Embedded magnet type motor

Abstract

To provide an embedded magnet type motor capable of suppressing demagnetization of a permanent magnet while suppressing a decrease in torque and an increase in cost in a configuration including an open type gap portion.SOLUTION: An embedded magnet motor 1 includes: a permanent magnet 9 inserted into a magnet hole 11 provided in a rotor core 8; an open type gap unit 18 connected from the magnet hole 11 to an outer peripheral surface of the rotor core 8; and a magnet holding unit 20 which is in contact with a side surface of the permanent magnet 9 and forms a closed type gap unit 19 not connected to the outer peripheral surface of the rotor core 8 on the side surface.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to interior magnet motors. [Background technology]

[0002] Conventionally, in embedded magnet motors in which permanent magnets are arranged inside the rotor core, gaps called flux barriers are provided around the permanent magnets to block magnetic flux. In such cases, when the magnetic flux that flows due to the reverse magnetic field generated by the stator coil passes through the gaps, it passes through the corners of the permanent magnets, causing demagnetization. Therefore, it has been proposed to suppress demagnetization by narrowing some of the gaps connected to the magnet holes, as in Patent Document 1, providing multiple gaps around the magnet holes, or filling the gaps with non-magnetic resin, for example. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-155242 A [Patent Document 2] JP 2017-123779 A Summary of the Invention [Problem to be solved by the invention]

[0004] From the viewpoint of blocking magnetic flux, it is considered effective to provide a gap that connects from the magnet holes to the outer peripheral surface of the rotor core. Hereinafter, a gap that connects from the magnet holes to the outer peripheral surface of the rotor core will be referred to as an open gap.

[0005] However, in the case of a configuration with open-type gaps, even if some of the open-type gaps are narrowed, the torque may decrease. Also, if the number of gaps provided around the permanent magnet increases, the inductance may decrease, resulting in a decrease in torque. Also, filling the gaps with non-magnetic material increases costs.

[0006] The present disclosure has been made in consideration of the above-mentioned circumstances, and its purpose is to provide an embedded magnet motor that is capable of suppressing demagnetization of permanent magnets while suppressing torque reduction and cost increase in a configuration that includes an open gap portion. [Means for solving the problem]

[0007] An embedded magnet motor according to one embodiment of the present disclosure comprises a permanent magnet inserted into a magnet hole provided in a rotor core, an open gap connecting the magnet hole to the outer peripheral surface of the rotor core, and a magnet holding portion that contacts a side surface of the permanent magnet and forms a closed gap on that side surface that is not connected to the outer peripheral surface of the rotor core. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic diagram showing an embedded magnet motor according to an embodiment as viewed from the axial direction; [Diagram 2] An enlarged view of region II in FIG. [Diagram 3] FIG. 3 is an enlarged view of region III in FIG. 2. [Figure 4] A diagram showing the flow of leakage magnetic flux in comparison with a conventional structure example. [Diagram 5] A diagram showing the demagnetization factor distribution in comparison with a conventional structure example. [Figure 6] A diagram showing an example of a modified shape of the magnet holder. [Figure 7] A diagram showing the relationship between the holding part angle and torque and demagnetization rate [Figure 8] Diagram showing the relationship between the holding part angle and the magnetic path [Figure 9] Figure 1 showing other examples of magnet holder shapes [Figure 10] Figure 2 showing other examples of magnet holder shapes [Figure 11] Figure 3 showing other examples of magnet holder shapes [Figure 12] Figure 4 showing other examples of magnet holder shapes [Figure 13] Figure 5 showing other examples of magnet holder shapes DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment will be described with reference to the drawings. As shown in Fig. 1, an embedded magnet motor 1 of this embodiment includes a stator 2, a rotor 3, and a shaft 4. Hereinafter, the direction along the rotation axis (J) of the rotor 3 will be referred to as the axial direction, the direction around the rotation axis (J) will be referred to as the circumferential direction, and the direction from the rotation axis (J) along the outer periphery of the rotor 3 will be referred to as the radial direction. The stator 2 and rotor 3 are housed in a case (not shown), and the case is provided with a bearing member such as a bearing that rotatably supports the shaft 4.

[0010] The stator 2 includes a stator core 5 formed in a generally hollow cylindrical shape by stacking electromagnetic steel sheets of a predetermined shape in the axial direction, and coils 7 inserted into slots 6 formed on the inner peripheral surface of the stator core 5 as shown in FIG. 2. A plurality of slots 6 are formed at predetermined intervals in the circumferential direction in a state in which they penetrate the inner peripheral surface of the stator 2 in the axial direction. The coils 7 are fixed to the stator core 5 by winding a wire such as an enameled wire into the slots 6, or by fitting a wire that has been wound in advance into the slots 6. Note that a bus bar may be used as the coils 7.

[0011] The rotor 3 includes a rotor core 8 formed in a generally hollow cylindrical shape, for example, by axially laminating electromagnetic steel sheets punched into a predetermined shape, and a plurality of permanent magnets 9 arranged inside the rotor core 8. A shaft 4 is fixed in the hollow portion of the rotor core 8, for example, by press fitting, and rotates integrally with the rotor 3 relative to the stator core 5 about a rotation axis (J).

[0012] As shown in Fig. 2, the permanent magnets 9 are formed in a generally rectangular shape when viewed from the axial direction of the rotor core 8, and have relatively short short side surfaces and relatively long long side surfaces. In this embodiment, the permanent magnets 9 are generally equal in length in the short direction, while the permanent magnets 9 arranged on the inner periphery of the multi-layer structure are longer in the long direction. Each permanent magnet 9 is magnetized along the short direction. In this embodiment, the permanent magnets 9 are formed with flat chamfered corners, but this shape is merely an example, and it is possible to form permanent magnets with non-chamfered corners or with curved chamfered corners.

[0013] These permanent magnets 9 are arranged in pairs at positions symmetrical with respect to a virtual line (VL) passing through the rotation axis (J), in a roughly V-shape with the distance between them being relatively short on the radially inner side and relatively long on the radially outer side. In this embodiment, the pair of permanent magnets 9 are arranged side by side along the radial direction. Hereinafter, the structure in which the pair of permanent magnets 9 are arranged side by side in the radial direction will be referred to as a multi-layer structure for convenience, and the multiple permanent magnets 9 constituting this multi-layer structure will also be referred to as a magnet group for convenience. In the case of FIG. 2, one magnet group of the multi-layer structure is composed of four permanent magnets 9.

[0014] As shown in Fig. 1, the magnet groups are arranged at eight equal positions in the circumferential direction of the rotor core 8. Adjacent magnet groups are arranged so that the magnetization directions of the permanent magnets 9 are alternately opposite to each other. Therefore, the embedded magnet motor 1 has eight magnetic poles 10 formed at equal positions in the circumferential direction. However, the structure shown in Figs. 1 and 2 is just an example, and the shape and number of the slots 6, the number and arrangement of the magnetic poles 10 of the rotor 3, the shape of the permanent magnets 9, etc. are not limited to this.

[0015] The permanent magnets 9 are inserted into a plurality of magnet holes 11 formed in the rotor core 8. Each magnet hole 11 is connected to a gap for forming a flux barrier. Specifically, each magnet hole 11 is connected to an inner gap 12 on the radially inner side, that is, on the virtual line (VL) side which is the center of the magnetic pole 10. This inner gap 12 is a closed type that is not connected to the outer circumferential surface of the rotor core 8. A first bridge portion 13 is formed along the virtual line (VL) between the inner gaps 12 which are on the outer circumferential side in the multi-layer structure. A second bridge portion 14 is formed along the virtual line (VL) between the inner gaps 12 which are on the inner circumferential side in the multi-layer structure.

[0016] Moreover, each magnet hole 11 located on the inner periphery side in the multi-layer structure is connected to an outer void 15 on the radially outer side, that is, on the side opposite to the imaginary line (VL). An outer periphery bridge portion 16 is formed on the outer periphery side of the outer void 15. In other words, the outer void 15 is a closed type that is not connected to the outer periphery surface of the rotor core 8. Moreover, the inner void 12 and the outer void 15 each have a protrusion 17 formed therein, which extends along the side surface of the permanent magnet 9 and contacts the permanent magnet 9 to hold the permanent magnet 9 in a predetermined position.

[0017] On the other hand, magnet holes 11 located on the outer periphery side in the multi-layer structure are connected, on the radially outer side, to open gaps 18 that connect from magnet holes 11 to the outer periphery surface of rotor core 8, and closed gaps 19 that are connected to magnet holes 11 but not connected to the outer periphery surface of rotor core 8, as shown in Fig. 3. Note that in Fig. 3, to make the drawing easier to see, a gap is intentionally provided between permanent magnets 9 and magnet holes 11.

[0018] A magnet holding portion 20 is provided so as to separate the open gap 18 and the closed gap 19. The magnet holding portion 20 is connected to a connecting bridge portion 21 which is an extension of a part of the outer circumferential surface of the rotor core 8, and on the side of the permanent magnet 9 facing the open gap 18, a closed gap 19 is formed which is surrounded by the magnet holding portion 20, the connecting bridge portion 21, and the rotor core 8 and is connected to the magnet hole 11 but is not connected to the outer circumferential surface of the rotor core 8. Hereinafter, the short side surface of the permanent magnet 9 with which the magnet holding portion 20 is in contact will be referred to as the short side surface 9a for convenience.

[0019] The magnet holding portion 20 is formed so that its width (W1) is equal to or smaller than the width (W2) of the short side surface 9a of the permanent magnet 9, and is in contact with the short side surface 9a within a predetermined width (W3). Furthermore, on the open-type gap portion 18 side, the magnet holding portion 20 is in contact with the short side surface 9a at a position that does not overlap the chamfered portion 22a of the permanent magnet 9. Therefore, between the contact position of the magnet holding portion 20 and the inner surface of the magnet hole 11, there is a gap that is equal to or larger than the apparent width (W4) of the chamfered portion 22a when viewed from the short side surface 9a.

[0020] On the other hand, in this embodiment, the magnet holding portion 20 contacts the short side surface 9a on the closed gap portion 19 side, inside the intersection point between the short side surface 9a and the chamfered portion 22b. Therefore, the short side surface 9a of the permanent magnet 9 is exposed to the closed gap portion 19 by a predetermined width (W5) between the contact position of the magnet holding portion 20 and the chamfered portion 22b.

[0021] Moreover, the magnet holding portion 20 is formed in a generally rectangular shape except for the portion that contacts the permanent magnet 9. The corners of the magnet holding portion 20, the connection portion between the magnet holding portion 20 and the connecting bridge portion 21, and the connection portion between the connecting bridge portion 21 and the rotor core 8 are chamfered into a curved shape by so-called fillet processing. This reduces the concentration of stress at the corners and connections. The magnet holding portion 20 is formed so as to be generally parallel to the wall surface 8a of the rotor core 8 that forms the open-type gap portion 18 and the wall surface 8b of the rotor core 8 that forms the closed-type gap portion 19.

[0022] Furthermore, by providing an auxiliary holding portion 23, in which a portion of the rotor core 8 protrudes and comes into contact with the chamfered portion 22b of the permanent magnet 9, stress applied to the magnet holding portion 20, the connecting bridge portion 21, etc. Note that the width (W1) of the magnet holding portion 20, the width (W3) of the magnet holding portion 20 that comes into contact with the short side surface 9a, and the positional relationship and range of the magnet holding portion 20 that comes into contact with the short side surface 9a are only examples, and can be set appropriately based on the size and shape of the permanent magnet 9, and so as to have the strength to hold the permanent magnet 9.

[0023] Next, the operation and effects of the above-mentioned configuration will be described. As mentioned above, from the viewpoint of blocking magnetic flux, it is considered effective to provide gap 103 that connects magnet hole 101 to the outer circumferential surface of rotor core 102, as shown as an example of a conventional structure in Fig. 4. On the other hand, if open gap 103 is provided, the flow of magnetic flux indicated by the dashed dotted line will bulge significantly outward, and as a result, demagnetization will occur even further inside permanent magnet 9.

[0024] Furthermore, for example, if a portion of the gap 103 is narrowed so as to serve as the holding structure 104 for the permanent magnet 9, the demagnetization is suppressed, but there is a problem that the torque decreases. Also, if many gaps are provided around the permanent magnet 9, the inductance decreases, and the torque decreases. Moreover, filling the gap 103 with a non-magnetic material increases costs.

[0025] Therefore, in this embodiment, in a configuration including an open-type gap portion 18, it is possible to suppress demagnetization of the permanent magnet 9 while suppressing a decrease in torque and an increase in cost. Specifically, as shown in Fig. 4 as an example of an embodiment structure, in addition to the open-type gap portion 18, a magnet holding portion 20 is provided that is in contact with the side surface of the permanent magnet 9 and forms a closed-type gap portion 19 on the side surface that is not connected to the outer circumferential surface of the rotor core 8. This suppresses leakage magnetic flux indicated by the dashed line, and reduces the bulge of magnetic flux, thereby suppressing demagnetization. This is because the magnetic path of the gap portion is shorter than when only the open-type gap portion 18 is provided.

[0026] Fig. 5 shows the simulation results of the demagnetization factor distribution in the conventional structure example and the embodiment structure example. Note that Fig. 5 shows the region divided into a region where the demagnetization factor is less than 20% (R1), a region where the demagnetization factor is in the range of 20% to 30% (R2), a region where the demagnetization factor is in the range of 30% to 40% (R3), and a region where the demagnetization factor is more than 40% (R4).

[0027] As can be seen from the simulation results, in the case of the embodiment structure, the region (R4) where the demagnetization rate exceeds 40% is significantly smaller than that of the conventional structure, and demagnetization is suppressed. If the demagnetization rate in the conventional structure is X [%] and the torque is Y [Nm], the embodiment structure has a result that the demagnetization rate is smaller than X and the torque is larger than Y, and both the demagnetization rate and the torque can be improved. In other words, by adopting the embodiment structure, it is possible to achieve a good balance between the performances of the flux barrier, the torque, and the demagnetization rate, which are related to each other and may have a trade-off relationship, and it is possible to improve both the demagnetization rate and the torque. The demagnetization rate represented by X is calculated based on the reduction rate of the peak value of the induced voltage before and after demagnetization.

[0028] According to the embodiment described above, the following effects can be obtained. The embedded magnet motor 1 comprises a permanent magnet 9 inserted in a magnet hole 11 provided in a rotor core 8, an open gap 18 connecting from the magnet hole 11 to the outer circumferential surface of the rotor core 8, and a magnet holding portion 20 that contacts a side surface of the permanent magnet 9 and forms a closed gap 19 on said side surface that is not connected to the outer circumferential surface of the rotor core 8. As a result, in a configuration that includes the open gap 18, leakage flux can be reduced and swelling caused when leakage flux flows can be suppressed, and demagnetization of the permanent magnet 9 can be suppressed while suppressing a decrease in torque and an increase in cost.

[0029] Furthermore, magnet holding portion 20 contacts the radially outer side surface of permanent magnet 9 when viewed from the axial direction which is the center of rotation of rotor core 8. This makes it possible to suppress the demagnetization rate of portions of permanent magnet 9 which are easily demagnetized. Furthermore, the permanent magnet 9 is formed in a shape having a relatively short side surface and a relatively long side surface when viewed from the axial direction which is the center of rotation of the rotor core 8, and the magnet holding portion 20 contacts the short side surface of the permanent magnet 9. This makes it possible to suppress the demagnetization rate of the permanent magnet 9 in portions that are easily demagnetized.

[0030] Furthermore, a plurality of permanent magnets 9 are provided lined up in the radial direction of the rotor core 8, and the magnet holder 20 is provided corresponding to at least one of the plurality of permanent magnets 9. In this embodiment, the magnet holder 20 is provided corresponding to the permanent magnet 9 that is the outermost in the radial direction. This makes it possible to suppress the demagnetization factor at the position where the open gap 18 is expected to be provided.

[0031] Incidentally, the magnet holder 20 is not limited to the shape exemplified in Fig. 3, and may have other shapes. For example, as shown in Fig. 6, the angle (α) between a line segment (L1) along the short side surface 9a of the permanent magnet 9 when viewed from the axial direction and a line segment (L2) along a linear portion of the side surface of the magnet holder 20 on the open-type gap portion 18 side can be changed. Hereinafter, the angle (α) between the line segments (L1) and (L2) is referred to as the holder angle for convenience, and the explanation will be given assuming that the center side of the magnetic pole 10 is 0 degrees.

[0032] At this time, the line segment (L2) is generally parallel to the wall surface 8a of the rotor core 8 that forms the open gap portion 18, and the line segment (L3) along the straight portion of the side surface of the magnet holding portion 20 on the closed gap portion 19 side is generally parallel to the wall surface 8b of the rotor core 8 that forms the closed gap portion 19. In addition, the line segment (L2) and the line segment (L3) are generally parallel to each other.

[0033] Fig. 7 shows the relationship between torque and demagnetization factor when the holding part angle is changed from 5 degrees to 105 degrees. For example, point (P5) in Fig. 7 shows the result when the holding part angle is 5 degrees, point (P15) shows the result when the holding part angle is 15 degrees, and the same is true for other points. Also, the auxiliary line drawn at the position where the demagnetization factor is X [%] and the auxiliary line drawn at the position where the torque is Y [Nm] both show the demagnetization factor and torque in the conventional structure example shown in Fig. 4.

[0034] From the results in Fig. 7, it can be seen that the demagnetization rate is improved compared to the conventional structure regardless of the holder angle. This is due to the provision of magnet holder 20. On the other hand, it can be seen that the torque is improved compared to the conventional structure when the holder angle is in the range of approximately 5 degrees to 80 degrees. It can also be seen that if the holder angle is in the range of approximately up to 90 degrees, it is possible to obtain torque at the same level as the conventional structure example and improve the demagnetization rate.

[0035] In addition, the torque starts to decrease when the retaining portion angle exceeds 75 degrees, and decreases significantly at 105 degrees, but this is not expected to be a problem with the retaining portion angle. In other words, when the retaining portion angle is set to approximately 105 degrees, as shown by the dashed line in Figure 8, a narrow region (R10) is formed between the retaining portion angle and the outer gap portion 15 located on the inner circumference side of the multi-layer structure, narrowing the q-axis magnetic path, which is thought to cause magnetic saturation.

[0036] Therefore, if a magnetic path can be secured, for example, by providing a magnet holding portion 20 corresponding to the inner permanent magnet 9 in a multi-layer structure, it is believed that the torque can be improved even if the holding portion angle is set to 105 degrees.

[0037] Furthermore, based on these results, it is believed that the demagnetization rate can be suppressed by setting the retaining portion angle in the range of approximately 5 degrees to 105 degrees, more preferably in the range of approximately 5 degrees to 90 degrees, and even more preferably in the range of approximately 5 degrees to 80 degrees.

[0038] In addition, the shape of the magnet holding portion 20 can be modified in addition to the above-mentioned holding portion angle. For example, as shown in Fig. 9, a connecting bridge portion 21A can be positioned between the short side surface 9a of the permanent magnet 9 and the outer peripheral surface of the rotor core 8, and a magnet holding portion 20A connected to the connecting bridge portion 21A can be provided. In this case, an auxiliary gap portion 24 recessed from the outer peripheral surface of the rotor core 8 can be provided in the connecting bridge portion 21A. With such a configuration, it is possible to obtain the same effects as those of the above-mentioned embodiment structure example, such as suppressing demagnetization of the permanent magnet 9 while suppressing a decrease in torque and an increase in cost in a configuration including an open-type gap portion 18.

[0039] 10, a magnet holder 20B that forms a plurality of closed-type gaps 19 can be provided on the short side surface 9a of one permanent magnet 9. With such a configuration, it is possible to obtain the same effects as the above-described embodiment structure example, such as suppressing demagnetization of the permanent magnet 9 while suppressing torque reduction and cost increase in the configuration having the open-type gaps 18.

[0040] 11, a configuration can be adopted in which a plurality of magnet holders 20C are provided on the short side surface 9a of one permanent magnet 9, each forming a closed-type gap portion 19. With such a configuration, it is possible to obtain the same effects as the above-described embodiment structure example, such as suppressing demagnetization of the permanent magnet 9 while suppressing a decrease in torque and an increase in cost in a configuration including an open-type gap portion 18.

[0041] 12, a magnet holder 20D and a connecting bridge 21D may be provided with corners that are not filleted, provided that the necessary strength is ensured by the strength design. In this case, some corners may be filleted. With such a configuration, it is possible to obtain the same effects as the above-described embodiment structure example, such as suppressing demagnetization of the permanent magnet 9 while suppressing torque reduction and cost increase in the configuration with the open gap 18.

[0042] Also, as shown in FIG. 13, a magnet holding portion 20E may be provided in the conventional configuration shown in FIG. 4. In this case, since the conventional holding structure 104 is considered to be provided in a state capable of holding the permanent magnet 9, the degree of freedom in designing the strength calculation, shape, dimensions, contact area, etc. of the magnet holding portion 20E can be increased. Even with such a configuration, in a configuration including an open-type gap portion 18, it is possible to obtain the same effect as the above-mentioned embodiment structure example, such as suppressing demagnetization of the permanent magnet 9 while suppressing torque reduction and cost increase. Although not shown, the shape examples shown in FIG. 9 to FIG. 13 can be combined with each other to the extent that they do not compete with each other. Also, it can be applied to a permanent magnet 9 with a shape in which the corners are not chamfered.

[0043] The above-described embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0044] In the drawings, 1 indicates an embedded magnet motor, 8 indicates a rotor core, 9 indicates a permanent magnet, 9a indicates a short side surface, 11 indicates a magnet hole, 18 indicates an open gap portion, 19 indicates a closed gap portion, and 20 indicates a magnet holder.

Claims

1. a permanent magnet inserted into a magnet hole provided in the rotor core; an open gap portion that is continuous from the magnet hole to the outer peripheral surface of the rotor core; a magnet holding portion that contacts a side surface of the permanent magnet and forms a closed gap on the side surface that is not connected to the outer circumferential surface of the rotor core, The permanent magnets are arranged in pairs at positions that are symmetrical with respect to an imaginary line that passes through the centers of the magnetic poles, in a V-shape where the distance between them is relatively long on the radially outer side, The magnet holding portion is connected to a connecting bridge portion that extends from a portion of the outer peripheral surface of the rotor core, and the side surface on the closed-type gap side is parallel to the wall surface of the rotor core that forms the closed-type gap.

2. 2. The interior magnet motor according to claim 1, wherein the magnet holding portion is in contact with a radially outer side surface of the permanent magnet when viewed from the axial direction which is the center of rotation of the rotor core.

3. The permanent magnet is formed in a shape having a relatively short side surface and a relatively long side surface when viewed from an axial direction which is the center of rotation of the rotor core, 3. The interior permanent magnet motor according to claim 1, wherein the magnet holding portion is in contact with a short side surface of the permanent magnet.

4. The pair of permanent magnets are arranged in a radial direction of the rotor core, 3. The interior magnet motor according to claim 1, wherein the magnet holder is provided corresponding to at least one of the plurality of permanent magnets arranged in a radial direction.

5. 3. The interior permanent magnet motor according to claim 1, wherein the magnet holder defines a plurality of closed gaps on a side surface of one of the permanent magnets.

6. 3. The interior permanent magnet motor according to claim 1, wherein a plurality of the magnet holders are provided on a side surface of one of the permanent magnets.

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