JPH08102012A - Magnetic head - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a video head with less spacing loss even when the shortest recording wavelength is 0.5 µm, less tape disturbance at the time of head entry, and less RF deterioration. [Structure] A head chip 30 is composed of a core in which two metal plates are bonded together, and is provided with a winding hole for winding a coil. On both sides of the gap 33, glass welded portions 39 welded with glass are provided. Head chip 3
0 has a chip width D in the central portion with the gap 33, but has a side surface 35 from a point Y which is a predetermined distance from the central portion.
And the side face 36 is inclined inward, the chip width is gradually narrowed, and finally the chip width is reduced to about the chip width h. Since the tape hits into the tape with a narrow contact width h, the impact at the time of hitting is small and the tape is less disturbed. Further, the air can be released by gradually expanding, and the spacing loss can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head provided in a rotary head of a VTR and suitable for use as a video head for recording / reproducing video signals.

[0002]

2. Description of the Related Art FIG. 5 shows a head chip of a general video head which is provided on a rotary head of a VTR and records / reproduces a video signal. 5A and 5B are views showing the shape of a general head chip, FIG. 5A is a perspective view showing the shape of the head chip, and FIG. 5B is a detailed view of the vicinity of the gap when the head chip is viewed from above. C) is a side view of the head chip in contact with the tape. As shown in FIG. 5, the head chip 90 is composed of a core 91 formed by bonding two metal plates together. The core 91 is provided with a winding hole 92 for winding a coil. Also, tape 50
The gap 9 in the curved head surface 94 that contacts the
On both sides of 3, there are provided glass welding portions 95 in which round cuts are made and welded with glass.

In a video head using such a head chip 90, a video signal is recorded by generating a magnetic line of force in the core 91 by passing a signal current through a coil (not shown) wound in a winding hole 92 to generate a gap. This is done by creating a stray magnetic field in 93 and thereby magnetizing the tape 50. In addition, reproduction is performed by picking up magnetic lines of force generated from the tape 50 at both poles of the gap 93 and passing them through the core 91 to generate an electromotive force in the coil.

Further, in such a head chip 90, as shown in FIG. 5, the contact width Tr between the video head and the tape is substantially equal to the chip width D of the head chip 90, and the contact width Tr is also equal to the contact width Tr. Is the track width Tw of 2
It was a thick shape with a width more than double. The contact state between the tape and the video head in this video head was strong at the head tip shoulder portion X shown in FIG. 5C and weak at the central portion Z. That is, the tape was pushed up at the shoulder tip X of the head, and the air film near the center Z was thick.
When this air film becomes thick, spacing loss occurs and the RF waveform deteriorates. The size of the spacing loss is expressed by Equation 1.

[0005]

[Equation 1]

When the air film weakens the contact between the head and the tape and the spacing loss exceeds a predetermined value, the tape tension is increased to strengthen the contact between the head and the tape. For example, in a 180 ° winding drum of 1/2 inch tape, a tension of about 40 g is applied so that the air film is 0.02 μm at the center of the head.
It was suppressed to the extent.

[0007]

However, when the shortest recording wavelength is about 0.7 .mu.m to 1.0 .mu.m, there is no problem in the above-mentioned method, but the shortest recording wavelength is 0.
If the thickness is 5 μm or less, the adverse effect of spacing loss cannot be prevented, and there is a problem that RF deterioration becomes large.

For example, when the tape tension of 40 g as described above is applied and the thickness of the air film in the central portion of the head is about 0.02 μm, when the shortest recording wavelength is about 0.5 μm, the spacing loss is calculated from the equation (1). It will be over 0.3db. As a result, the RF reproduction output is, for example, as shown in FIG.
It deteriorates as shown in. FIG. 6 is a diagram showing deterioration of the RF reproduction output, in which the horizontal axis represents the rotation angle of the head and the vertical axis represents the level of the RF reproduction output. FIG. 6A shows a state in which a thick air film is generated when the head rushes into the tape and the output is significantly deteriorated, and FIG. 6B shows a state in which the output is deteriorated on average. In both cases, the broken line portion is the original output.

In order to prevent the influence of this spacing loss, it is possible to further increase the tape tension. However, increasing the tape tension causes problems such as increased head friction, increased tape damage, deterioration of format compatibility, and complicated servo system.
It is practically impossible to further increase the tape tension in order to solve the above problem.

Further, when the head rushes into the tape or the tape is released from the contact with the head,
There is also a problem that the tape receives a considerable impact from the end portion of the head, which disturbs the surface pressure of the tape and causes fluctuations in the contact with the head. This problem also becomes a sensitive problem that has a large influence on RF deterioration particularly when the shortest recording wavelength is about 0.5 μm.

Therefore, it is an object of the present invention to reduce the spacing loss even when the shortest recording wavelength is about 0.5 μm, reduce the disturbance of the tape when the head rushes in, and prevent the RF deterioration. It is to provide a magnetic head that can be used.

[0012]

When the head rushes into the tape, if the air layer is not taken in, that is, the air in the central portion of the head is allowed to escape, the air film does not become thick. Further, when the head plunges into the tape, it is possible to soften the impact and to minimize the disturbance of the tape if it plunges into the tape gradually.
That is, the above problem can be solved by adopting a structure of a head chip in which air is allowed to come into contact with the tape little by little while escaping.

Therefore, the magnetic head of the present invention is a magnetic head for recording / reproducing a signal, which is provided in a rotary head of a magnetic recording / reproducing apparatus, in which the tape near the head gap substantially contacts the head surface. The magnetic head has a head chip in which the contact width of the tape is gradually narrowed in the direction in which the magnetic head penetrates the tape.

Preferably, in the magnetic head of the present invention, the portion of the head chip is further formed so that the contact width of the tape becomes gradually narrower in the direction opposite to the direction in which the magnetic head projects into the tape. It is a magnetic head.

Specifically, in the head chip, the head chip width in the direction parallel to the head gap gradually becomes wider than the direction in which the tape penetrates into the tape, becomes the maximum near the head gap, and further in the direction in which the head chip penetrates. It has a rhombic shape that gradually narrows in the opposite direction.

Preferably, only the vicinity of the head surface of the tip portion of the head chip is formed in the above shape.

[0017]

According to the magnetic head of the present invention, when the tape is plunged into the tape, the plunge is performed with a narrow abutting width, and the abutting width is gradually widened, so that the head and the abutting tape gradually come into contact with each other. , The impact from the end of the head can be suppressed and the disturbance of the tape can be minimized. Also,
Since the contact width is gradually widened, air easily escapes, air is prevented from being entrained, and the air film becomes thinner.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A video head which is an embodiment of the magnetic head of the present invention will be described with reference to FIGS. First,
A VTR head drum using the video head of the present invention will be described with reference to FIGS. 1 and 2. Figure 1
It is a figure which shows the state in which the tape is wound around the VTR head drum. The head drum 10 has a configuration in which a thin rotary drum 20 is sandwiched between an upper fixed drum 11 and a lower fixed drum 12. The video head 24 is provided on the rotary drum 20 so as to protrude by a predetermined amount from the diameters of the upper and lower fixed drums. Further, the lower fixed drum 11 is provided with a lead 15 which is a step for aligning the upper and lower sides of the tape.

At the time of recording or reproducing, the tape 50 is wound around the head drum 10 along the lead 15 by about 180 °. Then, the video head 24 provided on the rotary drum 20 rotates while rubbing the tape 50 to record and reproduce a magnetic signal.

The structure of the rotary drum 20 is shown in FIG.
FIG. 2 is a diagram showing the configuration of the rotary drum 20, (A)
Is a diagram showing a configuration of the rotary drum 20, and FIG. 6B is a diagram showing a mounting state of the video head 24. Video head 24
Are fixed to the head base 22 with an adhesive. The head base 22 to which the video head 24 is fixed is fixed to the rotary scanner 21 at predetermined four positions by mounting screws 23.

Next, the head chip 3 of the video head 24
0 will be described with reference to FIG. 3A and 3B are detailed views for explaining the head chip 30, where FIG. 3A is a perspective view showing the shape of the head chip 30, FIG. 3B is a part of a top view seen from the direction of the head surface, and FIG. FIG. 6 is a side view showing a state where the head chip 30 and the tape 50 are in contact with each other.

The head chip 30 is composed of a core 31 formed by sticking two metal plates together. The core 31 is provided with a winding hole 32 for winding a coil. On both sides of the gap 33, glass welded portions 39 welded with glass are provided. The head chip 30 has the gap 33.
The center width of the certain head chip 30 has the chip width D, but the side surfaces 35a, 35b and the side surfaces 36a, 36b are inclined inward from the point Y which is a predetermined distance from the center portion, and the chip width is gradually narrowed. Finally, the chip width is finally reduced to about h.

The operation of recording / reproducing the video signal by the head chip 30 is the same as that of the conventional head chip 90 described above. In addition, the head chip 30 of this embodiment
Has a longitudinal length L of 1.9 mm and a chip width D of 10
The narrowed chip width h is 0 μm and 50 μm.

In such a head chip 30,
When rushing into the tape, the contact with the tape is started with the narrowed chip width h, so that the impact from the head end portion becomes small. Further, since the tape and the head gradually contact with each other along the side surfaces 35a and 35b, the disturbance of the tape at the time of impact can be softened. Further, the disturbance of the tape that occurs when the tape and the head are not in contact with each other can be softened by the side surfaces 36a and 36b.

Further, since the contact area between the tape and the head is rhombic, the area becomes relatively small as compared with the conventional case, and as a result, the surface pressure increases and the contact becomes good. Further, the tension can be concentrated in the vicinity of the gap, and the air can escape easily, so that the spacing loss can be reduced.

The present invention is not limited to this embodiment, and various modifications and variations are possible. For example, the shape of the head chip is not limited to the case shown in FIG. A modification thereof is shown in FIG. 4A and 4B are detailed diagrams illustrating a head chip 40 that is a modified example of the head chip 30, where FIG. 4A is a perspective view showing the shape of the head chip 40, and FIG. 4B is a top view as seen from the direction of the head surface. Part of
(C) is a side view showing a state where the head chip 40 and the tape 50 are in contact with each other. The head chip 40 also
The head chip 30 has the same configuration as that of the head chip 30, but differs from the head chip 30 in that the tip width, that is, the contact width, is narrowed down only at the tip portion of the head chip 40. With such a configuration, the same effect as that of the head chip 30 can be obtained, and further, the mechanical strength of the head chip can be secured.

The fine shape of each part may be any shape. For example, the edge portion Y in the contact width direction shown in FIGS. 3B and 4B may have an R shape. In this case, by doing so, it is possible to reduce the concentration of tape tension, and at the same time,
It is also effective as a countermeasure against burrs during processing. Other,
The shape other than the shape of the head surface portion according to the present invention such as the shape of the winding portion of the head chip may be any suitable shape.

Further, as the rotary head to which the video head of the present invention is applied, as shown in FIG. 1, a rotary head of the type in which the video head fixed to the rotary drum is output from between the upper and lower fixed drums is used. did. However, the present invention can be applied to a rotary head in which the head and the upper drum are integrally rotated. Further, the material of the head chip may be any suitable magnetic material such as ferrite, sendust, or amorphous, or may be a composite of these materials.

[0029]

According to the magnetic head of the present invention, since the contact width of the tape is changed and narrowed and gradually widened at the time of plunging, the impact at the time of plunging the head is suppressed and the disturbance of the tape is minimized. can do. Moreover, since the contact width is gradually widened, the air easily escapes, the air is prevented from being caught, and the thickness of the air film is reduced. As a result, it is possible to provide a magnetic head that can prevent RF deterioration by reducing spacing loss and tape disturbance when the head rushes in, even when the shortest recording wavelength is about 0.5 μm. can do.

[Brief description of drawings]

FIG. 1 is a diagram showing a state in which a tape is wound around a VTR head drum.

2A and 2B are diagrams showing the configuration of the rotary drum shown in FIG. 1, wherein FIG. 2A is a diagram showing the configuration of the rotary drum, and FIG. 2B is a diagram showing a mounting state of a video head.

FIG. 3 is a diagram illustrating a head chip of the magnetic head of the present invention, FIG. 3A is a perspective view showing the shape of the head chip;
(B) is a part of a top view seen from the direction of the head surface,
(C) is a side view showing a state where the head chip and the tape are in contact with each other.

4A and 4B are diagrams illustrating a modified example of the head chip of the magnetic head of the present invention, FIG. 4A is a perspective view showing the shape of the head chip, and FIG. 4B is a part of a top view seen from the direction of the head surface. , (C) are side views showing a state where the head chip and the tape are in contact with each other.

5A and 5B are views showing the shape of a general head chip, FIG. 5A is a perspective view showing the shape of the head chip, and FIG.
Is a detailed view of the gap near the head chip seen from above,
(C) is a side view showing a state in which the head chip is in contact with the tape.

6A and 6B are diagrams showing deterioration of RF reproduction output, in which FIG. 6A shows a state in which the output remarkably deteriorates when the head enters the tape, and FIG. 6B shows a state in which the output deteriorates on average. is there.

[Explanation of symbols]

 10 ... Head drum 11 ... Upper fixed drum 12 ... Lower fixed drum 15 ... Lead 20 ... Rotating drum 24 ... Video head 30, 40 ... Head chip 31, 41 ... Core 32, 42 ... Winding hole 33, 43 ... Gap 34, 44 ... Head surface 35, 36, 45, 46 ... Side surface 39, 49 ... Glass welded portion 50 ... Tape 90 ... Head chip 91 ... Core 92 ... Winding hole 93 ... Gap 94 ... Head surface 95 ... Glass welded portion

Claims (4)

[Claims] 1. A magnetic head for recording / reproducing a signal, which is provided on a rotary head of a magnetic recording / reproducing apparatus, wherein a portion of the tape in the vicinity of the head gap, which is substantially in contact with the head surface, hits the tape. A magnetic head having a head chip whose width is gradually narrowed in a direction in which the magnetic head penetrates the tape. 2. The magnetic head according to claim 1, wherein the portion of the head chip is further formed so that the contact width of the tape becomes gradually narrower in the direction opposite to the direction in which the magnetic head projects into the tape. 3. The head chip has a head chip width in a direction parallel to the head gap, which is gradually wider than a direction in which the head chip is projected, is maximized in the vicinity of the head gap, and is further in a direction opposite to the direction in which the tape is projected. The magnetic head according to claim 2, wherein the magnetic head has a rhomboidal shape that gradually narrows toward the top. 4. The magnetic head according to claim 1, wherein only the vicinity of the head surface at the tip of the head chip is formed in the shape.