JPH0944828A - Dynamic tracking head device, rotary drum device and magnetic recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a specified contact pressure between a magnetic head and a magnetic tape to lessen the wear of the magnetic head even if an ambient temp. changes, and to suppress reproduction noises. SOLUTION: The one-side ends of two sheets of bimorphs 14, 15 are mounted at an L-shaped head base 11. The other-side ends of the bimorphs 14, 15 are connected by an elastic material, such as U-shaped carbon beak 18. The magnetic head 19 is adhered to the rear surface of this carbon beak 18. The head base 11 is molded of a power metallurgical alloy composed of molybdenum and copper and the coefft. of thermal expansion thereof is set at <=6×10<-6> / deg.C, smaller than heretofore. Then, even if the ambient temp. changes, the fluctuation in the position of the magnetic head 19 is suppressed to a lower level and, therefore, the contact pressure of the magnetic head 19 and the magnetic tape is kept approximately constant. Thereby, the wear of the magnetic head is lessened and the life can be made longer. In addition, the reproduction noises can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic tracking head device, a rotary drum device and a magnetic recording / reproducing device suitable for application to a VTR or the like capable of variable speed reproduction. More specifically, the present invention relates to a dynamic tracking head device, a rotary drum device, and a magnetic recording / reproducing device that are intended to prevent the head from being displaced due to temperature changes by molding the head base with a material having a small linear expansion coefficient.

[0002]

2. Description of the Related Art In a magnetic head device of a rotary head type video tape recorder, one of the upper and lower drums around which a magnetic tape as a recording medium is wound and guided and run, or a middle drum arranged between the upper and lower drums, etc. Is rotatable, and a magnetic head is attached to this rotating drum. The tip of the magnetic head slightly projects from the outer peripheral surface of the drum.

On the other hand, a dynamic tracking head has been developed as one technique for keeping the tracking operation of a magnetic head with respect to a recording track on a recording medium with high accuracy. This dynamic tracking head, when playing back a recording track recorded at a regular speed on a recording medium at a variable speed such as slow, still, or high speed, the head locus deviates from the recording track and noise appears in the reproduced image. In order to prevent this from happening, the head is slightly displaced in the width direction of the recording track, and the position of the magnetic head is aligned with the recording track so that a reproduced image without noise is obtained.

The dynamic tracking head is also called a bimorph head. The bimorph is formed by laminating two polarized piezoelectric ceramic plates so that one expands and the other contracts. The bimorph can be supported on a cantilever and a tip can be displaced by applying a voltage. If a magnetic head is attached to the tip of this bimorph, the head position can be freely changed by controlling the voltage.

[0005]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention
The racking head device has one magnetic reproducing head or
Attached to the tip of a two-element piezoelectric element (bimorph)
The opposite end of the bimorph is molded by aluminum die casting
Is fixed to the formed head base with screws, for example. F
Coefficient of linear expansion of aluminum die-casting that constitutes the saddle base
Is 18.6 × 10 ^-6(/ ° C) and expands due to temperature changes
Tensioned or reduced and attached to the tip of the bimorph
The magnetic read head is displaced considerably. Changes in environmental temperature
The change in position of the magnetic read head due to
Swell. As shown in the figure, from aluminum die casting
Dynamic tracking using a head base
The temperature of the
The magnetic head moves inward from the surface of the rotating drum
The magnetic head is displaced in the backward direction and the magnetic head is
It is displaced in a direction projecting from the surface of the rotating drum. In this example
When the temperature is + 80 ° C., the temperature is 20.
It retreats 8 μm and projects 22.3 μm at −40 ° C.

As described above, when the temperature in the vicinity of the magnetic head rises, the magnetic head is largely displaced in the direction in which the contact with the magnetic recording medium is weakened, so that it is impossible to secure sufficient contact with the magnetic recording medium. Therefore, it becomes impossible to reliably reproduce the signal recorded on the magnetic recording medium.

On the other hand, when the temperature in the vicinity of the magnetic head is lowered, the magnetic head is largely displaced in the direction in which the contact with the magnetic recording medium is strengthened, so that the magnetic head and the magnetic recording medium come into contact with each other with an excessive force. The head wear increases and the head life shortens.

Conventionally, in order to deal with the fact that the head retracts when the temperature becomes high, it is planned that the head will retract due to an increase in environmental temperature during use, and the protrusion amount of the head is, for example, 35 μm with respect to a reference value. The final adjustment at the time of manufacturing is usually performed with the protrusion protruding from the beginning. This is because in a normal environment, the temperature rises as the operating time increases. However, in this case, since the magnetic head comes into contact with the magnetic recording medium with an excessive force at the beginning of the operation, the head wear is increased and the magnetic recording medium may be damaged.

Therefore, the present invention has solved the above-mentioned problems, and suppresses the influence of temperature change to a small level.
The present invention proposes a dynamic tracking head device, a rotary drum device, and a magnetic recording / reproducing device that can minimize the generation of noise and prolong the life of the head.

[0010]

In order to solve the above problems, in a dynamic tracking head device according to a first aspect of the present invention, a magnetic head, a bimorph for displacing the magnetic head in the track width direction, and a bimorph are provided. A dynamic tracking head device having a head base for holding is characterized in that the head base is molded of powder metallurgy alloy of molybdenum and copper.

According to a second aspect of the present invention, in the rotary drum device having a dynamic tracking head, the dynamic tracking head holds a magnetic head, a bimorph for displacing the magnetic head in the track width direction, and a bimorph. To this end, a head base made of powder metallurgy alloy of molybdenum and copper is provided.

According to a third aspect of the present invention, there is provided a magnetic recording / reproducing apparatus provided with a rotary drum having a dynamic tracking head, wherein the dynamic tracking head displaces the magnetic head and the magnetic head in a track width direction. And a head base molded of a powder metallurgy alloy of molybdenum and copper for holding the bimorph.

In the present invention, the head base has a powder metallurgy alloy of molybdenum and copper (coefficient of linear expansion: 6 × 10 ^-6 /
Since it is molded at (° C), the linear expansion coefficient is about 1/3 compared to the conventional aluminum die cast (linear expansion coefficient 18.6 x 10 ^-6 / ° C), so even if the temperature change is large, the magnetic head It is possible to suppress the change in the amount of protrusion of the rotating drum relative to the rotating drum.

Further, the powder metallurgy alloy of molybdenum and copper has a mechanical strength higher than that of other materials having a small coefficient of linear expansion, such as powder metallurgy alloy of tungsten and copper and ceramic materials.
It is excellent in terms of specific gravity, conductivity, cost, and the like, which makes it possible to manufacture a dynamic tracking head at low cost with high strength and compactness.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Next, one embodiment of a dynamic tracking head device, a rotary drum device and a magnetic recording / reproducing device according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view of a dynamic tracking head device 1 according to the present invention. In this dynamic tracking head device 1, two bimorphs 14 and 15 are provided along a horizontal side portion 13 from a vertical side portion 12 of a head base 11 having an L-shaped cross section. Bimorph 1
The screws 4 and 15 are fixed to the vertical side portion 12 with setscrews 16 and 17.

The tips of the bimorphs 14 and 15 are connected by a U-shaped elastic body, for example, a carbon beak 18.
A magnetic head 19 is attached to the lower surface of the carbon beak 18 by, for example, adhesion. Head base 11
Is formed of a powder metallurgy alloy of molybdenum and copper, and the weight expansion ratio of molybdenum 92: copper 8 is set so that the linear expansion coefficient is 6 × 10 ⁻⁶ / ° C.

In the dynamic tracking head device 1, one is extended and the other is contracted by adjusting the voltage applied to the bimorphs 14 and 15.
As a result, the tips of the bimorphs 14 and 15 can be moved up and down, and the magnetic head 19 can be displaced in the W direction, that is, in the direction perpendicular to the plate surfaces of the bimorphs 14 and 15.

Dynamic tracking head device 1
As shown in FIG. 2, the middle drum 31 of the rotary drum 3 is
The head base 11 is attached by fixing the front end of the head base 11 with set screws 20 and 21. Rotating drum 3
The upper drum 32 and the lower drum 33 above and below the middle drum 31.
And the tip of the magnetic head 19 projects from the lead surfaces 32a, 33a of the upper drum 32 and the lower drum 33 around which the magnetic tape 4 (FIG. 3) is wound by a dimension d. When the middle drum 31 rotates, the magnetic head 19 moves in the A direction along the track 41 of the magnetic tape 4 wound around the middle drum 31 and traveling as shown in FIG. At this time, when the magnetic tape 4 travels at a slow speed, a still speed, a fast speed, or the like, the magnetic head 19 may be displaced from the track 41 and noise may be generated as it is. Therefore, here, when the magnetic tape 4 travels at a variable speed, a controlled voltage is applied to the bimorphs 14 and 15 to displace the magnetic head 19 in the W direction so that the track 41 is accurately traced.

Further, in this dynamic tracking head device 1, the head base 11 is formed of a powder metallurgy alloy of molybdenum and copper, and the linear expansion coefficient is set to 6 × 10 ^-6 / ° C., so that the ambient temperature is Even if it changes, the protrusion amount d of the magnetic head 19 does not change so much as compared with the conventional case where the head base is molded by aluminum die casting.

FIG. 4 shows the relationship between the ambient temperature in the dynamic tracking head device 1 and the change Δd in the protrusion amount d of the magnetic head 19. As you can see from the figure,
When the temperature is 22 ° C., the change Δd in the protrusion amount d is −4.3 μm at 60 ° C., and Δd = −6.6 μm at 80 ° C. The symbol indicates that the tip of the magnetic head 19 has retracted toward the center of the rotary drum 3. When the temperature is -20 ° C, Δd =
At a temperature of +4.8 μm and −40 ° C., Δd = + 7.0 μm. The + sign indicates that the tip of the magnetic head 19 has moved in a direction further projecting from the surface of the rotary drum 3.

As described above, in the dynamic tracking head device 1 of the present invention, the protrusion amount d of the magnetic head 19 does not change so much even if the ambient temperature changes, and the head base has an aluminum die unlike the conventional case. It can be suppressed to about 1/3 as compared with the dynamic tracking head device molded by casting (see FIGS. 4 and 7).

Therefore, even if the ambient temperature changes, the contact pressure between the magnetic head 19 and the magnetic tape 4 can always be kept constant, so that the wear of the magnetic head 19 can be reduced and the life can be extended. Together with the magnetic head 19
It is possible to prevent the generation of noise due to insufficient contact pressure of the magnetic tape 4.

Besides the powder metallurgy alloy of molybdenum and copper,
For example, there are materials having a small linear expansion coefficient, such as a powder metallurgy alloy of tungsten and copper, and a ceramic material. However, considering the usage environment and usage conditions of the dynamic tracking head device 1, the mechanical strength, the specific gravity, the conductivity, and the cost are considered. Therefore, as the material of the head base 11, a powder metallurgy alloy of molybdenum and copper is preferable.

The powder metallurgy alloy of molybdenum and copper is
The linear expansion coefficient can be arbitrarily changed depending on the mixing ratio. In the above-described embodiment, the weight ratio of molybdenum to copper is 9
By setting it to 2: 8, the coefficient of linear expansion is 6 × 10 ^-6 / ° C.
However, the linear expansion coefficient may be further reduced by changing the mixing ratio.

5 and 6, a single signal of 32 MHz is recorded on the magnetic tape 4 by a video tape recorder (not shown) which is a magnetic recording / reproducing apparatus to which the rotary drum 3 is applied.
The waveform of the video signal when this is reproduced is shown. FIG.
A reproduced waveform at a normal temperature (+ 24 ° C.) is shown, and FIG. 6 shows a reproduced waveform at a high temperature (+ 45 ° C.).

A waveform 51 in FIG. 5 is a waveform in which a recording signal is reproduced by a dynamic tracking head using a conventional head base molded by aluminum die casting, and the undulation of the waveform is about 2 dB. The output of the head as viewed from the amplifier noise 52 of the same channel as the reproduced waveform 51 is -39.9 dB, and the output C / N of the head as viewed from the sliding noise 53 is -33.2 dB.

Waveforms 54 and 57 are the head base 11 made of the powder metallurgy alloy of molybdenum and copper according to the present invention.
The waveform is a waveform reproduced from the recording signal by the dynamic tracking head device 1 using the waveform, and the waviness of the waveform is about 2 dB which is almost equal to the waviness of the waveform 51 reproduced by the conventional dynamic tracking head.

The output of the head as seen from the reproduced noises 54 and 57 and the amplifier noises 55 and 58 of the same channel this time is -43.7 dB, and the output C / N of the head as seen from the sliding noises 56 and 59 is It is -35.5 dB.

When the environmental temperature is raised to + 45 ° C. from the state of FIG. 5, the waveform as shown in FIG. 6 is obtained. The swell of the waveform 61 reproduced from the recording signal by the conventional dynamic tracking head is as large as about 5 dB. It is considered that this is because the magnetic head retracts due to the temperature rise and the contact pressure between the magnetic head and the magnetic tape becomes weak.

The output of the head as seen from the amplifier noise 62 of the same channel is -34.5 dB, and the sliding noise 63
The output C / N of the head seen from is -30.7 dB,
They are decreased by 5.4 dB and 2.5 dB, respectively. This also proves that the contact pressure between the magnetic head and the magnetic tape has weakened.

On the other hand, the undulations of the waveforms 64 and 67 when the recording signal is reproduced by the dynamic tracking head device 1 of the present invention is about 3 dB, and no great change is observed as compared with the case of 22 ° C. , The contact pressure between the magnetic head 19 and the magnetic tape 4 also shows little change.

The output of the head as seen from the amplifier noises 65 and 68 of the same channel is -41.6 dB, and the sliding noise 6
The output C / N of the head viewed from 6, 69 is -33.9 dB.
The changes are 2.1 dB and 1.4 dB, respectively, which are very small, which also proves that there is no change in the contact pressure between the magnetic head 19 and the magnetic tape 4.

[0034]

As described above, according to the present invention, the magnetic head is attached to the tip of the bimorph, and the other end of the bimorph is attached to the head base made of powder metallurgy alloy of molybdenum and copper.

Therefore, according to the present invention, since the dimensional change of the head base is small even if the ambient temperature changes, the contact pressure between the magnetic head and the magnetic recording medium can be kept substantially constant, and the magnetic head can be maintained. It is possible to reduce the wear of the disk and prolong the life thereof, and it is possible to suppress reproduction noise.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a dynamic tracking head device 1 according to the present invention.

FIG. 2 is a diagram showing a configuration of a rotary drum 3.

FIG. 3 is a diagram showing a configuration of a magnetic tape 4.

FIG. 4 is a diagram showing an influence of ambient temperature in the dynamic tracking head device 1.

FIG. 5 is a waveform diagram of a reproduced signal at room temperature (+ 24 ° C.).

FIG. 6 is a waveform diagram of a reproduction signal at a high temperature (+ 45 ° C.).

FIG. 7: Conventional dynamic tracking head device 1
It is a figure which shows the influence of the surrounding temperature in.

[Explanation of symbols]

 1 Dynamic Tracking Head Device 3 Rotating Drum 11 Head Base 14, 15 Bimorph 19 Magnetic Head

Claims (9)

[Claims] 1. A dynamic tracking head device having a magnetic head, a bimorph for displacing the magnetic head in the track width direction, and a head base for holding the bimorph, wherein the head base is molybdenum and copper. A dynamic tracking head device characterized by being molded from the powder metallurgy alloy of. 2. A rotary drum device having a dynamic tracking head, wherein the dynamic tracking head comprises a magnetic head, a bimorph for displacing the magnetic head in the track width direction, and molybdenum and copper for holding the bimorph. A rotary drum device, comprising: a head base molded of powder metallurgy alloy; 3. A magnetic recording / reproducing apparatus provided with a rotary drum having a dynamic tracking head, wherein the dynamic tracking head includes a magnetic head, a bimorph for displacing the magnetic head in a track width direction, and the bimorph. A magnetic recording / reproducing apparatus comprising: a head base molded of a powder metallurgy alloy of molybdenum and copper for holding the magnetic recording medium. 4. The dynamic tracking head device according to claim 1, wherein the weight ratio of molybdenum to copper of the powder metallurgy alloy is 92: 8. 5. The rotary drum device according to claim 2, wherein the weight ratio of molybdenum to copper of the powder metallurgy alloy is 92: 8. 6. The magnetic recording / reproducing apparatus according to claim 3, wherein the weight ratio of molybdenum to copper of the powder metallurgy alloy is 92: 8. 7. The linear expansion coefficient of the head base is 10 ×.
The dynamic tracking head device according to claim 1, wherein the dynamic tracking head device has a temperature of 10 ^-6 / ° C or less. 8. The linear expansion coefficient of the head base is 10 ×.
The rotary drum device according to claim 2, wherein the rotary drum device has a temperature of 10 ^-6 / ° C or less. 9. The linear expansion coefficient of the head base is 10 ×.
The magnetic recording / reproducing apparatus according to claim 3, wherein the magnetic recording / reproducing apparatus has a temperature of 10 ^-6 / ° C or less.