JPH06290535A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To provide a magnetic disk device constituted so as to use a stepping motor as a spindle motor. CONSTITUTION:In the magnetic disk device, when a magnetic disk 2 housed in a cartridge 1 is loaded, the hub 3 of the magnetic disk 2 is magnet chucked on a turntable 4, and the turntable 4 and the magnetic disk 2 are rotated at a fixed speed by a spindle motor 5, and magnetic recording/reproducing is performed by that a magnetic head is slided and in contact with the magnetic disk 2. The hybrid type stepping motor is adopted as the spindle motor 5, and an omission part 18b provided on the outer periphery of a lower core 18 is detected by a pickup 21 provided on a stator 11, and the pulse omission is used as an index signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk device, and more particularly to a magnetic disk device configured to use a stepping motor as a spindle motor.

[0002]

2. Description of the Related Art In a magnetic disk device for recording / reproducing data on / from a flexible magnetic disk called a floppy disk, for example, when an information signal is recorded for each track formed on a disk recording surface, First, the index signal is recorded, and after the magnetic disk rotates by a certain angle, the recording of the information signal is started. When reproducing, an information signal to be reproduced is output by opening a gate circuit for reproducing an information signal based on the reproduced index signal.

For example, in the case of a 5-inch magnetic disk,
An index detection hole is formed in the magnetic disk itself, and the index detection hole is obtained by an optical sensor to obtain an index signal. However, in the case of a 3.5-inch magnetic disk, since the magnetic disk is housed in the cartridge, it is not possible to form an index detection hole in the magnetic disk itself. Therefore, in a magnetic disk device in which a 3.5-inch magnetic disk is mounted,
A magnet is provided on the outer circumference of the rotor of the motor that rotationally drives the turntable on which the magnetic disk is mounted, and a Hall element that detects passage of the magnet is provided at a position facing the outer circumference of the rotor. Detects the constant angular position of the rotor and indirectly defines the index position of the magnetic disk.

[0004]

However, in the conventional magnetic disk device, it is common to use a direct drive servomotor as the turntable driving motor. When this type of servo motor is used, a magnet must be bonded to the outer circumference of the rotor in order to detect the index position, and a space for mounting the Hall element outside the rotor is required.

Further, in the magnetic disk device, price competition in the market is severe, and there is a limit to the cost reduction of the servo motor itself. Therefore, it is necessary to consider using a motor other than the servo motor.

Therefore, an object of the present invention is to provide a magnetic disk device which solves the above problems.

[0007]

SUMMARY OF THE INVENTION The present invention is a magnetic disk apparatus for magnetically recording / reproducing by rotating a turntable on which a magnetic disk is mounted at a constant speed by a motor and moving a magnetic head along the magnetic disk. In, the motor is formed by a stepping motor having a rotor and a stator formed annularly outside the rotor,
One of a plurality of teeth formed on the outer circumference of the rotor of the stepping motor is provided with a missing portion, and a pickup for detecting the missing portion is provided on the inner circumference between the stators of the stepping motor. To do.

[0008]

The stepping motor is used to rotate the turntable, and the stepping motor is provided with the missing portion and the pickup for detecting the index signal, thereby eliminating the need for providing an element for detecting the index signal outside the motor. Therefore, the installation space can be reduced accordingly.

[0009]

1 and 2 show an embodiment of a magnetic disk device according to the present invention.

In both figures, when a magnetic disk 2 housed in a cartridge 1 is mounted in a flexible magnetic disk device (hereinafter simply referred to as "magnetic disk device"), a hub 3 of the magnetic disk 2 is placed on a turntable 4. Magnetically chucked, the turntable 4 and the magnetic disk 2 are rotated at a constant speed by the spindle motor 5, and a magnetic head (not shown) is brought into sliding contact with the magnetic disk 2 to perform magnetic recording / reproduction.

The turntable 4 is supported on the rotary shaft 6 of the spindle motor 5, and the rotary shaft 6 has bearings 7,
It is supported by 8. Spindle motor 5 is substrate 9
Is fitted and fixed in the mounting hole 9a.

As the spindle motor 5, a hybrid type stepping motor is adopted. Therefore, in the spindle motor 5, the rotor 10 is connected to the rotary shaft 6,
An annular stator 11 is arranged on the outer periphery of the rotor 10. The stator 11 is insert-molded in a synthetic resin casing 13 to reduce its weight.

An annular support member 14 for holding the bearing 8 is fitted on the bottom portion of the casing 13, and the casing 13 is
A reinforcing plate 15 for holding the bearing 7 is provided on the upper part of the
Is insert molded.

The rotor 10 has a disk-shaped magnet 16
And an upper core 17 and a lower core 18 provided above and below the magnet 16, respectively. The magnet 16 is magnetized to have an N pole on the upper side and an S pole on the lower side. The upper core 17 and the lower core 18 are made of a laminated core in which thin iron cores are laminated, and a plurality of teeth 17a and 18a project at a constant pitch on the outer circumference of each core.

In this embodiment, as shown in FIG. 3, the lower core 18 is provided with a cutout portion 18b on the outer periphery thereof. The missing portion 18b has the teeth 18a removed, and is provided only at one location on the outer periphery of the lower core 18.

The stator 11 has eight tooth poles 11a to 11a on its inner circumference.
11h protrudes, and a plurality of teeth 1 facing the teeth 17a and 18a of the rotor 10 are provided at the ends of the tooth poles 11a to 11h.
9 project at a constant pitch. And each tooth pole 11
Coils 20a to 20h are wound around the roots of a to 11h.

The pitch of the teeth 19 of the stator 11 and the rotor 1
The pitch with the teeth 17a and 18a of 0 is slightly deviated, and the coils 20a to 20h of the above tooth poles 11a to 11h are slightly displaced.
When a drive current is applied to the teeth 17a, 18a and the teeth 19
A magnetic flux passes between the teeth and the teeth 17a, 18a of the rotor 10.
Rotates in the circumferential direction so as to be aligned with the teeth 19 of the stator 11. In the present embodiment, the coil 2 of each tooth pole 11a to 11h
Of the coils 0a to 20h, the coils 20a, 20c, 20e, 2
0 g is energized as a one-phase coil and the other coil 20
b, 20d, 20f and 20h are energized as two-phase coils.

Therefore, the coil 2 of each tooth pole 11a to 11h
0a to 20h are two coils of one phase and two coils arranged every other one.
The coils of the phases are alternately energized, which causes the above-described alignment phenomenon to rotate the rotor 10. That is, the spindle motor 5 including the above stepping motor controls the energization of the coils 20a to 20h so that the spindle motor 5 rotates at a constant speed at the number of rotations required for magnetic recording / reproduction, and thereby the rotor 10 is rotationally driven.

A pickup 21 for detecting rotation is provided between the tooth poles 11a and 11b. The pickup 21 includes a core 22 protruding from the inner circumference of the stator 11 toward the center and a coil 23 wound around the core 22. Each time the teeth 17 a and 18 a of the rotor 10 pass in front of the core 22. A current is induced in the coil 23 and a detection pulse is output. However, when the missing portion 18b provided on the outer periphery of the lower core 18 passes in front of the pickup 21, no detection pulse is obtained, and this missing pulse is used as an index signal.

Since the pickup 21 for detecting rotation is provided inside the spindle motor 5 as described above,
You can attach a magnet to the outer circumference of the rotor as before,
The work of attaching the hall element to the outside of the motor is not necessary, the assembly work can be simplified, and the installation space of the hall element can be reduced to save space.

FIG. 4 shows an index signal detection circuit.

In the figure, the coils 20a to 20h of the tooth poles 11a to 11h are connected to a two-phase excitation driver 24,
The excitation driver 24 is the one-phase coil 20 as described above.
a, 20c, 20e, 20g and two-phase coils 20b, 2
0d, 20f, and 20h are alternately excited at a predetermined cycle to rotate the rotor 10 at a constant speed.

Further, the pickup 21 includes a comparator 2
5 and detects that the missing portion 18b has passed in front of the pickup 21. Furthermore, the comparator 2
The output of 5 is supplied to a re-trigger type monostable multivibrator (monostable multivibrator, hereinafter referred to as “monomulti”) 26.

A pattern generator 27 outputs a command to the two-phase excitation driver 24 to drive the spindle motor 5 to rotate at a constant speed in order to detect an index when the magnetic disk is mounted. Is commanded to ignore the signal from the pickup 21 until the rotation speed reaches a predetermined constant speed.

When the rotor 10 makes one revolution, the mono-multi 26 outputs an index signal based on the detection signal from the pickup 21 which has detected the passage of the missing portion 18b.

Now, referring to the waveform diagram of FIG. 5, the rotor 1
The rotation detection operation of 0 will be described.

As shown in FIG. 5 (A), the teeth 17a and 18a formed on the outer periphery of the rotor 10 have N poles and S poles, respectively.
They are poles and are arranged alternately.

When the teeth 17a and 18a of the rotor 10 pass in front of the pickup 21, the detection signal from the pickup 21 becomes as shown in FIG. 5 (B). That is, the output level of the comparator 25 becomes equal to or higher than the reference value (threshold value) when the teeth 17a and 18a pass in front of the pickup 21, and the reference value (threshold value) when the missing portion 18b passes in front of the pickup 21. It becomes the following.

Therefore, the output of the comparator 25 is as shown in FIG.
The pulse waveform is as shown in (C), and the pulse cannot be obtained only when the missing portion 18b passes. Mono Multi 2
6, the output is kept at the H level during the time constant τ by the retrigger output from the comparator 25, that is, until the metastable time elapses, and the retrigger is not output when the missing portion 18b passes, so that the metastable is generated. The output is set to the L level when the time has elapsed.

The retrigger is output when the tooth 18a passes in front of the pickup 21. In the mono-multi 26, the time constant τ is the pitch (interval) of the teeth 18a, that is, S
It is set to be longer than the pole cycle T and shorter than 2T. Therefore, when the tooth 18a is detected, the retrigger is output before the time constant τ elapses, so that the output of the monomulti 26 is maintained at the H level.
However, since the retrigger is not output when the missing portion 18b is detected, the output of the mono-multi 26 switches to the L level when the time constant τ has elapsed from the retrigger that was output before that.

Therefore, the output of the monomulti 26 is as shown in FIG.
The pulse waveform is as shown in (D), and an L-level pulse is output as an index signal immediately after passing through the missing portion 18b. Therefore, the magnetic disk device records / reproduces information recorded on each recording track based on this index signal.

Since one pulse is output from the mono-multi 26 every time the rotor 10 makes one revolution, the number of revolutions of the rotor 10 can be calculated by counting this index signal.
That is, the number of rotations of the turntable 4 and the magnetic disk 2 can be measured.

[0033]

As described above, in the magnetic disk drive according to the present invention, the stepping motor is used to drive the turntable in rotation, and the stepping motor is provided with the missing portion and the pickup for detecting the index signal. Since it is not necessary to provide an element for detecting the index signal outside the motor, the installation space can be reduced accordingly. Therefore, when selecting a motor that rotationally drives a turntable, it is considered to use a servo motor or a stepping motor that has been conventionally used, so that the selection range of the motor is widened and the degree of freedom in design is increased. Features such as being enhanced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of a magnetic disk device according to the present invention.

FIG. 2 is a cross-sectional view of a stepping motor.

FIG. 3 is an enlarged view showing a missing portion provided on the outer circumference of the rotor.

FIG. 4 is a circuit diagram of an index signal detection circuit.

FIG. 5 is a waveform diagram of an index signal detection circuit.

[Explanation of symbols]

 1 Cartridge 2 Magnetic Disk 4 Turntable 5 Spindle Motor 10 Rotor 11 Stator 11a to 11h Tooth Pole 16 Magnet 17 Upper Core 17a, 18a, 19 Teeth 18 Lower Core 18b Missing Part 20a to 20h Coil 21 Pickup 24 Two-Phase Excitation Driver 25 Comparator 26 Monostable Multivibrator 27 Pattern Generator

Claims (1)

[Claims] 1. A magnetic disk device for rotating a turntable on which a magnetic disk is mounted by a motor at a constant speed to move a magnetic head along the magnetic disk for magnetic recording / reproduction, wherein the motor is a rotor. A stepping motor having a stator formed annularly outside the rotor, wherein one of a plurality of teeth formed on the outer circumference of the rotor of the stepping motor is provided with a missing portion, A magnetic disk drive, wherein a pickup for detecting the missing portion is provided on an inner circumference between the stators.