JPS6027089B2 - Composite magnetic head device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composite magnetic head device in which a magnetic head for recording/reproducing and a magnetic head for erasing, or a magnetic head for recording and a magnetic head for reproducing are integrally combined. .

2. Description of the Related Art The following composite magnetic head devices are known for use in cameras, video tape recorders, and the like.

The one shown in FIG. 1 is a known case in which a recording/reproducing magnetic head core 2 and an erasing magnetic head core 3 are housed and integrated in a case 1 whose tape contact surface side is curved in a series with a predetermined radius. There is.

By the way, this composite magnetic head has a magnetic head 3 in which one of the recording/reproducing magnetic head cores 2 2a, the other 2b of the recording/reproducing magnetic head core 2, and the erasing magnetic head 3 are combined with a shield plate 4 interposed therebetween. After two blocks are placed in a case 1, they are molded and fixed with a resin 5 such as epoxy. Therefore, the assembly block to be integrated has a complicated structure, making it difficult to manufacture and significantly reducing productivity. Since the gap 7 of the recording/reproducing magnetic head core 2 and the gap 8 of the erasing magnetic head 3 are located on the tape contact surface 6 which is curved in series, the respective gaps 7 and 8 are connected to the traveling magnetic field. There are drawbacks such as the fact that the magnetic tape does not come into reliable center contact with the twilling surface of the tape, so that signals cannot be accurately recorded on the predetermined tracks of the magnetic tape and cannot be reproduced accurately. Further, the recording/reproducing magnetic head core 2 is usually made of permalloy, and the erasing magnetic head core 3 is made of ferrite. Therefore, when finishing the tape contacting surface 6 by polishing, the degree of polishing varies, making it difficult to polish with a constant curvature. Furthermore, the magnetic head core 2 for recording/reproducing and the magnetic head core 3 for erasing are shielded via the shield plate 4, but since two cores 2 and 3 are contained within one case 1, the magnetic head core 2 for erasing There is a drawback that the flux of the magnetic head core 3 cannot be completely shielded. In the case shown in FIG. 2, in order to eliminate the drawbacks of the one shown in FIG. A recording/reproducing magnetic head core 2 and an erasing magnetic head core 3 are respectively arranged. Since each magnetic head core is arranged in each curved portion 6a, 6b in this way, the curved portion 6a,
6b radius and gaps 7, 8 between each magnetic head core 2, 3
Accurate tape touch can be obtained at the center of the head surface of the magnetic tape by matching the position with the magnetic tape head, but this accuracy depends on assembly accuracy and processing accuracy such as polishing, so variations occur for each product. In particular, since the tape abutting surface 6 has a twin-crested shape, it is difficult to polish each magnetic head core 2, 3. The grindstone must be formed to have a concave portion corresponding to the two curved portions 6a and 6b, and furthermore, in order to grind two members with different hardnesses, a grindstone is required in which two members suitable for each are bonded. It is difficult to manufacture grindstones. It is particularly difficult to achieve dimensional accuracy during final polishing. In this case as well, three blocks are combined into one case 1, similar to the one shown in Fig. 1 above.
The structure is complicated and manufacturing is difficult because it is built into the magnetic head, and the disadvantages of not being able to shield the flux from the erasing magnetic head core 3 cannot be eliminated.

Furthermore, what is shown in FIG. 3 is a magnetic recording/reproducing head 9 and an erasing magnetic head 10 in which the magnetic head core 2 for recording/reproducing and the magnetic head core 3 for erasing are constructed by separate cases or resin molds, respectively. are mechanically joined together using screws 11, etc.

That is, the recording/reproducing magnetic head core 2 is fixed in one shield case 12 with epoxy resin 13 or the like.
A recording/reproducing magnetic head 9 is arranged. On the other hand, the erasing magnetic head core 3 is arranged and fixed in the case of one block 14 molded with phenol resin or the like to constitute the erasing magnetic head 10.

A tapped hole 15 is formed in the recording/reproducing magnetic head 9, and a female threaded hole 16 into which a screw 11 is screwed is formed in the erasing magnetic head 10 so as to extend in the direction of the groove. A screw 11 is inserted into the female threaded hole 16 and screwed into the tapped hole 15, thereby combining the erasing magnetic head 10 and the recording/reproducing magnetic head 9 to form one composite magnetic head device. With this configuration, each magnetic head core 2, 3 is located at the center of the head supporting surface of the magnetic tape.
The manufacturing is easy because the gaps 7 and 8 are fixed, and the tape contacting surfaces of the magnetic head cores 2 and 3 can be individually polished.

However, temporary fixing is required when joining together with the screws 11 and standing up, and since the screws 11 are then used for fixing, it is difficult to position the tape contact surface. A shield case 12 of the recording/reproducing magnetic head 9 in which a tapped hole is formed
Since the wall thickness is about 0.8 ribs, not only the twilling strength cannot be obtained, but also the accuracy will deviate. In particular, since the erasing magnetic head 10 is constituted by a resin block 14, it is subject to backlash and the like depending on temperature conditions, resulting in poor accuracy and reliability. Furthermore, since the female threaded hole 16 is drilled, a two-part mold is required. Further, in order to prevent the resin 13 from leaking from the tap hole 15 of the recording/reproducing magnetic head 9, it is necessary to fill the hole. Therefore, the present invention was devised to eliminate the drawbacks of the above-mentioned conventional methods, and it improves tape touch, facilitates manufacturing and assembly, and improves dimensional accuracy. The aim is to provide a highly reliable composite magnetic head device that ensures mechanical strength, and its gist is to provide a first magnetic head that holds a magnetic head element in a metal case, The second case holds the magnetic head element inside the resin molded case.
In a composite magnetic head device formed by integrating two magnetic heads, the mold case is embedded with an elastic metal piece having a joining protrusion on the surface where both magnetic heads are joined, and projection welding is performed. The two magnetic heads are joined and integrated by means of the above-mentioned method.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 4, 20' is a recording/reproducing magnetic head constituting the first magnetic head, which is one of the composite magnetic head devices A according to the present invention, and 21 is the other magnetic head of the composite magnetic head device A. This is an erasing magnetic head that constitutes a certain second magnetic head.

These two magnetic heads, the recording/reproducing magnetic head 20 and the erasing magnetic head 21, are each constructed separately in advance. In the above-mentioned recording/reproducing magnetic head 20', a recording/reproducing magnetic head core 23 as a magnetic head element positioned and fixed to a core block is disposed in a shield case 22 which is a metal case, and then an epoxy resin is installed. 24 or the like.

The tape contact surface 25 side of the shield case 22 is curved with a predetermined radius, and the corresponding contact surface 25 is curved with a predetermined radius.
The tape contacting surface 27 of the magnetic head core 23 facing the through hole 26 of No. 5 is polished with a grindstone and finished to exact dimensional accuracy along with the position of the gap 28 (No. 7
(see figure). On the other hand, the erasing magnetic head 21 has an erasing head core 3, which is a magnetic head element, inside a mold case 29 made of a resin mold such as phenol resin.
0, and a pair of concave portions 31, 31 and 32, 32 formed near both upper and lower ends of the molded case 29, and a metal made of a rust-free material such as 18-18 stainless steel or phosphor bronze so as to be in contact with the circumferential portions of the pair. Pieces 33 and 33 are arranged.

That is, these metal pieces 33 and 33 are inserted into a mold in advance and arranged in the mold case 29 when the mold case 29 is formed when resin molding is performed. Here, the concave portions 31, 31 and 32,
Reference numeral 32 denotes a portion where a mold for holding the metal piece in the mold is arranged, and when molded, the mold portion remains in the mold as a recess. The tape contacting surface 30a of the erasing head core 30 is finished by polishing or the like to achieve accurate dimensional accuracy. As shown in FIGS. 5a and 5b, the metal piece 33 is attached to the holding part 34 and
It consists of side walls 35, 36 formed upright on both sides of the holding part 34, and holding parts 37, 38 roughly extended and bent from these side walls 35, 36.
A bent portion 39 is formed by bending into a mountain shape at an angle of 0.00.

By forming this bent portion 39, the entire metal piece 33 is made to have elasticity. Furthermore, two or three joining protrusions 4 are provided on one side wall portion 35.
0 is formed protrudingly, and its width W is larger than the full width W2 of the molded case 29. That is, the metal piece 33 is configured to have elasticity as a whole, and the concave portions 31 and 32 of the molded case 29
Since the bent portion 39 is disposed so as to be sandwiched between the peripheral edges, the bent portion 39 may be deformed to have a U-shaped cross section or the like to have an elastic effect. Alternatively, as shown in FIG. 6, the entire structure may be formed into a prismatic shape, with bent portions 39 formed on each of the two holding portions 34, 34.

Note that three protrusions 40 may be formed to ensure stable bonding, but two protrusions 40 are also sufficient. The metal piece 33 formed as described above is molded into a molded case so that the joining protrusion 40 is located on the side where one of the magnetic heads, the recording/reproducing magnetic head 20, is located, as shown in FIG. 29.

By forming the metal piece 33 in this way, the dimensional tolerance when inserted into the mold case 29 can be absorbed by the elastic bent part 39, and furthermore, when molded with resin, the side wall of the metal piece 33 No resin is applied to 35 and 36. The recording/reproducing magnetic head 20 and the erasing magnetic head 21 configured as described above are positioned and held between one electrode 41 and the other electrode 42 as shown in FIG. At this time, the joining protrusion 40 of the metal piece 33 disposed on the erasing magnetic head 21 is positioned and aligned with one side of the shield case 22 of the recording/reproducing magnetic head 20 . When a current of several hundred amperes is passed from one electrode 41 to the other electrode 42, this current flows through the metal pieces 33, 33, the shield case 22 of the recording/reproducing magnetic head 20, and then flows to the other electrode 42. . At this time, the protrusion 40 of the metal piece 33 is melted and joined to the shield case 22 made of permalloy. By such projection welding, the recording/reproducing magnetic head 20 and the erasing magnetic head 21 are joined to form a composite magnetic head A. In order to form the composite magnetic head A by projection welding, as shown in the cross-sectional view of FIG. Furthermore, since there is no need to drill tap holes in the shield case 22 of the recording/reproducing magnetic head 20, manufacturing and assembly are facilitated.

Further, since there is no need for a screwing process, reliability in dimensional accuracy can be obtained, and a product with good combined strength can be obtained. By the way, in this way, the composite magnetic head device A
When joining the recording/reproducing magnetic head 20 and the erasing magnetic head 21, it is difficult to adjust the position of the tape contact surface 45 of each magnetic head 20 and 21.
By joining by projection welding, delicate dimensional accuracy can be accurately obtained and joining is easy.

At this time, since the erasing magnetic head 21 is not required to have exact dimensional accuracy unlike the recording/reproducing magnetic head 20, it is particularly effective for accurately hitting the tape during recording/reproducing. As described above, according to the present invention, it is easy to polish the tape supporting surface of the head core, and accurate dimensional accuracy can be achieved.

Further, by reducing the number of parts, workability such as assembly can be improved, and a highly reliable product can be obtained. In the embodiment, a magnetic head for recording/reproducing and a magnetic head for erasing are bonded together, but other two magnetic heads such as a magnetic head for recording and a magnetic head for reproducing are bonded together. Of course, it can also be applied to a composite magnetic head that joins.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views showing conventional composite magnetic heads, respectively. FIG. 4 is a front view showing a recording/reproducing magnetic head constituting one part of the composite magnetic head constituting the present invention and an erasing magnetic head constituting the other, and FIGS. Fig. 5a is a perspective view thereof, Fig. 5b is a plan view thereof, and Fig. 6 is a front view showing a metal piece according to another embodiment. . FIG. 7 is a plan view showing a state in which two magnetic heads are joined by projection welding according to the present invention, and FIG. 8 is a sectional view showing the state in which two magnetic heads are joined by the above method according to the present invention. 2
0...Magnetic head for recording/reproduction, 21...
Erasing magnetic head, 22...shield case,
29. ．．・．． ．．・Mold case, 33...Metal piece, 40...Protrusion. Figure 1 Figure 2 Figure 3 Figure 6 Figure 4 Figure 5 A Figure 5 B Figure 7 Figure 8

Claims (1)

[Claims] 1. A composite magnetic head device comprising a first magnetic head that holds a magnetic head element in a metal case and a second magnetic head that holds a magnetic head element in a synthetic resin molded case. An elastic metal piece having a protrusion for joining is embedded in the case on the surface where both magnetic heads are joined, and the two magnetic heads are joined and integrated by projection welding. Composite magnetic head device.