U.S. patent application number 11/607069 was filed with the patent office on 2007-04-05 for magnetic tape cartridge.
Invention is credited to Sadamu Kuse, Manabu Nose, Shihoko Takashima.
Application Number | 20070076316 11/607069 |
Document ID | / |
Family ID | 36125260 |
Filed Date | 2007-04-05 |
United States Patent
Application |
20070076316 |
Kind Code |
A1 |
Kuse; Sadamu ; et
al. |
April 5, 2007 |
Magnetic tape cartridge
Abstract
A magnetic tape cartridge comprises: a magnetic tape on which
data tracks and servo tracks are provided; a casing housing the
magnetic tape therein: and a storing section which stores values of
tape width detected during data recording onto the data tracks of
the magnetic tape and from which the stored values of tape width
are read out during data reproduction from the data tracks of the
magnetic tape.
Inventors: |
Kuse; Sadamu; (Osaka,
JP) ; Nose; Manabu; (Osaka, JP) ; Takashima;
Shihoko; (Osaka, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
36125260 |
Appl. No.: |
11/607069 |
Filed: |
December 1, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11236536 |
Sep 28, 2005 |
7158339 |
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11607069 |
Dec 1, 2006 |
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Current U.S.
Class: |
360/69 ; 360/132;
360/77.12; G9B/15.036; G9B/15.048; G9B/15.077 |
Current CPC
Class: |
G11B 15/26 20130101;
G11B 15/602 20130101; G11B 15/43 20130101 |
Class at
Publication: |
360/069 ;
360/132; 360/077.12 |
International
Class: |
G11B 19/02 20060101
G11B019/02; G11B 23/02 20060101 G11B023/02; G11B 5/584 20060101
G11B005/584 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 30, 2004 |
JP |
2004-287969 |
Claims
1. A magnetic tape cartridge comprising: a magnetic tape on which
data tracks and servo tracks are provided; a casing housing the
magnetic tape therein: and a storing section which stores values of
tape width detected during data recording onto the data tracks of
the magnetic tape and from which the stored values of tape width
are read out during data reproduction from the data tracks of the
magnetic tape.
2. A magnetic tape cartridge according to claim 1, wherein the
storing section is constructed by a semiconductor memory provided
on or in the casing.
3. A magnetic tape cartridge according to claim 1, wherein the
storing section is constructed by a portion of the magnetic tape.
Description
[0001] This application is a Continuation of co-pending application
Ser. No. 11/236,536, filed on Sep. 28, 2005, the entire contents of
which are hereby incorporated by reference and for which priority
is claimed under 35 U.S.C. .sctn. 120.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a magnetic tape cartridge
being capable of managing size changes of magnetic tapes housed in
the cartridge.
[0003] Magnetic tapes are used in various applications such as
audio tapes, video tapes and computer tapes. Particularly in the
field of data backup tapes, magnetic tapes having recording
capacities of several hundreds of gigabytes or more per reel have
been commercialized along with increasing mass storage of hard
disks, which are targeted for gigabyte backup. Further,
mass-storage backup tapes which will go beyond 1 terabytes from
this time forward have been proposed, for which implementation of
higher recording densities is indispensable.
[0004] With a view to increasing the capacity of data that can be
recorded on a magnetic tape, it has been in progress to increase
the number of data tracks by reducing the width of a data track,
which is so called recording density enhancement of data tracks.
For example, with a magnetic tape having a width of 1/2 inch (about
12.7 mm), the number of data tracks reaches about several hundreds
of tracks, causing the width of data tracks to be as narrow as 20
.mu.m or less.
[0005] In parallel with this, the head for recording and
reproducing data on a magnetic tape is provided by adopting a
multichannel head in which a plurality of magnetic heads are
disposed on a head unit. In the multichannel head, a tracking servo
technology have been introduced so as to allow each magnetic head
to accurately trace on each data track of narrow width. This is a
technology that a servo signal previously written on the magnetic
tape is read by a servo head provided in the head unit and then an
actuator is driven according to the read signal so that even if the
track position has changed widthwise during recording and
reproducing operation, the head unit can be positionally controlled
in the widthwise direction of the magnetic tape, thus enabling each
magnetic head to follow each data track.
[0006] Such tracking servo technologies come in two kinds of
methods. One of the technologies is the magnetic servo method,
which includes forming a servo signal on a magnetic layer by
magnetic recording and reading this signal magnetically to do servo
tracking. The other is the optical servo method, in which a servo
signal made from a recessed portion array is formed on a back layer
by laser irradiation and then read optically to perform servo
tracking.
[0007] A description is given below about the tracking servo method
by taking the magnetic servo method as an example. FIG. 1
schematically shows a relative positional relation between a
magnetic tape 1 and a head unit 2 in this case, and FIG. 2
schematically shows the structure of the head unit 2. As shown in
these figures, a servo track group 4 in which servo signals have
been written is provided on the magnetic layer of the magnetic tape
1. On the head unit 2, on the other hand, normally provided are at
least one servo head 12a/12b and a plurality of data head groups 11
for higher data transfer rate. In recording and reproducing
operations, the head unit 2 runs on the magnetic tape 1 in a
longitudinal direction X. In this operation, if the magnetic tape 1
has swung in the widthwise direction (Y direction in FIG. 1), the
signal derived from the servo head 12a/12b that traces the servo
track changes and the actuator (not shown) is activated
responsively, by which the whole head unit 2 is moved in the
widthwise direction (Y direction) of the magnetic tape 1, with the
result that the positional relation between the magnetic tape 1 and
the head unit is recovered correctly.
[0008] One example of such tracking servo technologies is described
in JP 2002-157722 A. In this case, the head unit is equipped with
not only a normal servo track reading head but also a preceding
reading head that reads positional information about the servo
track, with a view to further improving the tracking servo
precision.
[0009] In this connection, the magnetic tape slightly varies in the
size of width along the longitudinal direction, and the amount of
the variation changes depending on temperature, humidity and the
preservation state of tapes. Also, there are errors of relative
positions among the magnetic heads on the head unit because of
limitations of machining precision. Such width variations of
magnetic tapes and errors of the relative positions among the
magnetic heads as shown above, it could be predicted, have large
influences on the tracking precision against further enhancement of
the density of data tracks 3 of magnetic tapes. This is an issue
that could not be managed only by the tracking servo technology for
controlling the position of the head unit in the widthwise
direction of the magnetic tape. Therefore, for example, JP
2003-173508 A proposes a technique of reading jogging servo
signals, which have been written in the data tracks of the magnetic
tape, by chips of the individual heads and then driving jogging
actuators for the individual head chips based on the read signals
to thereby control the jogging of the head chips.
[0010] In addition, JP 2001-35046 A discloses a technique of, in a
running state of a flexible tape such as a magnetic tape, detecting
width of the tape contactlessly at high precision and then
controlling the tension of the magnetic tape so that the detected
tape width becomes a targeted tape width. However, this is a
technique of performing the detection of tape width as well as the
control of the tape tension in the running state in order to
achieve stable running and uniform take-up of the magnetic tape.
That is, the technique is other than to control the tape tension in
consideration of influences exerted on the tracking precision by
such variations in the magnetic tape width or errors of the
relative positions among the individual magnetic heads as described
above.
[0011] For magnetic tapes, as described above, there is a tendency
that the data track width will decrease more and more from this
time on under the trend toward higher recording densities. As a
result of this, there has emerged a fear that correct reading of
data may be unachievable because of significant increases in
deviation of the positional relation between magnetic head and data
track, i.e., differences between servo track--data track distance
and servo head--recording/reproducing head distance in the tape
width direction caused by not only widthwise swings of the tape
during recording and reproducing operations as described above but
also occurrence of widthwise size changes of the magnetic tape due
to changes in temperature, humidity and the preservation state of
the tape. This point is described in detail below.
[0012] In conventional recording/reproducing method for magnetic
tapes, data recording is performed at a specified recording track
width. Preferably, this recording track width is as smaller as
possible because the number of tracks on the magnetic tape can be
increased so that the recording capacity is increased. On the other
hand, a lower limit value for the recording track width is
determined naturally from considerations of the tracking servo
precision, dimensional differences due to differences in expansion
coefficient between head unit and magnetic tape caused by
temperature and humidity variations, changes in tape width due to
the leaving after taking-up, and the like. As the recording track
width decreases beyond this lower-limit value, the reproducing head
becomes more likely to be misaligned from the recording track,
which causes data signal reading to become usable, leading to
increases in error rate. In order to allow larger margins of track
misalignment during data reproduction, normally, the recording
track width is so designed as to be larger than the track width
relative to the reading reproducing head. Therefore, there occurs
no problem only if the relative position between recording track
and reproducing head after tracking servo falls within the margin
range.
[0013] Among the factors of the relative position shifts between
recording track and reproducing head, the widthwise swing of the
tape during the running can be managed with improvement of the
performance of the tracking servo. However, if there occur the
dimensional differences and tape width changes due to the leaving
after taking-up, caused by differences in expansion coefficient
between head unit and magnetic tape owing to temperature and
humidity variations, that is, if the difference between a distance
from a servo head to the data head located farthest from the servo
head (e.g., servo head 12a and data head 11b, or servo head 12b and
data head 11a shown in FIG. 2) and its corresponding distance from
the servo track and the data track becomes a significant value
relative to the aforementioned margin, those differences would
matter irrespectively of the performance of the tracking servo.
[0014] For instance, if the above-mentioned distance from a servo
head to the data head located farthest from the servo head is 2500
.mu., the recording head width is 20 .mu.m and the track width of
the reproducing head is 12 .mu.m, then the difference margin of the
reproducing head is only 4 .mu.m or so on one side relative to the
reference position. With respect to expansions of the head unit and
the magnetic tape due to temperature and humidity, the difference
due to humidity is larger, and therefore from the viewpoint of
humidity expansion coefficient, in the case of a magnetic tape
having a humidity expansion coefficient of 2.times.10.sup.-5/% RH,
a humidity change of 40% RH during a reproduction relative to a
recording would cause a difference of 2.0 .mu.m at a maximum in
this system. On this account, whereas data tracks in the vicinity
of the servo track bear no problem with amplitudes of up to about 8
.mu.m against in-running widthwise swings of the tape, the data
track located farthest from the servo track undergoes a decrease of
amplitude allowance to about 4 .mu.m. This would considerably
matter in further enhancement of the recording density of magnetic
tapes in the future.
[0015] As a solution to such problems, the method described in JP
2003-173508 A has been proposed. However, in this method, since the
jogging servo signals are written in the data tracks of the
magnetic tape, data recording area inevitably decreases
correspondingly. This would form an obstacle to implementing
magnetic tapes of high recording density.
SUMMARY OF THE INVENTION
[0016] The present invention having been accomplished in view of
these and other problems, an object of the invention is to provide
a magnetic tape cartridge capable of correctly recording and
reproducing data without causing errors even with occurrence of
size changes in the widthwise direction of a magnetic tape as a
recording and reproducing technique suitable for recording density
enhancement of magnetic tapes.
[0017] In order to achieve the above object, the present invention
provides a magnetic tape cartridge including:
[0018] a magnetic tape on which data tracks and servo tracks are
provided;
[0019] a casing housing the magnetic tape therein: and a storing
section which stores values of tape width detected during data
recording onto the data tracks of the magnetic tape and from which
the stored values of tape width are read out during data
reproduction from the data tracks of the magnetic tape.
[0020] In the present invention, the storing section may be
constructed by a semiconductor memory provided on or in the casing,
and may be constructed by a portion of the magnetic tape.
[0021] According to the present invention, even if the magnetic
tape has changed in size, the tape width during data recording can
be maintained constant by the tension control, based on the values
of tape width stored in the storing section during data recording
onto the data tracks of the magnetic tape, exerted during data
reproduction. Thus, there occurs no track displacement between
recording track and reproducing head, making it implementable to
fulfill data recording without errors.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The present invention will be further described with
reference to the accompanying drawings wherein like reference
numerals refer to like parts in the several views, and wherein:
[0023] FIG. 1 is an outlined view showing an example of the
tracking servo method to be used for recording and reproduction of
magnetic tapes;
[0024] FIG. 2 is a schematic enlarged view showing an example of
the arrangement configuration of the head provided on the head unit
of FIG. 1;
[0025] FIG. 3 is a graph showing an example of the correlation
between tape tension and tape width according to an embodiment of
the invention;
[0026] FIG. 4 is a block diagram showing an example of the
configuration of a recording/reproducing apparatus for magnetic
tapes according to an embodiment of the invention; and
[0027] FIG. 5 is an outlined structural view showing an example of
a recording/reproducing system for magnetic tapes to which the
invention is applied.
[0028] FIG. 6 is an schematic view of a magnetic tape cartridge
having a magnetic tape housed therein and a storing section which
is composed of a semiconductor memory in the cartridge itself.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] The present invention is targeted for a magnetic tape
cartridge for recording and reproducing data while performing servo
tracking on a magnetic tape having data tracks and servo tracks.
The tracking servo method in this case may be either a magnetic
servo method or an optical servo method. Below given is a
description on a case where the present invention is applied to a
system in which data recording and reproducing is performed while
servo tracking is being performed on the magnetic tape 1 by the
magnetic servo method by using the head unit 2 as shown in
foregoing FIGS. 1 and 2. However, even in the case of the optical
servo method, basically, the present invention may be carried out
with the same structure as shown below.
[0030] First, a magnetic tape recording/reproducing system is
briefly explained. FIG. 4 is an outlined structural view showing an
example of such a recording/reproducing system. As shown in FIG. 4,
the magnetic tape recording/reproducing system includes a tape feed
unit 5 for feeding out the magnetic tape 1, a take-up unit 6 for
taking up the magnetic tape 1, a feed motor 7 for driving the tape
feed unit 5, a take-up motor 8 for driving the take-up unit 6, and
a motor controller 9 for controlling the individual motors 7 and 8.
By controlling the individual motors 7 and 8, the motor controller
9 can control the tape feed speed of the tape feed unit 5 and the
take-up speed of the take-up unit 6.
[0031] Between the tape feed unit 5 and the take-up unit 6, and
along the tape running path from the former to the latter, the head
unit 2 for performing data recording and reproduction with the
magnetic tape 1, a plurality of guide rollers 30 for guiding the
magnetic tape 1 along a specified direction, and a tape width
measuring instrument 10 for detecting the tape width of the
magnetic tape 1 (means 24 for detecting the tape width). Then, the
magnetic tape 1 is made to run from the tape feed unit 5 toward the
take-up unit 6, and data recording and reproduction with the
magnetic tape 1 is performed by the head unit 2 while the servo
tracking by the magnetic servo method is in progress. In this case,
magnetic tape width is detected by the tape width measuring
instrument 10 in both recording and reproduction of data.
[0032] Next, the magnetic tape recording/reproducing apparatus
which is applicable to such system as shown above is explained. As
shown in FIG. 5, the magnetic tape recording/reproducing apparatus
21 includes a means 24 for detecting magnetic tape width, a storing
section 25 to store the tape width, a means 26 for reading the tape
width, a means 27 for making a comparison between the tape width in
data recording and the tape width in data reproduction (means for
comparing the tape widths between recording and reproduction
operations), and a means 28 for controlling tape tension. In
addition, in FIG. 5, a data recording state 22 and a data
reproducing state 23 are surrounded by broken lines, respectively,
to allow an intuitive grasping of timings at which individual means
are involved.
[0033] The means 24 for detecting magnetic tape width, may be
implemented by conventionally known means, which is exemplified by
a technique that position detection sensors for monitoring both
edges of the magnetic tape 1, respectively, are placed on the
running path of the magnetic tape 1, or a technique that with at
least two particular servo tracks provided on the magnetic tape 1,
variations of the distance between the two servo tracks are
determined from servo signals read by the servo heads 12a and 12b
on the head unit 2 as shown in FIG. 2 and then the value of the
tape width is obtained from the relationship between the
inter-servo-track distance and the tape width.
[0034] It is noted that on condition that means for detecting the
tape width without using the head unit is the used, providing
position detection sensors for monitoring both edges of the
magnetic tape 1 on a substrate made of the same material as the
head unit makes it possible to manage fine size changes of the head
unit due to temperature or the like.
[0035] The storing section 25 to store the tape width and the means
26 for reading the tape width are implemented by conventionally
known means, which is exemplified by providing a storage element
such as semiconductor memory in the cartridge itself of the
magnetic tape cartridge having the magnetic tape housed therein (in
the casing itself in which the magnetic tape is housed), or
providing a place for storage in part of the magnetic tape (e.g., a
portion forward of data recording/reproducing portion of the tape
in its longitudinal direction) so that an exclusive or bi-use
magnetic head is used for storage and reading.
[0036] The means 27 for comparing tape widths between recording and
reproducing operations may be implemented by conventionally known
means, which is exemplified by a process including detecting a
magnetic tape width at all times or from time to time by means for
detecting the magnetic tape width during data reproduction and then
comparing, by a comparison operation circuit, the tape widths in
data recording stored on the storage element included in the
foregoing cartridge or on the magnetic tape with values read by the
means 26 for reading the tape width, and further sending a control
signal to the means 28 for controlling tape tension.
[0037] The means 28 for controlling tape tension may be implemented
by conventionally known means, which is exemplified by a means for
controlling the torques of the feed reel and the take-up reel, or a
means for providing pinch-roll capstans on both sides of the tape
running system with the head unit sandwiched therebetween to
control their rotational speeds and thereby control the
tension.
[0038] The recording/reproducing method for the magnetic tape
cartridge according to the present invention is to perform data
recording and reproduction while detecting the magnetic tape width
in both recording and reproduction of data for the magnetic tape 1
in the following manner with the use of such the
recording/reproducing apparatus as described above.
[0039] First, in data recording, magnetic tape width is detected at
all times or from time to time by the means 24 for detecting
magnetic tape width. The resulting tape widths are stored on the
storage element included in the cartridge or on the magnetic tape 1
at all times or from time to time by the storing section 25 to
store tape widths, together with positional information of the tape
in its longitudinal direction.
[0040] Next, in data reproduction, the magnetic tape width is
detected by the means 24 for detecting a magnetic tape width, at
all times or from time to time. Concurrently with this, tape widths
in data recording stored on the storage element included in the
cartridge or on the magnetic tape 1 are read by the means 26 for
reading a tape width (tape width measuring instrument 10 in FIG.
4), and further tape widths in recording and reproducing operations
are compared therebetween at various positions of the tape in its
longitudinal direction by the means 27 for comparing tape widths
between recording and reproducing operations. Based on these
results, tape tension is controlled in response to the tape width
by the means 28 for controlling tape tension, so that the tape
width is maintained equal to the tape width in recording operation.
Generally, as shown in FIG. 3, there can be seen a correlation
between tape tension and tape width change, so that the tape width
can be controlled by controlling the tape tension. With such
measures, even if the tape width has changed relative to that of
data recording due to environmental conditions (temperature,
humidity) in data reproduction, and the preservation condition of
the tape, data tracks can be reproduced with the tape width in data
recording. Thus, no track displacement occurs during data
reproduction, so that reproduction without errors become
implementable.
[0041] As described above, according to the present invention, data
recording and reproduction is performed in such a manner that that
even when the magnetic tape has changed in size, tape tension is
controlled so that the tape width during data reproduction is
maintained equal to that of data recording. Thus, even with changes
in use environments or tape preservation conditions, the distance
between servo track and data track is maintained constant at all
times, making it implementable to reproduce data without causing
errors. As a consequence of this, a recording/reproducing method
and a recording/reproducing apparatus for magnetic tapes suitable
for recording density enhancement can be realized.
[0042] Although the present invention has been fully described by
way of examples with reference to the accompanying drawings, it is
to be noted that various changes and modifications will be apparent
to those skilled in the art. Therefore, unless otherwise such
changes and modifications depart from the scope of the present
invention, they should be construed as being included therein.
* * * * *