JPH0734250B2 - Composite magnetic head - Google Patents

Description

TECHNICAL FIELD The present invention relates to a composite magnetic head used for recording / reproducing of a video tape recorder (hereinafter referred to as VTR).

[Conventional technology]

FIG. 3 is a perspective view showing the back surface of a conventional composite magnetic head used for improving the reproduction image quality of a still image in a VTR. In FIG. 3, (1) is a composite magnetic head,
(2) is a head base, (3) and (4) are head chips fixed to the tip of the head base (2), (7) is a split groove formed in the head base (2), (12) is a head base fixing surface, 13) is the inner end of the split groove surface, 8 is a mounting hole, and 8d is the gear gap between the gear of the head chip 3 and the gear of the head chip 4.

The head chips (3) and (4) have different azimuth angles of their gears. In the VHS standard VTR, the head chip (3) is in the L (left) direction, and the head chip (4) is in the R (right) direction. Is. Head chip (3),
The gap d between the gears in (4) is the relative speed of the tape and head.
It is an integral multiple of the product of Vr and the horizontal scanning period H.

FIG. 4 is a schematic plan view showing a rotary drum to which such a composite magnetic head (1) is attached. In the figure, (5) is a rotary drum, and (6) is a single head base with one head chip attached. It is a magnetic head. The azimuth of the head chip of the single magnetic head (6) is in the R (right) direction. Compound magnetic head (1) head chip (3) gear head and single magnetic head (6)
The gear tip of the head chip is arranged at a position opposed to the center of rotation of the rotary drum by 180 °.

In such a structure, signal recording and normal reproduction are performed by the head chip (3) of the composite magnetic head (1) and the head chip of the single magnetic head (6). Still image reproduction is performed by the azimuth angle of the head chip (3) of the composite magnetic head (1) and the single magnetic head (6).
Since the same track cannot be reproduced by these two head chips due to azimuth loss due to the different azimuth angles of the two head chips, a single magnetic head (6) head chip and a head chip (4) having the same azimuth are used. . Since the head chip (4) of the composite magnetic head (1) and the head chip of the single magnetic head (6) both have the same azimuth angle, the same track can be reproduced, and accordingly, the same screen is reproduced and the movement of the motion is suppressed. Even if you play a part of a scene as a still image,
A screen without deterioration can be obtained. As can be understood from the above description, the rotary drum (5) has the composite magnetic head (1) and the single magnetic head (6), and the composite magnetic head is used during signal recording and normal reproduction and still image reproduction. The two head chips (3) and (4) of the head are switched to either one.

Now, assuming that the gear gap d between the gear tip of the head tip (3) of the composite magnetic head (1) and the gear tip of the head tip (4) deviates from the specified value (an integral multiple of Vr × H),
When a normally recorded tape is reproduced as a still image, the phase of the reproduction signal from each head is deviated between the heads, which causes horizontal fluctuation in the reproduction screen. The size of d is, for example, Vr × H
If Vr = 5.8 m / s and H = 63.5 μs, then d = 736.6 μm. If the allowable fluctuation of the screen due to the error of the gear gap d is set to 1 μs at the maximum on the time axis, the maximum error of the gear gap d is 5.8 μm at the maximum. That is, when the gear gap d is in the range of 736.6 ± 5.8 μm, the screen shake is 1 μs, so there is no practical problem.

By the way, the composite magnetic head (1) is fixed to the rotary drum (5) by the fixing screw (9) using the mounting hole (8) as shown in FIG. As shown in FIG. 5 and FIG. 6, the screws (10) and (11) screwed into the screw holes provided in the rotary drum (5) are pushed toward the head base (2) side, and the head base (2) is pushed. The height of the head chips (3) and (4) from the drum rotation surface is adjusted by forcibly displacing the head.

The split groove (7) provided in the head base (2) is provided so that the head chips (3) and (4) can be independently adjusted easily, and the adjustment screw (10) is provided. Alternatively, the deformation caused by the pressing force of (11) is prevented from propagating to each other. If the split groove (7) is short, the contact pressure of the contact part between the adjusting screw (10) or (11) and the head base (2) when the head base (2) is forcibly displaced by pushing the adjusting screw (10) or (11). There is a risk that the head base (2) locally undergoes creep deformation at the contact portion. Therefore, the split groove (7) is structured to be as long as possible.

[Problems to be solved by the invention]

In the conventional composite magnetic head as described above, when fixed to the rotary drum (5) as shown in FIG. 6, the gap d between the head chips (3) and (4) changes as compared with that before the fixation. It was That is, since the lower surface around the inner end (13) of the split groove (7) is in contact with the upper surface of the rotating drum (5), the head base (2) is distorted by the tightening load of the fixing screw (9). In particular, stress imbalance occurs in the vicinity of the inner end (13) of the split groove (7), and as a result, the spacing of the split groove (7) changes, and along with that, the gear tip and the head tip (3) of the head tip (3) change. The gear gap distance d from the gear gap of 4) also changes. Normally, the tightening load with the fixing screw (9) is 100
~ 150kg. The change in the gear gap d at that time was measured to be about 5 to 10 μm. Thus, it was revealed that when the still screen was reproduced, it caused an unacceptable shake on the screen. As described above, the conventional composite magnetic head has an unfavorable problem that the deterioration of the screen can be visually recognized when reproducing the still screen.

The present invention has been made to solve the above problems, and obtains a composite magnetic head capable of preventing a change in the gap between gears due to a tightening load of a fixing screw when the head is fixed to a rotary drum by using the fixing screw. The purpose is to

[Means for solving problems]

In the composite magnetic head according to the present invention, the ratio (l / t) between the distance (l) from the inner end of the split groove to the outer edge where the head of the fixing screw contacts the head base and the plate thickness (t) of the head base are (l / t). It is designed to be a certain value or more.

(Operation) In the present invention, since l / t is set to be a certain value or more, the stress generated in the head base by the tightening axial force of the fixing screw does not propagate to the periphery of the inner end portion of the split groove, Therefore, the inner end of the split groove is not strained.

〔Example〕

FIG. 1 is a sectional view showing a composite magnetic head of one embodiment of the present invention fixed to a rotary drum.
3) is exactly the same as the conventional composite magnetic head described above. The distance from the inner end (13) of the split groove (7) to the outer edge (A) of the contact portion between the head of the fixing screw and the head base (2) is l, and the plate thickness of the head base (2) is t. The composite magnetic head according to the present invention is configured to have l / t 0.9. The other structure is the same as the conventional example.

Next, the rationale for selecting l / t0.9 will be described. Conventionally, when a flat plate such as the head base (2) is tightened with a screw (9), the tightening force of the screw (9) is at an angle of about 45 ° in the plate thickness direction of the head base (2) as shown in FIG. It is well known to be transmitted. If there is a defect such as the split groove (7) in the portion where stress is generated in the head base (2) due to the tightening force, the stress field becomes non-uniform and a slight deformation occurs around the split groove (7). The gear gap (d) of the head chips (3) and (4) also changes.

Therefore, head bases having various plate thicknesses are prepared, and the amount of change in the gap between the head chips (3) and (4) when the head (2) is tightened and the screw (9) is tightened ( The relationship between Δg) and the ratio (l / t) was investigated. The results are shown in FIG. As can be seen from this figure, Δg is large when the distance (l) is small with respect to the plate thickness (t), but Δg decreases with an increase in l, and Δg≈0 at l / t0.9. That is, it can be seen that Δg≈0 depends not only on the plate thickness (t) but also on the distance (l), and also on the ratio (l / t) between them.

As is clear from the above description, when the head base (2) is configured so as to be 1 / t0.9, the gap (d) between the head chips (3) and (4) does not change when the fixing screw (9) is tightened. It will be.

Although the head base (2) is formed of a flat plate in the above embodiment, a recess is provided in the top surface of the head base with which the head of the fixing screw (9) comes into contact, and the plate thickness at that portion is set. Even if ta is set to l / ta 0.9, the same effect is obtained.

〔The invention's effect〕

As described above, since the head of the fixing screw has a ratio of the distance from the outer edge of the portion in contact with the head base to the inner end of the split groove and the plate thickness of the head base to 0.9 or more,
The distance between the head chips does not change when the head base is fastened to the rotating drum with the fixing screw. Therefore, the spacing between the head chips does not fluctuate even if the tightening force fluctuates during head assembly, and a VTR with stable performance can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state in which a composite magnetic head according to an embodiment of the present invention is fixed to a rotary drum, and FIG. 2 is a change amount of a gear gap between head chips when a head base is screwed to the rotary drum. Fig. 3 is a plot of experimental results showing the relationship with l / t, Fig. 3 is a perspective view of a conventional composite magnetic head seen from the back side, and Fig. 4 is a plan view showing an example of head arrangement using the composite magnetic head. 5 is a perspective view showing an assembled state of a conventional composite magnetic head and a rotary drum, FIG.
The figure is a sectional view thereof. In the figure, (1) is a composite magnetic head, (2) is a head base, (3) and (4) are head chips, (5) is a rotary drum that is an attached body, (7) is a split groove, and (8) is Mounting holes, (12) is a head base fixing surface, (13) is an inner end of a split groove, (A) is an outer edge, (l) is a distance, and (t) is a plate thickness. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] 1. At least two head chips arranged in parallel for recording and reproducing by closely running a magnetic tape, and a flat head base on the lower surface provided with a split groove for forming a mounting portion of each head chip. The composite magnetic head is adapted to be fixed to a mounted body with a fixing screw, and at least one of the two divided by the split groove of the head base is adjusted by forced displacement so that the heights of the respective head chips are matched. In the head, the distance from the outer edge of the contact portion between the head base and the fixing screw to the inner end of the split groove is 1
The composite magnetic head has a ratio (l / t) of 0.9 or more, where t is a plate thickness of the head base which is in contact with at least the fixing screw. 2. A composite magnetic head according to claim 1, wherein the head base has a uniform plate thickness satisfying l / t0.9. 3. A recess is formed in the upper surface of the head base at the portion where the fixing screw comes into contact, and the plate thickness of this head base portion is ta.
Then, the composite magnetic head according to claim 1 configured to satisfy l / ta 0.9.