Motors, robots equipped with motors

Abstract

One of the objectives of the present invention is to provide a motor that is advantageous for cost reduction while suppressing performance degradation. [Solution] The motor 100 includes a stator 2 which includes an iron core 21 having a plurality of radially extending teeth 22 and a plurality of slots 24, and windings 25 wound around the slots 24, and a rotor 3 which includes a magnet 32 ​​which has magnetic poles 33 radially opposite to the plurality of teeth 22. The iron core 21 is formed integrally in the circumferential direction, the magnet 32 ​​is made of a material with a residual magnetic flux density of 1.4T or more, and the core utilization rate of the iron core 21 is less than 60%.

Description

Technical Field

[0001] The present invention relates to a motor and a robot provided with the motor.

Background Art

[0002] Motors having a rotor and a stator are known. For example, Patent Document 1 describes an electric motor including a rotor having a permanent magnet and a stator having teeth arranged facing the rotor. The rotor of this electric motor has an iron core and a permanent magnet disposed in an insertion hole of the iron core, and the residual magnetic flux density of the permanent magnet is 1.3 T or more.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The inventor has obtained the following recognition. There is a need for a motor that is small, satisfies desired performance, and can be cost-reduced. In order to increase torque performance, it is conceivable to perform high-density winding by hand winding. However, this method cannot be automated and thus becomes costly. Also, in order to achieve high-density winding, it is conceivable to adopt a split core in which the iron core is divided into a plurality for each tooth. However, with this method, post-processes such as wiring work after winding increase, and it becomes costly because dedicated equipment is used. Further, in a multi-pole multi-slot specification, the core back, which is the connecting portion of the split core, becomes narrow, the assembly property deteriorates, and it becomes costly because a cutting process of the core after connection is added in order to assemble accurately.

[0005] In conventional motor configurations, reducing winding density to lower costs leads to a performance degradation problem. Therefore, conventional motors have been insufficient in providing a motor that is advantageous for cost reduction while minimizing performance degradation.

[0006] This invention has been made in view of these problems, and one of its objectives is to provide a motor that is advantageous for cost reduction while suppressing performance degradation. [Means for solving the problem]

[0007] To solve the above problems, a motor according to one aspect of the present invention comprises a stator including an iron core having a plurality of radially extending teeth and a plurality of slots, and windings wound around the slots, and a rotor including a magnet having magnetic poles radially opposite to the plurality of teeth. The iron core is integrally formed in the circumferential direction, the magnet is made of a material with a residual magnetic flux density of 1.4T or more, and the core utilization rate of the iron core is less than 60%.

[0008] Another aspect of the invention is a robot, which is equipped with the above-mentioned motor.

[0009] Furthermore, any combination of the above components, or in which the components or expressions of the present invention are mutually substituted among methods, systems, etc., are also valid embodiments of the present invention. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a motor that is advantageous for cost reduction while suppressing performance degradation. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view of the motor of the first embodiment, obtained by cutting it with a plane perpendicular to the axial direction. [Figure 2] This is a side view showing the robot of the second embodiment. [Modes for carrying out the invention]

[0012] The present invention will be described below with reference to the drawings, based on preferred embodiments. In embodiments and modifications, the same or equivalent components and members will be denoted by the same reference numerals, and redundant explanations will be omitted as appropriate. In addition, the dimensions of the members in each drawing will be enlarged or reduced as appropriate to facilitate understanding. Furthermore, some members that are not important for explaining the embodiments will be omitted from the drawings. When describing identical or equivalent components separately, uppercase letters such as A, B, and C will be added to the end of the reference numerals.

[0013] Furthermore, while terms including ordinal numbers such as "first" and "second" are used to describe various components, these terms are used solely to distinguish one component from others, and do not limit the components themselves.

[0014] [First Embodiment] A motor 100 according to the first embodiment of the present invention will be described with reference to Figure 1. Figure 1 is a cross-sectional view of the motor 100. This figure is a cross-sectional view taken by a plane perpendicular to the rotation axis La of the rotor 3 of the motor 100.

[0015] Hereafter, the direction parallel to the axis of rotation La will be referred to as the "axial direction," and the circumferential direction and radial direction of a circle centered on the axis of rotation La will be referred to as the "circumferential direction" and "radial direction," respectively.

[0016] The motor 100 includes a rotor 3 and a stator 2. The motor 100 can be any motor having a rotor 3 and a stator 2; in this example, it is a radial gap type inner rotor motor. The motor 100 may also be an outer rotor motor. As an example, the motor 100 is suitably used to drive the joints of a robot.

[0017] The stator 2 comprises an iron core 21 having an annular core back 23 surrounding the axis of rotation La, a plurality of teeth 22 extending radially from the core back 23, and a plurality of slots 24 formed between two adjacent teeth 22.

[0018] The plurality of teeth 22 are arranged at predetermined intervals in the circumferential direction. The number of teeth 22 may be a multiple of 3, but is preferably 9 or more from the viewpoint of ensuring performance, and is 12 in this example. The number of teeth 22 is preferably 18 or less from the viewpoint of ensuring productivity.

[0019] The iron core 21 is an integral non-divided core formed in the circumferential direction. The iron core 21 is formed by stacking a predetermined number of electromagnetic steel sheets such as silicon steel sheets punched by pressing in the axial direction and performing insulation treatment and the like.

[0020] The stator 2 includes windings 25 wound around slots 24. In this example, the windings 25 are formed by so-called nozzle winding, in which an electric wire is supplied from the tip of a nozzle that rotates around the teeth 22 and wound around the teeth 22. As an example, the windings 25 are three-phase star-connected.

[0021] The rotor 3 includes a hollow cylindrical rotor cylindrical portion 31 surrounding the rotation axis La and magnets 32 fixed to the outer periphery of the rotor cylindrical portion 31. The rotor 3 is rotatably supported about the rotation axis La by bearing means not shown. A plurality of magnetic poles 33 are provided on the outer peripheral surface of the magnet 32 facing the stator 2 by magnetization. Although there are known combinations of the number of teeth and the number of magnetic poles, the number of magnetic poles 33 in this example is 14. This combination has relatively small cogging. Since the rotor 3 in this example is a surface magnet type, the magnetic flux from the magnet 32 can be directly guided to the teeth 22, which is advantageous for improving performance.

[0022] The magnet 32 in this example is 14 segment magnets divided for each magnetic pole. In this case, it is relatively easy to obtain a high magnetic force. The magnet 32 may be an annular magnet integrally formed in the circumferential direction. In this case, the assembly is relatively easy. The rotor cylindrical portion 31 is formed of a magnetic material and functions as a back yoke of the magnet 32. The magnet 32 is surrounded by the iron core 21 with a radial gap 41 interposed therebetween. The radial gap 41 is also referred to as a radial gap.

[0023] Explain the core utilization rate of the iron core 21. Hereinafter, unless otherwise specified, the "area" refers to the cross-sectional area viewed from the axial direction. In a conventional motor, the circumferential width of the teeth and the radial width of the core back 23 were increased, and the core utilization rate was set to 70% or more. However, in the motor 100 of the 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 enlarged, making it easier to realize the aligned winding of the winding 25. The core utilization rate can be calculated by Equation 1. Core utilization rate R = Area C / (Area C + Area S) × 100% ·· (Equation 1) Note that Area C is the total area of the iron core 21, and Area S is the total area of the slot 24.

[0024] Explain the residual magnetic flux density of the magnet 32. Hereinafter, unless otherwise specified, the "residual magnetic flux density" refers to the residual magnetic flux density of the material constituting the magnet 32. In a conventional motor, a magnet with a residual magnetic flux density of 1.3 T or less was used. However, in the motor 100 of the embodiment, the residual magnetic flux density of the magnet 32 is 1.4 T or more (hereinafter referred to as the "residual magnetic flux density condition"). In this case, since the magnetic flux linkage number of the winding 25 increases, it becomes easier to ensure the torque performance even when the residual magnetic flux density condition is combined with the core utilization rate condition.

[0025] Explain the occupation ratio of the winding 25. Hereinafter, unless otherwise specified, the "occupation ratio" refers to the ratio of the effective cross-sectional area of the winding to the area of the slot. In a conventional motor, in order to ensure performance, the occupation ratio was set to 40% or more. In this case, it can be easily realized with a split core, but in a non-split core that is integrated in the circumferential direction, only manual winding with low productivity can be used, which has been an obstacle to cost reduction. In the motor 100 of the embodiment, the occupation ratio of the winding 25 is set to 30% or less (hereinafter referred to as the "occupation ratio condition"). In this case, even in an integral core that is not divided in the circumferential direction, the winding 25 can be formed using the above-described nozzle winding or flyer winding, so that cost reduction by automation becomes easy. Combining the occupation ratio condition with the core utilization rate condition and the residual magnetic flux density condition can ensure performance and is also advantageous for cost reduction.

[0026] The radial gap 41 between the magnet 32 ​​and the teeth 22 will be explained. Hereafter, unless otherwise specified, "radial gap" refers to the difference in radius between the magnet and the teeth. In conventional motors, the radial gap was set to 2% or more of the outer diameter of the stator. In this case, the magnetic resistance of the radial gap was large, and the performance of the magnet could not be fully utilized.

[0027] In the motor 100 of this embodiment, the radial gap 41 between the magnet 32 ​​and the teeth 22 is set to a value greater than 0.4% of the outer diameter of the stator 2 and less than 1% (hereinafter referred to as the "radial gap condition"). For example, if the outer diameter of the stator 2 is 50 mm, the radial gap 41 can be set to a value greater than 0.2 mm and less than 0.5 mm, which is greater than 0.4% of 50 mm and less than 1%. In this case, the magnetic resistance of the radial gap is reduced, the permeance coefficient is increased, and the performance of the magnet can be easily achieved. By combining the radial gap condition with the core utilization rate condition, residual magnetic flux density condition, and space factor condition, desired performance can be easily ensured while reducing costs.

[0028] The surface magnetic flux density of the magnetic poles is explained below. In conventional motors, the maximum value of the surface magnetic flux density of the magnetic poles was set to 0.9T or less when the magnets faced the teeth. However, in the motor 100 of this embodiment, the maximum value of the surface magnetic flux density of the magnetic poles 33 is 1.1T or more when the magnets 32 face the teeth 22 (hereinafter referred to as the "surface magnetic flux density condition"). In this case, the number of magnetic flux linkages in the winding 25 increases, making it easier to secure torque performance even when combined with the above-mentioned configuration conditions. This surface magnetic flux density condition can be achieved by adjusting the permeance coefficient of the magnetic circuit of the magnet 32.

[0029] The operation of the motor 100 in this embodiment will now be described. In the motor 100, the rotor 3 rotates due to the torque generated based on the driving principle of a known brushless motor. In the motor 100, when a three-phase drive current is supplied to the winding 25 from a drive circuit (not shown), a rotating magnetic field is generated on the inner circumference of the iron core 21. Due to the interaction between this rotating magnetic field and the magnetic field of the magnetic pole 33 of the magnet 32, torque is generated on the rotor 3 relative to the stator 2, and this torque causes the rotor 3 to rotate.

[0030] The features of the motor 100 of the first embodiment will now be described. The motor 100 includes a stator 2 which includes an iron core 21 having a plurality of radially extending teeth 22 and a plurality of slots 24, and windings 25 wound around the slots 24, and a rotor 3 which includes a magnet 32 ​​which has magnetic poles 33 radially opposite to the plurality of teeth 22. The iron core 21 is formed integrally in the circumferential direction, the magnet 32 ​​is made of a material with a residual magnetic flux density of 1.4T or more, and the core utilization rate of the iron core 21 is less than 60%.

[0031] This configuration eliminates the need to connect cores after winding, compared to a split core, simplifying post-processing such as winding connection 25 and resulting in cost reduction. Furthermore, because the core 21 is a single unit, its strength is relatively high, making it less prone to deformation even when the core back and teeth width are narrowed to less than 60%, thus ensuring high precision. Lowering the core utilization rate widens the slots, making it easier to wind the windings evenly and effectively increasing the number of windings. Combining such a stator with a magnet 32 ​​having a residual magnetic flux density of 1.4T or higher minimizes performance degradation. As a result, a motor that offers cost reduction while minimizing performance degradation can be provided. A core utilization rate of 40% or higher is preferable.

[0032] For example, in motor 100, the space factor of the windings 25 in slot 24 is 30% or less. In this case, the amount of windings is reduced compared to when the space factor is high, which improves productivity and is advantageous for cost reduction. Even with a low space factor, the performance degradation can be minimized by combining it with a magnet 32 ​​having a residual magnetic flux density of 1.4T or more. In addition, the increased space within the slot makes it easier to pass the winding nozzle through, improving productivity and allowing the windings to be more aligned. Aligned windings reduce winding resistance, which is advantageous for performance improvement. A space factor of 20% or more is preferable.

[0033] As an example, in motor 100, the radial gap 41 between the magnet 32 ​​and the teeth 22 is less than 1% of the outer diameter of the stator 2. In this case, the magnetic resistance seen from the magnet 32 ​​is reduced, and the magnetic flux density in the radial gap 41 increases to near the residual magnetic flux density, which is advantageous for performance improvement compared to when the radial gap 41 is large. As a result, performance degradation can be minimized even when combined with a core utilization rate of less than 60% and a space factor of 30% or less. The radial gap 41 is preferably 0.1 mm or larger. The outer diameter of the stator 2 is the diameter of the cylinder that circumscribes the stator 2.

[0034] For example, in motor 100, with the magnet 32 ​​facing the teeth 22, the maximum surface magnetic flux density of the magnetic pole 33 is 1.1T or higher. In this case, it is advantageous for performance improvement compared to when the surface magnetic flux density is low. In particular, performance degradation can be minimized even when combined with a core utilization rate of less than 60% and a space factor of 30% or less.

[0035] As an example, the motor 100 has an inner rotor structure in which the rotor 3 is surrounded by the stator 2, and a frameless structure in which the outer surface of the iron core 21 is the outer surface of the motor 100. In this case, because there is no frame, the motor 100 can be easily incorporated into mounted equipment such as robots.

[0036] For example, in motor 100, there are 12 teeth 22 and 14 magnetic poles 33, and the magnet 32 ​​has a segmented structure divided by magnetic pole. In this case, because the number of teeth is relatively small, high-density winding is possible, and productivity can be improved compared to when there are many teeth.

[0037] The above is a description of the first embodiment.

[0038] [Second Embodiment] Referring to Figure 2, the configuration of the robot 200 according to the second embodiment will be described. Figure 2 is a schematic side view showing the robot 200 according to this embodiment. The robot 200 is an articulated robot having multiple arms connected via multiple joints from the tip end to the base end. The robot 200 of this embodiment has six joints 210 and six arms 220. A motor 100 from the first embodiment is incorporated into each joint 210. The robot 200 performs a predetermined operation by rotating the arms 220 around the joints 210 as the rotor 3 of the motor 100 rotates.

[0039] The above has been explained based on embodiments. These are illustrative examples, and it will be understood by those skilled in the art that various modifications and changes are possible within the scope of the claims of the present invention, and that such modifications and changes are also within the scope of the claims of the present invention. Accordingly, the descriptions and drawings herein should be treated as illustrative rather than limiting.

[0040] Other variations are described below. In this description and drawings, components and members that are the same as or equivalent to those in the first embodiment are denoted by the same reference numerals. Descriptions that overlap with the above description will be omitted as appropriate, and the description will focus on configurations that differ from those described above.

[0041] In the description of the embodiments, an example was shown in which the rotor 3 is of the surface magnet type, but the present invention is not limited to this. The rotor may also be of the embedded magnet type.

[0042] In the description of the embodiments, an example was shown in which the winding 25 is formed by nozzle winding, but the present invention is not limited thereto. For example, the winding may be formed by so-called flyer winding.

[0043] In the description of the embodiments, Figure 1 shows an example in which the windings 25 are wound in an aligned manner, but the present invention is not limited thereto. For example, the windings may be wound in a so-called "barrel winding" configuration. In barrel winding, the upper layer of windings fits into a recess formed between the lower layer of windings.

[0044] In the description of the embodiments, an example was given in which the rotor 3 is hollow, but the present invention is not limited thereto. For example, the rotor may have a shaft at its center of rotation.

[0045] Each of these modifications produces the same functions and effects as the first embodiment.

[0046] Any combination of the embodiments and modifications described above is also useful as an embodiment of the present invention. The new embodiments resulting from these combinations possess the combined effects of both the respective embodiments and modifications. [Explanation of Symbols]

[0047] 2 stator, 3 rotor, 21 core, 22 teeth, 23 core back, 24 slot, 25 winding, 31 rotor cylinder, 32 magnet, 33 magnetic pole, 41 radial clearance, 100 motor, 200 robot.

Claims

1. A stator comprising an iron core having multiple teeth and multiple slots extending in the radial direction, and windings wound around the slots, A rotor including a magnet having magnetic poles radially opposite to the plurality of teeth, The aforementioned iron core is formed integrally in the circumferential direction, The magnet is made of a material with a residual magnetic flux density of 1.4T or higher. A motor in which the utilization rate of the aforementioned iron core is less than 60%.

2. The motor according to claim 1, wherein the space factor of the winding in the slot is 30% or less.

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

4. The motor according to claim 3, wherein, when the magnet is facing the teeth, the maximum value of the surface magnetic flux density of the magnetic pole is 1.1T or more.

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

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

7. A robot comprising the motor described in claim 1.

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