JPH07249204A - Joined ferrite magnetic head - Google Patents

Abstract

PURPOSE:To suppress the demagnetization generated by magnetization of a magnetic head by disposing a polycrystalline ferrite which is the cause for magnetization only in the central part of the head where a winding groove is formed. CONSTITUTION:The polycrystalline ferrite disposed in the central part 7 consists of a polycrystalline ferrite having a high magnetic permeability. The average magnetic permeability is, therefore, increased and a high reproduced output is obtd. at the time of reproduction. The polycrystalline ferrite has the nature that its coercive force is larger and the magnetization is easier as the ratio occupied by the entire part of a head core is higher. However, the polycrystalline ferrite is disposed only in the part where the winding groove 5 is formed in such a case and, therefore, the coercive force in magnetic circuit parts is suppressed to be at a lower level and eventually the demagnetization is suppressed by the decreased magnetization. Consequently, there are no more generation of sliding noises and the distortion of the reproduced output and electromagnetic conversion characteristics are enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head useful for, for example, a video tape recorder (hereinafter referred to as VTR), and more particularly to a bonded ferrite magnetic head formed by bonding a single crystal ferrite and a polycrystalline ferrite. .

[0002]

2. Description of the Related Art In recent years, with the advent of so-called digital VTRs and the demand for miniaturization and lengthening of magnetic recording / reproducing devices such as VTRs, high density recording and short wavelength recording have been promoted. Correspondingly, high coercive force magnetic recording media have come into use.

For this reason, it has become difficult to achieve both the recording characteristics and the reproducing characteristics with a single ferrite head conventionally used for a VTR. Therefore, in order to ensure compatibility between the recording characteristic and the reproducing characteristic, development of a so-called bonded ferrite magnetic head in which a single crystal ferrite and a polycrystalline ferrite are bonded is under way.

In the bonded ferrite magnetic head 101, for example, as shown in FIG. 6, a medium sliding surface portion 102 represented by a magnetic gap g is a single crystal ferrite having a high saturation magnetic flux density, and a portion occupying most of the rest. 103
Is a polycrystalline ferrite having a high magnetic permeability.

The reason why the single crystal ferrite is used for the medium sliding surface portion 102 is that the recording characteristics of the magnetic head are taken into consideration, and a high saturation magnetic flux density is required at the time of recording. On the other hand, the reason why the polycrystalline ferrite is used for the other portion 103 is that high magnetic permeability is required during reproduction.
With this structure, high density recording is possible even though it has a simple structure similar to a single ferrite head.
Furthermore, excellent electromagnetic conversion characteristics can be obtained.

[0006]

In the above-mentioned bonded ferrite magnetic head, most of the material constituting the magnetic circuit except the medium sliding surface portion 102 is made of polycrystalline ferrite having high magnetic permeability. Has been done. However, since the coercive force of polycrystalline ferrite is very large,
By repeating recording / reproducing, the head is magnetized, and demagnetization is caused accordingly. Therefore, good recording / reproducing cannot be expected for the high coercive force magnetic recording medium.

Therefore, the present invention has been proposed in view of such conventional circumstances, and an object thereof is to provide a magnetic head which suppresses demagnetization caused by magnetization of the magnetic head and is excellent in electromagnetic conversion characteristics. To do.

[0008]

In a bonded ferrite magnetic head according to the present invention, at least one of the magnetic core halves has a winding groove, these magnetic core halves are bonded and integrated, and the abutting surfaces thereof are joined to each other. A magnetic head in which a magnetic gap is formed. The medium sliding surface portion of the magnetic gap is made of single crystal ferrite, the central portion where the winding groove is formed is made of polycrystalline ferrite, and the back portion is made of single crystal ferrite. The above-mentioned problem is solved by.

Also, in this bonded ferrite magnetic head, the medium sliding surface portion is from the medium sliding surface to the depth zero position of the magnetic gap, and the central portion is from the depth zero position of the magnetic gap to the bottom surface of the winding groove. .

[0010]

In the bonded ferrite magnetic head according to the present invention,
Since the polycrystalline ferrite that causes magnetization is provided only in the central portion of the head where the winding groove is formed, the proportion of polycrystalline ferrite in the entire head is reduced, and demagnetization due to magnetization is suppressed. Therefore, both the recording characteristic and the reproducing characteristic can be achieved, and extremely good electromagnetic conversion characteristics can be achieved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described in detail below with reference to the drawings. As shown in FIG. 1, the bonded ferrite magnetic head of the present embodiment has a pair of magnetic core halves 1 and 2 forming a closed magnetic circuit, and these magnetic core halves 1 and 2 are bonded and integrated. A magnetic gap g functioning as a recording / reproducing gap between the abutting surfaces.
Is formed.

The track width Tw of the magnetic gap g is
The magnetic core halves 1 and 2 are regulated by track width regulation grooves 3 and 4 formed in an abutting surface on the abutting surfaces. Therefore, the track width Tw of the magnetic gap g is
Is the opposing length of the gap forming surface parallel to the magnetic gap g left by the track width regulating grooves 3 and 4.

Further, the depth of the magnetic gap g is regulated by the winding groove 5 around which the coil is wound. The winding groove 5 is an inclined surface 5 that regulates the depth of the magnetic gap g.
a, a coil winding surface 5b parallel to the abutting surfaces of the magnetic core halves 1 and 2, and a bottom surface 5c perpendicular to the abutting surfaces of the magnetic core halves 1 and 2.

The inclined surface 5a serves not only to control the depth of the magnetic gap g but also to reduce the leakage magnetic flux between the magnetic core halves 1 and 2 in the winding groove portion. The intersection of the inclined surface 5a and the facing surface of the magnetic core half body 2 is the zero depth position of the magnetic gap g.

The coil winding surface 5b functions as a winding surface for winding the winding. The bottom surface 5c is the coil winding surface 5
The coil winding surface 5b for winding the winding around b for a predetermined number of turns
Serves to regulate the length of.

Particularly, in this junction ferrite magnetic head, the medium sliding surface portion 6 represented by the magnetic gap g is single crystal ferrite, the central portion 7 where the winding groove 5 is formed is polycrystalline ferrite, and the back portion 8 is single. Crystal ferrite 3
It has a layered structure.

The medium sliding surface portion 6 is a region from the medium sliding surface 9 represented by the magnetic gap g to the depth zero position of the magnetic gap g. The central portion 7 is an area from the depth zero position of the magnetic gap g to the bottom surface 5c of the winding groove 5 (area indicated by hatching in FIG. 1). The back portion 8 is an area from the bottom surface 5c of the winding groove 5 to the back surface 10 opposite to the medium sliding surface 9.

The single crystal ferrite provided on the medium sliding surface portion 6 and the back portion 8 are both made of single crystal ferrite having a high saturation magnetic flux density. The use of single crystal ferrite for the medium sliding surface portion 6 is based on the fact that the single crystal ferrite has a high saturation magnetic flux density in consideration of recording characteristics. It also contributes to the reduction of sliding noise on the magnetic recording medium. Therefore, at the time of recording, the single crystal ferrite provided on the medium sliding surface portion 6 can realize sufficient recording on the high coercive force magnetic recording medium.

On the other hand, the polycrystalline ferrite provided in the central portion 7 is made of polycrystalline ferrite having a high magnetic permeability. Therefore, during reproduction, the average magnetic permeability of the head becomes high and a high reproduction output can be obtained. Polycrystalline ferrite has a property that the coercive force is increased and the magnetization becomes easier as the proportion of the whole head core increases. However, in this embodiment, since the polycrystalline ferrite is provided only in the portion where the winding groove 5 is formed, the coercive force in the magnetic circuit portion can be suppressed low, and as a result, the demagnetization is reduced due to the decrease in the magnetization. Can be suppressed. Therefore, according to the magnetic head of the present embodiment, the occurrence of sliding noise and the distortion of the reproduction output signal are eliminated, and the electromagnetic conversion characteristics can be improved.

Here, the demagnetization amount of the magnetic head actually manufactured under the following conditions was measured. The magnetic heads measured were magnetic heads made of single crystal ferrite alone (this is called experimental head 1), magnetic heads made of single crystal ferrite for the medium sliding surface portion and back portion, and polycrystalline ferrite for the central portion (this was Experimental heads 2 and 3), a magnetic head in which the medium sliding surface portion was made of single crystal ferrite, and the other portions were made of polycrystalline ferrite (this is an experimental head 4).
It is). The experimental head 2 and the experimental head 3
The lengths of the polycrystalline ferrites in the depth direction are 0.3 mm and 1 mm, respectively.

The amount of demagnetization is measured by each experimental head 1, 2,
Record constant frequency on magnetic tape with 3 and 4, respectively,
The recorded reproduction signal is reproduced to reproduce reproduction level V ₁
To measure. Then, the reproduction output level V ₂ after repeating this 10 times or more is measured. Then, the demagnetization amount is obtained from the initial reproduction output level V ₁ and the final reproduction output level V ₂ . The demagnetization amount is represented by the following equation (1).

Demagnetization amount = [(V ₁ −V ₂ ) / V ₁ ] × 100 ... Equation (1)

As shown in FIG. 2, the demagnetization amount of each magnetic head was 10 for the experimental head 1 made of single crystal ferrite alone.
It is shown as a relative value when it is 0%.
The experimental heads 2 and 3 each having a three-layer structure of polycrystalline ferrite / single crystal ferrite are slightly demagnetized as compared with the experimental head 1, but the recording / reproducing does not cause much difference. However, in the experimental head 4 in which only the medium sliding surface portion is made of single crystal ferrite and the other portions are made of polycrystalline ferrite, a decrease of as much as 10% is observed as compared with the experimental head 1 made of single crystal ferrite alone.

As is clear from the results of this experiment, by using a three-layer structure of single crystal ferrite / polycrystalline ferrite / single crystal ferrite, it is possible to obtain a demagnetization amount approximately the same as that of a single crystal ferrite single head. it can.

By the way, a junction ferrite magnetic head having a three-layer structure of single crystal ferrite / polycrystalline ferrite / single crystal ferrite is manufactured in the following manner. First, as shown in FIG. 3, the single crystal ferrite substrate 1 is made into a predetermined size from the single crystal ferrite ingot 11.
Cut out 2.

Next, a polycrystalline ferrite substrate 13 having a predetermined size is similarly cut out from an unillustrated polycrystalline ferrite ingot as shown in FIG. Next, these single crystal ferrite substrate 12 and polycrystalline ferrite substrate 13
After mirror-polishing both main surfaces in the thickness direction, as shown in FIG. 5, single crystal ferrite substrates 12 and polycrystalline ferrite substrates 13 are alternately laminated and joined together.

Then, the ferrite block integrally bonded is subjected to winding groove processing, track width regulation groove processing and the like to complete a magnetic head.

[0028]

As is apparent from the above description, according to the bonded ferrite magnetic head of the present invention, the winding groove is formed in order to suppress the proportion of the polycrystalline ferrite which causes the magnetization of the head. Since the polycrystalline ferrite is provided only in the central part and the single crystal ferrite is used in the other parts, the demagnetization due to the suppression of the magnetization can be greatly reduced.
It is possible to achieve both the recording characteristic and the reproducing characteristic originally possessed by the bonded ferrite magnetic head. Therefore, due to the excellent electromagnetic conversion characteristics of the bonded ferrite magnetic head of the present invention,
Recording and reproduction can be sufficiently performed on a high coercive force magnetic recording medium.

[Brief description of drawings]

FIG. 1 is a perspective view of a bonded ferrite magnetic head to which the present invention is applied.

FIG. 2 is a characteristic diagram showing measurement results of demagnetization amounts of various magnetic heads manufactured by experiments.

FIG. 3 is a perspective view showing a manufacturing process of a single crystal ferrite substrate.

FIG. 4 is a perspective view showing a manufacturing process of a polycrystalline ferrite substrate.

FIG. 5 is a front view showing a manufacturing process of a bonded ferrite substrate.

FIG. 6 is a perspective view of a conventional bonded ferrite magnetic head.

[Explanation of symbols]

 1, 2 magnetic core halves 3, 4 track width regulation groove 5 winding groove 5a winding groove inclined surface 5b winding groove coil winding surface 5c winding groove bottom surface 6 medium sliding surface portion 7 center portion 8 back part

Claims (2)

[Claims] 1. A bonded ferrite magnetic head in which a pair of magnetic core halves each having a winding groove formed in at least one magnetic core half are bonded and integrated, and a magnetic gap is formed between the abutting surfaces thereof. The medium sliding surface part that the magnetic gap exhibits is single crystal ferrite, the central part where the winding groove is formed is polycrystalline ferrite,
A bonded ferrite magnetic head having a back portion made of single crystal ferrite. 2. The medium sliding surface portion is from the medium sliding surface to the depth zero position of the magnetic gap, and the central portion is from the depth zero position of the magnetic gap to the bottom surface of the winding groove. The bonded ferrite magnetic head according to claim 1.