The present invention relates to a magnetic disk device,
such as it is known from
US-A- 5 134 530
.
In a magnetic disk device, in general, read and write operations
are carried out, with respect to a magnetic disk rotating at a high speed, by a
magnetic head floating over the magnetic disk, and a positioning operation of the
magnetic head is performed by driving a magnetic head arm carrying the magnetic
head at the forward end thereof.
Above the magnetic disk, on the other hand, an air flow
is generated, by the high-speed rotation of the magnetic disk, and acts as an external
force against the magnetic head or the magnetic head arm. The external force of
the air flow, though low in absolute value, acts as an unforeseeable external disturbance
affecting the positioning operation, and therefore is not negligible in the case
where the track density is high and a high positioning accuracy is required.
In view of the situation described above, it is desirable
to provide a magnetic disk device in which the magnetic recording density can be
improved by improving the positioning accuracy.
In embodiments of the present invention there is provided
a magnetic disk device in which a wind shield member is arranged, with a small gap,
above a magnetic recording surface of a magnetic disk in a region of the magnetic
disk on the rotationally upstream side of a magnetic head arm. The air flow generated
over the magnetic recording surface by the high-speed rotation of the magnetic disk
flows in the direction of rotation of the magnetic disk and, therefore, the air
flow impinges against the wind wield member before impinging against the magnetic
head arm. As a result, the external force exerted by the air flow on the magnetic
head arm is reduced, and therefore an unstable factor in the positioning operation
is reduced, so that the magnetic head can be driven accurately to the correct position.
An arrangement of this kind is shown in
US 5134530
(Seagate Technologies).
In the present invention, as defined by claim 1, the shield
members have a curved guide surface corresponding to the disk edge so that for assembly
they can be inserted and then rotated into place between the disks.
The air flow generated over the magnetic disk has such
a speed distribution that the speed becomes a maximum on the outer peripheral portion
of the magnetic disk, and therefore the wind shield member is arranged at least
on the outer peripheral portion of the magnetic disk.
The generation of an excessively turbulent flow due to
the air flow impinging against the wind shield member acts as a resistance force
to the rotation of the magnetic disk. Therefore, a curved guide surface for guiding
the air flow to the outside of the magnetic disk after impinging against the wind
shield member is preferably formed on the edge of each wind shield member on the
rotationally upstream side thereof.
Also, each wind shield member prevents the direct impact
of the air flow against the magnetic head arm, and therefore, a surface element
opposed to the magnetic recording surface of the magnetic disk is not necessarily
required. In the case where opposed surface portions of a predetermined area are
formed and placed in proximity to the upper and lower surfaces of the magnetic disk,
however, an air bearing structure is formed between the upper and lower surfaces
of the magnetic disk and the opposed surface portions, thereby making it possible
to suppress displacement of the magnetic disk in the direction of its thickness
(the disk fluttering phenomenon). Reference will now be made, by way of example,
to the accompanying drawings, in which:
- Fig. 1 is a view showing a magnetic device according to an embodiment of the
present invention;
- Fig. 2A is a cross-sectional views of Fig. 1, taken in line 2A-2A in Fig. 1;
- Fig. 2B is a cross-sectional view showing a modification of the magnetic disk
device of Fig. 2A;
- Fig. 2C is a cross-sectional view showing another modification of the magnetic
disk device of Fig. 2A;
- Fig. 3A is a cross-sectional views of the magnetic disk device, taken on line
3A-3A in Fig. 2A;
- Fig. 3B is a cross-sectional view, taken in line 3B-3B in Fig. 2B, illustrating
the operation of fixing the wind shield block;
- Figs. 4A to 4F are schematic cross-sectional views of examples of the wind shield
member, cut away along the direction of rotation of the magnetic disk;
- Fig. 5A is a view showing a method of mounting the wind shield member;
- Fig. 5B is a view showing another method of mounting the wind shield member;
- Fig. 6A is a view showing a modification of the wind shield member;
- Fig. 6B is a view showing a further modification of the wind shield member;
- Fig. 7A is a view showing a further modification of the wind shield member;
and
- Fig. 7B is a view showing a further modification of the wind shield member.
Figs. 1 to 3A show a magnetic disk device of an embodiment
of the present invention. The magnetic disk device comprises a box-shaped disk case
8 comprising a base body 8a and a cover plate 8b coupled with each other, and magnetic
disks 1, magnetic head arms 2 and a wind shield block 6 are hermetically accommodated
in the disk case 8. Each magnetic disk 1 has a magnetic recording surface on each
of the upper and lower surfaces thereof, and a plurality of the magnetic disks 1
are rotatably arranged about a rotation axis c1. A shroud 8c for surrounding the
outer peripheries of the magnetic disks 1 is arranged as near as possible to the
outer peripheries of the magnetic disks 1 in the disk case 8, thereby preventing
generation of disk fluttering phenomenon which arises due to the air flow between
vertically adjacent magnetic disks 1.
The magnetic head arms 2 are rotationally driven about
a rotation axis c2 by a magnetic circuit 9 in such a manner that a magnetic head
slider 2a held by the magnetic head arm 2 at the forward end thereof can be moved
to a predetermined position above or below the magnetic disk 1 by energization of
the magnetic circuit 9.
The wind shield block 6 is made of a hard material such
as aluminum and includes a support post 7 and a plurality of wind shield members
3, 3, integral with and transversely extending from the support post 7. The wind
shield block 6 is fixed to the base body 8a by engaging a fixing element 10 such
as a screw into a threaded hole 7b formed in the lower end of the support portion
7, as shown in Fig. 2A. Alternatively, the wind shield block 6 can be fixed to the
base body 8a and the cover plate 8b, as shown in Fig. 2B, as required.
The support post 7 of the wind shield block 6, has a curved
surrounding surface 7a having a curvature slightly larger than the curvature of
the outer periphery of the magnetic disk 1, as viewed from above, as shown in Fig.
3A, and in the state fixed to the disk case 8, the curved surrounding surface 7a
surrounds the outer periphery of the magnetic disks 1 thereby to prevent the generation
of the disk fluttering phenomenon.
The upper and lower surfaces of the wind shield members
3 have smooth surface portions 5 in opposed relation to the upper and lower surfaces
of the corresponding magnetic disks 1, and are arranged above or below the magnetic
disks 1 with a small gap maintained between the opposed surface portion 5 and the
lower or upper surface of the magnetic disk 1. The wind shield member 3 is arranged
in a region of the magnetic disk 1 adjacent to and on the rotationally entrance
side of the magnetic head arm 2 (upstream side of the magnetic head arm 2 in view
of the air flow), i.e. in the region on the left side of the magnetic head arm 2
in this embodiment in which the magnetic disk 1 rotates counterclockwise as indicated
by arrow A in Fig. 1. Also, the edge of each wind shield member 3 on the rotationally
entrance side is formed as a curved guide surface 4 with the central portion thereof
having a concave shape, as viewed from above.
In this embodiment comprising a plurality of magnetic disks
1 stacked vertically, each wind shield member 3 is inserted in the gap between the
adjacent magnetic disks 1, as shown in Fig. 2, and the curved guide surface 4 is
formed utilizing the thickness component of the wind shield member 3. This curved
guide surface 4 can be formed by a surface perpendicular to the opposed surface
portion 5, as shown in Figs. 4A and 4B. As alternatives, the curved guide surface
4 can be formed by a curved surface protruding on the rotationally entrance (upstream)
side, as shown in Figs. 4C and 4D, or by a curved surface in an acute form on the
rotationally entrance side, as shown in Figs. 4E and 4F. Also, in the case where
the cross-sectional shape of the wind shield member 3 is formed in the shape which
becomes progressively thinner toward the rear edge (end on the rotationally exit
side), as shown in Figs. 4A to 4F, the generation of turbulent flow at the rear
edge can be prevented.
The wind shield block 6 described above can be mounted
in such a manner that it is set at a position shown by the chain line in Figs. 5A
and 5B beforehand, and after the assembly work of the magnetic disks 1 is completed,
it is rotated (Fig. 5A) to set the wind shield members 3 above or below the magnetic
disks 1. A movement in parallel (Fig. 5B), is outside the scope of the present invention.
In this case, when moving the wind shield block 6 to the mounting position, the
spigot portion 7c formed in the lower end or the upper end of the support post 7
can be used as a holding part for the mounting tool.
For surrounding the outer periphery of the magnetic disks
1 in closer proximity to the curved surrounding surface 7a, the wind shield block
6 is required to be fixed with a higher accuracy. For this purpose, the base body
8a includes a positioning wall 11 for abutment of the half surface of the support
portion 7 on the side of the magnetic disk 1 (Fig. 3B). The positioning wall 11
can restrict the motion of the support post 7 at least in the X-Y perpendicular
directions and in the direction of &thgr; (rotation) in a plan view. However, in
the case of the configuration in which the wind shield block 6 is led to the fixed
position by rotation, as shown in Fig. 5A, arcuate portions 13 and 13' connected
to the curved surrounding surface 7a by a common normal line are desirably formed
on the support post 7 and the positioning wall 11 about the threaded hole 7b and
the fixing element through-hole 12 on the base body 8a. With this configuration,
first, the arcuate portions 13 and 13' are abutted against each other, and thereafter,
the curved surrounding surface 7a is rotated along the arcuate portions 13 and 13'
until the curved surrounding surface 7a comes into contact with the corresponding
portion 11a of the positioning wall 11. In this simple way, an accurate fixed position
and orientation can be ensured for an improved assembly workability.
Also, a protrusion 15 may be formed on the support portion
7, as shown in Fig. 2C. With this configuration, the protrusion 15 is loosely fitted
in the fixing element through-hole 12, instead of abutting the arcuate portions
13 and 13' against each other, to improve the assembly workability.
In this embodiment, therefore, the air flow generated above
or below the magnetic disks 1 with the rotation of the magnetic disks 1 impinges
against the curved guide surface 4 before it impinges against the magnetic head
arm 2, and is guided to the outside of the magnetic disks 1 along the curvature
guide surface 4, as indicated by arrow B in Fig. 1. In order to assure the smooth
air flow toward the outside of the magnetic disks 1, a reservoir 14 for the air
flow released by the curved guide surface 4 is formed on the disk case 8. The entrance
to the reservoir 14 is formed with a leading curved portion 14a for smoothly leading
the air flow into the reservoir 14 (Figs. 5A and 5B)
As a result, the magnetic head arms 2 are not subjected
to an unstable force by the air flow generated over the magnetic disks 1, and the
fact that each magnetic disk 1 is held by the opposed surface portions 5 in the
direction of the thickness can prevent the disk fluttering phenomenon.
Although each wind shield member 3 is arranged to reach
about one half of the radius of the magnetic disk 1 in the aforementioned case,
only the outer peripheral portion of the magnetic disk 1 can be covered as shown
in Fig. 6A. In this case, in spite of a somewhat reduced air bearing effect, the
rotation resistance component of the magnetic disks 1 due to the air bearing effect
is reduced, thereby making it possible to reduce the size of the motor for rotating
the magnetic disks 1.
It is possible though outside the scope of the present
invention, for the curved guide surface 4 to be formed with a convex curved surface
at the center, as shown in Fig. 6B, instead of by a concave curved shape at the
center. In this case, the generated air flow, as indicated by arrows B and B' in
Fig. 6B, branches toward the rotational center and toward the outer periphery of
the magnetic disk 1 at a position in the vicinity of the top (forward end of bombarding
air flow) of the curved guide surface 4. Thus, the air flow in the neighborhood
of the outer peripheral portion which has a high flow rate and a large external
force exerted on the magnetic head arm 2 at the time of impingement can be led out
of the magnetic disk 1.
Further, as shown in Figs. 7A and 7B, by increasing the
area of the opposed surface portions 5, the air bearing effect is increased and
the disk fluttering phenomenon can be suppressed even more effectively. In this
case, as shown in Fig. 7B, the arrival of the air flow at the magnetic head arm
2 can be remarkably reduced by forming the magnetic disk 1 in such a manner that
the region of the magnetic disk 1 from the outer periphery to the innermost periphery
of the magnetic recording portion is covered.
As is clear from the foregoing description, according to
an embodiment of the present invention, the influence of the air flow flowing over
the disks can be reduced, and therefore the positioning accuracy can be improved.
