JP3172376B2 - Magnetic head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head incorporated in a cassette tape recorder or the like, and more particularly to a magnetic head capable of shielding externally induced noise.

[0002]

2. Description of the Related Art FIGS. 6 and 7 show an example of a magnetic head incorporated in a cassette tape recorder or the like.

In FIG. 1, a magnetic head 1 has a substantially rectangular parallelepiped box-shaped shield case 2 loaded with magnetic cores 3, 3,... For recording, reproducing and erasing. , Magnetic recording media (magnetic tape)
The tape guides 5, 5 on a plate for guiding the traveling of the vehicle 4 are attached.

[0004] The tape sliding surfaces (magnetic recording medium sliding surfaces) 3a, 3a,... Of the magnetic cores 3, 3,.
A gap is formed on each side, and a shield plate 6 is provided between adjacent magnetic cores 3. Each of the magnetic cores 3, 3,... Incorporates a coil bobbin 9 around which a coil (not shown) is wound. Further, at a portion sandwiching the gap G on the front surface of the shield case 2,
The arc-shaped grooves 7, 7 are formed. This groove 7
This is to prevent the magnetic powder from being exposed on the magnetic tape 4 and the tape sliding surface 3a to prevent spacing loss. The magnetic head 1 is provided with an attachment plate 8 for attaching the main body of the magnetic head 1 to a tape recorder or the like.

[0005]

However, in recent years, when the magnetic head having the above-described structure is incorporated in a tape recorder of a car stereo device mounted on an automobile or the like, the following problems occur. In other words, equipment such as automobiles is becoming very complicated with a large number of electronic components incorporated therein.
As a result, the number of noise sources is very large, and this noise has an adverse effect on the magnetic head.

Accordingly, the present applicant has filed a Japanese Patent Application No. Hei 1-21838.
Has proposed reducing external induction noise by covering a part of the magnetic head other than the sliding surface of the magnetic recording medium with a shield cover. The outline is shown in FIG. The shield cover 10 is made of a magnetic material such as permalloy, and includes a back plate 11, both side plates 12, 12, top plates 13, 13, and bottom plates 14, 14. By adopting this configuration, the S / N ratio can be improved by about 2 to 4 dB.

However, such an improvement in the S / N ratio is not only insufficient, but also has a problem that the man-hour and the cost are increased by attaching the shield cover.

In addition, other improvements such as increasing the thickness of the shield plate or shield case and making the magnetic permeability equal to that of the magnetic core have been conventionally performed. Not only does it cost, but also S / N
The ratio improvement was also insufficient.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and focuses on the relative positions of a magnetic core, a shield plate, and a shield case, and aims to further prevent adverse effects of external induction noise on the entire magnetic head. And

[0010]

SUMMARY OF THE INVENTION The first aspect of the present invention in order to solve the above problems, a plurality of coils are wound
And a magnetic core between each of the plurality of magnetic cores.
In a magnetic head having a shield plate housed and fixed in a shield case, the magnetic core has an outer surface facing substantially in parallel with the inner surface of the shield case, and magnetic recording from one end of the outer surface. A front surface extending toward the medium side, and a back surface extending substantially perpendicularly to the outer surface from the other end of the outer surface; a gap forming surface of the magnetic core is provided on the front surface; The length between the outer surface of the magnetic core and the inner surface of the shield case is at least 0.3 times and at most 0.75 times the length of the gap forming surface of the magnetic core and the inner surface of the shield case. Along with the length of the back of the magnetic core and the back of the shield case,
0.55 times or more and 0.8 times or less the length of the front surface of the magnetic core and the back surface of the shield case , and
Length between the outer surface of the shield plate and the inner surface of the shield case
The outer surface of the magnetic core and the inside of the shield case.
The length is 0.25 times or more and 0.75 times or less the length of the side surface .

According to a second aspect of the present invention, in order to solve the above problem, an outer surface of the shield plate and the shield case are provided.
The length of the inner surface of the magnetic core is equal to the length of the outer surface of the magnetic core.
0.3 times or more and 0.7 times or more of the length with the inner surface of the case
And below .

According to a third aspect of the present invention, in order to solve the above-mentioned problem, an outer surface of the magnetic core and a shield case are provided.
The length of the inner surface, the gap forming surface of the magnetic core the shield case inside surface and 0.4 times the length of the 0.
It is 75 times or less .

According to a fourth aspect of the present invention, in order to solve the above-mentioned problem, a back surface of the magnetic core and a back surface of the shield case are provided.
The length of the surface is equal to the length of the front surface of the magnetic core and the shield case.
The length is 0.65 times or more and 0.8 times or less the length of the back surface of the metal .

[0014]

[0015]

[0016]

According to the first aspect of the present invention, the length between the outer surface of the magnetic core and the inner surface of the shield case is increased, and the length between the back surface of the magnetic core and the back surface of the shield case is increased. Plus the outer surface and shield of the magnetic core
Approximately in the middle of the inner surface of the case, the outer surface of the shield plate
Position ensures that the adverse effects of externally induced noise
Can be prevented.

[0017]

[0018]

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1, a magnetic head 1 is provided with magnetic cores 3, 3,... For recording, reproducing, erasing and the like in a substantially rectangular box-shaped shield case 2, and the right and left sides of the shield case 2. , Magnetic recording media (magnetic tape)
The plate- like tape guides 5, 5 for guiding the traveling of the vehicle 4 are attached respectively. Each of the magnetic cores 3, 3,...
Are substantially flat with the inner surface 2b of the shield case 2, respectively.
Between the outer surface 3b and one end of the outer surface 3b
From the magnetic core 3 to the magnetic recording medium side.
Tape sliding contact surface 3a and outer surface 3b from the other end of outer surface 3b.
b and a substantially U-shaped back surface 3c extending substantially vertically.
The two halves are the end of the tape sliding contact surface 3a and the end of the back surface 3c.
Part.

[0021] In addition, each of the magnetic core 3, 3, ... are,
The sliding surface of the tape against which the halves were joined (the sliding surface of the magnetic recording medium)
Surface) gaps are formed between 3a, 3a,...
End portions of the tape sliding surfaces 3a, 3a,...
Are the gap forming surfaces 3d of the magnetic core 3. A shield plate 6 is provided between adjacent magnetic cores 3. Each of the magnetic cores 3, 3,... Incorporates a coil bobbin 9 around which a coil (not shown) is wound.

In the present invention, the positional relationship among the magnetic core 3, the shield plate 6, and the shield case 2 is set as follows.

The length (x) of the outer surface 3b of the magnetic core 3 and the inner surface 2b of the shield case 2 is the length (L1) of the gap forming surface 3d of the magnetic core 3 and the inner surface 2b of the shield case 2. 0.3 times or more, and preferably 0.4 times or more.

The length (y) of the back surface 3c of the magnetic core 3 and the back surface 2c of the shield case 2 is 0.55 of the length (L2) of the front surface 3a of the magnetic core 3 and the back surface 2c of the shield case. Times or more, preferably 0.65 times or more.

Further, the length (s) between the outer surface 6b of the shield plate 6 and the inner surface 2b of the shield case 2 is
The length (x) of the outer surface 3b of the magnetic core 3 and the inner surface 2b of the shield case 2 is set to 0.25 to 0.75 times, preferably 0.3 to 0.7 times. .

FIG. 3 shows the magnetic head shown in FIGS. 1 and 2 when the position of the outer surface of the magnetic core is changed in the X direction when the shield case and the shield plate are kept at the conventional positions. It shows the output result of the external induction noise. The measuring method measures the noise output in a uniform magnetic field of 3 kHz and 1.5 Oe on the outer channel 1 or 4 out of the magnetic heads for 4 tracks and 4 channels. In the conventional magnetic head, the length (x) between the outer surface 3b of the magnetic core 3 and the inner surface of the shield case 2 is very small, for example, x is about 0.15L1, so that the external induction noise is -4.
It was about 5 dBV. Further, even if the shield cover as shown in the conventional example is attached, the improvement can only be made up to about -48 dBV. However, in the present invention, external induction noise can be greatly improved by increasing x. For example, in order to improve the magnetic head to a level equivalent to that of a magnetic head having a conventional shield cover, x may be set to about 0.3L1.
Is set to 0.4L1 or more, a sufficiently satisfactory magnetic head for car stereo can be obtained. However, since it is necessary to secure a minimum winding space for the coil wound around the coil bobbin, it is preferable that x be 0.75 L1 or less. At this time, by reducing the size of the magnetic core 3 without changing the size of the shield case 2 from that of the related art, the magnetic path length as a magnetic circuit is reduced, and the reproduction efficiency is improved. Therefore, as the noise is reduced, the number of turns of the coil can be reduced, thereby further improving the S / N ratio dramatically.

FIG. 4 shows the magnetic head shown in FIG. 1 and FIG. 2 when the shield case and the shield plate are kept at the conventional positions and the position of the back surface of the magnetic core is changed in the Y direction. It shows the output result of the induction noise. The measuring method measures the noise output in a uniform magnetic field of 3 kHz and 1.5 Oe on the outer channel 1 or 4 out of the magnetic heads for 4 tracks and 4 channels. In the conventional magnetic head, the length (y) of the back surface 3c of the magnetic core 3 and the back surface 2c of the shield case 2 is small.
Since it was about 2, the external induction noise was about -45 dBV. Further, even if the shield cover as shown in the conventional example is attached, the improvement can only be made up to about -48 dBV. However, in the present invention, y
, The external induction noise can be greatly improved. For example, to improve the magnetic head to a level equivalent to that of a magnetic head having a conventional shield cover, y may be set to about 0.55L2, and y may be set to 0.6.
If it is 5L2 or more, a sufficiently satisfactory magnetic head for car stereo can be obtained. However, since it is necessary to secure the minimum winding space of the coil wound around the coil bobbin, it is desirable that y is 0.8L2 or less. At this time, by reducing the size of the magnetic core 3 without changing the size of the shield case 2 from that of the conventional case, the magnetic path length as a magnetic circuit is reduced.
The regeneration efficiency is improved. Therefore, the number of coil turns can be reduced with a reduction in noise, thereby further reducing S
/ N ratio can be dramatically improved.

Here, from the results of FIGS. 3 and 4, the cause of the contribution of the position of the magnetic core to the improvement of noise can be considered as follows. Conventionally, noise has been improved by changing the thickness or material of the shield plate or shield case, or providing another shield member inside or outside the magnetic head. Therefore, little consideration has been given to the position of the magnetic core in the shield case, and in order to ensure the maximum reproduction sensitivity, the number of turns of the coil must be about 1000 turns. I needed to make it bigger. However, when the magnetic core approaches the shield case side, noise passing through the shield case flies to the magnetic core, and the shielding effect is reduced. Therefore, it is considered that the noise flying to the magnetic core can be reduced by increasing the distance between the shield case and the magnetic core.

FIG. 5 shows the magnetic head shown in FIGS. 1 and 2 when the position of the outer surface of the shield plate is changed in the X direction when the shield case and the magnetic core are kept at the conventional positions. It shows the output result of the external induction noise. The measuring method measures the noise output in a uniform magnetic field of 3 kHz and 1.5 Oe on the outer channel 1 or 4 out of the magnetic heads for 4 tracks and 4 channels. In the conventional magnetic head, the outer surface 3b of the magnetic core 3 and the outer surface 6b of the shield plate 6 are provided at substantially the same position. For example, since s is substantially equal to x, the external induction noise is -45 dBV. It was about. Further, even if the shield cover as shown in the conventional example is attached, the improvement can only be made up to about -48 dBV. However, in the present invention, external induction noise can be greatly improved by making s somewhat smaller than x. For example,
To improve to the same level as a magnetic head with a conventional shield cover, s should be from 0.25x to 0.75x
S may be set to about s, and s may be increased from 0.3x to 0.7.
With x, a sufficiently satisfactory magnetic head for a car stereo can be obtained. More preferably, s is set to 0.1.
It is desirable to set to about 5x.

Here, the reason why the position of the shield plate has contributed to noise reduction can be considered as follows. First, when the shield plate is moved closer to the shield case, the amount of noise passing through the shield plate increases, and the amount of noise passing through the magnetic core decreases. This has been conventionally considered. However, if the shield plate is too close to the shield case side, the magnetic resistance decreases when viewed from the entire magnetic head, so that the amount of noise applied to the entire magnetic head increases, resulting in noise passing through the magnetic core. It is thought that the amount of will increase.
Therefore, as described above, if s is changed from 0.3x to 0.7x, a sufficiently satisfactory magnetic head for car stereo can be obtained. More preferably, s is set to about 0.5x. It would be desirable.

In the present invention, when the shield case and the shield plate are kept at the conventional positions, the position of the outer surface of the magnetic core is changed in the X direction, or the shield case and the shield plate are kept at the conventional positions. When the position of the back surface of the magnetic core is changed in the Y direction, or the position of the outer surface of the shield plate is changed in the X direction when the shield case and the magnetic core are kept at the conventional position. However, the present invention is not limited to this, and the external induction noise is improved by the ratio of each length. Therefore, for example, in the experimental results of FIG. 3, when the position of the inner surface of the shield case is changed in the X direction when the magnetic core and the shield plate are kept at the conventional positions, the results shown in FIG. Similar results are obtained.

In the present invention, the relationship between the length of the outer surface of the magnetic core and the inner surface of the shield case and the length between the gap forming surface of the magnetic core and the inner surface of the shield case, The relationship between the length of the shield case back and the length of the front of the magnetic core and the back of the shield case, or the length of the outer surface of the shield plate and the inner surface of the shield case, and the outer surface of the magnetic core and the shield case The relationship between the inner surface and the length has been described. By combining these relationships in various ways, the magnetic head is configured in an optimal positional relationship, thereby providing an excellent magnetic head against external induction noise. Of course you can.

[0033]

According to the magnetic head of the present invention, the length between the outer surface of the magnetic core and the inner surface of the shield case is equal to the length between the gap forming surface of the magnetic core and the inner surface of the shield case. The length between the back of the magnetic core and the back of the shield case is at least 0.55 times the length of the front of the magnetic core and the back of the shield case, or By setting the length between the outer surface of the shield plate and the inner surface of the shield case to be 0.25 to 0.75 times the length of the outer surface of the magnetic core and the inner surface of the shield case, Either the length between the outer surface and the inner surface of the shield case is longer, or the length between the back of the magnetic core and the back of the shield case is longer, or the outer surface of the magnetic core and the inner surface of the shield case. Almost in the middle between the shield Outer surface of the is located. This allows
Noise reduction equivalent to that of a magnetic head with a conventional shield cover attached can be performed by the magnetic head body. Therefore, not only does the man-hour for mounting the shield cover be reduced, but also the manufacturing cost can be reduced, and a magnetic head excellent in mass productivity can be provided.

According to the magnetic head of the present invention, the length between the outer surface of the magnetic core and the inner surface of the shield case is 0.4 times the length between the gap forming surface of the magnetic core and the inner surface of the shield case. The length between the back of the magnetic core and the back of the shield case is at least 0.65 times the length of the front of the magnetic core and the back of the shield case,
Alternatively, by making the length between the outer surface of the shield plate and the inner surface of the shield case 0.3 to 0.7 times the length of the outer surface of the magnetic core and the inner surface of the shield case,
Further, noise can be improved. Thereby, a sufficiently satisfactory magnetic head for a car stereo can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a magnetic head according to the present invention.

FIG. 2 is a diagram showing a positional relationship among a magnetic core, a shield plate, and a shield case according to the embodiment of the present invention.

FIG. 3 is an output result of external induction noise when the position of the outer surface of the magnetic core is changed in the X direction when the shield case and the shield plate are kept at the conventional positions in the present invention. FIG.

FIG. 4 shows output results of external induction noise when the position of the back surface of the magnetic core is changed in the Y direction when the shield case and the shield plate are kept at the conventional positions in the present invention. It is a graph shown.

FIG. 5 is an output result of external induction noise when the position of the outer surface of the shield plate is changed in the X direction when the shield case and the magnetic core are kept at the conventional positions in the present invention. FIG.

FIG. 6 is a perspective view showing a conventional magnetic head.

FIG. 7 is a sectional view showing a conventional magnetic head.

FIG. 8 is a perspective view showing another conventional magnetic head.

[Explanation of symbols]

 Reference Signs List 1 magnetic head 2 shield case 2b inner surface of shield case 2c back surface of shield case 3 magnetic core 3a front surface of magnetic core 3b outer surface of magnetic core 3c back surface of magnetic core 3d gap forming surface of magnetic core 6 shield plate 6b shield plate Outer surface

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 5/10-5/115

Claims (4)

(57) [Claims] A plurality of magnetic cores each having a coil wound thereon, and a plurality of magnetic cores interposed between each of the plurality of magnetic cores.
A magnetic plate , wherein the magnetic core has an outer surface facing the inner surface of the shield case in a state substantially parallel to the inner surface of the shield case, and one end of the outer surface facing the magnetic recording medium. And a back surface extending substantially perpendicularly to the outer surface from the other end of the outer surface, wherein a gap forming surface of the magnetic core is provided on the front surface, and the magnetic core The length between the outer surface of the magnetic core and the inner surface of the shield case is not less than 0.3 times and not more than 0.75 times the length of the gap forming surface of the magnetic core and the inner surface of the shield case. The length between the back surface of the magnetic core and the back surface of the shield case is not less than 0.55 times and not more than 0.8 times the length of the front surface of the magnetic core and the back surface of the shield case; Outside of the board
The length between the surface and the inner surface of the shield case is
The length between the outer surface of the core and the inner surface of the shield case
It is characterized by being not less than 0.25 times and not more than 0.75 times.
Magnetic head. 2. An outer surface of the shield plate and the shield.
The inner surface of the case is longer than the outer surface of the magnetic core.
0.3 or more times the length with the inner surface of the shield case.
The magnetic head of claim 1, wherein Rukoto Do and 7 times or less. 3. The gap between the magnetic core and a length between an outer surface of the magnetic core and an inner surface of the shield case is formed.
0.4 more than double the length of the surface and the inner surface of the shield case
2. The magnetic head according to claim 1 , wherein the ratio is 0.75 times or less . 4. A back surface of said magnetic core and said shield case.
The length of the back surface of the magnetic core is equal to the length of the front surface of the magnetic core.
0.65 times or more and 0.8 times or less the length of the back of the case
2. The magnetic head according to claim 1, wherein: