JP3307038B2 - Magnetic recording medium and magnetic recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium including a flexible magnetic recording medium such as a floppy disk and a magnetic recording apparatus, and more particularly, to accurate tracking using continuous servo signals. The present invention relates to a magnetic recording medium and a magnetic recording device for performing the method.

[0002]

2. Description of the Related Art Floppy disk drives are widely used for recording information such as computers and word processors. In a normal floppy disk drive, the head is positioned by open-loop control (control without feedback) using a step motor.
There was a problem that the positioning accuracy was poor and the track density could not be increased.

In recent years, an optical servo system has been proposed in which a groove is provided in a magnetic recording medium and the position of the head is measured by reading the groove position with an optical sensor provided integrally with the head. According to this method, since the head is positioned by closed loop control (feedback control), the positioning accuracy is improved, and a track density one digit higher than that of the conventional device can be realized.

There has also been proposed a method of performing closed loop control using a magnetic servo signal. For example, the frequency of a normal signal is shifted by half a track from a data track between sectors of a magnetic recording medium. There is a sector servo method in which a signal of a frequency is recorded and the head is positioned based on the strength of the signal.

[0005]

However, there are various problems in the above-described tracking servo system. That is, the optical servo method requires a light emitting device and an optical detecting device integrated with the magnetic head, so that the overall shape of the head becomes large, and a load is applied to the actuator to drive them integrally. There is a problem that the production cost increases. In the sector servo method, there is a problem in tracking accuracy because the servo signal is intermittent for each sector.

The present invention has been made in view of the above-described problems of the conventional tracking control in a magnetic recording apparatus, and has a magnetic recording medium capable of performing closed loop control of a head position by an inexpensive tracking control mechanism having a simple structure. It is an object of the present invention to provide a magnetic recording apparatus using the same.

[0007]

In order to achieve the above object, a magnetic recording medium of the present invention is a disk-shaped magnetic recording medium having a magnetic layer on a non-magnetic substrate, wherein A servo signal comprising a magnetic signal due to magnetization in the in-plane radial direction, and a plurality of servo signals on which the servo signal is recorded.
Servo tracks are arranged concentrically and the servo tracks
Characterized in that the magnetization direction is inverted according to the rotation angle.
I do. The magnetic recording apparatus of the present invention, the magnetic above described
A magnetic recording device that can use a recording medium,
A data recording / reproducing means for generating and / or detecting a magnetic flux in a circumferential direction of a magnetic recording medium; a servo signal detecting means for detecting a magnetic flux in a radial direction of the magnetic recording medium; and a servo signal detected by the servo signal detecting means. And a moving means for integrally moving the data recording / reproducing means and the servo signal detecting means.

[0008]

FIG. 1 is a schematic sectional view showing an example of a magnetic recording medium according to the present invention along a circumferential direction. A magnetic layer 12 having a thickness of about 2 μm mainly composed of a magnetic powder and a binder is provided on a non-magnetic substrate 11 made of polyethylene terephthalate, and a servo signal for tracking and recording / reproduction of data are provided on the magnetic layer. Is recorded. The magnetic layer can be formed on both sides of the base film.

As the magnetic powder, for example, Fe, Ni, C
o, Fe-Co alloy, Fe-Ni alloy, Fe-Co-N
i alloy, Fe-Ni-Zn alloy, Fe-Co-Ni-C
powder of a ferromagnetic metal such as r alloy, Co—Ni alloy or the like or a magnetic alloy containing these as a main component, γ
-Fe ₂ O ₃ , Fe ₃ O ₄ , Co-containing γ-Fe ₂ O ₃ ,
Various ferromagnetic powders such as iron oxide magnetic powders such as Co-containing Fe ₃ O ₄ and metal oxide magnetic powders such as CrO ₂ , barium ferrite and strontium ferrite are exemplified.

As the binder, those having excellent adhesion to the support and abrasion resistance are appropriately used. For example, polyurethane resins, polyester resins, cellulose derivatives such as cellulose acetate butyrate, cellulose diacetate, and nitrocellulose, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinylidene chloride copolymers, and vinyl chloride-acrylic copolymers Vinyl chloride resins such as polymers,
Examples include various synthetic rubbers such as a styrene-butadiene copolymer, an epoxy resin, and a phenoxy resin. These can be used alone or as a mixture of two or more. By further including a low molecular weight polyisocyanate compound having a plurality of isocyanate groups in the magnetic paint, a three-dimensional network structure can be formed in the magnetic layer, and the mechanical strength can be improved. In addition, various additives such as a lubricant, an abrasive, an antistatic agent, and a dispersant can be used in the magnetic paint as needed.

Examples of the non-magnetic substrate include polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polypropylene and polyethylene; cellulose derivatives such as cellulose acetate; various plastics such as polycarbonate, polyamide and polyimide; and glass. Can be used. In the lower part of the magnetic layer, a magnetic signal based on magnetization in a direction penetrating the paper plane, that is, in a radial direction of the magnetic recording medium, is recorded, and is used as a servo signal. On the other hand, a data signal based on the magnetization in the circumferential direction of the magnetic recording medium is usually recorded in the upper part of the magnetic layer. Therefore, when the data signal is recorded, the servo signal and the data signal are separated by the magnetization. The directions are orthogonal. As a result, the data recording / reproducing means for generating and / or detecting the magnetic flux in the circumferential direction of the magnetic recording medium hardly detects the servo signal, and the servo signal detecting means for detecting the magnetic flux in the radial direction of the magnetic recording medium uses the data signal. Is difficult to detect. As a result, the servo signal and the data signal can be obtained almost independently of each other.

FIG. 2 is a schematic plan view showing how a servo signal is recorded in an example of the magnetic recording medium of the present invention. In the figure, for the sake of simplicity, data signals to be recorded on the upper layer are not shown, and only a part of the disk-shaped magnetic recording medium is shown. Servo tracks 1 to 5 on which servo signals are recorded are arranged concentrically, and the direction of magnetization is sequentially reversed for each servo track along the radial direction. If the track pitch of the servo track is too large, the accuracy of tracking deteriorates, and if it is too small, it does not make much sense.Therefore, the track pitch of the required data track is the same order, usually the track pitch of the data track. The same track pitch is used.

A servo track may be provided between data tracks recorded on the upper layer of the magnetic layer, that is, a servo track may be provided between two data tracks. However, a servo signal in the lower layer leaks out. Normally, servo tracks and data tracks are provided at corresponding positions above and below the magnetic layer in order to suppress adverse effects on data signals. In FIG. 2, the reversal of the magnetization direction of each servo track is performed at every constant rotation angle. Since the induction type head detects only a change in magnetic flux, when the magnetic recording medium of the present invention is used in a magnetic recording device having such a head, the direction of magnetization needs to be reversed according to the rotation of the medium. The reversal of the magnetization direction of each servo track does not necessarily have to be performed at every fixed rotation angle. However, in this case, the rotation of the magnetic recording medium makes it possible to convert the servo signal into an AC signal having a certain frequency, thereby reducing noise components. Is easily removed by a means such as a filter.

The length of the recording section of each servo track (FIG. 2)
Medium d) is preferable to be large because the output decreases when the value is small, but the output decreases even if it is too large.
Since the accuracy of tracking deteriorates, the length is usually set to about 10 to 1000 times the length of the recording wavelength of the data signal. In order to record the servo signal as described above in the lower layer of the magnetic layer, for example, an induction type head having a head gap having a width as large as the width of the servo track in the radial direction of the magnetic recording medium is used. A method of generating a magnetic flux along the radial direction of the recording medium may be used. Usually, the width of the track is sufficiently large with respect to the thickness of the magnetic layer (the width of the track is usually about 10 to several hundred μm), so that the magnetic flux generated by such an induction type head reaches the lower layer of the magnetic layer. The servo signal can be written.

FIG. 3 is a schematic perspective view showing an example of the magnetic head section of the magnetic recording apparatus according to the present invention. Magnetic head 30
Are three slider cores 31 made of hard ceramic and three head cores 3 made of a magnetically permeable material such as ferrite.
2, 33 and 34. The head cores 32, 33, and 34 each constitute an induction type magnetic head similar to a normal data read / write head. The head core 32 has a gap portion 35 in the circumferential direction of the magnetic recording medium to be arranged, and generates and / or detects a magnetic flux in the circumferential direction of the magnetic recording medium as data recording / reproducing means. The magnetic flux is generated and detected by generating a magnetic flux in the gap 35 by a coil (not shown) wound on the back surface.
Alternatively, the detection is performed by detecting a magnetic flux generated in the gap portion 35. The head cores 33 and 34 each have a gap 36 in the radial direction of the magnetic recording medium to be arranged.
And 37, and detects the magnetic flux in the radial direction of the magnetic recording medium as the servo signal detecting means. That is, the head core 3
As in the case of 2, the magnetic flux generated in the gaps 36 and 37 by the rotation of the magnetic recording medium is detected.

The gaps 36 and 37 for detecting a servo signal and the gap 35 for recording / reproducing data are orthogonal to each other. The gap 3
The widths of the gaps 6 and 37 are provided wider than the gap width of the gap portion 35, and are substantially the same as the widths of the servo tracks provided on the magnetic recording medium. Therefore, since the width of the track is usually sufficiently large with respect to the thickness of the magnetic layer, the gaps 36 and 37 can detect the magnetic flux generated by the magnetization of the lower layer of the magnetic layer, and can read the servo signal. Become. In addition, the gap 35 for data recording / reproduction has a relatively small width and a large azimuth angle, so that a servo signal is hardly read.

In order to improve the positional accuracy of the head cores 32, 33 and 34, they are preferably fixed to the same slider chip and integrated. In FIG. 3, since each head core is sandwiched and fixed to the slider chip, the positional accuracy between them is extremely high. The radial distance L between the gaps 36 and 37 in the magnetic recording medium is (k + ／) λ, where λ is the track pitch of the servo track of the magnetic recording medium to be arranged (where k is ｋ).
Is an arbitrary integer) is preferable for easy tracking. When the tracking method described later is adopted, the interval L must not be at least an integral multiple of the track pitch λ of the servo track.

FIG. 4 is a schematic diagram showing an example of a method for reading a servo signal from a magnetic recording medium according to the present invention.
4 (a), (b) and (c) show servo tracks 41, respectively.
, 42 and the induction type magnetic head 40 as a servo signal detecting means for detecting the magnetic flux in the magnetic recording medium in the radial direction, and the output waveform of the servo signal obtained at that time by the magnetic recording medium rotating means such as a spindle motor. And As shown in FIG. 4A, when the gap 43 of the magnetic head 40 is located at the center of the servo track 41, the amplitude of the sinusoidal signal obtained by the rotation of the magnetic recording medium becomes maximum. On the other hand, as shown in FIG. 4C, when the gap portion 43 of the magnetic head 40 is located exactly between the servo tracks 41 and 42, the amplitude of the obtained signal becomes minimum (zero). Also, as shown in FIG.
When the gap 43 is located between the center of the servo track 41 and the center of the servo track 41, the amplitude of the obtained signal has an intermediate value according to the position of the gap with respect to the servo track.

That is, the amplitude of the output signal of the magnetic head 40 changes sinusoidally with the movement of the head in the radial direction of the magnetic recording medium. Two servo signal detecting means such as an induction type magnetic head are provided, and as described above, the interval between them is (k + 但) λ (where k is an arbitrary integer, and λ is the track pitch of the servo track, respectively). ) And the change in the amplitude of the sinusoidal output signal that changes with the movement of the magnetic recording medium in the radial direction, the phases thereof are different from each other by １ ／ period. These correspond to making one a sine and the other a cosine. Therefore, if a signal corresponding to the amplitude is obtained from the servo signal obtained from each servo signal detecting means, the position of the head can be obtained from those values. Signals corresponding to sine and cosine are the same as signals of a so-called linear encoder, and position control based on those values is extremely simple.

For example, the servo signals obtained from the respective servo signal detecting means are input to a low-pass filter after full-wave rectification, and the average value corresponding to the amplitude is obtained, thereby obtaining a sine and a cosine (cosine) corresponding to the head position. SIN
θ, COS θ) signal. These are A / D-converted and input to a digital signal processor (DSP) to correct the zero point and the amplitude, and then the position is calculated by an arc tangent operation. This is combined with the value of the counter that counts the wave number of the sine / cosine signal to form a position signal.

The position control is performed, for example, by calculating a thrust command value by a normal PID algorithm and operating a linear actuator via a D / A converter and a power amplifier. As the moving means for integrally moving the data recording / reproducing means and the servo signal detecting means, a normal head positioning mechanism can be used in addition to the linear actuator. For example, a voice coil meter or a linear or rotary type step motor can be used. To achieve compatibility with magnetic recording media on which servo signals are not recorded, that is, when servo control is not performed, for example, a step motor is used as a head actuator and micro-step driving is used when used as a high-density drive. The system can be adopted.

In the above embodiment, an induction type magnetic head is used for both the data recording / reproducing means and the servo signal detecting means, but the magnetic signal recorded on the magnetic recording medium is recorded and / or reproduced. Any device having a function may be used. For example, a magnetoresistive element may be used to detect a magnetic signal. In the case where two servo signal detecting means such as an induction type magnetic head are provided, the interval between them is necessarily (k + λ) λ (
k does not need to be an arbitrary integer, and λ represents the track pitch of the servo track), and it is sufficient that the position of the head can be uniquely determined in the vicinity of the head by these servo signal detecting means.

[0023]

The magnetic recording medium of the present invention not only can perform accurate tracking, but also has a servo signal consisting of a magnetic signal due to magnetization in the in-plane radial direction. The interference with the magnetic data having the above is extremely small, and each signal can be obtained almost independently.

In addition, since the servo signal is provided in the lower layer of the magnetic layer, if an induction type magnetic head is used as the data recording / reproducing means and the width of this head gap is reduced, the lower layer of the magnetic layer can be obtained. No magnetic flux generated by the magnetization is detected, and the possibility that a servo signal is mixed into the magnetic data is extremely small. If the servo signal is provided in the lower layer of the magnetic layer, the effective recording area of the magnetic data does not decrease by recording the servo signal, and the servo signal can be recorded continuously. As compared with the case where the servo signal is provided intermittently, the tracking accuracy is increased, and more accurate tracking is possible.

Furthermore, if a plurality of servo tracks are arranged concentrically and servo signals are recorded in adjacent servo tracks at corresponding positions in the radial direction so that the magnetization directions are opposite to each other, the servo signal can be written. Very easily. For example, in addition to the writing method described in the embodiment, writing by a magnetization method can be performed. According to this method, a servo signal can be written to a magnetic recording medium at high speed, and a large amount of magnetic recording medium can be manufactured in a short time.

Since the magnetic recording apparatus of the present invention performs tracking by magnetic means, it does not require a light-emitting device or a light-receiving device for tracking unlike the optical servo system.
The size of the head can be reduced, and as a result, the load on the actuator that drives the head can be reduced, which is effective in reducing the size of the magnetic recording device and reducing the manufacturing cost. Further, if the data recording / reproducing means and the servo signal detecting means are integrated into one magnetic head, a device and a process for measuring and correcting the deviation between them are omitted. If the servo signal detecting means and the data recording / reproducing means are not integrated, their positional relationship may be
It is not always constant, and a certain deviation may occur between the track center position by the servo signal detecting means and the track center position by the data recording / reproducing means. In this case, it is necessary to measure this deviation in advance and correct the deviation. To measure the deviation, use a standard disk when assembling the drive and write this value to the ROM, or write a magnetic signal corresponding to the servo track to each medium, and measure the deviation when the drive is turned on. However, in the former case, the drive assembling process becomes complicated, and it may not be possible to cope with a change in deviation after assembly (caused by thermal expansion or mechanical shock). In the latter case, In some cases, the price of the medium becomes high, and time for measurement is required for each start-up.

Further, two servo signal detecting means are connected to each other (k + ／) λ (k is an arbitrary integer, λ
Represents the length corresponding to the track pitch of the servo track of the disk-shaped magnetic recording medium to be arranged, respectively)
If they are provided at a distance from each other, the position can be controlled by a simple method based on the magnitude of the amplitude of the servo signal obtained from them.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a magnetic recording medium according to the present invention along a circumferential direction.

FIG. 2 is a schematic plan view showing how a servo signal is recorded in an example of the magnetic recording medium of the present invention.

FIG. 3 is a schematic perspective view showing an example of a magnetic head unit of the magnetic recording device of the present invention.

FIG. 4 is a schematic diagram showing an example of a method for reading a servo signal from a magnetic recording medium according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Non-magnetic base 12 Magnetic layer 30 Magnetic head 31 Slider chip 32 Head core (for data recording / reproduction) 33, 34 Head core (for servo signal detection) 35, 36, 37 Gap part

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-172515 (JP, A) JP-A-62-88106 (JP, A) JP-A-1-184711 (JP, A) JP-A-63-1988 64610 (JP, A) JP-A-5-242470 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/596 G11B 21/10

Claims (7)

(57) [Claims] 1. A disk-shaped magnetic recording medium having a magnetic layer on a non-magnetic substrate, wherein a lower layer of the magnetic layer does not have a servo signal composed of a magnetic signal due to in-plane radial magnetization.
And a plurality of servo tracks on which the servo signals are recorded are concentric.
Arranged in a circular shape, the magnetization direction of the servo track is reversed according to the rotation angle.
A magnetic recording medium, comprising: 2. The method according to claim 1, wherein the magnetization direction of the servo track is constant.
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is inverted at each turning angle. 3. The magnetization direction of the servo track is reversed.
The recording of the data signal recorded on the magnetic recording medium is performed at intervals.
The wavelength is not less than 10 times and not more than 1000 times the length of the wavelength.
3. The magnetic recording medium according to 1 or 2. 4. A servo track fit Ri neighbor in the corresponding position in the radial direction, claim magnetization directions are opposite to each other
4. The magnetic recording medium according to any one of 1 to 3 . 5. The magnet according to claim 1, wherein
A magnetic recording device that can use a recording medium,
A data recording / reproducing means for generating and / or detecting a magnetic flux in a circumferential direction of a magnetic recording medium; a servo signal detecting means for detecting a magnetic flux in a radial direction of the magnetic recording medium; and a servo signal detected by the servo signal detecting means. A magnetic recording apparatus, comprising: a moving means for integrally moving the data recording / reproducing means and the servo signal detecting means on the basis of the data recording / reproducing means. 6. A disk drive having two servo signal detecting means along a radial direction of a disk-shaped magnetic recording medium to be arranged.
The magnetic recording device according to claim 5 . 7. The two servo signal detecting means are arranged such that (k + ／) λ (k is an arbitrary integer and λ is arranged along the radial direction of the disk-shaped magnetic recording medium to be disposed. 7. The magnetic recording apparatus according to claim 6 , wherein the lengths corresponding to the track pitches of the servo tracks of the disk-shaped magnetic recording medium are apart from each other by a distance).