Axial gap 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

Axial gap motor

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

[0002] 2. Description of the Related Art Conventionally, an axial gap motor has been known that has a rotor and a stator that is disposed in the direction in which the rotation axis of the rotor extends (see, for example, Patent Document 1).

[0003] JP 2016-77067 A

[0004] The axial gap motor of Patent Document 1 has a structure in which magnets are attached to the entire surface of the rotor. The axial gap motor of Patent Document 1 utilizes magnetic torque generated by magnetic flux formed between the magnet and the stator coil. However, motors generally can improve torque by utilizing reluctance torque generated by changes in magnetic flux in addition to magnetic torque.

[0005] An object of the present disclosure is to provide an axial gap motor that generates reluctance torque.

[0006] The axial gap motor according to the present disclosure is an axial gap motor having a rotor and a stator arranged axially opposite the rotor, wherein the rotor comprises a rotor core formed from radially stacked electromagnetic steel plates, a magnet embedded in the rotor core, and a space arranged between the magnet and the stator and formed by the electromagnetic steel plates, and the volume of the space is larger on the inner peripheral side of the rotor than on the outer peripheral side of the rotor.

[0007] According to the present disclosure, an axial gap motor that generates reluctance torque can be provided.

[0008] 1 is a diagram of an axial gap motor according to an embodiment of the present disclosure; 2 is a diagram of an axial gap motor according to a first embodiment of the present disclosure, viewed from the surface side of the rotor; 3 is a cross-sectional view taken along line A-A in FIG. 2; 4 is a schematic axial plan view showing the state of magnetic flux on the outer and inner peripheral sides of the rotor, where (a) is a cross-sectional view showing the I-I section (outer peripheral side of the rotor) in FIG. 3, and (b) is a cross-sectional view showing the II-II section (inner peripheral side of the rotor) in FIG. 3; 5 is a diagram of an axial gap motor according to a second embodiment of the present disclosure, viewed from the surface side of the rotor; 6 is a cross-sectional view taken along line B-B in FIG. 5; 7 is a diagram of an axial gap motor according to a third embodiment of the present disclosure, viewed from the surface side of the rotor; 8 is a cross-sectional view taken along line C-C in FIG. 7; 9 is a diagram of an axial gap motor according to a fourth embodiment of the present disclosure, viewed from the surface side of the rotor;

[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 may be a plug-in hybrid electric vehicle (PHEV) or an electric vehicle that can be externally charged or externally supplied with power.

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

[0011] The stator 2 faces the rotor 4 in the axial direction X and is disposed with a gap therebetween. The stator 2 has a plurality of coils 6. Each coil 6 is formed by winding a copper wire around an iron core formed of an iron core material (e.g., an electromagnetic steel sheet). As shown in FIG. 3 , the copper wire is wound in a direction perpendicular to the axial direction X. Therefore, when electricity flows through the copper wire, a magnetic flux is generated in the axial direction X (see the magnetic flux MS indicated by the imaginary line in FIG. 3 ). The stator 2 is fixed to a motor housing (not shown) or the like. In this embodiment, six stators 2 are arranged side by side in the circumferential direction R.

[0012] 2 , the rotor 4 includes a rotor core 8 and a plurality of first magnets 10 embedded in the rotor core 8. In this embodiment, the rotor 4 further includes second magnets 12 arranged between the plurality of first magnets 10.

[0013] The rotor 4 is rotatably mounted relative to the motor housing. The rotor 4 in this embodiment has a cylindrical shape. As shown in Fig. 3, the rotor 4 further includes a back surface 4b that faces the stator 2, a front surface 4a (an example of an opposite surface) opposite the back surface 4b across the rotor core 8, and a cylindrical motor shaft mounting hole 4c that is disposed at the center of the cylindrical shape and 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 in the radial direction D. The rotor core 8 holds the first magnets 10 and the second magnets 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 also have the property of easily passing magnetic flux on the same plane. Therefore, the rotor core 8 has the property that magnetic flux easily passes in the axial direction X, but is more difficult to pass in the radial direction D than in the axial direction X.

[0015] As shown in Fig. 2, a plurality of 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 with their south poles and north poles alternately spaced apart in the circumferential direction R. In this embodiment, six first magnets 10 are arranged. As shown in Fig. 3, the first magnets 10 are arranged with their north poles and south poles adjacent to each other when viewed in the axial direction X.

[0016] As shown in FIG. 2 , multiple 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 multiple first magnets 10. In this embodiment, the second magnets 12 are permanent magnets. The second magnets 12 are arranged with their south and north poles adjacent to each other in the circumferential direction R. The north pole of each second magnet 12 is arranged on the side of the first magnet 10 that is its south pole. The south pole of each second magnet 12 is arranged on the side of the first magnet 10 that is its north pole. In this embodiment, six second magnets 12 are arranged, the same as the number of first magnets 10. The second magnets 12 are arranged from the outer periphery to the inner periphery in the radial direction D. Therefore, the magnetic flux generated by the second magnets 12 repels or attracts the magnetic flux MS generated by the coil 6. This allows the second magnets 12 to smoothly rotate the rotor 4.

[0017] The first magnet 10 and the second magnet 12 are embedded in the rotor core 8. Specifically, grooves into which the first magnet 10 and the second magnet 12 fit are formed in the rotor core 8 located on the surface 4a side of the rotor 4. By embedding the first magnet 10 and the second magnet 12 in these grooves, the axial gap motor 1 can be made into an embedded magnet motor. In this embodiment, the first magnet 10 is embedded in the rotor core 8 with the surface 4a side of the first magnet 10 exposed. Like the first magnet 10, the second magnet 12 is embedded in the rotor core 8 with the surface 4a side of the second magnet 12 exposed. In this way, leaving the surfaces of the first magnet 10 and the second magnet 12 on the surface 4a side exposed makes it easier to manufacture the rotor 4. However, the first magnet 10 and the second magnet 12 may be completely embedded in the rotor core 8.

[0018] As shown in FIGS. 2 and 3 , the rotor 4 has a first magnet 10 disposed on the outer periphery of the rotor 4, and a space V formed by stacking electromagnetic steel sheets disposed on the inner periphery of the rotor 4 in the radial direction D. Furthermore, in this embodiment, as shown in FIG. 3 , the first magnet 10 is disposed offset toward the front surface 4 a from the center of the axial direction X of the rotor 4 (see center line Or in FIG. 3 ) when viewed in the axial direction X of the rotor 4. Similarly to the first magnet 10, the second magnet 12 is also disposed offset toward the front surface 4 a from the center of the axial direction X of the rotor 4 when viewed in the axial direction X of the rotor 4. As a result, a space V formed by stacking electromagnetic steel sheets is also formed on the back surface 4 b of the first magnet 10 and the second magnet 12. In this embodiment, as shown in FIG. 3 , the space V is disposed opposite 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 motor 1 of the first embodiment, by arranging the first magnet 10, the second magnet 12, and the space V in this manner, the volume of the space V is larger on the inner circumferential side of the rotor 4 than on the outer circumferential side of the rotor 4. In this way, the volume of the space V increases toward the inner circumferential side, so that the ratio between the cross-sectional area of ​​the magnets including the first magnet 10 and the second magnet 12 and the cross-sectional area of ​​the space V at each position in the radial direction D is made uniform. This makes the ratio between magnet torque and reluctance torque uniform between the outer circumferential side and the inner circumferential side of the rotor 4.

[0020] More specifically, as shown in FIG. 3 , in the axial gap motor 1, in the portion of the rotor 4 where the first magnet 10 is located, the magnetic flux MR generated by the first magnet 10 passes in the axial direction X. The magnetic flux MR repels or attracts the magnetic flux MS generated by the stator 2, generating a magnetic torque. Although not shown in FIG. 3 , the second magnet 12 also generates a magnetic torque, just like the first magnet 10. Meanwhile, in the portion of the space V of the rotor 4 where the first magnet 10 is not located in the axial direction X, the magnetic flux MS formed in the space V changes as the rotor 4 rotates, generating a 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 generates a magnetic torque.

[0021] The state of the magnetic flux will be explained in more detail with reference to FIGS. 4(a) and 4(b).

[0022] Figure 4(a) is a cross section taken along line I-I in Figure 3, specifically a schematic axial plan view showing the state of magnetic flux 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 magnetic flux MR in the axial direction X. The magnetic flux MR passes along the layers of the electromagnetic steel plates of the rotor core 8. The magnetic flux MS generated by the coil 6 repels or attracts the magnetic flux MR passing through the rotor core 8, thereby generating magnet torque.

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

[0024] FIG. 4(b) is a cross section taken along line II-II of FIG. 3, specifically a schematic axial plan view showing the state of magnetic flux in the inner peripheral portion where the first magnet 10 is not located. As shown in FIG. 4(b), in the space V in this portion, the influence of the magnetic flux MR of the first magnet 10 is weakened. Meanwhile, the second magnet 12 generates magnetic flux MR in the axial direction X. Therefore, on the inner peripheral side of the rotor 4, a magnetic torque is generated by the second magnet 12. In other words, the magnetic torque is weakened by the absence of the first magnet 10. Meanwhile, the cross-sectional area of ​​the space V in the axial direction X decreases from the outer peripheral side to the inner peripheral side. Therefore, the reluctance torque on the inner peripheral side is weaker than on the outer peripheral side. In this way, the ratio of magnetic torque to reluctance torque becomes uniform between the outer peripheral side and the inner peripheral side of the rotor 4.

[0025] In this way, the ratio of magnet torque to reluctance torque becomes uniform on the outer and inner sides of the rotor 4, thereby optimizing the torque ratio of reluctance torque to magnet torque at each position in the radial direction D, and improving the overall torque of the axial gap motor 1.

[0026] Second Embodiment Next, an axial gap motor 201 according to a second embodiment of the present disclosure will be described with reference to Fig. 5 and Fig. 6. Note that in the second embodiment, only the differences from the first embodiment will be described.

[0027] As shown in FIG. 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 formed by laminating electromagnetic steel sheets in the radial direction D, as in 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 periphery to the inner periphery in the radial direction D when viewed from the surface 204a side. An end 210a of the first magnet 210 in the circumferential direction R extends along the radial direction D. As shown in FIG. 6 , the thickness of the rotor core 208 in the axial direction X of the space V201 increases toward the inner periphery in the radial direction D of the rotor 204. The thickness of the first magnet 210 in the axial direction X decreases toward the inner periphery in the radial direction D of the rotor 204.

[0028] In the axial gap motor 201 configured in this manner, the ratio between the cross-sectional area of ​​the space V201 in the axial direction X and the cross-sectional areas of the first magnet 210 and the second magnet 212 is constant. This makes the ratio between magnet torque and reluctance torque uniform between the outer and inner sides of the rotor 204.

[0029] Third Embodiment Next, an axial gap motor 301 according to a third embodiment of the present disclosure will be described with reference to Fig. 7 and Fig. 8. Note that in the third embodiment, only the differences from the first and second embodiments will be described.

[0030] As shown in FIG. 7 , the rotor 304 of the axial gap motor 301 includes a rotor core 308, a first magnet 310, and a second magnet 312. The rotor core 308 is formed by laminating electromagnetic steel sheets in the radial direction D, as in the first embodiment. The first magnet 310 is exposed on a surface 304a of the rotor 304. The first magnet 310 extends from the outer periphery toward the inner periphery in the radial direction D when viewed from the surface 304a. The end 310a of the first magnet 310 in the circumferential direction R extends further inward in the circumferential direction R than in the radial direction D. As shown in FIG. 8 , in the third embodiment, the thickness of the first magnet 310 in the axial direction X is constant. By shaping the first magnet 310 in this way, the volume of the first magnet 310 decreases from the outer periphery toward the inner periphery of the rotor 304. This makes the ratio of the cross-sectional area of ​​the space V301 at a predetermined position in the radial direction D to the cross-sectional area of ​​the first magnet 310 and the second magnet 312 constant. Therefore, the ratio of magnet torque to reluctance torque becomes uniform between the outer and inner sides of the rotor 304.

[0031] Fourth Embodiment Next, an axial gap motor 401 according to a fourth embodiment of the present disclosure will be described with reference to Fig. 9. Note that 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 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 pieces. The other configurations are the same as those of the first embodiment. In this embodiment, the second magnet 412 is also divided into multiple pieces, just like the first magnet 410.

[0033] Dividing the first magnet 410 into a plurality of pieces in this way makes it possible to reduce eddy currents generated by the first magnet 410. This makes it possible to reduce eddy current loss in the axial gap motor 401.

[0034] As described above, according to the present disclosure, it is possible to provide an axial gap motor 1 that generates reluctance torque.

[0035] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the invention. In particular, the multiple modifications described in this specification can be combined as needed.

[0036] (a) In the above first to fourth embodiments, an example has been described in which the rotor 4 is disposed on one side of the stator 2. However, the present disclosure is not limited to this. Two rotors 4 may be disposed with the stator 2 sandwiched between them.

[0037] (b) In the above four embodiments, the first magnet 10 of the first embodiment is divided into multiple pieces, but the present disclosure is not limited to this. For example, the first magnet 210 of the second embodiment and the first magnet 310 of the third embodiment may be divided into multiple pieces.

[0038] 1, 201, 301, 401: Axial gap motor 2: Stator 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 motor having a rotor and a stator arranged axially opposite to the rotor, The rotor is a rotor core formed by radially stacked electromagnetic steel sheets; a magnet embedded in the rotor core; The magnets are arranged such that first magnets arranged in the circumferential direction and second magnets arranged in the radial direction are alternately arranged, and a space formed by the electromagnetic steel plates is provided between the first magnets, the second magnets, and the stator; Equipped with a volume of the space in the circumferential direction in which the second magnet is located in the radial direction is larger on the inner peripheral side of the rotor than on the outer peripheral side of the rotor; Axial gap type motor.

2. the volume increases toward the inner periphery of the rotor; 2. The axial gap motor according to claim 1.

3. the first magnet is disposed offset from the center of the rotor in the axial direction to the opposite side to the stator; 2. The axial gap motor according to claim 1.

4. The volume of the first magnet decreases toward the inner periphery of the rotor.

2. The axial gap motor according to claim 1.

5. At least one of the first magnet and the second magnet is divided into a plurality of magnets.

2. The axial gap motor according to claim 1.

6. The rotor has grooves formed on an opposite surface thereof, the opposite surface being disposed on the opposite side of the rotor core from the stator, the grooves accommodating the first magnet and the second magnet.

6. An axial gap motor according to claim 1.

7. the first magnet has an axial thickness that decreases toward the inner circumferential side in the radial direction of the rotor; 5. The axial gap motor according to claim 4.

8. A circumferential end of the first magnet extends inward in the circumferential direction relative to the radial direction.

5. The axial gap motor according to claim 4.

9. An axial gap motor having a rotor and a stator arranged axially opposite to the rotor, The rotor includes a rotor core formed of radially stacked electromagnetic steel plates; a magnet embedded in the rotor core; The magnets are arranged such that first magnets arranged in the circumferential direction and second magnets arranged in the radial direction are alternately arranged, and a space formed by the electromagnetic steel plates is provided between the first magnets, the second magnets, and the stator; Equipped with the second magnet has a first end portion on an inner circumferential side and a second end portion on an outer circumferential side in the radial direction of the rotor core, the space is larger on an inner peripheral side of the rotor than on an outer peripheral side of the rotor between the first end and the second end in the radial direction; Axial gap type motor.