JPH05103452A - Brushless motor - Google Patents

Abstract

(57) [Abstract] [Purpose] A stator having a stator core and a stator winding wound around the stator core, and a metal rotatably provided facing the magnetic pole surface of the stator core. In a brushless motor including a rotor having a system permanent magnet, an object thereof is to improve efficiency and increase output. [Structure] Metallic permanent magnet fine powder 5 covered with insulating material 6
With the configuration including the metal-based permanent magnet 3 formed by, the eddy current loss generated inside the metal-based permanent magnet 3 can be reduced to a substantially negligible level, motor efficiency can be improved, and magnetic flux density is high. The motor output can be increased by using the metal-based permanent magnet 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a stator having a stator core and a stator winding wound around the stator core, and is rotatably disposed so as to face a magnetic pole surface of the stator core. The present invention relates to a brushless motor including a rotor having a metallic permanent magnet member.

[0002]

2. Description of the Related Art In recent years, brushless motors using a permanent magnet for a rotor have been widely adopted for the purpose of improving control performance of rotating electric machines, high efficiency, bottom noise and the like. Furthermore, in order to improve the efficiency and increase the output of brushless motors, metal-based permanent magnets having a high magnetic flux density represented by rare earth metal-based permanent magnets have been adopted.

In order to prevent the metallic permanent magnets from scattering due to centrifugal force during rotation, a scattering prevention protective member is generally provided on the surface facing the magnetic pole surface of the stator core of the metallic permanent magnets.
It is arranged on a plane orthogonal to this plane.

As a control method for changing the rotation speed of the brushless motor, a PAM method for changing the value of the voltage applied to the stator winding and a PAM method for keeping the voltage constant and a voltage waveform having a relatively high frequency (several kHz to several kHz). There is a PWM method in which the average applied voltage is changed by turning on and off at several tens of kHz and changing the time ratio of on and off.

FIG. 4 is a main connection circuit diagram of a control circuit of a three-phase full-wave drive system and a brushless motor, FIG. 5 (a) and FIG.
(B) is an example of a voltage waveform and a current waveform applied to the motor stator winding by the PWM method. In FIG. 4, 7
Is an AC power supply (single phase is shown in the figure, but it may be three phases), 8 is a rectifying diode, 9 is a smoothing capacitor, 1
0 is a three-phase full-wave drive transistor, 11 is a brushless motor, Vu is a voltage applied to any one lead terminal of the brushless motor 11 and the negative side of the smoothing capacitor 9,
Iu is a current flowing through the lead terminal of the brushless motor 11 measuring Vu. In Iu, since Vu has a PWM waveform, a high frequency current corresponding to the PWM frequency is superimposed on the fundamental wave current.

On the other hand, even in the PAM system, the brushless motor which operates at a particularly high speed has a rapid change in the current Iu at the time of switching the energization of the three-phase full-wave driving transistor.
As in the WM method, the high frequency current is superimposed on the fundamental wave current.

[0007]

However, when a metal-based permanent magnet having a high magnetic flux density, which is represented by a rare earth metal-based permanent magnet, is adopted, a high frequency current superposed on the current Iu flowing through the lead terminal of the brushless motor 11 can be dealt with. As a result, high-frequency magnetic flux is generated, and this high-frequency magnetic flux is linked to the metallic permanent magnet. The electric resistance of metallic permanent magnets is approximately 10 ^−4.
Since current easily flows at about Ωcm, a large eddy current is generated inside the magnet. Since this eddy current causes the loss of the motor,
As a result, the efficiency of the brushless motor is significantly deteriorated, and there is no point in improving the efficiency and increasing the output of the brushless motor by using an expensive metal magnet.

In addition, non-magnetic metal materials such as stainless steel materials and non-magnetic non-magnetic materials such as glass fiber tape impregnated with varnish are often used as protective members for preventing scattering of metallic permanent magnets. There is a conductive tape material. The non-magnetic metal material requires a relatively small number of steps to be placed on the metal permanent magnet, but since the electric resistance is as low as that of the metal permanent magnet, eddy currents are generated inside the non-magnetic metal material during brushless motor operation. There is a problem that loss occurs, and since the non-magnetic non-conductive tape material does not cause eddy current loss because it is non-conductive, it takes a lot of man-hours to arrange it on the outer peripheral part of the metal-based permanent magnet. Had a problem.

The present invention solves the above-mentioned conventional problems, and an object thereof is to provide a brushless motor of high efficiency and high output.

[0010]

In order to achieve this object, the brushless motor of the present invention is provided with a metal-based permanent magnet formed of fine powder of metal permanent magnet covered with an insulating material.

[0011]

With this configuration, the electric resistance inside the metal-based permanent magnet becomes relatively large, and the eddy current loss generated inside the metal-based permanent magnet can be reduced to a substantially negligible level.

[0012]

Embodiment 1 An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a cylindrical stator iron core (stator winding is not shown), 2 is a rotor, and 3 is a metal system made of metal permanent magnet fine powder covered with an insulating material. Permanent magnets 4 are rotor cores arranged inside the metallic permanent magnets 3 to form a magnetic path with the cylindrical stator core 1;
Indicates the distance between the magnetic pole surface of the inner diameter of the stator core 1 and the outer diameter of the metallic permanent magnet 3.

In FIG. 2, 5 is a metal permanent magnet fine powder,
Reference numeral 6 is an insulating material which covers the metal permanent magnet fine powder 5 and insulates each metal permanent magnet fine powder 5.

The brushless motor configured as described above has the insulating material 6 for insulating the metal permanent magnet fine powder 5 from each other.
Since it is insulated by, the electric resistance inside the magnet becomes relatively large, and as a result, the eddy current loss generated inside the metallic permanent magnet can be reduced to a substantially negligible level. Therefore, the efficiency of the brushless motor can be improved, and the output can be increased by using the metal-based permanent magnet having a high magnetic flux density.

By using an inorganic insulating material such as glass as an insulating material for respectively insulating the metal permanent magnet fine powder 5, the mechanical strength of the metal permanent magnet 3 is improved to prevent scattering. When the protective member is abolished, not only the various problems described in the prior art disappear, but also
Distance d between the inner diameter of the stator core 1 and the outer diameter of the metallic permanent magnet 3
Can be made as small as possible, and the amount of magnetic flux inside the motor can be increased, and as a result, the efficiency of the brushless motor is improved.

The effect of eliminating the protective member for preventing the magnet from scattering can be applied not only to the surface of the metallic permanent magnet facing the stator core magnetic pole surface, but also to the surface orthogonal to this surface.

If the distance d between the magnetic pole surface of the inner diameter of the stator core 1 and the outer diameter of the metallic permanent magnet 3 is too small, the amount of high frequency magnetic flux interlinking with the metallic permanent magnet 3 increases.
The eddy current loss generated inside the metal-based permanent magnet 3 sharply increases and the efficiency of the brushless motor deteriorates. If the distance d is too large, the magnetic resistance of the magnetic circuit increases and a large amount of magnetic flux cannot be obtained, and the output of the brushless motor decreases. Therefore, there is an optimum range for the value of the distance d, and within the range of 0.3 to 3.0 mm, the eddy current loss does not increase sharply and the motor output does not decrease significantly.

As described above, according to this embodiment, the insulating material 6
By providing the metal-based permanent magnet 3 formed by the fine powder 5 of the metal-based permanent magnet covered with
The electric resistance inside the motor can be made relatively large, and as a result, the eddy current loss generated inside the metal-based permanent magnet 3 can be reduced to a substantially negligible level, and the efficiency of the brushless motor can be improved. The output can also be increased by adopting the metallic permanent magnet 3 having a high magnetic flux density.

(Embodiment 2) A second embodiment of the present invention will be described below with reference to the drawings.

In the first embodiment, a stator having a cylindrical stator core 1 and a stator winding provided on the stator core 1 and a rotor having an inner diameter of the stator core 1 facing each other are freely rotatable. The inversion type structure including the rotor 2 having the metal-based permanent magnet 3 provided in the above has been described. However, as shown in FIG. 3, the metal-based permanent magnet is provided on the outer periphery of the stator and the stator core 15. The outer permanent magnet 13 is also provided in the outer rotation type structure having the rotor 12 arranged on the outer diameter portion of the magnet 13 and the rotor core 14 that forms the magnetic path together with the stator core 15. The metal permanent magnet fine powder 5 covered with the insulating material 6 shown in FIG.
The same effect as the first embodiment can be obtained by forming

Needless to say, the same effect can be obtained not only when the stator and the rotor are cylindrical, but also when they are flat.

[0023]

As is apparent from the above description of the embodiments, the present invention has a high efficiency due to the structure including the metallic permanent magnet formed of the fine powder of the metallic permanent magnet covered with the insulating material. An excellent brushless motor with high output can be realized.

[Brief description of drawings]

FIG. 1 is a sectional view of essential parts of a brushless motor according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing the concept of a metal-based permanent magnet of a brushless motor according to first and second embodiments of the present invention.

FIG. 3 is a sectional view of an essential part of a brushless motor according to a second embodiment of the present invention.

FIG. 4 is a main circuit diagram of a three-phase full-wave drive PWM type control circuit for a brushless motor.

FIG. 5A is a waveform diagram of an applied voltage of a brushless motor in a PWM system, and FIG. 5B is a current waveform diagram of a brushless motor in a PWM system.

[Explanation of symbols]

 1 Stator core 2 Rotor 3 Metal permanent magnet 4 Rotor core 5 Metal permanent magnet Fine powder 6 Insulating material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masami Wada 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A stator having a stator core and a stator winding wound around the stator core, and a metallic permanent member rotatably disposed facing the magnetic pole surface of the stator core. A brushless motor including a rotor having a magnet, wherein the metal-based permanent magnet is formed of fine metal permanent magnet powder covered with an insulating material. 2. The surface of the metallic permanent magnet facing the stator core magnetic pole surface or the surface orthogonal to this surface does not have a conductive or non-conductive permanent magnet scattering prevention protection member. 1. The brushless motor according to 1. 3. The brushless motor according to claim 1, wherein the facing distance between the magnetic pole surface of the stator core and the surface of the permanent magnet is 0.3 to 3.0 mm.