U.S. patent application number 09/356056 was filed with the patent office on 2002-03-14 for magnetic disk apparatus with shroud having opening downstream of movable arm.
Invention is credited to IWAKURA, MASAO, KAIHO, MASAYUKI, KOBARI, TOSHIAKI, NAKAMURA, SHIGEO, SAKAI, KAZUO, SHIMIZU, HAYATO, TOGASHI, SHIGENORI.
Application Number | 20020030924 09/356056 |
Document ID | / |
Family ID | 26513633 |
Filed Date | 2002-03-14 |
United States Patent
Application |
20020030924 |
Kind Code |
A1 |
SHIMIZU, HAYATO ; et
al. |
March 14, 2002 |
MAGNETIC DISK APPARATUS WITH SHROUD HAVING OPENING DOWNSTREAM OF
MOVABLE ARM
Abstract
To suppress pressure fluctuation caused by insertion of arms
between disks, which arms support thereon magnetic heads, to reduce
disk flutter to thereby reduce disk driving power in a magnetic
disk apparatus, there are provided an open space not covered by a
shroud, which constitutes a part of a housing structure to cover a
side surface of a disk stack, and provided on a downstream side of
the arms relative to an airflow moving along surfaces of the disks
as the disks rotate, and a channel, which connects a space on an
upstream side of the arms and the open space not restricted by the
shroud on the downstream side of the arms, the channel being
provided with a linear section, which has a rectifying effect on
the airflow.
Inventors: |
SHIMIZU, HAYATO;
(RYUGASAKI-SHI, JP) ; IWAKURA, MASAO;
(ODAWARA-SHI, JP) ; NAKAMURA, SHIGEO;
(ODAWARA-SHI, JP) ; SAKAI, KAZUO; (IBARAKI-KEN,
JP) ; TOGASHI, SHIGENORI; (ABIKO-SHI, JP) ;
KAIHO, MASAYUKI; (IBARAKI-KEN, JP) ; KOBARI,
TOSHIAKI; (IBARAKI-KEN, JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
26513633 |
Appl. No.: |
09/356056 |
Filed: |
July 16, 1999 |
Current U.S.
Class: |
360/97.14 ;
G9B/33.042; G9B/5.23 |
Current CPC
Class: |
G11B 5/6005 20130101;
G11B 33/1446 20130101 |
Class at
Publication: |
360/97.03 |
International
Class: |
G11B 033/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 17, 1998 |
JP |
10-202912 |
Sep 17, 1998 |
JP |
10-262710 |
Claims
What is claimed is:
1. A magnetic disk apparatus comprising a plurality of magnetic
disks stacked on a rotating shaft, arms supporting thereon magnetic
heads and adapted to be inserted between said magnetic disks, a
rotary actuator for moving said arms, a housing having an
arcuate-shaped shroud, which surrounds the side surfaces of said
magnetic disks so as to permit movements of said arms and which is
concentric with said magnetic disks, a space opened from said
shroud and located on a downstream side of said arms relative to an
air flow, which is generated by the revolution of said magnetic
disks and moves on surfaces of said magnetic disks, an opening
provided on said shroud on an upstream side of said arms relative
to said airflow and having a greater width than that of a gap
defined between said magnetic disks and said shroud, and a cover,
which constitutes a part of said shroud to cover a voice coil motor
for driving said rotary actuator, and forms between said cover and
an inner wall of said housing a bypass channel for providing
communication between said opening and said opened space, and
wherein said bypass channel has a linear section of a predetermined
length extending from said opening.
2. A magnetic disk apparatus of claim 1, wherein said bypass
channel has a depth of 5D or more in a direction parallel to a
rotating shaft where D is a spacing of said linear section.
3. A magnetic disk apparatus of claim 1, wherein said bypass
channel has a linear section having a length of at least 5D or more
where D is a spacing of said linear section.
4. A magnetic disk apparatus of claim 1, wherein said bypass
channel has a linear section having a depth of 5D or more and a
length of at least 5D or more in a direction parallel to a rotating
shaft where D is a spacing of said linear section.
5. A magnetic disk apparatus of claim 1, wherein said cover covers
at least a side surface of said voice coil motor.
6. A magnetic disk apparatus of claim 1, wherein said cover is a
component which encloses a coil section of said voice coil motor
and at least a side surface of which is closed to prevent airflow
from coming into said voice coil motor from said bypass channel.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a magnetic disk apparatus, and more
particularly, a housing structure of a magnetic disk apparatus,
which houses therein a plurality of stacked rotating disks for
reading and writing information and a rotary actuator supporting a
head for reading and writing information on the disks, such that
the head be movable between the disks.
[0002] With conventional magnetic disk apparatuses, turbulence of
an air flowing between disks causes vibration of the disks called
"flutter". When a head is positioned on a disk generating such
flutter, the head is degraded in positional accuracy with respect
to tracks for reading and writing of information.
[0003] As a prior art (1), Japanese Patent Unexamined Publication
No. 10-162548 describes a method for forcedly generating an airflow
directed to outer peripheries of disks from inner peripheries
thereof. As a further prior art (2), there has been proposed a
method for reducing a spacing between rotating disks and a housing
called "shroud" which surrounds the disks and is formed
concentrically with the disks. Such shroud is a part of the housing
that is disposed in a magnetic disk apparatus to cover components
such as magnetic disks, an actuator for positioning of a head, and
the like, the shroud surrounding side surfaced of the disks.
[0004] An airflow generated around rotating disks includes a
primary flow, in which air is dragged by revolution of the disks to
flow in a circumferential direction, and a secondary flow, in which
air in the vicinity of disk surfaces flows toward outer peripheries
of the disks and air between the disks flows toward inner
peripheries of the disks. Since the secondary flow involves
unstable air turbulence, the prior art (1) is directed to
suppressing the occurrence of flutter by generating a forced
airflow directed toward the outer peripheries of the disks from the
inner peripheries thereof so as to reduce the unstable airflow
caused by the secondary flow.
[0005] The prior art (2) is directed to reducing flutter by
decreasing a gap between disks and a shroud to suppress that
incoming and outgoing of air on the and bottom surfaces of disks,
which would be produced in the event of the gap between the disks
and the shroud being large, to prevent a pressure difference
between the top and bottom surfaces from varying with the passage
of time.
[0006] As a prior art (3), Japanese Patent Unexamined Publication
No. 7-320478 describes a housing structure making use of an airflow
circulating in a housing of a magnetic disk apparatus for other
purposes than reduction of flutter, and discloses a method for
removing dust by means of a filter and cooling an interior of the
housing.
[0007] If the housing structure of a magnetic disk apparatus is the
same, flutter caused by turbulence of an air flowing between disks
increases substantially in proportion to a square of a disk radius
and the number of revolutions of the disks. Therefore, a housing
structure is needed, which reduces flutter having an adverse
influence on head positional accuracy, in reduction of track
intervals making magnetic disks high in capacity and in increase in
the number of revolutions required for achieving high speed.
[0008] Provided that the housing structure of a magnetic disk
apparatus is the same, the driving power for revolution of disks is
substantially proportional to third power of the number of
revolutions and fifth power of a disk radius. Accordingly, as with
flutter mentioned above, it is necessary to obtain a housing
structure that reduces an airflow tending to impose a burden on a
rotating driving force, thus reducing a disk driving power in
increasing the number of revolutions required for making the
magnetic disk apparatus high in speed.
[0009] However, the method for forcedly generating an airflow
directed toward outer peripheries of disks from inner peripheries
thereof offers the following problem. Such method for forcedly
generating an airflow directed toward outer peripheries of disks
from inner peripheries thereof becomes ineffective because
respective arms of a rotary actuator adapted to be inserted between
stacked disks block the airflow directed toward the outer
peripheries of the disks from the inner peripheries thereof if
these arms have a thickness half or more an interval between the
disks.
[0010] Also, the method, in which a gap between disks and a housing
called "shroud" and formed concentric with rotating disks is made
small, offers the problem set forth below.
[0011] With the method, in which a gap between disks and a housing
called "shroud" and formed concentric with rotating disks is made
small, one of the causes for occurrence of flutter can be dissolved
because it is possible to suppress fluctuation of pressure
difference with the passage of time, which is caused by incoming
and outgoing of an airflow on top and bottom surfaces of the disks,
even when arms of the rotary actuator are inserted between the
disks. However, when the arms are inserted between the disks, they
will block the primary airflow, which is dragged by the revolving
disks to flow in the circumferential direction. As a result, a high
pressure region is generated on an upstream side of the arms while
a low pressure region is generated on a downstream side of the
arms.
[0012] In addition, an air flowing in the circumferential direction
on the upstream side of the arms is curved toward the inner
peripheries of the disks by the arms to produce a high speed flow
directed toward the inner peripheries of he disks. Since such flow
directed toward the inner peripheries of the disks tends to return
around tip ends of the arms to the outer peripheries of the disks,
so it will merge with a flow on the downstream side of the arms to
generate turbulence, so that pressure difference between the high
pressure on the upstream side of the arms and the low pressure on a
downstream side of the arms fluctuates. Such pressure fluctuation
causes not only flutter but also a fluctuating force called "wind
turbulence" tending to swing the arms. Such swinging of the arms is
also responsible for degradation of the head positional accuracy in
the magnetic disk apparatus.
[0013] Thus, either of the method for forcedly generating an
airflow directed toward outer peripheries of disks from inner
peripheries thereof, and the method, in which a gap between disks
and a shroud is made small, disclosed in the prior art offers a
problem that pressure fluctuation generated upon insertion of the
arms between the disks cannot be reduced.
[0014] Meanwhile, the prior art (3) making use of an airflow
circulating in a housing of a magnetic disk apparatus also offers a
problem set forth below.
[0015] The low pressure region produced on the downstream side of
the arms draws in air from outside of the disks. Therefore, when
the shroud covers the downstream side of the arms to decrease a gap
between the downstream side of the arms and the shroud, high speed
airflow enters through the gap into spaces between the disks,
thereby causing a significant pressure fluctuation. Presence of a
flow passage connecting the upstream and downstream sides of the
arms will reduce pressure difference between the upstream and
downstream sides of the arms. Thus, pressure loss caused by the
insertion of the arms between the disks is reduced, so that the
driving power for revolution of the disks is correspondingly
reduced.
[0016] However, when a flow passage connecting the upstream and
downstream sides of the arms is defined in a rotating shaft of the
rotary actuator or inside the voice coil motor for driving of the
actuator, it inevitably results in a narrow flow passage with many
curves, and so causes a considerable pressure fluctuation between
disks for the similar reason as mentioned above. The foregoing flow
passage is effective in removing dust and cooling the voice coil
motor that generates heat. However, it is very likely that wind
turbulence and flutter increase when airflow flows through the arm
section and an interior of the voice coil motor, which are complex
in structure tending to easily develop flow turbulence. In
addition, it is unnecessary in a relatively small-sized magnetic
disk apparatus to cool the voice coil motor.
SUMMARY OF THE INVENTION
[0017] Accordingly, an object of the invention is to provide a
magnetic disk apparatus having a housing structure, which enables
suppressing pressure fluctuation, which would occur when arms of a
rotary actuator are inserted between the disks, to reduce flutter
and wind turbulence.
[0018] Another object of the invention is to provide a magnetic
disk apparatus having a housing structure, which can prevent
generation of additional pressure fluctuation on upstream and
downstream sides of arms, thus reducing driving power.
[0019] To these ends, the invention provides a magnetic disk
apparatus comprising a plurality of magnetic disks stacked on a
rotating shaft, arms supporting thereon magnetic heads and adapted
to be inserted between the magnetic disks, a rotary actuator for
moving the arms, a housing having an arcuate-shaped shroud, which
surrounds the side surfaces of the magnetic disks so as to permit
movements of the arms and which is concentric with the magnetic
disks, a space opened from the shroud and located on a downstream
side of the arms relative to an air flow, which is generated by the
revolution of the magnetic disks and moves on surfaces of the
magnetic disks, an opening provided on the shroud on an upstream
side of the arms relative to the airflow and having a greater width
than that of a gap defined between the magnetic disks and the
shroud, and a cover, which constitutes a part of the shroud to
cover a voice coil motor for driving the rotary actuator, and forms
between the cover and an inner wall of the housing a bypass channel
for providing communication between the opening and the opened
space, and wherein the bypass channel has a linear section of a
predetermined length extending from the opening.
[0020] The housing structure comprises a space not covered by the
shroud and provided on a downstream side of the arms, and a
channel, which connects an upstream side of the arms to the space
not covered by the shroud and provided on the downstream side of
the arms, the channel being provided with a linear section, which
has a rectifying effect on an airflow and has a depth of five times
or more a width of the channel and a length of five times or more
the width of the channel.
[0021] To the above ends, the bypass channel may be constructed to
have a depth of 5D or more in a direction parallel to a rotating
shaft where D is a spacing of the linear section.
[0022] Further, to the above ends, the bypass channel may be
constructed to have a linear section having a length of at least 5D
or more where D is a spacing of the linear section.
[0023] Still further, to the above ends, the bypass channel may be
constructed to have a linear section having a depth of 5D or more
and a length of at least 5D or more in a direction parallel to a
rotating shaft where D is a spacing of the linear section.
[0024] Further, to the above ends, the cover may be configured to
cover at least a side surface of the voice coil motor.
[0025] Further, to the above ends, the cover may be a component
which encloses a coil section of the voice coil motor and at least
a side surface of which is closed to prevent airflow from coming
into the voice coil motor from the bypass channel.
[0026] Still further advantages of the invention will become
apparent to those of ordinary skill in the art upon reading and
understanding the following detailed description of the preferred
and alternate embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The invention will be described in conjunction with certain
drawings which are for the purpose of illustrating the preferred
and alternate embodiments of the invention only, and not for the
purposes of limiting the same, and wherein:
[0028] FIG. 1 is a cross-sectional view illustrating a
configuration of a magnetic disk apparatus in accordance with the
invention;
[0029] FIG. 2 is a longitudinal sectional view illustrating a
housing structure of the magnetic disk apparatus of the
invention;
[0030] FIG. 3A through FIG. 3D are diagrams showing results of
comparison in pressure fluctuation and power consumption of the
device with and without a bypass channel in accordance with the
invention;
[0031] FIG. 4 is a cross-sectional view illustrating a
configuration of a magnetic disk apparatus according to a further
embodiment of the invention;
[0032] FIG. 5 is a cross-sectional view illustrating a
configuration of a magnetic disk apparatus according to a still
further embodiment of the invention; and
[0033] FIG. 6 is a graph showing an inflow angle of an airflow
relative to a ratio of a length of the linear section and a channel
width of the bypass channel.
DETAILED DESCRIPTION OF THE PREFERRED AND ALTERNATE EMBODIMENTS
[0034] An embodiment of the invention will be described with
reference to FIG. 1 through FIG. 3D. FIG. 1 is a cross-sectional
view showing a configuration of a magnetic disk apparatus in
accordance with the invention.
[0035] FIG. 2 is a longitudinal sectional view illustrating a
housing structure of the magnetic disk apparatus of the invention.
FIGS. 3A through 3D show results of comparison in pressure
fluctuation and power consumption of the device with and without a
bypass channel in accordance with the invention.
[0036] As shown in FIG. 1, the magnetic disk apparatus according to
the invention is constructed as set forth below. A magnetic disk
stack is composed of a plurality of disks 1 that are stacked on and
fixed to a magnetic disk rotating shaft 2 connected to a spindle
motor (not shown). Arms 4 are driven on a turning arm shaft 3. A
coil (not shown) is provided on the arms 4 toward the turning arm
shaft 3 to drive the arms 4, the coil and a magnet (referred to as
a "voice coil motor 6" for the sake of convenience) provided on a
side of a housing 10 constituting a rotary actuator. Magnetic disk
read/write head 5 are provided on tip ends of the arms 4. A motor
cover 21 is a part of the housing that surrounds the voice coil
motor 6, which constitutes the rotary actuator.
[0037] In addition to the components mentioned above, an
input/output signal wire 7 and a signal wire terminal 8 for the
magnetic head 5, a filter 9 for cleaning air in spaces between the
magnetic disks, etc. are received in the housing 10 of the magnetic
disk apparatus as required, and hermetically sealed to be isolated
from the outside of the housing. In this embodiment, the filter 9
is provided, and an air inlet for the filter 9 and an exhaust port
are provided in a part of a shroud, which covers an outer periphery
of the disks 1. However, it goes without saying that the filter 9
may be omitted.
[0038] Referring to FIG. 1, a direction of revolution of the disks
being fixed as indicated by an arrow 13, air flows between disks in
the direction indicated by the arrow 13. With respect to the
direction of the arrow 13, an upstream side of the arms 4 is
defined as a left side of the arms 4 as viewed in the drawing, and
a downstream side of the arms 4 is defined as a right side of the
arms 4 in the drawing. Ensured in an arm downstream space 11
located downstream of the arms 4 and outside the outer periphery of
the disk stack 1 is a space, which is not occupied by the shroud to
be free from the shroud, and which allows all the arms 4 of the
rotary actuator to move about the shaft 3 outside the disk stack
1.
[0039] As shown in FIG. 1, the signal wire 7 and the signal wire
terminal 8 for input/output for the magnetic head 5 are disposed in
the above-mentioned space. A shroud 12a defines a part of the
housing 10, which is formed to be concentric with the disk stack 1.
A shroud 12b constitutes a part of the housing structure of the
magnetic disk apparatus, and also defines a part of the motor cover
21 in the embodiment of the invention. Like the shroud 12a, the
shroud 12b is also shaped to be concentric with the disk stack 1.
Here, the concentric configuration means a shape having a wall
surface that is equidistant from the rotating shaft 2, to which the
disk stack 1 is fixed.
[0040] In the embodiment of the invention, the shrouds 12a and 12b
are formed to be concentric with the disk stack 1 in areas other
than areas where the arm downstream space 11 and the air
introduction passage into the filter 9 are located. The motor cover
21 is disposed on the upstream side of the shroud 12b positioned on
the upstream side of the arms such that a gap is provided between
the motor cover and the inner wall of the magnetic disk apparatus
housing 10 to form a shroud opening 12c.
[0041] A bypass channel 15 is defined by forming side surfaces of
the motor cover 21 and of the housing 10 to provide a parallel gap
between the shroud opening 12c and the arm downstream space 11. The
shroud 12b of the motor cover 21 located on the upstream side of
the arms is provided in the vicinity of the arms 4 so as to block
airflow toward the voice coil motor 6 but not to interfere with the
required turning of the arms 4. In addition, the motor cover 21 may
be formed either integrally with the housing 10 or formed as a
separate piece for assembly.
[0042] Air in the housing of the embodiment flows as indicated by
an arrow 14 in FIG. 1. Revolution of the disk stack 1 causes the
air to flow in the circumferential direction indicated by the arrow
13 between adjacent disks, so that the air flow is blocked by the
arms 4 to produce a high pressure area on the upstream side of the
arms 4. On the other hand, the air pressure decreases on the
downstream side of the arms 4 to cause an air in the arm downstream
space 11 to be drawn into between the disks. Here, the bypass
channel 15 connects the high pressure upstream side of and the low
pressure downstream side of the of the arms 4, so that the air flow
is caused as indicated by an arrow 14.
[0043] The configuration of the bypass channel 15 will now be
described with reference to FIG. 2 and FIG. 6. FIG. 2 is a
longitudinal sectional view showing the housing structure of the
magnetic disk apparatus in accordance with the invention, in which
a section associated with the rotary actuator is omitted. FIG. 6
shows a relationship between an inflow angle of airflow and a ratio
of a length of a linear section and a width of the bypass
channel.
[0044] As shown in FIG. 2, the bypass channel 15 is composed of
parallel walls to have a larger width D (denoted by 17 in the
drawing) than a gap h (denoted by 19 in the drawing) between the
shroud 12 and the disk stack 1 and a depth H (denoted by 18 in the
drawing) equal to or more than the height of the disk stack 1. The
depth H should be five times or more the width D. Because of the
depth H five times or more the width D, the pressure loss at the
shroud opening 12c can be maintained substantially at a constant
level even when the direction of the airflow entering into the
bypass channel 15 from the shroud opening 12c as shown in FIG. 1
varies depending on the position of the arms 4. Therefore, the
provision of the bypass channel 15 can be effective I reducing
pressure fluctuation irrespective of the position of the arms
4.
[0045] Moreover, the bypass channel 15 is provided with the linear
section, which has a length L (denoted by 16 in the drawing), as
shown in FIG. 1, corresponding to five times or more the width D.
The flow entering into the bypass channel 15 sometimes comes off to
generate a pulsating flow at a tip end, which forms a part of the
motor cover 21 toward the shroud opening 12c and at which the
bypass channel 15 is in contact with the shroud 12b. Even when such
pulsating flow is generated, the linear section having the length L
can attenuate flow speed fluctuation because the length L is at
least five times the width D. Since coming-off tending to generate
an airflow turbulence takes place mostly at the shroud opening 12c,
it suffices that the linear section is located on the downstream
side of the shroud opening 12c. So, portions of the bypass channel
15 except the linear section does not need to have a width D of one
fifth or less of the depth H and a rectangular-shaped cross section
as shown in FIG. 2.
[0046] Relationships among the length of the bypass channel and so
on will be described with reference to FIG. 6.
[0047] The axis of abscissa in a graph shown in FIG. 6 indicates an
inflow angle of an air flow entering into the bypass channel. With
the magnetic disk apparatus, such inflow angle varies depending on
a manner of mounting the opening or a position of the arms of the
rotary actuator. A tangent line of the disk stack 1 serves as a
reference for the inflow angle. Herein, such reference is provided
by a tangent line at an end of the disk stack 1 closest to the side
face of the magnetic disk apparatus, in which the bypass channel 15
is formed. A line 601 in the graph indicates an inflow angle, at
which air can flow into the bypass channel 15 despite of a pressure
loss in the bypass channel 15. Thus, the bypass channel in
accordance with the invention is made effective in an area 603 on
the left side of the line 601 in the graph.
[0048] The axis of ordinate in FIG. 6 indicates a ratio of length
to width L/D of the linear section. A curve 602 plots values of L/D
of a linear section L required for airflow turbulence to assume a
constant value in the bypass channel, relative to respective inflow
angles. The bypass channel exhibits a rectifying effect in a region
above the curve 602. As shown in the graph, an intersection point
of the line 601 and the curve 602 is in most cases near a point
where the value of L/D assumes 5. It is seen that, with the value
of L/D being 5 or more, airflow is generated in the bypass channel
irrespective of the manner of mounting of the opening and the
position of the arms of the rotary actuator, and that turbulence is
attenuated in the linear section to provide the rectifying
effect.
[0049] The analysis results shown in FIG. 6 are ones when the width
D of the linear section is one fifth or less of the depth H, and
are almost the same when the value of H/D is 5 or more. When the
value of H/D is smaller than 5, the bypass channel is increased in
pressure loss. Therefore, no airflow is sometimes generated in the
bypass channel depending on the position of the arms of the rotary
actuator, so that advantages of the invention cannot be obtained.
Likewise, if the width D of the bypass channel is smaller than the
shroud gap h, then the bypass channel is sometimes increased in
pressure loss, and advantages of the invention cannot be obtained.
Thus, as described above, advantages of the invention can be
obtained irrespective of the manner of mounting of the opening and
the position of the arms of the rotary actuator, provided that the
channel width D of the linear section of the bypass channel is
greater than the shroud gap h, the length L of the linear section
is 5D or more, and the depth H of the linear section is also 5D or
more.
[0050] In this manner, a pressure difference between the
high-pressure upstream side of and the low-pressure downstream side
of the arms 4 decreases. Furthermore, since airflow is rectified in
the linear section of the bypass channel 15, an airflow free from
turbulence comes into the arm downstream space 11 to be reduced
there in speed, and slowly enters into spaces between adjacent
disks so as not to impede airflow accompanying the revolution of
the disk stack 1. As described above, the airflow in the housing in
accordance with the invention reduces the pressure loss, which
would generate due to the pressure difference between the upstream
side of and the downstream side of the arms 4 as the result of the
presence of the arms to thereby reduce the driving torque required
for revolution of the disk stack 1 and to control an amplitude of
fluctuations in pressure difference between the upstream side of
and the downstream side of the arms 4 with the passage of time,
which is responsible for wind turbulence. Further, airflow entering
into the spaces between adjacent disks at the downstream side of
the arms is reduced in turbulence with the result that flutter is
reduced.
[0051] With reference to FIG. 3, advantages of the invention will
now be described by way of results obtained by analysis of unsteady
flow. FIG. 3A shows results obtained when disks have a diameter of
65 mm, a gap h between the shroud and the disks is 0.7 mm, and the
disks revolve at 12000 rpm.
[0052] A configuration 1 is shown in FIG. 3B, a configuration 2 is
shown in FIG. 3C, and a configuration 3 is shown in FIG. 3D. FIG.
3A shows comparison among these three configurations with respect
to a degree of influence (304) of flutter on positional accuracy, a
degree of influence (305) of wind turbulence on the positional
accuracy, and a ratio (306) of power consumption for revolutions
every disk. All the configurations shown in FIG. 3B through 3D are
the same except the shape of the housings.
[0053] 1 is not equipped with the bypass channel 15 of the
invention, and the shroud 12 covers the upstream side of the arms
4. 1, an air flows through a gap between the arm rotating shaft 3
and the voice coil motor 6 as indicated by an arrow 300 in FIG.
3B.
[0054] The configurations 2 and 3 are equipped with the bypass
channel 15 of the invention that has a width D of 2 mm and a depth
H of 20 mm. With the configuration 2, the motor cover 21 of the
invention is formed of a flat plate, and the linear section L of
the bypass channel is approximately 10 mm. Furthermore, with the
configuration 2, a gap between the rotating shaft 3 of and the
voice coil motor 6 of the rotary actuator is not closed.
Accordingly, almost the air flows as indicated by an arrow 301 in
the drawing while a part of the air flows in the voice coil motor
as indicated by an arrow 302 in the drawing.
[0055] With the configuration 3, the gap is closed, so that the air
flows as indicated by an arrow 303. Like the degree of influence
(304) of flutter on the positional accuracy, the degree of
influence (305) of wind turbulence on the positional accuracy and
the power consumption ratio (306) are indicated with those for the
configuration 1 being 100%. As apparent from FIGS. 3A through 3D,
the bypass channel 15 of the invention reduces the power
consumption as well as the influences of the flutter and wind
turbulence.
[0056] Another embodiment of the invention will be described with
reference to FIG. 4. FIG. 4 is a cross-sectional view showing a
configuration of a magnetic disk apparatus in another embodiment,
to which the invention is applied. This embodiment differs from the
embodiment shown in FIG. 1 in a manner of forming a bypass channel
15.
[0057] In the embodiment, components such as a shroud 12a and a
filter 9 are the same as those shown in FIG. 1. An arm downstream
space 11 is not provided with any shroud whereby a space sufficient
to permit all arms 4 of the rotary actuator to move about a shaft 3
outside a disk stack 1 is ensured. As with the configuration shown
in FIG. 1, a signal wire 7 and a signal wire terminal 8 for
input/output of a magnetic head 5 are arranged in the space.
[0058] As shown in FIG. 4, a motor cover 21 in the embodiment is
formed by having a shroud of a housing 10 extended to an upstream
side of the arms 4 and cutting off the same partly for the
provision of an opening 12c. A guide vane 20 for defining the
bypass channel 15 is formed by mounting a plate, which has been
made separately from the housing 10, so as to make the same
parallel to the inner wall of the housing 10.
[0059] In the embodiment shown in FIG. 4, the guide vane 20 is bent
downstream of the linear section of the bypass channel 15 so as to
block airflow into a voice coil motor 6. Further, a wall surface of
the bypass channel 15, which mates with the guide vane 20, may not
be defined by the inner wall of the housing 10 but may be defined
by mounting a flat plate to the housing 10 like the guide vane 20.
According to this embodiment, it is simply possible to obtain the
same effect as that in the aforesaid embodiment shown in FIG. 1
without forming the housing 10 in complicated manner.
[0060] A further embodiment of the invention will be described with
reference to FIG. 5. FIG. 5 is a cross-sectional view showing a
configuration of a magnetic disk apparatus in the further
embodiment, to which the invention is applied.
[0061] This embodiment differs from the embodiment shown in FIG. 1
in a manner of forming a bypass channel 15 and a shroud 12b on an
upstream side of the arms. In the embodiment, components such as a
shroud 12a and a filter 9 are the same as those shown in FIG. 1. An
arm downstream space 11 is not provided with any shroud whereby a
space sufficient to permit all arms 4 of the rotary actuator to
move about a shaft 3 outside a disk stack 1 is ensured. As with the
configuration shown in FIG. 1, a signal wire 7 and a signal wire
terminal 8 for input/output of a magnetic head 5 are arranged in
the space.
[0062] In the embodiments shown in FIGS. 1 and 4, the motor cover
21 is provided to constitute the bypass channel 15 and the shroud
12b on the upstream side of the arms, while in this embodiment any
motor cover 21 is not provided and an inner wall of the housing 10
is made a shroud which extends from a shroud 12a to an area, in
which an opening 12c is provided, to be concentric with the disk
stack 1 except inlet and outlet of air into a filter 9. The
remaining inner wall surface of the housing is formed to be
flat.
[0063] Then, a side surface 12b opposed to the disk stack is formed
on a casing 22 of a voice coil motor 6 to be arcuate in concentric
manner with the disk stack 1. Further, a side surface 21a of the
casing 22 opposed to the housing 10 is formed to be flat in
parallel to a planar portion of the inner side surface of the
housing 10. Here, the side surface 12b and the side surface 21a are
contiguous backward in FIG. 5 to be closed at least for the purpose
of blocking air flowing into the voice coil motor from the bypass
channel 15.
[0064] Without the provision of any motor cover 21, the bypass
channel 15 described in the embodiment of FIG. 1 can be constructed
by fixing the voice coil motor, which is provided with the casing
22 formed in this manner, to the housing 11 of the magnetic disk
apparatus. Thus, according to this embodiment, it is possible to
obtain the same effect as that in the embodiment of FIG. 1 simply
by changing the voice coil motor and without forming the housing 10
in complicated manner.
[0065] The invention can realize a magnetic disk apparatus having a
housing structure, which enables suppressing pressure fluctuation,
which would occur when arms of a rotary actuator are inserted
between the disks, to reduce flutter and wind turbulence and
prevent generation of additional pressure fluctuation upstream and
downstream of the arms, thus reducing driving power.
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