JP2696831B2 - Magnetic head - Google Patents

Description

The present invention relates to a magnetic head such as a floppy disk drive (hereinafter abbreviated as FDD), and particularly to a magnetic head suitable for high-density recording / reproduction. In this case, the occurrence of errors is reduced. [Summary of the Invention] The present invention provides a magnetic head such as an FDD which includes two coils and performs recording / reproduction by generating recording magnetic fluxes in mutually different directions. Reduce the coupling capacitance of these coils, raise the resonance frequency determined by the coupling capacitance and coil inductance, suppress noise from inductive noise sources, crosstalk from the head on the opposite side, etc., and reduce the magnetic flux of the erase head. In addition, the occurrence of errors such as erroneous recording and erroneous reproduction is reduced by compensating for the magnetic field generated due to the interference or the asymmetry of the magnetic recording. [Prior Art] FIG. 5 is an equivalent circuit diagram of a magnetic head and a recording system conventionally used in FDD. The magnetic head 1 includes a recording / reproducing head 2 and an erasing head 3. The recording / reproduction core 4 of the recording / reproduction head 2
A reproducing coil 5 is wound, and the recording / reproducing coil 5 is divided into a first coil 7 and a second coil 8 by a center tap 6. The number of turns of the first coil 7 and the number of turns of the second coil 8 are equal to each other.
0 turns. An erasing core 10 is disposed adjacent to the recording / reproducing core 4 (behind the disk moving direction indicated by the arrow a) via a spacer 9, and an erasing coil 11 is wound around the erasing core 10. ing. The pair of erasing gaps 12 formed in the erasing core 10 are located on both sides behind the recording / reproducing gap 13 formed in the recording / reproducing core 4. In this magnetic head 1, the center tap 6
Switch circuit from the first coil 7 to the second coil 8
The recording current is alternately caused to flow by the switching of 14, and the recording magnetic fluxes A and B in the directions different from each other are alternately generated in the recording / reproducing core 4 by the magnetomotive force of the coils 7 and 8. Then, a recording track magnetized for recording is formed on the disk at the recording / reproducing gap 13. Simultaneously with this recording, a DC erasing current is applied to the erasing coil 11 to generate an erasing magnetic flux E in a fixed direction in the erasing core 10 by the magnetomotive force of the erasing coil 11, thereby erasing both sides of the recording track at the erasing gap 12. It is configured to secure a guard band. The coils 7 and 8 described above are generally formed by bifilar winding shown in FIG. This bifilar winding,
The first coil 7 and the second coil 8 can be regarded as completely equivalent in the winding method in which two conductive wires are wound in pairs, except that the polarities of the first coil 7 and the second coil 8 are different. Therefore, the magnetic field generated in the recording / reproducing gap 13 at the time of recording (writing) is symmetrical in each polarity, and a peak shift (shift of a recording position) caused when the magnetic field is asymmetrical is prevented. [Problems to be Solved by the Invention] However, in the recording system of the conventional recording head,
As shown in FIG. 5, since the coupling capacitance C of the coils 7 and 8 exists, a resonance circuit is formed by the coils 7 and 8 and the coupling capacitance C. If there is an inductive noise source, the resonance frequency is reduced. There is a problem of being easily guided. The coupling capacitance C is relatively large because the coils 7, 8 are bifilar wound, while
The resonance frequency f ₀ in the above resonance circuit is as follows, where L is the inductance of the coils 7 and 8. , And decreases as the coupling capacitance C increases. In recent high-density media and heads, recording / reproducing at a higher frequency has become possible.
A signal of about five times is recorded / reproduced. If the above-mentioned resonance frequency f ₀ is about 3 to 5 times the maximum recording frequency (f _max ), inductive noise of the resonating frequency f ₀ is recorded on the medium, and the S on the already recorded recording surface is reduced. / N worsens, causing errors during playback. In particular, in a double-sided recording FDD, the magnetic heads on both sides of the floppy disk are arranged to face each other, and even when writing on one side, the magnetic head on the other side is moved together with the magnetic head on one side. Therefore, the write-side magnetic head becomes a source of inductive noise with respect to the pause-side magnetic head. As described above, the recording current is switched alternately, resulting in a substantially rectangular wave, which has a large odd harmonic component. Therefore, if the magnetic head resonates with a harmonic component that is 3 to 5 times the maximum recording frequency _fmax , it causes an error as described above. The above is called crosstalk. Further, asymmetry occurs in magnetic recording due to interference of magnetic flux leakage from an erasing head for forming a guard band disposed close to the recording / reproducing head, causing a peak shift during reproduction and an error. There is a fear. The present invention has been made in order to solve the above-described problems, and has been made to reduce the coupling capacitance of a recording / reproducing coil of a magnetic head to receive inductive noise from an external or a head on the opposite side of a double-sided FDD. It is an object of the present invention to provide a head that does not record / reproduce on a medium even when resonated, is resistant to inductive noise, does not generate crosstalk, and can prevent erroneous recording / erroneous reproduction due to interference of an erase head. [Means for Solving the Problems] In order to achieve the above object, a magnetic head according to the present invention has a configuration in which a second coil is concentrically arranged outside a first coil to generate recording magnetic fluxes in mutually different directions. A magnetic head having a recording / reproducing head to be driven and an erasing head having a third coil for generating an erasing magnetic flux, wherein a magnetic flux generated from the first coil and a magnetic flux generated from the second coil is generated. The polarity of the first coil and the polarity of the second coil are determined so that the difference and the leakage magnetic flux generated by the erase head cancel each other. [Operation] In general, since the capacitance between two conductors is inversely proportional to the distance between the conductors, the present invention separates and independently couples the two coils instead of separating them as in a conventional bifilar winding. Make it smaller. According to the present invention, the resonance frequency of the resonance circuit of the magnetic head, which is formed by the coupling capacitance and the inductance of the coil, is increased outside the recording / reproducing area of the magnetic head by reducing the coupling capacitance. Therefore, there is no possibility that external inductive noise or crosstalk from a magnetic head on the opposite side of a double-sided FDD resonates in a recordable frequency region, and is not recorded or reproduced on the medium. further,
The first problem that a peak shift occurs due to the difference between the two magnetic fluxes due to the difference between the magnetic flux emanating from the first coil and the magnetic flux emanating from the second coil, and the leakage magnetic flux of the erase magnetic flux of the adjacent erase head. Instead of individually addressing the second problem of peak shifts,
The magnetic flux difference between the two coils, which is the cause of the first problem, and the leakage magnetic flux of the erasing magnetic flux, which is the cause of the second problem, are mutually used, that is, the magnetic flux difference is canceled out to complicate the configuration. The solution can be achieved at once without adding a simple circuit or coil. Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The following embodiment shows a case in which the recording / reproducing head includes two coils, as in the conventional example, and alternately generates recording magnetic fluxes in different directions by switching. Therefore, the same portions as those of the conventional magnetic head are denoted by the same reference numerals, and description thereof will be omitted. FIG. 1 is a configuration diagram showing a reference example for understanding the present invention. The recording / reproducing coil 15 in this reference example is a bobbin 16
And a second coil 19 wound around the other half of the bobbin 16 with a partition 18 substantially at the center of the bobbin 16 interposed therebetween. It is pierced. In the above, the first coil 17 and the second coil 19 are divided and arranged by the partition 18. However, each coil 17, 19 is wound around two bobbins of the same shape, and is passed through the recording / reproducing core 4 in a series. You may wear it. In addition, partition
18 may be omitted, or by adjusting the thickness thereof, the coupling capacity of the two coils 17, 19 can be made smaller to a value in a desired range. In the case where two bobbins are wound, similarly, the coupling capacity can be further reduced by adjusting the distance between the bobbins to keep the coupling capacity within a desired range. According to the fabrication example, the conventional coupling capacitance of about 30 pF can be reduced to about 10 pF. In this reference example, the number of turns of the first coil 17 is configured to be larger than the number of turns of the second coil 19. The reason for this is that in the case of a high-density FDD magnetic head, the recording / reproducing head 2
And the erasing head 3 are close to each other, and the recording / reproducing head 2
When a fixed gap (guard band) is generated by performing trim erase on both sides of the recording track while recording with
This is for canceling the interference of the erasing (generally DC erasing) magnetic flux by the erasing head 3 because the magnetic flux is interfered. Second
FIGS. 7A, 7B, and 7C are explanatory diagrams of the interference of the erasing magnetic flux. In FIG. 7A, if the first coil and the second coil are equivalent in FIG. The magnetic fluxes B generated by the two coils are equal. However, the leakage magnetic flux E 'of the erasing magnetic flux E
(2), the recording magnetization on the medium becomes asymmetric as shown in (b), and a peak shift (the position indicated by the dotted line is a normal peak point) occurs during reproduction as shown in (c). Would. Therefore, as described above, the number of turns of the first coil is increased to compensate for A = B + E '. In the conventional bifilar winding, such a compensating winding is difficult, but in the present embodiment, the winding is independent and can be easily implemented. FIG. 3 is a configuration diagram of one embodiment of the present invention. The recording / reproducing coil 15 'in this embodiment is provided with a first coil on the bobbin 16'.
17 'is wound inside, and the second coil 19' is arranged so as to surround the first coil 17 ', that is, concentrically. But,
Although the two coils are independent and separated from each other to reduce the coupling capacitance, the first coil 17 'and the second coil 19' cannot be regarded as equivalent if they remain as they are. Is generated in the generated magnetic field. That is, since the second coil 19 'has a large gap with the recording / reproducing core 4, the leakage magnetic flux is large, and the efficiency of releasing the magnetic flux to the recording / reproducing gap 13 is low. In addition, the second coil has a large sectional area in the magnetic path, so that the inductance L is proportionally large. Further, although the influence is small, the second coil 19 'generates a smaller magnetic flux due to a longer total length of the conductor, a higher DC resistance, and a lower recording current. Note that a coupling capacity can be adjusted to be smaller by providing a partition 18 'and a gap between the two coils as in the reference example. In the present embodiment, the number of turns of the two coils 17 ', 19' is the same, and the polarity relationship between the two coils 17 ', 19' and the erasing coil 11 is designated, and the high-density FDD described in FIG. Of the erase head in the magnetic head described above. In FIG. 2, the polarity is determined so that the magnetic flux generated by the inner first coil becomes A and the magnetic flux generated by the outer second coil becomes B, thereby eliminating the asymmetry of the inner and outer coils. Cancel the asymmetry of the recording magnetic flux due to the leakage of the magnetic flux,
Make the magnetization on the media symmetric. In the above, if the asymmetry of the recording magnetic flux cannot be completely canceled, two coils 1
It may be adjusted by changing the number of turns of 7 ', 19'. FIG. 4 shows a recording current waveform flowing through the recording / reproducing coil at the time of writing. Usually, due to the inductance of the coil, if the resistance connected between the two coils is R _WD (FIG. 5), the rising time constant τ of the square wave is τ =
Although determined by the L / R _WD, the coupling capacitance C with the coil is large in this, overshoot as indicated by a dotted line is generated recording becomes unstable, appear as a fluctuation of the read data during playback, the error This may be a factor. According to the present embodiment, since the coupling capacitance is reduced, the overshoot can be reduced, and the above error can be prevented. The recording current of the rectangular wave has an odd-order harmonic component, and the lower-order harmonic has higher energy and is more likely to receive an error due to crosstalk. By moving the resonance point to a point exceeding ５5, low-order crosstalk and the like are prevented, and crosstalk and noise are prevented by setting the resonance point outside the recordable / reproducible area of the recording / reproducing head. The present invention can be applied to various recording apparatuses according to the gist, and can take various embodiments. [Effects of the Invention] As is clear from the above description, according to the magnetic head of the present invention, since the coupling capacitance is reduced, the magnetic head can be resistant to inductive noise. Talk can be avoided. On the other hand, the overshoot of the recording current waveform is reduced, the recording magnetization is stabilized, the fluctuation of the read data is reduced, and the error factor can be reduced. In addition, since it is not necessary to wind the conductor in pairs as in the conventional case, the winding process is easy, and it is easy to change the number of turns of two. You can get a small head for Further, in the magnetic head of the present invention, the interference of the erasing head disposed close to the recording / reproducing head can be canceled, and erroneous recording / erroneous reproduction due to the interference can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a reference example for understanding the present invention;
2 (a), 2 (b) and 2 (c) are explanatory diagrams of interference of erasing magnetic flux, FIG. 3 is a configuration diagram showing one embodiment of the present invention, FIG. 4 is a recording current waveform diagram during writing, FIG. 5 is an equivalent circuit diagram of a conventional magnetic head and a recording system, and FIG. 6 is an explanatory diagram of a conventional coil bifilar winding. 1 ... magnetic head, 17,17 '... first coil, 19,19'
... Second coil, A, B... Recording magnetic flux.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Toshio Kitamura               7 Bidet, Nantango, Nango, Uguisawa-cho, Kurihara-gun, Miyagi Prefecture               Omagne Co., Ltd.                (56) References JP-A-61-269212 (JP, A)                 JP-A-59-139120 (JP, A)                 JP-A-60-217511 (JP, A)                 Shokai 61-187005 (JP, U)                 62-117708 (JP, U)                 Showa 60-70913 (JP, U)

Claims (1)

(57) [Claims] In a magnetic head having a recording / reproducing head in which a second coil is concentrically stacked outside a first coil to generate recording magnetic fluxes in mutually different directions, and an erasing head having a third coil and generating an erasing magnetic flux. The first coil and the second coil are arranged so that a difference between a magnetic flux generated from the first coil and a magnetic flux generated from the second coil and a leakage magnetic flux generated by the erasing head cancel each other. A magnetic head, wherein the polarity of the second coil is determined. 2. 2. The magnetic head according to claim 1, wherein the polarity is determined such that a direction of a magnetic flux generated by the second coil and a direction of a leakage magnetic flux generated by the erasing head coincide with each other. Magnetic head.