JPS60261080A - Positioning device of magnetic head - Google Patents

Abstract

PURPOSE:To improve the accuracy of head positioning by writing in advance a position error signal (servo signal) to a magnetic disc, allowing the magnetic head to reproduce the position error signal and driving minutely a stepping motor by the position error. CONSTITUTION:A signal read by the magnetic head 11 is inputted to a position signal detecting section 14 via a head amplifier 12 and a filter 13. The level of the signal is detected by a synchronizing signal detecting circuit 15, a synchronizing signal is inputted to a timing signal generating circuit 16, two timing pulses delayed by different times from the synchronizing signal are generated, inputted to sample and hold circuits 17, 18, where they are sampled and held, a position signal is fed to a differential amplifier 19 and the position error signal is outputted. The position error signal is fed to an actuator drive section comprising an adder circuit 22, register 23, memories 24, 25, DA converters 26, 27 and drivers 28, 29 via a phase compensating circuit 20 and an AD converter 21 to drive a stepping motor 30 in a direction where the position error signal is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to improvements in magnetic recording and reproducing devices, and particularly to a magnetic recording and reproducing device that uses a stepping motor as a magnetic head positioning mechanism.

[Background of the invention]

In a magnetic recording/reproducing device such as a conventional floppy disk in which a magnetic disk is removable, the positioning error of the magnetic head is required to be below a certain tolerance value in order to maintain compatibility. This tolerance varies depending on the number of trunks per unit length, the dimensions of the magnetic head, etc. FIG. 1 shows an example of a magnetic head positioning device used in a conventional magnetic recording/reproducing device. In FIG. 1, 1 is a stepping motor, 2 is a pulley press-fitted onto the shaft of the stepping motor, 3 is a steel belt, 4 is a rail fixed to a chassis (not shown) of a magnetic recording/reproducing device, 5 is a carriage, and 6 is a head. Arms 7 and 8 are magnetic heads fixed to a carriage 5° head arm 6, 9 is a chucking device for fixing a magnetic disk (not shown) to a magnetic recording/reproducing device, and 10 is a reference track position sensor.

The operation of the head positioning device begins with the stepping motor 1 fixed to the chassis being rotated by a control signal.
The correct position changes in a step-like manner. Therefore, the pulley 2 also rotates in a stepwise manner. The rotation of the pulley 2 causes the carriage 5 to move linearly along the rail 4 via the steel belt 3. That is, the carriage 5 makes discrete linear movements in accordance with the stepped rotation of the stepping motor 1. Since the stepping motor 1 rotates at regular intervals, the carriage 5 performs linear motion at regular intervals. Therefore, the magnetic nozzles 7.8 attached to the carriage 5 and the head arm 6 perform linear movements at regular intervals. If this interval is set to the interval between tracks (the reciprocal of the track density), the throat will be magnetically positioned at the trunk position. The reference track position sensor 10 is used to detect when the magnetic head has reached the reference trunk position fi (usually the outermost track position M) by detecting the position of the carriage 5.

Positioning error factors in a magnetic recording/reproducing device using this 57'c magnetic head positioning device include (1)
Angle error of stepping motor (usually ±3%) (2) Absolute value accuracy of pulley diameter, (3) Accuracy of rail mounting to chassis, (4) Accuracy of magnetic disk chucking, (5)
) There is expansion and contraction due to temperature and humidity of the magnetic disk. In current magnetic recording and reproducing devices that use magnetic disks with a diameter of about 3 inches coated on Mylar film, the total of these is about 80 μm, and even if a well-known tunnel erase head is used, the track density is only 100 μm.
The TPI (Tracks Per Inch) has become a limit of 150 TPI, which is an obstacle to high-density recording.

[Purpose of the invention]

An object of the present invention is to improve head positioning accuracy and realize high-density recording in a magnetic head positioning device using a stepping motor.

[Summary of the invention]

In the present invention, a position error signal (servo signal) is written on a magnetic disk in advance, the position error signal is reproduced by a magnetic head, and the detected position error is used to slightly rotate a stepping motor to reduce the position error. , with increased track density. Furthermore, the driving of the stepping motor utilizes the fact that the rest position of the stepping motor after stepwise rotation changes minutely by controlling the internal magnetic field of the stepping motor.

[Embodiments of the invention]

The present invention will be described in detail below with reference to the drawings. Second
The figure shows one embodiment of the invention. In FIG. 2, 11 is a magnetic head, 12 is a hendo amplifier, 13 is a halo pass filter, 14 is a position error signal detection section, 15 is a synchronization signal detection circuit, 16 is a timing signal generation circuit, 17 and 18 are sample and hold circuits, 19 is a differential amplifier, 20 is a phase compensation circuit, 21 is an A/D converter, 22 is an adder circuit, 23
are registers, 24 and 25 are memories, 26 and 27 are D
28 and 29 are drivers, and 30 is a stepping motor.

The operation will be explained. First stepper motor 300
The rotation moves the magnetic head 11 in the trunk radial direction, as explained in FIG. A signal read from the magnetic disk by the magnetic head 11 is amplified by the head amplifier 12 and reproduced as data by a data discrimination circuit (not shown). The position error signal detection unit 14 detects a servo signal from among signals written on a magnetic disk as described later, and detects a position signal. The position error signal ERR obtained from the differential amplifier 19 passes through a phase compensation circuit 20 which is a filter circuit, is A/D converted by an A/D converter (analog-digital converter) 21, and is converted into digital data DERR.
becomes. The position error signal DERR, which is A/D converted digital data, is sent to the adder circuit 22. Register 23. A memory 24125, a D/A converter (digital-to-analog converter), and stepping motor drivers 28 and 29 are also added to the actuator drive unit to rotate the stepping motor 30 nine times in the direction in which the position error signal ER decreases. Therefore, the magnetic head 11 must travel correctly on the track in order to follow the servo signal written on the trunk, and data errors caused by changes in track position due to temperature, humidity, etc. can be prevented. can.

The position error signal detection section 14 will be explained in detail. First, an example of how to write servo signals and data will be explained using FIGS. 3 and 4.

Figure 3 is an example. The INDEX signal in FIG. 3 is a signal synchronized with the rotation of the magnetic disk, and usually one pulse is generated per rotation of the magnetic disk. Therefore, in FIG. 3, the magnetic disk rotates once from the INDEX signal to the INDEX signal.

As shown in the figure, servo signals and data signals are made to exist alternately during one round of the track. This is not a so-called servo surface servo that has a recording surface exclusively for viewing, but a data surface servo that has a coexistence of data and servo signals. Therefore, the position error signal detection section needs to extract the position error signal from the servo signal.

FIG. 4 is an example of a servo pattern. The so-called modified die pit method
This is a method called the bit method). Reference numeral 31 denotes a magnetic head. The arrow in the figure indicates the magnetization direction of the magnetic recording medium. Therefore, the magnetization is reversed at the boundary between the arrows. Now consider the case of positioning a magnetic head on track n. When the magnetic head runs along the center of track n, a reproduction signal having a peak is generated in the magnetic head 31 at each magnetization reversal.

If the vehicle travels along A in FIG. 3, a signal aK is generated; if the vehicle travels through B, signal b will be generated; and if the vehicle travels through C, signal C will be generated.

In this case, if the magnetic head 31 travels along the magnetic trunk center, the signal widths (track widths) crossing the patterns B and C will be equal, and the levels of the output signals and C will be equal.

When the magnetic head 31 off-tracks to the track n+1 side, the track width of the B pattern becomes wider, the b output increases, and the C
The track width of the pattern decreases and the C output decreases. When off-trunk to the track n-1 side, b decreases and C increases. Letting the track width of the magnetic head 31 be W and the off-track amount as X, the difference ERR between the b output and the C output is ER, K in R ((sound + X) = (summer - X)) = 2KXK:
It becomes a number. Therefore, ERR is proportional to the off-track amount XK.

Next, a method for detecting ERR will be explained. FIG. 6 shows the synchronizing signal detection circuit shown in FIG. 2, 32 is an input terminal, 33 is a comparator, 34 is a mono multivibrator, and 35 is an output terminal. FIG. 5 is a diagram showing timing. A signal from the magnetic head 11 is amplified, noise is removed by a filter 13, and then input to an input terminal 32. The comparator 33 generates a pulse as shown in level detection in FIG. 5 when the input voltage exceeds a certain voltage (d shown in FIG. 5). The mono multivibrator 34 generates a pulse P3 of a fixed time td based on the pulse, and generates a synchronization signal P4 shown in FIG. 5 when two pulses P1 and P2 are consecutive within a fixed time as in pattern A. do. Second
The timing signal generation circuit 16 shown in the figure generates a synchronization signal P4.
Sampling pulses Pb and Pc delayed by tdb and tdc are generated. This can be easily achieved using a mono-multivibrator. The sample and hold circuits 17 and 18 are realized by the configuration shown in FIG. In FIG. 7, 36 is an input terminal, 37 is an operational amplifier, 3
8 is a sample hold IC, 39 is an output terminal, and 40 is a control signal input terminal.

In operation, when a reproduction signal is applied to the input terminal 36, the operational amplifier 37. A peak hold circuit composed of a diode Di and a capacitor C holds the peak of the reproduced signal (or C) when a sampling pulse (P)) or PC is applied to the control terminal 40. Sampling I
C38 samples and holds at the falling edge of the sampling pulse pb or Pc. (Position signals b' and C' in FIG. 5) At the same time, a reset circuit constituted by an inverter INV and a transistor Q operates, discharging the charge accumulated in the capacitor C through R and preparing for the next peak hold. The position signals S and b' thus obtained from the reproduced outputs S and C are applied to the differential amplifier 19 in FIG. 2 to become an error signal ERR.

Next, a method for driving the stepping motor will be described. There are various types of stepping motors, and there are also various driving methods. Here, a case will be described in which a so-called hybrid type stepping motor is driven with two-phase excitation. FIG. 8 is a diagram showing its operating principle. When a constant current is passed through the two-phase windings while changing directions as shown in Figure 8, the magnetic field inside the stepping motor rotates ((41
口) ← → Paulownia) Therefore, the rotor also rotates in synchronization with the internal magnetic field.

If the resting position in the state (2) is taken as the trunk position, the magnetic head can be positioned at each trunk position as described in the prior art. However, two windings (
If the currents flowing through the α and β windings (here referred to as α and β windings) are set to a constant value, only discrete rotations will occur, so in order to achieve continuous rotation, the current ratio between the α and β windings must be All you have to do is change. FIG. 9 shows the rest position of the stepping motor when the current ratio of the α and β windings is changed. Normally it is stationary at the 0 point of two-phase excitation, but by changing the current ratio
You can see that you can freely stop it between tracks.

Therefore, it can be seen that the stepping motor can be stopped at any position by controlling the direction and magnitude of the current.

The stepping motor drive circuit of the present invention will be explained with reference to FIG. First, data as shown in FIG. 10 is written in the memories l 24 and 25.

The horizontal axis indicates each address, and the vertical axis indicates the value written corresponding to the address.

8-bit memory (e.g. mask ROM or PR,
OM), it is a value from 0 to FF (hexadecimal). The outputs of the memories 24 and 25 are sent to the D/A converter 26.
, 27 into an analog voltage, and a stepping motor driver (usually a power amplifier) 28, 29 causes a current to flow through the stepping motor according to the value written in the memory. Now, in FIG. 10, the broken lines indicate the static d-position in the case of normal two-phase excitation, respectively (a) in FIG.

(b), (c), ni). Now, if you increase the address now, it will rotate smoothly in one direction as shown in Figure 8 (A) → (B) → (C) → (A) → (A)... Conversely, if you decrease the address) → (c) → (b) → (a) →
) and reverse.

Therefore, the stepping motor can be smoothly rotated in any direction like a DC motor.

Therefore, a stepping motor can be used as well as an acticoator using a DC motor or a voice coil motor.

Now, the fabrication of the servo system shown in Figure 2 will be explained. The position error signal ERR obtained from the position error signal detection section 14 is sent to the A/D converter 2 according to a command from the timing signal generation circuit 16.
It is A/D converted at 1 and becomes an error signal DE)IR. Furthermore, [DER:R is added to the value of the register 23 which stores the address indicating the current position where the stepping motor is at rest, and the sum is stored in the register 23 again. The addresses given to the memories 24 and 25 are DF, Jl'1. H, and rotate the stepping motor 3o according to the driving principle described above. This operation is performed every time the magnetic head 11 travels through the servo area and a synchronization signal is generated.

If the direction of this rotation is set in the direction in which the error signal ERR decreases, the error signal becomes 0, and the magnetic head 11 always travels on a correctly defined track, and no data errors occur due to off-track.

In the present invention, the data written to the memory is linear data, but it is clear that a cosine function or the like may also be used.

The effect of the present invention is that positioning errors in a magnetic head positioning device using a stepping motor can be absorbed by the servo, and track density can be increased. In addition, the stepping motor drive circuit is stored in the memory 24,
25. Since it is composed of a register 23 and an addition circuit, the stepping motor can be stopped at any position, so when conventionally the stepping motor is moved minutely (for example, the example shown in Figure 9), it can only be moved by ±1/2 steps. This means that the servo pull-in range can be wider than in the conventional case. Furthermore, since the current position is stored in the register 23, the stepping motor is activated even when the servo signal cannot be detected (for example, when the head leaves the magnetic disk or when a dropout occurs in the servo signal). This has the advantage that the magnetic head does not come off the trunk because it holds its current position.

〔Effect of the invention〕

According to the present invention, it is possible to increase the track density and increase the recording density in a magnetic recording/reproducing device having a magnetic head positioning device using a stepping motor.

In a floppy disk drive using a 3-inch size (72 mm diameter) disk, the trunk density has been reduced to the conventional 100 TP I (Tracks Per Inc.
h) to 600 TP■, which increases the storage capacity by 6 times.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a conventional head positioning device, FIG. 2 is a block diagram of an embodiment of the present invention, FIG. 3 is an explanatory diagram of a track signal, FIG. 4 is an explanatory diagram of a servo signal, and FIG. 5 is an explanatory diagram of a servo signal. A diagram explaining the timing of the position error signal detection section, Figure 6 is a circuit diagram of the synchronization signal detection circuit, Figure 7 is a circuit diagram of the sample hold circuit, Figure 8 is a diagram explaining the principle of stepping motor rotation, and Figure 9 is a diagram of the stepping motor. FIG. 10, which is an explanatory diagram of the principle of motor drive, is an explanatory diagram of the contents of the memory. DESCRIPTION OF SYMBOLS 11... Magnetic head 14... Position error signal detection part 21... A/D converter, 22... Addition circuit 23...
...Register, 24, 25...Memory 26, 27
...D/A converter 30...stepping motor. Representative Patent Attorney Taka & Akio No. 1 Figure 0 No. 5 α l)c No. 7, Ward 6

Claims (1)

[Claims] A magnetic disk, a magnetic head for recording signals on the magnetic disk and detecting the recorded signals, means for detecting a position error signal written on the magnetic disk from the output of the magnetic head, and a stepping motor to detect the magnetic head. A magnetic recording/reproducing device has a memory and a means for giving an address to the memory, adds the address and the error signal, sets the value of ¥ again as the address of the memory, and further adds the address and the error signal to the memory.