JPS6248243A - Motor of permanent magnet system - Google Patents

Abstract

PURPOSE:To improve efficiency, by combining the magnetic poles of the titled motor with two kinds of permanent magnets at least with mutually different magnetic characteristic to organize one magnetic pole, and by increasing the density of the magnetic flux of the pole. CONSTITUTION:On the outer periphery of a rotor shaft 1, four quarter-circular permanent magnets 2 which are made of ferritic magnet material and are comparatively thick are equally arranged in the circumference. On the outer periphery of the magnets 2, a thin permanent magnet 6 which is made of rare earth magnet material excellent in magnetic characteristic is fixed and set confronting the magnets 2. In this manner, the magnets 2 are combined with the magnet 6 in the radial direction to organize a rotor. As a result, the density of the magnetic flux of the magnetic pole is increased, and the motor of high performance is economically produced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an electric motor using permanent magnets for its magnetic poles, and particularly to its magnetic pole structure.

BACKGROUND OF THE INVENTION A conventional permanent magnet electric motor will be described using a four-pole synchronous motor shown in FIG. 5 as an example. In the electric motor shown in FIG. 5, four permanent magnets 2 each having a quarter circle are circumferentially arranged around the outer periphery of a rotor shaft 1 to form a rotor. A slot 3 is cut into an armature core 4 made of laminated silicon steel plates, which serves as a magnetic path, and a motor winding a (not shown) is housed in this slot 3. The rotor including the permanent magnets 2 is rotatably housed in an internal hole formed in the armature core 4 with a predetermined gap therebetween. In the conventional electric motor constructed in this way, the magnetic flux density distribution on the rotor surface has a rectangular wave shape, as shown by the solid line 10 in FIG.

Problems to be Solved by the Invention In an electric motor that uses a permanent magnet that generally has a low magnetic flux density, such as a ferrite magnet, the magnetic operating point of the permanent magnet 2 is at point A on the characteristic line 13 shown in FIG. Then, move this operating point to point B to increase the magnetic flux density,
Consider a case where the efficiency of the electric motor is to be improved.

Generally, the following equation (1) is used as an approximate equation for a magnetic circuit.

B=Qm (1) flg Here, B and H are the magnetic flux density of the permanent magnet and the magnitude of the magnetic field at the operating point. Further, Qm is the thickness of the permanent magnet, and 2g is the gap length in the magnetic path.

Therefore, when moving the operating point in FIG. 4 from point A to point 8, the magnitude of the magnetic field H in FIG. 4 must be reduced to approximately 1/2. Therefore, according to equation (1) above, B/
In order to approximately double H, the thickness of the permanent magnet used must be
It is necessary to approximately double m. However, increasing the thickness of the permanent magnet inevitably means increasing the size of the electric motor, which is also disadvantageous in terms of cost. In addition, as shown in the figure, for electric motors that use permanent magnets on the rotor side, increasing the thickness of the permanent magnets increases the diameter of the rotor and increases the circumferential speed. OBJECT OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and aims to improve the efficiency of the motor by increasing the magnetic flux density of the magnetic poles used in the motor. , and structural varnish 1~
The purpose of the present invention is to provide a compact, high-performance permanent magnet electric motor that is reasonably reasonable.

Means for Solving the Problems In order to achieve this object, the permanent magnet electric motor according to the present invention is characterized in that a magnetic pole is constructed by combining at least two types of permanent magnets having different magnetic properties. do.

Effect: With the above structure, a magnetic pole with a large magnetic flux density can be formed without increasing the thickness of the permanent magnet, and efficiency can be improved without increasing the size of the electric motor.

Embodiments Next, preferred embodiments of the permanent magnet electric motor according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a cross-sectional view of a four-pole interphase motor according to an embodiment of the present invention, in which the outer periphery of a rotor shaft 1 is made of ferrite magnets and has a relatively thick quarter-circular shape. Four permanent magnets 2 are equally distributed in the circumferential direction. Then, on the outside of each permanent magnet 2, thin permanent magnets 5 made of rare earth magnets with good magnetic properties are arranged and fixed in a corresponding manner. An independent rotor is constructed by overlapping the permanent magnets 2 and 5 having the following characteristics. Reference numerals 3 and 4 indicate a slot and an armature core, respectively, which are the same as the slot and armature core described in connection with FIG.

In general, the magnetic properties of rare earth magnets are characteristic line 1 in Figure 4.
As shown in Fig. 4, the magnetic properties are better than those of ferrite magnets with low magnetic flux density, but their weight unit price is about 30 times more expensive than ferrite magnets, and there are price constraints on their widespread use. However, in this embodiment, this expensive rare earth magnet is used as the permanent magnet 5 only in the thin outer shell of the magnetic pole of the rotor, so the cost does not increase that much.

In this way, the rare earth magnets 5 are provided in the outer shell of the rotor, and are arranged in series in the magnetic circuit with the ferrite magnets 2 forming the inner shell, so that the magnetic flux density distribution on the rotor surface is as follows.
This is as shown by the broken line 11 in FIG. That is, as shown in FIG. 5, the magnetic flux density in a conventional electric motor using a ferrite magnet 2 as a rotor (indicated by a solid line 10 in FIG. 3)
Therefore, a high magnetic flux density can be obtained in the permanent magnet electric motor according to this embodiment.

The operating points of the ferrite magnet 2 and the rare earth magnet 5 at this time are the 0 point and the D point shown in FIG.
It is possible to increase the magnetic flux density and improve the efficiency of the motor without increasing the thickness of the motor. Note that when the rotor rotates and a demagnetizing force acts on the permanent magnet side due to the movement of the armature, the operating points of the ferrite magnet 2 and the rare earth magnet 5 move to points E and F in FIG. 4, respectively. However, most of this demagnetizing force acts on the ferrite magnet 2, which occupies most of the permanent magnets, so that the entire magnetic pole composed of the ferrite magnet 2 and the rare earth magnet 5 has good anti-demagnetizing characteristics.

FIG. 2 is a sectional view of a four-pole interphase motor according to another embodiment of the present invention. In the embodiment shown in FIG. 1, the outer circumferential surface of the ferrite magnet 2 is entirely covered with rare earth magnets 5, but in this embodiment, each ferrite magnet 2 is made up of quadrant-shaped segments (four in total). A fan-shaped rare earth magnet 5 is installed in the resulting recess by cutting out the central upper part of the ring-shaped magnets (arranged in the circumferential direction to form a ring-shaped magnet).
With this configuration, the magnetic flux density distribution on the rotor surface is approximated to a sinusoidal waveform, as shown by the solid line 12 in FIG. When the magnetic flux density distribution approaches a sinusoidal waveform in this way, compared to the case where the magnetic flux density distribution has a rectangular waveform 10, the pulsation of the motor torque decreases even if the armature winding is not short-pitch winding, and The assembly cost of the electric motor can be reduced.

As mentioned above, the explanation has been given using a four-pole electric motor as an example, but the present invention is not limited to this embodiment. It goes without saying that the present invention can be applied to various electric motors such as JJ machines, linear motors, and flat motors, and can also be applied to electric motors in which permanent magnets are used not on the rotor side but on the stator side.

Although the term "electric motor" is used in the present invention, as is well known, the principle of an electric motor and a generator is the same except that the direction of conversion of electric power and motive power is reversed, so the concept of the "electric motor" of the present invention is This includes generators.

Effects of the Invention According to the present invention, a magnetic pole is constructed by combining at least two types of permanent magnets with different magnetic properties, and it is possible to obtain a high-performance electric motor that is inexpensive, compact, and has improved efficiency. .

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a four-pole interphase motor according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a four-pole interphase motor according to another embodiment of the present invention, and FIG. 3 is a rotor surface. Magnetic flux density distribution diagram, 4th
The figure is a B-H characteristic diagram, and FIG. 5 is a sectional view of a conventional four-pole interphase motor. 1. Rotor

Claims (3)

[Claims] (1) A permanent magnet electric motor using permanent magnets for magnetic poles, characterized in that one magnetic pole is constructed by combining at least two types of permanent magnets with different magnetic characteristics. (2) A permanent magnet electric motor according to claim 1, characterized in that at least two types of permanent magnets having different magnetic properties are arranged in series in a magnetic circuit to constitute one magnetic pole. . (3) A permanent magnet according to claim 2, characterized in that a second permanent magnet with a high magnetic flux density is arranged above the center of the first permanent magnet, and the magnetic flux distribution is approximated to a sine wave. electric motor.