Permanent magnet used for linear / rotary actuator

Abstract

A permanent magnet (100) used in a linear / rotary actuator comprises the following on opposing surfaces: a first pole group having one first pole (1) or a plurality of first poles (1) at equal intervals in a circumferential direction, the first pole(s) (1) generating magnetic flux from an outer diameter side toward an inner diameter side in a radial direction; and a second pole group having one second pole (2) or a plurality of second poles (2) at equal intervals in the circumferential direction, the second pole(s) (2) generating magnetic flux from the inner diameter side toward the outer diameter side in the radial direction. The first pole group is disposed at a position that is separated from the second pole group by a prescribed distance in the axial direction and shifted in phase by an electrical angle of 180 degrees in the circumferential direction. A magnet region between the magnetic pole centers of the N pole or the S pole appearing on opposing surfaces of the first pole (1) and the adjacent second pole (2) is magnetized such that the orientation of the magnetic flux has at least a circumferential component.

Description

Permanent magnet used in a linear-rotary actuator

[0001] The present disclosure relates to a permanent magnet used in a linear-rotary actuator.

[0002] Conventionally, an actuator capable of being driven in a linear direction or a rotational direction has been known. In the actuator, a permanent magnet is provided in the armature or the mover. For example, the permanent magnet disclosed in Patent Document 1 is magnetized so that S poles and N poles are alternately arranged, and is arranged at a predetermined interval so as to face the stator of the rotating electric machine.

[0003] Japanese Patent Application Laid-Open No. 2016-32356

[0004] By the way, in fields such as, for example, an electronic component mounting apparatus or a semiconductor manufacturing apparatus, an actuator capable of being driven in both a linear direction and a rotational direction may be required. However, it is difficult to obtain a magnetic flux of a magnet capable of driving in both a linear direction and a rotational direction with a single permanent magnet. Therefore, it has been difficult for an actuator to be a so-called two-axis integrated type in which a single permanent magnet is driven in a linear direction and a rotational direction. Therefore, in the actuator, it is necessary to prepare a well-known driving mechanism in the linear direction and a driving mechanism in the rotational direction as disclosed in, for example, Patent Document 1, and since it becomes a two-axis separate type, there is a possibility that the machine base supporting these driving mechanisms becomes large.

[0005] The present disclosure has been made in view of the above, and an object thereof is to obtain a permanent magnet used in a linear-rotary actuator capable of being driven in both a linear direction and a rotational direction.

[0006] To solve the above-mentioned problems and achieve the objective, the permanent magnet used in the linear rotary actuator according to this disclosure is a cylindrical permanent magnet used in a linear rotary actuator and having a plurality of magnetic poles on a surface facing the armature or movable element constituting the linear rotary actuator, and having a first pole group having one pole or a plurality of poles equally spaced in the circumferential direction that generate a magnetic flux directed from the radial outer diameter side to the inner diameter side on the facing surface, and a second pole group having one pole or a plurality of poles equally spaced in the circumferential direction that generate a magnetic flux directed from the radial inner diameter side to the outer diameter side. The first pole group is positioned at a predetermined distance in the axial direction from the second pole group and at a position with an electrical angle phase shift of 180 degrees in the circumferential direction. The magnetic region between the centers of the N pole or S pole appearing on the facing surface of the first pole and the adjacent second pole is magnetized such that the direction of the magnetic flux has at least a circumferential component.

[0007] The permanent magnet used in the linear-rotating actuator according to this disclosure has the effect of being able to drive in both the linear and rotational directions.

[0008] Figure 1 shows a perspective view of a permanent magnet used in a linear-rotation actuator according to Embodiment 1. Figure 1 shows an explanatory diagram illustrating the orientation direction of the magnetic flux when viewing the cross-section of the permanent magnet at the dashed line X. Figure 2 shows an explanatory diagram illustrating the arrangement of magnetic poles necessary to obtain a magnetic flux that can be driven in both the linear and rotational directions. Figure 3 shows a perspective view of a permanent magnet used in a linear-rotation actuator according to Embodiment 2. Figure 4 shows a V-section illustrating the direction of the magnetic flux as viewed from the radial outer surface side of the permanent magnet. Figure 4 shows a perspective view of a permanent magnet used in a linear-rotation actuator according to Embodiment 3, with a magnetic pole aspect ratio of 1:1. Figure 6 shows a perspective view illustrating a linear-rotation actuator used in a linear-rotation actuator according to Embodiment 3, with a magnetic pole aspect ratio of 2:1. Figure 6 shows a schematic example of a linear-rotation actuator having the permanent magnet shown. Figure 7 shows a schematic example of a linear-rotation actuator having the permanent magnet shown. Figure 8 shows a linear-rotation actuator Figure 9 shows a cross-sectional view of a linear rotary actuator. Figure 9 shows a cross-sectional view of a magnetic flux density contour diagram. Figure 13 shows a perspective view of a permanent magnet used in a linear rotary actuator according to Embodiment 4. Figure 2 shows a modified example 1 of the permanent magnet used in a linear rotary actuator according to Embodiment 4. Figure 13 shows a side view from direction A. Figure 4 shows a perspective view of a modified example 2 of the permanent magnet used in a linear rotary actuator according to Embodiment 4. Figure 5 shows a perspective view of a permanent magnet used in a linear rotary actuator according to Embodiment 5. Figure 5 shows a perspective view of one of the small magnets constituting the permanent magnet in Embodiment 5. Figure 6 shows a perspective view of a permanent magnet used in a linear rotary actuator.

[0009] The permanent magnets used in the linear rotary actuator according to the embodiments of this disclosure will be described in detail below with reference to the drawings.

[0010] Embodiment 1. Figure 1 is a perspective view showing a permanent magnet used in a linear rotary actuator according to Embodiment 1. The linear rotary actuator comprises an armature (not shown), a movable element (not shown) facing the armature, and a permanent magnet 100 shown in Figure 1. As shown in Figure 1, the permanent magnet 100 is cylindrical and has multiple magnetic poles on the opposing surface facing the armature or movable element. The permanent magnet 100 is configured by magnetizing a magnet in a multiple rhombic shape. Specifically, the permanent magnet 100 has a first pole group having one pole or multiple poles at equal intervals in the circumferential direction that generate a magnetic flux directed from the radial outer diameter side to the radial inner diameter side, and a second pole group having one pole or multiple poles at equal intervals in the circumferential direction that generate a magnetic flux directed from the radial inner diameter side to the radial outer diameter side. Here, the first pole is referred to as the S pole and the second pole as the N pole. The first pole group is positioned at a predetermined distance in the axial direction from the second pole group, and at a position where the electrical angle is shifted by 180 degrees in the circumferential direction.

[0011] Figure 2 is an explanatory diagram showing the orientation direction of magnetic flux when viewing a cross-section of a permanent magnet along the dashed line X shown in Figure 1. Figures 2(A) to (C) each illustrate different magnetic flux orientation patterns. The arrows shown in Figures 2(A) to (C) indicate the orientation direction of the magnetic flux. The stars shown in Figure 2 indicate the centers of each magnetic pole. In Figure 2, the outer diameter side of the permanent magnet 100 is considered the opposing surface. As shown in Figure 2, the magnetic region between the centers of the N and S poles appearing on the magnetic surfaces of the first pole 1 and the adjacent second pole 2 is magnetized such that the direction of the magnetic flux has at least a circumferential component. As a result, the permanent magnet 100 can concentrate the magnetic flux and improve the maximum magnetic flux density, thereby increasing the torque and power generation of the rotating electric machine.

[0012] Figure 3 is an explanatory diagram showing the arrangement of magnetic poles necessary to obtain a magnetic flux that can be driven in both the linear and rotational directions. The linear direction is the direction along the axial direction of the permanent magnet 100. The rotational direction is the direction along the circumferential direction of the permanent magnet 100. As shown in Figure 3(A), in order to obtain a magnetic flux that can be driven in the linear direction, it is necessary to have alternating magnetic poles that generate magnetic flux in opposite directions along the axial direction of the cylindrical shape. Also, as shown in Figure 3(B), in order to obtain a magnetic flux that can be driven in the rotational direction, it is necessary to have alternating magnetic poles that generate magnetic flux in opposite directions along the circumferential direction of the cylindrical shape. Therefore, as shown in Figure 3(C), the arrangement of magnetic poles combining (A) and (B) is ideal. However, in order to achieve the arrangement of magnetic poles shown in Figure 3(C), the design of the necessary magnetization yoke is difficult, and furthermore, in the assembly method, positioning in the axial and circumferential directions relative to the shaft is difficult, making it difficult to attach the magnet to the shaft. In other words, in order to achieve the arrangement of magnetic poles shown in Figure 3(C), there is a problem of high difficulty in magnet manufacturing and assembly methods. Therefore, as shown in Figure 1, in the permanent magnet 100 of Embodiment 1, the difficulty in magnet manufacturing and assembly can be reduced by magnetizing the cylindrical magnet in multiple rhombus shapes. However, even if the first pole 1 and the second pole 2 are magnetized in a rhombus shape, it is actually difficult to magnetize the four corners with precision so that the tips are pointed. Therefore, the tips of the magnetized four corners may have a rounded shape. Also, magnets of the same pole may be partially connected.

[0013] As described above, the permanent magnet 100 used in the linear-rotating actuator according to this embodiment can obtain a magnetic flux that can be driven in both the linear and rotational directions by the first pole group and the second pole group, thus enabling the realization of a linear-rotating actuator that can be driven in both the linear and rotational directions. Therefore, the linear-rotating actuator can be applied to the tip mechanism of a robot arm that handles various parts, for example, in cases where driving in a confined space is required, such as in electronic component mounting equipment or semiconductor manufacturing equipment.

[0014] Embodiment 2. Next, the permanent magnet 101 used in the linear rotary actuator according to Embodiment 2 will be described. Figure 4 is a perspective view showing the permanent magnet used in the linear rotary actuator according to Embodiment 2. Figure 5 is an explanatory diagram showing the direction of the magnetic flux as viewed from the radial outer surface side of the permanent magnet in the V section shown in Figure 4.

[0015] As shown in Figure 4, the permanent magnet 101 in Embodiment 2 is cylindrical and has multiple magnetic poles on the opposing surface facing the armature or movable element. In the permanent magnet 101, the cylindrical magnet is magnetized in multiple rhombic shapes. Specifically, the permanent magnet 101 has a first pole group having one pole or multiple poles equally spaced in the circumferential direction that generate a magnetic flux directed from the radial outer diameter side to the radial inner diameter side, and a second pole group having one pole or multiple poles equally spaced in the circumferential direction that generate a magnetic flux directed from the radial inner diameter side to the radial outer diameter side. Here, the first pole is referred to as the S pole and the second pole as the N pole. The first pole group is positioned at a predetermined distance in the axial direction from the second pole group and at a position shifted by an electrical angle of 180 degrees in the circumferential direction.

[0016] As shown in Figures 4 and 5, the thin intermediate portion 3, which is the magnetic space region between the magnetic poles, is magnetized such that the magnetic flux is directed from the first pole 1 to the adjacent second pole 2 when the opposing surface is the outer circumferential surface of the cylinder. When the opposing surface is the inner circumferential surface of the cylinder, the intermediate portion 3, which is the magnetic space region between the magnetic poles, is magnetized such that the magnetic flux is directed from the second pole 2 to the adjacent first pole 1. In the permanent magnet 101 of Embodiment 2, since the intermediate portion 3 is magnetized such that the magnetic flux is directed from the first pole 1 to the adjacent second pole 2, the magnetic flux can be utilized more effectively.

[0017] Furthermore, even if the permanent magnet 101 is magnetized so that the first pole 1 and the second pole 2 form a rhombus shape, it is actually difficult to magnetize the four corners with precision so that they are pointed. For this reason, the magnetized corners may have a rounded shape. Also, magnets of the same pole may be partially connected.

[0018] Embodiment 3. Figure 6 is a perspective view of a permanent magnet used in a linear rotary actuator according to Embodiment 3, with a magnetic pole aspect ratio of 1:1. Figure 7 is a perspective view of a permanent magnet used in a linear rotary actuator according to Embodiment 3, with a magnetic pole aspect ratio of 2:1. The magnetic pole aspect ratio is the ratio of the diagonal length in the circumferential direction to the diagonal length in the axial direction of the magnetic pole.

[0019] As shown in Figure 6, in the permanent magnet 102A with a magnetic pole aspect ratio of 1:1, the diagonal length in the linear direction of the rhombus-shaped magnet is equal to the diagonal length in the rotational direction. As shown in Figure 7, in the permanent magnet 102B with a magnetic pole aspect ratio of 2:1, the diagonal length in the linear direction of the rhombus-shaped magnet is 0.5 times the diagonal length in the rotational direction.

[0020] Figure 8 is a schematic perspective view showing an example of a linear rotary actuator having a permanent magnet as shown in Figure 6. Figure 9 is a schematic perspective view showing an example of a linear rotary actuator having a permanent magnet as shown in Figure 7. The linear rotary actuator 500A shown in Figure 8 has a permanent magnet 102A that constitutes a movable element, a shaft 200 fitted into the inner circumferential surface of the permanent magnet 102A, a cylindrical magnetic pole core 300 which is the armature, and a coil 400 located inside the magnetic pole core. The linear rotary actuator 500B shown in Figure 9 has a permanent magnet 102B that constitutes a movable element, a shaft 200 fitted into the inner circumferential surface of the permanent magnet 102B, a cylindrical magnetic pole core 300 which is the armature, and a coil 400 located inside the magnetic pole core. The inner circumferential surface of the coil 400 faces the outer circumferential surfaces of the permanent magnets 102A and 102B. The permanent magnet 102A of the linear rotary actuator 500A shown in Figure 8 has a magnetic pole aspect ratio of 1:1. The permanent magnet 102B of the linear rotary actuator 500B shown in Figure 9 has a magnetic pole aspect ratio of 2:1. In the linear rotary actuators 500A and 500B, a magnetic gap S is generated between the permanent magnets 102A and 102B and the coil 400.

[0021] Figure 10 is a magnetic flux density contour diagram in cross-section of the linear rotary actuator shown in Figure 8. Figure 11 is a magnetic flux density contour diagram in cross-section of the linear rotary actuator shown in Figure 9. The magnetic flux density contour diagrams for the permanent magnets 102A, 102B, the magnetic pole core 300, the coil 400, and the magnetic gap S differ between the linear rotary actuator 500A shown in Figure 10 and the linear rotary actuator 500B shown in Figure 11. As shown in Figure 10, in the linear rotary actuator 500A, which uses a permanent magnet 102A in which the diagonal length in the circumferential direction of the magnetic pole is equal to the diagonal length in the axial direction, the magnetic flux density of the magnetic pole core 300 is made more uniform compared to the linear rotary actuator 500B shown in Figure 11, thus improving the magnetic properties.

[0022] Furthermore, to improve magnetic properties, it is not limited to the condition where the diagonal lengths in the axial direction and the diagonal lengths in the circumferential direction of the magnetic pole are exactly equal, as described above. It is sufficient that the ratio K of the axial diagonal length to the circumferential diagonal length of the magnetic pole satisfies the condition 0.6 ≤ K ≤ 1.4. If K does not satisfy 0.6 ≤ K ≤ 1.4, i.e., if K deviates significantly from 1.0, the magnetic flux density distribution of the magnetic pole core 300 will be biased towards either the linear or rotational direction, causing magnetic saturation and preventing effective utilization of the magnetic flux, which may lead to a decrease in the induced voltage constant. In actuators with a low induced voltage constant, a large current is required to produce the same torque in both the linear and rotational directions, resulting in large copper losses. Therefore, the range of K is determined by focusing on copper losses so that they are minimized. Note that the K at which copper losses are minimized varies slightly depending on the shape of the movable part. Therefore, the range of K needs to be set over a reasonably wide range. Therefore, for the copper loss ratio normalized with K=1, a copper loss ratio of 1.1 is set as the threshold, and the range of K is defined as 0.6 ≤ K ≤ 1.4, where the copper loss ratio is 1.1 or less.

[0023] Embodiment 4. Figure 12 is a perspective view showing a permanent magnet used in a linear-rotation actuator according to Embodiment 4. The permanent magnet 103 of Embodiment 4 shown in Figure 12 is composed of a combination of multiple rhombic magnets 40, 41 arranged on the opposing surfaces facing the armature or movable element that constitutes the linear-rotation actuator. Specifically, the permanent magnet 103 is formed by attaching a plurality of rhombic magnets 40 having a first pole 1 and a plurality of rhombic magnets 41 having a second pole 2 to a shaft (not shown). The permanent magnet 103 shown in Figure 12, like the permanent magnet 100 shown in Figure 1, can provide a magnetic flux that can be driven in both the linear and rotational directions. Ideally, the rhombic magnets 40, 41 shown in Figure 12 should have pointed tips at the four corners, but they may also have rounded tips. Also, magnets of the same pole may be partially connected.

[0024] Figure 13 is a perspective view showing Modification 1 of a permanent magnet used in a linear rotary actuator according to Embodiment 4. Figure 14 is a side view taken from direction A shown in Figure 13. The permanent magnet 103 of Modification 1 shown in Figures 13 and 14 is provided with grooves 50 along the axial direction at two opposing locations on its inner circumferential surface. The grooves 50 function as guides when a shaft (not shown) is fitted into the cylindrical interior of the permanent magnet 103, which is formed by combining a plurality of rhombic magnets 40, 41. The shaft has protrusions formed at positions corresponding to the grooves 50 that fit into the grooves 50. This makes it easy to position the shaft fitted into the inner circumferential surface of the permanent magnet 103, and simplifies the assembly process when manufacturing the linear rotary actuator. The grooves 50 are not limited to the semicircular shape shown, but may be rectangular, for example. Also, the grooves 50 are not limited to the two locations shown, but may be provided at one or three or more locations on the inner circumferential surface of the permanent magnet 103.

[0025] Figure 15 is a perspective view showing a modified example 2 of the permanent magnet used in the linear rotary actuator according to Embodiment 4. The permanent magnet 103 of Modified Example 2 shown in Figure 15 is provided with projections 51 along the axial direction at two opposing locations on its inner circumferential surface. Similar to the grooves 50 described above, the projections 51 function as guides when a shaft (not shown) is fitted into the cylindrical interior of the permanent magnet 103, which is formed by combining multiple magnets 40, 41. The shaft has grooves formed at positions corresponding to the projections 51 that fit into the projections 51. The projections 51 may have a shape that fits into the grooves of a spline shaft. In this way, the projections 51 can function not only as guides when fitting the shaft, but also as anti-rotation devices in the rotational direction. Furthermore, the projections 51 are not limited to the semicircular shape shown, but may be rectangular, for example. Also, the projections 51 are not limited to the two locations shown, but may be provided at one or three or more locations on the inner circumferential surface of the permanent magnet 103. Furthermore, the magnets constituting the permanent magnet 103 in Embodiment 4 are not limited to the rhombus shape shown in Figures 12 to 15, but may be of other shapes.

[0026] Embodiment 5. Next, the permanent magnet 104 used in the linear rotary actuator according to Embodiment 5 will be described. Figure 16 is a perspective view showing the permanent magnet used in the linear rotary actuator according to Embodiment 5. Figure 17 is a perspective view showing one of the small magnet pieces constituting the permanent magnet in Embodiment 5. Figure 18 is a perspective view showing the other small magnet piece constituting the permanent magnet in Embodiment 5. The dotted arrows shown in Figures 17 and 18 indicate the magnetization orientation.

[0027] As shown in Figure 16, the permanent magnet 104 of the linear rotary actuator according to Embodiment 5 is formed by combining two types of small magnets 10 and 11 that are divided into multiple pieces. Each small magnet 10 or 11 is fan-shaped, and its inner surface is attached to the surface of the shaft 200. As shown in Figure 17, one small magnet 10 is magnetized from diagonal corner 3 to corner 1 of the four corners of its outer surface. As shown in Figure 18, the other small magnet 11 is magnetized from diagonal corner 2 to corner 4 of the four corners of its outer surface. As shown in Figure 16, in the circumferential direction, four small magnets 10 and 11 are arranged alternately. In the axial direction, the small magnets 10 and 11 are also arranged alternately. The permanent magnet 104 groups four adjacent small magnets 10, 11 together, and concentrates the orientation of the magnetic flux of each small magnet 10, 11 at a single point where the four small magnets 10, 11 are in contact. As a result, the permanent magnet 104 of Embodiment 5 can reproduce the permanent magnet 100 of Embodiment 1. Note that the number of small magnets 10, 11 constituting the permanent magnet 104 is not limited to the number shown. For example, the small magnets 10, 11 arranged in the circumferential direction may be arranged so that their total number is an integer multiple of 2.

[0028] Figure 19 is a perspective view showing a modified example of one of the small magnets constituting the permanent magnet in Embodiment 5. Figure 20 is a perspective view showing a modified example of the other small magnet constituting the permanent magnet in Embodiment 5. The dotted arrows in Figures 19 and 20 indicate the magnetization orientation. Each small magnet 10A and 11A is fan-shaped, and its inner surface is attached to the surface of the shaft 200. Unlike the small magnet 10 shown in Figure 17, the one small magnet 10A shown in Figure 19 is magnetized such that, among the four corners of its outer surface, the magnetization penetrates from the radial outer diameter side towards the inner diameter side and exits to the outer diameter side, starting from diagonal corner 3 to corner 1. Unlike the small magnet 11 shown in Figure 18, the other small magnet 11A shown in Figure 20 is magnetized such that, among the four corners of its outer surface, the magnetization penetrates from the radial outer diameter side towards the inner diameter side and exits to the outer diameter side, starting from diagonal corner 2 to corner 4. By orienting the magnetic flux in this way, the performance of the magnet can be improved.

[0029] In the permanent magnet 104 for the linear rotary actuator according to Embodiment 5, the structure is formed by combining two types of small magnet pieces 10 and 11 that are divided into multiple pieces. Compared to a permanent magnet with a rhombus-shaped magnetization structure, it is easier to manufacture and can contribute to reducing manufacturing costs.

[0030] In addition, the permanent magnet 104 in Embodiment 5 may be configured to have grooves 50 or projections 51 along the axial direction on its inner circumferential surface, as shown in Figures 13 to 15.

[0031] Embodiment 6. The permanent magnet 105 used in the linear rotary actuator according to Embodiment 6 will be described. Figure 21 is a perspective view showing the permanent magnet used in the linear rotary actuator according to Embodiment 6.

[0032] As shown in Figure 21, the permanent magnet 105 of the linear rotary actuator according to Embodiment 6 is formed by combining a plurality of divided rhombic magnets 40, 41 and a plurality of rod-shaped magnets 42. The rhombic magnet 40 has a first pole 1. The rhombic magnet 41 has a second pole 2. The rod-shaped magnets 42 are arranged in the thin intermediate portion, which is the magnetic space region between the magnetic poles, and are magnetized such that when the opposing surface is the outer circumferential surface of a cylinder, the direction of the magnetic flux is from the first pole 1 to the adjacent second pole 2. The intermediate portion where the rod-shaped magnets 42 are arranged is magnetized such that when the opposing surface is the inner circumferential surface of a cylinder, the direction of the magnetic flux is from the second pole 2 to the adjacent first pole 1.

[0033] In addition, the permanent magnet 105 in Embodiment 6 may be configured to have grooves 50 or projections 51 along the axial direction on its inner circumferential surface, as shown in Figures 13 to 15.

[0034] The configurations shown in the above embodiments are examples only, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention.

[0035] 1 First pole, 2 Second pole, 3 Intermediate section, 10, 10A, 11, 11A Small magnet pieces, 40, 41, 42 Magnets, 50 Groove section, 51 Protrusion, 100, 101, 102A, 102B, 103, 104, 105 Permanent magnets, 200 Shaft, 300 Magnetic pole core, 400 Coil, 500A, 500B Linear rotary actuator.

Claims

1. A cylindrical permanent magnet used in a linear rotary actuator, having multiple magnetic poles on a surface facing the armature or movable element constituting the linear rotary actuator, wherein the magnet comprises: a first pole group having one pole or multiple poles equally spaced in the circumferential direction in the direction of a first pole that generates a magnetic flux directed from the radial outer diameter side to the radial inner diameter side on the facing surface; and a second pole group having one pole or multiple poles equally spaced in the circumferential direction in the direction of a second pole that generates a magnetic flux directed from the radial inner diameter side to the radial outer diameter side, wherein the first pole group is positioned at a predetermined distance in the axial direction from the second pole group and at a position shifted by an electrical angle of 180 degrees in the circumferential direction; and the magnetic region between the centers of the N pole or S pole appearing on the facing surface of the first pole and the adjacent second pole is magnetized such that the direction of the magnetic flux has at least a circumferential component.

2. The permanent magnet used in the linear rotary actuator according to claim 1, characterized in that the ratio K of the axial diagonal length to the circumferential diagonal length of the magnetic pole satisfies 0.6 ≤ K ≤ 1.

4.

3. The permanent magnet used in a linear rotary actuator according to claim 1 or 2, characterized in that the permanent magnet is formed by combining a plurality of divided magnets.

4. The permanent magnet is formed by combining a plurality of rhombic magnets to form a cylindrical shape, and has a first pole group having one pole or a plurality of poles spaced equally apart in the circumferential direction that generate a magnetic flux directed from the radial outer diameter side to the radial inner diameter side on the opposing surface, and a second pole group having one pole or a plurality of poles spaced equally apart in the circumferential direction that generate a magnetic flux directed from the radial inner diameter side to the radial outer diameter side, the first pole group is positioned at a predetermined distance in the axial direction from the second pole group and at a position with an electrical angle phase shift of 180 degrees in the circumferential direction, and the magnetic region between the magnetic pole centers of the N pole or S pole appearing on the opposing surface of the first pole and the adjacent second pole is magnetized such that the direction of the magnetic flux has at least a circumferential component, characterized in that it is a permanent magnet used in a linear rotary actuator according to claim 3.

5. The permanent magnet is formed into a cylindrical shape by combining two types of fan-shaped small magnets, each divided into multiple pieces; one of the small magnets is magnetized from one diagonal corner to the other of the four corners of its outer surface; the other small magnet is magnetized from one diagonal corner to the other of the four corners of its outer surface, each different from the other diagonal; the two types of small magnets are arranged alternately in the circumferential direction and alternately in the axial direction; and the four small magnets are arranged to concentrate the orientation direction of the magnetic flux of each small magnet at a single point where they meet, as described in 3.

6. A permanent magnet used in a linear rotary actuator according to any one of claims 1 to 4, characterized in that the intermediate portion, which is the magnetic space region between the magnetic poles, is magnetized such that when the opposing surface is the outer circumferential surface of a cylinder, the direction of the magnetic flux is from the first pole to the adjacent second pole, and when the opposing surface is the inner circumferential surface of a cylinder, the magnetic flux is magnetized such that it is from the second pole to the adjacent first pole.

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