JPH04295607A - Rotary magnetic head device - Google Patents

Abstract

PURPOSE:To improve the erasing rate of an erase head section irrespective of a difference in stiffness in a control head of a double-gap constitution. CONSTITUTION:In a control head constituted by integrating an erase head section 10E and control head section 10C, the gaps ge and gc of the sections 10E and 10C are asymmetrically arranged with respect to the apex P' of a tape contact face 17 so that the erasing rate of the section 10C can be improved. To be concrete, the gap ge is brought nearer to the apex P' and the gap gc is separated farther from the apex P'.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to a digital VTR that records and plays back component digital video signals, etc.
The present invention relates to a rotary magnetic head device suitable for application to (D-1 type VTR) and the like, and particularly to a rotary magnetic head device of a type in which a control head for recording and reproducing control signals is embedded in the lower drum side.

0002

2. Description of the Related Art In order to regulate the relative positional relationship between a video signal recorded on a magnetic tape and a rotating magnetic head, V
Regardless of the model of the TR, a control head for recording and reproducing control signals (CTL signals) is placed on the tape path close to the rotating drum. The distance from the control head to the rotating magnetic head is strictly determined so that the relationship between the control signal recorded on the magnetic tape and the corresponding video signal always remains constant.

On the other hand, as the magnetic tapes used have become thinner and thinner due to the increase in density in recent years, the relative positional relationship between the control signals and video signals recorded on the magnetic tapes may be disturbed if the usage environment conditions are different. I end up. Furthermore, when newly recording a control signal using an already recorded magnetic tape, the prerequisite is to erase the already recorded control signal before recording the new control signal.

[0004] However, if some portions are not erased, problems such as synchronization before and after the erased portions occur. To prevent this, an erasing head that is dedicated to control signals and has a high erasing rate is placed in front of the control head.

[0005] As described above, the control head and its erasing head are installed in a separate location from the rotating magnetic head device, but if this is done, the above-mentioned problems may occur, so these heads are embedded in the rotating drum. I have a plan. In this case, it is easier to attach the control head to the rotating drum by integrating the control head and the erasing head, so a control head with a double gap configuration in which the erasing head and the control head are integrated has been proposed. A specific example of a double gap type control head has been previously proposed by the present applicant (for example, Japanese Patent Application No. 2-85710).

The invention of this prior application is a double-gap system, and furthermore, it is a technical concept for improving the contact state of the rotating magnetic head and the control head with the magnetic tape by embedding the control head. , a specific example is presented.

FIG. 4 shows an example of a rotary magnetic head device according to a prior application that embodies this idea, and the rotary magnetic head device 1 has an upper drum 2, a lower drum 3, and a space between the upper drum 2 and the lower drum 3. The rotating magnetic head 4 is attached to the rotary magnetic head 4. As the rotating magnetic head 4, as mentioned above, D
In the case of the -1 type VTR, two heads are attached with an angular spacing of approximately 180° between them as shown in the figure. Then, one field of digital video signals is distributed and recorded on a plurality of tracks by these rotating magnetic heads 4.

Reference numeral 5 denotes an inclined guide formed on the lower drum 3 side. The angle of inclination differs depending on the wrap angle of the magnetic tape 6 with respect to the drum. Lower drum 3 in contact with inclined guide 5
A circular hole 8 is bored at a predetermined position, and a double-gap type control head 10 is embedded therein.

As shown in FIG. 5, the control head 10 has an erasing head section 10E on the front side with respect to the tape running direction.
A control head section 10 is formed with a gap ge that functions as
A gap gc for C is formed at a predetermined distance Ta (see FIG. 11).

When such a double-gap type control head 10 is embedded in the lower drum 3 side, the contact state (tape running state) with the magnetic tape 6 is ideally as shown in FIG. 6, for example. be. In order to realize this ideal contact state, a configuration as shown in FIG. 7 and subsequent figures is adopted.

This control head 10 is shown in FIGS. 7 to 9.
As shown in FIG. 2, a mask member 16 is joined to a core member 15 to which windings and wiring members are attached, and the whole is formed into a cylindrical shape. The diameter of the control head 10 is, for example, about 7 mm.

The tape contacting surface 17 is an aspherical surface (different spherical surface) with a different radius of curvature in the running direction of the magnetic tape 6 and in a direction perpendicular thereto. In other words, the tape contact surface 17 is polished with a first radius of curvature RH as shown in FIG. 8, and with a second radius of curvature RV as shown in FIG. 9 in the direction perpendicular to the tape running direction. For example, when the drum radius is 37.5 mm, the first radius of curvature RH is 30.0 to 35.0 mm (for example, 30.0 mm), and the second radius of curvature RV is a larger radius of curvature, for example, 300 mm. selected.

If the tape contacting surface 17 is aspherical with such a radius of curvature and the length of the head protrusion from the lower drum 3 is about 20 to 30 μm, the air film layer can be cut to a certain extent. magnetic tape 6
The relationship is as shown in FIG. That is, since the tape has the second radius of curvature RV in the direction perpendicular to the tape running direction, the tape shape in the gap 12 is similar to that of the tape contact surface 1.
7 and has the same thickness as the air film layer 13 formed on the upper drum 2 side. This reduces the spacing loss in the control head 10, and since the magnetic tape 6 around the rotating magnetic head 4 has an ideal tent shape, the spacing loss in the rotating magnetic head 4 also decreases.

[0014]

By the way, according to various experimental results, it has been found that the relationship between the head shown in FIG. 6 and the magnetic tape 6 is not constant regardless of the stiffness of the magnetic tape 6. As a result, a spacing S as shown in FIG. 10 occurs. As shown in FIG. 5, the apex of the tape contact surface 17 (the gap passing through this apex
, gc) is P, the position of the erasing head 10E from this vertex P is e, and the position of the control head 10C is r, then the spacing loss characteristic as shown in FIG. 11 is obtained. became.

In FIG. 11, the solid line is a characteristic curve of spacing loss when the stiffness is large (hard);
The broken line is a similar characteristic curve when the stiffness is small (soft), and in the case of the magnetic tape 6 with a large stiffness, the spacing loss is not so large, so the deterioration of the erasing characteristics especially in the erasing head section 10E is It's not much of a problem. However, when the stiffness is small, the spacing loss becomes significant and the erasing characteristics deteriorate significantly.

As a solution to this problem, the configuration shown in FIG. 12 or 13 can be considered. FIG. 12 shows a case where a control head 10 is used in which the contact width with respect to the magnetic tape 6 is made slightly wider than the conventional one, for example, the contact width W is processed to be about 800 μm, and the contact pressure against the tape contact surface 17 is increased. It is. However, even with this, in the case of a magnetic tape with low stiffness, the spacing loss becomes large and a sufficient erasing effect (erasing rate) cannot be obtained.

FIG. 13 shows the tape contacting surface of the control head 10 processed to form a wide tapered tape contacting surface 19 as shown in the figure. According to this, sufficient surface pressure cannot be ensured, so it does not contribute to improving spacing loss at all.

In addition to FIG. 12 or 13, for example, it is conceivable to blow air from the outside of the magnetic tape 6 while the magnetic tape 6 is in contact with the magnetic tape 6. When loading and unloading, a separate means must be devised to avoid the air blowing device, which is not practical.

Therefore, the present invention solves these conventional problems, and provides a control head embedded type that has a relatively simple structure, achieves an ideal tape contact state, and particularly improves the erasing rate. This paper proposes a rotating magnetic head device.

[0020]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a double-gap control head comprising an erasing head section for control signals and a control head section for recording and reproducing control signals. A rotating magnetic head device embedded in the lower drum side, the tape contacting surface of this control head is an asymmetrical curved surface in the tape running direction and the direction orthogonal to this, and the control head part is an erasing head. It is characterized in that it is located on the apex side of the tape contacting surface with respect to the tape contacting surface.

[0021]

[Operation] If the running conditions of the control head 10 and the magnetic tape 6 (particularly a magnetic tape with small stiffness) are carefully considered, the spacing loss characteristics as shown in FIG. 3 can be obtained. As is clear from the figure, the spacing loss is not uniform over the entire area of the tape contact surface 17; the point x near the start of tape entry is the farthest, gradually decreases from just before the apex P, and after the apex P, the spacing loss is the most distant. The distance is the closest at point y, and thereafter the distance is the same as that of the air film layer formed by the rotating magnetic head 4.

Therefore, in the present invention, the erasing head section 10E and the control head section 10 are arranged at equal intervals with respect to the vertex P.
Instead of arranging the gap C (shown by the solid line), the gap formation position is shifted as shown by the broken line. In other words, the gap formation position is shifted to a position where the spacing loss is reduced. In the figure, the erasing head section 10E is moved closer to the vertex P by a predetermined distance, and the control head section 10C is moved away from the vertex P by that amount. This is the gap interval Tb between the two (Fig. 11
(see) cannot be lowered below a certain value in order to prevent magnetic saturation.

By doing so, even when a magnetic tape with small stiffness is used, spacing loss is reduced and the erasing rate is improved.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an example of a rotary magnetic head device according to the present invention will be explained in detail with reference to the drawings. For convenience of explanation, the principle of the invention will be explained with reference to FIG. FIG. 3 is a diagram showing the state of the air film near the control head 10 while the tape is running.

When the tape running direction is taken as shown by the arrow, the air film layer near the tape contacting surface of the control head 10 is not uniform, and as shown in the figure, the air film layer on the tape entry side is thicker, and the tape It tends to become thinner on the exit side. There is a peak point of the air film layer on the tape entry side, and this peak point is located just before point x, which is located slightly on the tape entry side from the erasing head section 10E shown in FIG. Also, point y(
It was confirmed that the minimum point exists near the position of the control head portion 10C in FIG.

An example of the spacing loss caused by this air film layer is shown in FIG. Figure 3 and Figure 11
Comprehensively judging the relationship between the two heads, the conventional arrangement with respect to the tape contact surface 17, that is, the configuration in which the gaps ge and gc of each head are arranged at equal intervals with respect to the vertex P (Fig. 3
(the gap position is shown by a solid line), the spacing loss in the erase head section 10E is larger than that in the control head section 10C, and this tendency becomes more pronounced as the stiffness decreases (see FIG. 11). .

On the other hand, as is clear from FIG. 3, the air film layer tends to decrease in the direction from point x toward vertex P, and the air film layer changes only slightly near point y. Therefore, the gap forming position of the erasing head section 10E is shifted to the vertex P side from the current position, and the gap forming position of the control head section 10C is moved further away from the vertex P side by that amount, and a new position is created as shown by the broken line in FIG. If a gap forming position is selected, at least the erasing head section 10E
It can be seen that the spacing loss is improved compared to the current model. This tendency does not change even when the stiffness is small.

[0028] Here, it is conceivable that the gap position of the control head portion 10C may be the current position. However, as shown in FIG. 11, the current facing distance T between both heads is
Since a is approximated to the minimum distance that does not cause magnetic saturation, when the gap position of the erasing head section 10E is shifted to the vertex P side as shown in FIG. 3 (the position is e'),
It is preferable that the gap position of the control head portion 10C is also shifted as shown in FIG. 3 (the position is r'). When the current gap positions are formed at equal intervals, for example, about 0.5 mm apart from the apex P,
In this example, 0.3m from the new apex (denoted as P')
The gap of the erasing head section 10E is formed at the position m, and the gap of the control head section 10C is formed at a position 0.7 mm away from the vertex P'.

It has been found that by doing so, the erasing rate of the erasing head section 10E is improved by 10 dB or more compared to the current state. No particular change was observed in the recording/reproducing characteristics in the control head section 10C.

FIG. 1 shows a configuration embodying this principle. In FIG. 1, 21 is a center core, 22a, 2
2b is the back core, and both constitute an E-shaped core. These correspond to the core member 15 in FIG. back core 2
Windings 25 and 26 for the erasing head and the control head are wound around the bobbins 23 and 24 attached to the bobbins 2a and 22b, respectively. 27 and 28 are winding terminals, and 29 is a terminal plate to which these are attached. 30 is a case.

Center core 21 and back core 22a
, 22b is coated with a mask material 31 (such as ferrite) on the end face side.
7), and both sides of the mask material 31 provided in the center core 21 are filled with glass materials 32 and 33 to form gaps ge and gc. The gap ge for the erase head section 10E has a longer gap length than the gap gc for the control head section 10C.

The tape contacting surface 17 has an aspherical configuration as shown in FIG. 7, and the radius of curvature RH in the running direction is approximately 35.0 mm, as in FIGS. The radius of curvature RV is selected to be approximately 300.0 mm. A gap ge is formed at a position of about 0.3 mm toward the tape entry side from the apex P' of the tape contacting surface 17, and a gap gc is formed at a position of about 0.7 mm toward the tape exit side. Therefore, the position of the vertex P' is shifted to the tape entry side by ΔP compared to the conventional configuration. Incidentally, the control head 10 shown in FIG. 7 has a configuration as shown in FIG. 2, and gaps ge and gc are formed equidistantly apart from the vertex P.

In the present invention, the erasing head 1 is located asymmetrically with respect to the apex of the tape contacting surface so that the erasing rate can be improved.
Since a gap ge of 0E is formed, the shape and numerical values of the tape contacting surface described above are merely examples.

[0034]

[Effects of the Invention] As described above, the double-gap configuration control head used in the rotary magnetic head device according to the present invention forms the gap of the erasing head portion at an asymmetric position with respect to the apex of the tape contacting surface. It is something.

[0035] According to this, since the gap of the erasing head part can be arranged at a position where the spacing loss is small, the erasing rate can be improved even when the stiffness of the magnetic tape is small while increasing the surface pressure against the magnetic tape. Has characteristics that can be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a control head according to the present invention.

FIG. 2 is a conventional cross-sectional view used to explain FIG. 1;

FIG. 3 is an explanatory diagram of an air film layer used in the present invention.

FIG. 4 is a schematic configuration diagram of a rotary head device according to the present invention.

FIG. 5 is a front view of the double gap configuration control head used in FIG. 4;

FIG. 6 is a sectional view of the tape running state.

FIG. 7 is a perspective view of a control head with a double gap configuration.

FIG. 8 is a sectional view taken along the line XX in FIG. 7;

9 is a cross-sectional view taken along the Y-Y line in FIG. 7; FIG.

FIG. 10 is a sectional view of the tape running state.

FIG. 11 is an explanatory diagram of spacing loss.

FIG. 12 is a cross-sectional view of the tape running state when the control head used to explain the present invention is used.

FIG. 13 is a cross-sectional view of the tape running state when the control head used to explain the present invention is used.

[Explanation of symbols]

1 Rotating head device 2 Upper drum 3 Lower drum 4 Rotating magnetic head 6 Magnetic tape 10 Control head 10 with double gap configuration
E Erasing head section 10C Control head section 17 Tape contact surface ge, gc Gap P' Vertex

Claims (1)

[Claims] 1. A rotating magnetic head device in which a double-gap type control head is embedded in a lower drum side, and includes an erasing head section for control signals and a control head section for recording and reproducing control signals, The tape contacting surface of the head is formed into an asymmetrical curved surface in the tape running direction and the direction perpendicular thereto, and the control head section is positioned on the apex side of the tape contacting surface with respect to the erasing head section. A rotating magnetic head device characterized by: