JP7609697B2 - Motor - Google Patents

Description

This disclosure relates to a motor.

Patent document 1 discloses a motor that includes multiple magnets arranged in a ring shape and a coil arranged inside the multiple magnets. In this motor, magnets with magnetization directions along the radial direction of the motor and magnets with magnetization directions along the circumferential direction of the motor are arranged in a Halbach array so that magnetic flux from the magnets is concentrated in the coil.

JP 2011-024379 A

In motors with multiple magnets arranged in a Halbach array, like the motor described above, leakage of magnetic flux can occur along the axial direction of the motor from magnets whose magnetization direction is aligned with the radial direction of the motor. Not only does the leaked magnetic flux not contribute to the torque of the motor, but it can also adversely affect sensors placed around the motor. For this reason, there is a demand for technology to suppress leakage of magnetic flux along the axial direction of the motor from magnets arranged in a Halbach array.

This disclosure can be realized in the following forms:

(1) According to one aspect of the present disclosure, there is provided a motor including: a first magnet portion provided in an annular shape along a circumferential direction centered on a rotation axis of the motor; a second magnet portion provided in an annular shape along the circumferential direction and arranged to overlap the first magnet portion in an axial direction parallel to the rotation axis; and a coil portion arranged opposite the first magnet portion in a radial direction perpendicular to the rotation axis. In the first magnet section, a plurality of magnets including a first main magnet having a magnetization direction along the radial direction and a first sub-magnet having a magnetization direction along the circumferential direction are arranged in a Halbach array so that magnetic flux from the first magnet section is concentrated at the coil section, and in the second magnet section, a plurality of magnets including a second main magnet having a magnetization direction along the axial direction and a second sub-magnet having a magnetization direction along the circumferential direction are arranged in a Halbach array so that magnetic flux from the second magnet section is concentrated at the first magnet section, the second main magnet is arranged overlapping the first main magnet in the axial direction, and the second sub-magnet is arranged overlapping the first sub-magnet in the axial direction.
In this embodiment of the motor, the second magnet portion is disposed so as to overlap the first magnet portion in the axial direction, which suppresses leakage of magnetic flux from the first main magnet along the axial direction and increases the magnetic flux flowing from the first main magnet toward the coil portion, thereby suppressing leakage of magnetic flux from the motor along the axial direction and increasing the torque generated by the motor.
(2) In the motor of the above aspect, a length of the first sub magnet along the circumferential direction may be shorter than a length of the first main magnet along the circumferential direction.
With this type of motor, the magnetic flux from the first magnet portion can be more effectively concentrated toward the coil portion than in a configuration in which the length of the first sub-magnet along the circumferential direction is greater than or equal to the length of the first main magnet along the circumferential direction.
(3) In the motor of the above aspect, a thickness of the second magnet portion along the axial direction may be thinner than a thickness of the first magnet portion along the axial direction.
According to the motor of this configuration, it is possible to prevent the motor from becoming large in size in the axial direction.
(4) In the motor of the above aspect, the coil portion may be disposed between the rotating shaft and the first magnet portion.
According to the motor of this configuration, leakage of magnetic flux from the motor in the radial direction can be suppressed.
(5) In the motor of the above aspect, the second magnet portion may be disposed on both sides of the first magnet portion in the axial direction.
According to the motor of this configuration, it is possible to more effectively prevent the magnetic flux flowing out from the first main magnet from leaking along the axial direction.
The present disclosure may be realized in various forms other than a motor, for example, in the form of a permanent magnet rotor or the like.

FIG. 1 is an explanatory diagram showing a schematic configuration of a motor according to a first embodiment. Cross-sectional view taken along line II-II in FIG. FIG. 2 is an explanatory diagram showing the configuration of a field magnet portion. 13 is a graph showing the relationship between the thickness of the second magnet portion and the torque of the motor. FIG. 4 is a first explanatory diagram illustrating a magnetic field generated by the field magnet section of the first embodiment. FIG. 2 is a second explanatory diagram illustrating a magnetic field generated by the field magnet portion of the first embodiment. FIG. 11 is a first explanatory diagram illustrating a magnetic field generated by a field magnet section of a comparative example. FIG. 2 is a second explanatory diagram illustrating a magnetic field generated by a field magnet portion of a comparative example.

A. First embodiment:
FIG. 1 is an explanatory diagram showing a schematic configuration of a motor 10 in the first embodiment. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. FIG. 1 shows a cross section of the motor 10 along the rotation axis RX. As shown in FIG. 1, the motor 10 includes a rotor 100 and a stator 200. The rotor 100 is supported by a bearing (not shown) provided in the motor 10, and rotates around the rotation axis RX. In the following description, the direction from one end of the rotor 100 to the other end along the rotation axis RX is called the axial direction AD, and the direction perpendicular to the rotation axis RX and directed outward from the rotation axis RX is called the radial direction RD. The direction along the rotation direction of the rotor 100 is called the circumferential direction CD. These directions AD, RD, and CD are appropriately illustrated in each drawing.

In this embodiment, the motor 10 is configured as a vernier motor, that is, in this embodiment, the motor 10 is configured such that the relationship between the number of pole pairs Zs of the stator 200, the number of pole pairs Zr of the rotor 100, and the number of teeth p satisfies the following formula (1).
Zs=Zr±p...(1)

In this embodiment, the motor 10 is configured as an outer rotor type motor. That is, in this embodiment, the rotor 100 is disposed outside the stator 200 in the radial direction RD. The rotor 100 includes a rotor cup 110, a rotor core 120, and a field magnet section 130.

The rotor cup 110 is configured as a bottomed cylinder. The rotor cup 110 has a cylindrical portion 111, a bottom surface portion 112, and an output portion 113. The cylindrical portion 111 has a cylindrical shape centered on the rotation axis RX. The bottom surface portion 112 is provided so as to close one end of the cylindrical portion 111 in the axial direction AD. A through hole is provided in the center of the bottom surface portion 112. The output portion 113 is disposed inside the cylindrical portion 111. The output portion 113 has a cylindrical shape centered on the rotation axis RX. The output portion 113 is provided so as to protrude from the peripheral portion of the through hole of the bottom surface portion 112. An object OB that rotates together with the rotor 100 is connected to the output portion 113. In the following description, the bottom surface portion 112 side of the motor 10 is referred to as the lower side, and the opposite side to the bottom surface portion 112 is referred to as the upper side.

The rotor core 120 is fixed to the inner wall surface of the cylindrical portion 111. The rotor core 120 has a cylindrical shape centered on the rotation axis RX. In this embodiment, the rotor core 120 is made of multiple electromagnetic steel plates stacked along the axial direction AD.

The field magnet section 130 is fixed to the inner wall surface of the rotor core 120. The field magnet section 130 has a first magnet section 140 and a second magnet section 150. In this embodiment, two second magnet sections 150 are provided symmetrically above and below the first magnet section 140 in the axial direction AD and below the first magnet section 140 in the axial direction AD. The first magnet section 140 is composed of a plurality of permanent magnets arranged in a circular ring shape centered on the rotation axis RX. Each second magnet section 150 is composed of a plurality of permanent magnets arranged in a circular ring shape centered on the rotation axis RX. Each second magnet section 150 is arranged overlapping the first magnet section 140 in the axial direction AD. In the following description, the permanent magnet is simply called a magnet. The specific arrangement of the magnets of the first magnet section 140 and the specific arrangement of the magnets of the second magnet section 150 will be described later.

The stator 200 is disposed inside the field magnet section 130. The stator 200 includes a stator case 210, a stator core 220, and a field coil section 230. The stator case 210 has a cylindrical shape centered on the rotation axis RX.

The stator core 220 is fixed to the outer wall surface of the stator case 210. The stator core 220 is arranged to surround the stator case 210. In this embodiment, the stator core 220 is made of a plurality of electromagnetic steel plates laminated along the axial direction AD. As shown in FIG. 2, in this embodiment, the stator core 220 has 12 teeth 225 protruding outward in the radial direction RD. The 12 teeth 225 are arranged at equal intervals along the circumferential direction CD.

As shown in FIG. 1, the field coil section 230 is disposed between the rotation axis RX and the field magnet section 130. The field coil section 230 is disposed facing the first magnet section 140 in the radial direction RD. In this embodiment, the field coil section 230 has 12 coils 235. Each coil 235 is wound around a tooth 225. The 12 coils 235 are electrically connected to a power source (not shown) to form three phases, namely, U phase, V phase, and W phase.

When a current is supplied from the power source to each coil 235 of the field coil section 230, the field coil section 230 generates a magnetic field. A torque is transmitted to the object OB connected to the output section 113 by magnetic interaction between the magnetic field generated by the field coil section 230 and the magnetic field generated by the field magnet section 130.

Figure 3 is an explanatory diagram showing the configuration of the field magnet section 130. In Figure 3, a part of the field magnet section 130 is shown as viewed from the inside in the radial direction RD. In Figure 3, the stator 200 and the like are omitted. As shown in Figure 3, the first magnet section 140 has a first main magnet 141 having a magnetization direction MD along the radial direction RD and a first sub-magnet 142 having a magnetization direction MD along the circumferential direction CD. The magnetization direction MD means the direction in which magnetic flux flows from the S pole to the N pole inside the magnet. In Figure 3, the magnetization direction MD of each magnet is represented by an arrow. As shown in Figure 2, in this embodiment, the first magnet section 140 has 20 first main magnets 141 and 20 first sub-magnets 142.

As shown in FIG. 3, the first magnet section 140 has the first main magnet 141 and the first sub-magnet 142 arranged side by side in a Halbach array so that the magnetic flux flowing out from the first magnet section 140 is concentrated on the inside in the radial direction RD. More specifically, in this embodiment, the first main magnet 141 and the first sub-magnet 142 are arranged alternately along the circumferential direction CD. The magnetization directions MD of the two first main magnets 141 adjacent to each other across the first sub-magnet 142 are opposite to each other. The magnetization directions MD of the two first sub-magnets 142 adjacent to each other across the first main magnet 141 are opposite to each other. The first sub-magnet 142 arranged adjacent to the first main magnet 141 having the magnetization direction MD toward the inside of the radial direction RD has a magnetization direction MD toward the first main magnet 141. The first sub-magnet 142, which is arranged adjacent to the first main magnet 141 having a magnetization direction MD that faces outward in the radial direction RD, has a magnetization direction MD that faces the opposite side to the first main magnet 141.

The second magnet section 150 has a second main magnet 151 having a magnetization direction MD along the axial direction AD and a second sub-magnet 152 having a magnetization direction MD along the circumferential direction CD. The second main magnet 151 is arranged so as to overlap the first main magnet 141 in the axial direction AD, and the second sub-magnet 152 is arranged so as to overlap the first sub-magnet 142 in the axial direction AD. In this embodiment, the second magnet section 150 arranged above the first magnet section 140 in the axial direction AD has 20 second main magnets 151 and 20 second sub-magnets 152. The second magnet section 150 arranged below the first magnet section 140 in the axial direction AD has 20 second main magnets 151 and 20 second sub-magnets 152.

In the second magnet section 150, the second main magnet 151 and the second sub-magnet 152 are arranged side by side in a Halbach array so that the magnetic flux flowing out from the second magnet section 150 is concentrated on the first magnet section 140 side. More specifically, in this embodiment, the second main magnet 151 and the second sub-magnet 152 are arranged alternately along the circumferential direction CD. The magnetization directions MD of the two second main magnets 151 adjacent to each other across the second sub-magnet 152 are opposite to each other. The magnetization directions MD of the two second sub-magnets 152 adjacent to each other across the second main magnet 151 are opposite to each other. The second sub-magnet 152 arranged adjacent to the second main magnet 151 having the magnetization direction MD toward the first main magnet 141 has a magnetization direction MD toward this second main magnet 151. The second sub-magnet 152, which is arranged adjacent to the second main magnet 151 having a magnetization direction MD facing the opposite side to the first main magnet 141, has a magnetization direction MD facing the opposite side to the second main magnet 151.

In this embodiment, the length Ls1 of the first sub-magnet 142 along the circumferential direction CD is shorter than the length Lm1 of the first main magnet 141 along the circumferential direction CD. The width of the first sub-magnet 142 along the radial direction RD is the same as the width of the first main magnet 141 along the radial direction RD. The thickness ts1 of the first sub-magnet 142 along the axial direction AD is the same as the thickness tm1 of the first main magnet 141 along the axial direction AD. By making the length Ls1 of the first sub-magnet 142 along the circumferential direction CD shorter than the length Lm1 of the first main magnet 141 along the circumferential direction CD, the magnetic flux flowing out from the first magnet section 140 can be effectively concentrated on the inside of the radial direction RD.

In this embodiment, when viewed along the axial direction AD, the outer peripheral edge of the second sub-magnet 151 overlaps with the outer peripheral edge of the first main magnet 141. When viewed along the axial direction AD, the outer peripheral edge of the second sub-magnet 152 overlaps with the outer peripheral edge of the first sub-magnet 142. The length Ls2 of the second sub-magnet 152 along the circumferential direction CD is shorter than the length Lm2 of the second main magnet 151 along the circumferential direction CD. The width of the second sub-magnet 152 along the radial direction RD is the same as the width of the second main magnet 151 along the radial direction RD. The thickness ts2 of the second sub-magnet 152 along the axial direction AD is the same as the thickness tm2 of the second main magnet 151 along the axial direction AD. By making the length Ls2 of the second sub-magnet 152 along the circumferential direction CD shorter than the length Lm2 of the second main magnet 151 along the circumferential direction CD, the magnetic flux flowing out from the second magnet section 150 can be effectively concentrated on the first magnet section 140.

In this embodiment, the thickness of the second magnet section 150 along the axial direction AD is thinner than the thickness of the first magnet section 140 along the axial direction AD. In other words, the thickness tm2 of the second main magnet 151 along the axial direction AD is thinner than the thickness tm1 of the first main magnet 141 along the axial direction AD. The thickness ts2 of the second sub-magnet 152 along the axial direction AD is thinner than the thickness tm2 of the first sub-magnet 142 along the axial direction AD.

In this embodiment, the first main magnet 141 and the first sub-magnet 142 are adhered to the inner wall surface of the rotor core 120 by an adhesive. The second main magnet 151 is adhered to the first main magnet 141 by an adhesive, and the second sub-magnet 152 is adhered to the first sub-magnet 142 by an adhesive. As an adhesive for adhering the magnets 141, 142, 151, and 152, for example, an adhesive obtained by mixing a cyanoacrylate adhesive and an epoxy adhesive can be used.

Figure 4 is a graph showing the relationship between the thickness of the second magnet section 150 and the torque Tq output by the motor 10. In Figure 4, the horizontal axis represents the thickness of the second magnet section 150, and the vertical axis represents the torque. For reference, Figure 4 also shows with a dashed line the torque Tq0 of the motor 10 when the thickness of the second magnet section 150 is zero, in other words, when the second magnet section 150 is not provided. As shown in Figure 4, the greater the thickness of the second magnet section 150, the greater the torque Tq output by the motor 10. The greater the thickness of the second magnet section 150, the smaller the slope of the torque Tq.

FIG. 5 is a first explanatory diagram showing a magnetic field generated by the field magnet section 130 in this embodiment. FIG. 6 is a second explanatory diagram showing a magnetic field generated by the field magnet section 130 in this embodiment. FIG. 7 is a first explanatory diagram showing a magnetic field generated by the field magnet section 130b in the comparative example. FIG. 8 is a second explanatory diagram showing a magnetic field generated by the field magnet section 130b in the comparative example. The field magnet section 130b in the comparative example does not have the second magnet section 150. In FIGS. 5 to 8, the magnetic flux density vectors are represented by arrows. As shown in FIGS. 7 and 8, in the field magnet section 130b in which the second magnet section 150 is not provided, leakage of magnetic flux occurs that does not flow from the first main magnet 141 toward the field coil section 230 but flows along the axial direction AD. The leaked magnetic flux does not contribute to the torque of the motor 10. Furthermore, the leaked magnetic flux may adversely affect sensors arranged around the motor 10. In contrast, in this embodiment, as shown in Fig. 5, the second main magnet 151 having a magnetization direction facing the first main magnet 141 is arranged above the first main magnet 141 in the axial direction AD, which has a magnetization direction facing the field coil unit 230, thereby suppressing leakage of magnetic flux from the first main magnet 141 toward the upper side in the axial direction AD instead of toward the field coil unit 230. Although not shown in Fig. 5, the second main magnet 151 having a magnetization direction facing the first main magnet 141 is also arranged below the first main magnet 141 in the axial direction AD, which has a magnetization direction facing the field coil unit 230, thereby suppressing leakage of magnetic flux from the first main magnet 141 toward the lower side in the axial direction AD instead of toward the field coil unit 230. Furthermore, in this embodiment, as shown in FIG. 6, inside the second sub-magnet 152, a flow of magnetic flux occurs along the circumferential direction CD toward the second main magnet 151, which has a magnetization direction facing the first main magnet 141, and this magnetic flux flows from the second main magnet 151 to the first main magnet 141 and the field coil section 230 in that order.

According to the motor 10 in the present embodiment described above, the first magnet section 140 has the first main magnet 141 and the first sub-magnet 142 arranged in a Halbach array so that the magnetic flux is collected in the field coil section 230. The second magnet section 150 has the second main magnet 151 and the second sub-magnet 152 arranged in a Halbach array so that the magnetic flux is collected in the first magnet section 140. Therefore, the amount of magnetic flux leaking from the first magnet section 140 along the axial direction AD can be reduced, and the amount of magnetic flux toward the field coil section 230 can be increased. Furthermore, since the magnetic flux from the second magnet section 150 is collected in the first main magnet 141 having a magnetization direction facing the field coil section 230, the amount of magnetic flux toward the field coil section 230 can be further increased. Therefore, it is possible to suppress the magnetic flux from leaking from the motor 10 along the axial direction AD, and to increase the torque of the motor 10.

In addition, in this embodiment, the length Ls1 of the first sub-magnet 142 along the circumferential direction CD is shorter than the length Lm1 of the first main magnet 141 along the circumferential direction CD. Therefore, compared to a configuration in which the length Ls1 of the first sub-magnet 142 along the circumferential direction CD is equal to or longer than the length Lm1 of the first main magnet 141 along the circumferential direction CD, the magnetic flux from the first magnet section 140 can be more effectively collected toward the field coil section 230.

In addition, in this embodiment, the thickness of the second magnet section 150 is thinner than the thickness of the first magnet section 140. This prevents the rotor 100 from becoming larger in the axial direction AD and the motor 10 from becoming larger in the axial direction AD.

In addition, in this embodiment, the magnetic flux from the first magnet section 140 is collected in the field coil section 230 arranged on the inside in the radial direction RD. Therefore, it is possible to prevent magnetic flux from leaking from the motor 10 along the radial direction RD.

In addition, in this embodiment, the second magnet section 150 is disposed on both sides of the first magnet section 140 in the axial direction AD. This effectively prevents the magnetic flux flowing out from the first magnet section 140 from leaking along the axial direction AD.

B. Other embodiments:
(B1) The motor 10 in the above-described embodiment is configured as a vernier motor. However, the motor 10 may be configured as a motor other than a vernier motor, such as an induction motor or a synchronous motor.

(B2) The motor 10 in the above-described embodiment is configured as an outer rotor type motor. In contrast, the motor 10 may be configured as an inner rotor type motor. In other words, the rotor 100 may be disposed between the rotating shaft RX and the stator 200.

(B3) In the motor 10 of the above-described embodiment, the field magnet section 130 is fixed to the inner wall surface of the rotor core 120. In contrast, the field magnet section 130 may be embedded in the rotor core 120.

(B4) In the motor 10 of the above-described embodiment, the field magnet section 130 is provided in the rotor 100, and the field coil section 230 is provided in the stator 200. Alternatively, the field coil section 230 may be provided in the rotor 100, and the field magnet section 130 may be provided in the stator 200.

(B5) In the motor 10 of the above-described embodiment, the length Ls1 of the first sub magnet 142 along the circumferential direction CD is shorter than the length Lm1 of the first main magnet 141 along the circumferential direction CD. In contrast, the length Ls1 of the first sub magnet 142 along the circumferential direction CD may be greater than or equal to the length Lm1 of the first main magnet 141 along the circumferential direction CD.

(B6) In the motor 10 of the above-described embodiment, the thicknesses tm2, ts2 of the magnets 151, 152 of the second magnet section 150 along the axial direction AD are smaller than the thicknesses tm1, ts1 of the magnets 141, 142 of the first magnet section 140 along the axial direction AD. In contrast, the thicknesses tm2, ts2 of the magnets 151, 152 of the second magnet section 150 along the axial direction AD may be greater than or equal to the thicknesses tm1, ts1 of the magnets 141, 142 of the first magnet section 140 along the axial direction AD.

(B7) In the motor 10 of the above embodiment, the second magnet section 150 is provided on both sides of the first magnet section 140 in the axial direction AD. In contrast, the second magnet section 150 may be provided only on one side of the first magnet section 140 in the axial direction AD. For example, the second magnet section 150 may not be provided below the first magnet section 140 in the axial direction AD, but may be provided above the first magnet section 140 in the axial direction AD. Alternatively, the second magnet section 150 may not be provided above the first magnet section 140 in the axial direction AD, but may be provided below the first magnet section 140 in the axial direction AD. Even in this case, the magnetic flux flowing out from the first main magnet 141 can be prevented from leaking to the side where the second magnet section 150 is provided.

(B8) In the motor 10 of the above-described embodiment, the first magnet section 140 and the second magnet section 150 have multiple magnets arranged in a Halbach array in which the magnetization directions of adjacent magnets in the circumferential direction CD differ by 90 degrees. In contrast, the first magnet section 140 and the second magnet section 150 may have multiple magnets arranged in a Halbach array in which the magnetization directions of adjacent magnets in the circumferential direction CD differ by 45 degrees.

(B9) In the motor 10 of the above-described embodiment, the first magnet section 140 and the second magnet section 150 are each configured by arranging multiple magnets, each having one set of magnetic poles, in a circular ring shape. In contrast, at least one of the first magnet section 140 and the second magnet section 150 may be configured by a ring magnet, each having two or more sets of magnetic poles. In this case, the portion of the ring magnet that constitutes one set of magnetic poles is called the magnet.

The present disclosure is not limited to the above-described embodiments, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features in the embodiments corresponding to the technical features in each form described in the Summary of the Invention column can be replaced or combined as appropriate to solve some or all of the above-described problems or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.

10...motor, 100...rotor, 110...rotor cup, 111...cylindrical portion, 112...bottom portion, 113...output portion, 120...rotor core, 130...field magnet portion, 140...first magnet portion, 141...first main magnet, 142...first sub-magnet, 150...second magnet portion, 151...second main magnet, 152...second sub-magnet, 200...stator, 210...stator case, 220...stator core, 225...teeth, 230...field coil portion, 235...coil

Claims (5)

A motor,
A first magnet portion is provided in an annular shape along a circumferential direction centered on a rotation shaft of the motor;
a second magnet portion provided annularly along the circumferential direction and arranged to overlap the first magnet portion in an axial direction parallel to the rotation axis;
a coil portion disposed opposite the first magnet portion in a radial direction perpendicular to the rotation axis;
Equipped with
In the first magnet section, a plurality of magnets including a first main magnet having a magnetization direction along the radial direction and a first sub-magnet having a magnetization direction along the circumferential direction are arranged in a Halbach array so that magnetic flux from the first magnet section is concentrated in the coil section,
In the second magnet section, a plurality of magnets including a second main magnet having a magnetization direction along the axial direction and a second sub-magnet having a magnetization direction along the circumferential direction are arranged in a Halbach array so that magnetic flux from the second magnet section is concentrated in the first magnet section,
the second main magnet is disposed so as to overlap the first main magnet in the axial direction,
The second sub-magnet is disposed so as to overlap the first sub-magnet in the axial direction.
Motor. 2. The motor according to claim 1,
A motor, wherein a length of the first sub magnet along the circumferential direction is shorter than a length of the first main magnet along the circumferential direction. 3. The motor according to claim 1 or 2,
A motor, wherein a thickness of the second magnet portion along the axial direction is thinner than a thickness of the first magnet portion along the axial direction. The motor according to any one of claims 1 to 3,
The coil portion is disposed between the rotating shaft and the first magnet portion. The motor according to any one of claims 1 to 4,
A motor, wherein the second magnet portion is arranged on both sides of the first magnet portion in the axial direction.

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