Motor and robot including motor

Abstract

One purpose of the present invention is to provide a motor which is favorable for cost reduction while suppressing performance degradation. A motor (100) includes: a stator (2) including a core (21) having a plurality of teeth (22) and a plurality of slots (24) extending in a radial direction, and windings (25) wound around the slots (24); and a rotor (3) including a magnet (32) having magnetic poles (33) that face each other in the radial direction with respect to the plurality of teeth (22). The iron core (21) is integrally formed in the circumferential direction, the magnet (32) is formed from a material having a residual magnetic flux density of 1.4 T or more, and the iron core utilization rate of the iron core (21) is less than 60%.

Description

Motors, robots equipped with motors

[0001] This application claims priority based on Japanese Patent Application No. 2024-191178, filed on October 30, 2024. The entire contents of that Japanese application are incorporated herein by reference. Technical Field

[0002] This invention relates to a motor and a robot equipped with the motor. Background Technology

[0003] A motor having a rotor and a stator is known. For example, Patent Document 1 describes an electric motor having: a rotor having a permanent magnet; and a stator having teeth arranged opposite to the rotor. The rotor of this electric motor has an iron core and a permanent magnet disposed in an insertion hole in the iron core, the residual magnetic flux density of the permanent magnet being 1.3T or more.

[0004] Patent Document 1: International Publication No. 2022 / 019074

[0005] The inventors have realized the following: There is a demand for motors that are small, meet desired performance, and are cost-effective. To improve torque performance, high-density winding achieved by manual winding can be considered. However, this method cannot be automated, leading to increased costs. Furthermore, to achieve high-density winding, it is possible to divide the iron core into multiple segments per tooth. However, this method increases subsequent processes such as wiring after winding and requires specialized equipment, thus increasing costs. Moreover, in multi-pole, multi-slot configurations, the width of the core back, which serves as the connecting portion of the segmented cores, becomes narrower, resulting in decreased assemblability. Furthermore, to achieve high-precision assembly, an additional cutting process of the connected iron core is required, further increasing costs.

[0006] In conventional motor designs, reducing winding density to lower costs results in performance degradation. Therefore, conventional motors have limitations in their ability to simultaneously mitigate performance degradation and reduce costs. Summary of the Invention

[0007] The present invention was made in view of the above-mentioned problems, and one of its objectives is to provide a motor that can reduce costs while suppressing performance degradation.

[0008] To address the aforementioned issues, one embodiment of the present invention provides a motor comprising: a stator including an iron core and windings, the iron core having a plurality of radially extending teeth and a plurality of slots, the windings being wound and mounted in the slots; and a rotor including magnets having magnetic poles radially opposed to the plurality of teeth. The iron core is integrally formed circumferentially, the magnets are formed of a material with a residual magnetic flux density of 1.4T or more, and the iron core utilization rate is less than 60%.

[0009] Another embodiment of the present invention is a robot. This robot is equipped with the aforementioned motor.

[0010] Furthermore, any combination of the above-mentioned constituent elements, or embodiments obtained by substituting the constituent elements or expressions of the present invention among methods, systems, etc., are also valid as embodiments of the present invention.

[0011] Invention Effects

[0012] According to the present invention, a motor that can suppress performance degradation while facilitating cost reduction can be provided. Attached Figure Description

[0013] Figure 1 is a cross-sectional view of the motor of the first embodiment, cut in a plane orthogonal to the axial direction.

[0014] Figure 2 is a side view of the robot according to the second embodiment.

[0015] In the diagram: 2-Stator, 3-Rotor, 21-Iron core, 22-Gear, 23-Core back, 24-Slot, 25-Winding, 31-Rotor cylindrical part, 32-Magnet, 33-Magnetic pole, 41-Radial clearance, 100-Motor, 200-Robot. Detailed Implementation

[0016] Hereinafter, the present invention will be described based on preferred embodiments and with reference to the accompanying drawings. In the embodiments and modifications, identical or equivalent constituent elements and components are labeled with the same symbols, and repetitive descriptions are appropriately omitted. Furthermore, the dimensions of components in each drawing are appropriately enlarged or reduced for ease of understanding. Also, components that are not important in the description of the embodiments in each drawing are omitted. Furthermore, when identical or equivalent constituent elements are described separately, uppercase letters such as A, B, and C are added to the end of the symbols for illustrative purposes.

[0017] Furthermore, terms containing numbers such as 1, 2, etc., are used to describe various constituent elements, but these terms are only used to distinguish one constituent element from other constituent elements, and the constituent elements are not limited by these terms.

[0018] [First Implementation]

[0019] Referring to FIG1, the motor 100 according to the first embodiment of the present invention will be described. FIG1 is a cross-sectional view of the motor 100. This figure is a cross-sectional view obtained by cutting along a plane orthogonal to the rotation axis La of the rotor 3 of the motor 100.

[0020] Hereinafter, the direction parallel to the axis of rotation La will be called the "axial direction", and the circumferential direction and radial direction of the circle centered on the axis of rotation La will be called the "circumferential direction" and "radial direction", respectively.

[0021] Motor 100 includes a rotor 3 and a stator 2. Regarding motor 100, any motor with a rotor 3 and a stator 2 will suffice; in this example, it is a radial air gap type internal rotor motor. Motor 100 can also be an external rotor motor. As an example, motor 100 is suitably used to drive the joints of a robot.

[0022] The stator 2 has an iron core 21 having: an annular core back 23 around the rotation axis La; a plurality of teeth 22 extending radially from the core back 23; and a plurality of slots 24 formed between adjacent teeth 22.

[0023] Multiple teeth 22 are arranged at predetermined intervals in the circumferential direction. The number of teeth 22 can be a multiple of 3, but from a performance perspective, 9 or more is preferred; in this example, it is 12. From a productivity perspective, the number of teeth 22 is preferably 18 or less.

[0024] The iron core 21 is a non-segmented core integrally formed in the circumferential direction. The iron core 21 is formed by stacking a specified number of parts made by stamping and cutting electromagnetic steel sheets such as silicon steel sheets in the axial direction and performing insulation treatment.

[0025] The stator 2 has a winding 25 wound and mounted in a slot 24. In this example, the winding 25 is formed by so-called nozzle winding, that is, wire is supplied from the end of a nozzle that rotates around the teeth 22 and wound around the teeth 22. As an example, the winding 25 is a three-phase star connection.

[0026] The rotor 3 includes a hollow cylindrical rotor section 31 surrounding a rotation axis La; and a magnet 32 ​​fastened to the outer periphery of the rotor cylindrical section 31. The rotor 3 is supported by a bearing mechanism (not shown) and is capable of rotating around the rotation axis La. Multiple magnetic poles 33 are magnetized and arranged on the outer peripheral surface of the magnet 32 ​​opposite to the stator 2. Known combinations exist for the number of teeth and magnetic poles, but in this example, the number of magnetic poles 33 is 14. With this combination, the cogging torque is relatively small. The rotor 3 in this example is a surface magnet type, thus allowing the magnetic flux from the magnet 32 ​​to be directly guided to the teeth 22, which is beneficial for high performance.

[0027] In this example, magnet 32 ​​is composed of 14 segmented magnets divided by each magnetic pole. This makes it easy to obtain a relatively high magnetic force. Magnet 32 ​​can be a ring-shaped magnet integrally formed in the circumferential direction. This makes assembly relatively easy. The rotor cylindrical portion 31 is formed of magnetic material and functions as the back yoke of magnet 32. Magnet 32 ​​is surrounded by iron core 21 with a radial gap 41. The radial gap 41 is also referred to as the radial air gap.

[0028] The core utilization rate of the core 21 will be explained. Hereinafter, unless otherwise specified, "area" refers to the cross-sectional area viewed from the axial direction. In conventional motors, the core utilization rate is set to 70% or more by increasing the circumferential width of the teeth and the radial width of the core back 23. However, in the motor 100 of this embodiment, the core utilization rate is set to less than 60% (hereinafter referred to as the "core utilization rate condition"). In this case, the area of ​​the slot 24 is relatively increased, making it easier to achieve neat winding of the winding 25. Furthermore, the core utilization rate can be calculated using Equation 1.

[0029] Core utilization rate R = Area C / (Area C + Area S) × 100% (Equation 1)

[0030] In addition, area C is the total area of ​​iron core 21, and area S is the total area of ​​slot 24.

[0031] The remanent magnetic flux density of magnet 32 ​​will be explained. Hereinafter, unless otherwise specified, "remanent magnetic flux density" refers to the remanent magnetic flux density of the material constituting magnet 32. In conventional motors, magnets with a remanent magnetic flux density of 1.3T or less are used, but in the motor 100 of this embodiment, the remanent magnetic flux density of magnet 32 ​​is 1.4T or more (hereinafter referred to as the "remanent magnetic flux density condition"). In this case, since the flux linkage of winding 25 increases, torque performance can be easily ensured even when the remanent magnetic flux density condition is combined with the core utilization rate condition.

[0032] The slot ratio of winding 25 will be explained. Hereinafter, unless otherwise specified, "slot ratio" refers to the ratio of the effective cross-sectional area of ​​the winding to the area of ​​the slot. In conventional motors, the slot ratio is set to 40% or more to ensure performance. This is easily achieved in split cores, but in non-split cores that are circumferentially integrated, only low-productivity methods such as manual winding can be used, hindering cost reduction. In the motor 100 of this embodiment, the slot ratio of winding 25 is set to less than 40% (hereinafter referred to as the "slot ratio condition"). More preferably, the slot ratio condition can be set to 30% or less. In this case, even in a circumferentially unsplit integrated core, winding 25 can be formed using the aforementioned nozzle winding or fly fork winding, thus easily achieving cost reduction through automation. Even when the slot ratio condition is combined with the core utilization rate condition and the residual flux density condition, performance can be ensured, and cost reduction is also beneficial.

[0033] The radial clearance 41 between magnet 32 ​​and tooth 22 will be explained. Hereinafter, unless otherwise specified, "radial clearance" refers to the difference in radius between the magnet and the tooth. In conventional motors, the radial clearance is set to 2% or more of the stator's outer diameter. At this setting, the magnetic reluctance of the radial clearance is high, preventing the magnet from performing optimally.

[0034] In the motor 100 of this embodiment, the radial clearance 41 between the magnet 32 ​​and the tooth 22 is set to a value greater than 0.4% and less than 1% of the outer diameter of the stator 2 (hereinafter referred to as the "radial clearance condition"). For example, when the outer diameter of the stator 2 is 50 mm, the radial clearance 41 can be set to a value greater than 0.4% and less than 1% of 50 mm, that is, greater than 0.2 mm and less than 0.5 mm. At this time, the magnetic reluctance of the radial clearance decreases, the permeability increases, and the performance of the magnet can be easily utilized. By combining the radial clearance condition with the core utilization rate condition, the residual magnetic flux density condition, and the slot ratio condition, the desired performance can be easily ensured while achieving low cost.

[0035] The surface magnetic flux density of the magnetic poles will be explained. In conventional motors, the maximum value of the surface magnetic flux density of the magnetic poles is set to 0.9T or less when the magnet and tooth are facing each other. However, in the motor 100 of this embodiment, the maximum value of the surface magnetic flux density of the magnetic pole 33 is 1.1T or more when the magnet 32 ​​and tooth 22 are facing each other (hereinafter referred to as the "surface magnetic flux density condition"). At this time, since the flux linkage of the winding 25 increases, torque performance can be easily ensured even when combined with the above-mentioned structural conditions. This surface magnetic flux density condition can be achieved by adjusting the permeability of the magnetic circuit of the magnet 32.

[0036] The operation of the motor 100 according to the embodiment will be explained. In the motor 100, the rotor 3 rotates by torque generated according to the known drive principle of a brushless motor. In the motor 100, if a three-phase drive current is supplied to the winding 25 by a drive circuit not shown, a rotating magnetic field is generated on the inner circumference of the iron core 21. Through the interaction between this rotating magnetic field and the magnetic field of the magnetic poles 33 of the magnet 32, the rotor 3 generates torque relative to the stator 2, and the rotor 3 rotates by this torque.

[0037] The features of the motor 100 according to the first embodiment will be described. The motor 100 includes: a stator 2, which includes an iron core 21 and a winding 25, the iron core 21 having a plurality of radially extending teeth 22 and a plurality of slots 24, the winding 25 being wound and mounted in the slots 24; and a rotor 3, which includes a magnet 32, the magnet 32 ​​having magnetic poles 33 radially opposed to the plurality of teeth 22. The iron core 21 is integrally formed in the circumferential direction, the magnet 32 ​​is formed of a material with a residual magnetic flux density of 1.4T or more, and the iron core utilization rate of the iron core 21 is less than 60%.

[0038] According to this structure, compared to segmented cores, there is no need for the process of connecting the cores to each other after the windings, thus simplifying subsequent processes such as connecting the windings 25 and reducing costs. Furthermore, since it is a single piece, the core 21 has relatively high strength, so even if the width of the core back or teeth is reduced to less than 60% core utilization, it is not easily deformed, ensuring high precision. By reducing the core utilization, the slots are widened, making it easier to align and wind the windings, thus increasing the actual number of windings. By combining magnets 32 with a residual flux density of 1.4T or more on this stator, performance degradation can be minimized. As a result, a motor that reduces costs while suppressing performance degradation can be provided. Additionally, the core utilization is preferably 40% or more.

[0039] As an example, in motor 100, the slot ratio of winding 25 in slot 24 is 30% or less. In this case, compared to a higher slot ratio, the amount of winding is reduced, productivity is improved, and cost reduction is beneficial. Even with a lower slot ratio, performance degradation can be minimized by combining magnets 32 with a residual flux density of 1.4T or more. Furthermore, because the margin in the slots is larger, it is easier for the windings to pass through the nozzle, improving productivity and resulting in more neatly arranged windings. Winding alignment reduces winding resistance, which is beneficial for improving performance. Additionally, a slot ratio of 20% or more is preferred.

[0040] As an example, in motor 100, the radial clearance 41 between magnet 32 ​​and tooth 22 is less than 1% of the outer diameter of stator 2. In this case, the magnetic reluctance observed from magnet 32 ​​decreases, and the magnetic flux density of radial clearance 41 increases to near the remanent magnetic flux density, thus improving performance compared to a larger radial clearance 41. Consequently, even with a core utilization rate of less than 60% and a slot ratio of less than 30%, performance degradation can be minimized. Furthermore, radial clearance 41 is preferably 0.1 mm or more. The outer diameter of stator 2 is the diameter of the cylinder circumscribed around stator 2.

[0041] As an example, in motor 100, with magnet 32 ​​and tooth 22 facing each other, the maximum surface magnetic flux density of magnetic pole 33 is 1.1T or higher. This is more conducive to performance improvement compared to cases with low surface magnetic flux density. In particular, when the core utilization rate is less than 60% and the slot ratio is less than 30%, performance degradation can be minimized.

[0042] As an example, in motor 100, rotor 3 is an inner rotor structure surrounded by stator 2, and the outer peripheral surface of iron core 21 is the outer peripheral surface of motor 100 and has a frameless structure. In this case, since there is no frame, it can be easily assembled into mounted devices such as robots that carry motor 100.

[0043] As an example, in motor 100, the number of teeth 22 is 12, the number of magnetic poles 33 is 14, and the magnets 32 have a segmented structure divided by magnetic poles. In this case, the number of teeth is relatively small, so high-density winding is possible, and productivity can be improved compared to cases with a large number of teeth.

[0044] The above is a description of the first embodiment.

[0045] [Second Implementation]

[0046] Referring to FIG2, the structure of the robot 200 according to the second embodiment will be described. FIG2 is a schematic side view showing the robot 200 according to this embodiment. The robot 200 is a multi-joint robot having multiple arms connected from the end end to the base end via multiple joints. The robot 200 of this embodiment has 6 joints 210 and 6 arms 220. A motor 100 of the first embodiment is assembled in each joint 210. The robot 200 rotates by the rotor 3 of the motor 100, and the arms 220 rotate around the joint 210 to perform a predetermined action.

[0047] The above description is based on the embodiments. These are examples, and various modifications and alterations are possible within the scope of the present invention. Such modifications and alterations fall within the scope of the present invention, as will be understood by those skilled in the art. Therefore, the descriptions and drawings in this specification should be considered exemplary rather than limiting.

[0048] Hereinafter, other variations will be described. In the description and drawings, the same or equivalent components and parts as in the first embodiment are labeled with the same symbols. Explanations that are repeated above are omitted where appropriate, and structures that differ from the above description are described in detail.

[0049] In the description of the embodiments, an example of a rotor 3 being a surface magnet type is shown, but the present invention is not limited thereto. The rotor may be a magnet-embedded type.

[0050] In the description of the embodiments, an example of winding 25 being formed by winding through a nozzle is shown, but the invention is not limited thereto. For example, the winding can also be formed by winding through a so-called fly fork.

[0051] In the description of the embodiments, an example of winding 25 being neatly wound is shown in FIG1, but the present invention is not limited thereto. For example, the winding can be wound in a so-called "interlayer interleaved winding". Interlayer interleaved winding is a configuration in which the upper layer winding is accommodated in the recesses formed between the lower layer windings.

[0052] In the description of the embodiments, an example in which the rotor 3 is hollow is shown, but the present invention is not limited thereto.

[0053] For example, a rotor may have a shaft at its center of rotation.

[0054] These variations can achieve the same function and effect as the first embodiment.

[0055] Any combination of the above-described embodiments and modifications is also effective as an embodiment of the present invention. New embodiments generated by combination possess the effects of both the combined embodiments and modifications.

Claims

1. A motor comprising: a stator including an iron core and windings, the iron core having a plurality of radially extending teeth and a plurality of slots, the windings being wound and mounted in the slots; and a rotor including a magnet having magnetic poles radially opposed to the plurality of teeth, the iron core being integrally formed in the circumferential direction, the magnet being formed of a material having a residual magnetic flux density of 1.4T or more, and the iron core having a core utilization rate of less than 60%.

2. The motor according to claim 1, wherein, The slot ratio of the winding in the slot is less than 30%.

3. The motor according to claim 2, wherein, The radial gap between the magnet and the tooth is less than 1% of the outer diameter of the stator.

4. The motor according to claim 3, wherein, When the magnet and the tooth are facing each other, the maximum value of the surface magnetic flux density of the magnetic pole is 1.1T or more.

5. The motor according to claim 4, wherein, The rotor is an inner rotor structure surrounded by the stator, and has a frameless structure in which the outer peripheral surface of the iron core is the outer peripheral surface of the motor.

6. The motor according to claim 5, wherein, The number of teeth is 12, the number of magnetic poles is 14, and the magnet is a segmented structure divided according to the magnetic poles.

7. A robot having the motor of claim 1.

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