JP2753366B2 - Rotary drum device and magnetic head mounting method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head mounted on a rotary drum device used for a magnetic recording / reproducing device such as a VTR, and more particularly, to a structure of the magnetic head and a rotation of the magnetic head. The present invention relates to a mounting method for a drum device.

[Conventional technology]

For VTRs that require high image quality, multi-functionality, and high reliability, such as professional VTRs, a system that uses a recording / reproducing separation head, in which the recording head and playback head are independent, is required to fully exploit the performance of the magnetic head. Many. When performance is more important, the recording head is a metal head with high saturation magnetic flux density and high recording performance, and the reproducing head has a thick skin depth and the frequency characteristics of magnetic permeability are sufficient up to high frequencies of 50 MHz or more. A responsive and reliable ferrite head is often used.

On the other hand, the life of a magnetic head that slides on a magnetic tape at high speed is generally shorter than the life of a VTR body. Therefore, the magnetic head is replaced as a maintenance part in a certain period. However, considering the running cost of the VTR, the smaller the number of replacements, the better.

FIG. 2 is a view showing a head arrangement of a conventional rotary drum device (3). The figure shows a system in which recording / reproducing is performed by a total of four heads, that is, the recording magnetic heads 2, 2 'are 2ch and the reproducing magnetic heads 1, 1' are 2ch. In reality, there are also 4ch, 8ch and 16ch systems for recording 4ch, 8ch and 16ch reproduction.

In such a conventional recording / reproducing magnetic head separated type system, the recording magnetic heads 2, 2 'and the reproducing magnetic head
The gap depth G _dPB and G _dRec of 1,1 ′ are set between approximately 20 and 30 μm for both the recording and reproducing magnetic heads at the time of mounting on a rotating drum device from the viewpoint of initial performance and from the viewpoint of manufacturing process control. Therefore, no particularly clear depth difference is provided in the gap depth between the recording magnetic head and the reproducing magnetic head.

Also, the amount of head protrusion from the rotating head drum device
D _PB and D _Rec also did not have a distinct difference in protrusion amount.

When the recording magnetic head and the reproducing magnetic head are made of the same material, the wear speed of the two magnetic heads is almost the same, and when the head depth and the amount of protrusion are the same, the life of all the heads is almost the same, so the efficiency is high. Was good. However,
When the recording magnetic head and the reproducing magnetic head are made of different materials, the heads are slid with the same tape tension, so that the wear speeds of the two heads are different. Therefore, when the gap depth is the same, the life of the other one will expire even if one is still usable, and the magnetic head will need to be replaced. For the magnetic head replacement work, it is conceivable to replace only the magnetic head that has reached the end of its service life.However, it is not easy to replace a magnetic head positioned with high precision using only a simple jig. A method of exchanging the entire rotating section on which the magnetic head of the apparatus is mounted has been adopted. Therefore, in terms of running cost, head replacement has been inefficient.

In general, the spacing loss SL during recording and playback is
The SL coefficient of 54.6 × d / λ [dB] (d; effective spacing, λ; wavelength) at the time of reproduction is reported to be 90 to 130 for the SL coefficient at the time of recording / reproduction. Pacing loss is also large enough.

In particular, for business use, it is necessary to consider recording with importance, and it is necessary to minimize the loss during recording. For this reason, when a recording / reproducing head is made of a material with a different wear rate, the recording system is made of a soft metal material, but the recording system is made of a soft metal material and the reproducing system is made of a ferrite material. When mounting the magnetic head on the drum device,
If the head protrusion amount is determined only by the initial performance, the head touch of the reproducing head is good due to the running for a long time due to the difference in the amount of wear, but the head touch of the recording head deteriorates.

The gap depth is near zero (about 5 μm or less)
In the reproducing magnetic head, as the gap depth approaches zero, the reproducing efficiency increases, so that the reproducing output increases and is good.However, as for the recording magnetic head, the recording efficiency decreases as the gap depth approaches zero. It rises sharply, and the optimum recording current value changes suddenly. For this reason, it was necessary to equalize the recording near the gap depth of zero.

[Problems to be solved by the invention]

FIG. 3 shows head wear amounts of a metal recording head and a ferrite reproduction head. Generally, metal has a higher polishing rate than ferrite. For this reason, as shown in FIG. 3, when the tape is slid for a long time at the same gap depth, the difference in abrasion gradually increases. It was necessary to replace the head, and there was a problem in terms of running cost. Further, the head touch has not been optimized in consideration of the difference in wear rate. Furthermore, there was no consideration on the recording current characteristics of the recording magnetic head near the gap depth of zero.

An object of the present invention is to provide a magnetic head having the same head life and a stable and good performance in order to reduce running costs when the above-mentioned different types of magnetic heads are mounted on the same rotating drum device. is there.

Another object of the present invention is to provide a method for mounting a magnetic head which has good performance even when running for a long time when the magnetic head is mounted on a rotary drum device.

It is still another object of the present invention to provide an appropriate value of the initial gap depth near the gap depth of zero, taking into account the recording current characteristics of the recording magnetic head.

[Means for solving the problem]

To achieve the above object, it is a gap depth G _DREC drum mounting initial recording magnetic head that is deeper than the gap depth G _DPB the reproducing magnetic head.

Further, in order to keep the head touches of both heads good even during long running, the head protrusion amount D _Rec of the recording magnetic head when the drum is mounted is made larger than the head protrusion amount D _PB of the reproducing magnetic head.

[Action]

By making the gap depth G _dRec of the recording magnetic head when the drum is mounted deeper than the gap depth G _dPB of the reproducing magnetic head, the difference in the amount of wear between the recording magnetic head and the reproducing magnetic head, which is generally caused by the material difference, is reduced. The recording characteristics of the recording magnetic head are made almost stable until the head replacement time, by covering the difference in depth and leaving the gap depth of the recording magnetic head even when the gap depth of the reproducing magnetic head becomes zero. And the effective lives of both heads can be made substantially equal. Therefore, it is possible to reduce the running cost of head replacement.

Further, by making the head protrusion amount D _Rec of the recording magnetic head larger than the head protrusion amount D _PB of the reproducing magnetic head, it is possible to improve the head touch of the recording magnetic head having a large spacing loss for a long time.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a case where a total of four read magnetic heads 1, 1 'and two write magnetic heads 2, 2' are mounted on the rotary drum device 3. In the figure, two sets of recording / reproducing heads mounted opposite to each other are shown, but the present invention is not limited to this. Depending on the system, a flying erase head may be mounted, or four sets, eight sets, 16 sets, etc. Is also good. Further, each head is not limited to a single azimuth head in which one head chip is mounted on one head base 4. For example, a double azimuth head in which two head chips are mounted on one head base, or a large number of heads are mounted. A multi-channel magnetic head may be used. In addition, the reproducing magnetic head which may be equipped with a flying erase head has a good frequency response in a high frequency range,
For example, a magnetic head using a core material of a single crystal of Mn-Zn ferrite or Ni-Zn ferrite, or a polycrystal with reduced sliding noise. Gap length G _1PB the reproducing magnetic head, when the shortest recording wavelength of the system and lambda _o 0.35
λ _o <G _1PB <0.6λ _o is desirable. The recording magnetic head is
High saturation magnetic flux density. A magnetic head using a metal material such as Sendust or Fe-based or Co-based amorphous as the core material, or a metal near the gap and ferrite for other parts to concentrate magnetic flux only near the gap It is a magnetic head. The gap length G _1Rec of the recording magnetic head is desirably 0.45λ _o <G _1Rec <0.9λ _o . Although FIG. 1 shows a coil-winding type head, the present invention is not limited to this, and a thin-film magnetic head in which a coil is formed by a thin-film process may be used. A and B in the figure
Are the area A of the reproducing magnetic head tape sliding portion when viewed from the tape sliding surface side of the reproducing magnetic heads 1 and 1 'and the recording area when the recording heads 2 and 2' are viewed from the tape sliding surface side. This is the area B of the magnetic head tape sliding portion. Above A and B need not be AB when the reproducing magnetic heads 1 and 1 'and the recording magnetic heads 2 and 2' have different tape sliding member qualities. Generally, a recording magnetic head 2 using a soft metal material,
Since 2 ′ is more likely to wear than the reproducing magnetic heads 1 and 1 ′ using a hard ferrite material, it is preferable to set A <B to reduce the difference in wear speed. However, A≪
In B, the surface pressure of the recording magnetic head against the tape is smaller than the surface pressure of the reproducing magnetic head, so that the recording magnetic head has poor head touch. Therefore, from the experiment, Is desirable. Regarding A and B, there is another way of thinking.
That is, the soft magnetic material which is the core material of the recording magnetic heads 2 and 2 'is covered with a material harder than the reproducing magnetic head, so that the recording magnetic heads 2 and 2' are harder to wear than the reproducing magnetic heads 1 and 1 '.
This is a technique for reducing the difference in wear rate. In this case, A <B. However, if a material that is too hard is used, abrasion and scratching of the tape occur, and a material that is not so hard cannot be used. Therefore, the relationship between A and B is Good degree.

Therefore, from the above, the relationship between A and B is Becomes _{Within the} range where the above relational expression is satisfied, it is _preferable that the gap depths G _dPB and G _dRec of each magnetic head _satisfy the relation G _dRec = G _dPB + α (where α = 3 μm to 15 μm). That is, the recording magnetic heads 2, 2 '
The gap depth G _DREC, may 3~20μm larger than the gap depth G _DPB of reproducing magnetic heads 1 and 1 '. This is derived from the following two methods.

First, in the first method, as shown in FIG. 4, a metal-based recording magnetic head is generally softer in material than a ferrite-based reproducing magnetic head, so that the metal-based recording magnetic head wears out. Cheap. Therefore, compared with the initial gap depth G _dPB of the reproducing magnetic head determined from the initial performance of the ferrite reproducing magnetic head, the gap depth G _dRec of the recording magnetic head is _set to be deeper by α, and the time of the gap depth 0 of both heads is substantially _reduced. It is a technique to make it the same. In a combination using a Co-based amorphous material for the recording magnetic head and a Mn-Zn ferrite material for the reproducing magnetic head, the value of α is 3α.
10 μm.

As shown in FIG. 5, the second method is to reduce the initial gap depth so that the gap depth of the metal recording magnetic head remains γ even when the gap depth of the ferrite reproduction magnetic head becomes zero. This is a method for determining the difference α. This is for the following reason. First, considering the reproduction signal level at which the reproduction magnetic head depends on the gap depth, the relationship shown in FIG. 8 is established. As is clear from the figure, the reproduction level increases as the gap depth decreases. Therefore,
The reproducing magnetic head can be used until the gap depth becomes zero. On the other hand, FIG. 7 shows the optimum recording current characteristic in which the recording magnetic head depends on the gap depth. As is clear from the figure, the optimum recording current decreases as the gap depth decreases. On the other hand, FIG. 6 shows the dependence of the reproduction level on the recording current. In general, the recording current dependency of the reproduction level is broader in lower frequencies. The optimum recording current has a smaller value in a higher frequency range. When the maximum reproduction level of -0.5 dB is set as the allowable range of the recording current at each frequency, the hatched portions in the figure are the allowable ranges of the recording current Io, _HI , Io, and _LOW at the respective frequencies. In order to record at the maximum reproduction level at each frequency, it is necessary to perform recording equalization that lowers the high-frequency recording current slightly as compared to the low-frequency recording current, as is clear from the figure. However, recording equalization is generally not performed much because the circuit scale is large. In practice, the recording current value is set to be almost flat from low to high frequencies. Io
Is often set to a fixed Io _common part in the frequency band. Alternatively, in order to make the reproduction level difference small, the low-frequency recording current value is set in the area where the level fluctuation is large on the left side of the figure, and the low frequency is equalized about 1-3 dB lower than the high-frequency recording level. There is also. However, in any case, when the gap depth is reduced as shown in FIG. 7, the reproduction level is deteriorated unless the set value Io of the recording current value is changed. Therefore, in order to prevent the troublesome change of the set value Io of the recording current value, even if the gap depth of the reproducing magnetic head becomes 0, it is preferable that the gap depth of the recording magnetic head remains by γ. . This value is preferably about 3 μm 8 μm. Therefore, in this case, the initial gap depth difference α
Is about 3 μmα20 μm. In the above case,
The same applies to the case where the core material of the reproducing magnetic head and the core material of the recording magnetic head are the same. That is, a combination of a ferrite-based recording magnetic head and a ferrite-based reproducing magnetic head, or a combination of a metal-based recording magnetic head and a metal-based reproducing magnetic head may be used.

When the above first and second methods are combined, the initial gap depth difference α is 3 μmα20 μm.

Next, when the recording magnetic heads 2 and 2 'and the reproducing magnetic heads 1 and 1' formed by the first and second methods are mounted on the rotary drum device 3, the amount of protrusion from the outer peripheral surface of the rotary drum device 3 Indicates that the amount of protrusion of the recording magnetic head is D for the following reason.
_Rec, if the amount of protrusion of the reproducing magnetic head was set to D _PB, D _Rec =
It is preferable to mount the unit in a relational expression of D _PB + β (where β is 3 μm or more and 10 μm or less). This is because, as described above, the gap depth of the recording magnetic head is set deeper than that of the reproducing magnetic head. The projection amount of the system recording magnetic head can be secured larger than that of the reproducing head, and the surface pressure of the recording magnetic head can always be set larger than that of the reproducing magnetic head. Therefore, spacing loss at the time of recording can be reduced. However, if the protrusion amount difference β is too large, WOW or jitter is adversely affected. As a result of an experiment, it was found that the protrusion amount difference β was 3 μm or more and 10
μm or less is desirable.

Although the above embodiment describes the relationship between the recording magnetic head and the reproducing magnetic head, the present invention is not limited to this, and can be applied to a system equipped with, for example, flying erase heads 5, 5 '. FIG. 9 shows one embodiment. In this case, _assuming that the gap depth of the flying erase heads 5, 5 'is _GdFE , _GdRec = _GdFE + δ, where δ = 0 to 10 μm. This is for the following reason. Generally, a flying erase head needs to erase deeply (with a strong magnetic field) at a high frequency higher than the operating band in order to effectively erase a written signal. However, it is impossible to pass a large current through the erase head to obtain a strong magnetic field in consideration of isolation at a high frequency. As another method, it is conceivable to increase the number of coil turns of the erase head as compared with the recording head. However, it is desirable to avoid an increase in inductance due to an increase in the number of coil turns because of the relationship with the rotary transformer. Therefore, it is preferable to take a method of always making the recording efficiency of the erase head better than the recording efficiency of the recording head with the same inductance. Therefore, by setting the gap depth to satisfy the above relational expression, a flying erase head having a good erase effect can be obtained. The positional relationship between the flying erase heads 5, 5 'and the recording magnetic heads 2, 2' is preferably such that the flying erase head precedes the drum rotation direction.

〔The invention's effect〕

Since the present invention is configured as described above, the following effects can be obtained.

First, by making the gap depth G _dRec of the recording magnetic head deeper than the gap depth G _dPB of the reproducing magnetic head, the wear amount difference between the recording magnetic head and the reproducing magnetic head, which is generally caused by the material difference, is determined by the difference of the gap depth. Cover with
In addition, by leaving the gap depth of the recording magnetic head even when the gap depth of the reproducing magnetic head becomes zero, the recording characteristics of the recording magnetic head can be almost stabilized until the head replacement time, and the effective life of both magnetic heads Can be made substantially equal. Therefore, it becomes possible to reduce the running cost of head replacement.

Further, by making the head protrusion amount of the recording magnetic head larger than the head protrusion amount of the reproduction magnetic head, it is possible to maintain good head touch of the recording magnetic head having a large spacing loss for a long time.

[Brief description of the drawings]

FIG. 1 is a head arrangement diagram of one embodiment of the present invention, FIG. 2 is a conventional head arrangement diagram, FIG. 3 is a conventional head wear characteristic diagram,
FIGS. 4 and 5 are head wear characteristic diagrams according to the present invention, FIG. 6 is a recording current characteristic diagram of a reproducing level, FIG. 7 is a diagram showing a gap depth dependence of an optimum recording current, and FIG. FIG. 9 is a diagram showing the dependence of the level on the gap depth, and FIG. 9 is a head layout when a flying erase head is mounted. 1,1 '... reproducing magnetic head, 2,2' ... recording magnetic head 3 ... rotary drum device, 4 ... head base 5,5 '... flying erase head _GdPB , _GdRec : gap depth of reproducing and recording magnetic head ( D _PB , D _Rec … protrusion of read / write magnetic head

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-59-144028 (JP, A) JP-A-59-144018 (JP, A) JP-A-61-273714 (JP, A) JP-A-61-273714 117720 (JP, A) JP 55-34484 (JP, B1)

Claims (6)

(57) [Claims] 1. A rotary drum device (3) in which a recording magnetic head and a reproducing magnetic head are mounted separately and independently, wherein a gap depth (G _dRec ) of the recording magnetic head and a gap depth (G _dRec ) of the reproducing magnetic head are provided. G _dPB ), at least the sum of the tape sliding time of both magnetic heads is 100
_GdRec = _GdPB + α within a period of time, wherein the gap depth is such that α = 3 μm or more and 15 μm or less. 2. When a recording magnetic head and a reproducing magnetic head are mounted on a rotary drum device,
Projecting amount of the recording magnetic head and (D _Rec), the relationship between the amount of protrusion D _PB of reproducing magnetic heads, tape sliding time of both the magnetic head at the time within 100 hours, D _Rec = D _PB + β provided that beta = 3 μm or more and 10 μm or less. A method for mounting a magnetic head on a rotary drum device. 3. The recording magnetic head has a core member made of a metal member or a composite member of a metal and a ferrite member, and the reproduction magnetic head has a core member made of a ferrite member. Item 2. The rotary drum device according to Item 1. 4. The rotary drum device according to claim 1, wherein the recording magnetic head and the reproducing magnetic head have a core member made of a metal member or a composite member of a metal and a ferrite. 5. When the recording magnetic head and the reproducing magnetic head slide on the tape for a long time, and the gap depth (G _dPB ) of the reproducing magnetic head becomes 2 μm or less, the gap depth (G) of the recording magnetic head becomes lower. _dRec ) is at least 5 μm
The rotary drum device according to claim 1 having the above. 6. A rotary drum device on which a recording magnetic head and a flying erase head are mounted, wherein a gap depth (G _dFE ) of the flying erase head and a gap depth (G) of the recording magnetic head are provided.
_dRec ): G _dRec = G _dFE + δ, where _g is a gap depth such that δ = 0 μm or more and 10 μm or less.