Rotating Electric Machine

Abstract

To provide a rotary electric machine capable of torque improvement and efficiency improvement in accordance with a processing method capable of minimizing an eddy current loss that is generated on a rotor surface, and minimizing a thickness of a bridge part.SOLUTION: The present invention relates to a rotary electric machine comprising a rotor including a rotor core in which a plurality of magnet holes storing a plurality of magnets therein is formed, and a stator opposed to the rotor with a predetermined cavity interposed therebetween. The rotor core includes a bridge part in which a distance between the magnet hole and a face opposed with the stator becomes shortest in the vicinity of a (q) axis that is a magnetic pole boundary of the rotor. When surface roughness of the face of the bridge part opposed with the stator is defined as R1 and surface roughness of a face opposed with the stator in the vicinity of the (d) axis that is a magnetic pole center of the rotor is defined as R2, R1 and R2 are different.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a rotor that can achieve high torque density and high efficiency, and to a rotating electric machine using the rotor. [Background technology]

[0002] In order to meet the demand for smaller and lighter machines with the advancement of electrification, there is a demand for improving the torque density of rotating electric machines. Because the torque density of a rotating electric machine is expressed as the quotient of the torque of the rotating electric machine and the mass of the rotating electric machine, it is important to increase the torque of the rotating electric machine and reduce its weight.

[0003] Generally, methods for increasing the torque of a rotating electric machine include using permanent magnets or reluctance torque to improve the torque. For this reason, a so-called embedded magnet type, in which permanent magnets are embedded in the rotor core, is known as a rotor configuration that can increase the torque. Also, a method for reducing the weight of a rotating electric machine is known in which the number of poles of the rotating electric machine is increased and the stator and rotor are made thinner in the radial direction to reduce the weight.

[0004] Embedded magnet rotor cores have bridges to mechanically support the magnets, but the magnetic flux leaks from the bridges, which hinders the design of the limit for high torque. For this reason, it is desirable to make the bridges as thin as possible while still providing sufficient mechanical strength. In particular, because the magnet weight per pole of a multi-pole rotating electric machine is light in order to reduce weight, the bridges can still provide sufficient mechanical strength even if they are made thinner than the plate thickness of the core that constitutes the rotor core.

[0005] On the other hand, there were problems with the conventional machining technology for rotor cores. That is, punching has been used as a machining method for stator cores and rotor cores of rotating electric machines. While punching is excellent for mass production because a large number of cores can be produced using one punching die, there is a limit to the thickness of the narrowest part that can be punched, and the thickness of the narrowest part is generally about the plate thickness of the core to be punched. For example, if the plate thickness of the core is 0.5 mm, the minimum thickness that can be punched is also 0.5 mm. Therefore, even if sufficient mechanical strength can be guaranteed even if the thickness of the bridge part is narrower than the plate thickness, it is necessary to make it the same thickness as the plate thickness due to the limit of the machining technology. For this reason, with the conventional punching technology, due to the constraints of the minimum thickness that can be processed, the thickness of the bridge part cannot be narrowed sufficiently, which increases the leakage flux, which hinders the increase in the torque of rotating electric machines.

[0006] For example, Patent Document 1 discloses a technique for making the bridge thickness equal to or less than the plate thickness of the core. Patent Document 1 proposes a method for making the thickness dimension of the bridge part the minimum thickness necessary in terms of strength by punching out the core that will become the rotor core and then grinding it. This aims to make the thickness of the bridge part equal to or less than the thickness of the core. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2010-148161 A Summary of the Invention [Problem to be solved by the invention]

[0008] Patent Document 1 proposes a method of narrowing the bridge thickness by grinding the entire rotor core. However, such machining gives rise to the following problems.

[0009] First, when the rotor core is laminated and then the surface is ground, the cores that were electrically insulated from each other become conductive at the machined surface due to local deformation. Therefore, when the entire rotor core is ground, the rotor core surface becomes conductive over the entire circumference. When magnetic flux passes through such a rotor surface, eddy currents are generated in the conductive machined surface, generating heat, i.e., loss, on the rotor surface. In particular, since a large amount of magnetic flux passes through the conductive surface over the entire circumference of the rotor core surface and the electrical resistance of the conductive surface is small, large eddy currents flow and generate large losses. For this reason, in the method proposed in Patent Document 1, eddy current loss is generated on the rotor surface in exchange for reducing leakage flux by narrowing the thickness of the bridge portion, and there is a trade-off between high torque density and high efficiency. In particular, when eddy currents become large, they themselves generate brake torque, which can be a factor that inhibits high torque. In addition, when permanent magnets are used in the rotor, there is a risk that the magnets will be irreversibly demagnetized due to heat generation on the rotor surface close to the permanent magnets.

[0010] In view of the above circumstances, the present invention aims to provide a rotating electric machine that can achieve high torque and high efficiency by using a processing method that can minimize eddy current loss that occurs on the rotor surface and minimize the thickness of the bridge portion. [Means for solving the problem]

[0011] One example of the present invention is a rotating electric machine that includes a rotor having a rotor core in which multiple magnet holes are formed to house multiple magnets, and a stator that faces the rotor across a specified gap, in which the rotor core has a bridge portion near the q-axis, which is the magnetic pole boundary of the rotor, where the distance between the magnet hole and the surface facing the stator is the shortest, and where the surface roughness of the bridge portion's surface facing the stator is R1 and the surface roughness of the bridge portion's surface facing the stator near the d-axis, which is the magnetic pole center of the rotor, is R2, R1 and R2 are different in surface roughness. Effect of the Invention

[0012] According to the present invention, it is possible to provide a rotating electric machine capable of achieving high torque and high efficiency. [Brief description of the drawings]

[0013] [Figure 1] 3 is a diagram illustrating the configuration of a rotor before grinding in the first embodiment. FIG. [Diagram 2] FIG. 2 is an enlarged view of a portion of the rotor in FIG. [Diagram 3] 4A to 4C are diagrams illustrating the configuration of a rotor after grinding in the first embodiment. [Figure 4] FIG. 4 is an enlarged view of a portion of the rotor in FIG. [Diagram 5] 1A and 1B are diagrams illustrating the configuration of a rotor after grinding processing by a conventional method. [Figure 6] FIG. 2 is a diagram illustrating the surface roughness of a ground portion and a punched portion in Example 1. [Figure 7] FIG. 2 is a development view of a rotor core and end plates of the rotor in the first embodiment. [Figure 8] 10 is a diagram illustrating the configuration of a rotor before grinding in Example 2. FIG. [Figure 9] 10 is a diagram illustrating the configuration of a rotor after grinding in Example 2. FIG. [Figure 10] 13 is a diagram illustrating the configuration of a rotor before grinding in Example 3. FIG. [Figure 11] 13 is a diagram illustrating the configuration of a rotor after grinding in Example 3. FIG. [Figure 12] FIG. 11 is a structural diagram of an outer rotor type electric wheel in a fourth embodiment. [Figure 13] FIG. 11 is a structural diagram of an inner rotor type electric wheel in a fourth embodiment. [Figure 14] FIG. 11 is a schematic structural diagram of a railway vehicle in a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. EXAMPLES

[0015] The rotating electric machine to which the present invention is directed includes a stator and a rotor rotatably supported by the stator. A gap is provided between the stator and the rotor, and the stator and the rotor are arranged so as not to come into contact with each other. The rotating electric machine may be an inner rotor type in which the rotor is rotatably supported on the inner periphery of the stator, or an outer rotor type in which the rotor is rotatably supported on the outer periphery of the stator. In this embodiment, the inner rotor type will be described as an example.

[0016] 1 is a diagram illustrating the configuration of a rotor before grinding in this embodiment, in which (a) is a plan view of a rotor 11, and (b) is a side view of the rotor 11.

[0017] 1, a rotor 11 rotates about a rotation axis C. A shaft may be fixed to the rotor, and the rotating electric machine may include a frame that covers the stator and rotor. The rotor is connected to a load directly or via a structural member such as a shaft or frame, and transmits rotation and torque to the load as the rotor rotates.

[0018] The rotor 11 includes a rotor core 12 and a magnetic pole portion. The rotor core 12 is formed by laminating a plurality of core sheets. The rotor core 12 may be formed of an integrally molded solid member. It may also be formed by compression molding a powder magnetic material such as a dust core, or may be formed of an amorphous metal or a nanocrystalline material.

[0019] The magnetic pole portion may be a structure that utilizes the salient pole of the rotor core 12, for example, the magnetic pole portion of a switched reluctance motor or a synchronous reluctance motor. It may also be a magnetic pole portion of an embedded magnet type motor in which at least one permanent magnet is arranged in the magnetic pole portion. This embodiment can be applied to multiple poles (four or more poles). The stator facing the rotor 11 has the same rotation axis C as the rotor 11, but is not shown, and is composed of a stator core and coils that are made by laminating multiple core sheets. The stator core is composed of a circular stator back yoke, teeth connected to the back yoke and provided on the radial gap side, and slots provided between the teeth. The coils are wound so as to surround the teeth and slots. The core may be composed of an integrally molded solid member. It may also be composed of a powder magnetic material such as a dust core that has been compressed and molded, or may be composed of amorphous metal or nanocrystalline material.

[0020] The coils consist of in-slot coils inserted into the slots, coil ends that span between the slots in different positions, and leader wires that input current from an external circuit and connect the coils in different positions. To generate a rotating magnetic field in the air gap, coils of three different phases, for example U-phase, V-phase, and W-phase, are arranged. The phases of the fundamental wave components of the current input to the coils of each phase differ by 120° from each other, which generates a rotating magnetic field in the air gap and makes it possible to rotate the rotor.

[0021] In FIG. 1, the d-axis is the axis that passes through the center of the rotor's magnetic poles. When the rotor is skewed, a d-axis is defined for each magnetic pole central axis direction. The q-axis is the axis that passes through the rotor's magnetic pole boundaries. When the rotor is skewed, a q-axis is defined for each cross section in the magnetic pole central axis direction.

[0022] Magnet holes 13, 14 are holes for inserting permanent magnets provided in rotor core 12. There is a degree of freedom in the layout of the magnet holes within the rotor core, and although magnet holes 14 on the d-axis and magnet holes 13 on the q-axis are arranged alternately in Fig. 1, only one of the magnet holes may be used. Also, for example, magnet holes 13 may be further divided in the circumferential direction, resulting in a so-called U-shaped magnet hole arrangement, or a V-shaped magnet hole arrangement.

[0023] 2 is an enlarged view of a portion of the rotor 11 in FIG. 1. In FIG. 2, the bridge portion 17 is a narrow portion of the rotor core 12 sandwiched between the magnet hole 13 and the surface of the rotor core 12 on the radial gap side, and is located near the q-axis. The bridge portion is located within an electrical angle range of ±45° centered on the q-axis. Here, the electrical angle is an angle defined by 360° for one pole pair (=2 poles), and if the number of pole pairs is p, then the electrical angle is p times the mechanical angle (mechanical angle). In other words, the q-axis and d-axis in the direction of the central axis of one magnetic pole form an electrical angle of 90°.

[0024] It is desirable to narrow the bridge section 17 because it becomes a path for leakage magnetic flux that shorts out the magnetic flux of the permanent magnet. On the other hand, because the bridge section is a narrow section, it is also a part where large stress occurs due to the load of centrifugal force and electromagnetic force acting on the rotor. For this reason, the design of the thickness of the bridge section is determined by the balance between magnetic properties such as torque and mechanical strength.

[0025] As the number of poles on the rotor increases, the centrifugal force and electromagnetic load per pole decreases. For this reason, the more poles there are, the thinner the bridge section can be. However, since there is a limit to the thickness of the narrow parts that can be processed with core processing technology, the design of the thickness of the bridge section must also take into account the limits of the processing technology. With conventional punching processing, the maximum thickness that can be processed is generally equal to or greater than the thickness of the core sheet, so with conventional methods it is difficult to process bridge sections that are thinner than the thickness of the core sheet.

[0026] The protruding portion 15 is a core region provided near the q-axis on the radial gap side surface of the rotor core 12. The protruding portion 15 protrudes radially toward the gap further than the radial gap side surface of the rotor core 12 on the d-axis. The protruding portion 15 overlaps the bridge portion 17 in the radial direction, which increases the thickness of the bridge portion 17 by the amount of protrusion of the protruding portion 15. The protruding portion 15 is a region that exists in the rotor core 12 before grinding. Because the protruding portion 15 increases the thickness of the bridge portion 17, the rotor core 12 can be manufactured by ordinary punching.

[0027] As shown in FIG. 1(b), on the side surface of rotor 11, protrusions 15 and magnetic pole cores 16 are arranged alternately.

[0028] Fig. 3 is a diagram for explaining the configuration of the rotor after grinding in this embodiment. Also, Fig. 4 is an enlarged view of a part of the rotor 11 in Fig. 3. In Fig. 3 and Fig. 4, the same components as those in Fig. 1 and Fig. 2 are given the same reference numerals, and the description thereof will be omitted.

[0029] In Fig. 3 and Fig. 4, only the protruding portion 15 near the q-axis is locally ground. After local grinding, the thickness of the bridge portion 17 of the rotor core 12 is less than the core plate thickness due to grinding, which reduces leakage magnetic flux and improves torque density. In addition, the rotor core conductive portion is localized by cutting, which minimizes eddy current loss generated on the rotor core surface. Since only the protruding portion 15 is locally ground, as shown in Fig. 3(b), there is a difference in surface roughness between the ground portion of the protruding portion 15 and the non-ground portion of the magnetic pole center portion 16. In other words, if the surface roughness of the ground portion of the protruding portion 15 is R1 and the surface roughness of the non-ground portion of the magnetic pole center portion 16 is R2, R1 and R2 are different.

[0030] Fig. 5 is a diagram for explaining the configuration of a rotor after grinding by a conventional method. In Fig. 5, the same components as those in Fig. 3 are given the same reference numerals, and their explanation will be omitted. In Fig. 5, as described above, the conventional method is to narrow the bridge thickness by grinding the entire rotor core 12. Therefore, as shown in Fig. 5(b), both the inter-pole portion 18 and the magnetic pole center portion 16 have a surface roughness R1 on the ground surface.

[0031] 3 and 4, the ground portion of the protrusion 15 is the area remaining after the protrusion 15 is removed by grinding. At least a part of the ground portion is on the radial gap side of the bridge portion 17 of the rotor core 12. Grinding, i.e., mechanical processing such as polishing and cutting, generally allows for processing with higher accuracy than punching. Therefore, by post-processing the protrusion 15 by grinding, the thickness of the bridge portion 17 can be made thinner than the plate thickness of the core sheet.

[0032] The surface roughness R1 of the surface of the grinding portion of the protruding portion 15 is the surface roughness of the surface facing the stator of the bridge portion 17, and can also be said to be the surface roughness of the grinding portion of the rotor core 12. Since this surface is a ground surface, the surface roughness depends on the grinding accuracy.

[0033] When a lathe is used to grind the protruding portion 15, the grinding portion needs to protrude slightly toward the gap side from the surface of the rotor core 12 on the d-axis. That is, this is because full-circumference cutting is required to prevent protrusion. Grinding by lathe machining enables grinding in a short time, contributing to improved productivity and reduced manufacturing costs.

[0034] The surface roughness R2 of the surface of the non-grinding portion of the magnetic pole center portion 16 is the surface roughness of the surface facing the stator of the d-axis, which is the magnetic pole center of the rotor, and is located in the range of electrical angles ±45° centered on the d-axis. Also, the surface roughness R2 of the surface of the non-grinding portion is the laminated surface of the core sheets after punching, and the surface roughness depends on the cross-sectional deformation amount of each core sheet due to punching and the cumulative error due to core sheet lamination. Also, the inner surfaces of the magnet holes 13 and 14 are also non-grinding portions. If the surface roughness thereof is designated as R3, R3 is the same as R2.

[0035] The surface roughnesses R1, R2, and R3 are different from each other due to differences in the processing methods. Conversely, the fact that R1 is different from R2 and R3 indicates that the processing methods are different for R1 and R2, R3, indicating that the protruding portion is a grinding portion by post-processing. Generally, grinding has higher processing accuracy than punching, and the relationship is R1 < R2, R3.

[0036] Further, the range of electrical angle of ±45° centered on the d-axis does not have to be the surface roughness R2 of the surfaces of all non-grinding parts. It is sufficient if there is a region of non-grinding parts somewhere near the d-axis. As a result, the ground surfaces of the respective bridge parts are separated from each other somewhere on the d-axis, and the conductive parts of the ground surfaces do not short-circuit each other, making it possible to achieve both high torque density and high efficiency. That is, in the range of electrical angle of ±45° centered on the d-axis, on the surface facing the stator, there are regions with surface roughnesses R2a and R2b (<R2a), where R2a is the surface roughness R2 of the surface of the non-grinding part, and it is sufficient if R1 and R2a are different.

[0037] Also, when surface coating is performed after rotor assembly, the surface roughness becomes uniform over the entire circumference of the rotor surface. Also in this case, after peeling off the surface coating, the surface roughnesses of the soft magnetic material parts are R1 and R2 for the ground part and the non-ground part, respectively, and they are different from each other. That is, the presence or absence of grinding of the bridge part can be determined by the surface roughness of the soft magnetic material part of the core sheet. Note that the soft magnetic material part is the material part mainly composed of iron of the core sheet, and does not include lamination between core sheets, adhesives, coatings on the rotor surface, etc.

[0038] Note that the surface roughnesses R1, R2, and R3 are defined as the arithmetic mean roughness Ra that is not easily affected by local defects or the like. The arithmetic mean roughness Ra is obtained by extracting only a reference length L in the direction of the mean line from the roughness curve, taking the X-axis in the direction of the mean line of this extracted part and the Y-axis in the direction of the longitudinal magnification, and when the roughness curve is represented by y = f(x), it is the value obtained by the following formula (1) expressed in micrometers (μm).

[0039]

Equation

[0040] In general soft magnetic materials, the arithmetic mean roughness Ra of the punched part is 10 to 50, and in addition, the cumulative error also has an impact. On the other hand, the arithmetic mean roughness Ra of the ground part is less than 5, and there is no cumulative error due to post-processing.

[0041] Fig. 6 is a diagram for explaining the surface roughness of the ground portion and the punched portion (non-ground portion) in this embodiment. In Fig. 6, the same components as those in Fig. 3 are given the same reference numerals, and the description thereof will be omitted.

[0042] In FIG. 6, (b) shows a partially enlarged cross-sectional view of the protruding portion 15, which is the ground portion, and (c) shows a partially enlarged cross-sectional view of the magnetic pole center portion 16, which is the non-ground portion and punched portion. As shown in (c), the rotor core 12 is formed by laminating a plurality of core sheets 19, so that the punching process causes recesses due to sagging and fracture surfaces of the core sheets 19 and protrusions due to shear surfaces to appear regularly in the lamination direction. That is, periodic irregularities appear in the axial direction (lamination direction) indicated by the white arrow on the punched surface. This is a surface condition specific to the punching method of lamination, and the period of the irregularities coincides with the plate thickness of the core sheets 19, and the surface roughness is R2. On the other hand, as shown in (b), in the ground portion, the punched surface shown in (c) is ground, so there are no periodic irregularities on the ground surface, and the surface roughness is R1 ( <R2)となる。

[0043] In addition, the measurement range of the arithmetic mean roughness described above is set to a width greater than or equal to the thickness of core sheet 19 in the direction of the rotation axis, and also set to a width greater than or equal to the thickness of core sheet 19 in the circumferential direction perpendicular to this, so that surface roughnesses R1, R2, and R3 can be evaluated without being affected by local surface roughness on the order of nm to um.

[0044] FIG. 7 is a development view of the rotor core and end plates of the rotor in this embodiment. In FIG. 7, the same components as those in FIG. 3 are given the same reference numerals, and their description will be omitted. In FIG. 7, the end plates 20 are pressing plates for clamping the rotor core 12 from both ends. The end plates 20 prevent the laminated core sheets from peeling off, and prevent the permanent magnets from falling out of the magnet holes. There is no particular limitation on the material, such as metal or resin, but if the fluctuation amount of the magnetic flux leaking to the end plates 20 is large, it is preferable to use a non-magnetic material. In addition, it is preferable to use an insulating material with a high electrical resistivity in order to reduce eddy current loss in the end plates 20.

[0045] In addition, the ground parts are individually conductive, and when electrically connected to the end plate 20, the ground parts are electrically short-circuited. In this case, the electrical resistance of the short circuit is small, and the amount of magnetic flux penetrating the circuit increases significantly, so that the eddy current loss generated in the rotor 11 increases. On the other hand, by insulating the ground parts from at least one of the end plates 20, the above-mentioned short circuit is not formed. Therefore, the eddy current loss generated in the rotor 11 is small, and it is possible to achieve both high torque density and high efficiency. In addition, as a method of insulation, an electrical insulating member may be sandwiched between the rotor core 12 and the end plate 20, a space may be provided, or the end plate 20 may be made of an electrical insulator. In addition, as a method of providing a space, the diameter of at least one surface of the end plate 20 facing the rotor core 12 is made smaller than the diameter of the surface facing the gap of the rotor core 12. As a result, the ends of end plates 20 do not come into contact with the area with surface roughness R1, so that no short circuit is formed connecting end plates 20 and the area with surface roughness R1, and eddy current loss generated in rotor 11 can be suppressed.

[0046] Thus, according to this embodiment, the rotating electric machine has a surface roughness different from that of the other surfaces by grinding only the surface near the bridge part of the rotor core after lamination. Furthermore, the thickness of the bridge part can be narrowed by grinding compared to punching, so that leakage flux from the bridge part can be reduced and high torque density can be achieved. Furthermore, by limiting the grinding range to only the vicinity of the bridge part, the conductive area of ​​the core surface after grinding can be minimized, and eddy current loss generated on the rotor surface can be minimized, making it possible to achieve high efficiency. EXAMPLES

[0047] Fig. 8 is a diagram for explaining the configuration of the rotor before grinding in this embodiment. In Fig. 8, the same components as those in Fig. 1 are given the same reference numerals, and the description thereof will be omitted.

[0048] 8, magnet holes 21 on the q axis have a protrusion on the radial gap side of rotor core 12, and therefore bridge portion 17 also has a shape in which the surface on the radial magnet hole 21 side is protruding toward the radial gap side. Note that protrusion 15 is a region that radially overlaps bridge portion 17, similar to Example 1.

[0049] Fig. 9 is a diagram for explaining the configuration of the rotor after grinding in this embodiment. In Fig. 9, the same components as those in Fig. 8 are given the same reference numerals, and the description thereof will be omitted.

[0050] In FIG. 9, only the protrusion 15 near the q-axis is locally ground. After local grinding, the bridge portion 17 has an opening 22 that is interrupted midway. The opening 22 refers to the area where part of the circumferential direction of the bridge portion 17 is interrupted. The "bridge portion" here does not mean a "bridge" that connects the ends, but rather a "projection" or "claw" that holds the magnet. By interrupting part of the bridge portion, the leakage magnetic flux from the bridge portion can be further reduced.

[0051] Since only the protruding portion 15 is ground locally, as shown in FIG. 9(b), a difference in surface roughness occurs between the ground portion, the bridge portion 17, and the non-ground portion, the magnetic pole center portion 16.

[0052] Thus, according to this embodiment, the rotating electric machine has a surface roughness different from that of the other surfaces by grinding only the surface near the bridge part of the rotor core after lamination. Then, by cutting off a part of the bridge part by grinding, it is possible to further reduce leakage magnetic flux from the bridge part. Furthermore, as in the first embodiment, by limiting the grinding range only to the vicinity of the bridge part, it is possible to minimize the conductive area of ​​the core surface after grinding, and it is possible to minimize eddy current loss generated on the rotor surface and achieve high efficiency. EXAMPLES

[0053] Fig. 10 is a diagram for explaining the configuration of the rotor before grinding in this embodiment. In Fig. 10, the same components as in Fig. 1 are given the same reference numerals, and the description thereof will be omitted.

[0054] 10, the rotor core 12 has multiple magnetic barriers 23. The magnetic barriers 23 are holes provided in the rotor core 12 to control the magnetic flux of the rotor and give the rotor salience. The provision of the magnetic barriers 23 enables the rotor core 12 to generate reluctance torque.

[0055] The shape of the magnetic barrier is arbitrary, and although two U-shaped magnetic barriers 23 are provided in FIG. 10, they may be V-shaped, spoke-shaped, I-shaped, or the like, and the number of stages may be one or more. As long as an inductance difference is obtained between the d-axis through which the main magnetic flux passes and the q-axis between the magnetic poles, the shape of the magnetic barrier is not important. The magnetic barrier may be filled with air or other non-magnetic fluid. It may also be filled with a non-magnetic solid such as resin. Furthermore, it may be the rotor of a magnet-assisted synchronous reluctance motor with a magnet inserted in a part of it.

[0056] The rotor core 12 also includes a bridge portion 17 where the distance between the magnetic barrier 23 and the surface on the radial gap side is the shortest, and includes a protrusion 15 in an area radially overlapping with the bridge portion 17 .

[0057] Fig. 11 is a diagram for explaining the configuration of the rotor after grinding in this embodiment. In Fig. 11, the same components as those in Fig. 10 are given the same reference numerals, and the description thereof will be omitted. In FIG. 11, only the protruding portion 15 is locally ground. After the local grinding, the thickness of the bridge portion 17 of the rotor core 12 becomes equal to or less than the core plate thickness due to the grinding, so that the leakage magnetic flux can be reduced and the torque density can be improved. Further, the rotor core conduction portion due to cutting becomes local, and the eddy current loss generated on the rotor core surface can be minimized. Since only the protruding portion 15 is locally ground, as shown in FIG. 11(b), a difference in surface roughness occurs between the ground portion of the protruding portion 15 and the non-ground portion of the magnetic pole center portion 16. That is, if the surface roughness of the ground portion of the protruding portion 15 is R1 and the surface roughness of the non-ground portion of the magnetic pole center portion 16 is R2, then R1 and R2 are different.

[0058] Also, when the rotor core is manufactured by punching and laminating, the magnetic barrier 23 is also formed by punching. Therefore, the inner surface of the magnetic barrier 23 is also a non-ground portion, and if its surface roughness is R3, then R3 is the same as R2. Note that the surface roughness of the inner surface of the magnetic barrier 23 depends on the cross-sectional deformation amount of each core sheet due to the punching process and the cumulative error due to the core sheet lamination. Also, generally, grinding has higher machining accuracy than punching, and the relationship is R1 < R2, R3.

[0059] Thus, according to this embodiment, in addition to the same effects as in Embodiment 1, narrow bridging is also possible in the reluctance torque motor, whereby the reluctance torque can be improved and both torque density improvement and high efficiency can be achieved simultaneously.

Embodiment

[0060] In this embodiment, an application example using the rotating electrical machine having the rotor described in Embodiments 1 to 3 will be described.

[0061] FIG. 12 is a structural diagram of an outer rotor type electric wheel in this embodiment. In FIG. 12, (a) shows a developed view and (b) shows a completed view. In FIG. 12, the electric wheel 50 mainly includes a stator 51, a rotor 52, a rotor cover 53, and a wheel 54.

[0062] Fig. 13 is a structural diagram of the inner rotor type electric wheel in this embodiment. In Fig. 13, (a) shows a development view, and (b) shows a completed view. In Fig. 13, the electric wheel 60 mainly comprises a stator 61, a rotor 62, a stator cover 63, and a wheel 64.

[0063] In Figs. 12 and 13, an outer rotor type or inner rotor type rotating electric machine is used for the electric wheels 50 and 60. The rotors 52 and 62 of the rotating electric machine are connected to a rotor frame. The rotor frames are connected to the wheels 54 and 64 by connecting members. Tires are fitted to the wheels 54 and 64. In order to support the wheels 54 and 64 and the rotors 52 and 62 rotatably relative to the stator frame, the wheels 54 and 64 or the rotor frame are connected to the stator frame by bearings. Meanwhile, the stators 51 and 61 of the rotating electric machine are fixedly supported by the stator frame, and an electric circuit is also mounted on the stator frame. The electric circuit supplies power to the stator to rotate the rotors 52 and 62. The rotation of the rotors 52 and 62 is transmitted to the wheels 54 and 64 via the rotor frame and connecting members, causing the wheels 54 and 64 to rotate.

[0064] When the rotor described in the first to third embodiments is adopted, the torque density of the rotating electric machine is high, so that the rotating electric machine can be accommodated on the inner periphery side of the wheel 54, 64, and the wheel can be made gearless, i.e., the wheel can be directly driven. Conventional electric wheels use gears, which causes problems such as wear of the gears, noise, and an increase in the number of bearings used because the gears need to be supported. In contrast, the electric wheels 50, 60 using the rotating electric machine with high torque density of the present embodiment do not require gears, so that maintenance considering wear of the gears is not required, and there is no noise generated from the gears. In addition, the amount of bearings used is minimized, the risk of bearing wear is reduced, and the amount of maintenance work such as changing grease for the bearings can be reduced. In addition, since the volume of the rotating electric machine is small, the electric circuit can also be mounted inside the wheel 54, 64, and due to the synergistic effect with the gearless design, the electric wheels 50, 60 can be made small and lightweight.

[0065] Figure 14 is a schematic structural diagram of a railway vehicle in this embodiment. In Figure 14, an inner rotor type rotating electrical machine 71 is used for the railway vehicle 70. The rotating electrical machine 71 is fixedly supported on the bogie 73 by a support member 72. The rotor of the rotating electrical machine 71 is directly connected to the axle 74, and the rotating electrical machine 71 drives the wheel 75 via the axle 74.

[0066] Since the torque density of the rotating electrical machine 71 is high, the railway vehicle 70 can adopt the form of this embodiment, enabling gearless operation, that is, direct drive of the wheels. Conventional railway vehicles use gears, and problems such as gear wear, noise, and an increase in the number of bearings required due to the need to support the gears have occurred. In contrast, the railway vehicle 70 using the rotating electrical machine 71 with a high torque density in this embodiment does not require gears, so maintenance considering gear wear is unnecessary, and the noise generated from the gears disappears. Also, the amount of bearings used is minimized, the risk of bearing wear is reduced, and the amount of maintenance work such as grease replacement of the bearings can be reduced. Moreover, since the volume of the rotating electrical machine 71 is small, the railway vehicle can be made smaller and lighter due to the synergistic effect with gearless operation. Furthermore, the weight reduction of the bogie 73 reduces mechanical damage to the rails and wheels 75, contributing to the extended service life of the rails and wheels 75.

[0067] Although the above embodiments have been described, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above embodiments have been described in detail for easy understanding of the present invention and are not necessarily limited to those having all the configurations described. Also, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, for a part of the configuration of each embodiment, addition, deletion, or replacement with other configurations is possible.

Explanation of Reference Numerals

[0068] 11, 52, 62: rotor, 12: rotor core, 13, 14, 21: magnet hole, 15: protrusion, 16: pole center, 17: bridge portion, 18: inter-pole portion, 19: core sheet, 20: end plate, 22: opening, 23: magnetic barrier, 50, 60: electric wheel, 51, 61: stator, 53: rotor cover, 54, 64: wheel, 63: stator cover, 70: railway vehicle, 71: rotating electric motor, 72: support member, 73: bogie, 74: axle, 75: wheel.

Claims

1. A rotating electric machine including a rotor having a rotor core in which a plurality of magnet holes for accommodating a plurality of magnets are formed, and a stator facing the rotor with a predetermined gap therebetween, the rotor core includes a bridge portion in the vicinity of the q-axis which is a magnetic pole boundary of the rotor, whereby a distance between the magnet hole and a surface facing the stator is the shortest; A rotating electric machine characterized in that R1 and R2 are different in surface roughness of the surface of the bridge portion facing the stator in the vicinity of the d-axis which is the magnetic pole center of the rotor, where ...

2. 2. The rotating electric machine according to claim 1, the bridge portion is located within an electrical angle range of ±45° around the q-axis, A rotating electric machine, characterized in that the surface roughness R2 is the roughness of the surface of the rotor facing the stator within an electrical angle range of ±45° centered on the d-axis.

3. 3. The rotating electric machine according to claim 2, a surface facing the stator has a region having a surface roughness of R2a and R2b (<R2a) within a range of an electrical angle of ±45° around the d-axis, wherein R2=R2a, A rotating electric machine, characterized in that R1 and R2a are different from each other.

4. 2. The rotating electric machine according to claim 1, A rotating electric machine, wherein R1 and R2 are surface roughnesses of a soft magnetic material portion of the rotor core.

5. 2. The rotating electric machine according to claim 1, A rotating electric machine, wherein R1 and R2 satisfy R1<R2.

6. 2. The rotating electric machine according to claim 1, A rotating electric machine, characterized in that, when the surface roughness of the magnet hole is R3, R1 and R3 are different.

7. 7. A rotating electric machine according to claim 6, A rotating electric machine, wherein R1 and R3 satisfy R1<R3.

8. 7. A rotating electric machine according to claim 6, A rotating electric machine, wherein the surface roughness is a value defined as an arithmetic mean roughness.

9. 7. A rotating electric machine according to claim 6, A rotating electric machine, wherein R1 has an arithmetic mean roughness of less than 5, and R2 and R3 have an arithmetic mean roughness of 5 or more.

10. 2. The rotating electric machine according to claim 1, A rotating electric machine, characterized in that a surface of the rotor facing the stator in the vicinity of the d-axis which is the magnetic pole center of the rotor has periodic unevenness in the direction of the rotation axis of the rotor.

11. A rotating electric machine according to claim 10, The rotating electric machine according to the present invention, characterized in that the unevenness has a periodicity with one period being equal to a thickness of the laminated rotor core of the rotor.

12. 9. A rotating electric machine according to claim 8, The rotor core is formed by laminating core sheets, The measurement range of the arithmetic mean roughness is a width equal to or greater than the thickness of the core sheet in the rotation axis direction, and a width equal to or greater than the thickness of the core sheet in the circumferential direction perpendicular thereto, A rotating electric machine having the surface roughness measured in the measurement range.

13. 2. The rotating electric machine according to claim 1, A rotating electric machine, characterized in that a surface of the rotor core in the vicinity of the q-axis protrudes further toward the air gap than a surface of the rotor core in the vicinity of the d-axis.

14. 2. The rotating electric machine according to claim 1, end plates are disposed on both ends of the rotor core in the axial direction; A rotating electric machine characterized in that at least one of the end plates and the region R1 of the rotor core are electrically insulated from each other.

15. 2. The rotating electric machine according to claim 1, A rotating electric machine characterized in that the bridge portion is interrupted at a portion in the circumferential direction of the rotor core, and the magnet hole has an opening.

16. A rotating electric machine including a rotor having a rotor core in which a plurality of magnetic barriers are formed, and a stator facing the rotor with a predetermined gap therebetween, the rotor core includes a bridge portion that minimizes the distance between the magnetic barrier and a surface facing the stator; A rotating electric machine characterized in that R1 and R2 are different from each other when the roughness of the surface of the bridge portion facing the stator is R1 and the roughness of the surface of the d-axis, which is the magnetic pole center of the rotor, facing the stator is R2.

17. 17. A rotating electric machine according to claim 16, A rotating electric machine, characterized in that, when the surface roughness of the magnetic barrier is R3, R1 and R3 are different.

18. 18. A rotating electric machine according to claim 17, A rotating electric machine, wherein R1 and R3 satisfy R1<R3.

19. An electric wheel using the rotating electric machine according to claim 1 or 16, An electric wheel, characterized in that the rotating electric machine is directly connected to the wheel without a gear.

20. A railway vehicle equipped with the rotating electric machine according to claim 1 or 16, A railway vehicle, wherein the rotating electric machine is directly connected to wheels without a gear.

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