JPH0244324Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a magnetic head used in video tape recorders and the like, and is particularly suitable for densely recording high frequency signals on high coercive force media. (b) Prior Art A so-called 8 mm video format has been proposed for recording television signals over a long period of time using a small device. This is different from the conventional method because it uses a high coercive force medium (so-called metal tape).
In magnetic heads based on magnetic ferrite materials used in VTRs (β, VHS), the saturation magnetic flux density is not large enough, so effective recording and reproduction cannot be guaranteed. Therefore, while a center core is made of an alloy magnetic material with a high saturation magnetic flux density (Fe-Al-Si alloy, so-called sendust, amorphous magnetic alloy, etc.), a pair of reinforcing cores are attached to both sides of the center core. A composite magnetic head with improved characteristics (wear resistance) has been proposed. Figures 1 and 2 both show conventional examples of this type of magnetic head, and both have a pair of reinforcing cores arranged on both sides of a center core C in such a manner as to sandwich the center core. . The reinforcing core I ₁ in Fig. 1 is entirely made of glass, while the reinforcing core I 2 in Fig. ₂ has an upper part I ₂₁ corresponding to the front gap F made of glass, and a lower part I ₂₂ made of magnetic material such as ferrite. I am trying to configure it with . In the former case, the reinforcing core is easy to manufacture, so the manufacturing cost can be reduced, but on the other hand, the magnetic resistance of the rear magnetic path cannot be reduced, so the reproduction efficiency cannot be improved. The latter has advantages and disadvantages opposite to the former. FIG. 3 shows a magnetic head shown in Japanese Utility Model Application Publication No. 58-84614. This consists of a center core C' made of an amorphous magnetic alloy, a set of reinforcing cores _I3 made of an amorphous magnetic alloy of the same composition, and a portion corresponding to the front gap F made non-magnetic by crystallization. It is what it is. I ₃₁ indicates this non-magnetized region. Although this magnetic head is easy to manufacture and has the effect of improving playback output characteristics, since the tape contact surface is made of substantially the same material for both the center core and the reinforcing core, each core wears at the same rate. It has the disadvantage of showing a tendency to cause spacing loss.
If the reinforcing cores on both sides are more abrasive than the center core, the center core will constantly come into contact with the recording medium, making it difficult to suffer spacing loss. (c) Purpose of the invention The present invention has been devised in view of the above-mentioned drawbacks. It is intended to provide a head. (d) Structure of the invention The present invention is a composite magnetic head in which reinforcing cores are provided on both sides of a center core. It is characterized in that it is made of an amorphous magnetic alloy. The portion of the reinforcing core corresponding to the front gap of the center core is characterized in that the above-mentioned amorphous magnetic alloy is heated to crystallize and become non-magnetic. The reinforcing core of the magnetic head of this invention is made of an amorphous magnetic alloy, which is useful for improving the reproduction output characteristics, and the part of the center core corresponding to the front gap is made of crystalline amorphous magnetic material as a base material. It is easy to manufacture because it only requires heat treatment to increase the temperature, and since the reinforcing core is more abrasive than the center core, there is no risk of increasing spacing loss during use of the magnetic head. (E) Embodiment FIG. 4 is a partially cut away perspective view of the construction of an embodiment of the present invention. 1 in the figure is Fe-Al-
Center core made of Si-based alloy (Sendust),
6 and 6 are reinforcing cores whose base material is an amorphous magnetic alloy ₍ for example, Fe _4.5 Co _70.5 Si ₁₅ B ₁₀ ), which are _{symmetrically} made. The center core 1 includes a pair of pole pieces 2, 2, a spacer 3 forming a front gap F, and a coil window 4 defining the lower end of the front gap and for mounting a coil. Each pole piece 2 has tape contact surface 2
1, a gap forming surface 22 adjacent to the tape contact surface and hanging from the tape contact surface, and a ridge line 23 adjacent to the tape contact surface 21 and the gap forming surface 22 defining the track width T. Each includes 1
A pair of side surfaces 24, 24 are provided. In this embodiment, this pair of pole pieces is constructed by abutting core halves, so there is a so-called back gap 5 below the coil window 4, and a bonding material (silver) is placed between the back gap forming surfaces of each core half. (e.g., wax) 51 to ensure mechanical strength.
The center core 1 has a thickness of 10 to 30 μm, which is equal to the track width, and is in the form of a thin film about 3 mm in length and width. The reinforcing core 6 has a side surface 61 having approximately the same size as the magnetic path forming surface of the center core 1 , and is provided with a through hole 62 (see FIG. 6a) that passes through the side surface and communicates with the coil window 4. . A region 63 including the upper part of the reinforcing core 6 facing the front gap F is made non-magnetic by crystallizing an amorphous magnetic alloy. This crystallization process is possible by heating the base material to a temperature higher than its crystallization temperature.
For example, local heating is performed on the substrate 3 by laser irradiation. The laser irradiation conditions were a repetition frequency of 1 KHz, a pulse width of 90 ns, a laser beam diameter of 100 to 500 μm, and a laser output of 0.1 to 0.01 W. As a result, frequency 5M
For a base material with a magnetic permeability of about 500 at Hz,
It is possible to significantly reduce the magnetic permeability to about 40-60 and make it non-magnetic. The total thickness 64 of this reinforcing core 6 is approximately
It has a diameter of 50 μm, and is integrated with the center core 1 via an organic adhesive (not shown). Next, an example of a method for assembling the magnetic head of the present invention will be explained. The center core is manufactured according to the following steps. Two core block halves 7 and 7' made of sendust are prepared, a groove 71 that will become the coil window 4 is opened in one core block, and a spacer 3 such as SiO ₂ is vapor-deposited to define the gap length.
Attach by sputtering method or the like, and fill the bonding material filling groove 72 with silver solder 8 (FIG. 5a).
Next, the two core block halves 7, 7' are butted together, and the silver solder is melted and solidified to integrate them, and then, as shown in Fig. 5b.
Form the tape contact surface as shown by the dashed line P,
Furthermore, slicing is performed along the broken line Q to cut out a chip that is slightly thicker than the total thickness of the center core.
The center core 1 shown in FIG. 5C is manufactured by performing thickness processing. Manufacturing of the reinforcing core 6 and joining the reinforcing core to the center core 1 are performed in the following steps. First, 50μ
Prepare a ribbon 9 of amorphous magnetic alloy of approximately the same thickness as shown in FIG. 6A, and perform chemical etching to simultaneously open a through hole 91 and U-shaped through holes 92 and 93 that define the outer shape of the reinforcing core 6. . the result,
As shown, a large number of reinforcing core elements 6' are arranged at equal pitches R in the lateral direction. Next, a laser beam is applied to the region S shown in FIG. 6b under the above irradiation conditions to crystallize the region and make it non-magnetic (or have low magnetic permeability). Next, one of the center cores 1 is placed on the reinforcing core element that has been subjected to such treatment, and the two are fixed with adhesive, and then a ribbon that has been similarly crystallized is placed on top of the center core 1 so that each reinforcing core element has a center core. Place and glue to fit the core. Then, a three-layer composite magnetic head is obtained. A laser beam is used to separate individual magnetic heads from this series of magnetic heads. Processing conditions are, for example, repetition frequency 1MHz, pulse width 90ns, laser output 0.1~
0.5W, laser beam diameter 20-50μm. (f) Effects of the invention The invention has a structure in which the center core is made of an Fe-Al-Si alloy, and this center core is sandwiched with a reinforcing core made of an amorphous magnetic alloy that has been partially crystallized. Therefore, high-frequency signals such as video signals can be densely recorded and reproduced on high coercive force media such as metal tape.
The wear resistance of the center core can be backed up by the reinforcing core, and since the cross-sectional area of the rear magnetic path is increased, the reproduction output characteristics can be improved. Further, since the magnetic short circuit prevention means of the reinforcing core around the front gap of the center core is realized by crystallizing the base material, manufacturing is easy. Furthermore, due to the difference in wear between the center core and the reinforcing core, the reinforcing core is more likely to wear out than the other, so the center core can be kept in constant contact with the medium with minimal spacing loss over the entire usage period, allowing for shorter wavelengths. Deterioration of characteristics can be prevented.

[Brief explanation of drawings]

1, 2, and 3 are perspective views of a conventional magnetic head; FIG. 4 is a partially cutaway perspective view of an embodiment of the magnetic head of the present invention; and FIGS.
b, c are explanatory diagrams of the manufacturing process of the center core, No. 6
Figures a and b are explanatory diagrams of the manufacturing process of the reinforcing core. Explanation of main drawing numbers, 1 ... Center core, 6...
Reinforcement core, 63, S... Crystallized region, 4... Coil window, F... Front gap, 91... Through hole.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A tape contact surface, a gap forming surface adjacent to the tape contact surface and hanging from the tape contact surface,
A pair of pole pieces made of an Fe-Al-Si alloy having the tape contacting surface and a pair of side surfaces adjacent to the gap forming surface and including each end of the ridge line defining the track width is attached to the gap. a center core defined by an upper edge of a coil window formed by disposing a non-magnetic spacer between constituent surfaces and abutting them to form a front gap, and opening the lower end of the front gap in at least one of the pole pieces; They are arranged on both sides of the center core so as to sandwich the center core, a non-magnetic material portion is provided in a portion corresponding to the front gap, and a through hole communicating with the coil window is provided in a portion corresponding to the coil window. A magnetic head comprising: a set of reinforcing cores, each of the reinforcing cores being made of an amorphous magnetic alloy. (2) The magnetic head according to claim 1, wherein the non-magnetic material portion is formed by crystallizing the amorphous magnetic alloy.