Rotating electric machine

Abstract

The line voltage is reduced, and the output power is improved. [Solution] The rotating electric machine comprises a rotor having multiple magnetic poles including multiple flux barriers and multiple ribs, a stator having multiple teeth and forming a slot between two adjacent teeth, facing radially outward from the rotor with a predetermined air gap, and coils disposed within the slot. At least one of the multiple flux barriers is a central flux barrier positioned on the pole centerline, the innermost circumferential position of the central flux barrier is positioned at a distance of no more than the radial length (h) of the teeth from the outer diameter toward the inner diameter of the rotor, the distance (Wr) between two ribs positioned at both ends of the central flux barrier is greater than or equal to the shortest distance (Wt) in the circumferential direction of the teeth, and less than or equal to the distance (Ws) between the slot opening center, which is the center of the opening that opens to the inner circumferential surface of the stator, and the slot opening center of another slot adjacent to the slot (Wt≦Wr≦Ws).

Description

Technical Field

[0001] The present invention relates to a rotating electric machine.

Background Art

[0002] Various requirements are made for rotating electric machines, such as being small and lightweight and having a large output. Patent Document 1 discloses a rotating electric machine having a stator and a rotor disposed on the inner circumference of the stator, wherein the rotor has a rotor core fixed to a shaft, and a pair of magnet slots provided to face each other such that the distance therebetween decreases toward the inner diameter side around the d-axis, which is the magnetic pole center of the rotor core, a pair of magnets inserted into the pair of magnet slots, and a central flux barrier provided between the pair of magnet slots on the d-axis. When N is an integer of 2 or more, the magnet slots, the magnets, and the central flux barrier are configured in N layers, and a flux barrier layer composed of N layers is formed by the magnet slots composed of N layers and the central flux barrier composed of N layers. Also, the radial distance between the (N - 1)-th central flux barrier and the N-th central flux barrier is the smallest among the distances between the (N - 1)-th flux barrier layer and the N-th flux barrier layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the invention described in Patent Document 1, there is room for improvement in improving the output.

Means for Solving the Problems

[0005] A rotating electric machine according to a first aspect of the present invention comprises a rotor having a plurality of magnetic poles including a plurality of flux barriers and a plurality of ribs, a stator having a plurality of teeth and forming a slot between two adjacent teeth, facing radially outward from the rotor with a predetermined gap, and a coil disposed in the slot, wherein at least one of the plurality of flux barriers is a central flux barrier positioned on the pole centerline, the innermost circumferential position of the central flux barrier is positioned at a distance from the outer diameter of the rotor toward the inner diameter side that is less than or equal to the radial length of the teeth, the distance between the two ribs positioned at both ends of the central flux barrier is greater than or equal to the shortest distance in the circumferential direction of the teeth, and less than or equal to the distance between the slot opening center, which is the center of the opening of the slot that opens to the inner circumferential surface of the stator, and the slot opening center of another slot adjacent to the slot. [Effects of the Invention]

[0006] According to the present invention, the line voltage is reduced and the output is improved. [Brief explanation of the drawing]

[0007] [Figure 1] Cross-sectional view of one pole of a synchronous reluctance motor in the second embodiment. [Figure 2] A diagram showing the approximate shape of the magnetic flux lines for one pole in a cylindrical iron core. [Figure 3] A diagram showing magnetic flux density under specific conditions. [Figure 4] A schematic diagram showing the flow of magnetic flux when the relative sizes of the dimensions differ. [Figure 5] This figure shows the simulation results of calculating the line voltage and output using the circumferential distance of the rib as a parameter. [Figure 6] Figure showing the shape of one pole of the synchronous reluctance motor in Modification Example 1. [Figure 7] This figure shows the shape of one pole of a synchronous reluctance motor in the second embodiment. [Figure 8]This figure shows the shape of one pole of a synchronous reluctance motor in the third embodiment. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described below with reference to the drawings. The following description and drawings are illustrative for illustrating the present invention, and have been omitted and simplified as appropriate for clarity of explanation. The present invention can also be carried out in various other forms. The positions, sizes, shapes, and ranges of the components shown in the drawings may not represent the actual positions, sizes, shapes, and ranges, in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the positions, sizes, shapes, and ranges disclosed in the drawings.

[0009] —First Embodiment— A first embodiment of a synchronous reluctance motor, which is a rotating electric machine, will be described below with reference to Figures 1 to 5.

[0010] Figure 1 is a cross-sectional view of a synchronous reluctance motor 1. However, Figure 1 shows a cross-sectional view of one pole of the synchronous reluctance motor 1, which consists of multiple poles. As will be omitted from the following explanation, the synchronous reluctance motor 1 of this embodiment has a similar structure in parts other than those shown in Figure 1. The left and right directions in the figure represent the circumferential direction of the synchronous reluctance motor 1, the top and bottom directions represent the radial direction of the synchronous reluctance motor 1, and the front and back directions represent the axial direction of the synchronous reluctance motor 1.

[0011] The synchronous reluctance motor 1 comprises a stator 2 and a rotor 3. The stator 2 is positioned on the outer diameter side of the rotor 3 with a predetermined gap between them. The stator 2 has a stator core 4, and the inner circumferential surface of the stator core 4, i.e., the surface facing the rotor 3, is provided with a plurality of teeth 5 arranged at equal intervals in the circumferential direction. A slot 6, which is a space, is formed between each tooth 5. A coil 7 for generating a rotating magnetic field is wound around each tooth 5 via these slots 6. In this embodiment, the shape has been simplified for the sake of explaining the configuration. For example, in reality, unless the radius is very large, the stator 2 and rotor 3 will not be rectangular even for one pole, but in this embodiment, the stator 2 and rotor 3 are shown as approximately rectangular.

[0012] The rotor 3 comprises a rotor core 8 and a shaft 9, and the rotor core 8 and shaft 9 rotate together as a single unit. Multiple flux barriers 10 are formed on each pole of the rotor core 8. Of the multiple flux barriers 10, the flux barrier 10 formed on the d-axis, which is the pole centerline indicated by the symbol c, is called the central flux barrier 10C, and the flux barriers 10 other than the central flux barrier 10C are called peripheral flux barriers 10N. In Figure 1, since two layers of flux barriers 10 are provided, there are two central flux barriers 10C. Ribs 12 are provided between the peripheral flux barriers 10N and the central flux barriers 10C in the circumferential direction.

[0013] Let "h" be the radial length of tooth 5. In this case, the innermost position of at least one central flux barrier 10C is positioned at a distance of length h or less from the outer diameter to the inner diameter of the rotor 3. Specifically, of the two central flux barriers 10C shown in Figure 1, the upper central flux barrier 10C is positioned at a distance of length h or less from the outer diameter to the inner diameter of the rotor 3. More precisely, the upper central flux barrier 10C is positioned at a distance of length h or less from the outer diameter to the inner diameter of the rotor 3, not only at the upper outer circumference but also at the lower innermost position.

[0014] Also, define the circumferential distance between two ribs 12 arranged at both ends of the central flux barrier 10C as Wr, the shortest distance in the circumferential direction of the teeth as Wt, and the circumferential distance between the centers of the slot openings as Ws. At this time, as shown in FIG. 1, the dimensional relationship of Wr, Wt, and Ws is configured to satisfy Wt≤Wr≤Ws. Thereby, since the d-axis magnetic resistance increases and the d-axis inductance decreases, the voltage decreases and the output improves.

[0015] The reason why the voltage is reduced and the output is improved by satisfying the above dimensional relationship will be described below with reference to FIGS. 2 to 5.

[0016] FIG. 2 is a diagram showing a schematic of magnetic flux lines for one pole in a cylindrical core, and FIG. 3 is a diagram showing magnetic flux density under specific conditions. The center point 100 shown in the center of FIG. 2 is the center of the air gap on the pole center line c. The synchronous reluctance motor 1 is arranged with a flux barrier based on the magnetic flux distribution of the cylindrical core as shown in FIG. 2. This magnetic flux distribution was calculated under the conditions of a small winding magnetomotive force (5000 AT) and a large winding magnetomotive force (15000 AT), and the magnetic flux density on the pole center line at each winding magnetomotive force was analyzed. The winding magnetomotive force is the product of the number of turns of the coil and the input current. It is generally said that the magnetomotive force of a motor used for automobiles is about 7500 AT to 15000 AT. Calculations were made using a value slightly smaller than this general lower limit and a value of the general upper limit.

[0017] FIG. 3(a) is the calculation result of the magnetic flux density on the pole center line when the winding magnetomotive force is 5000 AT in the configuration of FIG. 2. The origin of FIG. 3(a) is the center point 100 shown in FIG. 2. In FIG. 3(a), the magnetic flux density from the origin to the inner diameter of the rotor is shown as the magnetic flux density of the rotor. The case where the air gap length is 0.4 mm is shown by a solid line, the case where the air gap length is 0.7 mm is shown by a broken line, and the case where the air gap length is 1.0 mm is shown by a dashed-dotted line.

[0018] As shown in Fig. 3(a), it can be seen that the magnetic flux density of the rotor decreases from the origin, which is the center of the air gap, with a certain slope, and the slope of the magnetic flux density becomes gentler beyond a certain point. Here, focusing on the point where the slope changes, it can be found that the distance from the origin to the change point is equal to the radial length h of the tooth. Also, the distance from the origin to the change point shows a similar trend regardless of the air gap length. The magnetic flux flowing from the tooth 5 through the air gap to the rotor decreases with a certain slope in the radial length of the tooth, but the magnetic flux disperses circumferentially beyond that length. As a result, the slope of the magnetic flux density becomes gentler on the pole center line. Therefore, by installing the flux barrier 10 at a position before the slope becomes gentler, the d-axis magnetic resistance can be increased and the d-axis inductance can be reduced. Thus, by arranging the central flux barrier 10C at a distance of h or less, which is the radial length of the tooth 5, from the outer diameter to the inner diameter of the rotor, the d-axis inductance can be more easily reduced.

[0019] Fig. 3(b) shows the calculation results of the magnetic flux density on the pole center line when the winding magnetomotive force is 15000 AT in the configuration of Fig. 2. The graph in Fig. 3(b) is plotted in the same way as Fig. 3(a), and the origin of the graph is the center point 100. In Fig. 3(b) as well, the air gap lengths are calculated under three conditions of 0.4 mm, 0.7 mm, and 1.0 mm in the same way as Fig. 3(a), and the correspondence between the line types and the gap lengths is the same. From Fig. 3(b), it can be seen that even when the winding magnetomotive force is 15000 AT, the magnetic flux density of the rotor decreases from the origin, which is the center of the air gap, with a certain slope, and the slope of the magnetic flux density becomes gentler beyond a certain point. Also, it can be found that the change point of the slope shows a similar trend regardless of the air gap length. In Fig. 3(b), since the winding magnetomotive force is larger than that in Fig. 3(a), the distance from the origin to the change point of the slope of the magnetic flux density is longer than the radial length h of the tooth.

[0020] Based on the above, using the results for 5000AT, which has a small winding magnetomotive force, as a baseline, by positioning the central flux barrier 10C within the length in the tooth radial direction from the outer diameter to the inner diameter of the rotor 3, the d-axis magnetic resistance can be increased and the d-axis inductance can be reduced. It can be seen that the smaller the winding magnetomotive force, the more necessary it is to position the central flux barrier 10C on the outer diameter side of the rotor 3. However, as mentioned above, a winding magnetomotive force of 5000AT is sufficiently small for an automotive motor, and even smaller winding magnetomotive forces are not expected, so the central flux barrier 10C only needs to be within a distance h from the outer diameter of the rotor 3.

[0021] Figure 4 is a schematic diagram showing the flow of magnetic flux when the dimensional relationships are different. As defined earlier, Wr is the circumferential distance between the two ribs 12 located at both ends of the central flux barrier 10C, Wt is the shortest circumferential distance of the teeth 5, and Ws is the circumferential distance between the centers of the slot openings. Figure 4(a) shows the flow of magnetic flux when the dimensional relationship is that of Comparative Example 1 (Wr≦Wt≦Ws), Figure 4(b) shows the flow of magnetic flux when the dimensional relationship is that of the rotor structure of this embodiment (Wt≦Wr≦Ws), and Figure 4(c) shows the flow of magnetic flux when the dimensional relationship is that of Comparative Example 2 (Wt≦Ws≦Wr).

[0022] In the case of Comparative Example 1 shown in Figure 4(a), where the dimensions are (Wr≦Wt≦Ws), the circumferential distance Wr of the rib 12 is shorter than the shortest distance Ws in the circumferential direction of the teeth. Therefore, the magnetic flux cannot be sufficiently obstructed by the central flux barrier, and the d-axis inductance is difficult to reduce. In the case of the dimensions of this embodiment shown in Figure 4(b), where the circumferential distance Wr of the rib 12 is longer than the shortest distance Wt in the circumferential direction of the teeth than in Comparative Example 1, the magnetic flux can be easily obstructed by the central flux barrier 10C, and the d-axis inductance can be reduced.

[0023] In the case of Comparative Example 2 shown in Figure 4(c), where the dimensions are (Wt ≤ Ws ≤ Wr), the central flux barrier 10C can sufficiently obstruct the magnetic flux. However, because the circumferential distance Wr of the rib 12 is longer than the circumferential distance Ws between the centers of the slot openings, the peripheral flux barriers 10N adjacent to the central flux barrier 10C, which are dependent on the dimensions of the central flux barrier 10C, cannot be made large. As a result, magnetic flux leaks through the outer diameter side of the peripheral flux barriers 10N, and this magnetic flux increases the induced voltage. Thus, the dimensional relationship of this embodiment is superior to that of Comparative Examples 1 and 2.

[0024] Figure 5 shows the simulation results of calculating the line voltage and output using the circumferential distance Wr between the two ribs 12 positioned at both ends of the central flux barrier 10C as a parameter. In Figure 5, the solid line shows the output and the dashed line shows the line voltage. Of the two vertical dashed lines shown in Figure 5, the left one is Wt and the right one is Ws. From Figure 5, it can be seen that the line voltage is minimal and the output is maximum when the dimensional relationship (Wt≦Wr≦Ws) of this embodiment in Figure 4(b) is met. On the other hand, the line voltage increases and the output decreases in the dimensional relationships of the first comparative example shown in Figure 4(a) and the second comparative example shown in Figure 4(c). Therefore, by adopting the dimensional relationship (Wt≦Wr≦Ws) in this embodiment, the d-axis inductance is reduced and the line voltage is reduced, thus improving the output.

[0025] According to the first embodiment described above, the following effects and advantages can be obtained. (1) The synchronous reluctance motor 1, which is a rotating electric machine, comprises a rotor 3 having multiple magnetic poles including multiple flux barriers 10 and multiple ribs 12, a stator 2 having multiple teeth 5 and forming a slot 6 between two adjacent teeth 5, facing radially outward from the rotor 3 with a predetermined air gap, and a coil 7 arranged in the slot 6. At least one of the multiple flux barriers 10 is a central flux barrier 10C positioned on the pole centerline. The innermost position of the central flux barrier 10C is positioned at a distance of no more than or equal to the radial length h of the teeth 5, from the outer diameter toward the inner diameter side of the rotor 3. The distance Wr between two ribs 12 positioned at both ends of the central flux barrier 10C is greater than or equal to Wt, which is the shortest distance in the circumferential direction of the teeth 5, and less than or equal to the distance Ws between the slot opening center, which is the center of the opening that opens to the inner circumferential surface of the stator in the slot 6, and the slot opening center of another slot adjacent to the slot (Wt ≤ Wr ≤ Ws). Therefore, the d-axis inductance is reduced and the line voltage is reduced, resulting in improved output.

[0026] (Variation 1) Figure 6 shows the shape of one pole of the synchronous reluctance motor 1 in Modification 1. In the first embodiment described above, the shape shown in the figure was simplified to emphasize the explanation of the configuration, but in this modification, a more realistic shape of the synchronous reluctance motor 1, specifically the shape of 1 / 6 of the circumference, is shown. Therefore, in Figure 6, curvature not seen in Figure 1 can be seen. The point that Wt ≤ Wr ≤ Ws is satisfied when the circumferential distance between the two ribs 12 arranged at both ends of the central flux barrier 10C is Wr, the shortest distance in the circumferential direction of the teeth is Wt, and the circumferential distance between the centers of the slot openings is Ws is the same as in the first embodiment.

[0027] One structural difference is that in Figure 1, both the first and second layers have a central flux barrier 10C, whereas in this modified example, only the first layer, which is closest to the outer circumference, has a central flux barrier 10C. The second layer has ribs 12 on the d-axis, which prevents deformation of the rotor core 8 even when a strong centrifugal force is applied to it. Permanent magnets may also be placed within the peripheral flux barrier 10N and the central flux barrier 10C.

[0028] —Second Embodiment— A second embodiment of the synchronous reluctance motor will be described with reference to Figure 7. In the following description, the same reference numerals are used for components that are the same as in the first embodiment, and the differences will be mainly explained. Points that are not specifically described are the same as in the first embodiment. This embodiment differs from the first embodiment mainly in that the stator slots are fully closed.

[0029] Figure 7 shows the shape of one pole of the synchronous reluctance motor 1A in the second embodiment. The difference between Figure 7 and Figure 6 is that the opening of the slot 6 in Figure 6 is fully closed in Figure 7. The other configurations are the same. In particular, the central flux barrier 10C is positioned at a distance of less than or equal to the radial length (h) of the teeth 5 from the outer diameter to the inner diameter side of the rotor 3, and the dimensional relationship Wt≦Wr≦Ws is satisfied when the circumferential distance between the two ribs 12 positioned at both ends of the central flux barrier 10C is Wr, the shortest distance in the circumferential direction of the teeth is Wt, and the circumferential distance between the centers of the slot openings is Ws. This makes it possible to obtain the same effects as in the first embodiment. Permanent magnets may be placed in the peripheral flux barrier 10N and the central flux barrier 10C.

[0030] According to the second embodiment described above, the following effects and advantages can be obtained. (2) Slot 6 is a fully closed slot. Therefore, even with the synchronous reluctance motor 1A, which employs a fully closed slot to reduce pulsation, the output can be improved in the same way as in the first embodiment.

[0031] —Third Embodiment— A third embodiment of the synchronous reluctance motor will be described with reference to Figure 8. In the following description, the same reference numerals are used for components that are the same as in the first embodiment, and the differences will be mainly explained. Points that are not specifically described are the same as in the first embodiment. This embodiment differs from the first embodiment mainly in that the stator slots are semi-closed.

[0032] Figure 8 shows the shape of one pole of the synchronous reluctance motor 1B in the third embodiment. The main differences between Figure 8 and Figure 6 are that the opening of the slot 6 in Figure 6 is semi-closed in Figure 8, and the flux barrier of the rotor 3 is approximately U-shaped. The other configurations are the same. In particular, the central flux barrier 10C is positioned at a distance of less than or equal to the radial length (h) of the teeth 5 from the outer diameter to the inner diameter side of the rotor 3, and the dimensional relationship Wt≦Wr≦Ws is satisfied when the circumferential distance between the two ribs 12 positioned at both ends of the central flux barrier 10C is Wr, the shortest distance in the circumferential direction of the teeth is Wt, and the circumferential distance between the centers of the slot openings is Ws. Permanent magnets may be placed in the peripheral flux barrier 10N and the central flux barrier 10C.

[0033] According to the third embodiment described above, the following effects and advantages can be obtained. (3) Slot 6 is a semi-closed slot. Therefore, even with the synchronous reluctance motor 1B, which employs a semi-closed slot that has a good balance between low pulsation and large absolute torque, the output can be improved in the same way as in the first embodiment.

[0034] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail for the purpose of explaining the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, parts of the configuration of each embodiment can be added, deleted, or replaced with other configurations. [Explanation of symbols]

[0035] 1...Synchronous reluctance motor, 2...Stator, 3...Rotor, 4...Stator core, 5...Teeth, 6...Slot, 7...Armature winding, 8...Rotor core, 9...Shaft, 10...Flux barrier, 10C...Central flux barrier, 10N...Peripheral flux barrier, 12...Rib, 100...Intersection of pole centerline and air gap center

Claims

1. A rotating electric machine comprising a rotor having multiple magnetic poles including multiple flux barriers and multiple ribs, a stator having multiple teeth, with slots formed between two adjacent teeth, and facing radially outward from the rotor with a predetermined air gap, and coils disposed within the slots, Of the plurality of flux barriers, at least one of the flux barriers is a central flux barrier positioned on the pole centerline. The innermost position of the central flux barrier is positioned at a distance of no more than or equal to the radial length (h) of the teeth, from the outer diameter of the rotor toward the inner diameter. A rotating electric machine in which the distance (Wr) between the two ribs positioned at both ends of the central flux barrier is greater than or equal to the shortest distance (Wt) in the circumferential direction of the teeth, and less than or equal to the distance (Ws) between the slot opening center, which is the center of the opening of the slot that opens to the inner circumferential surface of the stator, and the slot opening center of another slot adjacent to the slot (Wt ≤ Wr ≤ Ws).

2. In the rotating electric machine described in claim 1, A rotating electric machine in which the aforementioned slot is a fully closed slot.

3. In the rotating electric machine described in claim 1, A rotating electric machine in which the aforementioned slot is a semi-closed slot.

4. In a rotating electric machine according to any one of claims 1 to 3, A rotating electric machine in which a permanent magnet is inserted into one or more of the flux barriers.

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