JPH0646554A - Planar opposing brushless motor - Google Patents

Abstract

PURPOSE:To obtain a floppy disc which is made thinner than a conventional one. CONSTITUTION:The inventive brushless motor comprises a rotor yoke 12 constituted of a permanent disc magnet 11 multipolar magnetized in the thickness direction, a stator yoke 15 opposing to the rotor yoke 12, and a Hall element 14 fixed to the stator yoke 15 in predetermined relationship with the stator coil 13. Since the permanent magnet 11 is provided with a circumferential groove 16 in the surface opposing to the Hall element and sufficient thickness can be ensured at parts other than the groove 16, the brushless motor can be made thin without sacrifice of the magnetic characteristics of the permanent magnet 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor used in a floppy disk drive, and more particularly to a flat facing type brushless motor.

[0002]

2. Description of the Related Art In recent years, floppy disk devices have become thinner. The most important issue in reducing the thickness of a floppy disk device is reducing the thickness of the spindle motor for rotating the floppy disk. There are several types of spindle motors, but a plane-opposed brushless motor is often used. An example of a plane-opposed brushless motor used in the above-mentioned conventional floppy disk device will be described below with reference to the drawings.

FIG. 2 is an external perspective view of a conventional flat-opposed brushless motor. In FIG. 2, reference numeral 21 denotes a permanent magnet, which is magnetized in multiple poles and attached to the rotor yoke 12. Both the stator coil 13 and the Hall element 14 are attached to the stator yoke 15.

The operation of the flat-opposed brushless motor having the above structure will be described below.

The Hall element 14 is attached to the stator yoke 15 in order to detect the electrical positional relationship between the permanent magnet 21 attached to the rotor yoke 12 and the stator coil 13. While detecting the magnetic pole of the permanent magnet 21, the hall element 14 allows an appropriate drive current to flow through the stator coil 13 to efficiently generate torque in the motor for rotation. FIG. 3 is a cross-sectional view of the plane-opposed brushless motor shown in FIG. In order to realize the thinning, it is necessary to make the height of the stator coil 13 as low as possible, but as shown in FIG. 3, there is a limit to the thinning of the motor due to the restriction of the height of the Hall element 14. For example, stator yoke 1
5 has a thickness of 0.6 [mm], and the Hall element 14 has a thickness of 0.6
[Mm], the rotor yoke 12 has a thickness of 0.6 [mm], the permanent magnet 21 has a thickness of 0.8 [mm], and the gap between the stator and the rotor is 0.1 [mm]. It becomes 2.7 [mm]. Of these constituent elements, the stator yoke 15 and the rotor yoke 12 are difficult to be thin due to mechanical strength. The permanent magnet 21 used in a thin floppy disk device is often a rare earth magnet Nd-Fe-B, but the Nd-Fe-B magnet is due to mechanical stress generated during surface machining. The magnetic force is deteriorated by the surface plating applied to prevent the physical damage of the magnet surface and rust prevention, and the torque generation efficiency is reduced.
One cannot be thin. Due to the above problems, there has been a limit to the reduction in thickness of the spindle motor.

[0006]

However, in the above structure, the height of the Hall element restricts the height of the flat-opposed brushless motor, and it is difficult to further reduce the thickness.

In view of the above problems, it is an object of the present invention to provide a flat facing type brushless motor which is not restricted by the height of the Hall element.

[0008]

In order to achieve the above object, a flat opposed brushless motor according to the present invention includes a rotor having a disk shape and including permanent magnets magnetized in multiple poles in the thickness direction. , A stator yoke facing the rotor, a stator coil attached to the stator yoke, and a hall element attached to the stator yoke in a predetermined positional relationship with the stator coil, and the permanent magnet is A circular groove is provided on the surface facing the Hall element.

[0009]

In the above construction, by providing a circumferential groove on the surface of the permanent magnet facing the Hall element, the thickness of the permanent magnet is ensured, and the flat facing type without deteriorating the magnetic characteristics of the permanent magnet. Brushless motors can be made thinner.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A flat-faced brushless motor of a disk device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a flat-opposed brushless motor of a disk device according to an embodiment of the present invention. In the figure, 11 is a permanent magnet, 12 is a rotor yoke, and 13
Is a stator coil, 14 is a Hall element, and 15 is a stator yoke. These configurations are the same as in the conventional structure. However, in the present invention, a groove 16 on the circumference is formed on the surface of the permanent magnet 11 facing the Hall element 14. With the provision, the height of the motor is not restricted by the height of the upper surface of the Hall element 14 and the height of the lower surface of the permanent magnet 11, so that the planar opposed brushless motor can be thinned. At this time, the thickness of the portion other than the groove of the permanent magnet can be sufficiently secured, so that the magnetic characteristics of the permanent magnet 11 are not deteriorated.

[0012]

As described above, according to the present invention, the planar opposed brushless motor can be made thin by providing the circumferential groove on the surface of the permanent magnet attached to the rotor, the surface facing the Hall element. Therefore, the floppy disk device can be made thin by using the flat facing brushless motor of the present invention.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a flat opposed brushless motor according to an embodiment of the present invention.

FIG. 2 is an external perspective view of a conventional flat opposed brushless motor.

FIG. 3 is a sectional view of a conventional plane-opposed brushless motor.

[Explanation of Codes] 11 Permanent Magnet 12 Rotor Yoke 13 Stator Coil 14 Hall Element 15 Stator Yoke 16 Groove 21 Permanent Magnet

Claims (1)

[Claims] 1. A rotor yoke including a disk-shaped permanent magnet magnetized in the thickness direction and having multiple poles, a stator yoke facing the rotor yoke, and a stator yoke attached to the stator yoke. And a Hall element attached to the stator yoke in a predetermined positional relationship with the stator coil, and the permanent magnet has a circumferential groove on a surface facing the Hall element. A flat-faced brushless motor characterized in that