JPH08102004A - Magnetic head - Google Patents

Abstract

(57) [Abstract] [Purpose] Even if the head chip wears and the protrusion decreases,
(EN) Provided is a video head which can obtain a predetermined surface pressure and does not cause deterioration of an RF waveform. [Structure] A head chip 30 is processed into a constricted shape in a thickness direction at a tip end portion α corresponding to a protruding portion when provided on a rotary head. The thickness of the head chip is equal to the chip width D on the surface of the head and becomes gradually narrower,
At the central portion .alpha.3 of the protruding portion, the width is almost equal to the track width Tw and becomes the minimum, and then returns to the chip width D. As the head wears, the contact position with the tape shifts in the order of α0, α1, α2. As a result, the width Tr per tape is also narrowed, so that the surface pressure of the contact surface between the tape and the head can be prevented from lowering, the air film becomes thicker, the spacing loss increases and the RF waveform is prevented from deteriorating. be able to.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head which is provided, for example, on a rotary head of a VTR and is 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 as shown in FIG.
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 RF deterioration due to the air film, 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 was applied.

[0007]

In such a video head, when the head chip begins to wear, the RF waveform may deteriorate before the original life of the video head and the head may become defective. was there. The video head has a range in the depth direction (hereinafter referred to as head depth) which can be substantially recorded / reproduced in the gap. Then, when the wear of the head chip reaches this head depth, recording / reproducing with the video head becomes impossible. This state can be said to be the original life of the video head.

However, even though the wear of the video head has not reached the head depth, the RF waveform is deteriorated and the head may be defective. This is because the head tip wears and the protrusion of the head from the drum surface is reduced, the surface pressure of the contact surface between the head and the tape is reduced, the air film is thickened, the spacing loss is increased, and the RF waveform is increased. Is deteriorated. Particularly, when the minimum recording wavelength becomes 0.5 μm or less, such a defect is likely to occur. As a result, there is a problem that the video head becomes defective even though it does not have its original life, resulting in poor durability of the video head.

Therefore, it is an object of the present invention to provide a magnetic head which can obtain a predetermined surface pressure even when the head chip is worn and the protrusion is reduced, and the RF waveform is not deteriorated. In other words, despite the small wear of the magnetic head, spacing loss increases due to insufficient surface pressure of the tape, the RF waveform is prevented from being deteriorated, and the head defect is prevented, and the head depth is reduced to zero. It is an object of the present invention to provide a magnetic head that can be used until the end, that is, has a good durability.

[0010]

In order to solve the above-mentioned problems, the shape of the head chip is formed so as to prevent the reduction of the surface pressure even when the tip of the head is worn and the protrusion is reduced.

Therefore, the magnetic head of the present invention is a magnetic head for recording / reproducing a signal, which is provided in the rotary head of the magnetic recording / reproducing apparatus, and the width of the head chip in the depth direction of the head gap of the magnetic head. Is a magnetic head that is gradually thinned from the head gap in the depth direction.

Preferably, the head chip is gradually narrowed to a track width from the head surface to a position near the center of the protruding portion when the magnetic head is mounted on a rotary head.

Preferably, the width of the head chip is gradually reduced to the track width from the head surface to a position facing the depth direction by a substantially recordable / reproducible range of the head gap. .

Specifically, in the head chip, the width of the head chip is gradually narrowed by linearly inclining the tip portions of both side surfaces of the head chip substantially orthogonal to the head gap to the inside of the head chip. did.

More specifically, in the head chip, the width of the head chip is gradually narrowed by narrowing the tips of both side surfaces of the head chip, which are substantially orthogonal to the head gap, inside the head chip in an arc shape. did.

[0016]

According to the magnetic head of the present invention, the tip thickness of the head chip, which corresponds to the protrusion when the magnetic head is provided on the rotary head, has a shape in which the chip thickness is gradually reduced from the head surface toward the rotary head. Therefore, as the head wears, the tape contact width also narrows. as a result,
It is possible to prevent a decrease in surface pressure, prevent a defective head due to an increase in spacing loss, and effectively use the magnetic head until the original life when the head depth becomes zero.

[0017]

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 views for explaining the shape of the head chip 30. FIG. 3A is a side view showing a state where the head chip 30 and the tape 50 are in contact with each other, and FIG. 3B is a view from the direction of the head surface. It is a top view. The main structure of the head chip 30 and the recording / reproducing operation of the video signal by the head chip 30 are as follows.
This is the same as the conventional head chip 90 described above. Also,
The head chip 30 of this embodiment has a length L in the longitudinal direction of 1.9 mm and a chip width D of 100 μm.

As shown in FIG. 3, the head chip 30 is
It differs from the conventional head chip in that the tip portion α corresponding to the protruding portion when provided on the rotary head is processed to have a constricted shape in the thickness direction. That is, the thickness of the head chip is initially equal to the chip width D, but gradually becomes narrower, becomes substantially equal to the track width Tw at the position of the central portion α3 of the protruding portion, and returns to the chip width D again. In this embodiment, α is 40 μ
m.

In the head chip 30 having such a shape, the contact position with the tape shifts in the order of α0, α1, and α2 as the head wears. As a result, the width Tr per tape is initially equal to the chip width D and gradually becomes smaller. And α which is the central part of the protruding part
At point 3, the contact width Tr becomes the minimum. Hit width T at that time
r is approximately equal to the track width Tw. Then, in the head chip 30, the position of the central portion α3 of the protruding portion is aligned with the position where the head depth of the head chip 30 is zero. Therefore, when the wear reaches the position of α3, the life of this head chip ends.

As described above, in the head chip 30, as the head wears, the tape contact width also narrows, so that it is possible to prevent the surface pressure of the contact surface between the tape and the head from lowering, and with the wear of the head. It is possible to prevent deterioration of the RF waveform. Further, as a result, defective heads due to increased spacing loss can be eliminated, and the video head can be effectively used until the original life when the head depth becomes zero. It should be noted that it is easy to process the head chip into a shape like the head chip 30 of this embodiment, and since the side surface is narrowed down, the head chip may be mechanically affected. Absent.

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 that shown in FIG. A modification thereof is shown in FIG. FIG. 4 is a diagram illustrating a shape of a head chip 40 which is a modified example of the head chip 30, and FIG. 4A is a side view showing a state where the head chip 40 and the tape 50 are in contact with each other, and FIG. 4) is a top view seen from the direction of the head surface. The main structure of the head chip 40, the operation of recording / reproducing video signals, etc.
It is the same as the head chip 30.

In the head chip 40, the constriction at the tip of the head chip is not straight but arcuate. The shape of the constriction may be such a shape.
The shape of the constriction is determined according to the curvature of the head surface, the head material, the tape, the usage conditions, etc., and the relationship between the degree of wear and the surface pressure can be adjusted according to this shape. Therefore, the shape may be arbitrary according to the above conditions. In the head chip 40, the tape contact width Tr becomes sharply narrowed by the initial wear and becomes close to the track width Tw, and the tape contact width T becomes the latter wear in the latter half.
r is almost unchanged. Further, the head chip 40 has an advantage that processing becomes easier, in addition to the same advantages as the head chip 30.

Further, as a rotary head to which the video head of the present invention is applied, as shown in FIG. 1, a rotary head of a system 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. The fine shape of each part may be any shape. In addition, any 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.

[0027]

According to the magnetic head of the present invention, a predetermined surface pressure can be obtained even if the head chip is worn and the protrusion is reduced.
No deterioration of RF waveform occurs. Therefore, despite a relatively small amount of wear, the spacing loss increases and the RF
It was possible to provide a magnetic head which is prevented from being deteriorated due to waveform deterioration and can be used until the head depth, which is the original life of the magnetic head, becomes 0, that is, a durable magnetic head.

[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.

3A and 3B are views for explaining the shape of the head chip of the present invention, FIG. 3A is a side view showing a state where the head chip and the tape are in contact, and FIG. 3B is a view from the direction of the head surface. It is a top view.

FIG. 4 is a diagram for explaining a modified example of the head chip of the present invention, (A) is a side view showing a state where the head chip and the tape are in contact, and (B) is a direction of the head surface. It is the top view seen.

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 33, 43 ... Gap 34, 44 ... Head surface 35, 45 ... Glass welding part 50 ... Tape 90 ... Head chip 91 ... Core 92 ... Winding hole 93 ... Gap 94 ... Head surface 95 ... Glass welded portion

Claims (5)

[Claims] 1. A magnetic head for recording / reproducing a signal, which is provided in a rotary head of a magnetic recording / reproducing apparatus, wherein a width of a head chip in a depth direction of a head gap of the magnetic head is deeper than the head gap. A magnetic head that is gradually narrowed in the direction. 2. The head chip is such that the width of the head chip is gradually narrowed to a track width from the head surface to a position near the center of a protruding portion when the magnetic head is mounted on a rotary head. Magnetic head. 3. The width of the head chip is gradually reduced to a track width from the head surface to a position facing the depth direction by a substantially recordable / reproducible range of a head gap. Alternatively, the magnetic head described in 2. 4. A width of the head chip is gradually narrowed by linearly inclining tip portions of both side surfaces of the head chip, which are substantially orthogonal to a head gap, inside the head chip. The magnetic head according to any one of 1 to 3. 5. The width of the head chip is gradually narrowed by narrowing the end portions of both side surfaces of the head chip, which are substantially orthogonal to the head gap, inside the head chip in an arc shape. The magnetic head according to any one of 3 to 3.