Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-07-20
2001-04-10
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S090000, C384S107000, C029S898020
Reexamination Certificate
active
06215219
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a bearing system and a spindle motor assembly adopting the same, and more particularly, to a non-contact journal bearing system which compositely uses magnetic repulsion and hydrodynamic pressure, and a spindle motor assembly adopting the same.
2. Description of the Related Art
A bearing system guides and supports a rotating object.
FIG. 1
is a cross-sectional view of a motor-integrated video head drum assembly adopting a conventional bearing system.
Referring to
FIG. 1
, a stator
7
, a component of a motor, is installed on the upper portion of a base
6
in the center of which a fixed shaft
1
with a predetermined height, another component of the motor, is installed. Typical bearings
3
are installed at the upper and lower portions of the fixed shaft
1
. An inner ring
31
of the bearing
3
is pressed on and fixed to the fixed shaft
1
, and an outer ring
32
thereof is pressed on and fixed to the inner circumferential surface of a rotating body
2
penetrated by the fixed shaft
1
. A rotor
8
, a component of the motor, facing the stator
7
is installed on the lower portion of the rotating body
2
.
In such a structure, the rotating body
2
rotates, as it is supported by the typical ball bearings
3
. Each of a plurality of balls
33
of the ball bearing
3
is located in the cavity provided by two grooves with semicircular sections formed on the facing surfaces of an inner ring
31
and an outer ring
32
as shown in FIG.
2
. In order to support an axial load and a load of a direction vertical to an axial direction, the ball
33
diagonally contacts the inner ring
31
and the outer ring
32
at a predetermined angle.
As described above, when the rotating body is supported by the ball bearing
3
, the ball
33
and the inner and outer rings
31
and
32
contacting via the ball
33
become deformed due to mutual contact and rolling friction. Also, the rotation of the rotating body is unbalanced due to matching errors generated by processing imperfections of parts such as inner and outer rings, balls, etc. caused when the ball bearing is manufactured. Such an unbalanced rotation has been investigated and is known to cause irregular vibration due to various factors, in particular, non-repeatable run-out (NRRO). NRRO degrades the performance of a spindle motor for use in a high-density storage apparatus which requires super-accurate vibration. Even though the components of the ball bearing are manufactured by a super-accurate processing method to improve the vibration of the rotating body system, the durability of the rotating body system is deteriorated by abrasion and heat generation of the components due to friction caused by highspeed rotation. A ball bearing made of ceramic has recently been proposed, but the manufacture of the ball bearing is difficult because of the physical characteristics of ceramic, and the manufacturing cost is high.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a magnetic-hydrodynamic pressure bearing system which is easily manufactured and can exceedingly stably support a rotating body, and a spindle motor assembly adopting the same.
It is another objective of the present invention to provide a magnetic-hydrodynamic pressure bearing system which minimizes noise by adopting elements which make relative motions to each other in a non-contact manner, and has components whose durability is greatly improved, and a spindle motor assembly adopting the same.
Accordingly, to achieve the first objective, there is provided a bearing system comprising: a lower base on which a fixed shaft having a predetermined diameter is installed; a cylindrical body having a larger inner diameter than the fixed shaft, fit on the fixed shaft; first and second magnetic bodies installed on the upper and lower ends of the cylindrical body, respectively; a third magnetic body installed on the lower circumference of the fixed shaft so as to face the second magnetic body on the lower end of the cylindrical body, the third magnetic body having magnetic repulsion against the second magnetic body; a fourth magnetic body facing the first magnetic body on the upper end of the cylindrical body at a predetermined space, the fourth magnetic body having magnetic repulsion against the first magnetic body; and an upper base to which the fourth magnetic body is fixed and which is fixed to the upper portion of the fixed shaft.
To achieve the second objective, there is provided a bearing system comprising: a fixed shaft having a predetermined diameter; a base by which the fixed shaft is supported; and a cylindrical body penetrated by the fixed shaft, wherein the inner diameter of the cylindrical body is larger than the outer diameter of the fixed shaft, the cylindrical body includes a flat portion whose core is co-aligned with the core of the fixed shaft; a tapered portion extending from the flat portion to be distant from the fixed shaft; and a groove extending from the tapered portion and formed so as to become distant from the center of the fixed shaft, and the flat portion, the tapered portion, and the groove portion are formed on the inner circumferential surface of the cylindrical body.
In the bearing system according to the present invention, the inner diameter of the cylindrical body is larger than the outer diameter of the fixed shaft, the cylindrical body includes a flat portion whose core is co-aligned with the core of the fixed shaft; a tapered portion extending from the flat portion to be distant from the fixed shaft; and a groove portion extending from the tapered portion and formed so as to become distant from the center of the fixed shaft, and a predetermined number of flat portions, tapered portions, and groove portions are formed on the inner circumferential surface of the cylindrical body, the predetermined number being the number of flat portions, tapered portions, and groove portions required for the cylindrical body to become distant from the fixed shaft.
To achieve the objectives, there is provided a spindle motor assembly comprising: a spindle having a cylindrical part formed on the center, and a rotor formed on the lower portion; a lower base which penetrates the cylindrical part of the spindle, and on which a fixed shaft having a predetermined diameter is installed, and a stator facing the rotor is installed; a cylindrical body which has a larger inner diameter than the fixed shaft, is penetrated by the fixed shaft, and is inserted and fixed to the cylindrical part of the spindle; first and second magnetic bodies installed on the upper and lower ends of the cylindrical body, respectively; a third magnetic body installed on the lower circumference of the fixed shaft so as to face the second magnetic body on the lower end of the cylindrical body, the third magnetic body having magnetic repulsion against the second magnetic body; a fourth magnetic body facing the first magnetic body on the upper end of the cylindrical body at a predetermined space, the fourth magnetic body having magnetic repulsion against the first magnetic body; and an upper base to which the fourth magnetic body is fixed and which is fixed to the upper portion of the fixed shaft.
In the bearing system and the spindle motor assembly according to the present invention, preferably, the cylindrical body is constituted of two cylindrical bodies formed up and down, and flanges are formed on the far ends of the cylindrical portions. In the spindle motor assembly, it is preferable that when the cylindrical body is divided into two cylindrical bodies each having a flange, the cylindrical part of the spindle is formed according to the shape of the outer circumferential surface of the cylindrical body and the shape of the flange installed on the cylindrical body.
REFERENCES:
patent: 3326610 (1967-06-01), Baermann
patent: 5610463 (1997-03-01), Dunfield et al.
patent: 5722775 (1998-03-01), Thijsse et al.
patent: 5729065 (1998-03-01), Fremery et al.
pate
Burns Doane Swecker & Mathis L.L.P.
Nguyen Tran
Samsung Electronics Co,. Ltd.
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