JPS61288756A - Magnetizing device - Google Patents

Abstract

PURPOSE:To improve driving torque so that the space may be narrowed between a driving magnetic pole and a revolution-detecting magnetic pole. CONSTITUTION:A peripheral region 4a of an end face 4 is close to an exciting coil 11 and is formed into the shape corresponding to the coil form of an exciting coil 11. Consequently, an exciting coil 10 is wound up at a groove in circumference 8 so that it may creep under an exciting coil 11. With this magnetizing device, when an exciting coils 10 and 11 are excited, 8-poled driving magnetic pole and 120-poled revolution-detecting magnetic pole are magnetized to an end face of disk magnet, respectively. Besides, as there is no gap between exciting coils 10 and 11, it is possible to remove the non-magnetized portion so far come about. The space between the driving magnetic pole and revolution- detecting pole can therefore be narrowed. The driving magnetic pole can be formed in the wide parts of the magnet end face and the improvement of the driving torque be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for magnetizing a disc-shaped magnet incorporated in a rotor such as a direct drive type brushless motor.

[Prior Art] A direct drive type flat motor is a brushless coreless motor with no iron core in the armature, and has the advantages of being thin, light, and has low cogging torque. It is widely used as spindle motors for office automation equipment and drive motors for audio equipment.

The third type of rotor used in this type of flat motor is
As shown in the figure, a structure is known in which a disk-shaped magnet 14 is fixed to the bottom surface of a cup-shaped back yoke 12 with a drive shaft 13 fixed at the center. The disk-shaped magnet is usually a Ferrite magnet having anisotropy in the axial direction, and a driving magnetic pole is magnetized on the side 14a facing the armature coil (not shown) fixed to the stator yoke. It is something. A motor incorporating this rotor uses drive magnetic poles to control the number of rotations, and therefore has a drawback in that the detection accuracy of the number of rotations is low.

Therefore, as shown in Fig. 4, a cup-shaped back yoke 1
A rotor has been proposed and has been put into practical use, in which a disk-shaped magnet 15 is fixed to the outer peripheral edge of the rotor 2', in addition to the disk-shaped magnet 14'. ing.

Furthermore, recently, in order to reduce the number of parts, as shown in FIG. 5, a disk-shaped magnet 1 is installed on the bottom surface of the cup-shaped back yoke 12'' with a drive magnetic pole and a rotation speed detection magnetic pole magnetized on the same surface.
A rotor with a diameter of 4" has been proposed and put into practical use. According to this rotor, the accuracy of detecting the rotation speed can be improved without increasing the number of parts (Japanese Patent Application Laid-open No. 45712-1989).
(No.), is often used in the rotor of the spindle motor of floppy disk drives.

Conventionally, the method of magnetizing the drive magnetic pole and the rotation speed detection magnetic pole on the same end face of a disc-shaped magnet was to prepare two types of magnetizing devices and magnetize them in two separate steps. It was.

However, this method is inefficient and requires two magnetizing devices.

Therefore, recently, a magnetizing device as shown in FIG. 6 is used to simultaneously magnetize the driving magnetic pole and the rotation speed detection magnetic pole.

This magnetizing device includes a cylindrical core 1 made of a soft magnetic material such as pure iron, an excitation coil 10, and an excitation coil 11. The core 6 has grooves 6 radially formed from the center hole 5.
an inner peripheral core 2 having an end surface 4 partitioned into a fan shape;
It consists of a core 2 and an outer peripheral core 3 having an end surface 7 partitioned by a concentric radial groove 9, and a circumferential groove 8 between the cores 2 and 3.
is formed. An excitation coil 10 is wound around each groove 6, and an excitation coil 11 is wound around each groove 9. Further, the excitation coils 10 and 11 are each connected to two types of known capacitor-type magnetizing power supplies (not shown) of a pulsed magnetic field generation type.

Therefore, when a disk-shaped magnet (not shown) is set on the upper surface of the core 6 and each coil is energized, the excitation coil 10 magnetizes the drive magnetic pole, and the excitation coil 11 magnetizes the rotation speed detection magnetic pole. .

[Problems to be Solved by the Invention] According to the magnetizing device shown in FIG. 6, although two types of magnetization can be performed with one type of magnetizing device, Since there is a gap g (usually about 3 to 6 mm), there is a problem in that a non-magnetized portion is formed on the end face of the magnet. Furthermore, since the driving magnetic pole is not magnetized to the rotational speed detecting magnetic pole, there is also the problem that the driving torque decreases when the entire magnet is used as the driving magnetic pole.

It is an object of the present invention to solve the problems of the prior art described in (a) above, and to provide multi-pole magnetization capable of obtaining a sufficient rotation speed control signal using rotation speed detection magnetic poles without reducing the drive torque due to the drive magnetic poles. The object of the present invention is to provide a magnetizing device that can perform the following.

[Means for Solving the Problems] 4. The magnetizing device of the present invention divides one end surface of a cylindrical core made of a soft magnetic material into an inner end surface and an outer end surface by a circumferential groove provided in this end surface. A plurality of first magnetic pole faces are formed by providing radial grooves on the inner peripheral end face, and a plurality of first magnetic pole faces are formed by providing radial grooves on the outer peripheral end face at a pitch different from the above-mentioned grooves. a first excitation coil is wound around each of the first magnetic pole surfaces, and an outer edge of the first magnetic pole surface is a curved surface corresponding to the second excitation coil; , the first excitation coil is folded into the lower side of the outer edge.

[Example] The details of the present invention will be explained below with reference to the accompanying drawings.

FIG. 1 is a plan view showing an embodiment of the magnetizing device of the present invention, and FIG. 2 is a sectional view taken along the line AA in FIG.

In both figures, 1 is a cylindrical core made of soft magnetic material,
It is formed from a cylindrical inner circumferential core 2 and a cup-shaped outer circumferential core 3. A plurality of grooves 6 (eight in the figure) are formed in the end surface 4 of the inner circumferential core 2 radially from the center hole 5 . A circumferential groove 8 and a plurality of radial grooves 9 are provided on the end surface 7 side of the outer circumferential core 3.
(120 pieces in the figure) are formed. Above groove 6
A first excitation coil 10 is wound around each of the coils. Further, a second excitation coil 11 is wound around each of the grooves 9.

What should be particularly noted here is that the outer edge 4a of the end face 4 is close to the excitation coil 11 and is formed in a shape corresponding to the winding shape of the excitation coil 11. Therefore, the excitation coil 10 is wound in the circumferential groove 8 in such a manner that it goes under the excitation coil 11.

According to this magnetizing device, when the excitation coils 10 and 11 are energized, each of the 8 drive magnetic poles and the 120 rotation speed detection magnetic poles can be magnetized on the end face of the disc magnet. Moreover, since there is no gap between the excitation coils 10 and 11,
The conventional non-magnetized portion can be eliminated. At this time,
Each coil is connected to two types of magnetizing power sources as in the case of FIG. 6, but it is preferable to energize the coil 11 a short time after energizing the coil 10.

The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the present invention can be applied to the case where the driving magnetic pole is provided on the outer peripheral side of the rotation speed detection magnetic pole, or when the rotation speed detection magnetic pole is provided at the center of the magnet. Also, the magnetic pole for rotation speed detection is 1
It is not limited to one type, and two types may be used.

[Effects of the Invention] According to the present invention, since the distance between the driving magnetic pole and the rotation speed detection magnetic pole can be narrowed, the driving magnetic pole can be formed in a wide part of the magnet end face, and the driving torque can be improved. can.

[Brief explanation of drawings]

FIG. 1 is a plan view of a magnetizing device according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line A-A in FIG. 1, and FIGS.
) are a plan view and a cross-sectional view showing an example of a rotor for a brushless motor, respectively, FIGS. 4(a) and (b) are a plan view and a cross-sectional view showing another example of a rotor for a brushless motor, and FIG. ) and (b) are respectively a plan view and a sectional view showing another example of a rotor for a brushless motor, and FIG. 6 is a plan view of a conventional magnetizing device. 1: Core, 2: Inner core, 3: Outer core, 6: Groove, 8:
Circumferential groove, 9: groove, 10, 11: excitation coil brown 1 figure broom 2 times garbage

Claims (3)

[Claims] (1) One end face of a cylindrical core made of a magnetic material is divided into an inner end face and an outer end face by a circumferential groove provided on the end face, and grooves are provided radially on the inner end face. forming a plurality of first magnetic pole faces, forming a plurality of second magnetic pole faces by providing grooves radially on the outer peripheral side end face at a pitch different from the grooves; A first excitation coil is wound around each of the second magnetic pole surfaces, a second excitation coil is wound around each of the second magnetic pole surfaces, and an outer edge of the first magnetic pole surface is wound around the second magnetic pole surface. A magnetizing device characterized in that the first exciting coil has a shape corresponding to the winding shape of the exciting coil, and the first exciting coil is folded into the lower side of the outer edge. (2) One of the magnetic pole surfaces is a magnetic pole surface for magnetizing a driving magnetic pole, and the other magnetic pole surface is a magnetizing surface for magnetizing a speed detection magnetic pole. ) The magnetizing device described in section 2. (3) Claim (2), wherein the magnetic pole surface formed on the inner peripheral end surface is a magnetic pole surface for magnetizing a driving magnetic pole.
The magnetizing device described in Section 1.