JPS624768B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic head suitable for use in audio cassette tape decks, etc. More specifically, the present invention relates to a magnetic head suitable for use in audio cassette tape decks, etc. This invention relates to a composite magnetic head arranged close to the top of the head, a so-called recording-playback combination head (hereinafter referred to as an R&P combination head).

The design of this kind of R&P combination head,
One of the technical problems in manufacturing is the crossfeed, that is, leakage of magnetic flux from the recording head element to the reproduction head element.

When the playback function is operated to determine whether or not magnetization is present on the tape during recording, if the crossfeed is large, the output NCF from the crossfeed becomes the damage prevention output in contrast to the playback output S due to the magnetization on the tape.
Especially for audio, NCF is
It is required to be smaller than 50dB.

1 and 2 are drawings showing a conventional R&P combination head which has been put into practical use by the present applicant and has solved the problems of the crossfeed, etc., in which FIG. 1 is a front view and FIG. 2 is a front view. It is a schematic sectional view of the main part. The structure will be explained below based on the drawings. In the drawings, reference numeral 10 denotes a recording head element, which includes recording head cores 11, 11 made of ferrite. head core 1
1 and 11 are composed of a front core 111 formed with gaps 113 and 113 and rear cores 112 and 112 formed with coils 114 and 114 wound, and these cores are held by a core holder 12. . 13 is head core 11, 11
A shield plate for the channel is interposed between, 14 is a triple shield tube made of permalloy that houses these recording parts, 15 is a cylindrical shield case that further houses it, 16 is a shield tube; This is a dummy core made of ferrite inserted into a space formed by the head cores 11, 11. 20 indicates a reproducing head element;
The head element includes reproducing head cores 21, 21 made of ferrite. head core 21,
21 is composed of a front core 21 formed with gaps 213, 213 and rear cores 212, 212 formed with coils 214, 214 wound thereon, and these cores are held by a core holder 22. 23 is a channel shield plate interposed between the head cores 21, 21, 24 is a triple shield tube made of permalloy that houses these recycled parts, 25 is a cylindrical shield case that further houses the same, 26, 26 is a dummy core made of ferrite inserted into the space formed by the shield tube 24 and the head cores 21, 21. 30 is a cylindrical shield case that houses the cases 15 and 25. Here, the recording gap 113
and gap spacing (dimensions) of playback gap 213
l ₁ is set to 3.4mm. This 3.4mm consists of recording head core 11 and playback head core 2.
The width dimensions l ₂ and l ₃ of 1 are each 0.7 mm, the space for intervening the shield tubes 14 and 24 and the shield cases 15 and 25 is 1.0 mm, and the space for interposing the head core holders 12 and 22 is 1.0 mm. The total space for avoiding contact between the shield tubes 14 and 24 and the head cores 11 and 21 is 0.5 mm on both the recording and playback sides.

When recording or playing back on the magnetic tape 40 in such an R&P combination head, in order to ensure good recording and playback, that is, to suppress level fluctuations, both the recording gap 113 and the playback gap 213 should be connected to the tape 40. It is important to have close contact with the

Contact between the two gap and the tape is generally made by crimping a pad 50 made of felt material placed in the head insertion window of the cassette. The dimension L of this pad 50 in the tape running direction is determined by the standard to be 2.0 mm or more. Depending on the cassette, there are pads that are smaller than the gap spacing l ₁ (3.4 mm). Here, if the dimension L of the pad 50 is smaller than the gap interval l ₁ (3.4 mm), the pad 50
It is difficult to make close contact between the tape 40 and both the gap by using the chisel.

Therefore, in the past, capstans and pinch rollers were placed on both the tape feeding side and the tape winding side to ensure good contact between the tape and the gap even for such pads, and these were used to apply tension to the tape. Alternatively, tension was applied to the tape by applying a pad on the tape's unwinding side through the friction.

However, the former method makes the tape recorder expensive, and the latter method tends to cause deterioration such as wow and flutter.

From the standpoint of tape contact in the R&P combination head, it is desirable that the recording/playback gap distance _l1 and the pad dimension L satisfy the relationship l<L.

In the R&P combination head structure, the front core 11 of the head cores 11, 21
Width dimensions of core pieces 111b and 211b of 1,211
Reduce l ₂ and l ₃ and set the gap distance l ₁ to 50 pads.
If it is smaller than the minimum dimension L (2 mm), the width dimensions l ₂ and l ₃ of the core pieces 111b and 211b will be 0.3 mm at maximum.
In this case, the core piece 11 near the center of the front cores 111, 211 in FIG.
The contact area between the opposing legs of the rear cores 1b, 211b and the rear cores 112, 212 is about half that of the conventional one, and from the viewpoint of processing accuracy and assembly accuracy, a minute gap cannot be avoided at the joint, and this part This causes problems such as increased magnetic resistance and increased dispersion, resulting in decreased recording and playback efficiency.

Therefore, as a means to solve the increase in magnetic resistance, as shown in FIG.
A step B is provided on the gap side surface of b', 211b' to reduce the gap interval _l1 , and the front core 1
An attempt was made to manufacture one in which the abutting areas of the abutting (or overlapping) portions A and A of the rear cores 11 and 211 and the rear cores 112 and 212 were kept the same as before.

However, when a step B is provided in the front core 111, 211 forming the head gap 113, 213 in this way, it is very difficult to polish that surface. Also, the front core 1 forming the gaps 113, 213
11, 211 core pieces 111a, 211a and 11
It is necessary to polish the gap surfaces with 1b' and 211b' and ensure their parallelism with high precision. Otherwise, the gap length will become uneven, and the azimuth loss between the recording head and the playback head will become large, making it impractical. Unable to obtain R&P combination head.

Therefore, in order to correct the above problem, the present inventors
The combination head shown in FIGS. 4 and 5 was considered. The structure will be explained below based on the drawings. FIG. 4 is a front view of the R&P combination head, and FIG. 5 is a schematic sectional view of its essential parts. In this figure, the same parts as in FIGS. 1 to 3 are given the same numbers, and detailed explanation thereof will be omitted.

The recording head core 11 and the playback head core 21 are connected to front cores 111 and 21, respectively.
1 and rear cores 112 and 212. The front cores 111 and 211 include two core pieces 111a, 111b and 211a, 211b forming the recording gap 113 and the playback gap 213, and one of the core pieces 111.
The core pieces 111c and 211c are bonded to the inner surfaces of the core pieces 111c and 211b as shown in the figure. Core pieces 111c and 211c are rear core 1
Gap 11 from the butting surfaces A and A of 12 and 212
It has an elongated shape extending in 3,213 directions.
Reference numerals 17 and 27 indicate shield cases that house the head cores 11 and 21, respectively, and the shield cases are formed into a U shape by drawing. The head core 1 is mounted on the front of the shield cases 17 and 27.
Windows 171, 27 for exposing part of 1, 21
1 is formed.

In such an R&P combination head, cases with a plate thickness of 0.2 mm are used as the shield cases 17 and 27, and the dimensions l ₂ and l ₃ of the core pieces 111b and 211b of the front cores 111 and 211 are set to 0.4, respectively.
mm, and the dimensions of the core pieces 111c and 211c are l ₄ and l ₅
When the playback efficiency was measured with each head set to 0.3 mm, it was possible to obtain recording and playback efficiencies approximately equivalent to those of the R&P combination head shown in FIGS. 1 and 2. Although the dimensions l ₂ and l ₃ of the core pieces 111b and 211b of the front cores 111 and 211 are smaller than those of the conventional R&P combination head, there is one core piece on the side of the core pieces 111b and 211b.
11c and 211c are provided, and the front core 11
1,211 and the rear cores 112, 212 are enlarged, and the core pieces 111c, 211c are
This is because the core has an elongated shape extending in the direction of the gaps 113 and 213 to prevent the magnetic resistance of the core from increasing. It was also confirmed that the level fluctuation could be improved. Specifically, when we measured the level fluctuation for high frequency (10kHz), it was 2 to 3 dB according to the R&P combination head shown in Figs. 1 and 2, but the R&P combination head shown in Figs. 4 and 5 was
According to the &P combination head, it was possible to suppress the noise to less than 1 dB. This is recording gap 113
This is based on the fact that the gap interval _l1 of the reproduction gap 213 is made small. Furthermore, by making the plate thickness of the shield cases 17 and 27 even smaller, and by making the dimensions l ₂ and l ₃ of the core pieces 111b and 211b even smaller, the gap distance l ₁ can be further reduced, specifically down to 1.4 mm. succeeded in doing so.

It goes without saying that FIGS. 4 and 5 can also be applied to the R&P combination head having the shield structure shown in FIGS. 1 and 2.

As mentioned above, the R&P shown in Figures 4 and 5
According to the combination head, since the gap between the recording gap and the playback gap is narrowed, the contact between the two gap and the tape by the tape pad is better than that of the R&P combination head shown in Figs. 1 and 2. This can be done reliably, and improvements such as level fluctuations can be measured.
In addition, as shown in Figures 4 and 5, even though the above-mentioned gap spacing is reduced, the abutment area between the front core and rear core remains large, so the magnetic resistance can be kept small and the recording and playback efficiency of the head can be improved. It has the advantage of being able to prevent a decline in

It is an object of the present invention to correct the above-mentioned problems, to enable both the recording and playback gaps to be in good contact with the tape without providing a mechanical tape tensioning mechanism, to improve level fluctuations, and to improve recording and playback efficiency. To provide a method for manufacturing an R&P combination head that has good performance and is easy to manufacture.

An embodiment of the present invention will be described below based on the drawings. FIG. 6 is a process diagram showing the manufacturing process of the front core of the R&P combination head of the present invention. First, as shown in FIG. 6a, three rectangular head core materials 100, 200, and 300 are prepared, and the thickness of the head core materials 100, 200 is measured from one side of two of the head core materials 100, 200 near the remaining head core material 300. Slanted grooves 101, 20 extending in the direction and toward the rear surface, that is, the surface opposite to the tape (medium) running surface (the abutting portion with the rear core)
1, and these are adhered to the remaining head core material 300 with an adhesive, such as glass, as shown in FIG. 6a to form one front core block.
As a result, recording gap 102 and playback gap 2
02 is formed. Next, the surface of the core block on the gap 102, 202 side that will become the front media running surface is ground into a W shape as shown in FIG. 6b. Although the core block is ground into a W-shape here, the grinding shape does not have to be W-shape, and this step may be omitted. Next, the three head core materials of the core block 10
Channel shield plate insertion grooves 123 are formed at 0, 200, and 300, and shield case insertion grooves 301 are formed in the head core material 300 at the center, as shown in FIG. As shown in FIG.
Grooves 103, 203 are formed extending substantially perpendicularly to the front surface, that is, the surface that becomes the medium running surface, so as to connect to the grooves 01. Next, the front cores 111 and 2 are cut along the dashed line in FIG. 6c, and as shown in FIG.
11 is formed. Thereafter, the U-shaped rear cores 112, 212 formed separately from the front cores are butted against the rear portions of the front cores 111, 211 as shown in FIG. 6e, and these head cores are stored in a shield case, and then the head cores are The front surface of the tape is polished to form a tape sliding surface and the R&P
Complete the combination head.

According to the method for manufacturing a front core of the present invention described above, there is no need to provide a step in the head core material, so that workability is improved and a uniform gap can be formed. This provides a high quality, low cost R&P combination head.

[Brief explanation of the drawing]

Fig. 1 is a front view of a conventional R&P combination head, Fig. 2 is a schematic sectional view of the main part thereof, Fig. 3 is a schematic sectional view of the main part of the R&P combination head showing another example of the conventional one, and Fig. 4 is a schematic sectional view of the main part of the R&P combination head. 5 is a front view of an R&P combination used for explaining the present invention, FIG. 5 is a schematic sectional view of the main part thereof, and FIG.
FIG. 3 is a process diagram showing the manufacturing process of a front core of a combination head. DESCRIPTION OF SYMBOLS 10... Head element for recording, 11... Head core for recording, 20... Head element for playback, 21... Head core for playback, 111, 211... Front core, 11
2,212...Rear core, 111a, 111b, 1
11c, 211a, 211b, 211c... core piece, 17, 27... shield case.

Claims (1)

[Claims] 1. A recording head core formed by butting together a front core forming a recording gap and a rear core around which a coil is wound, and a playback head core formed by butting a front core forming a playback gap and a rear core around which a coil is wound. In a method for manufacturing a composite magnetic head, in which head cores are arranged close to each other on the same track and both of the head cores are separately shielded, first, second and third rectangular head core materials are arranged. An inclined groove is formed on one side of the second rectangular head core material on the side of the third rectangular head core material, extending from the vicinity of the gap in the thickness direction of the first and second rectangular head core materials and toward the abutting portion with the rear core. a step of joining the first and second head core materials to both sides of the third head core material with their inclined grooves inside to form one front core block; Step 3 of forming a groove for inserting a shield case in the head core material, and forming a groove extending substantially perpendicularly to the surface that will become the medium running surface so as to connect to the inclined groove from the abutment part of the front core block with the rear core. , a step of dividing the first and second head core materials together with the inclined groove into two and integrally forming one of them on one side of the third head core material; and cutting the front core block to a predetermined head thickness. At the same time, a step of dividing the front core block into two, a recording front core and a playback front core, by cutting the connecting piece formed in the front core block by the shield case insertion groove, and separating the recording front core and the playback front core. A process of butting a recording rear core and a reproduction rear core against the rear of a recording front core and housing the recording head core and reproduction head core in separate shield cases, and cylindrical polishing and tape sliding of the front surface of the front core. A method for manufacturing a composite magnetic head comprising a step of forming a surface.