JPH0114992Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a magnetic head used in magnetic recording and reproducing devices such as video tape recorders, and is particularly concerned with the generation of beats and the like caused by the intrusion of external radio waves such as medium-wave AM broadcast radio waves. The aim is to improve this.

Conventionally, a magnetic head 1 used in a magnetic recording/reproducing device such as a video tape recorder, as shown in FIG. A winding method using so-called balance winding in which coils 7, 7 are wound with the same number of turns on each core half 2, 4 of a head chip 6 formed by abutting the half body 4 with the gap surface 5 through the gap surface 5, respectively. It is structured accordingly.

When the external radio wave intrusion characteristics of the magnetic head 1 configured as described above were measured using a measurement system configured as shown in FIG. has a directional dependence as shown by the solid line A in FIG.

In the system for measuring the characteristics of external radio waves, a magnetic head 1 to be measured is attached to a rotating drum 9 for a video tape recorder which is rotationally driven by a motor 8. The distance r from this magnetic head 1 is approximately 56 cm.
A transmitting antenna 10 made of a copper wire wound nine times with a diameter of 1 mm is installed at a distance, and an external radio wave with a frequency of 693 KHz is transmitted from a transmitter 11 via this antenna 10. Then, while the magnetic head 1 is being rotated, the external radio wave that enters the magnetic head 1 is measured by a spectrum analyzer 13 through an amplifier 12.

As is clear from FIG. 3, the intrusion characteristics of external radio waves of the conventionally used magnetic head 1 measured by the measurement system described above are based on the abutting surfaces of the core halves 2 and 4. When it is a line, the input level of the external radio wave coming in from the 45 degree direction on the other core half 4 side where the notch recess 3 is formed is 10 db compared to the input level of the external radio wave coming in from the 45 degree direction on the one core half 2 side. This also causes significant differences depending on the input direction of external radio waves. As described above, the conventional magnetic head 1 has a significant directional dependence on the input direction of external radio waves.

When a magnetic head is mounted on a video tape recorder and the video tape recorder reproduces a video signal from the magnetic head, when an external radio wave jumps into the magnetic head, the frequency f ₁ of the external radio wave and the reduced converted chroma frequency f The difference f ₁ − f ₂ between ₂ becomes a beat and acts to prevent damage to the reproduced image, but
In the conventional magnetic head 1, the input level of the external radio wave coming in from the 45-degree direction on the other core half 4 side is at a level that clearly appears as a beat on the reproduced image, significantly deteriorating the image quality evaluation.

Therefore, the present invention eliminates the directional dependence of the external radio wave drop-in characteristics, suppresses the maximum value of the external radio wave drop-in level to a low value, and provides a magnetic field that provides good playback images when implemented in a magnetic recording/playback device such as a video tape recorder. It is intended to provide a head.

The magnetic head 21 constructed according to the present invention is
A head chip 25 is formed by abutting the gap surfaces 24 of the pair of core halves 22 and 23, and coils 26 and 27 are wound around each of the core halves 22 and 23 via the gap surfaces 24. This is what happens.

In the magnetic head 21 configured in this manner, the cross-sectional area of the winding portion 28 of one of the pair of core halves 22 and 23 is equal to that of the winding portion 29 of the other core half 23. It is formed larger than the cross-sectional area. That is, a notch recess 30 is formed in the winding portion 29 of the other core half 23 so as to constitute a winding hole through which the coils 26 and 27 wound around the respective core halves 22 and 23 are inserted. , by forming this notch recess 30, the cross-sectional area of the winding portion 28 of this one core half 22 is made smaller than that of the other core half 22.
The winding portion 29 of No. 3 is larger than the winding portion 29 of No. 3.

The number of turns of the coil 27 wound around the other core half 23 of the winding part 29 having a small cross-sectional area is 1.5 to 3 turns on one core half 22 having a large cross-sectional area of the winding part 28. Coil 26 with double the number of turns
is wound.

Here, each coil 2 is wound around one core half body 22 and the other core half body 23 through a gap surface 24.
When the external radio wave penetration characteristics of the magnetic head 21 are measured by changing the ratio of the number of turns 6 and 27 using the measurement system shown in Fig. 2, the external radio waves when the number of turns is changed are Fig. 5 shows a comparison of the maximum level points of the diving characteristics. At this time, one core half 2
2 and the coil 2 wound around the other core half 23
When comparing the case where the ratio of the number of turns of the coils 6 and 27 is 8:9, which is almost the same as that of the conventional balanced winding magnetic head 1, and assuming 0 db, the ratio of the number of turns of the coils wound around each core half 22 and 23 is The lowest level is the case where the windings are wound at a ratio of 2:1, and changes as shown in FIG. If the number of turns of the coil 26 wound around one core half 22 is set to 1.5 to 3 times the number of turns of the coil 27 wound around the other core half 23, then at the maximum level point 2~ 3db external radio wave jump characteristics are improved.

If the number of turns of the coil 26 of one core half 22 is set to 1.5 to 3 times the number of turns of the coil 27 of the other core half 23, the external radio wave penetration characteristics from each direction of the magnetic head 21 are as follows. As shown by the broken line B in FIG. 3, there is no directional dependence as a whole, and the input level at each point is kept low.

According to the present invention as described above, even if external radio waves are input to a magnetic head installed in a magnetic recording/reproducing device such as a video tape recorder, the input is within a range that does not substantially affect the quality of the reproduced image. level, and the quality of the reproduced image can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a conventional example. FIG. 2 is a schematic diagram showing a measurement sum for measuring the intrusion characteristics of external radio waves. FIG. 3 is a characteristic diagram showing characteristics of external radio wave intrusion from various directions in the conventional example and the present invention. FIG. 4 is a schematic diagram showing an embodiment of the present invention. FIG. 5 is a comparison diagram showing external radio wave jump characteristics depending on the turn ratio of the coils wound around one and the other core halves. 21... Magnetic head, 22... One core half, 2
3...Other core half, 26, 27...Coil, 2
8, 29... Winding section.

Claims (1)

[Scope of utility model registration request] In a magnetic head in which wires are wound on each of a pair of core halves through a gap plane, the core cross-sectional area of the winding portion of one of the core halves is the same as that of the winding portion of the other core half. , and the number of turns of the coil wound around the one core half is 1.5 to 3 times the number of turns of the coil wound around the other half of the core. magnetic head.