Stator of an axial gap type electric motor

Abstract

To obtain a stator for an axial gap type electric motor that can reduce the cogging torque generated between the rotor and the stator. [Solution] The stator 2 of this axial gap type electric motor comprises a stator core 21, a bobbin 22 provided on the opposing surface 211 of the stator core 21 which faces the rotor 1, and a coil group 23 provided on the opposing surface 211 of the stator core 21 via the bobbin 22, wherein the opposing surface 211 is a flat surface in which no slots are formed.

Description

Technical Field

[0001] This invention relates to a stator of an axial-gap type motor.

Background Art

[0002] Conventionally, a stator of an axial-gap type motor including a stator core and a coil group has been known. A plurality of slots are formed on a facing surface of the stator core that faces the rotor so as to extend in the radial direction. The plurality of slots are arranged side by side in the circumferential direction. The coil group has a plurality of coils. Each of the plurality of coils is inserted into a corresponding slot among the plurality of slots (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the configuration of the stator of the axial-gap type motor described in Patent Document 1, slots are formed in the stator core. As a result, there is a problem that cogging torque is generated between the rotor and the stator.

[0005] This invention has been made to solve the above-described problems, and an object thereof is to provide a stator of an axial-gap type motor capable of reducing cogging torque generated between a rotor and a stator.

Means for Solving the Problems

[0006] The stator of the axial gap type electric motor according to this invention comprises a stator core and a group of coils provided on the opposing surface of the stator core that faces the rotor, wherein the opposing surface is a flat surface in which no slots are formed. In the stator of the axial gap type electric motor according to this invention, the winding method of the coil group is a distributed winding. In the stator of the axial gap type electric motor according to this invention, the coil group comprises a first phase coil group, a second phase coil group, and a third phase coil group, and each of the first phase coil group, the second phase coil group, and the third phase coil group is provided on opposing surfaces. In the stator of the axial gap type electric motor according to this invention, the coil group is fixed to the stator core via adhesive. The stator of the axial gap type electric motor according to this invention comprises a pair of stator cores and a pair of coil groups provided one on each of the opposing surfaces of the pair of stator cores that face the rotor, and each of the opposing surfaces is a flat surface in which no slots are formed. [Effects of the Invention]

[0007] According to the stator of the axial gap type electric motor of this invention, the cogging torque generated between the rotor and the stator can be reduced. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view showing an axial gap type electric motor according to Embodiment 1. [Figure 2] Figure 1 is an exploded perspective view showing an axial gap type electric motor. [Modes for carrying out the invention]

[0009] Embodiment 1. Figure 1 is a perspective view showing an axial gap type motor according to Embodiment 1. Figure 2 is an exploded perspective view showing the axial gap type motor of Figure 1. The axial gap type motor according to Embodiment 1 comprises a rotor 1 and a stator 2.

[0010] The rotor 1 is rotatably supported relative to the stator 2. The direction along the axis of the rotor 1 is defined as the axial direction D1. The direction along the radius of the circle centered on the axis of the rotor 1 in a plane perpendicular to the axis of the rotor 1 is defined as the radial direction D2. The direction along the circumference of the circle centered on the axis of the rotor 1 in a plane perpendicular to the axis of the rotor 1 is defined as the circumferential direction D3.

[0011] The rotor 1 comprises a rotor yoke 11, a rotor holder 12, and a plurality of magnets 13.

[0012] The rotor yoke 11 is made of a magnetic material. The rotor yoke 11 comprises a plurality of rotor yoke pieces 111. The plurality of rotor yoke pieces 111 are arranged in a line in the circumferential direction D3. Each rotor yoke piece 111 is wedge-shaped. Each rotor yoke piece 111 is arranged such that the narrower part faces inward in the radial direction D2 and the wider part faces outward in the radial direction D2.

[0013] The rotor holder 12 is made of a non-magnetic material. The rotor holder 12 comprises a rotor holder center 121, a rotor holder outer periphery 122, and a rotor holder side plate 123.

[0014] The rotor holder center 121 is formed in a disc shape. A through hole 121a is formed in the inner portion of the rotor holder center 121 in the radial direction D2. The shaft 3 is inserted into the through hole 121a. The rotor holder center 121 is fixed to the shaft 3. Therefore, the rotor holder center 121 rotates together with the shaft 3 in the circumferential direction D3.

[0015] The outer circumference 122 of the rotor holder is formed in an annular shape. The outer circumference 122 of the rotor holder is positioned radially outward in the direction D2 relative to the center 121 of the rotor holder. The outer circumference 122 of the rotor holder is positioned so as to overlap with the center 121 of the rotor holder in the direction D2. The outer circumference 122 of the rotor holder is positioned coaxially with the center 121 of the rotor holder.

[0016] The rotor holder side plate portion 123 is positioned closer to the stator 2 than the rotor yoke 11 and the multiple magnets 13. The rotor holder side plate portion 123 is formed in a disc shape. The rotor holder side plate portion 123 is positioned across the rotor holder center 121 and the rotor holder outer periphery 122. The rotor holder side plate portion 123 is fixed to both the rotor holder center 121 and the rotor holder outer periphery 122. Therefore, the rotor holder 12 rotates in the circumferential direction D3 together with the shaft 3.

[0017] Multiple through holes 123a are formed in the rotor holder side plate portion 123 in the portion radially D2 outside the rotor holder center 121, penetrating the rotor holder side plate portion 123 in the thickness direction. The multiple through holes 123a are arranged in a line in the circumferential direction D3. The formation of multiple through holes 123a in the rotor holder side plate portion 123 reduces the weight of the rotor holder side plate portion 123.

[0018] Multiple through holes 123a are formed in the rotor holder side plate portion 123, thereby forming multiple support rods 123b on the rotor holder side plate portion 123. The multiple support rods 123b are arranged in a line in the circumferential direction D3. The multiple support rods 123b prevent the multiple rotor yoke pieces 111 and the multiple magnets 13 from detaching from the rotor holder 12 towards the stator 2 side.

[0019] Note that the rotor 1 may be provided on the side opposite to the stator 2 with respect to the rotor yoke 11 and the plurality of magnets 13, and may further include a rotor holder side plate portion similar to the rotor holder side plate portion 123. Thereby, the plurality of rotor yoke pieces 111 and the plurality of magnets 13 are suppressed from coming off the rotor holder 12 on the side opposite to the stator 2.

[0020] The plurality of magnets 13 are arranged side by side in the circumferential direction D3. The plurality of magnets 13 are arranged one by one between the respective rotor yoke pieces 111 arranged side by side in the circumferential direction D3. Each magnet 13 is magnetized in the circumferential direction D3. Each magnet 13 is arranged such that the poles on the opposing surfaces of a pair of mutually adjacent magnets 13 in the circumferential direction D3 coincide with each other. By arranging one magnet 13 between each of the plurality of rotor yoke pieces 111 arranged side by side in the circumferential direction D3, the axial gap type motor according to Embodiment 1 is an IPM motor.

[0021] If the number of pole pairs of the rotor 1 is n, the number of magnets 13 is 2×n. n is an integer of 1 or more. For example, when the number of pole pairs of the rotor 1 is 20, the number of magnets 13 is 40.

[0022] The stator 2 is arranged to face the rotor 1 in the axial direction D1. The stator 2 includes a stator core 21, a bobbin 22, and a coil group 23.

[0023] The shape of the stator core 21 is formed in an annular shape. The stator core 21 is made of a magnetic material. The surface of the stator core 21 facing the rotor 1 is defined as the opposing surface 211. The opposing surface 211 is a flat surface on which no slots are formed.

[0024] The shape of the bobbin 22 is formed in an annular shape. The bobbin 22 is provided on the opposing surface 211 of the stator core 21.

[0025] The coil group 23 comprises multiple coils. The coil group 23 is mounted on the stator core 21 via a bobbin 22. The coil group 23 is fixed to the stator core 21 via an adhesive (not shown). Any adhesive that can bond the coil group 23 to the stator core 21 is acceptable. Therefore, adhesives include, for example, varnish and molding materials.

[0026] The winding method of coil group 23 is distributed winding. Coil group 23 has a first-phase coil group 231, a second-phase coil group 232, and a third-phase coil group 233. Each of the first-phase coil group 231, the second-phase coil group 232, and the third-phase coil group 233 has multiple coils. Each of the first-phase coil group 231, the second-phase coil group 232, and the third-phase coil group 233 is provided on the opposing surface 211.

[0027] The number of coils in each of the first-phase coil group 231, the second-phase coil group 232, and the third-phase coil group 233 is n+1.

[0028] The portion of each coil in coil group 23 that lies along its radial direction is defined as the radial portion. Each coil has two radial portions. The total number of radial portions in coil group 23 is calculated by multiplying the number of coils in each of the first-phase coil group 231, second-phase coil group 232, and third-phase coil group 233 by the number of radial portions in each coil and the total number of radial portions in the first-phase coil group 231, second-phase coil group 232, and third-phase coil group 233. Therefore, the total number of radial portions in coil group 23 is (n+1) × 2 × 3.

[0029] The portion of the opposing surface 211 where the radial portions of the coils overlap is defined as a slot. If all the radial portions of the coils overlap into separate slots, the number of slots will be (n+1) × 2 × 3. Because the opposing surface 211 of the stator core 21 is flat, the number of slots can be other than (n+1) × 2 × 3.

[0030] Because the opposing surface 211 is a flat surface, the position of each coil in the coil group 23 relative to the stator core 21 can be freely determined, compared to the case where slots are formed on the opposing surface 211. This makes it easy to perform distributed winding for each coil in the coil group 23.

[0031] When slots are formed on the opposing surface 211, cogging torque is generated between the rotor 1 and the stator 2. Cogging torque is generated by the attractive force between the magnet 13 and the teeth of the stator core 21. Because the opposing surface 211 is a flat surface, the cogging torque generated between the rotor 1 and the stator 2 is reduced compared to when slots are formed on the opposing surface 211.

[0032] Next, the operation of the axial gap type motor according to Embodiment 1 will be described. When current is supplied to each coil of the coil group 23 from an external power source (not shown), a magnetic field is generated around each coil. Due to the interaction between the magnetic field generated in the stator 2 and the magnetic force of the magnet 13 in the rotor 1, the rotor 1 rotates in the circumferential direction D3 relative to the stator 2.

[0033] Because the opposing surface 211 of the stator core 21 is a flat surface, cogging torque is not generated between the rotor 1 and the stator 2. As a result, the rotor 1 can rotate smoothly in the circumferential direction D3 relative to the stator 2.

[0034] As described above, the stator 2 of the axial gap type electric motor according to Embodiment 1 comprises a stator core 21 and a coil group 23. The coil group 23 is provided on the opposing surface 211 of the stator core 21, which is the surface facing the rotor 1. The opposing surface 211 is a flat surface in which no slots are formed. With this configuration, the cogging torque generated between the rotor 1 and the stator 2 can be reduced. By reducing the cogging torque, the axial gap type electric motor can be made quieter. In addition, because the opposing surface 211 of the stator core 21 is a flat surface, the iron loss generated in the stator core 21 can be reduced.

[0035] Furthermore, in the stator 2 of the axial gap type electric motor according to Embodiment 1, the winding method of the coil group 23 is a distributed winding. With this configuration, because the opposing surface 211 is a flat surface, the position of each coil of the coil group 23 in the circumferential direction D3 relative to the stator core 21 can be freely determined. This makes it easy to perform a distributed winding for each coil of the coil group 23.

[0036] Furthermore, in the stator 2 of the axial gap type electric motor according to Embodiment 1, the coil group 23 includes a first-phase coil group 231, a second-phase coil group 232, and a third-phase coil group 233. Each of the first-phase coil group 231, the second-phase coil group 232, and the third-phase coil group 233 is provided on the opposing surface 211. With this configuration, the axial dimension D1 in the stator core 21 can be reduced because the opposing surface 211 is a flat surface. As a result, the axial dimension D1 in the stator 2, where each of the first-phase coil group 231, the second-phase coil group 232, and the third-phase coil group 233 is provided on the opposing surface 211, can be reduced.

[0037] Furthermore, in the stator 2 of the axial gap type electric motor according to Embodiment 1, the coil group 23 is fixed to the stator core 21 via adhesive. With this configuration, each coil of the coil group 23 can be fixed to the stator core 21 while freely determining the position D3 in the circumferential direction relative to the stator core 21 for each coil of the coil group 23.

[0038] In the axial gap type motor according to Embodiment 1, a configuration in which the stator core 21 is formed in an annular shape was described. However, the configuration is not limited to this. For example, the stator core 21 may be divided in the circumferential direction D3.

[0039] Furthermore, in the axial gap type motor according to Embodiment 1, a configuration in which the stator 2 is equipped with a bobbin 22 has been described. However, the configuration is not limited to this. For example, the stator 2 may be configured not to be equipped with a bobbin 22. Even in this case, the coil group 23 is fixed in an insulated state from the stator 2.

[0040] Furthermore, the axial gap type motor according to Embodiment 1 was described in which a configuration comprising one stator core 21 and one coil group 23 was provided. However, the configuration is not limited to this. For example, a configuration comprising a pair of stator cores 21 and a pair of coil groups 23 is also possible. In this case, one coil group 23 is provided on each of the opposing surfaces 211 of the pair of stator cores 21 that face the rotor 1. Each opposing surface 211 is a flat surface in which no slots are formed.

[0041] Although an axial gap type motor according to preferred embodiment 1 has been described above, the invention is not limited to the axial gap type motor according to embodiment 1 described above. Various modifications and transformations can be made to the axial gap type motor according to embodiment 1 described above without departing from the scope of the claims. [Explanation of Symbols]

[0042] 1 Rotor, 2 Stator, 3 Shaft, 11 Rotor yoke, 12 Rotor holder, 13 Magnet, 21 Stator core, 22 Bobbin, 23 Coil group, 111 Rotor yoke piece, 121 Rotor holder center, 121a Through hole, 122 Rotor holder outer circumference, 123 Rotor holder side plate, 123a Through hole, 123b Support rod, 211 Opposing surface, 231 First phase coil group, 232 Second phase coil group, 233 Third phase coil group.

Claims

1. Stator core (21) and A group of coils (23) is provided on the opposing surface (211) of the stator core (21) which is the surface facing the rotor (1), Equipped with, The stator of an axial gap type electric motor has a flat surface in which no slots are formed on the opposing surface (211).

2. The stator of the axial gap type electric motor according to claim 1, wherein the winding method of the coil group (23) is a distributed winding.

3. The coil group (23) comprises a first-phase coil group (231), a second-phase coil group (232), and a third-phase coil group (233). The stator of an axial gap type electric motor according to claim 1 or claim 2, wherein each of the first phase coil group (231), the second phase coil group (232), and the third phase coil group (233) is provided on the opposing surface (211).

4. The stator of an axial gap type electric motor according to claim 1 or claim 2, wherein the coil group (23) is fixed to the stator core (21) via adhesive.

5. A pair of stator cores (21) and A pair of coil groups (23) are provided on each of the opposing surfaces (211) of the pair of stator cores (21) that face the rotor (1), Equipped with, The stator of an axial gap type electric motor, wherein each of the aforementioned opposing surfaces (211) is a flat surface in which no slots are formed.

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