JPH0283858A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To carry out the fine control and to accurately control the revolving speed of a spindle motor as well by measuring the revolving speed of the spindle motor at short intervals by means of an optical encoder. CONSTITUTION:A magnetic recording medium is rotated by the spindle motor 11. And, the intervals of pulse outputs from the optical encoder 12 are counted by a counter part 13 and sent to a comparator part 15. Then, a value from the counter part 13 is compared with a reference value of a revolving speed reference value table 14 by the comparator part 15, and their difference is sent to a speed control part 16. And, a signal is sent from the comparator pat 15 to a driver 17 by the speed control part 16 in response to the difference, thus controlling the revolving speed of the spindle motor 11. By this method, the fine control can be preformed, while the revolving speed of the spindle motor can accurately be controlled.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a magnetic disk device.

In particular, the present invention relates to improvements in speed control circuits in magnetic disk drives.

[Prior Art] Conventionally, as a speed control circuit for a magnetic disk device, the one shown in FIG. 2 is known.

In the speed control circuit shown in the figure, a Hall element 2 is attached close to the outside of the spindle motor/rotor section l, and is attached inside the spindle motor rotor section 1 by rotation of the spindle motor rotor section l. The change in magnetic flux when the magnet 3 passes through the Hall element 2 is captured.

Then, the output from the Hall element 2 is detected by the shaping section 4 and the pulse interval counting section 5, and the number of revolutions of the spindle-motor is detected by counting the interval.

On the other hand, a rotation speed reference value table 6 is provided which defines a reference value of the rotation speed of the spindle motor.

Then, a comparison unit 7 compares the reference value of the rotation speed reference value table 6 and the output from the counting unit 5, and a spindle motor control unit 8 controls a spindle motor driver 9 so as to cancel the difference. By this, the rotation speed of the spindle motor is controlled.

[Problems to be Solved] In the conventional magnetic disk drive described above, since the number of magnets 3 inside the spindle ψ motor $ rotor section 1 is limited, the number of pulses obtained by one rotation of the spindle motor rotor section l is limited. There is also a problem that fine-grained control cannot be performed as a result.

Another problem is that the rotational speed of the spindle motor cannot be accurately measured due to the hysteresis characteristics of the magnetic material.

The present invention has been made in view of the above-mentioned problems.
An object of the present invention is to provide a magnetic disk device capable of finely and accurately controlling the rotational speed of a spindle motor.

[Means for Solving the Problem] In order to achieve the above object, a magnetic disk device of the present invention includes a spindle motor for rotating a magnetic recording medium, an optical encoder for detecting the number of rotations of the spindle motor, and an optical encoder for detecting the rotation speed of the spindle motor. A counting section that counts the output of the optical encoder, a rotation speed reference value table that determines a reference value of the rotation speed of the spindle motor, and a reference value of the rotation speed reference value table and the output from the counting section. The structure includes a comparison section that compares and outputs the difference, and a speed control section that controls the rotation speed of the spindle motor so as to cancel out the difference in accordance with the difference signal from the comparison section.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a speed control circuit in a magnetic disk device according to the present invention.

In the figure, 11 is a spindle motor that rotates the magnetic recording medium.

12 is an optical encoder directly connected to the shaft of the rotor portion of the spindle motor 11;
Detects the rotation speed.

A counting section 13 counts the output from the optical encoder 12.

Reference numeral 14 denotes a rotation speed reference value table, which determines a reference value for the rotation speed of the spindle motor 11.

A comparison section 15 compares the reference value of the one-rotation speed reference value table with the output from the counting section 13 and outputs the difference.

16 is a speed control section, which receives the difference signal 1 from the comparison section 15.
The rotation speed of the spindle motor 11 is controlled by controlling the driver 17 so as to cancel out the difference in accordance with the rotation speed 5a.

Therefore, in the above-described magnetic disk device, the interval between pulse outputs from the optical encoder 12 is equal to the interval between the pulse outputs from the counter 13.
The comparison unit 15 compares the value from the counting unit 13 with the reference value of the rotation speed reference value table 14 and sends the difference to the speed control unit 16. Then, the speed control section 16 sends a signal to the driver 17 in accordance with the difference from the comparison section 15, thereby controlling the rotation speed of the spindle motor.

[Effects of the Invention] As explained above, the present invention can perform fine control by measuring the rotation speed of the spindle motor at short intervals using an optical encoder, and can also adjust the rotation speed of the spindle motor. This has the effect of being able to control accurately.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a speed control circuit in a magnetic disk device according to the present invention, and FIG. 2 is a block diagram of a speed control circuit in a conventional device. 11 Spindle motor 12: Optical encoder 13: Counting section 14: Reference rotational speed table 15: Comparison section 16: Speed control section 17: Driver agent Patent attorney Kihei Watanabe

Claims (1)

[Claims] A spindle motor that rotates a magnetic recording medium, an optical encoder that detects the rotation speed of the spindle motor, a counter that counts the output of the optical encoder, and a reference for the rotation speed of the spindle motor. a rotation speed reference value table that determines the rotation speed reference value; a comparison section that compares the reference value of the rotation speed reference value table with the output from the counting section and outputs the difference; A magnetic disk drive comprising: a speed control unit that controls the rotational speed of the spindle motor so as to cancel out the difference.