JPH0652624A - Spindle motor for floppy disk device - Google Patents

Abstract

PURPOSE:To obtain the spindle motor having enough driving force even with its small size by disposing a magnet on an outer circumference of a rotor supported in freely rotatably by a bearing centering around a rotary shaft and rotationally driving the rotor in receiving magnetic lines of force from a stator surrounding the outer circumference. CONSTITUTION:A base 1 is fixed with a housing 2, which is fixed with a bearing 3, by which the shaft 6 is rotatably supported. Then, the shaft 6 is fixed with a hub 7 and the rotor 4, whose outer circumference is fitted with the magnet 9. The housing 2 is provided with the stator 5 consisting of iron cores 10 and coils 11 surrounded by the rotor 4, and from this stator 5, changeable magnetic lines of force are outputted to the magnet 9. Thus, by magnetic operation of the stator 5 and the magnet 9, the rotor 4 is rotated centering around the shaft 6. Now, magnetic pole parts, each consisting of the iron core 10 and the coil 11 are not arranged to surround the whole outer circumference of the rotor 4, where a part to be provided with a magnetic head 8 is exclusive of these magnetic poles, and the number of magnetic poles is selected in accordance with a motor driving system, i.e., three-phase or two-phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a spindle motor of a floppy disk device.

[0002]

2. Description of the Related Art In recent years, in floppy disk devices, there is a tendency toward downsizing and thinning of the device, and accordingly, there is a demand for downsizing of the mechanism part. In the spindle motor for rotating the medium in the mechanism section, it is necessary to satisfy both miniaturization and rotation stability at the same time.

FIG. 3 shows this spindle motor. A housing 32 is attached to the base 31, and a bearing 36 is provided at the center of the housing 32.
Further, a plurality of iron cores 33 and the iron cores 33 are provided on the housing.
A stator including a coil 35 wound on the upper side is provided. The stator emits magnetic lines of force varying outward from the tip of the radially extending iron core 33.

A shaft 34 to which a rotor 39 is fixed is inserted into the bearing 36, and the shaft 34 is rotatably supported. A magnet 40 is attached to a portion of the rotor 39 facing the above-mentioned stator.
The rotor 39 is rotationally driven by the interaction between 0 and the magnetic field lines output from the stator. A hub 37 is attached to the upper surface of the rotor 39, the medium is supported there, and the medium is rotated by the rotation of the rotor 39. Also, the base 31
Is provided with a head 38 drive mechanism (not shown).

[0005]

The above-mentioned spindle motor has the following problems in consideration of further miniaturization. In order to reduce the size, it is necessary to reduce the thickness of the magnet 40 and the size of the stator. For this reason, the rotation driving force must be reduced. In order to reduce the thickness, it is necessary to make the coil 35 small, which also causes a reduction in the rotational driving force.

Therefore, in the conventional spindle motor, the rotational driving force has to be sacrificed for downsizing.

[0007]

In the spindle motor of the present invention, a magnet is provided on the outer circumference of a rotor that is rotatably supported, and a stator that acts on the lines of magnetic force is provided along the outer circumference of the rotor.

[0008]

Embodiments of the present invention will now be described with reference to FIGS. 1 and 2. A housing 2 is fixed to the base 1, and a bearing 3 is fixed to the housing 2. A shaft 6 is rotatably supported on the bearing 3,
A hub 7 and a rotor 4 are fixed to the shaft 6.
A magnet 9 is attached to the outer circumference of the rotor 4.
A stator 5 is provided in the housing 2 so as to surround the rotor 4. This stator 5 also has an iron core 10 and a coil 11 similarly to the conventional example, but the changing magnetic force lines are output toward the inside. That is, rotor 4
To the magnet 9. This stator 5 and magnet 9
The rotor 4 is rotationally driven about the shaft 6 by the magnetic action of.

With the above-mentioned configuration, the first
Since the rotor is not on the stator, the thickness can be reduced accordingly. Secondly, it is not necessary to reduce the thickness of the magnet 9 for downsizing, and the magnet 9 having a sufficient size can be used. .

As is clear with reference to FIG. 2, the magnetic pole portion of the stator 5, which is composed of the iron core 10 and the coil 11, does not surround the entire outer circumference of the rotor 4. That is, this magnetic pole is omitted in the portion where the magnetic head 8 is provided. The number of the omitted magnetic poles is a multiple of 3 because this motor is a three-phase drive system, and is three in this embodiment.
The two magnetic poles are omitted. If the motor is a two-phase drive system, the magnetic poles in multiples of 2 can be omitted.

Although omission of the magnetic pole causes a decrease in driving force, a sufficient space for the magnetic head 8 can be secured. The decrease in driving force can be covered by the coil 11 and the magnet 9.

By providing the stator 5 on the outside, the moving range of the magnetic head 8 can be made to extend into a part of the stator, and a more compact floppy disk device can be provided.

[0013]

As described above, according to the configuration of the present invention, there is an effect that it is possible to provide a floppy disk device which has a sufficient driving force and which is miniaturized and thinned.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a plan view of the embodiment shown in FIG.

FIG. 3 is a sectional view of a conventional example.

[Explanation of symbols]

 1 Base 2 Housing 3 Bearing 4 Rotor 5 Stator

Claims (1)

[Claims] 1. A rotor having a magnet on its outer periphery and rotatably supported, and a coil wound around each of a plurality of iron cores radially arranged with respect to the rotation axis of the rotor along the outer periphery of the rotor. A spindle motor for a floppy disk drive, comprising a stator that is rotated.