Negative pressure air-lubricated bearing slider

Details Negative pressure air-lubricated bearing slider Negative pressure air-lubricated bearing slider

2001-06-06

2003-07-08

Korzuch, William (Department: 2653)

Dynamic magnetic information storage or retrieval

Fluid bearing head support

Disk record

Reexamination Certificate

active

06590746

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a negative pressure air-lubricated bearing slider in a magnetic recording apparatus, where a magnetic transducer is installed, and more particularly, to a slider in which flying stability is improved.
2. Description of the Related Art
In a magnetic recording apparatus, a slider flies above a disc by using air as a lubricant.
FIG. 1
shows the structure of a hard disc drive (HDD) as an example of the magnetic recording apparatus.
Referring to the drawing, in a driving apparatus of a hard disc drive
10
, a disc
11
placed on a spindle motor
12
rotates and a negative pressure air-lubricated bearing slider
14
is attached at a suspension
15
to correspond to the magnetic disc
11
. The negative pressure air-lubricated bearing slider
14
is moved by an actuator
16
which pivots so that the slider
14
moves to a desired position on a track
13
of the disc
11
. The disc
11
used as a recording medium has a circular shape and different information is recorded on each track
13
. Accordingly, to obtain desired information, the slider
14
moves in search of a corresponding track on the disc
11
. Here, a linear velocity and skew angle change according to the position of the track
13
and accordingly the flying height, a pitch angle, a roll angle of the slider
14
are changed.
Referring to
FIGS. 2A
,
2
B and
2
C, linear velocity
25
generated due to rotation of the disc
11
changes in proportion to the radius of the disc
11
at each of the tracks having different radii. Thus, the flying attitude of the slider
14
, that is, a flying height
21
, a pitch angle
22
, and a roll angle
23
, changes according to the position of each track.
The flying height
21
means the height between the slider
14
and the disc
11
at a position where a magnetic transducer
26
for recording/reproducing information. The pitch angle
22
means an angle made by the lengthwise direction of the slider
14
and the surface of the disc
11
. The roll angle
23
means an angle made by the widthwise direction of the slider
14
and the surface of the disc
11
. The skew angle
24
means an angle made by a tangent of a track of the disc
11
and a lengthwise direction
15
of the slider
14
. The skew angle
24
greatly affects generation of pressure to a bearing so that the flying attitude, that is, the flying height
21
, the pitch angle
22
, and the roll angle
23
, changes much according to the radius of the disc
11
.
Since about 2-3 micro inches or more is conventionally required for the flying height, even when the amount of a change in the flying height is somewhat great, such a change does not affect recording and reproducing of information. However, as the flying height is recently lowered to 1 micro inch or less, the range of a change in the flying height becomes small and stable flying is needed. When the range of a change in the flying height is great, recording and reproducing of information is difficult and collisions between the slider and the disc are frequently made so that durability and reliability of the whole system are lowered.
The relationship between a head writing field (Hw) and the coercivity (Hc) of a recording medium is expressed by the following equation.
Hw=a×Hc
  [Equation 1]
In Equation 1, when it is assumed that the coercivity of a recording medium fixed, the size of the head writing field is determined by a value a. As the value a decreases, the head writing field is reduced. This means that a head with a small writing field can sufficiently record information on a recording medium. The value a is related to the flying height that is a gap between the slider and the disc. Thus, the value a can be reduced by reducing the flying height. When the flying height is lowered, the size of bits related to a recording density is reduced so that a greater amount of information can be stored.
While the recording density increases as the flying height is lowered, the possibility that the slider collides with the disc by external interferences such as an outside impact, increases. To prevent this problem, various slider shapes have been suggested.
FIG. 3
shows the structure of a slider having a conventional shape which is disclosed in U.S. Pat. No. 3,823,416, which is the same as those shown in
FIGS. 2A
,
2
B and
2
C.
Referring to
FIG. 3
, rails
31
a
each having a taper
32
a
are formed at both sides on the bottom surface of a slider parallel to each other in the lengthwise direction. The slider having this shape is basically used in an initial form of a magnetic recording apparatus, and is named a taper flat (TF) slider. This slider is disadvantageous in that the flying height, the pitch angle, and the roll angle change very greatly with respect to changes in the disc linear velocity and the skew angle which are described above with reference to
FIGS. 2A
,
2
B, and
2
C. Since a magnetic transducer
26
is disposed at the rear of one rail at the back of the slider, the flying height is greatly affected by not only a change in the pitch angle, but also a change in the roll angle, so that it is difficult to maintain a constant flying height with respect to the radius of a disc.
The reasons for using the taper flat slider in spite of the above problems are as follows. First, since a linear actuator is mainly used instead of a rotary actuator, there is no need to consider an effect by the skew angle. Second, since the flying height is 4 micro inches or more, even when the amount of a change in the flying height with respect to the radius of a disc is large, recording and reproducing of information are not affected much.
FIG. 4
shows the structure of a slider which is disclosed in U.S. Pat. No. 5,473,485. Referring to the drawing, rails
31
b
each having a taper
32
b
at the front side of the slider are formed at both sides on the bottom surface of the slider to the middle portion of the slider. A pad
33
b
is formed in the middle of the rear side of the slider. The slider having the above structure is named a tri-pad slider and exhibits a stable flying attitude compared to the conventional taper flat slider.
However, as a need for a high density recording apparatus increases, the flying height between the slider and the disc is drastically reduced to 2 micro inches or less. A slider for generating negative pressure which enables a stable flying attitude with respect to the external interferences has been suggested.
FIG. 5
shows a negative pressure air-lubricated bearing slider disclosed in U.S. Pat. No. 3,855,625 which is named a zero-load slider.
Referring to
FIG. 5
, rails
31
c
are formed at both sides on the bottom surface of a slider parallel to each other. A bridge
35
c
is formed at the middle portion between both rails
31
c
to section the space between both rails
31
c
into a positive pressure space portion
33
c
and a negative pressure space portion
34
c.
The feature of the negative pressure slider having the above structure is as follows. Positive pressure that lifting the slider above the disc is generated at the positive pressure space portion
33
c
. Negative pressure corresponding to the positive pressure is generated at the negative pressure space portion
34
c
between air-bearing surfaces (ABS). According to the above structure, a suction force toward the disc is generated to the slider due to the negative pressure generated at the negative pressure space portion
34
c
so that great stiffness of an air bearing is formed while having light external load. However, in such a negative pressure slider, since the amount of a change in the roll angle is greatly generated according to a change in the skew angle, the flying height at the position where a magnetic transducer
26
is installed is much affected so that recording/reproducing is not performed properly. Also, in the case, in which a change with respect to roll, such as, track seek motion or lamp loading, is great, dynamic stability in a direction of rolling is

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