Rotary electrical machine

Abstract

The present invention comprises: a stator (2) that has a stator core (3) and armature windings (4); and a rotor (5) that has a rotor core (21) and permanent magnets (30) which are accommodated in magnet accommodation holes (22). The rotor core (21) has flux barriers (23) that are provided at the peripheral ends of each permanent magnet (30) and that suppress short-circuiting of magnetic flux, and bridges (25) that are provided so as to connect to the rotor core (21) at both outer peripheral ends of the flux barriers (23). Each bridge (25) is configured from a non-magnetic portion (50) that is composed of a non-magnetic material and is provided at least on the d-axis side of the center of the bridge (25), and a magnetic portion (60) that is composed of a magnetic material and is provided in a region other than that of the non-magnetic portion (50) and at least on the q-axis-side end.

Description

Rotating electrical machine

[0001] The present disclosure relates to a rotating electrical machine.

[0002] For example, in a rotating electrical machine used in an electric vehicle, a hybrid vehicle, etc., miniaturization, high output, and high efficiency are required from the viewpoints of resource saving and extending the cruising range of the vehicle. In a permanent magnet embedded type rotating electrical machine, a bridge is provided around the magnet accommodation hole of the rotor in order to improve the centrifugal force resistance strength. Generally, since the bridge is formed of an electromagnetic steel sheet made of a magnetic material like the rotor core, there is a concern that the magnetic flux of the magnet in the rotor leaks and short-circuits, leading to a decrease in torque or output. As a countermeasure against these, non-magnetization of the bridge is considered, but simply arranging the non-magnetic part considering only the flow of the magnetic flux from the permanent magnet cannot sufficiently obtain the torque improvement effect when a current is passed through the armature winding of the stator under load. (For example, refer to Patent Document 1 below.)

[0003] Japanese Patent No. 7538431

[0004] In Patent Document 1, a configuration is proposed to suppress the leakage of magnetic flux of the magnet to the bridge by non-magnetizing the q-axis side of the bridge, but this only considers countermeasures against the magnetic flux of the magnet in the rotor. Therefore, in Patent Document 1, although it is effective as a measure to improve the magnet torque, non-magnetizing the q-axis side of the bridge inhibits the magnetic path of the reluctance torque, and there is a possibility that the reluctance torque decreases. Therefore, the improvement effect on the total torque, which is the sum of the magnet torque and the reluctance torque, is limited.

[0005] Further, Patent Document 1 aims at torque improvement on the premise that the non-magnetic part in the bridge and the permanent magnet are in contact with each other, and does not disclose the case where a flux barrier generally adopted to improve the torque or output density of the rotating electrical machine is arranged between the permanent magnet and the bridge.

[0006] The present disclosure discloses a technique for solving the above problems, and aims to provide a rotating electrical machine that improves torque and output.

[0007] The rotating electric machine of the present disclosure comprises a stator having a stator core and armature windings provided on the stator core, and a rotor having a rotor core and permanent magnets housed in magnet housing holes of the rotor core, wherein the rotor core has flux barriers provided at the circumferential ends of the permanent magnets to suppress short circuits of magnetic flux, and bridges provided to connect the rotor cores at both outer peripheral ends of the flux barrier, and the bridges consist of a non-magnetic portion made of a non-magnetic material provided at least on the d-axis side of the central part of the bridge, and a magnetic portion made of a magnetic material provided at least at the q-axis side end in a region other than the non-magnetic portion.

[0008] The rotating electric machine of this disclosure can improve torque and output.

[0009] This is a cross-sectional view of a plane parallel to the axial direction in a rotating electric machine according to Embodiment 1. This is a partial cross-sectional view of a plane perpendicular to the axial direction in a rotating electric machine according to Embodiment 1. Figures 3A and 3B are diagrams illustrating the principle of torque increase in a rotating electric machine according to Embodiment 1. This is an explanatory diagram of the effects in a rotating electric machine according to Embodiment 1. This is an explanatory diagram of the effects in a rotating electric machine according to Embodiment 1. This is an explanatory diagram of the effects in a rotating electric machine according to Embodiment 1. This is a diagram illustrating the current phase. Figures 8A and 8B are partial cross-sectional views of a plane parallel to the axial direction in the rotor of a rotating electric machine according to a modified example of Embodiment 1. Figures 9A and 9B are partial cross-sectional views of a plane parallel to the axial direction in the rotor of a rotating electric machine according to a modified example of Embodiment 1. This is a partial cross-sectional view of a plane parallel to the axial direction in the rotor of a rotating electric machine according to a modified example of Embodiment 1. This is a partial cross-sectional view showing a plane parallel to the axial direction in the rotor of a rotating electric machine according to Embodiment 2. This is an explanatory diagram of the principle of torque increase in Embodiment 2.

[0010] Embodiment 1. Figure 1 is a cross-sectional view of a rotating electric machine according to Embodiment 1, taken from a plane parallel to the axial direction. As shown in Figure 1, the rotating electric machine 100 has a cylindrical housing 1, and holds a stator 2 inside the housing 1. The stator 2 is composed of a stator core 3 having an annular yoke portion 12 and a plurality of teeth 13 projecting in the radial direction, and armature windings (hereinafter referred to as coils) 4 wound around a plurality of slots 14 formed between the plurality of teeth 13. A rotor 5 is arranged inside the stator 2, and the rotating shaft 7 and the rotor 5 are rotatable via bearings 6 fitted to the housing 1. In Figure 1, the rotating shaft 7 of the rotor 5 is a solid shaft, but a hollow shaft can be used as a substitute, for example.

[0011] Figure 2 is a partial cross-sectional view of a rotating electric machine according to Embodiment 1, taken from a plane perpendicular to the axial direction. Figure 2 shows a partial cross-sectional view of the rotating electric machine 100 divided into eight equal parts in the circumferential direction, and shows a cross-sectional view corresponding to one magnetic pole. In the rotating electric machine 100 of Figure 2, the coil 4 of the stator 2 is, for example, a distributed winding with an outer diameter of 240 mm, and the rotor 5 is a permanent magnet synchronous motor equipped with a rotor core 21 and eight-pole permanent magnets 30 provided on the rotor core 21. The rotor core 21 is constructed by laminating electromagnetic steel sheets that easily pass magnetic flux in the axial direction. The rotor core 21 is provided with magnet housing holes 22 for housing the permanent magnets 30. Flux barriers 23 are arranged on both circumferential ends of the permanent magnets 30 to prevent short circuits of magnetic flux. The permanent magnets 30 are magnetized and embedded from the inner circumference side of the rotor towards the outer circumference (direction of arrow M), and in Figure 2, a single-pole permanent magnet 30 is shown. The permanent magnets adjacent to permanent magnet 30 in the circumferential direction, which are not shown in Figure 2, are magnetized in opposite directions, that is, from the outer circumference side to the inner circumference side of the rotor.

[0012] The rotating electric machine 100 shown in Figure 2 can utilize not only magnetic torque but also reluctance torque by embedding permanent magnets 30 within the rotor core 21, thereby achieving high torque. Here, magnetic torque is the torque generated by the attraction and repulsion between the poles created by the rotating magnetic field of the stator 2 and the magnetic poles of the permanent magnets 30 in the rotor 5. Reluctance torque is the torque generated by the attractive force between the poles created by the rotating magnetic field of the stator 2 and the salient poles of the rotor core 21. The sum of the magnetic torque and reluctance torque is the torque that actually acts on the rotating electric machine 100.

[0013] In Figure 2, the definitions of the d-axis and q-axis are explained. In the axis of the magnetic poles of the rotor 5, the direction of the magnetic flux created by the magnetic poles (the central axis of the permanent magnet 30) is defined as the d-axis, and the axis electrically and magnetically perpendicular to it is defined as the q-axis.

[0014] A pair of bridges 25 are provided between the outer periphery 22c of the flux barrier 23 and the outer periphery of the rotor 5. By connecting the d-axis side and the q-axis side of the rotor core 21 with the bridges 25, the centrifugal force resistance of the rotor core 21 can be improved. The bridges 25 are generally made of magnetic electrical steel sheets, just like the rotor core 21.

[0015] If the entire bridge 25 is made of magnetic material, the magnetic flux emitted from the permanent magnet 30 leaks into the bridge 25, causing a short circuit and leading to a decrease in the torque or output of the rotating electric machine 100. As a countermeasure, it is conceivable to form a non-magnetic section within the bridge 25, but depending on the location of the non-magnetic section, it may not be possible to obtain a sufficient improvement in the torque or output of the rotating electric machine 100 under load, and there is a concern that it may even lead to a decrease in torque or output.

[0016] Therefore, in this embodiment, as shown in Figure 2, a configuration is proposed in which a non-magnetic portion 50 is formed on the d-axis side of the bridge 25 and a magnetic portion 60 is formed on the q-axis side, thereby further improving the torque or output of the rotating electric machine 100.

[0017] In this embodiment, the region of the bridge 25 is basically assumed to be a region where a locally narrow rotor core is provided at the outer peripheral end of the flux barrier 23, connecting the rotor cores 21 on both sides in the circumferential direction of the flux barrier 23. For example, it is the region between the flux barrier 23 and the outer peripheral of the rotor core 21, and in particular on the q-axis side, it can be considered as a region that overlaps with the flux barrier 23 in the radial direction.

[0018] Furthermore, as in this embodiment, a characteristic feature of the flux barrier 23 is that the ends of the flux barrier 23 facing the outer circumference of the rotor core 21 are generally provided along the outer circumference of the rotor core, and a bridge 25 of generally constant width is provided. In a narrow sense, this region of the rotor core 21 of generally constant width may be considered as the bridge.

[0019] Figures 3A and 3B are diagrams illustrating the principle of torque increase in a rotating electric machine according to Embodiment 1. Figure 3A is a diagram illustrating the effect of preventing leakage of magnetic flux, and Figure 3B is a diagram illustrating the effect of improving reluctance torque using the excitation magnetic field of the stator.

[0020] In Figure 3A, conventionally, a portion of the magnetic flux generated from the permanent magnet 30, which is magnetized from the inner circumference to the outer circumference of the rotor, leaks into the bridge 25, causing a short circuit. However, in this embodiment, by forming a non-magnetic portion 50 on the d-axis side of the bridge 25, the flow of the magnetic flux becomes as shown by arrow H1. Therefore, short circuits of the magnetic flux can be suppressed, and the magnetic flux can be efficiently supplied to the stator 2. In other words, with the configuration of this embodiment, the flux linkage of the coil 4 of the stator 2 increases, mainly resulting in an increase in magnet torque.

[0021] In Figure 3B, by forming a non-magnetic section 50 on the d-axis side of the bridge 25 and a magnetic section 60 on the q-axis side of the bridge 25, the flow of magnetic flux effective for reluctance torque becomes as shown by arrow H2, and the bridge 25 can be utilized as an effective magnetic path for reluctance torque. By providing a non-magnetic section 50 on the d-axis side of the bridge 25, it is possible to prevent the magnetic flux shown in Figure 3A from flowing into the bridge 25, and the magnetic flux density on the q-axis side of the bridge 25 is reduced. By flowing magnetic flux through the magnetic section 60, which is the magnetic region on the q-axis side where the magnetic flux density has decreased, when a load is applied, the effect of improving reluctance torque is mainly obtained.

[0022] Conversely to this embodiment, if a magnetic portion is formed on the d-axis side of the bridge 25 and a non-magnetic portion is formed on the q-axis side of the bridge 25, the magnetic flux density on the d-axis side of the bridge 25 increases due to the inflow of magnetic flux from the magnet, making it unusable as a magnetic path for reluctance torque. On the other hand, although the magnetic flux density is reduced on the q-axis side of the bridge 25 because it is a non-magnetic portion, it cannot pass magnetic flux through it because it is a non-magnetic material, and therefore cannot be used as a magnetic path for reluctance torque.

[0023] Figures 4, 5, and 6 are explanatory diagrams of the effects in the rotating electric machine according to Embodiment 1. The torque was calculated by performing an electromagnetic field analysis using the rotating electric machine model described in Figure 2 above.

[0024] In Figures 4 to 6, the current phase was changed to 0°, 20°, and 45° under maximum load conditions, and the effect of the configuration of this embodiment (dashed lines in the figures, effect of Model 3) was confirmed.

[0025] Model 1 is a typical configuration in which the entire bridge is made of magnetic material. Model 2 is a model in which the d-axis side of the bridge is made of magnetic material and the q-axis side of the bridge is made of non-magnetic material. Model 3 is a model in which the d-axis side of the bridge is made of non-magnetic material and the q-axis side of the bridge is made of magnetic material. Model 3 is the model that adopts the configuration of this embodiment. Model 4 is a model in which the entire bridge is made of non-magnetic material. Note that the non-magnetic material in Models 2 and 3 is made up of a circumferential width of 2 mm. Furthermore, as an evaluation index for torque, the torque change rate of Models 2, 3, and 4 was calculated relative to Model 1, using Model 1 as the reference.

[0026] Here, we will explain the current phase using Figure 7. In Figure 7, the d-axis current id is the current component that flows in a direction parallel to the magnetic flux of the permanent magnet 30 relative to the rotating magnetic field of the stator 2. The q-axis current iq is the current component that flows in a direction perpendicular to the d-axis. That is, the d-axis current id and the q-axis current iq are orthogonal as vectors. The "current phase" shown in Figures 4 to 6 refers to the phase difference between the "composite vector of the d-axis current and the q-axis" shown in Figure 7 and the "q-axis". A current phase of 0° means that the current vector in Figure 7 coincides with the q-axis. When the current phase is 0°, no reluctance torque is generated, and only magnet torque is generated. Also, current phases of 20° and 45° are states at an angle of 20° or 45° from the q-axis, as shown in Figure 7. Theoretically, the reluctance torque is maximized when the current phase is 45°.

[0027] In the case of a current phase of 0° as shown in Figure 4, no reluctance torque is generated, so the effect of Model 3 in this embodiment is limited. As the ratio of reluctance torque increases, as shown in the case of a current phase of 20° as shown in Figure 5 and the case of a current phase of 45° as shown in Figure 6, Model 3 in this embodiment achieves a torque improvement effect equivalent to or better than the non-magnetic Model 4 (when the current phase is 20°) (when the current phase is 45°). This torque improvement effect is due to the fact that, as explained above, the magnetic path for reluctance torque is secured by forming the q-axis side of the bridge 25 with a magnetic part 60, while the non-magnetic part 50 on the d-axis side of the bridge 25 suppresses short circuits of the magnetic flux.

[0028] As described above, since torque is the sum of magnetic torque and reluctance torque, the configuration in this embodiment, where non-magnetic material is formed on the d-axis side and magnetic material is formed on the q-axis side, is the most effective when considering the effect of improving reluctance torque. Furthermore, by making not only the entire bridge but also parts of it non-magnetic, the manufacturing process or the cost required for non-magnetic treatment when demagnetizing the magnetic parts in post-processing can be reduced, thus achieving cost-effectiveness.

[0029] Furthermore, as a combination that can better utilize the effect of improving reluctance torque, for example, when controlling a rotating electric machine by vector control using an inverter, the current phase β is operated within the range of 0° < β < 90° or 90° < β < 180°. Here, when operating a rotating electric machine as a motor, the current phase β takes the range of 0° ≤ β ≤ 180°, but the three points of 0°, 90°, and 180° are excluded from this range. The reason for excluding the current phases of 0° and 180° is that the effect of this embodiment is to effectively utilize reluctance torque, and at current phases of 0° and 180°, only magnet torque is generated and no reluctance torque is generated, so the region excluding current phases of 0° and 180° is preferable in order to better obtain the effect of this embodiment. The reason for excluding the current phase of 90° is that it is a current phase in which no torque is generated.

[0030] Furthermore, in permanent magnet-embedded rotating electric machines, as explained later in Figure 11, the permanent magnets may be arranged in a roughly V-shape and in a multi-layer configuration of 1 to 3 layers in the radial direction. Adopting a distributed winding method for the stator winding is also a suitable application.

[0031] Next, an example of a process for demagnetizing a portion of the bridges in the rotor core of a rotating electric machine in this embodiment will be described. As a process for demagnetizing a portion of the bridges 25, for example, one method is to modify the composition or structure of the bridges 25 of the rotor core 21, which is made of electrical steel sheet, with a laser or the like, so that the magnetic flux flowing through the bridges 25 becomes more easily saturated, and the material becomes close to a non-magnetic material. As an example of a process for demagnetizing by modifying the composition or structure with a laser or the like, more specifically, it is conceivable to form a non-magnetic material by partially modifying the silicon-containing iron-based alloy, which is the magnetic material that makes up the general electrical steel sheet that makes up the rotor core 21, into austenitic non-magnetic stainless steel. For example, increasing the content of chromium and nickel, especially the nickel content, is effective as a demagnetizing treatment, and after performing a preliminary step of applying a metal powder containing at least nickel to the surface of the area to be demagnetized, the desired area can be partially modified into austenitic non-magnetic stainless steel by a heating process with a laser or the like, which involves melting and heat treatment. This modification process is carried out prior to the process of forming a surface insulating film on the electrical steel sheet in the manufacturing process of the rotor core 21, and the subsequent punching process in which the rotor core is punched into a predetermined shape.

[0032] Figures 8A, 8B, 9A, and 9B are partial cross-sectional views of a plane parallel to the axial direction in the rotor of a rotating electric machine according to a modification of Embodiment 1. In Figure 8A, a non-magnetic portion 501 is formed at a slight distance from the d-axis end of the bridge 25. By moving the non-magnetic portion 501 at a slight distance from the d-axis end, the magnetic portion 601 on the q-axis side becomes shorter, and there is a concern that the torque improvement effect will decrease due to the shortening of the magnetic path for utilizing reluctance torque. However, since the magnetic flux density in the air gap between the stator 2 and the rotor 5 also changes depending on the location or size of the non-magnetic portion 501, vibrations or noise originating from torque ripple, electromagnetic excitation force, etc. will also change, and this configuration may be a suitable shape when designing a magnetic circuit that is balanced in terms of overall performance. With this configuration, the torque or output improvement effect, which is the objective of this embodiment, can be obtained while also considering vibration and noise. In addition, the cost-effectiveness in terms of manufacturing costs can be improved by keeping the area of ​​the non-magnetic portion 501 small.

[0033] Figure 8B shows a configuration in which the non-magnetic portion 50B on the d-axis side is extended beyond the central part of the bridge 25 to a region closer to the q-axis side, and Figure 9A shows a configuration in which, in addition to the non-magnetic portion 503 on the d-axis side, a non-magnetic portion 504 is placed between the magnetic portions 603 and 604 on the q-axis side. In the cases of Figures 8B and 9A, as with the case of Figure 8A, the torque improvement effect cannot be obtained to the same extent as in the configuration of Figure 2. However, because a non-magnetic portion 502 or non-magnetic portion 503 is provided on the d-axis side and a magnetic portion 602 or magnetic portions 603, 604 is provided on the q-axis side, this is a modified design that can be designed while ensuring a torque improvement effect compared to the conventional configuration using only magnetic material, while also considering other characteristics caused by vibration or noise. In particular, in the example of Figure 9A, the non-magnetic portion 504 is positioned in a region of the bridge 25 relatively close to the q-axis. However, considering that the bridge 25 can be considered to extend to the region overlapping with the flux barrier 23 in the radial direction, a region of magnetic portion 604 is provided in the bridge 25 that is located closer to the q-axis than the region of non-magnetic portion 504. Furthermore, the configuration in which this magnetic portion 604 is connected to the rotor core 21 on the q-axis side is the same as in the configuration of Figure 2. Therefore, the region of magnetic portion 604 provided closer to the q-axis than the region of non-magnetic portion 504 in the bridge 25 can be utilized as an effective magnetic path for reluctance torque, and the effect of increasing reluctance torque common to this embodiment can be obtained. In addition, since the non-magnetic portion 503 is positioned on the d-axis side, an effect of increasing magnet torque can also be obtained by efficiently supplying magnetic flux to the stator 2 while suppressing short circuits of the magnetic flux.

[0034] Figure 9B shows a case where the non-magnetic portion formed on the d-axis side is divided into 505 and 506. A magnetic portion 605 is formed between the non-magnetic portion 505 and the non-magnetic portion 506, and a magnetic portion 606 is formed on the q-axis side of the non-magnetic portion 506. For example, when the magnetic material bridge 25 of the rotor core is subjected to non-magnetic modification with a laser in a later process, it is conceivable that the area that can be demagnetized at one time is limited due to the constraints of the laser irradiation width. By dividing the non-magnetic region and arranging it in series in the circumferential direction within the bridge, the magnetic resistance becomes close to that of a single continuous non-magnetic portion, and the effect of improving torque can be ensured. In addition, the effect of reducing manufacturing costs by reducing the number of laser irradiations can also be obtained.

[0035] Figure 10 is a partial cross-sectional view of a plane parallel to the axial direction in the rotor of a rotating electric machine according to a modified example of this embodiment. In Figure 10, in the bridge 250, in the thickness direction (radial direction of the rotor) which is approximately perpendicular to the direction connecting the rotor core 21 on the d-axis side and the q-axis side, the thickness of the bridge 250 on the q-axis side is greater than the thickness of the bridge 250 on the d-axis side. That is, the thickness of the magnetic part 60 on the q-axis side of the bridge 250 is configured to be greater than the thickness of the d-axis side, which is mainly formed by the non-magnetic part 50. The q-axis side of the bridge 250 is used as a magnetic path for reluctance torque, so by making it thicker, the magnetic resistance can be reduced and the amount of magnetic flux that can pass through can be increased, thereby obtaining a greater torque improvement effect. In addition, increasing the thickness of the bridge 250 also makes it possible to improve the centrifugal force resistance of the rotor core 21.

[0036] In this embodiment, the non-magnetic portion is formed along the entire thickness direction. However, to reduce manufacturing costs, placing the non-magnetic portion only in a part of the bridge's thickness direction, for example only on the outer circumference of the bridge, can also suppress short circuits of the magnetic flux, leading to improved cost-effectiveness. Furthermore, from the viewpoint of ensuring the magnetic portion of the bridge serves as a magnetic path for reluctance torque, it is preferable to configure the bridge closer to the stator, on the outer circumference of the rotor.

[0037] In this embodiment, a configuration with a single layer of permanent magnets has been described. However, even in the case of a configuration with two to three layers of permanent magnets arranged radially, which allows for greater utilization of reluctance torque, the torque improvement effect can be similarly obtained by applying the configuration of this embodiment not only to the first layer but also to the bridge portion of the second or third layer.

[0038] Figure 11 is a partial cross-sectional view of a plane parallel to the axial direction in the rotor of a rotating electric machine according to a modification of this embodiment. In Figure 11, the rotor core 21 has three layers of pairs of magnet housing holes 22A, 22B, and 22C formed in the rotor radial direction, which are substantially symmetrical with respect to the d-axis. Each pair of magnet housing holes 22A, 22B, and 22C is configured to be V-shaped such that the distance between them decreases as they move toward the inner circumference of the rotor core 21. Permanent magnets 30A, 30B, and 30C are housed in each of the magnet housing holes 22A, 22B, and 22C, and flux barriers 23A, 23B, and 23C are provided at the circumferential ends of each of the permanent magnets 30A, 30B, and 30C. Bridges 25A, 25B, and 25C are formed between the outer periphery of each flux barrier 23A, 23B, and 23C and the outer periphery of the rotor core 21. Non-magnetic sections 50A, 50B, and 50C are provided on the d-axis side of each bridge 25A, 25B, and 25C, and magnetic sections 60A, 60B, and 60C are provided on the q-axis side.

[0039] As shown in Figure 11, when permanent magnets 30A, 30B, and 30C are arranged in three layers, there are a total of six bridges 25A, 25B, and 25C on the outer circumference of the rotor core 21. In Figure 11, non-magnetic sections 50A, 50B, and 50C are provided on the d-axis side of all six bridges 25A, 25B, and 25C, but the combination is flexible; for example, non-magnetic sections 50A and 50B can be provided at four locations on the bridges 25A and 25B of the first and second layers. Increasing the number of non-magnetic sections will increase manufacturing costs, but will result in a greater improvement in torque. The principle of the torque increase effect is the same as described above. In Figure 11, an example is shown in which a pair of magnet housing holes approximately symmetrical with respect to the d-axis are formed in three layers in the rotor diameter direction, but the same can be applied to a case where a pair of magnet housing holes approximately symmetrical with respect to the d-axis are formed in N layers in the rotor diameter direction, where N is a natural number.

[0040] In this embodiment, for example, in electric vehicle applications, a rotating electric machine is used as a drive motor or generator. As explained in the background technology at the beginning, from the viewpoint of resource conservation or extending the driving range of vehicles, improvements in torque and output are required for miniaturization, high output, and high efficiency of rotating electric machines. In particular, there is a strong demand for miniaturization in electric vehicle applications, and recently, efforts have been made to reduce the diameter by increasing the rotational speed of the rotating electric machine by increasing the reduction ratio of the transmission, and in some cases the machine is used in the high rotational speed range of 20,000 rpm. As the rotational speed increases, the reduction in the strength of the rotor core due to centrifugal force becomes a problem, so there is a tendency to increase the thickness of the bridge. If this is done, the amount of magnetic flux leakage into the bridge increases and the torque decreases, so there is an even greater need for torque improvement by providing a non-magnetic material in part of the bridge, as in this embodiment.

[0041] Furthermore, due to the soaring prices of rare-earth magnets, there are cases where magnets with lower residual magnetic flux density are used to reduce costs. When magnets with lower residual magnetic flux density are used, the ratio of the amount of magnetic leakage into the bridge to the total magnetic flux of the permanent magnet increases further, reducing torque. Therefore, similar to the aforementioned increase in rotational speed, the torque improvement effect achieved by providing a non-magnetic material in part of the bridge, as in this embodiment, is even more desirable.

[0042] The rotating electric machine to which this embodiment is applied is not limited to any particular application and can be applied to rotating electric machines for various purposes. As explained in the above problem, applying this embodiment to a rotating electric machine used as a drive motor or generator in electric vehicle applications is a particularly suitable application example.

[0043] As described above, according to the present embodiment, a stator having a stator core and an armature winding provided on the stator core, and a rotor having a rotor core and a permanent magnet housed in a magnet housing hole of the rotor core are provided. The rotor core has a flux barrier provided at a circumferential end portion of the permanent magnet to suppress a short circuit of magnetic flux, and a bridge provided to connect the rotor cores at both outer peripheral sides of the flux barrier. The bridge is composed of a non-magnetic portion made of a non-magnetic material provided at least on the d-axis side rather than the central portion of the bridge, and a magnetic portion made of a magnetic material provided in a region other than the non-magnetic portion and at least at an end portion on the q-axis side. Therefore, by demagnetizing the d-axis side of the bridge, leakage magnetic flux can be reduced and torque increase can be achieved. Further, by forming the q-axis side of the bridge with a magnetic material, it can be utilized as a magnetic path for reluctance torque, and torque improvement can be achieved.

[0044] Further, in the rotor core, a pair of the magnet housing holes substantially symmetric with respect to the d-axis are formed in N layers (N is a natural number) in the rotor diameter direction. The pair of magnet housing holes are configured to have a V shape such that the distance between them becomes narrower toward the inner peripheral side of the rotor core. Each of the magnet housing holes houses the permanent magnet. A pair of the flux barriers are provided at circumferential end portions of each of the permanent magnets. A pair of the bridges are provided to connect the rotor cores at both outer peripheral sides of each of the flux barriers. At least a pair of each of the bridges is composed of a non-magnetic portion made of a non-magnetic material provided at least on the d-axis side rather than the central portion of the bridge, and a magnetic portion made of a magnetic material provided in a region other than the non-magnetic portion and at least at an end portion on the q-axis side. Therefore, even in a rotating electrical machine in which the permanent magnets are configured in N layers in a V shape, by demagnetizing the d-axis side of the bridge, leakage magnetic flux can be reduced and torque increase can be achieved. Further, by forming the q-axis side of the bridge with a magnetic material, it can be utilized as a magnetic path for reluctance torque, and torque improvement can be achieved.

[0045] Further, since the non-magnetic portion of the bridge is formed from the location where it is connected to the d-axis side of the rotor core toward the q-axis side, leakage flux from the d-axis side can be reduced, and the effect of torque improvement can be obtained.

[0046] Further, since the non-magnetic portion of the bridge is formed from the location where it is connected to the d-axis side of the rotor core across the central portion of the bridge toward the q-axis side, leakage flux from the d-axis side mainly for the magnet flux can be reduced, and the effect of torque improvement can be obtained. Also, although the utilization of the magnetic path of reluctance torque is reduced, it is effective, for example, in a rotating electric machine with concentrated windings of a stator winding having a small ratio of reluctance torque.

[0047] Further, since the bridge is configured such that the thickness of the bridge on the q-axis side is greater than the thickness of the bridge on the d-axis side in the thickness direction that is substantially orthogonal to the direction connecting the rotor cores on the d-axis side and q-axis side of the rotor, leakage flux from the d-axis side for the magnet flux can be reduced, and by increasing the thickness of the bridge on the q-axis side, a magnetic path for reluctance torque can be secured, and the effect of torque improvement can be obtained.

[0048] Further, since only a part of the non-magnetic portion of the bridge is formed in the thickness direction of the bridge, the manufacturing cost can be reduced by reducing the formation range of the non-magnetic portion within the range where the effect of torque improvement of the rotating electric machine is present.

[0049] Further, since the non-magnetic portion of the bridge is formed over the entire thickness direction of the bridge, leakage flux from the d-axis side mainly for the magnet flux can be reduced, and the effect of torque improvement can be obtained.

[0050] Further, since the non-magnetic portion of the bridge is formed only on the outermost bridge of the rotor, the manufacturing cost can be reduced by narrowing the formation range of the non-magnetic portion within the range where the effect of torque improvement of the rotating electric machine is present.

[0051] Furthermore, since the current phase β of the armature winding is operated within the range of 0° < β < 90° or 90° < β < 180°, the effect of torque improvement can be obtained by operating the rotating electric machine within the current phase range that generates reluctance torque.

[0052] Furthermore, since the non-magnetic portion of the bridge is formed by modifying the magnetic material constituting the rotor core to make it non-magnetic, it can be manufactured more easily by performing a non-magnetic treatment in a later process compared to when the bridge is constructed by combining different materials.

[0053] Embodiment 2. Figure 12 is a partial cross-sectional view showing a plane parallel to the axial direction of the rotor of the rotating electric machine according to Embodiment 2. As shown in Figure 12, when the cross-section parallel to the axial direction of the rotor core 21 is divided into left and right halves with the d-axis of the magnetic pole of the rotor core 21 as the boundary, a non-magnetic portion 50 is formed on the d-axis side and a magnetic portion 60 is formed on the q-axis side only in the bridge 25Y on the negative torque side with respect to the main torque direction T1 of the rotating electric machine 100. The bridge 25X on the positive torque side is a magnetic portion 60. Here, the main torque direction T1 refers to, for example, the power side in a drive motor for an electric vehicle, and the regenerative side in a generator.

[0054] In Figure 12, the torque direction is counterclockwise, and in powered operation (current phase β is 0° ≤ β < 90°), the rotation direction of the rotating electric machine 100 is the same counterclockwise direction as the torque, so the non-magnetic part 50 is positioned on the right half of one magnetic pole of the rotor core 21.

[0055] On the other hand, in the case of a generator where regenerative operation (current phase β is 90° < β ≤ 180°) is the primary mode of operation, the direction of torque is clockwise, opposite to the rotation direction of the rotating electric machine 100. In this case, the non-magnetic portion 50 is positioned on the left half of one magnetic pole of the rotor core 21. As described above, by forming the non-magnetic portion 50 only on the negative torque side bridge 25Y, the non-magnetic region can be reduced to less than half compared to the case where the non-magnetic portion is formed on all bridges 25, thereby reducing manufacturing costs. Furthermore, an improvement in torque can also be obtained.

[0056] Using the diagram illustrating the principle of torque increase in Embodiment 2 shown in Figure 13, we will explain the principle that forming a non-magnetic portion 50 on the negative torque bridge 25Y rather than the positive torque bridge 25X, as shown in Figure 12, results in a greater torque improvement effect. As shown in Figure 13, similar to Figure 12, when the direction T1 of the main torque is counterclockwise, the left side is the positive torque side and the right side is the negative torque side. Considering the flow of the main magnetic flux effective for reluctance torque in each bridge 25X and 25Y on the positive torque side and negative torque side, the flow on the positive torque side flows from the d-axis side to the q-axis side through bridge 25X (arrow H3), and the flow on the negative torque side flows from the d-axis side to the q-axis side through bridge 25Y (arrow H4).

[0057] As shown in the configuration of Embodiment 2 (Figure 12), if a non-magnetic section 50 is provided on the d-axis side and a magnetic section 60 on the q-axis side of the negative torque bridge 25Y, the area indicated by the circular dashed line E in Figure 13 becomes the non-magnetic section. This non-magnetic section blocks the magnetic path of the reluctance torque within the bridge on the positive torque side, but on the negative torque side, magnetic flux can flow into the bridge from the dashed line F in the figure of the stator 2, allowing the q-axis side to be used as the magnetic path. Therefore, providing it on the negative torque side allows for more effective utilization of the reluctance torque, resulting in an improved torque effect.

[0058] As described above, according to this embodiment, the non-magnetic portion of the bridge is formed only on bridges located in the rotor region on the negative torque side with respect to the positive torque direction of the main torque, with the d-axis of the rotor as the boundary. Therefore, manufacturing costs can be reduced by reducing the area in which the non-magnetic portion is formed within the range that is effective in improving the torque of the rotating electric machine.

[0059] Other embodiments. The non-magnetic materials in the non-magnetic parts described in each of the above embodiments are materials with lower saturation magnetic flux density or lower permeability compared to general magnetic materials used in rotor cores. Materials with lower saturation magnetic flux density and lower permeability can provide a greater improvement in torque or output.

[0060] Furthermore, regarding the non-magnetic parts described in each of the above embodiments, it is more desirable to use a material with a saturation magnetic flux density that is 5% or more lower than the magnetic material constituting the electromagnetic steel sheet of the rotor core, or a material with lower magnetic permeability, as this significantly enhances the effects described above. However, by using a material with a saturation magnetic flux density that is significantly lower than the magnetic material constituting the electromagnetic steel sheet of the rotor core, or a material with lower magnetic permeability, it is possible to obtain a certain level of the torque and output improvement effects described above.

[0061] As described above, according to this embodiment, the non-magnetic portion of the bridge is formed of a material with a lower permeability than the permeability of the rotor core. Therefore, compared to using a completely non-magnetic material, the torque improvement effect is greater while considering manufacturing costs, resulting in a higher cost-effectiveness.

[0062] Furthermore, since the non-magnetic portion of the bridge is formed from a material with a saturation magnetic flux density lower than that of the rotor core, the torque improvement effect is greater and the cost-effectiveness is higher, even considering manufacturing costs, compared to using a completely non-magnetic material.

[0063] While this disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but are applicable individually or in various combinations to the embodiments. Accordingly, countless variations not illustrated are envisioned within the scope of the art disclosed in this specification. For example, these include modifying, adding or omitting at least one component, or extracting at least one component and combining it with a component from another embodiment.

[0064] 1 Housing, 2 Stator, 3 Stator core, 4 Coil, 5 Rotor, 12 Yoke, 13 Teeth, 14 Slot, 21 Rotor core, 22 Magnet housing hole, 23 Flux barrier, 23A, 23B, 23C Flux barrier, 25 Bridge, 250 Bridge, 25A, 25B, 25C, 25X, 25Y Bridge, 30 Permanent magnet, 50 Non-magnetic part, 50A, 50B, 50C Non-magnetic part, 60 Magnetic part, 60A, 60B, 60C Magnetic part, 501, 502, 503, 504, 505, 506 Non-magnetic part, 601, 602, 603, 604, 605, 606 Magnetic part, 100 Rotating electric machine.

Claims

1. A rotating electric machine comprising: a stator having a stator core and armature windings provided on the stator core; and a rotor having a rotor core and permanent magnets housed in magnet housing holes of the rotor core, wherein the rotor core has flux barriers provided at the circumferential ends of the permanent magnets to suppress short circuits of magnetic flux, and bridges provided to connect the rotor core at both outer peripheral ends of the flux barrier, and the bridges comprising a non-magnetic portion made of a non-magnetic material provided at least on the d-axis side of the central part of the bridge, and a magnetic portion made of a magnetic material provided at least at the q-axis side end in the region other than the non-magnetic portion.

2. The rotating electric machine according to claim 1, wherein a pair of magnet housing holes, substantially symmetrical with respect to the d-axis, are formed in the rotor radial direction in N layers (where N is a natural number), the pair of magnet housing holes are configured to be V-shaped such that the distance between them decreases as they move toward the inner circumference of the rotor core, each of the magnet housing holes houses a permanent magnet, a pair of flux barriers are provided at the circumferential ends of each permanent magnet, a pair of bridges are provided to connect the rotor core at both outer circumference ends of each flux barrier, and at least one pair of bridges consists of a non-magnetic portion made of a non-magnetic material, provided at least toward the d-axis side of the central part of the bridge, and a magnetic portion made of a magnetic material, provided at least at the q-axis side end in a region other than the non-magnetic portion.

3. The non-magnetic portion of the bridge is formed extending from the point where it connects to the d-axis side of the rotor core toward the q-axis side, according to claim 1 or claim 2.

4. The non-magnetic portion of the bridge is formed extending from the point where it connects to the d-axis side of the rotor core, past the central part of the bridge, toward the q-axis side, according to claim 3.

5. The rotating electric machine according to any one of claims 1 to 4, wherein in the thickness direction which is substantially perpendicular to the direction in which the rotor core on the d-axis side and the rotor core on the q-axis side of the bridge is connected, the thickness of the bridge on the q-axis side is greater than the thickness of the bridge on the d-axis side.

6. The rotating electric machine according to any one of claims 1 to 5, wherein the non-magnetic portion of the bridge is formed only in part in the thickness direction of the bridge.

7. The non-magnetic portion of the bridge is formed over the entire thickness direction of the bridge, as described in any one of claims 1 to 5.

8. The rotating electric machine according to any one of claims 1 to 7, wherein the non-magnetic portion of the bridge is formed only on bridges located in the rotor region on the negative torque side with respect to the positive torque direction of the main torque, with the d-axis of the rotor as the boundary.

9. The rotating electric machine according to any one of claims 1 to 8, wherein the non-magnetic portion of the bridge is formed only on the outermost bridge of the rotor.

10. The rotating electric machine according to any one of claims 1 to 9, wherein the current phase β of the armature winding is operated in the range of 0° < β < 90° or 90° < β < 180°.

11. The rotating electric machine according to any one of claims 1 to 10, wherein the non-magnetic portion of the bridge is formed by non-magnetic modification of the magnetic material constituting the rotor core.

12. The rotating electric machine according to any one of claims 1 to 11, wherein the non-magnetic portion of the bridge is formed of a material with a magnetic permeability lower than that of the rotor core.

13. The rotating electric machine according to any one of claims 1 to 11, wherein the non-magnetic portion of the bridge is formed of a material with a saturation magnetic flux density lower than the saturation magnetic flux density of the rotor core.

Images