JPH06223488A - Spindle motor for driving floppy disk - Google Patents

Abstract

PURPOSE:To provide a stable index pulse reducing the fluctuation in a pulse width for the change in ambient temperature in the index pulse generating device of a spindle motor for driving a floppy disk. CONSTITUTION:An orthogonal MR element 7 is operated only with one side 18a of roughly symmetrical components of magnetic field generated from an index magnet by a single pole index magnet 6 fixed to the outer periphery of the rotor of the spindle motor for driving the floppy disk and the orthogonal MR element 7. Thus, the zero cross point of the obtained index pulse is detected, and by making that the leading edge of the pulse, the index pulse generating device is obtained which is capable of generating the stable index pulse reducing the fluctuation in the pulse width for the change in ambient temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a floppy disk index pulse generator.

[0002]

2. Description of the Related Art In recent years, floppy disk devices have become smaller,
The index pulse generator attached to the spindle motor is becoming smaller and smaller, and a more stable pulse generation method is required.

A conventional index pulse generator for a floppy disk will be described below.

FIG. 6 (a) is a half sectional view of a conventional index pulse generator for a floppy disk drive spindle motor, and FIG. 6 (b) is a partially enlarged plan view of a conventional index pulse generator for a floppy disk drive spindle motor. FIG. 7 and FIG. 7 are a magnetic flux density distribution and an index pulse waveform diagram in the conventional example.

In FIG. 6 (a), reference numeral 2 is a hub, which is a shaft 1.
Is inset. Reference numeral 3 is a hub magnet, and 9 is an FG magnet, which is integrally formed with the rotor frame 4.
A field magnet 5 is fixed to the rotor frame 4. An index magnet (single pole of S pole or N pole) 6 is fixed to a cutout portion of the FG magnet 9 and the rotor frame 4. Reference numeral 8 is a printed circuit board, 10 is an armature winding, 11 is an armature core, and 12 is a screw for fixing the housing 13 and the armature core 11. Reference numeral 14 is a bearing metal, and 15 is a sensor chip of the hall element 21.

The operation of the floppy disk drive spindle motor configured as described above will be described with reference to FIG. First, when the floppy disk is attached to the hub 2 and the rotor of the motor starts rotating in the direction of arrow A, F
The Hall element 21 mounted on the printed circuit board facing the index magnet 6 fixed to the G magnet 9 senses the magnetic flux B from the index magnet shown in FIG. The waveform is shaped by the Schmitt trigger circuit composed of VL and the high level threshold voltage VH, and the pulse P is generated once per one rotation as shown in FIG. 7, and is used as a reference for the writing position on the disc or the reading position of the recording signal. An index pulse that becomes a signal is generated. At this time, there is a gap between the magnetic center 16 of the index magnet 6 and the magnetic center 17 of the sensor chip of the Hall element 21.

[0007]

However, in the conventional configuration shown in FIG. 6, the magnetic flux density as shown by the broken line in FIG. 7 and this magnetic flux density are obtained from the temperature characteristics of the index magnet and the Hall element. Since the index pulse is generated, a timing deviation of Δt occurs at both the rising edge and the falling edge, which may hinder the writing to the disk or the reading of the recording signal.

The present invention solves the above-mentioned conventional problems, and provides an index pulse generator for a spindle motor for driving a floppy disk, which uses the conventional single-pole magnet as it is and has a small index timing deviation due to temperature change. The purpose is to do.

[0009]

In order to achieve this object, an index pulse generator for a spindle motor for driving a floppy disk according to the present invention uses a ferromagnetic orthogonal magnetoresistive effect element (hereinafter, orthogonal MR element) as an index sensor. And a unipolar index magnet, and using the symmetry of the magnetic field generated from this index magnet, the orthogonal MR element is operated only by the magnetic field on one side with the axis of symmetry or the magnetic center as the boundary axis. , The zero crossing point of the output of the orthogonal MR element is used as an index pulse.

[0010]

With this structure, the index magnet can use a conventional single-pole magnet, and by combining an orthogonal MR element facing the index magnet, two continuous pulses (positive or negative or negative positive) per one rotation of the motor can be used. ) Can be generated in order, and if this is used as an index pulse to detect the zero-cross point, the index timing deviation due to temperature change can be suppressed to a small level, and a stable pulse can be generated.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1A is a half sectional view of an index pulse generator of a spindle motor for driving a floppy disk according to an embodiment of the present invention, and FIG.
It is a partially expanded top view of (a). FIG. 2 is an enlarged sectional view of FIG. 3 is an enlarged perspective view of the index magnet, FIG. 4 (a) is an enlarged view of the orthogonal MR element, and FIG. 4 (b) is an enlarged view of the orthogonal MR element line element.

In FIG. 1, reference numeral 2 is a hub into which a shaft 1 is fitted. Reference numeral 3 is a hub magnet, and 9 is an FG magnet, which is formed integrally with the rotor frame 4 as a unit. 5
Is a field magnet and is fixed to the rotor frame 4. An index magnet (S pole) 6 is fixed to the FG magnet 9 and the cutout portion of the rotor frame 4. 8 is a printed circuit board, 10 is an armature winding, 11 is an armature core, 12 is a screw and a housing of 13 and the armature core 1
1 is fixed. 14 is bearing metal, 15 is orthogonal M
It is a sensor chip of the R element 7.

The operation of the index pulse generator for the floppy disk drive spindle motor configured as described above will be described with reference to FIG. First,
When the motor starts to rotate in the direction A of FIG. 1B, the motors closely face the index magnets 6 fixed to the FG magnets 9 and have their magnetic centers (orthogonal MR elements 1
7, the index magnet 16 is provided with a step h so that they do not coincide with each other, and the orthogonal MR element 7 mounted on the printed board causes a change in magnetic resistance due to the magnetic field 18a component. The orthogonal MR element has already been disclosed in Japanese Patent Publication No. 54-41335, but the orthogonal M element as shown in FIG.
If a two-phase differential type element of R element is used, the line element 22
When a and 22c show the maximum change, the line elements 22b and 22d show the minimum change, and the orthogonal MR shown in FIG.
The differential output H of the element is obtained, and the index pulse P shown in FIG. 5A is obtained through the amplifier and the Schmitt trigger circuit.

As described above, according to this embodiment, as shown in FIG.
An index pulse having a zero-crossing point as a leading edge as shown in (a) can be obtained, and the deviation of the index timing with respect to the ambient temperature change becomes very small as shown by the broken line, and a stable index pulse is obtained. be able to.

In this embodiment, the orthogonal MR element does not operate in the magnetic field 18c which is substantially symmetrical to the magnetic fields 18b and 18a parallel to the printed circuit board. Further, at this time, in order to make the orthogonal MR element 7 operate to be saturated, the magnetic field is of course strengthened, and the size of the index magnet 6 of FIG. 3 is different from the size 20a or 20b of the sensor chip 15 shown in FIG. It is assumed that the dimension 19a is large. Also, the output is when the rotation direction is reversed or when the magnetic center 17 of the sensor chip 15 of the orthogonal MR element 7 is arranged closer to the printed circuit board than the magnetic center 16 of the index magnet (when operated by the magnetic field 18c). It goes without saying that an output having the output phase inverted by 180 degrees, as shown in FIG.

[0017]

As described above, according to the present invention, a unipolar index magnet is fixed to the outer circumference of the rotor of a spindle motor that drives a disk to rotate, and a perpendicular MR element is arranged at a position facing the index magnet. The symmetry of the magnetic field that
By operating the R element, it is possible to realize an index pulse generator for a spindle motor for driving a floppy disk, which can generate an index pulse having good temperature characteristics with the zero cross point of the output voltage as the leading edge.

[Brief description of drawings]

FIG. 1A is a half cross-sectional view of an index pulse generator for a spindle motor for driving a floppy disk according to an embodiment of the present invention. FIG. 1B is an index pulse for a spindle motor for driving a floppy disk according to an embodiment of the present invention. Partially enlarged plan view of generator

FIG. 2 is an enlarged cross-sectional view of an index pulse generator for a floppy disk drive spindle motor according to an embodiment of the present invention.

FIG. 3 is an enlarged perspective view for explaining an index magnet.

FIG. 4A is an enlarged perspective view for explaining an orthogonal MR element, and FIG. 4B is an enlarged plan view for explaining a line element of the orthogonal MR element.

FIG. 5A is a waveform diagram for explaining an index pulse in one embodiment of the present invention. FIG. 5B is a waveform diagram for explaining an index pulse in another embodiment of the present invention.

FIG. 6A is a half sectional view of an index pulse generator of a floppy disk drive spindle motor in a conventional example. FIG. 6B is a partially enlarged plan view of an index pulse generator of a floppy disk drive spindle motor in a conventional example.

FIG. 7 is a waveform diagram for explaining an index pulse in a conventional example.

[Explanation of symbols]

 1 shaft 2 hub 3 hub magnet 4 rotor frame 5 field magnet 6 index magnet 7 orthogonal MR element 8 printed circuit board 9 FG magnet 10 armature winding 11 armature core 12 screw 13 housing 14 bearing metal 15 sensor chip 16 index magnet magnetic Center 17 Sensor magnetic center 18a, 18b, 18c Magnetic field lines 19a, 19b Index magnet size 20a, 20b Sensor chip size of orthogonal MR element 21 Hall element 22a, 22b, 22c, 22d MR line element

Claims (1)

[Claims] 1. An index pulse magnet having a single pole (S pole or N pole) is fixed to the outer periphery of a rotor of a spindle motor for rotating a floppy disk, and the ferromagnetic orthogonal magnetic resistance is opposed to the magnet. In the spindle motor for driving a floppy disk in which the effect element is arranged, the index pulse smagnet is a rectangular parallelepiped or a cube having one side larger than the vertical or horizontal dimension of the sensor chip of the ferromagnetic direct type magnetoresistive effect element. Then, the sensor chip of the ferromagnetic orthogonal magnetoresistive effect element is arranged at a position shifted above or below the magnetic center of the index pulse magnet, and the rotation axis of the spindle motor is regarded as the Z axis in a cylindrical coordinate system. The magnetic field component from the index magnet generated parallel to the cylindrical surface (r surface) It is operated by a magnetic field loop formed on the Z-axis positive side or negative side of the magnetic field line distribution that is almost vertically symmetrical with the magnet magnetic center as a boundary, and the zero cross point of the ferromagnetic orthogonal type magnetoresistive effect element output is used as an index pulse. Spindle motor for driving a floppy disk, which has a leading edge.