JPS58130422A - Magnetic head - Google Patents

Abstract

PURPOSE:To prevent contour phenomena in low frequencies by making the length from the center of the gap of a magnetic head up to the end of the magnetic pole with which a magnetic tape can contact slidingly at the upper stream part and the down stream part, different. CONSTITUTION:The length l1 and l2 of right and left cores 11, 12 of the gap 10 of a playback head at which the cores can contact slidingly with tapes are made different and the ratio l2/l1 is set to roughly 1.7-2.1, for example, 2. Thus, the contour phenomena which are waving phenomena generated in the stage of reproduction with low ferquencies, that is, long wavelengths are prevented effectively. More particularly, good results are obtained by setting the ratio l2/l1 roughly at 2; therefore, the utilization of said head to small-sized apparatus is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic head, and by configuring the magnetic head where the magnetic tape slides in sliding contact, the left and right lengths of the center gap of the magnetic head are configured to be different. It is an object of the present invention to provide a magnetic head that can effectively suppress the contour phenomenon, which is a waving phenomenon, has a good S, and can be sufficiently miniaturized.

In general, when reproducing a low frequency signal with a long recording wavelength, for example, a frequency of about 20 to 100 Hz, a contour phenomenon occurs in a reproducing head, which is a phenomenon in which the reproducing output waves.

This phenomenon is caused by the relationship between the length g of the portion where the core 1 of the magnetic head and the magnetic tape 2 make sliding contact and the recording wavelength λ of the magnetic tape 2. , if the number is an odd number...(1), the playback output corresponds to the crest of the wave, and if the number is an even number...(2), the playback output corresponds to the trough of the wave. Concave and convex waves are generated as the reproduction output of the magnetic head. That is, such a relationship can be qualitatively explained as shown in FIG. 2. Similarly, the value of such unevenness is that λ is smaller than λ at ′, but this is because the range of magnetic flux emitted from the magnetic tape becomes smaller as the wavelength becomes shorter.

In the case of a combination head for a cassette tape recorder, in which the recording head and the playback head are integrated, the core length of the playback head cannot be made sufficiently long due to space constraints, so the contour phenomenon is likely to occur. It becomes.

Conventionally, the following measures have been taken to deal with such a contour phenomenon. That is, the above (1), (2
) In order to disturb the relationship expressed by the equation ( ), a method called the so-called The cutting method or the cutting method requires complicated processing on the magnetic helad core, so in practice it is only used in special core assembly methods, and it is expensive. There is.

In addition, by increasing the core length of the magnetic head and configuring the tip of the shield case into a hyperpolished shape, the actual contact length between the magnetic tape and the core of the magnetic head can be reduced, and (11, (2) Some proposals have been made to blur the relationship shown by the formula, but if the core length is increased, the window of the shield case must be made larger;
This is undesirable because it becomes susceptible to the influence of externally induced magnetic fields, which requires measures such as double shielding. Furthermore, it is not possible to reduce the size to that extent. Furthermore, wear caused by friction with the magnetic tape causes distinct edges to appear in the magnetic helad core, and a contour phenomenon that satisfies equations (1) and (2) clearly occurs.

The present invention eliminates the above-mentioned drawbacks, and examples thereof will be described below.

FIG. 3 is an explanatory diagram of a main part of one embodiment of the magnetic head according to the present invention.

In the figure, 10 is the gap of the playback head, 11°1
2 are the cores on the left and right sides of this gap 10. The shape of the tip of the core 11, 12 on the side of the magnetic tape sliding contact surface is configured to allow the magnetic tape to slide in close contact with the magnetic tape, and the length of the sliding contact surface with the magnetic tape is adjusted to a smooth shape. That is, the length tl from the center of the gap 10 to the side edge of the core 11.12,
72 is about 1.7 to 2.1, for example 12.

Next, it will be explained that the magnetic head configured as described above is effective in suppressing the contour phenomenon.

Now, if we consider the case of a magnetic head as shown in Fig. 1, let Hx be the strength of the magnetic field generated from the magnetic core in the magnetic tape running direction (X direction) during recording.
Hx is expressed as a function of X, and if Hx is qualitatively illustrated, it will be as shown in FIG. In other words, the magnetic field near the gap is the strongest, and the magnetic field near the middle of the core is O
Therefore, the magnetic field near the end of the core is not 0, but has a small value that is the opposite of the magnetic field near the gap. Furthermore, when the relationship in equation (1) is satisfied during playback, the magnetization Ix in the X-axis direction of the magnetic tape is as shown in FIG. 5, and the polarity of magnetization near the gap and the end of the core are Nearby polarities are in opposite phase.

According to the reciprocity theorem, the total magnetic flux Φ interlinking with the reproducing coil is ΦHef■X−HxdX...(3)
Since the output of the reproducing head is represented by π, the larger the maximum value of Φ, the larger the output of the reproducing head.

Here, if we perform the integration of equation (3) taking into account the strength of the magnetic field Hx of the magnetic head and the polarity of the magnetization Ix of the magnetic tape, we find that Hx and Ix near the end of the core are in phase, so we get The integral value of the portion due to these becomes positive, increasing the integral value near the gap, that is, the main integral value, and the reproduced output exhibits a convex shape. In other words, this corresponds to case No. 1 in Figure 2.

In addition, in the case of calf 2, the magnetization Ix is as shown in FIG. 6, so Hx near the end of the core and 1
．． The relationship is in reverse phase with x, and the integral value of the portion due to these becomes negative, decreasing the main integral value, and the reproduced output exhibits a concave shape. That is, this corresponds to the case of g-8=λ 2 in FIG.

However, as in the above embodiment, core 1
For example, if the ratio of the length to the side edge of 1.12 is 2, Hx will be as shown in Figure 7, and
λ in the case of
If λ is set to Ix (A2=”, then Figs.
When considering the integral value of equation (3), it has the following tendency.

In other words, in case No. 1, the main integral value near the gap and the integral value contributed by the right half core 12 are the same as in the above case, but the value near the end of the left half core 11 is the same as the above case. Since Ix is extremely small and close to 0, there is almost no contribution from the integration near the end of the core 11, and the positive increase in the main integral value is halved. The main integral is the same as in the above case, and the integral value contributed by the right half of the core 12 is H.
Since x and Ix are in opposite phase, it appears as a negative value, but the integral value contributed by the left half core 11 is 1-
1 Since x and Ix are in phase, it appears as a plus,
As a result, the positive and negative parts cancel each other out, leaving only the main integral value. In other words, even if x is 1, and x is 2, λ
Even with λ, the degree of unevenness is small, indicating that the contour phenomenon can be effectively suppressed.

FIG. 8 is an explanatory diagram of another embodiment of the magnetic head according to the present invention.The structure in which the balls are about 1.7 to 21, for example 2 and 1, is the same as the structure of the above embodiment, but the core The only difference is the shape.

That is, 20 is a gap, and 21.22 are cores on the left and right sides of this gap 20.

Therefore, if the ratio of the lengths tl and t2 from the center of the gap 20 to the side edges of the core 21 and 22 where the magnetic tape can come into sliding contact is 2, the t□ contour phenomenon will be effective for the same reason as above. It can be suppressed.

FIG. 9 is an explanatory diagram when the magnetic head according to the present invention is used in a combination head.

In the figure, 30 is a recording head, 31 is a reproduction head,
The recording head 30 and the reproducing head 31 are separated by an interval ω (for example, 1
．． 8 fights or less].

32 is a gap of the reproducing head 31, and there are cores 33 and 34 on the left and right sides of this gap 31, and these cores 33.
Sliding length A1r of the tape running surface of No. 34 in the tape running direction
The relational expression stated in the above example is approximately 1.7.
~2.1, for example, 2, and the core 33 is provided on the side closer to the recording head 30 side.

35 is a magnetic tape, and 36 is a shield case.

For example, t□-0.15mm, l-2=0.3m
When the contour phenomenon is measured in the case where the contour effect is 2.m, as shown in FIG. It was possible to suppress it to within OdB. In the figure, the solid line shows the one according to the present invention, and the one-dot chain line shows the one when t+ = L2 = 0.3 mm.

By configuring the device so that the blood density was approximately 1.7 to 2.1, the contour phenomenon could be suppressed to the extent that it did not pose a practical problem.

As described above, in the magnetic head according to the present invention, the magnetic head core is configured such that the lengths from the center of the gap of the magnetic head to the pole tips on the left and right sides of the gap where the magnetic tape can slide are different, so that when reproducing a large recording wavelength, By the way, it is now possible to effectively suppress the contour phenomenon, which causes waves in the reproduced output.This contour phenomenon can be suppressed even by shortening the core length, making it possible to miniaturize the magnetic head, and to make it easier to store the magnetic head. Since the window of the shielding case can be made smaller, leakage magnetic flux from external devices such as power transformers and motors can be effectively shielded, and there is no reduction in S, and furthermore, in the case of a combination head with little space. The contour phenomenon can be suppressed simply by setting the length ratio to 2, for example, and there is no harm in shortening the core length of the playback head, so it is an extremely effective method in the case of a combination head, and it also eliminates the troublesome processing. It has the advantage that it can be manufactured extremely easily and at low cost since it does not require any additional processing.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of a conventional magnetic head, and Figure 2 is a contour diagram.
FIG. 3 is an explanatory diagram of the main part of an embodiment of the magnetic head according to the present invention, and FIGS. 4 to 7 are diagrams showing how the configuration of the magnetic head according to the present invention effectively suppresses the contour phenomenon. An explanatory diagram for explaining what can be done, FIG. 8 is an explanatory diagram of the main part of another embodiment of the magnetic head according to the present invention, and FIG. 9 is an explanatory diagram of the magnetic head according to the present invention when applied to a combination head. An explanatory diagram, FIG. 10, is an explanatory diagram of contour characteristics. 14! , 12.21.22.33.34...core,
10.20.32... Gap, 35... Magnetic tape. Patent applicant: Japan Victor Co., Ltd. Agent: Katsu Utaka: Self-1. Figure 4 Hx Figure 5 I Figure 6 Iχ Figure 7 h Figure 8 Figure 9

Claims (1)

[Claims] A magnetic head characterized in that a magnetic head core is configured such that the lengths from the center of the gap of the magnetic head to the pole tips on the left and right sides of the gap where the magnetic tape can slide are different.