Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-08-18
2001-03-27
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S06700R, C310S051000, C360S099040
Reexamination Certificate
active
06208050
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to thin motors, and more particularly, to thin type motors for driving data storage media, such as floppy disks.
BACKGROUND OF THE INVENTION
There is a current demand to manufacture as compact as possible disk drives and other devices for driving data storage media, and accordingly, there is a corresponding demand to manufacture as compact as possible the motors used to drive the media in such devices. In some applications, it is also desirable that such motors be as thin as possible.
Conventional motors used for driving storage media, such as floppy disks, typically employ a pair of ball bearing assemblies aligned with each other in the direction of the rotational axis of the motor to ensure stable operation of the motor. In order to reduce the height or thickness of a motor, i.e., the dimension of the motor in its axial direction, certain prior art motors have employed only a single ball bearing assembly. However, in these types of motors, additional measures have been required to ensure stable operation. Otherwise, because only a single ball bearing is employed, the motor would vibrate, wobble and/or wave the media during rotation, and in turn cause errors in recording and reproducing data on the media.
Japanese laid-open patent application number Hei6-202186 (Publication No. Hei 8-63872) shows a prior art approach for stabilizing the rotation of a motor, wherein the magnetic centers of the stator and driving magnet of the motor are offset relative to each other in the axial direction of the motor. This offset applies a magnetic bias to the ball bearing which is intended to eliminate or reduce any looseness in the bearing and, in turn, stabilize rotation of the motor. One problem associated with this approach in relatively thin motors is that the axial thicknesses of the stator and driving magnet are relatively small, and therefore the magnetic bias applied to the ball bearing is insufficient to stabilize rotation of the motor. The motor of this Japanese laid-open patent application employs an oil-impregnated bearing in addition to the single ball bearing. The oil-impregnated bearing is formed of a ring-like metal member which is impregnated with oil and seated between the rotatable shaft and a stationary member of the motor
Another thin type motor having a thickness of several millimeters and employing an oil-impregnated bearing is illustrated in FIG.
1
. The motor of
FIG. 1
is essentially the same as that illustrated in FIG. 6 of co-pending U.S. patent application Ser. No. 09/114,007, which is assigned to the Assignee of the present invention, and is hereby expressly incorporated by reference as part of the present disclosure. The motor of
FIG. 1
includes a cover plate
2
extending over an opening formed in a stationary member
1
, such as a chassis of a device for driving a floppy disk. A rotor hub
6
is formed integral with an upper end portion of a rotatably-mounted shaft
3
. A rotor yoke
8
is formed of a magnetic material, such as a ferrous material, and is fixedly fitted by means of coupling member
7
around a peripheral portion of the rotor hub
6
.
The rotor yoke
8
is composed of a substantially plate-like base
8
a
and a depending or bent-down section
8
b.
The base
8
a
defines an opening
9
, and the bent-down section
8
b
is formed integral with the base and projects downwardly from a peripheral end portion of the base. The coupling member
7
is fitted within the opening
9
of the base
8
a.
A chucking magnet
10
is attached to an upper face of the base
8
a
around the periphery of the opening
9
. The chucking magnet
10
serves to attract a metal portion
11
on the backside of a floppy disk, as shown in broken lines in
FIG. 1
, to secure the floppy disk on the rotor.
As also shown in
FIG. 1
, a primary drive magnet
15
is fitted within the bent-down section
8
b
of the rotor yoke
8
via an insertion member
14
. A stator
16
is arranged under the rotor yoke
8
so as to oppose the main magnet
15
with a predetermined space or gap therebetween. The -stator
16
is formed with a plurality of teeth
16
a
of a core (only one tooth is shown in the Figure), and an electromagnetic coil
16
b
is wound around each of the teeth.
A ring-like, oil-impregnated bearing
18
is fitted around a lower peripheral portion of the shaft
3
, and a ring-shaped bearing holder
19
is fixedly coupled or connected with the stationary member
1
and arranged outside of the oil-impregnated bearing. Also, an opening
20
is formed through the center of the bearing holder
19
, and a circular projection or upright section
21
extends around the periphery of the opening. The oil-impregnated bearing
18
is fixedly fitted within the opening
20
of the circular projection
21
so that an outer peripheral face of the oil-impregnated bearing
18
slides around an inner peripheral face of the circular projection
21
.
As further shown in
FIG. 1
, an elevated section
22
is formed on a radially outward upper peripheral surface of the bearing holder
19
. The stator
16
is supported in such a manner that an inner peripheral portion of the core of the stator is fitted to the elevated section
22
. An inner race
24
a
of a ball bearing
24
is fixedly fitted to the outside of the circular projection
21
of the bearing holder
19
to thereby support the ball bearing on the bearing holder. An outer race
24
b
of the ball bearing
24
, on the other hand, is fixedly fitted onto an inner peripheral wall
7
a
of the coupling member
7
.
In this type of construction, the shaft
3
rotates with the rotor hub
6
, the coupling member
7
, the rotor yoke
8
, the oil-impregnated bearing
18
, and the outer race
24
b.
The inner race
24
a
of the ball bearing
24
, on the other hand, is not rotated, but rather is fixedly secured to the bearing holder
19
. Thus, the outer peripheral surface of the oil-impregnated bearing
18
slides around the inner peripheral surface of the circular projection
21
of the bearing holder
19
.
The relatively thin motor shown in
FIG. 1
is an outer rotor type motor wherein the rotor extends radially outward beyond the stator
16
, and the primary drive magnet
15
is located outside of the stator. The rotor has a radius, i.e. the distance from the center of rotation to the outer periphery of the rotor, which is more than twice as large as the thickness of the motor in the axial direction. As described above, the thickness of the motor is reduced by the use of a single ball bearing
24
. In addition to the single ball bearing
24
, the oil-impregnated bearing
18
is provided to reduce vibration of the rotor, which is composed of the rotor hub
6
and the rotor yoke
8
, during its rotation.
One drawback associated with this type of bearing structure arises from the bearing holder
19
being mounted between the oil-impregnated bearing
18
and the ball bearing
24
. When the finishing accuracy on the inner and/or outer peripheral surfaces of the circular projection
21
is inadequate, and particularly when the finishing accuracy of the portions of these surfaces which contact the oil-impregnated bearing
18
and/or the ball bearing
24
is inadequate, rotational irregularity may be caused in the motor which can, in turn, significantly affect or reduce the rotational characteristics of the motor.
In addition, relatively complicated processing must be applied to the bearing holder
19
in order to manufacture the bearing holder as shown. As a result, a relatively hard material cannot be used to form the bearing holder. These factors further enhance the difficulties associated with increasing the life of the oil-impregnated bearing
18
.
Another drawback associated with bearing structures of this type, is that the bearing holder
19
mounted between the oil-impregnated bearing
18
and the bearing
24
makes it difficult to reduce the dimension of the motor in its radial direction.
Accordingly, a primary object of the present invention is to provide a bearing structure which allows t
Fujii Yoshio
Yamada Yosuke
Cummings & Lockwood
Dinh Le Dang
Nidec Corporation
Ramirez Nestor
LandOfFree
Motor and bearing structure for motor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Motor and bearing structure for motor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Motor and bearing structure for motor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2549417