JPH05109014A - Magnetic head - Google Patents

Abstract

PURPOSE:To obtain the magnetic head wherein its B-noise is reduced and its replay output characteristic is good by a method wherein a primary welding glass whose coefficient of thermal expansion has a value close to the coefficient of thermal expansion of a ferrite as the constituent material of a magnetic core is used. CONSTITUTION:A magnetic head element is composed of the following a front core 3 and a back core 4 which form a magnetic core constituting a closed magnetic circuit via a magnetic gap; and coil bobbins 5, 6 which are installed so as to be fitted to both cores 3, 4 and on which driving coils are wound. The following are provided: a core pressure member 7 which magnetically couples the front core 3 and the back core 4; and one pair of sliders 8, 9 which ensure the contact with a floppy disk. When a recording and reproducing operation is executed repeatedly, a B-noise which is generated by a leakage flux from a motor in a reproducing operation is suppressed in the following manner: the coefficient alphaC of thermal expansion of a welding glass is set at the coefficient alphaF of thermal expansion or lower of the magnetic core; and the difference between both coefficients alphaF and alphaC of thermal expansion is set at 10X10<-7> or lower. Thereby, it is possible to obtain a sufficient reproduction output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head suitable for writing or reading an information signal on a high density floppy disk or hard disk.

[0002]

2. Description of the Related Art Generally, a magnetic head for recording / reproducing on a disk-shaped magnetic disk such as a floppy disk or a hard disk has magnetic cores made of an oxide magnetic material such as Mn-Zn ferrite combined and integrated. The pair of composite and integrated magnetic cores is further joined and integrated with a non-magnetic member called a slider by glass fusion, or the magnetic core is fused and embedded in glass in the slider. Consist of the composition.

In this type of magnetic head, glass is first heated and melted to a working high temperature above its melting point, poured between the magnetic cores and then cooled, and the glass is fused between these magnetic cores to form a gap bond. After (primary fusion) is performed, the magnetic core integrated and joined is fused (secondary fusion) with glass and embedded and fixed to the slider.

At this time, when the above-mentioned secondary fusion was carried out, the glass used for the primary fusion (the primary fusion glass) was melted out and the gap length, the track width, etc. were deviated, which was obtained. The reliability of the magnetic head is greatly reduced. Therefore, the above-mentioned primary fused glass is used as a secondary fused glass (in some cases, when
This does not melt even in the subsequent fusion)
It is necessary to have a glass transition point higher than the melting point temperature at the time of the subsequent fusion.

Generally, the glass (2
As the next fusion glass, one having a fusion temperature of 500 ° C. or higher is used in order to ensure the minimum reliability (moisture resistance, hardness, etc.). Therefore, the primary fused glass is required to have a glass transition point of 500 ° C. or higher,
Usually, fused glass having a high melting point of 800 ° C. or higher is used. This high melting point fused glass is
Since it is chemically stable, it has the advantages that it can be washed with an organic solvent and that a strong bond can be obtained.

[0006]

However, when such a conventional magnetic head is used in, for example, a floppy disk drive or a hard disk drive in which recording / reproduction is repeated for each sector, repetitive recording / reproduction is performed. While performing, spike-like noise (so-called B-noise) is generated. It is considered that this influences the leakage flux from the motor during regeneration.

In a magnetic head for a so-called high density floppy disk of 4 M or more, since the gap length is very narrow, about 0.4 ± 0.1 μm, the reproduction output characteristic is low and the B-noise It will be greatly affected. Therefore, in such a magnetic head, it is strongly desired to reduce B-noise.

Therefore, the present invention has been proposed in view of the above-mentioned conventional circumstances, and an object thereof is to provide a magnetic head capable of suppressing B-noise and obtaining good reproduction output characteristics. To do.

[0009]

Means for Solving the Problems The inventors of the present invention have earnestly studied that they cannot achieve the above-mentioned object, and as a result, when the B-noise is generated due to the leakage flux from the motor at the time of reproduction, the gap between the magnetic cores is generated. It was found that B-noise can be suppressed by defining the thermal expansion coefficient of the fused glass used in bonding, and by defining the thermal expansion coefficient of this fused glass, the present invention has been completed. It was

That is, according to the present invention, in a magnetic head in which magnetic cores made of a ferrite material are joined and integrated by glass fusion, the thermal expansion coefficient α _{G of the} fused glass used for the glass fusion is the above-mentioned. Thermal expansion coefficient of magnetic core α _F
The difference between the thermal expansion coefficient α _F of the magnetic core and the thermal expansion coefficient α _G of the fused glass is 10 × 10 ⁻⁷ or less.

[0011]

When recording / reproducing is repeatedly performed using the magnetic head, B-noise is generated due to the leakage flux from the motor during reproduction. This B-noise is related to the coefficient of thermal expansion of the fused glass used for gap bonding between the magnetic cores in the magnetic head, and the coefficient of thermal expansion of the fused glass is the ferrite that is the constituent material of the magnetic core. If the coefficient of thermal expansion of the material is specified to be as close as possible, B-noise is reduced.

[0012]

EXAMPLES A magnetic head to which the present invention is applied will be described below based on specific examples. As shown in FIG. 1, the magnetic head 1 in the present embodiment has a front core 3 and a back core 4 which are magnetic cores forming a closed magnetic circuit via a magnetic gap, and a fitting arrangement for the front core 3 and the back core 4. A coil bobbin 5, 6 around which a drive coil to be installed is wound
A magnetic head element, a core pressing member 7 for magnetically coupling the front core 3 and the back core 4, and a pair of sliders 8 and 9 for ensuring contact with the floppy disk.

The front core 3 is made of Mn-Zn ferrite and is composed of a recording / reproducing head and an erasing head having substantially the same shape. The recording / reproducing head and the erasing head are joined and integrated by a non-magnetic material 10 such as fused glass so as not to magnetically interfere with each other. Side core portions 13 and 14 each having a substantially L shape are abutted on the side surfaces of the center core portions 11 and 12, respectively, to form the front core 3. The center core part 12
And a first magnetic gap g ₁ that operates as a recording / reproducing magnetic gap is formed on the abutting surface of the side core portion 14, and an erasing surface is formed on the abutting surface of the center core portion 11 and the side core portion 13. A second magnetic gap g ₂ is formed which acts as a magnetic gap.

The gap length in the first magnetic gap g ₁ may be arbitrarily selected, but in the present invention, for example, 4
In order to be compatible with a magnetic head for a high density floppy disk of M or more, the gap length is 0.5 μm.
Hereinafter, it is necessary to set the thickness to 0.4 ± 0.1 μm, for example.

The first magnetic gap g ₁ and the second magnetic gap g ₂ are joined by glass fusion, but in the present embodiment, the fused glass used for this glass fusion is used. , The coefficient of thermal expansion α _G of the ferrite material forming the front core 3 is α
_F (110 × 10 ^{−7 to} 115 × 10 ⁻⁷ ) or less, and the difference between the thermal expansion coefficient α _F of the magnetic core and the thermal expansion coefficient α _G of the fused glass is 10 × 10 ⁻⁷ or less. Use what you have.

Examples of glass materials having a coefficient of thermal expansion α _G in the above range include those having the compositions shown in Table 1 below.

[0017]

[Table 1]

B-noise can be reduced by using fused glass whose coefficient of thermal expansion α _G is close to the coefficient of thermal expansion α _F of the ferrite material.

On the other hand, the back core 4 is a pair of core members 1 formed to correspond to the core shape of the front core 3.
5, 5 and 16 are joined by the non-magnetic material 17 on the side surface side. The core members 15 and 16
Has center leg parts 18 and 19 and side leg parts 20 and 21 at positions facing the center core parts 11 and 12 and side core parts 13 and 14 of the front core 3, respectively, and is connected by connecting members 22 and 23. The plane shape is substantially U-shaped. Therefore, the center leg 1
By providing 8, 19 and side legs 20, 21,
It is possible to secure a joint area between the cores that increases the length of the front core 3 in the depth direction, and improve electromagnetic conversion characteristics.

The coil bobbins 5 and 6 are external terminals 24a, 24b and 24 formed by stamping a hoop material.
c and 25a, 25b, 25c by insert molding. A drive coil 26 is wound a predetermined number of times around the coil bobbin 5 through which the side core portion 13 of the front core 3 on the side where the erasing magnetic gap (second magnetic gap g ₂ ) is formed is inserted, and the winding start thereof is started. The winding ends are wound around the external terminals 24a and 24b, respectively. On the other hand, the coil bobbin 6 into which the side core portion 14 of the front core 3 on the side where the recording / reproducing magnetic gap (the first magnetic gap g ₁ ) is formed is inserted with a predetermined number of two drive coils 27. , The beginning and end of winding, and three external terminals for each common part (common) 25
It is wound around a, 25b, and 25c.

The front core 3 and the back core 4 are connected to the side core portions 13 and 14 of the front core 3 and the side leg portions 20 and 21 of the back core 4 in the through holes 5a and 6a of the coil bobbins 5 and 6, respectively. Come into contact with each other and are stacked in a so-called stacked state. That is, the side core portion 13
The one side surface 13a of the side leg portion 20 and the one side surface 20a of the side leg portion 20 are in contact with each other, and the one side surface 14a of the side core portion 14 and the one side surface 21a of the side leg portion 21 are in contact with each other to achieve magnetic coupling, thereby forming a closed magnetic circuit. Is configured. Therefore, the front core 3, the back core 4, and the coil bobbins 5 and 6 serve as a first magnetic recording / reproducing magnetic gap.
Magnetic head element having a magnetic gap g ₁ of ₁ , ie, a recording / reproducing head, and a magnetic head element having a _second magnetic gap g ₂ which operates as an erasing magnetic gap, ie, an erasing head.

The through holes 5 of the coil bobbins 5 and 6 are also provided.
A pair of core pressing pieces 28 and 29 of the core pressing member 7 for magnetically coupling the front core 3 and the back core 4 are inserted in the a and 6a. The core pressing member 7 includes a receiving portion 30 for a head pressing member (pivot) of a magnetic head supporting mechanism (not shown) provided on the back side of the magnetic head element, and the side core portions 13 and 1 described above.
4 and the side legs 20 and 21 together with the coil bobbin 5,
6 and core holding pieces 28 and 29 inserted into the inside.

The receiving portion 30 is provided in a substantially central portion of the connecting plate 31 having the receiving surface 30a of the pressing member so as to hang down in the contacting direction of the pressing member, and serves as a support against the impact of the pressing member. There is. On the other hand, the core pressing pieces 28, 29
Is a thin plate-like plate that hangs in the same direction as the receiving portion 30 at both ends along one side edge of the connecting plate 31.
It is provided integrally with. The core holding piece 2
The tip portions of the reference numerals 8 and 29 are formed in a substantially arc shape so that they can be easily inserted into the coil bobbins 5 and 6 and the workability can be improved. The core pressing member 7
Since it plays a role of alleviating the impact from the head pressing member, it is preferable to mold it with a plastic having relatively plasticity such as polyacetal resin or ABS resin.

Further, on the surface of the core pressing pieces 28, 29 opposite to the surface facing the magnetic head element, that is, on the surface opposite to the surface facing the side leg portions 20, 21 of the back core 4, Semi-conical projections 32 and 33 are formed to bring the front core 3 and the back core 4 into close contact with each other. Therefore, in the coil bobbins 5 and 6, the protrusions 32 and 33 provided on the core pressing pieces 28 and 29 are provided.
Contact the inner wall surfaces of the coil bobbins 5, 6 to elastically deform the core pressing pieces 28, 29 toward the back core 4 side, and the elastic force causes the core pressing pieces 28, 29 to move the side leg portions 20 of the back core 4. , 21 are pressed and supported. As a result,
The side leg portions 20 and 21 of the back core 4 and the side core portions 13 and 14 of the front core 3 are closely pressed and supported, and magnetic and mechanical coupling between the front core 3 and the back core 4 is ensured. Will be things. Therefore, no gap is created between the front core 3 and the back core 4, and the gap does not operate as a back gap when the magnetic head is driven.

Then, the magnetic head element having the above-described structure is sandwiched between the pair of sliders 8 and 9 for ensuring the contact characteristics with the floppy disk, thereby forming the magnetic head 1. That is, a pair of sliders having a substantially L-shaped cross section on both side surfaces on the sliding surface side of the front core 3 provided with the _first magnetic gap g ₁ and the second magnetic gap g ₂ of the magnetic head element with the floppy disk. The magnetic head 1 is configured by providing the elements 8 and 9.

In the magnetic head having the above structure, the front core 3 can be manufactured by the manufacturing method usually used in this type of magnetic head. For example, after a rectangular core block made of Mn-Zn ferrite is subjected to chamfering, coil winding grooves and glass grooves in the recording / reproducing head and the erasing head are formed on one main surface thereof.

Next, a dividing groove parallel to the coil winding groove and the glass groove is formed in the core block, the core block is divided, and the first core having the coil winding groove and the glass groove is formed. A block and a second core block used as a center core portion are formed.

Then, the surface on which the coil winding groove of the first core block is formed and the main surface of the second core block are abutting surfaces, and these first and second core blocks are abutted on the basis of the outer shape. Thus, the first magnetic gap g ₁ and the second magnetic gap g ₂ are formed. When the center core portion and the side core portion are butted, a gap film made of SiO ₂ or the like is interposed between these butted surfaces.

Subsequently, fused glass is filled in the glass groove formed in the first core block, and the center core portion and the side core portion are joined and integrated (primary fusion). Next, the surface of the second core block opposite to the surface facing the second core block is flat-polished so that the core thickness of the second core block becomes a predetermined value. At this time, the core thickness is set so that the distance between the magnetic gaps g ₁ and g _{2 of the} magnetic heads when the two magnetic heads (the recording / reproducing head and the erasing head) are arranged to face each other in the head traveling direction is close to each other. In addition, it is desirable to make the thickness as thin as possible. However, if the thickness is made too thin, the head efficiency is lowered due to the reduction of the core cross-sectional area. Therefore, it is determined from the viewpoint of the gap distance and the head efficiency.

Then, with respect to the joined body of the first core block and the second core block, a dividing groove is formed along the glass groove along the glass groove in the thickness direction at approximately the center of the glass groove, and the joined body is joined. Divide. As a result, a recording / reproducing head block and an erasing head block having exactly the same shape are formed. Subsequently, the surfaces of the obtained recording / reproducing head block and the erasing head block on the side of the second core block are butted, and the butted surfaces are joined and integrated (secondary fusion) by glass fusion.

Then, the head block thus joined and integrated is cut in a direction substantially orthogonal to the direction in which the glass groove extends to manufacture individual front cores. Next, one side surface of the obtained front head, which is a contact surface with the magnetic recording medium, is cylindrically polished. The cylindrical polishing is performed until the depths of the magnetic gaps g ₁ and g ₂ of the recording / reproducing head block and the erasing head block reach predetermined values. As a result, an arcuate magnetic recording medium contact surface is formed.

Therefore, in order to examine the reproduction output characteristics of such a magnetic head, the B-noise and the reproduction output of the obtained magnetic head were measured in the 4 MB mode. The above B
-The noise measurement method is as follows. As shown in FIG. 3, a magnetic disk 43 housed in a cartridge 42 is held on a disk table 41 having a substantially disk shape mounted on a spindle shaft 40 which is rotatably supported, and is connected to the spindle shaft 40. The disk table 41 is rotated by driving the spindle motor, and the magnetic gap for recording / reproducing of the magnetic head is mounted with the carriage 45 and the arm 44 so as to face the signal recording surface of the magnetic disk 43. Writing and reading of information signals were repeated. The magnetic head attached to the carriage 45 and the arm 44 has a mechanism that moves in the radial direction of the magnetic disk 43 by a motor 46 and a feed mechanism 47. In the measurement, the repetition of recording / reproducing with respect to the signal recording surface was set to 100 mS interval, which is equivalent to the case of repeating recording / reproducing for each sector. The regeneration time was 5 minutes.

When recording / reproducing was performed on the signal recording surface in this manner, spike noise was observed in the reproducing mode. Therefore, B-noise was examined by measuring the magnitude of this spike-like noise.

FIG. 2 shows B- when the thermal expansion coefficient of the fused glass used in each magnetic gap junction is changed.
It is a figure which shows the change of a noise and reproduction | regeneration output, respectively. Figure 2
In the figure, the horizontal axis represents the difference between the thermal expansion coefficient α _F of the magnetic core and the thermal expansion coefficient α _G of the fused glass, and the vertical axis represents B-noise or reproduction output. As shown in FIG. 2, when the difference between the thermal expansion coefficient α _F of the magnetic core and the thermal expansion coefficient α _G of the fused glass was suppressed to 10 × 10 ⁻⁷ or less as in this example, B -It has been found that the noise is extremely small and a high reproduction output can be obtained.

[0035]

As is apparent from the above description, in the present invention, the coefficient of thermal expansion of the primary fused glass is close to the coefficient of thermal expansion of the ferrite used as the constituent material of the magnetic core. Therefore, B-noise can be reduced even when the motors are arranged close to each other.
It is possible to provide a magnetic head having good reproduction output characteristics. In particular, the present invention is 4M with a small reproduction output.
It is very advantageous when used as a magnetic head for the above high density floppy disk.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a configuration of a magnetic head according to the present invention.

FIG. 2 is a characteristic diagram showing changes in B-noise and reproduction output with respect to a difference between a thermal expansion coefficient α _F of a magnetic core and a thermal expansion coefficient α _G of a fused glass.

FIG. 3 is a schematic diagram for explaining a method of measuring B-noise at the time of reproduction when repeatedly recording / reproducing.

[Explanation of symbols]

1 ... Magnetic head 3 ... Front core 4 ... Back core 5, 6 ... Coil bobbin 7 ... Core pressing member 8, 9 ... Slider 11, 12 ... Center core portion 13, 14 ... Side core part g ₁ ... 1st magnetic gap g ₂ ... 2nd magnetic gap

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Terashima 6-5 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Magne Products Co., Ltd.

Claims (1)

[Claims] 1. In a magnetic head in which magnetic cores made of a ferrite material are joined and integrated by glass fusion, the thermal expansion coefficient α of the fused glass used for the glass fusion.
_G is the thermal expansion coefficient α _F or less of the magnetic core, and the difference between the thermal expansion coefficient α _F of the magnetic core and the thermal expansion coefficient α _G of the fused glass is 10 × 10 ⁻⁷ or less. Characteristic magnetic head.