Rotor and motor

Abstract

A technology for reducing the d-axis inductance in a rotor is provided. A rotor (20) according to one embodiment of the present invention includes: permanent magnets (22, 23) which are housed in different magnet slots formed in a rotor core (21) and are magnetically arranged in series; and a flux barrier (cavity 24) which is provided near an end of each of the permanent magnets (22, 23) arranged in series magnetically, in a direction orthogonal to the direction of the main magnetic flux. Furthermore, a cavity (24) is provided in a manner that the flux barriers corresponding to each of the permanent magnets (22, 23) arranged in series magnetically are connected to each other. An electric motor (1) according to another embodiment of the present invention includes the above-mentioned rotor (20).

Description

Technical Field

[0001] The invention relates to a rotor and an electric motor. Background Art

[0002] For example, there is known a technique in which a slit extending in the protruding direction of stator teeth of a stator is formed to reduce the d-axis inductance and increase the reluctance torque (see Patent Document 1).

[0003] <Prior Art Literature>

[0004] <Patent Documents>

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-244738 Summary of the invention

[0006] <Problems to be Solved by the Invention>

[0007] However, Patent Document 1 does not describe a method for reducing the d-axis inductance on the rotor side.

[0008] An object of the present invention is to provide a technology for reducing the d-axis inductance in a rotor.

[0009] <Methods used to solve the problem>

[0010] In one embodiment of the present invention, a rotor is provided, comprising:

[0011] Iron core;

[0012] a plurality of permanent magnets which are housed in different magnet slots formed in the core and are magnetically arranged in series; and

[0013] a magnetic flux barrier provided near an end in a direction orthogonal to the direction of the main magnetic flux with respect to each of at least two permanent magnets magnetically arranged in series among the plurality of permanent magnets;

[0014] The magnetic flux barriers corresponding to each of the at least two permanent magnets magnetically arranged in series are connected to each other.

[0015] According to this embodiment, the rotor can increase the magnetic resistance in the d-axis direction by using a plurality of permanent magnets arranged magnetically in series. In addition, the rotor can suppress the situation where the magnetic flux at the end of one permanent magnet does not leak through the other permanent magnets connected in series magnetically because the magnetic flux barriers corresponding to each of at least two permanent magnets arranged magnetically in series are connected to each other. Therefore, the rotor can reduce the d-axis inductance.

[0016] In addition, in the above-mentioned embodiment,

[0017] The plurality of permanent magnets include a first permanent magnet having the highest coercive force and a second permanent magnet having a lower coercive force than the first permanent magnet.

[0018] Among the plurality of permanent magnets, the first permanent magnet is disposed on the magnetically outermost peripheral side, and the second permanent magnet is disposed on the magnetically inner peripheral side of the first permanent magnet.

[0019] In addition, in the above-mentioned embodiment,

[0020] The plurality of permanent magnets are each composed of one magnet component or a plurality of magnet components that are separated from each other and magnetically connected in parallel.

[0021] In at least one group of two permanent magnets that are magnetically arranged in series and adjacent to each other and included in the above-mentioned multiple permanent magnets, the total surface area of ​​the outer peripheral surface of the above-mentioned one magnet component or the outer peripheral surfaces of the above-mentioned multiple magnet components that constitute the magnetic inner peripheral side of the permanent magnet is larger than the total surface area of ​​the inner peripheral surface of the above-mentioned one magnet component or the inner peripheral surface of the above-mentioned multiple magnet components that constitute the magnetic outer peripheral side of the permanent magnet.

[0022] In addition, in another embodiment of the present invention,

[0023] An electric motor is provided, comprising the above-mentioned rotor.

[0024] <Effects of the Invention>

[0025] According to the above-described embodiment, it is possible to provide a technology for reducing the d-axis inductance in the rotor. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a cross-sectional view schematically showing the structure of the motor.

[0027] Figure 2 This is a cross-sectional view showing a first example of the structure of the rotor.

[0028] Figure 3 It is a cross-sectional view showing a second example of the structure of the rotor.

[0029] Figure 4 It is a cross-sectional view showing a third example of the structure of the rotor.

[0030] Figure 5 It is a cross-sectional view showing a fourth example of the structure of the rotor.

[0031] Figure 6 It is a cross-sectional view showing a fifth example of the structure of the rotor.

[0032] Figure 7 It is a cross-sectional view showing a sixth example of the structure of the rotor. DETAILED DESCRIPTION

[0033] Hereinafter, embodiments will be described with reference to the drawings.

[0034] [Basic structure of electric motor]

[0035] First, refer to Figure 1 , the structure of the electric motor 1 according to the present embodiment will be described.

[0036] Figure 1 It is a cross-sectional view of the electric motor 1 according to the present embodiment.

[0037] It should be noted that in Figure 1 In the embodiment, permanent magnets 22 and 23 are omitted (see Figure 2 to Figure 7 ) icon.

[0038] The electric motor (also referred to as a “motor”) 1 is mounted on, for example, a compressor of an air conditioner.

[0039] like Figure 1 As shown, the motor 1 includes a stator 10 , a rotor 20 , and a rotating shaft 30 .

[0040] The stator (also referred to as “stator”) 10 is disposed on the outer peripheral side of the electric motor 1 and is fixed to a case (not shown). The stator 10 includes a stator core 11 and a winding 12 .

[0041] The stator core 11 is formed of a ferromagnetic material such as an electromagnetic steel plate or a pressed powder core. The stator core 11 includes a substantially cylindrical back yoke 11A and a plurality of (nine in this example) teeth 11B radially protruding from the inner circumference of the back yoke 11A.

[0042] The plurality of teeth 11B are arranged at substantially equal intervals in the circumferential direction on the inner peripheral surface of the back yoke portion 11A. Slots for accommodating the winding 12 (hereinafter referred to as "winding slots") are formed between two circumferentially adjacent teeth 11B. In this example, nine winding slots are formed.

[0043] The winding 12 is wound around each of the plurality of teeth 11B by concentrated winding. An insulating member such as an insulating film made of PET (Polyethylene Terephthalate) is provided between the winding 12 and the teeth 11B.

[0044] It should be noted that the winding 12 may be wound across a plurality of teeth 11B by distributed winding. In addition, the number of teeth 11B, that is, the number of winding slots formed between adjacent teeth 11B, may be 8 or less, or 10 or more.

[0045] The rotor (also referred to as “rotor”) 20 is rotatably provided radially inside the stator 10 .

[0046] The rotating shaft 30 is supported so as to be rotatable relative to the housing of the electric motor 1 . Thus, the rotor 20 (rotor core 21 ) fixed to the rotating shaft 30 is rotatable relative to the housing and the stator 10 .

[0047] [Detailed structure of the rotor]

[0048] Next, refer to Figure 2 to Figure 7 , the detailed structure of the rotor 20 is described.

[0049] <First Example of Rotor Configuration>

[0050] Figure 2 It is a cross-sectional view showing a first example of the structure of the rotor 20 .

[0051] It should be noted that in Figure 2 , a half-circle of the cross-section of the rotor 20 having a substantially cylindrical shape and a hollow portion for inserting the rotating shaft 30 is depicted. Figure 3 to Figure 7 Same.

[0052] The rotor 20 includes a rotor core 21 and permanent magnets 22 and 23 embedded in the rotor core 21 .

[0053] The rotor core (also called "rotor core") 21 (an example of a core) is a component of the rotor 20, which is based on the magnetic circuit in the magnetic field of the current flowing through the winding of the stator 10, and the magnetic circuit in the magnetic field of the permanent magnets 22 and 23. "Magnetic circuit" refers to, for example, a part where the magnetic flux passing through is 1 / 10 or more of the average value when the motor 1 is driven to rotate. The rotor core 21 has a roughly cylindrical shape and is fixed to the rotating shaft 30. The rotor core 21 can be formed of a ferromagnetic material such as an electromagnetic steel plate or a pressed powder core. A space (hereinafter referred to as a "magnet slot") for burying each permanent magnet 22 and 23 is provided in the rotor core 21.

[0054] A plurality of permanent magnets 22 and 23 (six in this example) are buried in the rotor core 21 .

[0055] It should be noted that the number of permanent magnets 22 and 23 may be less than five or more than seven.

[0056] The six permanent magnets 22 are arranged at equal intervals in the circumferential direction at radial positions relatively close to the outer peripheral surface of the rotor core 21 .

[0057] The six permanent magnets 23 are respectively arranged at radially inner positions than the permanent magnets 22 and at substantially the same circumferential positions as the permanent magnets 22. Thus, the permanent magnets 22 and 23 are arranged in the radial direction.

[0058] The permanent magnet 22 has a relatively high coercive force. In addition, the permanent magnet 22 may have a relatively high magnetic force. The permanent magnet 22 is, for example, a neodymium sintered magnet.

[0059] The permanent magnet 23 has a relatively low coercive force. In addition, the permanent magnet 23 may have a relatively low magnetic force. The permanent magnet 23 is, for example, a ferrite magnet.

[0060] The permanent magnet 22 is composed of a magnet component. Specifically, the permanent magnet 22 has a substantially rectangular shape with one side being sufficiently longer than the other side when viewed in the axial direction, and is arranged so that the long side is substantially orthogonal to the radial axis at the substantially center. The permanent magnet 22 is magnetized so that the two ends in the short side direction have different magnetic poles.

[0061] The permanent magnet 23 includes two separate magnet components 23A and 23B. Specifically, the magnet components 23A and 23B each have a roughly rectangular shape in which the other side is sufficiently long relative to one side when viewed axially. The magnet components 23A and 23B having the roughly same elongated rectangular shape are symmetrically arranged in a convex V-shape radially inwardly with the radial axis (d axis) as the center. Thus, the permanent magnet 23 has a V-shaped shape that is convex radially inwardly with the radial axis as the center. The magnet components 23A and 23B are magnetized in a manner that has different magnetic poles at both ends in the short side direction.

[0062] Each of the six permanent magnets 22 is configured so that the magnetic pole magnetized on the side facing the stator 10 is different from the other permanent magnets 22 arranged adjacent in the circumferential direction. For example, when the side facing the stator 10 of one permanent magnet 22 is magnetized to the S pole, the side facing the stator 10 of the other permanent magnets 22 adjacent to the one permanent magnet 22 in the circumferential direction is magnetized to the N pole.

[0063] The six permanent magnets 23 (i.e., six groups of magnet components 23A, 23B) are each configured so that the magnetic poles magnetized on the side of the permanent magnet 22 facing the substantially same circumferential position are different from the side of the permanent magnet 22 facing the permanent magnet 23. The side of the permanent magnet 22 facing the permanent magnet 23 corresponds to the opposite side of the permanent magnet 22 facing the stator 10. Thus, the permanent magnets 22 and 23 are magnetically configured in series. In addition, the magnet components 23A and 23B are magnetically configured in parallel. Therefore, compared with the case where only one permanent magnet is configured in the radial direction, the magnetic resistance in the d-axis direction of the motor 1 (rotor 20) can be increased, thereby reducing the d-axis inductance Ld. Therefore, the salient pole ratio, which is equivalent to the ratio (Lq / Ld) of the d-axis inductance Ld to the q-axis inductance Lq, can be increased, thereby increasing the magnetic resistance torque of the motor 1. In particular, when the rotor 20 uses magnet members 23A and 23B having relatively low coercive force and magnetic force as the permanent magnets 23, it is possible to suppress cost increases and reduce the d-axis inductance Ld. This also applies to the second to sixth examples described below.

[0064] In addition, as described above, among the permanent magnets 22 and 23, the permanent magnet 22 arranged on the outermost side in the radial direction has the highest coercive force, and the permanent magnet 23 arranged on the inner side of the permanent magnet 22 has a relatively lower coercive force than the permanent magnet 22. Therefore, for the rotor 20, the demagnetization of the permanent magnets 22 and 23 can be suppressed by the action of the permanent magnets 22 having a relatively high coercive force. In addition, for the rotor 20, by adopting the permanent magnets 23 having a relatively low coercive force, the cost can be suppressed. Therefore, the rotor 20 can take into account both the cost suppression of the motor 1 and the suppression of the demagnetization of the permanent magnets 22 and 23. The same is true for the second to sixth examples described below.

[0065] In addition, as described above, the permanent magnet 23 has a V-shaped shape when viewed axially. Therefore, for the permanent magnet 23, compared with the case of an elongated rectangular shape such as the permanent magnet 22, its surface area (specifically, the total surface area of ​​the magnet component 23A and the magnet component 23B) can be relatively increased. Therefore, the rotor 20 can increase the magnetic flux of the magnetic field. In particular, when using magnet components 23A and 23B with relatively low coercive force and magnetic force as the permanent magnet 23, the rotor 20 can suppress the cost increase of the motor 1 and ensure the magnetic flux of the rotor 20. The same is true for the third example and the fifth example described below.

[0066] In addition, as described above, the permanent magnet 22 has an elongated rectangular shape when viewed in the axial direction, while the permanent magnet 23 has a V-shaped shape when viewed in the axial direction. As a result, the surface area of ​​the outer peripheral surface of the permanent magnet 23 (specifically, the total surface area of ​​the outer peripheral surfaces of the magnet component 23A and the magnet component 23B) is larger than the surface area of ​​the inner peripheral surface of the permanent magnet 22. Therefore, for the rotor 20, even when the magnetic force (i.e., magnetic flux density) of the permanent magnet 23 is relatively low, the magnetic flux based on the permanent magnet 23 can be increased, and the magnetic flux of the permanent magnet 22 that does not pass through the permanent magnet 23 can be reduced. Therefore, the rotor 20 can further reduce the d-axis inductance Ld. The same is true for the fifth example described below.

[0067] In addition, as described above, the permanent magnets 22 and 23 arranged at substantially the same circumferential position are buried in different magnet slots. As a result, the centrifugal force acting on the two permanent magnets 22 and 23 can be dispersed and borne by the wall portions of the corresponding two magnet slots. Therefore, compared with the case where the two permanent magnets 22 and 23 are buried in one magnet slot, the stress acting on the magnet slot portion of the rotor core 21 can be relatively small. Therefore, the durability against the centrifugal force during high-speed operation of the motor 1 can be ensured, and the d-axis inductance Ld based on the permanent magnets 22 and 23 can be reduced. In addition, for example, there is no need to adopt a process that reduces productivity, such as a pre-process of integrating the two permanent magnets 22 and 23 or a process of inserting the two separated permanent magnets 22 and 23 into the same slot, as in the case where the permanent magnets 22 and 23 are buried in the same magnet slot. Therefore, it is possible to suppress the reduction in productivity of the motor 1 and reduce the d-axis inductance Ld based on the permanent magnets 22 and 23. The same applies to the second to sixth examples described below.

[0068] It should be noted that the permanent magnets 22 and 23 may be of the same type and have substantially the same magnetic force and coercive force.

[0069] The magnet slots corresponding to the permanent magnets 22 of the rotor core 21 include hollow portions 24 .

[0070] The cavity 24 is provided at a position adjacent to both ends of the permanent magnet 22 in the long-side direction when the permanent magnet 22 is embedded in the magnet slot. Both ends of the permanent magnet 22 in the long-side direction correspond to both ends in the direction perpendicular to the direction of the main magnetic flux generated from the permanent magnet 22. Thus, the cavity 24 suppresses the short circuit of the magnetic flux at the ends in the direction perpendicular to the direction of the main magnetic flux of the permanent magnet 22, and acts as a magnetic flux barrier. This is because the magnetic permeability of the air present in the cavity 24 is lower than that of the material of the rotor core 21 (for example, electromagnetic steel plate, pressed powder core, etc.).

[0071] In addition, the cavity 24 expands radially inward to a position close to the other end of each of the set of magnet components 23A and 23B opposite to the one end adjacent to each other in the long side direction. The other end of each of the set of magnet components 23A and 23B opposite to the one end adjacent to each other in the long side direction corresponds to the two ends in the direction orthogonal to the direction of the main magnetic flux generated by the permanent magnet 23. Thus, the cavity 24 suppresses the short circuit of the magnetic flux at the end in the direction orthogonal to the direction of the main magnetic flux of the permanent magnet 23, and acts as a magnetic flux barrier.

[0072] The magnet slots corresponding to the permanent magnets 23 of the rotor core 21 include hollow portions 25 .

[0073] The cavity 25 is arranged (formed) between the facing ends of the magnet member 23A and the magnet member 23B (i.e., the portion corresponding to the bottom of the V-shape) when the permanent magnet 23, i.e., the magnet members 23A and 23B, are embedded in the magnet groove.

[0074] In rotor core 21 , inter-magnet core portion 21A surrounded by permanent magnets 22 , 23 and cavity 24 is connected to radially inner portions of permanent magnets 23 via two inner ribs 21B formed between magnet slots corresponding to permanent magnets 23 and cavity 24 .

[0075] It should be noted that, in place of at least one of the two inner ribs 21B, or in addition to the two inner ribs 21B, a rib (hereinafter referred to as an "outer rib" for convenience) connecting the inter-magnet core portion 21A to the portion radially outward of the permanent magnet 22 may be provided. In this case, the outer rib may be provided between the end of the permanent magnet 22 in a direction perpendicular to the direction of the main magnetic flux and the cavity 24, similarly to the inner rib 21B, or may be provided in a manner that cuts off the permanent magnet 22, similarly to the inner rib 21C described later. In this case, it is preferred that the number of inner ribs 21B is greater than the number of outer ribs. The same applies to the second to sixth examples described later.

[0076] In this way, the cavity 24 is arranged (formed) inside the rotor core 21 so that the magnetic flux barrier corresponding to the permanent magnet 22 and the magnetic flux barrier corresponding to the permanent magnet 23 are connected. As a result, the magnetic flux generated from the end of one of the permanent magnets 22 and 23 is prevented from leaking without passing through the other, thereby further reducing the d-axis inductance Ld. The same applies to the second to sixth examples described below.

[0077] It should be noted that at least a portion of the cavity 24 can be replaced with a component having a lower magnetic permeability than the material of the rotor core 21 (for example, a non-magnetic component). This is because, like the air present in the cavity 24, the lower the magnetic permeability compared to the material of the rotor core 21, the more it can function as a flux barrier that suppresses the short circuit of the magnetic flux. In addition, the cavity 24 (flux barrier) corresponding to each of the two permanent magnets 22 adjacent in the circumferential direction is not connected. The same applies to the second to sixth examples described below.

[0078] <Second Example of Motor Configuration>

[0079] Figure 3 2 is a cross-sectional view showing a second example of the structure of the rotor 20. Hereinafter, the description will be mainly focused on the parts different from the first example, and the description of the same or corresponding structures as the first example may be omitted.

[0080] like Figure 3 As shown, in this example, as in the case of the above-mentioned first example, the permanent magnet 22 is composed of one magnet member, which has an elongated rectangular shape when viewed in the axial direction.

[0081] In addition, in this example, the permanent magnet 23 is composed of a single magnet member, similarly to the permanent magnet 22. Specifically, similarly to the permanent magnet 22, the permanent magnet 23 has a substantially rectangular shape in which one side is sufficiently long relative to the other side when viewed in the axial direction, and is arranged so that the long side is substantially orthogonal to the radial axis at the substantially center. Similar to the permanent magnet 22, the permanent magnet 23 is magnetized so that the two ends in the short side direction have different magnetic poles.

[0082] As in the case of the first example, the permanent magnets 22 and 23 arranged at substantially the same circumferential position are magnetically arranged in series. Thus, as in the case of the first example, the rotor 20 can reduce the d-axis inductance Ld.

[0083] Also, similarly to the first example, the cavity 24 is disposed (formed) inside the rotor core 21 so that the flux barriers corresponding to the permanent magnets 22 communicate with the flux barriers corresponding to the permanent magnets 23. This can further reduce the d-axis inductance Ld.

[0084] In this example, the permanent magnets 22 and 23 are each formed of a single magnet component. This can reduce the number of components of the permanent magnets 22 and 23. Therefore, the rotor 20 can reduce the cost of the motor 1 and reduce the d-axis inductance Ld.

[0085] <Third Example of Motor Configuration>

[0086] Figure 42 is a cross-sectional view showing a third example of the structure of the rotor 20. The following description will focus on the parts different from the first and second examples, and the description of the same or corresponding structure as at least one of the first and second examples may be omitted.

[0087] like Figure 4 As shown, in this example, as in the first example, the permanent magnet 23 includes two magnet components 23A and 23B having substantially the same rectangular shape, which are symmetrically arranged in a radially inwardly convex V-shape around the radial axis (d-axis) when viewed axially.

[0088] In addition, in this example, the permanent magnet 22 includes two separate magnet components 22A and 22B, similar to the permanent magnet 23. Specifically, the magnet components 22A and 22B each have a roughly rectangular shape in which the other side is sufficiently long relative to one side when viewed axially. The magnet components 22A and 22B having the same roughly elongated rectangular shape are symmetrically arranged in a V-shape convex inwardly in the radial direction with the radial axis (d axis) as the center. Thus, similar to the permanent magnet 23, the permanent magnet 22 has a V-shaped shape convex inwardly in the radial direction with the radial axis as the center. The magnet components 22A and 22B are each magnetized in a manner that has different magnetic poles at both ends in the short side direction. Similar to the magnet components 23A and 23B, the magnet components 22A and 22B are magnetically arranged in parallel.

[0089] The magnet slots corresponding to the permanent magnets 22 of the rotor core 21 include hollow portions 26 .

[0090] The cavity 26 is arranged (formed) between the facing ends of the magnet member 22A and the magnet member 22B (i.e., the portion corresponding to the bottom of the V-shape) when the permanent magnet 22, i.e., the magnet members 22A and 22B, are buried in the magnet groove.

[0091] In this example, as in the first example, permanent magnets 22 and 23, specifically magnet components 22A and 22B and magnet components 23A and 23B, arranged at substantially the same circumferential position are magnetically arranged in series. Thus, as in the first example, the rotor 20 can reduce the d-axis inductance Ld.

[0092] Also, similarly to the first example, the cavity 24 is arranged (formed) inside the rotor core 21 so that the flux barriers corresponding to the permanent magnets 22 communicate with the flux barriers corresponding to the permanent magnets 23. This can further reduce the d-axis inductance Ld.

[0093] In addition, in this example, in addition to the permanent magnet 23, the permanent magnet 22 has a V-shaped shape when viewed axially. Therefore, for the permanent magnet 22, for example, its surface area (specifically, the total surface area of ​​the magnet component 22A and the magnet component 22B) can be relatively increased compared to the case of an elongated rectangular shape. Therefore, the rotor 20 can further increase the magnetic flux of the magnetic field. In addition, since the permanent magnet 22 has a V-shaped shape, the portion of the rotor core 21 that is radially closer to the outside than the permanent magnet 22 increases. Therefore, the rotor 20 can increase the q-axis inductance Lq, thereby further increasing the salient pole ratio (Lq / Ld). Therefore, the rotor 20 can increase the reluctance torque of the motor 1, thereby further improving the output of the motor 1.

[0094] <Fourth Example of the Configuration of the Motor>

[0095] Figure 5 2 is a cross-sectional view showing a fourth example of the structure of the rotor 20. The following description will focus on the parts different from the first to third examples, and the description of the structure identical or corresponding to at least one of the first to third examples may be omitted.

[0096] like Figure 5 As shown, in this example, as in the case of the above-mentioned first example, the permanent magnet 22 is composed of one magnet member having an elongated rectangular shape.

[0097] In this example, the permanent magnet 23 is composed of a magnet member having a U-shaped (arc-shaped) shape convex inward in the radial direction with the radial axis (d-axis) as the center. The permanent magnet 23 is magnetized in a manner that has different magnetic poles between the inner side and the outer side in the thickness direction of the U-shaped shape.

[0098] It should be noted that the permanent magnet 23 may include a plurality of (eg, three) separate magnet components, and may have a U-shape by a combination of the arrangement of the plurality of magnet components.

[0099] In this example, the permanent magnets 22 and 23 arranged at substantially the same circumferential position are magnetically arranged in series as in the first example. Thus, the rotor 20 can reduce the d-axis inductance Ld as in the first example.

[0100] Also, similarly to the first example, the cavity 24 is arranged (formed) inside the rotor core 21 so that the flux barriers corresponding to the permanent magnets 22 communicate with the flux barriers corresponding to the permanent magnets 23. This can further reduce the d-axis inductance Ld.

[0101] In addition, in this example, as described above, the permanent magnet 23 has a U-shaped shape. Therefore, the surface area of ​​the permanent magnet 23 can be relatively increased compared to the case of an elongated rectangular shape such as the permanent magnet 22. Therefore, the rotor 20 can increase the magnetic flux of the magnetic field. In particular, when the coercive force and magnetic force of the permanent magnet 23 are relatively low, the rotor 20 can suppress the increase in the cost of the motor 1 and ensure the magnetic flux of the rotor 20.

[0102] As described above, the permanent magnet 22 has an elongated rectangular shape, while the permanent magnet 23 has a U-shaped shape. As a result, the surface area of ​​the outer peripheral surface of the permanent magnet 23 is larger than the surface area of ​​the inner peripheral surface of the permanent magnet 22. Therefore, for the rotor 20, even when the magnetic force (i.e., magnetic flux density) of the permanent magnet 23 is relatively low, the magnetic flux based on the permanent magnet 23 can be increased, and the magnetic flux of the permanent magnet 22 that does not pass through the permanent magnet 23 can be reduced. Therefore, the rotor 20 can further reduce the d-axis inductance Ld.

[0103] <Fifth Example of Rotor Configuration>

[0104] Figure 6 2 is a cross-sectional view showing a fifth example of the structure of the rotor 20. The following description will focus on the parts different from the first to fourth examples, and the description of the structure identical or corresponding to at least one of the first to fourth examples may be omitted.

[0105] like Figure 6 As shown, in this example, as in the first example, the permanent magnet 22 is composed of a magnet member having an elongated rectangular shape, and the permanent magnet 23 includes magnet members 23A and 23B symmetrically arranged in a convex V-shape radially inwardly with the radial axis as the center.

[0106] In this example, in the rotor core 21 , the inner rib 21B of the first example is omitted, and the cavity 25 is replaced by the inner rib 21C.

[0107] The inner rib 21C is provided at a portion between the end portions of the magnet member 23A and the magnet member 23B facing each other (i.e., a portion corresponding to the bottom of the V-shaped shape). In the rotor core 21, the inter-magnet core portion 21A surrounded by the permanent magnets 22, 23 and the cavity 24 is connected to a portion radially inward of the permanent magnet 23 through the inner rib 21C. Thus, the magnet slots of the permanent magnets 23 are divided into magnet slots of the magnet member 23A and magnet slots of the magnet member 23B.

[0108] The cavity 24 is connected not only to the magnet slot of the permanent magnet 22, but also to the magnet slot of the permanent magnet 23 (specifically, the magnet slot of the magnet component 23A or the magnet slot of the magnet component 23B). As a result, there is no portion with a relatively high magnetic permeability such as the inner rib 21B between the magnet components 23A and 23B and the cavity 24 that corresponds to the magnetic flux barrier. Therefore, the function of the cavity 24 as a magnetic flux barrier for the permanent magnet 23 (magnet components 23A and 23B) is enhanced. Therefore, the rotor 20 can further suppress the situation where the magnetic flux generated from one end of the permanent magnets 22 and 23 leaks without passing through the other end, thereby further reducing the d-axis inductance Ld.

[0109] <Sixth Example of Rotor Configuration>

[0110] Figure 7 2 is a cross-sectional view showing a sixth example of the structure of the rotor 20. The following description will focus on the parts different from the first to fifth examples, and the description of the structure identical or corresponding to at least one of the first to fifth examples may be omitted.

[0111] In this example, as in the case of the fifth example described above, the permanent magnet 22 is composed of one magnet member having an elongated rectangular shape.

[0112] In this example, the permanent magnet 23 includes magnet members 23A and 23B which are symmetrically arranged on a substantially same straight line with the radial axis as the center and have an elongated rectangular shape when viewed in the axial direction.

[0113] As in the fifth example, an inner rib 21C is provided between the facing ends of the magnet member 23A and the magnet member 23B. In the rotor core 21, the inter-magnet core portion 21A surrounded by the permanent magnets 22, 23 and the cavity 24 is connected to the portion radially inward of the permanent magnet 23 through the inner rib 21C. Thus, the magnet slots of the permanent magnets 23 are divided into the magnet slots of the magnet member 23A and the magnet slots of the magnet member 23B.

[0114] As in the fifth example, the cavity 24 communicates not only with the magnet slots of the permanent magnet 22 but also with the magnet slots of the permanent magnet 23 (specifically, the magnet slots of the magnet member 23A or the magnet slots of the magnet member 23B). This can further reduce the d-axis inductance Ld.

[0115] <Other Examples of Rotor Configuration>

[0116] The configurations of the first to sixth examples described above may be combined as appropriate.

[0117] For example, in the rotor core 21 of the fourth example, the inner rib 21B can be omitted, and the inner rib 21C is provided in a manner such that the permanent magnet 23 having a U-shaped (arc-shaped) shape when viewed axially is cut into magnet parts 23A and 23B, as in the fifth and sixth examples.

[0118] [effect]

[0119] Next, the operation of the rotor 20 according to the present embodiment will be described.

[0120] In the present embodiment, the permanent magnets 22 and 23 are housed in different magnet slots formed in the rotor core 21 and are magnetically arranged in series. In addition, for each of the permanent magnets 22 and 23 arranged in series, a magnetic flux barrier (cavity 24) is provided near the end in a direction orthogonal to the direction of the main magnetic flux. Furthermore, the cavity 24 is provided so that the magnetic flux barriers corresponding to the permanent magnets 22 and 23 arranged in series are connected to each other.

[0121] Thus, the rotor 20 can increase the magnetic resistance in the d-axis direction by the permanent magnets 22 and 23 that are magnetically arranged in series. In addition, in the rotor 20, the magnetic flux barriers corresponding to the two permanent magnets 22 and 23 that are magnetically arranged in series are connected to each other, so that the magnetic flux at the end of one permanent magnet can be suppressed from leaking without passing through the other permanent magnet that is magnetically connected in series. Therefore, the rotor 20 can reduce the d-axis inductance Ld.

[0122] It should be noted that, as described above, more than three permanent magnets may be magnetically arranged in series. In this case, it is not necessary to connect the flux barriers corresponding to all permanent magnets, but the flux barriers corresponding to at least two of the three or more permanent magnets that are magnetically arranged in series may be connected to each other.

[0123] In the present embodiment, the coercive force of permanent magnet 22 is the highest among permanent magnets 22 and 23, and the coercive force of permanent magnet 23 is lower than that of permanent magnet 22. Furthermore, permanent magnet 22 is arranged at the outermost magnetic side, and permanent magnet 23 is arranged at the inner magnetic side compared with permanent magnet 23.

[0124] Thus, the permanent magnets 22 with high coercive force can suppress demagnetization of the permanent magnets 23. In addition, the use of the permanent magnets 23 with low coercive force can reduce costs. Therefore, the rotor 20 can reduce the cost of the motor 1 and suppress demagnetization of the permanent magnets 23.

[0125] It should be noted that, as described above, more than three permanent magnets may be magnetically arranged in series. In this case, a permanent magnet having the highest coercive force among the three or more permanent magnets may be arranged on the magnetically outermost circumference of the rotor core 21, and any combination of coercive forces of the other permanent magnets arranged on the magnetically inner circumference of the one permanent magnet may be used.

[0126] In addition, in the present embodiment, the permanent magnets 22 and 23 are each composed of a single magnet component or a plurality of magnet components (magnet components 22A, 22B, magnet components 23A, 23B) that are separated from each other and magnetically arranged in parallel. Furthermore, the surface area of ​​the outer peripheral surface of a single magnet component or the total outer peripheral surface of the magnet components 23A and 23B constituting the permanent magnet 23 on the magnetic inner peripheral side is larger than the surface area of ​​the inner peripheral surface of a single magnet component or the total inner peripheral surface of the magnet components 22A and 22B constituting the permanent magnet 22 on the magnetic outer peripheral side.

[0127] Thus, the rotor 20 can increase the outer peripheral surface or the total surface area of ​​the outer peripheral surfaces of the permanent magnets 23. Therefore, the rotor 20 can increase the magnetic flux even when the magnetic force of the permanent magnets 23 on the inner peripheral side is relatively low.

[0128] It should be noted that, as described above, more than three permanent magnets may be magnetically arranged in series. In this case, in the rotor core 21, the above relationship does not need to be established for all combinations of two permanent magnets that are magnetically arranged in series and adjacent to each other among the three or more permanent magnets that are magnetically arranged in series, and the above relationship only needs to be established for at least one group.

[0129] Although the embodiments have been described above, it should be understood that various changes in the embodiments and details may be made without departing from the spirit and scope of the claims.

[0130] Finally, this application claims priority based on Japanese Patent Application No. 2019-181001 filed on September 30, 2019, and the entire contents of the Japanese Patent Application are cited in this application by reference.

[0131] Description of Reference Numerals

[0132] 1 Electric motor

[0133] 10 Stator

[0134] 11 Stator core

[0135] 12 Winding

[0136] 20 Rotor

[0137] 21 rotor core (iron core)

[0138] 21A Iron core between magnets

[0139] 21B Inner rib

[0140] 21C Inner rib

[0141] 22 Permanent magnet

[0142] 22A, 22B Magnet parts

[0143] 23. Permanent magnet

[0144] 23A, 23B Magnet parts

[0145] 24 Hollow part (magnetic flux barrier)

[0146] 25 Hollow

[0147] 26 Hollow

[0148] 30 Rotation axis

Claims

1. A rotor comprising: Iron core; as well as at least three magnet groups, the at least three magnet groups are arranged adjacent to each other, All the magnet groups arranged on the rotor each include: a plurality of permanent magnets, which are housed in different magnet slots formed in the core and are magnetically arranged in series; as well as a magnetic flux barrier provided near an end in a direction orthogonal to the direction of the main magnetic flux with respect to each of at least two permanent magnets magnetically arranged in series among the plurality of permanent magnets; The flux barriers corresponding to each of the at least two permanent magnets arranged in series are connected to each other. The plurality of permanent magnets include a first permanent magnet and a second permanent magnet disposed at a radially inner position than the first permanent magnet. The flux barrier is connected to the magnet slot accommodating the first permanent magnet. The second permanent magnet comprises a plurality of separate magnet components. The magnet slots of the iron core corresponding to the second permanent magnets include hollow portions, and the hollow portions are disposed between facing ends of the magnet members when the plurality of magnet members are embedded in one of the magnet slots.

2. The rotor according to claim 1, wherein: The first permanent magnet has the highest coercive force, and the second permanent magnet has a coercive force lower than the coercive force of the first permanent magnet. Among the plurality of permanent magnets, the first permanent magnet is disposed on the magnetically outermost peripheral side, and the second permanent magnet is disposed on the magnetically inner peripheral side of the first permanent magnet.

3. The rotor according to claim 1 or 2, wherein: The plurality of permanent magnets are each composed of one magnet component or a plurality of magnet components that are separated from each other and magnetically connected in parallel. In at least one group of two permanent magnets that are magnetically arranged in series and adjacent to each other and included in the above-mentioned multiple permanent magnets, the total surface area of ​​the outer peripheral surface of the above-mentioned one magnet component or the outer peripheral surfaces of the above-mentioned multiple magnet components that constitute the magnetic inner peripheral side of the permanent magnet is larger than the total surface area of ​​the inner peripheral surface of the above-mentioned one magnet component or the inner peripheral surface of the above-mentioned multiple magnet components that constitute the magnetic outer peripheral side of the permanent magnet.

4. An electric motor comprising the rotor according to any one of claims 1 to 3.

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