JP3599066B2 - Permanent magnet type rotating electric machine - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a permanent magnet type rotating electric machine having a permanent magnet provided on a rotor.
[0002]
[Prior art]
Conventionally, in a permanent magnet type rotating electric machine, for example, when the rotor of the permanent magnet has eight poles and the stator has twelve slots, a protruding pole 11 protruding inside the ring-shaped stator 1 is provided as shown in FIG. A rotor 2 is provided opposite to the salient poles 11 with a gap therebetween, and a plurality of permanent magnets 3 having a quadrangular periphery are arranged on the outer periphery of the rotor 2 at equal intervals in the circumferential direction. If the permanent magnets 3 are arranged in parallel in the axial direction, and if the permanent magnets 3 are divided into four blocks (1) to (4), the blocks are geometrically congruent as shown in FIG. And the positional relationship between the permanent magnet 3 and the salient pole 11 in each block becomes completely equal. Since the magnetic flux distribution periodically changes from the boundary of each block, the cogging torque of each of these four blocks has exactly the same magnitude and phase. Therefore, the entire cogging torque is four times the cogging torque of each block, and there is a problem that the cogging torque is extremely large and smooth rotation cannot be performed.
As a method for solving this problem, the permanent magnet is formed into a so-called skewed shape having an inclination with respect to the axial direction. For example, as shown in FIG. There is disclosed an arrangement in which a plurality of permanent magnets 3B are arranged in the circumferential direction and a plurality of permanent magnets 3B are also arranged in the axial direction, and are slightly shifted in the circumferential direction as they progress in the axial direction to provide a skew effect ( For example, Japanese Utility Model Application Laid-Open No. 61-17876 and Japanese Utility Model Application Laid-Open No. 3-87552).
[0003]
[Problems to be solved by the invention]
However, when the permanent magnet of the related art is formed into a skewed shape, there is a problem that when the permanent magnet is formed by sintering or casting, the deformation is large and the number of processing steps is large.
Further, in the case where the permanent magnets are arranged shifted in the axial direction, magnetic poles having different polarities are close to each other in the axial direction, so that a magnetic flux flows between adjacent magnetic poles. For example, since the close to the N pole 3B _N S pole 3A _S and the permanent magnet 3B of the permanent magnet 3A shown in FIG. 7, between the S-pole 3A _S and N poles 3B _N without flowing to the stator As shown in FIG. 8, there is a problem that the magnetic flux distribution in the circumferential direction of the rotor does not become a sine wave, and the skew effect on cogging torque is reduced.
SUMMARY OF THE INVENTION An object of the present invention is to provide a permanent magnet type rotating electric machine having a low cogging torque while maintaining the skew effect by changing the arrangement of the permanent magnets.
[0004]
[Means for Solving the Problems]
In order to solve the above problem, the present invention provides a ring-shaped stator having a plurality of inwardly projecting salient poles, a plurality of permanent magnets facing the inside of the salient poles via a gap, and circumferentially. In a permanent magnet type rotating electric machine having a rotor in which magnets are arranged so as to protrude from an outer peripheral surface of a rotor core, the salient poles and the permanent magnets are divided into four blocks at equal intervals in a circumferential direction, The positional relationship between the salient poles and the permanent magnets in one pair of blocks symmetrically positioned with respect to the center of the rotor and in the other pair of blocks is geometrically congruent, respectively. The permanent magnets of the other pair of blocks are fixed in the circumferential direction so that the cogging torque generated in the one pair of blocks cancels out the cogging torque of the other pair of blocks. It was done.
In addition, the magnetic head includes the twelve poles of the salient poles and the eight poles of the permanent magnets, and positions the permanent magnets of the other pair of blocks in the circumferential direction with respect to the positions of the permanent magnets of the one pair of blocks. The cogging torque generated in the one pair of blocks is fixed at a position rotated by half the mechanical angle of one cycle of the cogging torque.
Further, a ring-shaped stator having a plurality of convex poles protruding inward is opposed to the inside of the salient poles of the stator via a gap, and is skewed in a circumferential direction and an axial direction to form a plurality of permanent magnets. In a permanent magnet type rotating electric machine including a rotor having magnets disposed therein, a gap between the permanent magnets adjacent in the axial direction is larger than a gap between the permanent magnets adjacent in the circumferential direction. is there.
[0005]
[Action]
By the above means, the cogging torque generated from one pair of blocks symmetrically positioned with respect to the center of the rotor and the cogging torque generated from the other pair of blocks are shifted by half a cycle, so that they cancel each other. The overall cogging torque is greatly reduced.
Further, since the S pole of one permanent magnet and the N pole of the permanent magnet adjacent in the axial direction are separated by a gap larger than the gap between the magnets adjacent in the circumferential direction, the S pole and the N pole adjacent in the axial direction are separated. No leakage magnetic flux is generated between them, and the magnetic flux distribution in the circumferential direction of the rotor becomes a sine wave, and the cogging torque is reduced.
[0006]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a front view showing a first embodiment of the present invention, and a permanent magnet type rotating electric machine having 8 poles and 12 slots will be described as an example.
In the drawing, reference numeral 1 denotes a ring-shaped stator, which is provided at equal intervals in a circumferential direction and has 12 salient poles 11 protruding inward, and 12 slots 12 between adjacent salient poles 11. Is formed, and the stator coil is accommodated in the slot 12. Reference numeral 2 denotes a rotor, and reference numeral 21 denotes a rotor core formed by laminating thin steel plates. Eight permanent magnets 3 each having a rectangular periphery are fixed to the outer periphery of the rotor core 21.
The method of arranging the permanent magnet 3 on the rotor 2 will be described. When the stator 1 and the rotor 2 are divided into four equal parts in the circumferential direction and divided into blocks (1) to (4), the center of the rotor 2 The permanent magnets 3 of the pair of blocks (1) and (3) located symmetrically with respect to are geometrically congruent, and are arranged at an angular interval obtained by dividing the outer circumference of the rotor 2 by the number of magnetic poles. I have. The permanent magnets 3 of the other pair of blocks (2) and (4) located symmetrically with respect to the center of the rotor 2 are geometrically congruent, respectively, and On the other hand, it is fixed at a position rotated by 7.5 degrees clockwise.
The positioning of the permanent magnets 3 is as follows. When the rotor core 21 is punched, a projection is provided on the outer periphery of the rotor core 21 in accordance with the position of the permanent magnet for each block, and the permanent magnet 3 is arranged in accordance with the projection. The permanent magnet can be easily positioned without increasing the number of processing steps.
[0007]
Here, the principle of generating the cogging torque will be described.
In the conventional example described with reference to FIG. 5, the permanent magnets 3 are arranged at equal intervals on the outer periphery of the rotor 2, and as shown in FIG. 6, four mutually geometrically congruent blocks (1) to (1) Since the cogging torques generated in 4) have the same phase and magnitude, the total cogging torque is four times the cogging torque of each block. One cycle of the cogging torque is a mechanical angle, which is an angle (15 degrees) obtained by dividing 360 degrees by the least common multiple (24) of the number of magnetic poles (8) and the number of slots (12).
Therefore, in order to balance, the permanent magnets 3 of the two geometrically congruent blocks (1) and (3) located symmetrically with respect to the rotation center of the rotor 2 are left as they are. Similarly, the positions of the permanent magnets 3 in the block (2) and the block (4) which are symmetrical with respect to the rotation center of the rotor 2 are set to 1/2 of 15 degrees which is 1/2 cycle of cogging torque in mechanical angle. Is rotated clockwise by 7.5 degrees from the permanent magnets 3 of the block (1) and the block (3), and the blocks (1) and (3) have different positional relations and are geometrically congruent. Make a relationship.
As a result, the cogging torque generated from the block (1) and the block (3) and the cogging torque generated from the block (2) and the block (4) are shifted by a half cycle as shown in FIG. The overall cogging torque is greatly reduced.
[0008]
FIG. 3 is a side view showing a second embodiment of the present invention, and shows a rotor provided with two rows of 8-pole permanent magnets in the axial direction.
In the figure, 2 is a rotor, 21 is a rotor core, and 3A is eight permanent magnets arranged at equal intervals on the outer periphery of the rotor core 21. 3B is equal intervals on the outer circumference of only the rotor core 21 as many as the permanent magnet 3A, and opening the wide gap G ₂ from the gap G ₁ between the circumferential direction of the magnet from the permanent magnet 3A in the axial direction, a mechanical angle It is arranged so as to be shifted in the circumferential direction by 7.5 degrees, which is 1/2 of 15 degrees, which is 1/2 cycle of the cogging torque, to provide a skew effect.
Therefore, since the separated by a gap _{G 1} is larger than gap _{G 2} magnets circumferentially adjacent to the N pole 3B _N S pole 3A _S and the permanent magnet 3B of the permanent magnet 3A, S pole 3A _S and N poles 3B _N and without magnetic flux leakage occurs between the, as shown in FIG. 4, the magnetic flux distribution in the circumferential direction of the rotor is a sine wave, the cogging torque is reduced.
[0009]
【The invention's effect】
As described above, according to the present invention, the circumferential positional relationship between the stator and the rotor is divided into a plurality of circumferentially identical blocks that are magnetically identical, and the fixed position of the permanent magnet is fixed for each block. Is moved so as to cancel the cogging torque, so that even with a permanent magnet having a rectangular periphery, the same effect as that obtained by skewing the permanent magnet is produced.
Also, when a plurality of permanent magnets are arranged in the axial direction and shifted in the circumferential direction, the gap between the magnets in the axial direction is made larger than the gap between the magnets in the circumferential direction to reduce the leakage magnetic flux. Since the generation of cogging torque is suppressed, there is an effect that a permanent magnet type rotating electric machine having extremely low cogging torque and low man-hour and cost for processing the permanent magnet can be provided.
[Brief description of the drawings]
FIG. 1 is a front view showing a first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a cogging torque according to the first embodiment of the present invention.
3A is a front view and FIG. 3B is a side view showing a second embodiment of the present invention.
FIG. 4 is an explanatory diagram showing a cogging torque according to a second embodiment of the present invention.
FIG. 5 is a front view showing a conventional example.
FIG. 6 is an explanatory diagram showing a cogging torque of a conventional example.
7A is a front view and FIG. 7B is a side view showing a conventional example.
FIG. 8 is an explanatory diagram showing a cogging torque of a conventional example.
[Explanation of symbols]
1 stator, 11 salient, 12 slots, 2 rotor 21 rotor core, 3, 3A, 3B permanent _magnet, G 1, _{G 2} gap

Claims (3)

A ring-shaped stator having a plurality of inwardly projecting salient poles, facing the inside of the salient poles via a gap, and projecting a plurality of permanent magnets in the circumferential direction from the outer peripheral surface of the rotor core. In the permanent magnet type rotating electric machine having the rotor arranged
Dividing the salient pole and the permanent magnet into four blocks at equal intervals in the circumferential direction,
The positional relationship between the salient poles and the permanent magnets in one pair of blocks and the other pair of blocks symmetrically positioned with respect to the center of the rotor is geometrically different from each other. A congruent arrangement,
The permanent magnets of the other pair of blocks are fixed in the circumferential direction so that the cogging torque generated in the one pair of blocks cancels the cogging torque of the other pair of blocks. And a permanent magnet type rotating electric machine. It has 12 poles of the salient poles and 8 poles of the permanent magnets, and positions the permanent magnets of the other pair of blocks in the circumferential direction with respect to the positions of the permanent magnets of the one pair of blocks. 2. The permanent magnet type rotating electric machine according to claim 1, wherein the rotating machine is fixed at a position rotated by a half of the mechanical angle of one cycle of the cogging torque generated in one of the blocks. A ring-shaped stator having a plurality of salient poles protruding inward, and a plurality of permanent magnets opposed to each other inside the salient poles of the stator via a gap and skewed in the circumferential and axial directions. In the permanent magnet type rotating electric machine having the arranged rotor,
A permanent magnet type rotating electric machine characterized in that a gap between the permanent magnets adjacent in the axial direction is larger than a gap between the permanent magnets adjacent in the circumferential direction.

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