GB2154359A

GB2154359A - Magnetic head

Info

Publication number: GB2154359A
Application number: GB08404245A
Authority: GB
Inventors: Shinji Furuichi
Original assignee: Hitachi Metals Ltd
Current assignee: Proterial Ltd
Priority date: 1984-02-17
Filing date: 1984-02-17
Publication date: 1985-09-04
Also published as: GB8404245D0

Abstract

Disclosed is a magnetic head having an I-shaped core portion 5 which is arranged such that cut-off portions 7 defining a track width (Tw Fig. 6) are provided only in the vicinity of a magnetic recording gap 8, and a C-shaped portion 6 defines the gap depth (Gd Fig. 7). The cut- out portions may be filled with glass which also bonds the core portions together. <IMAGE>

Description

SPECIFICATION Magnetic head The present invention relates to a high density recording/reproducing magnetic head of the floating type.

Recently, a magnetic head arranged in a floating manner relatively to a magnetic medium is widely used. In order to improve the recording density, in such a magnetic head, it is required to reduce the amount of floating of the head and shorten the recording frequency and to reduce the width of the recording truck. As the recording frequency is reduced, it has become required to reduce the magnetic circuit in size and to make higher the efficiency of the same. There is a problem, however, such that in order to reduce the recording track width to the order of 10 ,um, in a conventional monolithic type core slider, the mechanical working is very difficult and faults may occur in the core due to the contact with the magnetic medium in use.

In order to eliminate such a disadvantage as mentioned above, a so-called core slider of the composite type has been practically used in which, as shown in Fig. 1, a core 2 having a recording/reproducing gap is fixed in a slotted portion of a core slider 1 made of a non-magnetic ceramic material such as Ti CaO3, TiBaO3 through a non-magnetic material such as glass. Fig. 2 is an enlarged plan view which shows a portion of the core slider at which the core 2 is fixed. As shown in Fig.

2, the core 2 having a recording/reproducing gap 3 is fixed in the slotted portions of the non-magnetic ceramic core slider 1 through the non-magnetic material 4 such as glass.

As the core 2, there has been proposed a core having a track width Tw and a core width tw which is equal to the track width Tw as shown in Fig. 3. Since Tw = tw in this arrangement, as the track width Tw is reduced the core width tw also becomes small and therefore the limit of track width Tw is 50-60 ym because of the increase of the magnetic reluctance as well as the saturation of the magnetic circuit.

To eliminate such defects, such a core arrangement as shown in Fig. 4 in which TW < tw has been proposed and practically used. However, although the problems in the increase of magnetic reluctance and the saturation of magnetic circuit can be solved since the core width t can be selected to a sufficiently large value relative to the track width Tw, the limit of mechanical working of the track width Tw is 20-30 ym. Under the condition of such a thin track width, the handling of work becomes so difficult that yield is extremely lowered.

An object of the present invention is, therefore, to provide a magnetic head in which a narrow track can be easily realized for the purpose of high density recording.

In order to achieve the object mentioned above, used is a core which is arranged such that cut-off portions defining a track width is formed only in the vicinity of a magnetic recording gap in opposition to a recording medium and the remaining portion has a sufficiently large core width relative to the track width. The core portion provided with the cut-off portions is formed into a substantially I-shape and another substantially Cshaped core portion is disposed in opposition to the I-shaped core portion to form a magnetic circuit. The gap depth Gd of the core is defined by the C-shaped core portion.

The above and other objects, features and advantages will be apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: Figure 1 is a perspective view showing the outline of a composite core slider; Figure 2 is an enlarged plan view of a part of a composite head; Figure 3 is a perspective view of a conventional core tip; Figure 4 is a perspective view of a conventional core tip which is an improved one of the core tip of Fig. 3; Figure 5 is a perspective view of an embodiment of the core tip according to the present invention; Figures 6 and 7 are plan and front views of the core tip shown in Fig. 5; Figure 8 is an enlarged plan view of the core portion of the composite head according to the present invention; and Figure 9 is a perspective view of another embodiment of the core tip according to the present invention.

In Figs. 3, 6 and 7 showing an embodiment of the present invention, a substantially I-shaped core portion 5 is provided with cutoff portions 7 defining the track width Tw and a substantially C-shaped core portion 6 is fused to the core portion 5 with a material such as glass, with a recording gap 8 formed between the core portions. Reference numeral 9 designates a non-magnetic reinforcing material such as glass for increasing the strength of fuse-fixing between the core portions 5 and 6.

Fig. 8 is an enlarged plan view of a portion where the core assembly 2 of core portions 5 and 6 is fixed to a core slider 1 which is similar to that shown in Fig. 1, according to the present invention.

Each of the core portions 5 and 6 is formed from a material of Mn-Zn monocrystal ferrite or polycrystal ferrite, having an average thermal expansion coefficient a (20-300'C) of 1 10#130x10-7deg-1 and the core slider 1 is formed from a material such as TiCa03, Ti BaO3, having an average thermal expansion coefficient a of 100#125x10-7deg-1. The reinforce material corresponding to the non magnetic reinforcing mateial 9 as shown in Fig. 7 is glass having a softening point of 600-700 C and the non-magnetic material for fixing the core to the slider 1 is glass having a softening point of 350-430'C.

The core width tw is selected to 0. 1-0.2 mm and the track width Tw defined by the cutoff portions 7 is selected to 0.01-0.02 mm.

Glass having a softening point of 350or or more was embedded in the cut-off portions 7 when the core was produced in order to prevent the core from being broken. It is not always necessary to embed the glass in the cut-off portions 7 when the core is produced.

It is apparent that the glass may be embedded in the cut-off portions 7 at the same time when glass 10 is poured as a non magnetic material to fuse-fix the core slider 1 and the core assembly of the core portions 5 and 6. However, it is preferable to embed the glass in the cut-off portions 7 in advance in the view of prevention of break from occurring in the core in treatment of the same. After the assembly of the core portions 5 and 6 is fixed to the core slider 1 with the non-magnetic material such as glass 10, the entire assembly is subjected to machining such as polishing.

Differing from the conventional monolithic type core slider, in the composite type core slider there is an inconvenience that the depth of the gap cannot be viewed from the outside.

In order to make the gap depth to a predetermined value, therefore, it is necessary to set forward the step of machining with a specified portion of the core or the core slider as a referensc; point of machining, after the core slider 1 and the core assembly have fixed with each other. In order to machine a large quantity of with less error, it is necessary to form the gap depth Gd or Gd' of the core with very high accuracy.

In the case of the arrangement in which a substantially I-shaped core portion 5 and a substantially C-shaped core portion 6 each provided with cut-off portions 7, 7' are abutted to each other as shown in Fig. 9, for example in a picture head in a video tape recorder, the track width Tw is not the dimension defined by the cut-off portions but it is determined by the accuracy of abutment of the core portions. Further, it is necessary to measure the gap depth through the glass embedded in the cut-off portions and therefore there may occur unavoidable error of several ym.

According to the present invention, the track width Tw is defined by the cut-off portions 7 of the substantially I-shaped core portion 5 so that no error occurs due to the abutment of the core portions, and the gap depth is determined by the accuracy in machining of the depth Gd of the substantially Cshaped core portion 6 and therefore it can be set easily.

Having the arrangement as described above, the magnetic head according to the present invention has remarkable advantages that the track width is narrow, the dimensional accuracy is high, and the producing is easy.

Claims

1. A-composite type core slider magnetic head comprising a magnetic head core for performing magnetic recording/reproducing and a non-magnetic ceramic coreslider, said core being constituted by a substantially Ishaped core portion and a substantially Cshaped core portion, said substantially Ishaped core portion being partially formed with cut-off portions, a recording/reproducing track width of said head being defined by said cut-off portions, and a recording/reproducing gap depth being defined by said substantially C-shaped core portion.

2. A magnetic head according to claim 1, in which a non-magnetic material is embedded in said cut-off portions.

3. A magnetic head according to claim 2, in which said non-magnetic material is glass.

4. A magnetic head according to claim 2, in which said substantially I-shaped core portion and said C-shaped core portion are fixed with each other with said non-magnetic material.