JPS61263206A - Magnetizing method - Google Patents

Abstract

PURPOSE:To reduce the irregular rotation of a motor by forming the opposed side of magnets of a pole portion in circular shape, and forming the air gap magnetic flux density of the ends of multipolarized ferrite magnets in an approximate sinusoidal wave. CONSTITUTION:The sectional shape of a ringlike axial anisotropic ferrite magnet 4 is formed in a circular shape. When a magnetizing coil 5 is energized, since the section of a pole portion is formed in a circular shape, the end of the pole portion is magnetically saturated. As a result, since relatively large lines of magnetic flux pass the interior of the magnet 4, an air gap magnetic flux density distribution becomes a sinusoidal shape. Thus, the irregular rotation of the motor when the motor rotates at a low speed can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of applying multipolar magnetization to the end face of an axially anisotropic ferrite magnet used in a magnetic circuit of a small motor.

[Conventional technology]

Small magnet motors are used in the rotation mechanisms of audio and video equipment. These small motors are broadly classified into coreless motors, brushless motors, and stepping motors, and brushless motors are growing rapidly along with stepping motors.

Among these brushless motors, the most widely used brushless DC motor is shown in Fig. 4 (α1, (
4), a ring-shaped ferrite magnet 4 having anisotropy in the axial direction is fixed to the inner wall of the cup-shaped yoke 6 to form a magnetic circuit.

Recently, there has been a strong demand for smaller motors and higher performance, and accordingly, flat ring-shaped ferrite magnets (about 1.5 to 4 m thick) are being used.

This ring-shaped axially anisotropic ferrite magnet is magnetized with about 4 to 8 poles on its end face in a rotor state, and then incorporated into a motor. The magnetizing yoke binding for this purpose is, for example, shown in Figure 5 (
The structures shown in cL) and (h) are generally used.

In the figure, 1 is a yoke body made of a soft magnetic material such as pure iron, and has magnetic pole parts 21 to 28 formed at predetermined intervals in the axial direction, and a magnetizing coil 5 surrounding each magnetic pole part. are doing. The magnetizing coil is connected to a known pulsed magnetic field generating capacitor type magnetizing power source (not shown).

According to this magnetizing yoke, after the end faces of the magnetic pole parts 21 to 28 and the end face of the ferrite magnet 4 are brought into close contact with each other, the magnetizing coil 5
By energizing, a magnetic flux flow as shown in FIG. 6 is generated and magnetization is performed.

[Problem to be solved by the invention]

When magnetizing is performed using a conventional magnetizing yoke, the effective amount of magnetic flux necessary to drive the motor can be obtained, but the magnetic flux density distribution at the gap in the motor's magnetic circuit is trapezoidal as shown in Figure 7. Therefore, the current ripple becomes large,
This will cause uneven rotation. Also, since a recess is created between the magnetic poles, the magnetic field in the gap changes rapidly at the recess.
Cogging torque becomes large, causing motor vibration and noise.

The purpose of the present invention is to solve the problems of the prior art described above,
It is an object of the present invention to provide a magnetization method that can obtain an air gap magnetic flux density distribution that can reduce current ripple.

[Means for solving problems]

The magnetizing force method of the present invention is a method in which multipolar magnetization is performed by placing the magnetic pole part of a magnetizing yoke facing the end face of a ring-shaped axially anisotropic ferrite magnet, and when the magnetizing coil surrounding the magnetic pole part is energized. This uses a magnetized yoke with a shape such that at least a portion of the magnetic pole portion is magnetically saturated.

[Effect]

In the magnetizing yoke used in the present invention, the cross-sectional shape of the magnetic pole part is, for example, an arc. By having the magnetic pole part in such a shape, when the magnetizing coil is energized, the tip of the magnetic pole part is magnetically A saturated, sinusoidal waveform can be obtained.

〔Example〕

The details of the present invention will be explained below with reference to the drawings.

Figures 1 (+z) and (b) are perspective views of a magnetizing yoke according to an embodiment of the present invention, and Figure 2 is a diagram showing the flow of magnetic flux when the magnetizing yoke in Figure 1 is energized. FIG. 5 is a diagram showing the magnetic flux density waveform of the air gap.

In Fig. 1 (α) and (b), 1 is the yoke body, 2
1 to 28 are magnetic pole parts, and 5 is a magnetizing coil. The magnetic pole portion has an arcuate cross section as shown in FIG.

A spacer 5 made of a non-magnetic material is interposed between the ferrite magnet 4 and the magnetic pole portion 2'.

Next, when the magnetizing coil 5 is energized, the magnetic pole parts around which each coil is wound are alternately magnetized. For example, magnetic pole part 2'1
When the tip of the magnetic pole becomes the N pole, the magnetic pole parts 28 and 2'2 on both sides become S
Become the pole.

Here, since the cross section of the magnetic pole part is arcuate, a flow of magnetic flux occurs as shown in FIG. 2, and the tip of the magnetic pole part becomes magnetically saturated. As a result, magnetic flux lines with a relatively large radius pass through the inside of the 7-piece light magnet, and a sinusoidal air gap magnetic flux density distribution as shown in FIG. 5 can be obtained.

Further, in the present invention, a spacer is provided between the ferrite magnet and the magnetic pole part, but if the thickness is too large, the effective amount of magnetic flux will decrease, so it is desirable to make it as thin as possible, and specifically, it is less than tOm. Good. However, from the point of view of strength, approximately 0.5+ma or more is required. As mentioned above, the magnetization method of the present invention provides a sinusoidal air gap magnetic flux density, so current ripple is reduced.
It is possible to reduce rotational unevenness. In particular, such a waveform is extremely advantageous when the motor rotates at low speed (50052000r, p0m0).

〔Effect of the invention〕

As described above, according to the present invention, the air gap magnetic flux density distribution of the motor can be made sinusoidal, which is effective in improving motor performance.

[Brief Description of the Drawings] Fig. 1 (α) and (hl are respectively a plan view and a side view showing an example of a magnetizing yoke according to the present invention, Fig. 2 is an enlarged sectional view of the main part of Fig. 1, FIG. 5 is a diagram showing the air gap magnetic flux density distribution obtained by the present invention, and FIGS. 4 (α) and (A) are a plan view and a sectional view, respectively, showing an example of a magnetic circuit for a motor.
Figures 5 (α) and Cb) are a plan view and a side view showing an example of a conventional magnetizing yoke, Figure 6 is an enlarged sectional view of the main part of Figure 5, and Figure 7 is an example of a conventional magnetizing yoke obtained by the conventional method. FIG. 3 is a diagram showing an air gap magnetic flux density distribution. 1: Yoke body, 2.2', 2': Magnetic pole part, 5: Magnetizing coil, 4: Ferrite magnet, 5 Ni spacer. Representative Patent Attorney Takaishi Tachibana Ma - ゛,゛・2c4-・Z 5′, N. ,,, 10th (b Tsuku 2nd difficulty 31st 4th ('''"<b) 5th difficulty

Claims (1)

[Claims] 1. A magnetizing yoke having a plurality of magnetic pole parts wound with opposing magnetizing coils is provided on the end face of a disk-shaped ferrite magnet having axial anisotropy, and the magnetizing coils are energized to form the ferrite magnet. In the method of applying multipolar magnetization to the end face of
A method of magnetization, characterized in that the side of the magnetic pole portion facing the magnet is arcuate, and the air gap magnetic flux density at the end face of the multi-pole magnetized ferrite magnet is approximately sinusoidal.