JP2024006584A - linear motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a use amount of a heavy rare earth while suppressing an irreversible demagnetization of a permanent magnet in a linear motor.

SOLUTION: A linear motor comprises: a stator 12; and a movable element 11. The stator 12 contains a plurality of salient poles 10 arranged in a movement direction of the movable element 11 at a constant interval. The movable element 11 contains: a movable magnetic yoke 20; a plurality of teeth 13, 14, and 15 that are projected from the movable magnetic yoke 20, and arranged in a movement direction; three-phase AC wirings 16, 17, and 18 wound around the teeth respectively; and permanent magnets 22 and 23 arranged to each of a plurality of gaps formed in the teeth. In each of the teeth 13, 14, and 15, the permanent magnets 22 and 23 are arranged in the gap so that a magnetization direction is opposed to the adjacent permanent magnets 22 and 23. In each of the teeth 13, 14, and 15, the permanent magnet 23 that is positioned at the 2nd position from an end in a movement direction of the plurality of permanent magnets 22 and 23 has a magnetic coercive force higher than that of the other permanent magnet 22.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a linear motor used in industrial machines such as machine tools.

2. Description of the Related Art Conventionally, linear motors have been used in industrial machines such as machine tools as a means to achieve high speed and high precision. Linear motors are known, especially in machines with long travel distances, in which expensive permanent magnets are placed on the mover side, thereby reducing the amount of permanent magnets used and reducing the cost of the motor. Patent Document 1 discloses a configuration example of a linear motor.

FIG. 3 is a diagram illustrating a prior art linear motor. The linear motor includes a stator 12 and a movable element 111. In FIG. 3, the stator 12 is formed by laminating, for example, electromagnetic steel plates, and salient poles 10 are arranged on the surface at intervals of a pitch P so as to protrude from the stator magnetic yoke 21. Like the stator 12, the movable element 111 is also formed by laminating, for example, electromagnetic steel sheets. The mover 111 includes a mover magnetic yoke 20 and U, V, and W phase teeth 13, 14, and 15. The teeth 13, 14, and 15 are each arranged to be shifted relative to the salient pole 10 by P/3, which corresponds to 120 electrical degrees, in the X-axis direction. Three-phase AC windings 16, 17, and 18 of U, V, and W phases are wound around the teeth 13, 14, and 15, respectively. Teeth 13, 14, 15 each include a plurality of tooth elements 13E, 14E, 15E. Each tooth element 13E is arranged at a pitch of P/2, and a permanent magnet 19 is arranged between each tooth element 13E. Each tooth element 14E and each tooth element 15E also have a similar configuration. In each tooth 13, 14, 15, the permanent magnet 19 is arranged so that the magnetization direction is opposite to that of the adjacent permanent magnet 19. In FIG. 3, the direction of the arrow indicates the magnetization direction of the permanent magnet 19.

In such a linear motor, a long stroke movable range can be achieved simply by repeatedly arranging stator blocks, which have a simple structure and are formed by laminating inexpensive electromagnetic steel sheets. Furthermore, since the expensive permanent magnet 19 is placed on the movable element 111 side and the amount of permanent magnets used can be reduced, the manufacturing cost of the linear motor can be kept low.

Japanese Patent Application Publication No. 2006-109639

However, the conventional linear motor described above has the following problems.

In FIG. 3, the direction of the arrow indicates the magnetization direction of the permanent magnet 19, and the number of arrows indicates the amount of magnetic flux of the permanent magnet 19. As shown in FIG. 3, the permanent magnets 19 are arranged so that the magnetization direction is opposite to that of the adjacent permanent magnets 19. Due to this arrangement, the magnetic flux of the permanent magnets 19 and the adjacent permanent magnets 19 is mutually weakened, and the amount of magnetic flux is reduced. The amount of magnetic flux of the permanent magnets 19 differs depending on where they are placed. In each tooth 13, 14, 15 around which the winding of each phase is wound, the permanent magnet 19 located at the end of the permanent magnets 19 has an adjacent permanent magnet 19 only on one side. Therefore, the permanent magnet 19 located at the end has the largest amount of magnetic flux among the permanent magnets 19 because the magnetic flux can be weakened only from the permanent magnet 19 on one side. On the other hand, in each of the teeth 13, 14, 15, the permanent magnet 19 located second from the end has its magnetic flux weakened from the permanent magnet 19 located at the end with the largest amount of magnetic flux, so The amount of magnetic flux is small. Therefore, when a current is applied to the three-phase AC windings 16, 17, and 18 during operation of the linear motor, a magnetic field is applied to the permanent magnet 19 located second from the end in the opposite direction to the magnetization direction. In this case, irreversible demagnetization is most likely to occur.

Therefore, a configuration is desired that can suppress irreversible demagnetization of the permanent magnet 19 located second from the end in each tooth 13, 14, 15 around which the winding of each phase is wound. For example, the problem of irreversible demagnetization can be solved by uniformly employing permanent magnets that contain a large amount of heavy rare earth elements and have a high coercive force as all the permanent magnets 19. However, permanent magnets containing a large amount of heavy rare earth elements have the problem of high cost and high procurement risk.

An object of the present invention is to reduce the amount of heavy rare earths used in a linear motor while suppressing irreversible demagnetization of permanent magnets.

A linear motor according to the present invention includes a stator and a movable element disposed opposite to the stator and movable with respect to the stator, wherein the stator The mover includes a plurality of salient poles arranged at regular intervals in the moving direction of the mover, and the mover includes a mover magnetic yoke and a plurality of salient poles that protrude from the mover magnetic yoke toward the stator and are arranged in the moving direction. teeth, a three-phase AC winding wound around the teeth, a plurality of gaps formed in the teeth and lined up in the movement direction, and a permanent magnet arranged in each of the plurality of gaps of the teeth. and, in each of the teeth, the permanent magnet is arranged in the gap so that the magnetization direction is opposite to that of the adjacent permanent magnet, and in each of the teeth, among the plurality of permanent magnets, , the permanent magnet located second from the end in the moving direction has a higher coercive force than the other permanent magnets.

Moreover, the linear motor according to the present invention is a linear motor including a stator and a movable element disposed opposite to the stator and movable with respect to the stator, wherein the stator is , the mover includes a plurality of salient poles arranged at regular intervals in the moving direction of the mover, the mover includes a mover magnetic yoke, and a plurality of salient poles that protrude from the mover magnetic yoke toward the stator and extend in the moving direction. a plurality of teeth arranged in a row, a three-phase AC winding wound around the teeth, a plurality of gaps formed in the teeth and arranged in the movement direction, and arranged in each of the plurality of gaps of the teeth. a permanent magnet, in each of the teeth, the permanent magnet is arranged in the gap so that the magnetization direction is opposite to that of the adjacent permanent magnet, and in each of the teeth, a plurality of the permanent magnets Among the permanent magnets, the permanent magnet located second from the end in the moving direction has a larger dimension in the magnetization direction than the other permanent magnets.

According to the present invention, in each tooth, the permanent magnet located second from the end has a higher coercive force than the other permanent magnets (for example, a permanent magnet containing a large amount of heavy rare earth elements is used). Alternatively, since the dimension in the magnetization direction is large, irreversible demagnetization can be suppressed. In addition, other permanent magnets have lower coercive force or smaller dimensions (they do not use heavy rare earths or use a small amount of heavy rare earth) compared to the permanent magnet located second from the end. , the amount of heavy rare earths used can be reduced.

FIG. 1 is a diagram showing a schematic configuration of a linear motor according to an embodiment. FIG. 3 is a diagram showing a schematic configuration of a linear motor according to another embodiment. FIG. 1 is a diagram showing a schematic configuration of a conventional linear motor.

Embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the embodiments described herein. Identical elements in all drawings are designated by the same reference numerals, and redundant explanations will be omitted.

FIG. 1 is a diagram showing a schematic configuration of a linear motor according to an embodiment of the present invention. The linear motor includes a stator 12 and a movable element 11. The stator 12 is formed by laminating, for example, electromagnetic steel plates. Stator 12 includes a stator magnetic yoke 21 and a plurality of salient poles 10. The salient poles 10 protrude from the surface of the stator magnetic yoke 21 and are arranged at intervals of a pitch P in the X-axis direction (see FIG. 1). Note that the stator 12 extends in the left-right direction (X-axis direction), and only a portion thereof is shown in FIG.

The movable element 11 is arranged to face the stator 12 and is movable in the X-axis direction with respect to the stator 12. The X-axis direction is the direction in which the mover 11 moves. The shape and arrangement of each member of the movable element 11 are similar to those of the movable element 111 in FIG. 3. The mover 11 is formed by laminating, for example, electromagnetic steel plates. The mover 11 includes a mover magnetic yoke 20 and U-, V-, and W-phase teeth 13 , 14 , and 15 protruding from the mover magnetic yoke 20 toward the stator 12 . Teeth 13, 14, and 15 are lined up in the X-axis direction. The teeth 13, 14, and 15 are each arranged to be shifted relative to the salient pole 10 by P/3, which corresponds to 120 electrical degrees, in the X-axis direction. Three-phase AC windings 16, 17, and 18 of U, V, and W phases are wound around the teeth 13, 14, and 15, respectively.

Teeth 13, 14, 15 each include a plurality of tooth elements 13E, 14E, 15E. In the example of FIG. 1, the teeth 13 include six tooth elements 13E that protrude from the mover magnetic yoke 20. In addition, in FIG. 1, the reference numerals 13E (14E, 15E) for some teeth elements are omitted. Similar to teeth 13, teeth 14 include six teeth elements 14E, and teeth 15 include six teeth elements 15E. Each tooth element 13E is arranged at a pitch of P/2, and there is a gap between each tooth element 13E. Each tooth element 14E and each tooth element 15E also have a similar configuration. In this way, the movable element 11 includes a plurality of gaps lined up in the X-axis direction (movement direction).

Permanent magnets 22 and 23 are arranged in each of the plurality of gaps between the teeth 13, 14, and 15, respectively. In the teeth 13, the permanent magnets 22 and 23 are arranged in a gap so that the magnetization direction is opposite to that of the adjacent permanent magnets 22 and 23. The same applies to teeth 14 and 15. In FIG. 1, the direction of the arrow indicates the magnetization direction of the permanent magnets 22, 23, and the number of arrows indicates the amount of magnetic flux of the permanent magnets 22, 23.

Here, in the teeth 13, among the plurality of permanent magnets 22 and 23, the permanent magnet 23 located second from the end in the X-axis direction (movement direction) has a higher coercive force than the other permanent magnets 22. There is. That is, the permanent magnet 23 employs a permanent magnet (permanent magnet with high coercive force) that contains a larger amount of heavy rare earth elements than the permanent magnet 22, for example. This also applies to teeth 14 and 15. Thereby, it is possible to suppress irreversible demagnetization of the permanent magnet 23 located second from the end in each of the teeth 13, 14, and 15.

In the linear motor, when a current is applied to the three-phase AC windings 16, 17, and 18, a magnetic attraction force is generated between the movable element 11 and the stator 12 depending on their relative positions. As a result, a thrust force in the X-axis direction is generated in the movable element 11, and the movable element 11 moves relative to the stator 12.

According to the embodiment described above, a material with high coercive force (for example, a material containing a large amount of heavy rare earth elements) is selected only for the permanent magnet 23 that has the smallest amount of magnetic flux and is most likely to cause irreversible demagnetization, and for the other permanent magnets 22. A material with a relatively low coercive force (for example, a material that does not contain heavy rare earths or contains only a small amount) will be selected. Therefore, the amount of heavy rare earths used can be reduced, and costs and procurement risks can be reduced.

FIG. 2 is a diagram showing a schematic configuration of a linear motor according to another embodiment of the present invention. The linear motor of FIG. 2 is obtained by replacing the permanent magnet 23 (permanent magnet located second from the end of each tooth) in the linear motor of FIG. 1 with a permanent magnet 23a having a larger dimension in the magnetization direction. In FIG. 2, the permanent magnet 23a has a larger dimension in the magnetization direction than the permanent magnet 22. Here, the permanent magnet 23a may be made of a material with a low coercive force (for example, a material that does not contain heavy rare earth elements or contains only a small amount of heavy rare earth elements), like the permanent magnet 22. Since the permanent magnet 23a has a high demagnetization resistance by increasing the dimension in the magnetization direction, irreversible demagnetization can be suppressed even if the permanent magnet 23a is made of a material with a low coercive force. In the case of this embodiment, the amount of heavy rare earths used can be further reduced.

10 salient poles, 11, 11a, 111 mover, 12 stator, 13, 14, 15 teeth, 13E, 14E, 15E teeth element, 16, 17, 18 three-phase AC winding, 19 permanent magnet, 20 mover magnetism Yoke, 21 Stator magnetic yoke, 22, 23, 23a Permanent magnet.

Claims (2)

A linear motor comprising a stator and a movable element disposed opposite to the stator and movable with respect to the stator,
The stator includes a plurality of salient poles arranged at regular intervals in the moving direction of the movable element,
The movable element is
a mover magnetic yoke;
a plurality of teeth protruding from the movable magnetic yoke toward the stator and aligned in the moving direction;
a three-phase AC winding wound around the teeth;
a plurality of gaps formed in the teeth and lined up in the moving direction;
a permanent magnet disposed in each of the plurality of gaps of the teeth,
In each of the teeth, the permanent magnet is arranged in the gap so that the magnetization direction is opposite to that of the adjacent permanent magnet,
In each of the teeth, among the plurality of permanent magnets, the permanent magnet located second from the end in the moving direction has a higher coercive force than the other permanent magnets.
A linear motor characterized by: A linear motor comprising a stator and a movable element disposed opposite to the stator and movable with respect to the stator,
The stator includes a plurality of salient poles arranged at regular intervals in the moving direction of the movable element,
The movable element is
a mover magnetic yoke;
a plurality of teeth protruding from the movable magnetic yoke toward the stator and aligned in the moving direction;
a three-phase AC winding wound around the teeth;
a plurality of gaps formed in the teeth and lined up in the moving direction;
a permanent magnet disposed in each of the plurality of gaps of the teeth,
In each of the teeth, the permanent magnet is arranged in the gap so that the magnetization direction is opposite to that of the adjacent permanent magnet,
In each of the teeth, among the plurality of permanent magnets, the permanent magnet located second from the end in the moving direction has a larger dimension in the magnetization direction than the other permanent magnets.
A linear motor characterized by:

Images