Electric motor

Abstract

To provide an electric motor capable of generating low-speed high torque.SOLUTION: A rotor 120 includes a plurality of magnetic poles 122 each extending in a first direction D1, and is rotatable about a rotation axis 102. A stator 110 includes a plurality of electromagnet groups 130 arranged in a circumferential direction. Each of the electromagnet groups 130 includes a plurality of electromagnets 132 arranged in a second direction D2 which is not parallel with the first direction D1. The stator 110 is formed in such a way that a translational magnetic field generated by the plurality of electromagnets 132 moves in the second direction D2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to electric motors. [Background technology]

[0002] Electric motors that rotate at low speeds are required for applications such as high-performance robots. Conventionally, in order to obtain low-speed rotational motion, it was necessary to decelerate the rotational motion of an electric motor that rotates at medium or high speeds using a deceleration means such as a gear, which is a mechanical component.

[0003] In order to achieve low-speed rotation without using mechanical parts, electric motors with magnetic reduction gears (magnetic geared motors) have been proposed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2023-000506 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, magnetic geared motors have problems such as a complex structure, difficulty in reducing their size and weight, and high costs.

[0006] The present disclosure has been made in light of the above circumstances, and one of its exemplary objectives is to provide an electric motor capable of generating high torque at low speed. [Means for solving the problem]

[0007] An electric motor according to an embodiment of the present disclosure includes a stator having a multi-phase stator winding and a stator core, and a rotor including a plurality of magnetic poles each extending in a first direction and rotatable about a rotation axis. The stator has a plurality of electromagnet groups arranged in a circumferential direction, and each electromagnet group includes a plurality of electromagnets arranged in a second direction non-parallel to the first direction. The stator is configured such that a translational magnetic field generated by the plurality of electromagnets moves in the second direction.

[0008] Any combination of the above components, or mutual substitution of components or expressions between methods, devices, systems, etc., are also effective as aspects of the present invention or the present disclosure. Furthermore, the description in this section (Means for Solving the Problems) does not explain all essential features of the present invention, and therefore, subcombinations of the described features may also constitute the present invention. Effect of the Invention

[0009] According to one aspect of the present disclosure, low speed and high torque can be achieved with a simple configuration. [Brief description of the drawings]

[0010] [Figure 1] 1 is a perspective view of an electric motor according to an embodiment; [Diagram 2] FIG. 2 is a plan view of the electric motor of FIG. 1, seen along the rotation shaft. [Diagram 3] 2 is a diagram showing the positional relationship between a plurality of electromagnet groups and a plurality of magnetic poles in the electric motor of FIG. 1. [Figure 4] 4(a) to (f) are diagrams illustrating the translational magnetic field of the motor. [Diagram 5] FIG. 2 is a diagram illustrating the rotation angle of a rotor of an electric motor. [Figure 6] FIG. 2 is a perspective view showing a portion of a stator according to an embodiment. [Figure 7] FIG. 7 is a cross-sectional view of the electromagnet group in FIG. 6. [Figure 8] FIG. 2 is a perspective view showing a stator according to an embodiment. [Figure 9]FIG. 9 is a cross-sectional view of the stator of FIG. 8. [Figure 10] FIG. 11 is a perspective view of an electric motor according to a first modified example. [Figure 11] 11 is a diagram showing the positional relationship between a plurality of electromagnet groups and a plurality of magnetic poles in the electric motor of FIG. 10. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (Overview of the embodiment) A summary of some exemplary embodiments of the present disclosure will be described. This summary is intended to provide a simplified overview of some concepts of one or more embodiments for a basic understanding of the embodiments as a prelude to the detailed description that follows, and is not intended to limit the scope of the invention or disclosure. This summary is not intended to be an exhaustive overview of all possible embodiments, nor is it intended to identify key elements of all embodiments or to delineate the scope of some or all aspects. For convenience, the term "one embodiment" may be used to refer to one embodiment (example or variant) or multiple embodiments (examples or variants) disclosed in this specification.

[0012] An electric motor according to one embodiment includes a stator having a multi-phase stator winding and a stator core, and a rotor including a plurality of magnetic poles each extending in a first direction and rotatable about a rotation axis. The stator has a plurality of electromagnet groups arranged in a circumferential direction, and each electromagnet group includes a plurality of electromagnets arranged in a second direction non-parallel to the first direction. The stator is configured such that a translational magnetic field generated by the plurality of electromagnets moves in the second direction.

[0013] When the angle between the first direction and the second direction is α, the travel distance of the permanent magnet is reduced by a constant (<1) times that corresponds to α. This makes it possible to achieve low-speed, high-torque rotation.

[0014] The operation of this electric motor can be understood by analogy with a worm reducer, which is a mechanical component. In other words, if the translational magnetic field of the stator is likened to the rotation of the worm in a worm reducer, it is equivalent to the rotor, which corresponds to the worm wheel, rotating at a reduced speed.

[0015] In one embodiment, the first direction may be non-parallel to the axis of rotation and the second direction may be parallel to the axis of rotation.

[0016] In one embodiment, the first direction may be parallel to the axis of rotation and the second direction may be non-parallel to the axis of rotation.

[0017] In one embodiment, the multiple magnetic poles may be permanent magnets.

[0018] In one embodiment, the plurality of magnetic poles may be salient poles.

[0019] (Embodiment) The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing are given the same reference numerals, and duplicated descriptions are omitted as appropriate. In addition, the embodiments are illustrative rather than limiting the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0020] 1 is a perspective view of an electric motor 100 according to an embodiment. The electric motor 100 includes a stator 110 and a rotor 120. The electric motor 100 according to this embodiment is an inner rotor type permanent magnet motor.

[0021] The rotor 120 is rotatable around the rotation axis 102. The rotor 120 includes a plurality of magnetic poles 122_1 to 122_M. In this embodiment, the magnetic poles 122 are permanent magnets, and in this example, the number of poles M is 12. The plurality of permanent magnets are arranged such that the orientation of the magnetic poles alternates in the circumferential direction. The direction in which the magnetic poles 122 extend is referred to as a first direction D1.

[0022] The stator 110 includes a plurality of N electromagnet groups 130_1 to 130_N. The plurality of electromagnet groups 130_1 to 130_N are arranged at equal intervals in the circumferential direction. In this example, N=6, and the number of pole pairs of the stator 110 is two.

[0023] Each electromagnet group 130 includes a plurality of electromagnets 132_1 to 132_P arranged in a second direction D2 non-parallel to the first direction D1. In this example, P=6. Note that the first direction D1 and the second direction D2 are considered to be directions in a state in which the side surface of a cylinder (cylinder) is developed onto a plane.

[0024] In this embodiment, each magnetic pole 122 is twisted, with the first direction D1 being inclined with respect to the axis of rotation 102. The second direction D2 is parallel to the axis of rotation 102.

[0025] The multiple electromagnet groups 130_1 to 130_N, in other words the multiple electromagnets 132, are configured with a multi-phase stator winding and a stator core, as described below. The stator 110 is configured so that the magnetic field generated by the stator 110 moves in a second direction D2 according to the current flowing through the multi-phase stator winding. In a typical electric motor, the magnetic field generated by the stator is a rotating magnetic field that moves in the circumferential direction. Hereinafter, the magnetic field generated by the stator 110 in this embodiment will be referred to as a translational magnetic field or a moving magnetic field.

[0026] Fig. 2 is a plan view of the electric motor 100 of Fig. 1 as viewed along the rotating shaft 102. When M = 12, the interval (called rotor pitch) θr between adjacent magnetic poles 122 is 30°. When N = 6, the interval (called stator pitch) θs between adjacent electromagnets 132 is 60°.

[0027] Fig. 3 is a diagram showing the positional relationship between the multiple electromagnet groups 130 and the multiple magnetic poles 122 in the electric motor 100 of Fig. 1. The horizontal axis indicates the circumferential position (angle). The magnetic poles 122 are twisted by θs.

[0028] In general, the magnetic poles 122 are twisted by ps×θs, where ps is the number of pole pairs of the stator winding, and θs is the stator pitch.

[0029] 4(a) to 4(f) are diagrams for explaining the translational magnetic field of the electric motor 100. 4(a) to 4(f) show the state of the translational magnetic field over one period (360°) of the electrical angle φ.

[0030] φ=0° As shown in FIG. 4(a), in each of the plurality of electromagnet groups 130, the electromagnet 132_1 serves as a south pole and the electromagnet 132_4 serves as a north pole. φ=60° As shown in FIG. 4(b), in each of the plurality of electromagnet groups 130, the electromagnet 132_2 serves as a south pole and the electromagnet 132_5 serves as a north pole. φ=120° As shown in FIG. 4(c), in each of the plurality of electromagnet groups 130, the electromagnet 132_3 serves as a south pole and the electromagnet 132_6 serves as a north pole. φ=180° As shown in FIG. 4(d), in each of the plurality of electromagnet groups 130, the electromagnet 132_4 serves as a south pole and the electromagnet 132_1 serves as a north pole. φ=240° As shown in FIG. 4(e), in each of the plurality of electromagnet groups 130, the electromagnet 132_5 serves as a south pole and the electromagnet 132_2 serves as a north pole. φ=300° As shown in FIG. 4(f), in each of the plurality of electromagnet groups 130, the electromagnet 132_6 serves as a south pole and the electromagnet 132_3 serves as a north pole.

[0031] The translational magnetic field moves in the axial direction of the rotor while maintaining the spacing between the rows in the circumferential direction. With respect to the translational magnetic field of one period (360°) of the electrical angle φ, the rotor 120 rotates by an amount equal to the stator pitch θs.

[0032] Next, the advantages of the electric motor 100 will be described.

[0033] 5 is a diagram illustrating the rotation angle of the rotor of the electric motor 100. During one period (360°) of the electrical angle φ, the translational magnetic field moves a distance a, and the rotor 120 rotates a distance b. If the angle between the first direction D1 and the second direction D2 is α, then there is a relationship between the rotational distance b of the rotor 120 and the moving distance a of the translational magnetic field as follows: b = a tan α The following relationship holds. When α<45°, tan α<1. In other words, the rotation distance b of the rotor 120 is compressed by a certain number (tan α) times the moving distance a of the translational magnetic field, enabling low-speed rotation. At this time, the torque becomes 1 / tan α times, and high torque can be obtained.

[0034] The operation of the electric motor 100 can be understood by analogy with a worm reducer, which is a mechanical component. That is, the translational magnetic field generated by the stator 110 can be associated with the rotation of the worm in the worm reducer, and at this time, the rotor 120, which corresponds to the worm wheel, rotates at a reduced speed.

[0035] The electric motor 100 is unique in that the stator 110 generates a rotational force not by a rotating magnetic field but by a translational magnetic field including a vector component in the direction of the rotation axis. There are examples of magnetic worm reducers in which the teeth of the worm and worm wheel are replaced with permanent magnets arranged in a spiral shape, but the present disclosure differs in that it does not require the rotation of the worm, and the structure can be significantly simplified.

[0036] Next, a configuration example of the stator 110 will be described.

[0037] Fig. 6 is a perspective view showing a portion of a stator 110A according to an embodiment. One electromagnet group 130A of the stator 110A is shown in Fig. 6. In this example, P=3, and the electromagnet group 130A includes three electromagnets 132_1 to 132_3 adjacent to each other in a second direction D2 parallel to the rotation axis 102.

[0038] Fig. 7 is a cross-sectional view of the electromagnet group 130A of Fig. 6. The electromagnet group 130A includes a stator winding 112 and a stator core 114A. The stator core 114 has three protruding portions 116, and three-phase stator windings 112U, 112V, and 112W are wound around each of the protruding portions 116.

[0039] FIG. 8 is a perspective view showing a stator 110B according to an embodiment. A part of the stator 110B is cut away to show the internal structure of the stator 110B. The stator 110B is a claw-pole type stator, and includes a plurality of (six in this example) stator windings 112 and a stator core 114B. The stator core 114B has a plurality of (six in this example) annular cores 118 stacked in the direction of the rotating shaft 102. The annular cores 118 have claw poles (claws) 119 formed in portions corresponding to electromagnets 132 (also called inductors) on the inner periphery side facing a rotor (not shown). The stator windings 112 are wound inside each core 118.

[0040] FIG. 9 is a cross-sectional view of the stator 110B of FIG.

[0041] The configuration of stator 110 is not limited to those shown in Figs. 6 to 9, and may be configured using other known techniques, or may be configured using techniques that will be available in the future.

[0042] The present invention has been described above based on an embodiment. This embodiment is merely an example, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each processing step, and that such modifications are also within the scope of the present invention. Such modifications will be described below.

[0043] (Variation 1) 10 is a perspective view of an electric motor 100C according to Modification 1. In this modification, the extension direction of the magnetic poles 122 is parallel to the rotation axis 102, the arrangement direction of the electromagnets 132 in the electromagnet group 130 is non-parallel to the rotation axis 102, and the multiple electromagnets 132 are arranged with a circumferential rotation in the direction of the rotation axis 102.

[0044] FIG. 11 is a diagram showing the positional relationship between the plurality of electromagnet groups 130 and the plurality of magnetic poles 122 in the electric motor 100C of FIG.

[0045] 11, the movement distance of the translational magnetic field for one period of electrical angle is indicated by arrow a, and the corresponding rotation distance of the rotor 120 is indicated by arrow b. If the angle between the first direction D1 and the second direction D2 is α, then the relationship between the rotation distance b of the rotor 120 and the movement distance a of the translational magnetic field is as follows: b = a sinα The following relationship holds. Since sinα<1, the rotation distance b of the rotor 120 is compressed by a certain number (sinα) times the moving distance a of the translational magnetic field, enabling low-speed rotation. At this time, the torque becomes 1 / (sinα) times, and high torque can be obtained.

[0046] (Variation 2) The electric motor is not limited to a permanent magnet motor, and may be a reluctance motor. In this case, the magnetic poles 122 can be realized by a soft magnetic material formed so that the magnetic resistance has periodicity (salient poles) in the circumferential direction.

[0047] (Variation 3) The number M of magnetic poles 122, the number N of electromagnet groups 130, and the number P of electromagnets 132 included in the electromagnet group 130 are not limited to the combinations described in the embodiment, and it will be understood by those skilled in the art that there are various variations in these combinations and that such variations are also within the scope of the present invention.

[0048] (Variation 4) Both a first direction D1 in which the magnetic poles 122 extend and a second direction D2 in which the electromagnets 132 that form the electromagnet group 130 adjoin each other may be non-parallel to the rotation axis 102.

[0049] (Variation 5) Although the embodiment has been described as an inner rotor type, the technology according to the present disclosure can also be applied to an outer rotor type, and the outer rotor type is also included in the scope of the present invention.

[0050] The present invention has been described using specific terms based on the embodiments, but the embodiments merely illustrate the principles and applications of the present invention, and many modifications and changes in arrangement are permitted to the embodiments without departing from the spirit of the present invention as defined in the claims. [Explanation of symbols]

[0051] 100 Electric motor 102 Rotation axis 110 Stator 112 Stator Winding 114 Stator Core 120 Rotor 122 magnetic pole 130 Electromagnet group 132 Electromagnet D1 1st direction D2 2nd direction

Claims

1. a stator having a multi-phase stator winding and a stator core; a rotor including a plurality of magnetic poles each extending in a first direction and rotatable about a rotation axis; Equipped with the stator has a plurality of electromagnet groups arranged in a circumferential direction, each electromagnet group including a plurality of electromagnets arranged in a second direction non-parallel to the first direction; The electric motor, wherein the stator is configured such that a translational magnetic field generated by the plurality of electromagnets moves in the second direction.

2. 2. The electric motor of claim 1, wherein the first direction is non-parallel to the axis of rotation, and the second direction is parallel to the axis of rotation.

3. 2. The electric motor of claim 1, wherein the first direction is parallel to the axis of rotation and the second direction is non-parallel to the axis of rotation.

4. 4. The electric motor according to claim 1, wherein the plurality of magnetic poles are permanent magnets.

5. 4. The electric motor according to claim 1, wherein the plurality of magnetic poles are salient poles.

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