U.S. patent application number 12/241628 was filed with the patent office on 2009-06-04 for head, head suspension assembly, and disk device provided with the same.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. Invention is credited to Mitsunobu HANYU.
Application Number | 20090141402 12/241628 |
Document ID | / |
Family ID | 40612064 |
Filed Date | 2009-06-04 |
United States Patent
Application |
20090141402 |
Kind Code |
A1 |
HANYU; Mitsunobu |
June 4, 2009 |
HEAD, HEAD SUSPENSION ASSEMBLY, AND DISK DEVICE PROVIDED WITH THE
SAME
Abstract
According to one embodiment, a slider of a magnetic head is
provided with a negative-pressure cavity formed in a facing
surface, a leading step portion situated on the upstream side of
the negative-pressure cavity, a pair of side portions opposed to
each other, a trailing step portion situated on the outlet end side
of the negative-pressure cavity, and a pair of embossed portions
formed on the facing surface so as to project from the
negative-pressure cavity and provided on the outlet side of the
negative-pressure cavity with respect to an airflow. The embossed
portions individually extend along a second direction so as to be
situated individually on the opposite sides of the trailing step
portion and are formed so as to be lower than the trailing step
portion with respect to the negative-pressure cavity and flush with
an outlet-side end surface of the slider.
Inventors: |
HANYU; Mitsunobu; (Tokyo,
JP) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Tokyo
JP
|
Family ID: |
40612064 |
Appl. No.: |
12/241628 |
Filed: |
September 30, 2008 |
Current U.S.
Class: |
360/235.5 ;
G9B/5.229 |
Current CPC
Class: |
G11B 5/6082 20130101;
G11B 5/6005 20130101 |
Class at
Publication: |
360/235.5 ;
G9B/5.229 |
International
Class: |
G11B 5/60 20060101
G11B005/60 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2007 |
JP |
2007-311344 |
Claims
1. A head comprising: a slider comprising a facing surface opposed
to a surface of a rotatable recording medium, an inlet-side end
surface extending across the facing surface, and an outlet-side end
surface extending across the facing surface and is caused to fly by
an airflow produced between the recording medium surface and the
facing surface as the recording medium rotates; and a head portion
provided on the slider and configured to record information to the
recording medium and to reproduce the information from the
recording medium, the facing surface of the slider having a first
direction along the airflow and a second direction perpendicular to
the first direction, the slider comprising a negative-pressure
cavity defined by a recess formed in the facing surface and
configured to produce a negative pressure, a leading step portion
formed on the facing surface, projecting from the negative-pressure
cavity and situated on an upstream side of the negative-pressure
cavity with respect to the airflow, a pair of side portions
individually formed on the facing surface, projecting from the
negative-pressure cavity, extending from the leading step portion
toward the outlet end side of the slider in the first direction,
and opposed to each other with a space between the pair in the
second direction, a trailing step portion formed on the facing
surface, projecting from the negative-pressure cavity, situated on
an outlet side of the negative-pressure cavity with respect to the
airflow, and comprising a top surface opposed to the recording
medium, and a pair of embossed portions formed on the facing
surface, projecting from the negative-pressure cavity, and provided
on the outlet side of the negative-pressure cavity with respect to
the airflow, the embossed portions individually extending in the
second direction and being situated individually on the opposite
sides of the trailing step portion with respect to the second
direction, the embossed portions being lower than the trailing step
portion with respect to the negative-pressure cavity and flush with
the outlet-side end surface of the slider.
2. The head of claim 1, wherein a width of each embossed portion is
defined by an upstream end and the outlet-side end surface along
the first direction.
3. The head of claim 1, wherein the pair of embossed portions
continuously extend together in the second direction.
4. The head of claim 1, wherein the slider comprises a pair of
skirt portions formed on the facing surface and extending
individually from the side portions toward the embossed portions in
the first direction.
5. The head of claim 1, wherein the slider is a femto slider having
a length of 0.85 mm in the first direction and a width of 0.7 mm in
the second direction, a depth of the trailing step portion ranges
from 50 nm to 250 nm, and a depth of each embossed portion ranges
from 250 nm to 800 nm.
6. A head suspension assembly used in a disk device comprising a
disk recording medium and a drive section configured to support and
rotate the recording medium, the head suspension assembly
comprising: a head comprising a slider comprising a facing surface
opposed to a surface of a rotatable recording medium, an inlet-side
end surface extending across the facing surface, and an outlet-side
end surface extending across the facing surface and is caused to
fly by an airflow produced between the recording medium surface and
the facing surface as the recording medium rotates, and a head
portion, provided on the slider and configured to record
information to the recording medium and reproduce the information
from the recording medium; and a head suspension configured to
support the head for movement with respect to the recording medium
and to apply a head load directed toward the surface of the
recording medium to the head, the facing surface of the slider
having a first direction along the airflow and a second direction
perpendicular to the first direction, the slider comprising a
negative-pressure cavity defined by a recess formed in the facing
surface and configured to produce a negative pressure, a leading
step portion formed on the facing surface, projecting from the
negative-pressure cavity, and situated on an upstream side of the
negative-pressure cavity with respect to the airflow, a pair of
side portions individually formed on the facing surface projecting
from the negative-pressure cavity, extending from the leading step
portion toward the outlet end side of the slider in the first
direction, and opposed to each other with a space between the pair
in the second direction, a trailing step portion formed on the
facing surface, projecting from the negative-pressure cavity,
situated on an outlet side of the negative-pressure cavity with
respect to the airflow, and comprising a top surface opposed to the
recording medium, and a pair of embossed portions formed on the
facing surface, projecting from the negative-pressure cavity, and
provided on the outlet side of the negative-pressure cavity with
respect to the airflow, the embossed portions individually
extending in the second direction and being situated individually
on the opposite sides of the trailing step portion with respect to
the second direction, the embossed portions being lower than the
trailing step portion with respect to the negative-pressure cavity
and flush with the outlet-side end surface of the slider.
7. A disk device comprising: a disk recording medium; a drive
section configured to support and rotates the recording medium; a
head comprising a slider, comprising a facing surface opposed to a
surface of a rotatable recording medium, an inlet-side end surface
extending across the facing surface, and an outlet-side end surface
extending across the facing surface and is caused to fly by an
airflow produced between the recording medium surface and the
facing surface as the recording medium rotates, and a head portion
provided on the slider and configured to record information to the
recording medium and reproduce the information from the recording
medium; and a head suspension configured to support the head for
movement with respect to the recording medium and to apply a head
load directed toward the surface of the recording medium to the
head, the facing surface of the slider having a first direction
along the airflow and a second direction perpendicular to the first
direction, the slider comprising a negative-pressure cavity defined
by a recess formed in the facing surface and configured to produce
a negative pressure, a leading step portion formed on the facing
surface, projecting from the negative-pressure cavity and situated
on an upstream side of the negative-pressure cavity with respect to
the airflow, a pair of side portions individually formed on the
facing surface, projecting from the negative-pressure cavity,
extending from the leading step portion toward the outlet end side
of the slider in the first direction, and opposed to each other
with a space between the pair in the second direction, a trailing
step portion formed on the facing surface, projecting from the
negative-pressure cavity, situated on an outlet side of the
negative-pressure is cavity with respect to the airflow, and
comprising a top surface opposed to the recording medium, and a
pair of embossed portions which are formed on the facing surface,
projecting from the negative-pressure cavity, and provided on the
outlet side of the negative-pressure cavity with respect to the
airflow, the embossed portions individually extending in the second
direction and being situated individually on the opposite sides of
the trailing step portion with respect to the second direction, the
embossed portions being lower than the trailing step portion with
respect to the negative-pressure cavity and flush with the
outlet-side end surface of the slider.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2007-311344, filed
Nov. 30, 2007, the entire contents of which are incorporated herein
by reference.
BACKGROUND
[0002] 1. Field
[0003] One embodiment of the invention relates to a head used in a
disk device such as a magnetic disk device, a head suspension
assembly provided with the head, and a disk device provided with
the head suspension assembly.
[0004] 2. Description of the Related Art
[0005] A disk device, e.g., a magnetic disk device, includes a
magnetic disk, spindle motor, magnetic head, and carriage assembly.
The magnetic disk is arranged in a case. The spindle motor supports
and rotates the disk. The magnetic head writes and reads
information to and from the disk. The carriage assembly supports
the magnetic head for movement with respect to the magnetic disk.
The carriage assembly includes a rotatably supported arm and a
suspension extending from the arm. The magnetic head is supported
on an extended end of the suspension. The head includes a slider
attached to the suspension and a head portion on the slider. The
head portion is constructed including a reproducing element for
reading and a recording element for writing.
[0006] The slider has a facing surface (air bearing surface: ABS)
that is opposed to a recording surface of the magnetic disk. A
predetermined head load directed to a magnetic recording layer of
the disk is applied to the slider by the suspension. When the
magnetic disk device operates, an airflow is generated between the
disk in rotation and the slider. Based on the principle of
aerodynamic lubrication, a force (positive pressure) to fly the
slider above the recording surface of the disk acts on the facing
surface of the slider. By balancing this flying force with the head
load, the slider is flown with a given gap above the recording
surface of the disk. There is provided a disk device in which a
negative-pressure cavity or a dynamic pressure generating groove is
formed near the center of the facing surface of the slider in order
to prevent fluctuations of the flying height.
[0007] In a conventional magnetic disk, moreover, a lubricant is
spread thinly on the disk surface to reduce its abrasion by contact
with a magnetic head. Although most of the lubricant adheres to the
disk surface, a small portion may sometimes leave the disk surface
and adhere to a facing surface of a slider. If the lubricant
adheres to the slider, the adhesion increases gradually. If this
adhesion exceeds a certain level, the lubricant drops from the
slider onto the disk surface and forms a protuberance that adheres
to the disk surface. If this protuberance of the lubricant is
formed on the disk surface, the magnetic head unduly floats above
the disk surface as it passes over the protuberance, thereby
incurring a so-called high-fly write state. In some cases,
therefore, the magnetic head may fail to accurately write and read
information to and from the disk surface.
[0008] There is provided a device in which a plurality of
noncontinuous portions are arranged on a facing surface of a slider
to form standing-air regions that prevent a lubricant from adhering
to the surface of a slider by a surface tension between the slider
surface and the disk surface (e.g., Japanese Publication No.
2001-503903).
[0009] In the magnetic disk device, most of air that flows between
the disk surface and the slider forms regular flows that run from
the air inlet end side of the slider to the outlet end side.
However, some of the air forms backflows that run reversely between
the slider and the disk surface after having once run out of the
slider.
[0010] If such backflows occurs, the lubricant that is lifted above
the disk surface flows toward and adheres to the facing surface of
the slider. If the adhesion of the lubricant gradually increases,
the lubricant finally drops on the disk surface and forms a
protuberance that adheres to the disk surface. If this protuberance
of the lubricant is formed on the disk surface, as mentioned
before, the magnetic head unduly floats above the disk surface,
thereby incurring the so-called high-fly write.
[0011] Although the adhesion of the lubricant that is attributable
to the surface tension can be reduced in the conventional magnetic
disk device described above, it is difficult to suppress the
adhesion of the lubricant that is caused by the backflows.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0012] A general architecture that implements the various features
of the invention will now be described with reference to the
drawings. The drawings and the associated descriptions are provided
to illustrate embodiments of the invention and not to limit the
scope of the invention.
[0013] FIG. 1 is an exemplary plan view showing an HDD according to
a first embodiment of the invention;
[0014] FIG. 2 is an exemplary enlarged side view showing a magnetic
head portion of the HDD;
[0015] FIG. 3 is an exemplary perspective view showing the
disk-facing surface side of a slider of the magnetic head;
[0016] FIG. 4 is an exemplary plan view showing the disk-facing
surface side of the slider;
[0017] FIG. 5 is an exemplary sectional view taken along line V-V
of FIG. 4;
[0018] FIG. 6 is an exemplary conceptual diagram for illustrating
backflows between a disk surface and the slider;
[0019] FIG. 7 is an exemplary plan view showing a slider of a
magnetic head without embossed portions, given as Comparative
Example 1;
[0020] FIG. 8 is an exemplary plan view showing a slider of a
magnetic head as Comparative Example 2 in which embossed portions
are shifted from an outlet end surface of a slider toward the inlet
side;
[0021] FIG. 9 is an exemplary plan view showing the slider of the
magnetic head according to the first embodiment;
[0022] FIG. 10 is an exemplary diagram showing negative pressure
variations involved in changes of the groove depth of the sliders
of the magnetic according to the present embodiment and Comparative
Example 2, for the inner peripheral portion, middle portion, and
outer peripheral portion of the disk;
[0023] FIG. 11 is an exemplary diagram showing flying height
variations involved in changes of the groove depth of the sliders
of the magnetic according to the present embodiment and Comparative
Example 2, for the inner peripheral portion, middle portion, and
outer peripheral portion of the disk;
[0024] FIG. 12 is an exemplary plan view showing the disk-facing
surface side of a magnetic head according to a second embodiment of
the invention; and
[0025] FIG. 13 is an exemplary plan view showing the disk-facing
surface side of a magnetic head according to a third embodiment of
the invention.
DETAILED DESCRIPTION
[0026] Various embodiments according to the invention will be
described hereinafter with reference to the accompanying drawings.
In general, according to one embodiment of the invention, a head
comprises: a slider which has a facing surface opposed to a surface
of a rotatable recording medium, an inlet-side end surface
extending across the facing surface, and an outlet-side end surface
extending across the facing surface and is caused to fly by an
airflow which is produced between the recording medium surface and
the facing surface as the recording medium rotates; and a head
portion which is provided on the slider and records and reproduces
information to and from the recording medium, the facing surface of
the slider having a first direction along the airflow and a second
direction perpendicular to the first direction, the slider
including a negative-pressure cavity which is defined by a recess
formed in the facing surface and produces a negative pressure, a
leading step portion which is formed on the facing surface so as to
project from the negative-pressure cavity and situated on an
upstream side of the negative-pressure cavity with respect to the
airflow, a pair of side portions which are individually formed on
the facing surface so as to project from the negative-pressure
cavity, extend from the leading step portion toward the outlet end
side of the slider in the first direction, and are opposed to each
other with a space therebetween in the second direction, a trailing
step portion which is formed on the facing surface so as to project
from the negative-pressure cavity, is situated on an outlet side of
the negative-pressure cavity with respect to the airflow, and has a
top surface opposed to the recording medium, and a pair of embossed
portions which are formed on the facing surface so as to project
from the negative-pressure cavity and provided on the outlet side
of the negative-pressure cavity with respect to the airflow, the
embossed portions individually extending in the second direction
and being situated individually on the opposite sides of the
trailing step portion with respect to the second direction, the
embossed portions being lower than the trailing step portion with
respect to the negative-pressure cavity and flush with the
outlet-side end surface of the slider.
[0027] A first embodiment in which a disk device according to this
invention is applied to a hard disk drive (HDD) will now be
described in detail with reference to the accompanying
drawings.
[0028] As shown in FIG. 1, the HDD includes a case 12 in the form
of an open-topped rectangular box and a top cover (not shown). The
top cover is fastened to the case by screws so as to close the top
opening of the case.
[0029] The case 12 contains a magnetic disk 16, spindle motor 18,
magnetic heads 40, carriage assembly 22, voice coil motor (VCM) 24,
ramp load mechanism 25, board unit 21, etc. The magnetic disk 16
serves as a recording medium. The spindle motor 18 serves as a
drive section that supports and rotates the disk. The magnetic
heads write and read information to and from the disk. The carriage
assembly 22 supports the heads for movement with respect to the
disk 16. The VCM 24 rotates and positions the carriage assembly.
The ramp load mechanism 25 holds the magnetic heads in a retracted
position at a distance from the magnetic disk when the heads are
moved to the outermost periphery of the disk. The board unit 21
includes a head IC and the like.
[0030] A printed circuit board (not shown) is screwed to the outer
surface of a bottom wall of the case 12. The circuit board controls
the operations of the spindle motor 18, VCM 24, and magnetic heads
through the board unit 21.
[0031] The magnetic disk 16 has magnetic recording layers on its
upper and lower surfaces, individually. Lubricant 17, e.g., oil is
coated on the surfaces of the magnetic disk 16 with a thickness of
about 1 nm. The disk 16 is fitted on a hub (not shown) of the
spindle motor 18 and fixed on the hub by a clamp spring 17. If the
motor 18 is driven, the disk 16 is rotated at a predetermined speed
of, for example, 4,200 rpm in the direction of arrow B.
[0032] The carriage assembly 22 is provided with a bearing portion
26, which is fixed on the bottom wall of the case 12, and arms 32
that extend from the bearing portion. The arms 32 are situated
parallel to the surfaces of the magnetic disk 16 and spaced from
one another. They extend in the same direction from the bearing
portion 26. The carriage assembly 22 is provided with suspensions
38 that are elastically deformable elongated plates. Each
suspension 38 is formed of a leaf spring, of which the proximal end
is fixed to the distal end of its corresponding arm 32 by spot
welding or adhesive bonding and which extends from the arm.
Alternatively, each suspension may be formed integrally with its
corresponding arm 32. The arm 32 and the suspension 38 constitute a
head suspension, and the head suspension and the magnetic heads 40
constitute a head suspension assembly.
[0033] As shown in FIG. 2, each magnetic head 40 includes a slider
42 substantially in the shape of a rectangular parallelepiped and a
recording/reproducing head portion 44 on the slider. It is fixed to
a gimbal spring 41 that is provided on the distal end portion of
each suspension 38. Each magnetic head 40 is subjected to a head
load L that is directed to a surface of the magnetic disk 16 by the
elasticity of the suspension 38.
[0034] As shown in FIG. 1, the carriage assembly 22 includes a
support frame 45 that extends from the bearing portion 26
oppositely from the arms 32. The support frame supports a voice
coil 47 that constitutes a part of the VCM 24. The support frame 45
is molded from plastic and formed integrally on the outer periphery
of the voice coil 47. The voice coil 47 is situated between a pair
of yokes 49 that are fixed on the case 12 and, in conjunction with
these yokes and a magnet (not shown) fixed to one of the yokes,
constitutes the VCM 24. If the voice coil 47 is energized, the
carriage assembly 22 rotates around the bearing portion 26,
whereupon each magnetic head 40 is moved to and positioned in a
region over a desired track of the magnetic disk 16.
[0035] The ramp load mechanism 25 includes a ramp 51 and tabs 53.
The ramp 51 is provided on the bottom wall of the case 12 and
located outside the magnetic disk 16. The tabs 53 extend
individually from the respective distal ends of the suspensions 38.
As the carriage assembly 22 rotates to its retracted position
outside the magnetic disk 16, each tab 53 engages with a ramp
surface on the ramp 51 and is then pulled up along the slope of the
ramp surface, whereupon each magnetic head is unloaded.
[0036] The following is a detailed description of each magnetic
head 40. FIG. 3 is a perspective view showing the slider of the
magnetic head, FIG. 4 is a plan view of the slider, and FIG. 5 is a
sectional view of the slider.
[0037] As shown in FIGS. 3 to 5, the magnetic head 40 includes the
slider 42 that is substantially in the shape of a rectangular
parallelepiped. The slider has a rectangular disk-facing surface
(ABS) 43, inlet-side end surface 44a, outlet-side end surface 44b,
and a pair of side surfaces 44c. The disk-facing surface 43 faces a
surface of the magnetic disk 16. The end surfaces 44a and 44b and
the side surfaces 44c extend at right angles to the disk-facing
surface.
[0038] The longitudinal direction of the disk-facing surface 43 is
supposed to be a first direction X, and the transverse direction
perpendicular thereto to be a second direction Y. The slider 42 is
formed as a so-called femto slider, having a length L of 1.25 mm or
less, e.g., 0.85 mm, in the first direction X and a width W of 1.0
mm or less, e.g., 0.7 mm, in the second direction Y.
[0039] The magnetic head 40 is constructed as a flying head, in
which the slider 42 is caused to fly by airflows C (see FIG. 2)
that are produced between the disk surface and the disk-facing
surface 43 as the magnetic disk 16 rotates. When the HDD is
operating, the disk-facing surface 43 of the slider 42 never fails
to be opposed to the disk surface with a gap therebetween. The
direction of the airflows C is coincident with the direction of
rotation B of the magnetic disk 16. The slider 42 is located so
that the first direction X of the disk-facing surface 43 opposed to
the surface of the disk 16 is substantially coincident with the
direction of the airflows C.
[0040] As shown in FIGS. 3 to 5, a negative-pressure cavity 54, a
recess, is formed spanning from a substantially central part of the
disk-facing surface 43 to the outlet end side. The cavity 54 opens
downstream. The thickness of the slider 42 is adjusted to, for
example, 0.23 mm, and the depth of the cavity 54 to 600 to 1,300
nm, e.g., to 1,200 nm. The negative-pressure cavity 54 serves to
produce a negative pressure on the central part of the disk-facing
surface 43 at every feasible yaw angle for the HDD.
[0041] A substantially rectangular leading step portion 50 is
formed on the inlet-side end portion of the disk-facing surface 43.
The leading step portion 50 protrudes from the bottom surface of
the negative-pressure cavity 54 so as to be one level lower than
the disk-facing surface 43 and is situated on the inlet side of the
cavity 54 with respect to the airflows C.
[0042] A pair of side portions 46 are formed on the disk-facing
surface 43. They extend along the side edges of the surface 43 and
are opposed to each other with a space in the second direction Y
between them. The side portions 46 extend from the leading step
portion 50 toward the downstream end of the slider 42. The leading
step portion 50 and the pair of side portions 46 are arranged
symmetrically with respect to the central axis of the slider 42. As
a whole, they are substantially U-shaped, closed on the upstream
side and open downstream. The leading step portion 50 and the side
portions 46 define the negative-pressure cavity 54.
[0043] In order to maintain the pitch angle of the magnetic head
40, a leading pad 52 that utilizes an air film to support the
slider 42 protrudes from the leading step portion 50. The leading
pad 52 continuously extends throughout the area that covers the
width of the leading step portion 50 along the second direction Y,
and is formed in a position deviated downstream from the inlet-side
end surface 44a of the slider 42.
[0044] A side pad 48 is formed on each side portion 46 and connects
with the leading pad 52. The pads 52 and 48 are formed
substantially flat and form the disk-facing surface 43.
[0045] A first recess 56a and a second recess 56b are continuously
formed in each side pad 48. The first and second recesses 56a and
56b open toward the inlet-side end of the disk-facing surface 43 as
well as toward the magnetic disk surface. Each of the recesses 56a
and 56b has a rectangular shape defined by a pair of side edges,
which extend substantially parallel to the first direction X, and a
bottom edge, which connects the respective extended ends of the
side edges and extends substantially parallel to the second
direction Y. The second recess 56b is formed to be one level deeper
than the first recess 56b.
[0046] A pair of skirt portions 57 are formed on the disk-facing
surface 43 of the slider 42. They extend individually from the side
portions 46 toward the outlet-side end of the slider along the
first direction X. Each skirt portion 57 is formed to be deeper
than each side portion 46 and protrudes from the bottom surface of
the negative-pressure cavity 54.
[0047] The slider 42 includes a trailing step portion 58 that is
formed on the outlet-side end portion of the disk-facing surface 43
with respect to the airflows C. The trailing step portion 58 is
formed protruding from the bottom surface of the negative-pressure
cavity 54 so that its projection height is equal to that of the
leading step portion 50. In other words, the trailing step portion
58 is formed so that its depth from the disk-facing surface 43 is
equal to that of the leading step portion 50, ranging from 50 to
250 nm, e.g., 100 nm. The trailing step portion 58 is situated on
the downstream side of the cavity 54 with respect to the airflows C
and substantially in the center of the disk-facing surface 43 with
respect to the second direction Y. Further, the trailing step
portion 58 is slightly shifted from the outlet-side end surface 44b
of the slider 42 toward the inlet-side end surface 44a.
[0048] As shown in FIGS. 3 to 5, the trailing step portion 58 is
substantially in the shape of a rectangular parallelepiped, of
which two corner portions on the upstream side are chamfered. The
trailing step portion 58 has a top surface 58a that faces the
magnetic disk surface.
[0049] A trailing pad 60 that utilizes an air film to support the
slider 42 protrudes from the top surface 58a of the trailing step
portion 58. The trailing pad 60 is formed on the same height level
as the leading pad 52 and the side pads 48, and its surface
constitutes the disk-facing surface 43.
[0050] The trailing pad 60 includes a substantially rectangular
base portion 62 and a pair of wing portions 64 that extend from the
base portion to opposite sides along the second direction Y. At the
trailing step portion 58, the base portion 62 is provided on the
central axis D on the outlet end side and situated substantially in
the center with respect to the second direction Y. Each wing
portion 64 extends in the first direction X from the opposite ends
of the base portion 62 toward the upstream end of the slider
42.
[0051] The slider 42 is formed on the disk-facing surface 43 and
includes a pair of embossed portions 70. The embossed portions 70
are formed shallower than the negative-pressure cavity 54, project
above the bottom surface of the cavity 54, and are provided on the
outlet end side of the cavity 54 with respect to the airflows C.
The embossed portions 70 are each formed in the shape of a
rectangular plate, individually extend along the second direction
Y, and are situated individually on the opposite sides of the
trailing step portion 58 with respect to the second direction. The
embossed portions 70 are lower than the trailing step portion 58
with respect to the negative-pressure cavity 54, that is, deeper
than the trailing step portion with respect to the facing surface
43, having a depth of 200 to 800 nm, e.g., 400 nm. The top surface
of each embossed portion 70 is a flat surface that faces the
magnetic disk surface.
[0052] Further, the pair of embossed portions 70 are formed along
the outlet-side end of the slider 42, and the end surface of each
embossed portion is formed flush with the outlet-side end surface
44b of the slider 42. Each embossed portion 70 extends from near
the trailing step portion 58 to the vicinity of each corresponding
side surface 44c of the slider 42 along the second direction Y.
Further, each embossed portion 70 has a width d that extends
upstream from the outlet-side end surface of the slider 42 along
the first direction X. The pair of skirt portions 57 extend
individually from the side portions 46 toward the embossed portions
70, and their respective extended ends face the embossed portions
70 with small gaps between them.
[0053] As shown in FIG. 5, the head portion 44 of the magnetic head
40 includes a recording element and a reproducing element, which
record and reproduce information to and from the magnetic disk 16.
The reproducing and recording elements are embedded in the
downstream end portion of the slider 42 with respect to the
direction of the airflows C. The reproducing and recording elements
have a read/write gap (not shown) that is defined in the trailing
pad 60.
[0054] According to the HDD and the head suspension assembly
constructed in this manner, the magnetic head 40 is caused to fly
by the airflows C that are produced between the disk surface and
the disk-facing surface 43 as the magnetic disk 16 rotates. When
the HDD is operating, therefore, the disk-facing surface 43 of the
slider 42 never fails to be opposed to the disk surface with a gap
therebetween. As shown in FIG. 2, the magnetic head 40 flies in an
inclined posture such that the read/write gap of the head portion
44 is located closest to the disk surface.
[0055] Since the disk-facing surface 43 of the slider 42 is
provided with the negative-pressure cavity 54, the magnetic head 40
can produce a negative pressure on the central part of the surface
43 at every feasible yaw angle for the HDD. Further, the embossed
portions 70 are provided in the cavity at the air outlet end of the
slider 42. Therefore, the occurrence of so-called backflows such
that the airflows run reversely from the air outlet end side of the
slider to the air inlet end side can be suppressed, so that
adhesion of a lubricant to the slider can be reduced.
[0056] The following is a description of a mechanism for reducing
backflows in the slider. FIG. 6 is a conceptual diagram for
illustrating the backflows. A mathematical expression for obtaining
a flow rate Qx of backflows in the longitudinal direction of the
slider (first direction X) is given as follows:
Qx=.intg..sup.H.sub.0udz=VH/2-H.sup.3/12u.differential.P/.differential.x
[0057] In the above expression, u is the longitudinal speed
function of the slider, V is the disk speed, H is the gap height
between the disk surface and the slider ABS, .mu. is the
coefficient of viscosity, P is the air film pressure, and x is the
longitudinal direction of the slider.
[0058] It can be seen that the flow rate Qx can be effectively made
positive by reducing the gap height H if the disk speed V is
constant, since H.sup.3 exists in the second term of the above
equation. In the present embodiment, therefore, the embossed
portions 70 are arranged in the negative-pressure cavity on the air
outlet end side of the slider 42 to reduce the gap height H above
the disk surface. By doing this, the airflows can be changed from
backflows into regular flows (from the air inlet side to the outlet
side). In consequence, the backflows can be reduced to reduce the
adhesion of the lubricant to the slider.
[0059] The inventor hereof prepared the magnetic head according to
the embodiment described above and magnetic heads according to
comparative examples. For each of these magnetic heads, the flow
speed (state of backflows) of air that flows near the disk-facing
surface of the slider was analyzed, and the flying height of the
slider from the inner periphery to the outer periphery of the
magnetic disk was simulated. FIG. 7 shows a magnetic head according
to Comparative Example 1, FIG. 8 shows a magnetic head according to
Comparative Example 2, and FIG. 9 shows the magnetic head according
to the present embodiment. In these drawings, arrows represent
backflows, and it is indicated that the higher the density of the
arrows, the larger the backflows are.
[0060] The magnetic head according to Comparative Example 1 is not
provided with any embossed portions at the outlet-side end portion
of a negative-pressure cavity 54 of a slider 42, but shares other
configurations with the present embodiment. In the magnetic head of
Comparative Example 1, relatively large backflows occur from the
outlet-side end surface 44b of the slider 42 into the cavity
54.
[0061] The magnetic head according to Comparative Example 2 is
provided with embossed portions 70 formed at the outlet-side end
portion of a negative-pressure cavity 54 of a slider 42. Each
embossed portion is shifted from an outlet-side end surface 44b of
the slider toward the inlet end side, and a space is defined
between the outlet end surface and the embossed portion. Other
configurations are common to Comparative Example 2 and the present
embodiment.
[0062] In the magnetic head of the Comparative Example 2, compared
with the magnetic head of Comparative Example 1, although the
backflows are reduced, relatively large backflows occur in a region
between the outlet-side end surface 44b of the slider 42 and each
embossed portion 70.
[0063] In the magnetic head according to the present embodiment,
the backflows from the air outlet end of the slider 42 are
considerably reduced, when compared with Comparative Examples 1 and
2, as seen from FIG. 9. If the depth of the embossed portions 70
ranges from 250 to 800 nm, the embossed portions can produce an
effect to reduce the backflows as aforesaid.
[0064] FIG. 10 shows results of simulation of negative pressure
variations involved in changes of the depth (groove depth) of the
negative-pressure cavity of the magnetic head of Comparative
Example 2 and those involved in changes of the depth (groove depth)
of the embossed portions of the magnetic head of the present
embodiment. FIG. 11 shows results of simulation of head flying
height variations involved in changes of the depth of the cavity of
the magnetic head of Comparative Example 2 and those involved in
changes of the depth of the embossed portions of the magnetic head
of the present embodiment.
[0065] According to the magnetic head of Comparative Example 2, as
shown in FIGS. 10 and 11, the negative pressure is considerably
reduced and the head flying height is inevitably increased to an
extreme as the groove depth decreases, in any of positions
including a position (ID) that faces the inner periphery of the
magnetic disk, a position (MD) that faces a radially middle portion
of the disk, and a position (OD) that faces the outer periphery of
the disk.
[0066] According to the magnetic head of the present embodiment, on
the other hand, the negative pressure hardly changes and the head
flying height variations are hardly influenced if the depth of
(groove depth) of the embossed portions are changed, in any of the
positions including the position (ID) that faces the inner
periphery of the magnetic disk, the position (MD) that faces the
radially middle portion of the disk, and the position (OD) that
faces the outer periphery of the disk, as seen from the
diagrams.
[0067] As mentioned before, moreover, the effect to reduce the
backflows can be obtained only if the depth of the embossed
portions 70 is not larger than 800 nm. If a reduction in the
negative pressure is taken into consideration, however, the depth
of the embossed portions should preferably be adjusted to 200 nm or
more.
[0068] Accordingly, the embossed portions are provided in the
negative-pressure cavity on the air outlet end side of the slider
so as to be flush with the outflow-side end surface of the slider.
By doing this, backflows such that the airflows run reversely from
the air outlet side of the slider to the air inlet side can be
prevented, so that adhesion of the lubricant to the slider can be
reduced. Thus, there can be obtained a head of improved reliability
and stability, a head suspension assembly provided with the head,
and a disk device.
[0069] FIG. 12 shows a magnetic head 40 of a disk device according
to a second embodiment of this invention. According to the present
embodiment, each of embossed portions 70 formed in a slider 42 has
a large width along the first direction X and extends from an
outlet-side end surface 44b of the slider 42 to the vicinity of
each corresponding side pad 48.
[0070] In a magnetic head 40 of a disk device according to a third
embodiment of this invention, as shown in FIG. 13, moreover, a pair
of embossed portions 70 formed on a slider 42 are connected to each
other in the position of a trailing step portion 58 and
continuously extend along the second direction Y of the slider
These embossed portions 70 are formed flush with an outlet-side end
surface 44b of the slider.
[0071] In the second and third embodiments, the depth of the
embossed portions 70 above the disk-facing surface 43 is larger
than that of the trailing step portion 58. In these embodiments,
moreover, other configurations of the magnetic disk device
including the magnetic heads are the same as those of the foregoing
first embodiment, so that like reference numbers are used to
designate like portions, and a detailed description thereof is
omitted. Further, the same functions and effects of the first
embodiment can also be obtained with the second and third
embodiments.
[0072] While certain embodiments of the invention have been
described, these embodiments have been presented by way of example
only, and are not intended to limit the scope of the invention.
Indeed, the novel methods and systems described herein may be
embodied in a variety of other forms. Furthermore, various
omissions, substitutions and changes in the form of the methods and
systems described herein may be made without departing from the
spirit of the invention. The accompanying claims and their
equivalents are intended to cover such forms or modifications as
would fall within the scope and spirit of the invention.
[0073] The shapes, dimensions, etc., of the leading step portion,
trailing step portion, embossed portions, and pads of the slider
are not limited to the embodiment described herein but may be
varied as required. This invention is not limited to femto sliders
but may also be applied to pico sliders, pemto sliders, or any
other larger sliders. Further, two or more disks, instead of one,
may be regularly used in the disk device.
* * * * *