motor for rotating an information recording medium in a disk drive apparatus which avoids the aforementioned deficiencies of the prior art.
It is also an object of this invention to provide an improved motor for rotating a magnetic recording medium, such as a floppy disk, in a disk drive apparatus.
It is another object of this invention to provide an improved motor for rotating an information recording medium in a disk drive apparatus which eliminates use of expensive sintered metal oil retaining bearings.
It is a further object of the present invention to provide a motor for rotating an information recording medium in a disk drive apparatus which can rotate both a higher-capacity information recording medium and a lower-capacity information recording medium at different speeds.
The present invention relates to a motor for rotating a disk-shaped information recording medium which includes a stator; a rotor that rotates with respect to the stator with a shaft as a center of rotation when a drive winding is energized; a disk chucking portion for supporting the disk, which is provided on said rotor; a bearing that is provided on the side of the stator and rotatably supports the shaft of the rotor; a dynamic pressure generation section for generating dynamic pressure by filling a fluid between the bearing and the shaft when the shaft is rotated at a predetermined speed; a judging member for judging whether the disk-shaped information recording medium that is attached to the disk chucking portion is a first type capacity medium or a second type capacity medium; and a control section for supplying the drive winding of the stator with a drive signal for a first rotation speed when a judgment signal produced by the judging member indicates the first type capacity medium, and with a drive signal for a second rotation speed that is higher than the first rotation speed when the judgment signal indicates the second type capacity medium.
With the above configuration, both of a lower-capacity medium for relatively low speed rotation and a medium having a relatively high capacity can be rotated at rotation speeds suitable for the respective media.
In particular, the bearing functions as a sliding bearing in the case of a lower-capacity medium. In the case of a higher-capacity medium, the bearing enables highly accurate rotation by virtue of a dynamic pressure effect that is obtained by the dynamic pressure generation section.
As a further feature of the invention, the dynamic pressure generation section can be formed on a cylindrical inside surface of the bearing that is opposed to an outside circumferential surface of the shaft.
In addition, the dynamic pressure generation section can be formed on an outside circumferential surface of the shaft that is opposed to an inside surface of the bearing.
According to the invention, the judging member detects, through contact, a hole that is provided in a case of the disk-shaped information recording medium, and the control section supplies a drive signal to the drive winding of the stator for the second rotation speed when the judging member detects the hole.
The above, and other objects, features and advantages of the present invention, will become apparent in the following detailed description of a preferred embodiment which is to be read in conjunction with the accompanying drawings, and in which like reference numerals are used to identify the same or similar parts in the several views.
REFERENCES:
patent: 4570093 (1986-02-01), Morii et al.
patent: 5223758 (1993-06-01), Kataoka et al.
patent: 5426548 (1995-06-01), Fujii et al.
patent: 5541460 (1996-07-01), Dunfield et al.
patent: 5623382 (1997-04-01), Moritan et al.
patent: 5678929 (1997-10-01), Parsoneault et al.
patent: 5683183 (1997-11-01), Tanaka et al.
patent: 5847479 (1998-12-01), Wang et al.
patent: 5977676 (1999-11-01), Wijdenes
patent: 5994803 (1999-11-01), Jung
Kimura Toru
Kusaki Kenji
Frommer William S.
Frommer & Lawrence & Haug LLP
Ryan Matthew K.
Sony Corporation
Waks Joseph
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