U.S. patent application number 09/810267 was filed with the patent office on 2001-08-02 for negative pressure air bearing slider.
This patent application is currently assigned to Fujitsu Limited. Invention is credited to Koishi, Ryosuke, Mizoshita, Yoshifumi.
Application Number | 20010010612 09/810267 |
Document ID | / |
Family ID | 26550349 |
Filed Date | 2001-08-02 |
United States Patent
Application |
20010010612 |
Kind Code |
A1 |
Koishi, Ryosuke ; et
al. |
August 2, 2001 |
Negative pressure air bearing slider
Abstract
A negative pressure air bearing slider including a first air
bearing surface formed on the bottom of the slider body at the
upstream position so as to extend in the lateral direction of the
slider body, and a pair of second air bearing surfaces formed on
the bottom of the slider body separately from the first air bearing
surface at downstream positions spaced in the lateral direction so
as to define an air stream passage therebetween. The second air
bearing surfaces serve to generate positive pressures that are
spaced apart at downstream positions where a transducer element is
embedded in the slider body, so that the slider's stiffness to
rolling action can be enhanced. The cooperation of the front and
rear rails enables for the creation of a higher negative
pressure.
Inventors: |
Koishi, Ryosuke; (Kawasaki,
JP) ; Mizoshita, Yoshifumi; (Kawasaki, JP) |
Correspondence
Address: |
GREER, BURNS & CRAIN
300 S WACKER DR
25TH FLOOR
CHICAGO
IL
60606
US
|
Assignee: |
Fujitsu Limited
|
Family ID: |
26550349 |
Appl. No.: |
09/810267 |
Filed: |
March 16, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09810267 |
Mar 16, 2001 |
|
|
|
09334970 |
Jun 17, 1999 |
|
|
|
Current U.S.
Class: |
360/236.3 ;
360/235.8; 360/236; G9B/21.026; G9B/5.231 |
Current CPC
Class: |
G11B 21/21 20130101;
G11B 5/6005 20130101 |
Class at
Publication: |
360/236.3 ;
360/236; 360/235.8 |
International
Class: |
G11B 005/60; G11B
021/20 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 1998 |
JP |
10-272711 |
Nov 27, 1998 |
JP |
10-336834 |
Claims
What is claimed is:
1. A negative pressure air bearing slider comprising: a slider
body; a first air bearing surface formed on a bottom of the slider
body near an upstream end thereof, said first air bearing surface
extending in a lateral direction of the slider body; and a pair of
second air bearing surfaces formed on the bottom of the slider body
near a downstream end thereof, said pair of second air bearing
surfaces being separated from the first air bearing surface, and
said pair of second air bearing surfaces being spaced apart from
each other in the lateral direction so as to define an air stream
passage therebetween.
2. The negative pressure air bearing slider according to claim 1,
wherein said first air bearing surface is defined upon a lower
surface of a front rail that extends from the bottom of the slider
body near said upstream end, and wherein said front rail also
extends in the lateral direction of the slider body.
3. The negative pressure air bearing slider according to claim 2,
wherein said first air bearing surface is connected to the lower
surface of said front rail via a step.
4. The negative pressure air bearing slider according to claim 2,
wherein a pad is formed on the lower surface of said front rail so
as to prevent said first air bearing surface from sticking to a
disk surface of a storage disk when the slider body is seated upon
the disk surface.
5. The negative pressure air bearing slider according to claim 2,
wherein said pair of second air bearing surfaces are respectively
defined on lower surfaces of a pair of rear rails that extend from
the bottom of the slider body near the downstream end thereof,
further wherein said pair of rear rails are spaced apart from each
other in the lateral direction so as to define the air stream
passage therebetween.
6. The negative pressure air bearing slider according to claim 5,
wherein said second air bearing surfaces are each connected,
respectively, to the lower surfaces of a corresponding one of said
rear rails via a step.
7. The negative pressure air bearing slider according to claim 5,
wherein a pad is formed on the lower surface of at least one of
said rear rails so as to prevent the second air bearing surface
from sticking to a disk surface when the slider body is seated upon
the disk surface.
8. The negative pressure air bearing slider according to claim 5,
further including a pair of side rails that are formed on the
bottom of the slider body so as to extend downstream from lateral
ends of said front rail.
9. The negative pressure air bearing slider according to claim 8,
wherein said side rails each have a thickness in the lateral
direction that is smaller than the thickness in the lateral
direction of each of the rear rails.
10. The negative pressure air bearing slider according to claim 8,
wherein there is a groove formed between each of said side rails
and its corresponding one of said rear rails, whereby said groove
draws air running around said front rail into said air stream
passage.
11. The negative pressure air bearing slider according to claim 10,
wherein one of said second air bearing surfaces has a transducer
element embedded therein, and said second air bearing surface with
said transducer element has a surface area smaller than that of the
other second air bearing surface.
12. The negative pressure air bearing slider according to claim 11,
wherein said second air bearing surface with said transducer
element has an upstream end of a first width in the lateral
direction and a downstream end of a second width in the lateral
direction that is larger than said first width.
13. The negative pressure air bearing slider according to claim 11,
wherein said second air bearing surface with said transducer
element is connected to said corresponding rear rail via a step on
an upstream side thereof and said second air bearing surface
without said transducer is connected to said corresponding rear
rail via another step on an upstream side thereof, wherein said
step on said second air bearing surface with said transducer
element is located farther downstream than said other step on said
second air bearing surface without said transducer.
14. The negative pressure air bearing slider according to claim 13,
wherein said groove near said second air bearing surface with said
transducer is longer than said groove near said second air bearing
surface without said transducer.
15. The negative pressure air bearing slider according to claim 13,
wherein said groove near said second air bearing surface with said
transducer is approximately the same length as said groove near
said second air bearing surface without said transducer.
16. The negative pressure air bearing slider according to claim 13,
wherein said second air bearing surface with said transducer
element has a downstream end extending in the lateral direction
that is displaced upstream to be separated from said downstream end
of said slider body.
17. The negative pressure air bearing slide according to claim 5,
wherein one of said second air bearing surfaces has a transducer
embedded therein, and further wherein said second air bearing
surface with said transducer has a side portion thereof that is
angled such that an upstream end of said second air bearing surface
with said transducer is of a smaller width that a downstream end of
said same second air bearing surface.
18. The negative pressure air bearing slide according to claim 5,
wherein one of said second air bearing surfaces has a transducer
embedded therein, and further wherein said second air bearing
surface with said transducer is generally L-shaped such that an
upstream end thereof is of a smaller width that a downstream end
thereof.
19. A storage disk drive comprising: at least one disk adapted to
have information stored thereon; a motor for rotating said at least
one disk; an actuator arm adapted to swing about a shaft for
accessing different radial portions of said at least one disk; a
negative pressure air bearing slider located near a distal end of
said actuator arm; and wherein said negative pressure air bearing
slider includes: a slider body; a first air bearing surface formed
on a bottom of the slider body near an upstream end thereof, said
first air bearing surface extending in a lateral direction of the
slider body; and a pair of second air bearing surfaces formed on
the bottom of the slider body near a downstream end thereof, said
pair of second air bearing surfaces being separated from the first
air bearing surface, and said pair of second air bearing surfaces
being spaced apart from each other in the lateral direction so as
to define an air stream passage therebetween.
Description
[0001] The present invention relates to a negative pressure air
bearing slider intended to be employed in an information storage
device such as a magnetic disk drive.
BACKGROUND OF THE INVENTION
[0002] Air bearing sliders are often employed in magnetic disk
drives. The air bearing slider allows a transducer element to fly
above the disk surface of a magnetic disk when information is read
or written from or onto the magnetic disk. Alternatively, the
slider may be positioned below the magnetic disk, in which case the
slider flies a slight distance below the lower disk surface. Either
way, an air bearing surface (ABS) is defined on the surface of the
slider body that opposes the disk surface. When the storage disk
rotates, an air stream generated along the disk surface acts upon
the air bearing surface to separate the slider body a slight
distance from the disk surface. For the sake of simplicity,
throughout this specification, this separation will be referred to
as the flying height, regardless of whether the slider is above the
disk or below the disk.
[0003] Recently, higher and higher storage densities are being
expected in the field of magnetic disk drives. In order to achieve
a higher storage density, it is beneficial to reduce the flying
height of the slider body. However, as the flying height is
reduced, the slider body tends to collide with the disk surface
during flying.
[0004] Some prior art devices include a negative pressure air
bearing slider that is capable of generating negative pressure that
opposes the lift (or positive pressure) acting upon the air bearing
surface. The balance between the negative pressure and the lift
serves to restrict the flying height in this type of negative
pressure air bearing slider. The negative pressure serves to draw
the slider body toward the disk surface so that it is possible to
stabilize the flying behavior of the slider body. As a result, the
probability of collisions between the slider body and the disk
surface can be reduced.
[0005] The growing demand for higher storage densities requires
further improvements in the stability of the slider body, and at
the same time also requires an increased resistance to any rolling
action of the slider body. If sufficient resistance to rolling is
not present, the slider body tends to roll around its center axis
along the air stream during flying, and the slider body may collide
with the disk surface.
[0006] It is accordingly an object of the present invention to
provide a negative pressure air bearing slider with both increased
stability and an increased resistance to rolling during flying.
SUMMARY OF THE INVENTION
[0007] According to a first aspect of the present invention, there
is provided a negative pressure air bearing slider that includes a
first air bearing surface formed on a bottom of a slider body at an
upstream position so as to extend in a lateral direction of the
slider body; and a pair of second air bearing surfaces formed on
the bottom of the slider body separately from the first air bearing
surface at downstream positions that are spaced apart in the
lateral direction so as to define an air stream passage
therebetween.
[0008] With the aforementioned slider, the second air bearing
surfaces that are spaced apart in the lateral direction serve to
generate the lift or positive pressure at the downstream position
at which a transducer or head element is in general embedded in the
slider body. Since a pair of spaced lifts support the slider body
at the downstream position, it is possible to remarkably enhance
the slider body's stiffness to rolling action.
[0009] The first air bearing surface may be defined on the lower
surface of a front rail that extends from the bottom of the slider
body near an upstream end thereof. The front rail also extends in
the lateral direction of the slider body. The front rail foremost
receives the air stream along the disk surface, so that the
negative pressure generated behind the front rail cannot be
reduced. In addition, the second air bearing surfaces may be
respectively defined on lower surfaces of a pair of rear rails that
extend from the bottom of the slider body at the downstream
positions. These rear rails are spaced in the lateral direction so
as to define the air stream passage therebetween.
[0010] The first and second air bearing surfaces are preferably
connected to the lower surfaces of the front and rear rails via
steps. The steps serve to generate a higher positive pressure at
the first and second air bearing surfaces.
[0011] The negative pressure air bearing slider preferably includes
a pair of side rails that are formed on the bottom of the slider
body so as to extend downstream from the lateral ends of the front
rail. The side rails serve to prevent the air stream that flows
around the lateral ends of the front rail from entering the space
behind the front rail. Accordingly, it is possible to reliably
generate a higher negative pressure behind the front rail. In
particular, the side rails preferably have a thickness that is
smaller than that of the rear rails in the lateral direction. The
thinner side rails serve to enlarge a negative pressure cavity
surrounded by the side rails behind the front rail, so that the
negative pressure can be increased.
[0012] Moreover, a groove is preferably formed in the side rail so
as to draw air running around the front rail into the air stream
passage. The groove serves to avoid saturation of the negative
pressure at lower tangential velocities of the storage disk, even
if lower front and rear rails are employed. As a result, the groove
enables the negative pressure to reliably follow increases of the
tangential velocity, so that the negative pressure air bearing
slider may keep the flying height of the slider body constant,
irrespective of variations in the tangential velocity.
[0013] In addition, a pad may be formed on the lower surface of the
front or rear rail so as to prevent the first or second air bearing
surface from sticking to the disk surface of a storage disk when
the slider body is seated upon the disk surface. Such pads serve to
avoid the first or second air bearing surface from directly
contacting the disk surface. As a result, less adhesion of a
lubricating agent or oil spread over the disk surface acts on the
slider body, so that the slider body can immediately take off from
the disk surface at the beginning of rotation of the storage
disk.
[0014] Further, the second air bearing surface in which a
transducer element is embedded may have a surface area that is
smaller than that of the other second air bearing surface. The
smaller second air bearing surface with a transducer element serves
to keep the slider body in a slanted attitude by a roll angle.
Accordingly, it is possible to minimize the distance between the
bottom of the slider body and the disk surface around the
transducer element.
[0015] When the second air bearing surface with the transducer
element is intended to be smaller than the other air bearing
surface, the second air bearing surface with the transducer element
may have an upstream end extending by a first width in the lateral
direction so as to lead to the step, and a downstream end extending
by a second width that is larger than the first width in the
lateral direction. For example, in the case where the transducer
element comprises a magnetoresistance (MR) element, the MR element
should be protected between a pair of shield layers. If the shield
layers fail to have a lateral size that is large enough to shield
the MR element from magnetic interference of the vicinal magnetic
field, the MR element will not be able to correctly read data. In
general, the slider body is kept in a slanted attitude to bring the
downstream end closer to the disk surface. As long as the slanted
attitude is kept, the transducer element embedded in the slider
body at the downstream position can approach the disk surface.
Accordingly, the wider downstream end enables the second air
bearing surface to be of a smaller area, while still keeping the
larger lateral size of the shield layers at the same time.
[0016] In addition, when the second air bearing surface with the
transducer element is intended to be smaller than the other air
bearing surface, an upstream end extending in the lateral direction
so as to define the step in front of the second air bearing surface
with the transducer element may be disposed more downstream than an
upstream end extending in the lateral direction so as to define the
step in front of the other second air bearing surface. Such
disposition of the second air bearing surfaces serves to reduce the
length of the second air bearing surface with the transducer
element in the direction of air stream as compared with that of the
other second air bearing surface. Accordingly, the smaller second
air bearing surface can be realized to set the lift at the second
air bearing surface with the transducer element that is smaller
than that of the other second bearing surface. It is therefore
possible to reduce the lift at the second air bearing surface with
the transducer element without a reduction in the lateral width of
the shield layers.
[0017] When the upstream end of the second air bearing surface with
the transducer is displaced downstream as described above, it is
preferable to adjust the size of the groove between the rear and
side rails. For example, if the side rail fails to extend toward
the rear rail to follow the displacement of the upstream end of the
second air bearing surface, the groove becomes larger or wider. The
wider groove may release the negative pressure generated behind the
front rail. On the other hand, when the side rail is extended to
follow the displacement of the upstream end, a smaller or narrower
groove can be obtained, so that a higher negative pressure can be
maintained behind the front rail. A higher negative pressure
enables the second air bearing surface with the transducer element
to reliably approach the disk surface as closely as possible.
[0018] Furthermore, when the lift at the second air bearing surface
with the transducer element needs to be reduced, for example, the
position of the second air bearing surface can be determined
relative to the lower surface of the rear rail. The aforementioned
higher positive pressure generated at the steps depends upon not
only its areas and heights, in addition to the area of the second
air bearing surfaces, but also upon the extent of the lower
surfaces leading to the steps on the rear rails. Smaller lower
surfaces make less positive pressure, while larger surfaces make
larger positive pressure. Accordingly, if the lateral width of the
lower surface leading to the step facing outward of the slider body
on the rear rail is reduced, the lift can be reduced at the second
air bearing surface with the transducer element, since the step
facing outward of the slider body tends to receive a larger amount
of air stream than the step facing inward of the slider body.
[0019] Furthermore, when the lift at the second air bearing surface
with the transducer element needs to be reduced, for example, the
second air bearing surface with the transducer element may include
a downstream end extending in the lateral direction at the
downstream position and displaced upstream. The aforementioned
negative pressure air bearing slider has the maximum positive
pressure at the downstream end of the slider body. Accordingly,
when the downstream end is displaced upstream so as to reduce the
area of the second air bearing surface with the transducer element,
the lift can be efficiently reduced at the second air bearing
surface with the transducer element.
[0020] It should be noted that the negative pressure air bearing
slider of the present invention may be employed in storage disk
drives such as a hard disk drive unit (HDD).
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Preferred embodiments of the present invention are described
herein with reference to the drawings wherein:
[0022] FIG. 1 is a plan view illustrating an interior ofa hard disk
drive unit (HDD);
[0023] FIG. 2 is an enlarged perspective view illustrating a
negative pressure air bearing slider according to one embodiment of
the present invention;
[0024] FIGS. 3A-3B illustrate the distribution of pressure for the
negative pressure air bearing slider of FIG. 2;
[0025] FIG. 4 is a graph demonstrating the effect of atmospheric
pressure on the pressure generated on the negative pressure air
bearing slider;
[0026] FIG. 5 is a graph demonstrating the effect of the
grooves;
[0027] FIGS. 6A-6C schematically illustrate the production method
of the negative pressure air bearing slider;
[0028] FIGS. 7A-7F are schematic sectional views taken along the
line 7-7 in FIG. 2, and these figures illustrate the method of
configuring the bottom of the slider body;
[0029] FIGS. 8A-8B are schematic sectional views taken along the
line 7-7 in FIG. 2, and these figures also illustrate the method of
configuring the bottom of the slider body;
[0030] FIG. 9 is a plan view illustrating the configuration of the
bottom of the slider body of a modified version of the present
invention;
[0031] FIG. 10 is a plan view illustrating the configuration of the
bottom of the slider body of a second modified version of the
present invention;
[0032] FIG. 11 is a plan view illustrating the configuration of the
bottom of the slider body of a third modification of the present
invention;
[0033] FIG. 12 is a plan view illustrating the configuration of the
bottom of the slider body of a fourth modification of the present
invention;
[0034] FIG. 13 is a plan view illustrating the configuration of the
bottom of the slider body of a fifth modification of the present
invention;
[0035] FIG. 14 is a plan view illustrating the configuration of the
bottom of the slider body of a sixth modification of the present
invention; and
[0036] FIG. 15 is a plan view illustrating the configuration of the
bottom of the slider body of a seventh modification of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0037] FIG. 1 illustrates and interior structure of a hard disk
drive unit (HDD) 10 which is an example of one type of magnetic
disk drive used in the present invention. However, it should be
noted that the present invention may also be applied to other types
of disk drives, including magneto-optical (MO) drives, employing
floating sliders. The HDD 10 has a housing 11 for accommodating
magnetic disks 13, which are mounted on a spindle motor 12. A
negative pressure air bearing slider is positioned to oppose one
surface of the magnetic disk 13. The negative pressure air bearing
slider 14 is fixed at the tip end of a carriage arm 16, which is
capable of swinging about a shaft 15. When information is read or
written from or to the magnetic disk 13, the carriage arm 16 is
driven to rotate by the action of an actuator 17 comprising a
magnetic circuit, so that the negative pressure air bearing slider
14 is positioned above a target recording cylinder on the storage
disk 13. The interior space of the housing 11 can be closed with a
cover, not shown.
[0038] FIG. 2 illustrates the negative pressure air bearing slider
14 according to one embodiment of the present invention. The slider
14 has a slider body that includes a bottom 19 that is opposed to
the storage disk 13. A front rail 21 is formed to extend laterally
from the bottom 19 of the slider body at its upstream end.
Likewise, a pair of rear rails 23 are formed to extend from the
bottom 19 of the slider body at its downstream end. Rear rails 23
are spaced from each other in the lateral direction to define an
air stream passage 22 therebetween. The "upstream" and "downstream"
ends are defined based on the direction of the air stream 20 that
is generated when the magnetic disk 13 rotates.
[0039] A first air bearing surface 24 is defined on the lower
surface of the front rail 21 so as to extend in the lateral
direction of the slider body. A pair of second air bearing surfaces
25a, 25b are defined respectively on the lower surfaces of the rear
rails 23 so as to form a row in the lateral direction of the slider
body with the air stream passage 22 interposed therebetween. When
the magnetic disk 13 rotates and generates air stream 20 along the
disk surface, the air stream 20 acts on the first and second air
bearing surfaces 24, 25a, 25b. Lift is generated respectively on
the first and second air bearing surfaces 24, 25a, 25b, which
allows the slider body to fly above the disk surface. Since more
lift can be generated on the first air bearing surface 24 in this
negative pressure air bearing slider 14, the slider body maintains
a slanted attitude at pitch angle .alpha.. "Pitch angle .alpha."
may be referred to as the inclination angle along the longitudinal
direction of the slider body (i.e., in the direction of the air
stream 20). In the preferred embodiment, the pitch angle .alpha. is
preferably between approximately 50 and 150 .mu.rad.
[0040] The first and second air bearing surfaces 24, 25a, 25b are
connected respectively to the lower surfaces of the front and rear
rails 21, 23 via steps 27a, 27b, 27c. The steps 27a, 27b, 27c serve
to generate a larger lift at the first and second air bearing
surfaces 24, 25a, 25b, as described herein below.
[0041] The second air bearing surface 25a has a smaller surface
area than that of the second air bearing surface 25b. Accordingly,
a larger lift can be generated on the second air bearing surface
25b than the second air bearing surface 25a in this negative
pressure air bearing slider 14. As a result, the slider body
maintains a slanted attitude at a roll angle .beta.. "Roll angle
.beta." may be referred to as the inclination angle along the
lateral direction of the slider body (i.e., in the perpendicular
direction to the air stream 20). In the preferred embodiment, the
roll angle .beta. is preferably between approximately 10 and 80
.mu.rad.
[0042] A transducer or head element embedded in the slider body
exposes a read/write gap 28 at the second air bearing surface 25a
(which has a smaller area than surface 25b). The above-mentioned
pitch and roll angles .alpha., .beta. serve to minimize the
distance between the slider body and the disk surface near the
read/write gap 28.
[0043] A pair of side rails 29 are connected to the opposite
lateral ends of the front rail 21 so as to extend in the downstream
direction. The side rails 29 serve to prevent the air stream from
flowing around the lateral ends of the front rail 21, and from
entering the space behind the front rail 21. Accordingly, the air
stream crossing the first air bearing surface 24 spreads in the
direction vertical to the disk surface and generates negative
pressure behind the front rail 21. When the generated negative
pressure is balanced with the aforementioned lift on the first and
second air bearing surfaces 24, 25a, 25b, the flying height of the
slider body can be maintained at a substantially constant value.
Grooves 30 are defined between the side rails 29 and the rear rails
23, respectively, so as to draw the air stream flowing around the
lateral ends of the front rail 21 into the air stream passage
22.
[0044] A plurality of pads 31a, 31b, 31c, 31d are formed on the
lower surfaces of the front and rear rails 21, 23 so as to prevent
the first and second air bearing surfaces 24, 25a, 25b from
sticking to the disk surface of the magnetic disk 13 when the
slider body is seated on the disk surface. Moreover, the pad 31d,
which is located on the side of the second air bearing surface 25a
generating a smaller lift, is disposed more upstream than the pad
31c, which is located on the side of the second air bearing surface
25b generating a larger lift. Since the roll angle .beta. allows
the second air bearing surface 25a to come closer to the disk
surface, such disposition of the pad 31d helps to avoid collisions
of the pad 31d with the disk surface.
[0045] When the magnetic disk 13 starts to rotate, the air stream
20 starts to flow along the disk surface. The air stream 20 serves
to allow the negative pressure air bearing slider 14 seated on the
disk surface to take off from the disk surface. Prior to taking
off, the pads 31a, 31b, 31c, 31d keep the first and second air
bearing surfaces 24, 25a, 25b at a slight distance above the disk
surface. Accordingly, as a reduced surface area contacts the disk
surface, there is less adhesion of the lubricating agent or oil
that may be spread upon the disk surface acting upon the slider
body. Therefore, it is easier for the slider body to take off from
the disk surface. After taking off, the read/write gap 28 of the
transducer element performs the reading and writing operations.
[0046] When the air stream acts on the slider 14, as shown in FIG.
3 for example, the lift (or positive pressure) and the negative
pressure are generated along the bottom 19 of the slider body. FIG.
3 illustrates a pressure distribution (as calculated by a
conventional computer simulation) for one example of an embodiment
of the slider 14. The slider body in this negative pressure air
bearing slider 14 has a length of 1.25 mm, a width of 1 mm, and a
thickness of 0.3 mm. Of course other dimensions are also
contemplated as being within the scope of the invention.
[0047] As is apparent from FIGS. 3A and 3B, the air stream 20
generates a large positive pressure at the step 27a in front of the
first air bearing surface 24, namely, at the position B. The
positive pressure grows larger as the air stream 20 advances along
the first air bearing surface 24.
[0048] When the air stream 20 has crossed the front rail 21,
namely, at the position C, the positive pressure disappears.
Negative pressure appears in place of the positive pressure at the
position D. When the air stream 20 spreads in the direction
vertical to the disk surface behind the front rail 21 this negative
pressure is caused. In addition, the side rails 29 serve to prevent
the air stream 20 that strikes the front face of the front rail 21
and then passes around the front rail 21 from entering the space
behind the front rail 21. Accordingly, a larger negative pressure
can be generated behind the front rail 21.
[0049] Upon reaching the rear rails 23 the air stream 20 generates
other large positive pressures at the steps 27b, 27c in front of
the second air bearing surfaces 25a, 25b, namely, position E. The
positive pressure grows larger as the air stream 20 advances along
the second air bearing surfaces 25a, 25b. The positive pressure
disappears at the downstream ends of the second air bearing
surfaces 25a, 25b, namely, at the position F.
[0050] The balance between the positive pressure, at the positions
B to C and E to F, and the negative pressure, at the position D
serves to fix the flying height of the slider body in this negative
pressure air bearing slider 14. Moreover, when compared with
conventional sliders, the larger positive pressure of the present
invention is balanced with its larger negative pressure, so that
higher stability in flying behavior is expected. The steps 27a,
27b, 27c preferably have a height equal to or less than 0.2 .mu.m
in order to balance the positive and negative pressures with each
other.
[0051] In addition, the pair of second air bearing surfaces 25a,
25b create positive pressure at the downstream positions nearest to
the disk surface when the slider body has the slanted attitude of
pitch angle .alpha., which enhances the slider's resistance to
rolling.
[0052] In general, when the air pressure in the atmosphere where
the magnetic disk drive 10 operates is low, the positive pressure
at the first and second air bearing surfaces 24, 25a, 25b decreases
in proportion to the reduction in air pressure. Accordingly, it is
then necessary to reduce the negative pressure in proportion to the
decrease in the positive pressure. If the negative pressure is kept
constant when the positive pressure has been reduced, the flying
height of the slider body will be decreased.
[0053] FIG. 4 is a graph illustrating the effects of variations in
the air pressure. In the graph, the solid line shows the ratio of
the positive pressure at an air pressure of 0.7 atm to the positive
pressure at an air pressure of 1.0 atm. The dotted line shows the
ratio of the negative pressure at an air pressure of 0.7 atm to the
negative pressure at an air pressure of 1.0 atm. As is apparent
from the graph, the ratio of the positive pressure varies only
slightly in response to variations in the height H (FIG. 2) of the
front and rear rails 21, 23 (i.e., the variation in the depth of
the cavity surrounded by the front, side and rear rails 21, 29,
23). On the other hand, it can be observed that the difference
between the ratio of the positive pressure and the ratio of the
negative pressure decreases as the height of the front and rear
rails 21, 23 decreases. Specifically, front and rear rails 21, 23
of lower heights better enable the negative pressure to follow
variations in air pressure, so that it is possible to maintain a
constant flying height of the slider body irrespective of
variations in air pressure. It is expected that front and rear
rails 21, 23 of lower heights will allow the slider body to better
maintain a constant flying height at the various altitudes (with
different atmospheric pressures) where the magnetic disk drive 10
will be operated. In this example of the first embodiment, the
height H is preferably set to be no more than 2 .mu.m.
[0054] Front and rear rails 21, 23 of lower heights may cause a
saturation of the negative pressure at a relatively low tangential
velocity of the magnetic disk 13. Such saturation occurs when the
negative pressure cannot follow further increases of the lift or
positive pressure at the first and second air bearing surfaces 24,
25a, 25b as the tangential velocity of the magnetic disk 13
increases. The faster the tangential velocity becomes, the larger
the flying height of the slider body gets. For example, the flying
height of the slider body gets larger at positions nearer to the
periphery of the magnetic disk 13 at which the tangential velocity
is larger than at positions nearer to the center of the magnetic
disk 13.
[0055] The grooves 30 enable the negative pressure to follow the
tangential velocity in the negative pressure air bearing slider 14.
As shown in FIG. 5 for example, it is observed that the negative
pressure increases as the tangential velocity gets faster, even if
front and rear rails 21, 23 of lower heights are employed. A slider
without grooves 30 leads to a saturation of the negative pressure
at a lower tangential velocity, whereby the negative pressure
cannot increase anymore as the tangential velocity gets higher.
[0056] The grooves 30 are preferably positioned as far downstream
as possible. If so, the cavity surrounded by the front and side
rails 21, 29 becomes larger, so that a larger negative pressure can
be generated. In addition, the negative pressure area can be
shifted downstream. Accordingly, it is possible to further
stabilize the flying behavior of the slider body.
[0057] Next, a description will be made of the preferred method of
producing the negative pressure air bearing slider 14. As shown in
FIG. 6A, a plurality of transducer elements or magnetic head
elements are formed on the disk face of a wafer 40, which is
preferably made of Al.sub.2O.sub.3--TiC with an Al.sub.2O.sub.3
layer formed thereon. The transducer elements are respectively
formed in blocks, with each defining a single negative pressure air
bearing slider 14. For example, 10,000 sliders (arranged a row of
100 by a column of 100, 100.times.100=10,000) can be cut out from a
wafer of 5 inches in diameter. The transducer elements are covered
with a protection layer, preferably made of Al.sub.2O.sub.3.
[0058] As shown in FIG. 6B, the wafer 40 on which the transducer
elements are formed is cut off into wafer bars 40a comprising
sliders in a row. The exposed surface 41 of the wafer bar 40a is
configured into the bottom 19 of the slider body. Finally, as shown
in FIG. 6C, each of the negative pressure air bearing sliders 14 is
cut off from the wafer bar 40a.
[0059] Next, a more detailed description will be made for
explaining how to configure the bottom 19 of the slider body. As
shown in FIG. 7A, the exposed surface 41 of the wafer bar 40a is
covered with a diamond-like-carbon (DLC) layer 43 with a Si
adhesion layer 42 interposed therebetween. A further DLC layer 45
is then layered over the DLC layer 43 with a Si adhesion layer 44
interposed therebetween. A film resist 46 is formed on the surface
of the DLC layer 45 so as to pattern the contours of the pads 31a,
31b, 31c, 31d.
[0060] As shown in FIG. 7B, the DLC layer 45 and the Si adhesion
layer are etched using a reactive ion etching method so as to
expose the DLC layer 43. The tip ends of the pads 31a, 31b, 31c,
31d are configured according to the pattern. The resist 46 is then
removed as shown in FIG. 7C.
[0061] As shown in FIG. 7D, a photoresist 47 is formed to pattern
the contours of the first and second air bearing surfaces 24,25a,
25b. The configured pads 31a, 31b, 31c, 31d are covered with the
photoresist 47. After exposure and development, as shown in FIG.
7E, an ion milling method is conducted to etch the DLC layer 43,
the Si adhesion layer 42 and the body of Al.sub.2O.sub.3--TiC of
the wafer bar 40a. As a result, the first and second air bearing
surfaces 24, 25a, 25b are configured according to the pattern. At
the same time, the configuration of the pads 31a, 31b, 31c, 31d is
completed. Thereafter, the photoresist 47 is removed as shown in
FIG. 7F.
[0062] Then, as shown in FIG. 8A, a photoresist 48 is formed to
pattern the contours of the front, side and rear rails 21, 29, 23.
The configured pads 31a, 31b, 31c, 31d, and the configured first
and second air bearing surfaces 24, 25a, 25b are covered with the
photoresist 48. After exposure and development, an ion milling
method is conducted to further etch the body of
Al.sub.2O.sub.3--TiC of the wafer bar 40a. As a result, the front,
side and rear rails 21, 29, 23 are configured according to the
pattern. When the photoresist 48 is removed as shown in FIG. 8B,
the pads 31a, 31b, 31c, 31d appear on the tops of the front, side
and rear rails 21, 29, 23, with the tip ends protected by the DLC
layer 45. The first and second air bearing surfaces 24, 25a, 25b
likewise appear on the tops of the front and rear rails 21, 23,
with the tops protected by the DLC layer 43. The configuration of
the bottom 19 of the slider body is thus completed.
[0063] As shown in FIG. 9, for example, the second air bearing
surface 25a with the transducer element of the aforementioned
negative pressure air bearing slider 14 may include an upstream end
51 extending along a first width W1 in the lateral direction so as
to lead to the step 27b, and a downstream end 52 extending along a
second width W2 that is larger than the first width WI in the
lateral direction. For example, in the case where the transducer
element comprises a magnetoresistance (MR) element, the MR element
should be protected between a pair of shield layers 53. If the
shield layers 53 fail to have a lateral size that is large enough
to shield the MR element from magnetic interference of the vicinal
magnetic field, the MR element will not be able to correctly read
data off of the magnetic disk 13. The wider downstream end 52
enables the second air bearing surface 25a to be of a smaller area,
while still keeping the larger lateral size of the shield layers 53
at the same time, thereby making the lift of the second air bearing
surface 25b larger than the lift of the second air bearing surface
25a.
[0064] The wider downstream end 52 of the second width W2 can be
realized by varying the lateral width of the second air bearing
surface 25a in the longitudinal direction. For example, as shown in
FIG. 9, the second air bearing surface 25a may be continuously
enlarged along its lateral width from the upstream end 51 of the
first width W1 to the downstream end 52 of the second width W2. As
a modification, the second air bearing surface 25a may maintain the
first width W1 of the upstream end 51 along its longitudinal
direction until just before reaching the downstream end 52 of the
second width W2, as shown in FIG. 10, in which the second air
bearing surface 25a is generally L-shaped. FIG. 11 shows an
additional modification which is substantially a combination of
part of FIGS. 9 and 10, in which the second air bearing surface 25a
maintains the first width W1 of the upstream end 51 until the
lateral width of the second air bearing surface 25a starts to
continuously enlarge toward the second width W2 of the downstream
end 52.
[0065] When the lift at the second air bearing surface 25b is
intended to be larger than that of the second air bearing surface
25a with the transducer element, as shown in FIG. 12, an upstream
end 56 extending in the lateral direction so as to define the step
27b on the second air bearing surface 25a may be disposed more
downstream than an upstream end 55 extending in the lateral
direction so as to define the step 27c on the second air bearing
surface 25b. Such disposition of the second air bearing surfaces
25a, 25b serves to reduce the length of the second air bearing
surface 25a in the direction of the air stream as compared with
that of the second air bearing surface 25b. Accordingly, the
smaller second air bearing surface 25a can be realized to set the
lift at the second air bearing surface 25a with the transducer
element to be smaller than that of the second bearing surface 25b
without a transducer element. Thus, it is possible to reduce the
lift at the second air bearing surface 25a without a reduction in
the lateral width of the shield layers 53.
[0066] When the upstream end 56 of the second air bearing surface
25a is displaced downstream as described above, it is preferable to
adjust the size of the groove 30 between the rear and side rails
23, 29. As shown in FIG. 12, for example, if the side rail 29 fails
to extend toward the rear rail 23 to follow the displacement of the
upstream end 56 of the second air bearing surface 25a, the groove
30 becomes larger or wider. The wider groove 30 may release the
negative pressure generated behind the front rail 21 as describe
above. On the other hand, when the side rail 29 is extended to
follow the displacement of the upstream end 56 as shown in FIG. 13,
a smaller or narrower groove 30 can be obtained, so that a higher
negative pressure can be maintained behind the front rail 21. A
higher negative pressure enables the second air bearing surface 25a
to reliably approach the disk surface as closely as possible.
[0067] Furthermore, when the lift at the second air bearing surface
25a with the transducer element needs to be reduced, as shown in
FIG. 14, for example, the position of the second air bearing
surface 25a can be determined relative to the lower surface of the
rear rail 23. The aforementioned higher positive pressure generated
at the steps 27b, 27c depends not only upon their areas and
heights, in addition to the areas of the second air bearing
surfaces 25a, 25b, but also upon the areas of the lower surfaces
leading to the steps 27b, 27c on the rear rails 23. Smaller lower
surface areas make for less positive pressure, while larger lower
surface areas make for larger positive pressure. Accordingly, as
shown in FIG. 14, if the lateral width W3 of the lower surface area
leading to the step 27b facing outwardly of the slider body on the
rear rail 23 is reduced, the lift can be reduced at the second air
bearing surface 25a with the transducer element, since the step 27b
facing outwardly of the slider body tends to receive a larger
amount of the air stream than the step 27b facing inwardly of the
slider body.
[0068] Furthermore, when the lift at the second air bearing surface
25a with the transducer element needs to be reduced, as shown in
FIG. 15, for example, the second air bearing surface 25a may
include a downstream end 57 extending in the lateral direction at
the downstream position which can be displaced upstream. As
described above, the negative pressure air bearing slider 14 has
the maximum positive pressure at the downstream end of the slider
body as is apparent from FIG. 3. Accordingly, when the downstream
end 57 is displaced upstream so as to reduce the area of the second
air bearing surface 25a, the lift can be efficiently reduced at the
second air bearing surface 25a with the transducer element.
[0069] It should be noted that the negative pressure air bearing
slider 14 of the present invention may be employed in storage disk
drives other than the aforementioned hard disk drives (HDD) 10.
[0070] While various embodiments of the present invention have been
shown and described, it should be understood that other
modifications, substitutions and alternatives may be apparent to
one of ordinary skill in the art. Such modifications, substitutions
and alternatives can be made without departing from the spirit and
scope of the invention, which should be determined from the
appended claims.
[0071] Various features of the invention are set forth in the
appended claims.
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