JPH1064009A - Combined magnetic head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combined magnetic head capable of suppressing leakage magnetic flux from an erase head, improving a bit asymmetric characteristic and obtaining excellent erase efficiency. SOLUTION: Since thin film magnetic material 11 with high saturation magnetic flux density is provided on a fourth erasing core side part 8d side in an erasing gap 4, magnetic saturation in the vicinity of the gap is suppressed. In the state that the gap depth De of the E head 5 is shallower than the gap depth Dr of an R/W head 3, an erase magnetic field from the E gap 4 is kept to a high value, and the magnetomotive force of the E head 5 is reduced. Thus, since the sum total of erase magnetic flux becomes smaller than the sum total of recording magnetic flux, and the leakage magnetic flux leaking out from the E head 5 to the R/W head 3 is reduced relatively, distortion in a signal is reduced, and a signal error due to bit asymmetry is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composite magnetic head used for a floppy disk drive (FDD).

[0002]

2. Description of the Related Art In a magnetic head used for an FDD, a disk (magnetic recording medium) is moved relative to a recording / reproducing gap (hereinafter, referred to as an R / W gap) so as not to read a signal on an adjacent track during off-track. An erasing gap (hereinafter, referred to as E gap) is disposed on the front side or the rear side in the moving direction, and when a signal is recorded by a recording / reproducing head (hereinafter, referred to as R / W head), an erasing head (hereinafter, referred to as R / W head) is simultaneously formed. A DC current is passed through the
A method is employed in which DC erasure is performed in a gap to form guard bands having a fixed width on both sides of a recorded track.

However, in the current FDD magnetic head, since the gap between the R / W gap and the E gap is as small as 0.17 to 0.35 mm, the magnetic flux generated by the DC current of the E head is applied to the R / W head. Leak (ie, R
/ W head and E head interfere with each other), the recording signal is in a state where a kind of DC bias is applied, and the recording signal recorded on the disc may be distorted. R as described above
Various shielding directions have been proposed in order to prevent interference between the / W head and the E head, but it was difficult to completely shield due to a small gap interval.

In addition, the magnetic head for FDD has a characteristic that the strength of the magnetic field increases as the gap length increases, as shown in FIG. 9 described later, and various characteristics (gap loss as shown below). , Recording efficiency, etc.), and the following measures are taken according to the characteristics.
For convenience, the various characteristics and the countermeasures corresponding to the characteristics are divided into items of “gap loss”, “recording efficiency”, “gap length—magnetic field strength, gap depth—magnetic field strength”. This will be described below.

<< Gap loss >> Since the R / W gap performs not only recording but also reproduction, the R / W gap length during reproduction is
Loss (gap loss) represented by the following equation (1) according to B _g
L _g results.

[0006]

(Equation 1)

In order to cope with the gap loss L _g in the above equation (1), the R / W gap length B _g is set to a dimension of １ ／ or less of the shortest wavelength of the recording / reproducing signal to be used. I have.

Further, the E gap can be obtained only by erasing,
Since reproduction is not performed, the E gap length is set to a size larger than the R / W gap length _Bg . In this case, even if the dimension is set to be larger than the R / W gap length _Bg , if it is set too large, the leakage of magnetic flux in the track width direction increases, and the guard band width becomes uncertain. In the head, the E gap length is set so that the guard band width is not uncertain.

<< Recording Efficiency >> The recording efficiency α of the magnetic head (hereinafter, appropriately referred to as head efficiency) is represented by the following equation (2).

[0010]

(Equation 2)

[0011] Here, in the formula (2), a magnetic resistance R _g per unit length of the gap, as shown in equation (3) is inversely proportional to the gap cross-sectional area A _g. The magnetic resistance R _c per unit of core length, as shown in equation (4) is inversely proportional to the product mu · A _c relative permeability mu and core area A _c of the core.

[0012]

(Equation 3)

[0013]

(Equation 4)

[0014] To raise the head efficiency α is theoretically to reduce the magnetic resistance R _c (i.e. to increase the product μ · A _c.), Or increase the magnetic resistance R _g per unit length of the gap (Ie, reducing the gap cross-sectional area _Ag ). However, the relative permeability mu of the core, restricted by the material, and the core cross-sectional area A _c is not able to increase certain level since the gap distance is small, to increase the product mu · A _c above a certain value It is not possible. For this reason, a measure is taken by reducing the gap cross-sectional area _Ag . In this case, the gap cross-sectional area _Ag is represented by the following equation (5). Gap cross-sectional area _Ag = track width x gap depth ... (5) In equation (5), it is difficult to change the track width that defines the gap cross-sectional area _Ag because the guard band width is determined. It is. Therefore, in order to reduce the cross-sectional area A _g in improving the head efficiency alpha, gap depth (hereinafter referred to as the gap depth.) Of a shallow (less) must be employed a method of That was the actual situation. Even if the gap depth is made shallow, if it is made too shallow, the vicinity of the gap will be saturated during recording or reproduction, and the magnitude of the magnetic field tends to be suppressed to a certain value or less. In the case where the depth is too shallow, for example, a gap depth of 10 μm, 50 μm, 100 μm in FIG.
Of which corresponds to 10 μm. In this magnetic head, the gap depth is set so that the magnitude of the magnetic field cannot be suppressed below a certain value. Also, if the gap depth varies with the manufacturing, the head efficiency α will vary. The variation in the head efficiency α becomes more remarkable as the gap depth becomes smaller, even if the variation amount has the same magnitude, because the change rate becomes larger.

In a composite magnetic head in which an R / F head and an E head are combined, it is difficult to independently control the gap depth of the R / F head and the E head. It is common to control the gap depth of the associated R / W head. In this case, since the gap depth of the E head has a larger variation width than the gap depth of the R / W head, the gap depth of the E head is equal to or smaller than the efficiency change of the R / W head. To R / W
Generally, the gap depth is set larger than the head gap depth. For example, the gap depth of the R / W head is set to 20 to
The gap depth of the E head is set to 50 to 100 μm.

<< Gap Length-Magnetic Field Strength, Gap Depth-Magnetic Field Strength >> Regarding the relationship between the magnetic field strength from the gap (normalized by the holding power of the disk) and the magnetomotive force, the gap length Was obtained by the finite element method using as a parameter, a graph shown in FIG. 9 was obtained. As is clear from FIG. 9, the strength of the magnetic field increases as the gap length increases.

The relationship between the strength of the magnetic field and the magnetomotive force was determined by the finite element method using the gap depth as a parameter, and the graph shown in FIG. 10 was obtained. As is apparent from FIG. 10, when the gap depth increases, the magnitude of the magnetomotive force required to generate a magnetic field having a desired magnitude increases. In FIG. 10, the strength of the magnetic field on the vertical axis is a relative value when the coercive force of the disk (magnetic recording medium) is set to 1.0 (reference value).

As an example of the magnetic head for FDD as described above, there is a composite magnetic head 1 shown in FIGS. As shown in FIGS. 6 and 7, the composite magnetic head 1 includes an R / W head 3 having an R / W gap 2,
It has a structure in which an E head 5 having a gap 4 is combined.

The R / W head 3 has first, second, third, and fourth sides (hereinafter, first, second, third, and fourth sides) connected to each other so as to form a substantially rectangular ring. A recording / reproducing-side core (hereinafter, referred to as an R / W core) 6 of approximately 0.5 T made of ferrite and composed of 6a, 6b, 6c, and 6d, and the R / W core 6 A recording / reproducing coil (hereinafter, referred to as an R / W coil) 7 fitted to the third R / W core side portion 6c.
The R / W gap 2 is formed between the R / W core side portions 6a and 6d.

The E head 5 has first, second, third, and fourth side portions (hereinafter, referred to as "first", "second") connected to each other so as to form a substantially rectangular ring.
These are referred to as first, second, third, and fourth E core sides. ) 8a,
An erasing-side core (hereinafter, referred to as an E-core) 8 made of ferrite of approximately 0.5 T and composed of 8b, 8c, and 8d, and an erasing coil fitted to a third E-core side 8c of the E-core 8. (Hereinafter, referred to as an E coil) 9. An E gap 4 is formed between the first and fourth E core sides 8a and 8d as shown in FIG. The R / W head 3 and the E head 5 are combined by joining the first R / W core side 6a and the first E core side 8a. The gap between the R / W gap 2 and the E gap 4 is set to 0.17 to 0.35 mm. The length W (hereinafter, appropriately referred to as the width dimension of the composite magnetic head 1) from the side edge of the third R / W core side 6c to the side edge of the third E core side 8c. Is set to 3 to 6 mm.

In the composite magnetic head 1, a disk (not shown) is slid in contact with the disk running surface 10 to supply a recording current i _W (alternating current) to the R / W coil 7 to generate a recording magnetic flux H _w . Then, a signal is recorded on the disk by the recording magnetic field from the R / W gap 2. At the same time the E coil 9, and supplies the erase current i _e (DC) to generate an erase magnetic flux H _e, the erasing magnetic field from the E gap 104, making a guard band on either side by DC erasing of the recorded signal become.

[0022]

By the way, in the composite magnetic head 1 described above, the R / W head 3 is used as described above.
Gap depth D _r the gap depth D of E head 5
_Since it is set to be shallower than _e , the efficiency of the R / W head 3 is higher than the efficiency of the E head 5,
The relationship between the recording current flowing through the R / W coil 7 and the erasing current flowing through the E coil 9 is defined by the recording current and the erasing current shown in the following equation (6).

[0023] (R / W coil 7 turns) × (recording current) ≦ (E coil 9 turns) × (erase current) ... (6) Therefore, if Shimese recording magnetic flux H _w and erasure flux H _e, the following It will be represented by equation (7).

ΣRecording magnetic flux H _w ≦ ΣErasing magnetic flux H _e (7)

[0025] Therefore, the leakage flux H _er leaking from E head 5 R / W head 3, since the erase current i _e is DC, it in one direction of the magnetic flux, thereby the leakage magnetic flux H _er
The receiving recording magnetic flux H _w does not become normal and reverse the same amount, with respect to one direction of magnetization reversal, the magnetization reversal in the opposite direction does not become symmetric, so that the signals recorded on the disc is distorted. This distortion is generally called bit asymmetry and is one of the causes of signal errors during reproduction.

The present invention has been made in view of the above circumstances, and provides a composite magnetic head capable of improving bit asymmetry characteristics by suppressing magnetic flux leakage from an erasing head and obtaining good erasing efficiency. The purpose is to do.

[0027]

In order to achieve the above object, the present invention provides a composite magnetic head in which a recording / reproducing magnetic head having a recording / reproducing gap and an erasing magnetic head having an erasing gap are combined. A thin film having a high saturation magnetic flux density is formed on at least one of the two opposing surfaces of the erasing gap in the erasing magnetic head, and the gap depth of the erasing magnetic head is changed to the gap of the recording / reproducing magnetic head. The depth is set to be shallower than the depth, and the magnetomotive force of the erasing magnetic head is set to be smaller than the magnetomotive force of the recording / reproducing magnetic head.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A composite magnetic head according to an embodiment of the present invention will be described below with reference to FIGS.
In addition, the member shown in FIGS.
Description and illustration of the parts will be appropriately omitted.

The composite magnetic head 1 according to this embodiment
1 to 3 are different from the composite magnetic head 1 of FIGS. 6 to 8 as shown in FIGS.
0.2 to 6.0 μm of 1.0 to 1.2 T on the E core side 8d side of
The thin-film magnetic material 11 having a high saturation magnetic flux density such as Fe-Al-Si (Sendust) or 1.4-1.6 T FeTN;
That the gap depth D _e of the head 5 was set shallower than the gap depth D _r of the R / W head 3, and magnetomotive force (coil winding number × current) the magnetomotive force of the R / W head 3 E head 5 ( The difference is that the setting is made smaller than (the number of coil turns × current).

In the composite magnetic head 1, since the thin film magnetic material 11 having a high saturation magnetic flux density is formed on the side of the fourth E core side 8d in the E gap 4, saturation near the gap does not occur. Therefore, as described above, the E head 5
Even if the gap depth D _e are shallower than the gap depth D _r of the R / W head 3, since no erase magnetic flux from the E gap 104 decreases, the amount, caused the E head 5 The magnetic force can be reduced.

Therefore, the relationship between the number of coil turns and the current of the R / W head 3 and the E head 5 is expressed by the following equation (8): (number of turns of the R / W coil) × (recording current)> (E number of turns of the coil) × (erase current) ... (8) and thus, as shown by the following equation (9), it can be larger than the sum of the recording magnetic flux H _w to the sum of the erase magnetic flux H _e Becomes ΣRecording magnetic flux H _w > ΣErasing magnetic flux H _e ... (9)

Therefore, the E head 5 is moved to the R / W head 3
Since it is leaked out (goes around) the relatively smaller leakage flux H _{e r,} the distortion of the signal recorded on the disc is reduced, it is possible to reduce the signal error due to turn bit asymmetry.

In the above embodiment, the case where the thin-film magnetic material 11 having a high saturation magnetic flux density is provided on the side of the fourth E core side 8d in the E gap 4 has been described. A thin film magnetic material (not shown) having a high saturation magnetic flux density may be provided on the side of the E core side 8a.

[0034]

Next, the present invention was verified as follows, and good results were obtained. This verification example will be described below. First, assuming that the gap length is 3.0 μm and the gap depth is 10 μm, the composite magnetic head in which the thin film magnetic material having a high saturation magnetic flux density is not provided, the sendust is provided on the side of the fourth E core side 8 d in the E gap 4 (see FIG. 3). 1 to 3 on which a thin-film magnetic material 11 having a high saturation magnetic flux density is formed, and the first E-core side 8a side and the fourth E-core side 8d side in the E gap 4 The relationship between the strength of the magnetic field from the gap and the magnetomotive force was determined by the finite element method for the composite magnetic head 1 in which the thin-film magnetic material 11 made of Sendust and having a high saturation magnetic flux density was formed on both surfaces. Then, the graphs shown in FIG. 4 (represented by solid lines A, B, and C, respectively) were obtained. As a result, even if the gap depth is as shallow as 10 μm, as shown by solid lines B and C,
By providing Sendust's thin-film magnetic material 11 having a high saturation magnetic flux density, it was verified that effective magnetic field strength was obtained in the range from small magnetomotive force to large magnetomotive force without causing magnetic saturation in the vicinity of the gap. . Here, the effective magnetic field strength is the strength of a magnetic field having a relative value of 1.0 or more,
In this case, the force is equal to or higher than the holding force of the disk (magnetic recording medium), and erasing is possible.

A composite magnetic head 1 in which a gap length = 3.0 μm and a thin-film magnetic material 11 made of sendust and having a high saturation magnetic flux density of 1 μm is provided on the side of the fourth E core side 8 d in the E gap 4. , Gap depth = 10 μm,
The relationship between the strength of the magnetic field from the gap and the magnetomotive force was determined by the finite element method using 50 μm and 100 μm as parameters, and a graph shown in FIG.
Shown by E and F. )was gotten. As a result, it was verified that an effective magnetic field strength was obtained in a range from a small magnetomotive force to a large magnetomotive force.

[0036]

Since the present invention is a composite magnetic head constructed as described above, by providing a thin-film magnetic material having a high saturation magnetic flux density in the erasing gap, saturation near the gap is suppressed. Therefore, while the gap depth of the erasing gap is shallower than the gap depth of the recording / reproducing gap, the erasing magnetic field from the erasing gap is maintained at a high value, and the magnetomotive force of the erasing magnetic head can be reduced. . Therefore, the total sum of the erasing magnetic fluxes is smaller than the total sum of the recording magnetic fluxes, and the leakage magnetic flux leaking from the erasing magnetic head to the recording / reproducing magnetic head is relatively small, thereby recording on the disk. Signal distortion can be reduced, and the signal error due to bit asymmetry can be reduced. Further, since the signal error is reduced, the erasing efficiency is improved, and the guard band width can be kept constant to reduce the variation.

[Brief description of the drawings]

FIG. 1 is a plan view showing a composite magnetic head according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is an enlarged view of a portion B in FIG. 2;

FIG. 4 is a characteristic diagram showing a relationship between a magnetomotive force and a magnetic field strength of a composite magnetic head in which a thin film magnetic material having a high saturation magnetic flux density is attached differently.

FIG. 5 is a characteristic diagram showing a relationship between a magnetomotive force and a magnetic field strength of a composite magnetic head in which a gap depth is used as a parameter.

FIG. 6 is a plan view showing a conventional example of a composite magnetic head.

FIG. 7 is a sectional view taken along the line AA of FIG. 6;

FIG. 8 is an enlarged view of a portion B in FIG. 7;

FIG. 9 is a characteristic diagram showing a relationship between a magnetomotive force and a magnetic field strength in an example of a conventional magnetic head using a gap length as a parameter.

FIG. 10 is a characteristic diagram showing a relationship between a magnetomotive force and a magnetic field intensity in an example of a conventional magnetic head in which a gap depth is used as a parameter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Composite magnetic head 2 R / W gap 3 R / W head 4 E gap 5 E head 8 E core 8d Fourth E core side 11 Thin film magnetic material

Claims (1)

[Claims] 1. A composite magnetic head in which a recording / reproducing magnetic head having a recording / reproducing gap and an erasing magnetic head having an erasing gap are combined, wherein both faces of the erasing magnetic head in the erasing magnetic head are opposed to each other. A thin film having a high saturation magnetic flux density is formed on at least one of them, the gap depth of the erasing magnetic head is set shallower than the gap depth of the recording / reproducing magnetic head, and A composite magnetic head, wherein the magnetic force is set to be smaller than the magnetomotive force of the recording / reproducing magnetic head.