JPH09308205A - Brushless motor and magnet magnetizing device for motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a single discoid magnet both as a magnet for drive and as a magnet for attracting rotated body for the reduction of torque variations, by magnetizing the plane of a magnet that serves to drive motor in the surface magnetic flux waveform of sine wave, and the plane that serves to attract rotated body in the surface magnetic flux waveform of saturation wave. SOLUTION: A magnet 3 is plane-magnetized in multiple poles so that the surface magnetic flux waveform will be that of sine wave on one side 3a and that of trapezoidal wave on the other side 3b. The waveform of the driving torque of brushless motor is determined by the shape of coil 9 and the magnetization waveform of magnet 3; therefore, forming the surface magnetic flux waveform of the magnet 3 in interlinkage with the coil 9 on one side 3a into sine-wave form forms the driving torque waveform into sine-wave form and enables the reduction of torque variations.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor and a magnetizing device for a motor magnet. More specifically, the present invention relates to a brushless motor having a structure for fixing a rotating body such as a recording medium to a spindle by utilizing a magnetic attraction force. The present invention relates to a magnetizing device for a motor and a magnet for the motor.

[0002]

2. Description of the Related Art As a conventional brushless motor, a motor disclosed in Japanese Patent Application Laid-Open No. 3-26553 is known. FIG. 12 is a plan view of a conventional brushless motor, and FIG.
FIG. 14 is a sectional view of a conventional brushless motor, and FIG. 14 is a diagram showing a magnetized state of a magnet in the conventional brushless motor.

A conventional brushless motor has a frame 55.
The shaft 51 planted in the center of the
It is rotatably mounted integrally with the rotor 52 via a and 54b, and a magnet 53 is fixed to the rotor 52 as shown in FIG.

Further, on the frame 55, a coil 59 and a printed circuit board 5 are provided at positions facing the magnet 53.
7 and the back yoke 56 are fixed. Further, the magnet 53 is magnetized in a multipolar plane.

According to the structure of the brushless motor described above, the magnetic flux 60b generated on the one surface 53a of the magnet 53.
Forms a magnetic circuit that crosses the coil 59 and reaches the back yoke 56. Therefore, when the coil 59 is sequentially energized by a control circuit (not shown), the rotor 52 rotates according to Fleming's law.

The magnetic flux 60a generated on the other surface 53b is
Although not shown in the drawing, a suction force is generated through the gap to reach the rotating body and suck the rotating body.

[0007]

According to the above-mentioned conventional technique, the functions of the drive magnet as the brushless motor and the magnet for attracting the object to be rotated are realized by using the front and back surfaces of one disk-shaped magnet 53. Therefore, it is possible to reduce the number of parts, cost, and downsize the motor. It is effective to perform saturation magnetization, that is, trapezoidal magnetization, in order to reduce the variation of the attraction force and obtain a necessary and sufficient attraction force for the attraction magnet of the rotating body. Therefore, when one disk magnet 53 uses the front and back surfaces, trapezoidal magnetization is applied to both the front and back surfaces.

However, when trapezoidal magnetization is applied to the method of magnetizing the motor driving magnet, there is a big problem that the torque unevenness of the motor becomes large.
This is because in a brushless motor that controls the energization current of the drive coil of each phase according to the output waveform of the Hall element, the drive torque waveform is determined by the drive coil shape and the magnetizing waveform of the drive magnet. The closer the waveform is to the sine wave, the smaller the torque unevenness of the brushless motor. On the contrary, if the magnetizing waveform of the driving magnet is a trapezoidal wave, the torque unevenness becomes large.

An object of the present invention is to provide a brushless motor having less torque unevenness while using a single disk-shaped magnet as both a driving magnet and a magnet for attracting a rotating body, and yet another object. An object of the present invention is to provide a magnet magnetizing device capable of reducing torque unevenness of a brushless motor.

[0010]

According to the first aspect of the present invention,
In a brushless motor that drives a rotating body while exciting the motor and attracting the rotating body with one magnet, the surface of the magnet used for driving the motor is magnetized into a sinusoidal surface magnetic flux waveform. The surface for attracting the rotating body is characterized by being magnetized into a surface magnetic flux waveform having a saturated waveform.

According to a second aspect of the present invention, there is provided a pair of magnetizing yokes each having a plurality of salient poles having a magnetized surface along the circumferential direction and an exciting coil wound around the salient poles. Having a motor magnet between the pair of magnetizing yokes,
In a motor magnet magnetizing device for magnetizing the motor magnet by making the magnetized surfaces of the salient poles of each magnetized yoke face each other, the magnetized surface of the salient pole of one magnetizing yoke is a flat surface, The magnetizing surface of the salient pole of the other magnetizing yoke is a convex pole surface.

According to a third aspect of the present invention, in the motor magnet magnetizing device according to the second aspect, the magnetized surface of the salient pole is rotated by the magnetic flux from one magnetizing yoke having a flat magnetizing surface. Magnetize the surface that sucks the body,
The magnetizing surface of the salient pole is magnetized on the surface of the motor magnet that attracts the rotating body by the magnetic flux from the other magnetizing yoke.

The operation of the first aspect of the present invention will be described. In the brushless motor of the present invention, the surface of the circular magnet corresponding to the rotated body is trapezoidal-wave magnetized, and the other surface that interlinks with the coil and generates the magnetic flux for driving the motor is sinusoidal-wave magnetized. Has been done.

Therefore, the trapezoidal wave-magnetized surface generates a sufficient magnetic flux and a sufficient attraction force for attracting the rotating body. On the other hand, since the magnetic flux generated from the surface magnetized with the sine wave is spatially distributed in a sine wave shape, the generated torque of the brushless motor does not include a high frequency component, and as a result, torque unevenness can be reduced.

The operation of the invention according to claims 2 and 3 will be described. Since the magnetizing surface of one of the magnetizing yokes by the plurality of salient poles is a flat surface, the magnetizing waveform becomes a trapezoidal waveform on the surface of the motor magnet that is magnetized so as to face the surface. It is saturated and magnetized. Since the magnetizing surface of the other magnetizing yoke by the plurality of salient poles is a convex pole surface, the magnetizing waveform becomes a substantially sine wave on the surface of the magnet magnetized with respect to the convex pole surface, and The pole or south pole is magnetized with a sine wave.

Therefore, as in the case of the first aspect, the trapezoidal wave magnetized surface generates a sufficient magnetic flux to generate a sufficient attraction force for attracting the rotated body. On the other hand, since the magnetic flux generated from the surface magnetized with a sine wave is spatially distributed in a sine wave shape,
The generated torque of the brushless motor does not include high frequency components, and as a result, torque unevenness can be reduced.

[0017]

Embodiments of the present invention will be described below in detail.

(Structure) FIG. 1 is a sectional view of a brushless motor according to a first embodiment of the present invention, and FIG. 2 is a plan view of the brushless motor excluding a rotating body 11 which is a constituent element of the brushless motor shown in FIG. 3 and 4 are plan views of the magnet 3.

In the brushless motor, the shaft 1 implanted in the center of the frame 5 has two bearings 4
It is rotatably mounted integrally with the rotor 2 via a and 4b, and a disc-shaped magnet 3 is fixed to the rotor 2.

Further, a coil 9, a printed circuit board 7 and a back yoke 6 are fixed to the frame 5 at positions facing the magnet 3. The magnet 3 is magnetized so as to have a multi-pole surface, and the surface magnetic flux waveform is magnetized so that the one surface 3a has a sinusoidal waveform as shown in FIG. 5 and the other surface 3b has a trapezoidal waveform as shown in FIG. Has been done. In FIGS. 4 and 5, the horizontal axis represents the angle of the magnet 3 in the circumferential direction, and the vertical axis represents the magnetic flux density B.

(Operation) The operation of the brushless motor of the first embodiment is as follows. A magnetic flux 10b (indicated by an arrow in FIG. 1) generated on the one surface 3a of the magnet 3 traverses the coil 9 and reaches the back yoke 6, and a magnetic circuit is formed. When sequentially energized, a rotating magnetic field is generated and the rotor 2 rotates according to Fleming's law.

At this time, the magnetic flux 10b interlinking with the coil 9
Changes in a sinusoidal manner with time. In addition, the trapezoidal waveform magnetic flux 10a generated on the other surface 3b of the magnet 3
(Indicated by an arrow in FIG. 1) passes through the space and is rotated 11
Is reached, a suction force is generated, and the rotated body 11 is attracted to the rotor 2.

(Effect) Normally, the driving torque waveform of the brushless motor is determined by the shape of the coil 9 and the magnetizing waveform of the driving magnet 3, so that the coil 9 and the chain are connected like the brushless motor of the first embodiment. Magnets 3 to intersect
By making the surface magnetic flux waveform of the one surface 3a into a sine wave waveform,
The drive torque waveform also becomes a sine wave waveform, and torque unevenness can be reduced.

(Second Embodiment) (Structure) A magnetizing device for a brushless motor according to a second embodiment of the present invention will be described with reference to FIGS. 6 to 11. FIG. 6 is a sectional view showing a part of the magnetizing device in a developed state, and FIG.
Is a view as seen from the magnetized surface of the upper magnetized yoke portion 23a, FIG. 8 is a view as seen from the magnetized surface of the lower magnetized yoke portion 23b, and FIG. 9 is a waveform diagram showing a magnetized waveform for one surface of the magnet 3. Figure 1
Reference numeral 0 is a waveform diagram showing a magnetization waveform for the other surface of the magnet 3.

In the upper magnetizing yoke portion 23a of the magnetizing device for the brushless motor of the second embodiment, eight salient poles 20a are arranged at equal intervals along the circumferential direction in the magnetizing portion 22a, and each salient pole 20a has a salient pole 20a. An exciting coil 21a is wound around the periphery, and the winding direction of the exciting coil 21a is alternately reversed for each salient pole 20a. These exciting section 22a and exciting coil 21
The a is embedded in the upper base 25a of the non-magnetic material and is sealed with the resin material 26a.

Similarly to the upper magnetizing yoke portion 23a, the lower magnetizing yoke portion 23b has eight salient poles 20b arranged at equal intervals along the circumferential direction on the magnetizing portion 22b, and each salient pole 20b is surrounded by the salient poles 20b. , The exciting coil 21b is wound, and the exciting coil 2
The winding direction of 1b is alternately reversed for each salient pole 20b.
The exciting part 22b and the exciting coil 21b are embedded in a lower base 25b of a non-magnetic material and sealed with a resin material 26b.

However, the salient pole 20 of the upper magnetizing yoke portion 23a
The magnetized surface 27a of a forms a convex portion, while the magnetized surface 27b of each salient pole 20b of the lower magnetized yoke portion 23b is flat.

The base 25a of the upper yoke 23a,
Also, the base 25b of the lower yoke 23b is provided with a fitting pin 31 and a hole 32 at two positions respectively.

(Operation) The operation of the second embodiment is as follows. The magnet 3 is attached to the upper magnetizing yoke portion 23.
a, the pin 31 and the hole 32 are sandwiched by the lower magnetizing yoke portion 23b with reference to the fitting of the pin 31 and the hole 32, and then a salient pole 20 is applied to the coils 21a and 21b by a magnetizing power source (not shown).
N poles and S poles alternately appear on a and 20b.

The magnetized surfaces 27a of the salient poles 20a and 20b,
As shown in FIG. 11, the magnetic fluxes 24a and 24b are maximum on 27b, become weaker as the distance increases, and become zero at the intermediate point. Note that FIG. 11 is an explanatory diagram showing a magnetized state of the magnet 3 by the magnetizing device.

Magnetic flux 2 on the magnetized surface 27a of the salient pole 20a
4a becomes radial, and the magnetic flux 24b on the magnetized surface 27b of the salient pole 20b becomes substantially parallel. As a result, the waveforms of the magnetic fluxes 24a and 23b on the surfaces 3a and 3b of the magnet 3 become a sine wave waveform and a trapezoidal wave waveform as shown in FIGS. 9 and 10, respectively.

(Effect) According to the magnetizing device of the second embodiment, the surface magnetic flux waveform of the magnet 3 can be a sine wave waveform on one surface 3a and a trapezoidal waveform on the other surface 3b.

[0033]

According to the present invention, the torque unevenness of the brushless motor can be reduced without increasing the number of parts and the number of assembling steps. Therefore, it is possible to suppress vibration and noise due to torque unevenness. In addition, since it can be manufactured simply by changing the magnetizing waveform of the magnet, the size can be reduced without changing the parts or increasing the price.

According to the present invention, the magnetizing waveform of the magnet can be a sine wave on one side and a trapezoidal wave on the other side.
It can be manufactured at the same price as conventional magnetizing devices without using a special device, and in the magnetizing process,
A magnetizing device that does not increase the number of steps can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view of a brushless motor according to a first embodiment.

FIG. 2 is a plan view of the brushless motor according to the first embodiment.

FIG. 3 is a plan view of the magnet according to the first embodiment.

FIG. 4 is a waveform diagram showing a magnetization waveform on one surface of the magnet of the first embodiment.

FIG. 5 is a waveform diagram showing a magnetization waveform of the other surface of the magnet of the first embodiment.

FIG. 6 is a developed cross-sectional view of a part of the magnetizing device according to the second embodiment.

FIG. 7 is a view seen from a magnetized surface of an upper magnetized yoke portion according to the second embodiment.

FIG. 8 is a view as seen from a magnetized surface of a lower magnetized yoke portion according to the second embodiment.

FIG. 9 is a waveform diagram showing a magnetization waveform for one surface of the magnet of the second embodiment.

FIG. 10 is a waveform diagram showing a magnetization waveform for the other surface of the magnet of the second embodiment.

FIG. 11 is an explanatory diagram showing a magnetized state of a magnet by the magnetizing device according to the second embodiment.

FIG. 12 is a plan view of a conventional brushless motor.

FIG. 13 is a sectional view of a conventional brushless motor.

FIG. 14 is a diagram showing a magnetized state of a magnet in a conventional brushless motor.

[Explanation of symbols]

 1 Shaft 2 Rotor 3 Magnet 3a One surface 3b Other surface 4a Bearing 4b Bearing 5 Frame 6 Back yoke 7 Printed circuit board 9 Coil 10a Magnetic flux 10b Magnetic flux 11 Rotating body 20a Salient pole 20b Salient pole 21a Exciting coil 21a Exciting coil 22a Exciting part Part 23a Upper magnetizing yoke part 23b Lower magnetizing yoke part 25a Upper base 25b Lower base

Claims (3)

[Claims] 1. A brushless motor for driving a rotating body while exciting the motor and attracting the rotating body by one magnet, wherein a surface of the magnet used for driving the motor has a sinusoidal surface magnetic flux waveform. A brushless motor characterized in that the surface that is magnetized and that attracts the rotating body is magnetized into a surface magnetic flux waveform with a saturated waveform. 2. A motor magnet, comprising a pair of magnetizing yokes each having a plurality of salient poles having a magnetized surface along the circumferential direction and an exciting coil wound around the salient poles. A magnet magnetizing device for magnetizing the motor magnets by sandwiching the magnetizing yokes between the pair of magnetizing yokes so that the magnetizing surfaces of the salient poles of the magnetizing yokes face each other. The magnetizing surface of the salient pole is a flat surface, and the magnetizing surface of the salient pole of the other magnetizing yoke is a convex pole surface. 3. The magnetized surface of the salient pole is magnetized by a magnetic flux from one magnetizing yoke whose magnetized surface is a flat surface, and the magnetized surface of the magnet for motor attracts the rotated body. 3. The magnet magnetizing device for a motor according to claim 2, wherein the magnetic flux from the other magnetizing yoke having a convex pole surface magnetizes the surface of the motor magnet that attracts the rotated body.