Axial gap type motor

Abstract

This axial gap motor includes a rotor, and a stator disposed facing the rotor in an axial direction. The rotor is provided with a rotor core formed of an electromagnetic steel sheet stacked in a radial direction, a magnet embedded in the rotor core, and a space that is disposed between the magnet and the stator and is formed by the electromagnetic steel sheet. The volume of the space is greater on the inner-peripheral side of the rotor than on the outer-peripheral side of the rotor.

Description

Technical Field

[0001] The present disclosure relates to an axial-gap type motor.

Background Art

[0002] Conventionally, an axial-gap type motor having a rotor and a stator arranged in the direction in which the rotation axis of the rotor extends is known (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] In the axial-gap type motor of Patent Document 1, a structure is adopted in which magnets are attached to the entire surface of the rotor. In the axial-gap type motor of Patent Document 1, magnet torque generated by magnetic flux formed between the magnets and the coils of the stator is utilized. However, generally, in addition to magnet torque, a motor can improve torque by utilizing reluctance torque generated by a change in magnetic flux.

[0005] An object of the present disclosure is to provide an axial-gap type motor in which reluctance torque is generated.

Means for Solving the Problems

[0006] The axial gap motor according to this disclosure is an axial gap motor having a rotor and a stator arranged axially opposite to the rotor, wherein the rotor comprises a rotor core formed of radially stacked electromagnetic steel sheets, magnets embedded in the rotor core, and a space formed of the electromagnetic steel sheets and disposed between the magnets and the stator, the volume of the space being larger on the inner circumference side of the rotor than on the outer circumference side of the rotor. [Effects of the Invention]

[0007] According to this disclosure, an axial gap type motor that generates reluctance torque can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] A diagram of an axial gap motor according to one embodiment of the present disclosure. [Figure 2] A view of an axial gap motor according to the first embodiment of this disclosure, as seen from the rotor surface side. [Figure 3] Cross-sectional view AA in Figure 2. [Figure 4] This is a schematic axial view showing the magnetic flux state on the outer and inner sides of the rotor. (a) is a cross-sectional view of section II (outer side of the rotor) in Figure 3, and (b) is a cross-sectional view of section II-II (inner side of the rotor) in Figure 3. [Figure 5] A view of an axial gap motor according to a second embodiment of this disclosure, as seen from the rotor surface side. [Figure 6] Figure 5 shows a cross-sectional view of BB. [Figure 7] A view of an axial gap motor according to the third embodiment of this disclosure, as seen from the rotor surface side. [Figure 8] Cross-sectional view of CC in Figure 7. [Figure 9] A view of an axial gap motor according to the fourth embodiment of this disclosure, as seen from the rotor surface side. [Modes for carrying out the invention]

[0009] The axial gap motor 1 of this embodiment is a motor connected to a drive battery (not shown) mounted on a vehicle via an inverter (not shown). The vehicle is a plug-in hybrid vehicle (PHEV) or electric vehicle capable of external charging or external power supply.

[0010] <First Embodiment> A first embodiment of this disclosure will be described with reference to the drawings. As shown in Figure 1, the axial gap motor 1 includes a stator 2 and a rotor 4. In the following specification and drawings, the axial direction is denoted as X, the circumferential direction of the stator 2 and rotor 4 is denoted as R, and the radial direction of the stator 2 and rotor 4 is denoted as D, with the axis O of the axial gap motor 1 (see the center line in Figure 1) as the center.

[0011] The stator 2 is positioned opposite the rotor 4 in the axial direction X, and with a gap between it and the rotor 4. The stator 2 has multiple coils 6. Each coil 6 has copper wire wound around an iron core made of an iron core material (e.g., electrical steel sheet). As shown in Figure 3, the copper wire is wound in a direction perpendicular to the axial direction X. Therefore, when electricity flows through the copper wire, it generates a magnetic flux in the axial direction X (see the magnetic flux MS shown by the dashed line in Figure 3). The stator 2 is fixed to a motor housing (not shown) or the like. In this embodiment, six stators 2 are arranged in a row in the circumferential direction R.

[0012] As shown in Figure 2, the rotor 4 comprises a rotor core 8 and a plurality of first magnets 10 embedded in the rotor core 8. In this embodiment, the rotor 4 further comprises second magnets 12 positioned between the plurality of first magnets 10.

[0013] The rotor 4 is rotatably mounted on the motor housing. The rotor 4 in this embodiment is cylindrical in shape. As shown in Figure 3, the rotor 4 further comprises a back surface 4b which faces the stator 2, a front surface 4a (an example of an opposite surface) on the opposite side of the rotor core 8 between the back surface 4b and the rotor core 8, and a cylindrical motor shaft mounting hole 4c located at the center of the cylindrical shape, to which a motor shaft (not shown) can be fixed. The rotor 4 rotates the motor shaft fixed in the motor shaft mounting hole 4c.

[0014] The rotor core 8 is formed by concentrically winding electromagnetic steel sheets around the motor shaft mounting hole 4c and stacking the electromagnetic steel sheets radially in the direction D. The rotor core 8 holds the first magnet 10 and the second magnet 12, and also functions as a yoke that collects the magnetic flux generated by the multiple first magnets 10 and the multiple second magnets 12. Electromagnetic steel sheets have the characteristic of easily passing magnetic flux on the same plane. Therefore, the rotor core 8 has the characteristic that magnetic flux easily passes in the axial direction X, while magnetic flux does not easily pass in the radial direction D compared to the axial direction X.

[0015] As shown in Figure 2, multiple first magnets 10 are arranged around the motor shaft mounting hole 4c of the rotor 4. In this embodiment, the first magnets 10 are permanent magnets. The first magnets 10 are arranged alternately with a gap between the south pole and north pole in the circumferential direction R. In this embodiment, six first magnets 10 are arranged. As shown in Figure 3, the first magnets 10 are arranged with the north pole and south pole adjacent to each other when viewed in the axial direction X.

[0016] As shown in FIG. 2, a plurality of second magnets 12 are arranged around the motor shaft mounting hole 4c of the rotor 4. The second magnets 12 are arranged in the gaps formed between adjacent first magnets 10 among the plurality of first magnets 10. In the present embodiment, the second magnet 12 is a permanent magnet. The second magnets 12 are arranged such that the S pole and the N pole are adjacent to each other in the circumferential direction R. The second magnet 12 has the N pole arranged on the side of the first magnet 10 that becomes the S pole. The second magnet 12 has the S pole arranged on the side of the first magnet 10 that becomes the N pole. In the present embodiment, six second magnets 12 are arranged in the same number as the number of the first magnets 10. The second magnets 12 are arranged from the outer peripheral side to the inner peripheral side in the radial direction D. Therefore, the magnetic flux generated by the second magnet 12 repels or attracts the magnetic flux MS generated by the coil 6. As a result, the second magnet 12 has a function of smoothing the rotation of the rotor 4.

[0017] The first magnets 10 and the second magnets 12 are embedded in the rotor core 8. Specifically, grooves into which the first magnets 10 and the second magnets 12 are fitted are formed in the rotor core 8 located on the surface 4a side of the rotor 4. By embedding the first magnets 10 and the second magnets 12 in these grooves, the axial gap type motor 1 can be made a magnet-embedded type motor. In the present embodiment, the first magnet 10 is embedded in the rotor core 8 with the surface on the surface 4a side of the first magnet 10 exposed. Similarly to the first magnet 10, the second magnet 12 is also embedded in the rotor core 8 with the surface on the surface 4a side of the second magnet 12 exposed. By thus exposing the surfaces on the surface 4a side of the first magnets 10 and the second magnets 12, the rotor 4 can be easily manufactured. However, the first magnets 10 and the second magnets 12 may be completely buried in the rotor core 8.

[0018] As shown in FIGS. 2 and 3, the rotor 4 has the first magnet 10 disposed on the outer peripheral side of the rotor 4, and a space V formed by laminating electromagnetic steel sheets on the inner peripheral side in the radial direction D of the rotor 4 is disposed. In the present embodiment, further, as shown in FIG. 3, when viewed in the axial direction X of the rotor 4, the first magnet 10 is offset and disposed closer to the surface 4a side than the center of the rotor 4 in the axial direction X (see the center line Or in FIG. 3). Also, similar to the first magnet 10, the second magnet 12 is offset and disposed closer to the surface 4a side than the center of the rotor 4 in the axial direction X of the rotor 4 when viewed in the axial direction X. As a result, a space V in which electromagnetic steel sheets are laminated is also formed on the back surface 4b side of the first magnet 10 and the second magnet 12. In the present embodiment, as shown in FIG. 3, the space V is disposed at a position facing the position of the coil 6 of the stator 2. That is, the space V is disposed at a position overlapping the coil 6 when viewed in the axial direction X.

[0019] In the axial gap type motor 1 according to the first embodiment, by arranging the first magnet 10, the second magnet 12, and the space V in this way, the volume of the space V is made larger on the inner peripheral side of the rotor 4 than on the outer peripheral side of the rotor 4. In this way, by increasing the volume of the space V toward the inner peripheral side, the ratio of the cross-sectional area of the magnets including the first magnet 10 and the second magnet 12 at each position in the radial direction D to the cross-sectional area of the space V is made uniform. As a result, the ratio of the magnet torque to the reluctance torque is made uniform between the outer peripheral side and the inner peripheral side of the rotor 4.

[0020] More specifically, as shown in Figure 3, in the axial gap motor 1, the magnetic flux MR generated by the first magnet 10 passes through the axial direction X in the portion of the rotor 4 where the first magnet 10 is located. The magnetic flux MR generates magnetic torque by repelling or attracting the magnetic flux MS generated by the stator 2. Although not shown in Figure 3, the second magnet 12 also generates magnetic torque in the same way as the first magnet 10. On the other hand, in the portion of the rotor 4's space V where the first magnet 10 is not located in the axial direction X, the magnetic flux MS formed in space V changes with the rotation of the rotor 4, generating reluctance torque. Furthermore, the second magnet 12 is located even in the portion where the first magnet 10 is not located. Therefore, the second magnet 12 also generates magnetic torque.

[0021] The magnetic flux state will be explained in more detail using Figures 4(a) and 4(b).

[0022] Figure 4(a) is a cross-section II of Figure 3, specifically a schematic axial view showing the magnetic flux state in the outer peripheral portion where the first magnet 10 is located. As shown in Figure 4(a), the first magnet 10 and the second magnet 12 generate a magnetic flux MR in the axial direction X. The magnetic flux MR passes along the layers of electromagnetic steel sheets of the rotor core 8. The magnetic flux MS generated in the coil 6 generates magnet torque by repelling or attracting the magnetic flux MR passing through the rotor core 8.

[0023] On the other hand, the magnetic flux MS generated in coil 6 passes through the layers of electromagnetic steel sheets in space V in the rotor core 8. However, because the rotor 4 rotates, the relative position between space V and the stator 2 in the circumferential direction R changes. This causes a change in the magnetic flux MS. This change in magnetic flux MS generates reluctance torque.

[0024] Figure 4(b) is a cross-section of line II-II in Figure 3, and specifically, it is a schematic axial view showing the magnetic flux state in the inner circumference portion where the first magnet 10 is not located. As shown in Figure 4(b), in space V in this portion, the influence of the magnetic flux MR of the first magnet 10 is weakened. On the other hand, the second magnet 12 generates a magnetic flux MR in the axial direction X. Therefore, on the inner circumference side of the rotor 4, a magnetic torque is generated by the second magnet 12. In other words, the magnetic torque is weakened because the first magnet 10 is absent. On the other hand, the cross-sectional area in the axial direction X of space V decreases as you move from the outer circumference side to the inner circumference side. Therefore, the reluctance torque on the inner circumference side is weaker than on the outer circumference side. In this way, the ratio of magnetic torque to reluctance torque becomes uniform on the outer and inner circumference sides of the rotor 4.

[0025] In this way, by making the ratio of magnet torque to reluctance torque uniform on both the outer and inner circumference sides of the rotor 4, the torque ratio of reluctance torque to magnet torque at each position in the radial direction D is optimized, and the overall torque of the axial gap type motor 1 is improved.

[0026] <Second Embodiment> Next, the axial gap type motor 201 of the second embodiment of this disclosure will be described with reference to Figures 5 and 6. In the second embodiment, only the differences from the first embodiment will be described.

[0027] As shown in Figure 5, the rotor 204 of the axial gap motor 201 has a rotor core 208, a first magnet 210, and a second magnet 212. The rotor core 208 is made of electromagnetic steel sheets laminated radially D, similar to the first embodiment. The first magnet 210 is exposed on the surface 204a side of the rotor 204. The first magnet 210 extends from the outer circumference to the inner circumference in the radial direction D when viewed from the surface 204a side. The circumferential end 210a of the first magnet 210 extends along the radial direction D. As shown in Figure 6, the axial thickness X of the space V201 of the rotor core 208 increases as it moves toward the inner circumference in the radial direction D of the rotor 204. The axial thickness X of the first magnet 210 decreases as it moves toward the inner circumference in the radial direction D of the rotor 204.

[0028] In the axial gap type motor 201 configured in this way, the ratio of the cross-sectional area of ​​the space V201 to the cross-sectional areas of the first magnet 210 and the second magnet 212 remains constant when viewed in the axial direction X. As a result, the ratio of magnet torque to reluctance torque becomes uniform on the outer and inner sides of the rotor 204.

[0029] <Third Embodiment> Next, the axial gap type motor 301 of the third embodiment of this disclosure will be described with reference to Figures 7 and 8. In the third embodiment, only the differences from the first and second embodiments will be described.

[0030] As shown in Figure 7, the rotor 304 of the axial gap motor 301 has a rotor core 308, a first magnet 310, and a second magnet 312. The rotor core 308 is made of electromagnetic steel sheets laminated radially D, similar to the first embodiment. The first magnet 310 is exposed on the surface 304a side of the rotor 304. The first magnet 310 extends from the outer circumference to the inner circumference in the radial direction D when viewed from the surface 304a side. The end 310a of the first magnet 310 in the circumferential direction R extends inward from the radial direction D. As shown in Figure 8, in the third embodiment, the axial thickness X of the first magnet 310 is constant. By having the first magnet 310 in this shape, the volume of the first magnet 310 decreases from the outer circumference to the inner circumference of the rotor 304. This ensures that the ratio of the cross-sectional area of ​​the space V301 at a predetermined position in the radial direction D to the cross-sectional areas of the first magnet 310 and the second magnet 312 remains constant. As a result, the ratio of magnet torque to reluctance torque becomes uniform on both the outer and inner circumference sides of the rotor 304.

[0031] <Fourth Embodiment> Next, the axial gap type motor 401 of the fourth embodiment of this disclosure will be described with reference to Figure 9. In the fourth embodiment, only the differences from the first to third embodiments will be described.

[0032] As shown in Figure 9, the axial gap type motor 401 of the fourth embodiment differs from the first magnet 10 of the first embodiment in that the first magnet 410 is divided into multiple parts. The other configurations are the same as those of the first embodiment. In this embodiment, the second magnet 412 is also divided into multiple parts, similar to the first magnet 410.

[0033] By dividing the first magnet 410 into multiple parts in this way, the eddy currents generated by the first magnet 410 can be reduced. This reduces the eddy current loss of the axial gap type motor 401.

[0034] As described above, this disclosure provides an axial gap type motor 1 that generates reluctance torque.

[0035] <Other Embodiments> Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. In particular, the various modifications described herein can be combined as needed.

[0036] (a) In the first to fourth embodiments described above, an example was used in which the rotor 4 is arranged on one side of the stator 2, but the disclosure is not limited thereto. Two rotors 4 may be arranged on either side of the stator 2.

[0037] (b) In the four embodiments described above, an example was used in which the first magnet 10 of the first embodiment is divided into multiple parts, but the disclosure is not limited thereto. For example, the first magnet 210 of the second embodiment and the first magnet 310 of the third embodiment may be divided into multiple parts. [Explanation of symbols]

[0038] 1,201,301,401: Axial gap type motor 2: Status 4,204,304: Rotor 4a,204a,304a:Surface 8,208,308: Rotor core 10,210,310,401: First magnet V,V201: Space X: Axial direction, R: Circumferential direction, D: Radial direction

Claims

1. An axial gap type motor having a rotor and a stator arranged axially opposite to the rotor, The rotor is A rotor core formed from radially stacked electromagnetic steel sheets, The magnet embedded in the rotor core, The magnets are arranged alternately with first magnets arranged in the circumferential direction and second magnets arranged in the radial direction, and a space formed by the electromagnetic steel sheet is between the first magnets, the second magnets and the stator. Equipped with, Of the aforementioned space, the volume of the circumferential space where the second magnet is located in the radial direction is larger on the inner circumference side of the rotor than on the outer circumference side. Axial gap type motor.

2. The volume increases towards the inner circumference of the rotor. The axial gap type motor according to claim 1.

3. The first magnet is positioned offset from the stator to the axial center of the rotor, The axial gap type motor according to claim 1.

4. The volume of the first magnet decreases as it approaches the inner circumference of the rotor. The axial gap type motor according to claim 1.

5. At least one of the first magnet and the second magnet is divided into multiple parts. The axial gap type motor according to claim 1.

6. The rotor has grooves formed on the opposite side, which is located on the side opposite to the stator and the rotor core, for housing the first magnet and the second magnet. An axial gap type motor according to any one of claims 1 to 5.

7. The first magnet has a decreasing axial thickness as it approaches the inner circumference in the radial direction of the rotor. The axial gap type motor according to claim 4.

8. The circumferential end of the first magnet extends inward in the circumferential direction rather than in the radial direction. The axial gap type motor according to claim 4.

9. An axial gap type motor having a rotor and a stator arranged axially opposite to the rotor, The rotor comprises a rotor core formed from radially stacked electromagnetic steel sheets, The magnet embedded in the rotor core, The magnets consist of first magnets arranged circumferentially and second magnets arranged radially, with alternating arrangements of these magnets, and a space formed by the electromagnetic steel sheet between the first magnets, the second magnets, and the stator. Equipped with, The second magnet has a first end on the inner circumference and a second end on the outer circumference in the radial direction of the rotor core. The space is larger on the inner circumference side of the rotor than on the outer circumference side, between the first end and the second end in the radial direction. Axial gap type motor.

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