JPS6353711A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To obtain a magnetic disk device with high track density, by providing a driving circuit which controls a current being permitted to flow on the head coil of a thin film head, and reads/writes a bit of information on a recording medium from the thin film head based on the current, or performs the positioning of the thin film head being moved on the recording medium. CONSTITUTION:Assuming that a write current is permitted to flow on the head coils 4 in two thin film heads 1, and they are formed physically symmetrically right and left, and that the lengths of the widths of the right and left head cores are set as L, and an interval between the right and the left head cores, as S, a magnetic flux >=(X-Y) is generated to remove the influence of the bit of information remained unerased of the previous history by overwriting a bit of new information on the bit of information of previous history on a recording medium, and the part of the interval S between the head cores is also magnetized by the right and left head cores. At the time of permitting the write current to flow on the head coil, and generating a recording magnetic field at the tip of the head core, a leakage magnetic flux is generated from both sides of the head core, thereby, the phenomenon of write bleeding is generated, and write wider than the width of the head core is performed. It is possible to generate a state as if the write is performed by one head according to the condition of the S. In this way, it is possible to easily detect the aberration of the head.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a thin film head used when writing information to a recording medium or reading information from a recording medium, and a drive circuit that controls the current flowing through the thin film head. The present invention relates to a magnetic disk device equipped with a magnetic disk drive.

[Conventional technology]

First, the configuration of a conventional thin film head will be explained.

FIG. 15(A), CF is a configuration diagram showing the configuration of a conventional thin film head, and FIG. 15(A) is a front view of the thin film head.
FIG. 15(B) is a sectional view of the thin film head viewed from the side.

As shown in the figure, the thin film head 1 consists of a head coil 4 wound around a head core 23 having a head gap 5, and the head core 23 is divided into an upper core 2 and a lower core 3.

Such a thin film head 1 is composed of a combination of a magnetic thin film core material, a thin metal film conductor, and a thin film insulator, and is manufactured using ultrafine processing techniques similar to those used in semiconductor manufacturing. As is well known, the miniaturization of the core material in this thin-film head improves the conversion efficiency when converting electrical signals to magnetic signals, or from magnetic signals to electrical signals. Since the tip can be finely machined, it is attracting attention for its great advantages, such as the possibility of significantly increasing the track density in addition to the linear recording density in the circumferential direction of the track.

Here, the principle of conventional magnetic recording will be explained using FIG. 16.

FIG. 16 is a schematic diagram showing the principle of magnetic recording. As shown in the figure, when writing information on the recording medium 6, a current is passed in the direction of the arrow in the head coil 4 of the thin film rad 1, and the upper core 2. A magnetic field is generated in the head core z3 consisting of the lower core 3, and a part of the leakage magnetic flux generated from the head gap 5 is used to magnetize the magnetic film of the recording medium 6 in the direction of the arrow.

When reading information from the recording medium 6, the magnetic flux remaining on the recording medium 6 is picked up by the head gap 5 based on the thin film head 1 moving over the recording medium 6, and is wound around the head core 2.3. Information is detected using the induced voltage generated in the head coil 4.

FIG. 17 is a block diagram of a conventional magnetic disk drive circuit. In the figure, a write circuit 8 is connected to the head coil 4 of the thin film radar 1, and a modulation/demodulation circuit 10 is connected to the write circuit 8.

On the other hand, a read analog circuit 9 is connected to the head coil 4 in parallel with the write circuit 8, and a modulation/demodulation circuit 10 is connected to the read analog circuit 9.

Here, the readout analog circuit 9 includes a preamplifier 9a that amplifies the voltage generated in the head coil 4, and this preamplifier 9a.
To explain the operation of recording information on a recording medium using a thin film head, first, a write clock signal and write data are input from the outside. Modulation/demodulation circuit 10
For example, MFM (Modified Freq
Code conversion is performed using a modulation circuit such as Uency Modulation. Then, in the next write circuit 8,
A current pulse that allows sufficient saturation writing is generated on the recording medium 6, and this current pulse is passed through the head coil 4.

When reading information recorded on a recording medium, a preamplifier 9a amplifies the small successive signal voltages generated in the head coil 4, the next-stage differentiator circuit 9b differentiates the previous read voltage waveform, and then ≠≠Okayoshi≠A10-”h-term circuit 9
Pulse and output with c. And the next stage modem circuit 1
The demodulation circuit at 0 converts the input data into the same original code and sends it out along with the read clock.

FIGS. 18(A) to 18(D) show the above drive circuit.

By the way, in order to increase storage capacity in magnetic disk drives, generally speaking, recording density in the circumferential direction (referred to as linear recording density) is
By increasing the recording density in the trunk direction (track recording density), the recording capacity per recording medium surface is increased, and by stacking multiple recording media into a pack configuration, the storage capacity per magnetic disk device is increased. We are taking steps to increase capacity. However, in order to increase the recording density in the track direction, it is necessary to accurately maintain the positioning accuracy of the write/read heads facing the recording surfaces of multiple recording media. Head positioning information is written in advance on one side of the medium, and a servo head that reads the head positioning information is used to move the data head to the track position where the target data is to be written or read. This enables highly accurate head positioning.

FIG. 19 is a simplified diagram of a magnetic disk device that positions this thin-film head. In the figure, on a base 16 are a head transport motor 15, a carriage 14 that moves in parallel on the base 16 by the head transport motor, and a plurality of carriages. A disk spindle assembly 11 loaded with a recording medium is attached, and data surfaces 17a and 17b of the recording medium are mounted.
.

At 17d and 17e, thin film heads attached to the tip of the carriage 14 are positioned so as to float slightly.

Further, on the servo surface of the recording medium, a head positioning servo head, which is attached to the tip of a carriage 14 that detects a signal for positioning the thin film head 1, is positioned so as to float slightly.

Here, servo information read from the servo surface 17c included in the disk spindle assembly 11 via the servo head 13 is transmitted to a head positioning control circuit (not shown).
It is used for each of the seek operation and the on-track operation and is processed as an appropriate track positioning signal, and then used by the data heads 12a, 12b, 12c and the servo heads 13. This becomes a source signal for the head transport motor 15 for moving the carriage 14.

FIG. 20 is a conceptual diagram of servo information recorded in advance on a servo surface facing the head positioning servo head shown in FIG.

In the figure, only servo information written in advance on the servo surface is shown for convenience of explanation of the servo surface, and the servo surface information recording area 18 includes a landing area, a guard band area, and a servo area used for head positioning during seek operation. The servo area can be broadly divided into three areas.

An enlarged view of the servo information 19 shows a servo pattern commonly called a Guibit pattern in the above-mentioned servo area.

FIGS. 21A and 21B show servo readout waveforms when the servo information shown in FIG. 20 is read out by a servo head.

Servo information case in Figure 20^4-+MIEV E NT
The state when the servo head 5 is positioned between RACK (even track) and 0DDTRACK (odd track) is shown in (A), and the read waveform is shown in (B). This state is called on-trunk and data that moves together. Head 12a, 1
It is possible to write and read data to and from 2b and 12c. Specifically, the state where the difference between the positive voltage v0 and the negative voltage VtO of the waveform (B) read from the servo head at this time, that is, the value of (■.-V.) is zero, is on-trunk, and (VOVE) is EVEN if the voltage is negative
If it is shifted to the TRACK side and the voltage is positive, it is 0DDT.
It can be seen that the head has shifted to the RACK side.

[Problem that the invention seeks to solve]

As described above, conventional magnetic disk drives are configured with one head gap corresponding to one track of one recording medium, so the deviation due to head temperature is calculated in advance by one inch or sector on the data track. There is a drawback that a variable length data format for detecting and correcting written embedded positioning information cannot be applied, and only a fixed sector format can be used.

This invention was made in order to solve the above-mentioned problems, and it is possible to perform the same writing and reading operations as before, and also to detect head misalignment from the read analog signal. The purpose is to obtain equipment.

[Means for solving problems]

For this reason, the present invention provides two thin film heads 1 each having a head coil wound around a head core having a head gap.
are arranged on the same plane adjacent to each other on the head slider, and the current flowing through the head coils 4 of the two thin film heads 1 is controlled, or the thin film head l is
The apparatus is characterized in that it is provided with a drive circuit for reading and writing information onto the recording medium 6 or for positioning the thin film head moving on the recording medium 6.

[Effect]

The two thin film heads in this invention generate a magnetic field for writing information on or reading information from a recording medium.

This magnetic field is generated by passing current through the head coils of the two thin film heads using a drive circuit. Further, the drive circuit positions the thin film heads by detecting the current flowing through the head coils of the two thin film heads.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figures show two thin film heads according to the present invention arranged on a slider. Figure 1 (A) shows a case where two thin film heads according to the present invention are mounted on only one side of a 2-rail type slider, and Figure 1 (B) shows a case where two thin-film heads according to the present invention are mounted on only one side of a 2-rail type slider. FIG. 1(C) shows the case where the slider is mounted on the middle rail of a three-rail slider.

The cores 3 are arranged in parallel on the same plane adjacent to each other on the Hent slider. In this case, the lower core 3 may be separated, or the coil narrowed between the lower core and the upper core may be wound in multiple layers, or the wire rod may be wound around the upper core (or lower core) in a three-dimensional shape. It is also possible to have a structure.

Next, the intensity distribution of the magnetic field of the thin film head constructed as described above will be explained.

FIG. 3 shows a case where two thin film heads are arranged in parallel. Assuming that there are two thin-film spatula Pb head coils, and if the length of the left and right spatula core widths is S, and the spacing between the left and right head cores is S, then new information can be added to the recording medium on top of the previous information. In order to eliminate the influence of overwriting and unerasing information in the previous history, it is necessary to generate a magnetic field greater than or equal to XY, and to magnetize the portion of the head core interval S by the left and right head cores. Generally, when a write current is passed through the head coil to generate a recording magnetic field at the tip of the rad core, a leakage magnetic field is generated from both sides of the head core, resulting in the phenomenon of write bleeding, which causes writing to be wider than the width of the head core. Depending on the conditions of S, it is possible to achieve a state similar to that of a single head.

FIG. 4 is a diagram showing the arrangement conditions of the left and right cores of the thin film head according to the present invention.

Figure 4 (A) shows the side crosstalk during readout when the residual noise component is not considered.
, Tz indicate the state after writing including the writing blur shown in FIG. 3, and are indicated by arrow α.

β indicates side crosstalk during readout between discrete trunks. In the figure, the left core is more affected by the crosstalk amount α than the track T2, and the right core is more affected by the crosstalk amount β than the track T1. These two types of crosstalk become noise components when different types of information are written in the left core and right core, and if the amount thereof is large, the information on each track cannot be read out accurately. However, in the present invention, since the same type of information is written simultaneously, this crosstalk does not pose a problem.

Furthermore, FIG. 4(B) shows the influence of positional fluctuations on the head slider on which the thin film head is mounted. Generally, in a magnetic disk drive, as shown in FIG. 19, the data head 12a is moved onto an arbitrary track by moving the head transport motor 15 based on the head positioning servo information read by the servo head 13. 12b and 12c are moved and positioned, but there is some variation due to the tracking error of the servo head 13 and the influence of temperature and the like. One of the points of this invention is to correct these head positioning fluctuations so as to reduce them.

Figure 4 (B) shows the state after correction, and the signals generated from L+, Lt, LL, and IJz in the figure are written data that has been superimposed many times due to the previous head positioning fluctuation, and are generally erased. This noise is called residual noise, and is a problem when the left core and right core in the figure shift in position in the direction of the adjacent track position.

This noise is a factor that must be considered when determining the appropriate track pitch for a magnetic disk drive, but in a magnetic disk drive using the thin-film head of this invention, the trunk position facing each thin-film head can be accurately reproduced. It has the advantage that it is rarely a problem because it can be done.

Next, a drive circuit for a magnetic disk device according to the present invention will be explained.

5(A) to 5(C) are block diagrams of a write current drive circuit that causes a write current to flow through the head coils. FIG. 5(A) shows a method for flowing a write current to each head coil, and FIG. (B) shows a method in which head coils are connected in series and a write current is passed through the head coils connected in series, and FIG. A method is shown in which write currents are passed in opposite directions between both ends of the line and the lead line.

In this case, Fig. 5 (A) shows an equivalent write current drive circuit that allows the same write current to flow in parallel, and when the inductance of the left and right head coils is large, when a high-speed write pulse current is flowed. Applicable to the fifth
FIG. 3B has the advantage that it can be applied when the inductance of each head is small and a sufficiently high-speed pulse current can flow, and only one write drive circuit 20 is required.

Further, FIGS. 6(A) and 6(B) are block diagrams of a drive circuit when reading information by an induced voltage generated in the head coil, and FIG. 6(A) shows the head coil 4a.

4b is connected to preamplifiers 21a and 21b to simultaneously amplify the outputs read out, and then a synthesis amplifier 22 adds and synthesizes the left and right differential signals and outputs the resulting output. B) shows a type in which left and right coils 4a and 4b are connected in series and input to one preamplifier 21. Any of these connections and circuit configurations can be selected.

Next, the head positioning operation will be explained.

FIG. 7 is a diagram illustrating a method for detecting head positioning fluctuations. This assumes a case where data is written in advance and then read out, and it is assumed that there is a head deviation of ΔT between the writing state and the reading state.

FIG. 8 is a diagram showing signals read out from a pair of coils. 1.2 in the figure is the readout signal waveform of the coil 4a and the coil 4b. Taking the peak values V, , V, as an example, if the track deviation amount ΔT in FIG. 7 is zero, VI and
The values of 2 should be equal, and if the track deviation amount ΔT is deviated by 1/2 track, that is, by L in FIG. 7, then ▪ becomes zero and V2 remains the original V2. This is illustrated in the following Figure 9.

FIG. 9 is a diagram showing the relationship between the head deviation amount ΔT and the readout output voltage. As is clear from the figure, when the head deviates in the direction shown in Fig. 7, the readout voltage of the hector coil 4b does not change in output up to the amount of deviation, but the output of the head coil 4a attenuates linearly, and the head deviation amount ΔT When becomes L, it becomes zero.

When the direction of ΔT is negative, this becomes the same as in FIG. 9 by simply exchanging V and ■2. Therefore, the head deviation amount ΔT is expressed by the following formula, and the direction of head deviation can be determined from the polarity of (VZ VI)/V +.

Next, a circuit configuration for correcting head misalignment will be explained.

FIG. 1O is a block diagram of a drive circuit to which a head displacement detection circuit is added, and FIG. 11 is a signal waveform diagram at each stage of the drive circuit shown in FIG. 10. As shown in FIG. 10, the head deviation detection circuit includes a comparator circuit 23 and a low-pass filter circuit 24 to block high frequency signal components and detect head deviation signals within the head positioning system servo band.

FIG. 12 is a schematic diagram of the data format written on the data surface. In the figure, 25a and 25b are sink parts, 26
27 is an address field, 27 is a data field, and 28 is a data collection code field. The address section 26 is generally written in advance at the time of initialization, and is used for reading only until reformatted, and the sink section 25a in the figure
The address section 26 and the address section 26 are not generally open to users, but only the data section 27.

It is most convenient to use the head position deviation information used in this invention at 253.25b of the sink portion. The reason is that the sink sections 25a and 25b are connected to the address section 26. Data section 27. The reason for this is that there is information written in a single cycle to achieve phase synchronization with the data collection code section. If the information in this section is processed by the circuit shown in FIG. 10, head position deviation information can be extracted with high accuracy.

Next, the configuration of the head positioning system control circuit will be explained.

FIG. 13 is a block diagram of a head positioning system control circuit during on-track. Note that the circuit blocks required at the time of seek are omitted in the figure because they are not directly related to the present invention.

The control circuit can be broadly divided into a head transport motor (also called an actuator) 15, and a power amplifier circuit 29 that supplies a drive current to move the motor. Control system switching circuit 30 for switching between seek operation and on-track operation. A position detection circuit 31 for extracting a head positioning control signal from the head positioning servo information read from the servo head 13, a notch filter for removing mechanical vibration components included in the head positioning control signal, a gain adjustment amplifier, It is composed of a compensation circuit 32 consisting of a filter for integral compensation and 1-phase compensation.

The head position deviation information of the data head described above is corrected by adding or subtracting the drive signal that is the output of the control system switching circuit 30 to the power amplifier circuit 29, so to speak, forcibly moves the head transport motor 15. This makes it possible to reduce the displacement of the data head.

In addition, in the above example, a shape was explained in which the white lower core of the two helad cores is common and the upper core is separated, but it is also possible to have a shape in which both the lower core and the upper core are separated, or as shown in Fig. 14, the upper core is common. External String [Effect of the Invention] As explained above, the present invention has two thin-film heads each having a head coil wound around a head core having a spacing gap, which are arranged on the same plane adjacent to each other on a head slider. The current flowing through the head coils of the two thin film heads is controlled, or information is read or written from the thin film head onto the recording medium based on this current, or the thin film head is positioned as it moves over the recording medium. Since a drive circuit is provided, head displacement can be easily detected, and a magnetic disk device with high track density can be realized.

[Brief explanation of the drawing]

Fig. 1 is a layout diagram of two thin film heads showing an embodiment of the present invention, Fig. 2 is a configuration diagram of two thin film heads showing an embodiment of the invention, and Fig. 3 is a diagram showing the arrangement of two thin film heads showing an embodiment of the present invention. Figure 4 is a diagram showing the intensity distribution of the magnetic field generated in the head gap, Figure 4 is a diagram showing the arrangement conditions of the left and right cores of two thin film heads, and Figure 5 is a diagram showing the drive circuit of the present invention for writing information on a recording medium. Configuration diagram, No. 6
The figure is a configuration diagram of a drive circuit of the present invention that reads information from a recording medium, Figure 7 is an explanatory diagram of a method for detecting the positioning of a thin film head, and Figure 8 is an illustration of a method for detecting the positioning of a thin film head. Figure 9 is a diagram showing the waveform of the flowing current, Figure 9 is a diagram showing the relationship between the amount of deviation of the thin film head and the output voltage, Figure 10 is a configuration diagram of the drive circuit with an added circuit for detecting the deviation of the thin film head, and Figure 11 is a diagram showing the relationship between the amount of deviation of the thin film head and the output voltage. FIG. 10 is a waveform diagram at each stage of the drive circuit, FIG. 12 is a diagram showing the data formant written on the data surface of the recording medium, FIG. 13 is a block diagram of the head positioning system control circuit during on-track, and FIG. FIG. 14 is a diagram showing another embodiment of the present invention showing the structure of two thin film heads, FIG. 15 is a configuration diagram of a conventional thin film head, FIG. 16 is a diagram showing the principle of conventional magnetic recording, and FIG. 1
7 is a block diagram of a conventional drive circuit, FIG. 18 is a diagram showing signal waveforms at each stage of the drive circuit, FIG. 19 is a simplified diagram of a magnetic disk device showing the positioning of a conventional thin film head, and FIG.
Figure 0 is a conceptual diagram of servo information for head positioning, Figure 21.
The figure is a servo readout waveform diagram when servo information is read out. In the figure, 1 is a thin film head, 2 is an upper core, 3 is a lower core,
4 is a head coil, 5 is a head gap, 6 is a recording medium, 7 is a magnetization pattern, 8 is a write circuit, 9 is a read analog circuit, 10 is a modulation/demodulation circuit, 11 is a disk spindle assembly, 12a to 12c are data write/read heads , 13 is a servo head for head positioning, 14 is a carriage, 15 is a head transport motor, 16 is a base,
17a to 17e are data surfaces, 17c is a servo surface, 18 is a servo information recording area, 19 is an enlarged view of servo information, 20
2 is a write drive circuit, 21 is a preamplifier, 22 is a synthesis amplifier, 23 is a comparison circuit, 24 is a low-pass filter circuit, 25 is an AGC amplifier, 26 is an address section, 27 is a data section, 2
8 is a data collection code section, 29 is a power amplifier circuit, 30 is a control system switching circuit, 31 is a position detection circuit, 3
2 is a compensation circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Masu Oiwa A (and 2 others) Ward 1 (Δ) (B) (C)
3rd country (+) - (2) L Tevekoreg 4n code narrow P 13th country 181 yen 1 1 arm divider Tarouchi sword 2 Palette Φ ω /-+I r' Nt

Claims (6)

[Claims] (1) Two thin film heads made by winding a head coil around a head core having a head gap are arranged on the same plane on a head slider, and the current flowing through the head coils of the two thin film heads is controlled, Alternatively, a magnetic disk device is provided with a drive circuit that reads and writes information from a thin film head onto a recording medium based on this current, or positions the thin film head as it moves over the recording medium. (2) The magnetic disk device according to claim 1, wherein the drive circuit causes current to flow in parallel to the head coils of the two thin-film heads when writing information on the recording medium. (3) The drive circuit is characterized in that when writing information on a recording medium, the head coils of two thin film heads are connected in series, and a current is passed through the head coils connected in series. Magnetic disk device described in section. (4) A magnetic disk device according to claim 2 or 3, wherein the drive circuit adds currents generated in each thin film head when reading information from a recording medium. (5) The drive circuit is characterized in that when reading information from a recording medium, the head coils of each thin film head are connected in series, and the information is read using current generated in the head coils connected in series. A magnetic disk device according to claim 2 or 3. (6) Claims 2 to 5 are characterized in that the drive circuit performs the positioning based on the potential difference and polarity generated in the head coil of each thin film head when positioning the thin film head. The magnetic disk device according to any one of the paragraphs.