JPH0810981B2 - Permanent magnet type DC rotating electric machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC rotating electric machine using a permanent magnet, and more particularly to a field magnetic pole of the DC rotating electric machine suitable as a starter for an automobile.

[Background of the Invention]

Conventionally, as a DC machine of this type, for example, JP-A-57-5946 is used.
As described in Japanese Patent Publication No. 4, a magnet with a large coercive force is provided in the circumferential end and region of the permanent magnet that is subjected to the maximum demagnetization work by the armature reaction, and the central part is subject to the weak demagnetization action and the weak magnetization action. There is a magnetic pole structure using a magnetic name having a large residual magnetic flux density, and an auxiliary pole in the circumferential end region of the magnetic pole which is subjected to a magnetizing action by the armature reaction. However, Nd-Fe-B
When a high-performance rare earth magnet such as a (neodymium-iron-boron) -based magnet is used, there is a problem that the magnet is permanently demagnetized due to the demagnetization effect at high temperatures, but no consideration has been given to this point. .

[Object of the Invention]

The present invention has been made in view of the above-mentioned prior art, and in particular, a permanent magnet designed to improve permanent demagnetization proof strength at high temperature due to armature reaction in a DC rotating machine using a high-performance rare earth magnet for field. To provide a DC rotating electric machine.

[Outline of Invention]

The present invention has been made by paying attention to the fact that the field magnet has a high temperature when the size of a DC rotating electric machine is reduced by using a high-performance rare earth magnet.

That is, in a field pole that uses a high-performance rare earth magnet, a plurality of magnets are arranged in combination, and the magnet with the smallest coercive force temperature retention is placed on the demagnetizing field side of the armature reaction to permanently reduce the temperature. It is intended to improve magnetic proof strength.

Specifically, an Sm-Co (samarium-cobalt) -based magnet (coercive force temperature retention of about 0.1% / ° C) is placed on the demagnetizing field side and Nd-Fe
A B-type magnet (coercive force temperature coefficient of about 0.5% ° C.) is placed in close contact with the magnet to improve permanent demagnetization resistance at high temperatures.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. In the yoke 1, permanent magnets 21, 22 and an auxiliary pole 3 having a magnetic permeability higher than the reversible magnetic permeability of the permanent magnets are circumferentially arranged. Are fixed in parallel with each other to form one magnetic pole and face the armature 4. Therefore, when an electric current in the direction shown is applied to the winding of the armature 4, the armature 4
Rotates in the direction of the arrow. The armature reaction by the armature under load acts on the magnetic poles 21,22,3, but when the neutral point is set to 0, the demagnetization action in the rotation direction region θ ₁ and the counter rotation direction region θ ₂
Then it becomes the magnetizing effect. Both the demagnetizing action and the magnetizing action are greater at the end of the magnetic pole.

Therefore, in the present invention, for the purpose of downsizing the DC machine, Nd-Fe- which has energy several times larger than that of a conventional ferrite magnet is used.
A B (neodymium-number-boron) -based rare earth magnet is used. However, the disadvantage of this magnet is that the Kyuri point is about 1/2 of 350 ° compared to the Sm-Co (samarium-cobalt) -based rare earth magnet. , The coercive force of high temperature magnetism is greatly reduced (temperature retention is about 0.5% / ° C), and permanent demagnetization occurs when a large demagnetizing field acts at high temperature. In particular, when a high-performance rare earth magnet is used for the field, the size of the rotating electric machine, especially on the side of the field stator, can be reduced, but on the other hand, the field magnet becomes high in temperature due to armature current and the like. .

On the other hand, Sm-Co rare earth magnets have a high Curie point and a small temperature coefficient (temperature coefficient of about 0.1% / ° C), so stable magnetic characteristics can be obtained at high temperatures, but Sm, the main raw material, contains Nd in rare earth ores. It is an expensive magnet, as it contains only a few fractions.

Therefore, in the present invention, an Sm-Co rare earth magnet 21 having stable magnetic characteristics at high temperature is arranged in the main part on the demagnetizing field side, and an inexpensive and high-performance Nd-Fe-B magnet 22 is arranged in the rest. This makes it possible to prevent permanent demagnetization at high temperatures.

This division point is determined by selecting the most efficient point according to the performance of the permanent magnet. As described in detail above, a magnet having a small coercive force temperature coefficient in the demagnetizing action area by the armature reaction, an auxiliary pole in a part of the magnetizing action area, and a magnet having a coercive force temperature coefficient larger than the magnet in the middle portion. Since the magnetic pole structure is combined by using, the field pole can be manufactured at low cost by miniaturization.

As a result, the high-temperature permanent proof stress was improved by 40 to 60 ° C compared with the case of the Nd-Fe-B system magnet, and it became possible to design to withstand about 200 ° C.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide the permanent magnet type DC rotating electric machine that can easily improve the permanent demagnetization proof strength at high temperature caused by the armature reaction.

[Brief description of drawings]

FIG. 1 is a front view of a main part of a DC rotating electric machine of the present invention, and FIG. 2 is a magnet characteristic curve of the DC rotating electric machine of FIG. 1 ... Yoke, 21 ... Sm-Co permanent magnet, 22 ... Nd-Fe-B
Permanent magnet, 3 ... auxiliary pole, 4 ... armature.

Claims (1)

[Claims] 1. A permanent magnet in which a field magnetic pole composed of an even number of permanent magnets is arranged on an inner peripheral surface of a yoke, and an armature iron core arranged concentrically with the field magnetic pole is given a rotational excitation force. A direct-current rotating electric machine, wherein the field magnetic pole is a compound grindstone in which at least a permanent magnet is divided into two in the rotational direction, and the side that is subjected to the demagnetization action of the magnetic flux due to the armature reaction is made of a samarium-cobalt system.
Second permanent magnet of the neodymium-iron-boron system is provided in contact with the side surface of the first permanent magnet in the direction of increasing the magnetism, and the first permanent magnet is the second permanent magnet. A permanent magnet type DC rotating electric machine having a smaller temperature coefficient of holding force at a higher temperature than that of the above.