Motor and hard disk drive having a reduced vibration motor

Details Motor and hard disk drive having a reduced vibration motor Motor and hard disk drive having a reduced vibration motor

1999-03-19

2001-02-13

Ramirez, Nestor (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S261100

Reexamination Certificate

active

06188152

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a motor for use with an OA apparatus or an AV apparatus.
BACKGROUND OF THE INVENTION
In a hard disk drive for reading magnetic recording or content of record while rotating a hard disk at high speed, there is used a shaft-rotating type motor or such a shaft-fixed type motor as disclosed in U.S. Pat. No. 4,739,427.
The shaft-fixed type motor has, as shown in
FIG. 15
, a magnet
4
provided for a rotor
3
rotatably supported by a fixed shaft
1
a
through ball bearings
2
a
and
2
b,
and a stator winding
6
mounted on a stator core
5
so as to face the magnet
4
, for rotationally driving hard disks
7
placed on the rotor
3
around the shaft center thereof.
Generally, the vibration proof characteristic has the following tendency:
When the number of revolutions increases, the vibration proof characteristic is deteriorated, and the vibration proof characteristic is also deteriorated even when a disk load is increased.
Naturally, this vibration proof characteristic will be improved if a motor resonance point is improved. Therefore, as described above, there is generally adopted a both ends supported structure in which a proximal end of the fixed shaft
1
a
is fixed to a lower case
8
a
and a tip end portion is fixed to an upper case
8
b
with a machine screw
9
to improve the resonance point, or in a cantilever supporting structure, a shaft diameter is generally made large.
DISCLOSURE OF THE INVENTION
The conventional vibration proof characteristics have not posed any significant problems regarding ball bearing specifications for the following reasons:
In the ball bearing specifications, there is a small relation between the shaft diameter and current consumption because of rolling friction, and therefore, the shaft diameter a can be made large for use. Also, a shaft with a diameter of 5 mm or 6 mm has been used, and ball bearings of this class are low-priced, but there is a problem that the ball bearing becomes difficult to resist a shock because the resistance to load capability becomes low when the size of the ball bearing becomes small.
When great importance is attached on compactization and resistance to shock load, the support by fluid bearing in place of ball bearings is advantageous, and the specific structure is described in U.S. Pat. No. 5,590,003.
Hereinafter, the fluid bearing specifications will be studied.
Regarding the fluid bearing specifications, heretofore, we have been anxious to solve the maximum problem, i.e., how an increase in loss caused by fluid friction should be restricted. For this reason, it is most effective to reduce the shaft diameter and peripheral speed, and it is important to deal with the matter by the minimum shaft diameter in accordance with a disk load, the number of revolutions or the like.
It is an object of the present invention to provide a motor capable of reducing the loss as far as possible, and securing the minimum vibration proof performance and reliability by definitely defining the upper and lower limits for the minimum shaft diameter in conformity with the disk load, the service number of revolutions or the like in the fluid bearing specifications, and a hard disk drive loaded with this motor.
According to a motor of the present invention, there is provided a shaft-fixed type motor of the fluid bearing specifications, wherein the diameter d (mm) of the fixed shaft has been set so as to satisfy the relation of &agr;
3
·M1>d
3
>M1.
Also, according to the motor of the present invention, there is provided a shaft-rotating type motor of the fluid bearing specifications, wherein the diameter d (mm) of the fixed shaft has been set so as to satisfy the relation of &agr;
3
·M2>d
3
>M2.
Where in M1=J1·(N/1000)
2
·k
2
·D and M2=J2·(
N/
1000)
2
·k
2
·D, J
1and J2are coefficients to be experimentally determined. N(rpm) is a service number of revolutions, k is a number of disk-shaped recording media, D (inch) is a diameter of the disk-shaped recording medium, and &agr; is a ratio of the maximum diameter to the minimum diameter of the fixed shaft or the rotor shaft.
According to the present invention, the reduction of loss as far as possible, the minimum vibration proof performance and the reliability can be obtained.
According to a motor specified in a first embodiment of the present invention, there is provided a motor having a magnet provided for a rotor rotatably supported by a fixed shaft and a stator winding mounted on a stator core to face the foregoing magnet, for rotationally driving a disk-shaped recording medium placed on the foregoing rotor around its shaft center, wherein when the diameter of the fixed shaft is d (mm), the service number of revolutions is N (rpm), the number of the disk-shaped recording media is k, and the diameter of the disk-shaped recording medium is D (inch), the following relation has been set:
&agr;
3
·M
1
>d
3
>M
1
where M1=J1·(N/1000)
2
·k
2
·D, J1 being a coefficient to be experimentally determined and set to be 0.018±20%, and &agr; being a ratio of the maximum diameter to the minimum diameter of the fixed shaft.
According to a motor specified in a second embodiment of the present invention, there is provided a motor having a main magnet provided for a rotor rotatably supported by inserting a rotor shaft into the shaft hole in the fixed sleeve formed on the stator side, and a stator core mounted on the stator side to face the foregoing main magnet, for rotationally driving a disk-shaped recording medium placed on the foregoing rotor around its shaft center, wherein when the diameter of the foregoing rotor shaft is d (mm), the service number of revolutions is N (rpm), the number of the disk-shaped recording media is k, and the diameter of the disk-shaped recording medium is D (inch), the following relation has been set:
&agr;
3
·M
2>d
3
>M
2,
where M2=J2·(N/1000)
2
·k
2
·D, J2 being a coefficient to be experimentally determined and set to 0.0134±20%, and &agr; being a ratio of the maximum diameter to the minimum diameter of the rotor shaft.
A hard disk drive specified in a third embodiment of the present invention incorporates a motor described in either the first or second embodiments therein, and is characterized in that this motor rotationally drives a disk-shaped recording medium.


REFERENCES:
patent: 4739427 (1988-04-01), Kilmer et al.
patent: 5598047 (1997-01-01), Sakuragi et al.
patent: 5623382 (1997-04-01), Moritan et al.
patent: 5647672 (1997-07-01), Fukutani

Affiliated with

Also associated with

Rating

Motor and hard disk drive having a reduced vibration 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 hard disk drive having a reduced vibration motor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Motor and hard disk drive having a reduced vibration motor will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2571065