Rotor and Motor

Abstract

In the present invention, a rotor 1 comprises: a rotor body 2 having rotational axis A; a plurality of first permanent magnets 41 and a plurality of second permanent magnets 42 arranged alternatingly in the circumferential direction about the rotational axis A on the rotor body 2 and forming mutually different magnetic polarities; a plurality of third permanent magnets 43 arranged corresponding to each of the plurality of first permanent magnets 41 at an end surface 3a of the rotor body 2 and forming the same magnetic polarity as the first permanent magnets 41; and a plurality of fourth permanent magnets 44 arranged corresponding to each of the plurality of second permanent magnets 42 at the end surface 3a of the rotor body 2 and forming the same magnetic polarity as the second permanent magnets 42. The d-axis of each of the first permanent magnets 41 and the second permanent magnets 42, and the d-axis of each of the third permanent magnets 43 and the fourth permanent magnets 44 are shifted in the circumferential direction.

Description

[Technical field]

[0001] The technology disclosed herein relates to a rotor and a motor. [Background technology]

[0002] Conventionally, rotors with permanent magnets embedded in the rotor core have been known, as disclosed in Patent Document 1, for example. In this type of rotor, when the stator forms a rotating magnetic field, a magnetic torque is generated by the permanent magnets, and a reluctance torque is generated by the stator core. The total torque, which is the sum of the magnetic torque and the reluctance torque, becomes the motor output. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-191710 A Summary of the Invention

[0004] However, in the rotor described above, there is a phase difference between the current phase (electrical angle) at which the magnet torque is at its maximum and the current phase at which the reluctance torque is at its maximum. Therefore, the maximum value of the total torque is lower than the sum of the maximum values ​​of the magnet torque and the reluctance torque. In other words, the combined use of magnet torque and reluctance torque merely makes use of the complementary increase and decrease relationship that exists between the waveforms of both torques, and does not provide an additive total torque as represented by the sum of the maximum values ​​of both torques. Therefore, there is room for improvement in the motor's output efficiency.

[0005] The technology disclosed herein has been made in consideration of the above-mentioned points, and has an object to improve the output efficiency of a motor.

[0006] The rotor disclosed herein includes a rotor body having a rotation axis, a plurality of first permanent magnets and a plurality of second permanent magnets arranged alternately in a circumferential direction around the rotation axis in the rotor body and forming different magnetic poles, a plurality of third permanent magnets provided on an end face of the rotor body in the direction of the rotation axis corresponding to each of the first permanent magnets and forming the same magnetic pole as the first permanent magnets, and a plurality of fourth permanent magnets provided on an end face of the rotor body in the direction of the rotation axis corresponding to each of the second permanent magnets and forming the same magnetic pole as the second permanent magnets. The d-axis of each of the first permanent magnets and the second permanent magnets and the d-axis of each of the third permanent magnets and the fourth permanent magnets are offset in the circumferential direction.

[0007] The motor disclosed herein also includes a cylindrical stator and the above-mentioned rotor disposed inside the stator.

[0008] According to the above rotor, the output efficiency of the motor can be improved.

[0009] According to the above-described motor, the output efficiency of the motor can be improved. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of the motor. [Diagram 2] FIG. 2 is a plan view of the rotor as viewed in the direction of the rotation axis. [Diagram 3] FIG. 3 is a cross-sectional view taken along line XX shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line YY shown in FIG. [Diagram 5] FIG. 5 is a cross-sectional view taken along line ZZ shown in FIG. [Figure 6] FIG. 6 is a graph showing the total torque of the motor when the d-axis of the internal magnet and the d-axis of the external magnet coincide in the circumferential direction. [Figure 7]FIG. 7 is a graph showing the total torque of a motor when the d-axis of the internal magnet and the d-axis of the external magnet are misaligned in the circumferential direction. [Figure 8] FIG. 8 is a flowchart showing a method for manufacturing a rotor. [Figure 9] FIG. 9 is a diagram that illustrates a schematic diagram of a die in which a rotor core is disposed. [Figure 10] FIG. 10 is a view equivalent to FIG. 3, illustrating a rotor according to another embodiment with some parts omitted. [Figure 11] FIG. 11 is a view equivalent to FIG. 3, illustrating a rotor according to another embodiment with some parts omitted. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Exemplary embodiments will now be described in detail with reference to the accompanying drawings.

[0012] Fig. 1 is a cross-sectional view of a motor 100. Fig. 2 is a plan view of a rotor 1 viewed in the direction of a rotation axis A.

[0013] The motor 100 includes a rotor 1 that rotates around a predetermined rotation axis A, and a stator 6 that rotates the rotor 1 around the rotation axis A. A permanent magnet is embedded in the rotor 1. That is, the motor 100 is basically an IPM (Interior Permanent Magnet) motor. The motor 100 may further include a motor case 7. The motor case 7 houses the rotor 1 and the stator 6. The stator 6 is fixed to the motor case 7. The rotor 1 is supported by the motor case 7 so as to be rotatable.

[0014] Hereinafter, the direction in which the rotation axis A extends will be referred to as the "rotation axis direction." The circumferential direction centered on the rotation axis A will be referred to as the "circumferential direction." The radial direction centered on the rotation axis A will be referred to as the "radial direction." The side toward the rotation axis A in the radial direction will be referred to as the "radial inner side," and the side opposite the rotation axis A will be referred to as the "radial outer side."

[0015] The stator 6 includes a stator core 61 and a winding 62. The stator core 61 is made of a soft magnetic material and is formed, for example, from a plurality of electromagnetic steel plates stacked on top of each other.

[0016] The stator core 61 is formed in a cylindrical shape. The stator core 61 is fixed to the motor case 7. The stator core 61 is formed with a plurality of teeth 61a protruding toward the inside of the stator core 61. The plurality of teeth 61a are arranged at intervals in the circumferential direction of the stator core 61. The windings 62 are wound around the plurality of teeth 61a. When a current is supplied to the windings 62, the stator 6 generates a rotating magnetic field that rotates the rotor 1.

[0017] The rotor 1 comprises a rotor body 2 having a rotation axis A, a plurality of first permanent magnets 41 and a plurality of second permanent magnets 42 arranged on the rotor body 2, and a plurality of third permanent magnets 43 and a plurality of fourth permanent magnets 44 provided on an end face 3a of the rotor body 2 in the direction of the rotation axis.

[0018] At least a portion of the rotor body 2 is made of a soft magnetic material. The rotor body 2 has magnetic salience and generates reluctance torque in the rotating magnetic field generated by the stator 6. The rotor body 2 rotates around a rotation axis A. The rotor body 2 includes a cylindrical rotor core 3 and a shaft 5. The rotation axis A of the rotor body 2 coincides with the respective axial centers of the rotor core 3 and the shaft 5.

[0019] The rotor core 3 is a soft magnetic material. The rotor core 3 is formed, for example, from a plurality of electromagnetic steel plates stacked on top of each other. The rotor core 3 is formed in a cylindrical shape concentric with the stator core 61. The outer peripheral surface of the rotor core 3 forms the outer peripheral surface of the rotor body 2. The shape of a cross section of the rotor core 3 perpendicular to the rotation axis A is the same over the entire length of the rotor core 3 in the rotation axis direction. An air gap 10 is formed between the outer peripheral surface of the rotor core 3 and the inner peripheral surface of the stator core 61.

[0020] The shaft 5 is fitted inside the rotor core 3. The shaft 5 is fixed to the rotor core 3. The axis of the shaft 5 coincides with the rotation axis A. The shaft 5 is rotatably supported by the motor case 7 via bearings or the like. The rotor core 3 rotates together with the shaft 5 around the rotation axis A. The shaft 5 is made of a soft magnetic material.

[0021] The first permanent magnets 41 and the second permanent magnets 42 are alternately arranged in the circumferential direction around the rotation axis A in the rotor body 2, forming different magnetic poles. Specifically, the first permanent magnets 41 and the second permanent magnets 42 are alternately arranged at equal intervals in the circumferential direction in the rotor core 3. The first permanent magnets 41 and the second permanent magnets 42 generate magnet torque in the rotating magnetic field formed by the stator 6. The first permanent magnets 41 and the second permanent magnets 42 are provided in the same number, and in this example, three of each are provided.

[0022] The first permanent magnet 41 and the second permanent magnet 42 are embedded in the rotor core 3. More specifically, in this example, the first permanent magnet 41 and the second permanent magnet 42 are embedded in a portion of the rotor core 3 that is radially inward from the outer circumferential surface of the rotor core 3. In this example, the first permanent magnet 41 and the second permanent magnet 42 have the same shape as each other. In this way, the multiple first permanent magnets 41 and the multiple second permanent magnets 42 are permanent magnets provided inside the rotor core 3 and form the internal magnet 4a.

[0023] Fig. 3 is a cross-sectional view taken along line XX in Fig. 2. Fig. 4 is a cross-sectional view taken along line YY in Fig. 3. Fig. 5 is a cross-sectional view taken along line ZZ in Fig. 3. Hereinafter, unless otherwise specified, "cross-sectional shape" refers to a cross-sectional shape perpendicular to the rotation axis A.

[0024] The first permanent magnet 41 and the second permanent magnet 42 are formed in a plate shape extending in the rotational axis direction. More specifically, the first permanent magnet 41 and the second permanent magnet 42 extend over the entire length in the rotational axis direction of the rotor core 3. That is, an end face 41a in the rotational axis direction of the first permanent magnet 41 and an end face 42a in the rotational axis direction of the second permanent magnet 42 coincide with an end face 3a of the rotor core 3. The cross-sectional shapes of the first permanent magnet 41 and the second permanent magnet 42 are the same over the entire length in the rotational axis direction of the first permanent magnet 41 and the second permanent magnet 42.

[0025] The cross-sectional shape of each of the first permanent magnet 41 and the second permanent magnet 42 is linear. That is, the cross-sectional shape of each of the first permanent magnet 41 and the second permanent magnet 42 is a shape that extends along a predetermined reference line. The cross-sectional shape of each of the first permanent magnet 41 and the second permanent magnet 42 is a curved shape that is concave toward the radial inside (i.e., the rotation axis A), and in this example, is formed into a U-shape.

[0026] The rotor core 3 is formed with a plurality of first arrangement holes 31 into which the plurality of first permanent magnets 41 are respectively embedded, and a plurality of second arrangement holes 32 into which the plurality of second permanent magnets 42 are respectively embedded. Each of the first arrangement hole 31 and the second arrangement hole 32 is a single through hole that penetrates the rotor core 3 in the rotation axis direction. The cross-sectional shapes of each of the first arrangement hole 31 and the second arrangement hole 32 are the same as the cross-sectional shapes of the first permanent magnets 41 and the second permanent magnets 42. That is, the first permanent magnets 41 and the second permanent magnets 42 are embedded in the first arrangement hole 31 and the second arrangement hole 32 with substantially no gaps.

[0027] The third permanent magnet 43 and the fourth permanent magnet 44 are provided at positions corresponding to the first permanent magnet 41 and the second permanent magnet 42. Specifically, the third permanent magnets 43 are provided on the end face 3a of the rotor core 3 to correspond to the first permanent magnets 41, respectively, and form the same magnetic poles as the first permanent magnets 41. The fourth permanent magnets 44 are provided on the end face 3a of the rotor core 3 to correspond to the second permanent magnets 42, respectively, and form the same magnetic poles as the second permanent magnets 42.

[0028] As shown in Fig. 5, the third permanent magnets 43 and the fourth permanent magnets 44 are alternately arranged in the circumferential direction on the end face 3a of the rotor core 3. The third permanent magnets 43 and the fourth permanent magnets 44 form different magnetic poles. The third permanent magnets 43 and the fourth permanent magnets 44 generate magnet torque in the rotating magnetic field formed by the stator 6. In this way, the third permanent magnets 43 and the fourth permanent magnets 44 are permanent magnets provided outside the rotor core 3, not inside, and form an external magnet 4b.

[0029] More specifically, the third permanent magnets 43 and the fourth permanent magnets 44 are connected in the circumferential direction. That is, the external magnet 4b is formed of an annular plate member in which all the third permanent magnets 43 and all the fourth permanent magnets 44 are alternately connected in the circumferential direction. In this example, the outer diameter of the external magnet 4b is the same as the outer diameter of the rotor core 3. That is, the outer peripheral surface of the external magnet 4b coincides with the outer peripheral surface of the rotor core 3.

[0030] The external magnet 4b is formed to a size sufficient to cover the end face 41a of the first permanent magnet 41 and the end face 42a of the second permanent magnet 42. In this example, the external magnet 4b, i.e., the multiple third permanent magnets 43 and the multiple fourth permanent magnets 44, are provided on both end faces 3a of the rotor body 2.

[0031] Furthermore, in the rotor 1 of this example, the multiple first permanent magnets 41, the multiple second permanent magnets 42, and the two external magnets 4b are connected to form a single magnet unit 4. Specifically, each of the multiple third permanent magnets 43 is connected to an end face 41a of the first permanent magnet 41. Each of the multiple fourth permanent magnets 44 is connected to an end face 42a of the second permanent magnet 42. In other words, all of the first permanent magnets 41 and all of the second permanent magnets 42 are connected via the external magnet 4b.

[0032] Thus, the rotor 1 is provided with a set of magnet units 4 as permanent magnets, and the magnet units 4 have an internal magnet 4a and an external magnet 4b.

[0033] The first permanent magnet 41, the second permanent magnet 42, the third permanent magnet 43 and the fourth permanent magnet 44 are bonded magnets. The bonded magnets are permanent magnets formed of a material (hereinafter also referred to as "magnetic material") in which magnet powder and a binder for binding the magnet powder are mixed. The magnet powder is, for example, a powder of a neodymium magnet, a samarium iron nitrogen magnet, a samarium cobalt magnet, a ferrite magnet or an alnico magnet, or a mixture of two or more of these powders. The binder is, for example, a thermosetting resin such as an epoxy resin, a thermoplastic resin such as a polyamide resin, or a rubber. The bonded magnets can be molded like resins, and compared to sintered magnets, they have high dimensional accuracy and a high degree of freedom in shape.

[0034] The d-axis of each of the first permanent magnet 41 and the second permanent magnet 42 is offset in the circumferential direction from the d-axis of each of the third permanent magnet 43 and the fourth permanent magnet 44. In other words, the d-axis of the internal magnet 4a is offset in the circumferential direction from the d-axis of the external magnet 4b. The d-axis is the central axis of the permanent magnet and is the direction of the magnetic flux created by the magnetic poles formed by the permanent magnets.

[0035] Specifically, in the internal magnet 4a, as shown in Fig. 4, a d-axis 411 extending radially is formed in each of the multiple first permanent magnets 41, and a d-axis 422 extending radially is formed in each of the multiple second permanent magnets 42. On the other hand, in the external magnet 4b, as shown in Fig. 5, a d-axis 433 extending radially is formed in each of the multiple third permanent magnets 43, and a d-axis 444 extending radially is formed in each of the multiple fourth permanent magnets 44.

[0036] Here, as shown in Fig. 5, the d-axis 411 of the first permanent magnet 41 and the d-axis 433 of the third permanent magnet 43 are offset in the circumferential direction by a predetermined angle θ, and the d-axis 422 of the second permanent magnet 42 and the d-axis 444 of the fourth permanent magnet 44 are offset in the circumferential direction by a predetermined angle θ. The internal magnet 4a and the external magnet 4b are arranged so that the d-axes are set in this manner. Note that Fig. 5 shows only one each of the d-axis 411 of the first permanent magnet 41 and the d-axis 422 of the second permanent magnet 42.

[0037] The rotor 1 configured in this manner can improve the output efficiency of the motor 100. Fig. 6 is a graph showing the total torque Tt of the motor when the d-axis of the internal magnet 4a and the d-axis of the external magnet 4b are aligned in the circumferential direction. Fig. 7 is a graph showing the total torque Tt of the motor 100 when the d-axis of the internal magnet 4a and the d-axis of the external magnet 4b are misaligned in the circumferential direction.

[0038] Hereinafter, the reluctance torque generated by the rotor core 3 will be referred to as "reluctance torque Tr", the magnet torque generated by the internal magnet 4a will be referred to as "internal magnet torque Tma", and the magnet torque generated by the external magnet 4b will be referred to as "external magnet torque Tmb". The sum of the reluctance torque Tr, internal magnet torque Tma, and external magnet torque Tmb will be referred to as "total torque Tt". The rotor 1 rotates about the rotation axis A due to the total torque Tt. In other words, the total torque Tt corresponds to the output of the motor 100.

[0039] The reluctance torque Tr, the internal magnet torque Tma, and the external magnet torque Tmb each change according to the current phase. The current phase at which the reluctance torque Tr is maximum is different from the current phase at which the internal magnet torque Tma is maximum. When the d-axis of the internal magnet 4a and the d-axis of the external magnet 4b are aligned in the circumferential direction, as shown in FIG. 6, the external magnet torque Tmb changes in the same manner as the internal magnet torque Tma. In other words, the current phase at which the external magnet torque Tmb is maximum is the same as the current phase at which the internal magnet torque Tma is maximum, and is different from the current phase at which the reluctance torque Tr is maximum. In this case, the total torque Tt is maximum torque T1, for example, when the current phase is θa.

[0040] When the d-axis of the internal magnet 4a and the d-axis of the external magnet 4b are offset in the circumferential direction by a predetermined angle θ, the total torque Tt is as shown in Fig. 7. Specifically, the d-axis of the external magnet 4b is offset in the circumferential direction by a predetermined angle θ with respect to the d-axis of the internal magnet 4a so that the external magnet torque Tmb is maximized at the current phase θa described above. In other words, the d-axis of the external magnet 4b is offset so that the current phase at which the external magnet torque Tmb is maximized coincides with the current phase at which the combined torque of the reluctance torque Tr and the internal magnet torque Tma is maximized.

[0041] By doing so, the maximum torque T2 of the total torque Tt becomes higher than the above-mentioned maximum torque T1. In this way, the maximum torque of the total torque Tt increases, improving the output efficiency of the motor 100. In other words, according to the rotor 1 of this example, the provision of the external magnet 4b increases the magnet torque, and the increased magnet torque is effectively utilized as the output of the motor 100.

[0042] Furthermore, since the third permanent magnet 43 and the fourth permanent magnet 44 are respectively arranged at positions corresponding to the first permanent magnet 41 and the second permanent magnet 42 on the end face 3a of the rotor core 3, the first permanent magnet 41 and the second permanent magnet 42 can be prevented from coming out of the rotor core 3.

[0043] Moreover, since the external magnets 4b are provided on both end faces 3a of the rotor core 3, the first permanent magnets 41 and the second permanent magnets 42 can be reliably prevented from coming out of the rotor core 3.

[0044] Furthermore, each of the multiple third permanent magnets 43 is connected to the end face 41a of the first permanent magnet 41, and each of the multiple fourth permanent magnets 44 is connected to the end face 42a of the second permanent magnet 42, thereby reliably preventing the first permanent magnet 41 and the second permanent magnet 42 from coming loose from the rotor core 3.

[0045] In addition, by connecting the third permanent magnets 43 and the fourth permanent magnets 44 in the circumferential direction, the surface area of ​​the third permanent magnets 43 and the fourth permanent magnets 44 can be increased compared to a case where the third permanent magnets 43 and the fourth permanent magnets 44 are separated, for example. Therefore, the magnet torque by the external magnet 4b is further increased.

[0046] Next, a description will be given of a method for manufacturing the rotor 1. Fig. 8 is a flow chart showing a method for manufacturing the rotor 1. Fig. 9 is a schematic diagram showing a die M in which the rotor core 3 is placed.

[0047] First, in step S1, the rotor core 3, which is the rotor main body 2, is placed in a predetermined mold M. As described above, the rotor core 3 is formed with a plurality of first arrangement holes 31 in which the first permanent magnets 41 are arranged and a plurality of second arrangement holes 32 in which the second permanent magnets 42 are arranged.

[0048] 9, two external magnet spaces Ls in which two external magnets 4b are molded are formed in the die M. These external magnet spaces Ls are connected to the multiple first arrangement holes 31 and multiple second arrangement holes 32 of the rotor core 3. In other words, in the die M, a single space is formed by the multiple first arrangement holes 31, the multiple second arrangement holes 32, and the two external magnet spaces Ls.

[0049] In addition, the mold M is formed with a sprue Sp, a runner Ru, and a gate Ga as a flow path for the magnetic material of the internal magnet 4a (i.e., the first permanent magnet 41 and the second permanent magnet 42) and the external magnet 4b (i.e., the third permanent magnet 43 and the fourth permanent magnet 44). In this example, one sprue Sp is provided. The same number of runners Ru and gates Ga are provided. Specifically, two runners Ru and two gates Ga are provided. The number of runners Ru and gates Ga may be one each, three, or four each, and is set to a number less than the total number of the first arrangement holes 31 and the second arrangement holes 32. The two runners Ru are each branched off from the sprue Sp. The two gates Ga are each provided at the outlet end of the runner Ru, and are provided corresponding to a predetermined position of the space Ls for the external magnet.

[0050] In the following step S2, the magnet material is injected into the first arrangement hole 31, the second arrangement hole 32 and the space Ls for the external magnet, and the magnet unit 4 in which the internal magnet 4a and the external magnet 4b before magnetization are integrally formed is injection molded. In the mold M, the magnet material is diverted from the sprue Sp to two runners Ru, and then injected into one of the spaces Ls for the external magnet from each gate Ga. The magnet material injected into one of the spaces Ls for the external magnet flows into the other space Ls for the external magnet through the multiple first arrangement holes 31 and the multiple second arrangement holes 32. Next, the magnet material is filled into the multiple first arrangement holes 31 and the multiple second arrangement holes 32, and then filled into one of the spaces Ls for the external magnet. In this way, one magnet unit 4 before magnetization is solidified and molded.

[0051] In addition, if the first permanent magnet 41, the second permanent magnet 42, the third permanent magnet 43 and the fourth permanent magnet 44 are so-called anisotropic bonded magnets, orientation may be performed to align the direction of the magnetic powder in the magnetic material during the injection molding in step S2.

[0052] In the following step S3, magnetization is performed by a magnetizer. Specifically, the internal magnet 4a before magnetization, i.e., the first permanent magnet 41 and the second permanent magnet 42 before magnetization, are magnetized by the magnetizer so that different magnetic poles are formed. Also, the external magnet 4b before magnetization, i.e., the third permanent magnet 43 and the fourth permanent magnet 44 before magnetization, are magnetized by the magnetizer so that different magnetic poles are formed. At this time, magnetization is performed so that the d-axis of the internal magnet 4a and the d-axis of the external magnet 4b are shifted by a predetermined angle θ in the circumferential direction.

[0053] In the following step S4, the shaft 5 is attached to the rotor core 3. With the above, the manufacture of the rotor 1 is completed.

[0054] According to the manufacturing method of the rotor 1 described above, when the magnet unit 4 in which the internal magnet 4a and the external magnet 4b are connected is injection molded, in the mold M in which the rotor core 3 is installed, a single space is formed by the multiple first arrangement holes 31, the multiple second arrangement holes 32, and the space Ls for the external magnet. Therefore, the magnet material only needs to be injected into this single space. Therefore, in the mold M, the number of spaces into which the magnet material must be injected is reduced, so that the number of flow paths such as the runner Ru and the gate Ga can be reduced. This allows the cost related to the mold M to be reduced. As a result, the manufacturing cost of the rotor 1 can be reduced.

[0055] In this manner, the rotor 1 is provided with a plurality of first permanent magnets 41 and a plurality of second permanent magnets 42 that are alternately arranged in the circumferential direction on the rotor body 2 and form different magnetic poles, a plurality of third permanent magnets 43 that are positioned on the end face 3a of the rotor body 2 corresponding to the plurality of first permanent magnets 41, respectively, and form the same magnetic pole as the first permanent magnets 41, and a plurality of fourth permanent magnets 44 that are positioned on the end face 3a corresponding to the plurality of second permanent magnets 42, respectively, and form the same magnetic pole as the second permanent magnets 42. The d-axis of each of the first permanent magnets 41 and the second permanent magnets 42 and the d-axis of each of the third permanent magnets 43 and the fourth permanent magnets 44 are offset in the circumferential direction. Therefore, by shifting the d-axis of the first permanent magnet 41 and the second permanent magnet 42 from the d-axis of the third permanent magnet 43 and the fourth permanent magnet 44 so that the current phase at which the external magnet torque Tmb is maximized coincides with the current phase at which the combined torque of the reluctance torque Tr and the internal magnet torque Tma is maximized, the maximum torque of the total torque Tt becomes higher. This improves the output efficiency of the motor 100.

[0056] In addition, in the rotor 1 of this example, the third permanent magnet 43 and the fourth permanent magnet 44 are each provided at a position corresponding to the first permanent magnet 41 and the second permanent magnet 42 on the end face 3a of the rotor core 3, thereby preventing the first permanent magnet 41 and the second permanent magnet 42 from coming out of the rotor core 3.

[0057] Moreover, in the rotor 1 of this example, the multiple third permanent magnets 43 and the multiple fourth permanent magnets 44 are provided on both end faces 3a of the rotor core 3. Therefore, the first permanent magnets 41 and the second permanent magnets 42 can be reliably prevented from coming out of the rotor core 3.

[0058] Furthermore, in the rotor 1 of this example, each of the multiple third permanent magnets 43 is connected to the end face 41a of the first permanent magnet 41, and each of the multiple fourth permanent magnets 44 is connected to the end face 42a of the second permanent magnet 42. Therefore, the first permanent magnet 41 and the second permanent magnet 42 can be reliably prevented from coming out of the rotor core 3.

[0059] In addition, in the rotor 1 of this example, the third permanent magnets 43 and the fourth permanent magnets 44 are connected in the circumferential direction. Therefore, the surface area of ​​the third permanent magnets 43 and the fourth permanent magnets 44 can be increased compared to a case where the third permanent magnets 43 and the fourth permanent magnets 44 are separated, for example. Therefore, the external magnet torque Tmb can be further increased.

[0060] In the rotor 1 of this example, the first permanent magnet 41, the second permanent magnet 42, the third permanent magnet 43, and the fourth permanent magnet 44 are bonded magnets. Therefore, each permanent magnet can be easily formed into a desired shape. This is particularly effective in the case where the third permanent magnet 43 is connected to the end face 41a of the first permanent magnet 41 and the fourth permanent magnet 44 is connected to the end face 42a of the second permanent magnet 42, as described above.

[0061] Other Embodiments As described above, the above embodiment has been described as an example of the technology disclosed in this application. However, the technology in this disclosure is not limited to this, and can be applied to embodiments in which modifications, replacements, additions, omissions, etc. are appropriately performed. In addition, it is also possible to combine the components described in the above embodiment to form a new embodiment. In addition, among the components described in the attached drawings and detailed description, not only components essential for solving the problem but also components that are not essential for solving the problem in order to exemplify the technology may be included. Therefore, the fact that these non-essential components are described in the attached drawings and detailed description should not immediately be taken to mean that these non-essential components are essential.

[0062] For example, the magnetization direction of the external magnet 4b may be set as shown in Fig. 10. Fig. 10 is a view equivalent to Fig. 3, showing a rotor 1 according to another embodiment with some parts omitted.

[0063] Specifically, in the rotor 1 of this example, the magnetization direction Ha of each of the internal magnets 4a, i.e., the first permanent magnet 41 and the second permanent magnet 42, is set to a direction toward the radially outward side. In other words, the magnetization direction Ha of the internal magnet 4a is set to a direction perpendicular to the rotation axis A. The magnetization direction Hb of each of the external magnets 4b, i.e., the third permanent magnet 43 and the fourth permanent magnet 44, is set to a direction inclined toward the rotor body 2 as it moves toward the radially outward side. In other words, the magnetization direction Hb of the external magnet 4b is set to a direction that obliquely intersects with the rotation axis A.

[0064] By setting the magnetization direction Hb of the external magnet 4b in this way, the height h of the stator 6 can be reduced as shown in Fig. 10. In other words, if the magnetization direction of the external magnet 4b is set to a direction perpendicular to the rotation axis A like the magnetization direction Ha of the internal magnet 4a, the height of the stator 6 needs to be the height shown by the dashed line in Fig. 10, that is, the length obtained by adding the thickness of the two external magnets 4b to the height of the rotor core 3. In this example, by setting the magnetization direction Hb of the external magnet 4b as described above, the height h of the stator 6 can be reduced to, for example, the same height as the rotor core 3. Therefore, the motor 100 can be made smaller without significantly reducing the external magnet torque Tmb and thus the output of the motor 100.

[0065] The magnetization direction of the external magnet 4b may be set as shown in Fig. 11. Fig. 11 is a view equivalent to Fig. 3, showing a rotor 1 according to another embodiment with some parts omitted.

[0066] Specifically, in the rotor 1 of this example, the magnetization direction Ha of the internal magnet 4a is set to a direction toward the outside in the radial direction. In other words, the magnetization direction Ha of the internal magnet 4a is set to a direction perpendicular to the rotation axis A. The magnetization direction Hb of the external magnet 4b is set to a direction toward the rotor body 2 in the rotation axis direction. In other words, the magnetization direction Hb of the external magnet 4b is set to a direction perpendicular to the magnetization direction Ha of the internal magnet 4a.

[0067] By setting the magnetization direction Hb of the external magnet 4b in this manner, the magnetic flux of the external magnet 4b, like the magnetic flux of the internal magnet 4a, flows to the stator 6 through a portion of the rotor core 3 that is radially outward of the internal magnet 4a. Therefore, as shown in FIG. 11, the height of the stator 6 can be reduced, for example to the same height as the rotor core 3, and the air gap 10 can be reduced. Reducing the air gap 10 can suppress a decrease in the total torque Tt, i.e., a decrease in the output of the motor 100. Therefore, the motor 100 can be made smaller while further suppressing a decrease in the output of the motor 100.

[0068] Furthermore, the numbers of the first permanent magnets 41, the second permanent magnets 42, the third permanent magnets 43, and the fourth permanent magnets 44 are not limited to the above-mentioned numbers. That is, the number of poles of the rotor 1 is not limited to the above-mentioned numbers.

[0069] Further, the number of magnet units 4 is not limited to one set. That is, the number of external magnets 4b provided on one end face 3a of the rotor core 3 is not limited to one set. For example, one set of external magnets 4b may be formed by one third permanent magnet 43 and one fourth permanent magnet 44 in one section obtained by dividing the multiple third permanent magnets 43 and multiple fourth permanent magnets 44 provided on one end face 3a of the rotor core 3 into three in the circumferential direction. In this case, three sets of external magnets 4b are provided on one end face 3a of the rotor core 3. That is, three sets of magnet units 4 are provided on the rotor 1. In this way, two or six sets of magnet units 4 may be provided.

[0070] Moreover, the external magnet 4b may be provided on only one end surface 3a of the rotor core 3.

[0071] Furthermore, all of the first permanent magnets 41, the second permanent magnets 42, the third permanent magnets 43 and the fourth permanent magnets 44 may be formed separately and not connected to each other.

[0072] Moreover, the first permanent magnet 41, the second permanent magnet 42, the third permanent magnet 43 and the fourth permanent magnet 44 may be anisotropic bonded magnets or may be isotropic bonded magnets.

[0073] Furthermore, the cross-sectional shapes of the first permanent magnet 41 and the second permanent magnet 42 are not limited to curved shapes. For example, these cross-sectional shapes may be bent so as to be concave toward the rotation axis A. Specifically, these cross-sectional shapes may be, for example, V-shaped or W-shaped. Furthermore, the first permanent magnet 41 and the second permanent magnet 42 may be flat plate members whose cross-sectional shapes extend linearly.

[0074] Furthermore, the shaft 5 does not have to be made of a soft magnetic material. The shaft 5 may be formed integrally with the rotor core 3.

[0075] In addition, the d-axis of the external magnet 4b may be shifted in the circumferential direction relative to the d-axis of the internal magnet 4a so as to cancel out the cogging torque and torque ripple. In this case, the cogging torque and torque ripple can be reduced.

[0076] As described above, the rotor 1 according to the first aspect of the technique of the present disclosure includes the rotor body 2 having the rotation axis A, and the plurality of first permanent magnets 41 and the plurality of second permanent magnets 42 that are alternately arranged in the circumferential direction around the rotation axis A on the rotor body 2 and form different magnetic poles. The rotor body 2 is provided with a plurality of third permanent magnets 43, which are provided on an end face 3a in the direction of the rotation axis A of the rotor body 2 in correspondence with the plurality of first permanent magnets 41 and which form the same magnetic pole as the first permanent magnets 41, and a plurality of fourth permanent magnets 44, which are provided on an end face 3a in the direction of the rotation axis A of the rotor body 2 in correspondence with the plurality of second permanent magnets 42 and which form the same magnetic pole as the second permanent magnets 42. The d-axis of each of the first permanent magnets 41 and the second permanent magnet 42 and the d-axis of each of the third permanent magnets 43 and the fourth permanent magnet 44 are offset in the circumferential direction.

[0077] According to this configuration, the d-axis of the first permanent magnet 41 and the second permanent magnet 42 is shifted from the d-axis of the third permanent magnet 43 and the fourth permanent magnet 44 so that the current phase at which the external magnet torque Tmb is maximized coincides with the current phase at which the combined torque of the reluctance torque Tr and the internal magnet torque Tma is maximized, thereby increasing the maximum torque of the total torque Tt. This makes it possible to improve the output efficiency of the motor 100. In other words, the provision of the third permanent magnet 43 and the fourth permanent magnet 44 increases the magnet torque, and the increased magnet torque can be effectively utilized as the output of the motor 100.

[0078] In addition, in the rotor 1 according to the second aspect of the technique of the present disclosure, the multiple third permanent magnets 43 and the multiple fourth permanent magnets 44 in the rotor 1 according to the first aspect are connected in the circumferential direction.

[0079] According to this configuration, for example, the surface area or volume of the third permanent magnet 43 and the fourth permanent magnet 44 can be increased compared to a case where the third permanent magnet 43 and the fourth permanent magnet 44 are separated. Therefore, the external magnet torque Tmb can be further increased. Therefore, the output of the motor 31 is improved.

[0080] In addition, in a rotor 1 relating to a third aspect of the technology of the present disclosure, in the rotor 1 relating to the first or second aspect, a plurality of third permanent magnets 43 and a plurality of fourth permanent magnets 44 are provided on both end faces in the direction of the rotation axis A of the rotor body 2.

[0081] According to this configuration, a plurality of third permanent magnets 43 and a plurality of fourth permanent magnets 44 are provided on both end faces 3a of the rotor core 3, so that the third permanent magnets 43 and the fourth permanent magnets 44 can reliably prevent the first permanent magnets 41 and the second permanent magnets 42 from coming out of the rotor core 3.

[0082] In addition, in a rotor 1 relating to a fourth aspect of the technology of the present disclosure, in a rotor 1 relating to any one of the first to third aspects, each of the multiple third permanent magnets 43 is connected to an end face 41a in the direction of the rotation axis A of the first permanent magnet 41, and each of the multiple fourth permanent magnets 44 is connected to an end face 42a in the direction of the rotation axis A of the second permanent magnet 42.

[0083] According to this configuration, the first permanent magnets 41 and the second permanent magnets 42 can be more reliably prevented from coming out of the rotor core 3.

[0084] In addition, in a rotor 1 relating to a fifth aspect of the technology of the present disclosure, in a rotor 1 relating to any one of the first to fourth aspects, the magnetization directions of the third permanent magnet 43 and the fourth permanent magnet 44 are set in a direction that inclines toward the rotor body 2 as they move radially outward from the rotation axis A.

[0085] According to this configuration, the height h of the stator 6 can be reduced. In other words, when the magnetization directions of the third permanent magnet 43 and the fourth permanent magnet 44 are set to a direction perpendicular to the rotation axis A, the height of the stator 6 usually requires a length equal to the height of the rotor core 3 plus the thickness of the third permanent magnet 43 and the fourth permanent magnet 44. However, according to this technology, it is possible to reduce the height h of the stator 6 to, for example, approximately the same height as the rotor core 3. Therefore, the motor 100 can be made smaller without significantly reducing the output of the motor 100.

[0086] In addition, in a rotor 1 relating to a sixth aspect of the technology of the present disclosure, in a rotor 1 relating to any one of the first to fifth aspects, the first permanent magnet 41, the second permanent magnet 42, the third permanent magnet 43 and the fourth permanent magnet 44 are bonded magnets.

[0087] This configuration makes it easy to form the first permanent magnet 41 etc. into a desired shape. This is particularly effective in cases where the third permanent magnet 43 is connected to the end face 41a of the first permanent magnet 41 and the fourth permanent magnet 44 is connected to the end face 42a of the second permanent magnet 42.

[0088] Moreover, the motor 100 according to the seventh aspect of the technique of the present disclosure includes a cylindrical stator 6 and a rotor 1 according to any one of the first to sixth aspects that is disposed inside the stator 6.

[0089] According to this configuration, like the rotor 1 according to the first aspect, the output efficiency of the motor 100 can be improved. [Explanation of symbols]

[0090] 100 Motor 1 rotor 2 Rotor body 3 Rotor core (rotor body) 3a End face 41 First permanent magnet 41a End face 42 Second permanent magnet 42a End face 43 Third permanent magnet 44 4th permanent magnet 6 Stator A Rotation Axis

Claims

1. A rotor body having a rotating shaft; a plurality of first permanent magnets and a plurality of second permanent magnets that are alternately arranged in the rotor body in a circumferential direction around the rotation axis and form different magnetic poles; a plurality of third permanent magnets provided on an end surface of the rotor body in the direction of the rotation axis in correspondence with the plurality of first permanent magnets, the third permanent magnets forming the same magnetic poles as the first permanent magnets; a plurality of fourth permanent magnets provided on an end surface of the rotor body in the direction of the rotation axis in correspondence with the plurality of second permanent magnets, the fourth permanent magnets forming the same magnetic poles as the second permanent magnets, a d-axis of each of the first permanent magnet and the second permanent magnet is offset from a d-axis of each of the third permanent magnet and the fourth permanent magnet in the circumferential direction, the third permanent magnets and the fourth permanent magnets are provided on both end surfaces of the rotor body in a direction of the rotation axis, A rotor in which the multiple third permanent magnets and the multiple fourth permanent magnets are connected in the circumferential direction at each of the end faces of the rotor body, each of the multiple third permanent magnets is connected to an end face of the first permanent magnet in the direction of the rotation axis, and each of the multiple fourth permanent magnets is connected to an end face of the second permanent magnet in the direction of the rotation axis.

2. 2. The rotor according to claim 1, A rotor in which the magnetization directions of the third permanent magnet and the fourth permanent magnet are set in a direction that inclines toward the rotor body as it moves radially outward from the rotation axis.

3. 2. The rotor according to claim 1, The rotor, wherein the first permanent magnet, the second permanent magnet, the third permanent magnet, and the fourth permanent magnet are bonded magnets.

4. A cylindrical stator; A motor comprising: a rotor according to claim 1 disposed inside the stator.

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