KR930001103B1 - Magnetic disk device of bilateral head type - Google Patents

Abstract

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Description

Double-sided head magnetic disk device

1 shows a first embodiment of a double-sided head type magnetic disk device of the present invention.

2 is a view showing a schematic configuration of a main body of a double-sided head type magnetic disk device in FIG.

3 is an enlarged view of a portion of the magnetic head in FIG.

4 is a cross-sectional view showing an example of the characteristics of the low pass filter when the cutoff frequency of the low pass filter is changed in FIG.

FIG. 5 is a diagram showing an example of the characteristics of the resonant circuit when the Q value of the resonant circuit portion in the differentiator is changed in FIG.

6 is a diagram showing an example of the characteristics of the resonant circuit when the resonant frequency in the resonant circuit portion in the differentiator is changed in FIG.

7 shows a second embodiment of a double-sided head type magnetic disk device of the present invention.

8 shows an example of the effect of the device of FIG.

* Explanation of symbols for main parts of the drawings

10 magnetic disk device body 11 head carriage

12, 13: magnetic head 12a, 13a: read / write head section

14: magnetic disk 20, 40: double-sided head magnetic disk device

21: control circuit 22, 23: line

24: recorder 25: reader

26: recording circuit 30: preamplifier

31: low pass filter 32: differential meter

33: zero volt comparator 34: pulse shaping circuit

35: constant current source 36: resonant circuit portion

37: terminal 41, 42, 43, 44: line

The present invention relates to a magnetic disk device, and more particularly, to a double-sided head type magnetic disk device employing a so-called double-sided head.

In general, so-called double-sided head-type magnetic disk devices having a pair of magnetic heads are known for performing magnetic disk double-sided recording / reproducing.

The magnetic head in such a magnetic disk apparatus shifts the position of the read / write head portion 4 to 8 tracks (depending on the recording density) in the moving direction of the head carriage in order to avoid cross-talk between both recording surfaces of the magnetic disk. To be placed.

For this reason, the diameter is different from the track reproduced by the magnetic head portion abutting on the side 0 side of the magnetic disk and the track reproduced by the head portion of the magnetic head abutting the side one side.

For this reason, the difference in the resolution at the time of reading by the side was inevitable.

The degree of this difference tends to increase with increasing density of the recording, which is a problem especially in recent years when the densification of the recording is also intended.

An object of the present invention is to provide a double-sided head type magnetic disk device that solves the above problems.

Another object of the present invention is to provide a cutoff frequency of the low pass filter in the reading system so that the resolution of the track facing the side 0 side head portion is reduced to be equal to the resolution of the track facing the side 1 side head. It is an object of the present invention to provide a double-sided head type magnetic disk device in which a means for changing so that a certain amount becomes lower than when playing back is provided.

According to the present invention, the resolutions between the tracks facing the side 0 side heads and the tracks facing the side 1 side heads become equal after passing through the low pass filter, and are characterized by the difference in the position of the heads of the reproduction signals of the heads. This disappears.

Other objects and features of the present invention will become apparent from the description based on the drawings.

In FIGS. 1 and 2, the double-sided head type magnetic disk device body 10 has magnetic heads 12 and 13 attached to the head carriage 11, and the magnetic heads 12 and 13 are attached to each other. The rotating magnetic disk 14 is sandwiched and the head carriage 11 is moved in the arrow X direction.

The magnetic disk 14 has a side 0 on the back side and a side 1 on the front side. During the third phase, 00, 01, 02, 03... Indicates a track.

The read / write head portion 12a of the magnetic head 12 and the read / write head portion 13a (hereinafter referred to as the R / W head portion) of the magnetic head 13 have the former rather than the latter. Towards the inner circumference, it is biased by the dimension d for 8 tracks.

Reference numerals 12b and 13b denote sliders.

1 shows a double-sided head type magnetic disk device 20.

The R / W head portions 12a and 13a are connected to the switch SW1. The position SW1 is switched by the side selection signal from the control circuit 21 to the line 22, and selects the R / W head portions 12a and 13a.

The switch SW1 is connected to the switch SW2. The switch SW2 is switched by the read / write signal from the control circuit 21 to the line 23, and switches the R / W head portions 12a and 13a to the recording system 24 or the reading system 25. do.

The recording system 24 is made of a recording circuit 26 and a resistor R1 connected in series with the circuit 26, and has a structure similar to the conventional one.

The recording circuit 26 superimposes the recording data on the recording current and sends the recording data.

The reading system 25 is composed of a preamplifier 30, a low pass filter 31, a differentiator 32, a zero volt comparator 33, and a pulse shaping circuit 34.

The reading system 25 has a configuration different from that of the conventional low pass filter 31 and the fine powder 32 only.

In addition to the resistor R2 and the capacitor C1, the low pass filter 31 has a capacitor Ca connected in parallel with the capacitor C1 through the switch SW4.

The differentiator 32 is composed of an NPN transistor Tr, a constant current source 35, resistors R3, R4, R5, and a resonant circuit portion 36 consisting of a coil L1, a capacitor C2, and a resistor R6, and another circuit connected to the resonant circuit portion 36. Consists of parts.

With respect to the resistor R6, the resistor Rb is connected in parallel via the switch SW5.

Condenser Cb is connected in parallel with the capacitor C2 via the switch SW6.

For the coil L1, the coil Lb is connected in parallel via the switch SW7.

The control circuit 21 outputs a side selection signal to the lines 41 to 44, whereby the switches SW4 to SW7 can be opened and closed.

Next, the operation of the apparatus 20 will be described.

Data is recorded superimposed on the same recording current IW on the side 0 side or the side 1 side of the magnetic disk 14.

When the reading mode is set, the switch SW2 is switched to the contact point R.

When the side selection signal 0 is output from the control circuit 21, the switch SW1 is connected to the contact point 0, and the signals read from the track of the side 0 by the R / W head portion 13a are the switches SW1, SW2 and It is output from the output terminal 37 through the reading system 25.

When the side selection signal is converted from (0) to (1), the switch SW1 is connected to the contact point 1 in turn, and the R / W head portion 12a reads the readout signal 25 from the track of the side 1. It is output from the terminal 37 via.

When reading data, the characteristics of the read signal from side 0 and the characteristic of the read signal from side 1 are matched in several ways described below.

① A method of changing the cutoff frequency of the low pass filter 31.

The switch SW4 is opened and closed as shown in Table 1 by the side selection signal to the line 41.

TABLE 1

That is, when the side selection signal 1 is output and the recording data of the side 1 is read, the switch SW4 is open, the capacitor Ca is disconnected from the capacitor C1, and the cutoff frequency of the low pass filter 31 is f1 = It becomes 500 KHz, and the characteristic of the lowpass filter 31 is as showing by the line I (1) of FIG.

Moreover, FIG. 4 shows an example of the characteristic of the signal taken out from the output side of the low pass filter 31 when the oscillator is connected to the input side of the preamplifier 30. FIG.

When the side selection signal is switched to (0), the switch SW4 is closed, the capacitor Ca is connected to the capacitor C1, the low pass filter 31 changes the cutoff frequency from f1 to f0 = 450 KHz, and the characteristics of the low pass filter 31. Is as shown by approximately I (0) in FIG.

At the time of reproduction, the data read from the side 1 passes through the low pass filter 31 of the frequency characteristic represented by the line I (1), and the data read from the side 0 is of the frequency characteristic represented by the line I (0). It passes through the low pass filter 31.

As a result, the resolutions of the tracks in which the R / W head portions 13a and 12a face each other are the same, and the reading is based on the difference in the arrangement positions of the R / W head portions 13a and 12a. The characteristic difference of the signal disappears.

The cutoff frequency of the low pass filter 31 can also be changed by connecting a series circuit between the switch and the resistor in parallel to the resistor R2, changing the resistance value of the portion of the resistor R2 due to the opening and closing of the switch.

(2) A method of changing the Q value of the differentiator 32 (resonance circuit section 36).

The switch SW5 is opened and closed as shown in Table 2 by the side selection signal to the line 42.

TABLE 2

That is, when the side select signal 1 is output and the write data of the side 1 is read, the switch SW5 is closed, the resistor Rb is connected to the resistor R6, the Q value is Q1, and the resonance circuit section 36 The characteristic of becomes as shown by the line II (1) in FIG.

5 and 6 show the characteristics of the signal derived from the output side of the differentiator 32 when the oscillator is connected to the input side of the preamplifier 30.

When the side select signal is switched to (0), the switch SW5 is opened, the resistor Rb is disconnected from the resistor R6, the Q value is lower than Q1 and becomes Q0, and the characteristic of the resonant circuit section 36 is the fifth middle line II (0). Is indicated by).

Although the side 0 side is higher in resolution than the side 1, the output waveform of the differentiator 32 becomes equal in side 0 and 1 by changing Q value according to side as mentioned above.

In addition, Q0 and Q1 are the values in which the saddle of the DIF (Differential Output) signal does not cross zero. The value of Rb is 50 to 200 times R6.

③ A method of changing the resonance frequency of the differentiator 32 (resonance circuit section 36).

The switch SW6 is opened and closed by the side selection signal to the line 43 and the switch SW7 is opened and closed as shown in Table 3 by the side selection signal to the line 44.

TABLE 3

When the side selection signal 1 is output, the switch SW6 is open, the switch SW7 is closed, the capacitor Cb is disconnected from the capacitor C2, and the coil Lb is connected to the coil L1.

The resonant frequency f1 'is 500 KHz, and the characteristics of the resonant circuit section 36 are as indicated by line III (1) in the sixth diagram.

When the side select signal is switched to (0), the switch SW6 is closed, the switch SW7 is opened, the capacitor Cb is connected to the capacitor C2, and the coil Lb is disconnected from the coil L1.

As a result, the resonant frequency is lowered, and f0 '= 450 KHz, and the characteristics of the resonant circuit section 36 are represented by the line III (0) in the sixth way.

By changing the resonant frequency according to the side in this way, the characteristics of the signal read out from the side 0 and 1 are made uniform.

Furthermore, only one of the switches SW6 and SW7 may be opened and closed.

Moreover, the structure which performs only one of (1), (2), (3) of said (1), (2), (3) may be sufficient.

Next, a second embodiment of the present invention will be described.

7 shows a double-sided head disk apparatus 40 as a second embodiment of the present invention. In the figure, the same code | symbol is attached | subjected to the part corresponding to the structural part shown in FIG.

The recording system 24A is composed of a recording circuit 26, a resistor R1 connected in series with the circuit 26, a resistor R1 connected in parallel with the resistor RA, and a switch SW3 connected to the resistor Ra.

The switch SW3 is opened and closed by the side selection signal from the control circuit 21A to the line 27.

The reading system 25A includes a preamplifier 30, a low pass filter 31A, a differentiator 32A, a zero volt comparator 33, and a pulse shaping circuit 34.

A low pass filter 31A, a resistor R2 and a capacitor C1.

The differentiator 32A is composed of a resonant circuit portion 36A consisting of an NPN transistor Tr, a constant current source 35, resistors R3, R4, R5, and a coil L1, a capacitor C2, and a resistor R6.

The reading system 25A has the same configuration as the prior art.

Next, the operation of the apparatus 40 will be described.

First, the relationship between the recording current and the resolution, and the recording current and the overwrite characteristic will be described.

8 shows the state when the carriage 11 is stopped at an arbitrary position and the recording current is changed. In the figure, line IV (0) shows the resolution of side 0 of magnetic disk 14, and line IV (1) shows the resolution of side 1.

Since the R / W head portion 12a is located on the inner circumferential side of eight tracks from the R / W head portion 13a, the resolution of the side 1 is normally lower than that of the side 0.

When the recording current is increased, it is understood that the resolution decreases as the side 0 and side 1 enlarge the difference slightly.

Line V (0) shows the overwrite characteristic of side 0, and line V (1) shows the overwrite characteristic of side 1.

Overwrite characteristics are

Is defined.

Here, 1F refers to a modulated signal of the lowest frequency in the MFM recording system, and 2F refers to a modulated signal of the highest frequency.

By the lines V (0) and V (1), as the write current increases, the overwrite characteristic is saturated, and comparing side 0 with side 1 shows that the side 1 side saturates earlier than side 0. .

The apparatus 40 is intended to make both resolution and overwrite characteristics the same at side 0 and side 1.

The switch SW1 is opened and closed as shown in Table 4 by the side selection signal to the line 27.

That is, at the time of writing, the switch SW2 is connected to the contact W.

When data is written to the side 1, the switch SW1 is connected to the contact point 1 by the side selection signal 1 from the control circuit 21A, and the switch SW3 is open.

Data is superimposed on the recording current IW1 (= 7 mA) determined by V / R1, and is recorded on the side 1 of the magnetic disk 14 by the R / W head portion 12a via the switches SW2 and SW1.

When the side selection signal 0 is output from the control circuit 21A, SW1 is connected to the contact point 0, and SW3 is closed.

When the switch SW3 is closed, the resistance for determining the write current value becomes a combined resistance between R1 and Ra connected in parallel, and the resistance value is lower than R1.

As a result, the recording current IW1 increases to IW0, for example, 8 mA, and the data is superimposed on the recording current IW0, and the side of the magnetic disk 14 is formed by the R / W head portion 13a through the switches SW2 and SW1. 0 is recorded.

Next, the characteristic at the time of reading out the data recorded as mentioned above is demonstrated.

When the read mode is entered, the switch SW2 is switched to the contact point R.

When the side selection signal 0 is output from the control circuit 21A, the switch SW1 is connected to the contact point 0, and the signal read out by the track of the side 0 by the R / W head portion 13a is the switch SW1, SW2. And output from the output terminal 27 through the reading system 25A.

When the side selection signal 0 is switched to (1), the switch SW1 is switched to the contact point 1 and is output from the terminal 37 via the R / W head portion 12a.

Side 0 has a resolution corresponding to point A, and side 1 has a resolution corresponding to point B.

Both resolutions are approximately equal to about 75.

For this reason, the read margin for the signal read out from the side 0 and the read margin for the signal read out from the side 1 become the same without difference.

Next, the overwrite characteristic becomes the characteristic (-36 dB) of the point C at which the vertical line through the recording current IW0 = 8 mA intersects in the line V (0) in FIG. It becomes the characteristic (-36dB) of the point D where the vertical line through the V (1) layer recording current IW1 = 7mA intersects.

Both overwrite characteristics are clear at about -30 dB or less, and are a level without a problem.

Therefore, even though there is a shift between the R / W head portions 13a and 12a by the position of the dimension d in the system direction of the disk 14, from each of the R / W head portions 13a and 12a. The read signal is read out with the same resolution without any difference.

Moreover, the current values of the write currents IW0 and IW1 to be switched are the areas where the overwrite characteristics are saturated as described above, and are set to the same resolution.

Furthermore, although not shown in the low-pass filters 31 and 31A, in order to achieve uniformity between the resolution on the inner circumferential side of the magnetic disk and the resolution on the outer circumferential side, in the case of the 5.25 inch magnetic disk, the 44th track Means are provided for switching the cutoff frequency at the position.

Claims (6)

The head part 13a of the side 0 side which abuts on the side side of the magnetic disk 14, and the side one side head part which abuts on the side 1 side of the magnetic disc in the position where the track is plurally tracked with respect to this side 0 side head part ( 12a), a control circuit 21 for outputting a side selection signal for selecting the side of the disk, a low pass filter 31 for supplying a signal selectively read from the head portion of the set, and a low pass filter provided in the low pass filter. And cut-off frequency changing means (SW4) for changing the cut-off frequency according to the side selection signal and lowering when side 0 is selected when side 0 is selected. The head portion 13a on the side 0 side which abuts the side 0 side of the magnetic disk, and the side one side head portion 12 which abuts on the side 1 side of the magnetic disc at a position deviated by a plurality of tracks with respect to the side 0 side head portion; A differentiator 32 having a control circuit 21 for outputting a side selection signal for selecting the side of the disk, a resonant circuit section 36 for supplying a signal selectively read from the pair of head sections, and A double-sided head type magnetic disk device comprising Q-value changing means (WS5) which changes the Q value of the resonance loop portion according to the side selection signal to be lower than when the side 1 is selected when side 0 is selected. The head part 13a of the side 0 side which abuts the side 0 side of a magnetic disk, and the side 1 side head part 12a which abuts on the side 1 side of a magnetic disc in the position which deviated by several tracks with respect to this side 0 side head part. And the resonant frequency of the resonant circuit portion in response to the side select signal and the differentiator 32 having the resonant circuit portion 36 for supplying a signal selectively read from the pair of head portions, when side 0 is selected, side 1 A double-sided head type magnetic disk device comprising resonant frequency changing means (SW6, SW7) for changing lower than when selected. The head part 13a of the side 0 side which abuts the side 0 side of a magnetic disk, and the side 1 side head part 12a which abuts the side 1 side of a magnetic disc in the position which deviated by several tracks with respect to this side 0 side head part. And a control circuit 21 for outputting a side selection signal for selecting the side of the disc, and a current value of the write current selectively supplied to either one of the pair of head portions at the time of recording in accordance with the side selection signal. A double-sided head type magnetic disk device comprising: recording current changing means (SW8) for changing the current value to the head portion to increase than the current value to the side 1 side head portion. 5. The recording current changing means according to claim 4, wherein the recording current changing means comprises one resistor (R1) and another resistor (Ra) connected in parallel with the resistor via a switch (SW8), and the switch is opened and closed by a side selection signal. Double-sided head type magnetic disk device. 5. The write current changing means (R1, Ra) is characterized in that the current value to the side 0 side head portion is within the saturation region of the overwrite characteristic on the side 0 side, and the current value to the side 1 side head portion is over the side 1 side. A double-sided head type magnetic disk device configured to be within a saturation region of light characteristics.

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