JP2784917B2 - Magnetic head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head such as a floppy disk drive (hereinafter abbreviated as FDD), and more particularly to a magnetic head suitable for high-density recording / reproduction. / It belongs to the technical field of reducing errors during reproduction. 2. Description of the Related Art FIG. 4 is an equivalent circuit diagram of a magnetic head and a recording system conventionally used for FDD. The magnetic head 1 includes a recording / reproducing head 2 and an erasing head 3. A recording / reproducing coil 5 is wound around a recording / reproducing core 4 of the recording / reproducing head 2, and the recording / reproducing coil 5 is firstly coiled by a center tap 6.
And the second coil 8. The number of turns of the first coil 7 and the number of turns of the second coil 8 are equal to each other, for example, 160 turns. An erasing core 10 is disposed adjacent to the recording / reproducing core 4 (behind the disk moving direction indicated by arrow a) via a spacer 9, and an erasing coil 11 is wound around the erasing core 10. ing. Then, a pair of erase gaps 12 formed on the erase core 10 are formed on the recording / reproducing core 4.
It is configured to be located on both rear sides of the reproduction gap 13. In the magnetic head 1, at the time of recording, a recording current is alternately supplied from the center tap 6 to the first coil 7 and the second coil 8 by switching of the switch circuit 14, so that the two coils 7, 8 are activated. Recorded by magnetic force /
Recording magnetic fluxes A and B in mutually different directions are alternately generated in the reproducing core 4. Then, a recording track magnetized and recorded on the disk is formed at the recording / reproducing gap 13. At the same time as this recording, a DC erasing current is applied to the erasing coil 11,
An erase magnetic flux E is generated in the erase core 10 in a fixed direction by the magnetomotive force of the erase coil 11, and both sides of the recording track are erased at the erase gap 12 to secure a guard band. The above-mentioned coils 7 and 8 generally have a structure shown in FIG.
And formed by bifilar winding. This bifilar winding is a winding method in which two conductive wires are wound in pairs, and can be regarded as completely equivalent except that the first coil 7 and the second coil 8 have different polarities. 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. [0005] However, in the recording system of the above-mentioned conventional recording head, since the coupling capacitance C of the coils 7 and 8 exists as shown in FIG. A resonance circuit is formed by the capacitor C, and if there is an inductive noise source, there is a problem that resonance frequency is easily induced. The coupling capacitance C is relatively large because the coils 7 and 8 are bifilar wound. On the other hand, the resonance frequency f ₀ in the resonance circuit is f ₀ = 1/2 ₀ (LC ), And decreases when the coupling capacitance C is large. 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
Is deteriorated, which causes an error during reproduction. In particular, in a double-sided recording FDD, the magnetic heads on both sides of the floppy disk are arranged so as to face each other, and even when one side is written, the magnetic heads on the other side are moved together with the magnetic heads 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, and therefore 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 f _max , 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. SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it has been made possible to reduce the coupling capacity of a recording / reproducing coil of a magnetic head to reduce inductive noise from an external or double-sided FDD head on the opposite side. Even if it receives resonance, it does not record / reproduce on the media, is resistant to inductive noise, does not generate crosstalk, and can prevent erroneous recording / erroneous reproduction due to interference of the erasing head without any additional material. The aim is to get the head. A magnetic head according to the present invention for achieving the above object has a first coil and a second coil, and generates recording magnetic fluxes in different directions from each other. A magnetic recording / reproducing head which divides the first coil and the second coil in the direction of the recording magnetic flux and is arranged independently of each other; and an erasing head having a third coil for generating an erasing magnetic flux. In the head, the number of turns of the first coil and the number of turns of the second coil are different from each other, so that a leakage magnetic flux generated by the erasing head is offset. In general, the capacitance between two conductors is inversely proportional to the distance between the conductors. Therefore, the present invention does not separate the two coils and separates the coupling capacitance independently, as in the 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,
External inductive noise and crosstalk from a magnetic head on the opposite side of the double-sided FDD resonate in a recordable frequency region and are not recorded on or reproduced from the medium. Further, the number of turns of the first coil and the number of turns of the second coil are made different from each other to cancel the leakage magnetic flux generated from the erasing head, thereby forming a guard band for forming a guard band disposed close to the recording / reproducing head. The problem of asymmetry in magnetic recording due to the interference of magnetic flux leakage from the erasing head, causing a peak shift at the time of reproduction and causing an error is solved by utilizing the asymmetry of the magnetic flux generated by the first coil and the second coil. hand,
Settle without any additionals. Embodiments of the present invention will be described below in detail with reference to the drawings. The following embodiment shows a case where the recording / reproducing head has two coils and generates switching magnetic fluxes in different directions alternately by switching as in the conventional example. 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 block diagram showing an embodiment of the present invention. The recording / reproducing coil 15 according to the present embodiment is wound around the other half of the bobbin 16 with a first coil 17 wound around one half of the bobbin 16 and a partition 18 substantially at the center of the bobbin 16. The recording / reproducing core 4 includes the second coil 19. In the above description, the first coil 17 and the second coil 19 are divided and arranged by the partition 18, but each of the coils 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. The partition 18 may be omitted, or the two coils 17 and 19 may be adjusted by adjusting the thickness.
Can be set to a smaller value in a desired range. In the case of winding around two bobbins, the coupling capacity is similarly reduced by adjusting the distance between the bobbins,
It can be suppressed to a desired range. According to the manufacturing example, the coupling capacitance of about 30 pF can be reduced to about 10 pF. In this embodiment, if the number of turns of the first coil 17 and that of the second coil 19 are set to be the same, they can be regarded as substantially equivalent. Therefore, the magnetic field generated at the time of recording (writing) in the recording / reproducing gap 13. Is minimized. However, in this embodiment, the first coil 17 and the second coil 19 are not individually compensated, and the number of turns of the first coil 17 is larger than the number of turns of the second coil 19. Then, utilizing the asymmetry of the generated magnetic field, the asymmetry of the recording magnetic field due to the leakage magnetic flux of the erasing head is compensated. The reason for this is that in a high-density FDD magnetic head, the recording / reproducing head 2 and the erasing head 3 are close to each other. When a certain gap (guard band) is generated, erasing by the erasing head 3 (generally DC erasing)
This is to cancel the magnetic flux interference. FIGS. 2A, 2B and 2C are diagrams for explaining the interference of the erasing magnetic flux. In FIG.
If the coils are equivalent, the magnetic flux A generated by the first coil and the second
, The generated magnetic flux B of the coils becomes equal. However, the erasing magnetic flux E
(2), the recording magnetization on the medium becomes asymmetric as shown in (b), and the peak shifts during reproduction (the position indicated by the dotted line is the normal peak) as shown in (c). Point) occurs. Therefore, as described above, the number of turns of the first coil is increased, or the number of turns of the second coil is decreased, so that A = B + E 'is compensated. That is, the difference between the magnetic fluxes of the first coil and the second coil is offset. In the case of the conventional bifilar winding, such a compensating winding is difficult, but in the present embodiment, it can be easily implemented because the winding is independent. FIG. 3 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. 4), the time constant τ of the rise of the square wave
Is determined by τ = L / R _{WD. If the} coupling capacitance C of the coil is large, overshoot occurs as shown by a dotted line, recording becomes unstable, and appears as fluctuation of read data during reproduction. There is a possibility that this may be a factor in the occurrence of an error. According to the present embodiment, since the coupling capacitance is reduced, the overshoot can be reduced, and the error can be prevented. The recording current of the rectangular wave has an odd harmonic component, and the higher the harmonic, the larger the energy is and the error is likely to occur due to crosstalk. By moving the resonance point to a point exceeding 3 to 5 times the recording frequency, low-order crosstalk and the like are prevented, and the resonance point is set outside the recordable / reproducible area of the recording / reproducing head to reduce crosstalk and noise. To prevent. It should be noted that the present invention can be applied to various recording devices according to the gist thereof, and can take various embodiments such as being applied to a single magnetic head without an erasing core. As is apparent 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. Crosstalk from the user can be prevented. 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 a pair of conductor wires as in the conventional case, the winding process is easy, and it is easy to change the number of two turns. A small head can be obtained. 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 configuration diagram showing one embodiment of the present invention. FIGS. 2A, 2B and 2C are explanatory diagrams of interference of an erasing magnetic flux. FIG. 3 is a recording current waveform diagram during writing. FIG. 4 is an equivalent circuit diagram of a conventional magnetic head and a recording system. FIG. 5 is an explanatory diagram of a bifilar winding of a conventional coil. [Description of Signs] 1 ... Magnetic heads 17, 17 '... First coils 19, 19' ... Second coils A, B ... Recording magnetic flux

Continuation of the front page (72) Inventor Toshio Kitamura 7 Nango Shintanda, Uguisawa-cho, Kurihara-gun, Miyagi Prefecture Video Magne Co., Ltd. (56) References JP-A-61-269212 (JP, A) JP, A) JP-A-59-139120 (JP, A) JP-A-61-187005 (JP, U) JP-A-60-70913 (JP, U) JP-A-62-117708 (JP, U) (58) ) Surveyed field (Int.Cl. ⁶ , DB name) G11B 5/17

Claims (1)

(57) [Claims] A first coil and a second coil for generating recording magnetic fluxes in mutually different directions, and dividing the first coil and the second coil in the direction of the recording magnetic flux and disposing them independently of each other A recording / reproducing head and an erasing head having a third coil for generating an erasing magnetic flux, wherein the number of turns of the first coil and the number of turns of the second coil are different from each other. A magnetic head, wherein leakage magnetic flux generated from the head is offset. 2. 2. The magnetic head according to claim 1, wherein, of the first coil and the second coil, the number of turns of a coil that generates a magnetic flux in the same direction as the direction of the leakage magnetic flux is smaller than the number of turns of the other coil. 3. A magnetic head.