Title: Magnetic head
Abstract: A magnetic head having a sliding surface (120) on which a magnetic recording medium is slid, a magnetic gap g formed in the sliding surface for exchanging information signals with the magnetic recording medium, a track width controlling portion for prescribing a track width Tw of the magnetic gap g, with the track width controlling portion being formed by abutting a pair of magnetic core halves (110a, 110b) together, there being track width controlling grooves (111a to 111d) formed in each of the magnetic core halves, metal magnetic films (112a to 112f) provided in association with the magnetic gap g and with the track width controlling portion, and a groove (130) formed in at least one end of the magnetic gap g for extending substantially parallel to the sliding direction of the magnetic recording medium. A length L in μm between a first point of intersection P between the track width controlling groove (111b) formed in one of the magnetic core halves (110a) and one lateral edge of the groove (130) and a second point of intersection Q between the magnetic gap g and the other lateral edge of the groove is related with an intensity of the recording current I [mA] by L≧11.3×1nI-21.9. With the magnetic head, demagnetization produced in the recording track of the magnetic tape is prevented from being produced.
Patent Number: 6,894,868 Issued on 05/17/2005 to Onodera, et al.
| Inventors:
|
Onodera; Osamu (Saitama, JP);
Sato; Heikichi (Miyagi, JP);
Sakata; Katsumi (Miyagi, JP);
Aoki; Kaoru (Miyagi, JP)
|
| Assignee:
|
Sony Corporation (Tokyo, JP)
|
| Appl. No.:
|
381288 |
| Filed:
|
July 23, 2002 |
| PCT Filed:
|
July 23, 2002
|
| PCT NO:
|
PCTJP02/07444
|
| 371 Date:
|
August 28, 2003
|
| 102(e) Date:
|
August 28, 2003
|
| PCT PUB.NO.:
|
WO0301075 |
| PCT PUB. Date:
|
February 6, 2003 |
Foreign Application Priority Data
| Jul 23, 2001[JP] | 2001-221996 |
| Current U.S. Class: |
360/119; 360/122 |
| Intern'l Class: |
G11B 005/23; G11B005/18.7 |
| Field of Search: |
360/119,120,122,126
|
References Cited [Referenced By]
U.S. Patent Documents
| 5227940 | Jul., 1993 | Isomura et al.
| |
| 5594608 | Jan., 1997 | Dee.
| |
| 5708544 | Jan., 1998 | Kawashima et al.
| |
| 5905612 | May., 1999 | Honma et al.
| |
| Foreign Patent Documents |
| 11-161910 | Jun., 1999 | JP.
| |
| 2000-20910 | Jan., 2000 | JP.
| |
| 2001-28105 | Jan., 2001 | JP.
| |
Primary Examiner: Tupper; Robert S.
Attorney, Agent or Firm: Sonnenschein, Nath & Rosenthal LLP
Claims
1. A magnetic head comprising a sliding surface on which a magnetic recording
medium is slid, a magnetic gap formed in said sliding surface for exchanging information
signals with said magnetic recording medium, a track width controlling portion
for prescribing a track width of said magnetic gap, said track width controlling
portion being formed by abutting a pair of magnetic core halves, there being a
track width controlling groove formed in each of said magnetic core halves, a metal
magnetic film provided in association with said magnetic gap and said track width
controlling portion, and a groove formed in at least one end of said magnetic gap
for extending substantially parallel to the sliding direction of said magnetic
recording medium, wherein
a length L in μm between a first point of intersection between said track
width controlling groove formed in one of said magnetic core halves and one lateral
edge of said groove and a second point of intersection between said magnetic gap
and the other lateral edge of said groove is related with an intensity of the recording
current I [mA] by
2. The magnetic head according to claim 1 wherein the recording current intensity
I is 50 to 100 mAp-p.
3. The magnetic head according to claim 1 wherein a plurality of substantially
straight lines formed on said sliding surface, by a plurality of said track width
controlling grooves formed in one of said magnetic core halves, are arranged non-symmetrically
relative to an imaginary line extending perpendicular to said magnetic gap.
Description
BACKGROUND OF THE INVENTION
This invention relates to a magnetic head used for recording and/or reproducing
information signals, such as audio or video signals, for a magnetic recording medium,
such as a magnetic tape, or data signals, handled in an information processing
unit, such as a personal computer.
Up to now, a metal-in-gap (MIG) type magnetic head has been used as a magnetic
head for exchanging the information with a magnetic recording medium, such as a
magnetic tape.
The MIG type magnetic head is formed by abutting and bonding a pair of magnetic
core halves, formed of ferrites, to each other. With this magnetic head, a magnetic
gap is formed on abutment surfaces of the paired magnetic core halves abutted and
bonded to each other. Two track width controlling grooves are formed in each of
the paired magnetic core halves forming the magnetic head. These track width controlling
grooves control the track width of the magnetic gap when the paired magnetic core
halves are abutted and bonded together to form the magnetic gap. In the MIG type
magnetic head, a magnetic metal film is formed in the magnetic gap and in the track
width controlling grooves.
Towards one side, for example an overwrite side, of the magnetic gap of the
MIG type magnetic head, lying towards a recording track previously formed by sequentially
recording information signals on the magnetic tape, there is formed a groove extending
parallel to the tape running direction. This groove is provided for preventing
the so-called side erasure from occurrence. This side erasure is caused by the
unneeded stray magnetic flux from being produced from a track edge corresponding
to one end of the magnetic gap to disturb the pattern of the recording track recorded
on the magnetic tape.
Referring to FIG. 1, a magnetic head, formed by abutting and bonding a
pair of magnetic core halves to each other, is prepared by abutting a first magnetic
core half
10 and a second magnetic core half
20 to form a head block
1, by applying preset machining operations to this head block
1 and
by slicing the head block
1 into plural discrete magnetic heads.
FIG. 1 shows the head block
1 obtained on abutting the two paired, that
is first and second magnetic core half blocks
10 and
20, and on machining
the resulting product. The head block
1, shown in FIG. 1, is formed by abutting
and bonding the first and second magnetic core half blocks
10 and
20,
and is shown in a state prior to severing the block into discrete plural magnetic
heads. FIG. 1 shows the head block, yet to be severed into discrete plural magnetic
heads, looking from the tape sliding surface formed on each discrete magnetic head.
In the head block
1, formed on abutting the first and second magnetic
core
half blocks
10 and
20 to each other, there is formed as magnetic
gap g in the abutment surface of the first and second magnetic core half blocks
10 and
20, as shown in FIG.
1.
In the first magnetic core half block
10, forming the head block
1,
there are formed a first track width controlling groove
11 and a second
track width controlling groove
12 for controlling the track width of the
magnetic gap g. In the second magnetic core half block
20, there are similarly
formed a first track width controlling groove
21 and a second track width
controlling groove
22 for delimiting a track width Tw of the magnetic gap
g along with the first and second track width controlling grooves
11,
12
formed in the first magnetic core half block
10.
The track width Tw of the magnetic gap g, formed in the head block
1,
is controlled to high accuracy by the first and second track width controlling
grooves
11,
12 and
21,
22 formed in the first and second
magnetic core half blocks
10 and
20 abutted and bonded to each other,
respectively. The reason is that the width of the abutment surfaces of the first
and second magnetic core half blocks
10 and
20 delimiting the magnetic
gap g is precisely controlled by the first and second track width controlling grooves
11,
12 and
21,
22 provided in the first and second
magnetic core half blocks
10 and
20, respectively.
The head block
1 is sliced along first and second parallel slicing lines
E
3, E
4 on both sides of the magnetic gap g to sever a magnetic head
50. The surface of the so severed magnetic head
50, in which is formed
the magnetic gap g, serves as a sliding surface
51 on which slides the magnetic
tape. The magnetic tape is run in sliding contact with a sliding area on the sliding
surface
51, indicated by dotted lines E
1 and E
2 extending
parallel to each other.
In the sliding surface
51 of the magnetic head
50, severed from
the head block
1, there is formed a groove
30 for inhibiting side
erasure. This groove is formed towards one end of the magnetic gap g for extending
parallel to the tape running direction. The groove
30 is formed to affect
a portion of one end of the magnetic gap g.
On both sides of the magnetic gap g of the magnetic head
50, severed from
the head block
1, and in the first and second track width controlling grooves
11,
12,
21,
22, there are provided metal magnetic films.
These metal magnetic films, provided to the magnetic head
50, form magnetic
channels for the magnetic flux emanated from the magnetic head. In the groove
30
is charged e.g., glass.
With the magnetic head
50, including the groove
30 formed in the
tape sliding surface, it is possible to prevent the stray magnetic flux from being
emanated from the one end of the magnetic gap g provided with the groove
30,
thereby preventing side erasure otherwise caused by the stray magnetic flux.
Meanwhile, a tape streamer, as a recording and/or reproducing apparatus
for recording and/or reproducing data with the use of a magnetic tape as a recording
medium and also with the use of a rotary magnetic head device, is used for providing
backup of data handled in an information processing unit, such as a computer. Since
this sort of the recording and/or reproducing apparatus handles a large quantity
of data, the data transfer rate needs to be raised in order to record and/or reproduce
data promptly. For increasing the transfer rate, the frequency of the recording
current needs to be raised. If the frequency of the recording current is increased,
the current intensity of the recording current needs to be increased in order to
acquire a recording output of a predetermined level. That is, the intensity of
an optimum current for a recording output differs from one frequency to another.
For example, if the frequency of the recording current is 28 MHz, the recording
current to recording output characteristics, shown in FIG. 2A, are demonstrated,
with the optimum current value for a recording output being approximately 40 mAp-p.
If the frequency of the recording current is 42 MHz, the recording current to recording
output characteristics, shown in FIG. 2B, are demonstrated, with the optimum current
value for a recording output being approximately 70 mAp-p and, if the frequency
of the recording current is 56 MHz, the recording current to recording output characteristics
as shown in FIG. 2C are demonstrated, with the optimum current value for a recording
output being approximately 80 mAp-p.
With the magnetic head
50, used here, the depth length of the magnetic
gap g is 10 μm.
That is, for increasing the frequency of the recording current and for recording
data at a high transfer rate with optimum recording characteristics, it is necessary
to use a large recording current.
On the other hand, in the recording and/or reproducing apparatus used for recording
data handled in an information processing apparatus, it is a requirement to improve
reliability as an apparatus as well as durability. In order to meet these requirements,
the magnetic head used needs to be improved in durability. For improving the durability
of the magnetic head, it is necessary to improve the abrasion resistance of the
sliding surface, adapted for having sliding contact with the magnetic tape, and
to enlarge the depth length of the magnetic gap g.
If the depth length of the magnetic gap g of the magnetic head is increased,
the
intensity of the recording current needs to be increased.
FIGS. 3,
4 and
5 show the recording current—recording
output characteristics in case the frequency of the recording current is set to
28 MHz, 42 MHz and to 56 MHz, respectively, with the depth length of the magnetic
gap g being 4 μm and 10 μm, respectively. In FIGS. 3 to
5, the
recording current—recording output characteristics for the depth length
of the magnetic gap g of 4 μm and 10 μm are denoted as D and E, respectively.
When data is recorded using the recording current with the frequency of 28 MHz,
the magnetic head with the depth length of 4 μm exhibits characteristics
shown in FIG. 3D, with the recording output optimizing current intensity being
approximately 35 mAp-p, while the magnetic head with the depth length of 10 μm
shows characteristics shown in FIG. 3E, with the recording output optimizing current
intensity being approximately 40 mAp-p.
When data is recorded using the recording current with the frequency of 42 MHz,
the magnetic head with the depth length of 4 μm shows characteristics shown
in FIG. 4D, with the recording output optimizing current intensity being approximately
35 mAp-p, while the magnetic head with the depth length of 10 μm shows characteristics
shown in FIG. 4E, with the recording output optimizing current intensity being
approximately 70 mAp-p.
When data is recorded using the recording current with the frequency of 56 MHz,
the magnetic head with the depth length of 4 μm shows characteristics shown
in FIG. 5D, with the recording output optimizing current intensity being approximately
60 mAp-p, while the magnetic head with the depth length of 10 μm shows characteristics
shown in FIG. 5E, with the recording output optimizing current intensity being
approximately 80 mAp-p.
If, in the magnetic head, the depth length of the magnetic gap g is increased,
the recording output optimizing current intensity is increased. In particular,
when the frequency of the recording current is increased, the recording output
optimizing current intensity is increased further.
With the discrete magnetic head
50, severed from the head block
1,
shown in FIG. 1, the track width controlling groove
22 of the second magnetic
core half block
20 intersects one lateral edge of the parallel groove
30
on the left side in FIG. 1 at a first point of intersection shown in FIG.
1.
The metal magnetic film, forming the magnetic path as described above, is deposited
in the track width controlling groove
22 lying at this first point of intersection
F. It is noted that the unneeded stray magnetic flux is produced at and near this
first point of intersection F, with the stray magnetic flux increasing with the
intensity of the recording current.
When the recording track of the magnetic tape, on which the information signals
have already been recorded in the magnetic gap g, traverses the first point of
intersection F and its vicinity, demagnetization is produced under the influence
of the stray magnetic flux emanated from the first point of intersection F and
its vicinity. That is, demagnetization is produced in which the information signals
already recorded in the recording track in the magnetic gap g are partially erased
under the effect of the stray magnetic flux.
In particular, with the magnetic head in which the transfer rate of data to be
recorded on the magnetic tape is increased or in which the depth length of the
magnetic gap g is increased to improve durability, the intensity of the recording
current needs to be increased, as described above. If the intensity of the recording
current I is increased, the stray magnetic flux emanating from the first point
of intersection and its vicinity is also increased. For example, if the intensity
of the recording current I exceeds 50 mA, the noise level is increased due to demagnetization
in which the information signals already recorded on the magnetic tape are partially
erased by the stray magnetic flux emanating from the first point of intersection
F and its vicinity, so that information signals cannot be recorded with optimum
recording characteristics.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to overcome the aforementioned
problems and to provide a magnetic head by means of which information signals can
be recorded with an optimum S/N ratio.
It is another object of the present invention to provide a magnetic head by means
of which the transfer rate of the information signals to be recorded is raised
to enable efficient recording of information signals.
It is yet another object of the present invention to provide a magnetic head
in
which durability may be improved and which can be used for prolonged time.
The present invention provides a magnetic head including a sliding surface on
which a magnetic recording medium is slid, a magnetic gap formed in the sliding
surface for exchanging information signals with the magnetic recording medium,
a track width controlling portion for prescribing a track width of the magnetic
gap, the track width controlling portion being formed by abutting a pair of magnetic
core halves, there being a track width controlling groove formed in each of the
magnetic core halves, a metal magnetic film provided in association with the magnetic
gap and the track width controlling portion, and a groove formed in at least one
end of the magnetic gap for extending substantially parallel to the sliding direction
of the magnetic recording medium. A length L in μm between a first point
of intersection between the track width controlling groove formed in one of the
magnetic core halves and one lateral edge of the groove and a second point of intersection
between the magnetic gap and the other lateral edge of the groove is related with
an intensity of the recording current I [mA] by
By setting the length L in μm between a first point of intersection between
the track width controlling groove formed in one of the magnetic core halves and
one lateral edge of the groove and a second point of intersection between the magnetic
gap and the other lateral edge of the groove, that is the distance between the
metal films lying on both sides of the groove, as described above, it is possible
to prevent the demagnetization otherwise produced in the recording track of the
magnetic tape to maintain optimum recording characteristics.
By setting the intensity of the recording current I of the information signals
to 100 mA or less, it is possible to suppress the effect of the recording current
on the reproducing magnetic head, even though the reproducing magnetic head for
reproducing the information signals recorded by this recording head is mounted
in close proximity to the recording head. Thus, the magnetic head may be applied
with advantage to a rotary magnetic head device of the type adapted for verifying
the state of recording of the recorded signals.
According to the present invention, the plural substantially straight lines,
formed on the sliding surface by a plurality of track width controlling grooves
formed in one of the magnetic core halves, are arranged non-symmetrically relative
to an imaginary line extending perpendicular to the magnetic gap. With this magnetic
head, it is possible to provide a distance larger than a predetermined value between
the point of intersection of the track width controlling groove of at least one
magnetic core half and the side erasure prohibiting groove and the point of intersection
of one end of the magnetic gap g and the side erasure prohibiting groove to prevent
these points of intersection from being arranged close to each other.
Other objects, features and advantages of the present invention will become
more apparent from reading the embodiments of the present invention as shown in
the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of a head block formed for producing a conventional magnetic
head, looking from a magnetic tape sliding surface.
FIG. 2 is a graph showing the relationship between current values of plural
recoding currents having different frequencies and recording output characteristics.
FIG. 3 is a graph showing the relationship between current values of the recording
current, with the frequency of 28 MHz, and the recording output characteristics,
for different depths of the magnetic gap.
FIG. 4 is a graph showing the relationship between current values of the recording
current, with the frequency of 42 MHz, and the recording output characteristics,
for different depths of the magnetic gap.
FIG. 5 is a graph showing the relationship between current values of the recording
current, with the frequency of 56 MHz, and the recording output characteristics,
for different depths of the magnetic gap.
FIG. 6 is a perspective view showing a magnetic head according to the present invention.
FIG. 7 is a perspective view of the magnetic head according to the present invention,
looking from the sliding surface of the magnetic tape.
FIG. 8 is a graph showing the relationship between the intensity of the recording
current I [mA] and the values of the distance L (μm) between intersection
points P, Q for which the demagnetization phenomenon of recorded signals of the
magnetic tape may be prohibited from occurring.
FIG. 9 is a graph showing the relationship between the recording current and
the block error rate in case of overwriting.
FIG. 10 shows a portion of a manufacturing process for forming a sliding surface
of a magnetic head according to the present invention.
FIG. 11 is a schematic view showing a portion of a manufacturing process for
a MIG type magnetic head according to a modification of the present invention.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIENT
A magnetic head according to the present invention is now explained with reference
to several embodiments of the invention shown in the drawings.
The magnetic head according to the present invention is used in a tape streamer
magnetic head device which is a recording and/or reproducing apparatus used for
providing backup of data handled in an information processing apparatus, such as
a computer. In this recording and/or reproducing apparatus, a plural number of
magnetic heads are mounted on a rotary drum, on which the magnetic tape is wound,
and the magnetic tape running on the peripheral surface of the rotary drum is brought
into sliding contact with the magnetic head which is run in rotation by being mounted
on the rotary drum, thereby recording information signals, such as data, or reproducing
the information signals recorded on the magnetic tape.
The tape streamer, for which the magnetic head of the present invention is used,
is of the so-called read-after-write type, in which data recording is made by a
recording magnetic head as data already recorded by the recording magnetic head
is reproduced by a reproducing magnetic head, provided in rear of the recording
magnetic head, to check the data recording state. In a rotary magnetic head device
of the system described above has one or more recording magnetic heads and one
or more reproducing magnetic heads are mounted alternately on the rotary drum.
For example, plural recording magnetic heads for recording and plural reproducing
magnetic heads are alternately mounted at equi-angular intervals of, for example,
45°, along the circumference of the rotary drum.
The rotary drum has a diameter of 40 mm. The distance between magnetic gaps of
the recording magnetic head and the reproducing magnetic head, mounted at an equiangular
interval of 45° on the rotary drum of the above size is approximately 15.3 mm.
A magnetic head
100 of the present invention, used in this rotary type
magnetic
head device, is designed as a MIG (metal-in-gap) type magnetic head, as shown in
FIG.
6.
The MIG type magnetic head
100, according to the present invention, is
formed by abutting and bonding paired first and second magnetic core halves
110a,
110b, formed of ferrite, to each other. With this magnetic head
100,
a magnetic gap g is formed on abutment surfaces of the paired first and second
magnetic core halves
110a,
110b, abutted and bonded
to each other, with the interposition of a gap material, not shown. An upper surface
of the magnetic head in FIG. 6, to which faces the magnetic gap g, acts as a tape
sliding surface
120, on which slides the magnetic tape as a magnetic recording
medium. The center portion of the tape sliding surface
120, in which is
formed the magnetic gap g, is swollen outwards to a substantially arcuate surface
which is curved along the tape running direction.
The magnetic gap g facing the tape sliding surface
120 has a preset track
width Tw determining the width of a recording track formed by recording the information
signals on the magnetic tape. The track width Tw of the magnetic gap g is controlled
by the track with controlling grooves, which are provided in the first and second
magnetic core halves
110a,
110b, which are abutted
together to form the magnetic head
100, in a manner which will be explained subsequently.
Referring to FIG. 7, first to fourth track width controlling grooves
111a,
111b,
111c and
111d are formed in the
first magnetic half
110a and the second magnetic half
110b
abutted to each other to form the magnetic head
100. It is noted that
the third track width controlling groove
111c formed in the second
magnetic core half
110b is shown with a dotted line in FIG. 7 because
the groove is formed within a trimming groove
130 which will be explained subsequently.
On the bottom surfaces of the first to fourth track width controlling grooves
111a,
111b,
111c and
111d,
are provided in the first and second magnetic core halves
110a,
110b,
there are deposited metal magnetic films
112a,
112b,
112c and
112d, respectively. These metal magnetic films
112a,
112b,
112c and
112d are
deposited by forming films of magnetic metal as by sputtering.
On the abutment surfaces of the first and second magnetic core halves
110a,
110b, abutted to each other to form the magnetic gap g, there are
provided metal magnetic films
112e,
112f. These metal
magnetic films
112e,
112f are formed by forming films
of magnetic metal, such as by sputtering, simultaneously with the magnetic metal
films
112a to
112d provided in the first to fourth
track width controlling grooves
111a to
111d.
The metal magnetic films
112e,
112f are formed on
the abutment surfaces delimiting the magnetic gap g, so that, more correctly, the
track width Tw of the magnetic gap g is defined by the metal magnetic films
112e,
112f formed in the abutment surfaces and by the magnetic metal films
112a to
112d provided in the first to fourth track
width controlling grooves
111a to
111d.
The magnetic metal films
112a to
112d provided in
the first to fourth track width controlling grooves
111a to
111d
and the metal magnetic films
112e,
112f provided
on the abutment surfaces of the first to fourth track width controlling grooves
111a to
111d are e.g., metal magnetic films of high
magnetic permeability, formed of a ferromagnetic metal material, and form a magnetic
path along the longitudinal direction of the MIG magnetic head
100 of the
present invention, as shown in FIG. 6, to record information signals on a magnetic
tape or to reproduce the information signals recorded on the magnetic tape.
In the tape sliding surface
120, in which the magnetic gap g is opened,
and in which the track width Tw is delimited by the magnetic metal films
112a
to
112, providing the magnetic path, there is formed a trimming groove
130, operating as a pre-mentioned prohibiting groove, as shown in FIG.
7.
The trimming groove
130 is formed substantially parallel to the direction
indicated by arrow X
1 in FIG. 7 corresponding to the running direction
of the magnetic tape which is run in sliding contact with the tape sliding surface
120. This trimming groove
130 is formed at one end of the magnetic
gap g, for example, on the overwrite side towards the recording track, on which
the information signals have been recorded ahead of the magnetic tape, as shown
in FIG.
7.
Since the trimming groove
130 is formed on the information signal overwrite
side, it is possible to prevent unneeded stray magnetic flux from emanating from
the track edge of the magnetic gap g in such a manner as to prevent side erasure
which tends to disturb the recording pattern of the recording track formed by recording
the information signals on the magnetic tape. With the magnetic head
100
of the present invention, a point of intersection P between the metal magnetic
film
112b and the trimming groove
130 is formed, as shown
in FIG.
7.
On the other hand, a point of intersection Q between the metal magnetic film
112e
extending substantially parallel to the magnetic gap g of the first magnetic
core half
110a and the trimming groove
130 is formed, as shown
in FIG.
7.
In the magnetic head
100 according to the present invention, stray magnetic
flux is generated at the point of intersection P between the metal magnetic film
112b provided in the track width controlling groove
111b
and the trimming groove
130. It is necessary to inhibit this stray magnetic
flux to lower the effect on the recording track in which the information signals
have already been recorded.
The present inventors have found that, by controlling the distance L between
the point of intersection P between the metal magnetic film
112b and
the trimming groove
130 and the point of intersection Q between the metal
magnetic film
112e and the trimming groove
130, depending
on the intensity of the recording current I supplied to the magnetic head
100,
it is possible to inhibit the effect of the stray magnetic flux generated at the
point of intersection P.
That is, by controlling the distance between the points of intersection P, Q
depending on the intensity of the recording current, the phenomenon of demagnetization,
in which the pre-recorded signals on the magnetic tape are partially erased by
the unneeded stray magnetic flux emanating from the metal magnetic film
112b
at the point of intersection P, in case information signals are recorded on
the magnetic tape with the magnetic head
100 according to the present invention.
The present inventors have found the distance L (μm) for which the phenomenon
of demagnetization of the pre-recorded signals on the magnetic tape by the unneeded
stray magnetic flux emanated from the metal magnetic film
112b can
be inhibited when the recording current I, that is the current 40 mAp-p, 50 map-p,
75 mAp-p and 150 mAp-p, is supplied to the magnetic head
100. Specifically,
when the recording current I is 40 mAp-p, 50 mAp-p, 75 mAp-p and 150 mAp-p, the
values of the distance L (μm) between the point of intersection P and the
point of intersection Q are 19.5 μm, 22.3 μm, 26.8 μm and 34
μm, respectively. The relationship between the intensity of this recording
current I [mA] and the distance L (μm) between the points of intersection
P and Q, for which the phenomenon of demagnetization of the pre-recorded signals
on the magnetic tape can be inhibited, is shown in FIG.
8.
It should be noted that the distance L (μm) between the points of intersection
P and Q, for which the phenomenon of demagnetization of the pre-recorded signals
on the magnetic tape can be inhibited, is determined by the intensity of the recording
current I (mA) supplied, and is not affected by the frequency of the recording
current I [mA] used.
From the relationship between the intensity of the recording current I [mA]
and the distance L (μm) between the points of intersection P and Q, for which
the phenomenon of demagnetization of the pre-recorded signals on the magnetic tape
can be inhibited, the following relationship:
is derived.
An experiment was conducted for finding an error rate of errors per a preset
unit
number of bits, for example, 256 bits, when data handled on a computer using the
magnetic head
100 is overwritten on the magnetic tape. The results of the
experiment are shown in FIG.
9. The data overwrite on the magnetic tape
means overwrite recording on data, already recorded on the magnetic tape prior
to overwriting, without performing an independent erasure operation. The error
rate means the probability that the data recorded on the magnetic tape prior to
data overwrite is not completely erased but is left over. As shown in FIG. 9, the
block error rate is optimum for the recording current I of 50 mAp-p and, when the
recording current I is approximately 30 to 100 mAp-p, the block error rate may
be reduced such that data can be recorded as an optimum S/N is maintained.
With the magnetic head
100 according to the present invention, the transfer
rate of the information signals to be recorded may be raised, such that the information
signals can be recorded efficiently. Thus, the magnetic head of the present invention
can be used with advantage for a recording and/or reproducing apparatus employing
the recording current of a high intensity, such as 50 to 100 mAp-p, for a higher frequency.
With the magnetic head
100 according to the present invention, the block
error rate can be lowered and data can be recorded at an optimum S/N ratio, when
the recording current is approximately 50 to 100 mAp-p, so that, even when the
magnetic head of the present invention is applied to a recording and/or reproducing
apparatus of the pre-mentioned read-after-write system, the data stored on the
recording magnetic head can be read out accurately by the reproducing magnetic
head without affecting the reproducing magnetic head. In particular, when the magnetic
head is applied to a rotary magnetic head device in which recording magnetic heads
and reproducing magnetic heads are arranged at an equiangular distance of 45°
on a rotary drum 40 mm in diameter, with the distance between the magnetic gaps
g being approximately 15.3 mm, it is possible to inhibit the effect the recording
magnetic head has on the reproducing magnetic head to enable the data recorded
by the recording magnetic head to be read out correctly by the reproducing magnetic head.
Meanwhile, in the conventional MIG magnetic head, a track width controlling
groove
21 and a track width controlling groove
22 of the first magnetic
core half block
20, corresponding to the first magnetic core half
110a
of the MIG magnetic head
100 of the present invention, are arranged
symmetrically with respect to an imaginary line I perpendicular to the magnetic
gap g, as shown in FIG. 1 already explained.
That is, the track width controlling groove
21 and the track width controlling
groove
22 are formed at an angle θ
1 and at an angle of
θ
2, respectively, with respect to a parallel line to the imaginary
line I, with the angles θ
1 and θ
2 both being
e.g., 30°. Since the track width controlling groove
22 is formed in
this manner, the contact point between the metal magnetic film formed in the track
width controlling groove
22 and the parallel groove
30 is a point
of intersection F, as shown in FIG.
1.
On the other hand, the contact point between the metal magnetic film of the magnetic
core half block
20 of the magnetic gap g and the parallel groove
30
is a point of intersection H, as shown in FIG.
1. The length between the
points of intersection F and H is appreciably shorter than the length between the
points of intersection P and Q of the MIG magnetic head
100 of the present
invention. The result is that pre-mentioned phenomenon of demagnetization by the
unneeded stray magnetic field, generated in the metal magnetic film, is produced
at the point of intersection F of FIG. 1, thus erasing a portion of the signals
pre-recorded on the magnetic tape.
With the MIG magnetic head
100 according to the present invention, the
phenomenon of demagnetization, such as is produced in the conventional magnetic
head, in which part of the pre-recorded signals on the magnetic tape are erased,
is not produced and can be suppressed effectively.
With the magnetic head
100 according to the present invention, the track
width controlling groove
111b of the first magnetic core half
110a
is formed at an angle of approximately 90° relative to a line parallel
to the magnetic gap g, as shown in FIG.
7. Thus, when the metal magnetic
film
112b is formed on the track width controlling groove
11l
b,
such as by sputtering, the metal magnetic film
112b can be thinner
than other portions, and hence the metal magnetic film
112b can be
thinner at the pre-mentioned point of intersection P in FIG. 7 than other portions.
Thus, it is possible to reduce the unneeded stray magnetic field at the point of
intersection P to inhibit the phenomenon of demagnetization more effectively.
The hatched portions of FIGS. 6 and 7 are charged with a non-magnetic material,
such as glass, while the trimming groove
130 is also charged with the nonmagnetic
material, such as glass.
FIG. 10 shows a portion of the manufacturing process for forming the tape sliding
surface
120 shown in FIG.
7.
FIG. 10 shows the state prior to separation into plural magnetic heads shown
in FIG.
7. More specifically, first and second magnetic core halves
210a,
210b are abutted to each other to form a block of plural magnetic
heads. This block can be severed into plural MIG magnetic heads
100 by slicing
along cutting lines, not shown, lying outside dotted lines shown in FIG. 10, with
the dotted line being an abutment width processing line prescribing the area of
sliding contact with the magnetic tape. Since the first and second magnetic core
halves
210a,
210b are each comprised of a side-by-side
repetition of the same structures, only a portion of each of the magnetic core
halves is hereinafter explained.
Referring to FIG. 10, in a portion of the magnetic core halves forming
a sole MIG magnetic head
100, the abutting portions of the first magnetic
core half block
210a and the second magnetic core half block
210b
form the magnetic gap g with a metal magnetic film, not shown, in-between.
The track width controlling grooves
111a,
111b are
formed in the first magnetic core half block
210a. The track width
controlling groove
111a is formed at an angle θ, for example,
at an angle of 30°, as described above, relative to a line parallel to the
imaginary line I, as shown in FIG.
10. The track width controlling groove
111b is arranged at approximately 90° with respect to the magnetic
gap g. That is, the track width controlling groove
111a and so forth
are arranged non-symmetrically relative to the imaginary line I. The track width
controlling grooves
111c,
111d are formed in a manner
similar to the manner in which the track width controlling grooves
111a,
111b are formed. The state of FIG. 10 is achieved by abutting the
magnetic core half blocks to each other, using the second magnetic core half block
210b.
Meanwhile, the trimming groove
130 is formed in each magnetic gap
g of FIG.
10. Thus, by abutting the magnetic core halves, non-symmetrical
with respect to the imaginary line I, to each other, the distance between the points
of intersection P and Q may be elongated to enable the production of the MIG magnetic
head
100 unsusceptible to the phenomenon of demagnetization.
The magnetic head
100 according to the present invention may be formed
through the manufacturing process shown in FIG.
11.
Meanwhile, since FIG. 11 has many structural portions in common with FIG.
10, common structural portions are depicted by the same reference numerals and
are not explained, while only the points of difference are mainly explained.
In FIG. 11, the track width controlling grooves
111a,
111b
of the first magnetic core half block
210a shown on the lower
side in FIG.
11 and the track width controlling grooves
311d,
311c of the second magnetic core half block
310b shown
on the upper side in FIG. 11 are different, and hence the magnetic core half blocks
are non-symmetrical.
In this configuration, the length between the points of intersection P and Q
may
be elongated. As a consequence, not only the phenomenon of demagnetization in which
the information signals previously recorded on the magnetic tape are erased may
be prevented from occurrence, but also the angle of the track width controlling
grooves
311d,
311c on the upper side in the drawing
unrelated with the phenomenon of demagnetization may be selectively set as more
importance is attached to magnetic head characteristics.
For example, only the track width controlling groove
111b of the
first magnetic core half block
210a is set to an angle of approximately
90° relative to the magnetic gap g, as shown in FIG. 11, while the angle θ
of each of the remaining track width controlling grooves
111a,
311c,
311d may be set to the same value of, for example, 30°.
The present invention is not limited to the above-described embodiment, but may
be optionally modified without changing its purport.
Industrial Applicability
With the present invention, described above, a magnetic head may be provided
in which the recording current is increased and the transfer rate of the information
signals to be recorded is raised to enable the information signals to be recorded
efficiently. Moreover, the magnetic head is improved in durability and usable for
prolonged time.
*
