U.S. patent application number 09/271529 was filed with the patent office on 2002-05-09 for head carriage assembly and disk device incorporating thereof.
This patent application is currently assigned to Fujitsu Limited. Invention is credited to KOGANEZAWA, SHINJI.
Application Number | 20020054457 09/271529 |
Document ID | / |
Family ID | 13502160 |
Filed Date | 2002-05-09 |
United States Patent
Application |
20020054457 |
Kind Code |
A1 |
KOGANEZAWA, SHINJI |
May 9, 2002 |
HEAD CARRIAGE ASSEMBLY AND DISK DEVICE INCORPORATING THEREOF
Abstract
A head carriage assembly includes a head carriage having a
magnetic head at a first end part and a bearing between the first
end part and a second end part, the head carriage being pivotable
about a shaft cooperating with the bearing in such a manner that
the head moves in a radial direction of a rotating disk to be read.
The head carriage assembly further includes first driving means
provided at the second end of the head carriage and generating a
force for pivoting the head carriage and second driving means
generating a further force for pivoting the head carriage.
Inventors: |
KOGANEZAWA, SHINJI;
(KAWASAKI-SHI, JP) |
Correspondence
Address: |
GREER, BURNS & CRAIN
300 S WACKER DR
25TH FLOOR
CHICAGO
IL
60606
US
|
Assignee: |
Fujitsu Limited
|
Family ID: |
13502160 |
Appl. No.: |
09/271529 |
Filed: |
March 18, 1999 |
Current U.S.
Class: |
360/264.3 ;
G9B/5.197; G9B/5.216 |
Current CPC
Class: |
G11B 5/596 20130101;
G11B 5/5569 20130101 |
Class at
Publication: |
360/264.3 |
International
Class: |
G11B 005/55 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 20, 1998 |
JP |
10-072882 |
Claims
What is claimed is:
1. A head carriage assembly comprising: a head carriage having a
magnetic head at a first end part and a bearing between said first
end part and a second end part, said head carriage being pivotable
about a shaft cooperating with said bearing in such a manner that
said head moves in a radial direction of a rotating disk to be
read; first driving means provided at said second end of said head
carriage and generating a force for pivoting said head carriage;
and second driving means generating a further force for pivoting
said head carriage.
2. The head carriage assembly as claimed in claim 1, wherein said
head is a magnetic head.
3. The head carriage assembly as claimed in claim 1, wherein said
head carriage includes a hub part fitting to said shaft, and said
second driving means is provided at said hub part of said head
carriage.
4. The head carriage assembly as claimed in claim 1, wherein said
second driving means is provided at a location on a line passing
through said shaft and perpendicular to a longitudinal axis of said
head carriage.
5. The head carriage assembly as claimed in claim 4, wherein said
location of said second driving means is on the opposite side of a
center of rotation of the disk with respect to said longitudinal
axis.
6. The head carriage assembly as claimed in claim 4, wherein said
second driving means comprises a coil and a permanent magnet
opposing said coil.
7. The head carriage assembly as claimed in claim 6, wherein said
coil is provided on a chassis base in a horizontal manner and said
permanent magnet is provided at a lower surface of said hub
part.
8. The head carriage assembly as claimed in claim 6, wherein said
coil is provided on a chassis base in a horizontal manner and said
permanent magnet is provided at the same level as the center of
gravity of the head carriage.
9. The head carriage assembly as claimed in claim 6, wherein said
driving coil is vertically fixed on said chassis base and within an
arcuate slit formed in said hub part and said permanent magnet is
secured at the peripheral part of said bearing at the same level as
the center of gravity of the head carriage.
10. The head carriage assembly as claimed in claim 1, wherein said
second driving means is provided at a location on a longitudinal
axis of said head carriage between said first end and said
bearing.
11. The head carriage assembly as claimed in claim 10, wherein said
second driving means comprises a coil and a permanent magnet
opposing said coil.
12. The head carriage assembly as claimed in claim 11, wherein said
coil is provided on a chassis base in a vertical manner and within
an arcuate slit formed in said hub part; and said permanent magnet
is secured at the peripheral part of said bearing at the same level
as the center of gravity of the head carriage.
13. The head carriage assembly as claimed in claim 11, wherein said
coil is secured on a wall surface of an arcuate slit formed in said
hub part in a vertical manner; and said permanent magnet is
provided on a chassis base in a vertical manner and within said
arcuate slit formed in said hub part.
14. The head carriage assembly as claimed in claim 11, wherein said
coil is secured at the peripheral part of said bearing; and said
permanent magnet is provided on a chassis base in a vertical manner
and within an arcuate slit formed in said hub part.
15. The head carriage assembly as claimed in claim 11, wherein said
coil is provided on a chassis base in a vertical manner and within
an arcuate slit formed in said hub part; and said permanent magnet
is secured on a wall surface of said arcuate slit formed in said
hub part in a vertical manner.
16. The head carriage assembly as claimed in claim 11, wherein said
coil is provided on a chassis base in a horizontal manner; and said
permanent magnet is provided at a lower surface of said hub
part.
17. The head carriage assembly as claimed in claim 11, wherein said
coil is provided at a lower surface of said hub part; and said
permanent magnet is provided on a chassis base in a horizontal
manner.
18. A disk device comprising: 1) a chassis base; 2) a disk to be
rotated about a spindle fixed on said chassis base; 3) a head
carriage assembly comprising: a head carriage having a magnetic
head at a first end part and a bearing between said first end part
and a second end part, said head carriage being pivotable about a
shaft cooperating with said bearing in such a manner that said head
moves in a radial direction of said rotating disk to be read; first
driving means provided at said second end of said head carriage and
generating a force for pivoting said head carriage; and second
driving means also generating a force for pivoting said head
carriage; and 4) control means so as to operate said head carriage
assembly either in a seek operation in which said head is moved to
another track or in a track-following operation in which said head
is moved to follow a track on which said head is currently
placed.
19. The disk device as claimed in claim 18, wherein said head is a
magnetic head.
20. The disk device as claimed in claim 18, wherein said second
driving means is provided at a location on a line passing through
said shaft and perpendicular to a longitudinal axis of said head
carriage.
21. The disk device as claimed in claim 18, wherein, in said seek
operation, said control means actuates at least said first driving
means, and in said track-following operation, said control means
stops said first driving means and actuates said second driving
means if said second driving means has not been actuated in said
seek operation.
22. The disk device as claimed in claim 18, wherein said second
driving means is provided at a location on a longitudinal axis of
said head carriage between said first end and said bearing.
23. The disk device as claimed in claim 22, wherein, in said seek
operation, said control means actuates at least said first driving
means, and in said track-following operation, said control means
further actuates said second driving means.
24. The disk device as claimed in claim 23, wherein a magnitude of
a force generated by said first driving means is equal to a
magnitude of a force generated by said second driving means.
25. The disk device as claimed in claim 22, wherein, in said seek
operation, said control means actuates at least said first driving
means, and in said track-following operation, said control means
turns off said first driving means and actuates said second driving
means.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention generally relates to a head carriage
assembly and a disk device incorporating thereof, and particularly
relates to a magnetic head carriage assembly suitable for
high-density recording and a magnetic disk device incorporating
thereof.
[0003] 2. Description of the Related Art
[0004] There is a continuous effort toward developing magnetic disk
devices, for example, a 3.5-inch type, which devices are capable of
implementing a high-density recording. In order to achieve a
high-density recording, it is necessary to increase the value of
tracks per unit length (TPI) of magnetic disks. With such an
increased value of TPI, a width of each track will be narrowed, so
that it is necessary to improve a positioning accuracy of the
magnetic head. When the value of TPI is increased to 25000, a track
pitch will be 1 .mu.m, so that the positioning accuracy of the
magnetic head needs to be less than 0.1 .mu.m.
[0005] A basic way of improving the positioning accuracy of the
magnetic head is to increase a loop gain in a positioning-servo
system so as to obtain a higher crossover frequency in an open
loop. An upper limit of the loop gain in the positioning-servo
system depends on a natural frequency of the head carriage
supported at a bearing so as to be pivotable about a shaft.
Therefore, the magnetic disk device of the related art is designed
such that the head carriage has a high rigidity, so that the
natural frequency of the head carriage is increased and the loop
gain in the positioning-servo system is as great as possible.
[0006] However, even if the rigidity of the head carriage is
maximized, it is not possible to prevent a translational force from
acting on a bearing in a direction influencing the positioning of
the magnetic head. In other words, a translational mode occurs at
the bearing. Therefore, it is difficult to achieve a positioning
accuracy of less than 0.1 .mu.m of the magnetic head.
[0007] Japanese Laid-Open Patent Nos. 59-116965 and 8-306142
disclose magnetic head carriage assemblies which can prevent such a
translational mode from occurring at the bearing.
[0008] FIGS. 1A and 1B are diagrams showing a magnetic head
carriage assembly 10 described in Japanese Laid-Open Patent
No.59-116965. The magnetic head carriage assembly 10 includes a
head carriage 11 having a magnetic head 15 at one end and a bearing
12 at the other end. The magnetic head carriage assembly 10 also
includes magnetic driving mechanisms 13, 14 provided on both sides
of the bearing 12. The magnetic driving mechanisms 13, 14 are
driven simultaneously in mutually equal and opposite directions,
thus causing the head carriage 11 to pivot about the bearing 12.
The magnetic head 15 is moved in a radial direction of the rotating
magnetic disk 16 so as to implement seeking and positioning
operations. A translational force acting on the bearing 12 is
cancelled by equal and opposite forces F1, F2 which are exerted by
the magnetic driving mechanisms 13, 14 driven simultaneously.
[0009] FIG. 2 is a diagram showing a magnetic head carriage
assembly 20 described in Japanese Laid-Open Patent No. 8-306142.
The magnetic head carriage assembly 20 includes a head carriage 21
having a magnetic head 27 at one end and a bearing 22 at the other
end. The magnetic head carriage assembly 20 also includes magnetic
driving mechanisms 23, 24 provided on both sides of the bearing 22.
In the figure, reference numeral 25 show an axis in a longitudinal
direction of the head carriage 21. Reference numeral 26 show a line
passing through the bearing 22 and perpendicular to the axis
25.
[0010] The magnetic driving mechanisms 23, 24 are provided at
positions on an opposite side of the head carriage 27 with respect
to the line 26 (right hand side in FIG. 2). Forces F3, F4 are
produced by actuating the magnetic driving mechanisms 23, 24, so
that the head carriage 21 is pivoted about the bearing 22. The
magnetic head 27 is moved in a radial direction of the rotating
magnetic disk 28 so as to implement seeking and positioning
operations. A translational force acting on the bearing 22 is
reduced by the forces F3, F4 which are exerted by the magnetic
driving mechanism 23, 24.
[0011] With the magnetic head carriage assembly shown in FIG. 1A
and 1B, since the translational force acting on the bearing 12 is
cancelled out, it is possible to increase the loop gain in the
positioning-servo system and thus accurately positioning the
magnetic head. However, as can be seen from FIG. 1A, the magnetic
driving mechanism 14 constrains a freedom of a layout of the
magnetic disk 16 and the magnetic head carriage assembly 10.
Therefore, it is a problem that the magnetic head device cannot be
assembled easily. Also, it is a problem that information recorded
on the magnetic disc 16 may be degraded since the magnetic circuit
of the magnetic driving mechanism 14 is too close to the magnetic
disk 16.
[0012] According to the magnetic head carriage assembly 20 shown in
FIG. 2, the limitation of the layout between the magnetic disk 28
and the magnetic head carriage assembly 20 is reduced by a certain
amount compared to the magnetic head carriage assembly 10 shown in
FIG. 1. However, since the forces F3, F4 both include components in
the direction of the line 26, a translational force F5 is produced
which acts on the bearing 22. Therefore, a translational mode is
produced at the bearing 22. The translational force F5 acts in the
direction of the line 26, which direction influences the
positioning accuracy of the magnetic head 27 with respect to the
track. Therefore, it is difficult to improve the positioning
accuracy of the magnetic head.
SUMMARY OF THE INVENTION
[0013] Accordingly, it is a general object of the present invention
to provide a head carriage assembly and a disk device incorporating
thereof which can solve the problems above.
[0014] It is another and more specific object of the invention to
provide a magnetic head carriage assembly and a magnetic disk
device which can achieve an increased recording density while
achieving an accurate positioning of a magnetic head.
[0015] In order to achieve the above objects, a head carriage
assembly includes:
[0016] a head carriage having a magnetic head at a first end part
and a bearing between the first end part and a second end part, the
head carriage being pivotable about a shaft cooperating with the
bearing in such a manner that the head moves in a radial direction
of a rotating disk to be read;
[0017] first driving means provided at the second end of the head
carriage and generating a force for pivoting the head carriage;
and
[0018] second driving means generating a further force for pivoting
the head carriage.
[0019] In one aspect of the above-described head carriage assembly,
the second driving means is provided at a location on a line
passing through the shaft and perpendicular to a longitudinal axis
of the head carriage. Further, such a location may be on the
opposite side of a center of rotation of the disk with respect to
the longitudinal axis.
[0020] In another aspect of the above-described head carriage
assembly, the second driving means is provided at a location on a
longitudinal axis of the head carriage between the first end and
the bearing.
[0021] With the head carriage assembly described above, it is
possible to improve an accuracy of a track-following operation
while preventing the disk and the head carriage assembly from
interfering with each other.
[0022] It is still another object of the present invention to
provide a disk device which can achieve an increased recording
density while achieving an accurate positioning of a magnetic
head.
[0023] In order to achieve the above object, a disk device
includes:
[0024] 1) a chassis base;
[0025] 2) a disk to be rotated about a spindle fixed on the chassis
base;
[0026] 3) a head carriage assembly comprising:
[0027] a head carriage having a magnetic head at a first end part
and a bearing between the first end part and a second end part, the
head carriage being pivotable about a shaft cooperating with the
bearing in such a manner that the head moves in a radial direction
of the rotating disk to be read;
[0028] first driving means provided at the second end of the head
carriage and generating a force for pivoting the head carriage;
and
[0029] second driving means also generating a force for pivoting
the head carriage; and
[0030] 4) control means so as to operate the head carriage assembly
either in a seek operation in which the head is moved to another
track or in a track-following operation in which the head is moved
to follow a track on which the head is currently placed.
[0031] In one aspect of the above-described disk device, the second
driving means is provided at a location on a line passing through
the shaft and perpendicular to a longitudinal axis of the head
carriage. With this structure, since a translational force acting
on the head carriage is in a longitudinal direction of the head
carriage, no translational mode due to a rigidity of the bearing
will be excited in a positioning direction. Therefore, it is
possible to reduce the peak level of the translational mode so that
a resonance frequency limiting the servo bandwidth may be
increased.
[0032] In another aspect of the above-described disk device, the
second driving means is provided at a location on a line passing
through the shaft and perpendicular to a longitudinal axis of the
head carriage. With this structure, by actuating first and second
driving means during the track-following operation, a higher
primary resonance frequency is obtained so that the loop gain of
the positioning-servo system and the servo bandwidth is
increased.
[0033] In still another aspect of the above-described disk device,
the second driving means is provided at a location on a
longitudinal axis of the head carriage between the first end and
the bearing. With this structure, by actuating only second driving
means during the track-following operation, the translational mode
resulting from the rigidity of the bearing will be in phase with
the rigid body mode. Since this in phase mode does not affect the
stability of the servo-system, the loop gain of the
positioning-servo system and the servo band width are
increased.
[0034] Other objects and further features of the present invention
will be apparent from the following detailed description when read
in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIGS. 1A and 1B are a plan view and a cross-sectional
diagram, respectively, showing an example of a magnetic head
carriage assembly of the related art.
[0036] FIG. 2 is a plan view of another example of a magnetic head
carriage assembly of the related art.
[0037] FIGS. 3A and 3B are a plan view and a perspective view,
respectively, showing a magnetic disk device of a first embodiment
of the present invention.
[0038] FIG. 4 is a plan view showing a magnetic head carriage
assembly shown in FIG. 3A.
[0039] FIGS. 5A and 5B are a cross-sectional view and a plan view,
respectively, showing a secondary magnetic driving unit in FIG.
4.
[0040] FIG. 6 is a block diagram showing a circuit associated with
the magnetic head carriage assembly.
[0041] FIGS. 7A and 7B are timing charts showing operations of the
driving circuit.
[0042] FIGS. 8A and 8B are plan views illustrating effects on the
magnetic head carriage assembly during a track-following
operation.
[0043] FIGS. 9A and 9B are a plan view and a cross-sectional view,
respectively, showing a magnetic head carriage assembly provided on
a magnetic disk device of a first variant of the first embodiment
of the present invention.
[0044] FIGS. 10A and 10B are a plan view and a cross-sectional
view, respectively, showing a magnetic head carriage assembly
provided on a magnetic disk device of a second variant of the first
embodiment of the present invention.
[0045] FIGS. 11A and 11B are a plan view and a cross-sectional
view, respectively, showing a magnetic head carriage assembly
provided on a magnetic disk device of a second embodiment of the
present invention.
[0046] FIG. 12 is a block diagram showing a circuit associated with
the magnetic head carriage assembly.
[0047] FIGS. 13A and 13B are timing charts showing operations of
the driving circuit in a first mode of operation.
[0048] FIGS. 14A and 14B are plan views illustrating effects on the
magnetic head carriage assembly during a track-following operation
in the first mode of operation.
[0049] FIG. 15A is a graph showing a frequency response of the
magnetic head carriage assembly of the related art and FIG. 15B is
a graph showing a frequency response of the magnetic head carriage
assembly shown in FIGS. 11A and 11B in the first mode of operation,
both of which graphs being graphs of amplitude versus
frequency.
[0050] FIGS. 16A and 16B are timing charts showing operations of
the driving circuit in a second mode of operation.
[0051] FIGS. 17A and 17B are plan views illustrating effects on the
magnetic head carriage assembly during a track-following operation
in the second mode of operation.
[0052] FIG. 18A is a graph of phase versus frequency and FIG. 18B
is a graph of amplitude versus frequency, both of which graphs
showing frequency response of the magnetic head carriage assembly
in FIGS. 11A and 11B in the second mode of operation.
[0053] FIG. 19 is a cross-sectional view showing a magnetic head
carriage assembly provided on a magnetic disk device of a first
variant of the second embodiment of the present invention.
[0054] FIG. 20 is a cross-sectional view showing a magnetic head
carriage assembly provided on a magnetic disk device of a second
variant of the second embodiment of the present invention.
[0055] FIG. 21 is a cross-sectional view showing a magnetic head
carriage assembly provided on a magnetic disk device of a third
variant of the second embodiment of the present invention.
[0056] FIGS. 22A and 22B are a plan view and a cross-sectional
view, respectively, showing a magnetic head carriage assembly
provided on a magnetic disk device of a fourth variant of the
second embodiment of the present invention.
[0057] FIGS. 23A and 23B are a plan view and a cross-sectional
view, respectively, showing a magnetic head carriage assembly
provided on a magnetic disk device of a fifth variant of the second
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0058] In the following, principles and embodiments of the present
invention will be described with reference to the accompanying
drawings.
[0059] Although the present invention is directed to a head
carriage and a disk device, for the sake of convenience, the
following detailed description will be made with regards to a
magnetic head carriage and a magnetic desk device.
[0060] FIGS. 3A and 3B are a plan view and a perspective view,
respectively, showing a magnetic disk device 40 of a first
embodiment of the present invention. FIG. 4 is a plan view showing
a magnetic head carriage assembly 41 shown in FIG. 3A. FIG. 4 shows
a state where a magnetic head slider 42 is placed above a magnetic
disk 45 substantially at the middle of the radius of the disk
45.
[0061] FIGS. 5A is a cross-sectional view showing a secondary
magnetic driving unit shown in FIG. 4 taken along a line
IIIA-IIIA.
[0062] As shown in FIGS. 3A and 3B, the magnetic disk device 40
includes a box-shaped chassis base 44 which is provided with a
magnetic disk 45 rotatably supported by a spindle 46 and with a
magnetic head carriage assembly 41 incorporated in the chassis base
44.
[0063] As shown in FIG. 4, the magnetic head carriage assembly 41
has an arm-shaped head carriage 47. The head carriage 47 includes a
hub part 47a, an arm part 47b extending in an X2-direction from the
hub part 47a, and a fork- shaped part 47c extending in an
X1-direction from the hub part 47a.
[0064] As shown in FIG. 5A, a bearing 48 cooperates with a shaft 49
secured on the chassis base 44. The hub part 47a of the head
carriage 27 has a through-hole 47a2 which fits with the bearing 48.
Thus, the head carriage 47 is supported so as to be pivotable about
the shaft 49.
[0065] In FIG. 4, reference CX is an axis in a longitudinal
direction of the head carriage 47 and passes through the shaft 49.
Reference CY is a line passing through the shaft 49 and
perpendicular to the axis CX. Reference CZ, shown in FIG. 5, is a
longitudinal axis of the shaft 49. Here, X1 and X2 directions
indicate opposite directions of the axis CX, Y1 and Y2 directions
indicate opposite direct ions of the line CY, and Z1 and Z2
directions indicate opposite directions of the axis CZ.
[0066] At the X2-direction end of the arm part 47b, there is
provided a head suspension 50 having the head slider 42 with a
magnetic head at an edge of the head slider 42. The pivotal
movement of the head carriage 47 causes the magnetic head slider 42
to move in the radial direction of the rotating magnetic disk
45.
[0067] At the X1-direction end of the head carriage 47, there is
provided a main magnetic driving unit 51 which is actuated during a
seek operation. The main magnetic driving unit 51 corresponds to a
first driving means. The main magnetic driving unit 51 includes a
magnetic circuit unit 52 fixed on the chassis base 44 and a flat
quadrilateral driving coil 53 fixed on the fork-shaped part 47c of
the head carriage 47. The magnetic circuit unit 52 includes a
permanent magnet 54 provided adjacent the Z1-direction side of the
driving coil 53 and a yoke 55 provided adjacent the Z2-direction
side of the driving coil 53. The permanent magnet 54 has a flat
arcuate shape, and is divided into two segments which are polarized
into two polarities.
[0068] As shown in FIG. 4, a secondary magnetic driving unit 60 is
provided at a position on the line CY, on the Y1-direction side of
the shaft 49 and adjacent to the bearing 48. As can be seen in the
figure, the secondary magnetic driving unit 60 is provided within a
region of the hub part 47a. Also, "on the Y1-direction side of the
shaft 49" means "on the opposite side of the spindle 46 of the
magnetic disk 45 with respect to the axis CX". The secondary
magnetic driving unit 60 corresponds to a second driving means.
[0069] The secondary magnetic driving unit 60 is actuated during a
track-following operation. Therefore, a driving force required for
the secondary magnetic driving unit 60 may be smaller compared to
that required for the seek operation. Thus, the secondary magnetic
driving unit 60 has a relatively small size compared to the main
magnetic driving unit 51 and is assembled in a region within the
hub 47a when viewed in the plan view.
[0070] Referring now to FIGS. 5A and 5B, The secondary magnetic
driving unit 60 includes a flat quadrilateral driving coil 61 and a
permanent magnet 62, which are placed in a mutually opposing
manner. The secondary magnetic driving unit 60 further includes
yokes 63, 64. The driving coil 61 is secured on the top surface of
the yoke 63 and is secured on the chassis base 44. Of course, the
chassis base 44 may be constructed as a magnetic body so as to
serve as the yoke 63.
[0071] The permanent magnet 62 is secured at the lower surface of
the yoke 64 and is secured in a recessed part 47a1 at the lower
surface of the hub 47a. The permanent magnet 62 has a flat arcuate
shape, and is divided into two segments which are polarized into
two polarities. The size of the driving coil 61 is provided such
that an angle a between two sides 61a, 61b extending in radial
directions passing through the shaft 49 is the same as an angle a
between the corresponding sides of the driving coil 53. This is to
ensure that the secondary magnetic driving unit 60 can be operated
in a normal manner irrespective of the pivotal position of the head
carriage 47.
[0072] In the magnetic head carriage assembly 41 of the
above-described structure, as shown in FIGS. 3A and 3B, the
secondary magnetic driving unit 60 is provided at a position
substantially opposite to the magnetic disk 45 with respect to the
shaft 49. Therefore, the magnetic disk 45 and the magnetic head
carriage assembly 41 are positioned in a similar manner to the
positioning of the normal magnetic head carriage assembly (i.e., a
structure having the main magnetic driving unit 51 but not the
secondary magnetic driving unit 60). Thus, the magnetic disk device
30 can be assembled efficiently. Also, since the magnetic disk 45
is at a certain distance from the permanent magnet 62 of the
secondary magnetic driving unit 60, the recorded information on the
magnetic disk 45 will not be affected by a magnetic force of the
permanent magnet 62.
[0073] In the following, the magnetic disk device 40 will be
described with regards to its operation.
[0074] During operation of the magnetic disk device 40, the
magnetic head carriage assembly 41 operates under control of a
micro-controller unit (MCU) 70 shown in FIG. 6. In a reading
operation, information picked up from the rotating magnetic disk 45
by the magnetic head slider 42 is read by a read/write circuit 72.
In a writing operation, the information output from the read/write
circuit 72 is written into the magnetic disk 45 by the magnetic
head slider 42. Also, using the information picked up from the
rotating magnetic disk 45 by the magnetic head slider 42, a
position detecting circuit 73 detects a track 45a of the magnetic
disk 45 which is being traced by the magnetic head slider 42.
[0075] The MCU 70 generates a command for causing a seek operation
and a switching-over from the seek operation to the track-following
operation. This command is referred to as a seek command.
[0076] When a seek command is submitted from the MCU 70, a main
magnetic-driving-unit driver circuit 74 is operated, so that a
driving current is supplied to the driving coil 53 (see FIG. 4).
Then, the main magnetic driving unit 51 is actuated as shown in
FIG. 7A, causing the head carriage 47 to pivot such that the
magnetic head slider 42 is moved to a predetermined track. The main
magnetic driving unit 51 generates a comparatively great force F10,
so that the head carriage 47 is pivoted rapidly and the seek
operation is completed within a short period of time.
[0077] Once the magnetic head slider 42 is moved to the
predetermined track, a track-following command is submitted from
the MCU 70. Then, the main magnetic driving unit 51 stops its
operation and the secondary magnetic-driving-unit driver circuit 75
starts operating as shown in FIG. 7B. The secondary
magnetic-driving-unit driver circuit 75 supplies a driving current
to the driving coil 61 based on the information obtained from the
position detecting circuit 73. For this purpose, the secondary
magnetic driving unit 60 is actuated as shown in FIGS. 8A and 8B,
so that the head carriage 47 is pivoted through a very small angle
and the magnetic head slider 42 follows the track 45a of the
rotating magnetic disk 45. Of course, the secondary magnetic
driving unit 60 can also be actuated during the seek operation (not
shown).
[0078] During the track-following operation, the secondary magnetic
driving unit 60 generates forces F11 and F12, as shown in FIGS. 8A
and 8B. The force F11 generated by the secondary magnetic driving
unit 60 has an effect equivalent to a translational force F11a
being produced at the shaft 49. The force F12 generated by the
secondary magnetic driving unit 60 has an effect equivalent to a
translational force F12a being produced at the shaft 49. The
translational forces F11a, F12a act in the direction of the axis
CX, i.e., in the longitudinal direction of the head carriage 47.
This implies that at the magnetic head slider 42, the translational
forces F11a, F12a are acting in a longitudinal direction of the
track 45a of the magnetic disk 45 and not in the direction of the
width of the track 45a.
[0079] Therefore, the translational forces F11a, F12a act in a
direction which does not affect a positioning of the magnetic head
slider 42 against the track 45a. In other words, the translational
forces F11a, F12a act in a direction which does not affect the
track-following operation in which the magnetic head slider 42
follows the track 45a of the rotating magnetic disk 45.
Accordingly, the positioning accuracy of the magnetic head slider
42 against the track 45a is improved, and thus an accuracy of the
track-following operation is also improved.
[0080] The MCU 70, the bus 71, the position detecting circuit 73,
the main magnetic-driving-unit driver circuit 74 and the secondary
magnetic-driving-unit driver circuit 75 corresponds to control
means.
[0081] FIGS. 9A and 9B are a plan view and a cross-sectional view,
respectively, showing a magnetic head carriage assembly 41A
provided on magnetic disk device of a first variant of the first
embodiment of the present invention. The magnetic head carriage
assembly 41A is identical to the above-described magnetic head
carriage assembly 41 except for a secondary magnetic driving unit
60A. As shown in FIG. 9B, the secondary magnetic driving unit 60A
includes a permanent magnet 62A provided at the same level as the
center of gravity G of the head carriage 47A in the Z1-Z2
direction. A recessed part 47a1A at the lower surface of a hub 47aA
has a larger size compared to the above-described recessed part
47a1.
[0082] With this magnetic head carriage assembly 41A, there will be
no tipping mode produced which causes the head carriage assembly
41A to tip during the track-following operation. Accordingly, the
positioning accuracy of the magnetic head slider 42 against the
track 45a is improved, and thus an accuracy of the track-following
operation is also improved.
[0083] FIGS. 10A and 10B are a plan view and a cross-sectional
view, respectively, showing a magnetic head carriage assembly 41B
provided on a magnetic disk device of a second variant of the first
embodiment of the present invention. The magnetic head carriage
assembly 41B is identical to the above-described magnetic head
carriage assembly 41 except for a secondary magnetic driving unit
60B.
[0084] As shown in FIG. 10B, the secondary magnetic driving unit
60B includes a flat quadrilateral driving coil 61B, a permanent
magnet 62B and a yoke 63B. The driving coil 61B is vertically fixed
on the chassis base 44 by means of a coil support 70 and is placed
within an arcuate slit 47a1B formed in a hub part 47aB. The
permanent magnet 62B is secured at the peripheral part of the
bearing 48 and the yoke 63B is secured on a wall surface of the
arcuate slit 47a1B. The permanent magnet 62B is provided at the
same level as the center of gravity G of the head carriage 47B in
the Z1-Z2 direction.
[0085] With this magnetic head carriage assembly 41B, there will be
no tipping mode produced which causes the head carriage assembly
41B to tip during the track-following operation. Accordingly, the
positioning accuracy of the magnetic head slider 42 against the
track 45a is improved, and thus an accuracy of the track-following
operation is also improved.
[0086] FIGS. 11A and 11B are a plan view and a cross-sectional
view, respectively, showing a magnetic head carriage assembly 41C
provided a on magnetic disk device of a second embodiment of the
present invention. The magnetic head carriage assembly 41C is
identical to the above-described magnetic head carriage assembly 41
except for a secondary magnetic driving unit 60C.
[0087] The secondary magnetic driving unit 60C is provided at a
position on the line CX, on the X2-direction side of the shaft 49
(on the magnetic head slider 42 side) and adjacent to the bearing
48. As can be seen in the figure, the secondary magnetic driving
unit 60C is provided within a region of a hub part 47aC.
[0088] As shown in FIG. 11B, the secondary magnetic driving unit
60C includes a flat quadrilateral driving coil 61C, a permanent
magnet 62C and a yoke 63C. The driving coil 61C is vertically fixed
on the chassis base 44 by means of the coil support 70 and is
placed within an arcuate slit 47a1C formed in a hub part 47aC. The
permanent magnet 62C is secured at the peripheral part of the
bearing 48 and the yoke 63C is secured on a wall surface of the
arcuate slit 47a1C.
[0089] As shown in FIG. 11A, the magnetic head carriage assembly
41C is provided with the secondary magnetic driving unit 60C having
a reduced size. This secondary magnetic driving unit 60C is
provided adjacent to the bearing 48 and within a region of the hub
part 47aC. Therefore, the magnetic disk 45 and the magnetic head
carriage assembly 41C are positioned in a similar manner as in a
disk device where a normal magnetic head carriage device is used.
Therefore, the magnetic disk device can be assembled
efficiently.
[0090] FIG. 12 is a block diagram showing a circuit associated with
the magnetic head carriage assembly 41C. The magnetic head carriage
assembly 41C is operated under control of the micro-controller unit
(MCU) 70.
[0091] In order to achieve a required object, the magnetic head
carriage assembly 41C operates either in a first mode of operation
or in a second mode operation described below.
[0092] FIGS. 13A and 13B are timing charts showing operations of
the driving circuit in a first mode of operation. When a seek
command is submitted from the MCU 70, the main
magnetic-driving-unit driver circuit 74 is operated, so that a
driving current is supplied to the driving coil 53. Then, the main
magnetic driving unit 51 is actuated as shown in FIG. 13A, which
causes the head carriage 47C to pivot such that the magnetic head
slider 42 is moved to a predetermined track. During the seek
operation, the secondary magnetic driving unit 60C is not
actuated.
[0093] Once the magnetic head slider 42 has been moved to the
predetermined track, a track-following command is submitted from
the MCU 70. Then, the secondary magnetic-driving-unit driver
circuit 75 starts operating as well as the main
magnetic-driving-unit driver circuit 74, as shown in FIG. 13B.
[0094] FIGS. 14A and 14B are plan views illustrating effects on the
magnetic head carriage assembly 41C during a track-following
operation in the first mode of operation.
[0095] FIG. 14A shows a case where the magnetic head slider 42 is
offset from the center of the track 45a of the rotating magnetic
disk 45 in the direction towards the center of the magnetic disk
45. As shown in the figure, the main magnetic driving unit 51
produces a force F13 and the secondary magnetic driving unit 60C
produces a force F14, so that the head carriage 47C is slightly
pivoted in a clockwise direction so as to follow the track 45a.
[0096] FIG. 14B shows the other case where the magnetic head slider
42 is offset from the center of the track 45a of the rotating
magnetic disk 45 in the direction towards the periphery of the
magnetic disk 45. As shown in the figure, the main magnetic driving
unit 51 produces a force F15 and the secondary magnetic driving
unit 60C produces a force F16, so that the head carriage 47C is
slightly pivoted in a counterclockwise direction so as to follow
the track 45a.
[0097] Here, the gains of the amplifiers (not shown) on the output
side of the respective driver circuits 74, 75 are adjusted such
that the forces F13 and F14 are of equal magnitude and forces F15
and F16 are also of equal magnitude.
[0098] Thus, in both cases shown in FIGS. 14A and 14B, any
translational force acting on the shaft 49 is cancelled so that the
head carriage 47C is only subjected to a torque about the shaft 49.
That is to say, there will be no translational force acting on the
shaft 49.
[0099] FIG. 15A is a graph showing a frequency response of the
magnetic head carriage assembly of the related art (a structure
similar to that of the magnetic head carriage assembly 41 shown in
FIG. 11A but without the secondary magnetic driving unit 60C). FIG.
15B is a graph showing a frequency response of the magnetic head
carriage assembly shown in FIGS. 11A and 11B.
[0100] With the magnetic head carriage assembly of the prior art, a
translational force acts on the bearing which is an axis of pivotal
movement of the magnetic head carriage assembly. Therefore, as
shown in FIG. 15A, a resonance peak 100 occurs at a frequency fl
(approximately 4 kHz), which peak is mainly caused by a
translational rigidity of the bearing. A resonance peak 101 occurs
at a frequency f2 (approximately 8 kHz) which is higher that the
frequency f1, which peak is mainly caused by an in-plane mode of
the arm part 47b.
[0101] With the magnetic head carriage assembly 41C, since no
translational force acts on the shaft 49, hardly any translational
mode of the shaft 49 is excited. Therefore, as shown in FIG. 15B,
the above-described resonance peak 100 is not observed. Thus, a
primary resonant frequency limiting the servo bandwidth is
increased, and the crossover frequency of the open loop is
increased. Therefore, an accuracy of the track-following operation
is improved.
[0102] Also, the permanent magnet 62C is provided at the same level
as the center of gravity G of the head carriage 47C in the Z1-Z2
direction. Therefore, there will be no tipping mode produced which
causes the head carriage assembly 41C to tip during the
track-following operation. Thus, the track-following operation is
achieved with a higher accuracy.
[0103] FIGS. 16A and 16B are timing charts showing operations of
the driving circuit in a second mode of operation. Once the
magnetic head slider 42 is moved to the predetermined track in the
same manner as in the first mode, a track-following command is
submitted from the MCU 70. Then, the main magnetic driving unit 51
stops its operation and the secondary magnetic-driving-unit driver
circuit 75 starts operating as shown in FIG. 16B.
[0104] FIGS. 17A and 17B are plan views illustrating effects on the
magnetic head carriage assembly during a track-following operation
in the second mode of operation.
[0105] FIG. 17A shows a case where the magnetic head slider 42 is
offset from the center of the track 45a of the rotating magnetic
disk 45 in the direction towards the center of the magnetic disk
45. As shown in the figure, the secondary magnetic driving unit 60C
produces a force F17, so that the head carriage 47C is slightly
pivoted in a clockwise direction so as to follow the track 45a.
[0106] FIG. 17B shows the other case where the magnetic head slider
42 is offset from the center of the track 45a of the rotating
magnetic disk 45 in the direction towards the periphery of the
magnetic disk 45. As shown in the figure, the secondary magnetic
driving unit 60C produces a force F18, so that the head carriage
47C is slightly pivoted in a counterclockwise direction so as to
follow the track 45a.
[0107] In both cases shown in FIGS. 17A and 17B, the forces F17 and
F18 act at a position inward of the shaft 49 toward the magnetic
head slider 42. Therefore, frequency response of the magnetic head
carriage assembly 41C may be plotted as shown in FIGS. 18A and 18B.
As shown by a reference numeral 103 in FIG. 18A, a mode mainly
caused by the rigidity of the bearing occurs at the same phase as
the phase of the rigid body mode. Therefore, the stability of the
track-following operation is maintained.
[0108] Also, the permanent magnet 62C is provided at the same level
as the center of gravity G of the head carriage 47C in the Z1-Z2
direction. Therefore, there will be no tipping mode produced which
causes the head carriage assembly 41C to tip during the
track-following operation. Thus the track-following operation is
achieved at a higher accuracy. A primary resonant frequency
limiting the servo bandwidth occurs at a resonance peak 101, so
that the crossover frequency of the open loop is increased.
Therefore, the track-following operation is achieved with a higher
accuracy.
[0109] In the above-described first and second modes of operation,
the secondary magnetic driving unit 60C may or may not be used for
seek operations.
[0110] Now, first to fifth variants of the second embodiment of the
present invention will be described. Each of the variants involves
a variant of the secondary magnetic driving unit 60C.
[0111] FIG. 19 is a cross-sectional view showing a magnetic head
carriage assembly 41D provided on a magnetic disk device of a first
variant of the second embodiment of the present invention. The
magnetic head carriage assembly 41D includes a secondary magnetic
driving unit 60D. The secondary magnetic driving unit 60D has a
permanent magnet 62D on which is fixed and a flat driving coil 61D
which moves with the head carriage 47D. The permanent magnet 62D is
fixed vertically on the chassis base 44. The driving coil 61D is
fixed on a yoke 63D and is fixed on the wall surface of a slit
47a1D.
[0112] FIG. 20 is a cross-sectional view showing a magnetic head
carriage assembly 41E provided on a magnetic disk device of a
second variant of the second embodiment of the present invention.
The magnetic head carriage assembly 41E includes a secondary
magnetic driving unit 60E. The secondary magnetic driving unit 60E
has a permanent magnet 62E which is fixed and a flat driving coil
61E which moves with the head carriage 47E. The permanent magnet
62E is fixed on a yoke 63E and is vertically fixed on the chassis
base 44. The driving coil 61E is fixed on peripheral surface of the
bearing 48.
[0113] FIG. 21 is a cross-sectional view showing a magnetic head
carriage assembly 41F provided on a magnetic disk device of a third
variant of the second embodiment of the present invention. The
magnetic head carriage assembly 41F includes a secondary magnetic
driving unit 60F. The secondary magnetic driving unit 60F has a
flat driving coil 61F which is fixed and a permanent magnet 62F
which moves with the head carriage 47F. The driving coil 61F is
vertically fixed on the chassis base 44. The permanent magnet 62F
is fixed on a yoke 63F and is fixed on the wall surface of the slit
47a1F.
[0114] FIGS. 22A and 22B are a plan view and a cross-sectional
view, respectively, showing a magnetic head carriage assembly 41G
provided on a magnetic disk device of a fourth variant of the
second embodiment of the present invention. The magnetic head
carriage assembly 41G includes a secondary magnetic driving unit
60G. The secondary magnetic driving unit 60G has a flat driving
coil 61G which is fixed and a permanent magnet 62G which moves with
the head carriage 47G. The driving coil 61G is fixed on the upper
surface of a yoke 63G and is fixed on the chassis base 44. The
permanent magnet 62G is fixed on a yoke 64G and is fixed in a
recessed part 47a1G at the bottom surface of the hub part 47aG.
[0115] FIGS. 23A and 23B are a plan view and a cross-sectional
view, respectively, showing a magnetic head carriage assembly 41H
provided on a magnetic disk device of a fifth variant of the second
embodiment of the present invention. The magnetic head carriage
assembly 41H includes a secondary magnetic driving unit 60H. The
secondary magnetic driving unit 60H has a structure similar to that
of the above-described secondary magnetic driving unit 60G. The
secondary magnetic driving unit 60H has a permanent magnet 62H
which is fixed and a flat driving coil 61H which moves with the
head carriage 47H. The permanent magnet 62H is fixed on the upper
surface of a yoke 63H and is fixed on the chassis base 44. The
driving coil 61H is fixed on a yoke 63H and is fixed in a recessed
part 47a1H at the bottom surface of the hub part 47aH.
[0116] Also, in each of the embodiments, instead of the magnetic
head slider, it is possible to mount an optical head slider having
an optical head integrated into a slider. Therefore, the present
invention can be implemented in devices such as a suspension for an
optical head slider, an optical head slider supporting device and
an optical disk device.
[0117] Further, the present invention is not limited to these
embodiments, but variations and modifications may be made without
departing from the scope of the present invention.
[0118] The present application is based on Japanese priority
application No. 10-72882 filed on Mar. 20, 1998, the entire
contents of which are hereby incorporated by reference.
* * * * *