JPH0721536A - Rotary head device - Google Patents

Abstract

PURPOSE:To prevent the generation of head wear and to obtain a stable head output. CONSTITUTION:Notches 23, 24 existing in the succeeding part of the rotating direction of a drum in both side parts in the axial line direction of the drum of a magnetic head 21 are formed. A negative pressure is, therefore, generated in the region within these notches 23, 24 among the regions of the air film formed between the rotary drum and a magnetic tape T at the time of high- speed rotation of the drum and the magnetic tape T is drawn toward the surface of the rotating drum and, therefore, the magnetic tape T is brought into sure pressure contact with the magnetic head 21 by relatively low tape tension. Since the thickness of the air film is settable at approximately a specified size near the magnetic head 21, approximately the same pressure contact state is obtd. in the arbitrary position of tape winding and, therefore, the contact of the magnetic head 21 and the magnetic tape T is uniformalized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary head device suitable for use in a magnetic recording / reproducing apparatus such as a video tape recorder.

[0002]

2. Description of the Related Art Generally, a video tape recorder (hereinafter referred to as
It is called "VTR". In (), since a large amount of information can be recorded / reproduced and erased, a helical scan type VTR in which a magnetic tape is spirally wound around a rotating drum for scanning is widely used.

Therefore, as shown in FIGS. 5 and 6, the area where the rotary drum 1 and the magnetic tape 2 overlap with each other during tape scanning changes depending on the tape winding position, and is formed between the rotary drum 1 and the magnetic tape 2. The capacity of the air film 3 will be different. That is, the air film amount is large at the tape winding position inlet 4 with respect to the rotary drum 1 and small at the tape winding position outlet 5.

By the way, in this type of VTR rotary head device, it is necessary that the magnetic head 6 accurately contacts the pattern on the magnetic tape 2 at a constant pressure.

In the figure, reference numeral 7 is a fixed drum.

Conventionally, a rotary head device of this type having a magnetic head H as shown in FIGS. 7A to 7C has been adopted. This will be schematically described with reference to the same figure. In the figure, the reference numeral 11 indicates a tape contact surface formed of a gently curved surface by forming two notches 12 and 13 on both sides in the drum axial direction. 14 and a head main body having a gap 15 extending in a direction inclined with respect to the drum axis direction at the center of the tape contact surface 14 in the drum rotation direction.

The head main body 11 is entirely formed of a magnetic material such as ferrite, and is constructed so that it can rotate at a high speed together with a rotating drum (not shown) during tape scanning.

In the head main body 11, the dimension of the tape contact surface 14 in the drum axis direction is set to be substantially the width per tape, and the dimension of the gap 15 in the drum axis direction is set to be the substantially tape track width. .

Reference numeral T in FIG. 7 is a magnetic tape.

The tape scanning in the rotary head device thus constructed is performed by the magnetic tape T pressingly contacting the tape contact surface 14 of the head body 11.

[0011]

However, in the conventional rotary head device, the magnetic head H is brought into contact with the magnetic tape T even at the position where the air film amount is maximum, so that the rotary drum (not shown) is arranged in the radial direction. Because it is projected to
There is a problem that the magnetic head H is brought into contact with the magnetic tape T with a high pressing force at a position where the air film amount is minimum, and the magnetic head H is easily worn.

The fact that the amount of air film differs depending on the tape winding position means that the pressing contact state of the magnetic head H with respect to the magnetic tape 2 depends on the tape winding position, for example, the magnetic tape T contacts near the edge of the magnetic head H. Different, that is, the shape (tent shape) of the magnetic tape H at the head contact portion was different. As a result, the contact between the magnetic head H and the magnetic tape T becomes uneven in the tape width direction, and there is also a problem that a stable head output (RF waveform output) cannot be obtained.

The present invention has been made in view of such circumstances, and provides a rotary head device capable of preventing the occurrence of head wear and obtaining a stable head output.

[0014]

In the rotary head device according to the present invention, a concave portion is formed in the head, the concave portion opening to the tape contact side, and the concave portion is formed on both sides of the head gap in the drum axial direction, at least in the drum rotating direction. It is located at a position excluding the leading part of.

[0015]

According to the present invention, the negative pressure is applied to the area in the recess of the air film formed between the rotary drum and the tape during high-speed rotation of the drum, so that the tape is attracted to the surface of the rotary drum.

[0016]

Embodiments of the present invention will be described in detail below with reference to embodiments shown in the drawings.

FIGS. 1A and 1B are a plan view and a side view showing a contact state of a tape with a head of a rotary head device according to the present invention, and FIGS. 2A to 2C are also rotations according to the present invention. FIG. 5 is a front view, a side view, and a bottom view showing the main part of the head device.
The same reference numerals as in FIG. 8 are attached.

In FIG. 1, reference numeral 21 denotes a magnetic head for scanning the magnetic tape T, which has a tip surface 22a formed of a magnetic material such as ferrite and having a gently curved surface that bulges toward the tape contact side. Body 22
And a coil (not shown) wound around the head main body 22, and is attached to a rotary drum (not shown) for the VTR with the head tip end portion protruding outward in the drum radial direction.

Of the two edges of the head body 22 in the axial direction of the drum, except for the leading portion in the drum rotation direction, that is, the trailing portion in the drum rotation direction, two first notches that are perpendicular to each other are provided. Surfaces 23a and 24a and second cutout surface 2
Notches 23 and 24 having 3b and 24b are formed.

On the front end surface of the head body 22, a drum rotation direction trailing portion 25a having a drum axial direction dimension set to the tape contact width by the notches 23 and 24 and a drum rotation direction trailing portion. The front side T which is composed of a drum rotation direction preceding portion 25b connected to the portion 25a
A letter-shaped tape contact surface 25 is formed.

At the center of the head main body 22 in the drum rotating direction, a gap 2 extending in a direction inclined with respect to the drum axial direction and opening at the tape contact surface 25 is formed.
6 is formed.

The gap 26 of the head body 22 is
Has a dimension in the drum axis direction substantially set to the tape track width.

Further, reference numerals F and R in the figure denote acting force due to negative pressure on the magnetic tape T and a rotating drum (not shown).
Shows the head movement direction due to the rotation of.

In the rotary head device constructed as described above, when the rotary drum (not shown) rotates at high speed, the air layer moves together with the rotary drum (not shown) due to the viscosity of the air, so that the rotary drum (see FIG. An air film (FIG. 5) is provided between the outer peripheral surface of the magnetic tape T and the head contact surface of the magnetic tape T (not shown).
Is formed). At this time, the pressure due to the air film is mechanically balanced with the atmospheric pressure via the magnetic tape T, but since the pressure in the regions within the notches 23 and 24 in the region of the air film becomes negative pressure, the magnetic force is reduced. The tape T is pulled toward the outer peripheral surface of the rotating drum (not shown).
That is, when the contact position of the magnetic head 21 with respect to the magnetic tape T moves from the drum rotation direction leading portion 25b of the tape contact surface 25 to the drum rotation direction trailing portion 25a by the high speed rotation of the rotation drum (not shown), the rotation drum ( The gap between the outer peripheral surface of the magnetic tape T (not shown) and the head contact surface of the magnetic tape T rapidly increases in the notches 23 and 24. It is received from both sides in the axial direction and is displaced from the position shown by the two-dot chain line in FIG. 1B to the position shown by the solid line.

Therefore, in this embodiment, the magnetic tape T can be surely brought into pressure contact with the magnetic head 21 by the relatively low tape tension.

Further, in the present embodiment, the magnetic head 2
Since the air film thickness can be set to a substantially constant dimension in the vicinity of 1, the magnetic head 21 can obtain substantially the same pressure contact state as the pressure contact state of the magnetic head 21 with respect to the magnetic tape T at any position around the tape winding. The contact of the magnetic tape T can be made uniform.

By the way, the thickness of the air film is determined by using an optical displacement meter (photonic sensor) so that the rotary drum (not shown) is set on the basis of the tape position when the rotary drum (not shown) is stationary. It is measured in a state where the magnetic tape T floats from the drum surface with the rotation of (not shown).

In the present embodiment, the notches 23, 24 each having two first notch surfaces 23a, 24a and second notch surfaces 23b, 24b which are perpendicular to each other are provided as the recesses.
However, the present invention is not limited to this, and as shown in FIGS. 3A to 3C, three first cutout surfaces 31a and 32a and a first cutout surface 31a which are perpendicular to each other are provided. Even with the notches 31 and 32 having the two notch surfaces 31b and 32b and the third notch surfaces 31c and 32c, the same effect as that of the embodiment is achieved. That is, in short, the concave portion of the present invention may have a sectional view shape such that the sectional area of the air film largely changes at the position in the drum rotation direction.

Further, in this embodiment, the notches 23,
Although the formation position of 24 is set to the trailing side in the drum rotation direction, the present invention shows that the notch 4 is formed as shown in FIG.
It does not matter even if the formation positions of 1, 42 are set at the central portion in the drum rotation direction. In this case, notch 4
The notch surfaces 41a and 42a of 1, 42 are formed by gentle curved surfaces.

In addition to this, in the present embodiment, an example in which it is applied to a drum composed of two upper and lower drums (a fixed drum and a rotating drum) has been shown, but the present invention is not limited to this, and the middle drum rotates. The same as in the embodiment can be applied to a device having three drums of upper, middle and lower.

[0031]

As described above, according to the present invention, the head is provided with the concave portion that opens toward the tape contact side, and the concave portion is located on both sides of the head gap in the drum axial direction and at least the leading portion in the drum rotation direction. Since it is positioned at a position other than that, the negative pressure is applied to the region in the recess of the region of the air film formed between the rotary drum and the tape during high-speed rotation of the drum, so that the tape is attracted to the surface of the rotary drum.

Therefore, since the magnetic tape can be surely brought into pressure contact with the magnetic head by the relatively low tape tension, the occurrence of wear of the head can be prevented.

Further, the fact that the air film thickness can be set to a substantially constant size in the vicinity of the head makes it possible to obtain substantially the same pressure contact state at the tape winding arbitrary position as the pressure contact state of the head with respect to the tape. The hit can be made uniform, and a stable head output can be obtained.

[Brief description of drawings]

1A and 1B are a plan view and a side view showing a contact state of a tape with a head of a rotary head device according to the present invention.

2A to 2C are a front view, a side view, and a bottom view showing a head of a rotary head device according to the present invention.

3A to 3C are a front view, a side view, and a bottom view showing a head according to another second embodiment.

4A to 4C are a front view, a side view, and a bottom view showing a head according to another third embodiment.

FIG. 5 is a perspective view showing a conventional rotary head device.

FIG. 6 is a plan view showing a conventional rotary head device.

7A to 7C are a front view, a side view, and a bottom view showing a head of a conventional rotary head device.

8A and 8B are a plan view and a side view showing a contact state of a tape with a head of a conventional rotary head device.

[Explanation of symbols]

 21 ... Magnetic head 22 ... Head body 23 ... Notch 23a, 23b ... Notch surface 24 ... Notch 24a, 24b ... Notch surface 25 ... Tape contact surface 26 ... Gap R ... Head moving direction T ... Magnetic tape

Claims (3)

[Claims] 1. A rotary head device having a head for scanning a tape by rotating a drum, wherein a concave portion opening to the tape contact side is formed in the head, and the concave portion is formed on both sides of the head gap in the drum axial direction. The rotary head device is characterized in that it is positioned at a position excluding at least the leading portion in the drum rotation direction. 2. The rotary head device according to claim 1, wherein the formation position of the recess is set to the trailing side in the drum rotation direction. 3. The rotary head device according to claim 1, wherein the concave portion is formed at a central portion in the drum rotation direction.