JPH0580727B2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a method for manufacturing a core for a magnetic head,
In particular, when manufacturing a core for a magnetic head made of ferrite material, which is called a ferrite core,
The present invention relates to a method that can effectively prevent variations in magnetic gap width and track positional deviation.

(Prior Art) Ferrite cores made of ferrite as a core material have been known as cores for magnetic heads. As is well known, this ferrite core generally has a structure in which two ferrite members are butted against each other to form an annular magnetic path (magnetic circuit) between the ferrite members. The space formed is a hole for coil winding, while a magnetic gap with a predetermined gap is provided in the abutting portion of one of the ferrite members in the direction across the annular magnetic path. As is well known, predetermined recording and reproduction are performed on magnetic recording media such as magnetic tapes and magnetic disks.

By the way, in such a ferrite core, the core outer peripheral surface portion where the magnetic gap exists, in other words, the core facing surface or sliding contact surface facing the magnetic recording medium, is used for recording, reproducing, and erasing on the magnetic recording medium. A track of a predetermined width for performing such operations is provided so as to extend in the direction of movement relative to the magnetic recording medium. This track is determined to have a predetermined width depending on the type of magnetic recording medium that is opposed to or brought into sliding contact with a predetermined gap.
Generally, it is defined by grooves formed across the magnetic path portions on both sides of the magnetic gap.

On the other hand, in order to write as much information as possible to one magnetic recording medium, it is necessary to narrow the width of the above-mentioned tracks, but along with this, the corners of the ferrite member in the form of convex stripes that form such tracks have to be narrowed. There is a problem that the magnetic head and the magnetic recording medium may be damaged or destroyed due to contact with the magnetic recording medium or the like, causing serious accidents.

For this reason, Japanese Patent Publication No. 47-11107 and Japanese Unexamined Patent Publication No. 59
Publication No. 215022, etc. discloses that a non-magnetic material such as glass is filled into grooves formed on both sides of a convex strip of a predetermined width that constitutes the track of the magnetic head, which is provided in the magnetic head core. It is now clear that a method can be used to obtain the desired magnetic head by reinforcing the protrusions and subjecting them to a prescribed process to form a core for a magnetic head, and then winding the core. is being used.

(Problem) However, in the conventional method of manufacturing cores for magnetic heads (ferrite cores) in which the protrusions (tracks) are reinforced with non-magnetic materials such as glass, two ferrite members are bonded together. Therefore, when forming the core block (base material), since a non-magnetic material such as glass is used as a bonding agent, it was necessary to use two types of non-magnetic materials such as glasses with different melting temperatures.

That is, according to the method disclosed in the above-mentioned publication, first, two ferrite members are joined with molten glass (non-magnetic material) to form a core block having a magnetic gap, and then the necessary mirror polishing and gap depth creation are performed. After processing, grooving for installation, etc., grooves are formed on both sides of the protrusions to form protrusions of a predetermined width that serve as tracks for the magnetic head. The ridges are reinforced by filling them with reinforcing glass having a lower melting temperature than the molten glass used to join the two ferrite members.

Therefore, in such conventional methods, if the melting points of the two types of glass materials are close to each other, the two ferrite members constituting the core block are bonded together during the subsequent filling operation with the low-melting glass for reinforcement. There is a risk that the high melting point glass used for bonding will soften, and if such softening of the high melting point glass used for bonding occurs, the bonded portion of the two ferrite members will shift and the width of the magnetic gap will expand. This may cause problems such as changes in the gap width and misalignment of the track.

Of course, it is conceivable to use a glass with a higher melting point as the glass for joining the ferrite members, or a glass with a lower melting point as the glass for reinforcing the protruding stripes, but in the former case, it is necessary to melt the glass. Due to the use of high temperatures to achieve this, the ferrite portion near the magnetic gap is altered or eroded, making it difficult to achieve a narrow gap width, and in the latter case, the strength of the glass itself may be affected. This has the inherent problem that the original purpose of protecting the protruding stripes cannot be sufficiently achieved.

Under these circumstances, in the conventional method of manufacturing cores for magnetic heads, two types of nonmagnetic materials with different melting temperatures are used, which places significant restrictions on the selection of such nonmagnetic materials. .

(Solution Means) Here, the present invention has been made to solve the above-mentioned problems, and its features include (a) a plurality of By butting the ferrite members together and directly joining the abutting parts of the ferrite members, excluding the magnetic gap forming part, by solid phase reaction,
(b) filling a gap between the magnetic gap forming portions of the core block with a first non-magnetic material; (c) filling the integral core block with a magnetic head; so that a protrusion of a predetermined width corresponding to the track width is formed.
The method of manufacturing a core for a magnetic head includes the steps of: forming grooves on both sides of the protruding groove; and (d) filling the groove with a second non-magnetic material.

In the present invention, preferably, the formation of the groove and the filling of the second non-magnetic material include:
This is performed on the core block with the joint directly joined by solid phase reaction left on the outside of the magnetic gap forming part.

Further, the present invention is suitably applied to the manufacture of a core for a monolithic type magnetic head for a winchiestor that records information on a recording medium such as a magnetic disk, but in such a case, the above-mentioned After filling with the second non-magnetic material, ski grooves necessary for floating the magnetic head are formed substantially parallel to the protrusions.

Furthermore, according to a preferred embodiment of the invention,
At least the magnetic gap forming portion of at least one of the ferrite members forming the magnetic gap is made of single-crystal ferrite, and in particular, the entire core block is made of single-crystal ferrite. The magnetic gap forming surface of the portion composed of such single crystal ferrite is made to have a crystal plane of 111 or 100.

(Function/Effect) Therefore, according to the method of the present invention, a plurality of ferrite members can be directly joined by solid phase reaction without using a non-magnetic material (glass) for joining as in the past. Because it is an integral core block, even if the core block is heated in the subsequent step of filling the groove with the second non-magnetic material, the width of the magnetic gap formed in the core block will expand. There is virtually no possibility that the tracks (protruding stripes) will be misaligned. However, such a core block does not have a joint made of non-magnetic material.

The first non-magnetic material used in the present invention is filled into a magnetic gap forming gap formed in an integral core block to protect the magnetic gap forming gap, and is used to protect the magnetic gap forming gap. Since it is not intended for joining a plurality of ferrite members such as, the first non-magnetic material is softened by heating when filling the groove with the second non-magnetic material later. ,
This does not cause problems such as changes in the magnetic gap width or positional deviation of the tracks. Therefore, in the present invention, the first non-magnetic material and the second non-magnetic material are made of the same glass or the like. It is also possible to use a non-magnetic material, which greatly expands the range of non-magnetic materials that can be selected.

(Example) Hereinafter, the present invention will be explained in more detail with reference to the drawings.

First, as the ferrite member used in the present invention to form the core block, materials such as Mn-Zn ferrite and Ni-Zn ferrite are used, and these materials are used depending on the purpose. Generally, the plurality of ferrite members used in the present invention are made of the same material. Regarding the microstructure of each ferrite member, whether each ferrite member is a polycrystalline material, a single crystal material, or a composite material containing a polycrystalline portion and a single crystalline portion, Furthermore, it is also possible to use a combination of ferrite members having different texture structures.

One specific method for producing the desired core for a magnetic head according to the present invention using such a ferrite material is schematically shown in FIG. Note that a to j in FIG. 1 show an example of a process for manufacturing a monolithic type magnetic head core for a winchiestor.

As shown in FIG. A groove 6 for forming a hole for coil winding is formed on the surface facing the coil wire 4 in advance. Note that this grooving process is usually performed by cutting a block-shaped ferrite member with a diamond cutter or the like, but instead of this, a ferrite member having a shape such as a groove 6 for coil winding may be used. It is also possible to directly mold the material by a method such as a press molding method, and herein, grooving is used to include grooving performed at the same time as such molding.

Further, the ferrite member 2 has a predetermined depth (thickness):
Gap processing has also been applied in advance to remove only the surface. This gap processing is to recess the upper and lower contact portions 8a and 8b of the ferrite member 2 that is brought into contact with the ferrite member 4 by an amount β, and this removed thickness β is as described below. Width of magnetic gap 10 of ferrite core:
α will be formed. Note that, for this gap forming process, a method such as etching with acid or grinding with a diamond cutter is adopted. In addition, here, with respect to the magnetic gap forming portion of the ferrite member 2 having a C-shaped cross section,
Although the gap forming process is performed, there is no problem in replacing the gap forming process by performing the gap forming process as described above on the magnetic gap part of the other block-shaped ferrite member 4.

Note that the order of the gap machining process and the grooving process for the ferrite member 2 is different; for example, in the case illustrated in FIG. 1a,
After grooving to form the grooves 6, gap machining is performed to remove the ferrite member corresponding to β.

Then, for the ferrite member 2 that has undergone such gap machining process and grooving process,
The other block-shaped ferrite member 4 is placed one on top of the other so that the groove 6 is located between the ferrite members, in other words, the groove 6 is covered by the other ferrite member 4, They are butted against each other. By this butting, the upper and lower contact portions 8a and 8b of one ferrite member 2 are brought into contact with the side surface of the other ferrite member 4, thereby reducing the thickness removed in the gap processing step. A gap equal to β is
A magnetic gap 1 is formed between the two ferrite members 2 and 4 at the gap processing area.
This results in a gap α of 0.

Furthermore, when the two ferrite members 2 and 4 are butted together, it is desirable to interpose an acid that dissolves the ferrite, such as hydrochloric acid, nitric acid, sulfuric acid, etc., in the abutting portions. The reason for this is that the mutual positions of the ferrite members 2 and 4 are
The salts of ferrite components formed by such acids (e.g. iron nitrate, manganese nitrate, zinc nitrate, etc.) are fixed, and during subsequent heating, the oxides produced by decomposition of such salts are This is because it is effective in promoting the desired solid phase reaction. In addition to the above-mentioned acids, an aqueous solution of an inorganic acid salt containing a ferrite component can also be effectively used to bond the two ferrite members 2 and 4 when they are brought together, and the same effect can be obtained. .

Next, the ferrite members 2 and 4 which are abutted and combined in this manner are heated in that state, thereby causing a solid phase reaction at their abutting portions, and are sintered as a unit. Their direct joining is realized as shown in FIG. 1b. The core block 12, which is an integrally joined body, is composed of the ferrite members 2 and 4, but as shown in the figure, there is no difference in the abutting parts between them, and they are substantially integral and continuous. The hole 14 for coil winding is formed by the groove 6 so as to pass through it, while the gap-processed part of the ferrite member 2 and the other ferrite member 4 Predetermined gap between parts: α
A magnetic gap 10 of (β) is thus formed.

In order to reduce disturbances in the gap structure in the magnetic gap 10 of the integrated core block 12 formed in this way, a thickness corresponding to the gap width α is added by chemical treatment in the gap processing process. It is desirable to use a ferrite block whose at least the gap-forming portion is a single crystal as the ferrite member (herein 2) which is removed. In particular, in the present invention, the lower contact portions 8 of the ferrite members 2, 4
To prevent a rear gap from forming at b.
In order to join them together by solid phase reaction,
Since the magnetic gap 10 is sintered by heating to a high temperature to form an integral bond, if the gap forming surface of the magnetic gap 10 is made of polycrystalline ferrite, thermal etching is induced and the grain boundaries are formed. Therefore, in order to form the magnetic gap 10 that requires precision, it is desirable that at least the gap forming surfaces of both the ferrite members 2 and 4 be made of single crystal ferrite. .

Furthermore, the single crystal ferrite structure of at least the gap forming portion of the ferrite members 2 and 4 may be obtained by using a ferrite member having such a single crystal ferrite portion in advance, or by using a method previously proposed by the applicant in Japanese Patent Application No. 58-246262. This can be achieved by joining the two ferrite members 2 and 4 with the ferrite member and simultaneously growing a single crystal using the single crystallization method according to the following. In the present invention, the integral core block 12 obtained by joining the two ferrite members 2 and 4 is entirely composed of one single crystal ferrite.

Furthermore, in the present invention, when the magnetic gap 10 forming portion of the ferrite members 2 and 4 has a single-crystal ferrite structure, the magnetic gap forming surface is
It is desirable to select one crystal plane or 100 crystal planes, thereby making it possible to avoid the problem of surface irregularities during etching in the gap forming process.

Furthermore, since the sintering of ferrite by the solid-state reaction described above proceeds at a temperature of about 1100°C, direct integral joining of the abutting parts (surfaces) of the ferrite members 2 and 4 requires It is necessary to heat the material to a temperature of 1100° C. or higher for a predetermined period of time in an atmosphere with an equilibrium oxygen partial pressure in which the oxygen partial pressure is balanced with that of ferrite. However, when polycrystalline ferrite is used as the ferrite member, as mentioned above, thermal etching occurs and unevenness occurs on the forming surface of the magnetic gap 10, so the sintering temperature is preferably low; therefore, too high a sintering temperature should be avoided, with 1250°C or less being generally desirable. However, if the ferrite members 2 and 4 in which single-crystal ferrite exists at least on the forming surface of the magnetic gap 10 are used, any sintering temperature may be used, and there are no restrictions as described above. In order to eliminate the minute irregularities on the gap forming surface caused by gap processing by etching or grinding, it is desirable to raise the temperature of the solid phase reaction, and the effect is usually achieved at a temperature of 1350°C or higher. I can admit it.

In the case of the core block 12 obtained by directly joining the ferrite members 2 and 4 through such a solid-phase reaction, no foreign phase is observed in the joined portion, and the structure is substantially integrated. Unlike the conventional case in which the abutting portions of the ferrite members 2 and 4 constituting the core are joined by glass, a contact portion is inevitably formed between the ferrite members 2 and 4. The rear gap can be substantially eliminated, and the magnetic resistance of the magnetic path based on the rear gap can be substantially eliminated, effectively improving the head sensitivity.
As a result, the S/N characteristics can be improved.

Next, in order to protect the magnetic gap 10 portion of the core block 12, which is directly joined and integrated by this solid phase reaction, the gap is filled with glass as shown in FIG. 1c. It will be filled with a non-magnetic material such as No. 16.
This filling of glass 16 causes it to melt and
This is carried out by pouring into the gap of such magnetic gap 10, and generally, such magnetic gap 10 is
By placing rod-shaped solid glass in the part,
The glass 16 is filled by heating it to a temperature of about 600 to 900°C to melt it, and at that time, the atmosphere in the furnace also needs to be at an equilibrium oxygen partial pressure with the ferrite as described above. Generally, nitrogen (N ₂
It will be carried out in gas.

For the core block 12 in which the glass 16 is filled in the magnetic gap 10 in this way, a predetermined track width is formed on the surface on the side where the magnetic gap 10 is formed, as shown in FIG. 1e. As the part is configured, i.e. track width: w
In order to form the convex part 18 having a thickness of , grooves 20, 20 of an appropriate width are formed on both sides of the convex part 18.

Note that the groove length of the concave groove 20 is, as shown in FIG.
Although the magnetic gap 10 is provided over the entire length of the upper surface of the magnetic gap 2, in some cases, it may be provided only in the vicinity where the magnetic gap 10 is present. Further, it is desirable that the side surfaces of the protruding portion 18 formed by the grooves 20, 20 are formed as vertical surfaces. Furthermore, the groove depth of the concave groove 20:
d or d' is generally located below the gap bottom 22 of the magnetic gap 10, in other words the coil winding hole 14, as shown in FIGS. 1f and 1g.
It will be determined so that the groove bottom is located on the side.

By the way, in FIGS. 1f and 1g, the concave grooves 20 are shown at different groove depths: d or d'.
However, in Figure 1 f,
The concave groove 20 is formed while leaving the joint 24 formed by the joining operation based on the contact of the contact part 8a of the ferrite member 2 against the ferrite member 4 on the outside (on the upper side) of the magnetic gap 10. An example is shown in which grooving has been performed, and FIG.
2 is shown in a state in which grooving to form grooves 20 has been performed.

The core block 12 which has been subjected to the grooving process to form the concave grooves 20 in this way also has the following features:
As shown in FIG. 1h, the concave grooves 20 are filled with a non-magnetic material such as glass 26, thereby reinforcing the protrusions 18 that serve as tracks for the magnetic head. It will be. This operation of filling the glass 26 is carried out in the same manner as the filling of the glass 16 into the magnetic gap 10. That is, this is done by melting the glass 26 and pouring it into each groove 20.Generally, solid glass such as a rod is placed on each groove 20, and the glass is heated to a temperature of about 600 to 900°C. Filling with the glass 26 is performed by heating it to a temperature and melting it,
In addition, the atmosphere in the furnace at that time needs to have an equilibrium oxygen partial pressure with the ferrite as mentioned above.
Generally, it is carried out in nitrogen gas.

By reinforcing or protecting with a non-magnetic material such as glass 26, chipping of the corners of the protruding stripes 18 can be effectively prevented.
Since the filling operation of the glass 26 that brings about such an effect is performed on the integral core block 12 that is directly joined by solid phase reaction, when the glass 26 is heated and melted, Width due to softening of conventional bonding glass:
Problems such as changes in α and displacement of the track 18 do not occur at all.

However, since the core block 12 is an integral bonded body that does not use bonding glass as in the past, when the glass 16 filled in the magnetic gap 10 softens, the gap width α of the magnetic gap 10 and the track 18 change. It does not substantially affect the position, and therefore, it has become possible to use the same glass as the glass 16 for filling the magnetic gap 10 and the glass 26 for filling the groove 20. This allows the range of choices for the glasses 16 and 26 to be significantly expanded.

In addition, in the present invention, as shown in FIG. Although it is particularly recommended that the glass 26 be filled into the groove 20 by machining, as shown in FIG. After the gear depth is removed by grinding or other means, the track 1
There is no problem even if the grooving process and glass 26 filling operation specified in 8 are performed. Especially, the joint part 2
By performing such grooving and glass filling operations on the core block 12 with 4 remaining, the widening of the gap width α and the displacement of the track portion 18 can be more completely prevented. This means that they can be forced to do so.

The core block 12 in which the glass 26 is filled in the concave grooves 20 obtained in this way is processed by the conventional gear depth forming process, the forming process of the groove 28 for attaching the core gimbal, the diagonal cutting process, and the like process. Mirror polishing and the like are performed, and further processing is performed to form a yoke 30 for coil winding on the portion of the ferrite member 2 that forms the core block 12. Note that if the gear depth processing is performed before the grooving of the concave grooves 20 or the filling of the glass 26, it will not be performed here, and the core gimbal attachment Grooves 28 can also be formed in the integral core block 12 prior to such grooving or glass filling operations.

After slicing the core block 12 that has been processed as described above into individual chips, the slider portion of the portion facing the magnetic recording medium is further attached to the sliced block pieces as necessary for the slider portion to levitate. A ski groove process is performed to form the grooves 32, 32, and a chamfer process is performed to complete the magnetic head core (ferrite core) as shown in FIGS. 1i and 1j. .

Then, the magnetic head has a coil winding hole 1 with respect to the yoke 30 of the magnetic head core 34.
4, and such a magnetic head would be attached to the core gimbal by a mounting groove 28 in its bottom, as is known in the art.

Above, the method of the present invention has been briefly explained based on a specific example of manufacturing a core for a monolithic type magnetic head for a winchiestor as shown in FIG. The present invention can also be advantageously applied to the manufacture of cores for other magnetic heads such as, for example, and an example of the manufacture of a core for a VTR head is shown in FIG. Note that parts in this example that are similar to those in the above specific example are given the same reference numerals and will not be described in detail.

That is, when manufacturing a core for a VTR image head according to the present invention, first, as shown in FIG. 2a, grooves 6 and magnetic gaps 10 for forming holes for coil winding are formed. A ferrite member 2 which has been previously gap-processed to form a stepped portion with a predetermined depth of β and a longitudinal block-shaped ferrite member 4 are used, and these are shown in FIG. 2b. As if they were butted against each other,
An integral core block 12 is formed by forming a predetermined magnetic gap 10 at the abutting portion and directly joining the abutting portions by solid phase reaction.

Next, as shown in FIG. 2c, the magnetic gap 10 and the coil winding hole 14 in the vicinity thereof are filled with a non-magnetic material such as a predetermined glass 16, and then as shown in FIG. 2e. After applying the gear depth processing to leave the joint 24 as shown in FIG. 2, or by cutting and removing the joint 24 as shown in FIG. , a plurality of grooves 20 are formed parallel to each other, thereby forming a protrusion 18 having a track width defined by the grooves 20.

Then, as shown in FIG. 2g, a non-magnetic material such as a predetermined glass 26 is melted and filled into the groove 20 formed in the integral core block 12, thereby controlling the tracks of the magnetic head. After reinforcing or protecting the constituting protrusions 18,
By slicing each chip, a desired VTR image head core 36 as shown in FIG. 2h is obtained. The VTR image head is completed by winding the core 36 in a conventional manner.

Although two manufacturing examples of magnetic head cores (ferrite cores) according to the present invention have been described above, the present invention is by no means to be interpreted as being limited only to these specific examples, and the gist of the present invention is Unless departing from the above, the present invention may be implemented in forms with various changes, modifications, improvements, etc. based on the knowledge of those skilled in the art, and the present invention also includes:
It goes without saying that the present invention includes such embodiments.

For example, all of the above-illustrated embodiments disclose industrially advantageous techniques in which elongated blocks are processed and joined together to form core blocks in accordance with the present invention, and track blocks are processed and joined in accordance with the present invention. A concave groove that defines the width is formed, a predetermined nonmagnetic material is filled therein, and then a groove is formed to a predetermined size.
A method has been disclosed in which ferrite cores are cut out one by one and a plurality of them are manufactured at once, but of course the present invention can also be applied to the case where one such ferrite core is manufactured individually. It is possible to do so.

In addition, in the previous examples, a ring-shaped magnetic path (magnetic circuit) was created by a combination of two ferrite members.
was formed, but by constructing an annular magnetic path by three ferrite members or a combination of more ferrite members and directly joining them by solid phase reaction, an integral There is no problem in forming a ferrite block.

[Brief explanation of the drawing]

FIG. 1 shows an example of manufacturing a monolithic type magnetic head core for a winchiestor according to the present invention, in which FIG. 1a is a partial perspective view showing two ferrite members to be combined, and FIG. 1b 1c is a partial perspective view showing a core block obtained by directly joining these two ferrite members, FIG. Fig. 1 d is an enlarged front view of part A in Fig. 1 c, Fig. 1 e is a partial perspective view showing the state in which grooves are formed in the core block, and Figs. 1 f and g show the groove depths of the grooves, respectively. An enlarged front partial view of the gap forming part of the core block to explain the
Figure h is a partial perspective view showing a state in which the concave grooves formed in the core block are filled with a predetermined glass, and Figure 1 i is a completed ferrite cut out from the core block 12 and processed with a predetermined ski groove etc. FIG. 1J is a perspective view showing one of the cores, and FIG. 1J is a front view [left side view in FIG. FIGS. 2a to 2h are explanatory diagrams similar to FIG. 1, respectively showing the steps of manufacturing a core for a VTR image head. 2, 4: Ferrite member, 6: Groove, 8a, 8
b: Contact part, 10: Magnetic gap, 12: Core block, 14: Coil winding hole, 16: Glass,
18: Convex portion, 20: Concave groove, 22: Gap bottom, 24: Joint portion, 26: Glass, 30: Yoke, 32: Groove, 34: Core for magnetic head.

Claims (1)

[Scope of Claims] 1. By butting a plurality of ferrite members against each other so as to form an annular magnetic path and directly joining the contact portions of the ferrite members excluding the magnetic gap forming portion by solid phase reaction, forming an integral core block; filling a gap between the magnetic gap forming portions of the core block with a first non-magnetic material; and forming the integral core block to a predetermined width corresponding to the track width of the magnetic head. The method includes the steps of: forming grooves on both sides of the grooves so that the grooves are formed; and filling the grooves with a second non-magnetic material. A method for manufacturing a core for a magnetic head. 2. A patent characterized in that the grooves are formed and the second non-magnetic material is filled while leaving a bonded portion directly bonded by solid phase reaction on the outside of the magnetic gap forming portion. The manufacturing method according to claim 1. 3. After filling the second non-magnetic material, ski grooves necessary for levitation are formed substantially parallel to the convex stripes.
The manufacturing method according to item 1 or 2. 4. Claim 1, wherein at least the magnetic gap forming portion of at least one of the ferrite members forming the magnetic gap is made of single crystal ferrite.
The manufacturing method according to any one of Items 1 to 3. 5. The manufacturing method according to any one of claims 1 to 3, wherein the integral core block is composed of a single single crystal ferrite. 6. The manufacturing method according to claim 4 or 5, wherein the single crystal ferrite surface forming the magnetic gap is composed of a (111) or (100) crystal plane. Law.