JPS5899251A - Permanent magnet for rotary electric machinery - Google Patents

Abstract

PURPOSE:To improve the demagnetization resistance and reliability without deteriorating the torque characteristics by a method wherein the magnetic characteristics such as intrinsic coercive force, residual flux density are continuously changed in almost half side of the arc-segment type ferrite magnet. CONSTITUTION:The arc-segment type ferrite magnets 21 are fixed to the inside of a stator yoke 1 within the range of the angle thetam. The magnet 21 comprises the ferrite magnet 2 provided with high residual flux density Br in almost half side of the magnet in the arrow marked revolving direction and in the reverse direction as well as the ferrite magnets 30-35 almost continuously changing the proper coercive force rHc from high to low and said Br from low to high starting from the end to the central part in almost half side in the revolving direction. Through these procedures, the demagnetization due to reaction of armature may be prevented improving the reliability due to excellent demagnetization resistance even in the unfavorable conditions such as low temperature atmosphere, etc. without deteriorating the characteristics of the titled machinery.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a permanent magnet for a rotating electric machine, and more particularly to a permanent magnet for a small permanent magnet direct current motor or a generator having an arc segment-shaped ferrite magnet through an air gap between the armature and the armature. It is related to.

BACKGROUND ART Rotary electric machines using permanent magnets, particularly small motors, generators, etc. using arc segment-shaped 7-elite magnets have been widely used, and in recent years, the field of application of ferrite magnets has expanded to large motors as well. In particular, there have been an increase in the number of motors that have a very large load during startup, such as starter motors for engine startup and motors for driving the hub brakes of near conditioners. For this reason, since the demagnetizing field due to armature reaction is large, magnets with especially high demagnetizing strength among ferrite magnets are used. However, ferrite magnets, especially those for starter motors, can be significantly demagnetized due to overcurrent during abnormal conditions or starting current at low temperatures, and cannot be said to be sufficiently reliable in terms of reliability. As a countermeasure to this problem, as disclosed in JP-A No. 55-56456, a material with high intrinsic coercive force (hereinafter referred to as rHo) is used in the part where the demagnetizing field due to armature reaction is applied, and the remaining part is It has been proposed to use a material with high magnetic flux density (hereinafter referred to as Br). However, if the proportion of the material with high engineering Ha is small, demagnetization will occur near the joint between the above two materials, and conversely, if the proportion is large, the effective magnetic flux will decrease overall, resulting in a defect that the motor characteristics will deteriorate. there were.

FIG. 1 shows a conventional example in which two materials with different magnetic properties are combined, and a stator yoke l has arc segment-shaped ferrite magnets 21 in the range of angle θm. This arc segment-shaped 7-piece light magnet 2 has a high IHO material 3 at an angle θ of about V3 at 0 m from the end of the armature 4 in the rotation direction (arrow direction), that is, the running side. The other parts are made of high Br material to avoid demagnetization caused by the reaction of the electric machine preload. However, high Br
If xHa of material 2 is small, the second
As shown in the air gap magnetic flux density distribution diagram in the figure, significant demagnetization may occur due to the reaction of the electric machine pre-loading during one startup. Therefore, in order to avoid the above demagnetization for the high Br material 2, it is necessary to ensure xKa close to that of the high-quality HO magnet 3, and in that case, the Br will decrease by that amount from the balance between Br and xHc. Therefore, the amount of effective magnetic flux becomes small, which poses the problem that it is not optimal as a motor. (In Figure 2,
Curve number indicates the state after saturation magnetization, and curve b indicates the state demagnetized by the demagnetizing field in the armature reaction of excessive current. ) The present invention solves the above-mentioned problems of the conventional motor, and also does not cause deterioration of motor characteristics, and almost no demagnetization due to armature reaction occurs even under adverse conditions such as low temperature atmosphere.
The object of the present invention is to provide a permanent magnet for a rotating electrical machine made of a composite ferrite magnet that has excellent demagnetization resistance and high reliability.

The present invention uses a high Br material from the approximate center of the arc segment-shaped magnet to the end opposite to the rotational direction of the armature to ensure an effective amount of magnetic flux, and the remaining portion to which one demagnetizing field is applied is , the demagnetization resistance 0IHO corresponding to the demagnetizing field increases almost continuously in the direction of rotation of the armature, and Br
The magnetic flux is continuously decreased in the same direction to prevent demagnetization due to armature reaction and increase the amount of effective magnetic flux to improve the performance of the motor.

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

FIG. 3 is a sectional view of a permanent magnet DC motor, in which arc segment-shaped ferrite magnets 21 are fixed inside the stator rim 1 within an angle .theta.m. In this magnet 21, approximately half of the above-mentioned magnet 21 on the opposite side (running side) to the direction of rotation of the armature 40 (arrow direction) is a 7-piece light magnet 2 having a high Br, and the side in the same direction as the rotation direction (running side) One half of the peak on the side) is made up of 30 to 35 magnets. In other words, a ferrite magnet! ! No. 1 has a ferrite magnet 35 made of a high Br and low IHa material on the center side, and a ferrite magnet 30 made of a high xHo and low Br material on the end side.

Figure 4 is a magnetic flux density distribution diagram in the gap between the armature and the permanent magnet. Curve 11 shows the state after saturation magnetization, and curve 1 shows the state where i is reduced by the demagnetizing field due to the armature reaction of excessive current. show. As shown in FIG. 4, the permanent magnet of the present invention is very stable against external demagnetizing fields, exhibits little demagnetization, and can be used for highly reliable DC motors. In order to increase the demagnetization resistance of ferrite magnets, it is effective to increase zHo, but at the same time, the Br decreases, so the air gap magnetic flux density decreases, the amount of effective magnetic flux also decreases, and the torque performance of the motor also decreases. However, in the case of the present invention, the magnet 30 at the end has a high rH.
Even if C material is used, since the volume ratio of the magnet to the entire magnet is small, deterioration in motor performance can be minimized and a highly reliable motor can be obtained.

In order to continuously change the magnetic properties of the permanent magnet of the present invention, for example, by making magnets in which the contents of aluminum oxide and other metal oxides are continuously changed, and combining these magnets, the characteristic value can be changed. can be made of different magnets.

Fig. 6 shows another embodiment of the present invention, in which each magnet has a diameter of 2.36 cm on the outer periphery so that the magnetic flux can easily flow on the surface where the demagnetizing field is large in order to utilize the magnetic properties as effectively as possible.
.about.41 (equal magnetic characteristic surfaces) 22 are oblique.

FIG. 6 shows still another embodiment of the present invention,
This is an example of a DC brushless motor in which an armature has a fixed outer yoke 11, and a permanent magnet on the inner circumference rotates as a rotor through an air gap.

The arc segment-shaped ferrite magnet 121 is fixed to the outer periphery of the inner yoke 14, and is similar to the one shown in FIG. Similarly, a high Br ferrite magnet 12 is provided on the entry side, and ferrite magnets 43 to 49 are provided on the exit side, which are divided into seven parts from the center to the ends of the magnet 121. Thus, Br is changed from high to 4 low and IHc is changed from low to high from the magnet 49 at the center to the magnet 43 at the end.

In the case of this embodiment, the motor has a high resistance to a demagnetizing field caused by an armature reaction that occurs particularly during startup, and can be made to be a highly reliable motor.

The magnetic characteristics of the arc segment-shaped ferrite magnet are shown in FIG. 7 as a demagnetization characteristic curve. 2 in the figure is the characteristic of high Br material, 30
-35 is a characteristic of high IHO material.

As explained above, the present invention achieves the following effects by continuously changing the magnetic properties of the SRS in one half of an arc segment-shaped ferrite magnet in a rotating electric machine such as a DC motor.

l) Compared to the conventional DC motor using two types of composite magnets,
Reduced demagnetization resistance by 1 without reducing motor torque characteristics.
．． It can be improved by more than 3 times.

2) Compared to a DC motor that uses a single material, it is possible to improve both the stability against a demagnetizing field and the torque characteristics of the motor.

3) Regarding the silk characteristics of the motor, compared to the conventional composite magnet type, if the demagnetization resistance is the same, the present invention can be expected to improve performance by more than W.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a conventional motor. Figure 2 is a magnetic flux density distribution diagram in the air gap of the conventional example in Figure 1. Figure 3 is a sectional view of a permanent magnet DC motor according to an embodiment of the present invention. , FIG. 4 is a magnetic flux density distribution diagram of the air gap in the embodiment shown in FIG. 3, FIGS. 5, 6, and 6 are sectional views of motors according to other embodiments of the present invention, and FIG. 7 is a diagram of the ferrite of the present invention. FIG. 3 is a characteristic curve diagram showing the magnetic characteristics of a magnet. , 21.121: Arc segment-shaped ferrite magnet (
overall), 2.12 near-machined light magnet (high Br material), 30
~35.36~41.43~49; Ferrite magnets with different magnetic properties, 4.14: Armature agent Patent attorney Takashi Honma 7 Figure 3 @, 2, 2 Figure 4

Claims (1)

[Claims] 1. A permanent magnet for a rotating electric machine comprising at least two arc segment-shaped ferrite magnets arranged diametrically opposite to each other with a gap between them and the armature. A 7-piece light magnet with high residual magnetic flux density is used between the center of the permanent magnet and the end opposite to the rotation direction of the armature, and the remaining part is placed on the side opposite to the rotation direction of the armature. The residual magnetic flux density decreases almost continuously toward the end,
A permanent magnet for a rotating electrical machine, characterized in that it is a ferrite magnet having magnetic properties that increase its intrinsic coercive force. 2. A permanent magnet for a rotating electrical machine according to claim 1, wherein the intrinsic coercive force of the arc segment Y-shaped 7-element magnet whose magnetic properties change almost continuously is expressed by the following formula. However, % IHO, ---7 Intrinsic coercive force Lg of light magnet 0. ,, air gap Lm between armature and ferrite magnet, , thickness of arc segment-shaped ferrite magnet θ 000. The angle from the center to the end of the arc segment magnet 000. Total number of armatures