Spindle motor and its manufacturing method

Details Spindle motor and its manufacturing method Spindle motor and its manufacturing method

1998-12-01

2001-01-30

Cao, Allen T. (Department: 2754)

Dynamic information storage or retrieval

Dynamic mechanism subsystem

Specific detail of storage medium support or motion production

Reexamination Certificate

active

06181671

ABSTRACT:

TECHNICAL FIELD
The present invention relates to, for example, a spindle motor in a disc apparatus that rotates a disc.
BACKGROUND ART
Due to the increasing recording density of discs, a spindle motor used in a disc apparatus is required to rotate a disc while holding it precisely, and a disc apparatus is requested to further increase its transfer rate. Accordingly, the disc must be rotated at a high speed.
A configuration of a conventional general spindle motor S is described with reference to the side view in FIG.
8
. The spindle motor S comprises a rotor
4
mounted on a fixed portion
10
via a rotating shaft
5
and a turn table
3
(for example, a molding of a synthetic resin) attached to the top of the rotating shaft
5
. The rotor
4
is press-fitted and fixed to the rotating shaft
5
, and the turn table
3
is also press-fitted and fixed to the rotating shaft
5
. In this configuration, a disc
1
is rotated while being sandwiched between the turn table
3
and a clamper
2
.
With reference to the block diagram for rotation control in
FIG. 9
, the control of the spindle motor S in an actual disc apparatus D is described.
A rotation control section
21
drives the spindle motor S using motor driving
22
based on a linear speed instruction
20
. A head
24
reproduces a signal from the disc
1
, and a linear speed calculation means
26
determines a linear speed
27
from the head reproduced signal
25
as a feedback signal to a rotation control section
21
. In this manner, the spindle motor S executes so-called CLV control that uses a signal reproduced from the head to control the rotational speed of the disc
1
in such a way that a linear speed
27
is constant.
In the conventional spindle motor S in which the rotor
4
and the turn table
3
are each press-fitted to the rotating shaft
5
, the rotating shaft
5
constitutes the only coupled portion between the turn table
3
and the rotor
4
, so the rigidity between these components is weak, resulting in unwanted vibration in the path shown by arrow C as shown by the imaginary lines in FIG.
8
.
That is, if the turn table
3
and the rotor
4
are coupled together by simply press-fitting them to the rotating shaft
5
, then as they are rotationally driven, whirling occurs in which they move relatively.
The unwanted vibration caused by whirling adversely affects the rotation control characteristics of the spindle and the focus control characteristics of a pickup, thereby making each control system unstable. The effects of this unwanted vibration can be confirmed by measuring the loop characteristic of the control system. This is described with reference to FIG.
9
and the characteristic diagram in
FIG. 10
showing a CLV loop of the spindle motor S.
FIG. 10
shows a transfer function using the linear-speed instruction
20
as input and the linear speed
27
as output, wherein the horizontal axis indicates the frequency (Hz) while the vertical axis indicates the gain (dB) and phase (deg) of the loop characteristic.
As is apparent from
FIG. 10
, the gain increases near the frequency of 800 Hz. This is caused the above unwanted frequency, and when the conventional spindle motor S is used to increase the loop gain, the system may oscillate at the frequency of 800 Hz, thereby preventing the follow-up characteristic of disc rotation control from being improved.
The molding thickness of the turn table
3
is reduced to improve the molding accuracy. The reduced thickness of the apparatus limits its height and thus the height of the turn table
3
, thereby reducing the rigidity of the turn table. Furthermore, if the bearing of the spindle motor S is a sliding bearing. the diameter of the rotating shaft
5
is reduced to reduce the peripheral speed of the surface of the bearing in order to improve the lifetime expectancy of the bearing for fast rotations. In this case, the rigidity of the rotating shaft
5
decreases.
If the rigidity between the turn table
3
and the rotor
4
decreases as described above, the unwanted vibration is further increased by the vibration mode in which the rotor section
4
and the turn table section
3
including the disc
1
move relatively.
Japanese Patent Application Laid-Open No. 8-195010 discloses a technique for holding the disc
1
precisely. This application discloses a disc chucking mechanism having a centering function.
In addition, Japanese Patent Application Laid-Open No. 9-63164 discloses a technique using a spindle motor S having a disk chucking function in the turn table
3
to account for the reduced thickness and size of the apparatus. In this case, claws provided on the turn table
3
are used to chuck the disc. Either technique, however, is insufficient to restrain the unwanted vibration.
Thus, Japanese Patent Application Laid-Open No. 7-298586 discloses a configuration in which the rotor
4
of the spindle motor S and the turn table
3
are integrated together by means of adhesion or welding and in which the rotating shaft
5
is press-fitted to the turn table
3
.
In the spindle motor S disclosed in Japanese Patent Application Laid-Open No. 7-298586, the rotor
4
of the spindle motor S and the turn table
3
are integrated together by means of adhesion or welding, so this configuration is subjected to few effects of the vibration mode in which the turn table
3
and the rotor
4
move relatively.
Since, however, the deflection accuracy of the rotor
4
, however, is the sum of the deflection of the turn table
3
and the surface accuracy of the coupled portion between the rotor
4
and the turn table
3
, an insufficient shaft deflection accuracy causes the gravity of the rotor
4
section to be biased to increase the unwanted vibration when the spindle motor S is rotated at a high speed.
In addition, the method for welding the turn table
3
has an advantage of eliminating the need to apply an adhesive but has a disadvantage of causing hot distortion (the deformation of resin during a welding process) during welding, thereby hindering the accuracy of the turn table
3
from being controlled.
DISCLOSURE OF THE INVENTION
In view of these points, it is thus an object of this invention to provide a spindle motor that meet both requirements of reducing unwanted vibration occurring when a disc is rotated at a high speed and increasing the accuracy in holding the disc and that is easy to manufacture.
To achieve this problem, this invention comprises a turn table that holds a disc to rotate it, a rotor that applies rotational driving force to the turn table, and a rotating shaft fixed to the rotor on the rotation axis of the rotor, characterized in that the turn table and the rotor are arranged so as to have a predetermined gap therebetween, that the rotating shaft is fixed on the rotation axis of the turn table using a first support means, and that the turn table and the rotor are supported by a second support means consisting of a filler filled in the predetermined gap. The gap between the turn table and the rotor is a gap between the rotor and a protruding portion provided on the turn table in such a manner as to protrude to the rotor, or a gap between the turn table and a protruding portion provided on the rotor in such a manner as to protrude to the turn table. In the second support means, support is provided by filling the gap with an adhesive or an elastic member represented by a silicon rubber.
In addition, the gap between the turn table and the rotor is formed between the protruding portion of the turn table protruding to the rotor and a recessed portion provided in the rotor to oppose to the protruding portion of the turn table, or between the protruding portion of the rotor protruding to the turn table and a recessed portion provided in the turn table to oppose to the protruding portion of the rotor. Alternatively, the recessed portion is a hole into which the protruding portion of the turn table or rotor is loosely inserted to form the gap between the turn table and the rotor. The second support means supports the turn table on the rotational circumference of th

Affiliated with

Also associated with

Rating

Spindle motor and its manufacturing method does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Spindle motor and its manufacturing method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Spindle motor and its manufacturing method will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2454790